Mobile crane undercarriage

Abstract

To provide an undercarriage that is equipped with an expansion / contraction mechanism and suppresses deformation when a suspended cargo is suspended from a revolving super structure in front of or behind the undercarriage.SOLUTION: Each of a plurality of coupling members is configured to permit the displacement of a crawler frame from an expansion position to a contraction position by changing a relative position with respect to at least one of a car body and the crawler frame from an expansion connection state while being connected to at least the one of the car body and the crawler frame, and is disposed in a restraint state in which it is restrained by the crawler frame and the car body disposed at the contraction position.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an undercarriage of a mobile crane. [Background technology]

[0002] Conventionally, a mobile crane has been known. This mobile crane includes a lower traveling body capable of traveling on the ground, and an upper rotating body mounted on the lower traveling body. The upper rotating body includes a working device including a boom and a hoisting rope. The lower traveling body includes a car body, a right crawler frame, and a left crawler frame. The car body includes a car body main body that supports the upper rotating body rotatably around a rotation central axis, front axles extending from the car body main body to the right and left, respectively, and rear axles extending from the car body main body to the right and left, respectively, rear of the front axles. The right crawler frame extends in the front-rear direction on the right side of the car body main body, and the left crawler frame extends in the front-rear direction on the left side of the car body main body.

[0003] For example, the mobile crane in Patent Document 1 is equipped with an expansion / contraction mechanism for expanding the distance of the pair of crawler frames from the central axis of rotation in the left-right direction to increase safety when lifting a load, and for contracting the distance of the pair of crawler frames from the central axis of rotation in the left-right direction to reduce the transport width when the mobile crane is transported. In a mobile crane equipped with such an expansion / contraction mechanism, it is necessary to move each crawler frame in the left-right direction, for example by sliding, along the front and rear axles, so the front and rear axles have shapes that extend parallel to the left-right direction, and each crawler frame has a pair of axle supports that support the front and rear axles so that they can slide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-70339 A [Patent Document 2] JP 2017-171090 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the lower traveling body having a structure in which the front and rear axles extending in parallel in the left-right direction from the car body connect the car body to the left and right crawler frames as described above, the rigidity in the front-rear direction is lower than the rigidity in the left-right direction. Therefore, in a lifting operation (crane operation) of a mobile crane, when a load is suspended from the upper rotating body via the suspension rope of the working device in front of or behind the lower traveling body, the amount of downward displacement of the front or rear part of the car body tends to be larger than the amount of downward displacement of the right or left part of the car body when a load is suspended from the upper rotating body to the side of the lower traveling body.

[0006] Specifically, when a load is suspended from the upper rotating body in front of or behind the lower running body, the load that the car body receives from the upper rotating body causes deformations such as torsional deformation and bending deformation in the front and rear axles, and deformations also occur in the car body, so that the front or rear part of the car body is likely to be displaced downward. In addition, deformations are likely to occur in the left and right crawler frames in response to the deformations of the front and rear axles. As a result, the degree of deformation occurring in the lower running body varies with the change in the rotation position of the upper rotating body, which causes the position of the suspended load to fluctuate up and down, which may reduce the workability of the lifting operation. Therefore, it is desirable to reduce the deformation occurring in the lower running body when a load is suspended from the upper rotating body in front of or behind the lower running body by improving the rigidity in the front-rear direction of the lower running body.

[0007] Patent Document 2 discloses a technique of providing a pair of reinforcing members at the front and rear of the trunk of the car body in order to improve the rigidity of the front and rear parts of the car body. However, since various components such as a rotation motor for rotating the upper rotating body, gears, hydraulic piping, and electric wiring are arranged around the trunk of the car body, there are cases where it is not possible to secure enough space to arrange the pair of reinforcing members. In this case, the effect of suppressing the deformation of the car body by the pair of reinforcing members is limited.

[0008] In addition, when a load is suspended from the upper rotating body in front of the lower traveling body, the front end roller, which is the frontmost roller among the multiple rollers provided at the bottom of each crawler frame, becomes the tipping fulcrum of the mobile crane. In a structure in which the front axle and the rear axle extend in parallel in the left-right direction, such as the mobile crane in Patent Document 1, the axle support part, which is the part where the load is transmitted from the front axle to each crawler frame, and the tipping fulcrum are relatively far apart in the front-rear direction. For this reason, each crawler frame is likely to be largely deflected in the part between the axle support part and the tipping fulcrum. When a load is suspended from the upper rotating body in rear of the lower traveling body, each crawler frame is likely to be largely deflected for the same reason as above.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a lower running body of a mobile crane which is equipped with an expansion and contraction mechanism capable of expanding or contracting the distance from the central axis of rotation of the left and right crawler frames in the left-right direction, while undergoing minimal deformation when a load is suspended from the upper rotating body of the mobile crane in front of or behind the lower running body. [Means for solving the problem]

[0010] Provided is a lower running body of a mobile crane, comprising: a carbody including a carbody main body supporting an upper rotating body of the mobile crane rotatably around a central axis of rotation, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rear of the front axles, a right crawler frame extending in the front-rear direction on the right side of the carbody main body, a left crawler frame extending in the front-rear direction on the left side of the carbody main body, and a plurality of connecting members. The right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that the right crawler frame can change its left-right position relative to the front axle and the rear axle between an expanded position and a contracted position in which the distance between the central axis of rotation and the right crawler frame is smaller than that in the expanded position. The left crawler frame has a left front axle support part and a left rear axle support part that support the front axle and the rear axle, respectively, so that the left crawler frame can change its left-right position with respect to the front axle and the rear axle between an expanded position and a contracted position in which the distance between the swing center axis and the left crawler frame is smaller than that in the expanded position. The multiple connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member. The right front connecting member is configured to be able to be arranged in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is arranged in the expanded position and is connected to a portion of the right crawler frame that is forward of the right front axle support part. The right rear connecting member is configured to be able to be arranged in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is arranged in the expanded position and is connected to a portion of the right crawler frame that is rearward of the right rear axle support part. The left front connecting member is configured so that it can be arranged in an expanded connection state in which it is connected to the car body when the left crawler frame is arranged in the expanded position, and is connected to a portion of the left crawler frame forward of the left front axle support portion.The left rear connecting member is configured to be capable of being arranged in an expanded connection state in which it is connected to the carbody when the left crawler frame is arranged in the expanded position, and is connected to a portion of the left crawler frame rearward of the left rear axle support. Each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the retracted position by changing a relative position with respect to at least one of the carbody and the right crawler frame from the expanded connection state while remaining connected to at least one of the carbody and the right crawler frame. Each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the retracted position by changing a relative position with respect to at least one of the carbody and the left crawler frame from the expanded connection state while remaining connected to at least one of the carbody and the left crawler frame.

[0011] In this lower traveling body, each of the multiple connecting members is arranged in the expanded connection state during crane operation, and when the mobile crane is transported, the relative position changes from the expanded connection state, allowing the left and right crawler frames to be displaced from the expanded position to the contracted position, thereby making it possible to reduce deformation that occurs in the lower traveling body when a load is suspended from the upper rotating body in front of or behind the lower traveling body, while allowing the left and right crawler frames to be displaced from the expanded position to the contracted position by the expansion and contraction mechanism.

[0012] During crane operation, the right front connecting member and the left front connecting member arranged in the expanded connection state can receive a front load from the car body, which is a load that the car body receives from the upper rotating body when a load is suspended from the upper rotating body forward of the lower running body, and the right front connecting member can transmit the front load to a portion of the right crawler frame forward of the right front axle support portion, and the left front connecting member can transmit the front load to a portion of the left crawler frame forward of the left front axle support portion. In other words, the right front connecting member and the left front connecting member can support the car body forward of the right front axle support portion and the left front axle support portion at which the left and right crawler frames support the front axles. This suppresses deformation such as torsional deformation in the front axle and the rear axle, and suppresses deformation in the car body, so that the front portion of the car body is effectively suppressed from being displaced downward. When deformation such as torsional deformation is suppressed in the front axle and the rear axle, deformation of the left and right crawler frames is also suppressed. Therefore, it is possible to reduce deformation occurring in the lower traveling body when a load is suspended from the upper rotating body forward of the lower traveling body. The reason why deformation occurring in the lower traveling body can be reduced when a load is suspended from the upper rotating body rearward of the lower traveling body is the same as that described above. Also, since the front load is transmitted to portions of the left and right crawler frames forward of the right front axle support portion and the left front axle support portion, respectively, it is possible to reduce deflection of the left and right crawler frames. Similarly, since the rear load is transmitted to portions of the left and right crawler frames rearward of the right rear axle support portion and the left rear axle support portion, respectively, it is possible to reduce deflection of the left and right crawler frames.

[0013] Moreover, each of the right front connecting member and the right rear connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position by changing its relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state, and each of the left front connecting member and the left rear connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position by changing its relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state. In this way, the multiple connecting members do not impede the function of the expansion / contraction mechanism equipped in the lower traveling body, so the left and right crawler frames can be displaced to the contracted position. This makes it possible to reduce the transport width of the lower traveling body when transporting the mobile crane.

[0014] Furthermore, in this undercarriage, the operation of changing the relative positions of each of the multiple connecting members is performed while each of the multiple connecting members remains connected to at least one of the car body and the right crawler frame, which makes it possible to suppress a decrease in the workability compared to a case in which each of the multiple connecting members is detached from both the car body and the crawler frame.

[0015] the lower running body of the mobile crane further comprises a pair of right wheels rotatably supported on a front end and a rear end of the right crawler frame, a pair of left wheels rotatably supported on a front end and a rear end of the left crawler frame, a plurality of right rollers arranged at intervals in the front-rear direction between the pair of right wheels and rotatably supported on a lower part of the right crawler frame, the plurality of right rollers including a front-most right front end roller and a rear-most right rear end roller, and a plurality of left rollers arranged at intervals in the front-rear direction between the pair of left wheels and rotatably supported on a lower part of the left crawler frame, the plurality of left rollers including a front-most left front end roller and a rear-most left rear end roller, the right front connecting member has a right front load receiving surface facing the car body and a right front load transfer surface facing the right crawler frame, the left front connecting member has a left front load receiving surface facing the car body and a left front load transfer surface facing the left crawler frame, and each of the right front load receiving surface of the right front connecting member and the left front load receiving surface of the left front connecting member is a surface that can receive, from the car body, a front load that is a load that the car body receives from the upper rotating body when a load is suspended from the upper rotating body forward of the lower running body, and the right front load transfer surface is a surface that can transfer the front load to the right crawler frame, and the left front load transfer surface is a surface that can transfer the front load to the left crawler frame. It is preferable that the right front connecting member is configured so that a right front straight line, which is a straight line passing through any point included in the right front load receiving surface and any point included in the right front load transfer surface in a plan view, passes forward of the right front end roller or the right front end roller, and the left front connecting member is configured so that a left front straight line, which is a straight line passing through any point included in the left front load receiving surface and any point included in the left front load transfer surface in a plan view, passes forward of the left front end roller or the left front end roller.

[0016] The right and left front connecting members of the lower traveling body are configured so that the right and left front straight lines and the right and left front end rollers have the above-mentioned positional relationship, so that the front-to-rear distance between the portion of the right crawler frame to which the front load is transmitted via the right front connecting member and the front end of the right crawler frame can be effectively reduced, and the front-to-rear distance between the portion of the left crawler frame to which the front load is transmitted via the left front connecting member and the front end of the left crawler frame can be effectively reduced. This makes it possible to more effectively reduce deflection that occurs in the front portions of the left and right crawler frames when a load is suspended from the upper rotating body forward of the lower traveling body.

[0017] Here, when the car body receives a relatively large front load from the upper rotating body, the right front end roller and the left front end roller become approximate tipping fulcrums (front tipping fulcrums), so it is preferable that the right front straight line is a straight line passing through the right front end roller in a planar view, and the left front straight line is a straight line passing through the left front end roller in a planar view.

[0018] In this aspect, the right front connecting member and the left front connecting member can directly transmit the front load to the portions of the left and right crawler frames that correspond to the front tipping fulcrum, making it possible to more effectively reduce the deflection that occurs in the front portions of the left and right crawler frames due to the front load.

[0019] It is also preferable that the right front straight line is a straight line that further passes through the turning central axis in a plan view, and the left front straight line is a straight line that further passes through the turning central axis in a plan view.

[0020] In this embodiment, any point on the right front load receiving surface of the right front connecting member and any point on the right front load transfer surface of the right front connecting member can be positioned on a right front straight line passing through the turning center axis and the right front end roller in a plan view, and any point on the left front load receiving surface of the left front connecting member and any point on the left front load transfer surface of the left front connecting member can be positioned on a left front straight line passing through the turning center axis and the left front end roller in a plan view. This makes it possible to approximate the path along which the front load is transferred to the right crawler frame by the right front connecting member to the direction from the turning center axis toward the right front end roller, and to approximate the path along which the front load is transferred to the left crawler frame by the left front connecting member to the direction from the turning center axis toward the left front end roller, so that the front load is efficiently transferred to portions of the left and right crawler frames that correspond to the front tipping fulcrums.

[0021] In the lower running body of the mobile crane, it is preferable that the right front connecting member has a right front continuing portion that continues from the right front load receiving surface to the right front load transfer surface along the right front straight line in a planar view, and the left front connecting member has a left front continuing portion that continues from the left front load receiving surface to the left front load transfer surface along the left front straight line in a planar view.

[0022] In this aspect, the right front continuing portion continues without interruption from the right front load receiving surface to the right front load transfer surface along the right front straight line in a plan view, and the left front continuing portion continues without interruption from the left front load receiving surface to the left front load transfer surface along the left front straight line in a plan view.Therefore, the front load received by the right front load receiving surface and the left front load receiving surface is transmitted continuously and efficiently along the right front continuing portion and the left front continuing portion to the right front load transfer surface and the left front load transfer surface, and from these load transfer surfaces to the left and right crawler frames.

[0023] In the lower running body of the mobile crane, the right rear connecting member has a right rear load receiving surface facing the car body and a right rear load transfer surface facing the right crawler frame, and the left rear connecting member has a left rear load receiving surface facing the car body and a left rear load transfer surface facing the left crawler frame, and each of the right rear load receiving surface of the right rear connecting member and the left rear load receiving surface of the left rear connecting member is a surface that can receive, from the car body, a rear load that is a load that the car body receives from the upper rotating body when a load is suspended from the upper rotating body rearward of the lower running body, and the right rear load transfer surface is a surface that can receive the rear load from the car body. It is preferable that the right rear connecting member is configured so that a right rear straight line, which is a straight line passing through any point included in the right rear load receiving surface and any point included in the right rear load transfer surface in a planar view, passes rear of the right rear end roller or the right rear end roller, and the left rear connecting member is configured so that a left rear straight line, which is a straight line passing through any point included in the left rear load receiving surface and any point included in the left rear load transfer surface in a planar view, passes rear of the left rear end roller or the left rear end roller.

[0024] The right and left rear connecting members of the lower traveling body are configured so that the right and left rear straight lines and the right and left rear end rollers have the above-mentioned positional relationship, so that the front-to-rear distance between the portion of the right crawler frame to which the rear load is transmitted via the right rear connecting member and the rear end of the right crawler frame can be effectively reduced, and the front-to-rear distance between the portion of the left crawler frame to which the rear load is transmitted via the left rear connecting member and the rear end of the left crawler frame can be effectively reduced. This makes it possible to reduce deflection that occurs in the rear portions of the left and right crawler frames when a load is suspended from the upper rotating body rearward of the lower traveling body.

[0025] In addition, when the car body receives a relatively large rear load from the upper rotating body, the right rear end roller and the left rear end roller become approximate tipping fulcrums (rear tipping fulcrums), so it is preferable that the right rear straight line is a straight line passing through the right rear end roller in a planar view, and the left rear straight line is a straight line passing through the left rear end roller in a planar view.

[0026] In this aspect, the right rear connecting member and the left rear connecting member can directly transmit the rear load to the portions of the left and right crawler frames that correspond to the rear tipping fulcrums, making it possible to more effectively reduce deflection that occurs in the rear portions of the left and right crawler frames due to the rear load.

[0027] It is also more preferable that the right rear straight line is a straight line that further passes through the turning central axis in a plan view, and the left rear straight line is a straight line that further passes through the turning central axis in a plan view.

[0028] In this embodiment, any point on the right rear load receiving surface of the right rear connecting member and any point on the right rear load transfer surface of the right rear connecting member can be positioned on a right rear straight line passing through the turning center axis and the right rear end roller in a plan view, and any point on the left rear load receiving surface of the left rear connecting member and any point on the left rear load transfer surface of the left rear connecting member can be positioned on a left rear straight line passing through the turning center axis and the left rear end roller in a plan view. This makes it possible to approximate the path along which the rear load is transferred to the right crawler frame by the right rear connecting member to a direction from the turning center axis toward the right rear end roller, and to approximate the path along which the rear load is transferred to the left crawler frame by the left rear connecting member to a direction from the turning center axis toward the left rear end roller, so that the rear load is efficiently transferred to portions of the left and right crawler frames that correspond to the rear tipping fulcrums.

[0029] In the lower running body of the mobile crane, it is preferable that the right rear connecting member has a right rear continuing portion that continues from the right rear load receiving surface to the right rear load transfer surface along the right rear straight line in a planar view, and the left rear connecting member has a left rear continuing portion that continues from the left rear load receiving surface to the left rear load transfer surface along the left rear straight line in a planar view.

[0030] In this aspect, the right rear continuing portion continues without interruption from the right rear load receiving surface to the right rear load transfer surface along the right rear straight line in a planar view, and the left rear continuing portion continues without interruption from the left rear load receiving surface to the left rear load transfer surface along the left rear straight line in a planar view.Therefore, the rear load received by the right rear load receiving surface and the left rear load receiving surface is transmitted continuously and efficiently along the right rear continuing portion and the left rear continuing portion to the right rear load transfer surface and the left rear load transfer surface, and from these load transfer surfaces to the left and right crawler frames.

[0031] In the lower running body of the mobile crane, it is preferable that each of the right front connecting member and the right rear connecting member is configured so that it can be positioned in a restrained state in which it is restrained by at least one of the right crawler frame and the car body when arranged in the retracted position, and each of the left front connecting member and the left rear connecting member is configured so that it can be positioned in a restrained state in which it is restrained by at least one of the left crawler frame and the car body when arranged in the retracted position.

[0032] In this embodiment, each of the multiple connecting members is arranged in the constrained state, so that the relative displacement with respect to the crawler frame and the car body is limited. This makes it possible to prevent problems such as flapping of each of the multiple connecting members during transportation of the mobile crane. The constrained state may be a state in which each of the multiple connecting members is slightly displaced with respect to the crawler frame and the car body, within a range in which the flapping does not cause a problem during transportation of the mobile crane.

[0033] In the lower running body of the mobile crane, the right connecting member, which is at least one of the connecting members of the right front connecting member and the right rear connecting member, has a car body connection part that is rotatably connected to the car body, and a crawler connection part that is detachably connected to the right crawler frame arranged in the expanded position, and the right connecting member may be configured to be arranged in the constrained state by being detachably connected to the right crawler frame arranged in the reduced position so that when the crawler connection part is detached from the right crawler frame and the car body connection part remains connected to the car body, the right connecting member rotates relative to the car body at the car body connection part, thereby changing the relative position of the right connecting member to the car body and the right crawler frame from the expanded connection state, thereby allowing the right crawler frame to displace from the expanded position to the reduced position, and to be arranged in the constrained state by being detachably connected to the right crawler frame arranged in the reduced position.

[0034] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0035] In the lower running body of the mobile crane, the right connecting member further has a second crawler connection portion that can be detachably connected to the right crawler frame arranged in the retracted position, and the second crawler connection portion connected to the right crawler frame arranged in the retracted position may be configured to be positioned in a position closer to the right crawler frame in a planar view than a line segment connecting the car body connection portion and the crawler connection portion.

[0036] In this aspect, the right crawler frame arranged in the retracted position is connected to the second crawler connection part which is positioned at a position closer to the right crawler frame than the line segment, so that the right connecting member is less likely to interfere with the right crawler frame compared to when the portion of the right connecting member which is positioned on the line segment is connected to the right crawler frame.

[0037] In an embodiment of the present invention, in a lower running body of the mobile crane, a left connecting member which is at least one of the connecting members of the left front connecting member and the left rear connecting member has a car body connection portion rotatably connected to the car body, and a crawler connection portion detachably connected to the left crawler frame arranged in the expanded position, and the left connecting member is configured to be arranged in the constrained state by being detachably connected to the left crawler frame arranged in the expanded position, such that when the crawler connection portion of the left connecting member is detached from the left crawler frame and the car body connection portion of the left connecting member remains connected to the car body, the left connecting member rotates relative to the car body at the car body connection portion of the left connecting member so that a relative position of the left connecting member with respect to the car body and the left crawler frame changes from the expanded connection state, thereby allowing the left crawler frame to be displaced from the expanded position to the reduced position, and to be arranged in the constrained state by being detachably connected to the left crawler frame arranged in the reduced position.

[0038] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0039] In the lower running body of the mobile crane, the left connecting member may further have a second crawler connection portion that can be detachably connected to the left crawler frame arranged in the retracted position, and the second crawler connection portion connected to the left crawler frame arranged in the retracted position may be configured to be positioned in a position closer to the left crawler frame in a plan view than a line segment connecting the carbody connection portion of the left connecting member and the crawler connection portion of the left connecting member.

[0040] In this aspect, the left crawler frame arranged in the retracted position is connected to the second crawler connection part, which is positioned at a position closer to the left crawler frame than the line segment, so that the left connecting member is less likely to interfere with the left crawler frame compared to when the portion of the left connecting member located on the line segment is connected to the left crawler frame.

[0041] In the undercarriage of the mobile crane, the right front connecting member has a car body connection part rotatably connected to the car body and a crawler connection part detachably connected to the right crawler frame arranged at the expanded position, the left front connecting member has a car body connection part rotatably connected to the car body and a crawler connection part detachably connected to the left crawler frame arranged at the expanded position, and the right front connecting member is moved from the expanded connection state to the right crawler frame when the crawler connection part of the right front connecting member is detached from the right crawler frame and the right front connecting member rotates at the car body connection part relative to the car body while the car body connection part of the right front connecting member remains connected to the car body, so that the relative position of the right front connecting member with respect to the car body and the right crawler frame changes from the expanded connection state. the left front connecting member may be configured to allow the left crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the left front connecting member is detached from the left crawler frame and the car body connection portion of the left front connecting member remains connected to the car body, such that the relative position of the left front connecting member to the car body and the left crawler frame changes from the expanded connection state, and the right front connecting member and the left front connecting member may be configured to be arranged in the constrained state by connecting the right front connecting member and the left front connecting member to each other when the right crawler frame and the left crawler frame are each arranged in the contracted position.

[0042] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0043] In the undercarriage of the mobile crane, the right rear connecting member has a car body connection part rotatably connected to the car body and a crawler connection part detachably connected to the right crawler frame arranged at the expanded position, and the left rear connecting member has a car body connection part rotatably connected to the car body and a crawler connection part detachably connected to the left crawler frame arranged at the expanded position, and the right rear connecting member is moved from the expanded connection state to the right crawler frame when the crawler connection part of the right rear connecting member is detached from the right crawler frame and the right rear connecting member rotates at the car body connection part relative to the car body while the car body connection part of the right rear connecting member remains connected to the car body, so that a relative position of the right rear connecting member with respect to the car body and the right crawler frame changes from the expanded connection state. the left rear connecting member may be configured to allow the left crawler frame to be displaced from the expanded position to the reduced position when the crawler connection portion of the left rear connecting member is detached from the left crawler frame and the car body connection portion of the left rear connecting member remains connected to the car body, such that the relative position of the left rear connecting member to the car body and the left crawler frame changes from the expanded connection state, and the right rear connecting member and the left rear connecting member may be configured to be arranged in the restrained state by connecting the right rear connecting member and the left rear connecting member to each other when the right crawler frame and the left crawler frame are each arranged in the reduced position.

[0044] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0045] In the lower running body of the mobile crane, the right connecting member, which is at least one of the connecting members of the right front connecting member and the right rear connecting member, has a car body connection part that is detachably connected to the car body, and a crawler connection part that is connected to the right crawler frame arranged in the expanded position, and the right connecting member may be configured to allow the right crawler frame to displace from the expanded position to the reduced position by removing the car body connection part from the car body and changing the relative position of the right connecting member to the car body from the expanded connection state while the crawler connection part remains connected to the right crawler frame, and to be arranged in the constrained state by being detachably connected to the car body when the right crawler frame is arranged in the reduced position.

[0046] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0047] In the lower running body of the mobile crane, the left connecting member, which is at least one of the connecting members of the left front connecting member and the left rear connecting member, has a car body connection portion removably connected to the car body, and a crawler connection portion connected to the left crawler frame arranged in the expanded position, and the left connecting member may be configured to allow the left crawler frame to displace from the expanded position to the reduced position when the car body connection portion of the left connecting member is detached from the car body and the relative position of the left connecting member to the car body changes from the expanded connection state while the crawler connection portion of the left connecting member remains connected to the left crawler frame, and to be arranged in the constrained state by being detachably connected to the car body when the left crawler frame is arranged in the reduced position.

[0048] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0049] In the undercarriage of the mobile crane, the right front connecting member has a car body connection part that is detachably connected to the car body when the right crawler frame is disposed at the expanded position, and a crawler connection part that is rotatably connected to the right crawler frame, and the left front connecting member has a car body connection part that is detachably connected to the car body when the left crawler frame is disposed at the expanded position, and a crawler connection part that is rotatably connected to the left crawler frame, and when the car body connection part of the right front connecting member is removed from the car body and the crawler connection part of the right front connecting member remains connected to the right crawler frame, the right front connecting member rotates at the crawler connection part relative to the right crawler frame so that the relative position of the right front connecting member to the car body and the right crawler frame is changed to the expanded connection state. the right crawler frame is allowed to displace from the expanded position to the contracted position by changing from the expanded connection state, the left front connecting member is configured to rotate at the crawler connection part relative to the left crawler frame while the car body connection part of the left front connecting member is detached from the car body and the crawler connection part of the left front connecting member remains connected to the left crawler frame, thereby allowing the left crawler frame to displace from the expanded position to the contracted position, and the right front connecting member and the left front connecting member may be configured to be arranged in the constrained state by connecting the right front connecting member and the left front connecting member to each other when the right crawler frame and the left crawler frame are each arranged in the contracted position.

[0050] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0051] In the undercarriage of the mobile crane, the right rear connecting member has a car body connection part that is detachably connected to the car body when the right crawler frame is disposed at the expanded position, and a crawler connection part that is rotatably connected to the right crawler frame, and the left rear connecting member has a car body connection part that is detachably connected to the car body when the left crawler frame is disposed at the expanded position, and a crawler connection part that is rotatably connected to the left crawler frame, and when the car body connection part of the right rear connecting member is detached from the car body and the crawler connection part of the right rear connecting member remains connected to the right crawler frame, the right rear connecting member rotates at the crawler connection part relative to the right crawler frame so that the relative position of the right rear connecting member to the car body and the right crawler frame is changed to the expanded connection state. the right crawler frame is allowed to displace from the expanded position to the contracted position by changing from the expanded connection state, the left rear connecting member is configured to rotate at the crawler connection part relative to the left crawler frame while the car body connection part of the left rear connecting member is detached from the car body and the crawler connection part of the left rear connecting member remains connected to the left crawler frame, thereby allowing the left crawler frame to displace from the expanded position to the contracted position, and the right rear connecting member and the left rear connecting member may be configured to be arranged in the constrained state by connecting the right rear connecting member and the left rear connecting member to each other with the right crawler frame and the left crawler frame respectively arranged in the contracted position.

[0052] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0053] In the lower running body of the mobile crane, it is preferable that the car body has a connected portion to which the car body connecting portion is detachably connected when each of the right crawler frame and the left crawler frame is positioned in the expanded position, and that the car body connecting portion is detached from the connected portion and the connected portion can be connected to the corresponding one of the right crawler frame and the left crawler frame when each of the right crawler frame and the left crawler frame is positioned in the reduced position.

[0054] In this embodiment, the connected portion of the car body to which the car body connecting portion is connected when the left and right crawler frames are in the expanded position is connected to the corresponding one of the left and right crawler frames when the left and right crawler frames are in the contracted position. That is, the connected portion of the car body functions as a stopper to prevent the crawler frame in the contracted position from being displaced relative to the car body. Therefore, in this embodiment, it is not necessary to provide a separate stopper.

[0055] In the lower running body of the mobile crane, the right connecting member, which is at least one of the connecting members of the right front connecting member and the right rear connecting member, includes a first member and a second member, and has a car body connection portion provided on the first member and rotatably connected to the car body, a crawler connection portion provided on the second member and rotatably connected to the right crawler frame, and a connecting portion where the first member is rotatably connected to the second member, and the right connecting member may be configured such that the first member rotates relative to the car body at the car body connection portion, the second member rotates relative to the right crawler frame at the crawler connection portion, and the first member rotates relative to the second member at the connecting portion, so that a relative position of the right connecting member with respect to the car body and the right crawler frame changes from the expanded connection state, thereby allowing the right crawler frame to be displaced from the expanded position to the contracted position and being positioned in the restrained state.

[0056] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0057] In the lower running body of the mobile crane, it is preferable that at least one of the first member and the second member of the right connecting member has a rotation direction limiting portion that allows the first member to rotate relative to the second member in either a clockwise or counterclockwise direction in a planar view at the connecting portion, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a planar view.

[0058] In this embodiment, the first member can be rotated relative to the second member at the connecting portion in a preset appropriate direction.

[0059] In the lower running body of the mobile crane, the right crawler frame may have a rotation direction limiting portion that allows the first member of the right connecting member to rotate relative to the second member at the connecting portion in either a clockwise or counterclockwise direction in a plan view, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a plan view.

[0060] In this embodiment, the first member can be rotated relative to the second member at the connecting portion in a preset appropriate direction.

[0061] In the undercarriage of the mobile crane, the left connecting member, which is at least one of the connecting members of the left front connecting member and the left rear connecting member, includes a first member and a second member, and has a car body connection portion provided on the first member and rotatably connected to the car body, a crawler connection portion provided on the second member and rotatably connected to the left crawler frame, and a connecting portion where the first member is rotatably connected to the second member, and the left connecting member may be configured such that the first member rotates relative to the car body at the car body connection portion, the second member rotates relative to the left crawler frame at the crawler connection portion, and the first member rotates relative to the second member at the connecting portion, such that a relative position of the left connecting member with respect to the car body and the left crawler frame changes from the expanded connection state, thereby allowing the left crawler frame to be displaced from the expanded position to the contracted position and being positioned in the restrained state.

[0062] By adopting the above-described configuration, this aspect makes it possible to reduce the transport width of the lower running body without impeding the function of the expansion and contraction mechanism, while suppressing a decrease in workability when changing the relative positions of each of the multiple connecting members, and making it possible to suppress problems such as each of the multiple connecting members flapping when transporting the mobile crane.

[0063] In the lower running body of the mobile crane, it is preferable that at least one of the first member and the second member of the left connecting member has a rotation direction limiting portion that allows the first member to rotate relative to the second member in either a clockwise or counterclockwise direction in a planar view at the connecting portion, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a planar view.

[0064] In this embodiment, the first member can be rotated relative to the second member at the connecting portion in a preset appropriate direction.

[0065] In the lower running body of the mobile crane, the left crawler frame may have a rotation direction limiting portion that allows the first member of the left connecting member to rotate relative to the second member at the connecting portion in either a clockwise or counterclockwise direction in a plan view, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a plan view.

[0066] In this embodiment, the first member can be rotated relative to the second member at the connecting portion in a preset appropriate direction. Effect of the Invention

[0067] According to the present invention, a lower running body is provided which is equipped with the expansion and contraction mechanism and which undergoes little deformation when a load is suspended from the upper rotating body in front of or behind the lower running body. [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 is a side view showing an example of a mobile crane equipped with a lower traveling body according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view showing a lower traveling body according to the first embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Diagram 3] FIG. 2 is a plan view showing a lower traveling body according to the first embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Figure 4] FIG. 2 is a front view showing the lower traveling body according to the first embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Diagram 5] FIG. 2 is a right side view showing a right crawler frame of a lower traveling body according to the first embodiment. [Figure 6] FIG. 2 is a perspective view showing a car body and left and right crawler frames of a lower traveling body according to the first embodiment, illustrating a state in which the left and right crawler frames are disposed in a contracted position. [Figure 7]FIG. 2 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to the first embodiment, illustrating a state in which the left and right crawler frames are disposed in a retracted position. [Figure 8] FIG. 2 is a perspective view showing a lower traveling body according to a first modified example of the first embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Figure 9] FIG. 2 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a first modification of the first embodiment, showing a state in which the left and right crawler frames are disposed in a retracted position. [Figure 10] FIG. 11 is a perspective view showing a car body and left and right crawler frames of a lower traveling body according to Modification 2 of the first embodiment, illustrating a state in which the left and right crawler frames are arranged in a contracted position. [Figure 11] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a second modification of the first embodiment, illustrating a state in which the left and right crawler frames are disposed in a retracted position. [Figure 12] FIG. 11 is a perspective view showing a lower traveling body according to a second embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Figure 13] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a second embodiment, in which the left and right crawler frames are positioned in an enlarged position. [Figure 14] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a second embodiment, in which the left and right crawler frames are arranged in a retracted position. [Figure 15] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a modified example of the second embodiment, in which the left and right crawler frames are arranged in a retracted position. [Figure 16] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a modified example of the second embodiment, in which the left and right crawler frames are arranged in a retracted position. [Figure 17]FIG. 11 is a perspective view showing a car body and left and right crawler frames of a lower traveling body according to a modified example of the second embodiment, in which the left and right crawler frames are arranged in a contracted position. [Figure 18] FIG. 11 is a perspective view showing a lower traveling body according to a third embodiment, illustrating a state in which the left and right crawler frames are placed in an enlarged position. [Figure 19] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a third embodiment, in which the left and right crawler frames are positioned in an enlarged position. [Figure 20] FIG. 11 is a perspective view showing a car body and left and right crawler frames of a lower traveling body according to a third embodiment, in which the left and right crawler frames are shown in a state in which they are arranged in a contracted position. [Figure 21] FIG. 11 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a third embodiment, in which the left and right crawler frames are arranged in a retracted position. [Figure 22] FIG. 13 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a modified example of the third embodiment, in which the left and right crawler frames are positioned in an enlarged position. [Diagram 23] FIG. 13 is a plan view showing a car body and left and right crawler frames of a lower traveling body according to a modified example of the third embodiment, in which the left and right crawler frames are arranged in a retracted position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] Below, the lower traveling body of the mobile crane according to the embodiment will be described with reference to the drawings. Note that in the drawings, the characters "front", "rear", "right", "left", "up" and "down" are written, but these are based on the direction in which the lower traveling body moves forward and backward. In other words, the front-to-rear direction of the lower traveling body is the horizontal direction in which the crawler frame described below extends, and the left-to-right direction of the lower traveling body is a horizontal direction perpendicular to the front-to-rear direction. The up-down direction of the lower traveling body is a direction parallel to the central axis of rotation of the upper rotating body.

[0070] [Overall structure of mobile crane] As shown in Fig. 1, the mobile crane 100 according to this embodiment includes a lower traveling body 101 and an upper rotating body 102. The lower traveling body 101 supports the upper rotating body 102 from below so as to be able to rotate, and is configured to be able to travel on the ground.

[0071] The upper rotating body 102 is disposed on the lower traveling body 101. The upper rotating body 102 includes a rotating frame 103, a working device, a cab 104, and a counterweight 105. The working device, the cab 104, and the counterweight 105 are mounted on the rotating frame 103.

[0072] The working device is for performing work such as lifting a load (crane work). In this embodiment, the working device includes a boom 106, a lifting winch 107, a lifting rope 108, a hook device 109, a gantry 110, a hoisting winch 111, a lower spreader 112, a hoisting rope 113, an upper spreader 114, and a guy line 115. The working device is not limited to the specific example shown in FIG. 1, and may further include, for example, a jib (not shown) that can be attached to the tip of the boom. In the specific example shown in FIG. 1, the boom 106 is a lattice boom having a lattice structure, but is not limited thereto, and may be a telescopic boom that can change its length by extending and contracting.

[0073] The boom 106 is attached to the front of the revolving frame 103 so as to be able to be raised and lowered, and a hook device 109 for hoisting a load is suspended from the tip of the boom 106 via a hoisting rope 108. The hoisting winch 107 is mounted on the revolving frame 103, and hoists or lowers the hook device 109 by winding or unwinding the hoisting rope 108. The gantry 110 is erected on the rear of the revolving frame 103. One end of the guy line 115 is connected to the tip of the boom 106, and the other end is connected to the upper spreader 114. The lower spreader 112 is provided at the upper end of the gantry 110, and the lower spreader 112 and the upper spreader 114 are arranged at a distance from each other. A hoisting rope 113 is wound around the lower spreader 112 and the upper spreader 114. The hoisting winch 111 is mounted on the revolving frame 103, and winds or unwinds the hoisting rope 113 to reduce or increase the distance between the lower spreader 112 and the upper spreader 114. As the distance between the spreaders 112, 114 decreases or increases, the boom 106 is hoisted.

[0074] [Structure of the lower running body according to the first embodiment] Fig. 2 is a perspective view showing the lower traveling body 101 according to the first embodiment, Fig. 3 is a plan view thereof, and Fig. 4 is a front view thereof. Fig. 5 is a right side view showing the right crawler frame 2R of the lower traveling body 101 according to the first embodiment. Fig. 6 is a perspective view showing the car body and the left and right crawler frames of the lower traveling body 101 according to the first embodiment, and Fig. 7 is a plan view thereof.

[0075] In this embodiment, as shown in Fig. 1 and Fig. 3, the front-rear direction of the lower traveling body 101 is the longitudinal direction of the crawler frames 2R, 2L described later, and the front of the front-rear direction is the direction from the wheel 24R (drive tumbler) to the wheel 23R (idler) of each crawler frame, and the rear is the opposite direction. However, the front-rear direction of the lower traveling body 101 may be defined as the opposite direction to the direction defined in Figs. 1 to 3. Note that the wheels 23R, 24R are not shown in Fig. 2.

[0076] The lower traveling body 101 includes the car body 10, a swivel bearing 19 supported on the upper part of the car body 10, a right traveling device, a left traveling device, and a plurality of connecting members.

[0077] The carbody 10 supports an upper rotating body 102 of the mobile crane 100 so as to be rotatable about a central axis of rotation C via a slewing bearing 19. The upper rotating body 102 is mounted on the slewing bearing 19. When the ground is horizontal, the central axis of rotation C is approximately parallel to the vertical direction.

[0078] In this embodiment, the car body 10 has a car body main body 10A having a substantially rectangular parallelepiped shape, a front axle 13, a rear axle 14, a pair of crawler movement cylinders 15R, 15L, and a plurality of connected parts. A swivel bearing 19 is attached to the car body main body 10A. Note that the shape of the car body main body 10A is not limited to a substantially rectangular parallelepiped shape. The multiple connected parts of the car body 10 will be described later.

[0079] The front axle 13 extends from the car body main body 10A to the right and left, respectively, and the rear axle 14 extends from the car body main body 10A to the right and left, respectively, rearward of the front axle 13. Specifically, in the plan view shown in Fig. 3, the front axle 13 protrudes from the front part of the car body main body 10A to the right and left, respectively, and the rear axle 14 protrudes from the rear part of the car body main body 10A to the right and left, respectively. In this embodiment, each of the front axle 13 and the rear axle 14 has a columnar shape extending parallel to the left-right direction, specifically, a rectangular column shape.

[0080] The front axle 13 and the rear axle 14 are spaced apart in the front-to-rear direction. The front axle 13 is located forward of the turning center axis C, and the rear axle 14 is located rearward of the turning center axis C. The right side of the front axle 13 and the right side of the rear axle 14 connect the car body main body 10A to a right crawler frame 2R, which will be described later. The left side of the front axle 13 and the left side of the rear axle 14 connect the car body main body 10A to a left crawler frame 2L, which will be described later.

[0081] In addition, the structural member consisting of the car body main body 10A, the front axle 13 and the rear axle 14 may be composed of a single member, or the car body main body 10A, the front axle 13 and the rear axle 14 may be manufactured separately and then connected to each other.

[0082] Each of the right and left traveling devices is a device for traveling on the ground while supporting the car body 10. The right traveling device includes a right crawler frame 2R, a pair of right wheels 23R, 24R, a right crawler belt 25R, a plurality of right rollers 26, and a traveling drive device 29 (see FIG. 1). Similarly, the left traveling device includes a left crawler frame 2L, a pair of left wheels 23L, 24L, a left crawler belt 25L, a plurality of left rollers 26, and a traveling drive device 29.

[0083] The right crawler frame 2R includes a right frame main body 20R and a plurality of connected parts, and the left crawler frame 2L includes a left frame main body 20L and a plurality of connected parts. The respective connected parts of the left and right crawler frames 2R, 2L will be described later.

[0084] The right frame body 20R has a shape that extends in the front-rear direction to the right of the turning center axis C. The right frame body 20R has a right front axle support part 27 and a right rear axle support part 28. These axle support parts 27, 28 are provided at positions corresponding to the front axle 13 and the rear axle 14, respectively, and support the front axle 13 and the rear axle 14, respectively, so that the right frame body 20R can change its left-right position relative to the right side portion of the front axle 13 and the right side portion of the rear axle 14.

[0085] Specifically, the right front axle support 27 and the right rear axle support 28 support the front axle 13 and the rear axle 14, respectively, so that their left-right positions relative to the front axle 13 and the rear axle 14 can be changed between an expanded position and a contracted position in which the distance between the turning center axis C and the right crawler frame 2R is smaller than in the expanded position.

[0086] 2 and 5, each of the right front axle support part 27 and the right rear axle support part 28 has an inner surface that defines a through hole that penetrates the right frame main body 20R in the left-right direction. In this embodiment, the inner surface is composed of four surfaces (front surface, rear surface, bottom surface, and ceiling surface) that correspond to the four outer surfaces (front surface, rear surface, bottom surface, and top surface) of the corresponding axle of the front axle 13 and the rear axle 14. The front and rear surfaces restrict the corresponding axle from being displaced in the front-rear direction, and the bottom surface and top surface restrict the corresponding axle from being displaced in the up-down direction.

[0087] Similarly, the left frame body 20L has a shape that extends in the front-to-rear direction to the left of the turning center axis C. The left frame body 20L has a left front axle support part 27 and a left rear axle support part 28. These axle support parts 27, 28 are provided at positions corresponding to the front axle 13 and the rear axle 14, respectively, and support the front axle 13 and the rear axle 14, respectively, so that the left frame body 20L can change its left-right position relative to the left side portion of the front axle 13 and the left side portion of the rear axle 14.

[0088] The left front axle support part 27 and the left rear axle support part 28 support the front axle 13 and the rear axle 14, respectively, so that their left-right positions relative to the front axle 13 and the rear axle 14 can be changed between an expanded position and a contracted position in which the distance between the turning center axis C and the left crawler frame 2L is smaller than in the expanded position.

[0089] The specific structure of the axle support parts 27, 28 of the left frame main body 20L is similar to that of the axle support parts 27, 28 of the right frame main body 20R described above, and therefore a detailed description thereof will be omitted.

[0090] A pair of right wheels 23R, 24R are rotatably supported at the front end and rear end of the right frame main body 20R, respectively. In this embodiment, the right wheel 23R located on the front side is constituted by an idler, and the right wheel 24R located on the rear side is constituted by a drive tumbler. This drive tumbler is connected to a traveling drive device 29 (see FIG. 1) supported at the rear end of the right frame main body 20R at a position adjacent to the drive tumbler. The traveling drive device 29 includes, for example, a traveling motor and a traveling reducer. Note that the traveling drive device 29 is omitted from illustrations other than FIG. 1.

[0091] The right crawler belt 25R is a belt that is looped around the pair of right wheels 23R, 24R and can move around. In other words, the right crawler belt 25R is supported endlessly by the pair of right wheels 23R, 24R. The right crawler belt 25R is configured by connecting a number of crawler shoes.

[0092] The right wheel 24R, which is made of a drive tumbler, has a plurality of protrusions formed on its outer periphery along the circumferential direction so as to be engageable with the inner periphery of the right crawler belt 25R. The right wheel 24R is given a driving force from the travel drive device 29, and this driving force is transmitted to the right crawler belt 25R. This causes the right crawler belt 25R to move in an orbit. The right wheel 23R, which is made of an idler, rotates following the rotation of the right crawler belt 25R.

[0093] The right rollers 26 are each rotatably supported at a lower portion of the right frame main body 20R of the right crawler frame 2R. The right rollers 26 are disposed at intervals in the front-rear direction between the pair of right wheels 23R, 24R. The right rollers 26 press the right crawler belt 25R against the ground and guide the circular movement of the right crawler belt 25R.

[0094] In the following, the right roller 26 located furthest from the multiple right rollers 26 (in this embodiment, the right roller 26 closest to wheel 23R) will be referred to as the right front end roller 261, and the right roller 26 located furthest from the multiple right rollers 26 (in this embodiment, the right roller 26 closest to wheel 24R) will be referred to as the right rear end roller 262.

[0095] The structure of the pair of left wheels 23L, 24L, left crawler belt 25L, and multiple left rollers 26 in the left traveling device is similar to the structure of the pair of right wheels 23R, 24R, right crawler belt 25R, and multiple right rollers 26 in the right traveling device described above, except for the fact that they are symmetrical, so detailed explanations will be omitted. In the following, the left roller 26 located furthest from the multiple left rollers 26 (in this embodiment, the left roller 26 closest to the wheel 23L) will be referred to as the left front end roller 261, and the left roller 26 located furthest from the multiple left rollers 26 (in this embodiment, the left roller 26 closest to the wheel 24L) will be referred to as the left rear end roller 262.

[0096] A pair of crawler movement cylinders 15R, 15L of the car body 10 are disposed between the front axle 13 and the rear axle 14, and are hydraulic cylinders that connect the car body main body 10A to the right and left traveling devices. The tip of the right crawler movement cylinder 15R is fixed to the right crawler frame 2R of the right traveling device, and the tip of the left crawler movement cylinder 15L is fixed to the left crawler frame 2L of the left traveling device. Therefore, in response to the expansion and contraction movement of the right crawler movement cylinder 15R, the right crawler frame 2R of the right traveling device is displaced left and right relative to the car body main body 10A and the front and rear axles 13, 14, and in response to the expansion and contraction movement of the left crawler movement cylinder 15L, the left crawler frame 2L of the left traveling device is displaced left and right relative to the car body main body 10A and the front and rear axles 13, 14. 3 to 5 show a state in which the right crawler frame 2R and the left crawler frame 2L are arranged in the enlarged position, and FIGS. 6 and 7 show a state in which the right crawler frame 2R and the left crawler frame 2L are arranged in the reduced position.

[0097] The multiple connecting members include a right front connecting member 11R, a right rear connecting member 12R, a left front connecting member 11L, and a left rear connecting member 12L.

[0098] Each of the right front connecting member 11R and the right rear connecting member 12R has a car body connecting part 30 rotatably connected to the car body 10 around a vertical axis, a first crawler connecting part 31 detachably connected to the right crawler frame 2R arranged at the expanded position, and a second crawler connecting part 32 detachably connected to the right crawler frame 2R arranged at the contracted position. Each of the right front connecting member 11R and the right rear connecting member 12R is an example of a right connecting member.

[0099] Each of the left front connecting member 11L and the left rear connecting member 12L has a car body connecting part 30 rotatably connected to the car body 10 around a vertical axis, a first crawler connecting part 31 detachably connected to the left crawler frame 2L arranged in the expanded position, and a second crawler connecting part 32 detachably connected to the left crawler frame 2L arranged in the contracted position. Each of the left front connecting member 11L and the left rear connecting member 12L is an example of a left connecting member.

[0100] The multiple connected portions of the car body 10 include a right front connected portion 51R to which the car body connecting portion 30 of the right front connecting member 11R is connected so as to be rotatable around an axis in the vertical direction, a right rear connected portion 52R to which the car body connecting portion 30 of the right rear connecting member 12R is connected so as to be rotatable around an axis in the vertical direction, a left front connected portion 51L to which the car body connecting portion 30 of the left front connecting member 11L is connected so as to be rotatable around an axis in the vertical direction, and a left rear connected portion 52L to which the car body connecting portion 30 of the left rear connecting member 12L is connected so as to be rotatable around an axis in the vertical direction.

[0101] The multiple connected parts of the right crawler frame 2R include a right front connected part 61R and a right rear connected part 62R. The right front connected part 61R is detachably connected to the first crawler connection part 31 of the right front connecting member 11R when the right crawler frame 2R is disposed at the expanded position, and the right front connected part 61R is detachably connected to the second crawler connection part 32 of the right front connecting member 11R when the right crawler frame 2R is disposed at the contracted position. The right rear connected part 62R is detachably connected to the first crawler connection part 31 of the right rear connecting member 12R when the right crawler frame 2R is disposed at the expanded position, and the right rear connected part 32 of the right rear connecting member 12R is detachably connected to the first crawler connection part 31 of the right rear connecting member 12R when the right crawler frame 2R is disposed at the contracted position. The right front connected part 61R is located forward of the right front axle support part 27 and diagonally forward to the right of the right front connected part 51R of the car body 10. The right rear connected portion 62R is located rearward of the right rear axle support portion 28 and obliquely rearward and to the right of the right rear connected portion 52R of the car body 10.

[0102] The plurality of connected parts of the left crawler frame 2L include a left front connected part 61L and a left rear connected part 62L. The left front connected part 61L is detachably connected to the first crawler connection part 31 of the left front connecting member 11L when the left crawler frame 2L is disposed at the expanded position, and the left rear connected part 32 of the left front connecting member 11L is detachably connected to the left front connected part 61L when the left crawler frame 2L is disposed at the contracted position. The left rear connected part 62L is detachably connected to the first crawler connection part 31 of the left rear connecting member 12L when the left crawler frame 2L is disposed at the expanded position, and the left rear connected part 32 of the left rear connecting member 12L is detachably connected to the left front connected part 61L when the left crawler frame 2L is disposed at the contracted position. The left front connected part 61L is located forward of the left front axle support part 27, and is located diagonally forward to the left of the left front connected part 51L of the car body 10. The left rear connected portion 62L is located rearward of the left rear axle support portion 28 and obliquely rearward and to the left of the left rear connected portion 52L of the car body 10.

[0103] Specifically, the car body connection part 30 of the right front connecting member 11R is provided at one end part (base end part) of the right front connecting member 11R. The first crawler connection part 31 of the right front connecting member 11R is provided at the other end part (tip part) of the right front connecting member 11R. The second crawler connection part 32 of the right front connecting member 11R is provided at an intermediate part of the right front connecting member 11R. In this embodiment, the second crawler connection part 32 is located closer to the first crawler connection part 31 than the car body connection part 30.

[0104] The car body connection part 30 of the right front connecting member 11R includes a pin insertion hole H30 that penetrates one end of the right front connecting member 11R in the vertical direction, and a pin P30 that is inserted into the pin insertion hole H30. The first crawler connection part 31 of the right front connecting member 11R includes a pin insertion hole H31 that penetrates the other end of the right front connecting member 11R in the vertical direction, and a pin P31 that is inserted into the pin insertion hole H31. The second crawler connection part 32 of the right front connecting member 11R includes a pin insertion hole H32 that penetrates the middle part of the right front connecting member 11R in the vertical direction, and a pin that is inserted into the pin insertion hole H32. In this embodiment, the pin of the second crawler connection part 32 may be the same as the pin P31 of the first crawler connection part 31. That is, the pin P31 may be configured to be inserted into the pin insertion hole H31 of the first crawler connection part 31 when the right crawler frame 2R is arranged in the enlarged position, and to be inserted into the pin insertion hole H32 of the second crawler connection part 32 when the right crawler frame 2R is arranged in the retracted position. However, the pin of the second crawler connection part 32 may be different from the pin P31 of the first crawler connection part 31.

[0105] The right front connected portion 51R of the car body 10 has a pair of protruding pieces PL1 protruding forward from at least one of the right side portion of the car body main body 10A and the front axle 13. These protruding pieces PL1 are arranged at a distance from each other in the vertical direction. The vertical distance (gap) between the pair of protruding pieces PL1 is set to a value slightly larger than the vertical dimension (thickness) of the car body connecting portion 30 of the right front coupling member 11R so that the car body connecting portion 30 can be fitted between them.

[0106] Each of the pair of protruding pieces PL1 has a pin insertion hole H5. The pin insertion hole H5 of each of the pair of protruding pieces PL1 is arranged at the same position as the pin insertion hole H30 of the car body connecting part 30 in a plan view when the car body connecting part 30 of the right front connecting member 11R is fitted between the pair of protruding pieces PL1. With the car body connecting part 30 of the right front connecting member 11R fitted between the pair of protruding pieces PL1, the pin P30 is inserted into the pin insertion hole H30 of the car body connecting part 30 and the pin insertion hole H5 of each of the pair of protruding pieces PL1. As a result, the car body connecting part 30 of the right front connecting member 11R is connected to the car body 10 so as to be rotatable around an axis in the vertical direction. The right front connecting member 11R can rotate with respect to the car body 10 around the rotation central axis which is the center of the pin P30.

[0107] The right front connected portion 61R of the right crawler frame 2R has a pair of protruding pieces PL2 protruding leftward from the right frame main body 20R. These protruding pieces PL2 are arranged at a distance from each other in the up-down direction. The vertical distance (gap) between the pair of protruding pieces PL2 is set to a value slightly larger than the vertical dimensions (thickness) of the first crawler connection portion 31 and the second crawler connection portion 32 of the right front coupling member 11R so that these crawler connection portions 31, 32 can fit between them.

[0108] Each of the pair of protruding pieces PL2 has a pin insertion hole H6. When the right crawler frame 2R is arranged in the expanded position, the pin insertion hole H6 of each of the pair of protruding pieces PL2 is arranged in the same position as the pin insertion hole H31 of the first crawler connection part 31 in a plan view when the first crawler connection part 31 of the right front connecting member 11R is fitted between the pair of protruding pieces PL2. When the first crawler connection part 31 of the right front connecting member 11R is fitted between the pair of protruding pieces PL2, the pin P31 is inserted into the pin insertion hole H31 of the first crawler connection part 31 and the pin insertion hole H6 of each of the pair of protruding pieces PL2. As a result, the first crawler connection part 31 of the right front connecting member 11R is detachably connected to the right frame main body 20R of the right crawler frame 2R arranged in the expanded position.

[0109] Furthermore, when the right crawler frame 2R is disposed in the contracted position, the pin insertion hole H6 of each of the pair of protruding pieces PL2 is disposed in the same position as the pin insertion hole H32 of the second crawler connection part 32 in a plan view when the second crawler connection part 32 of the right front connecting member 11R is fitted between the pair of protruding pieces PL2. When the second crawler connection part 32 of the right front connecting member 11R is fitted between the pair of protruding pieces PL2, the pin P31 is inserted into the pin insertion hole H32 of the second crawler connection part 32 and the pin insertion hole H6 of each of the pair of protruding pieces PL2. As a result, the second crawler connection part 32 of the right front connecting member 11R is detachably connected to the right frame main body 20R of the right crawler frame 2R disposed in the contracted position.

[0110] In this embodiment, the second crawler connection part 32 of the right front connecting member 11R is located on a line segment connecting the car body connection part 30 and the first crawler connection part 31 in a plan view. Specifically, the pin insertion hole H32 in the second crawler connection part 32 of the right front connecting member 11R is located on a line segment connecting the center of the pin insertion hole H30 (center of the pin P30) in the car body connection part 30 and the center of the pin insertion hole H31 (center of the pin P31) in the first crawler connection part 31.

[0111] In addition, the structures of the car body connection part 30, first crawler connection part 31 and second crawler connection part 32 of the right rear connecting member 12R, the structures of the car body connection part 30, first crawler connection part 31 and second crawler connection part 32 of the left front connecting member 11L, and the structures of the car body connection part 30, first crawler connection part 31 and second crawler connection part 32 of the left rear connecting member 12L are similar to the structures of the car body connection part 30, first crawler connection part 31 and second crawler connection part 32 of the right front connecting member 11R except for their orientation, so detailed explanations will be omitted.

[0112] The right rear connected portion 52R of the car body 10 has a pair of protruding pieces PL1 protruding rearward from at least one of the right side portions of the car body main body 10A and the rear axle 14, the left front connected portion 51L of the car body 10 has a pair of protruding pieces PL1 protruding forward from at least one of the left side portions of the car body main body 10A and the front axle 13, and the left rear connected portion 52L of the car body 10 has a pair of protruding pieces PL1 protruding rearward from at least one of the left side portions of the car body main body 10A and the rear axle 14. The structures of these connected portions 52R, 51L, 52L are similar to those of the right front connected portion 51R of the car body 10 except for the orientation, so detailed explanations will be omitted.

[0113] Further, the right rear connected portion 62R of the right crawler frame 2R has a pair of protruding pieces PL2 protruding leftward from the right frame main body 20R, the left front connected portion 61L of the left crawler frame 2L has a pair of protruding pieces PL2 protruding rightward from the left frame main body 20L, and the left rear connected portion 62L of the left crawler frame 2L has a pair of protruding pieces PL2 protruding rightward from the left frame main body 20L. The structures of these connected portions 62R, 61L, 62L are similar to those of the right front connected portion 61R of the right crawler frame 2R except for the orientation, so detailed explanations will be omitted.

[0114] In the lower traveling body 101 having the above-described structure, each of the multiple connecting members 11R, 12R, 11L, and 12L is configured so as to be able to be placed in an expanded connection state.

[0115] The expanded connection state of the right front coupling member 11R is a state in which the right crawler frame 2R is disposed in the expanded position, the car body connection part 30 of the right front coupling member 11R is connected to the right front connected part 51R of the car body 10, and the first crawler connection part 31 of the right front coupling member 11R is connected to the right front connected part 61R of the right crawler frame 2R. The right front coupling member 11R disposed in the expanded connection state has a shape that extends diagonally forward and to the right from the car body 10 forward of the turning center axis C, and couples the car body 10 and the right crawler frame 2R.

[0116] The expanded connection state of the right rear coupling member 12R is a state in which, with the right crawler frame 2R disposed in the expanded position, the car body connection part 30 of the right rear coupling member 12R is connected to the right rear connected part 52R of the car body 10 and the first crawler connection part 31 of the right rear coupling member 12R is connected to the right rear connected part 62R of the right crawler frame 2R. The right rear coupling member 12R disposed in the expanded connection state has a shape that extends obliquely rearward and to the right from the car body 10 rearward of the turning center axis C, and couples the car body 10 and the right crawler frame 2R.

[0117] The expanded connection state of the left front connecting member 11L is a state in which, with the left crawler frame 2L arranged in the expanded position, the car body connecting part 30 of the left front connecting member 11L is connected to the left front connected part 51L of the car body 10 and the first crawler connecting part 31 of the left front connecting member 11L is connected to the left front connected part 61L of the left crawler frame 2L. The left front connecting member 11L arranged in the expanded connection state has a shape that extends diagonally forward and left from the car body 10 forward of the turning center axis C, and connects the car body 10 and the left crawler frame 2L.

[0118] The expanded connection state of the left rear connecting member 12L is a state in which, with the left crawler frame 2L disposed in the expanded position, the car body connecting part 30 of the left rear connecting member 12L is connected to the left rear connected part 52L of the car body 10 and the first crawler connecting part 31 of the left rear connecting member 12L is connected to the left rear connected part 62L of the left crawler frame 2L. The left rear connecting member 12L disposed in the expanded connection state has a shape that extends diagonally rearward and left from the car body 10 rearward of the turning center axis C, and connects the car body 10 and the left crawler frame 2L.

[0119] Each of the right front connecting member 11R and the right rear connecting member 12R is configured to allow the right crawler frame 2R to be displaced from the expanded position to the contracted position by changing its relative position with respect to the car body 10 and the right crawler frame 2R from the expanded connection state while remaining connected to the car body 10.

[0120] Specifically, each of the right front connecting member 11R and the right rear connecting member 12R is displaced from the expanded connection state as follows to allow the right crawler frame 2R to be displaced from the expanded position to the contracted position. The first crawler connection part 31 of the right front connecting member 11R is detached from the right crawler frame 2R, and the first crawler connection part 31 of the right rear connecting member 12R is detached from the right crawler frame 2R. The car body connection part 30 of the right front connecting member 11R and the car body connection part 30 of the right rear connecting member 12R remain connected to the car body 10. In this state, the right front connecting member 11R rotates at the car body connection part 30 relative to the car body 10, and the right rear connecting member 12R rotates at the car body connection part 30 relative to the car body 10, so that the relative positions of these connecting members 11R, 12R with respect to the car body 10 and the right crawler frame 2R change from the expanded connection state. This allows the right crawler frame 2R to be displaced from the expanded position to the contracted position.

[0121] Each of the left front connecting member 11L and the left rear connecting member 12L is configured to allow the left crawler frame 2L to be displaced from the expanded position to the contracted position by changing its relative position with respect to the car body 10 and the left crawler frame 2L from the expanded connection state while remaining connected to the car body 10.

[0122] Specifically, each of the left front connecting member 11L and the left rear connecting member 12L is displaced from the expanded connection state as follows to allow the left crawler frame 2L to be displaced from the expanded position to the contracted position. The first crawler connection part 31 of the left front connecting member 11L is detached from the left crawler frame 2L, and the first crawler connection part 31 of the left rear connecting member 12L is detached from the left crawler frame 2L. The car body connection part 30 of the left front connecting member 11L and the car body connection part 30 of the left rear connecting member 12L remain connected to the car body 10. In this state, the left front connecting member 11L rotates at the car body connection part 30 relative to the car body 10, and the left rear connecting member 12L rotates at the car body connection part 30 relative to the car body 10, so that the relative positions of these connecting members 11L, 12L with respect to the car body 10 and the left crawler frame 2L change from the expanded connection state. This allows the left crawler frame 2L to be displaced from the expanded position to the contracted position.

[0123] Each of the right front connecting member 11R and the right rear connecting member 12R is configured to be capable of being arranged in a restrained state in which it is restrained by the right crawler frame 2R and the car body 10 arranged in the retracted position. That is, the right front connecting member 11R is arranged in the restrained state because both ends of the right front connecting member 11R are connected to the car body 10 and the right crawler frame 2R by the second crawler connecting portion 32 of the right front connecting member 11R being detachably connected to the right front connected portion 61R of the right crawler frame 2R arranged in the retracted position. The right rear connecting member 12R is arranged in the restrained state because both ends of the right front connecting member 11R are connected to the car body 10 and the right crawler frame 2R by the second crawler connecting portion 32 of the right rear connecting member 12R being detachably connected to the right rear connected portion 62R of the right crawler frame 2R arranged in the retracted position.

[0124] Similarly, each of the left front connecting member 11L and the left rear connecting member 12L is configured to be capable of being arranged in a restrained state in which it is restrained by the left crawler frame 2L and the car body 10 arranged in the retracted position. That is, the left front connecting member 11L is arranged in the restrained state because both ends of the left front connecting member 11L are connected to the car body 10 and the left crawler frame 2L by the second crawler connecting part 32 of the left front connecting member 11L being detachably connected to the left front connected part 61L of the left crawler frame 2L arranged in the retracted position. The left rear connecting member 12L is arranged in the restrained state because both ends of the left front connecting member 11L are connected to the car body 10 and the left crawler frame 2L by the second crawler connecting part 32 of the left rear connecting member 12L being detachably connected to the left rear connected part 62L of the left crawler frame 2L arranged in the retracted position.

[0125] [Load transfer structure] Next, a load transfer structure provided on the lower running body 101 will be described in detail.

[0126] 3, the car body 10 has a plurality of load transfer surfaces for transferring the load received from the upper rotating body 102 to the plurality of connecting members 11R, 12R, 11L, and 12L, respectively. Specifically, the plurality of load transfer surfaces include a right front load transfer surface 5FR for transferring the load to the right front connecting member 11R, a right rear load transfer surface 5BR for transferring the load to the right rear connecting member 12R, a left front load transfer surface 5FL for transferring the load to the left front connecting member 11L, and a left rear load transfer surface 5BL for transferring the load to the left rear connecting member 12L.

[0127] The right front load transfer surface 5FR of the car body 10 is provided in a portion of the car body 10 forward of and to the right of the turning central axis C. The right rear load transfer surface 5BR of the car body 10 is provided in a portion of the car body 10 rear of and to the right of the turning central axis C. The left front load transfer surface 5FL of the car body 10 is provided in a portion of the car body 10 forward of and to the left of the turning central axis C. The left rear load transfer surface 5BL of the car body 10 is provided in a portion of the car body 10 rear of and to the left of the turning central axis C.

[0128] Each of the multiple connecting members 11R, 12R, 11L, 12L has a load receiving surface for receiving the load from the car body 10. Specifically, the right front connecting member 11R has a right front load receiving surface 3FR facing the right front load transfer surface 5FR of the car body 10. The right rear connecting member 12R has a right rear load receiving surface 3BR facing the right rear load transfer surface 5BR of the car body 10. The left front connecting member 11L has a left front load receiving surface 3FL facing the left front load transfer surface 5FL of the car body 10. The left rear connecting member 12L has a left rear load receiving surface 3BL facing the left rear load transfer surface 5BL of the car body 10.

[0129] The right front load receiving surface 3FR of the right front connecting member 11R and the left front load receiving surface 3FL of the left front connecting member 11L are surfaces that can receive a front load from the carbody 10, which is a load that the carbody 10 receives from the upper rotating body 102 when a load is suspended from the upper rotating body 102 forward of the lower running body 101. The front load that the right front load receiving surface 3FR and the left front load receiving surface 3FL receive from the carbody 10 is a portion of the total load that the carbody 10 receives from the upper rotating body 102 when a load is suspended from the upper rotating body 102 forward of the lower running body 101.

[0130] The right rear load receiving surface 3BR of the right rear connecting member 12R and the left rear load receiving surface 3BL of the left rear connecting member 12L are surfaces that can receive a rear load from the car body 10, which is a load that the car body 10 receives from the upper rotating body 102 when a load is suspended from the upper rotating body 102 rearward of the lower running body 101. The rear load that the right rear load receiving surface 3BR and the left rear load receiving surface 3BL receive from the car body 10 is a portion of the total load that the car body 10 receives from the upper rotating body 102 when a load is suspended from the upper rotating body 102 rearward of the lower running body 101.

[0131] Each of the multiple connecting members 11R, 12R, 11L, 12L has a load transfer surface for transferring the load received from the car body 10 to the crawler frame. Specifically, the right front connecting member 11R has a right front load transfer surface 4FR facing the right frame main body 20R of the right crawler frame 2R. The right rear connecting member 12R has a right rear load transfer surface 4BR facing the right frame main body 20R of the right crawler frame 2R. The left front connecting member 11L has a left front load transfer surface 4FL facing the left frame main body 20L of the left crawler frame 2L. The left rear connecting member 12L has a left rear load transfer surface 4BL facing the left frame main body 20L of the left crawler frame 2L.

[0132] The right front load transfer surface 4FR is a surface that can transfer the front load to the right crawler frame 2R, the left front load transfer surface 4FL is a surface that can transfer the front load to the left crawler frame 2L, the right rear load transfer surface 4BR is a surface that can transfer the rear load to the right crawler frame 2R, and the left rear load transfer surface 4BL is a surface that can transfer the rear load to the left crawler frame 2L.

[0133] The right crawler frame 2R has a right front load receiving surface 6FR for receiving the load from the right front connecting member 11R and a right rear load receiving surface 6BR for receiving the load from the right rear connecting member 12R. The left crawler frame 2L has a left front load receiving surface 6FL for receiving the load from the left front connecting member 11L and a left rear load receiving surface 6BL for receiving the load from the left rear connecting member 12L.

[0134] Specific examples of the load transfer surfaces of the car body 10 are as follows. The right front load transfer surface 5FR of the car body 10 may be formed, for example, by an inner peripheral surface that defines a pin insertion hole H5 provided in a pair of protruding pieces PL1 of the right front connected portion 51R. The other load transfer surfaces 5BR, 5FL, 5BL may be formed in the same manner as the right front load transfer surface 5FR.

[0135] Specific examples of the load receiving surfaces of each of the multiple connecting members 11R, 12R, 11L, 12L are as follows. The right front load receiving surface 3FR of the right front connecting member 11R may be formed by the outer peripheral surface of the pin P30 of the car body connecting part 30. The outer peripheral surface of this pin P30 faces the pin insertion holes H5 provided in a pair of protruding pieces PL1 of the right front connected part 51R. The other load receiving surfaces 3BR, 3FL, 3BL may be formed in the same manner as the right front load receiving surface 3FR.

[0136] Specific examples of the load transfer surfaces of the multiple connecting members 11R, 12R, 11L, 12L are as follows: The right front load transfer surface 4FR of the right front connecting member 11R may be formed by the outer peripheral surface of the pin P31 of the first crawler connecting part 31. The outer peripheral surface of this pin P31 faces pin insertion holes H6 provided in a pair of protruding pieces PL2 of the right front connected part 61R of the right crawler frame 2R.

[0137] In this case, the right front load receiving surface 6FR of the right crawler frame 2R may be formed by the inner circumferential surfaces that define the respective pin insertion holes H6 of the pair of projecting pieces PL2 of the right front connected portion 61R.

[0138] The other load transfer surfaces 4BR, 4FL, 4BL in the multiple connecting members may also be configured similarly to the right front load transfer surface 4FR, and the other load receiving surfaces 6BR, 6FL, 6BL in the left and right crawler frames 2R, 2L may also be configured similarly to the right front load receiving surface 6FR.

[0139] The right front connecting member 11R has a shape such that, in the plan view shown in Fig. 3, a right front straight line LA, which is a straight line passing through a point A1 included in the right front load receiving surface 3FR of the right front connecting member 11R and a point A2 included in the right front load transfer surface 4FR, passes through the right front end roller 261. The left front connecting member 11L has a shape such that, in the plan view shown in Fig. 3, a left front straight line LC, which is a straight line passing through a point C1 included in the left front load receiving surface 3FL of the left front connecting member 11L and a point C2 included in the left front load transfer surface 4FL, passes through the left front end roller 261. In this embodiment, the right front straight line LA is a straight line that further passes through the turning central axis C in the plan view, and the left front straight line LC is a straight line that further passes through the turning central axis C in the plan view.

[0140] However, point A1 on the right front load receiving surface 3FR and point A2 on the right front load transfer surface 4FR for defining the right front straight line LA are not limited to the above-mentioned positions. Point A1 may be another point included in the right front load receiving surface 3FR that can receive a front load from the right front load transfer surface 5FR of the car body 10, and point A2 may be another point included in the right front load transfer surface 4FR that can transfer a front load to the right front load receiving surface 6FR of the right crawler frame 2R. Specifically, the right front straight line LA may be a straight line passing through the rearmost point of the right front load receiving surface 3FR and the frontmost point of the right front load transfer surface 4FR in the plan view shown in FIG. 3, for example.

[0141] Similarly, point C1 on the left front load receiving surface 3FL and point C2 on the left front load transfer surface 4FL for defining the left front straight line LC are not limited to the above-mentioned positions. Point C1 may be another point included in the left front load receiving surface 3FL that can receive a front load from the left front load transfer surface 5FL of the car body 10, and point C2 may be another point included in the left front load transfer surface 4FL that can transfer a front load to the left front load receiving surface 6FL of the left crawler frame 2L. Specifically, the left front straight line LC may be, for example, a straight line passing through the rearmost point of the left front load receiving surface 3FL and the frontmost point of the left front load transfer surface 4FL in the plan view shown in FIG. 3.

[0142] The right front connecting member 11R has a right front continuing portion CX that continues from the right front load receiving surface 3FR to the right front load transfer surface 4FR along the right front straight line LA in a plan view, and the left front connecting member 11L has a left front continuing portion CX that continues from the left front load receiving surface 3FL to the left front load transfer surface 4FL along the left front straight line LC in a plan view. Specifically, the right front continuing portion CX continues from the right front load receiving surface 3FR to the right front load transfer surface 4FR while overlapping with the right front straight line LA in a plan view, and the left front continuing portion CX continues from the left front load receiving surface 3FL to the left front load transfer surface 4FL while overlapping with the left front straight line LC in a plan view.

[0143] In the plan view shown in Fig. 3, the right rear connecting member 12R has a shape such that a right rear straight line LB, which is a straight line passing through a point B1 included in the right rear load receiving surface 3BR of the right rear connecting member 12R and a point B2 included in the right rear load transfer surface 4BR, passes through the right rear end roller 262. In the plan view shown in Fig. 3, the left rear connecting member 12L has a shape such that a left rear straight line LD, which is a straight line passing through a point D1 included in the left rear load receiving surface 3BL of the left rear connecting member 12L and a point D2 included in the left rear load transfer surface 4BL, passes through the left rear end roller 262. In this embodiment, the right rear straight line LB is a straight line that further passes through the turning central axis C in the plan view, and the left rear straight line LD is a straight line that further passes through the turning central axis C in the plan view.

[0144] However, point B1 on the right rear load receiving surface 3BR and point B2 on the right rear load transfer surface 4BR for defining the right rear straight line LB are not limited to the above-mentioned positions. Point B1 may be another point included in the right rear load receiving surface 3BR that can receive the rear load from the right rear load transfer surface 5BR of the car body 10, and point B2 may be another point included in the right rear load transfer surface 4BR that can transfer the rear load to the right rear load receiving surface 6BR of the right crawler frame 2R. Specifically, the right rear straight line LB may be a straight line passing through the frontmost point of the right rear load receiving surface 3BR and the rearmost point of the right rear load transfer surface 4BR in the plan view shown in FIG. 3, for example.

[0145] Similarly, point D1 on the left rear load receiving surface 3BL and point D2 on the left rear load transfer surface 4BL for defining the left rear straight line LD are not limited to the above-mentioned positions. Point D1 may be another point included in the left rear load receiving surface 3BL that can receive a rear load from the left rear load transfer surface 5BL of the car body 10, and point D2 may be another point included in the left rear load transfer surface 4BL that can transfer a rear load to the left rear load receiving surface 6BL of the left crawler frame 2L. Specifically, the left rear straight line LD may be, for example, a straight line passing through the frontmost point of the left rear load receiving surface 3BL and the rearmost point of the left rear load transfer surface 4BL in the plan view shown in FIG. 3.

[0146] The right rear connecting member 12R has a right rear continuing portion CX that continues from the right rear load receiving surface 3BR to the right rear load transfer surface 4BR along the right rear straight line LB in a plan view, and the left rear connecting member 12L has a left rear continuing portion CX that continues from the left rear load receiving surface 3BL to the left rear load transfer surface 4BL along the left rear straight line LD in a plan view. Specifically, the right rear continuing portion CX continues from the right rear load receiving surface 3BR to the right rear load transfer surface 4BR while overlapping with the right rear straight line LB in a plan view, and the left rear continuing portion CX continues from the left rear load receiving surface 3BL to the left rear load transfer surface 4BL while overlapping with the left rear straight line LD in a plan view.

[0147] [Modification 1 of the first embodiment] Fig. 8 is a perspective view showing a lower body 101 according to the first modification of the first embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in an expanded position. Fig. 9 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower body 101 according to the first modification of the first embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in a contracted position.

[0148] The lower traveling body 101 according to the first modification of the first embodiment has a structure of a plurality of connecting members 11R, 12R, 11L, and 12L different from that of the lower traveling body 101 according to the first embodiment shown in Figures 2 and 7. The other configurations of the first modification are the same as those of the lower traveling body 101 according to the first embodiment, and therefore descriptions thereof will be omitted.

[0149] In the first modification shown in Figs. 8 and 9, each of the right front connecting member 11R and the right rear connecting member 12R has a member body extending from the car body connecting portion 30 to the first crawler connecting portion 31, and a second crawler connecting portion 32, and this second crawler connecting portion 32 is configured with a convex portion protruding from the member body in a direction approaching the right crawler frame 2R when each of the right front connecting member 11R and the right rear connecting member 12R is arranged in a restrained state. The second crawler connecting portion 32 configured with this convex portion has a pin insertion hole H32 that penetrates the convex portion in the vertical direction. The second crawler connecting portion 32 of the right front connecting member 11R and the second crawler connecting portion 32 of the right rear connecting member 12R are configured to be detachably connected to the right front connected portion 61R and the right rear connected portion 62R of the right crawler frame 2R arranged in the contracted position, respectively.

[0150] The second crawler connection portion 32 of the right front connecting member 11R connected to the right front connected part 61R of the right crawler frame 2R arranged in the contracted position and the second crawler connection portion 32 of the right rear connecting member 12R connected to the right rear connected part 62R of the right crawler frame 2R are each configured to be arranged at a position closer to the right crawler frame 2R than a line segment LS connecting the car body connection part 30 and the crawler connection part 31 in the plan view shown in Fig. 9. Specifically, in this embodiment, the line segment LS is a line segment connecting the center of the pin insertion hole H30 (center of the pin P30) in the car body connection part 30 and the center of the pin insertion hole H31 in the first crawler connection part 31.

[0151] Similarly, each of the left front connecting member 11L and the left rear connecting member 12L has a member body extending from the car body connecting portion 30 to the first crawler connecting portion 31, and a second crawler connecting portion 32, and this second crawler connecting portion 32 is configured with a convex portion protruding from the member body in a direction approaching the left crawler frame 2L when each of the left front connecting member 11L and the left rear connecting member 12L is arranged in a restrained state. The second crawler connecting portion 32 configured with this convex portion has a pin insertion hole H32 that penetrates the convex portion in the vertical direction. The second crawler connecting portion 32 of the left front connecting member 11L and the second crawler connecting portion 32 of the left rear connecting member 12L are configured to be detachably connected to the left front connected portion 61L and the left rear connected portion 62L of the left crawler frame 2L arranged in the retracted position, respectively.

[0152] The second crawler connection portion 32 of the left front connecting member 11L connected to the left front connected part 61L of the left crawler frame 2L arranged in the contracted position, and the second crawler connection portion 32 of the left rear connecting member 12L connected to the left rear connected part 62L of the left crawler frame 2L are each configured to be arranged at a position closer to the left crawler frame 2L than a line segment LS connecting the car body connection part 30 and the crawler connection part 31 in the plan view shown in Fig. 9. Specifically, in this embodiment, the line segment LS is a line segment connecting the center of the pin insertion hole H30 (center of the pin P30) in the car body connection part 30 and the center of the pin insertion hole H31 in the first crawler connection part 31.

[0153] With the second crawler connection part 32 of the right front connecting member 11R fitted between the pair of protruding pieces PL2, the pin P31 is inserted into the pin insertion hole H32 of the second crawler connection part 32 and the pin insertion hole H6 of each of the pair of protruding pieces PL2. As a result, the second crawler connection part 32 of the right front connecting member 11R is detachably connected to the right frame main body 20R of the right crawler frame 2R arranged in the retracted position. The structure for connecting the second crawler connection parts 32 of the other connecting members 12R, 11L, 12L is similar to that described above.

[0154] In this modified example 1, the second crawler connection part 32, which is located closer to the right crawler frame 2R than the line segment LS, is connected to the right crawler frame 2R located in the retracted position, so the right front connecting member 11R is less likely to interfere with the right crawler frame 2R compared to when the second crawler connection part 32 is located on the line segment LS of the right front connecting member 11R. The same effect as that of the right front connecting member 11R can be obtained for the second crawler connection parts 32 of the other connecting members 12R, 11L, 12L.

[0155] [Modification 2 of the First Embodiment] Fig. 10 is a perspective view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the second modification of the first embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in the contracted position. Fig. 11 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the second modification of the first embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in the contracted position.

[0156] The lower running body 101 according to the second modification of the first embodiment differs from the lower running body 101 according to the first embodiment shown in Fig. 7 in the connection structure when the multiple connecting members 11R, 12R, 11L, 12L are arranged in the restrained state. The other configurations of the second modification are similar to those of the lower running body 101 according to the first embodiment, and therefore descriptions thereof will be omitted.

[0157] As shown in Figures 10 and 11, the lower running body 101 of this modified example 2 further includes a first connecting member 91 for connecting the right front connecting member 11R and the left front connecting member 11L, and a second connecting member 92 for connecting the right rear connecting member 12R and the left rear connecting member 12L.

[0158] The first connecting member 91 includes an insertion portion 91A that can be inserted into the pin insertion hole H31 in the crawler connection portion 31 of the right front connecting member 11R, an insertion portion 91B that can be inserted into the pin insertion hole H31 in the crawler connection portion 31 of the left front connecting member 11L, and a connecting portion 91C that connects these insertion portions 91A, 91B with a gap between them.

[0159] The second connecting member 92 includes an insertion portion 92A that can be inserted into the pin insertion hole H31 in the crawler connection portion 31 of the right rear connecting member 12R, an insertion portion 92B that can be inserted into the pin insertion hole H31 in the crawler connection portion 31 of the left rear connecting member 12L, and a connecting portion 92C that connects these insertion portions 92A, 92B with a gap between them.

[0160] In this modified example 2, the right front connecting member 11R and the left front connecting member 11L are arranged in the constrained state by connecting the right front connecting member 11R and the left front connecting member 11L to each other by a first connecting member 91 with the right crawler frame 2R and the left crawler frame 2L respectively arranged in the retracted position. Similarly, the right rear connecting member 12R and the left rear connecting member 12L are arranged in the constrained state by connecting the right rear connecting member 12R and the left rear connecting member 12L to each other by a second connecting member 92 with the right crawler frame 2R and the left crawler frame 2L respectively arranged in the retracted position.

[0161] [Structure of the lower running body according to the second embodiment] Fig. 12 is a perspective view showing the lower traveling body 101 according to the second embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in an expanded position. Fig. 13 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the second embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in an expanded position. Fig. 14 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the second embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in a contracted position.

[0162] In this second embodiment, the car body connection portions 30 of each of the multiple connecting members 11R, 12R, 11L, and 12L are detachably connected to the car body 10, and the crawler connection portions 31 of each of the multiple connecting members 11R, 12R, 11L, and 12L are rotatably connected to the corresponding crawler frame around an axis in the vertical direction.

[0163] In the lower running body 101 of this second embodiment, the car body 10 further has a second right front connected portion 53R and a second left front connected portion 53L between the right front connected portion 51R (first right front connected portion 51R) and the left front connected portion 51L (first left front connected portion 51L) in the left-right direction.

[0164] The second right front connected part 53R is a connected part for restraining the right front coupling member 11R when the right crawler frame 2R is disposed at the contracted position. The second right front connected part 53R is located forward and to the right of the turning center axis C and to the left of the right front connected part 51R. In this embodiment, the second right front connected part 53R is disposed on a straight line parallel to the left-right direction passing through the right front connected part 51R in a plan view. The left-right distance between the right front connected part 51R and the second right front connected part 53R is set to be approximately equal to the left-right distance between the expanded position and the contracted position of the right crawler frame 2R.

[0165] The second left front connected part 53L is a connected part for restraining the left front coupling member 11L when the left crawler frame 2L is arranged at the contracted position. The second left front connected part 53L is located forward and to the left of the turning central axis C and to the right of the left front connected part 51L. In this embodiment, the second left front connected part 53L is arranged on a straight line parallel to the left-right direction passing through the left front connected part 51L in a plan view. The left-right distance between the left front connected part 51L and the second left front connected part 53L is set to be approximately equal to the left-right distance between the expanded position and the contracted position of the left crawler frame 2L.

[0166] In addition, the car body 10 further has a second right rear connected portion 54R and a second left rear connected portion 54L between the right rear connected portion 52R (first right rear connected portion 52R) and the left rear connected portion 52L (first left rear connected portion 52L) in the left-right direction.

[0167] The second right rear connected part 54R is a connected part for restraining the right rear coupling member 12R when the right crawler frame 2R is disposed at the contracted position. The second right rear connected part 54R is located rearward and to the right of the turning center axis C and to the left of the right rear connected part 52R. In this embodiment, the second right rear connected part 54R is disposed on a straight line parallel to the left-right direction passing through the right rear connected part 52R in a plan view. The left-right distance between the right rear connected part 52R and the second right rear connected part 54R is set to be approximately equal to the left-right distance between the expanded position and the contracted position of the right crawler frame 2R.

[0168] The second left rear connected part 54L is a connected part for restraining the left rear coupling member 12L when the left crawler frame 2L is disposed at the contracted position. The second left rear connected part 54L is located rearward and to the left of the turning central axis C and to the right of the left rear connected part 52L. In this embodiment, the second left rear connected part 54L is disposed on a straight line parallel to the left-right direction passing through the left rear connected part 52L in a plan view. The left-right distance between the left rear connected part 52L and the second left rear connected part 54L is set to be approximately equal to the left-right distance between the expanded position and the contracted position of the left crawler frame 2L.

[0169] The structure of each of the second right front connected portion 53R, the second left front connected portion 53L, the second right rear connected portion 54R and the second left rear connected portion 54L need only be such that the corresponding car body connecting portion 30 can be connected thereto, and is not particularly limited thereto; however, for example, the following may be adopted:

[0170] As shown in Figures 12 to 14, for example, the second right rear connected portion 54R has a pair of protruding pieces PL3 protruding rearward from at least one of the right side portions of the car body main body 10A and the rear axle 14. These protruding pieces PL3 are arranged at a distance from each other in the vertical direction. The vertical distance (gap) between the pair of protruding pieces PL3 is set to a value slightly larger than the vertical dimension (thickness) of the car body connecting portion 30 of the right rear coupling member 12R so that the car body connecting portion 30 can be fitted thereto.

[0171] Similarly, the second left rear connected portion 54L has a pair of protruding pieces PL3 protruding rearward from at least one of the left side portions of the car body main body 10A and the rear axle 14. These protruding pieces PL3 are arranged at a distance from each other in the vertical direction. The vertical distance (gap) between the pair of protruding pieces PL3 is set to a value slightly larger than the vertical dimension (thickness) of the car body connecting portion 30 of the left rear coupling member 12L so that the car body connecting portion 30 can be fitted thereto.

[0172] In this embodiment, the upper protruding piece PL3 of the second right rear connected portion 54R and the upper protruding piece PL3 of the second left rear connected portion 54L are configured as an integral structure, and the lower protruding piece PL3 of the second right rear connected portion 54R and the lower protruding piece PL3 of the second left rear connected portion 54L are configured as an integral structure. However, the upper protruding piece PL3 of the second right rear connected portion 54R and the upper protruding piece PL3 of the second left rear connected portion 54L may be configured as separate structures, and the lower protruding piece PL3 of the second right rear connected portion 54R and the lower protruding piece PL3 of the second left rear connected portion 54L may be configured as separate structures.

[0173] Each of the pair of protruding pieces PL3 of the second right rear connected portion 54R has a pin insertion hole H52. When the right crawler frame 2R is in the contracted position as shown in FIG. 14, the pin insertion hole H52 of each of the pair of protruding pieces PL3 is disposed at the same position as the pin insertion hole H30 of the car body connecting portion 30 in a plan view when the car body connecting portion 30 of the right rear connecting member 12R is fitted between the pair of protruding pieces PL3. When the car body connecting portion 30 of the right rear connecting member 12R is fitted between the pair of protruding pieces PL3, the pin P30 is inserted into the pin insertion hole H30 of the car body connecting portion 30 and the pin insertion hole H52 of each of the pair of protruding pieces PL3. As a result, the car body connecting portion 30 of the right rear connecting member 12R is detachably connected to the car body 10 at the second right rear connected portion 54R. In other words, the right rear connecting member 12R is positioned in the restrained state because both ends thereof are connected to the car body 10 and the right crawler frame 2R by connecting the car body connection portion 30 of the right rear connecting member 12R to the second right rear connected portion 54R.

[0174] The structures of the second right front connected portion 53R and the second left front connected portion 53L are similar to those of the second right rear connected portion 54R and the second left rear connected portion 54L described with reference to Figures 12 to 14, except for their orientation, so description thereof will be omitted.

[0175] In this embodiment, for example, when the angle of the right front connecting member 11R relative to the right crawler frame 2R in the expanded connection state is the same as the angle of the right front connecting member 11R relative to the right crawler frame 2R in the restrained state, the crawler connection part 31 of the right front connecting member 11R does not necessarily have to be connected to the right front connected part 61R of the right crawler frame 2R so as to be rotatable, and may be connected (fixed) to the right crawler frame 2R in a state in which the angle cannot be changed. However, even in this case, in order to improve the workability of the work of displacing the right crawler frame 2R from the expanded position to the contracted position and the work of detachably connecting the right front connecting member 11R to the car body 10 with the right crawler frame 2R arranged in the contracted position, it is preferable that the crawler connection part 31 of the right front connecting member 11R is configured to be rotatably connected to the right crawler frame 2R. The same applies to the other connecting members 12R, 11L, 12L.

[0176] [Modification of the second embodiment] Fig. 15 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to a modified example of the second embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in the contracted position. Fig. 16 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to a modified example of the second embodiment, showing a state in which the left and right crawler frames 2R, 2L are arranged in the contracted position.

[0177] The lower running body 101 according to this modified example of the second embodiment differs from the lower running body 101 according to the second embodiment shown in Fig. 14 in the connection structure when the multiple connecting members 11R, 12R, 11L, 12L are arranged in the restrained state. The other configurations of the modified example are similar to those of the lower running body 101 according to the second embodiment, and therefore description thereof will be omitted.

[0178] As shown in Figure 15, the connection structure of the lower running body 101 in this modified example when it is placed in a restrained state is similar to the connection structure of the lower running body 101 in the modified example 2 of the first embodiment described with reference to Figures 10 and 11 when it is placed in a restrained state.

[0179] The lower running body 101 according to the modified example of the second embodiment further includes a first connecting member 91 for connecting the right front connecting member 11R and the left front connecting member 11L, and a second connecting member 92 for connecting the right rear connecting member 12R and the left rear connecting member 12L. These connecting members 91, 92 are similar to the first connecting member 91 and the second connecting member 92 in the modified example 2 of the first embodiment. That is, the first connecting member 91 includes an inserting portion 91A that can be inserted into the pin insertion hole H30 in the car body connecting portion 30 of the right front connecting member 11R, an inserting portion 91B that can be inserted into the pin insertion hole H30 in the car body connecting portion 30 of the left front connecting member 11L, and a connecting portion 91C that connects these inserting portions 91A, 91B with a gap between them. The second connecting member 92 includes an insertion portion 92A that can be inserted into the pin insertion hole H30 in the car body connection portion 30 of the right rear connecting member 12R, an insertion portion 92B that can be inserted into the pin insertion hole H30 in the car body connection portion 30 of the left rear connecting member 12L, and a connecting portion 92C that connects these insertion portions 92A, 92B with a gap between them.

[0180] In this modified example, the right front connecting member 11R and the left front connecting member 11L are arranged in the constrained state by connecting the right front connecting member 11R and the left front connecting member 11L to each other by a first connecting member 91 with the right crawler frame 2R and the left crawler frame 2L respectively arranged in the retracted position. Similarly, the right rear connecting member 12R and the left rear connecting member 12L are arranged in the constrained state by connecting the right rear connecting member 12R and the left rear connecting member 12L to each other by a second connecting member 92 with the right crawler frame 2R and the left crawler frame 2L respectively arranged in the retracted position.

[0181] In the modified example shown in Figure 15, the right front connecting member 11R and the left front connecting member 11L are connected to each other in a state in which they are each positioned so as to extend diagonally forward from the crawler connection portion 31, and the right rear connecting member 12R and the left rear connecting member 12L are connected to each other in a state in which they are each positioned so as to extend diagonally rearward from the crawler connection portion 31, but this is not limited to the embodiment.

[0182] For example, as shown in FIG. 16, the right front connecting member 11R and the left front connecting member 11L may be connected to each other in a state in which they are each positioned so as to extend diagonally rearward from the crawler connection portion 31, and the right rear connecting member 12R and the left rear connecting member 12L may be connected to each other in a state in which they are each positioned so as to extend diagonally forward from the crawler connection portion 31.

[0183] Also, as shown in FIG. 17, the right rear connected portion 52R of the car body 10 may be configured to be connected to a car body restraint portion 63 provided on the right crawler frame 2R when the right crawler frame 2R is disposed in the contracted position. The car body restraint portion 63 is configured by a protruding portion protruding leftward from the right frame main body 20R of the right crawler frame 2R, and has a pin insertion hole H63 penetrating the protruding portion in the vertical direction. The pin insertion hole H63 is disposed in the same position as the pin insertion hole H5 of the right rear connected portion 52R of the car body 10 in a plan view when the right crawler frame 2R is disposed in the contracted position. By inserting the pin P30 into the pin insertion hole H63 and the pin insertion hole H5, both ends of the right rear connecting member 12R are connected to the car body 10 and the right crawler frame 2R, so that the right rear connecting member 12R is disposed in the contracted state.

[0184] Similarly, the left rear connected portion 52L of the car body 10 may be configured to be connectable to a car body restraint portion 63 provided on the left crawler frame 2L when the left crawler frame 2L is disposed at the contracted position. The car body restraint portion 63 is configured by a protruding portion protruding to the right from the left frame main body 20L of the left crawler frame 2L, and has a pin insertion hole H63 penetrating the protruding portion in the vertical direction. The pin insertion hole H63 is disposed at the same position as the pin insertion hole H5 of the left rear connected portion 52L of the car body 10 in a plan view when the left crawler frame 2L is disposed at the contracted position. By inserting the pin P30 into the pin insertion hole H63 and the pin insertion hole H5, both ends of the left rear connecting member 12L are connected to the car body 10 and the left crawler frame 2L, so that the left rear connecting member 12L is disposed in the contracted state.

[0185] Although not shown, the right front connected portion 51R of the car body 10 may be configured to be connectable to a car body restraint portion provided on the right crawler frame 2R when the right crawler frame 2R is arranged in the contracted position, and the left front connected portion 51L of the car body 10 may be configured to be connectable to a car body restraint portion provided on the left crawler frame 2L when the left crawler frame 2L is arranged in the contracted position. Each of these car body restraint portions has a similar structure to the car body restraint portion 63 described with reference to Fig. 17 except that the orientation is different.

[0186] In the second embodiment shown in Figs. 12 to 14, in order for the right front connecting member 11R, the left front connecting member 11L, the right rear connecting member 12R and the left rear connecting member 12L to be arranged in a constrained state as shown in Fig. 14, it is necessary to fix the car body connecting portion 30 of each connecting member to a pair of protruding pieces PL3 after each of the right crawler frame 2R and the left crawler frame 2L is arranged in the contracted position. On the other hand, in the modified example shown in Figs. 15 to 17, even if each of the right crawler frame 2R and the left crawler frame 2L is not arranged in the contracted position, for example, in the expanded position, the right front connecting member 11R and the left front connecting member 11L can be rotated to connect them with the first connecting member 91, and the right rear connecting member 12R and the left rear connecting member 12L can be rotated to connect them with the second connecting member 92. Therefore, in this modified example, the fixing work for arranging each connecting member in a constrained state is facilitated, and the number of steps of the work can be reduced. In this modification, the pair of protruding pieces PL3 as shown in FIG. 12 can be omitted.

[0187] 17 is equipped with a carbody restraining portion 63, there is no need to provide, for example, a fixing structure at the tip of the front axle 13 and the tip of the rear axle 14 as a structure for holding the left and right crawler frames 2R, 2L in the retracted position. This eliminates the need to provide pin holes for the fixing structure in the front axle 13 and the rear axle 14, and also eliminates the need to provide welding points for attaching fasteners, so that a decrease in the strength of the front axle 13 and the rear axle 14 can be suppressed.

[0188] [Structure of the lower running body according to the third embodiment] FIG. 18 is a perspective view showing a lower traveling body 101 according to the third embodiment. FIG. 19 is a plan view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the third embodiment. FIGS. 18 and 19 show a state in which the left and right crawler frames 2R, 2L are arranged in an expanded position. FIG. 20 is a perspective view showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to the third embodiment, and FIG. 21 is a plan view thereof. FIGS. 20 and 21 show a state in which the left and right crawler frames 2R, 2L are arranged in a contracted position.

[0189] The lower traveling body 101 according to the third embodiment differs from the lower traveling body 101 according to the first embodiment in the structure of the multiple connecting members 11R, 12R, 11L, and 12L. The other configurations of the third embodiment are similar to those of the lower traveling body 101 according to the first embodiment, and therefore descriptions thereof will be omitted.

[0190] In the third embodiment shown in Figs. 18 to 21, the left and right crawler frames 2R, 2L can be displaced between the enlarged position and the reduced position without removing the multiple connecting members 11R, 12R, 11L, 12L from the car body 10 and the left and right crawler frames 2R, 2L. This makes it unnecessary to fix the multiple connecting members 11R, 12R, 11L, 12L to the car body 10 or the left and right crawler frames 2R, 2L using pins, for example, in the operation of enlarging or reducing the left and right crawler frames (enlargement / reduction operation), and also makes it unnecessary to align the members with each other for the purpose of fixing (fine adjustment of position). Therefore, the enlargement / reduction operation of the left and right crawler frames 2R, 2L can be simplified, and the man-hours for the enlargement / reduction operation can be reduced. Specifically, it is as follows.

[0191] Each of the multiple connecting members 11R, 12R, 11L, and 12L includes a first member M1 and a second member M2, and the first member M1 is configured to be rotatably connected to the second member M2. In each of the multiple connecting members 11R, 12R, 11L, and 12L, the car body connecting portion 30 is provided on the first member M1 and is rotatably connected to the car body 10. The crawler connecting portion 31 is provided on the second member M2 and is rotatably connected to the corresponding crawler frame of the left and right crawler frames 2R and 2L. Each of the multiple connecting members 11R, 12R, 11L, and 12L further has a connecting portion 33 at which the first member M1 is rotatably connected to the second member M2.

[0192] The right front connecting member 11R is positioned in the restrained state, with the first member M1 rotating relative to the car body 10 at the car body connection portion 30, and the second member M2 rotating relative to the right crawler frame 2R at the crawler connection portion 31, and the first member M1 rotating relative to the second member M2 at the connection portion 33, causing the relative position of the right front connecting member 11R to the car body 10 and the right crawler frame 2R to change from the expanded connection state, thereby allowing the right crawler frame 2R to be displaced from the expanded position to the contracted position.

[0193] The right rear connecting member 12R is positioned in the restrained state, with the first member M1 rotating relative to the car body 10 at the car body connection portion 30, and the second member M2 rotating relative to the right crawler frame 2R at the crawler connection portion 31, and the first member M1 rotating relative to the second member M2 at the connection portion 33, causing the relative position of the right rear connecting member 12R to the car body 10 and the right crawler frame 2R to change from the expanded connection state, thereby allowing the right crawler frame 2R to be displaced from the expanded position to the contracted position.

[0194] The left front connecting member 11L is positioned in the restrained state, with the first member M1 rotating relative to the car body 10 at the car body connection portion 30, and the second member M2 rotating relative to the left crawler frame 2L at the crawler connection portion 31, and the first member M1 rotating relative to the second member M2 at the connection portion 33, causing the relative position of the left front connecting member 11L to the car body 10 and the left crawler frame 2L to change from the expanded connection state, thereby allowing the left crawler frame 2L to be displaced from the expanded position to the contracted position.

[0195] The left rear connecting member 12L is positioned in the restrained state, with the first member M1 rotating relative to the car body 10 at the car body connection portion 30, and the second member M2 rotating relative to the left crawler frame 2L at the crawler connection portion 31, and the first member M1 rotating relative to the second member M2 at the connection portion 33, causing the relative position of the left rear connecting member 12L to the car body 10 and the left crawler frame 2L to change from the expanded connection state, thereby allowing the left crawler frame 2L to be displaced from the expanded position to the contracted position.

[0196] Each of the connecting portions 33 of the multiple connecting members 11R, 12R, 11L, and 12L may have a structure as shown in FIG. 20. That is, an end portion 34 of the first member M1 opposite to the car body connecting portion 30 is configured by a pair of protruding pieces PL4, and an end portion 35 of the second member M2 opposite to the crawler connecting portion 31 is configured by a protruding piece PL5. The protruding piece PL5 of the second member M2 is fitted between the pair of protruding pieces PL4 of the first member M1. The pair of protruding pieces PL4 and the protruding piece PL5 each have a pin insertion hole H7 that penetrates in the vertical direction in this fitted state. A pin P33 is inserted into these pin insertion holes H7. As a result, the first member M1 is rotatably connected to the second member M2 at the connecting portion 33.

[0197] In this embodiment, each of the multiple connecting members 11R, 12R, 11L, 12L has a first member M1, a member main body including a car body connection portion 30 and an end portion 34, and a rotation direction limiting portion 36 extending from the member main body along the inner surface of the second member M2 when the left and right crawler frames 2R, 2L are each arranged in the expanded position. The rotation direction limiting portion 36 of each of the multiple connecting members 11R, 12R, 11L, 12L allows the first member M1 to rotate relative to the second member M2 in either a clockwise or counterclockwise direction in a plan view at the connecting portion 33 and prevents the first member M1 from rotating relative to the second member M2 in the other direction, clockwise or counterclockwise, in a plan view, when the left and right crawler frames 2R, 2L are each arranged in the expanded position.

[0198] Specifically, in the right front connecting member 11R, as shown in Fig. 19, the rotation direction limiting portion 36 extends diagonally forward and to the right from the tip of the member body of the first member M1 along the left side surface of the second member M2 and is disposed adjacent to the left side surface of the second member M2. Therefore, when the right crawler frame 2R is disposed in the expanded position as shown in Fig. 19, this rotation direction limiting portion 36 allows the first member M1 to rotate relatively to the second member M2 counterclockwise in plan view at the connecting portion 33, but prevents relative rotation clockwise in plan view.

[0199] In the right rear connecting member 12R, the rotation direction limiting portion 36 extends diagonally rearward to the right from the tip of the member body of the first member M1 along the left side surface of the second member M2 and is disposed adjacent to the left side surface of the second member M2. Therefore, when the right crawler frame 2R is disposed in the expanded position as shown in Fig. 19, this rotation direction limiting portion 36 allows the first member M1 to rotate relatively to the second member M2 in a clockwise direction in plan view at the connecting portion 33 while preventing the first member M1 from rotating relatively to the second member M2 in a counterclockwise direction in plan view.

[0200] In the left front connecting member 11L, the rotation direction limiting portion 36 extends diagonally forward and left from the tip of the member body of the first member M1 along the right side surface of the second member M2 and is disposed adjacent to the right side surface of the second member M2. Therefore, when the left crawler frame 2L is disposed in the expanded position as shown in Fig. 19, this rotation direction limiting portion 36 allows the first member M1 to rotate relative to the second member M2 in a clockwise direction in plan view at the connecting portion 33 while preventing the first member M1 from rotating relative to the second member M2 in a counterclockwise direction in plan view.

[0201] In the left rear connecting member 12L, the rotation direction limiting portion 36 extends diagonally rearward and left from the tip of the member body of the first member M1 along the right side surface of the second member M2 and is disposed adjacent to the right side surface of the second member M2. Therefore, when the left crawler frame 2L is disposed in the expanded position as shown in Fig. 19, this rotation direction limiting portion 36 allows the first member M1 to rotate relatively to the second member M2 counterclockwise in plan view at the connecting portion 33 while preventing relative rotation clockwise in plan view.

[0202] [Modification of the third embodiment] Fig. 22 and Fig. 23 are plan views showing the car body 10 and the left and right crawler frames 2R, 2L of the lower traveling body 101 according to a modified example of the third embodiment. Fig. 22 shows the left and right crawler frames 2R, 2L in an expanded position. Fig. 23 shows the left and right crawler frames 2R, 2L in a contracted position.

[0203] As shown in Figures 22 and 23, in this modification, the right crawler frame 2R further has a rotation direction limiting portion 37R and a rotation direction limiting portion 38R, and the left crawler frame 2L further has a rotation direction limiting portion 37L and a rotation direction limiting portion 38L.

[0204] The rotation direction limiting portion 37R has a shape that protrudes to the left side from the right frame main body 20R of the right crawler frame 2R, and is disposed so as to abut or be close to the right side surface of the second member M2 of the right front connecting member 11R when the right crawler frame 2R is disposed in the expanded position as shown in Fig. 22. Therefore, this rotation direction limiting portion 37R allows the first member M1 of the right front connecting member 11R to rotate relatively counterclockwise in plan view with respect to the second member M2 at the connecting portion 33 as shown in Fig. 23, while preventing it from rotating relatively clockwise in plan view.

[0205] The rotation direction limiting portion 38R has a shape that protrudes to the left side from the right frame main body 20R of the right crawler frame 2R, and is disposed so as to abut or be close to the right side surface of the second member M2 of the right rear connecting member 12R when the right crawler frame 2R is disposed in the expanded position as shown in Fig. 22. Therefore, this rotation direction limiting portion 38R allows the first member M1 of the right rear connecting member 12R to rotate relatively clockwise in plan view with respect to the second member M2 at the connecting portion 33 as shown in Fig. 23, while preventing it from rotating relatively counterclockwise in plan view.

[0206] The rotation direction limiting portion 37L has a shape that protrudes to the right from the left frame main body 20L of the left crawler frame 2L, and is disposed so as to abut or be close to the left side surface of the second member M2 of the left front connecting member 11L when the left crawler frame 2L is disposed in the expanded position as shown in Fig. 22. Therefore, this rotation direction limiting portion 37L allows the first member M1 of the left front connecting member 11L to rotate relatively clockwise in plan view with respect to the second member M2 at the connecting portion 33 as shown in Fig. 23, while preventing it from rotating relatively counterclockwise in plan view.

[0207] The rotation direction limiting portion 38L has a shape that protrudes to the right from the left frame main body 20L of the left crawler frame 2L, and is disposed so as to abut or be close to the left side surface of the second member M2 of the left rear connecting member 12L when the left crawler frame 2L is in the expanded position as shown in Fig. 22. Therefore, this rotation direction limiting portion 38L allows the first member M1 of the left rear connecting member 12L to rotate relatively counterclockwise in plan view with respect to the second member M2 at the connecting portion 33 as shown in Fig. 23, while preventing it from rotating relatively clockwise in plan view.

[0208] The present invention is not limited to the above-described embodiment. The present invention includes, for example, the following aspects.

[0209] (A) Car body connection and crawler connection Some of the four connecting members may be configured so that the car body connection portion is rotatably connected to the car body 10 and the crawler connection portion is detachably connected to the crawler frame, and the remaining connecting members of the four connecting members may be configured so that the car body connection portion is detachably connected to the car body 10 and the crawler connection portion is rotatably connected to the crawler frame.

[0210] (B) Regarding the parts where the car body connection part is connected and the parts where the crawler connection part is connected In the lower traveling body 101 according to the first embodiment, the part of the crawler frame to which the crawler connection part is connected when the connecting member is arranged in a restrained state is not limited to the aspect exemplified in the specification. In the lower traveling body 101 according to the second embodiment, the part of the car body to which the car body connection part is connected when the connecting member is arranged in a restrained state is not limited to the aspect exemplified in the specification.

[0211] (C) Right front line, right rear line, left front line and left rear line In the first and second embodiments, the multiple connecting members are configured such that, in a plan view, the right front straight line LA passes through the right front end roller 261, the right rear straight line LB passes through the right rear end roller 262, the left front straight line LC passes through the left front end roller 261, and the left rear straight line LD passes through the left rear end roller 262, but are not limited to such an aspect. The right front straight line LA may pass in front of or behind the right front end roller 261, the right rear straight line LB may pass behind or in front of the right rear end roller 262, the left front straight line LC may pass in front of or behind the left front end roller 261, and the left rear straight line LD may pass behind or in front of the left rear end roller 262.

[0212] In the above embodiment, the right front straight line LA is a straight line that connects the central position of the right front end roller 261 in the width direction (left-right direction) on the rotation central axis of the right front end roller 261 and the turning central axis C in a plan view, and the right rear straight line LB, the left front straight line LC, and the left rear straight line LD are similarly defined, but are not limited to such an embodiment. The right front straight line LA may be, for example, a straight line that connects the turning central axis C and any part of the right front end roller 261 that has been selected in advance in a plan view. The any part may be, for example, the rearmost and rightmost part of the right front end roller 261 in a plan view. Similarly, the right rear straight line LB may be, in a planar view, a straight line connecting the pivot axis C and any pre-selected portion of the right rear end roller 262, the left front straight line LC may be, for example, in a planar view, a straight line connecting the pivot axis C and any pre-selected portion of the left front end roller 261, and the left rear straight line LD may be, in a planar view, a straight line connecting the pivot axis C and any pre-selected portion of the left rear end roller 262.

[0213] (D) Orientation of the load suspended from the upper rotating body The present invention can suppress deformation of each crawler frame when a load is suspended from the upper rotating body with the load positioned in front of or behind the lower running body, but does not exclude the application of the present invention to a case where the load is suspended from the upper rotating body with the load positioned to the side of the lower running body.

[0214] (E) Crane specifications The crane according to the embodiment shown in Fig. 1 does not include a jib and a strut, but the specifications of the crane are not limited to those shown in Fig. 1. The crane according to the present disclosure may be a luffing crane including a jib, a front strut, and a rear strut, or may be a fixed jib crane including a jib and one strut. In addition, the crane according to the present disclosure may be a crane including a mast instead of a gantry (e.g., a large crane). [Explanation of symbols]

[0215] 2L: Left crawler frame 2R: Right crawler frame 10: Car body 10A: Car body 11L: Left front connecting member 11R: Right front connecting member 12L: Left rear connecting member 12R: Right rear connecting member 13: Front axle 14: Rear axle 26: Right roller, left roller 261: Right front roller, left front roller 262: Right rear roller, left rear roller 27: Left front axle support, right front axle support 28: Right rear axle support, left rear axle support 30: Car body connection part 31: Crawler connection part (first crawler connection part) 32: Second crawler connection part 33:Connection part 36, 37L, 37R, 38L, 38R: Rotation direction limiting section 100: Mobile crane 101: Lower running body 102: Upper rotating body C: Rotation center axis CX: Right front continuous part, left front continuous part, left rear continuous part, right rear continuous part LA: Right front straight line LB:Right rear straight line LC: Front left straight line LD: Left rear straight line LS : Line segment M1: First member M2: 2nd member

Claims

1. A lower running body of a mobile crane, a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to be detached from one of the car body and the right crawler frame and connected to the other member while changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state, thereby allowing the right crawler frame to be displaced from the expanded position to the contracted position, and is configured to be capable of being disposed in a constrained state in which the right crawler frame is constrained by both the right crawler frame and the car body that are disposed in the contracted position, The left front connecting member and the left rear connecting member are each configured to be detached from one of the members of the car body and the left crawler frame and to remain connected to the other member, thereby allowing the left crawler frame to displace from the expanded position to the retracted position by changing the relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state, and are also configured to be capable of being positioned in a constrained state in which they are constrained to both the left crawler frame and the car body that are positioned in the retracted position.

2. 2. The undercarriage of the mobile crane according to claim 1, a pair of right wheels rotatably supported on front and rear ends of the right crawler frame; a pair of left wheels rotatably supported on front and rear ends of the left crawler frame; a plurality of right rollers disposed at intervals in the front-rear direction between the pair of right wheels and rotatably supported on a lower portion of the right crawler frame, the plurality of right rollers including a right front end roller located at the forefront and a right rear end roller located at the rearmost; a plurality of left rollers disposed at intervals in the front-rear direction between the pair of left wheels and rotatably supported on a lower portion of the left crawler frame, the plurality of left rollers including a left front end roller located at the frontmost position and a left rear end roller located at the rearmost position, the right front connecting member has a right front load receiving surface facing the car body and a right front load transmitting surface facing the right crawler frame, the left front connecting member has a left front load receiving surface facing the car body and a left front load transmitting surface facing the left crawler frame, each of the right front load receiving surface of the right front connecting member and the left front load receiving surface of the left front connecting member is a surface that can receive, from the car body, a front load that is a load that the car body receives from the upper rotating body when a load is suspended from the upper rotating body forward of the lower running body, the right front load transfer surface is a surface that can transfer the front load to the right crawler frame, and the left front load transfer surface is a surface that can transfer the front load to the left crawler frame, the right front connecting member is configured such that a right front straight line, which is a straight line passing through any point included in the right front load receiving surface and any point included in the right front load transfer surface in a plan view, passes through the right front end roller or a side forward of the right front end roller, The left front connecting member is a lower running body of a mobile crane, and is configured so that a left front straight line, which is a straight line passing through any point included in the left front load receiving surface and any point included in the left front load transfer surface in a planar view, passes through the left front end roller or forward of the left front end roller.

3. A lower traveling body of the mobile crane according to claim 2, A lower running body of a mobile crane, wherein the right front straight line is a straight line passing through the right front end roller in a plan view, and the left front straight line is a straight line passing through the left front end roller in a plan view.

4. A lower traveling body of the mobile crane according to claim 3, A lower running body of a mobile crane, wherein the right front straight line is a straight line that further passes through the central axis of rotation in a plan view, and the left front straight line is a straight line that further passes through the central axis of rotation in a plan view.

5. A lower traveling body of a mobile crane according to any one of claims 2 to 4, the right front connecting member has a right front continuing portion that continues from the right front load receiving surface to the right front load transmitting surface along the right front straight line in a plan view, The left front connecting member has a left front continuing portion that continues from the left front load receiving surface to the left front load transfer surface along the left front straight line in a plan view, the lower running body of a mobile crane.

6. A lower traveling body of a mobile crane according to any one of claims 2 to 5, the right rear connecting member has a right rear load receiving surface facing the car body and a right rear load transmitting surface facing the right crawler frame, the left rear connecting member has a left rear load receiving surface facing the car body and a left rear load transmitting surface facing the left crawler frame, each of the right rear load receiving surface of the right rear connecting member and the left rear load receiving surface of the left rear connecting member is a surface that can receive a rear load from the car body, which is a load that the car body receives from the upper rotating body when a load is suspended from the upper rotating body rearward of the lower running body, the right rear load transfer surface is a surface that can transfer the rear load to the right crawler frame, and the left rear load transfer surface is a surface that can transfer the rear load to the left crawler frame, the right rear connecting member is configured such that a right rear straight line, which is a straight line passing through any point included in the right rear load receiving surface and any point included in the right rear load transfer surface in a plan view, passes through the right rear end roller or a side rearward of the right rear end roller, The left rear connecting member is a lower running body of a mobile crane, configured so that a left rear straight line, which is a straight line passing through any point included in the left rear load receiving surface and any point included in the left rear load transfer surface in a planar view, passes through the left rear end roller or rear of the left rear end roller.

7. A lower traveling body of a mobile crane according to claim 6, A lower running body of a mobile crane, wherein the right rear straight line is a straight line passing through the right rear end roller in a plan view, and the left rear straight line is a straight line passing through the left rear end roller in a plan view.

8. A lower body of a mobile crane according to claim 7, A lower running body of a mobile crane, wherein the right rear straight line is a straight line that further passes through the central axis of rotation in a plan view, and the left rear straight line is a straight line that further passes through the central axis of rotation in a plan view.

9. A lower traveling body of a mobile crane according to any one of claims 6 to 8, the right rear connecting member has a right rear continuing portion that continues from the right rear load receiving surface to the right rear load transmitting surface along the right rear straight line in a plan view, The left rear connecting member has a left rear continuing portion that continues from the left rear load receiving surface to the left rear load transfer surface along the left rear straight line in a plan view, the lower running body of a mobile crane.

10. A lower running body of a mobile crane, comprising: a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the contracted position by changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state while remaining connected to at least one of the car body and the right crawler frame; each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the contracted position by a change in a relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state while remaining connected to at least one of the car body and the left crawler frame; each of the right front connecting member and the right rear connecting member is configured to be capable of being disposed in a constrained state in which the right front connecting member and the right rear connecting member are constrained by at least one of the right crawler frame and the car body that are disposed in the retracted position; each of the left front connecting member and the left rear connecting member is configured to be capable of being disposed in a constrained state in which the left front connecting member and the left rear connecting member are constrained by at least one of the left crawler frame and the car body that are disposed in the retracted position; a right connecting member which is at least one of the right front connecting member and the right rear connecting member, has a car body connection portion which is rotatably connected to the car body, and a crawler connection portion which is detachably connected to the right crawler frame disposed at the expanded position, The right connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion is detached from the right crawler frame and the car body connection portion remains connected to the car body, causing the right connecting member to rotate relative to the car body at the car body connection portion so that the relative position of the right connecting member to the car body and the right crawler frame changes from the expanded connection state, and is positioned in the constrained state by being detachably connected to the right crawler frame positioned in the contracted position.

11. The undercarriage of the mobile crane according to claim 10, The right connecting member further has a second crawler connection portion that can be detachably connected to the right crawler frame when positioned in the retracted position, and the second crawler connection portion connected to the right crawler frame when positioned in the retracted position is positioned at a position closer to the right crawler frame in a plan view than a line segment connecting the car body connection portion and the crawler connection portion.

12. The undercarriage of the mobile crane according to claim 11, a left connecting member which is at least one of the left front connecting member and the left rear connecting member, the left connecting member having a car body connecting portion rotatably connected to the car body and a crawler connecting portion detachably connected to the left crawler frame disposed at the expanded position, the left connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the left connecting member is detached from the left crawler frame and the carbody connection portion of the left connecting member remains connected to the carbody, causing the left connecting member to rotate relative to the carbody at the carbody connection portion of the left connecting member so that a relative position of the left connecting member to the carbody and the left crawler frame changes from the expanded connection state, and the left connecting member is removably connected to the left crawler frame that is positioned in the contracted state, thereby allowing the left crawler frame to be displaced from the expanded position to the contracted position.

13. 13. The undercarriage of the mobile crane according to claim 12, the left connecting member further has a second crawler connection portion that can be detachably connected to the left crawler frame when positioned in the retracted position, and the second crawler connection portion connected to the left crawler frame when positioned in the retracted position is positioned at a position closer to the left crawler frame in a plan view than a line segment connecting the carbody connection portion of the left connecting member and the crawler connection portion of the left connecting member.

14. A lower running body of a mobile crane, comprising: a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the contracted position by changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state while remaining connected to at least one of the car body and the right crawler frame; each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the contracted position by a change in a relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state while remaining connected to at least one of the car body and the left crawler frame; each of the right front connecting member and the right rear connecting member is configured to be capable of being disposed in a constrained state in which the right front connecting member and the right rear connecting member are constrained by at least one of the right crawler frame and the car body that are disposed in the retracted position; each of the left front connecting member and the left rear connecting member is configured to be capable of being disposed in a constrained state in which the left front connecting member and the left rear connecting member are constrained by at least one of the left crawler frame and the car body that are disposed in the retracted position; the right front connecting member has a car body connection portion rotatably connected to the car body, and a crawler connection portion detachably connected to the right crawler frame disposed at the expanded position, the left front connecting member has a car body connection part rotatably connected to the car body, and a crawler connection part detachably connected to the left crawler frame disposed at the expanded position, the right front connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the right front connecting member is detached from the right crawler frame and the car body connection portion of the right front connecting member remains connected to the car body and the right front connecting member rotates with respect to the car body at the car body connection portion, thereby changing a relative position of the right front connecting member with respect to the car body and the right crawler frame from the expanded connection state, the left front connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the left front connecting member is detached from the left crawler frame and the car body connection portion of the left front connecting member remains connected to the car body and the left front connecting member rotates with respect to the car body at the car body connection portion, thereby changing a relative position of the left front connecting member with respect to the car body and the left crawler frame from the expanded connection state, The right front connecting member and the left front connecting member are arranged in the restrained state by connecting the right front connecting member and the left front connecting member to each other when the right crawler frame and the left crawler frame are each arranged in the retracted position, a lower running body of a mobile crane.

15. 15. The undercarriage of the mobile crane according to claim 14, the right rear connecting member has a car body connection portion rotatably connected to the car body, and a crawler connection portion detachably connected to the right crawler frame disposed at the expanded position, the left rear connecting member has a car body connection portion rotatably connected to the car body, and a crawler connection portion detachably connected to the left crawler frame disposed at the expanded position, the right rear connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the right rear connecting member is detached from the right crawler frame and the car body connection portion of the right rear connecting member remains connected to the car body and the right rear connecting member rotates with respect to the car body at the car body connection portion, thereby changing a relative position of the right rear connecting member with respect to the car body and the right crawler frame from the expanded connection state, the left rear connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position when the crawler connection portion of the left rear connecting member is detached from the left crawler frame and the carbody connection portion of the left rear connecting member remains connected to the carbody and the left rear connecting member rotates with respect to the carbody at the carbody connection portion so that a relative position of the left rear connecting member with respect to the carbody and the left crawler frame changes from the expanded connection state, The right rear connecting member and the left rear connecting member are arranged in the restrained state by connecting the right rear connecting member and the left rear connecting member to each other with the right crawler frame and the left crawler frame each being arranged in the retracted position, a lower running body of a mobile crane.

16. A lower running body of a mobile crane, comprising: a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the contracted position by changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state while remaining connected to at least one of the car body and the right crawler frame; each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the contracted position by a change in a relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state while remaining connected to at least one of the car body and the left crawler frame; each of the right front connecting member and the right rear connecting member is configured to be capable of being disposed in a constrained state in which the right front connecting member and the right rear connecting member are constrained by at least one of the right crawler frame and the car body that are disposed in the retracted position; each of the left front connecting member and the left rear connecting member is configured to be capable of being disposed in a constrained state in which the left front connecting member and the left rear connecting member are constrained by at least one of the left crawler frame and the car body that are disposed in the retracted position; a right connecting member which is at least one of the right front connecting member and the right rear connecting member, has a car body connection portion which is detachably connected to the car body, and a crawler connection portion which is connected to the right crawler frame disposed at the expanded position, The right connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the carbody connection part is detached from the carbody and the relative position of the right connecting member with respect to the carbody changes from the expanded connection state while the crawler connection part remains connected to the right crawler frame, and is positioned in the constrained state by being detachably connected to the carbody when the right crawler frame is positioned in the contracted position.

17. 17. The undercarriage of the mobile crane of claim 16, a left connecting member which is at least one of the left front connecting member and the left rear connecting member, the left connecting member having a car body connecting portion detachably connected to the car body and a crawler connecting portion connected to the left crawler frame disposed at the expanded position, the left connecting member allows the left crawler frame to displace from the expanded position to the contracted position when the carbody connection portion of the left connecting member is detached from the carbody and the relative position of the left connecting member to the carbody changes from the expanded connection state while the crawler connection portion of the left connecting member remains connected to the left crawler frame, and the left crawler frame is positioned in the constrained state by being detachably connected to the carbody when positioned in the contracted position.

18. A lower running body of a mobile crane, comprising: a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the contracted position by changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state while remaining connected to at least one of the car body and the right crawler frame; each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the contracted position by a change in a relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state while remaining connected to at least one of the car body and the left crawler frame; each of the right front connecting member and the right rear connecting member is configured to be capable of being disposed in a constrained state in which the right front connecting member and the right rear connecting member are constrained by at least one of the right crawler frame and the car body that are disposed in the retracted position; each of the left front connecting member and the left rear connecting member is configured to be capable of being disposed in a constrained state in which the left front connecting member and the left rear connecting member are constrained by at least one of the left crawler frame and the car body that are disposed in the retracted position; the right front coupling member has a car body connection portion that is detachably connected to the car body when the right crawler frame is disposed at the expanded position, and a crawler connection portion that is rotatably connected to the right crawler frame, the left front connecting member has a car body connection part that is detachably connected to the car body when the left crawler frame is disposed at the expanded position, and a crawler connection part that is rotatably connected to the left crawler frame, the right front connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the car body connection portion of the right front connecting member is detached from the car body and the crawler connection portion of the right front connecting member remains connected to the right crawler frame and the right front connecting member rotates at the crawler connection portion with respect to the right crawler frame, causing a relative position of the right front connecting member with respect to the car body and the right crawler frame to change from the expanded connection state, the left front connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position when the car body connection portion of the left front connecting member is detached from the car body and the crawler connection portion of the left front connecting member remains connected to the left crawler frame and the left front connecting member rotates at the crawler connection portion with respect to the left crawler frame so that a relative position of the left front connecting member with respect to the car body and the left crawler frame changes from the expanded connection state, The right front connecting member and the left front connecting member are arranged in the restrained state by connecting the right front connecting member and the left front connecting member to each other when the right crawler frame and the left crawler frame are each arranged in the retracted position, a lower running body of a mobile crane.

19. 20. The undercarriage of the mobile crane of claim 18, the right rear connecting member has a car body connection portion that is detachably connected to the car body when the right crawler frame is disposed at the expanded position, and a crawler connection portion that is rotatably connected to the right crawler frame, the left rear connecting member has a car body connection portion that is detachably connected to the car body when the left crawler frame is disposed at the expanded position, and a crawler connection portion that is rotatably connected to the left crawler frame, the right rear connecting member allows the right crawler frame to be displaced from the expanded position to the contracted position when the car body connection portion of the right rear connecting member is detached from the car body and the crawler connection portion of the right rear connecting member remains connected to the right crawler frame and the right rear connecting member rotates at the crawler connection portion with respect to the right crawler frame, causing a relative position of the right rear connecting member with respect to the car body and the right crawler frame to change from the expanded connection state, the left rear connecting member allows the left crawler frame to be displaced from the expanded position to the contracted position when the car body connection portion of the left rear connecting member is detached from the car body and the crawler connection portion of the left rear connecting member remains connected to the left crawler frame and the left rear connecting member rotates at the crawler connection portion with respect to the left crawler frame so that a relative position of the left rear connecting member with respect to the car body and the left crawler frame changes from the expanded connection state, The right rear connecting member and the left rear connecting member are arranged in the restrained state by connecting the right rear connecting member and the left rear connecting member to each other with the right crawler frame and the left crawler frame each being arranged in the retracted position, a lower running body of a mobile crane.

20. A lower traveling body of a mobile crane according to any one of claims 16 to 19, the car body has a connected portion to which the car body connecting portion is detachably connected when the right crawler frame and the left crawler frame are each disposed in the expanded position, A lower running body of a mobile crane is configured so that when the car body connection part is detached from the connected part and the right crawler frame and the left crawler frame are each positioned in the retracted position, the connected part can be connected to a corresponding one of the right crawler frame and the left crawler frame.

21. A lower running body of a mobile crane, comprising: a carbody including a carbody main body that rotatably supports an upper rotating body of the mobile crane around a rotating center axis, front axles extending from the carbody main body to the right and left, respectively, and rear axles extending from the carbody main body to the right and left, respectively, rearward of the front axles; a right crawler frame extending in a front-rear direction on a right side of the car body; a left crawler frame extending in the front-rear direction on the left side of the car body; A plurality of connecting members, the right crawler frame has a right front axle support portion and a right rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the right crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the right crawler frame is smaller than that in the expanded position, the left crawler frame has a left front axle support portion and a left rear axle support portion that support the front axle and the rear axle, respectively, so that a position of the left crawler frame in a left-right direction with respect to the front axle and the rear axle can be changed between an expanded position and a contracted position in which a distance between the turning center axis and the left crawler frame is smaller than that in the expanded position, The plurality of connecting members include a right front connecting member, a right rear connecting member, a left front connecting member, and a left rear connecting member, the right front connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is forward of the right front axle support portion, the right rear connecting member is configured to be capable of being disposed in an expanded connection state in which the right crawler frame is connected to the car body when the right crawler frame is disposed in the expanded position, and is connected to a portion of the right crawler frame that is rearward of the right rear axle support portion, the left front connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is forward of the left front axle support portion, the left rear connecting member is configured to be capable of being disposed in an expanded connection state in which the left crawler frame is connected to the car body when the left crawler frame is disposed in the expanded position, and is connected to a portion of the left crawler frame that is rearward of the left rear axle support portion, each of the right front connecting member and the right rear connecting member is configured to allow the right crawler frame to be displaced from the expanded position to the contracted position by changing a relative position with respect to at least one of the car body and the right crawler frame from the expanded connection state while remaining connected to at least one of the car body and the right crawler frame; each of the left front connecting member and the left rear connecting member is configured to allow the left crawler frame to be displaced from the expanded position to the contracted position by a change in a relative position with respect to at least one of the car body and the left crawler frame from the expanded connection state while remaining connected to at least one of the car body and the left crawler frame; each of the right front connecting member and the right rear connecting member is configured to be capable of being disposed in a constrained state in which the right front connecting member and the right rear connecting member are constrained by at least one of the right crawler frame and the car body that are disposed in the retracted position; each of the left front connecting member and the left rear connecting member is configured to be capable of being disposed in a constrained state in which the left front connecting member and the left rear connecting member are constrained by at least one of the left crawler frame and the car body that are disposed in the retracted position; a right connecting member which is at least one of the right front connecting member and the right rear connecting member includes a first member and a second member, and has a car body connection portion provided on the first member and rotatably connected to the car body, a crawler connection portion provided on the second member and rotatably connected to the right crawler frame, and a connecting portion through which the first member is rotatably connected to the second member, the right connecting member is arranged in the restrained state, wherein the first member rotates relative to the carbody at the carbody connection portion, the second member rotates relative to the right crawler frame at the crawler connection portion, and the first member rotates relative to the second member at the connection portion, thereby changing the relative position of the right connecting member with respect to the carbody and the right crawler frame from the expanded connection state, thereby allowing the right crawler frame to displace from the expanded position to the contracted position and being positioned in the restrained state.

22. 22. The undercarriage of the mobile crane of claim 21, At least one of the first member and the second member of the right connecting member has a rotation direction limiting portion that allows the first member to rotate relative to the second member in either a clockwise or counterclockwise direction in a planar view at the connecting portion, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a planar view.

23. 23. The undercarriage of the mobile crane according to claim 21 or 22, The right crawler frame is a lower running body of a mobile crane, and has a rotation direction limiting portion that allows the first member of the right connecting member to rotate relative to the second member at the connecting portion in either a clockwise or counterclockwise direction in a plan view, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a plan view.

24. A lower traveling body of a mobile crane according to any one of claims 21 to 23, a left connecting member which is at least one of the left front connecting member and the left rear connecting member includes a first member and a second member, and has a car body connection portion provided on the first member and rotatably connected to the car body, a crawler connection portion provided on the second member and rotatably connected to the left crawler frame, and a connecting portion through which the first member is rotatably connected to the second member, the left connecting member is positioned in the restrained state, wherein the first member rotates relative to the carbody at the carbody connection portion, the second member rotates relative to the left crawler frame at the crawler connection portion, and the first member rotates relative to the second member at the connection portion, causing a relative position of the left connecting member with respect to the carbody and the left crawler frame to change from the expanded connection state, thereby allowing the left crawler frame to displace from the expanded position to the contracted position, and the left connecting member is positioned in the restrained state.

25. 25. The undercarriage of the mobile crane of claim 24, At least one of the first member and the second member of the left connecting member has a rotation direction limiting portion that allows the first member to rotate relative to the second member in either a clockwise or counterclockwise direction in a planar view at the connecting portion, and prevents the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a planar view.

26. 26. The undercarriage of the mobile crane according to claim 24 or 25, the left crawler frame has a lower running body of a mobile crane, which allows the first member of the left connecting member to rotate relative to the second member at the connecting portion in either a clockwise or counterclockwise direction in a plan view, and has a rotation direction limiting portion for preventing the first member from rotating relative to the second member in the other of the clockwise and counterclockwise directions in a plan view.

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