JPH0643403U - Hydraulic auto tensioner - Google Patents

Abstract

(57) [Summary] [Object] The present invention prevents the inflow of air into a pressure chamber in a hydraulic autotensioner in which hydraulic oil and air are enclosed in a cylinder without lowering the support rigidity of the piston rod. Provide a structure that can. [Structure] A wear ring 12 assembled between a cylinder 1 and a piston rod 10 is formed from a boss 21 fitted to the piston rod 10, a flange 22 fitted to the cylinder 1, and a rib 23, and acted on the rib 23. An oil passage hole 13 is provided. The thickness of the boss 21 and the flange 22 is increased to secure the guide length for the cylinder and the piston rod.
The rib 23 is thinned to reduce the conduit resistance of the passage hole 13 to suppress the inflow of air.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a hydraulic auto tensioner used for adjusting tension of a timing belt of an automobile engine.

[0002]

[Prior art]

 As a hydraulic autotensioner of this type, as shown in FIG. 6, conventionally, a sleeve 2 into which a piston 3 is inserted is provided inside a cylinder 1, and a return spring 4 is incorporated between the sleeve 2 and the cylinder 1. There are some that are designed to reduce the device length.

The piston 3 divides the hydraulic oil chamber 5 provided inside the cylinder 1 into a pressure chamber 6 and a reservoir chamber 7, and the piston 3 has a passage 8 communicating the pressure chamber 6 and the reservoir chamber 7, and a pressure chamber. A check valve 9 is provided to close the passage 8 when the hydraulic oil pressure on the chamber 6 side is higher than that on the reservoir chamber 7 side.

Further, a piston rod 10 is connected to the piston 3, and a step ring 11 formed on the piston rod 10 is engaged with a wear ring 12 ′ that slides on the inner wall of the cylinder 1, and the wear ring 12 ′ is engaged. The upper end of the return spring 4 is brought into contact with the piston 3 and the piston rod 10 to exert a spring force in a direction in which the piston 3 and the piston rod 10 project outward.

A plurality of hydraulic oil passage holes 13 ′ are formed in the wear ring 12 ′, an oil seal 14 is provided in the opening of the cylinder 1, and an air layer 15 is provided inside the oil seal 14. Through which the hydraulic oil is sealed.

In the figure, 16 is a retainer, 17 is a spring for connecting the piston 3 and the piston rod 10, 18 is a tension pulley, 19 is a supporting arm thereof, and 20 is a timing belt.

In the structure described above, when the tension of the belt 20 increases and the piston 3 is pushed downward via the piston rod 10, the check valve 9 closes and hydraulic pressure acts, and the force from the belt is applied. Support. At this time, the hydraulic oil in the pressure chamber 6 leaks through a minute gap between the piston 3 and the sleeve 2, and the piston 3 is pushed in by that amount. .

On the contrary, when the tension of the belt 20 decreases and the piston rod 10 and the piston 3 project 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 up. Therefore, 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 and the reservoir chamber. Pour into 7.

In adjusting the tension of the belt as described above, the wear ring 12 ′ transmits the spring force of the return spring 4 to the piston rod 10 or fills and discharges the hydraulic oil into the reservoir chamber 7 through the passage hole 13 ′. It has a function as a bearing that receives a bending moment applied from the belt 20 to the piston rod 3 between the inner wall of the cylinder 1 and the piston rod 10, and guides the movement of the piston rod 10.

Therefore, the conventional wear ring 12 ′ uses a disk having a relatively large wall thickness in order to obtain a sufficient guide length with respect to the piston rod 10 and the inner wall of the cylinder 1, and the piston is attached to the disk. It is formed by providing a rod fitting hole and a hydraulic oil passage hole 13 '.

[0011]

[Problems to be solved by the device]

 By the way, in the hydraulic automatic 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 causes the belt 20 of the piston rod 10 to have a predetermined tension. However, in this case, since the pressure in the pressure chamber 6 sharply drops at the same time, the hydraulic oil on the upper side of the wear ring 12 'rapidly moves to the reservoir chamber 7 and the air in the air layer 15 simultaneously. It may flow into the reservoir chamber 7. There is no problem if the inflowing air stays in the reservoir chamber 7, but if it flows into the pressure chamber 6 through the passage 8 of the piston 3, there is a problem that the damping characteristic is deteriorated.

[0012] Such inflow of air has a large relationship with the conduit resistance in the passage hole 13 'of the wear ring 12' and the difference in viscosity between the hydraulic oil and air. That is, if the resistance of the hydraulic oil when passing through the passage hole 13 ′ of the air 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 the pressure chamber 6 It becomes easy to flow into.

From this point of view, in order to prevent the inflow of air into the pressure chamber 6, the inventor of the present invention enlarges the passage hole 13 ′ of the wafering 12 ′ and changes the conduit resistance to thereby release air. The change of the inflow condition was tested. In the test, as shown in FIG. 7, a wear ring 12 ′ provided with four circular passage holes 13 ′ (hereinafter referred to as “A type”), and as shown in FIG. About 2.5 times the size (hereinafter referred to as B type), and as shown in FIG. 9, the passage hole 13 'is larger than the B type and about 4.5 times the size of the A type. For each type, prepare a piston (3), push the piston (3) to the lowermost end of the cylinder (1), and then suddenly project the piston rod (10) outward to inject air into the press-fit chamber (6). I checked the condition.

As shown in FIG. 10, as shown in FIG. 10, the larger the passage hole, the smaller the amount of inflowing air. However, even in the C type, which has the largest passage hole, air flows into the pressure chamber and the size of the passage hole is increased. It was not enough to completely prevent the inflow of air just by changing it.

On the other hand, the conduit resistance of the passage hole 13 'can also be reduced by shortening the length of the passage hole. However, if the thickness of the wear ring 12 'is reduced in order to shorten the passage hole 13', the length of the inner wall of the cylinder 1 and the guide surface of the wear ring 12 'with respect to the piston rod 10 is reduced, so that the length of the wear ring 12' is reduced. There is a problem that the sliding surface pressure becomes small, the supporting rigidity of the piston rod 10 is lowered, and the wear ring is deformed and the smoothness of the movement of the piston rod is impaired.

The present invention is intended to solve the above problems, and by adding a worker to the shape of the wear ring, the piston rod can be slid smoothly and the supporting rigidity of the passage hole can be reduced without lowering the supporting rigidity. (EN) Provided is a hydraulic autotensioner capable of reducing the resistance of a pipeline and preventing hydraulic oil from flowing into a pressure chamber.

[0017]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention provides a wear ring with a ring-shaped boss whose inner circumference fits into a piston rod, a ring-shaped flange whose outer circumference fits into a cylinder inner wall, and the above boss. The flange is connected to a rib, and the rib is provided with a hydraulic oil passage hole.

[0018]

[Action]

 In the above structure, by setting the thickness of the boss and flange to a length that provides sufficient support for the piston rod and the inner wall of the cylinder, a large support rigidity for the piston rod can be secured, while the rib thickness is reduced. As a result, the conduit resistance of the through hole can be reduced, and the inflow of air into the through hole can be suppressed.

It is preferable that the size of the passage hole provided in the rib is set to the maximum within the range in which the strength of the rib connecting the boss and the flange can be guaranteed, but the range is the entire area of the wafering in plan view. It is desirable to set in the area range of 40 to 70%.

[0020]

【Example】

 1 and 2 show a hydraulic type automatic tensioner of the 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 parts are designated by the same reference numerals and the description thereof will be omitted.

As shown in the drawings, the wear ring 12 of the embodiment has a ring-shaped boss 21 whose inner peripheral surface fits into the piston rod 10 and a ring-shaped flange whose outer peripheral surface fits into the inner wall of the cylinder 1. 22 and 22 are joined by a rib 23, and the inner peripheral surface of the boss 21 is press-fitted and attached to the peripheral surface of the step portion 11 of the piston rod 10.

Further, the rib 23 is formed with three passage holes 13 each having a long hole shape.

The boss 21 and the flange 22 are formed so as to reliably support the bending moment applied to the piston rod 10 and to obtain a sufficient guide length for guiding the movement of the piston rod 10. .

On the other hand, the thickness of the rib 23 is set such that the rib 23 does not deform between the boss 21 and the flange 22 even when the piston rod 10 receives the maximum bending moment. Further, the area of the passage hole 13 is set to have 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 the circumferential groove 24 formed between the rib 23 and the boss 21 and the flange 22 is It is opposed to the sleeve 2 side.

In the structures shown in FIGS. 1 and 3, the boss 21 and the flange 22 of the air ring 12 fitted to the piston rod 10 and the cylinder 1 are formed to have a sufficient length to guide the movement of the piston rod. Therefore, it is possible to obtain the same supporting rigidity as that of the conventional wear ring for the piston rod 10. Further, since the length of the passage hole 13 is made short and the area of the hole is made large, the conduit resistance of the hydraulic oil becomes small and the inflow of air can be suppressed. As for D and E of FIG. 10, the structure of FIG. 1 is the D type and the structure of FIG. 3 is the E type, and like the respective types A, B, and C described above, the piston rod is rapidly projected after the piston is pushed in. The state of inflow of air into the pressure chamber when the pressure is applied is examined. As shown in FIG. 10, in all the structures of the examples, no air was observed, and stable damping characteristics could be obtained over a long period of time.

In addition, in each of the wear rings of types A, B, and C shown in FIGS. 7 to 9, many cutting processes are required to process the inner and outer diameters of the ring and to punch through holes. Further, in the wear ring 12 of the embodiment shown in FIG. 3, since the whole is formed to be thin, it can be molded 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 made larger than that of the boss 21 and the like, and the length of the guide surface 25 with respect to the inner wall of the cylinder 1 is made large.

By lengthening the guide surface 25 in this manner, the sliding surface pressure of the guide surface 25 with respect to the cylinder 1 can be lowered, and the conventional structure can be achieved between the connecting portion between the piston rod 10 and the piston 3 and the wear ring 12. Can support a larger bending moment.

In contrast to the example of FIG. 4, FIG. 5 shows that the flange 22 of the wear ring 12 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 that interferes with the extension of the flange 22, the flange 22 can be made longer than the structure of FIG.

In FIGS. 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]

【effect】

 As described above, according to the present invention, the resistance of the hydraulic oil through the through hole of the wear ring is reduced, so that even if the stroke of the piston rod changes significantly, it is possible to prevent air from flowing into the pressure chamber. It is possible to maintain stable damping characteristics over a long period of time.

Further, since the thickness of the boss and the flange fitted to the piston rod and the cylinder can be freely set regardless of the thickness of the passage hole, sufficient supporting rigidity for the piston rod can be ensured and the cylinder and the wear ring can be secured. The sliding surface pressure between them can be reduced, and the durability can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a hydraulic auto tensioner of 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 cross-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 the inflow amount of air into the pressure chamber.

[Explanation 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 Pass Hole 15 Air Layer 21 Boss 22 Flange 23 Rib 25 Guide Surface

Claims (1)

[Scope of utility model registration request] 1. A hydraulic fluid chamber provided inside a cylinder is divided into a pressure chamber and a reservoir chamber by a piston inserted in the cylinder, and the piston is provided with a passage communicating the pressure chamber and the reservoir chamber and a pressure on the pressure chamber side. A check valve that closes the passage when it increases from the reservoir chamber side is provided, a wear ring that slides along the inner wall of the cylinder is attached to the piston rod that is connected to the piston, and the piston rod is outwardly attached to the wear ring. In a hydraulic autotensioner to which a spring force is applied, the wear ring includes a ring-shaped boss having an inner periphery fitted to a piston rod, a ring-shaped flange having an outer periphery fitted to a cylinder inner wall, and the boss. And ribs that connect the flange and
A hydraulic automatic tensioner characterized in that a rib is provided with a hydraulic oil passage hole.