JP2684804B2 - Control device for positive displacement pump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for controlling a discharge capacity and a discharge pressure of a positive displacement pump.

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

As a discharge volume control device for that purpose, there is a conventional method disclosed in JP-A-1-
As described in Japanese Patent No. 262374, there is one in which the opening of the suction passage of the pump is adjusted to control the capacity of the pump. In this type of capacity control device, as is conventionally shown in the above-mentioned literature, the pump discharge pressure is detected by a pressure sensor, and based on the information from this, a microcomputer opens a variable throttle in the pump suction passage through a step motor. It was general to control and perform capacity control.

(Problems to be Solved by the Invention) However, in such a capacity control system, the pressure sensor, the microcomputer, and the step motor are expensive, which inevitably leads to a cost disadvantage. There is a problem in that it needs to be attached and requires a large pump installation space.

Further, the conventional displacement control device does not try to control the pump discharge pressure to a value required for the operation of the device,
When the pressure required for operation of the equipment is low, it is inevitable that the pump discharge pressure becomes excessive. In other words, a relief valve is normally connected to the operating pressure circuit of the equipment for safety.When the required pressure of the equipment is low as described above, the amount of working fluid consumed is small, and the internal pressure of the working pressure circuit causes the relief valve to open. It rises to the valve pressure. Therefore, the pump discharge pressure becomes excessive with respect to the required pressure of the equipment, and the drive energy of the pump is wasted by the pressure difference between the two.

For example, in the case of a pump used for an active suspension device, the required pressure of the suspension stroke control cylinder is at the minimum level while the vehicle is stopped or running straight on a good road, but the pump discharge pressure becomes the maximum relief valve opening pressure equivalent value. The pump driving energy is wasted by the pressure difference between the two.

The present invention provides a control device that constructs another capacity control system that does not cause the above-mentioned cost and space disadvantages, and also makes it possible to control the discharge pressure by utilizing this system. Therefore, it is an object of the present invention to solve the above-mentioned various problems all at once.

(Means for Solving the Problem) For this purpose, a control device for a positive displacement pump according to the present invention is a positive displacement pump capable of controlling a flow rate by controlling an opening of a suction device by means of a throttle means. The throttle means is constituted by valve means which receives pressure as pressure and whose opening is decreased, and whose opening is increased in response to the discharge pressure control force from the electromagnetic means in a direction opposite to the capacity control pressure. A controller of a pressure-operated device operated by a pump discharge pressure, wherein the discharge pressure control force from the electromagnetic means to the valve means is a value corresponding to an operating pressure upper limit value of the pressure-operated device under a constant pump discharge flow rate. It is characterized in that it is configured to be controlled.

(Function) The positive displacement pump performs a predetermined pump function by sucking and discharging the working fluid from the suction passage. During this time, the valve means forming the throttle means for controlling the opening degree of the pump suction passage receives the pump discharge pressure as the capacity control pressure to reduce the opening degree, and receives the discharge pressure control force from the electromagnetic means in the opposite direction. The opening degree of the pump suction passage is controlled so that the opening degree is increased and the forces resulting from these are balanced.

By the way, since the throttle means is composed of the valve means as described above, even a pump provided with a displacement control device can be greatly advantageous in terms of cost and space efficiency.

Further, as is apparent from the above description of the operation, on the one hand, the pump capacity can be controlled according to the pump discharge pressure to match the required capacity of the equipment operated by the pump discharge pressure, and on the other hand, the pump discharge pressure can be discharged. Not only the displacement control of the pump but also the discharge pressure control can be performed such that the pressure control force can be arbitrarily changed to match the demand of the operating device.

By the way, according to such a control device, expensive parts or large parts including the valve means are not required, and the volumetric pump to be controlled becomes expensive, and it becomes difficult to secure a large installation space. It can be avoided. Further, nevertheless, not only the capacity control but also the pump discharge pressure can be controlled.

In addition, according to the present invention, the electromagnetic means is a controller for pressure-operated equipment that is operated by pump discharge pressure,
Since the discharge pressure control force from the electromagnetic means to the valve means is controlled to be a value according to the operating pressure upper limit value of the pressure-operated device, the pump discharge pressure can be perfectly matched to the required pressure of the device. It is possible to reliably prevent waste of pump driving energy.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

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

The pump 1 comprises a pump housing 3 through which a pump drive shaft 4 is rotatably supported by bearings 5 and 6. An eccentric cam 4a is integrally formed 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 arranged on the outer periphery of the ring 8 at equal circumferential intervals. . Each of these radial pistons 9 extends in the radial direction of the eccentric cam ring 8 and is slidably fitted in a corresponding fixed cylinder 10 formed in the pump housing 3. The external opening 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 closed-end sleeve shape at the end close to the eccentric cam ring 8, and is pressed against the eccentric cam ring 8 by a spring 13. And each radial piston 9
Of the suction chamber 7 during the stroke of the radial piston
The side port 14 is formed at a position protruding and retracting inside.

The right end of the pump drive shaft 4 in the figure is a power supply end, and a portion of the pump drive shaft 4 close to the power supply end is sealed to the pump housing 3 by a seal 15. The other end of the pump drive shaft 4 seals against a passage member 16 attached to the pump housing 3.
Seal with 17. The passage member 16 includes a suction passage 18 and a discharge passage.
The discharge passages 19 are formed in the same number as the fixed cylinders 10. The suction passage 18 communicates with the suction chamber 7 through a communication port 20 formed in the pump housing 3, and each discharge passage 19 has a communication port 21 formed in the pump housing 3.
To communicate with the corresponding discharge chamber 12.

A delivery valve 22 is provided between the passage port 21 and the discharge passage 19, and this valve has a communication port at a pressure higher than its opening pressure.
When it is supplied from 21, the working fluid is supplied from this port to the discharge passage 19 and the working fluid in the opposite direction is not allowed at all.

End cover on the side of the passage member 16 far from the pump housing 3
23, a single groove 24 communicating with all the discharge passages 19 is formed, and a discharge port 25 reaching the groove is formed. An accumulator 26 for accumulating the pressure in the discharge port 25 and a pressure-operated device operated by this pressure.
A working pressure circuit 28 with 27 is connected.

Next, the control device 2 according to the present invention will be described, in which the working fluid that has reached the suction circuit 30 from the reservoir 29 is sucked into the suction passage 18
A spool valve 31 is provided as a valve means for adjusting the amount of gas flowing into the. This spool valve is constructed by slidably fitting the spool 33 in the valve body 32, and the valve body 32 has an intake circuit.
An inlet chamber 34 to which 30 is to be connected and an outlet chamber 35 to be connected to the suction passage 18 are formed. The spool 33 has a variable throttle 36 that changes its opening according to its stroke, and has an inlet chamber 34 and an outlet chamber 35.
Provide in between. At the right end of the spool 33 in the figure, a spring 37 for urging the spool 33 in the direction of increasing the opening of the variable throttle 36 is provided as a free piston.
38, the feedback plunger 39 is abutted to the other end of the spool 33, and the circuit 40 causes the operating pressure circuit 28 to operate.
The pump discharge pressure inside is used as a capacity control pressure. The chamber 49 facing the other end of the spool 33 is communicated with the outlet chamber 35 through the communication hole 33a provided in the spool 33, and the spool pressing force due to the pressure of the outlet chamber is canceled.

The valve body 32 is further bypassed with the variable throttle 36, and the inlet chamber is
A fixed orifice 41 that short-circuits between the outlet chamber 35 and the outlet chamber 35 is formed.

The spring 37 is housed in a chamber 42 defined by the free piston 38 from the outlet chamber 35, and a communication hole 38a passing between the chamber 42 and the outlet chamber 35 is formed in the free piston 38 to form a communication hole 38a.
The free piston 38 is allowed to freely stroke due to the displacement flow of the working fluid between the chambers 35 and 42 passing through.

An electromagnetic solenoid 43 as an electromagnetic means is coaxially provided opposite to the spool valve 31 with the free piston 38 interposed therebetween. The electromagnetic solenoid 43 includes a case 44 screwed into the spool valve body 32, and the coil 45 is housed in the case 44. Then, a slidable push rod 46, which penetrates the center of the coil 45 and receives an electromagnetic force corresponding to the amount of electricity to the coil 45 leftward in the drawing, is abutted against the free piston 38.

The energization amount to the coil 45 is controlled by the controller 48 that commands the operating pressure upper limit value of the pressure actuating device 27 according to the input information 47, and the energization amount is, for example, the operating pressure command upper limit value of the device 27, or piping to this. It corresponds to the pump discharge pressure, which is the sum of pressure loss due to resistance.

 The operation of the above embodiment will now be described.

Pump action The pump drive shaft 4 is rotated by the power supplied to it,
The eccentric cam 4 a integral with the shaft 4 reciprocates each radial piston 9 in the fixed cylinder 10 via the ring 8. During this reciprocating movement, each radial piston 9 pressurizes the working fluid in the discharge chamber 12 after the side port 14 is closed by the cylinder 10 in a stroke region away from the axis of the pump drive shaft 4. When the working fluid reaches or exceeds the opening pressure of the delivery valve 22, the discharge passage 19 is opened while opening the valve 22.
Is discharged. The working fluid discharged to each passage 19 in this way gathers in the groove 24, and is discharged from the discharge port 25 to the working pressure circuit.
28 accumulated pressure in accumulator 26 and equipment
Dedicated to 27 operations.

On the other hand, each radial piston 9 is allowed to flow into the discharge chamber 12 from the working fluid side port 14 in the suction chamber 7 after the side port 14 opens in the suction chamber 7 during the stroke toward the axis of the pump drive shaft 4. Replenish and prepare for the next discharge. At this time, the working fluid in the reservoir 29 is replenished in the suction chamber 7 through the suction passage 30, the inlet chamber 34, the variable throttle 36, the outlet chamber 35, the suction passage 18, and the communication port 20.

Displacement control During the operation of the pump, the displacement of the pump from the port 25 is displaced as follows.

The spool 33 has a feedback plunger at the left end in the figure.
The pressure in the circuit 28 (pump discharge pressure) is applied via 39,
The spring force of the spring 37 and the electromagnetic force from the push rod 46 (determined by the amount of electricity supplied to the coil 45 controlled by the controller 48) are applied to the right end in the figure, and the actuator stops at a position where the forces on both ends are balanced.

The pressure in the circuit 28 (pump discharge pressure) decreases while the pressure actuating device 27 requires a greater amount of working fluid for its operation. At this time, the spool 31 input via the plunger 39 with the pressure in the circuit 28 as the capacity control pressure causes the spool 33 to move from the above balance state due to the pressure decrease to the left in the figure by the electromagnetic force from the spring 37 and the push rod 46. Then, the opening of the variable throttle 36 is increased. Therefore, the working fluid suction limit from the reservoir 29 to the suction chamber 7 increases, and the working fluid supply capacity from the suction chamber 7 to the discharge chamber 12, and thus the pump discharge flow rate, increases correspondingly. You can match your requirements.

On the other hand, the pressure in the circuit 28 (pump discharge pressure) rises when the pressure-operated device 27 does not operate, or when the pressure-operated device 27 is in an operating state in which a slight amount of working fluid is not required. At this time spool valve
Reference numeral 31 causes the spool 33 to move rightward in the drawing due to the increase in the pressure, and reduces the opening of the variable throttle 36. Therefore, the working fluid supply capability from the reservoir 29 to the suction chamber 7, and hence the pump discharge flow rate, is reduced, and this can be suppressed to the required amount required by the pressure actuating device 27.

According to the above displacement control, the upper limit value of the pump discharge amount that increases as the pump rotational speed (the rotational speed of the shaft 4) increases is determined by the equipment.
It can be controlled to match the required flow rate of 27, so that the pump driving torque can be minimized to prevent waste of pump driving energy.

By adopting the configuration of this example for such capacity control, a large step motor can be pumped without the need for expensive pressure sensors, microcomputers, and step motors as in the past. It is possible to perform a predetermined discharge flow rate control without being attached to, which is very advantageous in terms of cost and space efficiency.

When the spool 33 fully strokes 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 chamber 34 and the outlet chamber 35 with a limited opening degree, and the suction chamber 7 is slightly closed. Even if the spool 33 is locked in this state, seizure of the piston 9 can be prevented by compensating the working fluid to the piston.

The discharge pressure control controller 48 commands the upper limit of the working pressure of the pressure actuating device 27 based on the input information 47, and additionally supplies the coil 45 with a current corresponding to the upper limit of the working pressure. This current has a current value corresponding to a pressure value obtained by adding a pressure loss amount due to piping resistance to the upper limit value so that the inside of the operating pressure circuit 28 has the above upper limit value.

That is, when the controller 48 issues an instruction to increase the operating pressure upper limit value of the pressure-actuated device, the amount of electricity to the coil 45 also increases accordingly. At this time, the electromagnetic solenoid 43 increases the electromagnetic force to the left in the drawing from the push rod 46 to the spool 33. As a result, the force due to the pump discharge pressure in the right direction on the spool 33 and the spring 37 on the left side in the drawing to the spool 33 are applied.
And the force due to the electromagnetic force is balanced at a higher pump discharge pressure, and the pump discharge pressure is adjusted by the pressure operating device 27.
It is possible to prevent the pump discharge energy from being wasted because the pump discharge pressure becomes excessive with respect to the required pressure.

By the above discharge pressure control, the pump operating characteristic as shown in FIG. 3 is obtained, and therefore the relief valve, which has been indispensable in the past, becomes unnecessary. Needless to say, when there are a plurality of pressure actuating devices 27, it is necessary to determine the energization amount to the coil 45 according to the highest operating pressure upper limit value among them.

FIG. 2 shows another example of the present invention. In this example, instead of providing the communication hole 38a in the free piston 38 and communicating the chamber 42 to the outlet chamber 35 as shown in FIG. A volume change compensating path 51 communicating with the valve body 32 is formed. In the example of FIG. 1, when the spool 33 rapidly strokes in the direction of increasing the opening degree of the variable throttle 36, the free piston 38 that follows this causes cavitation in the chamber 42 to remove the working fluid in the outlet chamber 35. Although it is drawn into the subchamber 42 and a response delay of the pump discharge action occurs, in this example, the drawing of the working fluid into the chamber 42 is caused by the inlet chamber 34.
Since it is performed by the working fluid in the inside, it is possible to prevent the response delay of the pump discharge action. Further, for the same reason, the pressure change in the chamber 42 becomes small, and the oscillation of the spool valve 31 can be suppressed.

In the example of FIG. 1 and FIG. 2, the pressure in the outlet chamber 35 is guided to the chamber 49 through the communication hole 33a to cancel the pressing force of the spool 33 due to the pressure in the outlet chamber 35. Since the pressure in the chamber 35 changes in accordance with the opening of the variable throttle 36, this pressure change may cause the spool 33 to become unstable and change the opening of the variable throttle.

In FIG. 4, in order to solve this problem, the chamber 49 is communicated with the inlet chamber 34 by the passage 61 formed in the valve body 32 so that the inside of the chamber 49 is kept unpressurized and the stroke of the spool 33 is not obstructed. In this case, since the fluctuating pressure is not input into the chamber 49, the spool 33 can be prevented from becoming unstable. Of course, in this case, it is needless to say that the cross-sectional area of the feedback plunger 39 must be increased because the force applied to the spool 33 in the right direction in the figure becomes smaller.

(Effects of the Invention) Thus, the control device of the volumetric pump of the present invention is as described above.
The valve means (spool 33 in the illustrated example), which forms a throttle means for controlling the opening degree of the pump suction passage, receives the pump discharge pressure as a capacity control pressure to reduce the opening degree, and discharges the electromagnetic means in the opposite direction. Pressure control force (Solenoid 43
The opening degree of the pump suction passage is controlled so that the opening degree is increased in response to the electromagnetic force).
Since the throttle means is composed of the valve means as described above, even a pump provided with a displacement control device can be greatly advantageous in terms of cost and space efficiency.

Further, as is apparent from the above description, on the other hand, the pump capacity can be controlled according to the pump discharge pressure to match the required capacity of the device operated by the pump discharge pressure,
On the other hand, not only the displacement control of the pump but also the discharge pressure control can be performed so that the pump discharge pressure can be arbitrarily changed by the discharge pressure control force to match the demand of the operating device.

According to such a control device, expensive parts and large parts including the valve means are not necessary, and the volumetric pump to be controlled is prevented from becoming expensive and being too large to secure the installation space. You can do it. Further, nevertheless, not only the capacity control but also the pump discharge pressure can be controlled.

In addition, according to the present invention, the electromagnetic means is a controller for pressure-operated equipment that is operated by pump discharge pressure,
Since the discharge pressure control force from the electromagnetic means to the valve means is controlled to be a value according to the operating pressure upper limit value of the pressure-operated device, the pump discharge pressure can be perfectly matched to the required pressure of the device. It is possible to reliably prevent waste of pump driving energy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a radial piston pump showing an embodiment of the control device of the present invention, FIG. 2 is a sectional view similar to FIG. 1 showing another example of the present invention, and FIG. FIG. 4 is an operational characteristic diagram of the pump shown in FIG. 2, and FIG. 4 is a sectional view similar to FIG. 1 showing still another example of the present invention. 1 ... Fixed cylinder type radial piston pump 2 ... Control device of the present invention, 4 ... Pump drive shaft 7 ... Suction chamber, 8 ... Eccentric cam ring 9 ... Radial piston, 10 ... Fixed cylinder 12 ... Discharge chamber , 14 …… Side port 18 …… Intake passage, 19 …… Discharge passage 22 …… Delivery valve, 24 …… Slit groove 25 …… Discharge port 31 …… Spool valve (valve means) 33 …… Spool, 34 …… Suction chamber 35 …… Outlet chamber, 36 …… Variable throttle 40 …… Capacity control pressure circuit 43 …… Electromagnetic solenoid (electromagnetic means) 45 …… Coil, 48 …… Controller 51 …… Capacity change compensation path

Claims (2)

(57) [Claims] 1. A volumetric pump capable of controlling a flow rate by controlling an opening of a suction passage by a throttle means, receives a discharge pressure of the pump as a capacity control pressure to reduce the opening degree, and opposes the capacity control pressure. The throttle means is constituted by valve means whose opening is increased in response to the discharge pressure control force from the electromagnetic means, and the electromagnetic means is a controller of a pressure operating device operated by pump discharge pressure. A control device for a positive displacement pump, characterized in that the discharge pressure control force from the valve means to the valve means is controlled to a value according to an upper limit value of the operating pressure of a pressure actuated device under a constant pump discharge flow rate. 2. The valve according to claim 1, wherein the discharge pressure control force is input to the valve means through a free piston that defines the outlet chamber of the valve means, and the valve partitioned by the free piston from the outlet chamber is used. A control device for a positive displacement pump provided with a volume change compensator that communicates with the inlet side of the valve means.