Work machine

Abstract

A work machine has a pressure adjusting device capable of adjusting a driving pressure of a swing hydraulic motor and a controller that controls the pressure adjusting device. The controller calculates a target pressure of the swing hydraulic motor based on a speed deviation of the target speed of the swing hydraulic motor calculated from an operation signal of an operation device and an actual driving speed of the swing hydraulic motor detected by a speed sensor, limits the target pressure as a calculation result so that an estimated input horsepower to the swing hydraulic motor when an imaginary driving pressure of the swing hydraulic motor reaches the target pressure after a prescribed time does not exceed a limit value, and controls the pressure adjusting device based on the limited target pressure.

Description

Technical Field

[0001] This invention relates to working machinery, and more specifically, to working machinery having a rotating body capable of rotation by a hydraulic motor. Background Technology

[0002] In hydraulic excavators and other hydraulic work machines, hydraulic actuators such as hydraulic cylinders drive the working device, which consists of linkage components such as the boom and stick. Additionally, a hydraulic motor, acting as a hydraulic actuator, drives the slewing body to rotate relative to the traveling body. In work machines, the parts driven by hydraulic actuators typically have large inertial mass, and the motion control during acceleration and deceleration accounts for a significant proportion of the work time. The acceleration and deceleration of the working device and the upper slewing body are determined by the thrust of the driving cylinder or the torque of the motor. Therefore, to control the cylinder thrust and motor torque, it is necessary to accurately control the driving pressure of the hydraulic actuator to the target value. In typical hydraulic excavators, the pressure of the hydraulic circuit is adjusted using relief valves or vent valves, thereby adjusting the acceleration and deceleration of the working device and the upper slewing body.

[0003] In contrast, Patent Document 1 describes a technique that adjusts the capacity (flow rate) of a hydraulic pump so that the pressure of the hydraulic pump (rotary pump), detected by a pressure detection device, becomes a predetermined target pressure during the rotational drive of the working machinery, thereby controlling the pressure of the pressurized oil supplied to the hydraulic motor (the output torque of the hydraulic motor). This technique allows for arbitrary adjustment of the hydraulic motor's output.

[0004] Furthermore, in the working machine described in Patent Document 1, hydraulic pump output control is performed when the hydraulic pump output may exceed the engine's maximum output. Specifically, if the hydraulic pump output is near the engine's maximum output, the target pressure of the hydraulic pump is reduced, thereby ensuring the hydraulic pump's ejection flow rate and achieving control (horsepower limit) that the hydraulic pump output does not exceed the engine's maximum output.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-234683 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] If the hydraulic actuator of a rotary hydraulic motor or other rotating system maintains a constant torque, it will continue to accelerate even without external force, thus increasing the required flow rate over time. In such a situation, as described in Patent Document 1, if the target pressure of the hydraulic pump suddenly decreases near or at the moment the product of the hydraulic pump's discharge flow rate and pressure reaches the engine's maximum output (limited horsepower), the torque of the rotary hydraulic motor will decrease sharply, potentially causing discomfort to the operator. On the other hand, if the target pressure of the hydraulic pump is suppressed to a low level beforehand to avoid reaching the engine's maximum output (limited horsepower), the engine's output (horsepower) cannot be fully utilized, especially during the start-up of the rotary hydraulic motor.

[0010] This invention was made to solve the above-mentioned problems, and its purpose is to provide a working machine that can drive a hydraulic actuator of a rotating system with appropriate torque or acceleration within a horsepower limit.

[0011] Methods for solving problems

[0012] This application contains several means for solving the above-mentioned problems. As one example, a working machine includes: a hydraulic pump that sprays pressurized oil; a rotating body capable of rotation; a hydraulic actuator that drives the rotating body to rotate via a supply of pressurized oil from the hydraulic pump; an operating device that outputs an operating signal instructing the movement of the rotating body; and a speed sensor that detects the drive speed of the hydraulic actuator. The working machine also includes: a pressure adjusting device capable of adjusting the drive pressure of the hydraulic actuator; and a controller that controls the pressure adjusting device, the controller performing the following actions: calculating a target speed of the hydraulic actuator based on the operating signal from the operating device; calculating a target pressure of the hydraulic actuator based on a speed deviation, wherein the speed deviation is the difference between the calculated target speed and the actual drive speed of the hydraulic actuator detected by the speed sensor; limiting the calculated target pressure such that the estimated horsepower input to the hydraulic actuator when the hypothetical drive pressure of the hydraulic actuator reaches the calculated target pressure after a predetermined time does not exceed a limit value; and controlling the pressure adjusting device based on the limited target pressure.

[0013] Invention Effects

[0014] According to the present invention, the pressure adjustment device is controlled by using a target pressure of the hydraulic actuator that is pre-limited by taking into account the estimated horsepower input to the hydraulic actuator at a future time after a predetermined time. Therefore, the hydraulic actuator can be driven with appropriate torque or acceleration within the horsepower limit.

[0015] Other issues, structures, and effects not mentioned above will be clarified through the following description of the implementation methods. Attached Figure Description

[0016] Figure 1 This is an external view of a hydraulic excavator, which is one embodiment of the working machinery of the present invention.

[0017] Figure 2 This is a hydraulic circuit diagram showing a hydraulic system of one embodiment of the working machinery of the present invention.

[0018] Figure 3 It constitutes Figure 2 The diagram shown is a control block diagram of a controller for a portion of one embodiment of the working machinery of the present invention.

[0019] Figure 4 It means Figure 3 The block diagram shown is a detailed representation 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.

[0020] Figure 5 It means Figure 3 The table shows the details of the target inlet throttling pressure calculation unit in the control block diagram of the controller.

[0021] Figure 6 It means Figure 3 The block diagram shown is a detailed diagram of the inlet throttling pressure limit value calculation unit in the controller's control block diagram.

[0022] Figure 7 It means Figure 3 The block diagram shown is a detailed diagram of the pump flow rate second target value calculation unit in the control block diagram of the controller.

[0023] Figure 8 It means Figure 3 The block diagram shown is a detailed diagram of the angular velocity deviation ratio calculation unit in the control block diagram of the controller.

[0024] Figure 9 It means Figure 3 The block diagram shown is a detailed representation of the pump flow control target value calculation unit and the vent opening target value calculation unit in the controller's control block diagram.

[0025] Figure 10 This is a graph showing the time waveform of the simulation results related to the movement of the hydraulic pump and hydraulic motor in a comparative example of a work machine according to an embodiment of the work machine of the present invention.

[0026] Figure 11This is a graph showing the time waveform of the simulation results related to the movement of the hydraulic pump and hydraulic motor relative to the rotary operation in one embodiment of the working machine of the present invention. Detailed Implementation

[0027] Hereinafter, embodiments of the work machinery of the present invention will be described using the accompanying drawings. In this embodiment, a hydraulic excavator will be used as an example of the work machinery.

[0028] [One Implementation Method]

[0029] First, use Figure 1 The general structure of a hydraulic excavator, which is one embodiment of the working machinery of the present invention, will be described. Figure 1 This is an external view of a hydraulic excavator, which is one embodiment of the working machinery of the present invention. Here, the description is given from the perspective of the operator seated in the driver's seat.

[0030] exist Figure 1 The hydraulic excavator comprises: a self-propelled lower traveling body 1 and an upper slewing body 2 rotatably mounted on the lower traveling body 1. The lower traveling body 1 and the upper slewing body 2 constitute the body of the hydraulic excavator. A front working device 3 for performing excavation operations is rotatably mounted on the front side of the upper slewing body 2.

[0031] The lower traveling body 1 has tracked traveling devices 11 on both the left and right sides. Figure 1 (Only one side is shown in the diagram). The traveling device 11 is driven by a traveling hydraulic motor 12, which acts as a hydraulic actuator.

[0032] The upper rotating body 2 is configured such that a rotary hydraulic motor 33 (described later) acts as a hydraulic actuator. Figure 2 The upper rotating body 2, including its reduction gear and a slewing device (not shown), is driven to rotate about the rotation axis x relative to the lower traveling body 1. The upper rotating body 2 has a cab 14 for the operator on its front side. A control lever 56 (see later description) is arranged in the cab 14 as an operating device. Figure 2 The upper rotating body 2 houses the hydraulic pump 31 (described later) and various valves 34, 35, 36, 37, 39, 40, 41, and 42 (see below). Figure 2 )wait.

[0033] The front working device 3 is, for example, a multi-joint type working device constructed by connecting multiple driven components in a manner that allows them to rotate in the vertical direction. The multiple driven components consist, for example, a boom 16, a stick 17, and a bucket 18, which serves as a working tool. The boom 16, stick 17, and bucket 18 are driven by a boom cylinder 21, a stick cylinder 22, and a bucket cylinder 23, which serve as hydraulic actuators, respectively.

[0034] Next, use Figure 2 The structure of a hydraulic system in one embodiment of the working machine of the present invention will be described. Figure 2 This is a hydraulic circuit diagram showing a hydraulic system of one embodiment of the working machinery of the present invention.

[0035] exist Figure 2 In this context, a hydraulic excavator has a lower traveling body 1, an upper slewing body 2, and a front working device 3 (all referred to as hydraulically driven). Figure 1 The hydraulic system 30. Furthermore, in Figure 2 In this document, only the hydraulic circuit related to the slewing hydraulic motor 33 of the upper slewing body 2 is shown, and the hydraulic circuits related to the travel hydraulic motor 12 of the driving travel device 11, the boom cylinder 21, the stick cylinder 22, and the bucket cylinder 23 of the driving front working device 3 are omitted.

[0036] The hydraulic system 30 includes: a hydraulic pump 31 driven by a prime mover 32 (e.g., an electric motor, engine) to inject pressurized oil; and a rotary hydraulic motor 33 driven by the supply of pressurized oil from the hydraulic pump 31 to rotate the upper rotating body 2. The hydraulic pump 31 is a variable-capacity pump and has a regulator 31a for adjusting the pump volume. The regulator 31a functions as a flow adjustment device capable of adjusting the injection flow rate of the hydraulic pump 31, and also as a pressure adjustment device capable of adjusting the drive pressure of the rotary hydraulic motor 33 by adjusting the injection flow rate of the hydraulic pump 31. The regulator 31a adjusts the pump volume, for example, according to a control signal from a controller 60. The rotary hydraulic motor 33 has a first port 33a and a second port 33b as a pair of input / output ports. The rotary hydraulic motor 33 is, for example, a fixed-capacity hydraulic motor.

[0037] Pressurized oil ejected from hydraulic pump 31 is supplied to rotary hydraulic motor 33 via load check valve 34 and directional control valve 35. Load check valve 34 is located on ejection line 44 connecting hydraulic pump 31 and directional control valve 35. Load check valve 34 allows pressurized oil to flow from hydraulic pump 31 to directional control valve 35, while preventing pressurized oil from flowing from directional control valve 35 back to hydraulic pump 31. Directional control valve 35 controls the flow (direction and flow rate) of pressurized oil supplied from hydraulic pump 31 to rotary hydraulic motor 33. Directional control valve 35 controls its position (stroke) based on a control signal (excitation current) from controller 60.

[0038] A relief valve 36 is installed on pipeline 47, which branches off from the ejection pipeline 44 and connects to the working oil tank 38. The relief valve 36 can adjust the ejection pressure of the hydraulic pump 31 according to its opening degree. That is, the relief valve 36 functions as a pressure regulating device, releasing pressurized oil ejected from the hydraulic pump 31 to the working oil tank 38 according to the opening degree, thereby adjusting the drive pressure of the rotary hydraulic motor 33. Furthermore, the ejection port of the hydraulic pump 31 is connected to the working oil tank 38 via a main relief valve 37. The main relief valve 37 specifies an upper limit for the ejection pressure of the hydraulic pump 31 and is configured to open when the ejection pressure of the hydraulic pump 31 exceeds the set pressure.

[0039] The first port 33a and the second port 33b of the rotary hydraulic motor 33 are connected to the directional control valve 35 via the first pipeline 45 and the second pipeline 46, respectively. The first port 33a and the second port 33b of the rotary hydraulic motor 33 are also connected to the first rotary relief valve 39 and the second rotary relief valve 40 via the first pipeline 45 and the second pipeline 46, respectively. The first rotary relief valve 39 and the second rotary relief valve 40 open when the pressure in the first pipeline 45 and the second pipeline 46 is above the set pressure, thereby connecting the first pipeline 45 and the second pipeline 46 to the working oil tank 38, thus providing overload protection for the rotary hydraulic motor 33. Furthermore, the first port 33a and the second port 33b of the rotary hydraulic motor 33 are connected to the supplementary first check valve 41 and the supplementary second check valve 42 via the first pipeline 45 and the second pipeline 46, respectively. The supplementary first check valve 41 prevents the flow of pressurized oil from the first pipeline 45 to the working oil tank 38, while allowing the flow of working oil from the working oil tank 38 to the first pipeline 45. The supplementary second check valve 42 prevents the flow of pressurized oil from the second pipeline 46 to the working oil tank 38, while allowing the flow of working oil from the working oil tank 38 to the second pipeline 46. The supplementary first check valve 41 and the supplementary second check valve 42 serve as anti-backlash valves for the rotary hydraulic motor 33.

[0040] First pressure sensors 51a and 51b are respectively installed on the first pipeline 45 and the second pipeline 46 to detect the pressure (driving pressure) at the first port 33a and the second port 33b of the rotary hydraulic motor 33. The first pressure sensors 51a and 51b output pressure detection signals to the controller 60 corresponding to the detected pressure at the first port 33a and the second port 33b (driving pressure). A second pressure sensor 52 is installed on the ejection pipeline 44 to detect the ejection pressure of the hydraulic pump 31. The second pressure sensor 52 outputs an ejection pressure detection signal corresponding to the detected ejection pressure to the controller 60. Additionally, a speed sensor 54 is installed on the rotary hydraulic motor 33 to detect the actual angular velocity (driving speed) of the rotary hydraulic motor 33. The speed sensor 54 outputs an angular velocity detection signal corresponding to the detected angular velocity to the controller 60.

[0041] The hydraulic system 30 also includes a joystick 56 as an operating device, which indicates the rotation of the upper rotating body 2 or the driving of the rotation hydraulic motor 33. The joystick 56 outputs an operating signal corresponding to the operating angle to the controller 60.

[0042] The controller 60 receives rotation operation signals from the joystick 56, angular velocity detection signals from the speed sensor 54 (the actual angular velocity of the rotary 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 and the pressure on the second port 33b of the rotary hydraulic motor 33 detected by the first pressure sensors 51a and 51b), and ejection pressure detection signals from the second pressure sensor 52 (the ejection pressure of the hydraulic pump 31 detected by the second pressure sensor 52). Based on these operation and detection signals, the controller 60 performs prescribed calculations and outputs control signals corresponding to the calculation results to the regulator 31a of the hydraulic pump 31, the directional control valve 35, and the relief valve 36. Details of this calculation will be described later. The controller 60 ultimately controls the drive pressure and motor flow of the rotary hydraulic motor 33 (the rotational movement of the upper rotating 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 relief valve 36.

[0043] Next, use Figure 3 The function of the controller, which constitutes part of one embodiment of the working machinery of the present invention, will be described in general terms. Figure 3 It constitutes Figure 2 The diagram shown is a control block diagram of a controller for a portion of one embodiment of the working machinery of the present invention.

[0044] exist Figure 3 In this embodiment, the controller 60, as a hardware structure, includes, for example, a storage device 61 composed of RAM, ROM, etc., and a processing device 62 composed of CPU, MPU, etc. The storage device 61 stores in advance programs and various information required for 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 relief valve 36. The processing device 62 appropriately reads the programs and various information from the storage device 61, executes processing according to the programs, thereby realizing various functions. The controller 60 of this embodiment performs drive control of the rotary hydraulic motor 33 by using speed control with a speed target value or pressure control with a pressure target value that pre-considers horsepower limitations, and mainly has the following control function units.

[0045] The controller 60 includes a directional control valve control unit 71, which receives a rotation operation signal from a lever 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, for example, the opening target value of the directional control valve 35 based on the rotation operation signal and referring to a first table (not shown), and converts the calculated opening target value into a drive command value (command current value) referring to a second table (not shown). The directional control valve control unit 71 outputs a drive control signal containing the drive command value to the directional control valve 35.

[0046] The controller 60 includes a target angular velocity calculation unit 73, which takes in a rotation operation signal from the operating device 56 and outputs the target angular velocity ωt of the rotary hydraulic motor 33. Details of the calculations performed by the target angular velocity calculation unit 73 will be described later.

[0047] The controller 60 includes a pump flow rate first target value calculation unit 74, which takes the calculation result of the target angular velocity calculation unit 73, i.e., the target angular velocity ωt of the rotary hydraulic motor 33, and outputs the pump flow rate first target value Qt1 of the hydraulic pump 31. The pump flow rate first target value Qt1 is derived from the target angular velocity ωt of the rotary hydraulic motor 33 and is a target value used for speed control of the rotary hydraulic motor 33. The details of the calculation of the pump flow rate first target value calculation unit 74 will be described later.

[0048] Additionally, the controller 60 includes: a target torque calculation unit 76, a target inlet throttle pressure calculation unit 77, an inlet throttle pressure limit value calculation unit 78, and a pump flow rate second target value calculation unit 79. These calculation units 76-79 derive the target value for pressure control of the rotary hydraulic motor 33, i.e., the second target value Qt2 of the pump flow rate of the hydraulic pump 31. The target torque calculation unit 76 takes the target angular velocity ωt of the rotary hydraulic motor 33 (the result of the calculation by the target angular velocity calculation unit 73), the actual angular velocity (drive speed) of the rotary hydraulic motor 33 from the speed sensor 54, and the rotary operation signal from the operating device 56, and outputs the target torque Tt of the rotary hydraulic motor 33. The target inlet throttle pressure calculation unit 77 takes the target torque Tt (the result of the calculation by the target torque calculation unit 76) and outputs the target inlet throttle pressure Pt of the rotary hydraulic motor 33. The inlet throttle pressure limit calculation unit 78 takes in the actual angular velocity (drive speed) and actual angular acceleration (drive acceleration) of the rotary hydraulic motor 33 from the speed sensor 54, and outputs a limit value PL for the inlet throttle pressure of the rotary hydraulic motor 33, which is used to limit the input horsepower to the rotary hydraulic motor 33 to below the horsepower limit value (horsepower limit). The pump flow rate second target value calculation unit 79 takes in the target inlet throttle pressure Pt, which is the result of the calculation by the target inlet throttle pressure calculation unit 77, the inlet throttle pressure limit value PL, which is the result of the calculation by the inlet throttle pressure limit value calculation unit 78, and the pressure (drive pressure) of the rotary hydraulic motor 33 from the first pressure sensors 51a and 51b, and outputs a second target value Qt2 for the pump flow rate. The details of the calculations of the target torque calculation unit 76, the target inlet throttle pressure calculation unit 77, the inlet throttle pressure limit value calculation unit 78, and the pump flow rate second target value calculation unit 79 will be described later.

[0049] The controller 60 also includes an angular velocity deviation ratio calculation unit 81, which takes into account the target angular velocity ωt of the rotary hydraulic motor 33 (the result of the calculation by the target angular velocity calculation unit 73) and the actual angular velocity of the rotary 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 for switching the drive control of the rotary hydraulic motor 33 to speed control or pressure control, and also an indicator for switching the opening and closing of the relief valve 36. Details of the calculation by the angular velocity deviation ratio calculation unit 81 will be described later.

[0050] Furthermore, the controller 60 includes a pump flow control target value calculation unit 83, which takes into account the first target value Qt1 of the pump flow (the result of the calculation by the first target value calculation unit 74), the second target value Qt2 of the pump flow (the result of the calculation by the second target value calculation unit 79), and the angular velocity deviation ratio R (the result of the calculation by the angular velocity deviation ratio calculation unit 81), calculates the pump flow control target value Qc of the hydraulic pump 31, and outputs a control signal corresponding to the pump flow control target value Qc to the regulator 31a of the hydraulic pump 31. The pump flow control target value Qc is the final control target value of the ejection flow rate (pump capacity) of the hydraulic pump 31. The details of the calculation by the pump flow control target value calculation unit 83 will be described later.

[0051] The controller 60 includes a venting opening target value calculation unit 85, which takes the angular velocity deviation ratio R, which is the result of the calculation by the angular velocity deviation ratio calculation unit 81, calculates the venting opening target value Vt of the venting valve 36, and outputs a control signal corresponding to the venting opening target value Vt to the venting valve 36. Details of the calculation by the venting opening target value calculation unit 85 will be described later.

[0052] Next, use Figures 4 to 10 An example detailing the operation of each function of the controller in one embodiment of the working machinery of the present invention will be described. Figure 4 It means Figure 3 The block diagram shown is a detailed representation 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.

[0053] like Figure 4 As shown, the target angular velocity calculation unit 73 calculates the target angular velocity (target speed) of the rotary hydraulic motor 33 based on the rotary operation signal input from the operating device 56, referring to Table 731. For example, it outputs the rotary operation signal within the range of -100 to +100. It outputs 0 in the non-operational state, -100 in the case of maximum left rotary operation, and +100 in the case of maximum right rotary operation. In Table 731, the left rotary angular velocity is set to - and the right rotary angular velocity is set to +, depending on the sign of the rotary operation signal. The target angular velocity calculation unit 73 then 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 below). Figure 8 Output.

[0054] 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 result of the calculation by the target angular velocity calculation unit 73. Furthermore, the first target value of the pump flow rate is calculated by multiplying the absolute value of the target angular velocity by the equivalent rotary volume q (the volume required to rotate the upper rotating body 2 at a unit angular velocity). The first target value of the pump flow rate is a value directly derived from the target angular velocity of the rotary hydraulic motor 33, and is a control value used for speed control of the rotary hydraulic motor 33. The pump flow rate first target value calculation unit 74 sends the calculated first target value of the pump flow rate to the pump flow rate control target value calculation unit 83 (see below). Figure 9 Output.

[0055] In the target torque calculation unit 76, firstly, the calculation unit 761 calculates the angular velocity deviation by subtracting the actual angular velocity (angular velocity detection value) of the rotary hydraulic motor 33 detected by the speed sensor 54 from the target angular velocity of the rotary hydraulic motor 33, which is the result of the calculation by the target angular velocity calculation unit 73. Next, the calculation unit 762 multiplies the angular velocity deviation, which is the result of the calculation by the calculation unit 761, by a preset proportional gain Kp. Then, based on the output value of the calculation unit 762, the target torque Tt of the rotary hydraulic motor 33 is calculated with reference to Table 763. However, based on the rotary operation signal, a torque limit value for the rotary hydraulic motor 33 is set using Table 764, and the set torque limit value is input into Table 763, thereby setting the upper and lower limits relative to the input value in Table 763. The target torque calculation unit 76 then outputs the target torque Tt, which is the result of the calculation, to the target inlet throttle pressure calculation unit 77 (described later). Figure 5 Output.

[0056] Figure 5 It means Figure 3 The table below shows the details of the target inlet throttle pressure calculation unit in the control block diagram of the controller. The target inlet throttle pressure calculation unit 77 calculates the target inlet throttle pressure of the rotary hydraulic motor 33 based on the rotation operation signal from the operating device 56 and the target torque of the rotary hydraulic motor 33, which is the result of the calculation by the target torque calculation unit 76. In the rotary hydraulic motor 33, the side where pressurized oil from the hydraulic pump 31 flows in is called the inlet throttle side, and the side where pressurized oil flows out is called the outlet throttle side. In this description, the first port 33a of the rotary hydraulic motor 33 is designated as the inlet throttle side during right rotation, and the second port 33b of the rotary hydraulic motor 33 is designated as the inlet throttle side during left rotation.

[0057] like Figure 5As shown, when the operating signal is greater than the threshold th1 (right turn indication) and the target torque Tt, as the result of the calculation by the target torque calculation unit 76, is positive (the direction of the torque is the same as the direction of right turn), the result (Tt / q) obtained by dividing the target torque Tt by the equivalent volume of the right turn is used as the target pressure value of the first port 33a, i.e., the target inlet throttling pressure. At this time, the target pressure of the second port 33b is 0. Furthermore, when the operating signal is greater than the threshold th1 and the target torque Tt, as the result of the calculation, is negative (the direction of the 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 - sign of the target pressure value of the second port 33b takes into account the negative sign of the target torque Tt.

[0058] On the other hand, when the operating signal is less than the threshold -th1 (indication for left turn) and the target torque Tt, as the result of the calculation, is negative, the result (-Tt / q), obtained by dividing the target torque Tt by the equivalent volume of the turn, is taken as the target pressure value of the second port 33b, i.e., the target inlet throttling pressure. The target pressure of the first port 33a is 0. Furthermore, when the operating signal is less than the threshold -th1 (indication for right turn) and the target torque Tt, as the result of the calculation, 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).

[0059] Furthermore, when the operating signal is a dead zone value from -th1 to th1, the inlet throttling side is the same as the previous port. The target pressure values ​​for the first port 33a and the second port 33b in this case are as follows: Figure 5 As shown.

[0060] In this way, the target inlet throttling pressure calculation unit 77 determines, based on the operation signal, which of the first port 33a and the second port 33b of the rotary hydraulic motor 33 is the inlet throttling side, and calculates the target pressure value (target inlet throttling pressure) of the inlet throttling side based on the target torque Tt of the rotary hydraulic motor 33, which is the result of the calculation by the target torque calculation unit 76.

[0061] Figure 6 It means Figure 3The block diagram shown illustrates the details of the inlet throttle pressure limit value calculation unit 78 within the controller's control block diagram. In the inlet throttle pressure limit value calculation unit 78, firstly, the calculation unit 781 multiplies the actual angular acceleration (angular acceleration detection value) of the rotary hydraulic motor 33 detected by the speed sensor 54 with a reference time (e.g., 0.3 seconds). 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 rotary hydraulic motor 33 detected by the speed sensor 54. These calculations estimate the angular velocity of the rotary hydraulic motor 33 at a future time after the reference time elapsed from the current moment when the controller 60 is operating. Alternatively, the controller can be configured to perform differential calculations based on the time series of the actual angular velocity (angular velocity detection value) of the rotary hydraulic motor 33 detected by the speed sensor 54, thereby calculating the actual angular acceleration.

[0062] Next, the calculation unit 783 takes the absolute value of the calculation result of the calculation unit 782 (the estimated value of the angular velocity of the rotary hydraulic motor 33 after a reference time from the current moment), and the calculation unit 784 multiplies the calculation result of the calculation unit 783 by the rotary equivalent volume q. This calculation estimates the drive flow rate of the rotary hydraulic motor 33 at a future time after a reference time from the current moment.

[0063] Furthermore, the calculation unit 785 divides the input horsepower limit value of the opposing rotary hydraulic motor 33 by the calculation result of the calculation unit 784 (the estimated flow rate of the rotary hydraulic motor 33 after a reference time from the current moment), and sets the upper and lower limits of the calculation result of the calculation unit 785 through Table 786. Thus, the limit value of the inlet throttling pressure of the rotary hydraulic motor 33 that does not exceed the horsepower limit is calculated.

[0064] Based on the inlet throttle pressure limit value calculated by the inlet throttle pressure limit calculation unit 78, the target inlet throttle pressure of the rotary hydraulic motor 33 is limited based on the calculation result of the target inlet throttle pressure calculation unit 77. Thus, a horsepower limit target inlet throttle pressure is calculated, taking into account the horsepower limit value and limiting the upper limit. That is, these calculations limit the target inlet throttle pressure so that when the driving pressure of the hypothetical rotary hydraulic motor 33 reaches the target inlet throttle pressure at a future time (after a predetermined time) after a reference time elapsed from the current time, the estimated horsepower input to the rotary hydraulic motor 33 does not exceed the horsepower limit value. The horsepower limit target inlet throttle pressure, as the calculation result, is input to the pump flow rate second target value calculation unit 79 (see below). Figure 7 ).

[0065] Figure 7 It means Figure 3The block diagram shown illustrates the details of the pump flow rate second target value calculation unit 79 within the controller's control block diagram. In the pump flow rate second target value calculation unit 79, firstly, the calculation unit 791 subtracts the actual inlet throttle pressure of the rotary hydraulic motor 33 (the pressure detection value on the inlet throttle side of the rotary hydraulic motor 33) detected by the first pressure sensors 51a and 51b from the input horsepower limit target inlet throttle pressure to calculate the pressure deviation. Next, a multiplication operation based on the proportional gain Kp2 of the calculation unit 792 is performed on the pressure deviation, which is the calculation result of the calculation unit 791, and a multiplication operation based on the integral gain Ki of the calculation unit 794 is performed after the integration processing based on the calculation unit 793. Next, the calculation unit 795 adds the calculation result of the calculation unit 793 to the calculation result of the calculation unit 794, and limits the upper and lower limits of the calculation result of the calculation unit 795 using Table 796, thereby calculating the second target value of the pump flow rate of the hydraulic pump 31. The second target value for pump flow is a value derived based on the difference between the target inlet throttle pressure and the actual inlet throttle pressure, i.e., the pressure deviation. It is a control value used for pressure control of the rotary hydraulic motor 33. Based on the limitations in Table 796, for example, the pressure is limited from 0 MPa to the set pressure of the main relief valve 37 in the hydraulic circuit. The second target value calculation unit 79 calculates the second target value for pump flow and sends it as a result to the pump flow control target value calculation unit 83 (see below). Figure 9 Output. In addition, in this description, the pressure detection values ​​of the first pressure sensors 51a and 51b are input to the calculation unit 791 for calculating the pressure deviation. However, when the ejection pressure of the hydraulic pump 31 is regarded as an approximation of the inlet throttling pressure of the rotary hydraulic motor 33, the pressure detection value of the second pressure sensor 52 may also be input to the calculation unit 791.

[0066] Figure 8 It means Figure 3The block diagram shown illustrates the details of the angular velocity deviation ratio calculation unit 81 in the controller's control block diagram. 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 rotary hydraulic motor 33 detected by the speed sensor 54 from the target angular velocity of the rotary hydraulic motor 33, which is the result of the calculation by the target angular velocity calculation unit 73. Next, after processing the target angular velocity of the rotary hydraulic motor 33, which is the result of the calculation by the target angular velocity calculation unit 73, by the calculation unit 812 (which prevents division by zero), the calculation unit 813 divides the angular velocity deviation, which is the result of the calculation by the calculation unit 811, by the target angular velocity of the rotary hydraulic motor 33 after processing by the calculation unit 812. The calculation unit 814 takes the absolute value of the result of the calculation by the calculation unit 813, thereby calculating the angular velocity deviation ratio. 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 sends the angular velocity deviation ratio, as the calculation result, to the pump flow control target value calculation unit 83 (see below). Figure 9 Output.

[0067] Figure 9 It means Figure 3 The block diagram shown illustrates the details of the pump flow control target value calculation unit 83 and the vent opening target value calculation unit 85 in the controller's control block diagram. In summary, the pump flow control target value calculation unit 83 calculates the pump flow control target value of the hydraulic pump 31 by adding the first target value of the pump flow (the result of the calculation by the first target value calculation unit 74) and the second target value of the pump flow (the result of the calculation by the second target value calculation unit 79) according to a ratio determined based on the output value of Table 831.

[0068] Specifically, Table 831 outputs a value ranging from 0 to 1 based on the angular velocity deviation ratio, which is the result of the calculation by the angular velocity deviation ratio calculation unit 81. In Table 831, for example, in the range where the angular velocity deviation ratio is less than the first threshold n1 (e.g., the range of 0.2 or less), the output value is set to 0 or a value close to 0. On the other hand, in the range where the angular velocity deviation ratio is greater than the second threshold n2, the output value is set to 1 or a value close to 1.

[0069] The calculation unit 832 multiplies the second target value of the pump flow rate by the output value of table 831, where the second target value of the pump flow rate is used for pressure control of the rotary hydraulic motor 33. On the other hand, the calculation unit 834 multiplies the first target value of the pump flow rate by the result of the calculation unit 833 after subtracting the output value of table 831 from 1, where the first target value of the pump flow rate is used for speed control of the rotary hydraulic motor 33. Finally, the calculation unit 835 calculates the target value of the pump flow rate control by adding the calculation result of the calculation unit 832 to the calculation result of the calculation unit 834.

[0070] Within a small range of angular velocity deviation ratios, the output value of Table 831 is set to approximately 0; therefore, the target value for pump flow control is the first target value for pump flow. Conversely, within a large range of angular velocity deviation ratios, the output value of Table 831 is set to approximately 1; therefore, the target value for pump flow control is the second target value for pump flow. That is, 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 rotary 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, pressure control is performed on the rotary hydraulic motor 33. Thus, the angular velocity deviation ratio becomes the indicator for switching the control of the rotary hydraulic motor 33 to speed control or pressure control.

[0071] The controller 60 calculates the target pump volume of the hydraulic pump 31 by dividing the target pump flow control value (which is the result of the calculation by the pump flow control target value calculation unit 83) by the target prime mover speed. Finally, the controller outputs a control signal corresponding to the target pump volume as the calculation result to the regulator 31a of the hydraulic pump 31. This controls the pump volume of the hydraulic pump 31.

[0072] The vent opening target value calculation unit 85 calculates the vent opening target value based on the angular velocity deviation ratio R, which is the result of the calculation by the angular velocity deviation ratio calculation unit 81, and refers to Table 851. In Table 851, when the angular velocity deviation ratio R is less than the first threshold n1, the opening of the vent valve 36 is set to be infinitely reduced. This is to reduce the loss caused by the outflow of pressurized oil from the vent valve 36 to the working oil tank 38. On the other hand, when the angular velocity deviation ratio is greater than the second threshold n2, the opening of the vent valve 36 is set to be maintained at a predetermined value. This is to control the pressure of the hydraulic circuit by changing the flow rate of the hydraulic pump 31. Furthermore, the first threshold n1 and the second threshold n2 can also be the same value. The controller 60 outputs a control signal corresponding to the vent opening target value, which is the result of the calculation by the vent opening target value calculation unit 85, to the vent valve 36. As a result, the opening degree of the vent valve 36 is controlled.

[0073] Next, the operation and effects of one embodiment of the work machine of the present invention will be explained by comparing its operation with that of a comparative example work machine. First, using... Figure 10 The operation of the hydraulic pump and the rotary hydraulic motor during the rotary operation in the comparative example machine will be explained. Figure 10 This is a graph showing the time waveform of the simulation results related to the movement of the hydraulic pump and the rotary hydraulic motor in a comparative example of a work machine according to an embodiment of the work machine of the present invention.

[0074] Figure 10Graph (A) shows the time variation of the rotary operation signal. Graph (B) shows the time variation of the hydraulic pump's discharge pressure and the rotary hydraulic motor's drive pressure. Graph (C) shows the time variation of the hydraulic pump's flow rate and the rotary hydraulic motor's flow rate. Graph (D) shows the time variation of the rotary hydraulic motor's angular velocity. Graph (E) shows the time variation of the rotary hydraulic motor's angular acceleration. Graph (F) shows the time variation of the hydraulic pump's output.

[0075] In the comparative example of the machine, if a slewing operation is input, the hydraulic pump's injection pressure is controlled to continuously rise until it reaches the set pressure of the main relief valve before the hydraulic pump's output reaches its horsepower limit. For example, as shown in Figure (A), the slewing operation begins at 1.0 on the horizontal axis (representing time). With a certain operation amount (e.g., full operation amount) input, the hydraulic pump's injection pressure rises sharply as shown in Figure (B) to reach the set pressure of the main relief valve, and the hydraulic pump's flow rate gradually increases as shown in Figure (C). If the product of the hydraulic pump's flow rate and injection pressure, i.e., the pump output, reaches the horsepower limit (around 1.75 on the horizontal axis (time) in Figure (F), control is executed to reduce the target flow rate of the hydraulic pump to prevent it from exceeding the pump output.

[0076] At this point, since the rotary hydraulic motor is accelerating as shown in Figure (D), if the target flow rate of the hydraulic pump is reduced, the pump's ejection pressure decreases sharply (refer to the initial sharp decrease near the horizontal axis 1.75 in Figure (B)). As a result, the angular acceleration of the rotary hydraulic motor decreases sharply (refer to the initial sharp decrease near the horizontal axis 1.75 in Figure (E)). Corresponding to this sharp decrease in ejection pressure, the hydraulic pump is controlled to increase the pump flow rate again. However, there is a certain time delay between obtaining the pressure detection value from the pressure sensor and controlling the pump volume. Therefore, repeated sharp increases and decreases in the ejection pressure of the hydraulic pump cause control oscillations (refer to the horizontal axis after 1.75 in Figure (B)). Therefore, due to the repeated sharp increases and decreases in the angular acceleration of the rotary hydraulic motor (refer to the horizontal axis after 1.75 in Figure (E)), the operator experiences a sense of unease. In addition, due to the repeated rapid increase and decrease of the hydraulic pump's injection pressure, the pump output temporarily exceeds the horsepower limit value repeatedly (refer to the horizontal axis 1.75 and beyond in Table (F), thus causing the machine body to vibrate.

[0077] Next, use Figure 11 The operation of the hydraulic pump and the rotary hydraulic motor during rotary operation in one embodiment of the working machine of the present invention will be described. Figure 11 This is a graph showing the time waveform of the simulation results related to the movement of the hydraulic pump and the rotary hydraulic motor relative to the rotary operation in one embodiment of the working machine of the present invention.

[0078] Figure 11 Charts (A) to (F) represent the objects and items that change over time. Figure 10 Charts (A) through (F) represent the same items. However, chart (B) also shows the time variation of the target pressure of the hydraulic pump 31 (the target pressure of the rotary hydraulic motor 33). In addition, chart (D) shows the time variation of the target angular velocity of the rotary hydraulic motor 33.

[0079] In this embodiment, when the angular velocity deviation ratio is large, the controller 60 estimates the angular velocity of the rotary hydraulic motor 33 at a future time after a reference time elapsed from the current time of calculation, and controls it based on the target pressure of the rotary hydraulic motor 33 (target ejection pressure of the hydraulic pump 31). The target pressure of the rotary hydraulic motor 33 is limited so that the input horsepower to the rotary hydraulic motor 33 at that future time, based on the estimated angular velocity, is below a horsepower limit value. Therefore, during the startup of the rotary hydraulic motor 33 when the angular velocity deviation ratio is large, the drive flow of the rotary hydraulic motor 33 is low (refer to the horizontal axis (time) 1.0 at the start of the rotary operation in Table (C)). Therefore, as shown in Table (B), the target pressure of the hydraulic pump 31 (target pressure (target inlet throttling pressure) of the rotary hydraulic motor 33) is set high, thereby increasing the rotational angular acceleration of the rotary hydraulic motor 33 (refer to the horizontal axis (time) 1.0 in Table (E)). Subsequently, as the angular velocity of the rotary hydraulic motor 33 increases, if the rotary hydraulic motor 33 is accelerated with the initial high drive pressure, the output of the hydraulic pump 31 (the horsepower supplied to the rotary hydraulic motor 33) reaches the horsepower limit. Therefore, through... Figure 6 The control operation shown pre-limits the target pump pressure (the product of the estimated flow rate and the target pump pressure) based on the estimated flow rate at a future time (after a predetermined time) elapsed from the current time. Thus, as shown in Figure (E), smooth and stable acceleration of the rotary hydraulic motor 33 is maintained, and as shown in Figure (F), the output of the hydraulic pump 31 is prevented from exceeding the horsepower limit. Therefore, the operation feels natural, and the desired rotary acceleration is achieved.

[0080] Furthermore, in this embodiment, the controller 60 controls the rotary hydraulic motor 33 based on the target speed when the angular velocity deviation ratio is small. For example, as shown in Figure (D), if the actual angular velocity of the rotary hydraulic motor 33 is close to the target angular velocity and the angular velocity deviation ratio is small near the horizontal axis (time) 2.5, the pump flow control target value is switched from the second target value for pump flow control for pressure control to the first target value for pump flow control for speed control. Through this speed control, the actual angular velocity of the rotary hydraulic motor 33 eventually matches the target angular velocity (refer to the area near the horizontal axis 2.7 in Figure (D)).

[0081] Furthermore, in this embodiment, the controller 60 controls the closure of the relief valve 36 by switching the control target value of the hydraulic pump 31 from pressure control to speed control. By using the relief valve 36 to cut off the flow of pressurized oil from the hydraulic pump 31 to the working oil tank 38, hydraulic losses can be reduced, enabling efficient rotary operation.

[0082] The hydraulic excavator according to one embodiment of the present invention described above includes: a hydraulic pump 31 that sprays pressurized oil; an upper rotating body 2 (rotating body) capable of rotating; a rotating hydraulic motor 33 (hydraulic actuator) that drives the upper rotating body 2 (rotating body) to rotate via a supply of pressurized oil from the hydraulic pump 31; an operating device 56 that outputs an operating signal instructing the operation of the upper rotating body 2 (rotating body); and a speed sensor 54 that detects the drive speed of the rotating hydraulic motor 33 (hydraulic actuator). Furthermore, it includes: a regulator 31a and a relief valve 36 as pressure adjustment devices, capable of adjusting the drive pressure of the rotating hydraulic motor 33 (hydraulic actuator); and a controller 60 that controls the regulator 31a and the relief valve 36 (pressure adjustment device). The controller 60 is configured to perform the following actions: calculate the target speed of the rotary hydraulic motor 33 (hydraulic actuator) based on the operation signal from the operating device 56; calculate the target pressure of the rotary hydraulic motor 33 (hydraulic actuator) based on the speed deviation, wherein the speed deviation is the difference between the target speed as a result of the calculation and the actual drive speed of the rotary hydraulic motor 33 (hydraulic actuator) detected by the speed sensor 54; limit the target pressure as a result of the calculation so that when the hypothetical drive pressure of the rotary hydraulic motor 33 (hydraulic actuator) reaches the target pressure as a result of the calculation after a specified time, the estimated horsepower input to the rotary hydraulic motor 33 (hydraulic actuator) does not exceed the limit value; and control the regulator 31a and the relief valve 36 (pressure adjustment device) based on the limited target pressure.

[0083] According to this structure, the regulator 31a and the relief valve 36 (pressure adjustment device) are controlled by using the target pressure of the rotary hydraulic motor 33 (hydraulic actuator), which is limited in advance considering the input horsepower to the rotary hydraulic motor 33 (hydraulic actuator) at a future time after a specified time. Therefore, the rotary hydraulic motor 33 (hydraulic actuator) can be driven with appropriate torque or acceleration within the horsepower limit.

[0084] Furthermore, the controller 60 of the hydraulic excavator in this embodiment is configured to estimate the angular velocity (drive speed) of the rotary hydraulic motor 33 (hydraulic actuator) at a future time (after a predetermined time) based on the actual angular velocity and actual angular acceleration of the rotary hydraulic motor 33 (hydraulic actuator) obtained from the detection value of the speed sensor 54, after a certain reference time has elapsed from the current time, thereby estimating the horsepower input to the rotary hydraulic motor 33 (hydraulic actuator) at a future time (after a predetermined time).

[0085] According to this structure, by using the actual drive speed and actual drive acceleration of the rotary hydraulic motor 33 (hydraulic actuator) obtained from the speed sensor 54, the drive speed of the rotary hydraulic motor 33 (hydraulic actuator) at a future moment (after a predetermined time) can be easily and accurately estimated. Therefore, the target pressure, as a result of the calculation, can be accurately limited so that the estimated horsepower input to the rotary hydraulic motor 33 (hydraulic actuator) does not exceed the horsepower limit. This estimated value is obtained from the accumulation of the estimated flow rate and the target pressure of the rotary hydraulic motor 33 (hydraulic actuator), and the estimated flow rate is calculated based on the estimated drive speed of the rotary hydraulic motor 33 (hydraulic actuator) at a future moment (after a predetermined time). Thus, the rotary hydraulic motor 33 (hydraulic actuator) can be driven with smooth acceleration without exceeding the horsepower limit.

[0086] In this embodiment, the pressure adjustment device includes a regulator 31a, which functions as a flow adjustment device and can adjust the drive pressure of the rotary hydraulic motor 33 (hydraulic actuator) by adjusting the ejection flow rate of the hydraulic pump 31. The controller 60 performs the following operations: calculates a first target value for the pump flow rate of the hydraulic pump 31 based on a target speed as a calculation result; calculates a second target value for the pump flow rate of the hydraulic pump 31 based on a restricted target pressure; calculates a speed deviation ratio, which is the ratio of the speed deviation to the target speed as a calculation result; if the speed deviation ratio as a calculation result is less than a first threshold n1, controls the regulator 31a (flow adjustment device) based on the first target value for the pump flow rate as a calculation result; on the other hand, if the speed deviation ratio as a calculation result is greater than a second threshold n2, as a pressure adjustment device that controls the pressure based on the restricted target pressure, controls the regulator 31a (flow adjustment device) based on the second target value for the pump flow rate as a calculation result.

[0087] According to this structure, during the startup of the rotary hydraulic motor 33 with a large speed deviation ratio, the estimated flow rate of the rotary hydraulic motor 33 (hydraulic actuator) is small. Therefore, the limited target pressure can be set higher accordingly. Thus, the acceleration of the rotary hydraulic motor 33 (hydraulic actuator) can be increased. On the other hand, if the speed deviation ratio is small, that is, if the target speed of the rotary hydraulic motor 33 (hydraulic actuator) is close to the drive speed, the regulator 31a (flow adjustment device) is controlled according to the first target value of the pump flow rate set based on the target speed. Therefore, the actual drive speed of the rotary hydraulic motor 33 (hydraulic actuator) can be accurately finely adjusted.

[0088] In addition, in this embodiment, the pressure regulating device also includes a relief valve 36, which releases pressurized oil ejected from the hydraulic pump 31 to the working oil tank 38. The controller 60 performs the following control: when controlling the regulator 31a (flow regulating device) according to a first target value of pump flow as a calculation result, it simultaneously controls the relief valve 36 to be closed; on the other hand, when controlling the regulator 31a (flow regulating device) according to a second target value of pump flow as a calculation result, it simultaneously maintains the relief valve 36 at a predetermined opening degree.

[0089] According to this structure, when speed control of the rotary hydraulic motor 33 (hydraulic actuator) is performed according to the target speed, the relief valve 36 is closed, thereby cutting off the flow of pressurized oil from the hydraulic pump 31 to the working oil tank 38 via the relief valve 36, thus reducing energy loss. On the other hand, when pressure control of the rotary hydraulic motor 33 (hydraulic actuator) is performed according to the target pressure, the relief valve 36 is opened, thereby allowing easy control of the drive pressure of the rotary hydraulic motor 33 (hydraulic actuator) by increasing or decreasing the flow rate of the hydraulic pump 31.

[0090] [Other Implementation Methods]

[0091] Furthermore, in one embodiment described above, an example of applying the invention to a hydraulic excavator is shown, and the invention can be widely applied to various working machines having a rotating body capable of rotation.

[0092] Furthermore, the present invention is not limited to the one embodiment described above, but also includes various modifications. The embodiments described above are detailed for the purpose of easily understanding and illustrating the present invention, and are not limited to having all the structures described. For example, a part of the structure of a certain embodiment may be replaced with the structure of another embodiment. In addition, the structure of another embodiment may be added to the structure of a certain embodiment. Furthermore, for a part of the structure of each embodiment, other structures may be added, deleted, or replaced.

[0093] For example, in one embodiment described above, an example was shown where a regulator 31a, which is a flow rate regulating device capable of adjusting the drive pressure of the rotary hydraulic motor 33, and a relief valve 36, which releases pressurized oil ejected from the hydraulic pump 31 to the working oil tank 38, were used as the structure. However, when the hydraulic pump is of fixed capacity, for example, the drive pressure of the rotary hydraulic motor 33 can also be adjusted by controlling the ejection flow rate of the hydraulic pump by changing the rotational speed of the prime mover 32. That is, the prime mover 32 functions as a flow rate regulating device capable of adjusting the ejection flow rate of the hydraulic pump by adjusting its rotational speed, and also functions as a pressure regulating device capable of adjusting the drive pressure of the rotary hydraulic motor 33 by adjusting the ejection flow rate of the hydraulic pump.

[0094] Symbol Explanation

[0095] 2… Upper rotating body (rotating body), 31… Hydraulic pump, 31a… Regulator (pressure adjustment device; flow adjustment device), 32… Prime mover (pressure adjustment device; flow adjustment device), 33… Rotary hydraulic motor (hydraulic actuator), 36… Relief valve (pressure adjustment device), 38… Working oil tank, 54… Speed ​​sensor, 56… Control lever (operating device), 60… Controller.

Claims

1. A work machine having: a hydraulic pump that discharges pressure oil; a swing body that is capable of swing operation; a hydraulic actuator that swing drives the swing body by supply of pressure oil from the hydraulic pump; an operation device that outputs an operation signal indicative of operation of the swing body; and a speed sensor that detects a drive speed of the hydraulic actuator, characterized by: the work machine having: a pressure adjusting device that is capable of adjusting a drive pressure of the hydraulic actuator; and a controller that controls the pressure adjusting device, the controller performing the following operations: calculating a target speed of the hydraulic actuator in accordance with the operation signal from the operation device; calculating a target pressure of the hydraulic actuator on the basis of a speed deviation, which is a difference between the target speed calculated as a result of the calculation and an actual drive speed of the hydraulic actuator detected by the speed sensor; limiting the target pressure calculated as a result of the calculation so that an input horsepower to the hydraulic actuator estimated when it is assumed that the drive pressure of the hydraulic actuator reaches the target pressure calculated as a result of the calculation after a prescribed time does not exceed a limit value; controlling the pressure adjusting device in accordance with the target pressure that is limited, the pressure adjusting device having a flow rate adjusting device that is capable of adjusting the drive pressure of the hydraulic actuator by adjusting a discharge flow rate of the hydraulic pump, the controller performing the following operations: calculating a pump flow rate first target value of the hydraulic pump on the basis of the target speed calculated as a result of the calculation; calculating a pump flow rate second target value of the hydraulic pump on the basis of the target pressure that is limited; calculating a speed deviation ratio, which is a ratio of the speed deviation with respect to the target speed calculated as a result of the calculation; in a case where the speed deviation ratio calculated as a result of the calculation is smaller than a first threshold value, performing control of the flow rate adjusting device in accordance with the pump flow rate first target value calculated as a result of the calculation; on the other hand, in a case where the speed deviation ratio calculated as a result of the calculation is larger than a second threshold value, performing control of the flow rate adjusting device in accordance with the pump flow rate second target value calculated as a result of the calculation as a result of control of the pressure adjusting device in accordance with the target pressure that is limited.

2. The work machine according to claim 1, characterized in that: the controller estimates the drive speed of the hydraulic actuator after the prescribed time on the basis of the actual drive speed and an actual drive acceleration of the hydraulic actuator obtained from a detection value of the speed sensor, thereby estimating the input horsepower to the hydraulic actuator after the prescribed time.

3. The work machine according to claim 1, characterized in that: the pressure adjusting device further has a relief valve that releases pressure oil discharged from the hydraulic pump to a working oil tank, the controller performing the following operation: in a case where control of the flow rate adjusting device in accordance with the pump flow rate first target value calculated as a result of the calculation is performed, simultaneously controlling the relief valve to a closed state. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ On the other hand, in a case where the control is executed on the flow rate adjusting device according to the pump flow rate second target value as the operation result, the bleed valve is controlled to be kept in a state where the opening degree is prescribed at the same time.

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