Coupling device, undercarriage and construction machine

Abstract

To provide a connector capable of facilitating connection of a car body with a crawler unit and reducing generation of metallic sound while suppressing a weight increase in a construction machine.SOLUTION: A connector includes: a pin connection part for connecting a crawler frame with a car body using one-axis pin; and a metal touch part positioned above the pin connection part. The metal touch part has: a move stopper fitted on either one of the car body and the crawler frame; and a plate mounted on the other. The move stopper has a plate-like sliding member and a metal frame surrounding the periphery of the sliding member. The plate is in a plate shape and when a crawler unit is connected with the car body, at least a part of a side edge thereof abuts on a surface of the sliding member, and a friction coefficient difference which is a difference between a maximum static friction coefficient and a dynamic friction coefficient of the sliding member is smaller than a friction coefficient difference of the frame.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a coupling device, a lower traveling body, and a construction machine. [Background technology]

[0002] Background Art Known construction machines, for example cranes, hydraulic excavators, pile drivers, and the like, include a lower running body equipped with a traveling means having a pair of crawlers, and an upper rotating body that is rotatably mounted on the lower running body and to which a boom is attached so as to be able to be raised and lowered.

[0003] Since such construction machines equipped with crawlers are transported loaded onto trailers or the like, the crawler unit including the crawlers may be removed from the car body to make the machine more compact during transportation. In this case, the construction machine requires a coupling device for attaching and detaching the crawler unit to and from the car body.

[0004] A known connecting device of this type is composed of a pin connection part that connects the car body and the crawler unit with a single axle, and a metal touch to receive the compressive reaction force generated by the rotation of the crawler around this single axle (see, for example, JP 2005-263016 A).

[0005] In the above-mentioned coupling device, the car body and the crawler unit are pin-coupled to each other via a single shaft, so that the car body and the crawler unit can be coupled together by mainly aligning the front and rear positions. This makes it easy to couple the car body and the crawler unit together. In addition, when the car body and the crawler unit are pin-coupled to each other via a single shaft, the crawler unit may rotate around the pin, but this rotation is prevented by abutting a part of the side edge of a plate-shaped plate provided on the crawler frame against a metal sliding surface provided on the car body. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-263016 A Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, efforts have been made to reduce the weight of construction machinery structures in order to reduce the weight during transportation. At the same time, there is a demand for increased capacity in construction machinery. In construction machinery that is lightweight and has increased capacity, the crawler frame is prone to deformation when turning. When the crawler frame deforms, in the above-mentioned metal-to-metal coupling device, metallic noise is likely to occur due to sliding at the metal-to-metal portion.

[0008] The occurrence of this metallic noise is not due to an inconvenience such as a lack of strength of the construction machine, but it tends to arouse anxiety among the operator, surrounding workers, and even local residents, so there is a demand for reducing the metallic noise.

[0009] Because this metallic sound is caused by deformation of the crawler frame, it is possible to reduce the metallic sound by increasing the rigidity of the crawler frame. However, increasing the rigidity of the crawler frame generally results in an increase in weight. Even though there is no strength problem with the construction machine, the weight increases unnecessarily, which goes against the demand for weight reduction.

[0010] Since metallic noise is generated by sliding at the metal touch part, it can be reduced by using a pin connection configuration with two or more axles, for example, without using a metal touch part in the connecting device. However, when using a pin connection with two or more axles, when connecting the car body and the crawler unit, it is necessary to simultaneously align the car body and the crawler unit in the vertical direction as well as the front-rear direction, which makes assembly work difficult. In addition, since the pins connecting the car body and the crawler unit are large, if the number of connecting pins increases, the number of hydraulic cylinders for insertion also increases, which tends to lead to an increase in the weight of the construction machine.

[0011] The present invention has been made based on the above-mentioned circumstances, and aims to provide a coupling device, a lower running body, and a construction machine that can easily couple a car body and a crawler unit while preventing an increase in the weight of the construction machine and reduce the generation of metallic noise. [Means for solving the problem]

[0012] A connecting device according to one embodiment of the present invention is a connecting device for connecting a crawler unit having a crawler frame and a crawler arranged on the crawler frame to a car body to which the crawler unit is detachably attached, the connecting device comprising: a pin connecting portion that connects the crawler frame to the car body with a single-axis pin; and a metal touch portion located above the pin connecting portion, the metal touch portion having a movement stop attached to one of the car body and the crawler frame and a plate attached to the other, the movement stop having a plate-shaped sliding member and a metal frame surrounding the periphery of the sliding member, the plate being plate-shaped, at least a portion of its side edge abutting against the surface of the sliding member when the crawler unit is connected to the car body, and a friction coefficient difference, which is the difference between the maximum static friction coefficient and the dynamic friction coefficient of the sliding member, is smaller than the friction coefficient difference of the frame.

[0013] A lower running body according to another aspect of the present invention comprises a crawler unit having a crawler frame and a crawler arranged on the crawler frame, a car body to which the crawler unit is detachably attached, and a connecting device of the present invention that connects the car body and the crawler unit.

[0014] A construction machine according to yet another aspect of the present invention includes the undercarriage of the present invention. Effect of the Invention

[0015] The coupling device, undercarriage, and construction machine of the present invention can easily couple the car body and crawler while preventing an increase in the weight of the construction machine, and can reduce the generation of metallic noise. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic side view showing a construction machine according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic plan view showing a lower traveling body in a state in which the crawler unit is connected to a car body in the construction machine of FIG. [Diagram 3] FIG. 3 is a schematic side view showing the configuration of the car body side of the coupling device of the undercarriage in FIG. [Figure 4] FIG. 4 is a schematic side view showing the configuration of the crawler unit side of the coupling device of the undercarriage in FIG. [Diagram 5] FIG. 5 is a schematic enlarged perspective view of the coupling device of FIG. [Figure 6] FIG. 6 is a schematic perspective view showing the vicinity of the metal touch portion when the crawler unit is connected to the car body. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line VII-VII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] [Description of the embodiment of the present invention] The metallic sound generated by sliding in the metal touch section is caused by the stick-slip phenomenon. That is, when the frame is deformed, a force is applied to the plate that is in contact with the sliding surface in the metal touch section. If the force is equal to or less than a certain value, the plate does not move due to the static friction force of the plate. However, if the force exceeds the static friction force, the plate moves. At this time, the plate slides in a direction in which the force caused by this deformation decreases, and stops when the force applied to the plate falls below the kinetic friction force. During this sliding, the metallic sound can be generated. The inventors have noticed that in this stick-slip phenomenon, if the difference between the coefficient of static friction and the coefficient of kinetic friction is small, the force applied to the plate is more likely to be lower than the kinetic friction force, and the sliding distance becomes shorter.

[0018] That is, a connecting device according to one embodiment of the present invention is a connecting device for connecting a crawler unit having a crawler frame and a crawler arranged on the crawler frame to a car body to which the crawler unit is detachably attached, the connecting device comprising: a pin connecting portion that connects the crawler frame to the car body with a single-axis pin; and a metal touch portion located above the pin connecting portion, the metal touch portion having a movement stop attached to one of the car body and the crawler frame and a plate attached to the other, the movement stop having a plate-shaped sliding member and a metal frame surrounding the periphery of the sliding member, the plate being plate-shaped, at least a portion of its side edge abutting against the surface of the sliding member when the crawler unit is connected to the car body, and a friction coefficient difference, which is the difference between the maximum static friction coefficient and dynamic friction coefficient of the sliding member, is smaller than the friction coefficient difference of the frame.

[0019] Since the coupling device has a single-axis pin connection, the car body and the crawler unit can be connected mainly by aligning the front and rear. This makes it easy to connect the car body and the crawler unit. In addition, since the coupling device does not require the installation of a new hydraulic cylinder, it is possible to prevent an increase in the weight of the construction machine. Furthermore, in the coupling device, a sliding member is provided at a position in the metal touch section where the plate attached to the crawler frame abuts against the car body when the crawler unit is connected to the car body. The friction coefficient difference of the sliding member is smaller than that of the frame surrounding the periphery of this sliding member. Therefore, the coupling device can reduce the generation of metallic sounds.

[0020] The frame may have a back plate with which the surface of the sliding member opposite to the surface with which the plate is in contact and an engagement groove with which the outer periphery of the sliding member is engaged, and the sliding member is attached to the frame by engaging with the engagement groove and fastening a bolt to the back plate. By fixing the sliding member to the frame using the engagement groove and the bolt in this manner, it is possible to improve durability in outdoor environments and ease of replacement while preventing a reduction in the effective surface area of ​​the sliding member.

[0021] The material of the sliding member is preferably a sintered metal impregnated with a self-lubricating resin or a lubricant. By using the sintered metal impregnated with a self-lubricating resin or a lubricant as the material of the sliding member, the static friction coefficient is maintained while the friction coefficient difference is reduced, so that the generation of metallic noise can be further reduced.

[0022] A lower running body according to another aspect of the present invention comprises a crawler unit having a crawler frame and a crawler arranged on the crawler frame, a car body to which the crawler unit is detachably attached, and a connecting device of the present invention that connects the car body and the crawler unit.

[0023] Since the undercarriage is equipped with the connecting device of the present invention, the car body and the crawler unit can be easily connected and the generation of metallic noise can be reduced.

[0024] A construction machine according to yet another aspect of the present invention includes the undercarriage of the present invention.

[0025] Since the construction machine is equipped with the undercarriage of the present invention, the car body and the crawler unit can be easily connected and the generation of metallic noise can be reduced.

[0026] Here, the "maximum static friction coefficient" and the "kinetic friction coefficient" respectively refer to the friction coefficients against a plate, and can be measured, for example, using the pin-on-disk method.

[0027] [Details of the embodiment of the present invention] Hereinafter, a construction machine according to an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0028] [Construction machinery] The construction machine 1 shown in Figure 1 comprises a lower running body 2, an upper rotating body 3 mounted on the lower running body 2 so as to be rotatable horizontally, a boom 4 attached to the upper rotating body 3 so as to be able to rise and fall, a hook 5, and a wire rope 6 from which the hook 5 hangs down from the tip of the boom 4.

[0029] <Upper rotating body> The upper rotating body 3 includes an operator's cabin 7 adjacent to an attachment portion of the boom 4, a boom hoisting winch (not shown) for raising and lowering the boom 4, and the like.

[0030] Of these, the operator's cabin 7 is a place where the operator gets in and operates the construction machine 1.

[0031] <boom> The boom 4 is attached to the upper rotating body 3 so as to be able to swing back and forth. The boom 4 has a sheave at its tip for guiding a wire rope 6.

[0032] <hook> The hook 5 is fixed to the lower end of the wire rope 6 and is used for lifting or lowering a load.

[0033] <Wire rope> The wire rope 6 is passed through a sheave at the tip of the boom 4 and wound around a winch (not shown) installed on the upper rotating body 3. The winch may be installed on the back side of the boom 4 (the side that is on top when the boom 4 is lowered).

[0034] <Lower running body> The lower traveling body 2 itself is one aspect of the present invention. As shown in FIG. 2, the lower traveling body 2 includes a pair of crawler units 8, a car body 9 to which the crawler units 8 are detachably attached, and a coupling device 10 that couples the car body 9 and the crawler units 8.

[0035] (Crawler unit) The crawler unit 8 is a traveling device of the lower traveling body 2, and as shown in FIG. 1, has a crawler frame 8a and a crawler 8b disposed on the crawler frame 8a.

[0036] (Car body) The car body 9 is a frame that supports the upper rotating body 3 and has a rotating bearing and the like for rotating the upper rotating body 3.

[0037] 2, the car body 9 has a pair of axles 9a extending outward in the left-right direction, one on each side with respect to the traveling direction of the lower traveling body 2. The pair of axles 9a are arranged in the front-rear direction with respect to the traveling direction of the lower traveling body 2. The crawler units 8 are attached to the ends of the pair of axles 9a via coupling devices 10. Note that the "left-right direction" refers to the left and right with respect to the forward movement direction of the lower traveling body 2.

[0038] [Connection device] The coupling device 10 is itself an embodiment of the present invention. The coupling device 10 is a coupling device for coupling the crawler unit 8 to the car body 9 to which the crawler unit 8 is detachably attached. As described above, the crawler unit 8 is attached to the ends of a pair of axles 9a, and since there is a pair of crawler units 8 on the left and right, the construction machine 1 has a total of four coupling devices 10.

[0039] 3 and 4, the coupling device 10 is mounted separately on the crawler frame 8a and the axle 9a of the car body 9. The coupling device 10 includes a pin coupling part 11 that couples the crawler frame 8a to the car body 9 with a single pin, a metal touch part 12 located above the pin coupling part 11, and a position adjustment part 13.

[0040] <Pin connection part> A known configuration can be used for the configuration of the pin connection portion 11. In the connection device 10 shown in Figs. 3 and 4, in order to configure the pin connection portion 11, a single first plate-like body 11a protruding from the tip of the axle 9a of the car body 9 and a pair of second plate-like bodies 11b protruding from the crawler frame 8a and arranged so as to sandwich the first plate-like body 11a from both sides when the crawler unit 8 is connected to the car body 9 are provided. The first plate-like body 11a and the pair of second plate-like bodies 11b are provided with a first insertion hole 11c and a pair of second insertion holes 11d into which a connection pin (not shown) can be inserted, respectively. The first insertion hole 11c and the pair of second insertion holes 11d are configured to be continuous when the crawler unit 8 is connected to the car body 9.

[0041] In the pin connection portion 11, a connection pin is inserted into a first insertion hole 11c and a pair of second insertion holes 11d that are continuous when the crawler unit 8 is connected to the car body 9, thereby connecting the crawler unit 8 and the car body 9. The above connection pin is inserted by, for example, a hydraulic cylinder. After the connection pin is inserted, it is preferable to pin the connection pin so that it does not fall out.

[0042] <Metal touch part> The metal touch portion 12 has a movement stop 12a attached to the car body 9, and a plate 12b attached to the crawler frame 8a and having a plate shape.

[0043] As shown in FIG. 5, the movement stopper 12a has a plate-shaped sliding member 12c and a metal frame 12d that surrounds the periphery of this sliding member 12c.

[0044] The plate 12b has a rectangular shape as shown in Fig. 6. One side of the plate 12b is parallel to the surface of the sliding member 12c and extends in the front-rear direction. This parallel side abuts against the surface of the sliding member 12c when the crawler unit 8 is connected to the car body 9. In other words, when the crawler unit 8 is connected to the car body 9, at least a part of the side edge of the plate 12b abuts against the surface of the sliding member 12c (hereinafter, this "part of the side edge" is also simply referred to as the "tip edge").

[0045] Since the pin connection portion 11 is a single-shaft connection, the crawler unit 8 can rotate around the connection pin. The metal touch portion 12 functions to prevent relative movement between the crawler unit 8 and the car body 9 due to this rotation. In the connection device 10, the weight is distributed so that the upper part of the crawler unit 8 moves inward when the crawler unit 8 is connected to the car body 9. As a result, a part of the side edge of the plate 12b abuts against the surface of the sliding member 12c, and the static friction prevents further movement.

[0046] (Frame) As shown in FIG. 7, the frame 12d has a back plate 12e that abuts on the surface opposite to the surface that abuts on the plate 12b of the sliding member 12c, and an engagement groove 12f that engages with the outer periphery of the sliding member 12c.

[0047] Examples of metals that form the frame 12d include stainless steel and steel.

[0048] (Sliding member) The sliding member 12c has a rectangular surface and is disposed so that the surface is parallel to the vertical direction and faces the crawler frame 8a. In addition, of the two pairs of opposing sides constituting the rectangular surface, one pair of sides extends in the front-rear direction and the other pair of sides extends in the vertical direction.

[0049] The friction coefficient difference, which is the difference between the maximum static friction coefficient and the dynamic friction coefficient of the sliding member 12c, is smaller than the friction coefficient difference of the frame 12d.

[0050] The material of the sliding member 12c is preferably a so-called oil-free bushing material, which has a solid lubricating effect and does not cause sliding failure due to oil shortage. Specifically, the material of the sliding member 12c may be a brass-based material with a cylindrical lubricating resin embedded therein, a sintered metal impregnated with a lubricant, a self-lubricating resin, etc. Among them, self-lubricating resin and sintered metal impregnated with a lubricant are preferred, and self-lubricating resin is more preferred. By using a self-lubricating resin or a sintered metal impregnated with a lubricant as the material of the sliding member 12c in this way, the friction coefficient difference can be reduced while maintaining the static friction coefficient, and the generation of metallic noise can be further reduced.

[0051] Examples of the self-lubricating resin include polytetrafluoroethylene (PTFE), polyacetal (POM), polyamide (PA), and polyphenylene sulfide (PPS). Among them, PTFE is preferable. The sliding distance of the portion of the plate 12b that abuts against the sliding member 12c is relatively small, at several mm. PTFE provides sufficient lubrication even in such a minute sliding state, and can maintain a low friction coefficient difference. The self-lubricating resin is preferably a resin with improved load resistance, such as a fiber-reinforced resin.

[0052] 5 and 7, the outer periphery of the sliding member 12c engages with the engagement groove 12f of the frame 12d, and is fastened to the back plate 12e of the frame 12d with bolts 12g. That is, the sliding member 12c is attached to the frame 12d by engaging with the engagement groove 12f and fastening to the back plate 12e with the bolts.

[0053] Since the frame deformation of the construction machine 1 occurs due to the movement of the load, the surface pressure acting on the sliding member 12c differs when the plate 12b slides upward and when it slides downward, and tends to be biased in one direction, which can easily cause separation and peeling. In this regard, the physical fastening method using the bolts 12g can fix the sliding member 12c more firmly, which can prevent separation and peeling.

[0054] On the other hand, when the sliding member 12c is fixed only by bolt fastening, there is a risk of shearing in the bolt 12g. To prevent this, it is necessary to increase the number of fastening bolts. However, when the number of fastening bolts is increased, the countersunk portion for embedding the head of the bolt 12g increases, and the area (effective surface area) of the sliding member 12c that can actually support the load decreases. Therefore, the fixing of the sliding member 12c by the engagement groove 12f is also used. In other words, the slippage of the sliding member 12c is mainly suppressed by the engagement groove 12f, and the lifting (peeling) of the sliding member 12c is mainly suppressed by the bolt fastening. This makes it possible to reduce the number of bolt fastenings required and to suppress a decrease in the effective surface area of ​​the sliding member 12c. In addition, since the sliding member 12c is likely to slip in the vertical direction, providing the engagement groove 12f at least on the upper edge side and the lower edge side of the sliding member 12c is effective in suppressing the slippage.

[0055] Furthermore, the sliding member 12c becomes worn and must be replaced, but fixing it with the engagement groove 12f and the bolt 12g has the advantage that the sliding member 12c can be easily detached when replacing it.

[0056] (plate) As described above, when the crawler unit 8 is connected to the car body 9, at least the leading edge of the plate 12b abuts against the surface of the sliding member 12c, but it is preferable that the entire leading edge abuts against the surface of the sliding member 12c. By abutting the entire leading edge against the surface of the sliding member 12c in this manner, the sliding of the plate 12b is made smooth and the stick-slip phenomenon can be prevented.

[0057] The plate 12b may be made of, for example, metal similar to the frame 12d.

[0058] In the coupling device 10, the plate 12b is positioned so that the car body 9 side is inclined diagonally upward when the crawler unit 8 is coupled to the car body 9, as shown in FIG. 6, but it can also be positioned horizontally.

[0059] (Position adjustment part) As shown in FIG. 3, the position adjustment section 13 has a recess 13a that is provided at the upper end of the first plate-like body 11a and is open at the top, and as shown in FIG. 4, a support shaft 13b that is bridged across a pair of second plate-like bodies 11b.

[0060] The support shaft 13b is provided so as to extend in the front-rear direction and engage with the recess 13a when the crawler unit 8 is connected to the car body 9. The positions of the recess 13a and the support shaft 13b are adjusted so that when the recess 13a and the support shaft 13b are engaged, the crawler unit 8 is stabilized by its own weight at a position where the first insertion hole 11c and the pair of second insertion holes 11d are continuous with each other.

[0061] Therefore, with this configuration, when connecting the crawler unit 8 to the car body 9, the position of the crawler unit 8 in the front-rear direction is adjusted so that the pair of second plate-shaped bodies 11b sandwich the first plate-shaped body 11a, and the support shaft 13b is engaged with the recess 13a, so that the first insertion hole 11c and the pair of second insertion holes 11d naturally become continuous. This position adjustment makes it possible to easily insert the connecting pin into the continuous first insertion hole 11c and the pair of second insertion holes 11d.

[0062] <Advantages> Since the pin connection part 11 of the coupling device 10 is a single shaft, the car body 9 and the crawler unit 8 can be connected by mainly aligning the front and rear. Therefore, the car body 9 and the crawler unit 8 can be easily connected. In addition, since the coupling device 10 does not require the installation of a new hydraulic cylinder, the weight of the construction machine 1 can be suppressed. Furthermore, the coupling device 10 has a sliding member 12c at a position where the plate 12b attached to the crawler frame 8a abuts against the car body 9 in the metal touch part 12 when the crawler unit 8 is connected to the car body 9. The friction coefficient difference of the sliding member 12c is smaller than that of the frame 12d surrounding the periphery of the sliding member 12c. Therefore, the coupling device 10 can reduce the generation of metallic sounds.

[0063] Since the undercarriage 2 and the construction machine 1 are provided with the coupling device 10 of the present invention, the car body 9 and the crawler unit 8 can be easily coupled together, and the generation of metallic noise can be reduced.

[0064] [Other embodiments] The above-mentioned embodiment does not limit the configuration of the present invention. Therefore, the above-mentioned embodiment may omit, replace or add components of each part of the above-mentioned embodiment based on the description in this specification and common technical knowledge, and it should be understood that all of these are within the scope of the present invention.

[0065] In the above embodiment, a construction machine equipped with a boom and a hook has been used as an example, but the construction machine of the present invention is not limited to one equipped with a boom and a hook, and may be one that has a crawler unit having a crawler frame and a crawler arranged on this crawler frame, and a car body to which this crawler unit is removably attached.

[0066] In the above embodiment, the stopper is attached to the car body and the plate is attached to the crawler frame, but the plate may be attached to the car body and the stopper may be attached to the crawler frame. In other words, the coupling device can achieve the same effect as long as the stopper is attached to one of the car body and the crawler frame and the plate is attached to the other.

[0067] In the above embodiment, the mechanism for attaching the sliding member to the frame has been described as including an engagement groove provided on the frame that engages with the outer periphery of the sliding member and a bolt that fastens the sliding member to the bottom of the frame, but the mechanism for attaching the sliding member to the frame is not limited to this. For example, the mechanism may be configured to attach the sliding member to the frame using an adhesive, double-sided tape, or the like.

[0068] In the above embodiment, the case where the connecting device has the position adjustment unit has been described, but the position adjustment unit is not limited to the above configuration. In addition, the position adjustment unit is not an essential component and can be omitted.

[0069] In the above embodiment, the plate is described as being square-shaped, but the plate is not limited to being square-shaped, and other shapes can be adopted as long as at least a portion of the side edge abuts against the surface of the sliding member when the crawler unit is connected to the car body. [Industrial Applicability]

[0070] As described above, the connecting device, undercarriage, and construction machine of the present invention can easily connect the car body and the crawler while preventing an increase in the weight of the construction machine, and can reduce the generation of metallic noise. [Explanation of symbols]

[0071] 1. Construction machinery 2 Undercarriage 3. Upper rotating body 4. Boom 5. Hook 6 Wire Rope 7 Pilot's Cabin 8 Crawler Unit 8a Crawler frame 8b Crawler 9 Car Body 9a Axle 10 Coupling device 11 Pin connection 11a First plate-like body 11b Second plate-like body 11c First insertion hole 11d Second insertion hole 12 Metal touch section 12a Stop moving 12b Plate 12c Sliding member 12d frame 12e Back plate 12f Engagement groove 12g bolt 13 Position adjustment section 13a Recess 13b Support shaft

Claims

1. A coupling device for coupling a crawler unit having a crawler frame and a crawler disposed on the crawler frame to a car body to which the crawler unit is detachably attached, comprising: a pin connection portion that connects the crawler frame to the car body with a single-shaft pin; The metal touch part located above the pin connection part Equipped with The metal touch part is a stopper attached to one of the car body and the crawler frame, and a plate attached to the other of the car body and the crawler frame; the stopper has a plate-shaped sliding member and a metal frame surrounding the sliding member, the plate is plate-shaped, and at least a portion of a side edge of the plate abuts against a surface of the sliding member when the crawler unit is connected to the car body; A coupling device in which a friction coefficient difference, which is the difference between the maximum static friction coefficient and the dynamic friction coefficient of the sliding member, is smaller than the friction coefficient difference of the frame.

2. The above frame is a back plate against which the sliding member is in contact with a surface opposite to a surface against which the plate is in contact; an engagement groove that engages with the outer periphery of the sliding member; having 2. The coupling device of claim 1, wherein said sliding member is attached to said frame by engaging said engaging groove and bolting said back plate.

3. 3. A connecting device according to claim 1 or 2, wherein the material of said sliding member is a self-lubricating resin or a sintered metal impregnated with a lubricant.

4. a crawler unit having a crawler frame and a crawler disposed on the crawler frame; a car body to which the crawler unit is detachably attached; A coupling device according to claim 1, 2 or 3 for coupling the car body and the crawler unit; A lower running body comprising:

5. A construction machine comprising the undercarriage according to claim 4.

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