Cushion for seat

Abstract

To provide a cushion for a seat which can reduce a burden on the waist of an occupant in a lying state of the occupant on the seat.SOLUTION: A sleeping-in-car cushion 10 includes a foamed body 20 which has a lower surface section 20A arranged on a seat surface of a seat cushion, a support surface section 20B which protrudes and curves to an opposite side of the boundary 18 viewed from a seat width direction and can support an occupant seated on a seat 12, and a pair of side face sections 20C extended from a seat width direction outside of the lower surface section 20A to a seat upper side and the seat width direction outside viewed from a seat front side, in a state of being arranged in a boundary 18 between a seat back 16 and a seat cushion in the seat 12.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a seat cushion. [Background technology]

[0002] The following Patent Document 1 discloses an invention related to a lumbar pillow. This lumbar pillow is placed on the seat on which the passenger sits, and reduces the burden on the passenger's lower back when seated on the seat. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-44849 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the prior art described in Patent Document 1 does not assume use when the occupant is lying down on the seat, such as when the occupant is resting, etc. In other words, the prior art described in Patent Document 1 has room for improvement in terms of reducing the burden on the occupant's lower back when the occupant is lying down on the seat.

[0005] In consideration of the above, an object of the present invention is to provide a seat cushion that can reduce the burden on the lower back of an occupant when the occupant is lying down on the seat. [Means for solving the problem]

[0006] The seat cushion of the first aspect has a foam body which, when placed at the boundary between the seat back and the seat cushion in the seat, is provided with a lower surface portion which is placed on the sitting surface of the seat cushion, a support surface portion which is convexly curved on the opposite side of the boundary when viewed from the seat width direction and is capable of supporting an occupant seated on the seat, and a pair of side surfaces which extend from the outer side of the lower surface portion in the seat width direction toward the upper side of the seat and toward the outer side in the seat width direction when viewed from the front side of the seat.

[0007] The seat cushion according to the first aspect is disposed at the boundary between the seat back and the seat cushion in the seat. In this aspect, the lower surface of the foam of the seat cushion is disposed on the seat surface of the seat cushion, and the support surface of the foam is curved and convex on the opposite side to the boundary between the seat back and the seat cushion when viewed from the seat width direction. Therefore, in this aspect, the support surface of the foam can support the lower back and the surrounding area of ​​the occupant lying on his back on the seat.

[0008] In order to disperse the pressure acting on the surface of the occupant's body from the foam, i.e., the body pressure, it is preferable to increase the length of the support surface in the seat width direction, i.e., the width of the support surface. However, if the foam is simply expanded in the seat width direction, it is considered that the foam may interfere with the side supports provided on the seat back or the seat cushion.

[0009] In this embodiment, the foam has a pair of side surfaces that extend from the outer sides of the lower surface of the seat width direction when viewed from the front side of the seat toward the upper side of the seat and the outer sides of the seat width direction. Therefore, in this embodiment, the side support can be stored below the seat on the side surfaces of the foam.

[0010] As a result, in this aspect, the width of the support surface portion is expanded to a position where it overlaps with the side support when viewed from above the seat, thereby reducing the body pressure acting on the occupant.

[0011] The seat cushion according to the second aspect is the seat cushion according to the first aspect, wherein the foam has a length in the seat width direction that decreases from the rear side of the seat to the front side of the seat when viewed from above the seat.

[0012] According to the seat cushion of the second aspect, the length of the foam in the seat width direction becomes shorter from the rear side of the seat to the front side of the seat, which makes it easier for the foam to fit between the side supports provided on the seat cushion, and allows the seat cushion and the seat cushion to be in close contact with each other.

[0013] A seat cushion according to a third aspect is the seat cushion according to the first or second aspect, wherein a groove extending in a seat width direction is formed in the support surface portion.

[0014] According to the seat cushion of the third aspect, a groove portion extending in the seat width direction is formed in the support surface portion of the foam, so that a portion of the support surface portion that is likely to deform due to the weight of the occupant can be set along the seat width direction.

[0015] The seat cushion of the fourth aspect is the seat cushion of the third aspect, wherein the groove portion, in a longitudinal section viewed from the seat width direction, comprises a front planar portion that constitutes the front part of the seat, a rear planar portion that constitutes the rear part of the seat, and a bottom surface portion that is connected to the front planar portion and the rear planar portion and has a concave arc shape, and the distance between the front planar portion and the rear planar portion increases with increasing distance from the support surface portion.

[0016] In the seat cushion according to the fourth aspect, the groove portion provided on the support surface portion of the foam includes, in a longitudinal section viewed in the seat width direction, a front planar portion constituting the front portion of the seat, a rear planar portion constituting the rear portion of the seat, and a bottom surface portion connected to the front planar portion and the rear planar portion and having a concave arc shape, and the distance between the front planar portion and the rear planar portion increases with increasing distance from the support surface portion.

[0017] Therefore, the longitudinal section of the groove as viewed from the seat width direction is in a state of expanding from the support surface portion toward the bottom surface portion. As a result, compared to a configuration in which the distance between the front side flat portion and the rear side flat portion is constant, the stress caused by the occupant's own weight generated in the portion of the foam around the groove becomes larger from the support surface portion toward the bottom surface portion, making it easier to deform the foam by the occupant's own weight. Moreover, since the bottom surface portion of the groove is formed in a concave arc shape as viewed from the seat width direction, it is possible to suppress the occurrence of a stress concentration point at the boundary between the front side flat portion and the rear side flat portion and the bottom surface portion when a load is applied around the groove. As a result, in this embodiment, it is possible to suppress damage to the portion of the foam around the groove.

[0018] The seat cushion of the fifth aspect is the seat cushion of the third or fourth aspect, wherein a plurality of the groove portions are formed in the support surface portion, and the portion between the groove portions in the support surface portion is a concave portion recessed toward the boundary portion.

[0019] According to the seat cushion of the fifth aspect, a plurality of grooves are formed on the support surface of the foam, and a protrusion extending in the seat width direction is formed between the grooves on the support surface side of the foam. In this aspect, the portion between the grooves on the support surface, i.e., the top of the protrusion, is a concave portion recessed toward the boundary. Therefore, the concave portion expands when it receives a load from the occupant, and the surface area of ​​the support surface that supports the occupant can be secured.

[0020] The seat cushion of the sixth aspect is the seat cushion of the fifth aspect, wherein, in the concave portions adjacent in the fore-and-aft direction of the seat when viewed from above the seat, the length of the concave portion on the front side of the seat in the fore-and-aft direction is shorter than the length of the concave portion on the rear side of the seat in the fore-and-aft direction.

[0021] According to the seat cushion of the sixth aspect, in the concave surface portions adjacent in the front-rear direction of the seat as viewed from above the seat, the length of the concave surface portion on the front side of the seat is shorter than the length of the concave surface portion on the rear side of the seat. That is, in this aspect, the length of the protrusion portion formed between the groove portions in the front-rear direction of the seat tends to become shorter from the rear side of the seat to the front side of the seat, so that the protrusion portion tends to be easily deformed by the weight of the occupant from the rear side of the seat to the front side of the seat. Therefore, in this aspect, the foam is brought into close contact with the lower side of the seat of the occupant's waist, and the waist can be supported in a stable state.

[0022] A seat cushion according to a seventh aspect is the seat cushion according to any one of the first to sixth aspects, wherein the seat cushion is a cushion for sleeping in a vehicle.

[0023] According to the seventh aspect of the seat cushion, the seat cushion is a vehicle overnight cushion, and when an occupant sleeps overnight in the vehicle, the vehicle overnight cushion is placed at the boundary between the seat back and the seat cushion, thereby dispersing the body pressure acting on the occupant sleeping on the seat. Effect of the Invention

[0024] As described above, the seat cushion according to the present invention has the excellent effect of reducing the burden on the lower back of an occupant when the occupant is lying down on the seat. [Brief description of the drawings]

[0025] [Figure 1]1 is a longitudinal sectional view seen from a seat width direction, which diagrammatically illustrates a configuration of a seat cushion according to an embodiment of the present invention. [Diagram 2] 2 is a front view (view taken in the direction of arrow 2 in FIG. 1) showing a schematic diagram of the configuration of the seat cushion according to the present embodiment, as seen from the front side of the seat. [Diagram 3] 3 is a plan view (view taken in the direction of arrow 3 in FIG. 1) showing a schematic configuration of the seat cushion according to the present embodiment, as seen from above the seat. [Figure 4] 1 is a perspective view seen from the front side of a seat, illustrating a state in which a seat cushion according to an embodiment of the present invention is in use. FIG. [Diagram 5] FIG. 2 is a reference perspective view showing a configuration of a seat cushion according to the embodiment. [Figure 6] 1 shows the configuration of a seat cushion for this embodiment, where (A) is a front view of the seat cushion, (B) is a rear view of the seat cushion, (C) is a plan view of the seat cushion, (D) is a left side view of the seat cushion, (E) is a right side view of the seat cushion, and (F) is a bottom view of the seat cushion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An example of an embodiment of the seat cushion according to the present invention will be described below with reference to Figures 1 to 6. Note that the arrows FR, UP, and RH shown as appropriate in each figure indicate the front side in the front-rear direction, the upper side in the up-down direction, and the right side in the width direction of the seat 12 on which the vehicle overnight cushion 10 serving as the seat cushion is placed, respectively. Note that in this embodiment, as an example, the seat 12 is used as a seat for an automobile, but the seat 12 may also be used as a seat for a vehicle such as an airplane or a ship.

[0027] As shown in FIG. 4, the seat 12 includes a seat cushion 14 that supports the buttocks and thighs of an occupant seated on the seat 12, a seat back 16 that supports the back of the occupant, and a headrest (not shown) that supports the head of the occupant.

[0028] The overnight cushion 10 is disposed on a boundary 18 between the seat cushion 14 and the seat back 16 in the seat 12. The overnight cushion 10 is disposed on the boundary 18, for example, when the seat back 16 is rotated from an upright state to the rear side of the seat with respect to the seat cushion 14 so that the longitudinal direction of the seat back 16 is horizontal, in a fully flat state, or when the seat back 16 is raised from the horizontal to the front side of the seat by about 60 degrees. In the following, unless otherwise specified, the overnight cushion 10 is assumed to be disposed on the boundary 18 when the seat back 16 is raised from the fully flat state by a predetermined angle.

[0029] As shown in FIG. 1, the vehicle camping cushion 10 is configured to include a foam 20 that constitutes the main portion thereof, and a skin 22 that covers the surface of the foam 20. The foam 20 is made of a flexible material having elasticity, and in this embodiment, as an example, the foam 20 is made of soft urethane foam. Note that this soft urethane foam has an apparent density of 15 to 30 (kg / m 3 ) and more preferably 21 (kg / m 3 ), the rebound resilience is set to 35-50(%), preferably 45(%), the hardness is set to 35-110(N), preferably 60(N), and the compression set is set to 3-35(%), preferably 5(%). The urethane foam constituting the foam 20 is not limited to those described above, and any suitable one can be used.

[0030] On the other hand, the skin 22 is constructed by sewing together a skin material made of synthetic leather, fabric, leather, or the like, and is formed into a bag shape capable of containing the foam 20 therein.

[0031] More specifically, the foam 20 is composed of a lower surface portion 20A that constitutes the lower portion of the seat, a support surface portion 20B that constitutes the upper portion of the seat, a pair of side surfaces 20C that constitute the outer portions of the seat in the width direction, and a back surface portion 20D that constitutes the rear portion of the seat.

[0032] The lower surface portion 20A has a rectangular shape with its longitudinal direction aligned with the seat width direction when viewed from below the seat, and is disposed on the seat surface 14A of the seat cushion 14 with a part of the cover 22 interposed therebetween.

[0033] The support surface portion 20B is curved in its entirety along a circular arc A1 with a curvature radius R1 that is convex on the opposite side to the boundary portion 18 of the seat 12 when viewed from the seat width direction, and is capable of supporting an occupant. As shown in Fig. 3, the length of the support surface portion 20B in the seat width direction decreases from the rear side of the seat to the front side of the seat when viewed from above the seat. The ratio of the length L1 in the seat width direction at the end of the support surface portion 20B on the rear side of the seat to the length L2 in the seat width direction at the end of the support surface portion 20B on the front side of the seat is set to about 8:5, but the ratio of L1 to L2 is not limited to this.

[0034] In addition, the support surface portion 20B has a plurality of grooves 24 extending in the seat width direction, for example, six grooves 24, which are formed in series in the seat front-rear direction. When viewed from above the seat, the distance between the grooves 24 is set to be shorter than the distance between the end of the support surface portion 20B on the seat front side and the seat-most front groove 24 and the distance between the end of the support surface portion 20B on the seat rear side and the seat-most rear groove 24.

[0035] Returning to Figure 1, in a longitudinal section viewed from the seat width direction, groove portion 24 is composed of a front planar portion 24A that constitutes the front portion of the seat, a rear planar portion 24B that constitutes the rear portion of the seat, and a bottom portion 24C that is connected to front planar portion 24A and rear planar portion 24B.

[0036] In detail, the front plane portion 24A and the rear plane portion 24B are formed so that, when viewed from the seat width direction, the distance between the front plane portion 24A and the rear plane portion 24B becomes longer as it moves away from the arc A1, which is the reference of the support surface portion 20B.

[0037] On the other hand, the bottom surface portion 24C is formed to have a concave shape, specifically an arc shape concave toward the opposite side to the arc A1, when viewed from the sheet width direction. Also, when viewed from the sheet width direction, a straight line S2 that passes through a vertex P1 of the bottom surface portion 24C and is perpendicular to a tangent line S1 of the bottom surface portion 24C that passes through the vertex P1 is perpendicular to the arc A1. In a vertical cross section viewed from the sheet width direction, the groove portion 24 is formed to have a shape that is approximately line-symmetrical with respect to the straight line S2, and the depth direction of the groove portion 24 coincides with the extension direction of the straight line S2.

[0038] Furthermore, as described above, by forming a plurality of grooves 24 in the foam 20, a protrusion 20E extending in the sheet width direction is formed in the foam 20 between adjacent grooves 24 in the front-rear direction of the sheet. The top of the protrusion 20E is a concave surface 20E1 recessed toward the boundary 18. That is, the portion between the grooves 24 in the support surface portion 20B of the foam 20 is a concave surface 20E1.

[0039] 3, in the present embodiment, in the concave surface portions 20E1 adjacent to each other in the seat front-rear direction, the length of the concave surface portion 20E1 on the front side of the seat is set to be shorter than the length of the concave surface portion 20E1 on the rear side of the seat in the seat front-rear direction. In other words, in the present embodiment, in the protrusions 20E adjacent to each other in the seat front-rear direction, the average length (thickness) in the tangent S1 direction of the protrusion 20E on the front side of the seat is set to be shorter than the average length in the tangent S1 direction of the protrusion 20E on the rear side of the seat.

[0040] 2, the side surface portion 20C extends from the outer end of the lower surface portion 20A in the seat width direction toward the upper side of the seat and toward the outer side in the seat width direction when viewed from the front side of the seat. A part of the side support 14B of the seat cushion 14 and a part of the side support 16A of the seat back 16 are disposed on the seat lower side of the side surface portion 20C.

[0041] Returning to FIG. 1, the back surface portion 20D extends from the end 20A1 on the rear side of the lower surface portion 20A to the rear upper side of the seat, connects the end 20A1 to the end 20B1 on the rear side of the support surface portion 20B, and is curved in a concave shape when viewed in the seat width direction, specifically, convex toward the front side and the upper side of the seat. The ratio of the length L3 in the front-rear direction of the foam 20 to the length L4 in the up-down direction of the seat is set to about 2:1, but the ratio of L3 to L4 is not limited to this. The foam 20 configured as above has a product center hardness of 20 to 70 (N), preferably 50 (N).

[0042] <Actions and Effects of the Present Embodiment> Next, the operation and effects of this embodiment will be described.

[0043] In this embodiment, as shown in Fig. 4, the overnight cushion 10 is disposed at the boundary 18 between the seat back 16 and the seat cushion 14 in the seat 12. Then, as shown in Fig. 1, the lower surface 20A of the foam 20 of the overnight cushion 10 is disposed on the seat surface 14A of the seat cushion 14, and the support surface 20B of the foam 20 is curved and convex on the opposite side of the boundary 18 when viewed from the seat width direction. Therefore, in this embodiment, the lower back and the surrounding area of ​​the occupant lying on his back on the seat 12 can be supported by the support surface 20B of the foam 20.

[0044] Incidentally, in order to disperse the pressure acting on the surface of the occupant's body from the foam 20, i.e., the body pressure, it is preferable to be able to increase the length of the support surface portion 20B in the seat width direction, i.e., the width of the support surface portion 20B. However, if the foam 20 is simply expanded in the seat width direction, it is considered that the foam 20 may interfere with the side support 16A of the seat back 16 and the side support 14B of the seat cushion 14.

[0045] 2, the foam 20 is provided with a pair of side portions 20C, which extend from the outer side of the lower surface portion 20A in the seat width direction to the upper side of the seat and the outer side of the seat width direction when viewed from the front side of the seat. Therefore, in this embodiment, a part of the side support 14B or the side support 16A can be accommodated on the lower side of the seat in the side portion 20C of the foam 20. As a result, in this embodiment, the width of the support surface portion 20B is expanded to a position where it overlaps with the side support 14B or the side support 16A when viewed from the upper side of the seat, and the body pressure acting on the occupant can be reduced.

[0046] 3, the length of the foam 20 in the seat width direction becomes shorter from the rear side of the seat to the front side of the seat, as viewed from above the seat. This makes it easier for the foam 20 on the front side of the seat to fit between the side supports 14B provided on the seat cushion 14, allowing the overnight cushion 10 and the seat cushion 14 to be in close contact with each other.

[0047] In addition, in this embodiment, a groove portion 24 extending in the seat width direction is formed in the support surface portion 20B of the foam 20, so that a portion of the support surface portion 20B that is likely to deform due to the weight of the occupant can be set along the seat width direction.

[0048] 1, in a longitudinal section viewed in the seat width direction, the groove 24 includes a front flat portion 24A constituting the front side of the seat, a rear flat portion 24B constituting the rear side of the seat, and a bottom surface 24C that is connected to the front flat portion 24A and the rear flat portion 24B and has a concave arc shape. The distance between the front flat portion 24A and the rear flat portion 24B increases with increasing distance from the support surface 20B.

[0049] Therefore, the longitudinal section of the groove 24 seen from the seat width direction is in a state of expanding from the support surface portion 20B toward the bottom surface portion 24C. As a result, compared to a configuration in which the distance between the front side flat portion 24A and the rear side flat portion 24B is constant, the stress caused by the weight of the occupant generated in the portion of the foam 20 around the groove 24 becomes larger from the support surface portion 20B toward the bottom surface portion 24C, and the foam 20 can be easily deformed by the weight of the occupant. Moreover, since the bottom surface portion 24C of the groove 24 is formed in a concave arc shape when seen from the seat width direction, it is possible to suppress the occurrence of a stress concentration portion at the boundary portion between the front side flat portion 24A and the rear side flat portion 24B and the bottom surface portion 24C when a load is applied to the periphery of the groove 24. As a result, in this embodiment, damage to the portion of the foam 20 around the groove 24 can be suppressed.

[0050] In this embodiment, a plurality of grooves 24 are formed in the support surface portion 20B, and a protrusion 20E extending in the seat width direction is formed between the grooves 24 in the portion of the foam 20 on the support surface portion 20B side. In this embodiment, the portion between the grooves 24 in the support surface portion 20B, i.e., the top of the protrusion 20E, is a concave portion 20E1 recessed toward the boundary portion 18. For this reason, the concave portion 20E1 expands when a load is applied from the occupant side, and the area of ​​the surface of the support surface portion 20B that supports the occupant can be secured.

[0051] In addition, in this embodiment, in the concave surface portions 20E1 adjacent to each other in the seat front-rear direction when viewed from above the seat, the length of the concave surface portion 20E1 on the front side of the seat is shorter than the length of the concave surface portion 20E1 on the rear side of the seat. That is, in this embodiment, the length of the protrusion 20E formed between the groove portions 24 in the seat front-rear direction tends to become shorter from the rear side of the seat to the front side of the seat, so that the protrusion 20E tends to be easily deformed by the weight of the occupant from the rear side of the seat to the front side of the seat. Therefore, in this embodiment, the foam 20 is brought into close contact with the lower part of the seat of the occupant's waist, and the waist can be supported in a stable state.

[0052] In addition, in this embodiment, when an occupant sleeps overnight in the vehicle, the vehicle sleeping cushion 10 is placed at the boundary portion 18, thereby dispersing the body pressure acting on the occupant sleeping on the seat 12.

[0053] As described above, with the vehicle overnight cushion 10 according to this embodiment, when the occupant is lying down on the seat 12, the burden on the lumbar region of the occupant can be reduced.

[0054] <Modifications of this embodiment> The following describes a modified example of the vehicle camping cushion 10 derived from the above embodiment. Note that the same components as those in the above embodiment are given the same reference numbers and the description thereof will be omitted.

[0055] In this modified example, the side portion 20C extends upward from the end of the lower portion 20A on the outer side in the seat width direction. That is, the vehicle camping cushion 10 according to this modified example includes a lower portion 20A that is arranged on the seat surface 14A of the seat cushion 14 when arranged at the boundary portion 18 between the seat back 16 and the seat cushion 14 in the seat 12, and a support surface portion 20B that is curved convexly on the opposite side of the boundary portion 18 as viewed from the seat width direction and can support an occupant seated on the seat 12, and a groove portion 24 that extends in the seat width direction is formed in the support surface portion 20B.

[0056] In this modified example, in a seat 12 in which the seat cushion 14 and the seat back 16 are not provided with side supports, the same functions and effects as those of the above-described embodiment are achieved.

[0057] Moreover, in this modification, the shape of the foam 20 can be simplified, and the yield in the production of the foam 20 can be improved.

[0058] In the above-described embodiment and modified example, a plurality of grooves 24 are formed in the support surface portion 20B, but the number of grooves 24 may be changed depending on the material of the foam 20 and the product center hardness required for the foam 20, or the like, or the foam 20 may not have grooves 24. In addition, the cross-sectional shape of the grooves 24 can also be appropriately changed depending on the specifications of the overnight stay cushion 10, etc.

[0059] In addition, as shown in Figures 5 and 6, depending on the material of the foam 20, the vehicle camping cushion 10 may be configured so that the foam 20 is not wrapped in a skin 22, i.e., the foam 20 comes into direct contact with the occupant.

[0060] Furthermore, the above-mentioned car sleeping cushion 10 is placed at the boundary between the seat and the backrest when the reclining seat is reclined, eliminating the gap that occurs between the human body and the reclining seat, and supporting the lower back. As shown in the reference diagram (Fig. 4) showing the usage state, the cushion is placed so that the bottom surface of the cushion contacts the seat and the back surface contacts the backrest, and the upper surface supports the lower back of the human body. It can be used in all reclining seats, for example, reclining seats used in automobile seats. It can also be used not only in general reclining seats, but also in reclining beds such as beach beds and hammocks. [Explanation of symbols]

[0061] 10. Car seat cushions 12 sheets 14 Seat cushion 14A Seat 16 シートバック 18 Realm Department 20 vesicle 20A Lower face 20B Support face 20C Side profile 20E1 Concave part 24 Goube 24A Front flat surface 24B Rear flat surface 24C bottom face

Claims

1. When the seat is disposed at the boundary between the seat back and the seat cushion, A lower surface portion disposed on the seat surface of the seat cushion; a support surface portion that is curved convexly on the opposite side of the boundary portion when viewed in the seat width direction and is capable of supporting an occupant seated on the seat; A pair of side surfaces extending from the outer sides of the lower surface portion in the seat width direction toward the upper side of the seat and the outer sides in the seat width direction when viewed from the front side of the seat; A seat cushion having a foam body comprising:

2. The length of the foam in the seat width direction becomes shorter from the rear side of the seat to the front side of the seat when viewed from above the seat. The seat cushion according to claim 1.

3. A groove portion extending in the sheet width direction is formed on the support surface portion. The seat cushion according to claim 1.

4. In a longitudinal cross section seen from the seat width direction, the groove portion includes a front planar portion constituting a portion on the front side of the seat, a rear planar portion constituting a portion on the rear side of the seat, and a bottom surface portion connected to the front planar portion and the rear planar portion and having a concave arc shape, The distance between the front plane portion and the rear plane portion increases with increasing distance from the support surface portion. The seat cushion according to claim 3.

5. A plurality of the grooves are formed in the support surface portion, A portion between the grooves in the support surface portion is a concave portion recessed toward the boundary portion. The seat cushion according to claim 3.

6. In the concave surface portions adjacent to each other in the front-rear direction when viewed from above the seat, the length of the concave surface portion on the front side of the seat in the front-rear direction is shorter than the length of the concave surface portion on the rear side of the seat in the front-rear direction. The seat cushion according to claim 5.

7. The seat cushion is a vehicle overnight cushion. The seat cushion according to claim 1.

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