Abstract:
There is provided an airbag coolant releasing device for releasing a coolant into an airbag. The device includes: a cylinder which is formed into a cylindrical shape; a coolant pack which is formed of a flexible film, wherein a coolant is sealed in the coolant pack and the coolant pack is received in the cylinder; a piston which is inserted into the cylinder; a drive unit which drives the piston with respect to the cylinder such that the piston presses the coolant pack; and a nozzle which is provided in an end portion of the cylinder which is located opposite to a side of the drive unit and which releases the coolant ejected from the coolant pack into the airbag.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a U.S. National Stage of International Application No. PCT/JP2012/069985 filed on Aug. 6, 2012, which claims the benefit of Japanese Patent Application No. 2011-205560 filed on Sep. 21, 2011. The entire disclosures of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a coolant releasing device which releases a coolant into an airbag of a vehicle such as a car so as to adjust the internal pressure of the airbag, and an airbag device having such a coolant releasing device. 
     BACKGROUND ART 
     An airbag device is provided in a vehicle such as a car. The airbag device has an airbag which is made of a cloth panel and formed into a bag-like shape so that the airbag can be unfolded and inflated to restrain a passenger when unfolding gas is blown into the airbag at the time of collision. In such an airbag device, proper control of the internal pressure of the airbag is required in order to reduce an acceleration peak received by the passenger while inflating the airbag early. To this end, for example, a proposal has been made that the internal pressure is set at relatively high pressure in order to unfold the airbag early immediately after collision, and the pressure is then reduced to reduce the acceleration received by the passenger who has been restrained. 
     In the background art, it has been general that exhaust units such as vent holes are provided in the airbag and characteristics of the airbag are tuned by the number of the exhaust units, the layout thereof, etc. so that the internal pressure of the airbag can be reduced to proper pressure after the airbag is unfolded and inflated. 
     In addition, in the background art, a proposal has been made that gas used for unfolding the airbag is cooled to reduce the internal pressure of the airbag to proper pressure. 
     When a liquid coolant is released at a predetermined timing while or after the airbag is unfolded and inflated, the unfolding gas can be cooled by the heat of evaporation of the coolant to reduce the internal pressure of the airbag. Thus, it is possible to obtain good passenger restraining performance. 
     As such a coolant releasing device, a device in which a coolant such as an antifreeze solution is sealed in the interior of a cylinder by a piston of silicon rubber etc. and the piston is pressed by use of gas generated by a micro gas generator (MGG) to thereby release the coolant has been proposed, for example, in Patent Literature 1. 
     In addition, another coolant releasing device in which a coolant is reserved in a tube-like container having a below-like fragile portion formed therein and the container is received in a cylinder so that the container can be compressed axially by a piston to release the coolant has been described in Patent Literature 2. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A-2011-116230 
     Patent Literature 2: JP-A-2011-116229 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     It is necessary to maintain the coolant releasing device not to leak the coolant, for example, over the lifetime of the vehicle (for at least 10 years by way of example). 
     In the case where the coolant is sealed in a gap between an inner circumferential surface of the cylinder and an outer surface of the piston made of rubber as disclosed in Patent Literature 1, the coolant is sealed between the rubber piston and the inner circumferential surface of the cylinder. Therefore, when foreign matter or the like enter the gap, there is a concern that the coolant may leak. 
     In addition, it is necessary to perform strict dimensional management on the piston having such a high sealing property and it is also necessary to perform accurate management as to the working for assembling the piston into the cylinder. Accordingly, there is a concern that the number of production steps may be increased and the cost caused thereby may be increased accordingly. 
     In addition, when the coolant is received in the tube-like container as disclosed in Patent Literature 2, it is necessary to pay additional cost for a mold etc. for forming the coolant container. In addition, such a container needs to be designed specially in accordance with the shape and size of the coolant releasing device. Therefore, there is a concern that the number of man-hours and cost required for the design, production of the mold, etc. may be further increased. 
     In consideration of the aforementioned problems, an object of the invention is to provide an airbag coolant releasing device in which leak of a coolant can be prevented by a simple configuration, and an airbag device provided with such an airbag coolant releasing device. 
     Solution to Problem 
     In order to solve the aforementioned problems, in an airbag coolant releasing device for releasing a coolant into an airbag, the device comprises: a cylinder which is formed into a cylindrical shape; a coolant pack which is formed of a flexible film, wherein a coolant is sealed in the coolant pack and the coolant pack is received in the cylinder; a piston which is inserted into the cylinder; a drive unit which drives the piston with respect to the cylinder such that the piston presses the coolant pack; and a nozzle which is provided in an end portion of the cylinder which is located opposite to a side of the drive unit and which releases the coolant ejected from the coolant pack into the airbag. 
     According to the airbag coolant releasing device, the coolant is sealed in the coolant pack made of the film so that leak resistance of the coolant can be improved without the necessity of sealing the coolant by the piston etc. in a normal situation (prior to collision). 
     In addition, such a coolant pack can be manufactured without use of a mold etc., inexpensively, and with a smaller number of man-hours. 
     Further, since it is not necessary to seal the coolant by the piston in a normal situation, the diameter of the piston and the diameter of the cylinder can be increased easily and the length of the cylinder in the direction of a central axis thereof can be shortened in comparison with that in an existing device which seals a coolant by a piston and whose capacity is equivalent. 
     In this manner, the whole length of the coolant releasing device can be made close to that of a disc-type inflator generating unfolding gas, and the coolant releasing device can be easily externally attached to a wall surface of the retainer in which the airbag is received, so that the coolant releasing device can be arranged side by side with the inflator. Thus, the coolant releasing device can be applied to an existing airbag device by minor design change. 
     In the invention, the coolant may be sealed in the coolant pack in a liquid state. 
     In the airbag coolant releasing device according to the present invention, the cylinder may comprise a first member that is provided with the nozzle and a second member that is removably attached to the first member, and the cylinder may comprise a temporary lock mechanism including a locking portion which is provided in one of the first member and the second member and a locked portion which is provided in the other of the first member and the second member so as to be engaged with the locking portion. 
     According to this configuration, the first member and the second member can be temporarily locked easily before the first member and the second member are finally fastened to each other. Thus, the working performance of the assembling step can be improved. 
     The nozzle may be provided with a conical body, and the conical body may be disposed in a center portion of an opening formed in an end face of the cylinder, and the conical body has a tip portion which is disposed on a side of the coolant pack. 
     According to this configuration, the coolant ejected from the cylinder collides with the conical body so that the coolant can form an excellent spray. 
     In addition, the coolant pack is pierced by the tip portion of the conical body so that the coolant pack can be ruptured surely to thereby release the coolant. 
     In addition, an airbag device comprises: an airbag which is formed into a bag-like shape and which is unfolded and inflated when unfolding gas is supplied into the airbag; a retainer, wherein, in a normal state, the airbag is folded and received in the retainer; an inflator which supplies the unfolding gas into the airbag; and an airbag coolant releasing device according to any one of claims  1  through  3  which releases a coolant into the airbag while or after the airbag is unfolded and inflated. 
     According to this configuration, it is possible to provide an airbag device having effects of the aforementioned airbag coolant releasing device. 
     In addition, in the airbag device according to the present invention, the inflator and the airbag coolant releasing device may be disposed adjacent to each other on the same wall surface portion of the retainer. 
     According to this configuration, the airbag coolant releasing device may be also applied to an existing airbag device by minor design change. 
     In addition, the airbag device according to the invention may have a configuration in which the nozzle of the airbag coolant releasing device is disposed to protrude toward an inner side of the retainer. 
     According to this configuration, the coolant can form a spray surely inside the airbag while or after the airbag is unfolded and inflated. 
     Advantageous Effects of Invention 
     As described above, according to the invention, it is possible to provide an airbag coolant releasing device which can prevent leak of a coolant by a simple configuration, and an airbag device provided with such a coolant releasing device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view showing the configuration of an airbag device having an embodiment of a coolant releasing device according to the present invention; 
         FIG. 2  is an exploded perspective view of a retainer peripheral portion in the airbag device in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view of the coolant releasing device in  FIG. 1 ; 
         FIGS. 4A and 4B  are perspective views of the outline of a coolant pack in the coolant releasing device in  FIG. 1 , wherein  FIG. 4A  shows a state before molding and  FIG. 4B  shows a state after molding; 
         FIG. 5  is a sectional view of the coolant releasing device in  FIG. 1  cut along a plane including a central axis of a cylinder, showing a state of the coolant releasing device before operation; 
         FIG. 6  is a sectional view of the coolant releasing device in  FIG. 1  cut along the plane including the central axis of the cylinder, showing a state of the coolant releasing device in operation; 
         FIG. 7  is a sectional view of the coolant releasing device in  FIG. 1  cut along the plane including the central axis of the cylinder, showing a state of the coolant releasing device after completion of operation; and 
         FIG. 8  is a view showing an example of a temporal history of acceleration of a dummy doll head portion in the airbag device in an embodiment and a comparison example of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of a coolant releasing device and an airbag device according to the invention will be described below. 
     The airbag device according to the embodiment is provided in a car such as a passenger car. For example, the airbag device is applied to a passenger seat airbag for front collision. The passenger seat airbag is provided in an installment panel in front of an passenger seat. Also, for example, the invention may be applied to a driver&#39;s seat airbag which is provided in a boss portion of a steering wheel, a knee bag which is provided in a lower portion of the installment panel to restrain a knee portion of a passenger, a side airbag which is provided in a side portion of a seat, a curtain airbag which is unfolded into a curtain-like shape along a side window, etc. Incidentally, the shapes, layout, etc. of respective constituent members may be changed suitably in accordance with the place where the airbag device is applied. 
     As shown in  FIG. 1 , an airbag device  1  is configured to have an airbag  10 , a retainer  20 , an inflator  30 , a coolant releasing device  100  etc. 
     For example, the airbag  10  is formed into a bag-like shape out of a plurality of panels which have been cut out from nylon-based or polyester-based cloth and sewed up together. In a normal situation, the airbag  10  is received in a folded state inside the retainer  20 . 
     On collision, unfolding gas generated by the inflator  30  is introduced into the airbag  10  so that the airbag  10  is unfolded and inflated inside the cabin of a vehicle to thereby restrain a not-shown passenger. 
     In  FIG. 2 , of the cloth panels constituting the airbag  10 , only a part in the periphery of the retainer  20  is cut out and illustrated. 
     As shown in  FIG. 2 , an inflator opening  11   a  and a coolant releasing device opening  11   b  are formed in a cloth panel  11  in the periphery of the retainer  20  of the airbag  10 . 
     The inflator opening  11   a  is a circular opening as a portion into which an end portion of the inflator  30  is inserted. 
     The coolant releasing device opening  11   b  is a circular opening as a portion into which an end portion of the coolant releasing device  100  is inserted. 
     The coolant releasing device opening  11   b  is disposed adjacently to the inflator opening  11   a.    
     In addition, openings are formed in the periphery of the inflator opening  11   a  and the coolant releasing device opening  11   b  so that bolts B for fixing a bag ring which will be described later can be inserted into the openings. 
     The retainer  20  is a container-like member in which the airbag  10  which has not been unfolded and inflated yet is folded and received. 
     In addition, the inflator  30  and the coolant releasing device  100  are provided in the retainer  20 . 
     The retainer  20  has a bottom face portion  21 , an upper face portion  22 , a lower face portion  23 , side face portions  24 , etc. The retainer  20  is formed into a box-like shape opened on the passenger side. 
     The bottom face portion  21  is disposed substantially oppositely to the passenger. The bottom face portion  21  is a flat platelike portion as a base portion to which the inflator  30  and the coolant releasing device  100  are attached. 
     An inflator opening  21   a  and a coolant releasing device opening  21   b  are formed in the bottom face portion  21 . 
     The inflator opening  21   a  is a circular opening as a portion into which the end portion of the inflator  30  is inserted. 
     The coolant releasing device opening  21   b  is a circular opening as a portion into which the end portion of the coolant releasing device  100  is inserted. 
     The coolant releasing device opening  21   b  is disposed adjacently to the inflator opening  21   a.    
     In addition, openings are formed in the periphery of the inflator opening  21   a  and the coolant releasing device opening  21   b  so that the bolts for fixing the bag ring which will be described later can be inserted into the openings. 
     The inflator opening  21   a  and the coolant releasing device opening  21   b  of the retainer  20  are disposed on top of the inflator opening  11   a  and the coolant releasing device opening  11   b  of the airbag  10 . 
     The upper face portion  22 , the lower face portion  23 , and the side face portions  24  are substantially flat plate-like portions disposed to protrude outward toward the passenger side from an upper end portion, a lower end portion and side surface portions of the bottom face portion  21 , respectively. 
     In addition, brackets  24   a  for attaching the retainer  20  to the vehicle body side are provided to outer surface portions of the side face portions  24 . 
     In addition, the retainer  20  is provided with the bag ring  25 . The bag ring  25  is a metal fitting disposed inside the airbag  10 . The bag ring  25  cooperates with the bottom face portion  21  to hold the cloth panel  11  to thereby fix the airbag  10  to the retainer  20 . 
     The bag ring  25  is formed into a rectangular plate-like shape. An outer circumferential edge portion of the bag ring  25  is folded back on the passenger side (on the opposite side to the bottom face portion  21 ). 
     An inflator opening  25   a  and a coolant releasing device opening  25   b  are formed in the bag ring  25 . 
     The inflator opening  25   a  is a circular opening serving as a portion into which the end portion of the inflator  30  is inserted. 
     The coolant releasing device opening  25   b  is a circular opening as a portion in which the end portion of the coolant releasing device  100  is inserted. 
     The coolant releasing device opening  25   b  is disposed adjacently to the inflator opening  25   a.    
     The plurality of bolts B protruding toward the bottom face portion  21  are provided in the bag ring  25 . 
     The bolts B are inserted into the openings formed in the cloth panel  11  of the airbag  10  and the bottom face portion  21  of the retainer  20 . 
     Nuts N are fastened to the bolts B so that the bag ring  25  is fixed to the retainer  20  to thereby fix the airbag  10 . 
     In addition, a part of the bolts B are fastened to both a flange of the inflator  30  and a flange of the coolant releasing device  100  so as to serve for fixing the inflator  30  and the coolant releasing device  100 . 
     The inflator  30  is an unfolding gas supply device which generates high-temperature unfolding gas for unfolding and inflating the airbag  10  based on a signal issued from a not-shown airbag controller. The inflator  30  is provided with a gas generating agent for generating nitrogen gas etc. during combustion and an ignitor which ignites the gas generating agent through a firelighter. 
     The inflator  30  is of a so-called disc-type inflator in which a fixation flange  30   a  is provided in the periphery of a body portion formed into a disc-like shape (a columnar shape having an axial length short with respect to its outer diameter). 
     The inflator  30  has a plurality of gas ejection holes formed in an outer circumferential surface portion located closer to the passenger side than the flange  30   a.    
     The flange  30   a  in which the gas ejection holes protrude inside the airbag  10  is fastened by the bolts B and the nuts N so that the inflator  30  is fixed to the bottom face portion of the retainer  20 . 
     In addition, a bracket  31  for fixing the airbag device  1  to the vehicle body is provided in an end portion of the inflator  30  opposite to the passenger side. 
     The coolant releasing device  100  is provided for releasing a coolant such as an antifreeze solution into the airbag  10  in accordance with a signal issued from the airbag controller during or after unfolding and inflation of the airbag  10  in order to reduce the internal pressure of the airbag  10 . 
     As shown in  FIG. 3  etc., the coolant releasing device  100  is configured to include a bottle lower part  110 , a bottle upper part  120 , a gasket  130 , a piston  140 , a micro gas generator (MGG)  150 , a coolant pack  160  etc. 
     The bottle lower part  110  and the bottle upper part  120  cooperate with each other to form a cylinder portion which receives the coolant pack  160  and the piston  140  for pressing the coolant pack  160 . 
     The bottle lower part  110  is configured so that one end portion (an opposite end portion to the airbag  10  side) of a body portion  111  formed into a cylindrical shape is substantially closed by an end face  112 . 
     A cylindrical mount portion  113  to which the MGG  150  is attached is formed in a center portion of the end face  112  so as to be substantially concentric to the body portion  111 . The mount portion  113  is formed to protrude from the end face  112  toward the opposite side to the body portion  111 . 
     A screw portion to which a cap  151  of the MGG  150  is fastened as will be described later is formed in an outer circumference surface of the mount portion  113 . 
     A flange  114  overhanging like a collar toward the outer diameter side from the outer circumferential surface is formed in an opposite end portion of the body portion  111  to the end face  112 . 
     A hooking portion  115  on which a stop portion  125  of the bottle upper part  120  is hooked is formed in a portion in an outer circumferential edge portion of the flange  114 . 
     The bottle upper part  120  is a member which is substantially shaped like a disc to close an open end portion of the body portion  111  of the bottle lower part  110 . 
     A flange  121  connected to the flange  114  of the bottle lower part  110  is formed in an outer circumferential edge portion of the bottle upper part  120 . 
     In addition, a nozzle  122  for ejecting a coolant from the interior of the cylinder into the airbag  10  is formed in a center portion of the bottle upper part  120 . 
     The nozzle  122  is configured such that a conical portion  124  having a sharp tip portion disposed to protrude toward the bottle lower part  110  is provided in a center portion of a circular opening  123 . 
     The conical portion  124  is supported by a coupling portion disposed between the conical portion  124  and an inner circumferential edge portion of the opening  123 . 
     The bottle upper part  120  is disposed so that the nozzle  122  protrudes outward from the bottom face  21  of the retainer  20  so as to be positioned inside the airbag  10  and the retainer  20 . 
     The stop portion  125  engaged with the hooking portion  115  of the bottle lower part  110  is formed in an outer circumferential edge portion of the flange  121 . 
     The stop portion  125  is shaped like a hook out of a protrusion which has a tip portion protruding toward the bottle lower part  110  from the outer circumferential edge portion of the flange  121  and which further protrudes on one circumferential side of the cylinder. 
     The stop portion  125  is locked on the hooking portion  115  of the bottle lower part  110  when the bottle upper part  120  is turned around the central axis of the cylinder with respect to the bottle lower part  110  in the state in which the flanges  114  and  121  of the bottle lower part  110  and the bottle upper part  120  are butted against each other. 
     The stop portion  125  and the hooking portion  115  are used for temporarily locking the bottle lower part  110  and the bottle upper part  120  on each other when they are assembled at the bag apparatus  1 . 
     The bottle lower part  110  and the bottle upper part  120  which are temporarily locked on each other are attached to the retainer  20 , and the bolts B protruding from the bag ring  25  are inserted into the openings of the flanges  114  and  121  and fastened with the nuts N. Thus, the bottle lower part  110  and the bottle upper part  120  are fixed to each other. 
     The gasket  130  is held between the flange  114  of the bottle lower part  110  and the flange  121  of the bolt upper part  120  so as to seal a gap between the flanges  114  and  121 . 
     For example, the gasket  130  is formed annularly out of a silicon-based rubber material. For example, the sectional shape of the gasket  130  taken along the diameter direction is formed into a rectangular shape. 
     The gasket  130  is fitted into a groove portion  114   a  formed in a face portion of the flange  114  of the bottle lower part  110  which faces a bottle upper part  120 . 
     The piston  140  is inserted into an inner diameter side of the body portion  111  of the bolt lower part  110 . The piston  140  is a substantially disc-like member which can move axially relatively to the bottle lower part  110 . 
     Upon reception of the pressure of gas generated by the MGG  150 , the piston  140  is driven to move toward the bottle upper part  120  to press and rupture the coolant pack  160  so as to release the coolant into the airbag  10 . 
     Piston ring grooves  141  which are, for example, circumferential grooves each having a rectangular section are formed in an outer circumferential surface of the piston  140 . 
     A piston ring  142  formed annularly, for example, out of silicon-based rubber etc. is assembled on the piston ring grooves  141 . The piston ring  142  seals a gap between the outer circumferential surface of the piston  140  and the inner circumferential surface of the body portion  111  of the bottle lower part  110  so as to prevent the coolant from flowing backward and the coolant releasing gas from leaking out during the operation of the unit. In addition, the piston ring  142  slides against the inner circumferential surface of the body portion  111  while the piston  140  is driven. 
     The MGG  150  is a drive unit which generates the coolant releasing gas, for example, by use of gunpowder so as to drive the piston  140 . 
     The MGG  150  is substantially formed into a columnar shape. The MGG  150  is inserted into the mount portion  113  of the bottle lower part  110  so as to be retained therein. 
     In addition, the cap  151  substantially formed into a cylindrical shape is provided in a rear end portion (an opposite end portion to the piston  140  side) of the MGG  150 . 
     A threaded portion formed in the inner circumferential surface of the cap  151  is fastened to the screw portion formed in the mount portion  113  so that the cap  151  is fixed to the bottle lower part  110  and hence the MGG  150  is fixed. 
     The coolant pack  160  is formed such that, for example, a pack made of a flexible film is formed into a bag-like shape to enclose the coolant such as an antifreeze solution therein. 
     The film constituting the coolant pack is formed such that, for example, a resin layer of polyethylene etc. is laminated, for example, on opposite surfaces of a base material made of an aluminum alloy. 
     As shown in  FIG. 4A , the coolant pack  160  is formed such that a rectangular film is folded back in the center portion and an outer circumferential edge portion  161  is welded in a state in which a coolant is enclosed between the folded portions of the rectangular film. 
     Then, the coolant pack  160  is inflated at its center portion and folded at its end portion, for example, by a worker so that the coolant pack  160  can be inserted into the inner diameter side of the bottle lower part  110 . Thus, the coolant pack  160  is molded to have such a shape that the coolant pack  160  can be inserted into a cylinder having a disc-like shape, a cubic shape or the like, as shown in  FIG. 4B . Due to the strength of the aluminum layer of the film, the coolant pack  160  can keep the shape molded thus. 
     The coolant pack  160  which has been molded is received in a region closer to the nozzle  122  than the piston  140  in the cylinder. 
     On this occasion, the coolant pack  160  is disposed to prevent its outer circumferential edge portion (welded portion) from facing the nozzle  122 . 
     Next, operation of the aforementioned airbag device  1  will be described. 
     When the not-shown airbag controller determines that it is necessary to unfold and inflate the airbag  10  based on an output of a collision detector such as an acceleration sensor or an output of a pre-crash detector for detecting a sign of collision, the ignitor of the inflator  30  is ignited to thereby start generation of high-temperature unfolding gas. 
     Unfolding gas ejected from the inflator  30  is blown into the airbag  10  folded inside the retainer  20  to thereby unfold and inflate the airbag  10 . 
     In addition, with a delay of a predetermined time from the start of generation of the unfolding gas from the inflator  30 , the airbag controller ignites the MGG  150  of the coolant releasing device  100  so as to start generation of coolant releasing gas from the MGG  150 . 
     In this manner, the piston  140  in the state shown in  FIG. 5  starts to move toward the nozzle  122  due to the pressure of the coolant releasing gas so that the piston  140  starts to press the coolant pack  160  as shown in the state shown in  FIG. 6 . 
     The coolant pack  160  pressed by the piston  140  is pressed against the bottle upper part  120  so that the internal pressure of the coolant pack  160  increases. Further, since the coolant pack  160  is pressed by the piston  140 , the coolant pack  160  partially entering the opening  123  of the nozzle  122  is pierced by the tip portion of the conical portion  124  so as to be ruptured. 
     Since the coolant released due to the rupture of the coolant pack  160  collides with the conical portion  124  of the nozzle  122  in a high pressure state, the coolant turns into a spray (spray S), which is released into the airbag  10  to cool the high-temperature unfolding gas inside the airbag  10  to thereby reduce the internal pressure rapidly. 
     Then, the release of the spray S of the coolant continues until the piston  140  abuts against the bottle upper part  120  as shown in  FIG. 7 . As soon as the piston  140  is stopped, the release of the spray S of the coolant is terminated. 
     On this occasion, substantially the whole amount of the coolant received in the coolant pack  160  is released into the airbag  10  so as to cool unfolding gas due to the latent heat of vaporization thereof etc. 
       FIG. 8  is a graph showing an example of a temporal history of acceleration of a dummy doll head portion during a collision test in the airbag device according to the embodiment. 
     The abscissa axis indicates a time elapsed after collision and the ordinate axis indicates acceleration (G) in the dump doll head portion. 
     In addition, data of the embodiment are indicated by the solid line while data of a comparative example of the invention are indicated by the broken line. 
     In an airbag device according to the comparative example, the coolant releasing device  100  has been removed from the airbag device  1  according to the embodiment. 
     In the embodiment, the coolant is released into the airbag  10  with a delay of a predetermined time after the airbag  10  is unfolded and inflated. The unfolding gas is cooled by the latent heat of vaporization of the coolant etc. so that the internal pressure of the airbag  10  can be prevented from increasing excessively. 
     Thus, it is possible to reduce a peak value of acceleration received by the dummy doll head portion, as shown in  FIG. 8 . 
     According to the coolant releasing device  100  and the airbag device  1  according to the aforementioned embodiment, it is possible to obtain the following effects. 
     (1) Since the coolant is enclosed in the coolant pack  160  made of the film, it is not necessary to seal the coolant by the piston  140  in a normal state so that leak resistance of the coolant can be improved. 
     In addition, such a coolant pack  160  can be manufactured inexpensively by a small number of man-hours without the necessity of any tool such as a mold, for example, by use of a commercially available film for retort pouch food and production facilities thereof. 
     (2) Since it is not necessary to seal the coolant by the piston  140  in a normal state, the diameter of the piston and the diameter of the cylinder can be increased easily and the length of the cylinder in the direction of the central axis can be shortened in comparison with that in an existing device which seals a coolant by a piston and whose capacity is equivalent. 
     In this manner, the whole length of the coolant releasing device  100  can be made close to that of the disc-type inflator  30 , and the coolant releasing device  100  can be easily externally attached to the bottom face  21  of the retainer  20  so that the coolant releasing device  100  can be arranged side by side with the inflator  30 . Thus, the coolant releasing device  100  can be applied to an existing airbag device by minor design change. 
     (3) Due to the stop portion  125  and the hooking portion  115  provided for temporarily locking the bottle lower part  110  and the bottle upper part  120  constituting the cylinder of the coolant releasing device  100 , the bottle lower part  110  and the bottle upper part  120  can be temporarily locked easily before the bottle lower part  110  and the bottle upper part  120  are coupled to each other finally. Thus, the working performance of the assembling step can be improved.
 
(4) Due to the configuration in which the conical portion  124  having the tip portion disposed on the coolant pack  160  side is disposed in the center portion of the opening  123  of the nozzle  122 , the coolant pack  160  is pierced by the sharp tip portion of the conical portion  124  so that the coolant pack  160  can be surely ruptured to thereby release the coolant. In addition, the coolant ejected from the cylinder can collide with the conical portion  124  to thereby form a spray S preferably.
 
     Incidentally, the scope of the present invention is not limited to the aforementioned embodiment. Any suitable change may be added to the configuration of the coolant releasing device and the configuration of the airbag device so that the shapes, structures, layout, etc. of respective members constituting the airbag device can be changed suitably. 
     For example, although the film constituting the coolant pack is formed such that a polyethylene layer is formed on opposite surfaces of an aluminum-based alloy layer in the embodiment, the present invention is not limited thereto. Alternatively, a film having another configuration may constitute the coolant pack. For example, the metal layer serving as the base material is not limited to an aluminum-based alloy but another material may be used. In addition, the resin layer formed on each of the surfaces of the metal layer may be made of another material such as PET. 
     In addition, the way of folding the coolant pack is not limited particularly. Any way of folding the coolant pack may be used as long as the coolant pack can be received in the cylinder.