Patent Description:
Conventionally, a knee airbag device for protecting a knee of an occupant when an impact is applied to a vehicle, such as when the vehicle is in a collision or the like, is known. Patent Document <NUM> describes a knee protection device as this type of device.

Specifically, the knee protection device described in Patent Document <NUM> has a case for storing an airbag and an inflator, and a cover for covering a vehicle rear side of the case, and is mounted below a steering column on a front side of a knee of a driver. In this device, the airbag expands when expansion gas discharged from the inflator flows into the airbag. At this time, the airbag pushes a door part of the cover to break an intended breakage part, causing the door part to open. The airbag expands and deploys along a lower surface of a column cover.

<CIT> discloses an airbag device for knee protection. <CIT> discloses a knee airbag device for a front passenger seat of a vehicle, the airbag being configured such that initial deployment of a central region of the airbag is suppressed by a flap.

Knee airbag devices have difficulty in increasing the width dimension of the airbag cushion due to limitations in a vehicle interior structure, and the like. Therefore, a width dimension of the airbag cushion may be approximately the same as or smaller than a space between the knees of an occupant. Furthermore, the space in front of the knees of the occupant is relatively small for airbag cushion expansion and deployment. Therefore, conventionally, depending on the position of a leg of an occupant, the airbag cushion may not deploy in front of an occupant's knees and may enter between the knees, preventing a desired restraining performance from being achieved.

In view of the foregoing, an object of the present invention is to provide a knee airbag device in which it is difficult for an airbag cushion to enter between knees of an occupant during expansion and deployment, and that can stably restrain a knee from a front side.

In order to solve the aforementioned problems, the present invention provides a knee airbag device for protecting a knee of an occupant, including: an airbag cushion stored in front of the knee of the occupant for expanding and deploying toward the knee side; an inflator for injecting expansion gas to expand the airbag cushion; a storage case for storing the airbag cushion, in which is formed an opening part through which the airbag cushion that has expanded and deployed by the expansion gas pops out; a first flap for covering the airbag cushion exposed through the opening part, such that the airbag cushion is retained in the storage case, and having a first weak part that breaks when pressed by the airbag cushion during expansion and deployment; and a second flap, which is a component with a larger dimension in a length direction than the first flap, for covering an outer surface of the first flap so as to transverse in an up-down direction or front-rear direction a center part of the airbag cushion in a lateral direction, the second flap having a second weak part that breaks when pressed by the airbag cushion after rupture of the first weak part. Note that with respect to the "up-down direction or front-rear direction", if the inclination angle is <NUM>° in an oblique direction, it can be said to be both an up-down direction and front-rear direction. If the inclination angle is not <NUM>°, it can be said to be a front-rear direction if the angle is near <NUM>°, and up-down direction if the angle is near <NUM>°.

The present invention may adopt a configuration in which notches are formed on both sides of the second flap in a width direction at the transversing part that transverses the center part, which are recessed toward the center in the width direction.

The present invention may adopt a configuration in which the notches are formed in a shape recessed in a curved manner toward the center in the width direction in a front surface view of the opening part.

The present invention may adopt a configuration in which the second flap has a pair of attachment parts for attaching the second flap to a vehicle side and a transversing part extending between the pair of attachment parts and transversing the center part, one of the pair of attachment parts is attached to a first flap attachment part provided on one side of the transversing part in a transverse direction of the storage case, and the other of the pair of attachment parts is attached to a second flap attachment part on the other side in the transverse direction of the storage case.

The present invention may adopt a configuration in which one end side of the first flap is attached to the first flap attachment part, and the other end side of the first flap is attached to the second flap attachment part.

The present invention may adopt a configuration in which at least one of the first flap attachment part and second flap attachment part is disposed near an edge part of the opening part.

The present invention may adopt a configuration in which the second flap is configured by integrating a first fabric attached to the first flap attachment part and a second fabric attached to the second flap attachment part.

The present invention may adopt a configuration in which the first flap is provided so as to transverse the opening part, and the first weak part is positioned in the center or near the center of the opening part in the transverse direction of the first flap.

The present invention may adopt a configuration in which the second weak part is positioned near an edge part of the opening part.

The present invention may adopt a configuration in which in the second flap, the transversing part that transverses the center part has an overlapping part where the transversing part is folded back a plurality of times in the length direction so as to overlap upon itself.

The present invention may adopt a configuration in which the overlapping part has a stitch part in which the fabric of the mutually overlapping portions of the transversing part are stitched together such that the folded state is maintained, and the stitch part breaks before the second weak part.

The present invention has: a first flap for retaining an airbag cushion in a storage case; and a second flap for covering an outer surface of the first flap so as to transverse in an up-down direction or front-rear direction a center part of the airbag cushion in a lateral direction. When expansion gas is injected from an inflator, the airbag cushion begins to expand and deploy, and the first flap breaks at the first weak part. In this manner, the second flap restrains the deployment of the center part of the airbag cushion until the second flap spreads and breaks at a second weak part. This suppresses the airbag cushion from deploying to a knee side and promotes deployment to an outer side in the lateral direction (e.g., a left-right direction of the vehicle). The airbag cushion spreads in the lateral direction as compared to a knee airbag device without a second flap.

Furthermore, in addition to the second flap, the present invention also has a first flap. Herein, the airbag cushion is usually stored in a folded and compressed state in the storage case. Therefore, if the first flap is not provided, the second flap will be pressed by the compression reaction force of the airbag cushion. On the other hand, the second flap is longer than the first flap and is attached in a relatively loosely taut or slack state with a length adjustment part, for example, a folded-back part. Therefore, when pushed by the compression reaction force described above, the second flap may further slacken, and the second weak part may not break at or near an intended break position. Thus, the deployment suppression described above may not be effective. In contrast, with the present invention, the first flap can suppress the second flap from slackening due to being pushed by the compression reaction force described above. Therefore, it is possible to provide a knee airbag device in which it is unlikely for an airbag cushion to enter between the knees of an occupant during expansion and deployment, and that can stably restrain the knees from the front side.

Embodiments of the present invention are described below in detail with reference to the drawings. Note that the following embodiments are examples of the present invention, and are not intended to limit the scope of the present invention, the application, or the uses thereof.

The present embodiment is a knee airbag device <NUM> for protecting a knee 5a of an occupant <NUM> seated on a seat <NUM> of a vehicle such as a car or the like. The knee airbag device <NUM> depicted in <FIG> is provided for a driver's seat. However, the knee airbag device <NUM> may be provided for another seat, such as a front passenger seat or the like. The knee airbag device <NUM> is provided in an instrument panel <NUM> of the vehicle, and when the vehicle is impacted, such as during a collision or the like, the airbag cushion <NUM> expands and deploys toward the occupant <NUM> to restrain the knee 5a of the occupant <NUM>.

Note that in this specification, the terms "upper" and "upper side" refer to a head direction of the occupant <NUM> seated in a regular position in the seat <NUM> and "lower" and "lower side" refer to a foot direction of the occupant <NUM>. Herein, the "regular position" refers to a position in a center of a seat cushion <NUM> of the seat <NUM> in the left-right direction with the back of the occupant <NUM> in contact with the backrest <NUM> from above and below. Furthermore, the terms "front" and "front side" refer to a front surface direction of the occupant <NUM> seated in the seat <NUM> in the regular position and "rear" and "rear side" refer to a back surface direction of the occupant <NUM>. Furthermore, the terms "left" and "left side" refer to a lefthand direction of the occupant <NUM> seated in the seat <NUM> in the regular position, and "right" and "right side" refer to the right-hand direction of the occupant <NUM>. Furthermore, the occupant <NUM> assumes an AM50 (a 50th percentile of an adult male in US) of a WorldSID (World Side Impact Dummy).

The knee airbag device <NUM> is disposed on a back side of a lower panel 8a of the instrument panel <NUM>, which is positioned in front of a shin 5b of the occupant <NUM>, as depicted in <FIG>. Herein, the lower panel 8a extends diagonally to the front and down in cross-sectional view. A first attachment member 9a and a second attachment member 9b protrude to the front from a back surface of the lower panel 8a. The first attachment member 9a and second attachment member 9b are formed in a plate shape and extend substantially horizontally. The first attachment member 9a and second attachment member 9b are spaced apart in the up-down direction. The knee airbag device <NUM> is attached to the first attachment member 9a and second attachment member 9b.

As depicted in <FIG> and <FIG>, the knee airbag device <NUM> has: the cushion <NUM> stored in front of the knee 5a of the occupant <NUM> and expanded and deployed toward the knee 5a side; an inflator <NUM> for injecting expansion gas for expanding the airbag cushion <NUM>; a storage case <NUM> for storing the airbag cushion <NUM>; a first flap (folding retention flap) <NUM> for covering the airbag cushion <NUM> exposed from an opening part <NUM> of the storage case <NUM>; and a second flap (inter-knee deployment suppression flap) <NUM> for covering an outer surface of the first flap <NUM>. In present embodiment, the first flap <NUM> and the second flap <NUM> are doubly provided for the airbag cushion <NUM> in the stored state.

The storage case <NUM> is a box body in which a horizontally long opening part <NUM> is formed through which the airbag cushion <NUM>, which is expanded and deployed by the expansion gas, pops out. The storage case <NUM> is attached to the back side of the lower panel 8a such that the opening part <NUM> faces the back surface of the lower panel 8a. The back surface of the lower panel 8a has a weak part 8b that breaks when pressed by the expansion pressure of the airbag cushion <NUM>. The weak part 8b is weaker in strength than other portions in the lower panel 8a and can be formed, for example, by a straight groove extending in the left-right direction.

The storage case <NUM> is a box body having: an upper surface plate <NUM>; a lower surface plate <NUM> facing the upper surface plate <NUM>; a bottom surface plate <NUM> extending between a front end part of the upper surface plate <NUM> and a front end part of the lower surface plate <NUM>; and a pair of side surface plates <NUM> extending between an end part of the upper surface plate <NUM> and an end part of the lower surface plate <NUM> in the left-right direction. The opening part <NUM> is formed between the rear end part of the upper surface plate <NUM> and the rear end part of the lower surface plate <NUM> in cross-sectional view. The upper surface plate <NUM> and lower surface plate <NUM> are formed in a rectangular shape in plan view. The upper surface plate <NUM> is longer in the front-rear direction between the upper surface plate <NUM> and the lower surface plate <NUM>.

The storage case <NUM> is a box body having a horizontally long opening part <NUM>. As depicted in <FIG>, the length in the left-right direction is longer than the length in the up-down direction when viewed from the opening part <NUM> side in a condition attached to the back side of the lower panel 8a. Hereinafter, with respect to the storage case <NUM>, the left-right direction in a front surface view from the opening part <NUM> side may be referred to as a longitudinal direction, and the up-down direction in the front surface view from the opening part <NUM> side may be referred to as a short direction.

In the storage case <NUM>, a plurality of hooks 26a, 27a are provided on an outer surface of the upper surface plate <NUM> and outer surface of the lower surface plate <NUM>, respectively. Each hook 26a, 27a is formed such that a tip end faces toward the bottom surface plate <NUM> side (front) (see <FIG>) and is disposed near the outer side of the edge part of the opening part <NUM>. The storage case <NUM> is attached to the first attachment member 9a by the plurality of hooks 26a on the upper surface plate <NUM> and to the second attachment member 9b by the plurality of hooks 27a on the lower surface plate <NUM>. The first attachment member 9a has a plurality of through holes (not depicted) through which the plurality of hooks 26a are inserted during attachment. The second attachment member 9b has a plurality of through holes (not depicted) through which the plurality of hooks 27a are inserted during attachment.

Note that the plurality of hooks 26a of the upper surface plate <NUM> configure the first flap attachment part to which a first attachment part <NUM> of the second flap <NUM> is attached. The plurality of hooks 27a of the lower surface plate <NUM> configure the second flap attachment part to which a second attachment part <NUM> of the second flap <NUM> is attached. One end side of the first flap <NUM> is also attached to the plurality of hooks 26a serving as the first flap attachment part, and the other end side of the first flap <NUM> is attached to the plurality of hooks 27a serving as the second flap attachment part. In the present embodiment, each hook 26a, 27a is disposed near the outer side of the edge part of the opening part <NUM>, making attachment of each flap <NUM>, <NUM> easy.

The airbag cushion <NUM>, inflator <NUM>, and rectification plate <NUM> are attached to the bottom surface plate <NUM> by a stud bolt <NUM>. The inflator <NUM> and rectification plate <NUM> are provided inside the airbag cushion <NUM>. The inflator <NUM> is provided inward of the rectification plate <NUM>. The rectification plate <NUM> is a plate material that rectifies the flow of gas injected from inflator <NUM> to the bag main body part 11a side of the airbag cushion <NUM>. The rectification plate <NUM> extends from an attachment point of the stud bolt <NUM> toward the bag main body part 11a side.

The airbag cushion <NUM> in the stored state has: the bag main body part 11a, which is provided on the opening part <NUM> side in the storage case <NUM> in a folded state; and a bag end part 11b extending from the bag main body part 11a to the bottom surface plate <NUM> side (see <FIG>). The bag main body part 11a protrudes slightly from the opening part <NUM> in a cross-sectional view. The bag main body part 11a is pressed down into the storage case <NUM> by the first flap <NUM>. In the airbag cushion <NUM>, the bag end part 11b is secured to the bottom surface plate <NUM> by the stud bolt <NUM>.

Configurations of the first flap <NUM> and second flap <NUM> are described in further detail. <FIG> depict the first flap <NUM> and second flap <NUM>, respectively, spread out and laid flat on a flat surface.

The first flap <NUM> is a strip-shaped fabric material having required lengths in the width and length directions, respectively, as depicted in <FIG>. Herein, the width direction of the first flap <NUM> is a direction in which the first flap <NUM> is oriented with the longitudinal direction of the storage case <NUM> when attached to the storage case <NUM>. The length direction of the first flap <NUM> is a direction in which the first flap <NUM> is oriented with the short direction of the storage case <NUM> when attached to the storage case <NUM>. These definitions for the width and length directions are the same for the second flap <NUM>, as depicted in <FIG>.

The first flap <NUM> is a fabric material (e.g., non-stretch material) for retaining the position and shape of the airbag cushion <NUM> in the stored state. The first flap <NUM> is formed as a straight strip, as depicted in <FIG>. The width of the first flap <NUM> is constant. The length of the first flap <NUM> is approximately the same length as the dimension in the short direction of the storage case <NUM>. Herein, "approximately the same length" means within +<NUM>% of the dimension in the short direction of the storage case <NUM>. The first flap <NUM> is provided to cover the opening part <NUM> and retain the airbag cushion <NUM> in the storage case <NUM>.

Each end part of the first flap <NUM> has a plurality of through holes 21a, 21b aligned in the width direction. The first flap <NUM> is attached to the storage case <NUM> by inserting the plurality of hooks 26a of the upper surface plate <NUM> through the plurality of through holes 21a at one end part and the plurality of hooks 27a of the lower surface plate <NUM> through the plurality of through holes 21b at the other end part. The first flap <NUM> transverse to the opening part <NUM> in the up-down direction (short direction) so as to contact a rear part of the airbag cushion <NUM> in the stored state.

The first flap <NUM> has a first weak part <NUM> that breaks when pressed by the airbag cushion <NUM>. The first weak part <NUM> is configured of a plurality of slits 31a. Each slit 31a is an elongated through hole and extends in the width direction of the first flap <NUM>. The plurality of slits 31a are aligned at a distance in the width direction of the first flap <NUM>. The strength of the first weak part <NUM> in the first flap <NUM> is weaker than other portions, and when pushed by the airbag cushion <NUM> during expansion and deployment, the first weak part <NUM> breaks. With the first flap <NUM> attached to the storage case <NUM>, the first weak part <NUM> is positioned at or near the center of the opening part <NUM> in the short direction (transverse direction) of the opening part <NUM>. Therefore, the first weak part <NUM> breaks immediately after the airbag cushion <NUM> begins to expand and deploy.

The second flap <NUM> is a fabric material (e.g., non-stretch material or stretch material) for temporarily restricting the deployment of a center part 11c (see <FIG>) of the expanding and deploying airbag cushion <NUM> toward the occupant <NUM>. The second flap <NUM> is configured of a single piece of fabric material. The second flap <NUM> is formed as a straight strip, as depicted in <FIG>. The second flap <NUM> covers the outer surface of the first flap <NUM> so as to transverse the center part 11c in the lateral direction of the airbag cushion <NUM> in the short direction (up-down direction) of the opening part <NUM>.

The second flap <NUM> has: a first attachment part <NUM> with a plurality of through holes 22a; a second attachment part <NUM> with a plurality of through holes 22b; and a transversing part <NUM> extending between the pair of attachment parts <NUM>, <NUM> and transversing the center part 11c of the airbag cushion <NUM>. The second flap <NUM> is attached to the storage case <NUM> by inserting the plurality of hooks 26a of the upper surface plate <NUM> through the plurality of through holes 22a of the first attachment part <NUM> and the plurality of hooks 27a of the lower surface plate <NUM> through the plurality of through holes 22b of the second attachment part <NUM>. Note that the through holes 22a, 22b of the second flap <NUM> are larger than the through holes 21a, 21b of the first flap <NUM>. This makes attachment of the second flap <NUM> to the storage case <NUM> easy.

On both sides of the transversing part <NUM> in the width direction, a pair of notches <NUM> are formed symmetrically about a center line passing through the center position in the width direction and recessed toward the center in the width direction. Each notch <NUM> is formed in the shape of an abbreviated isopod trapezoid with an upper bottom and lower bottom facing each other in the width direction of the second flap <NUM> and narrowing toward the center side in the width direction. In the front view of the opening part <NUM> with the second flap <NUM> attached to the storage case <NUM>, each notch <NUM> has a shape recessed in a curved manner toward the center in the width direction (see <FIG>). The transversing part <NUM> is configured of a transversing part main body 38a of constant width and a pair of connecting parts 38b that are continuous at each end of the transversing part main body 38a and become wider approaching the attachment parts <NUM>, <NUM>.

The second flap <NUM> is adjusted to be approximately the same length as the first flap <NUM> by folding back a plurality of times (even number of times) in the longitudinal direction thereof to provide an overlapping part <NUM> where the transversing part <NUM> overlaps upon itself (see <FIG>). The second flap <NUM> prior to providing the overlapping part <NUM> is larger in the dimension in the length direction than the first flap <NUM>. The dimension of the second flap <NUM> in the length direction is preferably at least <NUM> times the dimension of the first flap <NUM> in the length direction, and even more preferably at least <NUM> times (e.g., double) the dimension of the first flap <NUM> in the length direction. The overlapping part <NUM> has a retaining part <NUM> that retains the folded back state. The retaining part <NUM> is configured of a stitch part in which the fabric of the mutually overlapping transversing part <NUM> (fabric from the frontmost side to the backmost side) is stitched together. In the overlapping part <NUM>, the retaining part <NUM> extends in the lateral direction. The retaining part <NUM> breaks after the breakage of the first weak part <NUM> but prior to the breakage of a second weak part <NUM>. Note that the retaining part <NUM> may have a configuration other than a stitch part.

The second flap <NUM> has a second weak part <NUM> that breaks when pressed by the airbag cushion <NUM>, after rupture of the first weak part <NUM>. The second weak part <NUM> is configured of a plurality of slits 32a. Each slit 32a is an elongated through hole and extends in the width direction of the second flap <NUM>. The plurality of slits 32a are aligned at a distance in the width direction of the second flap <NUM>. In the second flap <NUM>, the strength of the second weak part <NUM> is weaker than other portions, and when pressed by the expansion pressure of the airbag cushion <NUM>, the second weak part <NUM> breaks. With the second flap <NUM> attached to the storage case <NUM>, the second weak part <NUM> is positioned near the upper surface plate <NUM> (near the edge part of the opening part <NUM>) in the short direction of the opening part <NUM>. The second weak part <NUM> is formed in the wider portion of the second flap <NUM>. Specifically, in present embodiment, the second weak part <NUM> is formed in the first attachment part <NUM>, which is wider than the transversing part <NUM>, instead of in the narrower transversing part <NUM>. The second weak part <NUM> is formed on a lower side of the line of the plurality of through holes 22a in the width direction in the first attachment part <NUM>.

An example of a numerical value range will be described for the lateral dimension of the opening part <NUM> in front view. The dimensions of the opening part <NUM> of the storage case <NUM> and the airbag cushion <NUM> in the stored state are, for example, <NUM> to <NUM>. Dimension (width) W1 of the transversing part main body 38a of the second flap <NUM> is <NUM> to <NUM>, which is <NUM>/<NUM> to <NUM>/<NUM> of the stored airbag cushion <NUM>. Furthermore, dimension W2 of an open portion not covered by the transversing part main body 38a is <NUM> to <NUM> on both the left and right.

With reference to <FIG>, an operation of the knee airbag device <NUM> and an effect of the embodiment will be described. When an impact is applied to the vehicle such as when the vehicle is in a collision or the like, the inflator <NUM> that has received a signal from a sensor injects expansion gas that starts to expand and deploy the airbag cushion <NUM>. In the knee airbag device <NUM>, the first flap <NUM> is first pushed to the outer side by the expansion pressure of the airbag cushion <NUM> and breaks at the first weak part <NUM>. Furthermore, the lower panel 8a is pushed to the outer side by the expansion pressure of the airbag cushion <NUM> and breaks at the weak part 8b. Furthermore, the lower panel 8a opens as the airbag cushion <NUM> expands, and the airbag cushion <NUM> expands to the outer side through the opening part in the lower panel 8a. <FIG> depicts the first flap <NUM> and lower panel 8a immediately after breaking.

Furthermore, when the first weak part <NUM> breaks, the expansion pressure of the airbag cushion <NUM> pushes the second flap <NUM> to the outer side. This causes the retaining part <NUM>, which is configured of a stitch part, to break. The second flap <NUM> gradually extends to the outer side at a folded-back point, as depicted in <FIG>. Furthermore, when the second flap <NUM> is fully extended to a certain extent, the second flap <NUM> suppresses the deployment of the center part 11c of the airbag cushion <NUM>.

Furthermore, a tensile force acting on the second weak part <NUM> increases. Therefore, after a short time from the beginning of deployment suppression of the center part 11c, the second flap <NUM> breaks at the second weak part <NUM>, as depicted in <FIG>. The second flap <NUM> breaks at approximately the same time that the airbag cushion <NUM> impacts the shin 5b. Until this breakage, the deployment suppression of the center part 11c by the second flap <NUM> is made in a region from an installation position of the lower panel 8a to the shin 5b, in cross-sectional view. In the knee airbag device <NUM>, when the second flap <NUM> breaks, the expansion and deployment of the airbag cushion <NUM> is completed immediately thereafter, and the right and left knees 5a are restrained by the airbag cushion <NUM>.

In present embodiment, the transversing part <NUM> of the second flap <NUM> restrains the deployment of the center part 11c of the airbag cushion <NUM> until the second flap <NUM> spreads and the second flap <NUM> breaks. This suppresses the airbag cushion <NUM> from deploying to the knee 5a side and promotes deployment in the left-right direction of the vehicle. The airbag cushion <NUM> spreads in the lateral direction as compared to a knee airbag device without the second flap <NUM>. Furthermore, a notch <NUM> recessed in the curved shape is formed on both sides in the width direction in the transversing part <NUM> of the second flap <NUM>, and the notch <NUM> also facilitates spreading in the lateral direction of the airbag cushion <NUM>.

Herein, <FIG> and <FIG> depict states in which expansion and deployment are completed in the knee airbag device <NUM> according to present embodiment, and <FIG> and <FIG> depict a state in which expansion and deployment is completed in the knee airbag device without the second flap <NUM>. In a knee airbag device without the second flap <NUM>, the airbag cushion <NUM> may enter between the knees 5a of the occupant <NUM>, and the airbag cushion <NUM> may not sufficiently deploy on the front side of the knees 5a such that the knees 5a of the occupant <NUM> are restrained by the airbag cushion <NUM>. This situation is more likely to occur with a small knee airbag device <NUM> where the lateral width of the opening part <NUM> of the storage case (<NUM> to <NUM>) is shorter than the distance between the knees 5a. Note that the distance between the knees 5a of the occupant <NUM> is often <NUM>.

In contrast, the airbag cushion <NUM> spreads in the lateral direction according to present embodiment. Therefore, even if the knee airbag device <NUM> is small, it is difficult for the airbag cushion <NUM> to enter between the knees 5a of the occupant <NUM> during expansion and deployment, allowing the airbag cushion <NUM> to deploy stably on the front side of the knees 5a and stably restrain the knees 5a from the front side.

Furthermore, in addition to the second flap <NUM>, the present embodiment also has the first flap <NUM>. Therefore, as described above, the compression reaction force of the airbag cushion <NUM> in the stored state prevents the second flap <NUM> from slackening by being pushed. Therefore, at least two flaps <NUM>, <NUM> can be provided to further stabilize and restrain the knee 5a from the front side.

Furthermore, the length of the second flap <NUM> is longer than the first flap <NUM> in the present embodiment. Herein, if the length of the second flap <NUM> is equal to the first flap <NUM>, the deployment suppression timing of the center part 11c by the second flap <NUM> is too early, and the airbag cushion <NUM> spreads in the lateral direction on a side closer to the opening part <NUM>. Therefore, the airbag cushion <NUM> may interfere with the instrument panel <NUM>. In contrast, in the present embodiment, the longer second flap <NUM> delays the deployment suppression timing described above, such that the airbag cushion <NUM> spreads in the lateral direction on a side closer to the knee 5a and the interference described above is suppressed. The second flap <NUM> has a length dimension where the second weak part <NUM> breaks after the bag main body part 11a pops out from the installation position of the lower panel 8a (position before the weak part 8b breaks) during expansion and deployment of the airbag cushion <NUM>. According to the present embodiment, it is possible to provide the knee airbag device <NUM> in which the airbag cushion <NUM> spreads smoothly in the lateral direction.

Furthermore, in the present embodiment, each flap attachment part 26a, 27a is used for the first flap <NUM> and second flap <NUM>. Furthermore, each flap attachment part 26a, 27a is also used to attach the storage case <NUM> to the vehicle body side. This simplifies the configuration of the knee airbag device <NUM>. Furthermore, each flap attachment part 26a, 27a is configured of three or more hooks. Therefore, it is difficult to cause deformation when each flap <NUM>, <NUM> is pressed by the airbag cushion <NUM>, and breakage of each weak part <NUM>, <NUM> can be made to occur in a stable period at or near the intended breakage position.

Furthermore, in the present embodiment, the second weak part <NUM> is positioned near the edge part of the opening part <NUM>. Therefore, for the second flap <NUM>, the length from the second weak part <NUM> to the lower surface plate <NUM> side is longer, making it easier to provide an overlapping part <NUM>. Furthermore, there is one overlapping part <NUM> in the present embodiment. In the present embodiment, work of adjusting the length of the second flap <NUM> is simple.

In this variation, as depicted in <FIG>, the retaining part <NUM> of the second flap <NUM> is configured of two stitch parts. Each retaining part <NUM> extends in the transverse direction of the second flap <NUM>. Each retaining part <NUM> straddles the overlapping part <NUM> and a non-overlapping part on an upper side thereof. Each retaining part <NUM> is spaced a required distance apart in the width direction of the second flap <NUM>.

In this variation, as depicted in <FIG>, the second flap <NUM> is configured by integrating a plurality of pieces of fabric <NUM>, <NUM>. Specifically, the second flap <NUM> is configured of the first fabric <NUM> attached to the first flap attachment part 26a and the second fabric <NUM> attached to the second flap attachment part 27a. The first fabric <NUM> and the second fabric <NUM> are integrated, for example, by a stitch part. The stitch part is provided at a point where an end part of the first fabric <NUM> and end part of the second fabric <NUM> are overlapped.

In this variation, the second weak part <NUM> is formed in the transversing part main body 38a in the second flap <NUM>, as depicted in <FIG>. The second weak part <NUM> can be provided, for example, on the first attachment part <NUM> side. However, the second weak part <NUM> may be formed at a different location than in this variation.

In this variation, the knee airbag device <NUM> is a low-mount type device, as depicted in <FIG>. The opening part <NUM> of the storage case <NUM> faces downward and faces the back surface of the lower panel 8a, which extends in the front-rear direction. The first flap <NUM> transverses the opening part <NUM> in the front-rear direction. Furthermore, the second flap <NUM> transverses in the front-rear direction the center part 11c of the airbag cushion <NUM> in the lateral direction.

Even in this variation, after the airbag cushion <NUM> begins to expand and deploy, the first weak part <NUM>, the retaining part (stitch part) <NUM>, and the second weak part <NUM> break in this order. Furthermore, the transversing part <NUM> of the second flap <NUM> restrains the deployment of the center part 11c of the airbag cushion <NUM> until the second flap <NUM> spreads and the second weak part <NUM> breaks. This causes the airbag cushion <NUM> to spread in the lateral direction.

In the embodiment described above, the first flap <NUM> and the second flap <NUM> may be attached to mutually different sites in the storage case <NUM>.

In the embodiment described above, the second flap <NUM> may be a fabric material without a notch <NUM> (e.g., a fabric material of constant width).

In the embodiment described above, both the first flap attachment part 26a and the second flap attachment part 27a are disposed near the edge part of the opening part <NUM>, but only one of the first flap attachment part 26a and the second flap attachment part 27a may be disposed near the edge part of the opening part <NUM>.

In the embodiment described above, the first weak part <NUM> may be a configuration other than a slit (e.g., a stitch part).

In the embodiment described above, the second weak part <NUM> may be a configuration other than a slit (e.g., a stitch part). For example, when two pieces of the fabric <NUM>, <NUM> are integrated by a stitch part, as in the second variation, the stitch part may configure the second weak part <NUM> without providing a plurality of slits 32a. In this case, the strength of the stitch part that integrates the two pieces of fabric <NUM>, <NUM> is such that the airbag cushion <NUM> approximately simultaneously breaks and restrains the shin 5b when the expansion and deployment of the airbag cushion <NUM> progresses and the tensile force acting on the second weak part <NUM> (stitch part) increases after the deployment of the center part 11c of the airbag cushion <NUM> is suppressed by the second flap <NUM>.

Claim 1:
A knee airbag device (<NUM>) for protecting a knee (5a) of an occupant (<NUM>), comprising:
an airbag cushion (<NUM>) stored in front of the knee (5a) of the occupant (<NUM>) and for expanding and deploying toward the knee side;
an inflator (<NUM>) for injecting expansion gas to expand the airbag cushion (<NUM>);
a storage case (<NUM>) for storing the airbag cushion (<NUM>), in which is formed an opening part (<NUM>) through which the airbag cushion (<NUM>) that has expanded and deployed by the expansion gas pops out; and
a first flap (<NUM>) for covering the airbag cushion (<NUM>) exposed through the opening part (<NUM>) such that the airbag cushion (<NUM>) is retained in the storage case (<NUM>), and having a first weak part (<NUM>) that breaks when pressed by the airbag cushion (<NUM>) during expansion and deployment; the knee airbag device (<NUM>) being characterised by:
a second flap (<NUM>) which is a component with a larger dimension in a length direction than the first flap (<NUM>), for covering an outer surface of the first flap (<NUM>) so as to transverse in an up-down direction or front-rear direction a center part (11c) of the airbag cushion (<NUM>) in a lateral direction, the second flap (<NUM>) having a second weak part (<NUM>) that breaks when pressed by the airbag cushion (<NUM>) after rupture of the first weak part (<NUM>).