JP2579571B2 - Hydraulic circuit with flow control of hydraulic machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art The disclosed technology relates to a hydraulic excavator such as a power shovel used for construction work, a hydraulic crane such as a hydraulic crane, and a hydraulic machine equipped with a plurality of hydraulic actuators in a mechanism thereof. Belongs to the technical field of hydraulic system to control.

[0002]

2. Description of the Related Art As is well known, it is desirable to obtain a large output stably in various industrial machines, and it is desirable that a considerable amount of work be performed accurately and without change over time. Various types of hydraulic machines are widely used. Particularly, in construction work and the like, various types of hydraulic machines are widely used because they can efficiently process work.

[0003] Although there is a simple type of hydraulic machine such as a hydraulic cylinder used as a single unit in this type of hydraulic machine, recently, a hydraulic excavator or a hydraulic crane capable of performing complicated work for multiple purposes has been recently used. Various types of crawler-type heavy machines capable of independently controlling left and right, such as a type having a plurality of hydraulic actuators, are used, and the discharge pressure from a single inclined plate type variable displacement hydraulic pump is used to control the hydraulic pressure. A hydraulic circuit equipped with a so-called load sensing system that maintains a pressure difference higher than a maximum load pressure of an actuator by a predetermined differential pressure and optimally controls the flow rate of pressurized oil by a flow control valve with pressure compensation is disclosed in, for example,
No. 116302, 1-197814, 1-31220
It has been developed as shown in the invention of Japanese Patent Publication No. 2 and has been put to practical use.

Such a load sensing system maintains a minimum flow rate such that the discharge amount of the hydraulic pump can be used for the maximum load pressure of the hydraulic actuator. It has a pressure compensation function of controlling the flow rate to a predetermined amount irrespective of pressure fluctuations, and can maintain individual operability of each hydraulic actuator.

[0005] In the operation of a plurality of hydraulic actuators, the load sensing system according to the related art has a relationship between a consumable flow rate of a required flow rate of hydraulic oil based on a predetermined signal from an operation lever and a maximum dischargeable flow rate of a hydraulic pump. As disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 1-312202, a high pressure selection line such as a high pressure selection valve or a differential pressure gauge for selecting a maximum load pressure is provided. A so-called anti-saturation mechanism is used to control the flow rate of the pressure oil through the flow control valve in order to avoid the appearance of a saturated state from the imbalance between the flow rate and the total required flow rate of the flow control valve.

[0006]

However, the high-voltage selection line and the anti-saturation mechanism in the conventional load sensing system have a complicated structure.
Further, there is a disadvantage that the management control of the pressure oil is complicated, and there is a disadvantage that not only initial costs but also maintenance costs and running costs are high.

[0007] The use of a load pressure detection system in the control of the flowing overpressure oil makes it possible to control the flow rate of the flowing pressure oil by a double system, thereby making the mechanism more complicated, making the handling operation difficult, and increasing the skill. There was a disadvantage that it required.

In recent years, although it is possible to use a microcomputer for various types of control, it has been difficult to optimize electrical control via the microcomputer for detecting load pressure. There was also an inconvenience.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of hydraulic control of a hydraulic machine having a plurality of hydraulic actuators based on the prior art described above, and to provide an excellent load sensing system. While taking advantage of the above, the load sensing system is simplified by adopting a method of directly detecting the flow rate of the pressure oil flowing through the circuit instead of the load pressure detection method, and a high-pressure selection line is provided in the load sensing system. An excellent hydraulic machine flow control that eliminates the need, simplifies the anti-saturation mechanism, and enables the stable operation of the hydraulic actuator to be performed by optimal control, which benefits the hydraulic technology application field in the transport and lifting industry. It is not intended to provide a hydraulic circuit.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a configuration of the invention of the present application, which has the above-mentioned claims and aims at the above objects, has a plurality of hydraulic units provided in a predetermined hydraulic machine. The hydraulic actuator of the preceding stage is connected to the operation control valve of the preceding stage, and a hydraulic flow sensor serving also as a holding check valve is interposed between the operation control valve and the flow control valve of the subsequent stage, and these valves are respectively arranged in parallel. The remote control valve is connected to the single flow rate calculation unit and also to the total consumption flow correction calculation unit. Also, the single flow calculation and the total consumption flow correction calculation unit are connected together, and each connection is a hydraulic passage or a lead wire. Each of the individual flow rate calculation units and the total consumption flow rate correction calculation unit are electrically connected by a command signal from the remote control valve and a signal from the hydraulic flow sensor. DOO if the comparison operation and the flow rate signal is a signal larger than from the remote control valve from the hydraulic flow sensor, decreases the opening of the flow control valve,
In the opposite case, the operating oil pressure is applied so as to adjust the opening of the flow control valve so as to increase it, and at the time of load sensing, the feedback of the tilt of the hydraulic pump is applied to give the load sensing action to each hydraulic actuator. When it exceeds the maximum flow rate, it is controlled to be the discharge flow rate of the maximum flow rate, and in the correction control of the total consumable flow rate, a signal for keeping the suppression rate constant is provided,
Smooth control of the supply flow rate of hydraulic oil to the hydraulic actuator is possible, improving the operability of the hydraulic actuator, and stabilizing without causing hunting phenomenon due to mutual interference between load sensing control and total consumption flow correction control. The technical measures to control the flow rate were taken.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

In the illustrated embodiment, for example, a plurality of (three in this embodiment) hydraulic actuators 1, 2, 3,..., Such as a hydraulic cylinder for raising and lowering a shovel of a hydraulic shovel, a right and left traveling crawler, etc. In this mode, stable operation control can be performed without hunting due to interference between the load sensing control and the total consumption flow correction control, and a simple anti-saturation mechanism is provided. It is.

In this embodiment, three hydraulic actuators are shown, but four or more hydraulic actuators may be used. In the illustrated embodiment, the third and subsequent hydraulic actuators are controlled. The mechanism is omitted.

Thus, each of the hydraulic actuators 1, 2, 3
… Has a hydraulic pilot type operation control valve 1
, And flow sensors 13, 23, 33, which also serve as holding check valves, are connected in series with the well-known flow control valves 12, 22, 32,. It has a structure well known to those skilled in the art, which moves the spool (not shown) provided therein to advance and retreat with the hydraulic pressure of the flowing pressure oil and detects the hydraulic pressure, or converts the hydraulic pressure as an electric signal and detects it. Yes, instruct increase or decrease of flow rate, as described later,
Each of the corresponding flow control valves 12, 22, 32,... Is operated.

A hydraulic passage connecting these valves
Are connected to a variable displacement hydraulic pump 6 of a tilting plate type via one hydraulic passage 5 so as to supply a set amount of hydraulic oil to each of the hydraulic actuators 1, 2, 3,. Has been.

Thus, the hydraulic actuators 15 and 25 have hydraulic actuators 1 and 25, respectively.
2 is a load sensing unit flow rate calculation unit for the hydraulic actuator 3 (the unit flow rate calculation unit for the actuators after the hydraulic actuator 3 is the same as that for the hydraulic actuators 1 and 2 described above, and is omitted). The parts 15 and 25 (the same applies hereinafter) are composed of a hydraulic comparison operation mechanism or an electric comparison operation mechanism known in the art, and hydraulically operated by a remote control valve 8 linked to a lever 7 provided in a driver seat or the like. Alternatively, they are electrically connected via the selection valves 16 and 26.

Then, in the remote control valve 8, as shown in FIG.
The spools 24 and 24 'are pressed via 23, and a hydraulic pressure proportional to the inclination of the lever 7 is output as a flow command signal. The output signal of the remote control valve 8 is transmitted to the operation control valves 11, 2
It is also led to the pressure receiving chambers of 1,31 ...

This hydraulic output signal is output from the low pressure sensor 2
5, 25 'to convert the electric signal into an electric signal, and to guide the electric signal to the single flow rate calculating units 15, 25.

Each of the single flow rate calculating units 15 and 25 includes a corresponding flow sensor 13, 23... And a flow control valve 1
2, 22, and 32, and the flow sensors 13, 2
The flow rate detection signal from 3 ... and the flow rate command signal from the remote control valve 8 are compared and calculated, and the output signals thereof are used to adjust and control the opening of each of the flow rate control valves 12, 22, 32.

The flow sensors 13, 23, and 33 use, for example, a sensor using a holding check valve disclosed in Japanese Patent Application No. 2-312051 of the prior application of the applicant, or as shown in FIG. A combination of a flow sensor 9, a holding check valve 10, and a pressure reducing valve 10 'is used.

In the flow sensor 9 shown in FIG. 2, when the passing flow rate increases, the opening degree of the holding check valve 10 increases and the pressing force of the spring also increases. Since the secondary pressure b with respect to the servo pressure a of the pressure reducing valve 10 'is proportional to the strength of the spring, the output pressure of the flow sensor 9 increases with the flow rate.

Of course, as described above, these oil pressure signals are also provided to the total consumption flow rate correction calculation unit 17.

The total consumption flow rate correction operation unit 17 compares the sum of the remote control signals from the individual flow rate operation units 15, 25... With the sum of the signals from the flow sensors 13, 23, 33. And output the deviation signal to each flow control valve 12, 22, 32
And the opening degree thereof is adjusted and controlled, and the total amount of the pressure oil supplied to each of the hydraulic actuators 1, 2, and 3 is input to the tilt control mechanism of the hydraulic pump 6 so that the hydraulic pressure can be adjusted. If the maximum discharge amount of the pump 6 is exceeded, the pump 6 is controlled so as to reach the maximum discharge amount.

As described above, the total consumption flow correction control in the total consumption flow correction operation unit 17 is performed by each of the flow control valves 12,
Signals with a constant suppression rate are given to 22, 32,.

As a means for extracting the flow rate detection signals from the flow sensors 13, 23, 33,... As electric signals, for example, a well-known converter 13 'shown in FIG. 3 can be used. Is spring 18
The displacement of the spool 19, which changes through the terminal 20, is converted into an electric signal by a magnetoresistive element 21 such as an MR element provided at a terminal 20, and is output as a flow rate detection signal through a lead wire 22.

In the above configuration, each hydraulic actuator
The flow detection signals from the individual flow sensors 13, 23, 33 ... of 1, 2, 3 ... and the command signals from the remote control valve 8 are compared and calculated by the individual flow calculation units 15, 25, respectively. In the total consumption flow correction calculation unit 17, the sum of the command signals from the remote control valve 8 and the flow sensor 13,
Computes the sum of the signals from 23, 33 ...
2, 22 and 32 are input with the suppression control signal and the opening is adjusted to a predetermined value. When the discharge flow from the hydraulic pump 6 reaches the maximum discharge amount, the total consumption flow correction control is performed and each hydraulic actuator is controlled. Smooth control and anti-saturation control of the supply flow rate of pressurized oil to 1, 2, 3… are possible, and stable control is achieved without hunting phenomenon due to interference between load sensing control and total consumption flow correction control. I can do it.

[0027]

As described above, according to the invention of this application, a load sensing system having a conventionally excellent merit in a hydraulic machine basically equipped with a plurality of hydraulic actuators can be provided without a high pressure selection line and an anti-saturation mechanism. This makes it possible to perform load sensing control without complicating the above.

In addition, the load sensing system can be realized by the direct detection method of the pressure oil flow rate instead of the load pressure detection method, so that the mechanism is not complicated and simple and reliable control can be performed. Is done.

[Brief description of the drawings]

 The drawings are explanatory diagrams of one embodiment of the invention of this application.

FIG. 1 is a flowchart of a load sensing system.

FIG. 2 is a schematic partial cross-sectional view of one embodiment of a flow sensor.

FIG. 3 is a cross-sectional view of another embodiment of the other embodiment.

FIG. 4 is a partial sectional view of a remote control valve.

[Explanation of symbols]

 6 Hydraulic pumps 1, 2, 3 Hydraulic actuators 11, 21, 31 Operation control valves 12, 22, 32 Flow control valves 13, 23, 33 Flow sensors 15, 25 Single flow rate calculation unit 17 Total consumption flow correction calculation unit 8 Remote control Valve 10 Holding check valve 10 'Regulator 13' Converter

Claims (3)

(57) [Claims] 1. A flow control system for a hydraulic machine in which a plurality of hydraulic actuators are connected in parallel to a hydraulic passage from a hydraulic pump, and an operation control valve and a flow control valve are interposed in series in front of each hydraulic actuator. In the hydraulic circuit, a hydraulic flow sensor having a holding check valve function is provided between the operation control valve and the flow control valve, and the hydraulic flow sensor and the remote control valve are connected to the flow control valve. It is connected to a calculation unit and the total consumption flow rate correction calculation <br/> unit, also single-body flow rate calculation unit and the total consumption flow correction
A flow control hydraulic circuit for a hydraulic machine, wherein the hydraulic circuit is connected to an arithmetic unit. 2. The hydraulic flow sensor according to claim 1, wherein
2. The hydraulic circuit according to claim 1, wherein the hydraulic circuit comprises a check valve and a pressure reducing valve . 3. The hydraulic pressure sensor according to claim 1, wherein said hydraulic flow sensor detects an oil pressure as an electric signal.
2. The hydraulic circuit according to claim 1 , further comprising a converter for converting the hydraulic pressure into a hydraulic pressure.