Patent Abstract:
A side airbag apparatus includes an airbag, an inflator and a limited thickness portion. The inflator supplies gas to the airbag. When the airbag is inflated and deployed, the limited thickness portion limits the inflation of the airbag such that the thickness of a portion of the airbag corresponding to an elbow portion of an occupant on the seat is less than the thickness of the remainder of the airbag with respect to the measurement between the occupant and the body side portion. The airbag includes an inflation portion that entirely surrounds the limited thickness portion and is inflated with gas from the inflator. This prevents an elbow portion of the occupant from receiving an excessive force directed laterally inward.

Full Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a side airbag apparatus that, when an impact equal to or greater than a predetermined value is applied to a vehicle body, is inflated and deployed between a sidewall of the vehicle body and an occupant seated on a seat of the vehicle. 
   Japanese Laid-Open Patent Publication No. 2002-362295 and Japanese Patent No. 2933894 disclose typical side airbag apparatuses. Such a side airbag apparatus, which is shown in  FIG. 12 , is typically embedded in a backrest  15  coupled to a seat portion  14  of a car seat  12 . Specifically, the side airbag apparatus is embedded in a side of the backrest  15  that faces the outside of the vehicle. At a collision, the side airbag apparatus inflates and deploys an airbag  31  from the side of the backrest  15  and along a sidewall of the vehicle body, or between a door  16  and an occupant P. 
   When the inflation and deployment of the airbag  31  are completed, a portion of the airbag  31  that corresponds to an elbow portion Pe of the occupant P has a relatively large measurement along the lateral direction of the vehicle. Therefore, the airbag  31  excessively push the elbow portion Pe laterally inward. That is, an upper arm of the occupant P is excessively pivoted about the shoulder by the airbag  31 . Accordingly, an excessive force is applied the chest of the occupant P. 
   SUMMARY OF THE INVENTION 
   The present invention was made for solving the above problems in the prior art. 
   Accordingly, it is an objective of the present invention to provide a side airbag apparatus that, when its airbag is inflated and deployed between an occupant seated on a seat and a sidewall of a vehicle body, prevents an elbow portion of the occupant from receiving an excessive force directed laterally inward, thereby preventing reliably protecting the chest of the occupant. 
   To attain the above object, the present invention provides a side airbag apparatus used in a vehicle. The side airbag apparatus includes an airbag, an inflator and a limited thickness portion. The inflator supplies gas to the airbag, thereby inflating and deploying the airbag between a body side portion of the vehicle and a seat located in the passenger compartment of the vehicle. When the airbag is inflated and deployed, the limited thickness portion limits the inflation of the airbag such that the thickness of a portion of the airbag corresponding to an elbow portion of an occupant on the seat is less than the thickness of the remainder of the airbag with respect to the measurement between the occupant and the body side portion. The airbag includes an inflation portion that entirely surrounds the limited thickness portion and is inflated with gas from the inflator. 
   Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
       FIG. 1  is a side view illustrating a car seat in which an airbag apparatus according to one embodiment is embedded, and an inflated and deployed airbag; 
       FIG. 2  is a cross-sectional view taken along line  2 — 2  of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view taken along line  3 — 3  of  FIG. 1 ; 
       FIG. 4  is a front view showing the deployed airbag; 
       FIG. 5  is a side view illustrating a seat in which an airbag according to another embodiment of the present invention is embedded; 
       FIG. 6  is a side view illustrating an airbag according to another embodiment of the present invention; 
       FIG. 7  is a side view illustrating an airbag according to another embodiment of the present invention; 
       FIG. 8  is a side view illustrating an airbag according to another embodiment of the present invention; 
       FIG. 9  is a side view illustrating an airbag according to another embodiment of the present invention; 
       FIG. 10  is a side view illustrating an airbag according to another embodiment of the present invention; 
       FIG. 11  is a side view illustrating an airbag according to another embodiment of the present invention; and 
       FIG. 12  is a plan view showing a prior art side airbag apparatus installed in the backrest of a car seat, when the airbag is inflated and deployed. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A side airbag apparatus  17  according to one embodiment of the present invention will now be described with reference to  FIGS. 1 to 4 . 
     FIG. 1  shows a side of a car seat  12 , and  FIG. 2  is a cross-sectional view taken along line  2 — 2  of  FIG. 1 . As shown in  FIG. 2 , the car seat  12 , on which an occupant P is seated, is provided on a bottom  11  of the vehicle body. The car seat  12  includes a seat portion  14  and a backrest  15 . The seat portion  14  is attached to the bottom  11  with a position adjusting mechanism  13  in between. The position adjusting mechanism  13  is used to adjust the position of the seat portion  14  along the longitudinal direction of the vehicle. The backrest  15  is attached to the rear end of the seat portion  14 . The side airbag apparatus  17  is installed in the backrest  15 . 
   The configuration of the side airbag apparatus  17  installed in the backrest  15  will now be described. 
   As shown in  FIG. 4 , the side airbag apparatus  17  includes an airbag  18 , an inflator  19 , and a case  20 . The airbag  18  is formed by sewing a pair of fire-proof woven fabric sheets  18   a ,  18   b . The inflator  19  is provided in the airbag  18  and functions as a gas generator. The case  20  accommodates the airbag  18  and the inflator  19 . As shown in  FIG. 1 , the case  20  is attached to a frame (not shown) of the backrest  15  of the car seat  12  and is embedded in a side of the backrest  15  that faces a sidewall of the vehicle body, or a door  16 . 
   A sensor (not shown) for detecting a lateral impact applied to the door  16  is provided in the door  16 . The impact sensor is connected to the inflator  19  with a control circuit (not shown). 
   The airbag  18  will now described in detail. 
   The airbag  18  is folded and accommodated in the case  20 .  FIGS. 1 and 4  show the inflated and deployed state of the airbag  18 . The airbag  18  is designed to be inflated and deployed frontward into a space between the occupant P seated on the seat portion  12  and the door  16 . 
   The outer peripheral portions of the fabric sheets  18   a ,  18   b  forming the airbag  18  are connected to each other with a sewing thread  21 . The inflator  19  has a nozzle  19   a . Gas injected by the injector  19  through the nozzle  19   a  is supplied to the interior of the airbag  18  through paths indicated by arrows of broken lines in  FIG. 4  to inflate and deploy the airbag  18 . As shown in  FIG. 1 , the airbag  18  has a dent portion  22 , or a limited thickness portion. The dent portion  22  corresponds to an elbow portion Pe of the occupant P, which is a joint between an upper arm and a lower arm. The entire area of the dent portion  22  is located within the outer periphery of the airbag  18  and is entirely surrounded by an inflation portion, which will be discussed below. As viewed from the side, the dent portion  22  has a substantially arcuate shape. As shown in  FIG. 2 , the dent portion  22  is formed flat by sewing the fabric sheets  18   a ,  18   b  with a reinforcing fabric sheet  23  in between with the sewing thread  24 . 
   As shown in  FIG. 3 , the elbow portion Pe does not represent only an elbow El of the occupant P, but represents a portion including the elbow El and parts adjacent to the elbow El. The parts adjacent to the elbow El include an upper arm UA (part between a shoulder Sh and the elbow El) and a forearm FA (part between the elbow El and a wrist Wr). Particularly, the parts adjacent to the elbow El include a lower part of the upper arm UA (part between the elbow El and the midpoint between the shoulder Sh and the elbow El) and an upper part of the forearm FA (lower arm, part between the elbow El and the midpoint between the wrist Wr and the elbow El). 
   The airbag  18  has a chest protecting portion  25  located above the dent portion  22 . The airbag  18  also has a lumbar region protecting portion  26  located below and rearward of the dent portion  22 . Further, the airbag  18  has a narrow portion  27  located below and frontward of the dent portion  22 . The narrow portion  27 , together with the dent portion  22 , protects the elbow portion Pe. As shown in  FIGS. 2 and 3 , the chest protecting portion  25  and the lumbar region protecting portion  26  have a greater thickness than that of the narrow portion  27 . As viewed from the side, the narrow portion  27  is formed as an arc that corresponds to a quarter circle and has a constant width. 
   In this embodiment, the chest protecting portion  25 , the lumbar region protecting portion  26 , and the narrow portion  27  form the inflation portion that entirely surrounds the dent portion  22 . 
   A harness  19   b  is connected to the lower end of the inflator  19 . The harness  19   b  is drawn out of the airbag  18  through an opening S, at which the fabric sheets  18   a ,  18   b  are not sewn to each other with the sewing thread  21 . The opening S also functions as a vent hole for discharging gas to the exterior after the airbag  18  is inflated and deployed. 
   The above described side airbag apparatus  17  operates in the following manner. When a sensor in the door  16  detects an impact equal to or greater than a predetermined value, the control circuit outputs an actuation signal to the inflator  19 . Based on the actuation signal, the inflator  19  instantly injects gas to the interior of the airbag  18 . The gas inflates and deploys the airbag  18  frontward as shown in  FIGS. 1 and 3  into the space between the door  16  and the occupant P so that the chest protecting portion  25 , the lumbar region protecting portion  26 , and the narrow portion  27  protect the occupant P. The gas in the inflated airbag  18  is discharged through the opening S, which functions as a vent hole. Accordingly, the airbag  18  is deflated. 
   This embodiment has the following advantages. 
   (1) As shown in  FIGS. 1 to 3 , when the airbag  18  is inflated and deployed between the door  16  and the occupant P, the dent portion  22  corresponds to the elbow portion Pe of the occupant P. Therefore, the dent portion  22 , which contacts the elbow portion Pe, prevents the elbow portion Pe from excessively moved laterally inward, thereby preventing the chest of the occupant is excessively pressed with the elbow portion. The occupant is therefore properly protected. 
   (2) The side airbag apparatus  17  has the narrow portion  27  located frontward of and below the dent portion  22 . The narrow portion  27  prevents the dent portion  22  from being bent and thus stabilize the orientation of the dent portion  22 . Therefore, the occupant is appropriately protected. 
   (3) The narrow portion  27  of the airbag  18  is shaped as an arc of a quarter circle having a constant width as viewed from the side. Therefore, gas is smoothly guided to the narrow portion  27 , and the narrow portion  27  is prevented from being bent. Accordingly, the inflation and deployment of the narrow portion  27  is reliably performed to protect the occupant. 
   (4) In the side airbag apparatus  17 , the reinforcing fabric sheet  23  is provided between the fabric sheets  18   a ,  18   b , and the sheets  23 ,  18   a ,  18   b  are sewn together with the thread  24  to form the dent portion  22  having a triple sheet structure. This increases the disruptive strength of the dent portion  22  during inflation and deployment of the airbag  18 . 
   It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
   As shown in  FIG. 5 , the side airbag apparatus  17  may be provided in the seat portion  14 . Alternatively, not illustrated, the side airbag apparatus  17  may be provided in a sidewall of the vehicle body. In these cases, an elbow portion of an occupant is prevented from being excessively pressed, and the chest of the occupant is appropriately protected. 
   As shown in  FIG. 6 , the side airbag apparatus  17  may be modified such that the dent portion  22  may be formed circular, and gas injected from the nozzle  19   a  of the inflator  19  passes through an area above the dent portion  22 . In other words, the dent portion  22  may be displaced downward relative to a gas flow direction B of the gas injected from the nozzle  19   a.    
   In this case, the flow of gas injected through the nozzle  19   a  does not collide with the dent portion  22 . This accelerates the provision of gas to the narrow portion  27  and thus accelerates the inflation and deployment of the narrow portion  27 . 
   Also, the circular shape of the dent portion  22  accelerates the provision of gas to the narrow portion  27 . This stabilizes the deployment speed (period to a complete inflation) and deployment behavior. 
   In the modified embodiment of  FIG. 6 , the position of the nozzle  19   a  may be lowered so that the dent portion  22  is located higher than the gas flow direction B. 
   As shown in  FIG. 7 , an outer circular dent portion  22 A and a lower dent portion  22 B may be provided such that a gas passage  29  is formed between the dent portions  22 A and  22 B. In this case, even if the main gas flow B collides with the upper dent portion  22 A, the gas passage  29  permits the gas to advance to the narrow portion  27 . This permits the airbag to be smoothly inflated and deployed. 
   By changing the sizes of and the distance between the outer and lower dent portions  22 A and  22 B, the thickness of the dent portions  22 A,  22 B can be easily adjusted. 
   In the modified embodiment of  FIG. 7 , the gas flow B may be directed toward the gas passage  29  between the outer dent portion  22 A and the lower dent portion  22 B. 
   As shown in  FIG. 8 , the gas flow B from the nozzle  19   a  of the inflator  19  may be directed to an area directly above the upper dent portion  22 A. In this case, compared to the modified embodiment shown in  FIG. 7 , gas is more quickly supplied to the narrow portion  27 . That is, the narrow portion  27  is reliably inflated and deployed. 
   As shown in  FIG. 9 , the position of the inflator  19  may be lowered in the airbag  18  so that the main gas flow B from the nozzle  19   a  is directed to the gas passage  29  between the upper and lower dent portions  22 A and  22 B. This modified embodiment permits gas to be quickly supplied to the narrow portion  27  through the passage  29 . 
   As shown in  FIG. 10 , the inflator  19  may be turned upside down so that the nozzle  19   a  is located at the lower side and the main gas flow B directed to the passage  29 . 
   As shown in  FIG. 11 , the gas flow B from the nozzle  19   a  may be directed to an area below the lower dent portion  22 B. 
   A predetermined space may be provided inside the dent portion  22  to permit gas flow. 
   In the illustrated embodiments, the case  20  may be omitted if the airbag  18  is accommodated, and inflated and deployed in a desirable manner. 
   In the illustrated embodiment, the inflator  19  is embedded in a side of the backrest  15  of the seat  12  that corresponds to the door  16 . However, the inflator  19  may be located elsewhere as long as the inflator  19  is capable of injecting gas into the airbag  18 . 
   In the illustrated embodiments, the dent portion  22  is formed substantially arcuate or circular. However, as long as the gas flow is taken into consideration, the shape of the dent portion  22  may be changed. For example, the dent portion  22  may be elliptic, triangular, square, trapezoidal. Alternatively, the dent portion  22  may be shaped like an elbow portion. Three or more dent portions  22  may be provided. 
   The fabric sheets  18   a ,  18   b  forming the airbag  18  may be locally coupled to each other to form the dent portion  22 . 
   In the illustrated embodiment, the present invention is applied to the airbag  18  to protect the lumbar region and chest of an occupant. However, the present invention may be applied to an airbag for protecting a shoulder of an occupant as well as the lumbar region and the chest. The present invention also may be applied to an airbag for protecting the lumbar region, the chest, the shoulders, and the head of an occupant. 
   Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

Technology Classification (CPC): 1