JP2004262302A - Axle case - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an axle case for enhancing the strength of a joining part of a body with a spindle. <P>SOLUTION: The axle case comprises a body 38 which is constituted of an upper member 30 and a lower member 31 which are joined with each other in a vertically overlapping manner with both end parts in the longitudinal direction formed in a substantially cylindrical shape, and substantially cylindrical spindles 33 to be joined with both end parts in the longitudinal method of the body 38. The vertical dimension of at least one set of joining end parts 1 and 2 between the body 38 and the spindles 33 is set to be smaller than that of adjacent parts 4 and 10 continuous to the joining end parts 1 and 2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an axle case, and more particularly to an axle case in which the strength of a joint between a main body and a spindle is improved.
[0002]
[Prior art]
The axle case is for accommodating a driving axle of a vehicle such as a truck, a differential gear, and the like. As shown in FIG. 7, the axle case extends in the vehicle width direction and is overlapped and joined vertically. The main body 38 includes a member 30 and a lower member 31 and has a substantially cylindrical shape at both ends in the longitudinal direction, and a substantially cylindrical spindle 33 joined to both longitudinal ends of the body 38. The upper and lower members 30 and 31 have a central portion in the longitudinal direction curved upward or downward, and a substantially circular hole (not shown) is formed in the central portion in the longitudinal direction of the main body 38. A hemispherical cover member 32 is attached to the main body 38 so as to cover the hole. Such an axle case 34 is also described in, for example, Patent Document 1 and the like.
[0003]
In such an axle case 34, both ends in the longitudinal direction of the main body 38 and the spindle 33 are welded to each other. That is, as shown in FIG. 8, the end of the main body 38 and the end of the spindle 33 are butted against each other and joined by fillet welding. FIG. 8 shows a cross section of an upper joining portion between the main body 38 and the spindle 33.
[0004]
By the way, various loads and moments act on the axle case 34 due to acceleration / deceleration and direction change of the vehicle, unevenness of the traveling road surface, and the like. In particular, a moment often acts to bend the axle case 34 upward or downward. For example, since wheels are provided on the outer peripheral portion of the spindle 33, when a reaction force is applied upward from the road surface, the longitudinal ends of the axle case 34 are lifted with the substantially central portion in the longitudinal direction as a fulcrum. Such a moment M1 (see FIG. 7) acts. As a result, stress is generated at the joint between the main body 38 and the spindle 33.
[0005]
For this reason, a relatively high strength is required at the joint between the main body 38 and the spindle 33. Therefore, conventionally, the welding penetration rate at the joint between the main body 38 and the spindle 33 is set to be 100% with respect to the plate thickness of the main body 38 and the spindle 33.
[0006]
In the case of butt welding of a plate material, when the penetration ratio is set to 100%, the plate material is generally welded from both the front and back sides. However, since the outer end of the spindle 33 has a reduced diameter, a welding rod is used. Is difficult to insert into the inside, and it is difficult to weld from behind. Therefore, when a large heat input is applied to secure a penetration rate of 100% only by welding from the front side, the molten metal drips on the back side of the joint and interferes with the drive axle incorporated in the axle case 34 and the like. There is a possibility that it will end up. In an extreme case, a hole is formed in the joint, which leads to oil leakage and a decrease in the strength of the joint.
[0007]
Therefore, as shown in FIG. 8, a cylindrical abutment 39 is inserted inside the joint between the main body 38 and the spindle 33. This can prevent the molten metal from dripping into the axle case 34 even when the penetration rate of welding is set to 100%. The abutment 39 may be integrally formed inside the main body 38 or the spindle 33.
[0008]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 08-067108
[Problems to be solved by the invention]
However, in such a conventional axle case, even if the welding penetration rate is set to 100%, a crack or the like may occur at the joint between the main body 38 and the spindle 33, and further improvement in strength has been desired.
[0010]
For example, the unwelded portion 40 at the contact surface between the main body 38 and the metal 39 and between the spindle 33 and the metal 39 acts as a crack formed in advance, and a stress is applied to the welding route portion 41 on the inner surface side of the joint. May be concentrated, and cracks may be generated therefrom.
[0011]
At the joint between the main body 38 and the spindle 33, residual stress is generated due to shrinkage of the weld metal after welding. At this time, the outer surface side of the joint has a longitudinal direction (right and left in the figure) which is advantageous in strength. Direction), but a longitudinal tensile stress, which is disadvantageous in strength, remains on the inner surface side of the joint.
[0012]
In other words, the inner surface of the joint between the main body 38 and the spindle 33 originally has a residual tensile stress, and the stress is concentrated when an external force is applied to the axle case 34. Is high.
[0013]
Therefore, an object of the present invention is to provide an axle case that solves the above-mentioned problem and improves the strength of a joint between a main body and a spindle.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a main body, which is composed of an upper member and a lower member which are vertically overlapped and joined, and whose both ends in the longitudinal direction are formed in a substantially cylindrical shape, and both ends in the longitudinal direction of the main body. An axle case comprising a substantially cylindrical spindle to be joined to the portion, wherein at least one of the joining ends of the main body and the spindle has a smaller vertical dimension than an adjacent portion continuous with the joining end. It is to be.
[0015]
According to this configuration, since a line passing through the center of the plate thickness between the main body and the spindle is formed to be bent, when a tensile stress occurs at the joint between the main body and the spindle, the point of action is changed to the plate at the joint. Deviates radially outward from the center of thickness. As a result, a moment acts such that a compressive stress is generated on the inner surface side of the joint. Therefore, two contradictory stresses, a tensile stress and a compressive stress, are generated on the inner surface side of the joint. Since these opposing stresses cancel each other, the stress generated on the inner surface side of the joint becomes smaller, which leads to an improvement in the strength and life of the joint.
[0016]
Here, the difference between the vertical dimension of the joint end and the vertical dimension of the adjacent part may be within a range of 20 to 50% of the plate thickness of the joint end.
[0017]
Further, the length of the joining end may be in the range of 1 to 2 times the plate thickness of the joining end.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
[0019]
FIG. 1 is an enlarged cross-sectional view of an upper joining portion between the main body of the axle case and the spindle according to the present embodiment. The schematic configuration of the axle case of the present embodiment is the same as that shown in FIG.
[0020]
That is, the axle case according to the present embodiment includes an upper member 30 and a lower member 31 which are vertically overlapped and joined, and a main body 38 having both ends in a substantially cylindrical shape in the longitudinal direction is formed. A substantially cylindrical spindle 33 joined to both ends in the longitudinal direction. The upper and lower members 30 and 31 have a central portion in the longitudinal direction curved upward or downward, and a substantially circular hole (not shown) is formed in the central portion in the longitudinal direction of the main body 38. A hemispherical cover member 32 is attached to the main body 38 so as to cover the hole.
[0021]
As shown in FIG. 1, the ends of the main body 38 and the spindle 33 abut against each other, and a cylindrical abutment 39 is inserted and arranged inside the abutting portion. Then, fillet welding is performed from the outer surface side (upper side in the figure) of the main body 38 and the spindle 33 to join them together. At this time, the penetration rate of welding is set to 100% with respect to the plate thickness T of the joining ends 1 and 2 of the main body 38 and the spindle 33. The thickness of the joining end 1 of the main body 38 is substantially equal to the thickness of the joining end 2 of the spindle 33.
[0022]
The feature of the axle case of the present embodiment is that the joint end 1 of the main body 38 with the spindle 33 is smaller in diameter than the adjacent portion 4 continuous with the joint end 1. Specifically, the main body 38 is connected to the joining end (reduced diameter portion) 1 formed to have the same diameter as the joining end 2 of the spindle 33 via the inclined portion 3, An adjacent portion 4 having a larger diameter than the end portion 1. That is, as shown in FIG. 2, the main body 38 has an end portion formed in a stepped shape. Such a stepped main body 38 can be relatively easily manufactured by molding each end into a stepped shape when the upper member 30 and the lower member 31 are press-formed.
[0023]
As described above, by reducing the diameter of the joint end 1 of the main body 38 from that of the adjacent part 4 continuous thereto, when a load or a moment acts on the axle case, the joint 5 between the main body 38 and the spindle 33 can be moved. In particular, the stress generated on the inner surface side of the joint 5 can be reduced, and the strength and life of the joint 5 can be improved. The reason will be described below.
[0024]
First, as shown in FIG. 2, in the upper joint portion between the main body 38 and the spindle 33, a region extending from the joint portion 5 on both sides in the longitudinal direction and having a constant width W is taken out as a microelement C. A side view of the microelement C is shown in FIG. In FIG. 3, the weld metal and the metal 39 are omitted for convenience.
[0025]
Now, it is assumed that a moment M2 acts on the axle case such that a tensile stress is generated at the upper joint portion 5 between the main body 38 and the spindle 33 (see FIG. 2). That is, a moment is applied to the axle case such that both ends are pressed downward with the substantially central portion in the longitudinal direction as a fulcrum. At this time, as shown in FIG. 3, a tensile stress TS is generated in the microelement C in a direction in which the main body 38 and the spindle 33 are separated from each other.
[0026]
Here, since the joining end 1 of the main body 38 is reduced in diameter with respect to the adjacent part 4, the line CL passing through the center of the thickness of the main body 38 and the spindle 33 is bent. On the other hand, the load acting on the joint portion 5 due to the tensile stress TS acts along the action line AL connecting the center of the plate thickness at both ends in the longitudinal direction of the microelement C. Therefore, the application point AP of the tensile stress TS at the joint 5 is shifted by a distance H outward (upper side) in the radial direction from the thickness center SC of the joint 5. As a result, as shown in the drawing, a local moment M3 acts on the joint 5 so as to push both sides of the center of the thickness SC of the joint 5 radially inward (downward). As a result, a tensile stress is generated on the outer surface side of the joint portion 5, and a compressive stress CS is generated on the inner surface side.
[0027]
As a result, on the inner surface side of the joint 5, a tensile stress TS generated by the moment M2 acting on the axle case and the tensile stress TS generated at a position deviated from the plate thickness center SC of the joint 5 are generated. And two compressive stresses CS, which are opposite to each other. Since these opposing stresses cancel each other, the stress generated on the inner surface side of the joint 5 is reduced, which leads to an improvement in the strength and life of the joint 5.
[0028]
In other words, the joining portion 5 has a substantially uniform tensile stress (+) at all positions in the radial direction as shown in FIG. 4A, and has a smaller thickness than the thickness center SC as shown in FIG. 4B. Two stresses are generated such that a tensile stress (+) occurs radially outward and a compressive stress (−) occurs radially inward of the plate thickness center SC. As a result, the stress generated at the joint 5 is as shown in FIG. 4C, and the stress generated on the inner surface side of the joint 5 is reduced.
[0029]
For example, in the conventional joint structure as shown in FIG. 8, since the line passing through the center of the plate thickness of the main body 38 and the spindle 33 is straight, the local moment M3 as shown in FIG. Only tensile stress is generated on the inner surface side of the portion. Therefore, compared with the present embodiment, a large tensile stress is generated on the inner surface side of the joint.
[0030]
As described above, in the axle case of the present embodiment, the joint end portion 1 of the main body 38 is smaller in diameter than the adjacent portion 4 continuous thereto, and the action point AP of the tensile stress TS generated in the joint portion 5 is changed to the joint portion 5. Is shifted from the center SC of the plate thickness to generate a compressive stress CS which cancels out the tensile stress TS on the inner surface side of the joint portion 5. As a result, the strength of the joint 5 is improved, and the life of occurrence of cracks and the life of fatigue fracture are extended. Therefore, according to the axle case of the present embodiment, it is possible to improve the strength and life of the joint 5 with a very simple structure and at low cost.
[0031]
In the axle case according to the present embodiment, the tensile stress generated on the outer surface side of the joint portion 5 increases, but this does not cause a serious problem. The reason is that there is no point where the stress is extremely concentrated on the outer surface side of the joint 5. In this case, stress concentrates on the toe 7 (see FIG. 1) at both ends in the longitudinal direction of the weld metal, but stress relief measures can be easily performed on the outer surface side of the joint 5. For example, stress concentration on the toe 7 can be avoided by grinding the outer surface of the joint 5 with a grinder or performing shot blasting. Further, since a compressive residual stress due to the contraction of the weld metal after welding exists on the outer surface side of the joint portion 5, a certain amount of tensile stress is absorbed. This is another reason why the outer surface side of the joint 5 is advantageous in strength. Therefore, even if the stress generated on the outer surface side of the joint 5 increases to some extent, the strength of the entire joint 5 can be improved by reducing the stress generated on the inner surface side.
[0032]
The present inventors, when confirming the effect of the present embodiment, when a moment is applied to a cylindrical member (pipe) having a reduced diameter at the end so as to push the end downward. Analysis (simulation) of the stress generated on the outer and inner surfaces of the upper section of the pipe was performed. The result is shown in FIG.
[0033]
In the figure, the horizontal axis represents the diameter reduction ratio of the pipe end with respect to the thickness of the pipe. The thickness of the pipe is T, and the difference between the basic diameter D1 of the pipe and the diameter D2 of the end (reduced diameter) is ΔD ( = D1-D2), it is represented by ΔD / T × 100%. In the figure, the vertical axis represents the stress generated on the outer and inner surfaces of the upper section of the pipe when the same moment is applied to a normal pipe whose end is not reduced in diameter. 1 shows the ratio of the stresses generated in FIG. In the drawing, the line indicated by a circle point indicates the stress generated on the inner surface of the upper section of the pipe, and the line indicated by a triangular point indicates the stress generated on the outer surface.
[0034]
As can be seen from the drawing, the stress generated on the inner surface decreases as the diameter reduction ratio increases from 0, that is, as the diameter of the pipe end decreases. However, the stress generated on the inner surface increases when the diameter reduction rate exceeds about 80%. In other words, it is understood that if the diameter of the end portion is too small, the effect of reducing the stress is reduced. Therefore, if only the inner surface side is considered, it is preferable that the diameter reduction ratio of the end portion be about 80%. However, as can be seen from the figure, the stress generated on the outer surface increases proportionally as the diameter reduction ratio of the end portion increases. The present inventors have found that in order to balance the stresses generated on the inner surface and the outer surface and optimally improve the overall strength of the joint portion 5, the diameter reduction ratio may be set within the range of 20 to 50%. confirmed. In other words, when the diameter reduction ratio is within this range, the stress generated on the inner surface can be sufficiently reduced, and the stress generated on the outer surface does not become excessively large, resulting in an optimum balance. Therefore, in the axle case according to the present embodiment as shown in FIG. 1, the difference between the diameter of the joining end 1 of the main body 38 and the diameter of the adjacent part 4 is set to be 20 It is preferable to be in the range of 50% to 50%.
[0035]
Furthermore, the present inventors have confirmed that it is preferable that the length L of the joining end portion 1 shown in FIG. 1 be within a range of 1 to 2 times the thickness T of the joining end portion 1. In other words, if the length L of the joint end 1 is too short, it is difficult to form the main body 38 (upper and lower members 30, 31). Conversely, if the length L is too long, the local moment M3 acting on the joint 5 (see FIG. 3). ) Is reduced, so that the stress reduction effect is reduced.
[0036]
In the above embodiment, the example in which the diameter of the joint end 1 of the main body 38 is reduced has been described, but the present invention is not limited in this respect. That is, as shown in FIG. 6A, the joining end 2 of the spindle 33 may be reduced in diameter with respect to the adjacent portion 10 which is continuous with the spindle 33, or as shown in FIG. The diameter of both the joint ends 1 and 2 of the spindle 33 may be reduced. In these embodiments, the same effects as in the embodiment shown in FIG. 1 can be obtained.
[0037]
Further, in the present invention, it is not always necessary to reduce the diameter of the joining ends 1 and 2 of the main body 38 and / or the spindle 33 over the entire circumference. That is, as described in the section of “Prior Art”, since the moment acting on the axle case often acts in the vertical direction, at least the vertical direction of the joining end portions 1 and 2 of the main body 38 and / or the spindle 33 is required. May be made smaller than the vertical dimension of the adjacent portions 4 and 10 that are continuous with the joining ends 1 and 2. In that case, the main body 38 and / or the spindle 33 may be fitted into a mold and compressed (pressed) in the vertical direction, and only the vertical dimension may be shortened without changing the horizontal dimension. Alternatively, the main body 38 and / or the spindle 33 may be simply crushed from above and below to form a substantially elliptical shape. When the main body 38 and / or the spindle 33 are simply crushed and formed, a mold or the like is not required, so that it is possible to provide at a lower cost. These processes may be performed before or after the main body 38 and the spindle 33 are joined.
[0038]
Up to now, the joint ends 1 and 2 of the main body 38 and / or the spindle 33 have been described as being reduced in diameter with respect to the adjacent parts 4 and 10. However, conversely, the adjoining part of the main body 38 and / or the spindle 33 may be reduced. Needless to say, diameters of 4, 10 may be increased.
[0039]
【The invention's effect】
In short, according to the present invention, an excellent effect that the strength of the joint between the main body and the spindle can be improved simply and at low cost is exhibited.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view of an upper joining portion between a main body and a spindle in an axle case according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a joint between a main body and a spindle in the axle case of FIG. 1;
FIG. 3 is an explanatory diagram for explaining stress generated at a joint between a main body and a spindle.
FIG. 4A shows a tensile stress generated at a joint between a main body and a spindle.
(B) shows the stress generated at the joint by the local moment acting on the joint between the main body and the spindle.
(C) shows the stress generated at the joint between the main body and the spindle.
FIG. 5 is a graph showing the relationship between the diameter reduction ratio of the pipe end and the stress generated on the outer and inner surfaces of the upper cross section of the pipe.
FIG. 6A is an enlarged cross-sectional view of an upper joining portion between a main body and a spindle in an axle case according to another embodiment of the present invention.
(B) is an enlarged sectional view of an upper joining portion between a main body and a spindle in an axle case according to another embodiment of the present invention.
FIG. 7 is a front view of the axle case.
FIG. 8 is an enlarged sectional view of an upper joint portion between a main body and a spindle in a conventional axle case.
[Explanation of symbols]
1, 2 joining ends 4, 10 adjacent portion 5 joining portion 30 upper member 31 lower member 33 spindle 38 main body

Claims (3)

A main body composed of an upper member and a lower member that are overlapped and joined together vertically, and both ends in the longitudinal direction are formed in a substantially cylindrical shape, and a substantially cylindrical spindle that is joined to both ends in the longitudinal direction of the main body. An axle case with
An axle case characterized in that at least one joint end of the main body and the spindle has a smaller vertical dimension than an adjacent part continuous with the joint end. The axle case according to claim 1, wherein a difference between a vertical dimension of the joint end and a vertical dimension of the adjacent part is within a range of 20 to 50% of a plate thickness of the joint end. 3. The axle case according to claim 1, wherein a length of the joint end is in a range of 1 to 2 times a plate thickness of the joint end.

Images