Title of Invention

"AN IMPROVED MINIATURE MOTOR APPARATUS"

Abstract

A miniature motor comprising a case having a permanent magnet fixedly fitted to the inner circumferential surface thereof, a rotor having an armature iron core and a commutator, and a case cap having power feeding brushes and input terminals, in which a connecting member made of an electrically conductive material is provided on the inner end face of the case cap; the connecting member is connected to one of the input terminals directly or via another electrically conductive member; the connecting member and the other input terminal are connected to the brushes via pigtail wires; the arm portions of torsion coil springs are brought in contact with the outer ends of the brushes to that the brushes are forced onto the commutator; and the pigtail wires are entwined around the arm portions.

Full Text

This invention relates generally to an improved miniature motor apparatus used for household electrical appliances, precision instruments, power tools and automotive electrical components, for example, and more specifically to a miniature motor in which interference between the pigtail wires constituting the power feeding device and other component members can be prevented, and the power feeding brushes can be stably brought into sliding contact with the commutator. A co-pending application No. 910/DEL/95 relates to a motor, wherein the novelty resides in the output shaft of a rotor of the said motor. Fig. 1 is a partially longitudinal sectional front view of a conventional type of miniature motor. In Fig. 1, numeral 1 refers to a case made of a metallic material, such as mild steel, formed into a bottomed hollow tubular shape and having a permanent magnet 2 of an arc segment shape, for example, fixedly fitted to the inner circumferential surface thereof. In the case. 1 fitted is the rotor 5 having the armature iron 3 and the commutator 4. Numeral 6 refers to a case cap made of a resin material and fitted to an open end of the case 1. Numeral 45 refers to a brush formed into a rectangular sectional shape, for example, and slidably fitted into a brush holder 15 formed into a hollow square tubular shape and provided on the inner end face of the case cap 6 so as to make sliding contact with the commutator 4. Numeral 46 refers to a varistor formed into a ring shape, for example, fixedly fitted concentrically between the armature iron core 3 and the commutator 4 and electrically connected between both to suppress electrical noise. Numeral 13 refers to a torsion coil spring to force the brush 45 onto the commutator 4. Numeral 8 denotes an input terminal fixedly fitted to the case cap 6 in such a manner as to pass through the case cap 6, and electrically connected on the inner end face of the case cap 6 to the brush 45 via the pigtail wire 14. Numerals 9 and 10 denote bearings each provided on the bottom of the case 1 and the case cap 6 to rotatably support the shafts 11 and 12 constituting the rotor 5. With the aforementioned construction, as electric current is fed from the input terminals 8 to a winding wound on the armature iron core 3 via the pigtail wires 14, the brushes 45 and the commutator 4 constituting the rotor 5, rotating force is imparted to the rotor 5 disposed in the magnetic field formed by the permanent magnet 2 fixedly fitted to the inner circumferential surface of the case 1, causing the rotor 5 to rotate to drive external equipment (not shown) via the shaft 11 on the output side. As a means for connecting the input terminal 8 to the pigtail wire 14 in a miniature motor of the aforementioned construction, there can be a means to directly connect by soldering an end of the pigtail wire 14, the other end of which is connected to the brushes 45, to the input terminal 8. There can also be a means to connect the input terminal 8 via a coupler terminal fixedly fitted to one end of the pigtail wire 14; the coupler terminal being connected to the input terminal 8 (see Japanese Published Unexamined Utility Model Publication No. Hei-3(1991)-7655, for example.) In addition, there can be a means to retain the middle part of the pigtail wire 14 with a pigtail-wire holder to prevent the brush 45 from getting out of the brush holder 15 when connecting the pigtail wire 14 to the input terminal 8 (see Japanese Published Unexamined Utility Model Publication No. Hei-5(1993)-7656, for example.) With the conventional construction, if the length of the pigtail wire 14 is too long, the middle part of the pigtail wire 14 could slack and curl up toward the armature iron core 3, interfering with the armature iron core 3 or the varistor 46 provided between the armature iron core 3 and the commutator 4. This could cause increased mechanical noise, or failure of the rotor 5 in extreme cases. If the pigtail wire 14 is too short, the sliding of the brush 45 in the brush holder 15 could be hampered, leading to unstable contact between the brush 45 and the commutator 4. Fig. 2 is an enlarged diagram of assistance in explaining the vicinity of the brush holder 15. Like parts are indicated by like numerals in Fig. 1. In Fig. 2, the brush 45 is preloaded by the torsion coil spring 13 so that the brush 45 is forced toward the left direction to make sliding contact with the commutator 4. If the pigtail wire 14 is too short, the connecting part 14a at which the pigtail wire 14 is connected to the brush 45 could move along a circular arc curve Cx in the figure around the connecting part 14b at which the pigtail wire 14 is connected to the input terminal 8. Thus, the sliding of the brush 45 in the brush holder 15 could be hampered, or the service life of the brush 45 could be shortened. When the pigtail wire 14 is connected to the input terminal 8 by soldering, solder could flow to the pigtail wire 14, forming a solidified part 14c in the vicinity of the connecting part 14b. As a result, the connecting part 14a at which the pigtail wire 14 is connected to the brush 45 could move along a circular arc curve C2 of a smaller radius, further aggravating the above problems. In recent years, there has been an increasing demand for less mechanical and electrical noise in miniature motors to such an extent that miniature motors are now required to have an electrical noise suppression element, such as a varistor 46, as shown in Fig. 1. Furthermore, with the increasing demand for smaller motors in recent years, the distance between the rotor 5 and a power feeding device having brushes 45 has become increasingly smaller. To cope with such a trend, there has also been a need for a means to prevent the pigtail wires 14 from curling up, and a means to ensure stable sliding of the brushes 45. Consequently, connecting or retaining the pigtail wires 14 using the methods disclosed in the aforementioned Japanese Utility Model Publications would be almost impossible in an extremely small internal space, leading to an increase in the number of parts. Moreover, it would even hamper motor downsizing. SUMMARY OF THE INVENTION This invention is intended to overcome the problems inherent in the prior art as described above. It is an object of this invention to provide a miniature motor which can solve the problems inherent in the prior art described above, prevent interference between the pigtail wire constituting the power feeding device, and ensure the smooth sliding of power-feeding brushes. To achieve these objectives, according to this invention, there is provided a miniature motor comprising a case made of a metallic material, for example, formed into a bottomed hollow tubular shape and having a permanent magnet fixedly fitted to the inner circumferential surface, a rotor having an armature iron core facing the permanent magnet and a commutator, and a case cap fitted to an open end of the case; a pair of brush holders for holding brushes that make sliding contact with the commutator and a pair of input terminals electrically connected to the brushes via pigtail wires or via pigtail wires and other electrically conductive members are provided on the case cap; and the rotor is rotatably supported by bearings each provided on the bottom of the case and the case cap, in which a connecting member made of an electrically conductive material is provided on the inner end. face of the case cap; the connecting member is connected to one of the input terminals directly or via another electrically conductive member; the connecting member and the other input terminal are connected to the brushes via pigtail wires; the brushes are pre loaded by the arm portions of torsion coil springs that are brought in contact with the outer ends of the brushes so that the brushes are forced onto the commutator; and the pigtail wire are entwined around the arm portions. Accordingly, the present invention relates to an improved miniature motor apparatus comprising: a case made of a metallic material, formed into a bottomed hollow tubular shape, and having permanent magnets fitted to the inner circumferential surface thereof, a rotor having an armature iron core and a commutator, and a case cap fitted to an open end of said case ; a pair of brush holders for holding brushes that make sliding contact with said commutator and a pair of input terminals electrically connected to said brushes via pigtail wires or another electrically conductive member being provided on said case cap; said rotor being rotatably supported by bearings each provided on the bottom of said case and said case cap, characterized in that a pair of connecting members made of an electrically conductive material are provided on the inner end face of said case cap in a mutually insulated state and in a point symmetrical with respect to the motor axis; one connecting member (16) being connected to one input terminal (8) via a positive temperature coefficient resistor (49) and the other connecting member (16) being connected to the other input terminal (8) directly; the brushes (45),(45) are connected to the other connecting member (16) or the other input terminal (8) with pigtail wires (14),(14); said brushes (45),(45) are preloaded by bringing arm portions (13a), (13a) of torsion coil springs (13),(13) into contact with the outer ends of said brushes (45),(45) so that said brushes (45),(45) are forced onto said commutator (4); and said pigtail wires (14),(14) entwined around said arm portions (13a),(13a) of torsion coil springs (13). BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig. 1 is a partially longitudinal sectional front view of a conventional type of miniature motor. Fig. 2 is an enlarged diagram of assistance in explaining the vicinity of the brush holder 15 in Fig. 1. Fig. 3 is an inner end view of a case cap used in the first embodiment of this invention. Fig. 4 is a cross-sectional side view taken substantially along line A-A of Fig. 3. Fig. 5 is an outer end view of a case cap used in the first embodiment of this invention. Fig. 6A and 6B are an enlarged plan view and enlarged end view of the brush holder 15 in Figs. 3 through 5. Fig. 7A is an enlarged plan view of the connecting member 16 in Figs. 3 through 5. Figs. 7B and 7C are views taken in the directions of arrows B and C of Fig. 7A, respectively. Figs. 8A and 8B are an enlarged plan view and enlarged side view of the input terminal 8 in Figs. 3 through 5. Fig. 9 through 11 are inner end views of the case cap 6 in the second through fourth embodiments of this invention. DETAILED DESCRIPTION OF THE EMBODIMENTS Figs. 3 and 5 are an inner end view and outer end view of a case cap in the first embodiment of this invention, Fig. 4 is a cross-sectional side view taken substantially along line A-A of Fig. 3. Like parts are indicated by like numerals used in Fig. 1. In Figs. 3 through 5, a brush holder 15 is made of an electrically conductive material, formed into a substantially U shape in end face profile, as will be described later, and disposed on the mounting portion 6a slightly protruding from the inner end face of the case cap 6 and fixedly fitted to the case cap 6 via the fixing pieces 20. The brush 45 is held in the brush holder 15 in such a manner as to be slidable in a groove 6b provided on the surface of the mounting portion 6a. The brush 45 is preloaded by the arm portion of a torsion coil spring 13 brought in contact with the rear end of the brush 45 so that the brush 45 is forced toward the center of the motor. Numeral 49 refers to a positive temperature coefficient resistor, and 50 to a capacitor. Next, numeral 16 refers to a connecting member made of an electrically conductive material, formed into a substantially U shape in planar profile, as will be described later, and fixedly fitted to the inner end face of the case cap 6 via a fixing piece 21 in such a state as to insulate from the brush holder 15. A pair of terminals 17 and 17 for connecting the capacitor 50 and a terminal 18 for connecting the pigtail wire 14 are integrally provided on the connecting member 16 in such a manner as to protrude from the inner end face of the case cap 6. On the input terminal 8 provided are a stopper (not shown), a lanced and raised piece 24 and a lanced and raised piece 52, as will be described later. The input terminal 8 is fixedly fitted to the case cap 6 in such a manner as to pass through the case cap 6, with one end thereof protruding into a connecting member 41. The input terminals 8 and 8 are connected to an open end 16a of the connecting member 16 via the positive temperature coefficient resistor 49, and directly to an open end 16b, respectively. Next, the capacitor 50 is connected across the terminals 17 and 17 of the connecting members 16 and 16 via a lead wire 60. With the aforementioned construction, power can be fed from the input terminal 8 to the connecting member directly or via the positive temperature coefficient resistor 49, and then to a pair of brushes 45 via the pigtail wires 14. The capacitor 50 is connected in parallel across the brushes 45 and 45. Thus, the miniature motor can be prevented from overheating and generating electrical noise. Figs. 6A and 6B are an enlarged plan view and enlarged end view of the brush holder 15 shown in Figs. 3 through 5. In Figs. 6A and 6B, the brush holder 15 has a notch 15a on part of the upper end surface thereof to allow the pigtail wire 14 shown in Figs. 3 and 4 to move therein, and is formed into a substantially U shape in cross section. The brush holder 15 has the fixing pieces 20 extending downward. The brush holder 15 formed in the aforementioned manner is fixedly fitted to the case cap 6 by inserting the fixing pieces 20 through the mounting holes 25 provided on the case cap 6 and bending the tips of the fixing pieces 20, as shown in Fig. 5. Fig. 7A is an enlarged diagram of assistance in explaining the connecting member 16 shown in Figs. 3 through 5. Figs. 7B and 7C are diagrams taken in the direction of arrows B and C of Fig. 7A. In Figs. 7A through 7C, the connecting member 16 is formed in substantially U shape in planar profile, with the open end 16a and 16b slightly extending outward. The length of the open end 16a is made slightly smaller than the other open end 16b to provide the positive temperature coefficient resistor 49, as shown in Figs. 3 and 4. A pair of terminals 17 are integrally provided on the edges of the open ends 16a and 16b by bending part of the connecting member 16 upward. Notches 17a are provided on the terminals 17. A terminal 18 is integrally formed on the other edge of the open end 16b by bending part of the connecting member 16 upward. A punched and bent piece 18a is provided on the terminal 18. Numeral 21 refers to fixing pieces integrally formed on the middle of the substantially U shaped part of the connecting member 16, and on the ends of the open ends 16a and 16b by bending part of the connecting member 16. A wide part 21a whose width is made larger than the width of the mounting hole provided on the case cap 6 shown in Figs. 3 through 5 is provided on the side part of the fixing piece 21 on the middle of the substantially U shaped part of the connecting member 16. Numeral 22 refers to projections provided on the outer surfaces of the fixing pieces 21 provided on the open ends 16a and 16b. Pushing pieces 21b are formed by bending part of the lower part of the fixing piece 21 provided on the open end 16a. Next, Figs. 8A and 8B are an enlarged plan view and enlarged side view of the input terminal 8 shown in Figs. 3 through 5. In Figs. 8A and 8B, numeral 23 refers to a stopper that is an upper part (on the side of the inner end face of the case cap 6) of the input terminal 8 whose width is made larger than the middle part. The stopper 23 is used for fixedly fitting the input terminal 8 to the case cap 6 by passing the stopper 23 through the case cap 6, as shown in Fig. 4, holding it in place, and bending the lanced and raised piece 52 right angles. Numeral 24 refers to a lanced and raised piece provided in the vicinity of the upper end of the input terminal 8. Numeral 26 refers to a slit for connecting a capacitor and other functional elements. By installing the input terminal 8, the connecting member 16 and the brush holder 15 formed in the aforementioned manner on the case cap 6 shown in Figs. 3 through 5, and inserting the positive temperature coefficient resistor 49, electrical connection between these members can be maintained. That is, the input terminal 8 and the connecting member 16 are brought into contact with the lanced and raised piece 24 and the projection 22 of the fixing piece 21. When the positive temperature coefficient resistor 49 is inserted in between the input terminal 8 and the connecting member 16, the lanced and raised piece 24 and the projection 22 of the fixing piece 21 are brought into contact with the surface of the positive temperature coefficient resistor 49. In such a state, even if an external force is exerted to pull out the positive temperature coefficient resistor 49 in Fig. 4, the lanced and raised piece 24 provided on the input terminal 8 cuts into the surface of the positive temperature coefficient resistor 49 to enhance the retaining effect. Moreover, the pushing pieces 21b provided on the fixing piece 21 of the connecting member 16 come in contact with the surface of the positive, temperature coefficient resistor 49, increasing stability in connection with the positive temperature coefficient resistor 49. Next, when the end of the pigtail wire 14 is connected to the terminal 18 of the connecting member 16 by soldering, the pigtail wire 14 is entwined around an arm portion 13a of the torsion coil, spring 13, as shown in Figs. 3 and 4. That is, in Fig. 3, the pigtail wire 14 is drawn from the upper end of the brush 45 and entwined around the arm portion 13a, leading to the terminal 18. The torsion coil spring 13 and the terminal 18 should preferably be provided on the same side with respect to the brush holder 15 on the inner end face of the case cap 6 and in proximity with each other. With the aforementioned construction, the pigtail wire 14 can be wired with enough slack, and yet the unwanted excessive slackening of wire can be prevented. Even when the brush 45 moves in the brush holder 15, the pigtail wire 14 is never ten-sioned abnormally because both the pigtail wire 14 and the arm portion 13a move or swing together. Thus, the brush 45 can move smoothly in the brush holder 15. Fig. 9 is an inner end view of the case cap 6 shown in the second embodiment of this invention. Like parts are indicated by like numerals used in Fig. 3. The embodiment in Fig. 9 is the same as that in the first embodiment except that one of the connecting member 16 is omitted, and that one of the pigtail wire 14 is connected directly to one of the input terminal 8. The brush 45 can therefore be moved smoothly in the brush holder 15 while preventing the unwanted slackening and abnormal tensioning of the pigtail wire 14. Figs. 10 and 11 are inner end views of the case cap 6 shown in the third and fourth embodiments of this invention. Like parts are indicated by like numerals used in Fig. 9. By disposing the input terminals 8 in an axially symmetrical fashion, as shown in Figs. 10 and 11, both the pigtail wires 14 can be directly connected to the input terminals 8 without using the connecting member 16 as shown in Figs. 3 and 9. In this invention, the pigtail wire 14 may be connected to a terminal portion provided on the brush holder 15, and a choke coil may be connected across the terminal portion and the terminal 18 of the connecting member 16. Moreover, the input terminal 8 may be connected directly to the connecting member 16 by omitting the positive temperature coefficient resistor 49. In short, any of various type of electrical controlling elements such as capacitor, choke coil, positive temperature coefficient resistor may be selectively installed in accordance with specifications required of a miniature motor. This invention having the aforementioned construction and operation can achieve the following effects: {1) A required minimum length of the pigtail wires for feeding power to the brushes can be used without causing unwanted slackening, and therefore interference with other component members can be prevented. (2) Since there is no fear of imparting to the brushes abnormal tension due to the pigtail wires or external force, the brushes can be moved smoothly, and the brushes can make sliding contact with the commutator in a stable state. This lead to stabilized motor performance and extended motor life. (3) Further miniaturization of motors is possible because interference between the rotor and the power feeding device can be prevented even if the distance between both is reduced. (4) Since the profile of the connecting member projected on the end face of the case cap is made point-symmetrical with respect to the motor axis, the number of component parts can be reduced, thus parts control and manufacturing costs can also be reduced. WE CALIM: 1. An improved miniature motor apparatus comprising: a case (1) made of a metallic material, formed into a bottomed hollow tubular shape, and having permanent magnets (2, 2) fixedly fitted to the inner circumferential surface thereof, a rotor (5) having an armature iron core (3) and a commutator (4), and a case cap (6) fitted to an open end of said case (1); a pair of brush holders (15, 15) for holding brushes (45, 45) that make sliding contact with said commutator (4) and a pair of input terminals (8, 8) electrically connected to said brushes (45, 45) via pigtail wires (14, 14) or another electrically conductive member being provided on said case cap (6); said rotor (5) being rotatably supported by bearings each provided on the bottom of said case (1) and said case cap (6), characterized in that a pair of connecting members (16, 16) made of an electrically conductive material are provided on the inner end face of said case cap (6) in a mutually insulated state and in a point symmetrical with respect to the motor axis; one connecting member (16) being connected to one input terminal (8) via a positive temperature coefficient resistor (49) and the other connecting member (16) being connected to the other input terminal (8) directly; the brushes (45, 45) are connected to the other connecting member (16) or the other input terminal (8) with pigtail wires (14, 14); said brushes (45, 45) are preloaded by bringing arm portions (13a, 13a) of torsion coil springs (13, 13) into contact with the outer ends of said brushes (45, 45) so that said brushes (45, 45) are forced onto said commutator (4); and said pigtail wires (14, 14) entwined around said arm portions (13a, 13a) of torsion coil springs (13). 2. An improved miniature motor apparatus as claimed in claim 1, wherein said connecting members (16, 16) are connected by a capacitor (50). 3. An improved miniature motor apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Documents:

909-del-1995-abstract.pdf

909-del-1995-claims.pdf

909-del-1995-correspondence-others.pdf

909-del-1995-correspondence-po.pdf

909-del-1995-description (complete).pdf

909-del-1995-drawings.pdf

909-del-1995-form-1.pdf

909-del-1995-form-13.pdf

909-del-1995-form-2.pdf

909-del-1995-form-3.pdf

909-del-1995-form-4.pdf

909-del-1995-form-6.pdf

909-del-1995-form-9.pdf

909-del-1995-gpa.pdf

909-del-1995-petition-138.pdf

909-del-1995-petition-others.pdf