Axle case structure

Abstract

To provide an axle case structure that restrains buckling deformation which occurs at a connection part of a shoulder round part on an upper surface of an axle case body which is bent downward in a convex shape by car weight and road surface reaction, and a horizontal part.SOLUTION: An axle case structure includes an axle case main body 7 having: a banjo part 3 with openings 2 formed at front and rear; horizontal parts 4 which are arranged on the left and right of the banjo part 3 and which is subjected to a car weight W; spindles 5 which are connected to outer ends in the car width direction of the horizontal parts 4 and which are subjected to a road surface reaction R; and shoulder round parts 6 connecting the banjo parts 3 and the horizontal parts 4. A ring 16 with a reinforcement flange is attached to the axle case main body 7. The ring 16 with a reinforcement flange includes: a central ring part 16a surrounding the opening 2 of the banjo part 3; and a reinforcing flange part 16b extending from the left and right in the car width direction of the central ring part 16a to a position beyond a connection part of the shoulder round part 6 and the horizontal part 4 outward in the car width direction .SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an axle case structure that increases the yield strength of the axle case body, which is bent and deformed downward in a convex shape due to the vehicle weight and road surface reaction force. [Background technology]

[0002] Fig. 1 shows an overall perspective view of a conventional so-called banjo-type axle case structure 1j, and Fig. 2 shows its exploded view. This axle case structure 1j has an axle case main body 7, which is made up of a banjo section 3 that bulges outward in the vertical direction and has openings 2 for accommodating differential mechanisms formed at the front and rear of the vehicle overall length, horizontal sections 4 located on either side of the banjo section 3 in the vehicle width direction, spindles 5 connected to the outer ends of the horizontal sections 4 in the vehicle width direction, and shoulder radius sections 6 that connect the banjo section 3 and the horizontal sections 4 and whose vertical dimension gradually decreases toward the outside in the vehicle width direction. As shown in Fig. 2, the axle case main body 7, excluding the spindle 5, is made up of two sheet metal parts 8 (hereinafter also referred to as side plates 8) with a grooved cross section, each divided into an upper and lower section. These side plates 8 are formed by press-molding a flat blank plate. In the opening 2 formed in the banjo portion 3 by welding the upper and lower side plates 8 together, a triangular cutout 9 is formed so that the opening edge is widened outward to the left and right in the vehicle width direction in order to reduce the width dimension of the blank plate, and a triangular plate 10 is welded to the cutout 9 (see Patent Document 1).

[0003] As shown in FIG. 1, the horizontal section 4 has a circular cross-sectional section 4a to which the spindle 5 is attached and a rectangular cross-sectional section 4b to which the suspension is attached. Road reaction force R acts upward on the spindle 5 via the wheels, and vehicle weight W acts downward on the rectangular cross-sectional section 4b via the suspension. A carrier (not shown) with a differential mechanism attached is attached to an opening 2 on the front side of the banjo section 3 in the vehicle length direction via a carrier mounting ring 11 shown in FIG. 2. The opening 2 on the rear side of the banjo section 3 in the vehicle length direction is covered by a cover 12. The cover 12 has a bowl-shaped cover main body 12a and a cover flange 12b formed along the outer periphery of the cover main body 12a. The cover flange 12b is welded circumferentially to the rear side of the banjo section 3 of the axle case main body 7 so as to cover the opening 2. Lubricating oil for lubricating the gears of the differential mechanism is stored inside the banjo section 3. This axle case structure 1j is subjected to vertical forces as its main loads. That is, the vehicle weight W is applied downward via the suspension to the rectangular cross-section portion 4a of the horizontal portion 4, and the road surface reaction force R is applied upward via the wheels to the spindle 5. These loads W and R cause elastic and plastic deformation in the axle case structure 1j.

[0004] FIG. 3(a) shows the deformation state of the axle case structure 1j when loads W and R are applied, with the amount of deformation magnified. Due to the loads W and R, the center axis of the axle case structure 1j is deformed downward in a convex shape, and the cover flange 12b is deformed from a perfect circle shape to an approximately rice ball shape. Furthermore, the shoulder radius portion 6 on the underside of the banjo portion 3 has a curvature radius The shoulder curve 6 on the upper surface is deformed in the direction of increasing curvature. radiusThe deformation of the cross section near the connection 13 between the shoulder radius portion 6 and the horizontal portion 4 of the axle case main body 7 is shown in Figure 3(b), a cross section taken along line IIIb-IIIb in Figure 3(a). As shown in Figure 3(b), the cross-sectional shape of the axle case main body 7 near the connection 13 between the shoulder radius portion 6 and the horizontal portion 4 is symmetrical about the central axis as shown by the dashed lines before the loads W and R are applied, but when the loads W and R are applied, the cross-sectional shape deforms asymmetrically in the vertical and horizontal directions as shown by the solid lines. The area where the amount of deformation is greatest in this cross-sectional area is the upper corner 14 on the carrier side of the axle case main body 7 (the front side in the vehicle overall length direction).

[0005] The deformations shown in Figures 3(a) and 3(b) can cause fatigue cracks in the welds of the triangular plate 10 near the banjo 3 and the cover flange 12b, potentially resulting in defects such as buckling near the connection 13 between the top shoulder radius 6 and the horizontal section 4. These defects occur more frequently as the deformation of the axle case structure 1j increases under loads W and R. Factors contributing to the increased deformation include reducing the thickness of the axle case body 7 and cover 12 to reduce weight and cost, limiting the cross-sectional dimensions (vertical dimensions) of the axle case body 7 due to vehicle layout constraints, resulting in insufficient strength against vertical bending, and applying vertical loads greater than those expected due to excessive loading. Each of these factors indicates a low rigidity of the axle case body 4 under loads W and R, particularly in the area from the shoulder radius 6 to the horizontal section 4, where the vertical dimensions gradually decrease.

[0006] Several methods have been implemented to address these problems. To address fatigue cracks in the welded portion near the banjo portion 3, measures have been taken such as increasing the thickness of the side plates 8 and cover 12 that make up the axle case main body 7, as well as increasing strength by welding a circular cover reinforcing ring 15 to the rear surface of the axle case main body 7 and welding the cover 12 to the cover reinforcing ring 15, as shown in Figure 2 (see Patent Document 2). To address buckling deformation near the connection 13 between the shoulder radius portion 6 and the horizontal portion 4 on the top surface of the axle case main body 7 shown in Figure 3(a), measures have been taken such as changing the material of the side plates 8 that make up the axle case main body 7 to a material with higher tensile strength, increasing the thickness of the side plates 8 to increase strength, or increasing the curvature of the shoulder radius portion 6. radius One possible measure would be to widen the shoulder radius portion 6 and connect it to the horizontal portion 4 as a gentle slope to ease stress concentration and suppress buckling deformation near the connection 13 between the shoulder radius portion 6 and the horizontal portion 4. Another possible measure would be to add reinforcing members located on the outer or inner surface of the axle case main body 7 to the buckling deformation area (near the connection 13 between the shoulder radius portion 6 and the horizontal portion 4 on the top surface of the axle case main body 7).

[0007] However, changing the thickness or shape of these components requires changes to the press-molding dies, which incurs significant costs and increases the overall thickness of the axle case body 7, resulting in an increase in product mass. In particular, adding a reinforcing member to address buckling deformation near the connection 13 between the shoulder radius section 6 and horizontal section 4 on the top surface of the axle case body 7 increases the product mass and cost of the additional part, as well as the cost of changing the production equipment. For the axle case body 7, an automotive part for which weight reduction and cost reduction are strongly required, measures that result in significant increases in product mass, dies, and equipment costs are something that should be avoided.

[0008] Furthermore, Patent Document 3 discloses a technology for increasing the bending rigidity of the axle case body 7, in which a cover 12 covering the opening 2 of the axle case body 7 is formed in a horizontally elongated shape. However, this technology increases the bending rigidity of the axle case body 7 against loads acting in the fore-and-aft direction of the axle case body 7 (front and rear in the overall vehicle length direction) by providing horizontal ribs on the horizontally elongated cover 12. However, because the cover 12 does not extend from the banjo portion 3 of the axle case body 7 to the horizontal portion 4 on the outer side of the shoulder radius portion 6 in the vehicle width direction, it is not possible to increase the bending rigidity near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 when a vertical load is applied. Even if the cover 12 were extended from the shoulder radius portion 6 to the horizontal portion 4, the cover 12 is thinner than the axle case body 7 and is hollow in structure, so it flexibly deforms under load, and the contribution of the cover 12 to the rigidity of the vertical load is extremely small. Furthermore, by expanding the cover 12 horizontally, the amount of lubricating oil stored inside increases, which is problematic from the perspective of the demand for weight reduction. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-262328 [Patent Document 2] Japanese Patent Publication No. 14402 / 1983 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-85392 Summary of the Invention [Problem to be solved by the invention]

[0010] As explained above, in the conventional axle case structure 1j shown in Figures 1 and 2, when road reaction force R is applied upward to spindle 5 via the wheel and vehicle weight W is applied downward to horizontal section 4 via the suspension, it bends convexly downward as shown in Figure 3(a), and this bending deformation can cause buckling deformation near connection 13 between shoulder radius section 6 and horizontal section 4 on the top surface of axle case main body 7. Effective measures to fundamentally address this buckling deformation include changing the plate thickness of axle case main body 7, enlarging the radius shape of shoulder radius section 6, and increasing rigidity with new reinforcing members, but these changes inevitably incur significant costs due to changes in press molding dies and production equipment, as well as a significant increase in product mass.

[0011] Therefore, the object of the present invention is to provide an axle case structure that can appropriately suppress buckling deformation that occurs near the connection between the shoulder curve portion and the horizontal portion on the upper surface of the axle case body when the axle case body is bent convexly downward due to the vehicle weight and road reaction force, with a minimal increase in mass and cost. [Means for solving the problem]

[0012] According to the present invention, which has been devised to achieve the above object, there is provided an axle case structure having an axle case body which comprises: banjo sections which are shaped to bulge in the vertical direction and have openings for accommodating differential mechanisms formed at the front and rear in the vehicle overall length direction; horizontal sections which are arranged on either side of the banjo section in the vehicle width direction and to which the vehicle weight is applied via suspension; spindles which are connected to the outer ends of the horizontal sections in the vehicle width direction and to which road surface reaction forces are applied via the wheels; and shoulder radius sections which connect the banjo section and the horizontal section and whose dimension in the vertical direction gradually decreases as they extend outward in the vehicle width direction, and a reinforcing flanged ring is attached to at least one of the front and rear sections in the vehicle overall length direction of the axle case body, and the reinforcing flanged ring has a central ring section which surrounds the opening of the banjo section, and reinforcing flange sections which extend outward in the vehicle width direction from the left and right sides of the central ring section in the vehicle width direction to positions beyond the connections between the shoulder radius sections and the horizontal sections. The reinforcing flanged ring is not bent to wrap around the upper and lower surfaces of the axle case body when attached to at least one of the front and rear surfaces in the vehicle overall length direction of the axle case body, but is formed in a plate shape that covers at least one of the front and rear surfaces, and the outer edge of the reinforcing flanged ring is welded to the axle case body along its circumferential direction.An axle case structure is provided, characterized by:

[0013] In the axle case structure of the present invention, the length of the horizontal portion may be different on the left and right sides in the vehicle width direction, and the length of the longer horizontal portion beyond the connection between the shoulder radius portion of the reinforcing flange portion and the horizontal portion may be longer than the length of the shorter horizontal portion beyond the connection between the shoulder radius portion of the reinforcing flange portion and the horizontal portion.

[0014] In the axle case structure of the present invention, a notch is formed in the opening of the banjo portion so as to widen the opening edge outward to the left and right in the vehicle width direction, and a ring with a reinforcing flange may be formed to cover the notch.

[0015] In the axle case structure of the present invention, the axle case body excluding the spindle is made up of sheet metal parts with a grooved cross section, divided into two parts, upper and lower, and these sheet metal parts are formed by press-molding a blank plate, and the blank plate before press-molding may have a shape in which the part that will become the missing part has been removed from the flat plate towards the inside of the plate width. [Effects of the Invention]

[0016] The axle case structure according to the present invention can provide the following effects. (1) A reinforcing flange ring attached to at least one of the front and rear surfaces of the axle case body has a central ring portion surrounding the opening of the banjo portion and reinforcing flange portions extending outward in the vehicle width direction from the left and right sides of the central ring portion to a position beyond the junction of the shoulder radius portion and the horizontal portion, and this reinforcing flange portion improves the vertical bending rigidity of the axle case body near the junction of the shoulder radius portion and the horizontal portion. As a result, buckling deformation caused by vehicle weight and road reaction force near the junction of the shoulder radius portion and the horizontal portion on the top surface of the axle case body can be appropriately suppressed. (2) Because the reinforcing flange of the reinforcing flange-equipped ring improves the vertical bending rigidity near the connection between the shoulder radius and horizontal sections of the axle case body, there is no need to change the shape or material of the axle case body or cover or add new reinforcing parts other than the ring to increase the vertical bending rigidity, and the existing axle case body and cover can be used as is. This makes it possible to reduce, at low cost, the buckling deformation that occurs near the connection between the shoulder radius and horizontal sections of the top surface of the axle case body due to vehicle weight and road reaction force. (3) The ring with reinforcing flanges has a central ring section that surrounds the opening of the banjo section, and reinforcing flanges that extend outward in the vehicle width direction from the left and right sides of the central ring section to a position beyond the connection between the shoulder radius section and the horizontal section (see Figure 4).Compared to conventional circular cover reinforcing rings and carrier mounting rings (see Figure 2), this ring has only the reinforcing flange section added.Therefore, with a minimal increase in mass, it is possible to suppress buckling deformation that occurs near the connection between the shoulder radius section and the horizontal section on the top surface of the axle case body due to vehicle weight and road reaction force. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an overall perspective view of an axle case structure showing a conventional example. [Figure 2] FIG. 2 is an exploded perspective view of the axle case structure. [Figure 3] 3(a) is an explanatory diagram showing the state in which the above-mentioned axle case structure is bent and deformed in a convex downward shape due to the vehicle weight W and road surface reaction force R, with the amount of deformation magnified, and FIG. 3(b) is a cross-sectional view taken along line IIIb-IIIb in FIG. 3(a). [Figure 4] 1 is an exploded perspective view of an axle case structure according to an embodiment of the present invention. FIG. [Figure 5] 5(a) is a front view of the axle case structure according to this embodiment, (b) is a cross-sectional view taken along line Vb-Vb in FIG. 5(a), and (c) is a cross-sectional view taken along line Vc-Vc in FIG. 5(a). [Figure 6]FIG. 2 is a front view of the axle case structure according to the present embodiment, illustrating how the lengths of the left and right reinforcing flange portions differ due to the difference in length between the left and right horizontal portions. [Figure 7] (a) is a front view of an axle case body without a triangular plate, and (b) is a front view of an axle case body showing a modified example of the present invention in which missing portions are formed on the left and right sides of the opening and are covered with a ring with a reinforcing flange. [Figure 8] This is an explanatory diagram showing the difference in width between the blank plate used when press-molding the side panel of the axle case body without the triangular plate shown in Figure 7(a) and the blank plate used when press-molding the side panel of the axle case body with the missing portion formed as shown in Figure 7(b). DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0019] (Outline of axle case structure 1) Figure 4 shows an exploded oblique view of an axle case structure 1 according to one embodiment of the present invention, Figure 5(a) shows a front view of the axle case structure 1, Figure 5(b) shows a cross section taken along line Vb-Vb in Figure 5(a), and Figure 5(c) shows a cross section taken along line Vc-Vc in Figure 5(a).

[0020] As shown in Figures 4 and 5(a), the axle case structure 1 of this embodiment includes an axle case main body 7, which includes a banjo section 3 bulging vertically and having openings 2 for accommodating differential mechanisms formed at the front and rear of the vehicle in the vehicle length direction; horizontal sections 4 arranged on either side of the banjo section 3 in the vehicle width direction and receiving the vehicle weight W (see Figure 1) via the suspension; spindles 5 connected to the outer ends of the horizontal sections 4 in the vehicle width direction and receiving the road reaction force R (see Figure 1) via the wheels; and shoulder radius sections 6 connecting the banjo section 3 and the horizontal section 4 and gradually decreasing in vertical dimension outward in the vehicle width direction. The horizontal section 4 has a circular cross-sectional section 4a to which the spindle 5 is attached and a rectangular cross-sectional section 4b to which the suspension is attached. The rectangular cross-sectional section 4b connected to the shoulder radius sections 6 has a substantially constant cross-sectional shape along the vehicle width direction. That is, at least the portion of the horizontal section 4 connected to the shoulder radius sections 6 is horizontal.

[0021] As shown in Figures 4, 5(a), and 5(b), reinforcing flanged rings 16 are attached to the front and rear surfaces of the axle case body 7 in the vehicle length direction. The reinforcing flanged ring 16 has a central ring portion 16a that surrounds the opening 2 of the banjo portion 3 and reinforcing flange portions 16b that extend outward in the vehicle width direction from the left and right sides of the central ring portion 16a to a position beyond the connection portion 13 between the shoulder curved portion 6 and the horizontal portion 4. As shown in Figure 4, the reinforcing flanged ring 16 on the front side in the vehicle length direction is formed with screw holes 17 for bolting a carrier (not shown) to which a differential mechanism is attached. A cover 12 is welded to the reinforcing flanged ring 16 on the rear side in the vehicle length direction. The cover 12 has a bowl-shaped cover main body 12a and a cover flange 12b formed along the outer periphery of the cover main body 12a, and the cover flange 12b is welded to the central ring portion 16a of the reinforcing flanged ring 16 along the circumferential direction. The outer edge of the reinforcing flanged ring 16 is welded along the circumferential direction to the axle case body 7. Reference numeral 18 in FIG. 5(b) denotes a weld bead.

[0022] In the axle case structure 1 according to this embodiment, the carrier mounting ring 11 of the conventional axle case structure 1j shown in FIG. 2 is replaced with a front reinforcing flange ring 16 shown in FIG. 4, and the conventional cover reinforcing ring 15 shown in FIG. 2 is replaced with a rear reinforcing flange ring 16 shown in FIG. 4. The reinforcing flange portions 16b of the carrier mounting ring 16 increase the vertical bending rigidity near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 of the axle case main body 7, thereby suppressing buckling deformation that occurs near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 on the top surface of the axle case main body 7. Furthermore, the triangular plate 10 shown in FIG. 2 has been eliminated as shown in FIG. 4, and the missing portion 9 formed as a result of its elimination is covered by the reinforcing flange portion 16b of the reinforcing flange ring 16 as shown in FIGS. 4 and 5(a). In other words, the reinforcing flange portion 16b of the reinforcing flange ring 16 also functions as a cover for the missing portion 9.

[0023] (Axle case body 7) As shown in Figure 4, in the axle case structure 1 according to this embodiment, the axle case body 7, excluding the spindle 5, is made up of two sheet metal parts 8 (side plates) with a grooved cross section, each divided into an upper and lower section. These side plates 8 are formed by press-molding a flat blank plate. In the opening 2 formed in the banjo portion 3 by welding the upper and lower side plates 8 together, a triangular cutout 9 is formed so that the edges of the opening are widened outward to the left and right in the vehicle width direction in order to reduce the unfolded width of the side plate 8, i.e., the width dimension of the blank plate. As shown in Figure 5(a), the cutout 9 is covered by the reinforcing flange portion 16b of the reinforcing flange-equipped ring 16.

[0024] (Reinforced flanged ring 16) As shown in Figure 4, in this embodiment, the reinforcing flanged ring 16 is attached to both the front and rear surfaces of the axle case main body 7 in the vehicle overall length direction. However, the reinforcing flanged ring 16 may be attached to only one of the front and rear surfaces of the axle case main body 7, provided that a predetermined increase in rigidity can be secured that can prevent buckling deformation that occurs near the connection 13 between the shoulder curved portion 6 and the horizontal portion 4 on the top surface of the axle case main body 7, as described above with reference to Figure 3.

[0025] That is, in the axle case structure 1 shown in Fig. 4, the front reinforcing flanged ring 16 may be replaced with the carrier mounting ring 11 shown in Fig. 2 while leaving the rear reinforcing flanged ring 16, or the front reinforcing flanged ring 16 may be replaced with the cover reinforcing ring 15 shown in Fig. 2 while leaving the front reinforcing flanged ring 16, or the rear reinforcing flanged ring 16 may be omitted. Note that the triangular plate 10 shown in Fig. 2 is attached to cover the missing portion 9 that is no longer covered by the reinforcing flanged ring 16.

[0026] As shown in Figure 6, the reinforcing flange ring 16 has a central ring portion 16a that surrounds the opening 2 of the banjo portion 3, and reinforcing flange portions 16b that extend outward in the vehicle width direction from the left and right sides of the central ring portion 16a to positions that extend beyond the connection portion 13 between the shoulder round portion 6 and the horizontal portion 4. The left-right length of the reinforcing flange portions 16b is within a range that includes the buckling deformation portion (the connection portion 13 between the shoulder round portion 6 and the horizontal portion 4) shown in Figure 3. The buckling deformation portion is the beginning of the gradual expansion of the cross-sectional dimension in the up-down direction from the rectangular cross-sectional portion 4b of the horizontal portion 4 to the shoulder round portion 6, i.e., the connection portion 13 between the horizontal portion 4 and the shoulder round portion 6.

[0027] (Length of the left and right reinforcing flange portions 16b of the reinforcing flanged ring 16) As shown in Figure 6, in an axle case structure 1 in which the banjo portion 3 is offset to one side in the left-right direction of the vehicle, the lengths (H1, H2) of the left and right horizontal portions 4 of the banjo portion 3 are different on the left and right sides in the vehicle width direction (H1 > H2), and buckling deformation is more likely to occur in the buckling deformation portion 13 on the side where the horizontal portion 4 is longer (the left side in Figure 6). That is, the moment arm (L1, L2) of the road surface reaction force R applied upward to the spindle 5 with respect to the buckling deformation portion 13 is such that the arm length (L1) on the left side (H1) where the horizontal portion 4 is longer is longer than the arm length (L2) on the right side (H2) where the horizontal portion 4 is shorter (L1 > L2), and therefore the buckling deformation portion 13 on the left side is more likely to buckle than the buckling deformation portion 13 on the right side.

[0028] For this reason, as shown in Figure 6, the length (X1) of the reinforcing flange portion 16b in the longer horizontal portion 4 beyond the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 is made longer than the length (X2) of the reinforcing flange portion 16b in the shorter horizontal portion 4 beyond the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4, thereby making the bending rigidity and yield strength of the left-side buckling deformation portion 13 higher than those of the right-side buckling deformation portion 13, and suppressing buckling deformation in the left-side buckling deformation portion 13, which is prone to buckling deformation.

[0029] (Plate thickness of ring 16 with reinforcing flange) The plate thickness of the front reinforcing flanged ring 16 shown in FIG. 4 is the same as that of the carrier mounting ring 11 shown in FIG. 2. For example, in an axle case structure 1 for a large vehicle (with an axle case main body 7 having a plate thickness of approximately 14 mm), the plate thickness of the reinforcing flanged ring 16 is equal to the plate thickness of the carrier mounting ring 11, approximately 15 mm. By making the plate thickness of the reinforcing flanged ring 16 of the present invention the same as that of the conventional carrier mounting ring 11, if the gears of the differential mechanism supported by the carrier attached to the conventional carrier mounting ring 11 do not interfere with the inner surface of the banjo portion 3 and the inner surface of the cover 12, then there will be no interference even if the conventional carrier mounting ring 11 is replaced with the reinforcing flanged ring 16 of the present invention. In other words, the front reinforcing flanged ring 16 is a component that combines the carrier mounting function due to its plate thickness equivalent to that of the carrier mounting ring 11 and the reinforcing function of the connection portion (buckling deformation portion) 13 between the shoulder curved portion 6 and the horizontal portion 4.

[0030] Furthermore, when the rear reinforcing flange ring 16 shown in FIG. 4 is applied to the axle case structure 1j equipped with the cover reinforcing ring 15 shown in FIG. 2, the plate thickness of the reinforcing flange ring 16 is set to the same plate thickness as the cover reinforcing ring 15. For example, in an axle case structure 1 for a large vehicle (the plate thickness of the axle case body 7 is approximately 14 mm), the "plate thickness of the reinforcing flange ring 16" = "plate thickness of the cover reinforcing ring 15" = "approximately 15 mm." By making the plate thickness of the reinforcing flange ring 16 of the present invention the same as that of the conventional cover reinforcing ring 15, if the inner surface of the cover 12 attached to the conventional cover reinforcing ring 15 does not interfere with the gears of the differential mechanism inside the banjo portion 3, there will be no interference even if the conventional cover reinforcing ring 15 is replaced with the reinforcing flange ring 16 of the present invention. In other words, the rear reinforcing flange ring 16 is a component that combines the cover reinforcing function with a plate thickness equivalent to that of the cover reinforcing ring 15, and the reinforcing function of reinforcing the connection portion (buckling deformation portion) 13 between the shoulder curve portion 6 and the horizontal portion 4.

[0031] (Improved section modulus due to reinforcing flanged ring 16) The cause of buckling deformation at the connection (buckling deformation portion) 13 between the shoulder curved portion 6 and the horizontal portion 4 of the axle case main body 7 is deformation of the rectangular cross section of the axle case main body 7, as shown in Figure 3(b), which is a cross section taken along line IIIb-IIIb in Figure 3(a). The reinforcing flanged ring 16 shown in Figure 4 reinforces the side of the axle case main body 7, thereby improving the cross-sectional performance of the rectangular cross section and suppressing deformation of the cross section near the buckling deformation portion 13. The effect of the reinforcing flanged ring 16 on cross-sectional performance will be explained below.

[0032] In the axle case structure 1 shown in Figure 5(a), Figure 5(b) shows a cross section of the rectangular cross-sectional portion 4b of the horizontal section 4 where the reinforcing flange portion 16b of the reinforcing flanged ring 16 is present, and Figure 5(c) shows a cross section of the portion where the reinforcing flange portion 16b is not present. For these cross sections, as an example of the dimensions of the axle case structure 1 for a large vehicle, the cross-sectional performance will be verified when the rectangular cross-sectional portion 4b of the horizontal section 4 of the axle case main body 7 has a height a of 160 mm, a width b of 140 mm, and a thickness c of 14 mm, and the height d of the reinforcing flange portion 16b of the reinforcing flanged ring 16 is 130 mm and a thickness e of 15 mm.

[0033] When the cross-sectional performance of each of the cross sections shown in Figure 5(b) and Figure 5(c) is calculated and compared using the section modulus, which is related to the stress value, the section modulus value of the portion where the reinforcing flange portion 16b is present shown in Figure 5(b) is 3.6 x 10^5 mm^3, while the section modulus value of the portion where the reinforcing flange portion 16b is not present shown in Figure 5(c) is 2.9 x 10^5 mm^3. The presence of the reinforcing flange portion 16b improves the cross-sectional performance by more than 20% compared to when the reinforcing flange portion 16b is not present. In other words, providing the reinforcing flange portion 16b can reduce the stress in the buckling deformation portion 13 by more than 20%, making it an effective measure against deformation.

[0034] If this improvement in cross-sectional performance were to be achieved simply by increasing the plate thickness c of the axle case body 7, the plate thickness c of the axle case body 7 would need to be changed from the previous 14 mm to 19 mm, which would result in a significant increase in the product mass of the modified axle case structure 1 by 28 kg, from 79 kg before the change to 107 kg. On the other hand, as shown in Figure 4, if a reinforcing flanged ring 16 is added, although the mass of the reinforcing flanged ring 16 increases, the four triangular plates 10 shown in Figure 2 are no longer necessary, so the increase in mass of the axle case structure 1 is limited to 10 kg, which is also an effective measure from the perspective of mass control.

[0035] Furthermore, in the axle case structure 1 according to this embodiment shown in Figure 4, the number of components of the axle case body 7, excluding the spindle 5, is significantly reduced from nine components (two side plates 8, four triangular plates 10, one carrier mounting ring 11, one cover reinforcement ring 15, and one cover 12) in the pre-measure (conventional product) shown in Figure 2 to five components (two side plates 8, two reinforcement flanged rings 16, and one cover 12).

[0036] Furthermore, because the reinforcing flanged ring 16 increases the bending rigidity and yield strength of the buckling deformation portion 13 and no modifications are made to the side plates 8, the upper and lower side plates 8 of the conventional axle case body 1j shown in FIG. 2 can be used in the axle case structure 1 shown in FIG. 4 without changing their shape or dimensions. In addition, when joining the front and rear reinforcing flanged rings 16 shown in FIG. 4 to the axle case body 7, the existing equipment process used to join the conventional carrier mounting ring 11 and cover reinforcing ring 15 shown in FIG. 2 to the axle case body 7 can be reused. As a result, the manufacturing cost of the axle case structure 1 according to this embodiment shown in FIG. 4 is lower than that of the conventional axle case structure 1j shown in FIG. 2.

[0037] (Missing part 9) As shown in Figures 4 and 5(a), the opening 2 of the banjo portion 3 has a notch 9 formed in it so that the opening edge widens outward to the left and right in the vehicle width direction, and a reinforcing flange ring 16 is formed to cover the notch 9. In this embodiment, in which the reinforcing flange ring 16 is added to both the front and rear of the axle case body 7, buckling deformation at the connection 13 between the shoulder curved portion 6 and the horizontal portion 4 can be suppressed. This also reduces the material costs of the upper and lower side plates 8 that make up the axle case body 7. As described above, the upper and lower side plates 8 are formed by press-molding flat blank plates to have a channel-shaped cross section. However, by forming a triangular notch 9 in the opening 2 of the banjo portion 3 of the axle case body 7, which is formed by welding the upper and lower side plates 8, so that the opening edge widens outward to the left and right in the vehicle width direction, the unfolded width of the side plate 8 is reduced, thereby reducing the width of the blank plate. This improves the material yield of the axle case body 7 and reduces material costs.

[0038] As shown in Figure 7(a), there is also an axle case structure 1a in which the opening 2 of the banjo portion 3 of the axle case main body 7 does not have the notch 9 that widens the opening edge to the left and right in the vehicle width direction, and the triangular plate 10 shown in Figure 2 is not present. While eliminating the triangular plate 10 is expected to be effective in suppressing fatigue cracking from the weld between the triangular plate 10 and the axle case main body 7, it also increases the expanded width of the side plate 8, which increases the width of the blank plate used to press-form the side plate 8, resulting in reduced material yield and increased material costs. Axle case structures 1a without the triangular plate 10 are used in vehicles with relatively light loads. Compared to axle case structures 1 for general large vehicles, their overall shape is narrower and longer, making them more susceptible to defects such as buckling deformation near the connection 13 between the shoulder curve portion 6 and the horizontal portion 4.

[0039] Figure 7(b) shows an axle case structure 1b in which reinforcing flange rings 16 are used to reinforce the joints 13 between the shoulder radius sections 6 and the horizontal sections 4. Reinforcing flange rings 16 are added to both the front and rear of the axle case body 7, and the areas near the joints 13 between the shoulder radius sections 6 and the horizontal sections 4, which require reinforcement, are double-layered (see Figure 5(b)) by the reinforcing flange portions 16b of the front and rear reinforcing flange rings 16. In the banjo section 3, which does not require reinforcement, a notch 9 is formed in the opening 2 so that the opening edge is significantly expanded outward to the left and right in the vehicle width direction and also slightly expanded vertically. The reinforcing flange portions 16b of the reinforcing flange rings 16 are formed to cover the notch 9. With this axle case structure 1b, the area of ​​the notch 9 in the opening 2 of the banjo section 3 can be expanded to the extent that it does not affect strength, significantly reducing the material cost of the side panels 8 while still meeting the required strength.

[0040] In FIG. 8, the developed shape of the side panel 8a (side panel 8a in FIG. 7(a)) when no cutout 9 is formed in the opening 2 is indicated by dots, and the developed shape of the side panel 8b (side panel 8b in FIG. 7(b)) when the cutout 9 is formed in the opening 2 is indicated by a two-dot chain line. As shown in FIG. 7(a), when no cutout 9 is formed in the opening 2, the developed shape of the side panel 8a has four protrusions 19 that protrude outward in the width direction of the blank panel B1, as indicated by dots in FIG. 8. When the blank panel B1 is press-molded, the protrusions 19 become abutment portions 20 of the upper and lower side panels 8a of the opening 2 in FIG. 7(a). On the other hand, when a cutout 9 is formed in the opening 2 as shown in FIG. 7(b), two depressions 21 that are recessed inward in the width direction of the blank panel B2 are formed, as indicated by two-dot chain lines in FIG. 8. When the blank panel B2 is press-molded, the depressions 21 become the depressions 9 in FIG. 7(b). In this way, by forming the notched portion 9, the width dimension of the blank plates B1 and B2 is reduced from W1 to W2 compared to a plate without the notched portion 9.

[0041] Specifically, as shown in FIG. 7(a), if no notch 9 is formed, the unfolded width W1 of the side panel 8a (the width of blank panel B1 shown in FIG. 8) is 380 mm. As shown in FIG. 7(b), if the notch 9 is formed, the unfolded width W2 of the side panel 8b (the width of blank panel B2 shown in FIG. 8) is 280 mm. In other words, in this study, the side panels 8 of the axle case body 7 can be reduced by more than 25%. The length L of the blank panels B1 and B2 is approximately 1700 mm, regardless of whether or not the notch 9 is formed. Thus, by applying the reinforcing flanged ring 16 and forming the notch 9 in the opening 2, the unfolded width of the side panels 8 can be narrowed, significantly reducing material costs.

[0042] (Actions and Effects) The axle case structure 1 according to this embodiment can provide the following effects.

[0043] As shown in Figure 6, reinforcing flange rings 16 attached to the front and rear of the axle case body 7 have a central ring portion 16a that surrounds the opening 2 of the banjo portion 3, and reinforcing flange portions 16b that extend outward in the vehicle width direction from the left and right sides of the central ring portion 16a to positions beyond the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4. These reinforcing flange portions 16b improve the vertical bending rigidity of the axle case body 7 near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4. As a result, buckling deformation caused by the vehicle weight W and road reaction force R near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 on the top surface of the axle case body 7 can be appropriately suppressed.

[0044] As shown in Figure 4, the reinforcing flange portion 16b of the reinforcing flange-equipped ring 16 improves the vertical bending rigidity near the connection 13 between the shoulder radius portion 6 and horizontal portion 4 of the axle case main body 7, so there is no need to change the shape or material of the axle case main body 7 or cover 12 or add a new reinforcing part other than the ring 16 to increase the vertical bending rigidity, and the existing axle case main body 7 and cover 12 can be used as is. This makes it possible to suppress, at low cost, buckling deformation that occurs near the connection 13 between the shoulder radius portion 6 and horizontal portion 4 on the top surface of the axle case main body 7 due to the vehicle weight and road reaction force described above.

[0045] As shown in Figure 4, the reinforcing flange ring 16 has a central ring portion 16a that surrounds the opening 2 of the banjo portion 3, and reinforcing flange portions 16b that extend outward in the vehicle width direction from the left and right sides of the central ring portion 16a to a position beyond the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4. Compared to the conventional circular cover reinforcing ring 15 and circular carrier mounting ring 11 shown in Figure 2, only the reinforcing flange portion 16b has been added. Therefore, with a minimal increase in mass, it is possible to suppress buckling deformation that occurs near the connection portion 13 between the shoulder radius portion 6 and the horizontal portion 4 on the top surface of the axle case main body 7 due to the vehicle weight W and road reaction force R described above.

[0046] As shown in Figure 6, this axle case structure 1 also has a specification in which the lengths (H1, H2) of the left and right horizontal sections 4 sandwiching the banjo section 3 are different on the left and right sides, and the length (X1) of the longer left horizontal section 4 beyond the connection 13 between the shoulder radius section 6 of the reinforcing flange section 16b and the horizontal section 4 is set longer than the length (X2) of the shorter right horizontal section 4 beyond the connection 13 between the shoulder radius section 6 of the reinforcing flange section 16b and the horizontal section 4. As a result, the bending rigidity (yield strength) of the left buckling section 13, which has a long moment arm (L1) of the road reaction force R and is prone to buckling, is higher than the bending rigidity (yield strength) of the right buckling section 13, which has a short moment arm (L2) of the road reaction force R and is less prone to buckling, and buckling of the left buckling section 13, which is prone to buckling, can be accurately suppressed with a minimum increase in mass.

[0047] As shown in Figure 4, in this axle case structure 1, a notch 9 is formed in the opening 2 of the banjo portion 3 so that the opening edge widens outward to the left and right in the vehicle width direction, and as shown in Figure 5(a), a reinforcing flange portion 16b of the reinforcing flange-equipped ring 16 is formed so as to cover the notch 9. This makes it possible to omit the conventional triangular plate 10 shown in Figure 2, thereby reducing the mass equivalent to the triangular plate 10 and reducing the labor costs for welding the triangular plate 10 to the notch 9.

[0048] As shown in Figure 4, in this axle case structure 1, the axle case body 7 excluding the spindle 5 is made up of sheet metal parts (side plates 8) with grooved cross sections divided into upper and lower halves, and a cutout 9 is formed in the opening 2 of each side plate 8, with each side plate 8 being formed by press-molding a blank plate. As shown by the two-dot chain line in Figure 8, the blank plate B2 before press-molding has a shape in which the portion that will become the cutout 9 (recessed portion 21) has been removed from a rectangular flat plate inward in the width direction of the flat plate (blank plate B2).

[0049] As a result, as shown in Figure 8, the width dimension W2 of the developed view (see the two-dot chain line in Figure 8) of side plate 8b having cutout 9 shown in Figure 7(b) is reduced from the width dimension W1 of the developed view (see the dots in Figure 8) of side plate 8a having no cutout 9 shown in Figure 7(a). Therefore, the width dimension of blank plate B2 of side plate 8b having cutout 9 is reduced from W1 to W2 compared to blank plate B1 of side plate 8a having no cutout 9, which improves the material yield of the axle case body 7 and reduces material costs.

[0050] The above describes a preferred embodiment of the present invention with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to the above-described embodiment, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention. [Industrial Applicability]

[0051] The present invention can be used in an axle case structure that increases the yield strength of the axle case body that is bent and deformed downward in a convex shape due to the vehicle weight and road surface reaction force. [Explanation of symbols]

[0052] 1 Axle case structure 2 aperture 3 Banjo Club 4 Horizontal section 5 spindles 6 Shoulder arc 7 Axle case body 8 Side panels as sheet metal parts 9 Missing parts 16 Reinforced flanged ring 16a Central ring section 16b Reinforced flange 13 Connection between shoulder curve and horizontal section H1 Length of horizontal section H2 Length of horizontal section X1: Length beyond the connection between the shoulder radius and horizontal part of the reinforcing flange X2: Length beyond the connection between the shoulder radius and horizontal part of the reinforcing flange B1 Blank plate when no missing part is formed B2 Blank plate when forming a missing part W vehicle weight R Road reaction force

Claims

1. An axle case structure comprising an axle case body comprising: banjo sections that are shaped to bulge in the vertical direction and have openings formed at the front and rear of the vehicle in the overall length direction to house differential mechanisms; horizontal sections that are arranged on either side of the banjo section in the vehicle width direction and to which the vehicle weight is applied via suspensions; spindles that are connected to the outer ends of the horizontal sections in the vehicle width direction and to which road surface reaction forces are applied via wheels; and shoulder curve sections that connect the banjo sections and the horizontal sections and whose vertical dimension gradually decreases as they extend outward in the vehicle width direction, a reinforcing flanged ring is attached to at least one of the front and rear surfaces of the axle case body in the vehicle overall length direction, the reinforcing flanged ring having a central ring portion surrounding the opening of the banjo portion, and reinforcing flange portions extending outward in the vehicle width direction from the left and right sides of the central ring portion in the vehicle width direction to positions beyond the connection portions between the shoulder curved portions and the horizontal portions; The axle case structure is characterized in that, when the reinforcing flanged ring is attached to at least one of the front and rear surfaces of the axle case body in the vehicle overall length direction, it is not bent so as to wrap around the upper and lower surfaces of the axle case body, but is formed in a plate shape that covers at least one of the front and rear surfaces, and the outer edge of the reinforcing flanged ring is welded to the axle case body along its circumferential direction.

2. The length of the horizontal portion is different on the left and right sides in the vehicle width direction, 2. The axle case structure according to claim 1, wherein the length of the reinforcing flange portion at the longer horizontal section beyond the connection between the shoulder radius portion and the horizontal section is longer than the length of the reinforcing flange portion at the shorter horizontal section beyond the connection between the shoulder radius portion and the horizontal section.

3. A notch is formed in the opening of the banjo portion so as to widen the opening edge outward to the left and right in the vehicle width direction, 3. The axle case structure according to claim 1, wherein the reinforcing flanged ring is formed so as to cover the missing portion.

4. The axle case body excluding the spindle is made up of sheet metal parts with a grooved cross section divided into upper and lower parts, and these sheet metal parts are formed by press molding a blank plate, 4. The axle case structure according to claim 3, wherein the blank plate before press molding has a shape in which a portion that will become the missing portion is removed from a flat plate inward in the plate width direction.

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