Seat back structure

A seat back structure includes a seat back panel, a cushion member disposed on a seating surface side of the seat back panel, and an intermediate member inserted into a space between the panel and the cushion member. The panel is comprised of a metal plate member and formed with an embossed portion protruding at the seating surface side, and a bead portion protruding at an opposite side from the embossed portion at a position surrounding the embossed portion. The intermediate member has a lower specific gravity than the cushion member and a higher hardness than the cushion member. The intermediate member is formed with a contacting portion contacting the embossed portion and a concaved portion denting toward the cushion member at a position corresponding to the bead portion. A space is formed between the concaved portion and the panel, at a position adjacent to the contacting portion.

BACKGROUND

The present invention relates to a seat back structure.

Seat backs of vehicles generally have a structure in which a cushion member is disposed on a seating surface side of a seat back panel made of metal. Since the seat back panel generally has quite a large area, it is comprised of a metal plate member to secure rigidity. However, the rigidity is insufficient with a simple plate member. JP2011-105049A discloses a seat back panel including a large number of V-shaped bead portions, which are formed vertically adjacent to each other in a seat back, in order to increase the rigidity of the seat back panel.

For a weight reduction of the seat back, an intermediate member is inserted into a space between a seat back panel and a cushion member is considered. For example, it is possible to reduce the weight, by using a member of which a specific gravity is lower than that of the cushion member and a hardness is higher than that of the cushion member to be the intermediate member, compared to a case where a cushion member forms the part corresponding to the intermediate member. Recently, a further reduction in weight is desired.

SUMMARY

The present invention is made in view of the above issues and aims to provide a seat back structure a seat back which is reduced in weight and comprised of a seat back panel, an intermediate member, and a cushion member, while securing the rigidity of the seat back.

According to one aspect of the present invention, a seat back structure is provided, which includes a seat back panel, a cushion member disposed on a seating surface side of the seat back panel, and an intermediate member inserted into a space between the seat back panel and the cushion member. The seat back panel is comprised of a metal plate member and formed with an embossed portion protruding at the seating surface side, and a bead portion protruding at an opposite side from the embossed portion at a position surrounding the embossed portion. The intermediate member has a lower specific gravity than the cushion member and a higher hardness than the cushion member. The intermediate member is formed with a contacting portion contacting the embossed portion and a concaved portion denting toward the cushion member at a position corresponding to the bead portion. A space is formed between the concaved portion and the seat back panel, at a position adjacent to the contacting portion.

According to the above structure, by forming the embossed portion and the bead portion surrounding the embossed portion, the seat back panel is significantly increased in rigidity and reduced in weight by being thinned accordingly. Especially since the embossed portion protrudes toward the direction opposite from the protruding direction of the bead portion, compared to a case where they protrude toward the same direction, the rigidity is increased even further. Moreover, by using the intermediate member and forming the space between the seat back panel and the intermediate member, a further reduction in weight is achieved.

The embossed portion may be formed at a position of the seat back panel corresponding to a headrest in vehicle width directions. In this case, when a seated passenger leans on the seat back panel, the weight of the passenger is firmly supported by the embossed portion of the seat back panel via the contacting portion of the intermediate member. Thereby a seated sensation is improved.

The embossed portion may include a plurality of embossed portions spaced apart from each other in vertical directions of the seat back, at the position corresponding to the headrest. This structure is suitable for improving the seated sensation more sufficiently.

The bead portion may have an annular shape extending continuously to surround the embossed portion. In this case, the rigidity of the seat back panel is increased even further.

The embossed portion may protrude more than the bead portion. This structure is suitable for, for example, easily forming a narrow bead portion.

DETAILED DESCRIPTION OF EMBODIMENT

Hereinafter, one embodiment of the present invention is described with reference to the accompanying drawings. First, a seat back panel is described in detail with reference toFIGS. 1 to 10, and then an intermediate member and a cushion member are described with reference toFIGS. 11 to 14.

FIG. 1illustrates a rear seat S of a vehicle, in which “1” indicates seat cushions, and “2” and “3” indicate left and right divided structures of a seat back (hereinafter, each of the divided structures is referred to as “the seat back”). The seat back2is applied for a single passenger and the seat back3is applied for two passengers. The seat back3is illustrated in a state where the cushion member, etc., are removed.

The seat back3has a seat back panel10and a frame20. The seat back panel10is comprised of a metal plate member (in this embodiment, a regular flat steel plate) and, inFIG. 1, illustrated in a simplified state where bead portions, embossed portions (described later) etc. are omitted.

The frame20has a rectangular main frame21disposed along an outer circumferential edge of the seat back panel10. For example, the main frame21has an upper part21aextending in vehicle width (lateral) directions along an upper edge of the seat back panel10, a lower part21bextending laterally along a lower edge of the seat back panel10, and a pair of left and right vertical parts21cand21dextending vertically along left and right edges of the seat back panel10, respectively. The frame20also has an auxiliary frame22coupling the upper part21ato the lower part21bof the main frame21. Such a frame20is comprised of one or more metal (in this embodiment, steel) pipe members and, for example, fixed at its four corners to the seat back panel10by welding.

The seat back3is coupled to the seat cushion1to be pivotable in front-and-rear directions of the seat back panel10(vehicle longitudinal directions) with respect to a pivot axis θ extending laterally, via brackets30and31provided in both lateral end parts of the main frame21. InFIG. 1, the seat back3is illustrated at its upright position, and at this upright position, a first lock member32provided in an upper-left end part of the main frame21is locked to a second lock member33provided on the vehicle body side, thus, the upright position is maintained.

The seat back3is also capable of taking a folded position in addition to the upright position illustrated inFIG. 1. For example, at the upright position ofFIG. 1, by releasing the first lock member32from the second lock member33and pivoting the seat back3forward by substantially 90 degrees, a surface facing backward (rearward) at the upright position faces upward to function as a loading surface where a load (baggage, goods, etc.) is placeable.

A pair of support tube parts34and a pair of support tube parts35are fixed (e.g., by welding) to the upper part21aof the main frame21. The two pairs of support tube parts34and35support headrest frames36and37to be vertically adjustable in position, respectively.

Similar to the seat back3, the seat back2is capable of selectively taking the upright position and the folded position. Further similar to the seat back3, the frame structure of the seat back2is comprised of a seat back panel and a frame. A headrest for the seat back2is denoted with the reference number “38.”

In addition to the state ofFIG. 1, where the seat backs2and3are at the upright position, a state where only the seat back2is at the folded position, a state where only the seat back3is at the folded position, and a state where both the seat backs2and3are at the folded position, are suitably selectable.

InFIG. 1, “40” and “41” indicate brackets for attaching child safety seats, “42” indicates a seat belt anchor, and “43” and “44” indicate seat belt guides. The brackets40and41and the seat belt anchor42are fixed to the seat back panel10by welding, for example. The seat belt guides43and44are fixed to the upper part21aof the main frame21.

Next, the seat back panel10is described in detail with reference toFIGS. 2 to 7. In this embodiment, the seat back panel10is formed by stamping a thin (in this embodiment, 0.4 mm) plain steel plate. The seat back panel10has flat surfaces that have large areas and extending vertically, in a center part and parts therearound which correspond to three sections R1to R3hatched inFIG. 5.

The three sections R1to R3are sections where rigidities are particularly lower and reinforcements thereof are strongly desired. In this embodiment, the rigidities in the sections R1to R3are increased by forming the bead portions and the embossed portions. Hereinafter, a method of forming the embossed portions and the bead portions in the sections R1to R3is described, and positions and directions thereof are described based on the state where the seat back panel10is at the upright position (the state ofFIG. 1).

First, in each of the sections R1to R3, two or more circular embossed portions50are formed vertically in line and spaced apart from each other, parallel to the extending directions of each of the sections R1to R3. The embossed portions50are formed by plastically deforming the sections so as to protrude at a seating surface side of the seat back panel10(the side facing forward at the upright position).

Two embossed portions50are formed in the section R1in this embodiment, and the two embossed portions50are vertically spaced apart from each other, at a position indicated by the reference character “H1” inFIG. 5. The position of H1is a lateral center position of the headrest frame37. In other words, the embossed portions50of the section R1is located so that when a passenger is seated corresponding to the headrest frame37, the embossed portions50are on the back of the passenger.

Similarly, two embossed portions50are formed in the section R3in this embodiment, and the two embossed portions50are vertically spaced apart from each other, at a position indicated by the reference character “H2” inFIG. 5. The position of H2is a center position of the headrest frame36in the lateral directions. In other words, the embossed portions50of the section R3is located so that when a passenger is seated corresponding to the headrest frame36, the embossed portions50are on the back of the passenger.

Each bead portion51is formed to surround one embossed portion50, has a rectangular shape (in this embodiment, substantially square), and is formed by plastically deforming the section so as to protrude at the rear side of the seat back panel10(the side facing rearward at the upright position). The bead portion51surrounding the embossed portion50is formed annularly and has a closed end.

In each of the sections R1to R3, the bead portions51surrounding the plurality of embossed portions50are formed continuously to each other. For example, adjacent bead portions51in the vertical directions share portions (sides) thereof extending laterally. In other words, in each of the sections R1to R3, a pair of left and right long bead portions (long portions) are formed to extend vertically and the pair of the left and right bead portions are coupled to each other by a short bead portion (short portion), so as to form a ladder structure as a whole. The embossed portions50are formed inside the sections surrounded by the upper, lower, left and right bead portions.

As illustrated inFIG. 7, the protrusion length of each bead portion51is indicated by the reference character “α1” and the protrusion length of each embossed portion50is indicated by the reference character “α2.” Note that α2>α1. For example in this embodiment, al is set to about 2 to 3 mm and α2is set to about 8 to 10 mm. Here, for the sake of convenience, although the embossed portion50and the bead portion51extend in the opposite directions from each other in the longitudinal directions (the embossed portion50extends toward the front side and the bead portion51extends toward the rear side), both of them are described as “protruding.”

Even outside the sections R1to R3, the seat back panel10is suitably formed with embossed portions60and bead portions61so that rigidity increases greatly as a whole. Note that the embossed portions60protrude at the front side of the seat back panel10, and the bead portions61protrude at the rear side of the seat back panel10. Further, the protrusion length of each embossed portion60is longer than that of each bead portion61(the same setting as the relationship between the embossed and bead portions50and51).

Note that inFIG. 2, “46” and “47” indicate attachment holes to attach the child-safety-seat attachment brackets40and41, respectively, and “48” indicates an attachment hole to attach the seat belt anchor42. Note that a thick cushion member is disposed on the front side of the seat back panel10while the rear side of the seat back panel10is covered by a thin cover sheet, so that the seat back panel10and the frame20are not visible from the outside.

Moreover, bead portions81formed annularly to extend circumferentially continuously (have a closed end) are formed to surround the attachment holes46and47, respectively. The bead portions81protrude toward the same direction as the bead portions51. By forming the bead portions81, the rigidity near the attachment holes46and47is increased. In this embodiment, the bead portions51partially constitute portions of the bead portions81. However, the bead portions51and81may be formed independently from each other without sharing a portion. Moreover, the bead portion51may be referred to as a first bead portion and the bead portion81may be referred to as a second bead portion.

In this embodiment, a bead portion which corresponds to the bead portion81is not formed to surround the attachment hole48for the seat belt anchor; however, a bead portion may be formed annularly to extend circumferentially continuously (have a closed end) to surround the attachment hole48.

Here, each rectangular bead portion51has two opposing sides extending laterally. The two sides of each bead portion51are arranged so as not to align with the two sides of the other bead portion51separately disposed laterally therefrom. Since each side of the bead portion51extending laterally is arranged so as not to align with the side of another bead portion51laterally adjacent thereto as described above, the torsional rigidity of the seat back panel10is particularly increased. Moreover, the embossed portions50formed in the sections surrounded by the bead portions51, respectively, are also arranged so as not to laterally align with each other, thus the torsional rigidity is increased even more.

The seat back2for a single passenger inFIG. 1, similar to the seat back3for two passengers, is comprised of a seat back panel10and a frame20, and flat surfaces thereof that have large areas are formed with the embossed portions50and60and the bead portions51,61and81described above.

The seat back panel10structured as above is significantly increased in rigidity by having, in its flat surfaces which have the large areas, the embossed portions50and the bead portions51annularly surrounding the embossed portions50. Especially since the embossed portions50protrude toward the direction opposite from the protruding direction of the bead portions51, compared to a case where they protrude toward the same direction, the rigidity is increased even more. Further, since each bead portion51surrounding one embossed portion50is formed annularly and has the closed end, the rigidity is increased even further. Moreover, since the bead portions51for the plurality of embossed portions50are formed continuously to each other, compared to a case where the bead portion51for a certain one of the embossed portions50is separated from the bead portion51for a different embossed portion50, the rigidity is increased more. Since each bead portion51is formed into a rectangle (particularly, substantially square), bending forces from various directions are advantageously resisted.

When the seat back3(or2) is at the upright position, although the embossed portions50with the longer protrusion length are located on the front side of the seat back panel10, since the cushion member is disposed on the front side of the seat back panel10, no problem arises from this large protrusion. Further, when the seat back3(or2) is at the folded position, since the protrusion length of the bead portions51located on the rear side of seat back panel10(i.e., the loading surface side where the load is placed) is short, no trouble is caused in placing the load.

To secure desirable (required) rigidity, at least 0.5 mm of thickness is conventionally required. However in this embodiment, equivalent rigidity is securable with 0.3 mm. Depending on the shape or number of the embossed portions50, the bead portions51etc., and the material of the seat back panel10and the like, the thickness may even be thinner. Therefore, by stamping a plain steel plate with the thickness of 0.2 mm to 0.5 mm, the weight is reduced more sufficiently than the conventional structure, while securing the required rigidity.

FIGS. 8 to 10illustrate modifications of the embossed portion50and the bead portion51, respectively. First,FIG. 8illustrates an example in which the embossed portion50is formed into a rectangle (substantially square). In this example, each side of the embossed portion50extends in parallel to a corresponding side of the bead portion51.

In the example ofFIG. 9, similar to the case ofFIG. 8, the embossed portion50is formed into a rectangle (substantially square), whereas the embossed portion50is arranged such that the respective sides thereof are inclined by substantially 45 degrees with respect to the sides of the bead portion51. The case ofFIG. 9is suitable in coping with the bending forces applied from a wider range of directions.

FIG. 10illustrates an example in which both of the embossed portion50and the bead portion51are formed into a circle. This case is also suitable in resisting external forces applied from various directions. As a modification of the case ofFIG. 10, while the bead portion51is a circle, the embossed portion50may be a rectangle (particularly, substantially square).

Next, the intermediate member and the cushion member attached to the seat back panel10are described with reference toFIGS. 11 to 14. As illustrated inFIG. 11, the cushion member80is for the passenger to directly contact with, is formed by covering urethane foam with an upholstery material, and thus has a sufficient cushioning characteristic. Due to the disposition of the intermediate member70, the cushion member80is thinned by the thickness of the intermediate member70.

The intermediate member70is disposed between the seat back panel10and the cushion member80. The intermediate member70is formed by, for example, EPP (expanded polypropylene), and a specific gravity is set lower than that of the cushion member and the hardness is set higher than that of the cushion member. By providing such an intermediate member70, compared to a case where the cushion member80forms the volume part corresponding to the intermediate member70, the weight is reduced.

The intermediate member70contacts (the seating surface side of) the seat back panel10with a suitable space therebetween. To describe this feature, first, the intermediate member70has contacting portions71in a back surface to contact the embossed portions50formed in the seat back panel10. As illustrated inFIG. 12, in the sections R1and R2illustrated inFIG. 5, each contacting portion71is formed as a flat surface extending over two or more embossed portions50, continuously in the vertical directions. In the section R3illustrated inFIG. 5, the contacting portion71is formed as a flat surface independently provided for each embossed portion50.

On the rear side of the intermediate member70, a concaved portion72is formed to surround each contacting portion71, specifically, the concaved portion72corresponds to the position of the closest bead portions51to the embossed portions50corresponding to the contacting portion71. By forming the concaved portions72, spaces K are formed between the seat back panel10and the intermediate member70(seeFIGS. 13 and 14), at positions corresponding to the bead portions51. The total area of all the spaces K occupies a significant part of the area of the intermediate member70. Thus, compared to a case where the concaved portions72are not formed in the intermediate member70(a case where the intermediate member70is adhered to the seat back panel also at the positions corresponding to the spaces K), the intermediate member70, i.e., the seat back S as a whole, is reduced in weight.

When a passenger leans on the seat back panel10, the weight of the passenger is firmly supported by (the embossed portions50of) the seat back panel10via the contacting portions71, and a good seated sensation is secured (improved).

As described above, with the combination of the weight reduction of the seat back panel10itself, the weight reduction by using the intermediate member70, and also the weight reduction by forming the spaces K between the seat back panel10and the intermediate member70(lightening of the intermediate member70), the overall sufficient weight reduction is achieved while securing the rigidity and the seated sensation.

Although the embodiment of the present invention is described above, the present invention is not limited to this, and suitable changes may be made within the range of the claims. The bead portion51surrounding the embossed portion50may extend circumferentially intermittently. The protrusion length of the bead portion51may be longer than that of the embossed portion50. When a single embossed portion50and the bead portion51surrounding this embossed portion50are defined as a single cell unit, (bead portions51of) adjacent cells may be separated from each other without being disposed continuously.

When a single embossed portion50and the bead portion51surrounding this embossed portion50are defined as a single cell unit, since the effect of increasing the rigidity increases as the area of the single cell unit (the area surrounded by the bead portion51) is smaller, it is suitable to set the area within a range of 100 square cm to 500 square cm. Further, it is suitable to set the area of the embossed portion50to about 10 to 30% of the area surrounded by the bead portion51. The rigidity increasing part comprised of the single cell unit may suitably be disposed in the flat surface portions where the rigidity is particularly required in the seat back panel10. For example, the disposition of the rigidity increasing part may suitably be selected from, for example, spreading the cell units per unit, disposing a plurality of cell units adjacently to each other, specifically in the case of disposing the plurality of cell units adjacently to each other, setting the extending direction thereof (arranged direction of the embossed portions50) to be the lateral directions or inclined, etc. Note that the purpose of the present invention is not limited to that described explicitly, and it implicitly includes providing what is expressed as substantially suitable or advantageous.

The present invention is suitable in weight reduction of a seat back.

DESCRIPTION OF REFERENCE CHARACTERS