JP2023107975A - vehicle seat - Google Patents

Abstract

To fix a lower connection member to side frames with sufficient strength.SOLUTION: A vehicle seat includes: a seating frame 2 which is a frame of a seating part on which an occupant is seated; and a seat back frame 1 supported by the seating frame 2. The seat back frame 1 includes: side frames SF which are disposed separating from each other in a lateral direction; and a lower connection member 30 which is disposed so as to be spanned between lower parts of the left and right side frames SF and connects the left and right side frames SF. The left and right side frames SF have: side wall parts 12A; and inner extension parts 13 which extend from rear ends of the side wall parts 12A to the inner side in the lateral direction and are positioned separating from each other. The lower connection member 30 has: a front wall part 31 disposed at the occupant side; and a rear wall part 32 connected to the rear side of the front wall part 31. The rear wall part 32 is formed with a through hole 38 into which another member enters, and the through hole 38 overlaps with the front wall part 31 in an anteroposterior direction.SELECTED DRAWING: Figure 6

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle seat, such as a vehicle seat, and more particularly to a vehicle seat that provides a comfortable sitting feeling for an occupant during a rear-end collision.

In the case of a so-called rear-end collision, in which the vehicle collides from the rear, such as when the vehicle is rear-ended, or when the vehicle is traveling backwards, the seated occupant's head tilts backward due to inertia, causing the neck to bend. There is a risk of receiving a shock.

Therefore, in order to protect the occupant's head and neck from the impact of a rear-end collision and reduce the impact on the neck, a headrest is provided above the seat back to support the occupant's head from behind. there is In order to effectively reduce the impact of a rear-end collision, it is desirable to quickly reduce the gap between the occupant's head and the headrest at the time of a rear-end collision.

For this reason, in the event of a rear-end collision, the occupant's upper body is moved rearward, the pressure-receiving member receives the load from this movement, and the headrest is moved forward to support the occupant's head and reduce the impact on the neck. A configured seat back has been proposed (Patent Document 1).

In addition, in the seat back frame of the vehicle seat described in Patent Document 1, the left and right side frames are composed of a plate-shaped lower frame (lower connecting member) and a reclining pivot disposed in front of the lower frame. are connected to each other by a shaft for dynamic support. In some cases, the lower frame does not have a simple plate shape as in Patent Document 2, but has flanges extending forward at the upper and lower ends. These lower frames are in a substantially vertical posture in a normal seated posture, and are in a slightly forward posture with respect to the upper part of the backrest (the part that the upper back of the occupant hits).

JP 2010-083269 A JP 2008-067723 A

By the way, since the lower connecting member receives a load from an occupant during a rear-end collision, it is desired that the lower connecting member be fixed to the side frame with sufficient strength.

SUMMARY OF THE INVENTION It is an object of the present invention to fix a lower connecting member to a side frame with sufficient strength.

A vehicle seat according to the present invention, which solves the above problems, includes a seating frame, which is a frame of a seating portion on which an occupant sits, and a seatback frame supported by the seating frame.
The seatback frame includes side frames that are spaced apart from each other in the left and right direction, and a lower connection member that is arranged to extend between the lower portions of the left and right side frames and connects the left and right side frames.

The left and right side frames have side wall portions and inner extension portions that extend inward in the left-right direction from the rear ends of the side wall portions and are positioned apart from each other.

The lower connection member has a front wall portion arranged on the occupant side and a rear wall portion connected to the rear of the front wall portion. The rear wall portion is formed with a through hole into which another member enters. The through hole overlaps the front wall portion in the front-rear direction.

With such a configuration, the lower connecting member can be fixed to the side frame with sufficient strength.

Further, in the vehicle seat described above, the front wall portion may be configured to extend away from the rear wall portion as it separates from the connection portion between the front wall portion and the rear wall portion.

Further, in the vehicle seat described above, the seat back frame is configured to be reclinable with respect to the seating frame, and a shaft connecting the left and right side frames is arranged on the rotation axis of the seat back frame. It may be configured to be located between the wall and the front wall.

Further, in the vehicle seat described above, the shaft may be provided at the widest point between the front wall portion and the rear wall portion.

Further, in the vehicle seat described above, the front end portion of the rear wall portion may be formed with a forwardly inclined bent portion.

According to the present invention, the lower connecting member can be fixed to the side frame with sufficient strength.

1 is a perspective view of a vehicle seat; FIG. It is a perspective view of a seat frame. 4 is an enlarged perspective view of a lower connecting member; FIG. It is the figure (a) and (b) explaining the angle of the front surface of a front wall part. FIG. 4 is a rear view of the seatback frame showing the welded portion of the rear wall and the inboard extension; FIG. 4 is a side cross-sectional view for explaining the mounting structure of the cover on the back surface of the seat back; FIG. 3 is a side cross-sectional view showing the seatback frame during normal operation; FIG. 4 is a side cross-sectional view showing the seatback frame during a weak rear-end collision; FIG. 4 is a side cross-sectional view showing the seatback frame at the time of a strong rear collision; It is a side sectional view of the lower connection member which concerns on a modification. FIG. 11 is a perspective view showing a modification of the relief portion of the lower connection member;

An embodiment of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a vehicle seat S, which is an example of the vehicle seat of the present invention, includes a seat back S1, a seating portion S2, and a headrest S3. In this specification, front, rear, left, and right refer to an occupant seated in the vehicle seat S in a normal state with the seat back S1 upright (not lying on one's back due to reclining).

A seat frame F as shown in FIG. 2 is provided in the vehicle seat S. As shown in FIG. The seat frame F is composed of a seat back frame 1, which is the frame of the seat back S1, and a seating frame 2, which is the frame of the seating portion S2. The seating frame 2 and the seatback frame 1 are connected via a reclining mechanism 3 (detailed structure is not shown). A cushion and an upholstery are provided on the outside of the seat back frame 1 and the seating frame 2, and a cover 5 (see FIG. 6) as an example of a member to be attached is attached to the back surface with a clip 51 as an example of a fixing member. Thus, the seat back S1 and the seating portion S2 are configured.

The seatback frame 1 includes side plates 10 that are spaced apart in the left and right direction and extend in the vertical direction, an upper frame 21 that connects the upper ends of the side plates 10, and the lower ends of the left and right side plates 10. It is configured in a frame shape by the lower connection member 30 . The upper frame 21 is formed by bending a metal pipe into a U shape, and has an upper connecting portion 21A extending left and right and connecting portions 21B extending downward from the left and right ends of the upper connecting portion 21A. The connecting portion 21B is connected to the upper end of the side plate 10 by welding.

The side plate 10 is composed of a lower member 12 made of sheet metal provided at a lower end portion, and an upper member 11 integrated with the upper portion of the lower member 12 by welding. The lower member 12 includes a side wall portion 12A and an inner extension portion 13 extending inward from the rear end of the side wall portion 12A.

As shown in FIG. 5, the inner extension portion 13 has an inclined edge portion 13A inclined at an angle γ with respect to the vertical direction so that the inner end portion goes from the inside to the outside as it goes from top to bottom. ing. The inclined edge portion 13A is a portion where the lower connecting member 30 and the inner extension portion 13 are welded together as described later. In addition, the inner extension portion 13 has a clip hole 13B as an example of a mounting hole into which a clip 51 for mounting the cover 5 on the back surface of the seat back S1 is inserted.

Returning to FIG. 2, the side frame SF of the seat back frame 1 is composed of the side plate 10 and the connecting portion 21B of the upper frame 21. As shown in FIG. A plate-like pressure receiving member 40 made of resin is arranged between the left and right side frames SF. member) 41 to the left and right side frames SF. Specifically, the upper connecting wire 41 has its end engaged with a bracket 43 welded to the connecting portion 21B, and the lower connecting wire 41 has a rotating member 45 that can swing back and forth at its lower end. connected to The rotating member 45 is fixed to the side plate 10 (upper member 11). When a large backward force is applied from the wire 41, the lower end of the wire 41 swings backward, allowing the pressure receiving member 40 to move greatly backward.

A pillar support portion 23 is provided on the upper frame 21 , and a headrest frame (not shown) is provided on the pillar support portion 23 . The headrest S3 is configured by providing a cushion member outside the headrest frame.

Next, details of the lower connection member 30 will be described. The lower connection member 30 is arranged so as to span between the lower portions of the left and right side frames SF. As a result, even when a load is applied from the side, the seat frame F can be prevented from collapsing in the left-right direction, and the load from the side can be transmitted to the center of the vehicle.

The lower connection member 30 is made of sheet metal, and as shown in FIG. It has an upper wall portion 33 , a lower flange 34 and a folded flange 35 .

The front wall portion 31 is positioned in front of the shaft 3S of the reclining mechanism 3 . The shaft 3S is arranged on the rotation axis of the seat frame 2 and the seat back frame 1, and is provided so as to connect the left and right side frames SF to each other in order to support the rotation of the reclining mechanism 3. Since the front wall portion 31 of the lower connection member 30 is positioned in front of the shaft 3S, the load applied from the occupant's buttocks or the like via the seat back cushion is not applied directly to the shaft 3S, but is applied to the front wall portion 31. Therefore, it is possible to alleviate the feeling of hitting the shaft 3S on the buttocks of the occupant.

As shown in FIG. 4(a), the front wall portion 31 has a front surface 31A that is parallel to the extending direction (straight line L1) of the connecting portion 21B or obliquely upward with respect to the extending direction in a side view. It has become. In the example of FIG. 4A, the front surface 31A faces upward at an angle α with respect to the straight line L1. The front wall portion 31 also faces upward at an angle β with respect to the rear wall portion 32 . As a result, the front wall portion 31 and the rear wall portion 32 are connected at their upper ends and open downward, so that the front wall portion 31 can secure a stroke for rearward deformation in the event of a rear-end collision. Note that the connecting portion 21B, which is a pipe that constitutes the side frame SF, is not straight when viewed from the side, but is curved so that the upper portion is raised or, conversely, is bent so that the upper portion lies down as shown in FIG. 4(b). Sometimes it is against. In such a case, the angle of the front face 31A with respect to the pipe (connecting portion 21B) refers to the angle of the pipe in the most standing direction.

The lower end of the front wall portion 31 extends below the lower end of the rear wall portion 32 . As a result, the front wall portion 31 can be enlarged to reduce the occupant's feeling of contact with the lower connecting member 30. In addition, since the front wall portion 31 is long from the upper end to the lower end, the front wall portion 31 can be displaced in the event of a rear-end collision. becomes easier to deform backwards.

The rear wall portion 32 is a wall connected to the side frames SF (the inner extension portions 13), and is a member that connects and supports the lower connection member 30 to the side frames SF. Specifically, as shown in FIG. 4A, the rear surface of the rear wall portion 32 is aligned with the front surface of the inner extension portion 13, and as shown in FIG. The inner extending portion 13 and the rear wall portion 32 are welded along the . Since the slanted edge portion 13A is slanted with respect to the vertical direction, even if the height direction overlap between the slanted edge portion 13A and the rear wall portion 32 is small, the required welding strength can be obtained by increasing the welding length. It is designed to be able to keep. The angle γ of the inclined edge 13A is desirably 20 degrees or more. When the angle γ is 20 degrees or more, the effect of increasing the weld length becomes large. The angle γ is more desirably 30 degrees or more, and even more desirably 40 degrees or more. Also, by setting the angle γ to 70 degrees or less, it is possible to prevent the inner extension portion 13 from becoming excessively acute.
Since the rear wall portion 32 is fixed to the side frames SF, rearward movement of the rear wall portion 32 is suppressed in the event of a rear-end collision. As a result, the rearward movement of the front wall portion 31 can be easily controlled.

As described above, the lower connection member 30 of the present embodiment has the front wall portion 31 and the rear wall portion 32 connected to the front wall portion 31, and thus is compared with a simple plate-shaped lower connection member. As a result, the rigidity against crushing in the left-right direction is increased, and the load from the sides can be efficiently transmitted to the center of the vehicle.

As shown in FIG. 3, the upper wall portion 33 has a flat plate shape extending substantially in the front-rear direction. As a result, the upper end of the front wall portion 31 and the upper end of the rear wall portion 32 are separated from each other appropriately in the front-rear direction, and the deformation stroke can be increased when the front wall portion 31 is deformed rearward. The connecting portion between the front wall portion 31 and the upper wall portion 33 has a gentle shape without edges due to the natural R shape formed when the upper wall portion 33 and the front wall portion 31 are bent. there is

The lower flange 34 is bent rearward from the lower end of the front wall portion 31 below the shaft 3S and extends rearward. The connecting portion between the front wall portion 31 and the lower flange 34 also has a gentle shape without edges due to the natural R shape formed when the lower flange 34 and the front wall portion 31 are bent. Also, the lower flange 34 is not connected to the rear wall portion 32, so that the lower connecting member 30 does not have a closed cross-sectional shape. Since the lower flange 34 and the rear wall portion 32 are not connected to each other in this way and there is a gap between them, the front wall portion 31 can be easily deformed rearward.

The folded flange 35 is folded back forward from the rear end of the lower flange 34 , and the front end of the folded flange 35 is positioned rearward of the lower end of the front wall portion 31 . Since the lower connection member 30 includes the lower flange 34 and the folded flange 35 in this manner, the cross-sectional area of the lower connection member 30 is increased. Therefore, the rigidity in the left-right direction is improved, and the load transmission in the lateral direction is improved. In addition, since the front end of the turn-up flange 35 is located behind the lower end of the front wall portion 31 (the connecting portion between the front wall portion 31 and the lower flange 34), the edge of the front end of the turn-up flange 35 can be The seat back cushion is not strongly hit, and the occupant's feeling of hitting the lower connecting member 30 can be suppressed, and damage to the seat back cushion can be suppressed.

Two through holes 38 are formed in the rear wall portion 32 of the lower connection member 30 , more specifically, from the rear wall portion 32 to the upper wall portion 33 . As shown in FIG. 6, the through hole 38 is used to prevent the tip of the clip 51 from interfering with the rear wall portion 32 of the lower connecting member 30 when the rear cover 5 is attached to the clip hole 13B with the clip 51. Acts as an escape. Therefore, the through hole 38 is provided at a position corresponding to each clip hole 13B.

As shown in FIG. 5, the lower connecting member 30 does not reach the side wall portion 12A, and a slight gap is provided between it and the side wall portion 12A. However, if manufacturing errors in the lower connecting member 30 and riding on the corners of the lower member 12 of the lower connecting member 30 are not a problem, both ends of the lower connecting member 30 are configured to abut against the side wall portion 12A. good too.

The operation of the vehicle seat S configured as described above at the time of a rear-end collision will be described.
As shown in FIG. 7, before a rear-end collision occurs, the rotating member 45 is at a position where the lower end thereof is swung forward, and the pressure receiving member 40 is positioned at the foremost position within its movable range. Although illustration of the rotating member 45 is omitted in FIGS. 7 to 9, the lower end of the rotating member 45 is positioned forward in the normal state of FIG.

When a relatively weak rear-end collision occurs, as shown in FIG. 8, the center portion of the seat back cushion 50 (the portion that hits the back of the occupant P) moves rearward, and the seat back cushion 50 moves the pressure receiving member 40 rearward. By pushing, the pressure receiving member 40 moves backward. At this time, the lower end of the rotating member 45 swings backward. Further, the inner surface side of the lower portion of the seat back cushion 50 (the portion that hits the buttocks of the occupant P) is slightly deformed by contact with the front surface 31A of the lower connecting member 30 . However, since the front surface 31A has a wide surface and is inclined slightly upward with respect to the connection portion 21B and the rear wall portion 32, the reaction force received by the lower connection member 30 from the buttocks of the occupant P is small. It acts as a pressure, and the occupant P feels a soft hit from the lower connection member 30. - 特許庁In addition, since the connecting portion between the front wall portion 31 and the upper wall portion 33 of the lower connecting member 30 and the connecting portion between the front wall portion 31 and the lower flange 34 form a gently curved surface, the occupant P is able to The connection member 30 does not give a strong hit feeling. Furthermore, since the front end of the folded flange 35 is positioned rearward of the lower end of the front wall portion 31, the edge of the front end of the folded flange 35 does not strongly hit the inner surface of the seat back cushion 50, thereby preventing the seat back cushion 50 from contacting the inner surface of the seat back cushion. 50 damage can be suppressed. Further, since the front wall portion 31 is located forward of the shaft 3S, the seat back cushion 50 does not directly hit the shaft 3S. Therefore, the occupant P does not feel the hit of the shaft 3S.

When a relatively strong rear-end collision occurs, as shown in FIG. 9, the central portion of the seat back cushion 50 is largely moved rearward, and accordingly the pressure receiving member 40 is also rearward while the connecting wire 41 is elastically deformed. move a lot. At this time, the seat back cushion 50 strongly hits the front surface 31A of the lower connection member 30, and the lower connection member 30 bends and deforms at the connecting portion between the front wall portion 31 including the upper wall portion 33 and the rear wall portion 32. . Therefore, even if a strong force is applied to the seat back cushion 50 from the buttocks of the occupant P, the front wall portion 31 of the lower connecting member 30 moves rearward to absorb the impact, and the occupant P is strong in the buttocks. I never feel touched. In particular, in the vehicle seat S of the present embodiment, the flat plate-like upper wall portion 33 extending substantially in the front-rear direction is provided between the front wall portion 31 and the rear wall portion 32 . By securing a space between them, the rearward deformation stroke of the front wall portion 31, that is, the impact absorption amount can be increased.

As in the case of a light rear-end collision, the connecting portion between the front wall portion 31 and the upper wall portion 33 of the lower connecting member 30 and the connecting portion between the front wall portion 31 and the lower flange 34 are smooth. Due to the curved surface, the occupant P is less likely to feel a strong impact from the lower connecting member 30. - 特許庁In addition, since the front end of the folded flange 35 is positioned rearward of the lower end of the front wall portion 31, the edge of the front end of the folded flange 35 does not strongly hit the inner surface of the seat back cushion 50, and the seat back cushion 50 does not come into contact with the inner surface of the seat back cushion. 50 damage can be suppressed. Furthermore, since the front wall portion 31 is located forward of the shaft 3S, the seat back cushion 50 does not directly hit the shaft 3S, and the feeling of the shaft 3S hitting the occupant P can be alleviated.

In the vehicle seat S of the present embodiment, the lower connecting member 30 is not flat like the conventional one, but has the front wall portion 31 and the rear wall portion 32 connected to each other at the upper portion. As a whole, the rigidity against the bending load in the front-rear direction is also improved. For this reason, conventionally, in the event of a rear-end collision, the center of the lower frame is bent rearward with respect to the side frames, bending in a doglegged shape when viewed from the top. However, in the vehicle seat S of the present embodiment, such deformation is less likely to occur. In other words, the lower connecting member 30 is likely to be deformed such that the front wall portion 31 approaches the rear wall portion 32, but is unlikely to be deformed so as to bend in a doglegged shape when viewed from above. deformation is also suppressed. In addition, since the lower connecting member 30 is provided so as to extend over the left and right side frames SF, when a load is applied that tends to deform the side frames SF inward, the front wall portion 31 does not move toward the inner surface of the side frames SF. Deformation of the side frame SF can be suppressed by contacting.

Further, in the vehicle seat S of the present embodiment, the lower connection member 30 is arranged so as to extend over the left and right side frames SF, and includes a front wall portion 31, a rear wall portion 32, an upper wall portion 33, a lower flange 34, and a lower flange 34. Since the turn-up flange 35 has a sufficient cross-sectional area, when the vehicle receives a collision load from the side, the vehicle seat S is prevented from collapsing in the left-right direction, and the load from the side is absorbed by the vehicle. can be transmitted to the center of In particular, since the lower connecting member 30 is welded to the inner extending portion 13 of the side frame SF at the inclined edge portion 13A, it is fixed to the side frame SF with a long welding length and sufficient strength. As a result, the rigidity of the seatback frame 1 can be increased, and the load from the sides can be efficiently transmitted to the center of the vehicle. In other words, the rigidity of the vehicle seat S in the left-right direction can be increased by increasing the weld length between the lower connection member 30 and the inner extension portion 13 without increasing the vertical size of the lower connection member 30 . .

In addition, in the vehicle seat S of the present embodiment, the rear wall portion 32 of the lower connecting member 30 has the through hole 38 as an escape portion, so that when the cover 5 on the back surface of the seat back S1 is attached, the clip 51 and the clip 51 are attached. Interference with the rear wall portion 32 is avoided, and assembly work is easy. That is, even if there is a slight error in the size or shape of the rear wall portion 32, interference between the clip 51 and the rear wall portion 32 can be avoided. There is no need to be overly careful, and it is easy to work. Further, since the relief portion is the through hole 38, the relief portion can be easily formed by blanking when the lower connecting member 30 made of sheet metal is manufactured by press working, which facilitates manufacturing.

Although the embodiments of the present invention have been described above, the present invention can be modified as appropriate and implemented as shown in other forms below.

For example, in the above-described embodiment, the lower connecting member 30 has the flat upper wall portion 33, but the upper wall portion 33' connecting the front wall portion 31 and the rear wall portion 32 is shown in FIG. It is good also as a shape bent by one R as shown.

Moreover, in the above-described embodiment, the relief portion of the lower connection member 30 is formed by the through hole 38, but as shown in FIG. 11, it may be formed by a concave portion 38'. By forming recesses 38 ′ instead of through holes 38 , a relief portion can be formed without reducing the strength of the rear wall portion 32 and interference between the clip 51 and the rear wall portion 32 can be avoided.

In the above embodiment, the front surface 31A of the front wall portion 31 is slanted upward with respect to the direction in which the pipe of the connection portion 21B extends in side view, but it may be parallel to the direction in which the pipe extends.

In the above-described embodiment, the pressure receiving member 40 is provided so that the occupant P is actively pushed into the seat back S1 at the time of a rear-end collision. good. However, when the pressure receiving member 40 is present, the lower connecting member 30 and the occupant P are more likely to approach each other, so the present invention can be effectively utilized in such a case.

In the above-described embodiment, the slanted edge 13A of the inner extension 13 is slanted with respect to the vertical direction so that the inner end goes from the inside to the outside as it goes from top to bottom. Conversely, the inner end may be slanted with respect to the vertical direction so that it goes from the outside to the inside as it goes from top to bottom.

In the above embodiment, the pressure-receiving member 40 is supported by the side frame SF by the connecting wire 41, but it can be supported by the side frame SF by another connecting member such as rubber or a belt.

In the above embodiment, the cover on the back of the seat back was exemplified as an example of the part to be attached, but it is also possible to attach a harness, switches to be operated in the back seat, a pocket on the back of the seat back, etc. as the part to be attached. can. Also, the mounting hole may be a hole for screwing a tapping bolt or a female screw hole instead of a simple hole, and the fixing member may be a bolt, a tapping bolt, a rivet, or the like.

Further, in the above-described embodiment, the vehicle seat S is shown as an application example of the vehicle seat, but the vehicle seat of the present invention can be applied to other vehicle seats, such as seats for ships and aircraft. can also

Reference Signs List 1 seatback frame 2 seating frame 3 reclining mechanism 3S shaft 5 cover 10 side plate 11 upper member 12 lower member 12A side wall portion 13 inner extension portion 13A inclined edge portion 13B clip hole 21 upper frame 21A upper connecting portion 21B connecting portion 23 pillar support portion 30 lower connection member 31 front wall portion 31A front surface 32 rear wall portion 33 upper wall portion 33' upper wall portion 34 lower flange 35 folded flange 38 through hole 38' recess 40 pressure receiving member 50 seat back cushion 51 clip F seat frame S for vehicle Seat S1 Seat back S2 Seat S3 Headrest SF Side frame

Claims (1)

A seat back frame supported by a seating frame that is a frame of a vehicle seat and a frame of a seating portion on which an occupant sits,
The seatback frame includes side frames spaced apart from each other in the left and right direction, and a lower connecting member arranged to extend between the lower portions of the left and right side frames and connecting the left and right side frames,
The lower connection member is a front wall portion disposed on the occupant side, and is a front wall portion that receives a load from the buttocks of the occupant in the event of a rear-end collision, and a rear wall portion that is connected to the rear of the front wall portion, made of sheet metal having a rear wall portion connected to the side frame, the front wall portion, and a connection portion connecting the front wall portion and the rear wall portion;
the front end of the front wall portion of the lower connecting member is positioned in front of the lower end of the pressure receiving member disposed between the left and right side frames;
The seat back frame is configured to be reclinable with respect to the seating frame,
A shaft connecting the left and right side frames is arranged on the rotation axis of the seat back frame,
The front wall portion is positioned in front of the shaft,
the lower end of the rear wall portion is formed below the upper end of the shaft in a state before a rear collision occurs;
A portion of the rear wall portion is positioned behind the shaft and overlaps the shaft when viewed from the rear,
The rear wall portion is provided with a through hole,
The seatback frame, wherein the through hole is positioned above the shaft.

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