JP2583374Y2 - Hydraulic auto tensioner - Google Patents

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 used for adjusting the tension of a timing belt of an automobile engine.

[0002]

2. Description of the Related Art As a conventional hydraulic auto tensioner of this type, as shown in FIG. 6, a sleeve 2 into which a piston 3 is inserted is provided inside a cylinder 1, and a return spring 4 is provided between the sleeve 2 and the cylinder 1. There is a device in which the length of the device is reduced by incorporating the device.

The piston 3 divides a hydraulic oil chamber 5 provided inside the cylinder 1 into a pressure chamber 6 and a reservoir chamber 7. The piston 3 has a passage 8 communicating the pressure chamber 6 and the reservoir chamber 7, and a pressure chamber 6. A check valve 9 is provided for closing the passage 8 when the hydraulic oil pressure in the chamber 6 increases from the reservoir chamber 7 side.

A piston rod 10 is connected to the piston 3 and a step 11 formed on the piston rod 10 is formed.
, A wear ring 12 ′ sliding on the inner wall of the cylinder 1 is engaged, and the upper end of the return spring 4 is brought into contact with the wear ring 12 ′ so that the piston 3 and the piston rod 10 project outward. Gives spring force.

[0005] The wear ring 12 ′ is formed with a plurality of hydraulic oil passage holes 13 ′, and an opening of the cylinder 1 is provided with an oil seal 14.
Hydraulic oil is sealed in the inside of the chamber 4 through an air space 15.

In FIG. 1, reference numeral 16 denotes a retainer, 17 denotes a spring for connecting the piston 3 and the piston rod 10, 18 denotes a tension pulley, 19 denotes a support arm thereof, and 20 denotes a timing belt.

In the above structure, when the tension of the belt 20 is increased and the piston 3 is pushed downward through the piston rod 10, the check valve 9 is closed and hydraulic pressure is applied.
Support the force from the belt. At this time, the hydraulic oil in the pressure chamber 6 leaks through a small gap between the piston 3 and the sleeve 2,
The piston 3 is pushed by that much. .

Conversely, when the tension of the belt 20 decreases and the piston rod 10 and the piston 3 protrude outward due to the spring force of the return spring 4, the pressure in the pressure chamber 6 decreases and the check valve 9 causes the passage 8 to move. Open. For this reason, the hydraulic oil in the reservoir chamber 7 moves to the pressure chamber 6 through the passage 8, and at the same time, the hydraulic oil on the upper side of the wear ring 12 ′ passes through the passage hole 13 ′ due to the pressure change in the cylinder. Flow into

In the belt tension adjustment as described above,
The wear ring 12 ′ transmits the spring force of the return spring 4 to the piston rod 10 and transmits the hydraulic oil to the passage hole 1.
A bearing that has a function of filling and discharging the reservoir chamber 7 through the 3 ′, receives a bending moment applied to the piston rod 3 from the belt 20 between the inner wall of the cylinder 1 and the piston rod 10, and guides the movement of the piston rod 10. There is a function as.

Therefore, the conventional wear ring 12 ′
In order to obtain a sufficient guide length for the piston rod 10 and the inner wall of the cylinder 1, a disk having a relatively large thickness is used, and a fitting hole for the piston rod and a passage hole 13 'for hydraulic oil are formed in the disk. It is provided and formed.

[0011]

By the way, in the hydraulic auto tensioner having the above structure, when the engine is restarted after the piston 3 is stopped while being pushed into the lowermost end of the sleeve 2, the piston rod 10 is moved to the belt position. 20
Protrudes rapidly until a predetermined tension is reached. In this case,
At the same time, the pressure in the pressure chamber 6 drops rapidly, so that the hydraulic oil on the upper side of the wear ring 12 ′ may rapidly move to the reservoir chamber 7, and the air in the air layer 15 may simultaneously flow into the reservoir chamber 7. There is no problem if this inflowing air stops in the reservoir chamber 7, but passes through the passage 8 of the piston 3 and passes through the pressure chamber 6.
When it flows into, there is a problem that the damping characteristics deteriorate.

The inflow of such air is caused by the wear ring 1
There is a great relationship between the pipeline resistance in the passage hole 13 'of 2' and the difference in viscosity between hydraulic oil and air. In other words, if the resistance when the hydraulic oil passes through the passage hole 13 ′ of the wear ring 12 ′ is large, a large amount of air with low viscosity flows into the reservoir chamber 7 before the hydraulic oil with high viscosity, and flows into the pressure chamber 6. Easy to flow.

From this point of view, in order to eliminate the inflow of air into the pressure chamber 6, the present inventor has made the passage hole 13 'of the wear ring 12' large and changed the pipe resistance to change the inflow of air. The change of state was tested. In the test, a wear ring 12 'provided with four circular passage holes 13' as shown in FIG.
As shown in FIG. 9, the passage hole 13 'is about 2.5 times larger than the A type (hereinafter referred to as B type), and as shown in FIG. Of about 4.5 times the size (hereinafter referred to as C type) of each type, and for each type, push the piston 3 down to the lowermost end of the cylinder 1 and then move the piston rod 1
0 was suddenly projected outward, and the state of air flowing into the press-fitting chamber 6 was examined.

[0014] As a result, as shown in Fig. 10, the larger the size of the passage hole, the smaller the amount of air flowing in. However, even in the C type having the largest passage hole, the air flows into the pressure chamber and the size of the passage hole is reduced. The change alone was not enough to completely prevent the inflow of air.

On the other hand, the pipe resistance of the passage hole 13 'can be reduced by shortening the length of the passage hole. However, in order to shorten the passage hole 13 ', the wear ring 1
When the thickness of 2 ′ is reduced, the length of the guide surface of the wear ring 12 ′ with respect to the inner wall of the cylinder 1 and the piston rod 10 is reduced, so that the sliding surface pressure with the cylinder 1 is reduced. The support rigidity is reduced, and there is a problem that deformation of the wear ring and smooth movement of the piston rod are impaired.

The present invention aims at solving the above-mentioned problems, and by devising the shape of the wear ring, the piston rod can slide smoothly and the pipe of the passage hole can be reduced without lowering the support rigidity. Road resistance,
An object of the present invention is to provide a hydraulic auto tensioner capable of preventing hydraulic oil from flowing into a pressure chamber.

[0017]

In order to solve the above-mentioned problems, the present invention provides a wear ring comprising a ring-shaped boss having an inner periphery fitted to a piston rod and a ring-shaped boss having an outer periphery fitted to a cylinder inner wall. And a rib connecting the boss and the flange, and the rib is provided with a passage hole for hydraulic oil.

[0018]

In the above structure, by setting the thickness of the boss and the flange to a length that can provide sufficient support for the piston rod and the inner wall of the cylinder, a large support rigidity for the piston rod can be ensured, while the thickness of the rib is increased. By reducing the thickness, the pipe resistance of the passage hole can be reduced,
The inflow of air into the passage hole can be suppressed.

The size of the through hole provided in the rib is preferably set to the maximum as long as the strength of the rib connecting the boss and the flange can be guaranteed, but the range is the entire area of the wear ring in plan view. Is desirably set in an area range of 40 to 70%.

[0020]

1 and 2 show a hydraulic auto-tensioner according to an embodiment. The structure of this auto tensioner is the same as the conventional one shown in FIG. 6 except for the shape of the wear ring, and the same components are denoted by the same reference numerals and description thereof will be omitted.

As shown in FIG.
2 is formed by connecting a ring-shaped boss 21 whose inner peripheral surface is fitted to the piston rod 10 and a ring-shaped flange 22 whose outer peripheral surface is fitted to the inner wall of the cylinder 1 with a rib 23, The inner peripheral surface of the boss 21 is
Is press-fitted and attached to the peripheral surface of the step portion 11.

The rib 23 has three elongated holes 13 formed therein.

The boss 21 and the flange 22 can reliably support the bending moment applied to the piston rod 10,
Further, it is formed such that a sufficient guide length for guiding the movement of the piston rod 10 is obtained.

On the other hand, even when the piston rod 10 receives the maximum bending moment, the thickness of the rib
The rib 23 is set to have such a size as not to cause deformation or the like between the flange 22 and the flange 22. The area of the passage hole 13 is
The size is set to the same size as the C type shown in FIG.

FIG. 3 shows an example in which the wear ring 12 is turned upside down with respect to the structure of FIG. 1, and a circumferential groove 24 formed between the rib 23 and the boss 21 and the flange 22 is shown.
Are opposed to the sleeve 2 side.

In the structure shown in FIGS. 1 and 3, the boss 21 and the flange 22 of the wear ring 12 fitted to the piston rod 10 or the cylinder 1 can be formed to have a sufficient length for guiding the movement of the piston rod. Thus, the same rigidity as that of the conventional wear ring can be obtained for the piston rod 10. In addition, since the length of the passage hole 13 is reduced and the area of the hole is increased, the pipeline resistance of the hydraulic oil is reduced, and the inflow of air can be suppressed. D and E in FIG. 10 correspond to FIG.
Is the D type, and the structure of FIG. 3 is the E type. As in the above-described types A, B, and C, the air flows into the pressure chamber when the piston rod is rapidly protruded after the piston is pushed. It is an examination of the state. As shown in FIG. 10, no air was mixed in any of the structures of the examples, and stable damping characteristics could be obtained over a long period of time.

In each of the types A, B, and C shown in FIGS. 7 to 9, a large amount of cutting is required for the inner and outer diameters of the ring and the drilling of the through holes. In addition, in the wear ring 12 of the embodiment shown in FIG. 3, since the whole is formed to be thin, it can be formed by press working, and the manufacturing cost can be reduced.

FIG. 4 shows another embodiment. In this example, the thickness of the flange 22 of the wear ring 12 is larger than that of the boss 21 or the like, and the length of the guide surface 25 with respect to the inner wall of the cylinder 1 is increased.

By increasing the length of the guide surface 25, the sliding surface pressure of the guide surface 25 against the cylinder 1 can be reduced. A larger bending moment can be supported.

FIG. 5 is the reverse of the example of FIG.
The second flange 22 is elongated downward, and the return spring 4 is fitted on the inner peripheral side of the flange 22. In this structure, since there is nothing to interfere with the extension of the flange 22, the flange 22 can be made longer than the structure of FIG.

4 and 5, if the guide surface 25 of the flange 22 is crowned, the edge load is eliminated, so that the wear of the cylinder 1 can be further reduced and the durability can be further improved.

[0032]

As described above, according to the present invention, since the pipeline resistance of the hydraulic oil caused by the passage hole of the wear ring is reduced, it is possible to prevent air from flowing into the pressure chamber even when the stroke of the piston rod changes greatly. Thus, stable damping characteristics can be maintained for a long period of time.

Further, since the thickness of the boss or the flange fitted to the piston rod or the cylinder can be freely set irrespective of the thickness of the passage hole, sufficient supporting rigidity for the piston rod can be secured, and the cylinder and the wear ring can be secured. This has the effect of reducing the sliding surface pressure between them and improving durability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a hydraulic auto tensioner according to an embodiment.

FIG. 2 is a plan view of the above wear ring.

FIG. 3 is a sectional view showing another embodiment.

FIG. 4 is a sectional view showing another embodiment.

FIG. 5 is a sectional view showing another embodiment.

FIG. 6 is a sectional view showing a conventional example.

FIG. 7 is a plan view showing a conventional A-type wear ring.

FIG. 8 is a plan view showing a conventional B-type wear ring.

FIG. 9 is a plan view showing a conventional C-type wear ring.

FIG. 10 is a graph showing an inflow amount of air into a pressure chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Sleeve 3 Piston 4 Return spring 5 Hydraulic oil chamber 6 Pressure chamber 7 Reservoir chamber 8 Passage 9 Check valve 10 Piston rod 12 Wear ring 13 Passage hole 15 Air layer 21 Boss 22 Flange 23 Rib 25 Guide surface

Claims (1)

(57) [Scope of request for utility model registration] A hydraulic oil chamber provided inside a cylinder is divided into a pressure chamber and a reservoir chamber by a piston inserted into the cylinder, and a pressure passage between the pressure chamber and the reservoir chamber is formed between the piston and the pressure chamber. A check valve that closes the passage when it is increased from the reservoir chamber side is provided, and a wear ring that slides along the inner wall of the cylinder is attached to a piston rod connected to the piston, and the piston rod faces the wear ring outward. In the hydraulic auto-tensioner having a spring force to protrude, a ring-shaped boss whose inner periphery is fitted to a piston rod, a ring-shaped flange whose outer periphery is fitted to a cylinder inner wall, And a rib connecting the flange,
A hydraulic auto-tensioner, wherein a hydraulic oil passage hole is provided in the rib.