JPH04214973A - Control device for positive displacement pump - Google Patents

Abstract

PURPOSE:To compact the space of a device in the direction of the axis of the device by providing a notch in a valve means used in controlling the opening of the suction passage of a positive displacement pump, the notch being adapted for guiding a feedback member which is actuated by capacity controlling pressure and causes the valve means to react. CONSTITUTION:In a control device 2 a notch 3a extending in the direction of the axis of a spool 33 is provided in the spool 33 which slides within the valve main bodies 32, 50 of a spool valve 31. A projecting portion 32a provided to the valve main body 32 is fitted into the notch and a feedback plunger 39 is freely slidably supported inside an axial notch 32b provided in the projecting portion 32a, while the feedback plunger 39 is made to overlap the spool valve. The opening of the spool valve is controlled to a position at which the force of the feedback plunger 39 to push the spool 33 due to the input of capacity controlling pressure is in equilibrium with forces exerted by a spring 37 and a solenoid 43.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the discharge capacity and pressure of a positive displacement pump.

0002

2. Description of the Related 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 current discharge pressure. As a capacity control device for this purpose, the applicant of the present application previously filed Japanese Patent Application No. 2-85
As described in No. 06, a pump has been proposed in which the capacity of the pump is controlled by adjusting the opening of the suction passage of the pump. In this capacity control device, the valve means receives the pump discharge pressure as a capacity control pressure, and responds in a direction opposite to the capacity control pressure via a feedback member extending in the axial direction of the valve means. In response to the discharge pressure control force, the opening of the suction passage for sucking the working fluid is controlled so that the force due to the capacity control pressure and the discharge pressure control force are balanced. With this opening control, the pump capacity is controlled according to the pump discharge pressure to match the required capacity of the equipment operated by the pump discharge pressure, and the pump discharge pressure can be arbitrarily changed by the discharge pressure control force to adjust the pump capacity to the operating equipment. can be adapted to the required pressure.

0003

However, in the above-mentioned capacity control device, the valve means and the feedback member that control the opening degree of the suction passage are arranged so that the end of the feedback member is located at the end of the valve means (for example, a spool valve). Since the components are arranged in a line in the axial direction so as to come into contact with each other, the space in the axial direction inevitably becomes large, resulting in an increase in the size of the entire device.

The present invention aims to solve the above-mentioned problems by providing an axial cutout within the valve means and guiding the feedback member within this cutout.

[0005]

[Means for Solving the Problems] For this purpose, the control device for a displacement pump of the present invention receives pump discharge pressure as a displacement control pressure, responds to the displacement control pressure via a feedback member, and responds to the displacement control pressure. A volume comprising a valve means whose opening degree is determined in response to a discharge pressure control force opposing the volume control pressure, and the valve means controls the opening of the suction passage to control the flow rate. The pump is characterized in that a cutout for guiding the feedback member in the axial direction is provided inside the valve means.

[0006]

[Operation] According to the present invention, while the volumetric pump performs a predetermined pumping action by sucking and discharging working fluid from the suction passage, the valve means uses the pump discharge pressure as the volume control pressure, and the valve means counteracts the pump discharge pressure as the volume control pressure. The opening of the pump suction passage is controlled by receiving a discharge pressure control force in a direction such that the opening of the pump suction passage is adjusted so that these forces are balanced. Therefore, the pump capacity is controlled according to the pump discharge pressure to match the required capacity of the equipment operated by the pump discharge pressure, and the pump discharge pressure is arbitrarily changed by the discharge pressure control force to meet the required pressure of the operated equipment. By adapting, waste of pump drive energy can be prevented. At this time, the present invention is provided with a notch inside the valve means that guides in the axial direction a feedback member that receives the pump discharge pressure as the displacement control pressure and causes the valve means to respond to the displacement control pressure. The feedback member may be housed within and overlapping the valve means. Therefore, the axial space of the entire device can be significantly reduced compared to the device disclosed in Japanese Patent Application No. 2-8506 mentioned above, and compactness can be achieved.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing 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 attached to the shaft 4 between these bearings.
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 has a corresponding fixed cylinder 10 formed in the pump housing 3 and extending in the radial direction of the eccentric cam ring 8.
The external open end of a fixed cylinder 10 that is slidably fitted therein 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. A side port 14 is formed in the circumferential wall of each radial piston 9 at a position where the side port 14 moves in and out of the suction chamber 7 during the stroke of the radial piston.

The right end of the pump drive shaft 4 in the drawing is defined 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. Pump drive shaft 4
The other end is a passage member 1 attached to the pump housing 3.
6 is sealed with a seal 17. 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 is connected to a communication port 20 formed in the pump housing 3.
Each discharge passage 19 communicates with the corresponding discharge chamber 12 through a communication port 21 formed in the pump housing 3. Communication port 21 and discharge passage 1
A delivery valve 22 is provided between 9 and 9, and this valve opens when a pressure higher than the valve opening pressure is supplied from the communication port 21, supplies working fluid from this port to the discharge passage 19, and prevents any working fluid from flowing in the opposite direction. be in a format that is not permitted. An end cover 2 is placed on the side of the passage member 16 that is far from the pump housing 3.
3, and in addition to forming one groove 24 that communicates with all the discharge passages 19, a discharge port 25 that reaches the groove is formed. 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 control device 2 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 fitting a spool 33 into valve bodies 32 and 50 so as to be slidable in the axial direction (left and right directions in the figure), and the valve body 32 is screwed into the left end of the valve body 50. Ru. At the center of the valve body 32, there is a protrusion 32 extending to the right in the figure.
A is formed inside the protrusion 32a, and an axial notch 32b for guiding the feedback plunger 39 is formed inside the protrusion 32a. The protrusion 32a is fitted into an axial notch 33a provided in the spool 33 from the left side in the figure.
is guided in the axial direction. Note that this notch 33a is formed to have an axial dimension that can ensure the stroke of the feedback plunger 39. The valve body 50 includes a suction circuit 30.
An inlet chamber 34 to be connected to the suction passage 18 and an outlet chamber 35 to be connected to the suction passage 18 are respectively formed. The spool 33 provides a variable throttle 36 between the inlet chamber 34 and the outlet chamber 35 whose opening degree changes according to its stroke. Flange 33 of spool 33
A spring 37 is applied to bias this in the direction of increasing the opening degree of the variable throttle 36, and the feedback plunger 39 is abutted against the right end of the notch 33a of the spool 33 in the figure, and the capacity control pressure circuit 40 is used to control the operating pressure circuit 28. The pump discharge pressure inside is used as the capacity control pressure. The chamber 49 facing the flange 33b of the spool 33 is communicated with the inlet chamber 34 through a communication hole 33c provided in the spool 33, thereby canceling out the spool pressing force due to the pressure in this inlet chamber.

An electromagnetic solenoid 43 is coaxially disposed near the right end of the spool 33 of the spool valve 31 in the drawing. This electromagnetic solenoid 43 is connected to a case 4 screwed to the spool valve body 32.
4, and a coil 45 is housed in this. Then, a slidable push rod 46 that penetrates the center of the coil 45 and receives an electromagnetic force in the left direction in the figure according to the amount of current applied thereto is brought into contact with the right end of the spool 33 in the figure. 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.

First, to explain the pump action, the pump drive shaft 4 is rotated by the power supplied thereto, and the eccentric cam 4a integrated with the shaft 4 reciprocates each radial piston 9 within the fixed cylinder 10 via the ring 8. let 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 range far from the axis of the pump drive shaft 4 . Then, this working fluid is delivered to the delivery valve 2.
When the pressure reaches the valve opening pressure 2 or higher, the valve 22 is opened and discharged into the discharge passage 19. The working fluid discharged into each passage 19 in this manner collects in the groove 24 and the discharge port 2
5 to the operating pressure circuit 28, where the pressure is accumulated in the accumulator 26 and used to operate the equipment 27. On the other hand, each radial piston 9 transfers the working fluid in the suction chamber 7 to the side port 14 after the side port 14 opens to the suction chamber 7 during the stroke toward the axis of the pump drive shaft 4.
It flows into the discharge chamber 12 and replenishes it in preparation for the next discharge. At this time, the working fluid in the reservoir 29 enters the suction chamber 7 through the suction circuit 30, the inlet chamber 34, the variable throttle 36, and the outlet chamber 35.
, the suction passage 18 and the communication port 20.

Next, the capacity control will be explained. During the pump operation, the pump discharge flow rate from the port 25 is controlled in the following manner. The pump discharge pressure in the operating pressure circuit 28 is guided through the capacity control pressure circuit 40 to a notch 32b provided inside the protrusion 32a of the valve body 32, and acts on the feedback plunger 39 to stroke it to the right in the figure. . Due to the stroke of the feedback plunger 39, a force due to the pump discharge pressure is applied to the right end of the notch 33a provided inside the spool 33 in the drawing, and this force closes the spool valve 31 (reduces the opening degree).
Acts on the direction. In addition, the spool 33 is subjected to the spring force of the spring 37 and the electromagnetic force (determined by the amount of current applied to the coil 45, which is controlled by the controller 48) from the push rod 46 at its right end in the figure in the opposite direction to the above. It stops at a position where the force due to the pump discharge pressure and the force due to this spring force and electromagnetic force are balanced. While the pressure-operated equipment 27 requires a large amount of working fluid for its operation, the circuit 28
The internal pressure (pump discharge pressure) decreases. At this time, the spool 31, which is input via the plunger 39 using the pressure in the circuit 28 as a capacity control pressure, moves the spool 33 from the above-mentioned equilibrium state to the left in the figure due to the electromagnetic force from the spring 37 and the push rod 46. and variable aperture 3
6 to increase the opening degree. Therefore, the working fluid suction limit from the reservoir 29 to the suction chamber 7 increases, and the suction chamber 7
The working fluid supply capacity from the pump to the discharge chamber 12 and thus the pump discharge flow rate is increased and can be adapted to the requirements of the pressure-operated equipment 27. On the other hand, when the pressure-operated device 27 is not operating or is in an operating state that requires only a small amount of operating fluid, the pressure within the circuit 28 (pump discharge pressure) increases. 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 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 pump rotation speed
The upper limit value of the pump discharge rate, which increases as the rotational speed of the shaft 4 increases, can be controlled to match the required flow rate of the device 27, and therefore the pump drive torque is kept to the minimum necessary to reduce the pump drive energy. Waste can be prevented.

By the way, in such capacity control, if the configuration as in this example is adopted, the feedback plunger 3
9 is housed in an axial notch 32b provided inside the protrusion 32a of the valve body 32, and this protrusion 32a is housed in a notch 33a provided inside the spool 33, thereby connecting the feedback plunger 39 and the spool. The valve 31 can be overlapped. Therefore, the axial space of the entire device can be significantly reduced compared to the device disclosed in Japanese Patent Application No. 2-8506, thereby realizing compactness. Furthermore, when the configuration as in this example is adopted, the axial direction of the spool valve 31 is ensured, and rattling of the spool valve is prevented, thereby improving the accuracy of capacity control.

Next, the discharge pressure control will be explained. The controller 48 instructs the upper limit of the operating pressure of the pressure-operated equipment 27 based on the input information 47, and also controls the current according to the upper limit of the operating pressure. It 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. That is, 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 push rod 46 to the spool 33 in the leftward direction in the drawing. As a result, the force due to the pump discharge pressure directed to the right in the drawing on the spool 33 and the force due to the spring 37 and the electromagnetic force directed to the left in the drawing to the spool 33 are balanced at a higher pump discharge pressure, and the pump discharge pressure is reduced to the pressure This can be adjusted to the upper limit of the operating pressure of the operating device 27, and it is possible to prevent the pump discharge pressure from becoming excessively high relative to the required pressure and the pump drive energy being wasted. Therefore, energy consumption can be significantly reduced by arbitrarily setting the pump discharge pressure to the minimum necessary pressure.

It should be noted that the present invention is not limited to the above-mentioned example, and can of course be modified in many ways. For example, although this example uses a fixed cylinder type radial piston as the volumetric pump, a volumetric pump that performs suction and discharge by the action of rotational input may be used instead.

[0017]

As described above, the control device for a positive displacement pump of the present invention is configured such that an axial notch is provided inside the valve means and the feedback member is guided within this notch. A member may be received within and overlapping the valve means. Therefore, the axial space of the entire device can be significantly reduced compared to the device disclosed in Japanese Patent Application No. 2-8506 mentioned above, and compactness can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a radial piston pump showing an embodiment of the control device of the present invention.

[Explanation of symbols]

1 Fixed cylinder type radial piston pump 2 Control device of the present invention 7 Suction chamber 12 Discharge chamber 18 Suction passage 19 Discharge passage 31 Spool valve (valve means) 32 Valve body 32a Projection 32b Notch 33 Spool 33a Notch 34 Inlet chamber 35 Outlet chamber 36 Variable throttle 40 Capacity control pressure circuit 43 Electromagnetic solenoid 48 Controller 50 Valve body

Claims (1)

[Claims] 1. A pump discharge pressure is input as a displacement control pressure and the pump responds to the displacement control pressure via a feedback member, and also receives a discharge pressure control force opposite to the displacement control pressure and responds thereto, comprising a valve means whose degree of opening is determined;
A volumetric pump in which the flow rate can be controlled by controlling the opening of the suction passage by means of the valve means, characterized in that a notch for guiding the feedback member in the axial direction is provided inside the valve means. control device.