VEHICLE SEAT, AND METHOD FOR MANUFACTURING VEHICLE SEAT

A vehicle seat has high designability and achieves control of a deployment speed of a side airbag. A seat includes: a bolster part; a shoulder part; a cover for each the bolster part and the shoulder part; and an airbag sleeve in the bolster part. The airbag sleeve includes; a first section extending along a first tear line serving as a seam of a first cover piece and a second cover piece; and a second section extending across a second lateral directional line serving as a seam of the second cover piece and a fourth cover piece. The first section is sewn with the second cover piece along the first tear line. The second section is sewn with a set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich a seam allowance extending along the second lateral directional line.

TECHNICAL FIELD

The present invention relates to a vehicle seat, and a method for manufacturing the vehicle seat.

BACKGROUND ART

A vehicle seat which includes a seatback accommodating an airbag device is preliminarily provided with an airbag deploying part (hereinafter, referred to as a “tear line”) serving as a seam extending in a longitudinal direction on a cover on a side part of the seatback to deploy an airbag when a vehicle is involved in a collision. Such a tear line has been conventionally formed on only each of bolster parts respectively located on both sides of a top board part of a seatback in a width direction and extending frontward and lateralward from the seatback around body side portions of an occupant, the top board part coming into contact with the back of the occupant. However, in recent years, an airbag device has become larger, and such a design as to form a tear line on a shoulder part located above the bolster part and extending frontward and lateralward around a shoulder of an occupant is developed.

For instance, each of Patent Literatures 1 to 2 discloses a seat having the aforementioned design. As shown inFIG.9, Patent Literature 1 describes a seatback which includes a cover located on a side part thereof and including four cover pieces S1to S4, i.e., two cover pieces S1, S2forming surfaces of shoulder parts, and two cover pieces S3, S4forming surfaces of bolster parts respectively located below the shoulder parts. The four cover pieces S1to S4are sewn together along a lateral directional line Y1, and an upper tear line Y2and a lower tear line Y3each extending in a longitudinal direction. In the seatback, webbing cloths41,42are sewn respectively with portions of the lower cover pieces S3, S4around the lower tear line Y3, and the webbing cloths41,42are respectively connected to portions of the upper cover pieces S1, S2around the upper tear line Y2via connecting cloths43,44so that the upper tear line Y2and the lower tear line Y3each extending in the longitudinal direction tear prior to the lateral directional line Y1when a side airbag deploys.

As shown inFIG.10toFIG.11, Patent Literature 2 describes a seatback which includes two sewn parts consisting of: a longitudinal directional tear line56between a seat surface cover part55a(covering a seat front surface) and a frame cover part55b(covering a seat side surface) of a seat cover55; and a lateral directional line57intersecting the tear line56. A pair of upper and lower webbing cloths58,59have their one ends sewn together at upper and lower positions on the longitudinal directional tear line56and across the lateral directional line57. This aims at firstly tearing the longitudinal directional tear line56formed by sewing the webbing cloths58,59together and subsequently tearing the lateral directional line57under a deployment pressure of an airbag (not shown) of an airbag device51.

In the seatback described in Patent Literature 1, the connecting cloths43,44shown inFIG.9extend across the lateral directional line Y1. Thus, in an attempt to form the lateral line Y1after forming the upper and lower tear lines Y2, Y3through sewing, the connecting cloths43,44would hinder forming of a three-dimensional section, like a pull-in section, along the lateral directional line Y1, the section having such a shape that the lateral directional line Y1protrudes from faces of the cover pieces S1to S4in a normal direction, i.e., frontward from the paper ofFIG.9. For instance, the connecting cloths43,44may fold down a seam allowance extending along the lateral directional line Y1. This causes a problem of a failure in realizing a seat having high designability.

By contrast, the seatback described in Patent Literature 2 includes the lateral directional line57formed through sewing in the same manner as the longitudinal directional tear line56shown inFIG.9toFIG.10, and thus has a possibility that the lateral directional line57entirely tears to open prior to the tear line56when a side airbag deploys, and faces a problem of difficulty in controlling a deployment speed of the side airbag.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Publication No. 2014-184900Patent Literature 2: Japanese Patent Publication Number 3975427

SUMMARY OF INVENTION

The present invention has been achieved in consideration of the circumstances described above, and has an object of providing a vehicle seat that has high designability and achieves control of a deployment speed of a side airbag.

A vehicle seat of the present invention includes a seatback accommodating an airbag device therein. The seatback includes: a top board part contactable with the back of an occupant; a bolster part located on a side of the top board part; a shoulder part located above the bolster part; a cover forming a surface of each of the bolster part and the shoulder part; and an airbag sleeve provided in at least one of the bolster part and the shoulder part to support the cover from inside when an airbag deploys. The cover includes; a first cover piece located on the bolster part and adjoining the top board part; a second cover piece located on the bolster part and being on a frame side farther away from the top board part than the first cover piece; a third cover piece located on the shoulder part and adjoining an upper side of the first cover piece; and a fourth cover piece located on the shoulder part and adjoining an upper side of the second cover piece. The first cover piece and the second cover piece are sewn together along a first tear line extending in a longitudinal direction of the seatback. The third cover piece and the fourth cover piece are sewn together along a second tear line extending continuously from the first tear line in the longitudinal direction. The first cover piece and the third cover piece are sewn together along a first lateral directional line extending in a crossing direction intersecting the first tear line. The second cover piece and the fourth cover piece are sewn together along a second lateral directional line extending continuously from the first lateral directional line in the crossing direction. The airbag sleeve includes: a first section extending along the first tear line or the second tear line; and a second section extending across the first lateral directional line or the second lateral directional line. The first section is sewn with at least one of the first to fourth cover pieces along the first tear line or the second tear line. The second section is sewn with at least one of a set of the first cover piece and the third cover piece and a set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich a seam allowance extending along the first lateral directional line or the second lateral directional line.

In the description, the term “top board part” represents a main part of the seatback, that is, a substantially board-shaped part (main board part) contactable with the back of an occupant. The term “frame side” represents a side or side portion constituting a side surface of the seatback and facing outward (side portion) on the bolster part in a width direction.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a preferable embodiment of the present invention will be described with reference to the accompanying drawings. The drawings appropriately show a “vehicular frontward and rearward direction X”, a “vehicular width direction Y”, and an “upward and downward direction Z” by using arrows.

A vehicle seat (hereinafter, referred to as a “seat1”) shown inFIG.1is configured to include a seatback3accommodating an airbag device9. Specifically, the seat1includes: a seat cushion2contactable with the buttocks of an occupant; a seatback3contactable with the back of the occupant; and the airbag device9. The airbag device9is accommodated in a side portion (right portion inFIG.1) of the seatback3that is closer to an unillustrated door of a vehicle.

As shown inFIG.1toFIG.5, the seatback3includes: a top board part30facing vehicular frontward X1and being contactable with the back of the occupant; a pair of bolster parts4located on both sides of the top board part30and adjoining thereto in the vehicular width direction Y; a pair of shoulder parts5located respectively above the pair of bolster parts4; a cover6forming a surface of each bolster part4and each shoulder part5; and a first airbag sleeve15and a second airbag sleeve16each provided in at least one of the bolster part4and the shoulder part5(the bolster part4in the embodiment) in a side portion (on the right side inFIG.1, and on the left side inFIG.2) of the seatback3that accommodates the airbag device9to support the cover6from inside when an airbag deploys.

Each bolster part4has a longitudinal cushion shape extending frontward and lateralward from the seatback3around a corresponding body side portion of the occupant. As shown inFIG.1toFIG.3, the bolster part4in the embodiment includes: a first cover piece11and a second cover piece12of the cover6to be described later; a cushion pad7covered with the first cover piece11and the second cover piece12; and a frame8supporting the cushion pad7. The bolster part4of the pair of bolster parts4that is located outward Y1(FIG.2) in the vehicular width direction accommodates the airbag device9and the airbag device9is fixedly attached to the frame8.

Each shoulder part5has a portion extending frontward and lateralward around a corresponding shoulder of the occupant. In the embodiment, the pair of shoulder parts5integrally extend in the width direction Y as shown inFIG.1, but may be separated from each other.

A surface of each of the bolster part4and the shoulder part5(on the right side inFIG.1) where the airbag device9is accommodated is formed by the cover6including a plurality of cover pieces sewn together as shown inFIG.1toFIG.2andFIG.5toFIG.6.

The cover6includes four cover pieces11to14as shown inFIGS.1to2andFIG.4toFIG.6. Specifically, the cover6includes: a first cover piece11located on the bolster part4and adjoining the top board part30(i.e., on the top board part side); a second cover piece12located on the bolster part4and being on a frame side (i.e., in a side portion to form a side surface of the seatback3) farther away from the top board part30than the first cover piece11; a third cover piece13located on the shoulder part5and adjoining an upper side (i.e., on the top board part side) of the first cover piece11; and a fourth cover piece14located on the shoulder part5and adjoining an upper side (i.e., on the frame side) of the second cover piece12.

First, sewing of the bolster part4will be described. As shown inFIG.1toFIG.2andFIG.4toFIG.7, the first cover piece11and the second cover piece12are sewn together along a first tear line17extending in a longitudinal direction D1of the seatback3. Specifically, as shown inFIG.7, an end11aon a side surface of the first cover piece11and an end12aof the second cover piece12face each other and are sewn together by a sewing thread22to form the first tear line17extending in the longitudinal direction D1. Besides, a first section15aof the first airbag sleeve15to be described later is sewn with the end12aof the second cover piece12by the sewing thread22in the inside of the end12athat is folded back.

Besides, the third cover piece13and the fourth cover piece14are sewn together for the shoulder part5. These cover pieces are sewn together along a second tear line18extending continuously from the first tear line17in the longitudinal direction D1, as shown inFIG.1andFIG.4toFIG.6.

As shown inFIG.4toFIG.6, the first cover piece11and the third cover piece13aligning in the upward and downward direction Z are sewn together along a first lateral directional line19extending in a lateral direction D2or crossing direction intersecting the first tear line17. As shown inFIG.6, the first lateral directional line19extends downward as advancing toward the top board part30of the seatback3, and forms a sewn portion of the first cover piece11and a cover piece31of the top board part30.

The lateral direction D2is sufficient to intersect the longitudinal direction D1without limitation to a direction perpendicularly intersecting the longitudinal direction D1, and thus may be slightly oblique to the perpendicularly-intersecting direction.

The second cover piece12and the fourth cover piece14aligning in the upward and downward direction Z are sewn together along a second lateral directional line20extending continuously from the first lateral directional line19in the lateral direction D2. Specifically, as shown inFIG.8, an upper end12bof the second cover piece12and a lower end14aof the fourth cover piece14face each other and are sewn together by a sewing thread23to form the second lateral directional line20extending in the lateral direction D2.

As shown inFIG.4, the two tear lines, i.e., the first tear line17and the second tear line18, each extending in the longitudinal direction D1, and the two lateral directional lines, i.e., the first lateral directional line19and the second lateral directional line20, each extending in the lateral direction D2, meet at a meeting point21.

As shown inFIG.2toFIG.3andFIG.5toFIG.6, in the embodiment, one end (specifically, the first section15ato be described later) of the first airbag sleeve15is sewn with the second cover piece12along the first tear line17extending in the longitudinal direction D1by the sewing thread22(seeFIG.7) and one end (specifically, a left end inFIG.5toFIG.6) of the second airbag sleeve16is sewn with the first cover piece11by the sewing thread22.

As shown inFIG.2, the first airbag sleeve15extends inside the second cover piece12to pass outward Y1of the airbag device9in the vehicular width direction Y, and has the one end (specifically, the first section15ainFIG.5toFIG.7) sewn with the second cover piece12near the first tear line17and another end fixed to the frame8. The second airbag sleeve16extends inward Y2of the airbag device9in the vehicular width direction Y, and has the one end sewn with the first cover piece11near the first tear line17and another end fixedly attached to the frame8. No cushion pad7is provided outward Y1of the airbag device9(on the frame side of the seat1) in the vehicular width direction Y, and the second cover piece12and the first airbag sleeve15solely shield the airbag device9from the outside of the seat.

Specifically, as shown inFIG.5toFIG.8, the first airbag sleeve15in the embodiment includes: the first section15aextending in a direction along the first tear line17to ensure tearing of the first tear line17when the airbag deploys; a second section15bextending across the second lateral directional line20, i.e., extending in a direction intersecting the second lateral directional line20, to relatively delay tearing of the second lateral directional line20when the airbag deploys; and a third section15cto be fixedly attached to the frame8(seeFIG.2). The concept of the airbag sleeve of the present invention includes the first airbag sleeve15.

As shown inFIG.7, the first section15ais sewn with the second cover piece12on a back surface thereof along the first tear line17.

Besides, as shown inFIG.8, the second section15bis sewn with a set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich a seam allowance extending along the second lateral directional line20. Specifically, the second section15bis sewn with an overlapping part25of the end12bof the second cover piece12and the end14aof the fourth cover piece14in the seam allowance extending along the second lateral directional line20by a sewing thread24in a state of enclosing the overlapping part25. In this manner, a firm enclosing portion26(seeFIG.5toFIG.6andFIG.8) is formed in such a manner that the second section15bencloses and sandwiches the overlapping part25.

The seat1having the above-described configuration is manufactured through the following steps (I) to (V):

(I) a cover piece preparation step of preparing, as components constituting the cover6forming a surface of each of the bolster part4and the shoulder part5, the first cover piece11to be located on the bolster part4and adjoin the top board part30, the second cover piece12to be located on the bolster part4and be on a frame side farther away from the top board part30than the first cover piece11, the third cover piece13to be located on the shoulder part5and adjoin an upper side of the first cover piece11, and the fourth cover piece14to be located on the shoulder part5and adjoin an upper side of the second cover piece12;

(II) a first section sewing step of sewing the first section15aof the first airbag sleeve15with at least one of the first to fourth cover pieces11to14, i.e., the second cover piece12in the embodiment, along the first tear line17;

(III) a tear line sewing step of sewing the first cover piece11and the second cover piece12on the bolster part4together along the first tear line17extending in the longitudinal direction D1of the seatback3, and sewing the third cover piece13and the fourth cover piece14on the shoulder part5together along the second tear line18extending in the longitudinal direction D1;

(IV) a lateral directional line sewing step of sewing the first cover piece11and the third cover piece13together along the first lateral directional line19extending in the lateral direction D2intersecting the first tear line17, and sewing the second cover piece12and the fourth cover piece14together along the second lateral directional line20extending continuously from the first lateral directional line19in the lateral direction D2; and

(V) a second section sewing step of sewing the second section15bof the first airbag sleeve15with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance (specifically, the overlapping part25inFIG.8) extending along the second lateral directional line20.

The first section sewing step (II) and the tear line sewing step (III) may be simultaneously executed in a state where the first section15aof the first airbag sleeve15overlaps at least one of the first to fourth cover pieces11to14along the first tear line17or the second tear line18.

Characteristics of the Embodiment

(1) In the seat1in the embodiment, as shown inFIG.5toFIG.6andFIG.8, the second section15bof the airbag sleeve is sewn with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line20. This allows the second lateral directional line20serving as a boundary between the shoulder part5and the bolster part4to form a three-dimensional section as being pulled in, and a seat having high designability can be provided.

The second section15bof the first airbag sleeve15is sewn across or to intersect the seam allowance extending along the second lateral directional line20, and thus, a tearing strength of the second lateral directional line20increases. This prevents the second lateral directional line20from tearing prior to the first tear line17and the second tear line18, and enables the airbag accommodated in the airbag device9to smoothly deploy as intended. As a result, control of a deployment speed of the airbag is achieved.

The seat1in the embodiment needs fewer airbag sleeves to be used than a conventional seat having a structure (seeFIG.10toFIG.11) including two airbag sleeves (webbing cloths) respectively at upper and lower positions across a lateral directional line. Further, only two portions of a tear line (the first tear line17) and a lateral directional line (the second lateral directional line20) are required for sewing of the first airbag sleeve15, and there is no need of replacement with a thicker thread for the sewing of the first airbag sleeve15lead to good operability.

(2) In the seat1in the embodiment, as shown inFIG.1toFIG.2, the bolster part4accommodates the airbag device9. As shown inFIG.5toFIG.7, the first section15aof the first airbag sleeve15is sewn with the second cover piece12along the first tear line17. The second section15bis sewn with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line20.

This configuration enables more accurate control of the deployment speed. Specifically, in the configuration in which the bolster part4accommodates the airbag device9, the largest pressure is applied to the second cover piece12of the first cover piece11and the second cover piece12constituting the surface of the bolster part4when the airbag device9comes into deployment, the second cover piece12being on the frame side to form a side surface of the seat farther away from the top board part30. Hence, the first tear line17extending in the longitudinal direction D1with the seam allowance of the second cover piece12and the second lateral directional line20extending in the lateral direction D2or crossing direction intersecting the longitudinal direction D1are likely to easily tear. Under the circumstances, in the configuration described above, first, sewing of the first section15aof the first airbag sleeve15with the second cover piece12along the first tear line17makes the first tear line17be more likely to tear when the airbag deploys. Further, sewing of the second section15bwith the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line20prevents the second lateral directional line20from tearing prior to the first tear line17when the airbag deploys.

(3) In the seat1in the embodiment, as shown inFIG.5toFIG.6andFIG.8, the second section15bof the first airbag sleeve15is sewn with an overlapping part25of the end12bof the second cover piece12and the end14aof the fourth cover piece14in the seam allowance extending along the second lateral directional line20by the sewing thread24in a state of enclosing and sandwiching the overlapping part25.

In this configuration, the overlapping part25of the end12bof the second cover piece12and the end14aof the fourth cover piece14in the seam allowance extending along the second lateral directional line20is sewn not only by the sewing thread23on the second lateral directional line20but also by the sewing thread24in such a manner that the second section15bof the first airbag sleeve15encloses and sandwiches the overlapping part25. In other words, the overlapping part25is dually sewn at two different portions. The sewing attains reliable prevention of tearing of the second lateral directional line20at the deployment of the airbag.

(4) The method for manufacturing a vehicle seat in the embodiment includes: the first section sewing step of sewing the first section15aof the first airbag sleeve15with the second cover piece12along the first tear line17; and the second section sewing step to be subsequently executed to sew the second section15bof the airbag sleeve with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line20.

This allows, in the same manner as (1) described above, the first lateral directional line19or the second lateral directional line20each serving as a boundary between the shoulder part5and the bolster part4to form a three-dimensional section as being pulled in, and a seat having high designability can be provided.

In the second section sewing step, the second section15bof the first airbag sleeve15is sewn across or to intersect the seam allowance extending along the second lateral directional line20, and thus, a tearing strength of the second lateral directional line20increases in the same manner as (1) described above. This prevents the second lateral directional line20from tearing prior to the first tear line17and the second tear line18each being a longitudinal directional line, and enables the airbag in the airbag device9to smoothly deploy as intended. As a result, it is possible to manufacture a seat that achieves control of a deployment speed.

Besides, in the same manner as (1) described above, the manufacturing method needs fewer air bag sleeves to be used, requires only two portions of a tear line and a lateral directional line for sewing of the first airbag sleeve15, and has no need of replacement with a thicker thread for the sewing of the first airbag sleeve15. The method thus achieves good operability.

The method for manufacturing a vehicle seat enables simultaneous execution of the first section sewing step and the tear line sewing step in a state where the first section15aof the first airbag sleeve15overlaps at least one of the first to fourth cover pieces11to14along the first tear line17or the second tear line18. This configuration enables simultaneous execution of sewing of the first section15aof the first airbag sleeve15and sewing of the cover pieces11,12together along the first tear line17(or sewing of the cover pieces13,14along the second tear line18), resulting in improving the operability.

Modifications

(A) Although the embodiment provides the first airbag sleeve15in the bolster part4as shown inFIG.2toFIG.3, the present invention is not limited thereto, and the first airbag sleeve may be provided in the shoulder part5. The first airbag sleeve15may be provided in each of the bolster part4and the shoulder part5. This configuration can exert the same operational effect as those described in (1) to (4) above.

(B) Although the cover6includes the four cover pieces11to14in the embodiment, the number of cover pieces is not limited thereto, and the cover may include five or more cover pieces depending on a design of the seat1.

(C) Although the first section15aof the first airbag sleeve15is sewn with the second cover piece12being on the frame side along the first tear line17and the second section15bis sewn with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line20in the embodiment as shown inFIG.5toFIG.6, the present invention is not limited thereto.

In the present invention, the first section15amay be sewn with at least one of the first to fourth cover pieces11to14along the first tear line17or the second tear line18, and the second section15bmay be sewn with at least one of the set of the first cover piece11and the third cover piece13and the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending along the first lateral directional line19or the second lateral directional line20.

Accordingly, modifications of the present invention may encompass various changes in the arrangement of the first section15aand the second section15bof the first airbag sleeve15as described below.

For instance, the first section15amay be sewn with the first cover piece11being closer to the top board part along the first tear line17. Alternatively, in a case of arranging two first airbag sleeves15sandwiching the first tear line17, their first sections15amay be sewn respectively with the first cover piece11being closer to the top board part and the second cover piece12being on the frame side along the first tear line17. Further alternatively, in a case of arranging the first airbag sleeve15in the shoulder part5, the first section15amay be sewn with either the third cover piece13or the fourth cover piece14along the second tear line18. Moreover, when two first airbag sleeves15are arranged in this case, their first sections15amay be respectively sewn with the third cover piece13and the fourth cover piece14.

The second section15bmay be sewn with the set of the first cover piece11and the third cover piece13in such a manner as to enclose and sandwich a seam allowance extending along the first lateral directional line19. Alternatively, in the case of providing two first airbag sleeves15, one of their two second sections15bmay be sewn with the set of the first cover piece11and the third cover piece13in such a manner as to enclose and sandwich the seam allowance extending along the first lateral directional line19, and the other second section may be sewn with the set of the second cover piece12and the fourth cover piece14in such a manner as to enclose and sandwich the seam allowance extending in the second lateral directional line20.

It is seen from these perspectives that a configuration in which the first section15ais sewn with at least one of the cover pieces11to14along the first tear line17or the second tear line18and the second section15bis sewn with the set of the cover pieces11,13or the set of the cover pieces12,14in such a manner as to enclose the seam allowance along the first lateral directional line19or the second lateral directional line20can exert the same operational effect as those described in (1) to (4) above regardless of various changes in the arrangement of the first section15aand the second section15bof the first airbag sleeve15.

Summary of Embodiment

The embodiment is summarized in the following manner.

A vehicle seat in the embodiment includes a seatback accommodating an airbag device therein. The seatback includes: a top board part contactable with the back of an occupant; a bolster part located on a side of the top board part; a shoulder part located above the bolster part; a cover forming a surface of each of the bolster part and the shoulder part; and an airbag sleeve provided in at least one of the bolster part and the shoulder part to support the cover from inside when an airbag deploys. The cover includes; a first cover piece located on the bolster part and adjoining the top board part; a second cover piece located on the bolster part and being on a frame side farther away from the top board part than the first cover piece; a third cover piece located on the shoulder part and adjoining an upper side of the first cover piece; and a fourth cover piece located on the shoulder part and adjoining an upper side of the second cover piece. The first cover piece and the second cover piece are sewn together along a first tear line extending in a longitudinal direction of the seatback. The third cover piece and the fourth cover piece are sewn together along a second tear line extending continuously from the first tear line in the longitudinal direction. The first cover piece and the third cover piece are sewn together along a first lateral directional line extending in a crossing direction intersecting the first tear line. The second cover piece and the fourth cover piece are sewn together along a second lateral directional line extending continuously from the first lateral directional line in the crossing direction. The airbag sleeve includes: a first section extending along the first tear line or the second tear line; and a second section extending across the first lateral directional line or the second lateral directional line. The first section is sewn with at least one of the first to fourth cover pieces along the first tear line or the second tear line. The second section is sewn with at least one of a set of the first cover piece and the third cover piece and a set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich a seam allowance extending along the first lateral directional line or the second lateral directional line.

In this configuration, the second section of the airbag sleeve is sewn with at least one of the set of the first cover piece and the third cover piece and the set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich the seam allowance extending along the first lateral directional line or the second lateral directional line. This allows the first lateral directional line or the second lateral directional line each serving as a boundary between the shoulder part and the bolster part to form a three-dimensional section as being pulled in, and a seat having high designability can be provided.

The second section of the airbag sleeve is sewn across or to intersect the seam allowance extending along the first lateral directional line or the second lateral directional line. Hence, a tearing strength of the first lateral directional line or the second lateral directional line increases. This prevents the first lateral directional line or the second lateral directional line from tearing prior to the first tear line and the second tear line, and enables the airbag to smoothly deploy as intended. As a result, control of a deployment speed is achieved.

In the vehicle seat, preferably, the bolster part accommodates the airbag device, the first section is sewn with the second cover piece along the first tear line, and the second section is sewn with the set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line.

This configuration enables more accurate control of the deployment speed. Specifically, in the configuration in which the bolster part accommodates the airbag device, the largest pressure is applied to the second cover piece of the first cover piece and the second cover piece constituting the surface of the bolster part when the airbag deploys, the second cover piece being on the frame side to form a side surface of the seat farther away from the top board part. Hence, the first tear line extending in the longitudinal direction with the seam allowance of the second cover piece and the second lateral directional line extending in the crossing direction intersecting the longitudinal direction are likely to easily tear. Under the circumstances, in the configuration described above, sewing of the first section of the airbag sleeve with the second cover piece along the first tear line makes the first tear line be more likely to tear when the airbag deploys. Further, sewing of the second section with the set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich the seam allowance extending along the second lateral directional line prevents the second lateral directional line from tearing prior to the first tear line when the airbag deploys.

In the vehicle seat, the second section is preferably sewn with an overlapping part of respective ends of the first cover piece and the third cover piece in a seam allowance extending along the first lateral directional line or with an overlapping part of respective ends of the second cover piece and the fourth cover piece in the seam allowance extending along the second lateral directional line in a state of enclosing and sandwiching the overlapping part.

In this configuration, the overlapping part of the respective ends of the cover pieces in the seam allowance extending along the first lateral directional line or the second lateral directional line is sewn not only on the first lateral directional line or the second lateral directional line but also with the second section of the airbag sleeve. In other words, the overlapping part is dually sewn at two different portions. The sewing attains reliable prevention of tearing of the first lateral directional line or the second lateral directional line at the deployment of the airbag.

A method for manufacturing a vehicle seat in the embodiment is a method for manufacturing a vehicle seat which includes a seatback accommodating an airbag device. The seat back includes: a top board part contactable with the back of an occupant; a bolster part located on a side of the top board part; a shoulder part located above the bolster part; a cover forming a surface of each of the bolster part and the shoulder part; and an airbag sleeve provided in at least one of the bolster part and the shoulder part to support the cover from inside when an airbag deploys. The airbag sleeve includes: a first section sewn with at least one of first to fourth cover pieces along a first tear line or a second tear line; and a second section sewn with at least one of a set of the first cover piece and the third cover piece and a set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich a seam allowance extending along a first lateral directional line or a second lateral directional line. The method includes: a cover piece preparation step of preparing, as components constituting the cover, the first cover piece to be located on the bolster part and adjoin the top board part, the second cover piece to be located on the bolster part and be on a frame side farther away from the top board part than the first cover piece, the third cover piece to be located on the shoulder part and adjoin an upper side of the first cover piece, and the fourth cover piece to be located on the shoulder part and adjoin an upper side of the second cover piece; a first section sewing step of sewing the first section of the airbag sleeve with at least one of the first to fourth cover pieces; a tear line sewing step of sewing the first cover piece and the second cover piece together along the first tear line extending in a longitudinal direction of the seatback, and sewing the third cover piece and the fourth cover piece together along the second tear line extending in the longitudinal direction; a lateral directional line sewing step of sewing the first cover piece and the third cover piece together along the first lateral directional line extending in a crossing direction intersecting the first tear line, and sewing the second cover piece and the fourth cover piece together along the second lateral directional line extending continuously from the first lateral directional line in the crossing direction; and a second section sewing step of sewing the second section of the airbag sleeve with at least one of the set of the first cover piece and the third cover piece and the set of the second cover piece and the fourth cover piece in such a manner as to enclose and sandwich the seam allowance extending along the first lateral directional line or the second lateral directional line. In the first section sewing step, the first section is sewn with at least one of the first to fourth cover pieces along the first tear line or the second tear line.

This configuration has a feature in: the first section sewing step of sewing the first section of the airbag sleeve with at least one of the first to fourth cover pieces along the first tear line or the second tear line; and the second section sewing step to be subsequently executed to sew the second section of the airbag sleeve with at least one of the set of the first cover piece and the third cover piece and the set of the second cover piece and the fourth cover piece in such a manner as to enclose the seam allowance extending in the first lateral directional line or the second lateral directional line. This allows the first lateral directional line or the second lateral directional line each serving as a boundary between the shoulder part and the bolster part to form a three-dimensional section as been pulled in, and a seat having high designability can be provided.

In the second section sewing step, the second section of the airbag sleeve is sewn across or to intersect the seam allowance extending along the first lateral directional line or the second lateral directional line, and thus, a tearing strength of the first lateral directional line or the second lateral directional line increases. This prevents the first lateral directional line or the second lateral directional line from tearing prior to the first tear line and the second tear line, and enables the airbag to smoothly deploy as intended. As a result, it is possible to manufacture a seat that achieves control of a deployment speed.

In the method for manufacturing a vehicle seat, the first section sewing step and the tear line sewing step are preferably simultaneously executed in a state where the first section of the airbag sleeve overlaps at least one of the first to fourth cover pieces along the first tear line or the second tear line.

This configuration enables simultaneous execution of sewing of the first section of the airbag sleeve and sewing of cover pieces together along a tear line, resulting in improving the operability.

Conclusively, a vehicle seat in the embodiment has high designability and achieves control of a deployment speed of a side airbag.

A method for manufacturing a vehicle seat in the embodiment enables manufacturing of a vehicle seat that has high designability and achieves control of a deployment speed of a side airbag.