Undercarriage of construction machinery

Abstract

A left vehicle width expansion device (15) causes a left side frame (6) to move left and right in relation to a center frame (5) by extending and contracting a rod (16B) of a hydraulic cylinder (16), and similarly, a right vehicle width expansion device moves a right side frame left and right to expand and contract the vehicle width of a lower traveling body (4). The hydraulic cylinders (16) of the left and right vehicle width expansion devices (15) are positioned between drive wheels (9) and idler wheels (10) and are attached to the side frames (6).

Description

[Technical Field]

[0001] The present invention relates to an undercarriage of a construction machine such as a hydraulic excavator or a hydraulic crane. [Background technology]

[0002] A hydraulic excavator, a typical example of construction machinery, comprises a self-propelled lower running body, an upper rotating body rotatably mounted on the lower running body, and a working device rotatably mounted on the front of the upper rotating body.

[0003] The lower running body comprises a center frame located in the center, side frames attached to both the left and right sides of the center frame while extending in the fore-and-aft direction, a drive wheel provided at one end of the side frame in the longitudinal direction, an idler wheel provided at the other end of the side frame in the longitudinal direction, and a track wound around the drive wheel and the idler wheel.

[0004] Some hydraulic excavators have a narrow-width configuration in which the width of the undercarriage is reduced to fit within the transport width limit, and a wide-width configuration in which the width of the undercarriage is increased to improve stability during work. In this configuration, the side frames are movable left and right (widthwise) relative to the center frame. The center frame is also provided with a hydraulic cylinder as a power source for moving the side frames (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-243852 Summary of the Invention

[0006] When transporting a hydraulic excavator, there are restrictions on dimensions such as width, height, and length, as well as restrictions on weight, etc. These dimensional and weight restrictions are imposed depending on the time of day and the route during which the hydraulic excavator is transported. For example, if the hydraulic excavator is not subject to a weight restriction, the side frames can be moved left and right to reduce the width of the lower traveling body, as in Patent Document 1, so that the dimensional restriction is not imposed. Also, if the hydraulic excavator is subject to a weight restriction, the left and right side frames can be removed from the center frame to reduce the weight of the vehicle body and thereby not be subject to the weight restriction.

[0007] However, because the hydraulic excavator in Patent Document 1 has hydraulic cylinders mounted on the center frame, even if the side frames are removed from the center frame, the weight of the vehicle body to be transported may not be sufficiently reduced due to the weight of the hydraulic cylinders and peripheral equipment for the hydraulic cylinders. In this case, the weight of the vehicle body must be reduced by removing the working equipment, which results in a problem of poor workability during transportation.

[0008] Furthermore, the hydraulic excavator in Patent Document 1 is configured such that the hydraulic cylinder is installed in a space formed by protruding the bottom surface of the center frame downward. As a result, the lower running body has a low minimum ground clearance because a portion of the bottom surface of the center frame protrudes downward. With a structure in which the minimum ground clearance of the lower running body is low, concrete pieces, rebar, etc. are likely to interfere with the center frame while the excavator is running, which could make it impossible to run the excavator at some work sites and reduce workability.

[0009] The present invention has been made in consideration of the problems of the prior art described above, and an object of the present invention is to provide a lower running body for a construction machine which can reduce the weight of the vehicle body simply by removing the side frames, making it possible to transport the vehicle body with simple work, and which can increase the number of work sites that can be traveled over by maintaining a high minimum ground clearance for the center frame, thereby improving workability.

[0010] The present invention relates to a lower traveling body of a construction machine comprising a center frame located at the center of a vehicle body, side frames attached to both the left and right sides of the center frame in a state extending in the front-rear direction and movable in the left-right direction relative to the center frame, drive wheels attached to one end of the side frames in the longitudinal direction, idler wheels attached to the other end of the side frames in the longitudinal direction, tracks wound around the drive wheels and the idler wheels, and a vehicle width expansion / contraction device that moves the side frames in the left-right direction relative to the center frame by extending or contracting a rod of a hydraulic cylinder, thereby expanding or contracting the vehicle width, wherein the hydraulic cylinder of the vehicle width expansion / contraction device is attached to the side frames and is located between the drive wheels and the idler wheels. The side frame is formed as a cylindrical body, and the hydraulic cylinder is disposed inside the side frame. are.

[0011] According to the present invention, the weight of the vehicle body can be reduced simply by removing the side frames, making it possible to transport the vehicle body with simple work. In addition, the minimum ground clearance of the center frame can be maintained high, increasing the number of work sites that can be traveled and improving workability. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a left side view showing a hydraulic excavator equipped with a lower traveling body according to an embodiment of the present invention. FIG. [Figure 2] FIG. 10 is a perspective view showing a state in which the side frames are attached to the center frame at a wide width position. [Figure 3] FIG. 10 is a perspective view showing a state in which the side frames are attached to the center frame at a narrow width position. [Figure 4] FIG. 4 is a perspective view showing the left running portion of the lower running body from the center frame side. [Figure 5] 5 is a perspective view showing the left running portion of FIG. 4 from below with part of the inner plate omitted. FIG. [Figure 6] 10 is a partially cutaway plan view showing a state in which the side frame is placed in a wide-width position by the vehicle width widening device. FIG. [Figure 7]10 is a partially cutaway plan view showing a state in which the side frame is placed in a narrow width position by the vehicle width expansion / contraction device. FIG. [Figure 8] 10 is a plan view showing the relationship between the side frame and the connecting portion of the vehicle width expansion / contraction device in a narrow width position. FIG. [Figure 9] FIG. 4 is a cross-sectional view showing a state in which the vehicle width expanding / reducing device is attached to a side frame. [Figure 10] FIG. 4 is a perspective view showing the mounting structure of the vehicle width expanding / reducing device to the side frame with the inner plate omitted. [Figure 11] FIG. 2 is a perspective view showing a mounting structure of the vehicle width expanding / reducing device to the center frame. [Figure 12] FIG. 4 is a perspective view showing a mounting structure of a connecting portion of the vehicle width adjusting device to a center frame. DETAILED DESCRIPTION OF THE INVENTION

[0013] Below, an undercarriage of a construction machine according to an embodiment of the present invention will be described in detail with reference to Figs. 1 to 12, taking as an example the undercarriage of a hydraulic excavator, which is a typical example of a construction machine.

[0014] 1, the hydraulic excavator 1 includes a lower traveling body 4 (to be described later), an upper rotating body 2 rotatably mounted on the lower traveling body 4, and a work device 3 rotatably mounted on the front of the upper rotating body 2 for performing work such as excavating earth and sand. The upper rotating body 2 and the lower traveling body 4 form a vehicle body.

[0015] The hydraulic excavator 1 of this embodiment is a large model having, for example, the maximum width dimension of the upper rotating body 2 that falls within the width limit when loaded onto a trailer for transportation. On the other hand, large hydraulic excavators 1 may be subject to height and weight restrictions if the transportation route includes underpasses, tunnels, underpasses, bridges, etc. In such cases, it is necessary to reduce the width and weight of the hydraulic excavator 1 loaded onto the trailer. Therefore, in this embodiment, a case where the width dimension of the lower traveling body 4 is reduced for transportation, and a case where the weight, width, and height dimensions are reduced by removing the left traveling section 14 and the right traveling section from the center frame 5 for transportation will be described.

[0016] Next, the configuration of the undercarriage 4 of the hydraulic excavator 1 will be described in detail. Note that the front-to-rear direction as seen by an operator riding on the upper rotating body 2 changes depending on the swing position of the upper rotating body 2. Therefore, in this embodiment, the configuration of the undercarriage 4 and the operation of expanding and contracting the vehicle width will be described by defining the side where the idler wheels 10 are provided as the front side, the side where the drive wheels 9 are provided as the rear side, and the direction perpendicular to the front-to-rear direction as the left-to-right direction (width direction).

[0017] The lower traveling body 4 has a width dimension larger than that of the upper rotating body 2 so that it can stably support the upper rotating body 2 and the work device 3 during travel and operation. However, if the width dimension of the lower traveling body 4 is formed larger than that of the upper rotating body 2, the width dimension of the lower traveling body 4 will exceed the limited width during transportation.

[0018] Therefore, the lower running body 4 is configured so that the mounting positions of the left and right side frames 6 relative to the center frame 5 (described later) can be moved in the width direction. Specifically, by arranging the left and right side frames 6 close to each other, the width dimension of the lower running body 4 is reduced, and the configuration is such that it fits within the limited width during transportation.

[0019] Furthermore, if the transportation route includes underpasses, tunnels, underpasses, bridges, etc., there are height and weight restrictions. For this reason, the undercarriage 4 is configured so that the left and right side frames 6 can be removed together with the drive wheels 9, idler wheels 10, crawler tracks 13, and vehicle width expansion / contraction device 15.

[0020] The lower running body 4 is for traveling on rough ground, muddy ground, etc. As shown in Figures 1 to 5, the lower running body 4 is composed of a center frame 5, a left side frame 6, a right side frame, drive wheels 9, idler wheels 10, tracks 13, and a vehicle width expansion / reduction device 15, which will be described later. The left side frame 6 to which the drive wheels 9, idler wheels 10, tracks 13, and vehicle width expansion / reduction device 15 are attached forms the left running section 14, and the right side frame to which the drive wheels, idler wheels, tracks, and vehicle width expansion / reduction device are attached forms the right running section.

[0021] As shown in Figures 2 and 3, the center frame 5 is located in the center of the lower running body 4. The center frame 5 is formed as a generally H-shaped sheet metal structure by welding multiple steel plates. The center frame 5 includes an upper plate 5A and a lower plate 5B that face each other with a gap between them in the vertical direction, a large-diameter cylinder 5C that is provided between the upper plate 5A and the lower plate 5B, a left front leg 5D and a left rear leg 5E that extend outward in the left-right direction (left side) from the left side of the upper plate 5A and the lower plate 5B with a gap between them in the front-rear direction, and a right front leg 5F and a right rear leg 5G that extend outward in the left-right direction (right side) from the right side of the upper plate 5A and the lower plate 5B with a gap between them in the front-rear direction.

[0022] A square-frame-shaped flange 5H is provided on the lower side of each of the left front leg 5D, left rear leg 5E, right front leg 5F, and right rear leg 5G. A plurality of bolt insertion holes 5J are provided at predetermined intervals in the vertical direction through each flange 5H. Bolts 7 (described below) for attaching the left side frame 6 and the like are inserted into each bolt insertion hole 5J.

[0023] 11 and 12, the lower plate 5B has a circular opening 5K for maintenance in the center, and cylindrical mounting portions 5L with their axes extending in the vertical direction are provided on both the left and right sides of the circular opening 5K. A pin member 20 for connecting the connecting portion 19 of the left vehicle width extension / reduction device 15 is inserted into the left mounting portion 5L. A pin member (not shown) for connecting the right connecting portion is inserted into the right mounting portion 5L.

[0024] The center frame 5 has a flat lower plate 5B. Below this lower plate 5B, only the connecting portion 19 and the flexible link 17, which are supported in a cantilevered state, are arranged. This allows the hydraulic excavator 1 to maintain a large minimum ground clearance from the ground to the lower plate 5B of the center frame 5.

[0025] As shown in Figures 2 and 3, the left side frame 6 is attached to the left side of the center frame 5, i.e., to the left front leg 5D and left rear leg 5E. The right side frame (not shown) is symmetrical to the left side frame 6 in the left-right direction and is attached to the right side of the center frame 5, i.e., to the right front leg 5F and right rear leg 5G. In this case, the left side frame 6 and the right side frame are movable in the left-right direction relative to the center frame 5. Note that the right side frame (right running section) is simply symmetrical to the left side frame 6 (left running section 14) in the left-right direction, so it will not be shown or described here.

[0026] The left side frame 6 is formed as a rectangular tube by an upper plate 6A, a lower plate 6B, an outer plate 6C, and an inner plate 6D, which extend in the front-to-rear direction. Idler wheel brackets 6E are provided at the front of the upper plate 6A, the lower plate 6B, the outer plate 6C, and the inner plate 6D, and drive wheel brackets 6F are provided at the rear of the upper plate 6A, the lower plate 6B, the outer plate 6C, and the inner plate 6D. A left front leg 5D, a left rear leg 5E, and three upper rollers 11, which will be described later, are attached to the upper plate 6A. Nine lower rollers 12, which will be described later, are attached to the lower plate 6B.

[0027] The upper plate 6A has a plurality of screw holes 6G, 6H (see FIG. 8) formed between the middle upper roller 11 and the front upper roller 11, and between the middle upper roller 11 and the rear upper roller 11. The plurality of screw holes 6G are arranged in a U-shape to correspond to the bolt insertion holes 5J formed in the flange portions 5H of the left front leg 5D and the left hind leg 5E, and bolts 7 for attaching the left front leg 5D and the left hind leg 5E are screwed into the plurality of screw holes 6H. In addition, bolts 7 for attaching leg guides 8 are screwed into the plurality of screw holes 6H.

[0028] As shown in FIG. 8, the left side frame 6 has an upper mounting plate 6J formed by extending the front-to-rear intermediate portion of the upper plate 5A inward (to the right) in the left-to-right direction. As shown in FIGS. 4, 5, and 10, the left side frame 6 also has a lower mounting plate 6K located at the vertical intermediate position of the inner plate 6D, spaced downward from the upper mounting plate 6J, and parallel to the mounting plate 6J. The upper and lower mounting plates 6J and 6K form a pair of mounting plates facing each other with a gap in the vertical direction. Because the mounting plates 6J and 6K are positioned toward the upper side of the side frame 6, a flexible link 17 (described later) attached between the mounting plates 6J and 6K can be positioned close to the lower plate 5B of the center frame 5.

[0029] Furthermore, the upper mounting plate 6J is formed with a notch 6L to avoid interference with the connecting portion 19 when the left side frame 6 is moved to the right to reduce the vehicle width. This allows the notch 6L to position the connecting portion 19 at the same height as the upper plate 5A. The notch 6L also allows the side frame 6 to be moved significantly in the left-right direction while avoiding interference with the connecting portion 19.

[0030] Furthermore, the mounting plates 6J, 6K are provided with pin holes 6M that penetrate in the vertical direction at a position forward of the rotation center (the center of the cylindrical body 5C of the center frame 5) of the upper rotating body 2. The pin holes 6M provided in the mounting plates 6J, 6K can firmly support a link pin 18 (flexible link 17) described below in a double-supported state.

[0031] As shown in Figure 9, a cylinder bracket 6N is provided on the left side frame 6, positioned toward the rear. The cylinder bracket 6N is attached to, for example, an inner plate 6D. Although the pin hole 6M is positioned toward the front and the cylinder bracket 6N is positioned toward the rear in this example, the pin hole 6M may be positioned toward the rear and the cylinder bracket 6N may be positioned toward the front. Furthermore, a link insertion opening 6P is provided on the inner plate 6D, positioned between the mounting plates 6J and 6K.

[0032] With the left front leg 5D and the left rear leg 5E of the center frame 5 placed on the upper plate 6A, the left side frame 6 is attached to the left front leg 5D and the left rear leg 5E by threading bolts 7 inserted into the bolt insertion holes 5J in the flange portion 5H into the corresponding screw holes 6G. In this case, when the side frame 6 is moved to the left and widened to the wide configuration (working configuration) as shown in Fig. 2, the side frame 6 is attached to the left front leg 5D and the left rear leg 5E using many bolts 7 so that it can withstand loads during travel and work. On the other hand, when the side frame 6 is moved to the right and narrowed to the narrow configuration (transporting configuration) as shown in Fig. 3, the side frame 6 is attached to the left front leg 5D and the left rear leg 5E using only a few bolts 7 because it is not subjected to large loads.

[0033] The leg guides 8 are provided on the upper plate 5A of the left side frame 6 adjacent to the rear side of the left front leg 5D and the front side of the left hind leg 5E. The two leg guides 8 sandwich the flange portion 5H of the left front leg 5D and the flange portion 5H of the left hind leg 5E between the upper plate 5A with a gap between them, thereby guiding the side frame 6 to move in parallel in the left-right direction relative to the left front leg 5D and the left hind leg 5E. The two leg guides 8 are attached to the upper plate 5A by bolts 7 inserted vertically and screwed into the threaded holes 6H.

[0034] As shown in Figures 1 to 5, the drive wheels 9 are mounted on drive wheel brackets 6F of the side frames 6. The drive wheels 9 are driven to rotate by a hydraulic motor as a power source. The idler wheels 10 are mounted on idler wheel brackets 6E of the side frames 6. The idler wheels 10 are biased forward by a track tensioning device (not shown).

[0035] A plurality of upper rollers 11, for example, three, are provided on the upper plate 5A of the side frame 6 at intervals in the front-to-rear direction. The upper rollers 11 guide the crawler belt 13 in the front-to-rear direction on the upper side of the side frame 6. A plurality of lower rollers 12, for example, nine, are provided on the lower plate 5B of the side frame 6 at intervals in the front-to-rear direction. The lower rollers 12 guide the crawler belt 13 in the front-to-rear direction on the lower side of the side frame 6.

[0036] The crawler belt 13 is wound around the drive wheel 9 and the idler wheel 10. The crawler belt 13 is configured to include a plurality of track links connected in an annular shape and a plurality of shoes attached to the outer periphery of the plurality of track links. The crawler belt 13 moves in an orbit between the drive wheel 9 and the idler wheel 10 as the drive wheel 9 is driven to rotate.

[0037] Here, the left traveling section 14 will be described. When transporting the hydraulic excavator 1, the left traveling section 14 is moved left and right relative to the center frame 5 or is removed from the center frame 5. The left traveling section 14 is configured including the side frame 6, drive wheels 9, idler wheels 10, three upper rollers 11, nine lower rollers 12, a crawler track 13, and a left-side vehicle width expansion / contraction device 15, which will be described later. The right traveling body is configured in the same manner as the left traveling section 14.

[0038] Next, a description will be given of the configuration and operation of the left vehicle width adjusting device 15, which is a characteristic feature of this embodiment. The right vehicle width adjusting device is similar to the left vehicle width adjusting device 15, so a description thereof will be omitted.

[0039] The left vehicle width adjustment device 15 constitutes part of the left running section 14. In other words, the vehicle width adjustment device 15 is a part that is removed together with the left running section 14 when it is removed from the center frame 5. In other words, the vehicle width adjustment device 15 is transported separately from the center frame 5 and the upper rotating body 2.

[0040] The left vehicle width expanding / reducing device 15 expands or contracts a rod 16B of a hydraulic cylinder 16 (described later) to move the left side frame 6 in the left-right direction relative to the center frame 5, thereby expanding or contracting the vehicle width. The left vehicle width expanding / reducing device 15 includes the hydraulic cylinder 16, a flexible link 17, a link pin 18, a connecting portion 19, and a pin member 20 (described later).

[0041] 6, 7, and 9, the hydraulic cylinder 16 is disposed inside the left side frame 6. Specifically, the hydraulic cylinder 16 is provided extending in the front-to-rear direction along the side frame 6 so as to be housed between the outer plate 6C and the inner plate 6D. The hydraulic cylinder 16 is also attached to the side frame 6, positioned between the drive wheel 9 and the idler wheel 10.

[0042] The hydraulic cylinder 16 includes a cylindrical tube 16A, a piston (not shown) inserted into the tube 16A so as to be axially movable, and a rod 16B having one end connected to the piston inside the tube 16A and the other end protruding from the tube 16A. One end of the tube 16A of the hydraulic cylinder 16 is attached to a cylinder bracket 6N of the side frame 6 so as to be rotatable in the horizontal direction about an axis extending in the vertical direction. The other end of the rod 16B is attached to one end 17C of the flexible link 17 so as to be rotatable in the horizontal direction.

[0043] However, if the hydraulic cylinders are mounted on the center frame, it is difficult to use large (high-output) hydraulic cylinders in order to reduce the weight of the center frame and upper rotating body when transporting them. Furthermore, if the hydraulic cylinders are located below the center frame, it is also difficult to use large hydraulic cylinders in order to prevent the minimum ground clearance from becoming too small. Furthermore, if the hydraulic cylinders are located below the center frame, they may be subject to collisions with rocks, concrete fragments, etc., or to the adhesion and accumulation of soil, sand, dust, etc.

[0044] In contrast, in the present embodiment, in a configuration in which the hydraulic cylinder 16 is mounted on the side frame 6, when the left running section 14 is removed for transportation, the hydraulic cylinder 16 is also removed. Therefore, the hydraulic cylinder 16 can be separated from the transportation weight of the center frame 5, and can be formed by a large hydraulic cylinder with high output. Furthermore, in a configuration in which the hydraulic cylinder 16 is mounted on the side frame 6, there is no hydraulic cylinder below the center frame 5, so the minimum ground clearance can be increased. Furthermore, the side frame 6 can protect the hydraulic cylinder 16 from rocks, concrete pieces, earth and sand, dust, etc.

[0045] The bent link 17 is disposed in the middle of the left side frame 6 in the front-rear direction. The bent link 17 is formed as a bent L-shaped structure with a bent portion 17A at the middle portion in the longitudinal direction. Specifically, as shown in FIGS. 6, 7, and 9, the bent link 17 has a pin hole 17B in the bent portion 17A, and a hydraulic cylinder 16 is connected to one end 17C extending from the bent portion 17A into the side frame 6. The bent link 17 also has another end 17D extending from the bent portion 17A, and this other end 17D is bent at an angle of, for example, 90 to 130 degrees with respect to the one end 17C.

[0046] The bent portion 17A of the bent link 17 is disposed between the mounting plates 6J, 6K of the left side frame 6, and a link pin 18 is inserted into the pin holes 6M, 17B, so that the bent link 17 is attached to the side frame 6 so as to be rotatable in the horizontal direction. In this state, one end 17C of the bent link 17 is rotatably connected to the tip of the rod 16B of the hydraulic cylinder 16. Meanwhile, one end 19A of a connecting portion 19, which will be described later, is rotatably connected to the other end 17D of the bent link 17.

[0047] Therefore, as shown in Fig. 6, when the rod 16B of the hydraulic cylinder 16 is contracted and one end 17C is rotated rearward, the other end 17D of the bent link 17 rotates inward (to the right) in the left-right direction. Also, as shown in Fig. 7, when the rod 16B of the hydraulic cylinder 16 is extended and one end 17C is rotated forward, the other end 17D of the bent link 17 rotates outward (to the left) in the left-right direction. This movement of the bent link 17 enables the hydraulic cylinder 16 to be disposed within the side frame 6, extending in the front-rear direction.

[0048] Furthermore, the flexible link 17 is disposed in the middle of the side frame 6 in the front-to-rear direction. Therefore, when a force is applied to move the left running section 14 via the flexible link 17, the expansion / contraction force can be transmitted equally to the front and rear sides of the left running section 14. In addition, the flexible link 17 is attached in a double-supported state between the mounting plates 6J and 6K, which provides high mounting strength and stable operability.

[0049] The connecting portion 19 connects the other end 17D of the flex link 17 to the center frame 5. The connecting portion 19 is rotatably provided in a cantilevered state on the underside of the lower plate 5B of the center frame 5. Specifically, the connecting portion 19 is formed by arranging oval plates facing each other with a gap in the vertical direction, so that one end 19A in the longitudinal direction of the connecting portion 19 sandwiches the other end 17D of the flex link 17, and the connecting portion 19 is connected to the other end 17D of the flex link 17 using a connecting pin 19C so as to be rotatable in the horizontal direction. Here, the connecting pin 19C can be easily removed downward from the connecting portion 19 by removing the retaining bolt 19D (see FIGS. 11 and 12).

[0050] 12, the other end 19B of the connecting portion 19 is a cylindrical boss, and a pin member 20 inserted through the boss of the other end 19B is inserted into a mounting portion 5L provided on the lower plate 5B of the center frame 5. As a result, the other end 19B of the connecting portion 19 is rotatably attached to the mounting portion 5L of the center frame 5 in a cantilevered state. The pin member 20 is secured to the upper surface of the lower plate 5B with, for example, bolts, nuts, etc. With this mounting structure, only the connecting portion 19 is disposed below the lower plate 5B of the center frame 5, so the minimum ground clearance of the center frame 5 can be maintained at a large dimension.

[0051] The vehicle width expanding / reducing device 15 according to this embodiment has the configuration as described above. Next, the vehicle width expanding / reducing operation of the undercarriage 4 using this vehicle width expanding / reducing device 15 will be described.

[0052] First, we will explain the width reduction work of reducing the width dimension of the lower traveling structure 4 in order to transition the hydraulic excavator 1 from the working mode to the transport mode. Specifically, this work involves moving the left traveling section 14 to the right and the right traveling section to the left.

[0053] First, remove the bolts 7 securing the left front leg 5D and the left rear leg 5E of the center frame 5 to the left side frame 6. Similarly, remove the bolts securing the right front leg 5F and the right rear leg 5G of the center frame 5 to the right side frame (the state shown in FIG. 6). In this state, as shown in FIG. 7, extend the rod 16B of the hydraulic cylinder 16 of the left vehicle width expansion / reduction device 15 to rotate one end 17C of the flexible link 17 forward and the other end 17D to the left. At this time, because the other end 17D of the flexible link 17 is connected to the center frame 5 via the connecting portion 19, the left side frame 6, i.e., the left running section 14, moves to the right (toward the center frame 5). Similarly, the right running section is moved to the left (toward the center frame 5) by the right vehicle width expansion / reduction device. This allows the left running section 14 and the right running section of the undercarriage 4 to move closer to each other, thereby reducing the vehicle width.

[0054] If the vehicle width of the lower traveling structure 4 is set to a dimension that fits within the transport width limit, the left side frame 6 and the right side frame are fixed to the legs 5D to 5G of the center frame 5 using bolts 7. As a result, the hydraulic excavator 1, including the lower traveling structure 4, fits within the transport width limit, and can therefore be transported by loading it onto a trailer.

[0055] Next, we will explain the work required to reduce the height and transport weight of the hydraulic excavator 1 due to height and weight restrictions imposed by underpasses, tunnels, underpasses, bridges, etc. along its transport route. In this case, the bolts 7 fastening the left and right side frames 6 to the legs 5D to 5G of the center frame 5 are removed. The connecting pin 19C connecting the left flex link 17 to the connecting portion 19 is removed to separate the flex link 17 from the connecting portion 19. The connecting pin connecting the right flex link to the connecting portion is removed to separate the right flex link from the connecting portion. Furthermore, the various hydraulic lines are disconnected. This allows the center frame 5 to be separated from the left and right side frames 6 and 6. The transported unit consisting of the upper rotating body 2 and center frame 5 is then lifted and loaded onto a transport trailer. This allows the height to be reduced and the transport weight to be reduced.

[0056] Thus, according to this embodiment, the left vehicle width expanding / reducing device 15 extends or retracts the rod 16B of the hydraulic cylinder 16 to move the left side frame 6 in the left-right direction relative to the center frame 5, and similarly, the right vehicle width expanding / reducing device moves the right side frame in the left-right direction to expand or reduce the vehicle width of the undercarriage 4. In addition, the hydraulic cylinders 16 of the left and right vehicle width expanding / reducing devices 15 are attached to the side frames 6, positioned between the drive wheels 9 and the idler wheels 10.

[0057] Therefore, by removing the left and right side frames 6 (left traveling section 14, right traveling section) from the center frame 5, the left and right vehicle width expansion / contraction devices 15 including the hydraulic cylinders 16 can also be removed together with the hydraulic excavator 1. This makes it possible to reduce the weight of the transported unit consisting of the upper rotating body 2 and center frame 5. As a result, the hydraulic excavator 1 can be transported with simple work. Furthermore, by providing the hydraulic cylinders 16 on the side frames 6, it is possible to use large, high-output hydraulic cylinders, enabling smooth expansion / contraction of the vehicle width.

[0058] Furthermore, with the hydraulic cylinders 16 attached to the side frames 6, a large minimum ground clearance can be maintained between the ground and the lower plate 5B of the center frame 5. This makes it less likely that concrete pieces, rebar, etc. will interfere with the center frame 5 while traveling or working, increasing the number of work sites that can be traveled over and improving workability.

[0059] The side frame 6 is formed as a cylindrical body, and the hydraulic cylinder 16 is disposed inside the side frame 6. Therefore, the hydraulic cylinder 16 can be protected from rocks, concrete pieces, earth and sand, dust, and the like.

[0060] The vehicle width expanding / reducing device 15 includes a hydraulic cylinder 16 extending in the front-rear direction along the side frame 6, a flexible link 17 having a flexible portion 17A rotatably attached to the side frame 6 and having one end 17C to which a rod 16B of the hydraulic cylinder 16 is connected pivoting in the front-rear direction, thereby causing the other end 17D to pivot in the left-right direction, and a connecting portion 19 connecting the other end 17D of the flexible link 17 to the center frame 5. Therefore, the flexible link 17 can switch the movement of the one end 17C in the front-rear direction to the movement of the other end 17D in the left-right direction. This allows the hydraulic cylinder 16 to be provided extending in the front-rear direction along the side frame 6.

[0061] The flexible link 17 is disposed in the middle in the front-to-rear direction of the side frame 6. Therefore, when a force is applied to move the left running section 14 via the flexible link 17, the expansion / contraction force can be transmitted equally to the front and rear sides of the left running section 14.

[0062] The connecting part 19 is rotatably mounted in a cantilevered state on the underside of the lower plate 5B of the center frame 5. Therefore, because only the connecting part 19 supported in a cantilevered state is located below the lower plate 5B, a large minimum ground clearance can be maintained between the ground and the lower plate 5B of the center frame 5, which also improves workability.

[0063] Furthermore, the side frame 6 is equipped with a pair of mounting plates 6J, 6K located inside in the left-right direction and facing each other with a gap in the up-down direction, and a link pin 18 attached to the pair of mounting plates 6J, 6K and extending in the up-down direction. A bending portion 17A of the bending link 17 is rotatably attached to the link pin 18 between the pair of mounting plates 6J, 6K. This allows the bending link 17 to be attached to the side frame 6 in a double-supported state, improving durability and operational reliability.

[0064] In the embodiment, an example has been described in which one set of vehicle width widening / reducing devices 15 is provided on the left side frame 6 and one set of vehicle width widening / reducing devices is provided on the right side frame. However, the present invention is not limited to this, and for example, two or more sets of vehicle width widening / reducing devices may be provided on the left side frame and two or more sets of vehicle width widening / reducing devices may be provided on the right side frame.

[0065] In the embodiment, the undercarriage 4 of a hydraulic excavator 1 has been used as an example of the undercarriage of a construction machine, but the present invention is not limited to this and can also be applied to the undercarriage of other construction machines, such as the undercarriage of a hydraulic crane. [Explanation of symbols]

[0066] 1. Hydraulic excavator (construction machinery) 2 Upper rotating body (car body) 4 Undercarriage 5 Center Frame 5B Lower plate 6 Left side frame 6J Upper mounting plate 6K Lower mounting plate 9 drive wheels 10 idler wheel 13 Tracks 14 Left running section 15 Left side vehicle width expansion device 16 Hydraulic cylinder 17 Flex Link 17A Bend part 17C,19A One end 17D,19B Other end 18 link pin 19 Connecting part

Claims

1. a center frame located in the center of the vehicle body; side frames attached to both the left and right sides of the center frame in a state of extending in the front-rear direction and movable in the left-right direction relative to the center frame; a drive wheel provided at one end of the side frame in the longitudinal direction; an idler wheel provided at the other end of the side frame in the longitudinal direction; a crawler belt wound around the drive wheel and the idler wheel; a vehicle width expanding / reducing device that expands or contracts a rod of a hydraulic cylinder to move the side frames in the left and right direction relative to the center frame, thereby expanding or contracting the vehicle width; In a lower running body of a construction machine comprising: The hydraulic cylinder of the vehicle width expansion / contraction device is located between the drive wheel and the idler wheel and attached to the side frame, The side frame is formed as a cylindrical body, The hydraulic cylinder is disposed inside the side frame.

2. A center frame located at the center of the vehicle body; side frames attached to both the left and right sides of the center frame in a state of extending in the front-rear direction and movable in the left-right direction relative to the center frame; a drive wheel provided at one end of the side frame in the longitudinal direction; an idler wheel provided at the other end of the side frame in the longitudinal direction; a crawler belt wound around the drive wheel and the idler wheel; a vehicle width expanding / reducing device that expands or contracts a rod of a hydraulic cylinder to move the side frames in the left and right direction relative to the center frame, thereby expanding or contracting the vehicle width; In a lower running body of a construction machine comprising: The hydraulic cylinder of the vehicle width expansion / contraction device is located between the drive wheel and the idler wheel and attached to the side frame, The vehicle width expanding / reducing device is The hydraulic cylinder is provided to extend in the front-rear direction along the side frame; a bending link having a bending portion rotatably attached to the side frame, and one end of which is connected to the hydraulic cylinder being rotated in the front-rear direction, thereby rotating the other end in the left-right direction; a connecting portion that connects the other end of the bent link to the center frame; A lower running body of a construction machine, comprising:

3. The undercarriage of the construction machine according to claim 2, The undercarriage of a construction machine is characterized in that the flexible link is disposed in the middle of the side frame in the front-rear direction.

4. The undercarriage of the construction machine according to claim 2, The lower running body of a construction machine is characterized in that the connecting portion is rotatably provided in a cantilevered state on the underside of the lower plate of the center frame.

5. The undercarriage of the construction machine according to claim 2, The side frames include a pair of mounting plates located inside in the left-right direction and facing each other with a gap in the up-down direction, and link pins attached to the pair of mounting plates and extending in the up-down direction, The undercarriage of a construction machine, wherein the bending portion of the bending link is rotatably attached to the link pin between the pair of mounting plates.

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