JPH059644B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a hydraulic drive in which a single rod cylinder such as an arm cylinder provided in a hydraulic excavator is driven and controlled by pressure oil discharged from a variable displacement hydraulic pump. Regarding equipment.

[Background of the invention]

Conventionally, this type of hydraulic drive device was
- There is one described in No. 1614. FIG. 10 is a circuit diagram showing this conventional hydraulic drive device, in which 1 is a variable displacement hydraulic pump whose discharge amount is controlled in accordance with a signal output from an operation lever (not shown); A single-rod cylinder is driven and controlled by the pressure oil discharged from the cylinder, such as an arm cylinder installed in a hydraulic shovel, and the ratio of the pressure receiving area on the head side to the pressure receiving area on the rod side is set to approximately 2:1. There is. Also, A and B are main pipes that connect the variable displacement hydraulic pump 1 and the arm cylinder 14, 8 is a tank, and 4 is a flushing system that detects the pressure in either of the main pipes A or B and communicates the low pressure side with the tank 8. Valve 5 is a relief valve that regulates the minimum pressure of main pipes A and B, 6 and 7 are main pipes A and B
This is a check valve installed to replenish oil.

FIG. 11 is a schematic side view of a hydraulic excavator equipped with the hydraulic drive device shown in FIG. 10. In this figure, 14 is the aforementioned arm cylinder;
is a boom cylinder, 15 is a bucket cylinder, 1
0 is a rotatable boom driven by a boom cylinder 13; 11 is an arm connected to the boom 10 and rotatable by an arm cylinder 14;
2 is connected to the arm 11, and the bucket cylinder 1
5 is a bucket that can be rotated, and these constitute a working machine. In addition, G is arm 1
1, the center of gravity including the bucket 12, etc., is the angle between the ground plane and a line passing through the connection between the boom 10 and the arm 11 and the center of gravity G.

In the hydraulic drive system configured as described above, the head side of the arm cylinder 14 becomes high pressure and the rod side becomes low pressure, or conversely, the rod side becomes high pressure and the head side becomes low pressure. Therefore, as shown in FIG. 11, a problem arises when the arm cylinder 14 is retracted from the excavating position in which the arm 11 is retracted the most to shift to the earth releasing position.

That is, at first, the weight of the arm 11 acts to contract the arm cylinder 14, the main pipe B side in FIG. do. When the variable displacement hydraulic pump 1 sends oil from the head side circuit of the arm cylinder 14 to the main conduit A side in order to extend the arm 11 from this state, the arm cylinder 14 is energized by the weight of the arm 11. operates at a speed corresponding to the amount of oil pumped out. At this time, the main pipe A is in communication with the tank 8 as described above. Then, as the arm 11 gradually assumes a nearly vertical posture, the energy due to the weight of the arm 11 decreases, and the operating speed of the arm cylinder 14 decreases. When the arm 11 passes the vertical position, the force applied to the arm cylinder 14 is reversed, the rod side or main line A becomes high pressure, the head side or main line B becomes low pressure, and the flushing valve 4 connects the main line B to the tank 8. Switches to communicate with. At this time, the arm cylinder 14 is rapidly accelerated to a speed determined by the discharge amount of the variable displacement hydraulic pump 1 and the pressure receiving area on the rod side.

FIG. 12a is a characteristic diagram showing the operating speed of the arm cylinder 14 corresponding to the angle shown in FIG. 11, and FIGS. 12b, c, and d are respectively
is an explanatory diagram illustrating the form of the arm 11 portion at 50°, 90°, and 130°. Note that S1 in FIG. 12a indicates the speed depending on the head side pressure receiving area of the arm cylinder 14 and the discharge amount of the hydraulic pump 1, and the form in the explanatory diagram of FIG. The form in the explanatory diagram of FIG. 12c corresponds to this. The form in the explanatory diagram of FIG. d corresponds to this. And S0 indicates the switching point of the flushing valve.

In this way, regarding conventional hydraulic drive devices,
As described above, when transitioning from excavation operation to earth dumping operation, the operating speed of the arm cylinder 14 is controlled according to the pressure in the main pipes A and B and the force due to the arm 11's own weight, so the flushing valve 4 is switched. However, the operating speed of the arm cylinder 14 is rapidly accelerated, which causes a shock and deteriorates the operability. In addition, the arm cylinder 14
Since the operating speed of the arm 11 is affected by the weight of the arm 11, the speed decreases due to free fall of the arm 11, resulting in poor operability.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned actual situation in the prior art, and its purpose is to provide a hydraulic drive device that can prevent speed changes of a single-rod cylinder regardless of changes in the force applied to the single-rod cylinder. It is in.

[Summary of the invention]

In order to achieve this object, the present invention provides a variable displacement hydraulic pump whose discharge amount is controlled in accordance with a signal output from an operating lever, and a variable displacement hydraulic pump whose drive is controlled by the pressure oil discharged from the variable displacement hydraulic pump. In a hydraulic drive device, the single rod cylinder and the variable displacement hydraulic pump form a closed circuit or a semi-closed circuit. A detection means is provided for detecting the direction of the load applied to the one-rod cylinder and outputting a signal, and the control valve is provided with a detection means for detecting the direction of the load applied to the single-rod cylinder and outputting a signal, and the variable load is adjusted according to an increase in the value of the signal output from the operating lever when the one-rod cylinder is contracted. The discharge amount of the displacement hydraulic pump is controlled to increase, and the flow rate of the valve is controlled to increase in accordance with an increase in the value of the signal output from the operating lever, and the detection means The flow rate of the valve when the load on the head side of the single rod cylinder is detected to be greater than the load on the rod side is when the detection means detects that the load on the rod side of the single rod cylinder is greater than the load on the head side. A control means is provided for controlling the flow rate to be smaller than the flow rate of the flow rate.

[Embodiments of the invention]

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

FIG. 1 is a circuit diagram showing the main configuration of an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a control section included in the circuit shown in FIG. 1. In these figures, the same components as those shown in FIG. 10 described above are designated by the same reference numerals.

The variable displacement hydraulic pump 1 is provided with an electric/hydraulic pump discharge amount control device 35, and this control device 3
5 controls the discharge amount of the hydraulic pump 1 according to an electric signal from a control section 30, which will be described later. Further, a valve for controlling the flow rate, for example, an electromagnetic proportional valve 20, is provided between the main pipe B constituting the head side circuit of the arm cylinder 14 and the tank 8. A relief valve 5 is arranged to regulate the minimum pressure of the main pipes A and B. Note that the valve opening degree of the electromagnetic proportional valve 20 is adjusted in accordance with a signal output from the control section 30. 40 is arm cylinder 1
4, that is, the pressure in the main pipe A, and outputs a signal P _A to the control section 30, that is, a pressure detector. Reference numeral 41 denotes pressure detection means, ie, a pressure detector, which detects the pressure on the head side of the arm cylinder 14, that is, the pressure in the main pipe B, and outputs a signal P _B to the control section 30.

The control unit 30 described above, as shown in FIG.
Lever signal X _L of operation lever 25, pressure detector 4
A multiplexer 30a that selectively outputs the analog signals P _A and P _B of 0 and 41, an A/D converter 30 D that converts the analog signal from the multiplexer 30 a into a digital signal, and outputs the digital signal; Central processing unit (CPU) that performs calculations
30c, a ROM memory 30d in which processing procedures, data conversion tables, etc. are stored, a RAM memory 30e in which numerical values, etc. during calculations by the CPU 30c are temporarily stored, a pump command value Q _P calculated by the CPU 30c, and The solenoid proportional valve command value Q _V is set to the pump discharge amount control device 35 and the solenoid proportional valve 2, respectively.
The output device 30f outputs to 0.

Note that FIG. 3 is a flowchart showing an overview of the processing procedure executed by the control unit 30, and FIGS. 4, 6, and 7 are flowcharts illustrating details of the processing procedure shown in FIG. , 9 shows the functional relationship, that is, lever signal X _L - pump command value
Q _P table, lever signal X _L - Solenoid proportional valve command value
Q _V (Q _VB ) table, lever signal X _L - solenoid proportional valve command value Q _V (Q _VA ) table, the contents of which are stored in advance in the above-mentioned ROM memory 30d.

Next, the operation of the embodiment configured as described above will be explained mainly according to the flowcharts shown in FIGS. 3, 4, 6, and 7.

First, in step A (block A) of the flowchart showing the outline of the processing procedure, the multiplexer 30a and the A/D converter 30b are operated, and the lever signal X _L of the operating lever 25 and the pressure detectors 40 and 4 are
1 signals P _A and P _B are input and temporarily stored in the RAM memory 30e.

Next, move on to step B (block B), and
Perform the calculation to obtain the pump tilting command value Q _P.
In this step B, as shown in detail in step B-1 of FIG. 4, the lever signal X _L is pumped according to the relationship of the X _L - Q _P table shown in FIG. Performs processing to convert into tilting command value Q _P. In addition, _XL shown in Figure 5 is (+)
The side shows the contraction direction of the arm cylinder 14, and the (-) side shows the extension direction.

Next, move to step C (block C) in FIG.
The direction of the load applied to the arm cylinder 14 is detected. In this procedure C, as shown in detail in FIG. 6, first in step C-1, the pressure in the pipe B, that is, the signal P _B which is the output of the pressure detector 41, and the head side pressure receiving area A _B of the arm cylinder 14 are measured. but
This is called by the CPU 30c, and the CPU 30c calculates the head side load F _B of the arm cylinder 14 from F _B =P _B ×A _B. Next, move on to step C-2,
The pressure in the pipe A, that is, the signal P _A that is the output of the pressure detector 41, and the rod side pressure receiving area A _A of the arm cylinder 14 are called, and the rod side load F _A of the arm cylinder 14 is calculated as follows: F _A = P _A ×A Required by _A. Next, proceeding to step C-3, the magnitude of the above-mentioned loads F _A and F _B is determined. If it is determined that F _A > F _B , that is, if it is determined that the arm cylinder 14 has a large load on the rod side, proceed to step C.
-4, the load direction flag F _S set on the RAM memory 30e is cleared (=0). Also,
If F _A ≧ F _B is determined in step C-3,
That is, if it is determined that the load on the head side of the arm cylinder 14 is large, the process moves to step C-5 and the load direction flag F _S is set (=1). That is, the pressure detectors 40, 41 and the control section 30
Detection means is configured to detect the direction of the load applied to the arm cylinder 14 by the CPU 30c and the like and output a signal.

Next, proceeding to step D (block D) in FIG. 3, a command to the electromagnetic proportional valve 20 is calculated. In this procedure D, as shown in detail in FIG. 7, it is determined whether the load direction flag F _S previously set in procedure D-1 is 1 or 0. If this determination is F _S =1, that is, if the load on the head side of the arm cylinder 14 is large, the process moves to step D-2, and the lever signal _XL is changed to _XL as shown in FIG.
Processing is performed to convert the solenoid proportional valve command value Q _V according to the relationship in the Q _V (Q _VB ) table. In addition, if it is determined in step D-1 that F _S =0, that is, the load on the rod side of the arm cylinder 14 is large, then step D-
Moving on to step 3, a process is performed to convert the lever signal X _L into an electromagnetic proportional valve command value Q _V according to the relationship of the X _L - Q _V (Q _VA ) table shown in Fig. 9 stored in the ROM memory 30d. .

Here, X _L - Q _V shown in Figures 8 and 9 above
(Q _VB ), _XL - Q _V (Q _VA ) tables will be explained. In both tables, when X _L < 0, Q _V is 0.
The setting is such that when X _L <0, that is, when the arm cylinder 14 is in the direction of extension, the amount of oil in the hydraulic circuit is insufficient. Therefore, since oil is supplied from the tank 8 to the check valve 6 or via the check valve 7, the electromagnetic proportional valve 20 must be closed. When X≧0, that is, the arm cylinder 14 is in the direction of contraction,
Since the oil in the hydraulic circuit becomes surplus, solenoid proportional valve 2
0 must be opened to allow excess oil to escape. In addition,
In this case, if the amount of oil flowing through the rod side of the arm cylinder 14 is q _P , and the amount of oil flowing out from the head side of the arm cylinder 14 due to this oil amount q _P is q _h , then approximately the oil amount q _V = q _h A command value Q _V for driving the electromagnetic proportional valve 20 is set so that -q _P flows into the tank 8 through the electromagnetic proportional valve 20.

Further, the reason why the value of Q _V is changed depending on the direction of the load applied to the arm cylinder 14 is as follows.
That is, when the load on the head side of the arm cylinder 14 is large, that is, when the load is supported on the head side of the arm cylinder 14, the speed of the arm cylinder 14 is determined by the oil passing through the electromagnetic proportional valve 20. If the opening degree of the electromagnetic proportional valve 20 is increased too much, the speed cannot be controlled. For this reason, in the table shown in Figure 8,
It is established so that the value of Q _V with respect to _XL is relatively small. At this time, if we strictly calculate Q _VB , it will be as follows.

If the cylinder speed is V, it is controlled by the bottom side of the arm cylinder, so V=(Q _P +Q _VB )/A _B. At this time, the inflow from the pump on the rod side is also Q _P , so V = Q _P /A _A , so (Q _P + Q _VB ) / A _B = Q _P /A _A , therefore, Q _VB = It is basically desirable to set Q _VB so that (A _B −A _A )・Q _P /A _A. However, this Q _VB can be changed slightly considering operability etc. Also, when the load on the rod side of the arm cylinder 14 is large, that is, when the load is supported by the rod side of the arm cylinder 14, the speed of the arm cylinder 14 can be controlled by the pump discharge amount. , V=Q _P /A _A. Therefore, if the opening degree of the electromagnetic proportional valve 20 is too small, pressure will build up in the pipe B due to the excess oil, and pressure will also build up on the rod side, that is, in the pipe A, through the arm cylinder 14.
A large amount of horsepower is required to drive the motor, resulting in wasted energy. For this reason, in the table shown in Figure 9, the value _{of Q V with} respect to We make it easy.

After the above procedure D is completed, the process moves to procedure E (block _{E )} shown in FIG. , and output to each of the electromagnetic proportional valves 20. Then, return to step A. Control unit 30
The process is always repeated from procedure A to procedure E.

In the embodiment configured in this manner, a flushing valve is not provided, and the opening degree of the electromagnetic proportional valve 20 is adjusted according to the functional relationship set in the ROM memory 30d of the control unit 30 illustrated in FIGS. 5, 8, and 9. In other words, the amount of excess oil flowing through the electromagnetic proportional valve is adjusted, and thereby the operating speed of the arm cylinder 14 is adjusted to the operating speed of the operating lever 2.
In other words, the speed of the arm cylinder 14 can be prevented from changing regardless of changes in the force applied to the arm cylinder 14 due to changes in the shape of the arm. Good operability is achieved without slowing down due to rapid acceleration or free fall of the arm.

Further, when the arm cylinder 14 is retracted, when the arm cylinder 14 is supporting the load on the head side, fine operation can be achieved by making the opening degree of the electromagnetic proportional valve 20 relatively small; When the cylinder 14 is supporting the load on the rod side, energy waste can be prevented by making the opening degree of the electromagnetic proportional valve 20 relatively large.

In the above embodiment, the arm cylinder 14 was used as an example of a single-rod cylinder, but the present invention is not limited thereto, and can be applied to any cylinder having a single-rod cylinder to which a force that changes in magnitude and direction can be applied. be.

〔Effect of the invention〕

Since the hydraulic drive device of the present invention is configured as described above, it is possible to prevent the speed of the single rod cylinder from changing regardless of changes in the force applied to the single rod cylinder, and therefore, the operation control is improved compared to the conventional one. In addition, it is possible to realize fine operation when a load is applied to the head side when a single rod cylinder is contracted, and it is possible to prevent pressure confinement in the main pipe line when a load is applied to the rod side during the same contraction. This has the effect of suppressing energy waste.

[Brief explanation of the drawing]

1 to 9 are explanatory diagrams showing one embodiment of the hydraulic drive device of the present invention, FIG. 1 is a circuit diagram showing the main configuration, and FIG. 2 is a control section provided in the circuit shown in FIG. 1. FIG. 3 is a flowchart showing an overview of the processing procedure executed by the control unit shown in FIG. 2, and FIGS. 4, 6, and 7 are respectively the processing steps shown in FIG. 3. 5, 8, and 9 are explanatory diagrams illustrating the functional relationships stored in the control unit shown in FIG. 3, and FIG. 10 is a flowchart illustrating the details of the conventional hydraulic drive system. FIG. 11 is a schematic side view of a hydraulic excavator equipped with the hydraulic drive device shown in FIG.
Figure 2a shows the 11th arm cylinder shown in Figure 10.
A characteristic diagram showing the operating speed corresponding to the angle θ shown in the figure, Fig. 12 b, c, and d are the angle θ shown in Fig. 11.
FIG. 4 is an explanatory diagram illustrating the form of the arm portion when the angles are 50°, 90°, and 130°, respectively. 1... Variable capacity hydraulic pump, 8... Tank, 1
4...Arm cylinder (single rod cylinder), 2
0...Solenoid proportional valve, 25...Operation lever, 30...
...Control unit, 30a...Multiplexer, 30b...
...A/D converter, 30c...Central processing unit (CPU), 30d...ROM memory, 30e...
RAM memory, 30f... Output device, 35... Electric/hydraulic pump discharge amount control device, 40, 41...
pressure detector.

Claims (1)

[Claims] 1 A variable displacement hydraulic pump whose discharge amount is controlled according to a signal output from an operating lever, and a single rod cylinder whose drive is controlled by pressure oil discharged from the variable displacement hydraulic pump, and this single rod cylinder. In a hydraulic drive device in which a rod cylinder and the variable displacement hydraulic pump form a closed circuit or a semi-closed circuit, a valve for controlling the flow rate is provided between the head side circuit of the single rod cylinder and the tank, and a valve is provided between the head side circuit of the single rod cylinder and the tank. A detection means is provided for detecting the direction of the load and outputting a signal, and when the single rod cylinder is contracted, the discharge amount of the variable displacement hydraulic pump increases in accordance with an increase in the value of the signal output from the operating lever. control like this,
and controlling the flow rate of the valve to increase in accordance with an increase in the value of the signal output from the operating lever, and detecting that the load on the head side of the single rod cylinder is greater than the load on the rod side. control means for controlling the flow rate of the valve when detecting that the flow rate of the valve is smaller than the flow rate when the detection means detects that the load on the rod side of the single rod cylinder is larger than the load on the head side; A hydraulic drive device characterized by being provided with.