Abstract:
A sensing and injury mitigation system for a vehicle to identify an object in an impact event is disclosed. The system includes an impact sensing unit comprising an impact sensor and a pressure sensing unit. The impact sensor has fluid-filled first and second tube portions. The pressure sensing unit has a housing and first and second pressure sensors located within the housing. The first tube portion of the impact sensor is attached to the first pressure sensor and the second tube portion of the impact sensor is attached to the second pressure sensor. The pressure sensing unit senses changes in fluid pressure within the tubes. In one embodiment, the tube portions of the impact sensor define a loop. In another embodiment, at least a portion of the first tube portion and at least a portion of the second tube portion share a common axis.

Description:
TECHNICAL FIELD 
     The disclosed inventive concept relates generally to pedestrian protection sensors for automotive vehicles. More particularly, the disclosed inventive concept relates to a pedestrian protection sensor for a vehicle having impact tubing attached to a sensor unit. 
     BACKGROUND OF THE INVENTION 
     Pedestrian-vehicle impact events are unfortunate but known occurrences as are impact events between vehicles and non-pedestrian objects. Vehicle object impact mitigation systems are known that can identify the location and size of an object impacted by the vehicle. Where such systems are associated with the front of the vehicle it is the width and location of the impact object that helps the vehicle&#39;s impact mitigation system to determine which, if any, active restraints should be deployed. Such systems may cause the vehicle to react differently depending on whether the impact object is a pedestrian or whether it is a non-pedestrian object. 
     Under the former circumstance, the vehicle impact mitigation system identifies a pedestrian and actively responds to the impact event. Active responses may be both external and internal. External responses might include, but not be limited to, bumper-mounted and hood-mounted airbags and hood-lifting systems. Internal responses might include, but not be limited to, the activation of steering wheel, dashboard, and seat belt airbags or side curtains. 
     On the other hand, if the vehicle impact mitigation system determines that the objected impact is not a pedestrian then no external response is needed although one or more of the above-mentioned internal responses may still be mandated. 
     In practice, the detection of a pedestrian impact requires full sensor coverage of the front end of the vehicle to minimize the potential injury to the pedestrian, and allow other non-pedestrian objects to impact the vehicle with no system detection/reaction. One known method of accomplishing this is through the use of two pressure sensors at opposite ends of the vehicle front end connected by a sealed tube. However, this architecture is not the most cost effective because it requires a pressure sensor at each end of the tube. 
     Accordingly, there is a need for a simple, inexpensive device for sensing the severity, location, and width of an impact. This information may be integrated with other sensor outputs by a control system to provide an intelligent crash mitigation system. 
     As in so many areas of vehicle technology there is always room for improvement related to the protection of pedestrians in a pedestrian-vehicle impact event. 
     SUMMARY OF THE INVENTION 
     The disclosed inventive concept overcomes the problems associated with known impact sensing arrangements. The disclosed inventive concept provides a sensing and injury mitigation system for a vehicle to identify an object in an impact event that overcomes the limitations of known systems. Particularly, the system of the disclosed inventive concept includes an impact sensing unit that includes an impact sensor and a pressure sensing unit. The impact sensor includes a first tube portion and a second tube portion. The pressure sensing unit includes a housing. Within the housing are located a first pressure sensor and second pressure sensor. One end of the first tube portion is fluidly attached to the first pressure sensor. One end of the second tube portion is fluidly attached to the second pressure sensor. The tube portions are filled with a fluid such as a gas. The pressure sensing unit senses a change in fluid pressure within one or both of the tube portions. 
     According to a first embodiment of the disclosed inventive concept, the first and second tube portions form a looped pressure tube. In this embodiment, one of the tube portions is provided on the front of an energy absorber and the other tube portions is provided either to the top of or to the back of the energy absorber, thus giving some assurance that in an impact event only the tube portion on the front of the energy absorber will be crushed whereby one part of the looped tube receives the pressure wave caused by the impact and the other part of the looped tube carries the pressure wave. If the distance between the crushed area and a sensor is short, the movement of the pressure wave is relatively fast. If the distance between the crushed area and a sensor is long, the movement of the pressure wave is relatively slow. By providing a sensor at each open end of the loop, a determination as to location of the impact to the front of the vehicle can readily be made. 
     According to a second embodiment of the disclosed inventive concept, the first tube portion and the second tube portion are separate tubes. In the first embodiment, the first and second tube portions of the looped pressure tube are straight and parallel. In the second embodiment, at least a part of the first tube portion and at least a part of the second tube portion share a common axis. 
     The system includes a controller to which the pressure sensing unit is attached. The system further includes a deployable protection element for protecting an individual. The deployable protection element may be external in the form of bumper-mounted and hood-mounted airbags and hood-lifting systems. In addition, the deployable protection element may be internal in the form of one or more of steering wheel, dashboard, and seat belt airbags or side curtains. 
     The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
         FIG. 1  is a simplified, perspective view of the forward portion of a motor vehicle including a pedestrian impact sensing system according to a preferred embodiment of the disclosed inventive concept; 
         FIG. 2  is a view similar to that of  FIG. 1  but illustrating a top plan view of the front end of the motor vehicle; 
         FIG. 3  illustrates a view of the impact sensing unit according to a preferred embodiment of the disclosed inventive concept shown relative to the bumper and energy absorber of a vehicle; 
         FIG. 4  illustrates a sectional view taken along line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a top plan view of the impact sensing unit according to an alternative embodiment of the disclosed inventive concept positioned in the forward portion of a motor vehicle; 
         FIG. 6  illustrates a sectional view of an alternate embodiment of the arrangement of the pressure tube relative to the energy absorber and the bumper of a vehicle taken along line  6 - 6  of  FIG. 5 ; 
         FIG. 7  illustrates a top plan view of an alternative embodiment of the pedestrian impact sensing system according to a preferred embodiment of the disclosed inventive concept; 
         FIG. 8  illustrates a back side view of the pressure tubes positioned on the energy absorber according to the embodiment of the pedestrian impact sensing system illustrated in  FIGS. 6 and 7 ; 
         FIG. 9  illustrates a sectional view of the assembly of pressure tubes and the energy absorber taken along line  9 - 9  of  FIG. 8 ; and 
         FIG. 10  illustrates a sectional view of the assembly of pressure tubes and the energy absorber taken along line  10 - 10  of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
     In general, the disclosed invention provides a sensing and injury mitigation system for a vehicle that provides a more cost-effective solution compared with known technologies through the use of a single housing for both pressure sensors. In this manner a single connector to the pressure tube and a single attachment to the vehicle is provided. 
     The disclosed inventive concept operates to determine a pedestrian impact based on the pressure wave generated at a certain point in the looped pressure tube by an impact. By relying on one pressure sensor attached to one open end of one leg of the looped pressure tube and another pressure sensor attached to the other open end of the other leg of the looped pressure tube, a measurement of the difference in signal time and distance travelled can be made and the impact position can thus be determined. The measurement relies on only one leg of the looped pressure tube being impacted and the other leg being isolated and protected from impact by an energy absorber. 
     Referring to  FIG. 1 , a simplified perspective view of the forward portion of a motor vehicle, generally illustrated as  10 , that includes a pedestrian impact sensing system according to a preferred embodiment of the disclosed inventive concept is illustrated. Referring to  FIG. 2 , a view similar to that of  FIG. 1  is illustrated but shows a top plan view of the motor vehicle  10 . A bumper assembly  12  is illustrated in the forward-most portion of the vehicle  10 . The bumper assembly  12  is covered by a relatively thin front fascia  14  to provide both an aerodynamic contour and to improve the appearance of the underlying bumper components. The shape and overall configuration of the vehicle  10  and the bumper assembly  12  shown in  FIGS. 1 and 2  are for illustrative purposes only and are not intended as being limiting. 
     Embedded within the vehicle  10  generally vehicle inward of the bumper assembly  12  is an energy absorber  16 . The energy absorber  16  may be composed of a variety of materials but is preferably composed of impact-resistant foam or a molded polymerized material. The energy absorber  16  is provided to absorb kinetic energy when the bumper assembly  12  experiences an impact event by being crushed or flattened or otherwise deformed. The energy absorber  16  may be formed from a variety of materials, including a foamed or a thin-walled polymerized material. 
     The bumper assembly  12  further includes a bumper  17 . Preferably but not absolutely, the bumper  17  is formed from an extruded metal, such as extruded aluminum. Alternatively, the bumper  17  may be formed from a rigid material. 
     Adjacent and vehicle inward of the energy absorber  16  is an impact sensing unit  18 . The impact sensing unit  18  includes an impact sensor  20  and a pressure sensing unit  22 . The pressure sensing unit  22  is attached to an electronic control unit  24 . The electronic control unit  24  can receive a signal from the pressure sensing unit  22  indicating that an impact event has occurred as determined by the amount of pressure change in the impact sensor  20  of the impact sensing unit  18  as will be discussed in greater detail below. 
     The electronic control unit  24  is attached to other components of the pedestrian protection system of the vehicle  10 . For example, the electronic control unit  24  may be attached to hood lift actuators  26  and  26 ′ that raise the vehicle hood in order to create more separation between the underside of the hood and rigid components beneath the hood. This added separation allows the hood to deflect downward under the pressure of a pedestrian strike. Accordingly, signals from the electronic control unit  24  may effect triggering of the hood lift actuators  26  and  26 ′ in order to lift the hood at an appropriate time. 
     The hood lift actuators  26  and  26 ′ are examples of active pedestrian protection. Other forms of pedestrian protection that could be triggered by the electronic control unit  24  include external air bags (not shown) for protecting pedestrians. 
     It may be that the type of impact determined by the electronic control unit  24  in response to the pressure sensing unit  22  is of the type that is not a pedestrian impact but instead is determined to be a non-pedestrian impact. In such an instance, the electronic control unit  24  would optionally signal an internal airbag control module  28  to initiate the release of one or more interior airbags (not shown) that include but are not limited to instrument panel and steering wheel airbags and curtain airbags. It is understood that the interior airbags may be initiated in the event of a pedestrian impact as well. 
     Referring to  FIG. 3 , the pressure sensing unit  22  includes a pressure sensing unit housing  23 . Within the pressure sensing unit housing  23  is a first pressure sensor  30  and a second pressure sensor  32 . The impact sensor  20  includes a looped pressure tube  33  having a first leg or pressure tube portion  34  and a second leg or pressure tube portion  36 . The looped pressure tube  33  and the related pressure sensors  30  and  32  contain a fluid such as a gas. The looped pressure tube  33  is preferably though not necessarily made from a flexible or semi-flexible polymerized material. Accordingly, the looped pressure tube  33  may be used in a wide range of packaging options. 
     The pressure sensing unit  22  of the disclosed inventive concept may optionally include a bidirectional, self-testing G-sensor  35  for safing (in order to prevent system malfunction) and a temperature sensor  37 . The temperature sensor  37 , if supplied, detects temperatures of the fascia  14  and the energy absorber  16  insofar as the temperatures of these components are subject to changes in ambient air temperature. The pressure sensing unit  22  may further include a piezoelectric transducer  39  for testing pressure sensitivity of the looped pressure tube  33  by generating a pressure pulse. The piezoelectric transducer  39 , if supplied, checks the pressure sensitivity each time the vehicle is started. 
     The first pressure tube portion  34  includes an open end  38  while the second pressure tube portion  36  includes an open end  42 . The first pressure tube portion  34  and the second pressure tube portion  36  are fluidly connected by a loop  44  such that the looped pressure tube  33  is continuous between the first open end  38  and the first open end  42 . The open end  38  of the first pressure tube portion  34  is fluidly attached to the first pressure sensor  30  while the open end  42  of the second pressure tube portion  36  is fluidly attached to the second pressure sensor  32 . 
     The looped pressure tube  33  of the impact sensing unit  18  is attached to the vehicle  10  by a mounting bracket  46  and the pressure sensor housing  22 . Optionally the impact sensor  20  may also be attached to the vehicle  10 . 
     Referring to  FIG. 4 , a sectional view of  FIG. 3 , taken along line  4 - 4  of that figure, illustrates relative position of the first pressure tube portion  34  fitted adjacent to the front of the energy absorber  16  while the second pressure tube portion  36  is fitted to the top side of the energy absorber  16 . It should be noted that the second pressure tube portion  36  could also be fitted to the bottom side of the energy absorber  16 . 
     An alternative to the arrangement shown in  FIGS. 1 through 4  and discussed in relation thereto is shown in  FIGS. 5 and 6 .  FIG. 5  illustrates a top plan view of the impact sensing unit according to an alternative embodiment of the disclosed inventive concept positioned in the forward portion of a motor vehicle and  FIG. 6  illustrates a sectional view of the sensing unit taken along line  6 - 6  of  FIG. 5 . 
     Like the embodiment of the pedestrian impact sensing system shown in  FIGS. 1 through 4 , the embodiment shown in  FIGS. 5 and 6  includes the vehicle  10  having the bumper assembly  12  covered by the thin front fascia  14 . The bumper  17  is again part of the bumper assembly  12 . 
     A looped pressure tube  48  having a first leg or pressure tube portion  50  and a second leg or pressure tube portion  52  is provided. The first pressure tube portion  50  and the second pressure tube portion  52  are connected by a loop  54 . The open ends of the looped pressure tube  48  are fluidly attached to the pressure sensing unit  22  in the same manner as described above with respect to the embodiment shown in  FIGS. 1 through 4 . An energy absorber  56  is provided between the fascia  14  and the bumper  17 . Like the energy absorber  16  described above, the energy absorber  56  may be composed of a variety of materials but is preferably composed of impact-resistant foam or a molded polymerized material. 
     As shown in  FIGS. 5 and 6 , the first pressure tube portion  50  is fitted adjacent the front of an energy absorber  56  while the second pressure tube portion  52  is fitted into a channel  58  formed on the back side of the energy absorber  52 . In this manner, the second pressure tube portion  52  is provided with protection from direct impact. 
     The looped pressure tubes  33  and  48  discussed above represent one approach to the pressure tube of the impact sensing unit of the disclosed inventive concept. However, this is not the only possible arrangement and an alternate pressure tube configuration is illustrated in  FIGS. 7 through 10 . 
     Referring to  FIG. 7 , an alternative embodiment of the pedestrian impact sensing system according to the disclosed inventive concept is shown, generally illustrated as  60 . The pedestrian impact sensing system  60  includes a pressure assembly  62  generally positioned adjacent to an energy absorber  63  that is itself positioned adjacent the fascia  14 . The bumper  17  is positioned adjacent the pressure assembly  62 . 
     The pressure assembly  62  comprises a pressure tube system  64  that includes a first pressure tube  66  and a second pressure tube  68 . The first pressure tube  66  and the second pressure tube  68  each contain a fluid such as a gas. The tube arrangement is better illustrated in  FIG. 8  which illustrates a back side view of the energy absorber  63  and the pressure tube system  64 . A pressure sensor housing  70  is provided that includes a first pressure sensor  72  and a second pressure sensor  74 . The open end of the first pressure tube  66  is attached to the second pressure sensor  74  and the open end of the second pressure tube  68  is attached to the first pressure sensor  72 . 
       FIG. 9  illustrates a sectional view of the energy absorber  63 , the first pressure tube  66 , the second pressure tube  68 , the first pressure sensor  72  and the second pressure sensor  74  enclosed within the pressure sensor housing  70  (shown in  FIGS. 7 and 8 ). The sectional view shown in  FIG. 9  is taken along line  9 - 9  of  FIG. 8 . The pressure sensor housing  70  is fitted within a recessed area  71  formed in the energy absorber  63 . 
       FIG. 10 , taken along line  10 - 10  of  FIG. 7 , illustrates a sectional view of the pedestrian impact sensing system  60  according to the present embodiment. As illustrated, the first pressure tube  66  and the second pressure tube  68  are positioned behind the energy absorber  63  but in front of the bumper  17 . 
     In operation, the impact sensing unit responds with a signal to the electronic control unit  24  in an impact event. The signal is generated by the pressure sensing unit  22  (or  22 ′) is itself a response to a change in pressure sensed in the pressure tube  33  or in either or both of the pressure tubes  66  and  68 . This is made possible by a pressure transducer (not shown) associated with the pressure sensor  30  (or  72 ) and the second pressure sensor  32  (or  74 ) that generates an electrical or electronic signal representative of the sensed pressure at all times. The signals generated by the first pressure sensor  30  (or  70 ) and the second pressure sensor  32  (or  72 ) are sent to the electronic control unit  24  where they may be digitized, integrated, measured, compared or otherwise electronically and/or mathematically processed in order to detect characteristics such as the magnitude, time and location of an impact on the impact sensing unit  18  (or  18 ′ or  70 ). It also may be possible to use the raw signals generated by the first pressure sensor  30  (or  72 ) and the second pressure sensor  32  (or  74 ) to actuate either a pedestrian protection element or a passenger protection element without significant processing by the electronic control unit  24 . 
     The disclosed inventive concept provides the packaging of the two pressure sensors  30  and  32  (or  72  and  74 ) adjacent one another in the same pressure sensing unit housing  23  (or  70 ) contributes to the efficiency of the design of the overall impact sensing unit  18  (or  18 ′) as compared with locating multiple sensors at separate, spaced apart locations. Fabrication, installation and servicing of the impact sensing unit  18  (or  18 ′) are all improved by the unitary construction of the pressure sensing unit  22  (or  22 ′). 
     Thus the disclosed invention as set forth above overcomes the challenges faced by known pedestrian protection sensing systems for vehicles by reducing both complexity and cost. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.