阅读说明：本技术 横向构件以及用于横向构件的制造方法 (Cross member and manufacturing method for cross member ) 是由 浅井哲也 奥本隆一 于 2019-07-26 设计创作，主要内容包括：公开了一种横向构件以及用于横向构件的制造方法。所述横向构件由具有给定的截面形状的金属板制成,构造车身框架的一部分,沿着车辆宽度方向延伸,并且具有设置在上板部的一部分中的发动机支座附接部。所述横向构件具有由沿着所述车辆宽度方向延伸的单个金属板制成的上横向构件,所述上横向构件在包括所述上板部的所述发动机支座附接部和所述发动机支座附接部的周围部的区域中相较于其余区域的厚度具有较大的厚度。(A cross member and method of manufacture for a cross member are disclosed. The cross member is made of a metal plate having a given sectional shape, configures a part of a vehicle body frame, extends in a vehicle width direction, and has an engine mount attachment portion provided in a part of an upper plate portion. The cross member has an upper cross member made of a single metal plate extending in the vehicle width direction, the upper cross member having a larger thickness in a region including the engine mount attachment portion of the upper plate portion and a peripheral portion of the engine mount attachment portion than a thickness of the remaining region.)

1. A cross member that is made of a metal plate having a given sectional shape, that configures a portion of a vehicle body frame, that extends in a vehicle width direction, and that has an engine mount attachment portion provided in a portion of an upper plate portion, characterized in that

The cross member has an upper cross member made of a single metal plate extending in the vehicle width direction, the upper cross member having a larger thickness in a region including the engine mount attachment portion of the upper plate portion and a peripheral portion of the engine mount attachment portion than a thickness of the remaining region.

2. The cross member of claim 1, wherein:

a step portion is provided in a first surface of the upper cross member;

a shaving mark portion provided on a second surface of the upper cross member, the second surface being a surface on a back side of a region reduced in thickness by the step portion; and

the thick portion is provided on a first side of the upper cross member in an extending direction of the upper cross member with respect to the step portion, and the thin portion is provided on a second side of the upper cross member in the extending direction of the upper cross member with respect to the step portion.

3. The cross member of claim 2 further comprising

A lower cross member, wherein:

the cross member having a closed cross-sectional configuration formed when the upper and lower cross members are engaged with one another;

the first surface of the upper cross member on which the stepped portion is provided faces an inner side of the closed-section structure; and

the second surface of the upper cross member on which the shaving mark portions are provided faces an outer side of the closed-section structure.

4. A cross member comprising an upper cross member made of a single metal plate, said upper cross member comprising

A first portion in which an engine mount attachment is provided; and

a second portion adjacent to the first portion and having a thickness less than a thickness of the first portion.

5. The cross member of claim 4 further comprising

A lower cross member connected with the upper cross member, wherein the upper cross member and the lower cross member form a closed cross section.

6. The cross member of claim 5, wherein:

the upper cross member includes a first surface facing an inner side of the closed cross section and a second surface facing an outer side of the closed cross section; and

a step is formed on the first surface between the first portion and the second portion.

7. The cross-member of claim 6, wherein the cross-member is a tubular member

A portion of the second surface corresponding to the step on the first surface is a flat surface.

8. The cross member of claim 4, wherein:

the upper cross member includes first and second side wall portions extending parallel to each other, and an upper wall portion connecting ends of the first and second side wall portions; and

the first portion is disposed within the upper wall portion.

9. A method of manufacturing a cross member, comprising:

stamping a metal plate so that a recess is formed on a first surface of the metal plate and a protrusion is formed on a second surface of the metal plate;

cutting the protruding portion of the metal plate after the punching; and

bending the metal plate into a predetermined sectional shape after the cutting.

10. The method of manufacturing according to claim 9, wherein the step of forming the resin layer is performed by a method of manufacturing a resin layer

The stamping includes: the second surface is punched with a punch in a state where the metal plate is placed on a base so that the first surface faces an upper surface of the base.

Technical Field

The present invention relates to a cross member and a manufacturing method for a cross member.

Background

As a vehicle body frame, the following structure is known: which includes a pair of left and right side members (also referred to as side frames) extending in the front-rear direction of the vehicle body, and a cross member (referred to as a frame structure) bridging between the side members. Generally, the cross member is made into a given sectional structure (e.g., a closed sectional structure) by, for example, punching a metal plate (high-strength steel plate or the like), thereby obtaining high rigidity.

Japanese unexamined patent application publication No. 2004-352022 (JP2004-352022a) discloses a cross member (floor cross member) formed to have a hat-shaped cross section by punching a metal plate.

Disclosure of Invention

As disclosed in JP2004-352022a, when the cross member is manufactured by stamping a metal plate (a metal plate having a uniform thickness dimension), the thickness dimension becomes uniform throughout the cross member. The thickness dimension is specified so that the portion of the cross member to which a particularly large load is applied has sufficient strength. Therefore, the remaining portion (the portion to which a relatively small load is applied) has an unnecessarily large thickness dimension. Therefore, with the manufacturing method according to the aforementioned prior art, there is a limitation in reducing the weight of the vehicle body by reducing the weight of the cross member.

As for a structure that realizes weight reduction of the cross member, it is considered to manufacture the cross member by integrally welding a plurality of plates having thickness dimensions different from each other. For example, as shown in FIG. 8, the cross member 60 includes an upper member 70 and a lower member 80. The upper member 70 is manufactured by welding a plurality of plates 71, 72, 73 having thickness dimensions different from each other, and the members 70, 80 are joined to each other by welding. For example, when an engine mount (not shown) is mounted on the central portion in the longitudinal direction of the cross member 60, a large load (a load in the up-down direction input from the engine through the engine mount) is applied to the central portion in the vehicle width direction of the upper member 70. In this case, the thickness dimension of the panel 72 located at the center is increased, while the thickness dimensions of the remaining panels 71, 73 are decreased. By so doing, it is possible to reduce the weight of the cross member 60 while obtaining sufficient rigidity against loads. The gusset plates 90 are respectively connected to both sides of the cross member 60 in the longitudinal direction by bolt fastening, and the cross member 60 is respectively connected to the longitudinal beams (not shown) through the gusset plates 90.

However, when the cross member 60 is manufactured as described above, the number of parts increases, and the structure may become complicated. Also, since welding is required in a plurality of places, manufacturing costs may be increased, thermal damage may occur at the welding position (strength at the welding position is reduced), and rust may occur (rust may occur at the peripheral portion of the welding position). Further, since the strength of the welding position (joint) is reduced (strength is reduced compared to the case where a separate structure is not used), there is a limitation in reducing the thickness dimension (thickness dimension of the panels 71, 73). As a result, there is a limit in reducing the weight of the cross member 60.

The invention provides a vehicle body cross member and a manufacturing method for the cross member, by which weight can be reduced while simplifying the structure and reducing welding positions due to a reduction in the number of parts.

A first aspect of the invention provides a cross member that is made of a metal plate having a given sectional shape, that configures a portion of a vehicle body frame, that extends in a vehicle width direction, and that has an engine mount attachment portion provided in a portion of an upper plate portion. The cross member has an upper cross member made of a single metal plate extending in the vehicle width direction, the upper cross member having a larger thickness in a region including the engine mount attachment portion of the upper plate portion and a peripheral portion of the engine mount attachment portion than a thickness of the remaining region.

According to the first aspect, the thick portion and the thin portion are provided in the upper cross member made of a single metal plate. A large thickness dimension is set for the thick portion, and a small thickness dimension is set for the thin portion. This means that, in the cross member, the thick portion constitutes a region to which a particularly large load is applied, including the engine mount attachment portion of the upper plate portion and the peripheral portion of the engine mount attachment portion. Also, the thin portion constitutes a portion to which a relatively small load is applied. Thus, on a single metal plate, a thickness dimension according to the applied load is obtained. As a result, an area where the thickness dimension is unnecessarily large can be reduced, thereby reducing the weight of the cross member. Further, since it is not necessary to integrally weld a plurality of panels having thickness dimensions different from each other (since it is not necessary to use the structure shown in fig. 8), the number of parts is reduced, and the structure is simplified. Also, since the welding positions are reduced, it is possible to reduce the manufacturing cost, suppress thermal damage, and suppress rust.

In the first aspect, a stepped portion may be provided in the first surface of the upper cross member; a shaving mark portion provided on a second surface of the upper cross member, the second surface being a surface on a back side of a region reduced in thickness by the step portion; and a thick portion provided on a first side of the upper cross member in an extending direction of the upper cross member with respect to the step portion, and a thin portion provided on a second side of the upper cross member in the extending direction of the upper cross member with respect to the step portion. The scraping mark portion may be regarded as a scraping mark formed when the surface portion of the upper cross member is scraped.

This means that, since the step portion is provided on the first surface of the upper cross member and the shaving mark portion is provided on the second surface, it is possible to provide a thick portion (a portion where the thickness is reduced due to the step on the first surface) and a thin portion (a portion where the thickness is reduced due to the step on the first surface) in the upper cross member made of a single metal plate.

In the above configuration, the cross member may further include a lower cross member. The cross member may have a closed sectional structure formed when the upper and lower cross members are engaged with each other, the first surface of the upper cross member on which the stepped portion is provided may face an inner side of the closed sectional structure, and the second surface of the upper cross member on which the shaving mark portion is provided may face an outer side of the closed sectional structure.

When an external force is applied to the cross member having the closed-section structure, tensile stress is generated on the outer side surface. In this case, when there is a step portion on the outer side surface, stress may concentrate on the step portion. In view of this, according to this solution, the step portion is provided on the inside surface (first surface), and the shaving mark portion is provided on the outside surface (second surface) so that the outside surface becomes an almost flat surface. Therefore, the tensile stress is not concentrated on the outer side surface. Due to this, reliability of the strength of the cross member can be enhanced.

A second aspect of the present invention provides a vehicle seat including an upper cross member made of a single metal plate. The upper cross member includes a first portion in which an engine mount attachment portion is disposed; and a second portion adjacent to the first portion and having a thickness less than a thickness of the first portion.

In a second aspect, the cross member may further include a lower cross member connected with the upper cross member. The upper cross member and the lower cross member may form a closed cross section.

In the above configuration, the upper cross member may include a first surface facing an inner side of the closed section and a second surface facing an outer side of the closed section, and a step may be formed on the first surface between the first portion and the second portion.

In the above configuration, a portion of the second surface corresponding to the step on the first surface is a flat surface.

In the second aspect, the upper cross member may include first and second side wall portions extending parallel to each other, and an upper wall portion connecting ends of the first and second side wall portions. The first portion may be disposed within the upper wall portion.

A third aspect of the present invention provides a manufacturing method for a cross member, including: stamping a metal plate so that a recess is formed on a first surface of the metal plate and a protrusion is formed on a second surface of the metal plate; cutting the protruding portion of the metal plate after the punching; and bending the metal plate into a predetermined sectional shape after the cutting.

In the cross member manufactured by the manufacturing method according to the third aspect, the stepped portion is formed in the outer edge of the portion of the first surface, which is formed into the recessed shape by the punching. In addition, the protruding portion of the second surface is cut at the time of cutting, thereby forming a cut mark portion. Thus, the thick portion is provided on the first side of the metal plate in the extending direction of the metal plate with respect to the stepped portion, and the thin portion is provided on the second side of the metal plate in the extending direction of the metal plate with respect to the stepped portion.

Further, with the cross member manufactured by this manufacturing method, an area where the thickness dimension is unnecessarily large can be reduced, and thus the weight can be reduced. Also, since it is not necessary to integrally weld a plurality of panels having thickness dimensions different from each other, the number of parts can be reduced, thereby simplifying the structure. Also, since the welding position is reduced, the manufacturing cost is reduced, the heat damage is suppressed and the rust is suppressed.

In the third aspect, the punching may include punching the second surface with a punch in a state where the metal plate is placed on a base so that the first surface faces the upper surface of the base.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

FIG. 1 is a perspective view of a vehicle body frame according to one embodiment;

FIG. 2 is a perspective view of the third cross member as viewed from the upper left side of the front portion of the vehicle body;

FIG. 3 is a plan view of a third cross member;

FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a cross-sectional view taken along line V-V of FIG. 2;

fig. 6 is an enlarged view of a portion VI in fig. 4;

fig. 7A is a view of a state before punching a metal plate in a manufacturing step of the third cross member;

fig. 7B is a view of a state before shaving in the manufacturing step of the third cross member after the metal plate is punched;

fig. 7C is a view of a step of cutting the protruding portion of the metal plate in shaving in the manufacturing step of the third cross member;

fig. 7D is a view of a step of joining two bent metal plates in a manufacturing step of the third cross member; and

fig. 8 is a perspective view describing a case where a cross member is manufactured by integrally welding a plurality of plates having thickness dimensions different from each other.

Detailed Description

Hereinafter, embodiments of the present invention are described with reference to the drawings. In this embodiment, a case where the present invention is applied to a cross member of a vehicle body frame configured as a so-called ladder frame is described.

Overview of vehicle body frame Structure

Fig. 1 is a perspective view of a vehicle body frame 1 according to an embodiment. In fig. 1, an arrow "front" (FR) indicates the front of the vehicle body, an arrow "UP" (UP) indicates the upward direction, an arrow "right" (RH) indicates the right of the vehicle body, and an arrow "left" (LH) indicates the left of the vehicle body.

As shown in fig. 1, the vehicle body frame 1 is provided with a pair of left and right side members 11 extending in the vehicle body front-rear direction on both outer sides in the vehicle width direction, respectively. Each side member 11 has a closed-section structure, and is provided with an intermediate portion 11a, a forward upper bent portion 11b, a front portion 11c, a rearward upper bent portion 11d, and a rear portion 11e that are continuous with each other in the vehicle body front-rear direction.

The intermediate portion 11a extends in the horizontal direction in the vehicle body front-rear direction within a given range between a position where a front wheel (not shown) is disposed and a position where a rear wheel (not shown) is disposed.

The forward upper bent portion 11b is continuous from the front end of the intermediate portion 11a, and has a shape bent upward toward the front of the vehicle body. The front portion 11c continues from the front end of the front upward curved portion 11b and extends toward the front of the vehicle body. The front wheels are disposed on the outer side of the front portion 11c in the vehicle width direction. Therefore, the dimension of the front portion 11c of the side member 11 in the vehicle width direction (the dimension between the left and right front portions 11 c) is set smaller than the dimension of the intermediate portion 11a in the vehicle width direction (the dimension between the left and right intermediate portions 11 a) in consideration of interference with the front wheels. Therefore, the forward upper bent portion 11b has a shape that is bent outward in the vehicle width direction toward the rear of the vehicle body.

The rearward-upward bent portion 11d is continuous from the rear end of the intermediate portion 11a, and has a shape that is bent upward toward the rear of the vehicle body. The rear portion 11e is continuous from the rear end of the rearward-upward bent portion 11d and extends toward the rear of the vehicle body. The rear wheels are disposed on the outer side of the rear portion 11e in the vehicle width direction. Therefore, the dimension of the rear portion 11e of the side member 11 in the vehicle width direction (the dimension between the left and right rear portions 11 e) is also set smaller than the dimension of the intermediate portion 11a in the vehicle width direction (the dimension between the left and right intermediate portions 11 a) in consideration of interference with the rear wheels. Therefore, the backward upward bent portion 11d has a shape bent outward in the vehicle width direction toward the front of the vehicle body.

The crash boxes 12 are respectively provided forward of the front portions 11c of the side members 11, so that the crash boxes 12 absorb energy (collision load) at the time of a frontal collision of the vehicle. A bumper reinforcement (not shown) extending in the vehicle width direction is bridged between the front end portions of the pair of left and right crash boxes 12.

A plurality of cross members 13a, 13b, 13d, 13e, 13f, 13g, 13h, 2 extending in the vehicle width direction bridge between the side members 11. In the drawings, reference numeral 13a denotes a first cross member, reference numeral 13b denotes a second cross member, reference numeral 2 denotes a third cross member, reference numeral 13d denotes a fourth cross member, reference numeral 13e denotes a fifth cross member, reference numeral 13f denotes a sixth cross member, reference numeral 13g denotes a seventh cross member, and reference numeral 13h denotes a rear cross member.

Each of the metal suspension support brackets 14 is disposed at a position of the front portion 11c of the side member 11 between the first cross member 13a and the second cross member 13 b. The suspension support bracket 14 protrudes outward in the vehicle width direction.

Further, cab mounting brackets 15a, 15b, 15c are respectively disposed in a rear end portion of the forward upper bent portion 11b of the side member 11, in a front end portion of the front portion 11c of the side member 11, and in a front end portion of the rearward upper bent portion 11d of the side member 11. The cab mounting brackets 15a, 15b, 15c protrude outward in the vehicle width direction, so that cab mounts (not shown) are attached to the cab mounting brackets 15a, 15b, 15c, respectively. Thus, the cab (not shown) may be connected to the side member 11 by means of cab mounts and cab mounting brackets 15a, 15b, 15 c.

Construction of the third cross member

This embodiment is characterized by the structure of the third cross member 2 among the cross members 13a, 13b, 13d, 13e, 13f, 13g, 13h, 2. This means that the third cross member 2 corresponds to a cross member according to the invention. Hereinafter, the third cross member 2 will be described.

Fig. 2 is a perspective view of the third cross member 2 as viewed from the upper left side of the front portion of the vehicle body. Fig. 3 is a plan view of the third cross member 2. In fig. 2 and 3, also the gussets 7 connecting the third cross member 2 to the longitudinal beam 11 are shown, respectively. In fig. 2 and 3, the arrow "front" indicates the vehicle body front, the arrow "up" indicates the upward direction, the arrow "right" indicates the vehicle body right direction, and the arrow "left" indicates the vehicle body left direction. Fig. 4 is a sectional view taken along line IV-IV in fig. 2. Fig. 5 is a sectional view taken along line V-V in fig. 2.

The third cross member 2 is made into a closed cross-sectional structure having a rectangular cross section (a given cross-sectional shape in the present invention) by welding two metal plates W1, W2. Specifically, the third cross member 2 is made such that an upper cross member (upper side metal plate) W1 and a lower cross member (lower side metal plate) W2 are integrally joined to each other. The upper cross member W1 has a sectional shape open on the lower side, and the lower cross member W2 has a sectional shape open on the upper side.

Further, the third cross member 2 includes a front wall portion 3, an upper plate portion 4, a rear wall portion 5, and a lower plate portion 6. The front wall portion 3 is located on the vehicle body front side, the upper panel portion 4 extends from the upper end edge of the front wall portion 3 toward the vehicle body rear side, the rear wall portion 5 extends downward from the rear end edge of the upper panel portion 4 (the end edge on the rear side in the vehicle body front-rear direction), and the lower panel portion 6 extends from the lower end edge of the rear wall portion 5 toward the vehicle body front side. Therefore, the front wall portion 3 and the rear wall portion 5 face each other in the vehicle body front-rear direction. Further, the upper plate portion 4 and the lower plate portion 6 face each other in the up-down direction.

In the center portion of the upper plate portion 4 in the vehicle width direction, an engine mount insertion hole (engine mount attachment portion) 41 is formed through the upper plate portion 4 in the up-down direction such that a lower portion of an engine mount (not shown) is inserted into the engine mount insertion hole 41. Further, in order to fasten the engine mount by bolts, bolt insertion holes 42 are formed in the peripheral portions of the engine mount insertion holes 41.

Also, the gusset plates 7 are respectively connected to both sides of the third cross member 2 in the longitudinal direction by bolts, so that the third cross member 2 is connected to the side member 11 through the gusset plates 7.

Thickness dimension of third cross member

The third cross member 2 is characterized in that a plurality of regions are provided in the upper cross member W1, and the regions have different thickness dimensions from each other. In this embodiment, four kinds of regions having thickness dimensions different from each other are provided. The region having the largest thickness dimension is referred to as a first region a, the region having the second largest thickness dimension is referred to as a second region B, the region having the third largest thickness dimension is referred to as a third region C, and the region having the smallest thickness dimension is referred to as a fourth region D.

As shown in fig. 6 (an enlarged view of a portion VI in fig. 4), in the structure in which the regions having the thickness dimensions different from each other are provided as described above, the stepped portions 22, 23 are provided by partially recessing the inner side surface (the first surface of the upper cross member in the present invention) 21 of the closed cross-sectional structure of the third cross member 2. Meanwhile, the outer side surface (the second surface of the upper cross member in the present invention) 24 of the closed cross-sectional structure is almost flat. Since the inner side surfaces 21 have different recess sizes, regions having different thickness sizes from each other are provided. This means that the thickness dimension is determined as the dimension between the outside surface 24 and the region where the distance from the outside surface 24 is changed by the steps 22, 23 on the inside surface 21 (dimensions t1, t2, t3 in fig. 6). The region having the larger recess dimension (the region where the thickness is more reduced by the step portions 22, 23) is configured as a region having a smaller thickness dimension. Therefore, the first side of the upper cross member W1 in the extending direction of the upper cross member W1 with respect to the steps 22, 23 (the portion where the thickness is not reduced by the steps 22, 23) is a region having a relatively large thickness dimension (thick portion), and the second side of the upper cross member W1 in the extending direction of the upper cross member W1 with respect to the steps 22, 23 (the portion where the thickness is reduced by the steps 22, 23) is a region having a relatively small thickness dimension (thin portion).

In fig. 6, two step portions 22, 23 are provided. Therefore, the left and right regions of the stepped portion 22 across the right in fig. 6 have different thickness dimensions. Of these regions, the region on the right side of the step portion 22 is a thick portion of the present invention (a portion having the thickness dimension t 1), and the region on the left side of the step portion 22 is a thin portion of the present invention (a portion having the thickness dimension t 2). Further, the left and right regions across the step portion 23 on the left side in fig. 6 also have different thickness dimensions. Of these regions, the region on the right side of the step portion 23 is a thick portion of the present invention (a portion having a thickness dimension t 2), and the region on the left side of the step portion 23 is a thin portion of the present invention (a region having a thickness dimension t 3).

As described above, in the present embodiment, since the present invention is applied to the third cross member 2, the thick portion and the thin portion are provided in the third cross member 2 (more specifically, the upper cross member W1 of the third cross member 2).

As a manufacturing method of providing the step portions 22, 23 by partially recessing the inner side surface 21 of the closed cross-sectional structure of the third cross member 2 and making the outer side surface 24 of the closed cross-sectional structure almost flat, punching and shaving of a metal plate (a metal plate serving as an upper cross member) W1 are carried out. Although details are provided later, punching is performed such that the first surface (the inner side surface 21 of the closed cross-sectional structure) of the metal plate W1 is formed into a recessed shape and the second surface (the outer side surface 24 of the closed cross-sectional structure) is formed into a protruding shape (the shape of the metal plate W1 when punching is completed is shown by a broken line in fig. 6). After the punching is completed, scraping is performed so as to cut the protruding portion of the second surface (the outer side surface 24 of the closed cross-sectional structure) of the metal plate W1 (the shape of the metal plate W1 when the scraping is completed is shown by a solid line in fig. 6), and the second surface (the outer side surface 24 of the closed cross-sectional structure) is made almost flat. This means that, in the first surface (the inside surface 21 of the closed cross-sectional structure), the recessed portion is held so as to provide the stepped portions 22, 23, and the protruding portion of the second surface (the outside surface 24 of the closed cross-sectional structure) is cut so that the second surface is made almost flat. Therefore, the above-described regions having thickness dimensions different from each other are formed in the single metal sheet W1.

When the metal plate W1 is processed in this way, since the protruding portion of the second surface (outer side surface) 24 is cut by scraping, a scraped mark portion (a scraped mark portion provided on the second surface 24 of the metal plate W1, the second surface 24 being a surface on the back of a region stepped down by the steps 22, 23) 25 is formed in a part of the second surface 24. The shaving mark portion 25 is a portion showing the cut surface of the portion where the protruding portion is cut and having a surface condition (surface glossiness, surface roughness, etc.) significantly different from that of the remaining portion (uncut portion). For example, in the case of treating the surface of the metal plate W1, the surface treatment layer is removed. In the case where an oxide film is present on the surface of the metal plate W1, the oxide film is removed. In some cases, a small edge remains in the outer edge portion of the shaving mark portion 25. Further, the scraped mark portion 25 does not have to be a completely flush surface with the rest portion, and may have a slightly convex shape (for example, about 0.1mm) than the rest portion.

In fig. 3, regions having thickness dimensions different from each other are filled with oblique lines so that the regions are distinguished from each other. Specifically, the first region a is filled with a solid line inclined downward to the left. The second region B is filled with a solid line inclined to the lower right. The third region C is filled with a dotted line inclined to the lower left. The fourth region D is filled with a dotted line inclined to the lower right. The thickness dimensions of the region A, B, C, D are, for example, 3.5mm for the first region a, 3.0mm for the second region B, 2.5mm for the third region C, and 2.0mm for the fourth region D. However, the thickness dimension is not limited to these values.

Location of application area

Next, the positions of the application areas A, B, C, D are described, respectively.

The first region a (the region having the largest thickness dimension of the region A, B, C, D) is applied to the peripheral portions (serving as the mount seats for the engine mount) of the engine mount insertion holes 41 and the bolt insertion holes 42 provided in the central portion of the upper plate portion 4 in the vehicle width direction. The second region B (region having the second largest thickness dimension of the region A, B, C, D) is applied to a portion of the upper plate portion 4 on the outer side in the vehicle width direction of the first region a, the central portion in the vehicle width direction of the front wall portion 3, and the central portion in the vehicle width direction of the rear wall portion 5. The third region C (the region having the third largest thickness dimension of the region A, B, C, D) is applied to a portion of the upper plate portion 4 on the outer side in the vehicle width direction of the second region B, a portion around a fourth region D described later, the outer portions of the front wall portion 3 on both sides in the vehicle width direction, and the outer portions of the rear wall portion 5 on both sides in the vehicle width direction. The fourth region D (the region having the smallest thickness dimension of the region A, B, C, D) is applied to the central portion of the third region C in the upper plate portion 4. As described above, in the third cross member 2, the thickness dimension of the area around the engine mount insertion hole 41 into which the lower portion of the engine mount is inserted is larger than the thickness dimension of the remaining area. Therefore, since a load in the up-down direction from the engine is input through the engine mount, the strength of the center portion in the vehicle width direction, where the stress tends to be high, can be enhanced.

Manufacturing step of third cross member

Next, a manufacturing step of the third cross member 2 configured as above is described.

The punching step, the shaving step, the bending step, and the joining step, which are the manufacturing steps of the third cross member 2, are carried out in the order mentioned below. In the punching step, a metal plate (a metal plate such as a high-strength steel plate, serving as an upper cross member) W1 is punched. In the shaving step, the metal plate W1 is shaved. In the bending step, the two metal plates W1, W2 are bent. In the joining step, the two metal plates W1, W2 are joined to each other.

Fig. 7A to 7D are views describing an outline of the manufacturing steps of the third cross member 2.

First, a metal sheet W1 sheared into a given shape (elongated shape) by a shearer (not shown) is placed on the punch 100 (see fig. 7A). The punch 100 includes: a base 102 on which the mold 101 is mounted; and a punch 103 that can move up and down with respect to the base 102. The mechanism that allows the punch 103 to move up and down is similar to a conventional punch, and therefore, the description thereof is omitted.

Then, when the punch 103 is moved downward toward the metal sheet W1 placed on the base 102 (punching step), a protruding portion is formed on the lower surface of the metal sheet W1, and a recessed portion is formed on the upper surface of the metal sheet W1 (see fig. 7B). Therefore, the outer portion of the metal plate W1 in fig. 7B is stepped upward with respect to the central portion. This means that the outer portion protrudes upward (becomes a protruding portion). Further, the outer edges of the protruding portions (protruding portions of the lower surface) obtained by the punching step will become the stepped portions 22, 23 later.

Further, the recess dimension of the recess portion is set smaller than the thickness dimension of the metal plate W1. Further, the depression size of the depression portion is set according to a thickness size (target thickness size) obtained in a shaving step described later. Therefore, the protruding dimension of the protruding portion of the punch 103 and the recessed dimension of the recessed portion of the die 101 are set so that the recessed dimension of the recessed portion becomes smaller as the target thickness dimension becomes larger.

After that, the punched metal sheet W1 is shaved. In the scraping, the upper surface of the metal plate W1 is cut into an almost flat shape. Specifically, the punch 103 is replaced with the punching jig 200 in a state where the punched metal sheet W1 is placed on the base 102. The lower surface of the press jig 200 is a flat surface. Also, the punching jig 200 is spaced apart from the base 102 so that there is a space for a scraping tool (cutting insert) 201 to pass between the punching jig 200 and the metal sheet W1. As shown in fig. 7C, as the cutting insert 201 passes through the space, the outer portion (the portion protruding upward) of the metal plate W1 is removed by cutting, and the upper surface of the metal plate W1 is formed as a substantially flat surface. This means that the outer portion is cut almost flush with the upper surface of the central portion of the metal plate W1.

In the metal plate W1 obtained in the shaving step, the region cut by the cutting blade 201 is processed into a thin portion, and the remaining portion is processed into a thick portion.

In fig. 7A to 7D, for the sake of simplifying the description, the following case is described: a thick portion is processed in the central portion of the metal plate W1, and a thin portion is processed outside the thick portion. However, actually, as described previously, four kinds of regions having thickness dimensions different from each other are provided in different positions of the third cross member 2, respectively. Thus, the punch 103 and the die 101 are manufactured such that these thickness dimensions can be obtained and more than one site formed during the punching step is cut by the cutting insert 201.

The metal plate (metal plate serving as the upper cross member) W1 having the regions of the thickness dimensions different from each other is manufactured as described above, the metal plate W1 and the other metal plate (metal plate serving as the lower cross member) W2 are respectively formed into an angular U-shape by punching or the like (bending step), and as shown in fig. 7D, the end edges of the metal plates W1, W2 are superposed on each other and welded to each other (joining step). Thus, a closed cross section having a substantially rectangular shape is made.