JP2004239191A - Hydraulic piston pump motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic piston pump motor having a DLC (Diamond Like Carbon) coating film. <P>SOLUTION: This hydraulic piston pump motor is provided with a cylinder block rotatably supported around a shaft, a plurality of pistons 1 provided within the cylinder block to be reciprocally movable, a swash plate 3 for reciprocally moving the pistons 1 in accordance with the rotation of the cylinder block, and a shoe 2 slidably contacting the swash plate 3 and rotatably connected to the pistons 1. A sliding surface 2b of the shoe 2 contacting the swash plate 3 is formed in a tapered shape dented like a recess, and the DLC coating film 9 is formed on the sliding surface 2b. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface treatment structure for a hydraulic piston pump / motor.
[0002]
[Prior art]
Diamond Like Carbon (hereinafter referred to as “DLC”) is an amorphous hard carbide having characteristics similar to diamond and has high hardness and excellent wear resistance. It is being used as a surface layer of required mechanical parts.
[0003]
A method of forming a DLC coating film as a surface treatment of a hydraulic piston pump / motor has been proposed by the present applicant as Japanese Patent Application No. 2000-211494.
[0004]
[Patent Document 1]
JP 2000-119843 A
[Problems to be solved by the invention]
However, in a hydraulic piston pump / motor having a DLC coating film, there is room for improving the starting efficiency and the like.
[0006]
In addition, since the conventional DLC coating film has poor adhesion and toughness, when formed on the sliding surface of the shoe or piston constituting the hydraulic piston pump / motor, the base material is deformed by receiving a load. As a result, it was easy to crack and peel off, which made practical use difficult.
[0007]
The present invention has been made in view of the above problems, and has as its object to put a hydraulic piston pump / motor having a DLC coating film into practical use.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a cylinder block rotatably supported around an axis, a plurality of pistons reciprocally housed in the cylinder block, and an oblique piston for reciprocating the piston as the cylinder block rotates. The present invention is applied to a hydraulic piston pump / motor including a plate and a shoe which is in sliding contact with the swash plate and rotatably connected to the piston.
[0009]
A sliding surface which is in sliding contact with the swash plate of the shoe is formed in a tapered shape depressed in a concave shape, and a DLC coating film is formed on the sliding surface.
[0010]
According to a second aspect of the present invention, in the first aspect, a DLC coating film is formed on a sliding surface of the piston that slides on the cylinder block and the shoe.
[0011]
According to a third aspect, in the first or second aspect, an intermediate layer is formed by sputtering a metal target alone on a work to form a bond layer, simultaneously sputtering the metal target and the graphite target, and gradually changing the target output. A layer is formed on the bond layer, a metal target and a graphite target are simultaneously sputtered, and a target output is made substantially constant, thereby forming a top layer on the intermediate layer having a metal ratio of 3 to 18%. It is characterized by having done.
[0012]
Function and Effect of the Invention
According to the first aspect, since the structure in which the DLC coating film is formed on the sliding surface of the shoe, the sliding surface of the shoe is maintained in a tapered shape by the DLC coating film having high hardness, and high startup efficiency is achieved. Will be kept.
[0013]
According to the second aspect, the structure in which the DLC coating film is formed on the sliding surface of the piston that slides on the cylinder block and the shoe reduces the frictional force by the high hardness DLC coating film, thereby improving the efficiency. .
[0014]
According to the third aspect, by setting the ratio of the metal in the top layer to a range of 3 to 18%, the adhesion and toughness of the top layer can be increased. And peeling can be prevented. Then, a decrease in hardness of the top layer can be suppressed, and abrasion resistance can be ensured. As a result, even if the DLC coating film is formed on each of the sliding surfaces of the shoe and the piston that receives a high load, cracking or peeling of the DLC coating film is avoided, and practical use is possible.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0016]
FIG. 2 shows a configuration of a piston pump to which the present invention is applied. To explain this, a plurality of cylinders 5b are formed at equal intervals on the same circumference in a cylinder block 5 which is rotated by a drive shaft 7, and a piston 1 reciprocating in the axial direction is housed in the cylinder 5b. You. A piston ball portion 1a is formed at the tip of the piston 1, and the piston ball portion 1a is rotatably fitted in a spherical hole 2a provided in the shoe 2. The shoe 2 rotates together with the cylinder block 5 while slidingly contacting the swash plate 3 by the sliding surface 2b.
[0017]
The swash plate 3 is fixed to a housing (not shown) in a state of being inclined at a predetermined angle with respect to the rotation center of the cylinder block 5, or in a variable type, the inclination angle is changed by an actuator. The valve plate 4 is configured to be in sliding contact with the valve plate 4 having a pair of ports 4d and 4e.
[0018]
When the cylinder block 5 is rotated by the drive shaft 7, the piston 1 that comes into contact with the swash plate 3 via the shoe 2 reciprocates once per rotation of the cylinder block 5, and operates, for example, from one port 4e of the valve plate 4. The fluid is sucked and the working fluid is discharged from the other port 4d.
[0019]
Hydraulic fluid pressure is introduced into the piston ball portion 1a and the sliding surface 2b of the shoe 2 via a passage 1c inside the piston 1 to slide between the spherical hole 2a of the shoe 2 and the piston ball portion 1a and to slide the shoe 2. A hydrostatic bearing is formed between the surface 2b and the swash plate 3 to reduce the solid contact surface pressure between them.
[0020]
As shown in FIG. 1, a DLC coating film 9 is formed on the sliding surface 2b of the shoe 2 which is in contact with the swash plate 3. Thereby, the sliding characteristic of the shoe 2 is improved from the start.
[0021]
A DLC coating film 9 is also formed on the sliding surface 1d of the piston 1 sliding on the cylinder 5b and on the sliding surface 1e of the piston ball portion 1a.
[0022]
The DLC coating film 9 is formed by an unbalanced magnetron sputtering method (hereinafter, referred to as “UBM sputtering method”).
[0023]
As shown in FIG. 4, the principle of sputtering is to form a plasma by performing glow discharge between the anodes with the target 11 as a cathode in a vacuum in which an inert gas such as argon is introduced, and forming ions in the plasma into the target 11. And bombards the atoms of the target 11, and deposits the atoms on a work 31 arranged to face the target 11 to form a film.
[0024]
According to the UBM sputtering method, magnets 12 and 13 having different magnetic properties are arranged at a central portion and a peripheral portion of a target 11 in a sputter evaporation source 10, and a part of magnetic lines generated by the strong magnet 12 while forming plasma is generated. By reaching the vicinity of the work 31 and applying a bias voltage to the work 31, a substance constituting the target material 14 is deposited on the work 31.
[0025]
FIG. 5 shows a basic configuration of the UBM sputtering apparatus 20. The vacuum chamber 21 is provided with four sputter evaporation sources 10a to 10d, and the work 31 is placed on a self-revolving work table 26 arranged at the center thereof, and the work 31 is coated from the outer periphery. A flat target serving as a film material is attached to the sputter evaporation sources 10a to 10d. The vacuum chamber 21 is filled with a predetermined amount of an inert gas such as argon and a hydrocarbon gas such as methane gas.
[0026]
For the sputtering evaporation sources 10a and 10c, graphite is used as a target, and for the sputtering evaporation sources 10b and 10d, a metal is used as a target.
[0027]
As shown in FIG. 3, the DLC coating film 9 is formed by sequentially laminating a bond layer 32, an intermediate layer 33, and a top layer 34 on the surface of a work (piston 1 or shoe 2) 31.
[0028]
FIG. 6 shows how the target output changes when the DLC coating film 9 is formed.
[0029]
The bond layer 32 is formed as a metal film by sputtering only the metal targets 10b and 10d. In forming the bond layer 32, as shown in FIG. 7, the output of the metal target of the sputter evaporation sources 10b and 10d is set to 100%, and the output of the graphite target of the sputter evaporation sources 10a and 10c is fixed to 0%. Sputtering is performed for a predetermined time.
[0030]
The intermediate layer 33 is formed as a gradient composition film of metal and carbon by simultaneously sputtering the metal targets of the sputter evaporation sources 10b and 10d and the graphite targets of the sputter evaporation sources 10a and 10c, and gradually changing the target output. In forming the intermediate layer 33, as shown in FIG. 7, while the output of the metal target of the sputter evaporation sources 10b and 10d is temporarily reduced from 100%, the output of the graphite target of the sputter evaporation sources 10a and 10c is reduced to 0. %, And is sputtered only for a predetermined period of time.
[0031]
The top layer 34 is formed by simultaneously sputtering the metal targets of the sputter evaporation sources 10b and 10d and the graphite targets of the sputter evaporation sources 10a and 10c, and keeping the target output substantially constant, with the metal targets of the sputter evaporation sources 10b and 10d and the sputter evaporation source 10a. , 10c are sputtered for a predetermined time while maintaining the sputtering rate of the graphite target in a predetermined range.
[0032]
In forming the top layer 34, as shown in FIG. 7, the output of the metal target of the sputter evaporation sources 10b and 10d is set to about 10%, and the output of the graphite target of the sputter evaporation sources 10a and 10c is set to about 90%. The ratio of the metal contained in the top layer 34 is set in a range of 3 to 18%. More preferably, the ratio of the metal contained in the top layer 34 is set in a range of 3 to 12%.
[0033]
The operation as described above will now be described.
[0034]
A bond layer 32 having a metal ratio of 100% and an intermediate layer 33 made of a gradient composition film of metal and carbon are provided on a metal work 31. By providing the top layer 34, the bonding strength of the top layer 34 to the work 31 can be increased.
[0035]
By setting the ratio of the metal of the top layer 34 in the range of 3 to 18%, the adhesion and toughness of the top layer 34 can be increased, and when the work 31 is deformed by a high load, cracking or peeling occurs. Can be prevented. Then, a decrease in hardness of the top layer 34 can be suppressed, and abrasion resistance can be ensured.
[0036]
As shown in FIG. 8 showing the relationship between the ratio of the metal contained in the top layer 34 and the toughness and hardness, by setting the ratio of the metal in the range of 3 to 18%, both the toughness and the hardness of the top layer 34 are increased. Can be Further, by setting the ratio of the metal contained in the top layer 34 to a range of 3 to 12%, both the toughness and the hardness of the top layer 34 can be significantly increased.
[0037]
On the other hand, conventionally, since the ratio of the metal contained in the top layer was 0%, the adhesion and toughness were insufficient, and there was a problem that the top layer was liable to crack or peel.
[0038]
As a result, even if the DLC coating film 9 is formed on each of the sliding surfaces 2b, 1d, and 1e of the shoe 2 and the piston 1 which are subjected to a high load, cracking and peeling of the DLC coating film 9 are avoided, and practical use is realized. Becomes possible.
[0039]
Due to the structure in which the DLC coating film 9 is formed on the sliding surface 2b of the shoe 2, the high hardness DLC coating film 9 maintains the tapered shape of the sliding surface 2b of the shoe 2 so that high startup efficiency is maintained. Dripping.
[0040]
Since the DLC coating film 9 is also formed on the sliding surface 1d sliding on the cylinder 5b of the piston 1 and the sliding surface 1e of the piston ball portion 1a, the frictional force is reduced by the DLC coating film 9 of high hardness. In addition, efficiency can be improved.
[0041]
It is apparent that the present invention is not limited to the above-described embodiment, and that various changes can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a sectional view of a piston, a shoe, and the like showing an embodiment of the present invention.
FIG. 2 is a sectional view of the hydraulic piston pump / motor.
FIG. 3 is a cross-sectional view of the DLC coating film.
FIG. 4 is an explanatory view showing the principle of the sputtering method.
FIG. 5 is a configuration diagram of a UBM sputtering apparatus.
FIG. 6 is a characteristic diagram showing how the target output changes.
FIG. 7 is a characteristic diagram showing the relationship between the ratio of metal contained in the top layer and toughness and hardness.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piston 1d, 1e Sliding surface 2 Shoe 2b Sliding surface 3 Swash plate 5 Cylinder block 9 DLC coating film 10a-10d Sputter evaporation source 20 UBM sputtering device 31 Work 32 Bond layer 33 Intermediate layer 34 Top layer

Claims (3)

A cylinder block rotatably supported about an axis, a plurality of pistons reciprocally mounted in the cylinder block, a swash plate for reciprocating the piston with rotation of the cylinder block, A hydraulic piston pump motor comprising: a shoe slidingly connected to the plate and rotatably connected to the piston;
A hydraulic piston pump / motor, wherein a sliding surface of the shoe that is in sliding contact with the swash plate is formed in a tapered shape with a concave shape, and a DLC coating film is formed on the sliding surface. The hydraulic piston pump motor according to claim 1, wherein a DLC coating film is formed on a sliding surface of the piston that slides on the cylinder block and the shoe. The DLC coating film forms an intermediate layer by sputtering only a metal target on a work to form a bond layer, and simultaneously sputtering a metal target and a graphite target on the bond layer and gradually changing the target output. A hydraulic piston, characterized in that a metal target and a graphite target are simultaneously sputtered on the intermediate layer and a top layer having a metal ratio in the range of 3 to 18% is formed by making the target output substantially constant. Pumps and motors.

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