Vehicle door frame structure and method of producing vehicle door frame

In a vehicle door frame structure including a sheet-metal member of a vehicle door frame, the sheet-metal member formed by a metal sheet includes a folded edge at an edge of the metal sheet, wherein an end of the folded edge is in noncontact with a remaining part of the metal sheet. The folded edge has an inclined shape which is inclined to increase a distance between the folded edge and the remaining part of the metal sheet in a direction from a bend of the folded edge to a free end of the folded edge.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the structure of a vehicle door frame in which hemming (empty hemming) is formed at an edge of a metal sheet and also relates to a method of producing such a door frame.

2. Description of Related Art

In vehicle door frames (door sashes), regardless of press-molded products or roll-formed products, sometimes hemming (empty hemming/press working), in which an edge of a single metal sheet is folded back, is performed instead of seaming, in which two metal (iron-based or aluminum-alloyed) sheets are joined. Typically, hemming is performed on the edge (vertical edge) of a design portion of a vertical pillar sash on the vehicle exterior side thereof. Principal purposes of hemming are to improve the outward appearance of the edge of a metal sheet and prevent this edge from rusting, and conventional hemming consists of an essential three-step process: down-flanging (90-degree bending), prehemming and rope-hemming. The first bending step (down-flanging) bends the edge of a metal sheet to substantially 90 degrees. The second bending step (prehemming) further bends the edge by approximately an additional 45 degrees (i.e., approximately 135 degrees with respect to the metal sheet before the first bending step), and the final step (rope-hemming) folds the edge back (by approximately 180 degrees with respect to the metal sheet before the first bending step) onto the major part of the metal sheet (the remainder of the metal sheet) while leaving an arc-shaped cross sectional portion (space/clearance/air pocket) in the folded edge. Rope-hemming is sometimes replaced by flat-hemming (0-degree (180-degree) bending) that folds the edge so as to completely lie on the major part of the metal sheet (the remainder of the metal sheet). A sealer (waterproofing agent) is usually applied to the door frame edge on which hemming has been performed to prevent the edge from rusting. In this specification, “hemming” (empty hemming) is defined as press-working an edge of a single metal sheet by folding the edge back without sandwiching any other metal sheet therebetween, whereas “seaming” is defined as press-working to join a first metal sheet with a second metal sheet by sandwiching the second metal sheet between the first metal sheet and the folded-back edge of the first metal sheet.

Conventional hemming consists of an essential three-step process: down-flanging, prehemming and rope-hemming (or flat-hemming) as described above, which has been common technical knowledge in the related art.

SUMMARY OF THE INVENTION

The present invention has been made by reviewing the above-described common technical knowledge and provides a vehicle door frame structure and a method of producing a vehicle door frame each of which makes it possible to simplify the manufacturing process of a vehicle door frame having one or more hems (empty hems).

Inventors of the present invention have achieved the present invention after reaching the conclusion that the reason why prehemming and rope-hemming (or flat-hemming) have been considered essential after down-flanging was because it was believed that it was necessary for the end (free end) of the folded edge to be brought into contact with the major part of the metal sheet (the remainder of the metal sheet), and that it is possible to sufficiently accomplish the above-described principal purpose of hemming (to improve the outward appearance of an edge of a metal sheet and prevent this edge from rusting) without needing to bring the free end of the folded edge into contact with the major part of the metal sheet.

According to an aspect of the present invention, a vehicle door frame structure is provided, including a sheet-metal member of a vehicle door frame, the sheet-metal member formed by a metal sheet including a folded edge at an edge of the metal sheet, wherein an end of the folded edge is in noncontact with a remaining part of the metal sheet. The folded edge has an inclined shape which is inclined to increase a distance between the folded edge and the remaining part of the metal sheet in a direction from a bend of the folded edge to a free end of the folded edge.

It is desirable for the sheet-metal member to include a vertical pillar sash of a door sash of the vehicle door frame, and for the folded edge to be formed at a vertical edge of a design portion of the vertical pillar sash on a vehicle exterior side thereof.

It is desirable for a waterproof agent to be applied between the end of the folded edge and the remaining part of the metal sheet.

It is desirable for an opening angle of the folded edge relative to the remaining part of the metal sheet is less than 25 degrees.

This opening angle can be the maximum possible bending angle of the folded edge (in other words, the minimum angle of the folded edge relative to the major part of the metal sheet) by a single bending operation (partial hemming/incomplete hemming) that is performed after down-flanging is performed on the metal sheet.

If the opening angle is greater than or equal to 25 degrees, there is a possibility of workability deteriorating when a sealer is applied to the folded edge in the manufacturing process of the door sash. Accordingly, it is not desirable that the opening angle be greater than or equal to than 25 degrees.

It is practical for a width of the metal sheet to progressively vary.

It is desirable for the metal sheet to be press-worked to form the sheet-metal member, together with the folded edge.

According to another aspect of the present invention, a method of producing a vehicle door frame is provided, including a sheet-metal member, which is formed by a metal sheet in which a folded edge is formed at an edge of the metal sheet, the method including down-flanging the edge of the metal sheet to form a bent edge, and partially hemming the bent edge of the metal sheet. The partially hemming of the bent edge of the metal sheet is performed in a single operation so that the folded edge is angled relative to a remaining part of the metal sheet so that a distance between the folded edge and the remaining part of the metal sheet increases with respect to a direction from a bend of the folded edge to a free end of the folded edge.

The method of producing a vehicle door frame according to the present invention forms the folded edge by only carrying out a two-step process: down-flanging and partial hemming (incomplete hemming).

It is desirable that a waterproof agent (sealer) be applied between the end of the folded edge, on which partial hemming has been performed, and the major part of the metal sheet.

The vehicle door frame structure according to the present invention can be applied to at least an edge of a design portion of a vertical pillar sash of a door sash.

According to the present invention, in the vehicle door frame structure, the conventional three-step process for forming a folded edge at an edge of a metal sheet can be reduced to a two-step process. This contributes to a significant cost reduction at the production site.

The present disclosure relates to subject matter contained in Japanese Patent Application No. 2012-238446 (filed on Oct. 30, 2012) which is expressly incorporated herein by reference in its entirety.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1shows, by way of example, a side elevational view of a motor-vehicle front door (front-left side door)10, to which the vehicle door frame structure according to the present invention is applied. Note that a lower half of the front door10is not shown inFIG. 1. The front door10is provided with a door body (an inner panel and an outer panel)11and a door sash (window frame)13which forms a window opening12immediately above the door body11.

The door sash13is provided with a curved upper sash14which receives the upper edge of a window pane G and a vertical pillar sash (sheet-metal member)15which extends along the associated (left) center pillar of a vehicle body (not shown) and receives the vertical edge of the window pane G.

The vertical pillar sash15of the prevent embodiment of the motor-vehicle front door10is made of a plurality of iron-based materials (metal sheets) which are joined together. Specifically, the vertical pillar sash15is provided with a main sash member21, a sub-sash member (weather strip retaining member)22and a weather strip retaining member23as shown inFIG. 2. The vehicle exterior side, the vehicle interior side, the vehicle body side and the window opening side (window pane side) are defined as shown inFIG. 2. Each of the sub-sash member22and the weather strip retaining member23is uniform in cross section and is formed by roll-forming (or can be formed by press-forming).

The main sash member21is provided with a design portion21a, a connecting portion21band a box-channel forming portion21c. The design portion21ais positioned on the vehicle exterior side, the connecting portion21bis formed by bending the end of the design portion21aon the window-opening side toward the vehicle interior side, and the box-channel forming portion21cis formed by bending the end of the connecting portion21bon the vehicle-interior side firstly toward the window-pane side and subsequently toward the vehicle exterior side. The width W of the design portion21aof the main sash member21varies (progressively varies) in the vertical direction (progressively increases in the downward direction). In addition, the length (width) D of the connecting portion21btoward the vehicle interior side also varies in the vertical direction (increases in the downward direction), and the shape of the box-channel forming portion21calso varies in accordance with variation in length (width) of the connecting portion21b. The main sash member21is formed by press-forming.

The sub-sash member22is provided with a design portion22a, a connecting portion (base wall)22band a glass run retaining portion22c. The design portion22ais positioned on the vehicle exterior side, the connecting portion22bextends along the connecting portion21band is formed by bending the vehicle-body side end of the design portion22atoward the vehicle interior side, and the glass run retaining portion22cis formed by bending the vehicle-interior side end of the connecting portion22btoward the window opening side. The glass run retaining portion22cis provided with a stepped retaining portion22d. The glass run retaining portion22cis positioned on the vehicle exterior side of the box-channel forming portion21cof the main sash member21.

The weather strip retaining member23is provided with a base wall23awhich extends along the connecting portion21b, and two retaining edges23band23cwhich are formed by bending the vehicle-exterior side end and the vehicle-interior side end of the base wall23ainwardly toward each other.

The main sash member21, the sub-sash member22and the weather strip retaining member23are joined together by spot-welding the connecting portion21b, the connecting portion22band the base wall23atogether. In addition, the main sash member21is provided at the vehicle-exterior side edge of the box-channel forming portion21cwith a welded wall21dwhich is overlaid onto and welded to the window-opening side edge of the glass run retaining portion22cof the sub-sash member22, and the box-channel forming portion21cand the glass run retaining portion22cform a box channel portion21x. The volume of the box channel portion21xincreases in a downward direction in accordance with variation in length of the connecting portion21band the box-channel forming portion21ctoward the vehicle interior side.

A known glass run (not shown) is held in the space formed by the design portion22a, the connecting portion22band the glass run retaining portion22cof the sub-sash member22, and a known weather strip (not shown) is held by the weather strip retaining member23. The glass run is in sliding contact with the vertical edge of the window pane G that moves up and down in the window opening12, and the weather strip comes into contact with a vehicle body and is elastically deformed when the front door10is closed. A vehicle-body side weather strip (not shown) which is pressed and elastically deformed by the box-channel forming portion21c(the box channel portion21x) is installed onto the vehicle body.

In the vertical pillar sash15that has the above described structure, hemming has been performed on the vehicle-body side edge (the right edge with respect toFIG. 2) of the design portion21aof the main sash member21, the window-opening side edge (the left edge with respect toFIG. 2) of the design portion22aof the sub-sash member22and the edge of the retaining edge23b, of the weather strip retaining member23, that faces the vehicle interior side. Out of these edges, the hemming formed on the design portion22ais a hemming in which an edge of the design portion22ais folded over inwardly (toward the vehicle interior side) onto itself (i.e., folded by 180 degrees) by roll-forming so that a hem (folded edge)22hlies on a remaining part of the metal sheet of the sub-sash member22, and the hemming on the retaining edge23bis a hemming in which an edge of the retaining edge23bis folded over outwardly (toward the vehicle exterior side) onto itself (i.e., folded by 180 degrees) by roll-forming so that a hem (folded edge)23hlies on a remaining part of the metal sheet of the weather strip retaining member23. The number of processes is not big problem when hemming is performed by roll-forming.

On the other hand, the vertical edge (the right edge with respect toFIG. 2) of the design portion21aof the main sash member21that is produced by press working is formed by partial hemming in which the end (free end) of a folded edge21hof the design portion21ais in noncontact with a remaining part of the metal sheet of the design portion21aas shown by an enlarged view inFIG. 3. The folded edge21hhas an inclined shape which is inclined to progressively increase the distance between the folded edge21hand the remainder of the metal sheet of the design portion21ain a direction from a bend21h′ to the free end of the folded edge21h, and an opening angle α of the folded edge21hrelative to the remainder of the metal sheet of the design portion21ais set at an angle of 20±5 degrees. This opening angle α is set smaller than 25 degrees. If the opening angle α is greater than or equal to 25 degrees, there is a possibility of the workability deteriorating when a sealer is applied to the end of the folded edge21hin the manufacturing process of the door sash13. If the opening angle α is smaller than 15 degrees, it is difficult to form the folded edge21hby a two-step press working process (i.e., a down-flanging step and the subsequent single partial hemming step).

FIGS. 4A and 4Bshow a process of forming the folded edge21hby partially hemming the end of the design portion21aby press-working.FIG. 4Ashows the down-flanging step andFIG. 4Bshows the partial hemming step. In the down-flanging step shown inFIG. 4A, the edge of the design portion21aof the main sash member21after it is formed is bent to an approximately right angle (90 degrees) to form a right-angle bent edge21v. Subsequently, in the partial hemming step shown inFIG. 4B, with the design portion21afixed, the right-angle bent edge21vis folded inwardly to an approximately 20 degrees with a punch (tool)3a.

As described above, one press working step (rope-hemming/flattening step) has been omitted by forming the folded edge21h, the end (free end) of which is in noncontact with the remainder of the metal sheet of the design portion21a, by a two-step process consisting of a down-flanging step and an partial hemming step, which can contribute to cost reduction. A sealer (waterproofing agent)24is applied (filled in) between the end of the folded edge21hand the design portion21aas a post-process for the purpose of waterproofing and rustproofing. Since the width W of the design portion21aof the main sash member21progressively varies, roll-forming is unsuitable for forming the main sash member21, and it is practical for the main sash member21to be formed by press-forming. In other words, if the main sash member21is formed by press-forming, the folded edge21hcan be formed by the above described two-step process.

Although the vertical pillar sash15of the above described embodiment of the motor-vehicle front door10is configured of three members: the main sash member21, the sub-sash member22and the weather strip retaining member23, it is possible for the vertical pillar sash15to be configured of two or more than three members.

FIGS. 5 and 6show another embodiment of the vehicle door frame structure according to the present invention, wherein the vehicle door frame structure according to the present invention has been applied to a mirror-mounting bracket (sheet-metal member)17of the front door10. The door sash13of the front door10is provided with a front pillar16positioned in front of an upper sash14and a vertical pillar sash15positioned behind the upper sash14, and the mirror-mounting bracket17that is made of a metal sheet is welded to the front pillar16to be fixed thereto. More specifically, the front pillar16is a roll-formed product having a uniform cross-section and provided with a design portion16a, a box channel portion16band a connecting portion16c. The design portion16ais positioned on the vehicle exterior side, the box channel portion16bis positioned on the vehicle interior side, the connecting portion16cconnects the design portion16aand the box channel portion16b, and the mirror-mounting bracket17is welded to the front (vehicle-body side) of end (the left end with respect toFIG. 6) of the design portion16aat the vehicle-body side. The mirror-mounting bracket17is press-formed and provided, at the vertical edge thereof on the vehicle-body side (the left side with respect toFIG. 6), with a folded edge17athat is folded toward the vehicle interior side. Similar to the folded edge21hof the previous embodiment of the vehicle door frame structure, the folded edge17ais in noncontact with the remainder of the main sheet of the mirror-mounting bracket17and has an inclined shape which is inclined to increase the distance between the folded edge17aand the remainder of the main sheet of the mirror-mounting bracket17in a direction toward the free end of the folded edge17a. Similar to the folded edge21h, a sealer (waterproofing agent)24is applied (filled in) between the end of the folded edge17aand the remainder of the main sheet of the mirror-mounting bracket17as a post-process for the purpose of waterproofing and rustproofing. Accordingly, an enlarged shape of the portion circled by a two-dot chain line III inFIG. 6is substantially identical to that shown inFIG. 3. A door mirror (not shown) is fixed to the mirror-mounting bracket17. Accordingly, not only can the present invention can be applied to a vertical pillar sash, but also another metal sheet which constitutes an element of a vehicle door frame.

FIGS. 7A,7B and7C show an overview of a conventional hemming;FIG. 7Ashows a down-flanging step,FIG. 7Bshows a prehemming step andFIG. 7Cshows a rope-hemming step. The down-flanging step shown inFIG. 7Ais identical to that shown inFIG. 4A. Namely, in the down-flanging step shown inFIG. 7A, an edge of a metal sheet1is bent to an approximately right angle (90 degrees) to form a right-angled edge1a. The subsequent prehemming step shown inFIG. 7Bis a step for bending the edge1afurther inwardly to an approximately 135 degrees to form an inclined edge1bwith a flattening punch (flattening tool)4a. The subsequent rope-hemming step shown inFIG. 7Cis a step for bending the edge1bfurther inwardly to form a folded edge1cwith a flattening punch (flattening tool)4bwith the metal sheet1fixed until the free end thereof comes into contact with a remaining part of the metal sheet (main sheet)1. In this manner, conventional hemming requires three working steps.