JP2000145904A - Free piston type auto tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a rod for the axial dimension of a piston, lessen the number of parts to be sealed of the piston and decrease the number of parts to reduce the cost by disposing the piston in the inner periphery of the rod, and taking only the outer peripheral surface of the piston as the sliding contact surface of the piston. SOLUTION: When the tension of a timing belt is increased and a rod 3 is moved downward through a cap 8 by the movement of an idler, oil pressure in a first oil chamber 7 is increased. Since inflow of working fluid from the first oil chamber 7 through an oil path 9 to a second oil chamber 8 is regulated by a check valve 12 at this time, the working fluid 7 in the first oil chamber 7 gradually flows through a sliding gap 13 between an oil chamber block 5 and the rod 3 into an internal space 17. Accordingly, the piston 6 is raised only for the oil entering the internal space 17 to loosen the timing belt, and increase in tension of the timing belt is slowly absorbed. On the contrary, when the tension of the timing belt V is decreased, the piston 6 is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-tensioner for properly maintaining the tension of a timing belt for an engine or for improving the life of the timing belt. The present invention relates to a free piston type auto tensioner that slides.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Utility Model Application Laid-Open No. 63-157 is disclosed.
No. 558 discloses a free piston type auto tensioner. FIG. 4 shows the free piston type auto tensioner 30 of the above publication. In this publication, body 31
A plunger 32 sliding in the body 31, a rod portion 33 formed integrally with the plunger 32 and protruding from the body 31, and a seal 34 between the inner periphery of the body 31 and the outer periphery of the rod portion 33, respectively. A free piston for pressurizing an oil chamber 38 between the piston 36 and the plunger 32, comprising a piston 36 slidably inserted through the piston 35 and an elastic member 37 for pressing the piston 36 toward the plunger 32; An auto tensioner 30 of the type is disclosed.

[0003]

In an auto tensioner, one end of a rod is attached to an idler in order to properly maintain the tension of the belt via an idler. In addition, since the tension of the belt changes due to a change in temperature or the temperature, it is impossible to operate the auto tensioner at an ideal position where a force in a direction perpendicular to the axial direction of the rod is not applied to the rod.
If a very large force is applied in a direction perpendicular to the axial direction of the rod, the rod may break. If the rod is broken, the tension of the belt cannot be adjusted properly, and the belt may rattle, causing abnormal noise or skipping of the belt, which is not preferable.

However, in the above-mentioned prior art, since the piston 36 is configured to slide on the outer periphery of the rod portion 33, at least the axial length of the piston 36, the stroke of the piston 36, and the elastic body 37 The length of the rod portion 33 is required to be equal to the length of the rod portion 33, and it is difficult to shorten the rod portion 33 in order to avoid breakage of the rod.

[0005] Therefore, it is a technical object of the present invention to provide a free piston type auto tensioner capable of shortening the axial length as much as possible in order to solve the above-mentioned problems.

[0006]

According to a first aspect of the present invention, there is provided a cylindrical body and an idler which is disposed in the body so as to be reciprocally movable in the axial direction of the body, and protrudes from the body. A rod that presses the belt-shaped power transmission member through the body, an oil chamber block that is formed on the inner periphery of the body, slidably arranges the rod, and constitutes a first oil chamber that stores hydraulic oil with the rod; and a rod. A piston that is formed on the inner periphery and forms a second oil chamber that stores hydraulic oil together with the inner circumferential surface of the rod; an oil passage that is formed on the rod and that communicates the first oil chamber and the second oil chamber; A hollow cylindrical first elastic member for urging in a direction protruding from the body, a cylindrical second elastic member for urging a piston in a direction for pressing the second oil chamber, a first oil chamber and a second oil Controls the flow of hydraulic oil between chambers and tensions the belt-like power transmission member Damping means for immediately allowing the propulsion movement of the idler by the first elastic member when lowered, and gradually allowing the retreating movement of the idler against the first elastic member when the tension of the belt-shaped power transmission member increases. Was.

According to the first aspect, since the piston is disposed on the inner periphery of the rod, it is not necessary to slide the piston on the outer periphery of the rod. Therefore, the rod can be shortened by the axial dimension of the piston. In addition, since the sliding contact surface of the piston is only the outer peripheral surface of the piston, the number of parts for sealing the piston with the conventional free piston type auto tensioner is reduced, and the number of parts, cost reduction and reliability are reduced. Is preferred.

[0008] The invention of claim 2 shows a specific configuration of the damping means in claim 1, and the damping means is disposed in an oil passage formed in the rod, and is provided from the second oil chamber to the first oil chamber. A check valve for permitting the flow of the hydraulic oil into the chamber and prohibiting the flow of the hydraulic oil from the first oil chamber to the second oil chamber; and an oil chamber capable of communicating between the first oil chamber and the second oil chamber. The sliding gap between the block and the rod is constituted.

According to the second aspect, when the tension of the belt-shaped power transmission member decreases, the rod tends to protrude from the body toward the propulsion movement of the idler by the urging force of the first elastic member. At this time, since the oil pressure in the first oil chamber is lower than the oil pressure in the second oil chamber, the check valve allows the hydraulic oil to flow from the second oil chamber into the first oil chamber, and the rod quickly projects from the body. The idler propulsion movement is immediately allowed. Further, when the tension of the belt-shaped power transmission member increases, the rod slides in a direction to decrease the volume of the first oil chamber against the urging force of the first elastic member. At this time, the check valve moves the first oil chamber to the second oil chamber.
Since the inflow of hydraulic oil into the oil chamber is prohibited, the pressure in the first oil chamber becomes high, the hydraulic oil in the first oil chamber flows out from the sliding gap toward the second oil chamber, and the rod gradually slides. Then the retreating movement of the idler is gradually allowed.

As described above, since the rod is attenuated in accordance with the change in the tension of the belt-like power transmission member, it is possible to always appropriately maintain the tension of the belt-like power transmission member.

[0011]

Embodiments of the present invention will be described with reference to the drawings. 1 to 3 are a cross-sectional view of a free piston type auto tensioner 1 according to the present embodiment and a diagram showing the operation thereof. A free piston type auto tensioner 1 according to the present embodiment is a crankshaft (not shown) of an engine.
Is used to always apply proper tension to the timing belt V, which is a belt-like power transmission member that transmits the power of the above to a camshaft (not shown), via an idler 4 whose outer periphery is engaged with the timing belt V. The tension is applied to the timing belt V.

A free-piston type auto tensioner 1 according to the present embodiment is provided inside a body 2 so as to be able to reciprocate in the axial direction of the body 2.
And a first oil chamber 7 formed on the inner periphery of the body 2 for slidably disposing the rod 3 and storing hydraulic oil together with the rod 3. , A piston 6 that is formed on the inner periphery of the rod 3 and forms a second oil chamber 8 that stores hydraulic oil together with the inner peripheral surface of the rod 3, and a first oil chamber that is formed on the rod 3. An oil passage 9 for communicating the oil passage 7 with the second oil chamber 8
A hollow cylindrical first elastic member 10 for urging the rod 3 in a direction protruding from the body 2, and a cylindrical second elastic member 11 for urging the piston 6 in a direction for pressing the second oil chamber 8.
When the tension of the timing belt V decreases by controlling the flow of the hydraulic oil between the first oil chamber 7 and the second oil chamber 8,
And damping means for immediately allowing the propulsion movement of the idler 4 by the elastic member 10 and gradually allowing the retreating movement of the idler 4 against the first elastic member 10 when the tension of the timing belt V increases.

The oil chamber block 5 is loosely fitted to the inner periphery of the body 2 and has a cylindrical shape at one end to slidably support the rod and constitutes a first oil chamber. It is held pressed against the bottom.

The rod 3 has a flange 3a extending radially outward, and the flange 3a and the oil chamber block 5
By arranging the first elastic member 10 therebetween, the rod 3 is always urged in a direction to protrude from the body 2. Further, a seal 14 is provided between the body 2 and the rod 3 to prevent the hydraulic oil from leaking to the outside. Further, a guide 15 for regulating the radial position of the rod 3 is provided below the seal 14.

The rod has an oil passage 9 which allows communication between the first oil chamber 7 and the second oil chamber 8, and an operation from the second oil chamber 8 to the first oil chamber 7 provided in the oil passage 9. A check valve 12 for allowing inflow of oil and prohibiting inflow of hydraulic oil from the first oil chamber 7 to the second oil chamber 8;
Are provided, and the oil passage 9, the check valve 12, and the rod 3
And the sliding gap 13 between the oil chamber block 5 and the oil chamber block 5 constitute damping means. The flow passage area of the sliding gap 13 is
, The working oil gradually leaks from the sliding gap 13 when the pressure in the first oil chamber 7 becomes high.

The piston 6 is disposed on the inner periphery of the rod 3,
A second oil chamber 8 is defined by a space defined by the end surface of the piston 6 and the inner periphery of the rod 3. In the configuration of the present invention, the piston 3 is disposed on the inner periphery of the rod 3 so that the rod 3 does not penetrate the piston 6. Therefore, compared to a conventional tensioner, the rod 3 has a length corresponding to the axial length of the piston. The length can be reduced. Further, the seal attached to the piston 6 only needs to be the seal ring 16 provided on the sliding surface with the inner periphery of the rod 3, and the number of seals attached to the piston 6 is smaller than that of the conventional auto tensioner, and the number of parts is reduced. Cost can be reduced.

The second elastic member 11 is installed in the rod 3 after the piston 6 is disposed on the inner periphery of the rod 3,
Is closed by a cap 18 to bias the piston 6 in a direction to pressurize the second oil chamber, and is configured in parallel with the first elastic member 10 in the axial direction. With this configuration, the entire length of the free piston type auto tensioner 1 is further reduced.

Next, the operation of the free piston type auto tensioner 1 will be described.

When the tension of the timing belt V increases,
The rod 3 moves in the direction of the arrow shown in FIG.
The oil pressure inside increases. At this time, the flow of hydraulic oil from the first oil chamber 7 to the second oil chamber 8 via the oil passage 9 is regulated by the action of the check valve 12, so that the hydraulic oil in the first oil chamber 7 is Through the sliding gap 13 between the inner circumference of the chamber block 5 and the outer circumference of the rod 3, the fluid gradually flows into the inner circumference of the body 2, the seal 14, and the internal space 17 defined by the outer circumference of the oil chamber block 5 and the rod 3. The internal space 17 communicates with the second oil chamber 8 through a communication hole 3 b provided in the rod 3,
The piston 6 rises by the amount that has entered the internal space 17. As a result, the timing belt V relaxes, and the increase in the tension of the timing belt V is slowly absorbed.

Next, when the tension of the timing belt V decreases, the rod 3 is pushed up by the first elastic member 10 in the direction of the arrow in FIG. 3, and the decrease in the tension of the timing belt V is quickly absorbed. When the rod 3 is pushed up, the oil pressure in the first oil chamber 7 becomes lower than the oil pressure in the second oil chamber 8,
The hydraulic oil in the second oil chamber 8 is introduced into the first oil chamber 7 from the oil passage 9 by the check valve 12. At this time, the piston 6 is urged by the spring 11 and quickly descends by the amount of the rod 3 withdrawn from the internal space 17.

According to the above-described operation, the movement of the idler 4 becomes quicker when the timing belt V is slackened, and the movement of the idler 4 is made slower when the timing belt V is tightened. As a result, the tension of the timing belt V is accurately adjusted.

As described above, according to the present embodiment, since the piston is disposed on the inner peripheral side of the rod, it is not necessary to set the axial length of the piston to the length of the rod.
The length of the rod can be reduced as much as possible.

Although the embodiments of the present invention have been described above, the present invention is not intended to be limited to the above-described embodiments, and any free piston type auto tensioner according to the gist of the present invention may be used. Any form may be used.

[0024]

According to the first aspect of the present invention, since the piston is disposed on the inner periphery of the rod, it is not necessary to slide the piston on the outer periphery of the rod. Therefore, the rod can be shortened by the axial dimension of the piston. it can. In addition, since the sliding contact surface of the piston is only the outer peripheral surface of the piston, the number of parts for sealing the piston with the conventional free piston type auto tensioner is reduced, and the number of parts, cost reduction and reliability are reduced. Is preferred.

According to the second aspect, the rod is attenuated in accordance with the change in the tension of the belt-like power transmission member, so that the tension of the belt-like power transmission member can always be appropriately maintained.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing the operation of the present embodiment.

FIG. 3 is a diagram showing the operation of the present embodiment.

FIG. 4 is a sectional view of a conventional auto tensioner.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Free piston type auto tensioner 2 ... Body 3 ... Rod 4 ... Idler 5 ... Oil chamber block 6 ... Piston 7 ... 1st
Oil chamber 8 Second oil chamber 9 Oil path 10 First elastic member 11 Second elastic member 12 Check valve 13 Sliding gap 16 Seal ring 17 ・ ・ ・ Internal space V ・ ・ ・ Timing belt (belt-shaped power transmission member)

Claims (2)

[Claims] 1. An auto-tensioner for constantly applying an appropriate tension to a belt-shaped power transmission member, wherein the auto-tensioner is disposed in the body so as to be able to reciprocate in the axial direction of the body.
A rod protruding from the body and pressing the band-shaped power transmission member via an idler; a first oil formed on the inner periphery of the body, slidably disposed on the rod, and storing hydraulic oil together with the rod. An oil chamber block that forms a chamber; a piston that is formed on the inner circumference of the rod, and that forms a second oil chamber that stores hydraulic oil together with the inner circumferential surface of the rod; An oil passage communicating with the second oil chamber, a hollow cylindrical first elastic member for urging the rod in a direction protruding from the body, and urging the piston in a direction for pressurizing the second oil chamber. A second elastic member having a cylindrical shape, wherein the idler is controlled by the first elastic member when the tension of the belt-shaped power transmission member is reduced by controlling the flow of hydraulic oil between the first oil chamber and the second oil chamber. Immediate allowance for propulsion Free-piston type auto-tensioner when the tension of the narrow was the band-like power transmission member is increased; and a damping means for gradually allowed backward movement of the idler against the first elastic member. 2. The damping means is disposed in an oil passage formed in the rod, and allows the flow of hydraulic oil from the second oil chamber to the first oil chamber to allow the hydraulic oil to flow from the first oil chamber to the second oil chamber. A check valve that inhibits the flow of hydraulic oil into the oil chamber; and a sliding gap between the oil chamber block and a rod that can communicate between the first oil chamber and the second oil chamber. The free-piston type auto tensioner according to claim 1, characterized in that: