WO2022191195A1

WO2022191195A1 - Chain tensioner

Info

Publication number: WO2022191195A1
Application number: PCT/JP2022/010039
Authority: WO
Inventors: 好一鬼丸
Original assignee: Ntn株式会社
Priority date: 2021-03-11
Filing date: 2022-03-08
Publication date: 2022-09-15
Also published as: JP2022138953A

Abstract

This chain tensioner comprises: a first sleeve (13) inserted into a plunger (10); a second sleeve (14) provided connected to the first sleeve (13); a check valve (15) embedded into the second sleeve (14); and a mating cylindrical surface (25) formed on the outer periphery of the second sleeve (14). The first sleeve (13) has a relief spring (34) that presses a sheet member (21) embedded therein, and the second sleeve (14) has a relief sheet surface (36) formed thereon. The sheet member (21), relief spring (34), and the relief sheet surface (36) constitutes a relief valve (38).

Description

chain tensioner

The present invention relates to a chain tensioner used to hold the tension of the chain.

As chain transmission devices used in automobile engines, for example, those that transmit the rotation of the crankshaft to the camshaft, those that transmit the rotation of the crankshaft to auxiliary equipment such as oil pumps, water pumps, superchargers, etc. , to transmit the rotation of the crankshaft to the balancer shaft, and to connect the intake and exhaust cams of a twin-cam engine. A chain tensioner is used to keep the tension of the chain in these chain drives in the proper range.

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

A cylinder is a tubular member having one end in the axial direction as a closed end and the other end in the axial direction as an open end. The plunger is a tubular member having an open end for insertion into the cylinder and a closed end for protruding from the cylinder. The sleeve is inserted into the plunger so that one end in the axial direction is inserted into the plunger and the other end in the axial direction projects from the plunger, and the end of the sleeve protruding from the plunger serves as the closed end of the cylinder. supported by The outer circumference of the sleeve and the inner circumference of the plunger are axially slidably fitted together. A return spring is installed between the insertion end of the sleeve into the plunger and the plunger to bias the plunger in the direction of protruding from the cylinder.

In addition, the chain tensioner of Patent Document 1 has a check valve at the insertion end of the sleeve into the plunger. The check valve divides the internal region of the sleeve and plunger into a reservoir chamber on the sleeve side and a pressure chamber on the plunger side. The check valve is a valve that allows oil to flow only from the reservoir chamber side to the pressure chamber side. The cylinder is formed with an oil supply passage for introducing oil supplied from the outside of the cylinder into the reservoir chamber. A cylindrical leak gap is formed between the outer circumference of the sleeve and the inner circumference of the plunger to allow oil to leak from the pressure chamber.

Here, the check valve has a valve seat in which a valve hole communicating between the pressure chamber and the reservoir chamber is formed, and a valve body that opens and closes the end of the valve hole on the side of the pressure chamber. The valve seat is seamlessly formed integrally with the sleeve at the end of the sleeve that is inserted into the plunger.

In the chain tensioner disclosed in Patent Document 1, when the tension of the chain increases during operation of the engine, the tension of the chain moves the plunger in the direction in which the plunger is pushed into the cylinder (hereinafter referred to as the "pushing direction"), thereby reducing the tension in the chain. absorb. At this time, a damping force is generated by the viscous resistance of the oil flowing out from the pressure chamber through the leak gap, so the plunger moves slowly.

On the other hand, when the tension of the chain becomes small while the engine is running, the urging force of the return spring and the hydraulic pressure in the pressure chamber move the plunger in the direction in which it protrudes from the cylinder (hereinafter referred to as the "protrusion direction"), thereby removing slack in the chain. Absorb. At this time, the check valve opens and oil flows into the pressure chamber from the reservoir chamber, so the plunger moves quickly.

JP 2019-152285 A

By the way, the chain tensioner of Patent Document 1 has a problem that the damping force changes greatly according to the temperature change. That is, in the chain tensioner of Patent Document 1, when the plunger moves in the pushing direction, the oil in the pressure chamber flows through the leak gap into the reservoir chamber. do. Here, since the viscosity of the oil increases as the temperature of the oil decreases, the viscous resistance of the oil flowing through the leak gap increases when the temperature of the oil is low, and the damping force increases. On the other hand, when the temperature of the oil is high, the viscous resistance of the oil flowing through the leak gap becomes low, and the damping force becomes small.

Therefore, if the size of the leak gap is set large, it is possible to prevent the damping force from becoming excessive at low temperatures, but there is a risk that the damping force at high temperatures will be too small, causing the chain to rattle. On the other hand, if the size of the leak gap is set small, it is possible to prevent the damping force from becoming too small at high temperatures, but there is a risk that the damping force at low temperatures will be excessive and the chain tension will be excessive. be.

Therefore, in order to obtain a stable damping force regardless of temperature changes, the inventors of the present application proposed that the chain tensioner disclosed in Patent Document 1 be designed so that oil is supplied from the pressure chamber when the pressure in the pressure chamber exceeds a preset pressure. We considered installing a relief valve to let the air escape. If a relief valve is provided, the pressure rise in the pressure chamber can be suppressed by opening the relief valve at low temperatures, preventing the damper force from becoming excessive. It is possible to secure the magnitude of the damping force due to the viscous resistance of the chain and prevent the chain from fluttering.

Here, when providing the relief valve in the chain tensioner of Patent Document 1, the inventor of the present application considered providing the relief valve at the position of the check valve at the insertion end of the sleeve into the plunger. In this way, when the relief valve is opened, the oil that flows out from the pressure chamber through the relief valve can be collected in the reservoir chamber, so it is possible to reduce the amount of oil consumed by the chain tensioner. .

Furthermore, the inventors of the present application proposed a method for assembling a relief valve at the position of the check valve at the insertion end of the sleeve into the plunger. A method of press-fitting was investigated.

However, it was found that if the relief valve was assembled using this method, the magnitude of the chain tensioner's damping force could become unstable.

That is, when a valve unit that integrates a relief valve and a check valve is press-fitted into the insertion end of the sleeve into the plunger, the deformation caused by the press-fitting slightly expands the outer diameter of the sleeve. Here, the inner diameter of the sleeve varies within the tolerance range, and the outer diameter of the valve unit also varies within the tolerance range. Therefore, it is difficult to keep the outer diameter of the sleeve constant. As a result, the size of the leak gap formed between the outer circumference of the sleeve and the inner circumference of the plunger may not be stable, and the damping force generated by the viscous resistance of the oil flowing through the leak gap may become unstable. It turns out that there is

The problem to be solved by the present invention is to provide a chain tensioner capable of obtaining a damping force of stable magnitude.

In order to solve the above problems, the inventors of the present application have proposed that members corresponding to the sleeves of the chain tensioner disclosed in Patent Document 1 are divided into a first sleeve for forming a reservoir chamber and a second sleeve for forming a leak gap. The inventors have come up with the idea of dividing the valve into two parts, incorporating the check valve into the second sleeve, and directly forming the seat surface of the relief valve on the second sleeve.

Based on this idea, the present invention provides a chain tensioner having the following configuration.
a cylinder having one end in the axial direction as a closed end and the other end in the axial direction as an open end;
a cylindrical plunger that is axially slidably inserted into the cylinder, has an open end for insertion into the cylinder, and a closed end that protrudes from the cylinder;
One end in the axial direction is inserted into the plunger, the other end in the axial direction is inserted into the plunger so as to protrude from the plunger, and the protruding end from the plunger is supported by the closed end of the cylinder. a first sleeve;
a second sleeve provided in connection with the insertion end of the first sleeve into the plunger and separate from the first sleeve;
The inner region of the first sleeve and the plunger is incorporated into the second sleeve so as to partition the inner region into a reservoir chamber on the first sleeve side and a pressure chamber on the plunger side. a check valve that only allows oil flow to the side of the pressure chamber;
a fitting cylindrical surface formed on the outer periphery of the second sleeve and axially slidably fitted to the inner periphery of the plunger;
a cylindrical leak gap formed between the fitting cylindrical surface and the inner circumference of the plunger for leaking oil from the pressure chamber;
an oil supply passage for introducing oil supplied from the outside of the cylinder into the reservoir chamber;
a return spring that biases the plunger in a direction of protruding from the cylinder;
The check valve has a seat member in which a valve hole communicating between the pressure chamber and the reservoir chamber is formed, and a valve body that opens and closes an end portion of the valve hole on the side of the pressure chamber,
The sheet member is provided axially movably with respect to the second sleeve,
The first sleeve incorporates a relief spring that axially presses the sheet member from the reservoir chamber side toward the pressure chamber side,
The second sleeve is formed with an annular relief sheet surface that contacts and supports the sheet member from the pressure chamber side,
The seat member, the relief spring, and the relief seat surface constitute a relief valve that releases oil from the pressure chamber to the reservoir chamber when the pressure in the pressure chamber exceeds a preset pressure.

In this way, when the temperature is low, the viscous resistance of the oil flowing through the leak gap increases, and the pressure in the pressure chamber tends to increase. The sheet member is separated from the relief sheet surface by the pressure, and the oil in the pressure chamber is released to the reservoir chamber through the gap between the sheet member and the relief sheet surface. Therefore, an increase in pressure in the pressure chamber is suppressed, and an excessive damping force can be prevented. On the other hand, when the temperature is high, it is possible to secure the magnitude of the damping force due to the viscous resistance of the oil flowing through the leak gap and prevent the chain from rattling.

Further, since the relief seat surface of the relief valve is formed on the second sleeve which is separate from the first sleeve, the constituent members of the relief valve can be assembled while the first sleeve and the second sleeve are separated, It is possible to secure the assembling workability of the relief valve. In addition, since the fitting cylindrical surface that is axially slidably fitted to the inner periphery of the plunger is formed directly on the outer periphery of the second sleeve having the relief seat surface, the member having the relief seat surface is press-fitted. It is possible to prevent the dimension of the fitting cylindrical surface from changing due to such factors as the above, and it is possible to control the dimension of the fitting cylindrical surface with high accuracy and constant. Therefore, the size of the leakage gap between the fitting cylindrical surface and the inner circumference of the plunger can be controlled with high dimensional accuracy, and a stable damping force can be obtained.

It is preferable that the first sleeve is formed with an oil passage for returning oil leaked from the pressure chamber through the leak gap to the reservoir chamber.

With this configuration, oil leaks from the pressure chamber through the leak gap when the plunger moves in the pushing direction, and part of the oil leaked from the pressure chamber at this time returns to the reservoir chamber through the oil passage. . Therefore, the amount of oil discharged from the chain tensioner to the outside can be reduced, and the oil consumption of the chain tensioner can be suppressed.

The outer circumference of the portion of the first sleeve inserted into the plunger is preferably formed to have a smaller diameter than the fitting cylindrical surface.

With this configuration, the gap between the outer circumference of the first sleeve and the inner circumference of the plunger becomes relatively large, and the viscous resistance of the oil flowing through the gap can be kept small. When the insertion length into the plunger changes, the magnitude of the damping force is less likely to change, and a stable damping force can be obtained.

The contact surface of the sheet member with the relief sheet surface or the relief sheet surface is provided with an air release groove for releasing air in the second sleeve to the reservoir chamber while the sheet member is in contact with the relief sheet surface. preferably formed.

With this configuration, the air existing in the second sleeve is discharged to the reservoir chamber through the air release groove, so that a more stable damping force can be obtained.

In addition, an air valve for discharging air in the second sleeve to the valve hole in a state where the valve body closes the end of the valve hole on the side of the pressure chamber is provided on the contact surface of the seat member with the valve body. It is preferable to form a draft groove.

By doing so, the air existing in the second sleeve is discharged to the reservoir chamber through the air release groove and the valve hole in order, so that a more stable damping force can be obtained.

The second sleeve can be slidably supported at an insertion end of the first sleeve into the plunger so as to allow radial movement of the second sleeve relative to the first sleeve.

With this configuration, even if there is a deviation between the axis of the first sleeve and the axis of the plunger inserted into the cylinder, the second sleeve moves radially relative to the first sleeve according to the deviation. , and the size of the leakage gap between the fitting cylindrical surface of the outer circumference of the second sleeve and the inner circumference of the plunger is made uniform in the radial direction. Therefore, it is possible to obtain a stable damper force.

An annular projection is formed at the end of the first sleeve inserted into the plunger,
A configuration may be adopted in which the second sleeve is formed with an annular recess that fits into the annular protrusion to radially position the second sleeve with respect to the first sleeve.

By doing so, it is possible to align the axial center of the first sleeve and the axial center of the second sleeve by fitting the annular projection and the annular recess.

In this case, the protruding end of the first sleeve from the plunger has an annular partial spherical surface supported in axial contact with the closed end of the cylinder,
It is preferable that the closed end of the cylinder has a concave tapered surface or a concave spherical surface that slidably supports the partial spherical surface so as to allow tilting of the first sleeve.

With this configuration, even if there is a misalignment between the axis of the first sleeve and the axis of the plunger inserted into the cylinder, the first sleeve tilts with respect to the cylinder in accordance with the misalignment. 2 The size of the leakage gap between the fitting cylindrical surface of the outer circumference of the sleeve and the inner circumference of the plunger is made uniform in the axial direction. Therefore, it is possible to obtain a stable damper force.

It is preferable to employ a configuration in which the return spring is supported by the second sleeve.

With this configuration, the second sleeve is pressed against the first sleeve by the reaction force of the force of the return spring that urges the plunger, thereby preventing the separation of the first and second sleeves due to vibrations of the engine or the like. can be done.

In the chain tensioner of the present invention, the relief seat surface of the relief valve is formed on the second sleeve, which is separate from the first sleeve. can be assembled, and it is possible to secure the assembling workability of the relief valve. In addition, since the fitting cylindrical surface that is axially slidably fitted to the inner periphery of the plunger is formed directly on the outer periphery of the second sleeve having the relief seat surface, the member having the relief seat surface is press-fitted. It is possible to prevent the dimension of the fitting cylindrical surface from changing due to such factors as the above, and it is possible to control the dimension of the fitting cylindrical surface with high accuracy and constant. Therefore, the size of the leakage gap between the fitting cylindrical surface and the inner circumference of the plunger can be controlled with high dimensional accuracy, and a stable damping force can be obtained.

1 is a diagram showing a chain transmission incorporating a chain tensioner according to a first embodiment of the present invention; FIG. Enlarged cross-sectional view of the vicinity of the chain tensioner in FIG. FIG. 3 is an enlarged cross-sectional view of the vicinity of the sheet member in FIG. 2 FIG. 4 is an enlarged cross-sectional view of the vicinity of the seat member showing the state in which the relief valve of FIG. 3 is opened; A diagram showing a modified example of the relief sheet surface of FIG. 3 and a contact surface with respect to the relief sheet surface. The figure which shows the modification which added the oil passage groove to the sheet|seat member of FIG. Cross-sectional view along line VII-VII in Fig. 6 4 is a perspective view of a seat member showing a modification in which air vent grooves are formed in the contact surface of the seat member in FIG. 3 with the relief sheet surface; FIG. FIG. 9 is an enlarged cross-sectional view of the vicinity of the seat member of the chain tensioner incorporating the seat member shown in FIG. 8 ; FIG. 4 is an enlarged cross-sectional view of the vicinity of the seat member in FIG. 3, showing a modification in which an air vent groove is formed on the contact surface of the seat member with the valve body; Enlargement of the vicinity of the seat member showing a modified example in which an air release groove is formed on the contact surface of the seat member with the relief seat surface of FIG. 3 and an air release groove is also formed on the contact surface of the seat member with the valve body cross section FIG. 2 is a cross-sectional view of a main part showing a chain tensioner according to a second embodiment of the invention; FIG. 12 is an enlarged cross-sectional view of the vicinity of the second sleeve in FIG. 12 FIG. 13 is an enlarged cross-sectional view of the vicinity of the projecting end from the plunger of the first sleeve in FIG. 12; Enlarged cross-sectional view showing a modified example in which the closed end of the cylinder in FIG. 14 is a concave spherical surface

Fig. 1 shows a chain transmission incorporating a chain tensioner 1 of the first embodiment of the invention. In this chain transmission device, a sprocket 3 fixed to a crankshaft 2 of an engine and a sprocket 5 fixed to a camshaft 4 are connected via a chain 6, and the chain 6 drives the rotation of the crankshaft 2. It is transmitted to the camshaft 4, and the rotation of the camshaft 4 opens and closes a valve (not shown) of the combustion chamber.

When the engine is running, the direction of rotation of the crankshaft 2 is constant (right rotation in the figure), and at this time, the chain 6 is drawn into the sprocket 3 as the crankshaft 2 rotates (right side in the figure). is the tight side, and the side (left side in the figure) sent out from the sprocket 3 is the slack side. A chain guide 8 supported so as to be swingable about a fulcrum shaft 7 is in contact with the slack side of the chain 6 . Chain tensioner 1 presses chain 6 via chain guide 8 .

As shown in FIG. 2, the chain tensioner 1 includes a tubular cylinder 9 having one end in the axial direction closed and the other end in the axial direction open, and is axially slidably inserted into the cylinder 9. and a plunger 10. A projecting end of the plunger 10 from the cylinder 9 presses the chain guide 8 .

　The cylinder 9 is integrally formed of an aluminum alloy. The cylinder 9 is fixed to an engine block (not shown) by fastening bolts 12 to a plurality of mounting pieces 11 integrally formed on the outer circumference of the cylinder 9 . Here, the cylinder 9 is attached so that the direction in which the plunger 10 protrudes from the cylinder 9 is inclined downward from the horizontal.

The plunger 10 is formed in a tubular shape with an open end inserted into the cylinder 9 of the plunger 10 and a closed end protruding from the cylinder 9 of the plunger 10 . The material of the plunger 10 is a ferrous material (for example, a steel material such as SCM (chromium molybdenum steel) or SCr (chromium steel)).

A first sleeve 13 is inserted into the plunger 10 so that one end in the axial direction is inserted into the plunger 10 and the other end in the axial direction protrudes from the plunger 10 . The first sleeve 13 is a cylindrical member with both ends in the axial direction open. The first sleeve 13, like the plunger 10, is made of a ferrous material. A protruding end of the first sleeve 13 from the plunger 10 is supported by the closed end of the cylinder 9 .

A second sleeve 14 that is separate from the first sleeve 13 is connected to the insertion end of the first sleeve 13 into the plunger 10 . The second sleeve 14 is a cylindrical member that is arranged in line with the first sleeve 13 in the axial direction. The axial length of the second sleeve 14 is shorter than the axial length of the first sleeve 13 , and can be set to, for example, ⅓ or less of the axial length of the first sleeve 13 . The second sleeve 14, like the plunger 10, is made of a ferrous material.

A check valve 15 is incorporated in the second sleeve 14 . The check valve 15 divides the internal region of the first sleeve 13 and the plunger 10 into a reservoir chamber 16 on the first sleeve 13 side and a pressure chamber 17 on the plunger 10 side. Here, the volume of the reservoir chamber 16 is constant and does not change even when the plunger 10 moves in the axial direction. On the other hand, the volume of the pressure chamber 17 expands when the plunger 10 axially moves in the direction of protruding from the cylinder 9 and contracts when the plunger 10 axially moves in the direction of being pushed into the cylinder 9 .

A return spring 18 is incorporated in the pressure chamber 17 . The return spring 18 is a compression coil spring formed by spirally winding a metal wire. One end of the return spring 18 is supported by the second sleeve 14 , and the other end presses the plunger 10 in the axial direction.

As shown in FIG. 3, the check valve 15 has a seat member 21 in which a valve hole 20 is formed, and a spherical valve body 22 that opens and closes the end of the valve hole 20 on the pressure chamber 17 side. The valve hole 20 is an axial through hole formed in the seat member 21 so as to communicate between the pressure chamber 17 and the reservoir chamber 16 . The valve body 22 is a steel ball. The axial movement range of the valve body 22 is limited by an end plate 23 formed on the second sleeve 14 . A plurality of through holes 24 are formed in the end plate 23 so that oil can pass through the end plate 23 . The check valve 15 restricts the flow of oil from the pressure chamber 17 side to the reservoir chamber 16 side and allows oil to flow only from the reservoir chamber 16 side to the pressure chamber 17 side.

The outer periphery of the second sleeve 14 is formed with a fitting cylindrical surface 25 that is axially slidably fitted to the inner periphery of the plunger 10 . The fitting cylindrical surface 25 is a cylindrical surface whose outer diameter does not change along the axial direction. The inner circumference of the plunger 10 is also a constant cylindrical surface whose inner diameter does not change along the axial direction. A leak gap 26 is formed between the fitting cylindrical surface 25 and the inner circumference of the plunger 10 to allow oil to leak from the pressure chamber 17 when the volume of the pressure chamber 17 is reduced. The leak gap 26 is a cylindrical minute gap with a radial width set in the range of 0.010 to 0.050 mm.

As shown in FIG. 2, the outer circumference of the portion of the first sleeve 13 inserted into the plunger 10 is a cylindrical surface with a constant outer diameter that does not change along the axial direction. It is formed to have a smaller diameter than the fitting cylindrical surface 25 on the outer periphery of the. Further, the outer circumference of the portion where the plunger 10 is inserted into the cylinder 9 is also a constant cylindrical surface whose outer diameter does not change along the axial direction. A portion of the inner circumference of the cylinder 9 that axially slidably supports the outer circumference of the plunger 10 is also a cylindrical surface whose inner diameter does not change along the axial direction. A cylindrical guide gap 27 is formed between the inner circumference of the cylinder 9 and the outer circumference of the plunger 10 . The radial width of the guide gap 27 is set larger than the radial width of the leak gap 26, and can be set in the range of 0.015 to 0.065 mm, for example.

The cylinder 9 and the first sleeve 13 are provided with an oil supply passage 30 for introducing oil supplied from an oil pump (not shown) outside the cylinder 9 into the reservoir chamber 16 . The oil supply passage 30 is formed between a cylinder-side oil passage 31 formed in the cylinder 9 so as to introduce oil from the outer circumference to the inner circumference of the cylinder 9 and between the inner circumference of the cylinder 9 and the outer circumference of the first sleeve 13 . and an oil passage 33 provided in a projecting portion of the first sleeve 13 from the plunger 10 .

The cylindrical space 32 is radially sandwiched between the inner periphery of the cylinder 9 and the outer periphery of the first sleeve 13 on the side closer to the closed end of the cylinder 9 than the insertion end of the plunger 10 into the cylinder 9 . area. An end portion of the cylinder-side oil passage 31 on the inner peripheral side of the cylinder 9 opens at a position connected to the cylindrical space 32 .

The oil passage 33 is a through hole formed through the first sleeve 13 in the radial direction. The oil passage 33 is also a part of the oil supply passage 30, and is an oil recovery hole for returning the oil that has leaked from the pressure chamber 17 to the tubular space 32 through the leak gap 26 from the tubular space 32 to the reservoir chamber 16. But also.

As shown in FIG. 3, the seat member 21 of the check valve 15 is a member formed separately from the second sleeve 14 and is provided axially movably with respect to the second sleeve 14 . The first sleeve 13 incorporates a relief spring 34 that axially presses the sheet member 21 from the reservoir chamber 16 side toward the pressure chamber 17 side. The relief spring 34 is a compression coil spring formed by spirally winding a metal wire. One end of the relief spring 34 is supported by a stepped portion 35 (see FIG. 2) formed on the inner circumference of the first sleeve 13, and the other end of the relief spring 34 presses the seat member 21 in the axial direction.

The seat member 21 is pressed against the relief seat surface 36 formed on the second sleeve 14 by the pressing force of the relief spring 34 . The relief seat surface 36 is an annular surface having a convex arcuate cross section that contacts and supports the seat member 21 from the pressure chamber 17 side (right side in the figure). A contact surface 37 of the sheet member 21 with the relief sheet surface 36 is a tapered surface that makes line contact with the relief sheet surface 36 at an annular portion.

Here, the seat member 21, the relief spring 34, and the relief seat surface 36 constitute a relief valve 38 that releases oil from the pressure chamber 17 to the reservoir chamber 16 when the pressure in the pressure chamber 17 exceeds a preset pressure. is doing. That is, when the pressure in the pressure chamber 17 becomes higher than the preset pressure, the pressure in the pressure chamber 17 causes the seat member 21 to move against the biasing force of the relief spring 34 as shown in FIG. side (right side in the figure) toward the reservoir chamber 16 side (left side in the figure) and separates from the relief sheet surface 36 . Then, the oil in the pressure chamber 17 escapes to the reservoir chamber 16 through the gap between the sheet member 21 and the relief sheet surface 36, and the pressure rise in the pressure chamber 17 is suppressed.

As shown in FIG. 3 , the second sleeve 14 is slidably supported at the insertion end of the first sleeve 13 into the plunger 10 to allow radial movement of the second sleeve 14 relative to the first sleeve 13 . It is Specifically, a flat surface 39 perpendicular to the axial direction is formed at the insertion end of the first sleeve 13 into the plunger 10, and the axial end surface 40 of the second sleeve 14 abuts on the flat surface 39 in the axial direction. 39 and the axial end surface 40 are in contact with each other so as to be slidable in the radial direction.

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

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 the direction of being pushed into the cylinder 9 to absorb the tension of the chain 6 . At this time, since the pressure in the pressure chamber 17 shown in FIG. 2 becomes higher than the pressure in the reservoir chamber 16, the check valve 15 is closed. Further, since the volume of the pressure chamber 17 is reduced in accordance with the movement of the plunger 10, oil leaks from the pressure chamber 17 through the leak gap 26 by the amount of the reduced volume. A damping force is generated by the viscous resistance, and the damping force prevents the chain 6 from fluttering. Most of the oil that has leaked from the pressure chamber 17 through the leak gap 26 into the tubular space 32 returns to the reservoir chamber 16 through the oil passage 33 . Also, part of the oil leaked from the pressure chamber 17 through the leak gap 26 into the cylindrical space 32 lubricates the guide gap 27 .

On the other hand, when the tension of the chain 6 shown in FIG. 1 decreases during engine operation, the plunger 10 moves in the projecting direction due to the biasing force of the return spring 18 and the hydraulic pressure in the pressure chamber 17 shown in FIG. Absorb relaxation. At this time, since the volume of the pressure chamber 17 expands according to the movement of the plunger 10, the pressure in the pressure chamber 17 becomes lower than the pressure in the reservoir chamber 16, and the check valve 15 opens. Then, oil flows from the reservoir chamber 16 through the check valve 15 into the pressure chamber 17, and the plunger 10 moves rapidly. At this time, oil is introduced into the reservoir chamber 16 from the outside of the cylinder 9 through the oil supply passage 30 .

Here, the viscosity of the oil increases as the temperature of the oil decreases. In addition, since each member contracts at low temperatures, the leak gap 26 also becomes smaller. Therefore, when the temperature is low, the viscosity resistance of the oil flowing through the leak gap 26 increases, and the pressure in the pressure chamber 17 tends to increase. When the pressure in the pressure chamber 17 becomes greater than the preset pressure, the pressure in the pressure chamber 17 causes the sheet member 21 to move away from the relief sheet surface 36 (see FIG. 4). The oil in the pressure chamber 17 is released to the reservoir chamber 16 through the gap between . Therefore, an increase in pressure in the pressure chamber 17 is suppressed, and an excessive damping force can be prevented.

When the engine is stopped and then restarted, generally, the oil level in the oil passage (not shown) outside the cylinder 9 is once lowered. It takes time before the oil supply to the tensioner 1 starts. In this case, from the time the engine is restarted until the oil supply is started, as shown in FIG. Thus, the pressure chamber 17 is kept filled with oil. Therefore, it is possible to generate a damping force immediately after the engine is restarted, and it is possible to suppress the chain 6 from fluttering.

In this chain tensioner 1, as shown in FIG. The constituent members of the relief valve 38 can be assembled while the sleeve 14 is divided, and the assembling workability of the relief valve 38 can be ensured.

In addition, since the chain tensioner 1 is formed with the fitting cylindrical surface 25 that fits directly on the outer periphery of the second sleeve 14 having the relief seat surface 36 and on the inner periphery of the plunger 10 so as to be slidable in the axial direction. Also, it is possible to prevent the dimension of the fitting cylindrical surface 25 from being changed due to press-fitting of the member forming the relief seat surface 36, etc., and the dimension of the fitting cylindrical surface 25 can be managed accurately and constantly. Therefore, the size of the leakage gap 26 between the fitting cylindrical surface 25 and the inner circumference of the plunger 10 can be controlled with high dimensional accuracy, and a stable damping force can be obtained.

Also, in this chain tensioner 1, oil leaks from the pressure chamber 17 through the leak gap 26 when the plunger 10 shown in FIG. 2 moves in the pushing direction. returns to the reservoir chamber 16 through the oil passage 33 formed in the first sleeve 13 . Therefore, the amount of oil discharged from the chain tensioner 1 to the outside can be reduced, and the amount of oil consumed by the chain tensioner 1 can be suppressed.

2, the outer circumference of the portion of the first sleeve 13 inserted into the plunger 10 is formed to have a smaller diameter than the fitting cylindrical surface 25 of the outer circumference of the second sleeve 14. Therefore, the gap between the outer circumference of the first sleeve 13 and the inner circumference of the plunger 10 is relatively large, and the viscous resistance of oil flowing through the gap is small. Therefore, when the insertion length of the first sleeve 13 into the plunger 10 changes due to the movement of the plunger 10, the magnitude of the damping force is less likely to change, and a stable damping force can be obtained.

Further, in the chain tensioner 1, as shown in FIG. 3, the second sleeve 14 is supported so as to allow radial movement of the second sleeve 14 with respect to the first sleeve 13. and the axis of the plunger 10 inserted into the cylinder 9, the second sleeve 14 moves radially with respect to the first sleeve 13 according to the deviation, The size of the leakage gap 26 between the fitting cylindrical surface 25 on the outer circumference of the second sleeve 14 and the inner circumference of the plunger 10 is made uniform in the radial direction. Therefore, it is possible to obtain a stable damper force.

In addition, as shown in FIG. 3, the chain tensioner 1 supports the return spring 18 with the second sleeve 14, so that the reaction force of the return spring 18 urging the plunger 10 (see FIG. 2) A second sleeve 14 is pressed against the first sleeve 13 . Therefore, it is possible to prevent the first sleeve 13 and the second sleeve 14 from separating due to engine vibration or the like.

In the above-described embodiment, the relief sheet surface 36 formed on the second sleeve 14 is an annular surface having a convex arcuate cross section, and the contact surface 37 of the sheet member 21 with the relief sheet surface 36 is a tapered surface. As described above, as shown in FIG. 5, the relief seat surface 36 formed on the second sleeve 14 may be a tapered surface, and the contact surface 37 of the sheet member 21 with the relief seat surface 36 may be an annular surface having a convex arcuate cross section. good.

A modified example of the sheet member 21 is shown in FIGS. In FIG. 6, the sheet member 21 is axially movable on the inner periphery of the first sleeve 13 or the second sleeve 14 to the reservoir chamber 16 side (left side in the figure) from the contact position with the relief sheet surface 36. An outer cylindrical surface 41 to be guided and an oil passage groove 42 axially penetrating the outer cylindrical surface 41 are formed so as to divide the outer cylindrical surface 41 in the circumferential direction. As shown in FIG. 7, a plurality of oil passage grooves 42 are provided at intervals in the circumferential direction. By adopting this configuration, the posture of the seat member 21 when the seat member 21 is separated from the relief seat surface 36 is stabilized by the outer cylindrical surface 41, and the oil flows when the seat member 21 is separated from the relief seat surface 36. The passage can be secured by the oil passage groove 42 .

As shown in FIGS. 8 and 9, an air vent groove 43 may be formed in the contact surface 37 of the sheet member 21 with the relief sheet surface 36 . 8 and 9, the air vent groove 43 is a groove extending across an annular portion where the seat member 21 and the relief seat surface 36 are in contact with each other. By providing the air vent groove 43, as shown in FIG. 9, when the sheet member 21 is in contact with the relief sheet surface 36, the air present in the second sleeve 14 passes through the air vent groove 43 to the reservoir chamber. 16 is discharged. Therefore, it is possible to obtain a more stable damper force. The air vent groove 43 may be provided on the relief sheet surface 36 .

As shown in FIG. 10, an air vent groove 44 may be formed in the contact surface of the seat member 21 with the valve body 22 (that is, the seat surface of the check valve 15). In FIG. 10, the air vent groove 44 is a groove that extends across an annular portion where the valve body 22 and the seat member 21 contact each other. When the air vent groove 44 is provided, when the valve element 22 closes the end of the valve hole 20 on the side of the pressure chamber 17 , the air existing in the second sleeve 14 flows through the air vent groove 44 and the valve hole 20 . in order to be discharged into the reservoir chamber 16 . Therefore, it is possible to obtain a more stable damper force.

As shown in FIG. 11, an air release groove 43 is formed in the contact surface 37 of the seat member 21 with the relief seat surface 36, and an air release groove 44 is formed in the contact surface of the seat member 21 with the valve body 22. is also possible.

12 to 14 show a chain tensioner 1 according to a second embodiment of the invention. Parts corresponding to those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 13, an annular projection 50 is formed at the insertion end of the first sleeve 13 into the plunger 10 . The annular projection 50 is an annular axial projection around the axis of the first sleeve 13 . The second sleeve 14 is formed with an annular recess 51 that fits into the annular protrusion 50 . The annular recess 51 is an annular axial recess around the axis of the second sleeve 14 . The second sleeve 14 is radially positioned with respect to the first sleeve 13 by fitting the annular projection 50 and the annular recess 51 .

As shown in FIGS. 12 and 14, the protruding end of the first sleeve 13 from the plunger 10 has an annular partial spherical surface 52 axially abutted against and supported by the closed end of the cylinder 9 . The partial spherical surface 52 is a portion of a spherical surface centered on the axis of the first sleeve 13 . The closed end of the cylinder 9 has a concave tapered surface 53 that slidably supports a partial spherical surface 52 to allow tilting of the first sleeve 13 .

The chain tensioner 1 of this embodiment can align the axial center of the first sleeve 13 and the axial center of the second sleeve 14 by fitting the annular projection 50 and the annular recess 51 together. Therefore, it is possible to stabilize the oil flow in the leak gap 26 .

Further, in the chain tensioner 1 of this embodiment, the end of the first sleeve 13 protruding from the plunger 10 is supported by the closed end of the cylinder 9 so as to be tiltable. When there is a deviation between the axial center of the plunger 10 inserted into the outer circumference of the second sleeve 14, the first sleeve 13 tilts with respect to the cylinder 9 according to the deviation, and the fitting cylindrical surface 25 of the outer circumference of the second sleeve 14 and the inner circumference of the plunger 10, the size of the leak gap 26 is made uniform in the axial direction. Therefore, it is possible to obtain a stable damper force.

It is preferable to set an interference between the annular convex portion 50 and the annular concave portion 51 shown in FIG. By doing so, the second sleeve 14 is fixed to the first sleeve 13 by the interference, so that the first sleeve 13, the second sleeve 14, the relief spring 34, the seat member 21, and the valve body 22 are integrated. It can be handled as an assembly (assie), and the assembling workability of the chain tensioner 1 can be improved.

When an interference is set between the annular protrusion 50 and the annular recess 51, the annular protrusion 50 and the annular recess 51 are separated from each other as shown in FIG. The axial length of the portion to be fitted is set short (for example, less than the radial thickness of the second sleeve 14 shown in FIG. 13), and the portion to which the annular convex portion 50 and the annular concave portion 51 are fitted is shortened. , preferably arranged so as not to radially overlap the fitting cylindrical surface 25 .

Although FIG. 14 shows an example in which the closed end of the cylinder 9 is formed with a concave tapered surface 53, the closed end of the cylinder 9 may be formed with a concave spherical surface 54 as shown in FIG. In FIG. 15, the partial spherical surface 52 of the protruding end of the first sleeve 13 from the plunger 10 is slidably supported by the concave spherical surface 54 formed at the closed end of the cylinder 9, and the sliding causes the first sleeve 13 to move. It is designed to allow tilting.

In the above embodiments, the chain tensioner 1 is incorporated in a chain transmission device that transmits the rotation of the crankshaft 2 to the camshaft 4. To be incorporated into a chain transmission that transmits power to accessories such as a water pump and a supercharger, a chain transmission that transmits the rotation of a crankshaft to a balancer shaft, or a chain transmission that connects intake and exhaust cams of a twin-cam engine. is also possible.

The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

1 Chain tensioner 9 Cylinder 10 Plunger 13 First sleeve 14 Second sleeve 15 Check valve 16 Reservoir chamber 17 Pressure chamber 18 Return spring 20 Valve hole 21 Seat member 22 Valve body 25 Fitting cylindrical surface 26 Leak gap 30 Oil supply passage 33 Oil passage Path 34 Relief spring 36 Relief seat surface 37 Contact surface 38 Relief valve 43 Air release groove 44 Air release groove 50 Annular protrusion 51 Annular recess 52 Partial spherical surface 53 Concave taper surface 54 Concave spherical surface

Claims

a cylinder (9) having one end in the axial direction as a closed end and the other end in the axial direction as an open end;
a cylindrical plunger (10) inserted slidably in the cylinder (9) in the axial direction, having an open end for insertion into the cylinder (9) and a closed end protruding from the cylinder (9); ,
One end in the axial direction is inserted into the plunger (10), the other end in the axial direction is inserted into the plunger (10) so as to protrude from the plunger (10). a first sleeve (13) whose projecting end is supported by the closed end of said cylinder (9);
a second sleeve (14) connected to the insertion end of the first sleeve (13) into the plunger (10) and separate from the first sleeve (13);
The internal area of the first sleeve (13) and the plunger (10) is divided into a reservoir chamber (16) on the first sleeve (13) side and a pressure chamber (17) on the plunger (10) side. a check valve (15) incorporated in the second sleeve (14) so as to allow oil to flow only from the reservoir chamber (16) side to the pressure chamber (17) side;
a fitting cylindrical surface (25) formed on the outer periphery of the second sleeve (14) and axially slidably fitted to the inner periphery of the plunger (10);
a cylindrical leak gap (26) formed between the fitting cylindrical surface (25) and the inner periphery of the plunger (10) for leaking oil from the pressure chamber (17);
an oil supply passage (30) for introducing oil supplied from outside the cylinder (9) into the reservoir chamber (16);
a return spring (18) that biases the plunger (10) in a direction of protruding from the cylinder (9);
The check valve (15) includes a seat member (21) formed with a valve hole (20) communicating between the pressure chamber (17) and the reservoir chamber (16), and a pressure valve in the valve hole (20). and a valve body (22) for opening and closing the end on the chamber (17) side,
The sheet member (21) is axially movably provided with respect to the second sleeve (14),
The first sleeve (13) incorporates a relief spring (34) that axially presses the seat member (21) from the reservoir chamber (16) side toward the pressure chamber (17) side. ,
The second sleeve (14) is formed with an annular relief seat surface (36) that contacts and supports the seat member (21) from the pressure chamber (17) side,
The seat member (21), the relief spring (34) and the relief seat surface (36) are released from the pressure chamber (17) when the pressure in the pressure chamber (17) exceeds a preset pressure. A chain tensioner forming a relief valve (38) for releasing oil to the reservoir chamber (16).
An oil passage (33) is formed in the first sleeve (13) to return oil leaked from the pressure chamber (17) through the leak gap (26) to the reservoir chamber (16). 1. The chain tensioner according to 1.
The chain tensioner according to claim 1 or 2, wherein the outer circumference of the portion of the first sleeve (13) inserted into the plunger (10) is formed to have a smaller diameter than the fitting cylindrical surface (25).
A contact surface (37) of the sheet member (21) with the relief sheet surface (36), or a state in which the sheet member (21) is in contact with the relief sheet surface (36). 4. A chain tensioner according to any one of claims 1 to 3, wherein an air release groove (43) is formed for discharging air in said second sleeve (14) to said reservoir chamber (16).
In a state in which the valve body (22) closes the end of the valve hole (20) on the pressure chamber (17) side, the first contact surface of the seat member (21) contacts the valve body (22). 5. The chain tensioner according to any one of claims 1 to 4, further comprising an air release groove (44) for discharging air in the second sleeve (14) to the valve hole (20).
Said second sleeve (14) is adapted to extend said first sleeve (13) into said plunger (10) to allow radial movement of said second sleeve (14) relative to said first sleeve (13). The chain tensioner according to any one of claims 1 to 5, wherein the chain tensioner is slidably supported at the insertion end.
An annular protrusion (50) is formed at the insertion end of the first sleeve (13) into the plunger (10),
The second sleeve (14) has an annular recess (51) that fits into the annular protrusion (50) to radially position the second sleeve (14) with respect to the first sleeve (13). 6. The chain tensioner according to any one of claims 1 to 5, wherein
the protruding end of the first sleeve (13) from the plunger (10) has an annular partial spherical surface (52) supported in axial contact with the closed end of the cylinder (9);
The closed end of the cylinder (9) has a concave tapered surface (53) or a concave spherical surface (54) slidably supporting the partial spherical surface (52) to allow tilting of the first sleeve (13). 8. The chain tensioner of claim 7, comprising:
The chain tensioner according to any one of claims 1 to 8, wherein the return spring (18) is supported by the second sleeve (14).