JPS622156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in pressure compensated variable displacement vane pumps.

Such a variable discharge amount vane pump operates a variable pump discharge amount device when the self-discharge pressure rises to a preset pressure so that the pump has a large displacement amount when the pressure is low and a small displacement amount when the pressure is high, that is, the dead head pressure. The discharge amount is made small.

In a hydraulic circuit using a variable discharge vane pump with this structure, compared to a hydraulic circuit that combines a constant discharge pump and a relief valve, the relief valve surge pressure is not absorbed, so inside the variable discharge vane pump, For example, surge pressure is likely to occur when an actuator suddenly stops or a valve is suddenly closed. This surge pressure is said to be approximately 1.5 to 3 times the set pressure of the variable displacement vane pump, that is, the dead bed pressure. For example, when the dead head pressure is set to a maximum of 70 kg/cm ² , the surge pressure is 200 kg/cm ² As a result, the sliding surfaces and parts of the pump are subjected to excessive loads, rapidly reducing the life of the pump, and on top of that, surge pressure in the hydraulic circuit connected to the pump is generated. This will shorten the life of operating equipment such as valves and actuators. In addition, this surge pressure caused excessive strain in the constituent members of the pumps and equipment, resulting in a decrease in the performance of the pumps and equipment.

In order to absorb the surge pressure of such a variable discharge vane pump, it has been proposed, for example, to provide a relief valve in the variable discharge vane pump to relieve a portion of the pump discharge pressure. Furthermore, as disclosed in, for example, Japanese Utility Model Application No. 58-9996, which is currently being filed by the present applicant, the sub-pressure chamber of the sub-piston is made to communicate directly with the relief valve to prevent the generation of surge pressure in this sub-pressure chamber. proposed a method to absorb pump surge pressure. however,
In any of these cases, when changing the pump set pressure, it is also necessary to change the set pressure of each relief valve. Otherwise, when the pump set pressure is lowered, surge pressure will occur, and conversely, the set pressure will increase. When the pressure is set too high, part of the pump discharge volume escapes from the relief valve to the tank, causing a loss in discharge volume and horsepower, and an increase in oil temperature. As a result, it is difficult to handle, the spring of the relief valve must be large, and the valve is difficult to open. Furthermore, as a method of absorbing surge pressure, it has been proposed to install, for example, an accumulator that can communicate with the discharge pressure oil of a variable discharge vane pump, or to install such an accumulator in combination with a relief valve. However, the accumulator is not only expensive, but also has drawbacks such as the capacity of the accumulator must be changed in response to the flow rate and pressure of the hydraulic circuit, and adjustment and other handling are difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a variable displacement vane pump which eliminates surge pressure and does not require adjustment even if the set pressure or deadhead pressure changes.

Another object of the present invention is to use a surge absorbing valve arranged in conjunction with the pump to absorb excess pressure oil in the sub-pressure chamber of the sub-piston in an amount corresponding to the response delay of the variable mechanism that generates surge pressure in the pressure-compensated variable discharge vane pump. It is an object of the present invention to provide a variable discharge amount pump which releases pressure to a tank through the pump and prevents the generation of surge pressure.

The above-mentioned and other objects and advantages of the present invention include a main piston that presses the ring in a direction that reduces the amount of eccentricity between the vane pump rotor and the ring, and a main piston that presses the pump discharge oil into the pressure chamber of the main piston. an oil path guided through a compensator;
a second oil passage that guides the pressure oil in the pressure chamber through a throttle; a sub-piston that is located on the opposite side of the main piston and presses in a direction to increase the amount of eccentricity; and a sub-piston that directs the pressure oil discharged from the pump A variable discharge amount vane pump having a third oil passage leading to a chamber,
A small piston to which pressure oil in the pressure chamber is guided, a valve device opened and closed by the small piston, a bypass oil passage that guides control pressure oil in the auxiliary pressure chamber to the valve device, and the valve device is opened. This can be achieved by a variable discharge amount vane pump characterized in that a surge absorbing valve consisting of a drain oil passage for guiding the control pressure oil from the valve device to the tank is arranged in conjunction with the surge absorbing valve.

The pressure of the pressure oil in the pressure chamber is throttled by a pressure compensator, and by appropriately selecting the throttle, even if the set pressure of the pump is changed, the set pressure (dead head pressure) will not go up or down with the same pump. Even if the set pressure is different between pumps with different maximum pressures, approximately 20Kg/cm ² to 30Kg
The pressure can be maintained within a relatively narrow range such as / ^cm2 . Therefore, even if the set pressure of the pump, ie, the deadhead pressure, is changed, there is no need to change the pressure setting of the surge absorption valve, and therefore, surge pressure can be efficiently removed without the need for additional adjustment.

The surge pressure absorption valve may be disposed inside or outside the pump, but preferably the oil passage and the bypass oil passage may be connected to each other in order to simplify piping and downsize the device. When the pump capacity is large and it is necessary to release a large amount of excess pump pressure oil to prevent the generation of surge pressure, preferably a relief valve operated by the valve device is provided in the bypass oil passage. You may go through it. Also,
In order to make the surge absorption performance more effective, the pressure oil in the pressure chamber is guided to the small piston through a throttle valve that is throttled only in the backward direction, and the return of the valve device is slightly controlled by the throttle valve. The amount of delay pump pressure oil released into the tank may be increased.

The valve device is preferably a poppet valve, but may also be a spool valve. More preferably, the valve device can be provided with a stopper that limits the degree of opening.

When the variable discharge amount vane pump of the present invention is used in a hydraulic circuit, for example, suppose that the cylinder suddenly reaches the end of its stroke in actual use. Then, the variable mechanism of the variable pump comes into play, and the pump delivery rate is reduced to an amount close to zero, ie, to the deadhead delivery rate. In the conventional known variable discharge amount vane pump, a surge pressure P _S is generated in the pump pressure P as shown by the solid line in FIG. 1 due to the response delay of the variable mechanism. After repeating some oscillatory waves, the dead head pressure stabilizes at _PDH . At this time, the main piston control pressure P _P is also a surge pressure that is almost the same as the pump pressure P ≒ P _S
is generated, and then the pump deadhead pressure P
The pressure at the dead head is stabilized at P _PDH , which is the control pressure corresponding to _DH . In the present invention, this control pressure P _P is applied to the small piston to open the valve device and release a part of the control pressure oil in the sub-pressure chamber of the sub-piston to the tank. This prevents abnormal pressure in the pressure chamber, allows the ring to move smoothly, and eliminates surge pressure. To be more precise, the set pressure at which the surge absorption valve operates is set to a pressure P _PR that is slightly higher than the dead head pressure P _PDH of the control pressure P _P , and the corresponding pump pressure corresponds to P _R. Then, the surge pressure P _S exceeding this P _R at the pump pressure P is removed, and at the control pressure P _P this P _PR
Surge pressures exceeding In addition, the responsiveness itself is improved to prevent abnormal pressure from occurring in the sub-pressure chamber of the sub-piston.

The invention will be explained in more detail with respect to exemplary preferred embodiments and with reference to the drawings, in which: FIG. Second
The portion of the variable discharge amount vane pump shown in the figure, excluding the surge absorption valve A, is the variable discharge amount vane pump disclosed in Japanese Patent Application Laid-Open No. 57-5585, and this portion itself does not constitute the present invention, so please refer to the details below. do not explain.

FIG. 2 shows a sectional view of a hydraulic variable displacement vane pump used in machine tools, industrial equipment, etc. taken along a plane perpendicular to the axes of the sub-piston and the main piston. FIG. 3 schematically shows FIG. 2 in a hydraulic circuit diagram. Inside the pump body 1,
A rotor 8 into which a plurality of vanes 9 are inserted so as to be freely removable in the radial direction, a ring 7 that is a variable device that surrounds the rotor 8, and a side plate (not shown) that is connected to the rotor 8 and the ring 7.
Served on both sides. The sub-piston 5 has one end in contact with the ring 7, and the other end is urged by a spring 10 so as to press the ring 7 toward the center _O1 of the rotor 8. Furthermore, the pump discharge pressure is applied to the oil passage 20 in the auxiliary pressure chamber 22 on which the auxiliary piston 5 acts.
(including an oil passage (not shown) communicating with the pump discharge oil chamber 15) through the throttle valve body 30,
It acts on the surface 5' of the sub-piston 5 which receives the pump discharge pressure, thereby urging the sub-piston 5 to press the ring 7 in the right direction as viewed in FIGS. 2 and 3. The main piston 4 is provided on the opposite side of the sub-piston 5 with respect to the center O ₁ of the rotor 8 and substantially coaxially with the sub-piston 5 . The main piston 4 has one end in contact with a ring 7 and the other end in contact with a discharge rate adjusting screw 13. The discharge amount adjusting screw 13 limits the maximum eccentricity of the ring 7 via the main piston 4. Pump discharge oil is guided to a pressure chamber 23 that operates the main piston 4 through an oil passage 21 (including an oil passage (not shown) that communicates with the pump discharge oil chamber 15) via a pressure compensator 3. The main piston 4 is biased to press the ring 7 in the left direction as viewed in FIGS. 2 and 3 by acting on the pressure-receiving surface 4'. The pressure compensator 3 controls the hydraulic pressure acting on the main piston 4, and the pressure compensator 3 controls the hydraulic pressure acting on the main piston 4.
It has a spool 6 biased in the closing direction, a pressure adjustment screw 14, and ports 17, 18, 19,
When the pump discharge pressure is lower than the pressure set by the pressure adjustment screw 14, the pressure receiving surface of the spool 6 closes the port 17 communicating with the oil passage 21 to the port 18. When the pump discharge pressure exceeds the set pressure, the pressure oil flows from the port 17 to the port 18 and flows into the pressure chamber 23. port 19
is a drain port communicating with the tank or pump drain section. In this embodiment, a second oil passage 24 is provided in the axial direction approximately in the center of the main piston 4, with one end opening in the pressure chamber and thus the surface 4', and the other end communicating with the tank (pump drain part) via the throttle 12. has been done.
The state shown in FIGS. 2 and 3 is also the position where the pump is stopped, and the ring 7 is pushed to the right by the spring 10 via the sub-piston 5.
The center of the rotor 8 and the center e of the rotor 8 are eccentric by the maximum eccentricity set by the discharge adjustment screw 13. When the rotor 8 is now rotated in the direction of the arrow (counterclockwise), the pump sucks oil from the lower suction chamber 26 through a port (not shown), and pump discharge oil at the discharge pressure P from the upper discharge chamber 15. is discharged through a port not shown. This pump discharge pressure P is the third oil passage 2
The pressure chamber 2 of the sub-piston 5 passes through the zero throttle valve body 30.
At the same time, it acts on the pressure receiving surface of the spool 6 of the pressure compensator 3 through the oil passage 21.

When the hydraulic pressure due to the pump discharge pressure P acting on this pressure receiving surface is smaller than the spring force of the spring 11 set by the pressure adjustment screw 14, the ring 7 The pump is pushed toward the right by the auxiliary piston 5 on which the resultant force of the spring force acts, and the pump discharges a discharge amount corresponding to the maximum eccentricity set by the discharge amount adjustment screw 13. When the pump discharge pressure P becomes high and the hydraulic pressure acting on the pressure receiving surface of the spool 6 becomes greater than the spring force of the spring 11, the spool 6 is moved to the right. Then, the pump discharge oil goes to oil path 2.
1 and enters the pressure chamber 23 of the main piston 4 through ports 17 and 18. This pressure oil is partly connected to the throttle 12 and the second
It passes through the oil passage 24 and escapes from the outlet 25 to the pump drain section (not shown) (eventually to the tank), but the constriction 12
The compressed oil increases the pressure in the pressure chamber 23 and increases the pressure on the surface 4'.
It acts on As the pump discharge pressure P increases, the rightward movement of the spool 6 increases, and the control pressure P _P in the pressure chamber 23 increases, and finally the hydraulic pressure due to the control pressure P _P acting on the surface 4' of the main piston 4 increases. overcomes the resultant force of the hydraulic pressure acting on the surface 5' of the sub-piston 5 and the spring 10, and moves the ring 7 to the left. Therefore, the discharge amount of the pump decreases, and the pump discharge pressure P becomes equal to the pressure set in advance with the pressure adjustment screw 14, that is, the dead head pressure _PDH.
When the ring 7 rises to this point, it becomes a dead head state in which pressure oil is no longer discharged, and the center O ₂ of the ring 7 becomes approximately equal to the center O ₁ of the rotor 8.

Next, when the pump discharge pressure P decreases below the set pressure _PDH , the spool 6 moves to the left, the amount of pressure oil flowing into the pressure chamber 23 decreases, and as a result, the pressure in the pressure chamber 23 decreases. So, ring 7
are the hydraulic pressure acting on the sub-piston 5 and the spring 1
It is moved to the right by the resultant force with 0. Therefore, the pump discharge amount increases and the pump returns to the state shown in FIGS. 2 and 3.

A shown in FIGS. 2 and 3 shows the surge absorption valve according to the present invention as a whole. The surge absorption valve A is a housing 101 that is integrated with the pressure compensator 3 (it may be a separate unit for ease of processing).
, a small piston 102 slidably fitted into a hollow hole bored in the housing 101 , and an oil passage 103 that guides control pressure oil in the pressure chamber 23 of the main piston 4 to the oil chamber 110 of the small piston 102 . and a valve device B having a poppet 107 connected by a small piston 102 and a small diameter connecting rod 105. The valve device B is pressed by a spring 108 so as to close the poppet 107 to the tank port T with respect to the pump discharge pressure port P, and the strength of this spring is adjustable by a screw 111. In the embodiment, a stopper 109 is provided to limit the opening degree of the poppet 107, but this prevents the poppet 107 from moving when the force pressing the small piston 102 due to surge pressure is very large compared to the spring force of the spring 108. This is provided for safety purposes to prevent problems such as inoperability due to excessive opening, and to arbitrarily adjust the maximum opening degree based on the magnitude of surge pressure in the hydraulic circuit. Control pressure oil in the sub-pressure chamber 22 of the sub-piston 5 is guided to the discharge oil port P through a bypass oil passage 104 including a pump internal passage (not shown).
The tank port T is communicated with a drain passage of the pump by a drain oil passage 106 including a pump internal passage (not shown).

The control pressure P _P in the oil chamber 23 of the main piston 4 guides the pump discharge oil through the pressure compensator 3,
And by appropriately selecting the restrictor 12 according to the pump rated discharge pressure and flow rate, it is usually 20Kg/cm ² ~
It can be set within a very narrow range such as 30Kg/ ^cm2 . This control pressure P _P can be maintained approximately within the above pressure range even if the set pressure, that is, the deadhead pressure changes, or even if the set pressures differ between pumps with different maximum pressures.
The strength of the spring 108 that presses the pot 107 is set to a pressure P _PR that is somewhat higher than the pressure P _PDH at the time of the dead head as explained earlier in FIG. 1, and the pump discharge pressure corresponding to this is P _R .

When the load on the hydraulic circuit for the pump, that is, the load applied by starting and stopping the actuator or opening and closing the valve, increases gradually, the pump pressure P generates a surge pressure P _S as shown in Figure 1. The pressure rises statically to the dead head pressure P _DH without any deterioration. At this time, the control pressure P _P also statically rises to the pressure P _PDH . At this time, the hydraulic pressure acting on the small piston 102 of the surge absorption valve A does not exceed the set pressure P _PR of the spring 108, so as shown in FIG.
As shown in FIG. 3, poppet 107 remains closed and valve assembly B is inactive.

On the other hand, when the pump load is such as when a cylinder suddenly reaches the end of its stroke and stops, or when a valve is completely and abruptly closed, a surge pressure P _S is generated in the hydraulic circuit and thus inside the pump. Then, the control pressure P _P also exhibits a similar peak pressure as explained in FIG. When the surge pressure of this control pressure P _P becomes larger than the set pressure P _PR , the poppet 107 is moved to the right as seen in FIGS. 22 control pressure oil escapes. As a result, the surge pressure P _S becomes the first
In the diagram, the pump pressure P _R corresponding to the above pressure P _PR
pressure in excess of When the control pressure P _P becomes smaller than the set pressure P _PR of the spring 108,
Since the poppet 107 is closed by the spring 108, the control pressure oil in the sub-pressure chamber 22 will not escape. Since this control pressure P _P is within a substantially narrow pressure range as described above, compared to the case where a conventional relief valve is provided to release the pump discharge pressure oil, the set pressure P There is no need to change _{the PR} , and the best surge absorption capacity can always be maintained regardless of the pump setting pressure. In the above, when surge pressure is generated, this surge pressure is also transmitted to the auxiliary pressure chamber 22 via the throttle valve body 30, and the auxiliary piston moves in a direction that prevents the ring 7 from moving in the direction of reducing the discharge amount to the deadhead state. 5. At the same time, the surge pressure is transmitted to the pressure chamber 23 of the main piston 4, so the main piston 4 presses the ring 7 toward the sub-piston, so the sub-pressure chamber 22 of the sub-piston 5 is is exposed to a pressure even higher than the surge pressure P _S , and the secondary piston 5 then pushes the ring 7 further to the right, resulting in a further increase in the surge pressure, but the present invention prevents such a situation.

As described above, in the variable discharge amount vane pump using the present invention, once the spring 108 is set,
Surge pressure can be effectively removed at all times without the need for troublesome adjustments, extending the life of the pump, and reducing machine accuracy, performance degradation, and distortion caused by excessive pressure loads. This makes it possible to prevent equipment damage.

In the preferred embodiment described above, the throttle valve body 30 is interposed in the third oil passage 20 that guides the pump discharge oil to the sub pressure chamber 22 of the sub piston 5. This is to delay the supply of pump discharge oil that is replenished from the pump when the control pressure oil escapes to the tank, and to more effectively lower the pressure in the sub-pressure chamber 22, so that the surge pressure is relatively small. If so, this may be omitted.

Figure 4 shows a surge absorption valve different from Figure 2,
FIG. 5 is a schematic diagram showing a hydraulic circuit diagram when the surge absorption valve of FIG. 4 is applied to a variable discharge amount vane pump as shown in FIG. 2. Components equivalent to those in FIGS. 2 and 3 are designated by the same reference numerals. In the embodiment shown in FIG. 4, the pump capacity is increased, and the auxiliary pressure chamber 22
If it is necessary to increase the relief amount of control pressure oil, install a relief valve 1 inside the pump or in the hydraulic circuit.
12, the control pressure oil of the auxiliary pressure chamber 22 is guided to the relief inlet 113 communicating with the bypass oil passage 104, and the discharge oil port P of the surge absorption valve A is connected to the oil passage 11.
4 communicates with the relief oil chamber 119. Then, the small piston 102 is actuated, and the poppet 107
When the oil chamber 119 is opened, the pressure in the oil chamber 119 decreases, the relief valve body 115 opens, and a large amount of the control pressure oil in the bypass oil passage 104 is released to the drain oil passage 117.

In FIG. 6, which shows yet another embodiment, the valve device is a spool valve having a small piston 101 and a spool 120 connected by a small diameter rod 105'.
0 closes the discharge oil port P to the tank port T, and the movement of the spool 120 is stopped by the stopper 1.
09'. This operation is almost the same as that of the poppet valve previously described with reference to FIGS. 2 and 3, and the explanation thereof will be omitted. In Fig. 6, in order to make the surge absorption performance even more effective, the main piston 4
The pressure oil in the pressure chamber 23 is transferred to the oil chamber 1 of the small piston 101.
Since the oil passage 103 leading to the oil passage 103 passes through a throttle valve 121 that is throttled only in the backward direction, the surge pressure decreases and the valve system, that is, the spool 120 in FIG. 6 throttles the return of the valve system that is closed by the coil spring 108'. A slight delay is provided by the valve 121 to increase the amount of control pressure oil in the auxiliary pressure chamber 22 that is relieved to the tank.

In the embodiment, the surge absorption valve A is arranged integrally with the pump, but it may be arranged outside the pump and connected to the pump by piping.

[Brief explanation of the drawing]

FIG. 1 shows a graph showing the relationship between pressure and time of a variable displacement vane pump, FIG. 2 shows a sectional view showing a preferred embodiment of the present invention, and FIG. 3 shows a hydraulic circuit diagram of FIG. Shown schematically in Figures 4 and 5.
The figures show another preferred embodiment of the present invention, FIG. 4 shows a surge absorption valve different from that in FIG. 2, and FIG. 5 shows a schematic hydraulic circuit diagram of a device using this surge absorption valve, FIG. 6 shows a schematic hydraulic circuit diagram illustrating yet another preferred embodiment of the present invention. A... Surge absorption valve, B... Valve device, 3... Pressure compensator, 4... Main piston, 5... Sub-piston, 7... Ring, 12... Throttle, 20...
...Third oil passage, 21...Oil passage, 22...Sub-piston chamber, 23...Pressure chamber, 24...Second oil passage, 30...
... Throttle valve body, 102... Small piston, 104...
Bypass oil path, 106... Drain oil path, 107...
...Poppet, 108...Spring, 108'...
...Coil spring, 109,109'...stopper,
112...Relief valve, 120...Spool, 1
21... Throttle valve.

Claims (1)

[Scope of Claims] 1. A main piston that presses the ring in a direction that reduces the amount of eccentricity between the rotor and the ring of the vane pump, and an oil passage that guides pressure oil discharged from the pump into the pressure chamber of the main piston via a pressure compensator. , a second oil passage that guides the pressure oil in the pressure chamber via a throttle; a sub-piston that is located on the opposite side of the main piston and presses in a direction to increase the amount of eccentricity; and a sub-piston that carries the pressure oil discharged from the pump. A variable discharge amount vane pump having a third oil passage leading to a pressure chamber, a small piston to which pressure oil in the pressure chamber is guided, a valve device opened and closed by the small piston, and a control pressure oil in the auxiliary pressure chamber. and a drain oil path that guides the control pressure oil from the valve device to the tank when the valve device is opened. vane pump. 2. The variable discharge amount vane pump according to claim 1, wherein the third oil passage is provided through a throttle valve body. 3. The variable discharge amount pump according to claim 1, wherein the oil passage and the bypass oil passage are communicated with each other. 4. The variable discharge amount pump according to claim 1, wherein the bypass oil passage is provided with a relief valve operated by the valve device. 5. The variable discharge amount pump according to claim 1, wherein the pressure oil in the pressure chamber is guided to the small piston via a throttle valve that is throttled only in the backward direction. 6. The valve device according to claim 1, wherein the valve device has a poppet that is biased in a closing direction by a spring, and the poppet is opened by the small piston against the spring. Variable displacement pump. 7. Claim 1, wherein the valve device is a spool valve that has a spool that is biased in a closing direction by a coil spring, and the spool is opened by the small piston against the coil spring. Variable discharge pump as described in section.