JPH0331915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of controlling a variable displacement pump.

(Prior Art) A conventional control device for a variable displacement pump of a hydraulic excavator will be explained with reference to FIGS. 1 and 2.
2 and 3 are variable displacement pumps; 4 is a 1 that drives the variable displacement pumps 1, 2, and 3 via a gear train mechanism 5;
There are two prime movers. The variable displacement pump 1 drives a right travel motor, a boom cylinder, and a bucket cylinder. In FIG. Of these, illustrations of the other cylinders and the right travel motor are omitted. Further, the variable displacement pump 2 drives a right travel motor, a boom cylinder, and an arm cylinder, but illustration of these motors and cylinders is omitted in FIG. 1. In addition, the variable displacement pump 3
drives the swing motor 13 in FIG. Further, 6 in FIG. 1 is a switching valve installed in the hydraulic circuit between the variable displacement pump 1 and the cylinder 9, 7 is a detector for the switching valve 6, 8 is a manual operation lever for the switching valve 6, In FIG. 2, 10 is a switching valve installed in the hydraulic circuit between the variable displacement pump 3 and the swing motor 13, 11 is a detector for the switching valve 10, and 12 is a manual operation lever for the switching valve 10. be. Also, 1 in Figure 1
4 is the swash plate of the variable displacement pump, 15 is its rotation center, and the swash plate 14 adjusts the discharge flow rate of the variable displacement pump 1 to "small" as its inclination angle θ approaches vertical, and becomes horizontal. Accordingly, the discharge flow rate of the variable displacement pump 1 is adjusted to be "large". Further, 16 and 17 are swash plate tilting servo cylinders arranged on the left and right sides of the rotation center 15, 39 is a sleeve, 18 is a spool, 1
9 is a spool drive device, 20, 21 are springs, 22, 23 are pistons and cylinders that change the preset amount of the springs 20, 21, 24 is a spring, 25 is a drain, 26, 27, 28 are hydraulic circuits, FIG. 29 is the variable displacement pump 3
, 30 is its rotation center, 31 and 32 are swash plate tilting servo cylinders arranged on the left and right sides of the rotation center 30, 33 is a sleeve, 34 is a spool, 35
is the spool drive device, 36 and 37 are the springs,
38 is a drain, and as is clear from the above explanation, the control device for the variable displacement pump 3 of the swing motor 13 is similar to the control device for the variable displacement pump 1, except that there is no piston or cylinder that changes the preset amount of the spring. . Further, the control device for the variable displacement pump 2 is similar to the control device for the variable displacement pump 1, except that the driven loads are changed to the left traveling motor, the boom cylinder, and the arm cylinder.

When the swash plate 14 of the variable displacement pump 1 is discharging pressure oil in equilibrium at a certain position, when the discharge pressure increases, the spool drive device 1 is discharged from the hydraulic circuit 27.
The pressure applied to spring 9 increases, causing spring 20,
The spool 18 moves to the left due to the force relationship with the drain 25 of the swash plate tilting servo cylinder 17.
are connected. On the other hand, servo cylinder 1 for tilting the swash plate
6 is supplied with pressure oil from the variable displacement pump 1, the swash plate 14 tilts counterclockwise (vertically) about the rotation center 15, and the discharge flow rate of the variable displacement pump 1 decreases. . The swash plate 14 and the spool 39 are connected, and when the swash plate 14 tilts in the counterclockwise direction (vertical direction), the sleeve 39
The servo cylinder 17 for tilting the swash plate is also driven to the left.
Communication between the drain 25 and the drain 25 is cut off, and the swash plate 14 stops.

Contrary to the above, when the discharge pressure of the variable displacement pump 1 decreases, the pressure applied to the spool drive device 19 from the hydraulic circuit 27 decreases, and the spool 18 moves to the right due to the force relationship with the springs 20 and 21. After moving, the hydraulic circuits 26 and 28 are connected. Therefore, the swash plate tilting servo cylinder 17 differentially moves in the extension direction, and the swash plate 14 tilts clockwise (horizontally) about the rotation center 15, causing the variable displacement pump 1
The discharge flow rate increases. At this time, the sleeve 39
The swash plate 14 also moves to the right, communication between the hydraulic circuits 26 and 28 is cut off, and the swash plate 14 stops. During the above control, the relationship between the discharge pressure and the discharge flow rate is
Due to the action of 0 and 21, it becomes like the broken line A in FIG. Further, the inclination angle θ of the swash plate 14 can be changed by a manual operation lever 8 of the switching valve 6. That is, the operating amount of the switching valve 6 is detected by the detector 7, and the detector 7 outputs a pressure signal according to the operating amount. This pressure signal is applied to spool drive 19 to move spool 18 and tilt swash plate 14. At this time, the discharge pressure and discharge flow rate are controlled so as not to exceed broken line A in FIG. The above control action is the same for the variable displacement pumps 2 and 3. Further, when the discharge pressure of the variable displacement pump 3 is low and the horsepower consumption of the variable displacement pump 3 is low, the force relationship between the discharge pressure of the variable displacement pump 3 and the spring 24 shown in FIG.
moves to the right, and the spool 18 further moves to the right via the springs 20 and 21, and the hydraulic circuit 2
6 and 28 are connected, and the swash plate tilting servo cylinder 1
7 operates in the extension direction, and the swash plate 14 rotates at the center of rotation 15.
It tilts clockwise (horizontally) around the center, the discharge flow rate of the variable displacement pump 1 increases, and the surplus horsepower of the variable displacement pump 3 is used by the variable displacement pump 1.

On the other hand, when the discharge pressure of the variable displacement pump 3 is high and the horsepower consumption of the variable displacement pump 3 is large, the piston 22 moves to the left due to the force relationship between the discharge pressure of the variable displacement pump 3 and the spring 24. The spool 18 further moves to the left via the spring 20, and the swash plate tilting servo cylinder 17 and the drain 25 are connected. On the other hand, since pressure oil is supplied to the servo cylinder 16 for tilting the swash plate from the variable displacement pump 1, the swash plate 14 tilts counterclockwise (vertically) about the rotation center 15, causing the variable displacement The discharge flow rate of the pump 1 decreases. In other words, the total horsepower consumption of the three variable displacement pumps 1, 2, and 3 is controlled within the range of the output horsepower of the prime mover 4.

(Problem to be Solved by the Invention) In the conventional control device for a variable displacement pump of a hydraulic excavator shown in FIGS. 1 and 2, the constant horsepower line (discharge pressure x discharge flow rate = constant) of the variable displacement pump is
Although it should be hyperbolic as shown in Figure B (dotted chain line), the springs 20 and 21
36 and 37, and it becomes the broken line A, so the output horsepower of the prime mover 4 is not effectively utilized by the difference between the hyperbola B and the broken line A, which is uneconomical. Also, to simplify the structure,
The horsepower consumption of the variable displacement pump 3 of the swing motor 13 is represented by the discharge pressure (the actual horsepower consumption is
(It is expressed by discharge pressure x discharge flow rate, so it is necessary to take the discharge flow rate into account.) Therefore, when the discharge pressure is high, even if the discharge flow rate is low, the horsepower will be high.
I regard it as such. Furthermore, since the factor of the rotational speed of the prime mover 4 is not included, there is a problem that the horsepower control changes depending on the rotational speed of the prime mover 4.

The present invention has been proposed in view of the above-mentioned problems, and an object thereof is to provide a control method for a variable displacement pump that can improve efficiency and operability.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for driving a load through one prime mover and a plurality of variable displacement pumps driven by the same prime mover. When the variable displacement pump in the section is started, pressure control is performed to adjust the flow rate to keep the discharge pressure of the variable displacement pump constant. After that, the flow rate is controlled to keep the horsepower consumption constant, and horsepower control is performed. The flow rate of the other variable displacement pumps is set by the smaller flow rate set value of the flow rate set value for the same pressure control and the flow rate set value for the same horsepower control.

Further, the present invention provides a method for driving a load through one prime mover and a plurality of variable displacement pumps driven by the same prime mover, and the swash plate angle of some of the variable displacement pumps. is detected by the swash plate angle detector, the discharge pressure of the variable displacement pump is detected by the discharge pressure detector, and the rotation speed of the prime mover is detected by the rotation speed detector, and these detected values are sent to the computing unit of the computing unit. , calculate the horsepower consumption of some of the variable displacement pumps based on these detected values, subtract the horsepower consumption of some of the variable displacement pumps from the output horsepower of the prime mover determined by the rotation speed of the prime mover, and calculate the horsepower of the other variable displacement pumps. The remaining power of the prime mover can be calculated by calculating the usable horsepower of the variable displacement pump, and calculating the upper limit of the flow rate that can be discharged by the other variable displacement pumps from this and the discharge pressure of the other variable displacement pumps mentioned above. This residual power is then consumed by the other variable displacement pump.

(Function) As described above, the variable displacement pump control method of the present invention is applicable to driving a load via one prime mover and a plurality of variable displacement pumps driven by the same prime mover. When the variable displacement pump starts, pressure control is performed to adjust the flow rate to keep the discharge pressure constant, and then the flow rate is controlled to keep the horsepower consumption constant, horsepower control is performed, and the same pressure control is performed. The flow rate of the other variable displacement pumps is set by the smaller flow rate setting value between the flow rate setting value of the engine and the flow rate setting value of the same horsepower control.

Among the variable displacement pumps, the swash plate angle of some of the variable displacement pumps is determined by a swash plate angle detector, the discharge pressure of the same variable displacement pump is determined by a discharge pressure detector, and the rotational speed of the prime mover is determined by a rotational speed detector. According to
These detected values are sent to the computing unit of the computing device, and based on these detected values, the horsepower consumption of some of the variable displacement pumps mentioned above is calculated, and from the output horsepower of the prime mover determined by the rotation speed of the prime mover. By subtracting the horsepower consumption of some of the variable displacement pumps mentioned above, the usable horsepower of the other variable displacement pumps is calculated, and from this and the discharge pressure of the other variable displacement pumps, the amount of horsepower that can be discharged by the other variable displacement pumps is calculated. By calculating the upper limit value of the flow rate, the residual power of the prime mover is determined, and this motive force is consumed by the other variable displacement pump.

(Example) Next, the variable displacement pump control method of the present invention will be explained with reference to FIG. 4, which shows an example of a configuration used for implementing the method. In FIG. 4, in order to simplify the explanation, this embodiment will be described as a three-pump system similar to the conventional example. 1, 2, 3 are three variable displacement pumps,
4 is connected to the variable displacement pump 1 via the gear train mechanism 5.
2 and 3; a rotation speed detector 106 detecting the rotation speed of the prime mover 4;
7, 108, 109 are the variable displacement pumps 1,
A discharge pressure detector for detecting the discharge pressure of 2 and 3, 1
19 is the manual operation lever for the right side travel motor, 120
is a manual operating lever for the bucket cylinder, 121 is a manual operating lever for the boom cylinder, 122 is a manual operating lever for the left travel motor, 123 is a manual operating lever for the arm cylinder, 124 is a manual operating lever for the swing motor, 113, 114, 115, 11
6, 117, 118 are the manual operation levers 119
a manipulated variable detector for detecting the manipulated variables of ~124, 11
0,111,112 are the variable displacement pumps 1,
a swash plate angle detector for detecting the swash plate angles of 2 and 3;
5 is a rotation speed detector 106 of the prime mover 4 and discharge pressure detectors 107, 10 of the variable displacement pumps 1, 2, 3.
8,109, operation amount detectors 113-118 of manual operation levers 119-124, and variable displacement pump 1,
The required swash plate angles of the variable displacement pumps 1, 2, 3 are calculated from the forces of the swash plate angle detectors 110, 111, 112 of the variable displacement pumps 1, 2, 3.
an arithmetic device that outputs the swash plate angle setting value of No. 3; 12;
6, 127, 128 are variable displacement pumps 1, 2,
Variable capacity pumps 1, 2, 3 by tilting the swash plate of 3.
This is an actuator that adjusts the discharge flow rate.

Next, the arithmetic unit 125 will be explained in detail with reference to FIG. 5. The outputs of the operation amount detector 114 and the operation amount detector 115 of the boom cylinder manual operation lever 121 are input to the flow rate setting devices 129, 130, 131, respectively.
The output of 131 is the high selector (among the input signals,
It is input to a high selector (high selector) 135 which outputs the maximum one. Also, the operation amount detector 116 of the manual operation lever 122 for the left travel motor connected to the variable displacement pump 2 and the manual operation lever 1 for the arm cylinder
The outputs of the operation amount detector 117 of 23 and the operation amount detector 115 of the boom cylinder manual operation lever 121 are input to the flow rate setting devices 132, 133, and 134, respectively.
The output of No. 4 is input to the high selector 136. Also, the swash plate angle detector 112 of the variable displacement pump 3 and the discharge pressure detector 10 of the variable displacement pumps 1, 2, and 3
7, 108, 109 and rotation speed detector 1 of prime mover 4
The output of 06 is input to the arithmetic unit 137. Further, the outputs of the high selector 135 and the arithmetic unit 137 are input to a low selector 138 (a low selector that outputs the minimum signal among input signals). Further, the outputs of the high selector 136 and the arithmetic unit 137 are input to the low selector 139. Further, the outputs of the low selector 138 and the rotation speed detector 106 of the prime mover 4 are input to the arithmetic unit 140 . Further, the output of the low selector 139 is input to the arithmetic unit 141. Further, the output of the arithmetic unit 140 is input to a limiter 142, and the output of the arithmetic unit 141 is input to a limiter 143, respectively. Also limiter 142 and variable displacement pump 1
The output of the swash plate angle detector 110 is output from the regulator 144.
and the output of the regulator 144 is input to the amplifier 147.
is input. Further, the outputs of the limiter 143 and the swash plate angle detector 111 of the variable displacement pump 2 are input to the regulator 145, and the output of the regulator 145 is input to the amplifier 148. Also amplifier 147, 148
The output of the actuators 126 and 127 in FIG.
and becomes an operation signal. Further, the output of the operation amount detector 118 of the manual operation lever 124 for the swing motor is input to the flow rate setting device 150. Also, the output of the discharge pressure detector 109 of the variable displacement pump 3 is
The signal is input to the arithmetic unit 151 shown in the figure. Also, the computing unit 15
1 and the output of the flow rate setting device 150 is the low selector 1.
52. In addition, the outputs of the rotation speed detector 106 and the low selector 152 of the prime mover 4 are
53. Further, the output of the operation amount detector 118 of the swing motor manual operation lever 124 is input to the signal generator 154, and the output of the signal generator 154 is input to the regulator 155. Also, the computing unit 153
The output of the regulator 155 is input to the low selector 156, and the limiter 157 of the low selector 156 is input to the low selector 156.
is input. Further, the outputs of the limiter 157 and the swash plate angle detector 112 of the variable displacement pump 3 are input to the regulator 146, and the output of the regulator 146 is input to the amplifier 149. Furthermore, the output of the amplifier 149 is sent to the actuator 128 shown in FIG. 4 and becomes an operating signal.

Next, the operation of the control device for the variable displacement pump shown in FIGS. 4 and 5 will be explained in detail. The manual operation levers 119, 120, and 121 move the spool that switches the flow path of the switching valve and increases or decreases the flow path area, and the pressure oil from the variable displacement pump 1 is transferred to the right travel motor, bucket cylinder, and boom cylinder. sent to. At this time, the operation amount of the switching valve is detected by the operation amount detectors 129, 130, and 131 (the stroke of the spool of the switching valve is detected). The flow rate setters 129, 130, and 131 output a flow rate set value for the variable displacement pump 1 based on the above-mentioned operation amount. This flow rate setting value is a function as shown in FIG. During normal operation of the hydraulic excavator, one of the operating levers is fully operated, so the high selector 135 selects the maximum flow rate setting value from among the above flow rate setting values and outputs it to the low selector 138. . This becomes the first setpoint signal that controls the swash plate angle of the variable displacement pump 1. Another set point signal is obtained as follows. Variable displacement pump 1, 2, 3
is driven by one prime mover 4, and in order to efficiently distribute the output horsepower of the prime mover 4 to these three variable displacement pumps 1, 2, and 3, the horsepower used by the variable displacement pump 3 must be calculated. , the output horsepower of the prime mover 4 may be deducted and the remaining amount may be used by the variable displacement pumps 1 and 2.

Here, the swash plate angle of the variable displacement pump 3 is detected by the swash plate angle detector 112, the discharge pressure of the variable displacement pump 3 is detected by the discharge pressure detector 109, and the rotation speed of the prime mover 4 is detected by the rotation speed detector 106. , these detected values are sent to the calculator 137, and the horsepower consumption of the variable displacement pump 3 is calculated based on these detected values. Subtracting the horsepower consumption, variable displacement pump 1,
The usable horsepower at variable displacement pumps 1 and 2 is calculated from this and the discharge pressure of variable displacement pumps 1 and 2.
In step 2, calculate the upper limit of the flow rate that can be discharged. This can be done by calculating the actual horsepower consumption of the variable displacement pump 3 based on the hyperbola of θ in FIG. This means that the residual power can be consumed by the variable displacement pumps 1 and 2, and can be fully utilized for the output of the prime mover 4. The above calculation can be expressed as follows.

Horsepower consumption 3 of the variable displacement pump ₃ = 1/η ₃ D ₃ Nφ ₃ P ₃ where η ₃ is the efficiency of the variable displacement pump 3.

Output horsepower of prime mover 4 = f (N) Usable horsepower 1 of variable displacement pump ₁ = (- ₃ ) x Usable horsepower 2 of variable displacement pump ₂ = (- ₃ ) (1-x) Here, P ₃ is pressure , D ₃ is a constant, N is the rotation speed of the prime mover 4, φ ₃ is the swash plate angle of the variable displacement pump 3, x
is the allocation ratio.

Maximum dischargeable flow rate of variable displacement pump 1 q ₁ = η _{1 1} /P ₁ Maximum dischargeable flow rate of variable displacement pump 2 q ₂ =η _{2 1} /P ₂ where q ₁ and q ₂ are variable displacement pumps 1 and 2 , P ₁ and P ₂ are the discharge pressures of the variable displacement pumps 1 and 2. Furthermore, the distribution ratio shown here is a value that can be set arbitrarily. Further, the maximum dischargeable flow rate obtained as a result of the calculation is obtained from the hyperbola B in FIG. 3 with respect to the discharge pressure.

Further, the flow rate set value outputted from the high selector 135 and the flow rate upper limit value outputted from the calculator 137 are inputted to the low selector 138, and the smaller signal of the two is discharged from the low selector 138.
Further, the output of the low selector 138 and the output of the rotation speed detector 106 of the prime mover 4 are input to the arithmetic unit 140 . This calculator 140 performs the following calculations.

φ ₁ =q ₁ /D ₁ N where q ₁ is the flow rate set value output from the low selector 138, D ₁ is a constant, and N is the rotation speed of the prime mover 4.

Then, the computing unit 140 outputs the swash plate angle setting value of the variable displacement pump 1. This swash plate angle setting value is input to a limiter 142, which limits the upper and lower limits of the tiltable range of the swash plate. Also Limituta 142
The swash plate angle setting value of the variable displacement pump 1 and the actual swash plate angle of the swash plate angle detector 110 of the variable displacement pump 1 are adjusted by the adjuster 144.
Here, control calculations, typically proportional, integral, and differential calculations using the actual swash plate angle as feedback, are performed (the same applies to the regulator 145), and the output of the regulator 144 is The output of the amplifier 147 is input to the amplifier 147, and the output of the amplifier 147 is sent to the actuator 126 to tilt the swash plate of the variable displacement pump 1. Note that the actuator 126 may be considered a commonly used electro-hydraulic actuator. The same applies to actuators 127 and 128. Further, the above-described control is also performed on the variable displacement pump 2. However, for the flow rate set value, the manipulated variables detected by the manipulated variable detectors 115, 116, 117 and the outputs of the flow rate setters 132, 133, 134 are input to the high selector 136, from which the maximum flow rate set value is output. . Also, this flow rate setting value and calculator 1
The maximum dischargeable flow rate value of the variable displacement pump 2 outputted from the variable displacement pump 37 is inputted to the low selector 139, and from here, the smaller value of the two is outputted. In addition, the output of the low selector 139 and the rotation speed detector 106
is input to the calculator 141 to calculate the swash plate angle setting value of the variable displacement pump 2. The output of the calculator 141 is also input to a limiter 143, which outputs the swash plate angle set value of the variable displacement pump 2, which limits the swash plate angle set value within the range of upper and lower limits. Further, this signal and the actual swash plate angle of the variable displacement pump 2 obtained by the swash plate angle detector 111 are input to the regulator 145 to perform control calculations, and the output from there is input to the amplifier 148. Furthermore, the output of the amplifier 148 is sent to the actuator 127 to tilt the swash plate of the variable displacement pump 2 to the swash plate angle setting value. Further, the variable displacement pump 3 is controlled as follows. Manual operation lever 124
The operation amount of the spool of the switching valve operated by is detected by the operation amount detector 118, and the output from there is inputted to the flow rate setter 150 to obtain the flow rate set value, which is inputted to the low selector 152. Further, the discharge pressure of the variable displacement pump 3 obtained by the discharge pressure detector 109 is input to the calculator 151 to perform the following calculation.

q ₃ = η _{3 3} / p ₃ where η ₃ is the efficiency of the variable displacement pump 3, ₃ is the maximum horsepower consumption of the variable displacement pump 3, p ₃ is the discharge pressure of the variable displacement pump 3, and q is the efficiency of the variable displacement pump 3. This is the discharge flow rate.

Then, the maximum dischargeable flow rate of the variable displacement pump 3 is determined and inputted to the low selector 152. Furthermore, the low selector 152 outputs the smaller input signal and inputs it to the arithmetic unit 153. The calculator 153 also receives the prime mover rotation speed from the rotation speed detector 106 as an input and performs the following calculation.

φ ₃ =q ₃ /D ₃ N where D ₃ is a constant and N is the rotation speed of the prime mover 4.

Then, the swash plate angle setting value _φ3 is output. The signal generator 154 detects that the manual operation lever 124 has been operated, and generates a variable capacity proportional to the amount of operation so that the set value is low when the amount of operation is small and high when the amount of operation is large. Outputs the pressure setting value of pump 3. Therefore, during the turning operation, the first swash plate angle setting value is selected from the low selector 156. This set value is a value determined from the discharge pressure of the variable displacement pump 3 and the engine rotation speed so as not to exceed the maximum horsepower of the variable displacement pump 3, as described above. Also low selector 15
6 is input to the limiter 157 to limit the swash plate angle set value within the upper and lower limit values of the swash plate, this is input to the regulator 146, and control calculations are performed using the actual swash plate angle. Input this output to amplifier 149,
The actuator 128 is moved by the output of the amplifier 149, and the swash plate of the variable displacement pump 3 is tilted. Each of the above elements (excluding the amplifier and detector) can be realized using a microcomputer. It can also be realized using analog elements or digital elements. As described above, the actual discharge pressure of the variable displacement pump 3 is input from the pump discharge pressure detector 109, and the pressure setting value is input from the signal generator 154 to the regulator 155, and the regulator 155 feeds back the actual discharge pressure. Then, control calculations such as proportional, integral, and differential calculations are performed, and a swash plate angle setting value is output (this function is referred to as pressure control). Also, the computing unit 15
3 and the output of the regulator 155 are input to the low selector 156, and the smaller one of them is output.

Generally, a swing system has a large inertia, so when the control lever is operated, it does not operate immediately, and the pump discharge pressure rises to the relief pressure, and the pump flow rate is relieved until it operates, and power is wasted. . On the other hand, with the above function, when operating the operating lever, assuming that the engine speed is constant, the flow rate set value is determined by the operating amount of the operating lever (see operating amount detector 118) within the maximum horsepower ₃ of the variable displacement pump 3. In other words, the swash plate angle setting value is
3 (this function is called horsepower control). If the actual discharge pressure of the variable displacement pump 3 is larger than the pressure setting value determined by the operating amount of the operating lever (see operating amount detector 118), the swash plate angle setting value is very low.
55. At the beginning of the rotation system drive, a large flow rate is not required, so the regulator 155
Of the outputs, the smaller swash plate angle setting value is selected by the low selector 156, and the variable displacement pump 3
flow rate is not wasted. Also, when the rotation system starts moving, the pressure decreases, but in this state,
Since the discharge pressure of the variable displacement pump 3 becomes low, a large value is always calculated as the latter swash plate angle setting value.

In order to perform the pressure control, it is necessary to adjust the discharge flow rate of the variable displacement pump 3. That is, if the pressure becomes higher than the set value, the discharge flow rate is reduced to lower the pressure. Conversely, if the pressure is not lower than the set value, the discharge flow rate is increased to raise the pressure.

Next, this pressure control will be explained in detail. “Some variable displacement pumps” described in the claims section
corresponds to the rotary pump in this embodiment.
This rotating pump 3 has a large inertia of the rotating system that drives it as described above, and conventionally, as shown in FIG. 7, when it is started, it is relieved and the power is wasted. On the other hand, in the present invention, as shown in FIG. 8, the flow rate is controlled to such an extent that only the leakage flow rate of the hydraulic system is discharged from the pump, thereby eliminating unnecessary relief. Of course, the pressure set by pressure control is set below the relief pressure.

Next, the operation of this pressure control system will be explained in more detail with reference to FIG.

(a) When the swing motor manual operation lever 124 is operated (operated by θ), the operation amount detector 118 converts it into a signal such as a voltage corresponding to the operation.

(b) This signal is input to the signal generator 154, and the signal generator 154 outputs a pressure setting value corresponding to the operation amount θ of the manual operation lever 124 for the swing motor. In other words, when the manipulated variable θ is small, it can move slowly, so the torque (∝pressure x flow rate) that moves the swing system can be small, but when the manipulated variable θ is large, you want to move quickly, so increase the torque. There is a need.
Since the flow rate is controlled here, this torque can be increased or decreased by changing the pressure setting.

(c) The regulator 155 performs calculation to adjust the discharge flow rate of the orbiting pump 3 so that the discharge pressure of the orbiting pump 3 is controlled to the pressure set value (P _3SET ) which is the output of the signal generator 154. That is, as shown in FIG. 10, the PID calculation is performed on the calculated value of (P _3SET -P _3ACT ) and the result is output.

(Output)=K{(P _3SET −P _3ACT )+1/T ₁ ∫(P _3SET −P
_3ACT )αt+TD×( _P3SET − _P3ACT )/αt} In other words, when “ _P3SET > _P3ACT ”, the output increases. This is a signal to increase the flow rate,
Conversely, when "P _3SET < P _3ACT ", the output decreases. This is the signal to reduce the flow rate.

(d) In the low selector 156, the adjuster 155
The smaller signal is selected between the output and the output of the arithmetic unit 153. Here, the output of the calculator 153 is set to the smaller flow rate value between the flow rate determined from the horsepower consumption set for the swing pump 3 and the flow rate set from the operating amount θ of the swing motor manual operation lever 124. On the other hand, it is one of the swash plate command values for the swing pump 3 determined from the actual engine speed. Further, the output of the calculator 153 is the other value of the swash plate command value of the orbiting pump 3 that provides the flow rate necessary to maintain the discharge pressure of the orbiting pump 3 at the pressure set value (P _3SET ).

(e) The necessity of the low selector 156 will be explained with reference to FIG. Even if the swing motor manual operation lever 124 is operated, the swing system does not move immediately, but starts moving after a while, and when it starts moving, the pressure decreases (see FIG. 8). If the pump swash plate is set using the signal ( _φ3SET2 ) in a stationary region, a flow rate higher than necessary will flow, resulting in relief. Therefore, in this area,
( _φ3SET1 ) signal sets the pump swash plate.
On the other hand, when the rotation system starts moving, the pressure decreases, so (P _3SET −P _3ACT ) increases. However, in this region, there is a set horsepower consumption for the orbiting pump 3, which cannot be exceeded. The signal (φ _3SET2 ) determined by this restriction is selected.

The reason for installing the high selector 135 is as follows. This high selector 135 is connected to the operation amount detector 113 of the manual operation lever 119 for the right travel motor via the flow rate setting devices 129, 130, 131.
and the operation amount detector 114 of the bucket cylinder manual operation lever 120 and the operation amount detector 115 of the boom cylinder manual operation lever 121. These right travel motors, bucket cylinders, and boom cylinders are operated singly or in combination, and speed commands are normally given to the operating levers 119, 120, and 121 that operate these devices. . That is, when operating the right traction motor, bucket cylinder, or boom cylinder at full capacity alone, it is necessary to generate the maximum flow rate (equal to the operating speed of each load).
On the other hand, when operating the right-hand travel motor, bucket cylinder, or boom cylinder in combination, for example, when operating the right-hand travel motor and bucket cylinder together, fully operate the control lever of the system for which the highest speed is desired. . If you want to move the whole thing slowly, you can operate the operating lever that provides the main movement by a large amount in the compound operation, and operate the operating levers of other systems at a speed ratio relative to this. At this time, the absolute value of speed is commanded to the operating lever that performs this main operation. In view of these actual usage situations, the high selector, which selects the largest signal rather than taking the sum, is more consistent with the operating feel. For the above reasons, the high selector 135 is installed.

(Effects of the Invention) As described above, the variable displacement pump control method of the present invention provides a method for controlling a part of the variable displacement pump when driving a load via one prime mover and a plurality of variable displacement pumps driven by the same prime mover. When the displacement pump is started, the flow rate is adjusted (adjusted) to maintain a constant discharge pressure of the variable displacement pump to control the pressure, and then the flow rate is controlled to maintain the horsepower consumption constant.
Horsepower control is performed, and the flow rate of other variable displacement pumps is set using the smaller flow rate setting value between the flow rate setting value of the same pressure control and the flow rate setting value of the same horsepower control, so the output of the prime mover can be fully utilized. can improve efficiency. Also, when starting some variable displacement pumps,
In addition to conventional horsepower control, pressure control has been introduced, which has the effect of improving operability.

Further, as described above, the variable displacement pump control method of the present invention applies the same method when driving a load via one prime mover 4 and a plurality of variable displacement pumps 1, 2, and 3 driven by the same prime mover 4. Among the variable displacement pumps 1, 2, and 3, the swash plate angle of the variable displacement pump 3 is determined by the swash plate angle detector 112, and the discharge pressure of the same variable displacement pump 3 is determined by the discharge pressure detector 109, and the rotational speed of the prime mover 4 is determined. are detected by the rotation speed detector 106, and these detected values are sent to the computing unit 137 of the computing unit 125, and based on these detected values, the horsepower consumption of the variable displacement pump 3 is computed, and the rotation of the prime mover 4 is The usable horsepower of the variable displacement pumps 1 and 2 is calculated by subtracting the consumption horsepower of the variable displacement pump 3 from the output horsepower of the prime mover 4 determined by the number, and the usable horsepower of the variable displacement pumps 1 and 2 is calculated.
The residual power of the prime mover 4 is determined by calculating the upper limit of the flow rate that can be discharged by the variable displacement pumps 1 and 2 from the discharge pressure of The output of the prime mover 4 can be fully utilized, which has the effect of improving efficiency.

[Brief explanation of the drawing]

Figures 1 and 2 are system diagrams showing a conventional variable displacement pump control device, Figure 3 is an explanatory diagram showing the relationship between discharge pressure and discharge flow rate of a variable displacement pump, and Figure 4 is a variable displacement pump according to the present invention. A system diagram showing a configuration example used to implement the pump control method, FIG. 5 is a system diagram showing details of the calculation device, and FIG. 6 is an explanatory diagram showing the relationship between the spool operation amount of the switching valve and the flow rate set value. , 7th
FIG. 8 is an explanatory diagram showing the relief state at startup of the conventional variable displacement pump control device, FIG. 8 is an explanatory diagram showing the no relief state at startup of the variable displacement pump control device of the present invention, and FIG. 9 10 is an explanatory diagram of the operation of the pressure control device for a variable displacement pump of the present invention, FIG. 10 is an explanatory diagram of the operation of the regulator, and FIG. 11 is an explanatory diagram showing the reason for installing the low selector. 1, 2, 3... Variable displacement pump, 4... Prime mover, 125... Arithmetic device, 118... Actuator operation amount detector, 150... Flow rate setting device, 1
09...Discharge pressure detector of variable displacement pump 3, 1
51...Arithmetic unit, 153...Arithmetic unit, 156...
Low selector, 112... Swash plate angle detector of variable displacement pump 3, 137... Arithmetic unit, 113-11
7...actuator operation amount detector, 129~
134...Flow rate setting device, 135...High selector, 138...Low selector, 139...Low selector, 140...Arithmetic unit, 141...Arithmetic unit,
144...Adjuster, 145...Adjuster.

Claims (1)

[Claims] 1. When driving a load through one prime mover and a plurality of variable displacement pumps driven by the same prime mover, when some of the variable displacement pumps are started, the discharge pressure of the same variable displacement pump is Pressure control is performed to adjust the flow rate so as to keep it constant, and then horsepower control is performed by controlling the flow rate to keep the horsepower consumption constant. A control method for a variable displacement pump, characterized in that the flow rate of another variable displacement pump is set by the smaller flow rate setting value among the set values. 2. When driving a load through one prime mover and multiple variable displacement pumps driven by the same prime mover, detect the swash plate angle of some of the variable displacement pumps among the same variable displacement pumps. Depending on the vessel,
The discharge pressure of the variable displacement pump is detected by a discharge pressure detector, and the rotation speed of the prime mover is detected by a rotation speed detector, and these detected values are sent to a computing unit of a computing device, and based on these detected values, Calculate the horsepower consumption of some of the variable displacement pumps mentioned above, and subtract the horsepower consumption of some of the variable displacement pumps from the output horsepower of the prime mover determined by the rotation speed of the prime mover, and use it with other variable displacement pumps. By calculating the horsepower, and calculating the upper limit of the flow rate that can be delivered by the other variable displacement pumps from this and the discharge pressure of the other variable displacement pump mentioned above, the residual power of the prime mover is determined, and this residual power is A method for controlling a variable displacement pump, characterized in that consumption is consumed by another variable displacement pump.