JP2001234848A - Reducer of swash plate excitation moment in swash plate type pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply reduce the excitation moment generated on a swash plate while completely equalizing pressure in a piston chamber positioned on top and bottom dead centers. SOLUTION: In a swash plate pump wherein a plurality of pistons 5 are disposed freely to project/retreat in a cylinder block 1 which is rotated by a rotary shaft 2 and whose end surface is rotated while abutting on a valve plate 7, and a pressure fluid is supplied for lubrication from a piston chamber 4 in the cylinder block through passages 5e, 9b formed on a head part and a piston shoe to a slide contact surface between a swash plate and the piston shoe as well as to make the piston a projecting/retreating motion through the piston shoe 8 by being brought into slide contact with the swash plate 9 for slantly rotating the top part 5a of each piston with respect to the rotary shaft; opening parts 14, 15 are disposed to communicate with the top dead center and the bottom dead center of the piston in the piston chamber positioned on those points in a region of the slide contact surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for reducing a vibration moment generated on a swash plate of a swash plate pump.

[0002]

2. Description of the Related Art Conventionally, as a swash plate type pump, an end face of a cylinder block rotated by a rotary shaft is brought into contact with a valve plate, and a plurality of piston heads provided in the cylinder block so as to be freely retractable are used as pistons. It is known that the swash plate is brought into contact with the swash plate via a shoe. When the cylinder block is rotated by the rotation shaft, the piston moves out of the cylinder block due to the inclination of the swash plate and is controlled by a valve plate. Then, an operation of sucking or discharging the fluid into the piston chamber is performed. In order to provide lubrication to the sliding surface between the swash plate and the piston shoe, a passage communicating with the piston chamber is provided in the head and the piston shoe, and the pressure fluid in the piston chamber is brought into contact with the sliding through the passage. To the surface.

[0003]

When the piston is located at the top dead center of the swash plate, the pressure in the piston chamber becomes minimum, and when it is located at the bottom dead center, it becomes maximum. This causes an oscillating moment to be generated in the swash plate due to the change, and the tilt angle changes, so that accurate control of the discharge amount cannot be performed and noise accompanying the vibration is generated, which is not preferable.

When the piston passes through the top dead center or the bottom dead center and fluid flows in and out between the control port of the valve plate and the piston chamber, a sudden pressure change occurs and noise is generated. A notch or the like is provided at the rim of the control port to make the pressure change slower, but according to this, the change in thrust generated by the piston becomes slower, and as a result, the excitation moment decreases. Can be done. However, the shape of the notch is different between the top dead center and the bottom dead center, and the pressure in the piston chamber located at the top dead center and the pressure in the piston chamber located at the bottom dead center are not the same pressure, and the excitation moment is At the point and the bottom dead center, the tilt angle control of the swash plate is adversely affected, and at the resonance rotational speed with the swash plate, there is a disadvantage that noise is generated due to the fine vibration of the swash plate.

[0005] vibration moment Me of the swash plate, as shown in the following ^{equation, # Me = R × sec 2} αΣ n k = 1 (A P × P CK + m
× z¨ _K ) cos θ _K (1) expressed by #. here,
R: Piston revolution radius, α: Swash plate tilt angle, A _P : Piston effective area, P _CK : Piston chamber pressure, m: Piston mass, z¨ _K : Second order differential value of piston axial displacement z _K , Θ
_K : Piston revolution angle position. According to this, it is understood that the influence of the pressure in the piston chamber at the top and bottom dead centers of the piston is very large.

SUMMARY OF THE INVENTION An object of the present invention is to completely reduce the vibration moment generated on the swash plate by completely equalizing the pressures of the piston chambers located at the upper and lower dead centers.

[0007]

According to the present invention, a plurality of pistons are provided so as to be able to protrude and retract in a cylinder block which is rotated by a rotating shaft and whose end face rotates in contact with a valve plate for controlling suction and discharge of fluid. The head of each piston is slid in contact with a swash plate that can be tilted with respect to the rotation shaft via a piston shoe to cause the piston to perform a retracting operation, and the sliding contact surface between the swash plate and the piston shoe is brought into contact with the swash plate. In a swash plate type pump for supplying a pressurized fluid from a piston chamber in the cylinder block for lubrication through a passage formed in a head and a piston shoe, the swash plate type pump is located in the area of the sliding contact surface and above the piston. The above object is achieved by providing openings at the dead center and the bottom dead center of the pressure regulating passage which communicate with the piston chamber located at these points. The object can be more appropriately achieved by providing a pressure regulating chamber in the middle of the pressure regulating passage or connecting a pressure source to the pressure regulating passage. The configuration of the swash plate is provided with an arc-shaped convex surface provided behind the arc-shaped concave surface provided in the pump casing to support the swash plate in a tiltable manner. The pressure regulation chamber may be constituted by a concave portion provided on the arc-shaped convex surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a cylinder block which is integrally mounted on a rotating shaft 2 and rotates in a pump case 3 together therewith. Reference numeral 4 denotes a plurality of piston chambers formed in the cylinder block 1, and a piston 5 is provided in each piston chamber 4 so as to be able to come and go. The end surface 1a of the cylinder block 1 is in contact with a valve plate 7 attached to a port end cover 6 constituting the pump case 3, and is provided on the port end cover 6 when the piston 5 is given a retracting operation. The working fluid is sucked from the tank into the piston chamber 4 through the flow path or discharged from the piston chamber 4 to the actuator.

The head 5a of the piston 5 is formed in a spherical shape, and a piston shoe 8 that is in sliding contact with the plate surface 9a of the swash plate 9 is fitted to the head 5a. In order to prevent seizure due to sliding contact between the plate surface 9a and the piston shoe 8, the head 5
The passages 9e and 5b are formed in the piston shoe 8 and a. The swash plate 9 is tiltably supported on the pump case 3 by a support shaft or a cradle. In the illustrated example, as shown in FIGS. 2 and 3, a semi-arc-shaped convex surface 9 b is provided on the back surface of the swash plate 9. A cradle was provided, and the convex surface 9b was fitted to a semicircular concave surface 10 provided on the pump case 3. The swash plate 9 is tilted by the force of the control cylinder 11 in contact with the projection 9c of the plate surface 9a and the force of the control spring 12 acting on the projection 9d, and the fluid pressure acting on the control cylinder 11 Is controlled, the convex surface 9b slides, and the swash plate 9 tilts at an appropriate tilt angle.

When the cylinder block 1 is rotated by the rotary shaft 2, the piston 5 rotates while sliding on the plate surface 9a of the swash plate 9, and according to the tilt angle of the swash plate 9 during one rotation. The fluid is sucked and discharged from the piston chamber 4 by reciprocating strokes over a distance. In general, the pressure in the piston chamber 4 changes suddenly at the top dead center A or the bottom dead center B, and a large vibration which vibrates the swash plate 9 due to the pressure difference between the piston chambers located at the top and bottom dead centers. As described above, a moment is generated and the tilt angle control of the swash plate is disturbed. As a result, there is a disadvantage that the discharge amount pulsates or a noise is generated. As described above, the pressure adjusting passage 13 for mutually communicating the piston chambers 4 located at the top dead center A and the bottom dead center B is provided in the area of the swash plate 9 in the area of the sliding surface of the piston shoe 8. Reference numerals 14 and 15 denote openings of the pressure control passage 13 opened at the top dead center A and the bottom dead center B, and reference numeral 16 denotes a pressure control chamber provided in the pressure control passage 13. The pressure regulation chamber 16 was formed by a concave portion 16a formed by cutting the arc-shaped convex surface 9b of the swash plate 9 and an arc-shaped concave surface 10 of the pump case 3 closing the convex surface 9b. It may be formed by providing a space with an appropriate volume inside.

In the present invention, the piston chambers 4 located at the top dead center A and the bottom dead center B are provided with the head 5a of the piston 5, the passages 5b and 9e of the piston shoe 8, and the pressure regulating passage 13
As a result, the swash plate 9 has the same pressure, and the vibration moment of the swash plate 9 is reduced. Specifically, as shown in FIG. 4, the sum of moments generated by the pressure of the piston chamber located on the high pressure side with respect to the tilt center line 17 of the swash plate 9 is the excitation moment Me, which is Me = R × sec
² θ × A _P ｛(P _CO × cos θ ₀ + P _C1 × cos θ ₁ + P _C2
× cos θ ₂ ) − (P _C3 × cos θ ₃ + P _C4 × cos
θ ₄ )｝. Incidentally, the expression (1) of the piston inertia force term (m × z¨ _K) is omitted because it is irrelevant to the present invention. In the present invention, the piston chambers 4 located at the top dead center A and the bottom dead center B have the same pressure, and P _C0 and P _{C4 in the above} equation have the same pressure and are eliminated, so that Me is reduced. I do. When the excitation moment is reduced, the vibration of the swash plate is significantly reduced, the tilt angle is controlled accurately, the pulsation of the discharge amount is reduced, and the noise is reduced.

The pressure regulating passage 13 is connected to an external pressure source 18 as shown in FIG. 5, and the pressure in the pressure regulating passage 13 is controlled by pressure control means such as throttles 19 and 20, whereby a swash plate is provided. 9 can be controlled, and arbitrary characteristics can be obtained.

[0013]

As described above, according to the present invention, the upper dead center and the lower dead center of the piston are located in the area of the sliding surface of the piston shoe of the tiltable swash plate. The opening of the pressure adjustment passage that communicates the piston chambers with each other is provided, so that the piston chambers located at the top and bottom dead centers have the same pressure, the vibration moment is reduced, and the vibration width of the swash plate is greatly reduced The tilt angle control can be performed relatively accurately, the vibration noise can be reduced, the pressure control passage can be provided relatively easily, and a pressure source is connected to the pressure control passage to control the pressure in the piston chamber. Has the effect of controlling the excitation moment and arbitrarily controlling the vibration characteristics of the swash plate.

[Brief description of the drawings]

FIG. 1 is a cut-away side view showing an embodiment of the present invention.

FIG. 2 is a front view of the swash plate of FIG. 1;

FIG. 3 is a side view of FIG. 2;

FIG. 4 is an explanatory diagram of a vibration moment of a swash plate.

FIG. 5 is an explanatory view of another embodiment of the present invention.

[Explanation of symbols]

1 cylinder block, 2 rotating shafts, 4 piston chambers,
5 piston, 5a head, 7 valve plate, 8
Piston shoe, 9 swash plate, 9a plate surface, 9b arc-shaped convex surface, 10 concave surface, 13 pressure regulating passage, 14.15 opening, 16 pressure regulating chamber, 16a concave portion, 18 pressure source, 5e
・ 9b passage,

Claims (4)

[Claims] A plurality of pistons are provided on a cylinder block which is rotated by a rotation shaft and whose end face is in contact with a valve plate for controlling suction and discharge of a fluid. A swash plate that is tiltable with respect to the shaft is slid into contact with the swash plate via a piston shoe to cause the piston to move in and out, and a sliding contact surface between the swash plate and the piston shoe is formed on the head and the piston shoe. In a swash plate type pump for supplying a pressurized fluid from a piston chamber in the cylinder block through a passage for lubrication, an upper dead center and a lower dead center of the piston in a region of the sliding contact surface. An apparatus for reducing a swash plate excitation moment in a swash plate pump, wherein openings of pressure regulating passages communicating with the piston chambers located at these points are provided. 2. A swash plate exciting moment reducing device in a swash plate pump according to claim 1, wherein a pressure adjusting chamber is provided in the pressure adjusting passage. 3. The swash plate excitation moment reducing device according to claim 1, wherein a pressure source is connected to said pressure regulating passage. 4. An arc-shaped convex surface which fits with an arc-shaped concave surface provided on a pump casing and supports the swash plate so as to be tiltable is provided behind the swash plate. 3. The swash plate excitation moment reducing device in a swash plate pump according to claim 2, wherein the pressure regulating chamber is constituted by a concave portion provided on the arc-shaped convex surface.