JP2006248756A - Frame of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively relieve stress concentration around a through-hole, while avoiding a large increase in its weight and cost, in a frame of a construction machine for arranging the through-hole on a side wall. <P>SOLUTION: The stress concentration is relieved by devising a hole shape of the through-hole 46 arranged on the side wall 44 of the frame 40 of the construction machine. Actually, a shape of the through-hole 46 is set so that curvature of the hole peripheral edge in a maximum stress angle position for maximizing an absolute value of stress generated around this circular hole when supposing the circular hole in a forming position of its through-hole 46, becomes smaller than curvature of the hole peripheral edge in a minimum stress angle position for minimizing the absolute value of the stress generated around the circular hole. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a frame constituting a construction machine such as a mobile crane.

A through-hole is often provided in the side wall of a frame of a construction machine as described in Patent Document 1 for various purposes. For example, various through holes are provided in the side wall of the frame when hydraulic piping or electrical wiring is passed through the inside or outside of the side wall, when welding with other members is performed, or when weight reduction is achieved. Become.
JP 2000-143156 A

  When an external force is applied to the frame having the through hole provided in the side wall as described above, stress concentration generally occurs around the through hole.

  For example, as shown in FIG. 6, in an upper swing frame 6 that is swingably installed on a lower traveling body 2 of a crane via a swing bearing 4, a load for supporting a boom suspension load at the rear end thereof. When the support portion 7 is provided, an upward tensile force F, which is a vertical force, acts on the load support portion 7. At this time, the rear portion of the upper swing frame 6 (with the load support portion 7 and If a circular through hole 8 is provided in the side wall 6a of the portion between the slewing bearing 4), stress concentration occurs around the through hole 8 due to the tensile force F. Specifically, the rear part of the upper turning frame 6 with respect to the part joined to the turning bearing 4 is regarded as a cantilever that receives an upward vertical load (tensile force F) at its free end. Then, a bending stress is generated in the cantilever beam, and a stress concentration in which the absolute value of the stress is remarkably increased at the specific angular position is generated on the periphery of the through hole 8.

  When such stress concentration occurs, if the frame is designed based on the maximum stress, the thickness of the entire frame becomes considerably large, and an increase in weight and material cost is inevitable. In addition, even if a reinforcing plate is attached to the portion where the stress concentration occurs to locally increase the cross-sectional area and section modulus, the thickness of the reinforcing plate is set to be considerably large considering the decrease in fatigue evaluation due to the welding work. Therefore, the reinforcing structure becomes heavy. Therefore, it is difficult to suppress an increase in weight and cost due to the reinforcing structure.

  In view of such circumstances, the present invention effectively reduces the stress concentration around the through hole in the frame of the construction machine provided with the through hole in the side wall while avoiding a significant increase in weight and cost. Objective.

  Generally, when the hole has a shape other than a circle, that is, when the curvature of the hole periphery is not constant over the entire circumference, the stress concentration tends to become more significant as the curvature becomes larger (that is, the curvature radius is smaller). In other words, if the curvature of the hole peripheral shape at a position where the stress concentration is significant is reduced (the curvature radius is increased), the degree of stress concentration can be reduced.

  The present invention has been made from such a viewpoint, and in the frame of a construction machine in which a through hole penetrating the inside and outside of the side wall is provided and a load in a specific direction is applied to the side wall, the shape of the through hole is Is a stress generated around the circular hole due to the addition of a load in the specific direction when a circular hole having a diameter substantially equal to the vertical dimension of the through hole is assumed at the formation position of the through hole. The curvature of the hole periphery of the through hole at the maximum stress angle position where the absolute value is the largest is the hole periphery of the through hole at the minimum stress angle position where the absolute value of the stress generated around the circular hole is the smallest. It is set so as to be smaller than the curvature.

  According to this configuration, the curvature of the actual peripheral edge of the through hole at the maximum stress angle position where the absolute value of the stress is maximum around the circular hole assumed at the formation position of the through hole is the minimum stress angle position. By setting the curvature smaller than the curvature, the difference between the maximum value and the minimum value of the stress around the through hole is reduced. Therefore, the stress concentration around the through hole can be effectively reduced without reinforcing the periphery of the through hole and with only simple reinforcement.

  Furthermore, if the shape of the hole periphery of the through hole is set so that the curvature of the hole periphery of the through hole is minimized at the maximum stress angle position or an angular position near the maximum stress angle position, the stress maximum value is more effectively reduced. be able to.

  The through hole may be a long hole having a straight portion extending linearly in an arbitrary direction at an intermediate portion thereof. In this case, the curvature of the portion excluding the straight portion is around the circular hole. It may be set based on the stress distribution.

  The present invention can be applied to frames of various construction machines. In particular, the present invention is mounted horizontally on a lower traveling body via a turning support portion so as to be able to turn horizontally from a place where the turning support portion is joined. In an upper swing frame of a crane in which a vertical force is applied to a load support location that is far from the center, the area from the location where the swing support is joined to the load support location is a cantilever beam that receives a large bending load. Therefore, when a side wall having a through hole is provided in this region, the shape of at least one of the through holes is substantially equal to the vertical dimension of the through hole at the position where the through hole is formed. When a circular hole having a diameter is imagined, the through hole at the maximum stress angle position where the absolute value of the stress generated around the circular hole becomes the largest with the addition of a vertical force to the load supporting portion. Around the hole By setting the rate to be smaller than the curvature of the hole periphery of the through hole at the minimum stress angle position where the absolute value of the stress generated around the circular hole is the smallest, the effect of the present invention can be improved. It can be demonstrated without.

  As described above, according to the present invention, in the frame of a construction machine in which a through hole is provided on the side wall, the weight and cost of the entire frame are significantly increased by appropriately setting the curvature of the hole periphery of the through hole. There is an effect that the stress concentration around the through hole can be effectively relaxed while avoiding the above.

  FIG.1 and FIG.2 shows the whole structure of the mobile crane 10 which concerns on embodiment of this invention.

  The crane 10 includes a lower traveling body 12 having left and right crawlers 11 and an upper revolving body 16 installed on the lower traveling body 12 via a revolving bearing 14 thereon.

  A boom mounting portion 16a is provided at the front end portion of the upper swing body 16, and the boom 18 is supported to be raised and lowered with the boom mounting portion 16a as a fulcrum. The boom 18 is a lattice boom in the illustrated example, and a main hook 20 and an unillustrated auxiliary hook are suspended from the tip of the boom 18.

  On the other hand, a first winch 22, a second winch 24, and a boom winch 26 are mounted on the upper swing body 16. Then, the main hook 20 is lifted by winding the winding wire rope 27 by the first winch 22, and the auxiliary hook is lifted by winding the unillustrated winding wire rope by the second winch 24. Further, the winding / unwinding of the wire rope 28 by the boom winch 26 causes the boom 18 to rotate (raise / lower) with the boom attachment portion 16a as a fulcrum.

  Specifically, a boom raising and lowering gantry 30 is provided at the rear of the upper swing body 16. The gantry 30 has a front compression member 31 arranged in an inclined posture and a rear tension member 32 arranged in a standing posture assembled in a mountain shape and their upper ends connected to each other. A sheave 34 is rotatably provided at the top of the gantry 30, and a wire rope 28 drawn from the boom winch 26 is hung on the sheave 34. On the other hand, one end of a guy cable 36 is connected to the tip of the boom 18, and upper and lower spreaders 37, 38 are attached to the other end of the guy cable 36 and the gantry 30, respectively. The wire rope 28 is hung between sheaves included.

  Therefore, in this crane 10, the boom 18 is moved by moving the spreader 37 closer to (or away from) the spreader 38 by winding (or unwinding) the wire rope 28 by the boom winch 26. The compression member 31 constituting the gantry 30 is caused to undulate and due to the weight of the boom 18, the main hook 20, the auxiliary hook, the wire rope 27, and the like and the load caused by the suspended load W at the tip of the boom 18. The compressive force Fc and the tensile force Ft act on the tension member 32, respectively.

  Next, the structure of the upper turning frame 40 constituting the upper turning body 16 will be described.

  The upper revolving frame 40 has a box shape with a hollow cross section, and the bottom wall of the front half thereof is joined to the revolving bearing 14. A compression member mounting hole 41 is provided at the upper end of the front side part of the left and right side walls 44, and a tension member mounting hole 42 is provided at the upper rear end.

  A pin (not shown) for connecting the upper revolving frame 40 and the compression member 31 of the gantry 30 is inserted into the compression member attachment hole 41. Similarly, the upper part of the tension member attachment hole 42 is inserted into the upper portion of the compression member attachment hole 41. A pin (not shown) for connecting the revolving frame 40 and the tension member 32 of the gantry 30 is inserted. Therefore, the location where the tension member mounting hole 42 is provided in the upper revolving frame 40 is a load support location to which an upward tensile force Ft which is a vertical force acting on the tension member 32 is applied. The load supporting portion is present at a position that is greatly separated from the joint portion of the slewing bearing 14 to the rear side in the horizontal direction. That is, a portion of the upper swing frame 40 on the rear side of the swing bearing 14 is in a cantilever state in which an upward load is applied to the rear end portion which is a free end portion and a bending moment M is generated. ing.

  The occurrence of such a bent state is not limited to the gantry type boom support structure as shown in the figure. For example, as disclosed in Japanese Patent Laid-Open No. 10-194681, a swingable mast is provided on the upper swing body, the mast and the boom tip are connected by a guy cable, and a small gantry is mounted on the rear of the upper swing frame. Also in a crane that provides a pulley mechanism between the top of the small gantry and the tip of the mast and raises and lowers the boom by extending and retracting the pulley mechanism by driving a winch, the upper revolving frame is similar to the above. The bending state will occur. Therefore, the present invention can be effectively applied to such a crane.

  Returning to FIG. 1 and FIG. 2, the upper revolving frame 40 that receives the bending load as described above includes side walls 44 facing left and right, and in these side walls 44 from the revolving bearing 14 to the tension member mounting hole. Through holes 46 and 48 that communicate the inside and outside of the side wall 44 are provided in the horizontal region up to 42.

  As shown in FIG. 3, the curvature of the shape of the peripheral edge of the through hole 46 changes according to the angular position, and the curvature reduces the degree of stress concentration around the through hole 46. Is set to Specifically, the load support in which the tension member mounting hole 42 is provided when a circular hole having a diameter substantially equal to the vertical dimension of the through hole 46 is assumed at the position where the through hole 46 is formed. The curvature of the peripheral edge of the through hole 46 at the maximum stress angle position at which the absolute value of the stress generated around the circular hole becomes the largest as the upward tensile force Ft is applied to the location is the circular hole. The shape of the through hole 46 is set so as to be smaller than the curvature of the peripheral edge of the through hole 46 at the minimum stress angle position where the absolute value of the stress generated around the minimum is the smallest.

  FIG. 4A exaggerates the bending deformation state of the upper revolving frame side wall 44 when a circular hole 46 ′ corresponding to the through hole 46 is assumed, and FIG. The result of having analyzed the stress distribution around the said circular hole 46 'in a deformation | transformation state by the finite element method is shown. FIG. 2B shows that the absolute value of the stress is higher as the mesh density attached to each divided element is smaller.

Originally, when the frame side wall 44 having the circular hole 46 ′ is bent and deformed with the line passing through the circular hole 46 ′ as a neutral axis, stress is concentrated around the circular hole 46 ′ at four angular positions in a direction of approximately 45 °. However, since the vertical dimension from the lower end of the circular hole 46 ′ to the lower edge of the frame is small in the illustrated example, the actual stress concentration is as shown in FIG. 4 (b). It is the maximum (about 41 kg / mm ² ) at the element E1 in the vicinity of the lower end and slightly angular position near the rear end.

  In view of such stress characteristics, the actual shape of the through hole 46 is, as shown in FIGS. 5A and 5B, an angular position in the vicinity of the maximum stress angular position as described above, and a position facing this position. The curvature of the hole periphery shape is minimized at a position 180 ° apart, and the angle position in the direction orthogonal to this is the angle position 90 ° apart from the maximum stress angle position and the angle where the stress is minimum. It is set so that the curvature is maximized at a nearby angular position.

In the case of the through hole 46 having such a shape, as shown in FIG. 5 (b), the maximum stress around the hole (in the figure, element 37 is about 37 kg as compared to the circular hole 46 'shown in FIG. 4 (b)). / mm ² ) is effectively reduced, and the high stress region is also effectively reduced. Therefore, stress concentration around the through hole 46 can be effectively reduced while avoiding a significant increase in the weight and material cost of the entire frame.

  On the other hand, the shape of the through hole 48 is a shape obtained by extending the shape of the through hole 46 in the horizontal direction. That is, the through hole 48 has a straight portion 48b linearly extending in the horizontal direction at the horizontal intermediate portion, and both end portions 48a have a stress distribution of the circular hole 46 'in the same manner as the through hole 46. Based on this, the curvature is changed. In other words, the through hole 48 has a shape obtained by deforming the left and right ends of a horizontally long oval shape. As described above, even in the case of a long hole having a straight portion extending in an arbitrary direction in the intermediate portion, it is possible to effectively relieve stress concentration by appropriately setting the curvature of both side portions.

  Since the stress distribution around the circular hole 46 ′ assumed at the formation position of the through hole 46 naturally changes depending on the formation position, the shape of the through hole 46 may be appropriately set according to the stress distribution. For example, assuming a model in which the vertical dimension of the frame 40 on both the upper and lower sides of the circular hole 46 'is sufficiently larger than the diameter of the circular hole 46', as described above, there is almost no circumference around the circular hole 46 '. Since the absolute value of the stress is maximized at the four angular positions in the 45 ° direction, the through hole 48 is formed in, for example, a substantially rhombus shape (however, in order to minimize the curvature at the portion corresponding to the maximum stress angular position. In order to prevent extreme stress concentration from occurring in the portion corresponding to the four vertices of the rhombus, the vertex portion is preferably an arc having a small radius of curvature.) The stress concentration around the hole can be effectively reduced.

  In the present invention, it is not always necessary to minimize the curvature at the maximum stress angle position of the circular hole, and the curvature of the peripheral edge of the through hole at least at the maximum stress angle position is smaller than the curvature of the peripheral edge at the minimum stress angle position. If the hole shape is formed, it is possible to reduce the difference between the maximum value and the minimum value of the absolute value of stress (that is, to reduce the stress concentration degree). However, if the shape of the hole periphery of the through hole is set so that the curvature of the hole periphery of the through hole is minimized at the maximum stress angle position or an angular position in the vicinity thereof, the stress maximum value is more effectively reduced. It becomes possible.

  Moreover, although the upward turning force Ft is added to the load support location of the upper turning frame 40 shown in the figure, conversely, a downward pressing force is applied to the load support location and the pressing force is applied. The present invention can be effectively applied to a frame that is dominant in strength design.

  Furthermore, the present invention is not limited to the upper swing frame of the crane, but in various frames that receive a load in a specific direction during operation, such as an upper swing frame of other construction machines such as a hydraulic excavator, a frame constituting a lower traveling body, The present invention can be widely applied when through holes are provided on the side walls for various purposes.

It is a front view which shows the whole structure of the mobile crane which concerns on embodiment of this invention. It is a top view which shows the whole structure of the said mobile crane. It is a front view which shows the principal part of the upper revolving frame contained in the said mobile crane. (A) is the figure which showed typically the bending deformation state of the said side wall at the time of imagining the circular hole in the formation position of the through-hole in the side wall of the said upper turning frame, (b) is the said circular hole in the said bending deformation state It is a figure showing stress distribution around. (A) is the figure which showed typically the bending deformation state of the side wall of the said upper turning frame, (b) is a figure which shows the stress distribution around the through-hole of the said upper turning frame in the said bending deformation state. It is a schematic diagram which shows an example of the conventional upper revolving frame.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mobile crane 12 Undercarriage 14 Slewing bearing (slewing support part)
16 Upper swing body 18 Boom 30 Gantry 32 Tensile member 40 Upper swing frame 42 Tensile member mounting hole 44 Frame side wall 46, 48 Through hole 46 'Circular hole 48b Linear portion

Claims (6)

  In a frame of a construction machine in which a through-hole penetrating the inside and outside of the side wall is provided in the side wall and a load in a specific direction is applied to the side wall, the shape of the through-hole is in a vertical direction of the through-hole at a position where the through-hole is formed The through hole at the maximum stress angle position where the absolute value of the stress generated around the circular hole with the addition of the load in the specific direction is maximized when a circular hole having a diameter substantially equal to the diameter of the circular hole is assumed. The curvature of the hole periphery is set to be smaller than the curvature of the hole periphery of the through hole at the minimum stress angle position where the absolute value of the stress generated around the circular hole is the smallest. And the frame of construction machinery.   2. The frame of the construction machine according to claim 1, wherein the shape of the hole periphery of the through hole is set so that the curvature of the hole periphery of the through hole is minimized at the maximum stress angle position or an angular position in the vicinity thereof. A construction machine frame characterized by that.   The frame of the construction machine according to claim 1 or 2, wherein the through-hole is a long hole having a linear portion extending linearly in an arbitrary direction at an intermediate portion thereof, and a curvature of a portion excluding the linear portion is the circular shape. A frame of a construction machine, which is set based on a stress distribution around a hole.   In an upper swing frame of a crane that is mounted on a lower traveling body through a swing support portion so as to be capable of swinging, and a vertical force is applied to a load support location that is horizontally separated from a location joined to the swing support portion. And a side wall having a through hole in a region from the place joined to the swivel support part to the load support place, and the shape of at least one of the through holes is the formation position of the through hole. The absolute value of the stress generated around the circular hole when a vertical force is applied to the load supporting portion when a circular hole having a diameter substantially equal to the vertical dimension of the through hole is assumed in FIG. The curvature of the hole periphery of the through hole at the maximum stress angle position where the maximum is the largest is more than the curvature of the hole periphery of the through hole at the minimum stress angle position where the absolute value of the stress generated around the circular hole is the smallest. small Kunar so on, the upper rotating frame of the crane, characterized in that it is set.   The upper turning frame of the crane according to claim 4, wherein the shape of the hole periphery of the through hole is set so that the curvature of the hole periphery of the through hole is minimized at the maximum stress angle position or an angular position in the vicinity thereof. An upper swing frame of the crane characterized by   6. The upper turning frame of a crane according to claim 4 or 5, wherein the through hole is a long hole having a straight portion extending linearly in an arbitrary direction at an intermediate portion thereof.

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