JPS59226702A - Load sensitive hydraulic device - Google Patents

Abstract

PURPOSE:To control pressure of a pump effectively, by varying the valve opening force of a pilot valve controlling relief pressure of a balance piston type relief valve circulating surplus oil of the pump to a tank by pressure at an inlet side of an actuator. CONSTITUTION:When an actuator 1A becomes active, the opening force of a pilot valve 20 is varied by pressing the spring of the pilot valve 20 by inlet side pressure through ducts 12b, 31a. As it becomes, therefore, that an opening of the pilot valve 20 is throttled according to the magnitude of a load and a balance piston type relief valve 13 is relieved by pressure corresponding to an actual load, through which the titled device is controlled so that a quantity of delivery of a pump 2 is increased by reducing pilot pressure to be sent to a pump 2 side. In addition to the above, a secondary side duct of the balance piston type relief valve 13 can be communicated with a tank 3 directly by making the pump 2 into a fixed capacity one.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a load-sensitive hydraulic system capable of efficiently controlling the discharge pressure of a hydraulic pump in response to load fluctuations occurring on a hydraulic actuator side.

[Prior art]

Various hydraulic equipment used in various fields generally include a hydraulic actuator that drives a driven device, a hydraulic pump that supplies pressure oil to this actuator, and a supply system that connects these actuators and pumps. A passageway and a return passageway to the tank, a relief valve that returns part of the pressure oil in the supply passageway to the tank side, a control unit that selectively connects the actuator to the pump, and the like are provided as appropriate.

By the way, in this type of hydraulic system, the load on the hydraulic actuator side varies depending on whether it is activated or not activated or the amount of work required on the driven device side. A variable displacement pump is generally used, and the pump is configured to be controlled depending on the magnitude of the load on the actuator side. By controlling the pump in this way, it is possible to improve the drive efficiency of the entire hydraulic system and save energy. It has been proposed by

However, with this type of conventional device, not only is the configuration complicated and costly, but it is also difficult to control the pump quickly and appropriately, causing problems in terms of responsiveness.
Moreover, if the load fluctuates significantly on the actuator side, it has the disadvantage that it tends to cause unstable pump movement.
It cannot be said that the pump can be controlled efficiently and stably, and some kind of countermeasure is desired.

That is, in conventional devices of this type, the opening and closing of the IJ-F valve provided in the supply path from the pump is generally controlled by guiding the inlet side pressure of the actuator, and the opening and closing of the IJ-F valve is generally controlled by guiding the inlet side pressure of the actuator. The system is configured so that the generated pressure is guided to the pump control unit as pilot pressure to adjust the discharge amount, but with this configuration, the pump cannot be controlled efficiently due to the delay in the relief valve's activation timing. However, if the load fluctuation is large, the movement of the IJ valve becomes unstable, and as a result, the movement of the pump also becomes unstable.

In particular, such load fluctuations on the actuator side are a big problem in devices where hydraulic actuators such as hydraulic cylinders and hydraulic motors are installed in multiple stages. It is desired that a device that can be controlled by

[Summary of the invention]

The present invention was made in view of these circumstances, and
A pilot pulp having a valve element that opens and closes this circuit is provided in the vent circuit of a relief valve that controls the discharge pressure of a hydraulic pump, and a set pressure of a cent spring that biases the valve element of this pilot valve in the valve closing direction is provided. Despite the simple configuration, the pump discharge pressure can be changed in response to load fluctuations on the actuator side by configuring it to be variable by a piston that is reversely actuated by the inlet side pressure of the hydraulic actuator. The purpose of the present invention is to provide an inexpensive load-sensitive hydraulic system that can efficiently and stably control the load and has excellent responsiveness.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

Fig. 1 shows an embodiment of the load-sensitive hydraulic system according to the present invention.
IC) is a hydraulic motor as a hydraulic actuator that drives various driven devices (not shown); 2 is a variable displacement hydraulic pump that supplies pressurized oil to each of these hydraulic motors IA, IB, and IC; 3 is a hydraulic pump A pressure oil supply passage 4 and its return passage 5 are provided between the hydraulic motors 1A, IB, IC1 pump 2, and tank 3, which are tanks for storing hydraulic oil.

In addition, 6 (6A, 6B, 6C) in the figure indicates each hydraulic motor IA.
, IB, IC is a pressure oil control unit that controls the pressure oil supplied from the pump 2 to the hydraulic motors 1A, IB, and IC from the supply passage 4 and the return passage 5 to the respective hydraulic motors 1A, IB, and IC;
8a; 7b, 81); 7c, 8c portions. As shown in the figure, the pressure oil control unit 6 includes a directional switching valve 9 that switches the direction of pressure oil supply to the motor 1 and rotates the motor 1 in the forward and reverse directions; It is comprised of a flow control valve 11 that controls the supply amount of pressurized oil to a desired amount using a variable orifice 10a and iQb incorporated therein.

In addition, 12a and 12b in the figure are the variable orifices 1 mentioned above.
0a and 10h are pilot passageways for guiding the upper and downstream hydraulic pressures to the flow control pulp 11, and 9a is an operating lever for manually switching the directional switching valve 9.

In addition, 13 in the figure is a balance piston type relief valve that is provided in a return passage 14 connected to the tank 3 from the middle of the pressure oil supply passage 4 and returns surplus oil of the pump 2 discharge amount to the tank 3, and is located downstream of the balance piston type relief valve. has safety valve 15 and orifice 16
bypass passages 16 having a diameter of a are provided in parallel, and these passages as a whole function as a relief valve (indicated by 17 in the figure) for selectively returning the pressure oil in the pressure oil supply passage 4 to the tank 3 side. It is configured.

Now, according to the present invention, in the circuit configuration described above, the hydraulic motors IA, IB, I as the hydraulic actuator 1
It is also possible to control the relief pressure of the relief valve 13 according to load fluctuations on the C side. It has a characteristic in that it is provided between 22 and 22.

To explain this in detail, this pilot valve 20
As is clear from the figure, there is a needle valve 25 as a valve body that opens and closes the left chamber 23 and the right chamber 24 constituting the vent circuit of the relief valve 13, and the needle valve 25 is biased in the valve closing direction. set springs 2B (26A, 26B), and set pressure of the set springs 260 to the hydraulic motor IA.
, IB, and a piston 27 that varies depending on the magnitude of the inlet side pressure of the IC. The left chamber 23 is connected to the IJ IJ valve 13 via the passage 23&.
This relief valve 13 is connected to the vent port 13 & of the
The pressure oil in the pressure oil supply passage 4 is guided as pilot pressure through the pressure oil supply passage 4, and its right chamber 24 is connected to the recirculation passage 14 between the relief valve 13 and the safety valve 15 through a passage 24a. Furthermore, the orifice 16 of the bypass path 16
It is connected to the left chamber Ha of the control cylinder section 21 of the pump 2 via the pilot pressure passage 22 via the upstream side a. In the figure, 21b is a piston of the control cylinder section 21, and 21c is a spring disposed in the right chamber 21d that biases the piston 21b toward the left chamber 2ia. It is a well-known practice that the piston 21b moves in the left-right direction depending on the magnitude of the pilot pressure introduced therein to variably control the discharge amount of the pump 2.

In addition, 28 in FIG. 2 is the pair of set springs 26.
This is a guide member interposed between A and 26B and slidably supported within the sleeve 28a, which is a pair of set springs 26A and 2 that are continuously arranged along the axial direction.
6B so that the sum of its urging force is applied to the needle valve 25 as a set pressure.

jf, the piston 27 is slidably supported within the valve body 20a, and the left pressure receiving part 27m has a passage 24a constituting the vent circuit of the relief valve 13, as well as the right chamber 24 of the needle valve 25. The pressure of the hydraulic motor IA is introduced through the passage 29 to the right pressure receiving surface 27b through the passage 30.

The inlet side pressures of IB and IC are led as pilot pressures. Here, each of these hydraulic motors IA, IB
.

As for the inlet side pressure at 1C, the directional control valve 9) also utilizes the pilot pressure passage 12b that detects the downstream pressure of the variable orifice 10m and 10b on the motor side, and branches branched from each of these pilot pressure passages 12b. Passage 31m, 3
1b and 31o are connected via shuttle valves 32m and 32b, and the output thereof is introduced into the passage 30. And the shuttle valves 32a and 32b mentioned above.
Among the inlet side pressures of each motor 1A, 1B, and IC,
The highest pressure is guided to the piston 27 side through the passage 30. Of course, when the directional control valves 9 of each motor = 9-7 1A, IB, and IC are switched to the non-operating position, no pilot pressure is generated, and when only one motor is operated, no pilot pressure is generated. The pilot pressure operates to actuate the piston 27. In addition, 33 in FIG. 2 is the set spring 26A.
, 26B together with a spring that controls the piston 27,
The piston 27 is moved until the force due to the hydraulic pressure applied to the right chamber 27b and the tension of these springs 33;
The relief pressure of is determined.

According to the hydraulic system having such a configuration, the pilot valve 20 allows the pump 2 to be connected to the hydraulic motors IA, IB,
Control is performed as follows according to load fluctuations on the IC side.

That is, while pump 2 is operated, hydraulic motor IA
, IB, and IC sides are all inactive, a portion of the pressure oil in the pressure oil supply passage 4 passes through the reflux passage 14 and passages 13a and 23a, which serve as a vent circuit for the relief valve 13, to the pilot pulp. The needle valve 25 of No. 20 is operated in the opening direction, whereby high pilot pressure acts on the control cylinder section 21 of the pump 2 through the passages 24m and 16.22, and it is operated at the minimum necessary discharge amount. Control as follows.

Then, until any one of the hydraulic motors IA, IB, and IC operates, the discharge amount and the pilot pressure generated by the pilot pulp 20 are maintained in a balanced state. This is because no pressure is generated on the inlet side of each motor IA, IB, and IC, so no acting force acts on the piston 27, and as a result, the needle valve 25 of the pilot pulp 20
It is clear that opening and closing are controlled only by the biasing force of the set springs 26A and 26B themselves.

Furthermore, when one motor is operated, for example by one person, the pressure on the inlet side increases depending on the load in the passages 12b, 31m and 3.
By acting on the piston 27 through 0 and moving it, the reset spring 26A.

26B is compressed to vary its set pressure. Then, the opening degree of the needle valve 25 of this pilot pulp 20 is reduced according to the magnitude of the load, and the relief valve 13 is relieved with a pressure commensurate with the actual load, that is, an EE force (of the actual load element). As a result, the pilot pressure sent to the pump 2 side is reduced and the discharge amount of the pump 2 is controlled to increase.

This control amount is quickly and appropriately controlled by following the pilot pressure from the motor 1A side that acts on the piston 27, and has the advantage of being excellent in terms of responsiveness and operating performance. be.

The control of the pump 2 according to such load fluctuations is the same even when two or three motors are driven in parallel, and the inlet side pressure on the motor side and the inside of the pilot pressure passage 22 are controlled. Depending on the magnitude of the pilot pressure, the piston 27 operates in a well-balanced manner to vary the set pressure for the needle valve 25 and appropriately control its opening degree.

If the relief pressure of the relief valve 13 is controlled using such a pilot pulp 20, the third
As shown in the figure, depending on the increase or decrease of the actual load.

Accordingly, the pump discharge pressure is appropriately controlled, which is highly effective.

Note that the present invention is not limited to the structure of the embodiment described above, and the shape and structure of each part may be modified as appropriate.

Of course, it can be changed. For example, many hydraulic actuators used in this type of hydraulic equipment are known in various fields, and the key is to appropriately and quickly control a pump for supplying pressure oil in accordance with the hydraulic actuator that causes load fluctuations. It is fine as long as it is something. Furthermore, the configuration of the pilot pulp 20, which is a feature of the present invention, is not limited to the specific example shown in FIG. 2, but may be modified as appropriate.

Further, according to the present invention, the relief pressure of the relief valve 13, which is conventionally set at the maximum pressure commensurate with the maximum load on the actuator side and cannot be varied, is variably controlled by the pilot pulp 20 according to the load on the actuator side. Therefore, the pump 2 is not limited to the variable displacement type shown in the above-mentioned embodiment, but can also be a fixed displacement type pump 2 as shown in FIG.
It can also be used to achieve the same effect. this is,
The pilot pulp 20 relieves the relief valve 13 with the pressure (of the actual load element) to appropriately control the supply pressure from the pump 2, reduce the load on the pump 2, reduce its driving force, and save energy. This can be easily understood from the fact that this will result in a transformation.

〔Effect of the invention〕

As explained above, according to the load-sensitive hydraulic system according to the present invention, the pilot pulp having the valve body whose set pressure is varied by the piston operated by the inlet side pressure on the actuator side is guided. As a result, the relief pressure of the relief valve that controls the surplus flow rate from the pump is controlled, so despite the simple configuration, pump discharge pressure can be quickly and appropriately controlled in response to load fluctuations on the actuator side. This has the excellent effect of being able to control the operation of the pump efficiently and stably, and exhibiting an energy saving effect.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the load-sensitive hydraulic system according to the present invention, Fig. 2 is a vertical cross-sectional view showing a specific example of a pilot valve that is a feature thereof, and Fig. 3 is a schematic diagram showing an embodiment of the load-sensitive hydraulic system according to the present invention. FIG. 4, a characteristic diagram for explaining the operating state, is a diagram showing another embodiment of the present invention. 1 (IA, IB, IC) ... Hydraulic motor (oil field actuator), 2 ... Hydraulic pump, 3 ...
Tank, 4... Urn supply passage, 5... Return passage, 9
...Directional switching valve, 12b...Pilot pressure passage, 13...Relief valve, 13a...Bent boat, 14...Recirculation path, 16...Bypass passage,
16a... Orifice, 20... Pilot valve, 21... Pump control cylinder section, 22...
... Pilot pressure passage, 25 ... Needle valve (valve body), 2
6 (26A, 26B)...Set spring, 2
7---Piston, 30: 31a, 31b, 31
c; 斥...Aisle. Pa) 15-

Claims (1)

[Claims] A hydraulic actuator that undergoes load fluctuations, a hydraulic pump that supplies hydraulic pressure to this hydraulic actuator, a balance piston type leaf valve that returns surplus oil from the discharge amount of this hydraulic pump to a tank, and the magnitude of the load on the hydraulic actuator side. a pilot pulp that controls the relief pressure of the relief valve according to the valve body, and a valve body that controls opening and closing of the vent circuit of the relief valve;
A load characterized by comprising a set spring that biases the valve body in the valve closing direction, and a piston that varies the set pressure by the set spring by introducing pressure on the inlet side of the hydraulic actuator. Sensitive hydraulic system.