JPS6049103A - Output control method of variable delivery pump - Google Patents

Abstract

PURPOSE:To achieve energy conservation of a pump by always limiting the driving power of the pump to a minimum by the control of a maximum discharge pressure, constant power control, and control of the difference of the delivery pressure and an actuator maximum operating pressure. CONSTITUTION:In a hydraulic system wherein a discharge circuit 3 of a variable delivery pump 1 is connected with actuators 12 to 15 in parallel through control valves 4 to 7, a detector 19 for detecting the discharge pressure P of the pump 1, and a detector 23 provided for shuttle valves 20 to 22 attached to actuator circuits 8 to 11 and detects a maximum values P2 among the operating pressures of the actuators are arranged. A detector 18 for detecting the position of a servo cylinder 16 to control the inclination angle, that is, the delivery rate of the variable delivery pump 1 is also provided in the system. On the basis of the above three data, the maximum output of the pump 1 is maintained below the maximum output of a prime mover 2 and the discharge pressure of the pump 1 is controlled not to exceed a maximum allowable pressure of the hydraulic system by a servo valve 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling a variable displacement pump.

Hydraulic systems, particularly δ11 pressure systems used in construction machinery, require the power output of the prime mover to be minimized. On the other hand, in the past, generally, a variable displacement pump was used, and the discharge pressure horn was made not to exceed the maximum allowable pressure of the hydraulic system connected to the pump, and
Constant horsepower control is performed to keep pump discharge pressure P×pump discharge mQ within a certain limit. However, with this constant horsepower control alone, the pump discharge pressure will rise to the maximum allowable pressure of the system regardless of the operating pressure of the actuator in the hydraulic system. , the amount exceeding the pressure difference required by the actuator control valve results in loss.

Therefore, while ensuring the necessary pressure difference with the actuator control valve, we decided to prevent unnecessary increases in pump discharge pressure by 1lJHJ.
There is a power match system (load sensing system) that controls the pump's discharge IJ (horn) according to the actuator's operating pressure, but this system does not perform the constant horsepower control described above, and There is a need to control the
There are problems such as the complicated structure and increased cost.

In view of these points, the present invention maintains the maximum output of a variable loss type pump below the maximum output of the prime mover, and within that range [11], the pump discharge pressure is maintained within the range [11] of the hydraulic system connected to the pump. 1 so as not to exceed the maximum allowable pressure of
At the same time, the pump discharge pressure is adjusted according to the operating pressure of the actuator, and the pump discharge pressure P and pump discharge 1f are adjusted.
The present invention provides a control method for a variable displacement pump that always minimizes the pump drive power determined by flQ to exhibit an energy saving effect, and that can be implemented at low cost with a simple circuit.

However, the present invention provides a hydraulic system in which several actuators are driven by a variable sound solid pump driven by an original tilJ. The maximum value is detected, and the pump output is adjusted based on these three detected values.
1i (to control, when the discharge pressure exceeds the maximum allowable pressure of the hydraulic system, reduce the discharge interval so that the discharge pressure becomes equal to or less than the maximum allowable pressure, and When the required power of the pump determined by the product of the discharge pressure and the discharge amount exceeds the output of the prime mover when the pressure is below the maximum allowable pressure and the required power of the pump is determined by the product of the discharge pressure and the discharge amount, the discharge amount is decreased so that the power is below a certain value determined by the output of the prime mover. Further, when the discharge pressure is below the maximum allowable pressure and the product is below a certain value determined by the output of the prime mover, the difference between the discharge pressure and the maximum value of the working pressure is within a predetermined range. A feature of the invention is that the discharge amount is controlled until the amount of discharge continues.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a hydraulic system in which one pump drives several actuators. In the figure, 1 is a variable foot pump connected to a prime mover 2.
Several actuators 12'' are connected to the discharge circuit 3 via several control valves 4 to 7 and actuator circuits 8 to 11.
15 are connected. The pump 1 is equipped with a servo cylinder 16 and a servo valve 17 for actuating the cylinder 16, as a servo cylinder 16 and a servo valve 17 for operating the cylinder 16. It is being taken. Furthermore, since the discharge ff1Q corresponds to the position of the servo cylinder 16, a detector 18 for detecting the position is connected to the cylinder 16 to detect the discharge ff1Q.

On the other hand, a detector 19 for detecting the discharge pressure P of the pump 1 is connected to the discharge circuit 3 of the pump 1, and each actuator circuit 8-11 is connected to a shaft valve 19-21, ~15 Actuation B-Maximum h of the back of the force
A detector 23 that selects and detects mP2 at a high voltage is connected.

24 hamster 1 rlni te, said & detector 18, 1
'J.

Input the detected value by 23 and calculate, 51! ! That is, a control signal is output based on the result, and the control signal is sent to the servo valve 17 via the interface 25, and the servo cylinder 16 is actuated to control the discharge ff1Q of the pump 1. There is.

Therefore, the pump 1 is now driven by the prime mover 2, and one or several of the control valves 4 to 7 are operated to control the pump 1.
supplying the discharge oil to one or several of the actuators 12 to 15), and when the actuator is operating, the detector 18 detects the discharge oil ff1Q of the pump 1.
, the discharge pressure P of the ribbon valve 1 is detected by the detector 19, and the high pressure is selected and derived from each actuator circuit 8-11 by the Shikame-1 Hell valve 19-21. The highest value P of the working pressure of
2 is detected by the detector 23.

Next, the detected values P, Q, P2 of these 3PJ are converted into electron H1
Send it to Arithmetic 1624, and according to the electronic separate Arithmetic 24) si 1 arithmetic,
A control signal is output based on the result, and the control signal is sent to the length valve 17 via the interface 25, and the servo cylinder 16 is actuated to control the discharge f of the pump 1.
f1Q is controlled as shown in FIG.

゛In Fig. 2, the line ■ represents the difference between the pump maximum discharge jT 1] 3, which is determined by the theoretical maximum operating pressure of the system, and the 8 differential pressure P1 [PI
=Ko -Q=ro (Q)] corresponds to the pump discharge ff1Q derived by subtracting the system maximum allowable pressure Pm
(P3-P l ), and the line ■ is the constant horsepower curve of the pump 1 determined by the output of the prime mover 2 (P-Q = + -
(constant), and Pl is the maximum discharge pressure of the pump 1, ff1Qi.

Next, the control procedure will be explained based on FIG.

(1) When the discharge pressure P of the pump 1 exceeds the system maximum allowable pressure Pm (line 1) (P>Pm), for example, when the discharge pressure P is at point Δ in Fig. 2, it is indicated by arrow A. The discharge amount Q of the pump 1 is reduced in this way, and the maximum pressure Ill tiIl is set so that the discharge pressure P of the pump 1 becomes equal to or less than the system maximum allowable pressure Pm.

(2) The discharge 11 force 1) of the pump 1 is expressed as 11
11D Large allowable pressure pm or less P≦l〕1T1), the product of the output pressure P and the discharge ff1Q is the output of the original 2.
: If the constant horsepower curve exceeds the constant value determined by (
P・Q>K+), for example, said pup 1 (P−Q) is the second
When it is at point B in the figure, the discharge ff1Q of the pump 1 is avoided to be decreased as shown by the arrow, and constant horsepower control is performed so that the ratio (P-Q) becomes a constant value of 1 or less.

(3) When the discharge pressure [ ] of the pump 1 is greater than or equal to the system maximum allowable pressure Pm (PzPm), the product of the discharge pressure]] and the discharge ff1Q is set to a constant value determined by the output of the prime mover 2 (constant horsepower curve ) In the following cases (1 for P・Q≦), for example, when the product (P'-Q) is at the 0 point within the range of line 1, ■ in Fig. 2, the discharge pressure P of the pump 1 and the maximum operating pressure P2 of the actuators 12 to 15 (
P-P2) is calculated, and the discharge ff1Q of pump 1 is adjusted so that the difference (P-P2) is within the range of a predetermined constant value (K14 to 13), similar to the load sensing system. control. That is, (1) When (P-Pz)>K++, the discharge ff1Q of the pump 1 is decreased.

■ When (P-P2)<Ki3, increase the discharge 11Q of the pump 1. −■ K+3
<(P-P2>) <K% and operate at the current discharge mQ.

Note that the range of the constant value (K1o to 13) corresponds to the pressure difference between upstream and downstream of the control valves 4 to 7 necessary for operating the actuators 12 to 15, taking into account pressure loss in the circuit.

”Go to (1) above・I'J III of <3) operates the servo valve 17 by the control function output from the electronic calculation II 24 via the interface 25 based on the three detected values P, Q, and P2. J: to control.

The above control reduces pump discharge ff1Q, maintains the current state,
Although it has been explained that the control is performed in three stages of increase, control accuracy can be further improved by performing more detailed control in five stages of rapid decrease, slow decrease, maintaining the status quo, slow increase, and rapid increase. In this case, five electromagnetic valves can be used as the servo valves 17, as shown in FIG.

In FIG. 3, 26 is a control i+I+ pressure source, 27 is a check valve, 28, 30.32 is a normally closed solenoid valve, 29.
31 is a normally closed solenoid valve, 33 is a throttle, and 34 is a tank. A circuit 35 led out from between solenoid valves 28 and 29 is connected to a hydraulic chamber 36 on the rod side of the servo cylinder 16, and solenoid valves 30 and 31 are connected to each other. A circuit 37 led out from between is connected to the head side hydraulic chamber 38 of the cylinder 16 ffQ. In this case, if pressure oil is supplied to the oil JJE chamber 36, the discharge amount of the pump 1 will be increased. is decreased, and if pressure oil is supplied to the hydraulic pressure v38, the discharge amount Q of the pump 1 is increased. In addition, each solenoid valve 28 to 32
is the control of the electronic computer 24 that is processed based on the three detected values P, Q, and P2. This selects the hydraulic chamber 36.38 that supplies pressure oil, and also selects the oil discharged from the hydraulic chamber 36.38.
The discharge amount is controlled. As shown in Table 1, it is controlled in five stages: rapid decrease, slow decrease, maintaining the status quo, slow increase, and rapid increase.

Table 1 The control in Table 1 above is the control υp from the electronic meter 1; 71fi24.
This is done by adding J: to the Jingo, and then the electronic counter [
24 will be explained based on the control shown in FIG. 4.

First, when the program is started, the deviation pressure P is proportional to the pump discharge amount Q set in advance in step S1.
1, and by subtracting the deviation pressure horn P1 by g from the pump maximum discharge pressure P3, which is set equal to the theoretical maximum allowable pressure of the hydraulic system, the system maximum allowable pressure corresponding to the pump discharge mQ can be obtained. pm is calculated (step S2). Next, in step $3, it is determined whether the pump discharge pressure P from the detector 19 input to this program exceeds the system maximum allowable pressure pm.

In the case of YFS in step S3, the differential pressure px between the pump discharge pressure P and the maximum allowable pressure pm is calculated in step S4,
In step S5, it is determined whether the differential pressure Px is a constant value of 11 or more. If YES in step $5, the process goes to step S6, where the control signal for the control Nα1 is output, and the solenoid valves 30, 31, and 32 are energized while the solenoid valves 28, 29 shown in FIG. 3 are kept demagnetized. , pump discharge mQ
is rapidly reduced, and the pump discharge pressure P reaches the system maximum of 9'.
The pressure is controlled to be 1 volume pressure Pm or less.

If No in the step S5, the process is sent to a step S7, where it is determined whether the differential pressure px is equal to or higher than a constant value of 1o, and if YES in the step S7, the process is sent to a step S8, where the control No. 2 control signals are output, and while the solenoid valves 28, 29, and 32 remain demagnetized, the solenoid valves 30.
31 is excited, the pump discharge mQ is slowly decreased, and the pump discharge pressure P is controlled so as not to exceed the system maximum allowable pressure pm.

If No in step S7, the control signal of control No. 3 is outputted to step S7, and the solenoid valve 29.3 remains demagnetized while the solenoid valve 28, 30.32 is demagnetized.
1 is energized and the current state is maintained.

On the other hand, if No in step S3 (Yo, step 8
10, and the product of pump discharge pressure P and discharge 11ftQ, which is determined by the output of prime mover 2, is constant (P・Q=1
= constant) on the constant horsepower curve is calculated, then in step S11 the differential pressure Py between the pump discharge pressure [) and the pressure Pk on the constant horsepower curve is calculated, and in step 812 the differential pressure Py is O It is determined whether or not it exceeds . In this step $12, if Y[S, the control is sent to the step $6 and is controlled by the control No. 1, and if NO, the pump discharge pressure P and the actuator 12 are determined in step S+3.
~15 maximum working pressure P2 differential pressure PzlfitJ
In step 814, it is determined whether the pump discharge pressure P is a constant value of 15 or more. YES in step 814
In the case of , it is sent to the step S6 and the control No.
If the answer is NO, it is determined in step 815 whether the differential pressure P2 is a constant value of 14 or more. In the case of YES in step 15, the process is sent to step $8, where the control according to the control 9111 No. 2 is performed.
In the case of step S16, the differential pressure pz is constant 11 K 1
It is determined whether the number is 3 or more. If YES in step S+a, the process is sent to step S9 and the control Nα3 is executed; if NO, step Sv
It is determined whether the difference f'XPZ is greater than or equal to a constant 1st shift KI2.

If YES in step 317, step 81
8, the control No. 4 (g) is output, and the solenoid valves 28, 29 are energized while the solenoid valves 30, 31, 21 are demagnetized, and the pump discharge amount Q is slowly increased. The differential pressure Py between the pump discharge pressure P and the maximum operating pressure P2 of the actuator is controlled to be within a predetermined range (K1z~14).

If the answer in step 817 is No, the process goes to step S19, where the control signal of control number 5 is output, and the solenoid valves 28 and 29 are activated while the solenoid valves 30 and 31 remain demagnetized.
．． 32 is excited, and the pump discharge ff1Q is rapidly increased so that the differential pressure pz between the pump discharge pressure P and the maximum operating pressure P2 of the actuator is within a predetermined range (K 13 to 14).
controlled so that

In addition, each of the above steps Se, Ss, 89・518S
The control signals No. 1 to 5 output at i are the pump discharge pressure horn P1, which is sampled at fixed time intervals (for example, 100 μs), the pump discharge pressure (P1), the maximum operating pressure (P2) of the actuator, and the maximum operating pressure (P2) of the actuator. The control ti11 enlightenment is based on the result of the arithmetic processing based on the detected value of the servo 'Ji' 1
7, and the control described above is performed.

By the way, in the above embodiment, the control υ11 of one pump has been described, but when two or more pumps are used, the control can be performed in the same manner as described above.

Next, another embodiment of the present invention will be described.

Figure 5 shows the case where several actuators are driven by two pumps driven by one prime mover.
It is a circuit diagram showing an example in which two pumps are controlled by one discharge foot control 0flR setting.
Two pumps la, 1b driven by FI1 machine 2
For the common servo cylinder 16J3 and servo valve 1
7 is set [C1 pump Ia, 1b discharge mQa, Qb
(Qa=Qb=Q) can be controlled simultaneously. In the figure, 3a, 3b are discharge circuits, 4'a,
5a, 6a, 6b.

5b, 4b are control valves, 8a, 9Fl, 10a, 10b,
9b, 8b, 10c are actuator circuits, 12a, 1
3a, 14a, 13b, 12b indicate actuators, and in this embodiment, actuator circuits 10a, 1ob derived from control valves 6a6b are connected to check valves 10c, 10.
d to the circuit 10e, and the actuator 14
Connected to a. Further, 18 is a discharge amount detector, 19a
, 19b is a discharge pressure detector, 21a, 21b, 22a.

22b is a shuttle valve, 23a and 23b are maximum operating pressure detectors of each actuator, and 39a.

39b indicates a relief valve.

Therefore, in this circuit, the discharge ff of each pump Ia, Ib
1Qa and Qb (Qa=Qb=Q) are detected by the detector 1B, and the discharge pressures Pa and pb of each pump 1a and 1b are individually detected by the detectors 19a and 19b, and the maximum operating pressure of each actuator is detected. The values are detected for each pump by the detectors 23a and 23b, and these detected values are sent to the computer 24 to perform the same control as described above.

However, in this case, as a condition for constant horsepower control, the pump 1
The sum of the discharge pressures Pa and Pb of a and 1b and the discharge ff1Q (7
) 槓 [(Pa+Pb)XQI is IFr! Whether the output of motive 2 exceeds a certain value K determined by J: [(Pa + Pb
)
The discharge ff1Q of both pumps 1a and 1b is controlled by the servo cylinder 16 so that the above-mentioned product is below a certain value, and when the product is below a certain value, the actuator is operated at the lowest operating pressure. For the pump, the discharge ff1Q of both pumps is controlled by 1tiII so that the differential pressure between the maximum operating pressure of the actuator connected to the pump and the discharge pressure of the pump is constant. In addition, Akuzini L
For the pump with a higher maximum operating pressure, the maximum operating pressure can be controlled by another pressure control valve, such as an overload relief valve.

When one fixed displacement pump is added to the circuit shown in Figure 5, that is, when one master machine drives two variable displacement pumps and one fixed displacement pump, the constant horsepower is The control condition is [(Pa+pb)xQ+pc -Qcl
>K, except for yelling, can be controlled using the same control procedure as in the case of Fig. 5 and 1i51. Here, pc indicates the discharge pressure of the fixed displacement pump, and Qc indicates the discharge amount (constant) of the same pump.

Figure 6 shows the case where several actuators are driven by two pumps driven by one prime mover.
This is a circuit diagram showing an example in which two pumps are individually controlled by two discharge rate control devices. In this example, two pumps ia, 1 driven by a prime mover 2 are
servo cylinders 1.6a, 16b and servo valves 17a, 17b are individually installed for both pumps 1a, 1.b.
The discharge fiQa, Qb of each pump 1a, Ib can be individually controlled, and the discharge amount detectors 18a, 18b individually detect the discharge fiQa, Qb of each pump 1a, Ib, and send them to the electronic bullet meter 24. , is the same as the case shown in FIG. 5, except that control signals are individually sent from the computer 24 to each servo valve 178, 17b via interfaces 25a, 25b.

The control in the circuit of FIG. 6 is basically the same as the control in the circuit of FIG. However, as a control condition for
For one pump, for example, 1b, its discharge pressure Pb
With the maximum output fixed so that the product of The discharge amount Qa is controlled so that [(Pa-Qa+Pa-Qa)>K] is satisfied so that the sum of the products of the discharge amounts does not exceed a certain value I determined by the output of the prime mover. In this case, it is possible to decide which pumps to control depending on the settings.For example, while the maximum output of the less frequently used pump is fixed, the output of the more frequently used pump is controlled. Alternatively, the output of the prime mover can always be maximized by selecting the pump to be controlled depending on the work content using a separate control circuit selection valve.

Furthermore, when one fixed displacement pump is added to the circuit shown in Fig. 6, the control conditions for the pump under which the maximum output is controlled are (pa-Qa+Pb・Qb+Pc-Qc).
>K, but the control can be performed in the same manner as in the case of FIG. 6. Here, Pc indicates the discharge pressure of the fixed displacement pump, and Qc indicates the discharge amount (constant) of the pump.

In each of the above embodiments, as a servo valve ↑17 for controlling the discharge amount, five solenoid valves 2 and 1 are used as shown in FIG.
8 to 32, check valve 27J) and comparison 33 are combined U
A servo valve 17 as shown in Fig. 7 was used.
' and a servo cylinder 16' may also be used. This servo valve 17' is made up of three 1δ type solenoid valves 40, 4, 1, 42 and a valve 43 combined as shown in the figure, and the servo valve 16' is formed at stage Iζ]. , the pump discharge ff1Q is decreased by supplying pressure oil to the hydraulic pressure 44 on the small diameter side, and the pump discharge ff1Q is increased by supplying pressure oil to the hydraulic pressure 45 on the large diameter side. In addition, each solenoid valve 40 to 42
is excited or demagnetized and opened and closed by a control signal from the computer 24, and depending on the combination of opening and closing, the discharge ff1Q can be reduced rapidly, slowly decreased, maintained as it is, or slow as shown in Table 2. It is controlled in five stages: increase, rapid increase.

Table 2 In this way, the servo valve 17 or 17' of the 0N-OFF type, which is a combination of several solenoid valves of 0N-OFF operation, is used to control the C reel to the positive cylinder 16 or 16', and the pump output amount is By controlling the pump discharge pressure, it is possible to improve the reliability against contamination of the hydraulic oil compared to the case of controlling using a conventional mechanical analog type servo valve. , the differential pressure between the discharge pressure and the actuator maximum operating pressure can be controlled with high precision.

As explained above, according to the present invention, by performing three types of control: control of the maximum pump discharge pressure, constant horsepower control, and control of the differential pressure between the discharge pressure and the actuator maximum operating pressure, Pump drive power can always be kept to a minimum, resulting in significant energy savings.

In addition, Jζ is used for the servo valve described in the above embodiment.
It is low cost and extremely easy to implement.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an example in which there is one pump, Figure 2 is a control characteristic diagram showing the relationship between pump discharge pressure and discharge amount to explain the control procedure, and Figure 3 is a nervo valve. of~
Figure 4 is a flow chart showing an example of processing by an electronic calculator. Figure 5 is a circuit diagram showing an example of control when two pumps are controlled simultaneously by one discharge 7H control device. Figure 6 shows two pumps and two discharge pumps up tx
FIG. 7 is a circuit diagram showing an example of control when the servo valves are individually controlled. 1.1a, 1b...variable displacement pump, 2...prime mover, 4.5, 6.7.4a, 4b, 5a, 5b. 6a, 6bQ-control valve, 12, 13, 14, 15°12
a, 12b, 13a, 13b, 14a-Actuator, 16.16'... Servo cylinder as a discharge amount control device, 17.17'... Servo valve, 18.
18a, 18b--Discharge amount detector, 19.19a, 1
9b - Discharge pressure detector, 23.23a. 23b...actuator maximum operating pressure detector, 2
4...Electronic computer, 25...Interface. Figure 1! Figure 2 Figure 3

Claims (1)

[Claims] 1. In a hydraulic system in which several actuators are driven by a variable displacement pump driven by a prime mover, the maximum value of the pump discharge pressure, pump discharge volume, and operating pressure of each actuator is detected. and controls the output of the pump based on these three detected values,
When the discharge pressure exceeds the maximum γ1 volume pressure of the hydraulic system, the discharge amount is reduced so that the discharge pressure is below the R large allowable pressure, and the discharge pressure is below the maximum allowable pressure and When the required power of the pump determined by the product of the discharge pressure and discharge amount exceeds the output of the prime mover,
Decrease the discharge amount so that the product is equal to or less than a certain value determined by the output of the prime mover, and further, when the discharge pressure is equal to or less than the maximum allowable pressure and the product is less than the constant value determined by the output of the prime mover, A method for controlling a variable displacement pump, characterized in that the discharge m is adjusted to 1Ii1111 so that the difference between the discharge pressure and the maximum value of the operating pressure falls within a predetermined range.