JPS6133272Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an output control device for a variable displacement hydraulic pump.

Conventional variable displacement hydraulic pumps, such as variable displacement vane pumps, variable displacement radial piston pumps, and swash plate type variable displacement axial piston pumps, have screws for adjusting the maximum discharge amount or springs for adjusting the maximum discharge pressure. An external force is applied to the variable element, and the displacement amount of the variable element is changed according to the displacement amount of the screw or the spring pressure, and the maximum discharge amount and discharge pressure of the pump are changed.

Therefore, when changing the output of the pump, if you want to change the maximum discharge pressure, change the spring pressure of the spring, and if you want to change the maximum discharge amount,
The screwing amount of the screw must be changed. However, if you try to automatically change the spring pressure or turn the screw while the pump is running,
The structure of the pump became complicated and impractical.
When setting the hydraulic pressure, either (a) a relief valve is used and a flow control valve is used to set the flow rate for the load instead of the discharge amount, or (b) two valves are used as shown in the hydraulic circuit diagram in Figure 4. A variable displacement hydraulic pump and a switching valve are used or
(c) Multiple pressure control valves are used.

However, as mentioned in (a), when a relief valve or flow control valve is used, part of the energy of the pressure fluid becomes heat when the pressure is reduced inside the valve, and this causes the hydraulic device to become a pressure fluid cooler. In addition to being large in size, there is a large power loss and power is wasted.As mentioned in (b), the method using a pump increases the size of the device itself and increases the cost. get high,
The method of using a plurality of pressure control valves as in case (c) has problems such as the piping that serves as a passage for the pressure fluid becomes complicated and the number of parts increases.

The purpose of the present invention is to provide an output control device for a variable displacement hydraulic pump that has a simple structure and can easily switch the pressure and maximum discharge amount of liquid discharged from the variable displacement hydraulic pump to arbitrary set values. By doing so, the above-mentioned conventional drawbacks are eliminated.

That is, the gist of the present invention is to provide an operating plunger in an operating cylinder that is disposed opposite to a variable element and applies an external force to the variable element to change the discharge amount of pressurized liquid discharged from a pump; A hydraulic pump having a pilot plunger in a pilot cylinder that changes the amount of displacement of the plunger, and a pressure control valve that controls pressure fluid to be sent to the rear chamber of the operating cylinder, the hydraulic pump having a pressure control valve that controls pressure fluid sent to the rear chamber of the operating cylinder. a pressure setting spring that applies an acting force from the rear chamber of the valve body in opposition to the acting force of the pressurized fluid; a spring pressure switching cylinder having a piston that adjustably switches the acting force of the spring in two stages; A switching valve is provided to selectively communicate the switching cylinder rear chamber and the pilot cylinder rear chamber with the pump discharge port or the low pressure section, a pressure fluid passage communicating between the pump discharge port and the valve body front chamber, and the valve body. The output control device for a variable displacement hydraulic pump is provided with a pressure fluid passage communicating between an operating cylinder rear chamber and the pump discharge passage or the low pressure portion by movement of the pump.

The configuration of an embodiment of the present invention will be described below with reference to the drawings in the case of a variable displacement vane pump.

In FIG. 1, on the inner periphery of the cam ring 3 supported in the pump chamber 2 of the vane pump 7 so as to be able to move laterally,
Each vane 6 of the rotor 5 rotates via the drive shaft 4
A variable displacement type that changes the amount of pressure fluid sucked in from the suction port 12 and discharged from the discharge port 12' in accordance with the eccentricity S between the axial center of the cam ring 3 and the axial center of the rotor 5. A pressure compensation spring 9 that applies an external force in the axial direction from the outer circumference of the cam ring 3 via a sliding shoe 8 and an operating plunger 10 is applied to one and the other of the left and right internal positions of the vane pump 7 from the outer circumference of the cam ring 3 to the axis. An operating cylinder 11 that applies an external force in the center direction is attached, and a pilot plunger 1 is installed at the rear of the operating cylinder 11 (towards the right in the figure).
4 protrudes into the operating cylinder 11 to control the retreating end position of the operating plunger 10 of the operating cylinder 11, thereby controlling the eccentricity s of the cam ring 3 and the rotor 5, that is, the maximum discharge amount of the vane pump 7. The pilot cylinder 13 is installed,
The retreating end position of the pilot plunger 14 of the pilot cylinder 13 corresponding to the large flow rate Q1 setting of the maximum discharge amount of the vane pump 7 is determined by an adjusting screw 18 attached to the vane pump 7 via a plug 15, an O-ring 16, and a nut 17. The forward end position of the pilot plunger 14 corresponding to the small flow rate Q2 setting of the maximum discharge amount of the vane pump 7 is adjusted by inserting a shim 19 of arbitrary thickness into the front part of the pilot plunger 14 in the pilot cylinder 13. .

Furthermore, pressure fluid is supplied from the vane pump 7 between the rear chamber 20 of the operating cylinder 11 and the discharge port 21 of the vane pump 7 by moving the valve body 23 against the biasing force of the pressure setting spring 22. Operation cylinder 1
1 and the eccentricity s of the cam ring 3 and rotor 5
A pressure control valve 24, that is, a valve body 25 that reduces
The spring pressure switching cylinder 27 of the pressure setting spring 22 is fixed with a nut 26, and in this case, the stroke of the piston 28 can be adjusted with a screw 29, and the parts that need to be sealed are sealed with O-rings 30, 31. , 32 is connected between the piston 28 of the spring pressure switching cylinder 27 and the shaft end of the valve body 23, the pressure control valve 24 in which the pressure setting spring 22 is inserted is connected via a washer 33, and the spring pressure switching The rear chamber 34 of the cylinder 27 and the rear chamber 35 of the pilot cylinder 13 are in communication with each other via a passage 36, and there are two positions between each rear chamber 34, 35 and the discharge port 21 of the vane pump 7. The switching valve 37 is connected, and
Inside the valve body 25 of the pressure control valve 24 are a washer 33 and a communication hole 38 formed in the valve body 23 and a drain port 39.
The front chamber 41 of the pilot cylinder 13 on the side of the pilot plunger 14 is also connected to the hydraulic tank 40 via a drain port 42.

Next, the operation of this embodiment will be explained.

First, when the switching valve 37 is in the OFF state shown in FIG. 1, the rear chamber 35 of the pilot cylinder 13 and the rear chamber 34 of the spring pressure switching cylinder 27 are
Because it is connected to the hydraulic tank 40 via
The pilot plunger 14 of the pilot cylinder 13 is positioned at the retreating end by the biasing force of the pressure correction spring 9, and the maximum discharge amount of the vane pump 7 is set to the large flow rate Q1 shown in FIG. 2, which is adjusted by the screw 18. In addition, the piston 28 is positioned at the rearward end due to the biasing force of the pressure setting spring 22, and
The spring pressure 2 corresponds to the P1 pressure in Fig. 2 adjusted by the screw 29, and in this state, the pressure fluid from the vane pump 7 moved the valve body 23 at the P1 pressure point in Fig. 2 and reduced the pressure. Pressure liquid is supplied to the rear chamber 20 of the operating cylinder 11 to control the operating plunger 1.
0 to adjust the eccentricity s of the cam ring 3 and rotor 5.
As a result, the discharge amount of the vane pump 7 gradually decreases, and the pressure setting spring 22
P1 pressure where the spring pressure and flow rate are balanced,
At Q1 flow rate, the pressure control valve 24 is cut off, and the hydraulic system is maintained at the P1-Q1 pressure-flow rate characteristic shown in FIG.

Next, when the switching valve 37 is turned on in this state, the pilot plunger 1 of the pilot cylinder 13
4 is located at the forward end, the maximum discharge amount of the vane pump 7 is set to the small flow rate Q2 shown in FIG. The spring pressure of the pressure setting spring 22 corresponds to the P2 pressure shown in FIG. The liquid moves the valve body 23 at the P2 pressure point in FIG. 2 and is supplied to the rear chamber 20 of the operating cylinder 11. As a result, the eccentricity s of the cam ring 3 and rotor 5 decreases, and the discharge amount of the vane pump 7 gradually decreases. At the same time, the pressure control valve 24 is cut off at the P2 pressure and Q2 flow rate where the spring pressure of the pressure setting spring 22 and the flow rate are balanced, and the hydraulic system is maintained at the P2-Q2/pressure-flow rate characteristic shown in FIG.

In the P2-Q2 characteristic portion, the discharge amount decreases from Q1 to Q2 after a certain pressure is reached due to the discharge pressure of the pressurized fluid that has entered the rear chamber 35 of the pilot cylinder 13, or the discharge pressure pressing the pressure compensation spring 9 on the opposite side of the ring 3, i.e., the area of the pilot plunger 14 multiplied by the discharge pressure, becomes greater than the biasing force of the pressure compensation spring 9. As a result, the minimum pressure is determined by the area of the pilot plunger 14. Furthermore, the set pressure of the hydraulic system can be changed arbitrarily by the screw 29 and the amount of screwing in of the spring pressure switching cylinder 27. The area of the piston 28 of the spring pressure switching cylinder 27 is set so that the force of the piston 28 in the left direction in the figure, generated by the set pressure Px, becomes greater than the biasing force of the spring 22.

The hydraulic circuit according to the embodiment of the present invention described above is shown in FIG.

Next, FIG. 3 is a hydraulic circuit diagram showing an example of the use of this embodiment. In this case, a solenoid valve is used as the switching valve 37, and the pump and pressure control valve are omitted from the diagram. , symbols Y and Z in the figures are respectively connected to the same symbol parts shown in FIG. Solenoid switching valve 37
When the electromagnetic solenoid SOL1 of the electromagnetic valve 44 is turned on in the OFF P1-Q1 characteristic, the large hydraulic cylinder 45, which requires a particularly large flow rate even at a small pressure, is operated forward, and the large hydraulic cylinder 45 is activated by the limit switch LS1. By confirming the forward end of the hydraulic cylinder 45, the electromagnetic solenoid SOL3 of the electromagnetic switching valve 37 and the electromagnetic solenoid SOL4 of the electromagnetic valve 47 move forward the small hydraulic cylinder 46, which requires particularly high pressure even with a small flow rate. is turned on to operate the small hydraulic cylinder 46 forward in the P2-Q2 characteristic, thereby increasing the pressure of the vane pump 7. As a result of being able to appropriately change the flow rate characteristics according to the load condition of the hydraulic circuit, the entire hydraulic system can be made much simpler and more compact than before, and power consumption can also be greatly reduced. be able to.

As described above, the output control device of the present invention can control the pressure liquid discharged from the pump to the desired flow rate and pressure, and only one control valve is required for this control, and when multiple control valves are used, It does not have the disadvantages of complicated piping and high cost, and the operating pressure can be changed in two stages by switching the switching valve, and the maximum discharge rate can be changed in two stages.If the device of this invention is incorporated into a machine tool, etc., it can be changed. This has the effect of simplifying the structure of the pressure and maximum discharge amount of the fluid discharged from the positive displacement hydraulic pump, so that it can be easily switched to any set value in accordance with the intended operating conditions even during machine operation.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram including a hydraulic circuit according to an embodiment of the present invention, Fig. 2 is a diagram of its operating characteristics, Fig. 3 is an explanatory diagram including a hydraulic circuit showing its usage state, and Fig. 4 is a conventional diagram. A hydraulic circuit diagram showing an example, FIG. 5 is a hydraulic circuit diagram of an embodiment of the present invention. 2... Pump chamber, 3... Cam ring, 5... Rotor, 6... Vane, 7... Variable displacement vane pump, 9... Pressure compensation spring, 10... Operating plunger, 11... Operating cylinder, 13 ……
Pilot cylinder, 14... Pilot plunger, 21... Discharge port, 23... Valve body, 24...
Pressure control valve, 27...Spring pressure switching cylinder, 37...Switching valve.

Claims (1)

[Claims for Utility Model Registration] An output control device for a variable displacement hydraulic pump consisting of the following components. a. An operating plunger in an operating cylinder that is installed opposite to a variable element and applies an external force to the variable element to change the amount of pressurized liquid discharged from the pump, and an operating plunger located on the back of the operating plunger that controls the amount of displacement of the operating plunger. Pilot plunger in the pilot cylinder to be changed. (b) a pressure setting spring that has a valve body that controls the pressure fluid sent to the rear chamber of the operating cylinder, and applies an acting force from the rear chamber of the valve body in opposition to the acting force of the pressure fluid applied from the front chamber of the valve body; A pressure control valve provided with a spring pressure switching cylinder having a piston that adjustably switches the acting force of the spring in two stages. c. A switching valve that selectively communicates the spring pressure switching cylinder rear chamber and the pilot cylinder rear chamber with the pump discharge port or the low pressure section. d A pressure fluid passage that communicates between the pump discharge port and the valve body front chamber, and a pressure fluid passage that communicates the operation cylinder rear chamber with the pump discharge port or the low pressure section by movement of the valve body.