Work machine

Abstract

The purpose of the present invention is to provide a work machine in which the pressure of an actuator can be controlled with high precision without causing a sudden pressure rise or oscillation when the actuator starts operating, thereby achieving good operability and controllability. Therefore, the controller calculates a pump first target flow rate for reducing a difference between an actuator target pressure and an actuator pressure, calculates a pump second target flow rate for reducing a difference between an actuator absorption flow rate and a pump flow rate, calculates a pump final target flow rate based on the pump first target flow rate and the pump second target flow rate, and calculates a pump final target flow rate based on the pump final target flow rate. And controlling the hydraulic pump according to the pump final target flow rate.

Description

Technical Field

[0001] The present invention relates to a working machine for performing oil supply and discharge control of a hydraulic actuator provided in a working machine such as a hydraulic excavator. Background Art

[0002] Generally, various hydraulic actuators are provided in working machines such as hydraulic excavators. As a system (hydraulic control system) for controlling the oil supply and discharge of such hydraulic actuators, the following system is known in the past: a hydraulic pump discharges working oil at a flow rate required according to an operation instruction, a directional control valve is used to switch the supply and discharge direction of the working oil relative to the hydraulic actuator, the inlet throttle opening of the directional control valve is used to control the supply flow rate of the working oil from the hydraulic pump to the hydraulic actuator, and the outlet throttle opening of the directional control valve is used to control the discharge flow rate from the hydraulic actuator to the working oil tank.

[0003] In such a system, even if a sudden signal change is input from the operating lever, such as full lever input, the hydraulic pump changes the discharge flow rate suddenly according to the input signal, and the inertial bodies such as the actuator to be operated and the structure connected to the front end thereof cannot immediately follow. Therefore, when the actuator starts to operate, there is a difference between the flow rate discharged from the hydraulic pump to the actuator and the flow rate absorbed by the actuator accompanying the operation of the actuator, which causes a sudden increase in pressure. As a result, a shock caused by sudden acceleration of the actuator and pressure fluctuation occurs, which may reduce operability when the operator manually operates the working machine, and may reduce controllability when the actuator is controlled by the controller.

[0004] Therefore, the following technology is known in the past: a directional control valve is switched to guide the working oil to the actuator, and a bypass throttling section is provided to discharge a portion of the discharge oil of the hydraulic pump to the oil tank, and the opening degree of the bypass throttling section is adjusted when the actuator starts to move, thereby adjusting the supply flow to the actuator and suppressing sudden pressure changes, thereby ensuring the operability of the working machine (for example, Patent Document 1).

[0005] In addition, there is also known a technique in which a discharge pressure (pump pressure) of a hydraulic pump is detected by a pressure sensor and fed back to a controller, and a pump flow rate is controlled according to the increase or decrease of the pump pressure, thereby suppressing a sudden pressure increase in an actuator (for example, Patent Document 2).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 3403535

[0009] Patent Document 2: Japanese Patent No. 5130353 Summary of the invention

[0010] Problems to be solved by the invention

[0011] However, when the bypass throttling unit is used to discharge oil to the oil tank as in Patent Document 1, the discharged pressure oil will become a loss, so the energy loss becomes larger. In addition, the bypass throttling unit is designed with opening characteristics for a specific action, so the performance also varies under various actions or operating conditions, which may impair the operability or controllability at the start of the action.

[0012] On the other hand, as in Patent Document 2, when pressure is measured and feedback control is used, constant pressure controllability can be maintained even for various actions or operating conditions. However, when the pressure at the measured time point is used to calculate the pump flow control command value, there is a delay time until the controller outputs the control command and the pump changes the flow rate, and the pressure changes generated during the delay time cannot be corrected. Therefore, depending on the performance of the feedback control system such as the action speed of the actuator, the response time of the component, and the calculation performance of the controller, the pressure may not be controlled.

[0013] The present invention has been made in view of the above problems, and an object of the present invention is to provide a working machine capable of controlling the pressure of the actuator with high accuracy without causing a sudden pressure rise and oscillation when the actuator starts to operate, thereby achieving good operability or controllability.

[0014] Means for solving problems

[0015] In order to achieve the above-mentioned purpose, the working device of the present invention comprises: a vehicle body; a working device installed on the vehicle body; an actuator that drives the vehicle body or the working device; a hydraulic pump; a directional control valve that controls the flow of pressure oil supplied from the hydraulic pump to the actuator; an operating lever that indicates the action of the actuator; and a controller that controls the directional control valve according to the input amount of the operating lever, wherein the working machine comprises: a pressure sensor that detects the pressure of the actuator, i.e., the actuator pressure; the controller calculates the target pressure of the actuator, i.e., the actuator target pressure, based on the input amount of the operating lever; the controller calculates the pressure used to reduce the pressure The target flow of the hydraulic pump which is the difference between the actuator target pressure and the actuator pressure is used as the first target flow of the pump, and the controller calculates the target flow of the hydraulic pump which is used to reduce the difference between the actuator absorption flow and the pump flow as the second target flow of the pump, wherein the actuator absorption flow is the flow absorbed by the actuator as the actuator is driven, and the pump flow is the flow supplied from the hydraulic pump to the actuator, and the controller calculates the final target flow of the hydraulic pump, i.e., the final target flow of the pump, based on the first target flow of the pump and the second target flow of the pump, and the controller controls the hydraulic pump according to the final target flow of the pump.

[0016] According to the present invention constructed as described above, the difference between the absorption flow rate and the flow rate of the hydraulic pump when the actuator starts to operate is reduced by feedforward control, and the difference between the actuator target pressure and the actuator pressure is reduced by feedback control. As a result, the pressure of the actuator can be controlled with high accuracy without causing a sudden pressure rise and oscillation when the actuator starts to operate, thereby achieving good operability and controllability.

[0017] Effects of the Invention

[0018] According to the working machine of the present invention, the pressure of the actuator can be controlled with high accuracy without causing a sudden pressure increase or oscillation when the actuator starts to operate, thereby achieving good operability and controllability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a side view of the hydraulic excavator in the embodiment of the present invention.

[0020] Figure 2A This is the circuit diagram of the hydraulic drive unit (1 / 2).

[0021] Figure 2B This is the circuit diagram of the hydraulic drive unit (2 / 2).

[0022] Figure 3 It is the functional block diagram of the controller.

[0023] Figure 4 This is a flowchart showing the processing of the controller related to pump flow rate control.

[0024] Figure 5 This is a flowchart showing the processing of the controller related to the directional control valve opening control.

[0025] Figure 6 1 is a flowchart showing the processing of the controller related to the relief valve opening control.

[0026] Figure 7 This is a diagram showing time-series changes in the operating lever input amount, actuator target pressure, actuator pressure, and actuator speed when a single operation is performed. DETAILED DESCRIPTION

[0027] Hereinafter, a hydraulic excavator will be described as an example of a working machine according to an embodiment of the present invention with reference to the accompanying drawings. In addition, in each figure, the same reference numerals are given to the same components, and repeated descriptions are appropriately omitted.

[0028] Figure 1 FIG. 2 is a side view of the hydraulic excavator according to the present embodiment. Figure 1As shown, the hydraulic excavator 901 includes: a traveling body 201; a revolving body 202, which is arranged on the traveling body 201 in a revolving manner to constitute a vehicle body; and a working device 203, which is mounted on the revolving body 202 in a manner that can rotate in the up-down direction, and performs sand excavation work, etc. The revolving body 202 is driven by a revolving motor 211, which is an actuator, that is, a hydraulic motor.

[0029] The working device 203 includes: a boom 204 mounted on the revolving body 202 in a manner that allows it to rotate in the up-down direction; an arm 205 mounted on the front end of the boom 204 in a manner that allows it to rotate in the up-down direction; a bucket 206 mounted on the front end of the arm 205 in a manner that allows it to rotate in the up-down direction; a boom cylinder 204a that is an actuator that drives the boom 204; an arm cylinder 205a that is an actuator that drives the arm 205; and a bucket cylinder 206a that is an actuator that drives the bucket 206. The working device 203 is provided with motion state detection devices 212, 213, and 214 that detect the posture and motion state of the boom 204, the arm 205, and the bucket 206. The revolving body 202 is provided with motion state detection devices 215 and 216 that detect the posture and rotation speed of the revolving body 202. As the operation state detection devices 212 to 216 , various sensors such as a tilt sensor, a rotation angle sensor, a stroke sensor, and an acceleration sensor (IMU) can be used.

[0030] A cab 207 is provided at the front side of the revolving body 202, and a counterweight 209 is installed at the rear side for ensuring the weight balance of the vehicle body. A machine room 208 is provided between the cab 207 and the counterweight 209. The machine room 208 accommodates an engine (not shown), hydraulic pumps 1 and 2 ( Figure 2A ), a rotary motor 211, a control valve 210, etc. The control valve 210 controls the flow of working oil from the hydraulic pump to each actuator.

[0031] Figure 2A and Figure 2B This is a circuit diagram of a hydraulic drive device mounted on the hydraulic excavator 901.

[0032] (structure)

[0033] The hydraulic drive device 902 includes two main hydraulic pumps (for example, a first hydraulic pump 1 and a second hydraulic pump 2 constituted by variable displacement hydraulic pumps), a pilot pump 111, and a hydraulic oil tank 3 for supplying oil to the hydraulic pumps 1, 2 and the pilot pump 111. The hydraulic pumps 1, 2 and the pilot pump 111 are driven by an engine (not shown).

[0034] The tilting 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 the command pressure acting on the flow control command pressure port 1a. The tilting 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 the command pressure acting on the flow control command pressure port 2a.

[0035] In the discharge flow path 40 of the first hydraulic pump 1, the right travel direction control valve 4, the arm second direction control valve 5, the boom first direction control valve 6, and the bucket direction control valve 7 are connected in parallel via the meter-in flow paths 41, 42, the meter-in flow paths 43, 44, the meter-in flow paths 45, 46, and the meter-in flow paths 47, 48, respectively. Check valves 13 to 16 are respectively arranged in the meter-in flow paths 41, 42, the meter-in flow paths 43, 44, the meter-in flow paths 45, 46, and the meter-in flow paths 47, 48, so as to prevent the pressure oil from flowing back to the discharge flow path 40.

[0036] The right travel direction control valve 4 controls the flow of the pressure oil supplied from the first hydraulic pump 1 to the right travel motor (not shown) of a pair of travel motors driving the travel body 201. The boom second direction control valve 5 controls the flow of the pressure oil supplied from the first hydraulic pump 1 to the boom cylinder 205a. The boom first direction control valve 6 controls the flow of the pressure oil supplied from the first hydraulic pump 1 to the boom cylinder 204a. The bucket direction control valve 7 controls the flow of the pressure oil supplied from the first hydraulic pump 1 to the bucket cylinder 206a.

[0037] To protect the circuit from excessive pressure rise, the discharge flow path 40 is connected to the hydraulic oil tank 3 via the check valve 26 and the relief valve 25. In addition, the discharge flow path 40 is connected to the hydraulic oil tank 3 via the relief valve 23 to discharge excess discharge oil of the first hydraulic pump 1.

[0038] In the discharge flow path 50 of the second hydraulic pump 2, the swing direction control valve 8, the left travel direction control valve 9, the arm first direction control valve 10, the boom second direction control valve 11, and the standby direction control valve 12 are connected in parallel via the meter-in flow paths 51, 52, the meter-in flow paths 53, 54, the meter-in flow paths 55, 56, the meter-in flow paths 57, 58, and the meter-in flow paths 59, 60, respectively. Check valves 17 to 21 are respectively arranged in the meter-in flow paths 51, 52, the meter-in flow paths 53, 54, the meter-in flow paths 55, 56, the meter-in flow paths 57, 58, and the meter-in flow paths 59, 60, so as to prevent the pressure oil from flowing back to the discharge flow path 50.

[0039] 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 travel direction control valve 9 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the left travel motor (not shown) of a pair of travel motors that drive the travel body 201. The boom first direction control valve 10 controls the flow of pressure oil supplied from the second hydraulic pump 2 to the boom 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 accessory such as a small splitter provided in place of the bucket 206.

[0040] In order to protect the circuit from excessive pressure rise, the discharge flow path 50 is connected to the hydraulic oil tank 3 via the check valve 27 and the relief valve 25. In addition, the discharge flow path 50 is connected to the hydraulic oil tank 3 via the relief valve 24 to discharge the remaining discharge oil of the second hydraulic pump 2. In addition, the discharge flow path 50 is connected to the discharge flow path 40 via the merging valve 22 to merge the discharge oil of the first hydraulic pump 1 and the second hydraulic pump 2.

[0041] exist Figure 2B In the embodiment, the discharge port of the pilot pump 111 is connected to the hydraulic oil tank 3 via the pilot relief valve 112 for generating the pilot primary pressure, and is connected to one input port of the electromagnetic valves 113a to 113j built in the electromagnetic valve unit 113 via the flow path 116 for supplying the discharge pressure discharged from the pilot pump 111. The other input ports of the electromagnetic valves 113a to 113j are connected to the hydraulic oil tank 3 via the flow path 117 for guiding the return oil from the electromagnetic valves 113a to 113j. The electromagnetic valves 113a to 113j respectively reduce the pilot primary pressure according to the command signal from the controller 114 and output it as the command pressure.

[0042] 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 the 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 the 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 directional control valve 6 via the 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 the 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 directional control valve 11 via the flow paths 124 and 125. The output port of the solenoid valve 113i is connected to the command pressure port 23a of the relief valve 23 via the flow path 126. The output port of the solenoid valve 113j is connected to the command pressure port 24a of the relief valve 24 via the flow path 127. In addition, for the sake of simplicity of description, the solenoid valve for the right travel direction control valve 6, the solenoid valve for the boom second direction control valve 5, the solenoid valve for the bucket direction control valve 7, the solenoid valve for the left travel direction control valve 9, the solenoid valve for the boom first direction control valve 10, and the solenoid valve for the standby direction control valve 12 are omitted from the figure.

[0043] A pressure sensor 91 for detecting the flow control command pressure of the first hydraulic pump 1 is provided in the flow path 118. A pressure sensor 92 for detecting the flow control command pressure of the second hydraulic pump 2 is provided in the flow path 119. A pressure sensor 93 for detecting the actuator pressure on the bottom side of the boom cylinder 204a is provided in the flow path 63 connecting the port Bm2B of the boom second directional control valve 11 and the boom cylinder 204a, and in the flow path 64 connecting the port Bm1B of the boom first directional control valve 6 and the boom cylinder 204a. A pressure sensor 94 for detecting the actuator pressure on the rod side of the boom cylinder 204a is provided in the flow path 65 connecting the port Bm2R of the boom second directional control valve 11 and the boom cylinder 204a, and in the flow path 66 connecting the port Bm1R of the boom first directional control valve 6 and the boom cylinder 204a. A pressure sensor 95 for detecting one actuator pressure of the swing motor 211 is provided in the flow path 73 connecting the port SwgR of the swing direction control valve 8 and the swing motor 211. A pressure sensor 96 for detecting another actuator pressure of the swing motor 211 is provided in the flow path 74 connecting the port SwgL of the swing direction control valve 8 and the swing motor 211. In addition, for the sake of simplicity of description, illustration of the arm cylinder 205a, the bucket cylinder 206a, the left travel motor not shown, the right travel motor not shown, and the pressure sensor for detecting the actuator pressure of the actuator driving the special accessory not shown is omitted.

[0044] The hydraulic drive device 902 has a boom operating lever 115a capable of switching the operation of the boom first directional control valve 6 and the boom second directional control valve 11, and an arm operating lever 115b capable of switching the operation of the arm first directional control valve 10 and the arm second directional control valve 5. In addition, in order to simplify the description, the right travel operating lever for switching the operation of the right travel direction control valve 4, the bucket operating lever for switching the operation of the bucket directional control valve 7, the swing operating lever for switching the operation of the swing direction control valve 8, the left travel operating lever for switching the operation of the left travel direction control valve 9, and the standby operating lever for switching the operation of the standby directional control valve 12 are omitted from the illustration.

[0045] The hydraulic drive device 902 has a controller 114. The controller 114 outputs a command signal to the solenoid valves 113a to 113j (including a solenoid valve not shown) of the solenoid valve unit 113 according to the input of the operating 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.

[0046] Figure 3 is a functional block diagram of the controller 114. Figure 3 In the figure, the controller 114 has: an actuator target pressure calculation unit 114a, a pump first target flow calculation unit 114b, an actuator speed calculation unit 114c, an actuator absorption flow calculation unit 114d, a pump flow calculation unit 114e, a confluence ratio calculation unit 114f, a pump second target flow calculation unit 114g, a pump final target flow calculation unit 114h, a pump flow control instruction output unit 114i, a directional control valve target opening calculation unit 114j, a directional control valve control instruction output unit 114k, a relief valve target opening calculation unit 114l, and a relief valve control instruction output unit 114m.

[0047] The actuator target pressure calculation unit 114a calculates the actuator target pressure P_TgtAct corresponding to the operating lever input amount according to the preset actuator target pressure characteristics relative to the operating lever input amount. The pump first target flow rate calculation unit 114b calculates the target flow rate of the hydraulic pumps 1 and 2 for reducing the difference between the actuator target pressure P_TgtAct calculated by the actuator target pressure calculation unit 114a and the actuator pressure P_Act obtained from the pressure sensors 93 to 96 as the pump first target flow rate Q_TgtPmp1.

[0048] The actuator speed calculation unit 114c calculates the actuator speed V_Act based on the operating state information obtained 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.

[0049] The pump flow rate calculation unit 114e calculates the pump flow rate Q_Pmp corresponding to the pump flow rate control command pressure obtained from the pressure sensors 91 and 92 according to the preset pump flow rate characteristics relative to the pump flow rate control command pressure. The confluence ratio calculation unit 114f calculates 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 and 2 as the confluence ratio R_Cnf 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 the target flow rate of the hydraulic pumps 1 and 2 for reducing the difference between the actuator absorption flow rate Q_Act and the pump flow rate Q_Pmp as the pump second target flow rate Q_TgtPmp2 based on 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.

[0050] The pump final target flow rate calculation unit 114h calculates the pump final target flow rate Q_TgtPmp based on the pump first target flow rate Q_TgtPmp1 calculated by the pump first target flow rate calculation unit 114b and the pump second target flow rate Q_TgtPmp2 calculated by the pump second target flow rate calculation unit 114g. The pump flow rate control command output unit 114i calculates the pump flow rate control command pressure relative to the pump final target flow rate Q_TgtPmp2 calculated by the pump final target flow rate calculation unit 114h according to the preset electromagnetic valve command signal characteristics relative to the pump final target flow rate Q_TgtPmp2, and outputs the pump flow rate control command signal corresponding to the pump flow rate control command pressure to the electromagnetic valves 113a and 113b for pump flow control.

[0051] 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 according to the directional control valve target opening characteristics relative to the operating lever input amount set in advance. 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 valve solenoid valves 113c to 113h according to the solenoid valve command signal characteristics relative to the directional control valve target opening a_TgtMS set in advance.

[0052] The relief valve target opening calculation unit 1141 calculates the relief valve target opening corresponding to the operating lever input amount according to the preset relief valve target opening characteristics relative to the operating lever input amount. The relief valve control command output unit 114m outputs a command signal corresponding to the relief valve target opening (relief valve control command signal) to the solenoid valves 113i and 113j for the relief valve according to the preset solenoid valve command signal characteristics relative to the relief valve target opening.

[0053] Figure 4 1 is a flowchart showing the processing of the controller 114 related to the pump flow rate control.

[0054] The controller 114 first determines whether there is no operation lever input (step S101). If it is determined in step S101 that there is no operation lever input (Yes), the flow ends.

[0055] When it is determined in step S101 that there is an operation lever input (NO), the actuator target pressure calculation unit 114a calculates the actuator target pressure P_TgtAct corresponding to the operation lever input amount according to the preset actuator target pressure characteristics with respect to the operation lever input amount (step S102).

[0056] Following step S102, the pump first target flow rate calculation unit 114b calculates the pump first target flow rate Q_TgtPmp1 based on the actuator target pressure P_TgtAct and the actuator pressure P_Act (step S103). Here, for example, the PID control method is used to calculate the pump first target flow rate Q_TgtPmp1 so that the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act becomes small.

[0057] In parallel with step S102 , the actuator speed calculation unit 114 c calculates the actuator speed V_Act based on the operation state information acquired from the operation state detection devices 212 to 216 (step S104 ).

[0058] 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 actuator specifications (step S105). Here, when the actuator is a hydraulic cylinder, the driving speed of the piston is calculated as the actuator speed V_Act, and the actuator absorption flow rate Q_Act is calculated by multiplying the driving speed by the pressure receiving area of ​​the piston.

[0059] Following step S106 , the pump flow rate calculation unit 114 e calculates the pump flow rate Q_Pmp corresponding to the pump flow rate control command pressure obtained from the pressure sensors 91 , 92 according to the preset pump flow rate characteristics with respect to the pump flow rate control command pressure (step S106 ).

[0060] Following step S107 , the confluence ratio calculation unit 114 f 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 114 e and the total pump flow rate Q_PmpSum of the hydraulic pumps 1 and 2 using Formula 1 (step S107 ).

[0061] [Mathematical formula 1]

[0062] R_Cnf=Q_Pmp / Q_PmpSum

[0063] Following step S107 , the pump second target flow rate calculation unit 114 g calculates the pump second target flow rate Q_TgtPmp2 for reducing the difference between the actuator absorption flow rate Q_Act and the pump flow rate Q_Pmp using equation 2 using the actuator absorption flow rate Q_Act and the confluence ratio R_Cnf (step S108 ).

[0064] [Mathematical formula 2]

[0065] Q_TgtPmp2=R_Cnf×Q_Pmp

[0066] Following step S108 , the pump final target flow rate calculation unit 114 h adds the pump first target flow rate Q_TgtPmp1 and the pump second target flow rate Q_TgtPmp2 using Mathematical Formula 3 to calculate the pump final target flow rate Q_TgtPmp (step S109 ).

[0067] [Mathematical formula 3]

[0068] Q_TgtPmp=Q_TgtPmp1+Q_TgtPmp2

[0069] Following step S109, the pump flow control instruction output unit 114i outputs a pump flow control instruction signal corresponding to the pump final target flow rate Q_TgtPmp to the solenoid valves 113a and 113b used for pump flow control according to the preset solenoid valve instruction signal characteristics relative to the pump final target flow rate Q_TgtPmp, and the process ends.

[0070] Figure 5 1 is a flowchart showing the processing of the controller 114 related to the directional control valve opening control.

[0071] The controller 114 first determines whether there is no operation lever input (step S201). If it is determined in step S201 that there is no operation lever input (Yes), the flow ends.

[0072] When 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 according to the pre-set directional control valve target opening characteristics relative to the operating lever input amount (step S202).

[0073] 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 solenoid valves 113c~113h used for the directional control valve in accordance with the pre-set solenoid valve command signal characteristics relative to the directional control valve target opening a_TgtMS (step S203), thereby ending the process.

[0074] Figure 6 1 is a flowchart showing the processing of the controller 114 related to the relief valve opening control.

[0075] The controller 114 first determines whether there is no operation lever input (step S301). If it is determined in step S301 that there is no operation lever input (Yes), the flow ends.

[0076] When it is determined in step S301 that there is an operation lever input (No), the relief valve target opening calculation unit 1141 calculates the relief valve target opening a_TgtBO corresponding to the operation lever input amount according to the preset relief valve target opening characteristics relative to the operation lever input amount (step S302).

[0077] Following step S302, the relief valve target opening calculation unit 1141 outputs the command signal (relief valve control command signal) corresponding to the relief valve target opening a_TgtBO to the solenoid valves 113i, 113j for the relief valve according to the pre-set solenoid valve command signal characteristics relative to the relief valve target opening a_TgtBO (step S303), and the process ends.

[0078] (action)

[0079] As an example of the action of the hydraulic drive device 902, the action when a single operation is performed is described. In the single operation, only the rotation motor 211 that rotates the rotating body 202 with large inertia or the boom cylinder 204a that supports the entire weight of the working device 203 and moves up and down at the same time is driven.

[0080] Figure 7 1 is a diagram showing time series changes in the operating lever input amount, actuator target pressure, actuator pressure, and actuator speed V_Act when a single operation is performed. In addition, the actuator pressure P_Act and the actuator speed V_Act when only pressure feedback control is performed are shown as a comparative example.

[0081] When the operator operates the rotary operating lever, the controller 114 calculates the actuator target pressure according to the operating lever input amount. The pump final target flow rate Q_TgtPmp is calculated based on the actuator target pressure, and a command signal is output to the solenoid valves 113a and 113b for pump flow control. The solenoid valve generates a pilot pressure corresponding to the command signal, and the hydraulic pumps 1 and 2 adjust the flow rate by changing the pump tilt in response to the pilot pressure. At this time, the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act is caused by two factors.

[0082] The first factor is the differential pressure P_Error1 between the actuator target pressure P_TgtAct and the actuator pressure P_Act, which is expressed by Mathematical Formula 4.

[0083] [Formula 4]

[0084] P_Error1=P_TgtAct-P_Act

[0085] 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 rates Q_Pmp of the hydraulic pumps 1 and 2, which is expressed by Mathematical Formula 5.

[0086] [Formula 5]

[0087] P_Error2=(K / V)×∫(Q_Pmp-Q_Act)dt

[0088] Here, K is the volume coefficient of the hydraulic oil, and V is the volume of the hydraulic oil.

[0089] In view of these two pressure error factors, the controller 114 calculates the first pump target flow rate Q_TgtPmp1 for reducing the differential pressure P_Error1, and calculates the second pump target flow rate Q_TgtPmp2 for reducing the pressure change P_Error2. Thus, the pump flow rate Q_Pmp is adjusted so that both the differential pressure P_Error1 and the pressure change P_Error2 become smaller, so that the actuator pressure P_Act can be controlled according to the actuator target pressure P_TgtAct. As a result, the actuator, i.e., the rotary motor, which drives the rotary body 202 with large inertia, can start to move well and accelerate without generating shock and vibration.

[0090] On the other hand, when only pressure feedback control is performed, P_Error1 can be reduced, but P_Error2 cannot be reduced. Therefore, the pressure change P_Error2 caused by the difference between the pump flow rate Q_Pmp and the actuator absorption flow rate Q_Act generated during the delay time of the pressure feedback control cannot be suppressed. For example, when the actuator absorption flow rate Q_Act is greater than the pump flow rate Q_Pmp, the flow rate is insufficient, such as Figure 7As shown in FIG. 1 , the actuator pressure P_Act does not reach the actuator target pressure P_TgtAct. In addition, when the pressure change amount P_Error2 is to be reduced by the pressure feedback control and the feedback gain is increased, a Figure 7 Oscillation as shown.

[0091] In addition, when the boom is operated independently, the flow rates of the hydraulic pump 1 and the hydraulic pump 2 are sometimes merged to drive the boom cylinder 204a. In this case, the controller 114 calculates the confluence ratio R_Cnf, and calculates the pump second target flow rate Q_TgtPmp2 for reducing the pressure change amount P_Error2 based on the contribution of the flow rates Q_Pmp of the hydraulic pumps 1 and 2 to the absorption flow rate Q_Act of the boom cylinder 204a. In this way, the flow rate adjustment amount of one hydraulic pump can be prevented from being offset by the other hydraulic pump, so that the boom cylinder 204a that supports the entire weight of the working device 203 and moves up and down can start to move well and accelerate without generating shocks and vibrations.

[0092] (Summarize)

[0093] In the present embodiment, the working machine 901 includes: a body 202; a working device 203 mounted on the body 202; actuators 204a, 205a, 206a, 211 that drive the body 202 or the working device 203; hydraulic pumps 1, 2; directional control valves 5 to 8, 10, 11 that control the flow of pressure oil supplied from the hydraulic pumps 1, 2 to the actuators 204a, 205a, 206a, 211; operating rods 115a, 115b that instruct the actuators 204a, 205a, 206a, 211 to move the hydraulic pumps 1, 2; and control levers 115a, 115b that instruct the actuators 204a, 205a, 206a, 211 to move the hydraulic pumps 1, 2. 1; and a controller 114, which controls the directional control valves 5 to 8, 10, and 11 according to the input of the operating levers 115a and 115b, wherein the operating machine 901 has: pressure sensors 93 to 96, which detect the pressure of the actuators 204a, 205a, 206a, and 211, that is, the actuator pressure P_Act, and the controller 114 calculates the target pressure of the actuators 204a, 205a, 206a, and 211, that is, the actuator target pressure P_TgtAc based on the input of the operating levers 115a and 115b. t, the controller 114 calculates the target flow of the hydraulic pumps 1 and 2 for reducing the difference between the actuator target pressure P_TgtAct and the actuator pressure P_Act as the first pump target flow Q_TgtPmp1, and the controller 114 calculates the target flow of the hydraulic pumps 1 and 2 for reducing the difference between the actuator absorption flow Q_Act and the pump flow Q_Pmp as the second pump target flow Q_TgtPmp2, wherein the actuator absorption flow Q_Act is driven by the actuators 204a, 205a, 206a, 211. The flow absorbed by the actuators 204a, 205a, 206a, 211, the pump flow Q_Pmp is the flow supplied from the hydraulic pumps 1, 2 to the actuators 204a, 205a, 206a, 211, the controller 114 calculates the final target flow of the first hydraulic pump, i.e., the pump final target flow Q_TgtPmp, based on the pump first target flow Q_TgtPmp1 and the pump second target flow Q_TgtPmp2, and the controller 114 controls the hydraulic pumps 1, 2 according to the pump final target flow Q_TgtPmp.

[0094] 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 is reduced by feedforward control when the actuators 204a, 205a, 206a, and 211 start to operate, 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 pressures of the actuators 204a, 205a, 206a, and 211 can be controlled with high accuracy without causing a sudden pressure rise and oscillation when the actuators 204a, 205a, 206a, and 211 start to operate, thereby achieving good operability and controllability.

[0095] In addition, the working machine 901 in this embodiment has: an action state detection device 212~216, which detects the action state of the vehicle body 202 or the working device 203, the actuators 204a, 205a, 206a, 211 are hydraulic cylinders 204a, 205a, 206a or hydraulic motors 211, and the controller 114 calculates the driving speed V_Act of the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 based on the information from the action state detection devices 212~216, and calculates the actuator absorption flow Q_Act, that is, the absorption flow of the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 according to the calculated driving speed V_Act. As a result, the pressure of the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 can be controlled with high precision without causing a sudden pressure increase and oscillation when the hydraulic cylinders 204a, 205a, 206a or the hydraulic motor 211 start to move, thereby achieving good operability and controllability.

[0096] In addition, the working machine 901 in the present embodiment includes: a plurality of hydraulic pumps 1, 2 that supply pressure oil to the actuators 204a, 205a, 206a, 211; and pump discharge state sensors 91, 92 that detect the discharge state of the plurality of hydraulic pumps 1, 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, 2 as the confluence ratio R_Cnf based on the information from the pump discharge state sensors 91, 92, and the controller 114 calculates the pump second target flow rate Q_TgtPmp2 based on the actuator absorption flow rate Q_Act and the calculated confluence ratio R_Cnf. Thus, the pump second target flow rate Q_TgtPmp2 can be calculated for each of the plurality of hydraulic pumps 1, 2 that supply pressure oil to the same actuator 204a, 205a, 206a, 211.

[0097] The embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments and includes various modifications. For example, the above embodiments are described in detail to explain the present invention in an easy-to-understand manner and are not limited to having all the structures described.

[0098] Explanation of symbols

[0099] 1…1st hydraulic pump, 1a…flow control command pressure port, 2…2nd hydraulic pump, 2a…flow control command pressure port, 3…working oil tank, 4…right travel direction control valve, 5…arm second direction control valve, 6…boom first direction control valve, 6a…command pressure port, 6b…command pressure port, 7…bucket direction control valve, 8…swing direction control valve, 8a…command pressure port, 8b…command pressure port, 9…left travel direction control valve, 10…arm first direction control valve, 11…boom second direction control valve, 11a…command pressure port, 11b…command pressure port, 12…preparation direction control valve, 13… 21 ... one-way valve, 22 ... confluence valve, 23 ... relief valve, 23a ... command pressure port, 24 ... relief valve, 24a ... command pressure port, 25 ... relief valve, 26, 27 ... one-way 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 calculation unit, 114c... actuator speed calculation unit, 114d... actuator absorption flow calculation unit, 114e... pump flow calculation unit, 114f... confluence ratio calculation unit, 114g... pump second target flow calculation unit, 114h... pump final target flow calculation unit, 114i... pump flow control command output unit, 114j... directional control valve target opening calculation unit, 114k... directional control valve control command output unit, 114l... relief valve target opening calculation unit, 114m... relief valve control command output unit, 115a... boom operating lever, 115b …arm operating lever, 116-127…flow path, 201…traveling body, 202…rotating body (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…operating room, 208…machine room, 209…counterweight, 210…control valve, 211…rotating motor (actuator), 212-216…action state detection device, 901…hydraulic excavator (working machine), 902…hydraulic drive device.

Claims

1. A working machine having: Car body; A working device mounted on the vehicle body; an actuator that drives the vehicle body or the working device; Hydraulic pumps; a directional control valve that controls the flow of pressurized oil supplied from the hydraulic pump to the actuator; an operating lever that indicates the action of the actuator; as well as a controller that controls the directional control valve according to an input amount of the operating lever, It is characterized in that The working machine includes: a pressure sensor for detecting the pressure of the actuator, that is, the actuator pressure; The controller calculates the target pressure of the actuator, that is, the actuator target pressure, based on the input amount of the operating lever. the controller 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 pump target flow rate, The controller calculates a target flow rate of the hydraulic pump for reducing a difference between an actuator absorption flow rate and a pump flow rate as a second pump target flow rate, wherein the actuator absorption flow rate is a flow rate absorbed by the actuator as the actuator is driven, and the pump flow rate is a flow rate supplied from the hydraulic pump to the actuator, The controller calculates the final target flow rate of the hydraulic pump, ie, the final pump target flow rate, based on the first pump target flow rate and the second pump target flow rate. The controller controls the hydraulic pump according to the pump final target flow rate.

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

3. The working machine according to claim 1, characterized in that: The working machine has: a plurality of hydraulic pumps including the hydraulic pump, which supply pressurized oil to the actuator; and a pump discharge state sensor for detecting the discharge state of the plurality of hydraulic pumps, The controller calculates 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 controller calculates the pump second target flow rate according to the actuator absorption flow rate and the calculated confluence ratio.

4. The working machine according to claim 1, characterized in that: The controller calculates the pump final target flow rate by adding the pump first target flow rate to the pump second target flow rate.

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