WO2023276808A1

WO2023276808A1 - Chain tensioner

Info

Publication number: WO2023276808A1
Application number: PCT/JP2022/024836
Authority: WO
Inventors: 好一鬼丸
Original assignee: Ntn株式会社
Priority date: 2021-06-29
Filing date: 2022-06-22
Publication date: 2023-01-05
Also published as: JP2023005479A

Abstract

Provided is a chain tensioner in which a check valve (15) is loosely fitted at an end of a plunger (10) inserted into a cylinder (9) and a return spring (24) is built into a pressure chamber (17) so as to press the check valve (15) against a plunger (10), wherein a retaining ring (51) for elastically tightening the outer periphery of the plunger (10) is accommodated in a retaining ring accommodation groove (50), and in the outer periphery of the plunger (10), a retaining ring engagement groove (52) is formed at a position shifted from a lubrication groove (31) toward an end of the plunger (10) that projects from the cylinder (9).

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.

The inventor of the present application has already proposed the one described in Patent Document 1 as a chain tensioner used for such applications. The chain tensioner disclosed in Patent Document 1 includes a cylindrical cylinder having one axial end closed and the other axial end open, a plunger axially slidably inserted into the cylinder, and a plunger. and a return spring that biases in the direction of protruding from the cylinder.

The plunger is formed in a cylindrical shape with an open end for insertion into the cylinder and a closed end for protruding from the cylinder. A check valve is provided at the insertion end of the plunger into the cylinder, and the space surrounded by the cylinder and the plunger is divided by the check valve into the storage chamber surrounded by the check valve and the plunger and the axial movement of the plunger. A pressure chamber is defined between the check valve and the closed end of the cylinder so that the volume varies accordingly.

An oil supply passage that introduces oil supplied from the outside of the cylinder is connected to the storage chamber. The oil supply passage includes a cylinder side oil supply hole formed in the cylinder so as to open to the inner periphery of the cylinder, an annular oil supply groove formed in the outer periphery of the plunger so as to communicate with the cylinder side oil supply hole, and the oil supply groove. and a plunger-side oil supply hole formed through the plunger in the radial direction so as to introduce oil into the storage chamber.

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, the oil in the pressure chamber flows out through the leakage gap formed between the cylindrical surface provided on the outer circumference of the insertion end of the plunger into the cylinder and the inner circumference of the cylinder, and the oil's viscous resistance generates a damping force, so the plunger moves slowly.

On the other hand, when the tension of the chain is reduced while the engine is running, the biasing force of the return spring moves the plunger in the direction in which it protrudes from the cylinder (hereinafter referred to as "protrusion direction") to absorb the slack in the chain. At this time, the check valve opens and oil flows from the storage chamber into the pressure chamber, so that the plunger moves quickly.

Here, when the plunger moves in the pushing direction according to the tension of the chain, the oil that leaks from the pressure chamber through the leak gap returns to the oil supply passage and circulates, so the amount of oil discharged from the chain tensioner to the outside is It is possible to reduce oil consumption in the chain tensioner.

JP 2020-153383 A

By the way, chain tensioners are roughly divided into internal tensioners and external tensioners. The internal tensioner is of a type that is attached to the wall surface of the engine and is used with the engine cover covering the entirety of the tensioner. On the other hand, the external tensioner is of the type that is inserted into a tensioner mounting hole formed through the engine cover so that the direction of the plunger protruding from the cylinder faces the inside of the engine cover. Internal tensioners are often used in four-wheel vehicles, and external tensioners are often used in motorcycles.

Also, the chain tensioner may be removed during overhaul or repair. When removing the chain tensioner, in the case of an internal tensioner, the engine cover is first removed, and the chain tensioner is removed from the wall surface of the engine with the entire chain tensioner exposed. It is possible to support the protruding part from the cylinder with a hand or the like, and the problem of the plunger falling out of the cylinder is unlikely to occur.

On the other hand, with an external tensioner, when removing the chain tensioner, the chain tensioner is pulled out from the tensioner mounting hole in the engine cover. At this time, since the chain tensioner is pulled out with the plunger protruding from the cylinder facing the inside of the engine cover, the protruding portion of the plunger from the cylinder cannot be supported by hand, and the plunger may fall out of the cylinder. There is In particular, if the chain tensioner is attached in such a manner that the plunger protrudes downward from the horizontal, the plunger tends to fall off the cylinder when the chain tensioner is removed.

Since the chain tensioner of Patent Document 1 is an internal tensioner, as described above, the problem of the plunger dropping out of the cylinder is unlikely to occur. Here, the inventor of the present application assumes that the chain tensioner of Patent Document 1 is used as an exterior type, and studied how to prevent the plunger of the chain tensioner of Patent Document 1 from coming off from the cylinder.

That is, the inventors of the present application have proposed that, in order to prevent the plunger from falling out of the cylinder when the chain tensioner of Patent Document 1 is removed, a retainer ring is housed in the inner periphery of the open end of the cylinder of the chain tensioner of Patent Document 1. A groove is formed, a retaining ring for elastically tightening the outer periphery of the plunger is accommodated in the retaining ring receiving groove, and the retaining ring is engaged with the lubricating groove on the outer periphery of the plunger to remove the plunger from the cylinder. We considered a configuration to prevent it from slipping out.

However, in the chain tensioner of Patent Document 1, when the plunger is retained from the cylinder by the above configuration, when the plunger moves to the maximum protruding position, the check valve provided at the insertion end of the plunger into the cylinder will open the plunger. It was found that there was a danger of falling out of the

That is, when the plunger moves in the direction of protruding from the cylinder, the return spring expands according to the movement of the plunger. When the plunger moves to the maximum protruding position (a position where the movement of the plunger in the protruding direction is blocked by the engagement between the retainer ring and the lubricating groove on the outer periphery of the plunger), the axial direction of the pressure chamber accommodating the return spring is increased. The length can be longer than the free length of the return spring.

On the other hand, in the chain tensioner of Patent Document 1, when the check valve is attached to the insertion end of the plunger into the cylinder, the check valve is not press-fitted but is fitted with a clearance. When the plunger moves in the axial direction according to the tension fluctuation of the chain, the check valve is pressed against the plunger by the return spring in the pressure chamber so that the check valve moves in the axial direction together with the plunger. there is

Therefore, if the axial length of the pressure chamber accommodating the return spring becomes longer than the free length of the return spring when the plunger moves to the maximum protruding position, the return spring will no longer press against the check valve. could fall off from the end of the plunger inserted into the cylinder.

Once the check valve falls off from the plunger, there is a possibility that problems such as assembling the check valve in the wrong direction may occur when the operator reassembles the check valve into the plunger.

The problem to be solved by the present invention is to provide a chain tensioner that consumes less oil and can prevent the check valve from falling off from the plunger.

In order to solve the above problems, the present invention provides a chain tensioner having the following configuration.
a cylindrical 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;
a check valve provided at the insertion end of the plunger into the cylinder;
a storage chamber surrounded by the check valve and the plunger;
a pressure chamber formed between the check valve and a closed end of the cylinder to vary in volume in response to axial movement of the plunger;
a cylinder-side oil supply hole formed in the cylinder so as to open to the inner circumference of the cylinder;
an annular lubricating groove formed on the outer periphery of the plunger so as to communicate with the cylinder-side lubricating hole;
a plunger-side oil supply hole formed radially through the plunger so as to introduce oil from the oil supply groove into the storage chamber;
a leakage gap formed between a cylindrical surface provided on the outer circumference of the end of the plunger inserted into the cylinder and the inner circumference of the cylinder;
a return spring that biases the plunger in a direction of protruding from the cylinder;
The check valve is loosely fitted to the insertion end of the plunger into the cylinder,
In a chain tensioner in which the return spring is incorporated in the pressure chamber so as to press the check valve against the plunger,
A retainer ring accommodating groove formed in the inner periphery of the cylinder accommodates a retainer ring that elastically tightens the outer periphery of the plunger,
a retainer ring for retaining the plunger from the cylinder by engaging the retainer ring at a position on the outer periphery of the plunger that is displaced from the oil supply groove toward the projecting end of the plunger from the cylinder; A chain tensioner characterized in that an engagement groove is formed.

With this arrangement, the oil that has leaked from the pressure chamber through the leak gap returns to the lubricating groove on the outer periphery of the plunger and circulates. Consumption can be reduced.

In addition, in order to prevent the plunger from coming off the cylinder, the retaining ring is not engaged with the lubricating groove on the outer periphery of the plunger, but rather is positioned at a position shifted from the lubricating groove toward the end of the plunger protruding from the cylinder. Since the plunger is engaged with the retaining ring engagement groove provided in , it is possible to prevent the return spring from extending to its free length when the plunger moves to the maximum protruding position. Therefore, even if the plunger moves to the most protruding position when removing the chain tensioner, it is possible to prevent the return spring from losing its pressing force against the check valve, and the check valve is pushed from the plunger's insertion end into the cylinder. It is possible to prevent falling off.

The axial length of the pressure chamber is shorter than the free length of the return spring when the plunger moves in the direction in which the plunger protrudes from the cylinder to a position where the retaining ring engaging groove engages with the retaining ring. configuration is preferred.

By doing so, it is possible to reliably prevent the return spring from extending to its free length when the plunger moves to the maximum protruding position, and to reliably prevent the check valve from falling off the plunger. It becomes possible.

The retaining ring engaging groove has a groove side surface on the insertion end side rising from the groove bottom of the retaining ring engaging groove to the insertion end side of the plunger into the cylinder, and a groove bottom of the retaining ring engaging groove. and a groove side surface on the protruding end side rising from the protruding end side of the plunger from the cylinder,
The rising angle of the groove side surface on the insertion end side is set in the range of 50° to 80°,
It is preferable to employ a configuration in which the rising angle of the groove side surface on the projecting end side is set within a range of 10° to 30°.

With this arrangement, the rising angle of the side surface of the groove on the protruding end side of the engaging groove for the retainer ring on the outer periphery of the plunger is set to 30° or less, so that the side surface of the groove on the protruding end side moves in the axial direction. When the retainer ring comes into contact with the retainer ring, the retainer ring can be pushed radially outward by a component force acting on the side surface of the groove on the projecting end side to expand the diameter of the retainer ring. Therefore, when assembling the chain tensioner, the operator can insert the plunger into the cylinder without expanding the retaining ring by hand, and the chain tensioner can be easily assembled. be. In addition, since the rising angle of the groove side surface on the insertion end side of the retainer ring engaging groove on the outer periphery of the plunger is set to 50° or more, the groove side surface on the insertion end side moves in the axial direction to move the retainer ring. When it abuts against the retaining ring, the retaining ring is prevented from being diametrically expanded and deformed, and the retaining ring can reliably receive the side surface of the groove on the insertion end side. Therefore, it is possible to reliably prevent the plunger from falling out of the cylinder when removing the chain tensioner.

the oil supply groove has a tapered surface that rises from the groove bottom of the oil supply groove toward the protruding end of the plunger from the cylinder;
It is preferable to employ a configuration in which the rising angle of the tapered surface is set within a range of 10° to 30°.

With this configuration, the rising angle of the tapered surface rising from the groove bottom of the oil supply groove to the protruding end side of the plunger from the cylinder is set to 30° or less, so that the tapered surface moves in the axial direction to prevent the plunger from coming off. When the retaining ring comes into contact with the ring, the component force acting on the tapered surface presses the retainer ring radially outward to expand its diameter. Therefore, when assembling the chain tensioner, the operator can insert the plunger into the cylinder without expanding the retaining ring by hand, and the chain tensioner can be easily assembled. be.

A tensioner (that is, a , an external tensioner).

In the chain tensioner of the present invention, the oil that leaks from the pressure chamber through the leak gap returns to the oil supply groove on the outer circumference of the plunger and circulates. low oil consumption. In addition, in order to prevent the plunger from coming off the cylinder, the retaining ring is not engaged with the lubricating groove on the outer periphery of the plunger, but rather is positioned at a position shifted from the lubricating groove toward the end of the plunger protruding from the cylinder. Since the plunger is engaged with the retainer ring engagement groove provided in the outer circumference of the plunger, the plunger is at the maximum protruding position (the plunger protruding direction ), the return spring can be prevented from expanding to its free length. Therefore, even if the plunger moves to the most protruding position when removing the chain tensioner, it is possible to prevent the return spring from losing its pressing force against the check valve, and the check valve is pushed from the plunger's insertion end into the cylinder. It is possible to prevent falling off.

1 is a diagram showing a chain transmission incorporating a chain tensioner according to a first embodiment of the present invention; FIG. Cross-sectional view along the II-II line in Fig. 1 Sectional view showing the initial set state of the chain tensioner shown in FIG. Cross-sectional view along the IV-IV line in Fig. 3 Cross-sectional view along the V-V line in Fig. 3 Enlarged view of the vicinity of the retainer ring in FIG. Enlarged view of the vicinity of the retaining ring engagement groove in FIG. A cross-sectional view showing a state in which the chain tensioner shown in FIG. 2 has moved to the maximum protruding position and the retaining ring is engaged with the retaining ring engagement groove. Enlarged view of the vicinity of the retainer ring in FIG. FIG. 2 is a diagram showing a state in which a chain tensioner according to a second embodiment of the present invention is viewed horizontally; Sectional view along line XI-XI in FIG. A diagram showing a modified example of the chain tensioner of FIG. A diagram showing another modification of the chain tensioner of FIG. Partial cross-sectional view showing a chain tensioner of a comparative example

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 inserted into the tensioner mounting hole 12 of the engine cover 11 with the open end facing inside the engine cover 11 . The tensioner mounting hole 12 is a through hole formed through the engine cover 11 from the outer surface to the inner surface. A flange portion 13 is formed on the outer circumference of the cylinder 9 . The flange portion 13 is fixed to the outer surface of the engine cover 11 with bolts 14 (see FIG. 1). A gasket (not shown) is sandwiched between the flange portion 13 and the outer surface of the engine cover 11 .

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 . A check valve 15 is provided at the insertion end of the plunger 10 into the cylinder 9 . The check valve 15 consists of a space surrounded by the cylinder 9 and the plunger 10, a storage chamber 16 surrounded by the check valve 15 and the plunger 10, and a check valve so that the volume changes according to the axial movement of the plunger 10. 15 and a pressure chamber 17 formed between the closed end of cylinder 9 .

The check valve 15 includes a valve seat 19 in which a valve hole 18 is formed, a spherical valve body 20 that opens and closes the end of the valve hole 18 on the side of the pressure chamber 17, and a valve body 20 from the open position to the closed position. and a retainer 22 for restricting the movement range of the valve body 20 . The valve hole 18 is an axial through hole formed in the valve seat 19 so as to communicate between the pressure chamber 17 and the storage chamber 16 . The check valve 15 restricts the flow of oil from the pressure chamber 17 side to the storage chamber 16 side and permits only the oil flow from the storage chamber 16 side to the pressure chamber 17 side.

The check valve 15 is loosely fitted to the insertion end of the plunger 10 into the cylinder 9 . That is, the valve seat 19 constituting the check valve 15 has a cylindrical outer peripheral surface, and the valve seat 19 has an interference on the cylindrical inner peripheral surface of the insertion end of the plunger 10 into the cylinder 9. It's stuck in place. The valve seat 19 is axially positioned by a stepped portion 23 formed on the inner circumference of the plunger 10 . The stepped portion 23 is a stepped portion whose diameter decreases from the end of the plunger 10 inserted into the cylinder 9 (left side in the drawing) toward the end of the plunger 10 protruding from the cylinder 9 (right side in the drawing). is.

A return spring 24 and an assist spring 25 are incorporated in the pressure chamber 17 . Each of the return spring 24 and the assist spring 25 is a coil spring formed by spirally winding a metal wire, and is incorporated in an axially compressed state.

The return spring 24 is formed in a conical shape whose outer diameter gradually decreases from one end to the other end. One end of the return spring 24 is supported by the closed end of the cylinder 9 , and the other end presses the plunger 10 in the axial direction via the check valve 15 . energized. Here, the other end (right end in the figure) of the return spring 24 presses the retainer 22 of the check valve 15 against the valve seat 19 and presses the valve seat 19 against the stepped portion 23 of the plunger 10 .

The assist spring 25 is formed in a cylindrical shape with an inner diameter larger than the outer diameter of the return spring 24 and is arranged coaxially so as to surround the outer periphery of the return spring 24 . One end of the assist spring 25 is supported by the closed end of the cylinder 9 , and the other end directly presses the axial end face of the insertion end of the plunger 10 into the cylinder 9 . biased in the direction.

As shown in FIG. 3, on the outer periphery of the plunger 10, from the end of the plunger 10 inserted into the cylinder 9 (left side in the drawing) to the end of the plunger 10 protruding from the cylinder 9 (right side in the drawing). A first cylindrical surface 30, an oil groove 31, and a second cylindrical surface 32 are formed in this order.

The first cylindrical surface 30 is a cylindrical surface formed on the outer periphery of the insertion end of the plunger 10 into the cylinder 9 . The oil supply groove 31 is an annular groove formed in a portion of the outer periphery of the plunger 10 adjacent to the first cylindrical surface 30 on the side of the projecting end of the plunger 10 from the cylinder 9 (on the right side in the drawing). be. The second cylindrical surface 32 is formed in a portion of the outer periphery of the plunger 10 adjacent to the oil supply groove 31 on the side of the projecting end of the plunger 10 from the cylinder 9 (on the right side in the drawing). It is a cylindrical surface having the same outer diameter as the cylindrical surface 30 . That is, oil supply groove 31 is formed between first cylindrical surface 30 and second cylindrical surface 32 .

A leak gap 33 is formed between the first cylindrical surface 30 on the outer circumference of the plunger 10 and the inner circumference of the cylinder 9 . The leak gap 33 is a cylindrical minute gap whose width in the radial direction is set in the range of 0.010 to 0.080 mm. Similarly, a guide gap 34 is formed between the second cylindrical surface 32 on the outer circumference of the plunger 10 and the inner circumference of the cylinder 9 . Like the leak gap 33, the guide gap 34 is also a cylindrical minute gap with a radial width set in the range of 0.010 to 0.080 mm.

As shown in FIG. 2, the engine cover 11 is formed with an oil hole 35 for supplying the chain tensioner 1 with oil delivered from an oil pump (not shown) of the engine. The oil hole 35 opens on the inner circumference of the tensioner mounting hole 12 .

The cylinder 9 is provided with a cylinder-side oil supply hole 36 for introducing oil supplied from the oil hole 35 of the engine cover 11 into the cylinder 9 . The cylinder-side oil supply hole 36 is a through hole formed through the cylinder 9 in the radial direction. The radially outer end of the cylinder-side oil supply hole 36 opens at a position communicating with the oil hole 35 of the engine cover 11 on the outer periphery of the cylinder 9 , and the radially inner end of the cylinder-side oil supply hole 36 opens to the cylinder 9 . The inner circumference of the plunger 10 is opened at a portion facing the outer circumference of the plunger 10 .

The oil supply groove 31 is formed on the outer periphery of the plunger 10 so as to communicate with the opening at the radially inner end of the cylinder-side oil supply hole 36 . The width dimension of the oil supply groove 31 is set larger than the moving stroke of the plunger 10 due to the elongation of the chain 6 (see FIG. 1) over time, and is set to, for example, 10 mm or more.

As shown in FIG. 4 , the plunger 10 is formed with a plunger-side oil supply hole 37 radially penetrating the plunger 10 so as to introduce oil from the oil supply groove 31 into the storage chamber 16 . A radially outer end of the plunger-side oil supply hole 37 opens to the bottom surface of the oil supply groove 31 .

As shown in FIG. 3, the chain tensioner 1 has an initial set state in which the plunger 10 is pushed into the cylinder 9 (the state shown in the drawing). It has a cylinder-side set groove 40 formed, a set ring 41 accommodated in the cylinder-side set groove 40, and a plunger-side set groove 42 formed on the outer circumference of the end of the plunger 10 protruding from the cylinder 9.

As shown in FIG. 5, the set ring 41 consists of a set ring main body 43 having a shape in which a part of the circumference is cut off, and a pair of diameter reduction operation pieces 44 provided at both ends of the set ring main body 43 . The set ring 41 is formed by bending a single metal wire. The pair of diameter reducing operation pieces 44 are arranged facing each other with a space in the circumferential direction, and the set ring main body 43 is reduced in diameter by operating the pair of diameter reducing operation pieces 44. It can be elastically deformed. The diameter reducing operation piece 44 is accommodated in a notch 45 formed radially through the open end of the cylinder 9 .

As shown in FIG. 6 , the cylinder-side set groove 40 includes a shallow groove portion 46 having a depth smaller than the wire diameter of the metal wire constituting the set ring 41 and a shallow groove portion 46 having a depth smaller than the wire diameter of the metal wire constituting the set ring 41 . It is composed of a deep groove portion 47 having a large depth. The deep groove portion 47 is formed continuously with the shallow groove portion 46 on the side of the insertion end of the plunger 10 into the cylinder 9 (on the left side in the drawing).

The set ring body 43 has an outer diameter dimension such that when it is assembled in the shallow groove portion 46 of the cylinder side set groove 40, it is elastically contracted in diameter and is elastically pressed against the groove bottom surface of the shallow groove portion 46. is formed as The cylinder-side set groove 40 and the plunger-side set groove 42 are disengaged from the plunger-side set groove 42 by further pushing the plunger 10, which is held in the initial set state, into the cylinder 9, thereby performing the initial set. can be released.

As shown in FIG. 3, the chain tensioner 1 includes a retaining ring housing groove 50 formed in the inner circumference of the open end of the cylinder 9, a retaining ring 51 housed in the retaining ring housing groove 50, and the plunger 10. and a retaining ring engaging groove 52 formed on the outer periphery of the ring. The retaining ring accommodating groove 50 is formed in the inner circumference of the cylinder 9 at a position shifted toward the insertion end of the plunger 10 into the cylinder (to the left in the drawing) from the cylinder-side set groove 40 . Further, the retainer ring engaging groove 52 is formed on the outer circumference of the plunger 10 at a position shifted from the oil supply groove 31 to the protruding end side (right side in the figure) of the plunger 10 from the cylinder 9 . That is, the retaining ring engaging groove 52 is formed in the second cylindrical surface 32 .

As shown in FIG. 5, the retainer ring 51 is composed of a retainer ring main body 53 having a shape in which a part of the circumference is cut away, and a pair of diameter-expanding operation pieces 54 provided at both ends of the retainer ring main body 53. Become. The retainer ring 51 is formed by bending a single metal wire rod. The pair of diameter-enlarging operation pieces 54 are arranged facing each other with an interval in the circumferential direction. 53 can be elastically deformed. The diameter expanding operation piece 54 is accommodated in a notch 45 formed radially through the open end of the cylinder 9 .

As shown in FIG. 6, the retainer ring accommodating groove 50 is formed to have a depth larger than the wire diameter of the metal wire material forming the retainer ring 51 . The retainer ring main body 53 is elastically expanded in diameter when fitted to the second cylindrical surface 32 on the outer periphery of the plunger 10, and has an inner diameter dimension that elastically tightens the second cylindrical surface 32. is formed as

As shown in FIG. 7, the retaining ring engaging groove 52 has a groove side surface 55 on the insertion end side rising from the groove bottom of the retaining ring engaging groove 52 to the insertion end side of the plunger 10 into the cylinder 9, It has a protruding end side groove side surface 56 that rises from the groove bottom of the retainer ring engaging groove 52 to the protruding end side of the plunger 10 from the cylinder 9 . Both the groove side surface 55 on the insertion end side and the groove side surface 56 on the protruding end side are tapered surfaces that are inclined with respect to the direction perpendicular to the axis. Further, oil supply groove 31 has a tapered surface 57 that rises from the groove bottom of oil supply groove 31 toward the projecting end of plunger 10 from cylinder 9 .

The rising angle θ1 of the groove side surface 55 on the insertion end side is set within the range of 50° to 80°. On the other hand, the rising angle θ2 of the groove side surface 56 on the projecting end side is set within the range of 10° to 30°. The depth of the groove bottom of the retainer ring engaging groove 52 is shallower than the wire diameter of the metal wire constituting the retainer ring 51 . Also, the rising angle θ3 of the tapered surface 57 is set within the range of 10° to 30°.

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 moves the plunger 10 shown in FIG. At this time, the pressure in the pressure chamber 17 becomes higher than the pressure in the storage chamber 16, so 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 33 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. The oil leaked from the pressure chamber 17 through the leak gap 33 returns to the oil groove 31, flows into the plunger-side oil supply hole 37, returns to the cylinder-side oil supply hole 36, passes through the guide gap 34, and flows into the plunger-side oil supply hole 36. It lubricates between the sliding surfaces of 10 and cylinder 9.

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 protruding direction due to the biasing forces of the return spring 24 and the assist spring 25 shown in FIG. do. 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 storage chamber 16, and the check valve 15 opens. Then, the oil flows from the storage 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 storage chamber 16 from the oil hole 35 of the engine cover 11 through the cylinder side oil supply hole 36 , the oil supply groove 31 , and the plunger side oil supply hole 37 .

In this way, in the chain tensioner 1, the oil that leaks from the pressure chamber 17 through the leak gap 33 returns to the oil supply groove 31 on the outer periphery of the plunger 10 and circulates, so that the oil is discharged from the chain tensioner 1 to the outside. is small, and the amount of oil consumed by the chain tensioner 1 can be suppressed.

By the way, during overhaul or repair, the chain tensioner 1 shown in FIG.

At this time, since the chain tensioner 1 is pulled out with the direction in which the plunger 10 protrudes from the cylinder 9 faces the inside of the engine cover 11, the protruding portion of the plunger 10 from the cylinder 9 cannot be supported by a hand or the like. 10 can fall out of the cylinder 9. In particular, if the chain tensioner 1 is attached in such a manner that the plunger 10 protrudes downward from the cylinder 9, the plunger 10 tends to fall off the cylinder 9 when the chain tensioner 1 is removed.

Therefore, in order to prevent the plunger 10 from falling out of the cylinder 9, as shown in FIG. 2, a retaining ring 51 for elastically tightening the outer periphery of the plunger 10 is accommodated, and the retaining ring 51 is engaged with the lubricating groove 31 on the outer periphery of the plunger 10 to retain the plunger 10 from the cylinder 9. Adoption is conceivable.

However, as shown in FIG. 14, if a configuration is adopted in which the plunger 10 is prevented from coming off by engaging the retaining ring 51 with the lubricating groove 31 on the outer periphery of the plunger 10, the plunger 10 cannot move to the maximum protruding position. , the axial length of the pressure chamber 17 accommodating the return spring 24 becomes longer than the free length of the return spring 24. As a result, the pressure force of the return spring 24 against the check valve 15 is eliminated, may drop from the insertion end of the plunger 10 into the cylinder 9.

Once the check valve 15 is detached from the plunger 10, when the operator reassembles the check valve 15 to the plunger 10, the check valve 10 is assembled in the wrong direction (for example, the front and back of the valve seat 19 are Inverted assembly) and other problems may occur.

To address this problem, the chain tensioner 1 of this embodiment engages the oil supply groove 31 on the outer periphery of the plunger 10 with a retainer ring 51 to retain the plunger 10 from the cylinder 9, as shown in FIG. Instead of the lubricating groove 31, the plunger 10 is engaged with the retaining ring engaging groove 52 separately provided at a position shifted from the oil supply groove 31 toward the projecting end of the plunger 10 from the cylinder 9. 10 has moved to the maximum protruding position (a position where the movement of the plunger 10 in the projecting direction is blocked by the engagement between the retaining ring 51 and the retaining ring engaging groove 52 on the outer periphery of the plunger 10), the return spring 24 can be prevented from extending to the free length. Therefore, when the chain tensioner 1 is extracted from the tensioner mounting hole 12 (see FIG. 1), even if the plunger 10 moves to the maximum protruding position, the pressure force of the return spring 24 against the check valve 15 is prevented from being lost. It is possible to prevent the check valve 15 from falling off from the insertion end of the plunger 10 into the cylinder 9 .

Here, as shown in FIG. 8, the axial length of the pressure chamber 17 when the plunger 10 moves in the direction in which the plunger 10 protrudes from the cylinder 9 to the position where the retaining ring engaging groove 52 engages with the retaining ring 51 If the position of the retainer ring engaging groove 52 is set so that L is shorter than the free length of the return spring 24, the return spring 24 extends to the free length when the plunger 10 moves to the maximum protruding position. It is possible to reliably prevent the check valve 15 from dropping off from the plunger 10 .

Also, in this chain tensioner 1, the valve seat 19 of the check valve 15 is not press-fitted into the insertion end of the plunger 10 into the cylinder 9, but is loosely fitted. It is possible to prevent the dimension of the first cylindrical surface 30 on the outer periphery of the end inserted into the cylinder 9 from changing, and it is possible to control the size of the leak gap 33 with high dimensional accuracy.

That is, when the valve seat 19 of the check valve 15 shown in FIG. 2 is press-fitted into the insertion end of the plunger 10 into the cylinder 9, the outer diameter dimension of the plunger 10 is slightly enlarged due to the deformation caused by the press-fitting. Here, the inner diameter of the plunger 10 varies within the tolerance range, and the outer diameter of the valve seat 19 also varies within the tolerance range. The amount of expansion of the diameter dimension also varies, and it is difficult to keep the outer diameter dimension of the plunger 10 constant. Therefore, when the valve seat 19 is press-fitted into the insertion end of the plunger 10 into the cylinder 9, it is difficult to keep the size of the leak gap 33 constant. size may be unstable. On the other hand, in the chain tensioner 1 of this embodiment, the valve seat 19 of the check valve 15 is loosely fitted to the insertion end of the plunger 10 into the cylinder 9, so that the plunger 10 is pushed into the cylinder 9 by press-fitting the valve seat 19 or the like. It is possible to prevent the dimension of the first cylindrical surface 30 on the outer circumference of the insertion end from changing into the inside 9, and it is possible to control the size of the leak gap 33 with high dimensional accuracy.

Further, since the chain tensioner 1 of this embodiment is configured such that the valve seat 19 of the check valve 15 is loosely fitted to the plunger 10, the press-fitting process for assembling the check valve 15 (the valve seat 19 to the plunger 10 using a press machine) (press-fitting step) is unnecessary, and the chain tensioner 1 can be easily assembled.

Further, in this chain tensioner 1, as shown in FIG. 7, the rising angle θ2 of the groove side surface 56 on the projecting end side is set to 30° or less, so that the groove side surface 56 on the projecting end side shown in FIG. When it moves in the direction and abuts on the retainer ring 51 , the retainer ring 51 can be pushed radially outward by a component force acting on the groove side surface 56 on the projecting end side to expand the diameter thereof. Therefore, when assembling the chain tensioner 1, the operator can insert the plunger 10 into the cylinder 9 without performing an operation such as expanding the retaining ring 51 by hand, and the chain tensioner 1 can be easily assembled. It is possible to assemble.

Further, in this chain tensioner 1, as shown in FIG. 7, the rise angle .theta.1 of the groove side surface 55 on the insertion end side is set to 50.degree. To prevent the retainer ring 51 from being deformed to expand its diameter when the retainer ring 55 is moved in the axial direction and brought into contact with the retainer ring 51, and to surely receive the groove side surface 55 on the insertion end side by the retainer ring 51.例文帳に追加can be done. Therefore, it is possible to reliably prevent the plunger 10 from falling out of the cylinder 9 when the chain tensioner 1 is removed.

7, the tapered surface 57 of the chain tensioner 1 has a rising angle .theta.3 of 30.degree. When the retaining ring 51 abuts against the tapered surface 57 , the component force acting on the tapered surface 57 presses the retainer ring 51 radially outward to expand its diameter. Therefore, when assembling the chain tensioner 1, the operator can insert the plunger 10 into the cylinder 9 without performing an operation such as expanding the retaining ring 51 by hand, and the chain tensioner 1 can be easily assembled. It is possible to assemble.

10 and 11 show a chain tensioner 1 according to a second embodiment of the invention. 2nd Embodiment differs only in the structure of the cylinder side oil supply hole 36 compared with 1st Embodiment, and the structure of other than that is the same. Therefore, parts corresponding to those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

As shown in FIG. 11, the cylinder 9 is formed with a cylinder-side oil supply hole 36 radially penetrating the lower portion of the cylinder 9 and an oil groove 60 formed on the outer circumference of the cylinder 9 . A radially outer end of the cylinder-side oil supply hole 36 opens to the lower outer periphery of the cylinder 9 . The oil groove 60 extends circumferentially around the outer periphery of the cylinder 9 so as to communicate between the opening of the radially outer end of the cylinder-side oil supply hole 36 and the oil hole 35 . Here, the opening of the radially outer end of the cylinder-side oil supply hole 36 is located below the oil hole 35 .

In this chain tensioner 1, the oil supplied from the oil hole 35 of the engine cover 11 (see FIG. 1) flows downward through the oil groove 60 on the outer circumference of the cylinder 9, and flows from the lower outer circumference of the cylinder 9 to the inside of the cylinder 9. Since the direction of the oil flowing through the oil groove 60 is opposite to the direction of the buoyancy acting on the air, the oil level in the oil hole 35 drops when the engine is stopped, and then the engine is restarted. When this is done, it is possible to effectively suppress the inflow of air into the cylinder 9 from the oil hole 35 .

As shown in FIG. 12, the O-ring 61 can be mounted at a position shifted to the open end side of the cylinder 9 (to the right in the figure) from the oil groove 60 on the outer periphery of the cylinder 9 . This prevents the oil supplied from the oil hole 35 from leaking inside the engine cover 11 through the space between the outer circumference of the cylinder 9 and the inner circumference of the tensioner mounting hole 12 (see FIG. 1). , and the oil consumption in the chain tensioner 1 can be effectively suppressed.

As shown in FIG. 13, an O-ring 62 may be further provided at a position displaced from the oil groove 60 on the outer periphery of the cylinder 9 to the flange portion 13 side (left side in the figure). A gasket between the flange portion 13 and the engine cover 11 is no longer required, and the outer surface of the engine cover 11 (see FIG. 1) need not be finished, so the cost of the engine cover 11 can be reduced.

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. However, the chain tensioner 1 transmits the rotation of the crankshaft 2 to the oil pump. , water pumps, superchargers, and other auxiliary equipment, chain transmissions that transmit the rotation of the crankshaft 2 to the balancer shaft, and chain transmissions that connect the intake and exhaust cams of a twin-cam engine. It is also possible to incorporate

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 11 Engine Cover 12 Tensioner Mounting Hole 13 Flange 15 Check Valve 16 Storage Chamber 17 Pressure Chamber 24 Return Spring 30 First Cylindrical Surface 31 Oil Groove 33 Leak Gap 36 Cylinder Side Oil Hole 37 Plunger Side Oil Supply Hole 50 Retaining ring accommodating groove 51 Retaining ring 52 Retaining ring engaging groove 55 Groove side surface 56 on insertion end side Groove side surface 57 on projecting end side Taper surface L Axial length of pressure chamber θ1 Groove side surface on insertion end side rise angle θ2 rise angle θ3 of the groove side surface on the protruding end side rise angle of the tapered surface

Claims

a cylindrical 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); ,
a check valve (15) provided at the insertion end of the plunger (10) into the cylinder (9);
a storage chamber (16) surrounded by the check valve (15) and the plunger (10);
a pressure chamber (17) formed between the check valve (15) and the closed end of the cylinder (9) such that the volume varies in response to axial movement of the plunger (10);
a cylinder side oil supply hole (36) formed in the cylinder (9) so as to open to the inner circumference of the cylinder (9);
an annular lubricating groove (31) formed in the outer periphery of the plunger (10) so as to communicate with the cylinder-side lubricating hole (36);
a plunger-side oil supply hole (37) formed radially through the plunger (10) so as to introduce oil from the oil supply groove (31) into the storage chamber (16);
a leakage gap (33) formed between a cylindrical surface (30) provided on the outer periphery of the end of the plunger (10) inserted into the cylinder (9) and the inner periphery of the cylinder (9);
a return spring (24) that biases the plunger (10) in a direction of protruding from the cylinder (9);
The check valve (15) is loosely fitted to the insertion end of the plunger (10) into the cylinder (9),
In a chain tensioner in which the return spring (24) is incorporated in the pressure chamber (17) so as to press the check valve (15) against the plunger (10),
A retaining ring (51) for elastically tightening the outer circumference of the plunger (10) is received in a retaining ring receiving groove (50) formed in the inner circumference of the cylinder (9),
The retainer ring (51) is engaged with the outer circumference of the plunger (10) at a position shifted from the lubricating groove (31) toward the projecting end of the plunger (10) from the cylinder (9). A chain tensioner characterized in that a retaining ring engagement groove (52) is formed to prevent the plunger (10) from detaching from the cylinder (9).
The pressure chamber (17) when the plunger (10) moves in the direction in which the plunger (10) protrudes from the cylinder (9) to a position where the retaining ring engaging groove (52) engages with the retaining ring (51). 2. Chain tensioner according to claim 1, wherein the axial length (L) of the return spring (24) is less than the free length.
The retaining ring engaging groove (52) is a groove on the insertion end side rising from the groove bottom of the retaining ring engaging groove (52) to the insertion end side of the plunger (10) into the cylinder (9). It has a side surface (55) and a groove side surface (56) on the protruding end side rising from the groove bottom of the retaining ring engagement groove (52) to the protruding end side of the plunger (10) from the cylinder (9). death,
The rising angle (θ1) of the groove side surface (55) on the insertion end side is set in the range of 50° to 80°,
The chain tensioner according to claim 1 or 2, wherein the rising angle (θ2) of the groove side surface (56) on the projecting end side is set within a range of 10° to 30°.
The oil supply groove (31) has a tapered surface (57) that rises from the groove bottom of the oil supply groove (31) to the protruding end side of the plunger (10) from the cylinder (9),
A chain tensioner according to any one of claims 1 to 3, wherein a rising angle (θ3) of said tapered surface (57) is set within a range of 10° to 30°.
The outer periphery of the cylinder (9) is fixed to the outer surface of the engine cover (11) in a state in which the cylinder (9) is inserted into a tensioner mounting hole (12) formed through the engine cover (11). 5. A chain tensioner according to any one of claims 1 to 4, wherein the flange portion (13) is formed to