JPS58204234A - Oil-pressure circuit for oil-pressure type excavator - Google Patents

Abstract

PURPOSE:To optimize the operating speed of an actuator at the maximum operation amount by a method in which when supplying pressure oil from a variable capacity discharge pump to plural actuators, a regulator having a discharge setter is provided to the discharge pump. CONSTITUTION:When the discharge pressures of variable capacity pumps 1 and 2 are raised, the discharge amounts of the pumps are lowered by regulators 28 and 29. When pilot pressure signal P is less than P1, the pump discharge amount becomes Q=Q1, and in the ranges of P1<=P<=P3, the pump discharge amount Q is increased. In the case of more than P3, the discharge amount is set to Q=Q3 and the inclination of angle of a swash plate is adjusted. Then, when supplying pressure oil from one of the variable capacity oil-pressure pumps 1 and 2 to plural actuators, e.g., an arm cylinder 11 or a boom cylinder 12, etc., a setter to set up the discharge of the pump to a set discharge amount at the time when the operation amount for each actuator is maximum is provided to the regulators 28 and 29.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a hydraulic circuit for a hydraulic excavator such as a hydraulic excavator.

In a hydraulic excavator, it is known to supply pressure oil to one actuator from two hydraulic pumps in order to increase the operating speed of the actuator, for example, an arm cylinder. An example of this is shown in FIG. The two variable displacement hydraulic pumps 1 and 2 are connected to directional control valve assembly devices 3 and 4, respectively, and are connected to a left travel directional control valve 5, a turning directional control valve 6, and a first directional control valve included in the directional control valve control device 3. The arm directional switching valve 7 and the first boom directional switching valve 8 supply pressure oil from the variable displacement hydraulic pump 1 to the left travel motor 9, swing motor 10, arm cylinder 11, and boom cylinder 12, respectively. In addition, the second boom directional control valve 13
, the second arm directional switching valve 14, the packet directional switching valve 15, and the right running directional switching valve 16, the pressure oil of the variable displacement hydraulic pump 2 is transferred to the boom cylinder 12, the arm cylinder 11, the packet cylinder 17, and the right running directional switching valve. are supplied to the motors 18, respectively. In this way, the arm cylinder 11 and the boom cylinder 12 are equipped with two variable displacement hydraulic pumps 1.
, 2 pressure oils can be combined and supplied. 19 is a pilot pump, 20 is a relief valve, 21
~26 is a pilot valve, 27 is a shuttle valve, 28.29
is a regulator, and a-7 is a pilot pressure signal circuit. The regulators 28, 29 are connected to the shuttle valve 27 from the pilot pressure signal circuit a%l as shown in FIG.
The pump discharge amount Q is adjusted in accordance with the highest pilot pressure signal P derived from the pump discharge amount, and at the same time, the pump discharge amount is adjusted in accordance with the pump discharge pressure.

In the hydraulic circuit shown in FIG.
2, the operating speed when the two pumps merge is optimal, but for the arm cylinder 11, the operating speed when the two pumps merge is too fast, causing a large kina shock at the end of the stroke of the arm cylinder 11, resulting in an increase in strength. This may be a problem.

In order to control the operating speed, it is possible to adjust the flow rate with the operating lever of the pilot valve 21, but this is difficult to operate, and the spools of the arm directional control valves 7 and 14 do not fully open. Arm cylinder 114 does not generate sufficient high pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic circuit for a hydraulic excavator that can solve the above problems and optimize the operating speed of the actuator when the amount of operation is at its maximum.

In order to achieve this objective, the present invention provides a discharge amount setting that controls a 5Vr regulator so that when the operation amount for each actuator is maximized, the pump discharge amount becomes an optimal amount predetermined for that actuator. It is characterized by having a means.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 3 shows an embodiment of the invention. In this embodiment, only the operating speed of the arm cylinder 11 is regulated. Components similar to those in FIG. 1 are designated by the same reference numerals.

A switching valve 31 is provided between the branch point 30 of the pilot pressure signal circuit leading to the regulators 28 and 29 and the regulator 29, and the arm pilot valve 21 is used as the switching pressure.
The pilot pressure signal output from is guided. Switching valve 3
1 communicates the output side of the shuttle valve 27 with the regulator 29 at the return position A, and communicates the regulator 29 with the tank at the switching position B.

When the pump discharge pressure increases, the regulators 28 and 29 lower the pump discharge amount Q, and as shown in FIG.
Assuming that Q = Qs is constant, in the range of Pl≦P≦P island, the pump discharge amount Q increases as the pilot pressure signal P increases.
The tilt angle of the swash plate (oblique shaft) is adjusted so that the pump discharge amount Q=Q is constant.

The pilot pressure signal P is kept below P4 by the relief valve 20.

When the operating lever of the arm pilot valve 21 is operated to a full stroke, the pilot pressure signal output from the arm pilot valve 21 switches the switching valve 31 to the switching position B. As a result, the input pressure to the regulator 29 becomes the tank pressure, and the discharge iIQ of the variable displacement hydraulic pump 2 is set to Ql. On the other hand, since the pilot pressure signal output from the arm pilot valve 21 is directly input to the regulator 28, when the manipulated variable is maximized,
When the pilot pressure signal P becomes 21 or more, the discharge amount Q of the variable displacement hydraulic pump 1 becomes Q.

becomes. Therefore, by fully opening the arm directional control valves 7 and 14, a flow rate (Q1+Q) flows into the arm cylinder 11 from the two variable displacement hydraulic pumps 1 and 2. By setting the regulator 29, Ql can be set to an appropriate value. For example, the operating speed of the arm cylinder 11 can be set to an optimal value.

When the other pilot valves 22 to 26 are operated, the switching valve 31 returns to the return position A, and each pilot valve 22 to 26
Since the pilot pressure signal from 6 is input to the regulators 28 and 29, the pump discharge amount corresponds to the pilot pressure signal. Therefore, for example, when the control lever of the boom pilot valve 26 is operated to a full stroke, a flow rate (Qa +Qs) flows into the boom cylinder 12. FIG. 4 shows another embodiment of the present invention. In this example,
In the switching position B, the switching valve 31 connects the output side of the pressure reducing valve 32 to the regulator 29 . The pressure reducing valve 32 reduces the pressure f to the pressure P of the pilot pump 19. Pressure P!
As shown in FIG. 2, is a value that satisfies Px<Pa<Pa. In this embodiment, it is possible to obtain a higher operating speed of the arm cylinder 11 than in the embodiment shown in FIG.

Of course, by setting the pressure P to an appropriate value, the optimum operating speed can be achieved.

FIG. 5 shows another embodiment of the invention. The switching valve 33 provided between the branch point 30 and the regulator 29 receives the highest pilot pressure signal outputted from the other pilot valves 22 to 26 except the arm pilot valve 21 as the switching pressure, and returns to the switching valve 33 . At position A, the regulator 29 is communicated with the tank, and at switching position B, the output side of the shuttle valve 34 is communicated with the regulator 29.

When the operating lever of the arm pilot valve 21 is operated alone at full stroke, the switching valve 33 is in the rear tightening position A.
Since the tank pressure is input to the regulator 29, the discharge amount Q of the variable displacement hydraulic pump 2 becomes Ql. Further, since the pilot pressure signal from the arm pilot valve 21 is inputted to the regulator 28 from the shuttle valve 34, the discharge amount Q of the variable displacement hydraulic pump 1 becomes Q. Therefore, the combined flow rate of the arm cylinder 11 is (Q).

+Q, ).

Arm pilot valve 21 and other pilot valves 22 to 2
6 is operated in combination with the other pilot valves 22 to 6.
26 pilot pressure signal causes the switching valve 33 to switch to the switching position B.
, and a pilot pressure signal is input to both regulators 28 and 29, so that the discharge amounts Q of the two variable displacement hydraulic pumps 1 and 2 both become Q. Therefore, the maximum amount of pressure oil is supplied to the arm cylinder 11 and other actuators that are operated in combination with it, and no shortage of oil occurs.

In the illustrated embodiment, the switching valves 31, 33 and the pressure reducing valve 32 are used as the discharge amount setting means of the present invention, but the present invention is not limited to such hydraulic means, and may be replaced by electrical means.

The discharge amount setting means is for arm cylinder llIC □
However, it can also be provided for all other actuators.

The present invention is not limited to a hydraulic circuit using two variable displacement hydraulic pumps, but can also be applied to a hydraulic circuit using one or more variable displacement hydraulic pumps. Furthermore, the present invention is applicable not only to open-circuit hydraulic circuits but also to closed-circuit hydraulic circuits. In that case, the variable displacement hydraulic pump is of a type in which the discharge direction can be switched, for example, a double tilting type, and instead of the directional switching valve, a logic valve or the like is used as the control valve.

As explained above, according to the present invention, when the operation amount for each actuator is maximized, the pump discharge amount is controlled by regulation 1 so that it becomes the optimal amount predetermined for that actuator. Since the amount setting means is provided, the operating speed of the actuator at the maximum operation amount can be optimized. This can save energy and improve the life of the actuator and other hydraulic equipment.

[Brief explanation of the drawing]

Figure 1 is a hydraulic circuit diagram of a conventional hydraulic excavator, Figure 2 is a characteristic diagram of its regulator and variable displacement hydraulic pump, and Figure 3 is a hydraulic circuit diagram of a conventional hydraulic excavator.
Figures 1 to 5 are hydraulic circuit diagrams showing embodiments of the present invention. 1.2...Variable displacement hydraulic pump, 5-8.13
~16... Directional switching valve, 9... Left travel motor, 10... Turning motor, 11 Old... Arm cylinder, 12... Arm cylinder , 17
...Packet cylinder, 18...Right travel motor, 21-26...Group/pilot valve, 28.2
9: Regulator, 31: Switching valve, 32: Old pressure reducing valve, 33: Switching valve.

Claims (1)

[Claims] 1. In the hydraulic circuit of a hydraulic excavator, in which pressure oil is supplied to multiple actuators by a control valve for each actuator from a variable displacement hydraulic pump whose discharge amount is adjusted by a regulator, Hydraulic pressure of a hydraulic excavator, characterized in that it is provided with a discharge amount setting means for controlling a regulator so that when the operation amount is maximized, the pump discharge amount becomes an optimal amount predetermined for the actuator. circuit.