JP2011149468A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chain tensioner having an air ejection mechanism dispensing with a process for pressing a plug body into a through hole. <P>SOLUTION: The chain tensioner 1 is formed by inserting a plunger 10 slidably into a cylinder 9, providing an oil feeding passage 21 for introducing a hydraulic fluid into a pressure chamber 20 surrounded by the plunger 10 and the cylinder 9, providing a check valve 22 at the pressure chamber 20 side end of the oil feeding passage 21, and incorporating a return spring 32 for energizing the plunger 10 in a projecting direction, into the pressure chamber 20. The projecting end of the plunger 10 from the cylinder 9 is provided with a through hole 33, and the through hole 33 is formed in tapered shape. The plug body 35 of tapered shape is fitted into the through hole 33, and the plug body 35 is held in the through hole 33 by the energizing force of the return spring 32. A spiral groove 34 serving for communication between the pressure chamber 20 and the outside is formed between the fitting surfaces of the plug body 35 and through hole 33. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a chain tensioner used for maintaining tension of a timing chain that drives a camshaft of an automobile engine.

  In general, an engine of an automobile transmits rotation of a crankshaft to a camshaft through a timing chain (hereinafter referred to as “chain”), and opens and closes a valve of a combustion chamber by the rotation of the camshaft. Here, in order to keep the chain tension within an appropriate range, a tension adjusting device composed of a chain guide provided so as to be able to swing around a fulcrum shaft and a chain tensioner that presses the chain via the chain guide is often used. It is done.

  As a chain tensioner incorporated in this tension adjusting device, a plunger is slidably inserted in a cylindrical cylinder having one end opened and the other end closed, and the plunger is inserted at the insertion end into the cylinder. An oil supply passage for introducing hydraulic oil into the pressure chamber surrounded by the plunger and the cylinder is provided, and an end of the oil supply passage on the pressure chamber side is connected to the pressure chamber side from the oil supply passage side. There is known a check valve that allows only the flow of hydraulic oil to the valve, and a return spring that urges the plunger in a direction protruding from the cylinder is incorporated in the pressure chamber (Patent Document 1).

  When the chain tension increases during engine operation, the chain tensioner moves in the direction in which the plunger is pushed into the cylinder (hereinafter referred to as “push-in direction”) due to the chain tension, and absorbs the chain tension. At this time, the hydraulic oil in the pressure chamber flows out through a leak gap between the sliding surface of the plunger and the cylinder, 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 engine operation, the plunger moves in a direction protruding from the cylinder (hereinafter referred to as “protruding direction”) by the urging force of the return spring, and absorbs the slackness of the chain. At this time, the check valve is opened and hydraulic oil flows into the pressure chamber from the oil supply passage, so that the plunger moves quickly.

  In such a chain tensioner, air may be mixed into the hydraulic oil supplied from the oil pump to the pressure chamber when the engine is started. In this case, when the chain tension increases, the air mixed in the pressure chamber Since the plunger moves by compressing, the damper action of the chain tensioner is reduced.

  In order to prevent this reduction in the damper action, the chain tensioner is provided with a mechanism for discharging the air in the pressure chamber.

  Specifically, a through hole having a constant inner diameter penetrating from the pressure chamber to the outside is provided at the protruding end of the plunger from the cylinder, and a cylindrical plug is press-fitted into the through hole (that is, inserted with a tightening margin). A spiral groove that communicates the pressure chamber with the outside is formed in the inner periphery of the through hole, and air in the pressure chamber is discharged to the outside through the spiral groove.

Japanese Patent No. 3635198

  However, the chain tensioner of Patent Document 1 may generate burrs when the plug body is press-fitted into the through-hole during assembly, and the burrs may be caught in the leak gap, or the spiral groove for venting air. There was a possibility of clogging. In addition, since the step of press-fitting the plug into the through hole is performed by a press machine, the press-fitting operation is complicated. Moreover, in order to secure the press-fitting allowance, it is necessary to process the outer shape of the plug body and the inner diameter of the through hole with high accuracy, and the processing cost is high.

  The problem to be solved by the present invention is to provide a chain tensioner having an air discharge mechanism that does not require a step of press-fitting a stopper into a through hole.

  In order to solve the above problem, a through hole penetrating from the pressure chamber to the outside is provided in the protruding end portion of the plunger from the cylinder, and the through hole is formed in a tapered shape having a small diameter from the pressure chamber side to the outside side. Then, a tapered plug body is fitted into the through-hole, the plug body is held in the through-hole by the urging force of the return spring, and the pressure chamber and the outside are interposed between the fitting surfaces of the plug body and the through-hole. An air vent passage communicating with the air was formed.

  In this case, the plug body is held in the through-hole by the urging force of the return spring, so that the plug body press-fitting step becomes unnecessary.

  Since the plug body is held in the through hole by the urging force of the return spring, for example, one end of the return spring can be directly received by the plug body. In this case, since there is no spring seat, the number of parts is small and the cost is low.

  Further, in order to hold the plug body in the through hole by the urging force of the return spring, a spring seat comprising a rod fitted into the return spring and a flange for receiving one end of the return spring is provided, and the spring seat is provided on the spring seat. The formed convex spherical surface may be received by the plug.

  Further, in order to hold the plug body in the through hole by the urging force of the return spring, one end of the return spring is received by the plug body, and a rod fitted into the return spring is formed integrally with the plug body. Also good. If it does in this way, since a return spring is positioned by radial direction by fitting with a rod, it can prevent that a return spring contacts with the inner periphery of a plunger and wears. Further, since the displacement of the return spring relative to the plug is prevented, the urging force of the return spring acts stably on the plug.

  As the air vent passage, an axial groove on the inner periphery of the through hole or the outer periphery of the plug body can be adopted, but a spiral groove is preferably adopted. In this way, the flow path length is longer than when an axial groove is employed, and the flow resistance of the hydraulic oil in the air vent path is increased. Therefore, in the chain tensioner by providing the air vent path, Oil consumption can be reduced.

  The spiral groove is preferably provided in multiple lines. In this way, even when any one of the multiple spiral grooves is clogged, the air in the pressure chamber can be exhausted through the other spiral grooves, so the reliability of the air discharge is improved. high.

  The plug body can be formed of a porous material having air permeability. If it does in this way, since the air in a pressure chamber will be discharged | emitted also through the inside of a plug body in parallel with the said air vent passage, the discharge performance of air can be ensured over a long period of time.

  Further, in order to solve the above-mentioned problem, a through-hole penetrating from the pressure chamber to the outside is provided at the projecting end portion of the plunger from the cylinder, and the through-hole has a tapered shape having a small diameter from the pressure chamber side to the outside side. A helical groove that is formed in the through hole, holds the steel ball in the through hole by the urging force of the return spring, and communicates the pressure chamber and the outside to the inner periphery of the through hole. May be formed. Even in this case, the steel ball is held in the through hole by the urging force of the return spring, so that the plug press-in step is not required.

The present invention can be applied to the following chain tensioner, for example.
1) The plunger is formed in a bottomed cylindrical shape whose opening end into the cylinder is open, and a screw rod having a male screw on the outer periphery that engages with a female screw formed on the inner periphery of the plunger is provided. The protruding end from the plunger is brought into contact with a rod seat provided in the cylinder, and the male screw and the female screw have a flank angle of the pressure side flank that receives pressure when a load is applied in a direction of pushing the plunger into the cylinder. However, a saw-tooth screw type chain tensioner is formed in a sawtooth shape larger than the flank angle of the play side flank.
2) A register ring that elastically tightens the outer periphery of the plunger is accommodated in an annular accommodating groove formed in the inner periphery of the cylinder, and the register ring is spaced apart from the outer periphery of the plunger at a certain interval in the axial direction. Engage with the formed circumferential grooves, and when a load in the direction in which the plunger protrudes from the cylinder is loaded in each of the circumferential grooves, the diameter of the register ring is expanded to allow the plunger to move. A ring-type chain tensioner provided with a tapered surface and a stopper surface that locks the register ring and restricts the movement of the plunger when a load in a direction of pushing the plunger into the cylinder is applied.

  In the chain tensioner according to the present invention, the plug body is held in the through hole by the urging force of the return spring, so that the press-in process of the plug body is unnecessary. Therefore, there is no possibility that press-fitting burrs will occur. In addition, since the press-fitting process using a press machine is unnecessary, assembly workability is high. Further, since it is not necessary to manage the press-fitting allowance, it is not necessary to process the outer shape of the plug body and the inner diameter of the through hole with high accuracy, and the processing cost is low.

The front view which shows the chain transmission apparatus incorporating the chain tensioner of 1st Embodiment of this invention 1 is an enlarged cross-sectional view near the chain tensioner of FIG. FIG. 2 is an enlarged cross-sectional view of the vicinity of the protruding end of the plunger from the cylinder. FIG. 3 is an enlarged sectional view showing an example in which a spring seat is added to one end of the return spring shown in FIG. FIG. 3 is an enlarged sectional view showing an example in which a rod is formed integrally with the plug shown in FIG. The expanded sectional view which shows the example which formed the spiral groove in the outer periphery of the plug body instead of the spiral groove of the inner periphery of the through-hole shown in FIG. An enlarged cross-sectional view showing an example in which a steel ball is fitted into a through hole having a spiral groove formed on the inner periphery The expanded sectional view which shows the chain tensioner of 2nd Embodiment of this invention

  FIG. 1 shows a chain transmission device incorporating a chain tensioner 1 according to a 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 around the fulcrum shaft 7, and the chain tensioner 1 presses the chain 6 through the chain guide 8.

  As shown in FIG. 2, the chain tensioner 1 includes a cylindrical cylinder 9 that is open at one end and closed at the other end, and a plunger 10 that is slidably inserted into the cylinder 9 in the axial direction. The cylinder 9 is inserted into the tensioner mounting hole 12 of the engine cover 11 with the opening end facing the inside of the engine cover 11, and the chain transmission is used in a state where the opening end of the cylinder 9 is obliquely upward. The The cylinder 9 has a male screw 13 and a cylindrical surface 14 formed on the outer periphery of the portion inserted into the tensioner mounting hole 12. The cylindrical surface 14 is located closer to the opening end of the cylinder 9 than the male screw 13 and has a smaller diameter than the outer diameter of the male screw 13.

  On the other hand, on the inner periphery of the tensioner mounting hole 12, an internal thread 15 that engages with an external thread 13 on the outer periphery of the cylinder 9 and a cylindrical surface 14 on the outer periphery of the cylinder 9 in order from the outer surface side to the inner surface side of the engine cover 11. A screw pilot hole 17 that forms an annular oil sump 16 and a cylindrical surface 18 that fits with the cylindrical surface 14 on the outer periphery of the cylinder 9 are formed. An oil outlet of an oil hole 19 formed in the engine cover 11 is opened in the screw prepared hole portion 17.

  The cylinder 9 is formed with an oil supply passage 21 for introducing hydraulic oil into a pressure chamber 20 surrounded by the cylinder 9 and the plunger 10. The oil supply passage 21 passes through the cylinder 9 in the radial direction, and an end on the outer diameter side thereof communicates with the oil reservoir 16, and an end on the inner diameter side communicates with the pressure chamber 20. Therefore, hydraulic oil supplied from an oil pump (not shown) through the oil hole 19 of the engine cover 11 is introduced into the pressure chamber 20 through the oil reservoir 16 and the oil supply passage 21 in order. A check valve 22 that allows only the flow of hydraulic oil from the oil supply passage 21 side to the pressure chamber 20 side is provided at the end of the oil supply passage 21 on the pressure chamber 20 side.

  A minute leak gap 23 is formed between the sliding surfaces of the plunger 10 and the cylinder 9, and hydraulic oil in the pressure chamber 20 flows out through the leak gap 23.

  A hexagonal head 24 for spanner engagement is formed at the closed end of the cylinder 9, and a spanner (not shown) is applied to the hexagonal head 24 so that the male screw 13 can be tightened. ing. A gasket 25 is sandwiched between the hexagonal head 24 and the engine cover 11. The gasket 25 seals between the hexagonal head 24 and the engine cover 11, and prevents hydraulic oil from leaking to the outside of the engine cover 11 through the screw gap between the male screw 13 and the female screw 15.

  The plunger 10 is formed in a bottomed cylindrical shape whose opening end into the cylinder 9 is open, and a female screw 26 is formed on the inner periphery thereof. A screw rod 28 having a male screw 27 that engages with the female screw 26 on the outer periphery is incorporated in the plunger 10. One end of the screw rod 28 protrudes from the plunger 10, and the protruding end is in contact with a rod seat 29 provided in the cylinder 9.

  The male screw 27 and the female screw 26 are formed in a sawtooth shape in which the flank angle of the pressure-side flank 30 that receives pressure when a load in the direction of pushing the plunger 10 into the cylinder 9 is applied is larger than the flank angle of the play-side flank 31. Has been.

  A return spring 32 that urges the plunger 10 in a direction to protrude from the cylinder 9 is incorporated in the pressure chamber 20. The return spring 32 is a coil spring, one end of which is supported by the screw rod 28 and the other end urges the plunger 10. The plunger 10 is in contact with the chain guide 8 at the protruding end from the cylinder 9.

  As shown in FIG. 3, an axial through hole 33 that penetrates from the pressure chamber 20 to the outside is provided at the protruding end portion of the plunger 10 from the cylinder 9. The through-hole 33 is formed in a tapered shape having a smaller diameter from the pressure chamber 20 side toward the outside, and a multiplicity of spiral grooves 34 are formed on the inner periphery thereof. A plug body 35 having a tapered outer peripheral surface is fitted in the through hole 33.

  The plug 35 receives one end of the return spring 32 and is held in the through hole 33 by the urging force of the return spring 32. The spiral groove 34 on the inner periphery of the through-hole 33 constitutes an air vent passage that communicates the pressure chamber 20 and the outside. The plug body 35 is formed of a porous material having air permeability (for example, a sintered metal or a sintered resin).

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

  When the tension of the chain 6 becomes smaller during the operation of the engine, the plunger 10 moves in the protruding direction by the urging force of the return spring 32 and absorbs the slack of the chain 6. At this time, the check valve 22 is opened, and the hydraulic oil supplied from the oil pump flows into the pressure chamber 20 through the oil supply passage 21, so that the plunger 10 moves quickly.

  On the other hand, when the tension of the chain 6 increases during engine operation, the plunger 10 moves in the pushing direction by the tension of the chain 6 and absorbs the tension of the chain 6. At this time, the screw rod 28 rotates with respect to the plunger 10 while repeating forward and backward movements within the range of the axial gap between the female screw 26 and the male screw 27 due to the vibration of the chain 6. Further, since the hydraulic oil in the pressure chamber 20 flows out through the leak gap 23 between the sliding surfaces of the plunger 10 and the cylinder 9 and a damper action is generated by the viscous resistance of the hydraulic oil, the plunger 10 moves slowly. To do.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. In this case, the chain 6 does not vibrate, so that the internal thread 26 of the plunger 10 is received by the external thread 27 of the screw rod 28. Ten positions are fixed. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  When the engine is stopped, the oil pump is stopped and the oil level of the hydraulic oil in the oil hole 19 and the oil supply passage 21 is lowered. Therefore, when the engine is restarted, air may be mixed into the hydraulic oil supplied to the pressure chamber 20 through the oil hole 19 and the oil supply passage 21. In this case, the air mixed in the pressure chamber 20 Is discharged to the outside through the spiral groove 34. Therefore, the damper action due to the air in the pressure chamber 20 is unlikely to decrease.

  In the chain tensioner 1, the plug body 35 is held in the through hole 33 by the urging force of the return spring 32, so that the press-fitting step of the plug body 35 is unnecessary. Therefore, there is no possibility that press-fitting burrs will occur. In addition, since the press-fitting process using a press machine is unnecessary, assembly workability is high. Further, since it is not necessary to manage the press-fitting allowance, it is not necessary to process the outer shape of the plug body 35 and the inner diameter of the through hole 33 with high accuracy, and the processing cost is low.

  Further, since the chain tensioner 1 is provided with a plurality of spiral grooves 34, even when any one of the spiral grooves 34 is clogged, the pressure chamber is passed through the other spiral groove 34. The air in 20 can be discharged. Therefore, the reliability of air discharge is high.

  Further, since the chain tensioner 1 forms the plug body 35 with a porous material having air permeability, the air in the pressure chamber 20 is discharged through the inside of the plug body 35 in parallel with the spiral groove 34. can do. Therefore, it is possible to ensure air discharge performance over a long period of time.

  An axial groove (not shown) may be formed in place of the spiral groove 34, and the axial groove may be employed as an air vent passage for communicating the pressure chamber 20 and the outside. Thus, it is preferable to employ the spiral groove 34. In this case, the flow path length becomes longer than in the case where an axial groove is employed, and the flow resistance of the hydraulic oil in the air vent passage increases, so that the chain tensioner 1 by providing the air vent passage is provided. Increase in oil consumption can be suppressed.

  As shown in FIG. 4, a spring seat 38 comprising a rod 36 fitted in the return spring 32 and a flange 37 for receiving one end of the return spring 32 is provided, and a convex spherical surface 39 formed on the spring seat 38 is plugged. May be received at 35.

  Further, as shown in FIG. 5, the rod 40 fitted into the return spring 32 may be formed integrally with the plug body 35. In this way, since the return spring 32 is positioned in the radial direction by fitting with the rod 40, it is possible to prevent the return spring 32 from coming into contact with the inner periphery of the plunger 10 and being worn. Further, since the displacement of the return spring 32 with respect to the plug body 35 is prevented, the urging force of the return spring 32 acts on the plug body 35 stably. Moreover, since the rod 40 can be picked up by fitting the plug 35 into the through hole 33 when the chain tensioner 1 is assembled, the assembling workability is high. The rod 40 and the plug body 35 can be integrally formed with a thermosetting resin, for example.

  In the above embodiment, the spiral groove 34 formed in the inner periphery of the through hole 33 is described as an example of the air vent passage between the fitting surfaces of the plug body 35 and the through hole 33, but as shown in FIG. Alternatively, a spiral groove 41 formed on the outer periphery of the plug body 35 may be employed. In FIG. 6, the spiral groove 41 is provided in multiple lines, and the plug body 35 is formed of a porous material having air permeability.

  As shown in FIG. 7, a steel ball 42 is fitted into the through-hole 33, the steel ball 42 is held in the through-hole 33 by the urging force of the return spring 32, and the pressure chamber 20 and the outside are connected to the inner periphery of the through-hole 33. A spiral groove 34 that communicates with each other may be formed. Even in this case, the steel ball 42 is held in the through-hole 33 by the urging force of the return spring 32, so that the step of press-fitting the plug body 35 is not necessary. Further, the steel ball 42 is less expensive than the tapered plug body 35.

  FIG. 8 shows a chain 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.

  An annular housing groove 52 is formed on the inner periphery of the cylinder 9, and a register ring 53 is housed in the housing groove 52 so as to be movable in the axial direction. The register ring 53 has a ring shape that lacks a part of the circumference, and is elastically deformable in the radial direction. The register ring 53 elastically tightens the outer periphery of the plunger 10 and engages with one of a plurality of circumferential grooves 54 formed on the outer periphery of the plunger 10 at regular intervals in the axial direction. .

  In each circumferential groove 54, when a load in the protruding direction is applied to the plunger 10, a taper surface 55 that allows the movement of the plunger 10 by expanding the diameter of the register ring 53, and a load in the direction in which the plunger 10 is pushed in Is provided with a stopper surface 56 that locks the register ring 53 and restricts the movement of the plunger 10 when the load is applied.

  As in the first embodiment, the protruding end portion of the plunger 10 from the cylinder 9 is provided with a tapered through hole 33, and a multi-threaded spiral groove 34 is formed on the inner periphery thereof. A tapered plug body 35 is fitted in the through hole 33. The plug 35 receives one end of the return spring 32 and is held in the through hole 33 by the urging force of the return spring 32.

  An operation example of the chain tensioner 51 will be described.

  When the tension of the chain 6 increases during the operation of the engine, the plunger 10 moves in the pushing direction by the tension of the chain 6 and absorbs the tension of the chain 6. At this time, since the damper force is generated by the viscous resistance of the hydraulic fluid flowing out from the pressure chamber 20 through the leak gap 23, the plunger 10 moves slowly.

  When the tension of the chain 6 is reduced during the operation of the engine, the plunger 10 moves in the protruding direction by the urging force of the return spring 32, and the slack of the chain 6 is absorbed. At this time, the check valve 22 is opened, and the hydraulic oil flows into the pressure chamber 20 from the oil supply passage 21, so that the plunger 10 moves quickly.

  Here, when the plunger 10 repeats advancing and retreating due to the vibration of the chain 6, the register ring 53 moves back and forth within the accommodation groove 52. Further, when the movement range in the protruding direction of the plunger 10 exceeds the movable range in the accommodation groove 52 of the register ring 53 due to the slack of the chain 6, the tapered surface 55 in the circumferential groove 54 causes the register ring 53 to move. Is expanded to allow the plunger 10 to move. At this time, the register ring 53 engages with the adjacent circumferential groove 54.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of the camshaft 4. In this case, the engagement of the register ring 53 and the circumferential groove 54 prevents the plunger 10 from moving in the pushing direction. The Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  When the engine is stopped, the oil pump is stopped and the oil level of the hydraulic oil in the oil hole 19 and the oil supply passage 21 is lowered. Therefore, when the engine is restarted, air may be mixed into the hydraulic oil supplied to the pressure chamber 20 through the oil hole 19 and the oil supply passage 21. In this case, the air mixed in the pressure chamber 20 Is discharged to the outside through the spiral groove 34. Therefore, the damper action due to the air in the pressure chamber 20 is unlikely to decrease.

  In the chain tensioner 51, the plug body 35 is held in the through hole 33 by the urging force of the return spring 32, so that a press-fitting process of the plug body 35 is not necessary. Therefore, there is no possibility that press-fitting burrs will occur. In addition, since the press-fitting process using a press machine is unnecessary, assembly workability is high. Further, since it is not necessary to manage the press-fitting allowance, it is not necessary to process the outer shape of the plug body 35 and the inner diameter of the through hole 33 with high accuracy, and the processing cost is low. Other effects are the same as those of the first embodiment.

1 Chain tensioner 9 Cylinder 10 Plunger 20 Pressure chamber 21 Oil supply passage 22 Check valve 26 Female thread 27 Male thread 28 Screw rod 29 Rod seat 30 Pressure side flank 31 Play side flank 32 Return spring 33 Through hole 34 Spiral groove 35 Plug body 36 Rod 37 Flange 38 Spring seat 39 Convex spherical surface 40 Rod 41 Spiral groove 42 Steel ball 51 Chain tensioner 52 Housing groove 53 Register ring 54 Circumferential groove 55 Tapered surface 56 Stopper surface

Claims (11)

A plunger (10) is slidably inserted in a cylindrical cylinder (9) whose one end is open and the other end is closed, and the plunger (10) is inserted into the cylinder (9). An oil supply passage (21) for introducing hydraulic oil is provided in a pressure chamber (20) formed in an open bottomed cylindrical shape and surrounded by the plunger (10) and the cylinder (9), and the oil supply passage (21 ) Is provided with a check valve (22) that allows only the flow of hydraulic oil from the oil supply passage (21) side to the pressure chamber (20) side at the end of the pressure chamber (20) side of the pressure chamber (20). In the chain tensioner in which the return spring (32) urged in the direction protruding from the cylinder (9) is incorporated in the pressure chamber (20),
A through hole (33) penetrating from the pressure chamber (20) to the outside is provided at the projecting end portion of the plunger (10) from the cylinder (9), and the through hole (33) is provided from the pressure chamber (20) side to the outside. A tapered plug body (35) is fitted into the through hole (33), and the plug body (35) is inserted into the through hole (33) by the urging force of the return spring (32). An air vent passage that is held in the hole (33) and communicates the pressure chamber (20) and the outside is formed between the fitting surfaces of the plug (35) and the through hole (33). Chain tensioner.   The chain tensioner according to claim 1, wherein one end of the return spring (32) is received by the plug (35).   A spring seat (38) comprising a rod (36) fitted in the return spring (32) and a flange (37) for receiving one end of the return spring (32) is provided, and formed on the spring seat (38). The chain tensioner according to claim 1, wherein the convex spherical surface (39) is received by the plug (35).   The end of the return spring (32) is received by the plug (35), and a rod (40) fitted into the return spring (32) is formed integrally with the plug (35). Chain tensioner.   The chain tensioner according to any one of claims 1 to 4, wherein the air vent passage is a spiral groove (34) formed in an inner periphery of the through hole (33).   The chain tensioner according to any one of claims 1 to 4, wherein the air vent passage is a spiral groove (41) formed on an outer periphery of the plug body (35).   The chain tensioner according to claim 5 or 6, wherein the spiral groove (34, 41) is provided in multiple lines.   The chain tensioner according to any one of claims 1 to 7, wherein the plug (35) is formed of a porous material having air permeability. A plunger (10) is slidably inserted in a cylindrical cylinder (9) whose one end is open and the other end is closed, and the plunger (10) is inserted into the cylinder (9). An oil supply passage (21) for introducing hydraulic oil is provided in a pressure chamber (20) formed in an open bottomed cylindrical shape and surrounded by the plunger (10) and the cylinder (9), and the oil supply passage (21 ) Is provided with a check valve (22) that allows only the flow of hydraulic oil from the oil supply passage (21) side to the pressure chamber (20) side at the end of the pressure chamber (20) side of the pressure chamber (20). In the chain tensioner in which the return spring (32) urged in the direction protruding from the cylinder (9) is incorporated in the pressure chamber (20),
A through hole (33) penetrating from the pressure chamber (20) to the outside is provided at the projecting end portion of the plunger (10) from the cylinder (9), and the through hole (33) is provided from the pressure chamber (20) side to the outside. The steel ball (42) is fitted into the through hole (33), and the steel ball (42) is inserted into the through hole (33) by the urging force of the return spring (32). The chain tensioner is characterized in that a spiral groove (34) is formed in the inner periphery of the through hole (33) to communicate the pressure chamber (20) with the outside.   The plunger (10) is formed in a bottomed cylindrical shape having an open end into the cylinder (9), and is engaged with a female screw (26) formed on the inner periphery of the plunger (10). A screw rod (28) having an outer periphery is provided, and a projecting end of the screw rod (28) from the plunger (10) is brought into contact with a rod sheet (29) provided in the cylinder (9), so that the male screw The flank angle of the pressure flank (30) that receives pressure when a load in the direction of pushing the plunger (10) into the cylinder (9) is applied to the play flank (31). The chain tensioner according to any one of claims 1 to 9, wherein the chain tensioner is formed in a sawtooth shape larger than a flank angle.   A register ring (53) for elastically fastening the outer periphery of the plunger (10) is accommodated in an annular accommodating groove (52) formed on the inner periphery of the cylinder (9), and the register ring (53) is The plunger (10) is engaged with a circumferential groove (54) formed at a constant interval in the axial direction on the outer periphery of the plunger (10), and the plunger (10) is inserted into each cylinder ( 9) When a load in the direction of protruding from 9) is applied, the diameter of the register ring (53) is increased to allow the plunger (10) to move, and the plunger (10) is connected to the cylinder (9). 10) A stopper surface (56) is provided for locking the register ring (53) and restricting the movement of the plunger (10) when a load in a direction to be pushed in is applied. Any Of the chain tensioner.

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