JPH05180202A - Flow control hydraulic circuit for hydraulic machinery - Google Patents

Abstract

PURPOSE:To eliminate a high-pressure selection line of a load sensing system and simplify an anti-saturation mechanism in hydraulic machinery having plural hydraulic actuators. CONSTITUTION:There are disposed flow sensors 13, 23 between pre-working control valves 11, 21 for respective hydraulic actuators 1, 2 and pre-flow control valves 12, 22. These are then connected to working flow control sections 15, 25 along with a remote control valve 8 and also to a total consumption possible flow rate compensation control section 17. Without a high-pressure selection line an anti-saturation mechanism is thus simplified and a load sensing system becomes possible, so that the system is simplified and the management control is facilitated, to enable cost reduction.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] The disclosed technology determines the flow rate of pressure oil to each hydraulic actuator of a hydraulic machine equipped with a plurality of hydraulic actuators in its mechanism such as a hydraulic excavator such as a power shovel used for construction work, a hydraulic crane, or the like. It belongs to the technical field of controlling hydraulic systems.

[0002]

2. Description of the Related Art As is well known, it is desirable to obtain a large output stably in various industrial machines, to perform a considerable amount of work with high accuracy and without change over time. The various hydraulic machines possessed by the above are widely used, and in particular, various ones are widely used in construction work and the like because they can efficiently handle the work amount.

In these hydraulic machines, there is a simple type in which a hydraulic actuator such as a hydraulic cylinder is used as a single unit, but recently, a hydraulic excavator or a hydraulic crane capable of multi-purpose processing complex work. Various crawler-type heavy machines with multiple hydraulic actuators are used, such as left and right independent control, and the maximum load of the hydraulic actuator is obtained by controlling the discharge pressure from a single inclined plate type variable displacement hydraulic pump. A hydraulic circuit equipped with a so-called load sensing system, which holds a pressure difference higher than a predetermined pressure by a predetermined differential pressure and optimally controls the flow rate of pressure oil by a flow control valve with pressure compensation, is disclosed in, for example, Japanese Patent Laid-Open No. 11630/1989.
No. 2, 1-197814, and No. 1-312202 gazettes have been developed and put into practical use as seen in the invention.

Such a load sensing system maintains a minimum flow rate such that the discharge amount of the hydraulic pump can be used as the maximum load pressure of the hydraulic actuator, and the flow rate control valve with pressure guarantee discharges the load pressure and the discharge amount of the hydraulic pump. It has a pressure compensating function that controls the flow rate to a predetermined amount irrespective of pressure fluctuations, and can maintain individual operability of each hydraulic actuator.

When operating a plurality of hydraulic actuators, the load sensing system up to now has the following relationship from the relationship between the consumable flow rate of the required flow rate according to a predetermined signal from the operating lever and the maximum dischargeable flow rate of the hydraulic pump.
As shown in the above-mentioned Japanese Patent Laid-Open No. 1-312202, a high-pressure selection line such as a high-pressure selection valve or a differential pressure gauge is provided, and the discharge flow rate of the pump and the total required flow rate of the flow rate control valve are A so-called anti-saturation mechanism is used to control the flow rate of the pressure oil passing through the flow rate control valve in order to avoid the appearance of a saturated state from the balance.

[0006]

However, the structure of the high-voltage selection line and the antisaturation mechanism in such a conventional load sensing system is complicated,
Further, there is a drawback that the management control is complicated, and there is a disadvantage that not only the initial cost but also the maintenance cost and the running cost are high.

Since the load pressure detection method is used in the control of the flow-over pressure oil, the flow rate of the flow-over pressure oil is controlled to form a double system, which makes the mechanism more complicated and difficult to handle. There was a drawback that it cost.

In spite of the recent possibility of using a microcomputer for various controls, there is a disadvantage that the detection of the load pressure hinders the optimal control of electric control.

[0009]

An object of the invention of this application is to solve the problem of hydraulic control of a hydraulic machine having a plurality of hydraulic actuators based on the above-mentioned prior art as a technical problem to be solved. While utilizing the load pressure detection method, the load sensing system is simplified by adopting a method that directly detects the flow rate of pressure oil flowing through the circuit, eliminating the need for a high pressure selection line in the load sensing system. Also, the anti-saturation mechanism is simplified, and stable operation of the hydraulic actuator can be performed by optimum control, which is an excellent flow rate control hydraulic pressure for hydraulic machinery that is useful in the field of hydraulic technology application in the transport heavy industry. It is intended to provide a circuit.

[0010]

In order to solve the above-mentioned problems, the structure of the invention of the present application, which is based on the above-mentioned claims and has the above-mentioned object, has a plurality of means provided for a predetermined hydraulic machine. A hydraulic actuator is connected to the operation control valve of the preceding stage, and a hydraulic flow sensor that doubles as a holding check valve is interposed between the operation control valve and the flow control valve of the preceding stage, and these valves are arranged in parallel and remote. It is connected to the unit flow rate control unit together with the control valve, and is also connected to the total consumable flow rate correction control unit, and the unit flow rate control and the total consumable flow rate correction control unit are also connected so that each connection is a hydraulic passage or an electrical connection. The individual flow rate control unit and the total consumable flow rate correction control unit are connected by a dynamic lead wire, and the command signal from the remote control valve and the hydraulic flow sensor are used. If the signal is greater than the flow rate signal from the remote control valve of the al signal from the comparison calculation and flow sensors, reducing the opening of the flow control valve,
In the opposite case, the operation hydraulic pressure is applied to adjust the opening of the flow control valve so as to increase it, and at the time of load sensing, feedback is applied to the tilt of the hydraulic pump to give load sensing action to each hydraulic actuator. When the maximum flow rate is exceeded, the discharge flow rate is controlled to be the maximum flow rate, and in the correction control of the total consumable flow rate, a signal that makes the suppression rate constant is given.
Smooth control of the pressure oil supply flow rate to the hydraulic actuator improves the operability of the hydraulic actuator and stabilizes without causing hunting due to mutual interference between load sensing control and total consumable flow rate correction control. The technical measures were taken to enable the controlled flow rate.

[0011]

An embodiment of the invention of this application will be described below with reference to the drawings.

In the illustrated embodiment, for example, a plurality of hydraulic actuators 1, 2, 3, ... Are loaded such as a hydraulic cylinder for lifting and lowering a shovel of a hydraulic excavator, a hydraulic cylinder such as left and right traveling crawlers, and the like. This is a mode in which the sensing control is performed, and stable operation control can be performed without causing a hunting phenomenon due to the interference between the load sensing control and the total consumable flow rate correction control, which has a simple anti-saturation mechanism. is there.

In this embodiment, three hydraulic actuators are shown, but four or more hydraulic actuators may be used. In the illustrated mode, the control mechanism is omitted after the third hydraulic actuator.

Thus, each hydraulic actuator 1, 2, 3
The hydraulic pilot type operation control valve 1 is located on the upstream side.
1, 21, 31 ... Are provided, and flow sensors 13, 23, 33, ... Also serving as holding check valves are connected in series between the well-known upstream flow control valves 12, 22, 32 ... A structure that is well known to those skilled in the art, which moves forward and backward with the hydraulic pressure of the pressure oil flowing through the spool installed inside and detects the hydraulic pressure, or converts the hydraulic pressure as an electric signal and detects it. .. are instructed to increase or decrease the flow rate, and the corresponding flow rate control valves 12, 22, 32 ... Are operated as described later.

A hydraulic passage for connecting each of these valves
14, 24, 34 ... Are connected to a variable displacement type hydraulic pump 6 of the tilt plate type via one hydraulic passage 5 so as to supply a set amount of pressure oil to each hydraulic actuator 1, 2, 3 ... Has been

Numerals 15 and 25 are load sensing single flow rate control units for the corresponding hydraulic actuators 1, 2, 3 ...
Since it corresponds to the case of 2, it is omitted. ), And these unit flow rate control units 15 and 25 (same below) are linked to a lever 7 provided in the driver's seat or the like, which is equipped with a known hydraulic comparison calculation mechanism or an electric comparison calculation mechanism. It is hydraulically or electrically connected to the remote control valve 8 via the selection valves 1 and 26.

In the remote control valve 8, as shown in FIG. 4, the spools 24, 24 'operated by the tappet 23 operated by the lever 7 have low pressure sensors 25,
A mode of electrically connecting to 25 'can be adopted.

The flow control valves 12, 22, 32 are connected to the flow sensors 13, 23, ... Corresponding to the individual flow control units 15, 25, respectively, and the operation control valves are connected.
Also connected to 11, 21, 31 and the flow sensor 13, 23, 33
The flow rate detection signal from the remote control valve 8 and the flow rate command signal from the remote control valve 8 are compared and calculated to adjust and control the openings of the flow rate control valves 12, 22, 32.
In the case of electrical connection to the connection circuit between 22 and 32, a valve is installed in a known electromagnetic proportional manner.

The individual unit flow rate control units 15 and 25 (the same applies to the third and subsequent units) are disclosed, for example, in Japanese Patent Application No.
The float control system disclosed in Japanese Laid-Open Patent Publication No. 312051, and in the hydraulic control system, a flow control valve 9 in which a pressure reducing valve is combined with a check valve as shown in FIG. 2 can be used, and the spool 10 can be used. When the stroke is changed by the input hydraulic pressure, the primary pressure (servo pressure) a is changed to the secondary pressure b.
As a result, the flow rate is converted to control the opening of the flow rate control valves 12, 22, 32 ... And compared with the secondary pressure from the remote control valve 8 so that the flow rate control valves 12, 22, 32 ...
Adjust the opening of.

Of course, as described above, these hydraulic signals are also provided to the total consumable flow valve control unit 17.

Then, in the total consumable flow rate valve control unit 17, the sum of the remote control signals from the individual flow rate control units 15, 25 ... Is compared with the sum of the signals from the flow sensors 13, 23, 33. It is calculated and input to each flow control valve 12, 22, 32 to adjust and control its opening degree.
If the sum of the amounts of pressure oil supplied to the hydraulic actuators 1, 2 and 3 is input to the tilt control mechanism of the hydraulic pump 6 and exceeds the maximum discharge amount of the hydraulic pump 6, the maximum discharge amount is set. It is controlled by.

As described above, the total consumable flow rate correction control in the total consumable flow rate valve control unit 17 is adapted to be given a signal with a constant suppression rate.

When the flow rate detection signals from the flow sensors 13, 23, 33 ... Are electrical signals and the flow rate command signal from the remote control valve 8 is a hydraulic signal, a single flow rate control unit as shown in FIG. 3 is used. Known conversion device using MR element
15 'is used to convert the hydraulic pressure flow through the displacement of the spring 18 into the resin terminal 20 by operating the spool 19.
The command signal of the flow rate is converted into an electric signal by the porcelain resistance element 21 such as the MR element provided in the above and is output from the lead wire 22.

In the above structure, each hydraulic actuator
The flow rate detection signals from the individual flow sensors 13, 23, 33 ... of 1, 2, 3 ... And the command signal from the remote control valve 8 are compared and calculated by the individual flow rate control units 15, 25. In the total consumable flow rate correction control unit 17, the sum of command signals from the remote control valve 8 and the flow sensor
The sum of the signals from 13, 23, 33 ... Is compared and calculated, and the suppression control signal is input to each flow control valve 12, 22, 32, ... When the maximum discharge amount is reached, total consumable flow rate correction control is performed, which enables smooth control of the flow rate of pressure oil supplied to each hydraulic actuator 1, 2, 3, ..., antisaturation control, and load sensing. Stable control can be performed without hunting phenomenon due to interference between control and total consumable flow rate correction control.

[0025]

As described above, according to the invention of the present application, a load sensing system, which has a merit that is conventionally excellent in a hydraulic machine basically equipped with a plurality of hydraulic actuators, does not require a high-voltage selection line, and an antisaturation mechanism. An excellent effect that load sensing control can be performed without complicating

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

[Brief description of drawings]

 The drawing is an illustration of one embodiment of the invention of this application.

FIG. 1 is a flow diagram of a load sensing system.

FIG. 2 is a partial cross-sectional schematic view of one mode of a single flow rate control mechanism section.

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

FIG. 4 is a partial sectional view of the connection of the output signal of the remote control to the low pressure sensor.

[Explanation of symbols]

 6… Hydraulic pump 1, 2, 3… Hydraulic actuator 11, 21, 31… Actuation control valve 12, 22, 32… Flow control valve 13, 23, 33… Flow sensor 15, 25… Single flow controller 17… Total consumption Possible flow rate correction control unit 8 ... Remote control valve

Claims (4)

[Claims] 1. A flow control system for a hydraulic machine, wherein 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 provided 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 rate control valve, and the single flow rate in which the hydraulic flow sensor and the remote control valve are connected to the flow rate control valve. A flow control hydraulic circuit for a hydraulic machine, characterized in that the control unit is connected to a total consumable flow rate correction control unit, and the single unit flow control unit and the total consumable flow rate correction control unit are connected. 2. A flow control hydraulic circuit for a hydraulic machine according to claim 1, wherein each of said connections is made by a hydraulic pipe. 3. A flow control hydraulic circuit for a hydraulic machine according to claim 1, wherein each of said connections is made by an electric lead wire. 4. The single flow rate control unit and the total consumable flow rate correction control unit have a mechanism for comparing and calculating a signal from a remote control valve and a signal from a hydraulic flow sensor. A flow control hydraulic circuit of the hydraulic machine according to the item 1.