JP5427690B2 - Excavator swivel frame - Google Patents

Description

  The present invention relates to a swivel frame of an excavator.

  In a conventional excavator, a turning frame to which a work attachment for excavation and a cylinder for raising and lowering a boom of the work attachment are attached is provided on the lower traveling body so as to be turnable around a vertical axis. Patent Document 1 below discloses an example of a swivel frame of such an excavator.

  The turning frame disclosed in Patent Document 1 is installed on a lower traveling body of an excavator via a turning bearing. The swivel frame has a center frame at the center in the width direction, and the center frame has a pair of center beams as side structures constituting side walls on both sides in the width direction. On the slewing bearing, the bottom plate of the slewing frame is fixed, and each side structure is erected on the bottom plate so as to extend in the front-rear direction.

  Each side structure includes two vertical plates extending in the front-rear direction in the region on the slewing bearing, and one vertical plate extending rearward from the rear end of the vertical plate. The two vertical plates are arranged in parallel to each other with a small gap in the width direction of the revolving frame, and their lower ends are welded to the upper surface of the bottom plate. The portions in the vicinity of the rear end portions of the two vertical plates are arranged obliquely so as to gradually approach each other toward the rear end, and the rear ends are welded to each other. The front end of the one vertical plate extending rearward is further welded to the welded portion between the rear ends of the two vertical plates. The welded portions of the rear ends of the two vertical plates and the front end of one vertical plate are arranged on a position slightly inside the slewing bearing. Therefore, at the position where each side structure intersects the rear portion of the slewing bearing, the one vertical plate is welded onto the bottom plate. An upper plate that connects the upper edge portions of the two vertical plates is provided between the upper edge portions of the region from the front end to the vicinity of the central portion in the front-rear direction. Further, another upper plate is provided so as to extend from the upper edge of the rear area of the two vertical plates to the rear end of the one vertical plate along the upper edge of the one vertical plate. The upper plate is welded along the extending direction to the upper edge of each vertical plate in a state of being arranged perpendicular to each vertical plate.

  A boom mounting bracket for mounting the base end portion of the boom of the work attachment is provided at the upper end portion of the two vertical plates and located in the vicinity of the center position of the swing bearing in the front-rear direction. Further, a cylinder mounting bracket for mounting a cylinder for raising and lowering the boom is provided at the front end portion of the two vertical plates and at the lower position of the vertical plate.

JP-A-8-165679

  In the revolving frame disclosed in Patent Document 1, it is difficult to reduce the weight and material cost while ensuring the strength and rigidity against the load applied during excavation by the work attachment.

  That is, in the above revolving frame, during excavation by the work attachment, a pulling force is applied to the boom mounting bracket obliquely upward in the forward direction, and a pressing force is applied to the cylinder mounting bracket obliquely downward in the rearward direction. In each side structure of the swivel frame, the two vertical plates having a large area, a portion in the vicinity of the front end of the one vertical plate, the bottom plate, and the top plate are applied during the excavation. It tries to secure strength and rigidity against force. However, the side structure has a Y-shaped structure in which the two vertical plates gradually approach each other toward the rear end and the rear ends are welded to each other. That is, in this structure, there is a portion where the vertical plate is disposed obliquely with respect to the excavation load in the front-rear direction, which is disadvantageous in terms of rigidity. Therefore, if a certain rigidity is to be ensured with such a structure, it is necessary to increase the thickness of the vertical plate, and if the thickness of the vertical plate is increased, its weight increases significantly. In other words, it is difficult to obtain high rigidity in place of weight in the structure of the turning frame.

  In addition, at the position where each of the side structures intersects the rear side portion of the slewing bearing, the one vertical plate is welded to the bottom plate, but the diagonally forward front hanging on the boom mounting bracket. The swing load applied to each side structure from the rear counterweight when traveling on a rough road is not distributed at the intersection between the one vertical plate and the slewing bearing. It will be concentrated on the welded part with the bottom plate. Therefore, in this configuration, the vertical plate extending in the front-rear direction is welded to the bottom plate along the longitudinal direction, and the welding area between the vertical plate and the bottom plate is large, but the load applied to the swivel frame during the excavation is to be resisted. It is difficult to obtain the required welding strength between the vertical plate and bottom plate. That is, it can be said that, in the above-mentioned swivel frame, it is difficult to obtain the required welding strength between the vertical plate and the bottom plate, although the welding work is troublesome due to welding over a wide area.

  The present invention has been made to solve the above-described problems, and has an object of having a strength and rigidity capable of sufficiently supporting a load applied during excavation by a work attachment while being low in weight, and work related to welding work. An object of the present invention is to provide a swivel frame for an excavator that can obtain the necessary welding strength between the side structure and the bottom plate while reducing the burden.

  In order to achieve the above object, the excavator swivel frame according to the present invention is provided on the lower traveling body so as to be able to swivel around the vertical axis via a swivel bearing so that the boom of the work attachment for excavation can be raised and lowered. A pivot frame of a shovel for supporting and supporting a cylinder for raising and lowering the boom, the pivot frame being disposed on the pivot bearing and supporting the boom and the cylinder; and A rear frame portion connected to the rear side and supporting a counterweight mounted on the excavator at a rear portion thereof from below, and the front frame portion is disposed on the slewing bearing so as to cover the slewing bearing from above. The front bottom plate to be fixed and the width direction of the swivel frame spaced apart from each other on the front bottom plate Left and right front side structures that support the boom and the cylinder, and each front side structure is made of a tube material extending in one direction, and one end of the front side structure is formed of the front bottom plate. It is welded to the upper surface, and at least a part of the welded portion is located in the arrangement region of the front portion of the slewing bearing as viewed from above, and the other end portion is located behind and above the one end portion. A first support member and a pipe member extending in one direction, and one end portion of the first support member is welded to the upper surface of the front bottom plate behind the one end portion of the first support member. A portion of the first support member is located in a region where the rear portion of the slewing bearing is disposed when viewed from above, and the other end is in front of and above the one end. A second support member welded to the end, and the front A cylinder that connects the cylinder and the one end of the first support member so that an axial pressing force of the cylinder acting from the cylinder during excavation by a work attachment is transmitted to the front portion of the swivel bearing. A pulling force acting from the boom during excavation by the connecting portion and the work attachment is transmitted to the rear portion of the swivel bearing via the other end portion of the first support member and the second support member. And a boom connecting portion that connects the boom and the other end of the first support member.

  In the present invention, the terms “front and rear” and “left and right” in the swing frame refer to the swing frame with respect to the lower traveling body so that the work attachment is located at the front part of the shovel and the counterweight is located at the rear part of the shovel. It means “front and rear” and “left and right” of the excavator in the arranged state.

  At the time of excavation by the work attachment, an axial pressing force is applied to the cylinder connecting portion from the cylinder for raising and lowering the boom, and a pulling force is applied to the boom connecting portion from the boom. At this time, in this swing frame, the pressing force acting on the cylinder connecting portion from the cylinder can be transmitted from the cylinder connecting portion to the front side portion of the swing bearing through the lower end portion of the first support member, and the boom is connected to the boom. The tensile force acting on the portion can be transmitted from the boom connecting portion to the rear side portion of the swing bearing through the upper end portion of the first support member and the second support member. For this reason, the load applied to the turning frame during excavation by the work attachment can be supported by the front side structure. As a result, with this turning frame, it is possible to ensure strength and rigidity against a load applied during excavation by the work attachment.

  Then, as a result of earnest study, the inventor of the present application rearwards from a portion welded to the upper surface of the bottom plate on the arrangement region of the front side portion of the swing bearing in the front side structure of the swing frame during excavation by the work attachment. An area extending diagonally upward and connected to the boom connecting part and the cylinder connecting part, and an area extending obliquely forward from the part welded to the upper surface of the bottom plate on the rear area of the slewing bearing to reach the boom connecting part It was found that a large load was applied to the other regions, but the other regions were not so heavily loaded. Based on this finding, the inventor of the present application, as described above, has a first support member made of a pipe material extending in one direction, one end of which is welded to the upper surface of the front bottom plate, and at least a part of the welded portion is made. A second support made of a tube material that is located in the arrangement region of the front portion of the slewing bearing as viewed from above, and that the other end portion is located behind and above the one end portion and extends in one direction. The member is welded to the upper surface of the front bottom plate at one end behind the one end of the first support member, and at least a part of the welded portion is viewed from above, and the rear portion of the slewing bearing is disposed. A swivel having a front side structure that is located within the region and is provided so that the other end is welded to the other end of the first support member at a position in front of and above the one end. Invented the frame.

  That is, in the conventional swivel frame, a vertical plate having a uniform thickness is erected on the bottom plate regardless of the load transmission path, and thus it is difficult to obtain high strength and rigidity for weight. On the other hand, in the present invention, in order to efficiently transmit the force acting on the cylinder and boom during excavation by the work attachment to the high-strength slewing bearing, a hollow tube material extending in one direction with a shape corresponding to the force transmission path. By combining the first support member and the second support member made of the above, it is possible to construct a turning frame having strength and rigidity capable of sufficiently supporting the force acting on the cylinder and the boom while being low in weight.

  In the conventional swing frame, at the position where the side structure intersects the rear portion of the swing bearing, one vertical plate of the side structure is welded onto the bottom plate, and the side structure When a tensile load is applied to the body diagonally upward, the load is intensively transmitted from one vertical plate to the portion of the bottom plate located at the intersection of the vertical plate and the swivel bearing. In the present invention, since the first support member and the second support member are made of the pipe material, the load can be transmitted from the tubular end portions of the first and second support members to the front bottom plate while being distributed. it can. As a result, in the present invention, the stress acting on the welded portion between the end portions of the first and second support members and the front bottom plate can be reduced. In addition, in the conventional swivel frame, a vertical plate having a certain thickness is uniformly welded to the bottom plate over a region extending in the front-rear direction, but the required welding strength is obtained although the welding area between the vertical plate and the bottom plate is large. It's hard to be done In contrast, in the present invention, one end portion of the first support member made of the pipe material is welded to the upper surface of the front bottom plate, and at least a part of the welded portion is viewed from above, and the front portion of the slewing bearing is arranged. The second support member made of pipe material is located on the upper surface of the front bottom plate, and at least a part of the welded portion is disposed on the rear portion of the slewing bearing as viewed from above. Since it is located in the installation area, the welding area can be concentrated on the portion where the load is applied. As a result, in the revolving frame of the present invention, the welding strength required between the side structure and the bottom plate can be obtained although the welding area between the side structure and the bottom plate is smaller than that of the conventional revolving frame. Therefore, in the swivel frame of the present invention, it is possible to obtain the necessary welding strength between the side structure and the bottom plate while reducing the work burden on the welding work.

  From the above, the swivel frame of the present invention has a strength and rigidity that can sufficiently support the load applied during excavation by the work attachment while having a low weight, and the side structure and the side structure while reducing the work burden on the welding work. Necessary welding strength with the bottom plate can be obtained.

  Further, in the above-mentioned conventional revolving frame, when the plate thickness of the two vertical plates is increased in order to ensure strength and rigidity, the lower end portion of each vertical plate is secured in order to ensure the welding strength between the vertical plate and the bottom plate. It is necessary to weld both the outer edge and the inner edge to the bottom plate, and the welding operation of the inner edge is performed in a narrow space between the two vertical plates. On the other hand, in the present invention, since the outer edges of the end portions of the first support member and the second support member made of the tube material need only be welded to the upper surface of the front bottom plate, the welding work can be a simple work. That is, in the present invention, the welding strength between the front side part structure and the bottom plate can be ensured by a simple welding operation.

  In the swivel frame of the excavator, the rear frame portions are provided at intervals in the width direction of the swivel frame, and are connected to corresponding ones of the left and right front side structures. A side structure and a connecting member that connects the left and right rear side structures; each of the rear side structures is made of a tube material extending in the front-rear direction, and the lower end of the second support member A third support member having a front end portion welded to a portion and a weight support portion for supporting the counterweight from below at the rear of the front end portion, and a pipe member extending in one direction, one end portion supporting the weight The second support member is welded to the third support member at a position near the front side of the second portion, and the other end portion is welded to the upper end portion of the second support member at a position forward and above the one end portion. Each having a support member. It is preferred.

  As a result of intensive studies, the inventor of the present application has found that when the counterweight is loaded on the rear portion of the rear frame portion in the swing frame, the rear portion of the swing bearing is arranged from the portion supporting the counterweight in the side structure. A region extending over the portion welded to the bottom plate on the installation region, a region extending diagonally forward from the portion supporting the counterweight toward the boom connecting portion, and a region where the rear plate of the slewing bearing is disposed A region extending from the part welded to the upper surface diagonally forward and an area of the front portion of the slewing bearing extending obliquely rearward from the region welded to the upper surface of the bottom plate. A large load is applied to the area extending to the intersection of the area extending toward the front and the area extending diagonally forward from the rear area of the slewing bearing, It is in an area other than the headline that not applied too much load. Based on this knowledge, the inventor of the present application, as described above, the third support member made of the pipe material extending in the front-rear direction is welded to the lower end portion of the second support member, and behind the front end portion. A weight support portion that supports the counterweight from below, and one end of a fourth support member made of a tube material extending in one direction is welded to the third support member at a position near the front side of the weight support portion, A swivel frame including left and right rear side structures in which the other end portion of the fourth support member is welded to the upper end portion of the second support member at a position in front of and above the one end portion. Invented.

  According to this configuration, when the counterweight is loaded on the weight support portion, the side structure extends from the weight support portion to the portion welded to the front bottom plate on the arrangement region of the rear portion of the swing bearing. A large load applied to the region can be supported by the lower ends of the third support member and the second support member. Further, a large load applied to a region extending from the weight support portion toward the boom connection portion in the side structure due to the loading of the counterweight can be supported by the fourth support member. In addition, a large load applied to a region extending diagonally forward from the portion welded to the upper surface of the front bottom plate on the rear region of the swivel bearing in the side structure due to the loading of the counterweight is the second structure. It can be supported by a support member. Also, by loading the counterweight, the side structure extends rearward and obliquely upward from the portion welded to the upper surface of the bottom plate on the arrangement area of the front portion of the slewing bearing, and extends from the weight support portion to the boom connection portion. The first support member can support a large load applied to a region connected to the intersection of the region extending in this manner and the region extending diagonally forward from the region where the rear portion of the slewing bearing is disposed. Therefore, according to this configuration, it is possible to ensure the strength and rigidity of the turning frame with respect to the load applied by the counterweight.

  Further, in the conventional swing frame, at the position where the side structure intersects the rear portion of the swing bearing, one vertical plate of the side structure is welded on the bottom plate, When a swinging load is applied from the counterweight to the side structure, the load is intensively transmitted from one vertical plate to the portion of the bottom plate located at the intersection of the vertical plate and the swivel bearing. On the other hand, in this configuration, the load applied by the counterweight is transferred from the third and fourth support members to the intersecting portion of the side structure and the swivel bearing in the front bottom plate through the first and second support members that are pipe materials. It is transmitted to the part that is located. Therefore, in this configuration, the load applied by the counterweight is distributed from the tubular ends of the first and second support members to the portion of the front bottom plate located at the intersection of the side structure and the swivel bearing. Can communicate. As a result, in this configuration, even when a load due to the counterweight is applied to the third support member, the stress acting on the welded portion between the end portions of the first and second support members and the front bottom plate is caused by the load. Can be reduced.

  In addition, in the conventional swing frame, a vertical plate having a uniform thickness is erected on the bottom plate regardless of the transmission path of the load applied by the counterweight. It is difficult to obtain rigidity. On the other hand, in this configuration, in order to efficiently transmit the load applied by the counterweight to the high-strength slewing bearing, the first to first hollow pipe members extending in one direction in a shape corresponding to the load transmission path. By combining the fourth support member, it is possible to construct a swivel frame having strength and rigidity that can sufficiently support the load of the counterweight while being low in weight.

  Further, as in the conventional revolving frame, the upper plate is welded to the upper edge of the vertical plate from the rear region of the two vertical plates of the side structure to the rear end of the single vertical plate. Therefore, in the configuration that supports the load applied to the region extending from the weight support portion toward the boom connection portion side by loading the counterweight, it is necessary to weld the upper plate to the upper edge of the vertical plate over a long range. The work burden on welding work is large. On the other hand, in this configuration, one end portion of the fourth support member made of the pipe material extending in one direction is welded to the third support member in the vicinity of the front side of the weight support portion, and the other of the fourth support members The end portion of the second support member is welded to the upper end portion of the second support member, and the load applied to the region extending from the weight support portion to the boom connection portion of the side structure by loading the counterweight by the fourth support member. It has come to support. Therefore, in order to install the fourth support member, the outer edge of one end of the tubular fourth support member is welded to the third support member and the outer edge of the other end is welded to the upper part of the second support member. You just have to do the work to do. Therefore, in this configuration, the strength and rigidity against the load applied to the region extending from the weight support portion to the boom connecting portion side of the side structure by loading the counterweight is ensured while reducing the work burden on the welding work. Can do.

  In the swivel frame of the excavator, the front bottom plate and the rear portion of the swivel bearing are fastened with bolts, and the one end portion of the second support member is a rear side of the swivel bearing in the front bottom plate. It is preferable to weld to the upper surface of the front bottom plate so as to surround a part fastened with a part and a bolt.

  For example, when the lower end portion of one vertical plate constituting the side structure is welded to the upper surface of the region between the two bolt fastening portions with respect to the rear side portion of the swing bearing in the bottom plate, A tensile force applied to the boom connecting portion during excavation is transmitted to a portion located between the bolt fastening portions of the bottom plate via the vertical plate, and there is a possibility that damage such as a crack may occur in this portion. On the other hand, in this configuration, one end of the second support member made of the pipe material extending in one direction surrounds a portion of the front bottom plate that is fastened to the rear portion of the swivel bearing with a bolt. Since it is welded to the upper surface of the front bottom plate, the tensile force transmitted through the second support member during the excavation is distributed around the fastening portion of the bottom plate with respect to the rear portion of the swivel bearing as compared with the above case. Can do. For this reason, it is possible to suppress the occurrence of damage such as cracks in a portion welded to the front side part structure around the fastening part with respect to the rear part of the swivel bearing of the front bottom plate due to the load applied during the excavation. .

  Further, in this configuration, a plurality of bolts are positioned inside one end portion of the second support member made of the tube material, and two bolts are positioned separately on both sides across the one end portion. It is possible to dispose bolts that fasten the front bottom plate and the rear portion of the slewing bearing. In this case, the bolts located inside one end of the second support member and located outside The bolts transmit the load from the front bottom plate to the rear portion of the slewing bearing, and the load applied to each bolt and the load applied to each portion of the bottom plate fastened by each bolt can be reduced.

  In the swivel frame of the excavator, the first support member has a planar rear surface, and the other end of the second support member is welded to the rear surface of the other end of the first support member. It is preferable that

  When the rear surface of the first support member is a curved surface and the end portion of the second support member is welded to the rear surface, the end portion of the second support member is aligned along the curved surface shape of the rear surface of the first support member. It is necessary to perform welding work, and the welding work becomes complicated. On the other hand, the first support member has a planar rear surface as in this configuration, and the other end of the second support member is on the rear surface of the other end of the first support member. In the case of welding, since the end portion of the second support member can be welded along a plane, the welding operation can be easily performed.

  In the configuration in which each rear side structure includes a third support member and a fourth support member, the second support member has a planar rear surface, and the front end portion of the third support member is It is welded to the rear surface of the one end portion of the second support member, and the other end portion of the fourth support member is welded to the rear surface of the other end portion of the second support member. Is preferred.

  When the rear surface of the second support member is a curved surface and the end portion of the third support member and the end portion of the fourth support member are welded to the rear surface, the second support member has a curved surface shape along the rear surface of the second support member. It is necessary to perform the welding operation of the end portions of the 3 support member and the fourth support member, and the welding operation becomes complicated. On the other hand, the second support member has a planar rear surface as in this configuration, and the end portions of the third support member and the fourth support member are welded to the rear surface of the second support member. In addition, since the end portions of the third support member and the fourth support member can be welded along the plane, the welding operation can be easily performed.

  In the configuration in which each of the rear side structures includes a third support member, the connecting member is disposed below the left and right rear side structures, and extends rearward from the front bottom plate. A rear bottom plate that connects lower end portions of the rear side structure, and the third support member is a flat lower surface that contacts the upper surface of the rear bottom plate, and is substantially perpendicular to the lower surface. It is preferable that the lower edge part of the side surface is welded to the upper surface of the rear side bottom plate along the longitudinal direction.

  When the lower surface of the third support member is a curved surface and the lower surface is welded to the upper surface of the rear bottom plate along the longitudinal direction of the third support member, the welding should be securely performed so as not to cause poor welding. Becomes difficult. On the other hand, in this configuration, the third support member has a planar lower surface that contacts the rear bottom plate and a side surface substantially perpendicular to the lower surface, and the lower edge portion of the side surface is in the longitudinal direction. Is welded to the upper surface of the rear bottom plate along the upper surface of the rear bottom plate so that the side surface of the third support member is substantially perpendicular to the upper surface of the rear bottom plate. Can be welded to the top surface. For this reason, in this structure, compared with the case where the lower surface of the third support member is curved, the third support member can be easily welded to the upper surface of the rear bottom plate so as not to cause poor welding. .

  As described above, according to the present invention, the side structure and the side structure have a strength and rigidity that can sufficiently support a load applied during excavation by a work attachment while being low in weight, and reduce a work burden on welding work. It is possible to provide a shovel swivel frame capable of obtaining a required weld strength with the bottom plate.

It is a side view of the shovel to which the turning frame by one Embodiment of this invention is applied. It is a perspective view showing the state where the turning frame by one embodiment of the present invention was mounted on the lower frame. It is a perspective view of the turning frame by one Embodiment of this invention. It is a figure which shows roughly the structure of the lower end part vicinity of the 2nd supporting member among the front side part structures of the turning frame shown in FIG. FIG. 4 is a side view of the turning frame shown in FIG. 3. It is a figure which shows the result of the simulation which investigated what kind of load acts on the side part structure body of a turning frame at the time of excavation by a work attachment. It is a figure which shows the result of the simulation which investigated what kind of load acted on the side part structure body of a turning frame when the shovel performed rough road driving | running | working in the state which loaded the counterweight. It is the figure which synthesize | combined the simulation result of FIG. 6, and the simulation result of FIG. It is a figure which shows the result of the simulation which investigated what kind of stress produced in the turning frame by a comparative example at the time of excavation by a work attachment. It is a figure which shows the result of the simulation which investigated what kind of stress produced in the turning frame by embodiment of this invention at the time of excavation by a work attachment. It is sectional drawing of the pipe material of the modification which can be used as a supporting member of a turning frame. It is sectional drawing of the pipe material of the other modification which can be used as a supporting member of a turning frame.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, an overall configuration of a shovel to which a turning frame according to an embodiment of the present invention is applied will be described with reference to FIG.

  The shovel includes a lower traveling body 102 and an upper swing body 104.

  The lower traveling body 102 is a so-called crawler traveling body. The lower traveling body 102 includes a lower frame 102a (see FIG. 2), left and right crawler frames 102b, and left and right crawlers 102c. A crawler frame 102b is attached to the left and right sides of the lower frame 102a, and a crawler 102c is attached around each crawler frame 102b. The lower traveling body 102 travels by rotating the left and right crawlers 102c.

  The upper swing body 104 is mounted on the lower traveling body 102 via the swing bearing 105. The upper swing body 104 can swing around the vertical axis. The upper swing body 104 includes the swing frame 2, a swing motor (not shown), a work attachment 106, a boom hoisting cylinder 108, an arm driving cylinder 110, a bucket driving cylinder 112, and other shovel components.

  The revolving frame 2 is a frame that serves as a base for the upper revolving structure 104, and is disposed below the upper revolving structure 104. The revolving frame 2 is configured to be revolved around the vertical axis with respect to the upper revolving structure 104 by a revolving motor (not shown).

  The work attachment 106 is for excavating the ground or the like. The work attachment 106 includes a boom 106a, an arm 106b, and a bucket 106c. The boom 106a is provided so that it can be raised and lowered around its base end. The arm 106b is attached to the tip of the boom 106a, and the bucket 106c is attached to the tip of the arm 106b. The boom 106a is raised and lowered by a boom raising and lowering cylinder 108. The arm 106b is driven by the arm driving cylinder 110 and swings with respect to the tip of the boom 106a. The bucket 106c is driven by the bucket driving cylinder 112 and swings with respect to the tip of the arm 106b. By driving these cylinders 108, 110, and 112, the boom 106a, the arm 106b, and the bucket 106c are operated, and excavation is performed by the bucket 106c.

  A counterweight 114 is mounted at the rear of the upper swing body 104 to balance the load applied to the upper swing body 104 during operation such as excavation by the work attachment 106.

  Next, with reference to FIGS. 2-5, the detailed structure of the turning frame 2 by this embodiment is demonstrated.

  As described above, the swing frame 2 according to the present embodiment is a base of the upper swing body 104. As shown in FIG. 2, the swing frame 2 is disposed on the lower frame 102a of the lower traveling body 102 via a swing bearing 105. It is provided so that it can turn around. The swivel frame 2 supports the boom 106a of the work attachment 106 so as to be raised and lowered, and supports the boom raising and lowering cylinder 108.

  Specifically, the revolving frame 2 includes a front frame portion 4 and a rear frame portion 6.

  The front frame portion 4 is a portion disposed on the swing bearing 105, and supports the boom 106a and the boom hoisting cylinder 108. The front frame portion 4 includes a front bottom plate 12 and left and right front side portion structures 14.

  The front bottom plate 12 is formed in a flat plate shape, and is fixed on the slewing bearing 105 so as to cover the slewing bearing 105 from above. Specifically, the front bottom plate 12 is fastened to the outer ring portion 105a of the slewing bearing 105 by a plurality of bolts (not shown). That is, a plurality of screw holes 12a (see FIG. 4) are formed at predetermined intervals along the circumferential direction of the slewing bearing 105 on the region of the front bottom plate 12 where the outer ring portion 105a of the slewing bearing 105 is disposed. . Bolts (not shown) for fastening the swivel bearing 105 from below to the screw holes 12a are respectively screwed together and tightened so that the bottom surface of the front bottom plate 12 and the swivel bearing 105 are fixed. The front bottom plate 12 and the outer ring portion 105a of the slewing bearing 105 are fastened to each other with the upper surface of the outer ring portion 105a in contact with each other.

  The front bottom plate 12 is mounted with the unillustrated turning motor. The swivel motor is attached to the rear region of the front bottom plate 12 at a position between the left and right front side structures 14 so that the drive shaft is disposed perpendicular to the front bottom plate 12. The drive shaft of the swing motor extends below the front bottom plate 12, and an external gear is provided at the tip. The external gear meshes with an internal gear disposed on the inner periphery of the inner ring portion 105 b of the slewing bearing 105. The inner ring portion 105 b of the slewing bearing 105 is provided on the lower frame 102 a of the lower traveling body 102. Then, when the turning motor is driven, the external gear rotates while meshing with the internal gear, so that the outer ring portion 105a of the turning frame 2 and the turning bearing 105 changes to the inner ring portion 105b of the turning bearing 105, in other words, the lower frame. It turns with respect to 102a.

  The left and right front side structures 14 are portions that support the boom 106a and the boom hoisting cylinder 108. The left and right front side structures 14 are provided on the front bottom plate 12 at intervals in the width direction of the revolving frame 2. The left and right front side structures 14 are configured to be bilaterally symmetric with respect to the center of the turning frame 2 in the width direction. Each front side structure 14 includes a first support member 16, a second support member 18, a cylinder connection portion 20, and a boom connection portion 22.

  The first support member 16 is made of a tube material extending in one direction. In this embodiment, this pipe material is a steel pipe having a square (square or rectangular) cross section integrally formed by pultrusion molding or the like.

  One end (lower end) of the first support member 16 is welded to the upper surface of the front bottom plate 12. An outer edge of the lower end portion of the first support member 16 is welded to the upper surface of the front bottom plate 12. The entire welded portion is located in the arrangement region of the front portion of the slewing bearing 105 as viewed from above. Note that it is only necessary that at least a part of the welded portion is located in the arrangement region of the front portion of the slewing bearing 105 as viewed from above. In this case, it is preferable from the viewpoint of effectively supporting the load that the center position of the welded portion is positioned on the center line of the width of the front side portion of the slewing bearing 105 in the radial direction of the slewing bearing 105. May be arranged at a position slightly deviated from such a position in the front-rear direction, the outer side in the width direction of the revolving frame 2 or the inner side in the width direction.

  The other end (upper end) of the first support member 16 is located behind and above the lower end. That is, the first support member 16 linearly extends rearward and obliquely upward from the welded portion at the lower end with respect to the front bottom plate 12. The inclination angle of the first support member 16 is such that the boom connection portion 22 is positioned behind and above the cylinder connection portion 20 in the positional relationship between the cylinder connection portion 20 and the boom connection portion 22 attached to the first support member 16. The positional relationship is set as follows. That is, the inclination angle of the first support member 16 is set according to the relative positional relationship between the boom hoisting cylinder 108 and the boom 106a.

  The first support member 16 has a flat front surface and a rear surface that are inclined in the front-rear direction and arranged in parallel to the width direction of the revolving frame 2, and the front and rear surfaces and the front bottom plate 12. The left and right sides of the plane are arranged perpendicularly to the upper surface of the flat plate. For this reason, the part by which the lower end part of the two plate-shaped parts which comprise the front surface and the rear surface of the 1st support member 16 was welded to the front side baseplate 12 is extended in the left-right direction. Thus, the two plate-like portions constituting the front surface and the rear surface of the first support member 16 have the strength and rigidity of the front bottom plate 12 with respect to the load when a bending load in the left-right direction is applied to the front bottom plate 12. It has a function as a kind of rib for improving. Moreover, the part where the lower end part of the two plate-shaped parts which comprise the left and right both sides | surfaces of the 1st support member 16 was welded to the front side baseplate 12 is extended in the front-back direction. For this reason, the two plate-like portions constituting the left and right side surfaces of the first support member 16 have the strength and rigidity of the front bottom plate 12 with respect to the load when a bending load in the front-rear direction is applied to the front bottom plate 12. It has a function as a kind of rib for improving.

  The second support member 18 is formed of a steel pipe having a square cross section that extends in one direction similar to the first support member 16. One end (lower end) of the second support member 18 is welded to the upper surface of the front bottom plate 12 behind the lower end of the first support member 16. The outer edge of the lower end portion of the second support member 18 is welded to the upper surface of the front bottom plate 12. The entire welded portion is located in the arrangement region of the rear portion of the slewing bearing 105 as viewed from above. Note that at least a part of the welded portion only needs to be located in the arrangement region of the rear portion of the slewing bearing 105 when viewed from above. In this case, it is preferable from the viewpoint of effectively supporting the load that the center position of the welded portion is located on the center line of the width of the rear portion of the slewing bearing 105 in the radial direction of the slewing bearing 105. The portion may be arranged at a position slightly deviated from such a position in the front-rear direction or the width direction outer side or the width direction inner side of the revolving frame 2.

  The lower end portion of the second support member 18 is welded to the upper surface of the front bottom plate 12 so as to surround a portion of the front bottom plate 12 that is fastened with the rear portion of the swivel bearing 105 and the bolt not shown. Yes. Specifically, as shown in FIG. 4, the lower end portion of the second support member 18 has two screw holes 12 a adjacent to each other in the region disposed on the rear portion of the swivel bearing 105 in the front bottom plate 12. It welds to the upper surface of the front side baseplate 12 so that it may enter the inner side of the welding part of the said lower end part seeing from upper direction.

  Further, the other end portion (upper end portion) of the second support member 18 is positioned forward and above the lower end portion of the second support member 18. In other words, the second support member 18 extends linearly from the welded portion at the lower end with respect to the front bottom plate 12 toward the front obliquely upward. The inclination angle of the second support member 18 with respect to the upper surface of the front bottom plate 12 and the inclination angle of the first support member 16 with respect to the upper surface of the front bottom plate 12 are equal, as shown in FIG. The upper end portion of the second support member 18 is welded to the rear surface of the upper end portion of the first support member 16. That is, the first support member 16, the second support member 18, and the front bottom plate 12 are disposed so as to form a substantially isosceles triangle when viewed from the side, and the two support members 16, 18 and the front bottom plate 12 The enclosed region is a space where no support member is provided. Further, the inclination angle of the second support member 18 is set to an appropriate value so that a force applied from the boom 106a to the boom connecting portion 22 described later can be transmitted to the rear side portion of the swing bearing 105 via the second support member 18. It is set to an angle.

  The second support member 18 has a flat front surface and a rear surface that are inclined in the front-rear direction and arranged in parallel with the width direction of the revolving frame 2, and the front and rear surfaces and the front bottom plate 12. The left and right sides of the plane are arranged perpendicularly to the upper surface of the flat plate. For this reason, the part where the lower end part of the two plate-shaped parts which comprise the front surface and the rear surface of the 2nd supporting member 18 was welded to the front side base plate 12 is extended in the left-right direction. Thus, the two plate-like portions constituting the front surface and the rear surface of the second support member 18 have the strength and rigidity of the front bottom plate 12 with respect to the load when a bending load in the left-right direction is applied to the front bottom plate 12. It has a function as a kind of rib for improving. Moreover, the part where the lower end part of the two plate-shaped parts which comprise the both left and right side surfaces of the second support member 18 is welded to the front bottom plate 12 extends in the front-rear direction. Therefore, the two plate-like portions constituting the left and right side surfaces of the second support member 18 have the strength and rigidity of the front bottom plate 12 with respect to the load when a bending load in the front-rear direction is applied to the front bottom plate 12. It has a function as a kind of rib for improving.

  When the unillustrated swing motor is driven, a bending load that causes the swing shaft of the swing motor to shake due to the swing torque acts on the front bottom plate 12. At this time, the left and right first support members 16 and the second support members 18 function as ribs for improving the rigidity of the front bottom plate 12 with respect to the bending load in the front-rear direction and the left-right direction as described above. Bending deformation of the front bottom plate 12 in the front-rear and left-right directions is suppressed. As a result, in the present embodiment, the portion of the side structure that is welded to the upper surface of the bottom plate suppresses the shake of the swing motor as compared with the swing frame formed by only the vertical plate extending in the front-rear direction. The angle of deviation of the pivot axis from the vertical position relative to the front bottom plate 12 can be suppressed.

  The cylinder connecting portion 20 connects the base end portion of the boom hoisting cylinder 108 and the lower end portion of the first support member 16. The cylinder connecting portion 20 is configured so that the axial pressing force of the cylinder 108 acting on the cylinder connecting portion 20 from the boom hoisting cylinder 108 during excavation by the work attachment 106 is transmitted to the front portion of the swing bearing 105. The base end portion of the undulation cylinder 108 and the lower end portion of the first support member 16 are connected.

  Specifically, the cylinder connecting portion 20 includes two connecting plates 20a as shown in FIG. The two connecting plates 20a are welded to the front surface of the region of the first support member 16 that extends slightly from the lower end to the upper side. Both the connecting plates 20 a are disposed at a distance from each other in the width direction of the revolving frame 2, and are provided perpendicular to the front surface of the first support member 16. Both connecting plates 20a are formed with holes 20b at the same position. A mounting portion (not shown) provided at the base end portion of the boom hoisting cylinder 108 (see FIG. 1) is disposed between both the connecting plates 20a. In this state, the holes 20b of the connecting plates 20a and the cylinders 108 are connected to each other. A boom raising / lowering cylinder 108 is coupled to the cylinder connecting portion 20 by inserting a cylinder mounting pin (not shown) extending in the width direction of the revolving frame 2 into the hole portion of the mounting portion.

  The two connecting plates 20a of the cylinder connecting portion 20 are rearward along the axial direction of the boom hoisting cylinder 108 from the boom hoisting cylinder 108 via the cylinder mounting pin (not shown) when excavating the ground or the like by the work attachment 106. A pressing force (see FIG. 5) directed obliquely downward acts. This pressing force is transmitted from both connecting plates 20a to the front portion of the slewing bearing 105 through the lower end portion of the first support member 16 and the portion of the front bottom plate 12 where the lower end portion of the first support member 16 is welded. The

  The boom connecting portion 22 connects the base end portion of the boom 106 a and the upper end portion of the first support member 16. The boom connecting portion 22 is configured so that the pulling force acting on the boom connecting portion 22 from the boom 106 a during excavation by the work attachment 106 is on the rear side of the swing bearing 105 via the upper end portion of the first support member 16 and the second support member 18. The base end portion of the boom 106a and the upper end portion of the first support member 16 are connected so as to transmit to the portion.

  Specifically, as shown in FIG. 3, the boom connecting portion 22 is composed of a single connecting plate 22a. The connecting plate 22 a is welded to the front surface of a region extending from the upper end portion of the first support member 16 to the vicinity of the central portion in the longitudinal direction of the first support member 16. The connecting plate 22 a is welded to a position near the outer edge in the width direction of the revolving frame 2 in the front surface of the first support member 16, and is provided perpendicular to the front surface of the first support member 16. A hole 22b is formed in the connecting plate 22a. The hole 22b is disposed so that the center thereof is located on the extension line of the center line of the second support member 18 (center line extending in the longitudinal direction of the second support member 18) when viewed from the side. A mounting portion (not shown) provided at the base end portion of the boom 106a (see FIG. 1) is arranged between the connecting plates 22a of the left and right front side structures 14, and in this state, the left and right connecting plates 22a The boom 106a is coupled to the left and right boom connecting portions 22 by inserting boom mounting pins (not shown) extending in the width direction of the revolving frame 2 into the hole portions of the hole 22b and the boom 106a.

  When the work attachment 106 excavates the ground or the like by the work attachment 106, a pulling force (see FIG. 5) that acts obliquely upward from the boom 106a acts on the connecting plate 22a of the boom connecting portion 22 via the boom mounting pin (not shown). This pulling force is applied to the slewing bearing 105 through a portion where the lower end of the second support member 18 among the upper end of the first support member 16, the second support member 18 and the front bottom plate 12 is welded from the connecting plate 22a. Transmitted to the rear part. Further, when the inclination angle in the direction in which the tensile force is directed is smaller than the inclination angle of the second support member 18, a downward force is applied to the first support member 16 in the longitudinal direction.

  The rear frame portion 6 (see FIG. 3) is connected to the rear side of the front frame portion 4. The rear frame portion 6 supports the counterweight 114 from below at the rear portion. Various components other than the counterweight 114 are mounted on the rear frame portion 6. The rear frame part 6 includes left and right rear side part structures 34 and a connecting member 35.

  The left and right rear side structures 34 are provided at intervals in the width direction of the revolving frame 2. Each rear side structure 34 is welded and integrated with a corresponding one of the left and right front side structures 14. The left and right rear side structures 34 are configured to be symmetrical with respect to the center in the width direction of the revolving frame 2. Each rear side part structure 34 includes a third support member 40 and a fourth support member 42.

  The 3rd support member 40 consists of a pipe material extended in the front-back direction. In the present embodiment, the pipe material constituting the third support member 40 is a steel pipe having a square (rectangular or square) cross section. The third support member 40 has a front end portion welded to the rear surface of the lower end portion of the second support member 18. The third support member 40 includes a weight support portion 40b that supports the counterweight 114 from below at the rear of the front end portion. The weight support portion 40b is composed of a portion of the third support member 40 in the vicinity of the rear end portion. The third support member 40 has a flat lower surface that comes into contact with the upper surface of a rear bottom plate 32 (described later) of the connecting member 35. The upper and lower surfaces of the third support member 40 are planes parallel to the upper surface of the rear bottom plate 32 described later, and the left and right side surfaces of the third support member 40 are the upper and lower surfaces of the third support member 40 and It is a plane perpendicular to the upper surface of the rear bottom plate 32 to be described later.

  The fourth support member 42 is made of a pipe material extending in one direction. In the present embodiment, the pipe material constituting the fourth support member 42 is a steel pipe having a square (rectangular or square) cross section. One end portion of the fourth support member 42 is welded to the upper surface of the third support member 40 at a position near the front side of the weight support portion 40b. The outer edge of this one end is welded to the upper surface of the third support member 40. The other end portion of the fourth support member 42 is welded to the rear surface of the upper end portion of the second support member 18 at a position in front of and above the one end portion. That is, the fourth support member 42 linearly extends from the welded portion with respect to the third support member 40 toward the front obliquely upward. The fourth support member 18 has a flat upper surface and a lower surface that are inclined in the front-rear direction and arranged in parallel to the width direction of the revolving frame 2, and its upper and lower surfaces and a rear side described later. It has two planar left and right side surfaces arranged perpendicular to the upper surface of the bottom plate 36.

  The connecting member 35 connects the left and right rear side structures 34. The connecting member 35 has a rear bottom plate 36 and a standing portion 37.

  The rear bottom plate 36 is a flat plate that is disposed below the left and right rear side structure 34 and extends rearward from the rear end of the front bottom plate 12. The rear side bottom plate 36 connects the lower ends of the left and right rear side part structures 34 to each other. Specifically, the third support members 40 of the left and right rear side structure 34 are welded in a state where they are placed on the rear bottom plate 36. Of the third support member 40 of each rear side structure 34, the lower edge of the side surface located on the inner side in the width direction of the revolving frame 2 is welded to the upper surface of the rear bottom plate 36 along its longitudinal direction (front-rear direction). Has been.

  As shown in FIG. 3, the standing portion 37 is erected on the rear bottom plate 36 and connects the weight support portions 40 b of the left and right third support members 40. The standing portion 37 is made of a flat plate, extends between the left and right third support members 40 in the width direction of the revolving frame 2, and is disposed perpendicular to the upper surface of the rear bottom plate 32. The left and right end portions of the standing portion 37 are welded to corresponding side surfaces among the opposing side surfaces of the left and right third support members 40. Moreover, the lower end part of the standing part 37 is welded to the upper surface of the rear side bottom plate 36 along the longitudinal direction.

  Next, various simulations performed to examine the effect of the excavator turning frame 2 according to the present embodiment will be described.

  First, a simulation was conducted to investigate what loads act on the side structure of the swivel frame when excavating with the work attachment and when the excavator is running on a rough road with the counterweight loaded. . This simulation was performed on a swivel frame having a single vertical plate arranged so that the side structure covers almost the entire surface when viewed from the side. FIG. 6 shows a simulation result for excavation by the work attachment, and FIG. 7 shows a simulation result for a rough road run with the counterweight loaded. In FIG. 6, a relatively dark area A surrounded by a two-dot chain line is an area where a large load is applied, and areas other than the area A are areas where a load is not applied so much. In FIG. 7 as well, a relatively dark area B surrounded by a two-dot chain line is an area where a large load is applied, and areas other than the area B are areas where a load is not applied so much.

  From the results shown in FIG. 6, when excavating with the work attachment, the side connecting structure extends rearward and obliquely upward from a portion welded to the upper surface of the bottom plate on the arrangement region of the front portion of the slewing bearing, and the boom connecting portion and the cylinder A large load acts on the area connected to the connecting portion and the area extending from the part welded to the upper surface of the bottom plate to the boom connecting portion on the arrangement area of the rear portion of the slewing bearing. It can be seen that the load does not act so much on the other areas.

  In addition, from the results shown in FIG. 7, when the excavator performs rough road traveling with the counterweight loaded, the rear structure of the side structure is supported from the support portion of the counterweight along the lower edge of the side structure. An area extending over the area welded to the upper surface of the bottom plate on the arrangement area of the side part, an area extending from the support portion of the counterweight toward the boom connecting section, and an arrangement area of the rear portion of the slewing bearing A region extending diagonally forward and upward from a portion welded to the top surface of the bottom plate, and extending rearward and obliquely upward from a region welded to the top surface of the bottom plate on the arrangement region of the rear portion of the slewing bearing, from the support portion of the counterweight A large load is applied to the region extending to the boom connecting portion side and the region connected to the intersection of the rear portion of the slewing bearing and the region extending obliquely forward, but the other regions. It was found that does not act so much the load.

  FIG. 8 shows the result of combining the simulation result of FIG. 6 and the simulation result of FIG. In the side structure, a relatively dark area surrounded by a two-dot chain line or a broken line shown in FIG. 8 is subjected to a large load due to either excavation by a work attachment or loading of a counterweight. On the other hand, the load due to both of these factors does not act much on the other regions. Based on this result, the inventor applied the first to fourth support members 16, 18, 40, 42 so as to support the load applied by excavation by the work attachment and the load applied by the loading of the counterweight. The revolving frame 2 according to the above-described embodiment was configured. That is, in order to efficiently transmit the load applied during excavation by the work attachment and the load applied by the counterweight to the high-strength slewing bearing, the first to fourth shapes as described above have shapes corresponding to the load transmission paths. Support members 16, 18, 40 and 42 were combined.

  Further, a swivel frame of a comparative example having a vertical plate provided so as to cover substantially the entire side structure when viewed from the side and an upper plate welded so as to be perpendicular to the upper edge of the vertical plate. In addition, a simulation for investigating the difference in the stress generated in the swivel frame due to the load applied during the excavation was performed on the swivel frame having the same configuration as that of the above embodiment. Of the simulation results, the results for the comparative example are shown in FIG. 9, and the results for the present embodiment are shown in FIG.

  In the swivel frame according to the comparative example shown in FIG. 9, a large stress is generated in the region C in the vicinity of the portion welded to the vertical plate of the side structure on the arrangement region of the rear portion of the swivel bearing in the bottom plate. I understood. In contrast, in the swing frame according to the embodiment shown in FIG. 10, the bottom plate is welded to the lower end portion of the second support member of the front side structure on the arrangement region of the rear portion of the swing bearing. Although the stress is generated in the region near the site, the stress value was found to be almost halved with respect to the stress value generated in the corresponding region C of the comparative example of FIG. This is because, in the above-described embodiment, the end of the second support member welded to the upper surface of the front bottom plate on the arrangement region of the rear portion of the slewing bearing due to the fact that the second support member is made of pipe material. The welding area of the part is compared with the welding area where the lower end of the vertical plate crossing the arrangement area of the rear part of the slewing bearing is welded to the upper surface of the bottom plate on the arrangement area as in the slewing frame of the comparative example As a result, it is considered that the load is distributed in the welded portion in the embodiment as compared with the comparative example. From this result, according to the swivel frame of the above embodiment, the load applied during the excavation in the vicinity of the portion welded to the lower end of the second support member on the arrangement region of the rear portion of the swivel bearing in the bottom plate. It has been found that it is possible to suppress the occurrence of damage such as cracks due to the above.

  As described above, in the swivel frame 2 of the shovel according to the present embodiment, during excavation by the work attachment 106, the pressing force acting on the cylinder connecting portion 20 from the boom hoisting cylinder 108 is applied from the cylinder connecting portion 20 to the first support member 16. Can be transmitted to the front portion of the slewing bearing 105 through the lower end portion of the swing bearing 105, and the tensile force acting on the boom connecting portion 22 from the boom 106a can be transmitted from the boom connecting portion 22 to the upper end portion of the first support member 16 and the second support member. It can be transmitted to the rear part of the slewing bearing 105 via the member 18. For this reason, the load applied to the turning frame 2 during excavation by the work attachment 106 can be supported by the front side structure 14. As a result, in the revolving frame 2 of the present embodiment, it is possible to ensure strength and rigidity against a load applied during excavation by the work attachment 106.

  Further, in the swing frame 2 of the present embodiment, a force transmission path for efficiently transmitting the force (load) acting on the boom hoisting cylinder 108 and the boom 106 a during excavation by the work attachment 106 to the high-strength swing bearing 105. Since the first support member 16 and the second support member 18 made of a hollow pipe material extending in one direction with a shape corresponding to the above are combined, the force acting on the boom hoisting cylinder 108 and the boom 106a is sufficiently supported with low weight. The swivel frame 2 has the strength and rigidity that can be achieved. Moreover, in this embodiment, since the support member is not arrange | positioned in the area | region where a load is not applied so much at the time of the said digging among the front side part structures 14, reduction of material cost can be aimed at.

  Further, in the present embodiment, the first support member 16 and the second support member 18 are made of a pipe material, so that the load is distributed from the tubular end portions of both the support members 16 and 18 to the front bottom plate 12. Can communicate. As a result, in the present embodiment, when a tensile load is applied from the boom 106a to the front side structure 14 obliquely upward and forward, or when the excavator travels on a rough road, the counter is added to the rear side structure 34. When a vertical swing load is applied from the weight 114, the stress acting on the welded portion between the end portions of the first support member 16 and the second support member 18 and the front bottom plate 12 due to these loads is reduced. be able to.

  In the present embodiment, one end of the first support member 16 and the second support member 18 made of a pipe material extending in one direction is welded to the upper surface of the front bottom plate 12, and the first support member 16 is welded. At least a part of the portion is located in the arrangement region of the front portion of the slewing bearing 105 when viewed from above, and at least a part of the welded portion of the second support member 18 is located behind the slewing bearing 105 when viewed from above. Since it is located in the arrangement | positioning area | region of a part, a welding area can be concentrated on the part to which a load is applied. As a result, in this embodiment, although the welding area of the front side part structure 14 and the front bottom plate 12 is small, the required welding strength between the front side part structure 14 and the front bottom plate 12 can be obtained. That is, in the present embodiment, the necessary welding strength between the front side part structure 14 and the front side bottom plate 12 can be obtained while reducing the work burden on the welding work.

  In the present embodiment, one end of both tubular support members 16 and 18 can be easily welded to the upper surface of the front bottom plate 12 along the outer edge thereof, and both support members 16 and 18 can be easily welded. The welding strength with respect to 18 front side bottom plates 12 can be secured.

  Further, in the present embodiment, when the counterweight 114 is loaded on the weight support portion 40b, the front bottom plate is disposed on the arrangement region of the rear portion of the swing bearing 105 from the weight support portion 40b of the side structures 34, 14. 12 can be supported by the third support member 40 and the lower end portion of the second support member 18. Further, the fourth support member 42 can support a large load applied to a region extending from the weight support portion 40 b toward the boom connection portion 22 in the side structures 34 and 14 by the counter weight 114. Further, the loading of the counterweight 114 causes a large area extending diagonally forward from the portion welded to the upper surface of the front bottom plate 12 on the rear region of the swivel bearing 105 of the side structures 34 and 14. The load can be supported by the second support member 18. Further, by loading the counterweight 114, the weight support portion extends rearward and obliquely upward from a portion welded to the upper surface of the front bottom plate 12 on the arrangement region of the front portion of the swing bearing 105 in the front side portion structure 14. The first support member 16 supports a large load applied to an area connected to the intersection of the area extending from 40 b toward the boom connecting portion 22 and the area extending rearwardly from the rear area of the swing bearing 105. be able to. Therefore, in the present embodiment, it is possible to ensure the strength and rigidity of the turning frame 2 with respect to the load applied by loading the counterweight 114.

  In this embodiment, in order to efficiently transmit the load applied by the counterweight 114 to the high-strength slewing bearing 105, each support made of a hollow tube extending in one direction in a shape corresponding to the load transmission path. Since the members 16, 18, 40, and 42 are combined, the swivel frame 2 is strong and rigid enough to support the load of the counterweight 114 despite its low weight. In the present embodiment, since the support member is not disposed in the region where the load by the counterweight 114 does not act so much, the material cost can be reduced.

  In the present embodiment, one end portion of the fourth support member 42 made of a pipe material extending in one direction is welded to the third support member 40 at a position near the front side of the weight support portion 40b and the fourth support member is supported. The other end portion of the member 42 is welded to the upper end portion of the second support member 18, and the fourth support member 42 allows the counterweight 114 to be loaded from the weight support portion 40 b out of the side structures 34 and 14. A load applied to a region extending toward the boom connecting portion 22 is supported. Therefore, in this embodiment, in order to install the fourth support member 42, the outer edge of one end of the tubular fourth support member 42 is welded to the third support member 40 and the outer edge of the other end is used. It is only necessary to perform the work of welding on the upper part of the second support member 18. Therefore, in this embodiment, the load applied to the region extending from the weight support portion 40b to the boom connecting portion 22 side of the side structure 34, 14 by loading the counterweight 114 is reduced while reducing the work load on the welding work. Strength and rigidity can be secured.

  In the present embodiment, one end portion of the second support member 18 made of a pipe material extending in one direction surrounds a portion of the front bottom plate 12 that is fastened to the rear portion of the swing bearing 105 with a bolt. Since it is welded to the upper surface of the front bottom plate 12, the tensile force transmitted through the second support member 18 during the excavation can be distributed around the fastening portion of the front bottom plate 12 with respect to the rear portion of the slewing bearing 105. it can. For this reason, it suppresses that damage, such as a crack, arises in the site | part welded with the front side part structure 14 around the fastening part with respect to the rear side part of the turning bearing 105 among the front side bottom plates 12 by the load applied at the time of the said excavation. be able to.

  Further, in the present embodiment, two bolts are located inside one end of the second support member 18 made of a tube material, and two bolts are provided on both outer sides of the one end of the second support member 18. It is possible to arrange a bolt for fastening the front bottom plate 12 and the rear portion of the slewing bearing 105 so that the bolts are located separately (see FIG. 4). For this reason, a load is transmitted from the front bottom plate 12 to the rear side portion of the swing bearing 105 by each bolt positioned inside one end of the second support member 18 and each bolt positioned outside. The load applied to each part fastened by each bolt among the applied load and the front bottom plate 12 can be reduced.

  In the present embodiment, the first support member 16 has a flat rear surface, and the upper end portion of the second support member 18 is welded to the rear surface of the upper end portion of the first support member 16. The upper end portion of the support member 18 can be welded along a plane. For this reason, the welding operation can be easily performed.

  In the present embodiment, the second support member 18 has a planar rear surface, and the end portions of the third support member 40 and the fourth support member 42 are welded to the rear surface of the second support member 18. Therefore, the end portions of the third support member 40 and the fourth support member 42 can be welded along the plane. For this reason, the welding operation can be easily performed.

  In the present embodiment, the third support member 40 has a flat lower surface that contacts the upper surface of the rear bottom plate 32 and both side surfaces substantially perpendicular to the lower surface. Since the lower edge of the side surface located on the inner side in the width direction of the swivel frame 2 is welded to the upper surface of the rear bottom plate 32 along the longitudinal direction, the side surface of the third support member is substantially perpendicular to the upper surface of the rear bottom plate. In this state, the lower edge portion of the side surface can be welded to the upper surface of the rear bottom plate along the longitudinal direction. For this reason, in this structure, compared with the case where the lower surface of the third support member is curved, the third support member can be easily welded to the upper surface of the rear bottom plate so as not to cause poor welding. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, only the rear side structure 34 in the revolving frame 2 may have a structure other than the structure shown in the above embodiment. Specifically, a vertical plate such as a conventional turning frame may be attached behind the second support member 18 of the front side structure 14. Moreover, you may provide the back side part structure body of various other structures.

  Moreover, the pipe material which comprises a 1st-4th supporting member is not limited to a square steel pipe. For example, the pipe material constituting the first to fourth support members may be a pipe material having a circular cross section or a pipe material having another cross-sectional shape.

  Moreover, the pipe material used for the first to fourth support members is not limited to an integrally molded pipe material. For example, as shown in FIG. 11, a flat steel plate is applied to both end edges forming the opening of the C-shaped steel, and the outer ends of the both end edges of the C-shaped steel and the corresponding end portions of the steel plates are respectively welded. May form a tubular material having a square cross section, and the tubular material may be used for the first to fourth support members. In this case, the thickness of the C-shaped steel and the thickness of the steel plate can be made different from each other. Moreover, as shown in FIG. 12, the pipe material which has a square cross section may be formed by welding two L-shaped steels in combination with each other, and the pipe material may be used for the first to fourth support members. In this case, the thickness of one L-shaped steel and the thickness of the other L-shaped steel can be made different from each other. And in such a structure, while securing a certain thickness in the plate-shaped part which receives a big load among the plate-shaped parts which comprise one support member, the part which does not receive much load other than that The wall thickness can be reduced. As a result, it is possible to ensure strength and rigidity while further reducing the weight.

2 Revolving frame 4 Front frame part 6 Rear frame part 12 Front side base plate 14 Front side part structure 16 First support member 18 Second support member 20 Cylinder connection part 22 Boom connection part 34 Rear side part structure 35 Connection material 36 Rear bottom plate 40 Third support member 42 Fourth support member 102 Lower traveling body 105 Slewing bearing 106 Work attachment 106a Boom 108 Boom hoisting cylinder (cylinder)
114 counterweight

Claims (6)

An excavator is provided on a lower traveling body so as to be able to turn around a vertical axis via a turning bearing, and supports a boom of a work attachment for excavating, and supports a cylinder for raising and lowering the boom. A swivel frame,
A front frame portion disposed on the slewing bearing and supporting the boom and the cylinder;
A rear frame part connected to the rear side of the front frame part and supporting a counterweight mounted on the excavator at the rear part from below;
The front frame portion is provided on a front bottom plate fixed on the slewing bearing so as to cover the slewing bearing from above, and provided on the front bottom plate at a distance from each other in the width direction of the slewing frame, Left and right front side structures supporting the cylinder,
Each of the front side structures is made of a pipe material extending in one direction, one end of which is welded to the upper surface of the front bottom plate, and at least a part of the welded portion is seen from above, the front side of the slewing bearing. The first support member is located in the arrangement area of the portion, and the other end portion is located behind and above the one end portion, and the pipe member extends in one direction, and the one end portion is the first end portion. 1 is welded to the upper surface of the front bottom plate behind the one end of the support member, and at least a part of the welded portion is located in an arrangement region of the rear portion of the slewing bearing as viewed from above. A second support member welded to the other end of the first support member at a position in front of and above the other end of the other end, and acting from the cylinder during excavation by the work attachment The cylinder axis A cylinder connecting portion that connects the cylinder and the one end portion of the first support member so that the pressing force is transmitted to the front portion of the slewing bearing, and acts from the boom during excavation by the work attachment The boom and the other end of the first support member so that a tensile force is transmitted to the rear portion of the pivot bearing via the other end of the first support member and the second support member. Excavator swivel frames each having a boom connecting portion that connects the two. The left and right rear side structures, which are provided at intervals in the width direction of the revolving frame and connected to corresponding ones of the left and right front side structures, and And a connecting material for connecting the left and right rear side structures.
Each of the rear side structures is composed of a pipe material extending in the front-rear direction, and a front end portion welded to the lower end portion of the second support member and a weight support portion that supports the counterweight from below at the rear of the front end portion. And a tube member extending in one direction, one end of which is welded to the third support member at a position near the front side of the weight support, and the other end is one end. The excavator turning frame according to claim 1, further comprising a fourth support member welded to an upper end portion of the second support member at a position in front of and above the portion. The front bottom plate and the rear portion of the slewing bearing are fastened with bolts,
The one end portion of the second support member is welded to an upper surface of the front bottom plate so as to surround a portion of the front bottom plate that is fastened with a rear portion of the slewing bearing and a bolt. Item 3. A shovel turning frame according to Item 1 or 2. The first support member has a planar rear surface,
The swivel frame of the shovel according to any one of claims 1 to 3, wherein the other end portion of the second support member is welded to a rear surface of the other end portion of the first support member. The second support member has a planar rear surface,
The front end of the third support member is welded to the rear surface of the one end of the second support member;
The swivel frame of the excavator according to claim 2, wherein the other end portion of the fourth support member is welded to a rear surface of the other end portion of the second support member. The connecting member is disposed on the lower side of the left and right rear side part structures and extends rearward from the front bottom plate, and connects the lower side bottom plates of the left and right rear side part structures. Including
The third support member has a planar lower surface contacting the upper surface of the rear bottom plate and a side surface substantially perpendicular to the lower surface, and a lower edge portion of the side surface extends along the longitudinal direction in the rear side. The swivel frame of the excavator according to claim 2, which is welded to the upper surface of the side bottom plate.