Work machinery

Abstract

The purpose of the present invention is to provide a work machine that realizes good operability and controllability by precisely controlling the pressure of an actuator without causing a sudden increase in pressure or hunting when the actuator begins to operate. To achieve this purpose, a controller calculates a pump first target flow rate for minimizing the difference between an actuator target pressure and the actuator pressure, calculates a pump second target flow rate for minimizing the difference between an actuator absorption flow rate and a pump flow rate, calculates a pump final target flow rate on the basis of the pump first target flow rate and the pump second target flow rate, and controls a hydraulic pump according to the final target pump flow rate.

Description

[Technical Field]

[0001] The present invention relates to a work machine, such as a hydraulic excavator, for controlling oil supply and discharge to a hydraulic actuator provided in the work machine. [Background technology]

[0002] Generally, various hydraulic actuators are provided in work machines such as hydraulic excavators. A widely known system for controlling the supply and discharge of hydraulic oil to such hydraulic actuators (hydraulic control system) is configured to discharge hydraulic oil from a hydraulic pump at a flow rate required by an operation command, switch the supply and discharge direction of the hydraulic oil to and from the hydraulic actuator using a directional control valve, control the supply flow rate of hydraulic oil from the hydraulic pump to the hydraulic actuator using a meter-in opening of the directional control valve, and control the discharge flow rate from the hydraulic actuator to a hydraulic oil tank using a meter-out opening of the directional control valve.

[0003] In such systems, even if a sudden signal change is input from the control lever, such as a full-lever input, and the hydraulic pump suddenly changes the discharge flow rate in response to the input signal, the inertial bodies, such as the actuator being operated and the structures connected to it, cannot immediately follow. As a result, when the actuator starts moving, a difference occurs between the flow rate discharged from the hydraulic pump to the actuator and the flow rate absorbed by the actuator as it operates, leading to a sudden rise in pressure. This can cause a shock due to sudden acceleration of the actuator or a pressure surge, which can reduce operability when the operator is manually operating the work machine, or controllability when the actuator operation is controlled by a controller.

[0004] Therefore, a conventional technique is known in which hydraulic oil is guided to the actuator by switching a directional control valve, and a bleed-off throttle is provided to discharge part of the oil discharged from the hydraulic pump into a tank. The opening degree of the bleed-off throttle is adjusted when the actuator starts to move, thereby adjusting the flow rate supplied to the actuator and suppressing sudden pressure fluctuations, thereby ensuring the operability of the work machine (for example, Patent Document 1).

[0005] There is also known a technology that detects the discharge pressure (pump pressure) of a hydraulic pump using a pressure sensor and feeds it back to a controller, and controls the pump flow rate according to the increase or decrease in pump pressure to suppress a sudden increase in pressure in the actuator (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3403535 [Patent Document 2] Patent No. 5130353 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when oil is discharged into a tank using a bleed-off throttle as in Patent Document 1, the discharged pressure oil is lost, resulting in a large energy loss. Also, because the opening characteristics of the bleed-off throttle are designed for a specific operation, performance can vary across a variety of operations and operating conditions, potentially impairing operability and controllability when starting to move.

[0008] On the other hand, when pressure is measured and feedback control is used, as in Patent Document 2, it is possible to maintain a certain level of pressure controllability even under various operating conditions. However, there is always a delay between the time when the pressure at the time of measurement is used to calculate a pump flow rate control command value, when the controller outputs the control command, and when the pump changes the flow rate, and it is not possible to correct for pressure fluctuations that occur during this delay. Therefore, it may not be possible to control the pressure depending on the performance of the feedback control system, such as the operating speed of the actuator, the response time of the components, and the calculation performance of the controller.

[0009] The present invention has been made in view of the above-mentioned problems, and its object is to provide a work machine that achieves good operability and controllability by accurately controlling the actuator pressure without causing a sudden rise in pressure or hunting when the actuator starts to move. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides a working machine including a vehicle body, a working implement attached to the vehicle body, an actuator that drives the vehicle body or the working implement, a hydraulic pump, a directional control valve that controls the flow of pressurized oil supplied from the hydraulic pump to the actuator, an operation lever that commands the operation of the actuator, and a controller that controls the directional control valve in accordance with an input amount of the operation lever, the working machine including a pressure sensor that detects an actuator pressure that is the pressure of the actuator, the controller calculates an actuator target pressure that is the target pressure of the actuator based on the input amount of the operation lever, calculates a target flow rate of the hydraulic pump that reduces the difference between the actuator target pressure and the actuator pressure as a first target pump flow rate, calculates a target flow rate of the hydraulic pump that reduces the difference between an actuator absorption flow rate that is the flow rate absorbed by the actuator as the actuator is driven, and a pump flow rate that is the flow rate supplied from the hydraulic pump to the actuator, calculates a final target pump flow rate that is a final target flow rate of the hydraulic pump based on the first target pump flow rate and the second target pump flow rate, and controls the hydraulic pump in accordance with the final target pump flow rate.

[0011] According to the present invention configured as described above, the difference between the absorption flow rate and the hydraulic pump flow rate when the actuator starts to move is reduced by feedforward control, and the difference between the actuator target pressure and the actuator pressure is reduced by feedback control. This makes it possible to accurately control the actuator pressure without causing a sudden rise in pressure or hunting when the actuator starts to move, thereby achieving good operability and controllability. [Effects of the Invention]

[0012] According to the working machine of the present invention, good operability and controllability can be achieved by accurately controlling the actuator pressure without causing a sudden rise in pressure or hunting when the actuator starts to move. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a side view of a hydraulic excavator according to an embodiment of the present invention. [Figure 2A] Hydraulic drive system circuit diagram (1 / 2) [Figure 2B] Hydraulic drive system circuit diagram (2 / 2) [Figure 3] Controller functional block diagram [Figure 4] 1 is a flowchart showing the processing of a controller related to pump flow rate control. [Figure 5] 1 is a flowchart showing the processing of a controller related to the opening control of a directional control valve. [Figure 6] 10 is a flowchart showing the processing of a controller related to bleed-off valve opening control. [Figure 7] A diagram showing the time series changes in the control lever input amount, actuator target pressure, actuator pressure, and actuator speed when an individual operation is performed. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a hydraulic excavator will be described as an example of a work machine according to an embodiment of the present invention with reference to the drawings. In each drawing, the same reference numerals are used to designate the same components, and redundant description will be omitted where appropriate.

[0015] Fig. 1 is a side view of a hydraulic excavator according to this embodiment. As shown in Fig. 1, the hydraulic excavator 901 includes a running body 201, a revolving body 202 that is rotatably disposed on the running body 201 and constitutes a vehicle body, and a working device 203 that is attached to the revolving body 202 so as to be rotatable in the vertical direction and that performs work such as excavating earth and sand. The revolving body 202 is driven by a revolving motor 211 that is a hydraulic motor that is an actuator.

[0016] The working device 203 includes a boom 204 attached to the revolving unit 202 so as to be rotatable in the vertical direction, an arm 205 attached to the tip of the boom 204 so as to be rotatable in the vertical direction, a bucket 206 attached to the tip of the arm 205 so as to be rotatable in the vertical direction, a boom cylinder 204a which is an actuator that drives the boom 204, an arm cylinder 205a which is an actuator that drives the arm 205, and a bucket cylinder 206a which is an actuator that drives the bucket 206. The working device 203 is equipped with motion state detection devices 212, 213, and 214 that detect the attitudes and motion states of the boom 204, the arm 205, and the bucket 206. The revolving unit 202 is equipped with motion state detection devices 215 and 216 that detect the attitude and rotation speed of the revolving unit 202. A variety of sensors can be used as the motion state detection devices 212 to 216, such as an inclination sensor, a rotation angle sensor, a stroke sensor, and an acceleration sensor (IMU).

[0017] A cab 207 is provided at the front position on the rotating body 202, and a counterweight 209 is attached at the rear position to ensure the weight balance of the vehicle body. A machinery room 208 is provided between the cab 207 and the counterweight 209. The machinery room 208 houses an engine (not shown), hydraulic pumps 1 and 2 (shown in FIG. 2A), a swing motor 211, a control valve 210, etc. The control valve 210 controls the flow of hydraulic oil from the hydraulic pump to each actuator.

[0018] 2A and 2B are circuit diagrams of a hydraulic drive system mounted on a hydraulic excavator 901. FIG.

[0019] (composition) The hydraulic drive unit 902 includes two main hydraulic pumps (for example, a first hydraulic pump 1 and a second hydraulic pump 2, which are variable displacement hydraulic pumps), a pilot pump 111, and a hydraulic oil tank 3 that supplies oil to the hydraulic pumps 1 and 2 and the pilot pump 111. The hydraulic pumps 1 and 2 and the pilot pump 111 are driven by an engine (not shown).

[0020] The tilt angle of the first hydraulic pump 1 is controlled by a regulator attached to the first hydraulic pump 1. The regulator of the first hydraulic pump 1 has a flow control command pressure port 1a, and is driven by a command pressure acting on the flow control command pressure port 1a. The tilt angle of the second hydraulic pump 2 is controlled by a regulator attached to the second hydraulic pump 2. The regulator of the second hydraulic pump 2 has a flow control command pressure port 2a, and is driven by a command pressure acting on the flow control command pressure port 2a.

[0021] The right travel direction control valve 4, the arm second direction control valve 5, the boom first direction control valve 6, and the bucket directional control valve 7 are connected in parallel to the discharge flow path 40 of the first hydraulic pump 1 via meter-in flow paths 41 and 42, meter-in flow paths 43 and 44, meter-in flow paths 45 and 46, and meter-in flow paths 47 and 48, respectively. Check valves 13 to 16 are arranged in the meter-in flow paths 41 and 42, meter-in flow paths 43 and 44, meter-in flow paths 45 and 46, and meter-in flow paths 47 and 48, respectively, to prevent backflow of pressure oil into the discharge flow path 40.

[0022] The right traveling directional control valve 4 controls the flow of pressure oil supplied from the first hydraulic pump 1 to the right traveling motor (not shown) of the pair of traveling motors that drive the traveling body 201. The arm second directional control valve 5 controls the flow of pressure oil supplied from the first hydraulic pump 1 to the arm cylinder 205a. The boom first directional control valve 6 controls the flow of pressure oil supplied from the first hydraulic pump 1 to the boom cylinder 204a. The bucket directional control valve 7 controls the flow of pressure oil supplied from the first hydraulic pump 1 to the bucket cylinder 206a.

[0023] The discharge flow path 40 is connected to the hydraulic oil tank 3 via a check valve 26 and a relief valve 25 to protect the circuit from excessive pressure buildup. The discharge flow path 40 is also connected to the hydraulic oil tank 3 via a bleed-off valve 23 to discharge excess oil discharged from the first hydraulic pump 1.

[0024] The swing directional control valve 8, the left traveling directional control valve 9, the first arm directional control valve 10, the second boom directional control valve 11, and the standby directional control valve 12 are connected in parallel to the discharge passage 50 of the second hydraulic pump 2 via meter-in passages 51 and 52, meter-in passages 53 and 54, meter-in passages 55 and 56, meter-in passages 57 and 58, and meter-in passages 59 and 60. Check valves 17 to 21 are arranged in the meter-in passages 51 and 52, meter-in passages 53 and 54, meter-in passages 55 and 56, meter-in passages 57 and 58, and meter-in passages 59 and 60, respectively, to prevent backflow of pressure oil into the discharge passage 50.

[0025] The swing direction control valve 8 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the swing motor 211. The left traveling direction control valve 9 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the left traveling motor (not shown) of the pair of traveling motors that drive the traveling body 201. The arm first direction control valve 10 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the arm cylinder 205a. The boom second direction control valve 11 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the boom cylinder 204a. The standby direction control valve 12 controls the flow of pressure oil supplied from the second hydraulic pump 2 to an actuator (not shown) that drives a special attachment such as a chopper that is provided in place of the bucket 206.

[0026] The discharge flow path 50 is connected to the hydraulic oil tank 3 via a check valve 27 and a relief valve 25 to protect the circuit from excessive pressure buildup. The discharge flow path 50 is also connected to the hydraulic oil tank 3 via a bleed-off valve 24 to discharge excess oil discharged from the second hydraulic pump 2. The discharge flow path 50 is also connected to the discharge flow path 40 via a confluence valve 22 to merge the oil discharged from the first hydraulic pump 1 and the second hydraulic pump 2.

[0027] 2B, the discharge port of pilot pump 111 is connected to hydraulic oil tank 3 via pilot relief valve 112 for generating pilot primary pressure, and is also connected to one input port of solenoid valves 113a to 113j built into solenoid valve unit 113 via flow path 116 that supplies discharge pressure discharged from pilot pump 111. The other input ports of solenoid valves 113a to 113j are connected to hydraulic oil tank 3 via flow path 117 that guides return oil from solenoid valves 113a to 113j. Each of solenoid valves 113a to 113j reduces the pilot primary pressure in response to a command signal from controller 114 and outputs it as a command pressure.

[0028] The output port of the solenoid valve 113a is connected to the flow control command pressure port 1a of the regulator of the first hydraulic pump 1 via a flow path 118. The output port of the solenoid valve 113b is connected to the flow control command pressure port 2a of the regulator of the second hydraulic pump 2 via a flow path 119. The output ports of the solenoid valves 113c and 113d are connected to the command pressure ports 6a and 6b of the boom first direction control valve 6 via flow paths 120 and 121. The output ports of the solenoid valves 113e and 113f are connected to the command pressure ports 8a and 8b of the swing direction control valve 8 via flow paths 122 and 123. The output ports of the solenoid valves 113g and 113h are connected to the command pressure ports 11a and 11b of the boom second direction control valve 11 via flow paths 124 and 125. The output port of the solenoid valve 113i is connected to the command pressure port 23a of the bleed-off valve 23 via a flow path 126. The output port of the solenoid valve 113j is connected to the command pressure port 24a of the bleed-off valve 24 via a flow path 127. For the sake of simplicity, the solenoid valve for the right traveling directional control valve 6, the solenoid valve for the arm second directional control valve 5, the solenoid valve for the bucket directional control valve 7, the solenoid valve for the left traveling directional control valve 9, the solenoid valve for the arm first directional control valve 10, and the solenoid valve for the standby directional control valve 12 are not shown in the figure.

[0029] A pressure sensor 91 that detects the flow rate control command pressure of the first hydraulic pump 1 is provided in the flow path 118. A pressure sensor 92 that detects the flow rate control command pressure of the second hydraulic pump 2 is provided in the flow path 119. A pressure sensor 93 that detects the actuator pressure on the bottom side of the boom cylinder 204a is provided in the flow path 63 that connects the port Bm2B of the boom second direction control valve 11 and the boom cylinder 204a, and in the flow path 64 that connects the port Bm1B of the boom first direction control valve 6 and the boom cylinder 204a. A pressure sensor 94 that detects the actuator pressure on the rod side of the boom cylinder 204a is provided in the flow path 65 that connects the port Bm2R of the boom second direction control valve 11 and the boom cylinder 204a, and in the flow path 66 that connects the port Bm1R of the boom first direction control valve 6 and the boom cylinder 204a. A pressure sensor 95 that detects the pressure of one of the actuators of the swing motor 211 is provided in a flow path 73 that connects the port SwgR of the swing direction control valve 8 and the swing motor 211. A pressure sensor 96 that detects the pressure of the other of the actuators of the swing motor 211 is provided in a flow path 74 that connects the port SwgL of the swing direction control valve 8 and the swing motor 211. For the sake of simplicity, pressure sensors that detect the actuator pressure of the actuators that drive the arm cylinder 205a, the bucket cylinder 206a, the left traveling motor (not shown), the right traveling motor (not shown), and the special attachment (not shown) are not shown in the figure.

[0030] The hydraulic drive unit 902 is equipped with a boom operation lever 115a that can switch the boom first direction control valve 6 and the boom second direction control valve 11, and an arm operation lever 115b that can switch the arm first direction control valve 10 and the arm second direction control valve 5. To simplify the explanation, the travel right operation lever that switches the travel right directional control valve 4, the bucket operation lever that switches the bucket directional control valve 7, the swing operation lever that switches the swing directional control valve 8, the travel left operation lever that switches the travel left directional control valve 9, and the standby operation lever that switches the standby directional control valve 12 are not shown in the figure.

[0031] The hydraulic drive system 902 includes a controller 114. The controller 114 outputs command signals to solenoid valves 113a to 113j (including solenoid valves not shown) of the solenoid valve unit 113 in accordance with the input amounts of the operation levers 115a and 115b, the output values ​​of the operation state detection devices 212 to 216, and the output values ​​of the pressure sensors 91 to 96.

[0032] Fig. 3 is a functional block diagram of controller 114. In Fig. 3, controller 114 has an actuator target pressure calculation unit 114a, a pump first target flow rate calculation unit 114b, an actuator speed calculation unit 114c, an actuator absorption flow rate calculation unit 114d, a pump flow rate calculation unit 114e, a confluence ratio calculation unit 114f, a pump second target flow rate calculation unit 114g, a pump final target flow rate calculation unit 114h, a pump flow rate control command output unit 114i, a directional control valve target opening calculation unit 114j, a directional control valve control command output unit 114k, a bleed-off valve target opening calculation unit 114l, and a bleed-off valve control command output unit 114m.

[0033] The actuator target pressure calculation unit 114a calculates an actuator target pressure P_TgtAct corresponding to the operating lever input amount in accordance with a preset actuator target pressure characteristic for the operating lever input amount. The pump first target flow rate calculation unit 114b calculates, as a pump first target flow rate Q_TgtPmp1, a target flow rate for the hydraulic pumps 1 and 2 to reduce the difference between the actuator target pressure P_TgtAct calculated by the actuator target pressure calculation unit 114a and the actuator pressure P_Act acquired from the pressure sensors 93 to 96.

[0034] The actuator speed calculation unit 114c calculates the speed V_Act of the actuator based on the operating state information acquired from the operating state detection devices 212 to 216. The actuator absorption flow rate calculation unit 114d calculates the flow rate Q_Act absorbed by the actuator based on the actuator speed V_Act calculated by the actuator speed calculation unit 114c and the specification information of the actuator.

[0035] The pump flow rate calculation unit 114e calculates a pump flow rate Q_Pmp corresponding to the pump flow rate control command pressure acquired from the pressure sensors 91, 92 in accordance with pump flow rate characteristics relative to a preset pump flow rate control command pressure. The confluence ratio calculation unit 114f calculates, as a confluence ratio R_Cnf, the ratio of the pump flow rate Q_Pmp of each hydraulic pump to the total pump flow rate Q_PmpSum of the hydraulic pumps 1, 2, based on the pump flow rate Q_Pmp calculated by the pump flow rate calculation unit 114e. The pump second target flow rate calculation unit 114g calculates, as a pump second target flow rate Q_TgtPmp2, a target flow rate of the hydraulic pumps 1, 2 to reduce the difference between the actuator absorption flow rate Q_Act and the pump flow rate Q_Pmp, from the actuator absorption flow rate Q_Act calculated by the actuator absorption flow rate calculation unit 114d and the confluence ratio R_Cnf of each hydraulic pump calculated by the confluence ratio calculation unit 114f.

[0036] A pump final target flow rate calculation unit 114h calculates a pump final target flow rate Q_TgtPmp based on the first pump target flow rate Q_TgtPmp1 calculated by the first pump target flow rate calculation unit 114b and the second pump target flow rate Q_TgtPmp2 calculated by the second pump target flow rate calculation unit 114g. A pump flow rate control command output unit 114i calculates a pump flow rate control command pressure for the pump final target flow rate Q_TgtPmp2 calculated by the pump final target flow rate calculation unit 114h in accordance with preset solenoid valve command signal characteristics for the pump final target flow rate Q_TgtPmp2, and outputs a pump flow rate control command signal corresponding to the pump flow rate control command pressure to the solenoid valves 113a, 113b for pump flow rate control.

[0037] The directional control valve target opening calculation unit 114j calculates a directional control valve target opening a_TgtMS corresponding to the operating lever input amount in accordance with a preset directional control valve target opening characteristic for the operating lever input amount. The directional control valve control command output unit 114k outputs a command signal (directional control valve control command signal) corresponding to the directional control valve target opening a_TgtMS calculated by the directional control valve target opening calculation unit 114j to the directional control solenoid valves 113c to 113h in accordance with a preset solenoid valve command signal characteristic for the directional control valve target opening a_TgtMS.

[0038] Bleed-off valve target opening calculation unit 114l calculates a bleed-off valve target opening corresponding to the operating lever input amount in accordance with preset bleed-off valve target opening characteristics relative to the operating lever input amount. Bleed-off valve control command output unit 114m outputs a command signal (bleed-off valve control command signal) corresponding to the bleed-off valve target opening to bleed-off valve solenoid valves 113i, 113j in accordance with preset solenoid valve command signal characteristics relative to the bleed-off valve target opening.

[0039] FIG. 4 is a flowchart showing the processing of the controller 114 relating to pump flow rate control.

[0040] The controller 114 first determines whether or not there is an operation lever input (step S101). If it is determined in step S101 that there is no operation lever input (YES), the flow ends.

[0041] If it is determined in step S101 that there is an operating lever input (NO), the actuator target pressure calculation unit 114a calculates the actuator target pressure P_TgtAct corresponding to the operating lever input amount in accordance with the actuator target pressure characteristics relative to the operating lever input amount that are set in advance (step S102).

[0042] Following step S102, the pump first target flow rate calculation unit 114b calculates a pump first target flow rate Q_TgtPmp1 based on the actuator target pressure P_TgtAct and the actuator pressure P_Act (step S103). Here, the pump first target flow rate Q_TgtPmp1 is calculated using, for example, a PID control method so as to reduce the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act.

[0043] In parallel with step S102, the actuator speed calculation unit 114c calculates the actuator speed V_Act based on the operation state information acquired from the operation state detection devices 212 to 216 (step S104).

[0044] Following step S104, the actuator absorption flow rate calculation unit 114d calculates the actuator absorption flow rate Q_Act based on the actuator speed V_Act and information such as the actuator specifications (step S105). Here, if the actuator is a hydraulic cylinder, the piston drive speed is calculated as the actuator speed V_Act, and the actuator absorption flow rate Q_Act is calculated by multiplying the drive speed by the pressure-receiving area of ​​the piston.

[0045] Following step S106, the pump flow rate calculation unit 114e calculates the pump flow rate Q_Pmp according to the pump flow rate control command pressure acquired from the pressure sensors 91, 92, in accordance with the pump flow rate characteristics relative to the preset pump flow rate control command pressure (step S106).

[0046] Following step S107, the confluence ratio calculation unit 114f calculates the confluence ratio R_Cnf of each hydraulic pump using the pump flow rate Q_Pmp of each hydraulic pump calculated by the pump flow rate calculation unit 114e and the total pump flow rate Q_PmpSum of hydraulic pumps 1 and 2 according to equation 1 (step S107).

[0047]

number

[0048] Following step S107, the pump second target flow rate calculation unit 114g uses the actuator absorption flow rate Q_Act and the confluence ratio R_Cnf to calculate the pump second target flow rate Q_TgtPmp2 to reduce the difference between the actuator absorption flow rate Q_Act and the pump flow rate Q_Pmp using equation 2 (step S108).

[0049]

number

[0050] Following step S108, the pump final target flow rate calculation unit 114h adds the first pump target flow rate Q_TgtPmp1 and the second pump target flow rate Q_TgtPmp2 using Equation 3 to calculate the pump final target flow rate Q_TgtPmp (step S109).

[0051]

number

[0052] Following step S109, the pump flow control command output unit 114i outputs a pump flow control command signal corresponding to the pump final target flow rate Q_TgtPmp to the solenoid valves 113a, 113b for pump flow control in accordance with the solenoid valve command signal characteristics for the preset pump final target flow rate Q_TgtPmp, and then ends the flow.

[0053] FIG. 5 is a flowchart showing the processing of the controller 114 relating to the directional control valve opening control.

[0054] The controller 114 first determines whether or not there is an operation lever input (step S201). If it is determined in step S201 that there is no operation lever input (YES), the flow ends.

[0055] If it is determined in step S201 that there is an operating lever input (NO), the directional control valve target opening calculation unit 114j calculates the directional control valve target opening a_TgtMS corresponding to the operating lever input amount in accordance with the preset directional control valve target opening characteristics for the operating lever input amount (step S202).

[0056] Following step S202, the directional control valve control command output unit 114k outputs a command signal (directional control valve control command signal) corresponding to the directional control valve target opening a_TgtMS to the directional control valve solenoid valves 113c to 113h in accordance with the solenoid valve command signal characteristics for the directional control valve target opening a_TgtMS that have been set in advance (step S203), and then ends the flow.

[0057] FIG. 6 is a flowchart showing the processing of the controller 114 relating to the bleed-off valve opening control.

[0058] The controller 114 first determines whether or not there is an operation lever input (step S301). If it is determined in step S301 that there is no operation lever input (YES), the flow ends.

[0059] If it is determined in step S301 that there is an operating lever input (NO), the bleed-off valve target opening calculation unit 114l calculates the bleed-off valve target opening a_TgtBO corresponding to the operating lever input amount in accordance with a preset bleed-off valve target opening characteristic for the operating lever input amount (step S302).

[0060] Following step S302, the bleed-off valve target opening calculation unit 114l outputs a command signal (bleed-off valve control command signal) corresponding to the bleed-off valve target opening a_TgtBO to the solenoid valves 113i, 113j for the bleed-off valve in accordance with the solenoid valve command signal characteristics for the preset bleed-off valve target opening a_TgtBO (step S303), and then ends the flow.

[0061] (operation) As an example of the operation of the hydraulic drive unit 902, we will explain the operation when a single operation is performed to drive only the swing motor 211, which rotates the swing body 202, which has a large inertia, or the boom cylinder 204a, which moves the working device 203 up and down while supporting the entire weight of the working device 203.

[0062] 7 is a diagram showing time series changes in the control lever input amount, actuator target pressure, actuator pressure, and actuator speed V_Act when a single operation is performed. Note that the actuator pressure P_Act and actuator speed V_Act when only pressure feedback control is performed are shown as a comparative example.

[0063] When the operator operates the swing control lever, the controller 114 calculates the actuator target pressure based on the control lever input amount. A pump final target flow rate Q_TgtPmp is calculated based on this actuator target pressure, and a command signal is output to solenoid valves 113a, 113b for controlling the pump flow rate. The solenoid valves generate pilot pressure according to the command signal, and upon receiving this pilot pressure, hydraulic pumps 1, 2 change the pump displacement to adjust the flow rate. At this time, the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act is caused by two factors.

[0064] The first factor is the differential pressure P_Error1 between the actuator target pressure P_TgtAct and the actuator pressure P_Act, and is expressed by equation 4.

[0065]

number

[0066] The second factor is the pressure change amount P_Error2 caused by the difference between the actuator absorption flow rate Q_Act and the flow rate Q_Pmp of the hydraulic pumps 1 and 2, and is expressed by equation 5.

[0067]

number

[0068] where K is the bulk modulus of the hydraulic fluid and V is the volume of the hydraulic fluid.

[0069] In response to these two pressure error factors, the controller 114 calculates a first pump target flow rate Q_TgtPmp1 to reduce the differential pressure P_Error1, and calculates a second pump target flow rate Q_TgtPmp2 to reduce the pressure change amount P_Error2. This adjusts the pump flow rate Q_Pmp so that both the differential pressure P_Error1 and the pressure change amount P_Error2 are reduced, thereby enabling the actuator pressure P_Act to be controlled in accordance with the actuator target pressure P_TgtAct. As a result, the swing motor, which is the actuator that drives the swing body 202, which has a large inertia, can be smoothly started and accelerated without causing shock or hunting.

[0070] On the other hand, when pressure feedback control is performed alone, P_Error1 can be reduced, but P_Error2 cannot be reduced. As a result, the pressure change P_Error2 caused by the difference between the pump flow rate Q_Pmp and the actuator absorption flow rate Q_Act that occurs during the delay time of pressure feedback control cannot be suppressed. For example, if the actuator absorption flow rate Q_Act is higher than the pump flow rate Q_Pmp, the flow rate will be insufficient, and as shown in Figure 7, the actuator pressure P_Act will not reach the actuator target pressure P_TgtAct. Furthermore, if the feedback gain is increased in an attempt to reduce the pressure change P_Error2 using pressure feedback control, hunting as shown in Figure 7 may occur.

[0071] Furthermore, when boom-only operation is performed, the boom cylinder 204a may be driven by merging the flow rates of hydraulic pump 1 and hydraulic pump 2. In this case, the controller 114 calculates the merging ratio R_Cnf and determines the degree to which the flow rates Q_Pmp of hydraulic pumps 1 and 2 each contribute to the absorption flow rate Q_Act of the boom cylinder 204a, and then calculates a second pump target flow rate Q_TgtPmp2 for reducing the amount of pressure change P_Error2. This prevents the flow rate adjustment amount of one hydraulic pump from being canceled out by the other hydraulic pump, and therefore the boom cylinder 204a, which moves up and down while supporting the entire weight of the working implement 203, can be smoothly started and accelerated without shock or hunting.

[0072] (summary) In this embodiment, the system includes a vehicle body 202, a working device 203 attached to the vehicle body 202, actuators 204a, 205a, 206a, 211 that drive the vehicle body 202 or the working device 203, hydraulic pumps 1 and 2, directional control valves 5 to 8, 10, and 11 that control the flow of pressure oil supplied from the hydraulic pumps 1 and 2 to the actuators 204a, 205a, 206a, and 211, and an operation lever 115a that commands the operation of the actuators 204a, 205a, 206a, and 211. In a work machine 901 having pressure sensors 93 to 96 for detecting actuator pressure P_Act, which is the pressure of actuators 204a, 205a, 206a, 211, and a controller 114 for controlling directional control valves 5 to 8, 10, 11 in accordance with the input amounts of operation levers 115a, 115b, the controller 114 detects actuator pressure P_Act, which is the target pressure of actuators 204a, 205a, 206a, 211, based on the input amounts of operation levers 115a, 115b. The actuator target pressure P_TgtAct is calculated, and the target flow rates of the hydraulic pumps 1 and 2 for reducing the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act are calculated as a first pump target flow rate Q_TgtPmp1. The actuator absorption flow rate Q_Act is the flow rate absorbed by the actuators 204a, 205a, 206a, 211 as the actuators 204a, 205a, 206a, 211 are driven, and the actuator absorption flow rate Q_Act is the flow rate absorbed by the actuators 204a, 205a, 206a, 211 as ... are driven. The target flow rate of hydraulic pumps 1 and 2 for reducing the difference with the pump flow rate Q_Pmp supplied to 204a, 205a, 206a, and 211 is calculated as a second pump target flow rate Q_TgtPmp2, and a final pump target flow rate Q_TgtPmp, which is the final target flow rate of the first hydraulic pump, is calculated based on the first pump target flow rate Q_TgtPmp1 and the second pump target flow rate Q_TgtPmp2, and hydraulic pumps 1 and 2 are controlled according to the final pump target flow rate Q_TgtPmp.

[0073] According to the present embodiment configured as described above, the difference between the absorption flow rate Q_Act and the flow rate Q_Pmp of the hydraulic pumps 1 and 2 when the actuators 204a, 205a, 206a, and 211 start to move is reduced by feedforward control, and the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act is reduced by feedback control. As a result, the pressure of the actuators 204a, 205a, 206a, and 211 can be accurately controlled without causing a sudden rise in pressure or hunting when the actuators 204a, 205a, 206a, and 211 start to move, thereby achieving good operability and controllability.

[0074] Furthermore, the work machine 901 in this embodiment is equipped with operation state detection devices 212-216 that detect the operation state of the vehicle body 202 or the work implement 203, and the actuators 204a, 205a, 206a, 211 are hydraulic cylinders 204a, 205a, 206a or hydraulic motor 211, and the controller 114 calculates the drive speed V_Act of the hydraulic cylinders 204a, 205a, 206a or hydraulic motor 211 based on information from the operation state detection devices 212-216, and calculates the absorption flow rate of the hydraulic cylinders 204a, 205a, 206a or hydraulic motor 211, which is the actuator absorption flow rate Q_Act, based on the calculated drive speed V_Act. This allows the pressure of the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 to be accurately controlled without causing a sudden rise in pressure or hunting when the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 start moving, thereby achieving good operability and controllability.

[0075] Furthermore, the work machine 901 in this embodiment is equipped with a plurality of hydraulic pumps 1 and 2 that supply pressure oil to the actuators 204a, 205a, 206a, and 211, and pump discharge state sensors 91 and 92 that detect the discharge states of the plurality of hydraulic pumps 1 and 2, and the controller 114 calculates the ratio of the pump flow rate Q_Pmp to the total pump flow rate Q_PmpSum of the plurality of hydraulic pumps 1 and 2 as the confluence ratio R_Cnf based on information from the pump discharge state sensors 91 and 92, and calculates a second target pump flow rate Q_TgtPmp2 based on the actuator absorption flow rate Q_Act and the calculated confluence ratio R_Cnf. This makes it possible to calculate the second target pump flow rate Q_TgtPmp2 for each of the plurality of hydraulic pumps 1 and 2 that supply pressure oil to the same actuators 204a, 205a, 206a, and 211.

[0076] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations. [Explanation of symbols]

[0077] 1...first hydraulic pump, 1a...flow control command pressure port, 2...second hydraulic pump, 2a...flow control command pressure port, 3...hydraulic oil tank, 4...right travel directional control valve, 5...arm second directional control valve, 6...boom first directional control valve, 6a...command pressure port, 6b...command pressure port, 7...bucket directional control valve, 8...swing directional control valve, 8a...command pressure port, 8b...command pressure port, 9...left travel directional control valve, 10...arm first directional control valve, 11...boom second directional control valve, 11a...command pressure port, 11b...command pressure port, 12...backup directional control valve, 13 to 21...check valves, 22...merging valve, 23... Bleed-off valve, 23a... Command pressure port, 24... Bleed-off valve, 24a... Command pressure port, 25... Relief valve, 26, 27... Check valve, 40... Discharge flow path, 41 to 48... Meter-in flow path, 50... Discharge flow path, 51 to 60... Meter-in flow path, 63 to 66, 71 to 74... Flow path, 91, 92... Pressure sensor (pump discharge state sensor), 93 to 96... Pressure sensor, 111... Pilot pump, 112... Pilot relief valve, 113... Solenoid valve unit, 113a to 113j... Solenoid valve, 114... Controller, 114a... Actuator target pressure calculation unit, 114b ...Pump first target flow rate calculation unit, 114c...Actuator speed calculation unit, 114d...Actuator absorption flow rate calculation unit, 114e...Pump flow rate calculation unit, 114f...Confluence ratio calculation unit, 114g...Pump second target flow rate calculation unit, 114h...Pump final target flow rate calculation unit, 114i...Pump flow rate control command output unit, 114j...Directional control valve target opening calculation unit, 114k...Directional control valve control command output unit, 114l...Bleed-off valve target opening calculation unit, 114m...Bleed-off valve control command output unit, 115a...Boom operation lever, 115b...Arm operation lever, 116 to 127...Flow path, 2 01...Traveling body, 202...Swing body (vehicle body), 203...Working device, 204...Boom, 204a...Boom cylinder (hydraulic cylinder, actuator), 205...Arm, 205a...Arm cylinder (hydraulic cylinder, actuator), 206...Bucket, 206a...Bucket cylinder (hydraulic cylinder, actuator), 207...Operator's cab, 208...Machine room, 209...Counterweight, 210...Control valve, 211...Swing motor (actuator), 212-216...Operation state detection device, 901...Hydraulic excavator (working machine), 902...Hydraulic drive unit.

Claims

1. The car body and a working device attached to the vehicle body; an actuator that drives the vehicle body or the working device; A hydraulic pump; a directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to the actuator; an operating lever for instructing the operation of the actuator; A working machine including a controller that controls the directional control valve in accordance with an input amount of the operation lever, a pressure sensor for detecting an actuator pressure, the pressure of the actuator; The controller calculating an actuator target pressure, which is a target pressure of the actuator, based on an input amount of the operating lever; calculating a target flow rate of the hydraulic pump for reducing a difference between the actuator target pressure and the actuator pressure as a first target pump flow rate; calculating a target flow rate of the hydraulic pump as a second target pump flow rate for reducing a difference between an actuator absorption flow rate, which is a flow rate absorbed by the actuator as the actuator is driven, and a pump flow rate, which is a flow rate supplied from the hydraulic pump to the actuator; calculating a final target pump flow rate, which is a final target flow rate of the hydraulic pump, based on the first target pump flow rate and the second target pump flow rate; Controlling the hydraulic pump in accordance with the final target pump flow rate A work machine characterized by:

2. 2. The work machine according to claim 1, an operating state detection device for detecting an operating state of the vehicle body or the working device; the actuator is a hydraulic cylinder or a hydraulic motor, The controller calculates the drive speed of the hydraulic cylinder or the hydraulic motor based on information from the operation state detection device, and calculates the absorption flow rate of the hydraulic cylinder or the hydraulic motor, which is the actuator absorption flow rate, based on the calculated drive speed. A work machine characterized by:

3. 2. The work machine according to claim 1, a plurality of hydraulic pumps including the hydraulic pump that supply pressure oil to the actuator; a pump discharge state sensor for detecting a discharge state of the plurality of hydraulic pumps; The controller calculating a ratio of the pump flow rate to a total pump flow rate of the plurality of hydraulic pumps as a confluence ratio based on information from the pump discharge state sensor; The second target pump flow rate is calculated based on the actuator absorption flow rate and the calculated confluence ratio. A work machine characterized by:

4. 2. The work machine according to claim 1, The controller The first target pump flow rate and the second target pump flow rate are added together to calculate the final target pump flow rate. A work machine characterized by:

Images