JP4551844B2 - Air bag device for knee protection - Google Patents

Description

  The present invention relates to a knee protection airbag device that is disposed on the front side of an occupant seated in a passenger seat or a driver's seat and can protect the occupant's knee in the event of a vehicle collision.

  Conventionally, in a knee protection airbag device, an airbag that inflates to protect a passenger's knee, an inflator that supplies inflation gas to the airbag, and a folded airbag and inflator are stored and held in the vehicle. Mounted on the front side of the seated occupant's knee, comprising a case with an open rear side and an airbag cover that covers the case opening and can be opened when the airbag is inflated. (For example, refer to Patent Document 1).

  In addition, the airbag cover includes an upper door portion and a lower door portion that are opened at both the upper and lower sides by being pushed when the airbag is inflated by breaking the surrounding planned breakage portion. The part to be broken is formed with a thin wall thickness, and is arranged on the horizontal line part arranged on the leading end side of the upper and lower door parts, and the left and right edge sides of the upper and lower door parts. The left vertical line portion and the right vertical line portion extending from the left and right ends of the horizontal line portion to both sides in the vertical direction are formed in a substantially H shape when viewed from the rear side.

  The airbag is configured such that a portion housed in the case when the inflation is completed is an upstream portion of the inflation gas, and a portion protruding rearward from the case opening is the downstream portion of the inflation gas. It had been.

  Further, the inflator is configured such that the gas supply port portion that supplies the inflation gas toward the rear side into the airbag is shifted to one side in the left-right direction of the opening of the case as viewed from the rear side in the upstream portion of the airbag. I was allowed to place.

Further, in the airbag of the knee protection airbag device, when projecting from the opening of the case at the time of inflation, the downstream portion is folded substantially symmetrically so as to be inflated substantially symmetrically on both the left and right sides, Some of them are housed in a case together with the upstream portion (see, for example, Patent Document 2).
JP 2004-203226 A JP 2003-170801 A

  However, in the conventional knee protection airbag device, the upper and lower airbag covers are used to quickly open and inflate the airbag when the airbag is inflated. When the planned fracture portion around the door portion is formed with a thickness close to the limit that can be formed by injection molding, the following problems occur.

  That is, when the gas supply port portion of the inflator is disposed so as to be offset to one side in the left-right direction of the opening of the case, the horizontal line portion of the planned breaking portion is behind the gas supply port portion when the airbag device is activated. Breaking from the position causes the upper and lower doors to open from the gas supply port side. In this state, when the upper and lower doors are opened, the downstream portion of the airbag is folded symmetrically so as to be inflated substantially symmetrically on both the left and right sides, and the airbag is stored in the case. However, the gas supply port side of the airbag is in a mode of completing the inflation in advance. For this reason, there has been a problem in that the airbag is inflated quickly in a balanced manner on the left and right.

  In consideration of installing a knee protection airbag device in a narrow space on the front side of the occupant's knee, and considering a configuration in which the inflated airbag can protect the occupant's left and right knees The case in which the airbag protrudes preferably has a horizontally long, substantially rectangular parallelepiped shape that extends in the left-right direction while suppressing the width in the vertical direction, and the opening of the case that protrudes the airbag also has a horizontally long shape that extends in the left-right direction. A substantially rectangular shape is desirable.

  The inflator is a cylinder type in which the axial direction is arranged in the left-right direction so as not to be bulky in the vertical direction, considering that the airbag device for knee protection is installed in the narrow space on the front side of the occupant's knee In addition, a type in which a gas supply port that discharges an inflating gas toward the rear side is disposed on one end side thereof, and an end in the axial direction protrudes from the case. In order to suppress the inflator, it is desirable to hold the inflator in the case so that the substantially entire length is within the width dimension of the case in the left-right direction. Therefore, it is desirable to dispose the gas supply port portion of the inflator so as to be shifted to one side in the left-right direction of the opening of the case.

  The present invention solves the above-described problem, and even if the gas supply port portion of the inflator is disposed so as to be offset to one side in the left-right direction of the opening of the case, the upper and lower door portions of the airbag cover An object of the present invention is to provide a knee protection airbag device that can be smoothly opened while suppressing variation in the left-right direction.

The airbag device for knee protection according to the present invention stores and holds an airbag that inflates to protect a passenger's knee, an inflator that supplies inflation gas to the airbag, a folded airbag, and an inflator. A front side of a seated occupant's knee, comprising: a case having an opening at the rear side of the vehicle; and an airbag cover that covers the opening of the case so as to be opened when the airbag is inflated and is attached to the case Mounted on
The airbag cover is made of synthetic resin, and has an upper door portion and a lower door portion that are opened when the airbag is inflated by breaking the surrounding planned breakage portion,
The parts to be ruptured are formed with a thin wall thickness, and are arranged on the left and right edge sides of the horizontal line part arranged on the leading end side of the upper and lower door parts and the upper and lower door parts, respectively. The left vertical line portion and the right vertical line portion extending from the left and right ends of the horizontal line portion to both sides in the vertical direction are formed in a substantially H shape when viewed from the rear side,
The portion of the airbag that is housed in the case when the inflation is completed is the upstream portion of the inflation gas, and the portion that protrudes rearward from the opening of the case when the inflation is completed is the downstream portion of the inflation gas. The side part is folded in a substantially left-right symmetric shape, and is configured to be accommodated in the case together with the upstream part,
The inflator is arranged so that the gas supply port for supplying the inflation gas toward the rear side into the airbag is shifted to one side in the left-right direction of the opening of the case as viewed from the rear side in the upstream portion of the airbag An air bag device for knee protection configured as described above,
The horizontal line part in the planned breakage part of the airbag cover is
To start rupture starting from around the center of the horizontal line of the horizontal line at the time of rupture,
Thick part and thin part by gradually and continuously changing the thickness between thick part that thickens, thin part that is thinner than thick part, and thick part and thin part In contrast, the gradual change portion that is continuous with the thickness matched,
The thick wall portion is disposed so as to extend to the left and right sides with respect to the rear position of the gas supply port portion as a position in the left-right direction, and at least to the vicinity of the vertical line portion on the side close to the gas supply port portion. Set up
The thin part is disposed with a gradually changing part interposed between the thin part and the center of the horizontal line part in the left-right direction except the vicinity of the rear side of the gas supply port part and the gradually changing part. , Extending to both the left and right sides, and being arranged up to the vicinity of the vertical line portion on the side away from the gas supply port portion.

  In the knee protection airbag device according to the present invention, when the inflation gas is supplied to the upstream portion of the airbag from the gas supply port portion of the inflator toward the rear side during operation, the airbag is The upstream side portion is pushed rearward so that the downstream side portion in a folded state protrudes from the opening of the case, and the horizontal line portion of the planned break portion of the airbag cover is to be broken. At the initial stage of the supply of the expansion gas, the upstream part of the position where the gas supply port is arranged is most strongly pushed backward, and as it moves away from the gas supply part in the left-right direction, the other upstream part In this part, the pressing force to the rear side is slightly reduced.

  However, in the horizontal line portion of the planned breaking portion, the thick portion is arranged on the rear side of the gas supply port portion so as to extend to the left and right sides starting from the rear of the gas supply port portion. Although it occurs, breakage at the thick part is suppressed. In addition, a thin portion is disposed in the center of the horizontal line portion in the left-right direction so as to be adjacent to the thick portion with a gradually changing portion interposed therebetween, and the influence of elongation to break the thick portion propagates. Furthermore, the expansion gas flowing from the vicinity of the gas supply port is supplied, and the upstream upstream portion itself in the vicinity of the horizontal center of the horizontal line portion also exerts a force that presses the downstream portion backward. Therefore, the portion of the thin portion near the center in the left-right direction of the horizontal line portion is the starting point of the break, and the break is propagated to both the left and right sides. The airbag cover is further broken, and the left and right vertical line portions are broken, so that the airbag cover can open the upper door portion and the lower door portion to both the upper and lower sides while suppressing variation in the left-right direction.

  At the same time, the downstream portion of the airbag that is folded in a substantially bilaterally symmetric shape is inflated substantially symmetrically in a balanced manner on both the left and right sides from the opening where the upper and lower doors are opened on both the upper and lower sides. The inflating is completed so that the occupant's knees can be protected.

  In addition, the horizontal line portion of the planned fracture portion connects the thin wall portion and the thick wall portion with a gradually changing portion interposed therebetween, so that stress concentration is caused at the end portion of the thick wall portion or the thin wall portion. Furthermore, since the thin-walled portion itself is disposed so as to extend to the left and right sides starting from the horizontal center of the horizontal line portion, it is near the horizontal center of the horizontal line portion, from the gradually changing portion. Breaking can be started stably from the region of the thin part that is separated.

  Therefore, in the knee protection airbag device according to the present invention, even if the gas supply port portion of the inflator is arranged so as to be offset to one side in the left-right direction of the opening of the case, the upper and lower door portions of the airbag cover Can be smoothly opened so as to be opened to both the upper and lower sides evenly from the vicinity of the center in the left and right direction to both the left and right sides while suppressing variation in the left and right direction.

And the length dimension of the left-right direction from the thick part side in the gradual change part between the thick part and the thin part to the rear position of the gas supply port part in the thick part, and the thick part and the thin part The length dimension in the left-right direction of the gradually changing portion between and the length dimension in the left-right direction of the thin-walled portion from the thin-walled portion side to the center in the left-right direction of the horizontal line portion in the gradually changing portion between the thick-walled portion and the thin-walled portion Are preferably arranged at a ratio of approximately 2: 1: 1.

  In such a setting, in the horizontal line part, the thick part occupies a long area of approximately ½ in the area between the rear position of the gas supply port part and the center in the horizontal direction of the horizontal line part. In addition, it can be easily prevented from breaking immediately after the supply of the expansion gas, and the gradually changing portion and the thin portion occupy almost half in the remaining half of the region, and stress concentration occurs. Can be easily suppressed, and a mode of breaking from a thin portion near the center in the left-right direction of the horizontal line portion can be easily secured.

  If the ratio is as described above, the rear position of the gas discharge port portion and the horizontal direction of the horizontal line portion are based on the two positions of the rear position of the gas discharge port portion and the center of the horizontal direction of the horizontal line portion. The position and length of each of the thick part, thin part, and gradual change part can be easily set between the center and the horizontal line part of the airbag cover along with the design change of the case etc. Even if the arrangement position of the gas supply port portion of the inflator is changed, it can be easily dealt with.

  Moreover, it is desirable to set the length dimension of the gradual change part between the thick part and the thin part in the left-right direction as 10 to 30 mm. If the length of the gradually changing portion is less than 10 mm, the thick and thin portions are made as thin as possible within the moldable range, and the difference in thickness between the thick and thin portions is clear. For example, when the thickness of the thick part is 0.80 mm, the thickness of the thin part is 0.65 mm, and the thickness difference is 0.15 mm, the end of the thick part or the thin part It is not possible to stably prevent breakage due to stress concentration at. Further, if the length dimension of the gradually changing portion exceeds 30 mm, the area in which the thick portion and the thin portion are provided becomes too narrow, and it is difficult to ensure the start of breakage in the vicinity of the horizontal center of the horizontal line portion.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the knee protection airbag device S of the embodiment has an instrument panel 5 on the front side of an occupant M seated in a passenger seat. The air bag 25 is disposed below the club box 7 on the lower side of the vehicle so as to be inflated so that the knee K (KL / KR) of the occupant M can be protected in the event of a vehicle collision. On the upper surface side of the instrument panel 5, a passenger seat airbag device 6 for deploying and inflating an airbag (not shown) is also mounted so as to protect the head and chest of the occupant M in the event of a vehicle collision. .

  In the present specification, the up / down / front / rear / left / right directions are based on the straight traveling time of the vehicle on which the airbag device S is mounted, and coincide with the up / down / front / back / left / right travel of the vehicle when traveling straight.

  The knee protection airbag device S includes a folded airbag 25, an inflator 20 that supplies inflation gas to the airbag 25, and the folded airbag 25 and inflator, as shown in FIGS. 20, and a case 11 that opens and opens the vehicle rear side, and an airbag cover 40 that covers the vehicle rear side of the case 11.

  As shown in FIGS. 2, 3, and 6, the case 11 is made of sheet metal and includes a box-shaped main body portion 12 and a panel portion 17 that extends outward from the rear end of the main body portion 12. The main body 12 has a substantially rectangular parallelepiped shape with a lateral wall shape extending in the left-right direction while suppressing the vertical dimension, and a bottom wall 15 that closes the vehicle front side of the circumferential wall 13. , And a substantially rectangular opening 12a extending horizontally in the left-right direction on the vehicle rear side. The airbag 25 is folded and accommodated in the main body 12 and protrudes rearward from the opening 12a of the main body 12 when inflated.

  A plurality of locking projections 14 for assembling the upper and lower connecting wall portions 42 and 43 of the airbag cover 40 to the case 11 are provided on the outer surface sides of the wall portions 13 a and 13 b facing the upper and lower sides of the peripheral wall portion 13. Is disposed. Each of the locking projections 14 is inserted into the locking holes 42a and 43a of the connecting wall portions 42 and 43 of the airbag cover 40 as a hook shape in which the tip is bent forward and away from the wall portions 13a and 13b. The peripheral edge of the locking holes 42a and 43a is locked, and the rearward movement of the airbag cover 40 relative to the case 11 is restricted. Further, an insertion hole 13e through which the end of the main body 21 of the inflator 20 can be inserted is formed in the right wall 13d of the left and right walls 13c and 13d in the peripheral wall 13 (FIG. 6). reference).

  The bottom wall portion 15 is formed with two insertion holes 15a through which the bolts 22c of the inflator 20 are inserted.

  The panel portion 17 is disposed to surround the upper side and the left and right sides around the opening 12a of the case 11, and is formed in a substantially flat plate shape extending in the left-right direction. In the panel portion 17, a plurality of insertion holes 17 a through which the connection wall portion 42 on the upper side of the airbag cover 40 is inserted are formed so as to penetrate in the front-rear direction on the upper side of the wall portion 13 a of the peripheral wall portion 13. ing. The insertion hole 17a is formed such that the peripheral edge of each locking hole 42a of the connecting wall portion 42 protrudes partly forward, and there are a plurality of insertion holes 17a in the left-right direction corresponding to the peripheral edge of each locking hole 42a. It is installed side by side. Further, in the vicinity of the left and right wall portions 13c and 13d of the peripheral wall portion 13 of the panel portion 17, insertion holes 17b through which the left and right side wall portions 44 and 45 of the airbag cover 40 are inserted are respectively penetrated in the front-rear direction ( (See FIG. 6). Further, a predetermined number of locking holes 17c and insertion holes 17d are disposed in the panel portion 17 so as to penetrate from the peripheral wall portion 13 to the left and right (see FIGS. 2, 4, and 5). ). Each locking hole 17c is inserted into the locking leg 64 of the airbag cover 40, and the periphery of the locking hole 17c is locked to the locking leg 64. The locking hole 17c has a peripheral edge of the panel portion 63 of the airbag cover 40. Regulates backward movement. Each insertion hole 17d fits and inserts the guide leg 65 of the airbag cover 40, and restricts the vertical and horizontal shifts in the panel portion 63 of the airbag cover 40 on the inner peripheral surface of the insertion hole 17d.

  Further, a predetermined number of attachment portions 18 for fixing the airbag device S to the body 1 side of the vehicle are formed in the vicinity of the outer peripheral edge of the panel portion 17. Each mounting portion 18 includes a mounting hole 18a. Then, bolts 3 for screwing the nuts 2a provided on the bracket 2 on the body 1 side to fix the mounting portions 18 to the body 1 side pass through the mounting holes 18a.

  As shown in FIGS. 2, 3, and 6, the inflator 20 is configured as a cylinder type in which the axial direction is disposed along the left-right direction of the vehicle, and includes a substantially cylindrical main body 21 and a diffuser 22. Yes. The main body 21 includes a generally cylindrical general portion 21a and a small-diameter small-diameter portion 21c protruding from the left end surface of the general portion 21a, and a plurality of gas discharge ports 21d are disposed on the outer peripheral surface of the small-diameter portion 21c. ,It is configured. The right end portion of the general portion 21a away from the small diameter portion 21c is a connector portion 21b that couples a lead wire (not shown) for inputting an operation signal.

  The diffuser 22 is made of sheet metal and includes a substantially half-divided cylindrical back plate portion 22 a that can cover the front side of the main body 21. The back plate portion 22a is provided with a plurality (two in the embodiment) of bolts 22c that protrude toward the front side of the vehicle, spaced apart in the left-right direction. The left and right ends of the back plate portion 22a are closed by substantially semi-disc shaped side wall portions 22d and 22f, and the left end side wall portion 22d has insertion holes 22e into which the tips of the small diameter portions 21c of the main body 21 can be inserted. Arranged. Further, the diffuser 22 is provided with a plurality of (in the embodiment, two) sandwiching portions 22b that connect the opposite edges of the back plate portion 22a at the top and bottom. Each clamping part 22b holds the main body 21 by clamping the outer peripheral surface of the main body 21 together with the pack plate part 22a by being plastically deformed so as to approach the back plate part 22a side. That is, the main body 21 is fixed to the diffuser 22 by inserting the back end of the small diameter portion 21c between the back plate portion 22a and each clamping portion 22b with the small diameter portion 21c side as the head, and inserting the tip of the small diameter portion 21c into the insertion hole of the side wall portion 22d. If the main body 21 is fitted to the rear surface side of the back plate portion 22a while being inserted into the back plate portion 22e and is plastically deformed so that each clamping portion 22b approaches the back plate portion 22a side, the main body 21 becomes the back plate portion 22a. The main body 21 can be fixed to the diffuser 22 by being sandwiched between the sandwiching portions 22b. At this time, the side wall portion 22f regulates the position of the end surface of the connector portion 21b of the main body 21.

  As will be described later, the inflator 20 is inserted into the airbag 25 when the airbag device S is assembled, and the bolts 22c that protrude from the airbag 25 are inserted into the insertion holes of the bottom wall portion 15 of the case 11. When the nut 23 is tightened by being inserted through the pin 15a, the air bag 25 and the case 11 are fixed.

  The inflator 20 receives an operation signal via a lead wire (not shown) when the airbag operation circuit mounted on the vehicle detects a frontal collision of the vehicle. In addition, when the airbag operation circuit mounted on the vehicle detects a frontal collision of the vehicle, an operation signal is simultaneously input to an inflator that inflates an airbag (not shown) of the passenger airbag device 6. It becomes.

  Further, when the inflator 20 is actuated after the airbag device S is mounted on the vehicle, the inflation gas G discharged from the plurality of gas discharge ports 21d is supplied to the diffuser 22 as shown in FIG. It is regulated by the back plate portion 22a, the side wall portion 22d, and the end surface of the main body 21 itself on the small diameter portion 21c side, and flows to the rear side of the small diameter portion 21c, and the inflator 20 supplies gas to the portion of the small diameter portion 21c. As the mouth portion 20a, the inflation gas G flows out backward and is supplied to the airbag 25.

  Further, in the case of the embodiment, when the inflator 20 is fixed to the case 11 and mounted on the vehicle, the gas supply port portion 20a has the axial direction of the inflator 20 as shown in FIGS. In a state along the horizontal direction in the horizontal direction, the case 11 is arranged so as to be offset toward the left wall 13c side of the case 11. In the case of the embodiment, the gas supply port portion 20a is disposed apart from the wall portion 13c by a dimension of about 1/6 of the width dimension LC of the opening 12a of the main body portion 12 of the case 11 in the left-right direction. Note that the width dimension LC in the left-right direction of the opening 12a is substantially equal to the width dimension L0 in the left-right direction of a horizontal line portion 52 of the planned fracture portion 51 described later (see FIGS. 2, 6, and 9). 1/6 substantially corresponds to the dimension of (L4-L1) obtained by subtracting the width dimension L1 from the width dimension L4 described later.

  The airbag 25 is formed of a woven fabric made of flexible polyester, polyamide yarn, or the like, and the shape when the deployment is completed is indicated by the two-dot chain line in FIG. 1 or the solid line in FIG. It has a width dimension in the left-right direction that can protect both knees KL and KR of M, and has a substantially rectangular plate shape in which the width dimension in the left-right direction on the lower end 25b side is narrowed in a tapered shape. And the airbag 25 is comprised so that the passenger | crew side wall part 26 may be arrange | positioned to the passenger | crew M side of the back side, and the vehicle body side wall part 27 may be arrange | positioned to the grab box 7 side of the front side at the time of completion of expansion | deployment. Yes. As shown in FIG. 7, the walls 26 and 27 are formed in substantially the same shape. Further, as shown in FIG. 13, wall portions 26 and 27 are connected in the airbag 25, and tethers 29 and 30 for regulating the thickness are provided so as to inflate the airbag 25 into a plate shape. It is arranged in two stages. The tethers 29 and 30 are arranged symmetrically so as to extend in the left-right direction. Reinforcing cloth 28 is disposed at the connecting portions (stitched portions) of the tethers 29 and 30 with the wall portions 26 and 27.

  Further, as shown in FIGS. 6 and 7, two insertion holes 27a and 27a and one insertion hole 27b are formed in a portion of the vehicle body side wall portion 27 on the lower end 25b side of the airbag 25 when the inflation and inflation are completed. Has been. Each bolt 22c of the inflator 20 is inserted through each insertion hole 27a, and the connector portion 21b of the main body 21 of the inflator 20 is inserted through the insertion hole 27b. The airbag 25 is attached to the case 11 by causing the connector portion 21 b of the inflator 20 to protrude from the insertion hole 27 b and sandwiching the periphery of each insertion hole 27 a between the diffuser 22 and the bottom wall portion 15 of the case 11. It has been. The airbag 25 is attached and fixed to the bottom wall portion 15 of the case 11 with the peripheral edge of the insertion hole 27 a as an attachment portion 25 e.

  Further, as shown in FIG. 13, the airbag 25 has a portion housed in the main body 12 of the case 11 when the inflation is completed as an upstream portion 31 of the inflation gas, and the opening 12 a of the case 11 when the inflation is completed. A portion protruding from the rear side to the rear side is configured as a downstream portion 32 of the inflation gas. As shown in FIGS. 7 and 13, the upstream portion 31 substantially coincides with a region near the attachment portion 25 e on the lower side of the tether 30 in the airbag 25.

  In the airbag 25 of the embodiment, the downstream side portion 32 is folded left and right symmetrically and is housed in the main body 12 of the case 11 together with the upstream side portion 31. In the vehicle mounted state housed in the case 11, as shown in FIGS. 3 and 6, the upstream portion 31 of the airbag 25 is disposed on the bottom wall portion 15 side of the case 11 in the vicinity of the inflator 20, and the downstream side The site | part 32 will be arrange | positioned in the opening 12a side of the rear end of the surrounding wall part 13 of the case 11 in the back side of the upstream site | part 31. FIG.

  The airbag 25 is folded in such a manner that the inflator 20 is accommodated in the airbag 25 so that the width of the airbag 25 can be accommodated in the body portion 12 of the case 11 in the horizontal direction, the front-rear direction, and the vertical direction. The lower ends (upper and lower edges) 25a and 25b and the left and right edges 25c and 25d are folded to the mounting portion 25e. In the case of the embodiment, first, as shown in FIG. 7A, the inflator 20 is inserted into the airbag 25 from the insertion hole 27b, and each bolt 22c protrudes from the insertion hole 27a. The occupant side wall portion 26 and the vehicle body side wall portion 27 are overlapped and spread flatly by projecting the 21b side from the insertion hole 27b.

  Then, as shown in FIG. 7B, the upper edge 25a is wound on the side of the vehicle body side wall 27 and roll-folded to form a folded body 34. After that, as shown in FIGS. 7B and 7C, the left and right end portions 34b and 34c of the folded body 34 are once folded toward the vehicle body side wall 27 and further, as shown in FIGS. Then, the end portions 34d and 34e near the folded fold are folded toward the occupant side wall portion 26 and brought close to the center 34a side in the left-right direction of the folded body 34 to form the folded body 35. The folding body 35 has a width dimension in the left-right direction and the up-down direction that can be stored in the case main body 12.

  Thereafter, as shown in FIG. 7D and FIG. 8A, when the vicinity of the attachment portion 27e is folded to the front side of the folding body 35, the folding completed body 36 in which the folding of the airbag 25 is completed can be obtained. The folding completion body 36 has width dimensions in the left-right direction, the up-down direction, and the front-rear direction that can be stored in the case main body 12.

  Thereafter, as shown in B to D of FIG. 8, the folding completion body 36 is wrapped using the belt-like wrapping material 38 by being hooked on the bolts 22 c and 22 c. The wrapping material 38 is used to prevent the airbag 25 from collapsing until the folding completion body 36 is accommodated in the case 11. When the airbag 25 is deployed and inflated, it is easily broken and is formed of a nonwoven fabric or the like.

  In the state where the folding completion body 36 is mounted on the vehicle, the end portions 34d and 34e are sequentially arranged on the lower side in the center of the folding body 34, and further, the end portions 34b and 34c side are disposed on the lower side. Then, the downstream portion 32 of the airbag 25 is disposed on the rear side of the upstream portion 31 and is accommodated in the main body 12 of the case 11 and mounted on the vehicle. It becomes a state.

  As shown in FIGS. 3 and 6, the airbag cover 40 is formed by injection molding from a synthetic resin such as a thermoplastic elastomer so as to cover the vehicle rear side of the folded airbag 25 and the case 11. And is connected and held to the case 11. The airbag cover 40 includes a cover main body portion 41 that covers the vehicle rear side in the vicinity of the peripheral wall portion 13 including the opening 12 a of the case 11, and a panel portion 63 that covers the vehicle rear side of the panel portion 17 of the case 11. Configured. In the embodiment, the airbag cover 40 is formed of a polyolefin-based thermoplastic elastomer.

  The cover main body 41 has four wall portions 42, 43, 44, and 45 projecting forward from the front side of the periphery in a substantially rectangular tube shape. The upper and lower wall portions 42 and 43 are locking holes 42a and 43a for inserting and locking the locking projections 14 provided on the wall portions 13a and 13b of the peripheral wall portion 13 of the case main body portion 12 as connecting wall portions 42 and 43, respectively. Are arranged so as to penetrate in the vertical direction. As described above, the peripheral edges of the locking holes 42a and 43b are formed so as to partially protrude forward so that they can be inserted into the respective insertion holes 17a of the case 11. The left and right wall portions 44 and 45 are disposed so as to be disposed outside the left and right wall portions 13 c and 13 d of the peripheral wall portion 13 through the insertion hole 17 b of the case 11.

  In the area surrounded by the four wall portions 42, 43, 44, and 45 in the cover main body portion 41, an upper door portion 47 and a lower door portion 49 that can be opened on both upper and lower sides are disposed. The upper and lower door portions 47 and 49 break the surrounding break planned portion 51, and the upper door portion 47 opens upward on the rear side with the hinge portion 48 extending in the left-right direction on the upper edge side as the center of rotation. The door portion 49 opens downward on the rear side, with the hinge portion 50 extending in the left-right direction on the lower edge side as the center of rotation.

  As shown in FIGS. 2, 3, 6, 9, and 12, the planned fracture portion 51 is formed with a reduced thickness, and the upper and lower door portions 47 and 49 approach each other at the tip 47 a and 49 a sides. The horizontal line portion 52 disposed on the left and right edges 47b, 47c, 49b, and 49c of the upper and lower door portions 47 and 49, and left extending from the left and right ends of the horizontal line portion 52 in the vertical direction. A vertical line portion 58 and a right vertical line portion 59 are formed so as to be substantially H-shaped when viewed from the rear side.

  In the vehicle-mounted state, the horizontal line portion 52 is disposed on the rear side of the inflator 20 and slightly in the upper position, parallel to the axial direction of the inflator 20. And, when the upper and lower door portions 47 and 49 are fully opened, the horizontal line portion 52 has both left and right ends so that the cover main body portion 41 does not block the opening 12a of the main body portion 12 of the case 11. Along with the right vertical line portions 58 and 59, it is set so as to be disposed slightly outward from the opening 12a of the main body portion 12 of the case 11.

  In addition, as shown in FIGS. 6, 10, and 11, the planned fracture portion 51 is formed with a groove 51 a having a substantially triangular cross section on the front side of the cover body portion 41, as shown in FIGS. The bottom 51b of the concave groove 51a has a curved surface, and a thin portion is disposed with a certain width w, so that the load at break can be adjusted by adjusting the thickness t1 and t2 of the portion. It is configured.

  And the thickness of the horizontal line part 52 is set so that the breakage may be started from the center 52a in the left-right direction at the time of breakage. That is, the horizontal line portion 52 is configured by providing three types of the thick portion 53, the thin portion 55, and the gradual change portion 54 as modes having different thicknesses. The thick portion 53 is a portion where the thickness is increased, the thin portion 55 is a portion that is thinner than the thick portion 53, and the gradual change portion 54 is between the thick portion 55 and the thin portion 55. The thickness is gradually and continuously changed so that the thick portion 53 and the thin portion 55 are connected to the same thickness.

  In the case of the embodiment, the thickness t1 of the thick portion 53 is 0.80 mm, and the thickness t2 of the thin portion 55 is 0.65 mm, which is close to the limit for forming the airbag cover 40 by injection molding. The thickness of the left and right vertical line portions 58 and 59 is set to 0.8 mm, which is the same as the thickness t1 of the thick portion 53.

  In the embodiment, as shown in FIG. 9, the thick wall portion 53 extends in the left and right sides with the rear position 52 b of the gas supply port portion 20 a of the inflator 20 as a base point as the horizontal position in the horizontal line portion 52. And at least the vicinity of the left vertical line portion 58 on the side close to the gas supply port portion 20a. In the case of the embodiment, since the thickness of the left vertical line portion 58 is the same as the thickness t1 of the thick portion 53, and no difference in thickness occurs, the thick portion 53 has the left vertical line portion 58. It arrange | positions so that it may continue.

  The thin portion 55 is disposed with a gradual change portion 54 interposed between the thin portion 55 and the thick portion 53, and the horizontal line portion except for the vicinity of the rear side of the gas supply port portion 20a and the gradual change portion 54. The center 52a in the left-right direction of 52 extends from the left and right sides to the vicinity of the right vertical line 59 on the side away from the gas supply port 20a.

  Further, in the case of the embodiment, the gas supply port portion 20a (in the thick portion 53 to the gradually changing portion 54 between the thick portion 53 and the thin portion 55 (specifically, the thick portion 53 side in the gradually changing portion 54)). Specifically, it is the center position in the left-right direction in the axial direction of the small-diameter portion 21c in which the plurality of gas discharge ports 21d are arranged, and includes the side wall portion 22d of the diffuser 22 and the end surface of the general portion 21a on the small-diameter portion 21c side. The length dimension L1 in the left-right direction up to the rear position 52b, the length dimension L3 in the left-right direction of the gradually changing portion 54 between the thick portion 53 and the thin portion 55, and the thickness The length in the left-right direction of the thin portion 55 from the gradually changing portion 54 between the meat portion 53 and the thin portion 55 (specifically, the thin portion 55 side of the gradually changing portion 54) to the horizontal center 52a of the horizontal line portion 52. The dimension L2 is approximately in a ratio of 2: 1: 1 (details If the value of “2” of the dimension L1 is used as a reference, L1: L3: L2 is a ratio of 2: (0.8 to 1.2) :( 0.8 to 1.2)). Has been.

  In the case of the embodiment, the length dimension L1 is 42 mm, the length dimension L2 is 25 mm, and the length dimension L3 is 20 mm. The length L0 of the horizontal line portion 52 in the left-right direction is 254 mm, the length L4 in the left-right direction of the thick portion 53 is 82 mm, and the length L5 of the thin portion 55 in the left-right direction. Is 137 mm.

  In the case of the embodiment, since the thickness of the right vertical line portion 59 is set to 0.8 mm, which is the same as the thickness t1 of the thick portion 53, the horizontal line portion 52 is located on the right end side of the thin portion 55. 56, the thin portion 55 is connected to the left vertical line portion 59. The adjusting portion 56 includes a gradually changing portion 56a on the thin portion 55 side in which the length dimension L6 in the left-right direction is 10 mm, and a thick portion 56b on the left vertical line portion 59 side in which the length dimension L7 in the left-right direction is 5 mm. , Is composed of. The thickness of the thick part 56b is set to 0.8 mm, which is the same as the thickness of the left vertical line part 59. Similar to the gradual change portion 54, the gradual change portion 56a gradually and continuously changes the thickness between the thick portion 56b and the thin portion 55, and with respect to the thick portion 56b and the thin portion 55, The wall thickness is matched and connected.

  Further, as shown in FIGS. 2, 4, and 5, the panel portion 63 of the airbag cover 40 is inserted into a locking hole 17 c provided in the panel portion 17 of the case 11 and locked to the peripheral edge. And a predetermined number of guide legs 65 to be inserted into the insertion holes 17d of the panel portion 17 are formed. Further, the panel portion 63 is configured such that when the locking leg 64 is formed on the periphery of the locking hole 17 c of the panel portion 17 of the case 11, the movement of the panel portion 63 to the front side is restricted. An abutment support portion 66 that abuts on the disc 17 is disposed at a predetermined position.

  The operation of mounting the knee protection airbag device S of the embodiment on a vehicle will be described. First, as described above (see FIGS. 7 and 8), the inflator 20 is accommodated in the airbag 25, and the airbag 25 is then stored. The downstream portion 32 is folded substantially symmetrically to form a folded body 36 and wrapped with a wrapping material 38.

  Thereafter, each bolt 22c of the inflator 20 is protruded from the insertion hole 15a, and the connector part 21b of the inflator body 21 is protruded from the insertion hole 13e so that the inflator 20 is folded into the case 11 together with the folded airbag 25. If the nut 23 is fastened to each bolt 22c from the front side of the bottom wall portion 15, the inflator 20 and the airbag 25 can be stored in the case 11 and attached to the case 11.

  Next, the airbag cover 40 is assembled to the case 11. The assembly of the airbag cover 40 to the case 11 is carried out by attaching the respective wall portions 42, 43, 49, 49 of the airbag cover 40 to the case peripheral wall portion 13 on the opening 12a side on the cover body 41 side. The locking protrusion 14 is inserted into the locking holes 42a and 43a of the upper and lower connecting wall portions 42 and 43, and is locked to the upper and lower connecting wall portions 42 and 43. Further, on the panel part 63 side, each guide leg 65 is inserted into the insertion hole 17d of the panel part 17 of the case 11, and each locking leg 64 is inserted into the locking hole 17c of the case panel part 17. If the airbag cover 40 is locked to the periphery, the airbag cover 40 can be connected and held to the case 11 and the knee protection airbag apparatus S can be assembled.

  A lead wire (not shown) extending from the airbag operating circuit is connected to the connector portion 21b of the main body 21 of the inflator 20, and a predetermined mounting portion 18 of the panel portion 17 of the case 11 is connected to the body using the bolt 3. If it fixes to the 1 side, the airbag apparatus S for knee protection can be mounted in a vehicle. In addition, the member shown with the code | symbol 9 of FIG.3, 4 and 5 is an undercover attached to a vehicle after the airbag apparatus S is mounted in the vehicle.

  When the operation signal is input to the main body 21 of the inflator 20 after the knee protection airbag device S is mounted on the vehicle, the inflation gas G is discharged from the gas discharge port 21d of the inflator 20, and the inflation gas. G flows from the gas supply port 20a of the inflator 20 to the rear side and is supplied into the airbag 25. Then, the airbag 25 is inflated to break the wrapping material 38 and push the upper and lower door portions 47 and 49 of the airbag cover 40 to break the planned break portion 51, so that the upper and lower door portions 47 are broken.・ Open 49 on both sides. As shown by the two-dot chain line in FIGS. 1 and 3 and the solid line in FIG. 13, the airbag 25 moves from the opening 12 a of the case 11 and the opening 61 of the upper and lower door portions 47 and 49 to the vehicle rear side. It expands and expands so that it protrudes and largely protrudes upward along the rear surface of the lid 7a of the grab box 7, and the expansion is completed. Therefore, even if the occupant M seated in the passenger seat moves forward, the inflated airbag 25 can accurately protect the knee K.

  In the embodiment, when the inflation gas G is supplied from the gas supply port portion 20a of the inflator 20 toward the rear side to the upstream portion 31 of the airbag 25 at the time of operation, the airbag 25 is The upstream portion 31 is pushed rearward so that the downstream portion 32 in the folded state protrudes from the opening 12a of the case 11, and the horizontal line portion 52 of the planned break portion 51 of the airbag cover 40 is broken. Try to let them.

  At the initial stage of supply of the expansion gas G, as shown in FIG. 6, the portion 31a of the upstream portion 31 at the position where the gas supply port portion 20a is arranged is most strongly pushed backward, and the gas supply port portion 20a As it moves away from the left and right direction, the upstream side portion 31 slightly reduces the pressing force toward the rear side.

  However, in the horizontal line portion 52 of the planned fracture portion 51, as shown in FIG. 9, the rear side of the gas supply port portion 20a has a thickness extending from the rear position 52b of the gas supply port portion 20a to the left and right sides. Since the meat part 53 is disposed, elongation occurs, but breakage at the thick part 53 is suppressed. A thin portion 55 is disposed at the center 52 a in the left-right direction of the horizontal line portion 52 so as to be adjacent to the thick portion 53 with the gradually changing portion 54 interposed therebetween. Further, the expansion gas G flowing from the vicinity of the gas supply port portion 20a is supplied, and the upstream portion 31b of the rear upstream portion 31 near the center 52a in the left-right direction of the horizontal line portion 52 (see FIG. 6) also applies a force that pushes the downstream portion 32 backward, so that the portion of the thin portion 55 near the center 52a in the left-right direction of the horizontal line portion 52 as shown in FIGS. However, the rupture starts and propagates to both the right and left sides. As a result, the entire portion of the horizontal line portion 52 of the planned rupture portion 51 breaks, as shown in FIGS. In addition, the left and right vertical line portions 58 and 59 are broken and the airbag cover Over 40, and an upper door portion 47 and a lower door portion 49, while suppressing the lateral direction of the variation can be opened on both upper and lower sides.

  At the same time, the downstream portion 32 of the airbag 25 that has been folded in a substantially bilaterally symmetrical manner from the openings 61 in which the upper and lower door portions 47 and 49 are opened on both the upper and lower sides protrudes substantially symmetrically on the left and right sides. Therefore, the inflation is completed in such a manner that the knee K of the occupant M can be protected.

  In addition, since the horizontal line part 52 of the planned breakage part 51 connects the thin part 55 and the thick part 53 with the gradual change part 54 interposed, the thick part 53 and the end part of the thin part 55 are connected. Further, stress concentration is not caused, and the thin wall portion 55 itself is disposed so as to extend to the left and right sides starting from the horizontal center 52a of the horizontal line portion 55, so that it is separated from the gradual change portion 54. Breaking can be started stably in the vicinity of the center 52a in the left-right direction of the horizontal line portion 52, which is the region of the thin-walled portion 55.

  Therefore, in the knee protection airbag device S of the embodiment, even if the gas supply port portion 20a of the inflator 20 is arranged to be shifted to the left side that is one side of the opening 12a of the case 11 in the left-right direction, The upper and lower door portions 47 and 49 of the airbag cover 40 can be smoothly opened so as to open evenly on both the upper and lower sides from the vicinity of the center 52a in the left and right direction to the left and right sides while suppressing variation in the left and right direction. .

  And in embodiment, the length dimension L1 of the left-right direction from the gradual change part 54 between the thick part 53 and the thin part 55 to the back position 52b of the gas supply port part 20a in the thick part 53, and thick wall The lateral length L3 of the gradual change portion 54 between the portion 53 and the thin portion 55, and the horizontal center 52a of the horizontal line portion 52 from the gradual change portion 54 between the thick portion 53 and the thin portion 55. The length L2 in the left-right direction of the thin wall portion 55 is disposed at a ratio of approximately 2: 1: 1.

  Therefore, in the horizontal line part 52, the thick part 53 occupies a substantially 1/2 long area in the area between the rear position 52b of the gas discharge port part 20a and the center 52a in the horizontal direction of the horizontal line part 52. In addition, the breakage immediately after the supply of the expansion gas G can be easily suppressed, and the gradually changing portion 54 and the thin-walled portion 55 occupy approximately half in the remaining half of the region. It is possible to easily suppress the occurrence of concentration, and to easily secure a mode of breaking from the portion of the thin portion 55 in the vicinity of the horizontal center 52a of the horizontal line portion 52.

  If the ratio is as described above, the rear position 52b of the gas discharge port portion 20a is based on the two positions of the rear position 52b of the gas discharge port portion 20a and the center 52a of the horizontal line portion 52 in the left-right direction. The positions and length dimensions L1, L2, and L3 of the thick portion 53, the thin portion 55, and the gradually changing portion 54 can be easily set between the horizontal line portion 52 and the center 52a in the left-right direction. Even if the arrangement position of the gas supply port portion 20a of the inflator 20 is changed with respect to the arrangement of the horizontal line portion 52 of the airbag cover 40 due to the design change of the case 11 or the like, it is easily dealt with. be able to.

  In the region between the rear position 52b of the gas discharge port portion 20a and the horizontal center 52a of the horizontal line portion 52 (referred to as a side-by-side region), the length dimension L1 of the thick portion 53 is the side-by-side region. If it is too smaller than 1/2 of the length dimension, the starting point of the breakage is likely to be greatly shifted from the vicinity of the center 52a in the left-right direction of the horizontal line portion 52 to the gas supply port portion 20a side. If the length dimension L1 is too larger than ½ of the length dimension of the juxtaposed region, a situation in which the length dimension L3 of the gradual change portion 54 is reduced is caused, and the boundary portion between the gradual change portion 54 and the thin portion 55 is caused. To the region of the thin portion 55, the breakage of the thick portion 54 is delayed, and the horizontal line portion 52 is difficult to break in a balanced manner on the left and right.

  Further, in the juxtaposed region, if the length dimension L3 of the gradually changing portion 54 is too longer than the length dimension L2 of the thin portion 55, the starting point of the break start at the horizontal line portion 52 is from the center 52a to the gas supply port portion. If the length dimension L3 of the gradually changing portion 54 is too shorter than the length dimension L2 of the thin-walled portion 55, the starting point of the break start at the horizontal line portion 52 is It becomes easy to shift | deviate from the center 52a to the side which approaches the gas supply port part 20a.

  In the embodiment, the length dimension L3 in the left-right direction of the gradual change portion 54 between the thick portion 53 and the thin portion 55 is set as 20 mm that secures a minimum of 10 mm or more. That is, since the length L3 is not less than 10 mm, the thick portion 53 and the thin portion 55 are made as thin as possible within the moldable range, and the thickness of the thick portion 53 and the thin portion 55 is as large as possible. In order to clarify the difference between the thick part 53 and the thick part 53, the thickness of the thick part is 0.80 mm, the thickness of the thin part is 0.65 mm, and the thickness difference is 0.15 mm. The start of breakage due to stress concentration at the end of the thin portion 55 can be stably prevented.

  In the embodiment, the adjusting portion 56 is provided with a gradual change portion 56a of 10 mm, and the vicinity of the adjusting portion 56 is set so that stress concentration hardly occurs.

  Moreover, if the length dimension of the gradual change parts 54 and 56a is too long so that it may exceed 30 mm, the area which provides the thick part 53 and the thin part 55 will become too narrow, and the horizontal center 52a of the horizontal line part 52 will become small. It becomes difficult to ensure the start of breakage in the vicinity. Therefore, it is desirable that the length dimension of the gradually changing portions 54 and 56a is 10 to 30 mm.

  Further, the difference in thickness between the thick portion 53 and the thin portion 55 can secure the moldable thickness of the thin portion 55, and the rupture load between the thin portion 55 and the thick portion 53 can be made different. It is desirable to set it as 0.15-0.3 mm. If it is less than 0.15 mm, it becomes difficult to provide a difference in breaking load between the thin portion 55 and the thick portion 53, and if it exceeds 0.3 mm, the length of the gradually changing portion 54 needs to be increased more than necessary. Because it ends up.

  Further, in the embodiment, the gas supply port portion 20a of the inflator 20 has a wall portion 13c that is approximately 1/6 of the width dimension LC (substantially equal to the width dimension L0) of the opening 12a of the case body 12 in the left-right direction. Although it is shown that the distance is 1/3 to 1/12 of the width dimension LC of the opening 12a (preferably 1/4 to 1/8), from the left and right wall portions 13c and 13d. The present invention can be favorably implemented when separated. This is because if the gas supply port 20a is disposed away from the one wall portion 13c / 13d by more than 1/3 of the width dimension LC of the opening 12a, the gas supply port 20a can be connected to the opening 12a. It is arranged near the center in the left-right direction (near the center 52a of the horizontal line portion 52), and there is little significance in providing the thick portion 53, the gradually changing portion 54, and the thin portion 55 on the horizontal line portion 52 of the planned fracture portion 51. On the contrary, if the gas supply port 20a is arranged away from the one wall portions 13c and 13d by less than or equal to 1/12 of the width dimension LC of the opening 12a, the gas supply port portion 20a is arranged so as to be too close to one of the wall portions 13c and 13d in the left-right direction, so that the horizontal line portion 52 can be obtained only by adjusting the thickness of the horizontal line portion 52 provided with the thick portion 53 and the thin portion 55. Start of break from around the center 52a This is because it is difficult to ensure.

  Further, as a molding material of the airbag cover 40 having the above-described configuration, an accurate breakage portion 51 in the cover main body portion 41 can be obtained even at a low temperature or a high temperature in a vehicle-mounted state where the airbag cover 40 is used. In order to ensure breakage and smooth bending deformation at the hinge (integral hinge) portions 48 and 50, an olefin-based or styrene-based thermoplastic elastomer can be preferably used.

It is the schematic perspective view seen from the back side which shows the vehicle mounting state of the airbag apparatus for knee protection of one embodiment in the present invention. It is a schematic front view of the airbag apparatus for knee protection of the embodiment. It is a schematic longitudinal cross-sectional view of the airbag apparatus for knee protection of the embodiment, and respond | corresponds to the III-III site | part of FIG. It is a schematic longitudinal cross-sectional view of the airbag apparatus for knee protection of the embodiment, and respond | corresponds to the IV-IV site | part of FIG. It is a schematic longitudinal cross-sectional view of the airbag apparatus for knee protection of the embodiment, and respond | corresponds to the VV site | part of FIG. It is a schematic cross-sectional view of the airbag apparatus for knee protection of the embodiment, and corresponds to the VI-VI part of FIG. It is a figure explaining the folding process of the airbag used for the airbag apparatus for knee protection of the embodiment in order. It is a figure explaining the lapping process after folding the airbag used for the airbag apparatus for knee protection of the embodiment in order. FIG. 3 is a diagram illustrating a positional relationship between the airbag cover and the inflator according to the embodiment, as viewed from the rear side when the knee protection airbag device is mounted on the vehicle. It is a general | schematic fragmentary longitudinal cross-section of the thick part of the horizontal line part in the fracture | rupture plan part of the airbag cover of the embodiment. It is a general | schematic fragmentary longitudinal cross-section of the thin part of the horizontal line part in the fracture | rupture scheduled part of the airbag cover of the embodiment. It is a figure explaining the open state of the upper / lower door part of an airbag cover at the time of the action | operation of the airbag apparatus for knee protection of the embodiment. It is a schematic longitudinal cross-sectional view which shows the state at the time of the completion | finish of operation | movement of the airbag apparatus for knee protection of the embodiment.

Explanation of symbols

11 ... Case,
12a ... opening,
20 ... Inflator,
20a ... Gas supply port,
25 ... Airbag,
31 ... upstream part,
32 ... downstream part,
40 ... Airbag cover,
47 ... Upper door,
49 ... Lower door,
51 ... planned fracture part,
52 ... Horizontal line part,
53 ... Thick part,
54. Gradual change part,
55 ... Thin part,
58 ... Left vertical line,
59 ... right vertical line,
G ... expansion gas,
M ... Crew,
K (KL / KR) ... Knee,
S: Air bag device for knee protection.

Claims (3)

An airbag that inflates the occupant's knees in a protective manner, an inflator that supplies inflation gas to the airbag, and a case in which the folded airbag and the inflator are stored and held, and the vehicle rear side is opened. And an airbag cover that covers the opening of the case so as to be openable when the airbag is inflated, and is attached to the case, and is mounted on the front side of the seated occupant's knees,
The airbag cover is made of synthetic resin, and includes an upper door portion and a lower door portion that are opened when the airbag is inflated by breaking the surrounding planned break portion and opening on both upper and lower sides.
The breakable portion is formed with a reduced thickness, and the horizontal line portion disposed on the front end side of the upper and lower door portions, and the left and right edge sides of the upper and lower door portions, respectively. The left vertical line part and the right vertical line part extending from the left and right ends of the horizontal line part to both sides in the vertical direction are formed in a substantially H shape when viewed from the rear side,
The portion of the airbag that is housed in the case when the inflation is completed is the upstream portion of the inflation gas, and the portion that protrudes rearward from the opening of the case when the inflation is completed is the downstream portion of the inflation gas. As described above, the downstream part is folded in a substantially bilaterally symmetrical shape, and is configured to be housed in the case together with the upstream part.
The inflator has a gas supply port portion that supplies inflation gas to the rear side toward the rear side, on one side in the left-right direction of the opening of the case as viewed from the rear side in the upstream portion of the airbag. An air bag device for knee protection configured to be offset and disposed,
The horizontal line portion in the planned break portion of the airbag cover is
To start rupture starting from the center of the horizontal line portion in the left-right direction at the time of rupture,
A thick portion that increases the thickness, a thin portion that is thinner than the thick portion, and a thickness that is gradually and continuously changed between the thick portion and the thin portion. And a gradual change portion that is continuous with the thickness corresponding to the thin portion and the thin portion,
The thick wall portion is disposed so as to extend to the left and right sides with respect to the rear position of the gas supply port portion as a position in the left-right direction, and at least the vertical line portion on the side close to the gas supply port portion To the vicinity,
The thin-walled portion is disposed with the gradually changing portion interposed between the thin-walled portion and the left and right sides of the horizontal line portion except for the vicinity of the rear side of the gas supply port portion and the gradually changing portion. A knee protecting airbag device, wherein the airbag device extends from the center of the direction to the left and right sides and extends to the vicinity of the vertical line portion on the side away from the gas supply port portion. A length dimension in the left-right direction from the thick-walled portion side in the gradually changing portion between the thick-walled portion and the thin-walled portion to a rear position of the gas supply port portion in the thick-walled portion, and the thick-walled portion The length dimension in the left-right direction of the gradually changing portion between the thin-walled portion and the thin-walled portion side of the gradually changing portion between the thick-walled portion and the thin-walled portion in the left-right direction of the horizontal line portion. 2. The knee protection airbag device according to claim 1, wherein a length dimension in a left-right direction of the thin portion to the center is arranged at a ratio of approximately 2: 1: 1.   The knee according to claim 1 or 2, wherein a length dimension in a left-right direction of the gradually changing portion between the thick portion and the thin portion is set as 10 to 30 mm. Protective airbag device.

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