Work machine

Abstract

To provide a work machine capable of reducing an environmental load.SOLUTION: A work machine comprises: a travel body 200 that supports a pair of arms 222 having a bulldozer 221 loaded at the tip so as to be liftable; a crank part 601 rotated by an electric motor disposed on the travel body 200 between the pair of arms 222; and a crank rod 608 that is pivotally connected at one end to the crank part 601 via a first pivotal connection part 604 and that pivotally connects the bulldozer 221 via a second pivotal connection part 607 so as to be vertically liftable.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a work machine. [Background technology]

[0002] As a related art, a hydraulic excavator is known in which an electric motor drives a hydraulic pump to pump hydraulic oil to a hydraulic actuator, thereby operating a work machine such as a blade (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-148775 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the demand for decarbonization, there has been an increasing demand for work machines such as hydraulic excavators that are driven by electric motors, such as those described in Patent Document 1. However, the work machine described in Patent Document 1 uses a hydraulic actuator, which causes problems such as the scattering of hydraulic oil due to damage to hydraulic piping, etc.

[0005] The present invention has been made in consideration of the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a work machine that can reduce the environmental load caused by the scattering of hydraulic oil and the like. [Means for solving the problem]

[0006] A work machine according to one embodiment of the present invention is a work machine comprising a running body that supports a pair of arms, each with a blade attached to its tip, so that the arms can be raised and lowered, and a battery unit, and is further provided with an electric motor that is disposed on the running body between the pair of arms and is supplied with power from the battery unit, a crank section that rotates by the electric motor, and a crank rod that is pivotally connected at one end to the crank section via a first pivotal connection and pivotally connects the blade via a second pivotal connection so that the blade can be raised and lowered up and down. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a work machine that can reduce the environmental load. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic left side view of a shovel according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic plan view of a shovel according to an embodiment of the present invention. [Figure 3] FIG. 2 is a schematic side view of the electric motor unit and the crank portion according to the embodiment of the present invention. [Figure 4] 2 is a schematic cross-sectional view of a traveling body of the shovel in the direction AA when the shovel according to the embodiment of the present invention places the blade on the ground. FIG. [Figure 5] FIG. 2 is a schematic cross-sectional view of a traveling body of a shovel in the direction AA when the shovel according to the embodiment of the present invention has raised the blade to its structurally highest position. [Figure 6] FIG. 2 is a schematic cross-sectional view of a traveling body of a shovel in the direction AA when the shovel according to the embodiment of the present invention has lowered the blade to its lowest structural position. [Figure 7] FIG. 1 is a schematic diagram of a drive system of a shovel according to an embodiment of the present invention. [Figure 8] 3 is a flowchart illustrating a method for controlling a shovel according to an embodiment of the present invention. [Figure 9] FIG. 10 is a schematic perspective view of a lower traveling body of a shovel according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings, taking an excavator 100 as a representative example of a work machine according to the present invention. Note that the traveling direction in which the traveling body 200 travels straight without rotating the upper rotating body 300 is referred to as the front-rear direction, and the direction perpendicular to the straight traveling direction on a plane is referred to as the left-right direction. These directions are set based on the operator seated in the driver's seat in the driver's cab.

[0010] As shown in Figures 1 and 2, the shovel 100 comprises a self-propelled running body 200, an upper rotating body 300 rotatably supported on the running body 200, and a working device 400 supported in front of the upper rotating body 300 so as to be freely rotatable up and down, and further comprises a drive system 500 that drives the shovel 100.

[0011] The traveling body 200 has a center frame 210 and side frames 211 that are paired symmetrically with the center frame 210 and extend in the front-to-rear direction, and drive wheels 213 driven by electric travel motors 212 are mounted on the rear ends of the left and right side frames 211, and a plurality of idler wheels 214 are arranged facing forward, and tracks 215 are wound around the drive wheels 213 and the idler wheels 214. Furthermore, an earth removal device 220 is supported in front of the center frame 210 so that it can be raised and lowered up and down.

[0012] The earth removal device 220 is equipped with a blade 221 arranged so as to be positioned at the tip of the running body 200, and an arm 222 consisting of a pair of left and right vertical plates extending parallel to each other toward the front, one end of which is attached to the back surface of the blade 221 and the other end of which is supported rotatably at the front of the center frame 210.

[0013] The center frame 210 is equipped with a drive mechanism 600 that enables the blade 221 to be raised and lowered. The drive mechanism 600 is equipped with an electric motor unit 610, which is the drive source, and a motion transmission mechanism that converts and transmits the rotation of the electric motor unit 610 into the raising and lowering motion of the blade 221 in front of the center frame 210 and between the arm 222.

[0014] The drive mechanism 600 includes an electric motor unit 610 housed in the front part of the center frame 210, which extends below the working device 400 to near the tip of the side frame 211, and a crank mechanism 620 as a motion transmission mechanism that transmits the rotational motion of the electric motor unit 610.

[0015] Crank mechanism 620 is connected to electric motor unit 610 so as to face left arm 222, and has a crank that rotates by the driving force of electric motor unit 610. Specifically, it is equipped with a disk-shaped crank portion 601 that is connected to the output shaft of electric motor unit 610 and is placed in a notch formed on the left side of the tip of center frame 210, a crank pin 602 that protrudes from crank portion 601 toward left arm 222 and is installed along the outer edge of crank portion 601, and a crank rod 608 that has a first pivoting portion 604 that pivots to crank pin 602 via rubber bushing 603 at one rear end, and a second pivoting portion 607 that pivots to a connecting portion 605 provided on the back surface of blade 221 at the front by a connecting pin 606.

[0016] The crank portion 601 and crank rod 608 of the crank mechanism 620 are installed parallel to the pair of arms 222, and the crank mechanism 620 is disposed between the pair of arms 222, so that the drive mechanism 600 can be designed compactly.

[0017] The crank rod 608 is formed shorter than the pair of arms 222, and by adjusting the fulcrum position, etc., the lifting force of the blade 221 can be increased, and the lifting speed can be reduced to a speed that is easy for the operator to operate.

[0018] The crank mechanism 620 is configured so that when the blade 221 is raised, the crank pin 602 moves in an arc above the center of rotation (crank fulcrum) of the crank section 601 in a side view. This allows the crank mechanism 620 to be designed compactly, and the raising action of the blade 221 prevents the crank rod 608 from interfering with other equipment on the machine or obstacles during paving work.

[0019] Drive mechanism 600 does not require a large torque by converting and transmitting the rotation of electric motor unit 610 into the lifting and lowering motion of blade 221 via a motion transmission mechanism such as crank mechanism 620, allowing drive mechanism 600 to be designed compactly. In particular, when performing leveling work using the blade, a large gap can be set between drive mechanism 600 and the ground, reducing the risk of interference with obstacles.

[0020] On the other hand, if the electric motor unit were to move directly to the lifting fulcrum of the blade without using a motion transmission mechanism like the present invention, a large torque would be required, which would require a high-torque motor and a large reduction gear, and the drive mechanism would be larger than the drive mechanism of the present invention, which could increase or decrease the risk of interference with obstacles during paving work. Therefore, the present invention not only has the effect of eliminating environmental pollution by not using a hydraulic actuator, but also has the effect of allowing the drive mechanism 600 to be designed compactly.

[0021] The rubber bushing 603 is formed by sealing elastic rubber between two metal tubes, and is fitted into the first pivot connection part 604 to support the crank pin 602, thereby reducing the load on the drive mechanism 600 when an impact is applied to the blade 221.

[0022] FIG. 4 is a schematic diagram of an electric motor unit 610 to which a crank portion 601 is attached.

[0023] The electric motor unit 610 is made up of an electric motor 611, a non-excitation brake 612, a reducer 613, and a rotation angle sensor 614, and is supported by the center frame 210 in a vibration-isolating manner.

[0024] The output shaft of the electric motor 611 is connected to the reducer 613 via the non-excitation brake 612, which stops the rotation of the output shaft when not energized, and when energized, the driving force of the electric motor 611 is input to the reducer 613, which rotates the output shaft of the electric motor unit 610 (reducer 613) at a predetermined reduction ratio.

[0025] Here, inverter 230, which supplies and controls power from battery unit 322 to electric motor unit 610, and inverter 231, which supplies and controls power to the corresponding left and right electric travel motors 212, are each disposed within center frame 210. Power from battery unit 322 disposed in upper rotating body 300 is distributed by junction box 330, and the distributed power is supplied to inverter 230 and inverter 231 via slip ring 340.

[0026] The crank portion 601 is mechanically connected to the output shaft of the reducer 613, and transmits an appropriate torque to the drive mechanism 600, allowing the blade 221 to move up and down smoothly.

[0027] The elevation height of the blade 221 can be calculated by detecting the rotation angle of the electric motor 611 using a rotation angle sensor 614, and the operator can operate the blade 221 based on the detection results. The rotation angle sensor 614 is attached to the center (center of rotation) of the crank part 601, which can reduce the risk of contact with obstacles during work.

[0028] The movement of the crank mechanism 620 and the movement of the earth removal device 220 linked thereto will be described with reference to FIGS.

[0029] FIG. 4 is a schematic cross-sectional view of the traveling body 200 in the direction AA when the blade 221 is lowered to the height of the design surface and placed on the ground during the leveling work of the shovel 100.

[0030] FIG. 5 is a schematic cross-sectional view of the traveling body 200 in the AA direction when the blade 221 is raised to the maximum height that can be raised structurally.

[0031] FIG. 6 is a schematic cross-sectional view of the traveling body 200 in the AA direction when the blade 221 is lowered to the maximum height that can be lowered structurally.

[0032] Drive mechanism 600 further includes, as a safety mechanism, a contact member 630 that is installed in front of a notch on the left side of the front part of center frame 210 and is arranged next to crank portion 601 on the left side of the notch. Abutment member 630 is located behind rotation angle sensor 614 in a position that does not interfere with rotation angle sensor 614, and is formed at approximately the same height as the installation height of rotation angle sensor 614.

[0033] The contact member 630 has a first contact portion 631 on the upper surface of the contact member 630 and a second contact portion 632 on the lower front surface of the contact member 630.

[0034] In Figure 5, when the crank portion 601 rotates clockwise (to one side) as viewed from the left side, the first abutment portion 631 abuts against the first pivot connection portion 604 from above (to one side), thereby determining a position where the crank portion 601 cannot structurally rotate any further in the clockwise direction.

[0035] Here, when the crank portion 601 rotates clockwise as viewed from the left side, the blade 221 rises. Therefore, the first contact portion 631 is in contact with the blade 221. This defines the maximum height that a building can be raised to structurally, i.e., the maximum height that it can be raised to.

[0036] Here, when the blade 221 is placed in the position shown in FIG. 4, the first pivot connection part 604 is located above and in front of the abutment part 630. By rotating the crank part 601 from this position toward the rear of the rotation angle sensor 614, the first pivot connection part 604 moves to the position shown in FIG. 5 where it abuts against the first abutment part 631.

[0037] That is, the crank pin 602 forms an arc above the center of rotation (crank fulcrum) of the crank portion 601, which allows the crank mechanism 620 to be designed compactly.

[0038] When the crank portion 601 rotates counterclockwise (to the other side) when viewed from the left side, the second abutment portion 632 abuts against the first pivot connection portion 604 from the front (to the other side), thereby determining a position where the crank portion 601 cannot structurally rotate further backward.

[0039] Here, when the crank portion 601 rotates counterclockwise (to the other side) when viewed from the left side, the blade 221 descends, and therefore the second abutment portion 632 determines the height to which the blade 221 cannot be structurally lowered any further, i.e., the lowest height to which it can be lowered.

[0040] Here, when the blade 221 is placed in the position shown in FIG. 4, the first pivot connection part 604 is located above and in front of the contact part 630. By rotating the crank part 601 from this position backward, passing in front of and below the rotation angle sensor 614, the first pivot connection part 604 moves to the position shown in FIG. 6 where it contacts the second contact part 632.

[0041] That is, the crank pin 602 forms an arc below the center of rotation (crank fulcrum) of the crank portion 601, which allows the crank mechanism 620 to be designed compactly.

[0042] Here, the abutment member 630 has, on the top and bottom, a first abutment portion 631 that can abut against the first pivot connection portion 604 from one side, and a second abutment portion 632 that can abut against the first pivot connection portion 604 from the other side, so that the crank pin 602 forms an arc of motion above and below the center of rotation (crank fulcrum) of the crank portion 601, thereby enabling the crank mechanism 620 to be designed compactly.

[0043] Furthermore, the electric motor 610 may be controlled so that the first pivotal connection part 604 cannot come into contact with the abutment member 630 when the operator raises or lowers the soil removal device 220. In this case, for example, if the electric motor unit 610 fails, overrun can be prevented, and damage to the crank mechanism 620 and the soil removal device 220 can be prevented.

[0044] By controlling the electric motor 610, the first pivotal connection portion 604 may be brought into a state in which it can abut against at least one of the first abutment portion 631 and the second abutment portion 632.

[0045] 6, the first pivot connection part 604 is located behind the imaginary line (dotted line) connecting the center of the crank part 601 to the center of the connecting pin 606, and therefore the shovel 100 can be supported by the blade 221 without the driving force of the electric motor 611. (Hereinafter, this posture will be referred to as the jack-up posture.) When in the jack-up posture, the shovel 100 can use the work implement 400 to push up the ground, thereby lifting the running body 200 off the ground, rotating the drive wheels 213 and moving the crawler belts 215, and cleaning mud and the like that has adhered to the drive wheels 213, the idler wheels 214, etc.

[0046] The work device 400 includes a boom 420 supported by a boom bracket 410 so as to be rotatable up and down, an arm 430 attached to the tip of the boom 420 so as to be rotatable up and down, a bucket 450 attached to the tip of the arm 430 so as to be rotatable up and down, an electric swing cylinder 411 for moving the boom bracket 410 horizontally disposed on the right side within the frame of the upper rotating body 300, an electric boom cylinder 421 installed in front of and below the boom 420 so as to move the boom 420 up and down, an electric arm cylinder 431 installed above the boom 420 so as to move the arm 430 back and forth, and an electric bucket cylinder 451 installed in front of the arm 430 so as to move the bucket 450 back and forth via a bucket link 440.

[0047] A cabin 310 equipped with a control device 311 therein is disposed on the left side of the upper rotating body 300 and to the right of the work machine 400, and a machine room 320 is formed around it.

[0048] The machine room 320 houses a number of devices, including an electric swing motor 321 that rotates the upper rotating body 300, a battery unit 322, and inverters 324a, 324b, 324c, 324d, and 324e that supply power from the battery unit 322 to and control the electric swing motor 321, the electric swing cylinder 411, the electric boom cylinder 421, the electric arm cylinder 431, and the electric bucket cylinder 451.

[0049] Next, the drive system 500 of the excavator 100 will be described with reference to FIG.

[0050] The drive system 500 includes a battery unit 322, a junction box 320 that distributes power from the battery unit 322, an operation unit 311, a control device 312, an electric swing motor 321, an electric swing cylinder 411, an electric boom cylinder 421, an electric arm cylinder 431, an electric bucket cylinder 451, inverters 324a, 324b, 324c, 324d, and 324e, a slip ring 340 that supplies power from the upper rotating body 300 side to the running body 200 side, an inverter 230, an electric motor unit 610, the inverter 231, left and right electric traveling motors 212, and a jack-up switch 313.

[0051] The drive system 500 is shown with high voltage power represented by solid lines and electrical signals represented by dotted lines.

[0052] The operation device 311 outputs the operation direction and operation amount of each operation lever constituting the operation device 311 (for example, the operation lever of the soil removal device 220) as an electric signal to the control device 312, and the control device 312 outputs a command signal according to the operation direction and operation amount to the inverters (inverters 324a, 324b, 324c, 324d, 324e, inverter 230, inverter 231) corresponding to the operated operation lever, and the inverters that have received the command signal supply power according to the command signal to the corresponding electric actuators (electric swing motor 321, electric swing cylinder 411, electric boom cylinder 421, electric arm cylinder 431, electric bucket cylinder 451, electric motor unit 610, and left and right electric travel motors 212), thereby driving the corresponding electric actuators. The corresponding electric actuators output rotation angle information of the electric motor detected to the control device 312, and the control device 312 reflects the rotation angle information in the command signal.

[0053] The jack-up switch 313 is a switch for enabling the excavator 100 to assume a jack-up position.

[0054] When the jack-up switch 313 is not enabled, and the operating device 311 corresponding to the electric motor unit 610 is operated (the operating lever of the earth removal device 220 is operated), the control device 312 executes a first control on the inverter 230 based on the detection result of the rotation angle sensor 614, which causes the electric motor unit 610 to rotate within a range where the first pivot connection portion 604 does not come into contact with the first abutment portion 631 and the second abutment portion 632.

[0055] Therefore, when working using the soil removal device 220, the first control is executed, so the first pivotal connection part 604 does not come into contact with the abutment member 630 and excessive load is not placed on the drive mechanism 600, thereby extending the life of not only the drive mechanism 600 but also the soil removal device 220.

[0056] When the jack-up switch 313 is enabled, if the operation of the operating device 311 corresponding to the electric motor unit 610 (operation of the operating lever of the earth removal device 220) is to raise the earth removal device 220, the control device 312 controls the inverter 230 based on the detection result of the rotation angle sensor 614 to rotate the electric motor unit 610 so that it operates within a range where the first pivot connection part 604 does not abut the first abutment part 631, and if the operation of the operating device 311 corresponding to the electric motor unit 610 (operation of the operating lever of the earth removal device 220) is to lower the earth removal device 220, based on the detection result of the rotation angle sensor 614, the control device 312 executes a second control to control the inverter 230 so that the rotation of the electric motor unit 610 operates until the first pivot connection part 604 abuts the second abutment part 632.

[0057] Therefore, by making it possible to switch between the first control and the second control using the jack-up switch 313, work using the soil removal device 220 can be carried out without compromising the lifespan of the equipment, and maintenance work such as removing mud from the wheels of the running body 100 can be carried out safely.

[0058] The control flow will be explained using Fig. 7. Fig. 7 is a flowchart relating to the control method.

[0059] If the jack-up switch 313 is enabled (S1: YES)

[0060] The operating lever (311) of the earth removal device is operated (S2).

[0061] The control device (312) executes the second control (S3:), and then ends the flow.

[0062] When the jack-up switch 313 is not enabled (S1: NO)

[0063] The operating lever (311) of the earth removal device is operated (S4).

[0064] The control device (312) executes the first control (S5:), and then ends the flow.

[0065] The flowchart shown in FIG. 8 is merely an example, and processes may be added or omitted as appropriate, processes may be repeatedly executed, and the order of processes may be changed as appropriate.

[0066] Next, another embodiment of the present invention will be described with reference to Figure 9. Note that the description of the same parts as those in the above-described embodiment will be omitted.

[0067] FIG. 9 is a schematic perspective view of a lower running structure 700 of a shovel according to another embodiment of the present invention.

[0068] The lower traveling body 700 is provided with a drive mechanism 800 that raises and lowers the blade 720 .

[0069] The drive mechanism 800 includes an electric motor unit 820 supported on a protruding portion at the front of the center frame 710 , and a crank mechanism 810 that transmits the rotational motion of the electric motor unit 820 .

[0070] The crank mechanism 810 includes a link that is a slender rod-shaped crank portion 812 that is rotated by an electric motor unit 820 , and a rod-shaped crankshaft 811 whose both ends are pivotally connected to the mounting portion of the blade 720 and the crank portion 812 .

[0071] The crank mechanism 810 forms an arc of motion above and below the center of rotation (crank fulcrum) of the crank portion 812, and by making the shape of the crank portion 812 a long, thin rod, it is possible to design a more compact drive mechanism.

[0072] Next, an embodiment of the present invention and modifications of other embodiments will be described.

[0073] The control device 312 may cause the buzzer device to emit a buzzer sound during the second control. In this case, the buzzer sound may be stopped when the first pivotal connection portion 604 abuts against the second abutment portion 632.

[0074] The second control may be a control in which, when the jack-up switch 313 is enabled, the control device 312 controls the inverter 324 based on the detection result of the rotation angle sensor 614 so that the inverter 324 automatically rotates the electric motor unit 610 until the first pivotal connection part 604 abuts on the second abutment part 632. In this case, the control device 312 can execute a control to disable the operation of the operating device 311.

[0075] Instead of the jack-up switch 313, the excavator 100 may be made to assume a jack-up posture by a specific operation of the earth removal device operating lever 311. In this case, the specific operation is to hold the earth removal device 220 in the lowest position (maximum forward tilt position of the operating lever) for a certain period of time, for example, several seconds, so that the control device 312 issues a command to the inverter 230 and controls the rotation of the electric motor unit 610 so that the first pivot connection part 604 abuts against the second abutment part 632.

[0076] The invention according to the embodiments of the present invention can be specified as follows:

[0077] <Appendix 1> A work machine comprising a traveling body that supports a pair of arms with blades attached to the tips thereof in a manner that allows them to be raised and lowered, and a battery unit, wherein an electric motor that is disposed on the traveling body between the pair of arms and that is supplied with power from the battery unit a crank portion rotated by the electric motor; and a crank rod pivotally connected at one end to the crank portion via a first pivotal connection portion and pivotally connecting the blade via a second pivotal connection portion so that the blade can be raised and lowered.

[0078] <Appendix 2> A work machine as described in Appendix 1, wherein the crank rod is parallel to the pair of arms.

[0079] <Appendix 3> A work machine according to appendix 1 or appendix 2, wherein the crank rod is shorter than the pair of arms.

[0080] <Appendix 4> A work machine as described in any one of Appendices 1 to 3, wherein the crank portion has a crank pin that protrudes from one of the pair of arms, and the crank pin is supported by the first pivot connection portion via an elastic body.

[0081] <Appendix 5> A work machine as described in any one of Appendices 1 to 4, further comprising an abutment member installed on the traveling body adjacent to the crank portion so as to be able to abut against the first pivot connection portion.

[0082] <Appendix 6> A work machine as described in Appendix 5, wherein the abutment member has a first abutment portion that can abut against the first pivotal connection portion from one side, and a second abutment portion that can abut against the first pivotal connection portion from the other side.

[0083] <Appendix 7> A work machine as described in Appendix 6, wherein the first contact portion is disposed above the second contact portion.

[0084] <Appendix 8> A work machine as described in any one of Appendices 5 to 7, wherein the abutment member is disposed rearward of the center of rotation of the crank portion.

[0085] <Appendix 9> A work machine according to appendix 8, further comprising a sensor that detects the rotation angle of the electric motor, the sensor being disposed at the center of rotation.

[0086] <Supplementary Note 10> A work machine as described in Supplementary Note 6 or Supplementary Note 7, further comprising a control device for controlling the electric motor, wherein the control device switchably executes a first control for controlling the electric motor so that the first abutment portion and the second abutment portion do not abut against the first pivotal connection portion, and a second control for abutting the second abutment portion against the first pivotal connection portion and supporting the work machine by the blade.

[0087] The various configurations described in the above-described embodiment, other embodiments, and modifications thereof can be adopted in appropriate combinations.

[0088] In the above, a shovel has been used as an example of a work machine, but the work machine is not limited to a shovel and may be a construction machine such as a wheel loader or a compact track loader, or an agricultural machine such as a tractor.

[0089] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these, and can be expanded or modified within the scope that does not deviate from the spirit of the invention. [Industrial Applicability]

[0090] The present invention relates to a work machine and has industrial applicability. [Explanation of symbols]

[0091] 100 Excavator (working machine) 200 Traveling body 221 Blade 221 222 Arm 601 Crank portion 604 First pivotal connection portion 607 Second pivotal support portion 608 Crank rod 611 Electric motor 630 Contact member

Claims

1. A work machine comprising a traveling body that supports a pair of arms, each with a blade attached to its tip, so that the arms can be raised and lowered, and a battery unit, the work machine comprising: an electric motor that is disposed on the traveling body between the pair of arms and is supplied with power from the battery unit; a crank portion that is rotated by the electric motor; and a crank rod that is pivotally connected at one end to the crank portion via a first pivotal connection and that pivotally connects the blade to the crank rod via a second pivotal connection so that the blade can be raised and lowered up and down.

2. The work machine of claim 1 , wherein the crank rod is parallel to the pair of arms.

3. The work machine of claim 2 , wherein the crank rod is shorter than the pair of arms.

4. 4. The work machine according to claim 3, wherein the crank portion has a crank pin that protrudes from one of the pair of arms, and the crank pin is supported by the first pivot connection portion via an elastic body.

5. 5. The working machine according to claim 1, further comprising a contact member disposed on the traveling body adjacent to the crank portion so as to be able to contact the first pivot connection portion.

6. 6. A work machine according to claim 5, wherein the abutment member has a first abutment portion capable of abutting against the first pivotal connection portion from one side, and a second abutment portion capable of abutting against the first pivotal connection portion from the other side.

7. The work machine according to claim 6 , wherein the first abutment portion is disposed above the second abutment portion.

8. The work machine according to claim 6, wherein the abutment member is disposed rearward of the center of rotation of the crank portion.

9. a sensor for detecting a rotation angle of the electric motor; The work machine of claim 8 , wherein the sensor is located at the center of rotation.

10. a control device for controlling the electric motor; 8. The work machine according to claim 7, wherein the control device switchably executes a first control that controls the electric motor so that the first abutment portion and the second abutment portion do not abut against the first pivotal connection portion, and a second control that causes the second abutment portion to abut against the first pivotal connection portion and supports the work machine by the blade.

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