Chain tensioner

Abstract

To provide a chain tensioner which has a relief valve at a position of a check valve and has a small number of components.SOLUTION: A valve seat member 26 of a check valve 13 is provided so as to be movable in an axial direction within a plunger 10 through a relief gap 31. A relief spring 30 is incorporated into the plunger 10. A stepped relief seat part 32 which contacts with and supports the valve seat member 26 is provided at an inner periphery of the plunger 10. The valve seat member 26, the relief seat part 32, and the relief spring 30 form a relief valve.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] Known chain tensioners used for such purposes include, for example, the one described in Patent Document 1. The chain tensioner in Patent Document 1 has a cylindrical cylinder with one axial end that is a closed end and the other axial end that is an open end, a cylindrical plunger that is slidably inserted into the cylinder in the axial direction and has an open end inserted into the cylinder and a closed end that protrudes from the cylinder, a return spring that urges the plunger in a direction that protrudes from the cylinder, and a check valve built into the plunger so as to divide the area surrounded by the cylinder and the plunger into a reservoir chamber on the cylinder side and a pressure chamber on the plunger side.

[0004] In addition, between the outer periphery of the plunger and the inner periphery of the cylinder, there are formed a leak gap that allows oil to leak from the pressure chamber when the plunger moves in the direction to be pressed into the cylinder, and an expanded gap that receives the oil leaked from the pressure chamber through the leak gap. The expanded gap is a gap with a larger radial dimension than the leak gap.

[0005] Furthermore, the cylinder is formed with a cylinder-side oil passage that opens to the inner circumference of the cylinder so that oil supplied from an oil hole in the engine block outside the cylinder can be introduced into an enlarged gap between the outer circumference of the plunger and the inner circumference of the cylinder. Also, the plunger is formed with a plunger-side oil passage that penetrates the plunger in the radial direction so that oil can be introduced from the enlarged gap into the reservoir chamber.

[0006] 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.

[0007] On the other hand, when the tension in the chain decreases while the engine is running, the force of the return spring causes the plunger to move 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, causing the plunger to move quickly.

[0008] When the plunger moves in the push-in direction and the volume of the pressure chamber decreases, oil leaking from the pressure chamber flows into the expanded gap. The oil in the expanded gap then returns to the reservoir chamber in the plunger through the plunger-side oil passage and is reused. This makes it possible for this chain tensioner to reduce oil consumption.

[0009] Furthermore, the chain tensioner in Patent Document 1 is provided with a relief valve at the position of the check valve inside the plunger to release oil from the pressure chamber to the reservoir chamber when the pressure in the pressure chamber exceeds a preset pressure. By providing this relief valve, it becomes possible to prevent the damping force caused by the leakage gap from becoming excessive in the high revolution range of the engine. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2017-89749 A Summary of the Invention [Problem to be solved by the invention]

[0011] Incidentally, the chain tensioner of Patent Document 1 has a large number of parts. That is, in the chain tensioner of Patent Document 1, the relief valve has a valve seat member of a check valve (a member in which a valve hole communicating between a pressure chamber and a reservoir chamber is formed, and the end of the valve hole on the pressure chamber side is opened and closed by a spherical valve body), a relief sleeve that slidably supports this valve seat member, a relief spring that presses the valve seat member, a pressing spring retainer that supports the relief spring, and a relief valve seat portion that contacts and supports the valve seat member against the biasing force of the relief spring, all of which are separate parts from the plunger. For this reason, the chain tensioner has a large number of parts.

[0012] Furthermore, the chain tensioner of Patent Document 1 has poor assembly properties for the relief valve. That is, in the chain tensioner of Patent Document 1, when assembling the relief valve into the plunger, it is necessary to press-fit the relief sleeve into the plunger and also press-fit the relief valve seat into the plunger. However, it is difficult to press-fit two parts into the plunger in order and position the two parts.

[0013] An object of the present invention is to provide a chain tensioner that has a relief valve in place of the check valve and has a reduced number of parts. [Means for solving the problem]

[0014] In order to solve the above problems, the present invention provides a chain tensioner having the following configuration. a cylindrical 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; a return spring that biases the plunger in a direction protruding from the cylinder; a check valve incorporated in the plunger so as to divide an area surrounded by the cylinder and the plunger into a pressure chamber on the cylinder side and a reservoir chamber on the plunger side, the check valve allowing only oil flow from the reservoir chamber side to the pressure chamber side; a leakage gap formed between an outer periphery of the plunger and an inner periphery of the cylinder, for allowing oil to leak from the pressure chamber when the plunger moves in a direction to be pushed into the cylinder; an enlarged gap having a radial dimension larger than that of the leak gap, the enlarged gap being formed between an outer periphery of the plunger and an inner periphery of the cylinder so as to receive oil leaked from the pressure chamber through the leak gap; a cylinder side oil passage that opens to an inner periphery of the cylinder and introduces oil supplied from the outside of the cylinder into the expanded gap; A plunger-side oil passage is formed radially penetrating the plunger and introduces oil from the enlarged gap to the reservoir chamber. The check valve is a chain tensioner having a valve seat member 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 member is provided axially movable within the plunger with a relief gap between an outer periphery of the valve seat member and an inner periphery of the plunger, the relief gap allowing passage of oil therebetween, a relief spring is mounted within the plunger, the relief spring having one end supported by the end of the plunger protruding from the cylinder and the other end pressing the valve seat member, thereby urging the valve seat member in a direction toward the end of the plunger inserted into the cylinder; a stepped relief seat portion is provided on an inner periphery of the plunger for contacting and supporting the valve seat member against the biasing force of the relief spring; a relief seat portion that is provided between the valve seat member and the relief spring and that is connected to the pressure chamber and the pressure chamber, the relief seat portion being connected to the relief valve and that is connected to the relief spring and that is connected to the pressure chamber and the pressure chamber being connected to the relief valve.

[0015] In this way, the relief spring is supported by utilizing the end of the plunger protruding from the cylinder, so there is no need to provide a member for supporting the relief spring inside the plunger, making it possible to reduce the number of parts.

[0016] It is preferable that the valve seat member has a configuration having a cylindrical portion that is guided axially movably on the inner circumference of the plunger across the relief gap, and an annular outer peripheral convex portion that is formed on the outer periphery of the axial end of the cylindrical portion and is supported in contact with the relief seat portion.

[0017] With this arrangement, the cylindrical portion of the valve seat member is guided by the inner periphery of the plunger, so that the attitude of the valve seat member can be stabilized when the valve seat member moves axially in response to the pressure in the pressure chamber.

[0018] It is preferable that a contact surface of the outer peripheral convex portion with the relief seat portion and a contact surface of the relief seat portion with the outer peripheral convex portion are formed in a tapered shape.

[0019] In this way, the outer peripheral convex portion of the valve seat member and the relief seat portion come into contact with each other via their tapered surfaces, making it easier for the center of the valve seat member to coincide with the center of the relief seat portion, and thereby stabilizing the posture of the valve seat member when it comes into contact with the relief seat portion.

[0020] It is preferable that the plunger comprises a cylindrical plunger body having an open end inserted into the cylinder and a closed end protruding from the cylinder, and a cylindrical press-fit part pressed into the insertion end of the plunger body inserted into the cylinder, and that the relief seat portion is formed in the press-fit part.

[0021] In this way, the relief valve can be easily assembled by sequentially inserting the relief spring and valve seat member into the plunger body from the insertion end of the plunger body into the cylinder, and then pressing a press-in part into the insertion end of the plunger body into the cylinder.

[0022] In this case, it is preferable to form a step portion on the inner circumference of the plunger body to receive the valve seat member when the valve seat member moves in a direction toward the protruding end of the plunger from within the cylinder, thereby regulating the movement range of the valve seat member.

[0023] In this way, the range of movement of the valve seat member is restricted by the step portion, so that when a pressure increase in the pressure chamber causes the valve seat member to move away from the relief seat portion, it is possible to prevent the valve seat member from moving too far and causing the position of the valve seat member to become unstable.

[0024] In this case, it is preferable that an oil groove is formed in the valve seat member so as to extend across the contact surface with the stepped portion.

[0025] With this configuration, when the valve seat member moves significantly and comes into contact with the stepped portion, oil can escape from the pressure chamber to the reservoir chamber via the oil groove formed on the contact surface of the valve seat member with the stepped portion.

[0026] Also, an oil groove may be formed in the step portion so as to extend across the contact surface with the valve seat member.

[0027] With this configuration, when the valve seat member moves significantly and comes into contact with the stepped portion, oil can escape from the pressure chamber to the reservoir chamber via the oil groove formed on the contact surface of the stepped portion with the valve seat member.

[0028] The return spring includes a first compression coil spring and a second compression coil spring arranged coaxially inside the first compression coil spring, the press-fit part has a cylindrical portion press-fitted into the inner periphery of the plunger body, and a flange portion seamlessly formed integrally with the cylindrical portion and extending radially outward and radially inward from one end of the cylindrical portion, The flange portion may have a seating surface formed thereon for receiving the first compression coil spring and the second compression coil spring.

[0029] In this way, the biasing force of the return spring can be strengthened without changing the valve opening pressure of the relief valve, thereby improving the ability of the plunger to follow the chain.

[0030] The return spring includes a first compression coil spring and a second compression coil spring arranged coaxially inside the first compression coil spring, an annular washer having an inner diameter smaller than an inner diameter of the press-fitting part is sandwiched between an insertion end of the plunger body into the cylinder and the first and second compression coil springs; The washer may have a seat surface formed thereon for receiving the first compression coil spring and the second compression coil spring.

[0031] In this way, the biasing force of the return spring can be strengthened without changing the valve opening pressure of the relief valve, thereby improving the ability of the plunger to follow the chain.

[0032] It is preferable that the plunger comprises a cylindrical plunger body open at both ends and a press-fit part pressed into the end of the plunger body protruding from the cylinder, and that the press-fit part forms the end of the plunger protruding from the cylinder.

[0033] In this way, the relief valve can be easily assembled by sequentially inserting the valve seat member and relief spring into the plunger body from the side of the end of the plunger body protruding from the cylinder, and then pressing a press-fit part into the end of the plunger body protruding from the cylinder.

[0034] The return spring includes a first compression coil spring and a second compression coil spring arranged coaxially inside the first compression coil spring, The plunger body has an inward flange portion formed seamlessly and integrally therewith, the inward flange portion extending radially inward from an insertion end of the plunger body into the cylinder, A configuration can be adopted in which a seat surface for receiving the first compression coil spring and the second compression coil spring is formed on the insertion end of the plunger body into the cylinder and on the inward flange portion.

[0035] In this way, the biasing force of the return spring can be strengthened without changing the valve opening pressure of the relief valve, thereby improving the ability of the plunger to follow the chain. Effect of the Invention

[0036] Because the chain tensioner of this invention supports the relief spring using the end of the plunger protruding from the cylinder, there is no need to provide a member for supporting the relief spring inside the plunger, making it possible to reduce the number of parts. [Brief description of the drawings]

[0037] [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] An enlarged cross-sectional view of the valve seat member and its surroundings in FIG. [Figure 4] FIG. 4 is a diagram showing a state in which the valve seat member shown in FIG. 3 is separated from the relief seat portion. [Diagram 5] FIG. 3 is a diagram showing a modified example in which an oil groove is formed on the contact surface of the valve seat member in FIG. 2 with the relief seat portion. [Figure 6] Cross-sectional view taken along line VI-VI in Figure 5. [Figure 7] FIG. 3 is a diagram showing a modified example in which an oil groove is formed on the contact surface of the relief seat portion of FIG. 2 with the valve seat member. [Figure 8] Cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] FIG. 3 is a diagram showing a modification of the return spring and press-fit part of FIG. 2. [Figure 10] FIG. 3 is a diagram showing a modified example of the valve seat member and the retainer shown in FIG. 2. [Figure 11] FIG. 11 shows a modification in which a washer is added to the modification in FIG. 10 and a double compression coil spring is used as the return spring. [Figure 12] FIG. 3 is a diagram showing a chain tensioner according to a second embodiment of the present invention, corresponding to FIG. 2. [Figure 13] FIG. 13 is a diagram showing a modified example in which an inward flange portion is formed on the plunger body of FIG. 12 and a double compression coil spring is used as the return spring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The cylinder 9 is integrally formed from an aluminum alloy. The cylinder 9 is fixed to an engine block (not shown) by fastening bolts 12 (see FIG. 1) to a plurality of mounting pieces 11 that are integrally formed on the outer periphery of the cylinder 9.

[0042] The plunger 10 is formed in a cylindrical shape with an end of the plunger 10 inserted into the cylinder 9 open and an end of the plunger 10 protruding from the cylinder 9 closed. In this embodiment, the plunger 10 is composed of a cylindrical plunger body 10A with an end of the plunger 10 inserted into the cylinder 9 open and an end of the plunger 10 protruding from the cylinder 9 closed, and a cylindrical press-in part 10B press-fitted into the end of the plunger body 10A inserted into the cylinder 9. The material of the plunger body 10A is metal (for example, steel such as SCM or SCr). The material of the press-in part 10B is metal or resin.

[0043] A check valve 13 is incorporated at the end of the plunger 10 on the side where it is inserted into the cylinder 9. The check valve 13 divides the area surrounded by the cylinder 9 and the plunger 10 into a pressure chamber 14 on the side of the closed end of the cylinder 9 and a reservoir chamber 15 on the side of the end of the plunger 10 protruding from the cylinder 9. The volume of the pressure chamber 14 expands when the plunger 10 moves axially in the direction protruding from the cylinder 9, and contracts when the plunger 10 moves axially in the direction being pushed into the cylinder 9. On the other hand, the volume of the reservoir chamber 15 does not change and remains constant even if the plunger 10 moves axially.

[0044] A fitting cylindrical surface 16 is formed on the outer periphery of the plunger body 10A, which is fitted axially slidably to the inner periphery of the cylinder 9. The fitting cylindrical surface 16 is a cylindrical surface whose outer diameter does not change along the axial direction. The inner periphery of the cylinder 9 is also a cylindrical surface whose inner diameter does not change along the axial direction. A leak gap 17 is formed between the fitting cylindrical surface 16 and the inner periphery of the cylinder 9, which allows oil to leak from the pressure chamber 14 when the plunger 10 moves in a direction to be pushed into the cylinder 9. The leak gap 17 is a cylindrical minute gap whose radial width is set to a range of 0.010 to 0.050 mm.

[0045] In addition, a small-diameter outer diameter surface 18 having an outer diameter smaller than that of the fitting cylindrical surface 16 is formed on the outer periphery of the plunger body 10A on the side closer to the protruding end of the plunger 10 from the cylinder 9 (the right side in the figure) with respect to the fitting cylindrical surface 16. An enlarged gap 19 having a radial dimension larger than that of the leak gap 17 is formed between the small-diameter outer diameter surface 18 and the inner periphery of the cylinder 9. The axial length of the enlarged gap 19 is set to be longer than the movement stroke of the plunger 10 with respect to the elongation of the chain 6 (see FIG. 1) over time, and is set to, for example, 10 mm or more. The enlarged gap 19 is formed adjacent to the leak gap 17 in the axial direction so as to receive oil leaked from the pressure chamber 14 through the leak gap 17.

[0046] Further, on the outer periphery of the plunger body 10A, a second fitting cylindrical surface 20 that fits axially slidably on the inner periphery of the cylinder 9 is formed on the side closer to the end of the plunger 10 protruding from the cylinder 9 (the right side in the drawing) relative to the small-diameter outer diameter surface 18. The second fitting cylindrical surface 20 is a cylindrical surface having the same outer diameter dimension as the fitting cylindrical surface 16.

[0047] The cylinder 9 is formed with a cylinder-side oil passage 21 that introduces oil supplied from an oil pump (not shown) outside the cylinder 9 into the enlarged gap 19. The cylinder-side oil passage 21 opens into a portion of the inner periphery of the cylinder 9 that faces radially the small-diameter outer diameter surface 18 of the outer periphery of the plunger body 10A.

[0048] The plunger body 10A is formed with a plunger-side oil passage 23 that introduces oil from the enlarged gap 19 to the reservoir chamber 15. The plunger-side oil passage 23 is a hole formed radially penetrating the plunger body 10A. The end of the plunger-side oil passage 23 on the outer periphery side of the plunger body 10A opens to the small-diameter outer diameter surface 18.

[0049] A return spring 24 is incorporated in the pressure chamber 14. The return spring 24 is a compression coil spring made of a metal wire wound in a spiral shape. One end of the return spring 24 is supported by the closed end of the cylinder 9, and the other end presses the insertion end of the plunger 10 into the cylinder 9 in the axial direction, and this pressing force urges the plunger 10 in the direction of protruding from the cylinder 9.

[0050] As shown in Fig. 3, the check valve 13 has a valve seat member 26 in which a valve hole 25 that communicates between the pressure chamber 14 and the reservoir chamber 15 is formed, and a spherical valve body 27 that opens and closes the end of the valve hole 25 on the pressure chamber 14 side. A retainer 28 that limits the movement range of the valve body 27 is attached to the valve seat member 26. A check spring 29 that urges the valve body 27 from the valve open position toward the valve closed position is assembled between the retainer 28 and the valve body 27. The check valve 13 limits the flow of oil from the pressure chamber 14 side to the reservoir chamber 15 side, and allows oil to flow only from the reservoir chamber 15 side to the pressure chamber 14 side.

[0051] As shown in Fig. 2, a relief spring 30 is incorporated in the plunger 10. The relief spring 30 is a compression coil spring made of a metal wire wound in a spiral shape. One end of the relief spring 30 is supported by the end of the plunger 10 protruding from the cylinder 9, and the other end of the relief spring 30 presses the valve seat member 26 in the axial direction.

[0052] The outer periphery of the relief spring 30 is directly fitted into the inner periphery of the plunger 10. The axial length of the relief spring 30 is longer than half the axial length of the plunger 10. The valve seat member 26 is biased by the pressure of the relief spring 30 in a direction toward the insertion end of the plunger 10 into the cylinder 9.

[0053] 3 and 4, the valve seat member 26 is provided to be movable in the axial direction within the plunger 10, with a relief gap 31 that allows oil to pass between the outer periphery of the valve seat member 26 and the inner periphery of the plunger 10 (press-fit part 10B in this embodiment). A stepped relief seat portion 32 that contacts and supports the valve seat member 26 against the biasing force of the relief spring 30 is provided on the inner periphery of the plunger 10. The relief seat portion 32 is formed in the press-fit part 10B.

[0054] The valve seat member 26, the relief seat portion 32 and the relief spring 30 constitute a relief valve that releases oil from the pressure chamber 14 to the reservoir chamber 15 when the pressure in the pressure chamber 14 exceeds a preset pressure.

[0055] The press-fit part 10B has a cylindrical portion 33 that is press-fitted into the inner periphery of the plunger body 10A, and a flange portion 34 that extends radially outward from one end of the cylindrical portion 33. The flange portion 34 abuts against the end of the plunger body 10A that is inserted into the cylinder 9 in the axial direction.

[0056] The valve seat member 26 has a cylindrical portion 35 that is guided axially movably on the inner circumference of the plunger 10 (in this embodiment, the cylindrical portion 33 of the press-in part 10B) with a relief gap 31 between them, and an outer peripheral convex portion 36 that is formed on the outer periphery of the axial end of the cylindrical portion 35 and is supported in contact with the relief seat portion 32.

[0057] 3, the contact surface of the outer peripheral protrusion 36 with the relief seat portion 32 is formed in a concave taper shape that gradually becomes smaller in diameter along the pressing direction of the relief spring 30. In addition, the contact surface of the relief seat portion 32 with the outer peripheral protrusion 36 is also formed in a convex taper shape that gradually becomes smaller in diameter along the pressing direction of the relief spring 30.

[0058] A step portion 37 is formed on the inner periphery of the plunger body 10A on the side closer to the end of the plunger 10 protruding from within the cylinder 9 (the right side in the drawing) relative to the relief seat portion 32. The step portion 37 receives the valve seat member 26 when the valve seat member 26 moves in the direction toward the end of the plunger 10 protruding from within the cylinder 9 (to the right in the drawing), thereby restricting the movement range of the valve seat member 26 (see FIG. 5).

[0059] Next, an example of the operation of this chain tensioner 1 will be described.

[0060] 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 14 shown in FIG. 2 becomes higher than the pressure of the reservoir chamber 15, so the check valve 13 is closed. In addition, the volume of the pressure chamber 14 decreases with the movement of the plunger 10, so oil leaks from the pressure chamber 14 through the leak gap 17 by the amount of the reduced volume. At this time, the viscous resistance of the oil flowing through the leak gap 17 generates a damping force, which prevents the chain 6 from flapping. Here, when the plunger 10 moves in the pushing direction and the volume of the pressure chamber 14 decreases, the oil leaking from the pressure chamber 14 flows into the expanded gap 19. The oil in the expanded gap 19 returns to the reservoir chamber 15 in the plunger 10 through the plunger-side oil passage 23 and is reused.

[0061] On the other hand, when the tension of the chain 6 shown in FIG. 1 decreases during engine operation, the force of the return spring 24 shown in FIG. 2 and the oil pressure of the pressure chamber 14 move the plunger 10 in the protruding direction, absorbing the slack in the chain 6. At this time, the volume of the pressure chamber 14 expands in response to the movement of the plunger 10, so that the pressure of the pressure chamber 14 becomes lower than the pressure of the reservoir chamber 15, and the check valve 13 opens. Then, oil flows from the reservoir chamber 15 through the check valve 13 into the pressure chamber 14, and the plunger 10 moves quickly. At this time, oil is introduced from outside the cylinder 9 into the reservoir chamber 15 through the cylinder side oil passage 21, the expanded gap 19, and the plunger side oil passage 23 in this order.

[0062] When the engine operates in a high revolution range, a high-frequency excitation force continues to act on the plunger 10 from the chain 6, so that the damping force generated by the oil flowing through the leak gap 17 tends to become excessive. At this time, if the pressure in the pressure chamber 14 becomes higher than a preset pressure, the pressure in the pressure chamber 14 causes the valve seat member 26 to move away from the relief seat portion 32, as shown in Fig. 4, and the oil in the pressure chamber 14 is released to the reservoir chamber 15 through the relief gap 31 and the gap between the valve seat member 26 and the relief seat portion 32 in that order. This suppresses the pressure rise in the pressure chamber 14, and prevents the damping force from becoming excessive.

[0063] This chain tensioner 1 supports the relief spring 30 by utilizing the end of the plunger 10 protruding from the cylinder 9, so there is no need to provide a member for supporting the relief spring 30 inside the plunger 10, making it possible to reduce the number of parts.

[0064] Furthermore, in this chain tensioner 1, the compression coil spring that constitutes the relief spring 30 has a large coil diameter and a long axial length, so that the pressing force applied from the relief spring 30 to the valve seat member 26 is extremely stable, eliminating variation in the opening pressure of the relief valve and ensuring stable operation of the relief valve.

[0065] In addition, this chain tensioner 1 employs a valve seat member 26 consisting of a cylindrical portion 35 that is guided along the inner circumference of the plunger 10 so as to be able to move in the axial direction, and an outer peripheral convex portion 36 that is supported in contact with the relief seat portion 32. Therefore, the posture of the valve seat member 26 is stable when it moves axially in response to the pressure in the pressure chamber 14.

[0066] Furthermore, in this chain tensioner 1, the outer peripheral convex portion 36 of the valve seat member 26 and the relief seat portion 32 come into contact with each other via their tapered surfaces, so that the center of the valve seat member 26 and the center of the relief seat portion 32 tend to coincide, and the attitude of the valve seat member 26 when it comes into contact with the relief seat portion 32 is stable.

[0067] Furthermore, this chain tensioner 1 employs a plunger 10 consisting of a plunger body 10A and a cylindrical press-fit part 10B press-fitted into the insertion end of the plunger body 10A into the cylinder 9, so that the relief valve can be easily assembled by inserting the relief spring 30 and the valve seat member 26 into the plunger body 10A in this order from the side of the insertion end of the plunger body 10A into the cylinder 9, and then press-fitting the press-fit part 10B into the insertion end of the plunger body 10A into the cylinder 9. Also, when assembling the relief valve, only one part (press-fit part 10B) needs to be press-fitted.

[0068] Furthermore, this chain tensioner 1 has a step portion 37 formed on the inner circumference of the plunger body 10A, which restricts the movement range of the valve seat member 26. Therefore, when the valve seat member 26 moves away from the relief seat portion 32 due to a pressure increase in the pressure chamber 14, it is possible to prevent the valve seat member 26 from moving too far and causing the position of the valve seat member 26 to become unstable.

[0069] As shown in Figures 5 and 6, it is preferable to form oil grooves 38 extending across the contact surface with the step portion 37 of the valve seat member 26. In this way, when the valve seat member 26 moves significantly and comes into contact with the step portion 37, as shown in Figure 5, it becomes possible for oil to escape from the pressure chamber 14 to the reservoir chamber 15 via the oil grooves 38 formed on the contact surface with the step portion 37 of the valve seat member 26. In the figures, the oil grooves 38 are a plurality of grooves that extend radially through the contact surface with the step portion 37 of the valve seat member 26 from the outer periphery of the valve seat member 26 to the position of the valve hole 25 (see Figure 6).

[0070] 7 and 8, an oil groove 39 may be formed that extends across the contact surface of a step portion 37 on the inner circumference of the plunger body 10A with the valve seat member 26. In this way, as shown in FIG. 7, when the valve seat member 26 moves significantly and comes into contact with the step portion 37, oil can be released from the pressure chamber 14 to the reservoir chamber 15 via the oil groove 39 formed on the contact surface of the step portion 37 with the valve seat member 26.

[0071] 9 shows a modified example of the return spring 24 and the press-fit part 10B. In the figure, the return spring 24 is composed of a first compression coil spring 24a and a second compression coil spring 24b arranged coaxially inside the first compression coil spring 24a. The first compression coil spring 24a is a cylindrical coil spring that extends along the inner circumference of the cylinder 9. The second compression coil spring 24b is a conical coil spring that contracts in diameter from the closed end of the cylinder 9 toward the plunger 10.

[0072] The press-fit part 10B has a cylindrical portion 33 that is press-fitted into the inner circumference of the plunger body 10A, and a flange portion 34 that extends radially outward and radially inward from one end of the cylindrical portion 33. The cylindrical portion 33 and the flange portion 34 are formed seamlessly as a single unit. The flange portion 34 is formed with a seating surface that receives the first compression coil spring 24a and the second compression coil spring 24b.

[0073] 9 is adopted, it is possible to strengthen the biasing force of the return spring 24 without changing the valve opening pressure of the relief valve, and to improve the ability of the plunger 10 to follow the chain 6.

[0074] Fig. 10 shows modified examples of the valve seat member 26 and the retainer 28. In Fig. 10, an annular protrusion 40 surrounding the valve hole 25 is formed on the surface of the valve seat member 26 facing the pressure chamber 14. The retainer 28 is fixed to the valve seat member 26 by fitting onto the outer periphery of the annular protrusion 40.

[0075] FIG. 11 shows a modified example in which a washer is added to FIG. 10 and a double compression coil spring is used as the return spring. In FIG. 11, the return spring 24 is composed of a first compression coil spring 24a and a second compression coil spring 24b arranged coaxially inside the first compression coil spring 24a, as in the modified example shown in FIG. 9. Between the insertion end of the plunger body 10A into the cylinder 9 and the first compression coil spring 24a and the second compression coil spring 24b, a ring-shaped washer 41 having an inner diameter smaller than the inner diameter of the press-fit part 10B is sandwiched. The washer 41 is formed with a seat surface for receiving the first compression coil spring 24a and the second compression coil spring 24b.

[0076] 11, it is possible to strengthen the biasing force of the return spring 24 without changing the valve opening pressure of the relief valve, thereby improving the ability of the plunger 10 to follow the chain 6.

[0077] Figure 12 shows a chain tensioner 1 according to a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the configuration of the plunger body and the press-fit parts, and the other configurations are the same. Therefore, parts corresponding to the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0078] The plunger 10 is composed of a cylindrical plunger body 10A with both ends open, and a press-fit part 10C press-fitted into the end of the plunger body 10A protruding from the cylinder 9. The plunger body 10A is made of metal. The press-fit part 10C is made of metal or resin.

[0079] The valve seat member 26 is provided to be movable in the axial direction within the plunger 10, with a relief gap 31 that allows oil to pass between the outer periphery of the valve seat member 26 and the inner periphery of the plunger body 10A. The relief seat portion 32 is formed on the inner periphery of the plunger body 10A.

[0080] The press-fit part 10C is in contact with the chain guide 8. One end of the relief spring 30 is supported by the press-fit part 10C. The press-fit part 10C has a cylindrical part 42 that is press-fitted and fixed to the end of the plunger body 10A protruding from the cylinder 9, and an end plate part 43 that closes one end of the cylindrical part 42.

[0081] This chain tensioner 1 employs a plunger 10 consisting of a plunger body 10A and a press-fit part 10C press-fitted into the end of the plunger body 10A protruding from the cylinder 9, so that the relief valve can be easily assembled by inserting the valve seat member 26 and the relief spring 30 into the plunger body 10A in this order from the side of the end of the plunger body 10A protruding from the cylinder 9, and then press-fitting the press-fit part 10C into the end of the plunger body 10A protruding from the cylinder 9. Also, when assembling the relief valve, only one part (press-fit part 10C) needs to be press-fitted.

[0082] Fig. 13 shows a modified example of the return spring 24 and the plunger body 10A. In the figure, the return spring 24 is composed of a first compression coil spring 24a and a second compression coil spring 24b arranged coaxially inside the first compression coil spring 24a, similar to the modified example shown in Fig. 9.

[0083] The plunger body 10A is formed with an inward flange portion 44 that extends radially inward from the end of the plunger body 10A inserted into the cylinder 9. The end of the plunger body 10A inserted into the cylinder 9 and the inward flange portion 44 are formed with seats that receive the first compression coil spring 24a and the second compression coil spring 24b.

[0084] 13, it is possible to strengthen the biasing force of the return spring 24 without changing the valve opening pressure of the relief valve, thereby improving the ability of the plunger 10 to follow the chain 6.

[0085] In each of the above embodiments, an example has been described 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. However, the chain tensioner 1 can also be incorporated into a chain transmission device that transmits the rotation of the crankshaft 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 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.

[0086] 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]

[0087] 1 Chain tensioner 9 Cylinders 10 Plunger 10A plunger body 10B Press-fit parts 10C Press-fit parts 13 Check valve 14 Pressure Chamber 15 Reservoir Room 17 Leak gap 19 Expanded Gap 21 Cylinder side oil passage 23 Plunger side oil passage 24 Return spring 24a First compression coil spring 24b Second compression coil spring 25 Valve hole 26 Valve seat material 27 Valve body 30 Relief spring 31 Relief gap 32 Relief seat part 33 Cylindrical section 34 Flange section 35 Cylinder section 36 Outer periphery protrusion 37 Step 38 Oil groove 39 Oil groove 41 Washer 44 Inward flange

Claims

1. A cylindrical 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); a return spring (24) that biases the plunger (10) in a direction protruding from the cylinder (9); a check valve (13) incorporated in the plunger (10) so as to divide an area surrounded by the cylinder (9) and the plunger (10) into a pressure chamber (14) on the cylinder (9) side and a reservoir chamber (15) on the plunger (10) side, and which allows oil to flow only from the reservoir chamber (15) side to the pressure chamber (14) side; a leak gap (17) formed between an outer periphery of the plunger (10) and an inner periphery of the cylinder (9), which allows oil to leak from the pressure chamber (14) when the plunger (10) moves in a direction to be pushed into the cylinder (9); an enlarged gap (19) formed between an outer periphery of the plunger (10) and an inner periphery of the cylinder (9) so as to receive oil leaked from the pressure chamber (14) through the leak gap (17), the enlarged gap having a radial dimension larger than that of the leak gap (17); a cylinder-side oil passage (21) that opens to an inner periphery of the cylinder (9) and introduces oil supplied from the outside of the cylinder (9) into the expanded gap (19); a plunger-side oil passage (23) formed radially penetrating the plunger (10) and introducing oil from the expanded gap (19) to the reservoir chamber (15); The check valve (13) is a chain tensioner having a valve seat member (26) in which a valve hole (25) communicating between the pressure chamber (14) and the reservoir chamber (15) is formed, and a valve body (27) for opening and closing an end of the valve hole (25) on the pressure chamber (14) side, the valve seat member (26) is provided axially movable within the plunger (10) with a relief gap (31) that allows oil to pass between an outer periphery of the valve seat member (26) and an inner periphery of the plunger (10); A relief spring (30) is incorporated in the plunger (10), one end of which is supported by the end of the plunger (10) protruding from the cylinder (9) and the other end of which presses the valve seat member (26), thereby urging the valve seat member (26) in a direction toward the end of the plunger (10) inserted into the cylinder (9), a stepped relief seat portion (32) is provided on the inner periphery of the plunger (10) for contacting and supporting the valve seat member (26) against the biasing force of the relief spring (30); the valve seat member (26), the relief seat portion (32), and the relief spring (30) constitute a relief valve in which, when the pressure in the pressure chamber (14) becomes greater than a preset pressure, the valve seat member (26) moves away from the relief seat portion (32) to release oil through the relief gap (31) between the outer periphery of the valve seat member (26) and the inner periphery of the plunger (10) to the reservoir chamber (15); the relief spring (30) is a compression coil spring made of metal wire wound in a spiral shape, the outer periphery of the relief spring (30) is directly fitted into the inner periphery of the plunger (10), and one end of the relief spring (30) is directly supported by the end of the plunger (10) protruding from the cylinder (9) without any other member therebetween.

2. 2. The chain tensioner according to claim 1, wherein the valve seat member (26) has a cylindrical portion (35) that is guided axially movably on the inner circumference of the plunger (10) with the relief gap (31) disposed therebetween, and an outer peripheral convex portion (36) that is formed on the outer periphery of the axial end of the cylindrical portion (35) and is supported in contact with the relief seat portion (32).

3. 3. The chain tensioner according to claim 2, wherein a contact surface of the outer peripheral protrusion (36) with the relief seat portion (32) and a contact surface of the relief seat portion (32) with the outer peripheral protrusion (36) are formed in a tapered shape.

4. 4. The chain tensioner according to claim 1, wherein the plunger (10) comprises a cylindrical plunger body (10A) whose end inserted into the cylinder (9) is open and whose end protruding from the cylinder (9) is closed, and a cylindrical press-fit part (10B) press-fitted into the end of the plunger body (10A) inserted into the cylinder (9), and the relief seat portion (32) is formed in the press-fit part (10B).

5. 5. The chain tensioner according to claim 4, wherein a stepped portion (37) is formed on an inner circumference of the plunger body (10A) for receiving the valve seat member (26) when the valve seat member (26) moves in a direction toward the end of the plunger (10) protruding from within the cylinder (9) and thereby regulating the movement range of the valve seat member (26).

6. 6. The chain tensioner according to claim 5, wherein the valve seat member (26) is formed with an oil groove (38) extending across a contact surface with the stepped portion (37).

7. 6. The chain tensioner according to claim 5, wherein the step portion (37) is formed with an oil groove (39) extending across a contact surface with the valve seat member (26).

8. The return spring (24) includes a first compression coil spring (24a) and a second compression coil spring (24b) arranged coaxially inside the first compression coil spring (24a), The press-fit part (10B) has a cylindrical portion (33) that is press-fitted into the inner periphery of the plunger body (10A), and a flange portion (34) that is seamlessly formed integrally with the cylindrical portion (33) and extends radially outward and radially inward from one end of the cylindrical portion (33), 8. The chain tensioner according to claim 4, wherein the flange portion (34) is formed with seating surfaces for receiving the first compression coil spring (24a) and the second compression coil spring (24b).

9. The return spring (24) includes a first compression coil spring (24a) and a second compression coil spring (24b) arranged coaxially inside the first compression coil spring (24a), an annular washer (41) having an inner diameter smaller than an inner diameter of the press-fit part (10B) is sandwiched between an insertion end of the plunger body (10A) into the cylinder (9) and the first compression coil spring (24a) and the second compression coil spring (24b); 8. The chain tensioner according to claim 4, wherein the washer (41) is formed with seats for receiving the first compression coil spring (24a) and the second compression coil spring (24b).

10. 4. The chain tensioner according to claim 1, wherein the plunger (10) comprises a cylindrical plunger body (10A) open at both ends and a press-fit part (10C) press-fitted into the end of the plunger body (10A) protruding from the cylinder (9), and the press-fit part (10C) forms the end of the plunger (10) protruding from the cylinder (9).

11. The return spring (24) includes a first compression coil spring (24a) and a second compression coil spring (24b) arranged coaxially inside the first compression coil spring (24a), The plunger body (10A) has an inward flange portion (44) extending radially inward from an insertion end of the plunger body (10A) into the cylinder (9) and formed seamlessly and integrally therewith; 11. The chain tensioner according to claim 10, wherein a seating surface for receiving the first compression coil spring (24a) and the second compression coil spring (24b) is formed on an insertion end of the plunger body (10A) into the cylinder (9) and on the inward flange portion (44).

Images