Front subframe for a motor vehicle and motor vehicle

Abstract

A subframe for a motor vehicle is proposed, characterized by stiffened force paths for transferring forces acting during a frontal crash to the bolts used to connect the subframe to the body. The bolts are designed to fail under controlled conditions, so that the subframe deforms only minimally during the crash, thus increasing the potential for deformation in other areas, such as the body's longitudinal members. A motor vehicle with such a subframe is further proposed.

Description

[0001] The invention relates to a front subframe for a motor vehicle, wherein the subframe has a right rear screw receptacle, a left rear screw receptacle, a right front screw receptacle, and a left front screw receptacle for connecting the subframe to a body of a motor vehicle. The invention further relates to a motor vehicle with such a subframe.

[0002] A subframe is a common component in automotive engineering. The body-side pivot points of the wheel suspension are attached to the subframe, and the assemblies, i.e. the engine, transmission and steering gear, are usually also attached to the front subframe. The subframe can also be referred to as a chassis subframe or axle carrier. The subframe often consists of several components that are joined together during production of the subframe. Such components can, for example, be an upper shell and a lower shell, which, in simple terms, each form an upper half and a lower half of the subframe. When joined together, the result is a complex hollow profile. In most cases, the upper and lower shells are joined together by a material bond, primarily by welding.However, additional connecting elements can penetrate the upper and lower shells to attach add-on components to the subframe or to attach the subframe to the bodyshell of the vehicle. To prevent possible deformation of the subframe caused by this, several spacers or distance pieces are often arranged between the upper and lower shells to ensure the specified shape or distance between the top and bottom of the subframe is maintained.

[0003] In the event of an accident or crash, particularly a head-on crash, the impact of a motor vehicle against an obstacle causes various parts of the vehicle to deform. An important goal in the design of a motor vehicle is to reduce the resulting deceleration effects on the vehicle occupants. In the event of a head-on crash, the aim is to design the front of the vehicle in such a way that, through defined deformations over the greatest possible distance in the direction of travel, as much of the vehicle's kinetic energy as possible is converted into deformation energy. The absolute speed of the occupants has therefore already been reduced as much as possible by the time the passenger compartment has essentially come to a standstill and the further deceleration of the occupants has to be absorbed by belt systems and airbag systems.

[0004] State-of-the-art subframes are typically not optimized for such situations. Thus, it can often happen that a state-of-the-art subframe experiences relatively minor deformation during such a frontal crash, but otherwise transmits the forces acting on it relatively directly to the vehicle body and thus also to the passenger compartment. However, the subframe can also deform and still limit the dynamic deformation path due to its continued connection to the body.

[0005] US 2019 / 0300059 A1 describes a subframe designed in such a way that, in the event of a frontal impact, a lever system pulls the subframe's fastening bolts out of their corresponding mounts, weakening the connection between the subframe and the body. The system is structurally complex and requires a precisely predetermined deformation of certain components during a frontal impact to achieve the desired effect.

[0006] DE 10 2011 102 116 A1 discloses a front subframe for a motor vehicle to which a crash structure can be connected. At least one stiffening structure is provided that reinforces the crash structure in a connection area for the front subframe, to which the crash structure can be connected to the front subframe in a force-fitting and / or form-fitting manner.

[0007] EP 1 591 349 A1 describes a subframe for the front axles of passenger cars, comprising two spaced-apart side members aligned in the vehicle's longitudinal direction, and at least one cross member connecting the two side members. Each cross member is connected to the side member via a node element. The node element is a cast part with at least one integrated side member support surface adjacent to the lower support surface of the side member, and at least one integrated cross member support surface adjacent to the lower support surface of the cross member, as well as at least one integrated connection point for connecting or supporting vehicle components.

[0008] EP 3 434 562 A1 describes a front axle subframe for a vehicle with a first shell element and a second shell element which is rigidly connected to the first shell element and defines a cavity with the same, with a cross bridge for supporting a vehicle drive unit which is connected to the first shell element and / or the second shell element by a screw connection, and with a sleeve-like spacer element for inserting a screw for body connection, wherein the spacer element is arranged at one of its ends on a through hole of the first shell element and extends within the cavity in the direction of a through hole of the second shell element.In order for the subframe to have significantly greater stability, in particular greater bending strength, while maintaining or only slightly increasing the weight, the spacer element is provided with a sleeve-like section for receiving a screw of the screw connection of the cross bridge.

[0009] DE 10 2011 122 556 B3 discloses an axle assembly for a motor vehicle, wherein axle guides are coupled to a motor vehicle body via an axle subframe, and the axle subframe has a front body connection for connection to the motor vehicle body. The front body connections are screw-connected to the body, whereby the axle subframe disengages from the body when a force threshold is reached. This prevents damaging the motor vehicle body when a corresponding force is introduced via the axle subframe, thus reducing repair costs in certain motor vehicle accidents. The front body connection is designed as a one-piece deep-drawn component.

[0010] DE 100 58 115 A1 discloses a subframe module for a motor vehicle, comprising a front cross member and a rear cross member connected via two longitudinal members to form a closed subframe, which is designed to be attached to a vehicle body from below and to surround an engine compartment when attached. At least two lines for a gaseous or liquid medium are provided on the front cross member, running parallel to one another. Each line extends substantially across the width of the subframe, and the connections are arranged such that flow can pass through at least two lines in opposite directions.

[0011] It is therefore the object of the present invention to propose a subframe of the type mentioned at the outset which reliably has advantageous crash behavior which is suitable for reducing the decelerations acting on the occupants in the event of a frontal crash.

[0012] The object is achieved according to the invention by a subframe of the type mentioned above, which has first reinforcement elements for transmitting a force acting on a front side of the subframe during a frontal crash into a region of the right rear screw receptacle and into a region of the left rear screw receptacle. The object is further achieved by a motor vehicle with such a subframe.

[0013] The invention is based on the finding that a design in which the screws connecting the subframe to the body of the motor vehicle fail as early as possible in the event of a frontal crash, thereby breaking the connection between the subframe and the body, exhibits advantageous crash behavior. In this way, the entire subframe can move a few centimeters towards the passenger compartment during the crash without undergoing any major deformation. This increases the dynamic deformation path. The impact energy can then be specifically absorbed, for example, by longitudinal members of the body of the motor vehicle, which have a relatively large deformation range and can therefore effectively brake the passenger compartment over a relatively long distance.

[0014] Unlike in the known prior art, the invention does not provoke a specific deformation of the subframe in order to loosen a screw or bolt and pull it out of the corresponding hole, but rather structurally strengthens the subframe so that during a crash, large forces act directly on the screws that connect the subframe to the body of the motor vehicle. This ensures that these screws break early during the course of the accident, thus breaking the connection between the subframe and the body of the motor vehicle. The design according to the invention makes it possible to specifically reinforce and stiffen the force path from an area in which a force is introduced into the subframe in the event of a frontal crash to an area in which the respective screws are located, in other words to the screw receptacles.This results in a defined overload of the bolts and, as a result, a timely bolt failure, so that an additional distance can be released for movement of the subframe, which leads to the advantages described in the event of a frontal crash.

[0015] Typically, during a frontal crash, components located in front of the subframe as seen in the direction of travel, such as the vehicle's engine or transmission, or even an oil pan, exert forces on the subframe in the direction of the vehicle interior. The reinforcement measures couple the movement of the respective component to the subframe bolts, so that the subframe bolts are deliberately overloaded in the event of a crash. This allows the subframe to shift rearward and the vehicle's deceleration is reduced. The crash-optimized subframe structure, which uses local reinforcements to deliberately overload the subframe bolt connections in the event of a crash, causing them to fail, allows the entire vehicle greater deformation travel and - while maintaining the same vehicle length - enlarges the front crumple zone in the event of a crash.These local reinforcements are geometrically designed so that in the event of a crash, they are aligned with the direction of movement of the engine or other components located in front of the subframe. This ensures that the engine or other components located in front of the subframe have the necessary clearance during normal driving and collide with the subframe in a defined manner in the event of a crash. This collision between the engine or the other components located in front of the subframe impacts the crash-optimized subframe structure, which transmits this momentum to the bolted connections and utilizes the high forces from the movement of the engine or the other components located in front of the subframe to deliberately overload these bolted connections.

[0016] It is possible to implement the inventive concept as a crash-optimized subframe structure with a multi-shell design, which represents a continuous structural component between the collision points of the subframe with the engine or other components located in front of the subframe and the bolt connection point or the respective bolt receptacle. This ensures that the elements of the subframe exhibit no local compliance, so that the load from the engine contact is fully transferred to the bolt connection points and does not lead to deformation of the subframe.

[0017] Two first reinforcement elements may be present. In particular, a right first reinforcement element and a left first reinforcement element may be present. The subframe may be designed symmetrically with respect to the reinforcement elements relative to a plane of symmetry extending in the direction of travel.

[0018] According to an advantageous embodiment, the first reinforcing elements extend from an upper outer wall of the subframe to a lower outer wall of the subframe. The first reinforcing elements can thus connect an upper outer wall of the subframe to a lower outer wall of the subframe. In other words, the first reinforcing elements can extend vertically across the entire extent of the subframe in the region in which the first reinforcing elements run. The upper outer wall of the subframe and the lower outer wall of the subframe are generally aligned horizontally or nearly horizontally and can be quickly deformed and buckled in a frontal crash.The design described above allows stabilization to be achieved and forces acting in the horizontal direction to be directed through the subframe without causing any major deformation of the subframe.

[0019] Accordingly, the first reinforcement elements can each have at least one substantially vertically oriented first wall section. The first wall section can have the form of a partition wall oriented substantially vertically and in the direction of travel between an outer section of the subframe and a central section of the subframe. As already described above, such a configuration prevents, in particular, buckling of the subframe. Due to the absence of corresponding deformation, the forces can be efficiently directed into the areas of the rear screw receptacles.

[0020] According to a further development of the invention, it is possible for the first reinforcing elements to each have at least one substantially vertically oriented second wall section, which runs at a distance from the first wall section and substantially parallel to the first wall section. This further stiffens the subframe. Thus, following the model described above, a plurality of partition walls running vertically and substantially in the direction of travel can be provided. One of the wall sections, for example the second wall section, can also be arranged in an edge region of the subframe and thus represent a lateral outer wall of the subframe. It is therefore possible for the second wall sections to each form a lateral outer wall of the subframe.

[0021] It can advantageously be provided that the first reinforcement elements each have a length corresponding to at least 80%, preferably at least 90%, of the extension of the subframe in a direction of travel. In other words, depending on the other configuration of the subframe, the first reinforcement elements can provide a direct force path from a front side of the subframe, for example from a front side of the subframe, to a rear side or to an element of the subframe arranged in the immediate vicinity of the rear side.

[0022] According to a preferred embodiment, the first wall sections, the second wall sections, an upper side of the subframe, and a lower side of the subframe can form a box-shaped profile over at least 50% of the length of the subframe as viewed in the direction of travel. The entire subframe thus acquires a honeycomb-like structure, resulting in increased stability and rigidity.

[0023] According to a development of the invention, the subframe can have second reinforcing elements for transmitting a force acting on a front side of the subframe during a frontal crash into an area of ​​the right front screw receptacle and into an area of ​​the left front screw receptacle. In order to direct forces acting on a front area or a front side of the subframe to the rear screws and thus to the rear screw receptacles, force paths are necessary that are approximately aligned in the direction of travel. The positions of the front screw receptacles, however, are often only a relatively small distance from the front of the subframe when viewed in the direction of travel. The force paths from this front side or from force introduction areas in the subframe therefore often have to have an alignment that deviates significantly from the direction of travel.For example, a connecting line between such a force introduction point and the corresponding rear screw receptacle can form an angle of at least 45° or at least 60° with the direction of travel. At the same time, the distance to be bridged is usually shorter than in the case of the rear screw receptacles. Therefore, second reinforcement elements can be provided to accommodate these requirements.

[0024] For example, the second reinforcement elements can each comprise a corner reinforcement plate, which is secured on the one hand to a substantially horizontally extending outer surface of the upper outer wall of the subframe and on the other hand to a substantially vertically extending outer surface of a tower structure supporting a front screw receptacle. The aforementioned connections can be established, for example, by welds.

[0025] It is possible for the second reinforcement elements to be cap-shaped. For example, the second reinforcement elements can be closed on three sides and one top side, and open on the fourth side and the bottom side. Such a three-dimensional design allows for efficient transmission of force, including in a direction with a portion transverse to the direction of travel and thus transverse to the typical direction of force application in a frontal crash.

[0026] According to a preferred embodiment, the subframe has first stiffening elements that connect a top side of the subframe to a bottom side of the subframe and have a first wall portion running substantially in the direction of travel and a second wall portion running substantially transversely to the direction of travel. The second wall portion running substantially transversely to the direction of travel can be fixed to a substantially vertically extending outer surface of a tower structure that supports a front screw receptacle. This connection can be a welded joint, for example. The first stiffening means are thus suitable both for transmitting forces in the direction of travel and for transmitting forces transversely to the direction of travel.In the direction of travel, the forces can be transferred from the first wall sections to the rear screw receptacles, and transversely to the direction of travel, the forces can be transferred from the second wall sections to the front screw receptacles. The first wall section and the second wall section can form an angle of approximately 90°, for example, an angle between 75° and 105°. Preferably, the first wall section and / or the second wall section are vertically aligned.

[0027] The first stiffening elements can consist of a sheet metal, each with two rolled sections. A first rolled section can be arranged at an end section of the first stiffening element, and a second rolled section can be arranged in the boundary region between the first wall portion and the second wall portion. The first stiffening elements can be designed as a single piece. Due to the described rolled sections, the first stiffening elements can assume the additional function of a spacer between an upper side of the subframe and an underside of the subframe. The rolled sections can have a cylindrical basic structure, which allows screws, which can be used, for example, to attach add-on parts to the subframe, to run through the rolled sections.It is thus possible that the first stiffening elements are penetrated by first vertically aligned screws and by second vertically aligned screws.

[0028] The first stiffening elements can be arranged in a region between the first reinforcing elements and the second reinforcing elements. In other words, the first stiffening elements can be arranged within the box-shaped profile if the first wall sections, the second wall sections, an upper side of the subframe, and a lower side of the subframe form a box-shaped profile. The aforementioned structures then jointly form a sub-region of the subframe that is extremely stiff in the direction of travel and extends from a front side of the subframe into a region of the rear screw receptacles that are typically arranged in a rear end region of the subframe, as seen in the direction of travel. The aforementioned sub-regions are typically arranged in a left outer or right outer region of the subframe.

[0029] According to a further development, the subframe has second stiffening elements. The second stiffening elements can have the form of a metal profile with an approximately U-shaped cross-section, wherein the metal profile is arranged in a front lateral region of the subframe and has a first side section which extends in the direction of a front screw receptacle, and wherein the metal profile has a second side section which extends in the direction of a rear screw receptacle. The second stiffening elements can be arranged on an underside of an upper wall of the subframe. In particular, the second stiffening elements can be fastened to the underside of the upper wall of the subframe by means of a welded connection. The second stiffening elements can also be arranged in a region between the first reinforcing elements and the second reinforcing elements.If first stiffening elements are present, the first stiffening elements can be arranged behind the second stiffening elements as viewed in the direction of travel. It is possible for the second side section of the second stiffening elements to be supported on the first stiffening elements. The second stiffening elements can be supported by a front edge on the first stiffening elements. In particular, the second stiffening elements can be supported by a front edge of an inner wall of the second stiffening elements on the second rolled section of the first stiffening elements. This creates a force path that runs entirely through specially designed components that are capable of transmitting the forces occurring during a frontal crash to the screw receptacles without deformation or almost without deformation.

[0030] A motor vehicle according to the invention can have additional reinforcement plates on the front and rear so-called support brackets. In other words, the motor vehicle can have additional reinforcement elements in the area of ​​the body-side screw receptacles for attaching the subframe to the body. The kinematics can thus be optimized by stiffening the body shell at the subframe's screw connection points. These are designed so that they also exhibit no local compliance in the event of a crash, so that the force impulse from the subframe (pushed by the engine during a crash) acts entirely on the screw, and the introduced energy leads to overloading of the screw.A further optimization of this crash-optimized subframe structure consists in the adaptation of the kinematics of the body shell (for example via the movement of the longitudinal members in the event of a crash), via which additional forces are introduced into the screw connections, which act on the screw connections together with the forces from the subframe reinforcement.

[0031] All of the above-mentioned elements of the subframe and the body can be made of metal. For example, they can be sheet metal, particularly sheet steel elements. The subframe elements can be connected to one another by means of a material bond, particularly by means of welded joints.

[0032] Embodiments of the invention are explained in more detail with reference to the drawings and the following description. They show: Fig. 1: a first perspective view of a subframe according to the prior art, Fig. 2: a second perspective view of a subframe according to the prior art, Fig. 3: a schematic perspective view of a first embodiment of a subframe according to the invention, Fig. 4: the first embodiment of the invention measured subframe 2 in a perspective side view, Fig. 5: first embodiment of the subframe 2 according to the invention in a second perspective side view, Fig. 6: a perspective detailed view of the first embodiment of the subframe according to the invention, Fig. 7: a plan view of a part of the first embodiment of the subframe according to the invention, Fig. 8: a front region of a longitudinal member of a body of a motor vehicle, and Fig. 9: a rear region of a longitudinal member of a body of a motor vehicle.

[0033] The Fig. 1 and Fig. 2 each show a perspective view of a subframe 102 according to the prior art. Such a subframe 102 is often constructed in a shell design with an upper shell 104 and a lower shell 106, which are connected to one another via welded joints. The upper shell 104 and the lower shell 106 are formed from three-dimensionally shaped sheet metal parts. The subframe 102 has a total of four screw receptacles 110, which are provided to receive screws with which the subframe 102 is connected to a vehicle body (not shown). The left front screw receptacle 110.1 and the right front screw receptacle 110.2 are arranged on the tower elements 108. The tower elements 108 represent two metal elements protruding upward from the rest of the subframe body, which bring the front screw receptacles 110.1 and 110.2 to the required height. The rear screw receptacles 110.3 and 110.4 penetrate both the upper shell 104 and the lower shell 106. Furthermore, the subframe 102 has two spacers 112, which are also arranged between the upper shell 104 and the lower shell 106 and have through-openings that are designed congruent with holes in the upper shell 104 and the lower shell 106, so that the spacers 112 can be penetrated by screws or bolts with which further components can be fastened to the subframe 102. In the front left and front right areas there is a force introduction area 114, which is typically subjected to forces during a frontal crash. In . Fig. 2 it can be seen that the upper shell 104 and the lower shell 106 have only a few connecting elements apart from the outer contour, so that the subframe 102 according to the prior art is susceptible to deformation when forces are introduced in the direction of travel into the force introduction areas 114.

[0034] Fig. Figure 3 shows a schematic perspective view of a first embodiment of a subframe 2 according to the invention. The subframe 2 comprises a floor element 4, a front cross member 6, a rear cross member 7 and two tower elements 8. As in the subframe according to the prior art from the Fig. 1 and Fig. 2, the subframe 2 has four screw receptacles 10.1, 10.2, 10.3, and 10.4. The positions of the four screw receptacles 10 are designed congruently with the subframe according to the prior art, so that the subframe 2 according to the invention can be used instead of the subframe according to the prior art without further adaptations to the body of already fully developed motor vehicles.

[0035] The subframe 2 has two first longitudinal profiles 30, which extend from a front side of the subframe 2 to a rear side of the subframe 2 essentially in the direction of travel. The subframe 2 also has two second longitudinal profiles 32, which adjoin the first longitudinal profiles 30 on the outside. First upper side portions 20 belonging to the first longitudinal profiles 30 and second upper side portions 22 belonging to the second longitudinal profiles 32. These, together with the front cross member 6 and the rear cross member 7, form an upper surface of the subframe 2. First rear side portions 24 belonging to the first longitudinal profiles 30 and second rear side portions 26 belonging to the second longitudinal profiles 32, together with a third rear side portion 28 belonging to the rear cross member 7, form a rear surface of the subframe 2. The first longitudinal profiles 30 and / or the second longitudinal profiles 32 can form the first reinforcing elements.

[0036] The first longitudinal profiles 30 have first wall sections 12 in the form of vertically extending, inner side walls of the longitudinal profiles 30. The first wall sections 12 extend vertically and essentially in the direction of travel up to an area in which the rear screw receptacles 10.3 and 10.4 are located. Accordingly, the first wall sections 12 are suitable for directing forces acting in the direction of travel from a front area of ​​the subframe 2 to the areas of the rear screw receptacles 10.3 and 10.4.

[0037] The figure further shows that the second longitudinal profile 32 also has reinforcing elements in the form of the second wall sections 14. In the illustrated embodiment, these wall sections 14 are also designed in the form of a vertically extending side wall of the second longitudinal profile 32, running essentially in the direction of travel. The second wall sections 14 are therefore also suitable for directing forces acting in the direction of travel from a front region of the subframe 2 to the regions of the rear screw receptacles 10.3 and 10.4. In other words, in the illustrated embodiment, a continuous load path is stiffened via a further bulkhead plate in the form of the second wall section 14, running parallel to the load direction. In the illustrated embodiment, the first reinforcing elements are thus formed by the first wall sections 12 and the second wall sections 14.

[0038] In the Fig. 3 also shows a small portion of a first stiffening element 16. The first stiffening element 16 is arranged adjacent to a lower region of the left front turret element 8. On the right side of the subframe 2, in the region of the front right turret element 8, such a first stiffening element is also arranged. However, this is not visible in the perspective shown. The first stiffening elements 16 are supported on the turret elements 8 and can be connected to them via a welded joint.

[0039] Also in the Fig. 3 shows the two second reinforcement elements 18, which are formed by cap-like sheet metal profiles that rest on the first longitudinal profiles with several lower edges and are additionally supported by at least one edge on the tower elements 8. The second reinforcement elements are therefore suitable for directing forces acting in the direction of travel from a front region of the subframe 2 to the areas of the front screw receptacles 10.1 and 10.2.

[0040] Fig. 4 shows the first exemplary embodiment of the subframe 2 according to the invention in a perspective side view. In the perspective shown, the function and course of the second wall section 14 are particularly clearly visible. The second wall section 14 runs with a first portion from an area near the tower element 8, initially almost rearward as seen in the direction of travel, and then has a second portion which runs in a direction inclined further inwards. The first wall section 14 is supported on the first stiffening element 16 and connects the floor element 4 to both the first upper side portion 20 and the second upper side portion 22. The second upper side portion 22 is part of the second longitudinal profile 32, so that the second upper side portion 22 is designed as a single piece with the second wall section 14.Weld seams for connecting the corresponding elements can be provided on the horizontally extending edges of the second wall section 14, which border the base element 4 and the first upper side portion 20. Likewise, a vertically extending weld seam can connect the vertically extending front edge of the second wall section 14 to the first stiffening element 16. In the left edge area of ​​the . Fig. 4 shows a small part of the second stiffening element 62, which will be described in more detail later.

[0041] Fig. 5 shows the first embodiment of the subframe 2 according to the invention in a second perspective side view, in which some components, namely in particular the tower element 8 and the second wall section 14, are shown transparent in order to make the components located behind them more clearly visible. Thus, in particular, the first stiffening element 16 and the second stiffening element 62 are more clearly visible. The second stiffening element 16 has a first wall portion 34 and a second wall portion 36. The first wall portion 34 runs essentially in the direction of travel, and the second wall portion 36 runs essentially transversely to the direction of travel. The second wall portion 36 is supported on the tower element 8.At the same time, a front edge of the second wall section 14 borders on a transverse side of the second wall portion 36, so that forces absorbed by the second wall portion 36 can be transmitted to the first stiffening element 16 in the direction of travel.

[0042] The second stiffening element 62 has a U-shaped cross-section and is fixed by its two upper edges to an underside of the first upper side portion 20 of the first longitudinal profile 30. The second stiffening element 62 thus stiffens the upper side of the first longitudinal profile 30, particularly in the front region of the latter, and thus prevents buckling of the first longitudinal profile when forces act in the direction of travel, particularly during a frontal crash.

[0043] Fig. 6 shows a perspective detailed view of the first exemplary embodiment of the subframe 2 according to the invention. In the view shown, the first upper side portion of the first wall section 12 is shown transparent, so that in particular the first stiffening element 16 and the second stiffening element 62 are clearly visible. The first stiffening element 16 consists of the first wall section 34, the second wall section 36, the first rolled section 38 and the second rolled section 40. The first wall section 34 connects the first rolled section 38 to the second rolled section 38, and the second wall section 36 extends from the first rolled section 36 at an angle of approximately 90° from the first wall section 34 in the direction of the tower element 8. The first wall section 34 thus runs approximately in the direction of travel, and the second wall section 36 runs approximately transversely to the direction of travel.The first stiffening element 16 extends vertically. Accordingly, the first wall portion 34 and the second wall portion 36 are also vertically aligned. The first rolled section 38 and the second rolled section 40 each have a hollow cylindrical basic shape, with the respective central axis also aligned vertically. The entire first stiffening element 16 is constructed in one piece. The first stiffening element 16 can be produced by forming a flat sheet metal, with a first end portion of the sheet metal being rolled up and now forming the second rolled section 38. The second rolled section 40 connects the front end of the first wall portion 34, viewed in the direction of travel, to the second wall portion 36, forming the previously described hollow cylindrical second rolled section 40.The first rolled section 38 has a first vertically extending through-opening 64, and the second rolled section 40 has a second vertically extending through-opening 66. The through-openings 64 and 66 can be penetrated by screws, which can be used to attach additional components to the subframe 2.

[0044] The second stiffening element 62 has a first side section 70 in the form of a first side wall and a second side section 72 in the form of a second side wall, opposite the first side section 70. The two side walls are each welded by their upper edges to the first wall section 12, shown transparently in the figure. A front edge of the first side wall is in contact with a front side of the subframe 2, in particular with a front side of the first longitudinal profile 30.

[0045] Fig. 7 shows a plan view of part of the subframe 2 according to the invention in accordance with the first exemplary embodiment. The first longitudinal profile 30, the second longitudinal profile 32, the tower element 8, the first stiffening element 16, and the second stiffening element 18 can again be seen. Furthermore, a first force path 46 and a second force path 48 are schematically shown. Both force paths 46 and 48 begin in a force introduction area 44, which is symbolically marked by a star. In this force introduction area 44, large forces regularly act on the subframe 2 due to a collision with the engine or another component during a frontal crash. The first force path 44, viewed in the direction of travel, runs along the first reinforcement element (not further visible in the figure) in the direction of the left rear screw receptacle 10.3.The second force path 46, starting from the force introduction area 44, initially runs diagonally rearward and outward and then along the second wall section into the rear area of ​​the subframe 2, from where the force is again directed into the area of ​​the left rear screw receptacle 10.3. The forces thus directed to the screw receptacle 10.3 reliably cause the screw (not shown) to fail, so that the subframe 2 is separated from the body of the motor vehicle.

[0046] It can also be seen that the force paths 46 and 48 run at least partially through the second reinforcement element 18, so that a portion of the force introduced into the force introduction region 44 is transferred outwards to the tower element 8, so that the screw arranged in the region of the front left screw receptacle 10.1 is also caused to fail. Part of the forces can be transferred from the second reinforcement element 18 to the second rolled section 40 of the first stiffening element 16 and subsequently via the second wall portion 36 of the first stiffening element 16 to the tower element 8. For this purpose, an edge 68 of the second wall portion 36 can be fixed, for example welded, to a vertically extending outer wall of the tower element 8.

[0047] Fig. 8 shows a front region of a longitudinal member 50 of a motor vehicle body (not shown in detail), as well as an enlarged section of the longitudinal member 50 in the lower region. The enlarged section shown in the lower region of the figure shows the so-called front support bracket 74, part of which the front connection point 52 is a part. The front connection point 52 has a tubular design and receives the screw that runs through the associated front screw receptacle of the subframe. In order to also stiffen the front connection point 52 and prevent the connection point 52 from buckling or bending, a first stiffening plate 56 and a second stiffening plate 58 are provided, which are partially toroidal in shape and are each fastened with a first edge to a wall of a body portion of the front support bracket 74 and with a second edge to an outer wall of the front connection point 52.The connections can be made by welds or other welded joints.

[0048] Fig.9 shows a rear region of a longitudinal member 50 of a motor vehicle body (not shown in detail) and, in the lower region, an enlarged section of the longitudinal member 50. In the lower region of the figure, the rear support bracket 76 is shown enlarged. The rear support bracket 76 serves, analogously to the front support bracket, to connect the subframe using the screws running through one of the rear screw receptacles 10.3 and 10.4. A third stiffening plate 60 is arranged on the rear support bracket 54. This third stiffening plate has a roughly triangular cross-section and rests with a lower edge on an upper side of a body element of the rear support bracket 76. The third stiffening plate 60 is supported with a rear edge, viewed in the direction of travel, on a vertically extending rear wall of the rear support bracket 76.The third stiffening plate 60 can be connected to the rear support bracket 76 by means of welds, in particular at the edges where it is in contact with the latter. List of reference symbols 2 subframes 4 floor element 6 front cross member 7 rear cross member 8 tower element 10 screw receptacles 12 first wall section 14 second wall section 16 first stiffening element 18 second stiffening element 20 first top side portion 22 second top portion 24 first back part 26 second back part 28 third back portion 30 first longitudinal profile 32 second longitudinal profile 34 first wall section 36 second wall section 38 first rolled section 40 second rolled section 44 Force introduction area 46 first power path 48 second power path 50 longitudinal members 52 front connection point 54 rear connection point 56 first stiffening plate 58 second stiffening plate 60 third stiffening plate 62 Second reinforcement element 64 passage opening 66 passage opening 68 edge 70 first page section 72 second page section 74 front support bracket 76 rear support bracket 102 subframe 104 upper shell 106 lower shell 108 tower element 110 screw receptacles 112 spacers 114 Force introduction area

Claims

[1] Front subframe (2) for a motor vehicle, wherein the subframe (2) has a right rear screw receptacle (10.4), a left rear screw receptacle (10.3), a right front screw receptacle (10.2) and a left front screw receptacle (10.1) for connecting the subframe (2) to a body of a motor vehicle, characterized by first reinforcement elements for transmitting a force acting on a front side of the subframe (2) during a frontal crash into an area of ​​the right rear screw receptacle (10.3) and into an area of ​​the left rear screw receptacle (10.4). [2] Front subframe (2) according to claim 1, characterized by that the first reinforcing elements each have at least one substantially vertically oriented first wall section (12). [3] Front subframe (2) according to one of the preceding claims, characterized bythat the first reinforcing elements each have at least one substantially vertically oriented second wall section (14) which is spaced from the first wall section (12) and runs substantially parallel to the first wall section (12). [4] Front subframe (2) according to claim 3, characterized by that the first wall sections, the second wall sections, an upper side of the subframe (2) and an underside of the subframe (2) form a box-shaped profile over at least 50% of the length of the subframe (2) viewed in the direction of travel. [5] Front subframe (2) according to one of the preceding claims, characterized by second reinforcing elements (14) for transmitting a force acting on a front side of the subframe (2) during a frontal crash into a region of the right front screw receptacle (10.2) and into a region of the left front screw receptacle (10.1). [6] Front subframe (2) according to one of the preceding claims, characterized by in that the second reinforcing elements (14) each have a corner reinforcing plate which is fixed on the one hand to a substantially horizontally extending outer surface of the upper outer wall and on the other hand to a substantially vertically extending outer surface of a tower structure (8) which carries a front screw receptacle (10.1, 10.2). [7] Front subframe (2) according to one of the preceding claims, characterized by that the second reinforcing elements (14) are cap-shaped. [8] Front subframe (2) according to one of the preceding claims, characterized byfirst stiffening elements (16) which connect an upper side of the subframe (2) to a lower side of the subframe (2) and have a first wall portion (34) running substantially in the direction of travel and a second wall portion (36) running substantially transversely to the direction of travel. [9] Front subframe (2) according to one of the preceding claims, characterized by a metal profile with an approximately U-shaped cross-section, wherein the metal profile is arranged in a front lateral region of the subframe (2) and has a first side section (70) which extends in the direction of a front screw receptacle (10.1, 10.2), and wherein the metal profile has a second side section (72) which extends in the direction of a rear screw receptacle (10.3, 10.4). [10] Motor vehicle with a front subframe (2) according to one of the preceding claims.

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