JPH03213683A - Control device for displacement pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for controlling the discharge capacity and discharge pressure of a positive displacement pump.

(Prior Art) In order to save pump drive energy, 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.

Conventionally, the discharge volume control device for this purpose has been
As described in Japanese Patent No. 262374, there is a pump in which the capacity of the pump is controlled by adjusting the opening of the suction passage of the pump. Conventionally, in this type of capacity 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 practice to control the capacity by controlling the

(Problem to be Solved by the Invention) However, in such a capacity 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.

In addition, conventional capacity control devices do not attempt to control the pump discharge pressure to the value required for the operation of the equipment, and when the pressure required for the operation of the equipment is low, the pump discharge pressure may become excessive. I can't help it. In other words, a relief valve is usually connected to the operating pressure circuit of the equipment for safety reasons, and when the required pressure of the equipment is low as described above, the amount of operating fluid consumed is small, and the internal pressure of the operating pressure circuit is reduced to open the relief valve. Increases to valve pressure. Therefore, the pump discharge pressure becomes excessive with respect to the required pressure of the equipment, and the driving energy of the pump is wasted by the difference in pressure between the two.

For example, in the case of a pump used in an active suspension system, the required pressure of the suspension stroke control cylinder is at the lowest level when stopped or when driving straight on a good road, but the pump discharge pressure is at a value equivalent to the maximum relief valve opening pressure. , the pump drive energy is wasted by the difference in pressure between the two.

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

(Means for Solving the Problems) For this purpose, the control device for a volumetric pump according to the present invention provides a volumetric pump that can control the flow rate by controlling the opening of the suction passage using a throttle means, and controls the discharge pressure of the pump by volumetric control. The throttling means is constituted by a valve means whose opening degree is determined by responding to this pressure as well as receiving a discharge pressure control force in a direction opposite to this capacity control pressure.

(Operation) A volumetric pump performs a predetermined pumping action by sucking working fluid through a suction passage and discharging it. During this time, the valve means receives the pump discharge pressure as the capacity control pressure and the discharge pressure control force in the opposite direction, and is set to an opening such that these forces are balanced to control the opening of the pump suction passage. do. Therefore, 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 arbitrarily changed by the discharge pressure control force. It can be matched to the requirements of the equipment.

By the way, such a control device does not require expensive or large parts including valve means, and can prevent the volumetric pump to be controlled from becoming expensive or becoming so large that it is difficult to secure installation space. can be avoided. Moreover, in spite of this, not only the capacity control but also the pump discharge pressure can be controlled, and this pump discharge pressure can be matched to the required pressure of the equipment, thereby preventing waste of pump drive energy.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the 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 in the radial direction 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 port 14 is formed by disposing it at a position that protrudes and retracts inside.

The right end of the pump drive shaft 4 in the figure is used as a power supply end, and 40 parts of the pump drive shaft near this end are sealed from the pump housing 3 by seals 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 same number of discharge passages 19 as the fixed cylinders 10 are formed. 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 communicates with the corresponding discharge chamber 12 through a communication port 21 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 opening pressure is supplied from the communication port 21 and supplies working fluid from this port to the discharge passage 19, and does not allow any working fluid to flow 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.
form. 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.

Next, the control device 2 according to the present invention will be explained. This device adjusts the amount of working fluid that has reached the suction circuit 30 from the reservoir 29 and flows 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.
2, an inlet chamber 34 to which the suction circuit 30 is connected, and an outlet chamber 35 to communicate with the suction passage 18 are formed. The spool 33 has a variable aperture 3 whose opening degree changes according to its stroke.
6 is provided between the inlet chamber 34 and the outlet chamber 35. A spring 37 that biases the spool 33 in the direction of increasing the opening of the variable throttle 36 acts on the right end of the spool 33 via the free piston 38, and a feedback plunger 39 is abutted against the other end of the spool 33, and the circuit 40 This causes the pump discharge pressure in the operating pressure circuit 28 to act as a capacity control pressure. The chamber 49, which the other end of the spool 33 faces, communicates with the outlet chamber 35 through a communication hole 33a provided in the spool 33, thereby canceling out the spool pressing force due to the pressure in the outlet chamber.

The valve body 32 further includes a fixed orifice 41 that bypasses the variable throttle 36 and short-circuits between the inlet chamber 34 and the outlet chamber 35.
form.

The spring 37 is housed in a chamber 42 separated from the outlet chamber 35 by the free piston 38, and is connected to the chamber 42 and the outlet chamber 3.
A communication hole 38a is formed in the free piston 38 to communicate between the chambers 35 and 5, so that the free piston 38 can freely stroke due to the displacement flow of the working fluid between the chambers 35 and 42 via the communication hole 38a.

On the opposite side of the spool valve 31 with the free piston 38 interposed therebetween, an electromagnetic solenoid 43 serving as an electromagnetic means is provided coaxially and oppositely. This electromagnetic solenoid 43 includes a case 44 screwed onto the spool valve body 32, and a coil 45 is housed in the case 44.

Then, a slidable bushing rod 46 that passes through the center of the coil 45 and receives electromagnetic force to the left in the figure according to the amount of current applied thereto is brought into contact with the free piston 38.

The amount of energization to the coil 45 is controlled by a controller 48 that commands the upper limit value of the operating pressure of the pressure-operated device 27 according to the input information 47, and the amount of energization is set to the upper limit value of the operating pressure command of the device 27, or the piping connected to this. Correspond to the pump discharge pressure, which is the sum of the pressure loss due to resistance.

The operation of the above embodiment will be explained next.

A pump drive shaft 4 of So/1 Sakuri 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 bubble 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 pistons 9 allows the working fluid in the suction chamber 7 to flow from the side boat 14 into the discharge chamber 12. refill and prepare for the next discharge. At this time, the working fluid in the reservoir 29 is replenished into the suction chamber 7 through the suction circuit 30, the inlet chamber 34, the variable throttle 36, the outlet chamber 35, the suction passage 18, and the communication boat 20.

During the above pump operation, the pump discharge flow rate from the boat 25 is controlled in the following manner.

The spool 33 is subjected to the pressure in the circuit 28 (pump discharge pressure) via the feedback plunger 39 at the left end in the figure, and the spring force of the spring 37 and the bushing rod 4 at the right end in the figure.
6 (determined by the amount of current applied to the coil 45 controlled by the controller 48), and the coil 45 is stopped at a position where the forces on both ends are balanced.

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. At this time, the spool 31, which is inputted via the plunger 39 using the pressure in the circuit 28 as a capacity control pressure, moves the spool 33 from the above-mentioned balanced state to the left in the figure due to the electromagnetic force from the spring 37 and the bushing rod 46. and increases the opening of the variable diaphragm 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 does not operate or is in an operating state that does not require a small amount of operating fluid, the circuit 28
The internal pressure (pump discharge pressure) increases.

At this time, the spool valve 31 is opened by the spool 3 due to the pressure increase.
3 to the right in the figure to reduce the opening of the variable diaphragm 36. Therefore, the working fluid supply capacity from the reservoir 29 to the suction chamber 7, and therefore 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 capacity control, the upper limit of the pump discharge amount, which increases as the pump rotation speed (rotation speed of the shaft 4) increases, is set to the device 2.
Therefore, the pump drive torque can be kept to the minimum necessary and waste of pump drive energy can be prevented.

By the way, if a configuration like this example is adopted for such capacity 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 discharge 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 chamber 34 and the outlet chamber 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.

The controller 48 controls the pressure-operated equipment 2 based on the input information 47.
7, and in addition, a current corresponding to this upper limit value of the operating pressure is supplied to the coil 45. This current is, for example, a current value corresponding to a pressure value obtained by adding the pressure loss due to piping resistance to the upper limit value so that the inside of the operating pressure circuit 28 reaches the above upper limit value.

In other words, when the controller 48 issues a command to increase the upper limit of the operating pressure of the pressure-operated device, the amount of current applied to the coil 45 increases accordingly. At this time, the electromagnetic solenoid 43 increases the electromagnetic force from the bushing rod 46 to the spool 33 in the left direction in the figure. As a result, the force exerted on the spool 33 by the pump discharge pressure to the right in the figure and the force exerted by the spring 37 and the MTli force directed to the left in the figure to the spool 33 are balanced at a higher pump discharge pressure, and the pump discharge pressure can be made to match the upper limit of the operating pressure of the pressure-operated device 27, and it is possible to prevent the pump discharge pressure from becoming excessive with respect to the required pressure and the pump drive energy being wasted.

By controlling the discharge pressure as described above, the pump operating characteristics as shown in FIG. 3 can be obtained, and therefore the above-mentioned relief valve, which was conventionally indispensable, becomes unnecessary. It goes without saying that when there are a plurality of pressure-operated devices 27, it is necessary to determine the amount of current to be applied 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 which the free piston 38 is provided with a communication hole 38a as shown in FIG. A volume change compensation path 51 is formed in the valve body 32.

In the example shown in FIG. 1, when the spool 33 rapidly strokes in the direction of increasing the opening of the variable throttle 36, the free piston 38 that follows this stroke causes cavitation in the chamber 42 to uniformly drain the working fluid in the outlet chamber 35. Pulled into the club room 42,
This causes a delay in the response of the pump discharge action, but in this example, the chamber 42
Since the working fluid in the inlet chamber 34 is drawn in by the working fluid in the inlet chamber 34, the above-mentioned delay in response of the pump discharge action can be prevented. Furthermore, for the same reason, the pressure change within the chamber 42 is reduced, and oscillation of the spool valve 31 can also be suppressed.

In the example shown in FIGS. 1 and 2, the pressure in the outlet chamber 35 is guided to the chamber 49 through the communication hole 33a to cancel out the pressing force on the spool 33 due to the pressure in the outlet chamber 35. Since the pressure within the chamber 35 changes depending on the opening degree of the variable throttle 36, there is a concern that this pressure change will cause the spool 33 to become unstable, causing a vicious cycle in which the variable throttle opening changes.

In order to solve this problem, the chamber 49 in FIG. 4 is communicated with the inlet chamber 34 through a passage 61 formed in the valve body 32, so that the inside of the chamber 49 is maintained in a pressure-free state so that the stroke of the spool 33 is not obstructed. In this case, since the fluctuating pressure within the chamber 49 is not input, it is possible to avoid the spool 33 becoming unstable. Of course, in this case, it goes without saying that it is necessary to increase the cross-sectional area of the feedback plunger 39 by an amount corresponding to the decrease in the force applied to the spool 33 in the right direction in the figure.

(Effects of the Invention) Thus, as described above, in the control device for a positive displacement pump of the present invention, the throttle means for controlling the opening of the suction passage of the pump is configured by the valve means (the spool valve 31 in the illustrated example) that responds to the pump discharge pressure. , since the displacement is controlled, the valve means is relatively inexpensive and compact, making the pump equipped with the displacement control device cost-effective;
The spooling efficiency of the pump can be increased.

Moreover, since the discharge pressure control force (in the illustrated example, electromagnetic force by the solenoid 43) is applied in the opposite direction to this displacement control device, and the pump discharge pressure is also controlled using the displacement control device, the pump discharge pressure can be controlled. It is possible to match the required pressure of the operating equipment and prevent waste of pump drive energy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a radial piston pump showing one 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. 3 is a sectional view of FIG. FIG. 4 is a sectional view similar to FIG. 1 showing still another example of the present invention. ■...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・
...Suction passage 19...Discharge passage 22...
・Delivery valve 24...Groove 25...Discharge port 31...Spool valve (valve means) 33...Spool 34...Suction chamber 35
...Exit chamber 36...Variable aperture 40.
... Capacity control pressure circuit 43 ... Electromagnetic solenoid (electromagnetic means) 45 ... Coil 51 ... Capacity change compensation path 48 ... Controller

Claims (1)

[Scope of Claims] 1. In a volumetric pump capable of controlling the flow rate by controlling the opening of the suction passage with a throttle means, the pump discharge pressure is treated as a volume control pressure in response to the volume control pressure, and the volume control pressure is opposed to the volume control pressure. 1. A control device for a volumetric pump, characterized in that the throttle means is constituted by a valve means whose opening degree is determined by receiving a discharge pressure control force in the direction and responding thereto. 2. In claim 1, the discharge pressure control force is generated by electromagnetic means, and the electromagnetic means is a controller of a pressure-operated device operated by pump discharge pressure, and the discharge pressure control force is an upper limit of the operating pressure of the pressure-operated device. A displacement pump control device configured to control the value according to the value. 3. In claim 1 or 2, the discharge pressure control force is input to the valve means through a free piston that partitions an outlet chamber of the valve means, and the chamber partitioned off from the outlet chamber by the free piston is separated from the outlet chamber by the valve means. A control device for a volumetric pump that is provided with a volume change compensation path that communicates with the inlet side of the means.