JPH11101319A - Hydraulic auto tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic auto tensioner preventing a cylinder external diametric surface from wearing due to contact with a tension adjusting spring to be excellent in responsiveness by a change of tension of a bolt. SOLUTION: An upper part opening of a cylinder 1 is sealed by mounting an oil seal 2, and in an upper part of a rod 3 inserted able to slide in this oil seal 2, a spring seat 4 is provided. In the inside of the cylinder 1, a hydraulic damper 10 is assembled, which shock absorbs press in force in the case that the cylinder 1 and the rod 3 are pressed in the direction relatively contracting. An end part of a tension adjusting spring 6 provided outside the cylinder 1 is received by the spring seat 4, the cylinder 1 and the rod 3 are pressed in the direction reverse to each other. In the spring seat 4, a cover 7 is provided, the end part of the tension adjusting spring 6 is prevented from moving in the diametric direction of the cylinder 1, an external diametric surface of the cylinder 1 is prevented from wearing by contact with the spring 6, also when the tension adjusting spring 6 is extended/contracted, hooking is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic auto-tensioner for maintaining a constant tension of a belt for driving an auxiliary machine such as an alternator.

[0002]

2. Description of the Related Art As this type of hydraulic auto-tensioner, the one already proposed by the present applicant has been known (Japanese Utility Model Laid-Open No. 5-10849).

In the above-mentioned hydraulic auto-tensioner, a rod is slidably penetrated through an oil seal for sealing an upper opening of a cylinder, and an elastic force of a tension adjusting spring is applied to the rod to provide an outward projecting property. ing.

Further, when the rod is pushed in due to an increase in the tension of the belt, the pushing force is buffered by a hydraulic damper provided inside the cylinder.

In the above-mentioned hydraulic auto tensioner,
Since the tension adjustment spring that gives the rod an outward projection is provided outside the cylinder, the spring constant is smaller than that of a hydraulic auto tensioner that incorporates a tension adjustment spring inside the cylinder. In addition, a tension adjusting spring having a large spring load can be used, and the responsiveness of the hydraulic auto tensioner can be improved.

[0006]

However, in the above-mentioned hydraulic auto tensioner, there is a possibility that the tension adjusting spring may expand and contract in a state of contact with the outer diameter surface of the cylinder due to a change in the tension of the belt or the vibration of the belt. At this time, the outer diameter surface of the cylinder is worn due to contact with the tension adjustment spring, or the tension adjustment spring is caught in expansion and contraction, which hinders the response of the auto tensioner to changes in belt tension. There is something left to do.

SUMMARY OF THE INVENTION It is a technical object of the present invention to improve a spring-mounted hydraulic auto-tensioner, prevent wear of a cylinder, and suppress a decrease in responsiveness.

[0008]

In order to solve the above-mentioned problems, according to the present invention, an upper opening of a cylinder filled with hydraulic oil is sealed by mounting an oil seal,
A spring seat is provided on the upper portion of a rod that slidably penetrates the oil seal, and the elastic force of a tension adjusting spring provided outside the cylinder is applied to the spring seat to press the rod and the cylinder in opposite directions. A hydraulic auto-tensioner configured to buffer a pushing force when the rod and the cylinder are pressed in a direction in which the rod and the cylinder are relatively contracted by a hydraulic damper provided in the cylinder; A configuration is employed in which a cylindrical cover for preventing the upper end from moving in the radial direction of the cylinder is provided.

In addition, a configuration is employed in which a bulging portion for preventing the lower end of the tension adjusting spring from moving in the radial direction of the cylinder is provided on a spring seat provided at a lower portion of the outer periphery of the cylinder.

Here, the cylindrical cover may be disposed between the tension adjusting spring and the cylinder, or may be fitted outside the tension adjusting spring.

In the hydraulic damper, a plunger slidable along the inner diameter surface of the cylinder is connected to the lower end of the rod, and the plunger has a pressure chamber formed below the plunger and a reservoir chamber provided above the plunger. To form a passage communicating with
A configuration in which a check valve for preventing the hydraulic oil in the pressure chamber from flowing into the reservoir chamber is provided in the passage may be employed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG.
Is filled with hydraulic oil, and the upper opening is sealed by mounting an oil seal 2.

A spring seat 4 is attached to an upper part of a rod 3 which slidably penetrates the oil seal 2, and a spring seat 5 is provided between the spring seat 4 and a spring seat 5 provided at a lower part of the outer periphery of the cylinder 1.
A tension adjusting spring 6 for pressing the cylinder 1 and the rod 3 in opposite directions is incorporated.

A cylindrical cover 7 is provided on the spring seat 4 on the rod side.
Is provided. The cover 7 is arranged between the cylinder 1 and the tension adjusting spring 6 and covers an upper opening of the cylinder 1. On the other hand, on the cylinder-side spring seat 5, there is provided an annular bulging portion 8 for preventing the lower end of the tension adjusting spring 6 from moving in the radial direction of the cylinder 1.

A hydraulic damper 10 is incorporated in the cylinder 1 to buffer the pressing force when the cylinder 1 and the rod 3 are pressed in a direction of relatively contracting.

The hydraulic damper 10 has a lower end of the rod 3 connected to a plunger 11 slidable along the inner diameter surface of the cylinder 1, and a pressure chamber 12 and a reservoir chamber 13 inside the cylinder 1.
The plunger 11 is provided with a passage 14 for communicating the pressure chamber 12 and the reservoir chamber 13, and a check valve 15 for preventing the hydraulic oil in the pressure chamber 12 from flowing into the reservoir chamber 13 is provided in the passage 14. I have.

In the figure, reference numeral 16 denotes a perforated wear ring for guiding the axial movement of the rod 3.

FIG. 2 shows an example of the use of the hydraulic auto-tensioner having the above structure. A spring seat 4 provided at the upper end of a rod 3 is connected to an engine block and a cylinder 1
Is connected to one end of a pulley arm 21 that is swingably supported about a shaft 20. A tension pulley 22 is rotatably supported at the other end of the pulley arm 21, and the tension pulley 22 is pressed against the belt 23 by a pressing force of the tension adjusting spring 6 of the hydraulic auto tensioner pressing the pulley arm 21.

In the above-described operating state of the hydraulic auto-tensioner, the tension of the belt 23 changes due to the fluctuation of the torque, and when the tension of the belt 23 increases, the cylinder 1 is pressed upward via the pulley arm 21. .

At this time, since the pressure in the pressure chamber 12 is higher than that in the reservoir chamber 13, the check valve 15 is
Is closed, and the upward pressing force applied to the cylinder 1 by the hydraulic oil sealed in the pressure chamber 12 is buffered.

When the pressing force for pressing the cylinder 1 is stronger than the elastic force of the tension adjusting spring 6, the hydraulic oil in the pressure chamber 12
Leakage occurs between the sliding surfaces of the cylinder 1 and the plunger 11 into the reservoir chamber 13, and the cylinder 1 slowly moves to a position where the elastic force of the tension adjusting spring 6 and the pressing force are balanced.

When the belt 23 becomes slack, the cylinder 1 moves downward by the elastic force of the tension adjusting spring 6, and the pulley arm 21 swings in the direction in which the tension pulley 22 stretches the belt 23.

At this time, since the pressure in the pressure chamber 12 becomes lower than the pressure in the reservoir chamber 13, the check valve 15 opens the passage 14, and the hydraulic oil in the reservoir chamber 13 flows from the passage 14 to the pressure chamber 12. For this reason, the cylinder 1 descends rapidly, and the tension pulley 22 swings rapidly in the direction of stretching the belt 23 to immediately absorb the slack of the belt 23.

When the tension of the belt 23 is adjusted as described above, the tension adjusting spring 6 repeats expansion and contraction due to a change in the tension of the belt 23 or vibration. In this case, if the tension adjusting spring 6 is in contact with the outer diameter surface of the cylinder 1, the cylinder 1 is worn or the tension adjusting spring 6 is caught and loses its function as a spring, and the tension of the belt 23 is reduced. Responsiveness to change is poor.

However, the tension adjusting spring 6 is held in a non-contact state with the outer diameter surface of the cylinder 1 by the cover 7 provided on the rod-side spring seat 4 and the bulging portion 8 provided on the cylinder-side spring seat 5. Therefore, wear of the cylinder 1 can be prevented, and a response delay due to the catch of the tension adjusting spring 6 can be prevented.

In the embodiment, the cover 7 provided on the spring seat 4 has a size that can be inserted between the cylinder 1 and the tension adjustment spring 6. However, the cover 7 may have a size that can be fitted outside the tension adjustment spring 6. .

[0027]

As described above, according to the present invention, the spring seat provided on the upper portion of the rod is provided with the cover disposed between the tension adjusting spring and the cylinder, so that the outer surface of the cylinder is brought into contact with the tension adjusting spring. It is possible to suppress abrasion of the radial surface and prevent a response delay due to the catch of the tension adjusting spring.

Further, since the cover covers the upper opening of the cylinder, it is possible to more reliably prevent dust from entering the inside of the cylinder.

Further, by providing the bulging portion on the spring seat provided on the cylinder, wear of the outer diameter surface of the cylinder due to contact with the tension adjusting spring can be more reliably prevented, and excellent responsiveness is obtained. An auto tensioner can be provided.

[Brief description of the drawings]

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

FIG. 2 is a front view showing a use state of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Oil seal 3 Rod 4 Spring seat 5 Spring seat 6 Tension adjusting spring 7 Cover 8 Swelling part 10 Hydraulic damper

Claims (2)

[Claims] An oil seal is provided to seal an upper opening of a cylinder filled with hydraulic oil, an oil seal is provided, a spring seat is provided on an upper portion of a rod slidably penetrating the oil seal, and tension is provided on the outside of the cylinder. The elastic force of the adjusting spring is applied to the spring seat to press the rod and the cylinder in opposite directions, and the pushing force when the rod and the cylinder are pressed in the direction of relative contraction is applied to the inside of the cylinder. In a hydraulic auto tensioner configured to buffer by a hydraulic damper provided, a hydraulic cover is provided on the spring seat so as to prevent a top end of a tension adjusting spring from moving in a radial direction of the cylinder. Type auto tensioner. 2. The swelling portion for preventing a lower end of a tension adjusting spring from moving in a radial direction of a cylinder is provided on a spring seat provided at a lower portion of an outer periphery of the cylinder. Hydraulic auto tensioner.