JP4556538B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine having an arm to which an attachment such as a hydraulic excavator is attached, and more particularly to the arm.

  In a construction machine such as a hydraulic excavator, for example, as disclosed in Patent Document 1 below, an upper swing body is pivotably disposed on an upper part of a lower traveling body, and a work arm is raised and lowered at the front portion of the upper swing body. It is installed freely. This working arm is composed of a boom, an arm and an attachment, the boom is configured to be raised and lowered by a boom cylinder, the arm is configured to be rotated by an arm driving cylinder provided on the boom, and the attachment is attached to the arm. It is comprised so that it may rotate with the cylinder for attachment drive provided.

Since the arm plays a role of supporting a load received during excavation work of the ground, the arm is required to have sufficient strength. On the other hand, the work arm is mounted in an overhanging position ahead of the upper swing body, and the work arm is moved to perform work.Therefore, weight reduction of the work arm is required in consideration of the weight balance of the entire aircraft. ing. Among them, the arm that is rotatably attached to the tip of the boom is a member that is particularly effective in reducing the weight.
Japanese Patent Laid-Open No. 2002-322626

  By the way, as shown in FIGS. 7 and 8, consider an arm 71 having a hollow structure arm body 72 formed by welding an upper plate 73 and a lower plate 78 to the upper and lower ends of a pair of side plates 79. . The arm 71 has a simple structure in which the upper plate 73 and the lower plate 78 are formed in a flat plate shape except for the bent portions 73a and 78a on the proximal end side, and is an arm of a type for the purpose of weight reduction. A bracket 74 for supporting an attachment driving cylinder 76 (see FIG. 9) is erected on the upper plate 73, and an arm driving cylinder 77 (see FIG. 9) is supported at the base end portion of the arm body 72. The bracket 75 is erected. When excavation work is performed using this arm 71, the force from the attachment driving cylinder 76 acts on the upper plate 73 of the arm 71 via the bracket 74, as shown in FIG. The force from the arm driving cylinder 77 is applied to the base end portion via the bracket 75. At this time, as shown in FIG. 10, the force by the attachment driving cylinder 76 acting on the upper plate 73 from the bracket 74 is in the right direction (arm base end direction) in the figure, while the base of the arm main body 72 is from the bracket 75. Since the force by the arm driving cylinder 77 acting on the end portion is in the upward direction (or upper left direction) in the figure, a compressive stress acts on the upper plate 73 of the arm body 72. For this reason, stress concentrates on the bending part 73a of the upper board 73, and there exists a possibility of reducing the fatigue life of the welding part of the upper plate 73 and the side plate 79 in this part. Further, when the strength of the upper plate 73 is insufficient, there is a possibility that bending deformation occurs in the bent portion 73a. Therefore, in this type, in order to ensure the strength of the arm 71, it is necessary to increase the thickness of the upper plate 73 and the like.

  On the other hand, Patent Document 1 discloses reinforcing an arm. Specifically, by providing both the pin hole for connecting the arm driving cylinder and the pin hole for connecting the attachment driving cylinder to the bracket provided on the arm, the force received from both cylinders is offset. Has been shown to let Further, this document describes that by increasing the welding length of the bracket, the stress generated at the welded portion can be relaxed, and the weight of the member can be reduced. However, in this case, it is difficult to think that the weight reduction of the arm can be effectively achieved because the bracket itself inevitably increases in size.

  Therefore, the present invention has been made in view of such a point, and an object thereof is to reduce the weight of the arm while maintaining the strength originally required for the arm.

  In order to achieve the above object, the present invention has a working arm including a boom, an arm, and an attachment, and an arm driving cylinder provided on the boom is attached to a base end portion of the arm of the working arm, An attachment is attached to the tip, and this attachment is a construction machine configured to be rotatable by an attachment driving cylinder attached to the arm, and the arm includes a pair of side plates, a first plate, An arm body having a rectangular shape with a second cross-section, and the arm plate being rotatably supported by the tip of the boom near the second plate in each side plate of the arm body A pivot center portion is provided, and the first plate of the arm body includes a tip side portion extending from a tip portion of the arm body, and the second plate than the tip side portion. A flat plate portion extending from the base end portion of the arm main body at a position spaced apart from the arm main body, and a step portion connecting the flat plate portion and the tip side portion in a step shape, closer to the tip portion than the rotation center portion. A bracket welded to the first plate to rotatably support the attachment driving cylinder at a position, the bracket being a surface far from the second plate at an end connected to the flat plate portion; An arm is connected to the outer surface of the flat plate portion without a step and is welded to the step portion so that the outer surface protrudes from the step portion toward the tip side, and supported by the bracket. The received force mainly acts on the flat plate portion as a compressive or tensile axial load.

  In this invention, since the force from the cylinder for driving the attachment acting on the bracket is received by the step portion of the first plate, local stress is unlikely to occur on the distal end side and the proximal end side of the bracket. The force from the attachment driving cylinder is transmitted in a concentrated manner especially to the flat plate portion of the first plate. At this time, the flat plate portion of the first plate is larger than the bracket when viewed in the direction of action of this force. Since it is arranged at a position far from the two plates and extends linearly to the vicinity of the mounting part of the arm driving cylinder, the force received at the step portion of the first plate is mainly a compression or tension axial load on the flat plate portion. Acts as At this time, even if a bending moment acts on the flat plate portion, it acts only slightly. In addition, since the height of the side plate on the base end side of the arm can be increased by providing the step portion on the first plate, the cross section of the arm main body with respect to the center of rotation in the arm main body on the base end side with respect to the stepped portion The next moment can be increased. As a result, it is possible to suppress the generation of a stress state that reduces the fatigue life of the welded portion between the first plate and the side plate constituting the arm body.

  Moreover, in this invention, the outer side surface which is a surface far from the 2nd board of the edge part connected to the said flat plate part in the said bracket is connected with the outer side surface of the said flat plate part without a level | step difference.

  With this configuration, it is possible to avoid stress concentration at the connection portion between the bracket and the outer surface of the flat plate portion, and thus the first plate can be formed thinner.

  The bracket preferably has an outer surface of the bracket disposed on a plane including the outer surface of the flat plate portion, and a portion other than the outer surface is disposed closer to the second plate than the plane.

  As described above, according to the construction machine according to the present invention, the rigidity around the rotation center portion can be improved in the arm body on the base end side with respect to the step portion, and the axial load is mainly generated in the flat plate portion of the first plate. Can be made. As a result, it is possible to reduce the thickness of the side plate and the first plate that make up the arm body, and to reduce the size of the bracket made of the thick plate, thus reducing the weight of the arm while maintaining fatigue strength at the welded part of the arm. Can be achieved.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the overall configuration of a crawler hydraulic excavator as a construction machine according to an embodiment of the present invention. As shown in this figure, the body (main body) of the hydraulic excavator is composed of a lower traveling body 1 and an upper swing body 2, and a work arm 3 is mounted on the front portion of the upper swing body 2 so as to be freely raised and lowered. Has been.

  The lower traveling body 1 is composed of left and right crawler frames 4 and crawlers (both are shown only on one side) 5, and both side crawlers 5 are individually rotated and driven by left and right traveling motors 6. The upper swing body 2 includes a swing frame 7, an operator cab 8, a machine room 9, and the like, and an engine or the like for driving a hydraulic pump (not shown) is disposed in the machine room 9. A boom cylinder 12 is provided at the front end of the upper swing body 2. The boom cylinder 12 is expanded and contracted by hydraulic oil supplied from the hydraulic pump.

  The work arm 3 includes a boom 11, an arm 13, and a bucket 18 as an attachment.

  The boom 11 is provided at the front end portion of the upper swing body 2, and the boom 11 is formed in a hollow shape having a rectangular cross section. The end of the boom cylinder 12 is pin-coupled to the side plate of the boom 11, and the boom 11 is configured to undulate when the boom cylinder 12 is expanded and contracted.

  An arm cylinder 14 as an arm driving cylinder is attached to the upper plate of the boom 11. Further, a bracket 15 made of a pair of flat plates disposed in parallel to the pivoting surface of the boom 11 is provided at the tip of the boom 11.

  The arm 13 is connected to the base end portion of the arm cylinder 14 in a rotatable manner, while the bucket 18 is rotatably connected to the tip portion. And in the intermediate part between the base end part of this arm 13, and the front-end | tip part, the front-end | tip part of the boom 11 is couple | bonded so that rotation is possible. It is rotatable with respect to the boom 11 around the tip. Hereinafter, the configuration of the arm 13 will be specifically described.

  As shown in FIGS. 2 and 3, the arm 13 includes an arm main body 25 formed in an elongated hollow body shape. A proximal end bracket 27 for pin-connecting the distal end portion of the arm cylinder 14 is provided at the proximal end portion 25 a of the arm body 25. The base end bracket 27 includes a pair of flat plates each having a pin insertion hole and provided in parallel with the rotating surface of the boom 11. On the other hand, a distal end bracket 28 for pin-coupling the bucket 18 is provided at the distal end portion 25 b of the arm body 25. The front end bracket 28 is composed of a pair of flat plates having pin insertion holes 27a and 28a, respectively.

  The arm body 25 has a rectangular cross section by connecting upper and lower ends (vertical ends in FIG. 2) of the pair of side plates 30 with an upper plate (first plate) 32 and a lower plate (second plate) 34, respectively. Is formed. The upper plate 32 and the lower plate 34 are welded to the side plate 30 so as to protrude slightly laterally from the side plate 30.

  Each side plate 30 is formed of a long and thin flat plate, and a reinforcing plate 36 is bonded to each side plate 30 at a lower portion in an intermediate portion in the length direction. The reinforcing plate 36 is provided with a boss portion 38 for pin-connecting the tip end portion of the boom 11. The boss portion 38 is formed in a cylindrical shape at the first intermediate portion 25 c between the base end portion 25 a and the tip end portion 25 b of the arm body 25, and a pin (not shown) is inserted into the through hole extending over the both side plates 30. Thus, the tip of the boom 11 can be pin-coupled. The boss portion 38 constitutes the rotation center portion referred to in the present invention. In this specification, the side close to the center of rotation in the direction orthogonal to the longitudinal direction of the side plate 30 is called the lower side, and the far side is called the upper side.

  FIG. 2 shows the distal end side portion 30b at the lower end portion of the side plate 30 that is closer to the distal end portion 25b side of the arm body 25 than the boss portion 38 extends in the left-right direction in the same figure, and the proximal end side portion 30a at the lower end portion. The side plate 30 is illustrated so as to extend obliquely upward to the right. In FIG. 2, reference numeral 40 denotes an end face that is generated by making the thickness of the side plate 30 constituting the arm main body 25 thicker at the base end portion and the distal end portion than the intermediate portion therebetween.

  The side plate 30 has a shape in which the width in the vertical direction of the figure gradually decreases from the first intermediate portion 25 c toward the base end portion 25 a of the arm body 25. Further, the side plate 30 gradually decreases in width in the vertical direction in the figure as it goes from the second intermediate portion 25d positioned closer to the distal end portion 25b of the arm body 25 to the distal end portion 25b of the arm body 25 than the first intermediate portion 25c. It has become a shape. Further, the width in the vertical direction of the side plate 30 in the range between the first intermediate portion 25 c and the second intermediate portion 25 d is approximately the same along the length direction of the arm body 25. The second intermediate portion 25d is a portion that receives a force from the bucket cylinder 44, as will be described later.

  The lower plate 34 is bent at the first intermediate portion 25 c of the arm body 25.

  The upper plate 32 is disposed closer to the base end portion 25a of the arm body 25 than the second intermediate portion 25d, and closer to the distal end portion 25b of the arm body 25 than the second intermediate portion 25d. It consists of the front end side part 32b and the level | step-difference part 32c arrange | positioned between these flat plate parts 32a and 32b. The flat plate portion 32a and the distal end side portion 32b are each formed in an elongated flat plate shape, but the distal end side portion 32b is longer than the flat plate portion 32a.

  The flat plate portion 32a extends linearly to the vicinity of the base end portion 25a of the arm body 25 on which the base end bracket 27 is provided, and the end portion of the flat plate portion 32a is configured to be curved in an arc shape. The plate 42 is smoothly connected. As a result, the base end portion 15a of the arm body 25 has a rounded shape as a whole. The base end plate 42 has an upper end connected to the upper plate 32 and a lower end connected to the lower plate 34. The base end plate 42 is welded to both side plates 30. The base end bracket 27 is provided across the base end plate 42 and the lower plate 34.

  The distal end side portion 32b extends linearly from the distal end portion 25b of the arm body 25 toward the stepped portion 32c.

  The step portion 32c is located at the second intermediate portion 25d in the length direction of the arm body 25. The step portion 32c is formed by the flat plate portion 32a of the upper plate 32 and the flat plate portion 32a when viewed in the left-right direction in FIG. The tip end side portion 32b closer to the boss portion 38 is connected in a step shape. The step portion 32c is slightly curved at both ends thereof, whereby the step portion 32c and the flat plate portions 32a and 32b are smoothly connected.

  A bracket 46 for supporting a bucket cylinder 44 as an attachment driving cylinder is provided on the stepped portion 32c. The bracket 46 is composed of a pair of flat plates arranged in parallel with the rotation surface of the arm 13, and each flat plate is formed thicker than the side plate 30 in the same manner as the arm shown in FIG. 8. Each flat plate is formed with a pin insertion hole 46a. Then, by inserting a pin (not shown) into the pin insertion hole 46a and connecting the base end portion of the bucket cylinder 44 with a pin, the bucket cylinder 44 can rotate within a predetermined range with the pin as an axis. The bucket cylinder 44 is disposed on the opposite side of the flat plate portion 32 a with respect to the bracket 46.

  The bracket 46 is welded to the upper plate 32 so as to straddle the distal end side portion 32b, the step portion 32c, and the flat plate portion 32a. That is, the weld line between the upper plate 32 and the bracket 46 is mainly formed in the stepped portion 32c, and this weld line extends to the tip side portion 32b and the flat plate portion 32a.

  Each flat plate constituting the bracket 46 is formed in a substantially triangular shape, and the bracket 46 protrudes from the step portion 32 c in a direction away from the boss portion 38. The pin insertion hole 46a is disposed closer to the distal end side portion 32b in the bracket 46.

  The base end portion 46b of the bracket 46, that is, the end portion 46b of the bracket 46 connected to the flat plate portion 32a has a shape in which the upper surface thereof is connected to the upper surface of the flat plate portion 32a of the upper plate 32 without being stepped, that is, substantially flush. It has become. The upper surface of the base end portion 46b extends linearly from the upper surface of the flat plate portion 32a. On the other hand, the end 46c of the bracket 46, that is, the end 46c of the bracket 46 connected to the front end 32b is connected to the front end 32b of the upper plate 32 in a smooth curved shape. The pin insertion hole 46 a of the bracket 46 is located between the distal end side portion 32 b and the flat plate portion 32 a when viewed in the extending direction of the distal end side portion 30 b at the lower end portion of the side plate 30. In the present embodiment, the upper surface of the base end portion 46b of the bracket 46 extends straight from the upper surface of the flat plate portion 32a. However, the upper surface of the bracket 46 is less than the plate thickness of the bracket 46 than the flat plate portion 32a. It is good also as a shape which protrudes upwards in the range of this, or it is good also as a shape which an upper surface positions below in the range within the plate | board thickness of the flat plate part 32a from the flat plate part 32a.

  The bucket cylinder 44 exerts a force on the bracket 46 within a predetermined angle range with a direction parallel to the extending direction of the distal end side portion 30b at the lower end portion of the side plate 30 accompanying expansion and contraction of the rod. At this time, the bucket cylinder 44 applies force from a portion of the bracket 46 opposite to the flat plate portion 32a.

  The bucket 18 is pin-coupled to the distal end bracket 28 of the arm 13 and connected to the distal end portion of the bucket cylinder 44 via a link mechanism 50. Thereby, the bucket 18 rotates with respect to the arm 13 as the bucket cylinder 44 expands and contracts.

  Next, the effect of the hydraulic excavator according to this embodiment will be described.

  First, the stress acting on the arm 71 having the shape shown in FIG. 7 will be described. The upper plate 73 of the arm 71 is not provided with a step portion, and the bracket 74 projects upward from the upper plate 73. The force acting on the bracket 74 is in a direction substantially parallel to the weld line. Therefore, in this configuration, as shown in FIG. 5, a force acting on the bracket 74 by the bucket cylinder causes a bending moment (indicated by a curved white arrow in FIG. 5) to occur on the upper plate 73 and the tip of the bracket 74 The local stress increases on the side and the base end side. For this reason, in order not to cause the fatigue life of the welded portion between the upper plate 73 and the side plate 79 to decrease, it is necessary to increase the thickness of the upper plate 73.

  On the other hand, in the arm 13 of the hydraulic excavator according to the present embodiment, a force from the bucket cylinder 44 acting on the bracket 46 is received by the step portion 32 c of the upper plate 32. That is, the force from the bucket cylinder 44 is mainly received by the entire stepped portion 32c rising from the tip side portion 32b to above the pin insertion hole 46a. For this reason, local stress is unlikely to occur on the distal end side and the proximal end side of the bracket 46, and the load on the welded portion of the bracket 46 is also reduced. The force from the bucket cylinder 44 is transmitted to the flat plate portion 32a of the upper plate 32 in a concentrated manner. Since the flat plate portion 32a of the upper plate 32 is arranged above the bracket 46 as viewed in the direction of the force and extends linearly to the vicinity of the proximal bracket 27, the step portion 32c of the upper plate 32 is used. As shown in FIG. 4, the received force mainly acts on the flat plate portion 32a as a compressive or tensile axial load. At this time, even if a bending moment acts on the flat plate portion 32a, it acts only slightly.

  Therefore, in this embodiment, an axial load can be applied mainly to the upper plate 32, so that the stress generated in the upper plate 32 can be reduced and the plate thickness of the upper plate 32 can be reduced. Further, since the load on the welded portion of the bracket 46 can be reduced, the welding area of the bracket 46 can be reduced. Thereby, the bracket 46 comprised with a thick board can be reduced in size. In addition, since the height of the side plate 30 on the arm base end side can be increased by providing the step portion 32c on the upper plate 32, the arm main body related to the boss portion 38 in the arm main body 25 on the base end side with respect to the step portion 32c. The sectional moment of inertia of 25 can be increased and the rigidity of this part can be improved. As a result, it is possible to suppress the occurrence of a stress state that reduces the fatigue life of the welded portion between the upper plate 32 and the side plate 30 constituting the arm body 25.

  Therefore, the thickness of the side plate 30 and the upper plate 32 can be reduced and the bracket 46 can be reduced in size, so that the weight of the arm 13 can be reduced while maintaining the fatigue strength at the welded portion of the arm 13. For example, a 20 ton class hydraulic excavator can reduce the weight by about 5%.

  In the present embodiment, the upper surface of the end portion 46b of the bracket 46 connected to the flat plate portion 32a is connected to the upper surface of the flat plate portion 32a without a step, so that stress concentration occurs at the connection portion between the bracket 46 and the upper plate 32. Generation | occurrence | production can be avoided and it becomes possible to form the upper board 32 thinner.

  In the present embodiment, the bracket 46 is welded to the upper plate 32 in a region straddling the flat plate portion 32a, the step portion 32c, and the distal end side portion 32b, so that the step portion 32c of the upper plate 32 is reinforced by the bracket 46. Thus, the stepped portion 32c can be formed thinner.

  Further, in the present embodiment, the flat plate portion 32a of the upper plate 32 that mainly receives the force from the arm cylinder 14 is formed to extend linearly to the base end portion 25a of the arm main body 25, and is connected to the end portion. Since the base plate 42 is formed in a curved shape, stress concentration due to this force can be suppressed. Thereby, the fatigue life of the welded part between the base end plate 42 and the side plate 30 can be effectively reduced. In this respect, the upper end portion of the base end plate 42 has a shape extending straight upward as shown in FIG. 6, and the end portion of the flat plate portion 32 a is connected to the upper end portion of the base end plate 42. Also good.

  In addition, if the top plate 32 has a shape in which the tip side portion 32b and the flat plate portion 32a are connected in a straight line without providing the step portion 32c, the height of the side plate 30 cannot be gained and the rigidity of the arm body 25 is improved. It will not be possible. In addition, since it is necessary to attach the arm cylinder 14 to the upper side of the base end plate 42, this also makes it impossible to cut the bending component acting on the upper plate 32, and the stress generated on the upper plate 32 increases. On the other hand, if the height of the side plate 30 of the arm main body 25 is increased overall without providing the stepped portion 32c, the rigidity of the arm main body 25 is improved, but there is a risk of causing the problem of interference of the arm 13, Also causes an increase in the weight of the arm tip. Therefore, as described above, it is effective to provide the step portion 32c on the upper plate 32 and increase the width of the side plate 30 on the base end side.

  In the present embodiment, an example in which the present invention is applied to a hydraulic excavator has been described. However, the present invention is not limited to this, and the present invention can be applied to, for example, a construction machine or the like in which a crusher is attached to the tip of the work arm 3. It can also be applied to other construction machines.

1 is a side view showing an overall configuration of a hydraulic excavator according to an embodiment of the present invention. It is a front view which shows the whole structure of the arm of the said hydraulic shovel. It is the elements on larger scale which expand and show the principal part of the arm. It is a characteristic view which shows the load which arises on the upper board of the said arm. It is a characteristic view which shows the load which arises in the upper board of the arm in which the upper board was formed linearly over the whole arm. It is the elements on larger scale which show the other structure of the arm in embodiment of this invention. It is a front view which shows the whole structure of the arm in which the upper board was formed linearly over the whole arm. It is sectional drawing in the VIII-VIII line of FIG. In a hydraulic excavator, it is a characteristic view which shows the force which an arm receives from an attachment drive cylinder and an arm drive cylinder at the time of excavation work. It is a characteristic view which shows the bending deformation which arises in the upper board of the arm shown in FIG.

3 Working arm 11 Boom 13 Arm 14 Arm cylinder (arm drive cylinder)
18 bucket (attachment)
25 arm main body 25a base end portion 25b tip end portion 30 side plate 32 upper plate 32a flat plate portion 32b tip end side portion 32c stepped portion 38 boss portion (rotation center portion)
42 Base end plate 46 Bracket 46b Base end (end)

Claims (2)

It has a working arm consisting of a boom, an arm and an attachment, and an arm driving cylinder provided on the boom is attached to the base end of the arm of this working arm, while an attachment is attached to the distal end. , A construction machine configured to be rotatable by an attachment driving cylinder attached to an arm,
The arm includes a pair of side plates, a first plate, and an arm body formed in a rectangular cross section having a second plate,
In the vicinity of the second plate in each side plate of the arm body, a rotation center portion for rotatably supporting the arm by a tip portion of the boom is provided,
The first plate of the arm body includes a distal end side portion extending from the distal end portion of the arm body, and a flat plate portion extending from the proximal end portion of the arm body at a position farther from the second plate than the distal end side portion, A stepped portion connecting the flat plate portion and the tip side portion in a stepped shape;
A bracket welded to the first plate for pivotally supporting the attachment drive cylinder at a position closer to the tip than the pivot center;
The bracket has an outer surface, which is a surface far from the second plate at the end connected to the flat plate portion, connected to the outer surface of the flat plate portion without a step, and protrudes from the step portion to the tip end side. , Welded to the step,
A construction machine characterized in that a force received by an arm by an attachment driving cylinder supported by the bracket acts mainly as a compression or tension axial load on the flat plate portion. The bracket is characterized in that the outer surface of the bracket is disposed on a plane including the outer surface of the flat plate portion, and a portion other than the outer surface is disposed on the second plate side than the plane. The construction machine according to claim 1.

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