JPH10299846A - Hydraulic type automatic tensioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a tension pulley from being inclined, also prevent the occurrence of partial abrasion over a thrust bearing surface at a fulcrum bearing part supporting an arm in such a way as to be freely rocked. SOLUTION: A tension pulley 5 is rotatably mounted to the rocking side end part of an arm 1 mounted to an engine block 4 in such a way as to be freely rocked. The rod 10 of an actuator 6 is connected with the arm 1, the arm 1 is pressed in one direction by the elastic force of a tension adjusting spring 12 permitting the rod 10 to be projected outward, and the tension pulley 5 is thereby pressed against a belt. The center axis of the rod 10 in the actuator 6 and the center line in width of the tension pulley 5 are arranged over the same plane, and the arm 1 is thereby prevented from being subjected to bending moment, the tension pulley is prevented from being inclined, and the occurrence of partial abrasion in a fulcrum bearing part at the rocking center of the arm 1, is also 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 mainly used for adjusting a tension of a belt for driving an auxiliary machine such as an alternator.

[0002]

2. Description of the Related Art A tension pulley is rotatably mounted on a swinging end of an arm which is swingably mounted on an engine block, and an arm is attached to the arm in a direction in which the tension pulley stretches a belt by an actuator connected to the arm. A hydraulic auto-tensioner in which the tension of the belt is kept constant by urging is described in U.S. Pat. No. 4,790,801 or Japanese Patent Publication No. Hei 2-500210.

An actuator incorporated in the hydraulic auto tensioner inserts a rear end portion of a rod into a cylinder filled with hydraulic oil, applies elasticity of a tension adjusting spring to the rod, and applies an elastic force to the rod outward. And the hydraulic pushing force acting on the rod is buffered by a hydraulic damper mechanism built in the cylinder. The tension adjustment spring and the hydraulic damper mechanism cause the belt tension fluctuation. To keep the belt tension constant.

[0004]

By the way, in the hydraulic auto tensioner described in the above specification and publication, the center of the width of the tension pulley and the center axis of the rod in the actuator are displaced in the width direction of the tension pulley. As a result, the arm tends to tilt due to moment load acting on the arm, and the tilt of the arm causes the tension pulley to tilt, causing the belt to hit one side, causing the belt to wear unevenly or to be fed sideways. There is.

Further, there is a disadvantage that uneven wear is apt to occur on a thrust bearing surface of a fulcrum bearing portion that supports the arm so that the arm can swing freely due to a moment load acting on the arm.

Further, since the tension adjusting spring provided on the actuator is provided inside the cylinder, the size of the spring itself is limited, and a case where a high belt tension is required or a variation in the tension application is reduced. Therefore, there is a disadvantage that the coil diameter of the tension adjusting spring cannot be adopted in a layout in which the coil diameter is increased and the spring constant is set low.

A first object of the present invention is to prevent inclination of a tension pulley and uneven wear on a thrust bearing surface of a fulcrum bearing for supporting an arm so that the arm can swing. Another object of the present invention is to provide a hydraulic auto tensioner.

Another object of the present invention is to provide a hydraulic auto-tensioner which can be laid out when a high belt tension is required or when the spring constant is set low.

[0009]

According to a first aspect of the present invention, there is provided an arm supported by a fixed portion so as to be swingable, and a rotating end provided on a swinging end of the arm. A tension pulley freely supported, and an actuator for urging the arm in a direction in which the tension pulley presses the belt, the actuator comprising a cylinder in which hydraulic oil is sealed, and a rear cylinder in the cylinder. A rod having an end slidably inserted therein, a tension adjusting spring for providing the rod with an outwardly projecting property, and a hydraulic damper mechanism incorporated in the cylinder to buffer a pushing force applied to the rod. In the hydraulic auto tensioner formed by the above, the center axis of the rod in the actuator and the width center line of the tension pulley are arranged on the same plane. It is adopted.

In order to solve the second problem, a second
According to the invention, the tension adjusting spring according to the first invention is provided outside the cylinder.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an arm 1 has a fulcrum shaft 2
It is supported so as to be able to swing around. Here, the fulcrum shaft 2 is fixed to an engine block 4 as a fixing portion shown in FIG.

A tension pulley 5 is rotatably supported at the swinging end of the arm 1, and the tension pulley 5 is connected to a belt 7 by an actuator 6 connected to the arm 1.
Is pressed against.

As shown in FIG. 2, the actuator 6
An oil seal 9 is attached to an upper opening of the cylinder 8, and a hydraulic oil and an air layer are sealed on the oil surface inside the oil seal 9. 11, the rod 10 is provided with an outward projecting property by a tension adjusting spring 12.

In this case, the hydraulic damper mechanism 11
The plunger 13 connected to the lower end of the plunger 13 is slidably incorporated in a sleeve 14 fitted to the lower part of the cylinder 8, and a pressure chamber 15 formed below the plunger 13 and a reservoir chamber 16 provided above the plunger 13. Are communicated through a passage 17 formed in the plunger 13, and a check valve 18 is attached to the passage 17. The check valve 18 is connected to the pressure chamber 1
When the pressure in the chamber 5 becomes higher than the pressure in the reservoir chamber 16, the passage 17 is closed, and the hydraulic oil in the pressure chamber 15 is prevented from flowing from the passage 17 to the reservoir chamber 16. 19 is plunger 1
3 shows a spring pressing the rod 3 against the rod 10.

The tension adjusting spring 12 is provided outside the cylinder 8, and the lower end thereof is received by a flange 20 provided on the lower part of the outer periphery of the cylinder 8, and the upper end thereof is in contact with a spring seat 21 attached to the upper end of the rod 10. The rod 10 comes into contact with the rod 10 so as to protrude outward.

In the actuator 6 having the above-described structure, the cylinder 8 penetrates a projecting piece 22 provided at the lower end thereof, and is supported swingably around a bolt 23 screwed into the engine block 4. The rod 10
The protruding piece 24 provided on the spring seat 21 is rotatably connected to a bolt 25 screwed into the arm 1.

In mounting the actuator 6 as described above, the actuator 6 is mounted such that the center axis a and the width center line b of the tension pulley 5 are arranged on the same plane on the rod 10.

In the hydraulic auto-tensioner having the above-described configuration, when the tension of the belt 7 changes due to the torque fluctuation and the belt 7 becomes slack, the rod 10 moves outward by the elastic force of the tension adjusting spring 12. The arm 1 swings in the direction in which the tension pulley 5 stretches the belt 7.

At this time, the plunger 1 together with the rod 10
3 moves upward, and the pressure in the pressure chamber 15 becomes lower than the pressure in the reservoir chamber 16. Therefore, the check valve 18 opens the passage 17, and the hydraulic oil in the reservoir chamber 16 is released from the pressure chamber 1.
Flow into 5.

For this reason, the rod 10 moves rapidly outward, and the tension pulley 5 immediately absorbs the slack of the belt 7.

On the other hand, when the tension of the belt 7 increases, the tension pulley 5 is pressed by the belt 7. At this time, since the arm 1 presses the rod 10 of the actuator 6, the pressure in the pressure chamber 15 becomes higher than the pressure in the reservoir chamber 16, and the check valve 18 closes the passage 17. By rod 1
The pushing force applied to zero is buffered.

When the static pushing force applied to the rod 10 is higher than the elastic force of the tension adjusting spring 12, the pressure chamber 15
Hydraulic oil in the inner part is formed by the outer peripheral surface of plunger 13 and sleeve 14.
Leaks into the reservoir chamber 16 from the minute gap between the inner peripheral surfaces of the plunger 13 and the plunger 13 retreats to a position where the elastic force of the tension adjusting spring 12 and the pushing force are balanced.

As described above, the tension pulley 5 moves quickly in the direction in which the belt 7 is stretched when the belt 7 is slackened, and moves backward slowly when the belt 7 is tensioned.
The followability of the tension pulley 5 to the change in the tension of the belt 7 is good, and the tension of the belt 7 can be always kept constant.

In the tension adjustment of the belt 7 as described above, the center axis a of the rod 10 in the actuator 6 and the width center line b of the tension pulley 5 are arranged on the same plane. And the pressing force of the tension adjusting spring 12 of the actuator 6 pressing the arm 1 via the rod 10 acts on the same plane. Are equal in the opposite direction, no moment load is generated on the arm 1.

Therefore, there is no inconvenience that the tension pulley 5 is tilted together with the arm 1, and uneven wear of the belt 7 and lateral feeding of the belt 7 can be prevented.

Further, it is possible to prevent uneven wear on the thrust bearing surface of the fulcrum bearing portion which supports the arm 1 so as to be swingable.

As shown in the embodiment, the tension adjusting spring 1
If 2 is provided outside the cylinder 8, the size of the tension adjusting spring 12 is not limited. For this reason, the belt tension can be increased by using the tension adjusting spring 12 having a strong spring force.

Further, by using the tension adjusting spring 12 having a large coil diameter and a low spring constant, it is possible to reduce the variation in the application of the tension and to improve the life of the belt 7.

[0030]

As described above, according to the present invention, since the center axis of the rod and the width center line of the tension pulley in the actuator are arranged on the same plane, the moment load is applied to the swingably supported arm. Can be prevented, and uneven wear and lateral running of the belt due to the inclination of the tension pulley can be prevented.

In addition, it is possible to prevent uneven wear on the thrust bearing surface of the fulcrum bearing portion that supports the arm so that it can swing.

Further, by providing the tension adjusting spring outside the cylinder, the size of the tension adjusting spring is less likely to be limited, and the tension adjusting spring can be used when a high belt tension is required or when the spring constant is set low. Layout can be enabled.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

[Description of Signs] 1 Arm 4 Engine Block 5 Tension Pulley 6 Actuator 7 Belt 8 Cylinder 10 Rod 11 Hydraulic Damper Mechanism 12 Tension Adjusting Spring

Claims (2)

[Claims] 1. An arm pivotally supported by a fixed portion, a tension pulley rotatably supported by a pivot end of the arm, and the arm in a direction in which the tension pulley presses a belt. The actuator comprises a cylinder in which hydraulic oil is sealed, a rod having a rear end slidably inserted in the cylinder, and an outwardly projecting property of the rod. In a hydraulic auto-tensioner formed by a tension adjusting spring to be applied and a hydraulic damper mechanism incorporated in the cylinder and buffering a pushing force applied to the rod, the center axis of the rod in the actuator and the tension pulley A hydraulic auto-tensioner, wherein a width center line and a center line are arranged on the same plane. 2. The hydraulic auto-tensioner according to claim 1, wherein the tension adjusting spring is provided outside a cylinder.