JP3567365B2 - Work arm structure of work machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a working arm structure of a working machine, and more particularly, to a working arm structure suitably used for a working arm of a working machine such as a boom of a hydraulic shovel.
[0002]
[Prior art]
A working machine such as a construction machine or a cargo handling machine includes one or a plurality of linked long working arms to which a working tool or the like is attached. For example, a hydraulic shovel, which is a typical work machine, is a boom that is a work arm that is vertically swingably attached to a body of a machine body, and a work arm that is vertically swingably attached to a tip of the boom. Arm. A bucket, which is a working tool, is attached to the tip of the arm so as to be vertically swingable.
[0003]
Since these working arms are formed to be long, they are formed in a box-shaped structure by plate members so as to have sufficient strength against bending, twisting, etc. and to reduce the weight.
[0004]
Referring to FIG. 7, the working arm will be described by taking the above-described boom as an example. The boom generally denoted by reference numeral 50 is formed in a box-shaped structure by welding various steel members to each other. That is, the boom 50 is formed into a box-shaped structure having a rectangular box-shaped cross-section and extending in the longitudinal direction by the upper plate 52, the lower plate 54, the left side plate 56, and the right side plate 58, which are plate members extending in the longitudinal direction. Have been. A connection bracket 60 provided with a bearing hole 60b for connection to the arm at one end in the longitudinal direction of the box-shaped structure, and a connection bracket 62 provided with a bearing hole for connection to the body of the body at the other end. It is attached.
[0005]
The bearing bracket 60 is formed in a forked shape by casting, forging, or a combination of steel members, and a bearing hole 60b is formed in each of the forked portions on an axis 60a orthogonal to the longitudinal direction of the boom 50. The bearing bracket 60 is butt-welded and joined to each end of the upper plate 52, the lower plate 54, the left side plate 56, and the right side plate 58 forming the box-shaped cross section of the boom 50. The position of the bearing hole 60b of the bearing bracket 60 in the longitudinal direction of the boom 50 is important for the function as a working arm. In welding and joining, the position of the bearing hole 60b is related to the connection bracket 62 at the other end by a jig or the like. The length L is defined as follows.
[0006]
[Problems to be solved by the invention]
The working arm structure of the conventional working machine of the above-described embodiment has the following problems to be solved.
[0007]
(1) Weld quality:
The position of the bearing bracket 60 in the butting direction of the butt welding of the bearing bracket 60 attached to the end of the working arm in the form described above with the end of each plate member forming a box-shaped cross section is determined. Since it is defined by the dimension L, it tends to fluctuate due to errors and variations in manufacturing dimensions and mounting dimensions of each plate member (the upper plate 52, the lower plate 54, the left side plate 56, and the right side plate 58). When these long plates are divided into a plurality of plates and joined, the fluctuation becomes even greater. Therefore, it is difficult to stabilize the quality of the butt weld.
[0008]
(2) Dimensional accuracy of bearing bracket:
When the welding gap in the butt weld changes, the amount of molten metal in the weld changes accordingly, and the thermal distortion of welding causes a change in the size of the bearing hole 60b, a displacement of the bearing hole 60b on the axis 60a, and the like. . In addition, since the fluctuation range of the thermal strain becomes large, it is difficult to predict the fluctuation amount, and it is difficult to appropriately maintain the dimensional accuracy.
[0009]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and a technical problem thereof is that a connecting bracket welded and attached to an end of a working arm formed into a box-shaped cross section by a plate member can be used to change the size of the plate member. It is an object of the present invention to provide a working arm structure of a working machine which can stabilize the quality of welding, reduce dimensional fluctuations due to thermal distortion of welding, and can be attached.
[0010]
[Means for Solving the Problems]
In the present invention, as a working arm structure for solving the above technical problem, a connecting bracket welded and attached to the longitudinal end of a working arm formed of a plate member, having a box-shaped cross section and extending in the longitudinal direction, is provided. A base portion sandwiched between ends of a pair of plate members facing each other in the box-shaped section and integrally joined to each of the plate members, and a bracket portion integrally joined to the base portion. The base is formed in a cylindrical shape, the plate member is abutted on the outer peripheral portion of the cylinder, and the bracket portion is provided at both ends in the axial direction of the cylindrical base with an annular shape to be joined to the cylindrical base. There is provided a working arm structure of a working machine, wherein the working arm structure is provided with a protrusion .
[0011]
By joining the base of the connection bracket to each of the plate members sandwiched between the pair of plate members, even if the relative position in the longitudinal direction of the working arm between the plate member and the base changes, the plate member and the base are joined. The condition of the welded portion does not fluctuate, the quality of welding is stabilized, and the fluctuation of thermal distortion is reduced. Further, the plate member is brought into contact with the outer peripheral portion of the cylinder to form a stable welded portion. Further, the bracket portion is attached to both ends of the cylindrical base to form a forked connecting bracket.
[0017]
Referring to FIG. 1, a hydraulic excavator generally designated by the reference numeral 2 includes a boom 6 which is a working arm attached to a body body 4 so as to be able to swing vertically, and a tip end of the boom 6 which swings vertically. An arm 8, which is a work arm movably attached, is provided. A bucket 10, which is a working tool, is attached to the tip of the arm 8 so as to be vertically swingable.
[0018]
Referring to FIG. 2 together with FIG. 1, the boom 6 is formed in a box-shaped structure by welding various steel members to each other. That is, the boom 6 is formed in a box-shaped structure having a rectangular box-shaped cross section by the upper plate 12, the lower plate 14, the left side plate 16, and the right side plate 18, which are plate members extending in the longitudinal direction. A connection bracket 20 having a bearing hole for connecting to the arm 8 is attached to one end in the longitudinal direction, and a connection bracket 22 having a bearing hole for connecting to the body 4 is attached to the other end.
[0019]
Referring to FIGS. 3 to 5 together with FIG. 2, the connection bracket 20 includes a base 21 and a pair of brackets 22 a and 22 b integrally joined to the base 21. The base 21 is joined to ends of an upper plate 12 and a lower plate 14, which are a pair of plate members facing each other in a box-shaped cross section. In the bracket portions 22a and 22b, bearing holes 20b are respectively formed on the same axis 20a.
[0020]
The base 21 has a cylindrical shape extending in a direction perpendicular to the longitudinal direction of the boom 6 and is formed by a pipe member or casting. The outer diameter of the cylinder is formed so as to abut between the ends of the upper plate 12 and the lower plate 14. The length of the cylinder is formed substantially the same as the width of the band of the upper plate 12 and the lower plate 14.
[0021]
The pair of bracket portions 22a and 22b are formed in a plate shape by forging or casting. The bracket portions 22a and 22b are substantially the same in the present embodiment. An annular protruding portion 22c for joining to the base 21 is formed on one plate-like surface of the bracket portions 22a and 22b. The protruding portion 22c is formed so as to protrude smoothly from the plate-like surface of each of the bracket portions 22a and 22b.
[0022]
In the base 21 and the brackets 22a and 22b formed as described above, the both ends of the base 21 and the protrusions 22c of the brackets 22a and 22b abut against each other, and as shown in FIG. Are welded together or by groove welding with a groove provided. In each of the bracket portions 22a and 22b, a bearing hole 20b is formed by machining with the same axis 20a in a state where the bearing hole 20b is welded, and the connection bracket 20 is completed.
[0023]
The connecting bracket 20 has a base 21 sandwiched between the ends of the upper plate 12 and the lower plate 14 as shown in FIG. 5, and the bearing hole 20a is positioned at the other end as shown in FIG. Is positioned at the position of the length L, and is welded to each of the upper plate 12 and the lower plate 14 from the side of the upper plate 12 and the lower plate 14 in the thickness direction by deep and penetration welding such as laser welding. Are joined. The base 21 and the upper plate 12 and the lower plate 14 are completely joined by this welding. However, if further strength is required, the outer peripheral portion of the base 21 and the tip of the upper plate 12 and the lower plate 14 may be connected. (Indicated by Y in FIG. 5). The bracket portions 22a and 22b are appropriately welded to the upper plate 12, the lower plate 14, the left side plate 16 and the right side plate 18 by relatively small fillet welding, and the connection bracket 20 at the end of the boom 6 is provided. The shape of the joint is adjusted.
[0024]
The operation of the working arm structure of the working machine as described above with reference to FIG. 1 will be described.
[0025]
(1) Weld quality:
The base 21 to which the bracket portions 22a and 22b are joined is sandwiched between the upper plate 12 and the lower plate 14 of the boom 6 by abutting the cylindrical outer peripheral portion thereof. L, and a stable welded portion is formed even if these relative positions change in the longitudinal direction (the direction indicated by X). Therefore, even if errors and variations occur in the manufacturing dimensions and mounting dimensions of each plate, the welded joint between the base 21 and the upper plate 12 and the lower plate 14 is stable, and stable quality welding is ensured. Is done. In addition, since the base 21 is joined to the protruding portion 22c of the bracket portions 22a and 22b which rises smoothly, the base 21 and the bracket portions 22a and 22b are firmly and integrally joined.
[0026]
(2) Dimensional accuracy of bearing bracket:
Since the base 21 to which the bracket portions 22a and 22b are attached and the upper plate 12, the lower plate 14, the left side plate 16, the right side plate 18, and the like become stable, the dimensions of the bearing hole 20b, Variations due to thermal distortion, such as displacement on the axis 20a, are reduced. Therefore, the repair work such as machining after the welding and joining is easily or obviated.
[0030]
【The invention's effect】
According to the working arm structure of the working machine configured according to the present invention, the connecting bracket welded and attached to the end of the working arm formed into a box-shaped cross section by the plate member is affected by the variation in the size of the plate member and the like. Thus, there is provided a working arm structure of a working machine that can stabilize welding quality and can be mounted with less dimensional fluctuation due to thermal distortion of welding.
[Brief description of the drawings]
FIG. 1 is a side view of a hydraulic excavator which is a typical work machine having a work arm structure of a work machine configured according to the present invention.
FIG. 2 is a perspective view of one boom of a working arm of the hydraulic excavator shown in FIG.
3 is a perspective view showing a part of a connecting bracket of the boom shown in FIG.
FIG. 4 is a cross-sectional view showing a joint between a bracket and a base of the connection bracket shown in FIG. 3;
FIG. 5 is a side view showing a joint between the base of the connection bracket shown in FIG. 3 and an upper plate and a lower plate, excluding one of the brackets;
FIG. 6 is a perspective view of another embodiment of the base of the connection bracket.
FIG. 7 is a perspective view of a conventional boom.
[Explanation of symbols]
2: Hydraulic excavator (work machine)
4: Airframe body 6: Boom (work arm)
8: Arm (work arm)
12: Upper plate (plate member)
14: Lower plate (plate member)
16: Left side plate (plate member)
18: Right side plate (plate member)
20: Connection bracket 20b: Bearing hole 21: Base 22a: Bracket 22b: Bracket 22c: Projection 50: Boom (work arm)
60: Connecting bracket

Claims (1)

A connection bracket which is formed by a plate member and has a box-shaped cross section and which extends in the longitudinal direction, and which is attached and welded to the longitudinal end thereof,
A base portion sandwiched between ends of a pair of plate members facing each other in the box-shaped cross section and integrally joined to each of the plate members, and a bracket portion integrally joined to the base portion. ,
The base is formed in a cylindrical shape,
The plate member is in contact with an outer peripheral portion of the cylinder,
The working arm structure of a working machine, wherein the bracket is attached to both ends of the cylindrical base in the axial direction with annular projections joined to the cylindrical base .

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