JPH0610078U - Base frame structure for construction machinery - Google Patents

Abstract

(57) [Summary] [Purpose] The main frame has a flexible structure to improve the durability and riding comfort of the vehicle body. A vertical cross-sectional shape of a main frame 13 that bridges between a pair of left and right track frames 11 and supports a slewing bearing pedestal 12 at substantially the center has a curved shape that is convex and continuous in the direction opposite to the load direction. Thus, the main frame 13 has a flexible structure without having excessive rigidity, and the impact when the vehicle body is dropped is mitigated to improve durability and riding comfort.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a base frame structure for a construction machine in which a main frame supporting a slewing bearing pedestal is formed on a track frame with a continuous curved shape such as a cylindrical surface, a spherical surface, or a parabolic surface.

[0002]

[Prior art]

 Construction equipment such as hydraulic excavators require a traveling function and a swing function as basic functions, and the undercarriage and the upper revolving structure are connected via a base frame structure. The base frame structure consists of roughly three blocks, as shown in the plan view and front view in FIGS. 3 and 4, respectively, and a pair of left and right track frames 1 supported by the lower traveling structure and a swing structure supporting the upper swing structure. It comprises a slewing bearing pedestal 2 for fixing the bearing, and a main frame 3 bridged between a pair of left and right track frames 1, 1 for supporting the slewing bearing pedestal 2 in the center. Both the left and right track frames 1 have an inverted U-shaped cross section, and are firmly attached to an endless track device (not shown). The slewing bearing pedestal 2 includes a mounting flange 4 for a slewing bearing (not shown) that rotatably supports an upper slewing body, and a cylinder 5 integrated with the mounting flange 4.

The main frame 3 has a total of four legs in the front, rear, left, and right sides and straddles between the left and right track frames 1 and 1. The leg ends are fixed to the track frame 1, and the pedestal 2 for swivel bearings is mounted on the upper surface of the central portion. Is fixed. The main frame 3 shown in this example includes a pair of upper and lower flanges 6 and 6'integrally formed in a trapezoidal shape including a central flat base portion 6a and four side extending leg portions 6b, and a pair of upper and lower flanges It is composed of eight webs 7 radially sandwiched between 6, 6 '. Each leg 6b is formed into a box-shaped three-dimensional shape by two webs 7 and obtains required rigidity such as torsional rigidity.

[0004]

The base frame structure 8 of the conventional construction machine described above has a trapezoidal pair of flanges 6 and 6'constituting the main frame 3 for the purpose of ensuring the minimum ground clearance of the vehicle body. Since the shoulder portion is bent, a high stress concentration is likely to occur locally at the bent portion where the base portion 6a and the leg portion 6b intersect. Since such stress concentration causes damage when subjected to repeated loads, the conventional base frame structure 8 has a thicker upper and lower flanges 6 and 6'from the viewpoint of ensuring member strength. 3 It is designed to increase the rigidity of the whole. However, if the rigidity of the main frame 3 as a whole is increased in this way, the weight of the vehicle body including the base frame structure 8 increases, and when the vehicle body falls during work, it extends from the lower traveling structure to the upper revolving structure via the base frame structure 8. As a result, the impact force increases, which not only adversely affects the structure of the upper revolving structure, but also transmits an excessive impact to workers who work on the upper revolving structure, which deteriorates the durability of the vehicle body and the riding comfort. However, there was a problem in that Further, if the bending degree of the base portion 6a and the leg portions 6b of the main frame 3 is increased in order to increase the minimum ground clearance of the vehicle body, the above problem becomes more remarkable. Therefore, the conventional base frame structure 8 has the minimum ground clearance. There was a problem that there was a limit to securing

[0005]

[Means for Solving the Problems]

 This invention solves the above problems and supports a pair of left and right track frames supported by the lower traveling body of a construction machine having a lower traveling body and an upper revolving body, and the upper revolving body. In the base frame structure of a construction machine, which comprises a slewing bearing pedestal that supports a slewing bearing and a main frame that bridges between the pair of left and right track frames, and that supports the slewing bearing pedestal in approximately the center, The vertical cross-sectional shape of is a curved shape that is convex and continuous in the direction opposite to the load direction.

[0006]

[Action]

 The main frame, which is bridged between a pair of left and right track frames and supports the slewing bearing pedestal in the approximate center, has a vertical curved cross section that is convex and continuous in the direction opposite to the load direction. With a flexible structure that does not have excessive rigidity, it is possible to reduce the impact when the vehicle falls and improve durability and riding comfort.

[0007]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. 1 and 2 are a plan view and a front view, respectively, showing an embodiment of a base frame structure for a construction machine according to the present invention.

A base frame structure 20 of a construction machine shown in FIGS. 1 and 2 supports a pair of left and right track frames 11 supported by an infinite track device (not shown) of a lower traveling body and an upper revolving body. A slewing bearing pedestal 12 for fixing a slewing bearing (not shown) and a four-legged main frame 13 bridged between the track frames 11 and 11 for supporting the slewing bearing pedestal 12 in the center. The left and right track frames 11 and the slewing bearing pedestal 12 have substantially the same shape as conventional ones. That is, the track frame 11 has an inverted U-shaped cross section on both the left and right sides and is firmly assembled to the endless track device (not shown). Further, the slewing bearing pedestal 12 includes a mounting flange 14 for a slewing bearing (not shown) that rotatably supports an upper revolving body, and a cylinder 15 in which the mounting flange 14 is integrally formed in a top opening in a flange shape. Consists of.

The main frame 13 has a pair of upper and lower flanges 16 and 16 'in which leg portions 16b extend in four directions from a base portion 16a having a circular hole passing through the center thereof, and a pair of upper and lower flanges 16 and 16' radially sandwich the flanges 16 and 16 '. It consists of eight webs 17 in total. The leg portions 16b of the upper and lower flanges 16 and 16 'sandwich two webs 17 at a predetermined distance from each other, and the leg ends are welded to the track frame 11. However, the leg end of the upper flange 16 is welded to the upper surface of the track frame 11, and the leg end of the lower flange 16 ′ is welded to the side surface of the track frame 11. The cylinder 15 of the slewing bearing pedestal 12 is fitted into a circular hole formed in the center of the base 16a of the flanges 16 and 16 ', and the fitted state is fixed by welding.

The pair of upper and lower flanges 16, 16 ′ has a curved shape which is convex and continuous in the direction opposite to the load direction. The web 17 sandwiched between the pair of upper and lower flanges 16 and 16 'also has a corresponding curved shape. That is, as is apparent from FIG. 2 when the base frame structure 20 is viewed from the front, the upper and lower flanges 16 and 16 'are formed by a part of a cylindrical surface here, and the upper and lower end surfaces of each web 17 have a circular contour. To have. Therefore, when viewed from the front, it is similar to the conventional flanges 6, 6 ', but when it is viewed from the front, it forms a smooth cylindrical surface whose tangent line changes continuously. There is no bending point corresponding to the trapezoidal shoulder part like 6 '. Therefore, the flanges 16 and 16 'are free from the stress concentration in which the stress is locally concentrated, and the eight webs 17 radially extending from the side surface of the cylinder 15 of the slewing bearing pedestal 12 form a continuous beam. Therefore, the rigidity of the main frame 13 itself can be sufficiently secured without increasing the plate thickness of the flanges 16 and 16 '. As described above, according to the base frame structure 20 described above, there is no location where local stress concentration occurs in the main frame 13, and therefore unnecessary thickness for securing rigidity is eliminated to reduce the structure weight. In addition, unlike the conventional base frame structure 8, since it has a flexible structure, the impact force at the time of dropping can be mitigated, and the durability and riding comfort of the vehicle body can be improved accordingly. In addition, since it has a continuous curved shape, it is possible to improve drivability by increasing the minimum ground clearance.

Although the curved shape of the main frame 13 is formed by the cylindrical surface in the above embodiment, the curved shape of the main frame 13 may be formed by a spherical surface or a paraboloid other than the cylindrical surface. In this case, the main frame 13 is radially sandwiched between a pair of upper and lower flanges 16 and 16 ′ forming a cylindrical surface, a spherical surface, or a parabolic surface, and a pair of upper and lower flanges 16 and 16 ′. It is composed of a plurality of webs 17 in which 16 and 16 'are opposed to each other at regular intervals.

[0012]

As described above, according to the present invention, the main frame, which is bridged between the pair of left and right track frames and supports the slewing bearing pedestal at approximately the center, is convex and continuous in the direction opposite to the load direction. Due to the curved shape, there is no stress concentration in the main frame, which can eliminate unnecessary thickness for securing rigidity and reduce the weight of the structure. Since it has a flexible structure without having excessive rigidity, it is possible to suppress the impact from the undercarriage to the upper revolving structure via the base frame structure when the vehicle body falls during work. This eliminates the inconvenience of adversely affecting the structure of the upper revolving structure and causing an excessive impact to the passengers of the upper revolving structure to make the ride uncomfortable, and also reduces the vehicle's minimum ground clearance. Is sufficiently secured to improve the traveling performance.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a base frame structure for a construction machine according to the present invention.

FIG. 2 is a front view of a base frame structure of the construction machine shown in FIG.

FIG. 3 is a plan view showing an example of a base frame structure of a conventional construction machine.

FIG. 4 is a front view of the base frame structure of the construction machine shown in FIG.

[Explanation of symbols]

 20 Construction Machine Base Frame Structure 11 Track Frame 12 Slewing Bearing Pedestal 13 Main Frame 14 Mounting Flange 15 Cylindrical 16 Upper Flange 16 'Lower Flange 17 Web

Claims (4)

[Scope of utility model registration request] 1. A pair of left and right track frames supported by the lower traveling body of a construction machine having a lower traveling body and an upper revolving body, and a slewing bearing pedestal supporting a revolving bearing for supporting the upper revolving body, In a base frame structure of a construction machine comprising a main frame that bridges between the pair of left and right track frames and supports the slewing bearing pedestal in substantially the center, a vertical cross-sectional shape of the main frame is set in a direction opposite to a load direction. A base frame structure for construction machinery, which has a convex and continuous curved shape. 2. The main frame is composed of a pair of upper and lower flanges each forming a cylindrical surface, and a plurality of webs radially sandwiched between the pair of upper and lower flanges and facing each other at regular intervals. A base frame structure for a construction machine according to claim 1. 3. The main frame is composed of a pair of upper and lower flanges each forming a spherical surface, and a plurality of webs radially sandwiched between the pair of upper and lower flanges so as to face each other at regular intervals. The base frame structure for a construction machine according to claim 1. 4. The main frame is composed of a pair of upper and lower flanges each forming a parabolic surface, and a plurality of webs radially sandwiched between the pair of upper and lower flanges so as to face each other at regular intervals. The base frame structure for a construction machine according to claim 1.