JP2010281067A - Truck frame of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce stress concentration on a weld part of a round drum, particularly on its toe position, due to load when a construction machine is operated. <P>SOLUTION: The round drum 42 is a substantially cylindrical member, and weld parts 43, 44 are formed by welding both upper and lower ends on the outer peripheral side to a lower face of a support plate 41 and to an upper face of a center frame 13. The outer peripheral surface of the round drum 42 is formed with an annular recess 45 whose cross section is of recessed circular arc shape over the whole periphery, in a position close to the weld part 44. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic excavator or other construction machine in which an upper swing body is connected to a lower traveling body via a swing device and working means is mounted on the upper swing body. Concerning structure.

  As a construction machine, for example, a hydraulic excavator includes a lower traveling body having left and right traveling means of a crawler type or a wheel type, and an upper turning body in which equipment such as excavation work means, a driver's cab, and an engine and a hydraulic pump are installed The lower traveling body and the upper swing body are connected via a swing device. Each of the lower traveling bodies has a track frame including left and right side frames connected to the traveling means and a center frame connecting both the side frames, and the support member on which the turning device is mounted is connected to the center frame. . Moreover, the turning frame which comprises an upper turning body is connected with a turning apparatus.

  The turning device includes an inner ring and an outer ring. The turning device includes a turning wheel provided with a turning bearing between the inner ring and the outer ring. A ring gear is formed on the inner peripheral surface of the inner ring. A pinion connected to the motor is configured to mesh with the ring gear. Therefore, the outer ring is connected to the turning frame, and the inner ring is connected to the lower traveling body side. However, the inner ring is not directly attached to the center frame of the lower traveling body, but is connected via a support member therebetween. The support member is composed of at least a cylindrical member made of metal and includes a round cylinder having a predetermined height, and the inner ring constituting the turning ring is directly connected to the upper end surface of the round cylinder, or the round A support plate is provided on the upper end surface of the trunk, and an inner ring is attached to the support plate. In this way, the swiveling device is arranged at a predetermined height position with respect to the center frame by interposing the round cylinder.

  By the way, the construction machine performs a predetermined work by the working means provided on the upper swing body, and a large work load acts during the work. In the case of a hydraulic excavator, it is configured to include excavation work means including a boom, an arm, and a bucket. When excavating earth and sand by the excavation work means, a large impact load due to, for example, excavation reaction force acts. In particular, when working under severe conditions such as rock excavation, a very large impact load acts. Such an impact load is transmitted from the excavating means to the turning frame and is received by the lower traveling body via the turning device. In the turning device, a load is transmitted from the outer ring to the inner ring through the turning bearing, and further, is transmitted to the round body that supports the inner ring.

  Here, the circular cylinder itself has sufficient strength, and is not damaged or deformed by the above-described impact load or the like. Also, the center frame connected with the round cylinder has sufficient strength. The round cylinder is arranged vertically to support the swivel device, and the center frame extends in the horizontal direction and is connected and fixed by welding means. For this reason, a shape change portion having a substantially right angle is generated at the transition portion from the circular cylinder to the center frame, and the welded portion is the lowest strength portion, and stress is concentrated at the welded portion. Therefore, when an impact load or the like repeatedly and frequently acts, there is a risk of damaging the welded part, such as cracking in the welded part, and there is a problem in durability. For example, if the build-up of the welded part is increased, the strength is improved accordingly. However, in order to perform large build-up welding, welding must be performed in multiple steps.

  In order to reduce the welding cost, it is only necessary to prevent stress from being concentrated on the welded portion, that is, to distribute the stress. As described above, Patent Document 1 and Patent Document 2 disclose a configuration in which stress is distributed so that stress is not concentrated on the welded portion of the round cylinder. In these patent documents, the round body is composed of a cylindrical main body part and a flange part connected to the lower end part of the main body part, and the outer end part of the flange part is butted against the center frame of the lower traveling body, It is configured to be fixed by welding means. And the connection part of a cylindrical main-body part and a flange part is set as the structure which forms a concave arc-shaped transition part by cutting.

JP-A-11-71785 JP 2005-145210 A

  As described above, by making the transition portion between the vertical wall portion of the round body and the horizontal wall portion of the center frame into an arc shape, a sharp shape change portion is not generated, and as a result, the swing device is turned from the upper swing body. It is possible to alleviate the concentration of the stress transmitted through the arc, and the stress is distributed by the arc-shaped transition portion, which acts on the welded portion between the round cylinder and the center frame. Stress is relieved. Therefore, cracks and damage at the transition portion from the circular cylinder supporting the swivel device to the center frame are prevented, and the durability is improved and the life is extended even if the weld overlay is not particularly increased. There is an advantage.

  However, the structure of the track frame disclosed in Patent Document 1 and Patent Document 2 is not necessarily free of problems. That is, after the round cylinder is formed, the transition portion from the vertical wall to the horizontal wall is cut, so that the manufacturing cost of the round cylinder increases due to the cutting. Here, from the viewpoint of dispersion of stress, it is better to increase the height dimension in the arc-shaped transition portion, that is, the vertical width of the upper and lower shape change point positions in the arc and to increase the curvature to some extent. However, the height direction dimension of the round cylinder is set based on the difference in height position between the center frame and the turning frame. Therefore, there are restrictions on the width dimension in the height direction of the arc-shaped transition part and the radius of curvature of the arc due to the height dimension of the circular cylinder, etc., and the curvature has a degree to distribute the stress necessary for the arc-shaped transition part. It may not be possible to

  In Patent Document 1, an arc having a constant radius of curvature is used, whereas in Patent Document 2, the curvature to be cut is changed in a plurality of stages from the flange portion to the main body portion of the round cylinder. The arc surface has a smaller radius of curvature, and the radius of curvature of the arc shape on the main body side is increased. If comprised in this way, the dispersion | distribution degree of the stress in the round cylinder of a limited height dimension can be improved more, and also the degree of partial thinning of a round cylinder is eased. However, since the cutting process is performed in a plurality of stages, the process becomes complicated and the number of man-hours increases, so that it becomes impossible to reduce the manufacturing cost.

  The present invention has been made in view of the above points. The object of the present invention is to apply stress to the welded portion of the round cylinder by a load during operation of the construction machine, by simply applying a simple process to the round cylinder. It is to reduce the concentration of the.

  In order to achieve the above-described object, the present invention is configured such that an upper swing body is pivotably connected to a lower traveling body via a turning device, and the lower traveling body includes side frames provided with left and right traveling means, A construction comprising a center frame for connecting the two side frames and a round cylinder interposed between the center frame and the turning device, the round cylinder being fixed to the center frame by welding means. A track frame of a machine, wherein welding is performed between the circular cylinder and the center frame so as to have an annular weld bead at a corner of at least one of the inner and outer circumferences of the circular cylinder. In this structure, an annular recess having a curved cross section is formed at the weld toe position of the weld bead of the weld to the round cylinder side or at a position above the weld toe position. It is an its characterized in that the the.

  The round cylinder is not provided with a flange portion, and its lower end is brought into direct contact with the center frame, and fillet welding is performed on a corner portion between the lower end and the center frame. On the other hand, the upper end portion of the round cylinder is connected to the inner ring side, but when this upper end side is fixed by welding means, in order to avoid direct welding to the inner ring having a ring gear formed on the inner peripheral surface, A support plate is interposed between the upper end of the round cylinder and the inner ring. Therefore, the upper end portion of the round cylinder is welded to the support plate.

  Welding can be performed on either or both of the inner and outer circumferences of the round cylinder. In order to easily weld without interfering with other members, welding is performed on the outer peripheral surface side. However, depending on the configuration of the swivel device, it may be desirable to perform the welding on the inner peripheral side. is there. The circular cylinder is formed with an annular recess having a concave curved cross section, and the annular recess is formed on a vertical wall surface of the circular cylinder. The surface on which the annular recess is formed is the same surface as the surface on which the weld bead is formed by the welded portion, and the annular recess is substantially the same position as the toe end position of the weld bead or the toe end. The position is slightly above the position.

  During the operation of the construction machine, impact loads or the like are repeatedly and frequently applied to the round cylinder. The most fragile part of the weld is the toe position of the weld bead. When repeated impact loads are applied, the weld bead surface is inclined from the surface of the weld bead that is substantially inclined to the vertical cylinder. The stress concentrates on the transition part of the film, and a damaged part such as a crack is generated. By forming an annular concavity on the vertical surface of the round cylinder, the shape change from the bead to the transition to the round cylinder is reduced, and the shape is close to the weld toe position. Since there are two change positions, the stress can be dispersed.

  Therefore, if the annular recess is a curved surface, it can be an elliptical surface or the like, but it can be a concave arcuate surface for ease of processing. By using such a simple shape, processing becomes easy. In addition, the depth of the deepest portion at the bottom of the annular recess is 1/10 or less of the thickness of the round cylinder, thereby minimizing the thickness of the round cylinder, and the concave part of the round cylinder. In spite of forming, it can have sufficient strength. The toe end position of the weld bead can coincide with the start end portion of the annular recess. However, it is necessary that the toe position of the weld bead does not overlap with the annular recess. Therefore, if the ease of processing is taken into consideration, the two are positioned slightly apart. In this case, the height position of the center of the circular arc of the annular recess is set to a position of 1/10 or less of the thickness of the round cylinder from the weld toe position. If the annular recess is provided at a position higher than this position, the stress dispersion function is lowered.

  By adding a simple process of forming an annular recess in the round cylinder, it is possible to reduce the concentration of stress on the welded part of the round cylinder due to the load during operation of the construction machine. Improves.

1 is an external view of a hydraulic excavator as an example of a construction machine provided with a track frame of the present invention. FIG. 2 is an external perspective view of a track frame of the hydraulic excavator in FIG. 1. It is sectional drawing which shows the structure of the turning apparatus provided in the hydraulic shovel of FIG. It is sectional drawing which shows the structure of the welding part of the round cylinder and center frame which show one Embodiment of this invention. It is a figure which shows the cross-section of the connection part between the round cylinder and center frame generally used conventionally. It is explanatory drawing which shows the distribution state of the stress of the structure of the prior art shown in FIG. It is a principal part enlarged view of FIG. It is explanatory drawing which shows the distribution state of the stress in the structure shown in FIG. It is a schematic block diagram of the apparatus for forming an annular | circular shaped recessed part in a round cylinder.

    Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a hydraulic excavator as an example of a construction machine. In the figure, 1 is a lower traveling body and 2 is an upper turning body. The lower traveling body 1 has traveling means 11 mounted on the left and right sides of the track frame 10 (FIG. 2), and the traveling means 11 is of a crawler type.

  As shown in FIG. 2, the track frame 10 includes a pair of left and right side frames 12 and a center frame 13, and the left and right traveling means 11 are respectively attached to the side frames 12. A center frame 13 is connected between the side frames 12 on both sides to which the traveling means 11 is mounted, and thereby the lower traveling body 1 is configured.

  The upper swing body 2 has a swing frame 20 on which a cab 21 is installed and excavation work means 22 is mounted. Further, a building 23 constituting a machine room is installed on the rear side of the swivel frame 20, and a counterweight 24 is provided at the rearmost position. The excavation work means 22 includes a boom 22a, an arm 22b, and a bucket 22c. The boom 22a, the arm 22b, and the bucket 22c are each driven by a hydraulic cylinder. For this reason, although illustration is omitted, equipment such as an engine and a hydraulic pump are installed inside the building 23.

  A turning device 3 is provided between the center frame 13 in the lower traveling body 1 and the turning frame 20 in the upper turning body 2. As shown in FIG. 3, the turning device 3 includes a turning wheel unit 33 including an outer ring 30, an inner ring 31, and a turning bearing 32 interposed between the outer ring 30 and the inner ring 31. A ring gear 31 a is formed on the inner peripheral surface of the inner ring 31. A pinion 34a provided on the output shaft of the turning motor 34 is engaged with the ring gear 31a. The outer ring 30 is fixed to the upper revolving unit 2 side, and the inner ring 31 is fixed to the lower traveling unit 1 side. Further, the turning motor 34 is mounted on the upper turning body 2 side. Accordingly, when the turning motor 34 is driven, the pinion 34a is rotationally driven, and the inner ring 31 provided with the ring gear 31a meshing with the pinion 34a turns. In FIG. 3, reference numeral 35 denotes a grease bath bottom wall constituting the grease bath, and 36 denotes a swivel joint provided at the turning center of the turning device 3.

  As shown in FIG. 4, the outer ring 30 in the turning device 3 is fixed to the turning frame 20 of the upper turning body 2 by bolts 37. On the other hand, as shown in FIG. 5, the inner ring 31 is fixed to the center frame 13 side of the track frame 10 of the lower traveling body 1 by bolts 38. However, the inner ring 31 is not directly fixed to the center frame 13, but the support member 40 is interposed between the inner ring 31 and the center frame 13. The support member 40 includes an annular support plate 41 and a round cylinder 42. The upper end of the round cylinder 42 is fixed to the support plate 41 and the lower end is fixed to the center frame 13 by welding, and the outer peripheral end of the grease bath bottom wall 35 is attached to the support plate 41. ing.

  Here, the circular body 42 is provided because the lower traveling body 1 is provided with traveling means 11, and the height position of the traveling means 11 and the height position of the upper revolving body 2 with the revolving frame 20. This is for making adjustments between and the like. The bolt 38 that connects the support plate 41 and the inner ring 31 is attached and detached at the upper position of the center frame 13, but the bolt 37 for connecting the outer ring 32 and the turning frame 20. Is attached and detached from below. Therefore, since the round cylinder 42 is provided and the lower surface of the support plate 41 is separated from the upper surface of the center frame 13, the bolt 37 can be easily attached and detached.

  The round cylinder 42 is a substantially cylindrical member, and upper and lower ends thereof are respectively fixed between the lower surface of the support plate 41 and the upper surface of the center frame 13, and welding is as shown in the figure. Fillet welding on the outer peripheral surface side of the round body 42 is performed. Therefore, the weld beads in the welded portions 43 and 44 have a substantially inclined surface shape, and are formed in a corner portion between the outer peripheral surface in the vertical state of the round body 42 and the center frame 13 in the horizontal plane. The welding may be performed on the inner peripheral surface of the round cylinder 42, or may be performed on both sides of the inner and outer periphery.

  As a typical work performed by the hydraulic excavator configured as described above, there is a work of excavating earth and sand and loading it onto a dump truck. In this work, first, the excavation work means 22 is operated, the earth and sand at the work site is excavated by the bucket 22c, the upper revolving unit 2 is turned to a predetermined angle by the turning device 3, and the excavation work means 22 is dump truck. The earth and sand accommodated in the bucket 22c is thrown into the loading platform of the dump truck. During this work, large vibrations are generated in the upper swing body 2. In particular, when the bucket 22 c cuts into the earth and sand, a large reaction force acts on the excavation work means 22. Further, after the earth and sand are accommodated in the bucket 22c, the boom 22a and the arm 22b are operated to lift the bucket 22c, and also when the earth and sand accommodated in the bucket 22c is put into the loading platform of the dump truck. However, a large impact and a load are transmitted to the upper swing body 2. Furthermore, since a large inertial force acts when the upper swing body 2 stops turning, a large vibration is also generated at this time.

  In this way, the load acting on the upper swing body 2 is transmitted to the lower traveling body 1 and is received by the ground at the ground contact portion of the traveling means 11 of the lower traveling body 1. Transmission of the load from the upper swing body 2 to the lower traveling body 1 is performed via the swing device 3. That is, a load transmission path is interposed from the turning frame 20 of the upper turning body 2 through the round body 42 to the track frame 10 of the lower traveling body 1. Stress acts on the load transmission path.

  Here, FIG. 5 shows a welded portion between the round cylinder and the center frame that has been generally used. In the figure, 142 is a round cylinder, 113 is a center frame, and 144 is a welded portion. When a load is applied during the operation, the load is transmitted from the upper swing body 2 to the lower traveling body 1 via the round body 142, but the stress in the load transmission path from the round body 142 to the center frame 113 is reduced. The distribution is as shown in FIG. In FIG. 6, a portion indicated by dots is a portion where stress acts substantially, and the higher the density of dots, the greater the stress than the lower density portion. As is clear from these figures, the toe portion p1 of the welded portion 144 on the outer peripheral surface of the circular cylinder 142 is the portion where the highest stress acts, and the stresses in the order of p2, p3, and p4 are sequentially increased. descend. The part p1 where the highest stress is concentrated is an extremely narrow part, but is the most vulnerable part in terms of strength. As described above, when stress concentrates in a narrow part, a problem such as a crack occurring in a welded part occurs.

  From the above, in order to alleviate the above-described stress concentration, in the present invention, as shown in FIG. 7, the circular cylinder 42 is provided with an annular recess 45 having a curved cross section. . Although this annular recess 45 is shallow, it is recessed by a dimension D with respect to the vertical line indicated by the alternate long and short dash line in FIG. Here, the annular recess 45 is formed on the surface of the round body 42 on the side where the welded portion 44 is formed, and is formed on the outer peripheral surface of the round body 42 in the present embodiment. The annular recess 45 has an arc shape in cross section and extends over the entire circumference of the round body 42.

  Therefore, in the configuration shown in FIG. 5, the stress distribution in the load transmission path from the circular cylinder 142 to the center frame 113 is that shown in FIG. 6, as shown in FIG. 7. In addition, by providing the annular recess 45 in the round cylinder 42, a shape change part is generated on the vertical wall surface of the round cylinder 42, and when viewed from the bead surface of the welded part 44, a concave curved shape is formed. Therefore, the degree of the shape change from the welded portion 44 to the surface of the round cylinder 42 is alleviated. As a result, in the circular cylinder 142 in the vertical state, a portion p1 to which a remarkably high stress acts is present in a narrow range, whereas the annular recess 45 is formed, which is shown in FIG. As described above, at the site P1 where the highest stress acts, the stress is lower than p1. As a result, a situation such as a crack occurring in the weld toe portion of the welded portion 44 does not occur, and the durability of the welded portion is improved. In addition, as shown in FIG. 8, as in the case of the circular cylinder 142, the stress decreases sequentially such as P2, P3, and P4.

  As shown in FIG. 7, in the load transmission path from the circular cylinder 42 to the center frame 13 through the welded portion 44, an arcuate annular recess 45 having a radius R and having a center O is formed in the circular cylinder 42. It is assumed that D ≦ 1 / 10T, where D is the maximum depth dimension of the annular recess 45 and T is the thickness dimension of the circular cylinder 42. If D exceeds 1 / 10T, the strength of the round cylinder 42 is lowered, which is not desirable.

  In addition, when the inclination angle of the outer surface of the welded portion 44 is θ, the tangent t at the starting end portion on the lower side of the circular arc of the annular recess 45 is an angle parallel or nearly parallel to the extension line of the inclination angle θ. It is desirable to do. If the starting end portion of the annular recess 45 and the toe position 44a of the welded portion 44 are made to coincide with each other, stress concentration in the welded portion 44 can be almost eliminated, and the durability of the welded portion 44 is improved. Becomes even better. However, since the welded portion 44 is provided on the entire circumference of the round body 42, it is difficult to weld so that the starting end portion of the annular recessed portion 45 coincides with the position of the toe-end portion of the welded portion 44 over the entire circumference. is there. Here, if the starting end portion of the annular recess 45 and the weld toe position of the welded portion 44 overlap, the degree of stress concentration increases, and the risk of damage to the welded portion 44 increases. Therefore, in order to easily perform the welding operation, a slight interval B can be provided between the welding line and the starting end position of the annular recess 45. This interval B is set to be in a range of 1/10 T or less from the toe position P of the welded portion 44. If it exceeds 1/10 T, the stress dispersion effect is reduced, which is not desirable.

  The annular recess 44 is formed in the round body 42 by a processing method such as cutting or laser brazing, but can be formed by the following processing method. That is, as shown in FIG. 9, the round body 42 is formed by bending a steel plate 50. As a processing apparatus for this purpose, two pressure rollers 51, 51 are provided on the inside. The pressure roller 52 is disposed at a position separated by a distance, and one pressure roller 52 is disposed on the outer side at a position between the pressure rollers 51 and 51. The steel plate 50 is processed to be bent into a cylindrical shape by feeding the steel plate 50 while rotationally driving these pressure rollers. The outer processing roller 52 is formed with an annular ridge 53 at an intermediate position thereof. Thereby, when performing the process of bending the steel plate 50 into a cylindrical shape, the annular recess 44 is formed at the same time. Therefore, in the process of bending the steel plate 50 to form the round body 42, the annular recess 44 is formed at the same time, and no special additional process is required.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper revolving body 3 Turning apparatus 10 Track frame 12 Side frame 13 Center frame 20 Turning frame 30 Outer ring 31 Inner ring 33 Turning wheel unit 40 Support member 41 Support plate 42 Round body 43, 44 Welding part 45 Annular recessed part

Claims (4)

An upper swing body is connected to the lower travel body via a swing device so as to be capable of swinging. The lower travel body includes a side frame provided with left and right travel means, a center frame connecting the two side frames, In a track frame of a construction machine, which is composed of a round cylinder interposed between a center frame and the turning device, and the circular cylinder is fixed to the center frame by welding means.
Between the round cylinder and the center frame, at least one side of the inner and outer circumferences of the round cylinder is welded so as to have an annular weld bead at the corner,
It is characterized in that an annular recess having a curved cross section is formed at a weld toe position of the weld bead of the weld part to the round body side or a position on the upper side from the weld toe position. Truck frame for construction machinery. The track frame for a construction machine according to claim 1, wherein the annular recess has a concave arc surface shape. The depth of the deepest part in the bottom face of the said annular recessed part was set as the structure made into 1/10 or less of the thickness dimension of the said round cylinder, The track frame of the construction machine of Claim 1 or Claim 2 characterized by the above-mentioned. . The center height of the circular arc of the annular recess is configured to be a position that is 1/10 or less of the thickness of the round cylinder from the weld toe position. A truck frame for a construction machine according to any one of the above.

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