JP2002333056A - Chain tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an axial length of a chain tensioner. SOLUTION: A female screw 4 is formed on an opening end part of a cylinder chamber 2 formed in a housing 1, and a plunger 5 having a male screw 6 to be engaged with the female screw 4 on its outer periphery, is built in the cylinder chamber 2. A rear end face of the plunger 5 is provided with a spring accommodation hole 7, and a spring 8 for outwardly pressing the plunger 5 is built in between a closed end of the spring accommodation hole 7 and a bottom of the cylinder chamber 2, whereby the axial length of the chain tensioner is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chain transmission, and more particularly to a chain tensioner for maintaining a constant chain tension of a camshaft driving chain transmission.

[0002]

2. Description of the Related Art A chain tensioner shown in FIG. 3 is conventionally known as a chain tensioner for maintaining a constant chain tension of a chain transmission for driving a camshaft. In this chain tensioner, a nut member 22 is fitted into an opening of a bottomed cylinder chamber 21 formed in a housing 20, and a female screw 23 formed on an inner periphery of the nut member 22 is formed.
Male screw 25 formed on the outer periphery of the screw rod 24
And a cap-shaped plunger 26 slidable along the inner periphery of the cylinder chamber 21 is fitted to the rear end of the screw rod 24, and the plunger 26 and the screw rod 24 are pressed by a spring 27. To provide outward protrusion.

An oil supply passage 29 is formed in the housing 20 and communicates with a pressure chamber 28 formed at the back of the plunger 26. The oil outlet side of the oil supply passage 29 reverses the flow of the hydraulic oil supplied into the pressure chamber 28. Check valve 30 for preventing
Is provided.

Here, the thread of the female screw 23 and the male screw 25 has a sawtooth shape in which the flank angle of the pressure side flank which receives the pushing force applied to the screw rod 24 is larger than the flank angle of the play side flank. The screw rod 2 is resiliently formed on the thread
4 is provided with a lead angle that moves in the axial direction while rotating.

[0005] The chain tensioner includes a spring 2
7 presses a chain guide 32 that is swingably supported about a shaft 31 by a screw rod 24 provided with an outward projecting property.
2, the slack side chain 3 of the cam shaft driving chain 33
3a is pressed to tension the chain 33.

When the slack side chain 33a vibrates due to the driving of the engine and a pushing force is applied to the screw rod 24 by the slack side chain 33a, the pushing force is applied to the hydraulic oil supplied into the pressure chamber 28 and When the pushing force is stronger than the elastic force of the spring 27, the operating oil in the pressure chamber 28 is transferred between the sliding surface of the plunger 26 and the cylinder chamber 21 and between the screw engaging portions of the female screw 23 and the male screw 25. The screw rod 24 and the plunger 26 are pushed out by the spring 27
It is made to retreat slowly to the position where it balances with the elasticity of.

When the slack side chain 33a becomes slack, the screw rod 2
4 and the plunger 26 are advanced and the slack side chain 3 is moved.
The slack of 3a is absorbed, and the tension of the slack side chain 33a is kept constant.

In the above chain tensioner, when the engine is stopped and the slack side chain 33a is tensioned due to the cam stop position and a pushing force acts on the screw rod 24, the pushing force is a static load.
The pushing force can be received at the screw engagement portion between the female screw 23 and the male screw 25, and the screw rod 25 and the plunger 26 can be prevented from retreating. For this reason, even if the engine is restarted and the slack side chain 33a is slackened, the slack amount is small and the screw rod 24 and the plunger 26 do not largely move outward, so that the air inside the pressure chamber 28 Has the feature that it can be prevented from entering.

[0009]

By the way, in the above-mentioned conventional chain tensioner, the spring 27 is provided at the back of the plunger 26, so that the screw rod 24 and the plunger 26 can be projected outward. If an attempt is made to use a spring having a long length for the purpose, a large space must be secured for accommodating the spring, and there is a disadvantage in that the overall length of the chain tensioner becomes long.

In addition, the vibration of the chain due to the fluctuation of the angular velocity and the fluctuation of the torque of the camshaft during one rotation of the crankshaft is absorbed by the axial movement by the rotation of the screw rod, and the slack side chain is released by the pressure of the hydraulic oil in the pressure chamber. Is maintained constant, the pressing force of the chain tensioner pressing the slack side chain is easily affected by the frictional resistance generated in the serrated screw portion. In order to avoid the influence, it is necessary to finish the female screw 23 of the nut member 22 and the male screw 25 of the screw rod 24 with high precision, and there is still a point to be improved in reducing the manufacturing cost.

It is an object of the present invention to provide an engine which
An object of the present invention is to reduce the axial length of a chain tensioner in which a plunger is prevented from being pushed by a pressure side flank of a serrated screw, and to reduce manufacturing costs.

[0012]

In order to solve the above-mentioned problems, according to the present invention, a female screw is provided on the inner periphery of an opening of a cylinder chamber formed in a housing, and the female screw is engaged with the female screw in the cylinder chamber. A plunger having a male screw on the outer periphery and a spring for pressing the plunger outward are incorporated. The housing is provided with an oil supply passage communicating with a pressure chamber formed at the back of the plunger. Buffering the pushing force applied to the plunger by the hydraulic oil supplied from the pressure chamber to the plunger and preventing the plunger from retreating by receiving a static load in the pushing direction applied to the plunger at the screw engagement portion between the female screw and the male screw. In the chain tensioner, the plunger is formed with an axial spring receiving hole which is opened at the rear end face. And is of the closed end of the spring housing holes employing the configuration as pressed by the spring.

As described above, by pressing the closed end of the axial spring receiving hole formed in the plunger with the spring, the axial length of the chain tensioner can be reduced as compared with the case where the rear end of the plunger is pressed with the spring. The size can be reduced.

In the chain tensioner according to the present invention, an axial thread clearance is formed in a thread engagement portion between the female screw and the male thread, and the screw clearance is set to be equal to or greater than the amplitude of the chain vibrating during operation of the engine. When the chain vibrates during operation, the plunger moves in the axial direction within the range of the axial screw clearance formed in the screw engaging part, so that the plunger smoothly moves without being affected by the frictional resistance of the screw engaging part. It can move in the axial direction and effectively absorb the vibration of the chain.

Further, by forming an axial screw clearance in the screw engaging portion, wear of the female screw in the screw engaging portion of the male screw can be suppressed, and the housing and the plunger can be made of an aluminum alloy. .

Since the housing and the plunger are made of an aluminum alloy, a manufacturing method by die casting can be adopted, so that finishing such as polishing is not required, and the manufacturing cost of the chain tensioner can be reduced. At the same time, the weight of the chain tensioner can be reduced.

Further, when an orifice restrictor for restricting the flow of hydraulic oil is provided in the oil supply passage, the check valve in the conventional chain tensioner can be omitted, so that the number of parts can be reduced and the cost can be further reduced. be able to.

In the chain tensioner according to the present invention, a compression coil spring is adopted as a spring, and a bent piece bent inward in the radial direction is provided at an end of the compression coil spring on the plunger pressing side. Compared to the case where the cut surface contacts the plunger,
The frictional resistance of the contact portion between the compression coil spring and the plunger can be reduced, and the plunger that moves in the axial direction while rotating can be smoothly moved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a first embodiment of a chain tensioner according to the present invention. As shown, a bottomed cylinder chamber 2 is formed in a housing 1, and a nut member 3 is press-fitted into a large-diameter hole 2 a provided at an open end of the cylinder chamber 2.

A female screw 4 formed on the inner periphery of the nut member 3
Is engaged with a male screw 6 formed on the outer periphery of the plunger 5.

The plunger 5 is slidable in the cylinder chamber 2, and the plunger 5 is formed with an axial spring receiving hole 7 opened at the rear end face. A spring 8 composed of a compression coil spring is incorporated between the closed end of the spring accommodating hole 7 and the bottom surface of the cylinder chamber 2, and the spring 8 gives the plunger 5 an outward protruding property.

As shown in FIG. 1 (II), a bent piece 8a facing inward in the radial direction is formed at the end of the spring 8 which presses the plunger 5, and the bent piece 8a is Line contact with closed end.

The housing 1 is provided with an oil supply passage 10 communicating with a pressure chamber 9 formed at the back of the plunger 5, and an orifice throttle 11 for restricting the flow of hydraulic oil is formed in the oil supply passage 10. .

The thread of the female screw 4 formed on the nut member 3 and the thread of the male screw 6 formed on the outer periphery of the plunger 5 are formed on the pressure flank which receives the pushing force when the plunger 5 is pushed in the axial direction. The flank angle of the flank 12 is larger than the flank angle of the play-side flank 13, and the flank angle is larger than
A lead angle at which the plunger 5 moves outward while rotating due to the elastic force of the spring 8 is provided on the serrated thread.

When the plunger 5 is pressed in the axial direction by a static load, the serrated thread receives the static load by the female screw 4 and the pressure-side flank 12 of the male screw 6, and the plunger 5 retreats. It is designed to prevent that.

An axial screw clearance δ is formed between the screw engagement portions of the female screw 4 and the male screw 6. Screw clearance δ
Is the slack side chain 33a shown in FIG.
Is greater than or equal to the amplitude of the slack side chain 33a when vibrates.

Generally, during operation of the engine, the slack side chain vibrates with an amplitude of about 0.2 mm. Therefore, the screw clearance δ is set to 0.2 mm or more.

If the screw clearance δ is made unnecessarily large, the displacement of the plunger 5 when the engine is restarted from the stop state in which the slack side chain is tightened and the slack side chain becomes slack increases, and the slackness becomes large. Side chain 33a
May vibrate and generate abnormal noise. In order to prevent such inconvenience, the screw clearance δ is set to 2 mm.
It is as follows. That is, the screw clearance δ is 0.2 to 2
mm.

The chain tensioner shown in the first embodiment has the above-mentioned structure. When the tension of the camshaft driving chain 33 shown in FIG. The chain guide 32 shown in FIG. 3 is pressed by the applied plunger 5, and the slack side chain 33 a of the chain 33 is tensioned by the chain guide 32.

When the engine is started in the use state of the chain tensioner as described above, the slack side chain 33a vibrates due to a change in the angular velocity during one rotation of the crankshaft or a fluctuation in the torque of the camshaft, and the tension changes. When the slack side chain 33a is slackened, the plunger 5 moves outward by the pressing of the spring 8, and absorbs the slackness of the slack side chain 33a.

On the other hand, when the slack side chain 33a is tightened, the plunger 5 is pushed by the slack side chain 33a. At this time, the hydraulic oil supplied into the pressure chamber 9 tries to flow back to the supply passage 10 side, but the oil supply passage 10
Is provided with an orifice restrictor 11, so that the flow is regulated. Therefore, the pushing force applied to the plunger 5 is buffered by the hydraulic oil in the pressure chamber 9.

[0032] Instead of the orifice throttle 11, a porous body may be provided in the oil supply passage 10 to regulate the flow of hydraulic oil.

As described above, when the slack side chain 33a vibrates during operation of the engine, the plunger 5
Axial clearance δ formed between the screw engaging portion of the male screw 6
, The plunger 5 moves smoothly in the axial direction without being affected by the frictional resistance of the screw engagement portion, and the vibration of the slack side chain 33a can be absorbed very effectively. it can.

Further, since the plunger 5 moves within the range of the screw clearance δ and absorbs the vibration of the slack side chain 33a, the wear of the screw engaging portion can be suppressed. For this reason, the housing 1 and the plunger 5 can be made of an aluminum alloy. In this case, since the housing 1 and the plunger 5 can be manufactured by die casting, the manufacturing cost can be reduced, and the weight of the chain tensioner can be reduced.

Here, the temperature rises with the operation of the engine, and the thermal expansion caused by the temperature rise increases the center-to-center distance between the sprockets on which the chain 33 shown in FIG. 3 is mounted, and the slack side chain 33a is strongly tensioned. Then, the plunger 5 is pressed by the slack side chain 33a. When the pressing force is stronger than the elasticity of the spring 8, the plunger 5 retreats while rotating, and the hydraulic oil in the pressure chamber 9 flows between the sliding surface of the plunger 5 and the cylinder chamber 2 and between the screw engagement of the female screw 4 and the male screw 6. And the plunger 5 stops at a position where the elasticity of the spring 8 and the pressing force are balanced.

When the chain 33 is elongated and the slack side chain 33a is slackened, and the slack amount is larger than the axial clearance δ of the screw engaging portion, the plunger 5 advances while rotating due to the elastic force of the spring 8. Loose chain 33
Absorb the slack of a.

As described above, when the plunger 5 moves back and forth while rotating, the spring 8 pressing the plunger 5
Is configured such that the coil cut surface is in contact with the plunger 5, the contact resistance between the plunger 5 and the spring 8 is large, and the plunger 5 cannot be rotated smoothly.

However, the contact between the plunger 5 and the spring 8 is caused by the bent piece 8a provided at the end of the spring 8.
Is in line contact with the closed end of the spring housing hole 7, so that the frictional resistance of the contact portion between the plunger 5 and the spring 8 is extremely small, and as a result, the plunger 5 can be rotated very smoothly.

When the engine is stopped, the slack side chain 33a may be tensioned due to the stop position of the cam provided on the cam shaft. At this time, since the plunger 5 is pushed by the slack side chain 33a, the pressure side flanks 12 of the female screw 4 and the male screw 6 are engaged with each other. here,
Since the pressing force for pushing the plunger 5 is a static load without vibration, the pressing force is received by the pressure side flanks 12 engaged with each other, and the plunger 5 is not pushed.

For this reason, even if the engine is restarted and the slack side chain 33a becomes slack, the slack amount is extremely small and the plunger 5 projects little, so that air enters the pressure chamber 9. There is no inconvenience that the slack side chain 33a vibrates to generate abnormal noise.

As shown in FIG. 1 (I), a spring housing hole 7 opening at the rear end surface of the plunger 5 is formed, and the closed end of the spring housing hole 7 is pressed by a spring 8 to thereby move the rear end of the plunger. Compared with a conventional chain tensioner in which the spring is pressed by a spring, the length of the chain tensioner in the axial direction can be reduced.

FIG. 2 shows a second embodiment of the chain tensioner according to the present invention. The chain tensioner shown in this embodiment and the chain tensioner shown in the first embodiment are different from each other in the means for regulating the flow of hydraulic oil in the pressure chamber 9 and the configuration of the contact portion between the plunger 5 and the spring 8. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the second embodiment, a check valve 14 is provided on the oil outlet side of the oil supply passage 10 to prevent the hydraulic oil in the pressure chamber 9 from flowing back to the oil supply passage 10 side.

A spring seat 15 is provided between the closed end of the spring receiving hole 7 and the end of the spring 8 so that the spherical surface 15a formed on the spring seat 15 is brought into point contact with the closed end of the spring receiving hole 7. I have to.

As described above, by providing the check valve 14 on the oil outlet side of the oil supply passage 10, the plunger 5
It is possible to correspond to the engine specification in which the input load to the engine is large.

A spring seat 15 is provided between the plunger 5 and the end of the spring 8, and the spherical surface 15 a of the spring seat 15 is brought into point contact with the closed end of the spring accommodating hole 7. Frictional resistance between each other can be reduced,
The plunger 5 can be rotated very smoothly. In the embodiment, the female screw 4 is provided on the inner circumference of the opening of the cylinder chamber 2 by attaching the nut member 3. However, the female screw 4 may be formed directly on the inner circumference of the opening of the cylinder chamber 2.

[0047]

As described above, according to the present invention, the plunger is formed with the spring receiving hole which is opened at the rear end face, and the closed end of the spring receiving hole is pressed by the spring. The length in the direction can be reduced in size.

Also, between the female and male screw engagement portions,
By forming an axial thread clearance that is greater than the amplitude of the chain that vibrates during engine operation, the vibration of the chain during engine operation can be absorbed very effectively, and wear of the screw engagement part can be suppressed. it can. For this reason, the housing and the plunger can be made of an aluminum alloy, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 (I) is a longitudinal sectional front view showing a first embodiment of a chain tensioner according to the present invention, and FIG. 1 (II) is a sectional view taken along the line II in FIG. 1 (I).

FIG. 2 is a longitudinal sectional front view showing a second embodiment of the chain tensioner according to the present invention;

FIG. 3 is a longitudinal sectional front view showing a conventional chain tensioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 2 Cylinder chamber 4 Female screw 5 Plunger 6 Male screw 7 Spring storing hole 8 Spring 8a Bending piece 9 Pressure chamber 10 Oil supply passage 11 Orifice throttle δ Screw clearance

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoyoshi Izutsu, 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture (72) Inventor Katsuhisa 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture F Term (reference) 3J049 AA08 BB13 BB17 BB23 BB35 BC07

Claims (7)

[Claims] An internal thread is provided on an inner periphery of an opening of a cylinder chamber formed in a housing, and a plunger having an external thread on the outer periphery for engaging with the internal thread is provided in the cylinder chamber, and the plunger is directed outward. The housing is provided with an oil supply passage communicating with a pressure chamber formed at the back of the plunger, and a pressing force applied to the plunger by hydraulic oil supplied from the oil supply passage into the pressure chamber is incorporated in the housing. In a chain tensioner configured to buffer and prevent a retreat of a plunger by receiving a static load in a pushing direction applied to the plunger in a screw engagement portion of the female screw and the male screw, an axial direction opening at a rear end surface of the plunger. And a closed end of the spring storage hole is pressed by the spring. A chain tensioner characterized by: 2. An axial thread clearance is formed in a thread engagement portion between the female screw and the male screw, and the thread clearance is set to be equal to or greater than the amplitude of a chain vibrating during engine operation.
The chain tensioner described in. 3. The chain tensioner according to claim 1, wherein a throttle restricting a flow of hydraulic oil is provided in the oil supply passage. 4. The method according to claim 3, wherein said throttle comprises an orifice.
The chain tensioner described in. 5. The chain according to claim 1, wherein the spring is formed of a compression coil spring, and a bent piece that is bent inward in the radial direction is provided at an end of the compression coil spring on the plunger pressing side. Tensioner. 6. The chain tensioner according to claim 1, wherein the housing is made of an aluminum alloy. 7. The chain tensioner according to claim 1, wherein the plunger is made of an aluminum alloy.