JP4880441B2 - Chain tensioner - Google Patents

Description

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

  In general, an engine transmits rotation of a crankshaft to a camshaft through a timing chain housed in an engine room in an engine cover, and the rotation of the camshaft opens and closes a valve in a combustion chamber. 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 chain pressing plunger is inserted into a bottomed cylindrical cylinder so as to be slidable in the axial direction, and a return spring that biases the plunger in a direction protruding from the cylinder is provided. An oil supply passage is provided in the cylinder to allow hydraulic oil to flow into the pressure chamber in the cylinder, and a check valve that allows only the flow of hydraulic oil in the direction in which the hydraulic oil flows into the pressure chamber is provided in the oil supply passage. Is known (Patent Document 1).

  During operation of the engine, this chain tensioner urges the plunger in the direction protruding from the cylinder by the pressure of the hydraulic oil supplied from the oil pump to the pressure chamber through the oil supply passage and the spring force of the return spring. When the chain is pressed and the tension of the chain decreases, the plunger moves in a direction protruding from the cylinder to absorb the slack of the chain. At this time, since the hydraulic oil is supplied into the pressure chamber through the oil supply passage, the plunger moves quickly and quickly absorbs the slack of the chain.

  On the other hand, when the tension of the chain increases, the plunger moves in a direction in which the plunger is pushed into the cylinder by the tension of the chain, and absorbs the tension of the chain. At this time, the check valve is closed, and the hydraulic oil in the pressure chamber leaks outside the cylinder through the leak passage between the plunger and the sliding surface of the cylinder, so the plunger moves slowly and stabilizes the chain tension. Keep in state.

  Further, the chain tensioner is provided in any one of a plurality of circumferential grooves in which a register ring provided so as to be movable in the axial direction within a certain range with respect to the cylinder is formed on the outer periphery of the plunger at intervals in the axial direction. Is engaged. Each circumferential groove has an asymmetric cross-sectional shape along the axis of the plunger, and when the plunger is pressed in the direction protruding from the cylinder, the register ring engages and disengages the circumferential groove adjacent in the axial direction, Although the plunger moves in the protruding direction, when the plunger is pressed in the direction to be pushed into the cylinder, the engagement between the register ring and the circumferential groove is not released, and the movement of the plunger is restricted.

  Therefore, when this chain tensioner is used, when the chain extends due to changes over time, the plunger moves in the direction protruding from the cylinder to absorb the chain extension, and when the chain extension increases, The register ring engages and disengages the circumferential groove, thereby allowing the plunger to move in a direction protruding from the cylinder.

In addition, when the engine is stopped, when the chain tension increases due to fluctuations in the rotational resistance of the camshaft, the movement of the plunger into the cylinder is limited by the engagement of the register ring and the circumferential groove. When the engine is restarted, the amount of movement of the plunger in the direction protruding from the cylinder is suppressed. Therefore, the amount of expansion of the pressure chamber due to the movement of the plunger is less likely to exceed the amount of hydraulic oil supplied by the oil supply pump, and air does not easily enter the pressure chamber due to the expansion of the pressure chamber volume.
Japanese Patent No. 3670911

  However, in this chain tensioner, the engagement position between the register ring and the circumferential groove changes with the length corresponding to the interval between the adjacent circumferential grooves as the minimum unit. When the engagement position of the circumferential groove changes, the amount of protrusion of the plunger from the cylinder suddenly increases, and the chain tension may become excessive.

  In addition, this chain tensioner needs to form a plurality of circumferential grooves on the outer periphery of the plunger, and the circumferential groove has a special cross-sectional shape along the axis of the plunger, so that the manufacturing cost is high.

  The problem to be solved by the present invention is that a chain tensioner that restricts the movement of the plunger into the cylinder in order to prevent air from entering the pressure chamber when the engine is restarted. It is to prevent the tension from becoming excessive and to reduce the manufacturing cost of the chain tensioner.

  In order to solve the above problems, a resistance ring that penetrates the plunger so as to be movable in the axial direction is provided so as to be movable in the axial direction within a certain range with respect to the cylinder, and a plurality of resistances extending from the resistance ring to the inner diameter side. The claw is formed to be inclined in a taper shape that reduces the diameter toward the open side of the cylinder, the tip of the resistance claw is brought into contact with the outer periphery of the plunger, and the plunger moves in a direction in which the plunger is pushed into the cylinder. The chain tensioner has a configuration in which the sliding resistance when sliding with the claw is greater than the sliding resistance when the plunger moves in a direction protruding from the cylinder and slides with each of the resistance claws. Adopted.

  In the chain tensioner, when the engine is stopped, the slack side belt is in tension due to the cam stop position, and the sliding movement of the plunger against the resistance claw of the resistance ring restricts the movement of the plunger in the direction of being pushed into the cylinder. . Therefore, when the engine is restarted, the amount of movement of the plunger in the protruding direction from the cylinder is suppressed, and the amount of expansion of the pressure chamber volume due to the movement of the plunger exceeds the amount of hydraulic oil supplied by the oil pump. Air does not easily enter the pressure chamber.

  Also, in this chain tensioner, when the vibration of the chain increases, the plunger slides against the resistance claw according to the vibration of the chain and moves in the direction of protruding from the cylinder. Sometimes, the plunger slides against the resistance claw by a dynamic load transmitted from the chain and moves in a direction to be pushed into the cylinder, so that the chain tension is not excessive.

  Further, the chain tensioner penetrates the outer periphery of the plunger so as to be slidable in the axial direction in an elastically expanded state at a position closer to the rear end side than the contact position of the outer periphery of the plunger with the resistance claw. It is possible to add a configuration in which a stopper ring is provided, and a stopper groove that is continuous in the circumferential direction is formed at a position closer to the rear end side than the contact position of the outer periphery of the plunger with the stopper ring. When the chain tensioner is removed from the engine, the plunger moves in a direction projecting from the cylinder. However, the stopper ring is held in contact with the resistance claw, and the stopper ring falls into the stopper groove and is moved to the plunger. Is retained from the cylinder.

  The chain tensioner of the present invention limits the movement of the plunger in the direction of being pushed into the cylinder by the sliding resistance of the plunger against the resistance claw, so that when the chain vibration increases, the amount of protrusion of the plunger from the cylinder increases. Even after that, when the vibration of the chain becomes small, the plunger moves in the direction of being pushed into the cylinder, and the tension of the chain is hardly excessive.

  Also, when a static load is applied from the chain to the chain tensioner when the engine is stopped, the plunger's sliding resistance against the resistance claw restricts the movement in the direction in which the plunger is pushed into the cylinder, so that the plunger is pushed into the cylinder. It is not necessary to form a plurality of circumferential grooves for restricting the movement in the direction on the outer periphery of the plunger, and the manufacturing cost is low.

  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 the crankshaft 2 of the engine and a sprocket 5 fixed to the 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 pressed by the chain tensioner 1 via a chain guide 8 supported so as to be swingable about a fulcrum shaft 7. The chain tensioner 1 is fixed to an engine block (not shown) with bolts 9.

  As shown in FIG. 2, the chain tensioner 1 has a plunger 11 slidably inserted in a cylindrical cylinder 10 with one end opened so as to be slidable in the axial direction. The volume of the inner pressure chamber 12 changes.

  The cylinder 10 is formed with an oil supply passage 13 that communicates an oil supply pump (not shown) outside the cylinder 10 with the pressure chamber 12, and the end of the oil supply passage 13 on the pressure chamber 12 side is connected to the oil supply pump. A check valve 14 that allows only the flow of hydraulic oil into the pressure chamber 12 is provided.

  The oil pump connected to the pressure chamber 12 via the oil supply passage 13 operates in conjunction with the engine. When the engine is operating, the oil pump is also operated to operate in the pressure chamber 12. When oil is supplied and the engine is stopped, the oil supply pump is also stopped and the supply of hydraulic oil to the pressure chamber 12 is stopped.

  Between the sliding surfaces of the plunger 11 and the cylinder 10, a leak gap 15 that allows the pressure chamber 12 to communicate with the engine room outside the cylinder 10 is formed. The leak gap 15 is very small and restricts the flow rate of the hydraulic oil flowing from the pressure chamber 12 to the engine room.

  A return spring 16 that urges the plunger 11 in a direction to protrude from the cylinder 10 is incorporated in the pressure chamber 12.

  An inner diameter enlarged portion 18 having an inner diameter larger than the outer diameter of the sliding surface 17 with the plunger 11 is formed at the end of the cylinder 10 on the open side, and between the inner circumference of the inner diameter enlarged portion 18 and the outer circumference of the plunger 11. Further, a resistance ring 19 that penetrates the plunger 11 so as to be movable in the axial direction is incorporated so as to be movable in the axial direction. As shown in FIG. 3A, the resistance ring 19 is restricted in the range of movement in the direction in which it is pushed into the cylinder 10 by the stepped portion 20 formed on the inner periphery of the cylinder 10 and having a large diameter on the open side of the cylinder 10. The moving range in the direction protruding from the cylinder 10 is restricted by a retaining ring 21 attached to the inner periphery of the inner diameter enlarged portion 18 of the cylinder 10.

  As shown in FIGS. 4 and 5, the resistance ring 19 is formed with a plurality of resistance claws 22 extending toward the inner diameter side, and the tips of the resistance claws 22 are in contact with the outer periphery of the plunger 11. Each resistance claw 22 is inclined in a taper shape with a diameter reduced toward the open side of the cylinder 10, and slides when the plunger 11 moves in a direction to be pushed into the cylinder 10 and slides with each resistance claw 22. The resistance becomes larger than the sliding resistance when the plunger 11 moves in the direction protruding from the cylinder 10 and slides with each resistance claw 22.

  As shown in FIG. 2, a stopper ring 23 is provided on the outer periphery of the plunger 11 at a position on the rear end side of the contact position of the resistance claw 22 so as to be slidable in the axial direction. The stopper ring 23 is formed in a C shape in which the inner diameter is smaller than the outer diameter of the plunger 11 in a natural state before being fitted to the outer circumference of the plunger 11, and is fitted on the outer circumference of the plunger 11 in an elastically expanded state. Are combined.

  In addition, a stopper groove 24 that is continuous in the circumferential direction is formed on the outer periphery of the plunger 11 at a position closer to the rear end side than the contact position of the stopper ring 23.

  A radial through hole 26 is formed in the distal end portion 25 of the plunger 11, and the plunger 11 is moved to the stroke end in the direction in which the plunger is pushed into the cylinder 10 as shown in FIGS. 4 and 5. By inserting the pin 28 through the through hole 26 and the radial through hole 27 formed in the inner diameter enlarged portion 18 of the cylinder 10, the plunger 11 can be held in a state of being pushed into the cylinder 10.

  Therefore, as shown in FIGS. 4 and 5, the chain tensioner 1 is shipped with the plunger 11 pushed to the stroke end, the chain tensioner 1 is assembled into the chain transmission device of the shipping destination, and then the pin 28 is pulled out. The plunger 11 can be protruded from the cylinder 10 and the chain 6 can be stretched.

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

  When the chain 6 vibrates during operation of the engine, the plunger 11 moves in the axial direction according to the tension of the chain 6 and absorbs the fluctuation of the tension of the chain 6. At this time, as shown in FIG. 3A, the resistance ring 19 is integrated with the plunger 11 in the axial direction within a range of an axial gap formed between the step portion 20 of the cylinder 10 and the retaining ring 21. Moving.

  Further, when the tension of the chain 6 is reduced during operation of the engine, the plunger 11 protrudes from the cylinder 10 by the pressure of the hydraulic oil supplied from the oil pump to the pressure chamber 12 and the spring force of the return spring 16. The chain guide 8 is pushed and moved to absorb the slack of the chain 6. At this time, since the hydraulic oil is supplied into the pressure chamber 12 through the oil supply passage 13, the plunger 11 moves quickly and quickly absorbs the slack of the chain 6.

  On the other hand, when the tension of the chain 6 increases during the operation of the engine, the plunger 11 moves in the direction in which the plunger 11 is pushed into the cylinder 10 by the tension of the chain 6 and absorbs the tension of the chain 6. At this time, the check valve 14 is closed and the hydraulic oil in the pressure chamber 12 is leaked to the engine room through the leak gap 15, so that the plunger 11 moves slowly and keeps the tension of the chain 6 in a stable state.

  Further, when the chain 6 extends due to a change with time, and the plunger 11 moves in a direction protruding from the cylinder by the extension, the resistance ring 19 is held in contact with the retaining ring 21, and when the chain 6 further extends, the plunger 11 It slides against the resistance claw 22 and moves in a direction protruding from the cylinder 10. At this time, since the resistance claw 22 is inclined in a tapered shape, the sliding resistance of the plunger 11 with respect to the resistance claw 22 is small, and the plunger 11 moves smoothly without being restricted by the resistance claw 22.

  Further, when the engine is stopped, when the slack side belt becomes in tension due to the cam stop position and the tension of the chain 6 increases, the plunger 11 moves in a direction to be pushed into the cylinder 10 as shown in FIG. The resistance ring 19 is held in contact with the step portion 20 of the cylinder 10. At this time, since the resistance claw 22 is inclined in a tapered shape, the sliding resistance of the plunger 11 with respect to the resistance claw 22 is large, and the movement in the direction in which the plunger 11 is pushed into the cylinder 10 is limited by the sliding resistance. . Therefore, when the engine is restarted, the amount of movement of the plunger 11 in the direction protruding from the cylinder 10 is suppressed, and the amount of expansion of the volume of the pressure chamber 12 due to the movement of the plunger 11 reduces the amount of hydraulic oil supplied by the oil supply pump. It is difficult to exceed the air pressure, and it is difficult for air to enter the pressure chamber 12 due to the volume expansion of the pressure chamber 12.

  Further, when the chain tensioner 1 is removed from the chain transmission device for maintenance and inspection of the chain tensioner 1, the plunger 11 moves to the stroke end in the direction protruding from the cylinder 10 by the urging force of the return spring 16. To do. At this time, as shown in FIG. 3C, the stopper ring 23 is held in contact with the resistance claw 22, and the stopper ring 23 falls into the stopper groove 24 to prevent the plunger 11 from coming off the cylinder 10.

  The chain tensioner 1 has a plunger 11 according to the vibration of the chain 6 when the vibration of the chain 6 becomes larger than the range of the axial clearance formed between the step portion 20 of the cylinder 10 and the retaining ring 21. Slides with respect to the resistance claw 22 and moves in a direction protruding from the cylinder 10, but when the vibration of the chain 6 is reduced thereafter, the plunger 10 is moved by the dynamic load transmitted from the chain 6 to the resistance claw. Since it slides with respect to 22 and moves in the direction of being pushed into the cylinder 10, the tension of the chain 6 is unlikely to be excessive.

  Further, when a static load is applied from the chain 6 to the chain tensioner 1 when the engine is stopped, the movement of the plunger 11 in the direction in which the plunger 11 is pushed into the cylinder 10 is limited by the sliding resistance of the plunger 11 with respect to the resistance claw 22. It is not necessary to form a plurality of circumferential grooves on the outer periphery of the plunger 11 for limiting the movement of the plunger 11 in the direction in which the plunger 11 is pushed into the cylinder 10, and the manufacturing cost is low.

  The resistance ring 19 is designed so that the following conditions are established for the plate thickness, the number of resistance claws, and the angle of the resistance claws according to the sliding resistance applied to the plunger 11. The plunger 11 can be slid in the direction protruding from the cylinder 10 by the sum of the urging force of the return spring 16 and the pressure of the hydraulic oil supplied from the oil pump, and in the direction to be pushed into the cylinder 10 when the engine is stopped. A condition in which sliding is not performed by a static load acting on the plunger 11 from the chain 6 but is slidable by a dynamic load acting on the plunger 11 from the chain 6 during engine operation.

  6 to 8 show a chain tensioner 31 according to a second embodiment of the present invention. Portions corresponding to the first embodiment of the chain tensioner 31 are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted.

  As shown in FIG. 6, in the chain tensioner 31, the cylinder 10 is inserted into a tensioner mounting hole 33 formed in the engine cover 32, and a flange portion 34 formed integrally with the outer periphery of the cylinder 10 is bolted to the engine cover 32. It is fixed with. In addition, an O-ring 36 that prevents hydraulic oil from leaking from the engine room covered with the engine cover 32 is provided on the outer periphery of the cylinder 10.

  An escape passage 38 that allows the pressure chamber 12 to communicate with the engine room is formed at the distal end portion 37 of the plunger 11, and the pressure in the pressure chamber 12 is set to a predetermined pressure at the opening of the escape passage 38 on the pressure chamber 12 side. A relief valve 39 is provided that opens when the pressure increases.

  Further, a lock pin 40 extending in a radial direction from the outer periphery of the tip portion 37 is fixed to the tip portion 37 of the plunger 11, and the plunger 11 is pushed in the cylinder 10 as shown in FIGS. 7 and 8. The plunger 11 is pushed into the cylinder 10 by hooking a hook 42 supported so as to be swingable about a support shaft 41 extending in the radial direction from the outer periphery of the cylinder 10 to the lock pin 40 while moving to the stroke end. It can be held in a state.

  The chain tensioner 31 operates in the same manner as the chain tensioner 1 of the first embodiment and absorbs the tension fluctuation of the chain 6. Further, when the tension of the chain 6 suddenly increases, the pressure in the pressure chamber 12 rises, the relief valve 39 opens, and the hydraulic oil in the pressure chamber 12 is released to the engine room through the escape passage 38. Therefore, the plunger 11 is quickly moved in the direction in which the plunger 11 is pushed into the cylinder 10, and the tension of the chain 6 is prevented from becoming excessive.

  Similarly to the first embodiment, the chain tensioner 31 also protrudes from the cylinder 10 by sliding the plunger 11 against the resistance claw 22 according to the vibration of the chain 6 when the vibration of the chain 6 becomes large. After that, when the vibration of the chain 6 becomes small, the plunger 10 slides with respect to the resistance claw 22 and moves in the direction to be pushed into the cylinder 10, so that the tension of the chain 6 becomes excessive. Hateful. Moreover, it is not necessary to form a plurality of circumferential grooves for restricting the movement of the plunger 11 in the direction in which the plunger 11 is pushed into the cylinder 10, and the manufacturing cost is low.

The front view which shows the chain transmission apparatus incorporating the chain tensioner of 1st Embodiment of this invention Front sectional view of the chain tensioner shown in FIG. (A) is an enlarged sectional view in the vicinity of the resistance ring of the chain tensioner shown in FIG. 2, and (b) is moved in the direction in which the plunger of the chain tensioner shown in FIG. 2 is pushed into the cylinder. FIG. 2C is an enlarged cross-sectional view in the vicinity of the resistance ring showing a state where it is held in contact with the stepped portion. FIG. 2C is a diagram in which the plunger of the chain tensioner shown in FIG. Enlarged sectional view of the vicinity of the resistance ring 2 is a bottom sectional view showing a state where the plunger of FIG. 2 is held in a state where the plunger is pushed into the cylinder. End view of the chain tensioner shown in FIG. Plan sectional drawing which shows the chain tensioner of 2nd Embodiment of this invention Plan sectional drawing which shows the state hold | maintained in the state which pushed the plunger of FIG. 6 in the cylinder The front view which shows the open end vicinity of the cylinder of FIG.

Explanation of symbols

10 Cylinder 11 Plunger 12 Pressure chamber 13 Oil supply passage 14 Check valve 15 Leak gap 16 Return spring 19 Resistance ring 22 Resistance claw 23 Stopper ring 24 Stopper groove

Claims (2)

  A return for urging the plunger (11) in a direction protruding from the cylinder (10) by inserting a plunger (11) for pressing the chain into the bottomed cylindrical cylinder (10) so as to be slidable in the axial direction. A spring (16) is provided, and an oil supply passage (13) is provided in the cylinder (10) for allowing hydraulic oil to flow into the pressure chamber (12) in the cylinder (10) whose volume changes as the plunger (11) moves. The oil supply passage (13) is provided with a check valve (14) that allows only the flow of hydraulic oil in the direction in which the hydraulic oil flows into the pressure chamber (12), and the hydraulic oil in the pressure chamber (12) is supplied. A leak gap (15) for leaking outside the cylinder (10) is provided between the sliding surfaces of the plunger (11) and the cylinder (10), and penetrates the plunger (11) so as to be movable in the axial direction. A resistance ring (19) to be moved is provided so as to be movable in the axial direction within a certain range with respect to the cylinder (10), and a plurality of resistance claws (22) extending from the resistance ring (19) to the inner diameter side are provided to the cylinder (10). ), The tip of the resistance claw (22) is brought into contact with the outer periphery of the plunger (11), and the plunger (11) is pushed into the cylinder (10). The sliding resistance when sliding with the resistance claws (22) by moving in the direction in which the plunger (11) protrudes from the cylinder (10) moves to the resistance claws (22). Chain tensioner that is larger than the sliding resistance when sliding.   The outer periphery of the plunger (11) is slidable in the axial direction on the outer periphery of the plunger (11) in a state where the diameter is elastically expanded to a position on the rear end side with respect to the contact position with the resistance claw (22) A stopper ring (23) to be penetrated is provided, and a stopper groove (24) continuous in the circumferential direction is formed at a position closer to the rear end side than a contact position with the stopper ring (23) on the outer periphery of the plunger (11), When the plunger (11) moves in a direction protruding from the cylinder (10), the stopper ring (23) is held in contact with the resistance claw (22), and the stopper ring (23) is held in the stopper groove. The chain tensioner according to claim 1, wherein the chain tensioner falls into (24) to prevent the plunger (11) from coming off from the cylinder (10).

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