seat belt device

Abstract

To provide a seat belt device which achieves improvement of stability of restraint on a waist of a lap belt.SOLUTION: A seat belt device 200 has a lap belt 212 extending in a lateral direction along a waist front surface of an occupant P seated on a seat 100. The lap belt includes: first webbing W1 and second webbing W2 which are formed in belt-like shapes and held overlapped with each other during a normal time; a first joint part 213 and a second joint part 214 which join the first webbing and the second webbing at both ends in a width direction of the lap belt; an air chamber C provided between the first webbing and the second webbing; a gas generator 260 which supplies a gas for deployment to the air chamber according to detection of a collision of a vehicle or a warning sign of the collision; and a joint breaking part 280 which causes one of the first joint part and the second joint part to break and holds the other in a joint state according to supply of the gas for deployment to the air chamber.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a seat belt device for restraining an occupant seated in a vehicle seat. [Background technology]

[0002] 2. Description of the Related Art Seat belt devices for vehicles and the like are known that have an airbag that deploys from a belt (webbing). As a technique relating to such a seat belt device, Patent Document 1 describes a seat belt device in which a longitudinal intermediate portion of a lap belt is inserted into a cylindrical cover, and an airbag is housed inside the cover. Patent Document 2 describes an airbag device in which an airbag is deployed from a lap belt, in which gas is injected into the lower part of the airbag and flows into an upper chamber through a passage. Patent Document 3 describes a knee airbag that deploys while rising toward the knees of an occupant, and is held in place by a lap belt after fully inflating. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-51744 A [Patent Document 2] Special Publication No. 2007-518628 [Patent Document 3] Special Publication No. 2005-514251 Summary of the Invention [Problem to be solved by the invention]

[0004] During a frontal collision of a vehicle, rear seat occupants may behave differently than front seat occupants. Specifically, the distance between the knees of rear seat passengers and the seatbacks of the front seats changes depending on the seat position and seatback angle, which changes how the rear seat passengers' lower bodies are restrained in the event of a collision. This may change the position of the seatbelt (lap belt) around the rear seat passengers' waists, which may result in the desired upper body movement with the lap belt as the fulcrum. In particular, if the lap belt comes off from the rear seat passenger's waist (pelvic area) during a collision and moves up toward the abdomen, this can cause increased pressure on the abdomen. In view of the above-mentioned problems, an object of the present invention is to provide a seat belt device that improves the stability of the lap belt in restraining the lumbar region. [Means for solving the problem]

[0005] In order to solve the above-described problems, a seat belt device according to one embodiment of the present invention is a seat belt device having a lap belt that extends in a left-right direction of an occupant seated in a vehicle seat along the front of the waist of the occupant, wherein the lap belt comprises first and second webbings formed in strips and held in an overlapping state, a first joint portion that joins the first webbing and the second webbing at a first end portion in the width direction of the lap belt, a second joint portion that joins the first webbing and the second webbing at a second end portion in the width direction of the lap belt, an air chamber provided between the first webbing and the second webbing, a gas generator that supplies deployment gas to the air chamber in response to detection of a vehicle collision or a precursor to a collision, and a joint breaking portion that breaks one of the first joint portion and the second joint portion and keeps the other joined in response to the supply of deployment gas to the air chamber. According to this, by supplying deployment gas while one of the first and second joints of the lap belt is broken, the first webbing and the second webbing separate on the broken side, and the cross section of the lap belt deploys into a fan shape. This allows adjustment of the state of contact between the lap belt and the occupant and the direction of the load input, preventing the lap belt from rising above the occupant's waist and resting on the abdomen. For example, if the lower joint in the area that contacts the front of the occupant's waist breaks, a rotational moment can be generated in the lap belt in a direction that causes the lower end of the lap belt to move forward relative to the upper end, pushing the lap belt downward and preventing it from rising above the waist. This effect is particularly effective when, for example, the occupant's upper body is tilted backward at a relatively large angle while seated in the seat, when the occupant is sitting relatively shallowly in the seat, or when the occupant's physique is relatively small. On the other hand, for example, if the upper joint in the area that contacts the front of the occupant's waist breaks, the expanded upper area of the lap belt will be pressed downward by the occupant's upper body (chest, etc.) which is leaning forward due to the significant deceleration during the collision, thereby pushing the lap belt downward and preventing it from rising from the waist.

[0006] In the present invention, the vehicle may be configured to include a deployment gas retaining member that is provided on one of the first joint portion and the second joint portion on the side where the rupture occurs, and that is accommodated in a folded state between the first webbing and the second webbing before the rupture occurs, and that retains the deployment gas in the air chamber with an end portion of the first webbing and an end portion of the second webbing spaced apart. This makes it possible to retain the deployment gas inside the lap belt and maintain the shape after deployment even when the first webbing and the second webbing are separated on one of the joint sides, thereby making it possible to appropriately obtain the above-mentioned effects.

[0007] In the present invention, the joint breaking portion may include a tension difference generating portion that generates a tension difference between the tension of the first webbing and the tension of the second webbing when the tension in the longitudinal direction of the lap belt becomes equal to or greater than a predetermined value, causing the first joint portion or the second joint portion to break. This allows the first or second joint to be broken using a mechanical configuration that does not require electronic control in response to an increase in lap belt tension caused by, for example, the activation of a pretensioner or the behavior of an occupant during a collision, thereby achieving the above-mentioned effect.

[0008] In the present invention, the seat belt may include a shoulder belt extending obliquely from the front of the chest of the occupant along the shoulders and formed continuously with one end of the lap belt, and a tongue portion where the lap belt and the shoulder belt are connected in a folded-back state, wherein the gas generator supplies the deployment gas from the side of the lap belt opposite the tongue portion, and the tongue portion has a flow blocking portion that blocks the flow of the deployment gas from the lap belt side to the shoulder belt side. According to this, when the lap belt is formed integrally with the shoulder belt, the deployment gas can be supplied only to the lap belt portion with a simple configuration to deploy the lap belt.

[0009] In the present invention, the joint breaking portion can be configured to be switchable between a first breaking mode that breaks only the first joint portion and a second breaking mode that breaks only the second joint portion. This allows the selection of either the first or second breaking mode depending on the occupant's physique, seated posture, etc., thereby optimizing the shape of the lap belt after deployment, and further improving the occupant restraint performance. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to provide a seat belt device that improves the stability of the lumbar region restraint by the lap belt. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the configuration of a rear part of a vehicle body having a seat belt device according to a first embodiment of the present invention; [Figure 2]1 is a schematic perspective view showing the configuration of a seatbelt device and its surroundings in a first embodiment, showing a state in which an occupant is seated.

[0023] FIG. [Figure 3] 1 is a diagram showing the configuration of a control system for a seat belt device in a first embodiment. [Figure 4] 1 is a schematic cross-sectional view showing the outer belt of the first embodiment cut along a plane perpendicular to the longitudinal direction, illustrating a state before the lap belt is deployed. FIG. [Figure 5] 3A and 3B are diagrams illustrating a configuration of a joint breaking mechanism provided in the tongue in the first embodiment. [Figure 6] FIG. 2 is a schematic cross-sectional view showing the outer belt of the first embodiment cut along a plane perpendicular to the longitudinal direction, illustrating the state after the lap belt has been deployed. [Figure 7] 3A and 3B are diagrams illustrating a state in which an occupant is restrained when a collision occurs in the seatbelt device of the first embodiment. [Figure 8] 5A and 5B are diagrams schematically showing an occupant restraining state when a collision occurs in a seatbelt device according to a second embodiment of the present invention. [Figure 9] 10 is a diagram showing a schematic configuration of a joint breaking portion in a seatbelt device according to a third embodiment of the present invention. FIG. [Figure 10] FIG. 10 is a diagram showing the configuration of a control system for a seat belt device in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment A first embodiment of a seat belt device to which the present invention is applied will be described below. The seat belt device of the first embodiment is provided, for example, in a rear seat of an automobile such as a passenger car having two rows of seats in the front and rear. FIG. 1 is a diagram showing the configuration of the rear part of a vehicle body having a seat belt device of the first embodiment. FIG. 1 shows a side view of the vehicle body as seen from the vehicle width direction.

[0013] The vehicle 1 has a vehicle interior 10 which is a space for accommodating passengers. The rear portion of the passenger compartment 10 is disposed adjacent to the rear wheels RW. The vehicle 1 has, for example, front seats and rear seats arranged in two rows in the longitudinal direction. The seat 100 to which the seat belt device of the first embodiment is attached is provided for a rear seat and is disposed in the rear part of the vehicle interior 10.

[0014] FIG. 2 is a schematic perspective view showing the configuration of the seatbelt device and its surroundings in the embodiment, showing a state in which an occupant is seated. The seat 100 is configured to include a seat cushion 110, a seat back 120, a headrest 130, and the like. The seat cushion 110 has a seating surface on which the lumbar region (pelvis region), buttocks, and thighs of the occupant are placed. The seat cushion 110 has a seat surface portion 111 , an inner portion 112 , and an outer portion 113 .

[0015] The seat surface 111 is a portion of the seat cushion 110 on which the buttocks of the occupant P rest. For example, a plurality of (for example, two) seating surfaces 111 can be arranged on the seat cushion 110 of one vehicle, spaced apart in the vehicle width direction.

[0016] The inner portion 112 is a portion of the seat cushion 110 that is arranged on the inner side of the seat surface portion 111 in the vehicle width direction. For example, in a vehicle provided with two seating surfaces 111, the inner portion 112 is provided in the center in the vehicle width direction. In a vehicle provided with two seating portions 111, when three passengers are seated in the vehicle width direction, the middle passenger may be seated on the inner portion 112.

[0017] The outer portion 113 is a portion of the seat cushion 110 that is arranged on the outer side of the seat surface portion 111 in the vehicle width direction. The outer portion 113 is disposed adjacent to the inner trim of a rear side door (not shown) used for passenger P to get in and out of the vehicle.

[0018] The seat back 120 is a portion that protrudes upward from the rear end portion of the seat cushion 110 and is a portion that mainly supports the back of the occupant. The seat back 120 is made of a porous material having elasticity, similar to the seat cushion 110, and is covered with a skin. The seat back 120 is tilted backward so that the upper end is closer to the rear of the vehicle than the lower end. The rearward tilt angle of the seat back 120 can be adjusted (changed) by a well-known reclining mechanism (not shown).

[0019] The headrest 130 is a member disposed so as to protrude upward from the upper end of the seat back 120. The headrest 130 has a function of absorbing the impact by receiving the head of the occupant P that moves backward due to inertial force when the vehicle is hit by a rear-end collision, for example.

[0020] The seatbelt device 200 is worn by an occupant P seated in the seat 100 and has a three-point seatbelt that restrains the occupant P in the event of a collision or other accident. The seatbelt device 200 includes an outer belt 210, an inner belt 220, a tongue 230, a buckle 240, a belt anchor 250, a retractor 260, an inflator 270, a joint breaking mechanism 280, and the like.

[0021] The outer belt 210 has a shoulder belt 211, a lap belt 212, etc. that are continuously and integrally formed from a belt-like first webbing W1, a second webbing W2, etc. (see Figures 4 and 6) made of, for example, a polyester fiber woven fabric. The shoulder belt 211 is a portion that is provided obliquely along the front of the upper body from the shoulder of the occupant P on the outer side in the vehicle width direction to the waist of the occupant P on the inner side in the vehicle width direction. An upper portion of the shoulder belt 211 is connected to a retractor 260 that is disposed at the rear side near the upper end of the seat back 120 and the outer end in the vehicle width direction.

[0022] The lap belt 212 is a part that is provided along the occupant P's waist and stretched across the waist on both sides. The end of the lap belt 212 on the tongue 230 side (the end on the inner side in the vehicle width direction when worn) is connected to the inner belt 220 via the tongue 230 and the buckle 240 when worn. The end of lap belt 212 opposite to tongue 230 (the end on the outer side in the vehicle width direction when worn) is connected to the floor portion of the vehicle body via belt anchor 250. The lap belt 212 is between the seat surface portion 111 and the outer portion 113 of the seat cushion 110 and is drawn out above the seat cushion 110 from a slit provided near the end portion on the seat back 120 side. The lap belt 212 is a so-called air belt that is deployed by being supplied with deployment gas in the event of a collision of the vehicle 1. This will be described in detail later.

[0023] The inner belt 220 is a band-shaped webbing provided on the inner side of the occupant P's waist in the vehicle width direction. The lower end of the inner belt 220 is fixed to the floor of the vehicle body below the seat cushion 110. The inner belt 220 is between the seat surface portion 111 and the inner portion 112 of the seat cushion 110, and is drawn out above the seat cushion 110 from a slit provided near the end portion on the seat back 120 side. A buckle 240 is connected to the upper end of the inner belt 220 .

[0024] The tongue 230 is a member provided at the boundary between the shoulder belt 211 and the lap belt 212 of the outer belt 210. The tongue 230 is inserted so that the outer belt 210 can pass through on the shoulder belt 211 side and the lap belt 212 side, and is detachably attached to the buckle 240 when the occupant P fastens the seat belt. Furthermore, inside the tongue 230, a joint breaking mechanism 280, which will be described later, is provided.

[0025] The buckle 240 is a member to which the tongue 230 is detachably attached. The tongue 230 is locked to the buckle 240 by, for example, the occupant P gripping it with his / her hand and inserting the tab portion protruding from the main body portion into an opening formed in the buckle 240 to a predetermined depth. The buckle 240 is provided with a release button (not shown). When the occupant P presses the release button, the buckle 240 unlocks the tongue 230 .

[0026] The belt anchor 250 is a connecting member for attaching the end of the outer belt 210 on the lap belt 212 side to the vehicle body. The belt anchor 250 is disposed below the rear part of the seat cushion 110, between the seat surface portion 111 and the outer portion 113.

[0027] The retractor 260 has a function of winding up and storing the excess portion of the outer belt 210 when the seat belt device 200 is not worn, and also has a function of unwinding the wound-up outer belt 210 when the seat belt device 200 is worn. The retractor 260 is disposed at the upper end of the seat back 120 and on the rear side of the end region on the outer side in the vehicle width direction (behind the shoulders of the occupant P). The retractor 260 includes a pretensioner 261 (see FIG. 3) that forcibly winds up the outer belt 210 using, for example, a chemical (explosive) type actuator to increase the tension of the outer belt 210 and enhance the restraining force of the occupant P in the event of a vehicle collision.

[0028] The inflator 270 has, for example, a chemical (explosive) type gas generator, and supplies gas for deployment to the inside of the lap belt 212 of the outer belt 210 (between a first webbing W1 and a second webbing W2, which will be described later). The inflator 270 operates in response to a command from a seatbelt control unit 300 (described later) and generates gas for deployment. The inflator 270 is provided near the end of the outer belt 210 on the lap belt 212 side (near the belt anchor 250), and is capable of introducing deployment gas from the end of the lap belt 212 opposite to the tongue 230 side.

[0029] The seat belt device 200 has a control system 300, which will be described below, for controlling the inflator 270 and other components. FIG. 3 is a diagram showing the configuration of a control system for a seat belt device in the first embodiment. The control system 300 includes a seat belt control unit 310 . The seatbelt control unit 310 is configured as a microcomputer having, for example, an information processing section such as a CPU, a storage section such as a RAM or a ROM, an input / output interface, and a bus connecting these. For example, in the case where an airbag device having an airbag that deploys in the vehicle cabin is provided, the seatbelt control unit 310 may be configured to be shared (shared) with an airbag control unit that controls the airbag device.

[0030] The seatbelt control unit 310 is connected to an inflator 270, a pretensioner 261, a collision sensor 311, and the like. As described above, the seatbelt control unit 310 has the function of issuing activation commands to the inflator 270 and the pretensioner 261. The collision sensor 311 is, for example, an acceleration sensor that detects acceleration acting on the vehicle body. The collision sensor 311 can be used in common with the collision sensor used to control the airbag device described above.

[0031] When the seatbelt control unit 310 determines, based on the output of the collision sensor 311, that the vehicle 1 has experienced a collision in which the occupant P is displaced forward relative to the vehicle body due to inertial force, such as a full-frontal collision, a frontal offset collision (small offset collision), or an oblique collision, the seatbelt control unit 310 issues an operation command to the inflator 270 to start generating deployment gas, and issues an operation command to the pretensioner 261 to wind up the upper end of the shoulder belt 211 of the outer belt 210 and increase the tension acting on the outer belt 210, in order to restrain the occupant P using the seatbelt device 200.

[0032] The configuration of the outer belt 210 in the seatbelt device 200 of the first embodiment will be described in more detail below. FIG. 4 is a schematic cross-sectional view showing the outer belt of the first embodiment cut along a plane perpendicular to the longitudinal direction, illustrating the state before the lap belt is deployed. The outer belt 210 is configured to include a first webbing W1, a second webbing W2, an upper string 213, a lower string 214, an upper panel 215, a lower panel 216, and the like.

[0033] As described above, the first webbing W1 and the second webbing W2 are strip-shaped members made of a woven polyester fiber fabric or the like. The first webbing W1 and the second webbing W2 have a degree of rigidity that allows them to generally maintain their cross-sectional shape even when subjected to the pressure of the deployment gas, and are coated with an airtight and heat-resistant coating to prevent leakage of the deployment gas. During normal use of the vehicle (before a collision occurs), the first webbing W1 and the second webbing W2 are overlapped with a minute gap between them that is large enough to accommodate the upper panel 215 and the lower panel 216 in a folded state.

[0034] The upper string 213 and the lower string 214 are members that join the upper end and the lower end of the first webbing W1 and the second webbing W2, respectively. The upper string 213 and the lower string 214 are made of flexible threads made of polyamide synthetic resin fibers such as nylon. The upper string 213 and the lower string 214 are sewn together, for example, by wave sewing on the first webbing W1 side and the second webbing W2 side, exposing each string at equal intervals. The upper string 213 is formed to have a strength higher than that of the lower string 214 against shear forces so as not to break when a joint breaking mechanism 280 (described later) is activated.

[0035] The upper panel 215 and the lower panel 216 are made of flexible base fabric panels formed by knitting fibers made of polyamide synthetic resin such as nylon. The upper panel 215 and the lower panel 216 are deployment gas retaining members that retain deployment gas introduced into the lap belt 212 . The upper panel 215 is formed in a strip shape along the longitudinal direction of the outer belt 210. The upper panel 215 is disposed in a region between the upper string 213 and the lower string 214 and adjacent to the upper string 213 .

[0036] The lower panel 216 is formed in a strip shape along the longitudinal direction of the outer belt 210 . The lower panel 216 is disposed in a region between the upper string 213 and the lower string 214 and adjacent to the lower string 214 . The lower panel 216 is formed to be wider than the upper panel 215, and a middle portion in the width direction is accommodated in a folded state between the first webbing W1 and the second webbing W2. Both widthwise ends of the upper panel 215 and the lower panel 216 are continuously joined to the first webbing W1 and the second webbing W2, for example, by adhesion or welding, along the longitudinal direction of the outer belt 210 in a state capable of sealing out the deployment gas.

[0037] In the first embodiment, a joint breaking mechanism (joint breaking portion / tension generating portion) 280 is provided that breaks the lower string 214 when the tension acting on the lap belt 212 exceeds a predetermined value. FIG. 5 is a diagram schematically showing the configuration of a joint breaking mechanism provided in the tongue in the first embodiment. The joint breaking mechanism 280 is provided inside the tongue 230 and includes an inner roller 281, an outer roller 282, an inner roller gear 283, an outer roller gear 284, and the like.

[0038] The joint breaking mechanism 280 is provided at a folding back portion where the outer belt 210 is folded back inside the tongue 230 between the shoulder belt 211 side and the lap belt 212 side. At the folded-back portion, the first webbing W1 is disposed on the inside and the second webbing W2 is disposed on the outside. The inner roller 281 is a cylindrical member that is provided inside the folded portion and around which the first webbing W1 is wound. The outer roller 282 is a columnar member that is provided on the outside of the folded-back portion and comes into contact with the second webbing W2. The inner roller 281 and the outer roller 282 are supported by the tongue 230 in a state in which they can rotate about their respective central axes which are arranged in parallel. The central axes of the inner roller 281 and the outer roller 282, together with the central axes of the inner roller gear 283 and the outer roller gear 284, are supported so as to be capable of relative displacement in the approaching and separating directions. For ease of understanding, FIG. 5 shows a gap between the first webbing W1 and the second webbing W2, but in reality, the outer roller 282 has the function of pressing the second webbing W2 to bring the first webbing W1 and the second webbing W2 into close contact with each other.

[0039] The inner roller gear 283 is a gear such as a spur gear that is arranged coaxially with the inner roller 281 and fixed to the inner roller 281 . The outer roller gear 284 is a gear such as a spur gear that is arranged coaxially with the outer roller 282 and fixed to the outer roller 282 . For ease of understanding, in FIG. 5, only the pitch circles of the inner roller gear 283 and the outer roller gear 284 are shown by dashed lines. The inner roller gear 283 and the outer roller gear 284 do not mesh with each other during normal use of the vehicle (non-crash), and are configured so that at least one of the central axes moves and they mesh with each other only when a relatively large tension acts on the outer belt 210, such as that exerted by the operation of the pretensioner 260. The number of teeth of the inner roller gear 283 is set to be larger than the number of teeth of the outer roller gear 284 . Therefore, when the inner roller gear 283 and the outer rotor gear 284 are engaged with each other, a rotational speed difference occurs between the inner roller 281 and the outer roller 282, with the inner roller 281 having a lower peripheral speed.

[0040] In the first embodiment, when the seatbelt control unit 310 determines that the vehicle 1 has collided based on the output of the collision sensor 311, the seatbelt control unit 310 issues an activation command to the pretensioner 261, and forcibly winds up and pulls the outer belt 210. As a result, tensions T1 and T2 act on the first webbing W1 and the second webbing W2 of the shoulder belt 211, respectively. The tensions T1 and T2 have the same magnitude. On the other hand, tensions T3 and T4 are generated in the first webbing W1 and the second webbing W2 of the lap belt 212, respectively. However, due to the difference in peripheral speed between the inner roller 281 and the outer roller 282 described above, friction is generated acting on the first webbing W1, resulting in a tension difference ΔT (T4-T3) in which the tension T3 is smaller than the tension T4. This tension difference ΔT acts as a shear force on the lower string 214, causing it to break. On the other hand, the upper string 213 is made strong enough to withstand this tension difference by, for example, increasing the thickness of the thread, so that it will not break.

[0041] When the lower string 214 is broken and deployment gas is supplied from the inflator 270, the lap belt 212 portion of the outer belt 210 deploys as an air belt. FIG. 6 is a schematic cross-sectional view showing the outer belt of the first embodiment cut along a plane perpendicular to the longitudinal direction, illustrating the state after the lap belt has been deployed. The first webbing W1 and the second webbing W2 rotate relatively in a direction in which the lower end sides open. Between the lower end portions of the first webbing W1 and the second webbing W2, the folded lower panel 216 unfolds, and the tension acting between the end portions and the pressure of the deployment gas causes the webbing to be stretched in a curved shape with a protruding downwards.

[0042] As a result, the cross section of the lap belt 212 taken along a plane perpendicular to the longitudinal direction has a sector shape as shown in FIG. The area surrounded by the first webbing W1, the second webbing W2, the upper panel 215, and the lower panel 216 functions as an air chamber C that is filled with and retains deployment gas. At this time, the inner roller 281 and the outer roller 282 press the first webbing W1 and the second webbing W2 together, thereby preventing (blocking) airflow between the lap belt 212 and the shoulder belt 211. As a result, the flow of the deployment gas supplied from the belt anchor 250 side from the lap belt 212 side to the shoulder belt 211 side is prevented, and even with a relatively small-output inflator 270, only the lap belt 212 portion can be deployed efficiently. The inner roller 281 and the outer roller 282 function as the flow blocking portion of the present invention.

[0043] FIG. 7 is a diagram schematically showing an occupant restraining state in the seatbelt device of the first embodiment when a collision occurs. As shown in FIG. 7, according to the first embodiment, a rotational moment M can be generated in the lap belt 212 at the central portion in the vehicle width direction such that the lower end moves forward relative to the upper end. This pushes the lap belt 212 downward, ensuring a force F that presses the occupant P against the seat cushion 110, and preventing the occupant P from rising from the waist.

[0044] According to the first embodiment described above, the following effects can be obtained. (1) When the lower string 214 joining the lower ends of the first webbing W1 and the second webbing W2 of the lap belt 212 is broken, the lower ends of the first webbing W1 and the second webbing W2 are separated from each other by supplying deployment gas into the interior of the lap belt 212, and the cross section of the lap belt 212 is deployed into a fan shape with an open bottom. This allows adjustment of the state of contact between the lap belt 212 and the occupant P and the load input direction, preventing the lap belt 212 from rising relative to the occupant's waist and coming into contact with the abdomen. Specifically, a rotational moment M can be generated in the direction in which the lower end of the lap belt 212 moves forward relative to the upper end, pushing the lap belt 212 downward and preventing it from rising from the waist. (2) By providing the upper panel 215 and the lower panel 216 between the first webbing W1 and the second webbing W2, even when the first webbing W1 and the second webbing W2 are separated at their lower end sides, it is possible to retain the deployment gas inside the lap belt 212 and maintain the shape after deployment, thereby making it possible to appropriately obtain the above-mentioned effects. (3) By providing a joint breaking mechanism 280 that generates a tension difference ΔT between the first webbing W1 and the second webbing W2 in response to an increase in tension T1 to T4 acting on the outer belt 210, the lower string 214 can be broken by a mechanical configuration that does not require electronic control in itself in response to an increase in tension on the outer belt 210 caused by the operation of the pretensioner 261 or the forward leaning behavior of the occupant P during a collision, thereby achieving the above-mentioned effects. (4) The inner roller 281 and the outer roller 282 seal the deployment gas in the lap belt 212, so that even if the lap belt is formed integrally with the shoulder belt, deployment gas can be supplied only to the lap belt 212 with a simple configuration to deploy it.

[0045] Second Embodiment Next, a second embodiment of a seat belt device to which the present invention is applied will be described. In the following embodiments, the same reference numerals are used to designate parts common to the previous embodiments, and explanations thereof will be omitted, with differences being mainly described. In the second embodiment, the structure of the outer belt 210 shown in Figs. 4, 6, etc. is inverted in the width direction (vertical direction in Figs. 4 and 6) of each webbing W1, W2. That is, the upper panel 215 is made expandable, and the joint breaking mechanism 280 breaks the upper string 213 and maintains the lower string 214. As a result, when the deployment gas is supplied to the lap belt 212, the lap belt 212 deploys so that the upper panel 215 side (upper end side) spreads out in front of the occupant's waist.

[0046] FIG. 8 is a diagram schematically showing an occupant restraining state in the seatbelt device of the second embodiment when a collision occurs. As shown in FIG. 8, according to the second embodiment, the upper body of occupant P, who is leaning forward due to the significant deceleration at the time of the collision, presses downward on the expanded upper region of lap belt 212, thereby pushing lap belt 212 downward, ensuring a force F that presses occupant P against seat cushion 110 and preventing lap belt 212 from rising from the waist.

[0047] Third Embodiment Next, a third embodiment of a seat belt device to which the present invention is applied will be described. In the third embodiment, depending on the condition of the occupant, etc., either the upper string 213 or the lower string 214 is selectively broken, making it possible to select between a deployment form similar to that of the first embodiment in which the lower part of the lap belt 212 is spread out, and a deployment form similar to that of the second embodiment in which the upper part of the lap belt 212 is spread out.

[0048] In the third embodiment, instead of the joint breaking mechanism 280 of the first embodiment, either the upper string 213 or the lower string 214 can be selectively broken by an upper actuator 312 and a lower actuator 313 described below. FIG. 9 is a diagram schematically showing the configuration of a joint breaking portion in a seatbelt device of the third embodiment. The upper actuator 312 and the lower actuator 313 are provided near the end of the lap belt 212 on the belt anchor 250 side, and are connected to the upper string 213 and the lower string 214, respectively. The upper actuator 312 and the lower actuator 313 are, for example, chemical or electric actuators, and have the function of pulling the upper string 213 and the lower string 214 in response to an operation command from the seat belt control unit 310, thereby breaking the joint between the first webbing W1 and the second webbing W2. In the third embodiment, the upper panel 215 and the lower panel 216 both have an expandable and extendable configuration, similar to the lower panel 216 in the first embodiment.

[0049] FIG. 10 is a diagram showing the configuration of a control system for a seat belt device in the third embodiment. In the control system 300A of the third embodiment, an upper actuator 312 and a lower actuator 313 are further connected to the seatbelt control unit 310. The control system 300A further includes an occupant state detection unit 320. The occupant state detection unit 320 detects information relating to the posture, physique, etc. of the occupant P seated in the seat 100. The occupant state detection unit 320 can be configured as a microcomputer having, for example, an information processing unit such as a CPU, a storage unit such as a RAM or a ROM, an input / output interface, and a bus connecting these. The occupant state detection unit 320 is communicably connected to the seatbelt control unit 310 via an in-vehicle LAN such as a CAN or directly.

[0050] The occupant state detection unit 320 is connected to a pressure sensor 321, a seat position sensor 322, an imaging device 323, and the like. The pressure sensor 321 is provided under the seat surface 111 of the seat cushion 110, and generates an output corresponding to the surface pressure applied to the upper surface of the seat surface 111. The occupant state detection unit 320 is capable of determining the weight of the occupant P based on the output of the pressure sensor 321 and estimating the size of the physique of the occupant P from the weight. In addition, the pressure sensor 321 is capable of detecting surface pressure at multiple measurement points distributed in the fore-and-aft direction of the vehicle, and the occupant state detection unit 320 is capable of estimating whether the occupant P is sitting deeply or shallowly in the seat 100 (the fore-and-aft position of the center of pressure) based on the detected pressure distribution.

[0051] The seat position sensor 322 detects the rearward tilt angle of the seat back 120 adjusted by the reclining mechanism. The imaging device 323 includes a camera that captures an image of the occupant P seated in the seat 100, and an image processing unit that processes the image captured by the camera. The imaging device 323 has a function of estimating the physique and seated posture of the occupant P through image processing.

[0052] The seatbelt control unit 310 determines whether to activate the upper actuator 312 or the lower actuator 313 in the event of a collision, based on the physique and seated posture of the occupant P estimated by the above-mentioned sensors. For example, when the lap belt 212 is deployed in a manner in which the lower portion thereof spreads out as in the first embodiment (see FIG. 7), this is effective when the occupant P's upper body is tilted backward at a large angle or when the occupant P is sitting shallowly in the seat 100. Also, even if the occupant P is small in size, the force of the occupant's chest to push the lap belt 212 downward may be insufficient as shown in Figure 8, so the deployment mode in which the downward spread is as shown in Figure 7 is advantageous.

[0053] On the other hand, when the lap belt 212 is deployed in a manner in which the upper part thereof spreads out as in the second embodiment (see FIG. 8), this is effective when the angle of backward inclination of the upper body of the occupant P is small (close to an upright position), when the occupant P is sitting deep in the seat 100, or when the occupant P has a large build. The seat belt control unit 310 can be configured to, for example, set evaluation values for the occupant's physique, the angle of backward tilt of the upper body, and the front and rear positions of the buttocks, perform weighting processing with a predetermined weighting coefficient to generate a judgment value, and compare this judgment value with a preset threshold value to determine whether to activate the upper actuator 312 or the lower actuator 313.

[0054] According to the third embodiment described above, by selecting either the first breaking mode, which breaks the lower string 214, or the second breaking mode, which breaks the upper string 213, depending on the occupant's physique, seated posture, etc., it is possible to optimize the shape of the lap belt 212 after deployment, and further improve the restraint performance of the occupant P.

[0055] (Variation) The present invention is not limited to the above-described embodiment, and various modifications and variations are possible, and these are also within the technical scope of the present invention. (1) The configurations of the seat belt device and the vehicle are not limited to the above-described embodiments, and may be modified as appropriate. For example, the shape, structure, material, manufacturing method, arrangement, number, etc. of each member constituting the seat belt device can be changed as appropriate. (2) The configuration of the joint breaking portion in each embodiment is an example, and the joint may be broken by other methods. (3) In each embodiment, the first webbing and the second webbing are joined by sewing using a string, for example. However, the joining is not limited to this, and the joining may be performed by other methods. For example, adhesion, fusion, welding, etc. can be used as appropriate so as to achieve a bond strength that allows breaking. Alternatively, a separate member such as a tether having a weakened portion may be provided across the ends of the first webbing and the second webbing to form a joint. (4) In each embodiment, the base fabric panel is provided only between the ends of the first webbing and the second webbing. However, this is not limited to this. For example, a configuration may be adopted in which a tubular body made of a base fabric panel is disposed between the first webbing and the second webbing. (5) In the third embodiment, the information (physique, posture) acquired (estimated) about the occupant is one example, and other information may be acquired and used to determine the deployment mode of the lap belt (whether the upper or lower end is to be opened). Furthermore, the method for acquiring each piece of information is not limited to that in the third embodiment, and can be changed as appropriate. (6) In each embodiment, the seat belt device is provided in the rear seats (second row seats) of a passenger car as an example, but the present invention is not limited to this and can be applied to front seats and seats in the third row and beyond. In addition, the vehicle type is not limited to passenger cars and can be changed as appropriate. (7) In each embodiment, the inflator is provided on the belt anchor side of the outer belt, but the location of the inflator (gas generator) is not limited to this and may be changed as appropriate. For example, the inflator may be provided on the tongue side. In this case, a so-called double retractor type configuration may be used, in which a retractor is provided at each end of the outer belt on the shoulder belt side and on the lap belt side. [Explanation of symbols]

[0056] 1 car, 10 compartments P Passenger RW Rear Wheel 100 Seat 110 Seat Cushion 111 Seat part 112 Inner part 113 Outer part 120 Seat back 130 Headrest 200 Seat belt device 210 Outer belt 211 Shoulder belt 212 Lap belt 213 Upper string 214 Lower string 215 Upper panel 216 Lower panel 220 Inner Belt 230 Tongue 240 Buckle 250 Belt Anchor 260 Retractor 261 Pretensioner 270 Inflator 280 Joint rupture mechanism 281 Inner Roller 282 Outer Roller 283 Inner Roller Gear 284 Outer Roller Gear 300,300A control system 310 seat belt control unit 311 collision sensor 312 Upper actuator 313 Lower actuator 320 Occupant state detection unit 321 Pressure sensor 322 Seat position sensor 323 Imaging device W1 First webbing W2 Second webbing C Air chamber

Claims

1. A seat belt device having a lap belt extending in the left-right direction of an occupant seated in a vehicle seat along the front of the occupant's waist, The lap belt is a first webbing and a second webbing formed in a belt shape and held in an overlapping state; a first joining portion joining the first webbing and the second webbing at a first end portion in the width direction of the lap belt; a second joining portion joining the first webbing and the second webbing at a second end portion in the width direction of the lap belt; an air chamber provided between the first webbing and the second webbing; a gas generator that supplies deployment gas to the air chamber in response to detection of a vehicle collision or a collision precursor; a joint breaking portion that breaks one of the first joint portion and the second joint portion and maintains the other joint portion in a joined state in response to the supply of the deployment gas to the air chamber; A seat belt device comprising:

2. a deployment gas retaining member that is provided on the side of the first joint portion or the second joint portion where the rupture occurs, and that is accommodated in a folded state between the first webbing and the second webbing before the rupture occurs, and that retains the deployment gas in the air chamber with the end of the first webbing and the end of the second webbing spaced apart; 2. The seat belt device according to claim 1,

3. The joint breaking portion has a tension difference generating portion that generates a tension difference between the tension of the first webbing and the tension of the second webbing when the tension in the longitudinal direction of the lap belt becomes equal to or greater than a predetermined value, causing the first joint portion or the second joint portion to break.

3. The seat belt device according to claim 1 or 2, wherein:

4. a shoulder belt extending obliquely from the front of the chest of the occupant along the shoulders and formed continuously with one end of the lap belt; a tongue portion at which the lap belt and the shoulder belt are connected in a folded-back state, the gas generator supplies the deployment gas from the side opposite to the tongue portion side of the lap belt, The tongue portion has a flow blocking portion that blocks the flow of the deployment gas from the lap belt side to the shoulder belt side.

4. The seat belt device according to claim 1, wherein:

5. The joint breaking unit is switchable between a first breaking mode in which only the first joint breaks and a second breaking mode in which only the second joint breaks.

5. The seat belt device according to claim 1, wherein:

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