JPH04295191A - Control device for volume pump - Google Patents

Abstract

PURPOSE:To perform stable control of a delivery flow rate on the whole of a pump throughout the whole area of a spool stroke by providing a plurality of sets of valve means (spool valves) for controlling the opening of a suction passage in a state to change opening control characteristics, in a variable capacity pump, such as a radial piston pump. CONSTITUTION:In a radial piston pump 1, spool valves 31-1 and 31-2, serving as a valve means, connected to suction circuits 30-1 and 30-2 and capacity control circuits 40-1 and 40-2 have springs 37-1 and 37-2, respectively, being different in characteristics, such as a spring constant and a set force. By properly setting the characteristics of the springs, the characteristics of a spool opening area responding to a spool stroke for secondary curveform characteristics (desired characteristics) on the whole of the pump 1. Thus, the characteristics of a delivery flow rate to a spool opening area are brought into an approximately linear state and stable control of a delivery flow rate can take place.

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 and responds to the pump discharge pressure as the capacity control pressure, and also responds to the discharge pressure control force in the direction opposite to this capacity control pressure. The opening degree of the suction passage for sucking the working fluid is controlled to such an opening degree that the force 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

[Problems to be Solved by the Invention] In the conventional pump described above, the change in the discharge flow rate with respect to the spool opening area is as shown in FIG. The amount of change in the flow rate becomes excessive for a minute displacement of the spool valve, and the flow rate control characteristics by the spool valve become unstable. In order to improve this unstable phenomenon, for example, the spool opening area relative to the spool stroke may be changed in a quadratic curve as shown by the solid line in FIG. Realizes quadratic curve characteristics.

However, when the spool end face of the pump is configured with a notch so as to have the above characteristics, the stroke required until the spool opening area reaches a predetermined area is undesirably increased compared to a case without the notch as shown by the dotted line in the figure. I end up. This stroke increase is because the maximum stroke of the electromagnetic proportional solenoid that strokes the spool is usually 2 m.
Since the diameter of the spool is about m, it cannot be absorbed completely and the spool diameter has to be increased. However, when the spool diameter is increased, the control accuracy of the flow rate characteristics relative to the capacity control pressure (pump discharge pressure) decreases due to increased friction, the spring that acts as a reaction force to the force due to the capacity control pressure becomes larger, and the inertial mass of the spool increases. An increase in the number of points causes a problem in which the responsiveness deteriorates.

An object of the present invention is to solve the above-mentioned problems by using a plurality of sets of valve means having different opening control characteristics in combination.

[0006]

[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, and responds to the displacement control pressure. In the displacement pump, the displacement pump is provided with a valve means whose opening degree is determined in response to the discharge pressure control force, and the valve means can control the opening of the suction passage to control the flow rate. The present invention is characterized in that a plurality of sets of means are provided, and each set has different opening control characteristics.

[0007]

[Operation] According to the present invention, while the volumetric pump performs a predetermined pump action by sucking and discharging working fluid from the suction passage, a plurality of valves are provided to individually control the opening of each suction passage. Each of the means receives the pump discharge pressure as a capacity control pressure and receives a discharge pressure control force in a direction opposite to the pump discharge pressure, and controls the opening of the suction passage by adjusting the opening such that these forces are balanced. At this time, each valve means is
Since the respective opening degree control characteristics are set to be different from each other, the opening degree control characteristics of the entire pump can be obtained by superimposing each of the above-mentioned opening degree control characteristics. Therefore, by appropriately setting the opening control characteristics of each of the valve means, opening control characteristics almost similar to those shown by the solid line in FIG. 6 can be obtained without increasing the size of the valve due to an increase in stroke, and stable A volumetric pump with flow control characteristics can be realized.

[0008]

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.
It is slidably fitted inside. 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. 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 the communication port 2 formed in the pump housing 3.
0 communicates with the suction chamber 7, and each discharge passage 19 communicates with the corresponding discharge chamber 12 through a communication port 21 formed in the pump housing 3. A delivery valve 22 is provided between the communication port 21 and the discharge passage 19, and this valve opens when a pressure higher than the valve opening pressure is supplied from the communication port 21 to supply working fluid from this port to the discharge passage 19, and vice versa. It shall be of a type that does not allow any working fluid in the opposite direction. An end cover 23 is attached to the side of the passage member 16 that is far from the pump housing 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 connects the reservoir 29 to the suction circuit 30-1,
A spool valve 31-1 as a valve means is used to adjust the amount of working fluid that reaches 30-2 flowing into the suction passage 18.
, 31-2. These spool valves are A-
As shown in FIG. 2, which is a sectional view of A, the valve bodies 32, 50
A spool 33 is fitted inside the spool 33 so as to be slidable in the axial direction (horizontal direction in the figure), and a spring 37-
Only the characteristics of No. 1, 37-2 are different. The valve body 32 is screwed onto the left end of the valve body 50, and an axial notch 32a for guiding the feedback plunger 39 is formed inside the valve body 32. The valve body 50 is shown in FIG. 3(a).
FIG. 3 (b
), (c), the suction circuits 30-1, 30-
2, an axial sleeve 51 into which the spool 33 is to be fitted, an oil passage 53 that communicates the inlet chamber 34 with a circumferential groove 52 provided in the sleeve 51, and an oil passage 53 that communicates with the suction passage 18. An oil passage 55 that communicates the outlet chamber 35 with a circumferential groove 54 provided in the sleeve 51 is formed. As shown in FIG. 1, the spool 33 fitted into the valve body 50 provides a variable throttle 36 between the inlet chamber 34 and the outlet chamber 35 whose opening degree changes according to its stroke.

Inside the sleeve 51 of the valve body 50, a notch 33 is formed at the right end of the spool 33, as shown in FIG.
a is provided, and springs 37-1 and 37-2 are applied to bias the spool 33 in the direction of increasing the opening of the variable throttle 36. The spring constants and setting forces of the springs 37-1, 37-2 are set individually, and the springs 37-1, 37-2
Accordingly, the opening control characteristics of the spool valves 31-1 and 31-2 are set to be different. In addition, the spool valve 31
In order to individually set the opening degree control characteristics of springs 37-1 and 31-2, the spool diameters may be made different instead of making the characteristics of the springs 37-1 and 37-2 different. Further, a feedback plunger 39 is abutted against the left end of the spool 33 in the figure, and the pump discharge pressure in the operating pressure circuit 28 is caused to act as a capacity control pressure by the capacity control pressure circuits 40-1 and 40-2.

An electromagnetic solenoid 43 is coaxially disposed near the right end of the spool 33 of the spool valve in the figure. 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. And coil 4
A slidable push rod 46 that passes through the center of the spool 33 and receives an electromagnetic force to the left in the figure according to the amount of current applied thereto is abutted against 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 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 of the operating pressure command of the device 27, for example, or to the piping connected thereto. 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. First, to explain the pump action, the pump drive shaft 4 is rotated by the power supplied to it, and an eccentric cam 4a integrated with this shaft 4 is rotated.
makes each radial piston 9 reciprocate within a fixed cylinder 10 via a 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 range far from the axis of the pump drive shaft 4 . 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 valve 22. The working fluid thus discharged into each passage 19 collects in the groove 24, reaches the working pressure circuit 28 through the discharge port 25, is accumulated in the accumulator 26, and is used for operating the equipment 27. On the other hand, each radial piston 9 is
After the side port 14 opens into the suction chamber 7 during the stroke toward the axis of the pump drive shaft 4, the suction chamber 7
The working fluid inside flows into the discharge chamber 12 from the side port 14 to replenish it 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 circuits 30-1, 30-2, the inlet chamber 34, the oil passage 53, the circumferential groove 52, the sleeve 51, the circumferential groove 54, the oil passage 55, It is replenished via the variable throttle 36, 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 to the notches 32a provided inside the valve body 32 in the spool valves 31-1, 31-2, respectively, through the capacity control pressure circuits 40-1, 40-2. It acts on the feedback plunger 39 to stroke it to the right in the drawing. Due to the stroke of the feedback plunger 39, the spool 33 is subjected to a force due to the pump discharge pressure on its left end in the figure, and the force is applied to the spool valves 31-1 and 31-1.
Acts in the direction of closing -2 (reducing the opening). The spool 33 also has a spring 37-1 at its right end in the drawing.
, 37-2 and the electromagnetic force from the push rod 46 (controlled by the controller 48 and determined by the amount of current applied to the coil 45) are applied in the opposite direction to the above, and the force due to the pump discharge pressure and this force are It stops at a position where the spring force and the electromagnetic force are balanced. Pressure operated equipment 2
While 7 requires a large amount of working fluid for its operation, the pressure in circuit 28 (pump discharge pressure) decreases. At this time, the spools 31-1 and 31-2, which are input via the plunger 39 with the pressure in the circuit 28 as the capacity control pressure,
Due to this pressure drop, the spool 33 is moved from the above-mentioned equilibrium state to the left in the figure by the electromagnetic force from the spring 37 and the push rod 46, and the opening degree 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 ability to supply working fluid from the suction chamber 7 to the discharge chamber 12, and therefore the pump discharge flow rate, increases accordingly.
This can be adapted to the requirements of the pressure-operated equipment 27. On the other hand, when the pressure-operated device 27 does not operate 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 valves 31-1 and 31-2 move the spool 33 to the right in the figure due to the pressure increase, thereby reducing the opening of the variable throttle 36. Therefore, the ability to supply working fluid 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 capacity control described above, the upper limit value of the pump discharge amount, which increases as the pump rotation speed (rotation speed of the shaft 4) increases, can be controlled to match the flow rate required by the device 27, and the pump drive torque is increased as required. This can be minimized to prevent waste of pump drive energy.

By the way, for such capacity control, in the configuration of this example, the characteristics (spring constant, set force) of the springs 37-1, 37-2 of the spool valves 31-1, 31-2 are set to different values. Therefore, for example, the characteristic of the spool opening area with respect to the spool stroke in the spool valve 31-1 provided with the spring 37-1 is expressed by the dashed line in FIG. When the characteristics of the spool opening area are set as shown by the dotted line in Fig. 4, the pump 1 as a whole will have almost quadratic curve characteristics as shown by the solid line in Fig. 4, which will turn into the quadratic curve characteristics shown by the solid line in Fig. 6. It is nothing but the desired characteristic that is approximated. Therefore, by changing the discharge flow rate with respect to the spool opening area from the quadratic curve characteristic shown in FIG. 5 to an almost linear characteristic, stable discharge flow rate control can be realized over the entire spool stroke. Since the configuration is such that the spool diameter is not increased, various problems associated with the enlargement of the spool diameter in the conventional example can be eliminated.

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
6 to the spool 33 in the leftward direction in the drawing. As a result, the force due to the pump discharge pressure is applied to the spool 33 in the right direction in the figure, and the force of the spring 3 is applied to the spool 33 in the left direction in the figure.
7 and the force due to the electromagnetic force described above are balanced at a higher pump discharge pressure, and the pump discharge pressure can be adjusted to the upper limit of the operating pressure of the pressure-operated device 27, and the pump discharge pressure is excessive compared to the required pressure. This can prevent the pump drive energy from 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.

[0018]

Effects of the Invention As described above, since the control device for a positive displacement pump of the present invention uses a combination of a plurality of sets of valve means having different opening control characteristics, the opening control characteristics of each of the valve means can be appropriately set. By doing so, it is possible to obtain opening control characteristics substantially similar to those shown by the solid line in FIG. 6 without causing an increase in the size of the valve due to an increase in stroke, and it is possible to realize a volumetric pump with stable flow control characteristics.

[Brief explanation of 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 taken along the line AA in FIG. 1;

FIG. 3(a) is a sectional view on the axis of the valve body of the above embodiment, and FIG. 3(b) is a BB sectional view of (a).
(c) is a CC sectional view of (a).

FIG. 4 is a characteristic diagram showing the characteristics of the spool opening area with respect to the spool stroke of the same example.

FIG. 5 is a characteristic diagram showing the characteristics of the discharge flow rate with respect to the spool opening area in a conventional example.

FIG. 6 is a characteristic diagram showing the characteristics of the spool opening area with respect to the spool stroke in a conventional example.

[Explanation of symbols]

1 Fixed cylinder type radial piston pump (displacement pump). 2 Control device of the present invention 18 Suction passage 30-1 Suction circuit 30-2 Suction circuit 31-1 Spool valve (valve means) 31-2 Spool valve (valve means) 32 Valve body 33 Spool 34 Inlet chamber 35 Outlet chamber 36 Variable throttle 37-1 Spring 37-2 Spring 40-1 Capacity control pressure circuit 40-2 Capacity control pressure circuit 43 Electromagnetic solenoid 48 Controller 50 Valve body

Claims (1)

[Claims] Claim 1: A pump discharge pressure is input as a capacity control pressure and the pump responds to the capacity control pressure, and also receives a discharge pressure control force opposite to the capacity control pressure and responds thereto to determine the opening degree. In the volumetric pump, the displacement pump is equipped with a valve means that controls the opening of the suction passage by the valve means to control the flow rate. A control device for a positive displacement pump, characterized by: