JP2020045978A - Chain tensioner - Google Patents

Abstract

To provide a chain tensioner having high following performance to loosening of a chain, and reduced in outflow of an oil.SOLUTION: A chain tensioner includes a tubular cylinder 9 opened at one end and closed at the other end, a cylindrical plunger 10, a return spring 33, a pressure chamber 18 changing a volume in accompany with axial movement of the plunger 10, a check valve 20 permitting only flow of an oil from the inside of the plunger 10 into the pressure chamber 18, a leak gap c0 formed between an outer periphery of the plunger 10 and an inner periphery of the cylinder 9, an oil supply passage 31 for introducing the oil from the outside to the inside of the cylinder 9, and a communication passage 30 for communicating the leak gap c0 with the inside of the plunger 10. It further includes a circumferential seal groove 35 formed on an outer periphery 32 of the plunger 10 at one end side with respect to the oil supply passage 31, and a seal ring 36 disposed in the seal groove 35, and a seal gap c1 is defined between an outer periphery 36d of the seal ring 36 and an inner periphery 14 of the cylinder 9.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a chain tensioner used for holding a chain in tension.

  Examples of a chain transmission device used for an engine of an automobile or the like include a device that transmits rotation of a crankshaft to a camshaft, a device that transmits rotation of a crankshaft to an auxiliary device such as an oil pump, and a device that transmits rotation of a crankshaft to a balancer shaft Or an engine that connects an intake cam and an exhaust cam of a twin cam engine to each other. A chain tensioner is used to keep the chain tension of these chain transmissions in an appropriate range.

  In general, a chain tensioner generates a hydraulic damper by oil supply from an engine to keep the fluctuation of the chain tension constant. However, since oil supply is stopped when the engine is stopped, a predetermined hydraulic damper may not be able to be generated after the engine is started until the pressure chamber inside the chain tensioner is filled with oil. In such a case, there is a problem that the chain tensioner is greatly pushed in, causing flapping and abnormal noise of the chain. Therefore, many chain tensioners are provided with a mechanism called a no-back mechanism to prevent the plunger from being pushed in beyond a certain amount.

  In addition, by circulating oil inside the chain tensioner, oil is prevented from flowing out of the chain tensioner, and by storing the oil inside the chain tensioner, a hydraulic damper can be generated immediately after the engine starts. There is also a chain tensioner (for example, see Patent Documents 1 and 2).

  For example, a chain tensioner 40 shown in FIG. 8 includes a cylindrical cylinder 9 having one end opened and the other end closed, a plunger 10 slidably supported in the inner periphery of the cylinder 9 in the axial direction, and a plunger 10. The plunger 10 includes a reservoir chamber 27 formed inside the cylinder 10 and a pressure chamber 18 formed at the other end of the plunger 10 in the cylinder 9 and having a volume that changes with the axial movement of the plunger 10.

  The cylinder 9 has an oil supply passage 31 for introducing oil supplied by an oil pump, and the oil supply passage 31 is opened in an oil supply space 28 formed between the outer periphery of the plunger 10 and the inner periphery of the cylinder 9. are doing. A leak gap is formed between the outer circumference of the plunger 10 and the inner circumference of the cylinder 9, and the leak gap and the oil supply space 28 communicate with the reservoir chamber 27 through the communication passage 30.

Japanese Patent Publication No. 3-010819 JP 2015-183767 A JP 2015-172435 A

  In the chain tensioner 40, in order to suppress the amount of oil flowing out, it is preferable that the leak gap is small.

  On the other hand, in order to adjust the damping force of the chain tensioner 40, it is necessary to adjust the size of the leak gap. Therefore, for example, in an engine that does not require a high damping force, it is necessary to increase the size of the first leak gap 19 from the pressure chamber 18 to the oil supply space 28. However, when the size of the first leak gap 19 is increased, the size of the second leak gap 29 extending from the oil supply space 28 to one end of the cylinder 9 is also increased, so that the amount of oil flowing out of the second leak gap 29 to the outside is increased. Leads to

  In this regard, Patent Literature 3 discloses that a seal ring is arranged between the inner surface of a cylinder and the outer surface of a plunger, and the outflow of oil to the outside of the chain tensioner is constant regardless of the size of the leak gap. Like that. However, when the seal ring is arranged between the inner surface of the cylinder and the outer surface of the plunger, there is a problem that the sliding resistance between the cylinder and the plunger increases. An increase in the sliding resistance is not preferable because it deteriorates the ability to follow the chain looseness.

  Accordingly, an object of the present invention is to provide a suitable chain tensioner which is excellent in followability to looseness of a chain and has a small oil outflow amount.

  In order to solve the above problems, the present invention provides a cylindrical cylinder having one end opened and the other end closed, and an insertion end into the cylinder which is supported slidably in the axial direction on the inner periphery of the cylinder. A cylindrical plunger having a protruding end from the cylinder closed; a return spring for urging the plunger in a direction protruding from the cylinder; and a cylinder inside the cylinder so that the volume changes with the axial movement of the plunger. A pressure valve formed between the outer circumference of the plunger and the inner circumference of the cylinder, and a check valve configured to allow only the flow of oil from the inside of the plunger to the pressure chamber; A leak gap for allowing oil to leak from the pressure chamber when the pressure is reduced, an oil supply passage for introducing oil from the outside to the inside of the cylinder, A communication passage communicating with the inside of the lancer, a circumferential seal groove provided on the outer periphery of the plunger at one end side from the oil supply passage, and a seal ring disposed in the seal groove to seal the leak gap. A chain tensioner having a seal gap between the outer periphery of the seal ring and the inner periphery of the cylinder is provided.

  Here, a configuration can be adopted in which the seal gap is equal to or smaller than the leak gap due to expansion of the seal ring due to a temperature change.

  Further, the seal ring may be provided with an abutment which is divided in a circumferential direction, and a circumferential gap between opposing surfaces of the abutment may be changed in accordance with a temperature change of the seal ring.

  At this time, it is possible to adopt a configuration in which the circumferential gap between the facing surfaces is set to be zero at any temperature in the range of 80 ° C to 120 ° C.

  Further, the opposing surfaces are each inclined to the same side with respect to a direction parallel to the axis, and the opposing surfaces are slidable in the axial direction according to a temperature change of the seal ring while the opposing surfaces are in contact with each other. Can be adopted.

  In each of these aspects, it is possible to adopt a configuration in which the seal ring has a linear expansion coefficient larger than the linear expansion coefficients of the plunger and the cylinder.

  Further, a configuration may be adopted in which an oil supply space communicating with the leak gap is formed between the outer periphery of the plunger and the inner periphery of the cylinder.

  According to the present invention, it is possible to provide a suitable chain tensioner which is excellent in following up the slackness of the chain and has a small oil outflow amount.

Overall view showing a chain transmission incorporating a chain tensioner (A) is a right side view of the chain tensioner of FIG. 1, and (b) is a rear view thereof. FIG. 2 is a longitudinal sectional view showing a chain tensioner according to an embodiment of the present invention. (A) is an enlarged view of a main part A of FIG. 3, (b) and (c) are further detailed views thereof. Front view of the plunger of FIG. 5A is an enlarged view showing a state where a gap is open, FIG. 5B is an enlarged view showing a state where a gap is closed, and FIG. 5C is a view showing an enlarged view showing a state where the gap is closed; Enlarged view showing a state where it is pressed from both sides and slides in the axial direction 6A is an enlarged view showing a state in which a gap is largely opened, and FIG. 6B is an enlarged view showing a state in which a gap is slightly reduced. Longitudinal sectional view showing a conventional chain tensioner

  FIG. 1 shows a chain transmission incorporating a chain tensioner 1 according to an embodiment of the present invention. In this chain transmission, a sprocket 3 fixed to a crankshaft 2 of an engine and a sprocket 5 fixed to two camshafts 4 are connected via a chain 6. The chain 6 transmits the rotation of the crankshaft 2 to the camshaft 4 and rotates the camshaft 4 to open and close the valve of the combustion chamber.

  The rotation direction of the crankshaft 2 when the engine is operating is constant (right rotation in FIG. 1), and at this time, the chain 6 is pulled into the sprocket 3 with the rotation of the crankshaft 2 (see FIG. 1). The portion on the right side is the tension side, and the portion on the side sent out from the sprocket 3 (the left side in FIG. 1) is the slack side. Then, a chain guide 8 supported swingably around a fulcrum shaft 7 is in contact with the slack side portion of the chain 6. The chain tensioner 1 presses the chain 6 via the chain guide 8.

  As shown in FIGS. 2 and 3, the chain tensioner 1 has a cylindrical cylinder 9 having one end opened and the other end closed, and a plunger 10 supported on the inner periphery of the cylinder 9 so as to be slidable in the axial direction. And A protruding end 17 of the plunger 10 protruding from one end of the cylinder 9 presses the chain guide 8.

  The cylinder 9 is integrally formed of metal (for example, aluminum alloy). The cylinder 9 is fixed to the engine wall by tightening bolts 12 inserted into holes 11a (see FIG. 2B) of a plurality of mounting pieces 11 integrally formed on the outer periphery of the cylinder 9. The cylinder 9 is attached to the engine wall so that the direction in which the plunger 10 protrudes from the cylinder 9 faces upward.

  The plunger 10 is formed in a tubular shape in which the other end inserted into the cylinder 9 is open and the protruding end 17 from the one end of the cylinder 9 is closed. The material of the plunger 10 is an iron-based material (for example, a steel material such as SCM (chrome molybdenum steel) or SCr (chrome steel)).

  At the other end in the cylinder 9, a pressure chamber 18 whose volume changes with the axial movement of the plunger 10 is formed. The volume of the pressure chamber 18 increases when the plunger 10 moves in the protruding direction, and decreases when the plunger 10 moves in the pushing direction.

  The outer circumferences 15 and 32 of the maximum diameter portion of the plunger 10 are cylindrical surfaces, and the inner circumference 14 of the cylinder 9 is also a cylindrical surface. The size of the gap between the outer circumferences 15 and 32 of the maximum diameter portion of the plunger 10 and the inner circumference 14 of the cylinder 9 is very small, and is set in the range of 0.005 to 0.10 mm in radius difference. The gap between the outer circumferences 15 and 32 of the maximum diameter portion of the plunger 10 and the inner circumference 14 of the cylinder 9 is a leak gap c0 for allowing oil to leak from the pressure chamber 18 when the volume of the pressure chamber 18 is reduced.

  An oil supply space 28 communicating with the leak gap c0 is formed between the outer periphery of the plunger 10 and the inner periphery of the cylinder 9. The oil supply space 28 is formed annularly between the concave portion 16 formed on the entire outer periphery of the plunger 10 and the inner periphery 14 of the cylinder 9.

  The concave portion 16 for forming the oil supply space 28 is provided at the axial center of the plunger 10, and the outer circumferences 15 and 32 of the largest diameter portion of the plunger 10 are provided at one end and the other end with the concave portion 16 interposed therebetween. Exists. Hereinafter, the leak gap c0 on the other end side of the recess 16, that is, on the pressure chamber 18 side is referred to as a first leak gap 19, and the leak gap c0 on one end side of the recess 16, that is, on the protruding end 17 side of the plunger 10. This is referred to as a second leak gap 29.

  A step portion 22 connected to the first leak gap 19 is formed at the other end of the oil supply space 28. A step 23 connected to the second leak gap 29 is formed at one end of the oil supply space 28.

  The step portions 22 and 23 are always located in the cylinder 9 regardless of the position of the plunger 10 when the plunger 10 advances or retreats. That is, the entire outer periphery 15 of the largest diameter portion of the plunger 10 constituting the first leak gap 19 is always accommodated in the cylinder 9. For this reason, when the plunger 10 moves in the axial direction according to the fluctuation in the tension of the chain 6, the axial length of the first leak gap 19 does not change. Therefore, a constant damping force can be exerted regardless of the position of the plunger 10 in the axial direction.

  A check valve that allows only the flow of oil from the inside of the plunger 10 to the pressure chamber 18 side and restricts the flow of oil from the pressure chamber 18 to the inside of the plunger 10 at the insertion end of the plunger 10 into the cylinder 9. 20 are provided. The check valve 20 has a valve seat 21, a check ball 25, and a retainer 26. The valve seat 21 is provided at an insertion end of the plunger 10 into the cylinder 9. The bubble sheet 21 is provided with a valve hole 21a penetrating in the axial direction. The check ball 25 is a spherical valve body that opens and closes the valve hole 21a from the pressure chamber 18 side. The retainer 26 regulates the moving range of the check ball 25.

  The internal space of the plunger 10 is a reservoir chamber 27 having a diameter larger than the diameter of the valve hole 21a of the check valve 20.

  A return spring 33 is incorporated in the pressure chamber 18. The other end of the return spring 33 is supported by the bottom portion 13 of the cylinder 9, and one end presses the plunger 10, thereby urging the plunger 10 in the direction in which the plunger 10 protrudes from the cylinder 9. In this embodiment, the return spring 33 presses the plunger 10 via the valve seat 21 of the check valve 20, but the return spring 33 may directly press the plunger 10.

  The plunger 10 is provided with a communication passage 30 that communicates between the oil supply space 28 and the reservoir chamber 27. The communication passage 30 communicates with the first leak gap 19 and the second leak gap 29 through the oil supply space 28.

  The communication passage 30 is provided so as to be located on the upper half circumference of the plunger 10 with the mounting piece 11 of the cylinder 9 fixed to the engine wall surface. Specifically, the communication passage 30 is provided in an upper portion in the radial direction of the plunger 10 and within a range corresponding to a half of the outer peripheral dimension of the plunger 10. In particular, in this embodiment, the communication passage 30 is It is provided so as to be located on the top of the outer circumference of the ten. Therefore, when air exists inside the reservoir chamber 27, the air can be smoothly discharged from the communication passage 30.

  Further, as shown in FIG. 3, the cylinder 9 is provided with an oil supply passage 31 for introducing oil from outside to inside of the cylinder 9. The oil supply passage 31 is a through hole that penetrates the cylinder 9 in the radial direction. An inlet 34 of the oil supply passage 31 (see FIG. 2B) is connected to an oil supply port on the engine wall side. The outlet of the oil supply passage 31 opens to the cylindrical surface on the inner periphery of the cylinder 9 and faces the oil supply space 28. The oil supplied from the oil pump of the engine is introduced into the cylinder 9 from outside through the oil supply passage 31.

  When the plunger 10 receives a load input in the pushing direction, the oil in the pressure chamber 18 flows into the reservoir chamber 27 through the first leak gap 19, the oil supply space 28, and the communication passage 30. Therefore, when it is necessary to supply oil into the pressure chamber 18 so that the plunger 10 moves in the protruding direction, the oil in the reservoir chamber 27 can be used immediately as oil for supplying to the pressure chamber 18. . Therefore, the amount of oil flowing out from the second leak gap 29 to the outside of the chain tensioner 1 can be suppressed, and as a result, the chain tensioner 1 can generate a damper force immediately after the start of the engine.

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

  When the tension of the chain 6 increases during operation of the engine, the plunger 10 moves in the pushing direction into the cylinder 9 due to the tension of the chain 6, and absorbs the tension of the chain 6. Since the volume of the pressure chamber 18 decreases in accordance with the movement of the plunger 10, the pressure in the pressure chamber 18 becomes higher than the pressure in the reservoir chamber 27 inside the plunger 10, and the check valve 20 closes. Then, oil flows from the pressure chamber 18 to the oil supply space 28 through the first leak gap 19. At this time, a damper force is generated by viscous resistance of the oil flowing through the first leak gap 19, and the plunger 10 moves slowly. Further, the oil returns from the oil supply space 28 to the reservoir chamber 27 through the communication passage 30.

  The oil in the pressure chamber 18 returns to the reservoir chamber 27 through a path passing through the first leak gap 19, the oil supply space 28, and the communication passage 30, so that the returned oil corresponds to the outside of the cylinder 9 from the second leak gap 29. The amount of oil that flows out of the tank is reduced.

  On the other hand, when the tension of the chain 6 decreases during operation of the engine, the plunger 10 moves in the projecting direction by the urging force of the return spring 33, and absorbs the slack of the chain 6. At this time, since the volume of the pressure chamber 18 increases in accordance with the movement of the plunger 10, the pressure of the pressure chamber 18 becomes lower than the pressure of the reservoir chamber 27, and the check valve 20 opens. Then, the oil flows from the reservoir chamber 27 into the pressure chamber 18 through the valve hole 21a of the check valve 20, so that the plunger 10 moves quickly. At this time, oil is introduced into the reservoir chamber 27 from the outside of the cylinder 9 through the oil supply passage 31, the oil supply space 28, and the communication passage 30 by the pressure of the oil pump. For this reason, the pressure in the reservoir chamber 27 does not easily drop, and the chain 6 is excellent in following up the slack.

  Further, in the chain tensioner 1, since the reservoir chamber 27 having a diameter larger than the diameter of the valve hole 21a of the check valve 20 is formed inside the plunger 10, the amount of oil stored in the plunger 10 is increased. Can be secured. For this reason, immediately after the engine is started, even when there is no oil supply from the engine to the chain tensioner 1, the damper force can be generated by using the oil stored inside the plunger 10.

  Here, the outer circumferences 15 and 32 of the largest diameter portion of the plunger 10 have the same diameter, and the inner circumference 14 of the cylinder 9 is continuous with the same diameter over its entire length. That is, the first leak gap 19 and the second leak gap 29 have the same distance between the gaps. For this reason, for example, if an attempt is made to increase the interval between the first leak gaps 19 to adjust the damping force of the chain tensioner 1, the interval between the second leak gaps 29 is also increased. When the second leak gap 29 is enlarged, the amount of oil flowing out of the chain tensioner 1 from the second leak gap 29 increases.

  Therefore, in the present invention, as shown in FIGS. 3 and 4A, a circumferential seal groove 35 is provided on the outer periphery of the plunger 10 at one end side from the oil supply passage 31, and in the seal groove 35, A seal ring 36 for sealing a leak gap c0 (corresponding to the second leak gap 29) between the outer periphery 32 of the plunger 10 and the inner periphery 14 of the cylinder 9 is provided. Further, as shown in FIG. 4B, a seal gap c1 is set between the outer periphery 36d of the seal ring 36 and the inner periphery 14 of the cylinder 9. Therefore, even if the leak gap c0 is enlarged for adjusting the damping force of the chain tensioner 1, the outflow of oil from the leak gap c0 to the outside of the chain tensioner 1 can be suppressed by the seal ring 36 and the seal gap c1. This makes it possible to provide the chain tensioner 1 which is excellent in following up the slackness of the chain 6 and has a small oil outflow amount.

  As a material of the seal ring 36, a resin material can be adopted. In addition, the seal ring 36 has a larger linear expansion coefficient than the plunger 10 and the cylinder 9. As a material forming the seal ring 36, for example, a fluorine-based resin material can be adopted.

  The seal gap c1 is set in advance at a low temperature, for example, at the time of assembling the seal ring 36 into the seal groove 35, before attaching the chain tensioner 1 to the engine wall surface, or at the time of cold before or immediately after the start of the engine. In an environment under a normal temperature lower than the set predetermined temperature, the leak gap c0 is set to be larger than the leak gap c0. FIG. 4B shows such a low temperature situation.

  Further, the seal gap c1 is set to be less than or equal to the leak gap c0 due to the thermal expansion of the seal ring 36 in a high temperature environment, for example, in a hot environment after a warm-up operation of the engine or in a high temperature environment equal to or higher than a predetermined temperature. Is set to FIG. 4C shows a situation at such a high temperature. In FIG. 4C, the seal gap c1 reduced under the high temperature is indicated by a symbol c1 'as a reduced seal gap. Also, regarding the radial thickness d1 of the seal ring 36, in FIG. 4C, the thickness d1 expanded at a high temperature is indicated by the symbol d1 'as the expanded thickness.

  Since the cylinder 9 and the plunger 10 are both made of a metal material, the size of the leak gap c0 is assumed to be substantially the same regardless of whether the temperature is low or high.

  Here, the reduced seal gap c1 ′, which is smaller than at the time of low temperature due to the thermal expansion of the seal ring 36, may be the same as the leak gap c0, or may be smaller than the leak gap c0 unless the gap becomes zero. Is also good. However, it is desirable to set the reduced seal gap c1 'so as not to impair the damping force characteristics of the chain tensioner 1. The width b1 in the axial direction of the seal ring 36 (see FIG. 4B) is sufficiently smaller than the entire length of the plunger 10 in the axial direction, so that even if the reduced seal gap c1 ′ is smaller than the leak gap c0. In addition, the effect on the setting of the damping force of the chain tensioner 1 can be reduced. Further, at high temperatures, the viscosity of the oil is small, so that the sealing gap c1 at high temperatures is set to be a reduced sealing gap c1 ′ smaller than the sealing gap c1 at low temperatures, so that the oil outflow is reduced. It is effective in doing.

  As shown in FIG. 4B, the width b1 of the seal ring 36 in the axial direction is set smaller than the width b0 of the seal groove 35. The same applies to the seal ring 36 after the thermal expansion in FIG. In FIG. 4C, the width b1 in the axial direction of the seal ring after the thermal expansion is indicated by a reference numeral b1 'as the width after the expansion. The width b1 'after expansion is also set smaller than the width b0 of the seal groove 35. Since the width b1 in the axial direction of the seal ring 36 is always smaller than the width b0 of the seal groove 35 irrespective of the temperature condition, the end faces 36e and 36f of the seal ring 36 and the side surfaces 35b and 35c of the seal groove 35 are formed. In between, there are always gaps b2, b3 (in FIG. 4 (c), gaps b2, b3 after thermal expansion of seal ring 36 are indicated as gaps b2 ′, b3 ′ after expansion). For this reason, an oil reservoir can be formed by the interposition of the gaps b2 and b3, which can contribute to suppression of the outflow of oil.

  4B and 4C, the inner circumference 36c of the seal ring 36 is always in contact with the bottom surface 35a of the seal groove 35. A plunger 10 is inserted into the cylinder 9 because a corner processing portion 36g such as a chamfered portion or a rounded portion is provided at a ridge between the outer periphery 36d of the seal ring 36 and the side surfaces 36e and 36f. At this time, the seal ring 36 is prevented from being damaged.

  Further, as shown in FIG. 5, the seal ring 36 has an abutment 37 at one location in the circumferential direction of the annular member, the member being divided in the circumferential direction. The provision of the joint 37 allows the seal ring 36 to heat the material by changing the circumferential gap w1 between the facing surfaces 36a and 36b of the joint 37 in accordance with the temperature change of the seal ring 36. Can absorb swelling. Thereby, a stable sealing performance can always be exhibited regardless of the temperature condition.

  For example, as shown in FIG. 6A, the gap 37 between the facing surfaces 36a and 36b in the circumferential direction of the member has a gap w1 (w1> 0) between the facing surfaces 36a and 36b in the circumferential direction at a low temperature such as normal temperature. Is set. At a high temperature, as shown in FIG. 6B, the seal ring 36 is displaced from the plunger 10 due to the difference in linear expansion coefficient between the plunger 10 and the seal ring 36 (linear expansion coefficient of the plunger 10 <linear expansion coefficient of the seal ring). Also greatly expands, and the gap w1 between the facing surfaces 36a and 36b is reduced. In FIG. 6B, the reduced gap w1 is indicated by a reduced gap w1 '(w1' = 0 in the figure). By reducing the gap w1 between the facing surfaces 36a and 36b, it is possible to further suppress the outflow of oil from the second leak gap 29 during operation of the engine.

  Further, the gap w1 between the facing surfaces 36a and 36b gradually decreases as the temperature of the seal ring 36 rises, and at a certain temperature, the facing surfaces 36a and 36b come into contact with each other and become zero. The temperature at which the circumferential gap w1 between the facing surfaces 36a and 36b becomes zero is desirably set to any temperature in the range of 80 ° C. or more and 120 ° C. or less. Here, the set temperature at which the clearance w1 becomes zero is the upper limit of the temperature range that can be taken by the members constituting the chain tensioner 1 (in this embodiment, the upper limit temperature of the oil temperature in the normal use state of the engine of the automobile). 120 ° C.) and an end temperature of the warm-up operation of the engine (in this embodiment, 80 ° C. in accordance with the oil temperature at the end of warm-up in a normal vehicle engine use state). I have.

As shown in FIGS. 5 and 6, the facing surfaces 36a and 36b of the abutment 37 have their facing surfaces 36a and 36b oriented in the same direction with respect to a direction parallel to the axis of the plunger 10. That is, in the figure, the one end is inclined so as to face upward.

  For this reason, after the opposing surfaces 36a and 36b come into contact with each other and become zero, when the temperature of the seal ring 36 further rises, as shown in FIG. It can slide in the direction. In the figure, the sliding amount in the axial direction between the facing surfaces 36a and 36b is indicated by a reference symbol w2. Therefore, even if the temperature rises after the opposing surfaces 36a and 36b abut each other at a high temperature, the opposing surfaces 36a and 36b (the mating surfaces) can slide in the seal groove 35 in the axial direction. 36 does not expand more than necessary to the outer diameter side and does not hinder the operation of the plunger 10 in the axial direction. As shown in FIG. 6C, the width b1 in the axial direction of the seal ring 36 is smaller than the width b0 of the seal groove 35, so that such an operation can be realized.

  The dimensions of the seal ring 36, such as the width b1 in the axial direction and the thickness d1, are set so that the volume of the seal ring 36 does not become larger than the volume in the seal groove 35 even after thermal expansion. Is desirable. Thus, it is possible to more reliably prevent the sliding resistance of the plunger 10 against the cylinder 9 from increasing.

  Further, it is desirable that the outer diameter of the seal ring 36 in a free state in which no external force is applied at a low temperature, particularly at normal temperature, is set to be larger than the inner diameter of the inner circumference 14 of the cylinder 9. Thereby, in a state where the plunger 10 is incorporated in the cylinder 9, the sealing property to the inner circumference 14 of the cylinder 9 can be improved by the elasticity of the seal ring 36.

  FIG. 7 shows a modification of the seal ring 36. In the seal ring 36 of this modification, opposing surfaces 36a and 36b are formed in a stepped shape, respectively, to form a so-called step-cut abutment 37.

  The one facing surface 36a of the abutment 37 is formed at a position where the circumferential position is shifted from each other on both sides in the axial direction with the center of the axial width b1 of the seal ring 36 interposed therebetween. The two opposing surfaces 36a, 36a are surfaces in a direction parallel to the axial direction of the plunger 10, respectively, and the two opposing surfaces 36a, 36a are parallel to the axial direction of the plunger 10, respectively. The direction may be inclined with respect to the direction.

  The two opposing surfaces 36a, 36a whose positions in the circumferential direction are shifted are connected by a connecting surface 36i extending along the circumferential direction. Although the connecting surface 36i is a surface orthogonal to the axial direction of the plunger 10, a configuration in which the connecting surface 36i is inclined with respect to a surface orthogonal to the axial direction of the plunger 10 is also conceivable.

  Similarly, the other facing surface 36b of the abutment 37 is formed at a position where the circumferential position is deviated from each other on both sides in the axial direction with the center of the axial width b1 of the seal ring 36 interposed therebetween. The two opposing surfaces 36b, 36b are surfaces in a direction parallel to the axial direction of the plunger 10, respectively. However, the two opposing surfaces 36b, 36b are similarly set in the axial direction of the plunger 10, respectively. The direction may be inclined with respect to the parallel direction.

  The two opposing surfaces 36b, 36b whose positions in the circumferential direction are shifted are connected by a connecting surface 36h extending in the circumferential direction. The connecting surface 36h is a surface orthogonal to the axial direction of the plunger 10, but a configuration in which the connecting surface 36h is inclined with respect to a surface orthogonal to the axial direction of the plunger 10 is also conceivable.

  FIG. 7A shows a state in which the gap between the opposing surfaces 36a and 36b is largely open, and FIG. 7B shows a state in which the gap between the opposing surfaces 36a and 36b is slightly reduced. In this manner, the circumferential gap w3 between the facing surfaces 36a and 36b of the abutment 37 changes according to the temperature change of the seal ring 36, so that the thermal expansion of the material can be absorbed.

  For example, in FIG. 7A, a gap w3 (w3> 0) is set between the facing surfaces 36a and 36b in the circumferential direction of the member in the abutment 37 of the seal ring 36 at a low temperature such as normal temperature. I have. At a high temperature, as shown in FIG. 7B, the seal ring 36 is displaced from the plunger 10 due to a difference in linear expansion coefficient between the plunger 10 and the seal ring 36 (linear expansion coefficient of the plunger 10 <linear expansion coefficient of the seal ring). Also greatly expands, and the gap w3 between the facing surfaces 36a and 36b is reduced. In FIG. 7B, the reduced gap w3 is indicated by a reduced gap w3 '. The point that the gap w3 between the opposing surfaces 36a and 36b may be gradually reduced with an increase in the temperature of the seal ring 36 so that the opposing surfaces 36a and 36b abut at a certain temperature and become zero may be described above. This is the same as the embodiment.

  Although the connecting surface 36i and the connecting surface 36h have a positional relationship of not contacting each other regardless of the temperature condition, they may have a positional relationship of contacting each other. Further, after the opposing surfaces 36a and 36b contact each other at a certain temperature and the gap w3 becomes zero, when the temperature further rises, the gap is interposed between the connecting surface 36i and the connecting surface 36h. The subsequent thermal expansion can be absorbed by the gap between the connecting surface 36i and the connecting surface 36h.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Chain tensioner 9 Cylinder 10 Plunger 14 Inner circumference 18 Pressure chamber 20 Check valve 28 Oil supply space 30 Communication passage 31 Oil supply passage 32 Outer circumference 33 Return spring 35 Seal groove 36 Seal ring 36a, 36b Opposing surface 36d Outer circumference 37 Abutment c0 Leak gap c1 Seal gap w1, w3 gap

Claims (7)

A cylindrical cylinder (9) having one end open and the other end closed;
A cylindrical plunger (10) which is slidably supported in the axial direction on the inner periphery of the cylinder (9) and has an open end inserted into the cylinder (9) and a closed end protruding from the cylinder (9); When,
A return spring (33) for urging the plunger (10) in a direction protruding from the cylinder (9);
A pressure chamber (18) formed in the cylinder (9) such that the volume changes with the axial movement of the plunger (10);
A check valve (20) for allowing only oil flow from inside the plunger (10) to the pressure chamber (18);
Oil is formed between the outer circumference (32) of the plunger (10) and the inner circumference (14) of the cylinder (9), and when the volume of the pressure chamber (18) is reduced, oil is discharged from the pressure chamber (18). A leak gap (c0) to be leaked,
An oil supply passage (31) for introducing oil from the outside to the inside of the cylinder (9),
A communication path (30) for communicating the leak gap (c0) with the inside of the plunger (10);
A circumferential seal groove (35) provided on the outer periphery (32) of the plunger (10) at one end side of the oil supply passage (31);
A seal ring (36) arranged in the seal groove (35) to seal the leak gap (c0);
With
A chain tensioner in which a seal gap (c1) is set between an outer circumference (36d) of the seal ring (36) and an inner circumference (14) of the cylinder (9).   The chain tensioner according to claim 1, wherein the seal gap (c1) is smaller than the leak gap (c0) due to expansion of the seal ring (36) due to a temperature change.   The seal ring (36) includes an abutment (37) divided in a circumferential direction, and a circumferential gap (w1, w3) between opposing surfaces (36a, 36b) of the abutment (37) is formed by the seal. The chain tensioner according to claim 1, wherein the chain tensioner changes according to a temperature change of the ring.   The gap (w1, w3) in the circumferential direction between the facing surfaces (36a, 36b) is set to be zero at any temperature in a range of 80 ° C or more and 120 ° C or less. Chain tensioner.   The opposing surfaces (36a, 36b) are inclined to the same side with respect to a direction parallel to the axis, and the opposing surfaces (36a, 36b) come into contact with each other to prevent a temperature change of the seal ring (36). 5. The chain tensioner according to claim 3, wherein the chain tensioner is slidable in the axial direction accordingly.   The chain tensioner according to any one of claims 1 to 5, wherein the seal ring (36) has a coefficient of linear expansion greater than that of the plunger (10) and the cylinder (9).   The oil supply space (28) communicating with the leak gap (c0) is formed between the outer periphery of the plunger (10) and the inner periphery of the cylinder (9). The described chain tensioner.

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