Abstract:
A method of inflating an airbag with a fluid includes sending a signal to open a first valve and opening the first valve. The method also includes directing a control pressure through the first valve and toward a second valve. The method further includes throttling the second valve in response to the control pressure. The throttling of the second valve produces a variable inflation mass flow rate of the fluid at a second valve outlet. Opening the first valve and closing the first valve are performed as a step function to achieve a desired predetermined variable inflation mass flow rate of the airbag.

Description:
TECHNICAL FIELD 
     The disclosure generally relates to airbag inflators and specifically to control systems for airbag inflators that may be tailored for anticipated events. 
     BACKGROUND 
     An airbag is typically inflated with a pressurized source of gas. While airbags originally included single stage inflators, or inflators that would supply a constant effective flow area for a variable pressure, some recent airbag inflators have been adapted to supply more than one flow rate to inflate the airbag. These ‘dual stage’ airbag inflators typically are initiated by a control logic that determines what ‘type’ of crash event is being experienced and provides a selected flow rate to inflate the airbag. However, these dual stage inflators typically provide only adaptive vents, adaptive columns, dual-stage pyro inflators, or other systems that provide limited utility. Hybrid pyro inflators may also be used, but are sensitive to pressure waves within the system that affect the burn and subsequent development of gas flow and pressure. 
     With continual development in understanding crash dynamics and what parameters would be useful in altering inflation mass flow rates and to what degree, dual stage airbag inflators may no longer provide a desired flow rate for a specific initiating event that can be somewhat accurately detected and compensated for in an airbag inflation sequence. What is needed, therefore, is an apparatus and method for inflating an airbag that may be tailored to a specific defined initiation event. A favorable apparatus would be readily altered for use in different vehicle types, such as small cars, medium duty trucks, and light duty trucks. 
     SUMMARY 
     An illustrative embodiment includes a method of inflating an airbag with a fluid. The method includes sending a signal to open a first valve and opening the first valve. The method also includes directing a control pressure through the first valve and toward a second valve. The method further includes throttling the second valve in response to the control pressure. The throttling of the second valve produces a variable inflation mass flow rate of the fluid at a second valve outlet. Opening the first valve and closing the first valve are performed as a step function to achieve a desired predetermined variable inflation mass flow rate of the airbag 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, preferred illustrative embodiments are shown in detail. Although the drawings represent some embodiments, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present invention. Further, the embodiments set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
         FIG. 1  is a schematic view of an airbag inflator system according to an embodiment. 
         FIG. 2  is a schematic view of a control valve according to an embodiment, illustrated in a first configuration. 
         FIG. 3  is a schematic view of a control valve according to an embodiment, illustrated in a second configuration. 
         FIG. 4  is a graphical representation of various mass flow rates for selected exemplary operational modes of the system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an embodiment of an airbag inflator system  20 . The system  20  includes a gas supply container  22 , a main valve  24 , a control valve  26 , an airbag  28 , a control module  30 , a flow meter  32 , a primary gas pressure sensor  34 , a secondary gas pressure sensor  36 , occupant sensors  38 , and crash sensors  40 . The main valve  24  is connected to the module  30  via a communication link  50  and is opened by the module  30  to connect the gas supply container  22  with the control valve  26 . The primary gas pressure sensor  34  senses the pressure inside the gas supply container  22  and is connected to the module  30  via a communication link  52 . The secondary gas pressure sensor  36  senses the pressure inside the control valve  26  and is connected to the module  30  via a communication link  54 . The flow meter  32  senses the mass flow of gas between the control valve  26  and the airbag  28  and is connected to the module  30  via a communication link  56 . 
     In the embodiment illustrated, the gas supply container  22  is a source of stored gas at about 12,000 psi (kpa), although other suitable gas supplies may be used. The control valve  26  is opened with pyrotechnics, although other opening mechanisms may be used. The airbag  28  is a conventional airbag of standard or non-standard design. 
     As best seen in  FIG. 2 , the control valve  26  includes a valve body  70 , a main inlet  72 , a main outlet  74 , and a vent  76 . In the embodiment illustrated, the body  70  houses a solenoid valve  80 , a ring valve  82 , and an actuation piston  84 . Specifically, the body  70  defines an inlet passageway  90  that opens into a shared passageway  92  that opens to both a ring valve inlet  94  and a solenoid valve inlet  96 . The solenoid valve inlet  96  opens to a solenoid valve chamber  100  which is in fluid communication with a piston cylinder  102  at a first cylinder end  104  and a solenoid valve vent  106 . The ring valve inlet  94  includes a ring valve seat mating surface  110  and a ring valve plate chamber  112  that opens to both a control valve outlet  114  and the piston cylinder  102  at a second cylinder end  116 . 
     The solenoid valve  80  is positioned within the solenoid valve chamber  100 . The solenoid valve is switchable between a first configuration, or an open configuration, where the solenoid valve inlet  96  is in fluid communication with the first cylinder end  104  of the piston cylinder  102 , and a second, or closed, configuration, where the solenoid valve inlet  96  is in fluid communication with the solenoid valve vent  106 . The control valve  26  includes a ring valve seat  120 , a ring valve plate  122 , a ring valve plunger  124 , and the piston  84  attached to the ring valve plunger  124 . The ring valve seat  120  is circumscribed by the ring valve seat mating surface  110 . The ring valve plate  122 , the ring valve plunger  124 , and the piston  84  are attached to move axially along an axis A-A as a single device. The ring valve seat  120  is defined in part by a seat inlet surface  130  and a seat mating surface  132 . The ring valve plate  122  is defined in part by a plate outlet surface  136  and a plate mating surface  138 . The ring valve seat  120  includes ring valve apertures  140  formed therein where each ring valve aperture  140  opens to both the seat inlet surface  130  and the seat mating surface  132 . The ring valve plate  122  includes ring valve plate apertures  142  formed therein where each ring valve plate aperture  142  opens to both the plate outlet surface  136  and the plate mating surface  138 . The ring valve seat  120  and the ring valve plate  122  matingly engage with the seat mating surface  132  in contact with the plate mating surface  138  so as to permit a flow of fluid therethrough. That is, both the ring valve seat  120  and the ring valve plate  122  align such that at least a portion of the ring valve apertures  140  align with at least a portion of the ring valve plate apertures  142 , in the embodiment illustrated. 
     The solenoid valve  80  includes a solenoid valve plunger  150 , a coil  152 , and a spring  154 . As best seen in  FIG. 2 , when the solenoid valve  80  is in the first (open) configuration, the plunger  150  seals the solenoid valve vent  106  from the solenoid valve chamber  100 . As best seen in  FIG. 3 , when the solenoid valve  80  is in the second (closed) configuration, the plunger  150  seals the solenoid valve inlet  96  from the solenoid valve chamber  100 . 
     As best seen in  FIG. 2 , when the plate mating surface  138  of the ring valve plate  122  is mated with the seat mating surface  132  of the ring valve seat  120 , the partial alignment of the apertures  140 ,  142  create an effective area EA 1  at the mating surfaces  132 ,  138  for flow of a fluid (not numbered) therethrough. As best seen in  FIG. 3 , when the plate mating surface  138  of the ring valve plate  122  is spaced from the seat mating surface  132  of the ring valve seat  120 , the fluid may flow through the apertures  140 ,  142  while not restricted by the effective area EA 1 , to create an effective area EA 2  for flow of a fluid therethrough. The effective area EA 2  may generally be the lesser combined area of apertures  140  and the combined area of apertures  142 . 
     When the solenoid valve  80  is in the first configuration, ( FIG. 2 ) any fluid that flows into the solenoid valve  80  will be directed toward the first cylinder end  104  of the piston cylinder  102 . When enough fluid enters the first cylinder end  104  of the piston cylinder  102  at a sufficient pressure, the piston  84  is urged toward the ring valve seat  120 , thereby urging the ring valve plate  122  to matingly engage the ring valve seat  120  such that surface  132  contacts the surface  138 . Therefore, when the solenoid valve  80  is in the first configuration, the control valve  26  will limit the flow of the fluid by permitting flow through effective area EA 1 . 
     When the solenoid valve  80  is in the second configuration, no fluid will flow into the solenoid valve  80  and the first end  104  of the piston chamber  102  will be vented through the solenoid valve vent  106  to atmosphere. The flow of fluid through the apertures  140  will urge the ring valve plate  122  to move away from the ring valve seat  120 . Therefore, when the solenoid valve  80  is in the second configuration, the control valve  26  will limit the flow of the fluid by permitting flow through effective area EA 2 . 
     Referring back to  FIG. 1 , the flow meter  32  detects the mass flow of the fluid between the control valve outlet  114  and the airbag  28  and sends a signal to the control module  30  via the link  56 . The primary gas pressure sensor  34  detects the gas pressure within the gas supply container  22  and sends a signal to the control module  30  via the link  52 . The secondary gas pressure sensor  36  detects the gas pressure within the first end  104  of the cylinder  102  and sends a signal to the control module  30  via the link  54 . In the embodiment illustrated, the occupant sensors  38  include occupant position, seat belt status (buckled, unbuckled, etc. . . . ) weight, and height, and the crash sensors  40  include vehicle weight, vehicle speed, estimated weight and speed of potential collision vehicle, etc. Collectively, these inputs to the occupant sensors  38  and the crash sensors  40  are referred to as inflation parameters. 
     The control module  30  includes a microprocessor  200 . A portion of the control logic of the microprocessor  200  is illustrated schematically at  208 . The control module  30  is connected to the occupant sensors  38  via a communication link  210 . The control module  30  is connected to the crash sensors  40  via a communication link  212 . The control module  30  is connected to the solenoid valve  80  via a communication link  214 . 
       FIG. 4  illustrates exemplary embodiments desired variable inflation mass flow rates for anticipated events. That is, differing crash events may be counter acted by deploying an airbag differently, depending upon various detected inflation parameters. 
     In a first event, labeled ‘small car, event  1 ’, the airbag  28  is deployed as the main valve  24  is opened and the control valve  26  is opened in the second state to permit a flow through the second effective area EA 2 . Accordingly, the mass flow rate illustrated for the first event is a high flow rate that diminishes with the reduction in pressure in the gas supply container  22 . 
     In a second event labeled ‘small car, event  4 ’, the airbag  28  is deployed as the main valve  24  is opened and the control valve  26  is opened in the second state for approximately 3 milliseconds (ms) to permit a flow through the second effective area EA 2 . The control valve  26  is then switched to the first state ( FIG. 2 ) for approximately 27 milliseconds (ms) to permit a flow through the first effective area EA 1 . Accordingly, the mass flow rate illustrated for the second event is a high flow rate for 3 ms, switching to a low flow rate for about 27 ms, and then returning back to a higher flow rate that diminishes with the reduction in pressure in the gas supply container  22 . 
     In a third event labeled ‘light truck, event  6 ’, the airbag  28  is deployed as the main valve  24  is opened and the control valve  26  is opened in the second state for approximately 3 milliseconds (ms) to permit a flow through the second effective area EA 2 . The control valve  26  is then switched to the first state ( FIG. 2 ) to permit a flow through the first effective area EA 1  which yields a low flow rate that diminishes with the reduction in pressure in the gas supply container  22 . 
     In a fourth event labeled ‘medium truck, event  3 ’, the airbag  28  is deployed as the main valve  24  is opened and the control valve  26  is opened in the second state for approximately 3 milliseconds (ms) to permit a flow through the second effective area EA 2 . The control valve  26  is then switched to the first state ( FIG. 2 ) for approximately 7 milliseconds (ms) to permit a flow through the first effective area EA 1  which yields a low flow rate. The control valve  26  is then switched to the second state from the first state and then oscillated between the first state and the second state 5 times with the oscillations occurring about every 2 ms. The control valve is maintained in the second state for about 10 ms and then switched back to the first state. Accordingly, the mass flow rate illustrated for the fourth event is a high flow rate for 3 ms, switching to a low flow rate for about 7 ms, and then oscillating between a higher flow rate and a lower flow rate, then maintaining a higher flow rate that diminishes with the reduction in pressure in the gas supply container  22 , then finishing with a low flow rate that diminishes with the reduction in pressure in the gas supply container  22 . 
     While  FIG. 4  presents exemplary embodiments of desired airbag inflation curves, it is understood that an infinite number of examples may exist as newly developed crash simulations and detectors for potential crash and occupant parameters are available. 
     In operation of the system  20 , the control module  30  may interpret signals from the crash sensors  40  as a crash event. This interpretation may involve only one sensor (such as an accelerometer) or multiple crash sensors  40 . When a determination is made that a crash event is occurring, or is imminent, the control module  30  will evaluate information from the occupant sensors to determine input parameters such as occupant position, seat belt status (buckled, unbuckled, etc. . . . ) weight, height, to name a few, and determine what inflation curve to employ. Importantly, an inflation curve, such as the exemplary inflation curves of  FIG. 4 , may be determined by a look-up table, may be standard curves selected for various ranges of parameters, or may be determined by an algorithm exclusively for each individual event. 
     Once a desired inflation curve is determined, the control module  30  will then deploy the system  20  so as to inflate the airbag  28  to simulate, or closely emulate the desired curve. Importantly, data from actual crash tests may be incorporated into the deployment logic to encourage the selection of an appropriate inflation curve. The control module  30  will open the main valve  24  and switch the solenoid valve  80 , if required, the effect the desired inflation curve (as best seen in  FIG. 4 ). 
     The preceding description has been presented only to illustrate and describe exemplary embodiments of the methods and systems of the present invention. It is not intended to be exhaustive or to limit the invention to any precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. The invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. The scope of the invention is limited solely by the following claims.