JPH0882278A - Swash plate type hydraulic rotating machine and manufacture thereof - Google Patents

Abstract

PURPOSE: To connect a piston to a sliding member with suitable drawing strength, to improve working efficiency at the time of manufacture, and to reduce the manufacturing cost. CONSTITUTION: A spherical joint part 17 of a piston shoe 16 is fitted to a recessed spherical part 32 of a piston 31, and the caulking part 31A of the piston 31 is reduced in diameter to connect the piston 31 to the piston shoe 16. After that, the piston 31 and the piston shoe 16 are subjected to soft nitriding processing, whereby the piston 31 and the piston shoe 16 can be connected to each other with suitable drawing strength without cracks in the caulking part 31A. Furthermore, as the need of a turning process of the piston 31 to the caulking part 31A prior to the step of connecting the piston 31 to the piston shoe 16 can be eliminated, the working efficiency at the time of manufacturing the piston 31 and so on can be improved remarkably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swash plate type hydraulic rotary machine preferably used for a swash plate type hydraulic pump, a hydraulic motor and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a swash plate type hydraulic rotating machine, a piston shoe as a sliding member is swingably provided on the tip side of the piston in order to reciprocate the piston in the cylinder.
A piston shoe slides together with the cylinder block on a swash plate inclined with respect to the axis of the cylinder block.

Therefore, FIG. 4 shows a swash plate type hydraulic motor as a swash plate type hydraulic rotating machine according to this type of prior art.

In the drawing, reference numeral 1 denotes a casing, which is a cylindrical main casing 1 having one axial end closed.
A main casing 1A and a rear casing 1B fixed to the other axial end of the main casing 1A.

Reference numeral 2 denotes a swash plate located inside the casing 1 and fixed to one axial end of the main body casing 1A.
Is a body casing 1A made of, for example, an iron-based metal
It has a sliding contact surface 2A that is inclined with respect to the axis line.

A valve plate 3 is located inside the casing 1 and faces the swash plate 2. The valve plate 3 is fixed to the rear casing 1B. Further, the valve plate 3 has a pair of eyebrow ports 4, 5
The eyebrow ports 4 and 5 communicate with a supply / discharge passage (not shown) formed in the rear casing 1B.

Reference numeral 6 is rotatably supported by the casing 1 through bearings 7 and 8 in a state of penetrating the swash plate 2 and the valve plate 3,
A rotary shaft having a spline formed at an axially intermediate portion, 9 represents a cylinder block spline-connected to the rotary shaft 6, and the cylinder block 9 is adapted to rotate with the rotary shaft 6 while slidingly contacting the valve plate 3. ing.

.. are opposed to the swash plate 2 and are a plurality of cylinders bored in the axial direction of the cylinder block 9.
Each cylinder 10 has a valve plate 3 through a communication passage 11.
It is designed to communicate with the eyebrow ports 4 and 5.

The cylinders 12, 12, ...
It shows a piston slidably inserted therein, and a concave spherical surface portion 13 is formed at the tip end side of each piston 12. Further, in the axial direction of each piston 12, an oil chamber 14 that opens at the center of the bottom of the concave spherical surface portion 13 and an oil passage 15 that communicates with the oil chamber 14 are formed.

Reference numerals 16, 16, ... Depict piston shoes as slidable members swingably connected to the tip end side of each piston 12. Each piston shoe 16 is made of iron-based metal and has a concave shape. The disk portion 1 as a sliding portion including a spherical joint portion 17 that fits into the spherical portion 13 and a seal land portion 20 described later that slides on the sliding contact surface 2A of the swash plate 2.
And 8 are integrally formed. And the disk unit 1
A circular static pressure pocket 19 is formed at the center of the end surface of 8, and a portion surrounding the static pressure pocket 19 from the outside in the radial direction is a seal land portion 20 that is in sliding contact with the sliding contact surface 2A of the swash plate 2.
Has become.

Further, in the axial direction of the piston shoe 16,
An oil passage 21 is provided which communicates with the static pressure pocket 19 and guides the pressure oil in the cylinder 10 into the static pressure pocket 19. Then, each piston shoe 16 is always brought into contact with the swash plate 2 by the piston shoe pressing plate 22 so as to slide on the sliding contact surface 2A of the swash plate 2 as the cylinder block 9 rotates. .

The swash plate type hydraulic motor according to the prior art is constructed as described above, and its operation will be described below.

Pressure oil discharged from a hydraulic pump (not shown) passes through a supply passage provided in the rear casing 1B, one eyebrow port 4 of the valve plate 3 and a communication passage 11 of the cylinder block 9. It is supplied into the cylinder 10. As a result, the hydraulic pressure of the pressure oil supplied into the cylinder 10 acts in the direction in which the piston 12 is extended from the inside of the cylinder 10, and pushes the piston 12 in the axial direction.
6 is pressed against the swash plate 2. Here, since the swash plate 2 is inclined with respect to the axis of the piston 12, the piston shoe 16 slides on the sliding contact surface 2A, and the piston 12 rotates the cylinder block 9 by the reaction force of the pressing force. The rotary shaft 6 rotates together with the cylinder block 9.

That is, each cylinder 1 of the cylinder block 9
In the supply process in which the pressure oil is supplied into the cylinder 0, the piston 12 extends from the inside of the cylinder 10 to apply a rotational force to the cylinder block 9 and the rotary shaft 6. Further, in the discharge stroke in which the piston 12 shrinks into the cylinder 10, each communication passage 11 communicates with the other eyebrow port 5 as the cylinder block 9 rotates, and the piston 12 communicates the oil liquid in the cylinder 10 with each other. It discharges to the discharge passage side through 11 and the eyebrow port 5.

On the other hand, when the above-mentioned swash plate type hydraulic motor is operated, the pressure oil in the cylinder 10 is stored in the static pressure pocket 19 provided in each piston shoe 16 in the oil passage 15 and the oil chamber 1.
4 and the oil passage 21, and an appropriate oil film is formed between the sliding contact surface 2A of the swash plate 2 and each piston shoe 16 by this pressure oil, so that the friction loss between them is reduced. Has become.

By the way, the piston 12 and the piston shoe 16 used in the swash plate type hydraulic motor and the like according to the prior art as described above have a concave spherical surface portion 13 formed at the tip end side of the piston 12 and a spherical joint portion of the piston shoe 16. By fitting 17 and shrinking (caulking) the tip edge of the piston 12, the piston shoe 16 is coupled to the piston 12 so as to swing smoothly.

A method of connecting the piston 12 and the piston shoe 16 will be described with reference to FIGS. 5 to 7.

First, as shown in FIG. 5, a piston 12 having a concave spherical surface portion 13, an oil chamber 14, an oil passage 15 and the like is formed by turning a chromium molybdenum steel (SCM435 or the like). After the quenching treatment is performed, the tempering treatment is performed at, for example, 600 to 640 ° C., and then the soft nitriding treatment such as gas soft nitriding or tuftride is performed (soft nitriding treatment step).

As a result, the nitride compound layer 23 having excellent wear resistance and fatigue resistance is formed on the surface of the piston 12. Then, after the soft nitriding treatment, the outer peripheral side of the crimped portion 12A located on the tip side of the piston 12 is turned by a lathe or the like for a reason to be described later, and the nitride compound layer 23 formed there from the surface side of the crimped portion 12A is removed. Remove (turning process).

Then, the spherical joint portion 17 of the piston shoe 16 described above is fitted into the concave spherical surface portion 13 of the piston 12,
By reducing the diameter of the caulking portion 12A of the piston 12 over the entire circumference (caulking in the direction of arrow F), the spherical joint portion 17 of the piston shoe 16 is recessed in the piston 12 as shown in FIGS. 6 and 7. The piston shoe 16 is held in the spherical surface portion 13 so as not to be pulled out, and the piston shoe 16 is provided on the tip side of the piston 12.
Are swingably coupled (coupling step).

[0021]

Here, the piston 12
When connecting the piston shoe 16 and the piston shoe 16,
The reason why the nitride compound layer 23 is removed from the surface side of the crimped portion 12A by turning the outer peripheral side of the crimped portion 12A will be described below.

First, as shown in FIG. 8, the surface of the base material D such as the piston 12 is subjected to a soft nitriding treatment to form a base material D.
A nitride compound layer F is formed on the surface of the via a diffusion layer E. On the other hand, as shown in FIG. 9, when the nitride compound layer F is removed by cutting, the diffusion layer E is formed on the surface of the base material D.
Will be left. Then, in a state where the nitride compound layer F is formed on the surface of the base material D via the diffusion layer E, as shown in FIG.
As shown in, the surface hardness becomes Hv 500 or more at a position where the depth is 0.1 mm or less from the surface of the base material D, and the surface hardness decreases according to the depth from the surface of the base material D.

Therefore, the surface hardness of the piston 12 can be increased by forming the nitride compound layer 23 by soft nitriding. However, since the nitride compound layer 23 formed on the surface of the piston 12 is generally excellent in hardness, but is brittle, cracks and the like easily occur around the caulked portion 12A during caulking, and cracks and the like occur around the caulked portion 12A. In that case, the drawing strength will be reduced.

That is, the piston 12 is soft-nitrided,
With the nitride compound layer 23 still formed on the surface side of the caulking portion 12A, the spherical joint portion 17 of the piston shoe 16 is fitted into the concave spherical surface portion 13 of the piston 12, and the piston 12 and the piston shoe 16 are caulked. When the piston 12 and the piston shoe 16 are pulled in mutually opposite axial directions, the force (hereinafter referred to as pull-out strength) when the piston shoe 16 separates from the piston 12 is As indicated by sample (a) in FIG. 11, the value is relatively low, and the piston shoe 16 is separated from the piston 12 when a withdrawal force larger than this is applied.

Therefore, in the prior art, after the piston 12 is soft-nitrided, the surface of the caulked portion 12A is turned to remove the nitride compound layer 23 from the surface of the caulked portion 12A. There is. Then, after removing the nitride compound layer 23 from the surface of the caulking portion 12A, the spherical joint portion 17 is fitted to the concave spherical surface portion 13 to reduce the diameter of the caulking portion 12A, and the piston 12 and the piston shoe 16 are joined. (See FIG. 6) Like the sample (b) shown in FIG. 11, the drawing strength can be improved to about 1.5 times that of the sample (a) described above.

However, in the prior art, when the piston 12 and the piston shoe 16 are connected, the piston 1
After the soft nitriding treatment is performed on 2, the surface side of the caulked portion 12A of the piston 12 is turned, and the caulked portion 12A
Since the nitride compound layer 23 is removed from the surface side of the above, there is a problem in that this removing work takes time and the workability during manufacturing deteriorates.

When the turning depth from the surface of the caulking portion 12A is insufficient in the turning process for the caulking portion 12A, the nitride compound layer 23 remains on the surface of the caulking portion 12A, and the caulking at the joining step is performed. Due to the processing, as shown in FIG. 7, cracks K are easily generated in the caulked portion 12A,
There is a problem that the drawing strength is reduced.

When the turning depth from the surface of the crimped portion 12A becomes excessively large, the nitride compound layer 23 can be reliably removed, but the thickness of the crimped portion 12A becomes thin, and the piston If the caulking portion 12A is turned with the shaft 12 deviated from the axis, the thickness of the caulking portion 12A becomes uneven, and in any case, the pulling strength is reduced. Cause.

In this way, the soft nitrided piston 1
Since strict machining accuracy is required for the turning process for the second caulking part 12A, not only the workability at the time of manufacturing including the turning process for the caulking part 12A is significantly lowered, but also the manufacturing cost of parts is increased. There is a problem of inviting.

The present invention has been made in view of the above-mentioned problems of the prior art. The piston and the sliding member can be joined with an appropriate pulling strength, and the workability at the time of manufacturing can be greatly improved, and the manufacturing cost can be reduced. It is an object of the present invention to provide a method for manufacturing a swash plate type hydraulic rotating machine that can also reduce the number.

[0031]

In order to solve the above-mentioned problems, the present invention provides a casing provided with a swash plate, and a casing provided on the casing via a rotary shaft to rotate in opposition to the swash plate. A cylinder block, a plurality of pistons slidably provided in a plurality of cylinders formed in the cylinder block and having a concave spherical surface portion formed on the tip side, and a spherical joint portion fitted to the concave spherical surface portion. A swash plate type hydraulic rotating machine including a plurality of sliding members which are swingably coupled to the tip end side of each piston via the cylinder block and slide on the swash plate as the cylinder block rotates. Applied.

The feature of the structure adopted by the invention of claim 1 is that a soft nitriding layer is formed on the surface side of each piston and each sliding member in which the spherical joint portion is joined to the concave spherical surface portion. There is something I did.

According to a second aspect of the present invention, there is provided a method for manufacturing a swash plate type hydraulic rotary machine, in which a heat treatment step of quenching and tempering each piston and a soft nitriding treatment of each sliding member are performed. A soft nitriding step, and a coupling step of fitting the spherical joint portion of each soft nitrided sliding member to the concave spherical surface portion of each heat treated piston to reduce the diameter of the tip side of each piston, It comprises a second soft nitriding treatment step of performing a soft nitriding treatment on each piston and each sliding member joined in the joining step.

[0034]

According to the swash plate type hydraulic rotating machine of the present invention, a soft nitriding layer is formed on the front surface side of each piston and each sliding member which are coupled to each other through the spherical joint portion fitted to the concave spherical surface portion. By forming the above, each piston and each sliding member can be coupled with an appropriate pulling strength without involving a turning process for removing the soft nitriding layer from the surface side of the piston tip.

According to the manufacturing method of the swash plate type hydraulic rotating machine of the second aspect of the present invention, after connecting each piston and each sliding member, each combined piston and each sliding member are Since the soft nitriding treatment is performed, the piston and the sliding member can be coupled with an appropriate pulling strength without generating a crack or the like on the tip side of the piston. Moreover, it is possible to eliminate the turning process or the like on the tip side of the piston in the previous stage of the connecting step of connecting the piston and the sliding member.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 31 denotes a piston according to this embodiment. The piston 31 has a concave spherical surface portion 32 formed on the tip end side and a concave spherical surface at the central portion in the axial direction, similar to the piston 12 according to the prior art. Oil chamber 3 opening at the center of the bottom of the portion 32
3, and oil passages 34 communicating with the oil chamber 33 are formed respectively. Then, the spherical joint portion 17 of the piston shoe 16 is fitted to the concave spherical surface portion 32 of the piston 31, and the caulking portion 31A of the piston 31 crimped in the diameter reducing direction holds the stopper 31 in a retaining state. A piston shoe 16 is swingably connected to the.

However, on the surface side of the piston 31 and the piston shoe 16 according to the present embodiment, a nitride compound layer 35 as a soft nitriding layer is formed by the manufacturing method described later, and at the caulking portion 31A of the piston 31. It differs from the prior art in that no turning is applied.

Now, a method of manufacturing the swash plate type hydraulic rotating machine according to this embodiment will be described with reference to FIG.

In the figure, the piston 31 has a concave spherical surface portion 32, an oil chamber 33, an oil passage 34, etc. formed by turning a chromium / molybdenum steel (SCM435 etc.), and is formed in a substantially cylindrical shape as a whole. There is. And this piston 3
After the quenching process is performed on No. 1, for example, 600 to 6
Up to the heat treatment step of performing the tempering treatment at 40 ° C., the manufacturing method of the piston 12 according to the prior art is the same as that of the prior art, but in this embodiment, the soft nitriding treatment is not performed after the heat treatment step. Piston 3 at this stage
No nitride compound layer is formed on the surface side of No. 1.

On the other hand, the piston shoe 16 is manufactured by the same method as the conventional manufacturing method.

Then, the spherical joint portion 17 of the piston shoe 16 is fitted into the concave spherical surface portion 32 of the piston 31, and the caulking portion 31A on the tip end side of the piston 31 is reduced in diameter over the entire circumference (in the direction of arrow F). The concave spherical surface portion 3 by
The spherical joint portion 17 is held in the inside of the piston 2 so as not to be pulled out, and the piston shoe 16 is swingably coupled to the tip end side of the piston 31 (coupling step).

Here, since the nitride compound layer is not formed on the surface side of the caulking portion 31A of the piston 31 in the joining step, even if caulking is performed to reduce the diameter of the caulking portion 31A over the entire circumference, It is possible to reliably prevent the occurrence of cracks or the like around the portion 31A. Therefore, as described in the related art, the turning step accompanied by the troublesome turning for removing the nitride compound layer 23 from the surface side of the caulked portion 12A of the piston 12 is unnecessary, and the piston 31
It is possible to significantly improve the workability in manufacturing such as, and to reduce the component manufacturing cost. Further, since the wall thickness on the tip side of each piston can be made uniform, it is possible to easily control the accuracy of parts.

Next, for example, gas soft nitriding treatment is applied to the piston 31 and the piston shoe 16 that are joined in the joining step (second soft nitriding treatment step). As a result, a nitride compound layer 35 as a soft nitride layer having excellent wear resistance and fatigue resistance is formed on the surface side of the piston 31 and the piston shoe 16.

Then, the seal land portion 20 of the piston shoe 16 is ground to remove the oxide layer (scale) 36 adhering to the end surface of the seal land portion 20 during the second soft nitriding process (scale removal). Process).
As a result, as shown in FIGS. 1 and 2, the piston 31 is swingably coupled to the tip side, and the piston 31 having the nitride compound layer 35 formed on the surface side thereof is manufactured.

Here, the piston 31 and the piston shoe 1
When the pull-out strength with No. 6 was measured, as shown as the sample (c) in FIG. 11, a pull-out strength, which was slightly lower than that of the above-mentioned sample (b), was significantly improved as compared with the sample (a). Therefore, it was confirmed that the piston 31 and the piston shoe 16 were joined together with an appropriate pulling strength.

The swash plate type hydraulic motor according to the present embodiment is provided with the piston 31 and the like manufactured through the above-mentioned steps, and its basic operation is not different from that of the prior art.

However, in this embodiment, the soft nitriding treatment is not performed on the piston 31 in the preceding stage of the joining step,
In the state where the crack is surely prevented from being generated around the caulking portion 31A during the caulking process in the joining step, the piston 3
The piston shoe 16 is swingably connected to the tip side of 1,
In the second soft nitriding process performed thereafter, the piston 31 and the piston shoe 16 that have been combined are subjected to a soft nitriding process, so that the piston 31 and the piston shoe 16 can be combined with an appropriate pulling strength. it can. Therefore, as described in the prior art, the piston 12
A turning process for removing the nitride compound layer 23 from the surface side of the caulking portion 12A is unnecessary, and workability at the time of manufacturing the piston 31 and the like can be significantly improved, and
The component manufacturing cost can be reduced.

Further, the piston 31 and the piston shoe 16
The second soft nitriding step is performed after the joining step of swingably joining the cylinders 1 and 2, so that the surface side of the piston 31 and the piston shoe 16 is hardened.
The wear resistance of the piston 31 and the piston shoe 16 that slide with respect to 0 and the swash plate 2 and the like can be enhanced, and durability and life can be significantly improved.

Other constitutions and effects of the swash plate type hydraulic motor according to the present embodiment are the same as those of the prior art shown in FIG.

Although the swash plate type hydraulic motor has been described as an example in the above embodiment, the present invention is not limited to this and can be applied to, for example, a swash plate type hydraulic pump.

[0052]

As described in detail above, according to the swash plate type hydraulic rotary machine of the invention of claim 1, the pistons and the sliding members coupled to each other through the spherical joint portion fitted in the concave spherical portion are provided. By forming the soft nitriding layer on the surface side of the member, each piston and each sliding member can be separated with appropriate pulling strength without turning work to remove the soft nitriding layer from the surface side of the piston tip. Can be combined.

According to the method of manufacturing the swash plate type hydraulic rotating machine of the second aspect of the invention, the spherical joint portion of each sliding member is fitted to the concave spherical surface portion of each piston, and the tip end side of each piston is fitted. After each piston and each sliding member are connected by reducing the diameter, the nitrided compound layer is formed on the tip side of the piston because the combined piston and each sliding member are soft-nitrided. The diameter of the tip side of the piston can be reduced in a state where the piston and the sliding member are joined together with proper pulling strength without causing cracks or the like on the tip side of the piston. Moreover, since the turning process for removing the soft nitrided layer from the surface side of the tip of the piston before connecting the piston and the sliding member can be dispensed with, the workability at the time of manufacturing the piston is greatly improved. It is possible to improve the cost and reduce the manufacturing cost of parts. Further, since the wall thickness on the tip side of each piston can be made uniform, it is possible to easily control the accuracy of parts.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a piston and a piston shoe according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part in FIG.

FIG. 3 is a vertical cross-sectional view showing each manufacturing process of the piston and the piston shoe in FIG.

FIG. 4 is a vertical sectional view showing a swash plate type hydraulic motor according to a conventional technique.

5 is a vertical cross-sectional view showing each manufacturing process and the like of the piston in FIG.

6 is a cross-sectional view showing a piston and a piston shoe in FIG.

FIG. 7 is an enlarged cross-sectional view showing a main part in FIG.

FIG. 8 is a cross-sectional view showing a state in which a nitride compound layer is formed on the surface of a base material.

9 is a cross-sectional view showing a state where the nitride compound layer in FIG. 8 is removed.

FIG. 10 is a characteristic diagram showing a relationship between surface depth and hardness of a base material.

FIG. 11 is a diagram of samples (a), (b), and (c) showing pull-out strengths between a piston and a piston shoe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Swash plate 6 Rotating shaft 9 Cylinder block 10 Cylinder 16 Piston shoe (sliding member) 17 Spherical joint part 18 Disk part (sliding part) 21 Oil passage 31 Piston 32 Concave spherical surface part 35 Nitride compound layer (soft nitriding layer) )

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Kimura, 650 Kintatemachi, Tsuchiura City, Ibaraki Prefecture Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (72) Inventor, Kazuyuki Ino, 650 Kintatecho, Tsuchiura City, Ibaraki Hitachi Construction Machinery Co., Ltd. (72) Inventor Tsuyoshi Kobayashi 650 Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd.

Claims (2)

[Claims] 1. A casing provided with a swash plate, a cylinder block provided on the casing via a rotary shaft and rotating in opposition to the swash plate, and a plurality of cylinders bored in the cylinder block. A plurality of pistons slidably provided with a concave spherical surface portion formed on the distal end side, and swingably coupled to the distal end side of each piston via a spherical joint portion fitted to the concave spherical surface portion, In a swash plate type hydraulic rotating machine comprising a plurality of sliding members that slide on the swash plate as the cylinder block rotates, each piston having a spherical joint portion coupled to the concave spherical surface portion. And a soft nitriding layer formed on the surface side of each sliding member. 2. A casing provided with a swash plate, a cylinder block provided on the casing via a rotary shaft and rotating in opposition to the swash plate, and a plurality of cylinders bored in the cylinder block. A plurality of pistons slidably provided with a concave spherical surface portion formed on the distal end side, and swingably coupled to the distal end side of each piston via a spherical joint portion fitted to the concave spherical surface portion, A method for manufacturing a swash plate type hydraulic rotating machine comprising a plurality of sliding members that slide on the swash plate as the cylinder block rotates, wherein quenching and tempering treatment is performed on each piston. A heat treatment step, a first soft nitriding step of performing a soft nitriding treatment on each of the sliding members, and a spherical joint portion of each soft nitriding sliding member on the concave spherical surface portion of each of the heat treated pistons. To reduce the tip of each piston. A method for manufacturing a swash plate type hydraulic rotating machine, comprising: a connecting step of making a diameter; and a second soft nitriding treatment step of performing a soft nitriding treatment on each piston and each sliding member joined in the joining step.