JPH01193401A - Hydraulic circuit - Google Patents

Abstract

PURPOSE:To prevent a shortage of oil that is encountered when plural actuators are simultaneously operated by setting, on the upstream side of a flow rate sensor on a bypass route, a variable flow metering valve for varying the opening thereof responding to the operational amounts of a control lever. CONSTITUTION:A variable flow metering valve 13 is set on the upstream side of a flow rate sensor 11 on a bypass route 10, and the opening of the variable flow metering valve 13 is controlled based on a signal from a displacement gauge 16 which detects the operational stroke of a control lever 14. When the operational stroke is within a minute range, the above-mentioned mechanism is led to the decrease in the flow rate on the bypass route 10 and to the decrease in the flow rate as detected by the flow sensor 11, and, as a result, to the increase in the discharge of a variable pump 1. Therefore, a shortage of oil that is encountered when plural actuators are simultaneously operated can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that allows a plurality of actuators to be operated simultaneously.

[Conventional technology]

As shown in FIG. 8, by providing a plurality of valves, for example, first, second, and third valves 2°3.4 in the discharge path of the variable hydraulic pump 1, and switching the response valves, a plurality of actuators, for example, Pressure oil can be supplied to the first, second, and third actuators 5, 6.7, and a check valve 8 and a variable throttle valve 9 are provided on the inlet port 4a side of the third valve 4. When the valves 3 are switched at the same time, the variable throttle valve 9 operates to throttle the flow rate flowing to the third valve 4, and the oil circuit is configured to match the speeds of the third actuator 7 and the second actuator 6 so that they can be operated simultaneously. Are known.

On the other hand, a flow rate sensor 11 is provided in the bypass path 10, and the detected flow rate of this flow rate sensor 11 is fed back to the capacity control member 12 of the variable pump 1. When the detected flow rate is large, that is, when pressure oil is not supplied to the actuator, the variable pump 1 The capacity (discharge amount) of the variable pump 1 is decreased, and the discharge amount of the variable pump 1 is increased when the detected flow rate is small, that is, when pressure oil is being supplied to the actuator.

[Problem to be solved by the invention]

With such a hydraulic circuit, when the second valve 3 and the third valve 4 are simultaneously operated with a small stroke from the neutral position N to the pressure oil supply position I or ■, a part of the pressure oil discharged from the variable pump 1 is transferred to the second valve
The third actuator 6.7 is supplied with the remaining part, and the remaining part flows out into the bypass path 10, so the flow rate sensor 11 detects a certain amount of flow rate, and the discharge rate of the variable pump 1 decreases from the maximum discharge rate. - In particular, when the variable throttle valve 9 is throttled to improve simultaneous operation, the bypass path 10
Since the outflow amount increases, the decrease in pump discharge amount is noticeable.

For this reason, the flow rate supplied to the second and third valves 3.4 may be insufficient, and pressure oil may not be supplied to the third actuator.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a hydraulic circuit capable of solving the above-mentioned problems.

[Means and actions for solving the problem] Bypass path 10
A variable throttle valve 13 is provided on the upstream side of the flow rate sensor 11, and a controller is provided to throttle the variable throttle valve 13 according to the operating stroke of the operating lever 14. The discharge amount of the variable pump is increased within the range of minute operation strokes to prevent the oil amount from running out.

〔Example〕

As shown in FIG. 1, a variable throttle 13 is provided on the upstream side of the flow rate sensor 11 in the bypass path 10.

The variable throttle 13 is configured to be sequentially throttled as shown in FIG. 2 depending on the current value supplied to the solenoid 13a.

The answer is a pilot pressure P from a switching mechanism 15 that generates a pilot pressure P11P2 proportional to the operating stroke of the operating lever 14 shown in FIG.

P2 as the first or second pressure receiving part 41+42+31+32.2
1.22 from the neutral position ■ to the first or second position.
The first or second device I is switched to device I or
The switching mechanism 15 is also provided with a displacement meter 16 for detecting the operating stroke of the operating lever 14.

The inlet port 17 and the first or second port 18, 19 are communicated with each other according to the operation stroke as shown in FIG.
0, it is shut off according to the operating stroke as shown in FIG. 4(b).

Further, the throttle valve 911 is throttled as shown in FIG. 5 by the current value supplied to the solenoid 9a.

Figure 6 is a control circuit diagram, with the first, second and third
Detection signals (operation strokes) from the displacement meters 16 of the switching mechanisms 15 corresponding to the valves 2, 3.4 are input to the controller 21, and when detection signals are input from two or more displacement meters 16, the solenoid of the variable diaphragm 13 is activated. 13a is supplied with a current proportional to the displacement jl (operation stroke) as shown in FIG. 7, and at the same time, a current is supplied to the solenoid 9a of the throttle valve 9.

Since this is the case, a plurality of valves, for example, the first valve 2 and the third valve
When valve 3 is operated simultaneously, variable throttle 1 is controlled by controller 17.
A current corresponding to the operation stroke is supplied to the solenoid 13a of No. 3, and the variable throttle 13 is sequentially narrowed down so that the opening area is sequentially reduced.
The flow rate flowing through the pump is decreased, the flow rate detected by the flow rate sensor 11 is decreased, and the discharge amount of the variable pump 1 is sequentially increased.

Therefore, when a plurality of actuators are operated simultaneously, the discharge amount of the variable pump 1 increases within the small operation stroke range, and pressure oil will not be supplied to one of the actuators due to insufficient oil amount.

Note that when the operating lever 14 is operated beyond the micro operation stroke range, no pressure oil flows into the bypass passage 10, and the flow rate detected by the flow rate sensor 11 becomes zero, so that the discharge amount of the variable pump 1 becomes maximum.

〔Effect of the invention〕

Variable throttle valve 1 according to the operating stroke of the operating lever 14
3 is throttled to reduce the flow rate flowing through the bypass passage 10 when within the fine operation stroke range, thereby reducing the flow rate detected by the flow rate sensor 11, and thereby increasing the discharge amount of the variable pump 1.

Therefore, when a plurality of valves are operated simultaneously and a plurality of actuators are simultaneously operated, it is possible to prevent pressure oil from being unable to be supplied to one of the actuators due to insufficient oil amount when within the fine operation stroke range.

[Brief explanation of the drawing]

Figures 1 to 7 show embodiments of the present invention, Figure 1 is a hydraulic circuit diagram, Figure 2 is a chart showing the relationship between the area of the variable throttle valve and the current value, and Figure 3 is an explanation of the switching mechanism. Figure 4 is a diagram showing the relationship between valve area and operating stroke, Figure 5 is a diagram showing the relationship between throttle valve flow rate and current value, Figure 6 is a control circuit diagram, and Figure 7 is a diagram showing the relationship between the flow rate and current value of the throttle valve. Diagram showing the relationship between currents, No. 8
The figure is a conventional circuit diagram. 1 is a variable pump, 2.3.4 is the first, second, third valve, 5
．． 6.7 are first, second and third actuators, 8 is a check valve, 9 is a variable throttle valve, 10 is a bypass path, 11 is a flow rate sensor, 13 is a variable throttle valve, 14 is an operating lever, 2
1 is the controller. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] The discharge path of the variable pump 1 has a neutral position N where the discharge pressure oil flows out to the bypass path 10 and an inlet port 17 where the discharge pressure oil flows out to the bypass path 10.
A plurality of valves are connected in parallel, and a check 8 and a variable throttle valve 9 are provided on the upstream side of the inlet port 17 of the valves. In addition, in a hydraulic circuit in which a flow rate sensor 11 for controlling the discharge amount of the variable pump 1 is provided in the bypass path 10, a variable throttle valve 13 is provided upstream of the flow rate sensor 11 in the bypass path 10, and the valve is switched. A hydraulic circuit characterized in that a controller 21 is provided that throttles the variable throttle valves 9 and 13 in accordance with the operating stroke of the operating lever 14.