JPH1028U - Hydraulic auto tensioner - Google Patents

Abstract

(57) [Summary] [Object] To provide a structure capable of increasing the spring force of a return spring without increasing the cylinder length and spring constant. A gap for mounting a spring is provided between a cylinder and an outer peripheral surface of a sleeve, and a return spring is incorporated into the gap. Further, the bottom of the sleeve 2 is fixed to the cylinder 1 by the fixing bolt 21 to prevent the sleeve 2 from coming off.

Description

[Detailed description of the invention]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic auto tensioner used for adjusting the tension of an engine timing belt and the like.

[0002]

[Prior art]

 Conventionally, as a hydraulic auto-tensioner for reducing the weight of a cylinder, a separate sleeve 2 "is provided inside a cylinder 1" made of a light alloy, as shown in FIG. In this case, a piston 3 is slidably inserted.

In this structure, the hydraulic oil chamber 4 inside the cylinder 1 ″ is divided into a pressure chamber 5 and a reservoir chamber 6 by a piston 3, and the piston 3 is provided with a passage 7 that communicates the pressure chamber 5 and the reservoir chamber 6. A check valve 8 for opening and closing the passage 7 is provided at the exit of the passage.

In addition, a piston rod 9 is connected to the piston 3, and a step 11 formed on the piston rod 9 is engaged with a bearing 11 that slides on the inner peripheral surface of the cylinder 1 ″. A return spring 12 ″ is incorporated between the upper end of the sleeve 2 ″ and gives a spring force to the piston 3 and the piston rod 9 in a direction to project outward.

The above-mentioned sleeve 2 ″, the piston 3 sliding inside, the pressure chamber 5 and the reservoir chamber 6 in the sleeve 2 ″, the passage 7 of the piston 3, and the check valve 8 constitute a buffer mechanism.

In the drawing, 13 is a retainer, 14 is a spring for connecting the piston 3 and the piston rod 9, 15 is an oil seal, 16 is a tension pulley, 17 is a support arm thereof, 18 is a support shaft, and 19 is a tension adjustment. Belt.

[0007]

[Problems to be solved by the invention]

 In the hydraulic auto-tensioner having the above structure, the belt tension is adjusted by changing the spring force of the return spring 12, but in order to increase the spring force of the return spring 12, the total length of the spring 12 must be reduced. Either increase the length or increase the spring constant.

However, in the conventional auto tensioner shown in FIG. 3, since the return spring 12 is incorporated between the sleeve 2 ″ and the bearing 11, when the total length of the return spring 12 is increased, the total length of the cylinder 1 ″ is increased. Becomes large as it is, making it difficult to mount it on an engine or the like.

On the other hand, if the spring constant of the return spring 12 is increased in order to suppress the increase in the cylinder length, it is difficult to keep the spring force of the entire return spring within a predetermined range, and the required belt tension is reduced. There is a problem that it is difficult to match the spring force.

Accordingly, the present invention is to provide a structure that can set the spring force of the return spring large without increasing the cylinder length or changing the spring constant.

[0011]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a sleeve inside a cylinder, and divides a hydraulic oil chamber inside the cylinder into a pressure chamber and a reservoir chamber by a piston slidably inserted into the sleeve. A passage that connects the pressure chamber and the reservoir chamber is formed in the piston, and a check valve that closes the passage when the hydraulic oil pressure on the pressure chamber side rises above the reservoir chamber is provided in the passage, and the piston is connected to the piston. A bearing that is guided along the inner peripheral surface of the cylinder is attached to the piston rod, and a hole through which hydraulic oil passes is provided in the bearing, so that the piston rod exerts a spring force in a direction that protrudes outside the cylinder. In a hydraulic auto tensioner with a return spring to be applied, a spring is attached between the outer peripheral surface of the sleeve and the inner peripheral surface of the cylinder. The gap is provided, incorporating the above-mentioned return spring to the gap, one end of the return spring as well as engaged with the bearing, the other end is obtained by a structure engaged with the bottom surface of the gap.

[0012] In addition to the above configuration, a configuration in which the bottom of the sleeve is fixed to the cylinder by fixing means, an inner peripheral step is provided at the lower end of the inner peripheral surface of the cylinder, and the inner peripheral step is provided. The bottom surface of the above-mentioned spring mounting gap is formed by the upper surface of the above-mentioned. The outer peripheral step is provided at the lower end of the outer peripheral surface of the above-mentioned sleeve, and the bottom surface of the above-mentioned spring mounting gap is formed by the upper surface of the above-mentioned outer peripheral step. Further, it is possible to adopt a configuration in which the sleeve is fixed to the cylinder bottom by the spring force of the return spring acting on the bottom surface.

[0013] In order to solve the above-mentioned problems, a rod that is pushed in the axial direction when the tension of the belt increases, a return spring that presses the rod toward the slack side of the belt, and an action acting on the rod. And a buffer mechanism for buffering the pushing force.The buffering mechanism has a bottomed sleeve filled with oil, and a piston that moves together with the rod is slidably incorporated into the sleeve, and is inserted into the sleeve. A pressure chamber and a reservoir chamber are formed, a passage for communicating the two chambers with the piston is provided, and a check valve for closing the passage when the pressure of the pressure chamber becomes higher than the pressure of the reservoir chamber is provided in the passage; The return spring may be provided outside the buffer mechanism.

[0014]

[Action]

 According to the above configuration, since the return spring and the sleeve overlap in the length direction of the cylinder, only the entire length of the spring can be increased without increasing the cylinder length. Also, since the spring length can be increased, the spring force can be set large without changing the spring constant.

[0015]

FIG. 1 shows a hydraulic auto-tensioner according to an embodiment. The basic structure of this auto-tensioner is the same as that of the conventional one shown in FIG.

The main difference of this embodiment from the conventional one is that a gap 20 for attaching a spring is provided between the outer peripheral surface of the sleeve 2 and the inner peripheral surface of the cylinder 1, and the return spring 12 is provided in the gap 20. And that the bottom of the sleeve 2 is fixed to the cylinder 1 by fixing bolts 21.

An inner peripheral step 22 is provided at the lower end of the inner peripheral surface of the cylinder 1, and the upper surface of the inner peripheral step 22 forms a bottom surface of the gap 20 and serves as a spring seat 24 at the same time.

One end of the return spring 12 is engaged with the spring seat 24, and the other end is engaged with the bearing 11 connected to the piston rod 9, and applies an outward spring force to the piston rod 9. doing.

In the case of the structure shown in FIG. 3, the sleeve 2 is prevented from coming off by press-fitting to the cylinder. Is integrally fixed to the cylinder 1 to prevent slipping out.

In the above-described structure, the length of the return spring 12 can be increased by the length of the sleeve 2 and the return spring 12 overlapping with each other in the length direction. Therefore, the cylinder length is reduced without increasing the cylinder length. In this state, the overall length of the return spring 12 can be increased, and the spring force can be increased. For example, in the structure of FIG. 1, when the entire length of the return spring 12 is increased so that the spring force is increased by about 50%, compared with the structure shown in FIG. The total length could be reduced to about 70%.

Further, since the entire length of the return spring 12 can be lengthened, the spring constant can be set small, and the spring force of the spring can be made to exactly match the required belt tension value.

FIG. 2 shows another embodiment. In this example, an outer peripheral step 23 is provided at the lower end of the outer peripheral surface of the sleeve 2 ′, and the upper surface of the outer peripheral step 23 forms a bottom surface of the gap 20, and at the same time, serves as a spring seat 25. One end of the return spring 12 is engaged with the spring seat 25, and the other end is engaged with the bearing 11, and applies an outward spring force to the piston rod 9.

Further, since the sleeve 2 ′ is prevented from coming off on the bottom surface of the cylinder 1 ′ by the spring force of the return spring 12, the fixing of the sleeve 2 ′ by the fixing bolt is eliminated. In the structure of this embodiment, since the cylinder 1 'can be made a sealed structure, the sleeve 2' can be formed not in a bottomed cylindrical shape as shown in the figure but in a cylindrical shape with both ends opened.

In any of the above embodiments, when the tension of the belt 19 increases, the tension pulley 16 swings, and the pressing force acting on the piston rod 9 increases. As a result, the piston 3 constituting the buffer mechanism is pushed in, and the hydraulic oil in the pressure chamber 5 leaks into the reservoir chamber 6 from the gap between the piston 3 and the cylinders 1 and 1 ', thereby damping the movement of the piston 3. For this reason, the tension pulley 16 swings slowly and responds to an increase in belt tension.

Conversely, when the tension of the belt 19 decreases, the piston rod 9 protrudes outward due to the spring force of the return spring 12, and when the piston 3 rises following this movement, the pressure in the pressure chamber 5 increases. And the check valve 8 opens the passage 7. For this reason, the hydraulic oil in the reservoir chamber 6 moves to the pressure chamber 5 through the passage 7, and the piston rod 9 projects rapidly, causing the tension pulley 16 to swing quickly in accordance with the movement of the belt. At this time, the piston 3 stops at the balance point between the pressing force acting on the piston rod 9 and the spring force of the return spring 12.

[0026]

【effect】

 As described above, this invention incorporates a return spring outside the sleeve and overlaps the sleeve and the spring in the length direction, so the overall length of the return spring can be increased without increasing the cylinder length, and the compact A simple shape can increase the spring force.

Further, since the total length of the return spring can be increased, the spring force can be set large without changing the spring constant, and there is an advantage that the spring force can be adjusted accurately.

Furthermore, even if air is generated by agitation of the working oil by the return spring, there is an advantage that the air does not easily enter the pressure chamber.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a sectional view of another embodiment.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Cylinder 2, 2' Sleeve 3 Piston 4 Hydraulic oil chamber 9 Piston rod 12 Return spring 20 Interval 21 Fixing bolt 22 Step 23 Step 24 Spring seat 25 Spring seat

Claims (5)

[Utility model registration claims] A hydraulic oil chamber in a cylinder is divided into a pressure chamber and a reservoir chamber by a piston slidably inserted in the sleeve. A piston is slidably inserted into the sleeve. In addition to forming a passage communicating with the chamber, a check valve for closing the passage when the hydraulic oil pressure on the pressure chamber side increases from the reservoir chamber is provided in the passage, and a piston rod connected to the piston is provided with a piston rod of the cylinder. A hydraulic type in which a bearing guided along the inner peripheral surface is mounted, a hole through which hydraulic oil passes is provided in the bearing, and a return spring is attached to the piston rod to apply a spring force in a direction protruding outside the cylinder. In the auto tensioner, a spring mounting gap is provided between the outer peripheral surface of the sleeve and the inner peripheral surface of the cylinder, and A hydraulic spring, wherein one end of the return spring is engaged with the bearing and the other end is engaged with the bottom surface of the gap. 2. The hydraulic auto-tensioner according to claim 1, wherein the bottom of the sleeve is fixed to the cylinder by fixing means. 3. The cylinder according to claim 1, wherein an inner peripheral step is provided at a lower end of the inner peripheral surface of the cylinder, and a bottom surface of the spring mounting gap is formed by an upper surface of the inner peripheral step.
The hydraulic auto tensioner according to 1. 4. An outer peripheral step is provided at a lower end of an outer peripheral surface of the sleeve, and the upper surface of the outer peripheral step forms a bottom surface of the spring mounting gap. The hydraulic auto-tensioner according to claim 1, wherein the sleeve is fixed to a cylinder bottom. 5. A rod which is pushed in the axial direction when the tension of the belt is increased, a return spring which pushes the rod toward the slack side of the belt, and a buffer mechanism which buffers a pushing force acting on the rod. The buffer mechanism has a bottomed sleeve filled with oil, and a piston that moves with the rod is slidably incorporated in the sleeve to form a pressure chamber and a reservoir chamber in the sleeve. A passage connecting both chambers is provided,
A hydraulic auto-tensioner in which a check valve is provided in the passage to close the passage when the pressure in the pressure chamber becomes higher than the pressure in the reservoir chamber, and the return spring is provided outside the buffer mechanism.