JPH0624599Y2 - Sealed auto tensioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a sealed auto tensioner.

[Conventional technology]

Japanese Patent Laid-Open No. 59-126144 discloses a sealed auto tensioner suitable for use in a timing belt for a camshaft of an internal combustion engine. The hermetically-sealed autotensioner includes a plunger slidably inserted in the housing, a piston rod slidably inserted in the hollow portion of the plunger, and a piston rod formed in the hollow portion of the plunger below the piston rod. Equipped with a hydraulic chamber, a reservoir formed below the plunger in the housing, and an oil passage formed in the plunger in the radial direction from the hydraulic chamber, and operates when force is applied to the piston rod from the outside. The oil flows from the pressure chamber through the radial oil passage and the clearance between the housing and the plunger to the reservoir, and the minute clearance causes the oil flow to resist and thereby act as an oil damper. Has become.

[Problems to be solved by the invention]

In the sealed auto tensioner as described above, the working oil is enclosed in the hydraulic chamber and the reservoir, so that it is not necessary to supply the oil when using. A seal is thus used to seal the hydraulic oil. The seal is mounted in a compressed state and placed on the sliding portion. The seal itself forms the sliding surface. Therefore, if the mating sliding surface is scratched, the seal will be damaged. By the way, in the above-mentioned automatic tensioner, the piston rod can be projected to the outside from the end opening of the housing and can be engaged with the belt or the like. The piston rod moves up and down to adjust the belt tension,
Therefore, it is formed slidably with respect to the plunger. However, the piston rod slides on the plunger in the lower half and the upper half is free. When engaged with a belt or the like, the piston rod also receives a lateral force at its free upper end, which causes the lower half slides to tilt relative to each other. For this reason, there has been a problem that the sliding parts are mutually galled and the sliding surface is damaged. If the sliding surface is damaged, the seal will be damaged as described above.

[Means for solving problems]

The sealed autotensioner according to the present invention comprises a plunger slidably inserted into a housing, a piston rod slidably inserted into a hollow portion of the plunger, and a piston rod below the piston rod in the hollow portion of the plunger. A hydraulic chamber formed therein, a reservoir formed below the plunger in the housing, and an oil passage formed in the plunger in a radial direction from the hydraulic chamber, wherein the piston rod has an end opening portion of the housing. And the clearance between the end opening of the housing and the piston rod is smaller than the clearance between the sliding portion between the plunger and the piston rod.

〔Example〕

FIG. 2 shows a belt transmission device for a camshaft of an internal combustion engine. An endless timing belt 10 is stretched between a crank pulley 12 and cam pulleys 14 and 16, and an idler tension pulley 18 is arranged between the pulleys. Two
The idler tension pulleys 18 are mounted at fixed positions, but one idler tension pulley 18 is supported by a pivot arm 20 which is rotatable about one point as a fulcrum and can move according to the belt tension. A seal type auto tensioner 22 is arranged so as to engage with the pivot arm 20.

As shown in FIG. 1, a sealed auto tensioner 22.
Comprises a cylindrical housing 24 having one end open, a hollow cylindrical plunger 26 slidably inserted into the housing 24, and a piston rod 28 slidably inserted into the plunger 26. Piston rod 28
The upper end of the is protruded from the housing 24 and can be engaged with the pivot arm 20. Plunger 2
A hydraulic chamber 30 is formed below the piston rod 28 in the hollow part of 6, and a reservoir 32 is formed below the plunger 26 inside the housing 24. Plunger 2
6 is formed with a radial hole 34 extending from the hydraulic chamber 30 to the outer peripheral portion thereof, which increases the pressure in the hydraulic chamber 30 when a force is applied to the piston rod 28 from the outside, so that the plunger 26 The working oil in the internal hydraulic chamber 30 flows to the reservoir 32 through the radial hole 34 and the minute clearance between the inner peripheral portion of the housing 24 and the outer peripheral portion of the plunger 26. Since the clearance between the housing 24 and the plunger 26 is small, the oil can only flow in small amounts, and therefore even if the piston rod 28 receives a large force, the piston rod 28
Can only move slowly, thus forming an oil damper and dampening the movement of the piston rod 28.

A small hole 36 is formed in the bottom wall of the plunger 26, and a check ball 38 that allows only the flow from the reservoir 32 to the hydraulic chamber 30 is arranged therein. That is, the check ball 38 is urged by the spring 40 and the small hole 3
The opening 6 on the hydraulic chamber 30 side is closed.
Therefore, when the piston rod 28 rises, the hydraulic chamber 3
When the zero pressure drops, the oil can return to the hydraulic chamber 30 through the eyelet 36.

The plunger 26 has a stepped outer shape, and the upper outer shape is small. The spring 42 is arranged between a spring seat 44 arranged on the step portion of the plunger 26 and a spring seat 46 fixed to the housing 24, and urges the plunger 26 downward toward the reservoir side. The spring 42 pushes the piston rod 28 through the oil in the reservoir 32 and the hydraulic chamber 30 to apply a predetermined tension to the belt. That is, when the belt pushes the piston rod 28 downward, the pressure in the hydraulic chamber 30 rises, so that the oil moves from the hydraulic chamber 30 to the reservoir 3 while buffering the movement of the piston rod 28 as described above.
2 to increase the pressure in the reservoir 32. When the pressure in the reservoir 32 rises, the plunger 26 moves upward and stops when it balances the spring force of the spring 42. This is equivalent to the spring 42 acting on the piston rod 28. The larger the force applied to the piston rod 28, the larger the displacement of the spring 42, and the smaller the force applied to the piston rod 28, the smaller the displacement of the spring 42. Get smaller. In this way, the tension of the belt is automatically adjusted.

Further, a seal 48 is arranged between the housing 24 and the plunger 26, and a seal 50 is arranged between the plunger 26 and the piston rod 28. These seals 48 and 50 are formed of a seal member having an X-shaped cross section and seal the respective sliding portions.

The housing 24 is an upper body 24A screwed to each other.
And the lower body 24B, the upper body 24A can be coupled to the lower body 24B after the plunger 26 and the piston rod 28 are attached to the lower body 24B. An upper end of the upper body 24A is a flat plate-shaped end wall 52, and an end opening 54 for passing the piston rod 28 is formed in the end wall 52. The spring seat 46 for the spring 42 described above is formed as the inner surface of the end wall 52.

In the present invention, the diameter of the end opening 54 is relatively small, and the clearance between the end opening 54 of the housing 24 and the piston rod 28 is smaller than the clearance at the sliding portion between the plunger 26 and the piston rod 28. It is getting smaller. Therefore, when the piston rod 28 receives a force from a belt or the like and the component of the lateral force is contained therein, the piston rod 28 hits the inner surface of the end opening 54 of the housing 24, and the piston rod 28 is pushed by the plunger. 26 to prevent tilting. Therefore, the sliding portion between the plunger 26 and the piston rod 28 is not damaged, and thus the seal 50 is not damaged.

[Effect of device]

As described above, according to the present invention, it is possible to obtain a hermetically-sealed automatic tensioner having excellent seal durability.

[Brief description of drawings]

FIG. 1 is a sectional view showing a hermetically-sealed automatic tensioner according to the present invention, and FIG. 2 is a view showing a camshaft transmission of an internal combustion engine to which the automatic tensioner of FIG. 1 is attached. 10 ... Belt, 22 ... Auto tensioner, 24 ... Housing, 26 ... Plunger, 28 ... Piston rod, 30 ... Hydraulic chamber, 32 ... Reservoir, 54 ... End opening.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Yoshio Okabe 2-1, Asahi-cho, Kariya city, Aichi Aisin Seiki Co., Ltd. (72) Creator Yukori Kobayashi 2-1-1, Asahi-machi, Kariya city, Aichi prefecture Within Seiki Co., Ltd. (56) Reference JP-A-61-294249 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A plunger slidably inserted in a housing, a piston rod slidably inserted in a hollow portion of the plunger, and a hydraulic pressure formed below the piston rod in the hollow portion of the plunger. A chamber, a reservoir formed below the plunger in the housing, and an oil passage formed in the plunger in a radial direction from the hydraulic chamber, the piston rod projecting outward from an end opening of the housing. A sealed autotensioner characterized in that a clearance between an end opening of the housing and a piston rod is smaller than a clearance at a sliding portion between the plunger and the piston rod.