Method of Manufacturing Formed Product

This application claims the benefit of Japanese Patent Application No. 2024-074376 filed on May 1, 2024 with the Japan Patent Office, the entire disclosure of which is incorporated herein by reference.

The present disclosure relates to a method of manufacturing a formed product.

For example, Japanese Unexamined Patent Application Publication No. 2002-192247 discloses a technique for obtaining a formed product by pressing plate members placed on each other.

As in the technique of the aforementioned Document, in a case where a formed product having a top plate portion and a vertical wall portion is obtained by pressing plate members placed on each other, there has been a problem that a gap between each of the plate members are likely to occur due to springback in which a bent material deforms in a direction of returning to its original shape. If the gap between each of the plate members increases after the pressing, it may cause inconvenience in subsequent operations, such as welding or assembling.

One aspect of the present disclosure is, in a method of manufacturing a formed product having a top plate portion and a vertical wall portion by pressing plate members placed on each other, to allow reduction in an amount of springback of the plate members during the pressing.

One mode of the present disclosure is a method of manufacturing a formed product having a top plate portion and a vertical wall portion by pressing plate members placed on each other. In the method of manufacturing the formed product, the plate members comprise a first member and a second member.

The first member includes a first top plate corresponding portion, a first vertical wall corresponding portion, and an extending portion. The first top plate corresponding portion corresponds to one part of the top plate portion of the formed product. The first vertical wall corresponding portion corresponds to at least one part of the vertical wall portion of the formed product. The second member includes a second top plate corresponding portion, and a second vertical wall corresponding portion. The second top plate corresponding portion corresponds to an other part of the top plate portion of the formed product. The second vertical wall corresponding portion corresponds to at least an other part of the vertical wall portion of the formed product. The second top plate corresponding portion of the second member is placed on the first member.

In any planes parallel to the plate members, a downstream side in a direction in a plan view from the first vertical wall corresponding portion and the second vertical wall corresponding portion toward the first top plate corresponding portion and the second top plate corresponding portion is referred to as an inner side, and a downstream side in a direction in a plan view from the first vertical wall corresponding portion and the second vertical wall corresponding portion toward a side opposite to the first top plate corresponding portion and the second top plate corresponding portion is referred to as an outer side. Furthermore, an end portion of the first member on the outer side is referred to as a first end, and an end portion of the second member on the outer side is referred to as a second end. The first end is located on the outer side with respect to the second end. The extending portion is a region of the first member from the first end to a portion of the first member on which the second end is placed.

A direction from the first member toward the second member is referred to as a moving direction. In the method, joining the first member and the second member to each other is performed by welding the first top plate corresponding portion and the second top plate corresponding portion to each other in a state where the first member is placed on the second member to include the extending portion. Furthermore, curving the first vertical wall corresponding portion, the second vertical wall corresponding portion, and the extending portion of the plate members toward the moving direction is performed by moving a metal press mold in the moving direction in a state where the first top plate corresponding portion and the second top plate corresponding portion after the joining are clamped to thereby make the metal press mold contact the extending portion.

In addition, forming the top plate portion and the vertical wall portion is performed by further moving the metal press mold in the moving direction in a state where the first vertical wall corresponding portion, the second vertical wall corresponding portion, and the extending portion are curved by the metal press mold to thereby press the first vertical wall corresponding portion and the second vertical wall corresponding portion of the plate members by the metal press mold.

In such a method of manufacturing, the top plate portion and the vertical wall portion can be formed after the metal press mold is made to contact the extending portion to curve the plate members. In other words, the top plate portion and the vertical wall portion are formed after the plate members are slightly curved. Therefore, it is possible to reduce springback of the vertical wall portion.

In one mode of the present disclosure, the metal press mold may comprise a vertical wall-forming portion and a shoulder portion. The vertical wall-forming portion is a portion for forming the vertical wall portion. The shoulder portion contacts blank materials (that is, the first member and the second member) at first among portions of the metal press mold. The shoulder portion is located on a downstream side in the moving direction with respect to an end of the vertical wall-forming portion on the downstream side in the moving direction and includes a surface on the outer side with respect to the vertical wall-forming portion whose angle to the moving direction is greater than an angle of the vertical wall portion to the moving direction. In the curving, the second end may be disposed on the inner side with respect to the shoulder portion, and the first vertical wall corresponding portion, the second vertical wall corresponding portion, and the extending portion of the plate members may be curved toward the moving direction by the shoulder portion contacting the extending portion.

In such a method of manufacturing, a configuration can be achieved in which the plate members are curved by the shoulder portion contacting the extending portion. In addition, by appropriately setting a shape of the shoulder portion, the degree to which the first member and the second member are curved can be effectively set.

In one mode of the present disclosure, the metal press mold may have a step shape having surfaces substantially parallel to the top plate portion. In this case, the metal press mold may comprise a first surface and a second surface as the surfaces. The first surface is located on an upstream side in the moving direction. The second surface is located on the downstream side in the moving direction. In the curving, the first vertical wall corresponding portion, the second vertical wall corresponding portion, and the extending portion of the plate members may be curved toward the moving direction by the second surface contacting the extending portion. In the forming of the top plate portion and the vertical wall portion, a flange portion that extends toward the outer side from the vertical wall portion may be formed by the first surface contacting the extending portion.

In such a method of manufacturing, also at in a case of manufacturing the formed product having the flange portion, it is possible to form the top plate portion and the vertical wall portion after the plate members are curved.

In one mode of the present disclosure, in the forming of the top plate portion and the vertical wall portion, the forming of the flange portion may be completed on the inner side with respect to the shoulder portion. It should be noted that the forming of the flange portion may be started while the shoulder portion coming into contact with the flange portion and then completed on the inner side with respect to the shoulder portion.

In such a method of manufacturing, it is possible to make the shoulder portion contact the plate members from further outer side, and thus it is possible to form the top plate portion, the vertical wall portion and the flange portion after the plate members are sufficiently curved.

In one mode of the present disclosure, a plate thickness of the second member is equal to or greater than a plate thickness of the first member.

In such a method of manufacturing, a second moment of area of the first member is likely to be equal to or smaller than a second moment of area of the second member, and thus the effect of curving the first member is more likely to be obtained. As a result, it is possible to reduce the springback of the first member and to reduce the gap between the first member and the second member.

In one mode of the present disclosure, the first member and the second member may be welded to each other in the vertical wall portion after the top plate portion and the vertical wall portion are formed.

In such a method of manufacturing, since the springback of the vertical wall portion is reduced, the gap between the first member and the second member becomes smaller. Therefore, welding operation can be performed effectively.

In one mode of the present disclosure, the formed product may be an automobile part. In such a method of manufacturing, it is possible to effectively manufacture the formed product to be applied to the automobile part.

A formed productshown inis a press-formed product obtained by pressing plate members placed on each other. The formed productis used for, for example, an automobile part, such as a front pillar, a rocker, and a center-pillar, or other automobile component part, such as a pillar portion, and a frame portion of an automobile. The formed productand a method of manufacturing the formed productcan be applied not only to an automobile component part but also to various other parts or products.

The formed productis obtained by performing press-forming including bending on a first memberand a second membereach made of a steel plate. Each of the first memberand the second memberbefore the press-forming is, for example, a blank material obtained by cutting out a portion from a rolled steel plate. In one example, each of the first memberand the second memberis made of a cold-rolled steel plate, a hot-rolled steel plate, or an alloyed zinc-coated steel plate. In the present embodiment, an alloyed zinc-coated steel plate is used. A plate thickness of each of the first memberand the second membermay be 0.6 mm to 2.0 mm. For example, the plate thickness of each of the first memberand the second memberis 1.0 mm. In the present disclosure, an application range of a tensile strength of each of the first memberand the second memberis 270 MPa to 1470 MPa. In a case where the tensile strength of each of the first memberand the second memberis within the application range, effects of the present disclosure can be obtained. More preferably, in a case where the tensile strength of each of the first memberand the second memberis 980 MPa to 1470 MPa, a gap between the first memberand the second memberis more likely to occur, and thus a contribution of the present disclosure is more likely to be achieved. The tensile strength of each of the first memberand the second memberin the present embodiment is, for example, around 1470 MPa.

The plate thicknesses of the first memberand the second membermay be different from each other. Specifically, the plate thickness of the second membermay be greater than the plate thickness of the first member. In this case, for example, the plate thickness of the first membermay be 0.8 mm and the plate thickness of the second membermay be 1.2 mm. Hereinafter, a configuration will be described in which the plate thickness of the second memberis greater than the plate thickness of the first member.

The formed productis formed in a saddle shape having a height. The “saddle shape” as used herein refers to a shape having a top plate portion,, and a vertical wall portion,that is located on both sides of the top plate portion,and that extends in directions intersecting the top plate portion,. The formed productis used to cover an elongated object, such as a cable and a columnar member, along its longitudinal directions, or to reinforce other plate members by being attached thereto.

The formed productis obtained by processing the plate members. The formed productcomprises the first memberand the second memberas the plate members. Hereinafter, the first memberand the second memberare also collectively referred to as “two plate members”.

The first memberincludes the top plate portion, the vertical wall portion, and a flange portion. The second memberis placed on the first memberfrom below the first member. In, for explanation purposes, the top plate portionis shown as an upper portion of the formed product. However, the formed productmay be used in any orientation. For example, the formed productmay be used in an orientation that is upside down compared to the orientation shown in.

The top plate portionis substantially flat plate-shaped and is substantially rectangular-shaped in a plan view. A length of the top plate portionin its width directions (that is, left-right directions in) is, for example, around 150 mm, and a length of the top plate portionin its longitudinal directions (that is, “b” in) is, for example, around 350 mm. Two welding portionsJ are formed at a center of the top plate portion. In the two welding portionsJ, the top plate portionof the first memberand the top plate portionof the second memberare joined to each other by spot-welding. Hereinafter, a plane in which the top plate portionis located may be simply referred to as “top plate portion”.

Portions along two opposite edges of the top plate portionare bent. Each of the bent portions includes the vertical wall portion. The vertical wall portionis a portion that is flat plate-shaped, adjacent to the top plate portion, and contiguous to the top plate portion, and that extends from the top plate portionin a direction intersecting the plane in which the top plate portionis located. A length of the vertical wall portion(that is, a height from the top plate portionto the flange portion) is, for example, around 60 mm.

Additionally, welding portionsJ are formed in the vertical wall portion,. Two welding portionsJ are formed in the vertical wall portion,(that is, a total of four welding portionsJ are formed in the formed product). Adding the two welding portionsJ in the top plate portion,, the first memberand the second memberof the formed productare joined to each other via a total of six welding portionsJ,J.

The flange portionis formed to overhang from an end of the vertical wall portion. In other words, the flange portionextends outward from the end of the vertical wall portion. The flange portionextends generally parallel to the top plate portion. The flange portionis substantially flat plate-shaped and is substantially rectangular-shaped in a plan view. A length of the flange portionin its width directions is, for example, around 20 mm.

As shown in, a left half and a right half of the formed productof the present embodiment are symmetrical. Therefore, the following explanation may be made focusing on only one of the left half and the right half of the formed product. It should be noted that the left half and the right half of the formed productdo not necessarily need to be symmetrical.

As shown in, an end portion of the first memberin its width directions is referred to as a first endE, and an end portion of the second memberin its width directions is referred to as a second endE. The second memberdoes not reach the flange portionof the first member, and the second endE is located between the top plate portionand the flange portionof the first member. That is, a length of the vertical wall portionof the second member(that is, a height from the top plate portionto the second endE) is shorter than the length of the vertical wall portionof the first member.

As shown in, a region of the first memberfrom the first endE to a portion of the first memberon which the second endE is placed is defined as an “extending portion”. The extending portionincludes a part of the vertical wall portionof the first member(that is, a portion of the vertical wall portionon a side closer to the flange portionwith respect to the second endE) and the flange portion.

In the two plate members before main forming (S), which will be described below, a portion corresponding to a whole of the top plate portion,of the formed productis also referred to as “top plate corresponding portion”. The top plate corresponding portion includes: a first top plate corresponding portion that is the top plate corresponding portion of the first member; and a second top plate corresponding portion that is the top plate corresponding portion of the second member. Similarly, a portion corresponding to a part of the vertical wall portionof the formed product(that is, a portion of the vertical wall portionon a side closer to the top plate portionwith respect to the second endE) and a portion corresponding to a whole of the vertical wall portionare also referred to as “vertical wall corresponding portion”. The vertical wall corresponding portion includes: a first vertical wall corresponding portion that is the vertical wall corresponding portion of the first member; and a second vertical wall corresponding portion that is the vertical wall corresponding portion of the second member.

As shown in, and the like, in any planes parallel to the two plate members (for example, the top plate portion,), a portion on a downstream side in a direction in a plan view from the vertical wall corresponding portion toward the top plate corresponding portion is defined as “inner side”, and a portion on a downsteram side in a direction in a plan view from the vertical wall corresponding portion toward an opposite side to the top plate corresponding portion is defined as “outer side”.

Each ofis a cross-sectional view of a press-forming devicefor forming the formed product. The press-forming devicecomprises a first metal press moldas a punch, a second metal press moldas a die, and a blank holder. The first metal press moldand the second metal press moldare displaceable relative to each other in height directions of the formed productby a driving mechanism (not shown). The height directions of the formed productare, for example, directions perpendicular to the top plate portion, which correspond to vertical directions in. The press-forming deviceis configured such that the second metal press moldis displaced in the height directions without the first metal press moldbeing displaced. Among the height directions, a direction in which the second metal press moldis moved during the pressing is referred to as “moving direction M”. It should be noted that, the first metal press moldmay be displaced in the height directions instead of the second metal press mold, or both the second metal press moldand the first metal press moldmay be displaced in the height directions.

The blank holderis attached to the second metal press moldto face the first metal press moldand is disposed vertically above the first metal press mold. The second metal press moldhas a built-in mechanism, such as a gas cylinder. The blank holderis configured to be moved downward by the mechanism, such as a gas cylinder, at the same time as the second metal press moldbegins to be moved in the vertical directions, and to be able to clamp the first memberand the second memberbetween the blank holderand the first metal press moldbefore the second metal press moldcontacts the two plate members.

The second metal press mold, the first metal press mold, and the blank holderwork together to perform the press-forming. The second metal press moldand the first metal press moldare interlockable with each other and face each other across a space therebetween before press working. In one example, the second metal press moldhas a concave shape, and the first metal press moldhas a convex shape.

Each of the first metal press moldand the second metal press moldhas a shape that conforms to the shape of the formed product. Specifically, each of the first metal press moldand the second metal press moldcomprises a vertical wall-forming portion,, a flange-forming portion,, a depth-extending portion,, and a shoulder portion,, respectively. The vertical wall-forming portion,is a portion for forming the vertical wall portion,. The flange-forming portion,is a portion for forming the flange portion. The depth-extending portion,is a wall-like portion that extends substantially in the vertical directions and is a portion that couples the flange-forming portion,and the shoulder portion,to each other, respectively.

The shoulder portion,is a surface parallel to the flange-forming portion,. The shoulder portion,is located on the outer side and on a downstream side in the moving direction M with respect to the flange-forming portion,, respectively. The shoulder portion,is located on the downstream side in the moving direction M with respect to an end of the vertical wall-forming portion,on the downstream side in the moving direction M and is located on the outer side with respect to the vertical wall-forming portion,, respectively.

The shoulder portion,includes a surface whose angle to the moving direction M is greater than that of the vertical wall portion,. In other words, the angle formed by the moving direction M (that is, a vertical straight line) and the surface included in the shoulder portion,(for example, a surface extending generally along horizontal directions) is greater than an angle formed by the moving direction M and a surface included in the vertical wall portion,(for example, a surface extending generally along the vertical directions).

Accordingly, the second metal press moldhas a step shape. The term “step shape” as used herein referred to a shape having surfaces substantially parallel to the top plate portion,(for example, the flange-forming portionand the shoulder portion).

Next, a method of manufacturing the formed productwill be explained. In the present embodiment, operations are performed in accordance with a procedure shown into manufacture the formed product.

In the method of manufacturing the formed product, as shown in, blanking (S) is performed at first. The term “blanking” as used herein refers to an operation of cutting out blank materials for materials of the formed productby, for example, cutting out portions from a rolled steel plate. At this time, the second memberis cut out so that a length of the second memberin its width directions is shorter than a length of the first memberin its width directions.

Subsequently, in S, the two plate members, that is, the first memberand the second memberare joined to each other by welding the top plate portionand the top plate portion. In the welding, as shown in, the two plate members are arranged so that the second memberis completely covered by the first memberin a plan view. Specifically, the second endE, which is the end portion of the second member, is disposed so as to locate on the inner side with respect to the first endE, which is the end portion of the first member, and in this state, the two welding portionsJ are formed.

In the configuration of the present embodiment, the first memberand the second memberare made of the same materials, and a thickness tof the second memberis greater than a thickness to of the first member, as shown in. In this case, second moments of area of the two plate members are compared and expressed by bt/12≤bt/12, which indicates that the second moment of area of the first memberis equal to or smaller than the second moment of area of the second member. It is considered that, in such a case, an effect of curving the first memberis more likely to be obtained, and that an amount of springback of the first memberbecomes equal to or smaller than an amount of springback of the second member. It should be noted that “b” is a width of a material (for example, a length in the longitudinal directions in). In other words, it is considered that, in a case where the first memberand the second memberare made of the same materials, if the thickness tof the second memberis equal to or greater than the thickness to of the first member, a gap between the vertical wall portionand the vertical wall portionis reduced.

Subsequently, in S, the top plate portion,of the two plate members, in which the two welding portionsJ are formed, is clamped. That is, in a state where a space is formed between the blank holderand the first metal press mold, the two plate members, in which the two welding portionsJ are formed, are placed on the first metal press mold, as shown in. At this time, the first memberis disposed on a side closer to the second metal press mold(that is, vertically upper side) with respect to the second member. In a line of sight along the moving directions M, the second endE is disposed on the inner side with respect to the shoulder portion. This is intended to enable the shoulder portionto contact the extending portion.

Then, as shown in, the blank holderis moved in the moving direction M to close the space between the blank holderand the first metal press mold. In this way, the top plate portion,of the two plate members is clamped between the blank holderand the first metal press mold.