JPH0512810U - Hydraulic auto tensioner - Google Patents

Abstract

(57) [Summary] [Purpose] The weight and durability of the cylinder and piston are improved, enabling low-cost manufacturing. [Structure] The cylinder 1 and the piston 3 are made of an aluminum alloy, and the sliding surface of the piston 3 with respect to the cylinder 1 and
The valve seat 9 and the like are surface-hardened. By hardening the piston 3 in this manner, the cylinder 1 and the piston 3 are
It is possible to reduce the wear of the sliding portion and reduce the processing cost.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

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

[0002]

[Prior art and its problems]

 Conventionally, as a hydraulic autotensioner of this type, an iron sleeve is inserted inside a cylinder made of a light alloy such as an aluminum alloy, and the pressure chamber of the hydraulic oil chamber is formed inside the sleeve to reduce weight. It has been proposed to improve durability. (Japanese Patent Application No. 63-135603) However, in the structure in which the steel sleeve is provided in the cylinder, the number of parts is increased, the weight cannot be reduced sufficiently, and the man-hours for assembling and the man-hours for assembling are increased, resulting in an increase in manufacturing cost. There are disadvantages.

In order to solve the above problems, the steel sleeve may be eliminated and the piston may be formed of a light alloy of the same material as the cylinder, but both the cylinder and the piston may be of the same light alloy. When it is formed by, there is a problem that wear due to sliding of both is severe and durability is poor.

On the other hand, as a measure against wear of aluminum alloys and the like, conventionally, various surface treatments have been considered to increase wear resistance by applying a hard alumite coating or electroless plating on the surface of the alloy, and they are also put to practical use. Has been done.

However, when such a surface treatment is applied to the inside of the cylinder, the inside of the cylinder is in the shape of a deep hole, and the treatment liquid cannot flow through, so that it is difficult to perform a uniform surface treatment. There is. In addition, the inside of the cylinder has a large surface area, and in addition, if an oxide film is formed, the accuracy of the inner diameter becomes poor.Therefore, it is necessary to finish the inner diameter of the cylinder by post processing, resulting in high processing cost. There is also a problem.

Therefore, an object of the present invention is to provide a hydraulic autotensioner that realizes weight reduction and durability improvement of a cylinder and a piston and that can manufacture them at low cost.

[0007]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention divides the hydraulic oil chamber inside the cylinder into a pressure chamber and a reservoir chamber by means of a piston that slides on the inner surface of the cylinder, and connects the pressure chamber and the reservoir chamber to the piston. And a check valve that closes the passage when the hydraulic oil pressure on the pressure chamber side exceeds that in the reservoir chamber, and the piston rod connected to the piston and the piston rod that protrudes out of the cylinder. In a hydraulic autotensioner that applies a spring force in the same direction, the cylinder and piston are made of light alloy, and the sliding surface of the piston with respect to the cylinder is surface hardened.

[0008]

[Action]

 In the above structure, by increasing the surface hardness by hardening treatment, the wear resistance of the sliding surface of the piston is greatly improved, and the piston can be provided with durability comparable to that of iron. In this way, if one of the pistons is hardened between the cylinder and the piston, the frictional resistance at the sliding portions of the two is reduced, and the abrasion generated at the sliding portions can be suppressed.

Further, by performing hardening treatment only on the surface of the piston, the treatment area can be reduced and treatment can be performed at low cost.

As the above-mentioned surface hardening treatment, oxide film treatment such as hard alumite, electroless plating, ceramic coating and the like can be used.

[0011]

Embodiment FIG. 1 shows a hydraulic autotensioner of an embodiment.

As shown in the figure, a hydraulic oil chamber 2 is provided inside a cylinder 1, and a piston 3 is slidably inserted into the hydraulic oil chamber 2. The piston 3 causes the hydraulic oil chamber 2 to be pressured. It is divided into a chamber 4 and a reservoir chamber 5.

A piston rod 7 is fitted in a hole 6 provided in the center of the piston 3, and a passage 8 that connects the pressure rod 4 and the reservoir chamber 5 is formed in the piston rod 7 and the piston 3. A ball-shaped check valve 10 is attached to the valve seat 9 provided at the outlet of the passage 8. The check valve 10 closes the passage 8 when the pressure chamber 4 is pressurized, and opens when the pressure is reduced. It is like this.

A bearing 12 that slides on the inner peripheral surface of the cylinder 1 is engaged with a step portion 11 provided on the piston rod 7, and a spring seat 14 is attached to the step portion 12 formed on the inner surface of the cylinder 1. A return spring 15 is provided between the bearing 12 and the spring seat 14 for applying a spring force in the protruding direction to the piston 3 and the piston rod 7.

In addition, in the figure, 16 is a valve retainer, 17 is a coupling spring between a piston and a piston rod, 18 is an oil seal, 19 is a belt such as a timing belt, 20 is a tension pulley, and 21 is its The support arm 22 is a support shaft.

In the above structure, the cylinder 1 and the piston 3 are made of aluminum alloy and are integrally formed by a die casting method.

Further, as shown in FIG. 2, the contact surface of the piston 3 with other members, that is, the sliding surface 23 with respect to the cylinder 1, the surface of the central hole 6 into which the piston rod 7 is fitted, and The valve seat 9 with which the check valve 10 abuts is surface-hardened. By this hardening treatment, a hard coating 24, which is comparable in hardness to the hardened steel, is formed on each of the above contact surfaces to suppress sliding wear due to contact with other members. The surface hardening treatment may be provided on the entire surface of the piston 3. Further, since the wear of the piston 3 is concentrated on the sliding surface 23 with respect to the cylinder 1, sufficient durability life can be obtained even if the hard coating 24 is formed only on the sliding surface 23.

The aluminum alloy forming the cylinder 1 and the piston 3 is always kept at a constant size with respect to the temperature change during actual use in which the gap between them is about -40 ° C to 160 ° C. As described above, alloys having similar linear expansion coefficients are set in combination. This is because the change in the leak clearance between the cylinder 1 and the piston 3 due to the temperature change is eliminated and the leak down time of the hydraulic oil is not affected.

In the above embodiment, when the tension of the belt 19 increases, the tension pulley 20 swings and the pressing force acting on the piston rod 7 increases. As a result, when the piston 3 is pushed in, the hydraulic oil in the pressure chamber 4 moves to the reservoir chamber 5 from the leak gap between the piston 3 and the cylinder 1 to buffer the movement of the piston 3.

On the contrary, when the tension of the belt 19 is reduced, the piston rod 7 is projected outward by the spring force of the return spring 15, and the tension pulley 20 is moved in the opposite direction. When the piston rod 7 and the piston 3 move up following this movement, the pressure chamber 4 is depressurized and the check valve 10 opens the passage 8. For this reason, the hydraulic oil in the reservoir chamber 5 smoothly moves to the pressure chamber 4, and the piston rod 7 rapidly projects.

In the above embodiment, the cylinder 1 and the piston 3 are made of aluminum alloy, but they can be made of magnesium alloy, other light metal, or a combination thereof.

Further, although the return spring 15 for adjusting the tension is provided inside the cylinder 1, for example, a return spring is provided between the arm 21 and the fixed portion of the tension pulley 20 so that the spring is applied to the piston rod from the outside of the cylinder. Power may be applied.

[0023]

【effect】

 As described above, according to the present invention, the cylinder and the piston are made of a light alloy, and the necessary surface of the piston is hardened, so that the cylinder and the piston can be formed at a low processing cost, and the weight and wear resistance of both can be reduced. Therefore, it is possible to provide a highly durable and reliable auto tensioner.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a hydraulic auto tensioner of an embodiment.

FIG. 2 is an enlarged sectional view of a similar piston.

[Explanation of symbols]

 1 Cylinder 2 Hydraulic Oil Chamber 3 Piston 4 Pressure Chamber 5 Reservoir Chamber 7 Piston Rod 8 Passage 9 Valve Seat 10 Check Valve 15 Return Spring 23 Sliding Surface 24 Hard Film

Claims (1)

[Scope of utility model registration request] 1. A hydraulic oil chamber inside a cylinder is divided into a pressure chamber and a reservoir chamber by a piston that slides on the inner peripheral surface of the cylinder, and a passage that connects the pressure chamber and the reservoir chamber is formed in the piston. A check valve is provided in the passage to close the passage when the hydraulic oil pressure on the pressure chamber side exceeds that in the reservoir chamber, and a spring force is applied to the piston and the piston rod connected to the piston in the direction of projecting to the outside of the cylinder. The hydraulic autotensioner is characterized in that the cylinder and the piston are made of a light alloy, and the sliding surface of the piston with respect to the cylinder is subjected to a surface hardening treatment.