Abstract:
An auxiliary chassis for a motor vehicle is formed as a generally rectangular structure for holding an engine, transmission and other equipment. The auxiliary chassis is mounted to front end structural members at a position spaced from and below the structural member forming a further impact absorbing structure.

Description:
This is a continuation of copending application International Appln. No. PCT/EP00/04059 filed May 5, 2000, now WO 00/71406A1 which is incorporated by reference herein. The International application was published in German on Nov. 30, 2000 by the International Bureau. 
    
    
     BACKGROUND OF THE INVENTION 
     DE 197 03 504 A1 discloses an auxiliary chassis for a motor vehicle, serving to enhance a transverse rigidity of the vehicle. The auxiliary chassis comprises side parts, each in turn comprising at least two points of articulation for swingable articulation of a transverse or oblique caster connected to a wheel mount and a monocoque transverse member arranged between the side parts, which, at installation of the auxiliary chassis in the motor vehicle, is offset from a line connecting the centers of the wheels. This auxiliary chassis is distinguished in that the cross-section of the transverse member comprises a half-open profile whose opening, at installation of the auxiliary chassis in the motor vehicle, points substantially in the direction opposed to the line connecting the wheel centers. The transverse member, when used in the front axle region, may serve as a bottom girt to accommodate an electrohydraulic pump system, an ABS/EDS device, and/or a standing heater. Also, the bottom girt may be utilized for attachment of hydraulic lines of the front brake circuit or other cabling. 
     DE 3,522,447 A1 shows a lengthwise member of a truck for the front part of a motor vehicle. A motor vehicle comprises two such lengthwise members, extending directly behind the bumper, which they support. The lengthwise members are connected in the front-end portion to a transverse member and in their rear end portion to a posterior transverse member. The forward one-third of the lengthwise member is releasably attached to the rear portion of the lengthwise member, so that the two anterior portions of the lengthwise member together with the transverse member form a structure capable of being pre-assembled to form a unit, with other vehicle components, such as the bumper, the radiator, a condenser, an air conditioning system, a metal plate for spotlights etc. 
     With the auxiliary chassis according to DE 4,129,538 A1 and the structure according to DE 3,522,447 A1, portions of the front carriage of a motor vehicle may be preassembled and installed as a unit in the bodywork of the vehicle. However, there is a considerable need for an additional, more efficient assembly of the vehicle parts, for assembly outlay is one of the substantial cost items in the production of a motor vehicle. 
     The object of the invention, then, is to configure a motor vehicle in such manner that assembly is substantially simplified and accelerated. 
     SUMMARY OF THE INVENTION 
     The full auxiliary chassis according to the invention serves to accommodate and suspend the engine, the transmission and other auxiliary parts, such as an electrohydraulic control device, a radiator, a guidance transmission, an ABS/EDS device or the like. The full auxiliary chassis includes a rear transverse member, a front transverse member, and two side members connected to form, a closed horizontal generally rectangular structure. This structural unit may be installed in the motor vehicle in the preassembled state, with engine, transmission and auxiliary equipment. This reduces assembly outlay considerably, since the complete powerplant with all auxiliaries can be preassembled in a module, this preassembly taking place independently of any passenger car assembly line. The prefabricated module is then placed in the vehicle and connected therewith in a single operation. 
     The result is a definite reduction of manufacturing time on the passenger car assembly line and a considerable reduction of costs. The productivity of a motor vehicle plant is thereby increased. 
     A further essential advantage of preassembling such a module on the full auxiliary chassis is that at preassembly, all parts to be assembled are readily accessible, since they are not covered by bodywork parts, thus improving quality. Specifically, robots may be employed to process the connections, performing these operations very dependably and economically. This permits a further reduction of costs with simultaneous improvement of quality. 
     In a preferred embodiment of the invention, the side members are connected to the transverse members by bolts, so that in the event of damage to a transverse or lengthwise member or to a unit connected to these, only a single transverse or lengthwise member, as the case may be, need be removed, and the corresponding transverse or lengthwise member or unit connected thereto replaced. 
     In another preferred embodiment of the invention, the front transverse member is of a generally horizontal U-shaped configuration in top view, with a long traverse section and two shorter legs extending generally in the lengthwise direction of the vehicle. The legs are integrally connected to the traverse. Thus, in the first place, in maintenance of the vehicle, a front subunit, bearing for example a radiator, intake air cooler and condenser, may be pulled from the engine compartment of the vehicle, and in the second place, the transverse member forms a stable unit that, in a collision, will transmit the energy of deformation to the lengthwise members, which will then deform correspondingly. In particular, the two legs may serve as deformation parts and accommodate a great deal of energy of deformation within a short travel. The auxiliary chassis according to the invention, therefore, provides additional collision protection in addition to the bumper itself. 
     The invention will now be illustrated by way of example with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a full auxiliary chassis according to the invention in top view. 
     FIG. 2 shows the full auxiliary chassis of FIG. 1 in side view. 
     FIG. 3 shows a section of a lengthwise member along the line AA in FIG. 2 according to a first embodiment of the invention, 
     FIG. 4 shows a section of the lengthwise member along the line AA in FIG. 2 according to a second embodiment of the invention, and 
     FIG. 5 shows a section of the transverse member along the line BB in FIG.  1 . 
    
    
     DESCRIPTION OF THE INVENTION 
     The full auxiliary chassis  1  according to the invention includes a front transverse member  2 , two lengthwise side members  3 ,  4  and a rear transverse member  5 . The front transverse member is of U-shaped configuration in top view (FIG. 1) with a long traverse  6  and two shorter legs  7 . The two legs  7  and the traverse  6  form an integral unit. The front transverse member is preferably configured as a part formed by means of internal high pressure, so that it bounds a cavity in its interior. On the front transverse member  2 , near the ends of the long traverse  6 , nozzles  8 ,  9  (inlet/outlet) may be arranged. The front transverse member  2  may be employed as an intake air duct to convey air from one side of the vehicle to the other side of the vehicle, and additionally as a sub-intake air cooler. 
     In the corner regions of the front transverse member  2  and somewhat outward from the nozzles  8 ,  9 , there are accommodations  10  with vertical holes  11  for attaching the full auxiliary chassis to a motor vehicle. 
     The free ends of the legs  7  each comprise a vertical surface  12  in which a threaded hole is formed. On the frontal spaces  12 , the lengthwise members  3 ,  4  are attached to vertical surfaces  12  with matching faces, and fastened by means of a bolt  13 . The lengthwise members  3 ,  4  form a more or less rectilinear continuation of the legs  7 , being angled somewhat inward in their rearward portion. At the vertex of the angling of the left lengthwise member  3  as viewed in the direction of travel, an accommodation  14  is provided for the transmission, meaning that the transmission is mounted at point  14 . 
     The lengthwise members  3 ,  4  extend rearward some distance beyond the rear transverse member  5 , and, in the region neighboring upon the rear transverse member  5 , they comprise a form suitable for accommodation and lodgment of a transverse or oblique caster  15  with kits bearings  16 ,  17 . The lengthwise members  3 ,  4 , at their rear ends, comprise an additional accommodation  18  with through holes  19  for attaching the full auxiliary chassis  1  to the vehicle. 
     The lengthwise members  3 ,  4  are each attached to the rear transverse member  5  by several bolts  20 . 
     The rear transverse member  5 , in cross section, comprises a U-shaped form open upwards, having a floor segment  21  and two wall segments  22 ,  23 . The forward wall segment  23  in the direction of travel is higher than the rearward wall segment  22  in the direction of travel and is cropped doubly angled rearward at its upper end. Preferably, the transverse member is configured according to the teaching of DE 197 03 504 A1, and arranged on the vehicle with respect to the drive axle. 
     At the rear transverse member  5 , lines  24  are attached for the servo control. Above the rear transverse member, at a short distance, the steering gear  25  (shown dot-dashed) is arranged, the ends of its linkage extending beyond the transverse member  5 . 
     The lengthwise members  3 ,  4  extend through a region very narrowly bounded spatially between the tire envelope curve  26  of the vehicle and the transmission. To simplify the drawing, FIG. 1 shows only the oil casing  27  of an automatic transmission, instead of the complete transmission. The tire envelope  26  encircles the outer boundary of the vehicle tire in all guidance positions. To provide a high strength of the lengthwise members  3 ,  4  in this narrow region, the cross-sectional form is of maximal size. 
     According to a first embodiment of the invention (FIG.  3 ), the side members  3 ,  4  consist of a sheet-metal structure having an outer sheet-metal shell  28  angled off inward at its bottom edge and an inner sheet-metal shell  29  welded to the outer sheet-metal shell  28  to make a hollow profile of more or less rectangular cross-section, having high rigidity by virtue of this spatial form. At the lower margin, the two sheet-metal shells  28 ,  29  form a welding flange  30  projecting horizontally inward toward the other side member and serving for attachment of a noise capsule  31 . The outer shell  28  is drawn far upward for enhanced stability and may be attached to a lengthwise structural member  32  of the body assembly by means of a bolt  33 . 
     Another embodiment of the side members  3 ,  4  is shown in FIG. 4, configured as a casting. These side members  3 ,  4  have a narrow but high U-shaped cross section, open at the bottom, fitting between the tire envelope  26 , the oil casing  27  and a gear case  34 . The lengthwise member  3 ,  4  thus consists of an outer side wall  35  and an inner side wall  36 , and a top wall  37 . The outer side wall  35 , to enhance the rigidity of the lengthwise member  3 ,  4 , is extended upward over the top wall  37  by means of a stiffening web  38 . At the lower end of the inner side wall  36 , a horizontal web  39  projecting inward toward the other side member is formed. This horizontal web  39  lends the lengthwise member  3 ,  4  a high moment of resistance to deflections in a horizontal plane. In addition, it can be employed to attach a bottom noise capsule  31 . 
     Independently of the embodiment of the lengthwise members  3 ,  4 , their bottom edges, especially in the front end region, may be configured as skids  40 . The skids  40  preferably extend forward to beneath the rear end region of the legs  7  of the front transverse member  2 , and are deeper than the extreme contour, so that upon vehicle contact with a curb, the skids will come into contact with the curb first, protecting the equipment. 
     The full auxiliary chassis  1  according to the invention is preassembled as a module before installation in the vehicle, an engine, transmission and other auxiliary equipment being integrated onto the module. Examples of such auxiliary equipment are a radiator  41 , an intake air cooler  42 , an oil casing  27 , a condenser, an electro-hydraulic control means  43  or an ABS/EDS device  44 . The complete module is lifted at assembly from below into the vehicle bodywork on a conveyor belt, and rigidly connected to the lengthwise member  32 . In so doing, the full auxiliary chassis is bolted at the accommodations  10  to a supporting and spacing plate  45  attached to the front end of the member  32  and fastened by means of a spacer tube  46  and a long bolt  47  to a front end structural member  32  of the vehicle body at front end of the side members  3 ,  4  and to the structural member  32  at the accommodations  18  at the rear end of the side members  3 ,  4 . The full auxiliary chassis, at least in the forward region, is preferably arranged at a definite distance below the structural member  32 , the distance D being about 20 to 40 cm (FIG.  2 ). At the front end of the structural member  32 , a bumper  48  is attached. By the arrangement of the full auxiliary chassis  1  under the bumper  48 , the full auxiliary chassis  1  forms a second shock-absorbing element in addition to the bumper  48 . 
     In a collision, legs  7  of the front transverse member  2  act as deformation parts, capable of absorbing energy of deformation. In a severe collision, the lengthwise members  3 ,  4  may be deformed as well. 
     The screw connections between the full auxiliary chassis  1  and the structural members  32  are preferably designed to tear off in an accident, so that the deformation of the structural member  32  will not be limited by elements connected to the full auxiliary chassis, such as engine, transmission and the like. In this way, the structural members can absorb more energy of deformation before the passenger compartment is damaged. This may lead to a further enhancement of the safety of the vehicle. 
     The transmission attached to the lengthwise member  3  at the location  14  will detach from the lengthwise member  3  in a collision, and drop down, not interfering with the deformation of parts located above it. 
     The deformation behavior of the legs  7  serving as deformation parts and of the side members  3 ,  4  can be influenced by the location of the junctions between the full auxiliary chassis and the structural members  32 . The farther back the connections are arranged, the longer the deformation part becomes, and the more energy of deformation it can absorb. The farther forward the connections lie, the more the front transverse member of the full auxiliary chassis  1  will act as additional bumper, able to bear against barriers and in particular to penetrate soft barriers. 
     With the full auxiliary chassis  1 , the assembly of a vehicle is much accelerated, since the complete powerplant can be preassembled on the full auxiliary chassis. Here it is of advantage that the several connections are freely accessible, so that the employment of robots is possible. Furthermore, the entire powerplant module can be checked for defects prior to installation in the vehicle. 
     The full auxiliary chassis according to the invention leads to a definite reduction of manufacturing time and hence of manufacturing costs on the passenger car assembly line. Besides, a considerable gain in quality is realized. 
     Another advantage of the invention results from the fact that the accommodation  14  for the transmission is arranged on the lengthwise member  3  close to the front wheel axis  49  of the vehicle, keeping the starting and stopping torque small, as well as the resulting dipping or bobbing motion of the front carriage. This leads to increased riding comfort. 
     The invention has been illustrated in detail above in terms of an embodiment by way of example. However, the invention is not limited to this concrete example. The scope of the invention for example also includes an embodiment in which the front transverse member is not a monocoque part but a welded two-shell assembly.