Auxiliary frame for a motor vehicle and method for its manufacture

Abstract

Auxiliary frame (1) for a motor vehicle for receiving and / or supporting at least one vehicle component, comprising a frame element (2) formed by two cross members (4, 5) spaced apart from each other in the longitudinal direction (x-direction) of the motor vehicle and longitudinal members (6, 7, 8) connecting the cross members (4, 5) to each other, wherein the cross members and longitudinal members (4, 5;6, 7, 8) define at least one opening (11, 12) between them, to which opening (11, 12) at least one planar stiffening element (13, 14) made of a plastic or a fiber-reinforced plastic is assigned, and wherein the at least one stiffening element (13, 14) is arranged within the at least one opening (11, 12), wherein the stiffening element (13, 14) is positively connected to the frame element (2), characterized in that at least one positive locking element (15) is arranged on the frame element (2), which is embedded in the plastic matrix (18) of the stiffening element (13, 14) as a result of a plastic injection molding process for producing the stiffening element (13, 14).

Description

[0001] The invention relates to a subframe for a motor vehicle according to the combination of features of claim 1 of the invention. According to claim 10 of the invention, it further relates to a method for manufacturing such a subframe.

[0002] From EP 0 941 912 B1, a generic subframe for a motor vehicle is known in which a planar stiffening element is provided between two longitudinal members. This stiffening element is intended to act as a shear field and transfer a force introduced into one of the two longitudinal members of the subframe – for example, in an accident – ​​to the opposite longitudinal member. The stiffening element arranged between the two longitudinal members of the subframe is intended, in particular, to prevent a typical displacement of the two longitudinal members of the subframe relative to each other (parallelogram deformation) in a side impact. The stiffening element consists of a metal sheet and is fixed to the subframe by bolts via brackets arranged on the longitudinal members.DE 10 2008 006 006 A1 describes a subframe of a motor vehicle, designed in particular as an axle carrier, with lateral longitudinal members arranged essentially in the longitudinal direction of the vehicle, and with a plate-like stiffening element made of light metal or plastic, in particular fiber-reinforced plastic. The plate-like stiffening element is placed on the subframe from below and connected to the vehicle body both directly and indirectly via the subframe by means of detachable fasteners, such as screws. DE 10 2012 2015 099 A1 describes a subframe of a motor vehicle designed as an axle carrier, comprising a first and a second longitudinal member, at least one cross member connecting the two longitudinal members, and a plate-shaped element made of fiber-reinforced plastic, which is screwed to the first and second longitudinal members and forms a shear field.The two longitudinal beams are preferably made of cast aluminum, whereas a fiber-reinforced plastic is proposed for at least one crossbeam.

[0003] The object of the invention is to provide an alternative subframe of the generic type compared to the prior art described above, which, while retaining the advantages of the prior art, namely ensuring lightweight construction combined with high strength and stiffness of the subframe, is simpler to manufacture. Furthermore, it is an object of the invention to provide a method for manufacturing such a subframe.

[0004] The problem is solved by an auxiliary frame for a motor vehicle for receiving and / or supporting at least one vehicle component, comprising a frame element formed by two cross members spaced apart from each other in the longitudinal direction (x-direction) of the motor vehicle, and longitudinal members connecting the cross members to each other, wherein the cross members and longitudinal members define at least one opening between them, to which opening at least one planar stiffening element made of a plastic or a fiber-reinforced plastic is assigned, and wherein the at least one stiffening element is arranged within the at least one opening and is positively connected to the frame element.

[0005] This measure advantageously reduces the effort required to manufacture the subframe. In particular, costly fastening measures for attaching the stiffening element to the subframe frame using state-of-the-art mechanical fasteners, which involve increased material costs and weight, are no longer necessary.

[0006] The dependent claims describe preferred further developments or embodiments of the invention.

[0007] The frame element is preferably a one-piece cast part, which is easy and cost-effective to manufacture. More preferably, the frame element is made of a light metal, in particular aluminum or an aluminum alloy. Such a material advantageously meets the desired lightweight construction requirements. As further provided by the invention, at least one interlocking element is arranged on the frame element, which, as a result of a plastic injection molding process for manufacturing the stiffening element, is embedded in the plastic matrix of the stiffening element. This creates a particularly strong bond between the frame element and the stiffening element. To further reduce manufacturing costs, the at least one interlocking element is preferably formed integrally with the frame element or a transverse and / or longitudinal member thereof.Preferably, at least one positive locking element is formed by a pin element extending into the opening.

[0008] An even stronger connection between the frame element and the stiffening element is achieved by designing the pin element with at least one undercut. To further increase the stiffness and strength of the subframe without increasing its weight, the at least one stiffening element, made of fiber-reinforced plastic, is preferably reinforced by fibers, fabrics, and / or woven threads embedded in the plastic matrix, wherein diagonally arranged and intersecting threads are provided in the fabric and / or woven threads with respect to the frame element. In an advantageous embodiment of the invention, to improve the drag coefficient of the vehicle, the at least one stiffening element is arranged in a region of the frame element close to the ground.

[0009] The process for manufacturing a subframe for a motor vehicle is characterized by the following steps: a) Provision of a frame element comprising a front and rear cross member viewed in the longitudinal direction (x-direction) of the vehicle, which are spaced apart from each other and connected to each other by means of longitudinal cross members, wherein the cross members and longitudinal cross members define at least one opening between them, and comprising at least one positive locking element, b) Inserting the frame element into an injection mold, c) Arrangement of at least one fabric and / or thread mesh between the transverse and longitudinal crossbeams of the frame element that define at least one opening, and d) Injecting a plastic matrix into the said opening in such a way that the at least one form-locking element or both the at least one form-locking element and the at least one fabric and / or thread lay-up is / are embedded in the plastic matrix and, after the plastic matrix has hardened, a plate-shaped stiffening element is formed which is form-locking with the frame element.

[0010] The invention is explained in more detail below with reference to an exemplary embodiment shown schematically in the drawings. However, it is not limited to this embodiment, but encompasses all embodiments defined by the claims. The drawings show:

[0011] Fig. 1 a support frame designed according to the invention in a top view,

[0012] Fig. 2 the auxiliary frame Fig. 2 in a perspective view from the rear of the vehicle, and

[0013] Fig. 3 the detail “Z” after Fig. 2.

[0014] The Fig. 1 and Fig. Figure 2 shows the auxiliary frame designed according to the invention. 1 The subframe 1 For example, it is an axle carrier and is arranged in the front section of a motor vehicle (not shown in detail) to receive and / or support one or more vehicle components, such as wheel guides, steering gears and the like.

[0015] said support framework 1 It includes, firstly, a frame element 2 The frame element 2 points in the direction of travel 3 seen a first, front and a second, rear crossbeam 4 , 5 The crossbeams are spaced apart from each other when viewed in the longitudinal direction (x-direction) of the vehicle. 4 , 5 are secured by means of two laterally arranged longitudinal crossbeams 6 , 7They are interconnected. Furthermore, according to this embodiment, there is a connection between the two lateral longitudinal crossbeams. 6 , 7 a third longitudinal beam 8 planned. Furthermore, various recordings are planned. 9 for connecting said vehicle components to the subframe 1 as well as fastening points 10 for attaching the auxiliary frame 1 shown on the vehicle body. The frame element, designed here as a closed frame, 2 The component is preferably manufactured as a single-piece casting using a known casting process and is further preferably made of a light metal, for example, aluminum or an aluminum alloy. The invention also naturally encompasses a subframe constructed from several individual parts. 1 (not shown in the drawing). The crossbeams and longitudinal beams 4 , 5 ; 6 , 7 , 8of the frame element 2 limit the distance between two openings 11 , 12 or rather, these openings form 11 , 12 of the frame element 2 out of.

[0016] Secondly, the support framework includes 1 two flat stiffening elements 13 , 14 Made of fiber-reinforced plastic. One stiffening element each. 13 , 14 is within the aforementioned openings 11 , 12 arranged and takes the clear width of the respective opening 11 , 12 one. The stiffening elements 13 , 14 They thus function as shear fields and transfer their power to the subframe 1 acting forces or thrust forces. To improve the vehicle's drag coefficient, the stiffening elements are... 13 , 14 present in a ground-level area of ​​the frame element 2 ordered (see especially Fig. 2).

[0017] The stiffening elements 13 , 14 are form-fitting with the frame element 2 of the auxiliary framework 1 connected. The frame element has this feature. 2 via a multitude of positive locking elements 15 in the form of pin elements 16 The tenon elements 16 are connected to the respective opening 11 , 12 pointing surface sections of the transverse and / or longitudinal trusses 4 , 5 ; 6 , 7 , 8 fastened. The pin elements 16 are preferably located around the perimeter of the respective opening 11 , 12 arranged.

[0018] In contrast, the pin elements 16 even only in limited sections of the frame element 2 , for example, only in the area of ​​the crossbeams 4 , 5 or the longitudinal beams 6 , 7 , 8be arranged (not shown graphically). Fig. Figure 3 shows only examples of pin elements. 16 in the area of ​​the opening 12 on the front cross member 4 .

[0019] The aforementioned pin elements are preferred. 16 one-piece with the cross and longitudinal beams 4 , 5 ; 6 , 7 , 8 respectively with the frame element 2 formed and thus created during the casting process according to this exemplary embodiment. The pin elements 16 are each in the form of a T-profile with a profile web. 16a and one perpendicular to the profile rib 16a directed profile flange 16b trained. By means of their profile bridge 16a are the pin elements 16 on the frame element 2 held. The free end of the pin element 16 is through the profile flange 16b formed, which forms the profile rib16a projecting laterally and thus undercutting 17 trains ( Fig. 3).

[0020] However, the invention is not limited to such positive locking elements. 15 , but encompasses any suitable type of positive locking element 15 For example, even a single positive locking element can 15 or a form-fitting contour in the form of something not shown in the drawing, the respective opening 11 , 12 a circumferential flange element limiting and extending into the same, which, with regard to the preferably one-piece frame element, is provided 2 preferably in one piece with the frame element 2 is formed. The positive locking element 15 The flange element in question can have a preferably circumferential rest at its free end, which forms an undercut. 17 trains.

[0021] The positive locking elements15 , the pin elements are present 16 , are the result of a plastic injection molding process for the production of the respective stiffening element 13 , 14 into the plastic matrix 18 of the stiffening element 13 , 14 embedded. For this purpose, it is embedded with the aforementioned positive locking elements. 15 in the form of said pin elements 16 equipped frame element 2 positioned within a plastic injection mold not shown in the drawing, but known per se, and are moved during the injection of the plastic matrix 18 into the openings 11 , 12 the positive locking elements 15 or pin elements 16 overmolded. After the plastic matrix has cured. 18 is particularly due to the undercuts formed 17 the pin elements 16 an extremely strong joint between the frame element 2and the stiffening elements 13 , 14 created.

[0022] To avoid increasing the weight of the subframe 1 to further increase its stiffness and strength are according to Fig. 3 the stiffening elements 13 , 14 fiber-reinforced, for example, glass or carbon fiber reinforced. According to this embodiment, one or more fabrics are arranged one above the other. 19 with regard to the frame element 2 preferably diagonally arranged and intersecting threads 20 into the plastic matrix 18 embedded, thereby the auxiliary frame 1 with regard to its arrangement in the motor vehicle, it is optimized for load, especially in the transverse direction of the vehicle (y-direction) and is designed to be particularly stiff.

[0023] Alternatively or in combination with said tissue(s) 19Directed and / or undirected fibers and / or woven fibers may also be used. A woven fiber structure is understood to be a sheet-like structure consisting of one or more layers of parallel, elongated fibers. 20 consists of the threads. 20 Different layers can be oriented differently, for example intersecting in the top view, especially in relation to the frame element. 2 be arranged diagonally and intersect (not shown in the drawing). Reference symbol list 1 Subframe 2 frame elements 3. Direction of travel 4 crossbeams 5 crossbeams 6 Longitudinal crossbeam 7 Longitudinal crossbeam 8 Longitudinal crossbeam 9th entry 10 Mounting point 11 Opening 12 Opening 13 Stiffening element 14 Stiffening element 15 Positive locking element 16 pin element 16a Profile bridge 16b profile flange 17 Undercut 18 plastic matrix 19 tissues 20 threads QUOTES INCLUDED IN THE DESCRIPTION

[0024] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0025] EP 0941912 B1

[0002] DE 102008006006 A1

[0002] DE 1020122015099 A1

[0002]

Claims

[1] Auxiliary frame ( 1 ) for a motor vehicle for receiving and / or supporting at least one vehicle component, with a frame element ( 2 ), the crossbeams arranged at a distance from each other in the longitudinal direction (x-direction) of the motor vehicle ( 4 , 5 ) as well as the crossbeams ( 4 , 5 ) interconnecting longitudinal beams ( 6 , 7 , 8 ) is formed, with the transverse and longitudinal traverses ( 4 , 5 ; 6 , 7 , 8 ) at least one opening between them ( 11 , 12 ) limit which opening ( 11 , 12 ) at least one planar stiffening element ( 13 , 14 ) is made of a plastic or a fiber-reinforced plastic, and wherein the at least one stiffening element ( 13 , 14 ) within at least one opening (13 , 14 ) arranged and connected to the frame element ( 2 ) is positively connected. [2] Auxiliary frame ( 1 ) according to claim 1, characterized by that the frame element ( 2 ) is a one-piece cast part. [3] Auxiliary frame ( 1 ) according to claim 2, characterized by that the frame element ( 2 ) consists of a light metal, in particular aluminum or an aluminum alloy. [4] Auxiliary framework ( 1 ) according to one of claims 1 to 3, characterized by that on the frame element ( 2 ) at least one positive locking element ( 15 ) is arranged, which is the result of a plastic injection molding process for the production of the stiffening element ( 13 , 14 ) into the plastic matrix ( 18 ) of the stiffening element ( 13 , 14 ) is embedded. [5] Auxiliary framework ( 1 ) according to claim 4, characterized bythat at least one positive locking element ( 15 ) one-piece with the frame element ( 2 ) or a transverse and / or longitudinal beam ( 4 , 5 ; 6 , 7 , 8 ) is trained in the same. [6] Auxiliary framework ( 1 ) according to claim 4 or 5, characterized by that at least one positive locking element ( 15 ) through an opening ( 11 , 12 ) inward-reaching pin element ( 16 ) is formed. [7] Auxiliary framework ( 1 ) according to claim 6, characterized by that the pin element ( 16 ) with at least one undercut ( 17 ) is trained. [8] Auxiliary framework ( 1 ) according to any one of claims 1 to 7, characterized by that at least one stiffening element made of fiber-reinforced plastic ( 13 , 14 ) through into the plastic matrix ( 18 ) embedded fibers, tissue ( 19) and / or is reinforced with thread lay-up, with respect to the frame element ( 2 ) diagonally arranged and intersecting threads ( 20 ) in the tissue ( 19 ) and / or filament fabrics are provided. [9] Auxiliary framework ( 1 ) according to any one of claims 1 to 8, characterized by that at least one stiffening element ( 13 , 14 ) in a low-lying area of ​​the frame element ( 2 ) is arranged. [10] Method for manufacturing an auxiliary frame ( 1 ) for a motor vehicle according to one of claims 1 to 9, characterized by the following steps: a) Provision of a framework element ( 2 ), with a front and rear cross member viewed in the longitudinal direction of the vehicle (x-direction) 4 , 5 ), which are spaced apart from each other by means of longitudinal crossbeams ( 6 , 7 , 8 ) are connected to each other, with the cross and longitudinal beams (4 , 5 ; 6 , 7 , 8 ) at least one opening between them ( 11 , 12 ) limit, and with at least one positive locking element ( 15 ), b) Inserting the frame element ( 2 ) into an injection mold, c) if necessary, arrangement of at least one tissue ( 19 ) and / or thread mesh between which there is at least one opening ( 11 , 12 ) limiting transverse and longitudinal beams ( 4 , 5 ; 6 , 7 , 8 ) of the frame element ( 2 ), and d) Injection of a plastic matrix ( 18 ) into said opening ( 11 , 12 ) such that at least one positive locking element ( 15 ) or both the at least one positive locking element ( 15 ) as well as at least one tissue ( 19 ) and / or filament fabric into the plastic matrix ( 18) is / are embedded and after the plastic matrix has hardened ( 18 ) a form-fitting connection with the frame element ( 2 ) connected plate-shaped stiffening element ( 13 , 14 ) is trained.

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