JP5311226B2 - Auto tensioner - Google Patents

Description

  The present invention relates to an auto tensioner mainly used for maintaining tension of a chain or a toothed belt for driving a camshaft of an automobile engine.

  In general, the engine of an automobile transmits rotation of a crankshaft to a camshaft via a chain or a toothed belt (hereinafter, a chain will be described as an example), and the rotation of the camshaft opens and closes a valve of a combustion chamber. To do. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device consisting of a chain guide that can swing around a fulcrum shaft and an auto tensioner that presses the chain via the chain guide is often used. It is done.

  As an auto tensioner incorporated in the tension adjusting device, for example, an auto tensioner using a hydraulic damper mechanism such as an auto tensioner described in Patent Document 1 is known.

  The auto tensioner described in Patent Document 1 is filled with hydraulic oil in a cylindrical housing with one end open and the other end closed, and the rod moves in the axial direction with one end protruding from the housing. The annular gap between the rod and the housing is sealed with a sealing member, a sleeve is coaxially provided in the housing, and a piston is slidably inserted into the sleeve, and the piston housing is closed. A pressure valve formed on the end side and a reservoir chamber formed on the open end side of the piston housing are provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side. The pressure chamber communicates with the reservoir chamber via a second passage that restricts the flow rate of the hydraulic oil, and the piston is disposed in the pressure chamber. Incorporate spring urges the is obtained by supporting the rod in the piston.

  When the chain tension increases during engine operation, the auto tensioner moves in the direction in which the rod is pushed into the housing (hereinafter referred to as “push-in direction”) due to the chain tension, and absorbs the tension of the chain. At this time, the hydraulic oil flows from the pressure chamber to the reservoir chamber through the second passage that restricts the flow rate of the hydraulic oil, and a damper action is generated by the viscous resistance of the hydraulic oil, so that the rod moves slowly.

  On the other hand, when the tension of the chain is reduced during engine operation, the rod is moved in a direction protruding from the housing (hereinafter referred to as “protruding direction”) by the biasing force of the spring, and the slackness of the chain is absorbed. At this time, the check valve is opened, and hydraulic oil flows from the reservoir chamber to the pressure chamber through the first passage, so that the rod moves quickly.

  Further, as an auto tensioner incorporated in the tension adjusting device, there is known an auto tensioner using screw friction like the auto tensioner described in Patent Document 2.

  The auto tensioner described in Patent Document 2 is filled with hydraulic oil in a cylindrical housing with one end open and the other end closed, and the rod moves in the axial direction with one end protruding from the housing. The annular gap between the rod and the housing is sealed with a seal member, a nut member is provided coaxially in the housing, and a male screw that engages with an internal screw of the nut member is provided on the outer periphery. A screw rod is provided, a spring is provided to urge the screw rod toward the open end of the housing, and the insertion end of the rod into the housing is supported by the screw rod.

  In this auto tensioner, when the tension of the chain increases during engine operation, the load in the pushing direction applied to the rod by the tension of the chain is received by the male screw of the screw rod and the female screw of the nut member. The accompanying slip between the male and female threads accumulates and the rod gradually moves in the pushing direction to absorb chain tension. At this time, since the slip between the male screw and the female screw accompanying the vibration of the chain is minute, the moving speed of the rod is limited, and a damper action occurs.

  On the other hand, when the tension of the chain becomes small during engine operation, the rod moves in the protruding direction by the biasing force of the spring, and absorbs the slack of the chain.

JP 2006-90440 A JP 2007-24200 A

  By the way, when the engine is stopped, the chain tension may increase depending on the stop position of the camshaft.

  At this time, in the auto tensioner described in Patent Document 1, the rod largely moves in the pushing direction due to the tension of the chain. Therefore, when the engine is restarted, the chain is slackened, and the engine may not be started smoothly.

  On the other hand, in the auto tensioner described in Patent Document 2, even if the chain tension increases when the engine is stopped, the chain is stationary without vibration, and therefore, between the male screw of the screw rod and the female screw of the nut member. No sliding occurs and the rod does not move. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

  On the other hand, in the auto tensioner described in Patent Document 1, since the amount of movement of the piston increases according to the amplitude of the chain, when the amplitude of the chain during engine operation is large (for example, in the engine in a specific rotation range) Even when resonance occurs or when the rotational fluctuation of the camshaft or crankshaft during the combustion cycle is large), it is possible to sufficiently absorb the vibration of the chain.

  In contrast, the auto tensioner described in Patent Document 2 does not change the amount of slip between the male screw and the female screw even when the amplitude of the chain changes. The vibration of the chain cannot be sufficiently absorbed, and the chain tension may be excessive.

  The problem to be solved by the present invention is that the vibration of the chain can be sufficiently absorbed even when the amplitude of the chain is large, and even if the chain tension increases when the engine is stopped, the engine can be started smoothly. It is to provide a possible auto tensioner.

  In order to solve the above-mentioned problems, hydraulic oil is filled in a cylindrical housing with one end opened and the other end closed, and the plunger can move in the axial direction with one end protruding from the housing. The annular gap between the plunger and the housing is sealed with a sealing member, and a sleeve is coaxially provided in the housing, and a piston is slidably inserted into the sleeve. A first passage provided with a check valve that allows only the flow of hydraulic oil from the reservoir chamber side to the pressure chamber side between the pressure chamber formed in the piston chamber and the reservoir chamber formed on the open end side of the piston housing The pressure chamber and the reservoir chamber through a second passage that restricts the flow rate of the hydraulic oil, and the piston is directed toward the open end of the housing. Incorporating a piston spring that biases, a stopper is provided for restricting the range of movement of the piston toward the closed end of the housing, and the plunger is formed into a bottomed cylindrical shape with the insertion end into the housing open, A screw rod having a male screw on its outer periphery that engages with a female screw formed on the inner periphery of the plunger is provided, a return spring is provided to urge the screw rod in a direction to protrude from the plunger, and the protruding end of the screw rod from the plunger A configuration in which the piston is supported by the piston is employed in the auto tensioner.

  When the chain tension increases during engine operation, the auto tensioner moves in a direction in which the plunger is pushed into the housing by the chain tension, and absorbs the chain tension. At this time, the hydraulic oil flows from the pressure chamber to the reservoir chamber through the second passage that restricts the flow rate of the hydraulic oil, and a damper action is generated by the viscous resistance of the hydraulic oil, so that the plunger moves slowly.

  On the other hand, when the tension of the chain is reduced during the operation of the engine, the plunger moves in a direction protruding from the housing by the urging force of the piston spring to absorb the slack of the chain. At this time, the check valve is opened and hydraulic oil flows from the reservoir chamber to the pressure chamber through the first passage, so that the plunger moves quickly.

  When the chain extends over time, the screw rod and the plunger gradually rotate relative to each other due to the vibration of the chain, and the protruding amount of the screw rod from the plunger increases. As a result, the amount of protrusion of the plunger from the housing increases, and the chain elongation can be absorbed.

  When the engine is stopped, the chain tension may increase depending on the stop position of the camshaft.In this case, the chain is stationary without vibration, so slippage occurs between the screw rod male screw and plunger female screw. The screw rod and the plunger do not rotate relative to each other. Further, the piston moves toward the closed end of the housing due to the tension of the chain, but since the moving range is regulated by the stopper, the plunger moves only slightly in the pushing direction. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.

  As the stopper, for example, a stepped portion formed on the inner periphery of the sleeve so that the closed end side of the housing has a smaller diameter than the open end side of the housing can be adopted.

  If an assist spring that urges the plunger in a direction in which the plunger protrudes from the housing is incorporated in the housing, the followability of the plunger with respect to fluctuations in chain tension can be improved.

  A retaining protrusion for retaining the piston from the sleeve can be provided on the inner periphery of the open end side of the housing of the sleeve. In this way, when the load in the pushing direction applied to the plunger is released (for example, when the auto tensioner is removed from the engine to maintain the engine), the piston is released from the sleeve by the biasing force of the piston spring. Can be prevented.

  For example, a retaining ring attached to the inner periphery of the sleeve may be employed as the retaining protrusion, but it is inexpensive to employ a retaining protrusion formed by crimping the end surface of the sleeve.

  A sub-reservoir chamber communicating with the reservoir chamber may be provided in the upper portion of the housing, and an air reservoir may be provided on the hydraulic oil in the sub-reservoir chamber. If it does in this way, the volume change in the housing accompanying movement of a plunger can be absorbed by the air pocket, and movement of a plunger becomes smooth.

  For example, the first passage may be provided between the inner and outer circumferences of the housing and the sleeve, or may be provided in the piston. When provided in the piston, the check valve can be composed of a spherical valve body that opens and closes an opening on the pressure chamber side of the first passage, and a retainer that regulates a moving range of the valve body. A steel ball can be used as the valve body, but if a ceramic ball is used, the valve body can be reduced in weight, and the responsiveness of the check valve to the pressure change in the pressure chamber is improved.

  As the second passage, for example, a small-diameter hole penetrating the piston may be employed, but a small gap formed between the sliding surface of the piston and the sleeve is inexpensive.

  The male screw and the female screw are formed in a sawtooth shape in which the flank angle of the pressure side flank that receives pressure when a load in the direction of pushing the screw rod into the plunger is applied is larger than the flank angle of the play side flank. Can be adopted.

  The auto tensioner according to the present invention can start the engine smoothly because the pushing amount of the plunger is small when the chain tension increases when the engine is stopped. Further, even when the amplitude of the chain during operation of the engine is large, it is possible to sufficiently absorb the vibration of the chain.

The front view which shows the chain transmission device incorporating the auto tensioner of 1st Embodiment of this invention Fig. 1 is an enlarged cross-sectional view near the auto tensioner. Enlarged cross-sectional view along line III-III in FIG. FIG. 2 is an enlarged cross-sectional view of the vicinity of the piston showing a process in which the plunger shown in FIG. 2 moves in the protruding direction. FIG. 2 is an enlarged cross-sectional view in the vicinity of the piston showing a process in which the plunger shown in FIG. 2 moves in the pushing direction. The expanded sectional view which shows the auto tensioner of 2nd Embodiment of this invention FIG. 6 is an enlarged sectional view taken along line VII-VII.

  FIG. 1 shows a chain transmission incorporating the auto tensioner 1 according to the first embodiment of the present invention. In this chain transmission device, a sprocket 3 fixed to an engine crankshaft 2 and a sprocket 5 fixed to a camshaft 4 are connected via a chain 6, and the chain 6 rotates the crankshaft 2. This is transmitted to the camshaft 4, and the valve (not shown) of the combustion chamber is opened and closed by the rotation of the camshaft 4.

  The chain 6 is in contact with a chain guide 8 that is swingably supported about the fulcrum shaft 7, and the auto tensioner 1 presses the chain 6 through the chain guide 8.

  As shown in FIG. 2, the auto tensioner 1 includes a cylindrical housing 9 that is open at one end and closed at the other end, and a plunger 10 that is inserted into the housing 9 with one end protruding from the housing 9. . The housing 9 is fixed to a side surface of the engine block 13 (see FIG. 3) by tightening bolts 12 into a plurality of attachment pieces 11 formed integrally on the outer periphery of the housing 9.

  The housing 9 is filled with hydraulic oil. A wear ring 14 that supports the outer periphery of the plunger 10 so as to be movable in the axial direction and an oil seal 15 that seals the annular gap between the plunger 10 and the housing 9 are mounted on the inner periphery of the open end of the housing 9. Yes.

  The plunger 10 is formed in a bottomed cylindrical shape whose opening end into the housing 9 is open. A screw rod 16 is inserted into the plunger 10 with one end protruding from the insertion end of the plunger 10 into the housing 9, and formed on the outer periphery of the screw rod 16 on the female screw 17 formed on the inner periphery of the plunger 10. A male screw 18 is engaged with the screw.

  The male screw 18 and the female screw 17 have a sawtooth shape in which the flank angle of the pressure side flank 19 that receives pressure when a load in the direction of pushing the screw rod 16 into the plunger 10 is applied is larger than the flank angle of the play side flank 20. Is formed.

  Here, the flank angle of the pressure side flank 19 is the friction resistance between the pressure side flank 19 and 19 of the male screw 18 and the female screw 17 when a load in a direction of pushing the screw rod 16 into the plunger 10 is statically applied. Is set to a size that prevents the screw rod 16 from rotating. Further, the flank angle of the play side flank 20 is determined by sliding the screw between the play side flank 20 and 20 of the male screw 18 and the female screw 17 when a load in a direction in which the screw rod 16 protrudes from the plunger 10 is statically applied. The size is set such that the rod 16 is allowed to rotate.

  A return spring 21 is incorporated between the plunger 10 and the screw rod 16. One end of the return spring 21 is supported by the plunger 10 via the spring seat 22, and the other end presses the screw rod 16 in a direction protruding from the plunger 10.

  Here, the plunger 10 is urged in a direction protruding from the housing 9 by the reaction force of the return spring 21. The plunger 10 has a protruding end from the housing 9 in contact with the chain guide 8, and presses the chain 6 through the chain guide 8.

  The spring seat 22 is formed in a spherical shape in which the contact surface with the plunger 10 is in point contact with the plunger 10, thereby reducing the rotational resistance between the screw rod 16 and the plunger 10.

  In the housing 9, an iron sleeve 23 is provided coaxially with the housing 9. The sleeve 23 is closed at the closed end side of the housing 9 and is open at the open end side of the housing 9. The closed end of the sleeve 23 is formed integrally with the sleeve 23 by press molding, and a flange 24 is formed on the outer periphery of the closed end of the sleeve 23 simultaneously with the press molding.

  A piston 25 is inserted into the sleeve 23 so as to be slidable in the axial direction. The piston 25 supports the protruding end of the screw rod 16 from the plunger 10. A pressure chamber 26 is formed on the closed end side of the housing 9 of the piston 25 via the piston 25, and a reservoir chamber 27 is formed on the open end side of the housing 9 of the piston 25.

  On the inner periphery of the sleeve 23, a step portion 28 is formed in which the closed end side of the housing 9 has a smaller diameter than the open end side of the housing 9, and the portion on the open end side of the housing 9 from the step portion 28 is a piston. 25 is configured to slide. The step portion 28 functions as a stopper that receives the piston 25 and restricts the moving range when the piston 25 moves to the closed end side of the housing 9.

  A piston spring 29 that urges the piston 25 toward the open end of the housing 9 is incorporated in the pressure chamber 26. Further, a retaining protrusion 30 for retaining the piston 25 from the sleeve 23 is provided on the inner periphery of the end portion of the sleeve 23 on the open end side of the housing 9. The retaining protrusion 30 is formed by caulking the end surface of the sleeve 23.

  A first passage 31 that communicates the pressure chamber 26 and the reservoir chamber 27 is formed in the piston 25. A check valve 32 that allows only the flow of hydraulic oil from the reservoir chamber 27 side to the pressure chamber 26 side is provided at the end of the first passage 31 on the pressure chamber 26 side.

  The check valve 32 includes a spherical valve body 33 that opens and closes the opening of the first passage 31 on the pressure chamber 26 side, and a retainer 34 that regulates the movement range of the valve body 33. A steel ball can be used as the valve body 33, but if a ceramic ball is used, the valve body 33 can be reduced in weight, and the responsiveness of the check valve 32 to the pressure change in the pressure chamber 26 is improved.

  Further, the pressure chamber 26 and the reservoir chamber 27 communicate with each other via a second passage 35 that restricts the flow rate of the hydraulic oil. Here, the second passage 35 is a minute gap formed between the sliding surfaces of the piston 25 and the sleeve 23.

  An assist spring 36 is incorporated in the housing 9. One end of the assist spring 36 is supported by the flange 24 on the outer periphery of the end portion of the sleeve 23, and the other end presses the insertion end of the plunger 10 into the housing 9, and the plunger 10 protrudes from the housing 9 by the pressing. It is energizing in the direction to do. The assist spring 36 compensates the urging force of the piston spring 29 and improves the follow-up performance of the plunger 10 with respect to fluctuations in the tension of the chain 6.

  A sub reservoir chamber 37 is provided in the upper part of the housing 9. A small inner diameter portion 38 and a large inner diameter portion 39 are formed on the inner periphery of the housing 9 in order from the closed end side to the open end side of the housing 9. The auxiliary reservoir chamber 37 communicates with the reservoir chamber 27 via a communication hole 40 formed on the outer periphery of the housing 9 and an annular space formed between the large inner diameter portion 39 of the housing 9 and the plunger 10. An air reservoir 41 is provided on the hydraulic oil in the auxiliary reservoir chamber 37, and the upper surface opening is sealed with a seal cap 42. The air reservoir 41 smoothes the movement of the plunger 10 by absorbing the volume change in the housing 9 accompanying the movement of the plunger 10.

  Next, an operation example of the auto tensioner 1 will be described.

  When the tension of the chain 6 is reduced during the operation of the engine, the plunger 10 moves in a direction in which the plunger 10 protrudes from the housing 9 by the biasing force of the piston spring 29 and the assist spring 36, and the slack of the chain 6 is absorbed. At this time, as shown in FIG. 4, the pressure in the pressure chamber 26 becomes lower than the pressure in the reservoir chamber 27, the check valve 32 is opened, and the reservoir chamber 27 operates from the reservoir chamber 27 to the pressure chamber 26 through the first passage 31. Since the oil flows, the plunger 10 moves quickly.

  On the other hand, when the tension of the chain 6 increases during the operation of the engine, the tension of the chain 6 moves in the direction in which the plunger 10 is pushed into the housing 9 to absorb the tension of the chain 6. At this time, as shown in FIG. 5, the pressure in the pressure chamber 26 becomes higher than the pressure in the reservoir chamber 27 and the check valve 32 is closed, so that the pressure chamber 26 passes from the pressure chamber 26 to the reservoir chamber 27 through the second passage 35. The hydraulic oil flows, a damper action is generated by the viscous resistance of the hydraulic oil, and the plunger 10 moves slowly.

  When the chain 6 extends over time, the screw rod 16 and the plunger 10 gradually rotate relative to each other due to the vibration of the chain 6, and the amount of protrusion of the screw rod 16 from the plunger 10 increases. As a result, the protruding amount of the plunger 10 from the housing 9 is increased, and the elongation of the chain 6 can be absorbed.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. At this time, since the chain 6 is stationary without vibrating, no slip occurs between the male screw 18 of the screw rod 16 and the female screw 17 of the plunger 10, and the screw rod 16 and the plunger 10 do not rotate relative to each other. Further, the piston 25 moves toward the closed end of the housing 9 due to the tension of the chain 6, but since the moving range of the piston 25 is restricted by the inner peripheral step portion 28 of the sleeve 23, the plunger 10 is slightly Only moves in the pushing direction. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  As described above, the auto tensioner 1 can start the engine smoothly because the pushing amount of the plunger 10 when the tension of the chain 6 becomes large when the engine is stopped is small.

  Further, in the auto tensioner 1, the movement amount of the piston 25 increases according to the amplitude of the chain 6. Therefore, when the amplitude of the chain 6 during operation of the engine is large (for example, resonance occurs in the engine in a specific rotation range). Even when it occurs, or when the rotational fluctuation of the camshaft 4 or the crankshaft 2 during the combustion cycle is large), the vibration of the chain 6 can be sufficiently absorbed.

  In addition, since the auto tensioner 1 produces a damper action with the hydraulic oil sealed in the housing 9, it is not necessary to supply hydraulic oil from the engine oil pump, and the cost is low.

  Since the auto-tensioner 1 is provided with the retaining projection 30 on the sleeve 23, when the load in the pushing direction applied to the plunger 10 is released (for example, the auto-tensioner 1 is installed in the engine block for maintenance of the engine). The piston 25 can be prevented from coming out of the sleeve 23 by the urging force of the piston spring 29 when it is removed from the sleeve 13.

  In the above embodiment, the minute gap between the sliding surfaces of the piston 25 and the sleeve 23 is used as the second passage 35. However, the sliding surface between the piston 25 and the sleeve 23 is sealed with an O-ring or the like, and the piston 25 has a minute amount. A through hole may be formed. In this case, a minute through hole formed in the piston 25 becomes the second passage 35.

  In the above embodiment, the oil seal 15 is employed as a seal member that seals the annular gap between the plunger 10 and the housing 9, but another seal member such as an O-ring may be used instead of the oil seal 15. .

  In the above-described embodiment, the step portion 28 is described as an example of a stopper that restricts the movement range of the piston 25. However, a small-diameter sleeve (not shown) separate from the sleeve 23 is fitted into the sleeve 23. It is good also as a stopper. Alternatively, the distance between adjacent coils of the piston spring 29 may be set small, and the movement range of the piston 25 may be restricted by the seating of the piston spring 29. In this case, the opposing surface of the adjacent coil of the piston spring 29 serves as a stopper.

  6 and 7 show an auto tensioner 51 according to a second embodiment of the present invention. Portions corresponding to the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The plunger 10 is supported on the inner periphery of the housing 9 so as to be movable in the axial direction. An axial groove 52 is formed on the inner periphery of the housing 9 over the entire length of the housing 9.

  The pressure chamber 26 and the reservoir chamber 27 communicate with each other via a first passage 31 provided with a check valve 32. The first passage 31 includes an annular space between the inner and outer periphery of the housing 9 and the sleeve 23, an axial groove 52 on the inner periphery of the housing 9, a radial groove 53 on the closed end of the housing 9, and a closed end of the sleeve 23. And a through hole 55 formed in 54. The closed end 54 of the sleeve 23 is formed separately from the sleeve 23 and is press-fitted into the sleeve 23 and fixed.

  The auxiliary reservoir chamber 37 communicates with the reservoir chamber 27 through a communication hole 40 formed on the outer periphery of the housing 9 and an axial groove 52 on the inner periphery of the housing 9.

  In the auto tensioner 51, the insertion portion of the plunger 10 into the housing 9 is supported by the inner periphery of the housing 9, so that the axis of the plunger 10 is not easily tilted. Therefore, misalignment hardly occurs between the male screw 18 and the female screw 17, and the frictional resistance between the male screw 18 and the female screw 17 is stable.

DESCRIPTION OF SYMBOLS 1 Auto tensioner 9 Housing 10 Plunger 15 Oil seal 16 Screw rod 17 Female screw 18 Male screw 19 Pressure side flank 20 Play side flank 21 Return spring 23 Sleeve 25 Piston 26 Pressure chamber 27 Reservoir chamber 28 Step part 29 Piston spring 30 Retaining protrusion 31 First 1 passage 32 check valve 33 valve body 34 retainer 35 second passage 36 assist spring 37 auxiliary reservoir chamber 41 air reservoir 51 auto tensioner

Claims (10)

  The cylindrical housing (9) with one end opened and the other end closed is filled with hydraulic oil, and the plunger (10) is axially projected into the housing (9) with one end protruding from the housing (9). The annular gap between the plunger (10) and the housing (9) is sealed with a seal member (15), and a sleeve (23) is provided coaxially in the housing (9). (23) The piston (25) is slidably inserted into the pressure chamber (26) formed on the closed end side of the housing (9) of the piston (25), and the housing of the piston (25) ( 9) a reservoir chamber (27) formed on the open end side, and a check valve (32) that allows only the flow of hydraulic oil from the reservoir chamber (27) side to the pressure chamber (26) side. Connected via one passage (31) Then, the pressure chamber (26) and the reservoir chamber (27) are communicated with each other via a second passage (35) that restricts the flow rate of the hydraulic oil, and the piston (25) is placed in the pressure chamber (26) with a housing ( 9) A piston spring (29) that urges toward the open end side is incorporated, and a stopper (28) that restricts the movement range of the piston (25) to the closed end side of the housing (9) is provided. (10) is formed into a bottomed cylindrical shape that opens the insertion end into the housing (9), and the external thread (18) that engages with the internal thread (17) formed on the inner periphery of the plunger (10) And a return spring (21) for urging the screw rod (16) in a direction protruding from the plunger (10), and a plunge of the screw rod (16). Autotensioner the protruding end of the (10) supported by said piston (25).   The stopper (28) is a step (28) formed on the inner periphery of the sleeve (23) such that the closed end side of the housing (9) has a smaller diameter than the open end side of the housing (9). Item 2. The auto tensioner according to Item 1.   The auto tensioner according to claim 1 or 2, wherein an assist spring (36) for urging the plunger (10) in a direction protruding from the housing (9) is incorporated in the housing (9).   The retaining projection (30) for retaining the piston (25) from the sleeve (23) is provided on the inner periphery of the open end side of the housing (9) of the sleeve (23). The auto tensioner described in Crab.   The auto tensioner according to claim 4, wherein the retaining protrusion (30) is formed by caulking an end face of the sleeve (23).   An auxiliary reservoir chamber (37) communicating with the reservoir chamber (27) is provided at an upper portion of the housing (9), and an air reservoir (41) is provided on the hydraulic oil in the auxiliary reservoir chamber (37). The auto tensioner according to any one of 1 to 5.   The first passage (31) is provided in the piston (25), and the check valve (32) is a spherical valve body (33) that opens and closes the opening on the pressure chamber (26) side of the first passage (31). And a retainer (34) for restricting the range of movement of the valve body (33).   The auto tensioner according to claim 7, wherein the valve body (33) is a ceramic ball.   The auto tensioner according to any one of claims 1 to 8, wherein the second passage (35) is a minute gap formed between the sliding surfaces of the piston (25) and the sleeve (23).   The male screw (18) and the female screw (17) are such that the flank angle of the pressure side flank (19) that receives pressure when a load in the direction of pushing the screw rod (16) into the plunger (10) is applied is The auto tensioner according to any one of claims 1 to 9, wherein the auto tensioner is formed in a sawtooth shape larger than a flank angle of the flank (20).

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