JPS63120901A - Hydraulic driving device - Google Patents

Abstract

PURPOSE:To prevent change in the speed of a hydraulic cylinder from resulting from a variation in a load direction by detecting load pressure acting on a hydraulic cylinder to control the opening of a directional control valve according to a load pressure signal. CONSTITUTION:A hydraulic circuit is provided with pressure detecting means 4, 5, and output from the means 4, 5 is inputted into a control means 7. When pressure in a hydraulic cylinder 1 becomes lower than a specified pressure, an operational target signal is limited to a small value, and the signal having the small value is fed to the driving part of a directional control valve 2 to limit the opening of the valve 2. Change in the operating speed of the cylinder 1 can be therefore prevented from resulting from a variation in a load acted on the cylinder 1 without provision for a counterbalance valve. Thus accuracy in tracing a locus and operational ability during manual operation can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is installed in a civil engineering construction machine such as a hydraulic excavator, and prevents a change in the speed of a hydraulic cylinder depending on the direction of a load applied to the hydraulic cylinder, and prevents the hydraulic cylinder from changing its speed. The present invention relates to a hydraulic drive device that can improve trajectory control accuracy of a drive body and improve manual operability.

<Prior Art> In hydraulic excavators and the like, the direction of the load applied to the hydraulic cylinder changes frequently during work. At this time, the operating speed of the hydraulic cylinder is determined by the flow rate supplied to the hydraulic cylinder via the directional control valve, that is, the meter-in flow rate, when the direction of the load opposes the direction of expansion and contraction of the hydraulic cylinder; When coincides with the expansion/contraction direction of the hydraulic cylinder, it is determined by the flow rate discharged from the hydraulic cylinder to the tank via the directional switching valve, that is, the meter-out flow rate. Since the meter-in flow rate and the meter-out flow rate generally have different characteristics, the speed of the hydraulic cylinder will change due to changes in the direction of the load applied to the hydraulic cylinder, and this will cause the packet attached to the end of the arm to change. The precision in controlling the trajectory of the cutting edge will be reduced, and the operability when manually operating the hydraulic cylinder will be impaired.

<Problems to be Solved by the Invention> Conventionally, in order to prevent the speed change of the hydraulic cylinder due to the change in the direction of the load applied to the hydraulic cylinder as described above,
A hydraulic drive device has been proposed in which a counterbalance valve is disposed in a hydraulic circuit that communicates a hydraulic pump and a hydraulic cylinder. However, in this conventional hydraulic drive device, although the above-mentioned speed change of the hydraulic cylinder can be prevented by providing a counterbalance valve, there are problems such as increased pressure loss and hunting of the counterbalance valve. There is.

The present invention has been made in view of the actual state of the prior art described above, and its object is to prevent speed changes of a hydraulic cylinder due to changes in the direction of the load applied to the hydraulic cylinder without providing a counterbalance valve. The purpose of the present invention is to provide a driving device.

Means for Solving the Problems In order to achieve this object, the present invention provides a pressure detection means for detecting the load pressure acting on a hydraulic cylinder and outputting a load pressure signal, and an operation command for operating the hydraulic cylinder. and a control means for inputting the signal and the load pressure signal and outputting an operation signal for controlling the operation of a directional control valve that controls the flow of pressure oil supplied from the hydraulic pump to the hydraulic cylinder. a first calculation means for outputting an operation target signal corresponding to the operation command signal outputted from the operation command means according to the functional relationship between the determined operation command signal and the operation target signal corresponding to the operation signal; The second calculation means outputs a correction signal capable of limiting the value of the operation target signal output from the first calculation means in accordance with the load pressure signal.

Effect> The present invention is constructed as described above, so that when the pressure in the part of the hydraulic cylinder to which pressure oil is supplied from the hydraulic pump decreases below a predetermined pressure due to the load applied to the hydraulic cylinder, pressure detection is performed. The operation target signal outputted from the second calculation means is limited to a small value in accordance with the load pressure signal outputted from the means, and the operation target signal having this small and limited value is output to the drive section of the directional control valve. Therefore, the opening degree of the directional control valve is limited, and the hydraulic cylinder can operate at a speed commensurate with the discharge amount of the hydraulic pump regardless of changes in the load applied to the hydraulic cylinder, and without any counterbalance valve. There's nothing necessary.

<Example> Hereinafter, the hydraulic drive device of the present invention will be explained based on the drawings.

FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing basic components of a control means provided in the embodiment shown in FIG.

In FIG. 1, 1 is a hydraulic cylinder, 3 is a variable displacement hydraulic pump that supplies pressure oil to this hydraulic cylinder 1, and 2 is a direction that controls the flow of pressure oil supplied from the variable displacement hydraulic pump 3 to the hydraulic cylinder 1. The switching valve 3a is a discharge amount control means for controlling the discharge amount of the variable displacement hydraulic pump 3. 4.5
is a pressure detecting means for detecting the load pressure acting on the hydraulic cylinder 1. Of these, the pressure detecting means 4 detects the pressure on the head side of the hydraulic cylinder 1 and outputs a load pressure signal Po, and the pressure detecting means 5 detects the pressure on the head side of the hydraulic cylinder 1. Detects the pressure on the rod side of No. 1 and outputs a load pressure signal PR. Reference numeral 6 denotes an operation command means consisting of an operating lever etc. that outputs an electric signal, and the hydraulic cylinder 1
Outputs an operation command signal X that activates the

Reference numeral 7 denotes a control means to which the above-mentioned pressure detection means 4.5, operation command means 6, discharge amount control means 3a, and driving section of the directional control valve 2 are connected, and which has logical judgment, arithmetic functions, etc., and receives the operation command signal X. , load pressure signals PH and PR are input, an operation signal Y is output to the drive section of the directional control valve 2, and a target discharge amount signal Z is output to the discharge amount control means 3a, as shown in FIG. It has the basic components shown below. That is,
In this FIG. 2, 8 is a predetermined operation command signal X.
and the operation target signal Y' corresponding to the above-mentioned operation signal Y, the first calculation means 9 outputs the operation target signal Y' corresponding to the actuation command signal X that is actually output. Load pressure signals PH, P according to operation command signal
This is a second calculation means that outputs a correction signal K that can limit the value of the operation target signal Y' outputted from the first calculation means 8, depending on the load pressure signal P. The second calculation means 10 determines the value of the load pressure signal P at a predetermined pressure value P that affects the operating speed of the hydraulic cylinder 1. When the pressure is smaller than the predetermined pressure value P, a correction signal K having a value smaller than "1" is output.

When the value is larger than 1, a correction signal K having a value of "1" is output.

11 is a multiplier that calculates the product of the operation target signal Y' and the correction signal and outputs this as an operation signal Y to the drive section of the directional control valve 2; 12 is a predetermined operation command signal X; It is a third calculation means that outputs a target discharge amount signal Z corresponding to the operation command signal X output from the operation command means 6 according to the functional relationship with the target discharge amount signal Z that controls the discharge amount of the hydraulic pump 3. .

In the embodiment configured in this way, for example, when the rod of the hydraulic cylinder 1 moves to the first left and extends, the first actuation command signal X output from the actuation command means 6 is used. Operation command signal X is sent from the calculation means 8 of 1 to the multiplier 11
The operation target signal Y' corresponding to is pressed. On the other hand, the operation command signal X is also output to the selection means 9 and the third calculation means 12.

Then, a target discharge amount signal Z corresponding to the operation command signal X is outputted from the third calculation means 12 to the discharge amount control means 3a, thereby restricting the discharge amount of the variable displacement hydraulic pump 3. Further, in the selection means 9, the operation command signal
Of the load pressure signals PH and PR, the load pressure signal P on the side to which pressure oil is supplied from the directional control valve 2 during the extension operation of the hydraulic cylinder 1, that is, on the head side, is selected according to the load pressure signal P. As a result, the second calculation means 10 outputs a correction signal K corresponding to the load pressure signal P to the multiplier 11. In this multiplier 11, the operation target signal Y' and the correction signal are multiplied by
output to the drive unit.

From this, when the head side pressure of the hydraulic cylinder 1 is lower than the predetermined pressure value Po, the operation signal Y for the directional control valve 2 becomes a small value limited by the correction signal K having a value smaller than "1". .

Therefore, when the discharge oil from the variable displacement hydraulic pump 3 is supplied to the head side of the hydraulic cylinder 1 as described above and the hydraulic cylinder 1 is operating in the direction of extension,
When the external force acting on the hydraulic cylinder 2 is in the direction of extension of the hydraulic cylinder 1, the hydraulic cylinder 1 attempts to extend at a speed greater than the flow rate corresponding to the flow rate supplied to the head side by the above-mentioned external force, and the head side pressure (load pressure signal P
When M) becomes smaller than a predetermined pressure value Po,
The opening degree of the directional control valve 2 is limited, and the operating speed of the hydraulic cylinder 1 is reduced, eventually being balanced at a speed commensurate with the flow rate supplied to the head side.

Contrary to the above, even when the hydraulic cylinder 1 contracts, the pressure on the rod side to which pressure oil is supplied (load pressure signal PR) is lower than the predetermined pressure value Po due to the external force applied to the hydraulic cylinder 1. When the value decreases, the value of the correction signal becomes “1”.
”, and the operation signal Y is limited to a small value.
is output to the directional switching valve 2, thereby limiting the opening degree of the directional switching valve 2, and eventually the operating speed of the hydraulic cylinder 1 is controlled to a speed commensurate with the flow rate supplied to the rod side.

The flow rate supplied to the rod side or the head side of the hydraulic cylinder 1 is determined by the operation of the discharge amount control means 3a that controls the discharge amount of the variable displacement hydraulic pump 3, that is, by the target operation signal Z. As a result, the speed of the hydraulic cylinder 1 commensurate with the discharge amount of the variable displacement hydraulic pump 3 according to the operation command signal Z can be obtained.

In the embodiment configured in this way, it is possible to prevent changes in the operating speed of the hydraulic cylinder 1 due to fluctuations in the load applied to the hydraulic cylinder 1 without providing a counterbalance valve as described above, and the trajectory It is possible to improve accuracy during control or improve operability during manual operation. Therefore, it is possible to suppress an increase in pressure loss due to the provision of a counterbalance valve, and suppress hunting.

In the above embodiment, a directional control valve 2 having a general three-position, four-boat structure is provided between the variable displacement hydraulic pump 3 and the hydraulic cylinder 1, but the present invention is not limited to this.
A switching valve structure is adopted in which the part that connects the hydraulic cylinder 1 and the variable displacement hydraulic pump 3 and the part that connects the hydraulic cylinder 1 and the tank can be independently controlled, and the opening degree of the part that connects with the tank is limited. The opening degree of the connection portion with the pump may be maintained at a large value, and in this way, power loss can be reduced.

Further, a configuration may be adopted in which a known compensation element is provided to compensate the operation signal Y to the directional switching valve 2 to prevent hunting accompanying switching of the directional switching valve 2.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of the hydraulic drive device of the present invention, and FIG. 2 is a block diagram showing the basic components of a control means provided in the embodiment shown in FIG. 1... Hydraulic cylinder, 2... Directional switching valve, 3... Variable displacement hydraulic pump, 3a...
...discharge amount control means, 4.5 ... pressure detection means, 6 ... operation command means, 7 ... control means, 8 ... first calculation means, 9... selection means, 10... second calculation means, 11...
. . . Multiplier, 12 . . . Third calculation means. Figure 1 1: De-white out > 5” 4,5
:Pressure ram exit hand Iz2: way mms child
6:f'F? 1fi-9 means 4 steps 3: Qt8'1lB
ffH, ;T>f 7J'JfF'fR
3σ11 Output tfJ Tsu Means 2 Figure 8: 1At- Clearance Means 9: fL Selection Means lO: Straw 2- Operation Hand I2 11: Multiplier 12: 3rd-Hama 1 Hand

Claims (2)

[Claims] (1) A hydraulic cylinder and a hydraulic pump that is installed in a civil engineering construction machine and supplies pressure oil to drive the hydraulic cylinder;
A hydraulic drive device comprising a directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the hydraulic cylinder, and an operation command means for outputting an operation command signal for operating the hydraulic cylinder. comprising a pressure detection means for detecting a working load pressure and outputting a load pressure signal, and a control means for inputting the operation command signal and the load pressure signal and outputting an operation signal for controlling the operation of the directional control valve, The control means outputs an operation target signal corresponding to the operation command signal output from the operation command means according to a predetermined functional relationship between the operation command signal and the operation target signal corresponding to the operation signal. 1 calculation means;
A hydraulic drive device comprising: second calculation means for outputting a correction signal capable of limiting the value of the operation target signal output from the first calculation means in accordance with the load pressure signal. (2) The control means generates a target discharge corresponding to the operation command signal output from the operation command means according to a functional relationship between a predetermined operation command signal and a target discharge amount signal that controls the discharge amount of the hydraulic pump. The hydraulic drive device according to claim 1, further comprising a third arithmetic means for outputting a quantity signal.