JP4067070B2 - Work machine support structure of work vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a work machine support structure for a work vehicle.
[0002]
[Prior art]
Examples of the work vehicle having a work machine supported so as to be swingable in the vertical direction include a hydraulic excavator and a mobile crane. 6 to 8 show a conventional construction support structure of a hydraulic excavator, and the hydraulic excavator will be described below as an example.
As shown in FIG. 6, an upper swing body 2 is mounted on the lower traveling body 1 so as to be rotatable. A cab 4, a machine cab 5 incorporating an engine and hydraulic equipment, and a counterweight 6 are mounted on the upper part of the revo frame 3 disposed at the bottom of the upper swing body 2. A work machine 20 having a boom 7, an arm 8 and a bucket 9 is mounted so as to be swingable in the vertical direction. The boom 7, the arm 8, and the bucket 9 are driven by hydraulic cylinders 10, 11, and 12, respectively.
[0003]
A boom support structure for supporting the boom 7 of such a hydraulic excavator will be described with reference to FIGS.
FIG. 7 is a perspective view showing the boom base end portion 13. In the figure, the base end portion 13 of the boom 7 has a pair of left and right support legs 15R, 15L branched in a bifurcated manner, and the support legs 15R, 15L are respectively attached to the bottom plate of the revo frame 3 by foot pins 16, 16. It is rotatably supported by a pair of left and right boom support portions 14A and 14B provided upright on 3a.
[0004]
FIG. 8 is a cross-sectional view taken along line BB in FIG. 7 and shows the structure of the boom support portion 14A in detail. Note that the boom support portion 14B has the same structure, and the boom support portion 14A will be described here.
In FIG. 8, reinforcing plates 17b and 17b are provided to face the inner side surfaces of the pair of side plates 14a and 14b, respectively. The upper ends of the reinforcing plates 17b and 17b extend to the vicinity of the upper ends of the side plates 14a and 14b, the periphery is welded to the inner surfaces of the side plates 14b and 14b, and the lower ends are between the inner surfaces of the side plates 14a and 14b. Are welded to the partition plate 18 provided at the P and Q portions.
The side plates 14a, 14b, the reinforcing plates 17b, 17b, and the support leg portion 15L are respectively provided with pin holes 21, 23, 22 and the foot pins 16 pass through these pin holes 21, 23, 22 in the left-right direction. Thus, the support leg portion 15L is pivotally supported rotatably.
The plate thickness of the reinforcing plates 17b, 17b is uniformly t1. Further, the gap between the inner side surface 17j of the outer reinforcing plate 17b and the outer side surface 15a of the supporting leg portion 15L is s2, and the gap between the inner side surface 17f of the inner reinforcing plate 17b and the inner side surface 15b of the supporting leg portion 15L is s3. . Here, the gap s3 is larger than the gap s2, and the inner side surface 15b of the support leg 15L does not come into contact with the inner side surface 17f of the reinforcing plate 17b even if the boom 7 is displaced maximum in the left direction by the maximum thrust load in the left direction. Is set to
[0005]
Next, the behavior when the maximum thrust load F is applied to the boom 7 in the left direction will be described with reference to FIG.
When the maximum thrust load F acts on the boom 7 in the left direction, first, the support leg portion 15L of the boom 7 moves to the left, and the outer side surface 15a of the support leg portion 15L becomes the inner side surface 17j of the outer reinforcing plate 17b. Abut. Next, the outer side surface 15a of the support leg portion 15L is displaced leftward with the upper end point t of the inner side surface 17j of the outer reinforcing plate 17b as a fulcrum, and is in a state like a two-dot chain line. Therefore, the side plate 14a receives the load component F3 in the left direction from the outer surface 15a of the support leg portion 15L of the boom 7 at the upper end point t of the outer reinforcing plate 17b.
Here, the distance from the upper end of the reinforcing plate 17b to the partition plate 18 is L3, and the distance between the shaft center of the foot pin 16 and the partition plate 18 is L2. At this time, since the maximum bending moment M3 expressed by the mathematical expression “M3 = L3 × F3” acts on the welded portion P of the partition plate 18, the stress σ3 resulting from the maximum bending moment M3 is applied to the welded portion P. appear.
[0006]
Moreover, as another prior art of the working machine support structure in the work vehicle, for example, there is one disclosed in Japanese Patent No. 2684025, and FIG. 9 is an explanatory view of the main part of the boom support structure. According to the publication, a boom foot pin is installed on a pair of side plates that are erected in parallel and spaced apart from each other on a frame, and a base end of the boom is supported rotatably around the boom foot pin. In a boom support structure in a construction machine or the like, an inner doubling plate 33 is welded to the inner surface of the side plate 32 in the vicinity of the boom foot pin 35, and an outer doubling plate 34 is welded to the outer surface. The upper end surfaces of the doubling plate 33 and the outer doubling plate 34 are welded to the lower surface 31a of the top plate 31 welded to the upper end of the side plate 32, respectively.
Thereby, it is described that the bending rigidity in the vicinity of the boom foot pin 35 can be improved, and stress can be prevented from concentrating on the lower weld toe G portion of the inner doubling plate 33 and in the vicinity thereof.
[0007]
[Problems to be solved by the invention]
However, the conventional work machine support structure for a work vehicle has the following problems.
In the structure shown in FIG. 8, when a maximum thrust load F is applied to the boom in the left direction, the boom 7 is displaced to the left as indicated by a chain line, and the welding portion P of the partition plate 18 has a maximum bending moment M3 (= L3). × F3) acts, but since the distance L3 is large, the maximum bending moment M3 is also large. Therefore, a large stress .sigma.3 is generated in the welded portion P of the partition plate 18, and stress concentration occurs in the welded portion P. Due to this stress concentration, there is a problem in that the weld P is cracked and easily damaged.
In the technique disclosed in Japanese Patent No. 2684025, the bending rigidity in the vicinity of the boom foot pin 31 can be improved, but the boom is displaced by the thrust load acting on the boom, and the side surface of the boom is When the top plate 31 and the inner doubling plate 33 are brought into contact with the upper end portions, a large bending moment acts on the inner doubling plate 33 and the side plate 32, and thus the inner doubling plate 33 and the inner doubling plates 33 are coupled to each other. There is a problem that a large stress is generated in a welded portion with a distance plate (corresponding to the above-mentioned partition plate).
[0008]
The present invention pays attention to the above-mentioned conventional problems, and the work machine support structure for a work vehicle can reduce the stress generated in the welded portion between the side plate and the partition plate when the work machine is displaced due to the thrust load acting on the work machine. The purpose is to provide.
[0009]
[Means, actions and effects for solving the problems]
In order to achieve the above object, according to a first aspect of the work machine support structure for a work vehicle according to the present invention, a pair of side plates are erected in parallel and spaced apart from each other on a frame. The base end portion of the work implement is inserted and inserted with a predetermined gap, and the foot pin is inserted into the pin hole provided in the pair of side plates and the pin hole provided in the base end portion of the work implement. In the work machine support structure of a work vehicle in which a base plate is rotatably supported and a partition plate is welded between the side plates at the lower part of the pair of side plates, the side plate is an inner surface, In addition to having a reinforcing plate at the boss near the pin hole, the reinforcing plate is formed so that the gap between the vicinity of the shaft center of the foot pin and the base end of the upper work machine is larger than the lower gap. Yes.
According to the first invention, even if a thrust load acts on the work machine (or a boom in the case of a hydraulic excavator) and the work machine is displaced, the work machine base end does not contact the upper end of the side plate. In addition, since the abutting portion of the reinforcing plate on the inner side of the side plate contacts below the center of the foot pin, the point of action of the bending moment acting on the side plate is lowered, thereby reducing the bending moment. Accordingly, since the stress generated in the welded portion between the side plate and the partition plate fixed between the side plates is reduced, the welded portion is not cracked and can be prevented from being damaged.
Also, since the side plate has a reinforcing plate on the inner surface and in the boss near the pin hole for inserting the foot pin, it is between the vicinity of the shaft center of the foot pin of the side plate and the base end of the upper working machine. It is possible to perform the processing for forming the gap so as to be larger than the lower gap on the reinforcing plate side. Therefore, the processing can be facilitated because the processing can be performed with a predetermined thickness and shape on the side of the small and light reinforcing plate rather than handling a large and heavy side plate. In addition, since the side plate main body does not need to be processed, it is not necessary to change the design of the side plate main body, so that it can be made the same as the conventional one, thereby preventing an increase in manufacturing cost.
[0011]
According to a second invention, in the configuration of the first invention, the reinforcing plate of the side plate is a single plate in which a taper surface is formed by gradually increasing the thickness from above to below.
According to the second invention, the reinforcing plate is gradually thickened from the upper side to the lower side to form a tapered surface. Therefore, when the working machine is displaced due to the thrust load acting on the working machine, the base of the working machine is The outer surface of the end portion is in uniform contact with the tapered surface of the reinforcing plate. Accordingly, the surface pressure of the contact portion is reduced, and damage such as indentation does not occur on the outer surface of the work equipment base end portion and the taper surface of the reinforcing plate, thereby improving durability. Further, since the reinforcing plate is constituted by a single plate, the taper processing is easy and the welding to the side plate body is easy.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described below with reference to FIGS. 1 to 5, the same components as those in FIGS. 6 to 8 are denoted by the same reference numerals.
1 to 4 show a first embodiment of a work machine support structure for a work vehicle according to the present invention. First, an outline of a boom base end portion of a hydraulic excavator will be described with reference to FIGS. 1 is a perspective view of a boom base end portion, and FIG. 2 is a cross-sectional view taken along line AA of FIG.
As shown in FIG. 1, the base end portion 13 of the boom 7 of the work machine 20 has a pair of left and right support legs 15R and 15L bifurcated, and the support legs 15R and 15L are foot pins 16 and 16 respectively. Thus, it is rotatably supported by a pair of left and right boom support portions 14L and 14R which are erected substantially in parallel on the bottom plate 3a of the revo frame 3.
As shown in FIG. 2, the pair of left and right boom support portions 14L and 14R have a pair of left and right side plates 14a and 14b, respectively, and a partition plate 18 is provided between the lower portions of the pair of left and right side plates 14a and 14b. Are welded.
The support leg portions 15L and 15R of the base end portion 13 are respectively fitted with a predetermined gap as will be described later between the pair of side plates 14a and 14b, and are pivotally supported by the foot pins 16.
[0013]
Based on FIGS. 3 and 4, the structure of the boom support portions 14L and 14R will be described in detail. Since the boom support portions 14L and 14R have the same structure, the boom support portion 14L will be described here. FIG. 3 is a detailed view of the boom support portion 14L, and FIG. 4 is a Z view of FIG. 3 and shows a welded state between the reinforcing plate 17a, the side plate 14a, and the partition plate 18.
As shown in FIGS. 3 and 4, reinforcing plates 17a and 17b are provided on the inner surfaces of the side plates 14a and 14b, respectively. The upper ends of the reinforcing plates 17a and 17b extend to the vicinity of the upper ends of the side plates 14a and 14b, the periphery is welded to the inner side surfaces of the side plates 14a and 14b at the M portion, and the lower ends are attached to the partition plate 18. It is welded at P part and Q part.
The side plates 14a and 14b, the reinforcing plates 17a and 17b, and the support leg portion 15L are respectively provided with pin holes 21, 23, and 22 that pass through these pin holes 21, 23, and 22 in the left-right direction to form foot pins. 16 is inserted, and thereby the supporting leg portion 15L is pivotally supported.
[0014]
The reinforcing plate 17a is composed of plates 17c and 17d having different thicknesses, and the plates 17c and 17d are welded to each other at the axial center position N of the foot pin 16 whose distance from the partition plate 18 is L1. . The plate 17c is in the lower half portion from the axis of the foot pin 16, and the plate thickness is t1. The plate 17d is in the upper half of the axis of the foot pin 16, and the plate thickness is t2, where t2 <t1. As a result, the relationship between the clearance s2 between the inner surface 17e of the plate 17c and the outer surface 15a of the support leg 15L and the clearance s4 between the inner surface 17k of the plate 17d and the outer surface 15a of the support leg 15L is expressed as s2. <S4.
The distance between the upper end portion of the plate 17c (equal to the axial center height of the foot pin 16) and the partition plate 18 is L1, and the distance between the upper end of the plate 17d and the partition plate 18 is L3.
The relationship between the gap s2 and the gap s4 is that the maximum thrust load F acts on the boom 7 in the left direction, and the outer surface 15a of the support leg portion 15L moves leftward with the upper end point p of the plate 17c of the reinforcing plate 17a as a fulcrum. Even when the displacement is maximum, a predetermined gap s1 is set between the outer surface 15a of the support leg 15L and the upper end point q of the plate 17d of the reinforcing plate 17a. In the present embodiment, the above relationship is set by the relationship between the plate thickness t2 of the plate 17d and the plate thickness t2 of the plate 17d. Therefore, the outer surface 15a of the support leg 15L and the upper end point q of the plate 17d of the reinforcing plate 17a are not in contact with each other.
[0015]
The thickness of the reinforcing plate 17b is uniformly t1.
A predetermined gap s3 is provided between the inner side surface 17f of the reinforcing plate 17b and the inner side surface 15b of the support leg 15L. Here, the clearance s3 is set to be larger than the clearance s2, so that even if the maximum thrust load is applied to the boom 7 in the left direction and the boom 7 is displaced to the maximum in the left direction, the inner side surface 15b of the support leg portion 15L is reinforced. The inner surface 17f of the plate 17b is prevented from contacting.
[0016]
Next, the function and effect will be described with reference to FIG.
When the maximum thrust load F is applied to the boom 7 in the left direction, first, the support leg 15L of the boom 7 moves to the left, and the outer surface 15a of the support leg 15L is the inner surface of the plate 17c of the reinforcing plate 17a. Abuts against 17e. Next, the outer surface 15a of the support leg 15L is displaced leftward with the upper end point p of the plate 17c of the reinforcing plate 17a as a fulcrum, and is inclined as shown by the two-dot chain line in the figure, as described above. Since a predetermined gap s1 is secured between the upper end point q of the plate 17d of the reinforcing plate 17a, the outer surface 15a of the support leg portion 15L and the upper end point q of the plate 17d of the reinforcing plate 17a are in contact with each other. Do not touch.
[0017]
Accordingly, the side plate 14a receives the load component F1 in the left direction from the outer surface 15a of the support leg portion 15L at the upper end point p of the plate 17c of the reinforcing plate 17a.
As a result, the maximum bending moment M1 expressed by the mathematical expression “M1 = L1 × F1” acts on the welded portion P of the partition plate 18.
On the other hand, in the conventional structure shown in FIG. 8, the maximum bending moment M3 (= L3.times.F3) acts on the weld P. At this time, as shown in FIG. 3, L1 <L3 and F1.apprxeq.F3. Therefore, M1 <M3. Accordingly, the stress .sigma.1 generated in the welded part P is .sigma.1 <.sigma.3, and it is possible to prevent the welded part P from cracking.
[0018]
Next, 2nd Embodiment of the working machine support structure of the working vehicle which concerns on this invention is described with reference to FIG.
In this embodiment, in the first embodiment described above, the reinforcing plate 17a is constituted by a single plate reinforcing plate 17g, and the reinforcing plate 17g has a tapered surface 17h on the upper half portion from the axis of the foot pin 16. Is provided so that the thrust load of the boom 7 is received by the tapered surface 17h.
The distance between the upper end of the reinforcing plate 17g and the partition plate 18 is L3, and the distance between the shaft center of the foot pin 16 and the partition plate 18 is L1.
In the reinforcing plate 17g, the thickness of the lower half portion from the axis of the foot pin 16 is uniformly t1. Further, the plate thickness of the upper half portion from the shaft center of the foot pin 16 is t3 at the upper end, and is gradually increased from the upper end toward the lower side to be tapered, and is t1 at the shaft center position of the foot pin 16. Thus, the clearance s2 between the inner surface 17i below the vicinity of the shaft center of the foot pin 16 of the reinforcing plate 17g and the outer surface 15a of the support leg 15L, and the inner surface of the reinforcing plate 17g above the vicinity of the shaft center of the foot pin 16 The relationship of the gap s5 between the taper surface 17h (here, the taper surface 17h) and the outer surface 15a of the support leg 15L is set to satisfy s2 <s5.
Here, it is assumed that the distance between the central portion r of the tapered surface 17h and the partition plate 18 is L2. The slope of the taper surface 17h is set so that the outer side 15a of the support leg portion 15L uniformly contacts the taper surface 17h when the maximum thrust load F is applied to the boom 7 in the left direction.
[0019]
Further, a gap s3 is provided between the inner side surface 17f of the reinforcing plate 17b and the inner side surface 15b of the support leg 15L. Here, the gap s3 is larger than the gap s2, and even when the maximum thrust load acts on the boom 7 in the left direction and the boom 7 is displaced maximum in the left direction, the inner side surface 15b of the support leg portion 15L remains within the reinforcing plate 17b. It is set not to contact the side surface 17f.
[0020]
Next, the function and effect will be described with reference to FIG.
When the maximum thrust load F is applied to the boom 7 in the left direction, first, the support leg portion 15L of the boom 7 moves to the left, and the outer surface 15a of the support leg portion 15L contacts the inner side surface 17i of the reinforcing plate 17g. Touch. Next, the outer surface 15a of the support leg portion 15L is displaced leftward with the s point of the reinforcing plate 17g (the lower end point of the tapered surface 17h) as a fulcrum, and is inclined as shown by the two-dot chain line in the figure. Uniformly contact the taper surface 17h.
Therefore, the side plate 14a receives the load component F2 in the left direction uniformly from the outer surface 15a of the support leg portion 15L of the boom 7 by the tapered surface 17h of the reinforcing plate 17g. Here, assuming that a load of F2 is received in the left direction at the central point r of the taper surface 17h, the maximum bending moment M2 represented by the formula "M2 = L2 * F2" is applied to the welded portion P of the partition plate 18. Act.
On the other hand, in the conventional structure shown in FIG. 8, the maximum bending moment M3 (= L3.times.F3) acting on the weld P acts, and as shown in FIG. 5, L2 <L3 and F2.apprxeq.F3. Therefore, M2 <M3.
Similarly, when a load smaller than the maximum thrust load F is applied to the boom 7 in the left direction, the outer surface 15a of the support leg portion 15L is displaced in the left direction with the s point of the reinforcing plate 17g as a fulcrum. It does not contact the tapered surface 17h of the plate 17g. Therefore, assuming that a load of F2a is received in the left direction at the point s of the reinforcing plate 17g, the maximum bending moment M2a represented by the mathematical expression “M2a = L1 × F2a” acts on the welded portion P of the partition plate 18. In comparison with the prior art in FIG. 8, L1 <L3 and F2a≈F3, so that M2a <M3.
From the above, the stress σ2 generated in the weld P in the present embodiment is σ2 <σ3 with respect to the stress σ3 in the conventional structure, and it is possible to prevent the weld P from cracking.
[0021]
Further, the maximum thrust load of the boom 7 is uniformly received by the tapered surface 17h of the reinforcing plate 17g. Therefore, the surface pressure between the outer surface 15a of the support leg 15L and the tapered surface 17h of the reinforcing plate 17g is reduced, and the outer surface 15a of the supporting leg 15L and the tapered surface 17h of the reinforcing plate 17g can be prevented from being damaged.
[0022]
As described above, according to the work machine support structure for a work vehicle according to the present invention, in the side plate or the side plate reinforcing plate, the gap between the foot pin shaft vicinity and the upper boom support leg portion is set to the lower side. By making it larger than the gap, the height of the acting point of the boom thrust load acting on the side plate or the reinforcing plate is lowered, and the bending moment acting on the welded portion of the partition plate provided between the pair of left and right side plates Is greatly reduced. Accordingly, since the stress acting on the welded portion of the partition plate is reduced, the welded portion is not cracked and can be prevented from being damaged.
[0023]
In the above-described embodiment, an example in which the base end portion of the boom has a bifurcated support leg portion is shown, but the present invention is not limited to this, for example, a boom that is not branched, or a branching into three or more branches It can also be applied to booms and the like.
Moreover, although demonstrated using the example which provided the reinforcement board in the side plate, it is not limited to this, It is applicable also to the instruction | indication structure which supports a boom only by a side plate.
Furthermore, although the boom support structure of the hydraulic excavator has been described as an example of an applied model, any work machine support structure that supports the work machine of the work vehicle with a pair of parallel side plates may be used. It can also be applied to the boom support structure.
[Brief description of the drawings]
FIG. 1 is a perspective view of a boom base end portion of a work machine support structure for a work vehicle according to the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is a detailed view of the structure of the boom support part of the first embodiment.
4 is a Z view of FIG. 3;
FIG. 5 is a detailed view of the structure of the boom support part of the second embodiment.
FIG. 6 is a side view of a hydraulic excavator according to the present invention.
FIG. 7 is a perspective view showing an example of a boom base end portion.
8 is a cross-sectional view taken along the line BB in FIG.
FIG. 9 is a structural diagram showing another example of a conventional boom support section.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Lower traveling body, 2 ... Upper turning body, 3 ... Revo frame, 4 ... Driver's cab, 5 ... Machine cab, 6 ... Counterweight, 7 ... Boom, 8 ... Arm, 9 ... Bucket 10, 11, 12, ... Hydraulic cylinder, 13 ... boom base end, 14L, 14R ... boom support, 14A, 14B ... boom support, 14a, 14b ... side plate, 15L, 15R ... support leg, 16 ... foot pin, 17a, 17b, 17g ... Reinforcing plates, 17c, 17d ... plates, 18 ... partition plates, 20 ... working machines, 21, 22, 23 ... pin holes.

Claims (2)

A pair of side plates (14a, 14b) are erected parallel to each other on the frame, and a base end portion (15L, 15R) of the work machine (7) is interposed between the pair of side plates (14a, 14b). Are inserted and fitted with a predetermined gap (s2, s3), the pin hole (21) provided in the pair of side plates (14a, 14b) and the base end (15L, 15R) of the work machine (7) A foot pin (16) is inserted into the pin hole (22) provided in the base and the base end (15L, 15R) of the work machine (7) is rotatably supported, and the pair of side plates (14a, 14b) in the lower part of the work machine support structure of the work vehicle in which the partition plate (18) is welded between the side plates,
The side plate (14a) has a reinforcing plate (17a, 17g) at the boss portion near the pin hole (21) on the inner side surface, and the reinforcing plate (17a, 17g) from the vicinity of the shaft center of the foot pin (16). Work of the work vehicle characterized in that the gap (s4, s5) between the upper work equipment (7) and the base end (15L, 15R) is larger than the lower gap (s2) Machine support structure. The work machine support structure for a work vehicle according to claim 1 ,
A work machine support structure for a work vehicle, wherein the reinforcing plate (17g) of the side plate (14a) is a single plate having a tapered surface (17h) formed by gradually increasing thickness from above to below.

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