JPH04351301A - Controller for hydraulic circuit - Google Patents

Abstract

PURPOSE:To provide a controller capable of accurately controlling operation of a hydraulic circuit with good stability and rapid responsiveness according to operation of operating means. CONSTITUTION:A ratio of a required total flow rate on the basis of an operating quantity of operating levers 9a, 9b to a maximum dischargeable flow rate based on a discharge pressure is calculated. If the ratio is 1 or more, a coefficient is set in 1 while if it is less than 1, the coefficient is set in a value of the ratio. Main valves 6a, 6b are controlled on the basis of a value obtained by multiplying the operating quantity by the coefficient, and an inclining rotation quantity is calculated based on a value obtained by multiplying the maximum dischargeable flow rate by the coefficient. The inclining rotation quantity is corrected according to an inclining rotation quantity on the basis of a deflection between a differential pressure between the discharge pressure and a maximum load pressure, and a specific value of the differential pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit control device for controlling the operation of a hydraulic circuit using a variable displacement hydraulic pump as a hydraulic power source.

0002

2. Description of the Related Art Various means have been proposed in the past as control means for a hydraulic circuit that drives a plurality of hydraulic actuators using a variable displacement hydraulic pump (hereinafter simply referred to as a hydraulic pump). The most typical example thereof is a flow rate comparison type control means shown in, for example, US Pat. No. 4,712,376. This means calculates the total consumed flow rate (required total flow rate) at that point from the sum of the input signals of each operating lever that drives and controls each hydraulic actuator, and on the other hand, detects the discharge pressure of the hydraulic pump and calculates the amount from this detected value. Find the maximum dischargeable flow rate of the hydraulic pump at the time. If the required total flow rate is less than or equal to the maximum dischargeable flow rate, the displacement volume variable mechanism (hereinafter represented by a swash plate) of the hydraulic pump is driven based on the required total flow rate to control the discharge flow rate, and If the required total flow rate exceeds the maximum dischargeable flow rate, the input signal of each control lever is multiplied by the value obtained by dividing the maximum dischargeable flow rate by the required total flow rate, and the slope is adjusted based on the total flow rate obtained as a result. Drive the board. As a result, each hydraulic actuator is supplied with pressure oil at a flow rate commensurate with the operating amount of the operating lever and the maximum dischargeable flow rate of the hydraulic pump.

0003

[Problems to be Solved by the Invention] The above-mentioned flow rate comparison type control means is stable because it does not constitute a servo loop, and has excellent quick response because the required total flow rate can be obtained immediately when each operating lever is operated. ing. However, the required total flow rate is only a predicted value, and the accuracy of the obtained required total flow rate may not be satisfactory depending on the temperature of the oil and various other conditions. Therefore, if the predicted total required flow rate is large, the discharge pressure of the hydraulic pump will increase and the discharged oil will be relieved; conversely, if the predicted total required flow rate is small, the hydraulic pump discharge pressure will decrease and the flow rate will be insufficient. will occur. SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic circuit control device that solves the above-mentioned problems in the prior art, has excellent stability and quick response, and is capable of highly accurate control.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a variable displacement hydraulic pump that discharges pressure oil according to the amount of tilting of a variable displacement mechanism, and a variable displacement hydraulic pump that is driven by the variable displacement hydraulic pump. a plurality of hydraulic actuators, operating means for controlling the drive of each of these hydraulic actuators, and control for controlling the flow rate to the corresponding hydraulic actuator by operating according to an opening command value based on the operation amount of each of these operating means. a first calculation means for calculating a required total flow rate of pressurized oil based on the operation amount of each of the operation means; and a maximum dischargeable flow rate based on the discharge pressure of the variable displacement hydraulic pump. a second calculation means for calculating the ratio of the maximum dischargeable flow rate and the required total flow rate; a coefficient calculation means for determining 1 as a coefficient when the ratio of the maximum dischargeable flow rate and the required total flow rate is 1 or more; and a coefficient calculation means that determines the ratio as a coefficient when the ratio is less than 1; opening command value correction means for correcting the command value by the coefficient; third calculation means for calculating the tilting amount based on the discharge flow rate command value obtained by correcting the maximum dischargeable flow rate by the coefficient; and the variable capacity. Calculating a correction value for the amount of tilting determined by the third calculating means based on the difference between the discharge pressure of the hydraulic pump and the maximum load pressure of each of the hydraulic actuators and a prescribed differential pressure. a fourth calculation means; and a fifth calculation means for calculating a tilting command value of the variable displacement mechanism based on the calculation value of the third calculation means and the calculation value of the fourth calculation means. It is characterized by:

[0005]

[Operation] When the operating means is operated, the required total flow rate required by the hydraulic actuator is calculated, and at the same time, the maximum dischargeable flow rate of the hydraulic pump is calculated based on the discharge pressure of the hydraulic pump. Here, the maximum dischargeable flow rate is divided by the required total flow rate, and if the division value is 1 or more, the coefficient is set to 1, and if it is less than 1, the coefficient is set to the division value. After determining the coefficient in this manner, an opening command value corrected using the coefficient is output to the control valve. At the same time, for the variable displacement mechanism, the amount of tilting is determined based on the discharge flow rate command value obtained by correcting the maximum dischargeable flow rate by the relevant coefficient, and
This amount of tilting is corrected by a correction value obtained based on the difference between the differential pressure between the discharge pressure of the hydraulic pump and the maximum load pressure of each hydraulic actuator, and a predefined differential pressure, and the corrected tilting amount is Outputs the amount of rotation as an appropriate amount of tilting.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the illustrated embodiments. FIG. 1 is a hydraulic circuit diagram using a hydraulic circuit control device according to an embodiment of the present invention. In the figure, 1 is a hydraulic pump;
a is a swash plate of the hydraulic pump 1; 2 is a regulator that drives the swash plate 1a; 3a and 3b are solenoid valves that control the drive of the regulator 2; 4 is a tilt amount that detects the amount of tilt of the swash plate 1a. It is a detector. 5a and 5b are hydraulic cylinders driven by the pressure oil of the hydraulic pump 1; 6a and 6b are main valves that control the flow to the hydraulic cylinders 5a and 5b, respectively; 7a and 7b
8 is a directional control valve mechanically connected to the main valves 6a and 6b;
A and 8b are pressure compensation valves interposed between the main valves 6a and 6b and the directional control valves 7a and 7b. 9a and 9b are operating levers 10a for operating the hydraulic cylinders 5a and 5b, respectively;
, 10b is a manipulated variable detector that outputs an electric signal proportional to the manipulated variable of each operating lever. 11 is an unload valve, 1
2 indicates a pressure sensor that detects the discharge pressure of the hydraulic pump 1. 13 is a shuttle valve that selects and outputs the higher pressure of the hydraulic cylinders 5a5b. A differential pressure sensor 14 detects the differential pressure between the discharge pressure of the hydraulic pump 1 and the pressure (maximum load pressure) selected by the shuttle valve 13, and outputs an electric signal proportional to the differential pressure. 15 is a controller that inputs various signals, performs necessary arithmetic control, and outputs the results as command values. Here, the pressure compensation valves 8a, 8
Let me explain the function of b. As shown, the pressure compensation valve 8
A shuttle valve 13 is installed in one of the pilot ports of a and 8b.
The maximum load pressure selected in , and the output side pressure of the main valves 6a, 6b are input to the other pilot port, thereby having the function of making the input side pressure approximately equal to the maximum load pressure. Therefore, the differential pressure generated before and after the main valves 6a and 6b becomes equal, and the flow rate of pressure oil supplied to the main valves 6a and 6b becomes equal.
The value corresponds to the stroke of b.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 and 3. FIG. 2 is a block diagram explaining the functions of the controller 15, and FIG. 3 is a characteristic diagram showing the relationship between the spool displacement of the main valve and the flow rate. When the operating levers 9a, 9b are operated to drive the hydraulic cylinders 5a, 5b, the amount of the operation is input to the controller 15. Controller 1
5 calculates the required total flow rate Qva in the required total flow rate calculating section 151 based on these manipulated variables, and calculates the maximum dischargeable flow rate Qpmax of the hydraulic pump 1 in the maximum flow rate calculating section 152 based on the output signal of the pressure sensor 12. . These values are input to the coefficient calculating section 153, and the coefficient α is determined. This coefficient α is calculated from the total required flow rate Qva to the maximum dischargeable flow rate Q
divided by pmax, and if the division value is 1 or more, α=1
, is less than 1, it is determined that α=divider value. on the other hand,
The operation amounts of the operation levers 9a and 9b are multiplied by the coefficient α in a multiplier 154, and these multiplied values are converted into a displacement amount converter 155.
is input. Each displacement converter 155 calculates the respective flow rates Q5a and Q5b based on the input multiplication value,
From these flow rates, the stroke amounts X5a and X5b of the main valves 6a and 6b are determined based on the characteristics shown in FIG. Here, the above characteristics are stored in the storage section of the controller 15, and are shown in FIG.
G5a is the characteristic of cylinder 5a, G5b is the characteristic of cylinder 5b
shows the characteristics of These characteristics were created by actual measurements for the set values of the differential pressures before and after the main valves 6a and 6b, but since there are various errors in the mechanism and changes in oil temperature, they may vary within a certain range. It is impossible to avoid variations, and in this sense it can be called a predicted flow rate value. The controller 15 outputs an opening command signal to the main valves 6a, 6b according to the stroke amounts X5a, X5b obtained based on such characteristics. The main valves 6a, 6b are driven according to this output, and flow the above-mentioned flow rates Q5a, Q5b. Further, the required total flow rate Qva is multiplied by a coefficient α, this multiplied value is compared with the flow rate Qp at that time, and the deviation is inputted to the tilt command generation section 157. Tilt command generation unit 157
outputs a numerical value according to a predetermined characteristic having a dead zone f according to the input deviation, and this numerical value is multiplied by the value (60/Dp ・N) set in the setting section 158 to obtain the tilting amount Y.
2 is obtained. However, Dp is the capacity of the hydraulic pump 1, and N is the rotation speed of the hydraulic pump 1. Further, the characteristics of the tilting command generating section 157 are also stored in the storage section of the controller 15. Note that the flow rate Qp is obtained by multiplying the amount of tilting Y, which will be described later, by a value (Dp·N/60).

[0008] The above-mentioned tilting amount Y2 is determined by the operation levers 9a, 9
When b is manipulated, it is calculated stably (without hunting) and quickly. Then, when the tilting amount Y2 is outputted from the controller 15 to the solenoid valves 3a and 3b,
The swash plate 1a is driven accordingly, and the hydraulic pump 1 can quickly follow changes in the required total flow rate Qva without saturation. However, as is clear from the description of the characteristics shown in FIG. 3, the flow rate actually obtained based on the required total flow rate Qva is not necessarily accurate and is only a predicted value. Therefore, in this embodiment, a known means called load sensing control is employed to obtain a highly accurate tilting amount. Therefore, the controller 15 detects the discharge pressure Ps of the hydraulic pump 1 and the maximum load pressure PLm from the differential pressure sensor 14.
The differential pressure ΔPLs with respect to
The deviation from s0 is calculated, and this deviation is multiplied by a predetermined constant K to calculate the tilting amount Y1. Through this feedback control, if the differential pressure ΔPLs is larger than the specified value ΔPLs0 (if the above deviation is a negative value), it is determined that the discharge flow rate of the hydraulic pump 1 is too large, and the tilting amount Y1 becomes a negative value. , the previously obtained tilting amount Y2 is added to the adder 156
conversely, the differential pressure ΔPLs is reduced to the specified value ΔPL
If it is smaller than s0 (if the above deviation is a positive value), it is determined that the discharge flow rate of the hydraulic pump 1 is too small, and since the tilting amount Y1 becomes a positive value, the previously obtained tilting amount Y2
is incremented in adder 156. The amount of tilting Y1 in this case is used as a correction value to correct the amount of tilting Y2 found by the previous control, so there is no need to increase the gain in this load sensing control system, and therefore hunting may occur. That's not it. Conversely, from the perspective of load sensing control, there is no risk of hunting, so there is no need to install a mechanical damper, resulting in cost reduction. Thus, the tilting amounts Y1 and Y2 obtained by both control systems are added by the adder 156,
The corrected tilting amount Y is output from the controller 15 to the solenoid valves 3a and 3b, and as a result, the hydraulic pump 1 can discharge the required flow rate with high accuracy regardless of the conditions such as oil temperature at that time. Can be done. In addition, in the description of the above embodiment, a configuration in which the main valve and the directional switching valve are mechanically connected has been described, but this can also be replaced with a normal control valve. Furthermore, it is clear that the load is not limited to a hydraulic cylinder, but may also be a hydraulic motor.

[0009]

As described above, in the present invention, so-called load sensing control is combined with flow comparison type control, and the tilting amount based on the required total flow rate (predicted value) of the former is corrected by the feedback control of the latter. As a result, while maintaining the stability and quick response characteristics of the former, the inaccuracies can be compensated for with the high precision control that is the characteristic of the latter, and the operation of the hydraulic circuit can be controlled with excellent stability and speed. It is highly responsive and can be controlled with high precision. Furthermore, by using the latter control result as a correction for the former control result, the latter gain can be reduced, and hunting can be prevented from occurring.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram using a hydraulic circuit control device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating the functions of the controller shown in FIG. 1.

FIG. 3 is a characteristic diagram of flow rate versus stroke of the main valve shown in FIG. 1;

[Explanation of symbols]

1 Hydraulic pump 1a Swash plate 2 Regulator 3a Solenoid valve 3b Solenoid valve 5a Hydraulic cylinder 5b Hydraulic cylinder 6a Main valve 6b Main valve 7a Directional switching valve 7b Directional switching valve 8a Voltage compensation valve 8b Voltage compensation valve 9a Operation lever 9b Operation lever 12 Pressure sensor 13 Shuttle valve 14 Differential pressure sensor 15 Controller

Claims (1)

[Claims] Claim 1: A variable capacity hydraulic pump that discharges pressure oil according to the amount of tilting of a variable displacement mechanism, a plurality of hydraulic actuators driven by the variable capacity hydraulic pump, and a drive system for each of these hydraulic actuators. In a hydraulic circuit comprising operating means for controlling, and a control valve operating according to an opening command value based on the operating amount of each of these operating means to control the flow rate to a corresponding hydraulic actuator,
a first calculation means for calculating a required total flow rate of pressure oil based on the operation amount of each of the operation means; a second calculation means for calculating a maximum dischargeable flow rate based on the discharge pressure of the variable displacement hydraulic pump; , a coefficient calculation means that sets 1 as a coefficient when the ratio of the maximum dischargeable flow rate and the required total flow rate is 1 or more, and sets the ratio as a coefficient when it is less than 1; and an opening that corrects the opening command value with the coefficient. degree command value correction means; third calculating means for calculating the tilting amount based on the discharge flow rate command value obtained by correcting the maximum dischargeable flow rate by the coefficient; and the discharge pressure of the variable displacement hydraulic pump and the respective hydraulic pressures. a fourth calculation means for calculating a correction value for the tilting amount obtained by the third calculation means based on a deviation between a pressure difference between the maximum load pressure of the actuator and a prescribed pressure difference; a fifth calculating means for calculating a tilting command value of the variable displacement mechanism based on the calculated value of the third calculating means and the fourth calculating means; Control device.