JP6367676B2 - Hydraulic circuit control device and hydraulic circuit control method - Google Patents

Description

  The present invention relates to a hydraulic circuit control device and a hydraulic circuit control method.

  Conventionally, in the field of construction machinery such as hydraulic excavators, a hydraulic circuit in which an actuator is connected to a variable displacement pump driven by an engine and capable of adjusting a discharge flow rate from the outside via a plurality of closed center type directional control valves. Is used. This hydraulic circuit can control a variable displacement pump by calculation of an electronic control unit so that a closed center type directional control valve can be substituted for a center bypass type directional control valve. (Referred to as “virtual bleed-off control”).

  Virtual bleed-off control mathematically replaces the bleed-off characteristics of the bleed-off hydraulic system with a center bypass type directional control valve, that is, the part that controls the pressure supplied to each actuator and the flow rate of control oil. Thus, the discharge pressure of the variable displacement pump is controlled by calculation by the electronic control unit. In the conventional bleed-off control, control is performed while actually returning a part of the control oil pumped by the variable displacement pump to the oil tank, so that the variable displacement pump cannot be effectively used. On the other hand, virtual bleed-off control controls the center bypass from the directional control valve by controlling the discharge pressure of the variable displacement pump as if the hydraulic circuit had a bleed-off characteristic by calculation by an electronic control unit. By omitting the passage, only the control oil having the actually required flow rate can be discharged.

  For example, in Patent Document 1, when an actuator performs a desired operation, a virtual discharge flow rate of a pump is set to a predetermined value, and bleed-off is performed according to an operation amount input from operation means such as a joystick. It is described that a virtual bleed-off flow is calculated and the variable displacement pump is controlled so that control oil having a flow rate excluding the virtual bleed-off flow is discharged from the variable displacement pump. As the value of the discharge flow rate, for example, the maximum discharge flow rate by the pump can be used.

International Publication WO2013 / 128622 (paragraph 0032)

  However, in a hydraulic circuit provided with a plurality of actuators, the required flow rate differs for each actuator due to its specifications, and setting the virtual discharge flow rate of the pump more than necessary may cause a reduction in efficiency. Moreover, since the virtual discharge flow rate of the pump is set to a predetermined constant value in the control method described in Patent Document 1, a value that is equal to or greater than the assumed maximum discharge flow rate is set as the virtual discharge flow rate of the pump. There is a need to. For this reason, there is a problem in that useless pressure is generated even in the fine operation region, and the variable displacement pump cannot be effectively used.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a variable displacement pump in a virtual bleed-off hydraulic system so that the discharge pressure is suitable for the operation amount of the actuator. It is an object of the present invention to provide a new and improved hydraulic circuit control device and a hydraulic circuit control method that can be controlled.

  In order to solve the above-described problem, according to one aspect of the present invention, a variable displacement pump and a plurality of actuators connected to the variable displacement pump via respective directional control valves are provided, and each of the directional controls is provided. In each of the hydraulic circuit control devices for controlling the hydraulic circuit configured to switch the operation direction of the actuator by operating the direction control valve based on an operation amount input to the valve, each of the direction control A virtual discharge flow rate setting unit that sets a virtual discharge flow rate of the variable displacement pump based on the operation amount for the valve, and virtual outputs from all the direction control valves based on the operation amount for each of the direction control valves. A bleed-off flow rate calculation unit that calculates a bleed-off flow rate and a total estimated actuator that is an estimated flow rate to all the actuators. And a pump controller that obtains a virtual discharge pressure based on a difference obtained by subtracting the data flow rate and the bleed-off flow rate from the virtual discharge flow rate, and controls the variable displacement pump based on the virtual discharge pressure. A control device for the hydraulic circuit is provided, which can solve the above-described problems.

  The virtual discharge flow rate setting unit may calculate the virtual discharge flow rate by performing a weighting operation on the virtual flow rate to each of the actuators according to the operation amount.

  Further, the bleed-off flow rate calculation unit, based on the total bleed-off area obtained by combining and calculating the virtual bleed-off area of each directional control valve according to the operation amount and the calculation of the virtual flow rate to the actuator, The bleed-off flow rate may be calculated.

  In order to solve the above problems, according to another aspect of the present invention, a variable displacement pump and a plurality of actuators each connected to the variable displacement pump via a directional control valve are provided. In a hydraulic circuit control method for controlling a hydraulic circuit configured to switch an operation direction of the actuator by operating the directional control valve based on an operation amount input to the directional control valve, Setting a virtual discharge flow rate of the variable displacement pump based on the manipulated variable for the directional control valve; and virtual bleed from all the directional control valves based on the manipulated variable for each of the directional control valves. Calculating an off flow rate, a total estimated actuator flow rate that is an estimated flow rate to all the actuators, and the A step of obtaining a virtual discharge pressure based on a difference obtained by subtracting a lead-off flow rate from the virtual discharge flow rate, and controlling the variable displacement pump based on the virtual discharge pressure. A method is provided.

  As described above, according to the present invention, in the virtual bleed-off hydraulic system, the variable displacement pump can be controlled so that the discharge pressure is suitable for the operation amount of the actuator.

1 is a circuit diagram showing a configuration of a hydraulic circuit according to a first embodiment of the present invention. It is a block diagram which shows the control processing of the variable displacement pump which concerns on the same embodiment. It is a control block diagram of the control device according to the embodiment. It is a figure which shows the pressure characteristic of the hydraulic circuit which concerns on the same embodiment. It is a control block diagram of the control apparatus which concerns on 2nd Embodiment.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<First Embodiment>
[1. Overall configuration of hydraulic circuit]
First, an example of the configuration of the hydraulic circuit according to the first embodiment of the present invention will be described. FIG. 1 shows a hydraulic circuit for controlling a plurality of hydraulic actuators 1a, 1b. This hydraulic circuit is configured as a hydraulic circuit applicable to, for example, a hydraulic excavator operated by a plurality of hydraulic actuators. The actuators 1a, 1b,... Are connected to the discharge circuit 3 of the variable displacement pump 2 driven by the engine E via closed center type directional control valves 4a, 4b, respectively.

  In the hydraulic circuit of FIG. 1, only two actuators 1a and 1b and two closed center type directional control valves 4a and 4b are shown. As the variable displacement pump 2, a known pump such as an axial piston pump having a pump displacement control mechanism such as a swash plate can be used. Hereinafter, a variable displacement pump capable of controlling the discharge flow rate by adjusting the inclination of the swash plate will be described as an example.

  The hydraulic circuit includes a pump pressure control device 6 for controlling the discharge pressure of the variable displacement pump 2. The pump pressure control device 6 is connected to the discharge circuit 3 of the variable capacity pump 2. The pump pressure control device 6 includes a control valve 6b and a negative electromagnetic proportional valve 6c. The pressure of the discharge circuit 3 (hereinafter referred to as “actual discharge pressure”) Preal acts on one end face of the spool of the control valve 6b. Further, the elastic force of the spring 6d and the control oil pressure P'c controlled by the negative electromagnetic proportional valve 6c act on the other end face of the spool of the control valve 6b. An appropriate area difference is given to both ends of the spool, and the position of the spool of the control valve 6b is controlled by the balance of these forces.

  The negative electromagnetic proportional valve 6c is a valve that functions as a proportional relief valve. A spring force is applied to one end face of the piston of the electromagnetic proportional valve 6c, and control supplied to the other end face based on the control oil pressure P'c and a control signal P'tgt from the control device 12. The force generated by the proportional solenoid 6a that varies in proportion to the current acts. The position of the piston of the electromagnetic proportional valve 6c is controlled by the balance of these forces, and the control oil at a predetermined flow rate is released according to the position of the piston, and the pressure P'c acting on the spool of the control valve 6b is adjusted.

  As described above, the actual pump discharge pressure Preal of the variable displacement pump 2 is input to the pump pressure control device 6, and is output via the control valve 6b when the control device 12 controls the electromagnetic proportional valve 6c. The pressure can be adjusted. A control piston 7 is connected to the output side of the pump pressure control device 6, and the stroke amount of the control piston 7 is changed by changing the pressure output from the pump pressure control device 6. Can be controlled. Therefore, the actual pump discharge pressure Preal of the variable displacement pump 2 can be controlled.

  The closed center type directional control valves 4a and 4b are provided with a proportional solenoid 8 for moving the spool. When the solenoid driving amplifier 13 is operated by the operation lever 9 such as an electric joystick via the control device 12, the proportional solenoid 8 is excited according to the inclination angle of the operation lever 9. As a result, the spools of the closed center type directional control valves 4a and 4b move to desired positions, and the actuator port 10 is controlled to have an opening area corresponding to the movement distance. As a result, control oil having a flow rate corresponding to the opening area is supplied to the actuators 1a and 1b. Such an opening area is also referred to as a “bleed-off area”.

  A command amount such as an inclination angle of the operation lever 9 for operating each closed center type direction control valve 4a, 4b or a movement amount of the spool of each closed center type direction control valve 4a, 4b is electrically detected by a sensor. The The detected command amount or movement amount is a parameter indicating the operation amount Sk (k = 1, 2,...) Of each closed center type directional control valve 4a, 4b. In the example of FIG. 1, a command electric signal transmitted from the operation lever 9 to the solenoid drive amplifier 13 via the control device 12 is used as a parameter indicating the operation amount Sk.

  The closed center type directional control valves 4a and 4b are actually valves without a bleed-off flow path, and if neglecting a slight leakage of control oil on the circuit, the actual pump discharge flow rate of the variable displacement pump 2 (hereinafter, This is referred to as “actual pump discharge flow rate.”) Qreal and total actuator flow rate Qa are substantially equal. In the hydraulic circuit described in the present embodiment, a plurality of actuators 1a, 1b,... Are connected to one variable displacement pump 2, and the total actuator flow rate Qa is all closed center type directional control. This means the sum of the flow rates of the control oil supplied to the actuators 1a, 1b... Via the actuator ports 10 in the valves 4a and 4b.

  The variable displacement pump 2 includes a tilt amount sensor 11 for measuring the tilt of the swash plate, and is variable by multiplying the tilt amount detected by the tilt amount sensor 11 by the rotational speed N of the variable displacement pump 2. The actual pump discharge flow rate Qreal of the displacement pump 2 can be calculated. Since there is almost no leakage of control oil from the closed center type directional control valves 4a and 4b, the calculated actual pump discharge flow rate Qreal is set to the estimated value Qai of the total actuator flow rate Qa (hereinafter referred to as “total estimated actuator flow rate Qai”). ").

  In the present embodiment, the control device 12 includes an A / D converter 12a, a computing unit (CPU) 12b, a D / A converter 12c, and a storage unit 14. The memory | storage part 14 is a memory | storage element illustrated by RAM, ROM, etc., and memorize | stores the program and various information which are performed by CPU12b. In the control device 12, arithmetic processing is performed based on various electric signals input to the control device 12. In the present embodiment, the control device 12 functions as a virtual discharge flow rate setting unit, a bleed-off flow rate calculation unit, and a pump control unit.

[2. Control processing of hydraulic circuit]
Next, the control process of the hydraulic circuit executed by the calculation process by the control device 12 according to the present embodiment will be specifically described. FIG. 2 is a block diagram showing control of the pump discharge pressure by the control device 12 of the hydraulic circuit according to the present embodiment. The CPU 12b of the control device 12 executes arithmetic processing shown by a block diagram within a dotted line B in FIG.

  The control device 12 obtains the first virtual discharge obtained based on the maximum discharge pressure Pmax of the variable displacement pump 2 as the system pressure and the characteristic curve defining the relationship between the discharge pressure P of the variable displacement pump 2 and the discharge flow rate Q. The pressure Pidea1 is compared with the second virtual discharge pressure Pidea2 obtained based on the operation amount Sk, and the variable displacement pump 2 is controlled using the obtained minimum value as the pump discharge pressure command value Ptgt. In the present embodiment, the maximum discharge pressure Pmax of the variable displacement pump 2 is included in the comparison target. The reason why the maximum discharge pressure Pmax is included is to prevent a discharge pressure equal to or higher than the maximum discharge pressure Pmax of the variable displacement pump 2 from being indicated as the pump discharge pressure instruction value Ptgt of the variable displacement pump 2. However, the maximum discharge pressure Pmax is not always necessary as long as the present invention is implemented.

(Calculation of first virtual discharge pressure)
The first virtual discharge pressure Pidea 1 is obtained from the horsepower calculation of the engine based on the actual pump discharge flow rate Qreal of the variable displacement pump 2. Specifically, as described above, the actual pump discharge flow rate Qreal can be obtained by multiplying the tilt amount detected by the tilt amount sensor 11 by the rotation speed of the variable displacement pump 2. The actual pump discharge flow rate Qreal is converted to a first virtual discharge pressure Pideal 1 based on a characteristic curve that defines the relationship between the discharge pressure P and the discharge flow rate Q of the variable displacement pump 2.

  The product of the discharge pressure P and the discharge flow rate Q of the variable displacement pump 2 represents the horsepower of the engine, and the first virtual discharge pressure Pidea1 is the value of the discharge flow rate Q of the variable displacement pump 2 from the viewpoint of the horsepower of the engine. Try to set an upper limit. The characteristic curve is, for example, a constant discharge flow rate Q regardless of the discharge pressure P up to a predetermined pressure P1, and the product of the discharge pressure P and the discharge flow rate Q is constant in a region exceeding the pressure P1. It is preferable that

(Calculation of second virtual discharge pressure)
The second virtual discharge pressure Pidea2 is based on the operation amount Sk of the closed center type directional control valves 4a and 4b by a process different from the process of obtaining the first virtual discharge pressure Pidea1 based on the characteristic curve. It is obtained by the arithmetic processing shown in the alternate long and short dash line A. An example of the arithmetic processing within the one-dot chain line A in FIG. 2 will be specifically described with reference to the control block diagram in FIG.

  As shown in FIG. 3, the control device 12 first receives information on the operation amount Sk (k = 1, 2...) Of each closed center type directional control valve 4a, 4b. A virtual discharge flow rate (hereinafter referred to as “virtual pump discharge flow rate”) Qidea of the variable displacement pump 2 is determined based on Sk (k = 1, 2,...). That is, the control device 12 executes processing as a virtual discharge flow rate setting unit. In the first embodiment, the sum S1 + S2 +... + Sn of the operation amounts Sk (k = 1, 2,...) Of all the directional control valves 4a, 4b. Based on the stored virtual pump discharge flow rate characteristic, a virtual pump discharge flow rate Qidea corresponding to the operation amount S is obtained. The virtual pump discharge flow rate characteristic is set such that, for example, the virtual pump discharge flow rate Qidea increases in proportion to the total manipulated variable S increasing.

  Further, the control device 12 determines the total of the virtual bleed-off flow paths of the closed center type directional control valves 4a, 4b,... According to the total manipulated variable S based on the virtual bleed-off characteristics stored in advance. The opening area Ab is obtained. This total opening area is also referred to as “total bleed-off area”. The calculated virtual total opening area Ab is multiplied by the m-th root of the second virtual discharge pressure Pidea2 calculated at this time, and further multiplied by the flow coefficient Kq of the center bypass directional control valve. Obtain the bleed-off flow rate Qb. That is, the control device 12 executes processing as a bleed-off flow rate calculation unit. The m-th root may be a square root, for example. Of course, the actual closed center type directional control valves 4a, 4b,... Are of the closed center type without the bleed-off flow path, and the total opening area Ab of the virtual bleed-off flow path is a calculated value. .

  This virtual bleed-off characteristic indicates the relationship between the virtual total opening area Ab and the total manipulated variable S in the closed center type directional control valves 4a, 4b... Used, the center bypass type direction in the conventional bleed-off hydraulic system. It can be set by obtaining in advance using a design method similar to the bleed-off characteristic of the control valve. In the present embodiment, since the virtual pump discharge flow rate Qidea is variable according to the total operation amount S, when the virtual pump discharge flow rate Qidea is set to be small, the virtual total opening area Ab is also small. Set to be a value.

  Then, the controller 12 subtracts the total estimated actuator flow rate Qai and the virtual bleed-off flow rate Qb from the virtual pump discharge flow rate Qidea to obtain a flow rate value ΔQ (ΔQ = Qidea−Qai−Qb). At this time, in reality, there is almost no leakage of control oil from the closed center type directional control valves 4a, 4b..., So if the leakage amount is set to 0, the actual pump discharge flow rate Qreal of the variable displacement pump 2 It becomes equal to the total actuator flow rate Qa. Therefore, the value of the actual pump discharge flow rate Qreal can be used as the total estimated actuator flow rate Qai. Then, the second virtual discharge pressure Pidea2 can be calculated by dividing and integrating the obtained flow rate value ΔQ by the piping compression coefficient C′p of the pump piping system using a digital filter or the like.

(Indication of pump discharge pressure)
Returning to FIG. 2, the control device 12 compares the obtained first virtual discharge pressure Pidea 1 and second virtual discharge pressure Pidea 2, and further the maximum discharge pressure Pmax of the variable displacement pump 2, and determines the minimum value of them. The pump discharge pressure command value Ptgt is set. Then, the control device 12 controls the discharge pressure of the variable displacement pump 2 in a closed loop based on the control signal P′tgt that is inverted by subtracting the pump discharge pressure command value Ptgt from the maximum discharge pressure Pmax of the pump. . That is, the control device 12 executes processing as a pump control unit.

  As a result, the solenoid drive amplifier 5 receives the control signal P′tgt of the control device 12 and strengthens the excitation of the proportional solenoid 6a of the negative electromagnetic proportional valve 6c. As a result, in inverse proportion to the magnitude of the excitation, in other words, the pressure P′c of the negative electromagnetic proportional valve 6c is proportionally controlled according to the pump discharge pressure instruction value Ptgt, whereby the control valve 6b is Operated. As a result, the control piston 7 moves the pump capacity control mechanism to control the pump capacity, that is, the pump discharge flow rate. As a result, the discharge pressure of the variable displacement pump 2 is controlled, and the control valve 6b is operated against the pressure P'c of the negative electromagnetic proportional valve 6c. As described above, since the pump discharge pressure is controlled in a closed loop, the actual pump discharge pressure Preal is substantially equal to the pump discharge pressure instruction value Ptgt.

  In the present embodiment, the negative electromagnetic proportional valve 6c is used, and the variable displacement pump 2 can be driven with the maximum pressure when the control signal P'tgt is not output. However, a positive electromagnetic proportional valve may be used instead of the negative electromagnetic proportional valve. In this case, the process of inverting the pump discharge pressure command value Ptgt is omitted, and the pump discharge pressure command value Ptgt and the control signal P′tgt are treated as equal.

[3. Example of hydraulic circuit operation]
In the control of the hydraulic circuit executed as described above, the second virtual discharge pressure Pidea2 is smaller than the first virtual discharge pressure Pidea1 in most operating regions, that is, in a situation where there is no fear of engine stall. Thus, the second virtual discharge pressure Pidea2 becomes the pump discharge pressure instruction value Ptgt, and control is performed. Control of the variable displacement pump 2 with the second virtual discharge pressure Pidea2 as the pump discharge pressure command value Ptgt is performed as follows.

  For example, when the operation lever 9 is not operated, the closed center type directional control valves 4a, 4b... Are in the neutral position, and zero is input to the control device 12 as the total operation amount S. In this case, since the total opening area Ab of the virtual bleed-off flow path calculated by the control device 12 is maximized, the second virtual discharge pressure Pidea2, that is, the pump discharge pressure command value Ptgt is a small value. The variable displacement pump 2 discharges control oil based on the pump discharge pressure command value Ptgt. After the actual pump discharge pressure Preal of the discharge circuit 3 of the pump piping system is compressed to the pump discharge pressure command value Ptgt and increased, The actual pump discharge flow rate Qreal requires only a slight leakage of the circuit.

  On the other hand, when the operation lever 9 is operated and the closed center type directional control valves 4a, 4b,... Are operated in the switching position direction, the total opening area Ab of the virtual bleed-off flow path calculated by the control device 12 is Get smaller. Then, since the virtual bleed-off flow rate Qb decreases, the flow rate value ΔQ increases, and as a result of integration, the pump discharge pressure command value Ptgt increases. As a result, the virtual bleed-off flow rate Qb is increased at a certain total operation amount and the flow rate value ΔQ converges to zero. Therefore, the pump discharge pressure instruction value in which the virtual pump discharge flow rate Qidea and the virtual bleed-off flow rate Qb are balanced. It converges to Ptgt and equilibrates.

  At this time, since the virtual pump discharge flow rate Qidea is set according to the total operation amount S of the direction control valves 4a, 4b,..., The virtual total opening area Ab can be reduced. The pump discharge pressure can also be kept low. Therefore, useless pressure can be suppressed. Even when the closed center type directional control valves 4a, 4b... Are operated in the switching position direction, the variable displacement pump 2 discharges control oil based on the pump discharge pressure instruction value Ptgt, but the operation lever 9 is operated. As is the case with the actual pump discharge flow rate Qreal, only a slight leakage of the circuit is required.

  If the actual pump discharge pressure Preal is higher than the load pressure of the actuators 1a, 1b,..., The actuators 1a, 1b,. Then, the actual pump discharge flow rate Qreal increases to maintain the actual pump discharge pressure Preal at the pump discharge pressure command value Ptgt, and the moving speed of the actuators 1a, 1b,... Increases, so the total estimated actuator flow rate Qai increases. The flow rate value ΔQ becomes a negative value and decreases. Therefore, the pump discharge pressure command value Ptgt decreases and the virtual bleed-off flow rate Qb decreases.

  Then, the pump discharge pressure command value Ptgt and, as a result, the actual pump discharge pressure Preal decreases, the acceleration of the actuator decreases, and gradually converges to the actual pump discharge flow rate Qreal and the actual pump discharge pressure Preal that maintain the actuator speed corresponding to the operation amount. And equilibrate. At this time, since the virtual pump discharge flow rate Qidea is not larger than necessary, it quickly converges to the actual pump discharge flow rate Qreal and the actual pump discharge pressure Preal that maintain the actuator speed corresponding to the operation amount. During this time, the bleed-off operation is performed only by calculation in the control device 12, and the actual pump discharge flow rate Qreal is limited to the amount supplied to the actuators 1a, 1b,.

  Accordingly, the bleed-off flow rate does not actually flow, and the actual pump discharge pressure Preal does not increase more than necessary, so that the pump efficiency is not wasted. Further, since the bleed-off flow path is not required for the closed center type directional control valves 4a, 4b,..., The configuration is simple and inexpensive, and the operability is improved. Furthermore, since the pump discharge flow rate is not limited by the horsepower characteristics of the engine, the pump efficiency is further improved.

  On the other hand, when the control is performed with the second virtual discharge pressure Pidea2 as the pump discharge pressure command value Ptgt, if the discharge flow rate of the variable displacement pump 2 is continuously increased despite the heavy engine load, the engine stall is increased. May occur. However, in such a case, the second virtual discharge pressure Pidea2 calculated based on the operation amount S of the closed center type directional control valves 4a and 4b is calculated based on the horsepower characteristics of the engine. The virtual discharge pressure Pidea1 is exceeded, and control is performed using the first virtual discharge pressure Pidea1 as the pump discharge pressure command Ptgt. Therefore, in the control process of the variable displacement pump 2 according to the present embodiment, if there is a possibility of an engine stall, the pump discharge pressure command value Ptgt is switched to the first virtual discharge pressure Pidea1, so that the engine stall is avoided. be able to.

[4. Pressure characteristics]
FIG. 4 is a diagram for explaining the characteristics of the pump discharge pressure in the hydraulic circuit. In FIG. 4, the solid line indicates the virtual pump discharge flow rate Qidea, the total opening area Ab of the virtual bleed-off flow path, the real pump discharge flow rate Qreal, and the real pump discharge pressure Preal in the hydraulic circuit according to the present embodiment, and the broken line indicates the virtual pump. The virtual pump discharge flow rate Qidea, the total opening area Ab ′ of the virtual bleed-off flow path, the actual pump discharge flow rate Qreal ′, and the actual pump discharge pressure Preal ′ when the discharge flow rate is fixed at the maximum value are shown.

  In the hydraulic circuit according to the present embodiment, the virtual pump discharge flow rate Qidea is set proportionally larger as the total operation amount S of the direction control valves 4a, 4b,. On the other hand, the virtual total opening area Ab is set proportionally smaller as the total operation amount S of the direction control valves 4a, 4b. Therefore, in the region where the operation amount is small and the actuator flow rate is small, the virtual total opening area Ab is reduced, and the actual pump discharge pressure Preal can be reduced.

[5. Summary]
As described above, according to the hydraulic circuit according to the first embodiment, the virtual pump discharge flow rate Qidea used for calculating the second virtual discharge pressure Pidea2 is the total operation of the direction control valves 4a, 4b,. It is set according to the amount S. Therefore, in the region where the operation amount is small, the total opening area Ab of the virtual bleed-off flow paths of the direction control valves 4a, 4b,... Can be reduced, and the actual pump discharge pressure Preal becomes uselessly increased. Can be prevented. Further, according to the hydraulic circuit according to the first embodiment, since the actual pump discharge pressure Preal can be suppressed, fuel consumption can also be reduced.

<Second Embodiment>
As in FIG. 1, the hydraulic circuit according to the second embodiment of the present invention is a hydraulic circuit configured using a plurality of actuators 1a, 1b,..., And calculates the second virtual discharge pressure Pidea2. Is different from the control device according to the first embodiment. In the present embodiment, the total opening area (total bleed-off area) Ab of the virtual bleed-off flow path used for the calculation of the second virtual discharge pressure Pidea2 is obtained by a synthetic calculation in consideration of the characteristics of each actuator. It is configured to be. That is, the total bleed-off area Ab is obtained by combining the virtual bleed-off area of each closed center type directional control valve according to the calculation of the operation amount and the virtual discharge flow rate input to each directional control valve. It is like that. Hereinafter, the control processing of the hydraulic circuit according to the second embodiment will be described with reference to the control block diagram of FIG.

  FIG. 5 is a view for explaining the calculation process of the second virtual discharge pressure Pidea 2 in the present embodiment, and shows the calculation process by the control device 12 shown in a one-dot chain line A in FIG. 2. . As in the case of the first embodiment, the second virtual discharge pressure Pidea2 is a flow value ΔQ (ΔQ = Qidea−Qai) obtained by subtracting the total estimated actuator flow Qai and the bleed-off flow Qb from the virtual pump discharge flow Qidea. −Qb) is obtained, and the flow rate value ΔQ is integrated using a digital filter or the like, and is divided by the piping compression coefficient C′p of the virtual pump piping system. An arithmetic expression of the second virtual discharge pressure Pidea2 can be expressed by the following expression 1.

  In FIG. 5, in determining the total opening area Ab of the virtual bleed-off flow path used for the calculation of the bleed-off flow rate Qb, the control device 12 operates the operation amount Sk (k = 1, 2, 2) of each closed center type directional control valve. ... N) is received, and the virtual bleed-off area Abk (k = 1, 2,... N) of each directional control valve is obtained based on the preset virtual bleed-off characteristics. Then, the control device 12 uses the calculated virtual bleed-off area Abk (k = 1, 2,... N), and the total opening of the virtual bleed-off channel corresponding to the virtual bleed-off characteristic. An area (total bleed-off area) Ab is obtained by a synthesis operation of the following formula 2.

  In the above equation 2, n is the total number of actuators, and the control device 12 determines the reciprocal of the square of the virtual bleed-off area Abk (k = 1, 2,... N) of each directional control valve. The reciprocal of the square root of the sum of the values obtained by multiplying by the coefficient vk (k = 1, 2,... N) set according to the virtual bleed-off area Abk of the directional control valve The total opening area Ab of the virtual bleed-off flow path is obtained. The control device 12 obtains a virtual bleed-off flow rate Qb based on the virtual total opening area Ab, and calculates a second virtual discharge pressure Pidea2.

  The coefficient vk is a coefficient set for each actuator, and can be set so that the value of the coefficient vk increases as the virtual bleed-off area Abk increases. Each actuator has different characteristics, and the maximum actuator flow rate is also different. In the example of the hydraulic excavator, the actuator flow rate required for the actuator for lowering the boom is small between the actuator for raising the boom and the actuator for lowering the boom. This is because the boom tends to drop due to its own weight. Therefore, the second virtual discharge pressure Pidea2 is obtained by performing weighting calculation in accordance with the characteristics of the actuator using the coefficient vk and placing importance on the actuator that requires a larger actuator flow rate.

  The coefficient vk can be set as follows, for example.

Wk(s)：各アクチュエータの重み関数
W(s)：各アクチュエータの重み関数の最大値
s(s1,…,sn)：方向制御弁の操作量
Wq_k(s1,…,sn)：各アクチュエータに対応する方向制御弁の操作量がｓｋのときの重み係数
Qidea_k(sk)：各アクチュエータに対応する方向制御弁の操作量がｓｋのときの仮想ポンプ吐出流量

Wk (s): Weight function of each actuator
W (s): Maximum value of the weight function of each actuator
s (s1, ..., sn): Operating amount of directional control valve
Wq_k (s1, ..., sn): Weighting factor when the operation amount of the directional control valve corresponding to each actuator is sk
Qidea_k (sk): Virtual pump discharge flow rate when the operation amount of the directional control valve corresponding to each actuator is sk

  Here, the virtual pump discharge flow rate Qidea that is variable in accordance with the operation amount S for each directional control valve can be obtained as follows, for example.

  The virtual total opening is the same as the calculation method of the second virtual discharge pressure Pidea 2 described in the first embodiment except that the total opening area Ab of the virtual bleed-off flow path is combined and calculated as described above. A virtual bleed-off flow rate Qb is obtained by multiplying the area Ab by the m-th root of the second virtual discharge pressure Pidea2 calculated at this time and further multiplying by the flow coefficient Kq of the center bypass type directional control valve. The m-th root may be a square root, for example.

  The control device 12 compares the obtained second virtual discharge pressure Pidea2, the first virtual discharge pressure Pidea1 derived from the engine horsepower characteristics, and the maximum pump discharge pressure Pmax with each other, and compares the minimum value with the pump discharge pressure command value. The variable capacity pump 2 is controlled by setting to Ptgt.

  By controlling the variable displacement pump 2 in accordance with the control process of the hydraulic circuit according to the second embodiment, the first virtual discharge pressure Pidea1 in the most operation region, that is, in the state where there is no fear of engine stall. The second virtual discharge pressure Pidea2 having a smaller value becomes the pump discharge pressure instruction value Ptgt, and control is performed. By controlling the variable displacement pump 2 based on the second virtual discharge pressure Pidea2, it is possible to obtain operability that matches the required characteristics of each actuator.

  Further, since the second virtual discharge pressure Pidea 2 itself is obtained without considering the horsepower of the engine, the efficiency of the variable displacement pump 2 can be utilized to the maximum. On the other hand, when the engine load is high, since the calculated second virtual discharge pressure Pidea2 exceeds the first virtual discharge pressure Pidea1, the first virtual discharge pressure Pidea1 becomes the pump discharge pressure command value Ptgt. Will be controlled. Therefore, in a situation where engine stall is likely to occur, the actual pump discharge flow rate Qreal of the variable displacement pump 2 is suppressed based on the horsepower of the engine, and therefore engine stall can be prevented.

  The coefficient vk is not limited to the above example. For example, when the required discharge pressure is corrected according to the operation state of each actuator, an optimum coefficient vk can be set according to the purpose.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1a, 1b Actuator 2 Variable displacement pump 4a, 4b Closed center type directional control valve 6 Pump pressure control device 6b Control valve 6c Electromagnetic proportional valve 7 Control piston 12 Control device

Claims (4)

A variable displacement pump, and a plurality of actuators connected to the variable displacement pump via directional control valves, respectively, and operating the directional control valve based on an operation amount input to each of the directional control valves. In the hydraulic circuit control device for controlling the hydraulic circuit configured to switch the operation direction of the actuator by
A virtual discharge flow rate setting unit that sets a virtual discharge flow rate of the variable displacement pump based on the operation amount for each of the directional control valves;
A bleed-off flow rate calculation unit that calculates virtual bleed-off flow rates from all of the directional control valves based on the operation amount for each of the directional control valves;
The total estimated actuator flow rate , which is an estimated flow rate to all the actuators obtained by multiplying the amount of tilt of the variable displacement pump by the rotation speed of the variable displacement pump , and the bleed-off flow rate, the virtual discharge flow rate. A virtual discharge pressure based on a difference subtracted from the pump, and a pump control unit that controls the variable displacement pump based on the virtual discharge pressure;
An apparatus for controlling a hydraulic circuit, comprising:   2. The hydraulic circuit according to claim 1, wherein the virtual discharge flow rate setting unit calculates the virtual discharge flow rate by performing a weighting operation on a virtual flow rate to each of the actuators according to the operation amount. Control device.   The bleed-off flow rate calculation unit is configured to calculate the bleed-off amount based on a total bleed-off area obtained by combining the virtual bleed-off area of each of the directional control valves according to the operation amount and the calculation of the virtual flow rate to the actuator. 3. The hydraulic circuit control device according to claim 2, wherein the hydraulic circuit control device is configured to calculate a flow rate. A variable displacement pump, and a plurality of actuators connected to the variable displacement pump via directional control valves, respectively, and operating the directional control valve based on an operation amount input to each of the directional control valves. In the hydraulic circuit control method for controlling the hydraulic circuit configured to switch the operation direction of the actuator,
Setting a virtual discharge flow rate of the variable displacement pump based on the operation amount for each of the directional control valves;
Calculating virtual bleed-off flow rates from all the directional control valves based on the manipulated variable for each of the directional control valves;
The total estimated actuator flow rate , which is an estimated flow rate to all the actuators obtained by multiplying the amount of tilt of the variable displacement pump by the rotation speed of the variable displacement pump , and the bleed-off flow rate, the virtual discharge flow rate. Obtaining a virtual discharge pressure based on the difference subtracted from, and controlling the variable displacement pump based on the virtual discharge pressure;
A method of controlling a hydraulic circuit, comprising:

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