WO2012057241A1

WO2012057241A1 - Hydraulic pressure circuit control method

Info

Publication number: WO2012057241A1
Application number: PCT/JP2011/074745
Authority: WO
Inventors: 憲平山路
Original assignee: ボッシュ・レックスロス株式会社
Priority date: 2010-10-28
Filing date: 2011-10-27
Publication date: 2012-05-03
Also published as: JP2014015945A

Abstract

Provided is a control method of a variable capacity pump with which it is possible to control according to a bleed-off characteristic of each actuator with a high degree of freedom. [Solution] An actual discharge volume and an actual discharge pressure of a variable capacity pump, and a degree of operation of each directional control valve, are detected. A first virtual discharge pressure is determined from the actual discharge volume of the variable capacity pump on the basis of a characteristic curve which establishes a relation between the discharge pressure and the discharge volume of the variable capacity pump. The actual pump discharge volume is treated as an actuator flow which is necessary for the actuator. A bleed-off area of a closed-center directional control valve is determined according to the degree of operation. A bleed-off flow is determined on the basis of the bleed-off area. A second virtual discharge pressure of the variable capacity pump is determined on the basis of a value obtained by subtracting the actuator flow and the bleed-off flow from the actual discharge volume of the variable capacity pump. The variable capacity pump is controlled on the basis of the smaller of either the first or second virtual discharge pressure.

Description

Control method of hydraulic circuit

The present invention relates to a hydraulic circuit control method applied to a machine such as a construction machine that uses a bleed-off hydraulic system.

The applicant of the present invention relates to a hydraulic circuit used in the field of construction machinery such as a hydraulic excavator and a plurality of closed center type directional control valves in a variable displacement pump driven by an engine and adjustable in pump discharge amount from the outside. Patent Documents 1 and 2 disclose a method of controlling the variable displacement pump by electrical calculation so that the actuators are connected via the respective valves, and the closed center type directional control valve is replaced with a center bypass type directional control valve. Proposed in

The operation of the circuit disclosed in Patent Document 2 will be briefly described with reference to FIGS. 6 and 7. An operation amount for operating the actuator is input to the controller including the calculation means. The controller calculates the virtual pump discharge pressure command P _idea by calculating the bleed-off characteristic of the closed center type directional control valve using the virtual pump discharge amount Q _idea , the pump discharge amount estimated value and the operation amount as parameters, and the closed-loop pressure control The pump discharge command Q _pc is transmitted to the variable displacement pump by calculation. In the variable displacement pump, the actual discharge amount Q _real is calculated, and the difference between this discharge amount Q _real and the actuator flow rate Q _a is multiplied by the coefficient (1 / Cp) of the actual pump piping system and further integrated. Thus, the actual pump discharge pressure P _real is obtained.

Japanese Patent No. 3471638 Japanese Patent No. 3745038

The horsepower calculation in the controller is based on a characteristic curve that defines the relationship between the discharge pressure and the discharge flow rate of the virtual pump based on the actual pump discharge pressure P _real when calculating the discharge amount Q _idea of the virtual pump. Making a decision. In this characteristic curve, control is normally performed such that the discharge flow rate is constant up to a predetermined pressure P1, and the product of the pressure and the flow rate is constant when the pressure P1 is exceeded.
However, since the discharge amount Q _idea of the virtual pump decreases when the pressure P1 is exceeded, in the subsequent bleed-off calculation process, the characteristic calculation is divided into cases where the pressure P is less than P1 and exceeds P1. There is a need to do. In the region exceeding P1, when the actual pump discharge amount _Qreal is small, the horsepower is calculated based on the actual pump discharge pressure _Preal even though the actuator load is small. In addition, if the rated horsepower is reached, a calculation result that lowers the actual pump discharge amount _Qreal is obtained, and the horsepower of the pump cannot be used effectively.

Therefore, the present invention can determine the bleed-off characteristic of the directional control valve without affecting the bleed-off characteristic of each actuator without being affected by the calculation of the horsepower characteristic of the pump, and effectively uses the horsepower of the pump. It is an object of the present invention to provide a hydraulic circuit control method that can be used.

In order to solve the above problems, the inventors have found a solution as follows.
In other words, the hydraulic circuit control method according to the present invention includes a plurality of closed center type directional control valves in a variable displacement pump driven by an engine and having an adjustable pump discharge amount from the outside. A hydraulic circuit control method for controlling the variable displacement pump so that the closed center type directional control valve is substituted for a center bypass type directional control valve in a hydraulic circuit having an actuator connected thereto, The variable displacement pump detects the actual discharge amount, the actual discharge pressure, and the operation amount of each directional control valve, and based on the characteristic curve that defines the relationship between the discharge pressure and the discharge amount of the variable displacement pump, the variable The first virtual discharge pressure is determined from the actual discharge amount of the capacity pump, the actual pump discharge amount is set as an actuator flow rate required for the actuator, and the operation is performed. The bleed-off area of the closed center type directional control valve is determined according to the bleed-off flow, and the bleed-off flow is determined based on the bleed-off area. The second virtual discharge pressure of the variable displacement pump is determined on the basis of the value obtained by subtracting, and the smaller one of the first and second virtual discharge pressures is determined. Based on this, the variable displacement pump is controlled.
According to a second aspect of the present invention, in the hydraulic circuit control method according to the first aspect, a plurality of the variable displacement pumps are connected to the engine, and a plurality of the variable displacement pumps are connected to the plurality of variable displacement pumps. The actuator is connected via a closed center type directional control valve, a ratio of horsepower distributed to the variable displacement pumps of the engine is determined according to the operation amount of each actuator, and the distributed each The first virtual discharge pressure is determined from the horsepower and the actual discharge amount of the variable displacement pump.
According to a third aspect of the present invention, in the method of controlling a hydraulic circuit according to the first aspect, the characteristic curve has a constant discharge amount up to a predetermined discharge pressure region, and a region exceeding the predetermined pressure. Is characterized in that the product of the discharge pressure and the discharge flow rate is constant.
According to a fourth aspect of the present invention, in the method for controlling a hydraulic circuit according to the first aspect, the first virtual discharge pressure is a discharge pressure of the variable displacement pump required for each actuator. The horsepower of the variable displacement pump that is calculated as a sum and distributed to the actuators is determined in advance, and for each of the actuators, the actual discharge amount from the distributed horsepower to the actuators, and the first or By subtracting the value obtained by integrating the smaller one of the second virtual discharge pressures, the surplus horsepower for each actuator is calculated, and the horsepower of one actuator is The sum of the surplus horsepower of the remaining actuators is added to the horsepower distributed to the actuators.
According to a fifth aspect of the present invention, in the hydraulic circuit control method according to the first aspect, the first virtual discharge pressure is variable in accordance with an operation amount of each directional control valve. It is characterized by.

As described above, according to the present invention, the virtual pump discharge amount is used when calculating the bleed-off flow rate, so that the control of the bleed-off flow rate is not affected by the actual horsepower calculation of the pump. Even in the horsepower calculation area, the pump horsepower can be effectively utilized even when the actual pump discharge amount is small and the actual load on the actuator is small.

FIG. 1 is a hydraulic circuit diagram for explaining a control method for a variable displacement pump according to an embodiment of the present invention. Block diagram for explaining the control of FIG. Explanatory drawing of the part enclosed with the dotted line A of FIG. Block diagram for explaining another embodiment of the present invention Block diagram for explaining another embodiment of the present invention Block diagram for explaining conventional bleed-off characteristic calculation Block diagram for explaining conventional bleed-off characteristic calculation

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a hydraulic circuit applied to a hydraulic excavator or the like for controlling the operation of a plurality of hydraulic actuators 1, which are closed to a discharge circuit 3 of a variable displacement pump 2 driven by a drive motor PM. It is connected via the center closed center type

directional control valves

4, 4.
The variable displacement pump 2 is a known one such as an axial piston pump having a pump displacement control mechanism such as a swash plate.
In the present specification, the term “closed center type directional control valve” refers to a valve configured not to bypass oil to the tank when the spool is in the neutral position. Refers to a valve configured to bypass the oil to the tank when the spool is in the neutral position.

An output of the solenoid drive amplifier 5 as a command input and a discharge side pressure of the pump 2 as a feedback input are connected to the input side of the pump pressure control device 6, and a control piston 7 is connected to the output side of the pump pressure control device 6. Is connected.
The pump pressure control device 6 includes a control valve 6b and a negative electromagnetic proportional valve 6c. The actual pump discharge pressure P _real of the pump 2 and the elastic force of the spring 6d are negative at both ends of the spool of the control valve 6b. type electromagnetic proportional valve 6c pressure signal P ^'c is controlled such by, but on both ends of the spool are suitable Naru area difference is given, the control valve 6b is accordingly, they are controlled by their balance.
Negative solenoid proportional valve 6c the pressure signal P ^'c, and the controller 12, the signal P' of the input side facing the spring and to the proportional solenoid 6a is that in proportion to the control current input based _idea is variable Controlled by balance with generated force.
In this embodiment, as shown in the block diagram of FIG. 2, the virtual pump discharge pressure command P _idea obtained from the bleed-off characteristic calculation is subtracted from the maximum discharge pressure of the pump in order to perform negative control. The inverted signal P ′ _idea is transmitted to the proportional solenoid 6c of the negative electromagnetic proportional valve.
With the above configuration, the virtual pump discharge pressure command P _idea is inverted to the negative type, and then the proportional solenoid 6a of the pump pressure control device 6 is excited through the solenoid drive amplifier 5, and the excitation is performed through the negative type electromagnetic proportional valve. The control valve 6b is operated in inverse proportion to the size of the valve (and therefore in proportion to the virtual pump discharge pressure command P _idea ). As a result, the control piston 7 moves the pump displacement control mechanism, and the pump displacement, that is, the pump discharge. Control the amount large or small.
In the present specification, the “negative type” means that the output value gradually decreases with respect to the input value.

In the example described, a proportional relief valve is used as the negative electromagnetic proportional valve 6c. However, by subtracting from the pump discharge pressure, an electromagnetic proportional pressure reducing valve is used in the present invention. The system means that the pump can be moved at a predetermined pressure or the like when a signal is not obtained, and the output value gradually decreases when a signal is input.

The closed center type directional control valve 4 includes a proportional solenoid 8 for moving the spool. When the solenoid drive amplifier 13 is operated by the electric joystick 9 via the controller 12, the closed directional control valve 4 is in accordance with the inclination angle of the electric joystick 9. The proportional solenoid 8 is excited, the spool of the closed center type directional control valve 4 is moved to a desired position, and the

actuator ports

10 and 10 are controlled to the opening areas Ac1 and Ac2 according to the moving distance.

A command amount such as an inclination angle of an operation lever for operating each closed center type directional control valve 4 or a movement amount of a spool of each closed center type directional control valve 4 is electrically detected by a sensor, and the command amount or movement is detected. The operation amount signal S based on the operation amount of each closed center type directional control valve 4 is set as the operation amount, and in the example of FIG. 1, the command electric signal from the electric joystick 9 to the solenoid drive amplifier 13 via the controller 12 is the operation amount. Used as a signal.

The actuator flow rate Q _a is closed because de center type directional control valve 4 is actually a Allport closed valve without bleed-off channel, ignoring the slight leakage of the circuit, the actual output of the pump 2 The quantity Q _real can be substituted for the actuator flow rate Q _a .
In this embodiment, the actuator flow rate Q _a is obtained by providing the variable displacement pump 2 with a discharge amount detection sensor 11 and multiplying the tilt amount detected by the discharge amount detection sensor 11 by the rotation speed of the pump 2. and to calculate the actuator flow rate Q _a.
As the discharge amount detection sensor, for example, when the variable displacement pump 2 is a swash plate type variable displacement pump or a radial pump, a potentiometer or the like can be used.

These electric signals are calculated by a controller 12 including an A / D converter 12a, a calculator 12b, and a D / A converter 12c. The calculator 12b automatically performs the calculation shown in the block diagram of FIG. Run in a controlled manner.

In the present embodiment, in the controller 12, the first virtual pressure obtained from the maximum discharge pressure of the variable displacement pump 2 and the characteristic curve that defines the relationship between the discharge pressure of the variable displacement pump 2 and the discharge flow rate. The variable displacement pump 2 is controlled based on the minimum value obtained by comparing either the discharge pressure or the second virtual discharge pressure obtained based on the operation amount. The reason why the maximum discharge pressure of the variable displacement pump 2 is compared is to prevent a discharge pressure higher than the maximum discharge pressure of the variable displacement pump 2 from being indicated as the discharge pressure of the variable displacement pump 2. The maximum discharge pressure is not always necessary as long as the present invention is implemented.
The actual discharge amount of the variable displacement pump 2 is converted into a first virtual discharge pressure by a characteristic curve as shown. The characteristic curve is such that the discharge amount is constant with respect to the discharge pressure up to a predetermined pressure P1, and the product of the discharge pressure and the discharge amount is constant in a region exceeding P1. preferable.
On the other hand, the second virtual discharge pressure is obtained from the discharge amount of the variable displacement pump 2 by a process indicated by a dotted line A in FIG.

The processing within the dotted line A in FIG. 2 will be described below with reference to FIG.
First, as shown in FIG. 3 receives an input of an operation amount S _k of the plurality of closed center directional control valve 4, their sum S ₁ + S ₂ + ··· take S _n, the operation amount of the total Let it be signal S. At this time, each input may be weighted or an appropriate calculation process may be performed. Next, the opening area Ab of the bleed-off flow path of the closed center type directional control valve corresponding to the planned bleed-off characteristic is obtained from the manipulated variable signal S, and the bleed-off characteristic value Xb is obtained by multiplying it by Kq (flow coefficient). Of course, the actual closed center type directional control valve 4 is a closed center without a bleed-off flow path, and this opening area Ab is a value in calculation. The bleed-off characteristic is determined by determining in advance the relationship between the opening area Ab and the operation amount S.

Further, the virtual discharge amount Q _idea of the variable displacement pump 2 is set to a predetermined value.
At this time, since the maximum discharge amount of the variable displacement pump 2 is a known number, this value can also be used.

The actuator flow rate, as described above, for example, from inputted as a flow rate signal from the actual pump discharge quantity Q _real, flow rate value Xa calculated by subtracting the actual pump discharge quantity Q _real virtual pump discharge quantity Q _idea bleed Corresponds to off flow rate. The virtual pump discharge pressure command P _idea is calculated by dividing this Xa by Xb and calculating the value to the nth power (n is an integer of 3 or more). Then, based on the virtual pump discharge pressure command P _idea , the discharge pressure is closed-loop controlled. That is, the solenoid drive amplifier 5 receives the control signal based on the virtual pump discharge pressure command P _idea and increases or decreases the excitation of the electromagnetic proportional valve 6a, and subtracts the subtraction between the virtual pump discharge pressure P _idea and the actual pump discharge pressure P _real. The control piston 7 controls the pump discharge amount in accordance with a command from the control valve 6b, using the negative electromagnetic proportional valve 6c and the control valve 6b.

When the electric joystick 9 is not operated, the closed center type directional control valve 4 is in the neutral position, and zero is input to the controller 12 as the operation amount signal S. In this case, the opening area of the bleed-off passage which is calculated by the controller 12 because maximized, virtual pump discharge pressure P _idea becomes a small value. Pump 2 based on the virtual pump discharge pressure P _idea do discharge, but compresses the actual pump discharge pressure P _real discharge circuit of the pump piping system to a virtual pump discharge pressure P _idea, After boosts the actual pump The discharge amount requires only a small amount of leakage in the circuit, and the actuator speed, that is, the actuator flow rate is almost zero, and at this time, Xa = Q _max and the virtual pump discharge pressure P _idea = (Q _max / (Kq × Ab )) ⁿ .

When the electric joystick 9 is operated and the closed center type directional control valve 4 is operated in the switching position direction, the opening area of the bleed-off flow path calculated by the controller 12 becomes small, and the virtual pump discharge pressure P _idea is once The total pump discharge amount is set to a value when returning from the narrowed bleed-off flow path to the tank with a small area. Since the pump discharge pressure is closed-loop controlled, the actual pump discharge pressure P _real is substantially equal to the value of the virtual pump discharge pressure P _idea . If the actual pump discharge pressure P _real is higher than the load pressure, the actuator 1 is accelerated and the oil begins to flow. Therefore, the pump discharge amount is increased to keep the actual pump discharge pressure P _real at the virtual pump discharge pressure P _idea. However, as the actuator speed increases, the bleed-off flow rate decreases, so the virtual pump discharge pressure P _{idea and} consequently the actual pump discharge pressure P _real decreases, the actuator acceleration decreases, and the actuator speed gradually matches the operating amount. It converges and balances the pump discharge amount and discharge pressure to be maintained. During this time, the bleed-off operation is performed only by calculation within the controller, and the actual pump discharge amount Q _real is limited to the amount supplied to the actuator 1 if the leakage on the circuit is ignored. Therefore, there is no waste of energy because the bleed-off flow rate does not flow, and since the bleed-off flow path is not required for the closed center type directional control valve, the configuration is simple and inexpensive, and the operability is improved.

Next, another embodiment of the present invention will be described with reference to FIG.
FIG. 4 shows a modified example of the horsepower calculation in the block diagram of FIG.
In the illustrated example, the number of actuators 1 connected to the variable displacement pump 2 is two, and the horsepower of the variable displacement pump 2 is distributed to each actuator 1 at a ratio of 0.5 in advance. The first virtual discharge pressure is calculated as the total discharge pressure of the variable displacement pump 2 required for each actuator 1.
Each actuator 1 is obtained by integrating the actual discharge amount to each actuator 1 and the smaller one of the first and second virtual discharge pressures from the distributed horsepower. The surplus horsepower for each actuator 1 is calculated by subtracting the obtained value.
The horsepower of one actuator 1 is set to a value obtained by adding the total horsepower of the remaining actuators to the horsepower distributed to the actuator 1.
According to this configuration, surplus horsepower distributed to each actuator can be effectively utilized.

Next, another embodiment of the present invention will be described using the block diagram of FIG.
In the present embodiment, the operation of the controller 12 is performed according to the block diagram shown in FIG. 5 with the same hydraulic circuit configuration as in FIG.
In the illustrated example, input of operation amounts S1, S2,..., Sk,..., Sn of the plurality of closed center type directional control valves 4 is received. For these, the opening area Ab of the bleed-off flow path of the closed center type directional control valve corresponding to the planned bleed-off characteristic is obtained by the following equation. In the formula, Abk corresponds to Sk.

If the variable displacement pump is controlled by the above configuration, operability in accordance with the required characteristics of each actuator can be obtained.

Further, if the first virtual discharge pressure is made variable according to the operation amount of each directional control valve (for example, the flow rate of the pump is increased in a quadratic function according to the operation amount), Solving the single operation reduces the resistance at the meter-in throttle, avoids energy loss, enhances the shunt control effect at meter-in during combined operation, and allows combined operation of actuators with different loads.

Claims

In a hydraulic circuit in which an actuator is connected to a variable displacement pump that is driven by an engine and the pump discharge amount can be adjusted from the outside through a plurality of closed center directional control valves, the closed center directional control valve has a center A hydraulic circuit control method for controlling the variable displacement pump so as to replace a bypass type directional control valve,
Detect the actual discharge amount of the variable displacement pump, the actual discharge pressure and the operation amount of each directional control valve,
Based on a characteristic curve that defines the relationship between the discharge pressure and the discharge amount of the variable displacement pump, a first virtual discharge pressure is determined from the actual discharge amount of the variable displacement pump,
The actual discharge amount of the variable displacement pump is the actuator flow rate required for the actuator,
Determine the bleed-off area of the closed center type directional control valve according to the operation amount,
Determining the bleed-off flow rate based on the bleed-off area;
Determining a second virtual discharge pressure of the variable displacement pump based on a value obtained by subtracting the actuator flow rate and the bleed-off flow rate from an actual discharge amount of the variable displacement pump;
A control method for a hydraulic circuit, wherein the variable displacement pump is controlled based on a smaller one of the first and second virtual discharge pressures.
A plurality of the variable displacement pumps are connected to the engine, and the actuator is connected to each of the variable displacement pumps via the plurality of closed center directional control valves,
According to the operation amount for each actuator, determine the ratio of horsepower distributed to each variable displacement pump of the engine,
2. The hydraulic circuit control method according to claim 1, wherein a first virtual discharge pressure is determined from each of the distributed horsepower and an actual discharge amount of the variable displacement pump.
2. The characteristic curve according to claim 1, wherein a discharge amount is constant up to a predetermined discharge pressure region, and a product of discharge pressure and discharge flow rate is constant in a region exceeding the predetermined pressure. The control method of the hydraulic circuit as described in.
The first virtual discharge pressure is calculated as the sum of the discharge pressures of the variable capacity pump required for each actuator,
Predetermining the horsepower of the variable displacement pump distributed to each actuator,
For each actuator, it is obtained by integrating the actual discharge amount to each actuator and the smaller one of the first and second virtual discharge pressures from the distributed horsepower. To calculate the surplus horsepower for each actuator,
2. The hydraulic circuit control method according to claim 1, wherein the horsepower of one of the actuators is a value obtained by adding the total of the surplus horsepower of the remaining actuators to the horsepower distributed to the actuators.
2. The hydraulic circuit control method according to claim 1, wherein the first virtual discharge pressure is variable in accordance with an operation amount of each directional control valve.