JPH0754147B2 - Hydraulic drive mechanism controller - Google Patents

Description

The present invention relates to a hydraulic drive mechanism for driving a load connected to a hydraulic motor by connecting a variable displacement hydraulic pump and a hydraulic motor in a closed circuit. The present invention relates to a hydraulic drive mechanism control device for controlling.

[Conventional technology]

In recent years, in hydraulic machines such as hydraulic shovels and hydraulic cranes, a closed hydraulic circuit with less circuit loss tends to be used as the hydraulic circuit. In such a hydraulic closed circuit, the control of the discharge amount of both tilt variable displacement hydraulic pumps (hereinafter referred to as hydraulic pumps) forming the hydraulic closed circuit is combined with the pressure cutoff control for preventing the relief loss. The control means and the means for controlling only the driving pressure are commonly used. By the way, these means can control only either acceleration (force) or speed of an actuator driven by a hydraulic pump, but not both, by an operation signal from an operation lever. However, when operating an operating lever to drive the hydraulic machine, it is usual for the operator of the hydraulic machine to sensuously control both acceleration (force) and speed. It shouldn't be.

Therefore, a control means for controlling both acceleration (force) and speed by an operation signal to eliminate the above-mentioned dissatisfaction is disclosed in JP-A-58-7276.
No. 2 is disclosed. This will be described with reference to the drawings.

FIG. 6 is a system diagram of a conventional hydraulic drive mechanism controller.
In the figure, 1 is a prime mover such as an engine, 2 is a hydraulic pump driven by the prime mover 1, 2a is a variable displacement mechanism of the hydraulic pump 2 (hereinafter, this is represented by a swash plate), and 2b is a swash plate.
It is the operation mechanism of 2a. The operating mechanism 2b operates the swash plate 2a and outputs a signal Y corresponding to the position of the swash plate 2a. Three
Is a hydraulic motor connected to the hydraulic pump 2 by the main circuits A and B, and 4 is a load driven by the hydraulic motor 3. There are various loads 4 such as an upper swing body of a hydraulic shovel. Reference numeral 5 is a charge pump, 6 is a low pressure relief valve of a charge circuit, 7a and 7b are check valves connecting the charge circuit and the main circuits A and B, and 8a and 8b are crossover relief valves. Reference numeral 9 denotes an operation lever of the load 4, which outputs an operation signal X _L proportional to the operation amount thereof. 10a, 10b respectively detect the main circuit A, the pressure of B, the pressure signal P _a which is proportional to the detected pressure, and outputs the P _b. Reference numeral 11 is an electrohydraulic servo valve that controls the operating mechanism 2b by controlling the supply of pressure oil to the operating mechanism 2b, and 12 is a pilot pump that serves as a hydraulic source of the operating mechanism 2b. 13 inputs the respective signals Y, X _L, Pa, Pb, and executes a predetermined operation, the control on the basis of these values, electro-hydraulic Sapo valve
It is a control device that outputs a control signal i to 11, and is configured by a microcomputer. The structure of the controller 13 is shown in FIG.

FIG. 7 is a system configuration diagram of the control device 13. In the figure, 13
a is a multiplexer that switches and inputs each signal Y, _XL , Pa, Pb, 13b is an A / D converter that converts these input signals into digital signals, 13c is a calculation, control procedure and functions necessary for calculation ROM (Read Only Memory) for storing etc., 13d
Is a RAM (random access memory) for temporarily storing input signals, calculation results, etc., 13e is a CPU (central processing unit) for performing calculation and control according to the processing procedure stored in the ROM 13c, and 13f is a calculation It is a driver circuit that outputs a control signal (current signal) i obtained by control.

Next, the operation of the apparatus shown in FIG. 6 will be described with reference to the flow chart shown in FIG. Here, it is assumed that the hydraulic closed circuit shown in FIG. 6 is in a state in which pressure oil is discharged from the hydraulic pump 2 to the main circuit A side and the hydraulic motor 3 is driven. The tilt Y of the swash plate at this time is (+). First, the controller 13 includes the multiplexer 13a and the A / D converter 13
Each signal _XL , Pa, Pb, Y is read via b (step S-10
1). Next, the signals Pa and Pb are taken out and the pressures between the main circuits A and B are compared (step S-102). In this case, since the pressure on the main circuit A side is equal to or higher than the pressure on the main circuit B side (Pa ≧ Pb), the process proceeds to step S-103, and the signal Pa at that time is set as the representative pressure signal P. Next, it is determined whether the swash plate tilt command value X calculated and output in the procedure one cycle before is positive or negative (step S-104). in this case,
The command value X is positive because the pressure oil continues to be discharged to the main circuit A side (discharge amount Q _p ). On the contrary, if the command value X of the previous cycle is positive, the pressure oil is being discharged to the main circuit A side, and P _a > P _b , so that a positive load (load) is applied to the motor 3. It is possible to determine that a state in which a force is acting on 4) is acting.

If so, the process proceeds to step S-105. In step S-105, obtains the target pressure P _c of the main circuit A side corresponding to the signal X _L. The target pressure P _c is obtained by taking out the value previously stored in the ROM 13c according to the characteristic shown in FIG. In FIG. 9, the horizontal axis signal X _L is the vertical axis target pressure P _c is are convex. That is, the target pressure P _c is the signal X _L
Is expressed as a function [f _pcr (X _L )] of. The target pressure P _c varies between the values P _crmin and P _crmax in proportion to the signal X _L. When the target pressure _Pc is obtained, the representative pressure P determined in step S-103 is subtracted from the target pressure _Pc to obtain the pressure deviation P '(step S-110).

Next, the swash plate tilt increment value ΔX required to eliminate this pressure deviation P ′ is obtained. (Procedure S-111). This can be obtained by taking out the value stored in the ROM 13c according to the characteristic shown in FIG. In FIG. 10, the horizontal axis indicates the pressure deviation P ′, and the vertical axis indicates the increment value ΔX. The increment value ΔX is expressed as a function [f _ΔX (P ′)] of the deviation P ′, and within the predetermined range of the deviation P ′, the value + ΔX _O and Δ
Change proportionally with X _O. As is apparent from the calculation of step S-110 and FIG. 10, when the pressure P _a on the main circuit A side is lower than the target pressure P _c , the deviation P ′ is positive, so the increment value ΔX is also positive, and the pressure When P _a is larger than the target pressure P _c , the deviation P ′ becomes negative and the increment value ΔX also becomes negative.

Then, the process moves to Step S-112, calculates a deviation Z between the operation signal X _L and the swash plate tilt command value X output in the previous cycle of the operation lever 9 entered in step S-101, then, Deviation Z
Is positive or negative (step S-113).
If the deviation Z is positive, the command value X of the previous cycle is set to the step S.
-111 is added to calculate the new swash plate tilt command value X for this cycle (step S-11
4) If the deviation Z is negative, the swash plate tilt command value X is calculated by subtracting the swash plate tilt increment value ΔX obtained in step S-111 from the command value X in the previous cycle (procedure). S-11
Five). The new swash plate tilt command value X obtained in step S-114 or step S-115 is compared with the swash plate position (swash plate tilt amount) Y, and the operation signal i for reducing the difference between the two is output to the driver circuit 13f.
To the electrohydraulic servo valve 11 via. This allows
Both acceleration (force) and velocity will be controllable.

Since the above steps S-101 to S-120 are executed once per ΔT time, the time change rate of the swash plate tilt command value is dx.
/ dt ≒ ΔX / ΔT becomes, when the discharge pressure of the hydraulic pump 2 (the main circuit pressure side A) P _a becomes higher swash plate speed of the hydraulic pump 2 is reduced, abnormal rise of the discharge pressure is prevented. Further, in the steps S-112~S-120, by comparing the lever operation signal X _L and the swash plate tilt command value X, since switching the sign of the tilting increment ΔX by the sign of the deviation Z , the maximum value of the command value X is limited by the operation signal X _L.

On the other hand, as described above, when the operation lever 9 is returned to the neutral position direction from the state in which the hydraulic oil is discharged from the hydraulic pump 2 to the main circuit A side and the hydraulic motor 3 is operating in the positive load (during braking). Consider a case where the hydraulic motor 3 receives a force due to the inertia of the load 4 or the load 4. In this case, since the pressure on the main circuit B side becomes higher than the pressure on the main circuit A side, the process proceeds to steps S-101, S-102, S-106, and the pressure P is set as the representative pressure P.
_b is selected. Next, in step S-107, it is determined whether the swash plate tilt command value X output in the previous cycle is positive or negative. In this case, since the swash plate 2a is on the side that discharges the pressure oil to the main circuit A side, that is, the (+) side, X> o. Therefore, the procedure proceeds to step S-109, and the target pressure P _c is set as the brake pressure P _CB . After that, steps S-110 to S-120 are executed.

FIG. 11 shows the pressure P of the main circuits A and B when the above control is executed.
_a, it is a graph showing the relationship between P _b, and the discharge flow rate Q _P of the hydraulic pump. In the figure, the horizontal axis represents the main circuit pressure, and the vertical axis represents the discharge flow rate. When a positive load is applied to the hydraulic motor 3, that is, in the first and third quadrants of the figure, the maximum values of the circuit pressure and the hydraulic pump discharge flow rate are both limited by the value of the operation signal X _L of the operation lever 9. It On the other hand, when a negative load is applied to the hydraulic motor 3, that is, in the second and fourth quadrants of the figure, the maximum value of the hydraulic pump discharge flow rate is the same as in the case of a positive load.
Limited by X _L. However, as is apparent from the flow charts and figures above, the maximum value of circuit pressure is
It is limited to a predetermined value P _CB regardless X _L.

In the above configuration, when the load 4 is accelerated, the acceleration (force) and the speed of the load are controlled according to the operation amount of the operation lever according to the characteristics of the first quadrant or the third quadrant of the graph shown in FIG. Therefore, it is possible to obtain a good operational feeling for the operator of the machine or device.

[Problems to be Solved by the Invention]

However, at the time of deceleration of the load 4, as described above, the discharge amount Q _P of the hydraulic pump 2 can be limited by the characteristics of the second quadrant or the fourth quadrant, but the deceleration (brake force) pressure P _CB becomes a constant value. It is controlled and cannot be restricted. Therefore, no matter which speed range the hydraulic motor 3 is decelerated from, the operating lever 9
A constant braking force is always applied regardless of the operation amount of. Such a phenomenon is a phenomenon that deviates from the operation feeling of the operator who wants to obtain a braking force according to the amount of returning the operation lever 9 in the neutral direction. Also, its pressure P _CB
Is usually set to the maximum value of the desired braking force, so even if you want to apply the braking force gently, the maximum braking force will act, and the operability will not only deteriorate significantly. If there is a load that easily collapses, there is a danger that the load will collapse at the moment when the braking force is applied.

The object of the present invention is to solve the above-mentioned problems in the conventional technology,
An object of the present invention is to provide a hydraulic drive mechanism control device that can obtain good operability that matches the operation interval of the operator even during deceleration and that can perform a gentle stop.

[Means for Solving the Problems]

In order to achieve the above object, the present invention provides an operation for detecting an operation amount of an operation lever in a hydraulic drive mechanism in which a variable displacement hydraulic pump driven by a prime mover and a hydraulic motor connected to a load are connected by a hydraulic closed circuit. A lever detector, a tilt amount detector that detects the tilt amount of the variable displacement hydraulic pump, a pressure detector that detects the pressure of both main circuits of the hydraulic closed circuit, and a suction side pressure of the variable displacement hydraulic pump. And a discharge side pressure are compared with each other. When the suction side pressure is determined to be high by the comparison means, a target brake pressure is obtained according to the output signal of the operation lever detector. Brake pressure take-out means, correction value take-out means for obtaining a correction value for correcting the brake pressure according to a tilt command value of the variable displacement hydraulic pump, and the brake pressure Correction means for correcting the target brake pressure with a correction value, and tilt control for controlling tilt of the variable displacement hydraulic pump based on the target value obtained by the correction means and the detection value of the tilt amount detector. And means are provided.

[Action]

The suction side pressure and the discharge side pressure of the variable displacement hydraulic pump are compared, and when it is determined that the suction side pressure is high, the target brake pressure corresponding to this is obtained based on the output signal of the operation lever detector. The target brake pressure is small when the output signal is large, and is large when the output signal is small.
Next, based on the tilt command of the variable displacement hydraulic pump at that time, a brake pressure correction value corresponding to this is obtained. This brake pressure correction value is small when the absolute value of the tilt command is large, and is large when the absolute value of the tilt command is small. The corrected target value is obtained by subtracting the brake pressure correction value from the target brake pressure. The tilt of the variable displacement hydraulic pump is controlled based on the corrected target value and the detected value of the tilt amount detector.

[Examples] Hereinafter, the present invention will be described based on illustrated examples.

FIG. 1 is a system diagram of a hydraulic drive mechanism control device according to an embodiment of the present invention. In the figure, the same parts as those shown in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. 13 'is a control device. The control device 13 'is different from the control device 13 shown in FIG. 6 in part of its calculation and control means. The other parts of the hydraulic drive mechanism controller are the same as those shown in FIG.

The operation of this embodiment will be described with reference to the flow chart shown in FIG. In the hydraulic closed circuit, when the hydraulic pump 2 discharges pressure oil to the main circuit A side (or the main circuit B side) and the hydraulic motor 3 is driven by this pressure oil, the processing procedure is shown in FIG. The procedure is the same, and in FIG. 2, the same steps as those in FIG. 7 are designated by the same reference numerals.
Now, consider a case where the hydraulic pump 2 discharges pressure oil to the main circuit A side and the hydraulic motor 3 drives the load 4 and then the operation lever 9 is returned to the neutral direction in order to apply braking. In this case, since the brake pressure is generated on the main circuit B side, the processing of steps S-101, S-102, S-106, and S-107 is executed, and since X> o, the processing is performed in step S. Move on to -134.

In step S-134, taken out an operation signal X _L, determine the target braking pressure P _CB as a function of the value X _L [f _{PCB 2} (X _L)]. The target brake pressure P _CB will stores the characteristics shown in FIG. 3 (b) in ROM, is obtained by taking out a value corresponding to the value X _L from ROM. In Fig. 3 (b), the horizontal axis is the signal
X _L , and the vertical axis is the target brake pressure P _CB .

The above state is when the signal _XL is (+) (hydraulic pump 2
Is discharging the pressure oil to the main circuit A side), the pressure P _b on the main circuit B side is higher than the pressure X _a . in this case,
Target braking pressure P _CB is in proportion to the signal X _L changes from the pressure P _CBmin to a pressure P _CBmax, as signal X _L is close to 0, that is, as the operating lever 9 is returned to near the neutral position, the target braking pressure Grows. Then, the operating lever 9 is operated on the opposite side beyond the neutral position, the signal X _L is (-) becomes a (the reversed lever), the target braking pressure P _CB is the maximum pressure P _CBmax constant. Thus, when the operator slightly returns the operation lever 9 to the neutral position to apply a small braking force, the target brake pressure becomes a small value, and the operation lever 9 is largely returned to the neutral direction to apply a large braking force. Then, the target brake pressure becomes a large value.

When the target brake pressure _PCB is obtained, the process _proceeds to step S-1.
Move to 35. In step S-135, the correction value P _of is obtained as a function [f _pof2 (X)] of the swash plate tilt command value X output in the previous cycle. This correction value P _of is in the stopped state (X =
It is a value for reducing the target brake pressure as it approaches 0) to obtain a gentle stop. The correction value P _of is obtained by storing the characteristic shown in FIG. 4 (b) in the ROM and extracting the value corresponding to the value X from the ROM. In FIG. 4B, the horizontal axis shows the swash plate tilt command value X, and the vertical axis shows the correction value P _of . In this case, since the hydraulic pump 2 is in the state of discharging pressure oil to the main circuit A side, the command value X is (+), and the correction value P _of is greater than the command value X by the value P. _Decrease from _ofmax to 0. The value 0 is the point where the absolute value of the command value X is the maximum value X _max .

Thus the correction value P _of in the obtained then taken out of the target Pureki pressure P _CB determined previously, a target of the target braking pressure P _CB by subtracting the correction value P _of the main circuit B side The pressure P _C is calculated (step S-136). As can be seen from this subtraction process, when the command value X is large, the target brake pressure
When the subtracted value from P _CB is small and the target pressure P _C is close to the target brake pressure P _CB , the required braking force can be obtained, and conversely, when the command value X is small (close to the stopped state). In the case), the subtracted value from the target brake pressure P _CB is large, and the target pressure P _C becomes a value that is lower than the target brake pressure P _CB to some extent, and thus a sudden stop due to a large braking force can be alleviated.

When the target pressure P _C (brake pressure in this case) is obtained by the procedure S-136, the procedure S-110 to the procedure S-120 will be performed thereafter.
Is executed, the procedure returns to step S-101 again, and the same procedure is repeated. Contrary to the above example, the process when the hydraulic oil is discharged from the hydraulic pump 2 to the main circuit B side and the operation lever 9 is returned to the neutral position direction from this state also follows the above process. In this case, the processing is from step S-102 to step S
-103, S-104, S-131, S-132, S-133, executed,
The characteristics used in step S-131 are shown in FIG. 3 (a).
The characteristics used in step S-132 are shown in FIG. 4 (a). Further, the same processing as described above is performed when the hydraulic motor 3 such as traveling on a slope is rotated by inertial force.

FIGS. 5A to 5E are time charts for explaining the operation of the apparatus of this embodiment during deceleration. At time t ₀ , when the operation lever 9 that was operated rapidly until then is returned to the neutral position to stop the machine and the device (in the case of sudden stop), the operation signal as shown in FIG. X _L becomes 0. In response to this, the swash plate tilt command value X also tries to return to 0 as shown in FIG. 5 (b), the suction side pressure of the hydraulic pump 2 increases, and the braking force starts to work. At the same time, the procedure S-
131 or target brake pressure P _CB obtained in step S-134
Since X _L = 0, according to the characteristics of FIGS. 3 (a) and 3 (b), the maximum value P _CBmax is obtained as shown in FIG. 5 (c), and this value is X _L = 0. It is kept constant as long as there is. On the other hand, since the swash plate tilt command value X is slide into reduced as shown in FIG. 5 (b) according to X _L = 0, steps S-132 or Step S
The correction value P _of obtained in −135 increases according to the characteristics shown in FIGS. 4 (a) and 4 (b), as shown in FIG. 5 (d). Alternatively, the target pressure P _C (target pressure on the suction side of the hydraulic pump 2) obtained in step S-136 gradually decreases from time t ₀ to stop time t ₁ as shown in FIG. 5 (e). The braking force becomes gentle as you approach the stop.

Thus, in the present embodiment, the target brake pressure is obtained according to the predetermined characteristic based on the operation signal, and the correction value is obtained according to the predetermined characteristic based on the swash plate tilt command value.
Since the target pressure is obtained by subtracting the correction value from the target brake pressure, the greater the braking force, the greater the braking force as the operating lever is returned during deceleration. You can get sex. Further, when the operation amount for returning the operation lever is small, the brake pressure becomes low, so that the operability at the time of fine operation is improved.
Further, even when the operating lever is slightly returned to the neutral direction to perform the braking operation at the time of high speed driving, the braking force becomes small, and the risk of collapse of the load is eliminated. Furthermore, since the brake pressure is reduced as the vehicle is stopped,
You can get a gentle stop. Also, load 3 during deceleration
The energy possessed by the engine can be recovered by a hydraulic pump to rotate the prime mover 1, and thus the energy required for driving auxiliary machinery such as a generator driven by the prime mover 1 and the energy for internal loss of the prime mover itself can be obtained. Can be supplemented.

〔The invention's effect〕

As described above, in the present invention, when the suction side pressure of the hydraulic pump is higher than the discharge side pressure, the target brake pressure is obtained based on the operation signal of the operation lever, and the brake pressure is determined based on the tilt command of the hydraulic pump. The correction value is calculated, the target brake pressure is corrected by the brake pressure correction value, and the tilt of the hydraulic pump is controlled based on the target value and tilt amount obtained by this correction. Good operability that matches the feeling can be obtained, and the drive can be stopped gently. In addition, the energy that the load has during deceleration can be recovered by the hydraulic pump and the prime mover can be rotated. This enables the energy required to drive auxiliary machinery such as a generator driven by the prime mover and the internal loss of the prime mover itself to be consumed. Energy can be supplemented.

[Brief description of drawings]

FIG. 1 is a system diagram of a hydraulic drive mechanism control device according to an embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation of the control device shown in FIG. 1, and FIGS. 3 (a) and 3 (b) are Target brake pressure characteristic diagram, FIGS. 4 (a) and (b) are correction value characteristic diagrams, and FIGS. 5 (a), (b), (c), (d), and (e) are FIG. 6 is a time chart for explaining the operation of the control device shown in FIG. 6, FIG. 6 is a system diagram of a conventional hydraulic drive mechanism control device, FIG. 7 is a system configuration diagram of the control device shown in FIG. 6, and FIG. 8 is FIG. 9 is a characteristic chart of target pressure, FIG. 10 is a characteristic chart of swash plate tilt increment value, and FIG. 11 is a characteristic chart of pressure and flow rate. 2 ... hydraulic pump, 2a ... swash plate, 2b ... operating mechanism, 3 ...
… Hydraulic motor, 4 …… Load, 9 …… Operating lever, 10a, 10
b …… Pressure detector, 11 …… Electro-hydraulic servo valve, 13 ′ ……
Control device.

Claims (1)

[Claims] 1. A variable lever hydraulic pump driven by a prime mover and a hydraulic drive mechanism in which a hydraulic motor connected to a load is connected by a hydraulic closed circuit, and an operating lever detector for detecting the operating amount of an operating lever, and the variable. A displacement amount detector that detects the displacement amount of the displacement hydraulic pump, a pressure detector that detects the pressure of both main circuits of the hydraulic closed circuit, and a suction side pressure and a discharge side pressure of the variable displacement hydraulic pump. Comprising a comparison means for comparing, when the suction side pressure is determined to be high by this comparison means, a brake pressure take-out means for obtaining a target brake pressure according to the output signal of the operation lever detector, A correction value extracting means for obtaining a correction value for correcting the brake pressure according to a tilt command value of the variable displacement hydraulic pump, and the target by the brake pressure correction value. And correction means for correcting the rake pressure,
A hydraulic drive mechanism control comprising: tilting control means for controlling tilting of the variable displacement hydraulic pump based on the target value obtained by the correcting means and the detection value of the tilting amount detector. apparatus.