JPH109351A - Chain tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chain tensioner which can prevent a chain from slackening to a great extent when an engine is stopped. SOLUTION: A nut 4 made by sintered molding is attached to the opening of a cylinder chamber 3 formed in a housing 1, and a threaded shaft 6 is fitted in female threads 5 furnished in the inner circumferential mating position of the nut 4. The female threads 5 and the male thread on the shaft 6 are formed in sawteeth. When a chain A is tightened to cause the shaft 6 to be intruded, it is received by the pressure side flanks having a larger flank angle of the sawteeth threads so that the shaft 6 is locked, and thereby the chain A is precluded from slackening. In the cylinder chamber 3, a plunger 7 is slidably installed at the back of the shaft 6, and an oil supply passage 9 is furnished as leading to a pressure chamber 8 formed at the back of the plunger 7. The shaft 6 is energized so as to be willing to protrude with the oil pressure supplied to the pressure chamber 8 through the passage 9, and when the chain A has slackened, the shaft 6 is protruded so as to absorb the slack.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chain tensioner for maintaining a constant tension of a chain such as a camshaft driving chain.

[0002]

2. Description of the Related Art A chain tensioner shown in FIG. 6 is known as a chain tensioner for keeping the tension of a camshaft driving chain constant. This chain tensioner has a housing 30
A plunger 32 and a spring 33 are assembled in a cylinder chamber 31 formed in the cylinder 33, and the chain A is pressed by the plunger 32 provided with the projecting property by the spring 33.

[0003] An oil supply passage 35 communicates with a pressure chamber 34 formed at the back of the plunger 32.
When the plunger 32 moves outward and the pressure in the pressure chamber 34 decreases, the check valve 36 is opened, and the oil supply pump drives the oil to flow oil from the oil supply passage 35 to the pressure chamber 34. I try to make it.

In the above-described chain tensioner, when the chain A is tensioned and a pushing force is applied to the plunger 32, the pushing force is buffered by oil sealed in the pressure chamber 34, and when the chain A becomes slack, a spring is released. Since the plunger 32 is rapidly moved outward by the elasticity of the tension 33 to tension the chain A, the followability of the plunger 32 to the fluctuation in the tension of the chain A is good.
It has a feature that the tension of the chain A can always be kept constant.

[0005]

In the above-mentioned chain tensioner, when the engine is stopped, the plunger 32 is pushed by the tensioned chain A due to the stop position of the cam provided on the cam shaft, and the pressure chamber 34 is pressed. Oil leaks from the sliding surface between the plunger 32 and the cylinder chamber 31, and the plunger 32 is at the retracted position.

For this reason, when the chain is loosened due to the start of the engine, the plunger largely moves outward. At this time, since the hydraulic pump is just after starting and the discharge amount is small, sufficient oil cannot be supplied to the pressure chamber, air enters the pressure chamber, the damping characteristics are reduced by the intruded air, and the chain There is a problem that the function of the tensioner cannot be exhibited.

In order to solve the problem, Japanese Utility Model Laid-Open No. 64-255
In the chain tensioner described in Japanese Patent Publication No. 57, a ratchet pawl is swingably mounted on a housing, and the ratchet pawl is engaged with a rack provided on the outer periphery of the plunger to prevent the plunger from retreating. However, since the engagement portion between the ratchet pawl and the rack receives a load from the chain, the chain becomes excessively tensioned immediately after the rack is moved by one pitch, and there is a problem in durability.

An object of the present invention is to provide a chain tensioner having excellent durability which can prevent a large slack of a chain at the time of starting an engine.

[0009]

In order to solve the above-mentioned problems, according to the present invention, a housing is provided with a cylinder chamber which is open at an end face thereof, and a nut member made of a sintered molded product is provided in an opening of the cylinder chamber. And a screw shaft is screw-engaged with a female screw provided at a position facing the inner periphery of the nut member. A plunger is slidably incorporated into the cylinder chamber at the back of the screw shaft. An oil supply passage, which communicates with a pressure chamber formed on the back and is supplied with a hydraulic pressure of a predetermined pressure, is provided. The female screw and the male screw thread formed on the outer periphery of the screw shaft are screwed into the pressure side receiving the pushing force of the screw shaft. The flank of the flank has a serrated shape larger than the flank angle of the play-side flank, and the serrated thread has a lead angle at which the screw shaft moves outward by hydraulic pressure supplied to the pressure chamber. Have adopted the growth.

The oil supply passage is provided with a check valve for opening the oil supply passage when the pressure in the pressure chamber becomes lower than the oil pressure supplied to the oil supply passage, and the screw shaft is provided in the pressure chamber via a plunger. May be incorporated with a spring that imparts protrusion.

[0011]

As described above, since the threads of the female screw of the nut member and the male screw of the screw shaft are formed in a sawtooth shape, when the chain is tensioned by the stop of the engine and a pushing force is applied to the screw shaft, the pushing force is reduced. It can be received at the pressure flank where the flank angle of the thread is large.

For this reason, the screw shaft is locked and not pushed in, the chain is held in a tensioned state, and the chain is prevented from being largely loosened when the engine is started.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 to 4 show a first embodiment of the present invention. As shown, the housing 1 has a plurality of mounting pieces 2 on its outer periphery which are bolted to a fixed portion such as an engine cylinder block. The housing 1 is provided with a cylinder chamber 3 that is open at the tip end surface.

A nut member 4 is fixed to the opening of the cylinder chamber 3 via means such as press fitting. The nut member 4 is made of a sintered product, and is provided with a female screw 5 at a position facing the inner periphery as shown in FIG.

Here, if the angle θ of the thread portion range of the female screw 5 exceeds 60 °, the material density at the time of embossing is reduced
And the female screw 5 having high strength cannot be obtained. For this reason, the angle θ of the thread portion range of the female screw 5
Is 60 ° or less.

A screw shaft 6 is screw-engaged with the nut member 4, and a plunger 7 is slidably mounted on the back of the screw shaft 6. By incorporating the plunger 7 into the cylinder chamber 3, a pressure chamber 8 is formed at the back of the plunger 7. The housing 1 is provided with an oil supply passage 9 communicating with the pressure chamber 8. A predetermined oil pressure is supplied to the oil supply passage 9, and the oil pressure causes the spherical surface 7 a formed at the tip of the plunger 7 to make point contact with the flat rear end surface 6 a of the screw shaft 6.

As shown in FIG. 3, the thread of the male screw 10 formed on the outer circumference of the female screw 5 and the screw shaft 6 of the nut member 4 is formed on the pressure side flank 1 which receives the pushing force of the screw shaft 6.
1 has a flank angle larger than the flank angle of the play side flank 12, and the screw shaft 6 is set to be loose in the protruding direction and locked in the pushing direction from the relationship between the flank angle and the lead angle of the serrated thread. It is a condition.

Here, the loosening condition means that the screw shaft 6 is smoothly moved outward while being rotated by the hydraulic pressure supplied from the oil supply passage 9 to the pressure chamber 8, while the locking condition is the static condition. Even if an axial force acts on the screw shaft 6, the screw does not move into the cylinder chamber 3, and when the vibration of the chain acts on the screw shaft 6 via the chain pressing member (dynamic), the screw is This means that the screw shaft 6 is gradually rotated and pushed to a position where the hydraulic pressure of the pressure chamber 8 and the pushing force are balanced with each other.

The chain tensioner having the above structure fixes the housing 1 to a fixed portion such as a cylinder block or the like, supplies oil pressure from the oil supply passage 9 to the pressure chamber 8, and provides a screw shaft 6 having an outwardly projecting property. Chain pressing member 1
3 is pressed to apply tension to the chain A.

In the use state of the chain tensioner shown in FIG. 1, when the engine is stopped in the chain A for driving the cam shaft, the chain A
When the engine is started, the chain A becomes slack.

Here, when the chain A is tightened by starting the engine, a pushing force acts on the screw shaft 6. At this time, the pushing force acting on the screw shaft 6 acts on the pressure side flank 11 in the screw engagement portion of the female screw 5 and the male screw 10, and the screw shaft 6 is formed by the relationship between the flank angle and the lead angle of the pressure side flank 11. Since the lock condition is set, the screw shaft 6 is locked and does not retreat, and the chain A is held in a tensioned state to prevent slack from occurring.

When the pushing force becomes higher than the oil pressure supplied to the pressure chamber 8, the screw shaft 6 slowly rotates and retreats. When the pushing force and the oil pressure are balanced, the screw shaft 6 stops and the chain A Is kept in a predetermined tension state.

As described above, when the chain A is tightened due to the stop of the engine, the screw shaft 6 is locked and not pushed in, and the chain A is maintained in a tightened state. It can prevent loosening.

When the chain A is loosened when the engine is started, the screw shaft 6 is pressed outward by the hydraulic pressure supplied from the oil supply passage 9 to the pressure chamber 8.

Since the screw shaft 6 is loosened outwardly due to the relationship between the flank angle of the play side flank 12 and the lead angle, the screw shaft 6 smoothly moves outward while rotating. At this time, since the screw shaft 6 and the plunger 7 are in point contact with each other, the screw shaft 6 rotates smoothly and moves outward quickly, and the slack of the chain A is small. Removed.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, a spring 14 for pressing the plunger 7 against the rear end of the screw shaft 6 is incorporated in the pressure chamber 8. A check valve 15 is provided at an oil outlet of the oil supply passage 9.

Here, the check valve 15 is connected to the pressure chamber 8.
Is lower than the pressure of the oil pressure supplied to the oil supply passage 9, the oil supply passage 9 is opened.

Further, similarly to the first embodiment, the screw shaft 6 is set to have a slack condition in the protruding direction and a locking condition in the pushing direction from the relationship between the flank angle and the lead angle of the serrated screw thread. I have.

The slack condition referred to here is the spring 14
Means that the screw shaft 6 smoothly moves outward while being rotated by the pressing force. On the other hand, the lock condition means that the screw shaft 6 does not retreat even if it is suddenly pushed in, and the chain When the vibration of acts on the screw shaft 6,
The screw shaft 6 rotates and retreats slowly to a position where the pressing force and the pushing force of the spring 14 are balanced.

Since the other structure is the same as that of the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.

In the chain tensioner having the above structure, when the chain A is tightened due to the stop of the engine, the screw shaft 6 is pushed in, and the pushing force is applied to the thread at the screw engagement portion between the screw shaft 6 and the nut member 4. Acts on the pressure side flank 11.

For this reason, similarly to the chain tensioner shown in the first embodiment, the screw shaft 6 locks and does not retreat.

As described above, even if the chain A is tightened, the screw shaft 6 does not retreat significantly, so that it is possible to prevent the chain A from being largely loosened.

When the engine is started, the chain A
When the screw shaft 6 is loosened, the screw shaft 6 is set to a slack condition in the projecting direction due to the relationship between the flank angle of the play side flank 12 and the lead angle. Move quickly in the direction of chain A
Absorbs slack.

At this time, the plunger 7 also moves together with the screw shaft 6 by the pressing force of the spring 14, so that the pressure chamber 8
, The check valve 15 opens the oil supply passage 9. Therefore, the oil pressure supplied to the oil supply passage 9 is supplied to the pressure chamber 8.

As described above, even if the chain A is tightened due to the stop of the engine, the screw shaft 6 does not retreat greatly, and the chain A is maintained in a tightened state. However, the slack amount is small, and the screw shaft 6 does not protrude much outward.

For this reason, the pressure drop in the pressure chamber 8 when the engine is restarted is small, and air enters the oil in the pressure chamber 8, or air precipitates out of the oil, and the damper effect is reduced. Occurrence is extremely low.

[0039]

As described above, the present invention has the following effects.

According to the first aspect of the present invention, the thread of the female screw of the nut member and the external thread of the screw shaft has a serrated shape in which the flank angle of the pressure side flank is larger than the flank angle of the play side flank. According to the relationship between the flank angle and the lead angle, the screw shaft was locked in the pushing direction and loosened in the protruding direction, so even if the chain was tightened due to the engine stop, the screw shaft did not retreat greatly and the engine was restarted. At times, the chain can be prevented from significantly loosening.

Further, since the pressing force acting on the screw shaft is received by the pressure side flank of the thread of the female screw and the male screw, it is possible to realize a chain tensioner excellent in durability and generating less noise.

Further, since the nut member is formed of a sintered molded product, the cost is lower than that of a nut member having a female thread formed by cutting, and the cost of the chain tensioner is reduced.

According to the second aspect of the present invention, since the housing is made of aluminum, the cost of the chain tensioner can be further reduced.

According to the third aspect of the present invention, a spring that presses the plunger is incorporated in the pressure chamber and a check valve is provided in the oil supply passage, so that the chain is tightened by the stop of the engine and the screw shaft is pushed in. Then, the check valve closes the oil supply passage, and the screw shaft is prevented from being pushed by the hydraulic pressure sealed in the pressure chamber. For this reason, even if the chain is loosened due to the restart of the engine, the screw shaft and the plunger do not largely move outward, so that air does not enter the oil in the pressure chamber or precipitate from the oil. Can be prevented,
The optimal damper function can always be exhibited.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional front view showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional plan view of the above.

FIG. 3 is an enlarged sectional view of a screw engaging portion between the nut member and the screw shaft according to the first embodiment;

FIG. 4 is a front view of the nut member.

FIG. 5 is a longitudinal sectional front view showing a second embodiment of the invention.

FIG. 6 is a sectional view showing a conventional chain tensioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 3 Cylinder chamber 4 Nut member 5 Female screw 6 Screw shaft 7 Plunger 8 Pressure chamber 9 Oil supply passage 10 Male screw 11 Pressure side flank 12 Play side flank 14 Spring 15 Check valve

Claims (3)

[Claims] 1. A housing having a cylinder chamber open at an end face thereof, a nut member made of a sintered molded product fixed to an opening of the cylinder chamber, and a female screw provided at a position facing the inner periphery of the nut member. A screw shaft is screw-engaged, a plunger is slidably mounted on the back of the screw shaft in the cylinder chamber, and the housing communicates with a pressure chamber formed on the back of the plunger, and a hydraulic pressure of a predetermined pressure is supplied. The screw thread of the male screw formed on the outer circumference of the female screw and the screw shaft has a serrated shape in which the flank angle of the pressure side flank receiving the pushing force of the screw shaft is larger than the flank angle of the play side flank. A chain tensioner having a serrated thread provided with a lead angle at which a screw shaft moves outward by hydraulic pressure supplied to the pressure chamber. 2. The chain tensioner according to claim 1, wherein said housing is made of aluminum. 3. A check valve for opening the oil supply passage when the pressure of the pressure chamber becomes lower than the pressure of the oil pressure supplied to the oil supply passage, and the oil supply passage is connected to the screw shaft via a plunger. The chain tensioner according to claim 1 or 2, wherein a spring for imparting protrusion is incorporated.