JP2020051070A - Construction machine pump control device and construction machine - Google Patents

Abstract

To provide a technique capable of performing a horsepower reducing control with a simple configuration in a construction machine including a variable displacement pump capable of changing a discharge amount and a fixed displacement pump capable of changing a discharge amount.SOLUTION: A pump control device 10 comprises: an absorption torque setting unit 6 for setting the absorption torque of variable displacement pumps 3 and 4; a pump control unit 7 for controlling the discharge amount of the variable displacement pumps 3 and 4; a lever operation sensor 9; a first output unit 81; a second output unit 82; and a torque reduction amount determining unit 83. The first output unit 81 outputs a first torque reduction value T3, and the second output unit 82 outputs a second torque reduction value Ton the basis of a deviation between a target engine speed and an actual engine speed. The torque reduction amount determining unit 83 decreases the weight of the first torque reduction value T3 and increases the weight of the second torque reduction value Tas the elapsed time from the detection of the operation of a fixed displacement pump 5 increases.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pump control device including a variable displacement pump and a fixed displacement pump.

  2. Description of the Related Art A conventional hydraulic excavator is known that uses both a variable displacement pump whose discharge amount can be changed by a pump regulator and a fixed displacement pump whose discharge amount cannot be changed. For example, Patent Literature 1 discloses a hydraulic shovel in which a variable displacement pump drives a hydraulic actuator that performs an attachment operation or the like, while a fixed displacement pump drives a dozer cylinder.

  In such a hydraulic excavator, control is performed to keep the total pump torque (horsepower) constant according to the total pump pressure of all pumps including the fixed displacement pump (dozer pump). Specifically, the total pump torque is calculated from the total pump pressure, and the discharge amount of the variable displacement pump is controlled so that the calculated pump torque does not exceed the allowable torque of the engine. In detail, when the total pump torque may exceed the set value during the operation of the dozer, the horsepower reduction control that reduces the torque of the variable displacement pump according to the increase of the pump pressure of the fixed displacement pump is performed. Done.

  However, there is a time delay between the time when the dozer is operated and the time when the discharge amount change is completed by the above-described horsepower reduction control. Therefore, when the dozer pump pressure rises rapidly, the horsepower reduction control is not in time, and an engine stall due to overtorque may occur. There is.

  In view of the above, in Patent Literature 1, a variable relief valve is provided in a pump circuit of a dozer pump (fixed displacement pump), and a preset pressure of the dozer pump is set to a preset value when operating the dozer cylinder to a preset value. Relief pressure gradual increase control that increases with time is performed.

JP 2014-98453 A

  However, in the invention described in Patent Document 1, in order to perform horsepower control, it is necessary to additionally provide a variable relief valve (electromagnetic relief valve) in a pump circuit of a fixed displacement pump (dozer pump), which increases cost. There's a problem.

  Therefore, the present invention provides a technology capable of performing horsepower reduction control with a simpler configuration in a construction machine including a variable displacement pump capable of changing the discharge amount and a fixed displacement pump capable of changing the discharge amount. The purpose is to:

  In order to achieve the above object, the present invention provides an absorption torque setting unit that sets an absorption torque of a variable displacement pump capable of changing a discharge amount, based on the absorption torque and a pump pressure of the variable displacement pump. Pump control means for controlling the discharge amount of the variable displacement pump, operation detecting means for detecting operation of the fixed displacement pump whose discharge amount cannot be changed, and operation of the fixed displacement pump detected by the operation detecting means A first output unit that outputs a first torque reduction value used for reducing the absorption torque in response to the determination of the absorption torque, based on a deviation between an engine target rotation speed and an actual engine rotation speed. A second output unit that outputs a second torque reduction value used for reduction, and a pump torque of the variable displacement pump based on the first torque reduction value and the second torque reduction value. Determining means for determining the amount of reduction, wherein the determining means decreases the weight of the first torque reduction value as the elapsed time from the detection of the operation of the fixed displacement pump increases, (2) A pump control device for a construction machine, wherein the weight of the torque reduction value is increased.

  Here, the operation detecting means includes a lever operation detecting sensor for detecting a lever operation amount, and the lever operation amount is a lever operation amount for operating a driven object driven by the fixed displacement pump as a hydraulic pressure source. Preferably, the operation detecting means detects the operation of the fixed displacement pump based on the lever operation amount detected by the lever operation detection sensor.

  Further, it is preferable that the first torque reduction value increases as the operation amount of the lever operation increases.

  Further, the operation detecting means includes a pump pressure sensor for detecting a pump pressure of the fixed displacement pump, and the first torque reduction value increases as the pump pressure detected by the pump pressure sensor increases. Is preferred.

  The present invention also provides a lower traveling body, an upper revolving body pivotally mounted on the lower traveling body, a dozer provided on the lower traveling body and driven by a dozer cylinder, and a variable discharge amount. A displacement pump configured as a fixed displacement pump that cannot change the discharge amount, and a dozer pump that is a hydraulic source of the dozer cylinder; absorption torque setting means for setting an absorption torque of the variable displacement pump; Pump control means for controlling the discharge amount of the variable displacement pump based on the pump pressure of the variable displacement pump, operation detection means for detecting the operation of the dozer pump, and operation of the dozer pump by the operation detection means. A first output unit that outputs a first torque reduction value for reducing the absorption torque in response to the detection of the operation; A second output unit that outputs a second torque reduction value for reducing the absorption torque based on a deviation between a target rotation speed and an actual engine rotation speed, the first torque reduction value and the second torque reduction value Deciding means for deciding a pump torque reduction amount of the variable displacement pump based on the above, wherein the deciding means comprises: There is further provided a construction machine wherein the weight of the torque reduction value is reduced and the weight of the second torque reduction value is increased.

  According to the first aspect of the present invention, the weight of the first torque reduction value is large and the weight of the second torque reduction value is small immediately after the operation of the fixed displacement pump is detected, so that the load on the fixed displacement pump is reduced. Can respond to the rapid rise of Thereafter, since the first torque reduction value gradually decreases and the weighting of the second torque reduction value increases, control can be performed in consideration of both the engine output and the pump load. Therefore, in a construction machine including a variable displacement pump that can change the discharge amount and a fixed displacement pump that cannot change the discharge amount, it is possible to perform the horsepower reduction control with a simpler configuration without adding an electromagnetic relief valve or the like. It is possible.

  According to the pump control device for a construction machine according to the second aspect, the operation of the fixed displacement pump is detected based on the lever operation amount detected by the lever operation detection sensor. Therefore, the cost can be reduced as compared with a case where a pump pressure sensor is provided in a fixed displacement pump and the operation of the fixed displacement pump is detected using the pump pressure sensor.

  According to the pump control device of the third aspect, the first torque reduction value increases as the lever operation amount increases. Therefore, when it is assumed that the lever operation amount is small and the load of the fixed displacement pump is also small, The amount of reduction in pump torque of the variable displacement pump does not need to be excessive.

  According to the pump control device of the fourth aspect, the first torque reduction value increases as the pump pressure of the fixed displacement pump detected by the pump pressure sensor increases, so that the load of the fixed displacement pump is small. In addition, the amount of reduction in pump torque of the variable displacement pump does not need to be excessive. Further, since the first torque reduction value is output based on the actually measured value of the pump pressure of the fixed displacement pump, the first torque reduction value is output as compared with the case where the first torque reduction value is output according to the operation amount of the lever operation. It is also possible to output the reduction value more accurately.

  According to the construction machine according to the fifth aspect, in a construction machine including a variable displacement pump that can change the discharge amount and a dozer pump that is a fixed displacement pump that cannot change the discharge amount, without adding an electromagnetic relief valve or the like. It is possible to perform the horsepower reduction control with a simpler configuration.

1 is a schematic side view illustrating a construction machine (a hydraulic shovel) according to an embodiment of the present invention. 1 is a hydraulic circuit diagram illustrating a pump control device of a hydraulic shovel according to a first embodiment. 7 is a graph showing a relationship between an elapsed time T from detection of operation of a fixed displacement pump and a coefficient α in Expression 3. 4 is a flowchart for explaining the operation of the embodiment. FIG. 5 is a hydraulic circuit diagram illustrating a pump control device for a hydraulic shovel according to a second embodiment. 7 is a graph showing a relationship between a lever operation amount S and a torque reduction value T3.

<1. First Embodiment>
A pump control device for a construction machine according to a first embodiment of the present invention will be described with reference to FIGS. Here, a hydraulic excavator 1 shown in FIG. 1 is illustrated as an example of a construction machine.

  As shown in FIG. 1, the excavator 1 includes a crawler-type lower traveling body 11, an upper revolving body 12 rotatably mounted on the lower traveling body 11, and a work attachment mounted on the upper revolving body 12. 13 are provided.

  A dozer 14 is mounted on the lower traveling body 11. The dozer 14 is driven up and down by a dozer cylinder (not shown) to perform a leveling operation for leveling the ground while traveling in a ground contact state, and a soil carrying operation for pushing and transporting the soil.

  As shown in FIG. 2, the hydraulic shovel 1 includes variable displacement pumps 3 and 4 driven by the engine 2 as a power source, and fixed displacement pumps 5 driven by the engine 2 as a power source.

  The variable displacement pumps 3 and 4 are examples of a pump provided as a turning motor that drives the lower traveling body 11 to turn and a hydraulic source of a hydraulic actuator for each operation of the work attachment 13.

  The variable displacement pumps 3 and 4 are provided with pump regulators 31 and 41 for changing the tilt (discharge flow rate). The displacement of the variable displacement pumps 3 and 4 is controlled via pump regulators 31 and 41 according to a displacement command signal from a pump control unit 7 described later.

  The variable displacement pumps 3 and 4 are provided with pump pressure sensors 33 and 43 for detecting the pump pressures of the variable displacement pumps 3 and 4, respectively. Each pump pressure detected by the pump pressure sensors 33 and 43 is input to the pump control unit 7 of the pump control device 10.

  The fixed displacement pump 5 is an example of a dozer pump provided as a hydraulic pressure source for a dozer cylinder (not shown) of the dozer 14. Unlike the variable displacement pumps 3 and 4, the fixed displacement pump 5 is not provided with a pump regulator. Therefore, the discharge flow rate of the fixed displacement pump 5 is always constant without being changed.

  As for the variable displacement pumps 3 and 4 and the fixed displacement pump 5 described above, constant horsepower control is performed to keep the total maximum pump horsepower constant in accordance with their total pump pressure (also referred to as total pump pressure). Will be Specifically, the total pump torque is calculated from the total pump pressure, and the discharge amounts of the variable displacement pumps 3 and 4 are controlled so that the calculated pump torque does not exceed the allowable torque of the engine 2.

  As shown in FIG. 2, the excavator 1 includes an engine speed detection unit 25 and a lever operation detection sensor 9.

The engine speed detector 25 detects the engine speed (specifically, the engine actual speed _Ng ) of the engine 2 and outputs the detected engine speed to a second output unit 82 described later.

  The lever operation detection sensor 9 detects a lever operation amount S of a lever (not shown) for operating the dozer 14 and outputs the detected operation amount S to a first output unit 81 described later. Note that the lever operation detection sensor 9 is an example of an operation detection unit according to the present invention. The dozer 14 is an example of a driven object according to the present invention because it is driven by the fixed displacement pump 5 as a hydraulic pressure source and is operated by a lever (not shown).

  Subsequently, the pump control device 10 (portion surrounded by a broken line in FIG. 2) that controls the pump pressure of the variable displacement pumps 3 and 4 will be described.

  The pump control device 10 includes an absorption torque setting unit 6, a pump control unit 7, a first output unit 81, a second output unit 82, and a torque reduction amount determination unit 83.

  The absorption torque setting unit 6 is a processing unit that sets the absorption torque (pump torque) of the variable displacement pumps 3 and 4.

  The pump control unit 7 determines each discharge amount (tilt) of the variable displacement pumps 3 and 4 based on the absorption torque input from the absorption torque setting unit 6 and each pump pressure of the variable displacement pumps 3 and 4. This is a processing unit to be controlled. Specifically, the pump control unit 7 outputs each tilt command signal to the pump regulators 31 and 41 and controls each discharge amount of the variable displacement pumps 3 and 4 via the pump regulators 31 and 41.

  The first output unit 81 is a processing unit that outputs a first torque reduction value T3 used for reducing the absorption torque output from the absorption torque setting unit 6.

  Specifically, the first output unit 81 determines that the operation of the lever of the dozer 14 is performed based on the lever operation amount S output from the lever operation detection sensor 9 as an operation of the fixed displacement pump 5 (dozer pump). To detect. When the operation of the fixed displacement pump 5 is detected, the first output unit 81 calculates the first torque reduction value T3 using the following equation (1).

_{T3 = PP3 max × q3 ÷ 2π} (1)

In the equation (1), PP3 _max (Mpa) is a relief set pressure (maximum value) of the fixed displacement pump 5. q3 (cc / rev) is the discharge amount of the fixed displacement pump 5. T3 (N · m) is a first torque reduction value calculated by Expression (1).

  The first output unit 81 outputs the first torque reduction value T3 calculated by the equation (1) to the torque reduction amount determination unit 83.

The second output unit 82 is a processing unit that outputs a second torque reduction value T _ess for reducing the absorption torque output from the absorption torque setting unit 6.

Specifically, the second output unit 82 outputs the second torque reduction value T _ess using the following equation (2) based on the deviation between the engine target speed N _gr and the actual engine speed N _g .

T _ess = K _p × (N _gr −N _g ) + K _i ∫ (N _gr −N _g ) dt (2)

In the formula (1), N _gr is the engine target revolution speed set in advance, N _g is the engine actual rotation speed output from the engine speed detecting unit 25. K _p is the integral gain in the proportional gain, _{K i} is likewise PI control in the PI control. T _ess (N · m) is a second torque reduction value calculated by Expression (2).

The second output unit 82 outputs the second torque reduction value T _ess calculated by Expression (2) to the torque reduction amount determination unit 83.

The torque reduction amount determining unit 83 is a processing unit that determines the pump torque reduction amount Td of the variable displacement pumps 3 and 4 based on the first torque reduction value T3 and the second torque reduction value T _ess .

  Specifically, the torque reduction amount determination unit 83 calculates the pump torque using the following equation (3) based on the time (hereinafter, simply referred to as elapsed time T) since the operation of the fixed displacement pump 5 was detected. The reduction amount Td is determined.

Td = α × T3 + (1−α) × T _ess (3)

In the equation (3), α is a coefficient having the characteristic shown in the graph of FIG. 3, that is, the characteristic that it decreases as the elapsed time T increases. More specifically, the coefficient α becomes “1” when the elapsed time T is 0 (T = 0), and then decreases as the elapsed time T increases, and when the elapsed time T becomes Tn (T = Tn). ) To “0”. Therefore, according to the equation (3), the pump torque reduction amount Td is set such that the larger the elapsed time T, the smaller the weight of the first torque reduction value T3 and the larger the weight of the second torque reduction value T _ess. Is determined.

  The torque reduction amount determining section 83 outputs the pump torque reduction amount Td calculated by the equation (3). Specifically, the torque reduction amount determining unit 83 outputs the pump torque reduction amount Td to a subtractor provided between the absorption torque setting unit 6 and the pump control unit 7. The subtracter reduces the absorption torque output from the absorption torque setting unit 6 based on the pump torque reduction amount Td, and outputs the reduced absorption torque to the pump control unit 7.

  As shown in FIG. 2, the lever operation amount S output from the lever operation detection sensor 9 is input to the torque reduction amount determination unit 83. The torque reduction amount determining unit 83 detects that the lever operation amount S has been input as an operation of the fixed displacement pump 5. When the operation of the fixed displacement pump 5 is detected, the torque reduction amount determination unit 83 starts measuring the elapsed time T.

  Subsequently, the operation of the pump control device 10 (the torque reduction amount determining unit 83) in the present embodiment will be described with reference to the flowchart of FIG. The processing of the flowchart in FIG. 4 is repeatedly executed at a certain timing.

  In step S1, the torque reduction amount determining unit 83 determines whether the operation of the fixed displacement pump 5 has been detected. As described above, in the present embodiment, the lever operation of the dozer 14 is detected as the operation of the fixed displacement pump 5 (dozer pump).

  When the operation of the fixed displacement pump 5 is detected (that is, when the lever operation of the dozer 14 is performed) (S1: YES), the torque reduction amount determination unit 83 starts counting the elapsed time T (step S2). ).

  In step S3, the torque reduction determining unit 83 determines the coefficient α based on the elapsed time T. After determining the coefficient α, the torque reduction amount determining unit 83 calculates the pump torque reduction amount Td using the above equation (3) (step S4).

  In step 5, it is determined whether the operation of the fixed displacement pump 5 (that is, the lever operation of the dozer 14) has been completed. When it is determined that the operation of the fixed displacement pump 5 has been completed (S5: YES), the processing of the flowchart in FIG. 4 ends. On the other hand, if it is determined that the operation of the fixed displacement pump 5 has not been completed (S5: NO), the process returns to step S3, and the above-described processing is repeated.

  On the other hand, if the operation of the fixed displacement pump 5 is not detected in step S1 described above (that is, if the lever operation of the dozer 14 is not performed) (S1: NO), the torque reduction amount determination unit 83 determines the elapsed time. T is initialized (T = 0) (step S6), and further, the pump torque reduction amount Td is initialized (Td = 0) (step S7).

According to the pump control device 10 according to the above-described embodiment, the weight of the first torque reduction value T3 is large and the weight of the second torque reduction value T _ess is small immediately after the operation of the fixed displacement pump 5 is detected. It is possible to cope with a sudden rise of the load on the mold pump 5. Thereafter, the first torque reduction value T3 gradually decreases, and the weighting of the second torque reduction value T _ess increases, so that control can be performed in consideration of both the engine output and the pump load. Therefore, in the hydraulic excavator 1 including the variable displacement pumps 3 and 4 that can change the discharge amount and the fixed displacement pump 5 that cannot change the discharge amount, the horsepower can be reduced with a simpler configuration without adding an electromagnetic relief valve or the like. It is possible to control.

  Further, according to the pump control device 10 according to the above-described embodiment, the operation of the fixed displacement pump 5 is detected based on the lever operation amount S of the dozer 14. Therefore, for example, the cost can be reduced as compared with a case where a pump pressure sensor is separately provided in the fixed displacement pump 5 and the operation of the fixed displacement pump 5 is detected using the pump pressure sensor.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, an example in which the torque reduction amount is determined based on the actual pump pressure (actually measured value) of the fixed displacement pump 5 will be described. Hereinafter, differences from the first embodiment will be mainly described, and the description of the already described contents will be appropriately omitted.

  As shown in FIG. 5, in the second embodiment, the lever operation detection sensor 9 (FIG. 2) is not provided, and a pump pressure sensor 53 is provided instead. The pump pressure sensor 53 is a sensor for detecting the pump pressure of the fixed displacement pump 5, and outputs the pump pressure PP3 of the fixed displacement pump 5 as an actually measured value.

  The pump pressure PP3 output from the pump pressure sensor 53 is input to the first output unit 81 and the torque reduction amount determination unit 83, respectively.

  The first output unit 81 calculates a first torque reduction value T3 based on the pump pressure PP3. Specifically, the first output unit 81 calculates the first torque reduction value T3 using the following equation (4).

    T3 = PP3 × q3 ÷ 2π (4)

  In the equation (4), PP3 (Mpa) is the pump pressure (actually measured value) of the fixed displacement pump 5 output from the pump pressure sensor 53. q3 (cc / rev) indicates the discharge amount of the fixed displacement pump as in the first embodiment. T3 (N · m) is a first torque reduction value used for calculating the pump torque reduction amount Td by the torque reduction amount determining unit 83 (Equation (3)).

  Further, the torque reduction amount determining unit 83 detects the operation of the fixed displacement pump 5 based on the input pump pressure PP3, and starts counting the elapsed time T.

In the first embodiment, since the pump pressure sensor 53 is not provided, the relief set pressure PP3 of the fixed displacement pump 5 is calculated in the calculation of the first torque reduction value T3 as shown in the above-described equation (1). _max (maximum value) is used. Therefore, actually, even when the load of the fixed displacement pump 5 is small, the first torque reduction value T3 is set to be large, and as a result, the torque of the variable displacement pumps 3, 4 is reduced more than necessary. In some cases.

  On the other hand, in the second embodiment, the pump pressure PP3 (actually measured value) output from the pump pressure sensor 53 is used in the calculation of the first torque reduction value T3, as shown in the above equation (4). Can be Therefore, when the load of the fixed displacement pump 5 is small, the first torque reduction value T3, and thus the pump torque reduction amount Td of the variable displacement pumps 3 and 4, do not become excessive. Further, the first torque reduction value T3 is output based on the actually measured value of the pump pressure PP3 of the fixed displacement pump 5. Therefore, the first torque reduction value T3 can be output more accurately than in the first embodiment in which the first torque reduction value T3 is output according to the input of the operation amount of the lever operation.

<3. Modification>
The pump control device for a construction machine according to the present invention is not limited to the above embodiment, and various modifications and improvements can be made within the scope described in the claims.

In the above-described embodiment, the case where the first torque reduction value T3 is calculated using the above-described equation (1) has been described as an example. However, the present invention is not limited to this, and a graph (FIG. 6) corresponding to the lever operation amount S shown in FIG. Function). In the graph (function) shown in FIG. 6, as the lever operation amount S increases from 0 to Sn, the first torque reduction value T3 also gradually increases from 0. Then, the first torque reduction value T3 at the time when lever operation amount S becomes Sn becomes maximum _{T3 max.} Thereafter, does not follow the increase of the lever operation amount S, the first torque reduction value T3 maintains the maximum value T3 _max.

  According to such a modification, the first torque reduction value T3 is output as a variable value that increases as the lever operation amount S increases. Therefore, when it is assumed that the lever operation amount S is small and the load of the fixed displacement pump 5 is small, if the first torque reduction value T3, and consequently the pump torque reduction amount Td of the variable displacement pumps 3 and 4, is excessive, You don't have to.

1 hydraulic excavator, 2 engines, 3 and 4 variable displacement pumps, 5 fixed displacement pumps,
6 absorption torque setting unit, 7 pump control unit, 9 lever operation detection sensor,
10 pump control device, 11 undercarriage, 12 upper revolving structure,
13 work attachment, 14 dozer, 25 engine speed detector,
31, 41 pump regulator, 33, 43 pump pressure sensor, 53 pump pressure sensor,
81 first output unit, 82 second output unit, 83 torque reduction amount determination unit,
_Ng engine actual speed, _Ngr engine target speed, PP3 pump pressure,
PP3 _max relief set pressure, S lever operation amount, T elapsed time, T3 torque reduction value,
T3 _max maximum value, Td pump torque reduction amount, T _ess torque reduction value, α coefficient

Claims (5)

Absorption torque setting means for setting an absorption torque of a variable displacement pump capable of changing a discharge amount,
Pump control means for controlling the discharge amount of the variable displacement pump based on the absorption torque and the pump pressure of the variable displacement pump,
Operation detection means for detecting the operation of the fixed displacement pump in which the discharge amount cannot be changed,
A first output unit that outputs a first torque reduction value used for reducing the absorption torque in response to detection of the operation of the fixed displacement pump by the operation detection unit;
A second output unit that outputs a second torque reduction value used for reducing the absorption torque, based on a deviation between the engine target rotation speed and the actual engine rotation speed;
Determining means for determining a pump torque reduction amount of the variable displacement pump based on the first torque reduction value and the second torque reduction value;
With
The determining means decreases the weight of the first torque reduction value and increases the weight of the second torque reduction value as the elapsed time from the detection of the operation of the fixed displacement pump increases. The construction equipment pump control device. The operation detection unit includes a lever operation detection sensor that detects a lever operation amount,
The lever operation amount is an operation amount of a lever for operating a driving target that drives the fixed displacement pump as a hydraulic pressure source,
2. The pump control device for a construction machine according to claim 1, wherein the operation detection unit detects an operation of the fixed displacement pump based on the lever operation amount detected by the lever operation detection sensor. 3. .   The pump control device for a construction machine according to claim 2, wherein the first torque reduction value increases as the operation amount of the lever operation increases. The operation detecting means includes a pump pressure sensor that detects a pump pressure of the fixed displacement pump,
The pump control device for a construction machine according to claim 1, wherein the first torque reduction value increases as the pump pressure detected by the pump pressure sensor increases. An undercarriage,
An upper revolving structure that is rotatably mounted on the lower traveling structure,
A dozer provided on the undercarriage and driven by a dozer cylinder;
A variable displacement pump that can change the discharge rate,
A dozer pump that is configured as a fixed displacement pump that cannot change the discharge amount, and is a hydraulic pressure source of the dozer cylinder;
Absorption torque setting means for setting the absorption torque of the variable displacement pump,
Pump control means for controlling the discharge amount of the variable displacement pump based on the absorption torque and the pump pressure of the variable displacement pump,
Operation detection means for detecting the operation of the dozer pump,
A first output unit that outputs a first torque reduction value for reducing the absorption torque in response to detection of the operation of the dozer pump by the operation detection unit;
A second output unit that outputs a second torque reduction value for reducing the absorption torque based on a deviation between the engine target rotation speed and the actual engine rotation speed;
Determining means for determining a pump torque reduction amount of the variable displacement pump based on the first torque reduction value and the second torque reduction value;
With
The construction means wherein the determining means decreases the weight of the first torque reduction value and increases the weight of the second torque reduction value as the elapsed time from the detection of the operation of the dozer pump increases. machine.

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