Work machine and control method of work machine

Abstract

To suppress vibration of a vehicle body.SOLUTION: A work machine includes a vehicle body frame, a work machine, at least one electric motor, and a controller. The work machine includes: a boom supported by the vehicle body frame; an arm connected to the boom; and an attachment connected to the arm. The electric motor generates a driving force for relatively moving the attachment with respect to the vehicle body frame. The controller controls angular acceleration of the work machine, based on the determination result whether or not a rotation moment acting on the work machine at an end part of the movable range of the work machine is equal to or less than a threshold value.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present disclosure relates to a work machine and a control method for a work machine.

Background Art

[0002] As a conventional technique, a work machine described in Japanese Patent Application Laid-Open No. 2003-184133 (Patent Document 1) is exemplified. This work machine is provided with a vibration suppression device. The vibration suppression device suppresses vibration during acceleration and deceleration of a movable part that is rotationally driven by a hydraulic actuator with respect to an upper swing body. The vibration suppression device includes a rotation angle sensor and a controller.

[0003] The rotation angle sensor detects the respective rotation angles of the boom, arm, and bucket, and inputs an angle signal to the controller. The controller calculates the rotational moment generated during acceleration and deceleration of the boom, arm, and bucket, and calculates the moment of inertia of the entire work machine with respect to the center of rotation about which the work machine tends to rotate due to the rotational moment. The controller determines whether the angular acceleration around the center of rotation of the entire hydraulic excavator exceeds a preset allowable angular acceleration from the rotational moment and the moment of inertia of the entire hydraulic excavator. When the allowable angular acceleration is exceeded, the controller corrects the command signal related to the boom, arm, and bucket, and limits the acceleration and deceleration of the boom, arm, and bucket.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a work machine, when vibration occurs in the vehicle body, the vibration is transmitted to the cab mounted on the vehicle body, and the riding comfort of the operator sitting in the cab deteriorates.

[0006] In the present disclosure, a working machine capable of suppressing the vibration of a vehicle body and a control method for the working machine are proposed.

Means for Solving the Problems

[0007] A working machine according to an aspect of the present disclosure includes a vehicle body frame, a working machine, at least one electric motor, and a controller. The working machine includes a boom supported by the vehicle body frame, an arm connected to the boom, and an attachment connected to the arm. The electric motor generates a driving force for relatively moving the attachment with respect to the vehicle body frame. The controller limits the angular acceleration of the working machine based on a determination result as to whether or not a rotational moment acting on the working machine at an end of the movable range of the working machine is equal to or less than a threshold value.

[0008] A control method for a working machine according to an aspect of the present disclosure includes the following steps. The first step is to determine whether or not a rotational moment acting on the working machine at an end of the movable range of the working machine, which is supported by the vehicle body frame and relatively moves with respect to the vehicle body frame by the driving force of the electric motor, is equal to or less than a threshold value. The second step is to limit the angular acceleration of the working machine based on the result of the above determination.

Advantages of the Invention

[0009] According to the working machine and the control method for the working machine of the present disclosure, the vibration of the vehicle body can be suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In the drawings, for convenience of explanation, the configuration may be omitted or simplified in some cases. It is also initially planned that any configurations are extracted from the embodiments and combined arbitrarily.

[0012] In the following description, "up", "down", "front", "rear", "left", and "right" are directions based on the operator seated on the driver's seat 4S in the cab 4.

[0013] <Overall Configuration> FIG. 1 is a side view schematically showing the configuration of an electric excavator 30 as an example of a working machine. FIG. 1 shows a schematic configuration of the electric excavator 30 viewed from the side from the right. As shown in FIG. 1, the electric excavator 30 of the embodiment mainly includes a revolving body 2, a traveling body 5, and a working device 10. The revolving body 2 and the traveling body 5 constitute the vehicle body 1 of the electric excavator 30.

[0014] The traveling body 5 has a pair of left and right crawler devices 5Cr. Each of the pair of left and right crawler devices 5Cr has a crawler. When the pair of left and right crawlers are rotationally driven, the electric excavator 30 self-propels. The traveling body 5 may have wheels (tires) instead of the crawler devices 5Cr.

[0015] The revolving body 2 is rotatably installed with respect to the traveling body 5. The revolving body 2 mainly has a vehicle body frame 3, a cab 4, and a counterweight 6. The cab 4 and the counterweight 6 are mounted on the vehicle body frame 3.

[0016] The operator boards the cab 4 and operates the electric excavator 30. The cab 4 is arranged, for example, on the front left side (front side of the vehicle) of the revolving body 2. Inside the cab 4, a driver's seat 4S for the operator to sit on is arranged. In the present disclosure, the electric excavator 30 is operated from inside the cab 4, but the electric excavator 30 may be remotely operated wirelessly from a location away from the electric excavator 30. The counterweight 6 is arranged on the rear side (rear side of the vehicle) of the revolving body 2 with respect to the cab 4. The counterweight 6 is arranged at the rear part of the revolving body 2.

[0017] The working device 10 is supported by the revolving body 2 at the front part of the revolving body 2, for example, on the right side of the cab 4. The working device 10 has a boom 11, an arm 12, and a bucket 13.

[0018] The base end portion of the boom 11 is rotatably connected to the revolving body 2 by the boom foot pin 15. The boom foot pin 15 extends in the left - right direction and penetrates the base end portion of the boom 11. The boom 11 is supported by the vehicle body frame 3. The base end portion of the arm 12 is rotatably connected to the tip end portion of the boom 11 by the arm connection pin 16. The arm connection pin 16 extends in the left - right direction and penetrates the tip end portion of the boom 11 and the base end portion of the arm 12. The bucket 13 is rotatably connected to the tip end portion of the arm 12 by the attachment connection pin 17. The attachment connection pin 17 extends in the left - right direction and penetrates the tip end portion of the arm 12 and the base end portion of the bucket 13.

[0019] The bucket 13 constitutes the tip end portion of the working machine 10. The bucket 13 of the embodiment is connected to the boom 11 via the arm 12. The bucket 13 moves relative to the boom 11 by rotating about the attachment connection pin 17 and / or the arm 12 rotates about the arm connection pin 16. The bucket 13 is configured to be relatively movable with respect to the boom 11.

[0020] The bucket 13 has a plurality of blades. The tip end portion of the bucket 13 is referred to as the cutting edge 13A. Note that the bucket 13 may not have blades. The tip end portion of the bucket 13 may be formed of a straight - shaped steel plate.

[0021] The bucket 13 is an example of an attachment that is detachably attached to the tip end of the working machine 10 and is rotatable with respect to the arm 12. Depending on the type of work, the attachment can be replaced with a breaker, a grapple, or a lifting magnet, etc.

[0022] The working machine 10 has a bucket link 21. The bucket link 21 has a first member 22 and a second member 23. The first member 22 and the second member 23 are connected so as to be relatively rotatable. The first member 22 and the second member 23 are pin-connected by a link pin 24. The first member 22 is rotatably connected to the arm 12 by a link pin 25. The second member 23 is rotatably connected to a bracket at the base of the bucket 13 by a link pin 26.

[0023] The first member 22 has a rod-like shape. The first member 22 is connected to the second member 23 at one end and to the arm 12 at the other end. The second member 23 has a rod-like shape. The second member 23 is connected to the first member 22 at one end and to the bucket 13 at the other end.

[0024] Figure 2 is a perspective view of the vehicle body frame 3 and the working machine 10. Figure 3 is a plan view of the vehicle body frame 3 and the working machine 10. The vehicle body frame 3 has a pair of left and right vertical plates 7, 8. The vertical plates 7, 8 extend in the front-rear direction (the left-right direction in the figure in Figure 3). The vertical plates 7, 8 are arranged at intervals in the width direction (left-right direction) of the swivel body 2. The vertical plates 7, 8 are composed of plates standing in the vertical direction and are arranged at a distance from each other in the left-right direction. The driver's cab 4 is arranged to the left of the left vertical plate 7. The working machine 10 is arranged between the vertical plates 7, 8 in the left-right direction. The working machine 10 is arranged to the right of the left vertical plate 7 and to the left of the right vertical plate 8.

[0025] <Electric motor 100> The electric excavator 30 of the embodiment includes at least one electric motor. In the electric excavator 30, the driving force for driving the working machine 10 to relatively move the attachment with respect to the vehicle body frame 3 is generated by the electric motor 100. The electric motor 100 can drive the working machine 10. When the boom 11 and the arm 12 are driven by the electric motor 100, the operation of the working machine 10 becomes possible. The electric motor 100 is disposed on the vehicle body frame 3. The electric motor 100 has a boom electric motor 110 and an arm electric motor 140. Both the boom electric motor 110 and the arm electric motor 140 are supported by the vehicle body frame 3. The boom electric motor 110 and the arm electric motor 140 are disposed on the right side of the working machine 10.

[0026] The boom electric motor 110 drives the boom 11 and generates a driving force for relatively moving the boom 11 with respect to the vehicle body frame 3 with the base end portion of the boom 11 as a fulcrum. The boom 11 can be relatively rotated with respect to the vehicle body frame 3 about the boom foot pin 15 by the drive of the boom electric motor 110. The boom foot pin 15 is disposed across both the left and right vertical plates 7 and 8. The left end of the boom foot pin 15 is supported by the left vertical plate 7, and the right end of the boom foot pin 15 is supported by the right vertical plate 8. Thereby, the boom 11 is supported by the vehicle body frame 3 so as to be rotatable about the boom foot pin 15.

[0027] The boom electric motor 110 has a pair of first boom electric motors 111 and second boom electric motors 121. The first boom electric motor 111 and the second boom electric motor 121 have the same specifications. The first boom electric motor 111 and the second boom electric motor 121 have the same rated output. Here, the rated output of the electric motor means the maximum output that the electric motor can safely achieve under specified conditions.

[0028] The arm motor 140 generates a driving force that drives the arm 12 and causes the arm 12 to relatively move with respect to the vehicle body frame 3 with the tip of the boom 11 as a fulcrum. The arm 12 is rotatable relative to the vehicle body frame 3 about the arm connection pin 16 and rotatable relative to the boom 11 about the arm connection pin 16 by the drive of the arm motor 140. When the boom 11 is relatively moved with respect to the vehicle body frame 3 while maintaining the relative position of the arm 12 with respect to the boom 11, the arm 12 will relatively move with respect to the vehicle body frame 3. In this case, the arm 12 is driven by the arm motor 140.

[0029] The arm motor 140 has a pair of first arm motors 141 and second arm motors 151. The first arm motor 141 and the second arm motor 151 have the same specifications. The first arm motor 141 and the second arm motor 151 have the same rated output.

[0030] <Power transmission device> The electric excavator 30 of the present embodiment includes a power transmission device that mechanically transmits the driving force generated by the motor 100 to the working machine 10. The power transmission device will be described below.

[0031] FIG. 4 is a diagram showing a schematic configuration of a power transmission device that transmits a driving force to the boom 11. The power transmission device has a first boom output gear 119, a second boom output gear 129, and a boom gear member 131.

[0032] The boom gear member 131 has a substantially fan-shaped shape and has a tooth profile on the arc portion of the substantially fan shape. As shown in FIGS. 2 and 3, the boom gear member 131 is fixed to the side surface of the boom 11, more specifically, the right surface of the boom 11. The boom gear member 131 is disposed at the base end portion of the boom 11. The boom gear member 131 is integrally with the boom 11 and is rotatable about the boom foot pin 15.

[0033] The output gear 119 for the first boom is an external gear and meshes with the gear member 131 for the boom. The output gear 119 for the first boom is arranged concentrically with the electric motor 111 for the first boom. The electric motor 111 for the first boom transmits the driving force to the output gear 119 for the first boom. The output gear 129 for the second boom is an external gear and meshes with the gear member 131 for the boom. The output gear 129 for the second boom is arranged concentrically with the electric motor 121 for the second boom. The electric motor 121 for the second boom transmits the driving force to the output gear 129 for the second boom.

[0034] FIG. 5 is a skeleton diagram of the power transmission path from the electric motor 111 for the first boom and the electric motor 121 for the second boom to the gear member 131 for the boom.

[0035] A planetary gear reducer 113 is provided in the power transmission path from the electric motor 111 for the first boom to the gear member 131 for the boom. In the present embodiment, the electric motor 111 for the first boom and the planetary gear reducer 113 have an integral structure. The power transmission device that transmits the driving force of the electric motor 111 for the first boom to the gear member 131 for the boom includes a geared motor 117 in which the electric motor 111 for the first boom and the planetary gear reducer 113 are integrated.

[0036] The planetary gear reducer 113 has a plurality of rotating elements. The plurality of rotating elements of the planetary gear reducer 113 include a sun gear 114, a planetary gear 115, and a ring gear 116. The output shaft 112 of the electric motor 111 for the first boom is connected to the sun gear 114. The driving force of the electric motor 111 for the first boom is input to the sun gear 114.

[0037] The planetary gear reducer 113 and the output gear 119 for the first boom are connected by a connecting shaft 118. More specifically, the connecting shaft 118 has one end connected to the planetary carrier that supports the planetary gear 115 and the other end connected to the output gear 119 for the first boom. The planetary carrier and the output gear 119 for the first boom are connected via the connecting shaft 118. The connecting shaft 118 may be arranged concentrically with the output shaft 112.

[0038] A planetary gear reducer 123 is provided in the power transmission path from the second boom motor 121 to the boom gear member 131. In the present embodiment, the second boom motor 121 and the planetary gear reducer 123 have an integral structure. The power transmission device that transmits the driving force of the second boom motor 121 to the boom gear member 131 includes a geared motor 127 in which the second boom motor 121 and the planetary gear reducer 123 are integrated.

[0039] The planetary gear reducer 123 has a plurality of rotating elements. The plurality of rotating elements of the planetary gear reducer 123 include a sun gear 124, a planetary gear 125, and a ring gear 126. The output shaft 122 of the second boom motor 121 is connected to the sun gear 124. The driving force of the second boom motor 121 is input to the sun gear 124.

[0040] The planetary gear reducer 123 and the second boom output gear 129 are connected by a connecting shaft 128. More specifically, the connecting shaft 128 has one end connected to the planetary carrier that supports the planetary gear 125 and the other end connected to the second boom output gear 129. The planetary carrier and the second boom output gear 129 are connected via the connecting shaft 128. The connecting shaft 128 may be arranged concentrically with the output shaft 122.

[0041] The first boom output gear 119 meshes with the boom gear member 131. The driving force generated by the first boom motor 111 is transmitted to the boom gear member 131 via the first boom output gear 119. The second boom output gear 129 meshes with the boom gear member 131. The driving force generated by the second boom motor 121 is transmitted to the boom gear member 131 via the second boom output gear 129. The boom gear member 131 receives the transmission of the driving force from the first boom motor 111 and the second boom motor 121, and rotates integrally with the boom 11 to which the boom gear member 131 is fixed. Thereby, the boom 11 is rotationally driven about the boom foot pin 15.

[0042] The planetary gear reducer 113, the connecting shaft 118, and the boom 1 output gear 119 mechanically transmit the driving force generated by the boom 1 motor 111 to the boom 11. The planetary gear reducer 123, the connecting shaft 128, and the boom 2 output gear 129 mechanically transmit the driving force generated by the boom 2 motor 121 to the boom 11. The planetary gear reducers 113, 123, the connecting shafts 118, 128, the boom 1 output gear 119, and the boom 2 output gear 129 constitute a boom power transmission device that mechanically transmits the driving force generated by the boom motor 110 to the boom 11.

[0043] The boom power transmission device is disposed on the side opposite to the cab 4 with respect to the work implement 10. In the case of the configuration of the embodiment in which the cab 4 is disposed on the front left side of the vehicle body frame 3 and the cab 4 is disposed on the left side with respect to the work implement 10, the boom power transmission device is disposed on the right side with respect to the work implement 10.

[0044] FIG. 6 is a diagram showing a schematic configuration of a power transmission device 160 that transmits a driving force to the arm 12. The power transmission device 160 that mechanically transmits the driving force generated by the arm motor 140 to the arm 12 includes a first arm output gear 149, a second arm output gear 159, an arm gear member 161, a rotating member 162, and an arm link 170.

[0045] The arm gear member 161 has a substantially fan-shaped shape and has a tooth shape on the arc portion of the substantially fan shape. As shown in FIGS. 2 and 3, the arm gear member 161 is separate from the boom gear member 131 and is disposed to the right of the boom gear member 131 away from the boom gear member 131. A gap is interposed between the boom gear member 131 and the arm gear member 161 in the left-right direction. The arm gear member 161 is disposed at the base end portion of the boom 11. The arm gear member 161 is concentric with the boom foot pin 15 and rotates relative to the vehicle body frame 3.

[0046] The output gear 149 for the first arm is an external gear and meshes with the gear member 161 for the arm. The output gear 149 for the first arm is arranged concentrically with the electric motor 141 for the first arm. The electric motor 141 for the first arm transmits a driving force to the output gear 149 for the first arm. The output gear 159 for the second arm is an external gear and meshes with the gear member 161 for the arm. The output gear 159 for the second arm is arranged concentrically with the electric motor 151 for the second arm. The electric motor 151 for the second arm transmits a driving force to the output gear 159 for the second arm.

[0047] The power transmission path from the electric motor 141 for the first arm and the electric motor 151 for the second arm to the gear member 161 for the arm is the same as the power transmission path to the boom gear member 131 shown in FIG. 5. A planetary gear reducer is provided in the power transmission path from the electric motor 141 for the first arm to the gear member 161 for the arm. The electric motor 141 for the first arm and the planetary gear reducer are of an integral structure. A planetary gear reducer is provided in the power transmission path from the electric motor 151 for the second arm to the gear member 161 for the arm. The electric motor 151 for the second arm and the planetary gear reducer are of an integral structure. The gear member 161 for the arm rotates by receiving the transmission of the driving force from the electric motor 141 for the first arm and the electric motor 151 for the second arm.

[0048] The rotating member 162 is fixed to the gear member 161 for the arm and rotates relative to the vehicle body frame 3 concentrically with the boom foot pin 15 integrally with the gear member 161 for the arm.

[0049] The arm link 170 has a first link member 171, a second link member 172, and an intermediate member 173. The intermediate member 173 is connected to the boom 11 via a pin 178. The boom 11 has a bent shape when viewed from the side, and the intermediate member 173 is connected to the bent portion of the boom 11.

[0050] The first link member 171 has a rod-like shape. The first link member 171 extends along the boom 11. At its first end, the first link member 171 is connected to the rotating member 162 via a connecting pin 177. At its second end, the first link member 171 is connected to the intermediate member 173 via a connecting pin 174. The first link member 171 connects the rotating member 162 and the intermediate member 173. The first link member 171 transmits the driving force generated by the arm motor 140 and transmitted to the rotating member 162 via the arm gear member 161 to the intermediate member 173.

[0051] The second link member 172 has a rod-like shape. The second link member 172 extends along the boom 11. At its first end, the second link member 172 is connected to the intermediate member 173 via a connecting pin 175. At its second end, the second link member 172 is connected to the arm 12 via a connecting pin 176. The second link member 172 connects the intermediate member 173 and the arm 12. The second link member 172 transmits the driving force generated by the arm motor 140 and transmitted to the intermediate member 173 via the arm gear member 161, the rotating member 162, and the first link member 171 in sequence to the arm 12.

[0052] The intermediate member 173 may have a substantially polygonal shape. The first link member 171 and the second link member 172 may be connected to the intermediate member 173 near different vertices of the substantially polygonal shape of the intermediate member 173. The intermediate member 173 is not limited to a substantially polygonal shape and may have any shape. For example, the intermediate member 173 may have a rod-like shape and its proximal end may be connected to the boom 11.

[0053] The arm link 170 (the first link member 171, the second link member 172, and the intermediate member 173) transmits power to the arm 12 by the relative rotational movement of the arm gear member 161 and the rotating member 162 with respect to the vehicle body frame 3.

[0054] Although an example in which the power transmission device 160 has a rod-shaped link member has been described, the power transmission device 160 may have a mechanism other than the link member as long as it can mechanically transmit the driving force of the arm motor 140 to the arm 12. For example, the power transmission device 160 may have any one or a combination of a steel cable, a chain, a pulley, a rack and pinion, and the like.

[0055] <Double motor drive> Generally, in a gear mechanism, there is backlash, which is a gap provided between the tooth surfaces of meshing gears, so the positioning accuracy of a movable member connected to the driven gear decreases. In the case of a working machine, the backlash of the gear mechanism provided at the base portion of the boom 11 causes misalignment of the attachment at the tip of the working machine 10. To reduce the backlash, the power transmission device of the embodiment is a double motor drive that drives one gear member using two electric motors.

[0056] Specifically, the boom gear member 131 that transmits the driving force to the boom 11 is driven by the first boom motor 111 and the second boom motor 121. The arm gear member 161 that transmits the driving force to the arm 12 is driven by the first arm motor 141 and the second arm motor 151. Hereinafter, the double motor drive will be described using, as an example, the structure in which the arm gear member 161 is driven by the first arm motor 141 and the second arm motor 151.

[0057] FIG. 7 is a schematic diagram of the double motor drive. Note that in FIG. 7, since the double motor drive is schematically illustrated, the shape of the arm gear member 161, the arrangement of the first arm output gear 149 and the second arm output gear 159 with respect to the arm gear member 161, and the like are different from those of the embodiment shown in FIG. 6.

[0058] The arm gear member 161 fixed to the swing member 162 meshes with a first arm output gear 149 and a second arm output gear 159. The first arm output gear 149 is connected to a first arm motor 141, and when the first arm motor 141 is rotationally driven, the first arm output gear 149 rotates. The second arm output gear 159 is connected to a second arm motor 151, and when the second arm motor 151 is rotationally driven, the second arm output gear 159 rotates.

[0059] In the arrangement shown in FIG. 7, for each gear, the clockwise direction is defined as the positive direction of rotation, and the counterclockwise direction is defined as the negative direction of rotation.

[0060] By the coordinated control of the first arm motor 141 and the second arm motor 151, backlash removal control for bringing the tooth surfaces of the gears into contact without a gap can be executed to increase the positioning accuracy of the attachment at the tip of the work implement 10. Also, in order to improve the efficiency of the power transmission device, the backlash removal control can be made non-executable. By switching between the execution and non-execution of the backlash removal control, either a highly accurate attachment position or highly efficient power transmission can be selected. Also, by adopting a highly efficient planetary gear mechanism, regeneration using the kinetic energy of the work implement 10 becomes possible.

[0061] When executing the backlash removal control, the first arm motor 141 constantly applies an offset torque in the positive direction to the arm gear member 161, and the second arm motor 151 constantly applies an offset torque in the negative direction to the arm gear member 161.

[0062] When stopping the arm gear member 161, the first arm motor 141 and the second arm motor 151 apply offset torques of the same magnitude but in opposite directions to the arm gear member 161. The magnitude of the total torque of the torque loaded on the arm gear member 161 by the first arm motor 141 and the torque loaded on the arm gear member 161 by the second arm motor 151 is zero.

[0063] At this time, both the output gear 149 for the first arm and the output gear 159 for the second arm attempt to rotate in opposite directions and sandwich the gear member 161 for the arm. With the tooth surfaces of the output gear 149 for the first arm in contact with the tooth surfaces of the gear member 161 for the arm and the tooth surfaces of the output gear 159 for the second arm in contact with the tooth surfaces of the gear member 161 for the arm, the gear member 161 for the arm is held. By pressing both the output gear 149 for the first arm and the output gear 159 for the second arm against the gear member 161 for the arm, backlash can be suppressed.

[0064] When rotating the gear member 161 for the arm in the counterclockwise direction at a low speed, the torque generated by the first-arm electric motor 141 is increased. By increasing the torque of the first-arm electric motor 141, the gear member 161 for the arm is driven in the negative direction (counterclockwise direction). At this time, the second-arm electric motor 151 continues to apply an offset torque in the direction opposite to the rotation direction of the gear member 161 for the arm. The first-arm electric motor 141 drives the gear member 161 for the arm, and the second-arm electric motor 151 is in a state of applying a slight brake to the gear member 161 for the arm.

[0065] When rotating the gear member 161 for the arm in the clockwise direction at a low speed, the torque generated by the second-arm electric motor 151 is increased. By increasing the torque of the second-arm electric motor 151, the gear member 161 for the arm is driven in the positive direction (clockwise direction). At this time, the first-arm electric motor 141 continues to apply an offset torque in the direction opposite to the rotation direction of the gear member 161 for the arm. The second-arm electric motor 151 drives the gear member 161 for the arm, and the first-arm electric motor 141 is in a state of applying a slight brake to the gear member 161 for the arm.

[0066] At this time, both the output gear 149 for the first arm and the output gear 159 for the second arm attempt to rotate in opposite directions and sandwich the gear member 161 for the arm. The tooth surface of the output gear 149 for the first arm comes into contact with the tooth surface of the gear member 161 for the arm, and the tooth surface of the output gear 159 for the second arm comes into contact with the tooth surface of the gear member 161 for the arm. By pressing both the output gear 149 for the first arm and the output gear 159 for the second arm against the gear member 161 for the arm, backlash can be suppressed.

[0067] By executing backlash removal control, the positioning accuracy of the attachment at the tip of the working machine 10 can be increased, and high-precision work using the attachment becomes possible.

[0068] When backlash removal control is not executed, no offset torque is applied from the first arm motor 141 and the second arm motor 151 to the gear member 161 for the arm. In order to rotate the gear member 161 for the arm at high speed, driving torque in the same direction is applied from the first arm motor 141 and the second arm motor 151 to the gear member 161 for the arm.

[0069] Both the first arm motor 141 and the second arm motor 151 apply driving torque to the gear member 161 for the arm. Neither the first arm motor 141 nor the second arm motor 151 applies a brake to the gear member 161 for the arm. By not executing backlash removal control, power can be transmitted to the gear member 161 for the arm with high efficiency. Although the positioning accuracy of the attachment at the tip of the working machine 10 is lowered, it does not matter because high positioning accuracy is not required for the attachment during high-speed movement.

[0070] The power transmission path from the first arm motor 141 to the first arm output gear 149 has an efficient planetary gear reducer. The power transmission path from the second arm motor 151 to the second arm output gear 159 has an efficient planetary gear reducer. When backlash removal control is not executed, when a large external force acts on the attachment at the tip of the working machine 10 due to the attachment colliding with an object or the like, the external force is transmitted through the planetary gear reducer to the first arm motor 141 and the second arm motor 151.

[0071] The rotor parts of the first arm motor 141 and the second arm motor 151 have no contact parts other than the bearings that rotatably support the rotor parts. Therefore, when a large external force acts, an angular displacement occurs in the rotor part. As a result of the first arm motor 141 and the second arm motor 151 getting out of phase, it is possible to prevent damage to the planetary gear reducer.

[0072] During the execution of the backlash removal control, the attachment at the tip of the working machine 10 is stopped or, if it moves, it moves at a low speed. Since the moving speed of the attachment at the tip of the working machine 10 is small and the impact when the attachment collides with an object is small, damage to the planetary gear reducer is prevented.

[0073] <Attachment motor 220> FIG. 8 is a diagram showing a schematic configuration of a power transmission device 210 that transmits driving force to the bucket 13. FIG. 9 is a schematic diagram of the power transmission device 210 as viewed from the direction of arrow IX in FIG. 8. In the electric excavator 30, the attachment motor 220 generates a driving force for driving the bucket 13. The motor 100 has the attachment motor 220.

[0074] The attachment motor 220 can drive the bucket 13. When the bucket 13 is driven by the attachment motor 220, the bucket 13 can operate. The bucket 13 can rotate relative to the arm 12 about the attachment connecting pin 17 by being driven by the attachment motor 220. The power transmission device 210 mechanically transmits the driving force generated by the attachment motor 220 to the bucket 13.

[0075] The attachment motor 220 is mounted on the arm 12. A buffer mechanism 229 is attached to the arm 12. The buffer mechanism 229 has a function of buffering the load input to the arm 12. The attachment motor 220 is mounted on the arm 12 via the buffer mechanism 229. The attachment motor 220 has a pair of first motor 221 and second motor 231. The first motor 221 and the second motor 231 have the same specifications. The first motor 221 and the second motor 231 have the same rated output.

[0076] The output shaft of the first motor 221 is connected to the flexible shaft 222. The flexible shaft 222 has a proximal end connected to the first motor 221. The distal end of the flexible shaft 222 is connected to the bevel gear 223. The bevel gear 223 meshes with the bevel gear 224. The bevel gear 224 is connected to the planetary gear reducer 225.

[0077] The planetary gear reducer 225 has a plurality of rotating elements. The plurality of rotating elements of the planetary gear reducer 225 include a sun gear, a planetary gear, and a ring gear. The bevel gear 224 is connected to the sun gear of the planetary gear reducer 225. The driving force of the first motor 221 is input to the sun gear of the planetary gear reducer 225 via the flexible shaft 222 and the bevel gears 223, 224.

[0078] The planetary gear reducer 225 reduces the rotation of the first electric motor 221, increases the driving force, and outputs it. The planetary carrier of the planetary gear reducer 225 is connected to the output shaft 227. The output shaft 227 has one end connected to the planetary carrier and the other end connected to the pinion 228. The pinion 228 meshes with the rack 240.

[0079] The output shaft of the second electric motor 231 is connected to the flexible shaft 232. The flexible shaft 232 has a proximal end connected to the second electric motor 231. The distal end of the flexible shaft 232 is connected to the bevel gear 233. The bevel gear 233 meshes with the bevel gear 234. The bevel gear 234 is connected to the planetary gear reducer 235.

[0080] The planetary gear reducer 235 has a plurality of rotating elements. The plurality of rotating elements of the planetary gear reducer 235 include a sun gear, a planetary gear, and a ring gear. The bevel gear 234 is connected to the sun gear of the planetary gear reducer 235. The driving force of the second electric motor 231 is input to the sun gear of the planetary gear reducer 235 via the flexible shaft 232 and the bevel gears 233, 234.

[0081] The planetary gear reducer 235 reduces the rotation of the second electric motor 231, increases the driving force, and outputs it. The planetary carrier of the planetary gear reducer 235 is connected to the output shaft 237. The output shaft 237 has one end connected to the planetary carrier and the other end connected to the pinion 238. The pinion 238 meshes with the rack 240.

[0082] The pinions 228, 238 and the rack 240 are supported by the support member 250 via the pin 251. The support member 250 is fixed to the arm 12. The rack 240 and the pinions 228, 238 are supported by the arm 12 via the support member 250.

[0083] The rack 240 is coupled to a link pin 24 that connects the first member 22 and the second member 23 of the bucket link 21. The rack 240 is connected to the bucket 13 via the bucket link 21.

[0084] The driving force generated by the first electric motor 221 is transmitted to the pinion 228, causing the pinion 228 to rotate. The driving force generated by the second electric motor 231 is transmitted to the pinion 238, causing the pinion 238 to rotate. The rack 240 moves longitudinally according to the rotation of the pinions 228 and 238.

[0085] As the rack 240 moves away from the arm connection pin 16 that connects the boom 11 and the arm 12 and approaches the attachment connection pin 17 that connects the arm 12 and the bucket 13, the bucket 13 is rotationally driven about the attachment connection pin 17. The bucket 13 moves in the excavation direction (the direction in which the cutting edge 13A of the bucket 13 approaches the arm 12. In FIG. 8, it is the counterclockwise direction about the attachment connection pin 17).

[0086] As the rack 240 moves away from the attachment connection pin 17 and approaches the arm connection pin 16, the bucket 13 is rotationally driven about the attachment connection pin 17. The bucket 13 moves in the dump direction (the direction in which the cutting edge 13A of the bucket 13 moves away from the arm 12. In FIG. 8, it is the clockwise direction about the attachment connection pin 17).

[0087] The rack 240 meshes with the pinion 228 and the pinion 238. The pinion 228 is connected to the first electric motor 221, and the pinion 228 rotates when the first electric motor 221 is rotationally driven. The pinion 238 is connected to the second electric motor 231, and the pinion 238 rotates when the second electric motor 231 is rotationally driven. The power transmission device 210 is double-motor driven, using two electric motors, namely the first electric motor 221 and the second electric motor 231, to drive a single gear member, the rack 240.

[0088] By the coordinated control of the first electric motor 221 and the second electric motor 231, backlash removal control can be executed to improve the positioning accuracy of the bucket 13. Also, in order to improve the efficiency of the power transmission device 210, it is also possible not to execute the backlash removal control.

[0089] The rotation directions and the generated driving forces of the first electric motor 221 and the second electric motor 231 are adjusted according to the operation of the operator for operating the bucket 13. The operator sitting in the driver's seat 4S can move the bucket 13 in the excavation direction by moving the operation lever arranged on the right side of the driver's seat 4S to the left with the right hand, or move the bucket 13 in the dump direction by moving the operation lever to the right. According to the intention of the operator, the bucket 13 at the tip of the work machine 10 can be moved at high speed with high efficiency, moved at a very low speed with high position accuracy, or stopped with high position accuracy.

[0090] When the positioning accuracy of the attachment at the tip of the work machine 10 is not required, it is also possible to use single motor drive in which any one or more of the boom gear member 131, the arm gear member 161, and the rack 240 are driven by one electric motor.

[0091] The attachment electric motor 220 that generates the driving force for driving the bucket 13 does not necessarily have to be mounted on the arm 12. The attachment electric motor 220 may be arranged on the vehicle body frame 3. It is also possible to adopt a configuration in which the driving force generated by the attachment electric motor 220 fixed to the vehicle body frame 3 is mechanically transmitted to the bucket 13 via the attachment power transmission device.

[0092] <System Configuration> FIG. 10 is a block diagram showing a schematic configuration of a control system for controlling the electric excavator 30. Only a part of the system constituting the electric excavator 30 of the embodiment is shown in FIG. 10. The electric excavator 30 includes a work implement attitude detector 40 that detects the attitude of the work implement 10, and a controller 50 that controls the operation of the electric excavator 30.

[0093] The work implement attitude detector 40 includes a boom angle sensor 41, an arm angle sensor 42, and an attachment angle sensor 43. The boom angle sensor 41 detects the angle of the boom 11 with respect to the vehicle body frame 3. The arm angle sensor 42 detects the angle of the arm 12 with respect to the boom 11 in a region where the arm 12 rotates in a side view. The attachment angle sensor 43 detects the angle of the bucket 13 with respect to the arm 12 in a region where the bucket 13 rotates in a side view. The boom angle sensor 41, the arm angle sensor 42, and the attachment angle sensor 43 output angle detection signals to the controller 50.

[0094] The boom angle sensor 41, the arm angle sensor 42, and the attachment angle sensor 43 may be potentiometers or rotary encoders. The boom angle sensor 41 may be attached around the boom foot pin 15. The arm angle sensor 42 may be attached around the arm connection pin 16. The attachment angle sensor 43 may be attached around the attachment connection pin 17.

[0095] The boom angle sensor 41 may be an IMU (Inertial Measurement Unit) attached to the boom 11. The arm angle sensor 42 may be an IMU attached to the arm 12. The attachment angle sensor 43 may be an IMU attached to the bucket link 21 (first member 22).

[0096] The controller 50 is configured to include a CPU (Central Processing Unit) and the like. The controller 50 has a storage unit 58 and a timer 59.

[0097] The storage unit 58 is a non-volatile memory and is provided as an area for storing necessary data. The storage unit 58 stores a control program for controlling various operations of the electric excavator 30 and various data necessary for the execution of the control program. The storage unit 58 also temporarily stores working data generated along with the operation of the electric excavator 30. The controller 50 executes various processes for controlling the operation of the electric excavator 30 by executing the control program stored in the storage unit 58. The timer 59 measures time.

[0098] The controller 50 outputs a control signal for operating the working machine 10 to the electric motor 100. The controller 50 outputs a control signal for relatively moving the boom 11 with respect to the vehicle body frame 3 to the boom electric motor 110. The controller 50 outputs a control signal for relatively moving the arm 12 with respect to the vehicle body frame 3 to the arm electric motor 140. The controller 50 outputs a control signal for relatively moving the bucket 13 with respect to the arm 12 to the attachment electric motor 220.

[0099] The controller 50 has an angle acquisition unit 51, an angular acceleration calculation unit 52, an attachment total weight calculation unit 53, a moment of inertia calculation unit 54, a rotational moment calculation unit 55, and an angular acceleration limit unit 56.

[0100] <Vibration suppression control> FIG. 11 is a flowchart showing the flow of a process for suppressing the vibration of the vehicle body 1 in the electric excavator 30. With appropriate reference to FIGS. 10, 11 and subsequent figures, the process for suppressing the vibration of the vehicle body 1 during the operation of the electric excavator 30 will be described.

[0101] In step S1, the angle acquisition unit 51 receives a detection signal of the angle of the boom 11 with respect to the vehicle body frame 3 from the boom angle sensor 41. The angle acquisition unit 51 receives a detection signal of the angle of the arm 12 with respect to the boom 11 from the arm angle sensor 42. The angle acquisition unit 51 receives a detection signal of the angle of the bucket 13 with respect to the arm 12 from the attachment angle sensor 43. The angle acquisition unit 51 acquires the current posture of the working machine 10. The angle acquisition unit 51 stores the angles of the boom 11, the arm 12, and the bucket 13 and the time when the angles were acquired in the storage unit 58.

[0102] In step S2, the angular acceleration calculation unit 52 reads from the storage unit 58 the time before the time when the angle of the working machine 10 was acquired in step S1 and the angles of the boom 11, the arm 12, and the bucket 13 at that time. The angular acceleration calculation unit 52 calculates the angular velocity of the rotating working machine 10 using the elapsed time, the angle of the working machine 10 at the start time of the elapsed time, and the angle of the working machine 10 at the end time of the elapsed time. The angular acceleration calculation unit 52 calculates the angular acceleration of the working machine 10 from the change in the angular velocity of the working machine 10 with respect to the passage of time.

[0103] In step S3, the attachment total weight calculation unit 53 calculates the weight of the load mounted on the bucket 13 (the in-bucket load value).

[0104] FIG. 12 is a schematic diagram of a working machine for explaining the balance of moments. As shown in FIG. 12, in the embodiment, the current load value W in the bucket 13 is detected from the balance of moments. Specifically, the current load value W in the bucket 13 is detected from the balance of each moment around the boom foot pin 15. Here, the balance of each moment around the boom foot pin 15 is expressed by the following formula (1).

[0105]

Equation

[0106] In Equation (1), Tboom is the torque generated by the boom motor 110. Tarm is the torque generated by the arm motor 140. Tbucket is the torque generated by the attachment motor 220. Mboom is the moment around the boom foot pin 15 of the boom 11. Marm is the moment around the boom foot pin 15 of the arm 12. Mbucket is the moment around the boom foot pin 15 of the bucket 13. W is the current load value in the bucket 13. L is the horizontal distance from the boom foot pin 15 to the attachment connection pin 17.

[0107] Tboom is calculated based on the rated output of the boom motor 110 and the rotational speed of the boom motor 110. Tarm is calculated based on the rated output of the arm motor 140 and the rotational speed of the arm motor 140. Tbucket is calculated based on the rated output of the attachment motor 220 and the rotational speed of the attachment motor 220.

[0108] Mboom is calculated by the product (r1 × M1) of the distance r1 between the center of gravity C1 of the boom 11 and the boom foot pin 15 and the self-weight M1 of the boom 11. The position of the center of gravity C1 of the boom 11 is calculated from the angle A1 of the boom 11 with respect to the vehicle body frame 3 and the like. The self-weight M1 of the boom 11 and the like are stored in the storage unit 58.

[0109] Marm is calculated by the product (r2 × M2) of the distance r2 between the center of gravity C2 of the arm 12 and the boom foot pin 15 and the self-weight M2 of the arm 12. The position of the center of gravity C2 of the arm 12 is calculated from the angle A2 of the arm 12 with respect to the boom 11 and the like. The self-weight M2 of the arm 12 and the like are stored in the storage unit 58.

[0110] Mbucket is calculated by the product (r3 × M3) of the distance r3 between the center of gravity C3 of the bucket 13 and the boom foot pin 15 and the self-weight M3 of the bucket 13. The position of the center of gravity C3 of the bucket 13 is calculated from, for example, the angle A3 of the bucket 13 with respect to the arm 12. The self-weight M3 of the bucket 13 and the like are stored in the storage unit 58.

[0111] In calculating the current load value W in the bucket 13, based on the posture of the work machine 10 acquired by the angle acquisition unit 51, the attachment total weight calculation unit 53 calculates the positions of the centers of gravity C1, C2, and C3. The attachment total weight calculation unit 53 calculates the respective distances r1, r2, and r3 between the centers of gravity C1, C2, C3 and the boom foot pin 15.

[0112] The attachment total weight calculation unit 53 reads the self-weight M1 of the boom 11 from the storage unit 58 and calculates the product of the distance r1 and the self-weight M1 as the moment Mboom around the boom foot pin 15 of the boom 11. The attachment total weight calculation unit 53 reads the self-weight M2 of the arm 12 from the storage unit 58 and calculates the product of the distance r2 and the self-weight M2 as the moment Marm around the boom foot pin 15 of the arm 12. The attachment total weight calculation unit 53 reads the self-weight M3 of the bucket 13 from the storage unit 58 and calculates the product of the distance r3 and the self-weight M3 as the moment Mbucket around the boom foot pin 15 of the bucket 13.

[0113] The attachment total weight calculation unit 53 reads the length L1 of the boom 11 and the length L2 of the arm 12 from the storage unit 58. The attachment total weight calculation unit 53 calculates the horizontal distance L from the boom foot pin 15 to the attachment connection pin 17 based on the angles A1 and A2 calculated above and the lengths L1 and L2 of the boom 11 and the arm 12.

[0114] The attachment total weight calculation unit 53 substitutes each torque Tboom, Tarm, Tbucket, each moment Mboom, Marm, Mbucket, and the distance L calculated as described above into the above formula (1). As a result, the attachment total weight calculation unit 53 calculates the current load value W in the bucket 13. The attachment total weight calculation unit 53 calculates the sum of the self-weight M3 of the bucket 13 and the load value W, which is the weight of the load mounted on the bucket 13, as the total weight of the bucket 13 (attachment). By calculating the total weight of the bucket 13 in this way, it becomes possible to calculate the inertial moment Ib and the rotational moment Hb, which will be described later, with higher accuracy.

[0115] Returning to FIG. 11, in step S4, the inertial moment calculation unit 54 calculates the inertial moment Ib around the boom foot pin 15. The inertial moment Ib varies according to the change in the posture of the work machine 10. The inertial moment Ib varies according to the weight of the load mounted on the bucket 13.

[0116] The inertial moment calculation unit 54 calculates the inertial moment of the boom 11 around the boom foot pin 15 based on the self-weight M1 of the boom 11, the length L1, and the angle A1. The inertial moment calculation unit 54 calculates the inertial moment of the arm 12 around the boom foot pin 15 based on the self-weight M2 of the arm 12, the lengths L1 and L2 of the boom 11 and the arm 12, and the angles A1 and A2. The inertial moment calculation unit 54 calculates the inertial moment of the bucket 13 and the mounted load around the boom foot pin 15 based on the total weight of the attachment calculated as described above, the lengths L1 and L2 of the boom 11 and the arm 12, and the angles A1 and A2. The inertial moment calculation unit 54 calculates the sum of these inertial moments as the inertial moment Ib.

[0117] In step S5, the rotational moment calculation unit 55 calculates the product of the inertial moment Ib and the angular acceleration of the work machine 10 calculated in step S2 as the rotational moment Hb of the boom 11. That is, the rotational moment Hb of the boom 11 is represented by the following formula (2).

[0118]

Number

[0119] In Equation (2), v is the speed of the boom 11 rotating about the boom foot pin 15, and t is the time. The angular acceleration of the boom 11 is the time derivative of the speed of the boom 11.

[0120] FIG. 13 is a graph showing the relationship between the posture of the boom 11 and the speed of the boom 11. The horizontal axis of FIG. 13 is the angle A1 (unit: °) of the boom 11 with respect to the vehicle body frame 3, and the vertical axis is the speed of the boom 11. The angle A1 becomes a positive value when the arm connection pin 16 is above the boom foot pin 15. As shown in FIG. 13, the movable range of the boom 11 is in the range where the angle A1 is approximately minus 45° to approximately plus 100°. The angle A1 of approximately minus 45° is one end of the movable range of the boom 11. The angle A1 of approximately plus 100° is the other end of the movable range of the boom 11.

[0121] At the end of the movable range of the boom 11, the speed of the boom 11 becomes zero, and as the rotating boom 11 approaches the end of the movable range, the speed of the boom 11 decreases. The slope of the graph shown in FIG. 13 is the angular acceleration of the boom 11. The rotational moment calculation unit 55 calculates the product of the angular acceleration at the time of deceleration of the boom 11 and the moment of inertia Ib as the rotational moment acting on the working machine 10 at the end of the movable range of the boom 11.

[0122] In step S6, the angular acceleration limiting unit 56 reads out the threshold value of the rotational moment from the storage unit 58. The threshold value of the rotational moment is stored in the storage unit 58 in advance. The threshold value of the rotational moment is set, for example, as a value such that the crawler device 5Cr does not lift off the ground. The angular acceleration limiting unit 56 compares the rotational moment acting on the working machine 10 at the end of the movable range of the boom 11 calculated in step S5 with the threshold value, and determines whether or not the rotational moment is less than or equal to the threshold value.

[0123] If it is determined that the rotational moment is greater than the threshold value (NO in step S6), there is a possibility that the crawler device 5Cr will lift off the ground due to the rotational moment when the boom 11 reaches the end of the movable range. When the crawler device 5Cr lifts off the ground, the impact when the crawler device 5Cr touches the ground again is large, and vibrations occur in the vehicle body 1. Therefore, in that case, in step S7, the angular acceleration limiting unit 56 limits the angular acceleration of the work machine 10. The angular acceleration limiting unit 56 limits the angular acceleration of the work machine 10 based on the result of the determination in step S6.

[0124] FIG. 14 is a graph showing the relationship between the posture of the boom 11 and the speed of the boom 11 after the angular acceleration is limited. Similar to FIG. 13, the horizontal axis of the graph in FIG. 14 is the angle A1 of the boom 11, and the vertical axis is the speed of the boom 11. The movable range of the boom 11 is the same as in FIG. 13. As shown in FIG. 14, when moving toward the end of the movable range of the boom 11, the speed of the boom 11 gradually decreases. Compared with FIG. 13, the slope of the graph becomes smaller. The angular acceleration of the boom 11 when moving toward the end of the movable range is limited.

[0125] The rotational moment Hb of the boom 11 is calculated as the product of the moment of inertia Ib and the angular acceleration, as represented by the above formula (2). By reducing the angular acceleration of the boom 11, the value of the rotational moment Hb acting on the boom 11 at the end of the movable range of the boom 11 becomes smaller. The lifting of the crawler device 5Cr from the ground when the boom 11 reaches the end of the movable range is suppressed. Since the event of the crawler device 5Cr lifting off and then touching the ground again can be suppressed, vibrations of the vehicle body 1 can be suppressed. Since the transmission of vibrations to the driver's cab 4 mounted on the vehicle body 1 is suppressed, the riding comfort of the operator riding in the driver's cab 4 can be improved.

[0126] In step S8, the angular acceleration limiting unit 56 determines a posture for reducing the angular velocity. In FIGS. 13 and 14, the maximum value of the speed of the boom 11 is the same. In order to gradually reduce the speed of the boom 11 and make the speed zero at the end of the movable range, it is necessary to set a position farther from the end of the movable range as the starting point for reducing the speed. In the example shown in FIG. 13, the reduction of the speed of the boom 11 starts at a position about 20° away from the end of the movable range. On the other hand, in FIG. 14, the reduction of the speed of the boom 11 starts at a position about 40° away from the end of the movable range.

[0127] As described above, the moment of inertia of the working machine 10 changes depending on the posture of the working machine 10 and also changes depending on the load value W. The angular acceleration limiting unit 56 determines the posture of the moving working machine 10 when the moving working machine 10 starts to reduce its speed according to the moment of inertia of the working machine 10 around the boom foot pin 15. By doing so, the riding comfort of the operator can be improved without sacrificing the workability of the electric excavator 30 as much as possible.

[0128] The process returns to step S6, and the determination as to whether or not the rotational moment is less than or equal to the threshold value is executed again. If it is determined in the determination of step S6 that the rotational moment is less than or equal to the threshold value (YES in step S6), the process ends ( "End" in FIG. 11).

[0129] In the embodiment, an example in which the electric motor 100 has a boom electric motor 110 and an arm electric motor 140 individually has been described. The electric motor 100 that generates the driving force for the boom 11 and the arm 12 does not necessarily have to be provided separately. A configuration may be adopted in which power is distributed from the output shaft of one electric motor 100 and transmitted to the boom 11 and the arm 12 as driving forces respectively. In this case, the switching of the transmission of the driving force to the boom 11 and the arm 12 may be performed by an operation of an operator boarding the cab 4.

[0130] In the embodiment, an example has been described in which the cab 4 is arranged on the front left side of the vehicle body frame 3, the working machine 10 is arranged on the right side of the cab 4, and the boom motor 110 and the arm motor 140 are arranged on the right side of the working machine 10. However, the arrangement is not limited to this. For example, by arranging the cab 4 behind the working machine 10, it becomes possible to arrange the motors 100 on both the left and right sides of the working machine 10, so that the degree of freedom in arranging the motors 100 can be improved.

[0131] In the embodiment, an electric excavator 30 provided with an electric motor that generates a driving force for driving the working machine 10 has been described. The electric excavator 30 may be an electric vehicle in which the driving force for the traveling of the traveling body 5 and the turning of the revolving body 2 with respect to the traveling body 5 is also generated by an electric motor. The electric excavator 30 may not be provided with an internal combustion engine. The electric excavator 30 may not be provided with a hydraulic circuit.

[0132] In the embodiment, an example in which the power transmission device has a planetary gear reducer has been described. Instead of the planetary gear reducer, the power transmission device may have a spur reducer in which a plurality of gears are combined by meshing one gear with one gear.

[0133] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated 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 be included.

Explanation of reference numerals

[0134] 1 Body, 2 Swiveling body, 3 Body frame, 4 Driver's cab, 4S Driver's seat, 5 Traveling body, 5Cr Crawler device, 10 Working machine, 11 Boom, 12 Arm, 13 Bucket, 15 Boom foot pin, 16 Arm connection pin, 17 Attachment connection pin, 30 Electric excavator, 40 Working machine attitude detector, 41 Boom angle sensor, 42 Arm angle sensor, 43 Attachment angle sensor, 50 Controller, 51 Angle acquisition unit, 52 Angular acceleration calculation unit, 53 Attachment total weight calculation unit, 54 Moment of inertia calculation unit, 55 Rotation moment calculation unit, 56 Angular acceleration limit unit, 58 Memory unit, 59 Timer, 100 Electric motor, 110 Boom electric motor, 140 Arm electric motor, 160, 210 Power transmission device, 220 Attachment electric motor.

Claims

1. A vehicle body frame, a boom supported by the vehicle body frame, an arm connected to the boom, and an attachment connected to the arm, a working machine including the same, at least one electric motor that generates a driving force for relatively moving the attachment with respect to the vehicle body frame, a controller that limits an angular acceleration of the working machine based on a determination result as to whether a rotational moment acting on the working machine at an end of a movable range of the working machine is equal to or less than a threshold value. A working machine comprising:

2. further comprising a working machine attitude detector that detects an attitude of the working machine, wherein the controller calculates a total weight of the attachment using the attitude of the working machine and the driving force generated by the electric motor, calculates a moment of inertia about a rotation axis of the working machine using the attitude of the working machine and the total weight of the attachment, and calculates the rotational moment using the moment of inertia. The working machine according to claim 1.

3. The working machine according to claim 1, wherein the controller determines an attitude of the working machine when the moving working machine begins to reduce its speed.

4. The electric motor includes a boom electric motor that generates a driving force for relatively moving the boom with respect to the vehicle body frame with a base end portion of the boom as a fulcrum. The working machine according to any one of claims 1 to 3.

5. The electric motor includes an arm electric motor that generates a driving force for relatively moving the arm with respect to the vehicle body frame with a tip end portion of the boom as a fulcrum. The working machine according to any one of claims 1 to 3.

6. The electric motor includes an attachment electric motor that generates a driving force for relatively moving the attachment with respect to the arm. The working machine according to any one of claims 1 to 3.

7. The attachment is a bucket, wherein the total weight of the attachment includes the self-weight of the bucket and the weight of a load mounted on the bucket. The working machine according to claim 2.

8. determining whether a rotational moment acting on a working machine supported by a vehicle body frame and relatively moving with respect to the vehicle body frame by a driving force of an electric motor at an end of a movable range of the working machine is equal to or less than a threshold value; limiting an angular acceleration of the working machine based on a result of the determination. A control method for a working machine comprising:

Images