JP2019124071A - Hydraulic shovel - Google Patents

Abstract

To provide a hydraulic shovel reducing stress in a weld portion connecting a boss and a side plate and improving fatigue life of a weld portion, without lowering rigidity of a boss.SOLUTION: A hydraulic shovel comprises a boss 25 including a boss main body portion 51 in which a pin insertion hole 51a is formed and a collar portion 52, and configures a connection portion rotatably connecting a plurality of components by the boss 25 and a connection pin 19. The hydraulic shovel further comprises a work arm 11 with a rectangular cross section comprising a plurality of plate members. The boss 25 further includes an annular shaped backing plate portion 53 which is provided on an outer periphery portion of the collar portion 52, whose surface is positioned at an inner side of the work arm 11 than a surface of the collar portion 52 in an axial direction of the pin insertion hole 51a and which is welded to a plate member 21 via a weld portion 61. The boss 25 includes a groove 54 provided at a position corresponding to a part of a region where the weld portion 61 extend, in the collar portion 52. Plate thickness tg of the collar portion 52 in a part where the groove 54 is provided is equal to or larger than 85% of plate thickness tp of the plate member 21, and smaller than the plate thickness tp.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a hydraulic shovel, and more particularly to a boss structure suitable for use in a boom or an arm of a hydraulic shovel.

  The hydraulic shovel is provided with a working arm constituted by components such as a boom and an arm. In order to operate the work arm, a telescopic member such as a hydraulic cylinder is attached to the work arm via a freely rotatable (rotatable) shaft. The boom and the arm often have a welded structure of box-shaped steel plates. The rotary shaft to which the hydraulic cylinder is attached is supported by a bearing member called a boss provided on a side plate constituting the boom or arm. The boss is often fixed to the side plate by welding.

  The boss receives loads in various directions from the hydraulic cylinder via the rotation shaft. Therefore, various stresses are generated in the welded portion where the boss and the side plate are joined in accordance with the movement of the boom and the arm, the load condition thereof and the like. As a method of reducing the stress which arises in the welding part of a boss | hub and a side plate, the thing of patent document 1-patent document 3 is known.

  In the boom structure of a construction machine in which the boss is fixed to the side plate by welding the flange portion formed on the boss to the side plate of the boom, the technology described in Patent Document 1 produces stress in the welded portion between the side plate and the flange portion of the boss. By forming a groove-shaped thickness adjustment portion in the flange portion of the boss to prevent concentration and improve the reliability of the boom, the thickness of the side plate at the welding position and the thickness of the flange portion and Are equal.

  According to the technique described in Patent Document 2, a relatively thin flange-like connecting portion is integrally formed around a thick boss portion provided with a shaft insertion hole, and a plate member is connected to this connecting portion via a welded joint portion. In the welded structure integrally connected, the stepped portion is provided in the middle of the flange-like connecting portion which is gradually thinned from the boss portion, and the thickness is rapidly changed from the thick portion to the thin portion by the stepped portion. .

  The technique (working machine) described in Patent Document 3 provides a working device configured by movably connecting a plurality of constituent members with a connecting member such as a pin on an airframe, and an arm that is a component of the working device. By providing a crack observation groove in the vicinity of the connecting member on the surface of the above, it is intended to facilitate the detection of the crack and to prevent the occurrence of the crack at a location other than the crack observation groove. More specifically, the arm is coupled to another component (e.g., a boom) of the working apparatus via a connecting member by a bearing member fitted to an arm body of a box-shaped cross section formed of a plurality of plate members. There is. The bearing members are each provided with bearing plates at both ends of a bearing cylinder fitted to the connecting member, and the bearing plates are welded to the plate members of the arm main body. In the arm having such a configuration, a crack observation groove is provided on the surface of a plate member constituting the arm main body in the vicinity of the bearing member in which a crack is easily generated.

JP, 2012-219441, A Unexamined-Japanese-Patent No. 9-3956 JP, 2007-16543, A

  However, the conventional techniques described in Patent Document 1 to Patent Document 3 have the following problems.

  As in the technique described in Patent Document 1, by making the thickness of the welded portion provided on the outer peripheral portion of the boss equal to the thickness of the side plate, it is possible to make the stress generated in the both equal. However, the fatigue strength is different between the welded portion and the welded portion, and the fatigue strength of the welded portion is smaller than that of the welded portion. Therefore, if the thickness of the welded portion and the thickness of the side plate are made equal to make the generated stress of the both substantially the same, a fatigue crack is generated from the welded portion. For example, in the case where the load acting on the boss causes bending deformation of the side plate in the out-of-plane direction (direction of the inner and outer sides of the box shape of the boom), Are approximately equal, the bending stress in the weld, the outer peripheral portion of the flange portion of the boss, and the side plate become approximately equal. Therefore, fatigue failure occurs in a welded portion of lower strength.

  The technique described in Patent Document 2 is intended to reduce the load on the welded portion by making stress concentration easily occur in the step portion provided in the middle of the connection portion of the boss which is the welded portion. However, if a step is provided at the connection portion of the boss, the wide area of the boss becomes thin, and the rigidity of the boss itself is reduced.

  In the technology described in Patent Document 3, a crack observation groove is provided in a plate member (side plate) of an arm main body in which a position from a bearing cylinder of a bearing member coupled to a connection member is farther than a welding portion. That is, in the transmission path of the force that acts on the bearing member via the connecting member, the welding portion is located closer to the load application point than the crack observation groove. Therefore, in the crack observation groove, consideration for suppressing the occurrence of the crack itself in the welded portion or reducing stress concentration in the welded portion which is a cause of the crack is not sufficient.

  The present invention has been made based on the above-described matters, and an object thereof is to reduce the stress of a weld that joins a boss and a side plate without reducing the rigidity of the boss and improve the fatigue life of the weld. It is to provide a hydraulic shovel that can be made to

  The present application includes a plurality of means for solving the above-mentioned problems, and an example thereof is a boss having a boss main body portion in which a pin insertion hole is formed and a collar portion formed on the outer peripheral portion of the boss main body portion. In a hydraulic shovel including a connecting portion configured to relatively connect a plurality of parts rotatably by the boss and the connecting pin inserted into the pin insertion hole, the cross section is formed in a rectangular shape by a plurality of plate members. The work arm is formed, and one plate member of the plurality of plate members and the outer periphery of the collar are joined via a weld, and the boss is provided on the outer periphery of the collar A circle whose surface is located inside the working arm with respect to the surface of the collar with respect to the axial direction of the pin insertion hole, and the collar is joined via a weld to the plate member to which the collar is joined The boss further includes an annular abutment plate, and the boss The groove has a groove provided at a position corresponding to a part of the extension region of the welded portion, and the groove is closer to the boss body portion than the welded portion in the radial direction of the boss. Plate thickness of the flange portion of the portion provided with the groove is 85% or more of the plate thickness of the plate member to which the boss is joined, and the plate of the plate member to which the boss is joined It is characterized by being smaller than thickness.

According to the present invention, the grooved portion of the collar deforms more than the other portion of the collar and the plate member welded to the collar, for loads of various sizes received by the boss from the connecting pin. Thus, the bending stress of the welded portion including the non-welded portion generated at the boundary between the fitting plate portion of the boss and the plate member is relaxed, and the fatigue life of the welded portion including the non-welded portion is extended. Therefore, the durability and reliability of the hydraulic shovel are improved.
Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows the hydraulic shovel which concerns on the 1st Embodiment of this invention. It is a side view showing the work front of the hydraulic shovel concerning a 1st embodiment of the present invention. It is sectional drawing which looked at the work front of the hydraulic shovel which concerns on the 1st Embodiment of this invention shown in FIG. 2 from III-III arrow. It is sectional drawing to which the junction part (welding part) of the side plate of the boom shown by code | symbol X of FIG. 3, and a boom center boss | hub was expanded. It is explanatory drawing which shows the excavation posture at the time of the largest load generation | occurrence | production in the hydraulic shovel of a comparative example. It is a cross-sectional view which cut the boom of the hydraulic shovel of a comparative example in the position of a boom center boss (boss part), and is a figure showing the modification state of the boom at the time of bucket pushing load. It is a cross-sectional view which cut the boom of the hydraulic shovel of a comparative example in the position of a boom center boss (boss part), and is a figure showing the modification state of the boom at the time of bucket pulling load. It is a figure explaining how to take the angle on the non-welding part which arises in the boundary (clearance) of the side plate of the boom in the hydraulic shovel of a comparative example, and the abutment plate part of a boom center boss (boss part). It is a characteristic view which shows stress distribution of the non-welding part which arises in the boundary (clearance) of the side plate of the boom in the hydraulic shovel of a comparative example, and the abutment board part of a boom center boss (boss part). It is a side view showing a boom of a hydraulic shovel concerning a 1st embodiment of the present invention. It is sectional drawing to which the groove provided in the collar part of the boom center boss | hub shown by code | symbol Y of FIG. 3 was expanded. The characteristic view showing the relation of the maximum stress of the corner bottom of the groove bottom of the flange to each condition of the groove provided in the flange of the boom center boss (boss) in the hydraulic shovel according to the second embodiment of the present invention is there. In the hydraulic shovel according to the second embodiment of the present invention, the maximum stress of the corner of the groove bottom of the groove with respect to the radius of curvature of the corner of the groove bottom of the groove provided in the flange of the boom center boss (boss) It is a characteristic view showing a relation. It is a side view showing a boom of a hydraulic shovel concerning a 3rd embodiment of the present invention. It is a side view showing a boom of a hydraulic shovel concerning a 4th embodiment of the present invention. It is sectional drawing which shows a part including the groove provided in the flange part of the boom center boss | hub in the boom of the hydraulic shovel which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows a part containing the groove provided in the flange part of the boom center boss | hub in the boom of the hydraulic shovel which concerns on the 6th Embodiment of this invention.

  Hereinafter, an embodiment of a hydraulic shovel of the present invention will be described using the drawings.

First Embodiment
First, an entire configuration of a hydraulic shovel according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is an entire configuration view showing a hydraulic shovel according to a first embodiment of the present invention.

  In FIG. 1, the hydraulic shovel 100 includes a self-propelled crawler lower traveling body 1 and an upper revolving structure 2 rotatably mounted on the lower traveling body 1 via a pivot bearing device 4. . A work front 3 is attached to a front end portion of the upper swing body 2 so as to be capable of pivoting (pivoting).

  The upper swing body 2 includes a frame 6 as a support structure, a cab 7 installed on the front side on the frame 6, a counterweight 8 provided at the rear end of the frame 6, a cab 7 and a counterweight 8 And a machine room 9 disposed therebetween. In the cab 7, an operation device for instructing the operation of the lower traveling body 1, the work front 3 and the like, a driver's seat and the like (both not shown) on which an operator is seated are arranged. The counterweight 8 is for weight balance with the work front 3. In the machine room 9, an engine, a hydraulic pump (both not shown) and the like are accommodated.

  The work front 3 is an articulated work device for performing a digging operation and the like, and the boom 11 and the arm 12 constituting the work arm, and the bucket 13 as a work tool (attachment) attached to the tip of the work arm And consists of. The proximal end side of the boom 11 is rotatably attached to the front end of the frame 6. The proximal end of the arm 12 is rotatably attached to the distal end of the boom 11. The base end of the bucket 13 is rotatably attached to the distal end side of the arm 12. A bucket link 15 is provided between the tip end of the arm 12 and the bucket 13.

  The boom 11 is pivoted by a pair of boom cylinders 16 (only one is shown in FIG. 1). The arm 12 is rotated by an arm cylinder 17. The bucket 13 is rotated by the bucket cylinder 18 via the bucket link 15. That is, the boom cylinder 16, the arm cylinder 17 and the bucket cylinder 18 constitute a driving device for driving the boom 11, the arm 12 and the bucket 13, respectively. In the present embodiment, the boom cylinder 16, the arm cylinder 17 and the bucket cylinder 18 are constituted by hydraulic cylinders.

  The front end of the frame 6 and the proximal end of the boom 11, the distal end of the boom 11 and the proximal end of the arm 12, and the proximal end of the bucket 13 and the distal end of the arm 12 are respectively connected by a connecting pin 19. The connecting pins 19 are supported by the brackets and bosses of the respective structures. Similarly, one end of the boom cylinder 16 and the central portion of the boom 11 are connected by a connecting pin 19, and the connecting pin 19 is supported by the brackets and bosses of the respective structures.

  Next, the structure of each part of the work front which constitutes a part of 1st Embodiment of the hydraulic shovel of this invention is demonstrated using FIGS. FIG. 2 is a side view showing the working front of the hydraulic shovel according to the first embodiment of the present invention, and FIG. 3 is a working front of the hydraulic shovel according to the first embodiment of the present invention shown in FIG. FIG. 4 is an enlarged cross-sectional view of a joint portion between the side plate of the boom and the boom center boss shown by the symbol X in FIG.

  In FIG. 2, most of the boom 11 and the arm 12 constituting the working arm are formed into a box shape having a rectangular cross section by a plurality of plate members, and a boss is formed on a predetermined plate member of the plurality of plate members. It is joined by welding.

  Specifically, as shown in FIGS. 2 and 3, the boom 11 is a box which is curved in an arch shape and extends in one direction (generally in the left and right direction in FIG. 2), and is a box having a rectangular cross section. It has a mold structure. The box-shaped structure is disposed on the upper end side of the side plates 21 and a pair of plate members called side plates 21 facing each other at intervals in the width direction (horizontal direction in FIG. 3) of the hydraulic shovel 100 and having bosses welded. It is formed by welding a plate member called upper plate 22 and a plate member called lower plate 23 disposed on the lower end side of both side plates 21 by welding.

  Similarly, as shown in FIG. 2, the arm 12 is provided with a box-shaped structure which is long and extends in one direction (generally in the left and right direction in FIG. 2) and which has a rectangular cross section. The box-shaped structure includes a pair of plate members called side plates 31 extending in one direction while facing each other with an interval in the width direction of the hydraulic shovel 100, and a plate member called an upper plate 32 disposed on the upper end side of both side plates 31. And a plate member called a lower plate 33 disposed on the lower end side of the side plates 31, and a rear plate closing an opening on the base end side (rear end side) formed by the side plates 31, the upper plate 32 and the lower plate 33. It is formed by welding a plate member called 34 by welding.

  One boss 25 to which one end of the boom cylinder 16 (see FIG. 1) is connected is provided at the central portion in the longitudinal direction of the side plates 21 of the boom 11. The boss 25 provided at the center of the side plate 21 of the boom 11 is called a boom center boss (boss). The boom 11 includes a boom center boss 25 to which one end of the boom cylinder 16 is connected, and is driven by the boom cylinder 16. Both boom center bosses 25 have a similar configuration.

  As shown in FIG. 3, the boom center boss 25 has a boss main body 51 in which a pin insertion hole (through hole) 51 a is formed, and a flange 52 formed on the outer periphery of the boss main body 51. There is. The boss main portion 51 is formed such that the dimension (thickness) in the axial direction of the pin insertion hole 51 a is larger than the plate thickness dimension of the flange portion 52. The flange portion 52 is formed to extend radially outward from the outer peripheral portion of the boss main portion 51 in an annular manner. The ends of the two boom center bosses 25 located on the inner side of the boom 11 in the boss main body 51 are connected by the pipe 60, and the outer peripheral edge of the flange 52 is abutted against the side plate 21 and welded (welded Through)). In this joint portion (welded portion) 61, the thickness at the butt between the flange portion 52 and the side plate 21 and the vicinity thereof is approximately the same so that the applied load (force) is transmitted smoothly from the boom center boss 25 to the side plate 21. It is set to become. In addition, the flange portion 52 has a curved surface portion 52 a having a thickness gradually increasing toward the boss main body 51 in the vicinity of the boss main body 51. The boom cylinder 16 is rotatably coupled to the boom 11 by inserting the connection pin 19 into the pin insertion hole 51 a of the boom center boss 25 and supporting the connection pin 19 by the boom center boss 25.

  The welding between the boom center boss 25 and the side plate 21 is performed from the outside of the structure of the boom 11 because the structure of the boom 11 has a rectangular cross section. In order to prevent melting of the weld metal into the structure of the boom 11 during welding, the inner portion of the boom 11 is located at a portion where the flange 52 of the boom center boss 25 and the side plate 21 are butt-joined and joined. , The abutment plate portion 53 is provided. Specifically, an annular abutment plate portion 53 is integrally provided on the outer peripheral portion of the flange portion 52. The abutment plate portion 53 protrudes from the back surface of the collar portion 52 (surface facing the inner side of the structure of the boom 11) radially outward (outside of the projecting direction of the collar portion 52) beyond the outer peripheral edge of the collar portion 52 It is formed. That is, the abutment plate 53 has a surface (a surface facing the outside of the structure of the boom 11) a surface of the flange 52 (a surface facing the outside of the structure of the boom 11) with respect to the axial direction of the pin insertion hole 51a. It is provided so that a position may be shifted inside the structure of boom 11 rather than. As described above, when the collar 52 and the abutment plate 53 are integrally formed, the load acting on the collar 52 is also transmitted to the abutment plate 53 and acts, and both the collar 52 and the abutment plate 53 are loaded. It deforms according to.

  The butting plate portion 53 of the above-described structure also has a function of positioning the side plate 21 with respect to the boss 25 in addition to the function of preventing the weld metal from falling off when butting the flange portion 52 of the boss 25 and the side plate 21. ing. As shown in FIG. 4, the abutment plate portion 53 is in a state of being joined to the side plate 21 via a welding portion 61 that joins the flange portion 52 and the side plate 21. Further, due to various factors, it is difficult to bring the side plate 21 and the backing plate portion 53 into close contact completely, and a slight gap is generated between the side plate 21 and the backing plate portion 53. Therefore, a non-welded portion 62 exists in the boundary (gap) between the side plate 21 and the fitting plate portion 53 in the welded portion 61. The non-welded portion 62 generates higher stress than the other portions of the welded portion 61. This is because the non-welded portion 62 is susceptible to the deformation of both the flange portion 52 and the abutment plate portion 53 and the deformation of the side plate 21.

  Hereinafter, of both surfaces of the boss 25 and the flange 52 of the boss 25 and the abutment plate 53 of the boss 25, the surface facing the outside of the working arm (the boom 11 and the arm 12) having a rectangular cross section is referred to as a surface The surface of the working arm facing inward is referred to as the back surface.

  Returning to FIG. 2, the boom 11 further includes a boss 26 that couples the boom 11 and the frame 6 (see FIG. 1). The arm 12 is provided with an arm boss 36 for connecting the boom 11 and the arm 12 and a boss (not shown) for connecting the arm 12 and the bucket 13. Further, brackets 40 for attaching hydraulic cylinders are provided on the boom 11, the arm 12 and the bucket 13, respectively. The bracket 40 and the hydraulic cylinder are rotatably pin-connected.

  Thus, the working arm consisting of the boom 11 and the arm 12 is provided with the bosses 25, 26 and 36, through which the working arm is connected to the frame 6 or the components of the working arm Specifically, the boom 11 and the arm 12) are connected, or other parts (specifically, the bucket 13) are connected to the working arm. That is, the connecting pins 19 inserted into the bosses 25, 26, 36 and the pin insertion holes 51a of the bosses 25, 26, 36 constitute a connecting portion for rotatably connecting a plurality of parts to each other (relatively) Do.

Next, the characterizing portion of the first embodiment of the hydraulic shovel of the present invention will be described using the drawings while showing the state of the boom at the time of excavation in the hydraulic shovel of the comparative example.
First, the state at the time of excavation in the hydraulic shovel of the comparative example will be described with reference to FIGS. FIG. 5 is an explanatory view showing an excavating posture at the time of maximum load generation in the hydraulic shovel of the comparative example, and FIG. 6 is a cross-sectional view of a boom of the hydraulic shovel of the comparative example cut at the position of a boom center boss (boss portion), FIG. 7 is a cross-sectional view of the boom of the hydraulic excavator of the comparative example cut at the position of the boom center boss (boss portion) at the time of the bucket pushing load, and the boom deformation at the time of the bucket pulling load FIG. 8 is a view showing a state, and FIG. 8 is a view for explaining how to take an angle on a non-welding portion that occurs in the boundary (gap) between the side plate of the boom and the abutment plate portion of the boom center boss (boss portion) in the hydraulic excavator of the comparative example; FIG. 9 is a characteristic diagram showing a stress distribution of a non-welding portion generated at the boundary (gap) between the side plate of the boom and the abutment plate portion of the boom center boss (boss portion) in the hydraulic shovel of the comparative example. In addition, regarding the structure of the hydraulic shovel of the comparative example shown in FIGS. 5-9, the same code | symbol shall be attached | subjected to the part similar to the structure of the hydraulic shovel concerning the 1st Embodiment of this invention.

  In FIG. 5, the hydraulic shovel of the comparative example is in a posture in which the bucket 13 is excavating below (underground) the position of the lower traveling body 1. As shown in this figure, it is a typical digging posture of a hydraulic shovel to get on the fill and dig below the lower traveling body 1. Hydraulic excavators are usually designed for maximum power in this position. The same applies to the hydraulic shovel 100 according to the first embodiment of the present invention.

  A load from the boom cylinder 16 acts on the boss 25 of the boom 11 of the hydraulic excavator of the comparative example shown in FIG. 5 via the connection pin 19 inserted into the pin insertion hole 51a (see FIG. 3). Due to this load, as shown in FIGS. 6 and 7, the flange 52 of the boss 25 and the abutment plate 53 and the side plate 21 of the boom 11 are out of plane (the direction of the outer surface side of the structure or the direction of the inner surface Bending deformation occurs. As a result, stress is generated in the flange 52 of the boss 25, the abutment plate 53, the side plate 21, the flange 52 and the welded portion 61 between the abutment plate 53 and the side plate 21. Specifically, when a tensile load is applied to the boom cylinder 16, as shown in FIG. 6, the boss main body 51 of the boss 25 and the pipe 60 serving as a boss connection member are deformed upward by a convex shape. Out-of-plane bending deformation occurs in the flange 52 of the boss 25 and the contact plate 53, the side plate 21, the upper plate 22, and the lower plate 23 that constitute the boss 25. On the other hand, when a compressive load is applied to the boom cylinder 16, as shown in FIG. 7, the boss main body 51 and the pipe 60 are deformed downward to a convex shape, whereby the flange 52 of the boss 25, the abutment plate 53, and the side plate An out-of-plane bending deformation occurs in the upper plate 22 and the lower plate 23. Also in the case of the hydraulic shovel 100 according to the first embodiment of the present invention, such a deformation of the boom 11 occurs similarly.

  The bending deformation of the flange 52 of the boss 25 and the abutment plate 53 and the side plate 21 generates high stress in the welded portion 61 joining the flange 52 and the abutment plate 53 and the side plate 21. In particular, the non-welding portion 62 (see FIG. 4) at the boundary (gap) between the abutment plate 53 and the side plate 21 is affected by both the deformation of the flange 52 and the abutment plate 53 and the deformation of the side plate 21. . Therefore, higher stress tends to be generated in the non-welded portion 62 than in the other portions of the welded portion 61. The stress of the welded portion 61 including the non-welded portion 62 fluctuates according to the operation of the boom cylinder 16. Fatigue failure occurs when the stress value and the number of cycles of stress variation exceed the threshold value inherent to the weld material. It is known that the threshold value of the fatigue failure in the welded portion 61 is smaller than that of the welded member, since residual stress and residual deformation often occur due to heat during welding in the welded portion 61 for joining the members to be welded. ing. That is, in the boom 11, fatigue failure is more likely to occur in the welded portion 61 than in the flange portion 52 and the abutment plate portion 53 of the side plate 21 and the boss 25. In particular, there is a possibility that a fatigue crack may occur at the non-welded portion 62 present at the boundary (gap) between the applied plate portion 53 and the side plate 21. Such a situation is the same as in the case of the hydraulic shovel 100 according to the first embodiment of the present invention.

  FIG. 9 is a characteristic diagram showing the stress distribution of the non-welding portion 62 at the boundary (gap) between the side plate 21 of the boom 11 and the abutment plate portion 53 of the boom center boss 25 (boss portion) in the hydraulic excavator of the comparative example. In FIG. 9, the horizontal axis θ indicates the angular position on the non-welded portion 62 (welded portion 61). This angular position is, as shown in FIG. 8, based on the position (0.degree.) At which the annular non-welded portion 62 (see FIG. 4) approaches the top plate 22 of the boom 11 the most. Looking at 25 is represented by a clockwise angle. The vertical axis σw indicates the stress of the non-welding portion 62, and the digging load state of the operation pattern of the bucket 13 in the back and forth direction under the situation shown in FIG. Is the stress produced by

  In FIG. 9, the portion of the non-welded portion 62 at the angular position θ where the stress σw of the non-welded portion 62 is large corresponds to a portion where a large bending stress is generated. The stress σw of the non-welded portion 62 at an angular position near 315 ° is particularly large.

  Next, the characterizing portion of the first embodiment of the hydraulic shovel of the present invention will be described with reference to FIG. 3, FIG. 10, and FIG. FIG. 10 is a side view showing a boom of a hydraulic shovel according to a first embodiment of the present invention, and FIG. 11 is an enlarged sectional view of a groove provided in a flange portion of a boom center boss shown by symbol Y in FIG. .

  As described above, in the hydraulic excavator of the comparative example, the flange 52 of the boss 25, the abutment plate 53, and the side plate 21 are deformed by bending deformation of the flange 52 and abutment plate 53 of the boss 25 and the side plate 21 of the boom 11. High stress is generated in the welded portion 61 to be joined. In particular, high stress occurs in the non-welded portion 62 at the boundary (gap) between the side plate 21 and the backing plate portion 53.

  Therefore, in the present embodiment, as shown in FIG. 3 and FIG. 10, the groove 54 is provided in the vicinity of the weld portion 61 on the surface side of the boss 25 so as to reduce the thickness of the flange 52. The welding portion 61 is provided on the outer periphery of the flange portion 52 of the boss 25, and the groove 54 is provided between the boss main body portion 51 and the welding portion 61. The groove 54 is formed in an arc shape centering on the axial center A of the pin insertion hole 51 a of the boss 25. The plate thickness tg of the portion of the flange 52 provided with the groove 54 is set to be smaller than the plate thickness tp of the side plate 21 to which the boss 25 is welded. As shown in FIG. 11, the groove 54 has an R portion with a suitable radius of curvature rg at the corner 55 of the groove bottom, and is configured such that the stress concentration of the corner 55 of the groove bottom does not occur. ing.

  Further, as described above, in the hydraulic shovel of the comparative example, the stress of the non-welded portion 62 at an angular position near 315 ° is relatively larger than the stress of the non-welded portion 62 at another angular position θ There is.

  Therefore, in the present embodiment, as shown in FIG. 10, boom 11 is referred to a position where annular non-welding portion 62 (see FIG. 4) is closest to upper plate 22 of boom 11 (0 °). Forming the groove 54 in an arc shape extending a predetermined angular position ± α ° around 315 ° at a clockwise angular position θ (same definition as the angular position θ in FIG. 8) as viewed from the outside of the boss 25 doing. That is, the groove 54 is provided at an angular position corresponding to a portion where the stress of the non-welded portion 62 becomes relatively high in the region where the non-welded portion 62 extends.

  Next, the operation and effect of the first embodiment of the hydraulic shovel of the present invention will be described with reference to FIGS. 3 to 7, 9 and 10. FIG.

  A load acts on the boss 25 of the boom 11 shown in FIG. 3 from the boom cylinder 16 (see FIG. 1) via the connection pin 19 inserted into the pin insertion hole 51a. By this load, bending deformation similar to the bending deformation in the out-of-plane direction shown in FIGS. 6 and 7 occurs in the flange portion 52 of the boss 25 and the fitting plate portion 53 and the side plate 21 of the boom 11. For this reason, stress is generated in the flange portion 52 of the boss 25 and the welded portion 61 between the contact plate portion 53 and the side plate 21. In particular, high stress occurs in the non-welded portion 62 present at the boundary (gap) between the side plate 21 and the cover plate portion 53 shown in FIG. 4.

  In the present embodiment, the bending deformation in the out-of-plane direction of the portion provided with the groove 54 in the flange portion 52 shown in FIG. 3 becomes larger than the other portions of the flange portion 52 and the side plate 21. This is because the plate thickness tg of the portion provided with the groove 54 in the flange 52 is smaller than the other portions of the flange 52 and the plate thickness tp of the side plate 21. By generating the out-of-plane bending due to the load acting on the boss 25 mainly in the flange portion 52 of the portion provided with the groove 54, the amount of bending deformation in the out-of-plane direction of the welded portion 61 including the non-welded portion 62 is relatively It is reduced. For this reason, the stress of the welded portion 61 including the non-welded portion 62 decreases, and the effect of increasing the fatigue life of the welded portion 61 including the non-welded portion 62 is produced. Further, the processing of the groove 54 reduces the mass of the boss 25 and produces the effect of weight reduction.

  Further, in the present embodiment, the groove 54 is provided between the boss main body 51 and the welding portion 61. For this reason, in the transmission path of the load acting on the boss 25 via the connection pin 19, the groove 54 is positioned closer to the load application point Ld than the weld portion 61. Therefore, by causing the bending deformation in the out-of-plane direction mainly to occur at the portion where the groove 54 of the collar portion 52 is provided, the effect of suppressing the bending stress of the welded portion 61, particularly the non-welded portion 62 is further enhanced.

  Further, in the present embodiment, the groove 54 is provided only at the position corresponding to the portion where the stress of the non-welded portion 62 becomes high in the region where the non-welded portion 62 extends. Specifically, a groove 54 extending a predetermined angular position ± α ° around the angular position of 315 ° is provided. Thereby, when the stress distribution as shown in FIG. 9 occurs in the digging posture in which the maximum digging load as shown in FIG. 5 is generated, the stress peak of the non-welded portion 62 can be efficiently reduced. As a result, the fatigue life of the hydraulic shovel 100 can be extended. Furthermore, a position (this embodiment) corresponding to a part of the region (the entire periphery in the present embodiment) in which the weld portion 61 including the non-welded portion 62 extends in the surface side portion of the flange portion 52 In the embodiment, since the groove 54 is provided at a predetermined angular position ± α ° around the angular position of 315 °, the overall rigidity of the flange 52 hardly decreases.

  As described above, according to the first embodiment of the hydraulic excavator of the present invention, the portion provided with the groove 54 in the flange portion 52 is provided for the load of various sizes received by the boss 25 from the connecting pin 19. A non-welding portion 62 generated at the boundary between the abutment plate portion 53 of the boss 25 and the side plate (plate member) 21 by being deformed more than the side plate (plate member) 21 welded to the other part of the portion 52 and the flange 52 And the bending stress of the welded portion 61 is relaxed, and the fatigue life of the welded portion 61 including the non-welded portion 62 is extended. Therefore, the durability and the reliability of the hydraulic shovel 100 are improved.

Second Embodiment
Next, a second embodiment of the hydraulic shovel of the present invention will be described using FIGS. 12 and 13. FIG. FIG. 12 shows the relationship of the maximum stress at the corner of the groove bottom of the flange with respect to the conditions of the groove formed in the flange of the boom center boss (boss) in the hydraulic shovel according to the second embodiment of the present invention Characteristic diagram, FIG. 13 shows the groove bottom of the flange with respect to the radius of curvature of the corner of the groove bottom of the groove provided in the flange of the boom center boss (boss) in the hydraulic shovel according to the second embodiment of the present invention It is a characteristic view showing a relation of maximum stress of a corner. In FIGS. 12 and 13, the same components as in the first embodiment are designated by the same reference numerals as in the first embodiment, and the detailed description thereof will be omitted.

  The characteristic diagram at the left end in FIG. 12 is the value (%) obtained by dividing the plate thickness tg (see FIG. 3) of the flange 52 of the portion provided with the groove 54 by the plate thickness tp (see FIG. 3) of the side plate 21. It shows the relationship with the maximum stress σg at the corner 55 (see FIG. 11) of the groove bottom of the groove 54 of the flange 52. The second characteristic diagram from the left is the value (%) obtained by dividing the radial width Wg (see FIG. 3) of the groove 54 by the outer diameter Df (see FIG. 3) of the flange 52 and the groove of the groove 54 of the flange 52 The relationship between the bottom corner 55 and the maximum stress σg is shown. The third characteristic diagram from the left is the radial position of the groove 54 (twice the distance from the axis A of the pin insertion hole 51a) Dg (see FIG. 3) divided by the outer diameter Df of the flange 52 ( %) And the maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52. The characteristic diagram at the right end is clockwise when looking at the boss 25 from the outside of the boom 11 with reference to the position (0 °) at which the annular non-welded portion 62 (welded portion 61) approaches the top plate 22 of the boom 11 the most. Angle α ° (see FIG. 10) indicating the circumferential position of the longitudinal edge of the groove 54 centered on 315 ° in the angular position and the maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52 And their relationship with

  As apparent from the characteristic diagram at the left end of FIG. 12, the maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52 as the plate thickness tg of the flange 52 of the portion provided with the groove 54 increases. Becomes smaller. As apparent from the second characteristic diagram from the left in FIG. 12, as the radial width Wg of the groove 54 decreases, the maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52 decreases. As apparent from the third characteristic diagram from the left in FIG. 12, as the radial position Dg of the groove 54 decreases, the maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52 decreases. As apparent from the characteristic diagram at the right end of FIG. 12, as the angle α ° indicating the circumferential position of the longitudinal edge of the groove 54 decreases, that is, as the length of the groove 54 decreases, The maximum stress σg at the corner 55 of the groove bottom of the groove 54 of the flange 52 decreases.

  The solid line L shown in FIG. 12 is a limit value of stress which does not cause fatigue failure in the design cycle number, which is obtained from the fatigue life curve of the material constituting the flange 52. From the characteristic diagrams shown in FIG. 12, it is preferable to set the following conditions as the shape of the groove 54. In the present embodiment, the following conditions are set, and the flange portion 52 of the boss 25 is fatigued in design repetition number. It does not cause destruction.

  The first condition is that the value obtained by dividing the plate thickness tg of the flange 52 of the portion provided with the groove 54 by the plate thickness tp of the side plate 21 is 85% or more. In addition, since it is necessary to make the bending deformation of the groove 54 smaller than that of the side plate 21, the value obtained by dividing the plate thickness tg of the flange 52 by the plate thickness tp of the side plate 21 is less than 100%. The second condition is that the value obtained by dividing the radial width Wg of the groove 54 by the outer diameter Df of the flange 52 is 4.5% or less. Further, the value obtained by dividing the radial width Wg of the groove 54 by the outer diameter Df of the flange 52 is 1% from the minimum groove width determined from the radius of curvature which does not cause fatigue failure at the groove bottom corner 55 of the groove 54 It is above. The third condition is that a value obtained by dividing the radial direction position Dg of the groove 54 by the outer diameter Df of the flange portion 52 is 85% or less. And, since the groove 54 needs to be provided between the boss main portion 51 and the welding portion 61, the radial position Dg of the groove 54 is set to the outer diameter Df of the flange portion 52 in consideration of the outer diameter of the boss main portion 51. The value divided by is 50% or more. The fourth condition is to form an arc-shaped groove 54 centered on the axial center A of the pin insertion hole 51a, and the angle α ° indicating the circumferential position of the end of the groove 54 in the lengthwise direction is 35 ° or less is there. And it is 5 degrees or more from the easiness of processing of the groove 54 and the effect of design repetition number improvement of the non-welding part 62. That is, the groove 54 is formed in the range of 280 ° to 350 °.

  13 shows a value (%) obtained by dividing the radius of curvature rg (see FIG. 11) of the corner 55 of the groove bottom of the groove 54 by the plate thickness tp (see FIG. 3) of the side plate 21 and the groove 54 of the flange 52 Relationship with the maximum stress .sigma.g of the corner 55 of the groove bottom. As apparent from FIG. 13, as the radius of curvature rg increases, the maximum stress σg at the bottom 55 of the groove bottom of the groove 54 of the flange 52 decreases and asymptotically approaches a certain value. The solid line L shown in FIG. 13 is a limit value of stress which does not cause fatigue failure in the design cycle number, which is obtained from the fatigue life curve of the material constituting the flange 52.

  Therefore, in the present embodiment, from the characteristic diagram shown in FIG. 13, the groove 54 is such that the value obtained by dividing the radius of curvature rg of the corner 55 of the groove bottom of the groove 54 by the plate thickness tp of the side plate 21 is 4% or more. By setting the shape of (1), the flange 52 of the boss 25 does not cause fatigue failure in the design repetition number. Further, the radius of curvature rg does not become larger than the plate thickness tp of the side plate 21, so the value obtained by dividing the radius of curvature rg of the corner 55 of the groove bottom of the groove 54 by the plate thickness tp of the side plate 21 is less than 100%. is there.

  As described above, according to the second embodiment of the hydraulic shovel of the present invention, the same effect as that of the first embodiment described above can be obtained, and the flange portion 52 of the boss 25 can be designed repeatedly It is possible to ensure that fatigue failure does not occur in

Third Embodiment
Next, a third embodiment of the hydraulic shovel of the present invention will be described with reference to FIG. FIG. 14 is a side view showing a boom of a hydraulic shovel according to a third embodiment of the present invention. In FIG. 14, the same components as in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the detailed description thereof is omitted.

  The third embodiment of the hydraulic shovel according to the present invention shown in FIG. 14 is different from the first embodiment in the range in which a groove is formed. The formation range of the groove according to the present embodiment is set in consideration of the following. The stress distribution of the non-welded portion 62 shown in FIG. 9 is premised on the digging posture as shown in FIG. In this stress distribution, a peak having a peak P1 at an angular position near the maximum stress σw of 315 ° exists in the range of 225 ° to 360 °. However, when excavating in a posture slightly different from the posture shown in FIG. 5, the peak P1 of the maximum stress σw in the stress distribution shown in FIG. 9 is any angle in the range of 315 ° to 225 ° to 360 ° of the mountain. It is assumed that the position shifts. Therefore, in the flange portion 52 of the boss 25A, the boss 25A from the outside of the boom 11 with the annular non-welded portion 62 (welded portion 61) closest to the top plate 22 of the boom 11 as a reference (0 °). An arc-shaped groove 54A centered on the axial center A (see FIG. 3) of the pin insertion hole 51a is formed in the range of 225 ° to 360 ° at the angular position θ clockwise.

  According to the hydraulic shovel of the third embodiment of the present invention described above, the same effect as that of the first embodiment described above can be obtained.

  Further, according to the present embodiment, since the groove 54A whose angular position θ extends from 225 ° to 360 ° is provided in the flange 52, in the stress distribution of the non-welded portion 62 shown in FIG. The peak of the maximum stress σw present in the range of 360 ° can be reliably reduced. Therefore, even in the case of excavating in a posture slightly different from the excavation posture as shown in FIG. 5, the fatigue life of the non-welded portion 62 can be reliably improved.

Fourth Embodiment
Next, a fourth embodiment of the hydraulic shovel of the present invention will be described with reference to FIG. FIG. 15 is a side view showing a boom of a hydraulic shovel according to a fourth embodiment of the present invention. In FIG. 15, the same components as in the first embodiment are designated by the same reference numerals as in the first embodiment, and the detailed description thereof will be omitted.

  The fourth embodiment of the hydraulic shovel according to the present invention shown in FIG. 15 is different from the first embodiment in the range in which a groove is formed. The formation range of the groove according to the present embodiment is set in consideration of the following. The stress distribution of the non-welded portion 62 shown in FIG. 9 is premised on the digging posture as shown in FIG. In this stress distribution, a peak (225 ° to 360 °) having a first peak P1 at which the maximum stress σw becomes a maximum value and a peak (0 ° to 90) having a second peak P2 at which the maximum stress σw becomes a second °) is present. However, when excavating in a posture different from the drilling posture shown in FIG. 5, the first peak P1 of the maximum stress .sigma.w in the stress distribution shown in FIG. 9 is shifted within the range of 225.degree. To 360.degree. And the second peak P2. Is assumed to be offset within the range of 0 ° to 90 °. Therefore, the boss 25B from the outside of the boom 11 with respect to the position at which the annular non-welded portion 62 (welded portion 61) approaches the top plate 22 of the boom 11 most at the flange 52 of the boss 25B. And at an angular position θ clockwise, in the range of 0 ° to 90 ° and in the range of 225 ° to 360 °, one continuous centering on the axis A of the pin insertion hole 51a (see FIG. 3) An arcuate groove 54B is formed.

  According to the fourth embodiment of the hydraulic shovel of the present invention described above, the same effect as that of the first embodiment described above can be obtained.

  Further, according to the present embodiment, since one groove 54B extending from 0 ° to 90 ° and 225 ° to 360 ° in the angular position θ is provided in the flange portion 52, the non-welding shown in FIG. In the stress distribution of the portion 62, in addition to the peak of the maximum stress σw existing in the range of 225 ° to 360 °, the second peak of stress existing in the range of 0 ° to 90 ° can also be reduced. Therefore, the fatigue life of the non-welded portion 62 can be reliably improved also in the case of excavating in a posture largely different from the excavation posture as shown in FIG. 5.

Fifth Embodiment
Next, a fifth embodiment of the hydraulic shovel of the present invention will be described with reference to FIG. FIG. 16 is a cross-sectional view showing a portion including a groove provided in a flange portion of a boom center boss in a boom of a hydraulic excavator according to a fifth embodiment of the present invention. In FIG. 16, the same components as in the first embodiment are denoted by the same reference numerals as in the first embodiment, and the detailed description thereof will be omitted.

  The fifth embodiment of the hydraulic shovel according to the present invention shown in FIG. 16 is different from the first embodiment in that the groove 54C is not on the surface side of the flange 52 of the boss 25C but on the back surface of the flange 52. Is provided. Specifically, a groove 54C is formed on the back surface side of the boss 25 in the vicinity of the weld portion 61 of the boss 25C so as to reduce the thickness of the flange 52. The weld portion 61 is provided on the outer periphery of the flange portion 52 of the boss 25C, and the groove 54C is provided between the boss main portion 51 in which the pin insertion hole 51a is formed and the weld portion 61. The groove 54C is partially formed in an arc shape around an axial center A (see FIG. 3) of the pin insertion hole 51a of the boss 25C. That is, in the flange portion 52, the groove 54 is provided at a position corresponding to a part of the region where the non-welded portion 62 extends. The plate thickness tg of the flange 52 of the portion provided with the groove 54C is set to be smaller than the plate thickness tp of the side plate 21 to which the boss 25 is welded. The groove 54C has an R portion with a suitable radius of curvature rg at the corner 55 of the groove bottom as in the first embodiment shown in FIG. Is configured to prevent waking up.

  In the present embodiment, the bending deformation in the out-of-plane direction in the flange 52 of the portion provided with the groove 54C is larger than the other portions of the flange 52 and the side plate 21. This is because the plate thickness tg of the flange 52 of the portion where the groove 54C is provided is smaller than the plate thickness of the flange 52 and the plate thickness tp of the side plate 21. Bending deformation in the out-of-plane direction of the welded portion 61 including the non-welding portion 62 (see FIG. 4) by mainly generating out-of-plane bending due to a load acting on the boss 25C at the flange portion 52 of the portion provided with the groove 54C. The amount is relatively reduced. As a result, the bending stress of the welded portion 61 including the non-welded portion 62 is reduced, and the effect of increasing the fatigue life of the welded portion 61 including the non-welded portion 62 is produced. In addition, since the mass of the boss 25C is reduced by the processing of the groove 54C, the weight reduction effect is also produced.

  Further, the groove 54 </ b> C is provided between the boss main body 51 and the welding portion 61. For this reason, in the transmission path of the load acting on the boss 25C, the groove 54C is positioned closer to the load application point Ld than the weld portion 61. By generating the bending deformation in the out-of-plane direction in the groove 54C, the effect of suppressing the bending stress of the welded portion 61 is enhanced.

  As described above, according to the fifth embodiment of the hydraulic shovel of the present invention, the same effect as that of the first embodiment described above can be obtained.

  Further, according to the present embodiment, since the groove 54C is processed on the back surface side of the boss 25C, rainwater and seawater that cause corrosion and rust do not accumulate in the groove 54C. Therefore, the aged deterioration of the boom 11 can be suppressed, and the reliability of the boom 11 can be improved.

Sixth Embodiment
Next, a sixth embodiment of the hydraulic shovel of the present invention will be described with reference to FIG. FIG. 17 is a cross-sectional view showing a portion including a groove provided in a flange portion of a boom center boss in a boom of a hydraulic excavator according to a sixth embodiment of the present invention. In FIG. 17, the same components as in the first embodiment are designated by the same reference numerals as in the first embodiment, and the detailed description thereof is omitted.

  The sixth embodiment of the hydraulic shovel according to the present invention shown in FIG. 17 is different from the first embodiment in that plural grooves 54D are provided on the surface side of the flange portion 52 of the boss 25D instead of one. It is. Specifically, two grooves 54D are processed on the surface side of the boss 25D in the vicinity of the weld portion 61 so as to reduce the thickness of the flange 52. The two grooves 54D are arc-shaped centered on the axial center A (see FIG. 3) of the pin insertion hole 51a of the boss 25D, and are formed so as to be different in radial position. Each of the two grooves 54D is provided at an angular position corresponding to the area where the stress of the non-welding part 62 becomes high in the extending area of the non-welding part 62. Specifically, for example, it is formed over the range of the same angular position (315 ° ± α °) as in the first embodiment. That is, the two grooves 54D are provided in the range of substantially the same angular position θ. The plate thickness tg of the flange 52 of the portion provided with the grooves 54D is set to be smaller than the plate thickness tp of the side plate 21 to which the boss 25D is welded. The plate thickness tg of the flange 52 of the portion provided with the two grooves 54D does not have to be the same. That is, the two plate thicknesses tg may be set to different sizes (dimensions).

  In the present embodiment, the plurality of grooves 54D operate as follows. The load acting on the bosses 25D exerts a force on the side plate 21 welded to the collar portion 52 and the collar portion 52 in order to cause bending deformation in the out-of-plane direction. By this force, bending deformation occurs in the flange 52 of the portion provided with the two grooves 54D, so the bending deformation of the welded portion 61 including the non-welded portion 62 (see FIG. 4) is reduced accordingly. As a result, the stress of the welded portion 61 including the non-welded portion 62 is reduced, and the fatigue life of the welded portion 61 including the non-welded portion 62 is improved.

  According to the hydraulic shovel of the sixth embodiment of the present invention described above, the same operation and effect as those of the first embodiment described above can be obtained.

  Further, according to the present embodiment, since the grooves 54D are provided at two different positions in the radial direction in the flange 52, the case where only one groove 54 is provided as in the first embodiment described above and In comparison, both the depth and width of each groove 54D can be reduced. By reducing the shape of the groove 54D in this way, the stress at the corner 55 of the groove bottom of the flange 52 can be alleviated, so that the fatigue life of the corner 55 of the groove bottom of the flange 52 is improved. Produce Further, by forming a plurality of grooves 54D in the boss 25D, a further weight reduction effect is also produced.

[Other embodiments]
The present invention is not limited to the present embodiment, but includes various modifications. The above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to one having all the described configurations. Part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for part of the configurations of the respective embodiments.

  For example, in the first to sixth embodiments of the hydraulic shovel according to the present invention described above, an example is shown in which the abutment plate portion 53 is integrally formed on the outer peripheral portion of the flange portion 52. A configuration is also possible in which an annular member is fixed to the back surface side of the flange portion 52 by welding or the like to provide an abutment plate portion. Even in such a structure, the load acting on the flange 52 is transmitted to the abutment plate as in the case where the collar 52 and the abutment plate 53 are integrally formed, and the collar 52 and the abutment plate Both deform according to the load.

  Also, in the sixth embodiment described above, an example of the configuration in which the two grooves 54D are provided in the flange portion 52 of the boss 25D has been shown, but also a configuration in which the three or more grooves are provided in the flange portion 52 of the boss 25D It is possible. Also in this case, the same operation and effect as those of the sixth embodiment can be obtained.

  11: Boom, 12: Arm, 16: Boom cylinder, 19: Linking pin, 21: Side plate, 22: Upper plate, 23: Lower plate 25, 25 A, 25 B, 25 C, 25 D ... Boom center boss (boss), 51 ... Boss body 51, Pin insertion hole 52, Collar 53, Counter plate 54, 54A, 54B, 54C, 54D Groove, 55 Corner of groove bottom 61 Welds 100 Hydraulic pressure Shovel

Claims (9)

It has a boss having a boss main body portion in which a pin insertion hole is formed and a flange portion formed on an outer peripheral portion of the boss main body portion, and a plurality of parts are relative to each other by the boss and a connection pin inserted in the pin insertion hole. In a hydraulic shovel in which a connecting portion that rotatably connects is configured:
A work arm having a rectangular cross section formed by a plurality of plate members;
One plate member of the plurality of plate members and an outer peripheral portion of the flange portion are joined via a welding portion;
The boss is provided on the outer peripheral portion of the collar, the surface of which is located inside the working arm with respect to the surface of the collar in the axial direction of the pin insertion hole, and the collar is joined It further has an annular annular plate portion joined to the plate member via a welding portion,
The boss has a groove provided at a position corresponding to a part of the extension area of the weld in the collar portion,
The groove is disposed closer to the boss main body than the weld in the radial direction of the boss.
The thickness of the flange of the grooved portion is 85% or more of the thickness of the plate to which the boss is joined and is smaller than the thickness of the plate to which the boss is joined. Hydraulic excavator characterized by. In the hydraulic shovel according to claim 1,
The plurality of plate members of the working arm includes a side plate and a top plate,
The boss is joined to the side plate,
The groove is formed in an arc shape centered on the axial center of the pin insertion hole,
The formation range of the groove is that the angular position in the clockwise direction when looking at the boss from the outside of the working arm is in the range of 280 degrees to 350 degrees on the basis of a point where the welded part is closest to the upper plate. Features hydraulic excavators. In the hydraulic shovel according to claim 1,
The width of the radial direction of the groove is 1% or more and 4.5% or less of the outer diameter of the flange portion. In the hydraulic shovel according to claim 1,
A hydraulic shovel characterized in that a value obtained by doubling the distance from the groove to the axis of the pin insertion hole is 50% or more and 85% or less of the outer diameter of the flange portion. In the hydraulic shovel according to claim 1,
The hydraulic shovel according to claim 1, wherein a radius of curvature of a corner of a bottom of the groove is 4% or more and less than 100% of a thickness of the plate member to which the boss is joined. In the hydraulic shovel according to claim 1,
The plurality of plate members of the working arm includes a side plate and a top plate,
The boss is joined to the side plate,
The groove is formed in an arc shape centered on the axial center of the pin insertion hole,
The formation range of the groove is that the angular position in the clockwise direction when looking at the boss from the outside of the working arm is from 225 degrees to 360 degrees with reference to a point where the welded part is closest to the upper plate. Hydraulic shovel. In the hydraulic shovel according to claim 1,
The plurality of plate members of the working arm includes a side plate and a top plate,
The boss is joined to the side plate,
The groove is formed in an arc shape centered on the axial center of the pin insertion hole,
The formation range of the groove is such that the angular position from the outside of the working arm viewed from the outside of the working arm is 0 degrees to 90 degrees and 225 degrees from the point where the welded part is closest to the upper plate. A hydraulic shovel characterized by being 360 degrees. In the hydraulic shovel according to claim 1,
The said groove is provided in the back side which turns to the inner side of the said working arm in the said collar part. The hydraulic shovel characterized by the above-mentioned. In the hydraulic shovel according to claim 1,
The hydraulic shovel is characterized in that a plurality of the grooves are provided such that radial distances from the axial center of the pin insertion hole are different.

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