Working machinery

Abstract

This work machine comprises: a pressure adjustment device capable of adjusting a driving pressure of a turning hydraulic motor; and a controller that controls the pressure adjustment device. The controller calculates a target pressure of the turning hydraulic motor, on the basis of a speed deviation between a target speed of the turning hydraulic motor calculated on the basis of an operation signal of an operation device and an actual driving speed of the turning hydraulic motor detected by a speed sensor, limits the target pressure of the calculation result so that an input horsepower to the turning hydraulic motor which is estimated on the assumption that the driving pressure of the turning hydraulic motor reaches the target pressure after a predetermined time does not exceed a limit value, and controls the pressure adjustment device on the basis of the limited target pressure.

Description

Technical Field

[0001] The present invention relates to a working machine, and more particularly to a working machine provided with a revolving body capable of revolving by a hydraulic motor.

Background Art

[0002] In a hydraulic working machine such as a hydraulic excavator, a working device composed of link members such as a boom and an arm is driven by a hydraulic actuator such as a hydraulic cylinder. Further, a revolving body is rotationally driven with respect to a traveling body by a hydraulic motor which is a hydraulic actuator. In a working machine, a portion driven by a hydraulic actuator generally has a large inertial mass, and operation control during acceleration and deceleration occupies a large proportion of the working time. The acceleration and deceleration of the working device and the upper revolving body are determined by the driving cylinder thrust or the motor torque. Therefore, in order to control the cylinder thrust and the motor torque, it is required to accurately control the driving pressure of the hydraulic actuator to a target value. In a general hydraulic excavator, the acceleration and deceleration of the working device and the upper revolving body are adjusted by adjusting the pressure of a hydraulic circuit by a relief valve, a bleed-off valve, or the like.

[0003] On the other hand, Patent Document 1 describes a technique for controlling the pressure of pressure oil supplied to a hydraulic motor (the output torque of the hydraulic motor) by adjusting the capacity (flow rate) of a hydraulic pump (swing pump) so that the pressure of the hydraulic pump detected by a pressure detection device during the swing drive of a working machine becomes a predetermined target pressure. According to this technique, it is said that the output of the hydraulic motor can be arbitrarily adjusted.

[0004] Further, in the working machine described in Patent Document 1, when there is a possibility that the output of the hydraulic pump exceeds the maximum output of the engine, output control of the hydraulic pump is performed. Specifically, when the output of the hydraulic pump is near the maximum output of the engine, by reducing the target pressure of the hydraulic pump, while securing the discharge flow rate of the hydraulic pump, control (horsepower limitation) is realized in which the output of the hydraulic pump does not exceed the maximum output of the engine.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-234683 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In rotary hydraulic actuators such as swing hydraulic motors, if the torque is kept constant, the required flow rate will continue to increase over time if no external force is acting on it. Under these circumstances, if the target pressure of the hydraulic pump is suddenly reduced at the moment when the product of the discharge flow rate and pressure of the hydraulic pump approaches or reaches the maximum output (horsepower limit) of the engine, as in the technology described in Patent Document 1, the torque of the swing hydraulic motor will drop sharply, which may cause discomfort to the operator. On the other hand, if the target pressure of the hydraulic pump is kept low in advance so as not to reach the maximum output (horsepower limit) of the engine, the engine's output (horsepower) cannot be fully utilized, especially when the swing hydraulic motor starts moving.

[0007] The present invention was made to solve the above-mentioned problems, and its objective is to provide a work machine that can drive a rotary hydraulic actuator with appropriate torque and acceleration within the horsepower limit. [Means for solving the problem]

[0008] The present invention includes multiple means for solving the above problems. To give one example, in a work machine comprising a hydraulic pump that discharges pressurized oil, a slewing body capable of slewing motion, a hydraulic actuator that drives the slewing body to slewing motion by supplying pressurized oil from the hydraulic pump, an operating device that outputs an operating signal to instruct the movement of the slewing body, and a speed sensor that detects the driving speed of the hydraulic actuator, the present invention further comprises a pressure adjustment device capable of adjusting the driving pressure of the hydraulic actuator and a controller that controls the pressure adjustment device, wherein the controller calculates the target speed of the hydraulic actuator based on the operating signal from the operating device, and calculates the target pressure of the hydraulic actuator based on the speed deviation, which is the difference between the calculated target speed and the actual driving speed of the hydraulic actuator detected by the speed sensor, From the detection value of the speed sensor, the actual driving speed and actual driving acceleration of the hydraulic actuator are obtained Estimated Based on the drive speed after a predetermined time of the hydraulic actuator, The horsepower supplied to the hydraulic actuator does not exceed the limit value. The pressure limit value of the hydraulic actuator is calculated. , Depending on the calculated pressure limit value The pressure regulator is configured to control the pressure regulator based on a limited target pressure. [Effects of the Invention]

[0009] According to the present invention, the pressure regulator is controlled using a predetermined target pressure of the hydraulic actuator, taking into account the horsepower input to the hydraulic actuator estimated at a future time after a predetermined period of time. This makes it possible to drive the hydraulic actuator with appropriate torque and acceleration within the horsepower limit range. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] This is an external view showing a hydraulic excavator as one embodiment of the work machine of the present invention. [Figure 2] This is a hydraulic circuit diagram showing a hydraulic system mounted on one embodiment of the work machine of the present invention. [Figure 3] Figure 2 is a control block diagram of a controller that constitutes a part of one embodiment of the work machine of the present invention. [Figure 4] Figure 3 is a block diagram showing the details of the target angular velocity calculation unit, the first target pump flow rate calculation unit, and the target torque calculation unit in the controller's control block diagram. [Figure 5] This is a correspondence table showing the details of the target meter-in pressure calculation unit in the controller control block diagram shown in Figure 3. [Figure 6] Figure 3 is a block diagram showing the details of the meter-in pressure limit calculation unit in the control block diagram of the controller shown. [Figure 7] This block diagram shows the details of the second target value calculation unit for pump flow rate in the controller shown in Figure 3. [Figure 8] Figure 3 is a block diagram showing the details of the angular velocity deviation ratio calculation unit in the controller's control block diagram. [Figure 9] Figure 3 is a block diagram showing the details of the pump flow rate control target value calculation unit and the bleed-off opening target value calculation unit in the controller's control block diagram. [Figure 10] This figure shows the time waveform of the simulation results regarding the behavior of the hydraulic pump and hydraulic motor during a rotation operation in a comparative example work machine with respect to one embodiment of the work machine of the present invention. [Figure 11] This figure shows the time waveform of the simulation results regarding the behavior of the hydraulic pump and hydraulic motor during a rotation operation in one embodiment of the work machine of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the work machine of the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator will be used as an example of a work machine. [One Embodiment] First, the schematic configuration of a hydraulic excavator as one embodiment of the work machine of the present invention will be described using Figure 1. Figure 1 is an external view showing a hydraulic excavator as one embodiment of the work machine of the present invention. Here, the explanation will be given from the perspective of an operator seated in the driver's seat.

[0012] In FIG. 1, the hydraulic excavator includes a self - propelled lower traveling body 1 and an upper revolving body 2 mounted rotatably on the lower traveling body 1. The lower traveling body 1 and the upper revolving body 2 constitute the body of the hydraulic excavator. A front working device 3 for performing excavation work and the like is rotatably attached to the front side of the upper revolving body 2.

[0013] The lower traveling body 1 has crawler - type traveling devices 11 (only one side is shown in FIG. 1) on both the left and right sides. The traveling device 11 is driven by a traveling hydraulic motor 12 which is a hydraulic actuator.

[0014] The upper revolving body 2 is configured to be rotationally driven about a rotation axis x with respect to the lower traveling body 1 by a revolving device (not shown) including a revolving hydraulic motor 33 (see FIG. 2 described later) which is a hydraulic actuator and its reduction mechanism. The upper revolving body 2 has a cab 14 on its front side where an operator rides. A joystick 56 (see FIG. 2 described later) as an operating device described later is arranged in the cab 14. The upper revolving body 2 houses a hydraulic pump 31, various valves 34, 35, 36, 37, 39, 40, 41, 42 (see FIG. 2 described later), etc.

[0015] The front working device 3 is, for example, an articulated working device configured by connecting a plurality of driven members so as to be rotatable in the vertical direction. The plurality of driven members are composed of, for example, a boom 16, an arm 17, and a bucket 18 as a working tool. The boom 16, the arm 17, and the bucket 18 are each driven by a boom cylinder 21, an arm cylinder 22, and a bucket cylinder 23 which are hydraulic actuators.

[0016] Next, the configuration of the hydraulic system mounted on an embodiment of the working machine of the present invention will be described with reference to FIG. 2. FIG. 2 is a hydraulic circuit diagram showing the hydraulic system mounted on an embodiment of the working machine of the present invention.

[0017] In Figure 2, the hydraulic excavator is equipped with a hydraulic system 30 that hydraulically drives the lower traveling body 1, the upper slewing body 2, and the front working device 3 (see Figure 1 for both). Note that in Figure 2, only the hydraulic circuit for the slewing hydraulic motor 33 that drives the slewing of the upper slewing body 2 is shown, and the hydraulic circuits for the traveling hydraulic motor 12 that drives the traveling device 11, and the boom cylinder 21, arm cylinder 22, and bucket cylinder 23 that drive the front working device 3 are omitted.

[0018] The hydraulic system 30 includes a hydraulic pump 31 driven by a prime mover 32 (e.g., an electric motor or engine) to discharge pressurized oil, and a slewing hydraulic motor 33 that drives the upper slewing body 2 to slewing by the supply of pressurized oil from the hydraulic pump 31. The hydraulic pump 31 is a variable displacement pump and has a regulator 31a that adjusts the pump volume. The regulator 31a functions as a flow rate adjustment device that can adjust the discharge flow rate of the hydraulic pump 31, and also functions as a pressure adjustment device that can adjust the driving pressure of the slewing hydraulic motor 33 by adjusting the discharge flow rate of the hydraulic pump 31. The regulator 31a adjusts the pump volume in response to a control signal from the controller 60, for example. The slewing hydraulic motor 33 has a pair of input / output ports, a first port 33a and a second port 33b. The slewing hydraulic motor 33 is, for example, a fixed displacement hydraulic motor.

[0019] The pressurized oil discharged from the hydraulic pump 31 is supplied to the slewing hydraulic motor 33 via a load check valve 34 and a directional control valve 35. The load check valve 34 is located on the discharge line 44 connecting the hydraulic pump 31 and the directional control valve 35. The load check valve 34 allows the flow of pressurized oil from the hydraulic pump 31 to the directional control valve 35, while blocking the flow of pressurized oil from the directional control valve 35 to the hydraulic pump 31. The directional control valve 35 controls the flow (direction and flow rate) of pressurized oil supplied from the hydraulic pump 31 to the slewing hydraulic motor 33. The position (stroke amount) of the directional control valve 35 is controlled according to a control signal (excitation current) from the controller 60.

[0020] A bleed-off valve 36 is provided on line 47, which branches off from the discharge line 44 and connects to the hydraulic oil tank 38. The bleed-off valve 36 allows the discharge pressure of the hydraulic pump 31 to be adjusted according to its opening degree. In other words, the bleed-off valve 36 functions as a pressure regulating device that can adjust the drive pressure of the swing hydraulic motor 33 by releasing the pressurized oil discharged from the hydraulic pump 31 into the hydraulic oil tank 38 according to its opening degree. The discharge port of the hydraulic pump 31 is also connected to the hydraulic oil tank 38 via a main relief valve 37. The main relief valve 37 defines the upper limit of the discharge pressure of the hydraulic pump 31 and is configured to open when the discharge pressure of the hydraulic pump 31 exceeds the set pressure.

[0021] The first port 33a and the second port 33b of the swing hydraulic motor 33 are connected to the directional control valve 35 via the first line 45 and the second line 46, respectively. The first port 33a and the second port 33b of the swing hydraulic motor 33 are connected to the first swing relief valve 39 and the second swing relief valve 40 via the first line 45 and the second line 46, respectively. The first swing relief valve 39 and the second swing relief valve 40 open when the pressure in the first line 45 and the second line 46 exceeds a set pressure, respectively, thereby connecting the first line 45 and the second line 46 to the hydraulic oil tank 38, and thus perform an overload prevention function for the swing hydraulic motor 33. In addition, the first port 33a and the second port 33b of the swing hydraulic motor 33 are connected to the first makeup check valve 41 and the second makeup check valve 42 via the first line 45 and the second line 46, respectively. The first makeup check valve 41 blocks the flow of pressurized oil from the first line 45 to the hydraulic oil tank 38, while allowing the flow of hydraulic oil from the hydraulic oil tank 38 to the first line 45. The second makeup check valve 42 blocks the flow of pressurized oil from the second line 46 to the hydraulic oil tank 38, while allowing the flow of hydraulic oil from the hydraulic oil tank 38 to the second line 46. The first makeup check valve 41 and the second makeup check valve 42 are responsible for the anti-void function of the slewing hydraulic motor 33.

[0022] First pressure sensors 51a and 51b are provided on the first line 45 and the second line 46, respectively, to detect the pressure (drive pressure) on the first port 33a side and the second port 33b side of the slewing hydraulic motor 33. The first pressure sensors 51a and 51b output pressure detection signals to the controller 60 according to the detected pressure on the first port 33a side and the second port 33b side (drive pressure). A second pressure sensor 52 is provided on the discharge line 44 to detect the discharge pressure of the hydraulic pump 31. The second pressure sensor 52 outputs a discharge pressure detection signal to the controller 60 according to the detected discharge pressure. In addition, a speed sensor 54 is installed on the slewing hydraulic motor 33 to detect the actual angular velocity (drive speed) of the slewing hydraulic motor 33. The speed sensor 54 outputs an angular velocity detection signal to the controller 60 according to the detected angular velocity.

[0023] The hydraulic system 30 further includes a joystick 56 as an operating device for instructing the rotational movement of the upper rotating body 2 or the driving of the rotational hydraulic motor 33. The joystick 56 outputs an operating signal to the controller 60 according to its operating angle.

[0024] The controller 60 acquires a rotation operation signal from the joystick 56, an angular velocity detection signal from the speed sensor 54 (the actual angular velocity of the rotation hydraulic motor 33 detected by the speed sensor 54), pressure detection signals from the first pressure sensors 51a and 51b (the pressure on the first port 33a side and the pressure on the second port 33b side of the rotation hydraulic motor 33 detected by the first pressure sensors 51a and 51b), and a discharge pressure detection signal from the second pressure sensor 52 (the discharge pressure of the hydraulic pump 31 detected by the second pressure sensor 52). Based on these operation signals and detection signals, the controller 60 performs predetermined calculations and outputs control signals to the regulator 31a, directional control valve 35, and bleed-off valve 36 of the hydraulic pump 31 according to the calculation results. Details of these calculations will be described later. The controller 60 ultimately controls the drive pressure and motor flow rate of the rotation hydraulic motor 33 (the rotation operation of the upper rotation body 2) by directly controlling the pump volume (pump flow rate) of the hydraulic pump 31, the drive of the directional control valve 35, and the drive of the bleed-off valve 36.

[0025] Next, the general functions of a controller that constitutes a part of one embodiment of the work machine of the present invention will be explained using Figure 3. Figure 3 is a control block diagram of a controller that constitutes a part of one embodiment of the work machine of the present invention shown in Figure 2.

[0026] In Figure 3, the controller 60 includes, for example, a storage device 61 consisting of RAM or ROM, and a processing device 62 consisting of a CPU or MPU. The storage device 61 has programs and various information necessary to control the pump volume (pump flow rate) of the hydraulic pump 31, the drive of the directional control valve 35, and the drive of the bleed-off valve 36 stored in advance. The processing device 62 reads programs and various information from the storage device 61 as appropriate and performs various functions by executing processing according to the programs. The controller 60 in this embodiment controls the drive of the swing hydraulic motor 33 by speed control using a speed target value or pressure control using a pressure target value that takes horsepower limits into consideration in advance, and mainly includes the following control function units.

[0027] The controller 60 has a directional control valve control unit 71 that receives a rotation operation signal from the joystick 56, which is an operating device, and outputs a drive control signal to the directional control valve 35. The directional control valve control unit 71 calculates the target opening value of the directional control valve 35 by referring to a first table (not shown) from the rotation operation signal, and converts the calculated target opening value into a drive command value (command current value) by referring to a second table (not shown). The directional control valve control unit 71 outputs a drive control signal of the drive command value to the directional control valve 35.

[0028] The controller 60 includes a target angular velocity calculation unit 73 that receives a rotation operation signal from the operating device 56 and outputs a target angular velocity ωt of the rotation hydraulic motor 33. Details of the calculations performed by the target angular velocity calculation unit 73 will be described later.

[0029] The controller 60 includes a pump flow rate first target value calculation unit 74 that receives the target angular velocity ωt of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73, and outputs a first target value Qt1 for the pump flow rate of the hydraulic pump 31. The first target value Qt1 for the pump flow rate is derived from the target angular velocity ωt of the slewing hydraulic motor 33 and is a target value used for speed control of the slewing hydraulic motor 33. Details of the calculation by the pump flow rate first target value calculation unit 74 will be described later.

[0030] The controller 60 also includes a target torque calculation unit 76, a target meter-in pressure calculation unit 77, a meter-in pressure limit value calculation unit 78, and a second target pump flow rate calculation unit 79. These calculation units 76 to 79 derive the second target pump flow rate Qt2 of the hydraulic pump 31, which is a target value used for pressure control of the slewing hydraulic motor 33. The target torque calculation unit 76 takes in the target angular velocity ωt of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73, the actual angular velocity (drive speed) of the slewing hydraulic motor 33 from the speed sensor 54, and the slewing operation signal from the operating device 56, and outputs the target torque Tt of the slewing hydraulic motor 33. The target meter-in pressure calculation unit 77 takes in the target torque Tt, which is the calculation result of the target torque calculation unit 76, and outputs the target meter-in pressure Pt of the slewing hydraulic motor 33. The meter-in pressure limit calculation unit 78 receives the actual angular velocity (drive speed) and actual angular acceleration (drive acceleration) of the swing hydraulic motor 33 from the speed sensor 54, and outputs a limit value PL for the meter-in pressure of the swing hydraulic motor 33 to limit the horsepower input to the swing hydraulic motor 33 to below the horsepower limit value (horsepower limit). The pump flow rate second target value calculation unit 79 receives the target meter-in pressure Pt, which is the calculation result of the target meter-in pressure calculation unit 77, the meter-in pressure limit value PL, which is the calculation result of the meter-in pressure limit calculation unit 78, and the pressure (drive pressure) of the swing hydraulic motor 33 from the first pressure sensors 51a and 51b, and outputs a pump flow rate second target value Qt2. Details of the calculations of the target torque calculation unit 76, target meter-in pressure calculation unit 77, meter-in pressure limit calculation unit 78, and pump flow rate second target value calculation unit 79 will be described later.

[0031] The controller 60 also includes an angular velocity deviation ratio calculation unit 81 that takes in the target angular velocity ωt of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73, and the actual angular velocity of the slewing hydraulic motor 33 from the speed sensor 54, and outputs an angular velocity deviation ratio R. The angular velocity deviation ratio R is an indicator that switches the drive control of the slewing hydraulic motor 33 between speed control and pressure control, and is also an indicator that switches the opening and closing of the bleed-off valve 36. Details of the calculation by the angular velocity deviation ratio calculation unit 81 will be described later.

[0032] Furthermore, the controller 60 includes a pump flow rate control target value calculation unit 83 that takes in the first target pump flow rate Qt1, which is the calculation result of the first target pump flow rate calculation unit 74, the second target pump flow rate Qt2, which is the calculation result of the second target pump flow rate calculation unit 79, and the angular velocity deviation ratio R, which is the calculation result of the angular velocity deviation ratio calculation unit 81, calculates the pump flow rate control target value Qc for the hydraulic pump 31, and outputs a control signal corresponding to the pump flow rate control target value Qc to the regulator 31a of the hydraulic pump 31. The pump flow rate control target value Qc is the final control target value for the discharge flow rate (pump capacity) of the hydraulic pump 31. Details of the calculation by the pump flow rate control target value calculation unit 83 will be described later.

[0033] The controller 60 includes a bleed-off opening target value calculation unit 85 that receives the angular velocity deviation ratio R, which is the calculation result of the angular velocity deviation ratio calculation unit 81, calculates the opening target value Vt of the bleed-off valve 36, and outputs a control signal to the bleed-off valve 36 according to the opening target value Vt. Details of the calculation performed by the bleed-off opening target value calculation unit 85 will be described later.

[0034] Next, an example of the details of the calculations of each function of the controller in one embodiment of the work machine of the present invention will be explained using Figures 4 to 10. Figure 4 is a block diagram showing the details of the target angular velocity calculation unit, the pump flow rate first target value calculation unit, and the target torque calculation unit in the control block diagram of the controller shown in Figure 3.

[0035] As shown in Figure 4, the target angular velocity calculation unit 73 calculates the target angular velocity (target speed) of the slewing hydraulic motor 33 by referring to the table 731 based on the slewing operation signal input from the operating device 56. The slewing operation signal is output in a range from -100 to +100, for example. 0 is output for no operation, -100 for the maximum amount of left slewing operation, and +100 for the maximum amount of right slewing operation. In the table 731, the angular velocity for left slewing is represented as - and the angular velocity for right slewing is represented as +, depending on the sign of the slewing operation signal. The target angular velocity calculation unit 73 outputs the calculated target angular velocity to the pump flow rate first target value calculation unit 74, the target torque calculation unit 76, and the angular velocity deviation ratio calculation unit 81 (see Figure 8, described later).

[0036] In the pump flow rate first target value calculation unit 74, the calculation unit 741 takes the absolute value of the target angular velocity, which is the calculation result of the target angular velocity calculation unit 73. Furthermore, the pump flow rate first target value is calculated by multiplying the absolute value of the target angular velocity by the equivalent slewing volume q (the volume required to rotate the upper slewing body 2 at a unit angular velocity). The pump flow rate first target value is directly derived based on the target angular velocity of the slewing hydraulic motor 33 and is a control value for controlling the speed of the slewing hydraulic motor 33. The pump flow rate first target value calculation unit 74 outputs the calculated pump flow rate first target value to the pump flow rate control target value calculation unit 83 (see Figure 9 described later).

[0037] In the target torque calculation unit 76, first, the calculation unit 761 calculates the angular velocity deviation by subtracting the actual angular velocity (angular velocity detection value) of the slewing hydraulic motor 33 detected by the velocity sensor 54 from the target angular velocity of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73. Next, the calculation unit 762 multiplies the angular velocity deviation, which is the calculation result of the calculation unit 761, by a preset proportional gain Kp. Then, the target torque Tt of the slewing hydraulic motor 33 is calculated by referring to the table 763 based on the output value of the calculation unit 762. However, the torque limit value of the slewing hydraulic motor 33 is set using the table 764 based on the slewing operation signal, and the set torque limit value is input to the table 763 to set the upper and lower limits of the input values ​​to the table 763. The target torque calculation unit 76 outputs the calculated target torque Tt to the target meter-in pressure calculation unit 77 (see Figure 5 described later).

[0038] Figure 5 is a correspondence table showing the details of the target meter-in pressure calculation unit in the control block diagram of the controller shown in Figure 3. The target meter-in pressure calculation unit 77 calculates the target meter-in pressure of the swing hydraulic motor 33 based on the swing operation signal of the operating device 56 and the target torque of the swing hydraulic motor 33, which is the calculation result of the target torque calculation unit 76. In the swing hydraulic motor 33, the side into which pressurized oil from the hydraulic pump 31 flows is called the meter-in side, and the side into which pressurized oil flows out is called the meter-out side. In this explanation, the first port 33a of the swing hydraulic motor 33 is considered the meter-in side when turning to the right, and the second port 33b of the swing hydraulic motor 33 is considered the meter-in side when turning to the left.

[0039] As shown in Figure 5, if the operation signal is greater than the threshold th1 (instruction to turn right) and the sign of the target torque Tt calculated by the target torque calculation unit 76 is positive (the direction of torque is the same as the direction of right turn), the calculation result (Tt / q) obtained by dividing the target torque Tt by the equivalent turning volume q is set as the target pressure value of the first port 33a, i.e., the target meter-in pressure. In this case, the target pressure of the second port 33b is 0. Also, if the operation signal is greater than the threshold th1 and the sign of the target torque Tt calculated is negative (the direction of torque is opposite to the direction of right turn), the target pressure value of the first port 33a is set to 0 and the target pressure value of the second port 33b is set to (-Tt / q). The negative sign of the target pressure value of the second port 33b takes into account that the sign of the target torque Tt is negative.

[0040] On the other hand, if the operating signal is smaller than the threshold -th1 (instruction to turn left) and the sign of the calculated target torque Tt is negative, the calculation result (-Tt / q) obtained by dividing the target torque Tt by the equivalent turning volume q is set as the target pressure value of the second port 33b, i.e., the target meter-in pressure. The target pressure of the first port 33a is 0. Also, if the operating signal is smaller than the threshold -th1 (instruction to turn right) and the sign of the calculated target torque Tt is positive, the target pressure value of the second port 33b is set to 0, and the target pressure value of the first port 33a is set to (Tt / q).

[0041] Furthermore, if the operating signal is within the dead zone from -th1 to th1, the meter-in side shall be the same port as the previous port. In this case, the target pressure values ​​for the first port 33a and the second port 33b shall be as shown in Figure 5.

[0042] In this way, the target meter-in pressure calculation unit 77 determines, based on the operation signal, which of the first port 33a and the second port 33b of the swing hydraulic motor 33 is the meter-in side, and calculates the target pressure value on the meter-in side (target meter-in pressure) based on the target torque Tt of the swing hydraulic motor 33, which is the calculation result of the target torque calculation unit 76.

[0043] Figure 6 is a block diagram showing the details of the meter-in pressure limit calculation unit 78 in the control block diagram of the controller shown in Figure 3. In the meter-in pressure limit calculation unit 78, first, the calculation unit 781 multiplies the actual angular acceleration (angular acceleration detection value) of the swing hydraulic motor 33 detected by the speed sensor 54 by a reference time (for example, 0.3 seconds), and then the calculation unit 782 adds the calculation result of the calculation unit 781 to the actual angular velocity (angular velocity detection value) of the swing hydraulic motor 33 detected by the speed sensor 54. These calculations estimate the angular velocity of the swing hydraulic motor 33 at a future time after the reference time has elapsed from the current time at the time of calculation by the controller 60. It is also possible to configure the controller to calculate the actual angular acceleration by performing a differential operation based on the time series of the actual angular velocity (angular velocity detection value) of the swing hydraulic motor 33 detected by the speed sensor 54.

[0044] Next, the calculation unit 783 takes the absolute value of the calculation result of the calculation unit 782 (estimated angular velocity of the slewing hydraulic motor 33 after the reference time has elapsed from the current time), and the calculation unit 784 multiplies the calculation result of the calculation unit 783 by the equivalent slewing volume q. This calculation estimates the drive flow rate of the slewing hydraulic motor 33 at a future time after the reference time has elapsed from the current time.

[0045] Furthermore, the calculation unit 785 divides the calculation result of the calculation unit 784 (estimated flow rate of the swing hydraulic motor 33 after a reference time has elapsed from the current time) by the horsepower input limit value to the swing hydraulic motor 33, and sets upper and lower limits on the calculation result of the calculation unit 785 using the table 786 to calculate a limit value for the meter-in pressure of the swing hydraulic motor 33 that does not exceed the horsepower limit.

[0046] The target meter-in pressure of the swing hydraulic motor 33, calculated by the target meter-in pressure calculation unit 77, is limited by the meter-in pressure limit value calculated by the meter-in pressure limit value calculation unit 78. This calculates a horsepower-limited target meter-in pressure with an upper limit that takes the horsepower limit value into consideration. In other words, these calculations limit the target meter-in pressure so that the horsepower input to the swing hydraulic motor 33, estimated when the drive pressure of the swing hydraulic motor 33 is assumed to reach the target meter-in pressure at a future time after a reference time has elapsed (after a predetermined time), does not exceed the horsepower limit value. The calculated horsepower-limited target meter-in pressure is input to the pump flow rate second target value calculation unit 79 (see Figure 7 below).

[0047] Figure 7 is a block diagram showing the details of the second pump flow rate target value calculation unit 79 in the control block diagram of the controller shown in Figure 3. In the second pump flow rate target value calculation unit 79, first, the calculation unit 791 calculates the pressure deviation by subtracting the actual meter-in pressure of the swing hydraulic motor 33 (pressure detected on the meter-in side of the swing hydraulic motor 33) detected by the first pressure sensors 51a and 51b from the input horsepower limit target meter-in pressure. Next, the pressure deviation calculated by the calculation unit 791 is multiplied by a proportional gain Kp2 by the calculation unit 792, and after integration processing by the calculation unit 793, it is multiplied by an integral gain Ki by the calculation unit 794. Then, the calculation unit 795 adds the calculation result of the calculation unit 793 and the calculation result of the calculation unit 794, and limits the calculation result of the calculation unit 795 to an upper and lower limit by the table 796, thereby calculating the second pump flow rate target value of the hydraulic pump 31. The second target pump flow rate is derived based on the pressure deviation, which is the difference between the horsepower limit target meter-in pressure and the actual meter-in pressure, and is a control value for controlling the pressure of the slewing hydraulic motor 33. The limit set by Table 796 is, for example, to limit the pressure from 0 MPa to the set pressure of the main relief valve 37 of the hydraulic circuit. The second target pump flow rate calculation unit 79 outputs the calculated second target pump flow rate to the pump flow rate control target value calculation unit 83 (see Figure 9 described later). In this explanation, the calculation unit 791 that calculates the pressure deviation receives the pressure detection values ​​from the first pressure sensors 51a and 51b, but if the discharge pressure of the hydraulic pump 31 can be considered to be an approximation of the meter-in pressure of the slewing hydraulic motor 33, it is also possible to input the pressure detection value of the second pressure sensor 52 to the calculation unit 791.

[0048] Figure 8 is a block diagram detailing the angular velocity deviation ratio calculation unit 81 in the control block diagram of the controller shown in Figure 3. In the angular velocity deviation ratio calculation unit 81, the calculation unit 811 calculates the angular velocity deviation by subtracting the actual angular velocity (angular velocity detection value) of the slewing hydraulic motor 33 detected by the velocity sensor 54 from the target angular velocity of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73. Next, the calculation unit 812 performs processing to prevent division by zero on the target angular velocity of the slewing hydraulic motor 33, which is the calculation result of the target angular velocity calculation unit 73. Then, the calculation unit 813 divides the angular velocity deviation, which is the calculation result of the calculation unit 811, by the target angular velocity of the slewing hydraulic motor 33 after processing by the calculation unit 812, and the calculation unit 814 calculates the angular velocity deviation ratio by taking the absolute value of the calculation result of the calculation unit 813. In other words, the angular velocity deviation ratio represents the ratio of the angular velocity deviation to the target angular velocity. The angular velocity deviation ratio calculation unit 81 outputs the calculated angular velocity deviation ratio to the pump flow rate control target value calculation unit 83 (see Figure 9, described later).

[0049] Figure 9 is a block diagram showing the details of the pump flow rate control target value calculation unit 83 and the bleed-off opening target value calculation unit 85 in the control block diagram of the controller shown in Figure 3. In general terms, the pump flow rate control target value calculation unit 83 calculates the pump flow rate control target value of the hydraulic pump 31 by adding the first pump flow rate target value, which is the calculation result of the first pump flow rate target value calculation unit 74, and the second pump flow rate target value, which is the calculation result of the second pump flow rate target value calculation unit 79, according to a ratio determined based on the output values ​​of table 831.

[0050] Specifically, Table 831 outputs values ​​in the range of 0 to 1 based on the angular velocity deviation ratio, which is the calculation result of the angular velocity deviation ratio calculation unit 81. In Table 831, for example, when the angular velocity deviation ratio is smaller than the first threshold n1 (for example, in the range of 0.2 or less), the output value is set to 0 or a value close to 0. On the other hand, when the angular velocity deviation ratio is larger than the second threshold n2, the output value is set to 1 or a value close to 1.

[0051] The calculation unit 832 multiplies the output value of table 831 by the second target pump flow rate value for pressure control of the slewing hydraulic motor 33. Meanwhile, the calculation unit 834 multiplies the calculation result of calculation unit 833, obtained by subtracting the output value of table 831 from 1, by the first target pump flow rate value for speed control of the slewing hydraulic motor 33. Finally, the calculation unit 835 calculates the target pump flow rate control value by adding the calculation result of calculation unit 832 and the calculation result of calculation unit 834.

[0052] In the range where the angular velocity deviation ratio is small, the output value of table 831 is set to approximately 0, so the pump flow rate control target value becomes the first pump flow rate target value. On the other hand, in the range where the angular velocity deviation ratio is large, the output value of table 831 is set to approximately 1, so the pump flow rate control target value becomes the second pump flow rate target value. In other words, when the angular velocity deviation ratio is small, for example, when the angular velocity deviation is small and the target angular velocity is high, the controller 60 performs speed control on the slewing hydraulic motor 33. Conversely, when the angular velocity deviation ratio is large, for example, when the angular velocity deviation is large and the target angular velocity is low, the controller 60 performs pressure control on the slewing hydraulic motor 33. Thus, the angular velocity deviation ratio serves as an indicator for switching the control of the slewing hydraulic motor 33 between speed control and pressure control.

[0053] The controller 60 calculates the target pump volume of the hydraulic pump 31 by dividing the pump flow control target value calculated by the pump flow control target value calculation unit 83 by the target prime mover speed. Finally, it outputs a control signal corresponding to the calculated target pump volume to the regulator 31a of the hydraulic pump 31. This controls the pump volume of the hydraulic pump 31.

[0054] The bleed-off opening target value calculation unit 85 calculates the bleed-off opening target value by referring to table 851 based on the angular velocity deviation ratio R, which is the calculation result of the angular velocity deviation ratio calculation unit 81. In table 851, if the angular velocity deviation ratio R is smaller than the first threshold n1, the opening of the bleed-off valve 36 is set to be as small as possible. This is to reduce losses due to the outflow of pressurized oil to the hydraulic oil tank 38 through the bleed-off valve 36. On the other hand, if the angular velocity deviation ratio is larger than the second threshold n2, the opening of the bleed-off valve 36 is set to be maintained at a predetermined value. This is to allow the pressure of the hydraulic circuit to be controlled by the flow rate change of the hydraulic pump 31. Note that the first threshold n1 and the second threshold n2 may be the same value. The controller 60 outputs a control signal to the bleed-off valve 36 that corresponds to the bleed-off opening target value calculated by the bleed-off opening target value calculation unit 85. This controls the opening degree of the bleed-off valve 36.

[0055] Next, the operation and effects of one embodiment of the work machine of the present invention will be described in comparison with the operation of a comparative example work machine. First, the behavior of the hydraulic pump and the slewing hydraulic motor during slewing operation in the comparative example work machine will be described using Figure 10. Figure 10 is a diagram showing the time waveform of the simulation results regarding the behavior of the hydraulic pump and the slewing hydraulic motor during slewing operation in the comparative example work machine, compared to one embodiment of the work machine of the present invention.

[0056] Graph (A) in Figure 10 shows the time variation of the swing control signal. Graph (B) shows the time variation of the discharge pressure of the hydraulic pump and the drive pressure of the swing hydraulic motor, and graph (C) shows the time variation of the pump flow rate of the hydraulic pump and the motor flow rate of the swing hydraulic motor. Graph (D) shows the time variation of the angular velocity of the swing hydraulic motor, and graph (E) shows the time variation of the angular acceleration of the swing hydraulic motor. Graph (F) shows the time variation of the output of the hydraulic pump.

[0057] In the comparative example's work machine, when a slewing operation is input, the hydraulic pump's output is controlled to maintain a constant discharge pressure until it reaches the set pressure of the main relief valve, until the pump's output reaches the horsepower limit. For example, as shown in graph (A), if the slewing operation starts when the horizontal axis (time) is 1.0 and a constant operation amount (e.g., full operation amount) is input, the discharge pressure of the hydraulic pump rises rapidly in response to the slewing operation, as shown in graph (B), to reach the set pressure of the main relief valve, while the flow rate of the hydraulic pump gradually increases, as shown in graph (C). When the product of the hydraulic pump's flow rate and discharge pressure, i.e., the pump output, reaches the horsepower limit (around 1.75 on the horizontal axis (time) in graph (F)), control is executed to reduce the target flow rate of the hydraulic pump in an attempt to avoid exceeding the pump output limit.

[0058] At this time, the slewing hydraulic motor is accelerating as shown in graph (D). Therefore, if the target flow rate of the hydraulic pump is reduced, the discharge pressure of the hydraulic pump will drop sharply (see the first sharp drop around 1.75 on the horizontal axis of graph (B)), and as a result, the angular acceleration of the slewing hydraulic motor will drop sharply (see the first sharp drop around 1.75 on the horizontal axis of graph (E)). In response to this sharp drop in discharge pressure, the hydraulic pump is controlled to increase the pump flow rate again. However, there is a certain time delay in acquiring the pressure detection value from the pressure sensor and controlling the pump volume, so the rapid increase and decrease in the discharge pressure of the hydraulic pump are repeated, causing control hunting (see the horizontal axis from 1.75 onwards in graph (B)). As a result, the rapid increase and decrease in the angular acceleration of the slewing hydraulic motor are repeated (see the horizontal axis from 1.75 onwards in graph (E)), which causes an unnatural feeling in the operator's operation. Furthermore, repeated rapid increases and decreases in the discharge pressure of the hydraulic pump cause the pump output to temporarily exceed the horsepower limit (see horizontal axis from 1.75 onwards in graph (F)), resulting in the machine's behavior becoming oscillating.

[0059] Next, the behavior of the hydraulic pump and the slewing hydraulic motor during a slewing operation in one embodiment of the work machine of the present invention will be explained using Figure 11. Figure 11 is a diagram showing the time waveform of the simulation results regarding the behavior of the hydraulic pump and the slewing hydraulic motor during a slewing operation in one embodiment of the work machine of the present invention.

[0060] The time-varying parameters shown in graphs (A) to (F) in Figure 11 are the same as those shown in graphs (A) to (F) in Figure 10. However, graph (B) also shows the time-varying target pressure of the hydraulic pump 31 (target pressure of the slewing hydraulic motor 33). Additionally, graph (D) shows the time-varying target angular velocity of the slewing hydraulic motor 33.

[0061] In this embodiment, when the angular velocity deviation ratio is large, the controller 60 estimates the angular velocity of the swing hydraulic motor 33 at a future time after a reference time has elapsed from the current time at the time of calculation. Based on this estimated angular velocity, it controls the swing hydraulic motor 33 based on a target pressure (target discharge pressure of the hydraulic pump 31) that is limited so that the horsepower input to the swing hydraulic motor 33 at that future time is less than or equal to the horsepower limit. For this reason, when the swing hydraulic motor 33 starts moving and the angular velocity deviation ratio is large, the drive flow rate of the swing hydraulic motor 33 is small (see the vicinity of 1.0 on the horizontal axis (time) when the swing operation starts in graph (C)). Therefore, the target pressure of the hydraulic pump 31 (target pressure of the swing hydraulic motor 33 (target meter-in pressure)) is set high as shown in graph (B) to increase the swing angular acceleration of the swing hydraulic motor 33 (see the vicinity of 1.0 on the horizontal axis (time) in graph (E)). Subsequently, when the angular velocity of the swing hydraulic motor 33 increases, if the swing hydraulic motor 33 is accelerated with the initial high drive pressure, the output of the hydraulic pump 31 (horsepower supplied to the swing hydraulic motor 33) will reach its horsepower limit. Therefore, the control calculation shown in Figure 6 limits the pump target pressure (product of estimated flow rate and pump target pressure) in advance according to the estimated flow rate at a future time (a predetermined time after a certain period of time has elapsed from the current time). This prevents the output of the hydraulic pump 31 from exceeding the horsepower limit, as shown in graph (F), while maintaining the smooth and stable acceleration of the swing hydraulic motor 33 as shown in graph (E). As a result, the desired swing acceleration can be obtained without causing any discomfort in the operating feel.

[0062] Furthermore, in this embodiment, the controller 60 controls the swing hydraulic motor 33 based on its target speed when the angular velocity deviation ratio is small. For example, as shown in graph (D), when the actual angular velocity of the swing hydraulic motor 33 approaches the target angular velocity and the angular velocity deviation ratio becomes small around 2.5 on the horizontal axis (time), the pump flow rate control target value is switched from the second target value for pressure control to the first target value for speed control. This speed control ultimately brings the actual angular velocity of the swing hydraulic motor 33 to match the target angular velocity (see around 2.7 on the horizontal axis of graph (D)).

[0063] Furthermore, the controller 60 in this embodiment controls the closing of the bleed-off valve 36 in accordance with the switching of the control target value of the hydraulic pump 31 from pressure control to speed control. By blocking the flow of pressurized oil from the hydraulic pump 31 to the hydraulic oil tank 38 with the bleed-off valve 36, hydraulic loss can be reduced, enabling efficient turning operations.

[0064] The hydraulic excavator according to one embodiment of the present invention described above comprises a hydraulic pump 31 that discharges pressurized oil, an upper rotating body 2 (rotating body) capable of rotational movement, a rotational hydraulic motor 33 (hydraulic actuator) that rotates the upper rotating body 2 (rotating body) by the supply of pressurized oil from the hydraulic pump 31, an operating device 56 that outputs an operation signal to instruct the movement of the upper rotating body 2 (rotating body), and a speed sensor 54 that detects the drive speed of the rotational hydraulic motor 33 (hydraulic actuator). Furthermore, it comprises a regulator 31a and a bleed-off valve 36 as pressure adjustment devices that can adjust the drive pressure of the rotational hydraulic motor 33 (hydraulic actuator), and a controller 60 that controls the regulator 31a and the bleed-off valve 36 (pressure adjustment device). The controller 60 calculates the target speed of the swing hydraulic motor 33 (hydraulic actuator) based on the operation signal from the operating device 56, calculates the target pressure of the swing hydraulic motor 33 (hydraulic actuator) based on the speed deviation, which is the difference between the calculated target speed and the actual driving speed of the swing hydraulic motor 33 (hydraulic actuator) detected by the speed sensor 54, limits the calculated target pressure so that the horsepower input to the swing hydraulic motor 33 (hydraulic actuator) does not exceed a limit value when it is assumed that the driving pressure of the swing hydraulic motor 33 (hydraulic actuator) reaches the calculated target pressure after a predetermined time, and controls the regulator 31a and the bleed-off valve 36 (pressure regulating device) based on the limited target pressure.

[0065] With this configuration, the regulator 31a and the bleed-off valve 36 (pressure regulating device) are controlled using a predetermined target pressure for the swing hydraulic motor 33 (hydraulic actuator), taking into account the horsepower input to the swing hydraulic motor 33 (hydraulic actuator) estimated at a future time after a predetermined period of time. This makes it possible to drive the swing hydraulic motor 33 (hydraulic actuator) with appropriate torque and acceleration within the horsepower limit range.

[0066] Furthermore, the controller 60 of the hydraulic excavator according to this embodiment is configured to estimate the horsepower input to the swing hydraulic motor 33 (hydraulic actuator) at a predetermined time in the future (after a predetermined time) based on the actual angular velocity and actual angular acceleration of the swing hydraulic motor 33 (hydraulic actuator) obtained from the detection value of the speed sensor 54.

[0067] With this configuration, the actual driving speed and actual driving acceleration of the swing hydraulic motor 33 (hydraulic actuator) obtained from the speed sensor 54 can be used to easily and accurately estimate the driving speed of the swing hydraulic motor 33 (hydraulic actuator) at a future time (after a predetermined time). Therefore, it is possible to correctly limit the target pressure of the calculation result so that the estimated horsepower input to the swing hydraulic motor 33 (hydraulic actuator), obtained by multiplying the estimated flow rate calculated from the estimated driving speed of the swing hydraulic motor 33 (hydraulic actuator) at a future time (after a predetermined time) and the target pressure of the swing hydraulic motor 33 (hydraulic actuator), does not exceed the horsepower limit. As a result, the swing hydraulic motor 33 (hydraulic actuator) can be driven with smooth acceleration without exceeding the horsepower limit.

[0068] Furthermore, in this embodiment, the pressure adjustment device includes a regulator 31a, which is a flow rate adjustment device capable of adjusting the drive pressure of the swivel hydraulic motor 33 (hydraulic actuator) by adjusting the discharge flow rate of the hydraulic pump 31. The controller 60 calculates a first target pump flow rate of the hydraulic pump 31 based on the calculated target speed, calculates a second target pump flow rate of the hydraulic pump 31 based on the limited target pressure, and calculates a speed deviation ratio, which is the ratio of the speed deviation to the calculated target speed. If the calculated speed deviation ratio is smaller than the first threshold n1, the controller 60 controls the regulator 31a (flow rate adjustment device) based on the calculated first target pump flow rate. On the other hand, if the calculated speed deviation ratio is larger than the second threshold n2, the controller 60 controls the regulator 31a (flow rate adjustment device) based on the calculated second target pump flow rate as control of the pressure adjustment device based on the limited target pressure.

[0069] With this configuration, when the swing hydraulic motor 33 starts moving with a large speed deviation ratio, the estimated flow rate of the swing hydraulic motor 33 (hydraulic actuator) is small, so the limited target pressure can be set higher. As a result, the acceleration of the swing hydraulic motor 33 (hydraulic actuator) can be increased. On the other hand, when the speed deviation ratio decreases, that is, when the target speed of the swing hydraulic motor 33 (hydraulic actuator) approaches the drive speed, the regulator 31a (flow rate adjustment device) is controlled based on the first target pump flow rate value set based on the target speed, so the actual drive speed of the swing hydraulic motor 33 (hydraulic actuator) can be precisely fine-tuned.

[0070] Furthermore, in this embodiment, the pressure regulating device is further equipped with a bleed-off valve 36 that releases the pressurized oil discharged from the hydraulic pump 31 into the hydraulic oil tank 38. When the controller 60 performs control of the regulator 31a (flow rate regulating device) based on the first target pump flow rate value calculated, it simultaneously controls the bleed-off valve 36 to a closed state. On the other hand, when the controller 60 performs control of the regulator 31a (flow rate regulating device) based on the second target pump flow rate value calculated, it simultaneously controls the bleed-off valve 36 to a predetermined opening degree.

[0071] With this configuration, when speed control is performed to control the swing hydraulic motor 33 (hydraulic actuator) based on a target speed, closing the bleed-off valve 36 blocks the outflow of pressurized oil from the hydraulic pump 31 to the hydraulic oil tank 38 via the bleed-off valve 36, thereby reducing energy loss. On the other hand, when pressure control is performed to control the swing hydraulic motor 33 (hydraulic actuator) based on a target pressure, opening the bleed-off valve 36 allows for easy control of the drive pressure of the swing hydraulic motor 33 (hydraulic actuator) by increasing or decreasing the flow rate of the hydraulic pump 31.

[0072] [Other embodiments] In the above-described embodiment, an example of applying the present invention to a hydraulic excavator was shown, but the present invention can be broadly applied to various types of work machines equipped with a slewing body.

[0073] Furthermore, the present invention is not limited to the embodiment described above, but includes various modifications. The embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those having all the configurations described. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0074] For example, in the embodiment described above, an example was shown in which a regulator 31a, which is a flow rate adjustment device that can adjust the discharge flow rate of the hydraulic pump 31, and a bleed-off valve 36 that releases the pressurized oil discharged from the hydraulic pump 31 to the hydraulic oil tank 38 were used as a pressure adjustment device that can adjust the drive pressure of the swivel hydraulic motor 33. However, if the hydraulic pump is of the fixed capacity type, it is also possible to adjust the drive pressure of the swivel hydraulic motor 33 by controlling the discharge flow rate of the hydraulic pump by changing the rotational speed of the prime mover 32, for example. That is, the prime mover 32 functions as a flow rate adjustment device that can adjust the discharge flow rate of the hydraulic pump by adjusting its rotational speed, and also functions as a pressure adjustment device that can adjust the drive pressure of the swivel hydraulic motor 33 by adjusting the discharge flow rate of the hydraulic pump. [Explanation of symbols]

[0075] 2…Upper rotating body (rotating body), 31…Hydraulic pump, 31a…Regulator (pressure regulator; flow rate regulator), 32…Prime motor (pressure regulator; flow rate regulator), 33…Rotating hydraulic motor (hydraulic actuator), 36…Bleed-off valve (pressure regulator), 38…Hydraulic oil tank, 54…Speed ​​sensor, 56…Joystick (control device), 60…Controller

Claims

1. A hydraulic pump that discharges pressurized oil, A rotating body capable of rotational movement, A hydraulic actuator that drives the rotating body to rotate by supplying pressurized oil from the hydraulic pump, An operating device that outputs an operating signal to instruct the movement of the rotating body, In a work machine equipped with a speed sensor for detecting the drive speed of the hydraulic actuator, A pressure adjustment device capable of adjusting the drive pressure of the hydraulic actuator, The system includes a controller that controls the pressure adjustment device, The aforementioned controller, Based on the operation signal from the aforementioned operating device, the target speed of the hydraulic actuator is calculated. Based on the speed deviation, which is the difference between the calculated target speed and the actual operating speed of the hydraulic actuator detected by the speed sensor, the target pressure of the hydraulic actuator is calculated. Based on the actual driving speed of the hydraulic actuator obtained from the speed sensor and the driving speed of the hydraulic actuator after a predetermined time estimated from the actual driving acceleration, a pressure limit value for the hydraulic actuator is calculated so that the horsepower supplied to the hydraulic actuator after the predetermined time does not exceed the limit value. The pressure regulator is configured to control the pressure regulator based on a limited target pressure determined according to the calculated pressure limit value. A work machine characterized by the following features.

2. A hydraulic pump for discharging pressurized oil, A rotating body capable of rotational movement, A hydraulic actuator that drives the rotating body to rotate by supplying pressurized oil from the hydraulic pump, An operating device that outputs an operating signal to instruct the movement of the rotating body, In a work machine equipped with a speed sensor for detecting the drive speed of the hydraulic actuator, A pressure adjustment device capable of adjusting the drive pressure of the hydraulic actuator, The system includes a controller that controls the pressure adjustment device, The aforementioned controller, Based on the operation signal from the aforementioned operating device, the target speed of the hydraulic actuator is calculated. Based on the speed deviation, which is the difference between the calculated target speed and the actual operating speed of the hydraulic actuator detected by the speed sensor, the target pressure of the hydraulic actuator is calculated. The target pressure calculated is limited so that the horsepower supplied to the hydraulic actuator, estimated when the drive pressure of the hydraulic actuator reaches the target pressure calculated after a predetermined time, does not exceed a limit value. The pressure regulator is configured to control the pressure regulator based on a limited target pressure. The pressure adjustment device includes a flow rate adjustment device capable of adjusting the drive pressure of the hydraulic actuator by adjusting the discharge flow rate of the hydraulic pump. The aforementioned controller, Based on the target speed obtained from the calculation, the first target value of the pump flow rate of the hydraulic pump is calculated. Based on the limited target pressure, the second target value for the pump flow rate of the hydraulic pump is calculated. The speed deviation ratio, which is the ratio of the speed deviation to the target speed of the calculation result, is calculated. If the calculated velocity deviation ratio is smaller than the first threshold, the flow rate adjustment device is controlled based on the calculated pump flow rate first target value. If the calculated velocity deviation ratio is greater than the second threshold, the control of the pressure regulator based on the limited target pressure is performed, and the control of the flow rate regulator is performed based on the calculated second target value of the pump flow rate. A work machine characterized by the following features.

3. In the work machine described in claim 2, The pressure regulating device further includes a bleed-off valve that releases the pressurized oil discharged from the hydraulic pump into the hydraulic oil tank. The aforementioned controller, When controlling the flow rate adjustment device based on the first target value of the pump flow rate calculated, the bleed-off valve is simultaneously controlled to be closed. When controlling the flow rate adjustment device based on the second target value of the pump flow rate calculated, the bleed-off valve is simultaneously controlled to maintain a predetermined opening degree. A work machine characterized by the following features.

Images