JP2002031040A - Surface treatment structure of hydraulic piston pump/ motor sliding part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment structure of a hydraulic piston pump/ motor sliding part suitable for using the corrosive working fluid of low lubricity. SOLUTION: A piston 1 (and/or a shoe 2) is made of a corrosion-resisting stainless steel or stainless alloy, and a sliding part 10a to a cylinder inner face and a sliding face 10b of a piston spherical part 1a are coated with DLC (Diamond like Carbon) thin films 11 (a sliding face 2b to a swash plate 3, of the shoe 2 is coated with a thin film 12a). The DLC thin films 11, 12a are composed of a carbon element with a dense amorphous structure, and attached to a base material by PVD processing or CVD processing with a thickness of approximately 1-5 μm. As the corrosion-resisting stainless steel or stainless alloy is used as the base material, the rusting can be prevented even when a part free from the DLC thin films 11, 12a is exposed to the corrosive working fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment structure for a sliding portion of a hydraulic piston pump / motor,
In particular, the present invention relates to a surface treatment structure of a sliding portion of a hydraulic piston pump / motor which is suitable when a working fluid having poor lubricity and corrosive is used.

[0002]

2. Description of the Related Art Generally, a swash plate type hydraulic piston pump
The motor is configured as shown in FIG. Figure 11
, The cylinder block 105 rotated by the drive shaft 107 includes a plurality of cylinders 1 at equal intervals on the same circumference.
The piston 105 that reciprocates in the axial direction is housed in the cylinder 105b. Piston 10
1, a piston ball portion 101a is formed at the tip of the spherical hole 10a provided in the shoe 102.
2a is rotatably fitted. The shoe 102 rotates together with the cylinder block 105 while sliding on the swash plate 103 by the sliding surface 102b. The piston 101 and the sliding surface 102b of the shoe 102
Hydraulic pressure is introduced through the internal passage 101c, and a hydrostatic bearing is formed between the spherical hole 102a of the shoe 102 and the piston ball portion 101a and between the sliding surface 102b of the shoe 102 and the swash plate 103. As a result, the solid contact surface pressure between the two is reduced. The swash plate 103 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 105, or in the case of a variable type, the inclination angle is changed by an actuator. A pair of ports 104d, 104e
It is configured to be in sliding contact with the valve plate 104 having

The cylinder block 10 is driven by a drive shaft 107.
When the cylinder 5 rotates, the piston 101 that comes into contact with the swash plate 103 via the shoe 102 makes one reciprocation for one rotation of the cylinder block 105. For example, the hydraulic fluid is sucked from one port 104 e of the valve plate 104, and the other is sucked. Port 104
The hydraulic fluid is discharged from d.

[0004] Such a swash plate type hydraulic piston pump
In the motor, various action forces described below act as the piston 101 reciprocates. That is, in the drawing, the piston 101 now starts moving in the compression direction from the extended state, and when discharging the fluid, the cylinder 105
A high fluid pressure is generated in b according to the load on the discharge passage side. The force in the axial direction of the piston 101 due to the fluid pressure is represented by F
Assuming that the piston 101 is 1, the swash plate 1
03, the swash plate 103 opposes the force F1 by the reaction force F2 in the direction perpendicular to the sliding surface. This force F2
Is different from the reciprocating direction of the piston 101 by the inclination angle of the swash plate 103, and couples F3 and F4 perpendicular to the reciprocating direction are applied to both ends of the fitting between the piston 101 and the inner peripheral surface of the cylinder 105b that slides the piston 101. generate. This couple F3
F4 generates a sliding surface pressure between the outer peripheral surface of the piston 101 and the inner peripheral surface of the cylinder 105b, and causes seizure and wear therebetween.

[0005] As a surface treatment structure for improving the seizure resistance and wear resistance of the piston sliding portion, there is a structure described in, for example, Japanese Utility Model Laid-Open Publication No. 64-13280.

According to this conventional example, physical vapor deposition (PV) is performed on a sliding portion of a steel piston hardened by nitriding or the like.
D) a hard film formed by coating a super-hard material, for example, carbide SiC, nitride TiN, or oxide Al ₂ O ₃ , to improve seizure resistance and wear resistance between the piston and the cylinder. It is.

[0007]

However, in the above conventional example, when a working fluid having poor lubricity and corrosiveness is used as the working fluid, the following problems occur. 1. Rust does not occur on the sliding portion of the piston coated with the super-hard film because the super-hard film itself has corrosion resistance. However, since the outer surface of the uncoated piston other than the sliding portion is also exposed to the corrosive working fluid, rust cannot be prevented. And
There has been a problem that this rust enters the sliding portion and peels off the coated thin film, causing malfunction of the pump / motor. 2. Furthermore, this super hard coating is PVD (Physical).
Although it is attached to the piston surface by a Vapor Deposition (physical vapor deposition) process, it is difficult to form a thin film having a uniform thickness inside, for example, in a hole or deep inside a depression. Therefore, there is a problem in that forming a super-hard film having corrosion resistance so as to enclose the entire part and adapting it to a corrosive working fluid increases the manufacturing cost.

In view of the above, the present invention has been made in view of the above-mentioned problems, and is suitable for a hydraulic piston pump / motor sliding portion which is suitable even when a fluid having poor lubricity and corrosive fluid is used as a working fluid. It is an object to provide a surface treatment structure.

[0009]

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 a tip of the piston having a spherical surface. Alternatively, in a hydraulic piston pump / motor having a shoe that slides and supports in a plane and a valve plate that slides on the back of the cylinder block and has a pair of ports, the sliding member of the hydraulic piston pump / motor is made of stainless steel. Alternatively, the sliding surface is formed by coating a DLC thin film with a stainless steel alloy.

According to a second aspect of the present invention, in the first aspect, the piston is brought into contact with a smooth surface provided on the shoe in a plane perpendicular to the piston axis, and is inclined relatively to the rotation axis of the cylinder block. A ring member rotating about an axis is a hydraulic piston pump / motor configured to spherically support the shoe and rotate the cylinder block and the ring member synchronously by a rotation transmitting mechanism.

According to a third aspect of the present invention, in the first or second aspect, the sliding member made of stainless steel or a stainless steel alloy has at least a surface portion of a sliding surface hardened, and the hardened surface. Is coated with a DLC thin film.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the sliding member made of stainless steel or a stainless alloy has Cr, S
i, Ti, Zr, Ge, Ru, Mo, W or at least one of them or an intermediate layer containing at least one element of carbon, nitrogen and oxygen is coated thereon, and a DLC thin film is formed on the surface of the intermediate layer. It is characterized by being coated.

In a fifth aspect based on the fourth aspect, the intermediate layer partially includes a composition having the same composition as that of the DLC thin film, and the ratio of the DLC composition is made of the stainless steel or the stainless alloy. On the side close to the substrate, the composition of the intermediate layer is set, and the composition of the intermediate layer is reduced and the proportion of the DLC composition is increased as approaching the DLC thin film.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the sliding member includes a piston that slides on the cylinder block and the shoe, a shoe that supports the piston, and a valve that slides on the cylinder block. It is characterized in that it is at least one of a cylinder block and a cylinder block that is in sliding contact with the valve plate.

According to a seventh aspect of the present invention, in any one of the second to sixth aspects, the sliding member is a shoe that is in sliding contact with a ring member, a ring member that is in sliding contact with a guide surface around an axis,
And at least one of a thrust plate slidingly in contact with the ring member from the back surface.

In an eighth aspect based on any one of the second to seventh aspects, the rotation transmission mechanism connects the joint connected to the ring member side and the joint connected to the cylinder block side. The sliding member is a member constituting the joint.

[0017]

Therefore, the first invention uses stainless steel or a stainless alloy which provides corrosion resistance for the base material of the sliding member, so that the surface of the sliding member not coated with the DLC thin film has corrosiveness. Rust can be prevented from being generated even when exposed to a working fluid.

The sliding surface of the sliding member has a DLC (Di
Since it is coated with an amber like carbon (thin film), it has good slipperiness and can improve seizure resistance and abrasion resistance.

In the second invention, a ring member is arranged so that the piston abuts on a smooth surface provided on the shoe in a plane perpendicular to the piston axis, and rotates about an axis inclined relative to the rotation axis of the cylinder block. When the operation is performed at a higher pressure by coating the sliding member of a hydraulic piston pump / motor, which supports the shoe spherically and rotates the cylinder block and the ring member synchronously by a rotation transmission mechanism, with a DLC thin film. Even if there is a low cost high pressure pump
It can be used as a motor.

In the third invention, since the surface of the substrate on which the DLC thin film is coated is cured to suppress its elastic deformation, the deformation applied to the hard DLC thin film is suppressed.
A strong sliding surface free from cracking and peeling can be formed, and seizure resistance, abrasion resistance and a low friction coefficient can be obtained.

In the fourth aspect, since the intermediate layer having high adhesion to the piston base is formed between the DLC thin film and the piston base, peeling of the DLC thin film can be prevented. That is, the linear expansion coefficient of the DLC thin film is relatively smaller than the linear expansion coefficient of the stainless steel substrate. For this reason, when frictional heat is generated on the sliding surface, cracks occur in the DLC thin film due to a difference in thermal expansion between the stainless steel substrate and the DLC thin film, and as a result, the DL
The C thin film peels off. However, in the present invention, since the adhesion of the intermediate layer to the stainless steel substrate is enhanced, the DLC thin film can be prevented from cracking and peeling.

According to the fifth aspect of the present invention, since the composition having the same structure as the DLC thin film is diffused from the DLC thin film toward the inner layer in the intermediate layer, the adhesive force between the intermediate layer and the DLC film is increased, and In addition, the peel strength of the DLC thin film can be further increased.

In the sixth aspect of the present invention, when the sliding surface of the piston that slides on the cylinder block and the shoe is coated with the DLC thin film, the sliding property between the cylinder and the shoe is improved, and seizure does not occur. In addition, when the sliding surface of the shoe that slides on the piston and the swash plate is coated with a DLC thin film, the sliding property between the piston and the swash plate is improved, and seizure and abnormal wear can be prevented. Further, when a DLC thin film is coated on the valve plate that slides on the cylinder block and / or on the cylinder block that slides on the valve plate, the slipperiness between the cylinder block and the valve plate is improved, and seizure does not occur.

In the seventh aspect, when a shoe in sliding contact with the ring member is coated with a DLC thin film, the slipperiness between the ring member and the shoe is improved, so that seizure or the like does not occur. Also, a DLC is applied to a ring member that slides on the guide surface around the axis or a thrust plate that slides on the ring member from the back.
When a thin film is coated, the sliding property of the ring member is improved, so that baking or the like does not occur.

According to the eighth aspect, when the sliding surfaces of the two joints are coated with the DLC thin film, wear of the engaging portions of the joints can be prevented, and the durability thereof can be improved.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the present invention,
This is an example in which the surface treatment structure of the present invention is applied to a piston and a shoe which are sliding members of a hydraulic piston pump / motor.

In FIG. 1, reference numeral 1 denotes a piston, and a piston ball portion 1a is integrally formed at the tip, and a base portion 1 is provided inside.
b has a passage 1c reaching the piston ball portion 1a. 2
Is a shoe having a spherical hole 2a for receiving the piston ball portion 1a and a sliding surface 2b in contact with the swash plate 3;
c, and the recess 2c communicates with the bottom of the spherical hole 2a through a passage 2g. The spherical hole 2a of the piston 1 is received in the spherical hole 2a of the shoe 2.
Both are assembled by caulking the edge of a. And
The internal pressure of the cylinder is introduced between the recess 2c of the sliding surface 2b of the shoe 2 and the swash plate 3 through the passages 1c and 2g to form a hydrostatic bearing to reduce the solid contact surface pressure between the two. ing.

The structure of the spherical connecting portion between the piston 1 and the shoe 2 is not limited to the above example, and for example, the structure shown in FIG. 2 is also possible. That is, in FIG. 2, a spherical hole 1e is formed at the tip of the piston 1 and a spherical portion 2h is formed integrally with the shoe 2. Then, by caulking the edge of the spherical hole 1e in a state where the spherical portion 2h of the shoe 2 is received in the spherical hole 1e of the piston 1, both are assembled.

The material of the piston 1 is stainless steel or a stainless alloy which provides corrosion resistance. The sliding portion 10a which slides in the cylinder (not shown in FIG. 1) and the sliding surface 10b of the piston ball portion 1a are provided. Makes the surface roughness of the base material as small as possible by polishing or the like, and the DLC (Di
amond Like Carbon) thin film 11 is coated. The material of the shoe 2 is the piston 1
The sliding surface 2b in contact with the swash plate 3 is made as small as possible and smooth by polishing or the like on the sliding surface 2b in contact with the swash plate 3 to obtain a DLC (Diamond Like Carbo).
n) The thin film 12a is coated.

In FIG. 2, the sliding portion 10a that slides in the cylinder (not shown) of the piston 1 makes the surface roughness of the base material as small as possible and coats it with a DLC thin film. Also, the sliding surface 2i of the ball portion 2h of the shoe 2 has the surface roughness as small and smooth as possible, and the DLC thin film 12b
Coating.

This DLC (Diamond Like)
Carbon) The thin films 11, 12a and 12b are made of carbide S
Compared with ultra-hard coatings such as iC, nitride TiN, oxide Al ₂ O _3, etc., hardness is high, low friction coefficient is obtained, wear resistance is excellent, and sliding characteristics are excellent. This DLC thin film 11, 1
2a and 12b are composed of a carbon element like diamond and graphite and have a dense amorphous structure.
VD (Physical Vapor Deposit)
ion, physical vapor deposition) or CVD (Ch)
The substrate is adhered to a substrate with a thickness of about 1 to 5 μm by an electrical vapor deposition (chemical vapor deposition) process.

In this embodiment, stainless steel or a stainless steel alloy having corrosion resistance is used as the base material of the piston 1 and the shoe 2, and the DLC thin films 11, 12a, and 12 are used.
Even if a portion not coated with b is exposed to a corrosive working fluid, rust can be prevented from being generated.

In the piston 1 of this embodiment, a sliding part 10a that slides in a cylinder (not shown) and a sliding surface 10b of the piston ball or a sliding surface 2i of the shoe ball 2h have a DLC (Diamond Like). (Carbon) Since the thin films 11 and 12b are coated, the sliding property between the inner peripheral surface of the cylinder and the shoe 2 is good. Therefore, even without providing a bush or the like in the cylinder or spherical part,
Sufficient lubricity is obtained, and there is no fear of seizing.

The shoe 2 of this embodiment has a sliding surface 2b in contact with the swash plate 3 and has a DLC (Diamond Like).
(Carbon) Since the thin film 12a is coated, the sliding property with the swash plate 3 is good. Therefore, even if the function of the hydrostatic bearing is reduced and the solid contact surface pressure between them is increased, abnormal wear of the shoe 2 does not occur. The case where the function of the hydrostatic bearing is reduced is, for example, when the piston 1 shifts from the suction process to the discharge process, and when the piston 1 shifts to the suction stroke, the liquid introduced into the hydrostatic bearing. The pressure may change suddenly and the contact state between the shoe 2 and the swash plate 3 may become unstable.

The DLC (Diamond Like)
When coating the thin films 11, 12a, and 12b, the surface roughness of the substrate to be coated is made as small as possible by polishing or the like.
This is for improving the adhesion of the C thin films 11, 12a, 12b.

In this embodiment, the sliding surfaces 10a and 10b of the piston and the sliding surface 2b of the shoe, or the sliding surface 10a of the piston 1 and the sliding surfaces 2a and 2b of the shoe 2 are all DLC. (Diamond Like Carbo
n) Although an example in which a thin film is coated has been described, the present invention can be practiced at only one of the places, and the object of the present invention can be achieved even with only one place.

The examples shown in FIGS. 3 to 6 are examples in which the present invention is applied to a sliding portion between a cylinder block as a sliding member and a valve plate.

In FIGS. 3 and 4, reference numeral 4 denotes a valve plate, and a sliding surface 4a which contacts a cylinder block (not shown).
Has a groove 4 extending in an arc shape which functions as a valve on the same circumference.
b, 4c are formed, and these grooves 4b, 4c
It communicates with the back of the valve plate 4 by d and 4e. In addition, 4
f is a through hole for receiving a rotation preventing pin (not shown).

The material of the valve plate 4 is made of stainless steel or a stainless alloy capable of obtaining corrosion resistance. The sliding surface 4a in contact with the cylinder block is made as smooth and smooth as possible by polishing or lapping. And DL
C (Diamond Like Carbon) thin film 1
3 is coated.

5 and 6, reference numeral 5 denotes a cylinder block having a sliding surface 5a which is in sliding contact with the sliding surface 4a of the valve plate 4. The sliding surface 5a has a passage 5c communicating with the cylinder 5b. Is open. The material of the cylinder block 5 is made of stainless steel or a stainless alloy capable of providing corrosion resistance. The surface of the base material on the sliding surface 5a in contact with the valve plate 4 is made as small and smooth as possible by polishing or lapping. DLC (Diamond Like Ca)
rbon) The thin film 14 is coated.

Incidentally, the contact surfaces shown in FIGS. 3 to 6 may cause seizure. This will be described with reference to FIG. 11. As a reaction force of the couples F3 and F4, F
5 and F6, the reaction forces F5 and F6 generate a rotational moment M on the entire cylinder block 105, and the rotational moment M tends to incline the cylinder block 105, and slides between the valve plate 104 and the cylinder block 105. The surface pressure was high in the upper part of the figure and lower in the lower part, causing a non-uniform state, which caused seizure between the two. However, in this embodiment, the sliding surfaces 4a, 5a of the valve plate 4 (and / or the cylinder block 5) have DLC (Diamon).
d Like Carbon) Since the thin films 13 and 14 are coated, the sliding property with the cylinder block 5 (or the valve plate 4) is good. Therefore, sufficient slip properties can be obtained and there is no fear of seizure.

Either of the examples of FIGS. 3 and 4 and the examples of FIGS. 5 and 6 is sufficient, but if both examples are implemented, the effect can be further improved.

In this embodiment, the base material of the valve plate 4 (and / or the cylinder block 5) is made of a stainless steel or a stainless alloy having corrosion resistance.
Outer surface of the valve plate 4 not coated with a DLC thin film,
For example, even if a portion such as the inside of the hole or the back surface is exposed to a corrosive working fluid, the generation of rust can be prevented, and no problem due to rust occurs.

FIG. 7 shows a third embodiment of the present invention.
This is an example in which the surface treatment structure of the present invention, in which a base material is subjected to hardening treatment when coating a DLC thin film, is applied to the same parts as the first embodiment of the piston and the shoe as sliding members for the hydraulic piston pump / motor.

In FIG. 7, the material of the piston 1 (and / or the shoe 2) is stainless steel or a stainless alloy capable of hardening the entire substrate or only the surface, and coats the DLC thin films 11, 12a. First, a hardening treatment 20 is applied to the sliding surfaces 10a, 10b, 2b. Examples of the method of the hardening treatment 20 include a quenching treatment, a solution heat treatment, a precipitation hardening treatment, a nitriding treatment and a soft nitriding treatment. By this hardening treatment 20, the sliding surfaces 10a, 10
b, 2b to reduce the elastic deformation, and then the DLC thin film 1
1,12a was coated on this surface.

When a compound layer is formed on the surface of the base material by the curing treatment 20, this compound layer is removed by polishing or the like, so that the adhesion to the DLC thin films 11 and 12a can be improved. . In addition, when the surface of the substrate on which the coating is to be applied is to be polished smoothly as small as possible, the adhesion to the DLC thin films 11 and 12a can be improved.

According to this configuration, since the elastic deformation of the surface of the base material can be suppressed to be small, the DLC is hard and has a small elastic deformation.
It has good compatibility with the thin films 11 and 12a, and does not cause cracking or peeling of the DLC films 11 and 12a due to elastic deformation of the base material.
A stronger sliding surface can be formed, seizure resistance,
Abrasion resistance and a low coefficient of friction can be obtained.

The surface treatment structure of this embodiment can be applied to the sliding surfaces 2i, 4a, 5a shown in FIGS. 2 to 6, and the present invention is applied to the sliding surfaces 2i, 4a, 5a shown in FIGS. And the one to which this surface treatment structure is applied.

FIGS. 8 and 9 show a fourth embodiment of the present invention, in which a surface treatment structure in which an intermediate layer is formed between a substrate and a DLC thin film in coating a DLC thin film is formed by a hydraulic piston pump. This is an example in which a piston of a motor is applied to a portion similar to that of the first embodiment.

In FIG. 8, a piston 1 is made of a stainless steel or a stainless alloy, which has corrosion resistance, and has a sliding portion 10a which slides in a cylinder (not shown).
An intermediate layer 21 having high adhesion to the base material is formed on the sliding surface 10b of the piston ball portion 1a by coating, and the DLC (D
iamond Like Carbon) thin film 11 and an intermediate layer 21 and DLC on a stainless steel substrate.
The thin film 11 has a laminated structure. The material of the intermediate layer 21 is Cr (chromium) · Si (silicon), Ti (titanium), Zr (zirconium) · Ge
One or more of (germanium), Ru (ruthenium), Mo (molybdenum), and W (tungsten) or a material containing at least one element of carbon, nitrogen, and oxygen.

The intermediate layer 21 has a high adhesion to the stainless steel base material and is free from cracks generated in the DLC thin film due to a difference in thermal expansion between the DLC thin film 11 having a relatively small linear expansion coefficient and the stainless steel base material having a large linear expansion coefficient. This is to increase the adhesion and prevent it. Therefore, if a crack occurs in the DLC thin film 11, the peeling subsequently occurs, and the peeling increases the frictional force, further increases the frictional heat, and further causes a chain reaction of cracking and peeling of the DLC thin film, which causes thermal expansion. This is very effective for improving the durability of the DLC thin film 11.

Further, the intermediate layer 21 is not formed as a single composition layer, but the composition 21a of the intermediate layer is increased near the surface of the base material. The composition 21b of the structure is gradually increased, and in the layer near the outermost surface, the composition 21a of the intermediate layer is small and the composition 21b of the same structure as the DLC thin film is increased. FIG. 9 is an example of transition of each composition ratio. Thus DL
When the ratio of the composition 21b having the same configuration as the C thin film and the composition 21a having the same configuration as the intermediate layer 21 is configured to be inclined, the adhesive force between the intermediate layer 21 and the DLC film 11 is increased, and the entire layer is peeled off. You can make it stronger.

In the above example, the intermediate layer is described as being directly coated on a substrate made of stainless steel or a stainless alloy. However, after the substrate is subjected to a hardening treatment shown in FIG. The effect of the two embodiments is synergistically achieved by coating.

The surface treatment structure of the present embodiment has a sliding surface 2b of the shoe 2 and sliding surfaces 2i, 4a, 5a shown in FIGS.
The present invention includes those in which the present surface treatment structure is applied to the sliding surface 2b of the shoe 2 and the sliding surfaces 2i, 4a, 5a shown in FIGS.

Although the above embodiments have been described with reference to the case where the present invention is applied to a swash plate type hydraulic piston pump / motor, a swash plate type hydraulic piston in which pistons are arranged on the same circumference of a cylinder block. The same can be applied to the sliding portion of the pump / motor.

The embodiment shown in FIG.
This is an example in which the present invention is applied to a sliding surface of a hydraulic piston pump / motor described in Japanese Patent No. 1975. In addition, the same components will be described with the same reference numerals.

In FIG. 10, one of the side walls 6a penetrates into the housing 6 closed by the side walls 6a and 6b.
A ring member 8 rotatably driven by a held input shaft 7 (an output shaft in the case of a motor) and a plurality of pistons 1 slidably provided on the other side wall 6b via a valve plate 4 so as to be rotatable. The held cylinder block 5, a rotation transmitting mechanism 9 for transmitting the rotation of the input shaft 7 to the cylinder block 5, and a shoe 2 for holding the protruding end of the piston 1 on the ring member 8.
And formed from The input shaft 7 and the rotation shaft of the cylinder block 5 are formed so as to be relatively inclined.

The piston 1 is provided with a cylinder 5 as in the prior art.
The piston 5 has a sliding surface 10 that slides with the piston 2 and is protruded by a spring 5d in the cylinder 5b. The protruding end contacts the shoe 2 at a contact surface 1d formed by a plane perpendicular to the axis of the piston 1. The shoe 2 has a smooth surface 2d in contact with the contact surface 1d of the piston 1 and a shoe sliding surface 2e in spherical contact with a spherical shoe receiving portion 8a provided on the ring member 8. The outer periphery of the ring member 8 is rotatably held on one side wall 6a via a ring member sliding surface 8b, and the back surface of the ring member 8 is connected to a thrust plate 6c provided in the one side wall 6a via the thrust plate sliding surface 8c. Contact. The valve plate 4 is in contact with the cylinder block 5 through its sliding surface 4a. The rotation transmission mechanism 9 includes a spline 9a provided at the end of the input shaft 7 and a spline 9b provided at the end of the cylinder block 5.
And has an intermediate shaft 9e having spline heads 9c and 9d at both ends to engage with the cylinder block 5 to transmit the rotation of the input shaft 7 to the cylinder block 5 at a constant speed. That is, the rotation transmission mechanism 9 has a structure having joints at both ends. And, between the contact surface 1d of the piston 1 and the smooth surface 2d of the shoe 2, between the shoe receiving portion 8a of the ring member 8 and the shoe sliding surface 2e of the shoe 2, the thrust plate sliding surface of the ring member 8 The hydraulic fluid pressure in the cylinder 5b is introduced between the cylinder 8c and the thrust plate 6c via passages 1c and 2f.

The sliding surfaces, namely, the sliding surface 10 of the piston 1 with the cylinder 5b, the sliding surface 1d of the piston 1 with the shoe 2d, the sliding surface 4a of the valve plate 4 with the cylinder block 5, the shoe 2, the sliding surface 2e with the ring member 8, the sliding surface 8b with the side wall 6a of the ring member 8, the thrust plate 6
c, the sliding surface 8c of the ring member 8 with the ring member 8, the sliding surface of the mating partner that slides on the sliding surface, and / or both of the sliding surfaces. Is coated with the DLC thin film. Further, the spline head 9 of the intermediate shaft 9e of the rotation transmitting mechanism 9
DLC thin films are coated on c and 9d, that is, on the sliding surfaces of the joints by any of the surface treatment structures of the above-described examples.

In this hydraulic piston pump / motor, the piston 1 and the shoe 2 have a contact surface 1 perpendicular to the axis of the piston 1.
d and the smooth surface 2d, the piston 1
No bending moment acts on, and the contact surface pressure and sliding frictional force generated between the piston 1 and the cylinder 5b are reduced to improve the mechanical efficiency. Moreover, each sliding surface has DLC
Since the thin film is coated, the sliding condition of each of the sliding surfaces is further improved, and can be applied to a working liquid having poor lubricity as a working liquid. Even when operated at a higher pressure, a low-cost high-pressure pump is used. -Can be used as a motor.

Further, since the spline heads 9c and 9d of the intermediate shaft 9e of the rotation transmitting mechanism are coated with the DLC thin film, the splines 9a to 9d can be prevented from being worn even when driven by rotation with fluctuation. , Its durability can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a surface treatment structure of a sliding portion of a hydraulic piston pump / motor showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a modification of FIG.

FIG. 3 is a front view in which one embodiment of the present invention is applied to a valve plate.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a front view in which one embodiment of the present invention is applied to a cylinder block.

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a sectional view of a surface treatment structure of a sliding portion of a hydraulic piston pump / motor showing another embodiment of the present invention.

FIG. 8 is a cross-sectional view of a surface treatment structure of a sliding portion of a hydraulic piston pump / motor showing still another embodiment of the present invention.

FIG. 9 is a graph showing a modification of FIG. 8;

FIG. 10 is a sectional view of a hydraulic piston pump / motor to which the surface treatment structure of the present invention is applied.

FIG. 11 is a schematic sectional view of a conventional hydraulic piston pump / motor.

[Explanation of symbols]

1 piston 2 shoe 2b, 2e, 2i, 4a, 5a, 8a, 8b, 8c, 1
0a, 10b Sliding surface 3 Swash plate 4 Valve plate 5 Cylinder block 6 Housing 7 Input shaft 8 Ring member 9 Rotation transmitting mechanism 11, 12a, 12b, 13, 14 DLC thin film 20 Hardening treatment 21 Intermediate layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Takashi Ito 2-4-1, Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Industry Co., Ltd. F-term (reference) 3H070 AA01 BB05 BB06 CC07 CC27 DD09 DD28 DD32 DD69 EE02 EE03 3H071 AA03 BB01 CC26 CC27 DD01 DD06 DD11 EE02 EE03 3H084 AA07 AA16 BB06 BB09 CC12 CC33 CC70

Claims (8)

[Claims] 1. A cylinder block rotatably supported around an axis, a plurality of pistons housed reciprocally in the cylinder block, and a shoe for slidingly supporting a tip of the piston on a spherical surface or a plane. A hydraulic piston pump / motor having a valve plate having a pair of ports slidably in contact with the back surface of the cylinder block, wherein the sliding member of the hydraulic piston pump / motor is formed of stainless steel or a stainless steel alloy, D on the surface
A surface treatment structure for a sliding portion of a hydraulic piston pump / motor characterized by being coated with an LC thin film. 2. A ring member which rotates the piston about an axis inclined relative to a rotation axis of the cylinder block, wherein the piston is brought into contact with a smooth surface provided on a shoe in a plane orthogonal to the piston axis. 2. A surface treatment structure for a sliding portion of a hydraulic piston pump / motor according to claim 1, wherein the shoe is supported on a spherical surface, and the cylinder block and the ring member are synchronously rotated by a rotation transmitting mechanism. 3. A sliding member made of stainless steel or a stainless alloy, wherein at least the surface of the sliding surface is hardened, and the hardened surface is coated with a DLC thin film. A surface treatment structure for a sliding portion of the hydraulic piston pump / motor according to claim 1 or 2. 4. The sliding member made of stainless steel or stainless alloy has a sliding surface of Cr, Si, T
at least one of i, Zr, Ge, Ru, Mo, W or at least one of carbon, nitrogen and oxygen
The hydraulic piston pump / motor slide according to any one of claims 1 to 3, wherein an intermediate layer containing a kind of element is coated, and the surface of the intermediate layer is coated with a DLC thin film. Moving part surface treatment structure. 5. The intermediate layer partially includes a composition having the same composition as that of the DLC thin film, and the proportion of the DLC composition is such that the composition of the intermediate layer is closer to the base made of stainless steel or stainless steel alloy. 5. The surface treatment of a sliding part of a hydraulic piston pump / motor according to claim 4, wherein the proportion of the composition of the intermediate layer is decreased and the proportion of the DLC composition is increased as approaching the DLC thin film. Construction. 6. A piston that slides on a cylinder block and a shoe, a shoe that supports the piston,
6. The hydraulic piston pump / motor slide according to claim 1, wherein at least one of a valve plate slidingly contacting the cylinder block and a cylinder block slidingly contacting the valve plate. Surface treatment structure. 7. The sliding member is at least one of a shoe that is in sliding contact with a ring member, a ring member that is in sliding contact with a guide surface around an axis, and a thrust plate that is in sliding contact with the ring member from the back. Claim 2
The hydraulic piston pump according to any one of 1 to 6,
Surface treatment structure of motor sliding part. 8. The rotation transmitting mechanism is configured by connecting a joint connected to a ring member side and a joint connected to a cylinder block side, and the sliding member is a member forming the joint. A surface treatment structure for a sliding portion of a hydraulic piston pump / motor according to any one of claims 2 to 7, wherein: