DE102006047894B4 - Side member and motor vehicle with at least one such - Google Patents

Abstract

Longitudinal member (3) in the front or rear of a motor vehicle, which in turn has a hollow profile structure and is subject to buckling and/or compressive stress in the event of a crash, such as a frontal and/or rear crash, and viewed in the longitudinal direction of the longitudinal member (3) via a has changing inherent rigidity, starting from the point at which the crash stress is introduced into the side member (3) on the front side, the inherent rigidity of the same decreases in a limited support section (3') directly adjoining said introduction point, characterized in that the limited support section (3') 5% to 30% of the free length of the side member (3), which in turn is defined by the section of the side member (3) from the point at which the crash stress is introduced or from the end of the member to the end wall (1) of the passenger cell (2) of the motor vehicle, is that the decrease in the inherent rigidity of the carrier section (3') is brought about by an inverse change in wall thickness thereof, and that the wall thickness-length gradient of the carrier section (3') is selected in a range from 1/10 to 1/2000.

Description

The invention relates to a side member in the front or rear end of a motor vehicle according to the preamble of claim 1 of the invention. The invention also relates to a motor vehicle with at least one longitudinal member of this type.

Known body concepts in sheet metal shell construction have largely exhausted the existing potential for saving weight and costs. Due to the high degree of constructive maturity, the use of other semi-finished products and materials is necessary to further reduce weight or costs. Another aspect is the crash performance. In order to meet various crash load cases, the absorption of higher and higher forces is necessary. The corresponding measures often lead to a larger vehicle overhang and also to higher masses.

In order to counteract this problem as far as possible, it has been known for some time to design side members arranged in the front or rear of the vehicle with a targeted material thickness distribution in a defined area in order to be able to advantageously influence the load absorption or the crash performance.

That's it DE 24 21 233 A1 a body structure for motor vehicles is known, which is formed by energy-absorbing supports and walls and which in turn have a different wall thickness profile adapted to the loads that occur. In particular, it is proposed here that the wall thickness in the area remote from the passenger compartment be less than in an area adjacent to the passenger compartment. Through the above measures, a continuous deformation of the carrier and walls with a uniform formation of folds is to be achieved under the action of force as a result of a crash. Comparable solutions are also with the DE 26 19 173 A1 , the DE 26 20 927 A1 , the EP 1 481 743 A2 and the DE 100 57 566 A1 disclosed, with longitudinal members being proposed here as well, which have an increasing wall thickness or strength or buckling resistance starting from a possible end-side introduction point of a crash stress.

Further measures for influencing the crash behavior of structural components on motor vehicles, in particular longitudinal members thereof, are known from the publications below. That's how she describes it DE 101 21 354 A1 a front end for a motor vehicle with a bumper arrangement and with lateral longitudinal beams with longitudinal beam heads, which are each connected to a bumper beam. At least one longitudinal member is assigned at least one sensor for absorbing impact energy outside the longitudinal member plane, the sensor being provided with an active means for indirect transmission of at least part of the impact energy to a longitudinal side of the associated longitudinal member. The DE 103 39 069 A1 describes a structural component of a motor vehicle body, such as a side member or rocker panel, which has a local stiffness-increasing deformation structure that is brought about by a hot forming process. The DE 10 2004 016 616 B3 describes longitudinal frame members on a motor vehicle body, which each have a cutout on their upper side in order to reduce their longitudinal rigidity in a predetermined deformation section. The DE 10 2004 016 803 B4 describes an energy absorption body for installation between a bumper and a side member area of a vehicle frame, with a first end provided for attachment to the bumper and a second end provided for attachment to the side member area. The energy absorption body has a hollow body cross section that is reduced in several stages from the second end to the first end. The DE 10 2004 027 783 A1 describes a support structure for a passenger car with longitudinal members arranged in the front end of the same, which have at least one deformation region with reduced deformation resistance. In order to adapt the deformation characteristics of the front end to those of an adjacent central tunnel section with reduced deformation resistance, the strength of the longitudinal member sections adjacent to the central tunnel section is also reduced in relation to the remaining longitudinal section of each longitudinal member, resulting in deformation sections of the longitudinal members. The DE 10 2005 045 297 A1 describes a support frame for a motor vehicle with a first and a second frame element running in the longitudinal direction of the motor vehicle, a deformation region being arranged between the two frame elements and being formed with a deformation structure.

In the meantime, it has been recognized that although an increase in the force level of a side member has a positive effect on a possible insurance rating test of the motor vehicle, this increase can also have a disadvantageous effect in the event of an offset crash, in that desired deformations and folds are adversely affected.

In view of this, the DE 199 33 734 A1 a supporting structure of vehicle bodies, with longitudinal members running on both sides in the front end, with the departure from tech In line with the usual practice, it is proposed that in the front area of the longitudinal member, which is first of all exposed to deformation in the event of an impact, this section should be specifically equipped with a higher deformation resistance, so that the longitudinal member already has high deformation resistance when deformation of the front end is just beginning. The high resistance to deformation is brought about, for example, by a rib structure provided in the front area of the side member, whereas in the wider area, but at least in the end area, there is no rib structure increasing the resistance to deformation.

The object of the invention is therefore to design a side member on motor vehicles in such a way that the highest possible force level of the same for crashes at low speeds, in particular also with regard to an insurance rating test of the motor vehicle, with optimal performance in an offset crash with the shortest possible length known deformation elements and low vehicle overhang is advantageously combined. In addition, it is the object of the invention to provide a motor vehicle with at least one longitudinal member of this type.

The stated object is achieved with the features of claims 1 and 16. Advantageous refinements of the invention result from the dependent claims.

In the case of a side member in the front or rear end of a motor vehicle, which itself has a hollow profile structure and is subject to buckling and/or compressive stress in the event of a crash, such as a frontal and/or rear crash, and has a changing inherent rigidity when viewed in the longitudinal direction of the side member, starting from the point at which the crash stress is introduced into the side member at the front, the inherent rigidity of the latter decreases in a limited section of the beam directly adjoining said point of introduction, the stated object is accordingly achieved in that the limited section of the beam is 5% to 30% of the free length of the longitudinal member, which in turn is defined by the section of the side member from the point at which the crash stress is introduced or from the end of the member to the front wall of the passenger compartment of the motor vehicle, is that the decrease in the inherent rigidity of the member section is caused by an inverse change in wall thickness of the same, and that the wall thickness-length gradient of the support portion is selected in a range from 1/10 to 1/2000.

Preferably, the limited beam portion is 10% to 25% of the free length of the side rail.

Provision is also preferably made for the wall thickness/length gradient of the carrier section to be selected in a range from 1/100 to 1/300.

The inherent rigidity of the carrier section can decrease continuously and/or in stages.

The course of the continuous decrease in the inherent rigidity of the carrier section can be based on a linear and/or curve function.

It is further proposed that a continuous course of the decrease in the inherent rigidity of the carrier section as a result of an inverse change in wall thickness according to a “flexible rolling method” known per se and a gradual course of the decrease in the inherent rigidity of the carrier section as a result of inverse change in wall thickness according to a “tailored blank” method known per se Application" or other suitable methods known per se can be implemented.

Furthermore, the gradual progression of the decrease in the inherent rigidity of the support section as a result of the inverse change in wall thickness can also be brought about by one or more reinforcement elements connected to the support section, which can be formed by flat sheet metal and/or by hollow or solid profile structures.

According to a preferred embodiment, the wall thickness of the carrier section varies in a range from approximately 0.5 mm to approximately 5 mm, particularly preferably in a range from approximately 1.5 mm to approximately 3 mm.

As the invention also provides, the carrier section of the side member has a section of such increased inherent rigidity in the area where the crash stress is introduced that peak loads resulting from said crash stress are advantageously absorbed.

Furthermore, the hollow profile structure of the carrier section can be formed by a hollow profile that is open and/or closed in cross section.

It can also prove to be expedient if the carrier section has different cross-sectional shapes and/or circumferences along its length.

Finally, at least one deformation element can be connected to the end face of the carrier section or longitudinal carrier via a bulkhead plate.

The invention also includes a motor vehicle with at least one side member designed according to the invention.

This side member is also suitable for a motor vehicle which is formed by a lightweight hybrid construction of the body with a light metal structure and a steel platform.

The proposed side member has several advantages over conventional ones. On the one hand, this improves the static and dynamic properties as well as the crash performance of the motor vehicle body itself. On the other hand, with the same performance or an increase in performance with regard to load absorption in the event of a crash, a weight reduction or, depending on the design, a reduction in the vehicle overhang is possible by shortening any deformation elements provided.

• 1 eine Kraftfahrzeugkarosserie in einer perspektivischen Seitenansicht mit einem im Vorderwagen angeordneten Längsträger,
• 2 einen erfindungsgemäß ausgebildeten Trägerabschnitt des Längsträgers nach 1 in einer Einzeldarstellung,
• 3 die schematische Darstellung eines inversen Wandstärkenverlaufes des Trägerabschnittes gem. einer ersten Ausführungsform,
• 4 der inverse Wandstärkenverlauf gem. einer zweiten Ausführungsform, und
• 5 der inverse Wandstärkenverlauf gem. einer dritten Ausführungsform.

The invention is explained in more detail below using the exemplary embodiments shown schematically in the drawings. Show it:

• 1 a motor vehicle body in a perspective side view with a longitudinal member arranged in the front end,
• 2 a support section of the longitudinal member designed according to the invention 1 in a single representation,
• 3 the schematic representation of an inverse wall thickness profile of the carrier section according to a first embodiment,
• 4 the inverse course of wall thickness according to a second embodiment, and
• 5 the inverse course of wall thickness according to a third embodiment.

1 shows one of two side members 3, which are arranged opposite one another as seen in the transverse direction of the vehicle and are arranged at a height offset in the area of the front wall 1 of the passenger compartment 2 of a motor vehicle body, which extends backwards from the front end 4 and is angled twice downwards in the area of the front wall 1 under the floor panel 5 of the passenger compartment 2 out and at least partially attached to the front wall 1 and / or the floor panel 5, preferably welded to the same.

The longitudinal beam 3 in turn has a hollow profile structure and is connected with its front end of the beam to a so-called bulkhead plate 6, which in turn is connected to the front by a deformation element 7 known per se. A bumper, which is not shown in detail but is known per se, is supported on said deformation element 7 .

As is known, the hollow profile structure can be formed by a hollow profile that is open or closed in cross section or seen over the length of the longitudinal beam 3 by a combination of such cross sections (not shown in detail).

acc. 1 In the present case, the longitudinal beam 3 is initially formed by a hollow profile 3a with a closed cross section. An additional U-shaped closing part 3b is also placed on the hollow profile 3a and is preferably connected to the hollow profile 3a by welding in such a way that the longitudinal member 3 now has a 2-chamber hollow profile.

Assuming that a frontal crash occurs, said front side member 3 is subject to buckling and/or compression stress. The acting forces "F" are transmitted via the side member 3 to adjacent body components, e.g. transferred to the area of passenger cell 2.

The side member 3 is usually designed in such a way that it is kinked or folded in areas or sections as a result of the acting forces “F” in such a way that as a result the highest possible absorption of the forces “F” is already effected in front of the passenger cell 2 .

Conventionally, attempts are made to influence such wrinkling by providing a targeted material thickness distribution in a defined area, namely such that the wall thickness in the area remote from the passenger cell 2 is less than in an area adjacent to the passenger cell 2. That is, the wall thickness of a front side member 3, for example, varies from lower to higher from front to rear in the prior art.

As already explained above, although an increase in the force level of such a side member 3 has a positive effect on an insurance rating test of the motor vehicle, it can also have a disadvantageous effect in the event of an offset or frontal crash.

In extensive tests it was found that in the event of a force being introduced into the side member 3, for example during an insurance rating test, voltage peaks occur in the vicinity of the load area and thus in the connection area to the bulkhead plate 6. The further away you are from the point where the load is introduced, the fewer overload zones are to be expected. In recognition of this, a defined interception of the stress or load peaks in this area in particular is indicated via a targeted distribution of the thickness of the wall of the side member 3 .

In a departure from what is technically customary, it is now provided that, starting from the front-side introduction point of the crash stress into the side member 3, present in the connection area of the same to the bulkhead plate 6, the inherent rigidity of the side member 3 in a limited beam section 3' directly adjoining said introduction point decreases.

The section of the longitudinal member 3 adjoining this carrier section 3' up to the end wall 1 can be constructed in the conventional manner, e.g. H., be designed with a constant, increasing or variable wall thickness or inherent rigidity.

In the extensive tests, it was also found that, depending on the vehicle type, the limited support section 3 'about 5% to about 30% of the free length of the longitudinal member 3, which in turn through the section of the longitudinal member 3 from the point of introduction of the crash stress or from the beam end to is defined approximately to the end wall 1 of the passenger compartment 2 of the motor vehicle, should preferably be approximately 10% to approximately 25% of the free length of the side member 3 in order to be able to intercept the occurring stress or load peaks particularly effectively.

Essentially, said decrease in the inherent rigidity of the longitudinal beam 3 in the beam section 3' is caused by a reduction in wall thickness from the front to the rear, referred to below as the inverse change in wall thickness.

As in particular from the 2 until 4 As can be seen, this inverse change in wall thickness and accordingly also the inherent rigidity of the support section 3′ of the side member 3 can continuously decrease in that a section 8a of the support section 3′ of greater material thickness or wall thickness and correspondingly greater inherent rigidity transitions into a section 8b of lesser material thickness/wall thickness and correspondingly less inherent rigidity .

This transition can, as in the 2 until 4 further shown, continuously via an intermediate transition region 8c or according to 5 stepwise directly from section 8a to section 8b.

Of course, several transition areas 8c, several steps and/or any combination of such areas are also conceivable and accordingly covered by the invention in order to bring about said inverse change in wall thickness (not shown in more detail).

It is easy for a person skilled in the art to understand that the section 8a of greater material thickness or inherent rigidity in particular must also be determined in terms of its length as a function of the basic performance of the side member 3 .

As a result of absorbing the load peaks in section 8a directly behind the bulkhead plate 6, the material thickness and therefore inherent rigidity of the immediately adjoining longitudinal member area, in this case the longitudinal member area (sections 8c, 8b) leading to the rear, can advantageously be reduced, which, depending on the design of the longitudinal member 3 in With regard to conventional a weight reduction or an increase in performance with the same weight results.

Furthermore, said interception of the load peaks in section 8a directly behind the partition plate 6 allows an advantageous adjustment of the deformation element 7, for example by making it shorter and thus shortening the vehicle overhang, which in turn has positive aspects in terms of pedestrian protection.

The change in wall thickness in the support section 3' can take place both inwards and outwards with regard to the hollow profile used.

As in the 3 and 4 shown in more detail, a continuous course 9 of the decrease in the wall thickness and accordingly also in the inherent rigidity of the support section 3' can take place according to a linear or curve function.

So are in 3 following section 8a in section 8c or transition area 8c, a ramp-shaped transition 9a of the inverse wall thickness or inherent rigidity curve 9 according to a linear function and in 4 a stepless transition 9b is shown according to a curve function (continuously drawn wall thickness progression).

Likewise, it can, like that 3 and 4 can also be seen, according to the wall thickness profile shown in dashed lines, to minimize the longitudinal extent of section 8a significantly, so that the ramp-shaped or stepless transition 9a, 9b starts as far as possible directly at the point where the crash stress is introduced or the partition plate 6.

"Flexible rolling processes" are particularly suitable for implementing such changes in wall thickness. With this method, a sheet metal blank with different material thicknesses is produced by varying the roll gap during the rolling process. Certainly others are too suitable measures known per se for reducing the thickness of the wall of the carrier section 3' are conceivable and are accordingly covered by the invention.

It is also conceivable to provide a change in the cross-sectional shape and/or the circumference simultaneously with the reduction in wall thickness over the length of the support section 3', which allows an even more refined adaptation of the change in inherent rigidity to defined conditions.

As far as the step-like progression 10 of the decrease in the wall thickness or the inherent rigidity of the support section 3' of the longitudinal member 3 is concerned, this can be done, for example, by a known "tailored blank application" or by using a non-illustrated one that is firmly connected to the support section 3' Reinforcing elements with a limited extent, such as flat metal sheets or also hollow or solid profile structures, which in turn can also form a multi-chamber profile with the support section 3' can be used.

In the context of said extensive tests, wall thicknesses of the carrier section 3' have proven particularly useful, which vary in a range from about 0.5 mm to about 5 mm, preferably in a range from about 1.5 mm to about 3 mm.

The wall thickness-length gradient of the carrier section 3' was selected in a range from 1/10 to 1/2000, preferably in a range from 1/100 to 1/300.

The above exemplary embodiments are essentially based on longitudinal members 3 in the front end of a motor vehicle body.

However, the invention also includes longitudinal members 3 (not shown in detail) in the rear section of the motor vehicle body. Starting from the free end of the beam or the point at which the crash stress is introduced at the front as a result of a rear-end crash, the inherent rigidity of the beam section 3′ according to the invention of such a rear longitudinal beam 3 or its wall thickness, viewed in the longitudinal direction of the vehicle, accordingly decreases from back to front.

Such a design of longitudinal members 3 has proven particularly successful on motor vehicles with a lightweight bodywork in hybrid construction with a light metal structure and a steel platform.

Reference List

1

bulkhead

2

passenger cell

3

side members

3'

carrier section

3a

closed hollow profile

3b

locking part

4

front car

5

floor pan

6

bulkhead plate

7

deformation element

8a

Section of higher material or wall thickness / inherent rigidity of the side member 3

8b

Section of lower material or wall thickness / inherent rigidity of the side member 3

8c

transition area

9

continuous decrease in wall thickness / inherent rigidity

9a

ramped transition (linear function)

9b

stepless transition (curve function)

10

gradual progression of the decrease in wall thickness / inherent rigidity

Claims (17)

Longitudinal member (3) in the front or rear of a motor vehicle, which in turn has a hollow profile structure and is subject to buckling and/or compressive stress in the event of a crash, such as a frontal and/or rear crash, and viewed in the longitudinal direction of the longitudinal member (3) via a has changing inherent rigidity, starting from the point at which the crash stress is introduced into the side member (3) on the front side, the inherent rigidity of the same decreases in a limited support section (3') directly adjoining said introduction point, characterized in that the limited support section (3') 5% to 30% of the free length of the side member (3), which in turn is defined by the section of the side member (3) from the point at which the crash stress is introduced or from the end of the member to the end wall (1) of the passenger cell (2) of the motor vehicle, is that the decrease in the inherent rigidity of the carrier section (3 ') is caused by an inverse change in wall thickness thereof, and that the wall thickness-length gradient of Carrier section (3 ') is selected in a range from 1/10 to 1/2000. Longitudinal member (3) after claim 1 , characterized in that the limited beam section (3') amounts to 10% to 25% of the free length of the longitudinal beam (3). Longitudinal member (3) after claim 1 or 2 , characterized in that the wall thickness-length gradient of the carrier section (3 ') is selected in a range from 1/100 to 1/300 Longitudinal member (3) according to one of Claims 1 until 3 , characterized in that the inherent rigidity of the support section (3') decreases continuously and/or in steps. Longitudinal member (3) after claim 4 , characterized in that the course (9; 9a, 9b) of the continuous decrease in the inherent rigidity of the carrier section (3') is based on a linear and/or curve function. Longitudinal member (3) after claim 4 or 5 , characterized in that the continuous progression (9; 9a, 9b) of the decrease in the inherent rigidity of the support section (3') as a result of inverse wall thickness change is implemented using a “flexible rolling method” known per se. Longitudinal member (3) after claim 4 , characterized in that the stepped course (10) of the decrease in the inherent rigidity of the support section (3') as a result of inverse wall thickness change is implemented using a tailored blank application known per se or other suitable methods known per se. Longitudinal member (3) after claim 4 , characterized in that the stepped progression (10) of the decrease in the inherent rigidity of the carrier section (3') as a result of the inverse change in wall thickness is brought about by one or more reinforcement elements connected to the carrier section (3'). Longitudinal member (3) after claim 8 , characterized in that the reinforcement elements are formed by flat metal sheets and/or by hollow or solid profile structures. Longitudinal member (3) according to one of Claims 1 until 9 , characterized in that the wall thickness of the carrier section (3 ') varies in a range from 0.5 mm to 5 mm. Longitudinal member (3) after claim 10 , characterized in that the wall thickness of the carrier section (3 ') varies in a range from 1.5 mm to 3 mm. Longitudinal member (3) according to one of Claims 1 until 11 , characterized in that the carrier section (3 ') in the region of the introduction point of the crash stress has a section (8a) of such increased inherent rigidity that load peaks are intercepted as a result of said crash stress. Longitudinal member (3) according to one of Claims 1 until 12 , characterized in that the hollow profile structure of the support section (3') is formed by a hollow profile which is open and/or closed in cross-section. Longitudinal member (3) according to one of Claims 1 until 13 , characterized in that the carrier section (3') has different cross-sectional shapes and/or circumferences along its length. Longitudinal member (3) according to one of Claims 1 until 14 , characterized in that at least one deformation element (7) is connected to the end face of the carrier section (3') via a bulkhead plate (6). Motor vehicle with at least one longitudinal member (3) according to one of Claims 1 until 15 . motor vehicle after Claim 16 , characterized in that this is formed by a lightweight body in hybrid construction with a light metal structure and a steel platform.

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