JPH0744839Y2 - Auto tensioner - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an autotensioner that keeps the tension of a belt or a chain constant.

[Conventional technology]

Generally, in a belt transmission device that transmits the rotation of an automobile engine to an automobile accessory such as an alternator, the tension of the belt is kept constant by using an auto tensioner for the purpose of improving the life of the belt and reducing noise. There is.

As the prior art of the above-mentioned auto tensioner, the actual breaker 63-17
There is one disclosed in Japanese Patent No. 5341. In this auto tensioner, as shown in FIG. 5, one end of a piston rod 31 incorporated inside the body 30 is fixed to the body 30, and the piston 32 is fixed to the other end of the piston rod 31. Cylinder 33 inserted with a small clearance outside piston 32
Is provided slidably along the inner surface of the body 30, and the cylinder 33 is pushed outward by a tension adjusting spring 34 incorporated inside the body 30.

Further, the inside of the body 30, the piston front chamber 35 and the piston rear chamber 36 are filled with hydraulic oil, and the piston rod 31
And the passage 37 formed in the piston 32, the piston front chamber 35
And a piston rear chamber 36 are communicated with each other, and a check valve 38 attached to the passage 37 prevents hydraulic fluid in the piston front chamber 35 from flowing to the piston rear chamber 36.

In the above auto tensioner, the tip of the cylinder 33 is brought into contact with the pulley arm 41 that is swingably supported about the pin 40, and the pulley arm 41 is deflected in one direction by the spring force of the tension spring 34. The supported tension pulley 42 is pressed against the belt 43, and the change in tension of the belt 43 is changed by the hydraulic oil inside the piston front chamber 35 and the tension adjusting spring 34.
The tension of the belt 43 is kept constant by absorbing the tension of the belt 43.

Here, in the auto tensioner shown in FIG. 5, since the hydraulic oil flows between the piston front chamber 35 and the piston rear chamber 36, the belt 36 is contaminated or deteriorated due to the adhesion of the hydraulic oil. It is possible to prevent the occurrence of such inconvenience.

[Problems to be solved by the device]

By the way, in the above-mentioned conventional autotensioner, since the inside of the body 30, the piston front chamber 35, and the piston rear chamber 36 are each filled with hydraulic oil, a large amount of hydraulic oil is required. In addition, the piston front chamber 35 due to expansion and contraction due to the temperature change of the hydraulic oil and movement of the cylinder 33
Since the volume change of the hydraulic oil is absorbed by the deformation of the diaphragm D of the reservoir chamber 39 provided at the rear end of the body 30, when the stroke amount of the cylinder 33 becomes large, it must be absorbed. Not possible, diaphragm D
Has the inconvenience of being damaged.

Further, the piston 32 is fixed to the piston rod 31 fixed to the body 30, and the cylinder 33 inserted outside the piston 32 is slidably inserted into the body 30. It is difficult to achieve coaxiality between the 33. For this reason, there is an inconvenience that twisting or an unnecessary radial load acts between the piston 32, the cylinder 33, and the body 30, resulting in malfunction or deterioration in durability. Further, in combination with the large number of parts, there is also a disadvantage that the assembly is very troublesome.

Therefore, the present invention solves the above-mentioned inconvenience, can easily absorb the change in the amount of hydraulic oil in the reservoir chamber, and can achieve stable operation, which is a sealed type with a small number of parts and easy to assemble. The technical issue is to provide an auto tensioner.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, in the present invention, a plunger is slidably inserted into a plunger insertion hole formed in a lower portion of the body and is opened in an axially formed insertion hole from an upper surface of the plunger. Between the lower closed end of the guide cylinder and the closed end of the plunger, insert the lower part of the guide cylinder, which has a closed end in the lower part and the inside is the reservoir chamber, with a small clearance between it and the inner peripheral surface of the insertion hole. Each of the hydraulic chamber and the lower part of the reservoir chamber formed in the above is filled with hydraulic oil to provide an air layer on the operating surface of the reservoir chamber, and the guide cylinder is connected to the internal reservoir chamber and the minute clearance in the radial direction. Is formed in the guide cylinder, and a passage communicating with the hydraulic chamber is formed at the closed end of the guide cylinder, and a check valve for preventing hydraulic oil from flowing from the hydraulic chamber to the reservoir chamber is attached to this passage. The spring receiver provided on the outer peripheral upper, it was adopted a structure incorporating a tensioning spring between the spring bearing and the plunger upper end.

[Action]

As described above, by filling the lower part of the reservoir chamber with the hydraulic oil, the change in the amount of the hydraulic oil in the reservoir chamber can be absorbed very easily by the air layer formed on the upper part of the reservoir chamber.

Further, since the guide tube is not fixed to the body, the body, the plunger and the guide tube are automatically aligned by incorporating the guide tube, the tension adjusting spring and the plunger in order inside the body. Therefore, the sliding surface of the plunger is not twisted or an unnecessary radial load is not generated, and stable operation can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 2 shows a first embodiment of the auto tensioner according to the present invention. As shown in the figure, the body 1 is formed with a plunger insertion hole 2 which opens at the lower surface of the body 1, and the plunger 3 inserted inside the plunger insertion hole 2 is attached to the inner circumference of the plunger insertion hole 2 and is attached to the sliding surface. It is slidable along the inner surface of the bearing 4.

A retaining ring 5 is attached to the lower portion of the inner periphery of the plunger insertion hole 2, and the retaining ring 5 and a shoulder portion 6 provided on the lower portion of the outer periphery of the plunger 3 abut each other to prevent the plunger 3 from coming off.

The plunger 3 is formed with an axial insertion hole 7 that opens on the upper surface, and the lower part of the guide cylinder 8 is inserted inside the insertion hole 7. A minute clearance 9 is provided between the outer peripheral surface of the guide cylinder 8 and the inner peripheral surface of the insertion hole 7.

Further, a seal groove 10 is formed on the inner peripheral upper part of the insertion hole 7,
The seal member 11 attached to the seal groove 10 is in close contact with the outer circumference of the guide cylinder 8 to seal the space therebetween.

The lower end of the guide cylinder 8 is closed, and a hydraulic chamber 13 is formed between the closed end 12 and the bottom surface of the insertion hole 7. On the other hand, the guide tube 8
The inside of the chamber is defined as a reservoir chamber 14, and the reservoir chamber 14 and the minute clearance 9 are formed in a radial hole 15 formed in the guide cylinder 8.
It communicates with. Further, the reservoir chamber 14 and the hydraulic chamber 13 are
A check valve 17 provided in the passage 16 is connected to the passage 16 formed in the closed end 12 of the guide cylinder 8 to prevent the hydraulic oil sealed in the hydraulic chamber 13 from flowing from the passage 16 to the reservoir chamber 14. .

Here, a predetermined amount of hydraulic oil is filled in the lower portion of the reservoir chamber 14, and the hydraulic oil is an air reservoir. The above-mentioned hydraulic oil is filled through the injection hole 18 formed in the upper end of the body 1, and the injection hole 18 is closed by screwing the plug body 19.

A spring bearing 20 is provided above the outer diameter of the guide cylinder 8, and a tension adjusting spring 21 is incorporated between the spring bearing 20 and the upper end of the plunger 3.

The plunger 3 is pushed down by the spring force of the tension adjusting spring 21.

FIG. 1 shows an example of use of the automatic tensioner having the above-mentioned structure. The automatic tensioner is arranged above one end of a roller arm 41 which is swingably supported about a pin 40. This auto tensioner is arranged with the hydraulic chamber 13 on the lower side, and the lower end of the plunger 3 is the roller arm.
The roller arm 41 is brought into contact with the other end of the roller 41 and pushes down the plunger 3 so that the roller arm 41 is deflected in one direction and is supported by the other end of the roller arm 41 so that the tension roller 42 is supported by the belt 43. Is pressed against.

When the force acting on the plunger 3 from the belt 43 via the tension roller 42 and the roller arm 41 becomes larger than the spring force of the tension adjusting spring 21 in the above-mentioned use state, the check valve 17 is closed and hydraulic pressure is applied. , Belt 43
Support the power from. At this time, the hydraulic oil in the hydraulic chamber 13 slightly flows into the reservoir chamber 14 through the minute clearance 9 between the plunger 3 and the guide cylinder 8 and the hole 15, and the plunger 3 is pushed into the body 1 by that much. .

On the other hand, when the force acting on the plunger 3 becomes smaller than the spring force of the tension adjusting spring 21, the plunger 3 is pushed out by the tension adjusting spring 21. At this time, since the pressure inside the hydraulic chamber 13 becomes lower than the pressure inside the reservoir chamber 14,
The check valve 17 opens and hydraulic oil flows from the reservoir chamber 14 through the passage 16 into the hydraulic chamber 13.

As described above, since the plunger 3 moves up and down with respect to the change in the tension of the belt 43, the tension of the belt 43 can be kept constant.

The amount of the hydraulic oil in the reservoir chamber 14 changes due to the movement of the hydraulic oil accompanying the movement of the plunger 3 and the expansion and contraction due to the temperature change. It is absorbed by the volume change of the air and the inflow and outflow of the air through the clearance between the plug 19 and the screw portion of the injection hole 18.

In the first embodiment, the spring bearing is integrally formed with the guide cylinder 8.
Although 20 is provided, as shown in FIG. 3, a tube body 22 is attached to the upper end of the guide tube 8 by means of adhesion or press fitting,
A flange 23 provided on the cylindrical body 22 may be used as a spring receiver.

FIG. 4 shows a second embodiment of the autotensioner according to the present invention. In this embodiment, the slide bearing 4 shown in FIG. 2 is omitted and the plunger 3 is inserted into the plunger insertion hole 2
The inner surface of the plunger insertion hole 2 is slid along the inner surface thereof, and a seal member 11 'is attached to the lower portion of the inner circumference of the plunger insertion hole 2 to prevent hydraulic oil from leaking.

Further, instead of the slide bearing 4 shown in FIG. 2, a cap 5'is attached to the lower end of the body 1, and the cap 5'prevents the plunger 3 from coming off.

Further, an air hole 24 in the radial direction is formed at the upper end of the body 1, and air is allowed to flow in and out of the guide cylinder 8 through the air hole 24. Other configurations and actions are the first.
The description is omitted because it is the same as the embodiment.

[Effect of device]

As described above, according to the present invention, the hydraulic oil is filled only in the lower part of the hydraulic chamber and the reservoir chamber, and the upper part of the reservoir chamber is used as an air reservoir. The volume change of the hydraulic oil can be easily absorbed by the air layer in the air reservoir, and the guide cylinder is provided with a hole for communicating the minute clearance with the reservoir chamber, so that when the pressure in the hydraulic chamber increases, The hydraulic oil in the chamber can be made to be an oil-sealed type that can flow to the reservoir chamber, and there is no external leakage of the hydraulic oil, and it is possible to prevent the inconvenience that the belt is contaminated with the hydraulic oil or deteriorates. .

The lower part of the guide cylinder is inserted inside the plunger inserted into the plunger insertion hole of the body, and the upper end of the guide cylinder is pressed against the bottom surface of the plunger insertion hole by the spring force of the tension adjusting spring. Is not fixed to the body, the body, the plunger, and the guide cylinder are automatically aligned by sequentially incorporating the guide cylinder, the tension adjusting spring, and the plunger in the plunger insertion hole of the body. For this reason, twisting and unnecessary radial load do not act between the body and the plunger, and between the plunger and the guide cylinder, and the followability of the plunger due to the change in belt tension is good,
A stable operating characteristic can be obtained, and the amount of hydraulic oil in the hydraulic chamber is reduced compared to the case where the tension adjusting spring is installed in the hydraulic chamber by incorporating the tension adjusting spring in the upper end of the plunger. be able to.

For this reason, the amount of dissolved air in the hydraulic oil in the hydraulic chamber is small, and even if the plunger moves downward and the pressure in the hydraulic chamber drops sharply, the dissolved air is less likely to break out and cavitation can be suppressed. it can.

Further, since the structure has a small number of parts, it is extremely easy to assemble.

[Brief description of drawings]

FIG. 1 is a front view showing an example of use of the automatic tensioner according to the present invention, FIG. 2 is a vertical sectional front view of the same automatic tensioner, and FIG. 3 is a sectional view showing another example of the same spring receiver. Is a vertical sectional front view showing a second embodiment of the same automatic tensioner, and FIG. 5 is a sectional view showing a conventional automatic tensioner. 1 ... Body, 2 ... Plunger insertion hole, 3 ... Plunger, 7 ... Insertion hole, 8 ... Guide tube, 9 ... Small clearance, 12 ... Closed end, 13 ... Hydraulic chamber, 14 ... Reservoir chamber,
15 …… hole, 16 …… passage, 17 …… check valve, 20 ……
Spring receiver, 21 …… tension adjusting spring.

Claims (1)

[Scope of utility model registration request] 1. A plunger is slidably inserted into a plunger insertion hole formed in the body and having a lower opening, and a closed end is provided in the lower part in an insertion hole formed axially from the upper surface of the plunger. And a reservoir chamber formed between the lower closed end of the guide cylinder and the closed end of the plunger. Is filled with hydraulic oil to form an air layer on the surface of the hydraulic oil in the reservoir chamber, and the guide cylinder is provided with a radial hole for communicating the internal reservoir chamber with the minute clearance. A passage communicating with the hydraulic chamber is formed at the closed end, a check valve for preventing hydraulic oil from flowing from the hydraulic chamber to the reservoir chamber is attached to the passage, and a spring receiver is provided on the outer peripheral upper portion of the guide cylinder. It received an auto tensioner incorporating a tension adjusting spring between the plunger upper end.