JP2013017608A - Seat back - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seat back capable of reducing the number of components, simplifying a structure, and improving assemblability.SOLUTION: A housing part for housing an armrest body 49 is formed in a seat back body. The armrest body 49 is supported on a seat back frame freely rotatably around the horizontal axis on a proximal end part side, and is structured in a manner freely switching to a housed state and to a using state. A stopper pin 35 is projectingly provided on an armrest supporting part 32 and, a guide groove part 52 is formed in the end in the width direction of the proximal end part of the armrest body 49. The guide groove part 52 is guided by the stopper pin 35, with the rotation around the horizontal axis of the armrest body 49. The armrest body 49 has, in the end in the width direction of the proximal end part, a bush 35 into which the horizontal axis is inserted and supported, wherein the guide groove part 52 is formed in the bush 50.

Description

The present invention
A storage portion for storing the armrest body of the armrest is formed in a seatback body including a seatback frame, a seatback pad supported by the seatback frame, and a skin material covering the seatback pad,
The armrest body is supported by the seat back frame so as to be rotatable about a horizontal axis on the base end side, and is stored in the storage portion, and is in a usage state protruding from the storage portion to the seat front side. Can be switched to
A stopper pin for setting a swinging range around the horizontal axis of the armrest body is protruded from the armrest support portion on the seat back frame side,
The present invention relates to a seat back in which a guide groove portion that is guided by the stopper pin along with the pivoting rotation of the armrest body around the horizontal axis is formed at the end portion in the width direction of the base end portion of the armrest body.

  Conventionally, in the above-described seat back, as disclosed in Patent Document 1, a bearing portion that supports the horizontal shaft and a guide groove portion are formed in a side frame (armrest frame) of the armrest.

JP 2005-287724 A

Generally, the side frame (armrest frame), the horizontal axis, and the stopper pin of the armrest are made of metal. Therefore, in the above-described conventional technology, it is necessary to provide a buffer member (for example, a bush) on the bearing portion, the horizontal shaft, the guide groove portion, etc. of the armrest to avoid contact between metal parts and to prevent generation of abnormal noise. It was. As a result, the number of parts increased, the structure became complicated, and the assemblability deteriorated.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a seat back that can reduce the number of parts, simplify the structure, and improve the assembling property. It is in.

The feature of the present invention is that
A storage portion for storing the armrest body of the armrest is formed in a seatback body including a seatback frame, a seatback pad supported by the seatback frame, and a skin material covering the seatback pad,
The armrest body is supported by the seat back frame so as to be rotatable about a horizontal axis on the base end side, and is stored in the storage portion, and is in a usage state protruding from the storage portion to the seat front side. Can be switched to
A stopper pin for setting a swinging range around the horizontal axis of the armrest body is protruded from the armrest support portion on the seat back frame side,
A seat back in which a guide groove portion that is guided by the stopper pin along with swinging rotation around the horizontal axis of the armrest body is formed at an end portion in a width direction of a base end portion of the armrest body,
The armrest main body includes a bush in which the horizontal axis is inserted and supported at an end portion in a width direction of a base end portion,
The guide groove is formed in the bush. (Claim 1)

The armrest body is provided with a bush in which the horizontal axis is inserted and supported at the end in the width direction of the base end, and the guide groove is formed in the bush.By molding the bush with a resin material, It can avoid that a horizontal axis and a stopper pin contact metal parts, and generation | occurrence | production of the noise resulting from the contact between metal parts can be prevented.
And, for example, compared with a technique in which a resin material such as a bushing as a buffer member is provided on the horizontal shaft, the bearing portion, the stopper pin, the guide groove portion, etc., in order to prevent the generation of noise due to contact between metal parts. In addition, the number of parts can be reduced, the structure can be simplified, and the assemblability can be improved. (Claim 1)

In the present invention,
The guide groove portion is formed substantially concentrically with a bearing portion of the bush supporting the horizontal shaft, and includes an inner peripheral wall and an outer peripheral wall facing each other and substantially concentric with the bearing portion,
A reinforcing portion for reinforcing the guide groove portion is provided on the radially outer side of the guide groove portion,
The reinforcing portion is located radially with respect to the reinforcing peripheral wall facing the outer peripheral wall, the reinforcing side wall connecting the outer peripheral wall and the widthwise ends of the reinforcing peripheral wall, and the axial center of the bearing portion, It is in the point provided with the some reinforcement rib which connects the outer peripheral wall and the wall surfaces of a reinforcement surrounding wall. (Claim 2)

  According to said structure, it can fully resist against the force added to a bush from a horizontal axis at the time of armrest use by the said reinforcement side wall, a some reinforcement rib, and a reinforcement surrounding wall. Therefore, the strength of the bush can be effectively improved, and the durability of the bush can be improved. (Claim 2)

In the present invention,
The reinforcing portion and the guide groove portion are formed on the bush so as to be located from above the bearing portion to the seat rear side in the use state of the armrest body,
The reinforcing peripheral wall portion on the seat rear side of the reinforcing portion in the use state of the armrest body is formed in a longitudinal cross-section arc shape,
If the outer surface of the reinforcing peripheral wall is smoothly connected to the arm placement surface of the armrest body portion to which the bush is attached, the following action can be achieved. (Claim 3)

When the armrest body rotates around the horizontal axis, the reinforcing peripheral wall portion having the arcuate section in the longitudinal section can be guided to the bottom of the storage portion, and the armrest body can be smoothly rotated. Thereby, the burden added to a horizontal axis can be reduced.
In addition, since the outer surface (design surface) of the reinforcing peripheral wall is smoothly connected to the arm placement surface of the armrest main body portion to which the bush is attached, the appearance quality of the armrest can be improved. (Claim 3)

In the present invention,
When the reinforcing peripheral wall portion on the front side of the seat of the reinforcing portion in the use state of the armrest body is formed in a corner portion having an L-shaped longitudinal section, the following action can be achieved. (Claim 4)

  In the structure in which the reinforcing peripheral wall portion on the seat front side of the reinforcing portion in the use state of the armrest main body is formed in an arc shape, a gap is formed between the design surface of the armrest main body portion to which the bush is assembled and the outer surface of the bush. However, according to the above-described configuration of the present invention, the reinforcing peripheral wall portion on the seat front side of the reinforcing portion in the use state of the armrest main body is formed at the corner portion of the L-shaped vertical section. The surface and the outer surface (design surface) of the reinforcing peripheral wall portion on the front side of the sheet of the reinforcing portion can be smoothly continued, and the appearance quality can be improved. (Claim 4)

In the present invention,
At the end of the guide groove in the use state of the armrest body on the seat rear side, an opening is formed that opens toward the side opposite to the longitudinal front end side of the armrest body,
As the armrest is assembled to the seat back body, the stopper pin enters the guide groove from the opening of the guide groove,
When a guide surface that guides the stopper pin to the opening is formed at an end of the reinforcing portion on the seat rear side when the armrest body is in use, the following effects can be obtained. (Claim 5)

As the armrest main body is assembled to the seat back main body, the stopper pin enters the guide groove portion from the opening at the end of the guide groove portion on the seat rear side. At this time, the guide surface at the end of the reinforcing portion on the rear side of the seat guides the stopper pin to the opening.
As a result, the stopper pin can be inserted into the guide groove portion after the bush is assembled to the armrest body portion to form the armrest body.
As a result, for example, after attaching the armrest body to the seatback frame side, there is no need to use means to assemble the stopper pin to the armrest support on the seatback frame side with bolts or nuts, reducing the number of parts and assembly man-hours. Can do. (Claim 5)

In the present invention,
When the cover portion that covers the bearing portion of the bush from the radially outer side of the bearing portion projects in a dish shape from the outer peripheral portion of the bearing portion to the radially outer side of the bearing portion, the following action is obtained. Can play. (Claim 6)

  The structure around the horizontal axis and the horizontal axis can be reliably covered with the cover portion, and safety can be improved. (Claim 6)

According to the present invention,
The number of parts can be reduced, the structure can be simplified, and a seat back that can improve the assemblability can be provided.

Perspective view of automotive seat The exploded perspective view which shows the assembly method of an armrest, a skin material, a seat back pad, and a seat back frame Exploded perspective view showing how to assemble armrest and hinge bracket Exploded perspective view of armrest (A) The perspective view which looked at the right side bush from the direction corresponding to the width direction outer side of an armrest, (b) The perspective view which looked at the right side bush from the direction corresponding to the width direction inner side of an armrest Side view of the armrest attached to the hinge bracket JJ cross section of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 shows an automobile seat 1. The seat 1 includes a seat cushion 2 that supports the occupant's buttocks and thighs, and a seat back 3 that supports the back of the occupant, and a headrest 4 that supports the head of the occupant at the upper end of the seat back 3. Are connected. In addition, an armrest 10 that supports an occupant's arm is provided on a left side portion of the seatback main body 51 that is a main body portion of the seatback 3.

[Structure of the seat back body 51]
As shown in FIG. 2, the seat back body 51 includes a seat back frame 9, a seat back pad 8 supported by the seat back frame 9, and a skin material 7 that covers the seat back pad 8.

  A storage recess 28 (corresponding to a storage portion) for storing the armrest body 49 of the armrest 10 is formed in the left portion of the seat back body 51. 2 is a square hole for the storage recess 28 formed in the seat back pad 8, and 28 </ b> B is a bottomed recess for the storage recess 28 formed in the skin material 7. The storage recess 28 is formed in a rectangular shape having a vertically long vertical section, and is open to the front side Fr of the seat.

[Structure of armrest 10]
As shown in FIGS. 6 and 7, the armrest 10 is supported by the seat back frame 9 (see FIG. 2) via the hinge mechanism H so as to be rotatable around the horizontal axis O of the horizontal axis 40 on the proximal end side. Armrest body 49, and a cover member 20 that is configured to be relatively rotatable around the horizontal axis O with respect to the armrest body 49 and is attached to the seat back frame 9 on the bottom side so as to cover the bottom of the storage recess 28. The armrest body 49 is stored in the storage recess 28 (see the solid line in FIG. 1), and the armrest body 49 is in the use state protruding from the storage recess 28 toward the seat front side Fr (see the two-dot chain line in FIG. 1). It is configured to be switchable between.

[Structure of armrest body 49]
The armrest main body 49 includes a bush 50 into which the horizontal shaft 40 is inserted and supported at the end in the width direction of the base end. That is, the armrest main body 49 is attached to the armrest main body portion 48 having a narrow base end portion and the narrow base end portion 15 (see FIG. 3) of the armrest main body portion 48 from the outer side in the width direction. It consists of a pair of resin-made bushes 50, and is formed with substantially the same width over the entire length in the longitudinal direction.

[Structure of armrest body 48]
As shown in FIG. 3, the armrest body portion 48 includes an armrest pad 12, an armrest frame 11 on which the armrest pad 12 is mounted, and a skin material 13 that covers the armrest pad 12. The armrest frame 11 is formed in a plate shape having a plurality of lightening holes 11H, and a cylindrical pipe member 14 along the width direction of the armrest main body portion 48 is welded and fixed to the base end portion of the armrest frame 11. The horizontal shaft 40 of the hinge mechanism H is inserted through the pipe material 14.

[Structure of hinge bracket 30]
The armrest body 49 is connected to the hinge bracket 30 attached to the seat back frame 9 via the hinge mechanism H.

  As shown in FIG. 3, the hinge bracket 30 includes a plate-like bracket body 31 positioned on the back side of the proximal end portion of the armrest body 49 in the retracted state (the lower end portion of the armrest body 49 in the retracted state), and the bracket A pair of left and right first rising walls 32 (an armrest support portion on the seat back frame side) that rises from both widthwise ends of the lower half of the main body 31 to the front side Fr of the seat and is located to the side of the base end of the armrest main body 49. Equivalent). The first rising wall 32 is provided with a stopper pin 35 that protrudes inward in the width direction of the hinge bracket 30 (inward in the armrest width direction). The stopper pin 35 sets a swing range of the armrest body 49 around the horizontal axis 40.

  The first rising wall 32 is formed in a mountain shape having an arcuate top when viewed from the side, and a circumferential portion 33 of the first rising wall 32 and both widthwise end portions 34 of the upper half of the bracket body 31 are hinges. The brackets 30 extend outward in the width direction of the bracket 30 and are continuous with each other. Thereby, the rigidity of the 1st standing wall 32 can be strengthened.

  A plurality of stud bolts 31H protrude from the bracket body 31 to the seat rear side Rr. The plurality of stud bolts 31H are inserted into bolt insertion holes H2 (see FIG. 2) of the lower attachment portion 29 of the seat back frame 9. Then, a nut is screwed and fastened to the stud bolt 31H from the back side of the seat back frame 9. In this way, the hinge bracket 30 is attached to the seat back frame 9, and the armrest body 49 is connected and supported to the seat back frame 9 via the hinge bracket 30.

[Structure of cover member 20]
As shown in FIGS. 3, 4, and 6, the cover member 20 includes a rectangular plate-like cover main body 21 that overlaps the bottoms of the bracket main body 31 and the storage recess 28 from the seat front side Fr, and the width direction of the cover main body 21. A pair of left and right second rising walls 22 interposed between the first rising wall 32 and an end portion in the width direction of the base end portion of the armrest main body 49 from the lower end portion of the both end portions 21S I have. The cover main body 21 is formed in the same rectangular shape and size as the bottom surface of the storage recess 28. That is, the cover member 20 is formed over substantially the entire length of the storage recess 28 in the vertical direction (the total length in the vertical direction), and covers substantially the entire bottom surface of the storage recess 28.

  A plurality of clips C projecting toward the seat rear side Rr are provided on the upper half 21J of the cover body 21. The clip engages with a clip hole H1 (see FIG. 2) of the upper mounting portion 19 of the seat back frame 9. A plurality of clip insertion holes and bolt insertion holes are formed in the skin material 7.

  As shown in FIG. 3, the second rising wall 22 is formed in a mountain shape having a circular arc shape in a side view, and is located on the outer side in the width direction of the armrest body 49. A peripheral portion 23 of the second rising wall 22 projects in a flange shape on the outer side W <b> 2 of the cover body 21 in the width direction. Accordingly, the rigidity of the second rising wall 22 can be increased, and the hinge mechanism H can be covered with the peripheral portion 23 of the second rising wall 22.

  As shown in FIGS. 3 and 4, the cover member 20 is provided with a protruding portion 24 that protrudes toward the corner between the bottom portion and the inner portion of the storage recess 28 and presses the skin material 7 of the corner. It has been. A vertical wall 25 extending in the vertical direction protrudes from both end portions 21S in the width direction of the cover body 21 above the second rising wall 22, and the protrusion 24 extends from the top of the vertical wall 25 to the cover body. It protrudes in the width direction outer side W2 of 21 in the flange shape, and is continued to the peripheral part 23 of the flange-shaped second rising wall 22.

[Structure of hinge mechanism H]
As shown in FIGS. 6 and 7, the hinge mechanism H includes a horizontal axis 40 that is inserted through the first rising wall 32 and the base end of the armrest body 49 through the horizontal axis insertion hole 22 </ b> H of the second rising wall 22. It is configured to be rotatably connected to each other. The horizontal shaft 40 includes a shaft portion 42 and a hexagonal column-shaped head portion 41, and a female screw portion is formed at an end portion (tip portion) of the shaft portion 42 opposite to the head portion 41, and a nut is attached to the female screw portion. It is screwed.

[Structure of bush 50]
As shown in FIGS. 3 to 7, an arcuate guide groove portion 52 that is substantially concentric with the bearing portion 57 is formed on the radially outer side of the cylindrical bearing portion 57 of the bush 50 that supports the horizontal shaft 40. (That is, a guide groove portion 52 is formed at the widthwise end of the base end portion of the armrest body 49), and a groove-shaped reinforcing portion 53 that reinforces the guide groove portion 52 is provided on the radially outer side of the guide groove portion 52. It has been. The bearing portion 57 is non-rotatably fitted in one end portion of the pipe member 14 of the armrest frame 11 (see FIG. 7).

  The reinforcing portion 53 and the guide groove portion 52 are formed in the bush 50 so as to be positioned from above the bearing portion 57 to the seat rear side Rr when the armrest body 49 is in use.

[Structure of guide groove 52]
As shown in FIG. 5A, FIG. 5B, and FIG. 6, the guide groove portion 52 is formed substantially concentric with the bearing portion 57 and is opposed to each other and substantially concentric with the bearing portion 57. The inner peripheral wall 52U and the outer peripheral wall 52J are provided, and the inner peripheral wall 52U and the outer peripheral wall 52J are provided with side walls 52T that connect ends on the inner side in the armrest width direction, and the armrest body 49 swings and rotates around the horizontal axis O. Accordingly, it is guided by the stopper pin 35 of the first rising wall 32 of the hinge bracket 30. At the end of the front side Fr of the guide groove 52 in the use state of the armrest main body 49, the armrest 10 receives the stopper pin 35 when the armrest 10 is swung to the rear side Rr of the seat and is in the retracted state of the vertical position. A first stopper wall 52S1 that prevents further swinging of the armrest 10 is formed.

[Structure of reinforcing portion 53]
The reinforcing portion 53 includes a reinforcing peripheral wall 53J that opposes the outer peripheral wall 52J, a reinforcing side wall 53S that connects one end portions of the outer peripheral wall 52J and the reinforcing peripheral wall 53J in the width direction, and a shaft core of the bearing portion 57. The outer peripheral wall 52J and the reinforcing peripheral wall 53J are provided with a plurality of reinforcing ribs 53H that are located radially and connect the wall surfaces of the reinforcing peripheral wall 53J. The outer peripheral wall 52J and the reinforcing peripheral wall 53J are set to have the same width, and the width of the reinforcing rib 53H is set to a width over substantially the entire width of the outer peripheral wall 52J and the reinforcing peripheral wall 53J.

  According to the above configuration, the reinforcing side wall 53S, the plurality of reinforcing ribs 53H, and the reinforcing peripheral wall 53J can sufficiently resist the force applied to the bush 50 from the horizontal shaft 40 when the armrest is used. Therefore, the strength of the bush 50 can be effectively improved, and the durability of the bush 50 can be improved.

  As shown in FIGS. 5 (a), 5 (b), and 6, the reinforcing peripheral wall portion 53J1 on the seat rear side Rr of the reinforcing portion 53 in the use state of the armrest body 49 is formed in an arc shape in the longitudinal section. Yes. As a result, when the armrest main body 49 rotates around the horizontal axis O, the reinforcing peripheral wall portion 53J1 having an arcuate longitudinal section is guided by the bottom of the storage recess 28, and the armrest main body 49 rotates smoothly. Therefore, the burden on the horizontal axis 40 can be reduced.

  The reinforcing peripheral wall portion 53J2 on the seat front side Fr of the reinforcing portion 53 when the armrest main body 49 is in use is formed at a corner portion having an L-shaped vertical section. Thereby, the design surface of the armrest body portion 48 and the design surface of the reinforcing portion 53 (design surface of the reinforcing peripheral wall portion 53J2 on the seat front side Fr) can be smoothly continued, and the appearance quality can be improved.

  The design surface (outer surface) of the reinforcing peripheral wall 53J is smoothly connected to the arm placement surface 48M (see FIG. 6) of the armrest body portion 48 to which the bush 50 is attached without any step. Therefore, the appearance quality of the armrest 10 can be improved.

  As shown in FIG. 5A, at the end of the guide groove 52 in the usage state of the armrest body 49 on the seat rear side Rr, on the side opposite to the longitudinal front end side of the armrest body 49 (seat rear side Rr). An opening 52 </ b> H that opens toward the front is formed, and the stopper pin 35 is configured to enter the guide groove 52 from the opening 52 </ b> H of the guide groove 52 as the armrest 10 is assembled to the seatback body 51.

  Further, a guide surface 53G for guiding the stopper pin 35 to the opening 52H is formed at the end of the reinforcing portion 53 on the seat rear side Rr when the armrest body 49 is in use. The guide surface 53G includes an outer surface of an end wall that spans between the ends of the reinforcing peripheral wall 53J and the outer peripheral wall 52J on the seat rear side Rr.

  At the end of the guide groove portion 52 on the rear side Rr of the seat, the armrest 10 receives the stopper pin 35 when the armrest 10 is swung to the front side Fr of the seat and is in a substantially horizontal posture. A second stopper wall 52S2 that prevents swinging is formed. The second stopper wall 52S2 rises outward in the armrest width direction from the side wall 52T of the guide groove portion 52, and one end portion in the width direction is connected to an outer peripheral portion of a cover portion 54 described later.

With the above configuration, as the armrest body 49 is assembled to the seat back body 51, the stopper pin 35 enters the guide groove 52 from the opening 52 </ b> H at the end of the guide groove 52 on the seat rear side Rr. At this time, the guide surface 53G at the end of the reinforcing portion 53 on the seat rear side Rr guides the stopper pin 35 to the opening 52H.
Accordingly, the stopper pin 35 can be inserted into the guide groove portion 52 after the bush 50 is assembled to the armrest body portion 48 to form the armrest body 49.
As a result, for example, after attaching the armrest body 49 to the seat back frame 9 side, there is no need to adopt means for attaching the stopper pin 35 to the first rising wall 32 of the hinge bracket 30 with bolts or nuts. Can be reduced.

As shown in FIGS. 5 (b) and 7, the cover portion 54 that covers the bearing portion 57 of the bush 50 from the radially outer side of the bearing portion 57 is disposed radially outward of the bearing portion 57 from the outer peripheral portion of the bearing portion 57. It protrudes in a dish shape on the side. Specifically, the cover portion 54 projects from one end portion (end portion on the outer side in the armrest width direction) of the bearing portion 57 into a dish shape (tapered shape) located radially outward as the inner side in the armrest width direction.
Thereby, the horizontal axis 40 and the surrounding structure can be reliably covered with the cover part 54, and safety can be improved. The upper outer peripheral portion of the cover portion 54 is connected to one end portion in the width direction of the inner peripheral wall 52U of the guide groove portion 52 (one end portion on the outer side in the armrest width direction of the inner peripheral wall 52U). Accordingly, the rigidity of the cover portion 54 can be increased.

As shown in FIG. 5B, a cross pin 55 having a cross-shaped cross section projects from the portion 54 on the seat front side Fr of the cover portion 54 to the seat front side Fr so as to protrude inward in the armrest width direction. .
Thereby, the bush 50 can be positioned at the time of assembly, and when the armrest main body 49 is rotated until the stopper pin 35 comes into contact, it is possible to prevent the entire guide from rotating.

According to the above configuration,
Since the armrest main body 49 includes a resin bush 50 into which the horizontal shaft 40 is inserted and supported at the end in the width direction of the base end portion, and the guide groove portion 52 is formed in the bush 50, the horizontal shaft 40 and the stopper pin are provided. It can avoid that 35 contacts metal parts and generation | occurrence | production of the abnormal noise resulting from the contact between metal parts can be prevented.
For example, in order to prevent the generation of noise caused by contact between metal parts, a resin material such as a bush as a buffer member is provided on the horizontal shaft 40, the bearing portion 57, the stopper pin 35, the guide groove portion 52, and the like. Compared to the provided technology, the number of parts can be reduced, the structure can be simplified, and the assemblability can be improved.

7 Skin material 8 Seat back pad 9 Seat back frame 10 Armrest 28 Storage portion 32 Armrest support portion (first rising wall)
35 Stopper pin 40 Horizontal shaft 48M Arm placement surface 49 Armrest body 50 Armrest body 50 Bush 51 Seatback body 52 Guide groove 52H Opening 52J Outer peripheral wall 52U Inner peripheral wall 53 Reinforcement part 53G Guide surface 53J Reinforcement peripheral wall 53J1 Reinforcing peripheral wall portion 53J2 on the rear side of the seat Reinforcing peripheral wall portion 53H on the front side of the seat of the reinforcing portion Reinforcing rib 53S Reinforcing side wall 54 Cover portion 57 Bearing portion Fr Seat front side Rr Seat rear side

Claims (6)

A storage portion for storing the armrest body of the armrest is formed in a seatback body including a seatback frame, a seatback pad supported by the seatback frame, and a skin material covering the seatback pad,
The armrest body is supported by the seat back frame so as to be rotatable about a horizontal axis on the base end side, and is stored in the storage portion, and is in a usage state protruding from the storage portion to the seat front side. Can be switched to
A stopper pin for setting a swinging range around the horizontal axis of the armrest body is protruded from the armrest support portion on the seat back frame side,
A seat back in which a guide groove portion that is guided by the stopper pin along with swinging rotation around the horizontal axis of the armrest body is formed at an end portion in a width direction of a base end portion of the armrest body,
The armrest main body includes a bush in which the horizontal axis is inserted and supported at an end portion in a width direction of a base end portion,
A seat back in which the guide groove is formed in the bush. The guide groove portion is formed substantially concentrically with a bearing portion of the bush supporting the horizontal shaft, and includes an inner peripheral wall and an outer peripheral wall facing each other and substantially concentric with the bearing portion,
A reinforcing portion for reinforcing the guide groove portion is provided on the radially outer side of the guide groove portion,
The reinforcing portion is located radially with respect to the reinforcing peripheral wall facing the outer peripheral wall, the reinforcing side wall connecting the outer peripheral wall and the widthwise ends of the reinforcing peripheral wall, and the axial center of the bearing portion, The seat back according to claim 1, comprising a plurality of reinforcing ribs connecting the outer peripheral wall and the wall surfaces of the reinforcing peripheral wall. The reinforcing portion and the guide groove portion are formed on the bush so as to be located from above the bearing portion to the seat rear side in the use state of the armrest body,
The reinforcing peripheral wall portion on the seat rear side of the reinforcing portion in the use state of the armrest body is formed in a longitudinal cross-section arc shape,
The seat back according to claim 2, wherein an outer surface of the reinforcing peripheral wall is smoothly connected to a mounting surface of an arm of an armrest main body portion to which the bush is attached.   The seat back according to claim 3, wherein the reinforcing peripheral wall portion on the front side of the seat of the reinforcing portion in the use state of the armrest body is formed in a corner portion having an L-shaped vertical section. At the end of the guide groove in the use state of the armrest body on the seat rear side, an opening is formed that opens toward the side opposite to the longitudinal front end side of the armrest body,
As the armrest is assembled to the seat back body, the stopper pin enters the guide groove from the opening of the guide groove,
5. The seat back according to claim 3, wherein a guide surface that guides the stopper pin to the opening is formed at an end of the reinforcing portion on the rear side of the seat when the armrest body is in use.   The cover part which covers the bearing part of the said bush from the radial direction outer side of the said bearing part protrudes in the shape of a dish from the outer peripheral part of the said bearing part to the radial direction outer side of the said bearing part. The seat back according to any one of the above.

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