Work machine

Abstract

To provide a work machine which can control a pump pressure equal to or greater than a certain level irrespective of a load condition, and which can stably supply a pressure required for a pilot oil pressure.SOLUTION: A work machine includes: an operation lever for outputting an operation signal for operating a work device; a hydraulic actuator for driving the work device; a variable capacity type hydraulic pump for supplying a pressure oil to the hydraulic actuator; a directional control valve for controlling the flow rate and the direction of the pressure oil which is supplied from the oil pressure pump to the hydraulic actuator; and a controller for controlling the hydraulic pump and the directional control valve according to the operation signal from the operation lever. The controller calculates a first target flow rate based on the operation amount of the operation lever, calculates a second target flow rate based on a pump target discharge pressure and a pump discharge pressure determined beforehand, and controls the hydraulic pump based on the target flow rate calculated based on the first target flow rate and the second target flow rate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a work machine. [Background technology]

[0002] A fluid pressure work machine such as a hydraulic excavator is configured with a work device having a boom, arm, etc., an upper rotating body, a lower traveling body, etc., and hydraulic actuators such as cylinders are driven by pressurized oil discharged from a hydraulic pump to operate the work device, upper rotating body, lower traveling body, etc. The thrust and speed of these hydraulic actuators are controlled by the flow rate and pressure of the pressurized oil supplied, and this is done by controlling the discharge rate of the hydraulic pump and the valve opening of a control valve provided in an oil passage between the hydraulic pump and the hydraulic actuator.

[0003] When each valve of the control valve is driven by a hydraulic pilot system, for example, a hydraulic source for the pilot circuit is required. As a pilot hydraulic source, a fixed displacement pilot pump is provided separately from the main hydraulic pump, and a relief valve is used to maintain a constant pressure. of pressure to and the main hydraulic pump discharge oil. pressure One known method is to use a pressure reducing valve to reduce part of the pressure to an appropriate level and use it as the primary pilot pressure. When using a pressure reducing valve, there is no need to keep the pilot pump constantly relieved, so energy efficiency is improved compared to the pilot pump method, although this depends on the operation method.

[0004] Hydraulic pump discharge oil pressure As a technique for reducing a part of the pressure to make it a pilot primary pressure, for example, Patent Document 1 discloses a technique for reducing a part of the pressure of a working fluid discharged from a pump. pressure oil The direction of the fluid is controlled by a pilot-operated control valve that is operated by a pilot pressure according to a manual operation signal. oil Main fluid pressure supplied to the hydraulic actuator Main hydraulic circuit and this main fluid pressure Main hydraulic Circuit hydraulicWorking fluid discharged from the pump pressure oil A part of the pilot system fluid pressure is extracted and supplied to the pilot pressure acting part of the pilot operated control valve when the pilot operated control valve is switched. hydraulic Fluid pressure circuit hydraulic A circuit arrangement is disclosed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-263304 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned prior art, when the control valve for the hydraulic actuator is not operated, of Bypass sequence valve installed upstream Hydraulic pressure pump of The discharge pressure is controlled, and when the hydraulic actuator is operated, the bypass sequence valve is opened, enabling the supply of pressurized oil to the hydraulic actuator.

[0007] However, the front work machine Work equipment As in the case where the weight acts in the direction of movement hydraulic Under negative actuator load conditions, hydraulic pump Discharge of Pressure and hydraulic Actuator of Meter-in pressure does not increase and the pilot hydraulic system circuit necessary required There is a risk that pressure may not be supplied.

[0008] The present invention has been made in view of the above, and is hydraulic pump of pressure Discharge pressure can be controlled to a certain level, and is used for pilot hydraulic systems. Required for the circuitThe object is to provide a work machine that can stably supply pressure. [Means for solving the problem]

[0009] The present application includes a plurality of means for solving the above-mentioned problems, and one example thereof is a work machine including a vehicle body, a working device attached to the vehicle body, an operation lever that outputs an operation signal for operating the working device, a hydraulic actuator that drives the working device, a variable displacement hydraulic pump that supplies pressure oil to the hydraulic actuator, a pump discharge pressure sensor that detects the discharge pressure of the hydraulic pump, a directional control valve that controls the flow rate and direction of pressure oil supplied from the hydraulic pump to the hydraulic actuator, and a controller that controls the hydraulic pump and the directional control valve in accordance with an operation signal from the operation lever, wherein the controller calculates a first target flow rate based on the operation amount of the operation lever, calculates a second target flow rate based on a predetermined pump target discharge pressure and the discharge pressure detected by the pump discharge pressure sensor, calculates a target flow rate of the hydraulic pump based on the first target flow rate and the second target flow rate, and controls the hydraulic pump based on the calculated target flow rate of the hydraulic pump. [Effects of the Invention]

[0010] According to the present invention, the pump pressure can be controlled to a constant level or higher regardless of the load conditions, and the present invention is suitable for use in a pilot hydraulic system. Required for the circuit Pressure can be supplied stably. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a schematic configuration of a hydraulic excavator, which is an example of a work machine. [Figure 2] FIG. 2 is a diagram illustrating the hydraulic circuit system of the hydraulic excavator together with the peripheral configuration including the controller. [Figure 3] FIG. 2 is a functional block diagram showing a calculation function for a target current of a pump flow rate control solenoid valve, among the processing functions of the controller, together with related configurations. [Figure 4] 4 is a flowchart showing the contents of calculation processing of the controller. [Figure 5] 5A and 5B are diagrams showing a pump target flow rate, a pump target discharge pressure, and a change in the pump discharge pressure over time. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described below with reference to the drawings. In the following description, a hydraulic excavator will be shown as an example of a construction machine, but the present invention can also be applied to other hydraulically driven construction machines.

[0013] Fig. 1 is a diagram showing a schematic configuration of a hydraulic excavator, which is an example of a work machine according to this embodiment, and Fig. 2 is a diagram showing the hydraulic circuit system of the hydraulic excavator, extracted together with the peripheral configuration including a controller.

[0014] As shown in FIG. 1, a hydraulic excavator 100, which is a construction machine, comprises a crawler-type lower running body 1 and an upper rotating body 2 which is rotatably attached to the upper part of the lower running body 1 and which, together with the lower running body 1, constitutes the body of the construction machine.

[0015] The lower traveling body 1 is driven to travel by left and right traveling hydraulic motors 11, 12 (only one of which is shown in FIG. 1, with the reference number of the other indicated in parentheses) which are hydraulic actuators having speed reducers. The upper rotating body 2 is driven to swing left and right relative to the lower traveling body 1 by torque generated by a swing hydraulic motor 10 which is also a hydraulic actuator.

[0016] A cab 2a in which the operator of the hydraulic excavator 100 sits is installed at the front of the upper rotating body 2, and a multi-joint front working device 3 (working device) is attached to the side of the cab 2a at the front of the upper rotating body 2 to perform work to form the target terrain, etc.

[0017] The front working mechanism 3 is configured by connecting a boom 4, an arm 5, and a bucket 6, each of which rotates vertically, and is driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, which are hydraulic actuators, respectively.

[0018] The operator's cab 2a is provided with an operation lever 13 that outputs operation signals for operating the boom cylinder 7, arm cylinder 8, bucket cylinder 9, swing hydraulic motor 10, and traveling hydraulic motors 11, 12, a gate lock lever 14 (operation lock lever) that selectively switches the hydraulic excavator 100 between an operable state (unlocked state) and a work-disabled state (locked state) (for example, by switching the operation signal output from the operation lever 13, i.e., the operation by the operation lever 13, between enabled and disabled), and a controller 32 that controls the overall operation of the hydraulic excavator 100. The operation lever 13 is intended to represent both the function as a pair of left and right lever devices for operating the front working implement 3 and the upper rotating structure 2 and the function as a pair of left and right traveling lever devices (travel pedals) for operating the lower traveling structure 1.

[0019] 2, the hydraulic circuit system includes a first hydraulic pump 20a and a second hydraulic pump 20b that are rotationally driven by a prime mover such as a diesel engine (not shown). The first hydraulic pump 20a and the second hydraulic pump 20b are provided with pump regulator control solenoid valves 22a and 22b that can change the pump flow rate, respectively.

[0020] The pump line to which the pressure oil discharged from the first hydraulic pump 20a is supplied is connected to the right-side traveling hydraulic motor 11, bucket cylinder 9, arm cylinder 8, and boom cylinder 7. A right traveling direction control valve 23, a bucket direction control valve 24, an arm 2 direction control valve 25, and a boom 1 direction control valve 26 that control the flow rate and direction of the pressure oil supplied from the first hydraulic pump 20a to the hydraulic actuators 7, 8, 9, and 11 are connected between the first hydraulic pump 20a and the hydraulic actuators 7, 8, 9, and 11, and the pressure oil discharged from the first hydraulic pump 20a is supplied to the hydraulic actuators 7, 8, 9, and 11 via the direction control valves 23, 24, 25, and 26.

[0021] The pump line to which the pressure oil discharged from the second hydraulic pump 20b is supplied is connected to the left traveling hydraulic motor 12, the attachment hydraulic actuator (not shown), the arm cylinder 8, the boom cylinder 7, and the swing hydraulic motor 10. A swing direction control valve 27, a boom 2 direction control valve 28, an arm 1 direction control valve 29, a backup direction control valve 30, and a left traveling direction control valve 31 are connected between the second hydraulic pump 20b and each of the hydraulic actuators 7, 8, 10, and 12 (hereinafter, including the attachment hydraulic actuators), and the pressure oil discharged from the second hydraulic pump 20b is supplied to each of the hydraulic actuators 7, 8, 10, and 12 via each direction control valve 27, 28, 29, and 30.

[0022] A bypass cut valve is provided at the most downstream of the center bypass oil passage of each directional control valve 23, 24, 25, 26, 27, 28, 29, 30, 31 in the pump lines of the first hydraulic pump 20a and the second hydraulic pump 20b. In addition, pump discharge pressure sensors 21a, 21b are provided at the most upstream of each directional control valve 23, 24, 25, 26, 27, 28, 29, 30, 31 in the pump lines of the first hydraulic pump 20a and the second hydraulic pump 20b.

[0023] The discharge pressures of the first hydraulic pump 20a and the second hydraulic pump 20b branch off from the most upstream position in the pump line and are connected to a common pressure reducing valve via a check valve. The pressure oil that has passed through the pressure reducing valve then passes through a check valve and an accumulator, then through a pilot circuit, and is directed to the solenoid proportional valve. The pilot pressure generated by the solenoid proportional valve acts on the directional control valves 23, 24, 25, 26, 27, 28, 29, 30, and 31 and the bypass cut valve, controlling the amount of movement of these valves. In addition, the pilot pressure that has passed through the pilot circuit is directed to the pump regulator control solenoid valves 22a and 22b, where it generates pilot pressure for controlling the pump regulator.

[0024] A supply path for pressure oil from the first hydraulic pump 20a and the second hydraulic pump 20b to the pilot circuit is provided with an electromagnetic proportional valve 14a that is controlled by a signal output from the controller 32 in accordance with the position of the gate lock lever 14. When the gate lock lever 14 is in a position that makes the hydraulic excavator 100 operable (for example, the raised position), the electromagnetic proportional valve 14a allows the supply of pressure oil from the first hydraulic pump 20a and the second hydraulic pump 20b to the pilot circuit, and when the gate lock lever 14 is in a position that makes the hydraulic excavator 100 inoperable (for example, the lowered position), the electromagnetic proportional valve 14a blocks the pressure oil from the first hydraulic pump 20a and the second hydraulic pump 20b to the pilot circuit.

[0025] FIG. 3 is a functional block diagram showing the target current calculation function of the pump flow rate control solenoid valve, among the processing functions of the controller, together with the related configuration.

[0026] In FIG. 3, the controller 32 includes a pump target flow rate calculation unit 32a, a memory unit 32b, a difference calculation unit 32c, a feedback control unit 32d, a feedforward calculation unit 32e, an addition unit 32f, a pump target flow rate selection unit 32g, and a solenoid valve target current calculation unit 32h.

[0027] The pump target flow rate calculation unit 32a calculates the pump target flow rate a according to a preset control map, based on the amount of operation of the control lever 13.

[0028] The storage unit 32b stores a preset target pump discharge pressure.

[0029] The difference calculation unit 32c calculates the difference between the sensor value (detection result) from the pump discharge pressure sensors 21a and 21b and the pump target discharge pressure from the storage unit 32b.

[0030] The feedback control unit 32d applies feedback control to the calculation result from the difference calculation unit 32c to calculate a pump target flow rate feedback term. The feedback control applied by the feedback control unit 32d is, for example, PID control.

[0031] The feedforward calculation unit 32e performs a feedforward calculation on the pump target discharge pressure from the storage unit 32b to calculate a pump target flow rate feedforward term. The calculation method used by the feedforward calculation unit 32e includes, for example, a method of calculating using an orifice equation from the opening characteristics of the directional control valves from the pumps (first hydraulic pump 20a and second hydraulic pump 20b) to the pressure oil tank when they are in the neutral position.

[0032] The adder 32f adds the pump target flow rate feedback term calculated by the feedback control unit 32d and the pump target flow rate feedforward term calculated by the feedforward calculation unit 32e to calculate the pump target flow rate b.

[0033] The pump target flow rate selection unit 32g selects the maximum value (here, the larger value) between the pump target flow rate a from the pump target flow rate calculation unit 32a and the pump target flow rate b from the addition unit 32f, and outputs it as the pump target flow rate.

[0034] The solenoid valve target current calculation unit 32h calculates a solenoid valve target current for flow rate control in accordance with a preset calculation map based on the pump target flow rate from the pump target flow rate selection unit 32g, and outputs the current to the pump regulator control solenoid valves 22a, 22b. As the calculation map, for example, design values ​​of the pumps (first hydraulic pump 20a and second hydraulic pump 20b) and solenoid valves (pump regulator control solenoid valves 22a, 22b) are used.

[0035] FIG. 4 is a flowchart showing the contents of the calculation process of the controller.

[0036] In FIG. 4, the controller 32 repeatedly performs the processes of steps S100 to S109 for each preset control period.

[0037] The controller 32 first obtains the operation amount of the operation lever from the operation lever 13 (step S100), and then obtains the pump discharge pressure as a sensor value (detected value) from the pump discharge pressure sensors 21a and 21b (step S101).

[0038] Next, a pump target flow rate a is calculated from the operation amount of the operating lever according to a control map previously set in the controller 32 (step S102).

[0039] Next, a pump target flow rate feedforward term (hereinafter referred to as FF term) is calculated from the pump target discharge pressure in accordance with a calculation method preset in the controller (step S103).

[0040] Next, the difference between the pump target discharge pressure and the pump discharge pressure sensor value is calculated (step S104).

[0041] Next, a feedback control (hereinafter referred to as FB control) preset in the controller is applied to the difference between the pump target discharge pressure and the pump discharge pressure sensor value to calculate a pump target flow rate FB term (step S105).

[0042] Next, the pump target flow rate FF term and the pump target flow rate FB term are added together to calculate the pump target flow rate b (step S106).

[0043] Next, the target pump flow rate a and the target pump flow rate b are compared, the maximum value (the larger value) is selected and output as the target pump flow rate (step S107).

[0044] Next, a target current for the electromagnetic valve for flow rate control is calculated from the pump target flow rate according to a map preset in the controller (step S108).

[0045] Subsequently, the controller 32 outputs the target current for the solenoid valve for controlling the pump flow rate to the solenoid valves 22a and 22b for controlling the pump regulator (step S109), and the process ends.

[0046] The effects of the present embodiment configured as above will be described.

[0047] In the following explanation, the operation of the arm 5 will be taken as an example to explain the effects, but similar effects can also be obtained when operating other hydraulic actuators such as the boom 4 and bucket 6.

[0048] <When not in operation> When the hydraulic excavator 100 is not being operated, the lever operation amount is minimized, and the pump target flow rate a (see the output of the pump target flow rate calculation unit 32a in FIG. 3) is also minimized. On the other hand, if the pump discharge pressure sensor value is small relative to the pump target discharge pressure, the pump target flow rate b (see the output of the feedback control unit 32d in FIG. 3) increases through feedback control. At this time, the pump target flow rate selection unit 32g selects the pump target flow rate b with a larger value, and calculates and outputs the solenoid valve target current for pump flow rate control based on this. When the discharge flow rate is high, pressure loss in the neutral oil passage increases, so the pump discharge pressure can be maintained at a constant level through feedback control. This makes it possible to supply a pressure above a certain level to the pressure reducing valve and ensure normal operation of the pilot hydraulic circuit.

[0049] <When working with the front work implement> The flow of pressure oil during arm retraction when the front working implement 3 is in the air will be described.

[0050] FIG. 5 is a diagram showing the pump target flow rate, the pump target discharge pressure, and the change over time of the pump discharge pressure according to this embodiment.

[0051] Before the operator operates the operating lever 13 corresponding to the arm 5, the pump target flow rate b calculated by feedback control is selected as the pump target flow rate, and the pump discharge pressure 53 is controlled according to the pump target discharge pressure 52.

[0052] When the operator operates the operating lever 13 corresponding to the arm 5 (operation ON), a pilot command acts on the arm 2 directional control valve 25 and the arm 1 directional control valve 29, and pressure oil from the first hydraulic pump 20a and the second hydraulic pump 20b is guided to the arm cylinder 8. In addition, the flow rates of the first hydraulic pump 20a and the second hydraulic pump 20b are controlled by a solenoid valve target current for pump flow rate control.

[0053] When the arm 5 starts moving, pressure acts to accelerate the arm cylinder 8, so the pump pressure becomes a high value. If the target pump pressure is set to several MPa, the pump discharge pressure will be higher than this. In this case, the target flow rate of the pump is selected as the pump target flow rate a calculated according to a preset control map, and the pressure oil discharged from the first hydraulic pump 20a and the second hydraulic pump 20b flows into the arm cylinder 8 through the directional control valves 25, 29. As a result, the vehicle body is controlled so as to operate the arm cylinder 8 at the target speed according to the preset control map.

[0054] A short time after the arm 5 starts moving, depending on conditions such as the weight of the front working implement 3, the arm cylinder 8 may exceed the speed at which the pressure oil discharged from the first hydraulic pump 20a and the second hydraulic pump 20b pushes the arm cylinder 8, resulting in a cylinder speed caused by the front working implement 3 falling due to its own weight. At this time, the pressure oil discharged from the first hydraulic pump 20a and the second hydraulic pump 20b is in a state close to no load, and the pump discharge pressure takes on a value smaller than the target pump discharge pressure. In this case, the target pump flow rate is selected as the pump flow rate, which attempts to maintain the target pump discharge pressure through feedback control. As a result, the first hydraulic pump 20a and the second hydraulic pump 20b discharge a sufficient amount of pressure oil to withstand the fall of the front working implement 3 due to its own weight, and the discharged pressure oil flows into the arm cylinder 8 through the directional control valves 25 and 29. At this time, the first hydraulic pump 20a and the second hydraulic pump 20b are not in a no-load state, and the pump discharge pressure is controlled to the target pump discharge pressure. This allows a pressure above a certain level to be supplied to the pressure reducing valve, ensuring normal operation of the pilot hydraulic circuit.

[0055] As described above, when the hydraulic actuator is not in operation, the pump discharge pressure can be controlled to the pump target discharge pressure by feedback control. In addition, there is little influence from hydraulic oil temperature or individual differences in hydraulic equipment. Furthermore, when the hydraulic actuator meter-in pressure exceeds the pump target discharge pressure, when the hydraulic actuator is in operation, the pump volume can be controlled to the pump target flow rate calculated in response to the operation of the operating lever 13, and a flow rate sufficient for operation can be supplied to the hydraulic actuator. In addition, the pump discharge pressure can be controlled while maintaining a pressure equal to or higher than the pump target discharge pressure. 。 Furthermore, during operation, when the hydraulic actuator meter-in pressure is equal to or lower than the pump target discharge pressure, the pump volume is controlled by feedback control so that the pump discharge pressure becomes the pump target discharge pressure, and the pump discharge pressure can be set to the pump target discharge pressure.

[0056] A known prior art technology controls pump discharge pressure using a bypass sequence valve located upstream of a hydraulic actuator directional control valve when the hydraulic actuator is not in operation, and opens the bypass sequence valve when the hydraulic actuator is in operation, allowing pressurized oil to be supplied to the hydraulic actuator. However, under conditions where the load on the hydraulic actuator becomes negative due to changes in weight, such as when the front work equipment is subjected to its own weight, the pump pressure and the meter-in pressure of the hydraulic actuator do not increase, and there is a risk that the necessary pressure cannot be supplied to the pilot hydraulic circuit. In other words, if the pump discharge pressure falls below the pressure required for pilot drive, normal pilot commands will not be applied to the entire pilot circuit, which can lead to unstable vehicle operation.

[0057] In contrast to this, in this embodiment, the system comprises a vehicle body (undercarriage 1, upper revolving body 2), a working implement (front working implement 3) attached to the vehicle body, an operating lever 13 that outputs an operation signal for operating the working implement, hydraulic actuators (boom cylinder 7, arm cylinder 8, bucket cylinder 9) that drive the working implement, variable displacement hydraulic pumps (first hydraulic pump 20a, second hydraulic pump 20b) that supply pressure oil to the hydraulic actuators, pump discharge pressure sensors 21a, 21b that detect the discharge pressure of the hydraulic pumps, directional control valves 26-31 that control the flow rate and direction of pressure oil supplied from the hydraulic pumps to the hydraulic actuators, and hydraulic pumps (first hydraulic pump 20a, second hydraulic pump 20b) that adjust the hydraulic pressure in response to an operation signal from the operating lever. In a work machine (hydraulic excavator 100) equipped with a controller 32 that controls a pump and a directional control valve, the controller 32 is configured to calculate a first target flow rate (pump target flow rate a) based on the amount of operation of an operating lever, calculate a second target flow rate (pump target flow rate b) based on a predetermined pump target discharge pressure and the detection results of a pump discharge pressure sensor, calculate a target flow rate for the hydraulic pump based on the larger of the first target flow rate and the second target flow rate, and control the hydraulic pump based on the target flow rate. Therefore, the pump pressure can be controlled to a certain level or higher regardless of load conditions, and the pressure required for the pilot hydraulic circuit can be stably supplied. That is, in this embodiment, by setting the pump target discharge pressure to a pressure higher than the pressure required for pilot drive, the pump discharge pressure will not fall below the pressure required for pilot drive, and vehicle body operation can be stabilized.

[0058] <Other> The present invention is not limited to the above-described embodiment, but includes various modifications within the scope of the gist thereof.

[0059] For example, in the above embodiment, a case where a predetermined target pump discharge pressure is used has been described as an example. However, the present invention is not limited to this. The target pump discharge pressure may be switched depending on the operating state of the vehicle body, i.e., one value may be selected from multiple set values ​​and set as the target pump discharge pressure. Specifically, for example, when the main pump is not being operated, the target pump discharge pressure may be lowered to the limit pressure at which the pilot hydraulic circuit operates normally to reduce the drive energy of the main pump, and when the main pump is being operated, the target pump discharge pressure may be raised to provide a margin for transient pressure drops. Alternatively, a low pressure may be set when the gate lock lever 14 (operation lock lever) provided in the cab 2a is in the locked state, and a higher pressure may be set when the gate lock lever 14 is in the unlocked state.

[0060] Furthermore, in the above embodiment, as shown in FIG. 3 etc., an example has been given in which the target pump flow rate is the larger of the target pump flow rate a (first target flow rate) calculated from the operation amount of the operating lever, the target pump flow rate b (second target flow rate) obtained by adding together the value obtained by applying feedback control to the difference between the target pump discharge pressure and the pump discharge pressure sensor value (target pump flow rate FB term) and the value obtained by applying feedforward calculation to the target pump discharge pressure (target pump flow rate FF term). However, in addition to this, the target pump flow rate may be a third target flow rate (target pump flow rate c) obtained by applying feedback control to the difference between the target pump discharge pressure and the pump discharge pressure sensor value (target pump flow rate FB term), and the largest value among the first target flow rate (target pump flow rate a), the second target flow rate (target pump flow rate b), and the third target flow rate (target pump flow rate c) may be used as the target pump flow rate.

[0061] Furthermore, for example, the present invention is not limited to those including all of the configurations described in the above embodiments, and also includes those in which some of the configurations are omitted. Furthermore, part of the configuration of one embodiment can be added to or substituted for the configuration of another embodiment. Furthermore, the configurations of the above control device, as well as their functions and execution processes, may be implemented in part or in whole by hardware (e.g., by designing logic that executes each function using an integrated circuit). Furthermore, the configurations of the above control device may be implemented as programs (software) that are read and executed by an arithmetic processing device (e.g., a CPU) to realize the functions of the configurations of the control device. Information related to the programs can be stored, for example, in semiconductor memory (flash memory, SSD, etc.), magnetic storage devices (hard disk drives, etc.), and recording media (magnetic disks, optical disks, etc.). [Explanation of symbols]

[0062] 1...lower traveling body, 2...upper rotating body, 2a...operator's cab, 3...front working device, 4...boom, 5...arm, 6...bucket, 7...boom cylinder, 8...arm cylinder, 9...bucket cylinder, 10...swing hydraulic motor, 11, 12...travel hydraulic motor, 13...operating lever, 14...gate lock lever, 14a...electromagnetic proportional valve, 20a...first hydraulic pump, 20b...second hydraulic pump, 21a, 21b...pump discharge pressure sensor, 22a, 22b...pump regulator control solenoid valve, 23...right traveling direction control valve, 24...bucket direction control valve, 25...arm Boom 2-way control valve, 26...Boom 1-way control valve, 27...Swing directional control valve, 28...Boom 2-way control valve, 29...Arm 1-way control valve, 30...Backup directional control valve, 31...Left travel directional control valve, 32...Controller, 32a...Pump target flow rate calculation unit, 32b...Memory unit, 32c...Difference calculation unit, 32d...Feedback control unit, 32e...Feedforward calculation unit, 32f...Adder, 32g...Pump target flow rate selection unit, 32h...Solenoid valve target current calculation unit, 51...Pump target flow rate, 52...Pump target discharge pressure, 53...Pump discharge pressure, 100...Hydraulic excavator

Claims

1. The car body and a working device attached to the vehicle body; an operating lever that outputs an operating signal for operating the working device; a hydraulic actuator that drives the working device; a variable displacement hydraulic pump that supplies pressure oil to the hydraulic actuator; a pump discharge pressure sensor for detecting the discharge pressure of the hydraulic pump; a directional control valve for controlling the flow rate and direction of pressure oil supplied from the hydraulic pump to the hydraulic actuator; a controller that controls the hydraulic pump and the directional control valve in response to an operation signal from the operation lever, The controller A first target flow rate is calculated based on the operation amount of the operating lever, and calculating a second target flow rate based on a predetermined target pump discharge pressure and the discharge pressure detected by the pump discharge pressure sensor; a target flow rate of the hydraulic pump is calculated based on the larger value of the first target flow rate and the second target flow rate, and the hydraulic pump is controlled based on the calculated target flow rate of the hydraulic pump.

2. 2. The work machine according to claim 1, The working machine is characterized in that the controller changes the pump target discharge pressure in accordance with an operating state of the working device.

3. 2. The work machine according to claim 1, an operation lock lever provided in a driver's cab on the vehicle body for switching between enabling and disabling operation by the operation lever; The working machine is characterized in that the controller changes the pump target discharge pressure in accordance with the position of the operation lock lever.

4. 2. The work machine according to claim 1, The controller calculating a second target flow rate based on a value obtained by applying feedback control to a difference between the predetermined target pump discharge pressure and a discharge pressure detected by a pump discharge pressure sensor, and a value obtained by applying feedforward calculation to the target pump discharge pressure; calculating a third target flow rate based on a value obtained by applying feedback control to a difference between the pump target discharge pressure and the detection result of the pump discharge pressure sensor; A work machine characterized in that the target flow rate of the hydraulic pump is calculated based on the largest value among the first target flow rate, the second target flow rate, and the third target flow rate.

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