Title of Invention	TENSIONER
Abstract	The amplitude ofa tensioner's second shaft member, to which an external input load is applied, is controlled precisely. Accommodated in a case 2 are: (1) a first shaft member 3 and a second shaft member 4, which are engaged by screw portions 8, 9, and (2) a torsion spring 5, which rotates and presses the fIrst shaft member 3 in one direction. The momentum of the torsion spring 5 is converted into the driving force of the second shaft member 4, while rotation of the second shaft member 4 is controlled. An elastic member 20 that generates resistance torque against an external input load applied to the second shaft member 4 is arranged between the first shaft member 3 and the second shaft member 4, so that the amplitude of the second shaft member 4 can be controlled precisely.

Title of Invention

TENSIONER

Abstract

The amplitude ofa tensioner's second shaft member, to which an external input load is applied, is controlled precisely. Accommodated in a case 2 are: (1) a first shaft member 3 and a second shaft member 4, which are engaged by screw portions 8, 9, and (2) a torsion spring 5, which rotates and presses the fIrst shaft member 3 in one direction. The momentum of the torsion spring 5 is converted into the driving force of the second shaft member 4, while rotation of the second shaft member 4 is controlled. An elastic member 20 that generates resistance torque against an external input load applied to the second shaft member 4 is arranged between the first shaft member 3 and the second shaft member 4, so that the amplitude of the second shaft member 4 can be controlled precisely.

Full Text	Field of the Invention The present invention relates to a tensioner for maintaining constant tension of a continuous timing belt or chain. Description of the Related Art A tensioner works to maintain constant tension of a timing chain or a timing belt that is used, for example, for an engine of an automobile, by pushing the timing chain or timing belt with a predetermined force if the timing chain or timing belt becomes loose or slack. Figure 13 shows the condition when a tensioner 100 is actually installed in the main body of an engine 200 of an automobile. A pair of cam sprockets 210,210 and a crank sprocket 220 are arranged in the main body of the engine 200, and a non-ended timing chain 230 encircles the pair of the cam sprockets 210,210 and the crank sprocket 220. A chain guide 240 is installed in a free-moving condition on the moving path of the timing chain 230, and the timing chain 230 slides on (the surface of) the chain guide 240. An installing part 250 is formed on the main body of the engine 200, and the tensioner 100 is fixed onto the installing part 250 with bolts 270 that penetrate through installing holes 260 on the installing part 250, Also, the main body of the engine 200 is supplied with lubricating oil (not shown). Figures 14 and 15 show a conventional tensioner 100. A rotating shaft 120 and a drive shaft 130 are integrally arranged in a case 110. The case 110 is comprised of a main body 111, which extends in the axial direction of the case so that the shafts 120 and 130 can be inserted therein, and flange parts 112 that extend from the main body 111 in the direction perpendicular to the axial direction. The flange parts 112 serve to attach the tensioner 110 onto the main body of the engine 200, and therefore installing holes 113, through which bolts to be screwed into the main body of the engine 200 penetrate, are formed to the flange parts 112. The main body 111 serves to accommodate parts that will be mentioned later, and therefore accommodation holes 114 that have the same inside diameters as the outside diameters of the parts to be accommodated therein are formed in the main body 111 in the axial direction. In order to connect the rotating shaft 120 to the drive shaft 130, a male screw portion 121 is formed on the outer surface of the rotating shaft 120 while a female screw portion 131 is formed on the inner surface of the drive shaft 130, and said connection is achieved by engaging said screw portions 121 and 131 with each other. A swivel plate 140 is arranged inside the case 110 that faces the base-end side of the rotating shaft 120 so as to be positioned inside the accommodation hole 114 and so as to support the base end of the rotating shaft 120. When the drive shaft 130 is connected with the rotating shaft 120, the drive shaft 130 is screwed and engaged with the front-side part of the rotating shaft 120 to approximately one-half of the overall length of said rotating shaft 120, and a torsion spring 150 is arranged on the back side of the rotating shaft 120 (for approximately one-half of the overall length of said rotating shaft 120) with which the drive shaft 130 is not screwed/engaged* A hooking portion 151 on one end of the torsion spring 150 is inserted into and fastened into a slit 123 that is formed at the base end of the rotating shaft 120, and another hooking portion 152 on the other end is fastened to the case 110. Accordingly, when assembled under the condition that the torsion spring 150 is twisted so as to have a specified torque, the rotating shaft 120 rotates due to the momentum of the torsion spring 150. At the front end of the case 110, a bearing 160 is fixed with a snap ring 170, and the drive shaft 130 penetrates through a slide hole 161 of the bearing 160, Both the cross-sectional shape of the inner surface of the slide hole 161 of the bearing 160 and the cross-sectional shape of the outer surface of the drive shaft 130 are approximately ovals, or parallel cuts, or other non-cirdular shapes, thereby restraining rotation of the drive shaft 130. The bearing 160 is formed into a flat shape of a specified thickness, and a plurality of fixing pieces 162 are formed on the outer peripheral side of the bearing 160. When the fixing pieces 162 are engaged with notch grooves 115 that are formed at the front end of the case 110, rotation of the entire bearing 160 is prevented. When rotation of the bearing 160 against the case 110 is prevented, the drive shaft 130 that penetrates through the bearing 160 is also prevented from rotating against the case 110 via the bearing 160. Thus, the drive shaft 130 moves toward or away from the case 110, under a rotation-restricted condition. A cap 180 is attached onto the tip of the drive shaft 130, and said cap 180 is brought into contact with a chain guide 240 that is inside said main body of the engine 200. Furthermore, a spacer 190 is arranged inside the case 110. The spacer 190 is formed into a tube-like shape that extends in the axial direction (driving direction) so as to surround the rotating shaft 120 and the drive shaft 130, so that the shafts 120 and 130, which are engaged with each other, are prevented from coming off from the tip end of the case 110. In order to prevent the shafts 120 and 130 from coming off, the rotating shaft 120 is formed so as to have jaws that can abut on the spacer 190. In the tensioner 100 of the above-mentioned structure, the rotating shaft 120 rotates due to a force that the torsion spring 150 gives to the rotating shaft 120, thereby giving momentum to the rotating shaft 120, and this rotation force is converted into the driving force of the drive shaft 130, so that the drive shaft 130 moves forwards. Thereby, the drive shaft 130 presses the timing chain 230 via both the cap 180 and die chain guide 240, thereby giving tension to the timing chain 230. In order to achieve stable operation of such a tensioner 100 by restraining the pressing volume (amplitude) of the drive shaft 130 against an external input load from the chain guide 240, the chain guide 240 needs to be held strongly. For this reason, the following measures are taken: (1) The spring torque of the torsion spring 150 is made large; (2) The lead angles of both the male screw portion 121 and the female screw portion 131, both of which serve to screw together the rotating shaft 120 and the drive shaft 130, are made small (for example, 12° is reduced to 9°); and (3) The diameter of the end face of the rotating shaft 120 is made large, so that the area of contact between the rotating shaft 120 and the swivel plate 140 (the case 110) is made large. However, when the above-mentioned measures are taken, the drive shaft 130 develops a strong tendency to drive (move forward). When the drive shaft 130 drives more than necessary, friction between the chain guide 240 and the chain 230 increases, which becomes an undesirable factor that creates a big loss of engine output. Japanese Unexamined Published Patent Application No. 2001 -21012>discloses a structure in which a friction plate is arranged on a case, a jaw-tike friction face of a large contacting area is formed on a portion (which is opposed to the friction plate) of a rotating shaft, and the friction face is held by an auxiliary spring so that the friction face cannot contact the friction plate. With this structure, when the externai input load from a chain guide is small, the friction face is not brought into contact with the friction plate, but when the external input load becomes more than a specified value, the friction face is brought into contact with the friction plate, so that a friction force can be generated. Thus, there is no need to take the above-mentioned measures (1) through (3). The loss of the engine's output can be reduced, and the amplitude of the drive shaft against a large external input load also can be controlled. The amplitude of the drive shaft can also be controlled by the structure of Japanese Unexamined Published Patent Application No. 2001-21012, But with this structure, amplitude restriction might need to be emphasized for certain kinds of engines. For the purpose of satisfying such a requirement, one object of the present invention is to provide a tensioner that can precisely control amplitude against an external input load. Summary of the Invention For the purpose of achieving the above-mentioned object, a tensioner set forth in Claim 1 is characterized such that (1) a first shaft member and a second shaft member, which are engaged by screw portions, and a torsion spring, which gives rotating momentum to the first shaft member in one direction, are accommodated in a case, and that (2) the rotating momentum of the torsion spring is converted into the driving force of the second shaft member while rotation of the second shaft member is controlled, and which is characterized such that an elastic member that generates resistance torque against an external input load that is applied to the second shaft member is arranged between said first shaft member and said second shaft member. According to the invention set forth in Claim 1, when the external input load is applied onto the second shaft member, a load is applied onto the elastic member that is arranged between the first shaft member and the second shaft member. Thereby, the elastic member generates resistance torque against the external input load, so that the amplitude of the second shaft member can be made small. According to the invention set forth in Claim 1, because an elastic member is arranged between the first shaft member and the second shaft member, the elastic member generates resistance torque whenever an external input load is applied. Accordingly, regardless of the amount of the external input load, resistance torque is generated and said torque controls the amplitude of the second shaft member, so that the amplitude can be controlled precisely. Also, there is no need to increase the driving force of the second shaft member by increasing the spring torque of the torsion spring or by making the lead angle of the screw portions small Therefore, friction between the chain guide and the chain does not become large, and the loss of the engine's output can be made small. The invention of Claim 2 is a tensioner as set forth in Claim 1, but characterized such that said elastic member is arranged between the first shaft member and the second shaft member while said elastic member is compressed by both the first and second shaft members, and the elastic member is a coil spring that generates friction torque between the first shaft member and itself through compression caused by an external input load. According to the invention described in Claim 2, the elastic member is a coil spring. The coil spring is compressed by both the first shaft member and the second shaft member, and also is compressed by the compression force that results when an external input load is applied onto the second shaft member. Due to this compression, friction torque is generated between the first shaft member and the coil spring, or the already generated friction torque increases, and therefore the rotation of the first shaft member is controlled. That is to say, when an external input load is applied, the second shaft member is pushed inside the case, so that the first shaft member rotates in the direction that is opposed to the rotation and pressing direction of the torsion spring, while a braking force due to the friction force of the compression spring acts against the reverse-direction rotation of the first shaft member (i.e., the direction that is opposite to the rotating momentum resulting from the torsion spring). As a result, the pressing volume (amplitude) of the second shaft member is controlled. According to the invention set forth in Claim 2, because the coil spring that is compressed by an external input load is also arranged between the first shaft member and the second shaft member, whenever an external input load is applied, the coil spring generates friction torque to restrain the rotation of the first shaft member, so that the amplitude of the second shaft member can be controlled precisely. The invention of Claim 3 is a tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is twisted by the external input load that is applied onto the second shaft member to generate a reaction force torque in the same direction as that of the rotation and pressing direction of said torsion spring. According to the invention described in Claim 3, when an external input load is applied onto the second shaft member, the coil spring is twisted and the reaction force torque is generated or increased, and thereby the pressing force onto the second shaft member by the external input load is reduced, so that the pressing volume (amplitude) of the second shaft member can be controlled. Also, according to the invention set forth in Claim 3, because the coil spring that is twisted by the external input load to generate the reaction force torque is arranged between the first shaft member and the second shaft member, the amplitude of the second shaft member can be controlled precisely according to the amount of external input load that is applied. The invention of Claim 4 is a tensioner as set forth in Claim 2, but characterized such that a swivel plate for supporting said coil spring is arranged on either said first shaft member or said second shaft member. The coil spring is supported by the swivel plate that is arranged on the shaft member, so that the connection between the coil spring and the shaft member is stabilized. As a result, even when the first shaft member rotates forward and backward repeatedly, the coil spring can easily cope with such rotation, thereby securing stable operation. The invention of Claim 5 is a tensioner as set forth in any one of Claims 2-A, but characterized such that the diameter of one end of the coil spring, which is on the side of the first shaft member, gradually decreases in the direction that is opposite to the driving direction of the second shaft member According to the invention described in Claim 5, because the diameter of the coil spring is small at the end on the first-shaft-member side, the spring slides on the first shaft member with large friction. Thus, friction torque between the first shaft member and the coil spring can be made large, so that the amplitude of the second shaft member can be controlled. The invention of Claim 6 is a tensioner as set forth in Claims 2-5, but characterized such that the coil-winding direction of said coil spring is opposite to the threading direction of the screw portion of the first shaft member. Because the coil-winding direction is opposite to the threading direction of the first shaft member, when the second shaft member is pushed in by an external input load and the first shaft member rotates, the coil spring is twisted in such a way that the coil diameter is reduced. Thereby, the coil spring does not expand its diameter or interfere with peripheral parts, such as the case, thereby facilitating smooth operation. The invention of Claim 7 is a tensioner as set forth in any one of Claims 2-6, but characterized such that a clutch part, which rotates along with said second shaft member's forward and backward movement, is formed on the second shaft member, one end of said coil spring is fastened to said clutch part, and the other end of said coil spring is fastened to the first shaft member. According to the invention described in Claim 7, because the clutch part formed on the second shaft member twists the coil spring, a reaction force torque is generated on the coil spring. Thereby, the amplitude of the second shaft member can be controlled. The invention of Claim 8 is a tensioner as set forth in Claim 1, but characterized such that said elastic member is a plate spring, a molded rubber element, or a molded resin element that (a) is arranged between both the first shaft member and the second shaft member under the condition that said elastic member contacts both the first shaft member and the second shaft member, and (b) is compressed by the external input load, so that friction torque is generated between the first shaft member and said elastic member. According to the invention described in Claim 8, a plate spring, a molded rubber element, or a molded resin element is used as the elastic member. The plate spring, the molded rubber element, or the molded resin element is deformed when an external input load is applied onto the second shaft member, to generate friction torque between the first shaft member and the elastic member. As a result, rotation of the first shaft member is controlled, so that the amplitude of the second shaft member also can be controlled. According to the invention described in Claim 8, because the plate spring, the molded i rubber element, or the molded resin element is arranged between the first shaft member and the second shaft member, whenever an external input load is applied, friction torque is generated, thereby enabling the amplitude of the second shaft member to be controlled precisely. The invention of Claim 9 is a tensioner as set forth in any one of Claims 1-8, but characterized such that a buffer plate is inserted between said elastic member and the first shaft member. The buffer plate that is inserted between the elastic member and the first shaft member prevents the elastic member from digging into the first shaft member. Therefore, the elastic member can be operated smoothly, and abrasion of both the elastic member and the first shaft member also can be controlled, thereby improving Brief Description of the Drawings Figure 1 is a plan view of a tensioner in a first embodiment of the present invention. Figure 2 is a cross-sectional view along the line C-C of Figure 1. Figure 3 is a perspective view illustrating the action of the coil spring, where (a) shows a conventional tensioner and (b) shows a tensioner in the first embodiment of the present invention. Figure 4 is a cross-sectional view showing a tensioner in a second embodiment of the present invention. Figure 5 is a partial cross-sectional view of variations of a second embodiment of the present invention. Figure 6 is a partial cross-sectional view showing other variations of the second embodiment. Figure 7 is a cross-sectional view of a tensioner in a third embodiment. Figure 8 is a cross-sectional view of a tensioner in a fourth embodiment. Figure 9 is a cross-sectional view of a tensioner in a fifth embodiment. Figure 10 is a cross-sectional view of a tensioner in a sixth embodiment. Figure 11 is a cross-sectional view of a tensioner in a seventh embodiment. Figure 12 is a cross-sectional view of a tensioner in an eighth embodiment. Figure 13 is a cross-sectional view of a tensioner that is installed onto the main body of an engine. Figure 14 is a plan view of a conventional tensioner. Figure 15 is a cross-sectional view along the line Q-Q of Figure 14. Description of the Preferred Embodiments Some embodiments of the present invention will be described in detail. For each embodiment, identical numbers are used to refer to identical elements. (First Embodiment) Figures 1-3 show a tensioner AI in a first embodiment of the present invention. The tensioner is equipped with a case 2, a first shaft member 3, a second shaft member 4, a torsion spring 5, a bearing 6, and a spacer 7. The case 2 is formed into an approximate T-shape in its cross-section, and flange parts 2b extend from the tip of a shell part 2a in the direction that is approximately perpendicular to the driving direction. An accommodation hole 2c extends from the shell part 2a to the portion of the flange parts 2b in the axial direction (driving direction). The edge of the accommodation hole 2c is open, and an assembly of the first and second shaft members 3,4, the torsion spring 5, and the spacer 7 is accommodated in the accommodation hole 2c. The flange parts 2b of the case 2 are to be attached onto a piece of equipment, namely the main body of an engine, and installing holes 2d, through which penetrate bolts (not shown) that are screwed into the main body of the engine, are formed in the flange parts. When the flange parts are attached onto the main body of the engine, the tip faces of the flange parts 2b are brought into contact with the installing part 250 of the main body of the engine 200, in a way that is similar to the arrangement shown in Figure 13, The first shaft member 3 rotates when it is given momentum by the torsion spring 5 (which will be mentioned again later), and the second shaft member 4 is moved forward from the case 2 by the rotation of the first shaft member 3. A shaft part 3a (on the base-end side of the first shaft member 3) and a screw portion 3b (on the tip-end side of the first shaft member 3) are integrally formed in the axial direction, and a male screw 8 is formed on the outer periphery of the screw portion 3b on the tip-end side of the first shaft member 3. Also, the base-end part of the shaft part 3a is brought into contact with a swivel plate 19 that is arranged in the case 2, so that the rotation of the shaft part 3a is supported. A slit 3e, into which the tip end of a fastening jig (not shown) is inserted for rotating the first shaft member 3, is formed on the base-end face of the shaft part 3a. The slit 3e is connected to a jig hole 2e formed on the base-end face of the shell part 2a of the case 2. The tip end of the fastening jig is inserted in the slit 3e from the jig hole 2e and the first shaft member 3 is rotated via the slit 3e, so that a torsion spring 5 (which will be mentioned later) can be fastened. The second shaft member 4 is formed into a tube-like shape, and a female screw 9, which is engaged with the male screw 8 of the first shaft member 3, is formed on the inner face of the second shaft member 4. The shaft members 3 and 4 are inserted into the accommodation holes 2c of the case 2 while the female screw 9 and the male screw 8 are engaged with each other. A cap 10 is attached to the tip end of the second shaft member 4. The cap 10 is comprised of a head part 10a and a leg part 10b. A spring pin 11 is pressure-inserted into both the leg part 10b and the tip portion of the second shaft member 4, while the head part 10a covers the tip portion of the second shaft member 4, and the leg part 10b is engaged with the tip portion of the second shaft member 4, so that the cap 10 is prevented from coming off and is fixed onto the second shaft member 4. The torsion spring 5 is put around the shaft part 3a of the first shaft member 3. A hooking portion 5a on one end of the torsion spring 5 is inserted into and fastened with a hook groove 2f that is formed on the case 2, while a hooking portion 5b on the other end of the torsion spring 5 is inserted into and fastened with the slit 3e that is formed on the bottom part of the first shaft member 3. Accordingly, when the torsion spring 5 is wound and torque is applied, the first shaft member 3 can rotate. The bearing 6 is attached to the tip portion of the case 2 and is fixed with a cover ring 13, The bearing 6 has a slide hole 6a through which the second shaft member 4 penetrates* The cross-sectional shape of each of (1) the inner face of the slide hole 6a of the bearing 6 and (2) the outer face of the second shaft member 4 is formed into an approximately oval shape, a D-cut, a parallel cut, or other non-circular shape, thereby restraining rotation of the second shaft member 4. The bearing 6 is formed into a flat shape of a predetermined thickness, and a plurality of fixing pieces 6b are radially formed on the outer periphery of the bearing. The fixing pieces 6b are engaged with notch grooves 2g that are formed at the tip portion of the case 2, so that rotation of the entire bearing 6 is prevented. The rotation of the bearing 6 is prevented against the case 2, so as to control the rotation of the second shaft member 4, which penetrates through the bearing 6, against the case 2 via the bearing 6. The shaft member 3 is engaged with the second shaft member 4 by screw portions 8,9, and the rotating force of the first shaft member 3, which is rotated by the rotating momentum of the torsion spring 5, is transferred to the second shaft member 4. Because the rotation of the second shaft member 4 is controlled by the bearing 6, the second shaft member 4 moves toward and away from the case 2. The spacer 7 is formed into a tube-like shape, and the screwing portions of both the first shaft member 3 and the second shaft member 4 are inserted inside the spacer 7. A flange part 3c, whose diameter is large, is formed at a boundary portion between the shaft part 3a and the screw portion 3b of the first shaft member 3, and the base end of the spacer 7 abuts on the flange part 3c. The tip portion of the spacer 7 is faced to and abuts on the bearing 6, thereby preventing the first and second shaft members 3,4 from coming off from the case 2. In addition, in this embodiment, a coil spring 20 is arranged as an elastic member. The coil spring 20 is arranged between the first shaft member 3 and the second shaft member 4. In this embodiment, the coil spring 20 is arranged between the screw portion 3b of the first shaft member 3 and the base end of the second shaft member 4. A compression spring, whose hooking portions on both ends are free ends, is used as the coil spring 20. One end 20a of the compression spring (namely the coil spring 20) is brought into contact with the second shaft member 4, and the other end 20b is brought into contact with the first shaft member 3, In this case, the other end 20b is brought into contact with the flange part 3c of the first shaft member 3. Both ends 20a, 20b of the coil spring 20 are brought into contact with both the shaft members 3,4, while the coil spring 20 is assembled in a condition that the coil spring 20 is compressed to a certain extent. Accordingly, when an external input load for pushing in the second shaft member 4 is applied, a compression force acts directly on the coil spring 20, whose tip end 20a is in contact with the second shaft member 4, thereby compressing the coil spring 20. Because the other end 20b of the coil spring 20 contacts the first shaft member 3, friction torque is generated between the coil spring 20 and the first shaft member 3 (or the already-generated friction torque is further increased) by the compression of the coil spring 20. Thereby, a braking force acts on the first shaft member 3, so that rotation of the first shaft member 3 is controlled. Figure 3 compares the action of this embodiment with the action of a conventional tensioner as shown in Figures 14 and 15, and the reference numbers in this embodiment are given to the elements of the conventional tensioner. As shown in Figure 3, rotating momentum^composed of a torque T is applied to the first shaft member 3 from the torsion spring 5. When an external input load F is applied, the second shaft member 4 is pushed into the case 2, so that the first shaft member 3 rotates against the rotating momentum of the torsion spring 5 and in the direction shown by the arrow D. In a tensioner with no coil spring 20, as shown in Figure 3(a), the shaft member rotates in the direction shown by the arrow D due to the rotation torque Tk, which corresponds to the external input load F. In this case, the rotational angle of the first shaft member 3 is designated as 03, and the amplitude of the second shaft member 4 corresponding to the angle 03 is designated as B. In this embodiment, as shown in Figure 3(b), a coil spring 20, which is a compression spring, is arranged between the first shaft member 3 and the second shaft member 4. When the external input load F is applied onto the second shaft member 4, the coil spring 20 is compressed, so that friction torque is generated between the bottom end 20b and the flange part 3c of the first shaft member 3, or the already-generated friction torque increases further. The friction torque Tl is a product of the axial direction load W of the coil spring 20, the radius r of the contact area between the first shaft member 3 and the coil spring 20, and the coefficient \x of the friction between the first shaft member and the coil spring (Tl = Wr«n). The friction torque Tl works as a brake against the rotation angle 92, at which the first shaft member 3 is forcibly rotated by the second shaft member 4 that is pushed in. Therefore, the rotation angle of the first shaft member is reduced from 02 to 91, so that pushing volume (amplitude) of the second shaft member 4 can be reduced to Bl. In this embodiment, the coil spring 20 is arranged between the first shaft member 3 and the second shaft member 4. Whenever an external input load F is applied, the coil spring 20 is compressed, so that friction torque is generated or increased. Accordingly, because the amplitude of the first shaft member 3 can be controlled regardless of the volume of the external input load F, the amplitude can be controlled precisely. Also, it is not necessary to increase the spring torque of the torsion spring 5, or to make the lead angle of the screw portions 8,9 small in order to increase the driving force of the second shaft member 4, so as to restrain the amplitude. Thus, the friction between the chain guide and the chain does not become large, and the loss of engine output can be made small. (Second Embodiment) Figure 4 shows a tensioner A2 in a second embodiment of the present invention, A buffer plate 22 is inserted between the compression spring, namely the coil spring 20, and the flange part 3c of a first shaft member 3. The buffer plate 22 is made of a metallic thin plate such as a washer, and is installed between the other end 20b of the coil spring 20 and the flange part 3c of the first shaft member 3. Such a buffer plate 22 is installed so that the other end 20b of the coil spring 20 can be prevented from digging into the first shaft member 3. Thus, the coil spring 20 can be smoothly operated, and abrasion of both the coil spring 20 and the first shaft member 3 can be controlled, thereby enhancing the durability of the tensioner. Figures 5 and 6 show a variation of this embodiment. In the embodiment of Figure 5, a buffer plate 22 (which is composed by laminating on one another the following three members: a metal washer 23 made of iron, stainless steel or the like; a resin washer 24 made of PTFE, namely polytetrafluoroethylene, or the like; and a metal washer 25) is inserted between the flange part 3c of the first shaft member 3 and the other end 20b of the coil spring 20. Also, a buffer plate composed of a metal washer 26 is inserted between one end 20a of the coil spring 20 and the second shaft member 4. In the embodiment of Figure 6, solid lubricant 27 made of PTFE or the like is coated on the outer face of the wire rod of the coil spring 20. A buffer plate, which is composed of a metal washer 23, is inserted between (a) one end of the coil spring 20 and (b) the flange part 3c of the first shaft member 3, and another buffer plate, which is composed of a washer 26, is inserted between (c) the other end of the coil spring 20 and (d) the second shaft member 4. By inserting various kinds of buffer plates between the coil spring 20 and the first shaft member 3 and/or the second shaft member 4, or by coating a solid lubricant on the coil spring 20, the friction coefficient between the coil spring 20 and the first shaft member 3 and/or the second shaft member 4 can be controlled as desired. Thus, friction torque that corresponds to one's purposes can be easily obtained. (Third Embodiment) Figure 7 shows a tensioner A3 in a third embodiment of the present invention. In the tensioner A3 of this embodiment, the two ends 20a, 20b of a compression spring, namely a coil spring 20, are supported by the first shaft member 3 and the second shaft member 4. That is to say, a projection 3g, whose outside diameter corresponds to the inside diameter of the coil spring 20, is formed between the flange part 3c and the screw portion 3b of the first shaft member 3, while a shoulder portion 4g, whose outside diameter corresponds to the inside diameter of the coil spring 20, is formed on the second shaft member 4 on the side that is near the first shaft member 3. The projection 3g and the shoulder portion 4g serve as swivel plates for supporting the ends of the coil spring 20. When the projection 3g and the shoulder portion 4g are inserted into the two ends 20a, 20b of the coil spring 20, a more-stable supporting condition can be obtained. Also, a metal washer 22 (which serves as a buffer plate) is installed between the other end 20b of the coil spring 20 and the flange part 3c of the first shaft member 3. In this embodiment, the coil spring 20 is also compressed to a certain extent. Because both ends of the coil spring 20 are supported by the first and second shaft members 3, 4, even when the reciprocating rotation of the first shaft member 3 is repeated, the operation can be smoothly and stably performed. The ends of the coil spring 20 can be stably supported by either one of the shaft members 3 and 4. (Fourth Embodiment) Figure 8 shows a tensioner A4 in a fourth embodiment of the present invention. In this embodiment, as is similar to the tensioner A3 of the third embodiment shown in Figure 7, the two ends 20a, 20b of a coil spring 20 are supported by shaft members 3,4, respectively. Accordingly, this tensioner can cope smoothly with the reciprocating rotation of the first shaft member 3. In addition, in this embodiment, the diameter of the coil spring 20 is made small where the coil spring 20 is positioned on the side of the first shaft member 3. That is to say, the diameter of one end of the coil spring 20 (i.e., the end that faces the first shaft member 3) gradually decreases in the direction that is opposite to the driving direction of the second shaft member 4. The other end 20b, whose diameter gradually decreases in the direction that is opposite to the driving direction of the second shaft member 4, is supported by a projection 3g of the first shaft member 3. Because of such a decreased diameter, the coil spring 20 and the first shaft member 3 can slide against each other, and therefore the friction torque between the coil spring 20 and the shaft member 3 can be increased, and the amplitude of the second shaft member 4 can be controlled. The coil spring 20, whose diameter is large on the side of the second shaft member 4, closely contacts the second shaft member 4, and therefore the fnctional torque generated from the coil spring 20 can be made large, and the rotational angle of the first shaft member 3 can be made small Also, the diameter, or the rate at which the diameter of the coil spring 20 changes (decreases) at its end can be changed as desired, and thus reaction torque can be controlled as desired. (Fifth Embodiment) Figure 9 shows a tensioner A5 in a fifth embodiment of the present invention. Also in this embodiment, an elastic member 30 is arranged between a first shaft member 3 and a second shaft member 4, but the elastic member 30 is made of a tubular molded resin element. A resin into which hard filler is mixed or the like can be used as said molded resin element* The elastic member 30 that is formed of a molded resin element is arranged between the first shaft member 3 and the second shaft member 4, and therefore the elastic member 30 is compressed by the external input load that is applied to the second shaft member 4. Due to this compression, frictional torque is generated between the elastic member 30 and the shaft member 3, or the frictional torque that has already been generated between those parts increases further. Thus, a braking force acts on the first shaft member 3 so that the amplitude of the second shaft member 4 can be controlled. Also, instead of the molded resin element, a molded rubber element, such as synthetic rubber, can be used. (Sixth Embodiment) Figure 10 shows a tensioner A6 in a sixth embodiment of the present invention. In this embodiment, an elastic member 31, which is arranged between a first shaft member 3 and a second shaft member 4, is composed of laminated layers of plate springs. The elastic member 31 that is composed of the laminated layers of plate springs is arranged between the first shaft member 3 and the second shaft member 4, and is compressed by an external input load that is applied to the second shaft member 4, so that frictional torque is generated between the elastic member 31 and the first shaft member 3, or the frictional torque that has already been generated between those parts further increases. In addition, a braking force due to friction is generated between each * of the plate springs that are laminated together. Thus, a braking force acts on the first shaft member 3 so that the amplitude of the second shaft member 4 can be controlled. (Seventh Embodiment) Figure 11 shows a tensioner A7 in a seventh embodiment of the present invention* In this embodiment, a second shaft member 4 is constituted with two members: (1) a main body 41 that is positioned on the side of an engine's main body, and (2) a clutch part 42 that is positioned on the side of the first shaft member 3 of the main body 41. Both the main body 41 and the clutch part 42 move forward from the case 2. Also, the clutch part 42 and the main body 41 are engaged with each other by isosceles-triangular fitting pawls 43 that are formed on both the clutch part 42 and the main body 41. A hooking portion 33a that is formed on one end of a coil spring 33 (which serves as an elastic member) is fastened with the clutch part 42. The coil spring 33 is attached to the screw portion 3b of the first shaft member 3, and the hooking portion 33b that is formed on the other end of a coil spring 33 is fastened with the flange part 3c of the first shaft member 1. In this embodiment, the coil spring 33 is arranged between the first shaft member 3 and the second shaft member 4 while being compressed. The coil spring 33 is also fastened with both shaft members 3,4 while it is twisted via the hooking portions 33a, 33b that are formed on both ends of the coil spring 33, As a result, the coil spring 33 has a reaction force against an external input load. In such an embodiment, when an external input load is applied to the second shaft member 4, the reaction torque of the coil spring 33 increases according to the angle and height of the fitting pawls 43. Therefore, in this embodiment, braking is applied against the external input load by both the torque of a torsion spring 5 and the reaction torque of the coil spring 33, so that the amplitude of the second shaft member 4 can be controlled precisely, (Eighth Embodiment) Figure 12 shows a tensioner A8 in an eighth embodiment of the present invention* In this embodiment, as is similar to the tensioner A7 of the seventh embodiment, a second shaft member 4 is comprised of a main body 41 (which is on the tip side) and a clutch part 42 (which is on the side of the first shaft member 3), and fitting pawls 43 are also formed on both the main body 41 and the clutch part 42. A coil spring 33 is arranged between the first shaft member 3 and the second shaft member 4, while the hooking portion 33a that is formed on one end of the coil spring 33 is fastened with the clutch part 42, and the hooking portion 33b that is formed on the other end of the coil spring 33 is fastened to the flange part 3c of the first shaft member 3. In this embodiment, the fitting pawls 43 are formed in a saw-tooth shape, so that the clutch part 42 cannot rotate in the reverse direction. Thus, once the second shaft member 4 moves forward, the clutch part 42 does not rotate in the reverse direction, and the reaction torque due to the coil spring 33 can be made large. (Ninth Embodiment) In this embodiment (although not shown in the drawings), in addition to the characteristics of this invention in the first through eighth embodiments, the coil-winding direction of the coil spring is opposite to the threading direction of the male screw portion 8 of the first shaft member 3. Thereby, when the first shaft member 3 rotates as the second shaft member 4 is pushed in due to an external input load, the coil spring is twisted in such a direction that the coil diameter is reduced. Accordingly, the coil diameter does not expand, so that it is possible to prevent the coil spring from interfering with peripheral parts, thus enabling smooth operation. Possibility of Industrial Utilization According to the invention described in Claim 1, because an elastic mejnber is arranged between a first shaft member and a second shaft member, when an external input load is applied the elastic member always generates resistance torque, so that the amplitude of the second shaft member can be controlled precisely. Also, because the friction between the chain guide and the chain does not become large, the loss of engine output can be minimized According to the invention described in Claim 2, in addition to the effects mentioned in Claim 1, because the coil spring that is arranged between the first shaft member and the second shaft member is compressed, frictional torque is generated so as to restrain the rotation of the first shaft member, so that the amplitude of the second shaft member can be controlled precisely. According to the invention described in Claim 3, in addition to the effects mentioned in Claim 1, because the coil spring that is arranged between the first shaft member and the second shaft member is twisted so as to generate reaction torque, the amplitude of the second shaft member can be controlled precisely or significantly, according to the amount of external input load that is applied. According to the invention described in Claim 4, in addition to the effects mentioned in Claim 2, because a swivel plate that supports the coil spring is installed on either the first shaft member or the second shaft member, even when the first shaft member rotates forward and backward repeatedly, it is possible to cope with such an action of the first shaft member, and thereby to secure stable operation. According to the invention described in Claim 5, in addition to the effects mentioned in Claims 2-4, frictional torque between the first shaft member and the spring can be made large, and the amplitude of the second shaft member can be controlled. In addition, the frictional torque can be set as desired by properly forming the shape of the spring. According to the invention described in Claim 6, in addition to the effects mentioned in Claims 2-5, because the coil-winding direction is opposite to the threading direction of the first shaft member, the coil diameter of the coil spring does not expand, and the coil does not interfere with peripheral parts such as the case, and therefore operation proceeds smoothly. According to the invention described in Claim 7, in addition to the effects mentioned in Claims 2-6, because the clutch part that is formed on the second shaft member twists the coil spring, reaction torque is generated on the coil spring, so that the amplitude of the second shaft member can be controlled. According to the invention described in Claim 8, in addition to the effects mentioned in Claim I, the plate spring, the molded rubber element, and the molded resin element are compressed so as to generate fractional torque between the first shaft member and the coil spring, and thereby the amplitude of a second shaft member can be controlled. According to the invention described in Claim 9, in addition to the effects mentioned in Claims 1-8, because the buffer plate prevents the elastic member from digging into the first shaft member, the elastic member can be smoothly operated, and abrasion of both the elastic member and the first shaft member can be controlled, thereby improving their durability. Claims What is claimed is: 1. A tensioner that is structured so that (1) a first shaft member and a second shaft member, which are engaged by screw portions, and a torsion spring, which gives rotating momentum to the first shaft member in one direction, are accommodated in a case, and that (2) the rotating momentum of the torsion spring is converted into the driving force of the second shaft member while rotation of the second shaft member is controlled, and which is characterized such that an elastic member that generates resistance torque against an external input load that is applied to the second shaft member is arranged between said first shaft member and said second shaft member. 2. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is (1) arranged between the first shaft member and the second shaft member while it is compressed by both shaft members, and (2) compressed by an external input load so as to generate frictional torque between the first shaft member and itself (the coil spring). 3. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is twisted by an external input load applied that is to the second shaft member so as to generate reaction torque in the same direction as the rotation and pressing direction of said torsion spring. 4. A tensioner as set forth in Claim 2, but characterized such that a swivel plate, which supports said coil spring, is installed on either said first shaft member or said second shaft member, 5. A tensioner as set forth in any of Claims 2-4, but characterized such that the diameter of one end of the coil spring, which is on the side of the first shaft member, gradually decreases in the direction that is opposite to the driving direction of the second shaft member. 6. A tensioner as set forth in any of Claims 2-5, but characterized such that the coil-winding direction of said coil spring is opposite to the threading direction of the screw portion of the first shaft member. 7. A tensioner as set forth in any of Claims 2-6, but characterized such that (1) a clutch part that rotates together with the forward and backward movement of said second shaft member is formed on the second shaft member, (2) one end of said coil spring is fastened to the clutch part, and that (3) the other end of said coil spring is fastened to the first shaft member. 8. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a plate spring, a molded rubber element, or a molded resin element that is (1) arranged put on while it is brought into contact with both the first shaft member and the second shaft member, and (2) compressed by an external input load so as to generate frictional torque between the first shaft member and itself (the elastic member). 9. A tensioner as set forth in any one of Claims 1-7, but characterized such that a buffer plate is inserted between said elastic member and the first shaft member. 10. A tensioner substantially as herein described with reference to the accompanying drawings.

Full Text

Field of the Invention
The present invention relates to a tensioner for maintaining constant tension of a continuous timing belt or chain.
Description of the Related Art
A tensioner works to maintain constant tension of a timing chain or a timing belt that is used, for example, for an engine of an automobile, by pushing the timing chain or timing belt with a predetermined force if the timing chain or timing belt becomes loose or slack.
Figure 13 shows the condition when a tensioner 100 is actually installed in the main body of an engine 200 of an automobile. A pair of cam sprockets 210,210 and a crank sprocket 220 are arranged in the main body of the engine 200, and a non-ended timing chain 230 encircles the pair of the cam sprockets 210,210 and the crank sprocket 220. A chain guide 240 is installed in a free-moving condition on the moving path of the timing chain 230, and the timing chain 230 slides on (the surface of) the chain guide 240. An installing part 250 is formed on the main body of the engine 200, and the tensioner 100 is fixed onto the installing part 250 with bolts 270 that penetrate through installing holes 260 on the installing part 250, Also, the main body of the engine 200 is supplied with lubricating oil (not shown).
Figures 14 and 15 show a conventional tensioner 100. A rotating shaft 120 and a drive shaft 130 are integrally arranged in a case 110. The case 110 is comprised of a main body 111, which extends in the axial direction of the case so that the shafts 120 and 130 can be inserted therein, and flange parts 112 that extend from the main body 111 in the direction perpendicular to the axial direction. The flange parts 112 serve to attach the

tensioner 110 onto the main body of the engine 200, and therefore installing holes 113, through which bolts to be screwed into the main body of the engine 200 penetrate, are formed to the flange parts 112. The main body 111 serves to accommodate parts that will be mentioned later, and therefore accommodation holes 114 that have the same inside diameters as the outside diameters of the parts to be accommodated therein are formed in the main body 111 in the axial direction.
In order to connect the rotating shaft 120 to the drive shaft 130, a male screw portion 121 is formed on the outer surface of the rotating shaft 120 while a female screw portion 131 is formed on the inner surface of the drive shaft 130, and said connection is achieved by engaging said screw portions 121 and 131 with each other. A swivel plate 140 is arranged inside the case 110 that faces the base-end side of the rotating shaft 120 so as to be positioned inside the accommodation hole 114 and so as to support the base end of the rotating shaft 120. When the drive shaft 130 is connected with the rotating shaft 120, the drive shaft 130 is screwed and engaged with the front-side part of the rotating shaft 120 to approximately one-half of the overall length of said rotating shaft 120, and a torsion spring 150 is arranged on the back side of the rotating shaft 120 (for approximately one-half of the overall length of said rotating shaft 120) with which the drive shaft 130 is not screwed/engaged*
A hooking portion 151 on one end of the torsion spring 150 is inserted into and fastened into a slit 123 that is formed at the base end of the rotating shaft 120, and another hooking portion 152 on the other end is fastened to the case 110. Accordingly, when assembled under the condition that the torsion spring 150 is twisted so as to have a specified torque, the rotating shaft 120 rotates due to the momentum of the torsion spring 150.
At the front end of the case 110, a bearing 160 is fixed with a snap ring 170, and the drive shaft 130 penetrates through a slide hole 161 of the bearing 160, Both the cross-sectional shape of the inner surface of the slide hole 161 of the bearing 160 and

the cross-sectional shape of the outer surface of the drive shaft 130 are approximately ovals, or parallel cuts, or other non-cirdular shapes, thereby restraining rotation of the drive shaft 130.
The bearing 160 is formed into a flat shape of a specified thickness, and a plurality of fixing pieces 162 are formed on the outer peripheral side of the bearing 160. When the fixing pieces 162 are engaged with notch grooves 115 that are formed at the front end of the case 110, rotation of the entire bearing 160 is prevented. When rotation of the bearing 160 against the case 110 is prevented, the drive shaft 130 that penetrates through the bearing 160 is also prevented from rotating against the case 110 via the bearing 160. Thus, the drive shaft 130 moves toward or away from the case 110, under a rotation-restricted condition.
A cap 180 is attached onto the tip of the drive shaft 130, and said cap 180 is brought into contact with a chain guide 240 that is inside said main body of the engine 200.
Furthermore, a spacer 190 is arranged inside the case 110. The spacer 190 is formed into a tube-like shape that extends in the axial direction (driving direction) so as to surround the rotating shaft 120 and the drive shaft 130, so that the shafts 120 and 130, which are engaged with each other, are prevented from coming off from the tip end of the case 110. In order to prevent the shafts 120 and 130 from coming off, the rotating shaft 120 is formed so as to have jaws that can abut on the spacer 190.
In the tensioner 100 of the above-mentioned structure, the rotating shaft 120 rotates due to a force that the torsion spring 150 gives to the rotating shaft 120, thereby giving momentum to the rotating shaft 120, and this rotation force is converted into the driving force of the drive shaft 130, so that the drive shaft 130 moves forwards. Thereby, the drive shaft 130 presses the timing chain 230 via both the cap 180 and die chain guide 240, thereby giving tension to the timing chain 230.

In order to achieve stable operation of such a tensioner 100 by restraining the pressing volume (amplitude) of the drive shaft 130 against an external input load from the chain guide 240, the chain guide 240 needs to be held strongly. For this reason, the following measures are taken: (1) The spring torque of the torsion spring 150 is made large; (2) The lead angles of both the male screw portion 121 and the female screw portion 131, both of which serve to screw together the rotating shaft 120 and the drive shaft 130, are made small (for example, 12° is reduced to 9°); and (3) The diameter of the end face of the rotating shaft 120 is made large, so that the area of contact between the rotating shaft 120 and the swivel plate 140 (the case 110) is made large.
However, when the above-mentioned measures are taken, the drive shaft 130 develops a strong tendency to drive (move forward). When the drive shaft 130 drives more than necessary, friction between the chain guide 240 and the chain 230 increases, which becomes an undesirable factor that creates a big loss of engine output.
Japanese Unexamined Published Patent Application No. 2001 -21012>discloses a structure in which a friction plate is arranged on a case, a jaw-tike friction face of a large contacting area is formed on a portion (which is opposed to the friction plate) of a rotating shaft, and the friction face is held by an auxiliary spring so that the friction face cannot contact the friction plate. With this structure, when the externai input load from a chain guide is small, the friction face is not brought into contact with the friction plate, but when the external input load becomes more than a specified value, the friction face is brought into contact with the friction plate, so that a friction force can be generated. Thus, there is no need to take the above-mentioned measures (1) through (3). The loss of the engine's output can be reduced, and the amplitude of the drive shaft against a large external input load also can be controlled.
The amplitude of the drive shaft can also be controlled by the structure of Japanese Unexamined Published Patent Application No. 2001-21012, But with this structure, amplitude restriction might need to be emphasized for certain kinds of engines.

For the purpose of satisfying such a requirement, one object of the present invention is to provide a tensioner that can precisely control amplitude against an external input load.
Summary of the Invention
For the purpose of achieving the above-mentioned object, a tensioner set forth in Claim 1 is characterized such that
(1) a first shaft member and a second shaft member, which are engaged by screw portions, and a torsion spring, which gives rotating momentum to the first shaft member in one direction, are accommodated in a case, and that (2) the rotating momentum of the torsion spring is converted into the driving force of the second shaft member while rotation of the second shaft member is controlled, and which is characterized such that an elastic member that generates resistance torque against an external input load that is applied to the second shaft member is arranged between said first shaft member and said second shaft member.
According to the invention set forth in Claim 1, when the external input load is applied onto the second shaft member, a load is applied onto the elastic member that is arranged between the first shaft member and the second shaft member. Thereby, the elastic member generates resistance torque against the external input load, so that the amplitude of the second shaft member can be made small.
According to the invention set forth in Claim 1, because an elastic member is arranged between the first shaft member and the second shaft member, the elastic member generates resistance torque whenever an external input load is applied. Accordingly, regardless of the amount of the external input load, resistance torque is generated and said torque controls the amplitude of the second shaft member, so that the amplitude can be controlled precisely.

Also, there is no need to increase the driving force of the second shaft member by increasing the spring torque of the torsion spring or by making the lead angle of the screw portions small Therefore, friction between the chain guide and the chain does not become large, and the loss of the engine's output can be made small.
The invention of Claim 2 is a tensioner as set forth in Claim 1, but characterized such that
said elastic member is arranged between the first shaft member and the second shaft member while said elastic member is compressed by both the first and second shaft members, and
the elastic member is a coil spring that generates friction torque between the first shaft member and itself through compression caused by an external input load.
According to the invention described in Claim 2, the elastic member is a coil spring. The coil spring is compressed by both the first shaft member and the second shaft member, and also is compressed by the compression force that results when an external input load is applied onto the second shaft member. Due to this compression, friction torque is generated between the first shaft member and the coil spring, or the already generated friction torque increases, and therefore the rotation of the first shaft member is controlled. That is to say, when an external input load is applied, the second shaft member is pushed inside the case, so that the first shaft member rotates in the direction that is opposed to the rotation and pressing direction of the torsion spring, while a braking force due to the friction force of the compression spring acts against the reverse-direction rotation of the first shaft member (i.e., the direction that is opposite to the rotating momentum resulting from the torsion spring). As a result, the pressing volume (amplitude) of the second shaft member is controlled.
According to the invention set forth in Claim 2, because the coil spring that is compressed by an external input load is also arranged between the first shaft member

and the second shaft member, whenever an external input load is applied, the coil spring generates friction torque to restrain the rotation of the first shaft member, so that the amplitude of the second shaft member can be controlled precisely.
The invention of Claim 3 is a tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is twisted by the external input load that is applied onto the second shaft member to generate a reaction force torque in the same direction as that of the rotation and pressing direction of said torsion spring.
According to the invention described in Claim 3, when an external input load is applied onto the second shaft member, the coil spring is twisted and the reaction force torque is generated or increased, and thereby the pressing force onto the second shaft member by the external input load is reduced, so that the pressing volume (amplitude) of the second shaft member can be controlled.
Also, according to the invention set forth in Claim 3, because the coil spring that is twisted by the external input load to generate the reaction force torque is arranged between the first shaft member and the second shaft member, the amplitude of the second shaft member can be controlled precisely according to the amount of external input load that is applied.
The invention of Claim 4 is a tensioner as set forth in Claim 2, but characterized such that a swivel plate for supporting said coil spring is arranged on either said first shaft member or said second shaft member.
The coil spring is supported by the swivel plate that is arranged on the shaft member, so that the connection between the coil spring and the shaft member is stabilized. As a result, even when the first shaft member rotates forward and backward repeatedly, the coil spring can easily cope with such rotation, thereby securing stable operation.

The invention of Claim 5 is a tensioner as set forth in any one of Claims 2-A, but characterized such that the diameter of one end of the coil spring, which is on the side of the first shaft member, gradually decreases in the direction that is opposite to the driving direction of the second shaft member
According to the invention described in Claim 5, because the diameter of the coil spring is small at the end on the first-shaft-member side, the spring slides on the first shaft member with large friction. Thus, friction torque between the first shaft member and the coil spring can be made large, so that the amplitude of the second shaft member can be controlled.
The invention of Claim 6 is a tensioner as set forth in Claims 2-5, but characterized such that the coil-winding direction of said coil spring is opposite to the threading direction of the screw portion of the first shaft member.
Because the coil-winding direction is opposite to the threading direction of the first shaft member, when the second shaft member is pushed in by an external input load and the first shaft member rotates, the coil spring is twisted in such a way that the coil diameter is reduced. Thereby, the coil spring does not expand its diameter or interfere with peripheral parts, such as the case, thereby facilitating smooth operation.
The invention of Claim 7 is a tensioner as set forth in any one of Claims 2-6, but
characterized such that
a clutch part, which rotates along with said second shaft member's forward and
backward movement, is formed on the second shaft member, one end of said coil spring is fastened to said clutch part, and the other end of said coil spring is fastened to the first shaft member.
According to the invention described in Claim 7, because the clutch part formed on the second shaft member twists the coil spring, a reaction force torque is generated on the

coil spring. Thereby, the amplitude of the second shaft member can be controlled.
The invention of Claim 8 is a tensioner as set forth in Claim 1, but characterized such that said elastic member is a plate spring, a molded rubber element, or a molded resin element that (a) is arranged between both the first shaft member and the second shaft member under the condition that said elastic member contacts both the first shaft member and the second shaft member, and (b) is compressed by the external input load, so that friction torque is generated between the first shaft member and said elastic member.
According to the invention described in Claim 8, a plate spring, a molded rubber element, or a molded resin element is used as the elastic member. The plate spring, the molded rubber element, or the molded resin element is deformed when an external input load is applied onto the second shaft member, to generate friction torque between the first shaft member and the elastic member. As a result, rotation of the first shaft member is controlled, so that the amplitude of the second shaft member also can be controlled.
According to the invention described in Claim 8, because the plate spring, the molded
i
rubber element, or the molded resin element is arranged between the first shaft member and the second shaft member, whenever an external input load is applied, friction torque is generated, thereby enabling the amplitude of the second shaft member to be controlled precisely.
The invention of Claim 9 is a tensioner as set forth in any one of Claims 1-8, but characterized such that a buffer plate is inserted between said elastic member and the first shaft member. The buffer plate that is inserted between the elastic member and the first shaft member prevents the elastic member from digging into the first shaft member. Therefore, the elastic member can be operated smoothly, and abrasion of both the elastic member and the first shaft member also can be controlled, thereby improving

Brief Description of the Drawings
Figure 1 is a plan view of a tensioner in a first embodiment of the present invention.
Figure 2 is a cross-sectional view along the line C-C of Figure 1.
Figure 3 is a perspective view illustrating the action of the coil spring, where (a) shows
a conventional tensioner and (b) shows a tensioner in the first embodiment of the
present invention.
Figure 4 is a cross-sectional view showing a tensioner in a second embodiment of the
present invention.
Figure 5 is a partial cross-sectional view of variations of a second embodiment of the
present invention.
Figure 6 is a partial cross-sectional view showing other variations of the second
embodiment.
Figure 7 is a cross-sectional view of a tensioner in a third embodiment.
Figure 8 is a cross-sectional view of a tensioner in a fourth embodiment.
Figure 9 is a cross-sectional view of a tensioner in a fifth embodiment.
Figure 10 is a cross-sectional view of a tensioner in a sixth embodiment.
Figure 11 is a cross-sectional view of a tensioner in a seventh embodiment.
Figure 12 is a cross-sectional view of a tensioner in an eighth embodiment.
Figure 13 is a cross-sectional view of a tensioner that is installed onto the main body of
an engine.
Figure 14 is a plan view of a conventional tensioner.
Figure 15 is a cross-sectional view along the line Q-Q of Figure 14.
Description of the Preferred Embodiments
Some embodiments of the present invention will be described in detail. For each embodiment, identical numbers are used to refer to identical elements.

(First Embodiment)
Figures 1-3 show a tensioner AI in a first embodiment of the present invention. The tensioner is equipped with a case 2, a first shaft member 3, a second shaft member 4, a torsion spring 5, a bearing 6, and a spacer 7.
The case 2 is formed into an approximate T-shape in its cross-section, and flange parts 2b extend from the tip of a shell part 2a in the direction that is approximately perpendicular to the driving direction. An accommodation hole 2c extends from the shell part 2a to the portion of the flange parts 2b in the axial direction (driving direction). The edge of the accommodation hole 2c is open, and an assembly of the first and second shaft members 3,4, the torsion spring 5, and the spacer 7 is accommodated in the accommodation hole 2c.
The flange parts 2b of the case 2 are to be attached onto a piece of equipment, namely the main body of an engine, and installing holes 2d, through which penetrate bolts (not shown) that are screwed into the main body of the engine, are formed in the flange parts. When the flange parts are attached onto the main body of the engine, the tip faces of the flange parts 2b are brought into contact with the installing part 250 of the main body of the engine 200, in a way that is similar to the arrangement shown in Figure 13,
The first shaft member 3 rotates when it is given momentum by the torsion spring 5 (which will be mentioned again later), and the second shaft member 4 is moved forward from the case 2 by the rotation of the first shaft member 3.
A shaft part 3a (on the base-end side of the first shaft member 3) and a screw portion 3b (on the tip-end side of the first shaft member 3) are integrally formed in the axial direction, and a male screw 8 is formed on the outer periphery of the screw portion 3b on the tip-end side of the first shaft member 3. Also, the base-end part of the shaft part 3a is brought into contact with a swivel plate 19 that is arranged in the case 2, so that the rotation of the shaft part 3a is supported. A slit 3e, into which the tip end of a

fastening jig (not shown) is inserted for rotating the first shaft member 3, is formed on the base-end face of the shaft part 3a. The slit 3e is connected to a jig hole 2e formed on the base-end face of the shell part 2a of the case 2. The tip end of the fastening jig is inserted in the slit 3e from the jig hole 2e and the first shaft member 3 is rotated via the slit 3e, so that a torsion spring 5 (which will be mentioned later) can be fastened.
The second shaft member 4 is formed into a tube-like shape, and a female screw 9, which is engaged with the male screw 8 of the first shaft member 3, is formed on the inner face of the second shaft member 4. The shaft members 3 and 4 are inserted into the accommodation holes 2c of the case 2 while the female screw 9 and the male screw 8 are engaged with each other. A cap 10 is attached to the tip end of the second shaft member 4. The cap 10 is comprised of a head part 10a and a leg part 10b. A spring pin 11 is pressure-inserted into both the leg part 10b and the tip portion of the second shaft member 4, while the head part 10a covers the tip portion of the second shaft member 4, and the leg part 10b is engaged with the tip portion of the second shaft member 4, so that the cap 10 is prevented from coming off and is fixed onto the second shaft member 4.
The torsion spring 5 is put around the shaft part 3a of the first shaft member 3. A hooking portion 5a on one end of the torsion spring 5 is inserted into and fastened with a hook groove 2f that is formed on the case 2, while a hooking portion 5b on the other end of the torsion spring 5 is inserted into and fastened with the slit 3e that is formed on the bottom part of the first shaft member 3. Accordingly, when the torsion spring 5 is wound and torque is applied, the first shaft member 3 can rotate.
The bearing 6 is attached to the tip portion of the case 2 and is fixed with a cover ring 13, The bearing 6 has a slide hole 6a through which the second shaft member 4 penetrates* The cross-sectional shape of each of (1) the inner face of the slide hole 6a of the bearing 6 and (2) the outer face of the second shaft member 4 is formed into an approximately oval shape, a D-cut, a parallel cut, or other non-circular shape, thereby

restraining rotation of the second shaft member 4.
The bearing 6 is formed into a flat shape of a predetermined thickness, and a plurality of fixing pieces 6b are radially formed on the outer periphery of the bearing. The fixing pieces 6b are engaged with notch grooves 2g that are formed at the tip portion of the case 2, so that rotation of the entire bearing 6 is prevented. The rotation of the bearing 6 is prevented against the case 2, so as to control the rotation of the second shaft member 4, which penetrates through the bearing 6, against the case 2 via the bearing 6.
The shaft member 3 is engaged with the second shaft member 4 by screw portions 8,9, and the rotating force of the first shaft member 3, which is rotated by the rotating momentum of the torsion spring 5, is transferred to the second shaft member 4. Because the rotation of the second shaft member 4 is controlled by the bearing 6, the second shaft member 4 moves toward and away from the case 2.
The spacer 7 is formed into a tube-like shape, and the screwing portions of both the first shaft member 3 and the second shaft member 4 are inserted inside the spacer 7. A flange part 3c, whose diameter is large, is formed at a boundary portion between the shaft part 3a and the screw portion 3b of the first shaft member 3, and the base end of the spacer 7 abuts on the flange part 3c. The tip portion of the spacer 7 is faced to and abuts on the bearing 6, thereby preventing the first and second shaft members 3,4 from coming off from the case 2.
In addition, in this embodiment, a coil spring 20 is arranged as an elastic member. The coil spring 20 is arranged between the first shaft member 3 and the second shaft member 4. In this embodiment, the coil spring 20 is arranged between the screw portion 3b of the first shaft member 3 and the base end of the second shaft member 4.
A compression spring, whose hooking portions on both ends are free ends, is used as the coil spring 20. One end 20a of the compression spring (namely the coil spring 20) is

brought into contact with the second shaft member 4, and the other end 20b is brought into contact with the first shaft member 3, In this case, the other end 20b is brought into contact with the flange part 3c of the first shaft member 3. Both ends 20a, 20b of the coil spring 20 are brought into contact with both the shaft members 3,4, while the coil spring 20 is assembled in a condition that the coil spring 20 is compressed to a certain extent.
Accordingly, when an external input load for pushing in the second shaft member 4 is applied, a compression force acts directly on the coil spring 20, whose tip end 20a is in contact with the second shaft member 4, thereby compressing the coil spring 20. Because the other end 20b of the coil spring 20 contacts the first shaft member 3, friction torque is generated between the coil spring 20 and the first shaft member 3 (or the already-generated friction torque is further increased) by the compression of the coil spring 20. Thereby, a braking force acts on the first shaft member 3, so that rotation of the first shaft member 3 is controlled.
Figure 3 compares the action of this embodiment with the action of a conventional tensioner as shown in Figures 14 and 15, and the reference numbers in this embodiment are given to the elements of the conventional tensioner. As shown in Figure 3, rotating momentum^composed of a torque T is applied to the first shaft member 3 from the torsion spring 5. When an external input load F is applied, the second shaft member 4 is pushed into the case 2, so that the first shaft member 3 rotates against the rotating momentum of the torsion spring 5 and in the direction shown by the arrow D.
In a tensioner with no coil spring 20, as shown in Figure 3(a), the shaft member rotates in the direction shown by the arrow D due to the rotation torque Tk, which corresponds to the external input load F. In this case, the rotational angle of the first shaft member 3 is designated as 03, and the amplitude of the second shaft member 4 corresponding to the angle 03 is designated as B.

In this embodiment, as shown in Figure 3(b), a coil spring 20, which is a compression spring, is arranged between the first shaft member 3 and the second shaft member 4. When the external input load F is applied onto the second shaft member 4, the coil spring 20 is compressed, so that friction torque is generated between the bottom end 20b and the flange part 3c of the first shaft member 3, or the already-generated friction torque increases further.
The friction torque Tl is a product of the axial direction load W of the coil spring 20, the radius r of the contact area between the first shaft member 3 and the coil spring 20, and the coefficient \x of the friction between the first shaft member and the coil spring (Tl = W*r«n). The friction torque Tl works as a brake against the rotation angle 92, at which the first shaft member 3 is forcibly rotated by the second shaft member 4 that is pushed in. Therefore, the rotation angle of the first shaft member is reduced from 02 to 91, so that pushing volume (amplitude) of the second shaft member 4 can be reduced to Bl.
In this embodiment, the coil spring 20 is arranged between the first shaft member 3 and the second shaft member 4. Whenever an external input load F is applied, the coil spring 20 is compressed, so that friction torque is generated or increased. Accordingly, because the amplitude of the first shaft member 3 can be controlled regardless of the volume of the external input load F, the amplitude can be controlled precisely.
Also, it is not necessary to increase the spring torque of the torsion spring 5, or to make the lead angle of the screw portions 8,9 small in order to increase the driving force of the second shaft member 4, so as to restrain the amplitude. Thus, the friction between the chain guide and the chain does not become large, and the loss of engine output can be made small.
(Second Embodiment)

Figure 4 shows a tensioner A2 in a second embodiment of the present invention, A buffer plate 22 is inserted between the compression spring, namely the coil spring 20, and the flange part 3c of a first shaft member 3. The buffer plate 22 is made of a metallic thin plate such as a washer, and is installed between the other end 20b of the coil spring 20 and the flange part 3c of the first shaft member 3.
Such a buffer plate 22 is installed so that the other end 20b of the coil spring 20 can be prevented from digging into the first shaft member 3. Thus, the coil spring 20 can be smoothly operated, and abrasion of both the coil spring 20 and the first shaft member 3 can be controlled, thereby enhancing the durability of the tensioner.
Figures 5 and 6 show a variation of this embodiment. In the embodiment of Figure 5, a buffer plate 22 (which is composed by laminating on one another the following three members: a metal washer 23 made of iron, stainless steel or the like; a resin washer 24 made of PTFE, namely polytetrafluoroethylene, or the like; and a metal washer 25) is inserted between the flange part 3c of the first shaft member 3 and the other end 20b of the coil spring 20. Also, a buffer plate composed of a metal washer 26 is inserted between one end 20a of the coil spring 20 and the second shaft member 4.
In the embodiment of Figure 6, solid lubricant 27 made of PTFE or the like is coated on the outer face of the wire rod of the coil spring 20. A buffer plate, which is composed of a metal washer 23, is inserted between (a) one end of the coil spring 20 and (b) the flange part 3c of the first shaft member 3, and another buffer plate, which is composed of a washer 26, is inserted between (c) the other end of the coil spring 20 and (d) the second shaft member 4.
By inserting various kinds of buffer plates between the coil spring 20 and the first shaft member 3 and/or the second shaft member 4, or by coating a solid lubricant on the coil spring 20, the friction coefficient between the coil spring 20 and the first shaft member 3 and/or the second shaft member 4 can be controlled as desired. Thus, friction torque

that corresponds to one's purposes can be easily obtained.
(Third Embodiment)
Figure 7 shows a tensioner A3 in a third embodiment of the present invention. In the tensioner A3 of this embodiment, the two ends 20a, 20b of a compression spring, namely a coil spring 20, are supported by the first shaft member 3 and the second shaft member 4.
That is to say, a projection 3g, whose outside diameter corresponds to the inside diameter of the coil spring 20, is formed between the flange part 3c and the screw portion 3b of the first shaft member 3, while a shoulder portion 4g, whose outside diameter corresponds to the inside diameter of the coil spring 20, is formed on the second shaft member 4 on the side that is near the first shaft member 3. The projection 3g and the shoulder portion 4g serve as swivel plates for supporting the ends of the coil spring 20. When the projection 3g and the shoulder portion 4g are inserted into the two ends 20a, 20b of the coil spring 20, a more-stable supporting condition can be obtained. Also, a metal washer 22 (which serves as a buffer plate) is installed between the other end 20b of the coil spring 20 and the flange part 3c of the first shaft member 3. In this embodiment, the coil spring 20 is also compressed to a certain extent.
Because both ends of the coil spring 20 are supported by the first and second shaft
members 3, 4, even when the reciprocating rotation of the first shaft member 3 is
* repeated, the operation can be smoothly and stably performed. The ends of the coil
spring 20 can be stably supported by either one of the shaft members 3 and 4.
(Fourth Embodiment)
Figure 8 shows a tensioner A4 in a fourth embodiment of the present invention. In this embodiment, as is similar to the tensioner A3 of the third embodiment shown in Figure 7, the two ends 20a, 20b of a coil spring 20 are supported by shaft members 3,4,

respectively. Accordingly, this tensioner can cope smoothly with the reciprocating rotation of the first shaft member 3.
In addition, in this embodiment, the diameter of the coil spring 20 is made small where the coil spring 20 is positioned on the side of the first shaft member 3. That is to say, the diameter of one end of the coil spring 20 (i.e., the end that faces the first shaft member 3) gradually decreases in the direction that is opposite to the driving direction of the second shaft member 4. The other end 20b, whose diameter gradually decreases in the direction that is opposite to the driving direction of the second shaft member 4, is supported by a projection 3g of the first shaft member 3.
Because of such a decreased diameter, the coil spring 20 and the first shaft member 3 can slide against each other, and therefore the friction torque between the coil spring 20 and the shaft member 3 can be increased, and the amplitude of the second shaft member 4 can be controlled. The coil spring 20, whose diameter is large on the side of the second shaft member 4, closely contacts the second shaft member 4, and therefore the fnctional torque generated from the coil spring 20 can be made large, and the rotational angle of the first shaft member 3 can be made small Also, the diameter, or the rate at which the diameter of the coil spring 20 changes (decreases) at its end can be changed as desired, and thus reaction torque can be controlled as desired.
(Fifth Embodiment)
Figure 9 shows a tensioner A5 in a fifth embodiment of the present invention. Also in this embodiment, an elastic member 30 is arranged between a first shaft member 3 and a second shaft member 4, but the elastic member 30 is made of a tubular molded resin element. A resin into which hard filler is mixed or the like can be used as said molded resin element*
The elastic member 30 that is formed of a molded resin element is arranged between the

first shaft member 3 and the second shaft member 4, and therefore the elastic member 30 is compressed by the external input load that is applied to the second shaft member 4. Due to this compression, frictional torque is generated between the elastic member 30 and the shaft member 3, or the frictional torque that has already been generated between those parts increases further. Thus, a braking force acts on the first shaft member 3 so that the amplitude of the second shaft member 4 can be controlled. Also, instead of the molded resin element, a molded rubber element, such as synthetic rubber, can be used.
(Sixth Embodiment)
Figure 10 shows a tensioner A6 in a sixth embodiment of the present invention. In this embodiment, an elastic member 31, which is arranged between a first shaft member 3 and a second shaft member 4, is composed of laminated layers of plate springs.
The elastic member 31 that is composed of the laminated layers of plate springs is
arranged between the first shaft member 3 and the second shaft member 4, and is
compressed by an external input load that is applied to the second shaft member 4, so
that frictional torque is generated between the elastic member 31 and the first shaft
member 3, or the frictional torque that has already been generated between those parts
further increases. In addition, a braking force due to friction is generated between each
* of the plate springs that are laminated together. Thus, a braking force acts on the first
shaft member 3 so that the amplitude of the second shaft member 4 can be controlled.
(Seventh Embodiment)
Figure 11 shows a tensioner A7 in a seventh embodiment of the present invention*
In this embodiment, a second shaft member 4 is constituted with two members: (1) a main body 41 that is positioned on the side of an engine's main body, and (2) a clutch part 42 that is positioned on the side of the first shaft member 3 of the main body 41. Both the main body 41 and the clutch part 42 move forward from the case 2. Also, the

clutch part 42 and the main body 41 are engaged with each other by isosceles-triangular fitting pawls 43 that are formed on both the clutch part 42 and the main body 41.
A hooking portion 33a that is formed on one end of a coil spring 33 (which serves as an elastic member) is fastened with the clutch part 42. The coil spring 33 is attached to the screw portion 3b of the first shaft member 3, and the hooking portion 33b that is formed on the other end of a coil spring 33 is fastened with the flange part 3c of the first shaft member 1. In this embodiment, the coil spring 33 is arranged between the first shaft member 3 and the second shaft member 4 while being compressed. The coil spring 33 is also fastened with both shaft members 3,4 while it is twisted via the hooking portions 33a, 33b that are formed on both ends of the coil spring 33, As a result, the coil spring 33 has a reaction force against an external input load.
In such an embodiment, when an external input load is applied to the second shaft member 4, the reaction torque of the coil spring 33 increases according to the angle and height of the fitting pawls 43. Therefore, in this embodiment, braking is applied against the external input load by both the torque of a torsion spring 5 and the reaction torque of the coil spring 33, so that the amplitude of the second shaft member 4 can be controlled precisely,
(Eighth Embodiment)
Figure 12 shows a tensioner A8 in an eighth embodiment of the present invention* In this embodiment, as is similar to the tensioner A7 of the seventh embodiment, a second shaft member 4 is comprised of a main body 41 (which is on the tip side) and a clutch part 42 (which is on the side of the first shaft member 3), and fitting pawls 43 are also formed on both the main body 41 and the clutch part 42. A coil spring 33 is arranged between the first shaft member 3 and the second shaft member 4, while the hooking portion 33a that is formed on one end of the coil spring 33 is fastened with the clutch part 42, and the hooking portion 33b that is formed on the other end of the coil spring

33 is fastened to the flange part 3c of the first shaft member 3.
In this embodiment, the fitting pawls 43 are formed in a saw-tooth shape, so that the clutch part 42 cannot rotate in the reverse direction. Thus, once the second shaft member 4 moves forward, the clutch part 42 does not rotate in the reverse direction, and the reaction torque due to the coil spring 33 can be made large.
(Ninth Embodiment)
In this embodiment (although not shown in the drawings), in addition to the characteristics of this invention in the first through eighth embodiments, the coil-winding direction of the coil spring is opposite to the threading direction of the male screw portion 8 of the first shaft member 3. Thereby, when the first shaft member 3 rotates as the second shaft member 4 is pushed in due to an external input load, the coil spring is twisted in such a direction that the coil diameter is reduced. Accordingly, the coil diameter does not expand, so that it is possible to prevent the coil spring from interfering with peripheral parts, thus enabling smooth operation.
Possibility of Industrial Utilization
According to the invention described in Claim 1, because an elastic mejnber is arranged between a first shaft member and a second shaft member, when an external input load is applied the elastic member always generates resistance torque, so that the amplitude of the second shaft member can be controlled precisely. Also, because the friction between the chain guide and the chain does not become large, the loss of engine output can be minimized
According to the invention described in Claim 2, in addition to the effects mentioned in Claim 1, because the coil spring that is arranged between the first shaft member and the second shaft member is compressed, frictional torque is generated so as to restrain the rotation of the first shaft member, so that the amplitude of the second shaft member can

be controlled precisely.
According to the invention described in Claim 3, in addition to the effects mentioned in Claim 1, because the coil spring that is arranged between the first shaft member and the second shaft member is twisted so as to generate reaction torque, the amplitude of the second shaft member can be controlled precisely or significantly, according to the amount of external input load that is applied.
According to the invention described in Claim 4, in addition to the effects mentioned in Claim 2, because a swivel plate that supports the coil spring is installed on either the first shaft member or the second shaft member, even when the first shaft member rotates forward and backward repeatedly, it is possible to cope with such an action of the first shaft member, and thereby to secure stable operation.
According to the invention described in Claim 5, in addition to the effects mentioned in Claims 2-4, frictional torque between the first shaft member and the spring can be made large, and the amplitude of the second shaft member can be controlled. In addition, the frictional torque can be set as desired by properly forming the shape of the spring.
According to the invention described in Claim 6, in addition to the effects mentioned in Claims 2-5, because the coil-winding direction is opposite to the threading direction of the first shaft member, the coil diameter of the coil spring does not expand, and the coil does not interfere with peripheral parts such as the case, and therefore operation proceeds smoothly.
According to the invention described in Claim 7, in addition to the effects mentioned in Claims 2-6, because the clutch part that is formed on the second shaft member twists the coil spring, reaction torque is generated on the coil spring, so that the amplitude of the second shaft member can be controlled.

According to the invention described in Claim 8, in addition to the effects mentioned in Claim I, the plate spring, the molded rubber element, and the molded resin element are compressed so as to generate fractional torque between the first shaft member and the coil spring, and thereby the amplitude of a second shaft member can be controlled.
According to the invention described in Claim 9, in addition to the effects mentioned in Claims 1-8, because the buffer plate prevents the elastic member from digging into the first shaft member, the elastic member can be smoothly operated, and abrasion of both the elastic member and the first shaft member can be controlled, thereby improving their durability.

Claims
What is claimed is:
1. A tensioner that is structured so that (1) a first shaft member and a second shaft member, which are engaged by screw portions, and a torsion spring, which gives rotating momentum to the first shaft member in one direction, are accommodated in a case, and that (2) the rotating momentum of the torsion spring is converted into the driving force of the second shaft member while rotation of the second shaft member is controlled, and which is characterized such that an elastic member that generates resistance torque against an external input load that is applied to the second shaft member is arranged between said first shaft member and said second shaft member.
2. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is (1) arranged between the first shaft member and the second shaft member while it is compressed by both shaft members, and (2) compressed by an external input load so as to generate frictional torque between the first shaft member and itself (the coil spring).
3. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a coil spring that is twisted by an external input load applied that is to the second shaft member so as to generate reaction torque in the same direction as the rotation and pressing direction of said torsion spring.
4. A tensioner as set forth in Claim 2, but characterized such that a swivel plate, which supports said coil spring, is installed on either said first shaft member or said second shaft member,
5. A tensioner as set forth in any of Claims 2-4, but characterized such that the

diameter of one end of the coil spring, which is on the side of the first shaft member, gradually decreases in the direction that is opposite to the driving direction of the second shaft member.
6. A tensioner as set forth in any of Claims 2-5, but characterized such that the coil-winding direction of said coil spring is opposite to the threading direction of the screw portion of the first shaft member.
7. A tensioner as set forth in any of Claims 2-6, but characterized such that (1) a clutch part that rotates together with the forward and backward movement of said second shaft member is formed on the second shaft member, (2) one end of said coil spring is fastened to the clutch part, and that (3) the other end of said coil spring is fastened to the first shaft member.
8. A tensioner as set forth in Claim 1, but characterized such that said elastic member is a plate spring, a molded rubber element, or a molded resin element that is (1) arranged put on while it is brought into contact with both the first shaft member and the second shaft member, and (2) compressed by an external input load so as to generate frictional torque between the first shaft member and itself (the elastic member).
9. A tensioner as set forth in any one of Claims 1-7, but characterized such that a buffer plate is inserted between said elastic member and the first shaft member.

10. A tensioner substantially as herein described with reference to the accompanying drawings.

Documents:

1549-chenp-2004-abstract.pdf

1549-chenp-2004-claims filed.pdf

1549-chenp-2004-claims granted.pdf

1549-chenp-2004-correspondnece-others.pdf

1549-chenp-2004-correspondnece-po.pdf

1549-chenp-2004-description(complete)filed.pdf

1549-chenp-2004-description(complete)granted.pdf

1549-chenp-2004-drawings.pdf

1549-chenp-2004-form 1.pdf

1549-chenp-2004-form 18.pdf

1549-chenp-2004-form 26.pdf

1549-chenp-2004-form 3.pdf

1549-chenp-2004-form 5.pdf

1549-chenp-2004-form 9.pdf

1549-chenp-2004-other document.pdf

1549-chenp-2004-pct.pdf

abs-1549-chenp-2004.jpg

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Patent Number

211862

Indian Patent Application Number

1549/CHENP/2004

PG Journal Number

02/2008

Publication Date

11-Jan-2008

Grant Date

13-Nov-2007

Date of Filing

12-Jul-2004

Name of Patentee

M/S. NHK SPRING CO., LTD

Applicant Address

10, Fukuura 3-chome, Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004,

Inventors:

#	Inventor's Name	Inventor's Address
1	KOBAYASHI, Takao	c/o NHK SPRING CO., LTD 3131, Miyadamura, Kamiina-gun, Nagano 399-4301,
2	AMANO, Tanehira	c/o NHK SPRING CO., LTD 3131, Miyadamura, Kamiina-gun, Nagano 399-4301,

PCT International Classification Number

F16H 7/08

PCT International Application Number

PCT/JP2002/013255

PCT International Filing date

2002-12-18

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2001-385253	2001-12-18	Japan