JP6175344B2 - Center of gravity variable device - Google Patents

Description

  The present invention relates to a variable center of gravity device mounted on an excavator such as a hydraulic excavator.

  Generally, in an excavator, an upper swing body is provided so as to be capable of swinging on an upper portion of a lower traveling body that travels. The upper swing body is provided with an excavation body that performs excavation work, and is provided with a counterweight having a weight that balances the excavation body. As a result, the hydraulic excavator is balanced in weight so that it does not fall over even if the excavated body is swung forward.

  Patent Document 1 discloses a device in which a damper cylinder is interposed between an upper swing body of a hydraulic excavator and a counter weight, and the damper cylinder expands and contracts as the counter weight moves up and down to suppress the swing of the upper swing body. Is disclosed.

  The apparatus includes an acceleration sensor attached to the rear part of the upper swing body, and a controller that controls a pressure guided to the oil chamber of the damper cylinder in accordance with a signal from the acceleration sensor. The controller performs control so that the pressurized hydraulic fluid supplied from the hydraulic source is guided to the oil chamber of the damper cylinder when the swing of the upper swing body is detected according to the signal from the acceleration sensor. As a result, when the swing of the upper swing body occurs during excavation work, the counterweight is moved downward by the damper cylinder, and the swing of the upper swing body is suppressed.

JP-A-6-10374

  However, in such a conventional apparatus, the counterweight is moved in the vertical direction and the center of gravity of the hydraulic excavator moves in the vertical direction, but there is a problem that the excavation force cannot be effectively increased.

  The present invention has been made in view of the above problems, and an object thereof is to provide a center-of-gravity variable device that can effectively increase excavation force.

The present invention includes a traveling body that is self-propelled, a revolving body that is provided at an upper portion of the traveling body and that revolves around a turning center axis, and a drilling body that is provided at a front portion of the revolving body and performs a digging operation. A center of gravity variable device mounted on a machine, wherein a first turntable that rotates when connected to the traveling body side and tilted with respect to the horizontal plane when the lower part is positioned parallel to the horizontal plane, A second turntable that is provided above the turntable, and whose lower part is inclined with respect to the horizontal plane when the upper part is positioned parallel to the horizontal plane, and is connected to the revolving body side, and is connected to the revolving body side; The third turntable that rotates relative to the second turntable, the first turntable, and the third turntable are synchronized and rotated in the same direction, and the first turntable and the second turntable are synchronized. , The first Comprising a controller in synchronism with emission table and third turntable is rotated in opposite directions at a higher rotational speed than the rotational speed which rotates in the same direction, the first turntable and the second turntable to each other The rotating body is relatively rotated, and the revolving body is tilted with respect to the traveling body.

  In the present invention, the first turntable and the second turntable rotate relative to each other to tilt the swiveling body with respect to the traveling body, so that the center of gravity of the excavator on which the center-of-gravity variable device is mounted can be It can be moved in the (horizontal plane direction). Thereby, for example, when the turning body is tilted forward with respect to the traveling body by the first turntable and the second turntable, the center of gravity of the excavator moves forward, so that the excavating force by the excavating body can be increased. it can.

1 is a side view of an excavator according to an embodiment of the present invention. It is a side view of an excavator which shows the time of excavation work. It is a perspective view of a traveling body and a biaxial turntable mechanism. It is a top view of a biaxial turntable mechanism. It is a front view of a biaxial turntable mechanism. It is sectional drawing of the biaxial turntable mechanism in alignment with the AA of FIG. 4B. It is a block diagram of a gravity center variable apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  As shown in FIGS. 1 and 2, the excavator (hydraulic excavator) 5 includes a traveling body (lower traveling body) 6 that travels, a revolving body (upper revolving body) 7 that revolves above the traveling body 6, An excavating body 10 extending forward from the body 7 and excavating earth and sand.

  The traveling body 6 includes left and right crawler devices 9 and a vehicle body 4 that supports the left and right crawler devices 9. The crawler device 9 travels by circulating a crawler belt (crawler belt) 19.

  The turning body 7 turns around the vertical axis with respect to the traveling body 6 by the operation of a biaxial turntable mechanism 101 described later. The swivel body 7 is mounted with an excavation body 10, an operator cab 20, a counterweight 21, an engine, a fuel tank, a battery, a hydraulic pressure source, and the like (not shown).

  The “vertical axis” means an axis extending in the vertical direction of the excavator 5 in a state where the excavator 5 is on a horizontal plane.

  The excavation body 10 includes a boom 11 that is rotatably supported around a horizontal axis that extends in the left-right direction of the swivel body 7, an arm 12 that is rotatably supported by the distal end portion of the boom 11, and a distal end portion of the arm 12. And a bucket 13 for excavating earth and sand. The boom 11, the arm 12, and the bucket 13 are each driven by a hydraulic cylinder (actuator) (not shown).

  The “horizontal axis” means an axis extending in the horizontal direction of the excavator 5 in a state where the excavator 5 is on a horizontal plane.

  The counterweight 21 is fixedly provided behind the revolving unit 7. When the weight of the counterweight 21 is balanced with the weights of the excavator 10 and the cab 20 and the like, the excavator 5 is prevented from falling.

  The excavator 5 travels by driving the traveling body 6 and moves to a place that becomes a scaffold during excavation work. During excavation work, the traveling by the traveling body 6 is stopped, and the revolving body 7 is swung to turn the excavating body 10 in the direction of excavation. In a state where the turning body 7 stops turning, the boom 13, the arm 12, and the bucket 13 of the excavation body 10 are operated to push the bucket 13 into the earth and sand, and then the excavation is performed by rotating the bucket 13. Scoop up etc. Thereafter, the swiveling body 7 is swung to turn the excavating body 10 in the other direction and the bucket 13 is rotated in the opposite direction to that during excavation, thereby discharging the earth and sand scooped up. During the excavation work, the excavator 10 is repeatedly operated.

  When excavating the bucket 13 into the earth or sand, if the earth or sand is hard, the reaction force received by the bucket 13 from the earth or sand causes the excavator 10 and the front part of the revolving body 7 to rotate upward, and the excavator 5 The front of is about to rise.

  In order to prevent the front portion of the excavator 5 from being lifted, the excavator 5 is provided with a center-of-gravity variable device 100 that makes the center of gravity of the revolving body 7 variable in conjunction with the excavation operation of the excavator 10. As shown in FIG. 2, the center-of-gravity variable device 100 includes a two-axis turntable mechanism 101 that tilts the swing body 7 around the horizontal axis, a controller 70 described later, a pressure sensor 75, and an inclination angle sensor 76.

  During excavation for pushing the bucket 13 into the earth and sand, the turning body 7 is rotated in the forward direction of pitching and stopped by the operation of the biaxial turntable mechanism 101. At this time, the center of gravity of the swing body 7 moves forward, so that the front portion of the excavator 5 can be prevented from floating and the excavation force for pushing the bucket 13 into the earth and sand can be increased.

  Hereinafter, a specific configuration of the biaxial turntable mechanism 101 will be described.

  As shown in FIGS. 3 and 4A to 4B, the biaxial turntable mechanism 101 includes a ring-shaped first turntable 40, a second turntable 50, and a third turntable 60. They are arranged in the vertical direction.

  The first turntable 40 is rotatably connected to the traveling body 6 side via a first rail 49 and a bearing 48. The vehicle body 4 is provided with an annular first rail 49. The first turntable 40 is supported by the first rail 49 via a bearing 48 so as to be rotatable about the first central axis O1. The first rail 49 constitutes an inner race of the bearing 48. The first turntable 40 is fastened to the outer race 41 of the bearing 48.

  As a drive mechanism for rotating the first turntable 40, an annular first rack 47 provided on the inner periphery of the first rail 49, a pinion 44 (see FIG. 6) meshing with the first rack 47, and the pinion 44 are rotated. And a first hydraulic motor 43 to be driven. The first hydraulic motor 43 is supported on the first turntable 40 via the bracket portion 42. When the pinion 44 is rotationally driven by the first hydraulic motor 43, the pinion 44 that meshes with the first rack 47 moves along the circumferential direction of the first rail 49, and the first turntable 40 moves along the first central axis O1. Rotates as the center.

  The second turntable 50 is rotatably connected to the upper part of the first turntable 40. An annular second rail 59 is provided at the upper end of the first turntable 40. The second turntable 50 is supported rotatably about the second central axis O <b> 2 via a bearing 58 that is in rolling contact with the second rail 59. The second rail 59 is constituted by the inner race of the bearing 58. The second turntable 50 is fastened to the outer race 51 of the bearing 58.

  The first turntable 40 is formed in a cylindrical shape in which the height in the vertical axis direction along the first central axis O1 gradually changes in the circumferential direction. The first turntable 40 is formed so that the upper part is inclined with respect to the horizontal plane when the lower part is positioned parallel to the horizontal plane. Thereby, the first central axis O1 and the second central axis O2 are inclined with respect to each other.

  As a drive mechanism for rotating the second turntable 50, an annular second rack 57 provided on the inner periphery of the second rail 59 and a pinion 56 that meshes with the second rack 57 (see FIGS. 3, 4C, and 5). And a second hydraulic motor 53 that rotationally drives the pinion 56. The second hydraulic motor 53 is supported on the second turntable 50 via the bracket portion 52. When the pinion 56 is rotationally driven by the second hydraulic motor 53, the pinion 56 meshing with the second rack 57 moves along the circumferential direction of the second rail 59, and the second turntable 50 moves along the second central axis O2. Rotates as the center.

  An annular third rail 69 is provided on the second turntable 50. The third turntable 60 is supported so as to be rotatable about the third central axis O3 via a bearing 68 that is in rolling contact with the third rail 69. The inner race of the bearing 68 is constituted by the third rail 69. The outer race of the bearing 48 is constituted by a third turntable 60.

  The second turntable 50 is formed in a cylindrical shape whose height in the second central axis O2 direction gradually changes in the circumferential direction. The second turntable 50 is formed such that the lower part is inclined with respect to the horizontal plane when the upper part is positioned parallel to the horizontal plane. Thereby, the second central axis O2 and the third central axis O3 are inclined with respect to each other.

  As a drive mechanism for rotating the third turntable 60, an annular third rack 67 provided on the inner periphery of the third rail 69, a pinion 66 (see FIG. 3) meshing with the third rack 67, and the pinion 66 are rotated. And a third hydraulic motor 63 to be driven. The third hydraulic motor 63 is supported on the third turntable 60 via a bracket part 62. The third turntable 60 is provided as an outer race of the bearing 68. When the pinion 66 is rotationally driven by the third hydraulic motor 63, the pinion 66 meshing with the third rack 67 moves along the circumferential direction of the third rail 69, and the third turntable 60 moves along the third central axis O3. Rotates as the center.

  Next, the operation of the biaxial turntable mechanism 101 will be described.

  As shown in FIG. 4B, in a state where the portion where the length in the height direction of the first turntable 40 is the shortest and the portion where the length in the height direction of the second turntable 50 is the longest overlap in a plan view. The third central axis O3 and the first central axis O1 extend coaxially with each other.

  When the revolving structure 7 is turned, only the first turntable 40 is turned. Thereby, the turning motion in which the turning body 7 rotates around the vertical axis around the first central axis O1 with respect to the traveling body 6 is performed.

  When the swivel body 7 is tilted, the first turntable 40 and the third turntable 60 are synchronized and rotated in the same direction, and the second turntable 50 is rotated twice with respect to the first turntable 40. Rotate in reverse direction at speed. Accordingly, the third central axis O3 of the third turntable 60 rotates around the horizontal axis extending in the left-right direction of the revolving body 7 without the revolving body 7 revolving with respect to the first central axis O1. Tilt in the pitching direction without slipping. By switching the rotation direction of the first turntable 40, the second turntable 50, and the third turntable 60, the revolving body 7 is rotated forward and tilted, and the revolving body 7 is directed rearward. The operation of rotating and returning to the original posture is switched.

  As shown in FIG. 2, in a state where the portion where the length in the height direction of the first turntable 40 is shortest and the portion where the length in the height direction of the second turntable 50 is longest overlap in plan view. The revolving unit 7 tilts at the maximum angle.

  The center-of-gravity variable device 100 is configured to include the first turntable 40, the second turntable 50, and the third turntable 60, but only the first turntable 40 and the second turntable 50 are included. It is good also as a structure with which the 2nd turntable 50 is connected with the turning body 7.

  As shown in FIG. 5, hydraulic passages 45, 55, and 65 that are connected to a hydraulic source (not shown) are connected to the first hydraulic motor 43, the second hydraulic motor 53, and the second hydraulic motor 53, respectively. The hydraulic fluid guided from the hydraulic source is supplied to and discharged from the hydraulic motors 43, 53, and 63 through the hydraulic passages 45, 55, and 65. Electromagnetic switching valves 44, 54 and 64 are interposed in the hydraulic passages 45, 55 and 65, respectively.

  The electromagnetic switching valve 44 has positions a, b, and c, and switches supply and discharge of hydraulic oil to and from the first hydraulic motor 43. In the operating position a, hydraulic oil from the hydraulic source is guided through the hydraulic passage 45 so as to rotate the first hydraulic motor 43 in one direction. At the stop position b, the hydraulic passage 45 is blocked, and the rotation operation of the first hydraulic motor 43 is stopped. In the operation position c, the hydraulic oil from the hydraulic source is guided through the hydraulic passage 45 to rotate the first hydraulic motor 43 in the reverse direction.

  Similarly, the electromagnetic switching valve 54 has positions d, e, and f, and switches supply and discharge of hydraulic oil to and from the second hydraulic motor 53. In the operation position d, hydraulic oil from the hydraulic source is guided through the hydraulic passage 55 so as to rotate the second hydraulic motor 53 in one direction. At the stop position e, the hydraulic passage 55 is blocked, and the rotation operation of the second hydraulic motor 53 is stopped. In the operating position f, hydraulic oil from the hydraulic source is guided through the hydraulic passage 55 so as to rotate the second hydraulic motor 53 in the reverse direction.

  Similarly, the electromagnetic switching valve 64 has positions g, h, and i, and switches supply and discharge of hydraulic oil to and from the third hydraulic motor 63. In the operating position g, hydraulic oil from the hydraulic source is guided through the hydraulic passage 65 so as to rotate the third hydraulic motor 63 in one direction. At the stop position h, the hydraulic passage 65 is blocked, and the rotation operation of the third hydraulic motor 63 is stopped. In the operating position i, hydraulic oil from the hydraulic source is guided to rotate the third hydraulic motor 63 in the reverse direction through the hydraulic passage 65.

  The flow direction of the hydraulic oil in the hydraulic passages 45, 55, and 65 is switched by the electromagnetic switching valves 44, 54, and 64, whereby the first hydraulic motor 43, the second hydraulic motor 53, and the third hydraulic motor 63 are moved in both forward and reverse directions. Rotating operation. As described above, the first hydraulic motor 43, the second hydraulic motor 53, and the third hydraulic motor 63 are connected to the first turntable 40, the second turntable 50, and the third turntable 60 through the pinions 46, 56, and 66, respectively. Rotate each.

  The configuration is not limited to the above, and an electric motor may be provided instead of the first hydraulic motor 43, the second hydraulic motor 53, and the third hydraulic motor 63.

  The center-of-gravity variable device 100 includes a controller 70 that controls the positions and opening degrees of the electromagnetic switching valves 44, 54, and 64 according to the operation of the excavation body 10 during excavation when the excavation body 10 performs an excavation operation.

  The controller 70 receives the turning command signal T and the excavation command signal S output from the operation lever 74 operated by the driver, and outputs the driving pressure detection signal P output from the pressure sensor 75 and the tilt angle sensor 76. The tilt angle detection signal A is received, and the operation of the biaxial turntable mechanism 101 is controlled in accordance with these signals.

  The turning command signal T is output when the turning body 7 is turned based on the operation of the operation lever 74 by the driver.

  The controller 70 controls the position and opening of the electromagnetic switching valve 44 according to the turning direction and the turning speed commanded based on the turning command signal T, and controls the rotation direction and the rotation speed of the first hydraulic motor 43.

  Thus, in the biaxial turntable mechanism 101, the first hydraulic motor 43 rotates to rotate the first turntable 40 about the first central axis O1, and the turning direction in which the swivel body 7 is commanded and Turn at the turning speed.

  The excavation command signal S is output when the excavation body 10 is excavated based on the operation of the operation lever 74 by the driver.

  The pressure sensor 75 detects a drive hydraulic pressure guided to a hydraulic cylinder that drives the bucket 13 for excavating earth and sand and outputs a drive pressure detection signal P corresponding to the drive hydraulic pressure.

  In response to the excavation command signal S, the controller 70 determines when the bucket 13 is moving toward the excavation part, and the driving pressure detection signal P is increased so that the bucket 13 is pushed into the excavation part (face). The positions and opening degrees of the electromagnetic switching valves 44, 54, 64 are controlled to rotate the first hydraulic motor 43, the second hydraulic motor 53, and the third hydraulic motor 63 in synchronization with each other. In this way, the biaxial turntable mechanism 101 rotates the revolving body 7 and the excavating body 10 in the direction before pitching and stops, so that the inertial force acting on the revolving body 7 and the excavating body 10 in the pitching direction acts on the front part of the excavator 5. Is suppressed, and the excavation force for pushing the bucket 13 into the earth and sand is increased.

  Further, the controller 70 determines when the bucket 13 is moving away from the excavation part according to the excavation command signal S, and performs control to rotate the revolving structure 7 in the post-pitching direction to return to the original posture. As a result, the third central axis O3 and the first central axis O1 extend coaxially, and the excavator 5 is prevented from tipping forward due to the weight of the excavator 10 or the like.

  The controller 70 is not limited to the configuration in which the operating state of the swing body 7 and the excavation body 10 is determined according to the driving pressure detection signal P of the pressure sensor 75, and the detection signal of the acceleration sensor that rotates the swing body 7 in the pitching direction. It is good also as a structure which determines the operation state of the turning body 7 and the excavation body 10 according to.

  The tilt angle sensor 76 detects the tilt direction and tilt angle at which the traveling body 6 tilts with respect to the vertical line of the ground, and outputs a tilt angle detection signal A corresponding to the tilt direction and tilt angle.

  The controller 70 controls the inclination angle and the inclination direction of the first central axis O1 and the third central axis O3 of the biaxial turntable mechanism 101 according to the inclination angle detection signal A of the traveling body 6, and moves the center of gravity of the revolving body 7 Thus, the swivel body 7 is tilted in the direction of decreasing the tilt angle with respect to the rotation center axis O and the vertical line C of the ground. When the excavator 5 goes up the hill, the center of gravity is applied behind the excavator 5. In that case, by rotating the first turntable 40 and the second turntable 50 and tilting the swivel body 7 forward, the balance can be maintained and the excavator 5 can be prevented from falling over. Further, when the excavator 5 goes down the slope, the center of gravity is applied in front of the excavator 5. Even in that case, by rotating the first turntable 40 and the second turntable 50 and tilting the revolving structure 7 backward, the excavator 5 can be prevented from falling over while maintaining the balance. Further, when the excavator 5 is on the ground inclined to the left, the balance is maintained by rotating the first turntable 40 and the second turntable 50 and tilting the excavator 5 to the right. Thus, the excavator 5 can be prevented from overturning.

  In the control system, an inclination angle sensor 76 that detects an inclination angle at which the traveling body 6 is inclined with respect to the vertical line C of the ground is used as a detector that detects the attitude of the excavator 5. However, the present invention is not limited to this, and a tilt angle sensor that detects the tilt angle at which the revolving body 7 tilts with respect to the vertical line C of the ground may be used as a detector that detects the attitude of the excavator 5.

  According to the above embodiment, there exists an effect shown below.

  [1] The center-of-gravity variable device 100 includes a first turntable 40 that rotates when the lower part is parallel to the horizontal plane and the upper part is inclined with respect to the horizontal plane and connected to the traveling body 6 side. A second turntable 50 which is provided above the turntable 40, and whose lower part is inclined with respect to the horizontal plane when the upper part is positioned parallel to the horizontal plane and which is connected to the revolving body 10 side and rotates. The first turntable 40 and the second turntable 50 are configured to rotate relative to each other to tilt the revolving body 10 with respect to the traveling body 6.

  Based on the above configuration, in the center-of-gravity variable device 100, the first turntable 40 and the second turntable 50 rotate relative to each other to tilt the revolving body 10 with respect to the traveling body 6. Can be moved in the front / rear / left / right direction (horizontal plane direction). Thereby, for example, if the turning body 10 is tilted forward with respect to the traveling body 6 by the first turntable 40 and the second turntable 50, the center of gravity of the excavator 5 moves forward. Drilling power can be increased.

  [2] In the center-of-gravity variable device 100, the third turntable 60 connected to the revolving structure 7 side and rotated with respect to the second turntable 50 is synchronized with the first turntable 40 and the third turntable 60. The first turntable 40 and the second turntable 50 are rotated in the same direction, and the first turntable 40 and the second turntable 50 are synchronized, so that the first turntable 40 and the third turntable 60 are synchronously rotated in the same direction. And a controller 70 that rotates in opposite directions at a high rotational speed.

  Based on the above configuration, the first turntable 40 and the third turntable 60 rotate in the same direction, and the first turntable 40 and the second turntable 50 rotate in opposite directions. Then, the second turntable 50 rotates at a rotational speed faster than the rotational speeds of the first turntable 40 and the third turntable 60. Thereby, the revolving structure 7 can be tilted straight with respect to the traveling body 6 without shifting in the left-right direction.

  [3] The excavated body 10 includes an actuator (hydraulic cylinder) driven by fluid pressure. The center-of-gravity variable device 100 further includes a pressure sensor (driving pressure detector) 75 that detects a fluid pressure when the actuator (hydraulic cylinder) is driven. The controller 70 is configured to rotate the first turntable 40, the second turntable 50, and the third turntable 60 when the fluid pressure detected by the pressure sensor 75 is equal to or higher than a predetermined fluid pressure. .

  Based on the above configuration, when the excavating body 10 excavates, for example, earth and sand, the fluid pressure of the actuator (hydraulic cylinder) becomes equal to or higher than a predetermined fluid pressure. At that time, the controller 70 rotates the first turntable 40, the second turntable 50, and the third turntable 60 to tilt the revolving structure 10. Thereby, excavation force can be increased when excavation body 10 excavates.

  [4] The excavating body 10 further includes an inclination angle sensor (attitude detector) 76 for detecting the attitude of the excavator 5. When the posture detected by the tilt angle sensor (posture detector) 76 is equal to or larger than a predetermined angle with respect to the horizontal plane, the controller 70 turns the first turntable 40, the second turntable 50, and the third turn The table 60 is configured to rotate.

  Based on the above configuration, the center of gravity is applied to the rear of the excavator 5 when the excavator 5 climbs the hill. Even in that case, in the center-of-gravity variable device 100, the balance is maintained by rotating the first turntable 40, the second turntable 50, and the third turntable 60 to tilt the swivel body 7 forward. Thus, the excavator 5 can be prevented from overturning. Further, when the excavator 5 goes down the slope, the center of gravity is applied in front of the excavator 5. Even in that case, in the center-of-gravity variable device 100, the balance is maintained by rotating the first turntable 40, the second turntable 50, and the third turntable 60 to tilt the revolving structure 10 backward. Thus, the excavator 5 can be prevented from overturning.

  The embodiment of the present invention has been described above. However, the above embodiment only shows a part of application examples of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, the variable center-of-gravity device 100 may include a switch operated by the driver, and the controller 70 may receive the signal from the switch and control the operation of the two-axis turntable mechanism 101 based on the driver's command. .

O1 1st central axis O2 2nd central axis O3 3rd central axis 5 Excavator 6 Running body 7 Turning body 10 Excavating body 40 1st turntable 50 2nd turntable 60 3rd turntable 70 Controller 75 Pressure sensor (drive pressure) Detector)
76 Inclination angle sensor (Attitude detector)
100 Center of gravity variable device

Claims (3)

An excavator comprising: a self-propelled traveling body; a revolving body that is provided on an upper portion of the traveling body and that revolves around a revolving center axis; and a drilling body that is provided at a front portion of the revolving body and performs a digging operation. A center-of-gravity variable device,
A first turntable that rotates when the lower part is parallel to the horizontal plane and the upper part is inclined with respect to the horizontal plane and connected to the traveling body;
A second turntable provided above the first turntable, wherein the lower part is inclined with respect to the horizontal plane when the upper part is positioned parallel to the horizontal plane, and is connected to the revolving body side to rotate ;
A third turntable connected to the revolving structure and rotating with respect to the second turntable;
The first turntable and the third turntable are synchronized and rotated in the same direction, the first turntable and the second turntable are synchronized, and the first turntable and the third turntable are synchronized. A controller that rotates in opposite directions at a rotational speed faster than the rotational speed that rotates in the same direction .
The center-of-gravity variable device, wherein the first turntable and the second turntable rotate relative to each other to tilt the swivel body with respect to the traveling body. The excavation body includes an actuator driven by fluid pressure,
A drive pressure detector for detecting a fluid pressure when the actuator is driven;
The controller rotates the first turntable, the second turntable, and the third turntable when the fluid pressure detected by the driving pressure detector is equal to or higher than a predetermined fluid pressure. The center of gravity variable device according to claim 1 . Further comprising an attitude detector for detecting the attitude of the excavator;
The controller is
The first turntable, the second turntable, and the third turntable are rotated when the posture detected by the posture detector is greater than a predetermined angle with respect to a horizontal plane. Item 3. The center of gravity variable device according to Item 1 or 2 .

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