Occupant restraint device

An air bag of an inflatable curtain device includes a first cell group and a second cell group whose internal spaces are independent from each other. A high-pressure gas discharged from opposite ends of a common inflater disposed between both of the first and second cell groups and is supplied to a high-pressure gas supply port in the first cell group and a high-pressure gas supply port in the second cell group. The first and second cell groups can be expanded simultaneously by the common inflater, whereby the entire air bag can be deployed promptly, but also even when one of the first and second cell groups and is damaged, the deployment of the other cell group can be achieved without hindrance.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an occupant restraint device which
 includes a deployable air bag disposed in a folded-up state along an upper
 edge of a door opening in a vehicle body. The air bag is expanded by a
 high-pressure gas generated by an inflater in a curtain-shape along an
 inner surface of a side of a vehicle compartment upon collision with a
 vehicle.
 2. Description of the Related Art
 Such an occupant restraint device is known, for example, from Japanese
 Patent Application Laid-open No.10-278723.
 The occupant restraint device described in the above Publication includes
 an inflater disposed at a lower portion of a front pillar and an attached
 air bag. A high-pressure gas generated by the inflater is supplied to a
 front end of the air bag, disposed along an upper edge of a door opening
 in a vehicle body, to deploy the air bag in a curtain-shape into a vehicle
 compartment.
 In general, the air bag of the occupant restraint device is comprised of a
 congregation of a large number of expandable cells and folded into an
 longitudinally elongated shape to extend from a front pillar past a center
 pillar to a rear pillar of the vehicle. When the high-pressure gas is
 supplied from the inflater to one end of such longitudinally elongated air
 bag, a time lag exists between the expansion of the first end of the air
 bag and the expansion of the opposite rear end. For this reason, the
 expansion of the rear end is retarded, resulting in a possibility of
 underperformance of the occupant restraint device. If the volume of the
 gas propelled by the inflater is increased in order to solve such problem,
 it is a possibility that the internal pressure in the cell or cells
 approximate the inflater is increased excessively, and as a result, such
 cell can be damaged. In addition, when a portion of the air bag is
 damaged, the high-pressure gas can still be supplied to a cell group
 extending from the inflater to short of the damaged portion to expand the
 cells of such group. However there is a difficulty in supplying
 high-pressure gas to a cell group located beyond of the damaged portion,
 thus incompletely expanding the cells of such cell group, resulting in
 reduced performance.
 The occupant restraint device described in the above Patent is designed to
 commonly fasten the folded air bag and an air bag holder to the vehicle
 body by a common bolt. The air bag is disposed within an air bag case made
 of a synthetic resin. The bolt is passed through a mounting portion,
 extending in a flange-shape, of the air bag case, the base end of the air
 bag and the air bag holder to fasten them to the vehicle body.
 In the known occupant restraint device, in order to reliably support the
 folded air bag on the air bag holder, it is necessary to accommodate the
 air bag within an air bag cover formed of a synthetic resin and having a
 high rigidity. When a simple air bag cover such as a fabric is used, it is
 difficult to correctly position the air bag in the air bag holder. An air
 bag cover having a high rigidity is requisite. However this is
 disadvantageous with respect to the weight and the cost.
 The front end of the air bag of the occupant restraint device described in
 the above Patent is disposed in a folded state in a space sandwiched
 between the front pillar and the front pillar garnish. The air bag, when
 expanded upon collision of the vehicle, enters a passage defined between
 the front pillar and a large number of rib-shaped energy absorbing members
 provided on an inner surface of the front pillar garnish. The expanding
 air bag forces the front pillar garnish open and the air bag fully deploys
 through the resulting opening into the vehicle compartment.
 In the above known occupant restraint device, however, a pointed or sharp
 corner or edge exists on the surface of each of the energy absorbing
 members facing the passage. For this reason, when the air bag is expanded
 to force the front pillar garnish open, there is a possibility that the
 air bag will be caught on the sharp comers of the energy absorbing
 members, whereby the smooth and even deployment of the air bag will be
 impeded damaging the air bag.
 In addition, the occupant restraint device described in the above Patent
 includes the inflater disposed at the lower portion of the front pillar,
 so that the high-pressure gas generated by the inflater is supplied to the
 front end of the air bag disposed along the upper edge of the door opening
 in the vehicle body, to deploy the air bag in the curtain-shape into the
 vehicle compartment.
 The above description for Japanese Patent Application Laid-Open No.
 10-278723 applies generally to the known prior art.
 In order to solve such problem, it is conceived that a plurality of cell
 groups, with their internal spaces independent from one another, are
 defined in the air bag, and the high-pressure gas is supplied to a
 high-pressure gas supply port provided in each of the cell groups.
 However, if additional inflaters are mounted in correspondence to the
 separate cell groups, the number of the inflaters is increased, increasing
 the cost and the weight of the device.
 The air bag of the inflatable curtain device described in the above Patent
 Application Laid-open No. 10-278723 includes the plurality of cells
 disposed in the longitudinal direction of the vehicle body, wherein the
 diameter of the cells in front and rear of the center pillar is larger
 than those of the other cells. Therefore, when a head of an occupant
 sitting on a front seat urges against the air bag toward the vehicle body,
 the larger-diameter cells are caught on a rear surface of the center
 pillar, whereby the forward movement of such cells is hindered. Thus, the
 tension of that portion of the air bag located ahead of the center pillar
 is maintained, leading to an enhanced performance of holding back the
 occupant sitting on the front seat.
 The occupant restraint performance required for an air bag of an inflatable
 curtain is the highest at a location approximate to a pillar having a high
 rigidity and relatively low at a location approximate to a door glass. For
 this reason, it is necessary to promptly expand those cells of the air bag
 which are located in the vicinity of the pillar. In the above known
 occupant restraint device, however, the diameter (and volume) of the cells
 located immediately in the rear of the pillar is larger, and for this
 reason, there is a possibility that the expansion of the larger-diameter
 cells takes more time than expansion of the other cells, resulting in a
 reduced occupant restraint performance.
 Such occupant holding-back device is known, for example, from Japanese
 Patent Application Laid-open No.9-254734.
 The occupant restraint device described in the above Patent is designed, so
 that an air bag is disposed in a vertically zigzag folded state within a
 cover and is expanded by a high-pressure gas supplied from an inflater to
 force a cut portion of a lower surface of the cover open to become
 deployed downwards into a vehicle compartment upon collision with another
 vehicle.
 FIGS. 26A to 26D show the course of deployment of the air bag of the above
 known occupant restraint device, wherein an upper base end of the air bag
 shown in section indicated by an open circle, and a lower tip end of the
 air bag is indicated by a black dot.
 The nonexpanded air bag is folded in the vertically zigzag manner (see FIG.
 26A). When the high-pressure gas is supplied from the inflater to the base
 end of the air bag, due to collision of the vehicle, the expansion of the
 air bag is started at its base end (see FIG. 26B). In the course of
 spreading of the expanded area of the air bag from the base end toward the
 tip end thereof, the tip end may be caught on the inner surface of the
 side of the vehicle compartment (on an inner surface of the pillar or a
 door) in some cases (see FIG. 26C). When the high-pressure gas is further
 supplied in this state to start the expansion of the air bag at its tip
 end, the rigidity of the air bag is increased by an increase in internal
 pressure, because the air bag is intended to extend straight. As a result,
 the tip end of the air bag may be strongly urged against the inner surface
 of the side of the vehicle compartment and the air bag maybe bent into a
 at an intermediate portion thereof and fail to be deployed smoothly and
 evenly downwards (see FIG. 26D).
 SUMMARY OF THE INVENTION
 Accordingly, it is a first object of the present invention to ensure that
 the air bag of the occupant restraint device is deployed promptly and
 reliably.
 It is a second object of the present invention to ensure that the air bag
 can be supported reliably on the air bag holder with a reduced number of
 parts using a simple air bag cover made of a material such as a fabric, or
 without use of an air bag cover.
 It is a third object of the present invention to ensure that the air bag of
 the occupant restraint device can be deployed smoothly from a space
 sandwiched between the front pillar and the front pillar garnish.
 It is a fourth object of the present invention to ensure that the
 high-pressure gas can be supplied reliably from a single inflater to a
 plurality of high-pressure gas supply ports defined in the air bag of the
 occupant restraint device.
 It is a fifth object of the present invention to ensure that the expansion
 speed of the air bag of the inflatable curtain device can be controlled to
 any level depending on the magnitude of the occupant restraint or holding
 back performance required for various portions of the air bag.
 It is a sixth object of the present invention to prevent the tip end of the
 air bag of the occupant restraint device from being caught on the inner
 surface of the side of the vehicle compartment, thereby failing to deploy
 smoothly in the course of deployment of the air bag.
 To achieve the above object, according to a first aspect and feature of the
 present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein the air bag comprises a first cell group and a second
 cell group which are disposed separately in a longitudinal direction of
 the vehicle body with their internal spaces independent from each other,
 the first and second cell groups being provided with a first high-pressure
 gas supply port and a second high-pressure gas supply port, respectively,
 to which the high-pressure gas is supplied from the common inflater.
 With the above arrangement, the internal space in the air bag is divided
 into the first and second cell groups, and the high-pressure from the
 common inflater is supplied to the first and second high-pressure gas
 supply ports provided in the first and second cell groups, respectively.
 Therefore, the first and second cell groups can be expanded simultaneously
 by the inflater, whereby the entire air bag can be deployed promptly, but
 also even when one of the first and second cell groups is damaged, the
 deployment of the other cell group can be achieved without hindrance.
 To achieve the first object, according to a second aspect and feature of
 the present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein the air bag comprises a single group of cells with
 their internal spaces communicating with one another, the cell group being
 provided at its front end with a first high-pressure gas supply port to
 which the high-pressure gas is supplied from a first inflater, and at its
 rear end with a second high-pressure gas supply port to which the
 high-pressure gas is supplied from a second inflater.
 With the above arrangement, the high-pressure gas is supplied from the
 first inflater to the first high-pressure gas supply port at the front end
 of the single cell group with the internal cell spaces communicating with
 one another, and the high-pressure is supplied from the second inflater to
 the second high-pressure gas supply port at the rear end of the cell
 group. Therefore, the entire air bag can be deployed promptly and
 uniformly, but also even when a portion of the cell group is damaged, the
 high-pressure gas can be supplied from the first or second inflater to the
 cells located in front and rear of the damaged portion to achieve the
 deployment of the air bag without hindrance.
 To achieve the second object, according to a third aspect and feature of
 the present invention, there is provided an occupant restraint device
 comprising an air bag which is supported in a folded-up state on an air
 bag holder fixed along an upper edge of a door opening in a vehicle body,
 so that the air bag is expanded by a high-pressure gas generated by an
 inflater upon collision of a vehicle and deployed in a curtain-shape along
 an inner surface of a side of a vehicle compartment, wherein the air bag
 holder comprises a body portion and support arms integrally formed of a
 synthetic resin and openably and closeably connected to the body portion,
 the support arms, the air bag and the body portion being commonly fastened
 to the upper edge of the door opening in the vehicle body by common bolts
 in a state in which the folded-up air bag has been supported on the
 support arms along the body portion.
 With the above arrangement, to support the air bag in the folded-up state
 on the air bag holder fixed along the upper edge of the door opening in
 the vehicle body, the air bag is supported on the support arms along the
 body portion of the air bag holder, and the support arms, the air bag and
 the body portion are commonly fastened to the vehicle body by the common
 bolts. Thus, the air bag holder and the air bag can be supported reliably
 on the vehicle body by a minimum number of the bolts without need for an
 air bag cover having a high rigidity, but also the air bag can be
 positioned correctly on the body portion of the air bag holder. Moreover,
 since the body portion and the support arms of the air bag holder are
 integrally formed into a unitary structure composed of synthetic resin,
 the number of parts and the number of assembling steps can be reduced, as
 compared with a case where support arms separate from the body portion are
 used.
 To achieve the third object, according to a fourth aspect and feature of
 the present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein a front end of the air bag is accommodated in a space
 sandwiched between a front pillar and a front pillar garnish, the front
 pillar garnish having energy absorbing members disposed on its inner
 surface, so that they are located in the rear of the air bag, a passage
 being defined between the front pillar and the energy absorbing members
 for assisting in the deployment of the air bag, the surface of each of the
 energy absorbing members facing the passage, i.e., clearance, being formed
 into a smooth curved surface having no sharpness.
 With the above arrangement, the front end of the air bag expanded upon
 collision of the vehicle enters the passage defined between the energy
 absorbing members provided on the inner surface of the front pillar
 garnish and the front pillar, whereby the air bag forces the front pillar
 garnish open by a produced pressure to become deployed through the
 resulting opening into the vehicle compartment. Since the surface of each
 of the energy absorbing members facing the passage is formed into a smooth
 curved surface having no sharpness, the air bag forcing the front pillar
 garnish open to become deployed is prevented from being caught on the
 energy absorbing members or from being damaged, and hence, the air bag can
 be deployed smoothly.
 To achieve the fourth object, according to a fifth aspect and feature of
 the present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein the occupant restraint device includes an inflater
 accommodated in an inflater case having a plurality of high-pressure gas
 ejecting ports which are connected to a plurality of high-pressure gas
 ejecting ports provided in the air bag, respectively.
 With the above arrangement, the plurality of high-pressure gas ejecting
 ports are provided in the inflater case having the inflater accommodated
 therein, and are connected to the plurality of high-pressure gas ejecting
 ports provided in the air bag, respectively. Therefore, the high-pressure
 gas discharged from the single inflater can be diverted by a simple
 structure and supplied reliably into the plurality of high-pressure gas
 supply ports in the air bag.
 To achieve the fifth object, according to a sixth aspect and feature of the
 present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein the air bag is comprised of a plurality of cells
 expandable by a high-pressure gas, a high-pressure gas supply passage
 provided along base ends of the cells to guide the high-pressure gas from
 an inflater, and through-bores for supplying the high-pressure gas from
 the high-pressure gas supply passage to the cells, the opening areas of
 the through-bores being varied depending on the positions of the cells.
 With the above arrangement, the air bag is comprised of the plurality of
 expandable cells, the high-pressure gas supply passage for guiding the
 high-pressure gas from the inflater, and the through-bores for supplying
 the high-pressure gas from the high-pressure gas supply passage to the
 cells, and the opening areas of the through-bores are varied depending on
 the positions of the cells. Therefore, the timings of expansion of the
 cells, to which the high-pressure gas is supplied from the inflater via
 the high-pressure gas supply passage and the through-bores, can be
 controlled to any level depending on the opening areas of the
 through-bores, thereby enhancing the occupant holding-back performance of
 the air bag.
 To achieve the sixth object, according to a seventh aspect and feature of
 the present invention, there is provided an occupant restraint device
 comprising an air bag disposed in a folded-up state along an upper edge of
 a door opening in a vehicle body, so that the air bag is expanded by a
 high-pressure gas generated by an inflater upon collision of a vehicle and
 deployed in a curtain-shape along an inner surface of a side of a vehicle
 compartment, wherein the air bag is folded double with its tip end
 superposed on its surface on the side of the vehicle compartment and is
 then folded up in a vertically zigzag manner.
 With the above arrangement, the air bag is first folded double with its tip
 end superposed on its surface on the side of the vehicle compartment and
 is then folded up in a vertically zigzag manner. Therefore, when the air
 bag is deployed, the zigzag folding-up of the air bag is released, and
 further, the double-folding of the air bag is released. In this course,
 the tip end of the air bag is passed through a position spaced apart from
 the inner surface of the side of the vehicle compartment (namely, a
 position closer to a central portion of the vehicle compartment). Thus, it
 is possible to prevent the tip end from being caught on the inner surface
 of the side of the vehicle compartment, thereby enabling the smooth and
 reliable deployment of the air bag.
 To achieve the above sixth object, according to an eighth aspect and
 feature of the present invention, there is provided an occupant restraint
 device comprising an air bag disposed in a folded-up state along an upper
 edge of a door opening in a vehicle body, so that the air bag is expanded
 by a high-pressure gas generated by an inflater upon collision of a
 vehicle and deployed in a curtain-shape along an inner surface of a side
 of a vehicle compartment, wherein the air bag is folded up in a vertically
 zigzag manner and then folded double in a widthwise direction, so that its
 tip end is covered with the air bag itself.
 With the above arrangement, the air bag is first folded up in a vertically
 zigzag manner and then folded double in the widthwise direction, so that
 its tip end is covered with the air bag itself. Therefore, in the course
 of deployment of the air bag, the tip end of the air bag cannot be exposed
 before releasing of the folded the air bag. Thus, it is possible to
 prevent the tip end from being caught on the inner surface of the side of
 the vehicle compartment, thereby enabling the smooth and reliable
 deployment of the air bag.
 The above and other objects, features and advantages of the invention will
 become apparent from the following description of the preferred
 embodiments taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The present invention will now be described by way of embodiments with
 reference to the accompanying drawings.
 First, a first embodiment of the present invention will be described with
 reference to FIGS. 1 to 13.
 As shown in FIG. 1, a door opening 14 for mounting of a front door 13
 between a front pillar 11 and a center pillar 12 is defined in a side of a
 vehicle body of a vehicle, and a door opening 17 for mounting a rear door
 16 between the center pillar 12 and a rear pillar 15 is also defined in
 the side of the vehicle body. A roof side rail 18 (see FIG. 4) extends in
 a longitudinal direction of the vehicle body to connect an upper end of
 the front pillar 11 and an upper end of the rear pillar 15. The roof side
 rail 18 partitions upper edges of the door openings 14 and 17 for the
 front door 13 and the rear door 16 from each other. An occupant restraint
 device C is mounted along the roof side rail 18. The occupant restraint
 devices C having the substantially same structures are mounted on left and
 right opposite sides of the vehicle body, respectively. The occupant
 restraint device which is mounted on the right side of the vehicle body,
 representative of both restraint devices, will be described below.
 As shown in FIG. 2, when an acceleration of a predetermined value or more
 is detected upon a side collision of the vehicle or during rolling-over of
 the vehicle, an air bag 21 of the occupant restraint device C is deployed
 downwards into a curtain-shape from the upper edges of the door openings
 14 and 17 to break in between occupants sitting on a front seat 19 and a
 rear seat 20 and an internal side face of the vehicle body, i.e., the
 front pillar 11, the center pillar 12, the rear pillar 15, a door glass
 13.sub.1 of the front door 13 and a door glass 16, of the rear door 16.
 As shown in FIG. 3, the air bag 21 extending in the longitudinal direction
 of the vehicle body is made by doubly superposing first and second ground
 fabrics 25 and 26 having substantially the same shapes to sew them along
 line 27. The first ground fabric 25, slightly larger than the second
 ground fabric 26, has a front end which slightly protrudes as an
 non-expandable portion 21.sub.1 from a front edge of the second ground
 fabric 26. The shapes of the first and second ground fabrics 25 and 26 can
 be selected as desired, and may be identical to each other.
 Nine cells 29a, 29b, 29c, 29d, 29e, 29f, 29g, 29h and 29i, a single first
 high-pressure as supply passage 30 and a single first high-pressure gas
 supply port 31 are provided in a front portion of the air bag 21 by sewing
 along line 28. The first high-pressure gas supply port 31 opens rearwards
 of the vehicle body at a base end (an upper end) of the air bag 21, and
 the first high-pressure gas supply passage 30 extends from such opening in
 a forward direction of the vehicle body along the base end of the air bag
 21. The first high-pressure gas supply passage 30 communicates with upper
 ends of the nine cells 29a to 29i through nine communication bores 32a,
 32b, 32c, 32d, 32e, 32f, 32g, 32h and 32i, respectively, and lower ends of
 the cells 29a to 28i extending downwards from the through-bores 32a to 32i
 are closed.
 Four cells 29j, 29k, 29l and 29m, a single second high-pressure gas supply
 passage 34 and a single second high-pressure gas supply port 35 are
 provided in a rear portion of the air bag 21 by sewing along line 33. The
 second high-pressure gas supply port 35 opens forwards of the vehicle body
 at the base end (upper end) of the air bag 21, and the second
 high-pressure gas supply passage 34 extends rearwards of the vehicle body
 from such opening along the base end of the air bag 21. The second
 high-pressure gas supply passage 34 communicates with upper ends of the
 four cells 29j to 29m through four through-bores 32j, 32k, 32l and 32m,
 respectively, and lower ends of the cells 29a to 28i extending downwards
 from the through-bores 32j to 32m are closed.
 The front nine cells 29a to 29i constitute a first group of cells 36
 communicating with one another, and the rear four cells 29j to 29m
 constitute a second group of cells 37 communicating with one another. As
 can be seen from FIG.8, the cells 29a to 29m are expanded into circular
 cross-sectional shape under the supplying of a high-pressure gas, thereby
 exhibiting a buffering effect to protect the occupant from the secondary
 collision. The first high-pressure gas supply port 31 for supplying the
 high-pressure gas to the first cell group 36 and the second high-pressure
 gas supply port 35 for supplying the high-pressure gas to the second cell
 group 37 are opposed to each other at a distance spaced apart from each
 other above that non-expandable portion 21.sub.2 of the air bag 21 in
 which no cells are formed.
 In this way, the first and second high-pressure gas supplying passages 30
 and 34 and the through-bores 32a to 32m for supplying the high-pressure
 gas to the cells 29a to 29m of the air bag 21 are defined by sewing of the
 first and second ground fabrics 25 and 26 for the air bag 21. Therefore,
 special members for defining the first and second high-pressure gas
 supplying passages 30 and 34 and the through-bores 32a to 32m are not
 required, which can contribute to reductions in number of parts and in
 weight of the occupant restraint device. In place of coupling the first
 and second ground fabrics 25 and 26 to each other by sewing along lines
 27, 28 and 33, the first and second ground fabrics 25 and 26 may be
 coupled to each other by bonding or welding.
 Six mounting bores 21a, 21b, 21c, 21d, 21e and 21f are defined along the
 base end of the air bag 21. The foremost mounting bore 21a is defined in
 the non-expandable portion 21.sub.1 extending in front of the first cell
 group 36. The subsequent three mounting bores 21b, 21c and 21d are defined
 above the first cell group 36, and the next one mounting bore 21e is
 defined above the non-expandable portion 21.sub.2. The rearmost mounting
 bore 21f is defined above the second cell group 37.
 Upon the side collision of the vehicle, the expanded cells 29a to 29i in
 the front first cell group 36 are deployed in an area from the upper
 portion of the front pillar 11 to the rear portion of the center pillar 12
 to hold back the occupant sitting on the front seat 19. The expanded cells
 29j to 29m in the rear second cell group 37 are deployed in an area from a
 central portion of the rear door 16 to a central portion of the rear
 pillar 15 to hold back the occupant sitting on the rear seat 20. At this
 time, the non-expandable portion 21.sub.2 of the air bag 21 is located at
 that front portion of the rear door 16 in which there is less possibility
 of an interference provided by the occupant sitting on the rear seat 20.
 Among the through-bores 32a to 32j in the nine cells 29a to 29i in the
 first cell group 36, the through bores 32f to 32i in the four cells 29f to
 29i located in the vicinity of the center pillar 12 have passage
 sectional-areas set larger than those of the through-bores 32a to 32e in
 the other five cells 29a to 29e. Among the through-bores 37j to 37m in the
 four cells 29j to 29m in the second cell group 37, the through bores 37l
 and 37m in the two cells 29l and 29m located in the vicinity of the rear
 pillar 15 have passage sectional-areas larger than those of the
 through-bores 37j and 37k in the other two cells 29j and 29k.
 As shown in FIGS. 4, 5 and 7, an inflater 41 adapted to expand the air bag
 21 by burning of a propellant is a generally cylindrical member, and has a
 high-pressure gas ejecting portion 41.sub.1 formed in the vicinity of one
 end thereof. The inflater 41 is supported in an inflater case 42, whose
 opposite ends open, through a plurality of supporting projections 42.sub.1
 protruding on an inner surface of the inflater case 42. Funnel-shaped
 diffusers 43 and 44 constituting a portion of the inflater case 42 are
 fixed to the opposite ends of the inflater 41, and a high-pressure gas
 ejecting port 59 defined in a tip end of the diffuser 43 located in a
 front position has an opening area set larger than that of a high-pressure
 gas ejecting port 59 defined in a tip end of the diffuser 44 located in a
 rear position.
 The front end of the inflater case 42, at which the front diffuser 43 is
 mounted, is fitted into the first high-pressure gas supply port 31 in the
 first cell group 36 of the air bag 21 and fixed thereto by a band 45. The
 rear end of the inflater case 42, at which the rear diffuser 44 is
 mounted, is fitted into the second high-pressure gas supply port 35 in the
 second cell group 37 of the air bag 21 and fixed thereto by a band 46.
 Therefore, the inflater 41 and the inflater case 42 having the inflater 41
 accommodated therein are disposed above the non-expandable portion
 21.sub.2 of the air bag 21 at such locations that they are sandwiched
 between the first and second high-pressure gas supply ports 31 and 35 in
 the first and second cell groups 36 and 37.
 In this way, the high-pressure gas is supplied from the common inflater 41
 to the first and second cell groups 36 and 37 and hence, the number of
 parts, the number of assembling steps, the weight and the cost can be
 reduced, as compared with a case where two inflaters are mounted in
 correspondence to the first and second cell groups 36 and 37. Moreover,
 since the inflater case 42 is disposed at such location that it is
 sandwiched between the first and second cell groups 36 and 37 of the air
 bag 21, it is possible to reduce the possibility that the occupant's body
 interferes with the inflater 41.
 The roof side rail 18 is formed into a closed sectional shape by welding an
 outer member 47, an inner member 48 and a center member 49 to one another,
 and a roof 50 connected to the roof side rail 18 is formed by welding an
 outer member 51 and an inner member 52 to each other. A weather strip 53
 is provided at a lower end of the roof side rail 18 to be able to abut
 against the rear door 16. A roof garnish 54 made of a synthetic resin is
 disposed to extend along the lower surface of the roof 50, and locked at
 its end edge to an end edge of a weather strip 53 which protrudes from the
 lower end of the roof side rail 18 toward a vehicle compartment. A lower
 surface of the roof garnish 54 opposed to the vehicle compartment is
 coated with a skin material 55 which is turned at the end edge of the roof
 garnish 54 to extend from the lower surface onto the upper surface. Thus,
 it is possible to prevent the end edge of the roof garnish 54 made of the
 synthetic resin from being broken and scattered upon application of a
 shock to the end edge of the roof garnish 54.
 In place of carrying out the treatment for extending the end edge of the
 skin material 55 onto the upper surface of the roof garnish 54, an
 anti-scattering sheet may be stretched in the vicinity of the end edge of
 the roof garnish 54, or an anti-scattering coating is provided on the end
 edge of the roof garnish 54 and then, only the lower surface of the roof
 garnish 54 may be covered with the skin material 55. Even in such case,
 similar function and effect can be achieved.
 A mounting bracket 56 is fitted over the central portion of the inflater
 case 42 having the inflater 41 accommodated therein, and is fastened to an
 upper portion of the inner member 48 of the roof side rail 18 by two bolts
 57, 57 passed through a pair of flanges 56.sub.1, 56.sub.1 of the mounting
 bracket 56. At this time, both of the mounting bore 21e located in the
 upper portion of the non-expandable portion 21.sub.2 of the air bag 21 and
 an air bag holder 61 which will be described hereinafter are fastened
 commonly to the inner member 48 of the roof side rail 18 by the lower bolt
 57.
 As can be seen from FIG. 9, the air bag 21 in a folded-up state is disposed
 within an air bag cover 58 formed of a non-woven fabric. The air bag cover
 58 is made by rolling a rectangular piece of fabric into a cylindrical
 shape and sewing the cylindrical piece of fabric along its lower edge.
 Easily-breakable slits 58.sub.1 are defined in a perforated manner in that
 side face of the air bag cover 58 which is opposed to the roof side rail
 18. The mounting bores 21a, 21b, 21c, 21d, 21e and 21f protruding from the
 upper end of the air bag 21 and the first and second high-pressure gas
 supply ports 31 and 35 protrude upwards through openings 58.sub.2 defined
 in the upper surface of the air bag cover 58.
 As can be seen from FIGS. 5 and 9, an air bag holder 61 made of a synthetic
 resin is mounted along the lower portion of the inner member 48 of the
 roof side rail 18, and serves as base, when the folded-up air bag 21 is
 supported on the roof side rail 18. The air bag holder 61 is divided into
 a plurality of sections in a direction of the length of the folded-up air
 bag 21, e.g., into two sections: a section corresponding to the first cell
 group 36 in the air bag 21 and a section corresponding to the second cell
 group 37 in the air bag 21 in the embodiment.
 The air bag holder 61 is a hollow member having a body portion 61.sub.1
 formed into an E-shape in cross section, and has openable and closeable
 support arms 61.sub.3 integrally formed, the body portion 61, and support
 arms 61.sub.3 forming a unitary structure, in its portions corresponding
 to the mounting bores 21b, 21c, 21d and 21f of the air bag 21 with thin
 hinge portions 61.sub.2 formed therebetween. In a state in which the
 support arms 61.sub.3 have been closed, the air bag 21 enclosed in the air
 bag cover 58 is retained in a sandwiched manner between the support arms
 61.sub.3 and the body portion 61.sub.1 and fastened to the inner member 48
 of the rood side rail 18 by bolts 62 which are passed through flanges
 61.sub.4 and 61.sub.5 provided on the body portion 61.sub.1 and the
 support arms 61.sub.3, respectively. At this time, the mounting bores 21b,
 21c, 21d and 21f in the air bag 21 protruding from the air bag cover are
 fastened commonly. Only the flanges 61.sub.4 and 61.sub.5 of the body
 portion 61.sub.1, and the support arm 61.sub.3 corresponding to the
 mounting bore 21e located above the non-expandable portion 21.sub.2 of the
 air bag 21 are fastened commonly by another bolt 57 (see FIG. 4) for
 fixing the mounting bracket 56 of the inflater 41.
 The flanges 61.sub.5 provided at the tip ends of the support arms 61.sub.3
 of the air bag holder 61 are adapted to be resiliently fitted into the
 flanges 61.sub.4 provided on the body portion 61.sub.1. If the flanges
 61.sub.4 and 61.sub.5 are fitted in a state in which the folded-up air bag
 21 has been retained between the body portion 61.sub.1 and the support
 arms 61.sub.3 of the air bag holder 61, the air bag holder 61 and the air
 bag 21 can be integrally fixed temporarily, whereby the efficiency of
 fixing them to the roof side rail 18 can be enhanced.
 The support arms 61.sub.3 of the air bag holder 61 and the mounting bores
 21b to 21f in the air bag 21 are fastened commonly by utilizing the bolts
 62 and 57 for fixing the air bag holder 61 to the rood side rail 18, as
 described above and hence, the number of the bolts 62 and 57 can be
 reduced to a minimum to lessen the number of parts and the number of
 assembling steps. Moreover, the support arms 61.sub.3 for supporting the
 air bag 21 to extend along the air bag holder 61 are formed integrally to
 make a single unitary structure, with the air bag holder 61 and hence, it
 is unnecessary to mount a special member for supporting the air bag 21 on
 the air bag holder 61. This can also contribute to a reduction in number
 of parts.
 As shown in FIGS. 6 and 9, the front pillar 11 for supporting the end of
 the front glass 63 is formed into the closed sectional shape by welding
 the outer member 64, the inner member 65 and the center member 66 to one
 another. The weather strip 53 is mounted at the rear end of the front
 pillar 11, and the front pillar garnish 67 is also mounted at the rear end
 of the front pillar 11 to cover the inner member 65. The non-expandable
 portion 21.sub.1 of the air bag 21 protruding from the air bag cover 58 is
 fastened to the inner member 65 of the front pillar 11 by the bolt 68
 passed through the mounting bore 21a defined in the non-expandable portion
 21.sub.1.
 A large number of ribs 69 are integrally formed, to make a single unitary
 structure, as energy absorbing members at predetermined distances
 vertically spaced apart from one another on that inner surface of the
 front pillar garnish 67 which faces rearwards of the air bag 21. A passage
 70 is defined between the inner member 65 of the front pillar 11 and the
 ribs 69 and has one end facing the air bag 21 and the other end facing the
 weather strip 53. Each of surfaces 69.sub.1 of the ribs 69 opposed to the
 passage 70 is formed into a smooth curved surface having no sharp edges.
 The air bag 21 is folded by a procedure shown in FIGS. 10A to 10C. In FIGS.
 10A to 10C, an open circle indicates the base end (upper end) of the air
 bag, and a black dot indicates the tip end (lower end) of the air bag 21.
 First, lower half of the air bag 21 is folded back in the direction of the
 inside of the vehicle body and superposed on the inner side of the vehicle
 body, as shown in FIG. 1OA. At this time, upper and lower halves of the
 air bag folded double may be temporarily partially fixed by an adhesive
 which is easily peeled off, or by a thread which is easily broken.
 Subsequently, the air bag 21 folded double is folded in a vertically
 zigzag manner to provide a reduced height, as shown in FIG. 10B, and
 folded up finally into a shape shown FIG. 10C. The air bag 21 folded up in
 this manner is enclosed in the air bag cover 58 and retained in the
 folded-up configuration.
 The operation of this embodiment will be described below.
 When an acceleration sensor has detected an acceleration equal to or larger
 than a predetermined value due to the side collision of the vehicle, the
 inflater 41 is ignited by a command from an air bag deployment control
 means, and a high-pressure gas generated by the burning of the propellant
 is ejected from the high-pressure gas ejecting portion 41.sub.1 of the
 inflater 41 into the inflater case 42. The high-pressure gas ejected into
 the inflater case 42 is supplied through the high-pressure gas ejecting
 port 59 in the front diffuser 43 into the first high-pressure gas supply
 port 31 in the first cell group 36 of the air bag 21, and flows from the
 first high-pressure gas supply port 31 via the first high-pressure gas
 supply passage 30 and the nine through-bores 29a to 29i into the nine
 cells 29a to 29i to expand the nine cells 29a to 29i. At the same time,
 the high-pressure gas ejected from the inflater 41 into the inflater case
 42 is supplied through the high-pressure gas ejecting port 60 in the rear
 diffuser 44 into the second high-pressure gas supply port 35 in the second
 cell group 37 of the air bag 21, and flows from the second high-pressure
 gas supply port 35 via the second high-pressure gas supply passage 34 and
 the four through-bores 32j to 32m into the four cells 29j to 29m to expand
 the four cells 29j to 29m.
 In such course, the hinge portions 61.sub.2 of the air bag holder 61 are
 broken by the pressure of the expanded first and second cell groups 36 and
 37, whereby the support arms 61.sub.3 are cut away from the body portion
 61, as shown in FIG. 12, and the slits 58.sub.1 (see FIG. 9) in the air
 bag cover 58 covering the folded air bag 21 are broken to enable the free
 expansion of the air bag 21. When the air bag 21 is further expanded, the
 end edge of the roof garnish is pushed down by the expansion pressure,
 whereby the engagement of the roof garnish 54 with the weather strip 53 is
 released to provide an opening. Therefore, the air bag 21 passed through
 such opening is deployed downwards into the vehicle compartment (see FIG.
 2).
 In the course of expanding the air bag 21 in the above manner, the
 non-expandable portion 21.sub.1 at the front end of the air bag 21, pulled
 to the expanded first cell group 36, enters the passage 70 defined between
 the inner member 65 of the front pillar 11 and the ribs 69 of the front
 pillar garnish 67. As a result, the front pillar garnish 67 is deformed by
 the pressure received from the non-expandable portion 21.sub.1 of the air
 bag 21 and disengaged from the weather strip 53, whereby the air bag 21 is
 deployed downwards through the resulting opening into the vehicle
 compartment. At this time, the non-expandable portion 21.sub.1 of the air
 bag 21 is guided to the ribs 69 of the front pillar garnish 67, but it is
 possible to reliably prevent the air bag 21 from being caught on the ribs
 69 to impede the smooth deployment of the air bag 21 or to damage the air
 bag.
 In the above-described embodiment, the non-expandable portion 21.sub.1 of
 the air bag 21 is accommodated between the front pillar 11 and the front
 pillar garnish 67, but an expandable cell may be accommodated in the
 non-expandable portion 21.sub.1.
 FIGS. 11A to 11D diagrammatically show the course of expansion of the air
 bag 21, wherein an open circle indicates the base end of the air bag 21,
 and a black dot indicates the tip end of the air bag 21. As already
 described with reference to FIGS. 10A to 10C, the air bag 21 is first
 folded double so that the tip end thereof extends to the inner side of the
 vehicle body at its tip end portion and then folded up in the vertically
 zigzag manner. Therefore, when the expansion of the air bag 21 in the
 folded-up state shown in FIG. 11A is started at its base end, as shown in
 FIG. 11B, the tip end of the air bag 21 is moved so that it falls in a
 direction away from the inner surface of the vehicle body (toward the
 central portion of the vehicle compartment), as shown in FIG. 11C. As a
 result, the air bag 21 can be deployed correctly, as shown in FIG. 11D,
 and it is possible to prevent such a deployment failure such as the tip
 end of the air bag 21 is caught on the inner surface of the vehicle body
 causing the air bag to fold at an intermediate portion thereof.
 The air bag cover 58 covering the folded-up air bag 21 also has a function
 to prevent the tip end of the deployed air bag from being caught on the
 inner surface of the vehicle body thereby promoting the correct
 deployment. More specifically, the slits 58.sub.1 in the air bag cover 58
 adapted to be broken upon the deployment of the air bag 21 are defined on
 the side opposed to the inner surface of the vehicle body. Therefore, when
 the slits 58.sub.1 are broken to provide the opening, the resulting
 reaction causes the air bag to be swung like a pendulum about the base end
 toward the central portion of the vehicle compartment. As a result, the
 distance between the tip end of the air bag 21 and the inner surface of
 the vehicle body is increased, whereby it is possible to prevent the tip
 end from being caught on the inner surface of the vehicle body to cause
 the deployment failure.
 When the air bag 21 is deployed in the above manner, the high-pressure gas
 generated by the inflater 41 is distributed to the first cell group 36 and
 the second cell group 37 by the front and rear diffusers 43 and 44. In
 this case, the high-pressure gas can be distributed in appropriate amounts
 to the first and second cell groups 36 and 37, respectively, to make
 uniform the time required for the deployment and the internal pressure in
 various portions of the air bag 21, because the opening area of the
 high-pressure gas ejecting port 59 in the diffuser 43 corresponding to the
 first cell group 36 having the larger volume is larger and the opening
 area of the high-pressure gas ejecting port 60 in the diffuser 44
 corresponding to the second cell group 37 having the smaller volume is
 smaller.
 In addition, since the sectional areas of the passageways of the
 through-bores 32f to 32i in four 29f to 29i of the nine cells 29a to 29i
 of the first cell group 36, which are located in the vicinity of the
 center pillar 12, are large and the sectional areas of the passageways of
 the through-bores 37l and 37m in two 29l and 29m of the four cells 29j to
 29m of the second cell group 37, which are located in the vicinity of the
 rear pillar 15, is large, a sufficient amount of the high-pressure gas can
 be supplied to the cells 29f to 29i, 29l and 29m located in the vicinity
 of the center pillar 12 and the rear pillar 15, requiring a large shock
 buffering performance as compared with the other portions, to promptly and
 reliably expand the air bag.
 Further, the air bag 21 is divided into the first and second cell groups 36
 and 37 which are independent from each other, so that the high-pressure
 gas does not flow from one of the first and second cell groups 36 and 37
 to the other. Therefore, even if one of the first and second cell groups
 36 and 37 is damaged to cause the leakage of the high-pressure gas, this
 influence can be prevented from being exerted to the other of the first
 and second cell groups 36 and 37. Yet further, suppose that the air bag
 includes a single cell group, and the high-pressure gas is supplied from
 one end of the single cell group, a time lag is generated by the time when
 the high-pressure gas reaches the other end of the cell group, whereby it
 is difficult to promptly deploy the entire air bag. In this embodiment,
 however, the non-uniform deployment of the air bag due to the time lag in
 supplying of the high-pressure gas is prevented, because the air bag is
 divided into the first and second cell groups 36 and 37 having the first
 and second high-pressure gas supply ports 31 and 35, respectively.
 When the acceleration generated due to the side collision of the vehicle is
 equal to or smaller than the predetermined value, the occupant restraint
 device C is not operated. However, when the occupant secondarily collides
 against the end edge of the roof garnish 54 facing the roof side rail 18
 due to a shock generated upon the side collision of the vehicle, the
 hollow body portion 61.sub.1 of the air bag holder 61 made of the
 synthetic resin is crushed to buffer the shock, but also the folded air
 bag 21 exhibits a function to enhance the shock buffering effect. In this
 way, the air bag holder 61 supporting the air bag 21 on the roof side rail
 18 has a function to act as a shock absorbing member and hence, the
 increases in number of parts and in cost can be inhibited, as compared
 with a case where the shock absorbing member is provided separately.
 A second embodiment of the present invention will be described with
 reference to FIG. 14.
 An air bag 21 in the second embodiment includes a first cell group 36 and a
 second cell group 36 which are adjacent each other, and a third cell group
 38 provided at the rear of the second cell group 37 with a non-expandable
 portion 21.sub.1 interposed therebetween. The first cell group 36 is
 comprised of a first high-pressure gas supply port 31, a first
 high-pressure gas supply passage 30 and five cells 29a, 29b, 29c, 29d and
 29e, and the second cell group 37 is comprised of a second high-pressure
 gas supply port 35, a second high-pressure gas supply passage 34 and four
 cells 29f, 29g, 29h and 29i. The third cell group 38 is comprised of a
 third high-pressure gas supply port 75, a third high-pressure gas supply
 passage 76 and four cells 29j, 29k, 29l and 29m. A high-pressure gas is
 supplied from longitudinally opposite ends of a first inflater 41a into
 the first and second high-pressure gas supply ports 31 and 35 in the first
 and second cell groups 36 and 37, and a high-pressure gas is supplied from
 a second inflater 41b into the third high-pressure gas supply port 75 in
 the third cell group 38.
 In the second embodiment, the first and second cell groups 36 and 37 are
 formed in a front portion of the air bag 21, and are independent from each
 other, and thereby the high-pressure gas does not flow from one of the
 first and second cell groups 36 and 37 to the other. Therefore, even
 according to the second embodiment, it is possible to prevent the
 influence of the damage of one of the first and second cell groups 36 and
 37 from being exerted to the other, and to reliably deploy the first and
 second cell groups 36 and 37 without a lag by the common first inflater
 41a.
 A third embodiment of the present invention will now be described with
 reference to FIG. 15.
 An air bag 21 in the third embodiment includes a third cell 38 which is
 similar to that of the air bag 21 in the second embodiment, but divided
 into a first cell subgroup 36' and a second cell subgroup 37'. A
 high-pressure gas is supplied from a second inflater 41b through a first
 high-pressure gas supply port 31' and a first high-pressure gas supply
 passage 30' to the first cell subgroup 36', and also supplied from the
 second inflater 41b through a second high-pressure gas supply port 35' and
 a second high-pressure gas supply passage 34' to the second cell subgroup
 37'.
 According to the third embodiment, the same function and effect as those of
 the front first and second cell groups 36 and 37 can be exhibited by the
 rear first and second cell subgroups 36' and 37'.
 A fourth embodiment of the present invention will now be described with
 reference to FIG. 16.
 Thirteen cells 29a, 29b, 29c, 29d, 29e, 29f, 29g, 29h, 29i, 28j, 29k, 29l
 and 29m in an air bag 21 in the fourth embodiment constitute a single cell
 group 77. A high-pressure gas is supplied from a first inflater 41a to a
 first high-pressure gas supply port 78 at a front end of the cell group
 77, and a high-pressure gas is supplied from a second inflater 41b to a
 second high-pressure gas supply port 79 at a rear end of the cell group
 77. A common high-pressure gas supply passage 80 connecting the first and
 second high-pressure gas supply ports 78 and 79 to each other communicates
 with the thirteen cells 29a to 29m.
 According to the fourth embodiment, the high-pressure gas can be supplied
 from opposite ends of the air bag 21 to promptly and uniformly expand the
 entire air bag 21. Moreover, even when a portion of the cell group 77 is
 damaged, the high-pressure gas is necessarily supplied from the first
 inflater 41a or the second inflater 41b to the cells 29a, 29b, 29c, 29d,
 29e, 29f, 29g, 29h, 29i, 29j, 29k, 29l, 29m located in front and rear of
 the damaged portion. Therefore, the expansion of the air bag 21 can be
 achieved without hindrance, leading to an enhanced reliability.
 A fifth embodiment of the present invention will now be described with
 reference to FIGS. 17 and 18.
 An inflater case 42 in the fifth embodiment includes a bottomed cylindrical
 body portion 81 closed at one end thereof and having an inflater 41
 accommodated therein, and a cap 82 adapted to close an opening at the
 other end of the body portion 81. High-pressure gas ejecting ports 59 and
 60 formed of notches are defined in the opposite ends of the body portion
 81 of the inflater case 41, and first and second high-pressure gas supply
 ports 31 and 35 in the air bag 21 are fixed by bands 45 and 46 to cover
 the ejecting ports 59 and 60. The amount of high-pressure gas ejected can
 be regulated to any value by rising the notches forming the high-pressure
 gas ejecting ports 59 and 60 to change the opening area.
 In the fifth embodiment, the two high-pressure gas ejecting ports 59 and 60
 are provided in the inflater case 42 having the inflater 41 accommodated
 therein, and are connected to the two high-pressure gas supply ports 31
 and 35 in the air bag 21, respectively. Therefore, even according to the
 fifth embodiment, the high-pressure gas ejected from the single inflater
 41 can be reliably supplied to the plurality of high-pressure gas supply
 ports 31 and 35, thereby contributing to the reductions in number of part
 and in cost.
 A sixth embodiment of the present invention will now be described with
 reference to FIGS. 19 and 20.
 An inflater case 42 in the sixth embodiment is a bottomed cylindrical
 member which is closed at one end thereof and in which an inflater 41 is
 accommodated. An opening in the other end of the inflater case 42 is
 utilized, as it is, as a high-pressure gas ejecting port 59, and a notch
 made at the one end of the inflater case 42 is used as a high-pressure gas
 ejecting port 60. A first high-pressure gas supply port 31 in a first cell
 group 36 and a second high-pressure gas supply port 35 in a second cell
 group 3 of an air bag 21 communicate with each other, and the inflater 41
 is inserted between the first and second high-pressure gas supply ports 31
 and 35 from an inflater inserting opening 83 defined in the vicinity of
 the second high-pressure gas supply port 35. An intermediate portion of
 the inflater case 42 is clamped by a band 45 to inhibit the communication
 between the first and second high-pressure gas supply ports 31 and 35 in
 the air bag 21, and a rear end of the inflater case 42 is clamped by a
 band 46 to close the inflater inserting opening 83 in the air bag 21. Even
 according to the sixth embodiment, the same function and effect as those
 in the fourth and fifth embodiments can be achieved.
 A seventh embodiment of the present invention will now be described with
 reference to FIG. 21.
 An air bag in the seventh embodiment includes thirteen cells 29a, 29b, 29c,
 29d, 29e, 29f, 29g, 29h, 29i, 29j, 29k, 29l and 29m which constitute a
 single cell group 77. A high-pressure gas is supplied from a first
 inflater 41a to a first high-pressure gas supply port 78 at a front end of
 the cell group 77, and a high-pressure gas is supplied from a second
 inflater 41b to a second high-pressure gas supply port 79 at a rear end of
 the cell group 77. A pipe member 91 made of a synthetic resin or a metal
 for connecting the first and second high-pressure gas supply ports 78 and
 79 is accommodated in the air bag 21 to extend along a base end of the air
 bag 21, and a high-pressure gas supply passage 80 is defined by the pipe
 member 91. Thirteen through-bores 32a, 32b, 32c, 32d, 32e, 32f, 32g, 32h,
 32i, 32j, 32k, 32l and 32m are defined in the pipe member 91 and
 communicate with the thirteen cells 29a to 29m, respectively. The
 sectional areas of passageways of the through-bores 32f to 32i in the six
 cells 29f to 29i opposed to the center pillar 12 and the rear pillar 15
 are larger than those of the through-bores 32a to 32e, 32j and 32k in the
 other seven cells 29a to 29e, 29j and 29k.
 According to the seventh embodiment, a high-pressure gas supply passage 80
 is defined by the pipe member 91 having a high rigidity as compared with
 the ground fabrics 25 and 26 of the air bag 21, and the through-bores 32a
 to 32m are defined in the pipe member 91. Therefore, the amount of the
 high-pressure gas supplied to each of the cells 29a to 29m can be
 controlled accurately to stabilize the deploying performance of the air
 bag 21.
 An eighth embodiment of the present invention will now be described with
 reference to FIGS. 22 and 23A to 23C.
 An air bag 21 in the eighth embodiment includes a single inflater 41 at a
 front end of a single cell group 77, and a single high-pressure gas supply
 passage 80 is defined integrally with a first ground fabric 25 and a
 second ground fabric 26 of the air bag 21. More specifically, when the
 first and second ground fabrics 25 and 26 are sewn to form the air bag 21,
 a pipe member 91 is attached by sewing, as shown in FIG. 23A, and thirteen
 through-bores 32a, 32b, 32c, 32d, 32e, 32f, 32g, 32h, 32i, 32j, 32k, 32l
 and 32m are previously defined in the pipe member 91. Then, the pipe
 member 91 is folded back and inserted into the air bag 21 to define the
 high-pressure gas supply passage 80, as shown in FIG. 23B. Thereafter, the
 inflater 41 is mounted to an end of the air bag 21, as shown in FIG. 23C.
 A high-pressure gas supplied from the inflater 41 to the high-pressure gas
 supply passage 80 within the pipe member 91 is supplied via the
 through-bores 32a to 32m defined in the pipe member 91 to cells 29a, 29b,
 29c, 29d, 29e, 29f, 29g, 29h, 29i, 29j, 29k, 29l and 29m.
 According the eighth embodiment, a pipe member 91 made of a material
 separate from the air bag is not required and hence, the number of parts
 and the cost can be reduced, but also the first and second ground fabrics
 25 and 26 can be formed into a double structure, leading to an increased
 strength.
 A ninth embodiment of the present invention will now be described with
 reference to FIGS. 24A to 25D.
 FIGS. 24A to 24C show a procedure for folding up an air bag 21. First, the
 air bag 21 is folded in a vertically zigzag manner from a state shown in
 FIG. 24A to a state shown in FIGS. 24B and 24C. At this time, a tip end of
 the air bag 21 is located at a widthwise (laterally) central portion of
 the air bag 21. Then, the air bag 21 folded in the zigzag manner is folded
 double downwards in a widthwise direction, and the tip end is sandwiched
 and hidden from a lateral direction by the air bag itself, as shown in
 FIG. 24D.
 FIGS. 25A to 25D shows a course of deployment of the air bag 21 folded up
 in the above manner. When a high-pressure gas is supplied from an inflater
 41 to a base end of the air bag 21 which is in the folded-up state, the
 air bag 21 is expanded sequentially in an order of from its base end to
 its tip end, as shown in FIGS. 25A to 25D. Therefore, the tip end of the
 air bag 21 maintained in the folded-up state up to the end of the
 expansion is covered with the air bag itself folded double in the
 widthwise direction and cannot be brought into contact with the inner
 surface of the side of the vehicle compartment. Thus, it is possible to
 reliably prevent such a deployment failure that the tip end of the air bag
 21 is caught on the inner surface of the vehicle compartment and bent at
 an intermediate portion of the air bag.
 Although the embodiments of the present invention have been described in
 detail, it will be understood that the present invention is not limited to
 the above-described embodiments, and various modifications may be made
 without departing from the spirit and scope of the invention defined in
 claims.
 For example, the air bag cover 58 is formed from the non-woven fabric in
 the embodiments, but may be formed from a sheet of any other material, and
 may be formed only by fastening such a sheet at a proper site by a
 breakable string. In any case, the air bag 21 in the folded-up state can
 be reliably supported on the body portion 61 of the air bag holder 61 by
 the support arms 61.sub.3 of the air bag holder 61.
 The number of the high-pressure gas supply ports 31 and 35 defined in the
 inflater case 42 is not limited to two and may be three or more.
 In addition, the sectional areas of the passageways of the through-bores
 32f to 32i, 32l and 32m in the cells 29f to 29i, 29l and 29m opposed to
 the center pillar 12 and the rear pillar 15 are larger in the embodiments.
 However, if the sectional area of the passageway of each of the
 through-bores 32a to 32m are changed depending on the distance from the
 inflater 41, 41a, 41b to each of the cells 29a to 29m, the entire air bag
 21 can be deployed with an appropriate timing.