Chair

Abstract

To provide a chair for activating a plurality of antigravity muscles required to keep a posture without making a user aware of it.SOLUTION: In a chair 100, a seat surface 2 gives an inclination to a pelvis of a sitting user. A rigid body column 311 includes: a lower end part fixed to a base 1; and an upper end part fixed to the seat surface 2 so as to allow the seat surface 2 to be inclinable over a whole periphery in a radial direction. An elastic body 313 is arranged on a lower side of the seat surface and generates restoring force over the whole periphery in the radial direction of the seat surface 2 in response to an inclination angle of the seat surface 2. An adjustment mechanism 314 is arranged between the elastic body 313 and the base 1 and adjusts strength of the restoring force of the elastic body 313. A rotary table 32 is arranged above the base 1 and rotated around a vertical axis based on power. A plurality of supporting columns 33 different in vertical length are arranged on an upper side of the rotary table 32, so as to support the seat surface 2 at upper end parts when the seat surface 2 is inclined. The motor 5 generates the power.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a chair. [Background technology]

[0002] Patent Document 1 discloses a chair that induces trunk exercise in the user by changing the seat in all directions while keeping the seat inclined in a predetermined direction. Patent Document 1 also discloses a chair that generates a seat tilt according to the user's inclination by connecting the base and seat with a free joint. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-235917 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the chair disclosed in Patent Document 1, the inclination of the seat is fixed, so it is expected that only the muscles required to maintain a specific posture of the user will be tense. Also, in this chair, the inclination of the seat is determined by the user's posture, so it is expected that the degree of muscle activation in response to the inclination will be limited. Therefore, the chair disclosed in Patent Document 1 has the problem that the user cannot unconsciously activate the multiple antigravity muscles required to maintain posture.

[0005] In view of such problems, the present disclosure aims to provide a chair that enables a user to unconsciously activate multiple antigravity muscles necessary for maintaining posture. [Means for solving the problem]

[0006] The chair of the present disclosure comprises: With the base, A seat that tilts the pelvis of a seated user; a rigid support column including a lower end portion fixed to the base and an upper end portion fixed to the seat surface so that the seat surface can be tilted over the entire radial circumference; an elastic body disposed below the seating surface and generating a restoring force over the entire radial circumference of the seating surface in accordance with the inclination angle of the seating surface; an adjustment mechanism disposed between the elastic body and the base for adjusting the magnitude of the restoring force of the elastic body; a rotating table that is installed above the base and that rotates around an axis in the vertical direction based on power; a plurality of support columns having different vertical lengths that are installed above the rotating table and support the seat at their upper ends when the seat is tilted; and a motor that generates the power.

[0007] The chair of the present disclosure comprises: The elastic body is The elastic body is arranged between the seat surface and the adjustment mechanism so that the central axis of the elastic body coincides with the central axis of the rigid support pillar, so as to generate a restoring force around the entire radial circumference of the seat surface according to the inclination angle of the seat surface.

[0008] The chair of the present disclosure comprises: The elastic body is One or more of the rigid support rods are arranged between the seat surface and the adjustment mechanism around the circumference of the rigid support rod so as to generate a restoring force around the entire circumference of the seat surface in the radial direction according to the inclination angle of the seat surface.

[0009] The chair of the present disclosure comprises: The adjustment mechanism includes: The surface that comes into contact with the elastic body is moved along the rigid support column to adjust the magnitude of the restoring force of the elastic body.

[0010] The chair of the present disclosure comprises: The rigid support includes a D-cut portion and a male thread portion disposed below the D-cut portion, The adjustment mechanism includes: a support portion including a through hole into which the D-cut portion is inserted; a nut portion that screws into the male thread portion; The elastic body is disposed between the seat surface and the support portion, the support portion is attached to the rigid support column in a state in which the D-cut portion is inserted into the through hole and is movable along the D-cut portion, The magnitude of the restoring force of the elastic body is adjusted by adjusting the amount of engagement of the nut portion with the male thread portion and moving the support portion along the D-cut portion.

[0011] With the above-described configurations, it is possible to provide a chair that induces effective trunk exercise and reduces the burden on the user while allowing the user to maintain good posture. [Effects of the Invention]

[0012] The present disclosure provides a chair that enables a user to unconsciously activate multiple antigravity muscles necessary for maintaining posture. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an example of the configuration of a chair according to a first embodiment. [Figure 2] 1 is a side view showing an example of the configuration of a support mechanism of a chair according to a first embodiment. FIG. [Figure 3] FIG. 2 is a side view showing an example of the configuration of a connecting pillar mechanism of the support mechanism of the chair according to the first embodiment. [Figure 4] 1 is a side view showing an example of the configuration of a support column of a chair according to a first embodiment. [Figure 5] 2 is a diagram showing an example of the configuration of a power transmission mechanism of the chair according to the first embodiment. FIG. [Figure 6] FIG. 10 is a side view showing an example of the configuration of a connecting pillar mechanism of a support mechanism of a chair according to a second embodiment. [Figure 7] FIG. 10 is a cross-sectional view showing an example of the configuration of a connecting pillar mechanism of a support mechanism of a chair according to a second embodiment. [Figure 8] FIG. 11 is a side view showing an example of the configuration of a connecting pillar mechanism of a support mechanism of a chair according to a third embodiment. [Figure 9] FIG. 11 is a top view showing an example of the configuration of a connecting pillar mechanism of a support mechanism of a chair according to a third embodiment. [Figure 10] FIG. 10 is a plan view showing an example of the arrangement of springs in a chair according to a third embodiment. [Figure 11] FIG. 10 is a plan view showing an example of the arrangement of springs in a chair according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, specific embodiments to which the present disclosure is applied will be described in detail with reference to the drawings. In each drawing, the same elements are designated by the same reference numerals, and for clarity of explanation, duplicate explanations will be omitted as necessary.

[0015] (First embodiment) First, the configuration of a chair 100 according to a first embodiment will be described with reference to FIGS. Fig. 1 is a perspective view showing an example of the configuration of a chair according to embodiment 1. As shown in Fig. 1, the chair 100 includes a base 1, a seat 2, a support mechanism 3, a power transmission mechanism 4, a motor 5, and a controller 6.

[0016] The base 1 is a foundation on which the components of the chair 100 are mounted. The seat surface 2 is a surface on which a user sits. The seat surface 2 provides an inclination to the pelvis of the seated user.

[0017] The support mechanism 3 is a mechanism interposed between the base 1 and the seat 2 and supports the seat 2. When a user is not seated on the seat 2, the support mechanism 3 keeps the seat 2 in a reference state. The reference state is, for example, a state parallel to the horizontal plane (xy plane). When a user is seated on the seat 2, the support mechanism 3 allows the seat 2 to tilt from the reference state, and further changes the direction in which the tilt is allowed over time around an axis in the vertical direction (z-axis direction). Specifically, the support mechanism 3 has the configuration shown in FIG. 2.

[0018] 2 is a side view showing an example of the configuration of the support mechanism 3 of the chair 100 according to the first embodiment. As shown in FIG. 2, the support mechanism 3 includes a connecting support mechanism 31, a rotating base 32, and a plurality of support pillars 33.

[0019] The connecting pillar mechanism 31 is a pillar mechanism that connects the base 1 and the seat 2. Specifically, the connecting pillar mechanism 31 has the configuration shown in Fig. 3. Fig. 3 is a side view showing an example of the configuration of the connecting pillar mechanism 31 of the support mechanism 3 of the chair 100 according to the first embodiment. As shown in Fig. 3, the connecting pillar mechanism 31 includes a rigid pillar 311, a ball joint 312, a spring (elastic body) 313, and a jack (adjustment mechanism) 314.

[0020] The rigid support 311 is a member made of steel or the like that is resistant to elastic deformation and has rigidity. The rigid support 311 includes a lower end portion that is fixed to the base 1. The rigid support 311 also includes an upper end portion that is fixed to the seat 2 so that the seat 2 can tilt over the entire radial direction. It is desirable that the central axis of the rigid support 311 coincides with the center or center of gravity of the seat 2.

[0021] The upper end of the rigid support 311 is fixed to the seat 2 by a ball joint 312. This eliminates translational movement of the seat 2 (i.e., movement of the seat 2 in the x and y directions) and gives the seat 2 freedom in its tilt angle. By installing the ball joint 312 as close as possible to the top surface of the seat 2 (i.e., the position of the user's pelvis), the amount of translational movement when the seat 2 tilts can be minimized. It is desirable to locate the center of rotation of the ball joint 312 inside the seat 2, for example by hollowing out the seat 2 from the bottom side.

[0022] The spring 313 is disposed below the seat 2. The spring 313 is disposed between the seat 2 and the jack 314 so as to generate a restoring force around the entire radial circumference of the seat 2 in accordance with the inclination angle of the seat 2. The restoring force is a force that acts when the spring 313 attempts to return to its original shape after elastic deformation. A standard is set for the predetermined amount of restoring force generated by the spring 313, and the spring 313 is disposed according to that standard. Specifically, the spring 313 is disposed so that the variation in the amount (value) of the restoring force generated by the spring 313 for each inclination direction of the seat 2 is within a certain range. In other words, the spring 313 is disposed so that the amount of restoring force generated by the spring 313 is approximately equal regardless of the inclination direction of the seat 2. In this embodiment, the spring 313 is disposed between the seat 2 and the jack 314, with the rigid support 311 disposed inside, and so that the central axis of the spring 313 coincides with the central axis of the rigid support 311. It is desirable to set the number of turns of spring 313 so that the variation in the amount of restoring force generated by spring 313 for each inclination direction of seat 2 falls within a certain range. Alternatively, spring 313 may use another reaction force generating mechanism such as a shock absorber.

[0023] The jack 314 is disposed between the spring 313 and the base 1. The rigid support 311 is inserted inside the jack 314. The jack 314 adjusts the magnitude of the restoring force of the spring 313. The jack 314 can increase or decrease the initial value of the spring 313 by vertically moving the contact surface with the spring 313. The jack 314 can adjust the magnitude of the restoring force against the inclination of the seat 2 by applying pressure to the spring 313.

[0024] The tilt of the seat 2 is permitted only around the pitch axis (y-axis) and roll axis (x-axis). To prevent the seat 2 from rotating around the yaw axis (z-axis), the spring 313 and the seat 2 are connected, and the spring 313 and the jack 314 are also connected.

[0025] Note that chair 100 may be configured using another elastic body in place of spring 313, as long as the approximate isotropy of the restoring force against the inclination of seat surface 2 is ensured. For example, a cylindrical elastomer may be used instead of metal spring 313.

[0026] Furthermore, in chair 100, the length of rigid support 311 may be adjustable so that the height of seat 2 can be adjusted to suit the user's body shape. In this case, chair 100 needs to be provided with a mechanism that can adjust the length independently of jack 314, which is an adjustment mechanism that adjusts the restoring force of spring 313, and with a configuration that allows adjustment of the restoring force over the entire adjustment range of the length of rigid support 311.

[0027] Returning to the explanation of Figure 2, the rotating table 32 includes a rotating section 321, a gear section 322, and a rotating base section 323. The rotating section 321 is, for example, a disk-shaped member, and is installed on the rotating base section 323 so as to rotate in the vertical direction (z-axis direction) in accordance with the rotation of the gear section 322. The gear section 322 is, for example, a pulley that moves in conjunction with the rotating section 321, and has teeth on its outer circumferential surface to which a belt or the like for receiving power from the power transmission mechanism 4 can be attached. The rotating table 32 also includes a through-hole (not shown) through which the connecting support mechanism 31 passes.

[0028] The support pillars 33 are columnar members provided on the upper surface (positive z-axis side) of the rotating part 321 of the turntable 32. The support pillars 33 support the seat 2 at their upper ends 331 when the user sits on the seat 2 and the seat 2 tilts. The multiple support pillars 33 are provided at equal intervals around the circumference on the upper surface of the rotating part 321, but the locations where they are provided can be individually set. Specifically, the support pillars 33 have the configuration shown in FIG. 4.

[0029] 4 is a side view showing an example of the configuration of the support pillar 33a of the chair 100 according to the first embodiment. The support pillar 33a includes an upper end portion 331a and a length adjustment portion 332a. The upper end portion 331a is, for example, a ball-shaped member, and supports the seat 2 when the seat 2 is tilted. By using a ball-shaped member for the upper end portion 331a, the swivel base 32 can be rotated with little resistance even if the user's weight acting on the seat 2 is concentrated in the tilt direction. The length adjustment portion 332a is, for example, a screw type, and adjusts the length of the support pillar 33a.

[0030] Here, support column 33b has the same configuration as support column 33a, i.e., upper end portion 331b and length adjustment portion 332b. Support column 33c also has the same configuration as support column 33a, i.e., upper end portion 331c and length adjustment portion 332c.

[0031] Hereinafter, unless there is a need to distinguish between them, upper end portion 331a, upper end portion 331b, and upper end portion 331c will be collectively referred to as upper end portion 331, and length adjustment portion 332a, length adjustment portion 332b, and length adjustment portion 332c will be collectively referred to as length adjustment portion 332.

[0032] Returning to the explanation of FIG. 2 , the vertical length of each of the multiple support columns 33 is determined so that the seat surface 2 tilts at a predetermined angle from the reference state when the user is seated. To generate this tilt, at least one of the multiple support columns 33 is adjusted to be shorter in the vertical direction than the other support columns 33. For example, support column 33b is adjusted to be shorter in the vertical direction than support column 33a. In other words, the length of support column 33b is adjusted so that the distance Lb between the upper end 331b of support column 33b and the underside of the seat surface 2 is greater than the distance La between the upper end 331a of support column 33a and the underside of the seat surface 2. Furthermore, support column 33b is adjusted so that its vertical length is shorter than that of support column 33c. The direction and angle at which the seat surface 2 is allowed to tilt are determined according to the lengths of support columns 33a, 33b, and 33c. Furthermore, it is preferable that the upper end portion 331a of the support pillar 33a and the upper end portion 331c of the support pillar 33c are in contact with the underside of the seat surface 2.

[0033] Returning to the explanation of Figure 1, the power transmission mechanism 4 is configured, for example, with a belt and pulleys or a chain and sprockets, and transmits the power generated by the motor 5 to the rotating table 32 of the support mechanism 3. Specifically, the power transmission mechanism 4 has the configuration shown in Figure 5.

[0034] Fig. 5 is a diagram showing an example of the configuration of the power transmission mechanism 4 of the chair 100 according to the first embodiment. As shown in Fig. 5, the power transmission mechanism 4 is configured to include a motor 5 that rotates at a reduction ratio of 25:1, an 11-tooth pulley, a 40-tooth pulley, a 28-tooth pulley, and a 47-tooth gear portion 322 of the rotating table 32 that are linked with the rotation of the motor 5, all connected by a belt. Because a high reduction ratio is required for very slow rotation in the power transmission mechanism 4, an extremely large total reduction ratio of 1,260:1 is adopted.

[0035] Returning to the explanation of Figure 1, the motor 5 is, for example, an electric motor, and generates power by rotation. The controller 6 controls the rotation of the motor 5. For example, the controller 6 can increase or decrease the rotation speed of the motor 5. The controller 6 may switch between increasing and decreasing the rotation speed of the motor 5 at predetermined intervals.

[0036] Next, an example of the operation of the chair 100 according to the first embodiment will be described. A user sits on the seat 2 of the chair 100. At this time, the seat 2 is supported by a plurality of support pillars 33 of the support mechanism 3. If at least one of the plurality of support pillars 33 is shorter in length than the other support pillars 33, the seat 2 is allowed to tilt. Here, the direction and angle at which the seat 2 is allowed to tilt are determined according to the length of each of the plurality of support pillars 33.

[0037] The user then operates the controller 6. The controller 6 controls the rotation of the motor 5 based on the user's operation. The motor 5 generates power based on the control of the controller 6 and transmits the power to the rotating table 32 of the support mechanism 3 via the power transmission mechanism 4. The rotating part 321 of the rotating table 32 rotates around a vertical axis based on the transmitted power, causing the installed multiple support columns 33 to rotate in the same direction. As a result, the direction in which the seat 2 is allowed to tilt changes over time.

[0038] As described above, chair 100 tilts the user's pelvis around the entire radial circumference of seat surface 2. The user activates the erector spinae muscles, which are deep muscles of the trunk, to stabilize the head position (i.e., line of sight) using chair 100, performing an unconscious movement to counteract the tilt of the pelvis. Therefore, chair 100 can induce trunk movement through this unconscious but active movement simply by sitting on it. In other words, by sitting on chair 100, the user can unconsciously activate multiple antigravity muscles necessary for maintaining posture.

[0039] Furthermore, a small inclination angle of the seat 2 is sufficient to activate the erector spinae muscles, which do not inherently generate large displacements, and a small inclination angle also makes it difficult for excessive head movement to occur. Therefore, with chair 100, the inclination of the seat 2 does not interfere with desk work such as typing or writing on a computer while seated, allowing users to turn their daily sitting time into health time.

[0040] Furthermore, according to the above-mentioned concept, it is the tilt of the pelvis that is important, and since translational movement is better avoided, a mechanism that allows only changes in posture angle with the above configuration is desired. Chair 100 is configured so that the upper end of rigid support column 311 of connecting support column mechanism 31 is fixed to seat 2 by ball joint 312. Therefore, chair 100 eliminates translational movement of seat 2 (i.e., movement of seat 2 in the x and y directions) and provides freedom of tilt angle of seat 2, that is, it can allow only changes in posture angle without translational movement.

[0041] Furthermore, if the posture angle were completely free, the inclination would be biased in one direction depending on the occupant's sitting habits, exacerbating poor posture, so the seat needs to have a restoring force that corresponds to the inclination. Since the required amount of this restoring force varies depending on the user's weight and posture habits, it is desirable to make it easily adjustable so that the burden on the user can be adjusted while allowing the user to maintain posture. Chair 100 is equipped with a mechanism that adjusts the restoring force using spring 313 and jack 314 of connecting support mechanism 31. Therefore, chair 100 can reduce the burden on the user while allowing the user to maintain posture.

[0042] (Second embodiment) Next, the configuration of a chair 200 according to a second embodiment will be described with reference to FIGS. The chair 200 basically has the same configuration as the chair 100 according to the first embodiment (base 1, seat 2, support mechanism 3, power transmission mechanism 4, motor 5, and controller 6). However, unlike the chair 100 according to the first embodiment, the chair 200 has an adjustment mechanism for adjusting the magnitude of the restoring force of the spring 313. Specifically, compared to the chair 100, the chair 200 has a connecting strut mechanism 41 in place of the connecting strut mechanism 31 in the support mechanism 3. The configuration of the connecting strut mechanism 41 of the support mechanism 3 of the chair 200 is specifically shown in FIGS. 6 and 7.

[0043] Fig. 6 is a side view showing an example of the configuration of the connecting pillar mechanism 41 of the support mechanism 3 of the chair 200 according to the second embodiment. Fig. 7 is a cross-sectional view showing an example of the configuration of the connecting pillar mechanism 41 of the support mechanism 3 of the chair 200 according to the second embodiment.

[0044] 6 and 7, compared to connecting column mechanism 31 of chair 100, connecting column mechanism 41 of chair 200 includes a rigid column 411 instead of rigid column 311, and a support portion 4121 and a nut portion 4122 instead of jack 314. Similarly to connecting column mechanism 31 of chair 100, connecting column mechanism 41 of chair 200 also includes a ball joint 312 and a spring 313.

[0045] The rigid support 411 includes the same configuration as the rigid support 311 described above, as well as a D-cut portion 4111 and a male screw portion 4112 disposed below the D-cut portion 4111.

[0046] The support portion 4121 and the nut portion 4122 are an adjustment mechanism that adjusts the magnitude of the restoring force of the spring 313. The support portion 4121 includes a through hole into which the D-cut portion 4111 is inserted. The support portion 4121 is attached to the rigid support 411 in a state in which the D-cut portion 4111 is inserted into the through hole and is movable along the D-cut portion 4111. The nut portion 4122 is threadedly engaged with the male thread portion 4112. The amount by which the nut portion 4122 is threaded into the male thread portion 4112 is adjusted, thereby moving the support portion 4121 along the D-cut portion 4111 and adjusting the magnitude of the restoring force of the spring 313.

[0047] (Third embodiment) Next, the configuration of a chair 300 according to a third embodiment will be described with reference to FIG. The chair 300 has the same configuration as the chair 100 of the first embodiment (base 1, seat 2, support mechanism 3, power transmission mechanism 4, motor 5 and controller 6), but the configuration of the connecting support mechanism 31 of the support mechanism 3 is different.

[0048] FIG. 8 is a side view showing an example of the configuration of the connecting support mechanism 31 of the support mechanism 3 of the chair 300 according to the third embodiment. As shown in FIG. 8, while a single spring 313 is arranged in the chair 100 according to the first embodiment, multiple springs 313 are arranged in the chair 300 according to the present embodiment. Here, a standard is set for the predetermined amount of restoring force generated by the multiple springs 313, and each of the multiple springs 313 is arranged according to that standard. Specifically, each of the multiple springs 313 is arranged so that the variation in the total amount (total value) of the restoring force generated by the multiple springs 313 for each tilt direction of the seat 2 is within a certain range. In other words, each of the multiple springs 313 is arranged so that the total amount of restoring force generated by the multiple springs 313 is approximately equal regardless of the direction in which the seat 2 is tilted. For example, each of the multiple springs 313 is arranged as shown in FIG. 9.

[0049] FIG. 9 is a top view showing an example of the configuration of the connecting support column mechanism 31 of the support mechanism 3 of the chair 300 according to the third embodiment. As shown in FIG. 9, each of the multiple springs 313 is arranged circumferentially (indicated by a dashed line in this figure) around the circumferential direction of the rigid support column 311. The number of springs 313 is not limited to four as shown in FIG. 9, and may be any number other than four. The number of springs 313 is preferably three or more, at least enough to support the seat surface 2 as a surface. It is more preferable that each of the multiple springs 313 is arranged at equal intervals around the circumferential direction of the rigid support column 311.

[0050] 10 and 11 are plan views showing an example of the arrangement of springs 313 in a chair 300 according to the third embodiment. For example, as shown in FIG. 10, the multiple springs 313 are arranged symmetrically about the axis of the rigid support 311. However, as shown in FIG. 10, when the seat 2 is tilted toward the direction where the springs 313 are present and when the seat 2 is tilted toward the direction where the springs 313 are not present (i.e., toward the space between the multiple springs 313), the total of the predetermined amount of restoring force generated by the multiple springs 313 may not fall within a certain range. Therefore, when the multiple springs 313 are arranged symmetrically about the axis of the rigid support 311, it is desirable to arrange a sufficient number of springs 313 so that the total restoring force falls within a certain range. Furthermore, as shown in FIG. 11, it is desirable to arrange the multiple springs 313 on the opposite side of the direction where the springs 313 are not present so that the multiple springs 313 are not symmetrical about the axis of the rigid support 311.

[0051] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention. [Explanation of symbols]

[0052] 1 base 2 Seat 3 Support mechanism 4 Power transmission mechanism 5 motors 6 Controller 31, 41 Connecting strut mechanism 32 Turntable 33, 33a, 33b, 33c support columns 311, 411 Rigid support 312 ball joint 313 Spring (elastic body) 314 Jack (adjustment mechanism) 321 Rotating part 322 Gear section 323 Rotating base 331, 331a, 331b, 331c upper end 332, 332a, 332b, 332c Length adjustment part 4111 D-cut section 4112 Male thread 4121 Support part 4122 Nut part 100, 200, 300 chairs

Claims

1. With the base, A seat that tilts the pelvis of a seated user; a rigid support column including a lower end portion fixed to the base and an upper end portion fixed to the seat surface so that the seat surface can be tilted over the entire radial circumference; an elastic body disposed below the seating surface and generating a restoring force over the entire radial circumference of the seating surface in accordance with the inclination angle of the seating surface; an adjustment mechanism disposed between the elastic body and the base for adjusting the magnitude of the restoring force of the elastic body; a rotating table that is installed above the base and that rotates around an axis in the vertical direction based on power; a plurality of support columns having different vertical lengths that are installed above the rotating table and support the seat at their upper ends when the seat is tilted; a motor that generates the power; chair.

2. The elastic body is The elastic body is disposed between the seat and the adjustment mechanism so that the central axis of the elastic body coincides with the central axis of the rigid support column, so that a restoring force is generated over the entire radial circumference of the seat according to the inclination angle of the seat. The chair of claim 1.

3. The elastic body is A plurality of rigid support rods are disposed between the seat surface and the adjustment mechanism in the circumferential direction of the rigid support rod so as to generate a restoring force over the entire radial circumference of the seat surface in accordance with the inclination angle of the seat surface. The chair of claim 1.

4. The adjustment mechanism includes: The surface that comes into contact with the elastic body is moved along the rigid support, and the magnitude of the restoring force of the elastic body is adjusted. The chair of claim 1.

5. The rigid support includes a D-cut portion and a male thread portion disposed below the D-cut portion, The adjustment mechanism includes: a support portion including a through hole into which the D-cut portion is inserted; a nut portion that screws into the male thread portion; The elastic body is disposed between the seat surface and the support portion, the support portion is attached to the rigid support column in a state in which the D-cut portion is inserted into the through hole and is movable along the D-cut portion, The amount of engagement of the nut portion with the male thread portion is adjusted, and the support portion is moved along the D-cut portion, thereby adjusting the magnitude of the restoring force of the elastic body. The chair of claim 1.

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