WO2022191198A1

WO2022191198A1 - Chain tensioner

Info

Publication number: WO2022191198A1
Application number: PCT/JP2022/010042
Authority: WO
Inventors: 武博高野; 誠二佐藤
Original assignee: Ntn株式会社
Priority date: 2021-03-11
Filing date: 2022-03-08
Publication date: 2022-09-15
Also published as: JP2022138972A

Abstract

In the present invention, an oiling passage (31) has an oil groove (32) formed facing an oil hole (30) in the surface of a cylinder (10), and an oil introduction hole (33) formed communicating with the interior of a cylinder body section (10A) from the oil groove (32). The oil introduction hole (33) is provided in a position lower than the oil hole (30) so as to have an oil inlet (33a). The oil groove (32) has a branching part (35) that branches into an upward flow path (36) and a downward flow path (37).

Description

chain tensioner

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

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

As a chain tensioner used for such applications, for example, the one described in Patent Document 1 is known. The chain tensioner disclosed in Patent Document 1 includes a cylinder, a plunger axially slidably inserted into the cylinder, a return spring that biases the plunger in the direction of protruding from the cylinder, and a plunger that moves in the direction of being pushed into the cylinder. and a hydraulic damper mechanism that generates a damping force due to the viscous resistance of the oil when the damping force is applied.

The cylinder has a cylinder body portion that is inserted into the tensioner mounting hole of the engine cover, and a cylinder flange portion that is integrally formed with the cylinder body portion and fixed in surface contact with the outer surface of the engine cover. The cylinder main body is a cylindrical portion having one axial end closed and the other axial end open, and is inserted into the tensioner mounting hole with the open end directed toward the inside of the engine cover.

An oil hole is formed in the engine cover to supply the chain tensioner with oil sent from the engine's oil pump. A cylinder of the chain tensioner is provided with an oil supply passage for introducing oil into the cylinder from an oil hole in the engine cover. The oil supply passage is an oil introduction hole formed to communicate from the surface of the cylinder to the inside of the cylinder.

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

On the other hand, when the tension of the chain becomes small while the engine is running, the plunger moves in the direction in which the plunger protrudes from the cylinder (hereinafter referred to as the "projection direction") due to the biasing force of the return spring and the pressure of the oil in the cylinder. Absorb relaxation.

Patent No. 5102238 (Fig. 2)

By the way, generally, when the engine stops, the oil pump of the engine also stops, so the oil level in the oil hole of the engine cover drops, and air accumulates in the oil hole. Therefore, when the engine is restarted, the air accumulated in the oil hole of the engine cover moves into the cylinder through the oil introduction hole and mixes with the oil in the cylinder. If air is mixed in with the oil in the cylinder, the plunger will move due to compression of the air in the cylinder when a load is applied to the plunger in the pushing direction, resulting in an unstable damper force. .

Therefore, in order to make it difficult for the air accumulated in the oil hole of the engine cover to flow into the cylinder when the engine is restarted, the chain tensioner disclosed in Patent Document 1 has an air bleeding passage branching from the middle of the oil introduction hole. are provided.

In the chain tensioner of Patent Literature 1, the oil introduction hole has an oil inlet that opens to the mating surface of the cylinder flange portion with the engine cover so as to receive oil directly from the oil hole of the engine cover. An air release hole is provided so as to branch upward from the middle of the oil introduction hole that communicates the oil inlet with the inside of the cylinder. It is possible to discharge to

However, when the inventors of the present application conducted an in-house prototype evaluation of the chain tensioner of Patent Document 1, when the engine was started, the air accumulated in the oil hole of the engine cover passed through the oil introduction hole of the cylinder and entered the inside of the cylinder. Although the air can be discharged through the air vent hole that branches upward from the middle of the oil introduction hole, a considerable amount of air still mixes with the oil in the cylinder. I found out.

Therefore, the inventors of the present application investigated and investigated the cause of air mixing into the oil in the cylinder. As a result, when only air flows into the oil introduction hole from the oil hole of the engine cover when the engine is started, the air can be smoothly discharged through the air vent hole that branches upward from the middle of the oil introduction hole. However, if the oil flowing from the oil hole in the engine cover to the oil introduction hole contains dispersed air in the form of bubbles, the air in the form of bubbles will not flow from the oil introduction hole into the air release hole. It was found that the oil flows through the oil introduction hole together with the oil and reaches the inside of the cylinder.

The problem to be solved by the present invention is to provide a chain tensioner that can effectively prevent air from entering the cylinder when starting the engine.

In order to solve the above problems, the present invention provides a chain tensioner having the following configuration.
a cylinder main body having one end in the axial direction as a closed end and the other end in the axial direction as an open end, which is inserted into a tensioner mounting hole formed in the engine cover with the open end directed toward the inside of the engine cover; a cylinder having a cylinder flange integrally formed with the cylinder main body and fixed in surface contact with an outer surface of the engine cover;
a plunger axially slidably inserted into the cylinder main body;
a return spring that biases the plunger in a direction of protruding from the cylinder main body;
an oil supply passage provided in the cylinder so as to introduce oil into the cylinder main body from an oil hole opening in the engine cover;
A chain tensioner comprising a hydraulic damper mechanism that generates a damping force by the viscous resistance of oil when the plunger moves in the direction of being pushed into the cylinder main body,
The oil supply passage includes an oil groove formed on the surface of the cylinder facing the oil hole so as to receive oil from the oil hole, and an oil groove for introducing oil in the oil groove into the cylinder main body. and an oil introduction hole formed in communication from the oil groove to the inside of the cylinder main body,
The oil introduction hole is provided so as to have an oil inlet at a position below the oil hole,
The chain tensioner according to claim 1, wherein the oil groove has a branch portion for branching the oil received from the oil hole into an upward flow path for bleeding air and a downward flow path connected to the oil inlet.

With this configuration, an oil groove for receiving oil from the oil hole of the engine cover is formed on the surface of the cylinder, and the oil groove has a branched portion that branches into an upward flow path and a downward flow path for bleeding air. Since the oil inlet of the oil introduction hole located below the oil hole is connected to the downward flow path branched downward from the branch, the oil received from the oil hole into the oil groove is in a state of air bubbles. Even if air is contained, the buoyancy acting on the air bubbles makes it difficult for the air to reach the oil inlet of the oil introduction hole connected to the downward flow path. can be discharged to Therefore, it is possible to effectively prevent air from entering the cylinder when the engine is started.

The downward flow path is preferably formed to have a flow area larger than the cross-sectional area of the oil hole.

By doing so, the flow area of the downward flow path becomes relatively large, so the influence of the buoyancy of the bubbles on the viscosity of the oil increases. Therefore, it is possible to effectively prevent air bubbles contained in the oil from reaching the oil inlet of the oil introducing hole through the downward flow path.

The oil groove has a pre-branch flow path for receiving oil from the oil hole and flowing it to the branch,
It is preferable to employ a configuration in which the pre-branch flow path has a flow area larger than the cross-sectional area of the oil hole.

With this configuration, since the pre-branch flow path having a relatively large flow area is provided upstream of the branch, the air bubbles contained in the oil and the oil move up and down before reaching the branch. easier to separate. Therefore, the air bubbles contained in the oil can be efficiently introduced into the upward flow path for air bleeding at the branch portion.

It is preferable that the pre-branching flow path is formed only by a horizontal direction or an upward flow path with respect to the horizontal direction.

In this way, the direction of movement of air bubbles due to buoyancy and the direction of oil flow in the pre-branch flow path do not become opposite to each other. Air bubbles and oil are smoothly separated vertically in the pre-branch flow path. Therefore, the air bubbles contained in the oil can be efficiently introduced into the upward flow path for air bleeding at the branch portion.

It is preferable that the pre-branch flow path is formed in a tapered shape in which the flow path area gradually increases from the position of the oil hole toward the branch portion.

In this way, when the oil flows from the position of the oil hole toward the branching portion, the oil passage area gradually expands, and the flow velocity of the oil gradually decreases. It is easy to combine in the front channel. Therefore, the air bubbles contained in the oil can be efficiently introduced into the upward flow path for air bleeding at the branch portion.

the branch portion is arranged to face the oil hole so as to receive oil directly from the oil hole;
It is preferable to employ a configuration in which a buffer chamber having a horizontal cross-sectional area larger than that of the downward flow path is formed in the branch portion.

With this arrangement, the buoyancy of the air bubbles has a greater effect on the viscosity of the oil in the buffer chamber formed in the branch. Therefore, the air bubbles contained in the oil and the oil are easily separated vertically at the branch, and the air bubbles contained in the oil can be efficiently introduced into the upward flow path for air release at the branch.

The surface of the cylinder can be a fitting surface of the outer circumference of the cylinder main body and the inner circumference of the tensioner mounting hole. That is, the oil groove can be formed on the fitting surface of the outer circumference of the cylinder main body and the inner circumference of the tensioner mounting hole.

The surface of the cylinder can be a mating surface of the cylinder flange portion with the outer surface of the engine cover. That is, the oil groove can be formed in a surface of the cylinder flange portion that is mated with the outer surface of the engine cover.

In the chain tensioner of the present invention, an oil groove for receiving oil from the oil hole of the engine cover is formed on the surface of the cylinder. Since it has a branch portion that branches into a downward flow path that connects to the oil inlet of the oil introduction hole located below the oil introduction hole and flows, when the oil received from the oil hole to the oil groove contains air in the form of air bubbles. Also, the air tends to be separated from the oil at the branched portion of the oil groove, and does not easily reach the oil inlet of the oil introduction hole connected to the downward flow path. Therefore, it is possible to effectively prevent air from entering the cylinder when the engine is started.

1 is a diagram showing a chain transmission incorporating a chain tensioner according to a first embodiment of the present invention; FIG. Enlarged view of the vicinity of the chain tensioner in Fig. 1 Cross-sectional view of the chain tensioner of Figure 2 Cross-sectional view along the IV-IV line in Fig. 2 Cross-sectional view along the V-V line in Fig. 2 The figure which shows the modification of the branch pre-flow path shown in FIG. FIG. 3 is a diagram showing another modification of the pre-branch flow path shown in FIG. 2; FIG. 3 is a diagram showing still another modification of the pre-branch flow path shown in FIG. 2; FIG. 2 is a cross-sectional view showing a chain tensioner according to a second embodiment of the invention; FIG. 3 is a diagram showing a chain transmission incorporating a chain tensioner according to a third embodiment of the invention; Enlarged cross-sectional view of the vicinity of the chain tensioner in FIG. Cross-sectional view along line XII-XII in FIG. Cross-sectional view along line XIII-XIII in FIG. The perspective view of the cylinder flange part shown in FIG. FIG. 4 is a sectional view showing a chain tensioner according to a fourth embodiment of the invention;

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 has a cylinder 10 fixed to the engine cover 9. The cylinder 10 has a cylinder body portion 10A to be inserted into the tensioner mounting hole 11 of the engine cover 9, and a cylinder flange portion 10B fixed to the outer surface 12 of the engine cover 9 in surface contact. The cylinder body portion 10A and the cylinder flange portion 10B are seamlessly integrally formed of an aluminum alloy.

The engine cover 9 is a wall that forms a chain storage chamber 13 in which the chain 6 (see FIG. 1) is stored. The tensioner mounting hole 11 is formed through the engine cover 9 from an outer surface 12 (a surface opposite to the chain housing chamber 13 side) to an inner surface (a surface on the chain housing chamber 13 side).

The cylinder flange portion 10B is fixed to the engine cover 9 with bolts 14. A mating surface 15 that comes into surface contact with the outer surface 12 of the engine cover 9 is formed on the cylinder flange portion 10B. A gap between the mating surface 15 and the outer surface 12 of the engine cover 9 is sealed by tightening the bolt 14 . A cylindrical fitting surface 16 that fits into the inner periphery of the tensioner mounting hole 11 is formed on the outer periphery of the cylinder main body 10A.

As shown in FIG. 3, the chain tensioner 1 includes a plunger 17 that is axially slidably inserted into the cylinder body 10A, and a return spring 18 that biases the plunger 17 in the direction of protruding from the cylinder body 10A. and a hydraulic damper mechanism 19 that generates a damping force due to the viscous resistance of the oil when the plunger 17 moves in the direction of being pushed into the cylinder body 10A.

The cylinder main body 10A is formed in a tubular shape with one end in the axial direction as a closed end and the other end in the axial direction as an open end. The cylinder main body 10A is inserted into the tensioner mounting hole 11 with the open end facing the inside of the engine cover 9 . The cylinder flange portion 10B is formed on the outer periphery of the closed end side of the cylinder body portion 10A.

The protruding end of the plunger 17 from the cylinder main body 10A presses the chain guide 8. The cylinder 10 is mounted in a posture in which the direction in which the plunger 17 protrudes from the cylinder main body 10A is inclined downward from the horizontal. The projection direction of the plunger 17 from the cylinder body portion 10A may be installed in a horizontal direction.

The plunger 17 is formed in a cylindrical shape with an open end inserted into the cylinder main body 10A and a closed protruding end of the plunger 17 from the cylinder main body 10A. The material of the plunger 17 is a ferrous material (for example, a steel material such as SCM (chromium molybdenum steel) or SCr (chromium steel)).

An inner sleeve 20 is inserted into the plunger 17 so that one end in the axial direction is inserted into the plunger 17 and the other end in the axial direction protrudes from the plunger 17 . The protruding end of the inner sleeve 20 from the plunger 17 is supported by the closed end of the cylinder main body 10A. A check valve 21 is provided at the insertion end of the inner sleeve 20 into the plunger 17 .

The check valve 21 divides the inner region of the inner sleeve 20 and the plunger 17 into a reservoir chamber 22 on the inner sleeve 20 side and a pressure chamber 23 on the plunger 17 side. Here, the volume of the reservoir chamber 22 does not change even if the plunger 17 moves in the axial direction, and is constant. On the other hand, the volume of the pressure chamber 23 increases when the plunger 17 axially moves in the direction of protruding from the cylinder body 10A, and decreases when the plunger 17 axially moves in the direction of being pushed into the cylinder body 10A. . The check valve 21 restricts the flow of oil from the pressure chamber 23 side to the reservoir chamber 22 side and allows only the oil flow from the reservoir chamber 22 side to the pressure chamber 23 side.

A return spring 18 is incorporated in the pressure chamber 23 . The return spring 18 is a compression coil spring formed by spirally winding a metal wire. One end of the return spring 18 is supported by the check valve 21, and the other end presses the plunger 17 in the axial direction.

A leak gap 24 is formed between the outer circumference of the inner sleeve 20 and the inner circumference of the plunger 17 to allow oil to leak from the pressure chamber 23 when the volume of the pressure chamber 23 is reduced. The leak gap 24 is a cylindrical minute gap with a radial width set in the range of 0.010 to 0.050 mm.

A cylindrical guide gap 25 is formed between the inner circumference of the cylinder main body 10A and the outer circumference of the plunger 17. The radial width of the guide gap 25 is set larger than the radial width of the leak gap 24, and can be set in the range of 0.015 to 0.065 mm, for example.

Here, the reservoir chamber 22, the pressure chamber 23, the check valve 21, and the leak gap 24 constitute the hydraulic damper mechanism 19. That is, when the plunger 17 moves in the direction of protruding from the cylinder main body 10A, the check valve 21 is opened, so that hydraulic oil is introduced from the reservoir chamber 22 into the pressure chamber 23, and the plunger 17 is pushed into the cylinder main body 10A. The check valve 21 is closed, and oil flows out from the pressure chamber 23 through the leak gap 24, and the viscous resistance of the oil generates a damping force.

A portion of the inner sleeve 20 protruding from the plunger 17 is provided with an oil passage 27 that communicates between the cylindrical space 26 and the reservoir chamber 22 . The cylindrical space 26 is radially sandwiched between the inner periphery of the cylinder body 10A and the outer periphery of the inner sleeve 20 on the side closer to the closed end of the cylinder body 10A than the insertion end of the plunger 17 into the cylinder body 10A. It is a cylindrical area where the The oil passage 27 is a through hole formed through the inner sleeve 20 in the radial direction.

As shown in FIGS. 2 and 5, the engine cover 9 is formed with an oil hole 30 for supplying the chain tensioner 1 with oil delivered from an oil pump (not shown) of the engine. The oil hole 30 is a round hole with a circular cross-sectional shape. The oil hole 30 opens on the inner circumference of the tensioner mounting hole 11 of the engine cover 9 .

The cylinder 10 is provided with an oil supply passage 31 that introduces the oil supplied from the oil hole 30 into the cylinder main body 10A. The oil supply passage 31 includes an oil groove 32 formed in the surface of the cylinder 10 (here, a cylindrical fitting surface 16 on the outer periphery of the cylinder main body 10A), and an oil in the oil groove 32 being supplied to the inside of the cylinder main body 10A. and an oil introduction hole 33 (see FIG. 4) formed so as to communicate from the oil groove 32 to the inside of the cylinder main body 10A so as to introduce the oil into the cylinder main body 10A.

As shown in FIG. 2 , the oil groove 32 has a pre-branch flow path 34 , a branch portion 35 , an upward flow path 36 and a downward flow path 37 . The pre-branch flow path 34 is a flow path that receives oil from the oil hole 30 and flows the oil to the branch portion 35 . The upstream end of the pre-branching flow path 34 is disposed radially facing the opening of the oil hole 30 on the inner circumference of the tensioner mounting hole 11 so as to directly receive the oil from the oil hole 30 . is connected to the branch portion 35 so that the oil flowing from the oil hole 30 flows into the branch portion 35 .

The pre-branch flow path 34 is formed only by the upward flow path with respect to the horizontal. In the drawing, as the pre-branch flow path 34, a flow path that extends upward to the upper right with respect to the horizontal and then extends upward to the upper left from the horizontal is shown. The pre-branch flow path 34 may further include a horizontal flow path. The pre-branch flow path 34 is a rectangular groove having a rectangular cross-sectional shape. The pre-branch flow passage 34 has a flow passage area (a cross-sectional area of the flow passage along a cross section perpendicular to the oil flowing direction) larger than the cross-sectional area of the oil hole 30 .

The branching portion 35 divides the oil received from the oil hole 30 into the pre-branching flow path 34 into the upward flow path 36 and the downward flow path 37 so as to flow the oil therethrough. This is the portion where the channel 37 is connected. The upward flow path 36 is an air bleeding flow path for discharging air upward from the branch portion 35, and communicates with the chain housing chamber 13 inside the engine cover 9 via an orifice passage 38 and an air bleeding passage 39. ing.

The upward flow path 36 is formed by extending upward from the branch portion 35 along the outer circumference of the cylinder body portion 10A. The upward channel 36 is a square groove with a square cross-sectional shape. The upward flow path 36 is formed to have a flow area larger than the cross-sectional area of the oil hole 30 . The orifice passage 38 is a minute annular groove formed on the outer circumference of the cylinder body portion 10A. The air release passage 39 is a gap formed between the inner periphery of the tensioner mounting hole 11 and the outer periphery of the cylinder body portion 10A.

As shown in FIG. 4, the downward flow path 37 is formed extending downward from the branch portion 35 along the outer periphery of the cylinder main body portion 10A. The downward channel 37 is a square groove with a square cross-sectional shape. The downward flow path 37 is formed to have a flow area larger than the cross-sectional area of the oil hole 30 . The downward flow path 37 is connected to the oil inlet 33 a of the oil introduction hole 33 . The oil introduction hole 33 is a hole that radially penetrates through the lower peripheral wall portion of the cylinder body portion 10A. The oil inlet 33a is an opening portion of the oil introduction hole 33 on the outer peripheral side of the cylinder body portion 10A. The oil inlet 33a is located below the opening position of the oil hole 30 (see FIG. 5).

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

When the tension of the chain 6 shown in FIG. 1 increases during engine operation, the tension of the chain 6 causes the plunger 17 to move in the direction of being pushed into the cylinder main body 10A, absorbing the tension of the chain 6. At this time, since the pressure in the pressure chamber 23 shown in FIG. 3 becomes higher than the pressure in the reservoir chamber 22, the check valve 21 is closed. Further, since the volume of the pressure chamber 23 is reduced in accordance with the movement of the plunger 17, oil leaks from the pressure chamber 23 through the leak gap 24 by the amount of the reduced volume. A damping force is generated by the viscous resistance, and the damping force prevents the chain 6 from fluttering. Most of the oil that has leaked from the pressure chamber 23 through the leak gap 24 into the tubular space 26 returns to the reservoir chamber 22 through the oil passage 27 . Also, part of the oil leaked from the pressure chamber 23 through the leak gap 24 into the cylindrical space 26 lubricates the guide gap 25 .

On the other hand, when the tension of the chain 6 shown in FIG. 1 decreases during engine operation, the plunger 17 moves in the projecting direction due to the biasing force of the return spring 18 and the hydraulic pressure in the pressure chamber 23 shown in FIG. Absorb relaxation. At this time, since the volume of the pressure chamber 23 expands according to the movement of the plunger 17, the pressure in the pressure chamber 23 becomes lower than the pressure in the reservoir chamber 22, and the check valve 21 opens. Then, oil flows from the reservoir chamber 22 through the check valve 21 into the pressure chamber 23, and the plunger 17 moves rapidly. At this time, as shown by chain-line arrows in FIGS. are introduced into the cylinder body portion 10A in order.

When the engine stops, the oil pump of the engine also stops, so the oil level in the oil hole 30 of the engine cover 9 drops and the oil hole 30 becomes filled with air. After that, when the engine is restarted, only air first flows into the oil groove 32 from the oil hole 30 of the engine cover 9 . At this time, the air passes through the pre-branch flow path 34 of the oil groove 32 , the branch portion 35 , the upward flow path 36 , the orifice passage 38 , and the air release passage 39 in order and is discharged to the chain housing chamber 13 . Subsequently, oil begins to flow into the oil groove 32 from the oil hole 30 of the engine cover 9 . At this time, air may be dispersedly contained in the oil in the form of air bubbles, but the air bubbles contained in the oil and the oil are separated up and down in the pre-branch flow path 34 by the buoyancy acting on the air bubbles. At the branch 35 , the air bubbles flow into the upward channel 36 and the oil flows into the downward channel 37 . The air bubbles that have flowed into the upward flow path 36 are discharged to the chain accommodation chamber 13 through the orifice passage 38 and the air release passage 39 in order. The oil that has flowed into the downward flow path 37 flows through the oil introduction hole 33 into the cylinder main body 10A.

In this chain tensioner 1, as shown in FIG. 2, an oil groove 32 is formed on the surface of the cylinder 10 to receive oil from an oil hole 30 of the engine cover 9, and the oil groove 32 serves as an upward flow path for bleeding air. 36 and a downward flow path 37, and an oil inlet 33a of the oil introduction hole 33 located below the oil hole 30 in the downward flow path 37 branching downward from the branch portion 35. (see FIG. 4) is connected, even if the oil received from the oil hole 30 into the oil groove 32 contains air in the form of air bubbles, the oil is connected to the downward flow path 37 by the buoyancy acting on the air bubbles. Air is less likely to reach the oil inlet 33a of the oil introduction hole 33, and the air can be effectively discharged through the upward flow path 36 for air bleeding. Therefore, it is possible to effectively prevent air from entering the cylinder 10 when the engine is started.

Further, in this chain tensioner 1, the downward flow path 37 shown in FIG. 2 has a flow area larger than the cross-sectional area of the oil hole 30. In the passage 37, the influence of the buoyancy of the air bubbles on the viscosity of the oil increases. Therefore, it is possible to effectively prevent air bubbles contained in the oil from reaching the oil inlet 33 a of the oil introduction hole 33 through the downward flow path 37 .

Further, in the chain tensioner 1, the pre-branch flow path 34 having a flow area larger than the cross-sectional area of the oil hole 30 is provided upstream of the branch portion 35, so that the air bubbles contained in the oil and the oil However, before reaching the branching portion 35, it is likely to separate vertically. Therefore, the air bubbles contained in the oil can be efficiently introduced into the upward flow path 36 for air bleeding at the branch portion 35 .

Further, in this chain tensioner 1, as shown in FIG. 2, the pre-branch flow path 34 is formed only in the horizontal direction or the upward flow path with respect to the horizontal direction. The direction of oil flow in the front flow path 34 is never reversed. Therefore, when the oil flows through the pre-branching flow path 34 , air bubbles contained in the oil and the oil are smoothly separated vertically in the pre-branching flow path 34 . As a result, the air bubbles contained in the oil can be efficiently introduced into the upward flow path 36 for air bleeding at the branch portion 35 .

As shown in FIG. 6, the pre-branch flow path 34 can be formed to have a portion that extends obliquely upward toward the branch portion 35 with respect to the axial direction of the cylinder main body portion 10A. In this way, when the cylinder 10 is mounted in a posture in which the plunger 17 (see FIG. 2) protrudes from the cylinder main body 10A in the horizontal direction or in a direction inclined below the horizontal direction, the branching is ensured. The front channel 34 can be slanted upward with respect to the horizontal. In addition, since the position of the branch portion 35 is relatively higher due to the inclination of the pre-branching channel 34, the length of the downward channel 37 is increased. Therefore, a relatively large amount of oil can be stored in the downward flow path 37 when the engine is stopped, and the oil can be used to quickly exert a damping force when the engine is started.

Further, as shown in FIG. 6, the pre-branch flow path 34 can be formed in a tapered shape in which the flow path area gradually expands from the position of the oil hole 30 toward the branch portion 35 . In this way, when the oil flows from the position of the oil hole 30 toward the branching portion 35, the flow area of the oil gradually expands, and the flow velocity of the oil gradually slows down. , are easily combined in the pre-branch flow path 34 . Therefore, the air bubbles contained in the oil can be efficiently introduced into the upward flow path 36 for air bleeding at the branch portion 35 .

As shown in FIG. 7, the pre-branching flow path 34 may be formed such that its entire length extends obliquely upward toward the branching portion 35 with respect to the axial direction of the cylinder main body portion 10A.

In the above embodiment, the pre-branch flow path 34 is formed on the side of the opening end of the cylinder main body 10A (on the right side in the drawing) with respect to the upward flow path 36 and the downward flow path 37. 8, the pre-branch flow path 34 is formed on the side of the closed end of the cylinder main body 10A (on the left side in the drawing) with respect to the upward flow path 36 and the downward flow path 37, and the pre-branch flow path 34 may be formed so as to extend obliquely upward toward the branch portion 35 with respect to the axial direction of the cylinder main body portion 10A. In this way, even when the cylinder 10 is mounted in a posture in which the projection direction of the plunger 17 (see FIG. 2) from the cylinder body portion 10A is tilted upward from the horizontal, the pre-branch flow path can be reliably 34 can be slanted upwards with respect to the horizontal.

FIG. 9 shows the chain tensioner 1 of the second embodiment. The second embodiment differs from the first embodiment only in the internal structure of the cylinder main body 10A, and the rest of the configuration (including the configuration of the oil supply passage 31) is the same. Therefore, parts corresponding to those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

A pressure chamber 23 surrounded by the cylinder body 10A and the plunger 17 is formed in the cylinder body 10A. A reservoir chamber 22 is formed at the closed end of the cylinder. A check valve 21 is provided between the pressure chamber 23 and the reservoir chamber 22 .

A leak gap 24 is formed between the outer circumference of the plunger 17 and the inner circumference of the cylinder main body 10A to allow oil to leak from the pressure chamber 23 when the volume of the pressure chamber 23 is reduced.

A relief passage 40 communicating between the pressure chamber 23 and the chain housing chamber 13 is formed at the projecting end of the plunger 17 from the cylinder main body 10A. The relief passage 40 is provided with a relief valve 41 that opens when the pressure in the pressure chamber 23 exceeds a preset pressure.

The oil introduction hole 33 is a hole radially penetrating through the lower peripheral wall portion of the cylinder main body 10A, and communicates between the oil groove 32 and the reservoir chamber 22 .

The reservoir chamber 22, the pressure chamber 23, the check valve 21, and the leak gap 24 constitute a hydraulic damper mechanism 19. That is, when the plunger 17 moves in the direction of protruding from the cylinder main body 10A, the check valve 21 is opened, so that hydraulic oil is introduced from the reservoir chamber 22 into the pressure chamber 23, and the plunger 17 is pushed into the cylinder main body 10A. The check valve 21 is closed, and oil flows out from the pressure chamber 23 through the leak gap 24, and the viscous resistance of the oil generates a damping force.

An assist spring 42 is incorporated between the insertion end of the plunger 17 into the cylinder body portion 10A and the closed end of the cylinder body portion 10A. The assist spring 42 has a function of enhancing the ability of the chain guide 8 to follow the chain 6 by assisting the biasing force of the return spring 18 pressing the plunger 17 .

The chain tensioner 1 of this second embodiment also has the same effects as those of the first embodiment.

Fig. 10 shows a chain transmission incorporating the chain tensioner 1 of the third embodiment of the invention. Compared to the first embodiment, the third embodiment differs from the first embodiment in that the opening position of the oil hole 30 of the engine cover 9, the mounting posture of the cylinder 10 with respect to the engine cover 9, the oil groove 32 formed in the cylinder 10, and the oil introduction hole 33 are different. Only the configuration is different, and other configurations are the same. Therefore, parts corresponding to those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The cylinder 10 is attached to the engine cover 9 so that the direction in which the plunger 17 protrudes from the cylinder body 10A is horizontal. The direction in which the plunger 17 projects from the cylinder main body 10A may be attached in a direction inclined downward from the horizontal.

As shown in FIG. 13, the engine cover 9 is formed with an oil hole 30 for supplying the chain tensioner 1 with oil delivered from an oil pump (not shown) of the engine. The oil hole 30 is a round hole with a circular cross-sectional shape. The oil hole 30 opens to the outer surface 12 of the engine cover 9 .

The cylinder 10 is provided with an oil supply passage 31 that introduces the oil supplied from the oil hole 30 into the cylinder main body 10A. The oil supply passage 31 includes an oil groove 32 formed in the surface of the cylinder 10 (here, the mating surface 15 of the cylinder flange portion 10B with the outer surface 12 of the engine cover 9), and the oil in the oil groove 32 through the cylinder body portion 10A. and an oil introduction hole 33 (see FIG. 11) formed so as to communicate from the oil groove 32 to the inside of the cylinder main body 10A so as to introduce the oil into the inside of the cylinder main body 10A.

As shown in FIG. 12, the oil groove 32 has a branch portion 35, an upward flow path 36 and a downward flow path 37. The branch portion 35 is arranged axially facing the opening of the oil hole 30 in the outer surface 12 of the engine cover 9 (see FIG. 13) so as to directly receive the oil from the oil hole 30 . A buffer chamber 43 is formed in the branch portion 35 . The buffer chamber 43 is a concave portion that is recessed in a columnar shape from the mating surface 15 of the cylinder flange portion 10B with the outer surface 12 of the engine cover 9 (see FIG. 13). As shown in FIG. 12 , both the vertical height dimension and the horizontal width dimension of the buffer chamber 43 are larger than the inner diameter of the oil hole 30 . Further, as shown in FIG. 13 , the cross-sectional area along the horizontal direction of the buffer chamber 43 is larger than the flow path area of the downward flow path 37 .

As shown in FIG. 12, the upward flow path 36 is formed to extend upward in an arc shape from the branch portion 35 along the outer circumference of the cylinder main body portion 10A. The upward channel 36 is a square groove with a square cross-sectional shape. The upward flow path 36 is formed to have a flow area larger than the cross-sectional area of the oil hole 30 .

As shown in FIG. 11, the upward flow path 36 is connected to an air bleeding passage 39 above the cylinder body 10A and communicates with the chain housing chamber 13 inside the engine cover 9 via the air bleeding passage 39. there is The air vent passage 39 is a minute gap formed between the inner periphery of the tensioner mounting hole 11 and the outer periphery of the cylinder body portion 10A. As shown in FIG. 14, the air vent passage 39 is formed by a D-cut portion 44 extending in the axial direction along the outer periphery of the upper portion of the cylinder body portion 10A. It can be formed by providing a portion of a shape obtained by removing the outer periphery of the

As shown in FIG. 12, the downward flow path 37 is formed to extend downward in an arc shape from the branch portion 35 along the outer circumference of the cylinder main body portion 10A. The downward channel 37 is a square groove with a square cross-sectional shape. The downward flow path 37 is formed to have a flow area larger than the cross-sectional area of the oil hole 30 . The downward flow path 37 is connected to the oil inlet 33 a of the oil introduction hole 33 .

As shown in FIG. 11, the oil introduction hole 33 includes a vertical hole portion 45 radially penetrating through the lower portion of the cylinder flange portion 10B and a vertical hole portion 45 extending from the mating surface 15 of the cylinder flange portion 10B. and a horizontal hole portion 46 formed extending in the axial direction so as to reach . A plug member 47 closes the end portion of the vertical hole portion 45 on the outer peripheral side of the cylinder flange portion 10B. The plug member 47 is a male screw member in the figure. An oil inlet 33a of the oil introduction hole 33 is an opening portion of the horizontal hole portion 46 of the oil introduction hole 33 on the mating surface 15 side. As shown in FIG. 12, the oil inlet 33a is located below the opening position of the oil hole 30. As shown in FIG.

An operation example of this chain tensioner 1 will be described. As in the first embodiment, when the engine stops, the oil pump of the engine also stops. After that, when the engine is restarted, only air first flows into the oil groove 32 from the oil hole 30 of the engine cover 9 . At this time, the air passes through the branch portion 35 of the oil groove 32 , the upward flow path 36 and the air release passage 39 in order and is discharged to the chain housing chamber 13 . Subsequently, oil begins to flow into the oil groove 32 from the oil hole 30 of the engine cover 9 . At this time, air may be dispersedly contained in the oil in the form of air bubbles, but the air bubbles contained in the oil and the oil are separated vertically by the buoyant force acting on the air bubbles at the branch portion 35, and the air bubbles flow upward. 36 and the oil enters the downward flow path 37 . Air bubbles that have flowed into the upward flow path 36 are discharged to the chain housing chamber 13 via the air vent passage 39 . The oil that has flowed into the downward flow path 37 flows through the oil introduction hole 33 into the cylinder main body 10A.

In this chain tensioner 1, as shown in FIG. 12, an oil groove 32 for receiving oil from an oil hole 30 is formed on the surface of the cylinder 10. The oil groove 32 is formed with an upward flow path 36 for bleeding air and a downward flow path 36. The oil inlet 33a of the oil introduction hole 33 positioned below the oil hole 30 is connected to the downward flow path 37 branching downward from the branch part 35. Therefore, even if the oil received in the oil groove 32 from the oil hole 30 contains air in the form of air bubbles, the buoyancy acting on the air bubbles causes the oil inlet of the oil introduction hole 33 connected to the downward flow path 37 to move. It is difficult for the air to reach 33a, and the air can be effectively discharged through the upward flow path 36 for removing air. Therefore, it is possible to effectively prevent air from entering the cylinder 10 when the engine is started.

Also, in this chain tensioner 1, the downward flow path 37 shown in FIG. In the passage 37, the influence of the buoyancy of the air bubbles on the viscosity of the oil increases. Therefore, it is possible to effectively prevent air bubbles contained in the oil from reaching the oil inlet 33 a of the oil introduction hole 33 through the downward flow path 37 .

Further, in this chain tensioner 1, as shown in FIG. 13, the buffer chamber 43 formed in the branch portion 35 has a larger cross-sectional area than the flow passage area of the downward flow passage 37. Therefore, in the buffer chamber 43, The effect of the buoyancy of air bubbles on the viscosity of oil increases. Therefore, the air bubbles contained in the oil and the oil are easily separated vertically at the branch portion 35, and the air bubbles contained in the oil can be efficiently introduced into the upward flow path 36 for air bleeding at the branch portion 35. can.

FIG. 15 shows the chain tensioner 1 of the fourth embodiment. The fourth embodiment differs from the third embodiment only in the internal structure of the cylinder main body portion 10A, and the rest of the structure is the same. Also, the internal structure of the cylinder body portion 10A is the same as that of the second embodiment. Therefore, the same reference numerals are given to the parts corresponding to the second embodiment and the third embodiment, and the description thereof is omitted.

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

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

1 Chain tensioner 9 Engine cover 10 Cylinder

10A Cylinder body

10B Cylinder flange 11 Tensioner mounting hole 12 Outer surface 15 Mating surface 16 Fitting surface 17 Plunger 18 Return spring 19 Hydraulic damper mechanism 30 Oil hole 31 Oil supply passage 32 Oil groove 33 Oil introduction Hole 33a Oil inlet 34 Pre-branch flow path 35 Branch portion 36 Upward flow path 37 Downward flow path 43 Buffer chamber

Claims

A tensioner mounting hole (11) formed in the engine cover (9) with one end in the axial direction as a closed end and the other end in the axial direction as an open end, with the open end facing the inside of the engine cover (9). and a cylinder flange (10B) formed integrally with the cylinder body (10A) and fixed in surface contact with the outer surface (12) of the engine cover (9). a cylinder (10) having
a plunger (17) axially slidably inserted into the cylinder body (10A);
a return spring (18) that biases the plunger (17) in a direction of protruding from the cylinder main body (10A);
an oil supply passage (31) provided in the cylinder (10) so as to introduce oil into the cylinder main body (10A) from an oil hole (30) opened in the engine cover (9);
A chain tensioner comprising a hydraulic damper mechanism (19) that generates a damping force by viscous resistance of oil when the plunger (17) moves in the direction of being pushed into the cylinder main body (10A),
The oil supply passage (31) includes an oil groove (32) formed in the surface of the cylinder (10) facing the oil hole (30) so as to receive oil from the oil hole (30); An oil introduction hole (33) formed in communication with the inside of the cylinder main body (10A) from the oil groove (32) so as to introduce the oil in the groove (32) into the inside of the cylinder main body (10A). ) and
The oil introduction hole (33) is provided so as to have an oil inlet (33a) at a position below the oil hole (30),
The oil groove (32) branches the oil received from the oil hole (30) into an upward flow path (36) for air bleeding and a downward flow path (37) connected to the oil inlet (33a). Chain tensioner, characterized in that it has a fork (35) that flows in a straight line.
The chain tensioner according to claim 1, wherein the downward flow path (37) is formed to have a flow area larger than the cross-sectional area of the oil hole (30).
The oil groove (32) has a pre-branch flow path (34) that receives oil from the oil hole (30) and flows it to the branch portion (35),
The chain tensioner according to claim 1 or 2, wherein the pre-branch flow path (34) has a flow area larger than the cross-sectional area of the oil hole (30).
The chain tensioner according to claim 3, wherein the pre-branch flow path (34) is formed only by a horizontal direction or an upward flow path with respect to the horizontal direction.
5. The pre-branching flow path (34) according to claim 3 or 4, wherein the pre-branching flow path (34) is formed in a tapered shape such that the flow path area gradually increases from the position of the oil hole (30) toward the branching portion (35). chain tensioner.
The branch portion (35) is arranged to face the oil hole (30) so as to receive oil directly from the oil hole (30),
3. The buffer chamber (43) according to claim 1 or 2, wherein the branch portion (35) is formed with a buffer chamber (43) having a horizontal cross-sectional area larger than the flow area of the downward flow path (37). chain tensioner.
7. The surface of the cylinder (10) according to any one of claims 1 to 6, wherein the surface (16) of the outer circumference of the cylinder main body (10A) is a fitting surface (16) with the inner circumference of the tensioner mounting hole (11). chain tensioner.
The chain according to any one of claims 1 to 6, wherein the surface of the cylinder (10) is a mating surface (15) of the cylinder flange (10B) with an outer surface (12) of the engine cover (9). tensioner.