JP6158049B2 - Construction machine arm - Google Patents

Description

  The present invention relates to a box-type structure having a rectangular cross section when viewed in the vertical direction from a pair of left and right side plates, a front plate joined to the front end of each side plate, and a rear plate joined to the rear end of each side plate. It is related with the arm of the construction machine by which the reinforcement board is arrange | positioned.

  In general, a hydraulic excavator, which is a typical example of a construction machine, is a self-propelled lower traveling body, an upper revolving body that is pivotably mounted on the lower traveling body, and a work that is attached to the upper revolving body so as to be able to move up and down. It is generally composed of an arm device. At the time of excavation work such as earth and sand, the work arm device is moved up and down, and the upper turning body is swung with respect to the lower traveling body, so that the excavation work such as earth and sand is performed.

  The working arm device includes a boom attached to the front part of the upper swing body so as to be movable up and down, an arm rotatably attached to the front part of the boom, and a work tool rotatably attached to the lower part of the arm. A work tool link disposed between the arm and the work tool, a boom cylinder that moves the boom up and down, an arm cylinder that turns the arm, and a work tool cylinder that turns the work tool. ing.

  The arm has a rectangular cross section when viewed in the vertical direction from a pair of left and right side plates, a front plate joined by welding to the front end of each side plate, and a rear plate joined by welding to the rear end of each side plate It is formed as a mold structure.

  A pair of left and right semicircular cutouts are formed at the upper rear end of each side plate. The notch is provided with a boom connection boss that is connected to the front portion of the boom by a connection pin. The boom connecting boss has a cylindrical boss extending in the left and right directions, and a pair of left and right flanges protruding in the radial direction from the outer peripheral surfaces of the left and right ends of the boss and extending in the circumferential direction. And have. Each collar is formed corresponding to each notch. And the outer surface of each collar part is welded and joined to the outer surface of each notch from the outer side of an arm.

  In order to increase the rigidity of the arm against bending load and torsion load due to excavation reaction force or the like, a rectangular reinforcing plate made of a flat plate is disposed inside the arm so as to partition the upper and lower portions of the arm. The outer periphery of the reinforcing plate is joined to the boss portion of the boom connecting boss, each flange portion of the boom connecting boss, each side plate, and the front plate by welding (for example, see Patent Document 1).

JP 2012-241423 A

  The conventional construction machine arm as described above has the following problems to be solved.

  The rigidity of the arm is enhanced by the reinforcement plate provided inside. However, when a load is applied during excavation work, the arm and the direction of the load, etc. There is a possibility that stress concentrates on the welded portion joining the outer surface of the part and the outer surface of each notch, and the welded portion is cracked.

  The present invention has been made in view of the above-mentioned facts, and its main technical problem is to reduce the stress generated around the boom connecting boss and to join the outer surface of each flange part and the outer surface of each notch. It is an object of the present invention to provide an arm of a construction machine that can prevent cracks in a welded part.

According to the present invention, as the arm for achieving the above technical problem, a pair of left and right side plates, a front plate joined to the front ends of the pair of side plates, and after joined to the rear ends of the pair of side plates A pair of left and right semicircular cutouts are formed at the upper rear ends of each of the pair of side plates. A boom connecting boss is disposed in the notch, and the boom connecting boss includes a cylindrical boss extending in the left and right directions, and a radial direction from the outer peripheral surfaces of the left and right ends of the boss. A pair of left and right flanges extending outward in the circumferential direction and corresponding to the pair of notches, each of the pair of flanges being joined to each of the pair of notches A reinforcing plate whose outer periphery is joined to the boss portion, the pair of flanges, the pair of side plates, and the front plate. A pair of left and right stepped portions recessed inward in the left and right directions are formed on the outer peripheral edges of each of the pair of collars, and each of the pair of collars is the reinforcing plate A pair of front flanges and a rear collar located behind the reinforcing plate, and the outer surfaces of the pair of stepped portions are in contact with the inner surfaces of the pair of notches. The outer surfaces of the pair of stepped portions are joined to the outer surfaces of the pair of notches, and the inner surfaces of the pair of stepped portions are respectively connected to the inner surfaces of the pair of notches in the rear flange. Each of the joints between the inner surfaces of the pair of stepped portions and the inner surfaces of the pair of notches in the rear collar is connected to the outer peripheral edge of the rear collar from the rear surface of the reinforcing plate. Extending to the rear end of the contact portion between each of the pair of stepped portions and each of the pair of notches, and then to the rear end of each of the pair of side plates Along the edge extending downward, construction machine arm is provided, characterized in that.

The reinforcing plate is preferred that extends from the boss portion to the front plate is bent toward the substantially parallel extending then forward and downward and the rear plate downward. A pair of left and right work tool cylinder brackets are joined to the outer surface of the front plate, and the outer periphery of the lower end of the reinforcing plate is joined to the inner surface of the front plate behind the pair of work tool cylinder brackets. Is convenient.

  In the arm of the present invention, the inner surface of each stepped portion is joined to the inner surface of each notch in the rear collar. For this reason, since the direction of the stress generated around the boom connection boss by excavation work is dominant in the downward direction, the stress generated around the boom connection boss is caused by the inner surface of each stepped portion and the inner surface of each notch. The stress generated around the boom connection boss can be effectively reduced, thereby joining the outer surface of each flange and the outer surface of each notch. It is possible to prevent cracks from occurring in the welded part.

The perspective view in the state where the left side plate of the arm concerning the present invention was removed. The principal part enlarged view seen from the A direction in FIG. Sectional drawing seen from the BB direction in FIG. The perspective view which expanded the boom cylinder boss | hub, the upper side board, etc. in FIG. The side view of the hydraulic excavator provided with the arm of the construction machine shown in FIG.

  Hereinafter, an arm of a construction machine configured according to the present invention will be described with reference to the embodiments shown in FIGS. 1 to 5 in a hydraulic excavator as a typical construction machine.

  This will be described with reference to FIG. The hydraulic excavator indicated as a whole by number 2 is attached to a self-propelled lower traveling body 4, an upper revolving body 6 that is pivotably mounted on the lower traveling body 4, and an upper revolving body 6 that can be raised and lowered. The work arm device 8 is generally configured. At the time of excavation work such as earth and sand, the work arm device 8 is moved up and down, and the upper turning body 6 is turned relative to the lower traveling body 4 so that the excavation work such as earth and sand is performed.

  The upper revolving structure 6 is a revolving frame 10 that forms a framework structure, a driver's cab 12 that is disposed on the left front portion of the revolving frame 10 and on which an operator gets on, and a rear portion of the revolving frame 10 that is an engine. And the like, and a counterweight 16 disposed behind the device storage chamber 14. Note that the front, rear direction, left and right directions used in the description of the present specification are boarded in the cab 12 with the tip of the work arm device 8 as shown in FIG. 5 in contact with the ground. It is the front, back, left, and right as seen by the workers.

  The work arm device 8 includes a boom 18 attached to the front part of the upper swing body 6 so as to be able to move up and down, an arm 20 attached to the front part of the boom 18 so as to be rotatable, and a lower part of the arm 20 to be rotatable. A work tool 22 attached to the arm 20, a work tool link 24 disposed between the arm 20 and the work tool 22, and a left and a right disposed on each side of the boom 18 to move the boom 18 up and down. A pair of boom cylinders 26, 26, an arm cylinder 28 that is disposed above the boom 18 and rotates the arm 20, and a work tool cylinder that is disposed in front of the arm 20 and rotates the work tool 22. 30.

  A description will be given with reference to FIG. The arm 20 has a pair of left and right side plates 32 and 32 extending upward and downward, a front plate 34 joined to the front ends of the side plates 32 and 32 by welding, and welded to the rear ends of the side plates 32 and 32. Is formed as a box-shaped structure having a rectangular cross section when viewed in the vertical direction from the rear plate 36 joined by.

  Further, since the arm 20 is a long welded structure having a total length of several meters, each of the side plates 32, 32, the front plate 34, and the rear plate 36 is divided in order to facilitate handling during manufacture. It has a structured.

  The side plates 32, 32 are a pair of left and right upper side plates 38, 38 located on the boom 18 side, a pair of left and right lower side plates 40, 40 located on the work tool 22 side, and each upper side plate 38, 38. And a pair of left and right intermediate side plates 42, 42 located between the lower side plates 40, 40. The lower ends of the upper side plates 38, 38 and the upper ends of the intermediate side plates 42, 42, and the lower ends of the intermediate side plates 42, 42 and the upper ends of the lower side plates 40, 40 are joined by welding.

  The upper ends of the upper side plates 38, 38 are formed to be curved upward and convex. A pair of left and right semicircular cutouts 38a and 38a are formed at the upper rear ends of the upper side plates 38 and 38, respectively. In each of the notches 38a and 38a, a boom connecting boss 44 connected to the front portion of the boom 18 by a connecting pin is disposed.

  This will be described with reference to FIGS. The boom connecting boss 44 extends in the circumferential direction by projecting outward in the radial direction from a cylindrical boss portion 44a that extends in the left and right directions and into which a connecting pin is inserted, and an outer peripheral surface on both left and right sides of the boss portion 44a. It has a pair of left and right fan-shaped flanges 44b and 44b. The outer periphery of the radius part of each collar part 44b and 44b has comprised the obtuse angle. Moreover, the outer periphery of the circular arc part of each collar part 44b, 44b is formed corresponding to each notch 38a, 38a.

  A pair of left and right step portions 44c and 44c recessed inward in the left and right directions are formed on the outer peripheral edges of the arc portions of the flange portions 44b and 44b. Each flange 44b, 44b is divided into front flanges 44d, 44d positioned in front of a reinforcing plate 64, which will be described later, and rear flanges 44e, 44e positioned behind the reinforcing plate 64.

  The outer surfaces of the step portions 44c and 44c are in contact with the inner surfaces of the notches 38a and 38a. And the outer surface of each level | step-difference part 44c, 44c is welded and joined from the outer side of the arm 20 to the outer surface of each notch 38a, 38a over the circular arc part outer periphery. And the inner surface of each level | step-difference part 44c, 44c is welded and joined from the inner side of the arm 20 to the inner surface of each notch 38a, 38a in the circular arc part outer periphery of each back collar part 44e, 44e. . Each of the joint portions 45, 45 formed by welding the inner surface of each stepped portion 44c, 44c and the inner surface of each notch 38a, 38a at the outer peripheral edge of the arc portion of each rear flange 44e, 44e is provided from the rear surface of the reinforcing plate 64. It extends to the rear end of the contact portion between each stepped portion 44c, 44c and each notch 38a, 38a along the outer peripheral edge of the arcuate portion of the rear flanges 44e, 44e, and then along the rear end outer edge of each upper side plate 38, 38. Extending downward.

  As shown in FIG. 1, the lower ends of the lower side plates 40 and 40 are formed to be curved upward and have a work tool connection boss 46 to which the work tool 22 is connected by a connection pin. . The work tool connection boss 46 is formed in a cylindrical shape extending in the left and right directions, and the outer peripheral surfaces on both the left and right direction sides are joined to the lower ends of the lower side plates 40 and 40 by welding.

  A pair of left and right circular holes 40a and 40a are formed in the upper portions of the lower side plates 40 and 40, respectively. A work tool link connecting boss 48 to which the work tool link 24 is connected by a connecting pin is disposed in each circular hole 40a, 40a. The work tool link connecting boss 48 is formed in a cylindrical shape extending in the left and right directions, and the outer peripheral surfaces on both the left and right directions are joined to the circular holes 40a and 40a by welding.

  The rear ends of the intermediate side plates 42, 42 extend vertically from the upper end to the lower end. In addition, the front ends of the intermediate side plates 42, 42 are inclined to the front from the upper part toward the lower part, and then inclined to the rear, and are formed in a square shape when viewed from the side.

  The front plate 34 includes an upper front plate 50 located on the boom 18 side, a lower front plate 52 located on the work tool 22 side, and an intermediate front plate 54 located between the upper front plate 50 and the lower front plate 52. It is composed of The front lower end of the upper front plate 50 and the upper end of the intermediate front plate 54, the lower end of the intermediate front plate 54 and the upper end of the lower front plate 52, the lower end of the lower front plate 52, and the outer periphery of the front of the work tool connecting boss 46 Each of the surfaces is joined by welding.

  The upper front plate 50 is bent upward and convex along the upper ends of the upper side plates 38 and 38. On the outer surface of the upper front plate 50, a pair of left and right arm cylinder brackets 56, 56 to which the arm cylinder 28 is coupled by a coupling pin are disposed. Each arm cylinder bracket 56, 56 is formed in a substantially triangular shape, and pin holes 56a, 56a into which connecting pins are inserted are opened in the upper part thereof. The arm cylinder brackets 56 and 56 are joined to the upper front plate 50 by welding at predetermined intervals in the left and right directions.

  The intermediate front plate 54 is bent in a square shape when viewed from the side along the front ends of the intermediate side plates 42 and 42. A pair of left and right work tool cylinder brackets 58 and 58 to which the work tool cylinder 30 is connected by a connection pin are disposed on the outer surface of the lower portion of the intermediate front plate 54 positioned below the bent part. Each of the work tool cylinder brackets 58 and 58 is formed in a substantially triangular shape, and pin holes 58a and 58a into which connecting pins are inserted are formed in the lower portions thereof. The respective work tool cylinder brackets 58 and 58 are joined to the intermediate front plate 54 by welding at predetermined intervals in the left and right directions.

  The rear plate 36 includes an upper rear plate 60 located on the boom 18 side and a lower rear plate 62 located on the work tool 22 side. And each of the rear lower end of the upper front plate 50 and the upper end of the upper rear plate 60, the lower end of the upper rear plate 60 and the upper end of the lower rear plate 62, the lower end of the lower rear plate 62 and the rear outer peripheral surface of the work tool connecting boss 46. Are joined by welding.

  The upper rear plate 60 is bent in the shape of an inverted letter when viewed from the side along the outer periphery of the radius portion forming the obtuse angle of each of the flange portions 44b, 44b. The upper rear plate 60 is welded from the outside of the arm 20 to the outer periphery of the radial portions of the flange portions 44b, 44b, in addition to the rear ends of the upper side plates 38, 38 and the rear ends of the intermediate side plates 42, 42. Are joined. The lower portion of the upper rear plate 60 and the lower rear plate 62 positioned below the bent portion extend vertically.

  Inside the arm 20, a reinforcing plate 64 in which a rectangular steel plate is bent is disposed. The reinforcing plate 64 extends from the outer peripheral surface of the lower end of the boss portion 44a downward in parallel with the lower portion of the upper rear plate 60 and the lower rear plate 62, and then is bent toward the front lower portion and extends to the intermediate front plate 54. ing.

  The outer periphery of the upper end of the reinforcing plate 64 is in contact with the outer peripheral surface of the lower end of the boss portion 44a and joined by welding. The outer circumferences of the left and right ends of the reinforcing plate 64 are brought into contact with the inner surfaces of the flange portions 44b and 44b, the inner surfaces of the upper side plates 38 and 38, and the inner surfaces of the intermediate side plates 42 and 42, and are joined by welding. The outer periphery of the lower end of the reinforcing plate 64 is in contact with the inner surface of the lower portion of the intermediate front plate 54 and joined by welding behind the respective work tool cylinder brackets 58 and 58.

  The upper portion of the reinforcing plate 64 positioned above the bent portion is substantially parallel to the lower portion of the upper rear plate 60 and the lower rear plate 62 with the contact portion between the reinforcing plate 64 and the lower end outer peripheral surface of the boss portion 44a facing upward. When extended, it is positioned so as to pass through the axis of the boss portion 44a.

  The operation of the arm 20 shown in FIGS. 1 to 5 as described above will be described.

  In the arm 20 of the present invention, the inner surface of each stepped portion 44c, 44c is welded from the inside of the arm 20 to the inner surface of each notch 38a, 38a at the outer peripheral edge of the arc portion of each rear flange 44e, 44e. Are joined. For this reason, the direction of the stress generated around the boom connection boss 44 by the excavation work is dominant in the downward direction, so the stress generated around the boom connection boss 44 is caused by the inner surface of each stepped portion 44c, 44c and each of the step portions 44c, 44c. Dispersed in the welded portion joining the inner surfaces of the notches 38a, 38a, the stress generated around the boom connecting boss 44 can be effectively reduced, whereby each flange portion 44b, It is possible to prevent the welded portion joining the outer surface of 44b and the outer surface of each notch 38a, 38a from cracking.

  Further, in the arm 20 of the present invention, the joint portions 45, 45 formed by welding the inner surfaces of the step portions 44c, 44c and the inner surfaces of the notches 38a, 38a at the outer peripheral edges of the arcuate portions of the rear flanges 44e, 44e. Each extends from the rear surface of the reinforcing plate 64 to the rear end of the contact portion between each stepped portion 44c, 44c and each notch 38a, 38a along the outer peripheral edge of each of the rear flanges 44e, 44e. The side plates 38 extend downward along the outer edges of the rear ends. For this reason, even if a dedicated jig is not used, the joint portions 45 and 45 formed by welding the inner surfaces of the step portions 44c and 44c and the inner surfaces of the cutouts 38a and 38a are provided on each step from the rear surface of the reinforcing plate 64. The throat thickness can be kept substantially constant up to the rear end of the contact portion between the portions 44c, 44c and the notches 38a, 38a. As a result, the joint portions 45 and 45 formed by welding the inner surfaces of the stepped portions 44c and 44c and the inner surfaces of the notches 38a and 38a have no portion where the throat thickness changes abruptly and stress concentration tends to occur. Strength will be secured.

  Further, the reinforcing plate 64 extends substantially in parallel with the lower portion of the upper rear plate 60 and the lower rear plate 62 downward from the outer peripheral surface of the lower end of the boss portion 44a, and is then bent downward in the front and lower direction. Extends to the inner surface. For this reason, since the downward direction is dominant in the direction of the stress generated around the boom connecting boss 44 by excavation work, the stress generated around the boom connecting boss 44 is distributed to the reinforcing plate 64. The stress generated around the boom connecting boss 44 can be effectively reduced, thereby cracking the welded portion joining the outer surface of each flange 44b, 44b and the outer surface of each notch 38a, 38a. Can be prevented from entering.

  Furthermore, the reinforcing plate 64 is brought into contact with the inner surface of the lower part of the intermediate front plate 54 at the rear of each work tool cylinder bracket 58, 58, and is joined by welding, so that the work tool cylinder 30 is expanded and contracted. In addition, the rigidity against the bending load acting so that the central portion is convex forward or backward when the intermediate front plate 54 is viewed in the vertical direction can be enhanced.

20: Arm 32: Side plate 34: Front plate 36: Rear plate 38: Upper side plate 38a: Notch 40: Lower side plate 40a: Circular hole 42: Middle side plate 44: Boom connection boss 44a: Boss portion 44b: Gutter 44c: Stepped portion 44d: Front flange portion 44e: Back flange portion 45: Joining portion between inner surface of each stepped portion and inner surface of each notch 50: Upper front plate 52: Lower front plate 54: Intermediate front plate 58: Work tool cylinder Bracket 58a: Pin hole 60: Upper rear plate 62: Lower rear plate 64: Reinforcement plate

Claims (3)

A box-shaped structure having a rectangular cross section when viewed in the vertical direction from a pair of left and right side plates, a front plate joined to the front ends of the pair of side plates, and a rear plate joined to the rear ends of the pair of side plates Is formed as
A pair of left and right semicircular cutouts are formed at the upper rear end of each of the pair of side plates, and a boom connecting boss is disposed in the pair of cutouts,
The boom connecting boss has a cylindrical boss extending in the left and right directions and a pair of notches extending in the circumferential direction by projecting radially outward from the outer peripheral surfaces of the left and right ends of the boss. A pair of left and right collars formed correspondingly, each of the pair of collars being joined to each of the pair of notches,
Inside the box-shaped structure, there is disposed a reinforcing plate whose outer periphery is joined to the boss portion, the pair of flanges, the pair of side plates, and the front plate,
A pair of left and right stepped portions recessed inward in the left and right directions are formed on the outer peripheral edges of each of the pair of collars, and each of the pair of collars is positioned in front of the reinforcing plate. It is divided into a front collar and a rear collar located behind the reinforcing plate,
The outer surfaces of the pair of stepped portions are in contact with the inner surfaces of the pair of notches, the outer surfaces of the pair of stepped portions are joined to the outer surfaces of the pair of notches, and the rear The inner surface of each of the pair of stepped portions is joined to the inner surface of each of the pair of notches in the collar portion ,
Each of the joints between the inner surfaces of the pair of stepped portions and the inner surfaces of the pair of notches in the rear collar is formed from the rear surface of the reinforcing plate along the outer periphery of the rear collar. Extending to the rear end of the contact portion between each of the step portions and each of the pair of notches, and then extending downward along the outer edge of the rear end of each of the pair of side plates .
A construction machine arm characterized by that. Reinforcing plate extends from the boss portion to the front plate is bent toward the substantially parallel extending then forward and downward and the rear plate downward, the arm of a construction machine according to claim 1 Symbol placement. A pair of left and right work tool cylinder brackets are joined to the outer surface of the front plate, and the outer periphery of the lower end of the reinforcing plate is joined to the inner surface of the front plate behind the pair of work tool cylinder brackets. The arm of the construction machine according to claim 1 or 2 .

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