JP7561700B2 - Chain tensioner - Google Patents

Description

This invention relates to a chain tensioner used to maintain tension in a chain.

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

The inventor of the present application has already proposed a chain tensioner for such an application, as described in Patent Document 1. The chain tensioner in Patent Document 1 has a cylindrical cylinder with one axial end closed and the other axial end open, a plunger inserted into the cylinder so as to be slidable in the axial direction, and a return spring that biases the plunger in a direction protruding from the cylinder.

The plunger is formed into a cylindrical shape with an open end inserted into the cylinder and a closed end protruding from the cylinder. A check valve is provided at the end of the plunger inserted into the cylinder, and the check valve divides the space surrounded by the cylinder and plunger into a storage chamber surrounded by the check valve and plunger, and a pressure chamber formed between the check valve and the closed end of the cylinder so that the volume changes in response to the axial movement of the plunger.

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

In the chain tensioner of Patent Document 1, when the tension in the chain increases while the engine is running, the tension in the chain causes the plunger to move in the direction in which it is pushed into the cylinder (hereinafter referred to as the "pushing direction"), absorbing the tension in the chain. At this time, oil in the pressure chamber flows out through a leak gap formed between the cylindrical surface on the outer periphery of the plunger's insertion end into the cylinder and the inner periphery of the cylinder, and the viscous resistance of the oil generates a damping force, causing the plunger to move slowly.

On the other hand, when the tension in the chain decreases while the engine is running, the force of the return spring causes the plunger to move in the direction in which it protrudes from the cylinder (hereafter referred to as the "protruding direction"), absorbing the slack in the chain. At this time, the check valve opens and oil flows from the storage chamber into the pressure chamber, causing the plunger to move quickly.

Here, when the plunger moves in the pushing direction in response 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 small, making it possible to reduce the amount of oil consumed by the chain tensioner.

JP 2020-153383 A

Chain tensioners can be broadly divided into internal and external tensioners. Internal tensioners are attached to the engine wall and are used while completely covered by an engine cover. On the other hand, external tensioners are attached by inserting the plunger into a tensioner mounting hole formed through the engine cover, with the plunger protruding from the cylinder facing the inside of the engine cover. Internal tensioners are often used in four-wheeled vehicles, while external tensioners are often used in two-wheeled vehicles.

The chain tensioner may also be removed during overhauls or repairs. When removing the chain tensioner, with an internal tensioner, the engine cover is first removed, and the entire chain tensioner is exposed before being removed from the engine wall. This means that when removing the chain tensioner, the part of the plunger protruding from the cylinder can be supported by hand, etc., making it less likely that the plunger will fall off the cylinder.

In contrast, with an external tensioner, when removing the chain tensioner, it is pulled out from the tensioner mounting hole in the engine cover. At this time, the chain tensioner is pulled out with the plunger protruding from the cylinder facing the inside of the engine cover, so the part of the plunger protruding from the cylinder cannot be supported by hand, etc., and there is a risk that the plunger will fall off the cylinder. In particular, if the chain tensioner is mounted in a position where the plunger protruding from the cylinder is pointing downward rather than horizontal, the plunger is likely to fall off the cylinder when the chain tensioner is removed.

The chain tensioner in Patent Document 1 is an internal tensioner, so as mentioned above, the problem of the plunger falling off the cylinder is unlikely to occur. Here, the inventors of the present application envisaged using the chain tensioner in Patent Document 1 as an external tensioner and considered ways to prevent the plunger of the chain tensioner in Patent Document 1 from falling off the cylinder.

In other words, in order to prevent the plunger from falling out of the cylinder when removing the chain tensioner of Patent Document 1, the inventor of the present application has devised a configuration in which a retaining ring accommodating groove is formed on the inner circumference of the open end of the cylinder of the chain tensioner of Patent Document 1, a retaining ring that elastically tightens the outer circumference of the plunger is accommodated in the retaining ring accommodating groove, and the retaining ring is engaged with an oil supply groove on the outer circumference of the plunger to prevent the plunger from falling out of the cylinder.

However, in the chain tensioner of Patent Document 1, if the plunger is prevented from coming out of the cylinder by the above configuration, it has been found that there is a risk that the check valve provided at the insertion end of the plunger into the cylinder may fall off the plunger when the plunger moves to the most protruding position.

In other words, when the plunger moves in a direction that protrudes from the cylinder, the return spring extends in response to the movement of the plunger. Then, when the plunger moves to its most protruding position (a position where the plunger's movement in the protruding direction is prevented by the engagement of the retaining ring with the oil supply groove on the outer periphery of the plunger), the axial length of the pressure chamber that houses the return spring may become 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 rather is clearance-fitted. Then, when the plunger moves axially in response to fluctuations in the tension of the chain, the check valve is pressed against the plunger by a return spring in the pressure chamber so that the check valve moves axially together with the plunger.

As a result, it was found that if the axial length of the pressure chamber housing the return spring becomes longer than the free length of the return spring when the plunger moves to its most protruding position, the return spring loses its pressing force against the check valve, and the check valve may fall off from the end of the plunger inserted into the cylinder.

Once the check valve falls off the plunger, problems may arise when an operator attempts to reassemble the check valve onto the plunger, such as installing the check valve in the wrong direction.

The problem that this invention aims to solve is to provide a chain tensioner that consumes less oil and can prevent the check valve from falling off 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 axial end as a closed end and the other axial end as an open end;
a cylindrical plunger that is slidably inserted into the cylinder in the axial direction, the plunger having an open end that is inserted into the cylinder and a closed end that protrudes from the cylinder;
A check valve provided at an end of the plunger inserted 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 so that a volume of the pressure chamber changes in response to axial movement of the plunger;
a cylinder side oil supply hole formed in the cylinder so as to open to an inner periphery of the cylinder;
an annular oil supply groove formed on an outer periphery of the plunger so as to communicate with the cylinder side oil supply hole;
a plunger-side oil supply hole formed radially penetrating the plunger so as to introduce oil from the oil supply groove to the storage chamber;
a leak gap formed between an inner periphery of the cylinder and a cylindrical surface provided on an outer periphery of an insertion end of the plunger into the cylinder;
a return spring that biases the plunger in a direction protruding from the cylinder,
The check valve is fitted with a clearance at an end of the plunger inserted into the cylinder,
In a chain tensioner, the return spring is incorporated in the pressure chamber so as to press the check valve against the plunger,
A retaining ring that elastically fastens the outer periphery of the plunger is accommodated in a retaining ring accommodating groove formed on the inner periphery of the cylinder,
a retaining ring engagement groove that engages with the retaining ring to prevent the plunger from coming out of the cylinder is formed on the outer periphery of the plunger at a position shifted toward the end of the plunger protruding from the cylinder relative to the oil supply groove.

In this way, oil that leaks from the pressure chamber through the leak gap returns to the oil supply groove on the outer periphery of the plunger and circulates, so the amount of oil discharged from the chain tensioner to the outside is small, making it possible to reduce oil consumption in the chain tensioner.

In addition, to prevent the plunger from falling out of the cylinder, the anti-slip ring is not engaged with the oil supply groove on the outer periphery of the plunger, but rather is engaged with an anti-slip ring engagement groove that is provided separately at a position shifted toward the end of the plunger protruding from the cylinder from the oil supply groove. This prevents the return spring from extending to its free length when the plunger moves to its most protruding position. Therefore, even if the plunger moves to its most protruding position when the chain tensioner is removed, the return spring's pressing force against the check valve can be prevented from disappearing, and the check valve can be prevented from falling out of the end of the plunger inserted into the cylinder.

It is preferable to adopt a configuration in which the axial length of the pressure chamber is shorter than the free length of the return spring when the plunger moves in the direction protruding from the cylinder to a position where the retaining ring engagement groove engages with the retaining ring.

In this way, it is possible to reliably prevent the return spring from extending to its free length when the plunger moves to its most extended position, and it is possible to reliably prevent the check valve from falling off the plunger.

the retaining ring engagement groove has an insertion end side groove side rising from a groove bottom of the retaining ring engagement groove toward an insertion end side of the plunger into the cylinder, and a protruding end side groove side rising from the groove bottom of the retaining ring engagement groove toward an end side of the plunger protruding 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 adopt a configuration in which the rising angle of the groove side surface on the protruding end side is set in the range of 10° to 30°.

In this way, the rise angle of the groove side on the protruding end side of the anti-slip ring engagement groove on the outer periphery of the plunger is set to 30° or less, so that when the groove side on the protruding end side moves axially and abuts against the anti-slip ring, the component force acting on the groove side on the protruding end side presses the anti-slip ring radially outward to expand its diameter. Therefore, when assembling the chain tensioner, the worker can insert the plunger into the cylinder without having to manually expand the diameter of the anti-slip ring, making it easy to assemble the chain tensioner. In addition, the rise angle of the groove side on the insertion end side of the anti-slip ring engagement groove on the outer periphery of the plunger is set to 50° or more, so that when the groove side on the insertion end side moves axially and abuts against the anti-slip ring, the anti-slip ring is prevented from expanding and deforming, and the groove side on the insertion end side can be reliably received by the anti-slip ring. Therefore, it is possible to reliably prevent the plunger from falling off the cylinder when removing the chain tensioner.

the oil groove has a tapered surface rising from a groove bottom of the oil groove toward a protruding end of the plunger from the cylinder,
It is preferable to adopt a configuration in which the rising angle of the tapered surface is set in the range of 10° to 30°.

In this way, the rising angle of the tapered surface that rises from the bottom of the oil groove to the end of the plunger protruding from the cylinder is set to 30° or less, so that when the tapered surface moves axially and abuts against the retaining ring, the retaining ring can be pressed radially outward by the component force acting on the tapered surface, expanding the diameter of the retaining ring. Therefore, when assembling the chain tensioner, the worker can insert the plunger into the cylinder without having to manually expand the diameter of the retaining ring, making it easy to assemble the chain tensioner.

This invention can be suitably applied to tensioners (i.e., external tensioners) in which a flange portion is formed on the outer periphery of the cylinder, and is fixed to the outer surface of the engine cover when the cylinder is inserted into a tensioner mounting hole formed through the engine cover.

In the chain tensioner of this invention, oil leaking from the pressure chamber through the leak gap returns to the oil supply groove on the outer periphery of the plunger and circulates, so the amount of oil discharged from the chain tensioner to the outside is small, and the amount of oil consumed by the chain tensioner is small. In addition, in order to prevent the plunger from coming off from the cylinder, the retaining ring is not engaged with the oil supply groove on the outer periphery of the plunger, but is engaged with a retaining ring engagement groove that is separately provided at a position shifted toward the protruding end of the plunger from the cylinder from the oil supply groove. This makes it possible to prevent the return spring from extending to its free length when the plunger moves to the most protruding position (the position where the engagement between the retaining ring and the retaining ring engagement groove on the outer periphery of the plunger prevents the plunger from moving in the protruding direction). Therefore, even if the plunger moves to the most protruding position when the chain tensioner is removed, it is possible to prevent the return spring from losing its pressing force against the check valve, and to prevent the check valve from falling off from the insertion end of the plunger into the cylinder.

FIG. 1 is a diagram showing a chain transmission device incorporating a chain tensioner according to a first embodiment of the present invention; 2 is a cross-sectional view taken along line II-II of FIG. FIG. 3 is a cross-sectional view showing an initial setting state of the chain tensioner shown in FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. A cross-sectional view taken along line V-V in FIG. FIG. 4 is an enlarged view of the vicinity of the retaining ring in FIG. 3 . FIG. 4 is an enlarged view of the vicinity of the retaining ring engagement groove of FIG. 3 ; FIG. 3 is a cross-sectional view showing a state in which the chain tensioner shown in FIG. 2 has moved to the most protruding position and the retaining ring has engaged with the retaining ring engagement groove. FIG. 9 is an enlarged view of the vicinity of the retaining ring in FIG. 8 . FIG. 13 is a horizontal view of a chain tensioner according to a second embodiment of the present invention. 11 is a cross-sectional view taken along line XI-XI of FIG. FIG. 11 is a diagram showing a modification of the chain tensioner of FIG. 10. FIG. 11 is a diagram showing another modified example of the chain tensioner of FIG. 10. FIG. 1 is a partial cross-sectional view showing a chain tensioner of a comparative example.

Figure 1 shows a chain transmission device incorporating a chain tensioner 1 according to a first embodiment of the present invention. In this chain transmission device, a sprocket 3 fixed to an engine crankshaft 2 and a sprocket 5 fixed to a camshaft 4 are connected via a chain 6, and the chain 6 transmits the rotation of the crankshaft 2 to the camshaft 4, and the rotation of the camshaft 4 opens and closes the valves (not shown) in the combustion chamber.

When the engine is running, the crankshaft 2 rotates in a constant direction (clockwise in the figure), and the part of the chain 6 that is pulled into the sprocket 3 as the crankshaft 2 rotates (right side of the figure) is the tight side, and the part that is sent out from the sprocket 3 (left side of the figure) is the slack side. The slack side of the chain 6 is in contact with a chain guide 8 that is supported so that it can swing around a fulcrum shaft 7. The chain tensioner 1 presses against the chain 6 via the chain guide 8.

As shown in FIG. 2, the chain tensioner 1 has a cylindrical cylinder 9 with one axial end closed and the other axial end open, and a plunger 10 inserted into the cylinder 9 so that it can slide in the axial direction. The end of the plunger 10 protruding from the cylinder 9 presses against the chain guide 8.

The cylinder 9 is inserted into the tensioner mounting hole 12 of the engine cover 11 with its open end facing inside the engine cover 11. The tensioner mounting hole 12 is a through hole that penetrates the engine cover 11 from the outer surface to the inner surface. A flange portion 13 is formed on the outer periphery 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 cylindrical shape with an open end inserted into the cylinder 9 and a closed end protruding from the cylinder 9. A check valve 15 is provided at the end of the plunger 10 inserted into the cylinder 9. The check valve 15 divides the space surrounded by the cylinder 9 and the plunger 10 into a storage chamber 16 surrounded by the check valve 15 and the plunger 10, and a pressure chamber 17 formed between the check valve 15 and the closed end of the cylinder 9 so that the volume changes in response to the axial movement of the plunger 10.

The check valve 15 has 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 pressure chamber 17 side, a valve spring 21 that urges the valve body 20 from the open position toward the closed position, and a retainer 22 that restricts the range of movement of the valve body 20. The valve hole 18 is an axial through hole formed in the valve seat 19 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 only allows the flow of oil from the storage chamber 16 side to the pressure chamber 17 side.

The check valve 15 is fitted with a gap at the end of the plunger 10 inserted into the cylinder 9. That is, the valve seat 19 constituting the check valve 15 has a cylindrical outer peripheral surface, and this valve seat 19 is fitted without any tightening margin into the cylindrical inner peripheral surface of the end of the plunger 10 inserted into the cylinder 9. The valve seat 19 is positioned in the axial direction by a step 23 formed on the inner circumference of the plunger 10. The step 23 is a stepped portion whose diameter decreases from the end of the plunger 10 inserted into the cylinder 9 (left side of the figure) to the end of the plunger 10 protruding from the cylinder 9 (right side of the figure).

A return spring 24 and an assist spring 25 are installed in the pressure chamber 17. Both the return spring 24 and the assist spring 25 are coil springs made of metal wire wound in a spiral shape, and are installed in an axially compressed state.

The return spring 24 is formed in a cone shape with an outer diameter that 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, and this pressure urges the plunger 10 in a direction that protrudes from the cylinder 9. Here, the other end of the return spring 24 (the right end in the figure) presses the retainer 22 of the check valve 15 against the valve seat 19, and also presses the valve seat 19 against the step 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 against the axial end face of the insertion end of the plunger 10 into the cylinder 9, and this pressing force urges the plunger 10 in the direction of protruding from the cylinder 9.

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

The first cylindrical surface 30 is a cylindrical surface formed on the outer periphery of the plunger 10 at the end inserted 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 end of the plunger 10 protruding from the cylinder 9 (the right side in the figure) relative to the first cylindrical surface 30. The second cylindrical surface 32 is a cylindrical surface having the same outer diameter as the first cylindrical surface 30, formed in a portion of the outer periphery of the plunger 10 adjacent to the end of the plunger 10 protruding from the cylinder 9 (the right side in the figure) relative to the oil supply groove 31. In other words, the oil supply groove 31 is formed between the first cylindrical surface 30 and the second cylindrical surface 32.

A leak gap 33 is formed between the first cylindrical surface 30 on the outer periphery of the plunger 10 and the inner periphery of the cylinder 9. The leak gap 33 is a minute cylindrical gap with a radial width 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 periphery of the plunger 10 and the inner periphery of the cylinder 9. Like the leak gap 33, the guide gap 34 is also a minute cylindrical 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 oil from the engine's oil pump (not shown) to the chain tensioner 1. The oil hole 35 opens to the inner circumference of the tensioner mounting hole 12.

The cylinder 9 is provided with a cylinder-side oil supply hole 36 that introduces oil supplied from an oil hole 35 in the engine cover 11 into the interior of the cylinder 9. The cylinder-side oil supply hole 36 is a through hole formed by penetrating the cylinder 9 in the radial direction. The radially outer end of the cylinder-side oil supply hole 36 opens at a position that communicates with the oil hole 35 in 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 at a portion of the inner periphery of the cylinder 9 that faces the outer periphery 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 to be larger than the movement stroke of the plunger 10 due to the elongation of the chain 6 (see FIG. 1) over time, for example, to a size of 10 mm or more.

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

As shown in FIG. 3, this chain tensioner 1 has a cylinder side set groove 40 formed on the inner circumference of the open end of the cylinder 9, a set ring 41 housed 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, in order to be able to hold the plunger 10 in the initial set state (the state shown in the figure) in which it is pressed into the cylinder 9.

As shown in FIG. 5, the set ring 41 is composed of a set ring body 43 with a portion of the circumference cut away, and a pair of diameter reduction operation pieces 44 provided at both ends of the set ring body 43. The set ring 41 is formed by bending a single metal wire. The pair of diameter reduction operation pieces 44 are arranged facing each other with a gap in the circumferential direction, and by operating the pair of diameter reduction operation pieces 44, it is possible to elastically deform the set ring body 43 so that the diameter of the set ring body 43 is reduced. The diameter reduction operation piece 44 is housed in a notch 45 formed radially penetrating the open end of the cylinder 9.

As shown in FIG. 6, the cylinder side set groove 40 is composed of a shallow groove portion 46 having a depth smaller than the wire diameter of the metal wire that constitutes the set ring 41, and a deep groove portion 47 having a depth larger than the wire diameter of the metal wire that constitutes the set ring 41. The deep groove portion 47 is formed to be continuous with the shallow groove portion 46 on the side of the insertion end of the plunger 10 into the cylinder 9 (the left side in the figure).

When the set ring body 43 is fitted into the shallow groove portion 46 of the cylinder side set groove 40, it is elastically deformed to reduce in diameter, and is formed to have an outer diameter dimension that allows it to be elastically pressed against the groove bottom surface of the shallow groove portion 46. The cylinder side set groove 40 and the plunger side set groove 42 are designed so that the set ring 41 can be disengaged from the plunger side set groove 42 and the initial set can be released by further pushing the plunger 10, which is held in the initial set state, into the cylinder 9.

As shown in FIG. 3, the chain tensioner 1 has a retaining ring receiving groove 50 formed on the inner circumference of the open end of the cylinder 9, a retaining ring 51 received in the retaining ring receiving groove 50, and a retaining ring engagement groove 52 formed on the outer circumference of the plunger 10. The retaining ring receiving groove 50 is formed on the inner circumference of the cylinder 9 at a position shifted toward the end of the plunger 10 inserted into the cylinder (left side in the figure) from the cylinder side set groove 40. The retaining ring engagement groove 52 is formed on the outer circumference of the plunger 10 at a position shifted toward the end of the plunger 10 protruding from the cylinder 9 from the oil supply groove 31 (right side in the figure). That is, the retaining ring engagement groove 52 is formed on the second cylindrical surface 32.

As shown in FIG. 5, the retaining ring 51 is composed of a retaining ring body 53 having a shape in which a portion of the circumference is cut off, and a pair of diameter expansion pieces 54 provided at both ends of the retaining ring body 53. The retaining ring 51 is formed by bending a single metal wire. The pair of diameter expansion pieces 54 are arranged facing each other with a gap in the circumferential direction, and by operating the pair of diameter expansion pieces 54, it is possible to elastically deform the retaining ring body 53 so that the diameter of the retaining ring body 53 increases. The diameter expansion pieces 54 are accommodated in a notch 45 formed radially penetrating the open end of the cylinder 9.

As shown in FIG. 6, the retaining ring housing groove 50 is formed to have a depth greater than the wire diameter of the metal wire that constitutes the retaining ring 51. The retaining ring body 53 is elastically expanded and deformed when fitted into the second cylindrical surface 32 on the outer periphery of the plunger 10, and is formed to have an inner diameter dimension that elastically tightens the second cylindrical surface 32.

As shown in FIG. 7, the retaining ring engagement groove 52 has an insertion end side groove side 55 that rises from the groove bottom of the retaining ring engagement groove 52 toward the insertion end of the plunger 10 into the cylinder 9, and a protruding end side groove side 56 that rises from the groove bottom of the retaining ring engagement groove 52 toward the protruding end of the plunger 10 from the cylinder 9. The groove side 55 on the insertion end side and the groove side 56 on the protruding end side are both tapered surfaces that are inclined relative to the axis-perpendicular direction. In addition, the oil supply groove 31 has a tapered surface 57 that rises from the groove bottom of the oil supply groove 31 toward the protruding end of the plunger 10 from the cylinder 9.

The rise angle θ1 of the groove side surface 55 on the insertion end side is set in the range of 50° to 80°. On the other hand, the rise angle θ2 of the groove side surface 56 on the protruding end side is set in the range of 10° to 30°. The depth of the groove bottom of the retaining ring engagement groove 52 is shallower than the wire diameter of the metal wire that constitutes the retaining ring 51. In addition, the rise angle θ3 of the tapered surface 57 is set in the range of 10° to 30°.

Next, we will explain an example of how this chain tensioner 1 works.

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 shown in FIG. 2 to move in a direction that pushes it into the cylinder 9, absorbing the tension of the chain 6. At this time, the pressure of the pressure chamber 17 becomes higher than the pressure of the storage chamber 16, so the check valve 15 is closed. In addition, the volume of the pressure chamber 17 decreases as the plunger 10 moves, so oil leaks from the pressure chamber 17 through the leak gap 33 by the amount of the decreased volume. At this time, the viscous resistance of the oil flowing through the leak gap 33 generates a damping force, which prevents the chain 6 from flapping. The oil leaking from the pressure chamber 17 through the leak gap 33 returns to the oil supply groove 31, and then flows into the plunger side oil supply hole 37, returns to the cylinder side oil supply hole 36, or passes through the guide gap 34 to lubricate the sliding surfaces of the plunger 10 and the cylinder 9.

On the other hand, when the tension of the chain 6 shown in FIG. 1 decreases while the engine is running, the force of the return spring 24 and the assist spring 25 shown in FIG. 2 causes the plunger 10 to move in the protruding direction, absorbing the slack in the chain 6. At this time, the volume of the pressure chamber 17 expands in response to the movement of the plunger 10, so that the pressure in the pressure chamber 17 becomes lower than the pressure in the storage chamber 16, and the check valve 15 opens. Then, oil flows from the storage chamber 16 through the check valve 15 into the pressure chamber 17, and the plunger 10 moves quickly. At this time, oil is introduced into the storage chamber 16 from the oil hole 35 in 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 this chain tensioner 1, 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 the amount of oil discharged from the chain tensioner 1 to the outside is small, making it possible to reduce the amount of oil consumed by the chain tensioner 1.

During overhaul or repair, the chain tensioner 1 shown in FIG. 1 may need to be removed from the tensioner mounting hole 12 in the engine cover 11.

At this time, the chain tensioner 1 is removed with the plunger 10 protruding from the cylinder 9 facing the inside of the engine cover 11, so the part of the plunger 10 protruding from the cylinder 9 cannot be supported by hand or the like, and the plunger 10 may fall off from the cylinder 9. In particular, if the chain tensioner 1 is attached in a position in which the plunger 10 protrudes from the cylinder 9 downward rather than horizontally, the plunger 10 is likely to fall off from the cylinder 9 when the chain tensioner 1 is removed.

To prevent the plunger 10 from falling off the cylinder 9, a configuration can be adopted in which a retaining ring receiving groove 50 is formed on the inner circumference of the open end of the cylinder 9, a retaining ring 51 that elastically tightens the outer circumference of the plunger 10 is received in the retaining ring receiving groove 50, and the retaining ring 51 is engaged with the oil supply groove 31 on the outer circumference of the plunger 10, thereby preventing the plunger 10 from falling off the cylinder 9, as shown in FIG.

However, as shown in FIG. 14, if a configuration is adopted in which the anti-slip ring 51 is engaged with the oil supply groove 31 on the outer periphery of the plunger 10 to prevent the plunger 10 from falling out, when the plunger 10 moves to the most protruding position, the axial length of the pressure chamber 17 that houses the return spring 24 becomes longer than the free length of the return spring 24. As a result, the pressing force of the return spring 24 against the check valve 15 disappears, and the check valve 15 may fall out from the insertion end of the plunger 10 into the cylinder 9.

If the check valve 15 falls off the plunger 10, when an operator subsequently reassembles the check valve 15 to the plunger 10, problems may arise, such as assembling the check valve 10 in the wrong direction (for example, assembling the valve seat 19 upside down).

In response to this problem, as shown in FIG. 8, the chain tensioner 1 of this embodiment does not engage the retaining ring 51 with the oil supply groove 31 on the outer periphery of the plunger 10 to prevent the plunger 10 from coming off the cylinder 9, but rather engages with the retaining ring engagement groove 52 that is provided separately at a position shifted toward the protruding end of the plunger 10 from the cylinder 9 from the oil supply groove 31. This prevents the return spring 24 from extending to its free length when the plunger 10 moves to the most protruding position (the position where the engagement between the retaining ring 51 and the retaining ring engagement groove 52 on the outer periphery of the plunger 10 prevents the plunger 10 from moving in the protruding direction). Therefore, when the chain tensioner 1 is removed from the tensioner mounting hole 12 (see FIG. 1), even if the plunger 10 moves to the most protruding position, it is possible to prevent the return spring 24 from losing its pressing force against the check valve 15, and to prevent the check valve 15 from falling off from the insertion end of the plunger 10 into the cylinder 9.

As shown in FIG. 8, if the position of the retaining ring engagement groove 52 is set so that the axial length L of the pressure chamber 17 is shorter than the free length of the return spring 24 when the plunger 10 moves in the direction protruding from the cylinder 9 to a position where the retaining ring engagement groove 52 engages with the retaining ring 51, the return spring 24 can be reliably prevented from extending to its free length when the plunger 10 moves to the most protruding position, and the check valve 15 can be reliably prevented from falling off the plunger 10.

In addition, this chain tensioner 1 does not press-fit the valve seat 19 of the check valve 15 into the end of the plunger 10 inserted into the cylinder 9, but instead fits with a gap, so it is possible to prevent the dimensions of the first cylindrical surface 30 on the outer periphery of the end of the plunger 10 inserted into the cylinder 9 from changing due to the valve seat 19 being pressed in, and it is possible to manage 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 pressed into the insertion end of the plunger 10 into the cylinder 9, the deformation caused by the press-fitting causes the outer diameter of the plunger 10 to expand slightly. Here, since 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 outer diameter of the plunger 10 when the valve seat 19 is pressed into the plunger 10 also varies, making it difficult to keep the outer diameter of the plunger 10 constant. Therefore, when the valve seat 19 is pressed 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, and the magnitude of the damping force generated by the viscous resistance of the oil flowing through the leak gap 33 may become unstable. In contrast, in the chain tensioner 1 of this embodiment, the valve seat 19 of the check valve 15 is fitted with a gap at the end of the plunger 10 inserted into the cylinder 9, so that the dimensions of the first cylindrical surface 30 on the outer periphery of the end of the plunger 10 inserted into the cylinder 9 can be prevented from changing due to the valve seat 19 being pressed in, etc., and the size of the leak gap 33 can be managed with high dimensional accuracy.

In addition, the chain tensioner 1 of this embodiment is configured so that the valve seat 19 of the check valve 15 is gap-fitted into the plunger 10, eliminating the need for a press-fitting process (a process of using a press to press the valve seat 19 into the plunger 10) to assemble the check valve 15, making the chain tensioner 1 easier to assemble.

In addition, as shown in FIG. 7, this chain tensioner 1 has a rise angle θ2 of the groove side surface 56 on the protruding end side set to 30° or less, so that when the groove side surface 56 on the protruding end side shown in FIG. 9 moves axially and abuts against the retaining ring 51, the retaining ring 51 can be pressed radially outward and expanded in diameter by the component force acting on the groove side surface 56 on the protruding end side. Therefore, when assembling the chain tensioner 1, the worker can insert the plunger 10 into the cylinder 9 without having to manually expand the diameter of the retaining ring 51, making it easy to assemble the chain tensioner 1.

In addition, as shown in FIG. 7, this chain tensioner 1 has a rise angle θ1 of the groove side surface 55 on the insertion end side set to 50° or more, so that when the groove side surface 55 on the insertion end side moves axially and abuts against the retaining ring 51 as shown in FIG. 9, the retaining ring 51 is prevented from expanding in diameter and deforming, and the groove side surface 55 on the insertion end side can be reliably received by the retaining ring 51. Therefore, it is possible to reliably prevent the plunger 10 from falling off the cylinder 9 when removing the chain tensioner 1.

In addition, as shown in FIG. 7, in this chain tensioner 1, the rising angle θ3 of the tapered surface 57 is set to 30° or less, so that when the tapered surface 57 moves axially and abuts against the retaining ring 51 shown in FIG. 9, the component force acting on the tapered surface 57 presses the retaining ring 51 radially outward, expanding the diameter. Therefore, when assembling the chain tensioner 1, the worker can insert the plunger 10 into the cylinder 9 without having to manually expand the diameter of the retaining ring 51, making it easy to assemble the chain tensioner 1.

Figures 10 and 11 show a chain tensioner 1 according to a second embodiment of the present invention. The second embodiment differs from the first embodiment only in the configuration of the cylinder side oil supply hole 36, and the rest of the configuration is the same. Therefore, parts corresponding to the first embodiment are given the same reference numerals and descriptions are omitted.

As shown in FIG. 11, the cylinder 9 is formed with a cylinder-side oil supply hole 36 that penetrates the lower part of the cylinder 9 in the radial direction, and an oil groove 60 formed on the outer periphery of the cylinder 9. The 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 is formed extending circumferentially around the outer periphery of the cylinder 9 so as to communicate between the opening at the radially outer end of the cylinder-side oil supply hole 36 and the oil hole 35. Here, the opening at the radially outer end of the cylinder-side oil supply hole 36 is located below the oil hole 35.

This chain tensioner 1 is configured so that oil supplied from the oil hole 35 in the engine cover 11 (see Figure 1) flows downward through the oil groove 60 on the outer periphery of the cylinder 9 and enters the interior of the cylinder 9 from the lower outer periphery of the cylinder 9. Because 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 when the engine is restarted, it is possible to effectively prevent air from flowing into the interior of the cylinder 9 from the oil hole 35.

As shown in Figure 12, an O-ring 61 can be attached at a position offset toward the open end 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 oil supplied from the oil hole 35 from leaking between the outer periphery of the cylinder 9 and the inner periphery of the tensioner mounting hole 12 (see Figure 1) and into the inside of the engine cover 11, making it possible to effectively reduce the amount of oil consumed by the chain tensioner 1.

As shown in FIG. 13, an O-ring 62 may be provided at a position shifted toward the flange portion 13 (to the left in the figure) from the oil groove 60 on the outer periphery of the cylinder 9. This eliminates the need for a gasket between the flange portion 13 and the engine cover 11, and eliminates the need to finish the outer surface of the engine cover 11 (see FIG. 1), making it possible to reduce the cost of the engine cover 11.

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

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

1 Chain tensioner 9 Cylinder 10 Plunger 11 Engine cover 12 Tensioner mounting hole 13 Flange portion 15 Check valve 16 Reservoir chamber 17 Pressure chamber 24 Return spring 30 First cylindrical surface 31 Oil supply groove 33 Leak gap 36 Cylinder side oil supply hole 37 Plunger side oil supply hole 50 Anti-slip ring accommodating groove 51 Anti-slip ring 52 Anti-slip ring engagement groove 55 Groove side surface on insertion end side 56 Groove side surface on protruding end side 57 Tapered surface L Axial length of pressure chamber θ1 Rise angle of groove side surface on insertion end side θ2 Rise angle of groove side surface on protruding end side θ3 Rise angle of tapered surface

Claims (5)

A cylindrical cylinder (9) having one axial end as a closed end and the other axial end as an open end;
a cylindrical plunger (10) that is slidably inserted into the cylinder (9) in the axial direction, the plunger having an open end inserted into the cylinder (9) and a closed end protruding from the cylinder (9);
A check valve (15) provided at the end of the plunger (10) inserted into the cylinder (9);
a reservoir (16) surrounded by the check valve (15) and the plunger (10);
a pressure chamber (17) formed between the check valve (15) and a closed end of the cylinder (9) such that the volume of the pressure chamber changes in response to the axial movement of the plunger (10);
a cylinder side oil supply hole (36) formed in the cylinder (9) so as to open to an inner periphery of the cylinder (9);
an annular oil supply groove (31) formed on the outer periphery of the plunger (10) so as to communicate with the cylinder side oil supply hole (36);
a plunger-side oil supply hole (37) formed radially penetrating the plunger (10) so as to introduce oil from the oil supply groove (31) to the storage chamber (16);
a leakage gap (33) formed between a cylindrical surface (30) provided on the outer periphery of the insertion end of the plunger (10) into the cylinder (9) and the inner periphery of the cylinder (9);
a return spring (24) that biases the plunger (10) in a direction protruding from the cylinder (9),
The check valve (15) is fitted with a clearance at the end of the plunger (10) inserted into the cylinder (9);
In a chain tensioner, 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) that elastically fastens the outer periphery of the plunger (10) is accommodated in a retaining ring accommodation groove (50) formed on the inner periphery of the cylinder (9),
a retaining ring engagement groove (52) that engages with the retaining ring (51) to prevent the plunger (10) from coming off from the cylinder (9) is formed on the outer periphery of the plunger (10) at a position shifted toward the end of the plunger (10) protruding from the cylinder (9) relative to the oil supply groove (31) ;
The cylinder side oil supply hole (36) penetrates the lower part of the cylinder (9) in the radial direction, and its radially outer end portion opens to the outer periphery lower part of the cylinder (9),
a cylinder side oil supply hole (36) disposed above the opening of the radially outer end of the cylinder side oil supply hole (36) and an oil hole (35) disposed above the opening of the cylinder side oil supply hole (36) and an oil groove (60) extending circumferentially around the outer periphery of the cylinder (9) are formed on the outer periphery of the cylinder (9) . A chain tensioner as described in claim 1, in which the axial length (L) of the pressure chamber (17) when the plunger (10) moves in a direction protruding from the cylinder (9) to a position where the retaining ring engagement groove (52) engages with the retaining ring (51) is shorter than the free length of the return spring (24). The retaining ring engagement groove (52) has an insertion end side groove side (55) rising from the groove bottom of the retaining ring engagement groove (52) toward the insertion end side of the plunger (10) into the cylinder (9), and a protruding end side groove side (56) rising from the groove bottom of the retaining ring engagement groove (52) toward the protruding end side of the plunger (10) from the cylinder (9),
The rising angle (θ1) of the groove side surface (55) on the insertion end side is set in the range of 50° to 80°,
3. The chain tensioner according to claim 1, wherein the rise angle (θ2) of the groove side surface (56) on the projecting end side is set in the range of 10° to 30°. The oil supply groove (31) has a tapered surface (57) rising from the bottom of the oil supply groove (31) toward the end of the plunger (10) protruding from the cylinder (9),
4. The chain tensioner according to claim 1, wherein the rising angle (θ3) of the tapered surface (57) is set in the range of 10° to 30°. A chain tensioner according to any one of claims 1 to 4, in which a flange portion (13) is formed on the outer periphery of the cylinder (9) and is fixed to the outer surface of the engine cover (11) when the cylinder (9) is inserted into a tensioner mounting hole (12) formed through the engine cover (11).

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