JPS6025641B2 - hydraulic circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic circuit in which two variable displacement pumps are driven by one prime mover and pressure oil is supplied from the pump to a plurality of actuators.

There are two known uses for this type of hydraulic circuit.

In other words, one type of usage is when the total power of each variable displacement pump is used effectively near the limit of the allowable value, and another type of usage is when the total power of each variable displacement pump is used clearly. , the total value of each power is less than the limit value.
There have been several hydraulic circuits used in the manner described above, as described below, but each has its own drawbacks. Example 1: A hydraulic circuit that is equipped with a dedicated variable displacement hydraulic pump and a shut-off valve for each application.

In this circuit, the number of pumps is 4, so the power divider should also be large-scale depending on the number of pumps.
Alternatively, it becomes necessary to increase the number of prime movers, and furthermore, the number of pressure piping increases. Therefore, it is disadvantageous from an economical standpoint and equipment layout design. Example 2 Hydraulic circuit using electro-hydro servo valve.

Although this circuit can reduce the number of pumps to two, it requires electrical control equipment, and also requires a sophisticated sieving device to manage waste in the hydraulic fluid for the servo valve, and requires constant maintenance. It requires attention and effort, and is disadvantageous in terms of layout design and economy. Example 3 The hydraulic circuit that controls each pump electrically or mechanically is
A detection device for the pump input torque is required, which is extremely large-scale as a power control method, and is impractical in terms of layout design and economy.

Example 4: In a circuit in which a pump discharge line is equipped with diverter valves and switching valves according to the predetermined number of actuators, the maximum pressure of the equipment is limited as the power increases, so the size of each valve and the diameter of the high-pressure piping are large. This is disadvantageous in terms of layout design and economy, and even when moving an actuator with a small power, full power is used, which is disadvantageous in terms of heat balance.

Example 5 A piston-spring type control device operated by the discharge pressure of a pump is installed, and a circuit for changing the slits and settings on the pump side has many restrictions in terms of layout design and lacks maneuverability in use.

The present invention provides a hydraulic circuit that improves the disadvantages of the secondary hydraulic circuit as described above.

According to the present invention, in a hydraulic circuit in which two variable displacement pumps are driven by one prime mover and pressure oil is supplied from the pump to a plurality of actuators, the stepped piston and the stepped piston are connected to each other. A piston/spring type pump discharge amount control device having a small diameter piston smaller in diameter than the small diameter portion of the piston and a spring opposing the thrust of the piston is installed in each of the pumps, and the two pressure receiving parts of the stepped piston are provided with The piping is such that the discharge pressure of the self-pump acts directly on one side and through a switching valve on the other, and the small-diameter piston is connected to the discharge pressure of the other pump or the switching valve through the switching valve. The piping is arranged so that the discharge pressure of the self-pump acts through the valve, and when the switching valve is in the first position, only the discharge pressure of the self-pump acts on the two pressure receiving parts of the stepped piston of the pump discharge amount control device. and the switching valve is
When in the position, the discharge pressure of the self-pump acts on one pressure receiving part of the stepped piston, and the discharge pressure of the other pump acts on the small diameter piston, thereby controlling the discharge amount of the pump. ing.

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a system diagram of a hydraulic device and a characteristic diagram of an actuator to which the present invention is applied. As shown in the figure, a gear Z is
1, Z2, Z3 via two variable displacement pumps PV1,
PV2 is driven, and pressure fluid is supplied from these pumps to four actuators M'1, M'2, M'3, and M'4. Assuming that the pressure-flow characteristics of each actuator are determined, for example, as shown in the figure, the power of each actuator is represented by KWI to KW4. Therefore, it is assumed that actuators MFI and MF3 must be operated simultaneously, the power of prime mover M must not exceed the sum of KWI+KW3, and actuators MF2 and M'4 are in independent operation; Actuators M'1 and MF3 are not operated, and the power KW2 and KW
Even if the sum of 4 is taken, it does not reach the sum of KWI and KW3, and there is no problem regarding the power limit. FIG. 2 shows a piston-spring type pump discharge amount control device S suitably implemented in a hydraulic circuit under the above conditions, and the control device S has the following features:
It has a housing 1. An operating cylinder 2 is built into the inside of the oscillator, and the cylinder 2 is connected to a rotation angle adjustment lever 4 of a hydraulic pump shown by a chain line through a bush 3.
is connected to. A sliding member 5 is provided inside the operating cylinder 2 and is biased by a spring 6, and a spring receiver 7 is provided at the right end of the operating cylinder and the sliding member 5.
is provided. A first spring 8, a second spring 9, and a third spring 10 are provided at each step of the spring receiver 7, and the right end of each spring is connected to the cover 11. First distance ring 12 provided at each step
, the second distance ring 13, and the third distance ring 14, respectively. On the other hand, a piston housing 16 is provided at the left end of the housing 1, and inside the housing 16 are a first chamber 17 and a second chamber 1.
8, a third chamber 19 is formed, each of which communicates with the boat days, C and K, respectively, and the first chamber 17
In the second chamber 18, there is a larger portion 2 of the stepped piston 20.
1 and a small light portion 22 are housed in the third chamber 19, and a small diameter piston 23 having a smaller diameter than the small diameter portion 22 of the stepped piston 20 is housed in the third chamber 19. Therefore, the stepped piston 2 has a large diameter part 21 that directly receives the pump's discharge pressure from the boat C, and a small diameter part 22 that selectively receives self-discharge pressure or atmospheric pressure from the boat C by a sliding valve. It looks like this. Further, the small diameter piston 23 receives its own discharge pressure or the discharge pressure of the other pump from the boat K via a switching valve. When the discharge pressure of the pump acts through each boat as described above, the thrust generated in the stepped piston 20 and the piston 23 acts on the operating cylinder 2, and moves the operating cylinder 2 to a position that balances the repulsive force of the spring. , the operating cylinder 2 directly mechanically operates the variable displacement part of the variable displacement hydraulic pump through the lever 4.

An example in which the piston spring type pump discharge amount control device S shown in FIG. 2 is incorporated into the hydraulic circuit shown in FIG. 1 is shown in FIGS. 3 and 4.

In these figures, the suffix 1 is attached to the reference numerals of the valve V and each part of the control device S in the circuit on the right, and the suffix 2 is attached to those on the left. In the figure, DI is a high-pressure line that flows the discharge oil of pump PVI to each actuator MF1 and M-circle 2, EI is a control line whose one end is connected to high-pressure line DI, and the other end reaches boat PII of switching valve VII. FI is a line connecting the boat HI of the control device SI and the control line EI, GI is a line connecting the boat CI of the control device SI and the boat AI of the switching valve VI, and 11 is a line connecting the boat PI of the switching valve VI and the line EI. line to tie,
LI is a line connecting the boat RI of the switching valve VI and the tank TI, and MI is a line connecting the boat KI of the control device SI and the boat AI 1 of the switching valve VII. On the left side of FIG.
are arranged, and each of these devices is connected by a line similar to the device on the right side described above, and these lines are given the same alphanumeric code, and the suffix is 2.
They differ only in certain respects. Therefore, line MI and boat B22 of switching valve V22 are line N, and line M
2 and the boat BII of the switching valve V11 are connected by a line ○. The hydraulic circuit according to the present invention is constructed as described above, and when the switching valves V1, V2, VI1, and V22 are all set to the 0 position as shown in the figure, a state of crossover control is entered as will be described below.

That is, the control device S1 of the pump PVI receives its own discharge pressure via the lines D1, E1, F1, and the boat HI, and receives the discharge pressure of the other pump PV2 through the lines D2, F1, and the boat HI.
E2, boats P22, B22, lines N, M1, and boat KI, and these pressures actuate the control device SI to control the pump PVI. Similarly, the left pump PV2 is controlled by receiving its own discharge pressure and the discharge pressure of the other pump PVI by the control device S2. In other words, the pumps PV1 and PV2 receive discharge pressure from each other and are controlled to cross each other.
In the above-mentioned hydraulic circuit, FIG. 4 shows a state in which each gate valve is switched to one position, that is, a state in which it is independently controlled.

In this state, regarding the right control device SI, the discharge pressure of the pump PVI is transferred to the boat HI through the lines E1, J1, the boat P1, AI via the lines E1, FI,
, line GI to boat CI, and to boat KI via line E1, boat PI1, AI1, and line MI. Since the pressures of the boats CI and KI are the same, the thrusts of the piston 23 cancel each other out.
The pressure receiving area of the small diameter portion 22 of the stepped piston 20 is larger than the pressure receiving area of the piston 23, so for the same pressure, the spring is retracted more during independent control, and as a result, the discharge amount of the pump PVI is increased. decreases, and the power KW2 and KW4 are K
It becomes smaller than W1 and KW3. As described above, according to the present invention, a piston/spring type pump discharge amount control device is attached to a variable displacement pump, and the discharge pressure of the pump is appropriately applied to the control device via a switching valve to control the pump. The circuit is structured, the control device itself is not simple, and the hydraulic circuit allows the size of the pilot switching valve and piping diameter to be small, which is advantageous in terms of installation design and economy, and operation is simple and quick, and remote control is also possible. Furthermore, it is reliable in operation and easy to maintain.

Another embodiment of the hydraulic circuit according to the present invention is shown in FIG.

Among the hydraulic equipment and hydraulic lines shown in FIG. 5, those corresponding to those shown in FIG. 3 or 4 are given the same reference numerals. However, in this embodiment, the switching valves VII1 and V222 are provided one each in the left and right circuits, and by switching the switching valves, the same control as in the previous embodiment is performed, and substantially the same machine The effect is produced.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a hydraulic circuit to which the hydraulic circuit according to the present invention is applied, FIG. 2 is a longitudinal sectional view showing an example of a piston/spring type pump discharge amount control device implemented in the present invention, and FIGS. FIG. 4 shows an embodiment of the hydraulic circuit according to the present invention, and FIG. 5 shows another embodiment of the hydraulic circuit according to the present invention. PV...Pump, V...Switching valve, S...
...'The can is the control device, 2...The operating cylinder, 3
...Push, 4...Turning angle adjustment lever, 5...Sliding member, 8, 9, 10...Spring, 20...
Stepped piston, 21...Large light part, 22...
Small portion, 23...Small diameter piston. Figure {Figure N Wave Figure 3 Figure 4 Figure S

Claims (1)

[Claims] 1. In a hydraulic circuit in which two variable displacement pumps are driven by one prime mover and pressure oil is supplied from the pump to a plurality of actuators, a stepped piston and a small diameter portion of the stepped piston are connected to the stepped piston. A piston/spring type pump discharge amount control device having a small diameter piston and a spring opposing the thrust of the piston is connected to each of the pumps, and the two pressure receiving parts of the stepped piston are equipped with a self-pump pump. The piping is such that the discharge pressure is applied directly to one side and through a switching valve to the other, and the small-diameter piston is connected to the discharge pressure of the other pump via the switching valve or to the self-pump via the switching valve. When the switching valve is in the first position, only the discharge pressure of the self-pump acts on the two pressure receiving parts of the stepped piston of the pump discharge rate control device, and the switching valve is in the first position. When in position 2, the discharge pressure of the self-pump acts on one pressure receiving part of the stepped piston, and the discharge pressure of the other pump acts on the small diameter piston, thereby controlling the discharge amount of the pump. Characteristic hydraulic circuit.