JP5877616B2 - Control method of variable displacement pump - Google Patents

Description

  The present invention relates to a control method for a variable displacement pump applied to a machine such as a construction machine using 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, a variable displacement pump driven by an engine and capable of adjusting a pump discharge flow rate from the outside, and a plurality of closed center type directional control valves. Patent Document 1 proposes a method of controlling a variable displacement pump by electric calculation so that a closed center type directional control valve is substituted for a center bypass type directional control valve. .

  This is done by mathematically replacing the bleed-off characteristic part of the bleed-off hydraulic system with a conventional center bypass type directional control valve, that is, the part that controls the pressure and flow rate to each actuator. Is used to control the discharge pressure of the variable displacement pump. In the conventional variable displacement pump, control was performed while actually returning a part of the control oil pumped by the variable displacement pump to the tank, so the variable displacement pump could not be used effectively. By controlling the discharge pressure of the variable displacement pump as if it had a bleed-off characteristic, the center bypass passage is eliminated from the directional control valve, and only the control oil at the actually required flow rate is discharged. Is possible.

JP 2007-205464 A

  In the control method of the variable displacement pump described in Patent Document 1, when calculating the pump discharge pressure instruction value (virtual pump discharge pressure command Pidea), the engine horsepower He is used as the pump discharge pressure as shown in FIG. An example is given in which the pump discharge flow rate Qidea is limited with the value divided by the command Pidea as the upper limit. However, a variable displacement pump is usually understood from a characteristic curve (hereinafter sometimes simply referred to as “characteristic curve”) that defines the relationship between the pump discharge pressure P and the discharge flow rate Q shown in FIG. Control is performed so that the discharge flow rate Q of the pump is constant up to a predetermined pressure P1, and the product of the discharge pressure P and the discharge flow rate Q is constant when the pressure P1 is exceeded. Therefore, when the flow rate of the control oil supplied to the actuator is small and the discharge pressure P exceeds the pressure P1, the pump discharge flow rate Q can be increased even though the pump discharge flow rate Q can be increased. As a result of calculation that lowers the pressure command Pidea is obtained, the pump discharge flow rate Q is limited, and the variable displacement pump may not be effectively used.

  On the other hand, in the control method of the variable displacement pump described in Patent Document 1, as shown in FIGS. 9A and 9B, the pump discharge pressure command value (pump discharge pressure command Pidea) is taken into account without considering the horsepower of the engine. An example of computing is also given. However, if the horsepower of the engine is not considered at all, the load of the variable displacement pump becomes too high, and there is a risk that engine stall will occur.

  Therefore, the present invention provides a variable displacement pump that can effectively use a variable displacement pump while avoiding the risk of engine stall in a method of controlling a variable displacement pump by calculation by a controller using a closed center type directional control valve. The object is to provide a control method.

In order to solve the above problems, the inventors have found a solution as follows.
In other words, the variable displacement pump control method of the present invention is driven by the engine and can adjust the pump discharge flow rate from the outside as described in claim 1, via one or a plurality of closed center type directional control valves. actuator Oite to how to control one or more variable displacement pump connected, detects the operation amount of the current discharge flow rate and the direction control valve of the variable displacement pump Te, maximum horsepower of the engine in the variable capacity characteristic line that defines the relationship between the discharge pressure and the discharge flow rate of the pump in a state indicating value, calculating a calculated value of the first ejection discharge pressure corresponding to the current discharge flow rate of the variable displacement pump , the variable capacity with the current discharge flow rate of the pump and actuator flow through said actuator, closed Sen which is set so as to decrease with an increase in the operation amount Virtual bleed off the area of the over-type directional control valve, and, on the basis of the calculated value of the current second discharge pressure of the variable displacement pump, determines the virtual bleed off flow, discharge of virtual of the variable displacement pump from the flow, so that the value obtained by subtracting the actuator flow rate and the virtual bleed off rate converges to 0, calculating a calculated value of the second ejection discharge pressure of the variable displacement pump, the second and controlling the variable displacement pump based on the smaller one the value of the calculated value or the calculated value of the second ejection discharge pressure of the first ejection discharge pressure.

Further, according to a second aspect of the present invention, there is provided the variable displacement pump control method according to the first aspect, wherein a plurality of the variable displacement pumps are connected to the engine, and one or each of the variable displacement pumps is connected to the engine. When one or a plurality of the actuators are connected via a plurality of the closed center type directional control valves, the ratio of the horsepower of the engine to be distributed to each of the variable displacement pumps is determined in advance or said in response to the operation amount of the closed center type directional control valve, determined to calculate the current calculated value of the from the discharge flow first ejection discharge pressure of the variable displacement pump respectively and the horsepower that is the distribution It is characterized by.

According to a third aspect of the present invention, there is provided the variable displacement pump control method according to the second aspect, wherein for each of the variable displacement pumps, the current of each variable displacement pump is calculated from the distributed horsepower. and discharge flow rate of the value of the smaller one of the calculated values of the first ejection discharge pressure calculated value or the second ejection discharge pressure, by subtracting a value obtained by integrating, each of said calculating the excess horsepower per variable displacement pump, the excess horsepower one variable displacement pump, based on the resulting horsepower by adding to the distributed horsepower other variable displacement pump, the first and calculates the calculated value of the ejection discharge pressure.

  In the present specification, the “closed center type directional control valve” means a valve configured not to bypass the control oil when the spool is in the neutral position. The “center bypass type directional control valve” refers to a valve configured to bypass the control oil when the spool is in the neutral position. The “negative type” means that the output value gradually decreases with respect to the input value, and the “positive type” means that the output value gradually increases with respect to the input value.

According to the control method of the variable displacement pump of the present invention, in a state where there is no fear of engine stall, the pump discharge pressure instruction value is obtained without considering the horsepower calculation of the engine, and the variable displacement pump can be used effectively. . In a state where the load of the variable displacement pump is large and there is a risk of engine stall, the pump discharge pressure command value is obtained in consideration of the horsepower of the engine, and engine stall can be prevented.
Furthermore, if the distribution of horsepower to each pump is changed according to the operating conditions, it will be possible to give priority to each actuator, which can be expected to improve operability and increase the engine horsepower. Furthermore, it becomes possible to utilize it effectively.

It is a hydraulic circuit diagram for demonstrating the control method of the variable displacement pump of the 1st Embodiment of this invention. It is a block diagram for demonstrating the control of FIG. It is explanatory drawing of the part enclosed by the dashed-dotted line A of FIG. It is a block diagram for demonstrating the 2nd Embodiment of this invention. It is a block diagram for demonstrating the 3rd Embodiment of this invention. It is a block diagram for demonstrating the modification of the 3rd Embodiment of this invention. It is a block diagram for demonstrating the conventional bleed-off characteristic calculation. It is a figure which shows the characteristic curve which defined the relationship between the discharge pressure and discharge flow rate of a pump. It is a block diagram for demonstrating the conventional bleed-off characteristic calculation.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment according to a control method for a variable displacement pump of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
1. First, a configuration example of a hydraulic circuit to which the variable displacement pump control method according to the first embodiment of the present invention can be applied will be described.

  FIG. 1 shows a basic example of a hydraulic circuit applied to a hydraulic excavator or the like that controls the operation of a plurality of hydraulic actuators 1a and 1b. The actuators 1a and 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 and 4b. The variable displacement pump 2 is a known pump such as an axial piston pump having a pump displacement control mechanism such as a swash plate.

  Connected to the input side of the pump pressure control device 6 are the output of the solenoid drive amplifier 5 as a command input and the discharge side pressure of the variable displacement pump 2 as a feedback input. Piston 7 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 Preal of the variable displacement pump 2, the elastic force of the spring 6d, and the pressure signal P′c controlled by the negative electromagnetic proportional valve 6c act on both ends of the spool of the control valve 6b. A suitable area difference is given to both ends of the control valve 6b, and the control valve 6b is appropriately controlled by the balance thereof.

  The negative electromagnetic proportional valve 6c is a valve that functions as a proportional relief valve, and is input based on the spring force, the pressure signal P′c on the input side facing the spring force, and the control signal P′tgt from the controller 12. Control is performed in balance with the force generated by the proportional solenoid 6a that is varied in proportion to the control current.

  The closed center type directional control valves 4a and 4b are provided with a proportional solenoid 8 for moving the spool. When the solenoid drive amplifier 13 is operated via the controller 12 by the operation lever 9 such as an electric joystick, The proportional solenoid 8 is excited according to the inclination angle of the 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.

  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 command amount or the movement amount is an operation amount signal S based on the operation amount 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 controller 12 is used as the operation amount signal S.

However, the closed center type directional control valves 4a and 4b are actually valves without a bleed-off flow path, and the actual pump discharge flow rate of the variable displacement pump 2 (current becomes substantially equal to the discharge flow rate) then QREAL an actuator flow rate Qa. In the hydraulic circuit described in the present embodiment, a plurality of actuators 1a and 1b are connected to one variable displacement pump 2, and the actuator flow rate Qa refers to all the closed center type directional control valves 4a, In 4b, this means the sum of the flow rates of the control oil supplied to the actuators 1a and 1b via the actuator port 10.

  In the present embodiment, the variable displacement pump 2 is provided with a tilt amount sensor 11, and the actual pump discharge flow rate Qreal is obtained by multiplying the tilt amount detected by the tilt amount sensor 11 by the rotation speed of the variable 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 referred to as an estimated value Qai of the actuator flow rate Qa (hereinafter referred to as “estimated actuator flow rate Qai”). ).

  As a method for detecting the actual pump discharge flow rate Qreal, for example, when the variable displacement pump 2 is a swash plate type variable displacement pump or a radial pump, the actual pump discharge flow rate Qreal is detected using a potentiometer or the like. It is also possible.

  In the present embodiment, the controller 12 includes an A / D converter 12a, a calculator 12b, and a D / A converter 12c. The controller 12 performs arithmetic processing based on various electrical signals input to the controller 12. The arithmetic unit 12b executes arithmetic processing shown in a block diagram within a dotted line B in FIG.

2. Next, the control method of the variable displacement pump 2 executed by the arithmetic processing by the controller 12 will be described in detail.

In the present embodiment, the controller 12 obtains the first virtual pressure obtained based on the maximum discharge pressure Pmax of the variable displacement pump 2 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 minimum obtained by comparing the discharge pressure (calculated value of the first discharge pressure) Pidea1 with the second virtual discharge pressure (calculated value of the second discharge pressure) Pidea2 obtained based on the operation amount signal S The variable displacement pump 2 is controlled with the value as the pump discharge pressure command value Ptgt.

  The reason why the maximum discharge pressure Pmax of the variable displacement pump 2 is included in the comparison target is that a discharge pressure not less than the maximum discharge pressure Pmax of the variable displacement pump 2 is not indicated as the pump discharge pressure command value Ptgt of the variable displacement pump 2 It is for doing so. However, the maximum discharge pressure Pmax is not necessarily required as long as the present invention is implemented.

  The first virtual discharge pressure Pidea1 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. Then, the actual pump discharge flow rate Qreal is converted into a first virtual discharge pressure Pidea1 based on a characteristic curve that defines the relationship between the discharge pressure P of the variable displacement pump 2 and the discharge flow rate Q. 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 this 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 with respect to 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 the region exceeding the pressure P1. It is preferable that

  The second virtual discharge pressure Pidea2 is based on the operation amount signal S 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 calculated | required by the arithmetic processing shown in the dashed-dotted 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 FIG.

  First, the virtual pump discharge flow rate Qidea of the variable displacement pump 2 is set to a predetermined value. As will be described later, the second virtual discharge pressure Pidea2 is calculated in a closed loop based on the flow rate value ΔQ obtained by subtracting the estimated actuator flow rate Qai and the virtual bleed-off flow rate Qb from the virtual pump discharge flow rate Qidea. In addition, the value of the virtual pump discharge flow rate Qidea may be set as appropriate. For example, since the maximum discharge flow rate Qmax of the variable displacement pump 2 is a known number, this value can be used. In the present embodiment, the maximum discharge flow rate Qmax of the variable displacement pump 2 is used as the virtual pump discharge flow rate Qidea.

  Next, the input of the operation amount signal S of the closed center type directional control valves 4a, 4b is received, and the closed center type direction control valves 4a, 4b corresponding to the operation amount signal S are received based on the virtual bleed-off characteristics stored in advance. The opening area Ab of the virtual bleed-off flow path is obtained. Although not shown in FIG. 3, the input of the operation amount signal Sk of the plurality of closed center type directional control valves 4a and 4b is accepted, and the sum S1 + S2 +. It is said. At this time, each input may be weighted or an appropriate calculation process may be performed.

  The calculated virtual opening area Ab is multiplied by the square root of the second virtual discharge pressure Pidea2 calculated at this time, and further multiplied by the flow coefficient Kq of the center bypass type directional control valve to generate a virtual bleed-off flow rate. Find Qb. Of course, the actual closed center type directional control valves 4a and 4b are of the closed center type without the bleed-off flow path, and the opening area Ab of the virtual bleed-off flow path is a calculation value. This virtual bleed-off characteristic shows the relationship between the virtual opening area Ab and the operation amount signal S in the closed center type directional control valves 4a and 4b to be used, and the bleed off of the center bypass type directional control valve in the conventional bleed off hydraulic system. It is determined by obtaining in advance using a design method similar to the characteristic.

  Then, the flow rate value ΔQ (ΔQ = Qidea-Qai-Qb) is obtained by subtracting the estimated actuator flow rate Qai and the virtual bleed-off flow rate Qb from the virtual pump discharge flow rate Qidea. At this time, in actuality, there is almost no leakage of control oil from the closed center type directional control valves 4a and 4b. Therefore, if the leakage amount is set to 0, the actual pump discharge flow rate Qreal and the actuator flow rate Qa of the variable displacement pump 2 Are equal. Therefore, the value of the actual pump discharge flow rate Qreal can be used as the estimated actuator flow rate Qai. 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.

  In this way, the controller 12 obtains the first virtual discharge pressure Pidea1 and the second virtual discharge pressure Pidea2, and then the first virtual discharge pressure Pidea1, the second virtual discharge pressure Pidea2, and the variable displacement pump. 2 is compared with the maximum discharge pressure Pmax, and the minimum value among them is set as the pump discharge pressure instruction value Ptgt. Then, the controller 12 performs closed-loop control of the discharge pressure of the variable displacement pump 2 based on a control signal P′tgt that is inverted by subtracting the pump discharge pressure instruction value Ptgt from the maximum discharge pressure Pmax of the pump.

  That is, the solenoid drive amplifier 5 receives the control signal P'tgt from the controller 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 of the negative electromagnetic proportional valve 6c is proportionally controlled in accordance with the pump discharge pressure instruction value Ptgt, thereby operating the control valve 6b. . As a result, the control piston 7 moves the pump capacity control mechanism, and the pump capacity, that is, the pump discharge flow rate is controlled to be large or small. As a result, the discharge pressure of the variable displacement pump 2 is controlled to be large and small, and the control valve 6b is operated against the pressure of the negative electromagnetic proportional valve 6c. Thus, since the pump discharge pressure is closed-loop controlled, 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.

  In the present embodiment, in most operation regions, that is, in a situation where there is no fear of engine stall, the second virtual discharge pressure Pidea2 having a value smaller than the first virtual discharge pressure Pidea1 is the pump discharge pressure command value Ptgt. 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 4 a and 4 b are in the neutral position, and zero is input to the controller 12 as the operation amount signal S. In this case, since the opening area Ab of the virtual bleed-off channel calculated by the controller 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 the 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 boosted, The actual pump discharge flow rate Qreal requires only a small amount of leakage in the circuit.

  On the other hand, when the operation lever 9 is operated and the closed center type directional control valves 4a and 4b are operated in the switching position direction, the opening area Ab of the virtual bleed-off flow path calculated by the controller 12 becomes small. 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 increases at a certain operation amount, and the flow rate value ΔQ converges to zero, so the virtual pump discharge flow rate Qidea and the virtual bleed-off flow rate Qb converge to the pump discharge pressure command value Ptgt that balances. And equilibrate. At this time, the variable displacement pump 2 discharges the control oil based on the pump discharge pressure instruction value Ptgt. However, the actual pump discharge flow rate Qreal needs only a small amount of leakage in the circuit as in the case where the operation lever 9 is not operated. And not.

  If the actual pump discharge pressure Preal is higher than the load pressure of the actuators 1a and 1b, the actuators 1a and 1b move and control oil begins to flow. 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 actuator increases, so the estimated actuator flow rate Qai increases and the flow rate value ΔQ is a negative value And getting smaller. Therefore, the pump discharge pressure command value Ptgt decreases, and the virtual bleed-off flow rate Qb decreases. Then, when the pump discharge pressure command value Ptgt and the actual pump discharge pressure Preal are lowered, 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. During this time, the bleed-off operation is performed only by calculation in the controller 12, and the actual pump discharge flow rate Qreal is limited to the amount supplied to the actuators 1a and 1b if the leakage on the circuit is ignored.

  Accordingly, the bleed-off flow rate does not actually flow, so there is no waste in pump efficiency, and the bleed-off flow path is not required for the closed center type directional control valves 4a and 4b. The nature will also improve. Further, since the discharge flow rate of the pump 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, the engine stall is increased if the discharge flow rate of the variable displacement pump 2 is continuously increased despite the heavy engine load. May occur. However, in such a case, the second virtual discharge pressure Pidea2 calculated based on the operation amount signal S of the closed center type directional control valves 4a, 4b is calculated based on the horsepower characteristics of the engine. Therefore, control is performed using the first virtual discharge pressure Pidea1 as the pump discharge pressure command Ptgt. Therefore, in the control method of the variable displacement pump according to the present embodiment, when there is a possibility of engine stall, the pump discharge pressure command value Ptgt is switched to the first virtual discharge pressure Pidea1, so that the occurrence of engine stall is avoided. be able to.

3. As described above, by controlling the variable displacement pump 2 in accordance with the variable displacement pump control method according to the present embodiment, most of the operation region, that is, the engine stall is controlled. In a state where there is no fear, control is performed by setting the second virtual discharge pressure Pidea2 having a value smaller than the first virtual discharge pressure Pidea1 to the pump discharge pressure instruction value Ptgt. Since the second virtual discharge pressure Pidea2 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.

[Second Embodiment]
As in the case of FIG. 1, the variable displacement pump control method according to the second embodiment of the present invention uses a second virtual circuit in a hydraulic circuit configured using a plurality of actuators 1a, 1b,. The calculation method of the discharge pressure Pidea2 is different from the case of the control method of the variable displacement pump according to the first embodiment. Hereinafter, the control method of the variable displacement pump of the present embodiment will be described with reference to the block diagram of FIG.

FIG. 4 is a view for explaining another method of calculating the second virtual discharge pressure Pidea2, and shows a calculation process by the controller 12 shown in a one-dot chain line A in FIG.
In FIG. 4, the controller 12 receives input of operation amounts S1, S2,..., Sk,..., Sn of a plurality of closed center type directional control valves 4a, 4b,. For the closed center type directional control valves 4a, 4b,..., 4n corresponding to the virtual bleed-off characteristic, the opening area Ab of the virtual bleed-off flow path as a whole is obtained by a synthesis operation using the following equation. Abk in the equation indicates a virtual bleed-off area Abk of each closed center type directional control valve 4a, 4b,..., 4n, and is a value having a correlation with each operation amount signal Sk. This is what we have already said.

  Except for the synthetic calculation of the opening area Ab of the virtual bleed-off channel in this way, the virtual opening area Ab is set to the virtual opening area Ab in the same manner as the calculation method of the second virtual discharge pressure Pidea2 described in the first embodiment. The virtual bleed-off flow rate Qb is obtained by multiplying the square 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.

  By controlling the variable displacement pump 2 according to the control method of the variable displacement pump according to the present embodiment, in the most operating region, that is, in the state where there is no fear of engine stall, the first virtual discharge pressure Pidea1 The second virtual discharge pressure Pidea2 having a smaller value becomes the pump discharge pressure instruction value Ptgt, and control is performed, so that operability that matches the required characteristics of the individual actuators can be obtained. Since the second virtual discharge pressure Pidea2 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.

[Third Embodiment]
In the variable displacement pump control method according to the third embodiment of the present invention, a plurality of variable displacement pumps are connected to the engine, and an actuator is connected to each of the variable displacement pumps via a closed center type directional control valve. The present invention relates to a method for controlling a connected variable displacement pump.

  In the control method for the variable displacement pump according to the present embodiment, other than the method for obtaining the first virtual discharge pressure Pidea1 obtained based on the characteristic curve that defines the relationship between the discharge pressure P and the discharge flow rate Q of the variable displacement pump. Can be implemented in the same manner as in the control method of the variable displacement pump according to the first embodiment. Hereinafter, a third embodiment of the present invention will be described with reference to FIG.

  When a plurality of variable displacement pumps are provided on the hydraulic circuit as in the present embodiment, the first virtual discharge pressure Pidea1 and the second virtual discharge pressure Pidea2 are provided for each variable displacement pump. And the pump discharge pressure command value Ptgt is obtained.

  FIG. 5 is a diagram for explaining a calculation method of the first virtual discharge pressure Pidea 1 by the controller in the control method of the variable displacement pump according to the present embodiment, and is “horsepower” in the block diagram of FIG. The modification of the part shown as "calculation" is shown. In the illustrated example, the number of variable displacement pumps 2a and 2b connected to the engine is two. For the sake of simplicity, it is assumed that one closed center type directional control valve 4a, 4b and actuator 1a, 1b are connected to each of the variable displacement pumps 2a, 2b. In the example of FIG. 5, the horsepower is distributed to each variable displacement pump 2a, 2b at a ratio of 0.5 in advance. Then, the controller 12 calculates the first virtual discharge of each variable displacement pump 2a, 2b from each horsepower distributed to each variable displacement pump 2a, 2b and the actual pump discharge flow rate Qreal of each variable displacement pump 2a, 2b. The pressure Pidea1 is calculated.

  Further, in the example of FIG. 5, the controller 12 determines the actual pump discharge flow rate Qreal and the pump discharge pressure command value Ptgt of each variable displacement pump 2a, 2b from the horsepower distributed for each variable displacement pump 2a, 2b. The surplus horsepower for each variable displacement pump 2a, 2b is calculated by subtracting the value obtained by integrating. Then, by adding the surplus horsepower of the other variable capacity pump 2b (2a) to the horsepower distributed to one variable capacity pump 2a (2b), the one variable capacity pump 2a (2b) can be used. The value is horsepower.

According to this configuration, together with the effect of the variable displacement pump control method according to the first embodiment, the surplus horsepower distributed to the variable displacement pumps 2a and 2b can be effectively utilized. The effect that can be obtained.
Note that the number of variable displacement pumps connected to one engine may be three or more. In this case as well, surplus horsepower in one variable displacement pump can be effectively utilized in other variable displacement pumps. become able to.

  Moreover, FIG. 6 is a figure shown in order to demonstrate the application example of 3rd Embodiment. In the example of FIG. 6, the ratio of the engine horsepower distributed to the variable displacement pumps 2a and 2b is not determined in advance, but is determined according to the operation amount of the closed center type directional control valves 4a and 4b. . At this time, weighting may be performed for each of the variable displacement pumps 2a and 2b, or an appropriate calculation process may be performed. According to the configuration of this modification, an actuator having a high load pressure or a high operational priority is connected to reflect the operation amount of each actuator 1a, 1b connected to each variable displacement pump 2a, 2b. The ratio of the horsepower that can be used by the variable displacement pumps 2a and 2b is adjusted. Therefore, the operability is improved, the horsepower of the engine can be used effectively, and the variable displacement pumps 2a and 2b can be used more effectively.

As described above, according to the control method of the variable displacement pump according to the third embodiment, the horsepower of the engine can be effectively utilized together with the effect of the method of the first embodiment. The effect that can be obtained.
A plurality of actuators may be connected to one or a plurality of variable displacement pumps connected to the engine. In this case, the calculation method of the second virtual discharge pressure Pidea2 in the second embodiment can be implemented in an appropriate combination.

[Other embodiments]
The first to third embodiments described above are merely examples of embodiments of the present invention, and these embodiments may be appropriately modified within the scope of the object of the present invention. Is possible.

  For example, if the discharge flow rate of the variable displacement pump is increased in a quadratic function according to the operation amount of the actuator, the resistance at the meter-in throttle section is reduced when operating one actuator alone, and energy loss is avoided. At the time of combined operation, the effect of diversion control in meter-in is enhanced, and combined operation of actuators with different loads becomes possible (refer to the portions where the flow rate is added in FIGS. 5 and 6).

Claims (3)

Is driven by the engine, it is possible to adjust the pump discharge flow rate from the outside, you in one or more of closed center type via a directional control valve how to control one or more variable displacement pump in which the actuator is connected And
Detecting the current discharge flow rate of the variable displacement pump and the operation amount of the directional control valve,
In the variable capacitance discharge pressure and relationship-determined characteristic line between the discharge flow rate of the pump in a state where the maximum value is horsepower of the engine, first ejection discharge pressure corresponding to the current discharge flow rate of the variable displacement pump and of calculating the calculated value,
The current discharge flow rate of the variable displacement pump is set as an actuator flow rate that flows through the actuator, a virtual bleed-off area of a closed center type directional control valve that is set to decrease as the operation amount increases , and A virtual bleed-off flow is determined based on the calculated value of the current second discharge pressure of the variable displacement pump, and the actuator flow and the virtual bleed-off flow are subtracted from the virtual discharge flow of the variable displacement pump. as values obtained converge to 0 by, calculating a calculated value of the second ejection discharge pressure of the variable displacement pump,
Control method for a variable displacement pump, wherein the controller controls the variable displacement pump based on the smaller one the value of the calculated value of the calculated value of the first ejection discharge pressure or the second ejection discharge pressure. When a plurality of the variable displacement pumps are connected to the engine, and one or a plurality of the actuators are connected to each of the variable displacement pumps via one or a plurality of the closed center directional control valves. In addition,
The ratio of the horsepower of the engine distributed to each of the variable displacement pumps is determined in advance or according to the operation amount of each of the closed center type directional control valves,
Control method for a variable capacity pump according to claim 1, characterized in that calculating a calculated value of said first ejection discharge pressure from the current discharge flow rate of the horsepower and each of the variable displacement pump that is the distribution. For each of said variable displacement pump, wherein the distributed horsepower, current and the discharge flow rate of each of the variable displacement pump, the calculated value or the calculated value of the second ejection discharge pressure of the first ejection discharge pressure Subtract the value obtained by integrating any smaller value, and calculate the excess horsepower for each of the variable displacement pumps,
Excess horsepower one variable displacement pump, based on the resulting horsepower by adding to the distributed horsepower other variable displacement pump, characterized by calculating a calculated value of said first ejection discharge pressure The method for controlling a variable displacement pump according to claim 2.

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