JP6169428B2 - Seat device - Google Patents

Description

  The present invention relates to a seat device having a reclining mechanism.

  2. Description of the Related Art Conventionally, there are some seat devices such as a railway vehicle that are provided with a reclining mechanism for providing a comfortable sitting comfort. In such a seat device, a seated person generally can recline the backrest held at the fulcrum by pushing the backrest backward with the back. In addition, there is a mechanism to which a slide mechanism for sliding the seat part back and forth is added.

  In general, in such a seat device, the backrest and the seat portion are connected by a link or the like, and the seat portion moves back and forth and up and down in conjunction with the movement of the backrest when reclining. With such a reclining mechanism, the seat device can change the sitting posture of the seated person, thereby providing the seated person with a feeling of rest and relaxation of the body.

  For example, Patent Document 1 below describes a chair with a reclining mechanism in which a seat portion is displaced rearward in conjunction with the backrest of the backrest. This chair is configured such that when the seat portion is displaced rearward, the seat portion is displaced such that the rear end is lowered and the front end is raised.

JP 2010-88814 A

  However, the reclining angle of the backrest and the angle of the seating surface are handled separately, and even if the conventional seating device moves at the same time, it cannot be said that the seating surface angle setting is appropriate for the reclining angle. For example, if the seating surface angle is set to be large in accordance with the full reclining, the opening angle of the seated person's body becomes small when not reclining (upright state), giving a tight feeling.

  In view of the circumstances as described above, an object of the present invention is to provide a seat device capable of realizing an optimum seating surface angle in accordance with the reclining angle of the backrest.

In order to achieve the above object, a seat device according to an embodiment of the present invention includes a seat portion, a support portion, a backrest portion, an interlocking mechanism, and an angle variable portion.
The said support part supports the said seat part so that a displacement is possible back and forth.
The said backrest part is arrange | positioned at the rear end of the said seat part, and is comprised so that reclining is possible.
The interlocking mechanism is provided between the seat portion and the backrest portion. The interlocking mechanism includes the backrest and the seat so that when the backrest reclines backward, the seat is displaced backward, and when the backrest is raised, the seat is displaced forward. Interlock.
The angle variable portion is provided between the seat portion and the support portion. The angle varying portion is configured to tilt the seat portion rearward so that the front end of the seat portion is raised when reclining the backrest portion, and to change the reclining angle of the backrest portion. Change the rate of change of the angle.

It is a perspective view showing a seat unit including a seat device concerning one embodiment of the present invention. It is a side view of the said seat apparatus. It is a partially broken perspective view which shows the internal structure of the said seat apparatus. It is a top view of the seat frame which comprises the seat part of the said seat apparatus. It is a side view which shows the internal structure of the principal part of the said seat apparatus. It is a side view of the principal part explaining typical operation | movement of the said seat apparatus.

A seat device according to an embodiment of the present invention includes a seat part, a support part, a backrest part, an interlocking mechanism, and an angle variable part.
The said support part supports the said seat part so that a displacement is possible back and forth.
The said backrest part is arrange | positioned at the rear end of the said seat part, and is comprised so that reclining is possible.
The interlocking mechanism is provided between the seat portion and the backrest portion. The interlocking mechanism includes the backrest and the seat so that when the backrest reclines backward, the seat is displaced backward, and when the backrest is raised, the seat is displaced forward. Interlock.
The angle variable portion is provided between the seat portion and the support portion. The angle varying portion is configured to tilt the seat portion rearward so that the front end of the seat portion is raised when reclining the backrest portion, and to change the reclining angle of the backrest portion. Change the rate of change of the angle.

  Since the seat device includes an angle variable portion that can change the rate of change of the seat angle with respect to the change of the reclining angle of the backrest portion, the seat surface is inclined to an angle appropriate to the reclining angle. Can be made.

The angle variable unit may include a first variable mechanism and a second variable mechanism.
The first variable mechanism is provided at the rear end of the seat portion, and displaces the rear end of the seat portion downward during reclining back of the backrest portion.
The second variable mechanism is provided on the front end side of the seat portion relative to the first variable mechanism, and displaces the upper end of the seat portion upward when reclining back the backrest portion. The second variable mechanism increases the rate of change of the upward displacement of the seat portion as the reclining angle toward the rear of the backrest portion increases.
With the above-described configuration, the seating surface angle increases as the reclining angle increases. Therefore, it is possible to set an appropriate seating surface angle following the reclining angle. In addition, since the seating surface angle can be reduced in the upright state, there is no feeling of cramping, thereby improving the comfort in sitting.

The second variable mechanism may include a first block and a guide member.
The first block is fixed to the seat portion, and has a first inclined surface inclined downward from the center side in the front-rear direction of the seat portion toward the front of the seat portion.
The guide member has a first peripheral surface portion that is fixed to the support portion and that can contact the first inclined surface with the width direction of the seat portion as an axial direction. The guide member is formed such that the curvature of the first peripheral surface portion increases from the front side of the seat portion toward the center side.
As a result, the seat surface angle can be greatly inclined as the reclining angle increases. Further, the seating surface angle can be controlled by the peripheral shape of the guide member, and an appropriate seating surface angle can be realized with a simple structure.

  The first block and the guide member may be made of different resin materials. Thereby, generation | occurrence | production of the noise at the time of sliding with a 1st inclined surface and a 1st surrounding surface part can be prevented.

The first variable mechanism may include a second block and a roller member.
The second block is fixed to the seat portion and has a second inclined surface that is inclined downward from the center side in the front-rear direction of the seat portion toward the rear of the seat portion.
The roller member has a second peripheral surface portion that is fixed to the support portion and that can contact the second inclined surface with the width direction of the seat portion as an axial direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a seat unit including a seat device according to an embodiment of the present invention. In the figure, an X axis and a Y axis indicate horizontal directions orthogonal to each other, and a Z axis indicates a height direction. Hereinafter, the configuration of the seat unit 1 will be described.

[Sheet unit]
The seat unit 1 according to the present embodiment is configured by a three-seat seat for a railway vehicle (for example, a bullet train), and typically, a plurality of rows are provided on both sides of the vehicle in the longitudinal direction (X-axis direction) of the vehicle. Has been. The seat unit 1 is configured to be rotatable on the floor of the vehicle by operating a foot pedal (not shown).

  The seat unit 1 includes three seat devices 1A, 1B, and 1C arranged in the Y-axis direction. Each of the seat devices 1A to 1C includes a seat portion 11 and a backrest portion 12 disposed at the rear end of the seat portion 11. The seat part 11 and the backrest part 12 have seat cushions 11a, 11b, 11c and back rests 12a, 12b, 12c, which are individualized for each of the seat devices 1A to 1C (in the figure, the seat cushion 11c and the back rest 12c). Are indicated by virtual lines).

  The seat unit 1 further includes armrests 21, 22, and 23. One armrest 21 is provided in the seat apparatus 1A, and the other armrest 22 is provided in the seat apparatus 1C. The armrest 23 is provided between the seat apparatus 1A and the seat apparatus 1B and between the seat apparatus 1B and the seat apparatus 1C, respectively. The armrests 21 to 23 are provided with operation portions (not shown) for reclining the backrest portions 12 of the seat apparatuses 1A to 1C, respectively.

[Seat equipment]
FIG. 2 is a side view of the seat apparatus 1C, and FIG. 3 is a partially broken perspective view showing the internal structure of the seat apparatus 1C. Hereinafter, the seat device 1C will be described by taking the seat device 1C as an example, but the other seat devices 1A and 1B are configured similarly to the seat device 1C.

(Support part)
The seat device 1 </ b> C includes a support unit 100. The support unit 100 is configured in common to the seat apparatuses 1A to 1C.

  As shown in FIG. 3, the support portion 100 includes a frame 110 that supports the seat frame 30 of the seat portion 11 and the back frame 40 of the backrest portion 12. The underframe 110 is composed of a frame body having a rear shaft 111 and a front shaft 112 that are parallel to the Y-axis direction, a connecting frame 113 that connects them, and the like.

  The seat frame 30 is fixed to the bottom of the seat cushion 11c, and is supported on the frame 110 so as to be displaceable in the front-rear direction.

  FIG. 4 is a plan view of the seat frame 30. The seat frame 30 includes a frame body 31, an auxiliary member 32, and a plurality of wave springs 33, and is individually provided in each of the seat devices 1A to 1C.

  The frame body 31 is made of a metal square pipe material bent into a substantially U shape, and ends of both arm portions 31 a and 31 b are connected to the backrest portion 12 via the interlocking mechanism 50. The auxiliary member 32 is made of a metal linear square pipe material extending in the Y-axis direction, and connects the arm portions 31a and 31b to each other. The plurality of wave springs 33 are bridged in parallel between the intermediate portion 31 c and the auxiliary member 32 via a plurality of hook members 34 respectively provided on the intermediate portion 31 c and the auxiliary member 32 of the frame body 31. It is. Between the wave springs 33 adjacent to each other, a fixture 35 is provided at an appropriate position so that the adjacent wave springs 33 are interlocked by a seating load.

  The back frame 40 has a rotation shaft S coupled to the armrest 22, and is configured to be capable of rotating around the rotation shaft S and reclining backward. The armrest 22 is fixed to the support portion 100 via the rear shaft 111 and the connecting frame 113 of the underframe 110.

(Interlocking mechanism)
The seat device 1 </ b> C includes an interlocking mechanism 50 provided between the seat portion 11 and the backrest portion 12. The interlocking mechanism 50 includes the backrest 12 and the seat 11 so that when the backrest 12 reclines back, the seat 11 is displaced backward, and when the backrest 12 is raised, the seat 11 is displaced forward. Interlock. The interlocking mechanism 50 is individually provided in each seat apparatus 1A-1C.

  FIG. 5 is a side view showing an internal structure of a main part of the seat device 1C. The interlocking mechanism 50 includes a pair of link members 51 that connect the back frame 40 of the backrest portion 12 and the seat frame 30 of the seat portion 11 to each other. The pair of link members 51 are pinned between a pair of arm portions 41 extending downward from the rotation center (rotation axis S) of the back frame 40 and the ends of both arm portions 31a and 31b of the frame body 31. They are connected via P1 and P2, respectively.

  Each link member 51 has a long hole 511 through which the pin P1 is inserted at one end, a long hole 512 through which the pin P2 is inserted at the other end, and a support hole through which the pin P3 is inserted at the center. 513. The long holes 511 and 512 extend from each end of the link member 51 toward the support hole 513, and the pins P1 and P2 are configured to be movable in the long axis direction of the long holes 511 and 512.

  The interlocking mechanism 50 further includes a pair of fixing members 52 that respectively fix the pair of link members 51 to the frame 110. One end of the fixing member 52 is rotatably connected to the support hole 513 of each link member 51 via a pin P3, and the other end of the fixing member 52 is fixed to the rear shaft 111 of the underframe 110.

  In the interlocking mechanism 50 configured as described above, when the backrest 12 (back frame 40) reclines backward (in the direction of the arrow A) with the rotation axis S as a fulcrum, the link member 51 is pushed by the pin P1. Rotates forward (in the direction of arrow B in FIG. 5) with the pin P3 as a fulcrum. Thereby, the seat part 11 (seat frame 30) is pushed by the pin P2, and is displaced back (in the same arrow C direction). On the other hand, when the backrest 12 (back frame 40) is raised from the reclining state to the upright state shown in FIG. 5, the seat 11 (seat frame 30) is displaced forward, contrary to the above.

(Angle variable part)
The seat apparatus 1 </ b> C further includes an angle variable unit 60 provided between the seat unit 11 and the support unit 100. The angle varying portion 60 tilts the seat portion 11 backward so that the front end of the seat portion 11 is raised when reclining the backrest portion 12, and changes the reclining angle of the backrest portion 12. Change the rate of change of the angle. The angle variable unit 60 is individually provided in each of the seat devices 1A to 1C.

  As shown in FIG. 5, the angle variable unit 60 includes a first variable mechanism 61 and a second variable mechanism 62.

  The first variable mechanism 61 is provided at the rear end of the seat portion 11 (seat frame 30), and displaces the rear end of the seat portion 11 downward when reclining the backrest portion 12 (back frame 40). In the present embodiment, the first variable mechanism 61 includes a pair of contact blocks 611 (second block) fixed to the rear end of the seat frame 30 and a pair of fixed blocks fixed to the rear shaft 111 of the support unit 100. And a roller member 612.

  The pair of abutment blocks 611 are fixed to the lower surface of the seat frame 30 near the ends of both arm portions 31a and 31b via a plurality of screw members, respectively. The contact block 611 includes an inclined surface 611a (second inclined surface) inclined downward from the center side in the front-rear direction (X-axis direction) of the seat frame 30 toward the rear of the seat frame 30, and the front-rear direction of the seat frame 30 And a flat surface 611b formed along the surface. The inclined surface 611a and the flat surface 611b are formed at the lower end of the contact block 611, and the flat surface 611b is provided on the front side of the inclined surface 611a so as to be continuous with the inclined surface 611a.

  The inclined surface 611a may be a linear tapered surface, an arcuate curved surface, or a composite shape thereof. The inclination angle of the inclined surface 611a is not particularly limited, and can be appropriately set according to the downward displacement amount (downhill gradient) with respect to the backward displacement amount of the seat portion 11.

  The pair of roller members 612 are respectively supported by the rear shaft 111 via the support beams 613 so as to face the lower ends of the contact blocks 611. The roller member 612 has a shaft portion 614 extending in the width direction (Y-axis direction) of the seat frame 30, and the shaft portion 614 is supported by the support beam 613, so that the roller member 612 can rotate with respect to the contact block 611. Composed.

  The roller member 612 has a constant curvature peripheral surface portion 612a (second peripheral surface portion) that can be in contact with the inclined surface 611a. The circumferential surface portion 612a supports the seat portion 11 that is displaced in the front-rear direction through the inclined surface 611a of the contact block 611, with the width direction (Y-axis direction) of the seat portion 11 being the axial direction. Thereby, when the seat portion 11 is displaced rearward, the lower end of the seat frame 30 can be displaced downward. The downward slope of the lower end of the seat frame 30 is determined by the inclination angle of the inclined surface 611a and the curvature of the peripheral surface portion 612a of the roller member 612. The flat surface 611b of the contact block 611 is formed so as not to contact the roller member 612 when the seat portion 11 is maximum displaced rearward, but is not limited thereto, and is formed so as to be able to contact the roller member 612. Also good.

  The contact block 611 is made of a polyamide-based resin material, but is not limited thereto, and an appropriate synthetic resin material or metal material may be used. The constituent material of the roller member 612 is not particularly limited, and an appropriate synthetic resin material is used in the present embodiment.

  On the other hand, the second variable mechanism 62 is provided closer to the front end side of the seat portion 11 (seat frame 30) than the first variable mechanism 61, and the seat portion is reclining to the back of the backrest portion 12 (back frame 40). 11 is displaced upward. The second variable mechanism 62 increases the rate of change of the upward displacement of the seat portion 11 as the reclining angle of the backrest portion 12 toward the rear increases.

  With the above-described configuration, the seating surface angle increases as the reclining angle increases. Therefore, it is possible to set an appropriate seating surface angle following the reclining angle. In addition, since the seating surface angle can be reduced in the upright state, there is no feeling of cramping, thereby improving the comfort in sitting.

  In the present embodiment, the second variable mechanism 62 includes a pair of contact blocks 621 (first block) fixed to the front end side of the seat frame 30 and a pair of guides fixed to the front shaft 112 of the support portion 100. Member 622.

  The pair of abutment blocks 621 are fixed to the lower surfaces of the arm portions 31a and 31b of the seat frame 30 on the intermediate portion 31c side via a plurality of screw members, respectively. The contact block 621 has an inclined surface 621a (first inclined surface) inclined downward from the center side in the front-rear direction (X-axis direction) of the seat frame 30 toward the front of the seat frame 30. The inclined surface 621a is formed at the lower end of the contact block 621.

  The inclined surface 621a may be a linear tapered surface, an arcuate curved surface, or a composite shape thereof. The inclination angle of the inclined surface 621a is not particularly limited, and can be set as appropriate according to the upward displacement amount (uphill gradient) with respect to the backward displacement amount of the seat portion 11.

  The pair of guide members 622 are fixed to the front shaft 112 so as to face the lower ends of the contact blocks 621. In the present embodiment, the pair of guide members 622 are rivet fixed to the front shaft 112. The guide member 622 has a peripheral surface portion 622a (first peripheral surface portion) that can contact the inclined surface 621a with the width direction of the seat portion 11 as the axial direction. The guide member 622 is formed so that the curvature of the peripheral surface portion 622a increases from the front side of the seat portion 11 toward the center side. For example, as shown in FIG. 5, the partial cylinder is crushed by a predetermined amount in the radial direction. It is formed in a slightly flattened shape.

  In the present embodiment, the pair of guide members 622 are formed in a partial cylindrical shape such that the thickness gradually increases from the front side to the rear side of the front shaft 112. In addition, flange portions 622b for preventing displacement of the contact block 621 are formed at the inner peripheral edge of each guide member 622, respectively.

  The peripheral surface portion 612 a supports the seat portion 11 that is displaced in the front-rear direction via the inclined surface 621 a of the contact block 621. As a result, when the seat portion 11 is displaced backward, the seat frame 30 can be displaced upward at the front end. The upward slope of the front end of the seat frame 30 is determined by the inclination angle of the inclined surface 621a and the curvature of the peripheral surface portion 622a of the guide member 622.

  The contact block 621 is made of a polyamide-based resin material, but is not limited thereto, and an appropriate synthetic resin material or metal material may be used. On the other hand, the constituent material of the guide member 622 is also not particularly limited. However, when a material different from the contact block 621 is used, the sliding surface between the inclined surface 621a of the contact block 621 and the peripheral surface portion 622a of the guide member 622 is used. Generation of abnormal noise can be suppressed.

  As a constituent material of the guide member 622, a resin material superior in sliding property and wear resistance to the constituent material (polyamide resin) of the contact block 621, for example, polyacetal (POM) can be used. As a result, the durability of the guide member 622 that is rivet-fixed to the front shaft 112 can be increased, and the contact block 621 that is relatively easy to attach and detach that is screwed to the seat frame 30 can be used as a member to be replaced. Therefore, it is possible to suppress a decrease in workability.

[Operation of seat device]
Next, details of the angle variable unit 60 will be described together with the operation of the seat apparatus 1C. Since the other seat apparatuses 1A and 1B perform the same operation, the description thereof is omitted here.

  6A to 6C are side views of a main part showing a typical operation of the seat apparatus 1C, in which A shows an upright state, and B and C show a reclining state, respectively.

  When the seat apparatus 1C is in the upright state, the seat frame 30 is supported by the support portion 100 (the rear shaft 111 and the front shaft 112) in a substantially horizontal state as shown in FIG. Accordingly, the seating surface of the seat 11 at this time is maintained at the initial angle of the upper surface of the seat cushion 11c as shown in FIG.

  Next, when the backrest 12 (back frame 40) is reclined back to the first angle a1 shown in FIG. The part 11 (seat frame 30) is displaced rearward. At this time, the rear end of the seat frame 30 is displaced downward along the peripheral surface portion 612 a of the roller member 612 by the first variable mechanism 61, and the front end of the seat frame 30 is moved by the second variable mechanism 62. It is displaced upward along the peripheral surface portion 622a. As a result, the seat frame 30 generally assumes a seat posture rotated by an angle b1 clockwise from the horizontal state in the figure.

  Subsequently, when the backrest 12 (back frame 40) is reclined to a second angle a2 larger than the first angle a1 as shown in FIG. 6C, the seat 11 (seat frame 30) is further displaced rearward. However, as a whole, the sitting posture rotated from the horizontal state by an angle b2 larger than the angle b1 is taken.

  As described above, the rotation angle of the seat frame 30 changes according to the reclining angle of the back frame 40. Further, when the backrest 12 is returned from the reclining state to the upright state, the seat frame 30 is displaced in the opposite direction to that described above.

  In the seat device 1 </ b> C of the present embodiment, the second variable mechanism 62 includes a second variable mechanism 62 including a guide member 622 whose curvature gradually increases from the front side to the rear side of the seat frame 30. Thereby, the change rate of the angle of the seat frame 30 can be changed with respect to the change of the reclining angle of the back frame 40. Specifically, the angle change rate of the seat frame 30 gradually increases as the reclining angle toward the rear of the back frame 40 increases.

  Therefore, according to the present embodiment, as the reclining angle increases, the seating surface angle increases. Therefore, it is possible to appropriately set the seating surface angle following the reclining angle. That is, when the reclining angle is small, it is possible to optimally control the seat posture such that the angle change rate of the seating surface is reduced and the angle change rate of the seating surface is increased as the reclining angle is increased. In addition, since the seating surface angle can be reduced in the upright state, there is no feeling of cramping, thereby improving the comfort in sitting.

  Further, according to the present embodiment, since the way of raising the front end of the seat frame 30 can be controlled by the shape of the peripheral surface portion 622a of the guide member 622, an appropriate seat surface angle can be realized with a simple structure.

  The amount of change in the reclining angle of the backrest 12 is not particularly limited, and can be set, for example, in the range of 30 ° to 40 ° from the upright state. On the other hand, the inclination angle of the seating surface can be set as appropriate, but from the viewpoint of maintaining the sitting comfort, it is preferable to set an optimum seating surface angle according to the reclining angle. For example, when the inclination angle of the backrest is 10 °, 15 °, 20 °, 25 °, and 37 °, the seating surface angles are 4 °, 6 °, 10 °, 14 °, and 23 °, respectively. In addition, the inclination angle of the seat frame 30 is set. According to the present embodiment, the seating surface angle can be realized by the shape of the peripheral surface portion 622a of the guide member 622.

  As described above, according to the present embodiment, since the angle variable unit 60 that can change the rate of change of the angle of the seat 11 with respect to the change of the reclining angle of the backrest 12 is provided, the reclining angle The seating surface can be inclined at an appropriate angle.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the seat device for three seats has been described as an example. However, the seat device is not limited to this. For example, the seat device may be a seat device for two seats or one seat. In addition, the present invention is not limited to a vehicle seat device, and can be applied to a home or office seat.

  Further, in the above embodiment, the peripheral surface portion 622a of the guide member 622 in the second variable mechanism 62 is formed in the above-described shape, so that the upward displacement amount of the front end of the seat frame 30 is controlled. In addition to this, it is also possible to adjust the inclination angle of the seat frame 30 by forming the peripheral surface portion 612a of the roller member 612 in the first variable mechanism 61 with a partially different curvature similarly to the guide member 622. It is.

DESCRIPTION OF SYMBOLS 1 ... Seat unit 1A, 1B, 1C ... Seat apparatus 11 ... Seat part 12 ... Backrest part 30 ... Seat frame 40 ... Back frame 50 ... Interlock mechanism 60 ... Angle variable part 61 ... 1st variable mechanism 62 ... 2nd Variable mechanism 100 ... support portion 611, 621 ... contact block 612 ... roller member 622 ... guide member

Claims (5)

A seat,
A support part that supports the seat part so as to be displaceable back and forth; and
A backrest that is disposed at the rear end of the seat and can be reclined;
The seat portion is provided between the seat back portion and the backrest portion, and when the backrest portion reclines backward, the seat portion is displaced rearward, and when the backrest portion occurs, the seat portion is displaced forward. An interlocking mechanism that interlocks the backrest and the seat;
The reclining angle of the backrest part is provided between the seat part and the support part, and the seat part is inclined rearward so that the front end of the seat part rises when reclining the backrest part. A seat device comprising: an angle variable unit that changes a rate of change of the angle of the seat with respect to the change of the angle. The seat device according to claim 1,
The angle variable part is:
A first variable mechanism that is provided at the rear end of the seat portion and that displaces the rear end of the seat portion downward when reclining the backrest portion;
A second variable mechanism that is provided on the front end side of the seat portion relative to the first variable mechanism, and that displaces the upper end of the seat portion upward when reclining the backrest portion;
The seat device according to claim 2, wherein the second variable mechanism increases the rate of change of the upward displacement of the seat as the reclining angle toward the rear of the backrest increases. The seat device according to claim 2,
The second variable mechanism is:
A first block having a first inclined surface fixed to the seat portion and inclined downward from the center side in the front-rear direction of the seat portion toward the front of the seat portion;
A first peripheral surface portion fixed to the support portion and having an axial direction in a width direction of the seat portion and capable of contacting the first inclined surface, wherein the curvature of the first peripheral surface portion is the seat And a guide member formed so as to increase from the front side to the center side of the seat. The seat device according to claim 3,
The first block and the guide member are configured by resin materials different from each other. The seat device according to claim 2 or 3,
The first variable mechanism includes:
A second block having a second inclined surface fixed to the seat portion and inclined downward from the center side in the front-rear direction of the seat portion toward the rear of the seat portion;
And a roller member having a second peripheral surface portion fixed to the support portion and having a width direction of the seat portion as an axial direction and capable of contacting the second inclined surface.

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