JPH05321994A - Auto tensioner - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to prevent air entrapment in a pressure chamber in an automatic tensioner. [Structure] First and second reservoirs are formed at both ends of a pressure chamber that generates a volume change due to movement of a plunger, the pressure chamber and the first reservoir communicate with each other through a minute gap, and the first reservoir and the second reservoir are separated from each other. The second reservoir and the pressure chamber are communicated with each other through the communication passage and the one-way valve. First
Although there is an air layer above the reservoir, it is separated from the second reservoir by the maximum volume of the pressure chamber, and a large amount of working fluid exists between the first reservoir and the second reservoir. (2) Air does not get caught in the pressure chamber when the working fluid moves from the reservoir to the pressure chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto tensioner.

[0002]

2. Description of the Related Art As an example of the prior art relating to the present invention, there is an "auto tensioner" disclosed in Japanese Utility Model Publication No. 3-13647. This conventional technique will be described with reference to FIG. 3. The cylinder 1 has a closed end 2 in the lower portion, and an oil seal 3 is incorporated in the inner upper portion. This oil seal 3 has a retaining ring 4 attached to the upper portion of the inner diameter surface of the cylinder 1.
The cylinder 1 is prevented from coming off and prevents the hydraulic oil and air filled in the cylinder 1 from leaking. A rod insertion hole 5 is formed in the center of the oil seal 3, and a lower end portion of a rod 6 slidably inserted into the rod insertion hole 5 has a lower end of a piston 7 slidably incorporated in the cylinder 1. It is inserted into the upper hole 8.

The rod 6 and the piston 7 are formed with a passage 11 for connecting a pressure chamber 9 formed below the piston 7 and a reservoir chamber 10 provided above the piston 7. The check valve 12 attached to the lower surface of the piston 7 opens the passage 11 when the pressure in the pressure chamber 9 becomes lower than the pressure in the reservoir chamber 10. In addition, the spring 13 installed below the piston 7 pushes up the piston 7 and pushes the piston 7 and the rod 6 together.
And are kept connected.

In the reservoir chamber 10, a bearing 14 is attached to the upper portion of the rod 6, and the bearing 14 serves as the cylinder 1.
The rod 6 is slidable along the inner diameter surface and holds the rod 6 in a state of being aligned with the axis of the cylinder 1. Further, the bearing 14 is provided with a passage 15 through which air and hydraulic oil can flow.

The outer peripheral portion of the annular spring seat 17 incorporated between the bearing 14 and the piston 7 is supported by a step portion 16 provided on the inner diameter surface of the cylinder 1. A predetermined gap is formed between the outer diameter surface of the rod 6 and the outer diameter surface of the rod 6. Between the spring seat 17 and the bearing 14, a pressure adjusting spring 18 that gives the rod 6 a projecting property is incorporated.

A tension roller 22 is attached to the tip of a roller arm 21 which is rotatably supported about the pin 20.
And the tip of the rod 6 engages with the roller arm 21. The tension roller 22 is engaged with, for example, a belt 23 of the engine, and the belt 23 is always given a proper tension by an auto tensioner. Now, when the engine is changed from the operating state to the stopped state, the tension of the belt 23 in the engaged portion of the auto tensioner increases under certain conditions, and the piston 7 passes through the tension roller 22, the roller arm 21 and the rod 6. Is pushed downward in the drawing. At this time, the working oil pressure in the pressure chamber 9 rises because the volume of the pressure chamber 9 tends to decrease, and the working oil in the pressure chamber 9 is removed from the clearance between the inner peripheral surface of the cylinder 1 and the outer peripheral surface of the piston 7. It flows into the reservoir chamber 10.

When the engine is started with the piston 7 lowered as described above, the tension of the belt 23 in the engaged portion of the auto tensioner sharply decreases, and therefore the tension of the pressure adjusting spring 18 is increased. Rod 6
And the piston 7 rises sharply. As a result, the hydraulic pressure in the pressure chamber 9 drops sharply, the check valve 12 opens, and the hydraulic fluid flows vigorously from the reservoir chamber 10 into the pressure chamber 9. At this time, since the inflow speed of the hydraulic oil is high, the air existing above the inside of the reservoir chamber 10 may mix into the pressure chamber 9 together with the hydraulic oil, which may adversely affect the operation of the automatic tensioner.

[0008]

Therefore, according to the present invention,
The technical issue is to prevent air entrapment in the pressure chamber of an auto tensioner.

[0009]

[Constitution of the invention]

[0010]

The technical means of the present invention taken to solve the above-mentioned technical problems of the present invention include a housing and a plunger slidably inserted in the housing with a minute gap. A pressure chamber defined by the housing and the plunger, a first reservoir formed on one axial side of the pressure chamber in the housing and communicating with the pressure chamber through a minute gap, and the inside of the first reservoir and the outside air. A sealing means for preventing communication, an air layer located above the first reservoir, and a second reservoir formed on the other side in the housing in the axial direction of the pressure chamber and communicating with the first reservoir via a communication passage, That is, the autotensioner is composed of a one-way valve that allows the working fluid to communicate with the pressure chamber from the second reservoir.

[0011]

According to the above-mentioned technical means of the present invention, only the working fluid flows from the second reservoir containing only the working fluid into the pressure chamber via the one-way valve when the internal pressure of the pressure chamber decreases. ..

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the technical means of the present invention will be described below with reference to the accompanying drawings.

The automatic tensioner 10 shown in FIGS. 1 and 2.
In the housing 11, a hole 12 having one end closed and the other end open is formed, and a sleeve 13 is formed in the hole 12.
Is inserted with a minute gap 14, and the wave washer 1
5, It is fixed via the flat washer 16 and the snap ring 17. The hole 18 and the recess 19 formed in the sleeve 13 are defined by a partition wall 20. A plunger 21 is slidably inserted into the hole 18 with a minute gap 22 and is urged toward the open end of the hole 12 by a spring 25, but the sliding movement amount is restricted by a snap ring 23. There is. Plunger 2
1 includes a rod portion 24 extending toward the open end of the hole 12.
Are integrally formed.

The recess 26 formed in the plunger 21 and the partition wall 20 face each other, and the closed space formed therein is defined as a pressure chamber 27. And the holes 12, 1
In FIG. 8, a portion above the plunger step surface 28 and below the sealing means 29 acts as the first reservoir 30,
It communicates with the pressure chamber 27 through the minute gap 22. The sealing means 29 is prevented from coming off by a snap ring 31, and prevents the outside air from communicating with the inside of the first reservoir 30. The recess 19 formed in the sleeve 13 is the housing 1
The first reservoir 30 is configured with the first reservoir 30 through the communication passage 33 formed in the sleeve 13. A communication hole 34 that communicates between the pressure chamber 27 and the second reservoir 32 is formed in the partition wall 20.
A one-way valve 35 that allows fluid communication from the second reservoir 32 to the pressure chamber 27 is provided in the.

The autotensioner 10 is used with the open end of the hole 12 facing upward as shown in the figure, and an appropriate amount of working fluid (oil or the like) is enclosed in the housing 11 and the first reservoir 30 is used.
An air layer 36 is formed in the. Here, the working fluid is enclosed in the first reservoir 30 up to a level at a position somewhat higher than the position where the communication passage 33 opens.

The auto tensioner 10 having the above structure
The operation of will be described.

The rod portion 24 and the plunger 21 receive a change in the tension of the engine belt (not shown) via a tension roller and a roller arm (not shown). The state shown in FIG. 1 is the state in which the tension of the belt is the lowest, and when the tension of the belt becomes higher from this state, the rod portion 24 and the plunger 21 move downward in the figure against the urging force of the spring 25. At this time, the pressure of the working fluid in the pressure chamber 27 increases, so that the working fluid in the pressure chamber 27 has a small gap 22.
To the first reservoir 30. Further, the tension of the belt is high to some extent, and the rod portion 24 and the plunger 21
When the tension of the belt becomes low when the belt is present at a position slightly lower than the position shown in the drawing, the rod portion 24 and the plunger 21 move upward in the drawing according to the urging force of the spring 25. At this time, the pressure of the working fluid in the pressure chamber 27 decreases, the one-way valve 35 opens, and the working fluid flows from the second reservoir 32 into the pressure chamber 27. At the same time 1st
The working fluid flows from the reservoir 30 into the second reservoir 32 via the communication passage 33.

In particular, when the engine is stopped, the tension of the belt at the position where the automatic tensioner 10 is engaged may become high, and the lower end of the plunger 21 is lowered to a position close to the lower end of the hole 18. Next, when the engine is started, the tension of the belt at the position where the auto tensioner 10 is engaged suddenly decreases, and the rod portion 24 and the plunger 21 rapidly move upward in the drawing in accordance with the urging force of the spring 25. In this case, the moving speed of the working fluid from the second reservoir 32 to the pressure chamber 27 and the first reservoir 30
The moving speed of the working fluid from the first reservoir 30 to the second reservoir 32 is very fast, and the air in the air layer 36 in the first reservoir 30 tries to be mixed into the second reservoir 32 via the communication passage 33. Since the second reservoir 32 and the second reservoir 32 are largely separated from each other and a large amount of working fluid exists between them, the one-way valve 35 is closed before the air reaches the second reservoir 32, and air is mixed in the pressure chamber 27. There is nothing to do. At this time, air enters halfway through the passage 33, but the one-way valve 3
By closing 5 the first reservoir 30 to the second reservoir 3
The movement of the working fluid to 2 is stopped, and the air returns to the air layer 36 of the first reservoir 30 by the buoyancy.

[0019]

As described above, in the autotensioner of the present invention, when the internal pressure of the pressure chamber drops, only the working fluid flows into the pressure chamber from the second reservoir in which only the working fluid exists via the one-way valve. .. That is, the air in the air layer existing in the first reservoir is greatly separated from the second reservoir, and when the one-way valve opens and the working fluid moves from the second reservoir to the pressure chamber, the air is mixed in the pressure chamber. Never.

[Brief description of drawings]

FIG. 1 is a sectional view of an automatic tensioner according to an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of a main part in FIG.

FIG. 3 shows a cross-sectional view of a prior art autotensioner.

[Explanation of symbols]

 10 auto tensioner, 11 housing, 21 plunger, 22 minute gap, 27 pressure chamber, 29 sealing means, 30 first reservoir, 32 second reservoir, 33 communicating passage, 35 one-way valve, 36 air layer.

Claims (1)

[Claims] 1. A housing, a plunger slidably inserted in the housing with a minute gap, a pressure chamber defined by the housing and the plunger, and an axial direction of the pressure chamber in the housing. A first reservoir that is formed on the side of the first reservoir and that communicates with the pressure chamber via the minute gap, a sealing unit that blocks communication between the inside of the first reservoir and outside air, and an air layer located above the inside of the first reservoir. And a second reservoir formed inside the housing on the other side in the axial direction of the pressure chamber and communicating with the first reservoir via a communication passage, and allowing fluid communication from the second reservoir to the pressure chamber. An auto tensioner consisting of a one-way valve that operates.