JP2010090965A - Chain tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the damper operation of a chain tensioner by suppressing the wear of the valve seat of a check valve. <P>SOLUTION: The chain tensioner 1 includes a plunger 10 slidably inserted into a cylinder 9 in the axial direction, a return spring 26 for energizing the plunger 10 in the protruding direction, an oil supply passage 13 provided in a pressure chamber 12 encircled by the cylinder 9 and the plunger 10 for introducing operating oil, and the check valve 14 provided at the end of the oil supply passage 13 on the side of the pressure chamber 12 for preventing the backflow of the operating oil, the check valve 14 consisting of the valve seat 16 having a valve hole 15, a check ball 17 for contacting/leaving the valve seat 16 to open/close the valve hole 15, and a retainer 18 for restricting the moving range of the check ball 17. A chromium diffusion layer 29 is provided on a contact face 28 of the valve seat 16 with the check ball 17. <P>COPYRIGHT: (C)2010,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, 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 return spring is inserted into a bottomed cylindrical cylinder with one end opened so as to be slidable in the axial direction, and the plunger is urged in a direction protruding from the cylinder. It is known that an oil supply passage for introducing hydraulic oil is provided in a pressure chamber surrounded by the cylinder and the plunger, and a check valve for preventing backflow of the hydraulic oil is provided at the end of the oil supply passage on the pressure chamber side. (Patent Documents 1 and 2).

  Here, the check valve includes a valve seat having a valve hole, a check ball that opens and closes the valve hole in contact with and away from the valve seat, and a retainer that regulates a moving range of the check ball. .

  The chain tensioner presses the chain with the protruding end of the plunger from the cylinder. During engine operation, the plunger repeatedly moves forward and backward according to the vibration of the chain, and the check valve opens and closes according to the movement of the plunger. To do.

  Further, when the chain tension increases while the engine is operating, the plunger moves in the direction in which the plunger is pushed into the cylinder by the chain tension (hereinafter referred to as “push-in direction”), and absorbs the chain tension. At this time, the hydraulic oil in the pressure chamber flows out through the leak gap between the sliding surface of the plunger and the cylinder, the flow rate of the hydraulic oil is limited, and a damper action is generated, 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, since the hydraulic oil supplied from the oil pump flows into the pressure chamber through the oil supply passage, the plunger moves quickly.

  Moreover, in the chain tensioner described in Patent Document 2, the plunger is formed in a bottomed cylindrical shape with an insertion end into the cylinder opened, and a male screw that engages with a female screw formed on the inner periphery of the plunger is provided on the outer periphery. And a projecting end of the screw rod from the plunger is supported by a valve seat of the check valve.

In this chain tensioner, when the tension of the chain increases during engine operation, the screw rod gradually rotates due to the vibration of the chain, and the plunger is allowed to move in the pushing direction. On the other hand, since the chain does not vibrate when the engine is stopped, even if the chain force increases depending on the stop position of the cam, the plunger's female screw is received by the screw rod's male screw and the position of the plunger is fixed. Therefore, when the engine is restarted, the chain is hardly slackened, and the engine can be started smoothly.
JP 2007-321899 A JP 2007-333095 A

  By the way, in these chain tensioners, since the check valve repeatedly opens and closes according to the vibration of the chain during engine operation, the valve seat of the check valve is likely to be worn. When this wear proceeds, a gap is generated between the check ball and the valve seat when the check ball closes the valve hole, and the damper action of the chain tensioner may become unstable.

  Further, in the chain tensioner described in Patent Document 2, since the screw rod rotates in accordance with the variation in chain tension, the contact surface of the valve seat with respect to the screw rod is easily worn. As this wear progresses, the frictional resistance between the screw rod and the valve seat increases, so that even if the chain tension increases during engine operation, the screw rod may not rotate.

  The problem to be solved by the present invention is to suppress wear of the valve seat of the check valve and to stabilize the damper action of the chain tensioner.

  In order to solve the above problems, a high hardness layer is provided on the contact surface of the valve seat with the check ball.

  In this way, the wear of the contact surface of the valve seat with the check ball is suppressed, so that when the check ball closes the valve hole, a gap is less likely to form between the check ball and the valve seat, and the damper function of the chain tensioner Is stable.

  The plunger is formed in a bottomed cylindrical shape having an insertion end into the cylinder 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, and the plunger of the screw rod When the protruding end from the valve seat is supported by the valve seat of the check valve, it is preferable to provide the high hardness layer on the contact surface of the valve seat with respect to the screw rod.

  If it does in this way, since the contact surface with respect to the screw rod of a valve seat becomes difficult to wear, the increase in the frictional resistance between a screw rod and a valve seat can be suppressed. For this reason, when the chain tension increases during engine operation, the screw rod reliably rotates to allow the plunger to move in the pushing direction. In addition, the high hardness layer on the contact surface of the valve seat with respect to the check ball can be formed simultaneously with the high hardness layer on the contact surface of the valve seat with the screw rod, so that the cost is low.

  As the high hardness layer, for example, a chromium diffusion layer can be adopted. When the hardness of the chromium diffusion layer is Hv 1400 to 1800, the wear resistance of the valve seat can be ensured. When the depth of the chromium diffusion layer is 5 μm or more, it is possible to prevent the base material from being exposed due to wear of the chromium diffusion layer, and when the depth is 30 μm or less, peeling of the chromium diffusion layer can be prevented.

  Further, a vanadium diffusion layer can be adopted as the high hardness layer, and when the hardness of the vanadium diffusion layer is Hv 2000 to 2600, the wear resistance of the valve seat can be ensured. When the depth of the vanadium diffusion layer is 5 μm or more, the vanadium diffusion layer can be prevented from being worn and the base material is exposed, and when the depth is 30 μm or less, the vanadium diffusion layer can be prevented from peeling.

  Moreover, a diamond-like carbon layer can be adopted as the high hardness layer, and when the hardness of the diamond-like carbon layer is Hv 1500 to 2000, the wear resistance of the valve seat can be ensured. When the depth of the diamond-like carbon layer is 5 μm or more, it is possible to prevent the base material from being exposed due to wear of the diamond-like carbon layer, and when the depth is 10 μm or less, the residual stress in the diamond-like carbon layer causes the diamond. It is possible to prevent the adhesion of the like carbon layer from being lowered.

  The chain tensioner of the present invention is provided with a high hardness layer on the contact surface of the valve seat with respect to the check ball. Therefore, the contact surface of the valve seat with respect to the check ball is less likely to be worn and can exhibit a stable damper action over a long period of time. it can.

  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 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 has a bottomed cylindrical cylinder 9 with one end opened, and a plunger 10 inserted into the cylinder 9 so as to be slidable in the axial direction. The cylinder 9 is fixed to an engine block (not shown) with bolts 11.

  An oil supply passage 13 that communicates with a pressure chamber 12 surrounded by the cylinder 9 and the plunger 10 is formed in the cylinder 9. The oil supply passage 13 is connected to an oil supply pump (not shown), and hydraulic oil sent from the oil supply pump is introduced into the pressure chamber 12. At the end of the oil supply passage 13 on the pressure chamber 12 side, a check valve 14 for preventing the backflow of hydraulic oil from the pressure chamber 12 to the oil supply passage 13 is provided.

  The check valve 14 includes a valve seat 16 having a valve hole 15, a check ball 17 that opens and closes the valve hole 15 in contact with and away from the valve seat 16, and a retainer 18 that regulates a moving range of the check ball 17. The valve seat 16 is press-fitted into the cylinder 9 and fixed.

  A minute leak gap 19 is formed between the sliding surfaces of the plunger 10 and the cylinder 9, and hydraulic oil in the pressure chamber 12 leaks through the leak gap 19.

  The cylinder 9 has a through hole 20 extending from the outer surface to the inner surface of the cylinder 9, and a screw 22 is screwed into a female screw 21 formed on the inner periphery of the through hole 20. The air in the pressure chamber 12 is discharged through the screw gap between the two.

  The plunger 10 is formed in a bottomed cylindrical shape whose opening end into the cylinder 9 is opened, and a female screw 23 is formed on the inner periphery thereof. A screw rod 25 having a male screw 24 that engages with the female screw 23 on the outer periphery is incorporated in the plunger 10. One end of the screw rod 25 protrudes from the plunger 10, and the protruding end is supported by the valve seat 16 of the check valve 14.

  A return spring 26 is incorporated between the plunger 10 and the screw rod 25. One end of the return spring 26 is supported by the screw rod 25, and the other end presses the plunger 10 via the spring seat 27, and the presser urges the plunger 10 in a direction to protrude from the cylinder 9. . The plunger 10 has a protruding end from the cylinder 9 abutting on the chain guide 8 and presses the chain 6 via the chain guide 8.

  The male screw 24 and the female screw 23 are formed in a sawtooth shape in which the flank angle of the pressure flank 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 flank. Yes.

  The valve seat 16 is a sintered product or a forged product, and is quenched to increase its strength. Further, as shown in FIG. 3, the valve seat 16 is provided with a high hardness chromium diffusion layer 29 on the contact surface 28 with respect to the check ball 17. As shown in FIG. 4, a chromium diffusion layer 29 is also provided on the contact surface 30 with respect to the screw rod 25.

  The chromium diffusion layer 29 on the contact surface 28 with respect to the check ball 17 and the chromium diffusion layer 29 on the contact surface 30 with respect to the screw rod 25 can be formed simultaneously by subjecting the valve seat 16 to chromizing treatment. The hardness of the chromium diffusion layer 29 is set in a range of Hv 1400 to 1800, and the formation of the chromium diffusion layer 29 ensures the wear resistance of the valve seat 16.

  The depth of the chromium diffusion layer 29 is preferably set in the range of 5 μm to 30 μm. When the thickness is 5 μm or more, the chromium diffusion layer 29 can be prevented from being worn and the base material can be prevented from being exposed. When the thickness is 30 μm or less, the separation of the chromium diffusion layer 29 can be prevented.

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

  During the operation of the engine, the plunger 10 repeats moving forward and backward according to the vibration of the chain 6, and the check valve 14 opens and closes according to the movement of the plunger 10. Here, when the tension of the chain 6 decreases, the plunger 10 moves in the protruding direction by the urging force of the return spring 26 and absorbs the slack of the chain 6. At this time, since the hydraulic oil supplied from the oil pump flows into the pressure chamber 12 through the oil supply passage 13, 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 hydraulic oil in the pressure chamber 12 flows out through the leak gap 19 between the sliding surfaces of the plunger 10 and the cylinder 9, and a damper action is generated, so that the plunger 10 moves slowly. Further, the screw rod 25 is gradually rotated by the vibration of the chain 6 and allows the plunger 10 to move in the pushing direction.

  When the engine is stopped, the tension of the chain 6 may increase depending on the stop position of a cam (not shown) connected to the camshaft 4. In this case, the chain 6 does not vibrate, so the female screw 23 of the plunger 10 is screw screw rod. The plunger 10 is received by 25 male screws 24 and the position of the plunger 10 is fixed. Therefore, when the engine is restarted, the chain 6 is hardly slackened, and the engine can be started smoothly.

  Since the chain tensioner 1 is provided with the chromium diffusion layer 29 on the contact surface 28 of the valve seat 16 with respect to the check ball 17, the contact surface 28 of the valve seat 16 with respect to the check ball 17 is not easily worn. When the hole 15 is closed, a gap is hardly generated between the check ball 17 and the valve seat 16. Therefore, a stable damper action can be exhibited over a long period of time.

  Further, in this chain tensioner 1, since the chromium diffusion layer 29 is also provided on the contact surface 30 of the valve seat 16 with respect to the screw rod 25, the wear of the contact surface 30 of the valve seat 16 with respect to the screw rod 25 is suppressed, and the screw The frictional resistance between the rod 25 and the valve seat 16 is difficult to increase. Therefore, when the tension of the chain 6 is increased during the operation of the engine, the screw rod 25 is reliably rotated, and the plunger 10 is allowed to move in the pushing direction.

  Here, the chrome diffusion layer 29 on the contact surface 28 with respect to the check ball 17 of the valve seat 16 can be formed simultaneously with the chrome diffusion layer 29 on the contact surface 30 with respect to the screw rod 25 of the valve seat 16. .

  In the above embodiment, the chromium diffusion layer 29 is described as an example of the high hardness layer provided on the surface of the valve seat 16, but a vanadium diffusion layer may be adopted instead of the chromium diffusion layer 29. In this case, if the hardness of the vanadium diffusion layer is Hv 2000 to 2600, the wear resistance of the valve seat 16 can be ensured. When the depth of the vanadium diffusion layer is 5 μm or more, the vanadium diffusion layer can be prevented from being worn and the base material is exposed, and when the depth is 30 μm or less, peeling of the vanadium diffusion layer can be prevented.

  Further, instead of the chromium diffusion layer 29, a diamond-like carbon layer may be adopted. In this case, if the hardness of the diamond-like carbon layer is Hv 1500 to 2000, the wear resistance of the valve seat 16 can be ensured. When the depth of the diamond-like carbon layer is 5 μm or more, it is possible to prevent the base material from being exposed due to wear of the diamond-like carbon layer, and when the depth is 10 μm or less, the residual stress in the diamond-like carbon layer causes the diamond. It is possible to prevent the adhesion of the like carbon layer from being lowered.

  FIG. 5 shows a chain tensioner 41 according to the 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 accommodation groove 43 for accommodating the register ring 42 is formed on the inner periphery of the cylinder 9, and the register ring 42 accommodated in the accommodation groove 43 elastically tightens the outer periphery of the plunger 10. A plurality of circumferential grooves 44 are formed on the outer periphery of the plunger 10 at regular intervals in the axial direction, and the register ring 42 is engaged with the circumferential grooves 44.

  In each circumferential groove 44, when the plunger 10 is pressed in a direction protruding from the cylinder 9, the diameter of the register ring 42 is increased to allow the plunger 10 to move, and the plunger 10 is placed in the cylinder 9. Is provided with a stopper surface 46 that locks the register ring 42 and restricts the movement of the plunger 10 when the chain 6 is pushed in the direction of pushing the chain 6. The engagement between the groove 44 and the register ring 42 limits the movement of the plunger 10 in the pushing direction.

  In order to improve the responsiveness of the check valve 14 to the pressure fluctuation in the pressure chamber 12, a valve spring 47 that urges the check ball 17 toward the retainer 18 is incorporated between the check ball 17 and the retainer 18.

  As in the first embodiment, the valve seat 16 is provided with a high hardness chromium diffusion layer (not shown) on the contact surface 28 with respect to the check ball 17. The hardness of the chromium diffusion layer is set in a range of Hv 1400 to 1800, and the depth of the chromium diffusion layer is set in a range of 5 μm to 30 μm.

  Similarly to the first embodiment, the chain tensioner 41 is also provided with a chromium diffusion layer on the contact surface 28 of the valve seat 16 with respect to the check ball 17, so that the contact surface 28 of the valve seat 16 with respect to the check ball 17 is not easily worn. When the check ball 17 closes the valve hole 15, a gap is hardly generated between the check ball 17 and the valve seat 16. Therefore, a stable damper action can be exhibited over a long period of time.

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 contact surface of the valve seat with respect to the check ball. FIG. 2 is an enlarged cross-sectional view of the vicinity of the contact surface of the valve seat with respect to the screw rod. The expanded sectional view which shows the chain tensioner of 2nd Embodiment of this invention

Explanation of symbols

1 Chain tensioner 9 Cylinder 10 Plunger 12 Pressure chamber 13 Oil supply passage 14 Check valve 15 Valve hole 16 Valve seat 17 Check ball 18 Retainer 23 Female thread 24 Male thread 25 Screw rod 26 Return spring 28 Check ball contact surface 29 Chromium diffusion layer 30 Screw rod Contact surface 41 for chain tensioner

Claims (11)

A return spring that slidably inserts a plunger (10) in a cylindrical cylinder (9) with an open end in an axial direction and urges the plunger (10) to protrude from the cylinder (9). (26), an oil supply passage (13) for introducing hydraulic oil is provided in the pressure chamber (12) surrounded by the cylinder (9) and the plunger (10), and the pressure chamber of the oil supply passage (13) is provided. A check valve (14) for preventing backflow of hydraulic oil is provided at the end on the (12) side, and the check valve (14) includes a valve seat (16) having a valve hole (15) and the valve seat (16 A chain tensioner composed of a check ball (17) that opens and closes the valve hole (15) in contact with and away from a) and a retainer (18) that restricts the movement range of the check ball (17).
A chain tensioner comprising a high hardness layer (29) provided on a contact surface (28) of the valve seat (16) with respect to a check ball (17).   The plunger (10) is formed in a bottomed cylindrical shape with an open end into the cylinder (9), and a male screw (24) engaged with a female screw (23) formed on the inner periphery of the plunger (10). And a projecting end of the screw rod (25) from the plunger (10) is supported by a valve seat (16) of the check valve (14), and the valve seat (16 2. The chain tensioner according to claim 1, wherein the high hardness layer (29) is provided on a contact surface (30) with respect to the screw rod (25).   The chain tensioner according to claim 1 or 2, wherein the high hardness layer (29) is a chromium diffusion layer.   The chain tensioner according to claim 3, wherein the hardness of the chromium diffusion layer (29) is in the range of Hv 1400 to 1800.   The chain tensioner according to claim 3 or 4, wherein the chromium diffusion layer (29) has a depth in the range of 5 to 30 µm.   The chain tensioner according to claim 1 or 2, wherein the high hardness layer (29) is a vanadium diffusion layer.   The chain tensioner according to claim 6, wherein the hardness of the vanadium diffusion layer is in a range of Hv 2000 to 2600.   The chain tensioner according to claim 6 or 7, wherein the vanadium diffusion layer has a depth of 5 to 30 µm.   The chain tensioner according to claim 1 or 2, wherein the high hardness layer (29) is a diamond-like carbon layer.   The chain tensioner according to claim 9, wherein the hardness of the diamond-like carbon layer is in a range of Hv 1500 to 2000.   The chain tensioner according to claim 9 or 10, wherein the diamond-like carbon layer has a depth of 5 to 10 µm.

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