JP2000154854A - Autotensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a length in the axial direction of the whole tensioner by reducing a stroke amount of a rod. SOLUTION: This autotensioner is provided with a bracket 10 attached so as to oscillate for an engine block, a bearing 21 attached to the bracket 10, an idler 20 which is provided on an outer peripheral side of the bearing 21 and has a pulley 22 coming into contact with a timing belt V, a body 31 formed integrally with the bracket 10, a rod 32 protruding from the body 31 to oscillate the bracket 10, and a tensioner body having a damping means damping the travel of the rod 32 so that the thrust motion of the idler 20 is immediately allowed when a tensile force of the timing belt V is reduced and the retraction motion of the idler 20 is gradually allowed when a tensile force of the timing belt V is increased. The idler 20 is constituted in such a way that a mounting hole 23 of the bearing 21 for the bracket 10 is eccentric for the center of rotation R of the bearing 21.

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 appropriately maintaining the tension of a timing belt for an engine in order to reduce noise or to extend the life of the timing belt.

[0002]

2. Description of the Related Art Conventionally known general auto tensioners include a bracket which is arranged to be swingable about a fulcrum with respect to a cylinder block of an engine, and a bearing which is rotatably attached to the bracket. And a tensioner body capable of swinging the bracket by projecting a rod from a body formed on the bracket, and the swinging movement of the bracket caused by the reciprocation of the rod causes the idler to press the timing belt, and This is to keep the belt tension constant.

[0003]

In the auto tensioner, one end of a rod is mounted on a bracket so as to appropriately maintain the tension of the belt via an idler. From the viewpoint of mounting the tensioner on a vehicle, the tensioner is not used. It is preferable to shorten the axial length. However, the stroke amount of the rod is set in consideration of the elongation of the belt due to aging, the deflection of the belt due to temperature change, and the dimensional tolerance of each member, and it is difficult to significantly reduce the stroke amount of the rod. there were.

In the conventional auto tensioner, the amount of pressing of the timing belt by the idler is set by the fulcrum between the end of the rod and the bracket. That is, the bracket swings around the fulcrum of the bracket in accordance with the reciprocation of the rod, and the amount of pressing of the timing belt by the idler is adjusted. Here, in the prior art, since the mounting portion between the bearing that holds the idler rotatably and the bracket is generally configured to coincide with the rotation center axis of the idler, when mounting the bearing to the bracket, The play at the time of assembly cannot be absorbed, and it is necessary to absorb the play at the time of assembly of each member by the stroke of the rod. Therefore, it is difficult to reduce the stroke of the rod, and there is a problem that the axial length of the tensioner body cannot be reduced.

Accordingly, it is a technical object of the present invention to provide an auto tensioner capable of shortening the axial length of the entire tensioner by shortening the stroke of the rod in order to solve the above problems. .

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention of claim 1 is an auto-tensioner for applying an appropriate tension to a belt-like power transmission member, which is swingably mounted on an engine block. An idler having a bracket to be mounted on the bracket, a bearing attached to the bracket, and a pulley provided on the outer peripheral side of the bearing and abutting on the belt-shaped power transmission member, a body integrally formed with the bracket, and protruding from the body to swing the bracket. When the tension of the rod to be moved and the belt-shaped power transmission member decreases, the idler's movement is attenuated to immediately allow the propulsion movement of the idler, and when the tension of the belt-shaped power transmission member increases, gradually allow the idler to retract. And a tensioner main body having a tensioner body having a Constructed as eccentric to the rotational center of the receiving. The specific configuration of the idler is defined in the claims
As shown in FIG. 2, the bearing of the idler has an inner race fixed to the bracket, and an outer race that is rotatable relative to the inner race and has a pulley disposed on the outer periphery thereof. The mounting portion is provided eccentrically with the center of rotation of the outer race.

According to the first aspect of the present invention, since the center of rotation of the idler is eccentric between the center of rotation of the bearing and the mounting position of the idler, when the auto tensioner is mounted on the engine block, the idler is not fixed to the bracket. Attach the bracket to the engine block so that it can swing. Then, the idler is swung about the mounting portion of the bearing to the bracket, and the idler is fixed to the bracket at a position where the bending of the belt-like power transmission member caused by the play due to the dimensional tolerance of each component is absorbed. This allows
When mounting the auto tensioner on the engine block, it is possible to absorb the backlash due to the dimensional tolerance of each part, and the stroke amount of the rod of the tensioner body does not need to consider the backlash due to the dimensional tolerance. Can be set in consideration of only the time-dependent change and the deflection due to the temperature change. Therefore, the stroke amount of the rod can be reduced.

In addition, since it is possible to absorb backlash due to dimensional tolerance of each part only by decentering the center of rotation of the bearing and the mounting position on the bracket, it is preferable without adding new parts and increasing the space. It is.

[0009] The invention of claim 3 is claim 1 or claim 2
A free piston type auto having a tensioner main body in which a first oil chamber formed between a rod and a body, and a second oil chamber in which a piston that operates in accordance with increase and decrease of hydraulic oil in the first oil chamber is disposed. It is a tensioner.

According to the third aspect, since the tensioner body is a free piston type auto tensioner, the inside of the tensioner is sealed, so that the tensioner body can be disposed on the engine block regardless of the direction in which the rod projects. Therefore, the degree of freedom of mounting the bracket to the engine block is improved.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view of an auto-tensioner 1 according to the present embodiment, and FIG. 2 is a sectional view taken along line AA of FIG. The auto-tensioner 1 according to the present embodiment is used to always apply proper tension to a timing belt V, which is a belt-like power transmission member that transmits power of a crankshaft (not shown) of an engine to a camshaft (not shown). The tension is applied to the timing belt V via an idler 4 whose outer periphery is engaged with the timing belt V.

The auto-tensioner 1 includes a bracket 10 swingably attached to an engine block,
Bearing 21 and bearing 21 attached to bracket 10
And an idler 20 having a pulley 22 abutting on the timing belt V provided on the outer peripheral side of the body, a body 31 formed integrally with the bracket 10, a rod 32 projecting from the body 31 and swinging the bracket 10, and a timing belt V. A tensioner body having damping means for attenuating the movement of the rod 32 so as to allow the propulsion movement of the idler 20 immediately when the tension decreases and to allow the retraction movement of the idler 20 gradually when the tension of the timing belt V increases. 30.

The bracket 10 is provided with a bolt insertion hole 11. By fixing the fulcrum bolt 12 to the engine block through the bolt insertion hole 11, the bracket 10 swings around the fulcrum bolt 12 on the engine block. Supported as possible.

The idler 20 is disposed on the outer periphery of the outer race 21c, with a bearing 21 having an inner race 21a fixed to the bracket 10, an outer race 21c rotatable relative to the inner race 21a via a ball 21b. And a pulley 22. The pulley 22 is fixed to the outer race 21 c of the bearing 21,
A timing belt V is in contact with the outer periphery of the pulley 22, and the pulley 22 rotates together with the operation of the timing belt V. At the inner peripheral side of the inner race 21a, a mounting hole 23 as a mounting portion to the bracket 10 is provided eccentrically with the rotation center R of the outer race 21c.
The bracket 10 is also provided with a mounting hole 13. By fixing the mounting hole 13 and the mounting hole 23 with the mounting bolt 24 via the washer 25, the idler 20 and the bracket 10 are fixed.

The tensioner body 30 will be described. The tensioner body 30 includes a first oil chamber 33 formed between the rod 32 and the oil chamber block 37, and a second oil chamber in which a piston 34 that operates in accordance with an increase or decrease in the amount of hydraulic oil in the first oil chamber 33 is arranged. 35 is a free piston type auto tensioner. The body 31 has a hollow cylindrical shape and is formed integrally with the bracket 10. The rod 32 is disposed inside the body 31 so as to be able to reciprocate in the axial direction of the body 31, and one end of the rod 32 projects from the body 31 and presses a pin 36 attached to the engine block. The other end of the rod 32 is the body 3
1 is slidably held by an oil chamber block 37, and the first end of the oil chamber block 37 and the other end of the rod 32.
An oil chamber 33 is constituted. The oil chamber block 37 holds the piston 34 so as to be slidable.
The second oil chamber 35 is constituted by the piston 7 and the piston 34. The first oil chamber 33 and the second oil chamber 35 can communicate with each other via an oil path 38 provided in an oil chamber block 37, and an operation from the first oil chamber 33 to the second oil chamber 35 in the oil path 38. A check valve 39 which inhibits the flow of oil and allows the flow of hydraulic oil from the second oil chamber 35 to the first oil chamber 33 is provided, an oil passage 38 and a check valve 3
9, the sliding gap 4 between the rod 32 and the oil chamber block 37
0 constitutes an attenuation means. The sliding gap 40
Is very small as compared with the flow passage area of the oil passage 38, and the hydraulic oil gradually leaks from the sliding gap 40 when the pressure of the first oil chamber 33 becomes high.

Between the outer periphery of the oil chamber block 37 and the inner periphery of the body 31, there is provided a hollow cylindrical first elastic member 41 for urging the rod 32 in a direction protruding from the body 31.
A cylindrical second elastic member 42 that urges the piston 34 in a direction that pressurizes the second oil chamber 35 is provided in the cylindrical portion of the oil chamber block 37.

The rod 32 has a flange portion 32a extending radially outward. By disposing the first elastic member 41 between the flange portion 32a and the oil chamber block 37, the rod 32 always has a body. It is urged in a direction protruding from 31. A plurality of slits 32b are formed in the flange portion 32a in the axial direction in order to reduce the resistance of the hydraulic oil when the rod 32 reciprocates. Further, in order to prevent the hydraulic oil from leaking outside, the body 31 and the rod 3
A seal 43 is provided between the two.

The assembly of the auto tensioner 1 will be described. The auto tensioner 1 according to the present embodiment is swingably attached to the engine block integrally with the bracket 10, and swings the bracket 10 by reciprocating the rod 32 to absorb the deflection of the timing belt V. First, with the rod 32 contracted, the bracket 10
Then, the fulcrum bolt 12 is inserted into the bolt insertion hole 11 and the bracket 10 is swingably attached to the engine block. At this time, the idler 20 is not fixed to the bracket 10, and the mounting bolt 24 is temporarily fixed to the mounting hole 23 of the bearing 21 so that the idler 20 rotates about the mounting hole 23 on the bracket 10 side. By pressing the pulley 22 against the timing belt V with a predetermined force from this state, the deflection of the timing belt V is absorbed, and the mounting bolts 24 are tightened to attach the inner race 21a to the bracket 10.
Fixed to. Thereafter, the rod 32 is projected from the body 31, so that an appropriate tension is applied to the timing belt V. According to the above-described assembling, since the deflection of the timing belt V due to the dimensional variation of each member can be adjusted after the bracket 10 is attached to the engine block, the timing belt V generated by the tolerance variation of each component such as the engine and the auto tensioner can be adjusted. The auto-tensioner 1 can be mounted on the engine block in a state where the deflection has been absorbed in advance.

Next, the operation of the tensioner main body 30 will be described.

When the tension of the timing belt V increases,
The rod 32 moves in the direction of entering the body 31,
The oil pressure in the first oil chamber 33 increases. At this time, the oil passage 38
The flow of hydraulic oil from the first oil chamber 33 to the second oil chamber 35 through the first oil chamber 33 is prohibited by the action of the check valve 39,
The hydraulic oil in the oil chamber 33 gradually flows into the seal 43, the inner circumference of the body 31, and the internal space 44 defined by the oil chamber block 37 through the sliding gap 40 between the oil chamber block 37 and the rod 32. The internal space 44 communicates with the second oil chamber 35 through a passage 37a.
The piston 34 moves by an amount corresponding to the infiltration of the piston 34. 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 32 is moved by the first elastic member 41 to the body 31.
From the idler 20
And the decrease in the tension of the timing belt V is promptly absorbed. When the rod 32 protrudes, the oil pressure in the first oil chamber 33 becomes lower than the oil pressure in the second oil chamber 35, and the hydraulic oil in the second oil chamber 35 flows from the oil passage 38 through the check valve 39 through the first oil passage 38.
It is introduced into the oil chamber 33. At this time, the piston 34 is urged by the second elastic member 42 and
It moves by the amount that 2 leaves.

According to the above-described operation, the idler 20 can move quickly with respect to the slack of the timing belt V,
Also, an idler 20 is used for tensioning the timing belt V.
Is slowed down, and the movement of the idler 20 is attenuated.
The tension of the timing belt V is accurately adjusted. In this manner, the stroke amount of the rod 32 may be set so as to absorb only the deflection of the timing belt V due to a change over time and a change in temperature. Therefore, the play due to the dimensional tolerance of each component of the auto tensioner 1 is considered. It is not necessary, and the stroke amount of the rod 32 in the tensioner main body 30 can be reduced, and the length of the tensioner main body 30 can be reduced.

The embodiments of the present invention have been described above. However, the present invention is not intended to be limited to the above-described embodiments, and any type of auto-tensioner in accordance with the gist of the present invention can be used. It may be in a form.

[0024]

According to the first and second aspects, when the auto tensioner is mounted on the engine block, it is possible to absorb the backlash due to the dimensional tolerance of each part, and the stroke of the rod of the tensioner main body can be reduced. It is not necessary to consider the dimensional tolerance of the members, and the stroke amount of the rod can be set in consideration of only the elongation of the belt-shaped power transmission member due to the temporal change and the deflection due to the temperature change. Therefore, the stroke amount of the rod can be set short.

Also, since the eccentricity between the center of rotation of the bearing and the mounting point on the bracket can absorb the backlash due to the dimensional tolerance of each part, it is preferable without adding new parts and increasing the space. It is.

According to the third aspect, since the tensioner body is a free piston type auto tensioner, the inside of the tensioner is sealed, so that the tensioner body can be disposed on the engine block regardless of the direction in which the rod projects. Therefore, the degree of freedom of mounting the bracket to the engine block is improved.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Auto tensioner 10 ... Bracket 20 ... Idler 21 ... Bearing 22 ... Pulley 23 ... Mounting hole 24 ... Mounting bolt 30 ... Tensioner main body 31 ... Body 32 ... Rod 33 ... First oil chamber 34 ... Piston 35 ... Second oil chamber 36 ... Pin 37 ... Oil chamber block 38 ... Oil path 39 ... Check valve 40 sliding gap 41 first elastic member 42 second elastic member 43 seal 44 internal space R center of rotation V timing belt (belt-shaped power transmission Element)

Claims (3)

[Claims] 1. An auto-tensioner for applying an appropriate tension to a belt-shaped power transmission member, comprising: a bracket mounted to be swingable with respect to an engine block; a bearing mounted to the bracket; and an outer peripheral side of the bearing. A pulley provided and abutting on the belt-shaped power transmission member;
A body integrally formed with the bracket, a rod projecting from the body and swinging the bracket, and immediately allowing the propulsion movement of the idler when the tension of the belt-shaped power transmission member decreases. A tensioner body having damping means for attenuating the movement of the rod so as to gradually allow the idler to retreat when the tension of the belt-shaped power transmission member increases, wherein the idler is a bearing for a bracket. An auto-tensioner characterized in that the mounting portion is eccentric with respect to the center of rotation of the bearing. 2. The bearing of the idler includes an inner race fixed to a bracket, and an outer race that is rotatable relative to the inner race and has a pulley disposed on an outer periphery thereof. 2. The auto-tensioner according to claim 1, wherein a mounting portion with the bracket is provided eccentrically with a rotation center of the outer race. 3. The tensioner body includes a first oil chamber formed between a rod and a body, and a second oil chamber provided with a piston that operates in accordance with an increase or decrease in hydraulic oil in the first oil chamber. 3. The auto-tensioner according to claim 1, wherein the auto-tensioner is a free piston type auto-tensioner.