JP2000199240A - Hydraulic excavator boom structure - Google Patents

Abstract

(57) [Problem] To provide a boom structure of a hydraulic shovel capable of increasing the strength of a welded portion in a boom curved portion and eliminating a reinforcing plate, thereby reducing the weight of the boom. SOLUTION: An oil pressure is formed by combining an upper plate 2, a lower plate 3, and side plates 4 and 5 in a box shape in cross section, and welding a connecting portion of each plate to form a boom 1 which is curved in a longitudinal direction. In the boom structure of the shovel, a J-shaped groove 4a is formed on at least one of the upper edge of the side plate and the lower edge of the side plate in the boom bending portion.
The boom 1 is formed by performing joint welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a boom constituting a front attachment of a hydraulic shovel.

[0002]

2. Description of the Related Art Conventionally, an upper swing body of a hydraulic shovel has
As shown in FIG. 9, a front attachment 53 including a bucket 50, an arm 51, and a boom 52 is provided. The boom 52 extends and retracts a hydraulic cylinder 54 provided between a boom center boss 52a and a turning frame (not shown). With this, it is configured to undulate.

As shown in FIG. 10, the boom 52 has an upper plate 52b, a lower plate 52 and left and right side plates 52d,
The four plates 52e are assembled in a box shape in cross section, and the connecting portions of the plates are welded to form a shape in the longitudinal direction.

In the boom 52, a curved portion near the boom center boss portion 52a is a portion where stress is particularly concentrated due to a load applied to the front attachment 53 at the time of work, and is reinforced.

Specifically, the reinforcement is to connect the boom center boss portion 52a and the upper plate 52b so as to partition the boom 52 in the cross-sectional direction in order to prevent the box-shaped cross-sectional shape of the boom 52 from being deformed. Plate 5 provided in this way
2f, a reinforcing plate 52g provided to connect the boom center boss 52a and the lower plate 52c, and a reinforcing plate 52h provided to reinforce the boom center boss 52a. 52i is a boom base and 52j is a boom tip bracket. The reinforcing plate 52k is a reinforcing plate provided to reinforce the boom other than the curved portion.

[0006]

However, in the conventional boom structure, the weight of the reinforcing plates 52f, 52g, and 52h attached to reinforce the boom curved portion is an obstacle to reducing the weight of the boom. In addition, since these reinforcing plates are all welded inside the boom, time is required for welding the reinforcing plates, thereby increasing the manufacturing cost of the boom.

Therefore, it has been studied to reduce the weight of the boom by eliminating the reinforcing plate at the boom curved portion. FIG.
10 is a cross-sectional view taken along the line AA in FIG. 10 and shows a cross-section of a curved portion of the boom 52. In this cross-sectional structure, when external force is applied to the boom 52 during excavation work, for example, when the reinforcing plates 52f, 52g, and 52h are all abolished, the upper plate 52b and the lower plate 52c may be deformed (two-dot chain line in the figure). 52b ', 52c'), side plates 52d and 52e.
Are deformed (two-dot chain lines 52d ', 52d ", 52
e ′, 52e ″), so-called out-of-plane deformation occurs.
As a result, the T-joint welds W1, W2, W
3, and the stress is concentrated on W4.

FIG. 12 shows a conventional groove for a T-joint weld W1.

[0009] In the same figure, a rectangular groove is formed at the upper end of the side plate 52d. 52b is an upper plate which is a material to be welded, RF indicates a root face of a groove, and a dimension t
Indicates the thickness of the root face. RG indicates a root gap which is a gap between the root face RF and the inner surface of the upper plate 52b, and g indicates a dimension of the gap.

[0010] The welding torch 55
When welding using is performed, arc ar occurs on the surface of the groove surface a near the torch, and sufficient penetration may not be obtained at the maximum depth portion a of the groove. . Reference numeral 55a denotes a nozzle of the welding torch 55, and reference numeral 56 denotes a welding wire. Thus, the upper plate 52b and the side plate 52
d, 52e, lower plate 52c and side plates 52d, 52e
Has the problem that the reliability of the weld cannot be ensured.

FIG. 13 shows a state where the above-mentioned sufficient penetration has not been obtained. As shown in the figure, a welding defect due to poor penetration occurs at the maximum depth portion A of the groove, and this welding defect may cause damage to the boom.

As described above, the conventional boom structure of the hydraulic excavator has a problem that the reinforcing plate cannot be eliminated and the boom cannot be reduced in weight because the reliability of the welded portion is low.

The present invention has been made in consideration of the above-described problems in the conventional boom structure, and has been proposed in order to improve the reliability of a welded portion in a curved portion of a boom and eliminate a reinforcing plate.
An object of the present invention is to provide a boom structure of a hydraulic shovel capable of reducing the weight of a boom.

[0014]

According to a first aspect of the present invention, there is provided a boom structure for a hydraulic excavator in which an upper plate, a lower plate, and a side plate are combined in a box shape in cross section, and a connecting portion of each plate is welded in a longitudinal direction. In a boom structure of a hydraulic excavator forming a boom curved in a letter shape, at least one of an upper edge of a side plate and a lower edge of a side plate in a boom bending portion is formed into a J-shaped groove, and a T-joint is formed on the side plate. The gist is to perform welding.

[0015] The boom structure of the second aspect is characterized in that a J-shaped groove is formed corresponding to a portion of the boom bending portion where the largest load acts.

The boom structure of the hydraulic shovel according to claim 3 is
A boom structure of a hydraulic shovel that combines an upper plate, a lower plate, and a side plate having a groove-shaped groove into a box shape in cross section, and forms a boom that is curved in a longitudinal shape by welding a connecting portion of each plate. In, the thickness of the root face in at least one of the joint portion between the side plate and the upper plate and the joint portion between the side plate and the lower plate in the boom bending portion is 1.2 to
3.0mm and root gap set to 0.3-0.6mm
The point is to perform joint welding.

[0017] The boom structure of the fourth aspect is characterized in that the root gap is set to 0.3 to 0.6 mm at a portion of the boom bending portion where the largest load acts.

According to the boom structure of the first aspect, since the distance between the welding wire of the welding torch and the groove surface is made constant by forming the J-shaped groove, the maximum depth of the groove can be maintained. However, sufficient penetration is performed, and the T-joint weld can be reliably welded. Thereby, since the reliability of the welded portion is improved, it is not necessary to arrange a reinforcing plate inside the boom to compensate for poor welding, and the boom can be reduced in weight.

According to the boom structure of the second aspect, it is possible to effectively reinforce the portion of the boom that requires the most strength.

According to the boom structure of the third aspect, since the thickness of the root face and the root gap are set to specific ranges to improve the penetration of the groove, the conventional groove is used. Even when performing T joint welding, the upper plate, the lower plate, and the side wall can be reliably welded. Therefore,
By improving the reliability of the welded portion, it is not necessary to compensate for poor welding with a reinforcing plate, and the boom can be reduced in weight.

According to the boom structure of the fourth aspect, it is possible to reliably reinforce the most necessary part of the boom.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.

FIGS. 1 to 7 show a first embodiment of a boom structure of a hydraulic shovel according to the present invention, and FIG. 8 shows a second embodiment of the same.

In FIG. 1, a boom 1 is constructed by assembling four plates including an upper plate 2, a lower plate 3, and left and right side plates 4 and 5 into a box shape in cross section, and as a whole, bending in a longitudinally curved shape. It is formed.

Reference numeral 6 denotes a boom base, which is pivotally supported by a turning frame (not shown) via a pin (not shown). On the other hand, a boom tip bracket 7 is connected to an arm (not shown) via a pin (not shown). A boom center boss portion 8 is provided on a curved portion of the boom 1, and a rod end of the hydraulic cylinder S is connected via a pin. 2a indicates an upper plate curved portion, and L1 indicates the curved length. 3a indicates a lower plate curved portion, and L2 indicates a curved length thereof.

A portion C in FIG. 1 shows a range in which the largest load acts when an external force is applied to the boom 1.

FIG. 2 is a sectional view taken along the line BB of FIG. 1 and shows a cross section of the boom 1. In FIG.
W6, W7 and W8 indicate T-joint welds at one corner of the boom.

FIG. 3 shows a combination of the side plate 4 and the upper plate curved portion 2a before welding. The upper edge of the side plate 4 extends over the length L3, that is, over the range where the largest load acts on the boom 1, and the upper edge of the side plate 4 has a J.
A shape groove 4a is formed. A J-shaped groove 4b is also formed on the lower edge of the side plate 4 over the length L4.

FIG. 4 is an enlarged view showing a joint structure between the side plates 4 and 5 and the upper plate curved portion 2a or the lower plate curved portion 3a, and shows a T-shaped joint welded portion W5 as a representative. is there.

In the figure, 4c is the groove surface of the J-shaped groove 4a, RF1 is the root face of the J-shaped groove 4a, RG1 is the root gap between the root face RF1 and the inner surface of the upper plate 2a, and the dimension t1 is Thickness of root face RF1, g1
Indicates the dimensions of the root gap RG. The welding torch 55 is the same as the conventional welding torch shown in FIG. 12, and the same reference numerals are given and the description is omitted.

In FIG. 4, the groove surface 4c is formed in a concave curved surface, and the groove angle θ between the groove surface 4c and the inner surface of the upper plate curved portion 2a becomes close to 90 ° at the maximum depth portion c. It is in a state of standing up until. Therefore, J-shaped groove 4
When welding is performed on a, even when the welding position of the welding torch 55 slightly changes from a predetermined welding angle, the distance between the welding wire 56 and the groove surface 4c is kept substantially constant,
Therefore, the arc ar surely hits the maximum depth portion c, and the molten metal can be sufficiently melted into the entire concave curved surface.

As described above, the J-shaped groove 4a is connected to the boom 1
Large load at (load such as tensile load, compression load, torsion, etc.)
In order to withstand the bending, the boom bending portion is specified, and the upper plate bending portion 2a is formed with a required length L3. Thereby, the required welding strength in the boom bending portion can be realized. In addition, for the T-shaped joint welded portion other than the curved portion, the conventional groove-shaped groove is used for welding to minimize the processing cost of the J-shaped groove 4a having high forming cost.

The dimension g1 of the root gap RG1 in the J-shaped groove 4a is set in the range of 0.3 to 0.6 mm. According to such a welded joint, the boom 1 requires the highest strength. It is possible to obtain a deep penetration that can reach the root face RF1 for a part, that is, for the range of the length L3.

FIG. 5 shows the result of welding performed on the J-shaped groove 4a, and the penetration is reliably obtained up to the root face RF1.

Next, an example of a method of forming the J-shaped groove 4a will be described.

In FIG. 6, the J-shaped groove 4a is machined by mounting a cutting tool 12 on the tip of the arm 11 of the articulated robot 10 and controlling the cutting tool 12 in three axes. The articulated robot 10 turns,
Since a plurality of operations such as forward and backward movement, up and down movement, and swinging can be simultaneously controlled, it is possible to accurately form the J-shaped groove 4a with respect to the lengths L3 and L4 of the upper and lower edges of the side plates 4 and 5. it can.

The arm 11 of the articulated robot 10
The cutting tool 12 can be detached and a gas cutting device 13 equipped with a gas torch 13a can be mounted.

In forming the J-shaped groove 4a, first, in order to perform rough finishing, a gas cutting device 13 is used.
Is attached to the distal end of the arm 11, and the upper and lower corners of the side plates 4 and 5 are gas-cut to form a groove. Next, the gas cutting device 13 is detached from the arm 11 and the cutting tool 12 is mounted.

A shaping cutter for J-shaped bevel cutting, for example, an end mill cutter 12a is detachably attached to the cutting tool 12, and the end mill cutter 12a is rotated to form the gas-cut groove-shaped groove. The surface is machined into a J-shaped groove. During machine finishing,
Since the surface to be cut has already been rough-finished into a concave groove in the previous process, the load at the time of cutting the end mill cutter 12a is small, so that the forming of the J groove can be efficiently performed. In addition, since the load at the time of cutting is small, the device of the cutting tool 12 and its driving source need only be relatively small.

FIG. 7 shows a distribution of a stress generated in a boom bending portion, for example, during excavation work. FIG. 3A shows a stress distribution generated in the upper plate bending portion 2a, and FIG. 3B shows a stress distribution generated in the lower plate bending portion 3a.

The distance from the center boss shown on the abscissa is set with the center of the center boss 8 being "zero" and the boom tip 7
The distance separating toward the side is indicated by a + value to the right of the center line CT, and the distance separating toward the boom base 6 is indicated by the center line C.
The value is shown on the left side of T with a negative value. In the graph, P1
Denotes a stress generated on the back side of the upper plate (inner side of the upper plate), and P2 denotes a stress generated on the front side of the upper plate (outer side of the upper plate).

In FIG. 7A, the stress value generated in the upper plate 2a has a peak at the center boss, and decreases as the distance from the center boss increases. Although the peak of the stress value changes depending on the strength of the members constituting the boom 1, the stress value appears particularly high when the distance from the center boss portion is in the range of +200 mm to -200 mm. Therefore, in the present embodiment, the range of +200 mm to -200 mm is set as the forming processing length L3 of the J-shaped groove 4a.

In the figure, d indicates the allowable unwelded length. In the boom strength analysis of the present invention, out-of-plane deformation of the boom side plate was confirmed, but in a situation where out-of-plane deformation occurs, the unwelded length of the T-joint weld greatly affects the boom strength. Therefore, for example, if welding is performed on the boom base side with a J-shaped groove 4a in a range of -200 mm, it can be calculated that the J-shaped groove surface 4c is reliably welded. Up to 4 mm. In the conventional welding structure, however, the reliability of the welded portion was not high, so that the allowable unwelded length was 2 mm.

On the other hand, in FIG. 7B, the stress value generated in the lower plate 3a is lower than the stress value generated in the upper plate 2a.
Similar to the stress characteristic shown in the upper plate 2a, the peak becomes near the center boss portion 8 and decreases as the distance from the center boss portion 8 increases. Therefore, the forming length L4 of the J-shaped groove 4a is set so that the distance from the center boss 8 to the lower plate 3a is in the range of +200 mm to -200 mm. In the graph,
P3 indicates the stress generated on the back side of the lower plate, and P4 indicates the stress generated on the front side of the lower plate.

Next, a second embodiment of the boom structure according to the present invention will be described with reference to FIG.

In the first embodiment, the boom side plates 4,
5, the J-shaped groove 4a, 4b is formed on the upper edge and the lower edge to increase the strength of the T-joint welded portion in the boom bending portion. Provided is a boom structure that can increase the welding strength of a boom curved portion while adopting a re-groove.

In a general welding method, the root face R
F and the root gap RG are both set to small values,
For the root gap RG, welding is usually performed at "zero".

However, since the curved portion of the boom 1 on which a large load acts is formed in a round shape, it is extremely difficult to machine the gas so that the root gap RG with respect to the inner surface of the upper plate curved portion 2a becomes zero. It is. Therefore, in the present embodiment, the penetration gap is improved by setting the root gap RG to a specific value.

According to the study of the inventor of the present invention, the root face RF2 is set to 1.2 to 3.0, preferably 1.5 to 2.5 mm, and the root gap RG is set to 0.3 to 0.6, more preferably.
When set to a value of 0.3 to 0.5, deep penetration was confirmed.

More specifically, when T-joint welding is performed using a groove with a groove angle of 45 ° and 50 °, the root face R
If F2 is less than 1.2, it is not preferable because it causes dropout, and if F2 is more than 3.0, the unwelded length is undesirably long. Further, if the root gap RG2 is less than 0.3, the unwelded length is undesirably long, and if it is more than 0.6, it is not preferable because it causes dropout. However, as for the root face RF, the thickness of the root face RF is not limited to the length L3 where the strength is most required in the boom, and the thickness of the root face RF is 1.2 to 3.0 mm for the other upper and lower edges of the side plates 4 and 5. It shall be processed.

As for welding conditions, the wire diameter is φ1.
The shielding gas was 2 mm / φ1.4 mm, the shielding gas was CO ₂ / Ar-CO ₂ , the torch angle was 22 °, and the thickness of the vertical plate was 14 mm.

As described above, in the upper plate curved portion 2a, the length L3
In the lower plate curved portion 3a, the thickness of the root face RF2 is set to 1.2 to 3.0 in the range of the length L4.
When the root gap RG is set to 0.3 to 0.6 mm, the strength of the welded portion of the T-shaped joint can be increased even if the groove has a concave shape.

[0053]

As is apparent from the above description,
According to the first aspect of the present invention, the penetration is sufficiently performed even in the maximum depth portion of the groove, and the reliability of the T-joint weld is improved. Therefore, there is no need to arrange a reinforcing plate inside the boom to compensate for poor welding, and the boom can be reduced in weight.

According to the second aspect of the present invention, it is possible to effectively reinforce the portion of the boom that requires the most strength.

According to the third aspect of the present invention, since the root gap is intentionally set to be large to improve the penetration of the groove, the T-joint welding is performed using the conventional groove. Even in this case, the upper plate, the lower plate, and the side wall can be reliably welded. Therefore, there is an advantage that the reliability of the welded portion can be improved at low cost by the conventional method.

According to the fourth aspect of the present invention, it is possible to effectively reinforce a portion requiring the most strength in a boom for performing T-joint welding using a groove.

[Brief description of the drawings]

FIG. 1 is a front view showing a boom structure of a hydraulic shovel according to the present invention.

FIG. 2 is a sectional view taken along line BB of FIG.

FIG. 3 is an enlarged view of a center boss of FIG. 1;

FIG. 4 is a cross-sectional view showing a welding method of a T-joint weld portion W5 in FIG.

FIG. 5 is a sectional view showing a welding result of FIG. 4;

FIG. 6 is a perspective view of an articulated robot that forms a J-shaped groove.

FIG. 7A is a stress distribution diagram generated on the upper plate,
FIG. 7B is a diagram showing the distribution of stress generated in the lower plate.

FIG. 8 is a cross-sectional view illustrating another welding method of the T-joint welding portion W5.

FIG. 9 is an explanatory view showing a configuration of a conventional front attachment.

FIG. 10 is an enlarged view of the boom shown in FIG.

11 is a sectional view taken along line AA of FIG.

FIG. 12 is a cross-sectional view showing a welding method of the T-joint weld portion W1 of FIG.

FIG. 13 is a sectional view showing a welding result by the welding method of FIG.

[Explanation of symbols]

 Reference Signs List 1 boom 2 upper plate 2a upper plate curved portion 3 lower plate 3a lower plate curved portion 4 side plates 4a, 4b J-shaped groove 4c groove surface 5 side plate 8 center boss portion

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shuji Yoshikawa 3-12-4 Gion, Asaminami-ku, Hiroshima City F-term in Aburaya Heavy Industries, Ltd. (reference) 4E081 YB01 YB10 YX02 YX08 YY12 YY14

Claims (4)

[Claims] 1. A boom structure of a hydraulic excavator in which an upper plate, a lower plate, and a side plate are combined in a box shape in cross section, and a connecting portion of each plate is welded to form a boom that is curved in a longitudinal direction. A hydraulic excavator characterized in that at least one of the upper edge of the side plate and the lower edge of the side plate in the boom bending portion is formed with a J-shaped groove, and T-joint welding is performed on the side plate. Boom structure. 2. The boom structure of a hydraulic shovel according to claim 1, wherein the J-shaped groove is formed corresponding to a portion of the boom bending portion where the largest load acts. 3. A boom which is bent in a longitudinally-shaped shape by combining an upper plate, a lower plate, and a side plate having a groove-shaped groove in a box-shaped cross-section and welding a connecting portion of each plate. In the boom structure of the hydraulic excavator, the thickness of the root face is set to 1.2 to 3.0 in at least one of the joint portion between the side plate and the upper plate and the joint portion between the side plate and the lower plate in the boom bending portion.
A boom structure for a hydraulic shovel, wherein T-joint welding is performed by setting the root gap to 0.3 to 0.6 mm. 4. The root gap is set at 0.3 to about a portion of the boom bending portion where the largest load is applied.
The boom structure of a hydraulic shovel according to claim 3, wherein the boom structure is set to 0.6 mm.