Patent Publication Number: US-2004056470-A1

Title: Selectively pressurized structural member for vehicle body and frame assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION  
     [0001] This application claims the benefit of U.S. Provisional Application No. 60/412,848, filed Sep. 23, 2002, the disclosure of which is incorporated herein by reference. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] This invention relates in general to body and frame assemblies for vehicles. In particular, this invention relates to an improved structure for a closed channel structural member for use in such a vehicle body and frame assembly that includes an interior portion that can be selectively pressurized under certain conditions, such as during a collision, to provide increased strength and absorb energy.  
       [0003] Many land vehicles in common use, such as automobiles, vans, and trucks, include a body and frame assembly that is supported upon a plurality of ground-engaging wheels by a resilient suspension system. The structures of known body and frame assemblies can be divided into two general categories, namely, separate and unitized. In a typical separate body and frame assembly, the structural components of the body portion and the frame portion of the vehicle are separate and independent from one another. When assembled, the frame portion of the assembly is resiliently supported upon the vehicle wheels by the suspension system and serves as a platform upon which the body portion of the assembly and other components of the vehicle can be mounted. Separate body and frame assemblies of this general type are found in most older vehicles, but remain in common use today for many relatively large or specialized use modern vehicles, such as large vans, sport utility vehicles, and trucks. In a typical unitized body and frame assembly, the structural components of the body portion and the frame portion are combined into an integral unit that is resiliently supported upon the vehicle wheels by the suspension system. Unitized body and frame assemblies of this general type are found in many relatively small modern vehicles, such as automobiles and minivans.  
       [0004] Traditionally, the various components of vehicular body and frame assemblies have been formed from open channel structural members, i.e., structural members that have a non-continuous cross sectional shape (such as U-shaped or C-shaped channel members, for example). For example, it is known to use one or more open channel structural members to form the side rails, the cross members, and other components of a ladder frame type of separate body and frame assembly. However, the use of open channel structural members to form the various components of vehicular body and frame assemblies has been found to be undesirable for several reasons. To address this, it has been proposed to form one or more of the components of the vehicular body and frame assemblies from closed channel structural members, i.e., structural members that have a continuous cross sectional shape (such as tubular or box-shaped channel members, for example). This cross sectional shape is advantageous because it provides strength and rigidity to the vehicle body and frame component. Also, closed channel structural members are well suited to be deformed to a desired shape by hydroforming, which is a well known process that uses pressurized fluid supplied within the closed channel structural member to deform it into conformance with a surrounding die. Hydroforming has been found to be a desirable forming process because portions of the closed channel structural member can be quickly and easily deformed to have a complex cross sectional shape.  
       [0005] Each of the various components of the vehicular body and frame assembly is designed in such a manner as to possess a predetermined amount of strength and rigidity so as to adequately support loads that are placed thereon during operation of the vehicle. When designing the structures of such components, consideration is usually given not only to the relatively small magnitudes of loads that are typically encountered during normal operating conditions of the vehicle, but also to the relatively large magnitudes of loads that might be encountered during extreme operating conditions of the vehicle, such as might occur during a collision. In order to provide maximum safety to the occupants of the vehicle, it is known to design some of all of the components of the vehicular body and frame assembly in such a manner as be capable of accommodating the relatively large magnitudes of the loads that might be encountered during extreme operating conditions of the vehicle. However, by designing these components in this manner, undesirable weight and cost is added to the overall vehicle body and frame assembly, which is inefficient in several regards. Furthermore, in many instances, this additional weight and expense unnecessary because most vehicles are not involved in collisions or operated under other such extreme operating conditions. Thus, it would be desirable to provide an improved structure for a closed channel structural member for use in a vehicle body and frame assembly that is designed to adequately support the relatively small magnitudes of loads that are typically encountered during normal operating conditions of the vehicle, but can be selectively strengthened to accommodate relatively large magnitudes of loads if and when the vehicle encounters extreme operating conditions, such as might occur during a collision.  
       SUMMARY OF THE INVENTION  
       [0006] This invention relates to an improved structure for a closed channel structural member for use in a vehicle body and frame assembly that includes an interior portion that can be selectively pressurized under certain conditions, such as during a collision, to provide increased strength and absorb energy. The closed channel structural member defines an enclosed interior portion or air space. A pressurizing device communicates with the interior portion and contains a quantity of a chemical material that, when properly excited, will expand rapidly into a gaseous form. An igniter or other structure is provided for exciting the chemical material contained within the pressurizing device under predetermined conditions, such as when a collision occurs. The expansion of the chemical material into a gaseous form rapidly increases the air pressure within the closed channel structural member, thus providing additional strength thereto to absorb energy during the collision. Although deformation of the closed channel structural member may occur as a result of the expansion of the chemical material, it is the containment of the highly pressurized gases within the closed channel structural member that increases the strength thereof during the collision.  
       [0007] Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 is an exploded perspective view of a vehicle body and frame assembly including a closed channel structural member and a pressurizing device for selectively pressurizing the interior of the closed channel structural member under certain conditions in accordance with this invention.  
     [0009]FIG. 2 is an enlarged perspective view of a portion of the closed channel structural member and the pressurizing device illustrated in FIG. 1.  
     [0010]FIG. 3 is a further enlarged sectional elevational view of the portion of the closed channel structural member and the pressurizing device illustrated in FIGS. 1 and 2.  
     [0011]FIG. 4 is a further enlarged sectional elevational view of the pressurizing device illustrated in FIGS. 1, 2, and  3 .  
     [0012]FIG. 5 is a block diagram of a control system for selectively actuating the pressurizing device illustrated in FIGS. 1 through 4.  
     [0013]FIG. 6 is an enlarged perspective view similar to FIG. 2 showing the closed channel structural member after actuation of the pressurizing device.  
     [0014]FIG. 7 is an enlarged perspective view similar to FIG. 6 showing the closed channel structural member after actuation of the pressurizing device and after it has been subjected the relatively large magnitudes of loads that might be encountered during extreme operating conditions of the vehicle, such as might occur during a collision. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0015] Referring now to the drawings, there is illustrated in FIG. 1 a portion of a vehicular body and frame assembly in accordance with this invention. The illustrated vehicular body and frame assembly is, in large measure, conventional in the art and is intended merely to illustrate one environment in which this invention may be used. Thus, the scope of this invention is not intended to be limited for use with the specific structure for the vehicular body and frame assembly illustrated in FIG. 1 or with vehicular body and frame assemblies in general. On the contrary, as will become apparent below, this invention may be used in any desired environment for the purposes described below.  
     [0016] The illustrated vehicular body and frame assembly is a separate type of body and frame assembly, including a frame portion, indicated generally at  10 , and a body portion, indicated generally at  11 . The illustrated frame portion  10  of the vehicular body and frame assembly is a ladder type frame portion, including a pair of longitudinally extending side rails  12  and  13  having a plurality of transverse cross members  14 ,  15 ,  16 , and  17  extending therebetween. The side rails  12  and  13  extend longitudinally throughout the entire length of the frame portion  10  and are generally parallel to one another. Each of the side rails  12  and  13  in the illustrated embodiment is formed from a single closed channel structural member having an upper wall, a lower wall, and a pair of side walls. However, it is known that one or both of the side rails  12  and  13  may be formed from a plurality of individually formed closed channel structural members that are secured together by any conventional means, such as by welding, riveting, bolting, and the like. Furthermore, it is known that portions of the side rails  12  and  13  may be formed from open channel structural members.  
     [0017] The cross members  14  through  17  extend generally perpendicular to the side rails  12  and  13  and may be formed having any conventional structure. The cross members  14  through  17  are spaced apart from one another along the length of the frame portion  13  and can be secured to the side rails  12  and  13  by any conventional means, such as by welding, riveting, bolting, and the like. When secured to the side rails  12  and  13 , the cross members  14  through  17  provide lateral and torsional rigidity to the frame portion assembly  10  of the vehicular body and frame assembly.  
     [0018] A plurality of body mount support brackets  18  are provided on the vehicle frame assembly  10 . The illustrated body mount support brackets  18  are stamped members that are secured to the side rails  12  and  13  of the vehicular body and frame assembly  10  by any conventional means, such as by welding, adhesives, and the like. The body mount support brackets  18  are provided to facilitate the connection of the body portion  11  and other various components (not shown) of the vehicle to the vehicular body and frame assembly  10 . To accomplish this, each of the body mount brackets  18  has an opening  18   a  formed therethrough. The openings  18   a  are sized in accordance with respective body mounts  11   a  provided on the body portion  11  of the vehicular body and frame assembly  10 . In a manner that is well known in the art, the body mounts  11   a  are received and supported within the openings  18   a  of the body mount support brackets  18  to connect the body portion  11  to the frame portion  10 .  
     [0019] The upper wall, the lower wall, and the pair of side walls of the closed channel side rail  13  define a hollow interior portion  21 , as best shown in FIGS. 2 and 3. The longitudinal extent of this interior portion  21  within the side rail  13  can, if desired, be limited by a pair of internal plates  22 , such as are shown in dotted lines in FIG. 1. The plates  22  can be secured to the inner surfaces of the side rail  13  by any conventional means, such as by welding, riveting, bolting, and the like. The plates  22  can cooperate with the upper wall, the lower wall, and the pair of side walls of the closed channel side rail  13  to define the interior portion  21  of the side rail in an air-tight manner, although such is not required. If desired, the interior portion  21  of the side rail  13  may be vented to the atmosphere by one or more vent holes, such as shown at  21   a . The purpose for such vent holes  21   a  will be described below.  
     [0020] The interior portion  21  may be provided at any desired location within the side rail  13 , and multiple interior portions  21  may be provided at different locations within the side rail  13  if desired. A similar interior portion (not shown), or a plurality of similar interior portions, may be provided within the other side rail  12 , the cross members  14  through  17 , or any other structural member of the frame portion  10  of the vehicular body and frame assembly. Furthermore, this invention may be practiced by providing similar interior portions within any of the structural members of a unitized body and frame assembly, such as described above.  
     [0021] A pressurizing device, indicated generally at  23 , communicates with the interior portion  21  of the side rail  13  for the purpose of selectively increasing the magnitude of the fluid pressure therein under certain conditions. In the illustrated embodiment, the pressurizing device  23  is supported within an opening  24  formed through the side rail  13 , although such is not required. The illustrated pressurizing device  23  may be secured to the side rail  13  by any conventional means, such as by welding, riveting, bolting, and the like. If desired, a plurality of such pressurizing devices  23  may communicate with the interior portion  21  of the side rail  13 .  
     [0022] The structure of the pressurizing device  23  is shown in detail in FIG. 4. As shown therein, the pressurizing device  23  includes a hollow housing  25  having a plurality of apertures  25   a  formed about the peripheral thereof. The apertures  25   a  are provided such that the interior of the housing  25  of the pressurizing device communicates with the interior portion  21  of the side rail  13 . The pressurizing device  23  also includes a quantity of a material  26  that is disposed within the interior of the housing  25 . The material  26  can be embodied as any material that, when properly excited, expands or changes state rapidly so as to cause a rapid increase in the volume thereof. The purpose for such material  26  will be discussed further below. If desired, a liner  27  may be provided within the interior of the housing  25  of the pressurizing device  23  to cover the apertures  25   a . The liner  27  can not only prevent the material  26  within the housing  25  from falling out through the apertures  25   a , but also can prevent the entry of dirt, water, and other contaminants within the housing  25  through such apertures  25   a . The pressurizing device  23  further includes an igniter  28  or other actuating mechanism that communicates with the interior of the housing  25 . The igniter  28  can be embodied as any conventional device that can selectively excite or otherwise cause the material  26  disposed within the housing  25  to expand or change state rapidly so as to cause a rapid increase in volume.  
     [0023] For example, the pressurizing device  23  can be embodied as an air bag inflator of the type that is generally used in the steering columns of vehicles as a safety device. In a typical an air bag inflator, the material  26  contained within the housing  25  of the pressurizing device  23  can, for example, be sodium azide (NaN 3 ) that is mixed with an oxidizer, such as iron oxide Fe 2 O 3 , cupric oxide CuO or molybdenum disulfide MoS 2 , and the igniter  28  can be embodied as a conventional pyrotechnic device. Under normal circumstances, the sodium azide material  26  is quite stable. When actuated, the igniter  28  can detonate a small amount of a conventional igniter compound. The heat from this ignition starts the reaction of the sodium azide with the oxidizer. As a result, a large volume of nitrogen gas is rapidly generated. This volume of nitrogen gas rapidly increases the magnitude of the fluid pressure within the interior portion  21  of the side rail  13 . Consequently, the strength and rigidity of the side rail  13  is rapidly increased in the vicinity of the interior portion  21 .  
     [0024]FIG. 5 is a block diagram of a control system, indicated generally at  30 , for selectively actuating the igniter  28  of the pressurizing device  23  in the manner described above. As shown therein, the control system  30  includes a sensor  31  that generates an output signal to a controller  32 . The sensor  31  can be embodied as any conventional sensor for detecting any desired operating condition of the vehicle in which the vehicular body and frame assembly is provided. For example, the sensor  31  can be an impact sensor that generates an electrical signal to the controller  32  when a portion of the vehicle is impacted, such as during a collision. Alternatively, the sensor  31  can be a remote sensor (radar, for example) that generates an electrical signal to the controller  32  in advance of an imminent collision. The sensor  31  may be provided on the frame portion  10  of the vehicular body and frame assembly or elsewhere on the vehicle as desired. The controller  32  can be responsive to the generation of the signal from the sensor  31  for actuating the igniter  28 . To accomplish this, the controller  32  is responsive to the generation of the signal from the sensor  31  for generating a signal to the igniter  28 , causing it to be actuated. The controller  32  can be embodied as any one of a variety of well known microprocessors or programmable controllers that are commonly available in the market.  
     [0025] When the igniter  28  is actuated in this manner, the gas that is released expands rapidly within the housing  25  of the pressurizing device  23 . Such gas breaks through the liner  27  and enters into the interior portion  21  of the side rail so as to rapidly increase the magnitude of the fluid pressure therein. Such fluid pressure increase causes increased forces to be exerted on the inner surfaces of the side rail  13 , thereby functioning to strengthen the side rail  13  at the location of the interior portion  21 . If provided as described above, the vent hole  21   a  can allow a portion of the gas within the interior portion  21  of the side rail  13  to escape therethrough, thereby limiting the amount of increase of the ambient pressure therein and allowing the gas to escape from the interior portion  21  after a predetermined period of time. The size of the vent hole  21   a  can be adjusted to control these parameters.  
     [0026] If desired, the fluid pressure within the interior portion  21  of the side rail  13  can be increased to such a magnitude as to cause deformation of a portion of the side rail  13  prior to impact. Such a situation is illustrated in FIG. 6. As shown therein, a portion of the side rail  13  has been expanded outwardly as a result of the increase in the fluid pressure within the interior portion  21  thereof. Such expansion can be designed to provide additional strength to the portion of the side rail  13 . Thereafter, as shown in FIG. 7, the side rail  13  can be deformed in a controlled manner after a collision. Such deformation functions to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle.  
     [0027] In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.