Patent Application
20100055488
1. Technical Field
The present invention relates to structural inners formed from tailor welded blanks, such as the type used in the manufacture of vehicle doors, and more particularly, to such a blank comprising a plurality of subparts joined by a non-linear weld and a method of reducing the mass of the same.
2. Background Art
Structural inners, such as the type used in vehicular door construction, provide support to interiorly housed components, and increase structural capacity. With respect to doors, for example, it is appreciated that inners provide side-impact reinforcement and form housings for electronic, door latching, and window components. The added weight of these inners, however, presents the increasing need to minimize the material associated therewith. As such, a multi-part light weight aluminum blank consisting of thin sheet metal sections of differing thickness (e.g., 0.8 and 1.8 mm) is typically used for construction, wherein the ratio of the sections results in the total mass of the inner. A vertical linear weld line is conventionally used to join the sections, and the thicker material is positioned towards the front of the inner so as to support the door hinges. The final location of the weld line is determined in part by the formability of the thin blank material near the linear weld.
As shown in prior art
The instant invention presents an innovative application of an engineered non-linear welded blank and method of reducing the mass of a structural inner that addresses the afore-mentioned concerns. Among other things, the inventive method is useful for producing a net mass saving in a structural inner, such as an automotive vehicle door inner, which increases fuel economy. By reducing the mass, the invention is further useful for reducing associated raw material costs, including reduced blank costs. The invention may be implemented using existing three-piece draw dies and requires minimal additional tryout. Moreover, the invention is useful for relocating the failure site to a new location more manageable by a controlled split device added to the draw die set. In this regard, the formability of the non-linear welded blank is also enhanced by the usage of the controlled split device. Finally, the invention is useful for providing improved blank nesting and fixturing for TWB manufacturing.
In a preferred embodiment, an objective of the invention is to reduce the amount of 1.8 mm stock used to manufacture door panels by relocating the weld line such that more of the 1.8 mm stock is replaced by 0.8 mm stock. The invention provides a means for redistributing the forming strains in a tailor welded blank, such that less thick material can be utilized in the draw stamping of the door inner. The curved or non-linear weld line presented strains the thin blank material more evenly in comparison to conventional linear weld applications, delays the initial necking, and the failure localization is relocated in line with the speaker hole. To effect the latter, a controlled split device in the draw die is utilized to maximize the benefit of the invention.
The above described and other features are exemplified by the following figures and detailed description.
Preferred embodiments of the invention are described in detail below with reference to the attached drawing figures of exemplary scale, wherein:
a is an elevation of a prior art door inner comprising first and second blanks having differing thickness and presenting a linear weld line having a lower third length, L1;
The present invention concerns a welded multi-part structural inner 10 presenting a contoured planar construction and a manufacturing application or method of reducing the mass of the same. More particularly, the invention provides an innovative approach to re-distribute the forming strains in a tailor welded blank (TWB) comprising relatively thick and thin steel sections (or “blanks”) 12,14, such that the amount of thin material utilized in the draw stamping of the inner 10 is increased in lieu of thick material (compare
As is known in the art, inners 10 are typically used to increase the structural capacity of or provide otherwise housing and/or reinforcing to an exterior structure, such as a front or rear vehicular door, as shown in the illustrated embodiment. Though described and illustrated with respect to a vehicular door embodiment, it is appreciated that the advantages of the present invention may be used with other applications, and with other vehicular structures, such as hoods, decklids, etc. That is to say, the following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
In a first aspect of the invention, and as best shown in
For example, in
As previously mentioned, the weld line contour is preferably optimized to relocate the failure to a suitable location, which allows further reduction of thick blank material near the lower edge of the inner 10. That is to say, optimal a2 raises the failure site away from the lower edge and towards the speaker hole 18, which enables the weld line 16 in the lower third to be further shifted forward. It is appreciated that forwardly shifting the weld line 16 in this area results in savings within the engineering scrap of the thin blank coil, which presents a maximum width or buy point at the intersection of S2 and S3. As such, it is appreciated that a wider thin blank 12 will not be required to supplant the thick material at this location; or, in other words reduction of the pitch of the thick blank 12 in this manner does not affect the mass penalty of the 0.8 mm blank 14.
In another aspect of the invention, a method of forming the inner 10 includes localizing and relocating the failure to a more manageable location, e.g., in line with the speaker hole 18 of the door. Here, it is appreciated that an otherwise conventional three-piece draw die 20 incorporating a controlled split device 22 may be used to control the formation of the split 24 during the drawing process, and that additional dies and/or tonnage pads are not required. That is to say, an existing three-piece production draw die can be retrofitted for use herein by adding the controlled split device 22 to engage the speaker scrap hole on the J-plane (i.e., the interior face generally parallel to the exterior surface of the door that defines the speaker hole, etc.) of the door inner 10. At this location, it is appreciated that the preferred split 24, post expansion, is entirely contained within the speaker hole 18, such that when the hole 18 is stamped the split 24 is discarded therewith.
In addition to the provisions of the non-linear weld 16, the formulation of a controlled split 24 can be used to great effectiveness for minimizing door mass, and increasing blank savings, and vehicle fuel economy, etc. More particularly, the control split 22 is used to effect material feed into the lower front corner of the inner 10 during the draw, as well as delay the localization and minimize the magnitude of the failure, which is preferably located within the shadow of the control split 24. As such, the split 24 is preferably located within the lower half of the hole 18 and spaced from the edge thereof, so as to leave room for expansion during drawing.
In a preferred embodiment, the controlled split device 22 is timed to engage the thin blank 14 at least 6 and more preferably 10 mm from bottom (i.e., the end of the drawing or stamping process). This, it is appreciated, increases the formability window of the split 24, and allows the weld line 16 at the thick blank buy point, p, to be moved even further forward. As a result, a 1.8 mm blank pitch as low as 372 mm may be realized in the illustrated embodiment.
In an exemplary door application, Table 1 shows relative mass savings for trimmed draw inners 10 contrasting conventional production inners against other mass reduction methods including the present non-linear weld line method:
Thus, from Table 1, the usage of the proposed non-linear welded blank with controlled split resulted in a reduction in the 1.8 mm blank 12 equal to 0.55 kg per door, or 2.0 kg per 4-door vehicle (not shown). Moreover, a sampling of the blank mass reduction of the 1.8 mm stock with a controlled split engaged at 8 and 10 mm off bottom of draw stroke was observed and predicted to provide net mass savings of 0.80, and 1.01 kg, respectively. The data was taken from a configuration where the weld line 16 was shifted forward from the buy-point an additional 12 mm, and for the 8 and 10 mm split engagements, the pitch was able to be additionally reduced by 25 mm while still meeting the formability requirements. Moreover, it was observed that the maximum thinning in the thin blank 14 at the weld line 16 on bottom of stroke was 19%, and that engaging the controlled split at 8 mm off bottom resulted in a maximum thinning on bottom of 17%. Therefore, it is appreciated that using a timing window to engage the controlled split device 22 between 6 and 10 mm off bottom of draw stroke results in additional robustness of the formability and additional mass and blank savings with the non-linear welded blank.
As shown in Table 1, shifted linear welds also exhibit mass savings, however, as previously mentioned, they require additional draw die, and/or tonnage pads to go from 80 to 120 tons of necessarily applied force. Moreover, it is appreciated that TWB's constructed with shifted linear welds do not pass formability requirements.
To effect raw material savings it follows that the reduction in the thick blank 12 must offset the penalty increase in the 0.8 mm material as a result of the forward change in location of the weld line 16. In the particular sampling, it was observed that a penalty increase of the 0.8 mm blank 14 of 0.69 kg resulted from the increase of material pitch dimension for the nesting of a two-out blank as is conventionally presented for a production door. That is to say, the convex portion of the blank 14 under a non-linear weld requires a wider starting blank. It is appreciated that a two-out blank is presented, such that per blank, the net penalty increase in mass of blank is 0.69/2 or approximately 0.35 kg.
When subtracting the thin blank penalty of 0.35 kg from the thick blank savings previously mentioned, it is appreciated that net mass savings up to 0.66 kg can be realized using the inventive method. It is also appreciated that the net cost savings resulting from the present invention depends upon the capitalized cost of the blanking and fixture costs for the TWB manufacturing, and the resultant piece cost increase of the TWB welding of the non-linear blank.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Also, as used herein, the terms “first”, “second”, and the like do not denote any order or importance, but rather are used to distinguish one element from another, and the terms “the”, “a”, and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. All ranges directed to the same quantity of a given component or measurement is inclusive of the endpoints and independently combinable.
This patent application claims priority to, and benefit from U.S. Provisional Patent Application Ser. No. 61/093,313, entitled “NON-LINEAR WELDED BLANK AND METHOD OF REDUCING MASS,” filed on Aug. 30, 2008; the disclosure of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61093313 | Aug 2008 | US |
