Abstract:
An airbag apparatus for a vehicle may include an inflator; a housing installed in a roof, and a cushion contained in the housing and configured to be deployed downwards by a gas discharged from the inflator to protect an occupant in the vehicle, wherein an upper surface of the cushion is supported by the roof when the cushion is in a deployed state, and a front surface of the cushion extends in a rear direction of the vehicle in an inclined shape to form a recess to prevent interference with a seatback of the front seat while the cushion is deployed downwards.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Korean Patent Application Number 10-2008-0121102 filed Dec. 2, 2008, the entire contents of which application is incorporated herein for all purpose by this reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to airbag apparatuses for vehicles and, more particularly, to an airbag apparatus for a vehicle which is installed in a roof and is deployed to protect a rear seat passenger when a vehicle collision occurs. 
     2. Description of Related Art 
     Hitherto, development of airbag apparatuses for vehicles has been focused on protecting front seat passengers. The reason for this results from the supposition that when a vehicle collision occurs, the risk of injury to front seat passengers resulting from collision with the steering wheel or the instrument panel is relatively high, but rear seat passengers who are disposed at positions father from the collision spot than the front seat passengers are comparatively safe. 
     However, when the vehicle is involved in a frontal collision, a rear seat passenger that is not wearing a safety belt may injure his/her head attributable to collision with the head of a front seat passenger or the seat back of the front seat. Taking into account the fact that the percentage of rear seat passengers who wear safety belts is much lower than that of front seat passengers, development of airbag apparatuses for protecting rear seat passengers is more aggressively required. 
     Meanwhile, in consideration of the above facts, an airbag apparatus of a vehicle for protecting a rear seat passenger was proposed, as shown in  FIG. 1 . However, in this approach, the airbag apparatus is installed in a seat back  110  of a front seat  100 . Hence, a cushion  130  is inflated just in front of the face of a rear seat passenger  200 , thus giving a feeling of anxiety to the rear seat passenger. Furthermore, depending on the position of the front seat  100  or an angle at which the seat back  110  is reclined, the direction in which the cushion  130  is deployed varies. To avoid this problem, the forward or backward movement of the front seat  100  or the reclining function of the seat back  110  must be restricted. However, this is not preferable, because it greatly reduces convenience of the front seat  100 . In the drawing, the reference numeral  120  denotes a housing which contains the cushion  130  therein. 
     The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of the present invention are directed to provide an airbag apparatus for a vehicle which can solve several problems of the conventional airbag apparatus installed in a seat back of a front seat and more effectively protect a rear seat passenger when the vehicle is involved in a frontal collision. 
     In an aspect of the present invention the airbag apparatus for a vehicle, may include an inflator, a housing installed in a roof, and a cushion contained in the housing and configured to be deployed downwards by a gas discharged from the inflator to protect an occupant in the vehicle, wherein an upper surface of the cushion is supported by the roof when the cushion is in a deployed state, and a front surface of the cushion extends in a rear direction of the vehicle in an inclined shape to form a recess to prevent interference with a seatback of the front seat while the cushion is deployed downwards, wherein the housing is installed between a front seat and a rear seat, wherein the cushion is shaped of “           ” when the cushion is completely deployed, and wherein the cushion is configured to have locally-different gas pressures therein.
     A gas pressure in front upper portion of the cushion may be higher than a gas pressure in a rear lower portion of the cushion and the gas pressure in the rear lower portion of the cushion may be higher than a gas pressure in a rear upper portion thereof, wherein a gas passage through which a gas flows is formed in the cushion so that a gas supplied from the inflator in the front upper portion of the cushion flows along an inner surface of the recess around the rear lower portion of the cushion and then charged into the rear upper portion of the cushion. 
     The cushion may be partitioned into a plurality of chambers by diaphragms, at least one chamber being disposed in the front upper portion of the cushion, at least one chamber being disposed in the rear lower portion thereof to fluid-communicate with the chambers disposed in the front upper portion of the cushion, and at least one chamber being disposed in the rear upper portion thereof to fluid-communicate with the chambers disposed in the rear lower portion of the cushion, wherein each chamber includes a gas pressure control member so as to control a gas pressure in the respective chamber and wherein the gas pressure control member is at least a gas hole formed on the diaphragm to control flow amount of a gas between adjacent chambers. 
     At least a vent hole may be formed in the chambers so as to discharge a gas outside the cushion. 
     In another aspect of the present invention, the chambers may include a first chamber formed between front and rear ends of the upper surface of the cushion and an upper end of the front surface thereof, a second chamber extending along a lower portion of the front surface below the first chamber and along a rear surface of the cushion upwards, and a third chamber disposed between the first chamber and the second chamber in a shape wherein the first chamber and the second chamber substantially surround the third chamber, wherein the first chamber has a shape protruding forwards so that, in the deployed state of the cushion, the first chamber is supported by the roof to withstand force applied to the rear surface of the cushion by the occupant, and wherein, in the deployed state of the cushion, the first chamber is highest in gas pressure and gas pressure in the second chamber is higher than gas pressure in the third chamber. 
     The diaphragms may include a first diaphragm for partitioning the first chamber and the second chamber, with at least a through hole formed through the first diaphragm so that a gas is drawn from the first chamber into the second chamber through the through hole, a second diaphragm for partitioning the second chamber and the third chamber, and a third diaphragm for partitioning the third chamber and the first chamber, wherein the first diaphragm and the third diaphragm are monolithically integrated with each other and partition the first chamber both from the second chamber and from the third chamber. 
     A first vent hole may be formed in the second chamber to discharge a gas outside the second chamber therethrough. A second vent hole may be formed in the second diaphragm to discharge a gas in the second chamber into the third chamber wherein a tether is provided between the second diaphragm and the rear surface of the cushion to determine a deployed shape of the second chamber. 
     In further another aspect of the present invention, the airbag apparatus for a vehicle may include an inflator, a housing installed in a roof between a front seat and a rear seat, a cushion contained in the housing, the cushion being deployed downwards by gas discharged by the inflator to protect a rear seat passenger, and a gas passage configured such that the gas flows along an inner surface of the cushion and then around a rear surface of the cushion that faces the rear seat passenger, and the gas is charged into the cushion in a direction from a lower end to an upper end of the rear surface of the cushion, wherein a front surface of the cushion extends towards the rear surface thereof in an inclined shape and has a recess to prevent interference with a seat back of the front seat while the cushion is being deployed. 
     The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing a conventional airbag apparatus of a vehicle which is for protecting a rear seat passenger. 
         FIG. 2  is a schematic view showing an exemplary airbag apparatus for a vehicle, according to the present invention. 
         FIG. 3  is a view illustrating the external shape of the cushion shown in  FIG. 2 . 
         FIG. 4  is a view illustrating the internal construction of the cushion shown in  FIG. 2 . 
         FIG. 5  is another view illustrating the internal construction of the cushion shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
       FIG. 2  illustrates deployment of the airbag apparatus according to various embodiments of the present invention. As shown in  FIG. 2 , a housing  20  is installed in a roof  1  between the front and rear seats. A cushion  30  is inflated and deployed downwards from the housing  20  by gas supplied from an inflator  10 , thus protecting a rear seat passenger. 
     The inflator  10  is preferably installed in a space defined between a roof panel  2  and a head liner  3 . A dual stage inflator which discharges gas in two stages is used as the inflator  10 . In the first stage, the inflator  10  inflates the cushion  30  within 30 ms. In the second stage, the inflator  10  discharges gas again at the moment at which the rear seat passenger  200  collides with the cushion  30  (from this moment on, reduction in the pressure of the cushion  30  begins), so that the pressure of the cushion  30 , in particular, the pressure of a first chamber  41  (see,  FIG. 4 ) is maintained higher than a predetermined value such that a front end of an upper portion of the cushion  30  can be reliably supported by the head liner  3 . 
     The housing  20  is also installed in the space between the roof panel  2  and the head liner  3 . The lower surface of the housing  20  may be covered with the head liner  3  or, alternatively, it may be exposed outside the head liner  3 , that is, to the passenger compartment. In the former case, a tear line for ensuring deployment of the cushion  30  is formed. In the latter case, an airbag door is provided in the lower surface of the housing  20 . Furthermore, the housing  20  must be firmly fixed to the roof  1 , because the cushion  30  needs to be reliably suspended by the housing  20  when the cushion  30  is completely deployed. 
     Referring to  FIG. 3  showing the external appearance of the cushion  30  along with  FIG. 2 , the cushion  30  includes upper, rear and front surfaces  31 ,  32  and  33  which define therein a closed space  40  for maintaining gas pressure. Here, for the sake of description, the surfaces are distinguished from each other merely depending on the position when the cushion  30  is deployed, but they do not necessarily embody separate fabric pieces which are connected by sewing to form the cushion  30 . The closed space  40  includes a plurality of chambers  41 ,  42  and  43  (see,  FIG. 4 ) which are formed by partitioning the closed space  40  using diaphragms  50 , and gas passages  70  through which the chambers  41 ,  42  and  43  communicate with each other (see,  FIGS. 2 ). 
     The upper surface  31  is fastened to the housing  20 . When the cushion is deployed, a portion of the upper surface  31 , other than the portion thereof which is fastened to the housing  20 , is extracted to outside the head liner  3 . Particularly, when the cushion is deployed, a front portion of the upper surface  31  unfolds forwards and is supported by the head liner  3 . Here, it is preferable that the front portion of the upper surface  31  come into surface contact with the head liner  3 . Various well-known techniques can be used in the structure for fastening the upper surface  31  to the housing  20 . 
     The rear surface  32  is the portion of the cushion which comes into direct contact with the face or chest of the rear seat passenger  200 . The rear surface  32  extends downwards from the rear end of the upper surface  31  in an approximately vertical direction. As such, the reason for the rear surface  32  extending in an approximately vertical direction just ahead of the rear seat passenger  200  is that when the vehicle is involved in a frontal collision, a distance that the rear seat passenger  200  is moved forwards by inertia and an impact applied to the rear seat passenger  200  can be reduced by the rear surface  32 . Particularly, in the case of the rear seat passenger  200  who is not wearing the safety belt, the above structure of the rear surface  32  can prevent the rear seat passenger  200  from springing forwards due to impact inertia through the space between a front seat  100  and the head liner  3 . More preferably, the lower end of the rear surface  32  extends to the space between the thigh and abdomen of the rear seat passenger  200 . 
     The front surface  33  extends from the front end of the upper surface  31  to the lower end of the rear surface  32  in a curved shape. A recess  34  is formed in the front surface  33  to avoid interference with the front seat  100  when the cushion is deployed. Particularly, the recess  34  has a shape corresponding to a moving trajectory along which a headrest  140  moves when a seat back  110  has been tilted forwards and backwards after the seat back  110  has been moved to the rearmost position and the headrest  140  has been lifted to the uppermost position. The recess  34  having the above shape ensures smooth deployment of the cushion  30  and prevents the cushion  30  which is inflating from striking with great force the face of a front seat passenger  300  who is reclined on the front seat  100  after having tilted the seat back  110  thereof backwards. 
     The gas passages  70  are formed such that gas discharged from the inflator  10  is charged into the cushion  30  by first flowing towards the front end of the upper surface  31 , then flowing downwards along the inner surface of the front surface  34 , and finally flowing in the direction from the lower end of the rear surface  32  to the upper end thereof. Because of the above structure of the gas passages  70 , first, gas can be first supplied towards the front end of the upper surface  31  such that a force with which the head liner  3  supports the cushion  30  is ensured from the initial stage of the deployment of the cushion  30 ; secondly, the cushion  30  can be prevented from rapidly inflating in the direction of the rear seat passenger  200 , thus preventing the rear seat passenger  200  from being injured by the deployment of the cushion  30 . 
     Meanwhile, in  FIG. 2 , a portion designated by the reference numeral  43  is empty space (a third chamber which will be explained later). This empty space effectively absorbs impact applied to the rear seat passenger  200  (in particular, the face of the passenger  200 ) which collides with the rear surface  32 . In  FIG. 3 , a portion designated by the reference numeral  73  is a first vent hole which functions to absorb impact applied to the rear seat passenger  200  by reducing gas pressure in the cushion  30  at the moment when the rear seat passenger  200  collides with the cushion  30 . The first vent hole  73  is formed in the second chamber ( 42 : see  FIG. 4 ) which will be explained in detail later. The first vent hole  73  originally is in a closed state and is opened only when the pressure in the second chamber  42  exceeds a predetermined pressure. 
     The internal construction of the cushion  30  will be described with reference to  FIGS. 4 and 5 . As shown in  FIGS. 4 and 5 , the closed space  40  in the cushion  30  is partitioned into the first, second and third chambers  41 ,  42  and  43  by diaphragms  51 ,  52  and  53 . 
     The first chamber  41  is disposed between the front and rear ends of the upper surface  31  and the upper end of the front surface  33  and has a shape which protrudes forwards. The first chamber  41  is partitioned off from the second chamber  42  by the first diaphragm  51  and is partitioned off from the third chamber  43  by the third diaphragm  53 . The cushion  30  that is completely deployed is supported on the head liner  3  by the first chamber  41 . When a vehicle collision occurs, shear force (between the upper surface and the housing) and approximately clockwise force (as shown in  FIG. 4 ) are applied to the cushion  30  by the rear seat passenger  200  that collides with the rear surface  32 . At this time, the cushion  30  withstands the clockwise force thanks to the first chamber  41  which is supported by the head liner  3 . 
     The first chamber  41  needs to maintain a relatively high gas pressure to ensure that the first chamber  41  is supported by the head liner  3  with sufficient force. Gas discharged from the inflator  10  is first supplied into the first chamber  41  through a gas hole  71 . At least a gas pressure control member such as a through hole  72  may be formed through the first diaphragm  51  to appropriately control the flow of gas from the first chamber  41  into the second chamber  42 . According to various embodiments of the present invention, the first diaphragm  51  is integrated with the third diaphragm  53 ; in other words, they are made of a single piece of fabric. Meanwhile, depending on the case, the inflator  10  may be installed in the cushion  30 . 
     The second chamber  42  extends along the front surface  33  and the rear surface  32  below the first chamber  41 . The second chamber  42  is partitioned off from the third chamber  43  by the second diaphragm  52 . The second diaphragm  52  is fastened at a first end thereof to a boundary between the first and third diaphragms  51  and  53  and fastened at a second end thereof to the upper end of the rear surface  32  or the rear end of the upper surface  31 . A tether  60  which connects the second diaphragm  52  to the rear surface  32  is connected to a medial portion of the second diaphragm  52 . The tether  60  functions to determine the deployed shape of the second chamber  42  and the deployed shape of the third chamber  43 . Based on the tether  60 , the second chamber  42  is divided into a first chamber section  42   a  which is disposed at the lower position, and a second chamber section  42   b  which is disposed at the upper position. Gas which is drawn into the first chamber section  42   a  of the second chamber  42  through the through hole  72  flows upwards in the second chamber section  42   b  of the second chamber  42 . 
     Furthermore, in various embodiments of the present invention, the first vent hole  73  and/or another gas pressure control member such as a second vent hole  74  for controlling pressure in the second chamber  42  may be formed in the second chamber  42 . Gas is discharged to outside of the second chamber  42  through the first vent hole  73 , and gas flows through the second vent hole  74  from the second chamber  42  into the third chamber  43  that is empty space. 
     The third chamber  43  is disposed between the first chamber  41  and the second chamber  42  in a shape in which the first chamber  41  and the second chamber  42  surround the third chamber  3 . In the exemplary embodiment, although the second end of the second diaphragm  52  has been illustrated as being connected to the rear surface  32  or the upper surface  31 , it may be connected to the third diaphragm  53 . 
     Comparing pressures in the first, second and third chambers  41 ,  42  and  43  to each other, the pressure in the first chamber  41  is maintained at the highest level. After the first chamber  41 , the second chamber  42  is next highest. The pressure in the third chamber  43  is the lowest. In various embodiments of the present invention having the above-mentioned construction, the cushion  30  can be reliably supported by the roof  1  and impart a fluffy feel to the rear seat passenger  200  who collides with the rear surface  32 . Meanwhile, in  FIG. 5 , a portion designated by the reference numeral  20  indicates a position at which the housing containing the cushion  30  is disposed. 
     As described above, an airbag apparatus for a vehicle according to various embodiments of the present invention may be installed in a roof of the vehicle and thus does not impose restrictions on the design of a front seat. 
     Furthermore, deployment of a cushion is prevented from being impeded by the front seat, so that the function of protecting a rear seat passenger can be reliably ensured. 
     As well, when the cushion is deployed it is prevented from striking not only the rear seat passenger but also the face of a front seat passenger. 
     In addition, the airbag apparatus of the present invention can effectively absorb impact force applied to the rear seat passenger when the vehicle is involved in a frontal collision. 
     For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “downwards”, “lower”, “front”, and “rear” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures. 
     The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.