Chair

Abstract

A chair according to the present invention is provided with a seat, a backrest, and a support structure for supporting the seat and the backrest. The backrest is provided with an arm part and a back bearing part. The support structure includes a first shaft portion, a second shaft portion, a third shaft portion, a fourth shaft portion, a support, an arm support portion, and a support link.

Description

Technical Field

[0001] The present invention relates to a chair. Background Art

[0002] Conventionally, as a chair for office use or the like, a chair having a support structure that moves the seat backward as the backrest tilts is known (for example, Patent Document 1).

[0003] The support structure disclosed in Patent Document 1 includes an arm portion that forms a part of the backrest, a support link, and four shafts located below the seat. The seat is connected to two upper shafts of the four shafts via a rail. The support link is supported by two front shafts of the four shafts. The arm portion of the backrest is supported by two rear shafts of the four shafts. If the backrest tilts with respect to the vertical direction, the arm portion tilts with respect to the horizontal direction, and the support link tilts, and the seat moves backward.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-049736 Summary of the Invention

[0007] (I) Technical Problems to be Solved

[0008] However, in the chair described in Patent Document 1, it is necessary to increase the size of the support structure that supports the support link and the backrest in the front-rear direction. As a result, as the support structure becomes larger, the space below the seat is occupied by the support structure, and there is a problem that the designability of the chair is reduced.

[0009] The present invention has been completed in view of the above problems, and an object thereof is to provide a chair that ensures a large space below the seat and improves the designability.

[0010] (II) Technical Solution

[0011] One embodiment of the chair of the present invention includes: a seat; a backrest that can tilt relative to the seat; and a support structure that supports the seat and the backrest. The backrest has: an arm portion supported by the support structure; and a back receiving portion located above the arm portion in the vertical direction and supported by the arm portion. The support structure includes: a first shaft portion extending in a first direction intersecting the vertical direction and supporting the seat so as to be rotatable; a second shaft portion located rearward of the first shaft portion in a second direction intersecting the vertical direction and the first direction, extending in the first direction, and supporting the seat so as to be rotatable; a third shaft portion located below the first shaft portion in the vertical direction, extending in the first direction, and supporting the arm portion so as to be rotatable; a fourth shaft portion located rearward of the third shaft portion in the second direction and extending in the first direction; a support that supports the third shaft portion and the fourth shaft portion; an arm support portion rotatably supported by each of the first shaft portion and the third shaft portion, capable of tilting relative to the second direction in a manner linked to the rotation of the arm portion around the third shaft portion, and supporting the arm portion; and a support link having a first link support portion and a second link support portion, the first link support portion rotatably supported by the second shaft portion, the second link support portion rotatably supported by the fourth shaft portion, and the support link located rearward of the first shaft portion and the third shaft portion in the second direction.

[0012] In such a support structure, the arm support portion and the seat can rotate relative to each other around the first shaft portion. The seat and the support link can rotate relative to each other around the second shaft portion. The arm support portion and the support can rotate relative to each other around the third shaft portion. The support and the support link can rotate relative to each other around the fourth shaft portion.

[0013] In the chair of the above-described manner, when the seated person presses the back receiving portion backward with the back facing the rear in the second direction while seated on the seat, the armrest rotates about the third shaft portion in linkage with the movement of the back receiving portion. As the armrest rotates, the armrest support portion that supports the armrest also rotates about the third shaft portion. As the armrest support portion rotates, the armrest support portion that supports the armrest also rotates about the third shaft portion. The first shaft portion supported by the armrest support portion moves backward in the second direction while rotating about the third shaft portion. The seat supported by the first shaft portion moves backward in the second direction. As the seat moves, the second shaft portion that supports the seat so as to be rotatable also moves backward in the second direction. The second shaft portion is supported by the support link so as to be rotatable. The support link rotates about the fourth shaft portion. That is, the second shaft portion moves backward in the second direction while rotating about the fourth shaft portion. Therefore, the seat supported by the first shaft portion and the second shaft portion moves backward in the second direction in a manner of depicting a locus that combines the rotation of the armrest support portion about the third shaft portion and the rotation of the support link about the fourth shaft portion. At this time, the seat that supports the third shaft portion and the fourth shaft portion does not move in the second direction. In other words, the seat, the first shaft portion, and the second shaft portion move relatively backward with respect to the seat.

[0014] According to the chair of the above-described manner, when the seated person presses the back receiving portion backward, the back receiving portion tilts with respect to the vertical direction. As the back receiving portion tilts, the seat can move backward with respect to the seat, that is, the seat can be directly pulled backward.

[0015] In addition, since the support link is located behind the first shaft portion and the third shaft portion in the second direction, it is not necessary to arrange the support link in the front in the second direction. Therefore, the support structure can be miniaturized, the space in the front in the second direction in the space below the seat becomes larger, and the space occupied by the support structure arranged below the seat can be reduced. That is, a larger space can be ensured below the seat, and the designability of the chair can be improved.

[0016] In addition, the seat is supported by the second shaft portion located behind the first shaft portion so as to be rotatable. The second shaft portion is not directly connected to the backrest but is supported by the support link. Therefore, a state is formed in which the downward movement range of the second shaft portion is restricted. In other words, by restricting the rotation range of the support link, the downward movement range of the second shaft portion is restricted. In addition, since the height of the support link is also restricted, the downward movement range of the second shaft portion is restricted. In a state where the movement of the second shaft portion is restricted in this way, the second shaft portion is supported so as to be able to tilt backward and downward. Therefore, the backward and downward tilt of the seat is not affected by the tilt of the backrest. Therefore, by appropriately setting the height of the support link and the rotation range of the support link, a chair can be provided in which the amount of backward and downward tilt of the support link to the seat is not excessive.

[0017] In a chair according to one aspect of the present invention, it is also possible that the backrest can tilt relative to the seat within a tilting range between a front limit position and a rear limit position in the second direction, and when the backrest is in the front limit position, the support link stands upright in the vertical direction, or the support link is inclined relative to the vertical direction such that the second shaft portion is located more forward in the second direction than the fourth shaft portion.

[0018] In the chair according to the above aspect, when the backrest receiving portion is in the front limit position, a state is formed in which the support link does not tilt backward. Therefore, even when the backrest receiving portion reaches the rear limit position, the amount of movement of the support link downward and backward can be reduced. A chair can be provided in which the amount of tilting of the support link downward and backward with respect to the seat is not excessive.

[0019] In a chair according to one aspect of the present invention, it is also possible that a first distance between the first shaft portion and the third shaft portion is greater than a second distance between the second shaft portion and the fourth shaft portion.

[0020] In the chair according to the above aspect, a chair can be provided in which the amount of tilting of the support link downward and backward with respect to the seat is not excessive.

[0021] In a chair according to one aspect of the present invention, it is also possible that in the vertical direction, the position of the second shaft portion is located above the position of the third shaft portion.

[0022] In the chair according to the above aspect, a chair can be provided in which the amount of tilting of the support link downward and backward with respect to the seat is not excessive.

[0023] In a chair according to one aspect of the present invention, it is also possible that the seat has a lower surface in the vertical direction and a recess provided on the lower surface, and the first shaft portion and the second shaft portion are received inside the recess.

[0024] In the chair according to the above aspect, when viewed from the second direction and the first direction, the first shaft portion and the second shaft portion do not protrude outside the recess. Therefore, in terms of the appearance of the chair, the design can be improved.

[0025] In a chair according to one aspect of the present invention, it is also possible that the seat has a seat main body, the seat main body has the lower surface on which the recess is formed, the support structure has a seat receiving member, the seat receiving member is received inside the recess, the seat receiving member supports the first shaft portion and the second shaft portion, and when viewed in the first direction, the seat receiving member overlaps with the seat main body.

[0026] In the chair according to the above-described manner, when viewed from the second direction and the first direction, the seat receiving member that supports the first shaft portion and the second shaft portion does not protrude to the outside of the recess. Therefore, in terms of the appearance of the chair, the designability can be improved. Moreover, in the operation of assembling the components that make up the chair, it is possible to first axially support the backrest and the seat receiving member with each other, and then perform the operation of housing the seat receiving member in the seat main body. Thus, the assembly operation can be simply performed.

[0027] In the chair according to one embodiment of the present invention, the arm support portion may be a support connector that can be disassembled and assembled relative to the arm portion.

[0028] In the chair according to the above-described manner, the support connector can be disassembled and assembled relative to the arm portion.

[0029] In the chair according to one embodiment of the present invention, the support connector may include: a first connector support portion that is rotatably supported by the first shaft portion; a second connector support portion that is rotatably supported by the third shaft portion; and a notch portion that is provided between the first connector support portion and the second connector support portion and is formed in a substantially U-shape when viewed in the first direction.

[0030] In the chair according to the above-described manner, a larger space can be ensured below the seat, improving the designability.

[0031] (III) Advantageous Effects

[0032] In the chair according to the embodiment of the present invention, a larger space can be ensured below the seat, improving the designability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a perspective view of a chair according to an embodiment of the present invention as viewed obliquely from the front.

[0034] Figure 2 is an exploded perspective view of a part of a chair according to an embodiment of the present invention, and is a view showing a part of the components constituting the seat and the support structure.

[0035] Figure 3 is a perspective view of a part of the operating mechanism of the seat constituting a chair according to an embodiment of the present invention.

[0036] Figure 4 is a perspective view of a part of the operating mechanism inside a support base that is a part of the support structure constituting a chair according to an embodiment of the present invention, and is a view showing a state where the support base cover is removed.

[0037] Figure 5It is an exploded perspective view of a part of a chair showing an embodiment of the present invention, and is a view showing the components constituting the backrest and the support structure respectively.

[0038] Figure 6 It is a side view showing an enlarged view of the main part of the arm portion of the backrest of a chair showing an embodiment of the present invention.

[0039] Figure 7 It is a perspective view showing the first seat bearing member of the support structure of a chair showing an embodiment of the present invention.

[0040] Figure 8 It is a perspective view showing the second seat bearing member of the support structure of a chair showing an embodiment of the present invention.

[0041] Figure 9 It is a perspective view showing the support connector of the support structure of a chair showing an embodiment of the present invention.

[0042] Figure 10 It is a perspective view showing the seat of the support structure of a chair showing an embodiment of the present invention.

[0043] Figure 11 It is a perspective view showing the seat cover of the support structure of a chair showing an embodiment of the present invention.

[0044] Figure 12 It is a side view showing locally the structure formed by combining the seat, the backrest and the support structure of a chair showing an embodiment of the present invention, and is a view showing the state where the backrest is arranged at the front limit position.

[0045] Figure 13 It is a side view showing locally the structure formed by combining the seat, the backrest and the support structure of a chair showing an embodiment of the present invention, and is a view showing the state where the backrest is arranged at the rear limit position.

[0046] Figure 14A It is a side view for explaining the method of combining the arm portion of the backrest of a chair showing an embodiment of the present invention with the support connector constituting the support structure.

[0047] Figure 14B It is a side view for explaining the method of combining the arm portion of the backrest of a chair showing an embodiment of the present invention with the support connector constituting the support structure. Detailed Embodiment

[0048] A chair showing an embodiment of the present invention will be described with reference to the accompanying drawings.

[0049] In the following description, structures having the same or similar functions are denoted by the same reference numerals. Also, repetitive descriptions of these structures are sometimes omitted. The drawings are schematic or conceptual, and the relationships between the thicknesses and widths of the respective parts, the ratios of the sizes between the parts, etc. are not necessarily the same as in reality.

[0050] In the following description, for the sake of convenience, the direction forward of the sitter sitting on seat 1 in a regular posture is referred to as "front", and the opposite direction is referred to as "rear". In addition, the up-down and left-right orientations in the following description are consistent with the orientations centered on the sitter when the sitter is sitting on seat 1 in a regular posture. Further, in the drawings, an arrow FD pointing forward, an arrow BD pointing backward, an arrow UD pointing upward, an arrow DD pointing downward, an arrow RD pointing rightward, and an arrow LD pointing leftward are shown.

[0051] The upward direction UD and the downward direction DD are consistent with the up-down direction (direction of gravity).

[0052] The downward direction DD may also be simply referred to as "top view". The upward direction UD and the downward direction DD may also be referred to as the up-down directions UD, DD.

[0053] The front direction FD and the rear direction BD respectively correspond to a second direction intersecting the up-down direction. The front direction FD and the rear direction BD may each be a direction parallel to the horizontal plane or an inclined direction inclined with respect to the horizontal plane. The front direction FD and the rear direction BD may also be referred to as the front-rear directions FD, BD. Here, the "horizontal plane" means a plane orthogonal to the up-down direction.

[0054] The right direction RD and the left direction LD respectively correspond to a first direction intersecting the up-down direction and the second direction. That is, the right direction RD and the left direction LD are directions intersecting the up-down direction and the front-rear directions FD, BD. The right direction RD or the left direction LD may also be simply referred to as "side view". The right direction RD and the left direction LD may also be referred to as the left-right directions RD, LD.

[0055] In addition, there are cases where a plane parallel to the front-rear directions FD, BD and the left-right directions RD, LD is referred to as the "horizontal direction" or the "horizontal plane".

[0056] <Chair 100>

[0057] As Figure 1 shown, the chair 100 of the present embodiment includes a seat 1, a backrest 2, an elastic member 23, and a support structure 3. The chair 100 is used in a state where the chair 100 is placed on the ground FS and a sitter is sitting on the seat 1.

[0058] The backrest 2 is connected to the seat 1 in a linked manner via a support structure 3. In other words, in the structure of the chair 100, the backrest 2 is not directly supported by the seat 1.

[0059] <seat 1>

[0060] As Figure 1 , Figure 2 and Figure 3 shown, the seat 1 has a seat main body 4 and an operating mechanism 5.

[0061] <seat main body 4>

[0062] The seat main body 4 is a plate-shaped member that elastically supports the buttocks and thighs of the seated person.

[0063] The seat main body 4 is a plate parallel to the front-rear direction FD, BD or a direction inclined with respect to the front-rear direction FD, BD and parallel to the left-right direction RD, LD. The seat main body 4 has a seat plate lower surface 4L facing the downward direction DD and a seat upper surface 4U facing the upward direction UD. The seat plate lower surface 4L faces the ground FS. The seat plate lower surface 4L is an example of a "lower surface". The seat plate upper surface 4U is a curved surface having a three-dimensional shape corresponding to the shapes of the buttocks and thighs of the seated person. The seat plate upper surface 4U is covered with a stretching material 4M. As the material constituting the seat main body 4, a known resin material or metal material is used. The material of the stretching material 4M is, for example, a cloth such as a net.

[0064] A support mechanism storage portion 6 and an operating mechanism storage portion 7 are formed on the seat plate lower surface 4L.

[0065] The support mechanism storage portion 6 and the operating mechanism storage portion 7 are each an example of a "recess". In order to distinguish each of the support mechanism storage portion 6 and the operating mechanism storage portion 7, the support mechanism storage portion 6 may also be referred to as a "first recess", and the operating mechanism storage portion 7 may be referred to as a "second recess".

[0066] <support mechanism storage portion 6>

[0067] The support mechanism storage portion 6 is formed substantially at the center of the seat main body 4 in the front-rear direction FD, BD and the left-right direction RD, LD.

[0068] The support mechanism storage portion 6 has a support concave surface 6A formed inside the support mechanism storage portion 6. Four seat bearing fastening holes 6B are formed on the support concave surface 6A. The four seat bearing fastening holes 6B are each, for example, a threaded hole.

[0069] Regarding the depth of the support mechanism housing portion 6 from the lower surface 4L of the seat plate toward the upward direction UD, the support mechanism housing portion 6 has a depth 6D from the edge portion 6C of the support mechanism housing portion 6 to the support concave portion surface 6A in the upward direction UD. The depth 6D of the support mechanism housing portion 6 can be appropriately set according to the design of the seat main body 4 and the seat bearing member 40 described later.

[0070] <Operating mechanism housing portion 7>

[0071] The operating mechanism housing portion 7 has a rod housing portion 7A and a wire housing portion 7B.

[0072] In the present embodiment, the rod housing portion 7A is formed at a position more forward than the support mechanism housing portion 6 in the front direction FD and at a position more to the right than the support mechanism housing portion 6 in the right direction RD. The position of the rod housing portion 7A is not limited to Figure 2 the position shown. The rod housing portion 7A has a rod concave portion surface 7C formed inside the rod housing portion 7A. A shaft fixing hole 7D is formed in the rod concave portion surface 7C. The shaft fixing hole 7D is, for example, a threaded hole.

[0073] The wire housing portion 7B is, for example, a groove formed in the lower surface 4L of the seat plate. The depth of the operating mechanism housing portion 7 from the lower surface 4L of the seat plate toward the upward direction UD is appropriately set according to the size of each of the plurality of components constituting the operating mechanism 5. In the direction in which the wire housing portion 7B extends, the wire housing portion 7B has a locally formed bent portion and a straight portion.

[0074] In Figure 2 the example shown, when viewed in the upward direction UD, the wire housing portion 7B is formed in a substantially U-shaped configuration. The shape of the wire housing portion 7B is set according to the design of the chair 100 considering the position of the rod housing portion 7A. For example, depending on the position of the rod housing portion 7A in the front-back direction FD, BD and the left-right direction RD, LD, that is, the position of the rod housing portion 7A in the horizontal direction, the shape of the wire housing portion 7B can be an I-shaped configuration or an inverted L-shaped configuration. When the shape of the wire housing portion 7B is an I-shaped configuration, for example, the operating mechanism 5 can be provided on the lower surface 4L of the seat plate at intervals so as to be arranged with the support structure body 3 in the left-right direction RD, LD.

[0075] <Operating mechanism 5>

[0076] As Figure 2 、 Figure 3 and Figure 4 shown, the operating mechanism 5 has an operating portion 10, a wire structure body 11, a pressing portion 12, an operating portion cover 13, and a wire holding claw 14. In addition, Figure 3 shows a state in which the operating portion 10 is separated from the lower surface 4L of the seat plate. Figure 4This represents a part of the operating mechanism 5 disposed inside the support 60 that forms part of the support structure 3. In Figure 4 the illustration of the support cover 65 is omitted. The support 60 and the support cover 65 will be described later.

[0077] The operating mechanism 5 is housed in the rod housing portion 7A and the wire housing portion 7B on the lower surface 4L of the seat plate. Moreover, a part of the operating mechanism 5 is housed in the support 60.

[0078] <Operating portion 10>

[0079] The operating portion 10 has a rod support shaft 10A, a rod plate 10B, a wire support portion 10C, and a rod 10D. The operating portion 10 is housed in the rod housing portion 7A.

[0080] <Rod support shaft 10A>

[0081] The rod support shaft 10A extends in the up-down direction UD, DD. The rod support shaft 10A has a threaded groove portion 10E, a rotational support portion 10F, and a head 10G. The head 10G is located at the end of the rod support shaft 10A in the downward direction DD. The threaded groove portion 10E is threadedly fixed to the shaft fixing hole 7D. Thus, the threaded groove portion 10E is fixed to the operating mechanism housing portion 7. The rod support shaft 10A supports the rod plate 10B so that the rod plate 10B can rotate around the rotational support portion 10F. As the material constituting the rod support shaft 10A, a known resin material or metal material is used.

[0082] <Rod plate 10B>

[0083] The rod plate 10B extends in a direction orthogonal to the up-down direction UD, DD. The rod plate 10B has a support end portion 10H and a rotational end portion 10I. A support shaft hole 10J is formed in the support end portion 10H. The rotational support portion 10F is inserted into the support shaft hole 10J. The diameter of the support shaft hole 10J is smaller than the diameter of the head 10G. Thus, the rod plate 10B is prevented from falling off the operating mechanism housing portion 7 in the downward direction DD by the head 10G. As the material constituting the rod plate 10B, a known resin material or metal material is used.

[0084] <Wire support portion 10C>

[0085] The wire support portion 10C is a protrusion protruding downward from the rod plate 10B in the direction DD. The wire support portion 10C is located between the support end portion 10H and the rotational end portion 10I in the direction in which the rod plate 10B extends. The wire support portion 10C is fixed to a hole formed in the rod plate 10B.

[0086] <Rod 10D>

[0087] The rod 10D extends in the up-and-down directions UD and DD. The upper end of the rod 10D in the upward direction UD is fixed to the rotating end 10I of the rod plate 10B. The rod 10D is, for example, a part for a seated person to operate the operation unit 10 with a finger. The rod 10D can rotate around the rod support shaft 10A. Specifically, the rod 10D can move in a manner of depicting an arc-shaped trajectory in the horizontal direction. The arc-shaped trajectory refers to a part of an arc of a circle centered on the rod support shaft 10A.

[0088] As the material constituting the rod 10D, a known resin material or metal material is used. The rod 10D can be formed of the same component integrally with the rod plate 10B, or can be separated from the rod plate 10B in a manner separated from the rod plate 10B.

[0089] The operation unit 10 having such a structure is housed in the rod housing portion 7A. Considering the operability of the operation unit 10 and the chair 100 by the seated person, the position of the operation unit 10, the position and shape of the rod housing portion 7A are set.

[0090] If explained based on the lever principle related to the fulcrum, the point of force, and the point of action, in the operation unit 10 having the above structure, the rod support shaft 10A corresponds to the fulcrum, the rod 10D corresponds to the point of force, and the wire support portion 10C of the rod plate 10B corresponds to the point of action. In the structure utilizing such a lever principle, the rod 10D and the wire support portion 10C are in the horizontal direction.

[0091] Regarding the relative positional relationship of the rod support shaft 10A, the rod 10D, and the wire support portion 10C in the extending direction of the rod plate 10B, it is appropriately set in consideration of the lever principle and the operability of the chair 100.

[0092] <Wire structure 11>

[0093] The wire structure 11 has an outer tube 11A, an inner wire 11B, a first wire engaging end 11F (first engaging end), and a second wire engaging end 11S (second engaging end). In the front-back directions FD and BD and the left-right directions RD and LD, the wire structure 11 is supported by the wire housing portion 7B. The length of the wire structure 11 is set according to the formation pattern of the wire housing portion 7B formed on the lower surface 4L of the seat plate and the design of the chair 100.

[0094] <Outer tube 11A>

[0095] The outer tube 11A is, for example, a soft resin-made cylindrical body. The outer tube 11A has flexibility. A space is formed inside the outer tube 11A. This space extends in the extending direction of the outer tube 11A. The outer tube 11A is housed and fixed in the wire housing portion 7B. The wire housing portion 7B statically holds the outer tube 11A. As such an outer tube 11A, a known outer tube is used.

[0096] <Inner wire 11B>

[0097] The inner wire 11B has a structure in which, for example, multiple thin metal wires are woven in, and has flexibility. The inner wire 11B is located in the inner space of the outer tube 11A and can move relative to the outer tube 11A held by the wire storage portion 7B. In other words, the inner wire 11B can move inside the fixed outer tube 11A while deforming in a manner that extends along the extending direction of the outer tube 11A. As such an inner wire 11B, a known inner wire is used.

[0098] <First wire engaging end 11F>

[0099] The first wire engaging end 11F is connected to the front end (first front end) of the inner wire 11B. Inside the rod storage portion 7A, the first wire engaging end 11F engages with the wire support portion 10C. The first wire engaging end 11F can rotate around the wire support portion 10C. The engaging structure between the first wire engaging end 11F and the wire support portion 10C is not particularly limited. For example, a structure in which the wire support portion 10C and the first wire engaging end 11F each have a hook and the two hooks engage can also be adopted. Alternatively, the wire support portion 10C has a small diameter portion with a smaller diameter and a large diameter portion with a diameter larger than that of the small diameter portion, and the first wire engaging end 11F engages with the small diameter portion.

[0100] <Second wire engaging end 11S>

[0101] The second wire engaging end 11S is connected to the front end (second front end) of the inner wire 11B located on the upper surface of the support cover 65. On the upper surface of the support cover 65, the second wire engaging end 11S engages with the pressing portion 12.

[0102] <Pressing portion 12>

[0103] As Figure 4 shown, the pressing portion 12 has a pressing body 12A, a pressing support shaft 12B, a pressing engaging portion 12C, and a pressing force generating portion 12G.

[0104] <Pressing body 12A>

[0105] The pressing body 12A has, for example, a substantially triangular shape. The shape of the pressing body 12A is not limited to a substantially triangular shape. As long as it has a pressing support shaft 12B, a pressing engaging portion 12C, and a pressing force generating portion 12G, the shape of the pressing body 12A is appropriately selected. As the material constituting the pressing body 12A, a known resin material or metal material is used.

[0106] At Figure 4In the example shown, the pressing portion 12 has a thickness in the direction indicated by symbol T, a height in the direction indicated by symbol H, and a length in the direction indicated by symbol L. In the following description, the expressions "thickness direction T", "height direction H", and "length direction L" are sometimes used to describe the pressing portion 12. Further, the height direction H is a direction parallel or inclined with respect to the up-down directions UD and DD. The thickness direction T is a direction parallel or inclined with respect to the front-back directions FD and BD. The length direction L is a direction parallel or inclined with respect to the left-right directions RD and LD.

[0107] <Pressing support shaft 12B>

[0108] The pressing support shaft 12B forms a part of the pressing body 12A. The pressing support shaft 12B extends along the thickness direction T. The pressing support shaft 12B supports the pressing body 12A in such a manner that the pressing body 12A can rotate about the pressing support shaft 12B. Further, the pressing support shaft 12B may be formed of the same member integrally with the pressing body 12A, or may be separated from the pressing body 12A in a manner separated from the pressing body 12A.

[0109] In the present embodiment, the pressing support shaft 12B is supported by a later-described support cover 65 so as to be rotatable. As long as the pressing body 12A can rotate about the pressing support shaft 12B, the pressing support shaft 12B may also be supported by the support 60.

[0110] <Pressing engagement portion 12C>

[0111] The pressing engagement portion 12C is formed on the pressing body 12A at a position away from the pressing support shaft 12B in the height direction H. The pressing engagement portion 12C forms a part of the pressing body 12A. The pressing engagement portion 12C has a wire insertion groove 12D and a wire support groove 12E. The wire insertion groove 12D is a groove through which the second wire engagement end 11S is inserted when the second wire engagement end 11S is hooked on the pressing portion 12. The wire support groove 12E is a groove that supports the second wire engagement end 11S.

[0112] <Wire insertion groove 12D>

[0113] The wire insertion groove 12D is formed, for example, to extend from the upper end 12U of the pressing body 12A toward the inside of the pressing body 12A in the height direction H. The depth of the wire insertion groove 12D in the height direction H is not particularly limited, and the wire insertion groove 12D only needs to have a depth sufficient to support the second wire engagement end 11S. The wire insertion groove 12D is located approximately at the center in the thickness direction T.

[0114] <Wire support groove 12E>

[0115] The wire support groove 12E has a shape corresponding to the shape of the second wire engagement end 11S.

[0116] The wire support groove 12E is provided on the surface of the pressing body 12A on the side opposite to the second wire engaging end 11S. The wire support groove 12E is formed to extend toward the inside of the pressing body 12A in the longitudinal direction L or in a direction inclined with respect to the longitudinal direction L. The depth of the wire support groove 12E in the longitudinal direction L is not particularly limited, and the wire support groove 12E only needs to have a depth sufficient to support the second wire engaging end 11S.

[0117] The engaging structure between the pressing engaging portion 12C and the second wire engaging end 11S is not particularly limited. For example, a structure in which the pressing engaging portion 12C and the second wire engaging end 11S each have a hook and the two hooks are engaged may be employed.

[0118] <Pressing force generating portion 12G>

[0119] The pressing force generating portion 12G is formed on the pressing body 12A at a position away from the pressing support shaft 12B in the longitudinal direction L. In Figure 4 the illustrated example, the pressing force generating portion 12G is a surface that is a part of the pressing body 12A. The pressing force generating portion 12G is located below the pressing body 12A in the height direction H.

[0120] If explained based on the lever principle related to the fulcrum, the force point, and the point of action, in the pressing portion 12 having the above structure, the pressing support shaft 12B corresponds to the fulcrum, the pressing engaging portion 12C corresponds to the force point, and the pressing force generating portion 12G corresponds to the point of action. In a structure utilizing such a lever principle, the pressing engaging portion 12C and the pressing force generating portion 12G are located in the height direction H. In other words, the pressing engaging portion 12C and the pressing force generating portion 12G are located in a direction different from the horizontal direction. The relative positional relationship of the pressing support shaft 12B, the pressing engaging portion 12C, and the pressing force generating portion 12G in the height direction H and the longitudinal direction L is appropriately set in consideration of the lever principle and the operability of the chair 100.

[0121] <Operation portion cover 13>

[0122] As Figure 2 shown, the operation portion cover 13 is a portion that is fitted to the rod storage portion 7A. A through hole 13A is formed in the operation portion cover 13. The rod 10D is inserted through the through hole 13A. The shape of the through hole 13A is an arc shape so that the rod 10D can move within the arc-shaped movement range. Using fastening members such as bolts (not shown), the operation portion cover 13 is fastened to the seat main body 4. In a state where the operation portion cover 13 is fitted to the rod storage portion 7A, a part of the rod 10D passing through the through hole 13A protrudes from the lower surface 4L of the seat plate, and the operation portion 10 is stored in the space formed between the operation portion cover 13 and the rod storage portion 7A.

[0123] <Wire retaining claw 14>

[0124] The wire retaining claw 14 is provided on the lower surface 4L of the seat plate in the extending direction of the groove-shaped wire storage portion 7B. The wire retaining claw 14 holds the wire structure 11 disposed within the wire storage portion 7B. The wire retaining claw 14 is fixed to the lower surface 4L of the seat plate using a fastening member such as a bolt (not shown), for example. The wire retaining claw 14 shields the opening end portion of the groove-shaped wire storage portion 7B in the downward direction DD at an appropriate position in the horizontal direction. Thereby, the wire retaining claw 14 prevents the wire structure 11 from falling off the wire storage portion 7B in the downward direction DD. Additionally, the wire retaining claw 14 may be integrally formed with the lower surface 4L of the seat plate.

[0125] <Backrest 2>

[0126] The backrest 2 is tiltable relative to the seat 1.

[0127] As Figure 1 、 Figure 5 and Figure 6 shown, the backrest 2 has an arm portion 20, a backrest receiving portion 21, an elastic member support portion 24, and a backrest cover 25. The backrest 2 is a portion that supports the back of the seated person. As the material constituting the arm portion 20, the backrest receiving portion 21, the elastic member support portion 24, and the backrest cover 25, a known resin material or metal material is used.

[0128] <Arm portion 20>

[0129] The arm portion 20 is supported by the support structure 3.

[0130] The arm portion 20 is formed in a substantially L-shape when viewed in the right direction RD. The arm portion 20 has a vertical arm 20A and a horizontal arm 20B. The vertical arm 20A is located below the seat main body 4. The vertical arm 20A extends in the up-down direction UD, DD. The horizontal arm 20B extends in the front-back direction FD, BD. The vertical arm 20A may be formed of the same member integrally with the horizontal arm 20B, or may be separated from the horizontal arm 20B in a split manner.

[0131] The vertical arm 20A supports the backrest receiving portion 21. The horizontal arm 20B has an arm opening 20C, a first support arm 20F, a second support arm 20S, and a reinforcing arm 20D. The arm opening 20C is an opening through which a part of the elastic member 23 is inserted when the elastic member 23 is mounted on the back surface of the vertical arm 20A facing the back direction BD. The reinforcing arm 20D extends in the left-right direction RD, LD. The reinforcing arm 20D is provided between the first support arm 20F and the second support arm 20S. Thereby, the strength of the horizontal arm 20B is improved.

[0132] <First support arm 20F>

[0133] The first support arm 20F has a first shaft support hole 26F. The first shaft support hole 26F is provided on the side of the first support arm 20F opposite to the longitudinal arm 20A. In other words, the first shaft support hole 26F is located in front of the first support arm 20F in the forward direction FD. The first support arm 20F is mounted to the rear portion of the support 60 via the first shaft support hole 26F. The first support arm 20F has a first arm groove 27F provided between the first shaft support hole 26F and the reinforcing arm 20D. The first arm groove 27F opens toward the left direction LD.

[0134] Figure 6 is a magnified view showing an enlarged view of the portion indicated by symbol A of Figure 5 . In other words, Figure 6 is a side view partially showing the first support arm 20F as viewed from the second support arm 20S in the right direction RD. The first arm groove 27F has an obliquely opening groove 28A, a front - rear extending groove 28B, and a groove inner portion 28C. The first arm groove 27F opens toward the left direction LD. In other words, the first arm groove 27F is exposed in the space between the first support arm 20F and the second support arm 20S.

[0135] The obliquely opening groove 28A is formed in the first support arm 20F so as to extend in the groove inclination direction 29A. Here, the groove inclination direction 29A is the direction from the arm upper surface 29T of the first support arm 20F toward the inside of the first support arm 20F. In other words, the groove inclination direction 29A is a direction inclined with respect to the extending direction 20E in which the first support arm 20F extends. The obliquely opening groove 28A opens in the upper direction UD and the left direction LD on the arm upper surface 29T.

[0136] The obliquely opening groove 28A has two obliquely grooved walls 28N1, 28N2 facing each other. The width between the two obliquely grooved walls 28N1, 28N2 is slightly wider than the diameter of the right - arm engaging portion 51J described later. Thus, the obliquely opening groove 28A enables the right - arm engaging portion 51J to be inserted between the obliquely grooved walls 28N1, 28N2.

[0137] The front - rear extending groove 28B is formed in the first support arm 20F so as to be connected to the obliquely opening groove 28A in the groove inclination direction 29A. The front - rear extending groove 28B extends in the extending direction 20E. The front - rear extending groove 28B opens in the groove inclination direction 29A and the left direction LD.

[0138] The front - rear extending groove 28B has two extending grooved walls 28M1, 28M2 facing each other. The extending grooved wall 28M1 is the surface connected to the obliquely grooved wall 28N1. The extending grooved wall 28M2 is the surface connected to the obliquely grooved wall 28N2.

[0139] The width between the two extending groove walls 28M1 and 28M2 is slightly wider than the diameter of the right arm engaging portion 51J described later. Thus, the front and rear extending groove 28B enables the right arm engaging portion 51J to be inserted between the extending groove walls 28M1 and 28M2.

[0140] The inner part 28C of the groove is the part located at the rearmost of the front and rear extending groove 28B. In other words, the inner part 28C of the groove is the part at the end of the front and rear extending groove 28B in the groove extending direction 29B. The groove extending direction 29B is a direction parallel to the extending direction 20E. The inner part 28C of the groove opens toward the extending direction 20E and the left direction LD.

[0141] The inner part 28C of the groove has a curved surface. The curved surface of the inner part 28C of the groove has a shape along the surface shape of the right arm engaging portion 51J.

[0142] <Second support arm 20S>

[0143] The second support arm 20S has a second shaft support hole 26S. The second shaft support hole 26S is provided on the second support arm 20S on the side opposite to the longitudinal arm 20A. In other words, the second shaft support hole 26S is located in front of the second support arm 20S in the front direction FD. The second support arm 20S is mounted on the rear part of the support 60 via the second shaft support hole 26S. The second support arm 20S has a second arm groove 27S provided between the second shaft support hole 26S and the reinforcing arm 20D. The second arm groove 27S opens toward the right direction RD.

[0144] The second arm groove 27S has an obliquely opening groove 28A, a front and rear extending groove 28B, and an inner part 28C of the groove in the same manner as the first arm groove 27F of the first support arm 20F. The second arm groove 27S opens toward the right direction RD. In other words, the second arm groove 27S is exposed in the space between the first support arm 20F and the second support arm 20S.

[0145] The obliquely opening groove 28A is formed in the second support arm 20S so as to extend in the groove inclined direction 29A. Here, the groove inclined direction 29A is a direction from the upper surface 29T of the arm of the second support arm 20S toward the inside of the second support arm 20S. In other words, the groove inclined direction 29A is a direction inclined with respect to the extending direction 20E in which the second support arm 20S extends. The obliquely opening groove 28A opens toward the upper direction UD and the right direction RD on the upper surface 29T of the arm.

[0146] The obliquely opening groove 28A has two obliquely arranged groove walls 28N1 and 28N2 facing each other. The width between the two obliquely arranged groove walls 28N1 and 28N2 is slightly wider than the diameter of the left arm engaging portion 51R described later. Thus, the obliquely opening groove 28A enables the left arm engaging portion 51R to be inserted between the obliquely arranged groove walls 28N1 and 28N2.

[0147] The front - and - rear extending groove 28B is formed in the second support arm 20S in a manner that it is connected to the obliquely - opening groove 28A in the groove inclination direction 29A. The front - and - rear extending groove 28B extends in the extending direction 20E. The front - and - rear extending groove 28B opens toward the groove inclination direction 29A and the right direction RD.

[0148] The front - and - rear extending groove 28B has two extending groove walls 28M1 and 28M2 that face each other. The extending groove wall 28M1 is the surface connected to the oblique groove wall 28N1. The extending groove wall 28M2 is the surface connected to the oblique groove wall 28N2.

[0149] The width between the two extending groove walls 28M1 and 28M2 is slightly wider than the diameter of the left - arm engaging portion 51R described later. Thus, the front - and - rear extending groove 28B enables the left - arm engaging portion 51R to be inserted between the extending groove walls 28M1 and 28M2.

[0150] The inner part 28C of the groove is the part located at the rearmost of the front - and - rear extending groove 28B. In other words, the inner part 28C of the groove is the part at the end of the front - and - rear extending groove 28B in the groove extending direction 29B. The groove extending direction 29B is a direction parallel to the extending direction 20E. The inner part 28C of the groove opens toward the extending direction 20E and the right direction RD.

[0151] The inner part 28C of the groove has a curved surface. The curved surface of the inner part 28C of the groove has a shape along the surface shape of the left - arm engaging portion 51R.

[0152] The second arm groove 27S and the first arm groove 27F are in an axially - symmetric relationship with respect to the central axis CL (refer to Figure 1 ) that passes through the center of the chair 100 in the left - right direction RD, LD and extends in the front - rear direction FD, BD.

[0153] <Back - supporting part 21>

[0154] The back - supporting part 21 is located above the longitudinal arm 20A in the up - down direction UD, DD. The back - supporting part 21 is supported by the longitudinal arm 20A.

[0155] The back - supporting part 21 is arranged more rearward than the seat 1 in the rear direction BD. The back - supporting part 21 can tilt relative to the seat 1. The back - supporting part 21 has a back - supporting support part 21A and a back - supporting surface forming part 21B. The back - supporting support part 21A is fastened to the longitudinal arm 20A using fastening members such as bolts (not shown). Thus, the back - supporting support part 21A is supported by the arm part 20. The back - supporting part 21 extends in the up - down direction UD, DD and can tilt in the up - down direction UD, DD in linkage with the rotation of the arm part 20. The material of the tensile material forming the back - supporting surface forming part 21B is, for example, a cloth such as a net.

[0156] In addition, the backrest bearing portion 21A can also be integrally formed with the longitudinal arm 20A. A known cushioning member covered with a fabric can also be installed on the backrest surface forming portion 21B. The backrest surface forming portion 21B can also be covered with a fabric.

[0157] <Elastic member support portion 24>

[0158] The elastic member support portion 24 is a member that fixes the longitudinal spring portion 23A to the back surface 21C of the backrest bearing portion 21A. The elastic member support portion 24 uses fastening members such as bolts (not shown) to fasten the longitudinal spring portion 23A to the back surface 21C of the backrest bearing portion 21A.

[0159] <Backrest cover 25>

[0160] The backrest cover 25 is fixed to the longitudinal arm 20A so as to cover the elastic member support portion 24 and the longitudinal spring portion 23A. As a result, the elastic member support portion 24 and the longitudinal spring portion 23A do not protrude to the outside of the chair 100. By fastening the backrest cover 25 to the longitudinal arm 20A, the design of the chair 100 is improved.

[0161] <Elastic member 23>

[0162] The elastic member 23 is supported on the lower surface 4L of the seat plate of the seat 1. The elastic member 23 is, for example, a known leaf spring. The elastic member 23 is, for example, a plate-shaped member formed of a synthetic resin or metal. The elastic member 23 is formed in a substantially L-shape when viewed in the right direction RD. The elastic member 23 has a longitudinal spring portion 23A and a transverse spring portion 23B. The spring structure constituting the elastic member 23 is not limited to a leaf spring. Known springs other than leaf springs can be applied to the elastic member 23.

[0163] The elastic member 23 having the above structure elastically deforms in the up-down direction UD, DD and the front-back direction FD, BD by the rotation of the backrest 2. The elastic member 23 is a member that applies the restoring force caused by the elastic deformation to the seat 1 and the backrest 2, and returns the seat 1 and the backrest 2 to the front limit position 81. Here, the elastic deformation generated in the elastic member 23 means that the elastic member 23 elastically deforms by the action of the force applied to the elastic member 23. This will be specifically described.

[0164] The state of the chair 100 in which the occupant does not press the backrest 2 with the back is set as the initial state.

[0165] The state of the chair 100 in which the occupant presses the backrest 2 with the back is set as the tilting state.

[0166] "The elastic member 23 elastically deforms" means that the elastic member 23 elastically deforms in the process of the state of the chair 100 changing from the initial state to the tilting state.

[0167] Here, in a state where the elastic member 23 is assembled to the chair 100, that is, in an initial state, elastic deformation can also be pre-generated in the elastic member 23. In other words, in a state where the elastic member 23 is assembled to the chair 100, the elastic member 23 can also apply a restoring force (initial reaction force) to the components constituting the chair 100.

[0168] <Support structure 3>

[0169] As Figure 1 shown, the support structure 3 supports the lower surface 4L of the seat plate of the seat 1 and the backrest 2. Thus, the support structure 3 supports the chair 100 on the ground FS. In the present embodiment, the support structure 3 supports the seat 1 via the lower surface 4L of the seat plate, but the support structure 3 may also support the seat 1 via a portion other than the lower surface 4L of the seat plate. For example, the support structure 3 may support the seat 1 via the side surface of the seat 1 in the left - right directions RD, LD.

[0170] The support structure 3 includes legs 30, a seat - bearing member 40, and a shaft - support mechanism 50.

[0171] <Legs 30>

[0172] As Figure 1 shown, the legs 30 are provided on the ground FS.

[0173] The legs 30 have multiple legs 31 with a plurality of casters 31a and a leg post 33 that stands up from the central portion of the multiple legs 31 and has a gas spring 32 as a lifting mechanism built therein. The leg post 33 has an inner cylinder 34 and an outer cylinder 35. The outer cylinder 35 is fitted and supported by the multiple legs 31 in a non - rotatable manner. The lower portion of the inner cylinder 34 can rotate about an axis parallel to the up - down directions UD, DD. In other words, the lower portion of the inner cylinder 34 is supported so as to be able to rotate relative to the outer cylinder 35. The upper portion of the inner cylinder 34 is fixed to a support 60 constituting the shaft - support mechanism 50.

[0174] As the gas spring 32, a known gas spring is used. The gas spring 32 has, for example, a cylinder 32A, a piston 32B, and a locking mechanism 32C. Compressed gas is filled in the cylinder 32A. The piston 32B can move in the cylinder 32A in the up - down directions UD, DD. The locking mechanism 32C is a mechanism for fixing the position of the piston 32B in the up - down directions UD, DD or releasing the fixed state of the position of the piston 32B. Specifically, the locking mechanism 32C has a locking - release protrusion 32D that protrudes upward from the gas spring 32. As Figure 4 shown, the locking - release protrusion 32D is in slidable contact with the pressing - force generating portion 12G of the pressing portion 12.

[0175] <Seat - bearing member 40>

[0176] AsFigure 2 , Figure 5 , Figure 7 , Figure 8 , Figure 12 and Figure 13 As shown in Figure 13 , the seat bearing member 40 is housed in the support mechanism housing portion 6 below the seat plate 4L. The size of the support mechanism housing portion 6 in the front-back direction FD, BD and the left-right direction RD, LD, that is, in the horizontal direction, is set according to the size of the seat bearing member 40. The depth 6D of the support mechanism housing portion 6 is set to be greater than the height 40H of the seat bearing member 40 in the up-down direction UD, DD.

[0177] In other words, the support mechanism housing portion 6 can house the seat bearing member 40 inside the support mechanism housing portion 6. When observed in the left-right direction RD, LD, the seat bearing member 40 overlaps with the seat main body 4.

[0178] The seat bearing member 40 is composed of a first seat bearing member 41 and a second seat bearing member 42.

[0179] The first seat bearing member 41 and the second seat bearing member 42 are each composed of a metal plate. For example, the first seat bearing member 41 and the second seat bearing member 42 are respectively formed by known sheet metal processing. As long as they are composed of strength members having sufficient strength to support a sitter sitting on the seat 1, the type of material forming the seat bearing member 40 or the thickness of the metal plate is not particularly limited.

[0180] <First seat bearing member 41>

[0181] The first seat bearing member 41 has a first plate main body 41A, a first right plate portion 41B, and a first left plate portion 41C.

[0182] The first plate main body 41A extends parallel to the front-back direction FD, BD or a direction inclined with respect to the front-back direction FD, BD. The first plate main body 41A is connected to the first right plate portion 41B and the first left plate portion 41C in the left-right direction RD, LD. Four through holes 41D are provided in the first plate main body 41A. The positions of the four through holes 41D in the first plate main body 41A correspond one-to-one to the positions of the four seat bearing fastening holes 6B formed in the support concave surface 6A. Using fastening members such as bolts (not shown), the first plate main body 41A is fastened to the support mechanism housing portion 6 and fixed to the seat main body 4.

[0183] As a fixing structure for fixing the first seat bearing member 41 to the seat main body 4, for example, a known fixing structure using screws is adopted. In addition, the fixing structure is not limited to screw fixing.

[0184] The first right plate portion 41B is a portion that extends downward in the downward direction DD from the right end portion 41E of the first plate main body 41A in the right direction RD. A first right front hole 41G and a first right rear hole 41H are formed in the first right plate portion 41B. In the front-rear direction FD, BD, the first right front hole 41G is a hole provided at a position more forward than the first right rear hole 41H. In other words, in the front-rear direction FD, BD, the first right rear hole 41H is a hole provided at a position more rearward than the first right front hole 41G.

[0185] The first left plate portion 41C is a portion that extends downward in the downward direction DD from the left end portion 41F of the first plate main body 41A in the left direction LD. A first left front hole 41I and a first left rear hole 41J are formed in the first left plate portion 41C. In the front-rear direction FD, BD, the first left front hole 41I is a hole provided at a position more forward than the first left rear hole 41J. In other words, in the front-rear direction FD, BD, the first left rear hole 41J is a hole provided at a position more rearward than the first left front hole 41I.

[0186] A first seat bearing space 41K is formed between the first right plate portion 41B and the first left plate portion 41C in the left-right direction RD, LD. In other words, the first seat bearing member 41 is formed in a substantially C-shaped form that opens downward in the downward direction DD. A second seat bearing member 42 is disposed in the first seat bearing space 41K. The distance between the first right plate portion 41B and the first left plate portion 41C in the left-right direction RD, LD is greater than the distance between the second right plate portion 42B and the second left plate portion 42C of the second seat bearing member 42.

[0187] <Second seat bearing member 42>

[0188] The second seat bearing member 42 has a second plate main body 42A, a second right plate portion 42B, and a second left plate portion 42C.

[0189] The second plate main body 42A extends parallel to the front-rear direction FD, BD or a direction inclined with respect to the front-rear direction FD, BD. The second plate main body 42A is connected to the second right plate portion 42B and the second left plate portion 42C in the left-right direction RD, LD. The second plate main body 42A is fixed to the elastic member 23 using fastening members such as bolts (not shown).

[0190] The second right plate portion 42B is a portion that extends upward in the upward direction UD from the right end portion 42E of the second plate main body 42A in the right direction RD. A second right front hole 42G and a second right rear hole 42H are formed in the second right plate portion 42B. In the front-rear direction FD, BD, the second right front hole 42G is a hole provided at a position more forward than the second right rear hole 42H. In other words, in the front-rear direction FD, BD, the second right rear hole 42H is a hole provided at a position more rearward than the second right front hole 42G.

[0191] The second left plate portion 42C is a portion that extends upward in the upward direction UD from the left end portion 42F of the second plate main body 42A in the left direction LD. A second left front hole 42I and a second left rear hole 42J are formed in the second left plate portion 42C. In the front-back direction FD, BD, the second left front hole 42I is a hole provided at a position more forward than the second left rear hole 42J. In other words, in the front-back direction FD, BD, the second left rear hole 42J is a hole provided at a position more rearward than the second left front hole 42I.

[0192] A second seat receiving space 42K is formed between the second right plate portion 42B and the second left plate portion 42C in the right-left direction RD, LD. In other words, the second seat receiving space 42K is formed in a substantially C-shaped form that opens upward in the upward direction UD.

[0193] As Figure 12 and Figure 13 shown, the seat receiving member 40 is constituted by combining the first seat receiving member 41 and the second seat receiving member 42 in such a manner that the first plate main body 41A and the second plate main body 42A face each other. In this structure, the front ends of the second right plate portion 42B and the second left plate portion 42C are in contact with the first plate main body 41A, thereby defining the gap between the first seat receiving member 41 and the second seat receiving member 42. This gap is an elastic member insertion hole 43 for inserting the elastic member 23. In other words, the elastic member insertion hole 43 is a hole that communicates with the space shared by the first seat receiving space 41K and the second seat receiving space 42K. The elastic member 23 inserted through the elastic member insertion hole 43 into the interior of the seat receiving member 40 reaches the second seat receiving space 42K and is fixed to the second plate main body 42A.

[0194] <Shaft support mechanism 50>

[0195] As Figure 1 , Figure 4 , Figure 5 and Figures 9 - 11 shown, the shaft support mechanism 50 includes a support connector 51, a support link 55, a support 60, a support cover 65, a first shaft portion 71, a second shaft portion 72, a third shaft portion 73, a fourth shaft portion 74, and a rotation restricting pin 75. The support connector 51 and the support link 55 are each constituted by a metal plate. For example, the support connector 51 and the support link 55 are respectively formed by known sheet metal processing. As long as they are constituted by strength members having sufficient strength for supporting a sitter sitting on the seat 1, the type of material forming the support connector 51 and the support link 55 or the thickness of the metal plate is not particularly limited.

[0196] <Support connector 51>

[0197] As Figure 9 , Figure 12 and Figure 13As shown, the support connector 51 has a connector connection plate portion 51A, a connector right plate portion 51B, and a connector left plate portion 51C.

[0198] The connector connection plate portion 51A extends parallel to the up-down direction UD, DD or a direction inclined with respect to the up-down direction UD, DD. The connector connection plate portion 51A is connected to the connector right plate portion 51B and the connector left plate portion 51C in the left-right direction RD, LD.

[0199] The support connector 51 is rotatably supported by the first shaft portion 71 and the third shaft portion 73, respectively. The support connector 51 supports the support arm portion 20. The support connector 51 can be detached from and attached to the arm portion 20. The support connector 51 is an example of an "arm support portion".

[0200] The connector right plate portion 51B is a portion that extends forward in the forward direction FD from the right end portion 52 of the connector connection plate portion 51A in the right direction RD. The connector right plate portion 51B has an upper right plate portion 51D, a lower right plate portion 51E, and a right connection plate portion 51F. The right connection plate portion 51F connects the upper right plate portion 51D and the lower right plate portion 51E. In the up-down direction UD, DD, the upper right plate portion 51D is located above the lower right plate portion 51E. A connector upper right hole 51G is formed in the upper right plate portion 51D. A connector lower right hole 51H is formed in the lower right plate portion 51E. The upper right plate portion 51D is a portion that is rotatably supported by the first shaft portion 71 and is an example of a "first connector support portion". The lower right plate portion 51E is a portion that is rotatably supported by the third shaft portion 73 and is an example of a "second connector support portion".

[0201] An arm engagement portion 51J that protrudes in the right direction RD from the right outer side surface 51I of the connector right plate portion 51B is formed in the connector right plate portion 51B. The arm engagement portion 51J has a circular shape in a cross section orthogonal to the left-right direction RD, LD. The arm engagement portion 51J is an example of an "arm engagement portion". The arm engagement portion 51J is a portion that engages with the first arm groove 27F of the first support arm 20F when connecting the support connector 51 and the first support arm 20F.

[0202] In addition, the lower right plate portion 51E has a right elongated hole 51K. The right elongated hole 51K is located between the connector connection plate portion 51A and the connector lower right hole 51H in the front-rear direction FD, BD. The right elongated hole 51K extends in the up-down direction UD, DD or a direction inclined with respect to the up-down direction UD, DD. The right elongated hole 51K is a portion into which the rotation restricting pin 75 is inserted.

[0203] The left plate portion 51C of the connector is a portion that extends from the left end portion 53 of the connector connection plate portion 51A on the left direction LD along the front direction FD. The left plate portion 51C of the connector has an upper left plate portion 51L, a lower left plate portion 51M, and a left connection plate portion 51N. The left connection plate portion 51N connects the upper left plate portion 51L and the lower left plate portion 51M. In the up-down direction UD, DD, the upper left plate portion 51L is located above the lower left plate portion 51M. A connector upper left hole 51O is formed in the upper left plate portion 51L. A connector lower left hole 51P is formed in the lower left plate portion 51M. The upper left plate portion 51L is a portion that is rotatably supported by the first shaft portion 71 and is an example of a "first connector support portion". The lower left plate portion 51M is a portion that is rotatably supported by the third shaft portion 73 and is an example of a "second connector support portion".

[0204] An arm engaging portion 51R that protrudes toward the left direction LD from the left outer side surface 51Q of the left plate portion 51C of the connector is formed in the left plate portion 51C of the connector. The arm engaging portion 51R has a circular shape in a cross section orthogonal to the left-right direction RD, LD. The arm engaging portion 51R is an example of an "arm engaging portion". The arm engaging portion 51R is a portion that engages with the second arm groove 27S of the second support arm 20S when connecting the support connector 51 and the second support arm 20S.

[0205] In addition, a left long hole 51S is formed in the lower left plate portion 51M. The left long hole 51S is located between the connector connection plate portion 51A and the connector lower left hole 51P in the front-back direction FD, BD. The left long hole 51S extends along the up-down direction UD, DD or a direction inclined with respect to the up-down direction UD, DD. The left long hole 51S is a portion into which the rotation restricting pin 75 is inserted.

[0206] A cutout portion 51X is formed between the upper right plate portion 51D and the lower right plate portion 51E of the support connector 51. Similarly, a cutout portion 51Y is formed between the upper left plate portion 51L and the lower left plate portion 51M. The cutout portions 51X, 51Y are formed in a substantially U shape when observed in the left-right direction RD, LD.

[0207] A connector space 51T is formed between the right plate portion 51B and the left plate portion 51C of the connector in the left-right direction RD, LD. A first seat bearing member 41, a second seat bearing member 42, a support link 55, and a seat 60 are arranged in the connector space 51T. The distance between the right plate portion 51B and the left plate portion 51C of the connector in the left-right direction RD, LD is greater than the distance between the first right plate portion 41B and the first left plate portion 41C of the first seat bearing member 41.

[0208] <Support link 55>

[0209] As Figure 12 and Figure 13As shown, the shaft support mechanism 50 has two support links 55. Specifically, the shaft support mechanism 50 has a right support link 56 on the right side in the left-right directions RD, LD and a left support link 57 on the left side. The right support link 56 and the left support link 57 are respectively parts parallel to the up-down directions UD, DD or directions inclined with respect to the up-down directions UD, DD.

[0210] The right support link 56 extends parallel to the up-down directions UD, DD or a direction inclined with respect to the up-down directions UD, DD. A link upper right hole 56U and a link lower right hole 56L are formed in the right support link 56. In the up-down directions UD, DD, the link upper right hole 56U is located above the link lower right hole 56L. The link upper right hole 56U is a part supported so as to be rotatable relative to the second shaft portion 72 and is an example of a "first link support portion". The link lower right hole 56L is a part supported so as to be rotatable relative to the fourth shaft portion 74 and is an example of a "second link support portion".

[0211] The left support link 57 extends parallel to the up-down directions UD, DD or a direction inclined with respect to the up-down directions UD, DD. A link upper left hole 57U and a link lower left hole 57L are formed in the left support link 57. In the up-down directions UD, DD, the link upper left hole 57U is located above the link lower left hole 57L. The link upper left hole 57U is a part supported so as to be rotatable relative to the second shaft portion 72 and is an example of a "first link support portion". The link lower left hole 57L is a part supported so as to be rotatable relative to the fourth shaft portion 74 and is an example of a "second link support portion".

[0212] <Support 60>

[0213] As Figure 10 , Figure 12 and Figure 13 shown, the support 60 has a box shape provided on the upper part of the leg 30. Specifically, the box shape of the support 60 extends parallel to the front-back directions FD, BD or a direction inclined with respect to the front-back directions FD, BD, has a width in the left-right directions RD, LD, and has a thickness in the up-down directions UD, DD. The support 60 supports the third shaft portion 73 and the fourth shaft portion 74 in a state of being provided on the upper part of the leg 30.

[0214] In the up-down directions UD, DD, the support 60 has a support lower surface 61 and a support upper surface 62. The support lower surface 61 forms the lower surface of the box shape. The support upper surface 62 forms the upper surface of the box shape.

[0215] In the left-right directions RD, LD, the support 60 has a support right side portion 63 and a support left side portion 64. The support right side portion 63 and the support left side portion 64 form two side surfaces of the box shape.

[0216] The lower surface 61 of the support extends parallel to a direction inclined with respect to the front-rear direction FD and BD. The lower surface 61 of the support is connected to the right support portion 63 and the left support portion 64 of the support. A leg connection portion 61A for connecting the outer cylinder 35 of the leg 30 is provided on the lower surface 61 of the support. In other words, the support 60 is supported by the leg 30 via the leg connection portion 61A.

[0217] A support opening 62A opening in the upward direction UD is formed in the upper surface 62 of the support. A support cover 65 is disposed on the upper surface 62 of the support so as to cover the support opening 62A.

[0218] A right link support portion 63A is formed in the right support portion 63 of the support. A right front hole 63B, a right rear hole 63C, and a right central hole 63D of the support are formed in the right support portion 63 of the support. The right rear hole 63C is formed in the right link support portion 63A. The right link support portion 63A is a portion recessed from the right support portion 63 of the support in the left direction LD. The right link support portion 63A opens in the upward direction UD, the rear direction BD, and the right direction RD. That is, the right link support portion 63A is a concave portion that houses a part of the right support link 56 in such a manner that the right link support portion 63A can tilt in the rear direction BD. For example, in a state where the right support link 56 is supported by the right link support portion 63A, a configuration in which the right support link 56 does not protrude from the right support portion 63 of the support in the right direction RD may also be employed.

[0219] In the front-rear direction FD and BD, the right central hole 63D of the support is located between the right front hole 63B and the right rear hole 63C of the support. The right front hole 63B is a portion that supports the third shaft portion 73 so as to be rotatable. The right rear hole 63C is a portion that supports the fourth shaft portion 74 so as to be rotatable. The right central hole 63D of the support is a portion that supports the rotation restricting pin 75.

[0220] A left link support portion 64A is formed in the left support portion 64 of the support. A left front hole 64B, a left rear hole 64C, and a left central hole 64D of the support are formed in the left support portion 64 of the support. The left rear hole 64C is formed in the left link support portion 64A. The left link support portion 64A is a portion recessed from the left support portion 64 of the support in the right direction RD. The left link support portion 64A opens in the upward direction UD, the rear direction BD, and the left direction LD. That is, the left link support portion 64A is a concave portion that houses a part of the left support link 57 in such a manner that the left link support portion 64A can tilt in the rear direction BD. For example, in a state where the left support link 57 is supported by the left link support portion 64A, a configuration in which the left support link 57 does not protrude from the left support portion 64 of the support in the left direction LD may also be employed.

[0221] In other words, in the left - right directions RD and LD, the distance between the concave surface forming the right link support portion 63A facing the right direction RD and the concave surface forming the left link support portion 64A facing the left direction LD is smaller than the distance between the right side portion 63 and the left side portion 64 of the support.

[0222] In the front - rear directions FD and BD, the left central hole 64D of the support is located between the left front hole 64B and the left rear hole 64C of the support. The left front hole 64B is the portion that supports the third shaft portion 73 so as to be rotatable. The left rear hole 64C is the portion that supports the fourth shaft portion 74 so as to be rotatable. The left central hole 64D of the support is the portion that supports the rotation restricting pin 75.

[0223] An axial support mechanism 50 for the leg column 33 is built - in inside the support 60.

[0224] Moreover, as Figure 4 shown, a part of the locking release protrusion 32D of the gas spring 32 and the pressing body 12A of the pressing portion 12 is located inside the support 60. Specifically, the pressing force generating portion 12G constituting the pressing portion 12 is located inside the support 60. In other words, inside the support 60, the locking release protrusion 32D and the pressing force generating portion 12G can slide relative to each other.

[0225] <Support cover 65>

[0226] As Figure 11 shown, the support cover 65 has a substantially plate - like shape. The support cover 65 is a member provided on the upper surface 62 of the support so as to cover the support opening 62A. The support cover 65 has a front cover portion 66 and a rear cover portion 67. According to the shapes of the right link support portion 63A and the left link support portion 64A formed on the support 60, the width of the rear cover portion 67 in the left - right directions RD and LD is smaller than the width of the front cover portion 66. The support cover 65 does not expose the internal structure of the support 60 externally.

[0227] On the upper surface of the front cover portion 66, a cover opening 68 and a mechanism support portion 69 are provided. The cover opening 68 penetrates the front cover portion 66. The mechanism support portion 69 has a pressing body support portion 69A, two side walls 69B, an outer tube fixing portion 69C, and an inner wire insertion portion 69D. The pressing body support portion 69A is provided between the two side walls 69B. The pressing body support portion 69A is the portion that supports the pressing support shaft 12B of the pressing portion 12.

[0228] That is to say, in a state where the support cover 65 is mounted on the support 60, the support cover 65 supports the pressing portion 12 so as to be rotatable.

[0229] In a state where the pressing support shaft 12B is supported by the pressing body support portion 69A, a part of the pressing portion 12 passes through the cover opening 68 and is exposed in the space above the front cover portion 66. When observed in the front-rear direction FD, BD, the pressing body support portion 69A overlaps with the two side walls 69B. That is, when observed in the front-rear direction FD, BD, the two side walls 69B prevent the pressing body support portion 69A from being exposed.

[0230] The outer tube fixing portion 69C is provided between the two side walls 69B. The outer tube fixing portion 69C is a portion for fixing the end portion of the outer tube 11A shown in Figure 4 . Thus, the state where the outer tube does not move from the support cover 65 is maintained.

[0231] The inner wire insertion portion 69D is provided between the two side walls 69B. The inner wire insertion portion 69D is a concave portion or a hole portion through which the inner wire 11B passes. The inner wire 11B can pass through the inner wire insertion portion 69D and move relative to the outer tube 11A.

[0232] That is, the support cover 65 not only prevents the internal structure of the support 60 from being exposed on the appearance, but also forms a part of the support mechanism for the wire structure 11 and the pressing portion 12.

[0233] <The first shaft portion 71, the second shaft portion 72, the third shaft portion 73, the fourth shaft portion 74, and the rotation restricting pin 75>

[0234] As shown in Figure 5 , the first shaft portion 71, the second shaft portion 72, the third shaft portion 73, the fourth shaft portion 74, and the rotation restricting pin 75 extend along the left-right direction RD, LD, respectively. Each of such shaft portions and pins is, for example, a shaft formed of a known solid rod-shaped member. A hole is formed at a portion rotatably connected to each of these four shaft portions. A bearing may also be disposed between each of the four shaft portions and the hole. Each of the four shaft portions is formed of a known metal rod, for example. As long as it is formed of a strength member having sufficient strength for supporting a sitter sitting on the seat 1, the type of material forming each of the four shaft portions or the diameter of the metal rod is not particularly limited.

[0235] In the present embodiment, the case where the first shaft portion 71, the second shaft portion 72, the third shaft portion 73, the fourth shaft portion 74, and the rotation restricting pin 75 are each a solid rod-shaped member has been described. The above-described shaft portions and pins are not limited to solid rod-shaped members. For example, a hollow rod-shaped member can also be applied to the above-described shaft portions and pins.

[0236] <Specific structure of the shaft support mechanism 50>

[0237] Refer to Figure 5 , Figure 6 , Figure 9 , Figure 12 andFigure 13 , the specific structure and operation of the shaft support mechanism 50 are described. Figure 12 and Figure 13 In FIG. 1 , the seat receiving member 40 fixed to the seat 1 is shown, but the seat 1 is omitted. Figure 12 The back support portion 21 is shown in a state where the back support portion 21 is located at the front limit position 81 within the tilting range 80 of the back support portion 21 . Figure 13 The figure shows a state where the back support portion 21 is located at the rear limit position 82 within the tilting range 80 of the back support portion 21 .

[0238] <Support Structure by First Shaft Portion 71>

[0239] In the direction in which the first shaft portion 71 extends, the upper left plate portion 51L of the supporting connector 51, the first left plate portion 41C of the first seat supporting component 41, the second left plate portion 42C of the second seat supporting component 42, the second right plate portion 42B of the second seat supporting component 42, the first right plate portion 41B of the first seat supporting component 41, and the upper right plate portion 51D of the supporting connector 51 are arranged in sequence from the upper left plate portion 51L of the supporting connector 51 toward the right direction RD.

[0240] Two adjacent members among the above-mentioned members supported by the first shaft portion 71 may be separated so as not to contact each other. For example, a spacer such as a resin may be disposed between the two members.

[0241] The first shaft portion 71 passes through the first right front hole 41G and the first left front hole 41I of the first seat receiving component 41, the second right front hole 42G and the second left front hole 42I of the second seat receiving component 42, and the connector upper right hole 51G and the connector upper left hole 51O of the supporting connector 51. In order to prevent the first shaft portion 71 from falling out of these six holes, for example, C-shaped rings may be engaged at both ends of the first shaft portion 71 in the left-right directions RD and LD. In addition, a large-diameter portion having a diameter larger than the diameters of the six holes may be provided at one end of the first shaft portion 71, and a C-shaped ring may be engaged with the other end of the first shaft portion 71. The structure for preventing the first shaft portion 71 from falling out is not particularly limited.

[0242] As a structure for preventing the first shaft portion 71 from falling off, for example, a structure using rivets can also be adopted. That is, one side of the first shaft portion 71 has a head, and the other side of the first shaft portion 71 has a straight portion. In this case, the diameter of the head is larger than the diameter of the hole through which the first shaft portion 71 is inserted. Specifically, after the straight portion of the first shaft portion 71 is passed through the hole, the straight portion is deformed by riveting (Japanese: 加締める). As a result, in the first shaft portion 71, a large diameter portion is formed on the side opposite to the head. The large diameter portion is larger than the diameter of the hole through which the first shaft portion 71 is inserted.

[0243] The first shaft portion 71 is a rod-shaped member that penetrates the above six holes. The first shaft portion 71 does not necessarily have to be a single rod-shaped member. The first shaft portion 71 may also be composed of a pair of shaft portions that share the same axis and are separated from each other. In this case, one of the pair of shaft portions penetrates the first right front hole 41G of the first seat bearing member 41, the second right front hole 42G of the second seat bearing member 42, and the connector upper right hole 51G of the support connector 51. The other of the pair of shaft portions penetrates the first left front hole 41I of the first seat bearing member 41, the second left front hole 42I of the second seat bearing member 42, and the connector upper left hole 51O of the support connector 51.

[0244] The first shaft portion 71 supports the seat bearing member 40 fixed to the seat 1 so as to be rotatable.

[0245] The first shaft portion 71 supports the support connector 51 so as to be rotatable independently of the seat bearing member 40. In other words, the seat bearing member 40 and the support connector 51 can rotate relative to the first shaft portion 71.

[0246] The first shaft portion 71 moves in the front-back directions FD, BD as the seat 1 moves in the front-back directions FD, BD.

[0247] <Support Structure Based on the Second Shaft Portion 72>

[0248] In the direction in which the second shaft portion 72 extends, from the left support link 57 toward the right direction RD, the left support link 57, the first left plate portion 41C of the first seat bearing member 41, the second left plate portion 42C of the second seat bearing member 42, the second right plate portion 42B of the second seat bearing member 42, the first right plate portion 41B of the first seat bearing member 41, and the right support link 56 are arranged in sequence toward the right direction RD.

[0249] Two adjacent components among the above components supported by the second shaft portion 72 may also be separated from each other in a non-contact manner. For example, a spacer such as resin may be disposed between the two components.

[0250] The second shaft portion 72 penetrates the first right rear hole 41H and the first left rear hole 41J of the first seat bearing member 41, the second right rear hole 42H and the second left rear hole 42J of the second seat bearing member 42, the link upper right hole 56U of the right support link 56, and the link upper left hole 57U of the left support link 57. In order to prevent the second shaft portion 72 from falling out of these six holes, for example, C-rings may be engaged with both ends of the second shaft portion 72 in the right-left directions RD, LD. Alternatively, a large-diameter portion having a diameter larger than the diameter of the six holes may be provided at one end of the second shaft portion 72, and the C-ring may be engaged with the other end of the second shaft portion 72. The structure for preventing the second shaft portion 72 from falling out is not particularly limited.

[0251] As a structure for preventing the second shaft portion 72 from falling off, for example, a structure using a rivet can also be adopted. That is, one side of the second shaft portion 72 has a head, and the other side of the second shaft portion 72 has a straight portion. In this case, the diameter of the head is larger than the diameter of the hole through which the second shaft portion 72 is inserted. Specifically, after passing the straight portion of the second shaft portion 72 through the hole, the straight portion is riveted to deform the straight portion. As a result, a large-diameter portion is formed on the second shaft portion 72 on the side opposite to the head. The large-diameter portion is larger than the diameter of the hole through which the second shaft portion 72 is inserted.

[0252] The second shaft portion 72 is a rod-shaped member that penetrates the six holes described above. The second shaft portion 72 does not necessarily have to be a single rod-shaped member. The second shaft portion 72 can also be composed of a pair of shaft portions that share the same axis and are separated from each other. In this case, one of the pair of shaft portions penetrates the first right rear hole 41H of the first seat bearing member 41, the second right rear hole 42H of the second seat bearing member 42, and the link upper right hole 56U of the right support link 56. The other of the pair of shaft portions penetrates the first left rear hole 41J of the first seat bearing member 41, the second left rear hole 42J of the second seat bearing member 42, and the link upper left hole 57U of the left support link 57.

[0253] The second shaft portion 72 supports the seat bearing member 40 fixed to the seat 1 so as to be rotatable.

[0254] The second shaft portion 72 supports the support link 55 so as to be rotatable independently of the seat bearing member 40. In other words, the seat bearing member 40 and the support link 55 can rotate relative to each other around the second shaft portion 72.

[0255] The second shaft portion 72 moves in the front-back directions FD, BD as the seat 1 moves in the front-back directions FD, BD.

[0256] <Support structure based on the third shaft portion 73>

[0257] In the direction in which the third shaft portion 73 extends, the second support arm 20S, the lower left plate portion 51M of the support connector 51, the left side portion 64 of the support base, the right side portion 63 of the support base, the lower right plate portion 51E of the support connector 51, and the first support arm 20F are arranged in order from the second support arm 20S toward the right direction RD.

[0258] Two adjacent components among the components supported by the third shaft portion 73 can also be separated from each other without contacting each other. For example, a spacer such as resin can be arranged between the two components.

[0259] The third shaft portion 73 is statically supported by the support base 60.

[0260] The third shaft portion 73 passes through the first shaft support hole 26F of the first support arm 20F, the second shaft support hole 26S of the second support arm 20S, the connector lower right hole 51H and the connector lower left hole 51P of the support connector 51, and the support right front hole 63B and the support left front hole 64B of the support 60. The third shaft portion 73 is fastened to the first support arm 20F and the second support arm 20S using fastening members such as bolts (not shown).

[0261] The third shaft portion 73 is a rod-shaped member that passes through the above-mentioned six holes. The third shaft portion 73 is not necessarily a rod-shaped member. The third shaft portion 73 can also be composed of a pair of shaft portions that share the same axis and are separate from each other. In this case, one of the pair of shaft portions passes through the first shaft support hole 26F of the first support arm 20F, the connector lower right hole 51H that supports the connector 51, and the support right front hole 63B of the support 60. The other of the pair of shaft portions passes through the second shaft support hole 26S of the second support arm 20S, the connector lower left hole 51P that supports the connector 51, and the support left front hole 64B of the support 60.

[0262] The third shaft portion 73 supports the support connector 51 and the traverse arm 20B so as to be rotatable relative to the bracket 60. Thus, the support connector 51 can tilt about the third shaft portion 73 in the front-rear directions FD and BD in conjunction with the rotation of the arm portion 20.

[0263] Furthermore, the third shaft portion 73 is located below the first shaft portion 71 in the up-down directions UD and DD.

[0264] <Support Structure Based on Fourth Shaft Portion 74>

[0265] In the direction in which the fourth shaft portion 74 extends, from the left support link 57 toward the right direction RD, the left support link 57, the left link support support portion 64A of the support 60, the right link support support portion 63A of the support 60, and the right support link 56 are arranged in sequence toward the right direction RD.

[0266] Two adjacent members among the above-mentioned members supported by the fourth shaft portion 74 may be separated so as not to contact each other. For example, a spacer such as a resin may be disposed between the two members.

[0267] The fourth shaft portion 74 is statically supported by the support 60 .

[0268] The fourth shaft portion 74 penetrates through the lower right connecting rod hole 56L of the right support connecting rod 56, the lower left connecting rod hole 57L of the left support connecting rod 57, the right rear support hole 63C of the support 60, and the left rear support hole 64C of the support 60. In order to prevent the fourth shaft portion 74 from falling out of these four holes, for example, C-rings can be engaged at both ends of the fourth shaft portion 74 in the left-right directions RD and LD. Additionally, a large-diameter portion having a diameter larger than the diameters of the four holes can be provided at one end of the fourth shaft portion 74, and the C-ring can be engaged with the other end of the fourth shaft portion 74. The structure for preventing the fourth shaft portion 74 from falling out is not particularly limited.

[0269] As a structure for preventing the fourth shaft portion 74 from falling out, for example, a structure using rivets can also be adopted. That is, one side of the fourth shaft portion 74 has a head, and the other side of the fourth shaft portion 74 has a straight portion. In this case, the diameter of the head is larger than the diameter of the hole through which the fourth shaft portion 74 passes. Specifically, after passing the straight portion of the fourth shaft portion 74 through the hole, the straight portion is riveted to cause the straight portion to deform. As a result, a large-diameter portion is formed on the fourth shaft portion 74 on the side opposite to the head. The large-diameter portion is larger than the diameter of the hole through which the fourth shaft portion 74 passes.

[0270] The fourth shaft portion 74 is a rod-shaped member that penetrates through the above four holes. The fourth shaft portion 74 does not necessarily have to be a single rod-shaped member. The fourth shaft portion 74 can also be composed of a pair of shaft portions that share the same axis and are separated from each other. In this case, one of the pair of shaft portions penetrates through the lower right connecting rod hole 56L of the right support connecting rod 56 and the right rear support hole 63C of the support 60. The other of the pair of shaft portions penetrates through the lower left connecting rod hole 57L of the left support connecting rod 57 and the left rear support hole 64C of the support 60.

[0271] The fourth shaft portion 74 supports the right support connecting rod 56 and the left support connecting rod 57 so as to be rotatable relative to the support 60. In other words, the support connecting rod 55 can rotate around the fourth shaft portion 74 so that the inclination deflection between the direction in which the support connecting rod 55 extends and the up-down directions UD and DD changes. Moreover, the fourth shaft portion 74 is located more rearward than the third shaft portion 73 in the front-rear directions FD and BD.

[0272] <Rotation restricting pin 75>

[0273] The rotation limiting pin 75 is statically supported by the support 60. Specifically, the rotation limiting pin 75 passes through the right central hole 63D and the left central hole 64D of the support 60, the right elongated hole 51K of the connector right plate portion 51B, and the left elongated hole 51S of the connector left plate portion 51C. In order to prevent the rotation limiting pin 75 from falling out of these four holes, for example, C-rings can be engaged at both ends of the rotation limiting pin 75 in the left-right directions RD and LD. Alternatively, a large-diameter portion having a diameter larger than the diameters of the four holes can be provided at one end of the rotation limiting pin 75, and the C-ring can be engaged with the other end of the rotation limiting pin 75. The structure for preventing the rotation limiting pin 75 from falling out is not particularly limited. In the following description, the right elongated hole 51K and the left elongated hole 51S may sometimes be simply referred to as the elongated hole 51Z.

[0274] According to the shape of the elongated hole 51Z in the up-down directions UD and DD, the tilting range 80 of the back support portion 21 in the front-back directions FD and BD is defined. In other words, as the support connector 51 rotates, the position of the rotation limiting pin 75 relative to the elongated hole 51Z changes. For example, as Figure 12 shown, when the rotation limiting pin 75 is located at the lower part of the elongated hole in the elongated hole 51Z, in the tilting range 80, the back support portion 21 is located at the front limit position 81. Conversely, as Figure 13 shown, when the rotation limiting pin 75 is located at the upper part of the elongated hole in the elongated hole 51Z, in the tilting range 80, the back support portion 21 is located at the rear position. Thus, the tilting range 80 of the back support portion 21 is defined by the elongated hole 51Z.

[0275] <Combined structure of the support connector 51 and the arm portion 20>

[0276] As Figure 5 , Figure 6 and Figure 9 shown, the right arm engaging portion 51J of the support connector 51 is fitted into the first arm groove 27F of the first support arm 20F. Similarly, the left arm engaging portion 51R of the support connector 51 is fitted into the second arm groove 27S of the second support arm 20S. Thereby, the support connector 51 is connected to the arm portion 20.

[0277] In such a connection structure, the position of the first shaft support hole 26F coincides with the position of the lower right hole 51H of the connector, and the position of the second shaft support hole 26S coincides with the position of the lower left hole 51P of the connector.

[0278] <Method of combining the support connector 51 and the arm portion 20>

[0279] Next, with reference to Figure 6 , Figure 14A and Figure 14B , the method of combining the arm portion 20 and the support connector 51 will be described. Figure 14A andFigure 14B corresponding to Figure 6 . In Figure 14A and Figure 14B In the example shown, the extending direction 20E in which the first support arm 20F extends is inclined with respect to the front-back direction FD, BD, but the extending direction 20E does not necessarily need to be inclined with respect to the front-back direction FD, BD. As long as the support connector 51 can be easily coupled to the arm portion 20, the extending direction 20E can be parallel to the front-back direction FD, BD or can be parallel to the up-down direction UD, DD.

[0280] First, as Figure 14A shown, the support connector 51 is inserted into the space between the first support arm 20F and the second support arm 20S, and the right arm engaging portion 51J is inserted into the obliquely opening slot 28A of the first arm slot 27F, and the left arm engaging portion 51R is inserted into the obliquely opening slot 28A of the second arm slot 27S.

[0281] The right arm engaging portion 51J moves in the obliquely opening slot 28A of the first support arm 20F toward the slot inclination direction 29A. Inside the obliquely opening slot 28A, the right arm engaging portion 51J faces the two obliquely slot walls 28N1, 28N2 respectively and moves inside the obliquely opening slot 28A. The right arm engaging portion 51J sometimes contacts the two obliquely slot walls 28N1, 28N2 respectively. That is, the two obliquely slot walls 28N1, 28N2 respectively guide the right arm engaging portion 51J, restrict the moving direction of the right arm engaging portion 51J, and cause the right arm engaging portion 51J to move toward the slot inclination direction 29A. After that, the right arm engaging portion 51J reaches the end of the obliquely opening slot 28A in the slot inclination direction 29A, that is, the front-back extending slot 28B of the first support arm 20F.

[0282] At the same time as the movement of the right arm engaging portion 51J in the obliquely opening slot 28A, the left arm engaging portion 51R moves in the obliquely opening slot 28A of the second support arm 20S toward the slot inclination direction 29A. Inside the obliquely opening slot 28A, the left arm engaging portion 51R faces the two obliquely slot walls 28N1, 28N2 respectively and moves inside the obliquely opening slot 28A. The right arm engaging portion 51J sometimes contacts the two obliquely slot walls 28N1, 28N2 respectively. That is, the two obliquely slot walls 28N1, 28N2 respectively guide the left arm engaging portion 51R, restrict the moving direction of the left arm engaging portion 51R, and cause the left arm engaging portion 51R to move toward the slot inclination direction 29A. After that, the left arm engaging portion 51R reaches the end of the obliquely opening slot 28A in the slot inclination direction 29A, that is, the front-back extending slot 28B of the second support arm 20S.

[0283] Next, the right - arm engaging portion 51J moves in the front - and - rear extending groove 28B of the first support arm 20F toward the groove - extending direction 29B. Inside the front - and - rear extending groove 28B, the right - arm engaging portion 51J faces the two extending groove walls 28M1 and 28M2 respectively and moves inside the front - and - rear extending groove 28B. The right - arm engaging portion 51J sometimes contacts the two extending groove walls 28M1 and 28M2 respectively. That is to say, the two extending groove walls 28M1 and 28M2 respectively guide the right - arm engaging portion 51J, restrict the moving direction of the right - arm engaging portion 51J, and cause the right - arm engaging portion 51J to move in the groove - extending direction 29B. After that, the right - arm engaging portion 51J reaches the end of the front - and - rear extending groove 28B in the groove - extending direction 29B, that is, Figure 6 the groove inner part 28C of the first support arm 20F shown. In a state where the right - arm engaging portion 51J contacts the groove inner part 28C of the first support arm 20F, the right - arm engaging portion 51J and the first support arm 20F are positioned. In other words, the support connector 51 is connected to the first support arm 20F. In this state, the first shaft support hole 26F of the first support arm 20F and the third shaft portion 73 are fixed. Thus, the first support arm 20F can rotate around the third shaft portion 73.

[0284] At the same time as the movement of the left - arm engaging portion 51R in the front - and - rear extending groove 28B, the left - arm engaging portion 51R moves in the front - and - rear extending groove 28B of the second support arm 20S toward the groove - extending direction 29B. Inside the front - and - rear extending groove 28B, the left - arm engaging portion 51R faces the two extending groove walls 28M1 and 28M2 respectively and moves inside the front - and - rear extending groove 28B. The left - arm engaging portion 51R sometimes contacts the two extending groove walls 28M1 and 28M2 respectively. That is to say, the two extending groove walls 28M1 and 28M2 respectively guide the left - arm engaging portion 51R, restrict the moving direction of the left - arm engaging portion 51R, and cause the left - arm engaging portion 51R to move in the groove - extending direction 29B. After that, the left - arm engaging portion 51R reaches the end of the front - and - rear extending groove 28B in the groove - extending direction 29B, that is, Figure 6 the groove inner part 28C of the second support arm 20S shown. In a state where the left - arm engaging portion 51R contacts the groove inner part 28C of the second support arm 20S, the left - arm engaging portion 51R and the second support arm 20S are positioned. In other words, the support connector 51 is connected to the second support arm 20S. In this state, the second shaft support hole 26S of the second support arm 20S and the third shaft portion 73 are fixed. Thus, the second support arm 20S can rotate around the third shaft portion 73.

[0285] Thus, when the positional relationships of the arm portion 20 with respect to the front-back direction FD, BD and the up-down direction UD, DD of the support connector 51 are determined, the positional relationships of the elastic member support portion 24 integrated with the arm portion with respect to the front-back direction FD, BD and the up-down direction UD, DD of the seat receiving member 40 supported by the support connector 51 are determined. In this state, the elastic member 23 is connected to the elastic member support portion 24 and the seat receiving member 40. At this time, it is preferable to set the shape of the elastic member 23 in such a manner that an initial reaction force is generated in the elastic member 23. For example, it is preferable to set the shape of the elastic member 23 in such a manner that the angle formed between the longitudinal spring portion 23A and the transverse spring portion 23B which is L-shaped in side view changes.

[0286] In other words, in the state where the assembly of the arm portion 20 and the support connector 51 is completed, the elastic member 23 is attached to the arm portion 20. In this case, since deformation (initial reaction force) is generated in the elastic member 23, the elastic member 23 can be preferably attached to the arm portion 20.

[0287] By the above-described coupling method, the arm portion 20 having the first support arm 20F and the second support arm 20S can be connected to the support connector 51. Conversely, by releasing the fixed state of the first shaft support hole 26F and the second shaft support hole 26S with respect to the third shaft portion 73 and removing the right arm engaging portion 51J from the first arm groove 27F and removing the left arm engaging portion 51R from the second arm groove 27S, the support connector 51 can be removed from the arm portion 20.

[0288] That is, in the above-described coupling structure, the support connector 51 can be detached from and attached to the arm portion 20.

[0289] <Distance relationship among the first shaft portion 71, the second shaft portion 72, the third shaft portion 73, and the fourth shaft portion 74>

[0290] In the direction from the first shaft portion 71 toward the third shaft portion 73, the distance between the first shaft portion 71 and the third shaft portion 73 is defined as the first distance L1.

[0291] In the direction from the second shaft portion 72 toward the fourth shaft portion 74, the distance between the second shaft portion 72 and the fourth shaft portion 74 is defined as the second distance L2. Here, the first distance L1 is larger than the second distance L2.

[0292] <Positional relationship of the support link 55 with respect to the first shaft portion 71 and the third shaft portion 73>

[0293] The support link 55 having such a structure is located at a position more rearward than the first shaft portion 71 and the third shaft portion 73 in the front-back direction FD, BD. In other words, the support link 55 is located between the first shaft portion 71 and the back receiving portion 21, or between the third shaft portion 73 and the back receiving portion 21.

[0294] <Function of the support structure 3>

[0295] In the chair 100 of the above-described embodiment, when the seated person sits on the seat 1, if the seated person presses the back support portion 21 with the back facing the rearward direction BD, the arm portion 20 rotates about the third shaft portion 73 in conjunction with the movement of the back support portion 21. As the arm portion 20 rotates, the support connector 51 supporting the arm portion 20 also rotates about the third shaft portion 73. As the support connector 51 rotates, the support connector 51 supporting the arm portion 20 also rotates about the third shaft portion 73. The first shaft portion 71 supported by the support connector 51 moves in the rearward direction BD while rotating about the third shaft portion 73. The seat 1 supported by the first shaft portion 71 moves in the rearward direction BD. As the seat 1 moves, the second shaft portion 72 supporting the seat 1 so as to be rotatable also moves in the rearward direction BD. The second shaft portion 72 is rotatably supported by the support link. The support link rotates about the fourth shaft portion 74. That is, the second shaft portion 72 moves in the rearward direction BD while rotating about the fourth shaft portion 74. Therefore, the seat 1 supported by the first shaft portion 71 and the second shaft portion 72 moves in the rearward direction BD in a manner that describes a trajectory that combines the rotation of the support connector 51 around the third shaft portion 73 and the rotation of the support link around the fourth shaft portion 74. At this time, the support 60 that supports the third shaft portion 73 and the fourth shaft portion 74 does not move in the front-rear directions FD and BD. In other words, the seat 1, the first shaft portion 71, and the second shaft portion 72 move relative to the support 60 toward the rearward direction BD.

[0296] According to the chair 100 of this embodiment, when the seated person presses the back support portion 21 in the rearward direction BD, the back support portion 21 tilts relative to the up and down directions UD and DD. As the back support portion 21 tilts, the seat 1 can be moved in the rearward direction BD relative to the support 60, that is, the seat 1 can be directly pulled in the rearward direction BD.

[0297] Furthermore, since the support link 55 is located further back in the direction BD than the first shaft portion 71 and the third shaft portion 73 in the front-rear directions FD and BD, it is not necessary to arrange the support link 55 in front of the front-rear directions FD and BD. Therefore, the support structure 3 can be miniaturized, and the space in front of the front-rear directions FD and BD in the space where the seat plate lower surface 4L of the seat 1 is exposed becomes larger, and the space occupied by the support structure 3 arranged on the seat plate lower surface 4L of the seat 1 can be reduced. That is, a larger space can be ensured on the seat plate lower surface 4L of the seat 1, and the design of the chair 100 can be improved.

[0298] In addition, the seat 1 is supported by a second shaft portion 72 located in a rearward direction BD with respect to the first shaft portion 71 so as to be rotatable. The second shaft portion 72 is not directly connected to the backrest 2 but is supported by a support link 55. Therefore, a state is formed in which the downward movement range of the second shaft portion 72 is restricted. In other words, by restricting the rotation range of the support link 55, the downward movement range of the second shaft portion 72 is restricted. In addition, since the height of the support link 55 is also restricted, the downward movement range of the second shaft portion 72 is restricted. In a state where the movement of the second shaft portion 72 is restricted in this way, the second shaft portion 72 is supported so as to be tiltable in the rearward direction BD and the downward direction DD. Therefore, the tilting of the seat 1 in the rearward direction BD and the downward direction DD is not affected by the tilting of the backrest 2. Therefore, by appropriately setting the height of the support link 55 and the rotation range of the support link 55, it is possible to suppress an excessive tilting amount of the support link 55 in the rearward direction BD and the downward direction DD of the seat 1.

[0299] In the chair 100 according to the present embodiment, when the back receiving portion 21 is located at the front limit position 81, a state is formed in which the support link 55 does not tilt in the rearward direction BD. Therefore, even when the back receiving portion 21 reaches the rear limit position 82, it is possible to reduce the movement amount of the support link 55 in the rearward direction BD and the downward direction DD. It is possible to suppress an excessive tilting amount of the support link 55 in the rearward direction BD and the downward direction DD of the seat 1.

[0300] In the chair 100 according to the present embodiment, since the first distance L1 is larger than the second distance L2, it is possible to suppress an excessive tilting amount of the support link 55 in the rearward direction BD and the downward direction DD of the seat 1.

[0301] In the chair 100 according to the present embodiment, in the vertical direction UD, DD, the position of the second shaft portion 72 is located above the position of the third shaft portion 73, so it is possible to suppress an excessive tilting amount of the support link 55 in the rearward direction BD and the downward direction DD of the seat 1.

[0302] In the chair 100 according to the present embodiment, the seat 1 has a support mechanism storage portion 6 provided below the seat plate 4L. The first shaft portion 71 and the second shaft portion 72 are stored inside the support mechanism storage portion 6. Therefore, when viewed from the front-rear direction FD, BD and the left-right direction RD, LD, the first shaft portion 71 and the second shaft portion 72 do not protrude outside the support mechanism storage portion 6. Therefore, in terms of the appearance of the chair 100, the designability can be improved.

[0303] In the chair 100 according to the present embodiment, the seat 1 has a seat main body 4, and the seat main body 4 has a lower surface 4L of the seat plate in which a support mechanism housing portion 6 is formed. The support structure 3 has a seat bearing member 40 housed inside the support mechanism housing portion 6. The seat bearing member 40 supports the first shaft portion 71 and the second shaft portion 72, and when viewed in the left-right direction RD, LD, the seat bearing member 40 overlaps with the seat main body 4. That is, the depth 6D of the support mechanism housing portion 6 is greater than the height 40H of the seat bearing member 40. Therefore, when viewed from the front-rear direction FD, BD and the left-right direction RD, LD, the seat bearing member 40 that supports the first shaft portion 71 and the second shaft portion 72 does not protrude outside the support mechanism housing portion 6. Therefore, in terms of the appearance of the chair 100, the designability can be improved.

[0304] Moreover, in the operation of assembling the above components that make up the chair 100, the operation of first axially supporting the backrest 2 and the seat bearing member 40 with each other and then housing the seat bearing member 40 in the seat main body 4 can be performed. Thereby, the assembly operation can be simply performed.

[0305] In the chair 100 according to the present embodiment, cutout portions 51X, 51Y are formed in the support connector 51. Therefore, a larger space can be ensured below the seat 1, and the designability can be improved.

[0306] <Method of adjusting the height of the seat 1 using the operation mechanism 5>

[0307] Next, a method of adjusting the height of the seat 1 using the operation mechanism 5 will be described.

[0308] The method of adjusting the height of the seat 1 is performed through the following steps.

[0309] [1] Step 1: By rotating the lever 10D by the person sitting on the chair, the locked state of the gas spring 32 is released.

[0310] [2] Step 2: The downward movement of the seat in the downward direction DD or the upward movement of the seat in the upward direction UD

[0311] [3] Step 3: The downward movement of the seat in the downward direction DD or the upward movement of the seat in the upward direction UD

[0312] Next, Steps 1 to 3 will be described in sequence.

[0313] <Step 1>

[0314] First, in the initial state of the chair 100, the position of the seat 1 is fixed. Specifically, in the gas spring 32 that makes up the chair 100, the lock release protrusion 32D is not pressed. Therefore, the locking mechanism 32C fixes the position of the piston 32B in the up-down direction UD, DD, that is, the position of the seat 1 is fixed. In this state, Step 1 is performed.

[0315] While the sitter is seated on the chair 100, the sitter moves the lever 10D shown in the figure in the rotational operation direction 85 with a finger. As a result, the lever 10D rotates around the lever support shaft 10A, and the wire support portion 10C of the lever plate 10B rotates in the rotational operation direction 85. At this time, a moment based on the lever principle is generated, and a force greater than the force applied by the sitter to the lever 10D acts on the wire support portion 10C. This force acts on the first wire engagement end 11F connected to the wire support portion 10C and the inner wire 11B connected to the first wire engagement end 11F, and the inner wire 11B moves in the stretching direction 86. Figure 3 As shown in the figure, as the inner wire 11B moves, the second wire engagement end 11S connected to the inner wire 11B moves in the stretching direction 86. Further, the pressing engagement portion 12C engaged with the second wire engagement end 11S moves in the stretching direction 86. As a result, the pressing force generating portion 12G rotates around the pressing support shaft 12B in the rotational pressing direction 87. At this time, a moment based on the lever principle is generated, and a force greater than the tensile force applied to the inner wire 11B in the stretching direction 86 acts on the pressing force generating portion 12G. This force presses the locking release projection 32D of the gas spring 32 in the downward direction DD. As a result, the locked state of the gas spring 32 is released.

[0316] As Figure 4 shown, as the inner wire 11B moves, the second wire engagement end 11S connected to the inner wire 11B moves in the stretching direction 86. Further, the pressing engagement portion 12C engaged with the second wire engagement end 11S moves in the stretching direction 86. As a result, the pressing force generating portion 12G rotates around the pressing support shaft 12B in the rotational pressing direction 87. At this time, a moment based on the lever principle is generated, and a force greater than the tensile force applied to the inner wire 11B in the stretching direction 86 acts on the pressing force generating portion 12G. This force presses the locking release projection 32D of the gas spring 32 in the downward direction DD. As a result, the locked state of the gas spring 32 is released.

[0317] <Step 2>

[0318] When the locking release projection 32D is pressed, the fixed state of the position of the locking mechanism 32C is released. In a state where the fixed state of the position of the locking mechanism 32C is released, an upward force that causes the piston 32B to move in the upward direction UD is generated by the action of the compressed gas filled in the cylinder 32A of the gas spring 32. In this state, the sitter adjusts the height of the seat 1.

[0319] To lower the seat 1 in the downward direction DD, the sitter presses the seat 1 in the downward direction DD using their body weight or the like. Specifically, by making the pressing force greater than the upward force of the gas spring 32, the seat 1 can be easily lowered.

[0320] To raise the seat 1 in the upward direction UD, the sitter does not apply a force to the seat 1, and by using the upward force of the gas spring 32, the seat 1 can be easily raised.

[0321] <Step 3>

[0322] The operator releases the rotation of the lever 10D in the rotational operation direction 85. As a result, the pressing state of the locking release projection 32D is released. The locking mechanism 32C fixes the piston 32B in the gas spring 32. As a result, the position of the seat 1 is fixed.

[0323] <Effect obtained by the operating mechanism 5>

[0324] In the chair 100 equipped with the above-described operating mechanism 5, the air spring 32 can be operated using the wire structure 11. That is, it is not necessary to use the operation of a rod as in the prior art. In particular, since the flexible wire structure 11 is used, even if there are essential components constituting the chair 100 in the layout of the components disposed on the lower surface 4L of the seat plate, the arrangement of the wire structure 11 can be freely set so as to avoid such essential components. That is, regarding the layout of the lower surface 4L of the seat plate, the degree of freedom in arranging the rod 10D is increased.

[0325] Furthermore, moments based on the lever principle are generated at two locations. Therefore, the sitter can easily adjust the height of the air spring 32 with a small force.

[0326] Conventionally, the locking state of the air spring is released by lifting a rod located below the lower surface of the plate, and the height of the seat is adjusted. For example, when lowering the position of the seat, the direction in which the rod is lifted is different from the vertical direction in which the seat moves. Therefore, there is a problem of low operability.

[0327] In contrast, according to the present embodiment, the rotational operation direction 85 of the rod 10D is the horizontal direction. That is, by moving the rod 10D in a direction orthogonal to the vertical directions UD and DD of the seat 1, the force generated by the rod 10D operated in the horizontal direction can be transmitted to the air spring 32 by utilizing the moments generated at two locations, and the height of the seat 1 can be adjusted.

[0328] In addition, in the conventional structure using a rod, the rod protrudes from the support structure 3 in the left-right directions RD and LD. In this case, there is a problem of deterioration in the design of the chair 100.

[0329] In contrast, according to the present embodiment, since a rod is not used, the design of the chair 100 as viewed from the left-right directions RD and LD can be improved.

[0330] In addition, in the conventional structure using a rod, the rod located far from the lower surface 4L of the seat plate is operated. Therefore, when the sitter operates the rod, it is necessary to stretch the fingers into the space below the lower surface 4L of the seat plate and grope with the hand to confirm the position of the rod. Therefore, the operability is low.

[0331] In contrast, according to the present embodiment, when the sitter operates the rod 10D, while placing the fingers on the shape of the lower surface 4L of the seat plate, the sitter confirms the position of the rod 10D and operates the rod 10D. In other words, the lower surface 4L of the seat plate functions as a guiding surface for guiding the movement of the fingers, and the operability of the rod 10D is improved.

[0332] Moreover, the wire structure 11 is composed of an outer tube 11A, an inner wire 11B, a first wire engaging end 11F, and a second wire engaging end 11S. The wire structure 11 is a unit. By simply removing the operation unit cover 13, removing the first wire engaging end 11F from the wire support portion 10C, and removing the second wire engaging end 11S from the pressing engagement portion 12C, the wire structure 11 can be removed from the chair 100. Therefore, the replacement operation of the wire structure 11 can be easily performed.

[0333] Moreover, the operation mechanism 5 has a lever 10D that can rotate in the rotation operation direction 85. Therefore, the size of the operation mechanism 5 that rotates the lever 10D expands in the front-rear direction FD, BD and the left-right direction RD, LD, but thins in the up-down direction UD, DD. That is, it is not necessary to increase the size of the operation mechanism 5 of the seat main body 4, which is a plate-like member, in the up-down direction UD, DD, and the thickness of the seat main body 4 can be reduced.

[0334] Although the preferred embodiments of the present invention have been described, it should be understood that these are exemplary examples of the present invention and should not be regarded as limiting. Additions, omissions, substitutions, and other changes can be made without departing from the scope of the present invention. Therefore, the present invention should not be regarded as limited by the foregoing description, but is limited by the claims.

[0335] In addition, in the above-described embodiment, the chair 100 without armrests has been described. When the chair 100 is provided with armrests, the armrests extend upward in the UD direction from both side portions on the lower side of the seat 1. The armrests support the elbows and the front ends of the arms of the seated person.

[0336] Description of reference numerals

[0337] 1 ··· Seat

[0338] 2 ··· Backrest

[0339] 3 ··· Support structure

[0340] 4 ··· Seat main body

[0341] 5 ··· Operation mechanism

[0342] 100 ··· Chair.

Claims

1. A chair, comprising: A seat; A backrest that can tilt relative to the seat; and A support structure that supports the seat and the backrest, The backrest has: An arm portion supported by the support structure; and A back receiving portion located above the arm portion in the vertical direction and supported by the arm portion, The support structure includes: A first shaft portion extending in a first direction intersecting the vertical direction and supporting the seat so as to be rotatable; A second shaft portion located rearward of the first shaft portion in a second direction intersecting the vertical direction and the first direction, extending in the first direction, and supporting the seat so as to be rotatable; A third shaft portion located below the first shaft portion in the vertical direction, extending in the first direction, and supporting the arm portion so as to be rotatable; A fourth shaft portion located rearward of the third shaft portion in the second direction and extending in the first direction; A support base that supports the third shaft portion and the fourth shaft portion; An arm support portion rotatably supported by each of the first shaft portion and the third shaft portion, capable of tilting relative to the second direction in a manner linked to the rotation of the arm portion around the third shaft portion, and supporting the arm portion; and A support link having a first link support portion and a second link support portion, the first link support portion rotatably supported by the second shaft portion, the second link support portion rotatably supported by the fourth shaft portion, and the support link located rearward of the first shaft portion and the third shaft portion in the second direction.

2. The chair according to claim 1, wherein The backrest can tilt relative to the seat within a tilting range between a front limit position and a rear limit position in the second direction, When the backrest is in the front limit position, the support link stands upright in the vertical direction, or the support link is inclined relative to the vertical direction such that the second shaft portion is located forward of the fourth shaft portion in the second direction.

3. The chair according to claim 2, wherein A first distance between the first shaft portion and the third shaft portion is greater than a second distance between the second shaft portion and the fourth shaft portion.

4. The chair according to claim 3, wherein In the vertical direction, the position of the second shaft portion is located above the position of the third shaft portion.

5. The chair according to any one of claims 1-4, wherein The seat has a lower surface in the vertical direction and a recess provided on the lower surface, The first shaft portion and the second shaft portion are received inside the recess.

6. The chair according to claim 5, wherein The seat has a seat main body having the lower surface formed with the recess, The support structure has a seat receiving member received inside the recess, The seat receiving member supports the first shaft portion and the second shaft portion, When observed in the first direction, the seat bearing member overlaps with the seat main body.

7. The chair according to claim 1, wherein the arm support portion is a support connector that can be disassembled and assembled relative to the arm portion.

8. The chair according to claim 7, wherein the support connector has: a first connector support portion that is rotatably supported by the first shaft portion; a second connector support portion that is rotatably supported by the third shaft portion; and a notch portion that is provided between the first connector support portion and the second connector support portion and is formed in a substantially U-shape when observed in the first direction.

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