JP2009083550A - Knee protective airbag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a knee protective air bag for enabling a knee restricting part swelling in a substantially columnar shape for receiving knees to precisely receive both right-left knees. <P>SOLUTION: This knee protective airbag 40 has first and second tethers for connecting a knee side wall part 41 and a vehicle body side wall part 42. The first tether 51 partitions an upper end expansion chamber 44 and a lower side expansion chamber 49 for completing the expansion in the substantially columnar shape of extending in the lateral direction. The second tether 52 connects the front end 52a to the vehicle body side wall part 42 by matching with the front end 51a of the first tether, and connects the rear end 52b to the upper-lower intermediate vicinity and the central vicinity in the lateral direction up to a connecting part with the rear end 51b of the first tether from the upper edge 41a of the knee side wall part on the rear surface 44a side of the upper end expansion chamber. The second tether 52 restrains backward projection of the connecting part 41c so that the center in at least the lateral direction is dislocated to the front side in a rear surface side top part 44b of the upper end expansion chamber 44 of completing the expansion without arranging the second tether. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a knee protection airbag used in an airbag device for protecting a knee of a passenger such as a seated driver or a passenger on a passenger seat at the time of a vehicle collision.

  Conventionally, the knee protection airbag has the same outer shape so that the airbag can be inflated in a plate shape so that the airbag can be placed in the gap between the knee and the vehicle body side member on the front side of the passenger's knee. As a flat bag type that connects the outer peripheral edges of the knee side wall and the vehicle body side wall, a tether that regulates the separation distance between the knee side wall and the vehicle side wall is further disposed (see, for example, Patent Document 1). .

  Further, the conventional knee protection airbag has a small volume as a base fabric for an airbag constituting an outer peripheral wall with a volume reduced to 15 to 20 L so that it can be disposed in a narrow gap between the knee and the vehicle body side member. A coated cloth in which a coating layer made of silicon rubber or the like is provided on the woven cloth so as to prevent the inflation gas from escaping from the bag has been used.

Furthermore, in the conventional knee protection airbag, when receiving the knee, a tether is disposed in the vicinity of the contact portion with the shin so as not to press the shin portion below the knee as much as possible. It was. Furthermore, if the tether is only at one location, the portion in the vicinity of the case that protrudes from the case will newly swell so as to press the shin, so that the second tether is further provided below the tether. The tether is arranged, and the upper and lower two-stage tethers that are substantially parallel to each other are arranged in the entire airbag.
JP 2006-131186 A

  However, in the conventional knee protection airbag, tethers are provided in two upper and lower stages, and the thickness of the contact portion of the shin is reduced. Since the airbag has a reduced thickness, the overall volume of the airbag is reduced, and if the volume is reduced, when the inflation gas is released, the internal pressure decreases rapidly. In order to prevent the decrease, a coating layer for preventing escape of the expansion gas was provided.

  In other words, the conventional knee protection airbag has a structure in which two upper and lower tethers that are parallel to each other are provided so as to be able to receive the knee while suppressing unnecessary pressure on the shin, and is configured to inflate into a plate shape. In order to prevent a sudden drop in internal pressure due to the use of a coated fabric with a coating layer as the airbag fabric to be used, the production man-hour and cost of the airbag has been increased. Therefore, there has been a demand for manufacturing an airbag from a woven cloth of a non-coated cloth having a reduced number of steps and having no coating layer.

  Therefore, the present inventor makes it possible to receive the knee as much as possible without inflating into a plate shape or preventing gas leakage and pressing the shin as a configuration of the airbag that receives the knee. For this purpose, it is desirable to make the knee restraint that catches the knee itself as thick and wide as possible. As a result, it is possible to catch the entire front surface of both knees from the vicinity of the upper ends of both left and right shins. We focused on a configuration in which a large constraining area is arranged on the rear surface side and is swelled in a substantially cylindrical shape. In other words, if the knee restraint that catches the knee is inflated thickly in a substantially cylindrical shape, the knee restraint strongly presses the shin even if a slight gas leak occurs when the knee restraint catches the upper end of the knee or shin. This is because the knee restraint part itself can receive only the vicinity of the upper end of the shin and the knee itself before absorbing the kinetic energy of the occupant sufficiently moving forward, thereby suppressing the occupant's forward movement.

  However, when the knee restraint part is inflated thickly in a substantially columnar shape, when the airbag is inflated, an inflated part that does not contact the knee itself in the knee restraint part enters between the left and right knees, There are cases where both knees are pushed outward and the knees hit the knee restraint portion without facing each other, and in that case, the kinetic energy of the occupant moving forward cannot be absorbed accurately.

  An object of the present invention is to solve the above-described problem, and to provide a knee protection airbag in which a knee restraint portion that swells in a substantially columnar shape to receive a knee can accurately receive both left and right knees. To do.

The knee protection airbag according to the present invention is disposed under the front side of the seated occupant's knee, and is folded and stored in a case having a protruding opening that opens toward the rear side.
When inflating gas flows in, it expands and expands so as to extend upward while projecting rearward from the projecting opening, and a knee restraining part capable of receiving both the left and right knees is arranged on the front side of the knee. ,
A vehicle body side wall portion arranged on the front side of the knee side wall portion so that the outer peripheral wall at the completion of the expansion is arranged on the knee side and the knee side wall portion is connected to the outer peripheral edge of the knee side wall portion so as to face the knee side wall portion; , Configured as a flat bag type with the same outer shape,
Knee protection constructed by connecting a knee side wall part and a vehicle body side wall part to dispose a tether that regulates the thickness along the opposing direction of the knee side wall part and the vehicle body side wall part when expansion is completed. An airbag,
A knee restraint area is formed at the upper end of the airbag when inflation is completed, and a restraint area that can receive the entire front of the left and right knees from the vicinity of the upper end of both left and right shins is placed on the rear side, An upper end expansion chamber for completing expansion in a substantially columnar shape extending to
A first tether is disposed immediately below the upper end expansion chamber, and the first tether
The upper expansion chamber is disposed along the left and right direction of the vehicle so as to partition the upper expansion chamber and the lower expansion chamber that expands immediately below the upper expansion chamber when the expansion gas flows in. For a partition that is provided with a plurality of gas flow holes for disposing the main flow of the expansion gas flowing from the lower expansion chamber to the upper expansion chamber on the left and right sides so as to expand toward the center in the left-right direction. Configured as a tether, and
A second tether is disposed in the upper end expansion chamber so as to be connected to a connection portion to the vehicle body side wall portion on the front end side of the first tether and a knee side wall portion on the rear surface side of the upper end expansion chamber. Tether
The knee side wall portion on the rear surface side of the upper end expansion chamber is arranged such that at least the center in the left-right direction at the apex on the rear surface side of the upper end expansion chamber that has been expanded without providing the second tether is shifted to the front side. Connected in the vicinity of the middle in the vertical direction from the upper edge to the connection portion with the rear end of the first tether, and at least near the center in the horizontal direction,
It is arrange | positioned as a protrusion suppression tether which suppresses the protrusion to the back of the connection part connected with the rear surface side of an upper end expansion chamber.

  In the knee protection airbag according to the present invention, when the inflation is completed, the upper end inflation chamber as the knee restraint portion completes the inflation in a substantially columnar shape, and from the vicinity of the upper ends of the left and right shins of the occupant in the restraint area on the rear surface side. It is compressed while receiving the entire area of the front surfaces of both knees, avoiding the state of pressing the shin, and trying to absorb the kinetic energy of the occupant moving forward.

  At that time, the second tether as the protrusion restraining tether shifts at least the center in the left-right direction at the top projecting rearward on the rear surface side of the upper end expansion chamber which has been expanded without providing the second tether. In addition, the rear end side, near the middle in the vertical direction from the upper edge of the knee side wall portion on the rear surface side of the upper end expansion chamber to the connection portion with the rear end of the first tether, and at least near the center in the left-right direction, It is connected. For this reason, the central part in the left-right direction on the rear surface side of the upper end expansion chamber serving as the knee restraint portion is pulled to the front side by the second tether so that it does not easily enter between the left and right knees. The entire area of the front surface and the vicinity of the upper end of the shin are not displaced to the left and right sides, but are received in the restraining area in front of them in a state of facing each other.

  In the second tether, the rear end side is near the middle in the vertical direction from the upper edge of the knee side wall portion on the rear surface side of the upper end expansion chamber to the rear end of the first tether, and at least in the left-right direction. The front end side is connected to the side wall of the vehicle body at the same position as the front end of the first tether. Therefore, the upper end expansion chamber is an outer peripheral wall having a longitudinal cross section in the front-rear direction, from the connection portion of the vehicle body side wall portion at the front end of the first tether to the mutual upper edge of the vehicle body side wall portion and the knee side wall portion, From the upper edge of the side wall part to the connecting part to the knee side wall part at the rear end of the second tether, the thickness in the front-rear direction can be increased to expand greatly, and it expands into a substantially cylindrical shape, reducing the cushion effect Without stopping, the knee and the upper end of the shin can be received.

  Therefore, in the knee protection airbag according to the present invention, the knee restraint portion that swells in a substantially columnar shape to receive the knee does not push outward, and the cushion effect is maintained and the right and left knees are accurately received. Can do.

  If the airbag is a sewing bag, the front ends of the first tether and the second tether coincide with each other, and the front ends of the first tether and the second tether are sewn together and connected to the side wall of the vehicle body. Even if the knee protection airbag has the two-stage tether of the first and second tethers, the manufacturing process of the airbag can be simplified as much as possible.

  Further, the upper end expansion chamber expands in a substantially cylindrical shape and increases the thickness in the front-rear direction, but the gas flow hole arranged in the portion where the first tether is disposed extends from the lower expansion chamber to the upper end expansion chamber. The main flow of the inflating gas flowing in is arranged on both the left and right sides, and when the inflating gas flows in, the upper end expansion chamber swells in order from the left and right sides to the center in the left-right direction. That is, at the initial stage of inflation of the airbag, the upper end expansion chamber is deployed to the position of the upper end when the airbag has been completely inflated. In order to complete the expansion by increasing the thickness from the left and right sides to the center side, the front surfaces of both knees can be suitably received from the upper ends of both shins.

  If the second tether does not disturb the main flow of the right and left expansion gases flowing from the lower expansion chamber to the upper expansion chamber, the second tether not only near the center of the upper expansion chamber but also in the horizontal direction. You may arrange | position so that it may extend in a strip shape on both sides.

  The lower expansion chamber is provided with a mounting portion attached to the case at a portion of the side wall of the vehicle body so that the upper end expansion chamber can be supported from below when the inflation of the airbag is completed. It is desirable that the upper end side be separated from the case backward. With such a configuration, the airbag can be configured as two upper and lower chambers of an upper end inflating portion and a lower inflating chamber, and is larger than an airbag having a larger volume having three or more expansion chambers. In addition, it can be configured compactly, and manufacturing man-hours and costs can be reduced. In addition, the lower expansion chamber can detach the connecting portion to the vehicle body side wall on the front end side of the first and second tethers from the case when the expansion is completed. The restraint area on the rear surface side of the chamber can be accurately arranged from the upper end of the shin to the front position of the front surface of the knee.

In addition, the upper end expansion chamber is set so that the outer diameter at the completion of the expansion is in the range of 150 to 220 mm,
It is desirable that the second tether is set so that the rear surface side of the upper end expansion chamber that has been expanded without providing the second tether is partially shifted to the front side by 5 to 40 mm.

  In such a configuration, in the portion where the second tether is not disposed, the upper-end expansion chamber can secure an outer diameter dimension (thickness dimension in the front-rear direction) of 150 mm or more, and the knee side wall portion becomes the vehicle body side wall portion. The upper end of the knee or shin can be received without incurring a bottoming contact. Conversely, the upper end expansion chamber does not have an outer diameter exceeding 220 mm when expansion is completed, so even if the gap between the knee and the vehicle body side member (column cover, instrument panel, grab box, etc.) is narrow, It can smoothly enter the gap and swell, and even if the inflation is completed, the upper end of the knee or shin is not pushed back strongly.

  When the partial moving distance of the restraint area to the front side by providing the second tether is less than 5 mm, there is no significance in providing the second tether, and when it exceeds 40 mm, the second tether in the upper end inflating portion The vicinity of the connection part to the knee side wall on the rear end side is recessed in a wide area on the front side, and the part in contact with the front surface of the knee in the restraint area moves forward and is below the connection part. Swells so as to extend obliquely rearward and downward. Therefore, the rear surface of the region that receives the front surface of the knee itself moves to the front side and swells so as to extend obliquely downward and downward below the knee, in cooperation with the rear surface of the lower expansion chamber, As a result, it is easier to press the shin, and as a result, a situation in which the advantage of the configuration in which the knee restraint portion is substantially cylindrical so as to avoid the pressing state of the shin and receive the upper end of the knee and the shin is hindered. Easy and undesirable.

In the case of the above configuration, since the outer diameter of the upper end inflating portion is large, the airbag base fabric to be used may have some gas leakage even if it is not a coated fabric provided with a coating layer that does not cause gas leakage. Can be used. However, when the air permeability (Fragile method) exceeds 0.6 L / cm ² / min, if the upper end expansion chamber has a small volume with an outer diameter dimension (thickness dimension in the front-rear direction) of about 150 mm, gas leakage When the upper end of the knee or shin is received in the upper end expansion chamber as a knee restraint, it becomes difficult to ensure the effect of reducing the kinetic energy of the occupant. Is preferably 0.6 L / cm ² / min or less.

  And in this case, as an airbag base fabric that forms the knee side wall and the vehicle body side wall, it may be manufactured from a coated fabric provided with a coating layer made of silicon rubber or the like for preventing gas leakage on the woven fabric, If manufactured from a non-coated woven fabric without a coating layer, the manufacturing cost of the airbag can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. A knee protection airbag 40 according to an embodiment (hereinafter simply referred to as an airbag unless otherwise specified) is used in a knee protection airbag device S. As shown in FIGS. 1 and 4, this knee protecting airbag device S is a steering column on the front side of the vehicle of the driver MD so as to protect the knee K of the driver MD as an occupant. 9 is disposed below.

  As shown in FIG. 1, the steering column 9 includes a column main body 10 connected to the steering wheel 8 and a column cover 13 disposed so as to cover the column main body 10 below the steering wheel 8. ing. The column main body 10 includes a main shaft 11 and a column tube 12 that covers the periphery of the main shaft 11. The column cover 13 is made of a synthetic resin having a substantially rectangular tube shape, covers the column main body 10, and an instrument panel. (Hereinafter abbreviated as “instrument panel”) 14 protrudes backward (see FIG. 4).

  1 to 3, the knee protection airbag device S includes a folded airbag 40, an inflator 28 for supplying the inflation gas G to the airbag 40, the folded airbag 40 and the inflator 28. And a case 17 having an opening on the vehicle rear side, and an airbag cover 21 covering the vehicle rear side of the opening 18a in the case 17 is configured.

  In the present specification, unless otherwise specified, the vertical, front-rear, left-right directions are based on the state in which the knee protection airbag device S is mounted on the vehicle, and , Which coincides with the left and right directions.

  As shown in FIGS. 2 and 3, the case 17 is made of sheet metal and is disposed on the lower side of the steering column 9 (see FIG. 1). The case 17 is configured as a storage portion for storing the folded airbag 40. The box-shaped main body 18 and the panel 19 (see FIG. 4) extending outward from the main body 18 are configured. The main body portion 18 has a substantially rectangular tube shape with a bottom, and includes a substantially rectangular opening 18a on the vehicle rear side. A plurality of hooks 18 b and 18 c for assembling upper and lower connecting wall portions 25 and 26 (to be described later) of the airbag cover 21 to the case 17 are disposed on the upper and lower outer surface sides of the main body portion 18. The hooks 18b and 18c are inserted into the locking holes 25a and 26a of the connecting wall portions 25 and 26 in the airbag cover 21 to lock the peripheral edges of the locking holes 25a and 26a.

  In addition, two attachment holes 18d through which the attachment bolts 31 of the inflator 28 are inserted are formed in a portion of the bottom wall away from the opening 18a of the main body portion 18. Furthermore, an insertion hole 18e through which an end of the inflator 28 on the connector 33 side of the main body 29 (described later) of the inflator 28 can be inserted is formed in the wall portion on the right side of the main body 18 (see FIG. 3).

  The panel portion 19 is formed so as to surround the periphery of the opening 18a in the body portion 18 of the case 17, and the case 17 is placed on the body 1 side at five locations on the outer peripheral edge of the panel portion 19 as shown in FIG. In order to connect and fix, brackets 4, 5, 6, and 7 extending from the instrument panel reinforcement 2 and the like on the body 1 side are connected. Further, as shown in FIG. 2, an insertion hole 19 a through which the connecting wall portion 25 of the airbag cover 21 is inserted is formed above the main body portion 18 in the panel portion 19.

  The airbag cover 21 is formed of a thermoplastic elastomer such as olefin, and is configured to cover the vehicle rear side of the case 17 and is assembled to the case 17. The airbag cover 21 is disposed on the lower panel 14b side of the instrument panel 14 including the upper panel 14a and the lower panel 14b (see FIGS. 2 and 4). In the airbag cover 21, near the opening 18 a of the case 17, two door portions 23 that are opened on both the upper and lower sides are disposed around the hinge portion 23 a formed of an integral hinge. These door portions 23 are arranged around a thin portion to be broken 22 arranged in a substantially H shape when viewed from the rear. Around the door parts 23, 23, cover wall parts 24, 24 and connection wall parts 25, 26 extending forward so as to surround the main body part 18 of the case 17 are disposed (see FIGS. 3 and 2). . The cover wall portion 24 is disposed so as to cover both the left and right sides of the main body portion 18, and the connection wall portions 25 and 26 are disposed so as to cover the upper and lower sides of the main body portion 18. As described above, a plurality of hooks 18b and 18c respectively disposed above and below the main body portion 18 are inserted into the connecting wall portions 25 and 26, and the locking holes 25a and 26a are locked at the periphery. Is arranged.

  As shown in FIGS. 2 and 3, the inflator 28 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 29 and a diffuser 30. . A plurality of gas discharge ports 29 a are arranged on one end side (left end side in the case of the embodiment) of the main body 29. The connector 33 connected to the operation signal input lead wire 34 is connected to the other end side (right end side) of the main body 29. The diffuser 30 is made of a substantially cylindrical sheet metal that can cover the main body 29, and includes a clamp portion 30 a that clamps the main body 29 so as to reduce the diameter, and an expansion gas G that is discharged from the gas discharge port 29 a of the main body 29. And a plurality of (two in the embodiment) mounting bolts 31 projecting to the front side.

  The inflator 28 has an airbag operation circuit mounted on the vehicle via a lead wire 34 together with an airbag device (not shown) mounted on the steering wheel 8 when a frontal collision of the vehicle is detected. An operation signal is input.

  The mounting bolt 31 of the diffuser 30 protrudes from the mounting hole 43a of the airbag 40 when the airbag 40 is folded in a state in which the inflator 28 is accommodated, and the airbag 40 is moved to the body portion 18 of the case 17. When storing, the nut 32 is fastened by protruding from the case 17. Each attachment bolt 31 is fixed to the nut 32 and constitutes an attachment means for attaching the airbag 40 to the case 17 together with the inflator 28.

  As shown in FIGS. 5 and 7, the airbag 40 is formed from a woven fabric made of flexible polyester, polyamide yarn, or the like, and has a shape when the inflation is completed, and a width dimension in the horizontal direction on the lower side. It is made into the plate | board shape of the base base which narrows, the knee side wall part 41 arrange | positioned at the driver | operator MD side, the front side of the knee side wall part 41 so that it may continue from the outer periphery of the knee side wall part 41 and may oppose the knee side wall part 41 The vehicle body side wall part 42 arrange | positioned at the column cover 13 side used as this is comprised (refer the dashed-two dotted line of FIG. 1). The airbag 40 is a flat bag type in which the outer shape of the knee side wall portion 41 and the vehicle body side wall portion 42 are equal. The vehicle body side wall 42 on the lower edge 40b side of the airbag 40 is formed with mounting holes 43a and 43a through which the mounting bolts 31 and 31 of the inflator 28 can be projected, and the connector 29 side of the main body 29 of the inflator 28 An insertion hole 43b for projecting the end of this is opened (see FIG. 3). In the airbag 40, an arrangement portion of the attachment hole 43 a and the insertion hole 43 b is an attachment portion 43 that is attached to the main body portion 18 of the case 17.

  Further, the airbag 40 has an upper end (upper edge) 40a at the time of completion of the inflation, the thickness dimension in the opposing direction of the knee side wall 41 and the vehicle body side wall 42 is made thicker than other parts of the airbag 40, A knee restraining portion 45 for receiving the knee K is disposed (see FIGS. 9, 11, and 12). The knee restraint portion 45 of the embodiment has a restraint area 46 having a wide area on the rear surface 44a side that can receive the entire front surface of the left and right knees K from the vicinity of the upper end LU of the left and right shins L of the driver MD. Is configured. And the knee side wall part 41 and the vehicle body side wall part 42 are connected inside the airbag 40, and the thickness along the opposing direction of the knee side wall part 41 and the vehicle body side wall part 42 at the time of completion of inflation is regulated. A first tether 51 and a second tether 52 are provided. The first tether 51 is disposed as a partitioning tether that partitions the airbag 40 so as to be divided into a plurality of parts, and the second tether 52 partially pulls the restraint area 46 forward and then moves backward. It is arrange | positioned as a protrusion suppression tether which suppresses protrusion of this.

  Specifically, the first tether 51 is disposed on the upper end side of the airbag 40 when the inflation is completed, and an upper end expansion chamber 44 constituting the knee restraining portion 45 and a lower expansion chamber below the upper end expansion chamber 44. 49 and is divided into two upper and lower chambers.

  As shown in FIG. 6, a plurality of gas flow holes 53 for allowing the inflation gas G to flow from the lower inflation chamber 49 into the upper inflation chamber 44 are formed in the arrangement portion of the first tether 51 in the airbag 40. It is arranged. These gas flow holes 53 are used for expansion to flow into the upper expansion chamber 44 from the lower expansion chamber 49 defined by the first tether 51 so that the upper expansion chamber 44 expands from the left and right sides to the center in the left-right direction. The main flow MG of the gas G is set so as to be arranged on both the left and right sides. In the case of the embodiment, the entire circumference of the outer peripheral edge of the first tether 51 is joined (sewn) to the inner peripheral surfaces of the knee side wall 41 and the vehicle body side wall 42, and on both the left and right sides of the first tether 51 itself, Edge-side circulation holes 54 and 55 as two gas circulation holes 53 each having a large-diameter circular opening are provided, and three small-diameter circular openings are formed near the center in the left-right direction of the first tether 51 itself. A central flow hole 56 as a gas flow hole 53 is provided.

  Further, in the case of the embodiment, the total opening area of the edge-side circulation holes 54 and 55 arranged near the left and right sides respectively (the total opening area of the edge-side circulation holes 54 and 54 on each of the left and right sides or the edge-side circulation holes 55 and 55. The total opening area) is set larger than the total opening area of the central circulation holes 56 arranged in the vicinity of the center in the left-right direction (the total of the three central circulation holes 56). In the case of the embodiment, the inner diameter dimension d1 of each edge-side circulation hole 54, 55 is 30 mm, and the inner diameter dimension d2 of the central circulation hole 56 is 20 mm. The dimension between the central flow holes 56 on the left and right sides is wider than the opening width Wc (240 mm in the embodiment) of the opening 18a of the case 17 (300 mm in the embodiment).

  In the case of the embodiment, the upper end expansion chamber 44 as the knee restraint portion 45 has an outer diameter D1 when the airbag 40 is inflated alone along the vertical direction, as shown in FIG. 7C. Is 198 mm within the range of 150 to 220 mm, and the connection distance TL1 for connecting the knee side wall 41 and the vehicle body side wall 42 in the first tether 51 is 60 mm within the range of 50 to 90 mm. .

  Furthermore, in the case of the embodiment, the rear surface of the airbag 40 in the thickness direction when the inflation of the single airbag 40 is completed as shown in FIG. The top 49b protruding rearward on the 49a side is shifted forward by an offset amount (shift amount) OL of 60 mm within a range of 10 to 70 mm from the top 44b protruding rearward on the rear surface 44a side of the upper end expansion chamber 44. Are set to be offset.

  In the case of the embodiment, the airbag 40 has a width dimension W0 in the left-right direction of the flatly deployed airbag 40 that is not inflated 600 mm, and a length dimension H0 in the vertical direction from the mounting hole 43a to the upper edge 40a is 405 mm. The vertical dimension H1 from the mounting hole 43a to the first tether 51 is set to 125 mm (see FIG. 5). The connection part 42b to the vehicle body side wall part 42 which connected the front end 51a of the first tether 51 and the connection part 41b to the knee side wall part 41 which connected the rear end 51b are separated from the knee side wall part 41 and the vehicle body side wall part 42. When the peripheral edges are overlapped and overlapped, they are set at the same height position from the lower edge 40b of the airbag 40 (see A in FIG. 7).

  As shown in FIGS. 7A to 7C, the second tether 52 includes a connecting portion 42b to the vehicle body side wall portion 42 on the front end 51a side of the first tether 51, and a knee side wall portion 41 on the rear surface 44a side of the upper end expansion chamber 44. It is connected to. Then, the second tether 52 shifts at least the center 44d in the left-right direction at the top 44b protruding rearward on the rear surface 44a side of the upper end expansion chamber 44 which has been expanded without providing the second tether 52 to the front side. As described above, the rear end 52b side is located near the middle in the vertical direction from the upper edge 41a of the knee side wall 41 on the rear surface 44a side of the upper end expansion chamber 44 to the connection portion 41b with the rear end 51b of the first tether 51 (center 44c). And at least the vicinity of the center 44d in the left-right direction, and the rearward projection of the connecting portion 41c connected to the rear surface 44a side of the upper end expansion chamber 44 is suppressed.

  In the case of the embodiment, the connection distance TL2 between the connection part 42b of the front end 52a of the second tether 52 to the vehicle body side wall part 42 and the connection part 41c of the rear end 52b to the knee side wall part 41 does not provide the second tether 52. The rear surface 44a side of the upper end expansion chamber 44 that has been completely expanded is set to 130 mm so as to be partially shifted forward by a shift amount PL of 20 mm within a range of 5 to 40 mm.

  In the airbag 40 of the embodiment, as shown in FIG. 8, the airbag base fabric 57 constituting the outer peripheral wall is composed of an upper panel fabric 59, a lower front panel fabric 60, and a lower rear panel fabric 61. It is composed of sheets. Further, two reinforcing cloths 63 and 64 and a first tether cloth 66 are used for the airbag 40. The second tether 52 is integrally formed with the lower front panel cloth 60. That is, the lower front panel cloth 60 includes a main body 60a constituting the vehicle body side wall portion 42 of the lower expansion chamber 49 in which the attachment portion 43 is disposed, and a second tether portion for the second tether 52 from the upper end of the main body 60a. 60b. The second tether portion 60b is configured such that the distal end away from the main body 60a is a rear end portion 60c constituting the rear end 52b of the second tether 52, and the rear end portion 60c is connected to the connecting portion 41c of the knee side wall portion 41. A stitching portion 60d to be stitched and connected is provided. The upper panel cloth 59 is configured as a single piece in which the knee side wall portion 41 and the vehicle body side wall portion 42 in the area above the first tether 51 are connected with the upper edge 40a of the airbag 40 therebetween. (See A in FIG. 7). The main body 60 a of the lower front panel cloth 60 constitutes a part of the vehicle body side wall part 42 below the first tether 51, and the lower rear panel cloth 61 constitutes a part of the knee side wall part 41 below the first tether 51. ing. The airbag 40 sews the rear end 52b of the second tether 52 to the knee side wall 41 side of the upper panel cloth 59, and folds the upper panel cloth 59 at a position on the upper edge 40a side of the airbag 40. While sewing the left and right edges, the front end 51a of the first tether 51 and the upper end of the main body 60a of the lower front panel cloth 60 provided with the reinforcing cloth 64 with respect to the vehicle body side wall portion 42 on the lower end side of the upper panel cloth 59 Then, the part which becomes the front end 52a of the second tether 52 and the upper end of the reinforcing cloth 63 are overlapped and stitched, and the first tether 51 is in contact with the part of the knee side wall 41 on the lower end side of the upper panel cloth 59. The upper ends of the rear edge 51b and the lower rear panel cloth 61 are stitched, and then from the left and right edges of the upper panel cloth 59, through the left and right edges of the lower front panel cloth 60 (main body 60a) and the lower rear panel cloth 61, Overlap of outer peripheral edge applied to lower edge 40b of airbag 40 If sutured site each other can be formed.

In the case of the embodiment, the upper panel cloth 59, the lower front panel cloth 60, and the lower rear panel cloth 61 as the airbag base cloth 57 constituting the outer peripheral wall of the airbag 40 are the reinforcing cloths 63, 64 and the first Including the tether cloth 66, the woven cloth 58 is a non-coated cloth without a coating layer. More specifically, the woven fabric 58 used has an air permeability (Fragile method) of 0.5 L / cm ² / min, which is 0.6 L / cm ² / min or less.

  When the airbag 40 is folded, the knee side wall portion 41 and the vehicle body side wall portion 42 constituting the outer peripheral wall are overlapped with each other so that the outer peripheral edges coincide with each other, and the upper edge 40a side is lowered to the lower edge. Fold it so that it winds on the side of the vehicle body side wall portion 42 so as to approach the 40b side, and both the left and right edges of the roll are positioned below the center in the left-right direction of the folded part. Folded. At the time of folding, the inflator 28 is housed in the airbag 40 so that the mounting bolts 31 protrude from the mounting holes 43a and the end portions of the main body 29 can protrude from the insertion holes 43b. Note that the folded airbag 40 is appropriately wrapped with a wrapping sheet that prevents collapse.

  After the airbag 40 is folded in this way, the mounting bolts 31 of the inflator 28 are projected from the mounting holes 18d, and the end of the main body 29 of the inflator 28 on the connector 33 side is projected from the insertion hole 18e. Thus, if the inflator 28 and the folded airbag 40 are accommodated in the main body 18 of the case 17 and the nuts 32 are fastened to the mounting bolts 31, the inflator 28 and the main body 18 of the case 17 are connected. The airbag 40 can be attached and fixed (see FIG. 3).

  Thereafter, the hooks 18b and 18c of the body portion 18 of the case 17 are inserted and locked in the locking holes 25a and 26a of the connecting wall portions 25 and 26, and the airbag cover 21 is assembled to the case 17 (see FIG. 2). . Further, the outer peripheral edge of the panel portion 19 of the case 17 is attached and fixed to the body 1 side using the brackets 4, 5, 6 and 7, and the connector 33 connected with the lead wire 34 is connected to the main body 29 of the inflator 28. Connect to. Then, if the instrument panel 14 and the under cover 15 (see FIGS. 1 and 2) are attached, the knee protection airbag device S can be mounted on the vehicle.

  After the knee protection airbag device S is mounted on the vehicle, if an operation signal is input to the main body 29 of the inflator 28 via the lead wire 34, the inflation gas G is discharged from the gas discharge port 29a of the inflator 28 and inflated. The working gas G flows into the airbag 40 through the gas outlet 30b of the diffuser 30 (see FIG. 3). And the airbag 40 expand | swells, the wrapping sheet | seat which is not shown in figure is fractured | ruptured, Furthermore, the fracture | rupture planned part 22 is fractured | ruptured, and the door parts 23 and 23 of the airbag cover 21 are pushed open up and down both sides, FIG. As shown by the two-dot chain line 4, the knee MD of the driver MD can be protected and expanded while projecting rearward from the projecting opening 18 a of the case 17.

  In the airbag 40 of the embodiment, when the inflation is completed, the upper end inflation chamber 44 as the knee restraint portion 45 completes the inflation in a substantially columnar shape, and the left and right sides of the driver MD in the restraint area 46 on the rear surface 44a side. The whole area of the front surface of both knees K is received from the vicinity of the upper end LU of both shins L and is compressed to avoid the state of pressing the shins L and to absorb the kinetic energy that the driver MD moves forward (FIG. 9, FIG. 9). 11, 12).

  At this time, the second tether 52 as the protrusion restraining tether has at least the center 44d in the left-right direction in the top portion 44b protruding rearward on the rear surface 44a side of the upper end expansion chamber 44 that has been expanded without providing the second tether 52. The rear end 52b side in the vertical direction from the upper edge 41a of the knee side wall 41 on the rear surface 44a side of the upper end expansion chamber 44 to the connecting portion 41b with the rear end 51b of the first tether 51 so as to be shifted forward. It is connected near the middle (center 44c) and at least near the center 44d in the left-right direction (see A in FIGS. 5 and 7). Therefore, the vicinity of the center 44d in the left-right direction on the rear surface 44a side of the upper end expansion chamber 44 serving as the knee restraint portion 45 is pulled forward by the second tether 52 and enters between the left and right knees K. However, the entire front surface of the left and right knees K and the vicinity of the upper end LU of the shin L are not deviated to the outside of the left and right, and are received by the restraining area 46 in front of each other (see FIG. 12). ).

  The second tether 52 has a rear end 52b side in the vertical direction from the upper edge 41a of the knee side wall 41 on the rear surface 44a side of the upper end expansion chamber 44 to the connecting portion 41b with the rear end 51b of the first tether 51. Even if connected near the center 44c and at least near the center 44d in the left-right direction, the front end 52a side is connected to the vehicle body side wall portion 42 at the same position as the front end 51a of the first tether 51. Therefore, the upper end expansion chamber 44 is formed as an outer peripheral wall having a longitudinal cross section in the front-rear direction from a connecting portion 42b of the vehicle body side wall portion 42 of the front end 51a of the first tether 51, as shown in FIGS. Up to the upper edges 42a and 41a of the vehicle body side wall portion 42 and the knee side wall portion 41, and further, a connecting portion 41c from the upper edge 41a of the knee side wall portion 41 to the knee side wall portion 41 at the rear end 52b of the second tether 52. Until then, the thickness in the front-rear direction can be increased and the swell can be greatly expanded, and it can expand into a substantially cylindrical shape, and can receive the knee K and the upper end LU of the shin L without reducing the cushion effect. 12A to 12C, the operation state of the airbag 40 of the embodiment is indicated by a solid line, and the other configuration is the same as that of the airbag 40 of the embodiment without providing only the second tether 52. The operating state of the airbag 39 is indicated by a two-dot chain line. In the airbag 39 of the comparative example, as shown in FIG. 12B, the left and right knees K are greatly intruded and the left and right knees are pushed outward.

  Therefore, in the airbag 40 of the embodiment, the knee restraint portion 45 that swells in a substantially columnar shape to receive the knee K does not push outward, and the cushion effect is maintained and the left and right knees K are accurately received. be able to.

  Further, the airbag 40 of the embodiment is a sewing bag manufactured by sewing the airbag base fabric 57, and the front ends 51a and 52a of the first tether 51 and the second tether 52 coincide with each other. The front ends 51a and 52a of the first tether 51 and the second tether 52 can be joined together to be connected to the vehicle body side wall portion 42 (the main panel 60a of the upper panel cloth 59 and the lower front panel cloth 60). However, even if it is set as the structure provided with the two-step tether of the 1st tether 51 and the 2nd tether 52, the manufacturing process of the airbag 40 can be simplified as much as possible.

  In the embodiment, the upper end expansion chamber 44 expands in a substantially columnar shape and increases the thickness in the front-rear direction. However, the gas flow hole 53 disposed at the position where the first tether 51 is disposed is shown in FIG. As shown, the main flow MG of the expansion gas G flowing from the lower expansion chamber 49 to the upper end expansion chamber 44 is arranged on both the left and right sides, and when the expansion gas G flows, It swells in order from the both sides to the center side in the left-right direction. That is, at the initial stage of inflation of the airbag 40, as shown by the two-dot chain line in FIG. 4, both the left and right sides of the upper end expansion chamber 44 are deployed to the position of the upper end (upper edge) 40a when the airbag 40 is completely inflated. As shown in FIG. 10A, since the thickness can be kept thin, the driver MD is easily arranged on the front side of the knee K of the driver MD, and then the thickness is increased from the left and right sides to the center side. Since the expansion is completed further, the front surfaces of both knees K can be suitably received from the upper ends LU of both shins L.

  In addition, although the 2nd tether 52 of embodiment illustrated what was set as 120 mm (refer FIG. 8) of the narrow width dimension WT from the distance KL (refer FIG. 12, normally around 400 mm) of the right and left both knees K, If the flow of the main flow MG of the expansion gas G on the left and right sides flowing from the expansion chamber 49 to the upper end expansion chamber 44 is not obstructed, it is not only in the vicinity of the center 44d in the left and right direction of the upper end expansion chamber 44 but also on both sides in the left and right direction The second tether 52 </ b> A (see a two-dot chain line in FIG. 8) extending in the direction may be configured.

  Further, in the airbag 40 of the embodiment, the lower inflation chamber 49 includes a mounting portion 43 that is attached to the body portion 18 of the case 17 at the site of the vehicle body side wall portion 42, as shown in FIGS. Further, when the inflation of the airbag 40 is completed, the upper end inflation chamber 44 can be supported from below, and the upper end 49c side, which is the location of the first tether 51, is separated from the main body 18 of the case 17 backward. Has been. Therefore, the airbag 40 can be configured as two upper and lower chambers, that is, an upper expansion chamber 44 and a lower expansion chamber 49, and is more compact than an airbag having a larger volume having three or more expansion chambers. Can reduce the number of manufacturing steps and costs. Further, the lower expansion chamber 49 causes the front end 51a of the first tether 51 and the second tether 52 to be connected to the vehicle body side wall 42 on the side of the tether 52b from the main body 18 of the case 17 when the expansion is completed. Therefore, the upper end expansion chamber 44 can be stably supported, and the restraining area 46 on the rear surface 44a side of the upper end expansion chamber 44 can be accurately arranged from the upper end LU of the shin L to the front position of the front surface of the knee K. it can.

  Further, in the embodiment, the upper end expansion chamber 44 is set so that the outer diameter D1 at the completion of expansion is 198 mm within the range of 150 to 220 mm, and the second tether 52 The rear surface 44a side of the upper end expansion chamber 44 which has been expanded without being provided is set so as to be partially shifted forward by a shift amount PL of 20 mm within a range of 5 to 40 mm.

  In such a configuration, at the portion where the second tether 52 is not disposed, the upper end expansion chamber 44 can ensure an outer diameter dimension (thickness dimension in the front-rear direction) of 150 mm or more, and the knee side wall 41 is The upper end LU of the knee K or the shin L can be received without incurring bottoming that comes into contact with the vehicle body side wall portion 42 in contact with the column cover 13 as the vehicle body side member. On the contrary, the upper end expansion chamber 44 does not have an outer diameter D1 exceeding 220 mm when the expansion is completed. Therefore, even if the gap C between the knee K and the column cover 13 as the vehicle body side member is narrow, the upper end expansion chamber 44 is smooth in the gap. The upper end LU of the knee K and shin L is not pushed back strongly even if the expansion is completed.

  If the movement distance (shift amount) PL of the restraint area 46 due to the provision of the second tether 52 is less than 5 mm, it is not meaningful to provide the second tether 52, and if it exceeds 40 mm In the upper end expansion chamber 44, the vicinity of the connection part 41c to the knee side wall 41 on the rear end 52b side of the second tether 52 is recessed in a wide area on the front side, and the part in contact with the front surface of the knee K in the restraint area 46 is The entire region moves forward, and the portion below the connecting portion 41c swells so as to extend obliquely rearward and downward. Therefore, the rear surface 46b on the lower side of the region where the area for receiving the front surface of the knee K itself moves forward and swells so as to extend obliquely downward and downward below (see the two-dot chain line in FIG. 7B). However, in cooperation with the rear surface 49a of the lower expansion chamber 49, it becomes easier to press the shin L than the knee K, and as a result, the upper end LU of the knee K and the shin L is avoided by avoiding the pressing state of the shin L. Therefore, it is easy to cause a situation in which the advantage of the configuration in which the knee restraining portion 45 is substantially cylindrical is hindered, which is not desirable. Therefore, in the embodiment, the partial movement distance (shift amount) PL of the restraint area 46 by providing the second tether 52 is set to 20 mm within the range of 5 to 40 mm, and the knee restraint portion 45 Although the upper rear surface 46a and the lower rear surface 46b between the rear ends 52b of the second tethers 52 in the restraint area 46 move slightly forward, a large area is secured, and the knees K and shins are secured. The upper end LU of L can be received.

Furthermore, in the case of the embodiment, since the outer diameter D1 of the upper end expansion chamber 44 is large, the airbag base fabric 57 to be used is not a coated fabric provided with a coating layer that does not cause gas leakage. Those that cause gas leakage can be used. However, when the air permeability (Fragile method) exceeds 0.6 L / cm ² / min, the upper end expansion chamber 44 has a small volume with an outer diameter dimension (thickness dimension in the front-rear direction) D1 of about 150 mm. Since the internal pressure drop due to gas leakage becomes abrupt and it is difficult to secure the effect of reducing the kinetic energy of the driver MD when receiving the upper end LU of the knee K or shin L in the upper end expansion chamber 44 as the knee restraint portion 45. The air permeability of the airbag base fabric 57 is preferably 0.6 L / cm ² / min or less.

  In this case, the airbag base fabric forming the knee side wall 41 and the vehicle body side wall 42 may be manufactured from a coated fabric provided with a coating layer made of silicon rubber or the like for preventing gas leakage on the woven fabric. However, if it manufactures from the woven fabric of the non-coat cloth which does not provide a coating layer like the airbag 40 of embodiment, the manufacturing cost of the airbag 40 can be reduced.

Incidentally, as the same outer shape and the air bag embodiments, the air permeability of the air bag base fabric 47 (Frazier method) of 0.7 L / cm ² / min and 1.07L / cm ² / min and the two When Comparative Examples 1 and 2 were deployed and inflated as a vehicle-mounted specification similar to the airbag 40 of the embodiment and a seated dummy was collided, in Comparative Examples 1 and 2, the shin L Although the avoidance of the pressed state is only slightly worse than that of the embodiment, the restraining performance of the knee K becomes a situation where the inner surface is insufficient due to insufficient internal pressure, and the amount of kinetic energy absorbed by the upper end expansion chamber 44 is sufficient. Not NG (unusable).

  In the embodiment, the offset amount OL offset to the front side from the top portion 44b on the rear surface 44a side of the upper expansion chamber 44 in the top portion 49b on the rear surface 49a side of the lower expansion chamber 49 is set to 60 mm. If the offset amount OL is less than 10 mm, the lower expansion chamber 49 tends to strongly press the shin L, and if it exceeds 70 mm, the volume of the lower expansion chamber 49 that makes the volume smaller than the upper end expansion chamber 44 is small. A situation in which the first tether 51 cannot be detached from the main body portion 18 of the case 17 when the airbag 40 is completely inflated (see the rear surface 49a of the lower inflation chamber 49 indicated by a two-dot chain line in FIG. 7C). If the first tether 51 cannot be detached from the main body portion 18 of the case 17, the upper end expansion chamber 44 may be stably placed on the front side of the knee K. The OL is preferably in the range of 10 to 70 mm.

  Furthermore, in the embodiment, the first tether 51 has a connection distance TL1 for connecting the knee side wall portion 41 and the vehicle body side wall portion 42 of 60 mm. If the connection distance TL1 is less than 50 mm, the separation distance between the knee side wall 41 near the first tether 51 and the vehicle body side wall 42, that is, the thickness of the airbag 40 near the first tether 51 is thin. Thus, when a situation occurs in which the knee K is received at this portion, the knee side wall 41 is in contact with the vehicle body side wall 42 that is in contact with the column cover 13 as the vehicle body side member. As a result, the knee K cannot be sufficiently protected, and further, it becomes difficult to quickly supply the inflation gas G to the knee restraining portion 45 due to being constricted at this portion. Furthermore, if the connection distance TL1 between the knee side wall 41 and the vehicle body side wall 42 of the first tether 51 exceeds 90 mm, the lower expansion chamber 49 immediately below the first tether 51 increases its thickness, While it becomes difficult to ensure the above offset amount of 10 mm or more, the rear surface 49a of the lower expansion chamber 49 and the rear surface 46b of the lower side of the knee restraint portion 45 (upper end expansion chamber 44) cooperate to form the shin L. It becomes easy to invite the situation of pressing. Therefore, the first tether 51 desirably has a connection distance TL1 for connecting the knee side wall portion 41 and the vehicle body side wall portion 42 within a range of 50 to 90 mm.

  In the embodiment, the gas flow hole 53 is shown as a circular opening in the first tether 51 itself. However, the first tether 51 has a polygonal shape including a quadrangle such as an ellipse or a rectangle. You may make it open. Further, the edge of the first tether 51 is not partially connected to the knee side wall 41 or the vehicle body side wall 42, and a gas is generated between the edge of the first tether 51 and the knee side wall 41 or the vehicle body side wall 42. The circulation hole 53 may be used. For example, the left and right edges of the first tether 51 are arranged away from the left edge 40c and the right edge 40d on the inner peripheral surface side of the airbag 40, and the edge of the first tether 51 and the inner peripheral surface of the airbag 40 are disposed. You may comprise the clearance gap between these as the gas distribution | circulation hole 53. FIG.

  Furthermore, in the embodiment, the airbag 40 used in the knee protection airbag device S that is disposed below the steering column 9 and protects the knee K of the driver MD has been described as an example. You may apply this invention to the airbag of the airbag apparatus for knee protection arrange | positioned ahead of a seat.

It is a schematic longitudinal cross-sectional view which shows the vehicle mounting state of the airbag apparatus for knee protection in which the airbag of one Embodiment of this invention is used. It is a general | schematic expanded longitudinal cross-sectional view which shows the vehicle mounting state of the airbag apparatus for knee protection of embodiment. FIG. 3 is a schematic cross-sectional view showing a vehicle-mounted state of the knee protecting airbag device of the embodiment, corresponding to the III-III portion of FIG. 2. It is a front view of the vehicle mounting state of the airbag apparatus for knee protection of embodiment. It is a front view of the airbag of an embodiment. It is a cross-sectional view of the airbag of the embodiment, and corresponds to the VI-VI portion of FIG. It is the longitudinal cross-sectional view of the airbag of embodiment, and shows the state expanded slightly and the state at the time of completion | finish of single-piece | unit expansion, respectively, the VIIA-VIIA site | part of FIG. 5, and the VIIB-VIIB site | part , Corresponding to the VIIC-VIIC site. It is a front view which shows the main constituent materials of the airbag of embodiment. FIG. 3 shows the completion of inflation in the vehicle mounted state of the airbag of the embodiment, and shows the completion of inflation in the absence of a column cover as a surrounding vehicle body side member. It is a schematic longitudinal cross-sectional view explaining in order the expansion | swelling in the vehicle mounting state of the airbag of embodiment. It is a schematic longitudinal cross-sectional view which shows the time of completion | finish of expansion | deployment in the vehicle mounting state of the airbag of embodiment. It is a schematic cross-sectional view explaining the expansion | swelling in the vehicle mounting state of the airbag of embodiment sequentially.

Explanation of symbols

17 ... Case,
18a ... opening,
40 ... (Knee protection) Airbag,
41 ... knee side wall,
42 ... side wall of vehicle body,
43 ... Mounting part,
44 ... upper end expansion chamber,
44a ... rear side,
44b ... the top,
45 ... Knee restraint,
46: Restraint area,
49 ... lower expansion chamber,
49c ... upper end,
51. First tether,
52. Second tether,
53. Gas flow hole,
57 ... Airbag base fabric,
58 ... Woven cloth,
D1 ... outer diameter dimension (of the knee restraint),
PL ... shift amount,
S ... Air bag device for knee protection,
G ... expansion gas,
MG ... mainstream,
MD ... (Crew) Driver,
K ... knees,
L ... Shin.

Claims (5)

The seat is placed under the front side of the occupant's knee and is folded and stored in a case having a projecting opening that opens toward the rear side.
A configuration in which a knee restraining portion capable of receiving both right and left knees is disposed on the front side of the knee, while expanding and expanding so as to protrude upward from the projection opening when the inflation gas flows in; And
An outer peripheral wall at the time of completion of expansion is disposed on the front side of the knee side wall portion so as to face the knee side wall portion continuously from the outer peripheral edge of the knee side wall portion and the knee side wall portion disposed on the knee side. It is configured as a flat bag type with the vehicle body side wall and the outer shape being equal to each other.
A tether that connects the knee side wall portion and the vehicle body side wall portion and regulates the thickness along the facing direction of the knee side wall portion and the vehicle body side wall portion at the time of completion of expansion is disposed inside. Is a knee protection airbag
At the upper end when the airbag is completely inflated, the knee restraint portion is configured, and a restraint area capable of receiving the entire front surface of the left and right knees from the vicinity of the upper end of the left and right shins of the occupant is disposed on the rear side, An upper end expansion chamber that completes expansion in a substantially cylindrical shape extending in the left-right direction is disposed,
The first tether is disposed immediately below the upper end expansion chamber, and the first tether is
The upper end expansion chamber is disposed along the left-right direction of the vehicle so as to partition the upper end expansion chamber and the lower expansion chamber that expands immediately below the upper end expansion chamber when the inflating gas flows. A plurality of gas flow holes for arranging the main flow of the expansion gas flowing from the lower expansion chamber to the upper expansion chamber on the left and right sides are provided so as to expand from the left and right sides to the center in the left-right direction. It is configured as a partition tether to be installed, and
The second tether is arranged in the upper end expansion chamber so as to be connected to the connection portion to the vehicle body side wall portion on the front end side of the first tether and the knee side wall portion on the rear surface side of the upper end expansion chamber. And the second tether is
The rear end side is located on the rear surface side of the upper end expansion chamber so as to shift at least the center in the left-right direction at the top of the rear surface side of the upper end expansion chamber that has been expanded without providing the second tether. In the vicinity of the middle in the vertical direction from the upper edge of the knee side wall portion to the connection portion with the rear end of the first tether, and at least near the center in the horizontal direction,
A knee protection airbag, wherein the knee protection airbag is arranged as a protrusion restraining tether that suppresses backward protrusion of a connecting portion connected to the rear surface side of the upper end expansion chamber.   The lower expansion chamber includes a mounting portion attached to the case at a portion of the vehicle body side wall, and when the airbag is completely inflated, the first tether is arranged so that the upper expansion chamber can be supported from below. The knee protection airbag according to claim 1, wherein the knee protection airbag is configured so that an upper end side which is an installation site is detached rearward from the case. The upper end expansion chamber is set so that the outer diameter at the completion of expansion is within the range of 150 to 220 mm, and
The second tether is set so as to partially shift the rear surface side of the upper end expansion chamber, which has been expanded without providing the second tether, to the front side by 5 to 40 mm. The knee protection airbag according to claim 1 or 2. The said knee side wall part and the said vehicle body side wall part are comprised from the base fabric for airbags which sets an air permeability (fragile method) to 0.6 L / cm < ² > / min or less. Knee protection airbag. The knee protection airbag according to claim 4, wherein the airbag base fabric is formed of a woven fabric that is a non-coated fabric without a coating layer for preventing gas leakage.

Images