| Title of Invention | ROTATIONAL ANGLE SENSING DEVICE |
|---|---|
| Abstract | Abstract In a rotational angle sensing device, an intake module cover (11) forms a sensor receiving space (17) between the intake module cover (11) and a plate (12) to receive a rotational angle sensor (3) and a yoke (4, 5) and is made of a magnetic material. Thus, even when an external magnetic field and a magnetic body are placed near the rotational angle sensing device, the module cover (11) can absorb magnetism of the external magnetic field and the magnetic body. Thus, it is possible to limit a change in an output change characteristic of a Hall IC of the sensor (3) with respect to a rotational angle of a magnet (2). Furthermore, mounting portions (55) are formed in the cover (11) and are fixed to the housing (14). With the mounting portions (55), installation of the sensor (3) is eased. |
| Full Text | ROTATIONAL ANGLE SENSING DEVICE Description The present invention relates to a rotational angle sensing device. A known rotational angle sensing device includes an outer core (yoke) of a closed magnetic path type having in a symmetrical configuration (for example, refer to JP-2001-304806A). Also, another known rotational angle sensing device includes an open type yoke of an open magnetic path type having a symmetrical configuration (for example, refer to JP-2005-345250A and US-5164668B). In the above rotational angle sensing devices, which are described in JP-2001-304806A, JP-2005-345250A and US-5164668B, a magnetic flux, which is generated by the rotating magnet positioned in the center of the device, is effectively converged by elaborately designing an outskte yoke configuration as efficiently as possible. Then, the converged magnetic flux is transmitted to a magnetic sensing device (Hall IC), which is sandwiched between opposing portions of the yoke. Thereby, a rotational angle of a sensing object, which is rotated together with the magnet, is sensed by using an output change characteristic caused by a change in the rotational angle of the magnet. In another known rotational angle sensing device, a magnetic sensing element is disposed between two opposing magnets or is disposed radially inward of a circular magnet to detect a magnetic flux amount of the rotating magnet (for example, refer to JP-10-115505A or JP-2002-340513A). In the rotational angle sensing device described in JP-10-115505A or JP-2002-340513A, a magnetic sensing element is fixed to a circuit board, and an amount of a magnetic flux, which changes according to a change in a rotational angle of the magnet that rotates around the magnetic sensing element, is sensed with the magnetic sensing element. Here, as shown in FIG. 17, the rotational angle sensing device described in US-5164668B includes a magnet 101, a rotational angle sensor 102 and an open type yoke. The magnet 101 is fixed to an axial end of a rotatable shaft of a sensing object, such as a throttle valve. The rotational angle sensor 102 senses a rotational angle of the sensing object by using an output change characteristic of a magnetic sensing device (Hall IC) of the rotational angle sensor 102 with respect to a rotational angle of the magnet 101. The open type yoke forms a magnetic circuit (for example, open magnetic path) in corporation with the magnet 101 and the rotational angte sensor 102. The rotational angle sensor 102 has the magnetic sensing device fixed on a flat board 103. In addition, the open type yoke includes two magnetic bodies, i.e., first and second magnetic bodies 104, 105. The first and second magnetic bodies 104, 105 are arranged symmetrically about a vertical plane, which is vertical to a rotational axis of the rotatable shaft of the sensing object. Each of the first and second magnetic bodies 104, 105 includes a yoke main body 111 and a projection 112. The yoke main body 111 forms a gap between the yoke main body 111 and the magnet 101. The projection 112 projects toward a side of the rotational angle sensor 12 from an end edge of the yoke main body 111. It should be noted that the first and second magnetic bodies 104, 105 are disposed to be in parallel in a plate thickness direction to a rotational axis direction of the sensing object and are respectively opened at one side. Tip portions of the projections 112 formed for the respective first and second magnetic bodies 104, 105 are arranged to be opposed with each other in such a manner as to be spaced by a magnetic flux sensing gap. In addition, the magnet 101 is disposed to be rotatable relative to each of the yoke main bodies 111 formed in the respective first and second magnetic bodies 104, 105. The rotational angle sensor 102 is disposed inside the magnetic flux sensing gap formed between the opposing portions of the respective projections 112, and a gap is formed between the rotational angle sensor 102 and the opposing portion of each of the projections 112. In the rotational angle sensing device described in each of JP-2001-304806A and JP-2002-340513A, in a case where the convergence efficiency of the magnetic flux in the outside yoke (outer core) or sensitivity of the magnetic sensing element is increased, the output characteristic fluctuation of the device increases when a magnetic body (for example, fastening bolt or bracket of Fe family or the like) gets close to a product or when a product is subjected to radio wave noises. Therefore, the product (rotational angle sensing device) is mounted in a position where influence of the magnetic body is unlikely to be exerted, or a capacitor, which reduces the radio wave noises, is inserted in a detection circuit. However, this may cause a disadvantage of increasing a size of the entire product and deteriorating mountability of the product to a vehicle, such as an automobile. Particularly, the rotational angle sensing device described in each of JP-2005-345250A and US-5164668B is provided with an open type yoke of an open magnetic path type having a symmetrical configuration. In a case of such a symmetrical magnetic body (open type yoke), that is, an open type yoke of an open magnetic path type (the first and second magnetic bodies 104, 105), when an external magnetic field or an external magnetic field source (for example, alternator (AC generator) mounted in a vehicle or the like) or a magnetic body (for example, fastening bolt or bracket of iron based metal or the like) is disposed close to the rotational angle sensor 102, it raises the following disadvantage. That is, due to the influence from the external magnetic field or the magnetic body to the magnetic sensing device, the output change characteristic of the magnetic sensing device with respect to the rotational angle of the magnet 101 largely changes. In addition, in a case of the open type yoke of the open magnetic path type (the first and second magnetic bodies 104, 105), the tip portion (yoke opening end) in a plate length direction of each of the yoke main bodies 111 formed for the respective first and second magnetic bodies 104, 105 is opened. Therefore, the following disadvantage may occur. That is, the magnetic sensing device tends to be easily influenced by radio wave noises, so that the output change characteristic of the magnetic sensing device with respect to the rotational angle of the magnet 101 largely changes. It should be noted that the rotational angle sensing device described in JP-10-115505A uses a resin housing or cover, thereby possibly increasing the influence of the external magnetic field. Further, the rotational angle sensing device described in JP-2002-340513A is not formed in consideration of a material of a housing or the like particularly. An objective of the present invention is to provide a rotational angle sensing device, which effectively limits influences of radio wave noises, influences of an external magnetic filed and influences of a magnetic body onto a yoke or a rotational angle sensor without causing an increase in a size of the rotational angle sensing device and a deterioration in a mountability of the rotational angle sensing device. To achieve the objective of the present invention, there is provided a rotational angle sensing device, which includes at least one magnet, at least one rotational angle sensor, a yoke, a plate, a housing and a cover. The at least one magnet is fixed to a rotatable shaft of a sensing object. The at least one rotational angle sensor includes a magnetic sensing element, which senses a magnetic flux emitted from the at least one magnet. The at least one rotational angle sensor senses a rotational angle of the sensing object by using an output change characteristic of the magnetic sensing element with respect to a rotational angle of the at least one magnet. The yoke concentrates the magnetic flux emitted from the at least one magnet onto the at least one rotational angle sensor. The plate includes at least one yoke holding portion, which securely holds the yoke. The plate is installed to the housing. The housing is made of an electrically conductive material. The cover is made of a magnetic material and includes at least one mounting portion, which is fixed to the housing. The cover forms a sensor receiving space between the cover and the plate to receive the at least one rotational angle sensor and the yoke. The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: FIGS. 1A to 1C are schematic diagrams, each showing an entire construction of a rotational angle sensing device according to a first embodiment of the present invention; FIGS. 2A to 2C are schematic diagrams, each showing a modification of the major construction of the rotational angle sensing device according to the first embodiment; FIG. 3 is a schematic diagram showing an entire construction of an intake module of a rotational angle sensing device according to a second embodiment; FIG. 4 is a perspective view showing an intake air temperature sensor according to the second embodiment; FIG. 5 is a perspective view showing an intake air pressure sensor according to the second embodiment; FIG. 6 is a perspective view showing an entire construction of an intake module of a rotational angle sensing device according to a third embodiment; FIG. 7 is a bottom view showing an injection opening of thermosetting resin according to the third embodiment; FIG. 8 is a perspective view showing a major construction of the intake module according to the third embodiment; FIG. 9 is a perspective view showing a major construction of the rotational angle sensing device according to the third embodiment; FIG. 10 is a front view showing a major construction of the rotational angle sensing device according to the third embodiment; FIG. 11 is a schematic diagram showing a major construction of the rotational angle sensing device according to the third embodiment; FIG. 12 is a perspective view showing a major construction of a rotational angle sensing device according to a fourth embodiment; FIG. 13 is a schematic diagram showing a major construction of a rotational angle sensing device according to a fifth embodiment; FIG. 14 is a schematic diagram showing a major construction of the rotational angle sensing device according to the fifth embodiment; FIG. 15 is a schematic diagram showing a major construction of a rotational angle sensing device according to a sixth embodiment; FIG. 16 is a schematic diagram showing a major construction of a rotational angle sensing device according to a seventh embodiment; and FIG. 17 is a front view showing an entire construction of a previously proposed rotational angle sensing device. (First Embodiment) FIGS. 1A to 2 show a first embodiment of the present invention. Specifically, FIGS. 1A to 1C are diagrams showing an entire construction of a rotational angle sensing device. FIG. 2 is a diagram showing a modification of the major construction of the rotational angle sensing device. A control system of an internal combustion engine (engine control system) according to the present embodiment includes an electronically controlled fuel injection system, an intake module (intake air quantity control apparatus) and an engine control unit (ECU). The electronically controlled fuel injection system injects fuel into a combustion chamber of the internal combustion engine of a vehicle, such as a motorcycle (for example, single- cylinder four-cycle gasoline engine for a motorcycle: hereinafter referred to as engine). The intake module is incorporated into an intake system of the engine. The ECU controls the electronically controlled fuel injection system and the intake module. The electronically controlled fuel injection system is a system, which pressurizes fuel (for example, gasoline) at a predetermined pressure by an electric fuel pump and supplies the pressurized fuel to an injector (electromagnetic fuel injection valve) through a fuel filter, thereby injecting the fuel at optimal timing. The intake module of the present embodiment is an intake air quantity control apparatus (intake passage opening/closing device or system), which controls an intake air quantity, i.e., a quantity of intake air supplied into the combustion chamber of the engine based upon an operating amount (hereinafter, referred to as a throttle operating amount) of a throttle operating component (e.g., a throttle lever or a throttle handle of a vehicle, such as a motorcycle), which is operated by a driver. It should be noted that the throttle operating amount corresponds to an amount of depression (accelerator operating amount) of an accelerator pedal, which is depressed by a driver in a case of a four-wheeled vehicle. The intake module includes a throttle body (not shown), a throttle valve (sensing object not shown) and a rotational angle sensing device. The throttle body is incorporated into an intermediate part of an engine intake pipe connected to an intake port of the engine. The throttle valve is received in the throttle body in such a manner that the throttle valve is rotatable to open and close a throttle bore described below. The rotational angle sensing device senses a rotational angle of the throttle valve. The throttle body is integrally formed from a non-magnetic material (e.g., a resin material, such as thermoplastic resin or the like). The throttle body includes a cylindrical throttle bore wall (hereinafter referred to as cylindrical portion) and two cylindrical bearing potions. An intake passage (hereinafter referred to as the throttle bore) having a circular cross section is formed in the cylindrical throttle bore wall. The cylindrical bearing portions are provided at two opposed sides of the cylindrical throttle bore wall, which are opposed to each other in an axial direction that is perpendicular to an intake flow direction of the air in the throttle bore of the cylindrical portion. In addition, the throttle valve is connected integrally to a shaft 1, which extends linearly in the axial direction described above. The throttle vatve controls an intake air quantity, i.e., a quantity of intake air supplied into the combustion chamber of the engine through changing of the rotational angle of the throttle valve within an operable angular range that is between a fully closed position, at which the intake air quantity is minimized, and a fully opened position, at which the intake air quantity is maximized. The shaft 1 is a valve shaft that rotates integrally with the throttle valve. Two opposed axial ends of the shaft 1 are rotatably received in the two bearing portions, respectively, at the opposed sides of the cylindrical portion of the throttle body. One of the opposed axial ends (hereinafter, simply referred to as one end) of the shaft 1 penetrates through the cylindrical portion of the throttle body and projects outward from the throttle body. Furthermore, the other end of the shaft 1 penetrates through the cylindrical portion of the throttle body and projects outward from the throttle body. In addition, an accelerator lever is fixed to the other end of the shaft 1 by, for example, a metal bending process. A wire cable, which is driven synchronously with the throttle operating component (e.g., the throttle lever or the throttle handle), is connected to the accelerator lever. The intake module of the present embodiment has a non-contact type rotational angle sensing device (throttle opening degree sensing device). The rotational angle sensing device converts a throttle opening degree, which corresponds to a rotational angle (valve opening degree) of the throttle valve that is opened and closed in accordance with the throttle operating amount implemented by the driver, into an electrical signal to inform the opening degree of the throttle valve to the ECU. The rotational angle sensing device of the present embodiment includes a thin-plate shaped magnet (a permanent magnet: hereinafter referred to as a magnet) 2, a rotational angle sensor (hereinafter, referred to as a throttle opening degree sensor) 3, an open type yoke (a magnetic body of an open magnetic path type) and a casing. The magnet 2 is fixed to the one end of the shaft 1 of the throttle valve. The throttle opening degree sensor 3 includes a non-contact type magnetic sensing element, which senses the magnetic flux emitted from the magnet 2. The open type yoke concentrates the magnetic flux emitted from the magnet 2 on the throttle opening degree sensor 3. The casing receives the throttle opening degree sensor 3 and the open type yoke. The open type yoke includes first and second yoke segments 4, 5, which are formed as two plate-shaped yoke segments of the same type. A magnetic flux sensing gap is formed between the first and second yoke segments 4, 5 to receive the throttle opening degree sensor 3 therein. Here, the ECU of the present embodiment performs a fuel injection quantity control operation to control a valve-opening period of the injector in such a manner that a corresponding fuel injection quantity, which corresponds to an output of the throttle opening degree sensor 3, i.e., the electrical signal outputted from the throttle opening degree sensor 3, is supplied to each corresponding cylinder of the engine. In addition, the casing, which receives the throttle opening degree sensor 3 and the open type yoke, includes an intake module cover (a sensor cover, a magnetic shield cover) 11, a plate 12 and a housing 14. The plate 12 is fitted into the intake module cover 11. The housing 14 is mounted on an outer wall surface of the cylindrical portion of the throttle body. Shaft receiving holes 15, 16 penetrate through the plate 12 and the housing 14, respectively, in the axial direction of the shaft 1 of the throttle valve. The magnet mounting portion of the shaft 1 penetrates through the bearing receiving hole, which is formed in the bearing portion at the one side of the cylindrical portion of the throttle body, the shaft receiving hole 16, which is formed in the housing 14, and the shaft receiving hole 15, which is formed in the plate 12, so that the magnet mounting portion of the shaft 1 projects into the interior of the intake module cover 11 (e.g., the magnet mounting portion of the shaft 1 being disposed in a sensor receiving space 17 in the interior of the intake module cover 11). In this way, the magnet mounting portion of the shaft 1 is rotatably received in the interior of the intake module cover 11. The magnet 2 forms a magnet rotor, which rotates relative to the throttle opening degree sensor 3 and the open type yoke. The magnet 2 is held by and is fixed to the one end (the magnet mounting portion) of the shaft 1 of the throttle valve, so that the magnet 2 is rotated synchronously with rotation of the throttle valve, which serves as the sensing object. Specifically, the magnet 2 is held by and is fixed in a linear groove, which is formed in the shaft 1 of the throttle valve, by using fastening means, such as an adhesive or bonding. The magnet 2 has a square (or rectangular) shape when the magnet 2 is viewed in a direction perpendicular to a plane of FIG. 1A. More specifically, the magnet 2 is a cuboid-shaped permanent magnet, which stably produces a long lasting magnetic force. Furthermore, the magnet 2 is made of a rare-earth magnet (e.g., a samarium-cobalt (Sm-Co) magnet or a neodymium (Nd) magnet), an alnico magnet or a ferrite magnet. An N pole and an S pole are magnetized in the magnet 2 in such a manner that opposed ends of the magnet 2, which are opposed to each other in a longitudinal direction of the magnet 2, have the opposite polarities, respectively. In addition, the magnet 2 is magnetized to implement parallel magnetization in such a manner that lines of magnetic force in the magnet 2 are parallel to each other. Furthermore, the magnet 2 is magnetized in a radial direction, which is perpendicular to the rotational axis (rotational center axis) of the shaft 1 of the throttle valve. In this way, the magnetizing direction (the longitudinal direction) of the magnet 2 coincides with a diametrical direction, which is perpendicular to the rotational axis of the shaft 1 of the throttle valve. Furthermore, the magnetized surface (magnetic pole surface) at the one longitudinal side of the magnet 2 forms the N pole, and the magnetized surface (magnetic pole surface) at the other longitudinal side of the magnet 2 forms the S pole. Here, the magnet 2 is rotatable about the rotational center thereof within an operable angular range that is between the fully closed position and the fully opened position of the throttle valve, particularly in a magnet receiving space (magnet receiving portion) 19 formed in the interior of the open type yoke (between the first and second yoke segments 4, 5). In addition, in the present embodiment, when the throttle valve is placed in the fully closed position, the rotational angle of the magnet 2 becomes a minimum angle (for example, 0 degree) in the operable angular range (detection angular range) of the throttle valve. When the throttle valve is placed in an intermediate position, the rotational angle of the magnet 2 becomes an intermediate angle (for example, 45 degrees) in the operable angular range of the throttle valve. When the throttle valve is placed in the fully opened position, the rotational angle of the magnet 2 becomes a maximum angle (for example, 90 degrees) in the operable angular range of the throttle valve (refer to FIGS. IB and 1C). The throttle opening degree sensor 3 of the present embodiment is disposed in the magnetic flux sensing gap, which is formed between the first and second yoke segments 4, 5. Furthermore, the throttle opening degree sensor 3 includes a Hall IC, which senses the magnetic flux (a density of the magnetic flux) emitted from the magnetized surface at one side of the magnet 2. The Hall IC is an IC (integrated circuit), which includes a Hall element(s) and an amplifier circuit. The Hall element(s) serves as a non-contact type magnetic sensing element(s), an output of which changes according to a change in the magnetic flux density, i.e., the density of the magnetic flux (density of the magnetic flux passing through the Hall IC) passing through the magnetic flux sensing gap. The amplifier circuit amplifies the output of the Hall element(s). The Hall IC outputs an electrical voltage signal in accordance with the density of the magnetic flux (density of the magnetic flux passing through the Hall IC) passing through the magnetic flux sensing gap. It should be noted that the Hall IC may have a function of externally executing electrical trimming of a correction program(s) for an output gain adjustment, an offset adjustment and a temperature characteristic correction with respect to the magnetic flux density and may also have a self-diagnosis function for diagnosing, for example, breaking of wires or short-circuit. The Hall IC is sealed inside the resin housing (sealing member), which forms a main body (weight portion) of the throttle opening degree sensor 3. The resin housing is formed into a cuboid shape (thin plate-shape) and has opposed joint surfaces at opposed sides thereof, which are opposed with each other in a plate thickness direction of the resin housing. The opposed joint surfaces of the resin housing are in direct close contact with the first and second yoke segments 4, 5, respectively. A lead terminal group (a group of lead terminals) 3a, which serves as a sensor lead terminal group, extends out of the resin housing, which receives the Hall IC therein. In addition, the lead terminal group 3a of the throttle opening degree sensor 3 includes a single output-side lead terminal (a sensor output terminal), a single ground (GND)-side lead terminal (a sensor GND terminal) and a single power source-side lead terminal (a sensor power source terminal). The throttle opening degree sensor 3 is arranged in the magnetic flux sensing gap in such a manner that a perpendicular line, which extends through the rotational center of the magnet 2 and is perpendicular to the rotational axis (rotational center axis) of the shaft 1 of the throttle valve, passes through the center of the Hall IC. That is, the throttle opening degree sensor 3 is arranged in the magnetic flux sensing gap in such a manner that rotational center of the magnet 2 and the center of the Hall IC are positioned substantially on the same axis (same line). Here, when the magnet 2 is placed in such a manner that the longitudinal direction (the magnetizing direction) of the magnet 2 coincides with the direction of the magnetic flux sensing gap between the first and second yoke segments 4, 5, the rotational angle of the magnet 2 becomes the minimum angle (e.g., 0 degree) in the operable angular range. Furthermore, when the magnet 2 is placed in such a manner that the longitudinal direction (the magnetizing direction) of the magnet 2 is perpendicular to the direction of the magnetic flux sensing gap, the rotational angle of the magnet 2 becomes an angle (e.g., 90 degrees) in the operable angular range. In such a case, when the rotational angle of the magnet 2 becomes 90 degrees, the magnetic flux density, i.e., the density of the magnetic flux, which passes through the magnetic flux sensing gap, shows the maximum value, and the Hall IC outputs the maximum output value in the operable angular range. Furthermore, when the rotational angle of the magnet 2 becomes 0 degree, the magnetic flux density, i.e., the density of the magnetic flux, which passes through the magnetic flux sensing gap, shows the minimum value, and the Hall IC outputs the minimum output value in the operable angular range. XI I UUUILIUI 1/ II IV- II II VJWU\*. l/pi«l III iy U\-^l V-V- .JV-I l«J\SI «S I IU^ bVVU I I lU^I IV*L,I The open type yoke of the present embodiment includes the two divided yoke segments, i.e., the first and second yoke segments 4, 5, which are formed as the thin-plate shaped yoke segments of the same kind and which are opposed to each other while having the magnet receiving space 19 therebetween. The first and second yoke segments 4, 5 are formed to have a predetermined shape. Furthermore, the first and second yoke segments 4, 5 are made of a magnetic material (e.g., iron) and form one set of plate-shaped yoke segments (magnetic bodies) for concentrating the magnetic flux emitted from the magnet 2 on the throttle opening degree sensor 3, particularly on the Hall IC ■ (magnetic sensing element of the non-contact type). Each of the first and second yoke segments 4, 5 includes a yoke main body 21, 22 and a holding piece (a bent piece) 31, 32. The holding pieces 31, 32 of the first and second yoke segments 4, 5 hold the throttle opening degree sensor 3 therebetween in the thickness direction of the throttle opening degree sensor 3. An inner side surface of the first yoke segment 4 and an inner side surface of the second yoke segment 5 are opposed to each other in a plate thickness direction of the first and second yoke segments 4, 5 while the magnet 2 and the throttle opening degree sensor 3 are interposed between the inner side surface of the first yoke segment 4 and the inner side surface of the second yoke segment 5. In each of the first and second yoke segments 4, 5, a base end (a magnet side end, i.e., a yoke opening end portion 23) of the yoke main body 21, 22 forms a maximum width portion of the yoke segment 4, 5 where a plate width of the yoke segment 4, 5 is maximum. Also, in each of the first and second yoke segments 4, 5, a distal end (a throttte opening degree sensor 3 side end, i.e., a distal end of a sensor mounting part 33) of the holding piece 31, 32 forms a minimum width portion of the yoke segment 4, 5 where the plate width of the yoke segment 4, 5 is minimum. The plate width A of the yoke segment 4, 5 at this minimum width portion is equal to or greater than the plate thickness B of the magnet 2. Each of the first and second yoke segments 4, 5 is formed in such a manner that the plate width thereof decreases in a stepwise manner or decreased continuously from the yoke opening end portion 23 toward the distal end of the sensor mounting part 33. Specifically, each of the first and second yoke segments 4, 5 is tapered, so that the magnetic flux is converged from the yoke opening end portion 23 toward the distal end of the sensor mounting part 33 or toward the magnetic flux sensing gap. The yoke main body 21, 22 of each yoke segment 4, 5 is symmetrical about a plane, which includes a center axis (reference line) connecting between the rotational center of the magnet 2 and the thickness center of the throttle opening degree sensor 3 in the thickness direction of the throttle opening degree sensor 3, and which also includes the rotational axis of the shaft 1 of the throttle valve. Each yoke main body 21, 22 forms a predetermined air gap between the magnet 2 and the yoke main body 21, 22, and the yoke main bodies 21, 22 are opposed to each other. In addition, the yoke main bodies 21, 22 are opposed to each other in such a manner that the yoke main bodies 21, 22 are spaced from each other by a non-circular magnet receiving space 19, which rotatably receives the one end of the shaft 1 of the throttle valve and the magnet 2. The yoke main body 21, 22 of each yoke segment 4, 5 includes a plate-shaped yoke opposing portion 24 and a plate-shaped linear portion 25. The yoke opposing portions 24 of the yoke main bodies 21, 22 are opposed to each other at the end (the throttle opening degree sensor 3 side end), which is opposite from yoke opening end portion 23. In each yoke main body 21, 22, the linear portion 25 is bent relative to the yoke opposing portion 24 toward the magnet 2. The yoke opposing portion 24 of each yoke main body 21, 22 is a rectangular plate that is parallel to a radial perpendicular line, which is perpendicular to the rotational axis of the shaft 1 of the throttle valve. The holding piece 31, 32 is connected to one of two lateral edges of the yoke opposing portion 24, which are opposed to each other in a plate width direction of the yoke opposing portion 24. The linear portion 25 of each yoke main body 21, 22 includes the plate-shaped yoke opening end portion 23 at the opening side of the linear portion 25. The yoke opening end portion 23 is a magnet opposing portion, which is located at the opening side of each yoke main body 21, 22 and which forms a minimum air gap relative to the corresponding one of the opposed ends (opposed magnetized surfaces) of the magnet 2 that are opposed to each other in the magnetizing direction of the magnet 2 upon positioning of the magnet 2 and the shaft 1 at the maximum angle or therearound (e.g., 90 degrees or therearound) in the operable angular range of the throttle valve. The linear portion 25 of each yoke main body 21, 22 extends linearly from the yoke opening end portion 23 to the yoke opposing portion 24 in such a manner that the linear portion 25 is inclined by the predetermined inclination angle relative to the radial perpendicular line, which is perpendicular to the rotational axis of the shaft 1 of the throttle valve. Furthermore, the linear portion 25 is inclined in such a manner that the gap between the yoke opposing ends 24 is greater than the gap between the yoke opening end portions 23. Specifically, each yoke main body 21, 22, particularly the linear portion 25 of the yoke main body 21, 22 is inclined to satisfy the following condition. That is, when the magnet 2 rotates from the maximum angle, at which the minimum air gap is formed between the linear portion 25 and the magnet 2, toward the angular position where the minimum angle is made, the air gap between the linear portion 25 and the magnet 2 gradually increases. In each of the first and second yoke segments 4, 5, the holding piece 31, 32 is bent at a predetermined bending angle (an obtuse angle larger than a right angle) relative to the corresponding yoke main body 21, 22. In each of the first and second yoke segments 4, 5, the holding piece 31, 32 is connected to the one of the two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24, through a bending portion 34, which is bent in a substantially V-letter (or substantially U-letter) shape at an obtuse angle larger than a right angle. Here, it should be noted that the one of the two lateral edges of the yoke opposing portion 24 of the first yoke segment 4 is opposite from the one of the two lateral edges of the yoke opposing portion 24 of the second yoke segment 5. Each holding piece 31, 32 includes a linear portion 35, which extends linearly from the bending portion 34 toward the distal end of the sensor mounting part 33 in such a manner that the linear portion 35 is inclined relative to the perpendicular line, which is perpendicular to the plane of each of the yoke main bodies 21, 22. In addition, the sensor mounting part (the yoke opposing portion) 33 is provided to the distal end of the linear portion 35 of each holding piece 31, 32, so that the sensor mounting parts 33 of the holding pieces 31, 32 are opposed to each other via the magnetic flux sensing gap. Each holding piece 31, 32 is formed by bending a projection piece, which projects in the width direction of the yoke opposing portion 24 from the one of the two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24. Here, this projection piece is bent about the edge of the yoke opposing portion 24 toward the throttle opening degree sensor side (toward one side in the thickness direction of the yoke opposing portion 24). A bending angle of each holding piece 31, 32 relative to the corresponding yoke main body 21, 22 is set such that the throttle opening degree sensor 3 is placed within the plate widthwise dimension (plate width extent) of each yoke main body 21, 22. The bending angle of each holding piece 31, 32 relative to the corresponding yoke main body 21, 22 is set to be generally the same for the respective holding pieces 31, 32. Furthermore, in each holding piece 31, 32, an opposed surface of the sensor mounting part 33, which is opposed to the throttle opening degree sensor 3, is used as a contact surface, which directly contacts the opposed one of the magnetism-sensing surfaces of the throttle opening degree sensor 3. The sensor mounting part 33 of each holding piece 31, 32 serves as a sensor holding portion, which securely holds the throttle opening degree sensor 3, for example, through an adhesive or bonding upon clamping the throttle opening degree sensor 3 between the sensor mounting parts 33 of the holding pieces 31, 32. Here, the sensor mounting part 33 of the holding piece 31, which is placed on the front side in FIG. IB, forms a sensor upper-side mounting portion that holds and presses the throttle opening degree sensor 3 from the front side in the thickness direction of the throttle opening degree sensor 3 in such a manner that the sensor upper-side mounting portion closely or tightly contacts the opposed magnetism-sensing surface of the throttle opening degree sensor 3. Furthermore, the sensor mounting part 33 of the holding piece 32, which is placed on the back side in FIG. IB, forms a sensor lower-side mounting portion that holds and presses the throttle opening degree sensor 3 from the back side in the thickness direction of the throttle opening degree sensor 3 in such a manner that the sensor lower-side mounting portion closely or tightly contacts the opposed magnetism-sensing surface of the throttle opening degree sensor 3. The magnetic flux sensing gap is a gap, which has a constant width or distance between the sensor mounting part 33 of the holding piece 31 of the first yoke segment 4 and the sensor mounting part 33 of the holding piece 32 of the second yoke segment 5. The throttle opening degree sensor 3 is arranged in the magnetic flux sensing gap in such a manner that the rotational center of the magnet 2 and the thickness center of the Hall IC are generally located along the same axis (same line). The magnetic flux sensing gap is disposed in an intermediate part of a magnetic circuit, which is formed by the magnet 2, the throttle opening degree sensor 3 and the first and second yoke segments 4, 5. The intake module cover 11 has a relatively thin wall and is formed into a container shape by a magnetic material (e.g., an iron based metal material that contains, for example, 80% nickel). The intake module cover 11 forms a sensor receiving space 17 between the intake module cover 11 and an upper end surface of the plate 12 in FIG. 1A. Further, the tubular wall (side wall) 41 is formed integrally with the intake module cover 11 to surround the outer peripheral edges of the plate 12. A housing 14 side end (a lower end in FIG. 1A) of the tubular wall 41 is closed by a plate base of the plate 12. An opposite end (an upper end in FIG. 1A) of the tubular wall 41, which is opposite from the housing 14 side end of the tubular wall 41, is closed by a top wall plate (top wall) 42 that covers an upper portion of the sensor receiving space 17. The tubular wall 41 of the intake module cover 11 has an opening, which is opened externally. A connector 13, which is formed integrally with the plate 12 and will be described in detail below, is securely fitted into the opening of the tubular wall 41. Here, epoxy thermosetting resin (dielectric mold resin) is filled in the interior of the the intake module cover 11, i.e., in the sensor receiving space 17 of the intake module cover 11, to which the the plate 12 and the connector 13 are installed. The thermosetting resin is a seal member (potting material), which seals each lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3, each connector terminal of a connector terminal group 13a of the connector 13 and a plurality of conductors (conductor (copper wire) having insulation coating, conductive plate or the like). The conductors electrically connect between the lead terminals of the lead terminal group 3a of the throttle opening degree sensor 3 and the connector terminals of the connector terminal group 13a of the connector 13. The tubular wall 41 of the intake module cover 11 has two concave portions (anchoring portions) 43, 44 and mounting portions 55. The concave portions 43, 44 project toward a center of the sensor receiving space 17, and the mounting portions 55 are fixed to flanges 63 of the housing 14. The concave portions 43, 44 extend parallel to an extending direction of two sensor holding portions 51, 52, which are formed integrally in the plate 12. The two concave portions 43, 44 increase a contact area between the thermosetting resin and the tubular wall 41 of the intake module cover 11 to control a linear expansion movement of the thermosetting resin and electrical components sealed inside the thermosetting resin caused by a difference in linear expansion coefficient. In place of the two concave portions 43, 44, the tubular wall 41 of the intake module cover 11 may have a plurality of convex portions, which are formed by, for example, outwardly punching the tubular wall 41. Furthermore, a anchoring portion, such as a concave portion (or convex portion), which is used to anchor the thermosetting resin, may be formed along the entire circumference of the sensor receiving space 17 to limit the linear expansion movement of the thermosetting resin by increasing the contact area relative to the thermosetting resin. In this case, for example, anchoring portions, such as concave portions (convex portions), may be arranged one after another at predetermined intervals in the circumferential direction. In addition, as shown in FIGS. 2A to 2C, no anchoring portion may be provided in the tubular wall 41 of the intake module cover 11. The plate 12 is integrally formed from a non-magnetic material (e.g., a resin material, such as thermoplastic resin). The plate 12 includes the plate base and plate thick portions 53, 54. The plate base is installed in such a manner that the plate base closely contacts a top end surface of the housing 14. Each of the plate thick portions 53, 54 has a piate thickness that is greater than that of the plate base. The plate thick portions 53, 54 include convex-shaped sensor holding portions (yoke holding portion) 51, 52, respectively, which are disposed in such a manner that the plate thick portions 53, 54 project upward from a reference plane that extends along the top end surface of the plate base. The sensor holding portions 51, 52 include concave fitting grooves 61, 62, respectively, into which the yoke main bodies 21, 22 of the first and second yoke segments 4, 5 are securely fitted by, for example, press fitting. It should be noted that the yoke main bodies 21, 22 of the first and second yoke segments 4, 5 may be fixed into the fitting grooves 61, 62, respectively, through an adhesive or bonding. Furthermore, the shaft receiving hole 15 is formed in the plate base of the plate 12, particularly at a location between the two sensor holding portions 51, 52. A single connector housing of the connector 13 is formed integrally at a side of the plate 12. The connector 13 receives the connector terminal group 13a, which corresponds to the lead terminal group 3a that is pulled out of the main body (resin housing) of the throttle opening degree sensor 3. The connector 13 is a device, which includes a terminal base and a rectangular tubular connector shell. The terminal base holds the connector terminal group 13a. The rectangular tubular connector shell is disposed outside of the terminal base. The connector 13 connects between an ECU-side wiring harness and the throttle opening degree sensor 3 mounted on the plate 12. The housing 14 is a die cast product or an aluminum mold, which is made of an aluminum alloy mainly containing aluminum and is formed into a predetermined shape by the aluminum alloy. The housing 14 serves as a bracket for mounting the plate 12 and the intake module cover 11 onto an outer wall surface of the cylindrical portion of the throttle body. In addition, the plate 12 is mounted on the top end surface (housing top end surface) of the housing 14. Furthermore, the shaft receiving hole 16 is formed through the housing 14. The flanges 63 are formed integrally in the housing 14. The mounting portions 55 of the tubular wall 41 of the intake module cover 11 are fixed to the flanges 63 by the metal bending process for bending the mounting portions 55 against the flanges 63. In the present embodiment, the intake module cover 11 is fixed to the housing 14 by using fastening means (e.g., the metal bending process) in a state where the joint end surface (inner peripheral surface) of the tubular wall 41 of the intake module cover 11 is in surface-to-surface contact with the joint end surface (outer peripheral surface) of the respective flanges 63 of the housing 14. Next, an operation of the intake module cover, which includes the rotational angle sensing device of the present embodiment, will be briefly described with reference with FIGS. 1A to 2C. When the throttle operating component (e.g., the throttle lever or the throttle handle) is operated by the driver, the accelerator lever, which is connected to the throttle operating component through the wire cable, is rotated. Therefore, the throttle valve is rotated about the center axis (rotational axis) of the shaft 1 in accordance with the throttle operating amount caused by the driver. Thereby, the throttle bore, which is communicated with the combustion chamber of the engine, is opened at the corresponding degree, so that the engine rotational speed is changed to a corresponding speed, which corresponds to the throttle operating amount caused by the driver. Here, at the time of operating the engine at the idling speed, i.e., at the time of fully closing the throttle valve, the rotational angle of the magnet 2 becomes the minimum angle (e.g., 0 degree) in the operable angular range of the throttle valve. In this state, the center line of the magnet 2, which extends in the longitudinal direction of the magnet 2, coincides with the center line of the throttle opening degree sensor 3, which extends through the thickness center of the throttle opening degree sensor 3. In this state, the magnetic circuit is formed to create the flow of the magnetic flux through one of the magnetic poles (e.g., the N pole or S pole) of the magnet 2, the holding piece 31 of the first yoke segment 4 (specifically, through the linear portion 35 and the bent portion 34), the yoke main body 21 of the first yoke segment 4 (specifically, through the yoke opposing portion 24, the linear portion 25 and the yoke opening end portion 23), and the other one of the magnetic poles (e.g., the S pole or N pole) of the magnet 2 in this order. Also, the magnetic circuit is formed to create the flow of the magnetic flux through the N pole (or the S pole) of the magnet 2, the holding piece 32 (specifically, through the linear portion 35 and the bent portion 34), the yoke main body 22 (specifically, through the yoke opposing portion 24, the linear portion 25 and the yoke opening end portion 23) of the second yoke segment 5, and the S pole (or the N pole) of the magnet 2 in this order. At this time, the magnetic flux, which is emitted from the one of the magnetic poles of the magnet 2, does not pass through the magnetic flux sensing gap. Thus, the output of the Hall IC of the throttle opening degree sensor 3 with respect to the rotational angle of the magnet 2 becomes the minimum output value (nearly zero) in the operable angular range of the throttle valve. In addition, when a driver operates the throttle operating component to open the throttle valve to an intermediate position between the fully closed position and the fully opened position, the rotational angle of the magnet 2 becomes an intermediate angle (e.g., 45 degrees) in the operable angular range of the throttle valve. That is, the magnet 2 is rotated about the rotational center of the magnet 2 by 45 degrees in the counterclockwise direction in FIG. IB or 2B from the position of zero degree, so that the rotational angle of the magnet 2 becomes 45 degrees. At this time, the magnet 2 is positioned relative to the magnetizing direction (the longitudinal direction) of the magnet 2 in such a manner that the density (magnetic flux density) of the magnetic flux, which passes through the magnetic flux sensing gap and thereby crosses the Hall IC, reaches a middle level. In such a case, the magnetic circuit is formed to create the flow of the magnetic flux through the N pole (or the S pole) of the magnet 2, the yoke main body 21 of the first yoke segment 4 (specifically, through the linear portion 25 and the yoke opening end portion 23), and the S pole (or the N pole) of the magnet 2 in this order. Furthermore, the magnetic circuit is formed to create the flow of the magnetic flux through the N pole (or the S pole), the yoke main body 21 of the first yoke segment 4 (specifically, through the linear portion 25 and the yoke opposing portion 24), the holding piece 31 of the first yoke segment 4 (specifically, through the bent portion 34, the linear portion 35 and the sensor mounting part 33), the magnetic flux sensing gap (the throttle opening degree sensor 3), the holding piece 32 of the second yoke segment 5 (specifically, the sensor mounting part 33, the linear portion 35 and the bent portion 34), the yoke main body 22 of the second yoke segment 5 (specifically, through the yoke opposing portion 24, the linear portion 25 and the yoke opening end portion 23), and the S pole (or the N pole) of the magnet 2 in this order. Thereby, the output of the Hall IC of the throttle opening degree sensor 3 with respect to the rotational angle of the magnet 2 becomes a middle level between the minimum output value and the maximum output value in the operable angular range of the throttle valve. In addition, when the driver operates the throttle operating component to open the throttle valve to the fully opened position, the rotational angle of the magnet 2 becomes the maximum angle (e.g., 90 degrees) in the operable angular range of the throttle valve. That is, the magnet 2 is rotated about the rotational center of the magnet 2 by 45 degrees in the counterclockwise direction in FIG. IB or 2B from the position of 45 degrees, so that the rotational angle of the magnet 2 becomes 90 degrees. At this time, the center line of the magnet 2, which extends in the longitudinal direction of the magnet 2, becomes perpendicular to the center line of the throttle opening degree sensor 3, which extends through the thickness center of the throttle opening degree sensor 3 (see FIG. IB and 1C). In such a case, the magnetic circuit is formed to create the flow of the magnetic flux through the N pole (or the S pole), the yoke main body 21 of the first yoke segment 4 (specifically, through yoke opening end portion 23, the linear portion 25 and the yoke opposing portion 24), the holding piece 31 of the first yoke segment 4 (specifically, through the bent portion 34, the linear portion 35 and the sensor mounting part 33), the magnetic flux sensing gap (the. throttle opening degree sensor 3), the holding piece 32 of the second yoke segment 5 (specifically, the sensor mounting part 33, the linear portion 35 and the bent portion 34), the yoke main body 22 of the second yoke segment 5 (specifically, through the yoke opposing portion 24, the linear portion 25 and the yoke opening end portion 23), and the S pole (or the N pole) of the magnet 2 in this order. Therefore, almost all of the magnetic flux emitted from the magnetic pole surface of the magnet 2 passes through the magnetic flux sensing gap, so that the output of the Hall IC of the throttle opening degree sensor 3 with respect to the rotational angle of the magnet 2 becomes the maximum output value in the operable angular range of the throttle valve. Thus, in response to the change in the rotational angle of the magnet 2, the density of the magnetic flux, which passes through the magnetic flux sensing gap and thereby crosses the Hall IC, changes, so that the output of the Hall IC changes accordingly. Thereby, the throttle opening degree sensor 3 senses the throttle opening degree, which corresponds to the rotational angle of the throttle valve, through use of the change characteristic of the output (hereinafter, referred as an output change characteristic) of the Hall IC with respect to the rotational angle of the magnet 2. Further, the ECU, which receives the electrical signal (throttle opening degree signal) outputted from the Hall IC of the throttle opening degree sensor 3, computes a control target value (fuei injection timing and fuel injection quantity), which is required by the electronically controlled fuel injection system. The ECU indirectly computes the intake air quantity based on an intake pipe pressure measured at a location downstream of the throttle valve through an intake air pressure sensor. Then, the ECU computes a basic injection time period (a basic injection quantity) based on the above computed intake air quantity and a measured engine rotational speed. Then, the ECU determines a final injection time period (a fuel injection quantity, a target injection quantity) in view of the above basic injection time period and a correction amount (an injection quantity correction amount). The correction amount is determined based on the output value of the Hall IC of the throttle opening degree sensor 3. Furthermore, the ECU optimizes the fuel injection timing (injection timing, target injection timing) in such a manner that the fuel injection is terminated before an intake stroke of the engine. Now, advantages of the first embodiment will be described. As described above, in the rotational angle sensing device of the present embodiment, the throttle opening degree sensor 3 is sandwiched from the opposite sides in the thickness direction of the throttle opening degree sensor 3 by the holding pieces 31, 32 of the first and second yoke segments 4, 5 of the open type yoke. That is, the main body (resin housing) of the throttle opening degree sensor 3 is sandwiched between the sensor mounting part 33 of the holding piece 31 of the first yoke segment 4 and the sensor mounting part 33 of the holding piece 32 of the second yoke segment 5. Therefore, a gap is eliminated between each magnetism-sensing surface of the throttle opening degree sensor 3 and the corresponding opposed surface of the holding piece 31, 32 of the first or second yoke segment 4, 5. As a result, it is no longer required to accurately manage such a gap. In consequence, variations in the gap among products can be eliminated, so that characteristic variations among the products can be eliminated. That is, the output change characteristic of the Hall IC with respect to the rotational angle of the magnet 2 can be stabilized, and thereby variations in sensing accuracy among the products can be limited. Furthermore, the bending angle of each holding piece 31, 32 relative to the corresponding yoke main body 21, 22 of the yoke segment 4, 5 is set as the obtuse angle in such a manner that the throttle opening degree sensor 3 is placed within the plate widthwise dimension of each yoke main body 21, 22. In this way, an increase in the width dimension of the product can be limited. Thereby, a mounting space of the product in the vehicle can be easily secured. In each of the first and second yoke segments 4, 5, the base end (the magnet side end, i.e., the yoke opening end portion 23) of the yoke main body 21, 22 forms the maximum width portion of the yoke segment 4, 5 where the plate width of the yoke segment 4, 5 is maximum. Also, in each of the first and second yoke segments 4, 5, the distal end (the throttle opening degree sensor 3 side end, i.e., the distal end of the sensor mounting part 33) of the holding piece 31, 32 forms the minimum width portion of the yoke segment 4, 5 where the plate width of the yoke segment 4, 5 is minimum. The minimum width portion of the holding piece 31, 32 has the plate width, which is equal to or larger than the plate thickness of the magnet 2. In this way, the magnetic flux, which is emitted from the magnet 2, can be efficiently concentrated on the throttle opening degree sensor 3, particularly the Hall IC, so that the magnetic flux can be effectively applied across the the Hall IC. As a result, the output of the Hall IC is advantageously increased. In addition, the thin-plate shaped throttle opening degree sensor 3 is inclined within the plate width (within the yoke height) of the yoke opening end portion 23, which forms the maximum width portion of the yoke segment 4, 5, and the bending angle of the holding piece 31, 32 is set to be the same in the first and second yoke segments 4, 5. Thereby, components (i.e., the plate-shaped yoke segments) of the open type yoke become the common components. That is, the open type yoke (the first and second yoke segments 4, 5) is formed by combining the plate-shaped yoke segments (magnetic bodies) of the same kind, and thereby the components can be used in common, thus reducing the costs. Each of the first and second yoke segments 4, 5 is formed in such a manner that the plate width thereof decreases in a stepwise manner or decreases continuously from the yoke opening end portion 23 toward the distal end of the sensor mounting part 33. Specifically, each of the first and second yoke segments 4, 5 is tapered, so that the magnetic flux is converged from the yoke opening end portion 23 toward the distal end of the sensor mounting part 33 or toward the magnetic flux sensing gap. Therefore, even when a size of the throttle opening degree sensor 3 is small, the magnetic flux, which is emitted from the magnetized surface (pole surface) of the magnet 2, can be efficiently applied to the throttle opening degree sensor 3, particularly the Hall IC. That is, the magnetic flux, which is emitted from magnetized surface (pole surface) of the magnet 2, can be effectively concentrated on the throttle opening degree sensor 3, particularly the Hall IC. Thus, the magnetic flux emitted from the magnet 2 can be effectively applied across the Hall IC, and thereby the output of the Hall IC can be advantageously increased. As a result, it is possible to achieve a minimum profile of the product, which includes the throttle opening degree sensor 3 and the open type yoke. In the rotational angle sensing device of the present embodiment, the intake module cover 11, which forms the sensor receiving space 17 between the intake module cover 11 and the top end surface of the plate base of the plate 12, is made of the magnetic material (the iron based metal material). Thereby, even when an external magnetic field or an external magnetic field source (for example, an alternator or the like) and a magnetic body (an iron screw) are placed in close proximity to the rotational angle sensing device, the magnetism from the external magnetic filed source and the magnetic body can be absorbed by the intake module cover 11, which is made of the magnetic body. Therefore, the influence, which is applied from the external magnetic field source (external magnetic field) and the magnetic body to the throttle opening degree sensor 3, particularly the Hall IC, can be limited or reduced. Thus, it is possible to effectively limit the change in the output change characteristic of the Hall IC with respect to the rotational angle of the magnet 2 without a need for mounting the product to a location where the influence of the magnetic body is relatively small or a need for placing a capacitor, which reduces radio wave noises, in the circuit. That is, a quality of the product can be improved without an increase in the size of the product and without deteriorating the mountability of the product. In the rotational angle sensing device of the present embodiment, the intake module cover 11 is made of the magnetic material (e.g., the iron based magnetic metal material), which has the relatively small electrical resistance, and the housing 14 is made of an electrically conductive material (e.g., the nonmagnetic metal material, such as the aluminum alloy), which has the relatively small electrical resistance. Furthermore, a volume of the housing 14 is made larger than a volume of the intake module cover 11. Also, the joint end surface (inner peripheral surface) of the tubular wall 41 of the intake module cover 11 is in surface-to-surface contact with the joint end surface (outer peripheral surface) of the respective flanges 63 of the housing 14. Thereby, the radio wave noises, which approach the intake module cover 11, is released from the joint end surface of the tubular wall 41 of the intake module cover 11, which has the relatively small electrical resistance, to the flange 63 of the housing 14, which has a relatively large volume. Therefore, influence from the external magnetic field source and the magnetic body to the throttle opening degree sensor 3, particularly the Hall IC is limited. Thus, it is possible to effectively limit the change in the output change characteristic of the Hall IC with respect to the rotational angle of the magnet 2 without a need for mounting the product to a location where the influence of the magnetic body is relatively small or without a need for placing a capacitor, which reduces radio wave noises, in the circuit. That is, a quality of the product can be improved without an increase in the size of the product and without deteriorating the mountability of the product. In the rotational angle sensing device of the present embodiment, the flanges 63 of the housing 14, which is made of the aluminum alloy, are fixed to the tubular wall 41 of the intake module cover 11, which has the small linear expansion coefficient, by the metal bending process. Thus, the linear expansion movement of the epoxy thermosetting resin, which is filled inside the intake module cover 11, can be effectively limited. In addition, in the rotational angle sensing device of the present embodiment, the two concave portions 43, 44, which project toward the central portion of the sensor receiving space 17, are formed in the tubular wall 41 of the intake module cover 11. In consequence, the epoxy thermosetting resin, which is filled inside the intake module cover 11, is held by the two concave portions 43, 44, and thereby the linear expansion movement of the inner components (e.g., the throttle opening degree sensor 3 and the open type yoke) sealed in the thermosetting resin can be minimized. Thus, the output change characteristic of the Hall IC with respect to the rotational angle of the magnet 2 can be stabilized, and thereby variations in sensing accuracy among the products can be limited. Further, an electrical conduction failure, such as breaking of conductive wires, which electrically connect between the lead terminal group 3a of the throttle opening degree sensor 3 and the connector terminal group 13a of the connector 13, can be limited, so that the reliability of the throttle opening degree sensor 3 can be improved. That is, a product quality can be improved. Also, it is possible to limit an occurrence of an adverse phenomenon (migration), which is caused by separation of the thermosetting resin sheaths (covers) from the conductors that electrically connect between the lead terminal group 3a of the throttle opening degree sensor 3 and the connector lead terminal group 13a of the connector 13. When the thermosetting resin sheaths are separated from the conductors, it may cause a deterioration of the electrical insulation between the lead terminals of the lead terminal group 3a of the throttle opening degree sensor 3, a deterioration of the electrical insulation between the plurality of the conductors as well as a deterioration of the electrical insulation between the connector terminals of the connector terminal group 13a of the connector 13. In addition, in the rotational angle sensing device of the present embodiment, the mounting portions 55 are formed in the intake module cover 11. Therefore, the intake module cover 11 can be easily installed to the housing 14 and can be securely and stably fixed to the housing 14. (Second Embodiment) FIGS. 3 to 5 show a second embodiment of the present invention. Specifically, FIG. 3 is a diagram showing an intake module, which has a rotational angle sensing device according to the second embodiment. FIG. 4 is a diagram showing an intake air temperature sensor according to the second embodiment. FIG. 5 is a diagram showing an intake air pressure sensor according to the second embodiment. The intake module of the present embodiment includes the rotational angle sensing device (see the first embodiment), the intake air temperature sensor 6 and the intake air pressure sensor 7. The rotational angle sensing device includes the magnet 2, the throttle opening degree sensor 3 and the open type yoke. The intake air temperature sensor 6 measures the temperature (intake air temperature) of the intake air, which is supplied to the combustion chamber of the engine. Then, the intake air temperature sensor 6 coverts the measured intake air temperature into an electrical signal and supplies it to the ECU. The intake air pressure sensor 7 measures the pressure (intake air pressure) of the intake air, which is supplied to the combustion chamber of the engine. Then, the intake air pressure sensor 7 converts the measured intake air pressure into an electrical signal and supplies it to the ECU. The intake air temperature sensor 6 includes a temperature sensing element such as a thermistor, in which a resistance value changes in accordance with a change in the intake air temperature. The intake air temperature sensor 6 includes a thermistor portion 71, which has a distal end that is exposed in the intake passage. The thermistor of the thermistor portion 71 is sealed in epoxy resin. Further, two terminals 73 are sealed in a resin housing (sealing member) 72, which forms a main body of the intake air temperature sensor 6. The thermistor is fixed (electrically connected) between one ends of these terminals 73. Furthermore, the other ends of the terminals 73, which are opposite from the thermistor, extend out of the resin housing 72 and form a lead terminal group 6a. This lead terminal group 6a includes a single output side lead terminal (temperature sensor output terminal), which is connected to an output side of the thermistor, and a single power source side lead terminal (temperature sensor power source terminal), which is connected to a power source side of the thermistor. The intake air pressure sensor 7 includes a pressure sensing element (e.g., a piezoresistive element) and a pressure sensing circuit (e.g., an amplifier circuit). The pressure sensing element converts an intake air pressure, which is introduced from an air introducing passage (a sensing port), into an electrical signal. The pressure sensing circuit ampfiftes the electrical signal, which is supplied from the pressure sensing element. The pressure sensing element and the pressure sensing circuit are sealed in a resin housing (sealing member) 74, which forms the main body of the intake air pressure sensor 7. A lead terminal group 7a extends out of the resin housing 74, which receives the pressure sensing element and the pressure sensing circuit. This lead terminal group 7a includes a single ground (GND)-side lead terminal (pressure sensor GND terminal), a single output-side lead terminal (pressure sensor output terminal), and a single power source-side lead terminal (pressure sensor power source terminal). The ground (GND)-side lead terminal is connected to a ground terminal of the pressure sensing circuit. The output-side lead terminal is connected to an output terminal of the pressure sensing circuit. The power source-sid terminal of the pressure sensing circuit. In addition, the main body of the rotational angle sensing device (the yoke main bodies 21, 22 of the first and second yoke segments 4, 5 of the open type yoke), the main body of the intake air temperature sensor 6 and the main body of the intake air pressure sensor 7 are securely held by the plate 12. This plate 12 is fitted into the intake module cover 11 of the present embodiment. A single connector 13 is formed integrally at a side portion of the plate 12. A connector terminal group 13a is received in the connector 13 and is provided to correspond with the lead terminal group 3a of the main bodies (resin housings) of the throttle opening degree sensor 3, the lead terminal group 6a of the intake air temperature sensor 6 and the lead terminal group 7a of the intake air pressure sensor 7. The tubular wall 41 of the intake module cover 11 has an opening 45, which is opened externally. The connector 13 is fluid-tightly fitted into the opening 45 of the tubular wall 41 in such a manner that the connector 13 projects outwardly from an outer wall surface of the tubular wall 41 of the intake module cover 11. The connector 13 is a device, which includes a terminal base and a rectangular tubular connector shell. The terminal base holds the connector terminal group 13a. The rectangular tubular connector shell is disposed outside of the terminal base. The connector 13 connects an ECU-side wiring harness to the lead terminal group 3a of the throttle opening degree sensor 3, of the intake air temperature sensor 6 and of the intake air pressure sensor 7, which are mounted on the plate 12. The connector terminal group 13a includes first to fifth connector terminals (sensor-side connector terminal, external connection terminal and terminal), which are electrically connected to the lead terminals of the lead terminal group 3a of the throttle opening degree sensor 3, the lead terminals of the lead terminal group 6a of the intake air temperature sensor 6 and the lead terminals of the lead terminal group 7a of the intake air pressure sensor 7 through multiple conductors. The first connector terminal is electrically connected to the output-side lead terminal of the lead terminal group 6a of the intake air temperature sensor 6. The second connector terminal is electrically connected to the output-side lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3. The third connector terminal is electrically connected to the GND-side lead terminal of the lead terminal group 7a of the intake air pressure sensor 7 and also to the GND-side lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3. The fourth connector terminal is electrically connected to the output-side lead terminal of the lead terminal group 7a of the intake air pressure sensor 7. The fifth connector terminal is electrically connected the power source-side lead terminal of the lead terminal group 6a of the intake air temperature sensor 6, the power source-side lead terminal of the lead terminal group 7a of the intake air pressure sensor 7 and the power source-side lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3. Here, like in the first embodiment, epoxy thermosetting resin is filled in the interior of the intake module cover 11, i.e., in the sensor receiving space 17. The thermosetting resin is a seal member, which seals each lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3, each lead terminal of the lead terminal group 6a of the intake air temperature sensor 6, each lead terminal of the lead terminal group 7a of the intake air pressure sensor 7, the multiple conductors and each connector terminal of the connector terminal group 13a of the connector 13. Here, the ECU includes a microcomputer of a known structure having a CPU, a storage device (e.g., memories, such as a ROM and RAM), an input circuit and an output circuit. The CPU performs various control operations and computing operations. The storage device stores various programs and data. The ECU electronically controls the injectors according to the control programs or control logics stored in the memory when an ignition switch (not shown) is turned on (IG ON). The ECU forcefully terminates the above control operations according to the control programs or control logics when the ignition switch (not shown) is turned off (IG OFF). Furthermore, the sensor signals, which are outputted from the throttle opening degree sensor 3, the intake air temperature sensor 6 and the intake air pressure sensor 7, undergo analog-to-digital conversion through an A/D converter and are thereafter supplied to the microcomputer of the ECU. In addition, the sensor signals, which are outputted from various other sensors, undergo analog-to-digital conversion through the A/D converter and are thereafter supplied to the microcomputer of the ECU. These other sensors include, for example, a crank angle sensor, which senses a rotational angle of the crankshaft of the engine, and an intake air quantity sensor, which senses an intake air quantity supplied into the combustion chamber of the engine. Next, an operation of the intake module of the present embodiment, which is installed to the intake pipe of the engine will be briefly described with reference with FIGS. 3 to 5. When the throttle operating component (e.g., the throttle lever or the throttle handle) is operated by the driver, the accelerator lever, which is connected to the throttle operating component through the wire cable, is rotated. When the accelerator lever is rotated, the shaft 1, which is connected to the accelerator lever, is rotated. In consequence, the throttle valve rotates about the rotational axis of the shaft 1 in accordance with the throttle operating amount caused by the driver. Thereby, the intake passage, which is communicated with the combustion chamber of the engine, is opened at the corresponding degree, so that the engine rotational speed is changed to a corresponding speed, which corresponds to the throttle operating amount caused by the driver. At this time, the the ECU, which receives the sensor signals from the various sensors (e.g., the throttle opening degree sensor 3, the intake air temperature sensor 6 and the intake air pressure sensor 7), computes a control target value, which is required by the electronically controlled fuel injection system. The ECU indirectly computes the intake air quantity based on the intake pipe pressure measured at the location downstream of the throttle valve through the intake air pressure sensor 7. Then, the ECU computes the basic injection time period based on the above computed intake air quantity and the measured engine rotational speed. Then, the ECU determines the final injection time period (the fuel injection quantity) in view of the above basic injection time period and a correction amount. The correction amount is determined based on the sensor signals of the various sensors (e.g., the intake air temperature sensor 6 and the Hall IC). Furthermore, the ECU optimizes the fuel injection timing in such a manner that the fuel injection is terminated before the intake stroke of the engine. (Third Embodiment) FIGS. 6 to 11 show a third embodiment of the present invention. Specifically, FIG. 6 is a diagram showing an entire structure of an intake module according to the third embodiment. FIG. 7 is a diagram showing a resin injection opening (port) for injecting thermosetting resin according to the third embodiment. FIG. 8 is a diagram showing a major structure of the intake module according to the third embodiment. FIGS. 9 to 11 are diagrams showing a major structure of the rotational angle sensing device according to the third embodiment. The intake module of the present embodiment includes the rotational angle sensing device, the intake air temperature sensor 6 and the intake air pressure sensor 7. The rotational angle sensing device includes the magnet 2, the throttle opening degree sensor 3 and the open type yoke. The intake air temperature sensor 6 measures the temperature (intake air temperature) of the intake air, which is supplied to the combustion chamber of the engine. Then, the intake air temperature sensor 6 coverts the measured intake air temperature into an electrical signal and supplies it to the ECU. The intake air pressure sensor 7 measures the pressure (intake air pressure) of the intake air, which is supplied to the combustion chamber of the engine. Then, the intake air pressure sensor 7 converts the measured intake air pressure into an electrical signal and supplies it to the ECU. Further, the resin injection port 57 is formed in the plate 12 of the present embodiment. Epoxy thermosetting resin (mold resin) 10 is injected into the sensor receiving space 17 through the resin injection port 57. Accordingly, each lead terminal of the lead terminal group 3a of the throttle opening degree sensor 3, each connector terminal of the connector terminal group 13a of the connector 13 and the multiple conductors are insert molded by the dielectric mold resin 10, which is injected in to the sensor receiving space 17 through the resin injection port 57. Here, the multiple conductors may be conductors (e.g., copper wires), each of which has a dielectric sheath (cover), or conductive plates. These multiple conductors electrically connect the lead terminals of the lead terminal group 3a of the throttle opening degree sensor 3 to the connector terminals of the connector terminal group 13a of the connector 13. In the open type yoke of the present embodiment, each of the first and second yoke segments 4, 5 includes a bent portion 26 in the yoke main body 21, 22. The bent portion 26 is arcuately bent toward the magnet 2 side. In addition, two mounting portions 55 are integrally formed at two diametrically opposed outer parts of the tubular wall 41 of the intake module cover 11. The mounting portions 55 are formed as tab-like projections that contact the top end surfaces of the flanges 63 of the housing 14. The mounting portions 55 of the intake module cover 11 are securely fixed to the top end surfaces of the flanges 63 of the housing 14 by fastening screws (for example, iron based magnetic bodies) 64. Furthermore, the plate base of the plate 12 includes a convex-cylindrical portion 56. The cylindrical portion 56 rotatably receives the magnet mounting portion of the shaft 1 of the throttle valve. The cylindrical portion 56 is located between the two plate thickness portions 53, 54 (yoke holding portions 51, 52) and forms the magnet receiving portion 19 to rotatably receive the magnet 2. In the drawings, number 65 indicates a circular through hole, which receives the corresponding fastening screw 64. Here, in the rotational angle sensing device of the present embodiment, the fastening screws (for example, iron based magnetic bodies) 64 are placed near the throttle opening degree sensor 3 and the two yoke segments 4, 5. However, when the intake module cover 11 is made of the magnetic material (iron based metal material), magnetic influences of the fastening screws (e.g., iron based magnetic bodies) 64 can be absorbed by the intake module cover 11. As a result, the magnetism influences of the fastening screws (e.g., iron based magnetic bodies) 64 on the throttle opening degree sensor 3, particularly the Hall IC are limited or reduced. Thus, a change in the output change characteristic of the Hall IC with respect to the rotational angle of the magnet 2 can be limited. Furthermore, in the rotational angle sensing device of the present embodiment, the mounting portions 55 are formed in the diametrically opposed outer parts of the intake module cover 11. Therefore, the intake module cover 11 can be easily installed to the housing 14 and can be securely and stably fixed to the housing 14. (Fourth Embodiment) FIG. 12 shows a fourth embodiment of the present invention. Specifically, FIG. 12 is a diagram showing a major construction of a rotational angle sensing device according to the fourth embodiment. The open type yoke of the present embodiment includes the two divided yoke segments, i.e., the first and second yoke segments 4, 5. These yoke segments 4, 5 are formed as two different types of plate shaped yoke segments, which are opposed to each other while having the magnet receiving space 19 therebetween. Each of the first and second yoke segments 4, 5 is formed to have a corresponding predetermined shape. Furthermore, the first and second yoke segments 4, 5 are made of a magnetic material (e.g., iron) and form one set of plate-shaped yoke segments (magnetic bodies) for concentrating the magnetic flux emitted from the magnet 2 on the throttle opening degree sensor 3, particularly on the Hall IC (magnetic sensing element of the non-contact type). The first yoke segment 4 includes a yoke main body 21 and a holding piece 91. The yoke main body 21 is opened at one side. The holding piece 91 is bent by a predetermined bent angle relative to the yoke main body 21. The holding piece 91 of the first yoke segment 4 is connected to one of two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24, through a bent portion 34, which is bent in a substantially V-letter (or substantially U-letter) shape at an obtuse angle that is larger than a right angle. The holding piece 91 of the first yoke segment 4 is formed by bending a projection piece, which projects in the width direction of the yoke opposing portion 24 from the one of the two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24. Here, this projection piece is bent about the edge of the yoke opposing portion 24 toward the throttle opening degree sensor side (toward one side in the thickness direction of the yoke opposing portion 24). In this way, the sensor mounting part (yoke opposing portion) 33 of the first yoke segment 4 is formed at a back surface side of the holding piece 91 of the first yoke segment 4. The second yoke segment 5 includes a yoke main body 22 and a holding piece 92. The yoke main body 22 is opened at one side. The holding piece 92 is bent by a predetermined bent angle relative to the yoke main body 22. The holding piece 92 of the second yoke segment 5 is connected to one of two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24, through a bent portion 34, which is bent in a substantially V-letter (or substantially U-letter) shape at a generally right angle. Here, it should be noted that the one of the two lateral edges of the yoke opposing portion 24 of the second yoke segment 5 and the one of the two lateral edges of the yoke opposing portion 24 of the first yoke segment 4 are located on the same lateral side. The holding piece 92 of the second yoke segment 5 is formed by bending a projection piece, which projects in the width direction of the yoke opposing portion 24 from the one of the two lateral edges of the yoke opposing portion 24, which are opposed to each other in the width direction of the yoke opposing portion 24. Here, this projection piece is bent about the edge of the yoke opposing portion 24 toward the throttle opening degree sensor side (toward one side in the thickness direction of the yoke opposing portion 24). In this way, the sensor mounting part (yoke opposing portion) 33 of the second yoke segment 5 is formed at a front surface side of the holding piece 92 of the second yoke segment 5. It should be noted that the sensor mounting part 33 of each of the first and second yoke segments 4, 5 has the plate width, which is smaller than the plate width of the bent portion 34. (Fifth Embodiment) FIGS. 13 and 14 show a fifth embodiment of the present invention. Specifically, FIGS. 13 and 14 are diagrams showing a major construction of a rotational angle sensing device according to the fifth embodiment. The rotational angle sensing device of the present embodiment adopts a reversely warped configuration shown in FIGS. 13 and 14 as an open type yoke of symmetrical open magnetism path type for the purpose of improving linearity of the output change characteristic of the throttle opening degree sensor 3 with respect to the rotational angle of the magnet 2 for improving detection accuracy of the rotational angle. The throttle opening degree sensor 3 includes a magnetic sensing element (e.g., the Hall IC), an output of which changes in response to a change in a density of a magnetic flux that passes through a magnetic flux sensing gap formed between opposed parts (sensor mounting parts) 36 of the first and second yoke segments 4, 5. In addition, the throttle opening degree sensor 3 and the first and second yoke segments 4, 5 are received and held in the sensor receiving space 17, which is formed between the intake module cover 11 and the plate 12. Here, epoxy thermosetting resin (dielectric mold resin) is filled in the interior of the the intake module cover 11, i.e., in the sensor receiving space 17 of the intake module cover 11, to which the the plate 12 and the connector 13 are installed. Further, the intake module cover 11 has the mounting portions 55, which are formed at two opposed parts of the intake module cover 11 and are connected to the the housing 14. These mounting portions 55 are securely fixed to the top end surfaces of the flanges 63 of the housing 14 by the fastening screws 64. As shown in FIGS. 13 and 14, each of the first and second yoke segments 4, 5 includes a yoke opening-side extension portion 37, which extends from the lower end surface of the opposed portion 36 to form a predetermined air gap between the magnet 2 and the extension portion 37. The yoke opening-side extension portion 37 of each of the first and second yoke segments 4, 5 includes a linear portion 46 and a bent portion 49. The bent portions 49 of the first and second yoke segments 4, 5 are bent in a reverse U-letter shape from the opposite ends of the linear portions 46, which are opposite to each other, toward reversely warped portions 47. In addition, the reversely warped portion 47 of each of the first and second yoke segments 4, 5 includes an arc portion, which is in a reversely warped shape that is convex on the magnet 2 side. Here, a length of the arc shaped portion of the reversely warped portion 47 shown in FIG. 14 is smaller than that of the reversely warped portion 47 shown in FIG. 13. (Sixth Embodiment) FIG. 15 shows a sixth embodiment of the present invention. Specifically, FIG. 15 is a diagram showing a major construction of a rotational angle sensing device according to the sixth embodiment. The rotational angle sensing device of the present embodiment includes a magnet 2, two throttle opening degree sensors 3 and first and second yoke segments 4, 5. The magnet 2 is fixed to rotors 66, 67, which are rotated through rotation of a rotatable shaft of a sensing object, such as a throttle valve. The magnet 2, the throttle opening degree sensors 3 and the first and second yoke segments 4, 5 form a magnetic circuit (closed magnetic path). The throttle opening degree sensor 3 includes a magnetic sensing element (e.g., the Hall IC), an output of which changes in response to a change in a density of the magnetic flux that passes through the magnetic flux sensing gap formed between opposed parts (sensor mounting parts) 68, 69 of the first and second yoke segments 4, 5. In addition, the throttle opening degree sensors 3 and the first and second yoke segments 4, 5 are received and held in the sensor receiving space 17, which is formed between the intake module cover 11 and the plate 12. Here, epoxy thermosetting resin (dielectric mold resin) is filled in the interior of the the intake module cover n, i.e., in the sensor receiving space 17 of the intake module cover 11, to whk:h the the plate 12 and the connector 13 are installed. Further, the intake module cover 11 has the mounting portions 55, which are formed at two opposed parts of the intake module cover 11 and are connected to the the housing 14. These mounting portions 55 are securely fixed to the top end surfaces of the flanges 63 of the housing 14 by the fastening screws 64. (Seventh Embodiment) FIG. 16 shows a seventh embodiment of the present invention. Specifically, FIG. 16 is a diagram showing a major construction of a rotational angle sensing device according to the seventh embodiment. In the rotational angle sensing device of the present embodiment, a rotatable shaft of a sensing object, such as a throttle valve, is rotatably supported by a bearing member in the housing 14. In addition, cylindrical rotor cores (corresponding to the first and second yoke segments of the closed magnetic path type) 8, 9 are fixed to one end of the rotatable shaft. Two stator cores 75, 76 are placed radially inward of the rotor cores 8, 9 in a coaxial manner. One magnet 2 is securely held between one opposing portion 78 of the rotor core 8 and one opposing portion 78 of the rotor core 9, and another magnet 2 is securely held between another opposing portion 79 of the rotor core 8 and another opposing portion 79 of the rotor core 9. Each of the two magnets 2 is formed in a plate shape or a column shape. An N pole and an S pole are magnetized in parallel at opposed end surfaces, respectively, of each magnet 2. In addition, a small gap is formed between inner peripheral surfaces of the rotor cores 8, 9 and outer peripheral surfaces of the stator cores 75, 76 except two portions, which are adjacent to the magnets 2, respectively. Furthermore, a magnetic sensing gap of a constant width is formed between the stator cores 75, 76 in such a manner that the magnetic sensing gap extends diametrically through between the stator cores 75, 76 to form a parallel magnetic field. In this magnetic sensing gap, two throttle opening degree sensors 3 are arranged one after another in the diametrical direction in side by side relationship. The throttle opening degree sensors 3 and the rotor cores 8, 9 are received and held in the a sensor receiving space 17, which is formed between the intake module cover 11 and the plate 12. Further, the intake module cover 11 has the mounting portions 55, which are formed at two opposed parts of the intake module cover 11 and are connected to the the housing 14. These mounting portions 55 are securely fixed to the top end surfaces of the flanges 63 of the housing 14 by the fastening screws 64. Now, modifications of the above embodiments will be described. In the above embodiments, the rotational angle sensing device of the present invention is applied to the throttle opening degree sensing device, which senses a throttle opening degree that corresponds to the rotational angle of the throttle valve. Alternatively, the rotational angle sensing device of the present invention may be applied to an accelerator opening degree sensing device, which senses an accelerator opening degree that corresponds to an amount of depression of an accelerator pedal. In addition, the rotational angle sensing device of the present invention may be applied to a rotational angle sensing device, which senses a rotational angle of a valve (valve body of an air flow quantity control valve, such as an exhaust gas rerirariation quantity control valve), which opens and closes a fluid flow path formed in a housing. Further, the rotational angle sensing device of the present invention may be applied to a device, which drives the throttle valve through use of a drive source (e.g., an electric motor) to open and close the throttle valve. In the above embodiments, the plate-shaped or column-shaped magnet(s) 2 is used. Alternatively, the magnet(s) may be an elongated magnet, a needle-shaped magnet or a bar-shaped magnet depending on a need. In particular, when the opposed ends of the magnet, which are opposed to each other in the longitudinal direction of the magnet and are respectively magnetized with the opposite polarities, are made thinner (i.e., made to have a lower profile), linearity of the output voltage of the Hall IC (linearity of the output change characteristic of the Hall IC) with respect to the rotational angle of the magnet 2 can be advantageously improved. It should be noted that the above magnet(s) 2 may be replaced with a resin magnet(s), which is made by sintering powder of polyamide resin (PA), Nd, Fe, B. Further alternatively, an electromagnet(s), which generates a magnetomotive force upon energization, may be used in place of the magnet(s) 2. Further alternatively, a magnet rotor(s), which includes a permanent magnet and a rotor core (magnetic body), may be used in place of the magnet(s) 2. In the above embodiments, the operable angular range of the sensing object is set in the range of 0 degree to 90 degrees. Alternatively, the operable angular range of the sensing object may be set in a range of -45 degrees to +45 degrees or in a range of -90 degrees to 0 degree. In addition, in the above embodiments, the operating direction of the throttle valve is set to be the counterclockwise direction about the rotationai center of the magnet 2 in the drawings. Alternatively, the opening direction of the throttle valve may be set to be the clockwise direction about the rotational center of the magnet 2 in the drawings. Furthermore, the operable angular range of the sensing object may be increased from that of the first and second embodiments. In such a case, the operable angular range of the sensing object may be set to be in a range of 0 degree to 80 degrees or in a range of-80 degrees to +80 degrees. In the above embodiments, any one or more components of each embodiment may be combined with any one or more components of any one of the remaining embodiments within a scope and spirit of the present invention. Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. Claims 1. A rotational angle sensing device comprising: at least one magnet (2) that is fixed to a rotatable shaft (1) of a sensing object; at least one rotational angle sensor (3) that includes a magnetic sensing element, which senses a magnetic flux emitted from the at least one magnet (2), wherein the at least one rotational angle sensor (3) senses a rotational angle of the sensing object by using an output change characteristic of the magnetic sensing element with respect to a rotational angle of the at least one magnet (2); a yoke (4, 5, 8, 9) that concentrates the magnetic flux emitted from the at least one magnet (2) onto the at least one rotational angle sensor (3); a plate (12) that includes at least one yoke holding portion (51, 52), which securely holds the yoke (4, 5, 8, 9); a housing (14), to which the plate (12) is installed, wherein the housing (14) is made of an electrically conductive material; and a cover (11) that is made of a magnetic material and includes at least one mounting portion (55), which is fixed to the housing (14), wherein the cover (11) forms a sensor receiving space (17) between the cover (11) and the plate (12) to receive the at least one rotational angle sensor (3) and the yoke (4, 5). 2. The rotational angle sensing device according to claim 1, wherein the plate (12) is made of a non-magnetic material. 3. The rotational angle sensing device according to claim 1 or 2, wherein: each of the at least one rotational angle sensor (3) includes a lead terminal group (3a) that extends out of the magnetic sensing element thereof; and thermosetting resin (10) is filled in an interior of the cover (11) to seal the lead terminal group (3a) of each of the at least one rotational angle sensor (3). 4. The rotational angle sensing device according to claim 3, wherein the cover (11) includes at least one anchoring portion (43, 44), to which the thermosetting resin (10) is anchored. 5. The rotational angle sensing device according to claim 3 or 4, wherein: the plate (12) includes a connector (13) that includes a connector terminal group (13a), which corresponds to the lead terminal group (3a) of each rotational angle sensor (3); and a plurality of conductors, which electrically connect between the lead terminal group (3a) of each rotational angle sensor (3) and the connector terminal group (13a) of the connector (13), is sealed in the thermosetting resin (10). 6. The rotational angle sensing device according to any one of claims 1 to 5, wherein a volume of the electrically conductive material of the housing (14) is larger than a volume of the magnetic material of the cover (11). 7. The rotational angle sensing device according to any one of claims 1 to 6, wherein: the cover (11) has a relatively thin wall; and the rotatable shaft (1) of the sensing object is rotatably supported by the housing (14). 8. The rotational angle sensing device according to any one of claims 1 to 7, wherein: the housing (14) is made of a metal material, which includes aluminum as its main component; the cover (11) is made of a metal material, wrrich Includes iron as its main component; and the cover (11) forms a surface-to-surface contact with the housing (14) and is fixed to the housing (14). |
|---|
| Patent Number | 251776 | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Indian Patent Application Number | 1781/CHE/2007 | |||||||||||||||||||||
| PG Journal Number | 14/2012 | |||||||||||||||||||||
| Publication Date | 06-Apr-2012 | |||||||||||||||||||||
| Grant Date | 30-Mar-2012 | |||||||||||||||||||||
| Date of Filing | 10-Aug-2007 | |||||||||||||||||||||
| Name of Patentee | DENSO CORPORATION | |||||||||||||||||||||
| Applicant Address | 1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PREF. 448-8661, JAPAN | |||||||||||||||||||||
Inventors:
|
||||||||||||||||||||||
| PCT International Classification Number | G01B 5/14 | |||||||||||||||||||||
| PCT International Application Number | N/A | |||||||||||||||||||||
| PCT International Filing date | ||||||||||||||||||||||
PCT Conventions:
|
||||||||||||||||||||||