JP2504470Y2 - Piston pump controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an improvement of a control device for operating a piston pump with constant horsepower.

(Prior Art) Some swash plate type piston pumps are provided with a force feedback type control device as shown in FIGS. 5 and 6, for example, in order to perform operation with a constant horsepower.

In this figure, the swash plate 2 is slidably supported on the rolling surface formed on the pump body 8 through a bearing 40, and the tilt angle is changed by driving the regulator piston 41 connected to the center. There is.

The regulator piston 41 has different piston diameters at both ends, the pump discharge oil is directly guided to the oil chamber 42 which exerts hydraulic pressure on the small diameter portion 41A, and the pump discharge oil is servo-controlled 39 to the oil chamber 43 which exerts hydraulic pressure on the large diameter portion 41B. Guided through.

The servo regulator 39 accommodates a main spring 45 that comes into contact with a stay 44 integrated with a regulator piston 41 to detect the position of the regulator piston 41. A spring seat 46 supporting the other end of the main spring 45 is a pilot piston 47 driven by pump discharge oil.
The main spool 48 is formed integrally with the spring seat 49. The main spool 48 is slidably housed inside the regulator body 49, the end opposite to the pilot piston 47 is supported by an adjusting spring 50, and the other end of the adjusting spring 50 can be externally adjusted. 51 support. That is, the main spool 48
Is adapted to slide in the regulator body 49 in the axial direction according to the pump discharge pressure.

A port 52 that communicates with the oil chamber 43 of the regulator piston 41 and a port 53 that guides the pump discharge pressure are opened in the regulator body 49 so as to face the main spool 48. On the other hand, the main spool 48 is formed with an annular groove 54 that communicates these ports 52 and 53 in accordance with the sliding position, and the drain passage 55 opens inside the main spool 48 to the outer peripheral portion.

With the above configuration, when the pump discharge pressure fluctuates, the main spool 48 slides via the pilot piston 47, and the pressure introduced into the oil chamber 43 changes accordingly, displacing the regulator piston 41. At the same time, the moving position of the regulator piston 41 is fed back to the main spring 45 via the stay 44.

Therefore, for example, when the pump discharge pressure rises, the pilot piston 47 slides the main spool 48 to the left in FIG. 5 while compressing and contracting the main spring 45, and the annular groove 54 connects the ports 52 and 53 with each other to form the regulator piston. 41 oil chamber 43
The discharge pressure of the pump is supplied to. As a result, the pump discharge pressure acts on both sides of the regulator piston 41, but the force on the large diameter portion 41B side having a large cross-sectional area prevails and the regulator piston 41 moves to the right side in the figure. Therefore, the tilt angle of the swash plate 2 decreases, and the discharge amount decreases. The movement of the regulator piston 41 strengthens the compression force of the main spring 45, and when this balances with the pressing force of the pilot piston 47, the main spool 48 returns to the neutral position and the movement of the regulator piston 41 stops.

On the other hand, when the discharge pressure decreases, the repulsive force of the main spring 45 causes the main spool 48 to slide to the right in the figure, and the port 52 communicates with the drain 55. Therefore, the regulator piston 41 moves to the left, the tilt angle of the swash plate 2 increases, and the discharge amount increases.

As described above, in the servo regulator 39, when the discharge pressure of the pump increases, the tilt angle is reduced to decrease the discharge amount, and when the discharge pressure decreases, the tilt angle is increased to increase the discharge amount of the regulator piston 41. The drive control is performed, and the changed tilt angle is fed back to this control via the stay 44 integrated with the regulator piston 41, which allows the pump to produce a product of the discharge amount and the discharge pressure. It is driven under a certain amount of horsepower.

(Problems to be solved by the invention) By the way, in the case of this control device, a complicated structure is used, and many troublesome parts such as a regulator piston 41 having a different diameter and a stay 44 integrally formed therewith are used. Therefore, there is a problem that the cost is high, and the layout of the servo regulator 39 is limited due to the relationship with the stay 44, so that there are many design restrictions.

The present invention has been made in view of the above problems, and an object thereof is to provide a piston pump control device having a simpler configuration.

(Means for Solving Problems) The present invention is directed to a regulator piston that changes the tilt angle of a swash plate of a piston pump according to the driving pressure thereof, and the tilt angle increases in conjunction with the displacement of the swash plate. When the pump discharge pressure is increased by a pressure reducing valve that generates a secondary pressure by reducing the pump discharge pressure so that the pressure is reduced, and a spool that is displaced to a position where the secondary pressure and the pump discharge pressure are balanced. And a servo regulator that controls the drive pressure to be reduced when the secondary pressure increases while increasing the drive pressure supplied to the regulator piston. As the drive pressure increases, the swash plate tilts through the regulator piston. Control so that the angle decreases.

(Operation) When the pump discharge pressure increases, the servo regulator spool that was in a balanced state until then is displaced, and the drive pressure controlled by the servo regulator increases accordingly. This drive pressure causes the regulator piston to move to the swash plate. The tilting angle of is driven in a decreasing direction, which reduces the pump discharge amount. At the same time, as the tilt angle of the swash plate decreases, the secondary pressure generated by the pressure reducing valve increases, and this secondary pressure is fed back to the spool of the servo regulator.
The spool is pushed back against the pump discharge pressure, and thus the spool stands still at the position where the pump discharge pressure and the secondary pressure are balanced. As a result, the tilt angle of the swash plate is newly held at a position where the pump discharge pressure and the secondary pressure are newly balanced.

When the pump discharge pressure decreases, the drive pressure controlled by the servo regulator decreases, the tilt angle of the swash plate controlled via the regulator piston increases, and the pump discharge amount increases. As the tilt angle increases, the secondary pressure generated by the pressure reducing valve decreases, and the secondary pressure is fed back to the spool of the servo regulator to adjust the driving pressure to increase. The tilt angle of the swash plate is maintained at a position where the pump discharge pressure and the secondary pressure are balanced.

In this way, the tilt angle of the swash plate is feedback-controlled according to the pump discharge pressure, and the product of the piston pump discharge amount and discharge pressure is controlled to be substantially constant, that is, to operate with a constant horsepower. Is done.

(Embodiment) FIGS. 1 to 4 show an embodiment of the present invention.

FIG. 1 shows a main part of a swash plate type piston pump 1, 2 is a swash plate, 3 is a piston, and 4 is a cylinder block. The swash plate 2 is rotatably supported by the pump body 8 via a fulcrum 5 within a certain range, and a regulator piston 6 for rotationally driving the swash plate 2 is housed in the pump body 8. The regulator piston is driven by the discharge oil of the pump 1 supplied via the servo regulator 7.

The servo regulator 7 has a main spool 9 slidably accommodated inside a pump body 8 and is supported by adjusting springs 10 and 11 from both sides.
11 is an adjuster 12 that moves back and forth by external operation
It is supported by 13 and is configured so that the spring pressure can be adjusted from the outside. An oil chamber 14 for guiding the discharge oil of the pump 1 is formed around the adjusting spring 10, and an oil chamber 15 for guiding the secondary pressure of a differential pressure feedback valve 16 described later is formed around the adjusting spring 11. It is formed. As a result, the main spool 9 receives the hydraulic pressure of the oil chamber 14 and the pressure of the adjusting spring 10 from the left side of the figure, and the hydraulic pressure of the oil chamber 15 and the pressure of the adjusting spring 11 from the right side of the figure, and the balance position of these forces is obtained. Held in.

A port 17 communicating with the oil chamber 14 is opened on the side surface of the main spool 9 on the base end side (left side in the drawing). Further, the front end side of the main spool 9 is formed to have a smaller diameter than the base end side, and an annular gap formed between this small diameter portion and the pump body 8.
18 communicates with tank 19. On the other hand, a port 20 for supplying hydraulic pressure to the regulator piston 6 is opened in the pump body 8 so as to face the main spool 9.

Under the above configuration, the main spool 9 slides according to the secondary pressure of the differential pressure feedback valve 16 and functions as a control mechanism that connects and disconnects the port 17 and the port 20.

The differential pressure feedback valve 16 is housed in a sliding hole 21 formed in the pump body 8 so as to face the back surface of the swash plate 2 as a pressure reducing valve for feedback controlling the servo regulator 7. The differential pressure feedback valve 16 is slidably supported on the inside of the sleeve 22, the shoe 22 slidingly contacting the back surface of the swash plate 2, the sleeve 23 that slides axially in the sliding hole 21 following the shoe 22. The spool 24 and the spring 25 that biases the spool 24 toward the swash plate 2 are configured as movable members.

An oil chamber 26 that guides the discharge pressure of the pump 1 is defined between the spool 24 and the shoe 22, and an oil chamber 27 that communicates with the oil chamber 15 of the servo regulator 7 is formed around the spring 25 and the sleeve 23 and It is defined by facing the end of the spool 24. A through hole 22A for guiding the oil pressure of the oil chamber 26 to the inside of the sliding contact portion is formed in the shoe 22, the same oil pressure is applied to the front surface and the back surface of the shoe 22, and the shoe 22 is slanted due to the difference in the operating area of the oil pressure. It is held in sliding contact with the plate 2.

A port 28, which communicates with the oil chamber 27 through the inside of the spool 24, opens toward the sleeve 23 on the outer peripheral portion of the spool 24. Also, the port 29 that communicates with the oil chamber 26 is also spooled.
The outer periphery of 24 is opened toward the sleeve 23. On the other hand, an annular groove 30 is formed on the inner peripheral surface of the sleeve 23 so as to face the port 28. Further, an annular groove 31 is formed in the spool 24 so that the annular groove 30 communicates with the tank 19 in accordance with the relative position of the spool 24 and the sleeve 23, and a drain hole 32 that always communicates with the annular groove 31 has a wall surface of the sleeve 23. Formed across.

 Next, the operation will be described.

FIG. 1 shows a state in which the regulator piston 6 is in the most compressed state and the back surface of the swash plate 2 is in contact with the pump body 8 at the maximum tilt angle. In this state, the differential pressure feedback valve 16 includes the spool 24, the sleeve 23, the port 29, and the annular groove 30.
Is closed and the port 28 is in communication with the tank 19, and the oil chamber 27 is open to the tank 19. Therefore, no pressure acts on the oil chamber 15 of the servo regulator 7. Therefore, when the discharge pressure of the pump 1 acting on the oil chamber 14 on the opposite side rises, the main spool 9 is displaced to the right side in the figure, and the port 17 communicates with the port 20. As a result, pressure oil is supplied from the oil chamber 14 to the regulator piston 6, and the swash plate 2 is rotationally displaced in the direction in which the tilt angle is reduced by the regulator piston 6 driven in the protruding direction.

On the other hand, in the differential pressure feedback valve 16, the sleeve 23 is relatively displaced in the right direction and the spool 24 is displaced in the left direction in the drawing due to the increase in the discharge pressure of the pump 1 and the rotational displacement of the swash plate 2, and the annular groove 30 is eventually removed. The communication between the port 28 and the tank 19 is cut off, and the port 28 is connected to the port 29. As a result, the oil chamber 27
The next pressure is generated.

The relationship between the discharge pressure P of the pump 1, the secondary pressure P ₁ of the oil chamber 27, and the tilt angle α of the swash plate 2 at this time is shown in the following equations and FIG.

P · a = P ₁ · a + k (x ₀ −x) (1) where a: cross-sectional area of spool 24 k: spring constant of spring 24 x ₀ : initial deflection of spring 25 x: deflection of spring 25 Further, −x∝α (where α: each tilt) (2) Here, if P−P ₁ = ΔP, then ΔP = (k / a) · from the equations (1) and (2). (X ₀ −x) = k ₁ + k ₂ · α (3) The proportional relationship in FIG. 3 increases or decreases as indicated by the broken line depending on the initial deflection amount x ₀ of the spring 25, as is clear from the equation (3). However, this increase or decrease can be dealt with by adjusting the set load of the adjusting springs 10 and 11 of the servo regulator 7,
It is not necessary for the differential pressure feedback valve 16 to have a particular adjusting mechanism.

On the other hand, in the servo regulator 7, the discharge pressure P of the pump 1 is introduced into the oil chamber 14, and the secondary pressure P ₁ of the differential pressure feedback valve 16 is introduced into the oil chamber 15. Therefore, the relationship of the forces acting on the main spool 9 is expressed by the following equation.

P ・ a ₀ = P ₁・ a ₁ + F (4) However, a ₀ : Pressure receiving area of main spool 9 on oil chamber 14 side a ₁ : 〃 oil chamber 15 side 〃 F: Adjustment springs 10 and 11 set Load From equations (4) and (3), P · (a ₀ −a ₁ ) + (P−P ₁ ) · a ₁ = P · (a ₀ −a ₁ ) +
(K ₁ + K ₂ · α) · a ₁ = F where α ∝ Q (where Q: pump discharge amount) Therefore, Q = −k ₃ · P + k ₄ (where k ₃ and k ₄ are constants) expressed.

This relationship is graphed as shown in FIG. 4, and changes according to the set load F of the adjusting springs 10 and 11 as shown by the broken line. Therefore, by properly setting the set load F by externally operating the adjusters 12 and 13, the relationship between the discharge pressure P and the discharge amount Q can be approximated to a constant horsepower curve.

Since the regulator piston 6 and the differential pressure feedback valve 16 and the servo regulator 7 are connected only by hydraulic lines and there is no mechanical connection relationship, the servo regulator 7 can be arranged at any position.

(Effect of the Invention) As described above, the present invention uses the pressure reducing valve that responds to the tilt angle of the pump to generate the secondary pressure with respect to the pump discharge pressure,
Since the servo regulator feedback control is performed based on this secondary pressure, it is not necessary to mechanically connect the servo regulator and the regulator piston for feedback control, the regulator piston configuration is simplified, and the pump control device Manufacturing cost can be reduced.

Further, since the servo regulator can be freely arranged regardless of the position of the regulator piston, the degree of freedom in pump design is expanded.

[Brief description of drawings]

FIG. 1 is a structural diagram of a pump controller showing an embodiment of the present invention, FIG. 2 is a circuit diagram of the same, FIG. 3 is a graph showing the relationship between the differential pressure of the differential pressure feedback valve and the tilt angle, and FIG. The figure is a graph showing the relationship between the flow rate of the pump and the discharge pressure. FIG. 5 is a structural diagram of a pump control device showing a conventional example,
FIG. 6 is a circuit diagram of the same. 1 ... Pump, 2 ... Swash plate, 6 ... Regulator piston, 7 ... Servo regulator, 16 ... Differential pressure feedback valve, 9 ... Main spool.

Claims (1)

(57) [Scope of utility model registration request] 1. A regulator piston for changing the tilt angle of a swash plate of a piston pump according to its driving pressure, and the pump discharge so that the pressure decreases as the tilt angle increases in association with the displacement of the swash plate. When the pump discharge pressure is increased by the pressure reducing valve that generates the secondary pressure that is reduced pressure and the spool that is displaced to the position where the secondary pressure and the pump discharge pressure are balanced, the drive pressure supplied to the regulator piston is increased. And a servo regulator that controls the driving pressure to decrease when the secondary pressure increases, and controls so that the tilt angle of the swash plate via the regulator piston decreases as the driving pressure increases. Control device for piston pump.