JP2001090652A - Hydraulic rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic rotary machine capable of preventing the generation of erosive phenomena due to bubbles generated in an escape passage for escaping a highly pressurized oil when the delivery stroke is switched to the suction stroke, and thereby preventing the reduction in service life. SOLUTION: A retracted passage 17 one end of which opens to the wall face of an escape passage 15 having an opening in a communication passage 16 one end of which opens to the neighborhood of a top dead center of a piston between a delivery passage 5B and a suction passage 5A and the other end of which is connected to an oil tank, and the other end of which has an opening in the communication passage 16 connected to the oil tank, is drilled in a valve plate 5 with which a rotary block 6 slidably comes into contact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge passage formed on a sliding surface of a valve plate at a position opposed to an access passage connected to the bottom of a plurality of cylinders provided on a rotary block which rotates in association with a drive shaft. Shaft, swash plate or radial type hydraulic pump or hydraulic motor, etc., which has a relief passage which penetrates the oil passage communicating with the oil tank near the top dead center of the piston, Related to a hydraulic rotary machine.

[0002]

2. Description of the Related Art For example, as disclosed in JP-A-8-210242, a piston is guided by a swash plate inclined with respect to a drive shaft as a hydraulic motor for supplying pressure oil to a hydraulic circuit, and reciprocates. Swash plate piston pumps that perform a pumping action by moving are well known. FIG. 5 is a cross-sectional view of a conventional swash plate type piston pump passing through a rotating shaft. A rotating block 6 having a sliding groove formed in the inner space 2B of the outer cylinder 2 of the pump body 1 along the axial direction of the inner surface of the through hole is rotatably supported via left and right bearings 9A and 9B. The shaft 4 is connected to a sliding groove (spline).
A plurality of cylinders 7 are formed in the rotation block 6 at equal intervals along the circumferential direction, and a piston 8 is slidably fitted in each cylinder 7. With the rotation of the rotating shaft 4, the sliding plate 18 fitted with the tip end of the piston 8 has a predetermined inclination angle with respect to the rotating shaft 4, and slides on the sliding surface of the swash plate 10 fixed to the outer cylinder 2. Each of the pistons 8 reciprocates left and right in the cylinder 7 by rotating while sliding.

An access passage 7A communicating with the cylinder 7 is formed at an end of the rotary block 6 on the bottom side of the cylinder 7, so that when the rotary block 6 comes into sliding contact with the valve plate 5, a surface of the valve plate 5 is formed. It can communicate with the formed suction passage 5A or discharge passage 5B. As described above, each of the pistons 8 is moved to the corresponding cylinder 7 as the rotation shaft 4 rotates.
By reciprocating left and right inside, hydraulic oil is sucked into the cylinder 7 from the suction passage 5A and discharged to the discharge passage 5B.

[0004] From the discharge process in which the inlet / outlet passage 7A of the cylinder 7 communicates with the discharge passage 5B of the valve plate 5 to discharge hydraulic oil,
When switching to the suction process in which the hydraulic oil is sucked by communicating with the suction passage 5A, the high pressure (discharge pressure) in the cylinder 7 is gradually reduced to almost the suction pressure. A decompression process is performed so as to communicate with the access passage 7A. As described above, in order to gradually reduce the oil pressure in the cylinder 7, there is provided a narrow escape passage which is communicated with the inner space 2B of the outer cylinder 2 and is opened on the surface of the valve plate 5 as described later. By communicating with this escape passage, high-pressure oil in the cylinder 7 can be escaped.

FIG. 4 is a partially enlarged cross-sectional view of a valve plate including an escape passage and a bottom of a rotary block that slides on the valve plate. When the position of the cylinder 7 changes from the discharge process to the neutral process, and the access passage 7A communicates with the escape passage 15 opened on the surface of the valve plate 5, the high-pressure hydraulic oil in the cylinder 7 becomes thin.
Through the communication passage 16 at high speed through the inner space 2 of the outer cylinder 2.
It reaches B. Thus, when the inlet / outlet passage 7A of the cylinder 7 shifts from the neutral process to the suction process and communicates with the suction passage 5A, the oil pressure in the cylinder 7 has almost no pressure difference with the oil pressure in the suction passage 5A.

[0006]

The escape passage 1
5 is formed so as to have a considerably small diameter, so that the access passage 7
When A communicates with the escape passage 15, the flow velocity of the hydraulic oil flowing therethrough becomes very high. Therefore, at a position near the wall surface of the escape passage 15 for the hydraulic oil that flows out at a high speed, the hydraulic pressure in the radial direction is significantly reduced, and a cavitation phenomenon in which a negative pressure is generated occurs. As a result, air bubbles are generated in the hydraulic oil at a position near the wall surface of the escape passage 15, and are ejected from the escape passage 15 to the communication passage 16 side together with the hydraulic oil, and collide with the communication passage 16 facing the same. At this time, the bubbles in the hydraulic oil are crushed and give an impact to the nearby wall surface 16A, thereby causing erosion. in this way,
When the wall surface 16A of the communication passage 16 is eroded by bubbles in the hydraulic oil, the life of the piston pump body 1 is significantly reduced. The present invention has been made in order to solve such a problem in the prior art, and erosion caused by bubbles generated in an escape passage for escaping high-pressure oil in a cylinder when switching from a discharge stroke to a suction stroke. It is an object of the present invention to provide a hydraulic rotary machine capable of preventing occurrence of a phenomenon and a reduction in life due to the phenomenon.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, one end is provided on a valve plate provided with a discharge passage and a suction passage formed by a rotating block in sliding contact with a passage of a cylinder. A retraction having an opening in the wall of an escape passage opening near the top dead center of the piston and opening the other end in the outer cylinder communicating with the oil tank, and having an opening in the outer cylinder communicating the other end with the oil tank. A passage was drilled.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a swash plate type piston pump according to an embodiment of the present invention, which is taken through a rotary shaft. FIG. 2 is a front view of a valve plate on which a rotary block slides. FIG. It is a partial expanded sectional view of the bottom of the rotating block which slides on a board. The same reference numerals are given to portions which are the same as or can be regarded as the same as those in the conventional example, and redundant description thereof will be omitted.

In these figures, reference numeral 3 denotes a lid for closing the open end side of the outer cylinder 2 of the pump body 1, 6A denotes one end face of the rotary block 6 slidably in contact with the valve plate 5, and 11 denotes the inner periphery of the rotary block 6. And a coil spring 12 having one end locked to one end of the rotary block 6 and the other end locked to one end of a push rod described below. A push rod, which is slidably fitted to and is provided with an elastic force from a coil spring 11 locked at one end thereof and applied to a bushing described below, and a push bar 13 is supported by the rotary shaft 4 in a cylindrical hollow portion. The bushing 14 supports the other end of the rotating block 6 and slidably supports a shoe press plate described below at the outer peripheral portion of the spherical outer peripheral portion. A shoe, which will be described later, fits slidably along the Shoe pressing plate fitting hole is bored in, 17 is open in the middle of the passage 15 escape end, retraction path and the other end is open to the inner space 2B side of the outer periphery of the valve plate 5, 19
Is a shoe rotatably connected to the tip of the piston 8 via a spherical bearing and slidably in contact with the sliding surface of the swash plate 10. The inner space 2B of the outer cylinder 2 communicates with an oil tank for hydraulic oil (not shown).

Next, the operation of this embodiment will be described. The rotating shaft 4 connected to a prime mover (not shown) includes left and right bearings 9A, 9A.
It is driven and rotated by being supported by B. Then, the rotary block 6 coupled to the rotary shaft 4 in the sliding groove also rotates. The bushing 13 is urged by the coil spring 11 via the push rod 12 in a direction away from the rotary block 6 in parallel with the rotary shaft 4, and this urging force is transmitted from the bushing 13 to the shoe pressing plate 14, The holding plate 14 is a shoe 19
Is pressed against the sliding surface of the swash plate 10. In FIG. 1, the upper piston 8 is moved from the longest extension position to the shoe 1 guided to the fitting hole of the shoe holding plate 14 as the rotating block 6 rotates.
When the sliding movement 9 moves along the sliding surface of the swash plate 10, the piston 8 is pushed to the left.

At this time, the access passage 7A, which is connected to the cylinder 7 and opens at one end of the rotary block 6, slides along the sliding surface of the valve plate 5 and is formed on the surface of the valve plate 5. The hydraulic oil pushed out of the cylinder 7 with the movement of the piston 8 to the left moves to the hydraulic circuit from the inlet / outlet passage 7A to the hydraulic pump (not shown) via the discharge passage 5B. Discharged. Then, the lower piston 8 in FIG.
When the cylinder rotates, the access passage 7A of the cylinder 7 is disconnected from the discharge passage 5B, and soon communicates with the escape passage 15 so that the high-pressure hydraulic oil in the cylinder 7 is supplied to the thin escape passage 15A.
And gradually flows out to the communication passage 16 side.

At this time, since the hydraulic oil passing through the relief passage 15 has a high-speed flow, a negative pressure is generated in a portion close to the wall surface. Since one end of the inlet passage 17 opened to the empty 2B side is open, the hydraulic oil flows from the inner space 2B of the outer cylinder 2 to the inlet passage 17.
And is supplied in the middle of the escape passage 15. In this way, the negative pressure in the escape passage 15 is eliminated, so that it is possible to prevent bubbles from being generated near the wall surface of the escape passage 15. Therefore, the wall surface of the communication passage 16 facing the outlet opening of the escape passage 15 is eroded. Can be suppressed.

[0013]

As described above, according to the present invention, the valve plate is provided with the drawing passage having one end opened to the escape passage wall surface and the other end opened to the outer cylinder communicating with the oil tank. ,
It is possible to prevent the occurrence of erosion due to bubbles generated in the escape passage for escaping high-pressure oil in the cylinder at the time of switching from the discharge stroke to the suction stroke, and to prevent the life thereof from being shortened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a swash plate type piston pump according to an embodiment of the present invention, which passes through a rotation axis.

FIG. 2 is a front view of a valve plate on which the rotating block slides.

FIG. 3 is a partially enlarged cross-sectional view of a valve plate including an escape passage and a bottom portion of a rotary block that slides on the valve plate.

FIG. 4 is a partially enlarged cross-sectional view of a valve plate including an escape passage of a swash plate type piston pump according to a conventional example, and a bottom of a rotary block that slides on the valve plate.

FIG. 5 is a cross-sectional view of the swash plate type piston pump passing through the rotation axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump main body 2 Outer cylinder 2B Inner space 4 Rotary shaft 5 Valve plate 5A Suction passage 5B Discharge passage 6 Rotation block 7 Cylinder 7A In / out passage 8 Piston 10 Swash plate 13 Bushing 14 Shoe holding plate 15 Escape passage 16 Communication passage 17 Retraction passage 19 Shoe

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Sakairi 650, Kandate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Inside the Tsuchiura Plant Co., Ltd. (72) Inventor Yukihiro Motozawa 650, Kandamachi, Tsuchiura City, Ibaraki Prefecture Inside the Tsuchiura Plant, Hitachi Construction Machinery Co., Ltd. (72) Toki Soo 650, Kandamachi, Tsuchiura City, Ibaraki Prefecture Hitachi Construction Machinery Co. F term in the Tsuchiura factory (reference) 3H070 AA01 BB04 BB06 CC07 DD68

Claims (1)

[Claims] 1. A rotary block rotatably disposed in an outer cylinder in conjunction with a drive shaft, a plurality of cylinders provided on the rotary block in parallel with the drive shaft, and reciprocating in the cylinder, respectively. A piston provided movably, and an access passage, which is bored and connected to a bottom side of the cylinder of the rotary block and serves as an inflow / outflow passage of hydraulic oil in the cylinder, and fixed to the outer cylinder; A valve plate provided with a discharge passage and a suction passage through which the rotary block slides and the access passage communicates, and a piston top dead between the discharge passage and the suction passage on the sliding surface side of the valve plate; One end is open near the point, and the other end has an escape passage opening in the outer cylinder communicating with the oil tank.In the hydraulic rotary machine, in the valve plate, one end opens in the escape passage wall surface, The other end opens into the outer cylinder connected to the oil tank. A hydraulic rotary machine, wherein a suction passage having a mouth is formed.