Chain tensioner

Abstract

To provide a chain tensioner capable of developing damper force having a stable magnitude.SOLUTION: In the chain tensioner, a valve seat 22 of a check valve 17 is another member than an inner sleeve 16. On the outer periphery of the valve seat 22, a fitted cylindrical face 26 to be slidably fitted to the inner periphery of a plunger 10 in the axial direction is formed. Between the fitted cylindrical face 26 and the inner periphery of the plunger 10, a leak clearance 27 is formed. The valve seat 22 is supported at its end inserted into the plunger 10 of the inner sleeve 16 to allow the movement relative to the inner sleeve 16.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a chain tensioner used to maintain tension in a chain. [Background technology]

[0002] Chain transmission devices used in engines of automobiles and the like include, for example, those that transmit the rotation of the crankshaft to the camshaft, those that transmit the rotation of the crankshaft to accessories such as an oil pump, a water pump, a supercharger, etc., those that transmit the rotation of the crankshaft to a balancer shaft, those that connect the intake cam and the exhaust cam of a twin cam engine, etc. Chain tensioners are used to keep the tension of the chain in these chain transmission devices within an appropriate range.

[0003] As a chain tensioner for such an application, the inventor of the present application has already proposed one described in Patent Document 1. The chain tensioner of Patent Document 1 has a cylinder, a cylindrical plunger inserted into the cylinder so as to be slidable in the axial direction, and an inner sleeve inserted into the plunger.

[0004] The cylinder is a cylindrical member having one axial end as a closed end and the other axial end as an open end. The plunger is a cylindrical member having an open end inserted into the cylinder and a closed end protruding from the cylinder. The inner sleeve is inserted into the plunger such that one axial end is inserted into the plunger and the other axial end protrudes from the plunger, and the end of the inner sleeve protruding from the plunger is supported by the closed end of the cylinder. The outer periphery of the inner sleeve and the inner periphery of the plunger are fitted together slidably in the axial direction. A return spring is incorporated between the plunger and the end of the inner sleeve inserted into the plunger, for biasing the plunger in a direction protruding from the cylinder.

[0005] Also, in the chain tensioner of Patent Document 1, a check valve is provided at the end of the inner sleeve inserted into the plunger. The check valve divides the internal area of ​​the inner sleeve and the plunger into a reservoir chamber on the inner sleeve side and a pressure chamber on the plunger side. The check valve is configured to allow oil to flow only from the reservoir chamber side to the pressure chamber side. An oil supply passage is formed in the cylinder to introduce oil supplied from outside the cylinder into the reservoir chamber. A cylindrical leak gap is formed between the outer periphery of the inner sleeve and the inner periphery of the plunger to allow oil to leak from the pressure chamber.

[0006] The check valve has a valve seat with a valve hole that communicates between the pressure chamber and the reservoir chamber, and a valve body that opens and closes the end of the valve hole on the pressure chamber side. The valve seat is seamlessly formed integrally with the inner sleeve at the insertion end of the inner sleeve into the plunger.

[0007] In the chain tensioner of Patent Document 1, when the tension in the chain increases while the engine is running, the tension in the chain causes the plunger to move in a direction that pushes it into the cylinder (hereinafter referred to as the "pushing direction"), absorbing the tension in the chain. At this time, the plunger moves slowly because a damping force is generated by the viscous resistance of the oil that flows out from the pressure chamber through the leak gap.

[0008] On the other hand, when the tension in the chain decreases while the engine is running, the force of the return spring and the oil pressure in the pressure chamber move the plunger in the direction in which it protrudes from the cylinder (hereinafter referred to as the "protruding direction"), absorbing the slack in the chain. At this time, the check valve opens and oil flows from the reservoir chamber into the pressure chamber, so the plunger moves quickly. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2019-152285 A Summary of the Invention [Problem to be solved by the invention]

[0010] In the chain tensioner of Patent Document 1, when the plunger moves in the pushing direction, oil in the pressure chamber flows out into the reservoir chamber through the leak gap, and a damping force is generated by the viscous resistance of the oil flowing through the leak gap. The magnitude of this damping force can be adjusted to the desired magnitude by controlling the dimensions of the cylindrical leak gap formed between the outer periphery of the inner sleeve and the inner periphery of the plunger.

[0011] However, when the inventors of the present application prototyped and evaluated the chain tensioner of Patent Document 1 within their own company, they found that the magnitude of the damping force was not stable, and that in some cases the expected magnitude of damping force could not be obtained.

[0012] The inventor then investigated the cause of the unstable magnitude of the damping force and found that the positional accuracy of the inner sleeve relative to the plunger could cause the size of the leak gap to be uneven, resulting in the magnitude of the damping force being unstable.

[0013] For example, as shown in Figure 1 of Patent Document 1, when the end of the inner sleeve protruding from the plunger is pressed into and supported in a sleeve fitting recess formed in the closed end of the cylinder, if the concentricity between the center of the sleeve fitting recess and the center of the inner surface of the cylinder is low, a misalignment will occur between the axis of the inner sleeve pressed into the sleeve fitting recess and the axis of the plunger inserted into the cylinder, causing the size of the cylindrical leak gap formed between the outer periphery of the inner sleeve and the inner periphery of the plunger to be uneven in the circumferential direction, and as a result, the expected amount of damping force will not be obtained.

[0014] Furthermore, for example, as shown in Figure 6 of Patent Document 1, when the end of the inner sleeve protruding from the plunger is supported in axial contact with the inner surface of the closed end of the cylinder, if the flatness of the inner surface of the closed end of the cylinder or the perpendicularity to the axial direction is low, the axial direction of the inner sleeve supported by the inner surface of the closed end of the cylinder will be inclined relative to the axial direction of the plunger, and the size of the cylindrical leak gap formed between the outer circumference of the inner sleeve and the inner circumference of the plunger will be uneven in the axial direction, as a result, the expected magnitude of damping force will not be obtained.

[0015] In addition, for example, if a moment load acts on the plunger from the chain side and the moment load causes the plunger to tilt, the size of the cylindrical leak gap formed between the outer periphery of the inner sleeve and the inner periphery of the plunger becomes uneven in the axial direction, and as a result, the expected damping force cannot be obtained. In this case, there is also a risk of galling (localized welding) occurring between the outer periphery of the inner sleeve and the inner periphery of the plunger.

[0016] An object of the present invention is to provide a chain tensioner that is capable of obtaining a stable magnitude of damping force. [Means for solving the problem]

[0017] In order to solve the above problems, the present invention provides a chain tensioner having the following configuration. a cylinder having one axial end as a closed end and the other axial end as an open end; a cylindrical plunger that is slidably inserted into the cylinder in the axial direction, the plunger having an open end that is inserted into the cylinder and a closed end that protrudes from the cylinder; an inner sleeve having one axial end inserted into the plunger and the other axial end protruding from the plunger, the inner sleeve having an end protruding from the plunger supported by a closed end of the cylinder; a check valve that divides an internal region of the inner sleeve and the plunger into a reservoir chamber on the inner sleeve side and a pressure chamber on the plunger side, and allows oil to flow only from the reservoir chamber side to the pressure chamber side; an oil supply passage for introducing oil supplied from outside the cylinder into the reservoir chamber; a return spring that biases the plunger in a direction protruding from the cylinder, The check valve is a chain tensioner having a valve seat having a valve hole communicating between the pressure chamber and the reservoir chamber, and a valve body for opening and closing an end of the valve hole on the pressure chamber side, the valve seat is a separate member from the inner sleeve, The valve seat has an outer periphery formed with a cylindrical fitting surface that is axially slidably fitted to an inner periphery of the plunger, a cylindrical leak gap for leaking oil from the pressure chamber is formed between the fitting cylindrical surface and an inner periphery of the plunger, 13. A chain tensioner comprising: a valve seat supported at an end of the inner sleeve inserted into the plunger so as to allow relative movement with respect to the inner sleeve.

[0018] In this way, the valve seat is supported to allow relative movement with respect to the inner sleeve, and a fitting cylindrical surface for forming a leak gap is formed on the outer periphery of the valve seat, so that even if the positional accuracy of the inner sleeve relative to the plunger is low, the valve seat can move relative to the inner sleeve to equalize the size of the leak gap between the fitting cylindrical surface on the outer periphery of the valve seat and the inner periphery of the plunger, thereby obtaining a stable damping force.

[0019] It is preferable that the valve seat have a configuration having a cylindrical portion that fits onto the outer periphery of the inner sleeve with a radial gap so as to allow radial movement relative to the inner sleeve, and a seat main body portion that is supported in the axial direction at the insertion end of the inner sleeve into the plunger.

[0020] In this way, the valve seat can move radially relative to the inner sleeve within the range of the radial gap provided between the cylindrical portion of the valve seat and the outer periphery of the inner sleeve, so that even if there is a misalignment between the axis of the inner sleeve and the axis of the plunger inserted into the cylinder, the valve seat can move radially relative to the inner sleeve in accordance with that misalignment, making it possible to uniform the size of the leak gap between the mating cylindrical surface of the outer periphery of the valve seat and the inner periphery of the plunger in the radial direction, thereby making it possible to obtain a stable damping force.

[0021] It is preferable that the valve seat be slidably supported by an annular partial spherical surface formed at an end of the inner sleeve inserted into the plunger so as to allow tilting relative to the inner sleeve.

[0022] In this way, the valve seat is tiltably supported by the partial spherical surface of the insertion end of the inner sleeve into the plunger, so that even if the axial direction of the inner sleeve is tilted relative to the axial direction of the plunger inserted into the cylinder, the valve seat tilts relative to the inner sleeve in accordance with the tilt, making it possible to equalize the size of the leak gap between the fitting cylindrical surface on the outer periphery of the valve seat and the inner periphery of the plunger in the axial direction, thereby making it possible to obtain a stable damping force.

[0023] In addition, the valve seat can be configured to have an annular supported surface having a convex arc-shaped cross section that is slidably supported by an annular tapered surface formed at the insertion end of the inner sleeve into the plunger so as to allow tilting relative to the inner sleeve.

[0024] In this way, the valve seat can tilt relative to the inner sleeve, so that even if the axial direction of the inner sleeve is tilted relative to the axial direction of the plunger inserted in the cylinder, the valve seat can tilt relative to the inner sleeve in accordance with the tilt, making it possible to equalize the size of the leak gap between the fitting cylindrical surface on the outer periphery of the valve seat and the inner periphery of the plunger in the axial direction, thereby making it possible to obtain a stable damping force.

[0025] It is preferable that an oil passage be formed in the inner sleeve for returning oil leaked from the pressure chamber through the leak gap to the reservoir chamber.

[0026] With this configuration, when the plunger moves in the pushing direction, oil leaks from the pressure chamber through the leak gap, and some of the oil leaking from the pressure chamber returns to the reservoir chamber through the oil passage, reducing the amount of oil discharged from the chain tensioner to the outside and making it possible to suppress oil consumption in the chain tensioner.

[0027] In this case, it is preferable to provide an air vent passage in the cylinder, which connects from a cylindrical space radially sandwiched between the inner circumference of the cylinder and the outer circumference of the inner sleeve to the outside of the cylinder, on the side closer to the closed end of the cylinder than the insertion end of the plunger into the cylinder.

[0028] In this way, air present in the cylindrical space radially sandwiched between the inner periphery of the cylinder and the outer periphery of the inner sleeve is discharged to the outside of the cylinder through the air vent passage, making it difficult for air to remain in the cylindrical space. This makes it possible to prevent air present in the cylindrical space from entering the reservoir chamber through the oil passage formed in the inner sleeve, making it possible to obtain a stable damping force.

[0029] The air vent passage can be a threaded gap formed between a threaded hole formed penetrating from the outer periphery to the inner periphery of the cylinder and a male screw member screwed into the threaded hole.

[0030] a flange portion is formed at an end of the inner sleeve protruding from the plunger, the flange portion being brought into axial contact with a closed end of the cylinder; A rotation prevention protrusion is provided at a closed end of the cylinder, It is preferable to adopt a configuration in which a notch is formed in the flange portion, which engages with the anti-rotation protrusion to position the relative positions of the inner sleeve and the cylinder in the circumferential direction so that the oil passage is on the upper side.

[0031] In this way, the inner sleeve is positioned circumferentially relative to the cylinder so that the oil passage is on the upper side by engagement between the notch formed in the flange portion of the inner sleeve and the anti-rotation protrusion provided on the closed end of the cylinder, thereby enabling air present in the reservoir chamber to be smoothly discharged through the oil passage. Effect of the Invention

[0032] With the chain tensioner of this invention, even if the positional accuracy of the inner sleeve relative to the plunger is low, the valve seat moves relative to the inner sleeve, making it possible to equalize the size of the leakage gap between the cylindrical fitting surface on the outer periphery of the valve seat and the inner periphery of the plunger, thereby providing a stable damping force. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a diagram showing a chain transmission device incorporating a chain tensioner according to a first embodiment of the present invention. [Diagram 2] Enlarged cross-sectional view of the chain tensioner in Figure 1 [Diagram 3] Enlarged cross-sectional view of the check valve in Figure 2 [Figure 4] FIG. 3 is a cross-sectional view showing a modified example of the inner sleeve of FIG. [Diagram 5] FIG. 3 is a cross-sectional view showing a modification of the oil supply passage of FIG. [Figure 6]A cross-sectional view showing a modification in which an assist spring is added to the chain tensioner in Figure 2. [Figure 7] FIG. 1 is a cross-sectional view of a main portion of a chain tensioner according to a reference embodiment. [Figure 8] Enlarged cross-sectional view of the check valve in Figure 7 [Figure 9] An enlarged cross-sectional view of the check valve and the valve seat with different cylindrical lengths shown in FIG. [Figure 10] FIG. 9 is a cross-sectional view showing a modification of the valve seat of FIG. 8 . [Figure 11] FIG. 11 is a cross-sectional view showing the vicinity of a valve seat of a chain tensioner according to another embodiment of the present invention. [Figure 12] FIG. 3 is a cross-sectional view showing a modified example in which an air vent passage is provided in the cylinder shown in FIG. [Figure 13] FIG. 6 is a cross-sectional view showing a modified example in which an air vent passage is provided in the cylinder shown in FIG. [Figure 14] FIG. 5 is a cross-sectional view showing a modified example in which anti-rotation protrusions are provided to position the inner sleeve shown in FIG. 4 in the circumferential direction. [Figure 15] Cross-sectional view taken along line XV-XV in Figure 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] 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 transmits the rotation of the crankshaft 2 to the camshaft 4, and the rotation of the camshaft 4 opens and closes a valve (not shown) in a combustion chamber.

[0035] When the engine is running, the rotation direction of the crankshaft 2 is constant (clockwise in the figure), and at this time, the portion of the chain 6 that is pulled into the sprocket 3 as the crankshaft 2 rotates (right side in the figure) is tight, and the portion that is let out from the sprocket 3 (left side in the figure) is slack. The slack portion of the chain 6 is in contact with a chain guide 8 that is supported so as to be able to swing around a fulcrum shaft 7. The chain tensioner 1 presses the chain 6 via the chain guide 8.

[0036] 2, the chain tensioner 1 has a cylindrical cylinder 9 with one axial end being a closed end and the other axial end being an open end, and a plunger 10 inserted into the cylinder 9 so as to be slidable in the axial direction. The end of the plunger 10 protruding from the cylinder 9 presses against the chain guide 8.

[0037] The cylinder 9 is integrally formed from an aluminum alloy. The cylinder 9 is fixed to an engine block 13 (see FIG. 15) by fastening bolts 12 (see FIG. 1) to a plurality of mounting pieces 11 formed integrally on the outer periphery of the cylinder 9. Here, the cylinder 9 is mounted in a state in which the direction in which the plunger 10 protrudes from the cylinder 9 is inclined downward from the horizontal. A planar seating surface 14 (see FIG. 15) parallel to the axis of the cylinder 9 is formed on the outer periphery of the cylinder 9, and the seating surface 14 is abutted against an engine wall surface 15 (see FIG. 15) that extends vertically. The engine wall surface 15 is a side surface of the engine block 13.

[0038] 2, the plunger 10 is formed in a cylindrical shape with an open end thereof inserted into the cylinder 9 and a closed end thereof protruding from the cylinder 9. The plunger 10 is made of an iron-based material (e.g., a steel material such as SCM (chrome molybdenum steel) or SCr (chrome steel)).

[0039] An inner sleeve 16 is inserted into the plunger 10 such that one axial end is inserted into the plunger 10 and the other axial end protrudes from the plunger 10. The inner sleeve 16 is a cylindrical member with both axial ends open. The inner sleeve 16 is made of an iron-based material (e.g., SCr material or SCM material) like the plunger 10. The end of the inner sleeve 16 protruding from the plunger 10 is supported by the closed end of the cylinder 9.

[0040] A check valve 17 is attached to the end of the inner sleeve 16 inserted into the plunger 10. The check valve 17 divides the internal area of ​​the inner sleeve 16 and the plunger 10 into a reservoir chamber 18 on the inner sleeve 16 side and a pressure chamber 19 on the plunger 10 side. The volume of the reservoir chamber 18 does not change and is constant even if the plunger 10 moves in the axial direction. On the other hand, the volume of the pressure chamber 19 expands when the plunger 10 moves in the axial direction in the direction protruding from the cylinder 9, and contracts when the plunger 10 moves in the axial direction in the direction being pushed into the cylinder 9.

[0041] A return spring 20 is installed in the pressure chamber 19. The return spring 20 is a compression coil spring made of a metal wire wound in a spiral shape. One end of the return spring 20 is supported by the check valve 17, and the other end presses the plunger 10 in the axial direction, urging the plunger 10 in a direction protruding from the cylinder 9.

[0042] 3, the check valve 17 has a valve seat 22 in which a valve hole 21 is formed, a spherical valve element 23 that opens and closes the end of the valve hole 21 on the pressure chamber 19 side, a valve spring 24 that urges the valve element 23 from the open position to the closed position, and a retainer 25 that restricts the movement range of the valve element 23. The valve hole 21 is an axial through-hole formed in the valve seat 22 to communicate between the pressure chamber 19 and the reservoir chamber 18. The check valve 17 restricts the flow of oil from the pressure chamber 19 side to the reservoir chamber 18 side, and allows oil to flow only from the reservoir chamber 18 side to the pressure chamber 19 side.

[0043] A fitting cylindrical surface 26 is formed on the outer periphery of the valve seat 22, which is fitted to the inner periphery of the plunger 10 so as to be slidable in the axial direction. The fitting cylindrical surface 26 is a cylindrical surface whose outer diameter does not change along the axial direction and is constant. The inner periphery of the plunger 10 is also a cylindrical surface whose inner diameter does not change along the axial direction and is constant. A leak gap 27 is formed between the fitting cylindrical surface 26 and the inner periphery of the plunger 10, which allows oil to leak from the pressure chamber 19 when the volume of the pressure chamber 19 decreases. The leak gap 27 is a minute cylindrical gap whose radial width is set to a range of 0.010 to 0.050 mm.

[0044] As shown in Fig. 2, the outer periphery of the plunger 10 inserted into the cylinder 9 is a cylindrical surface whose outer diameter does not change along the axial direction. The inner periphery of the cylinder 9, which supports the outer periphery of the plunger 10 so that it can slide in the axial direction, also has a cylindrical surface whose inner diameter does not change along the axial direction. A cylindrical guide gap 28 is formed between the inner periphery of the cylinder 9 and the outer periphery of the plunger 10. The radial width of the guide gap 28 is set to be larger than the radial width of the leak gap 27, and can be set in the range of 0.015 to 0.065 mm, for example.

[0045] An oil supply passage 30 that introduces oil supplied from outside the cylinder 9 into the reservoir chamber 18 is provided in the cylinder 9 and the inner sleeve 16. The oil supply passage 30 is composed of a cylinder-side oil passage 31 formed in the cylinder 9 to introduce the oil supplied from outside the cylinder 9 into the inside of the cylinder 9, a cylindrical space 32 formed between the inner periphery of the cylinder 9 and the outer periphery of the inner sleeve 16, and an oil passage 33 provided in the portion of the inner sleeve 16 that protrudes from the plunger 10.

[0046] 15, the cylinder-side oil passage 31 is a hole formed penetrating from the outer periphery to the inner periphery of the cylinder 9. The end of the cylinder-side oil passage 31 on the outer periphery side of the cylinder 9 opens into the seating surface 14 so as to connect to an oil hole 34 that opens into the engine wall surface 15. The seating surface 14 is a mating surface with the engine wall surface 15. The oil hole 34 is an oil supply hole that supplies oil pumped from an oil pump (not shown) to the chain tensioner 1.

[0047] 2, the cylindrical space 32 is a cylindrical region radially sandwiched between the inner periphery of the cylinder 9 and the outer periphery of the inner sleeve 16 on the side closer to the closed end of the cylinder 9 than the insertion end of the plunger 10 into the cylinder 9. The end of the cylinder-side oil passage 31 on the inner periphery side of the cylinder 9 opens so as to connect to the cylindrical space 32.

[0048] The oil passage 33 is a through hole formed radially penetrating the inner sleeve 16. The oil passage 33 is also a part of the oil supply passage 30, and also an oil recovery hole for returning oil that has leaked from the pressure chamber 19 through the leak gap 27 into the cylindrical space 32 from the cylindrical space 32 to the reservoir chamber 18.

[0049] As shown in FIG. 3, the valve seat 22 is a separate member from the inner sleeve 16. The valve seat 22 is pressed against the inner sleeve 16 by the biasing force of the return spring 20. The valve seat 22 is supported at the end of the inner sleeve 16 inserted into the plunger 10 so as to allow relative radial movement with respect to the inner sleeve 16. Specifically, the valve seat 22 has a cylindrical portion 36 that fits into the outer periphery of the inner sleeve 16 with a radial gap 35 therebetween so as to allow radial movement with respect to the inner sleeve 16, and a seat body portion 37 that is supported in the axial direction at the end of the inner sleeve 16 inserted into the plunger 10. The contact surface of the seat body portion 37 with the inner sleeve 16 is a flat surface perpendicular to the axial direction.

[0050] Next, an example of the operation of this chain tensioner 1 will be described.

[0051] When the tension of the chain 6 shown in FIG. 1 increases during engine operation, the tension of the chain 6 causes the plunger 10 to move in a direction to be pushed into the cylinder 9, absorbing the tension of the chain 6. At this time, the pressure of the pressure chamber 19 shown in FIG. 2 becomes higher than the pressure of the reservoir chamber 18, so the check valve 17 is closed. In addition, the volume of the pressure chamber 19 decreases with the movement of the plunger 10, so oil leaks from the pressure chamber 19 through the leak gap 27 by the amount of the decreased volume. At this time, a damping force is generated by the viscous resistance of the oil flowing through the leak gap 27, and this damping force prevents the chain 6 from flapping. Most of the oil leaking from the pressure chamber 19 through the leak gap 27 to the cylindrical space 32 returns to the reservoir chamber 18 through the oil passage 33. In addition, a part of the oil leaking from the pressure chamber 19 through the leak gap 27 to the cylindrical space 32 lubricates the guide gap 28.

[0052] On the other hand, when the tension of the chain 6 shown in Fig. 1 decreases while the engine is running, the force of the return spring 20 shown in Fig. 2 and the oil pressure of the pressure chamber 19 move the plunger 10 in the protruding direction, absorbing the slack in the chain 6. At this time, the volume of the pressure chamber 19 expands in response to the movement of the plunger 10, so that the pressure of the pressure chamber 19 becomes lower than the pressure of the reservoir chamber 18, and the check valve 17 opens. Then, oil flows from the reservoir chamber 18 through the check valve 17 into the pressure chamber 19, and the plunger 10 moves quickly. At this time, oil is introduced into the reservoir chamber 18 from the oil hole 34 (see Fig. 15) outside the cylinder 9 through the oil supply passage 30.

[0053] When the engine is stopped and then restarted, the oil level in the oil hole 34 (see FIG. 15) generally drops once, so it takes time for oil to start being supplied from the oil hole 34 to the chain tensioner 1. In this case, between the time the engine is restarted and the time when oil starts being supplied from the oil hole 34, the oil that has previously accumulated in the reservoir chamber 18 flows into the pressure chamber 19 through the check valve 17, keeping the pressure chamber 19 filled with oil. Therefore, it is possible to generate a damping force immediately after the engine is restarted, making it possible to suppress fluttering of the chain 6.

[0054] 3, in this chain tensioner 1, the valve seat 22 can move radially relative to the inner sleeve 16 within the range of the radial gap 35 provided between the cylindrical portion 36 of the valve seat 22 and the outer periphery of the inner sleeve 16, so that even if there is a misalignment between the axial center of the inner sleeve 16 and the axial center of the plunger 10 inserted into the cylinder 9, the valve seat 22 can move radially relative to the inner sleeve 16 in accordance with the misalignment and be aligned, making it possible to uniform the size of the leak gap 27 between the mating cylindrical surface 26 on the outer periphery of the valve seat 22 and the inner periphery of the plunger 10 in the radial direction. Therefore, even if the concentricity between the center of the inner sleeve 16 and the center of the inner periphery of the cylinder 9 is low, a stable damping force can be obtained.

[0055] 2 moves in the pushing direction, oil leaks from the pressure chamber 19 through the leak gap 27, and some of the oil leaking from the pressure chamber 19 returns to the reservoir chamber 18 through the oil passage 33 formed in the inner sleeve 16. This makes it possible to reduce the amount of oil discharged from the chain tensioner 1 to the outside, and therefore makes it possible to suppress the amount of oil consumed by the chain tensioner 1.

[0056] Fig. 4 shows a modified example of the inner sleeve 16 of the above embodiment. In Fig. 4, a flange portion 38 that axially contacts the closed end of the cylinder 9 is formed on the end of the inner sleeve 16 protruding from the plunger 10. This makes it possible to stabilize the position of the inner sleeve 16 and to prevent the closed end of the cylinder 9, which is made of an aluminum alloy, from being indented due to contact with the inner sleeve 16.

[0057] Fig. 5 shows a modified example of the oil supply passage 30 of the above embodiment. In Fig. 5, the oil supply passage 30 is composed of a recess 39 formed in the closed end of the cylinder 9, and a hole 40 formed penetrating from the outer periphery of the cylinder 9 to the recess 39. In this modified example, the oil passage 33 provided in the inner sleeve 16 functions as an oil recovery hole for returning oil that has leaked from the pressure chamber 19 (see Fig. 2) through the leak gap 27 into the cylindrical space 32 from the cylindrical space 32 to the reservoir chamber 18 (it does not function as an oil supply passage for introducing oil supplied from outside the cylinder 9 into the reservoir chamber 18).

[0058] FIG. 6 shows a modified example in which an assist spring 41 is added to the above embodiment. In FIG. 6, the assist spring 41 that presses the end of the plunger 10 inserted into the cylinder 9 is incorporated in the cylindrical space 32. The assist spring 41 is a compression coil spring in which a metal wire is wound in a spiral shape. By providing this assist spring 41, the urging force in the direction in which the plunger 10 protrudes from the cylinder 9 increases, and it becomes possible to improve the followability of the chain guide 8 (see FIG. 1) to the chain 6. In addition, by supporting one end of the assist spring 41 with a flange portion 38 formed on the end of the inner sleeve 16 protruding from the plunger 10, the stability of the posture of the inner sleeve 16 can be improved.

[0059] Figures 7 and 8 show Reference form The parts corresponding to those in the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0060] The valve seat 22 is a separate member from the inner sleeve 16. The valve seat 22 is pressed against the inner sleeve 16 by the biasing force of the return spring 20. The valve seat 22 is supported at the insertion end of the inner sleeve 16 into the plunger 10 so as to allow movement in a tilting direction relative to the inner sleeve 16. Specifically, the valve seat 22 is slidably supported by an annular partial spherical surface 42 formed at the insertion end of the inner sleeve 16 into the plunger 10 so as to allow tilting relative to the inner sleeve 16. The partial spherical surface 42 is a part of a sphere having its center on the axis L of the inner sleeve 16.

[0061] The valve seat 22 has a cylindrical portion 36 that fits onto the outer periphery of the inner sleeve 16 with a radial gap 35 to allow radial movement relative to the inner sleeve 16, and a seat body portion 37 that is supported in the axial direction at the end of the inner sleeve 16 inserted into the plunger 10. The contact surface of the seat body portion 37 with the inner sleeve 16 is an annular tapered surface 43. The tapered surface 43 is in line contact with the partial spherical surface 42 at a circular portion.

[0062] In this chain tensioner 1, the valve seat 22 is tiltably supported by the partial spherical surface 42 at the insertion end of the inner sleeve 16 into the plunger 10, so that even if the axial direction of the inner sleeve 16 is tilted relative to the axial direction of the plunger 10 inserted into the cylinder 9, the valve seat 22 tilts and is aligned relative to the inner sleeve 16 in accordance with the tilt, and the size of the leak gap 27 between the mating cylindrical surface 26 on the outer periphery of the valve seat 22 and the inner periphery of the plunger 10 can be made uniform in the axial direction. Therefore, even if the axial direction of the inner sleeve 16 is tilted relative to the axial direction of the plunger 10, a stable damping force can be obtained.

[0063] Furthermore, this chain tensioner 1 is capable of preventing galling (localized welding) between the outer periphery of the inner sleeve 16 and the inner periphery of the plunger 10 even when a moment load acts on the plunger 10 from the chain guide 8 (see FIG. 1) and causes the plunger 10 to tilt due to that moment load.

[0064] Furthermore, as with the first embodiment, even if there is a misalignment between the axis of the inner sleeve 16 and the axis of the plunger 10 inserted into the cylinder 9, the valve seat 22 moves radially relative to the inner sleeve 16 in accordance with the misalignment, thereby making it possible to obtain a stable damping force.

[0065] 8 and 9, by varying the axial length of the cylindrical portion 36, multiple types of valve seats 22 with different axial lengths of the mating cylindrical surface 26 can be manufactured, and multiple types of chain tensioners 1 with different lengths of the leak gap 27 can be manufactured. In this way, multiple types of chain tensioners 1 with different damping forces can be manufactured by standardizing parts other than the valve seat 22 (plunger 10, inner sleeve 16, etc.). This reduces the manufacturing cost of the chain tensioner 1. By manufacturing multiple types of valve seats 22 with different outer diameter dimensions of the mating cylindrical surface 26, it is also possible to manufacture multiple types of chain tensioners 1 with different radial dimensions of the leak gap 27.

[0066] Figure 10 shows: Reference form 10 shows a modified example of the valve seat 22. In Fig. 10, the contact surface of the seat body portion 37 with the inner sleeve 16 is an annular partial concave spherical surface 44. The partial concave spherical surface 44 is a part of a concave spherical surface having its center on the axis L of the inner sleeve 16. The partial concave spherical surface 44 is in surface contact with the partial spherical surface 42.

[0067] Figure 11 shows: Other reference forms11 shows the vicinity of the valve seat 22 of the chain tensioner 1. In Fig. 11, the valve seat 22 has an annular supported surface 45 with a convex arc-shaped cross section. The supported surface 45 is slidably supported by an annular tapered surface 46 formed on the insertion end of the inner sleeve 16 into the plunger 10 so as to allow the valve seat 22 to tilt relative to the inner sleeve 16.

[0068] the above Each shape 12 and 13 , an air vent passage 47 can be provided that communicates from the cylindrical space 32 to the outside of the cylinder 9. The air vent passage 47 is a thread gap formed between a threaded hole 48 that penetrates from the outer periphery to the inner periphery of the cylinder 9 and a male screw member 49 screwed into the threaded hole 48.

[0069] By providing this air vent passage 47, air present in the cylindrical space 32 radially sandwiched between the inner periphery of the cylinder 9 and the outer periphery of the inner sleeve 16 is discharged to the outside of the cylinder 9 through the air vent passage 47, making it difficult for air to remain in the cylindrical space 32. As a result, it is possible to prevent the air present in the cylindrical space 32 from entering the reservoir chamber 18 through the oil passage 33 formed in the inner sleeve 16, making it possible to obtain a stable damping force.

[0070] 14 and 15, the inner sleeve 16 may be positioned in the circumferential direction by an anti-rotation projection 50. In Fig. 14 and 15, an anti-rotation projection 50 is provided at the closed end of the cylinder 9. Meanwhile, a flange portion 38 that axially contacts the closed end of the cylinder 9 is formed at the end of the inner sleeve 16 that protrudes from the plunger 10. A notch 51 that engages with the anti-rotation projection 50 is formed in the flange portion 38. The notch 51 and the anti-rotation projection 50 engage with each other to position the inner sleeve 16 relative to the cylinder 9 in the circumferential direction so that the oil passage 33 is on the upper side.

[0071] In this manner, the inner sleeve 16 is positioned circumferentially relative to the cylinder 9 so that the oil passage 33 is on the upper side due to engagement between the notch 51 formed in the flange portion 38 of the inner sleeve 16 and the anti-rotation protrusion 50 provided at the closed end of the cylinder 9. This makes it possible for air present in the reservoir chamber 18 to be smoothly discharged through the oil passage 33.

[0072] the above Each shape In the above embodiment, an example has been given in which the chain tensioner 1 is incorporated into a chain transmission device that transmits the rotation of the crankshaft 2 to the camshaft 4, but the chain tensioner 1 can also be incorporated into a chain transmission device that transmits the rotation of the crankshaft 2 to an auxiliary device such as an oil pump, a water pump, or a supercharger, a chain transmission device that transmits the rotation of the crankshaft 2 to a balancer shaft, or a chain transmission device that connects the intake cam and exhaust cam of a twin cam engine to each other.

[0073] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0074] 1 Chain tensioner 9 Cylinders 10 Plunger 16 Inner sleeve 17 Check valve 18 Reservoir Room 19 Pressure Chamber 20 Return spring 21 Valve hole 22 Valve seat 23 Valve body 26 Mating Cylindrical Surface 27 Leak gap 30 Fuel passage 32 Cylindrical Space 33 Oil passage 35 Radial clearance 36 Cylindrical section 37 Seat body 38 Flange 42 Partial sphere 45 Supported surface 46 Tapered surface 47 Air vent passage 48 screw holes 49 Male threaded member 50 Anti-rotation protrusion 51 Cutout

Claims

1. A cylinder (9) having one axial end as a closed end and the other axial end as an open end; a cylindrical plunger (10) that is slidably inserted into the cylinder (9) in the axial direction, the plunger having an open end inserted into the cylinder (9) and a closed end protruding from the cylinder (9); an inner sleeve (16) inserted into the plunger (10) such that one axial end is inserted into the plunger (10) and the other axial end is protruding from the plunger (10), and the end protruding from the plunger (10) is supported by a closed end of the cylinder (9); a check valve (17) that divides an internal region of the inner sleeve (16) and the plunger (10) into a reservoir chamber (18) on the inner sleeve (16) side and a pressure chamber (19) on the plunger (10) side and allows oil to flow only from the reservoir chamber (18) side to the pressure chamber (19) side; an oil supply passage (30) for introducing oil supplied from outside the cylinder (9) into the reservoir chamber (18); a return spring (20) that biases the plunger (10) in a direction protruding from the cylinder (9), The check valve (17) is provided in a chain tensioner having a valve seat (22) in which a valve hole (21) communicating between the pressure chamber (19) and the reservoir chamber (18) is formed, and a valve body (23) for opening and closing an end of the valve hole (21) on the pressure chamber (19) side, The valve seat (22) is a separate member from the inner sleeve (16), A cylindrical fitting surface (26) is formed on the outer periphery of the valve seat (22) to be axially slidably fitted on the inner periphery of the plunger (10), a cylindrical leakage gap (27) for leaking oil from the pressure chamber (19) is formed between the fitting cylindrical surface (26) and the inner periphery of the plunger (10); The valve seat (22) is supported at an insertion end of the inner sleeve (16) into the plunger (10) so as to allow relative movement with respect to the inner sleeve (16); the valve seat (22) has a cylindrical portion (36) that is fitted to an outer periphery of the inner sleeve (16) with a radial gap (35) therebetween so as to allow radial movement relative to the inner sleeve (16), and a seat body portion (37) that is axially supported at an end of the inner sleeve (16) that is inserted into the plunger (10), A chain tensioner characterized in that a contact surface of the seat body portion (37) with the inner sleeve (16) is a flat surface perpendicular to the axial direction.

2. 2. The chain tensioner according to claim 1, wherein the valve seat is slidably supported by an annular partial spherical surface formed at an end of the inner sleeve that is inserted into the plunger so as to allow tilting relative to the inner sleeve.

3. 3. The chain tensioner according to claim 1, wherein the inner sleeve (16) is formed with an oil passage (33) for returning oil leaked from the pressure chamber (19) through the leak gap (27) to the reservoir chamber (18).

4. 4. The chain tensioner according to claim 3, wherein the cylinder (9) is provided with an air bleed passage (47) that communicates with the outside of the cylinder (9) from a cylindrical space (32) that is radially sandwiched between the inner periphery of the cylinder (9) and the outer periphery of the inner sleeve (16) on a side closer to the closed end of the cylinder (9) than the insertion end of the plunger (10) into the cylinder (9).

5. 5. A chain tensioner according to claim 4, wherein the air bleed passage (47) is a thread gap formed between a threaded hole (48) formed penetrating from the outer periphery to the inner periphery of the cylinder (9) and a male threaded member (49) screwed into the threaded hole (48).

6. A flange portion (38) is formed at an end of the inner sleeve (16) protruding from the plunger (10) and abuts against a closed end of the cylinder (9) in the axial direction, A rotation prevention protrusion (50) is provided at the closed end of the cylinder (9), 6. A chain tensioner as claimed in any one of claims 3 to 5, wherein a notch (51) is formed in the flange portion (38) for circumferentially positioning the inner sleeve (16) and the cylinder (9) relative to each other so that the oil passage (33) is on the upper side by engaging with the anti-rotation protrusion (50).

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