JPH03199684A - Flow rate control device of variable displacement pump - Google Patents

Abstract

PURPOSE:To reduce the cost and size of a spool valve, and improve spacing efficiency of a pump by composing a throttle means which controls the opening of the intake passage of a variable displacement pump, of the spool valve which responds to a discharge pressure of the pump. CONSTITUTION:A flow rate control device 2 adjusts a rate of operational fluid which flows into an intake passage 18 from a reservoir 29 after reaching an intake circuit 30, and has a spool valve 31 acting as a valve means. A spring 37 which energizes a spool 33 in the direction of increasing the opening degree of a variable throttle 36 is put in operation at one end of a spool 33, and the other end of the spool 33 is faced to a chamber 38. A fixed orifice 41 which bypasses the variable throttle 36 and short-circuits a passage between an inlet port 34 and an outlet port 35 is formed on a valve main body 32. The spool valve is reduced in its cost and size, and the spacing efficiency of a pump is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flow rate control device for a variable displacement pump.

(Prior Art) It is preferable for a positive displacement pump to discharge the minimum amount required by the equipment to be operated at the future discharge pressure, in order to save pump driving energy.

For this purpose, the pump is of a variable displacement type, and its flow rate control device is one that controls the pump's flow rate by adjusting the opening of the suction passage of the pump, as described in Japanese Patent Application Laid-Open No. 1-262374. be. Conventionally, in this type of flow rate control device, as shown in the above-mentioned literature, the pump discharge pressure is detected by a pressure sensor, and based on this information, a microcomputer controls the opening of the variable throttle in the pump suction passage via a step motor. It was common to control the flow rate.

(Problem to be Solved by the Invention) However, in such a flow rate control system, the pressure sensor, microcomputer, and step motor are each expensive, so
This is unavoidable in terms of cost, and in addition, it is necessary to attach a large step motor to the pump, resulting in problems such as the need for a large space for installing the pump.

The object of the present invention is to solve the above-mentioned problems by providing an alternative flow control system that does not suffer from such cost and space disadvantages.

(Means for Solving the Problems) For this purpose, the flow rate control device of the present invention provides a variable displacement pump that is capable of controlling the flow rate by controlling the opening of the suction passage using a restricting means, by controlling the discharge pressure of the variable displacement pump. The throttling means is constituted by a valve means which responds to the biloft pressure and determines the degree of opening.

(Function) A variable displacement pump performs a predetermined pumping action by sucking working fluid through a suction passage and discharging it.

During this time, the valve means can respond to the pump discharge pressure as a pilot pressure, determine the degree of opening, control the opening of the suction passage of the pump, and control the flow rate of the pump according to the pump discharge pressure.

By the way, this flow control system does not require expensive or large parts, including valve means, and does not require expensive or large parts such as valve means, which would otherwise make variable displacement pumps expensive or difficult to secure installation space for. It is possible to avoid increasing the size.

(Example) Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment of the flow control device 2 of the present invention applied to a fixed cylinder type radial piston pump 1. As shown in FIG.

The pump 1 includes a pump housing 3, through which a pump drive shaft 4 passes and is rotatably supported by bearings 5 and 6. An eccentric cam 4a is integrally molded on the shaft 4 between these bearings, and this eccentric cam is housed in a suction chamber 7 formed in the pump housing 3. A ring 8 is rotatably fitted on the outer periphery of the eccentric cam 4a, and, for example, ten radial pistons 9 (only one is shown in the drawing) are provided on the outer periphery of the ring 8 at equal intervals in the circumferential direction. . Each of these radial pistons 9
extends radially of the eccentric cam ring 8 and is slidably fitted into a corresponding fixed cylinder 10 formed in the pump housing 3. The external open end of the fixed cylinder 10 is closed by a plug 11 to define a discharge chamber 12 between the plug 11 and the radial piston 9.

Each radial piston 9 has a bottomed sleeve shape with its end close to the eccentric cam ring 8 closed, and is pressed against the eccentric cam ring 8 by a spring 13. and each radial piston 9
On the peripheral wall of the radial piston, there is a suction chamber 7 during the stroke of the radial piston.
A side boat 14 is formed by disposing it at a position where it appears and retracts inside.

The right end of the pump drive shaft 4 in the figure is used as a power supply end, and a portion of the pump drive shaft 4 near this end is sealed from the pump housing 3 by a seal 15. The other end of the pump drive shaft 4 is sealed with a seal 17 against a passage member 16 attached to the pump housing 3. The passage member 16 has a suction passage 18 and a discharge passage 19, and the number of discharge passages 19 is the same as that of the fixed cylinders 10. The suction passage 18 communicates with the suction chamber 7 by a communication port 20 formed in the pump housing 3, and each discharge passage 19 communicates with the corresponding discharge chamber 12 by a communication port 2 formed in the pump housing 3.

Delivery valve 2 between communication boat 21 and discharge passage 19
2, this valve opens when a pressure higher than the valve pressure is supplied from the communication boat 21, supplies working fluid from this port to the discharge passage 19, and does not allow any flow of working fluid in the opposite direction. shall be.

An end cover 23 is attached to the side of the passage member 16 far from the pump housing 3, and in addition to forming one groove 24 communicating with all the discharge passages 19, a discharge port 25 leading to the groove is provided.
Format. An operating pressure circuit 28 having an accumulator 26 for accumulating future pressure and a pressure operating device 27 operated by the pressure is connected to the discharge port 25. This circuit 28 includes an accumulator 26 and a pressure-actuated device 2.
A relief valve 50 is connected between 7 and 7 to prevent the pressure inside the circuit 28 from exceeding the set pressure of the relief valve 50 for safety reasons.

Next, to explain the flow rate control device 2, this is a reservoir 29.
It adjusts the amount of working fluid that has reached the suction circuit 30 flowing into the suction passage 18, and includes a spool valve 31 as a valve means. This spool valve is constructed by slidably fitting a spool 33 into a valve body 32, and includes an inlet boat 34 to which a suction circuit 30 is connected to the valve body 32, and a suction passage 1.
8, respectively. The spool 33 has a variable aperture 3 whose opening degree changes according to its stroke.
6 is provided between the population port 34 and the exit boat 35.

A spring 37 is applied to one end of the spool 33 to bias it in the direction of increasing the opening of the variable throttle 36, so that the other end of the spool 33 faces the chamber 3B. This chamber 38 has an operating pressure circuit 2
A pilot pressure circuit 40 connected to 8 and having an orifice 39 supplies the pump discharge pressure in the working pressure circuit 28 as pilot pressure.

The valve body 32 is further formed with a fixed orifice 41 that bypasses the variable restrictor 36 and short-circuits between the artificial port 34 and the outlet boat 35, and in addition, a spring 37 is formed from the outlet port 35.
A leakage fluid return path 42 is formed to return the working fluid leaked into the storage chamber to the inlet boat 34.

The operation of the above embodiment will be explained next.

The soil pump drive shaft 4 is rotated by power supplied thereto, and an eccentric cam 4a integrated with the shaft 4 reciprocates each radial piston 9 within a fixed cylinder 10 via a ring 8. During this reciprocating movement, each radial piston 9 moves to the side port 1 in a stroke region far from the axis of the pump drive shaft 4.
4 is closed by the cylinder 10, the working fluid in the discharge chamber 12 is pressurized.

When the working fluid reaches the opening pressure of the delivery valve 22 or higher, it is discharged into the discharge passage 19 while opening the pulp 22. The working fluid thus discharged into each passage 19 gathers in the groove 24, reaches the working pressure circuit 28 from the discharge boat 25, is accumulated in the accumulator 26, and is used for operating the equipment 27.

On the other hand, after the side boat 14 opens into the suction chamber 7 during the stroke toward the axis of the pump drive shaft 4, each of the vial pistons 9 allows the working fluid in the suction chamber 7 to flow into the discharge chamber 12 from the side boat 14. Allow to refill and prepare for the next discharge. At this time, the working fluid in the reservoir 29 is contained in the suction chamber 7 through the suction circuit 30, the artificial boat 34, and the variable throttle 36.
, outlet port 35, suction passage 18 and communication port 20.

During the pump operation described above, the flow rate of the pump discharged from the boat 25 is controlled as follows.

While the pressure-operated device 27 requires a large amount of working fluid for its operation, the pressure in the circuit 28 (pump discharge pressure) decreases to a value below the set pressure of the relief valve 50.

At this time, the pressure inside the circuit 28 is used as the pilot pressure and the circuit 4
Due to this pressure drop, the spool valve 31, which is supplied to the chamber 38 by the pressure 0, moves the spool 33 to the left in the drawing by the spring 37, and increases the opening of the variable throttle 36. Therefore, the working fluid suction limit from the reservoir 29 to the suction chamber 7 increases, and the capability of supplying working fluid from the suction chamber 7 to the discharge chamber 12, and hence the pump discharge flow rate increases accordingly, which increases the pressure-operated equipment 27. It can be matched to your requirements.

On the other hand, when the pressure-operated equipment 27 is not operating or is in an operating state that requires only a small amount of operating fluid, the circuit 28
The internal pressure (pump discharge pressure) tends to rise above the set pressure of the relief valve 50. However, when the relief valve 28
circuit 18 opens to release excess pressure to reservoir 29.
The pressure inside is maintained at the set pressure of the relief valve 28. At this time, the spool valve 31 moves the spool 33 to the right in the figure due to the pressure increase, thereby reducing the opening degree of the variable throttle 36. Therefore,
The working fluid supply capacity from the reservoir 29 to the suction chamber 7, and thus the pump discharge flow rate, is reduced and can be kept to the required amount required by the pressure-operated device 27.

According to the above flow rate control, the upper limit value of the pump discharge amount Q, which increases as the pump rotation speed (rotation speed of the shaft 4) N increases, is controlled to match the required flow rate of the equipment 27, as shown in FIG. Therefore, as shown in FIG. 4, the pump drive torque T can be minimized to prevent waste of pump drive energy.

By the way, if a configuration like this example is adopted for such flow rate control, there is no need for expensive pressure sensors, microcomputers, or step motors as in the past, and a large step motor can be used for pumping. A predetermined flow rate control can be performed without the need for an additional device, which is highly advantageous in terms of cost and space efficiency.

Note that when the spool 33 makes a full stroke to the right in the figure, the variable throttle 36 is fully closed, but even in this state, the fixed orifice 41 communicates between the inlet boat 34 and the outlet port 35 at a limited opening, and the suction chamber 7 is slightly closed. To compensate for the flow of working fluid to the piston 9, seizing of the piston 9 can be prevented even if the spool 33 is locked in this state.

FIG. 2 shows a modification of FIG. 1. In the example shown in FIG. 1, the piston 9 is prevented from seizing by the fixed orifice 41 as described above, but in this example, the variable throttle 36 on the right side of the spool 33 in the figure is prevented from being fully closed. A stopper 43 is provided to limit the piston 9 to the illustrated position, thereby preventing the piston 9 from seizing.

In each of the above embodiments, the flow control device 2 is shown for the radial piston pump 1, but this device can also be applied to other types of positive displacement pumps. Further, although the spool valve 31 has been illustrated as the valve means of the flow rate control device 2, it goes without saying that other types of valves may be used.

(Effects of the Invention) As described above, in the flow rate control device of the present invention, the throttling means for controlling the opening of the suction passage of the pump is constituted by the valve means (the spool valve 31 in the illustrated example) that responds to the pump discharge pressure. The relatively low cost and compactness of this valve means makes the pump equipped with a flow control device cost advantageous and makes the pump space efficient.

In addition, when the fixed orifice 41 that bypasses the valve means is added as in claim 2 or 3, or the stopper 43 that prevents the valve means from being completely closed is added, the valve means is locked. Even if something happens, the amount of working fluid to the pump will never become zero, and seizure of the pump can be prevented.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a radial piston pump showing one embodiment of the flow rate control device of the present invention, FIG. 2 is a cross-sectional view similar to FIG. 1 showing another example of the present invention, FIGS. 3 and 4 1 and 2 are discharge flow rate characteristics and pump driving torque characteristics of the pump shown in FIGS. 1 and 2, respectively. 1...Fixed cylinder type radial piston pump 2...
・Flow rate control device 4... Pump drive shaft 7... Suction chamber 8... Eccentric cam ring 9... Radial piston 10... Fixed cylinder 12... Discharge chamber 14... Side boat 18...・Suction passage 19...Discharge passage 20, 21...Connection boat 22...Delivery valve 24...Groove
25...Discharge boat 31...Spool valve (valve means) 33...Spool 34...Suction boat 3
5... Outlet boat 36... Variable throttle 40... Pilot pressure circuit 41... Fixed orifice 43... Stopper Fig. 3

Claims (1)

[Claims] 1. In a variable displacement pump capable of controlling the flow rate by controlling the opening of the suction passage with a throttle means, the opening is determined by responding to the discharge pressure of the variable displacement pump as a pilot pressure. 1. A flow rate control device for a variable displacement pump, characterized in that the throttle means is constituted by a valve means. 2. The flow control device for a variable displacement pump according to claim 1, further comprising a fixed orifice that bypasses the valve means. 3. The flow control device for a variable displacement pump according to claim 1, further comprising a stopper for preventing said valve means from being fully closed.