Work machine

Abstract

A work machine comprises: a telescopic boom that has a plurality of booms; and an electric telescopic device that extends and contracts the telescopic boom. The electric telescopic device has: a feed screw part that extends in the axial direction of the booms; and a moving part that has a female screw part for engaging with the feed screw part and moves in the axial direction on the basis of relative rotation between the feed screw part and the female screw part to extend and contract the booms in a state of being engaged with the booms.

Description

Work equipment

[0001] The present invention relates to a work machine equipped with a telescopic boom.

[0002] Patent Document 1 discloses a mobile crane equipped with a telescopic boom in which multiple booms are nested and overlapped, and a hydraulic telescopic device (telescopic cylinder) for extending the telescopic boom.

[0003] Adjacent booms are connected by boom connecting pins. A boom that is released from this connection (hereinafter referred to as a movable boom) can move in the extension / retraction direction relative to other booms.

[0004] Furthermore, the telescopic device is connected to the movable boom via a cylinder connecting pin. In this state, when the telescopic device moves in the extension or retraction direction, the movable boom moves together with the telescopic device, causing the telescopic boom to extend or retract.

[0005] Japanese Patent Publication No. 2012-96928

[0006] Incidentally, the cranes described above are equipped with a mechanism for supplying hydraulic fluid to the telescopic gear. The hydraulic circuit that constitutes this mechanism is located on the telescopic boom together with the telescopic gear. This limits the design freedom of the telescopic boom.

[0007] The objective of the present invention is to provide a work machine that can improve the design flexibility of a telescopic boom.

[0008] One embodiment of the work machine according to the present invention comprises a telescopic boom having a plurality of booms, and an electric telescopic device for extending and retracting the telescopic boom, wherein the electric telescopic device has a feed screw portion extending in the axial direction of the boom, and a movable portion having a female screw portion that screws into the feed screw portion, and which moves in the axial direction based on the relative rotation between the feed screw portion and the female screw portion while engaged with the boom to extend and retract the boom.

[0009] According to the present invention, it is possible to provide a work machine that can improve the design flexibility of a telescopic boom.

[0010] Figure 1 is a schematic diagram of a mobile crane according to an embodiment of the present invention. Figure 2A is a schematic diagram illustrating the boom extension operation. Figure 2B is a schematic diagram illustrating the boom extension operation. Figure 2C is a schematic diagram illustrating the boom extension operation. Figure 2D is a schematic diagram illustrating the boom extension operation. Figure 2E is a schematic diagram illustrating the boom extension operation. Figure 2F is a schematic diagram illustrating the boom extension operation. Figure 3A is a schematic diagram illustrating the boom retraction operation. Figure 3B is a schematic diagram illustrating the boom retraction operation. Figure 3C is a schematic diagram illustrating the boom retraction operation. Figure 3D is a schematic diagram illustrating the boom retraction operation. Figure 3E is a schematic diagram illustrating the boom retraction operation. Figure 4 shows the telescopic boom, indicated by arrow A in Figure 2A. ａ This is a schematic diagram viewed from the direction shown. Figure 5A is a schematic diagram illustrating the operation of the first coupling mechanism. Figure 5B is a schematic diagram illustrating the operation of the first coupling mechanism. Figure 5C is a schematic diagram illustrating the operation of the first coupling mechanism. Figure 6A is a schematic diagram illustrating the operation of the second coupling mechanism. Figure 6B is a schematic diagram illustrating the operation of the second coupling mechanism. Figure 6C is a schematic diagram illustrating the operation of the second coupling mechanism. Figure 7 is a schematic diagram of the moving part. Figure 8 is the X of Figure 7. １ -X １ This is a cross-sectional view. Figure 9A is a schematic diagram illustrating the position of the second electric motor. Figure 9B is a schematic diagram illustrating a modified example 1 of the position of the second electric motor. Figure 9C is a schematic diagram illustrating a modified example 2 of the position of the second electric motor.

[0011] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Note that the crane according to the embodiment described later is an example of a work machine according to the present invention, and the present invention is not limited to the embodiments described later.

[0012] [Embodiment] A mobile crane 1 according to an embodiment of the present invention will be described with reference to Figures 1 to 8. First, an overview of the mobile crane 1 according to an embodiment of the present invention will be described with reference to Figure 1.

[0013] Examples of mobile cranes include rough terrain cranes, all-terrain cranes, truck cranes, or truck-mounted cranes. However, the work equipment is not limited to mobile cranes and may include other work equipment with a retractable boom (for example, an aerial work platform).

[0014] The mobile crane 1 has a telescopic boom 12 and an electrically operated telescopic device 2.

[0015] The telescopic boom 12 has multiple booms (specifically, a first boom 13 and a second boom 14) that are telescopically combined. Adjacent booms (specifically, the first boom 13 and the second boom 14) are connected by a second connecting pin P2 (see Figures 2A to 2E).

[0016] The electric telescopic device 2 moves the boom (specifically, the second boom 14) in the telescopic direction when extending or retracting the telescopic boom 12. At this time, the electric telescopic device 2 connects to the boom being moved via the first connecting pin P1. The electric telescopic device 2 also releases the connection between the boom being moved and the boom adjacent to it.

[0017] As shown in Figures 1 and 2A to 2E, the mobile crane 1 includes a traveling body 10, a turntable 11, a telescopic boom 12, an electric telescopic device 2, a wire rope 15, and a hook 16.

[0018] The turntable 11 is rotatably mounted on the upper part of the traveling body 10. The telescopic boom 12 has a first boom 13 and a second boom 14. The telescopic boom 12 extends and retracts based on the power of the electric extension device 2.

[0019] The telescopic boom 12 has its base end fixed to the turntable 11. The telescopic boom 12 is luffable and extendable.

[0020] The first boom 13 and the second boom 14 are examples of booms. In this embodiment, the telescopic boom 12 has two booms. However, the telescopic boom may have three or more booms.

[0021] The electric telescopic device 2 extends and retracts the telescopic boom 12. The wire rope 15 is supported by the telescopic boom 12. The wire rope 15 hangs down from the tip of the telescopic boom 12. The hook 16 is provided at the tip of the wire rope 15.

[0022] Next, the telescopic boom 12 will be described with reference to Figures 1 and 2A to 2F. The telescopic boom 12 has a first boom 13 and a second boom 14. The first boom 13 and the second boom 14 are combined in a telescopic manner. The second boom 14 is provided inside the first boom 13.

[0023] Figures 2A and 2B show the fully retracted state of the telescopic boom 12 (in other words, the second boom 14). Figures 2C and 2D show the intermediate extension state of the telescopic boom 12 (in other words, the second boom 14). Figures 2E and 2F show the fully extended state of the telescopic boom 12 (in other words, the second boom 14).

[0024] Hereafter, when referring to the fully retracted state, it means the fully retracted state of the telescopic boom 12 (in other words, the second boom 14) shown in Figures 2A and 2B. When referring to the intermediate extended state, it means the intermediate extended state of the telescopic boom 12 (in other words, the second boom 14) shown in Figures 2C and 2D. When referring to the fully extended state, it means the fully extended state of the telescopic boom 12 (in other words, the second boom 14) shown in Figures 2E and 2F.

[0025] Figures 2A to 2F are schematic cross-sectional views of the telescopic boom 12 as seen from above. In the following description, the Cartesian coordinate system (X, Y, Z) shown in each figure may be used to describe the structure of the telescopic boom 12. The Cartesian coordinate system (X, Y, Z) corresponds to the direction of the mobile crane 1 when the telescopic boom 12 is tilted forward.

[0026] Specifically, the X direction coincides with the front-to-back direction of the mobile crane 1. The X direction is also the extension and retraction direction of the telescopic boom 12. The X-+ side coincides with the front of the mobile crane 1. The X-+ side is also the extension direction of the telescopic boom 12. The X-- side coincides with the rear of the mobile crane 1. The X-- side is also the retraction direction of the telescopic boom 12.

[0027] Furthermore, the Y direction coincides with the left-right and width directions of the mobile crane 1. The Y-direction + side coincides with the left side when viewing the mobile crane 1 from behind. The Y-direction - side coincides with the right side when viewing the mobile crane 1 from behind.

[0028] The Z direction corresponds to the vertical direction of the mobile crane 1. The Z-positive side corresponds to the upper side of the mobile crane 1. The Z-negative side corresponds to the lower side of the mobile crane 1.

[0029] Hereinafter, when we refer to the front-to-back direction, left-to-right direction, and up-and-down direction, we mean the front-to-back direction, left-to-right direction, and up-and-down direction of the mobile crane 1 when the telescopic boom 12 is tilted forward.

[0030] The distance that the telescopic boom 12 (in other words, the second boom 14) moves from the fully retracted state to the fully extended state is referred to as the extension stroke of the telescopic boom 12 (in other words, the second boom 14).

[0031] The distance that the telescopic boom 12 (in other words, the second boom 14) moves from its fully extended state to its fully retracted state is referred to as the retraction stroke of the telescopic boom 12 (in other words, the second boom 14).

[0032] The intermediate extension state of the telescopic boom 12 (second boom 14) refers, for example, to a state where the second boom 14 is extended to 50% of its extension stroke.

[0033] The first boom 13 is an example of an outer boom. On the other hand, the second boom 14 is an example of an inner boom.

[0034] The telescopic boom 12 transitions from the retracted state shown in FIG. 2A to the extended state shown in FIGS. 1 and 2F by extending the second boom 14 disposed inside. An intermediate boom (not shown) may be provided between the first boom 13 and the second boom 14. The number of intermediate booms is not particularly limited.

[0035] The first boom 13 is cylindrical and has an internal space capable of accommodating the second boom 14. In the case of the present embodiment, the first boom 13 is also the base boom. The first boom 13 has a pair of first boom pin receiving portions 132 at the base end portion. The first boom pin receiving portions 132 are through holes coaxial with each other.

[0036] Hereinafter, the base end portion of the first boom 13 means the base end portion in the axial direction of the first boom 13. Also, the tip end portion of the first boom 13 means the tip end portion in the axial direction of the first boom 13. Also, the intermediate portion of the first boom 13 means the intermediate portion (that is, between the base end portion and the tip end portion) in the axial direction of the first boom 13.

[0037] The first boom pin receiving portions 132 are through holes coaxial with each other. Each of the first boom pin receiving portions 132 can engage with the second connecting pin P2 of the second boom 14 in the fully retracted state shown in FIGS. 2A and 2B.

[0038] The first boom 13 has a pair of intermediate boom pin receiving portions 133 at the intermediate portion. The intermediate boom pin receiving portions 133 are through holes coaxial with each other. Each of the intermediate boom pin receiving portions 133 can engage with the second connecting pin P2 of the second boom 14 in the intermediate extended state shown in FIGS. 2C and 2D.

[0039] The first boom 13 has a pair of second boom pin receiving portions 134 at the tip end portion. The second boom pin receiving portions 134 are through holes coaxial with each other. Each of the second boom pin receiving portions 134 can engage with the second connecting pin P2 of the second boom 14 in the fully extended state shown in FIGS. 2E and 2F.

[0040] The second boom 14 is cylindrical and has an internal space capable of accommodating the electric telescopic device 2. In the case of this embodiment, the second boom 14 is also the tip boom. The second boom 14 has a pair of base end side pin receiving portions 141a at the base end portion. Each of the pair of base end side pin receiving portions 141a is a through hole. Incidentally, the second boom may be an intermediate boom provided between the first boom 13 and the second boom 14.

[0041] The pair of base end side pin receiving portions 141a are coaxial through holes with each other. Each of the pair of base end side pin receiving portions 141a is detachably engaged with a pair of first connection pins P1 of the electric telescopic device 2 (specifically, the moving portion 3).

[0042] The second boom 14 has a pair of tip end side pin receiving portions 141b at the tip end portion. Each of the pair of tip end side pin receiving portions 141b is a through hole. Incidentally, the pair of tip end side pin receiving portions 141b engage with the first connection pins P1 of the tip end side moving portion 4B described later, for example, when the mobile crane 1 is traveling, to hold the position of the tip end side moving portion 4B. Since such a pair of tip end side pin receiving portions 141b do not need to support a large load, they may have a simpler structure than other pin receiving portions (specifically, the pair of base end side pin receiving portions 141a).

[0043] The pair of tip end side pin receiving portions 141b are coaxial through holes with each other. Each of the pair of tip end side pin receiving portions 141b is detachably engaged with a pair of first connection pins P1 of the electric telescopic device 2 (specifically, the moving portion 3).

[0044] Each of the first connection pins P1 is biased outward by a first biasing mechanism 435 (see FIGS. 5A to 5C) described later. Incidentally, the outside means the direction from the base end portion to the tip end portion of the first connection pin P1. The first connection pin P1 moves inward based on the operation of a first connection mechanism 43 described later. Incidentally, the inside means the direction from the tip end portion to the base end portion of the first connection pin P1.

[0045] In a state where the pair of first connection pins P1 and the pair of base end side pin receiving portions 141a are engaged (the state shown in FIG. 2B), the second boom 14 is movable in the telescopic direction together with the moving portion 3. Incidentally, the telescopic direction is the axial direction of the telescopic boom 12 (the left - right direction in FIGS. 2A to 2F).

[0046] Furthermore, the second boom 14 has a pair of boom pin receiving portions 142 at its base end. The pair of boom pin receiving portions 142 are provided around the base end pin receiving portion 141a. The pair of boom pin receiving portions 142 are coaxial through holes.

[0047] Each boom pin receiving portion 142 can engage with and disengage from a pair of second connecting pins P2. In Figures 2A to 2F, for the sake of explanation, the base end pin receiving portion 141a and the boom pin receiving portion 142 are shown offset in the axial direction of the telescopic boom 12.

[0048] In practice, the base end pin receiving portion 141a and the boom pin receiving portion 142 are aligned in the axial direction of the telescopic boom 12, and are positioned offset from each other in the circumferential direction of the telescopic boom 12.

[0049] Each second connecting pin P2 is supported on the inner surface of the second boom 14. Each second connecting pin P2 is movable in its own axial direction. Each second connecting pin P2 is biased outward by the second biasing mechanism 443 (see Figures 6A to 6C), which will be described later. Outward means in the direction from the base end to the tip end of the second connecting pin P2.

[0050] The second connecting pin P2 connects the first boom 13 and the second boom 14. The pair of second connecting pins P2 move inward based on the operation of the second connecting mechanism 44 (see Figures 6A to 6C), which will be described later. Inward means the direction from the tip to the base of the second connecting pin P2.

[0051] In the fully retracted state shown in Figure 2A, the second connecting pin P2 is inserted through the first boom pin receiving portion 132 of the first boom 13 and the boom pin receiving portion 142 of the second boom 14 so as to span across them. In this state, the first boom 13 and the second boom 14 are connected by the second connecting pin P2.

[0052] In the intermediate extension state shown in Figure 2C, the second connecting pin P2 is inserted through the intermediate boom pin receiving portion 133 of the first boom 13 and the boom pin receiving portion 142 of the second boom 14 so as to span across them. In this state, the first boom 13 and the second boom 14 are connected by the second connecting pin P2.

[0053] In the fully extended state shown in Figure 2F, the second connecting pin P2 is inserted through the second boom pin receiving portion 134 of the first boom 13 and the boom pin receiving portion 142 of the second boom 14 so as to span across them. In this state, the first boom 13 and the second boom 14 are connected by the second connecting pin P2.

[0054] As described above, when the first boom 13 and the second boom 14 are connected, the second boom 14 is prohibited from moving relative to the first boom 13. On the other hand, when the first boom 13 and the second boom 14 are not connected, the second boom 14 can move relative to the first boom 13. The states shown in Figures 2B, 2D, and 2E represent the state when the first boom 13 and the second boom 14 are not connected.

[0055] Furthermore, if an intermediate boom is provided between the first boom 13 and the second boom 14, one of the booms in the above description, the first boom 13 or the second boom 14, may be appropriately replaced with the intermediate boom, to the extent that it does not contradict the technical standards.

[0056] Next, the configuration of the electric telescopic device 2 will be described with reference to Figures 2A to 6C. The electric telescopic device 2 is an actuator that extends and retracts the telescopic boom 12. The electric telescopic device 2 has a feed screw section 21, a guide section 22, and a moving section 3.

[0057] The electric telescopic device 2 is located in the internal space of the second boom 14 when the telescopic boom 12 is in the fully retracted state (as shown in Figures 2A and 2B).

[0058] The lead screw section 21 is located inside the telescopic boom 12. It extends in the axial direction of the telescopic boom 12. The length of the lead screw section 21 is slightly shorter than the length of the first boom 13. The base end of the lead screw section 21 is fixed to the base end of the first boom 13. The tip of the lead screw section 21 is not supported by any other member. In other words, the lead screw section 21 is cantilevered to the turntable 11.

[0059] The lead screw portion 21 has a male thread portion 211 on its outer circumferential surface. The male thread portion 211 is a so-called trapezoidal thread. The male thread portion 211 is provided on the outer circumferential surface of the lead screw portion 21 from a first position to a second position.

[0060] The first position is the position where the base end movable part 4A of the movable part 3 is positioned when the telescopic boom 12 is fully retracted, as shown in Figure 2A. The second position is the position where the tip end movable part 4B of the movable part 3 is positioned when the telescopic boom 12 is fully retracted, as shown in Figure 2A.

[0061] The guide section 22 is located inside the telescopic boom 12. The guide section 22 is positioned along the feed screw section 21. The guide section 22 is located below the feed screw section 21. Figure 4 is a schematic diagram of the guide section 22. In Figure 4, the first boom 13 and the second boom 14 are shown by dashed lines. The guide section 22 is also schematically shown in Figures 5A to 6C.

[0062] Specifically, the guide portion 22 is a rail-shaped member with an opening at the top (in other words, the side closer to the lead screw portion 21). The guide portion 22 has a bottom plate portion 221, a first side plate portion 222, a second side plate portion 223, a tip-side fixing portion 231, a base-side fixing portion 232, and a roller 233. The bottom plate portion 221, the first side plate portion 222, and the second side plate portion 223 constitute the main body portion 22a of the guide portion 22.

[0063] The bottom plate portion 221 extends in the front-rear direction and is plate-shaped, parallel to both the front-rear and left-right directions. The first side plate portion 222 extends in the front-rear direction and is plate-shaped, parallel to both the front-rear and up-down directions. The first side plate portion 222 is provided at one end of the bottom plate portion 221 in the left-right direction (specifically, the left end in Figure 2A).

[0064] The second side plate portion 223 extends in the front-rear direction and is plate-shaped, parallel to both the front-rear and up-down directions. The second side plate portion 223 is provided at the other end of the bottom plate portion 221 in the left-right direction (specifically, the right end in Figure 2A).

[0065] The tip-side fixing portion 231 is provided at the tip of the main body portion 22a. The tip-side fixing portion 231 fixes the tip of the main body portion 22a to the tip of the feed screw portion 21.

[0066] The base-side fixing member 232 is provided at the base end of the main body portion 22a. The base-side fixing member 232 fixes the base end of the main body portion 22a to the base end of the feed screw portion 21. The base-side fixing member 232 is also a member that fixes the main body portion 22a and the feed screw portion 21 to the first boom 13.

[0067] The roller 233 is fixed to the lower end of the tip-side fixing portion 231 in a rotatable manner. The outer circumferential surface of the roller 233 is in contact with the inner surface of the second boom 14. In this way, the roller 233 supports the tip of the main body portion 22a relative to the second boom 14.

[0068] As shown in Figure 4, the guide section 22 supports the first wiring support member 224 and the second wiring support member 225. Figure 4 shows the telescopic boom, indicated by arrow A in Figure 2A. ａ This is a schematic diagram viewed from this direction. In Figure 4, for the sake of explanation, only the bottom plate portion 221 of the guide portion 22 is shown. Note that the first wiring support member 224 and the second wiring support member 225 may be arranged stacked on top of each other.

[0069] The first wiring support member 224 connects the base end of the guide portion 22 (in other words, the end on the X-direction side) to the base end side movable portion 4A of the movable portion 3. The first wiring support member 224 deforms to follow the movement of the base end side movable portion 4A. The first wiring support member 224 and the second wiring support member 225 may be flexible cable protection tubes such as so-called cable carriers (registered trademark).

[0070] The first wiring support member 224 supports the first wiring 226. In Figure 4, the first wiring 226 is shown by a dashed line. The first wiring 226 includes power wiring and signal wiring. The power wiring carries power supplied from the power supply unit 111 (see Figure 5A) to the base end moving part 4A. The power supply unit 111 is located on the turntable 11.

[0071] The signal wiring is the wiring through which signals transmitted and received between the control unit 112 (see Figure 5A) provided on the turntable 11 and the base end moving unit 4A pass. This first wiring 226 deforms together with the first wiring support member 224 to follow the movement of the base end moving unit 4A. In substance, the control unit 112 may be configured with a CPU, ROM, RAM, HDD, etc. connected by a bus, or with a single-chip LSI, etc.

[0072] The second wiring support member 225 connects the base end of the guide portion 22 (in other words, the end on the X-direction side) to the tip-side moving portion 4B of the moving portion 3. The second wiring support member 225 deforms to follow the movement of the tip-side moving portion 4B.

[0073] The second wiring support member 225 supports the second wiring 227. In Figure 4, the second wiring 227 is shown by a dashed line. The second wiring 227 includes power wiring and signal wiring. The power wiring is the wiring through which power supplied from the power supply unit 111 (see Figure 5A) to the tip-side moving part 4B passes.

[0074] The signal wiring is the wiring through which signals transmitted and received between the control unit provided on the turntable 11 and the tip-side moving unit 4B pass. This second wiring 227 deforms together with the second wiring support member 225 to follow the movement of the tip-side moving unit 4B.

[0075] The movable part 3, while engaged with the second boom 14, moves axially to extend or retract the second boom 14. The movable part 3 will be described below with reference to Figures 2A to 2F and 5A to 6C.

[0076] The movable part 3 has a base-side movable part 4A and a tip-side movable part 4B. The base-side movable part 4A and the tip-side movable part 4B have substantially the same configuration. The base-side movable part 4A and the tip-side movable part 4B correspond to examples of the first movable part and the second movable part, respectively.

[0077] The base-side movable part 4A is located closer to the base (rear end) of the telescopic boom 12 than the tip-side movable part 4B. In other words, the tip-side movable part 4B is located closer to the tip (front end) of the telescopic boom 12 than the base-side movable part 4A.

[0078] The configuration of the base-side movable part 4A will be described below with reference to Figures 5A to 8. Figures 5A to 8 are schematic diagrams showing the configurations of the base-side movable part 4A and the tip-side movable part 4B. The tip-side movable part 4B has a configuration that is almost the same as that of the base-side movable part 4A. Therefore, the configuration of the tip-side movable part 4B can be appropriately adapted from the description of the configuration of the base-side movable part 4A described later.

[0079] The base-side moving part 4A is an example of an electric coupling mechanism. The base-side moving part 4A includes a trunnion 41, a first drive unit 42, a first coupling mechanism 43, a second coupling mechanism 44, and a position detection unit 45. The base-side moving part 4A also includes a second drive unit 46.

[0080] Hereinafter, each element 41 to 46 constituting the base end movable part 4A will be described based on the state in which each element 41 to 46 is incorporated into the electric telescopic device 2.

[0081] The trunnion 41 is an example of the main body and is a member that supports the first drive unit 42, the first coupling mechanism 43, the second coupling mechanism 44, the position detection unit 45, and the second drive unit 46. Such a trunnion 41 unitizes the first drive unit 42, the first coupling mechanism 43, the second coupling mechanism 44, the position detection unit 45, and the second drive unit 46.

[0082] The trunnion 41 is sometimes referred to as the housing. The trunnion 41 may be box-shaped. However, the shape of the trunnion 41 is not particularly limited.

[0083] The trunnion 41 has a first through-hole 411 that penetrates the trunnion 41 in the axial direction. The lead screw portion 21 is inserted through the first through-hole 411 (see Figure 5A). Furthermore, a nut portion 462 of the second drive unit 46, which will be described later, is provided between the outer circumferential surface of the lead screw portion 21 and the inner circumferential surface of the first through-hole 411.

[0084] Furthermore, a sliding bearing 463 (see Figure 8) of the second drive unit 46, which will be described later, is provided between the outer circumferential surface of the nut portion 462 and the inner circumferential surface of the first through hole 411. In this way, the trunnion 41 is supported by the lead screw portion 21 via the nut portion 462 and the sliding bearing 463 of the second drive unit 46. In other words, the base end moving portion 4A is supported by the lead screw portion 21.

[0085] The trunnion 41 is engaged with the guide portion 22 in the left-right direction. Therefore, the rotation of the base end moving portion 4A is restricted by the engagement between the trunnion 41 and the guide portion 22.

[0086] Specifically, the trunnion 41 has anti-rotation parts 412a and 412b as a mechanism to restrict the rotation of the base end moving part 4A. The anti-rotation parts 412a and 412b are plate-shaped and are provided at the lower end of the trunnion 41. The left anti-rotation part 412a and the right anti-rotation part 412b face each other with a gap between them in the left-right direction.

[0087] The left anti-rotation portion 412a and the right anti-rotation portion 412b are provided so as to sandwich the guide portion 22. The left anti-rotation portion 412a and the right anti-rotation portion 412b engage with the guide portion 22 in the left-right direction.

[0088] Specifically, the left-side anti-rotation portion 412a is in contact with the left side surface of the first side plate portion 222 in the guide portion 22. Also, the right-side anti-rotation portion 412b is in contact with the right side surface of the second side plate portion 223 in the guide portion 22. Based on this engagement between the trunnion 41 (specifically, the anti-rotation portions 412a and 412b) and the guide portion 22, the rotation of the base end moving portion 4A is restricted.

[0089] Specifically, the left-side anti-rotation portion 412a restricts the base-side moving portion 4A from rotating to the left when it moves axially. The right-side anti-rotation portion 412b restricts the base-side moving portion 4A from rotating to the right when it moves axially. The direction of the rotational force acting on the base-side moving portion 4A is determined according to the orientation of the male screw portion 211 in the feed screw portion 21.

[0090] When the base-side movable part 4A moves, if a force acts on the base-side movable part 4A to rotate it to the left, the left-side anti-rotation part 412a and the first side plate part 222 slide against each other. Also, when the base-side movable part 4A moves, if a force acts on the base-side movable part 4A to rotate it to the right, the right-side anti-rotation part 412b and the second side plate part 223 slide against each other. This configuration contributes to suppressing rattling and rotation of the base-side movable part 4A when it moves.

[0091] The first drive unit 42 operates the first coupling mechanism 43 and the second coupling mechanism 44. As shown in Figures 5A to 6C, the first drive unit 42 includes a first electric motor 421, a brake mechanism 422, and a transmission mechanism 423.

[0092] The first electric motor 421 releases the connection between adjacent booms (specifically, the first boom 13 and the second boom 14). The first electric motor 421 also releases the connection between the boom (specifically, the second boom 14) and the moving section (specifically, the base-side moving section 4A and the tip-side moving section 4B).

[0093] The first electric motor 421 is, for example, a brushed DC motor or a brushless motor. The first electric motor 421 is supported by a trunnion 41. The first electric motor 421 is connected to a transmission mechanism 423. The first electric motor 421 is connected to a power supply unit 111 provided on the turntable 11 via a first wiring 226 (specifically, power wiring) supported by a first wiring support member 224.

[0094] The operation of the first electric motor 421 is controlled by a control unit 112 located on the turntable 11. The first electric motor 421 is connected to the control unit 112 via a first wiring 226 (specifically, a signal wiring) supported by a first wiring support member 224.

[0095] In the case of the tip-side movable section 4B, the first electric motor 421 is connected to the control unit 112 via a second wiring 227 (specifically, a signal wiring) supported by the second wiring support member 225.

[0096] The brake mechanism 422 is a so-called electromagnetic brake that applies braking force to the first electric motor 421. The brake mechanism 422 prevents the rotation of the output shaft of the first electric motor 421 when the first electric motor 421 is stopped. This maintains the state of the base end moving part 4A when the first electric motor 421 is stopped.

[0097] The brake mechanism 422 is connected to the power supply unit 111 provided on the turntable 11 via a first wiring 226 (specifically, a power wiring) supported by a first wiring support member 224.

[0098] In the case of the tip-side movable section 4B, the brake mechanism 422 is connected to the control unit 112 via a second wiring 227 (specifically, a power wiring) supported by the second wiring support member 225.

[0099] The brake mechanism 422 operates when the first coupling mechanism 43 or the second coupling mechanism 44, described later, is in a retracted state, and maintains the state of the first coupling mechanism 43 and the second coupling mechanism 44. The operation of the brake mechanism 422 is controlled by a control unit 112 provided on the turntable 11.

[0100] The brake mechanism 422 is connected to the control unit 112 via a first wiring 226 (specifically, a signal wire) supported by a first wiring support member 224. In the case of the tip-side moving part 4B, the brake mechanism 422 is connected to the control unit 112 via a second wiring 227 (specifically, a signal wire) supported by a second wiring support member 225.

[0101] The transmission mechanism 423 selectively transmits the power of the first electric motor 421 to the first coupling mechanism 43 and the second coupling mechanism 44.

[0102] The transmission mechanism 423 transmits the power of the first electric motor 421 to one of the coupling mechanisms, the first coupling mechanism 43 and the second coupling mechanism 44. While the transmission mechanism 423 is transmitting the power of the first electric motor 421 to one coupling mechanism, it does not transmit the power of the first electric motor 421 to the other coupling mechanism, the first coupling mechanism 43 and the second coupling mechanism 44.

[0103] The transmission mechanism 423 includes a transmission shaft 423a and a switchgear 423b.

[0104] The transmission shaft 423a is connected to the first electric motor 421 via a reduction gear (not shown). The transmission shaft 423a is also connected to a switchgear 423b. The transmission shaft 423a transmits the rotation of the first electric motor 421 to the switchgear 423b.

[0105] The switchgear 423b is fixed to the transmission shaft 423a. The switchgear 423b selectively transmits the power of the first electric motor 421 to either the first coupling mechanism 43 or the second coupling mechanism 44.

[0106] Here, when the first connecting mechanism 43 transitions from the expanded state to the contracted state, the rotation direction of the switchgear 423b (arrow A in Figures 5A to 5C) is... １ The direction indicated by is defined as the first rotational direction of the switchgear 423b.

[0107] Furthermore, when the first connecting mechanism 43 transitions from the contracted state to the expanded state, the rotation direction of the switchgear 423b (arrow A in Figures 5A to 5C) ２ The direction indicated by is defined as the second rotational direction of the switchgear 423b.

[0108] Furthermore, the state of the first connecting mechanism 43 shown in Figure 5A is the expanded state of the first connecting mechanism 43. The state of the first connecting mechanism 43 shown in Figure 5C is the contracted state of the first connecting mechanism 43. The state of the second connecting mechanism 44 shown in Figure 6A is the expanded state of the second connecting mechanism 44. The state of the second connecting mechanism 44 shown in Figure 6C is the contracted state of the second connecting mechanism 44.

[0109] First rotational direction A of switchgear 423b １ This is also the direction of rotation of the switchgear 423b when the second connecting mechanism 44 transitions from a contracted state (see Figure 6C) to an extended state (see Figure 6A).

[0110] Also, the second rotation direction A of the switchgear 423b ２ This is also the direction of rotation of the switchgear 423b when the second connecting mechanism 44 transitions from an expanded state (see Figure 6A) to a contracted state (see Figure 6C).

[0111] The first connecting mechanism 43 connects the second boom 14 and the base end side moving part 4A. Further, the first connecting mechanism 43 releases the connection between the second boom 14 and the base end side moving part 4A based on the power of the first electric motor 421.

[0112] The first connecting mechanism 43 transitions between an extended state (see FIG. 5A) and a contracted state (see FIG. 5C) under the control of the control unit 112.

[0113] FIGS. 5A to 5C are schematic views of the base end side moving part 4A. In the extended state of the first connecting mechanism 43 shown in FIG. 5A, the first connecting pin P1 and the base end side pin receiving part 141a of the second boom 14 are in an engaged state. In this engaged state, as shown in FIG. 2A, the second boom 14 and the base end side moving part 4A are connected.

[0114] Further, in the contracted state of the first connecting mechanism 43 shown in FIG. 5C, the first connecting pin P1 and the base end side pin receiving part 141a of the second boom 14 are in a disengaged state. In this disengaged state, the engagement between the second boom 14 and the base end side moving part 4A is released.

[0115] Specifically, the first connecting mechanism 43 includes a first rack bar 431, a first gear mechanism 432, a second gear mechanism 433, a first connecting pin P1, and a first biasing mechanism 435.

[0116] The first rack bar 431 moves in its axial direction in response to the power (specifically, rotation) transmitted from the switch gear 423b. The first rack bar 431 is located at the first position in the extended state (see FIG. 5A) of the first connecting mechanism 43.

[0117] On the other hand, the first rack bar 431 is located at the second position in the contracted state (see FIG. 5C) of the first connecting mechanism 43. That is, the first rack bar 431 moves between the first position and the second position.

[0118] In the extended state, when the switch gear 423b rotates in the first rotation direction A １ the first rack teeth of the first rack bar 431 mesh with the teeth of the switch gear 423b. From this state, when the switch gear 423b rotates in the first rotation direction A １As it rotates further, the first rack bar 431 moves in accordance with the rotation of the switchgear 423b.

[0119] Furthermore, the first rack bar 431 has a second rack tooth portion and a third rack tooth portion. The second rack tooth portion meshes with the first gear mechanism 432, which will be described later. The third rack tooth portion meshes with the second gear mechanism 433, which will be described later.

[0120] The first gear mechanism 432 rotates in accordance with the movement of the first rack bar 431. The first gear mechanism 432 also meshes with the first connecting pin P1.

[0121] The second gear mechanism 433 rotates in accordance with the movement of the first rack bar 431. The second gear mechanism 433 also meshes with the first connecting pin P1.

[0122] A pair of first connecting pins P1 are arranged on the same straight line. This pair of first connecting pins P1 is supported by a trunnion 41. The pair of first connecting pins P1 move in the axial direction of the pair in accordance with the rotation of the first gear mechanism 432 and the second gear mechanism 433.

[0123] The first biasing mechanism 435 returns the first coupling mechanism 43 to the extended state when the first electric motor 421 is de-energized and the brake mechanism 422 is OFF while the first coupling mechanism 43 is in the contracted state (see Figure 5C). The first biasing mechanism 435 then returns the pair of first coupling pins P1 to the reference position (in other words, the engaged state).

[0124] Such a first biasing mechanism 435 is composed of a pair of coil springs. Each of the coil springs constantly biases a pair of first connecting pins P1. The direction in which the pair of coil springs bias the pair of first connecting pins P1 is from the base end to the tip end of the pair of first connecting pins P1.

[0125] The second connecting mechanism 44 connects adjacent booms. Based on the power of the first electric motor 421, the second connecting mechanism 44 releases the connection between adjacent booms.

[0126] In this embodiment, the second connecting mechanism 44 connects the first boom 13 and the second boom 14. The second connecting mechanism 44 then releases the connection between the first boom 13 and the second boom 14 based on the power of the first electric motor 421.

[0127] The second coupling mechanism 44, under the control of the control unit 112, transitions between an extended state (see Figure 6A) and a retracted state (see Figure 6C) based on the rotation of the first electric motor 421.

[0128] In its extended state, the second connecting mechanism 44 becomes capable of engaging with a pair of second connecting pins P2. While engaged with the pair of second connecting pins P2, the second connecting mechanism 44 transitions from the extended state to the retracted state, thereby detaching the pair of second connecting pins P2 from the first boom 13.

[0129] Furthermore, the second connecting mechanism 44, while engaged with the pair of second connecting pins P2, transitions from a retracted state to an extended state, thereby engaging the pair of second connecting pins P2 with the first boom 13.

[0130] As shown in Figures 6A to 6C, the second connecting mechanism 44 includes a pair of second rack bars 441a and 441b, a synchronous gear 442, and a second biasing mechanism 443.

[0131] A pair of second rack bars 441a and 441b are each meshed with a synchronous gear 442. When the synchronous gear 442 rotates, one second rack bar 441a and the other second rack bar 441b move in opposite directions in the axial direction of the second rack bars 441a and 441b.

[0132] Each of the pair of second rack bars 441a and 441b has a locking claw at its tip. The locking claw engages with the second connecting pin P2 when the second connecting pin P2 is moved.

[0133] The second rack bar 441a moves in its axial direction in response to the power (specifically, rotation) transmitted from the switchgear 423b.

[0134] One of the second rack bars 441a is located in the first position when the second connecting mechanism 44 is extended. The other second rack bar 441a is located in the second position when the second connecting mechanism 44 is retracted. In other words, one of the second rack bars 441a moves between the first position and the second position.

[0135] From the extended state of the second coupling mechanism 44, the switchgear 423b moves in the second rotation direction A ２ When it rotates, the rack teeth of one of the second rack bars 441a engage with the teeth of the switchgear 423b.

[0136] From this state, the switchgear 423b rotates in the second rotation direction A. ２ As it rotates further, one of the second rack bars 441a moves in its own axial direction in accordance with the rotation of the switchgear 423b.

[0137] Furthermore, when one second rack bar 441a moves, the synchronous gear 442 rotates, causing the other second rack bar 441b to move in its own axial direction. The direction of movement of one second rack bar 441a and the direction of movement of the other second rack bar 441b are opposite.

[0138] The second biasing mechanism 443 is composed of a pair of coil springs. The second biasing mechanism 443 biases the base ends of the pair of second rack bars 441a and 441b toward the tip ends. In other words, the second biasing mechanism 443 biases the pair of second rack bars 441a and 441b toward each other.

[0139] When the second coupling mechanism 44 is in the contracted state, if the first electric motor 421 is de-energized and the brake mechanism 422 is turned OFF, the second coupling mechanism 44 is returned to the extended state. The second biasing mechanism 443 then returns the second coupling pin P2 to the reference position (in other words, the engaged state).

[0140] The position detection unit 45 is a non-contact type potentiometer. The position detection unit 45 has a detected object (not shown) and a sensor (not shown). The detected object is a magnet and is fixed to the transmission shaft 423a. The detected object rotates together with the transmission shaft 423a.

[0141] The object to be detected may be mounted on a member that rotates together with the output shaft of the first electric motor 421. The object to be detected rotates together with the output shaft of the first electric motor 421.

[0142] The sensor has a Hall element and is positioned facing the object to be detected in a predetermined direction. The sensor may be fixed to the trunnion 41 via a support (not shown).

[0143] The sensor outputs a voltage or current value corresponding to the phase of the object being detected. In other words, the sensor outputs a voltage or current value corresponding to the rotation angle of the transmission shaft 423a to which the object being detected is fixed (i.e., the rotation angle of the first electric motor 421).

[0144] The position detection unit 45 detects information regarding the position (in other words, the state) of the first connecting pin P1 according to the sensor's detected value. The position detection unit 45 also detects information regarding the position of the second connecting pin P2 according to the sensor's detected value.

[0145] Information regarding the position (in other words, state) of the first connecting pin P1 and information regarding the position of the second connecting pin P2 is the rotation angle of the first electric motor 421 from its reference position (specifically, the rotation angle of the transmission shaft 423a).

[0146] The position detection unit 45 is connected to the control unit 112 via a first wiring 226 (specifically, a signal wiring) supported by a first wiring support member 224. The position detection unit 45 sends the detected value to the control unit 112 via the first wiring 226 (specifically, a signal wiring).

[0147] In the case of the tip-side moving part 4B, the position detection unit 45 is connected to the control unit 112 via a second wiring 227 (specifically, a signal wiring) supported by the second wiring support member 225. The position detection unit 45 then sends the detected value to the control unit 112 via the second wiring 227 (specifically, a signal wiring).

[0148] The following describes an example of the operation of the first coupling mechanism 43 and the second coupling mechanism 44.

[0149] First, an example of the operation of the first coupling mechanism 43 will be described with reference to Figures 5A to 5C. The operation of the first coupling mechanism 43 is controlled by the control unit 112. The first coupling mechanism 43 transitions from an extended state to a retracted state based on the power of the first electric motor 421. Also, the first coupling mechanism 43 transitions from a retracted state to an extended state based on the biasing force of the first biasing mechanism 435.

[0150] When the first connecting mechanism 43 transitions from an expanded state to a contracted state, the pair of first connecting pins P1 are removed.

[0151] Figure 5A is a schematic diagram showing the extended state of the first connecting mechanism 43 and the engagement state between the pair of first connecting pins P1 and the pair of base-end pin receiving portions 141a of the second boom 14. Figure 5B is a schematic diagram showing the state of the first connecting mechanism 43 in the process of transitioning from the extended state to the retracted state.

[0152] Furthermore, Figure 5C is a schematic diagram showing the contracted state of the first connecting mechanism 43 and the detached state of the pair of first connecting pins P1 and the pair of base-end pin receiving portions 141a of the second boom 14.

[0153] When the first coupling mechanism 43 transitions from an expanded state to a contracted state, the control unit 112 (see Figure 5A) drives the first electric motor 421. The power of the first electric motor 421 is transmitted to a pair of first coupling pins P1 via the following first and second transmission paths.

[0154] The first transmission path is the path through which power from the first electric motor 421 is transmitted in the following order: (First transmission path) Switchgear 423b → First rack bar 431 → First gear mechanism 432 → First connecting pin P1 on the right side

[0155] The second transmission path is the path through which power from the first electric motor 421 is transmitted in the following order: (Second transmission path) Switchgear 423b → First rack bar 431 → Second gear mechanism 433 → First connecting pin P1 on the left side

[0156] Specifically, first, the switchgear 423b rotates in the first rotational direction (arrow A in Figure 5A) based on the power of the first electric motor 421. １ It rotates in the direction indicated by [the arrow].

[0157] In the first transmission path, when the switchgear 423b rotates in the first direction, the first rack bar 431 moves to the right in accordance with that rotation. In the description of the operation of the first coupling mechanism 43, the right and left sides refer to the right and left sides in Figures 5A to 5C.

[0158] Then, in the first transmission path, when the first rack bar 431 moves to the right, the first connecting pin P1 on the right side moves to the left side via the first gear mechanism 432. On the other hand, in the second transmission path, when the first rack bar 431 moves to the right, the first connecting pin P1 on the left side moves to the right side via the second gear mechanism 433.

[0159] The position detection unit 45 detects the position of the pair of first connecting pins P1. The position detection unit 45 sends the detected value to the control unit 112. The control unit 112 controls the brake mechanism 422 and the first electric motor 421 based on the detected value obtained from the position detection unit 45.

[0160] In this embodiment, when the position detection unit 45 detects a predetermined condition, the control unit 112 supplies power to the brake mechanism 422 to turn it ON. When the brake mechanism 422 is ON, it applies braking force to the first electric motor 421.

[0161] As a result, the operation of the first coupling mechanism 43 is restricted. As a result, the first coupling mechanism 43 is maintained in a retracted state, and the positions of the pair of first coupling pins P1 are maintained. Subsequently, the control unit 112 stops the first electric motor 421.

[0162] Next, the operation of the first connecting mechanism 43 when it transitions from a contracted state to an expanded state based on the biasing force of the first biasing mechanism 435 will be described.

[0163] When the first coupling mechanism 43 transitions from a retracted state to an expanded state, the pair of first coupling pins P1 enter the retracted state. The control unit 112 turns off the brake mechanism 422 when the first coupling mechanism 43 is in the retracted state. When the brake mechanism 422 is in the OFF state, it does not apply braking force to the first electric motor 421.

[0164] As a result, the first coupling mechanism 43 becomes capable of transitioning from a contracted state to an expanded state based on the biasing force of the first biasing mechanism 435. The operation of the first coupling mechanism 43 when it transitions from a contracted state to an expanded state is the reverse of the operation of the first coupling mechanism 43 when it transitions from an expanded state to a contracted state.

[0165] In other words, the first connecting mechanism 43 transitions from the contracted state shown in Figure 5C, through the state shown in Figure 5B, to the expanded state shown in Figure 5A. As a result, the pair of first connecting pins P1 enter the retracted state shown in Figure 5A.

[0166] Next, an example of the operation of the second connecting mechanism 44 described above will be explained with reference to Figures 6A to 6C.

[0167] The operation of the second coupling mechanism 44 is controlled by the control unit 112. The second coupling mechanism 44 transitions from an extended state to a retracted state based on the power of the first electric motor 421. The second coupling mechanism 44 also transitions from a retracted state to an extended state based on the biasing force of the second biasing mechanism 443.

[0168] When the second connecting mechanism 44 transitions from an expanded state to a contracted state while engaged with the pair of second connecting pins P2, the pair of second connecting pins P2 become disengaged. The control by the control unit 112 that causes the second connecting mechanism 44 to transition from an expanded state to a contracted state is called the disengagement operation control of the second connecting mechanism.

[0169] Figure 6A is a schematic diagram showing the extended state of the second connecting mechanism 44 and the engagement state between the pair of second connecting pins P2 and the pair of boom pin receiving parts of the first boom 13 (specifically, the first boom pin receiving part 132, the intermediate boom pin receiving part 133, or the second boom pin receiving part 134).

[0170] Figure 6B is a schematic diagram showing the state of the second connecting mechanism 44 during the transition from the extended state to the retracted state. Figure 6C is a schematic diagram showing the retracted state of the second connecting mechanism 44 and the detached state of the pair of second connecting pins P2 and the pair of boom pin receiving parts of the first boom 13 (specifically, the first boom pin receiving part 132, the intermediate boom pin receiving part 133, or the second boom pin receiving part 134).

[0171] The second coupling mechanism 44 transitions between an extended state and a retracted state based on the power of the first electric motor 421. Here, the position of the switchgear 423b shown in Figure 6A is the reference position of the switchgear 423b.

[0172] When the second coupling mechanism 44 transitions from the extended state to the retracted state, the control unit 112 drives the first electric motor 421 in the opposite direction to when the first coupling mechanism 43 is operated. The power of the first electric motor 421 is transmitted through the following path: (Transmission path) Switchgear 423b → One second rack bar 441a → Synchronous gear 442 → The other second rack bar 441b

[0173] First, the switchgear 423b rotates in the second direction (arrow A in Figure 6A) based on the power of the first electric motor 421. ２ It rotates in the direction indicated by the arrow. Then, the teeth of the switchgear 423b mesh with the rack teeth of one of the second rack bars 441a.

[0174] From this state, the switchgear 423b rotates in the second rotation direction A. ２ As it rotates further, one of the second rack bars 441a moves to the right side in Figure 6A in accordance with the rotation of the switchgear 423b. In the description of the operation of the second connecting mechanism 44, the right side and the left side refer to the right side and the left side in Figures 6A to 6C.

[0175] Then, as one of the second rack bars 441a moves to the right, the synchronous gear 442 rotates. And as the synchronous gear 442 rotates, the other second rack bar 441b moves to the left.

[0176] When the second connecting mechanism 44 transitions from an extended state to a retracted state while the pair of second rack bars 441a and 441b are engaged with the pair of second connecting pins P2, the pair of second connecting pins P2 detach from the pair of boom pin receiving parts of the first boom 13 (specifically, the first boom pin receiving part 132, the intermediate boom pin receiving part 133, or the second boom pin receiving part 134) (see Figure 6C).

[0177] The position detection unit 45 detects the position of a pair of second connecting pins P2. The position detection unit 45 sends the detected value to the control unit 112. The control unit 112 controls the brake mechanism 422 and the first electric motor 421 based on the detected value obtained from the position detection unit 45.

[0178] In this embodiment, when the position detection unit 45 detects a predetermined condition, the control unit 112 supplies power to the brake mechanism 422 to turn the brake mechanism ON. When the brake mechanism 422 is ON, it applies braking force to the first electric motor 421.

[0179] As a result, the operation of the second coupling mechanism 44 is restricted. In other words, the second coupling mechanism 44 is maintained in a contracted state, and the position of the pair of second coupling pins P2 is maintained. Subsequently, the control unit 112 stops the first electric motor 421.

[0180] Next, the operation of the second connecting mechanism 44 when it transitions from a contracted state to an expanded state based on the biasing force of the second biasing mechanism 443 will be described.

[0181] When the second connecting mechanism 44 transitions from a contracted state to an expanded state while engaged with the pair of second connecting pins P2, the pair of second connecting pins P2 enter the retracted state. The control unit 112 turns off the brake mechanism 422 when the second connecting mechanism 44 is in the contracted state. When the brake mechanism 422 is in the OFF state, it does not apply braking force to the first electric motor 421.

[0182] As a result, the second connecting mechanism 44 becomes capable of transitioning from a contracted state to an expanded state based on the biasing force of the second biasing mechanism 443. The operation of the second connecting mechanism 44 when it transitions from a contracted state to an expanded state is the reverse of the operation of the second connecting mechanism 44 when it transitions from an expanded state to a contracted state.

[0183] In other words, the second connecting mechanism 44 transitions from the contracted state shown in Figure 6C, through the state shown in Figure 6B, to the expanded state shown in Figure 6A. As a result, the pair of second connecting pins P2 enter the retracted state shown in Figure 6A.

[0184] The second drive unit 46 moves the base end moving part 4A along the lead screw part 21. The second drive unit 46 has a second electric motor 461 and a nut part 462. Also, as shown in Figure 8, the second drive unit 46 has a sliding bearing 463, a cover part 464, a first thrust bearing 465, and a second thrust bearing 466.

[0185] The second electric motor 461 rotates the nut portion 462. The second electric motor 461 is, for example, a brushed DC motor or a brushless motor. The second electric motor 461 is supported by the trunnion 41, as shown in Figure 7. Figure 7 is a schematic diagram showing the base end moving portion 4A as viewed from the X-direction side.

[0186] The second electric motor 461 is located in the lateral region of the base-side moving section 4A. The lateral region of the base-side moving section 4A refers to the region to the right or left of the feed screw section 21. In this embodiment, the second electric motor 461 is located in the left-side region of the base-side moving section. This configuration contributes to miniaturization of the base-side moving section 4A.

[0187] Furthermore, the second electric motor 461 is positioned offset in the axial direction of the telescopic boom 12 relative to the switchgear 423b described above. This configuration also contributes to miniaturization of the base end moving section 4A.

[0188] In this embodiment, the second electric motor 461 of the base end moving part 4A is provided on the base end side (X-direction - side) of the base end moving part 4A, as shown in Figure 9A. On the other hand, the second electric motor 461 of the tip end moving part 4B is provided on the tip end side (X-direction + side) of the base end moving part 4A, as shown in Figure 9A.

[0189] Furthermore, the number of second electric motors is not particularly limited. If there are two second electric motors, one of them may be positioned in the left-side region of the base-side moving part. The other second electric motor may be positioned in the right-side region of the base-side moving part.

[0190] Furthermore, the second electric motor may be a cylindrical (in other words, hollow) electric motor that covers the lead screw portion 21. In this case, the lead screw portion 21 may be inserted through the cylindrical second electric motor. The cylindrical second electric motor may be integrally formed with the nut portion. With such a configuration, the size of the moving part can be reduced. As a result, the design flexibility of the moving part is improved.

[0191] Furthermore, in this embodiment, the first electric motor 421 is positioned in the upper region of the base-side moving section 4A, as shown in Figure 7. The upper region of the base-side moving section refers to the region above the feed screw section 21. This configuration contributes to miniaturization of the base-side moving section 4A.

[0192] Furthermore, the first electric motor 421 may be positioned in the lateral region of the base end moving section 4A. In this case, the second electric motor 461 may be positioned in the upper region of the base end moving section 4A. In this embodiment, since the cross-sectional shape of the telescopic boom 12 is long in the vertical direction, it is easy to secure space in the upper region of the base end moving section 4A. For this reason, from the viewpoint of saving space, it is preferable that the larger of the first electric motor 421 and the second electric motor 461 be positioned in the upper region of the base end moving section 4A.

[0193] The second electric motor 461 has an output shaft 461a (see Figure 5A) and a motor-side gear 461b (see Figure 5A). The output shaft 461a is parallel to the X direction. The motor-side gear 461b is fixed to the tip of the output shaft 461a. The output shaft 461a meshes with the outer teeth 462c (see Figure 8) of the nut portion 462.

[0194] In this manner, the second electric motor 461 is connected to the nut portion 462. The second electric motor 461 rotates the nut portion 462 in a direction corresponding to the rotation direction of the output shaft 461a of the second electric motor 461.

[0195] The second electric motor 461 is connected to the power supply unit 111 provided on the turntable 11 via the first wiring 226 (specifically, power wiring) supported by the first wiring support member 224. In the case of the tip-side moving section 4B, the second electric motor 461 is connected to the power supply unit 111 provided on the turntable 11 via the second wiring 227 (specifically, power wiring) supported by the second wiring support member 225.

[0196] The nut portion 462 is an example of a female threaded portion and is cylindrical in shape. As shown in Figures 7 and 8, the nut portion 462 is located inside the first through hole 411 of the trunnion 41. The nut portion 462 has a female threaded portion 462a on its inner circumferential surface.

[0197] The female thread portion 462a is a so-called trapezoidal thread. The nut portion 462 also has a flange portion 462b on the outer circumferential surface of one end (specifically, the rear end) in the axial direction.

[0198] The flange portion 462b is ring-shaped. The flange portion 462b protrudes outward from the outer circumferential surface of the nut portion 462 in the radial direction. The nut portion 462 has outer teeth 462c on the outer circumferential surface of the flange portion 462b. The outer teeth 462c are provided around the entire circumference of the outer circumferential surface of the flange portion 462b.

[0199] Such a nut portion 462 is provided to cover the entire circumference of the lead screw portion 21. In other words, the lead screw portion 21 is inserted through the nut portion 462.

[0200] In this state, the female thread portion 462a of the nut portion 462 is screwed onto the male thread portion 211 of the feed screw portion 21. When the nut portion 462 rotates, the nut portion 462 moves axially based on the screwing of the female thread portion 462a and the male thread portion 211. The direction in which the nut portion 462 moves changes according to the direction of rotation of the nut portion 462.

[0201] As shown in Figures 7 and 8, the sliding bearing 463 is cylindrical and made of synthetic resin or metal. The sliding bearing 463 is provided so as to cover the entire outer surface of the nut portion 462. The sliding bearing 463 is provided between the outer surface of the nut portion 462 and the inner surface of the first through hole 411 in the trunnion 41.

[0202] The sliding bearing 463 supports the nut portion 462 relative to the trunnion 41, allowing the nut portion 462 to rotate relative to the trunnion 41. The sliding bearing 463 may have a slit in a part of its circumferential direction. This configuration improves the work efficiency of assembling the sliding bearing 463 to the nut portion 462. In addition, various bearings such as rolling bearings (specifically needle bearings) may be used instead of the sliding bearing 463.

[0203] The cover portion 464 is ring-shaped and fixed to the first end face (specifically, the front end face) of the nut portion 462 in the axial direction. The cover portion 464 is fixed to the nut portion 462 by fastening components such as screws.

[0204] The outer circumferential surface of the cover portion 464 protrudes outward in the radial direction of the nut portion 462 more than the outer circumferential surface of the nut portion 462.

[0205] The first thrust bearing 465 is ring-shaped. The first thrust bearing 465 is provided so as to cover the entire outer surface of the nut portion 462.

[0206] The first thrust bearing 465 is provided between the first end face (specifically, the front end face) of the trunnion 41 in the axial direction and the cover portion 464. The first thrust bearing 465 receives a load applied from the trunnion 41 in the first axial direction (specifically, towards the front).

[0207] Furthermore, when the nut portion 462 moves in the second axial direction (specifically, to the rear), the first thrust bearing 465 transmits the load in the second axial direction, which is transmitted from the nut portion 462 via the cover portion 464, to the trunnion 41.

[0208] The second thrust bearing 466 is ring-shaped. The second thrust bearing 466 is provided so as to cover the entire outer surface of the nut portion 462.

[0209] The second thrust bearing 466 is provided between the second end face (specifically, the rear end face) of the trunnion 41 in the axial direction and the flange portion 462b of the nut portion 462. The second thrust bearing 466 receives a load from the trunnion 41 in the second axial direction (specifically, the rear direction).

[0210] Furthermore, when the nut portion 462 moves in the first axial direction (specifically, towards the front), the second thrust bearing 466 transmits the axial load transmitted from the nut portion 462 to the trunnion 41. In particular, the second thrust bearing 466 receives the load of the movable portion 3 (specifically, the base end movable portion 4A and the tip end movable portion 4B) when the telescopic boom 12 is raised.

[0211] Furthermore, the first thrust bearing 465 bears a smaller load than the second thrust bearing 466. For this reason, the first thrust bearing 465 may be a thrust washer.

[0212] Next, we will briefly explain the operation of the second drive unit 46.

[0213] First, when the second electric motor 461 rotates in the first direction, the nut portion 462 rotates in the first direction based on the rotation of the second electric motor 461.

[0214] Furthermore, the first direction of the second electric motor 461 and the first direction of the nut portion 462 may be different directions or the same direction. The rotation direction of the second electric motor 461 and the rotation direction of the nut portion 462 are determined according to the connection structure between the second electric motor 461 and the nut portion 462.

[0215] When the nut portion 462 rotates in the first direction, the nut portion 462 moves in the first direction in the axial direction (specifically, towards the front) based on the screwing of the female thread portion 462a of the nut portion 462 with the male thread portion 211 of the feed screw portion 21.

[0216] Then, in accordance with the movement of the nut portion 462, the base end moving portion 4A moves in the first direction in the axial direction. In this way, when the nut portion 462 rotates in the first direction, the base end moving portion 4A moves in the first direction in the axial direction based on the relative rotation between the nut portion 462 and the lead screw portion 21.

[0217] Furthermore, when the second electric motor 461 rotates in the second direction, the nut portion 462 rotates in the second direction based on the rotation of the second electric motor 461.

[0218] Furthermore, the second direction of the second electric motor 461 and the second direction of the nut portion 462 may be different directions or the same direction. The rotation direction of the second electric motor 461 and the rotation direction of the nut portion 462 are determined according to the connection structure between the second electric motor 461 and the nut portion 462.

[0219] When the nut portion 462 rotates in the second direction, the nut portion 462 moves in the second direction in the axial direction (specifically, towards the rear) based on the screwing of the female thread portion 462a of the nut portion 462 with the male thread portion 211 of the feed screw portion 21.

[0220] Then, in accordance with the movement of the nut portion 462, the base end moving portion 4A moves in the second direction in the axial direction. Thus, when the nut portion 462 rotates in the second direction, the base end moving portion 4A moves in the second direction in the axial direction based on the relative rotation between the nut portion 462 and the lead screw portion 21.

[0221] As described above, in this embodiment, a configuration is adopted in which the base-side movable part 4A and the tip-side movable part 4B are moved by rotating the nut part 462 (hereinafter referred to as the first configuration). In contrast to this configuration, a configuration in which the base-side movable part 4A and the tip-side movable part 4B are moved by rotating the lead screw part 21 (hereinafter referred to as the second configuration) is also conceivable.

[0222] In the first configuration described above, the second electric motor 461 can be made smaller because it rotates the nut portion 462, which is lighter than the lead screw portion 21. As a result, the power required to extend and retract the telescopic boom 12 can be reduced.

[0223] Furthermore, in the first configuration described above, since the nut portions 462 provided on the base-side moving portion 4A and the tip-side moving portion 4B are rotated, the movement of the base-side moving portion 4A and the tip-side moving portion 4B can be controlled independently. For this reason, there is a high degree of design freedom regarding the control of extending and retracting the telescopic boom 12.

[0224] Furthermore, in the second configuration described above, a bearing (not shown) is required to rotatably support the feed screw portion 21 in order to rotate it. Such a configuration is structurally complex and may increase manufacturing costs. On the other hand, in the first configuration described above, there is no need to rotate the feed screw portion 21, so both ends of the feed screw portion 21 in the axial direction can be fixed. Such a configuration is simple and can reduce manufacturing costs.

[0225] The configuration of the base-side moving part 4A in the moving part 3 has been described above. The configuration of the tip-side moving part 4B in the moving part 3 is substantially the same as that of the base-side moving part 4A. Therefore, the above description of the configuration of the base-side moving part 4A may be appropriately interpreted to describe the configuration of the tip-side moving part 4B.

[0226] The following describes the boom extension / retraction control and the operation of the telescopic boom 12 in boom extension / retraction control performed by the mobile crane 1 according to this embodiment, with reference to Figures 2A to 3E. Figures 2A to 2F are schematic diagrams showing the operation of the telescopic boom 12 in boom extension control, where the telescopic boom 12 is extended. Figures 3A to 3E are schematic diagrams showing the operation of the telescopic boom 12 in boom contraction control, where the telescopic boom 12 is retracted.

[0227] Furthermore, in the following description, the operation of the first connecting mechanism 43 and the second connecting mechanism 44 of the base-side movable part 4A and the tip-side movable part 4B is as described above.

[0228] First, boom extension control will be explained with reference to Figures 2A to 2F. Boom extension control is performed by the control unit 112. Figure 2A shows the fully retracted state of the telescopic boom 12 (in other words, the second boom 14).

[0229] In the state shown in Figure 2A, the base end movable part 4A is located at the base end of the feed screw part 21. The position of the base end movable part 4A shown in Figure 2A is referred to as the first reference position of the base end movable part 4A.

[0230] Furthermore, the tip-side movable part 4B is located at the tip of the feed screw part 21. The position of the tip-side movable part 4B shown in Figure 2A is referred to as the second reference position of the tip-side movable part 4B.

[0231] In the state shown in Figure 2A, the first connecting mechanism 43 in the base-side movable section 4A is in the extended state. Therefore, the first connecting pin P1 of the first connecting mechanism 43 in the base-side movable section 4A is engaged with the base-side pin receiving portion 141a of the second boom 14. In this state, the base-side movable section 4A and the second boom 14 are connected.

[0232] Furthermore, in the state shown in Figure 2A, the second connecting mechanism 44 in the base end moving part 4A is in the extended state. In this state, the second connecting pin P2 of the second boom 14 is engaged with the first boom pin receiving part 132 of the first boom 13. Thus, the first boom 13 and the second boom 14 are connected.

[0233] In the state shown in Figure 2A, the first connecting mechanism 43 in the tip-side movable section 4B is in the extended state. Therefore, the first connecting pin P1 of the first connecting mechanism 43 in the tip-side movable section 4B is engaged with the tip-side pin receiving section 141b of the second boom 14. In this state, the tip-side movable section 4B and the second boom 14 are connected.

[0234] Furthermore, in this state, the second connecting mechanism 44 in the tip-side movable part 4B is in the extended state. That is, the tip-side movable part 4B is in a state where it can engage with the second connecting pin P2 of the second boom 14. The position of the second boom 14 shown in Figure 2A is the retracted position of the second boom 14.

[0235] The states of the telescopic boom 12 shown in Figure 2A are as follows: Position of base end movable part 4A: First reference position (first predetermined position) First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Second reference position (third predetermined position) First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Connected state Second boom 14 and base end movable part 4A: Connected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Retracted position

[0236] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2A to the state shown in Figure 2B. Figure 2B, like Figure 2A, shows the fully retracted state of the telescopic boom 12 (in other words, the second boom 14).

[0237] Specifically, the control unit 112 drives the first electric motor 421 of the base end moving part 4A to transition the second connecting mechanism 44 from the extended state to the retracted state. As a result, the second connecting pin P2 of the second boom 14 detaches from the first boom pin receiving part 132 of the first boom 13. In this state, the first boom 13 and the second boom 14 are not connected. Therefore, the second boom 14 is movable relative to the first boom 13.

[0238] Furthermore, the control unit 112 drives the first electric motor 421 of the tip-side moving section 4B to transition the first coupling mechanism 43 from the extended state to the retracted state. As a result, the first coupling pin P1 of the first coupling mechanism 43 in the tip-side moving section 4B detaches from the tip-side pin receiving section 141b of the second boom 14.

[0239] The states of the telescopic boom 12 shown in Figure 2B are as follows: Position of base end movable part 4A: First reference position (first predetermined position) First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Retracted state Position of tip end movable part 4B: Second reference position (third predetermined position) First connecting mechanism 43 of tip end movable part 4B: Retracted state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Connected state Second boom 14 and tip end movable part 4B: Unconnected state Position of second boom 14: Retracted position

[0240] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2B to the state shown in Figure 2C. Figure 2C shows the intermediate extension state of the telescopic boom 12 (in other words, the second boom 14).

[0241] First, the control unit 112 drives the second electric motor 461 of the base-side moving section 4A in the first direction. When the second electric motor 461 of the base-side moving section 4A is driven in the first direction, the nut section 462 of the base-side moving section 4A rotates in the first direction. Then, the base-side moving section 4A and the second boom 14 move forward.

[0242] The base end movable part 4A moves to the position shown in Figure 2C. The position of the base end movable part 4A shown in Figure 2C is the boom handover position. The boom handover position is, for example, the position where the second boom 14 is extended to 50% of its extension stroke.

[0243] The control unit 112 detects the position of the base end moving part 4A based on the detected value of the position detection unit 461c (see Figure 8). The position detection unit 461c is provided on the output shaft 461a of the second electric motor 461. The position detection unit 461c detects the position of the base end moving part 4A based on the rotation angle of the output shaft 461a.

[0244] The position of the position detection unit 461c is not limited to the position shown in Figure 8. The position detection unit 461c may be provided at a position where the rotation angle of the second electric motor 461 can be detected. With this configuration, a proximity sensor for detecting the position of the base end moving part 4A is not required.

[0245] Therefore, the distance between the first reference position and the boom handover position is shorter than the extension stroke of the second boom 14. Also, the distance between the second reference position and the boom handover position is shorter than the extension stroke of the second boom 14.

[0246] The control unit 112 moves the base end movable part 4A to the boom handover position, and then transitions the second connecting mechanism 44 of the base end movable part 4A from the retracted state to the extended state. As a result, the second connecting pin P2 of the second boom 14 engages with the intermediate boom pin receiving part 133 of the first boom 13.

[0247] Furthermore, the control unit 112 drives the second electric motor 461 of the base end moving part 4A and at the same time drives the second electric motor 461 of the tip end moving part 4B in the second direction. When the second electric motor 461 of the tip end moving part 4B is driven in the second direction, the nut portion 462 of the tip end moving part 4B rotates in the second direction. Then, the tip end moving part 4B moves backward.

[0248] The tip-side movable part 4B moves to the position shown in Figure 2C. The position of the tip-side movable part 4B shown in Figure 2C is the standby position of the tip-side movable part 4B. Also, the position of the second boom 14 shown in Figure 2C is the intermediate extension position of the second boom 14. The standby position of the tip-side movable part 4B corresponds, for example, to the position where the second boom 14 is extended to 50% of its extension stroke.

[0249] For the sake of explanation, the rotation direction of the second electric motor 461 when the base-side movable part 4A and the tip-side movable part 4B move forward will be referred to as the first direction. The rotation direction of the second electric motor 461 when the base-side movable part 4A and the tip-side movable part 4B move backward will be referred to as the second direction. The rotation direction of the second electric motor 461 in the base-side movable part 4A and the rotation direction of the second electric motor 461 in the tip-side movable part 4B may be the same or different.

[0250] Furthermore, after moving the base end moving part 4A to the boom handover position, the control unit 112 drives the first electric motor 421 of the base end moving part 4A to transition the first coupling mechanism 43 from the extended state to the retracted state. Then, the first coupling pin P1 of the first coupling mechanism 43 detaches from the base end pin receiving part 141a of the second boom 14.

[0251] As a result, the connection between the base end movable part 4A and the second boom 14 is released. The telescopic boom 12 then enters the state shown in Figure 2C. Note that the boom extension control may be terminated in the state shown in Figure 2C. In this case, the second boom 14 extends to a length equivalent to 50% of the extension stroke.

[0252] The states of the telescopic boom 12 shown in Figure 2C are as follows: Position of base end movable part 4A: Boom handover position (second predetermined position) First connecting mechanism 43 of base end movable part 4A: Retracted state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Standby position First connecting mechanism 43 of tip end movable part 4B: Retracted state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Connected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Unconnected state Position of second boom 14: Intermediate extension position

[0253] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2C to the state shown in Figure 2D. Figure 2D, like Figure 2C, shows the intermediate extension state of the telescopic boom 12 (in other words, the second boom 14).

[0254] First, the control unit 112 drives the second electric motor 461 of the base-side moving part 4A in the second direction. When the second electric motor 461 of the base-side moving part 4A is driven in the second direction, the nut portion 462 of the base-side moving part 4A rotates in the second direction. Then, the base-side moving part 4A moves backward. At this time, the second boom 14 does not move.

[0255] The base end movable part 4A moves toward the first reference position. The position between the boom handover position and the first reference position (specifically, the position of the base end movable part 4A shown in Figure 2D) is referred to as the retracted position of the base end movable part 4A.

[0256] Furthermore, the control unit 112 moves the base end movable part 4A backward and simultaneously drives the second electric motor 461 of the tip end movable part 4B in the second direction. When the second electric motor 461 of the tip end movable part 4B is driven in the second direction, the nut part 462 of the tip end movable part 4B rotates in the second direction. Then, the tip end movable part 4B moves backward.

[0257] The tip-side movable part 4B moves to the position shown in Figure 2D. The position of the tip-side movable part 4B shown in Figure 2D is the boom handover position.

[0258] When the tip-side movable section 4B moves to the boom handover position, the second connecting mechanism 44 of the tip-side movable section 4B is in an extended state. In this state, the second connecting mechanism 44 of the tip-side movable section 4B can engage with the second connecting pin P2 of the second boom 14. Therefore, when the tip-side movable section 4B moves to the boom handover position, the second connecting mechanism 44 of the tip-side movable section 4B engages with the second connecting pin P2 of the second boom 14.

[0259] Next, after the tip-side moving section 4B moves to the boom handover position, the control unit 112 transitions the first connecting mechanism 43 of the tip-side moving section 4B from the retracted state to the extended state. Then, the first connecting pin P1 of the first connecting mechanism 43 in the tip-side moving section 4B engages with the base-side pin receiving section 141a of the second boom 14. As a result, the tip-side moving section 4B and the second boom 14 are connected.

[0260] Subsequently, the control unit 112 drives the first electric motor 421 of the tip-side moving section 4B to transition the second connecting mechanism 44 of the tip-side moving section 4B from the extended state to the retracted state. As a result, the second connecting pin P2 of the second boom 14 detaches from the intermediate boom pin receiving section 133 of the first boom 13. The telescopic boom 12 then enters the state shown in Figure 2D.

[0261] The states of the telescopic boom 12 shown in Figure 2D are as follows: Position of base end movable part 4A: Retracted position (moving toward the first reference position) First connecting mechanism 43 of base end movable part 4A: Contracted state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Boom handover position (second predetermined position) First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Contracted state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Intermediate extension position

[0262] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2D to the state shown in Figure 2E. Figure 2E shows the fully extended state of the telescopic boom 12 (in other words, the second boom 14).

[0263] First, in the state shown in Figure 2D, the control unit 112 drives the second electric motor 461 of the base end moving part 4A in the second direction. When the second electric motor 461 of the base end moving part 4A is driven in the second direction, the nut portion 462 of the base end moving part 4A rotates in the second direction. Then, the base end moving part 4A moves backward.

[0264] The base end movable part 4A moves to the position shown in Figure 2E. The position of the base end movable part 4A shown in Figure 2E is the first reference position of the base end movable part 4A.

[0265] Furthermore, the control unit 112 drives the second electric motor 461 of the base end moving part 4A and at the same time drives the second electric motor 461 of the tip end moving part 4B in the first direction. When the second electric motor 461 of the tip end moving part 4B is driven in the first direction, the nut part 462 of the tip end moving part 4B rotates in the first direction. Then, the tip end moving part 4B moves forward.

[0266] The tip-side movable part 4B moves to the position shown in Figure 2E. The position of the tip-side movable part 4B shown in Figure 2E is the second reference position of the tip-side movable part 4B. Also, the position of the second boom 14 shown in Figure 2E is the extended position of the second boom 14. In the extended position, the second boom 14 is fully extended relative to the first boom 13.

[0267] The states of the telescopic boom 12 shown in Figure 2E are as follows: Position of base end movable part 4A: First reference position First connecting mechanism 43 of base end movable part 4A: Retracted state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Second reference position First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Retracted state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Extended position

[0268] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2E to the state shown in Figure 2F. Figure 2F is a diagram showing the fully extended state of the telescopic boom 12 (in other words, the second boom 14), similar to Figure 2E.

[0269] In the state shown in Figure 2E, the control unit 112 transitions the second connecting mechanism 44 of the tip-side moving part 4B from the retracted state to the extended state. As a result, the second connecting pin P2 of the second boom 14 engages with the second boom pin receiving part 134 of the first boom 13, resulting in the state shown in Figure 2F. The first boom 13 and the second boom 14 are then connected. In this state, the boom extension control ends. The state shown in Figure 2F is the working state of the telescopic boom 12.

[0270] The states of the telescopic boom 12 shown in Figure 2F are as follows: Position of base end movable part 4A: First reference position First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Second reference position First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Connected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Extended position

[0271] Furthermore, if an intermediate boom (not shown) is provided between the first boom 13 and the second boom 14, the boom extension control described above is performed on the intermediate boom. In the state shown in Figure 2F, the base-side movable part 4A and the tip-side movable part 4B are in their respective first positions. Therefore, in the state shown in Figure 2F, boom extension control can be started immediately on the intermediate boom. As a result, the time required to extend the telescopic boom 12 can be significantly reduced.

[0272] Next, boom retraction control will be explained with reference to Figures 3A to 3E. Boom retraction control is performed by the control unit 112. Figure 3A shows the fully extended state of the telescopic boom 12 (in other words, the second boom 14). The state of the telescopic boom 12 shown in Figure 3A is the same as the state of the telescopic boom 12 shown in Figure 2E.

[0273] Boom contraction control is a control that transitions the state of the telescopic boom 12 from the state of the telescopic boom 12 shown in Figure 2F to the state of the telescopic boom 12 shown in Figure 3E. The state of the telescopic boom 12 shown in Figure 3E is the same as the state of the telescopic boom 12 shown in Figure 2A. In other words, in boom contraction control, the telescopic boom 12 transitions in the reverse order of the boom extension control process.

[0274] First, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 2F to the state shown in Figure 3A. Specifically, the control unit 112 drives the first electric motor 421 of the tip-side moving section 4B to transition the second connecting mechanism 44 from the extended state to the retracted state.

[0275] As a result, the second connecting pin P2 of the second boom 14 detaches from the second boom pin receiving portion 134 of the first boom 13. In this state, the first boom 13 and the second boom 14 are not connected. Therefore, the second boom 14 is movable relative to the first boom 13. The telescopic boom 12 then takes on the state shown in Figure 3A.

[0276] The states of the telescopic boom 12 shown in Figure 3A are as follows: Position of base end movable part 4A: First reference position (third predetermined position) First connecting mechanism 43 of base end movable part 4A: Retracted state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Second reference position (first predetermined position) First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Retracted state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Extended position

[0277] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 3A to the state shown in Figure 3B. Figure 3B shows the intermediate extension state of the telescopic boom 12 (in other words, the second boom 14).

[0278] First, the control unit 112 drives the second electric motor 461 of the tip-side moving section 4B in the second direction. When the second electric motor 461 of the tip-side moving section 4B is driven in the second direction, the nut section 462 of the tip-side moving section 4B rotates in the second direction. Then, the tip-side moving section 4B and the second boom 14 move backward.

[0279] The tip-side movable part 4B moves to the position shown in Figure 3B. The position of the tip-side movable part 4B shown in Figure 3B is the boom handover position.

[0280] The control unit 112 moves the tip-side moving part 4B to the boom handover position, and then transitions the second connecting mechanism 44 of the tip-side moving part 4B from the retracted state to the extended state. As a result, the second connecting pin P2 of the second boom 14 engages with the intermediate boom pin receiving part 133 of the first boom 13. The second boom 14 and the first boom 13 are then connected.

[0281] Furthermore, after connecting the second boom 14 and the first boom 13, the control unit 112 drives the first electric motor 421 of the tip-side moving section 4B to transition the first connecting mechanism 43 of the tip-side moving section 4B from the extended state to the retracted state.

[0282] Then, the first connecting pin P1 of the first connecting mechanism 43 in the tip-side movable section 4B detaches from the base-side pin receiving section 141a of the second boom 14. As a result, the connection between the tip-side movable section 4B and the second boom 14 is released.

[0283] Furthermore, the control unit 112 drives the second electric motor 461 of the tip-side moving part 4B and, at the same time, drives the second electric motor 461 of the base-side moving part 4A in the first direction. When the second electric motor 461 of the base-side moving part 4A is driven in the first direction, the nut portion 462 of the base-side moving part 4A rotates in the first direction. As a result, the base-side moving part 4A moves forward.

[0284] The base-side movable part 4A moves to the position shown in Figure 3B. The position of the base-side movable part 4A shown in Figure 3B is the standby position of the base-side movable part 4A. Also, the position of the second boom 14 shown in Figure 3B is the intermediate extension position of the second boom 14. The standby position of the base-side movable part 4A corresponds, for example, to the position where the second boom 14 is extended to 40% of its extension stroke.

[0285] The states of the telescopic boom 12 shown in Figure 3B are as follows: Position of base end movable part 4A: Standby position First connecting mechanism 43 of base end movable part 4A: Retracted state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Boom handover position (second predetermined position) First connecting mechanism 43 of tip end movable part 4B: Retracted state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Connected state Second boom 14 and base end movable part 4A: Unconnected state Second boom 14 and tip end movable part 4B: Unconnected state Position of second boom 14: Intermediate extension position

[0286] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 3B to the state shown in Figure 3C. Figure 3C, like Figure 3B, shows the intermediate extension state of the telescopic boom 12 (in other words, the second boom 14).

[0287] First, the control unit 112 drives the second electric motor 461 of the tip-side moving section 4B in the first direction. When the second electric motor 461 of the tip-side moving section 4B is driven in the first direction, the nut section 462 of the tip-side moving section 4B rotates in the first direction. Then, the tip-side moving section 4B moves forward. At this time, the second boom 14 does not move.

[0288] The tip-side movable part 4B moves toward the second reference position. The position between the boom handover position and the second reference position (specifically, the position of the tip-side movable part 4B shown in Figure 3C) is referred to as the retracted position of the tip-side movable part 4B.

[0289] Furthermore, the control unit 112 moves the tip-side moving part 4B forward and at the same time drives the second electric motor 461 of the base-side moving part 4A in the first direction. When the second electric motor 461 of the base-side moving part 4A is driven in the first direction, the nut portion 462 of the base-side moving part 4A rotates in the first direction. Then, the base-side moving part 4A moves forward.

[0290] The base end movable part 4A moves to the position shown in Figure 3C. The position of the base end movable part 4A shown in Figure 3C is the boom handover position.

[0291] When the base-side movable part 4A moves to the boom handover position, the second connecting mechanism 44 of the base-side movable part 4A is in an extended state. In this state, the second connecting mechanism 44 of the base-side movable part 4A can engage with the second connecting pin P2 of the second boom 14. Therefore, when the base-side movable part 4A moves to the boom handover position, the second connecting mechanism 44 of the base-side movable part 4A engages with the second connecting pin P2 of the second boom 14.

[0292] Next, after the base-side moving section 4A moves to the boom handover position, the control unit 112 transitions the first connecting mechanism 43 of the base-side moving section 4A from the retracted state to the extended state. Then, the first connecting pin P1 of the first connecting mechanism 43 in the base-side moving section 4A engages with the base-side pin receiving section 141a of the second boom 14. As a result, the base-side moving section 4A and the second boom 14 are connected.

[0293] Subsequently, the control unit 112 drives the first electric motor 421 of the base end moving section 4A to transition the second connecting mechanism 44 of the base end moving section 4A from the extended state to the retracted state. As a result, the second connecting pin P2 of the second boom 14 detaches from the intermediate boom pin receiving section 133 of the first boom 13. The telescopic boom 12 then enters the state shown in Figure 3C.

[0294] The states of the telescopic boom 12 shown in Figure 3C are as follows: Position of base end movable part 4A: Boom handover position First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Retracted state Position of tip end movable part 4B: Retracted position (moving toward second reference position) First connecting mechanism 43 of tip end movable part 4B: Retracted state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Connected state Second boom 14 and tip end movable part 4B: Unconnected state Position of second boom 14: Intermediate extension position

[0295] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 3C to the state shown in Figure 3D. Figure 3D shows the fully retracted state of the telescopic boom 12 (in other words, the second boom 14).

[0296] First, in the state shown in Figure 3C, the control unit 112 drives the second electric motor 461 of the base end moving part 4A in the second direction. When the second electric motor 461 of the base end moving part 4A is driven in the second direction, the nut part 462 of the base end moving part 4A rotates in the second direction. Then, the base end moving part 4A and the second boom 14 move backward.

[0297] The base end movable part 4A moves to the position shown in Figure 3D. The position of the base end movable part 4A shown in Figure 3D is the first reference position of the base end movable part 4A.

[0298] Furthermore, the control unit 112 drives the second electric motor 461 of the base end moving part 4A and at the same time drives the second electric motor 461 of the tip end moving part 4B in the first direction. When the second electric motor 461 of the tip end moving part 4B is driven in the first direction, the nut part 462 of the tip end moving part 4B rotates in the first direction. Then, the tip end moving part 4B moves forward.

[0299] The tip-side movable part 4B moves to the position shown in Figure 3D. The position of the tip-side movable part 4B shown in Figure 3D is the second reference position of the tip-side movable part 4B. Also, the position of the second boom 14 shown in Figure 3D is the retracted position of the second boom 14. In the retracted position, the second boom 14 is completely retracted relative to the first boom 13.

[0300] The states of the telescopic boom 12 shown in Figure 3D are as follows: Position of base end movable part 4A: First reference position First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Retracted state Position of tip end movable part 4B: Second reference position First connecting mechanism 43 of tip end movable part 4B: Retracted state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Unconnected state Second boom 14 and base end movable part 4A: Connected state Second boom 14 and tip end movable part 4B: Unconnected state Position of second boom 14: Retracted position

[0301] Next, the control unit 112 transitions the state of the telescopic boom 12 from the state shown in Figure 3D to the state shown in Figure 3E. Figure 3E, like Figure 3D, shows the fully retracted state of the telescopic boom 12 (in other words, the second boom 14).

[0302] In the state shown in Figure 3D, the control unit 112 transitions the second connecting mechanism 44 of the base end moving part 4A from the retracted state to the extended state. As a result, the second connecting pin P2 of the second boom 14 engages with the first boom pin receiving part 132 of the first boom 13, resulting in the state shown in Figure 3E. The first boom 13 and the second boom 14 are then connected.

[0303] Furthermore, in the state shown in Figure 3D, the control unit 112 transitions the first connecting mechanism 43 of the tip-side moving section 4B from the retracted state to the extended state. Then, the first connecting pin P1 of the first connecting mechanism 43 in the tip-side moving section 4B engages with the tip-side pin receiving section 141b of the second boom 14, resulting in the state shown in Figure 3E. As a result, the tip-side moving section 4B and the second boom 14 are connected. In this state, the boom retraction control ends.

[0304] The states of the telescopic boom 12 shown in Figure 3E are as follows: Position of base end movable part 4A: First reference position First connecting mechanism 43 of base end movable part 4A: Extended state Second connecting mechanism 44 of base end movable part 4A: Extended state Position of tip end movable part 4B: Second reference position First connecting mechanism 43 of tip end movable part 4B: Extended state Second connecting mechanism 44 of tip end movable part 4B: Extended state First boom 13 and second boom 14: Connected state Second boom 14 and base end movable part 4A: Connected state Second boom 14 and tip end movable part 4B: Connected state Position of second boom 14: Retracted position

[0305] Furthermore, when the mobile crane 1 moves after the boom retraction control is completed, the control unit 112 moves the tip-side moving part 4B from the state shown in Figure 3E to the retracted position of the tip-side moving part 4B (the position shown in Figure 3C). Note that the position of the tip-side moving part 4B when the mobile crane 1 is moving may be the position shown in Figure 3E (in other words, the second reference position).

[0306] (Effects and benefits of this embodiment) The mobile crane 1 according to this embodiment described above provides a work machine that can improve the design freedom of the telescopic boom 12.

[0307] As described above, in the mobile crane 1 according to this embodiment, the telescopic device for extending and retracting the telescopic boom 12 is configured by an electrically operated electric telescopic device 2. Therefore, in the mobile crane 1 according to this embodiment, a hydraulic circuit for extending and retracting the telescopic boom 12 is unnecessary.

[0308] Conventionally, such hydraulic circuits were located in the internal space of the telescopic boom. This limited the design freedom of the internal space of the telescopic boom. On the other hand, in the case of the mobile crane 1 according to this embodiment, a hydraulic circuit for extending and retracting the telescopic boom 12 is unnecessary, so the design freedom of the internal space of the telescopic boom is not limited. Furthermore, in the case of a mobile crane equipped with a hydraulic circuit, the design freedom near the base end of the telescopic boom is limited by the hydraulic piping that sends hydraulic fluid from the slewing platform to the telescopic device (specifically, the telescopic cylinder). On the other hand, in the case of the mobile crane 1 according to this embodiment, hydraulic piping is unnecessary, so the design freedom near the base end of the telescopic boom can also be improved. As a result, the design freedom of the telescopic boom 12 can be improved according to the mobile crane 1 according to this embodiment.

[0309] Furthermore, in this embodiment, since a hydraulic circuit for extending and retracting the telescopic boom 12 is unnecessary, the hydraulic oil tank provided in the mobile crane 1 can be made smaller. As a result, according to this embodiment, the mobile crane 1 can be made smaller and more space-saving.

[0310] Furthermore, in the case of the mobile crane 1 according to this embodiment, not only the device for extending and retracting the telescopic boom 12, but also the devices for driving the first connecting mechanism 43 and the second connecting mechanism 44 of the base-side moving section 4A and the tip-side moving section 4B are configured as electrically powered devices. For this reason, the mobile crane 1 according to this embodiment allows for greater design flexibility of the telescopic boom 12.

[0311] Furthermore, the boom extension and retraction control implemented by the mobile crane 1 according to this embodiment, as described above, can significantly reduce the time required to extend or retract the telescopic boom 12.

[0312] If the telescopic boom 12 has three or more booms, a long time will be required to extend the entire telescopic boom if there is a long time between extending the first boom (specifically, the second boom 14) and starting to extend the second boom (specifically, the intermediate boom).

[0313] Furthermore, if there is a long delay between extending the first boom and starting to extend the second boom, the operator of mobile crane 1 may feel uneasy about whether the extension operation of the telescopic boom is being performed correctly.

[0314] In this embodiment, as described above, the base-side moving part 4A and the tip-side moving part 4B work together to extend and retract the telescopic boom 12, so the time from extending the first boom (specifically, the second boom 14) to starting to extend the second boom (specifically, the intermediate boom) can be significantly shortened.

[0315] Therefore, the first and second booms can be extended continuously. As a result, the time required to extend and retract the telescopic boom 12 can be significantly reduced. Furthermore, the operator of the mobile crane 1 does not have to worry about whether the extension operation of the telescopic boom is being performed correctly. Other functions and effects obtained from the mobile crane 1 according to this embodiment are as described above.

[0316] <Note> In the above embodiment, the electric telescopic device 2 has two movable parts (base-side movable part 4A and tip-side movable part 4B). The two movable parts cooperate to extend and retract one boom (specifically, the second boom 14).

[0317] However, the number of movable parts in an electric telescopic device is not limited to two. The number of movable parts in an electric telescopic device may be one or three or more. If there are three or more movable parts, the multiple movable parts cooperate to extend or retract a single boom.

[0318] Furthermore, the position of the second electric motor is not limited to the position of the second electric motor 461 in the above-described embodiment. Figure 9A is a schematic diagram showing the position of the second electric motor 461 of the base end moving part 4A and the tip end moving part 4B in the above-described embodiment.

[0319] As shown in Figure 9A, the second electric motor 461 of the base end moving part 4A is located on the base end side (in other words, the rear side) of the base end moving part 4A. The second electric motor 461 of the tip end moving part 4B is located on the tip end side (in other words, the front side) of the tip end moving part 4B.

[0320] In this configuration, as shown in Figure 2C, it is easy to design a structure that suppresses collision between the base-side moving part 4A and the tip-side moving part 4B when they are close together. In other words, as shown in Figure 2C, when the base-side moving part 4A and the tip-side moving part 4B are close together, contact between the second electric motor 461 of the base-side moving part 4A and the second electric motor 461 of the tip-side moving part 4B can be suppressed.

[0321] Furthermore, Figure 9B is a schematic diagram showing the positions of the second electric motor 461 of the base end movable part 4A and the tip end movable part 4B in the modified example 1. Note that the reference numerals in Figure 9B are the same as the reference numerals in Figure 9A.

[0322] In the modified example 1 shown in Figure 9B, the second electric motor 461 of the base end moving part 4A is located on the base end side (in other words, the rear side) of the base end moving part 4A. The second electric motor 461 of the tip end moving part 4B is located on the base end side (in other words, the rear side) of the tip end moving part 4B.

[0323] In this configuration, the side on which the second electric motor 461 is located becomes the lower side when the telescopic boom 12 is raised. In other words, when extending the telescopic boom 12, the second electric motor 461 is positioned on the side that pushes up the base-side moving part 4A and the tip-side moving part 4B. This configuration is advantageous in terms of the strength of the base-side moving part 4A and the tip-side moving part 4B. Furthermore, since the base-side moving part 4A and the tip-side moving part 4B can have the same structure, parts can be standardized.

[0324] Furthermore, Figure 9C is a schematic diagram showing the positions of the second electric motor 461 of the base end movable part 4A and the tip end movable part 4B in the modified example 2. Note that the reference numerals in Figure 9C are the same as the reference numerals in Figures 9A and 9B.

[0325] In the modified example 2 shown in Figure 9C, the second electric motor 461 of the base-side movable part 4A is located on the tip side (in other words, the front side) of the base-side movable part 4A. The second electric motor 461 of the tip-side movable part 4B is located on the base side (in other words, the rear side) of the tip-side movable part 4B.

[0326] In this modified example 2, the overall length of the feed screw section 21 can be shortened compared to the configuration shown in Figure 9C. This allows for miniaturization and weight reduction of the telescopic boom 12.

[0327] Furthermore, from the viewpoint of improving the efficiency of maintenance work on the base-side movable section 4A and the tip-side movable section 4B, it is preferable that the first boom 13 is configured to allow the operator to access the base-side movable section 4A and the tip-side movable section 4B from the external space of the first boom 13.

[0328] Specifically, the first boom 13 may have, for example, a maintenance through-hole (in other words, a manhole) near the center in the axial direction of the first boom 13. Both the base-side movable part 4A and the tip-side movable part 4B can move near the center in the axial direction of the first boom 13. Therefore, the operator can access the base-side movable part 4A and the tip-side movable part 4B through the maintenance through-hole.

[0329] Alternatively, the tip-side movable part 4B may be configured to move to the vicinity of the base end of the first boom 13. When the tip-side movable part 4B has moved to the vicinity of the base end of the first boom 13, the operator can access the base-side movable part 4A and the tip-side movable part 4B from the base end of the first boom 13.

[0330] The technical concept disclosed in the specification and drawings includes inventions obtained by arbitrarily combining the various configurations described in the embodiments described above. In particular, the technical concept disclosed in the specification and drawings includes inventions obtained by applying the various configurations disclosed in the specification and drawings to the basic configuration described above in any combination.

[0331] All disclosures in the specification, drawings, and abstract contained in the Japanese application No. 2024-162034, filed on September 19, 2024, are incorporated herein by reference.

[0332] The crane according to the present invention is not limited to a rough terrain crane, but may be various types of mobile cranes such as an all-terrain crane, a truck crane, or a truck-mounted crane (also called a cargo crane). Furthermore, the crane according to the present invention is not limited to a mobile crane, but may be any other crane equipped with a telescopic boom.

[0333] 1 Mobile crane 10 Traveling body 11 Turntable 111 Power supply unit 112 Control unit 12 Telescopic boom 13 First boom 132 First boom pin receiver 133 Intermediate boom pin receiver 134 Second boom pin receiver 14 Second boom 141a Base pin receiver 141b Tip pin receiver 142 Boom pin receiver 15 Wire rope 16 Hook P1 First connecting pin P2 Second connecting pin 2 Electric telescopic device 21 Feed screw unit 211 Male screw unit 22 Guide unit 22a Main body 221 Bottom plate unit 222 First side plate unit 223 Second side plate unit 224 First wiring support member 225 Second wiring support member 226 First wiring 227 Second wiring 231 Tip fixing unit 232 Base end fixing part 233 Roller 3 Moving part 4A Base end moving part 4B Tip end moving part 41 Trunnion 411 First through hole 412a, 412b Anti-rotation part 42 First drive part 421 First electric motor 422 Brake mechanism 423 Transmission mechanism 423a Transmission shaft 423b Switchgear 43 First coupling mechanism 431 First rack bar 432 First gear mechanism 433 Second gear mechanism 435 First biasing mechanism 44 Second coupling mechanism 441a, 441b Second rack bar 442 Synchronous gear 443 Second biasing mechanism 45 Position detection part 46 Second drive part 461 Second electric motor 461a Output shaft 461b Motor side gear 461c Position detection part 462 Nut part 462a Female thread section 462b Flange section 462c Outer teeth section 463 Sliding bearing 464 Cover section 465 First thrust bearing 466 Second thrust bearing

Claims

1. A work machine comprising: a telescopic boom having multiple booms; and an electric telescopic device for extending and retracting the telescopic boom, wherein the electric telescopic device has a feed screw portion extending in the axial direction of the boom; and a moving portion having a female screw portion that screws into the feed screw portion, and which, while engaged with the boom, moves in the axial direction based on the relative rotation between the feed screw portion and the female screw portion to extend and retract the boom.

2. The work machine according to claim 1, wherein the movable part comprises a first coupling mechanism that connects the boom and the movable part and releases the connection between the boom and the movable part using a first electric motor, and a second coupling mechanism that connects adjacent booms and releases the connection between adjacent booms using the first electric motor.

3. The working machine according to claim 1, wherein the moving part has a second electric motor for rotating the female screw part, and moves in the axial direction in accordance with the rotation of the female screw part.

4. The working machine according to claim 1, wherein the movable part comprises a first electric motor for releasing the connection between adjacent booms and releasing the connection between the boom and the movable part, and a second electric motor for rotating the female screw part, wherein the first electric motor is located in one of the upper region and the lateral region of the movable part, and the second electric motor is located in the other of the upper region and the lateral region.

5. The work machine according to claim 4, wherein the moving unit has two second electric motors, one of which is located in the left region of the moving unit, and the other second electric motor is located in the right region of the moving unit.

6. The working machine according to claim 1, wherein the moving part has a second electric motor for rotating the female screw part, and the second electric motor is cylindrical in shape and covers the feed screw part.

7. The work machine according to claim 1, having a guide portion arranged along the feed screw portion, wherein the moving portion comprises a main body portion that is prevented from rotating based on engagement with the guide portion and rotatably supports the female screw portion, and a second electric motor supported by the main body portion that rotates the female screw portion, and moves in the axial direction in accordance with the rotation of the female screw portion.

8. The work machine according to claim 7, wherein the second electric motor is supplied with power via wiring housed in the guide section.

9. The work machine according to claim 8, further comprising a wiring support member supported by the guide portion and deformable in accordance with the movement of the movable portion, wherein the wiring is supported by the wiring support member.

10. The electric telescopic device has a plurality of movable parts, and at least two of the movable parts cooperate to extend and retract one boom, as described in claim 1.

11. The working machine according to claim 1, wherein the moving part comprises a first moving part and a second moving part, the first moving part moves from a first predetermined position to a second predetermined position while connected to the boom to extend or retract the boom, and then releases the connection with the boom, and the second moving part moves from a third predetermined position to the second predetermined position, connects with the boom at the second predetermined position, and then moves to the third predetermined position to extend or retract the boom.

12. The work machine according to claim 11, wherein the distance between the first predetermined position and the second predetermined position is shorter than the distance over which one boom extends or retracts.

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