Patent Publication Number: US-2010127487-A1

Title: Sewing structure of facing sheet member for covering vehicle seat, method for producing the same, and air bag structure for vehicle seat

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sewing structure of facing sheet member for covering a vehicle seat, a method for producing the sewing structure and an air bag structure for a vehicle seat. 
     2. Description of the Related Art 
     A facing sheet member of a vehicle seat is for covering a pad part which forms an outer shape of a seat. Typically, the facing sheet member includes a surface member formed of leather and provided at a sitting side of the seat, a pad member (sheet-like form) bonded to a back face of the surface member, and a coating layer formed on a surface of the surface member. 
     Since the facing sheet member is for constituting a surface of the seat, the facing sheet member is likely to be subjected to friction and pressure due to motions of a passenger when he gets on or off the vehicle (pressure of the passenger). Particularly, in case where there is a protruded part in the facing sheet member, the pressure of the passenger is concentrated on this protruded part, and the facing sheet member is partially damaged or the coating layer on this part is peeled off. 
     In the meantime, the facing sheet member for the vehicle seat is typically formed by sewing a plurality of facing sheet pieces together into a shape of a bag. In those parts where the facing sheet pieces are sewn together, end parts of the facing sheet pieces are turned back inwardly (turned outside in) and sewn to each other. Therefore, these parts have a thickness twice as large as the other part of the facing sheet member, and are likely to become protruded parts. 
     In view of the above, JP-A-2007-289284 describes a structure for reducing the thickness of the end parts of the facing sheet pieces by providing overcasting along the end parts, thereby to reduce protrusion of the sewn parts as much as possible. 
     However, in JP-A-2007-289284, a work for providing the overcasting on the facing sheet pieces is troublesome more than expected, and the sewing work of the facing sheet member takes time. 
     It is of course possible to apply nonwoven fabric or the like to the sewn parts of the facing sheet pieces. That is, by attaching the nonwoven fabric to back faces of the facing sheet pieces (providing slidability), slidability with respect to the pad member is enhanced, whereby the pressure of the passenger is dispersed and reduced. However, this structure incurs an increase in number of components of the facing sheet member, and cannot be adopted in some cases, while taking production cost for the facing sheet member into consideration. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an aspect of the present invention to provide sewing structure of facing sheet member for covering a vehicle seat which reduces a thickness of sewn parts of a facing sheet member with a simple structure, a method for producing the sewing structure of the facing sheet member, and an air bag structure for a vehicle seat. 
     According to an exemplary embodiment of the present invention, there is provided a sewing structure of a facing sheet member for covering a vehicle seat, the facing sheet member being formed by sewing a plurality of facing sheet pieces together at respective end parts thereof, each of the facing sheet pieces comprising a surface member and a pad member laminated on the surface member. In the end part of each of the facing sheet pieces, at least a part of the pad member is removed or the pad member is not laminated on the surface member. The plurality of facing sheet pieces are sewed together using the surface members at the end parts thereof. 
     According to another exemplary embodiment of the present invention, there is provided a method for producing a sewing structure of a facing sheet member for covering a vehicle seat, the facing sheet member including a plurality of facing sheet pieces, each having a surface member and a pad member laminated on the surface member, the method comprising: removing at least a part of the pad member laminated on the surface member at an end part of each of the plurality of facing sheet pieces; and sewing the surface members of respective facing sheet pieces at the end parts thereof, in which the at least the part of the pad member is removed, to combine the respective facing sheet pieces. 
     According to another exemplary embodiment of the present invention, there is provided an air bag structure for a vehicle seat, the air bag structure comprising: an air bag provided in the vehicle seat; and a facing sheet member covering the vehicle seat. The facing sheet member being formed by sewing a plurality of sheet pieces together at respective end parts thereof, each of the facing sheet pieces comprising a surface member and a pad member laminated on the surface member. In the end part of each of the facing sheet pieces, at least a part of the pad member is removed or the pad member is not laminated on the surface member. The plurality of facing sheet pieces are sewed together using the surface members at the end parts thereof. 
     According to the above configuration, it is possible to reduce the thickness of the sewn parts of the facing sheet member by employing the more simple structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of a vehicle seat. 
         FIG. 2  is a vertical sectional view taken along a line II-II in  FIG. 1 ; 
         FIG. 3  is a vertical sectional view of a facing sheet member according to Embodiment 1; and 
         FIG. 4  is a vertical sectional view of a facing sheet member according to Embodiment 2. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments of the present invention will be described with reference to  FIGS. 1 to 4 . 
     As shown in  FIG. 1 , a vehicle seat  2  includes a seat cushion  4  and a seat back  6 . The seat back  6  has a concave part at a center thereof (a sitting part  6   a ) and convex parts at both sides thereof (both side parts  6   b ,  6   b ) for improving sitting comfort of a passenger. 
     The both side parts  6   b ,  6   b  of the seat back  6  have sewn parts SS where facing sheet pieces (described later) are sewn together. A sewing structure of a facing sheet member  6 S according to exemplary embodiments will be described while taking this seat back  6  as an example. 
     Embodiment 1 
     Referring to  FIG. 2 , the seat back  6  has a pad part  6 P which forms an outer shape of the seat, and a facing sheet member  6 S. 
     This facing sheet member  6 S is formed by sewing a plurality of facing sheet pieces such as a first facing sheet piece  11  and a second facing sheet piece  12  (described later) together into a shape of a bag. In the sewn parts SS in the facing sheet member  6 S, an end part E of each facing sheet piece is inwardly turned back (turned outside in) as described later, and are likely to become protruded parts. 
     In this exemplary embodiment, as shown in  FIG. 2 , when the pad part  6 P is covered with the facing sheet member  6 S, the sewn parts SS extending in a vertical direction of the seat are formed in the side parts  6   b  of the seat back  6 , while considering an appearance of the seat and the like. 
     However, the side parts  6   b  of the seat back  6  (in a convex shape) are likely to be contacted with the passenger, when he gets on or off the vehicle, and therefore, it is advantageous that the facing sheet member is smooth and flat, that is, without protruded part on which the pressure is concentrated. Accordingly, in this exemplary embodiment, by employing the below-described sewing structure of the facing sheet member  6 S, the thickness of the sewn parts SS is reduced. 
     (Facing Sheet Piece) 
     In this exemplary embodiment, the side part  6   b  of the seat back  6  includes the first facing sheet piece  11  forming a front face of the seat and the second facing sheet piece  12  forming a side face of the seat. Each of the facing sheet pieces  11 ,  12  includes a surface member  22  and a pad member  24 . These members  22 ,  24  are integrated (combined) by, for example, laminating process into double structure. That is, the pad member  24  is laminated on the surface member  22 . 
     This surface member  22  is a member constituting a sitting side of the facing sheet member  6 S, and is formed of material having adequate elasticity and strength. For example, the surface member may be natural leather or artificial leather. Additionally, a coating layer of dye or pigment (not shown) is formed on the sitting side of the surface member  22 . 
     The pad member  24  (sheet-like form) is preferably formed of softer material than the pad part  6 P, and may be formed of soft urethane foam, for example. 
     While considering sitting comfort of the facing sheet member  6 S, this pad member  24  has certain elasticity and has a thickness equal to or larger than the thickness of the surface member  22 . For this reason, if the pad member  24  is turned back outside in as it is, the thickness of the facing sheet member  6 S at the end parts becomes relatively larger due to the pad member  24  which is inwardly turned back. 
     (Sewing Structure) 
     In view of the above, in this exemplary embodiment, the facing sheet pieces  11 ,  12  are sewn to each other by the surface members  22  at the respective end parts E after the pad members  24  are removed from the end parts E of the facing sheet pieces  11 ,  12 . Specifically, referring to  FIG. 3 , the pad members  24  are respectively removed from the end part E of the first facing sheet piece  11  and the end part E of the second facing sheet piece  12 , whereby the respective end parts E of the facing sheet pieces  11 ,  12  have only the surface members  22 . A thickness of the end part E is reduced substantially to a half by removing the pad member  24 . The facing sheet pieces  11 ,  12  are sewn to each other using the surface members  22  of the respective end parts E, and thereafter, only the surface members  22  of the respective end parts E are inwardly turned back to be sewn to the back faces of the respective facing sheet pieces. 
     In this exemplary embodiment, as described above, the thickness of the sewn part SS which is formed in the side part  6   b  of the seat can be reduced with a relatively simple configuration of removing the pad members  24  from the end parts E of the facing sheet pieces  11 ,  12 . Accordingly, it is possible to prevent or reduce concentration of the pressure on the passenger to the sewn part SS. 
     Moreover, in this exemplary embodiment, the end parts E of the facing sheet pieces are sewed outside in, respectively. In other words, the end parts of the facing sheet pieces are stitched to the facing sheet pieces, respectively, while the end parts are turned. Accordingly, a pair of sewing lines SEW, SEW (double stitch) are formed on the facing sheet member  6 S. Accordingly, the appearance of the vehicle seat  2  can be enhanced. 
     In the meantime, an air bag (not shown) for protecting the passenger at occasion of collision of the vehicle may be provided in the side part  6   b  of the seat back  6 . This air bag is disposed inside the pad part  6 P of the vehicle seat, and expanded sideways of the seat by breaking the facing sheet member  6 S with a shock at collision of the vehicle. It is noted that as the air bag, an air bag described in, for example, JP-A-2007-145193 can be used. 
     Therefore, the sewn part SS in this exemplary embodiment is formed in a region covering the air bag. In this case, at occasion of collision of the vehicle, the air bag can be expanded by smoothly breaking the sewn part SS of the facing sheet member  6 S (the sewn part SS where the surface members  22  are sewn to each other outside in). 
     Embodiment 2 
     Since a basic structure in Embodiment 2 is substantially the same as a basic structure in Embodiment 1, those members which are common to both the embodiments will be denoted with the same reference numerals, and their detailed descriptions will be omitted. 
     In Embodiment 2, as shown in  FIG. 4 , a case where a single sewing line SEW (single stitch) is formed on the facing sheet member  6 S will be described. 
     In this exemplary embodiment, the end part E of the second facing sheet piece  12  is inwardly turned back, and arranged on a back face of the second facing sheet piece  12 . Then, the end part E of the first facing sheet piece  11  is arranged on the back face of the second facing sheet piece  12  in a state extended as it is (without being inwardly turned back). The end parts E of the two facing sheet pieces are overlapped and sewn to the back face of the second facing sheet piece  12 , whereby a single sewing line SEW (single stitch) can be formed. 
     In this manner, according to this exemplary embodiment, design variation of the facing sheet member  6 S is increased, and at the same time, connection between the two facing sheet pieces ( 11 ,  12 ) can be reinforced. 
     Test Example 
     Hereinafter, exemplary embodiments will be further described below, referring to a test example, but the present invention is not limited to the test example. 
     Example 1 
     In Example 1, the surface member  22  formed of natural leather and the pad member  24  formed of soft urethane foam were used (See  FIG. 3 ). The surface member  22  and the pad member  24  had the same thickness. In addition, a coating layer by semi-aniline dying was formed on a front face of the surface member  22 . 
     After the pad members  24  had been removed by 10±3 mm from the end parts E of the respective facing sheet pieces, the facing sheet pieces were sewn to each other using their terminal end parts E. Since the pad members  24  had been thus removed, the thickness of the end parts E was reduced to a half. Then, the end parts E of these facing sheet pieces were turned back outside in, and sewn to the back faces of the facing sheet pieces, respectively, by making a double stitch, thereby to produce the facing sheet member  6 S in a shape of a bag. Then, the pad part  6 P was covered with the facing sheet member  6 S, and the sewn parts SS were formed on the seat back  6  (See  FIG. 1 ). 
     Comparative Example 1 
     In Comparative Example 1, in the same manner as Example 1, the surface member  22  formed of natural leather and the pad member  24  formed of soft urethane foam were used. The surface member  22  and the pad member  24  had the same thickness. In addition, a coating layer by semi-aniline dying was formed on a front face of the surface member  22 . 
     The end parts E of the respective facing sheet pieces were sewn together without removing the pad members  24 . Then, the end parts E of these facing sheet pieces were turned back outside in, and sewn to the back faces of the facing sheet pieces, respectively, by making a double stitch, thereby to produce the facing sheet member  6 S in a shape of a bag. Then, the pad part  6 P was covered with the facing sheet member  6 S, and the sewn parts SS were formed on the seat back  6 . 
     (Endurance Test) 
     The endurance of the facing sheet member  6 S of Example 1 and Comparative Example 1 was measured by a test in which human movements such as up and down movement, forward and rearward movement, and twist movement were reproduced by a hip-shaped model. 
     Specifically, under the temperature of 20° C., the hip-shaped model having a sitting width of 39 cm was placed on the seat back  6  (sewn part SS), and load of 25 kg were applied to the hip-shaped model. In this state, the hip-shaped model was moved in up and down by 50 mm, in forward and rearward by 30 mm, and in twist by 15 degree repeatedly in this order, on the sewn part SS. Then, when the total number of this repetition reached 1000, 5000, and 10000, the damage of the facing sheet member  6 S was observed. The same test was conducted to the facing sheet member  6   s  of Comparative Example 1 
     (Test Results and Observation) 
     In the facing sheet member  6 S in Comparative example 1, abrasion has occurred when the total number of repletion has reached 1000 times. 
     It can be considered that the abrasion has occurred in the sewn part SS since the double stitch in the sewn part SS was hardened like a bead edge, and the coating layer on the surface of the facing sheet member  6 S was worn out. 
     In contrast, in the facing sheet member  6 S in Example 1, damage in the sewn part SS (crack, abrasion (whitened), wear) was not observed, even when the total number of repetition has exceeded 10000 times. From this result, it was proved that endurance of the facing sheet member  6 S in Example 1 at getting on and off the seat was enhanced by reducing the thickness of the sewn part SS to a half, by more than ten times than in Comparative test  1 . 
     While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 
     (1) In the exemplary embodiments, the structure for sewing the end parts E of the facing sheet pieces to the back faces of the facing sheet pieces (a case where the double stitch or the single stitch is formed) has been described. Different from this, it is also possible to leave the end parts E of the respective facing sheet pieces  11 ,  12  as they are, without sewing them to the back faces of the facing sheet pieces, after the facing sheet pieces have been sewn together using the surface members  22  of the respective end parts E to form the sewn part SS. That is, a structure without forming the sewing line SEW is also possible. 
     Moreover, different form the double stitch and the single stitch, out stitches of various types may be applied to the facing sheet member  6 S. 
     (2) As a method of joining the surface member to the pad member, it is possible to employ various methods such as sewing, bonding and so on, different from the laminating process as described above. 
     (3) Although the facing sheet member  6 S in a shape of a bag is shown as an example in the above exemplary embodiments, the shape of the facing sheet member  6 S may be in various shapes according to the shape of the vehicle seat  2 . 
     (4) The facing sheet member in the above-described exemplary embodiments may be formed by laminating another member (for example, a back substrate cloth) on the surface member  22  and the pad member  24 . In this case, it would be preferable to remove the pad member and the other member from the facing sheet pieces at the end parts thereof. 
     (5) The sewn part SS may be formed not only in the side parts  6   b , but also in the sitting part  6   a  and in other places of the seat back  6 . Particularly, it is desired that the sewn part SS in Embodiment 1 may be provided at a position where an air bag is disposed. 
     Further, the sewing structure of the facing sheet member  6 S according to the above-described exemplary embodiment can be applied to a seat structure of various types, such as the seat cushion  4 , different from the seat back  6 . 
     (6) Although the pad member  24  is entirely removed from the end parts E of the facing sheet pieces  11 ,  12  in the above exemplary embodiment, the pad member  24  may be not entirely removed from the end parts E of the facing sheet pieces  11 ,  12 . In other words, at least a part of the pad member  24  may be removed from the end parts E of the facing sheet pieces  11 ,  12 . Alternatively, in the end parts E of the facing sheet pieces  11 ,  12 , the pad member  24  may not be provided on the surface member  22 . In this case, each of the facing sheet pieces  11 ,  12  may be formed by laminating the pad member  24  shorter than the surface member  22  on the surface member  22 .