JP3476924B2 - Manufacturing method of swash plate type hydraulic rotary machine - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] FIELD OF THE INVENTION The present invention, manufacturing of the swash plate type liquid-pressure rotating machine suitably used in the hydraulic pump and a hydraulic motor or the like of the swash plate type <br / > Regarding the construction method. 2. Description of the Related Art In general, a swash plate type hydraulic rotary machine is provided with a piston shoe as a sliding member at a tip end of a piston so as to be swingable in order to reciprocate a piston in a cylinder.
The piston shoe slides on the swash plate inclined with respect to the axis of the cylinder block together with the cylinder block. FIG. 4 shows a swash plate type hydraulic motor as a swash plate type hydraulic rotary machine according to this type of the prior art. In the drawings, reference numeral 1 denotes a casing, and the casing 1 is a cylindrical main body casing 1 having one end closed in the axial direction.
A and a rear casing 1B fixed to the other axial end of the main casing 1A. [0005] A swash plate 2 is located in the casing 1 and fixed to one axial end of the main casing 1A.
Is formed of, for example, an iron-based metal, and
Has a sliding contact surface 2A that is inclined with respect to the axis. Reference numeral 3 denotes a valve plate located in the casing 1 and facing the swash plate 2, and the valve plate 3 is fixed to the rear casing 1B. The valve plate 3 has a pair of eyebrow-shaped ports 4 and 5.
Are formed, and the eyebrow-shaped ports 4 and 5 communicate with a supply / discharge passage (not shown) formed in the rear casing 1B. [0007] 6 is rotatably supported by the casing 1 through bearings 7 and 8 in a state where it penetrates the swash plate 2 and the valve plate 3.
A rotary shaft 9 having a spline formed at an axially intermediate portion, 9 denotes a cylinder block spline-coupled to the rotary shaft 6, and the cylinder block 9 rotates together with the rotary shaft 6 while sliding on the valve plate 3. ing. Are a plurality of cylinders facing the swash plate 2 and formed in the axial direction of the cylinder block 9.
Each cylinder 10 is connected to the valve plate 3
The eyebrow ports 4 and 5 communicate with each other. , 12,.
The figure shows a piston slidably inserted therein, and a concave spherical portion 13 is formed on the tip side of each piston 12. In the axial direction of each piston 12, an oil chamber 14 opening at the center of the bottom of the concave spherical portion 13 and an oil passage 15 communicating with the oil chamber 14 are formed. Reference numerals 16, 16,... Denote piston shoes as sliding members which are swingably connected to the distal ends of the pistons 12. Each of the piston shoes 16 is formed of an iron-based metal. The disk portion 1 as a sliding portion including a spherical joint portion 17 fitted to the spherical portion 13 and a seal land portion 20 described later sliding on the sliding contact surface 2A of the swash plate 2.
8 are integrally formed. And the disk unit 1
A circular static pressure pocket 19 is formed at the center of the end face of the swash plate 2, and a portion surrounding the static pressure pocket 19 from the radial outside is a seal land portion 20 slidingly contacting the sliding contact surface 2 </ b> A of the swash plate 2.
It has become. Further, in the axial direction of the piston shoe 16,
An oil passage 21 communicating with the static pressure pocket 19 and leading the pressure oil in the cylinder 10 into the static pressure pocket 19 is formed. Each piston shoe 16 is always in 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 now be described. The hydraulic oil discharged from a hydraulic pump (not shown) passes through a supply passage provided in the rear casing 1 B, 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 a direction to extend the piston 12 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 surface 2A, and the piston 12 rotates the cylinder block 9 by the reaction force of the pressing force. The rotation shaft 6 rotates together with the cylinder block 9. That is, each cylinder 1 of the cylinder block 9
In the supply step in which the pressure oil is supplied to the inside of 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 rotating shaft 6. In the discharge stroke in which the piston 12 contracts 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 the other communication passage. The liquid is discharged to the discharge passage via the eyebrow port 11 and the eyebrow port 5. On the other hand, during the operation of the swash plate type hydraulic motor described above, the pressure oil in the cylinder 10 is filled in the static pressure pocket 19 provided in each piston shoe 16 with the oil passage 15 and the oil chamber 1.
4 and the oil passage 21, an appropriate oil film is formed between the sliding contact surface 2 </ b> A of the swash plate 2 and each piston shoe 16 by this pressure oil, and the friction loss between the two 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 are connected to a spherical joint portion of the piston shoe 16 by a concave spherical portion 13 formed on the distal end side of the piston 12. The piston shoe 16 is coupled to the piston 12 so as to swing smoothly by fitting (17) and reducing (caulking) the distal end edge of the piston 12. Here, a method of connecting the piston 12 and the piston shoe 16 will be described with reference to FIGS. First, as shown in FIG. 5, a chromium-molybdenum steel (such as SCM435) is turned to form a piston 12 having a concave spherical portion 13, an oil chamber 14, an oil passage 15, and the like. , A tempering treatment is performed at, for example, 600 to 640 ° C., and then a nitrocarburizing process such as gas nitrocarburizing or tuftride is performed (a nitrocarburizing process). Thus, on the surface of the piston 12, a nitride compound layer 23 having excellent wear resistance and fatigue resistance is formed. After the nitrocarburizing treatment, the outer peripheral side of the caulked portion 12A located on the tip side of the piston 12 is turned by a lathe or the like for the reason described later, and the nitrided compound layer 23 formed therefrom from the surface side of the caulked portion 12A is removed. Remove (turning process). Next, the spherical joint portion 17 of the piston shoe 16 is fitted to the concave spherical portion 13 of the piston 12,
By reducing the diameter of the caulking portion 12A of the piston 12 over its entire circumference (caulking in the direction of arrow F), the spherical joint portion 17 of the piston shoe 16 becomes concave as shown in FIGS. The piston 12 is held in the spherical portion 13 in a retaining state.
Are swingably coupled (combining step). [0021] Here, the piston 12
When connecting the piston 1 and the piston shoe 16, the piston 1
The reason why the nitride compound layer 23 is removed from the surface of the caulked portion 12A by turning the outer peripheral side of the caulked 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 so that the base material D
A nitride compound layer F is formed on the surface of the substrate through 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. In a state where the nitride compound layer F is formed on the surface of the base material D via the diffusion layer E, FIG.
As shown in the figure, the surface hardness becomes Hv 500 or more at a depth of 0.1 mm or less from the surface of the base material D, and the surface hardness decreases in accordance with the depth from the surface of the base material D. Therefore, the surface hardness of the piston 12 can be increased by forming the nitrided compound layer 23 by soft nitriding. However, since the nitrided compound layer 23 formed on the surface of the piston 12 is generally excellent in hardness but brittle, cracks and the like are easily generated around the caulked portion 12A during caulking, and cracks and the like are generated around the caulked portion 12A. In such a case, the pull-out strength decreases. That is, the piston 12 is subjected to a soft nitriding treatment,
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 to the concave spherical 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 the directions opposite to each other in the axial direction, the force when the piston shoe 16 separates from the piston 12 (hereinafter referred to as pull-out strength) is As shown as a sample (a) in FIG. 11, the value becomes a relatively low value, and when a further withdrawal force is applied, the piston shoe 16 separates from the piston 12. For this reason, in the prior art, after the piston 12 is subjected to the soft nitriding treatment, the surface side of the caulked portion 12A is turned to remove the nitrided compound layer 23 from the surface of the caulked portion 12A. I have. Then, after removing the nitrided compound layer 23 from the surface of the caulked portion 12A, the spherical joint portion 17 is fitted to the concave spherical portion 13 to reduce the diameter of the caulked portion 12A, and the piston 12 and the piston shoe 16 are joined. In FIG. 6 (see FIG. 6), as in sample (b) shown in FIG. 11, the pull-out strength can be improved, for example, to about 1.5 times that of sample (a) described above. However, in the prior art, when connecting the piston 12 and the piston shoe 16, the piston 1
2 is subjected to a soft nitriding treatment, and then a turning process is performed on the surface side of the swaged portion 12A of the piston 12 to form the swaged portion 12A.
Since the nitride compound layer 23 is removed from the surface side of the above, there is a problem that it takes time to remove the nitride compound layer 23, and the workability at the time of manufacturing deteriorates. If the turning depth from the surface of the caulked portion 12A is insufficient in the turning of the caulked portion 12A, the nitrided compound layer 23 remains on the surface of the caulked portion 12A, and the caulking during the bonding process is performed. By processing, a crack K is easily generated in the caulked portion 12A as shown in FIG.
There is a problem that the pull-out strength is reduced. If the turning depth from the surface of the caulked portion 12A becomes excessive, the nitride compound layer 23 can be removed without fail, but the caulked portion 12A becomes thinner. If turning is performed on the swaged portion 12A in a state shifted from the axis of 12, the thickness of the swaged portion 12A becomes non-uniform, and in any case, the pull-out strength is reduced. Cause. As described above, the nitrocarburized piston 1
Since turning of the caulking portion 12A requires strict machining accuracy, not only the workability at the time of manufacturing including the turning process for the caulking portion 12A is remarkably reduced, but also the cost of manufacturing parts increases. There is a problem of inviting. The present invention has been made in view of the above-mentioned problems of the prior art, and can combine a piston and a sliding member with an appropriate pull-out strength, can greatly improve the workability in manufacturing, and reduce the manufacturing cost. It is an object of the present invention to provide a method of manufacturing a swash plate type hydraulic rotary machine capable of reducing the amount. [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 rotating shaft to face the swash plate. And a plurality of pistons slidably provided in a plurality of cylinders formed in the cylinder block and having a concave spherical portion formed on the tip side, and a spherical surface fitted to the concave spherical portion. A swash plate-type hydraulic pressure comprising: a plurality of sliding members slidably coupled to the distal ends of the pistons via joints and sliding on the swash plate as the cylinder block rotates. It is applied to a method for manufacturing a rotating machine. In the method of manufacturing a swash plate type hydraulic rotary machine according to the present invention, a heat treatment step of performing a quenching and tempering treatment on each piston and a first step of performing a nitrocarburizing treatment on each of the sliding members are provided. A soft nitriding step, and a coupling step of fitting the spherical joint of each sliding member subjected to the soft nitriding to the concave spherical part of each heat-treated piston and reducing the diameter of the distal end side of each piston, A second nitrocarburizing process for performing a nitrocarburizing process on each piston and each sliding member coupled in the coupling process. According to the manufacturing method of the swash plate type liquid-pressure rotating by [0035] the present invention, after binding with each piston and the sliding member, each piston and the sliding member coupled On the other hand, since the nitrocarburizing treatment is performed, the piston and the sliding member can be connected with appropriate pulling strength without generating a crack or the like on the distal end side of the piston. In addition, it is not necessary to perform a turning process or the like on the distal end side of the piston in a stage prior to the connecting step of connecting the piston and the sliding member. Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. In the embodiments, the same components as those of the above-described conventional technology are denoted by the same reference numerals, and description thereof will be omitted. In the drawing, reference numeral 31 denotes a piston according to the present embodiment. The piston 31 has a concave spherical portion 32 at the distal end side and a concave spherical portion at the axial center portion, substantially in the same manner as the piston 12 according to the prior art. Oil chamber 3 opening at the center of the bottom of section 32
3 and an oil passage 34 communicating with the oil chamber 33 are formed. The spherical joint portion 17 of the piston shoe 16 is fitted into the concave spherical portion 32 of the piston 31, and is held in a retaining state by the caulking portion 31 </ b> A of the piston 31 caulked in the diameter reducing direction. , A piston shoe 16 is swingably connected. However, on the surface side of the piston 31 and the piston shoe 16 according to the present embodiment, the nitride compound layer 35 as a soft nitride layer is formed by a manufacturing method described later, and the caulking portion 31A of the piston 31 is formed. It differs from the prior art in that no turning is performed. Here, a method for manufacturing the swash plate type hydraulic rotary machine according to the present embodiment will be described with reference to FIG. In the figure, a piston 31 has a concave spherical portion 32, an oil chamber 33, an oil passage 34, and the like by turning a chromium-molybdenum steel (such as SCM435), and is formed in a substantially cylindrical shape as a whole. I have. And this piston 3
After the quenching process is performed on
Up to the heat treatment step of performing the tempering treatment at 40 ° C., it is the same as the method of manufacturing the piston 12 according to the prior art, but in the present embodiment, unlike the prior art in that the soft nitriding treatment is not performed after the heat treatment step. At this stage, piston 3
No nitride compound layer was formed on the surface side of No. 1. On the other hand, the piston shoe 16 is manufactured by the same method as the manufacturing method according to the prior art. However, this
In this case, the piston shoe 16 is subjected to a soft nitriding treatment.
(First nitrocarburizing process). Then, the spherical joint portion 17 of the piston shoe 16 is fitted into the concave spherical portion 32 of the piston 31, and the caulking portion 31A on the distal end side of the piston 31 is reduced in diameter over its entire circumference (in the direction of arrow F). ), The concave spherical portion 3
The spherical joint portion 17 is retained in the 2 in a retaining state, and the piston shoe 16 is swingably connected to the distal end side of the piston 31 (connection step). Here, since no nitrided compound layer is formed on the surface side of the caulking portion 31A of the piston 31 in the joining step, even if caulking for reducing the diameter of the caulking portion 31A over the entire circumference, caulking is performed. The generation of cracks and the like around the portion 31A can be reliably prevented. Therefore, as described in the related art, a turning process involving a cumbersome turning process for removing the nitrided compound layer 23 from the surface side of the caulking portion 12A of the piston 12 becomes unnecessary, and the piston 31
And the like, the workability at the time of manufacturing can be greatly improved, and the cost of manufacturing parts can be reduced. In addition, since the thickness at the tip end side of each piston can be made uniform, the precision of parts can be easily managed. Next, the piston 31 and the piston shoe 16 combined in the combining step are subjected to, for example, a gas nitrocarburizing process (a second nitrocarburizing process). Thus, a nitrided compound layer 35 as a soft nitrided 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 attached to the end surface of the seal land portion 20 during the second nitrocarburizing step (scale removal). Process).
Thus, as shown in FIGS. 1 and 2, the piston shoe 16 is swingably connected to the distal end side, and the piston 31 having the nitride compound layer 35 formed on the surface side is manufactured. Here, the piston 31 and the piston shoe 1
When the pull-out strength of the sample No. 6 was measured, as shown as a sample (c) in FIG. 11, the pull-out strength was slightly lower than that of the sample (b) described above, but was significantly improved as compared with the sample (a). Therefore, it was confirmed that the piston 31 and the piston shoe 16 were connected with an appropriate pull-out strength. The swash plate type hydraulic motor according to the present embodiment includes the piston 31 manufactured through the above-described steps, and its basic operation is not particularly different from that according to the prior art. However, in the present embodiment, the nitrocarburizing process is not performed on the piston 31 at a stage prior to the bonding process.
In a state where cracks are reliably prevented from forming around the caulked portion 31A during caulking in the joining step, the piston 3
The piston shoe 16 is swingably connected to the tip end side of 1.
In the second nitrocarburizing process to be performed thereafter, by performing nitrocarburizing process on the coupled piston 31 and piston shoe 16, the piston 31 and the piston shoe 16 can be coupled with an appropriate pull-out strength. it can. Therefore, as described in the prior art, the piston 12
A turning process for removing the nitrided compound layer 23 from the surface side of the caulking portion 12A is not required, and workability during manufacturing of the piston 31 and the like can be greatly improved, and
Component manufacturing costs can be reduced. The piston 31 and the piston shoe 16
Since the second soft nitriding step is performed after the connecting step for swingably connecting the piston 31 and the surface side of the piston 31 and the piston shoe 16, the cylinder 1 is hardened.
The wear resistance of the piston 31 and the piston shoe 16 sliding with respect to the zero and the swash plate 2 and the like can be improved, and the durability and life can be greatly improved. The other structure, operation and effect of the swash plate type hydraulic motor according to this embodiment are the same as those of the prior art shown in FIG. In the above embodiment, the swash plate type hydraulic motor has been described as an example, but the present invention is not limited to this, and can be applied to, for example, a swash plate type hydraulic pump. [0052] [0053] As has been described above in detail, according to the manufacturing method of the swash plate type liquid-pressure rotating according to the present invention, a spherical joint portion of the sliding member to the concave spherical portion of each piston After fitting and reducing the diameter of the distal end side of each piston to connect each piston and each sliding member, the combined piston and each sliding member are subjected to nitrocarburizing treatment. In the state where the nitride compound layer is not formed on the tip side of the piston, the tip side of the piston can be reduced in diameter, and the piston and the sliding member can be properly pulled out without generating cracks or the like on the tip side of the piston. Can be combined. In addition, the turning process for removing the soft nitride layer from the front surface side of the piston at the stage before coupling the piston and the sliding member can be omitted, so that the workability in manufacturing the piston and the like is greatly improved. It is possible to improve the manufacturing cost and reduce the cost of manufacturing the parts. In addition, since the thickness at the tip end side of each piston can be made uniform, it is possible to easily manage the precision of parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal 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 longitudinal sectional view showing respective manufacturing steps and the like of a piston and a piston shoe in FIG. 1; FIG. 4 is a longitudinal sectional view showing a conventional swash plate type hydraulic motor. 5 is a longitudinal sectional view showing each manufacturing process of the piston in FIG. 4 and the like. FIG. 6 is a sectional view showing a piston and a piston shoe in FIG. 4; FIG. 7 is an enlarged sectional view showing a main part in FIG. 6; FIG. 8 is a cross-sectional view showing a state where a nitride compound layer is formed on a surface of a base material. 9 is a cross-sectional view showing a state where a nitride compound layer in FIG. 8 is removed. FIG. 10 is a characteristic diagram showing a relationship between a surface depth of a base material and hardness. FIG. 11 is a diagram of samples (a), (b), and (c) showing the withdrawal strength between the piston and the piston shoe. [Description of Signs] 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 part 35 Nitride compound Layer (nitrocarburized layer)

Continuing on the front page (72) Inventor Kenichi Kimura 650, Kandachicho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura Plant (72) Inventor Kazuyuki Ino 650, Kantachi-cho, Tsuchiura-shi Ibaraki Prefecture Hitachi Construction Machinery Co., Ltd. (72) Inventor Takeshi Kobayashi 650, Kandate-cho, Tsuchiura-shi, Ibaraki Pref. In the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. (56) References JP-A-5-60058 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) F04B 1/20

Claims (1)

(57) [Claim 1] A casing provided with a swash plate, a cylinder block provided on the casing via a rotating shaft, and rotated to face the swash plate, A plurality of pistons slidably provided in a plurality of cylinders formed in the piston and having a concave spherical portion formed on the distal end side, and a distal end of each piston through a spherical joint portion fitted to the concave spherical portion. swingably attached to the side, a method of manufacturing a swash plate type liquid-pressure rotating that with the rotation made by a plurality of sliding members sliding on the swash plate of the cylinder block, front A heat treatment step of performing a quenching and tempering treatment on each piston; a first nitrocarburizing treatment step of performing a nitrocarburizing treatment on each of the sliding members; and a nitrocarburizing treatment on the concave spherical portion of each of the heat-treated pistons. The spherical joint of each sliding member A swash plate type hydraulic system comprising: a coupling step of reducing the diameter of the distal end side of each piston; and a second nitrocarburizing step of performing a nitrocarburizing process on each of the pistons and the sliding members coupled in the coupling step. Manufacturing method of rotating machine.