JP7262256B2 - chain tensioner - Google Patents

Description

The present invention relates to a chain tensioner used for maintaining tension on a chain.

Examples of chain transmission devices used in automobile engines include 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, and those that transmit the rotation of the crankshaft. There are those that transmit to the balancer shaft, and those that 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.

A chain tensioner generally generates a hydraulic damper using oil supplied from an engine to keep chain tension constant. However, since the oil supply is stopped when the engine is stopped, it may not be possible to generate a predetermined hydraulic damper until the pressure chamber inside the chain tensioner is filled with oil after the engine is started. In such a case, there is a problem that the chain tensioner is largely pushed in, causing the chain to flutter and generate abnormal noise. Therefore, many chain tensioners have a mechanism called a no-back mechanism to prevent the plunger from being pushed in beyond a certain amount.

In addition, by circulating the oil inside the chain tensioner, it is possible to suppress the outflow of oil to the outside of the chain tensioner, and by storing the oil inside the chain tensioner, it is possible to generate a hydraulic damper immediately after the engine starts. There is also a chain tensioner that does this (for example, see Patent Documents 1 and 2).

For example, the chain tensioner 50 shown in FIG. 6 includes a cylindrical cylinder 9 with one end open and the other end closed, and a cylindrical plunger 10 axially slidably supported on the inner periphery of the cylinder 9. , a return spring 33 that biases the plunger 10 in the direction of protruding from the cylinder 9 toward one end, a reservoir chamber 27 formed inside the plunger 10, and a reservoir chamber 27 formed inside the cylinder 9 at the other end of the plunger 10. A pressure chamber 18 whose volume changes as the plunger 10 moves in the axial direction, and a check valve 20 provided at the insertion end of the plunger 10 into the cylinder 9 and allowing oil to flow only from the reservoir chamber 27 to the pressure chamber 18. and have.

The cylinder 9 has an oil supply passage 31 for introducing oil supplied by an engine oil pump or the like to the inside. It opens into the supply space 28 . A leak gap 19 is formed between the outer circumference of the plunger 10 and the inner circumference of the cylinder 9 . The leak gap 19 is a minute gap, and extends from the pressure chamber 18 through the oil supply space 28 to the opening at one end of the cylinder 9 . Further, the leak gap 19 and the oil supply space 28 are communicated with the reservoir chamber 27 through a communication passage 30 . In addition, a return spring 33 is provided to apply a thrust force to the plunger 10 so that the plunger 10 follows the flapping of the chain.

When the tension of the chain increases during engine operation, the tension of the chain causes the plunger 10 to move in the direction of being pushed toward the other end of the cylinder 9 (hereinafter referred to as the "pushing direction"), absorbing the tension of the chain. do. At this time, the check valve 20 is closed due to the pressure increase in the pressure chamber 18 side, and the oil flows out from the pressure chamber 18 to the oil supply space 28 side through the leak gap 19 . A damping force is generated by the viscous resistance of the oil passing through the leak gap 19 to prevent the chain from fluttering. At this time, part of the oil flows out of the chain tensioner 50 through the leak gap 19 on the one end side of the oil supply space 28 and returns to the engine side. However, since the leak gap 19 is a minute gap and the resistance of the flow path is large, most of the oil is returned from the oil supply space 28 to the reservoir chamber 27 through the communication passage 30 .

On the other hand, when the tension of the chain decreases during engine operation, the plunger 10 moves in the direction in which the plunger 10 protrudes from the cylinder 9 toward one end (hereinafter referred to as the "protrusion direction") due to the biasing force of the return spring 33, and the chain loosens. absorb. At this time, the check valve 20 opens and oil flows from the reservoir chamber 27 into the pressure chamber 18, so that the plunger 10 moves rapidly in the protruding direction.

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

In the conventional chain tensioner 50 shown in FIG. 6, the hydraulic damping force is generated by the oil stored inside the tensioner until the oil is supplied to the tensioner immediately after the engine is started. For this reason, the larger the spatial volume inside the plunger 10 is, the more the stored oil is increased, which is advantageous. However, in order to increase the spatial volume inside the plunger 10, it is necessary to increase the size (length and diameter) of the plunger 10, which leads to the problem of increasing the size and weight of the tensioner.

Also, as means for compensating for insufficient thrust of the plunger 10, a method of enhancing the elastic force of the return spring 33 is known. However, if the size of the tensioner is the same as that of the conventional tensioner, the wire diameter and the number of turns of the return spring 33 that can be incorporated therein are limited due to space limitations. Therefore, there is a limit to increasing the thrust applied to the plunger 10 by strengthening the return spring 33 . As a result, if the thrust of the spring is insufficient for the plunger's mass and operating conditions (acceleration), the plunger may not follow the chain, causing the chain to rattle or make noise.

SUMMARY OF THE INVENTION Accordingly, the problem to be solved by the present invention is to provide a chain tensioner that generates an appropriate thrust in response to changes in tension and fluttering of the chain.

In order to solve the above-mentioned problems, the present invention provides a cylindrical cylinder with one end open and the other end closed, and a cylindrical cylinder supported axially slidably on the inner periphery of the cylinder and having an open end inserted into the cylinder. and a cylindrical plunger whose projecting end from the cylinder is closed, a return spring that biases the plunger in a direction projecting from one end of the cylinder, and a volume that changes as the plunger moves in the axial direction. a pressure chamber formed in the cylinder; a check valve that allows oil to flow only from the inside of the plunger to the pressure chamber; an oil supply passage that introduces oil from the outside to the inside of the cylinder; and the return spring. and an auxiliary spring that has an elastic force smaller than that of the chain tensioner and biases the plunger in the direction of protruding from one end of the cylinder.

Here, the return spring and the auxiliary spring may be coil springs, and the auxiliary spring may have a larger coil diameter than the return spring and may be arranged coaxially with the return spring. .

Further, the return spring and the auxiliary spring may adopt a configuration in which coil spring winding directions are opposite to each other.

In each of these aspects, the check valve includes a valve seat attached to the end face facing the other end of the plunger, a valve hole formed in the valve seat, and a valve body that opens and closes the valve hole. In addition, the return spring may press the valve seat toward the end surface.

Further, the return spring may have a tapered shape with a smaller diameter on the end face side.

In each of these aspects, the total thrust (unit: N) of the return spring and the auxiliary spring within the stroke range of the plunger is 0.8 times or more the mass (unit: g) of the plunger. A set configuration can be adopted.

INDUSTRIAL APPLICABILITY The present invention can be a chain tensioner that generates an appropriate thrust following tension changes and fluttering of the chain.

1 is an overall view showing a chain transmission incorporating a chain tensioner according to an embodiment of the invention; FIG. (a) is a right side view of the chain tensioner of FIG. 1, and (b) is its rear view. 1 is a longitudinal sectional view showing a chain tensioner according to an embodiment of the invention; FIG. Enlarged view of main part of Fig. 3 FIG. 2 is a graph diagram schematically showing the characteristics of the chain tensioner of the embodiment of the invention; Longitudinal sectional view showing a conventional chain tensioner

FIG. 1 shows a chain transmission incorporating a chain tensioner 1 according to an embodiment of the invention. In this chain transmission, a sprocket 3 fixed to a crankshaft 2 of an engine and a sprocket 5 fixed to two camshafts 4 are connected via a chain 6, and the chain 6 connects to the crankshaft. 2 is transmitted to the camshaft 4, and the rotation of the camshaft 4 opens and closes the valve of the combustion chamber.

When the engine is running, the direction of rotation of the crankshaft 2 is constant (clockwise rotation in FIG. 1), and at this time, the chain 6 is drawn into the sprocket 3 as the crankshaft 2 rotates (right rotation in FIG. 1). The part on the right side) is the tight side, and the part on the side sent out from the sprocket 3 (the left side in FIG. 1) 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 FIGS. 2 and 3, the chain tensioner 1 comprises a cylindrical cylinder 9 with one end open and the other end closed, and a plunger 10 axially slidably supported on the inner periphery of the cylinder 9 . and A projecting end 17 of the plunger 10 projecting from one end of the cylinder 9 presses the chain guide 8 .

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

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

A pressure chamber 18 is formed at the other end of the cylinder 9, the volume of which changes as the plunger 10 moves in the axial direction. The volume of the pressure chamber 18 expands when the plunger 10 moves in the projecting direction, and contracts when the plunger 10 moves in the pushing direction.

At the insertion end of the plunger 10 into the cylinder 9, there is a check valve that allows oil to flow only from the inside of the plunger 10 to the pressure chamber 18 side and restricts the oil flow from the pressure chamber 18 to the inside of the plunger 10. 20 are provided. The check valve 20 includes a valve seat 21 provided at the insertion end of the plunger 10 into the cylinder 9, a valve hole 21a provided in the valve seat 21, and a spherical valve opening and closing the valve hole 21a from the pressure chamber 18 side. and a retainer 26 for restricting the movement range of the check ball 25 . The retainer 26 has a holding portion 26 a that prevents the check ball 25 from being detached toward the pressure chamber 18 , and a bottom portion 26 b that supports the holding portion 26 a on the valve seat 21 . A radial holding portion 26a rising from the bottom portion 26b toward the pressure chamber 18 is fitted to a cylindrical projection around the valve hole 21a of the valve seat 21. As shown in FIG.

Here, the inside of the plunger 10 is a reservoir chamber 27 having a larger diameter than the diameter of the valve hole 21 a of the check valve 20 . A valve seat 21 of the check valve 20 is attached to the other end of the reservoir chamber 27 . The valve seat 21 has a cylindrical or disc shape, and the valve hole 21a is formed so as to extend through the axial center of the valve seat 21 from one end side to the other end side. When the valve body 25 is separated from the valve hole 21a toward the other end, the pressure chamber 18 and the reservoir chamber 27 communicate with each other through the valve hole 21a.

As shown in FIG. 3 , a leak gap 19 is provided between the outer circumference 15 of the plunger 10 and the inner circumference 14 of the cylinder 9 to allow oil to leak from inside the pressure chamber 18 to outside the pressure chamber 18 . The size of the leak gap 19 can be set, for example, within a range of 0.005 to 0.100 mm as the difference in radius between the outer circumference 15 of the plunger 10 and the inner circumference 14 of the cylinder 9 .

An oil supply space 28 communicating with the leak gap 19 is formed between the outer circumference 15 of the plunger 10 and the inner circumference 14 of the cylinder 9 . The oil supply space 28 is annularly formed between the recess 16 formed on the entire outer periphery of the plunger 10 and the inner periphery 14 of the cylinder 9 . The recess 16 for forming the oil supply space 28 is provided in a range that communicates with the oil supply passage 31 even when the plunger 10 moves in the protruding direction and the pushing direction. There is a leak gap 19 on each side.

As shown in FIGS. 3 and 4, the pressure chamber 18 incorporates a return spring 33 . The other end 33b of the return spring 33 is supported by the bottom portion 13 of the cylinder 9, and the one end 33a presses the plunger 10, thereby urging the plunger 10 in the protruding direction.

Further, the pressure chamber 18 incorporates an auxiliary spring 34 having an elastic force smaller than that of the return spring 33 . The other end 34b of the auxiliary spring 34 is also supported by the bottom portion 13 of the cylinder 9, and the one end 34a presses the plunger 10, thereby urging the plunger 10 in the protruding direction.

As shown in FIGS. 3 and 4, each of the return spring 33 and the auxiliary spring 34 is a coil spring formed by spirally winding a wire. The outer diameter of the auxiliary spring 34 is larger than the outer diameter of the return spring 33 , and the auxiliary spring 34 is arranged on the outer diameter side of the return spring 33 . The auxiliary spring 34 and the return spring 33 are coaxially arranged so that the axis of the auxiliary spring 34 coincides with the axis of the return spring 33 .

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

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

Further, as shown in FIG. 3, the cylinder 9 is provided with an oil supply passage 31 for introducing oil from the outside to the inside of the cylinder 9 . The oil supply passage 31 is a through hole radially penetrating the cylinder 9 . The inlet of the oil supply passage 31 (see FIG. 2(b)) is connected to an oil supply port on the wall surface side of the engine. The outlet of the oil supply passage 31 is open to the inner cylindrical surface of the cylinder 9 and faces the oil supply space 28 . Through this oil supply passage 31 , oil supplied from the oil pump of the engine is introduced from the outside to the inside of the cylinder 9 .

An example of operation of this chain tensioner 1 will be described. During normal operation, when the tension of the chain 6 becomes greater than the thrust of the return spring 33 that urges the plunger 10, the tension of the chain 6 causes the plunger 10 to move in the pushing direction into the cylinder 9, and the tension of the chain 6 is increased. absorb. Then, the valve seat 21 moves to the pressure chamber 18 side together with the plunger 10 . Since the volume of the pressure chamber 18 is reduced as the plunger 10 and the valve seat 21 move, the pressure in the pressure chamber 18 becomes higher than the pressure in the reservoir chamber 27 and the check valve 20 is closed to seal the pressure chamber 18 . At this time, most of the oil that flows out from the pressure chamber 18 through the leak gap 19 returns to the reservoir chamber 27 through the oil supply space 28 and the communication passage 30 . A damping force is generated by the viscous resistance of the oil flowing through the leak gap 19 to prevent the chain 6 from fluttering.

Further, when the tension of the chain 6 becomes small during engine operation, the urging forces of the return spring 33 and the auxiliary spring 34 move the plunger 10 in the protruding direction to absorb the slackness of the chain 6 . At this time, since the volume of the pressure chamber 18 expands according to the movement of the plunger 10, the pressure in the pressure chamber 18 becomes lower than the pressure in the reservoir chamber 27, and the check valve 20 opens. Since oil flows from the reservoir chamber 27 into the pressure chamber 18 through the valve hole 21a of the check valve 20, the plunger 10 moves quickly. At this time, oil is introduced from the outside of the cylinder 9 into the reservoir chamber 27 through the oil supply passage 31 , the oil supply space 28 and the communication passage 30 by the pressure of the oil pump. Therefore, the pressure in the reservoir chamber 27 is less likely to drop, and the slackness of the chain 6 can be easily followed.

Further, in this chain tensioner 1, since the reservoir chamber 27 having a diameter larger than the diameter of the valve hole 21a of the check valve 20 is formed inside the plunger 10, the amount of oil stored inside the plunger 10 can be increased. can be secured. Therefore, even when the engine does not supply oil to the chain tensioner 1 immediately after the engine is started, the oil stored in the reservoir chamber 27 can be used to generate a damping force.

Here, the return spring 33 is required to have sufficient thrust (elastic force) to press the plunger 10 in the protruding direction in order to absorb the slackness of the chain 6 . However, if the return spring 33 that generates a large thrust force is used, the diameter (outer diameter) and length (overall length) of the return spring 33 will increase, so the space inside the pressure chamber 18 must also be increased. Therefore, there is a problem that the size of the entire tensioner is increased. Therefore, in the present invention, two coil springs for applying thrust to the plunger 10 are employed in order to obtain the necessary thrust of the plunger 10 without increasing the overall size of the tensioner. That is, in addition to the return spring 33, an auxiliary spring 34 having a coil outer diameter different from that of the return spring 33 is arranged as a coil spring that applies thrust to the plunger 10. As shown in FIG.

If thrust is applied to the plunger 10 only by the return spring 33 as in the conventional art, the thrust required to eliminate the slack in the chain 6 can be obtained depending on the stroke position of the plunger 10 (position used during operation). It may not be possible. However, by arranging the auxiliary spring 34 in addition to the return spring 33, it is possible to secure the necessary thrust force over the entire stroke of the plunger 10. FIG.

Here, in this embodiment, as shown in FIG. 4, the valve seat 21 of the check valve 20 is not press-fitted into the plunger 10, and the valve seat 21 has an end surface facing the other end side of the plunger 10. 10a. One end 34a of the auxiliary spring 34 is in direct contact with the end surface 10b of the plunger 10 near the outer diameter, and presses the plunger 10 in the protruding direction. Further, the return spring 33 contacts the hem 26b of the retainer 26 which contacts the end surface 21b of the valve seat 21, and presses the plunger 10 in the protruding direction via the valve seat 21. As shown in FIG.

Therefore, if the thrust applied to the plunger 10 by the elastic force of the auxiliary spring 34 is too strong, the valve seat 21 of the check valve 20 and the plunger 10 may separate. If the check valve 20 separates from the plunger 10 when the plunger 10 protrudes, the hydraulic damper may not operate normally. Therefore, in the present invention, when the auxiliary spring 34 is added, the thrust to the plunger 10 by the auxiliary spring 34 is set so as not to exceed the thrust by the return spring 33 in the stroke range of the plunger 10 when the chain tensioner 1 is in use. are doing. This prevents the valve seat 21 from separating from the plunger 10 .

Further, the total thrust (unit: N/Newton) of the return spring 33 and the auxiliary spring 34 within the stroke range of the plunger 10 is 0.8 times or more the mass of the plunger 10 (unit: g/gram). , the follow-up failure of the plunger 10 occurs under normal operating conditions (for example, a 4-cylinder engine, a rotational speed of the crankshaft 2 of the engine of 8000 rpm, and an acceleration of 86 G at a total amplitude of 0.6 mm of the plunger 10). stable damper characteristics can be provided. For example, when the plunger 10 has a mass of 30 g, the total thrust applied to the plunger 10 is preferably 30×0.8=24 N or more over the entire stroke of the plunger 10 .

FIG. 5 is a graph showing the relationship between the stroke amount of the plunger 10 and the thrust applied to the plunger 10. As shown in FIG. Reference character A in the drawing indicates the thrust force exerted by the return spring 33 on the plunger 10 . Symbol B indicates the thrust of the auxiliary spring 34 against the plunger 10 . Reference C indicates the thrust force that must be applied to the plunger 10 . The thrust B of the auxiliary spring 34 is smaller than the thrust A of the return spring 33 over the entire stroke range of the plunger 10 . The total thrust A+B of the return spring 33 and the auxiliary spring 34 is set to be equal to or greater than the required thrust C of the plunger 10 over the entire stroke range of the plunger 10 .

Further, as shown in FIG. 4, the return spring 33 and the auxiliary spring 34 have spiral winding directions opposite to each other. That is, when the spiral winding direction of the return spring 33 is one direction around the axis from one end 33a to the other end 33b, the spiral winding direction of the auxiliary spring 34 is axial from one end 34a to the other end 34b. Around the other direction. In this manner, the coil springs of the return spring 33 and the auxiliary spring 34 are wound in opposite directions, thereby preventing the springs from interfering with each other. In addition, even when the spring bends significantly when the spring is compressed, contact between the two can be prevented and a stable thrust can be obtained.

In this embodiment, the auxiliary spring 34 is a coil spring with a constant outer diameter over the entire length, while the return spring 33 has one end 33a facing the end surface 10a side and the other end facing the bottom portion 13 side. It is composed of a tapered coil spring having a smaller diameter than 33b. Further, the skirt portion 26b of the retainer 26 is positioned around the valve hole 21a of the valve seat 21 and is located relatively close to the inner diameter. Therefore, the small-diameter end 33 a of the return spring 33 can easily press the bottom portion 26 b of the retainer 26 , and the retainer 26 can be easily held by the valve seat 21 . One end 33a of the return spring 33 on the small diameter side is fitted to the outer periphery of the radial holding portion 26a rising from the hem portion 26b of the retainer 26 toward the pressure chamber 18, thereby fixing the one end 33a to the retainer 26 and the valve seat 21. Also, the effect of stabilizing the expansion and contraction of the return spring 33 can be expected.

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

1 Chain Tensioner 9 Cylinder 10 Plunger 10a End Face 18 Pressure Chamber 20 Check Valve 21 Valve Seat 21a Valve Hole 25 Valve Body (Check Ball)
31 Oil supply passage 33 Return spring 34 Auxiliary spring

Claims (5)

a cylindrical cylinder (9) with one end open and the other end closed;
A cylindrical plunger (10) which is axially slidably supported on the inner periphery of the cylinder (9) and has an open end for insertion into the cylinder (9) and a closed end for projecting from the cylinder (9). and a return spring (33) that biases the plunger (10) in a direction of protruding from one end of the cylinder (9);
a pressure chamber (18) formed in the cylinder (9) so that the volume changes with the axial movement of the plunger (10);
a check valve (20) that only allows oil to flow from the interior of the plunger (10) to the pressure chamber (18);
an oil supply passage (31) for introducing oil from the outside to the inside of the cylinder (9);
An auxiliary spring (34) having an elastic force smaller than that of the return spring (33) and directly abutting the plunger (10) to urge the plunger (10) in a direction of protruding from one end of the cylinder (9). and,
with
The check valve (20) includes a valve seat (21) attached to an end face (10a) facing the other end of the plunger (10), and a valve hole (21a) formed in the valve seat (21). , and a valve body (25) for opening and closing the valve hole (21a),
The return spring (33) is a chain tensioner that presses the valve seat (21) toward the end surface (10a) . The return spring (33) and the auxiliary spring (34) are coil springs, and the auxiliary spring (34) has a larger coil diameter than the return spring (33) and is coaxial with the return spring (33). 2. The chain tensioner of claim 1, wherein the chain tensioner is located at 3. The chain tensioner according to claim 2, wherein the return spring (33) and the auxiliary spring (34) have coil spring winding directions opposite to each other. The chain tensioner according to any one of claims 1 to 3, wherein the return spring (33) has a tapered shape with a smaller diameter on the side of the end face (10a). The total thrust (unit: N) of the return spring (33) and the auxiliary spring (34) within the stroke range of the plunger (10) is 0.0 of the mass (unit: g) of the plunger (10). The chain tensioner according to any one of claims 1 to 4 , which is set to a numerical value of 8 times or more.

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