Excavator and control system

Abstract

To provide a shovel and a control system allowing highly precise rotation control.SOLUTION: A shovel is provided with: a rotatable rotation body; a rotation motor to rotate the rotation body; a work machine loaded on the rotation body; a rotation control device controlled for rotational motion of the rotation body. The shovel, further, is provided with an inertia detection part detecting inertia of the work machine and a controller. The controller sets rotational acceleration of the rotation body according to control amount of the rotation control device. the controller corrects the set rotational acceleration by the inertia detected with the inertia detection part. The controller controls the rotation motor in accordance with the corrected rotational acceleration.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present disclosure relates to an excavator and a control system.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2009-174447 (Patent Document 1) discloses a hybrid excavator that uses an internal combustion engine and an electric motor in combination. The hybrid excavator described in the above document includes a slewing mechanism that is slewed by a slewing motor. The slewing motor slews the slewing mechanism according to the operation amount of a slewing operation lever while using electric energy supplied from a power generation motor or a battery under the control of a main controller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an excavator including a slewing body and a working machine mounted on the slewing body, when performing an operation of slewing the slewing body while moving the working machine, it is required to reduce fluctuations in the slewing speed of the slewing body and control slewing with high precision.

[0005] The present disclosure proposes an excavator and a control system capable of highly accurate slewing control with little fluctuation in slewing speed.

Means for Solving the Problems

[0006] An excavator according to an aspect of the present disclosure includes a slewing body that can slew, a slewing electric motor that slews the slewing body, a working machine mounted on the slewing body, and a slewing operation device that is operated for the slewing operation of the slewing body. The excavator further includes an inertia detection unit that detects the inertia of the working machine and a controller. The controller sets a slewing acceleration of the slewing body according to the operation amount of the slewing operation device. The controller corrects the set slewing acceleration according to the inertia detected by the inertia detection unit. The controller controls the slewing electric motor according to the corrected slewing acceleration.

[0007] A control system according to an aspect of the present disclosure includes a slewing body that can slew, a slewing electric motor that slews the slewing body, a working machine mounted on the slewing body, and a slewing operation device that is operated for the slewing operation of the slewing body. The control system further includes an inertia detection unit that detects the inertia of the working machine and a controller. The controller sets a slewing acceleration of the slewing body according to the operation amount of the slewing operation device. The controller corrects the set slewing acceleration according to the inertia detected by the inertia detection unit. The controller controls the slewing electric motor according to the corrected slewing acceleration.

Advantages of the Invention

[0008] The excavator and the control system of the present disclosure enable highly accurate slewing control with little variation in slewing speed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. In the specification and drawings, the same components or corresponding components are denoted by the same reference numerals, and duplicate explanations will not be repeated. Also, in the drawings, for convenience of explanation, the configuration may be omitted or simplified in some cases.

[0011] <Overall Configuration> In the embodiment, a hybrid excavator 100 will be described as an example of an excavator. FIG. 1 is a perspective view of a hybrid excavator 100 as an example of an excavator according to the embodiment.

[0012] As shown in FIG. 1, the hybrid excavator 100 has a main body 1 and a working machine 2 that operates hydraulically. The main body 1 has a revolving body 3 and a traveling body 5. The traveling body 5 has a pair of crawler belts 5Cr and a traveling motor 5M. The hybrid excavator 100 can travel by the rotation of the crawler belt 5Cr. The traveling motor 5M is provided as a drive source for the traveling body 5. The traveling motor 5M is a hydraulic motor that operates hydraulically. The traveling body 5 may have wheels (tires).

[0013] The slewing body 3 is disposed on and supported by the traveling body 5. The slewing body 3 is rotatable relative to the traveling body 5 about a slewing axis RX. The slewing axis RX is an imaginary straight line extending in the vertical direction and serving as the center of rotation of the slewing body 3. The slewing body 3 is rotatable relative to the ground about the slewing axis RX.

[0014] The slewing body 3 has a driver's cab 4 (cab). Inside the driver's cab 4, a driver's seat 4S on which an operator sits is provided. The operator (crew member) can board the driver's cab 4 and operate the working machine 2, perform a slewing operation of the slewing body 3 relative to the traveling body 5, and perform a traveling operation of the hybrid excavator 100 by the traveling body 5.

[0015] The slewing body 3 has an exterior cover 9. The exterior cover 9 covers the machine room. In the machine room, an engine 20, a hydraulic pump 25, a generator motor 21, an inverter 22, a capacitor 23, etc. shown in FIG. 2 are arranged.

[0016] The working machine 2 is mounted on the slewing body 3. The working machine 2 has a boom 6, an arm 7, and a bucket 8. The boom 6 is rotatably connected to the main body 1 (traveling body 5 and slewing body 3). Specifically, the base end portion of the boom 6 is rotatably connected to the slewing body 3 with a boom foot pin 13 as a fulcrum.

[0017] The arm 7 is rotatably connected to the boom 6. Specifically, the base end portion of the arm 7 is rotatably connected to the tip end portion of the boom 6 with a boom top pin 14 as a fulcrum.

[0018] The bucket 8 is rotatably connected to the arm 7. Specifically, the base end portion of the bucket 8 is rotatably connected to the tip end portion of the arm 7 with an arm top pin 15 as a fulcrum. The bucket 8 is an example of an attachment attachable to the tip of the working machine 2. Depending on the type of work, the attachment can be replaced with a breaker, a grapple, or a lifting magnet, etc. The hybrid excavator 100 is configured to be selectively attachable with a plurality of types of attachments to the tip of the working machine 2.

[0019] In the hybrid excavator 100 of the embodiment, the positional relationship of each part will be described with reference to the working machine 2.

[0020] The boom 6 of the working machine 2 rotates relative to the revolving body 3 about the boom foot pin 13. A specific portion of the boom 6 that rotates relative to the revolving body 3, for example, the tip of the boom 6, moves along an arc, and a plane including the arc is specified. When the hybrid excavator 100 is viewed in plan, this plane is represented as a straight line. The direction in which this straight line extends is the front-rear direction of the main body 1 or the front-rear direction of the revolving body 3, and hereinafter will simply be referred to as the front-rear direction. The left-right direction of the main body 1 (vehicle width direction) or the left-right direction of the revolving body 3 is a direction orthogonal to the front-rear direction in plan view, and hereinafter will simply be referred to as the left-right direction. The boom foot pin 13 extends in the left-right direction. The up-down direction of the main body 1 or the up-down direction of the revolving body 3 is a direction orthogonal to the plane defined by the front-rear direction and the left-right direction, and hereinafter will simply be referred to as the up-down direction.

[0021] In the front-rear direction, the side where the working machine 2 protrudes from the main body 1 is the front direction, and the direction opposite to the front direction is the rear direction. When looking in the front direction, the right side and the left side in the left-right direction are the right direction and the left direction, respectively. In the up-down direction, the side with the ground is the lower side, and the side with the sky is the upper side.

[0022] The front-rear direction is the front-rear direction of the operator sitting on the driver's seat 4S in the cab 4. The left-right direction is the left-right direction of the operator sitting on the driver's seat 4S. The up-down direction is the up-down direction of the operator sitting on the driver's seat 4S. The direction directly facing the operator sitting on the driver's seat 4S is the front direction, and the direction behind the operator sitting on the driver's seat 4S is the rear direction. When the operator sitting on the driver's seat 4S is facing forward, the right side and the left side are the right direction and the left direction, respectively. The foot side of the operator sitting on the driver's seat 4S is the lower side, and the overhead side is the upper side.

[0023] The working machine 2 further includes a boom cylinder 10, an arm cylinder 11, and a bucket cylinder 12. One end of the boom cylinder 10 is connected to the slewing body 3, and the other end is connected to the boom 6. The boom 6 can be driven with respect to the main body 1 by the boom cylinder 10. By this drive, the boom 6 can rotate in the vertical direction with respect to the slewing body 3 with the boom foot pin 13 as a fulcrum.

[0024] One end of the arm cylinder 11 is connected to the boom 6, and the other end is connected to the arm 7. The arm 7 can be driven with respect to the boom 6 by the arm cylinder 11. By this drive, the arm 7 can rotate in the vertical direction or the front-rear direction with respect to the boom 6 with the boom top pin 14 as a fulcrum.

[0025] One end of the bucket cylinder 12 is connected to the arm 7, and the other end is connected to the bucket link 17. The bucket 8 can be driven with respect to the arm 7 by the bucket cylinder 12. By this drive, the bucket 8 can rotate in the vertical direction with respect to the arm 7 with the arm top pin 15 as a fulcrum.

[0026] Each of the boom cylinder 10, the arm cylinder 11, and the bucket cylinder 12 is a hydraulic cylinder and is driven by hydraulic pressure.

[0027] <System Configuration> FIG. 2 is a schematic block diagram conceptually showing the system configuration of the hybrid excavator 100 according to the embodiment. As shown in FIG. 2, the hybrid excavator 100 includes an engine 20, a generator motor 21, an inverter 22, a capacitor 23, a slewing electric motor 24, a hydraulic pump 25, a control valve 28, and a controller 30.

[0028] The engine 20 is the driving source for the operation of the work machine 2. The engine 20 is the driving source for the travel of the hybrid excavator 100 by the traveling body 5. The engine 20 is an internal combustion engine, for example, a diesel engine. The output of the engine 20 is controlled by adjusting the amount of fuel injected into the cylinder. This adjustment is performed by the governor 20A attached to the fuel injection pump of the engine 20 being controlled by the controller 30. The output shaft of the engine 20 is connected to the drive shaft of the generator motor 21.

[0029] The generator motor 21 operates as a generator that generates electricity using the driving force generated by the engine 20. The generator motor 21 performs charge replenishment of the capacitor 23 and power supply to the swing electric motor 24 during swing acceleration. Further, the generator motor 21 operates as an electric motor (motor) driven by the electrical energy stored in the capacitor 23. The generator motor 21 utilizes the electrical energy discharged from the capacitor 23 for assist when accelerating the engine 20 during work. The generator motor 21 may be, for example, an SR (Switched Reluctance) motor with a simple structure and excellent heat resistance.

[0030] The inverter 22 converts and controls the current and voltage among the generator motor 21, the capacitor 23, and the swing electric motor 24. The inverter 22 controls the generator motor 21, the capacitor 23, and the swing electric motor 24 according to the control command value output from the controller 30. The inverter 22 is electrically connected to the capacitor 23 via a DC power line.

[0031] The capacitor 23 is a power storage device that stores power. The capacitor 23 is, for example, an electric double layer capacitor. The capacitor 23 stores the power generated by the generator motor 21 and also supplies power to the generator motor 21. The capacitor 23 is adopted to enable efficient instantaneous charging and discharging of electrical energy. The power storage device may be a secondary battery such as a nickel-metal hydride battery or a lithium-hydrogen battery.

[0032] The inverter 22 supplies the power discharged from the capacitor 23 to the swing electric motor 24. The swing electric motor 24 drives the swing body 3 with the electric energy stored in the capacitor 23. The swing body 3 is driven by the electric energy stored in the capacitor 23 and the power generated by the power generation motor 21. The swing electric motor 24 recovers the energy generated when the swing of the swing body 3 decelerates as electric energy and stores it in the capacitor 23. The swing electric motor 24 may be, for example, a PM (Permanent Magnet) motor. The swing electric motor 24 corresponds to the swing motor of the embodiment.

[0033] The drive shaft of the hydraulic pump 25 is connected to the output shaft of the engine 20 via the power generation motor 21. The hydraulic pump 25 is driven by the driving force generated by the engine 20. The hydraulic pump 25 discharges pressurized oil. The hydraulic pump 25 supplies the hydraulic oil used for driving the work implement 2 and traveling of the traveling body 5. The hydraulic pump 25 is connected to the engine 20 as a drive source and is an example of a hydraulic device driven by the engine 20. The hydraulic device also includes the boom cylinder 10, arm cylinder 11, bucket cylinder 12, and traveling motor 5M shown in FIG. 1.

[0034] The hydraulic pump 25 may be a variable displacement type hydraulic pump. The hydraulic pump 25 may be a swash plate type hydraulic pump having a variable swash plate. The angle of the variable swash plate is continuously controlled steplessly by the swash plate drive unit 25A according to the control command value output from the controller 30. The swash plate drive unit 25A is, for example, a solenoid.

[0035] The tank 26 is a tank that stores the oil used by the hydraulic pump 25. The oil stored in the tank 26 is sucked out from the tank 26 by driving the hydraulic pump 25 and supplied to the control valve 28. The pressure sensor 27 detects the pressure of the hydraulic oil discharged by the hydraulic pump 25 (pump discharge pressure). A detection signal indicating the pump discharge pressure detected by the pressure sensor 27 is input from the pressure sensor 27 to the controller 30.

[0036] The control valve 28 has respective operation valves for adjusting the supply amount of the hydraulic oil for each of the boom cylinder 10, the arm cylinder 11, the bucket cylinder 12, and the travel motor 5M. By operating each operation valve according to the control command value output from the controller 30, the supply amount of the hydraulic oil to the hydraulic actuators, that is, the boom cylinder 10, the arm cylinder 11, the bucket cylinder 12, and the travel motor 5M, is adjusted. The hydraulic oil is the oil supplied to the hydraulic actuator to operate the hydraulic actuator.

[0037] The hybrid excavator 100 includes an operating device operated by an operator. Specifically, the operating device includes a swing operating device 41, a work implement operating device 42, and a travel operating device 43. The swing operating device 41, the work implement operating device 42, and the travel operating device 43 are arranged in the cab 4.

[0038] The swing operating device 41 is operated for the swing operation of the swing body 3. The swing operating device 41 is, for example, an operation lever. The swing operation detection unit 41A detects the operation amount of the swing operating device 41. When the swing operating device 41 is an operation lever, the swing operation detection unit 41A detects the direction and angle of the tilt from the neutral position of the operation lever. The swing operation detection unit 41A outputs a detection signal to the controller 30. By controlling the inverter 22 by the controller 30 based on the detection signal, the swing electric motor 24 is driven and the swing body 3 performs a swing operation.

[0039] The work implement operating device 42 is operated for the operation of the work implement 2. The work implement operating device 42 is, for example, an operation lever. The work implement operation detection unit 42A detects the operation amount of the work implement operating device 42. When the work implement operating device 42 is an operation lever, the work implement operation detection unit 42A detects the direction and angle of the tilt from the neutral position of the operation lever. The work implement operation detection unit 42A outputs a detection signal to the controller 30. By controlling the control valve 28 by the controller 30 based on the detection signal, the boom cylinder 10, the arm cylinder 11, and the bucket cylinder 12 expand and contract appropriately, and the work implement 2 operates.

[0040] The traveling operation device 43 is operated for the operation of the traveling body 5. The traveling operation device 43 is, for example, an operation pedal. The traveling operation detection unit 43A detects the operation amount of the traveling operation device 43. When the traveling operation device 43 is an operation pedal, the traveling operation detection unit 43A detects the depression amount of the operation pedal. The traveling operation detection unit 43A outputs a detection signal to the controller 30. By controlling the control valve 28 by the controller 30 based on the detection signal, the traveling motor 5M is driven and the traveling body 5 travels.

[0041] The work implement operation device 42 and the traveling operation device 43 constitute a second operation device that is operated for the operation of the hybrid excavator 100 other than the turning control of the swing body 3. The second operation device is operated for the operation of the work implement 2, that is, the boom 6, the arm 7, and the bucket 8. The second operation device is operated for the operation of the traveling body 5.

[0042] Inside the cab 4, a right operation lever is arranged on the right side of the driver's seat 4S, and a left operation lever is arranged on the left side of the driver's seat 4S. The lowering and raising operations of the boom 6 may be performed according to the operation of the right operation lever in the front-rear direction, and the operations of the bucket 8 in the excavation direction and the dump direction may be performed according to the operation of the right operation lever in the left-right direction. The operations of the arm 7 in the dump direction and the excavation direction may be performed according to the operation of the left operation lever in the left-right direction, and the right and left turns of the swing body 3 may be performed according to the operation of the left operation lever in the front-rear direction.

[0043] One operation lever may have a function as the turning operation device 41 and a part of the functions of the work implement operation device 42. The turning operation device 41 and the work implement operation device 42 may be separate operation devices or integrated operation devices. That is, the turning operation device 41 and the second operation device do not necessarily have to be provided as separate operation devices. The same single operation device may be operated for the turning operation of the swing body 3 and for the operations other than the turning of the swing body 3.

[0044] The swing operation detection unit 41A, the work implement operation detection unit 42A, and the traveling operation detection unit 43A may be displacement sensors such as potentiometers, for example. The swing operation device 41, the work implement operation device 42, and the traveling operation device 43 are exemplified as electric operation devices in FIG. 2, but may be pilot hydraulic operation devices.

[0045] The input unit 45 is operated by the operator. The signal generated by the operation of the input unit 45 is output to the controller 30. The input unit 45 may have operation buttons, operation switches, a touch panel, and the like. The information input to the input unit 45 includes, for example, the type of attachment attached to the tip of the work implement 2, and also includes the operation mode of the swing operation of the swing body 3. The operation modes of the swing operation include a mode of swinging at high speed to improve work efficiency and a mode of swinging at low speed to reduce the sway of the suspended load.

[0046] The controller 30 is a controller that controls the operation of the entire hybrid excavator 100, and is configured to include a CPU (Central Processing Unit), a non-volatile memory, a timer, and the like. The controller 30 is mounted on the hybrid excavator 100. The controller 30 may be arranged outside the hybrid excavator 100. The controller 30 may be arranged at the work site of the hybrid excavator 100, or may be arranged at a remote location away from the work site of the hybrid excavator 100. The hybrid excavator 100 and the controller 30 arranged outside the hybrid excavator 100 may constitute a control system of the hybrid excavator 100.

[0047] <Excavation and loading work> Next, the excavation and loading work, which is a typical work performed by the excavator, will be described. FIG. 3 is a schematic diagram showing the excavation and loading work by the hybrid excavator 100.

[0048] The hybrid excavator 100 performs an excavation operation of scooping up an object to be excavated such as earth and sand into the bucket 8. The point P10 shown in FIG. 3 indicates the position of the bucket 8 when the excavation operation is completed. That is, the point P10 indicates the position where the slewing operation starts.

[0049] After the excavation operation is completed, the hybrid excavator 100 performs a hoist slewing operation in which the slewing body 3 slews while raising the boom 6, and discharges the object to be excavated in the bucket 8. The point P13 shown in FIG. 3 indicates the position of the bucket 8 when the slewing operation is completed. That is, the point P13 indicates the position where the object to be excavated in the bucket 8 is discharged onto the loading platform 202 of the dump truck 200. With the slewing body 3 stopped in the slewing posture, the working machine 2 faces the loading platform 202 of the dump truck 200. From the point P10 to the point P13, the slewing operation of the slewing body 3 is performed. The point P13 indicates the position of the bucket 8 when the hoist slewing operation is completed. From the point P10 to the point P13, the hoist slewing operation is performed.

[0050] The hybrid excavator 100 raises the boom 6 while slewing the slewing body 3 until the bucket 8 reaches the height at which it discharges earth and sand, and then stops the relative movement of the working machine 2 with respect to the slewing body 3 and slews the slewing body 3 to move the bucket 8 to the earth-discharging position. From the position of the slewing body 3 during the excavation operation shown by the dashed line in FIG. 3 to the position of the slewing body 3 at the end of the slewing operation shown by the solid line in FIG. 3, the slewing body 3 has slewed 90°. When performing the excavation operation, the working machine 2 is arranged to extend parallel to the extending direction of the crawler 5Cr. At the time when the slewing operation is completed, the working machine 2 extends in a direction perpendicular to the extending direction of the crawler 5Cr.

[0051] After the bucket 8 has moved to the earth-discharging position, the hybrid excavator 100 performs an earth-discharging operation of discharging the object to be excavated held by the bucket 8 onto the loading platform 202 of the dump truck 200 at the earth-discharging position.

[0052] After discharging the object to be excavated from the bucket 8, the hybrid excavator 100 performs a down swing operation in which the swing body 3 swings while lowering the boom 6. The hybrid excavator 100 moves the bucket 8 from the point P13 to the point P10 by tracing the locus of the bucket 8 during the hoist swing operation in the reverse direction. The hybrid excavator 100 swings the swing body 3 while stopping the relative movement of the working machine 2 with respect to the swing body 3, and then lowers the boom 6 while swinging the swing body 3 to move the emptied bucket 8 after the discharging operation to the start position of the excavation operation, that is, the point P10.

[0053] Based on the embodiment, the hybrid excavator 100 performs a series of processes of excavation operation, hoist swing operation, discharging operation, and down swing operation repeatedly to perform the operation of loading the object to be excavated into the dump truck 200.

[0054] <Calculation of the calculated load value W> Next, an example of a method for obtaining the weight of the current load in the bucket 8 will be described. FIG. 4 is a side view of the hybrid excavator 100 showing the configuration of the sensor attached to the working machine 2.

[0055] A cylinder pressure sensor 10A is attached to the head side of the boom cylinder 10. The cylinder pressure sensor 10A can detect the pressure (head pressure) of the hydraulic oil in the cylinder head side oil chamber of the boom cylinder 10. A cylinder pressure sensor 10B is attached to the bottom side of the boom cylinder 10. The cylinder pressure sensor 10B can detect the pressure (bottom pressure) of the hydraulic oil in the cylinder bottom side oil chamber of the boom cylinder 10.

[0056] Stroke sensors (detection units) 18A, 18B, and 18C are attached to the boom cylinder 10, the arm cylinder 11, and the bucket cylinder 12, respectively.

[0057] Each of the stroke sensors 18A, 18B, 18C and the cylinder pressure sensors 10A, 10B is electrically connected to the arithmetic unit 31 of the controller 30.

[0058] The arithmetic unit 31 calculates the boom angle θ1 based on the sensor output of the stroke sensor 18A in the boom cylinder 10. The arithmetic unit 31 calculates the arm angle θ2 based on the sensor output of the stroke sensor 18B in the arm cylinder 11. The arithmetic unit 31 calculates the bucket angle θ3 based on the sensor output of the stroke sensor 18C in the bucket cylinder 12. The boom angle θ1, the arm angle θ2, and the bucket angle θ3 may be calculated using an inertial measurement unit (IMU) attached to the boom 6, the arm 7, and the bucket 8, or may be calculated using angle sensors attached to the boom foot pin 13, the boom top pin 14, and the arm top pin 15, such as a potentiometer or a rotary encoder.

[0059] The arithmetic unit 31 acquires the head pressure and bottom pressure of the boom cylinder 10, the boom angle θ1, the arm angle θ2, and the bucket angle θ3.

[0060] In addition to the arithmetic unit 31, the controller 30 has a storage unit 32. Information such as the weights and shapes of the boom 6, the arm 7, and the bucket 8 is stored in the storage unit 32. These pieces of information may be stored in the storage unit 32 from the beginning, or may be input into the storage unit 32 by an operator's operation of the input unit 45 (Fig. 2).

[0061] The controller 30 (arithmetic unit 31) has a function of calculating the value (calculated load value) W of the weight of the current load in the bucket 8 based on the load of the boom cylinder 10. Specifically, the controller 30 (arithmetic unit 31) calculates the calculated load value W from the balance of the moments of the boom 6, the arm 7, and the bucket 8. The load of the boom cylinder 10 is a so-called axial force obtained from the head pressure and bottom pressure of the boom cylinder 10.

[0062] Fig. 5 is a schematic diagram of the working machine 2 for explaining the balance of moments for calculating the calculated load value W.

[0063] As shown in FIG. 5, in the embodiment, the current calculated load value W in the bucket 8 is calculated from the balance of each moment around the boom foot pin 13. Here, the balance of each moment around the boom foot pin 13 is expressed by the following formula (1).

[0064] Mboomcyl = Mboom + Marm + Mbucket + W × L ··· Formula (1) In Formula (1), Mboomcyl is the moment around the boom foot pin 13 due to the load of the boom cylinder 10. Mboomcyl is calculated from the load (head pressure and bottom pressure) of the boom cylinder 10. The head pressure of the boom cylinder 10 is detected by the cylinder pressure sensor 10A. The bottom pressure of the boom cylinder 10 is detected by the cylinder pressure sensor 10B. Based on the head pressure and bottom pressure of the boom cylinder 10, the moment Mboomcyl around the boom foot pin 13 due to the load of the boom cylinder 10 is calculated.

[0065] Mboom is the moment around the boom foot pin 13 due to the dead weight of the boom 6. Mboom is calculated by the product (r1 × M1) of the position of the center of gravity C1 of the boom 6 and the distance r1 between the boom foot pins 13 and the weight M1 of the boom 6. The position of the center of gravity C1 of the boom 6 is calculated from the boom angle θ1 and the like. The weight M1 of the boom 6 and the like are stored in the storage unit 32.

[0066] Marm is the moment around the boom foot pin 13 due to the dead weight of the arm 7. Marm is calculated by the product (r2 × M2) of the position of the center of gravity C2 of the arm 7 and the distance r2 between the boom foot pins 13 and the weight M2 of the arm 7. The position of the center of gravity C2 of the arm 7 is calculated from the arm angle θ2 and the like. The weight M2 of the arm 7 and the like are stored in the storage unit 32.

[0067] Mbucket is the moment around the boom foot pin 13 due to the self-weight of the bucket 8. Mbucket is calculated by the product (r3 × M3) of the distance r3 between the position of the center of gravity C3 of the bucket 8 and the boom foot pin 13 and the weight M3 of the bucket 8. The position of the center of gravity C3 of the bucket is calculated from the bucket angle θ3 and the like. The weight M3 of the bucket 8 and the like are stored in the storage unit 32.

[0068] W is the value of the weight of the current load in the bucket 8. L is the horizontal distance from the boom foot pin 13 to the arm top pin 15 (the part where the bucket 8 is supported by the arm 7). Based on the calculated boom angle θ1, arm angle θ2, the length of the boom 6, and the length of the arm 7, the horizontal distance L from the boom foot pin 13 to the arm top pin 15 is calculated.

[0069] By substituting each moment Mboomcyl, Mboom, Marm, Mbucket and the distance L calculated above into the above formula (1), the calculated load value W is calculated by the controller 30 (arithmetic unit 31).

[0070] As described above, the calculated load value W is calculated using the displacement amounts, head pressures, bottom pressures, etc. of the respective cylinders 10, 11, 12.

[0071] <Swing acceleration control> Hereinafter, the control of the swing acceleration of the swing body 3 in the hybrid excavator 100 based on the embodiment will be described. FIG. 6 is a block diagram for explaining the functional configuration of the arithmetic unit 31. The arithmetic unit 31 based on the embodiment includes a swing acceleration setting unit 52, a swing acceleration correction unit 54, a swing operation control unit 56, and a load calculation unit 58, as shown in FIG. 6.

[0072] The turning acceleration setting unit 52 sets the turning acceleration of the revolving body 3 according to the operation amount of the turning operation device 41. The turning acceleration correction unit 54 corrects the turning acceleration of the revolving body 3 set by the turning acceleration setting unit 52 according to the inertia of the working machine 2. The turning operation control unit 56 controls the turning electric motor 24 according to the turning acceleration of the revolving body 3 corrected by the turning acceleration correction unit 54. The load calculation unit 58 calculates the calculated load value W by, for example, the method described with reference to FIGS. 4 and 5. By controlling the turning acceleration of the revolving body 3, it is possible to reduce the fluctuation of the turning speed of the revolving body 3 and smoothly increase or decrease the revolving body 3, and it is also possible to arbitrarily set the increase amount per unit time of the turning speed of the revolving body 3.

[0073] FIG. 7 is a conceptual diagram of a plurality of maps MP1 to MP3 stored in the storage unit 32. The storage unit 32 stores a plurality of maps MP1 to MP3 showing the change in the turning acceleration of the revolving body 3 with respect to time and the change in the rotational speed of the turning electric motor 24 with respect to time. Although three maps MP1 to MP3 are illustrated in FIG. 7, actually, the storage unit 32 stores a large number of four or more maps.

[0074] In each of the maps MP1 to MP3, the turning acceleration of the revolving body 3 gradually increases from zero to the maximum value, and then gradually decreases from the maximum value to return to zero. In each of the maps MP1 to MP3, the time from the time t1 when the turning acceleration of the revolving body 3 starts to increase from zero to the time t2 when the turning acceleration of the revolving body 3 decreases and returns to zero is the same. The maximum value g2 of the turning acceleration of the revolving body 3 in the map MP2 is larger than the maximum value g3 of the turning acceleration of the revolving body 3 in the map MP3. The maximum value g1 of the turning acceleration of the revolving body 3 in the map MP1 is larger than the maximum value g2 of the turning acceleration of the revolving body 3 in the map MP2.

[0075] Among maps MP1 to MP3, the maximum value v1 of the rotational speed of the swing electric motor 24 in map MP1 is the largest. Among maps MP1 to MP3, the maximum value v3 of the rotational speed of the swing electric motor 24 in map MP3 is the smallest. The maximum value v2 of the rotational speed of the swing electric motor 24 in map MP2 is a value between the maximum value v1 in map MP1 and the maximum value v3 in map MP3.

[0076] In the example shown in FIG. 7, the rate of change of acceleration per unit time (i.e., jerk) when the swing acceleration of the swing body 3 increases or decreases is equal in each of the maps MP1 to MP3. Jerk is indicated by the slope of a graph with time on the horizontal axis and acceleration on the vertical axis. The jerks Ja1 when the swing acceleration increases in each of the maps MP1 to MP3 are equal to each other. The jerks Ja2 when the swing acceleration decreases in each of the maps MP1 to MP3 are equal to each other.

[0077] The jerk when the swing body 3 swings may be different in each of the maps MP1 to MP3. For example, in map MP1 where the maximum value of the swing acceleration is the largest, the jerk may be made larger than in the other maps MP2 and MP3. In map MP3 where the maximum value of the swing acceleration is the smallest, the jerk may be made smaller than in the other maps MP1 and MP2.

[0078] FIG. 8 is a flowchart showing an example of the control of the swing acceleration of the swing body 3 during hoist swing. As shown in FIG. 8, in step S1, a selection of an attachment attached to the tip of the work implement 2 is made. An operator operating the hybrid excavator 100 selects an attachment that is currently attached to the tip of the work implement 2 or that will be replaced with the tip of the work implement 2 for future work.

[0079] The operator uses the input unit 45 (Figure 2) to input the selection of the attachment to the controller 30. The input unit 45 has a function as an attachment selection input unit that accepts a selection input of which type of attachment among a plurality of types of attachments attachable to the tip of the working machine 2 is to be attached to the tip of the working machine 2.

[0080] In step S2, a selection of an operation mode related to the turning operation of the revolving body 3 is made. A plurality of operation modes related to the turning operation of the revolving body 3 are stored in the storage unit 32, and any one of the plurality of operation modes can be selected according to the content of the work. The operation mode of the turning operation includes, for example, a first operation mode in which the turning torque generated by the turning electric motor 24 is increased to perform the turning operation at high speed, and a second operation mode in which the turning torque generated by the turning electric motor 24 is decreased to perform the turning operation at low speed.

[0081] For example, when the hybrid excavator 100 performs excavation and loading work, the first operation mode is selected, and by turning at high speed, the cycle time can be shortened and the workability can be improved. When the hybrid excavator 100 performs a suspended load operation, the second operation mode is selected, and by turning at low speed, the load can be turned without swinging, so the safety can be improved. Also, by selecting the second operation mode, the operability of the working machine 2 during the turning operation can be improved.

[0082] The operator uses the input unit 45 to input the selection of the operation mode to the controller 30. The input unit 45 has a function as a mode selection input reception unit that accepts a selection input of the operation mode of the turning operation of the revolving body.

[0083] In step S3, the operator operates the turning operation device 41. The operation amount of the turning operation device 41 is detected by the turning operation detection unit 41A and input to the controller 30.

[0084] In step S4, the turning acceleration setting unit 52 sets the turning acceleration of the turning body 3 according to the operation amount of the turning operation device 41. The map MP1 shown in FIG. 7 corresponds to, for example, a map when the operation amount of the turning operation device 41 is relatively large. Typically, the map MP1 corresponds to a map when the operation amount of the turning operation device 41 is maximum. The map MP2 corresponds to, for example, a map when the operation amount of the turning operation device 41 is medium. The map MP3 corresponds to, for example, a map when the operation amount of the turning operation device 41 is relatively small.

[0085] The turning acceleration setting unit 52 reads an appropriate map according to the operation amount of the turning operation device 41 from the storage unit 32. The turning acceleration setting unit 52 sets the turning acceleration according to the read map as a command value of the acceleration when turning the turning body 3.

[0086] The turning acceleration setting unit 52 may set the turning acceleration of the turning body 3 according to the operation mode of the turning operation of the turning body 3 selected in step S2 and the operation amount of the turning operation device 41. For example, when the second operation mode for performing the turning operation at a low speed is selected, the turning acceleration setting unit 52 reads the map MP2 shown in FIG. 7 and sets the turning acceleration according to the map MP2 when the operation amount of the turning operation device 41 is maximum, and reads the map MP3 and sets the turning acceleration according to the map MP3 when the operation amount of the turning operation device 41 is medium.

[0087] The turning acceleration setting unit 52 may set the turning acceleration of the turning body 3 according to the type of attachment selected in step S1 and the operation amount of the turning operation device 41. For example, when the operation amount of the turning operation device 41 is a predetermined value, the turning acceleration setting unit 52 may read different maps from the storage unit 32 and set the turning acceleration of the turning body 3 depending on whether the attachment is the bucket 8 and whether the hybrid excavator 100 is a disassembled specification vehicle and the attachment is a small cutter or a grapple.

[0088] In step S5, it is determined whether or not the pressure of the pressure oil discharged by the hydraulic pump 25 is equal to or higher than a threshold value. The pressure of the pressure oil is detected by the pressure sensor 27 and input to the controller 30. The controller 30 receives an input of a detection signal indicating an increase in the pressure of the pressure oil from the pressure sensor 27.

[0089] When the pressure of the pressure oil increases and the load on the hydraulic pump 25 increases, it is assumed that the weight of the current load in the bucket 8 is large. When the pressure of the pressure oil is high, it is assumed that the weight of the load carried by the work machine 2 is large, and thus the inertia of the work machine 2 is large. The pressure sensor 27 corresponds to an inertia detection unit in an embodiment for detecting the inertia of the work machine 2. A map or table showing the relationship in which the pressure of the pressure oil discharged by the hydraulic pump 25 increases in accordance with the increase in the calculated load value W described with reference to FIGS. 4 and 5 may be stored in advance in the storage unit 32.

[0090] As described with reference to FIG. 3, during hoist turning, an operation of raising the work machine 2 is performed while turning the revolving body 3. When the weight of the load carried by the work machine 2 is large and the inertia of the work machine 2 is large, the operation of raising the work machine 2 becomes slower compared to when the bucket 8 is empty. If the revolving body 3 is turned at the set turning acceleration regardless of such a decrease in the operating speed of the work machine 2, the raising of the work machine 2 lags behind the turning of the revolving body 3, and the bucket 8 may not reach the point P13 (FIG. 3) which is the position for discharging the excavation target from the bucket 8.

[0091] Therefore, when it is determined in the determination of step S5 that the pressure of the pressure oil discharged by the hydraulic pump 25 is equal to or higher than the threshold value (YES in step S5), in step S6, the turning acceleration correction unit 54 corrects the turning acceleration set by the turning acceleration setting unit 52. Specifically, when it is determined that the pressure of the pressure oil detected by the pressure sensor 27 is equal to or higher than the threshold value, the turning acceleration correction unit 54 decreases the turning acceleration set according to the operation amount of the turning operation device 41.

[0092] In the setting in step S4, when the turning acceleration according to the map MP1 shown in FIG. 7 is set, the maximum value of the turning acceleration smaller than g1 shown in FIG. 7 may be reset by the correction in step S6. For example, in the setting in step S4, when the turning acceleration according to the map MP1 shown in FIG. 7 is set, it may be reset to the turning acceleration according to the map MP2 by the correction in step S6.

[0093] The turning acceleration is reduced according to the amount of the load carried by the working machine 2, so that the same hoist turning as that of a conventional hydraulic excavator other than the hybrid excavator 100 can be realized. Thereby, the work can be performed without giving the operator a sense of strangeness.

[0094] In step S7, the turning operation control unit 56 controls the turning electric motor 24 according to the turning acceleration corrected by the turning acceleration correction unit 54. When it is determined in the determination of step S5 that the pressure of the pressure oil discharged from the hydraulic pump 25 is less than the threshold value (NO in step S5), the process of step S6 is skipped, and the turning operation control unit 56 controls the turning electric motor 24 according to the turning acceleration set by the turning acceleration setting unit 52 in step S4. Then, the process ends (end).

[0095] FIG. 9 is a flowchart showing an example of the control of the turning acceleration of the revolving body 3 during the down turning. The processes of steps S11 to S14 shown in FIG. 9 are the same as steps S1 to S4 described with reference to FIG. 8, and thus the description thereof is omitted.

[0096] In step S15, it is determined whether or not the operation amount of the work machine operation device 42 operated for the lowering operation of the boom 6 is equal to or greater than the threshold value. The operation amount of the work machine operation device 42 is detected by the work machine operation detection unit 42A and input to the controller 30.

[0097] In a conventional hydraulic excavator that is not the hybrid excavator 100, the hydraulic oil supplied from the hydraulic pump is divided into the boom cylinder 10 and the swing hydraulic motor. When only the swing operation of the swing body 3 is performed without the operation of the working machine 2, if the flow rate of the hydraulic oil supplied to the swing hydraulic motor when performing the swing operation is compared with the flow rate of the hydraulic oil supplied to the swing hydraulic motor when performing a down swing, the latter may have a smaller flow rate of the hydraulic oil supplied to the swing hydraulic motor. Therefore, in a conventional hydraulic excavator, the speed of the swing body may decrease when performing a down swing. In the hybrid excavator 100 of the embodiment, when performing a down swing, if the swing body 3 is swung at a swing acceleration corresponding to the operation amount of the swing operation device 41, the swing speed of the swing body 3 may be so high that the bucket 8 cannot reach the point P10 (FIG. 3) which is the excavation start position.

[0098] Therefore, when it is determined in the determination of step S15 that the operation amount of the working machine operation device 42 operated for the operation of the boom 6 is equal to or greater than the threshold value (YES in step S15), in step S16, the swing acceleration correction unit 54 corrects the swing acceleration set by the swing acceleration setting unit 52. Specifically, when it is determined that the operation amount of the working machine operation device 42 is equal to or greater than the threshold value, the swing acceleration correction unit 54 decreases the swing acceleration set according to the operation amount of the swing operation device 41.

[0099] In the setting in step S14, when the swing acceleration according to the map MP1 shown in FIG. 7 is set, the maximum value of the swing acceleration smaller than g1 shown in FIG. 7 may be reset by the correction in step S16. For example, in the setting in step S14, when the swing acceleration according to the map MP1 shown in FIG. 7 is set, it may be reset to the swing acceleration according to the map MP2 by the correction in step S16.

[0100] By reducing the swing acceleration, a down swing similar to that of a conventional hydraulic excavator that is not the hybrid excavator 100 can be realized. As a result, the work can be performed without a sense of discomfort for the operator.

[0101] In step S17, the turning operation control unit 56 controls the turning electric motor 24 according to the turning acceleration corrected by the turning acceleration correction unit 54. When it is determined in the determination of step S15 that the operation amount of the work implement operation device 42 is less than the threshold value (NO in step S15), the process of step S16 is skipped, and the turning operation control unit 56 controls the turning electric motor 24 according to the turning acceleration set by the turning acceleration setting unit 52 in step S14. Then, the process ends (end).

[0102] In the above description with reference to FIG. 9, in response to the operation of the work implement operation device 42, typically the operation of lowering the boom 6, the turning acceleration of the revolving body 3 is reduced. Similarly, even when the work implement operation device 42 is operated for the operation of the arm 7 or the bucket 8, control is performed to reduce the turning acceleration of the revolving body 3. Even when the traveling operation device 43 is operated for the traveling of the traveling body 5, control is performed to reduce the turning acceleration of the revolving body 3. Therefore, when it is determined that the operation amount of the second operation device operated for the operation of the hybrid excavator 100 other than the turning operation of the revolving body 3 is equal to or greater than the threshold value, control is performed to reduce the turning acceleration.

[0103] <Operation and Effect> Although there is also a description that partially overlaps with the above description, the characteristic configurations, operations, and effects of the present embodiment will be summarized as follows.

[0104] As shown in FIGS. 8 and 9, the controller 30 controls the turning electric motor 24 according to the turning acceleration. Thereby, it is possible to reduce the fluctuation of the turning speed of the revolving body 3, smoothly increase and decrease the revolving body 3 without causing it to sway, and arbitrarily set the amount of increase per unit time of the turning speed of the revolving body 3.

[0105] As shown in FIG. 8, the controller 30 sets the turning acceleration of the revolving body 3 according to the operation amount of the turning operation device 41. The controller 30 corrects the set turning acceleration according to the inertia of the working machine 2 detected by the inertia detection unit. When the inertia of the working machine 2 is large, the operation of raising the working machine 2 becomes slow. By correcting the turning acceleration, the hybrid excavator 100 can perform the same operations as a conventional hydraulic excavator. As a result, work can be performed without a sense of discomfort for the operator, enabling highly accurate turning control.

[0106] As shown in FIG. 8, the controller 30 corrects the turning acceleration of the revolving body 3 set according to the operation amount of the turning operation device 41 by the amount of the load carried by the working machine 2. When the amount of the load carried by the working machine 2 is large, the operation of raising the working machine 2 becomes slow. By correcting the turning acceleration, the hybrid excavator 100 can perform the same operations as a conventional hydraulic excavator. As a result, work can be performed without a sense of discomfort for the operator, enabling highly accurate turning control.

[0107] As shown in FIG. 2, the pressure sensor 27 detects the pressure of the pressurized oil discharged by the hydraulic pump 25. As shown in FIG. 8, when the controller 30 determines that the pressure of the pressurized oil discharged by the hydraulic pump 25 is equal to or higher than the threshold value, the controller 30 decreases the turning acceleration set according to the operation amount of the turning operation device 41. When the pressure of the pressurized oil increases and the load on the hydraulic pump 25 increases, it is assumed that the weight of the current load in the bucket 8 is large. By decreasing the turning acceleration, the hybrid excavator 100 can perform the same operations as a conventional hydraulic excavator. As a result, work can be performed without a sense of discomfort for the operator, enabling highly accurate turning control.

[0108] As shown in FIG. 9, when the controller 30 determines that the operation amount of the work implement operating device 42 is equal to or greater than the threshold value, the controller 30 decreases the turning acceleration set according to the operation amount of the turning operation device 41. In a conventional hydraulic excavator, the hydraulic oil supplied from the hydraulic pump is branched into the boom cylinder 10 and the turning hydraulic motor. Since the hybrid excavator 100 can perform an operation imitating a conventional hydraulic excavator, work can be performed without a sense of strangeness for the operator, and highly accurate turning control can be achieved.

[0109] As shown in FIG. 9, when the controller 30 determines that the operation amount of the work implement operating device 42 for the operation of the boom 6 is equal to or greater than the threshold value, the controller 30 decreases the turning acceleration set according to the operation amount of the turning operation device 41. Since the hybrid excavator 100 can perform an operation imitating a conventional hydraulic excavator, work can be performed without a sense of strangeness for the operator, and highly accurate turning control can be achieved.

[0110] As shown in FIGS. 8 and 9, the controller 30 sets the turning acceleration according to the operation mode of the turning operation of the revolving body 3 and the operation amount of the turning operation device 41. By setting an appropriate turning acceleration according to the operation mode of whether to turn the revolving body 3 at high speed or low speed, workability can be improved.

[0111] As shown in FIGS. 8 and 9, the controller 30 sets the turning acceleration according to the type of attachment attached to the tip of the work implement 2 and the operation amount of the turning operation device 41. By setting an appropriate turning acceleration according to the type of attachment, workability can be improved.

[0112] As shown in FIG. 2, the hybrid excavator 100 further includes an engine 20 which is a drive source of the work implement 2. Since the hybrid excavator 100 that turns the revolving body 3 with the turning electric motor 24 and drives the work implement 2 with the engine can perform the same operation as a conventional hydraulic excavator during the hoist turning operation, work can be performed without a sense of strangeness for the operator, and highly accurate turning control can be achieved.

[0113] In the above-described embodiment, an example has been described in which the pressure sensor 27 that detects the pressure of the pressure oil discharged by the hydraulic pump 25 has a function as an inertia detection unit that detects the inertia of the work machine 2. However, the present invention is not limited to this example, and the inertia of the work machine 2 may be detected by any configuration. For example, the pressure of the work machine cylinder may be detected to determine the inertia of the work machine 2. The cylinder pressure sensors 10A and 10B shown in FIG. 4 may have a function as an inertia detection unit. Further, for example, the posture of the work machine 2 may be detected to determine the inertia of the work machine 2. The inertial measurement devices attached to the boom 6, the arm 7, and the bucket 8, or the angle sensors attached to the boom foot pin 13, the boom top pin 14, and the arm top pin 15, which were described with reference to FIG. 4, may have a function as an inertia detection unit.

[0114] In the above-described embodiment, as an example of an excavator, the hybrid excavator 100 that includes the engine 20 as a drive source of hydraulic equipment and drives the revolving body 3 with the swing electric motor 24 has been described. The excavator does not necessarily have to include an engine (internal combustion engine). The excavator may be an electric excavator in which the drive sources for the swing of the revolving body 3, the traveling by the traveling body 5, and the operation of the work machine 2 are all electric motors, and the electric motors are driven by the electric energy stored in the battery.

[0115] Although the embodiments have been described as above, it should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Description of Reference Numerals

[0116] 1 Body, 2 Working machine, 3 Slewing body, 4 Operator's cab, 4S Driver's seat, 5 Traveling body, 5Cr Crawler, 5M Traveling motor, 6 Boom, 7 Arm, 8 Bucket, 9 Exterior cover, 10 Boom cylinder, 10A, 10B Cylinder pressure sensor, 11 Arm cylinder, 12 Bucket cylinder, 13 Boom foot pin, 14 Boom top pin, 15 Arm top pin, 17 Bucket link, 18A, 18B, 18C Stroke sensor, 20 Engine, 20A Governor, 21 Generator motor, 22 Inverter, 23 Capacitor, 24 Slewing electric motor, 25 Hydraulic pump, 25A Swashplate drive unit, 26 Tank, 27 Pressure sensor, 28 Control valve, 30 Controller, 31 Arithmetic unit, 32 Memory unit, 41 Slewing operation device, 41A Slewing operation detection unit, 42 Working machine operation device, 42A Working machine operation detection unit, 43 Traveling operation device, 43A Traveling operation detection unit, 45 Input unit, 52 Slewing acceleration setting unit, 54 Slewing acceleration correction unit, 56 Slewing motion control unit, 58 Load arithmetic unit, 100 Hybrid excavator, 200 Dump truck, 202 Loading platform.

Claims

1. A rotatable revolving body, A turning electric motor for turning the revolving body, A working machine mounted on the revolving body, A turning operation device operated for the turning operation of the revolving body, A second operation device operated for the operation of the working machine, An inertia detection unit that detects the inertia of the working machine, And a controller, The controller sets the turning acceleration of the revolving body according to the operation amount of the turning operation device, corrects the set turning acceleration by the inertia detected by the inertia detection unit, and controls the turning electric motor according to the corrected turning acceleration, When the controller determines that the operation amount of the second operation device is equal to or greater than a threshold value during a downward turn in which the revolving body turns while lowering the working machine, the controller reduces the turning acceleration set according to the operation amount of the turning operation device. A hydraulic excavator.

2. The controller according to claim 1, wherein the turning acceleration set according to the operation amount of the turning operation device is corrected by the amount of load carried by the working machine.

3. The hydraulic excavator further includes a hydraulic pump that discharges pressure oil used for driving the working machine, and the inertia detection unit includes a pressure sensor that detects the pressure of the pressure oil. The controller according to claim 2, wherein when the controller determines that the pressure of the pressure oil is equal to or greater than a threshold value, the controller reduces the turning acceleration set according to the operation amount of the turning operation device.

4. The working machine includes a boom rotatably connected to the revolving body. The second operation device is operated for the operation of the boom. The hydraulic excavator according to any one of claims 1 to 3.

5. The hydraulic excavator further includes a mode selection input receiving unit that receives a selection input of an operation mode of the turning operation of the revolving body. The controller according to any one of claims 1 to 4, wherein the controller sets the turning acceleration according to the selected operation mode and the operation amount of the turning operation device.

6. A plurality of types of attachments can be selectively attached to the tip of the working machine. The controller according to any one of claims 1 to 5, wherein the controller sets the turning acceleration according to the type of the attached attachment and the operation amount of the turning operation device.

7. The hydraulic excavator according to any one of claims 1 to 6, further comprising an engine that is a drive source of the working machine.

8. A rotatable revolving body, A slewing motor for slewing the slewing body, A working machine mounted on the slewing body, A slewing operation device operated for the slewing operation of the slewing body, A second operation device operated for the operation of the working machine, An inertia detection unit for detecting the inertia of the working machine, And a controller, The controller sets a slewing acceleration of the slewing body according to an operation amount of the slewing operation device, corrects the set slewing acceleration by the inertia of the working machine, and controls the slewing motor according to the corrected slewing acceleration. The controller is a control system that reduces the slewing acceleration set according to the operation amount of the slewing operation device when it is determined that the operation amount of the second operation device is equal to or greater than a threshold value during a down slewing in which the slewing body slews while lowering the working machine.

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