Working machinery and control methods

Abstract

The present invention provides a work machine having a mobile body capable of behaving in accordance with the operator's intent, and a control method for the work machine. [Solution] The controller determines the target control amount for the prime mover, hydraulic pump, first flow control valve, and second flow control valve based on the amount of operation of the operating device. When the work machine and the vehicle are operated simultaneously and the load on the work machine exceeds a predetermined level, the controller changes the target control amount so that the flow rate of the hydraulic fluid supplied to the hydraulic cylinder increases.

Description

Technical Field

[0001] The present disclosure relates to a working machine and a control method.

Background Art

[0002] There is known a working machine that is driven by hydraulic pressure using hydraulic oil (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding a working machine having a traveling body driven by hydraulic oil, it is required that the behavior of the working machine conform to the intention of an operation by an operator. An object of the present disclosure is to provide a working machine having a traveling body that can behave in accordance with the intention of an operation by an operator and a control method for the working machine.

Means for Solving the Problems

[0005] According to one aspect of the present invention, a work machine comprises a vehicle body, a traveling body that supports the vehicle body so as to be drivable, a work machine supported on the vehicle body, an operating device that receives input of operating amounts for the traveling body and the work machine, a hydraulic system that drives the traveling body and the work machine, and a controller that controls the hydraulic system, wherein the hydraulic system comprises an engine, at least one hydraulic pump driven by the engine, a travel motor that drives the traveling body with hydraulic fluid discharged by the hydraulic pump, a hydraulic cylinder that drives the work machine with hydraulic fluid discharged by the hydraulic pump, a first flow control valve that controls the flow rate of hydraulic fluid supplied to the travel motor, and a second flow control valve that controls the flow rate of hydraulic fluid supplied to the hydraulic cylinder, wherein the controller determines target control amounts for the engine, the hydraulic pump, the first flow control valve and the second flow control valve from the operating amount of the operating device, and changes the target control amount so as to increase the flow rate of hydraulic fluid supplied to the hydraulic cylinder when the work machine and the traveling body are operated simultaneously and the load on the work machine exceeds a predetermined level. [Effects of the Invention]

[0006] According to the above embodiment, the work machine can behave in accordance with the operator's intent. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of the work machine according to the first embodiment. [Figure 2] This is a schematic block diagram showing the configuration of the drive system according to the first embodiment. [Figure 3] This is a schematic block diagram showing the configuration of the control device according to the first embodiment. [Figure 4] This flowchart shows a method for predicting a target flow rate after a certain period of time according to the first embodiment. [Figure 5] This is a flowchart showing the method for determining the target flow rate of a hydraulic pump according to the first embodiment. [Figure 6]This is a flowchart showing the combined operation assistance control according to the first embodiment. [Figure 7] This is a flowchart showing the control method for a hydraulic pump according to the first embodiment. [Figure 8] This is a block diagram showing the control of the hydraulic pump by the pump control unit according to the first embodiment. [Figure 9] This is a flowchart showing the method for determining the time constant according to the first embodiment. [Figure 10] This is a time chart of the target control amount of the first travel motor 112R in a comparative example where the hydraulic pump is controlled according to a steady-state time constant. [Figure 11] This is a time chart of the target control amount of the first travel motor 112R according to the first embodiment, which controls the hydraulic pump according to the transient time constant. [Figure 12] This is a flowchart showing the combined operation assistance control according to the second embodiment. [Figure 13] This is a schematic block diagram showing the configuration of a computer according to at least one embodiment. [Modes for carrying out the invention]

[0008] <First Embodiment> 《Configuration of the work machine》 The embodiments will be described in detail below with reference to the drawings. Figure 1 is a perspective view of a work machine 1 according to the first embodiment. The work machine 1 according to the first embodiment is, for example, a hydraulic excavator. The work machine 1 comprises a traveling body 110, a slewing body 120, a work machine 130, a driver's cab 140, and a machine room 150. The work machine 1, being a hydraulic excavator, excavates and levels soil and other materials at a work site. The traveling body 110 and the slewing body 120 constitute the vehicle body.

[0009] The traveling body 110 supports the working machine 1 so that it can travel. The traveling body 110 has a pair of left and right crawlers 111. The working machine 1 moves forward, turns, or moves backward by the rotation of the pair of crawlers 111. Hereinafter, the traveling motor 112 for driving the right crawler 111R is referred to as the first traveling motor 112R, and the traveling motor 112 for driving the left crawler 111L is referred to as the second traveling motor 112L. The traveling motor 112 has a speed change function. That is, the traveling motor 112 can switch between a low-speed mode in which it is driven at a first capacity and a high-speed mode in which it is driven at a second capacity smaller than the first capacity. The traveling motor 112 in the low-speed mode has a larger driving torque and a lower speed compared to the high-speed mode. Therefore, when the driving torque of the traveling motor 112 is low with respect to the traveling resistance, the control device 145 switches from the low-speed mode to the high-speed mode.

[0010] The revolving body 120 is rotatably supported by the traveling body 110. The revolving body 120 rotates with respect to the traveling body 110 by a revolving motor 127. The revolving body 120 supports the working machine 130, the cab 140, and the machine room 150.

[0011] The working machine 130 is operably supported by the vehicle body (revolving body 120) of the working machine 1. The working machine 130 includes a boom 131, an arm 132, and a bucket 133 as a working tool. The base end portion of the boom 131 is rotatably attached to the revolving body 120. The base end portion of the arm 132 is rotatably attached to the tip end portion of the boom 131. The bucket 133 is rotatably attached to the tip end portion of the arm 132.

[0012] The working machine 130 is driven by a plurality of actuators. The plurality of actuators include, for example, a boom cylinder 131C, an arm cylinder 132C, and a bucket cylinder 133C.

[0013] The boom cylinder 131C is a hydraulic cylinder for driving the boom 131. The base end portion of the boom cylinder 131C is attached to the revolving body 120. The tip end portion of the boom cylinder 131C is attached to the boom 131. The arm cylinder 132C is a hydraulic cylinder for driving the arm 132. The base end portion of the arm cylinder 132C is attached to the boom 131. The tip end portion of the arm cylinder 132C is attached to the arm 132. The bucket cylinder 133C is a hydraulic cylinder for driving the bucket 133. The base end portion of the bucket cylinder 133C is attached to the arm 132. The tip end portion of the bucket cylinder 133C is attached to the bucket 133.

[0014] The cab 140 is a place where the operator of the work machine 1 rides and performs operations and controls. The cab 140 is arranged, for example, on the left side portion of the front end of the revolving body 120. In the cab 140 of the work machine 1, a driver's seat 141 for the operator to sit on, an operating device 142 for operating the work machine 1, and a control device 145 for controlling the work machine 1 are provided. The operating device 142 is operated by the operator to operate the work machine 1. The operating device 142 outputs an operation signal according to the operation of the operator.

[0015] The control device 145 controls the work machine 1. The control device 145 receives an operation signal from the operating device 142. The control device 145 controls the traveling of the traveling body 110, the driving of the work implement 130, and the turning operation of the revolving body 120 based on the operation signal from the operating device 142.

[0016] The drive system 20 described later is arranged in the machine room 150. The machine room 150 is arranged, for example, behind the cab 140. The machine room 150 forms a space for arranging the drive system 20.

[0017] 《Configuration of the drive system 20》 FIG. 2 is a schematic block diagram showing the configuration of the drive system 20 according to the first embodiment. The drive system 20 includes an engine 121, a front hydraulic pump 122A, a rear hydraulic pump 122B, a front main oil passage 123A, a rear main oil passage 123B, a main connecting oil passage 124, a front control valve 126A, a rear control valve 126B, a swing motor 127, a boom cylinder 131C, an arm cylinder 132C, a bucket cylinder 133C, a first travel motor 112R, and a second travel motor 112L. Hereinafter, the front hydraulic pump 122A and the rear hydraulic pump 122B will be collectively referred to as hydraulic pump 122. Also, hereafter, the front main oil passage 123A and the rear main oil passage 123B will be collectively referred to as main oil passage 123. Also, hereafter, the front control valve 126A and the rear control valve 126B will be collectively referred to as control valve 126.

[0018] Engine 121 is the prime mover that drives the hydraulic pump 122. In the first embodiment, engine 121 is a diesel engine. Examples of engine 121 in other embodiments include a gasoline engine or an electric motor. The front hydraulic pump 122A and the rear hydraulic pump 122B are variable displacement pumps driven by the engine 121. The front hydraulic pump 122A supplies hydraulic fluid to the front main oil passage 123A. The rear hydraulic pump 122B supplies hydraulic fluid to the rear main oil passage 123B. The front hydraulic pump 122A is equipped with a front swash plate angle sensor 1221A that measures the inclination angle of the swash plate of the front hydraulic pump 122A. The rear hydraulic pump 122B is equipped with a rear swash plate angle sensor 1221B that measures the inclination angle of the swash plate of the rear hydraulic pump 122B. Since the capacity of the hydraulic pump 122 is determined by the inclination angle of the swash plate, the control device 145 can determine the discharge amount of the hydraulic pump 122 based on the measurement value of the swash plate angle sensor 1221. Furthermore, since the discharge volume of the hydraulic pump 122 changes not only with capacity but also with rotational speed, if the work machine 1 according to other embodiments controls the discharge volume of the hydraulic pump 122 by rotational speed, the work machine 1 may be equipped with a sensor that measures the rotational speed of the hydraulic pump 122 instead of the swash plate angle sensor 1221.

[0019] The main oil passage 123 is equipped with a pump discharge pressure sensor 1231 and a bleed valve 1232. The pump discharge pressure sensor 1231 measures the pressure of the hydraulic fluid discharged by the hydraulic pump 122. The bleed valve 1232 discharges the hydraulic fluid supplied when the actuator is not being driven. Even when the actuator is not being driven, the hydraulic pump 122 discharges the minimum flow rate of hydraulic fluid. Hereinafter, the pump discharge pressure sensor 1231 provided in the front main oil passage 123A will also be called the front pump discharge pressure sensor 1231A, and the pump discharge pressure sensor 1231 provided in the rear main oil passage 123B will also be called the rear pump discharge pressure sensor 1231B. Furthermore, the bleed valve 1232 provided in the front main oil passage 123A will also be called the front bleed valve 1232A, and the bleed valve 1232 provided in the rear main oil passage 123B will also be called the rear bleed valve 1232B.

[0020] The main connecting oil passage 124 connects the front main oil passage 123A and the rear main oil passage 123B. The main connecting oil passage 124 is equipped with a main confluence / separation valve 1241. The main confluence / separation valve 1241 is a shut-off valve that controls the opening and closing of the main connecting oil passage 124. This allows the main confluence / separation valve 1241 to switch between confluence or separation of the hydraulic fluid flowing through the front main oil passage 123A and the hydraulic fluid flowing through the rear main oil passage 123B.

[0021] The front control valve 126A is connected to the front main oil passage 123A. The front control valve 126A distributes the hydraulic fluid supplied from the front main oil passage 123A to the swing motor 127, the arm cylinder 132C, and the first travel motor 112R. Hereinafter, the set of the swing motor 127, arm cylinder 132C, and first travel motor 112R connected to the front control valve 126A will also be referred to as the front actuator unit UA. The swing motor 127 is equipped with a swing load pressure sensor 127P that measures the pressure (load pressure) on the inlet side of the swing motor 127. The arm cylinder 132C is equipped with an arm load pressure sensor 132CP that measures the pressure (load pressure) on the inlet side of the arm cylinder 132C. The first travel motor 112R is equipped with a front travel load pressure sensor 112RP that measures the pressure (load pressure) on the inlet side of the first travel motor 112R.

[0022] The rear control valve 126B is connected to the rear main oil passage 123B. The rear control valve 126B distributes the hydraulic fluid supplied from the rear main oil passage 123B to the boom cylinder 131C, the bucket cylinder 133C, and the second travel motor 112L. Hereinafter, the set of boom cylinder 131C, bucket cylinder 133C, and second travel motor 112L connected to the rear control valve 126B will also be referred to as the rear actuator unit UB. The boom cylinder 131C is equipped with a boom load pressure sensor 131CP that measures the pressure (load pressure) on the inlet side of the boom cylinder 131C. The bucket cylinder 133C is equipped with a bucket load pressure sensor 133CP that measures the pressure (load pressure) on the inlet side of the bucket cylinder 133C. The second travel motor 112L is equipped with a rear travel load pressure sensor 112LP that measures the pressure (load pressure) on the inlet side of the second travel motor 112L. The front control valve 126A or the rear control valve 126B may be provided with a port for supplying hydraulic fluid to actuators (such as breakers, grapples, and tilt rotators) installed on the work tool (attachment).

[0023] The control valve 126 has a flow control valve 1261 and a pressure compensation valve 1262 for each actuator. The flow control valve 1261 adjusts the flow rate of hydraulic fluid supplied to the corresponding actuator in response to a command from the control device 145.

[0024] Of the multiple flow control valves 1261, the flow control valve 1261 connected to the inlet side of the travel motor 112 is provided with a meter-in opening 1261A controlled by a command from the control device 145, as well as a bleed opening 1261B that returns a portion of the hydraulic fluid that has passed through the flow control valve 1261 to the tank. The opening of the bleed opening 1261B is linked to the opening of the meter-in opening 1261A. The bleed opening 1261B is closed when the opening of the meter-in opening 1261A is from fully open to a predetermined first opening, and the bleed opening 1261B is open when the opening of the meter-in opening 1261A is from the first opening to fully closed.

[0025] Here, we will explain the reason for providing the bleed opening 1261B. The work site on which the work machine 1 travels often has uneven surfaces. When the work machine 1 travels on such surfaces, the load resistance of the travel motor 112 fluctuates due to the unevenness of the surface. Fluctuations in the load resistance (load pressure) of the travel motor 112 cause the torque of the travel motor 112 to vibrate, which causes vibration and noise of the travel motor 112. If the operator is shaken by the vibration of the travel motor 112, the amount of operation of the travel lever operated by the operator may also vibrate. Since the vibration of the amount of operation of the travel lever resonates with the vibration of the travel motor 112, the vibration of the travel motor 112 may increase. If the flow control valve 1261 has a bleed opening 1261B, an amount of hydraulic fluid corresponding to the increase in the load pressure of the travel motor 112 can be returned to the tank through the bleed opening 1261B. This makes it possible to suppress vibrations of the travel motor 112 caused by fluctuations in the load pressure of the travel motor 112. On the other hand, when the operator is pressing the travel lever against the end of its range of motion, even if the operator is shaken by vibrations from the travel motor 112, the likelihood of vibrations occurring in the travel lever is low. Therefore, when operating at the maximum range of motion, the bleed opening 1261B closes, preventing a decrease in travel speed.

[0026] The pressure compensation valve 1262 compensates for the flow rate distribution to each actuator, even if the load pressure of each actuator provided on the same control valve 126 (main oil passage 123) is different, preventing the hydraulic fluid from being unevenly distributed to the actuators on the low-load side. The pressure compensation valve 1262 applies a pressure loss to the low-load shaft so that the outlet pressure of the flow control valve 1261 of the low-load actuator becomes equal to the outlet pressure of the flow control valve 1261 of the actuator with the maximum load pressure. As a result, the outlet pressures of each flow control valve 1261 become equal, enabling flow rate distribution using the area ratio of the meter-in opening 1261A. Therefore, the same control valve 126 is provided with an LS (load sensing) oil passage 128 that shares the hydraulic fluid at the outlet of each flow control valve 1261. The outlet circuit of each flow control valve 1261 is connected to the LS oil passage 128 via a check valve, and the LS oil passage 128 is connected to the circuit with the highest pressure among the outlet circuits of each flow control valve 1261. Furthermore, each pressure compensation valve 1262 is connected to the LS oil passage 128. As a result, the pressure compensation valve 1262 is subjected to the maximum load pressure in each actuator inlet circuit, thereby adjusting the pressure in the outlet circuit of each flow control valve 1261 to an equivalent pressure. Hereinafter, the LS oil passage 128 of the front control valve 126A will be referred to as the front LS oil passage 128A, and the LS oil passage 128 of the rear control valve 126B will be referred to as the rear LS oil passage 128B.

[0027] The LS connecting oil passage 129 connects the front LS oil passage 128A and the rear LS oil passage 128B. The LS connecting oil passage 129 is equipped with an LS confluence / separation valve 1291. The LS confluence / separation valve 1291 is a shut-off valve that controls the opening and closing of the LS connecting oil passage 129. This allows the LS confluence / separation valve 1291 to switch between confluence or separation of the hydraulic fluid flowing through the front LS oil passage 128A and the hydraulic fluid flowing through the rear LS oil passage 128B. When the front LS oil passage 128A and the rear LS oil passage 128B confluence, the maximum load pressure of the actuators connected to the front control valve 126A and the actuators connected to the rear control valve 126B is applied to each pressure compensation valve 1262.

[0028] Configuration of the control device 145 Figure 3 is a schematic block diagram showing the configuration of the control device 145 according to the first embodiment. The control device 145 according to the first embodiment includes a measurement value acquisition unit 51, an operation amount acquisition unit 52, a target flow rate determination unit 53, a valve control unit 54, an engine control unit 55, a pump control unit 56, a combined operation assistance unit 57, and a time constant determination unit 58.

[0029] The measurement value acquisition unit 51 acquires sensor data indicating the measured values ​​from various sensors (front pump discharge pressure sensor 1231A, rear pump discharge pressure sensor 1231B, slewing load pressure sensor 127P, arm load pressure sensor 132CP, front travel load pressure sensor 112RP, boom load pressure sensor 131CP, bucket load pressure sensor 133CP, rear travel load pressure sensor 112LP). If the front control valve 126A or the rear control valve 126B has a port for supplying hydraulic fluid to the attachment, the work machine 1 may also be equipped with a load pressure sensor for the attachment. The manipulated amount acquisition unit 52 receives operation commands from the operation device 142 and identifies the manipulated amount for each actuator. If the work machine 1 has an automatic control function, the manipulated amount acquisition unit 52 may acquire the manipulated amount calculated by the automatic control function. In other embodiments, the manipulated amounts may be generated by a controller other than the control device 145. The other controller may be located outside the work machine 1. The manipulated amount may be transmitted from the controller located outside the work machine 1 to the control device 145 mounted on the work machine 1. The operation device 142 may be a remote control device located outside the work machine 1. The work machine 1 may be remotely controlled by a remote control device located outside the work machine 1. When the work machine 1 is remotely controlled by a remote control device, a remote controller connected to the remote control device may generate an operation signal. The operation signal generated by the remote controller may be transmitted to the control device 145 mounted on the work machine 1.

[0030] The target flow rate determination unit 53 determines a target value for the flow rate of hydraulic fluid required to drive each actuator, according to the manipulated amount acquired by the manipulated amount acquisition unit 52. The valve control unit 54 controls the opening degree of the flow rate adjustment valve 1261 and bleed valve 1232 of each control valve 126 based on the target flow rate determined by the target flow rate determination unit 53 and the merging and separation state of the main oil passage 123. The engine control unit 55 controls the fuel injection amount and other parameters of the engine 121 so that the engine speed approaches the target speed through feedback control based on the measured rotational speed of the engine 121. The target speed is determined, for example, by the value indicated by the rotational speed adjustment knob acquired by the manipulated variable acquisition unit 52. The pump control unit 56 controls the swash plate angle of each hydraulic pump 122 based on the target flow rate determined by the target flow rate determination unit 53 and the merging and separation state of the main oil passage 123.

[0031] The combined operation assist unit 57 assists in combined operations, where the travel operation and the boom 131 raising operation are performed simultaneously, to ensure that the boom 131 raising operation is not interrupted. The time constant determination unit 58 determines the time constant of the low-pass filter used for control by the pump control unit 56. In other words, the time constant determination unit 58 determines the response characteristics of the filtering process used for control by the pump control unit 56.

[0032] Determining the target flow rate The target flow rate determination unit 53 determines the required flow rate corresponding to the control amount of each actuator based on a conversion table that shows the relationship between the control amount of each actuator and the required flow rate. Furthermore, the target flow rate determination unit 53 calculates a transient target flow rate by adding characteristics that take into account transient characteristics such as filtering processes to the required flow rate.

[0033] Figure 4 is a flowchart showing the method for calculating the transient target flow rate according to the first embodiment. The target flow rate determination unit 53 calculates the transient target flow rate for each actuator unit U and each actuator using the following procedure.

[0034] The target flow rate determination unit 53 obtains the manipulated amount of each actuator from the manipulated amount acquisition unit 52 and determines the required flow rate for each actuator from the acquired manipulated amounts according to a predetermined conversion table (step S1). The target flow rate determination unit 53 determines whether the sum of the required flow rates of the actuators is greater than the sum of the maximum flow rates of the hydraulic pumps 122 (step S2). If the sum of the required flow rates of the actuators is greater than the sum of the maximum flow rates of the hydraulic pumps 122 (step S2: YES), the target flow rate determination unit 53 determines the target value of the required flow rate for each actuator so that the sum matches the sum of the maximum flow rates of the hydraulic pumps 122, while maintaining the ratio of the required flow rates of each actuator (step S3). If the sum of the required flow rates of the actuators is less than or equal to the sum of the maximum flow rates of the hydraulic pumps 122 (step S2: NO), the target flow rate determination unit 53 determines the required flow rate determined in step S1 as the target value of the required flow rate for each actuator (step S4).

[0035] The target flow rate determination unit 53 performs the following steps S5 to S7 for each of the front main oil passage 123A and the rear main oil passage 123B. First, the target flow rate determination unit 53 determines the target transient flow rate for the next calculation cycle based on the current transient flow rate target value and the target requested flow rate identified in step S3 or step S4 (step S5). Specifically, the target flow rate determination unit 53 performs a filtering procedure to determine the target flow rate after one calculation cycle by adding a value obtained by multiplying the difference between the current transient flow rate target value and the target requested flow rate target value by a predetermined gain to the current transient flow rate target value. The filter may be, for example, a low-pass filter or a limiter that limits the rate of change. In this way, the target flow rate determination unit 53 can prevent abrupt changes in the target flow rate by filtering the requested flow rate. In the following, "transient flow rate target value" may simply be referred to as "flow rate target value".

[0036] Figure 5 is a flowchart showing the method for determining the target flow rate of the hydraulic pump 122 according to the first embodiment. Hereinafter, of the front actuator unit UA and the rear actuator unit UB, the one with the larger target flow rate will be called the first actuator unit U1, and the one with the smaller target flow rate will be called the second actuator unit U2. Also, of the front hydraulic pump 122A and the rear hydraulic pump 122B, the one corresponding to the first actuator unit will be called the first hydraulic pump, and the one corresponding to the second actuator unit will be called the second hydraulic pump. For example, if the target flow rate Qua of the front actuator unit UA is greater than the target flow rate Qub of the rear actuator unit UB, then the first actuator unit U1 is the front actuator unit UA, the second actuator unit U2 is the rear actuator unit UB, the first hydraulic pump is the front hydraulic pump 122A, and the second hydraulic pump is the rear hydraulic pump 122B. In this case, the target flow rate Qu1 = Qua of the first actuator unit U1 and the target flow rate Qu2 = Qub of the second actuator unit U2.

[0037] The target flow rate determination unit 53 determines whether the target value Qu1 of the flow rate of the first actuator unit, obtained by the process shown in Figure 4, is less than or equal to the flow rate threshold Qt1 of the first hydraulic pump, and whether the target value Qu2 of the flow rate of the second actuator unit is less than or equal to the flow rate threshold Qt2 of the second hydraulic pump (step S13). The flow rate threshold Qt may be a value obtained by subtracting a margin based on a predetermined safety factor from the maximum flow rate Qmax of the hydraulic pump 122. For example, the flow rate threshold Qt may be 90% of the maximum flow rate Qmax of the hydraulic pump 122.

[0038] If the target flow rate Qu1 of the first actuator unit is less than or equal to the flow rate threshold Qt1 of the first hydraulic pump and the target flow rate Qu2 of the second actuator unit is less than or equal to the flow rate threshold Qt2 of the second hydraulic pump (step S13: YES), the target flow rate determination unit 53 determines the target flow rate Qp1 of the first hydraulic pump to be the target flow rate Qu1 of the first actuator unit, and determines the target flow rate Qp2 of the second hydraulic pump to be the target flow rate Qu2 of the second actuator unit (step S14).

[0039] If the target flow rate of the first actuator unit exceeds the flow rate threshold of the first hydraulic pump, or if the target flow rate of the second actuator unit exceeds the flow rate threshold of the second hydraulic pump (step S13: NO), the target flow rate determination unit 53 determines whether the main connecting oil passage 124 is in a merged state or not (step S15). If the main connecting oil passage 124 is in a separated state (step S15: NO), the target flow rate determination unit 53 determines the target flow rate Qp1 of the first hydraulic pump to be the smaller of the target flow rate Qu1 of the first actuator unit and the maximum flow rate Qmax1 of the first hydraulic pump (step S16). The target flow rate determination unit 53 determines the target flow rate Qu2 of the second actuator unit to be the target flow rate Qp2 of the second hydraulic pump (step S17).

[0040] If the main connecting oil passage 124 is in a merging state (step S15: YES), the target flow rate determination unit 53 calculates a determined flow rate Qs by adding the larger of zero and the value obtained by subtracting the maximum flow rate Qmax1 of the first hydraulic pump from the target flow rate Qu2 of the second actuator unit (step S18). The target flow rate determination unit 53 determines whether the determined flow rate Qs is smaller than the minimum flow rate Qmin2 of the second hydraulic pump (step S19).

[0041] If the determined flow rate Qs is smaller than the minimum flow rate Qmin2 of the second hydraulic pump (step S19: YES), the target flow rate determination unit 53 determines the target value Qp2 of the flow rate of the second hydraulic pump to be the minimum flow rate Qmin2 of the second hydraulic pump (step S20). Next, the target flow rate determination unit 53 determines the target value Qp1 of the first hydraulic pump to be the flow rate obtained by subtracting the minimum flow rate Qmin2 of the second pump from the sum of the target value Qu1 of the flow rate of the first actuator unit and the target value Qu2 of the flow rate of the second actuator unit (step S21). In this case, a support flow rate (Qp2-Qu2), which is the total flow rate of the hydraulic fluid discharged by the second hydraulic pump minus the flow rate consumed by the second actuator unit, is supplied to the first actuator unit. The support flow rate at this time is the difference between the target value Qp1 of the flow rate of the first hydraulic pump and the target value Qu1 of the flow rate of the first actuator unit.

[0042] If the determined flow rate Qs is greater than or equal to the minimum flow rate Qmin2 of the second hydraulic pump (step S19: NO), the target flow rate determination unit 53 determines the target value Qp2 of the flow rate of the second hydraulic pump to be the determined flow rate Qs obtained in step S18 (step S22). Next, the target flow rate determination unit 53 determines the target value Qp1 of the first hydraulic pump to be the smaller of the maximum flow rate Qmax1 of the first hydraulic pump and the target value Qu1 of the flow rate of the first actuator unit (step S23). In this case, the support flow rate (Qp2-Qu2), which is the total flow rate of the hydraulic fluid discharged by the second hydraulic pump minus the flow rate consumed by the second actuator unit, is supplied to the first actuator unit. The support flow rate at this time is the difference between the minimum flow rate Qmin2 of the second hydraulic pump and the target value Qp2 of the flow rate of the second actuator unit. As a result, the control device 145 can use the difference between the minimum flow rate Qmin2 output by the second hydraulic pump and the flow rate Qp2 consumed by the second actuator unit as a support flow rate for the first actuator unit without releasing it through the bleed valve 1232.

[0043] As a result, the target flow rate determination unit 53 can determine the target value Qa for the flow rate of each actuator, the target value Qu for the flow rate of each actuator unit U, and the target value Qp for the flow rate of each hydraulic pump 122. By determining the target value Qp for the flow rate of the hydraulic pump 122 using the procedure described above, the supply flow rates of each hydraulic pump 122 can be made different even if the main oil passage 123 is merged. As a result, the control device 145 can supply a support flow rate from the second hydraulic pump to the first actuator unit if the target value Qu1 for the flow rate of the first actuator unit cannot be met by the maximum flow rate of the first hydraulic pump. The support flow rate according to the first embodiment is smaller than the flow rate passing through the main merge / separation valve 1241 when the supply flow rates of each hydraulic pump 122 are the same. As a result, the control device 145 can suppress the pressure loss that occurs in the main merge / separation valve 1241.

[0044] Valve control The valve control unit 54 controls the opening degree of the control valve 126 according to the target flow rate of the actuator determined by the target flow rate determination unit 53. As a result, each actuator is supplied with hydraulic fluid at a flow rate according to the target flow rate. On the other hand, the valve control unit 54 controls the opening degree of the flow control valve 1261 connected to the travel motor 112 according to the amount operated by the operating device 142, regardless of the target flow rate. Since the target flow rate does not necessarily correspond to the amount operated by the operating device 142, the target flow rate may be small even if the amount operated is at its maximum. Since the flow control valve 1261 connected to the travel motor 112 has a bleed opening 1261B, if the flow control valve 1261 is controlled according to the target flow rate, the opening degree of the flow control valve 1261 may fall below the first opening degree even if the amount operated is at its maximum, causing the bleed opening 1261B to open and the travel motor 112 to decelerate. Therefore, the valve control unit 54 according to the first embodiment controls the opening degree of the flow control valve 1261 connected to the travel motor 112 according to the amount operated by the operating device 142, regardless of the target flow rate. As a result, when the amount operated is at its maximum, the bleed opening 1261B is always closed, preventing deceleration of the travel motor 112.

[0045] Furthermore, when the main oil passage 123 is separated, the valve control unit 54 controls the opening degree of the bleed valve 1232 to discharge a flow rate equal to the difference between the minimum flow rate and the target flow rate if the target flow rate of at least one actuator unit U is smaller than the minimum flow rate of the corresponding hydraulic pump 122.

[0046] Engine control The engine control unit 55 controls the fuel injection amount of the engine 121 and other parameters so that the rotational speed of the engine 121 approaches a target value through feedback control based on the measured rotational speed of the engine 121. Specifically, the engine control unit 55 calculates the difference between the target value and the measured value of the engine rotational speed, and multiplies this by a predetermined gain Kp to determine the target value of the output torque (calculated target value). On the other hand, the engine control unit 55 has a function to set an upper limit for the output torque, and the final target value of the output torque is calculated from the smaller of the calculated target value of the output torque and the upper limit of the output torque.

[0047] (Assistance with complex operations) The work machine 1 may travel with the bucket 133 loaded in order to transport the load loaded in the bucket 133. If there are obstacles such as unevenness in the road surface during this travel, the operator will raise the boom 131 while the work machine 1 is moving to avoid contact between the obstacle and the bucket 133. When the boom 131 is raised with a load loaded in the bucket 133, the load pressure on the boom cylinder 131C becomes greater than the load pressure on the travel motor 112.

[0048] Furthermore, when the operator moves the vehicle 110, the control device 142 is typically operated to its maximum extent. On the other hand, when raising the boom 131 to avoid an obstacle, the amount of operation is usually small. Therefore, the opening of the flow control valve 1261 of the boom 131 is small, and the opening of the flow control valve 1261 of the travel motor 112 is large. In particular, as mentioned above, the opening of the flow control valve 1261 connected to the travel motor 112 is controlled according to the amount of operation of the control device 142, regardless of the target flow rate, so when the travel motor 112 is operated to its maximum extent, the opening of the flow control valve 1261 becomes maximum.

[0049] Hydraulic fluid tends to flow towards the side with the lower load and the side with the larger opening. Therefore, when performing a combined operation of traveling and raising the boom 131, most of the hydraulic fluid flows to the travel motor 112, and the amount of hydraulic fluid flowing to the boom 131 is small, which may result in the boom 131 hardly rising at all.

[0050] In the first embodiment, the combined operation assist unit 57 of the control device 145 changes the target control amount so as to increase the flow rate of hydraulic fluid supplied to the boom cylinder 131C when a combined operation of traveling and raising the boom 131 is performed and the load on the work machine 130 exceeds a predetermined level.

[0051] Specifically, the combined operation assistance unit 57 performs the following processing. Figure 6 is a flowchart of the combined operation assistance control according to the first embodiment. The combined operation assistance unit 57 determines, based on the operation amount of the operating device 142 acquired by the operation amount acquisition unit 52, whether the operation consists only of travel operation and boom 131 raising operation (step S31). In other words, the combined operation assistance unit 57 determines whether the travel operation and boom 131 raising operation are being performed simultaneously and no other operations are being performed. In other embodiments, the combined operation assist unit 57 may determine whether the travel operation and the boom 131 raising operation are being performed simultaneously, regardless of whether other operations are being performed.

[0052] If only the travel operation and the boom 131 raising operation are being performed (step S31: YES), the combined operation assist unit 57 determines whether the load pressure on the boom cylinder 131C exceeds a predetermined load threshold (step S32). The load threshold may be a value that is considered to be sufficiently high compared to the load related to travel. Alternatively, for example, the load threshold may be set according to the load pressure of the travel motor 112, such as a predetermined number of times the load pressure of the travel motor 112. In addition, in other embodiments, the combined operation assist unit 57 may determine whether the load on the boom 131 exceeds a predetermined level when the measured value of a payload meter (not shown) exceeds a predetermined threshold, instead of measuring the load pressure related to the boom cylinder 131C. Furthermore, in other embodiments, the combined operation assist unit 57 may determine whether the load on the boom 131 exceeds a predetermined level based on the type of work tool at the tip of the work implement 130.

[0053] If only the travel operation and the boom 131 raising operation are performed, and the load pressure on the boom cylinder 131C exceeds the load threshold (step S32: YES), the combined operation assist unit 57 determines whether the amount of operation for raising the boom 131 exceeds a predetermined operation amount threshold (step S33). The operation amount threshold may be a value that clearly indicates the operator's intention to raise the boom 131 at high speed (for example, 80%).

[0054] If only the travel operation and the boom 131 raising operation are performed, and the load pressure on the boom cylinder 131C exceeds the load threshold, and the amount of operation for raising the boom 131 exceeds the operation amount threshold (step S33: YES), the combined operation assist unit 57 outputs an instruction to the engine control unit 55 to increase the upper limit of the output torque of the engine 121 by a predetermined offset value (step S34). The engine control unit 55 determines the target value of the output torque by keeping the calculated target value of the output torque, which is calculated by feedback control of the rotational speed of the engine 121, below the upper limit of the output torque. Therefore, by increasing the upper limit of the output torque by the combined operation assist unit 57, the output that the engine can produce increases.

[0055] Next, the combined operation assistance unit 57 outputs an instruction to the valve control unit 54 to increase the opening degree of the flow control valve 1261 of the boom cylinder 131C by a predetermined amount compared to the opening degree determined from the target flow rate (step S35). The valve control unit 54 increases the opening degree of the flow control valve 1261 of the boom cylinder 131C by adding the opening degree instructed by the combined operation assistance unit 57 to the opening degree determined from the target flow rate. In other embodiments, the combined operation assistance unit 57 may output an instruction to multiply the opening degree determined from the target flow rate by a predetermined multiplier greater than 1. This allows the valve control unit 54 to facilitate the flow of hydraulic fluid into the boom cylinder 131C.

[0056] The combined operation assist unit 57 determines whether the opening of the flow control valve 1261 of the travel motor 112 is greater than the first opening (step S36). If the opening of the flow control valve 1261 of the travel motor 112 is greater than the first opening, the bleed opening 1261B of the flow control valve 1261 is closed. If the opening of the flow control valve 1261 of the travel motor 112 is greater than the first opening (step S36: YES), the combined operation assist unit 57 outputs an instruction to the valve control unit 54 to set the opening of the flow control valve 1261 of the travel motor 112 to the first opening (step S37). As a result, the valve control unit 54 can prevent the hydraulic fluid supplied to the travel motor 112 from returning to the tank through the bleed opening 1261B, while making it difficult for hydraulic fluid to flow to the travel motor 112.

[0057] The combined operation assist unit 57, through steps S34 to S37 described above, can circulate the hydraulic fluid necessary for raising the boom 131 to the boom cylinder 131C. In other embodiments, the combined operation assist unit 57 may perform only a portion of steps S34 to S37 described above. In this case as well, the amount of hydraulic fluid circulating to the boom cylinder 131C can be increased compared to the case where these processes are not performed.

[0058] Furthermore, if either the travel operation or the boom 131 raising operation is not performed (step S31: NO), if another actuator is being operated (step S31: NO), if the load pressure on the boom cylinder 131C does not exceed the load threshold (step S32: NO), or if the amount of operation for the boom 131 raising operation does not exceed the operation amount threshold (step S33: NO), the combined operation assist unit 57 will not assist the boom 131 raising operation as described in steps S34 to S37 above.

[0059] As mentioned above, the combined operation assistance unit 57 determines the load level based on the load pressure of each actuator measured by the load pressure sensor. However, if the load pressure sensor fails, the combined operation assistance unit 57 will be unable to properly determine the load pressure level. Therefore, the combined operation assistance unit 57 has a means to determine whether the load pressure sensor is in a faulty state, and if it determines that the load pressure sensor is faulty, it prohibits the change of the target control amount described above. An example of a method for detecting a faulty state of the load pressure sensor is as follows: Normally, a load pressure sensor has a defined voltage range in which it can normally detect the load pressure (normal detection voltage range). Therefore, the combined operation assistance unit 57 determines that the load pressure sensor is faulty if it detects a voltage that is significantly outside of that normal detection voltage range. For example, if the normal detection voltage range of the load pressure sensor is 0.5V to 4.5V, it will be determined that the sensor is faulty if the detected voltage is 0.3V or less or 4.7V or more.

[0060] Pump control The pump control unit 56 determines the upper limit capacity of the hydraulic pump 122 based on the target value of the output torque of the engine 121 calculated by the engine control unit 55. Based on the upper limit capacity and the target flow rate determined by the target flow rate determination unit 53, the pump control unit 56 determines a target value for the capacity of the hydraulic pump 122 and controls the swash plate of the hydraulic pump 122 according to that target value.

[0061] Figure 7 is a flowchart showing the control method for the hydraulic pump 122 according to the first embodiment. The pump control unit 56 acquires the target value of the engine output torque calculated by the engine control unit 55 (step S61).

[0062] The pump control unit 56 determines the acceleration torque required for the change in rotational speed from the time rate of change of the target rotational speed (target angular acceleration) (step S62). The time rate of change of the target rotational speed is determined, for example, by the amount of operation of the rotational speed adjustment knob acquired by the operation amount acquisition unit 52, or by whether or not deceleration control is performed. Note that if there is no change in the rotational speed of the engine 121, the acceleration torque is zero. The pump control unit 56 calculates the total upper limit torque that the front hydraulic pump 122A and the rear hydraulic pump 122B can output by subtracting the load torque from the auxiliary equipment, the rotational friction torque, and the acceleration torque from the target value of the output torque of the engine 121 (step S63).

[0063] In this way, the total upper limit torque that the hydraulic pump 122 can output is calculated from the target value of the output torque of the engine 121. As explained in step S34 of the combined operation assist unit 57, when only the travel operation and the boom 131 raising operation are performed, and the load pressure related to the boom cylinder 131C exceeds the load threshold, and the amount of operation for the boom 131 raising operation exceeds the operation amount threshold, the combined operation assist unit 57 increases the target value of the output torque of the engine 121. As a result, the total upper limit torque that the hydraulic pump 122 can output, i.e., the pump output, increases. In addition, in other embodiments, the combined operation assist unit 57 may output an instruction to the pump control unit 56 to increase the upper limit of the output torque of the hydraulic pump (e.g., catalog value) or the upper limit of the load torque by a predetermined offset value, in addition to increasing the target value of the output torque of the engine 121.

[0064] The pump control unit 56 determines the upper limit torque of the front hydraulic pump 122A and the upper limit torque of the rear hydraulic pump 122B by distributing the total upper limit torque calculated in step S63 according to the ratio of the load torques from the front hydraulic pump 122A and the rear hydraulic pump 122B (step S64). The load torque from the hydraulic pump 122 can be determined by dividing the product of the measured value of the discharge pressure of the hydraulic pump 122 and the target value of the hydraulic fluid flow rate by 2π.

[0065] Next, the pump control unit 56 determines an equitorque curve function that shows the relationship between the discharge pressure of the hydraulic pump 122 and the capacity of the hydraulic pump 122, based on the determined upper limit torque (step S65). The pump control unit 56 determines the upper limit capacity of the hydraulic pump 122 according to the measured value of the discharge pressure and the equitorque curve function (step S66).

[0066] The pump control unit 56 controls the hydraulic pump 122 by determining a command value for the swash plate angle based on the target flow rate and the upper limit capacity determined in step S66, and outputting this command to the hydraulic pump 122 (step S67). Specifically, the pump control unit 56 determines the pump capacity command value, i.e., the command value for the swash plate angle, in the following procedure.

[0067] Figure 8 is a block diagram showing the control of the hydraulic pump 122 by the pump control unit 56 and the time constant determination unit 58 according to the first embodiment. The pump control unit 56 includes a target capacity calculation block 571, an upper limit capacity calculation block 572, a target capacity limit block 573, a filter treatment block 574a for the target value of the flow rate, and a filter treatment block 574b for the pump pressure.

[0068] The target capacity calculation block 571 determines the target capacity of the hydraulic pump 122 by dividing the target flow rate by the rotational speed N. The upper limit capacity calculation block 572 determines the upper limit capacity of the hydraulic pump 122 according to the measured discharge pressure and the isotorque curve function. The upper limit capacity calculation block 572 determines the upper limit capacity in step S66 described above. The target capacity limiting block 573 limits the target capacity output by the target capacity calculation block 571 to be less than or equal to the upper limit capacity. The time constant determination unit 58 determines the filter time constant when the state related to the movement of the moving body 110 changes during its movement. The time constant determination unit 58 determines the first filter time constant, which is the time constant for the filter treatment block 573a, and the second filter time constant, which is the time constant for the filter treatment block 573b. The filter treatment block 574a outputs a value filtered using the first filter time constant determined by the time constant determination unit 58, relative to the target flow rate. The filter treatment block 574b outputs a value filtered using the second filter time constant determined by the time constant determination unit 58, relative to the pump discharge pressure. The filtering process in the filter treatment block 574 includes a first-order low-pass filter.

[0069] (Determination of the time constant) The first and second filter time constants are set based on, for example, a sensory evaluation when starting to move from a standstill. On the other hand, there are situations where, while the work machine 1 is moving, an increase in the amount of hydraulic fluid supplied to the travel motor 112 is required due to a change in its state. For example, acceleration is required when the travel state of the work machine 1 is changed from turning to straight-line travel. During turning, the load pressure of the outer wheel travel motor 112 is higher than that of the inner wheel travel motor 112. As a result, the discharge pressure of the outer wheel hydraulic pump 122 increases, and the upper limit capacity decreases. When the travel state of the work machine 1 switches from turning to straight-line travel, the load pressure of the travel motor 112 decreases, making acceleration possible, so an increase in the amount of hydraulic fluid is required for rapid acceleration. For example, when the work machine 1 is climbing a steep slope, if the torque of the travel motor 112 is insufficient in high-speed mode, the travel motor 112 switches to low-speed mode. In low-speed mode, the torque is high but the speed decreases, so it is necessary to increase the amount of hydraulic fluid supplied to the travel motor 112 to maintain the speed. An increase in the amount of hydraulic fluid is required to prevent deceleration associated with the mode switching of the travel motor 112.

[0070] On the other hand, the time constant set based on the subjective evaluation when starting to move from a standstill is kept relatively gradual, making it impossible to achieve the required speed in response to changes in the driving state, such as when switching from turning to straight driving or from high-speed mode to low-speed mode. The time constant determination unit 58 of the control device 145 according to the first embodiment reduces the first filter time constant and the second filter time constant when switching from turning to straight driving and when switching from high-speed mode to low-speed mode, that is, during the transient period of switching driving states. Hereinafter, the first filter time constant in the steady state will be called the first steady-state time constant, and the second filter time constant will be called the second steady-state time constant. The first filter time constant in the transient period will be called the first transient time constant, and the second filter time constant will be called the second transient time constant. The transient time constant is smaller than the steady-state time constant. In other words, the response characteristics related to the transient time constant are faster than the response characteristics related to the steady-state time constant. Furthermore, the transient time constant when switching from turning to straight-line driving and the transient time constant when switching from high-speed mode to low-speed mode may be different values.

[0071] Specifically, the time constant determination unit 58 determines the time constant of the low-pass filter using the following procedure. Figure 9 is a flowchart illustrating the method for determining the time constant according to the first embodiment. The time constant determination unit 58 determines whether the driving state of the traveling body 110 has switched from turning to straight driving (step S81). The time constant determination unit 58 determines that the driving state is turning if, for example, the difference in the operating amounts of the first traveling motor 112R and the second traveling motor 112L exceeds the switching determination threshold. On the other hand, the time constant determination unit 58 determines that the driving state is straight driving if, for example, the difference in the operating amounts of the first traveling motor 112R and the second traveling motor 112L is less than or equal to the switching determination threshold. The switching determination threshold may have hysteresis.

[0072] If the driving state of the vehicle 110 switches from turning to straight driving (step S81: YES), the time constant determination unit 58 determines whether the manipulated amounts of both the first driving motor 112R and the second driving motor 112L exceed the acceleration determination threshold (step S82). If the manipulated amounts of both the first driving motor 112R and the second driving motor 112L exceed the acceleration determination threshold (step S82: YES), the time constant determination unit 58 determines the filter time constant to the transient time constant (step S83). This is because the manipulated amounts related to driving exceed the acceleration determination threshold, indicating that the operator intends to accelerate.

[0073] If the driving state of the vehicle 110 has not switched from turning to straight driving (step S81: NO), or if the control amount of at least one of the first driving motor 112R and the second driving motor 112L does not exceed the acceleration determination threshold (step S82: NO), the time constant determination unit 58 determines whether the mode of the driving motor 112 has switched from high-speed mode to low-speed mode (step S84). If the mode of the driving motor 112 has switched from high-speed mode to low-speed mode (step S84: YES), the time constant determination unit 58 determines the filter time constant to the transient time constant (step S83).

[0074] If the driving state of the vehicle 110 has not switched from turning to straight driving, and the mode of the driving motor 112 has not switched from high-speed mode to low-speed mode (step S84: NO), the time constant determination unit 58 determines whether the currently applied time constant is a transient time constant (step S85). If the currently applied time constant is a steady-state time constant (step S85: NO), the time constant determination unit 58 determines the filter time constant to be a steady-state time constant (step S86). In other words, if the currently applied time constant is a steady-state time constant, the time constant determination unit 58 decides to continue applying the steady-state time constant.

[0075] If the currently applied time constant is a transient time constant (step S85: YES), the time constant determination unit 58 determines whether sufficient acceleration of the travel motor 112 has been achieved by control using the transient time constant (step S87). For example, the time constant determination unit 58 may determine that the travel motor 112 has been sufficiently accelerated if the rate of change over time of the target flow rate of the travel motor 112 determined by the target flow rate determination unit 53 is less than a predetermined threshold. Alternatively, the time constant determination unit 58 may determine that the travel motor 112 has been sufficiently accelerated if the rate of change over time of the upper limit capacity determined by the pump control unit 56 is less than a predetermined threshold. Alternatively, the time constant determination unit 58 may determine that the travel motor 112 has been sufficiently accelerated if a certain amount of time has elapsed since the time constant was switched from a steady-state time constant to a transient time constant.

[0076] If the time constant determination unit 58 determines that the travel motor 112 has achieved sufficient acceleration (step S87: YES), it determines the filter time constant to the steady-state time constant (step S86). In other words, when the travel motor 112 has achieved sufficient acceleration, the time constant determination unit 58 returns the time constant from the transient time constant to the steady-state time constant.

[0077] If the time constant determination unit 58 determines that the acceleration of the travel motor 112 is insufficient (step S87: NO), it determines the filter time constant to the transient time constant (step S83). In other words, if the acceleration of the travel motor 112 is insufficient, the time constant determination unit 58 decides to continue applying the transient time constant.

[0078] As a result, the time constant determination unit 58 can quickly increase the flow rate of hydraulic fluid supplied to the travel motor 112 by reducing the time constant of the low-pass filter by the pump control unit 56 from the time the state related to travel switches during travel until the travel body 110 is sufficiently accelerated.

[0079] Action / Effect In the first embodiment, the combined operation assist unit 57 of the control device 145 changes the target control amount so as to increase the flow rate of hydraulic fluid supplied to the boom cylinder 131C when the work implement 130 and the traveling body 110 are operated simultaneously and the load on the work implement 130 exceeds a predetermined level. Specifically, the combined operation assist unit 57 increases the output of the hydraulic pump 122, increases the opening degree of the flow control valve 1261 of the boom cylinder 131C, and decreases the opening degree of the flow control valve 1261 of the traveling motor 112. As a result, the control device 145 can quickly raise the boom 131 in combined operation of traveling and raising the boom 131.

[0080] Furthermore, the time constant determination unit 58 of the control device 145 according to the first embodiment changes the time constant of the low-pass filter used to control the hydraulic pump 122 when the state related to driving changes while the vehicle 110 is in motion. As a result, the control device 145 can appropriately and quickly accelerate the vehicle 110 when the driving state changes.

[0081] Here, we will explain the phenomenon where acceleration is delayed when switching between driving states if the time constant is not switched. Figure 10 is a time chart of the target control amounts for the travel motors 112R and 112L in a comparative example where the hydraulic pump 122 is controlled according to a steady-state time constant. Generally, the movement of the work machine 1 is prone to highly oscillating pressure fluctuations. Therefore, by setting large values ​​(steady-state time constants) for both the first and second filter time constants, vibrations are more easily suppressed. Figure 10 shows the situation when the travel state of the travel body 110 switches from turning to straight-line travel. Turning travel refers to a travel state in which the operator creates a difference in the amount of operation of the left and right travel motors (the amount of operation of the travel control levers operated to drive the left and right travel motors 112), resulting in a difference in the rotational speed of the left and right travel motors, and the work machine 1 turns towards the side of the lower-speed motor. Straight-line travel refers to a travel state in which the operator operates the left and right travel motors to the same amount (for example, fully operating both), causing the left and right travel motors to rotate at the same speed and the work machine 1 to move in a straight line. Figure 10 shows the changes in the control values ​​of the amount of operation of the lower-speed travel motor, load pressure, and pump capacity. In Figure 10, since the travel operation is switched from turning to straight-line travel at time t, the amount of operation of the lower-speed motor switches from a small amount to a large amount at time t. Here, as the amount of operation switches from a small amount to a large amount, both the pump upper limit capacity and the pump target capacity increase. However, because both the first and second filter time constants are large steady-state time constants, the increase in target pump capacity is very slow. In other words, even though the operator switches the travel state from turning to straight travel, the actual travel pattern of the work machine 1 does not switch from turning to straight travel for quite some time.

[0082] To improve this switching delay, switching the first filter time constant from the first steady-state time constant to the smaller first transient time constant at the timing when the driving state switches from turning to straight driving can accelerate the increase in the target pump capacity on the low-speed side. However, because the second filter time constant is the first steady-state time constant, the increase in the upper limit capacity is slow, and this upper limit capacity remains a limitation on the increase in the final pump capacity command value.

[0083] Figure 11 is a time chart of the target control values ​​of the travel motors 112R and 112L according to the first embodiment, which control the hydraulic pump 122 in accordance with the transition from a steady-state time constant to a transient time constant as the travel state changes from turning to straight-line travel. In the example shown in Figure 11, at time t, the vehicle's driving state switches from turning to straight-line driving. At time t, both the first filter time constant and the second filter time constant switch from steady-state time constants to smaller transient time constants, resulting in a significant improvement in both the low-speed pump target capacity and upper limit capacity. Consequently, the increase in the pump capacity command value ultimately calculated by the pump control unit 56 is also significantly improved.

[0084] As the command value for the low-speed pump capacity increases, the low-speed motor speed quickly reaches the high-speed motor speed. Therefore, when the operator switches the travel state from turning to straight-line travel, the actual travel pattern of the work machine 1 also quickly switches from turning to straight-line travel.

[0085] When the mode of the travel motor 112 switches from high-speed mode to low-speed mode, similar to the switching of the travel state, the load pressure of the travel motor 112 decreases significantly when switching from high-speed mode to low-speed mode. This increases the upper limit capacity, but if the transient upper limit capacity and target capacity follow the steady-state time constant, the flow rate discharged by the hydraulic pump 122 does not increase quickly, causing the travel motor 112 to decelerate. In contrast, the control device 145 according to the first embodiment controls the hydraulic pump 122 according to the transient time constant when switching from high-speed mode to low-speed mode, so that the flow rate discharged by the hydraulic pump 122 increases quickly and the speed of the travel motor 112 can be maintained.

[0086] Parameters related to changes in target control quantities applied during the transient period of switching between driving states (e.g., first transient time constant, second transient time constant, offset value of output torque of engine 121, offset value of output torque of hydraulic pump 122, offset value or multiplier of opening degree of flow control valve 1261) may be pre-set in the control device 145, for example, via a monitor provided in the driver's cab 140 or via a maintenance tool used by a service engineer.

[0087] <Second Embodiment> In the first embodiment, the control device 145 increases the output of the engine 121 and increases or decreases the opening of the flow control valve 1261 when the work implement 130 and the traveling body 110 are operated simultaneously and the load on the work implement 130 exceeds a predetermined level, thereby increasing the flow rate of hydraulic fluid supplied to the boom cylinder 131C. In contrast, the control device 145 in the second embodiment increases the flow rate of hydraulic fluid supplied to the boom cylinder 131C by separating the front main oil passage 123A and the rear main oil passage 123B.

[0088] Figure 12 is a flowchart showing the combined operation assistance control of the control device 145 according to the second embodiment. Similar to the first embodiment, the combined operation assist unit 57 determines whether or not to assist in the combined operation based on the determinations made in steps S31 to S33. If the combined operation assist unit 57 determines to assist in the combined operation (step S33: YES), it determines whether or not the front main oil passage 123A and the rear main oil passage 123B are separated (step S131). That is, the combined operation assist unit 57 determines whether or not the main confluence separation valve 1241 is closed. If the front main oil passage 123A and the rear main oil passage 123B are merged, that is, if the main confluence separation valve 1241 is open (step S131: NO), the combined operation assist unit 57 closes the main confluence separation valve 1241 and separates the front main oil passage 123A and the rear main oil passage 123B (step S132).

[0089] When the front main oil passage 123A and the rear main oil passage 123B are separated, the load pressure of the rear hydraulic pump 122B, which is not connected to the boom cylinder 131C, decreases, thereby reducing the load torque. This allows more torque from the engine 121 to be distributed to the front hydraulic pump 122A, and the target flow rate of the front hydraulic pump 122A can be increased compared to before the separation by the process shown in Figures 4 and 5. As a result, the control device 145 can increase the flow rate of hydraulic fluid supplied to the boom cylinder 131C.

[0090] If the front main oil passage 123A and the rear main oil passage 123B are separated, that is, if the main confluence separation valve 1241 is closed (step S131: YES), the control device 145 increases the flow rate of hydraulic fluid supplied to the boom cylinder 131C by processing steps S34 to S37, similar to the first embodiment.

[0091] <Third Embodiment> In the first embodiment, the control device 145 accelerates the vehicle 110 quickly by changing the time constant of the low-pass filter used to control the hydraulic pump 122 when the vehicle state switches from turning to straight driving and when the mode of the travel motor 112 switches from high-speed mode to low-speed mode. In contrast, in the third embodiment, the control device 145 outputs an instruction to further increase the output torque limit value of the engine 121 by a predetermined offset value when the vehicle state switches from turning to straight driving and when the mode of the travel motor 112 switches from high-speed mode to low-speed mode. As a result, the control device 145 in the third embodiment can accelerate the vehicle 110 quickly in response to the change in the vehicle state.

[0092] <Other Embodiments> Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes are possible. In other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel.

[0093] The work machine 1 in the above-described embodiment is a hydraulic excavator, but is not limited to this, and the work machine 1 in other embodiments may be other work machines such as a wheel loader or a bulldozer.

[0094] The work machine 1 according to the above embodiment is equipped with a swashplate type variable displacement pump as the hydraulic pump 122, but is not limited to this. For example, the hydraulic pump according to another embodiment may be a pump that changes the discharge amount by individually varying the rotational speed. In this case, the pump control unit 56 can control the rotational speed of the hydraulic pump 122.

[0095] The drive system 20 of the work machine 1 according to the above-described embodiment comprises two hydraulic pumps 122 and two main oil passages 123, but is not limited thereto. The drive system 20 of the work machine 1 according to other embodiments may comprise three or more hydraulic pumps 122 and three or more main oil passages 123. Furthermore, the drive system 20 according to other embodiments may comprise one hydraulic pump 122 and one main oil passage 123.

[0096] <Computer Configuration> Figure 13 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 90 includes a processor 91, main memory 92, storage 93, and an interface 94. The control device 145 described above is implemented in the computer 90. The operation of each processing unit described above is stored in storage 93 in the form of a program. The processor 91 reads the program from storage 93, loads it into main memory 92, and executes the above processing according to the program. The processor 91 also allocates memory areas in main memory 92 corresponding to each of the above-mentioned storage units according to the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and a microprocessor.

[0097] The program may be for implementing some of the functions that the computer 90 is to perform. For example, the program may perform functions in combination with other programs already stored in storage, or in combination with other programs implemented on other devices. In other embodiments, the computer 90 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to, or instead of, the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions implemented by the processor 91 may be implemented by the integrated circuit. Such an integrated circuit is also included as an example of a processor. In other embodiments, the computer 90 may be virtualized on one or more computers.

[0098] Examples of storage 93 include magnetic disks, magneto-optical disks, optical disks, and semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of the computer 90, or it may be an external medium connected to the computer 90 via an interface 94 or a communication line. Furthermore, if this program is delivered to the computer 90 via a communication line, the computer 90 that receives the delivery may load the program into the main memory 92 and execute the above processing. In at least one embodiment, storage 93 is a tangible storage medium that is not temporary.

[0099] Furthermore, the program may be intended to implement some of the functions described above. In addition, the program may be a so-called differential file (differential program) that implements the functions described above in combination with other programs already stored in storage 93.

[0100] The control device 145 according to the above embodiment may be composed of a single computer 90, or the configuration of the control device 145 may be divided among multiple computers 90, and the multiple computers may cooperate with each other to function as the control device 145. In this case, some of the computers 90 constituting the control device 145 may be mounted inside the work machine 1, and the other computers 90 may be provided outside the work machine 1. For example, if the work machine 1 is a remotely operated vehicle that receives operation commands from a remotely provided operating device and is driven by them, the control device 145 may be provided separately for the work machine 1 and the remote operating device. Also, for example, if the work machine 1 is a remotely operated vehicle that drives autonomously according to operation commands transmitted from a control device, the control device 145 may be provided separately for the work machine 1 and the control device. [Explanation of Symbols]

[0101] 1…Work machine 110…Traction unit 111…Track 112…Traction motor 112L…Second transport motor 112LP…Rear transport load pressure sensor 112R…First transport motor 112RP…Front transport load pressure sensor 120…Slewing unit 121…Engine 1211…Turbocharger 122…Hydraulic pump 1221…Swash plate angle sensor 1221A…Front swash plate angle sensor 1221B…Rear swash plate angle sensor 122A…Front hydraulic pump 122B…Rear hydraulic pump 123…Main oil passage 1231…Pump discharge pressure sensor 1231A…Front pump discharge pressure sensor 1231B…Rear pump discharge pressure sensor 1232…Bleed valve 1232A…Front bleed valve 1232B…Rear bleed valve 123A…Front main oil passage 123B…Rear main oil passage 124…Main connecting oil passage 1241…Main junction / separation valve 126…Control valve 1261…Flow control valve 1261A…Meter-in opening 1261B…Bleed opening 1262…Pressure compensation valve 126A…Front control valve 126B…Rear control valve 127…Slewing motor 127P…Slewing load pressure sensor 128…LS oil passage 128A…Front LS oil passage 128B…Rear LS oil passage 129…LS connecting oil passage 1291…LS junction / separation valve 130…Work equipment 131…Boom 131C…Boom cylinder 131CP…Boom load pressure sensor 132…Arm 132C…Arm cylinder 132CP…Arm load pressure sensor 133…Bucket 133C…Bucket cylinder 133CP…Bucket load pressure sensor 140…Operator's cab 141…Operator's seat 142...Operating device 145...Control device 150...Machine room 20...Drive system 51...Measurement value acquisition unit 52...Operational variable acquisition unit 53...Target flow rate determination unit 54...Valve control unit 55...Engine control unit 56...Pump control unit 57...Composite operation assistance unit 571...Target capacity calculation block 572...Upper capacity calculation block 573...Target capacity limit block 574a...Filtering block for target flow rate 574b...Filtering block for pump pressure 573b 58...Time constant determination unit 90...Computer 91...Processor 92...Main memory 93...Storage 94...Interface U...Actuator unit UA...Front actuator unit UB...Rear actuator unit.

Claims

1. The car body and, A traveling body that supports the aforementioned vehicle body so that it can move, A work machine supported by the aforementioned vehicle body, An operating device that receives input for the amount of operation of the traveling body and the work machine, A hydraulic system that drives the aforementioned traveling body and the aforementioned work implement, A controller that controls the hydraulic system, Equipped with, The hydraulic system is, The prime mover and At least one hydraulic pump driven by the aforementioned prime mover, A travel motor drives the traveling body using the hydraulic fluid discharged by the hydraulic pump, A hydraulic cylinder that drives the work machine with the hydraulic fluid discharged by the hydraulic pump, A first flow control valve controls the flow rate of hydraulic fluid supplied to the aforementioned travel motor, A second flow control valve controls the flow rate of hydraulic fluid supplied to the hydraulic cylinder, Equipped with, The aforementioned controller, From the amount of operation of the control device, the target control amounts for the prime mover, the hydraulic pump, the first flow control valve, and the second flow control valve are determined. When the work machine and the traveling body are operated simultaneously, and the load on the work machine exceeds a predetermined level, the target control amount is changed so that the flow rate of the hydraulic fluid supplied to the hydraulic cylinder increases. Agricultural machinery.

2. The aforementioned controller, When the work machine and the traveling body are operated simultaneously, and the load on the work machine exceeds a predetermined level, the target control amount of the opening degree of the second flow control valve is increased. The work machine according to claim 1.

3. The aforementioned controller, When the work machine and the traveling body are operated simultaneously, and the load on the work machine exceeds a predetermined level, the target control amount of the opening degree of the first flow control valve is reduced. The work machine according to claim 1.

4. The aforementioned controller, When the work implement and the traveling body are operated simultaneously, and the load on the work implement exceeds a predetermined level, the upper limit of the output of the hydraulic pump is increased. The work machine according to claim 1.

5. The at least one hydraulic pump includes a first hydraulic pump and a second hydraulic pump, A first main oil passage connecting the aforementioned travel motor and the first hydraulic pump, A second main oil passage connecting the hydraulic cylinder and the second hydraulic pump, A merger / separation valve for merging or separating the first main oil passage and the second main oil passage, Equipped with, The aforementioned controller, When the work implement and the traveling body are operated simultaneously, and the load on the work implement exceeds a predetermined level, the confluence and separation valve is closed. The work machine according to claim 1.

6. The aforementioned controller, The system accepts the setting of parameters related to the change of the target control amount, When the work implement and the traveling body are operated simultaneously, and the load on the work implement exceeds a predetermined level, the target control amount is changed according to the set parameter. The work machine according to claim 1.

7. The aforementioned controller, When the work implement and the traveling body are operated simultaneously, and the load on the work implement exceeds a predetermined level, the target control amount is changed according to a predetermined rate. The work machine according to claim 1.

8. The aforementioned controller, When the work implement and the traveling body are operated simultaneously, and the load on the work implement exceeds a predetermined level, and the amount of operation related to the work implement is greater than or equal to a threshold, the target control amount is changed so as to increase the flow rate of the hydraulic fluid supplied to the hydraulic cylinder. The work machine according to claim 1.

9. The work machine comprises a boom supported by the vehicle body, an arm supported by the boom, and a bucket supported by the arm. The aforementioned controller, When the boom and the traveling body are operated simultaneously, and the load on the boom exceeds a predetermined level, and no other operations are being performed, the target control amount is changed to increase the flow rate of the hydraulic fluid supplied to the hydraulic cylinder that drives the boom. The work machine according to claim 1.

10. The aforementioned controller, The level of load applied to the work machine is determined based on the measurement value of a pressure sensor that detects the pressure in a circuit connected to the work machine. A working machine according to any one of claims 1 to 9.

11. The aforementioned controller, Determine whether the pressure sensor is malfunctioning or not. If the pressure sensor is determined to be malfunctioning, the change in the target control amount is prohibited. The work machine according to claim 10.

12. The car body and, A traveling body that supports the aforementioned vehicle body so that it can move, The prime mover and At least one hydraulic pump driven by the aforementioned prime mover, A travel motor drives the traveling body using the hydraulic fluid discharged by the hydraulic pump, An operating device that receives input for the amount of operation of the aforementioned travel motor, A flow control valve that controls the flow rate of hydraulic fluid supplied to the aforementioned travel motor, Controller and Equipped with, The aforementioned controller, The target control amount is determined based on the required control amounts of the prime mover, the hydraulic pump, and the flow control valve, which are determined from the operating amount of the operating device, and the filtering procedure. The response characteristics of the filtering procedure are made different when the state related to the movement of the vehicle changes while the vehicle is in motion. Agricultural machinery.

13. The aforementioned controller, When the driving state of the vehicle switches from turning to straight driving, the response characteristics are made faster. The working machine according to claim 12.

14. The aforementioned drive motor is switchable between a low-speed mode driven at a first capacity and a high-speed mode driven at a second capacity smaller than the first capacity. The aforementioned controller, The response characteristics are made faster when the driving state of the vehicle switches from high-speed mode to low-speed mode. The working machine according to claim 12.

15. The aforementioned controller, After altering the response characteristics, the response characteristics are returned to their original state when the time rate of change of the target control amount of the flow control valve falls below a threshold. The working machine according to claim 12.

16. The aforementioned controller, The upper limit capacity of the hydraulic pump is determined by dividing the upper limit torque output of the prime mover by the discharge pressure of the hydraulic pump. After altering the response characteristics, when the time rate of change of the upper limit capacity falls below a threshold, the response characteristics are returned to their original state. The working machine according to claim 12.

17. The aforementioned controller, The response characteristics are restored when a predetermined time has elapsed since the state related to the aforementioned driving changed. The working machine according to claim 12.

18. The filtering procedure described above is The first filtering procedure is to impart response characteristics to the pump target flow rate. The working machine according to claim 12.

19. The filtering procedure described above is This is a second filtering procedure that assigns response characteristics to the pump's upper capacity limit, or to the pump pressure used to calculate the pump's upper capacity limit. The working machine according to claim 12.

20. The filtering procedure described above is This includes a first filtering process that provides a response characteristic to the target pump flow rate, and a second filtering process that provides a response characteristic to the pump upper capacity, or to the pump pressure used to calculate the pump upper capacity. The aforementioned controller, When the state related to the movement of the vehicle changes while the vehicle is in motion, the response characteristics of the first filtering procedure are made different, and the response characteristics of the second filtering procedure are made different. The working machine according to claim 12.

21. The aforementioned controller, When the state related to the movement of the vehicle changes while the vehicle is in motion, the upper limit of the output of the hydraulic pump is increased. The working machine according to claim 12.

22. The car body and, A traveling body that supports the aforementioned vehicle body so that it can move, A work machine supported by the aforementioned vehicle body, An operating device that receives input for the amount of operation of the traveling body and the work machine, A hydraulic system that drives the aforementioned traveling body and the aforementioned work implement, Equipped with, The aforementioned hydraulic system The prime mover and At least one hydraulic pump driven by the aforementioned prime mover, A travel motor drives the traveling body using the hydraulic fluid discharged by the hydraulic pump, A hydraulic cylinder that drives the work machine with the hydraulic fluid discharged by the hydraulic pump, A first flow control valve controls the flow rate of hydraulic fluid supplied to the aforementioned travel motor, A second flow control valve controls the flow rate of hydraulic fluid supplied to the hydraulic cylinder, A control method for a work machine equipped with, The steps include determining the target control amounts for the prime mover, the hydraulic pump, the first flow control valve, and the second flow control valve from the amount of operation of the control device, The steps include changing the target control amount so that the flow rate of the hydraulic fluid supplied to the hydraulic cylinder increases when the work machine and the traveling body are operated simultaneously and the load on the work machine exceeds a predetermined level, A control method for a work machine equipped with the following features.

23. The car body and, A traveling body that supports the aforementioned vehicle body so that it can move, The prime mover and At least one hydraulic pump driven by the aforementioned prime mover, A travel motor drives the traveling body using the hydraulic fluid discharged by the hydraulic pump, An operating device that receives input for the amount of operation of the aforementioned travel motor, A flow control valve that controls the flow rate of hydraulic fluid supplied to the aforementioned travel motor, A control method for a work machine equipped with, The target control amount is determined based on the required control amounts of the prime mover, the hydraulic pump, and the flow control valve, which are determined from the operating amount of the operating device, and the filtering procedure. The response characteristics of the filtering procedure are made different when the state related to the movement of the vehicle changes while the vehicle is in motion. A control method for a work machine equipped with the following features.

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