Title of Invention

TENSIONER

Abstract

A structure behaving stably even if the structure receives an input of high speed from an engine. A first shaft (3) and a second shaft (4), fixed through screw sections (8, 9), and a torsion spring (5) for rotationally urging the first shaft member (3) into one direction are received in a case (2), restraining the rotation of the second shaft member (4) to convert the rotational urging force of the torsion spring (5) into a propulsion force of the second shaft member (4). An elastic member (20) for axially urging the first shaft member (3) is provided, the elastic member (20) urging the first shaft member (3) such that a shaft end (3f) of the first shaft member (3) is in close contact with the case (2). Supporting members (25, 27) supporting the first shaft member (3) at at least two positions in the axial direction are arranged in the case (2).

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] TENSIONER; NHK SPRING CO., LTD., A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 10, FUKUURA 3-CHOME, KANAZAWA-KU, YOKOHAMA-SHI, KAN AG AWA 236-0004, JAPAN. THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. Field of the Invention The present invention relates to a tensioner that maintains constant tension of an endless belt or endless drive chain. Background of the Invention A tensioner pushes — with a predetermined force — a timing chain or timing belt used for a car engine, and acts in such a way that constant tension can be maintained even in the case of elongation of the belt or chain, so as to prevent slackness of said belt or chain. Fig. 12 shows how a tensioner 100 is incorporated into a car engine 200. Inside the car engine 200 are a pair of cam sprockets 210, 210, and a crank sprocket 220, and around those three sprockets an endless timing chain 230 is placed. A chain guide 240 is positioned in a specified place along the outside of the movement path of the chain 230 in such a way that said chain guide 240 can oscillate, and said timing chain 230 slides on the chain guide 240. The car engine 200 has a mounting surface 250 to which the tensioner 100 is affixed by bolts 270 that penetrate through-holes 260 on the mounting surface 250. The inside of the engine 200 is supplied with lubricating oil (not shown). Fig. 13 shows a generally used tensioner 100, in whose case 110 a turning shaft 120 and an impelling shaft 130 are installed. The case 110 has a body 111 that is elongated along its axis and in which the shafts 120 and 130 are inserted, and a flange 112 that is elongated along the intersecting perpendicular axis. The flange 112 is used for mounting the tensioner 100 on the engine 200. For this reason, the flange 112 has mounting holes 113, through which penetrate bolts that screw the tensioner 100 to the engine 200. The body 111 houses components described hereafter, and a hole 114 for housing that has a constant diameter along the entire length of said hole 114 is formed inside said body 111. The turning shaft 120 is installed onto the impelling shaft 130 by forming a male screw 121 on the outer surface of the turning shaft 120 and forming a female screw 131 on the inner surface of the impelling shaft 130, which two parts can then be screwed together. Inside the case 110, a strike plate 140 is arranged at the rear anchor side of the turning shaft 120 so that said strike plate 140 can be positioned inside the hole for housing 114, so as to support the rear anchor of the turning shaft 120. In an actual assembly, the impelling shaft 130 is screwed approximately halfway along the front portion of the turning shaft 120, and a torsion spring 150 is positioned approximately halfway along the back portion of the turning shaft 120, to which the impelling shaft 130 has not yet been screwed. A hook 151 on one end of the torsion spring 150 is inserted into a slit 123 that is formed at the rear anchor of the turning shaft 120, so that said hook 151 and said slit 123 engage each other, while another hook 152 on the other end of the torsion spring 150 engages with the case 110. Therefore, when the torsion spring 150 is installed under the condition that the torsion spring 150 has been twisted so as to generate torque, the turning shaft 120 turns due to the torque of the torsion spring 150. At the edge of the case 110, a bearing 160 is clamped by a retaining ring 170, and the impelling shaft 130 penetrates a hole 161 in which the bearing 160 slides. The inner surface of the hole 161 in which the bearing 160 slides and the outer surface of the impelling shaft 130 are formed so as to be elliptical, parallel cuts, or some other non-circular shape, thereby restricting the turning of the impelling shaft 130. The bearing 160 is formed in a flat plate shape of a predetermined thickness, and a plurality of fixed chips 162 (not shown) are formed on the periphery of the bearing 160. The fixed chips 162 are fastened with notched grooves 115 that are formed at the edge of the case 110, thereby preventing the bearing 160 from turning. Accordingly, the bearing 160 is prevented from turning against the case 110, and therefore the impelling shaft 130 that penetrates the bearing 160 also is prevented from turning against the case 110, and instead moves back and forth to and from the case 110. At the edge of the impelling shaft 130 is installed a cap 180 that contacts the Aforementioned chain guide 240 of the engine 200. Further, inside of the case 110 is a spacer 190 that has a tube-like shape and that surrounds the outside of the turning shaft 120 and the impelling shaft 130, thereby preventing the shafts 120 and 130, which are screwed together, from coming off of the edge of the case 110. The turning shaft 120 is formed to have a guard (not shown) for striking the spacer 190. In a tensioner 100 having the structure described above, the turning shaft 120 turns due to the torque of the torsion spring 150, and the torque is transformed into a forward-driving force on the impelling shaft 130, causing the impelling shaft 130 to move forward. Accordingly, the impelling shaft 130 pushes the timing chain 230 with the cap 180 and the chain guide 240, thereby applying pressure to the timing chain 230 and causing tension of said timing chain 230. The tensioner 100 shown in Fig. 13 cannot cope with the input load that results if great external load is imposed by the timing chain, and the impelling shaft 130 tends to be pushed back. Japanese Unexamined Patent Publication No. 2003-184968 discloses a conventional tensioner that can flexibly cope with such input load. This tensioner has basically the same structure as that shown in Fig. 13, though it includes a coil spring that is not on the structure in Fig. 13. The coil spring is positioned between the turning shaft 120 and the impelling shaft 130 so as to generate resistance torque to any external input load, thereby both preventing the impelling shaft from being pushed back and thus coping with any external input load. (Patent Document 1) Japanese Unexamined Patent Publication No. 2003-184968 In the tensioner of Japanese Unexamined Patent Publication No. 2003-184968, there is the problem that slanting and rising of the tensioner can occur, which means that stable behavior of said tensioner cannot be ensured, because the impelling shaft surges up and down when high-speed operation of the engine generates a high level of vibration, including lateral vibration. Here, high vibration includes both high load vibration and high-frequency vibration. The object of the present invention is to provide a tensioner that ensures stable behavior under such high levels of vibration, including lateral vibration. Disclosure of the Invention In order to attain the aforementioned objective, the invention cited in Claim 1 provides a tensioner that includes a case that contains a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction, thereby transforming the turning force into a forward-driving force for the second shaft without turning the second shaft. Said case also includes an elastic member that forces the first shaft along said shaft's axis so that the first shaft's end that is on the side opposite to the second shaft will contact said case. In the invention described in Claim 1, the elastic member pushes the end of the first shaft toward the case so as not to lift the first shaft from the case, but to constantly generate a certain amount of friction torque between the first shaft and the case. Therefore, the behavior of the entire tensioner, including the first shaft and the second shaft, which are screwed together, remains stable. The invention described in Claim 2 provides a tensioner that includes a case that contains a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction, thereby transforming said turning force into a forward-driving force for the second shaft without turning said second shaft. Said case also includes supporters that support the first shaft in at at least two places along said shaft's axis. In the invention described in Claim 2, the supporters support the first shaft in at least two places, so that the first shaft is supported rigidly. Therefore, even when there is lateral vibration, the first shaft remains straight, and the behavior of the entire tensioner, including the first shaft and the second shaft, which are screwed together, remains stable. The invention described in Claim 3 provides a tensioner that includes a case that contains a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction, transforming said turning force into a forward-driving force for the second shaft without turning the second shaft. Said case also includes an elastic member that forces the first shaft along said shaft's axis so that the first shaft's end that is on the side opposite to the second shaft will contact said case, and supporters that support the first shaft in at at least two places along said shaft's axis. In the invention described in Claim 3, the elastic member pushes the first shaft's end that is on the side opposite to the second shaft toward the case so that the first shaft does not rise from the case, and supporters support the first shaft in at least two places along said shaft's axis, so that the first shaft is supported rigidly. Therefore, even if there occurs a high level of vibration, including high load vibration or high-frequency vibration, the first shaft does not move upward, and if lateral vibration occurs the first shaft does not slant. Accordingly, stable behavior is ensured even when the engine is operating at high speed. The invention described in Claim 4 provides a tensioner as described in Claims 2 and 3, but wherein both of the supporters support the first shaft by pressing against the outside of said first shaft. In the invention described in Claim 4, the supporters support the first shaft by pressing against the outside of said first shaft, enabling said first shaft to be supported whether or not grooving and/or other processing has been done on the end of the first shaft, and leading to stable support of said first shaft. The invention described in Claim 5 provides a tensioner as described in any of Claims 1 through 4, but having the first shaft divided into an unthreaded shaft-part, which is supported by the aforementioned supporters, and a threaded shaft-part, which is screwed together with the second shaft and connected together so that said threaded shaft-part and said second shaft engage with each other. In the invention described in Claim 5, the unthreaded shaft-part and the threaded shaft-part of the first shaft, which are divided as mentioned above, engage with each other so that they turn in a united way, operating as a single shaft. Further, in the invention of Claim 5, lateral vibration generated by the engine is transferred to the second shaft, so that vibration is transferred to the first shaft's threaded shaft-part, which is engaged with the second shaft, and the threaded shaft-part of the first shaft moves from side to side in response to said lateral vibration. Said side-to-side movement reduces the lateral load. The unthreaded shaft-part of the first shaft, which is engaged with the threaded shaft-part of said first shaft, is supported at at least two places by the aforementioned supporters, and therefore the first shaft does not slant, so that the behavior of the entire tensioner remains stable. Brief Description of the Drawings Fig. 1 is a cross-sectional view of the tensioner in the first embodiment of the present invention. Fig. 2 is a cross-sectional view of the tensioner in the second embodiment of the present invention. Fig. 3 is a cross-sectional view of the tensioner in the third embodiment of the present invention. Fig. 4 is a cross-sectional view of a ring plate used as a supporter. Fig. 5 is a cross-sectional view of a ring guide used as a supporter. Fig. 6 is a side view of the first shaft divided into two parts. Fig. 7 is a cross-sectional view of the tensioner in the fourth embodiment of the present invention. Fig. 8 is a cross-sectional view of the tensioner in the fifth embodiment of the present invention. Fig. 9 is a cross-sectional view of the first shaft divided into two parts. Fig. 10 contains (a) a side view and (b) a front view of an unthreaded shaft-part in another structure of a first shaft that is divided into two parts. Fig. 11 contains (a) a side view and (b) a front view of a threaded shaft-part in another structure of a first shaft that is divided into two parts. Fig. 12 is a cross-sectional view of a tensioner attached to an engine. Fig. 13 is a cross-sectional view of a conventional tensioner. (Explanation of the Numbers Used in the Drawings) 2 Case 3 First shaft 4 Second shaft 5 Torsion spring 8 Male thread 9 Female thread 15 Strike plate (supporter) 20 Coil spring (elastic member) 25 Ring guide (supporter) 7 Ring plate (supporter) Preferred Embodiments of the Invention Hereafter, concrete descriptions will be given of preferred embodiments of the invention, referring to the drawings. For each embodiment, the same numbers are used for the same parts. (The first embodiment) Fig. 1 shows the first embodiment of the present invention, as the tensioner A1, which comprises a case 2, a first shaft 3, a second shaft 4, a torsion spring 5, a guide 6, and a spacer 7. The case 2 has a body 2a and a flange 2b that extends in an almost-right-angle direction from the body 2a. A housing hole 2c extends from the body 2a to the flange 2b along the axis of the case 2 (impelling direction). The housing hole 2c is open, and the first shaft 3, second shaft 4, the torsion spring 5 and the spacer 6 are housed in said hole in an assembled condition. The flange 2b includes through-holes for installation 2d that are penetrated by bolts (not shown) that affix the case 2 to the engine 200. When the case 2 is being affixed to the engine 200, the flange 2b's surface that is nearest to the engine (i.e., the right-side surface of the flange 2b in Figure 1) contacts the installation surface 250 of the engine 200, which latter two parts are shown in Fig. 12. The first shaft 3 turns as a result of being driven by the torsion spring 5, and the second shaft 4 is moved forward due to the turning of the first shaft 3. The first shaft 3 is formed in such a manner that the unthreaded shaft-part 3a at the rear anchor side and the threaded shaft-part 3b at the edge of the first shaft 3 are formed as a unified whole that extends along the axis of the first shaft 3, and a male thread 8 is formed on the outside of the threaded shaft-part 3b of the first shaft 3. The rear anchor (left-hand side in Figure 1 or 2) of the first shaft 3a contacts the strike plate 15, which supports the turning of the first shaft 3. The strike plate 15 serves to support the first shaft 3. The strike shaft 15 contacts the edge 3f of the first shaft 3 from what is the right side in Fig. 1, thereby supporting the first shaft 3. At the end 3f of the unthreaded shaft-part 3a, there is a slit 3e for inserting a jig (not shown) that is used for turning the first shaft 3. The slit 3e aligns with a jig hole 2e that is formed on the surface of the rear anchor of the body 2a, and the torsion spring 5 is wound by inserting the edge of the jig into the slit 3e through the jig hole 2e and using that tool to turn the first shaft 3. In the situation shown in Fig. 1, a stopper 16 has been inserted into both the jig hole 2e and the slit 3e so as to prevent the first shaft from turning. The inner surface of the jig hole 2e is female threaded, so that a seal bolt 18 (which will be described later) can be screwed into said jig hole 2e. The second shaft 4 has a tube-like form, and on its inner surface a female thread 9 is formed so that the male thread 8 of the first shaft 3 can be screwed into said second shaft 4. The first shaft 3 and the second shaft 4 are inserted into the housing hole 2c of the case 2, with the female thread 9 and the male thread 8 being screwed together. On the tip of the second shaft 4, a cap 10 is installed and a spring pin 11 is press-fitted to prevent the cap from separating from the second shaft 4. In this embodiment, the torsion spring 5 is arranged around the second shaft 4, and the threaded shaft-part 3b of the first shaft 3 is inserted into the torsion spring 5. A hook 5a on one end of the torsion spring 5 is inserted into a groove hook (not shown) so as to engage with said groove hook, while a hook (not shown) on the other end of the torsion spring 5 is inserted into the first shaft 3 so as to engage with said first shaft 3. Accordingly, winding the torsion spring 5 generates torque for turning the first shaft 3. A guide 6 is installed on the edge of the case 2 and is affixed to the case 2 by a circlip 13. The guide 6 has a guide hole 6a that enables the second shaft 4 to penetrate through the guide hole 6a along the axis of the second shaft 4. The inner surface of the guide hole 6a and the outer surface of the second shaft 4 have an elliptic shape, a D cut, a parallel cut or other non-circular shape, thereby preventing the turning of the second shaft 4. A plurality of fixed chips 6b are formed in a radial pattern on the outside of the guide 6, and the fixed chips 6b are fastened to notched grooves on the edge of the case 2, thereby preventing the guide 6 from turning. With the guide 6 being prevented from turning against the case 2, the second shaft 4, which penetrates through the guide 6, is prevented by the guide 6 from turning against the case 2. The second shaft 4 is screwed together with the threaded shaft-part 3b by screws 8 and 9 so that the turning of the first shaft 3, which is driven by the torque of the torsion spring 5, is transferred to the second shaft 4. But the guide 6 prevents the second shaft 4 from turning, thereby causing a back-and-forth motion of said second shaft against the case 2. The spacer 7 has a tube-like shape, and the screwed part of the threaded shaft-part 3b that is screwed together with the second shaft 4 is inserted into the inside of the tube. In this case, a large-diameter flange 3c is formed at the boundary between the unthreaded shaft-part 3a and the threaded shaft-part 3b, and the rear anchor of the spacer 7 contacts the flange 3c. The edge of the spacer 7 faces the guide 6 and — by making contact with the guide 6 — prevents the first shaft 3 and the second shaft 4 from coming off from the case 2. In the tensioner A1 attached to an engine, a seal bolt 18, by being screwed into the jig hole 2e of the case 2 after the stopper 16 has been pulled out from the case 2, prevents oil from leaking out of the jig hole 2e. In this embodiment, a coil spring 20 is arranged as an elastic member in the case 2, and the unthreaded shaft-part 3a of the first shaft 3 is inserted into the coil spring 20. A compression spring is used as the coil spring 20. The coil spring 20 is in a compressed form, the unthreaded shaft part 3a is inserted in said coil spring 20, a suppression annulus 21 is formed at the rear anchor of the unthreaded shaft-part 3a in a united form with the unthreaded shaft part 3a, and a suppression ring 22 is press-fitted into the housing hole 2c of the case 2. The coil spring 20 has free ends and is arranged between the suppression annulus 21 and the suppression ring 22 in a compressed form so that the end 3f of the first shaft 3 is forced against the strike plate 15. The coil spring 20 presses the end 3f of the first shaft 3 against the strike plate 15 so that the coil spring 20 forces the end 3f of the first shaft 3 to always exert pressure, via the strike plate 15, against the case 2. The unthreaded shaft-part 3a of the first shaft 3 penetrates through the suppression ring 22 having a space between the shaft part and the ring. The edge 3f of the first shaft 3 is pressed toward the case 2 due to the torque of the coil spring 20 as an elastic member, so that the first shaft 3 does not move upward from the case 2 even if the engine emits a high level of vibration in the form of high load vibration or high-frequency vibration. Constant torque is generated between the first shaft 3 and the case 2 (strike plate 15), leading to stable behavior even when vibration is at a high level. (The second embodiment) Fig. 1 shows the second embodiment of the present invention, as the tensioner A2. In this embodiment, a ring guide 25 is added against the strike plate 15 as a supporter. The ring guide 25 is press-fitted into the press-fit step 2g that is formed on the inner part of the case 2 so as to support the unthreaded shaft-part 3a of the first shaft 3. In addition, the unthreaded shaft-part 3a is supported from its outside so as to be able to be turned by the ring guide 25. In the unthreaded shaft-part 3a of the first shaft 3, an engagement slit 3h is formed to extend along the axis of the first shaft 3, and a hook 5b at the other end of the torsion spring 5 is inserted into the slit 3h so as to engage the unthreaded shaft-part 3a of the first shaft 3 and the torsion spring 5. In this structure, the unthreaded shaft-part 3a is supported by the strike plate 15 at the tip of the first shaft 3f and the middle part of the unthreaded shaft-part 3a is supported by the ring guide 25 so that the first shaft 3 will not slant even when lateral vibrations are received via the second shaft 4. Therefore, the first shaft 3 and second shaft 4 can behave stably, and the behavior of the entire tensioner remains stable. In this embodiment, the coil spring 20 is not provided as an elastic member as in the first embodiment, but the first shaft 3 is supported in two places, and thereby slanting of the first shaft 3 is prevented, which in turn promotes stable behavior. (The third embodiment) Figs. 3 through 5 show the third embodiment of the present invention, as tensioner A3. In this embodiment, the first shaft 3 is divided into two parts, an unthreaded shaft-part 31 and a threaded shaft-part 32. The unthreaded shaft-part 31 is located at the rear anchor side, while the threaded shaft-part 32 is located on the same side as the second shaft 4, and a male thread 8 is formed on the outside of the threaded shaft-part 32 so as to enable said first shaft 3 to be screwed together with the second shaft 4. The end faces of the unthreaded shaft-part 31 and the threaded shaft-part 32, which face each other, are formed so as to be able to engage with each other. As shown in Figs. 6 and 7, (1) a flange 3c is formed at the end face at the rear anchor side of the threaded shaft-part 32, (2) said flange 3c contacts the spacer 7, (3) a fitting projection 32a, which has a circular cross-section, protrudes from the flange 3c, and (4) an engagement projection 32b, which has a rectangular cross-section, protrudes from said fitting projection 32a. At the end face of the edge side of the unthreaded shaft part 31 that is connected with the threaded shaft-part 32 are formed (1) a fitting groove 31a into which the fitting projection 32a enters, and (2) an engagement slit 3h into which the engagement projection 32b enters so as to engage with said engagement slit 3h. As shown in Fig. 3, the hook 5b at one end of the torsion spring 5 enters into the slit 3h of the unthreaded shaft-part 31 so as to engage the torsion spring 5 with the first unthreaded shaft-part 31, so that the torque of the torsion spring 5 is transferred to the first unthreaded shaft-part 31. When the unthreaded shaft-part 31 and the threaded shaft-part 32 are connected with each other along the axis of the first shaft 3, the engagement projection 32b enters into the slit 3h so that the unthreaded shaft-part 31 and the threaded shaft-part 32 are engaged together and can turn as a unified object. Therefore, the first shaft can operate as a first shaft made as a single rod. At the rear anchor side of the unthreaded shaft-part 31, a suppression ring 21 is formed in a united form with the unthreaded shaft-part 31, and a small-diameter rod 33 protrudes from the suppression ring 21. A slit 3e for inserting a stopper 16 is formed at the end face of the rod 33. In this embodiment, a ring plate 27 and ring guide 25 serve as supporters that support the turning of the first shaft 3. The ring guide 25 is press-fitted into the press-fit step 2g that is formed in the case as in the second embodiment, supporting the middle part of the unthreaded shaft-part 31 of the first shaft 3. Fig. 5 shows a cross-section of the ring guide 25, which is press-fitted into the press fit stage 2g. The unthreaded shaft-part 31 is inserted into the through-hole at the center of the ring guide 25 so as to be supported by the ring guide 25. Accordingly, the ring guide 25 supports the unthreaded shaft-part 31 by pressing against the outside of the unthreaded shaft-part 31. The ring plate 27 is press-fitted into the housing hole 2c at the rear anchor side of the case 2. Fig. 4 shows a cross-section of the ring plate 27, at the center of which is formed a through-hole 27a for inserting the rod 33. The ring plate 27 supports the unthreaded shaft-part 31 via the inner surface of the through-hole 27a, and, together with the ring guide 25, also supports of the shaft 31 via the outside of said shaft 31. In such support of the ring plate 27, the slit 3e does not contact the case 2 and does not affect the torque of the unthreaded shaft-part 31, providing stable turning of the first shaft 3. In this embodiment, as in the second embodiment, the first shaft 3 is supported in two places, by the ring guide 25 and by the ring plate 27, thereby giving rigid support to said first shaft 3. Especially for this embodiment, the first shaft 3 is divided into two parts, an unthreaded shaft-part 31 and the a threaded shaft-part 32, which are screwed together with the second shaft 4, so that lateral vibration from the engine is transferred to the second shaft 4 and then to the threaded shaft-part 32. Therefore, the threaded shaft-part 32 moves side to side in response to lateral vibration, thereby reducing the lateral input load. The unthreaded shaft-part 31 that is engaged with the threaded shaft-part 32 is supported in two places, by the ring guide 25 and by the ring plate 27, thereby preventing slanting of the first shaft 3, which in turn provides stable support of the case. Accordingly, the behavior of the entire tensioner remains stable. Moreover, the first shaft 3 consists of two parts, the unthreaded shaft-part 31 and the threaded shaft-part 32, and that structure enhances flexibility in designing the tensioner. In this embodiment, a guide hole 6a (in a guide 6), through which the second shaft 4 penetrates under the condition that turning is prevented, is larger than the outer diameter of the second shaft 4. The guide hole 6a restricts the turning of the second shaft 4 and is formed in a non-circular shape similar to that of the second shaft 4 and in such a way that the opening of said guide hole 6a is larger than the cross-section of the second shaft 4. The guide hole 6a is large enough to ensure that there is enough space around the second shaft 4 so that said second shaft 4 can move from side to side in response to such movement of the threaded shaft-part 32, and the side-to-side swinging of the second shaft prevents the threads of the threaded shaft-part 32 from getting locked with those of the second shaft 4s. Accordingly, the part in which the threaded shaft-part 32 is screwed together with the second shaft 4 does not seize these screwed-together parts, so that the side-to-side movement of the second shaft 4 continues to cause the threaded shaft-part 32 (the first shaft 3) to turn smoothly, thereby ensuring smooth operation of the tensioner. (The fourth embodiment) Fig. 7 shows a fourth embodiment of the present invention, as the tensioner A4. In this embodiment of the tensioner, the first shaft 3 is divided into two parts, an unthreaded shaft-part 31 and a threaded shaft-part 32. The shape and structure of connection of the unthreaded shaft-part 31 and the threaded shaft-part 32 are the same as those of the tensioner A3 in the third embodiment, as shown in Fig. 6. In this embodiment, the first shaft 3 is supported in two places by two supports, the ring guide 25 and the ring plate 27. Such support by the ring guide 25 and the ring plate 27 is the same as that in the third embodiment, as shown in Figs. 4 and 5. Further, in this embodiment, a coil spring 20 is provided as an elastic member. The coil spring 20 is positioned in a compressed manner between the suppression ring 21 of the unthreaded shaft-part 31 of the first shaft 3 and the ring guide 25 that is press-fitted in the case 2, so that the end 3f of the first shaft 3 is forced to constantly contact the ring plate 27. Accordingly, the end 3f of the first shaft 3 is forced along the axis of the first shaft 3 so as to constantly contact the case 2. Therefore, even when there occurs a high level of vibration, such as high load vibration or high-frequency vibration, the first shaft 3 can be prevented from moving up from the case 2, which leads to stable behavior of the tensioner even when 'there occurs a high level of vibration. In this embodiment, as in the third embodiment, the first shaft 3 is divided into an unthreaded shaft-part 31, which is supported by the ring guide 25 and by the ring plate 27, and a threaded shaft-part 32, which are screwed together with the second shaft 4. The threaded shaft-part 32 swings side to side in response to lateral vibration from the engine, thereby preventing the threads of the threaded shaft-part 32 from getting locked with those of the second shaft 4, and also reducing the lateral input load. The unthreaded shaft-part 31, which is engaged with the threaded shaft-part 32, is supported in two places, by the ring guide 25 and by the ring plate 27, thereby preventing slanting of the first shaft 3, which in turn provides stable support of the case 2. Therefore, the behavior of the entire tensioner remains stable. In order to ensure said side-to-side movement of the threaded shaft-part 32, the guide hole 6a (of the guide 6) through which the second shaft 4 penetrates under the condition that turning is prevented, is larger than the diameter of the second shaft 4. Accordingly, in this embodiment, the first shaft does not move upward even when there is a high level of vibration, and — even when there is lateral vibration — said shaft moves side to side so as to reduce the lateral vibration, leading to stable behavior of the tensioner, even when the engine is operating at high speed. Moreover, the slit 3e of the unthreaded shaft-part 31 does not contact the case 2 and does not affect the torque of the unthreaded shaft-part 31, leading to stable turning of the first shaft 3. (The fifth embodiment) Fig. 8 shows a fifth embodiment of the present invention, as the tensioner A5. For this embodiment as the tensioner A5, as in the third and fourth embodiments, the first shaft 3 is divided into two parts, an unthreaded shaft-part 31 and a threaded shaft-part 32. The coil spring 20 is positioned in a compressed form between the suppression ring 21 of the unthreaded shaft-part 31 and the ring guide 25 that is press-fitted in the case 2, and the "end 3f of the first shaft 3 is forced to constantly contact the ring plate 27 (the case 2). In this embodiment, the middle part of the unthreaded shaft-part 31 of the first shaft 3 is supported by the ring guide 25, while the end 3f of the unthreaded shaft-part 31 is supported by the strike plate 15. In this embodiment, the end 3f of the first shaft 3 is pressed against the case 2 by the torque of the coil spring 20, so that the first shaft 3 is forced not to move upward from the case even when a high level of vibration is received from the engine. When lateral vibration is transferred from the engine to the second shaft 4, the threaded shaft-part 32, which is engaged with the second shaft 4, moves side to side in response to the lateral vibration, thereby reducing the lateral input load. Also, the unthreaded shaft-part 31, which is engaged with the threaded shaft-part 32, is supported in two places, by the ring guide 25 and by the ring plate 27, thereby preventing slanting of the first shaft 3, which in turn provides stable support of the entire tensioner A5. Therefore, even if the engine is operating at high speed, the behavior of the tensioner remains stable. In this embodiment, the guide hole 6a (of the guide 6), through which the second shaft 4 penetrates under the condition that turning is prevented, is larger than the diameter of the second shaft 4, ensuring that the threaded shaft-part 32 and the second shaft 4 can move side to side. (The sixth embodiment of the present invention) This embodiment includes another structure in which the first shaft 3 is divided into an unthreaded shaft-part 31 and a threaded shaft-part 32. In Fig. 9, the fitting projection 32a (of the threaded shaft-part 32) that protrudes from the flange 3c has a tapered shape. The fitting groove 31a of the unthreaded shaft-part 31 also has a matching tapered shape that enables said fitting groove 31a and the fitting projection 32a to closely contact each other. In this structure, the unthreaded shaft-part 31 can rigidly engage with the threaded shaft-part 32. In Figs. 10 and 11, the fitting projection 32a of the threaded shaft-part 32 is formed so as to have six facets (also see Fig. 11), and the fitting groove 31a of the unthreaded shaft-part31 is formed so as to match the fitting projection 32a. When the fitting projection 32a and the fitting groove 31a are engaged together, the unthreaded shaft-part 31 and the threaded shaft-part 32 are strongly connected to each other. In the embodiment just described, the first shaft 3 is supported in two places, but it can be supported at three or more places. Industrial Applicability The tensioner of the present invention provides a first shaft, which does not move upward or slant, behaving stably even when the engine is operating at high speed. WE CLAIM 1. A tensioner wherein a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction are housed in a case, and turning of the second shaft is restrained so that the turning force of the torsion spring is transformed into a forward-driving force that acts on the second shaft without turning said second shaft, and an elastic member is arranged such that said member applies pressure on the first shaft in its axial direction so as to make the first shaft's end that is on the side opposite to the second shaft contact said case. 2. A tensioner wherein a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction, are housed in a case, turning of the second shaft is restrained so that the turning force of the torsion spring is transformed into a forward-driving force that acts on the second shaft without turning said second shaft, and supporters that support the first shaft at at least two places along said shaft's axis are arranged in said case. 3. A tensioner wherein a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction, are housed in a case, turning of the second shaft is restrained so that the turning force of the torsion spring is transformed into a forward-driving force that acts on the second shaft without turning said second shaft, an elastic member is arranged such that said member applies pressure on the first shaft in its axial direction so as to make the first shaft's end that is on the side opposite to the second shaft contact said case, and supporters that support the first shaft at at least two places along said shaft's axis are arranged in said case. 4. A tensioner as described in Claim 2 or 3, wherein both of the supporters support the first shaft by pressing against the outside of said first shaft. 5. A tensioner as described in any of Claims 1 through 4, wherein the first shaft is divided into an unthreaded shaft-part, which is supported by the supporters, and a threaded shaft-part, which is screwed together with the second shaft, and the unthreaded shaft-part and the threaded shaft-part are connected together so as to engage each other. Dated this 21st day of June, 2006. FOR NHK SPRING CO., LTD. By their Agent (MANISH SAURASTRI) KRISHNA & SAURASTRI ABSTRACT A structure that maintains stable behavior even when receiving a high level of vibration from an engine. A tensioner that includes a case that contains a first shaft and a second shaft, which are screwed together, and a torsion spring that forces the first shaft to turn in one direction. Turning of the second shaft 4 is restrained so that the turning force of the torsion spring 5 is transformed into a forward-driving force that acts on the second shaft 4 without turning said second shaft. An elastic member 20 is arranged such that said member applies pressure on the first shaft 3 in its axial direction so as to make the first shaft's end 3f that is on the side opposite to the second shaft 4 contact said case. Supporters 25, 27 that support the first shaft 3 at at least two places along the axis of the shaft are arranged inside the case 2.

Documents:

728-mumnp-2006-abstract(granted)-(6-5-2008).pdf

728-mumnp-2006-abstract.doc

728-mumnp-2006-abstract.pdf

728-mumnp-2006-cancelled pages(24-10-2007).pdf

728-mumnp-2006-claims(amended)-(1)-(24-10-2007).pdf

728-mumnp-2006-claims(amended)-(24-10-2007).pdf

728-mumnp-2006-claims(granted)-(6-5-2008).pdf

728-mumnp-2006-claims.doc

728-mumnp-2006-claims.pdf

728-mumnp-2006-correspondance-received.pdf

728-mumnp-2006-correspondence(24-10-2007).pdf

728-mumnp-2006-correspondence(ipo)-(21-5-2008).pdf

728-mumnp-2006-description (complete).pdf

728-mumnp-2006-description(granted)-(6-5-2008).pdf

728-mumnp-2006-drawing(granted)-(6-5-2008).pdf

728-mumnp-2006-drawings.pdf

728-mumnp-2006-form 1(18-9-2006).pdf

728-mumnp-2006-form 18(12-12-2006).pdf

728-mumnp-2006-form 2(granted)-(6-5-2008).pdf

728-mumnp-2006-form 2(title page)-(21-6-2006).pdf

728-mumnp-2006-form 2(title page)-(granted)-(6-5-2008).pdf

728-mumnp-2006-form 3(18-9-2006).pdf

728-mumnp-2006-form-1.pdf

728-mumnp-2006-form-2.doc

728-mumnp-2006-form-2.pdf

728-mumnp-2006-form-3.pdf

728-mumnp-2006-form-5.pdf

728-mumnp-2006-power of attorney(4-10-2006).pdf

728-mumnp-2006-wo international publication report(21-6-2006).pdf

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