JP2003207001A - Hydraulic automatic tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable hydraulic auto-tensioner which prevents over a long time occurrence of inconveniences such as function degradation and abnormal noise due to cavitation, aeration, check delay, or the like, suppresses adhesive abrasion between a check ball and an annular ball seat, and reduces adsorption, without using expensive material. <P>SOLUTION: The hydraulic auto-tensioner 10 has a check valve 28 allowing communication between a high-pressure oil chamber 26 and a low-pressure oil chamber 27 in one direction from the low-pressure oil chamber 27 to the high-pressure oil chamber 26. Film 4 formed by TiN coating, TiCN coating, DLC coating, or electroless nickel deposition is disposed one or both of a surface of the annular ball seat 32 for receiving the check ball and a surface of the check ball 30 of the check valve 28. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automatically applying appropriate tension to transmission members such as endless annular flat belts, V-belts, toothed belts and chains. The present invention relates to a hydraulic auto tensioner. 2. Description of the Related Art A hydraulic auto tensioner 50 shown in FIG.
, A high-pressure oil chamber 58 is formed between the bottom wall 54 b of the inner cylinder 54 and the lower end surface of the piston portion 55, and a low-pressure oil chamber 59 is formed between the outer peripheral surface of the inner cylinder 54 and the inner peripheral surface of the casing 51. Is formed. The high-pressure oil chamber 58 and the low-pressure oil chamber 59 can communicate in one direction from the low-pressure oil chamber 59 to the high-pressure oil chamber 58 via a check valve 61 provided in a communication hole 60 in the bottom wall 54b. (JP-A-10-141453, JP-A-10-325448). [0003] As shown in FIG.
4, a communication hole 60 formed in the bottom wall 54b,
An annular ball seat 65 having an upper edge chamfered, and a check ball 66 received by the annular ball seat 65
And the bottom wall 5 of the inner cylinder 54 so as to surround the check ball 66.
4b, a spring 67 mounted between the retainer 67 and the check ball 66. [0004] The check ball 66 is formed of, for example, bearing steel having excellent wear resistance, and the annular ball seat 65 is formed of, for example, alloy steel having high hardness. Mechanical wear is prevented. However, since both 65 and 66 are the same kind of metal such as steel, the check ball 66 is
When the seat 5 is seated at a high contact pressure and receives a high oil pressure and keeps contacting at a high contact pressure, the two members 65 and 66 made of the same metal
There is a possibility that the following problems may occur due to adhesive wear of the steel. When the adhesive wear of the two 65, 66 advances, both 65, 6
Adsorption occurs between the 6 and causes cavitation and aeration. Further, since the opening of the check ball 66 is delayed due to the suction, the behavior of the check ball 66 becomes unstable, the function is deteriorated due to the check delay or the like, and the collision between the two 65, 66 due to the impulsive pressure fluctuation. Abnormal noise occurs. In order to cope with the problem of adhesive wear, the present inventor has previously formed the check ball 66 with Si ₃ N ₄ (silicon nitride), which is a kind of fine ceramic, and formed the annular ball sheet 65 with the above-mentioned structure. As described above, it was confirmed that when formed from alloy steel and the both 65 and 66 were made of a combination of different materials, the cohesive wear of both was significantly reduced.
However, the check ball 66 made of Si ₃ N ₄ is very expensive. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, to reduce the occurrence of sticking wear between a check ball and an annular ball sheet without using an expensive material, to reduce an adsorption phenomenon, and to reduce cavitation, aeration, It is an object of the present invention to provide a highly reliable hydraulic auto-tensioner that can prevent problems such as functional deterioration and abnormal noise due to a check delay or the like for a long time. To achieve the above object, a hydraulic auto tensioner according to the present invention comprises a high pressure oil chamber and a low pressure oil chamber in one direction from the low pressure oil chamber to the high pressure oil chamber. In a hydraulic auto-tensioner equipped with a check valve that allows communication, one or both of the surface of a check ball of the check valve and the surface of an annular ball seat that receives the check ball,
It is characterized in that a coating by TiN coating, TiCN coating, DLC coating or electroless nickel plating is provided. [0008] TiN (titanium nitride) coating or T
The coating by iCN (titanium carbonitride) coating is T
Not only a single layer film of iN or TiCN but also TiN or TiCN
A composite film or a multilayer film containing CN may be used. Further, a film forming method for applying a TiN coating and a TiCN coating is as follows.
Although not particularly limited, physical vapor deposition (PVD) such as vacuum vapor deposition, sputtering, and ion plating can be exemplified. The coating by DLC (diamond-like carbon) coating is an amorphous carbon thin film containing carbon as a main component and having a high hardness and a low friction coefficient. Is not particularly limited. The film formation method by the DLC coating is not particularly limited, and examples thereof include a chemical vapor deposition method (CVD) such as plasma CVD, and a physical vapor deposition method such as ionization vapor deposition, sputtering, and arc discharge. Electroless nickel plating is a method in which nickel ions in a solution are reduced and precipitated by using a chemical reducing agent without flowing an electric current from the outside to form a nickel film on the surface of a body to be plated. Although it does not specifically limit as a chemical reducing agent, A hypophosphite, a borohydride compound, a hydrazine compound, etc. can be illustrated. When hypophosphite is used, the plated portion becomes an alloy of nickel and phosphorus, and the ratio of phosphorus is not particularly limited. Although not particularly limited, it is preferable to perform heat treatment after electroless nickel plating to increase hardness. An electroless nickel plating method using hypophosphite as a chemical reducing agent includes the Kanigen method (Nippon Kanigen Co., Ltd.). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a hydraulic auto-tensioner according to the present invention will be described below with reference to FIGS. These hydraulic auto tensioners 10
Is a general-purpose product for automatically applying appropriate tension to transmission members such as endless annular flat belts, V-belts, toothed belts, and chains. The structure between the hydraulic auto tensioner and the transmission member is not particularly limited. First, the hydraulic auto-tensioner 10 of the embodiment shown in FIGS. 1 and 2 includes a bottomed cylindrical casing 14, and an annular collar 16 is rotatably provided on the lower surface of the casing 14. ing. A bottomed cylindrical cylinder 20 is inserted into the press-fitted portion 18 on the inner periphery of the casing 14 and is press-fitted and fixed. From the open end of the casing 14 to the inside of the cylinder portion 20b of the cylinder 20 (high-pressure oil chamber 26 described later)
The rod-shaped piston portion 21 at the lower end of the plunger 12
Are slidable up and down with a predetermined clearance 31. A casing 1 is provided above the plunger 12.
A long outer cylinder 37a that has entered the opening 4 and the plunger 1
A spring cover 37 integrally formed with a short inner cylinder press-fitted to the outer periphery of the cylinder 2 and a ceiling portion closing upper ends of both cylinders is press-fitted and fixed. A return spring 38 is mounted in a compressed state between the lower surface of the ceiling portion of the spring cover 37 and the spring seat 36, and urges the plunger 12 in the retreating direction (upward in the figure). In addition, a casing 14 is provided above the plunger 12.
A resin dust cover 33 is attached to the casing 14 so as to cover the open end of the casing 14 and extend up to the outer periphery of the casing 14, and the dust cover 33 moves up and down together with the plunger 12. A high-pressure oil chamber 26 is formed between the inner peripheral surface of the cylinder 20 and the lower end surface of the piston portion 21. Also,
A low-pressure oil chamber 27 is formed between the outer peripheral surface of the cylinder 20, the inner peripheral surface of the casing 14, and the spring cover 37,
The structure is such that the oil 11 is stored. High pressure oil chamber 26
And the low-pressure oil chamber 27 are separated from the low-pressure oil chamber 27 by a check valve 28 provided on the bottom wall 20 a of the cylinder 20.
Communication in one direction. The check valve 28 is, as shown in FIG.
A communication hole 29 formed in the bottom wall 20a of the cylinder 20 made of alloy steel; an annular ball sheet 32 formed by chamfering the upper edge of the communication hole 29;
2, a spherical check ball 30 formed of bearing steel, a retainer 2 fitted to the bottom wall 20 a of the cylinder 20 so as to surround the check ball 30, and mounted between the retainer 2 and the check ball 30. Spring 3. Check ball 30 and annular ball seat 3
Examples 1 to 3 for the combination of the coatings 4 provided in
Shown in (Example 1) As shown in FIG. 2 (b), the check ball 30 has a coating 4 shown in Aspects 1 to 4 (Table 1) on the entire surface.
Is not provided on the surface of the annular ball seat 32. (Example 2) The coating 4 shown in Aspect 5 to Aspect 8 (Table 1) is provided on the surface of the annular ball sheet 32, and the coating is not provided on the surface of the check ball 30. (Example 3) Check ball 30 and annular ball seat 3
The coatings 4 of the combinations shown in Embodiments 9 to 20 (Table 1) are provided on both of the surfaces of No. 2. [Table 1] The hydraulic auto-tensioner 10 of the embodiment configured as described above operates as follows. When the piston 21 is pushed in and the oil is about to flow from the high pressure oil chamber 26 to the low pressure oil chamber 27, the check ball 3
0 acts on the annular ball seat 32 to close the check valve 28. Next, when the piston 21 is urged upward by the elastic force of the return spring 38, as shown in FIG. 3, the oil is about to flow from the low-pressure oil chamber 27 to the high-pressure oil chamber 26 in FIG. The check ball 30 rises against the downward bias by the spring 3 mounted between the retainer 2 and the check ball 30, and separates from the annular ball seat 32. Next, when the piston 21 is pushed in, the check ball 30 is seated on the annular ball seat 32 and the check valve 28 is closed. The hydraulic auto tensioner 10 of the present embodiment
According to this, the following effects can be obtained. (1) Since both the check ball 30 and the annular ball sheet 32 are the same kind of metal, such as steel, the check ball 3
By providing the coating 4 on one or both of the surface 0 and the surface of the annular ball sheet 32, a different material is interposed between the contact surfaces of the two 30, 32, so that cohesive wear hardly occurs. (2) Check ball 3
Thus, the phenomenon of adsorption between the zero and the annular ball sheet 32 can be reduced. (3) In addition, by selecting the coating 4 having high hardness, such as TiN coating, TiCN coating, DLC coating, or electroless nickel plating, the effect that the coating hardly peels off and the adhesive wear hardly occurs over a long period of time. Can be sustained across. (4) Since the suction phenomenon can be reduced, the opening delay of the check ball 30 due to the suction is eliminated, and the behavior of the check ball 30 is stabilized, so that the functional deterioration due to the check delay or the like can be prevented. Further, cavitation and aeration at the check valve can be prevented. further,
Abnormal noise generated when the check ball 30 collides with the annular ball seat 32 due to impulsive pressure fluctuation is eliminated. Note that the present invention is not limited to the configuration of the above-described embodiment, and may be embodied with, for example, the following modifications without departing from the spirit of the invention. (1) TiN coating on the check ball surface
Providing a multilayer coating by a combination of TiCN coating, DLC coating or electroless nickel plating. (2) Providing a multilayer coating on the surface of the annular ball sheet by a combination of TiN coating, TiCN coating, DLC coating or electroless nickel plating. The hydraulic auto-tensioner according to the present invention is constructed as described above, so that the wear of the check ball and the annular ball sheet hardly occurs without using an expensive material. In addition, an excellent effect is obtained in that the device is a highly reliable device that can reduce the adsorption phenomenon and can prevent problems such as functional deterioration and abnormal noise due to cavitation, aeration, and check delay over a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing a hydraulic auto-tensioner according to a first embodiment of the present invention. FIG. 2A is an enlarged sectional view of a main part of the hydraulic auto-tensioner according to the embodiment, and FIG. 2B is a sectional view of a check ball and a ball seat. FIG. 3 is an enlarged cross-sectional view of a main part showing a state in which a check valve of the hydraulic auto tensioner according to the embodiment is open. FIG. 4 is a sectional view showing a conventional hydraulic auto tensioner. FIG. 5 is a sectional view showing a check valve of the hydraulic auto tensioner. [Description of Signs] 2 Retainer 3 Spring 10 Hydraulic auto tensioner 14 Casing 20 Cylinder 21 Piston section 26 High pressure oil chamber 27 Low pressure oil chamber 28 Check valve 30 Check ball 32 Ring ball seat 38 Return spring

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Claims (1)

Claims: 1. A hydraulic auto-tensioner provided with a check valve that enables a high-pressure oil chamber and a low-pressure oil chamber to communicate in one direction from a low-pressure oil chamber to a high-pressure oil chamber. On one or both of the surface of the check ball of the stop valve or the surface of the annular ball seat receiving the check ball,
A hydraulic auto-tensioner provided with a coating by TiN coating, TiCN coating, DLC coating or electroless nickel plating.