chair

Abstract

To allow an attachment structure for attaching a lumbar support to be inconspicuous in a backrest support body.SOLUTION: A backrest support body includes a supporter part 43 and a backrest body is supported by the supporter part 43. A lumbar support 61 is supported by the supporter part 43. The lumbar support 61 includes: a support body 62 extending in a right and left direction of the backrest body; and supporting bodies 63 for allowing the support body 62 to be supported by the supporter part 43. The supporter part 43 includes a first plate part 56 and a second plate part 57. Each of the supporting bodies 63 includes: a first support member 66 having a first outside support wall 74; and a second support member 67 having a second outside support wall 77. The supporter part 43 is held between the first outside support wall 74 and the second outside support wall 77 in a support area of each one of the supporting bodies 63.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a chair having a backrest structure with lumbar support. [Background technology]

[0002] As shown in Patent Document 1 and the like, some chairs have a lumbar support attached to the backrest. The lumbar support can be attached to the backrest later, and is also configured to be removable. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6566543 Summary of the Invention [Problem to be solved by the invention]

[0004] The mounting structure for attaching the lumbar support to the backrest must also be designed to accommodate use when the chair's lumbar support is not attached. For this reason, from the perspective of improving design, it is desirable for the backrest to be designed so that the configuration and structure related to the lumbar support attachment are not visible from the outside when the chair's lumbar support is not attached. [Means for solving the problem]

[0005] The chair that solves the above problem is a chair that includes a backrest structure, the backrest structure being a backrest support connected to a seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support that is supported by the support pillar and is disposed between the support pillar and the backrest body, the lumbar support including a support body extending in the left-right direction of the backrest body, and and a support body that supports the support main body on the support column portion, the support column portion having a first outer surface and a second outer surface facing in a direction different from the first outer surface, the support body having a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface, and in the support region of the support body on the support column portion, the first outer support wall and the second outer support wall sandwich the support column portion.

[0006] According to the above-described configuration, the lumbar support is supported by the support body sandwiching the support area of ​​the support pole, so that the structure for attaching the lumbar support to the support pole can be configured to be less noticeable in appearance.

[0007] In the chair, the support pillar may include an engaging portion in which the outer surface width between the first outer surface and the second outer surface of the support pillar is larger than the support opening width between the tip of the first outer support wall and the tip of the second outer support wall of the support, and the first outer support wall and the second outer support wall are positioned to cover the engaging portion. According to the above configuration, the first outer support wall and the second outer support wall are positioned to cover the engaging portion, allowing a lumbar support to be attached to the support pillar.

[0008] In the above chair, the support portion comprises a first plate portion having the first outer surface and a second plate portion having the second outer surface, the first plate portion and the second plate portion being connected at the base end side, and configured so that the outer surface widths of the tip portions of the first outer surface and the second outer surface are wider than the base end side, the tip portions of the first outer surface and the second outer surface are the engaging portions, and the first support member and the second support member may be connected to cover the engaging portions from each tip side or base end side of the first plate portion, sandwiching the first outer surface and the second outer surface.

[0009] According to the above configuration, the first support member and the second support member cover the engagement portion from the tip or base end side of the first plate portion and sandwich the first outer surface and the second outer surface, thereby allowing the lumbar support to be attached to the support portion.

[0010] In the above chair, the support portion may comprise a first plate portion having the first outer surface and a second plate portion having the second outer surface, the first plate portion and the second plate portion being connected at the base end, the outer surface width of the apex at the base end side of the respective tips of the first outer surface and the second outer surface being wider than the outer surface width of the tip portion of the first outer surface and the tip portion of the second outer surface, the apex being the engaging portion, and the first support member and the second support member being connected to cover the engaging portion from the respective tip side or base end side of the first plate portion and sandwich the first outer surface and the second outer surface.

[0011] With the above configuration, the first support member and the second support member can cover the engagement portion from the tip or base end side of the first plate portion and sandwich the first outer surface and the second outer surface, thereby attaching the lumbar support to the support portion.

[0012] In the chair, the support column may include a shape-changing portion for restricting vertical displacement of the support body relative to the support region. With this configuration, the support body can restrict vertical displacement of the support column from the support region.

[0013] In the above chair, the support pillar portion may comprise a first plate portion having the first outer surface and a second plate portion having the second outer surface, and may also comprise a shape-constant region having a constant shape in the vertical direction, with the support region within the shape-constant region, and the shape-changing portion may be an engaging portion that engages with the support body and is provided on the inner surface of at least one of the first inner surface of the first plate portion and the second inner surface of the second plate portion, and is positioned corresponding to at least one of the upper and lower ends of the support region.

[0014] According to the above configuration, the support body is engaged with the engagement portion, so that the support body is less likely to shift vertically relative to the support region even in the shape-fixed region. The engagement portion can be made less visible by providing it on the inner surface of the plate portion.

[0015] In the chair, the engaging portion may be a rib integral with at least one of the first inner surface and the second inner surface, and the tip of the rib may be configured to be lower than at least one of the tip of the first plate portion and the tip of the second plate portion. According to the above configuration, the rib is hidden by the first plate portion and the second plate portion, making it less noticeable.

[0016] In the chair described above, the support column may include a constant-shape region having a constant shape in the up-down direction, and an upper adjacent region and a lower adjacent region adjacent to the constant-shape region, wherein at least one of the upper adjacent region and the lower adjacent region has a different shape from the constant-shape region, the boundary between the constant-shape region and the adjacent region is the shape-changing portion, and the region including the boundary is the support region. According to the above configuration, since the support region includes the shape-changing portion whose shape changes, the support body is less likely to shift in the up-down direction relative to the support region.

[0017] In the above chair, the support pillar portion comprises a first plate portion having the first outer surface and a second plate portion having the second outer surface, and gradually becomes thicker or thinner from top to bottom, and either one of the first support member and the second support member comprises an inner support portion that supports the inner surface behind either one of the first outer surface and the second outer surface, and at least one of the outer interference portion where the outer support portion of at least one of the first outer support wall and the second outer support wall interferes with the outer surface facing the outer support portion, and the inner interference portion where the inner support portion interferes with the inner surface facing the inner support portion may be the shape-changing portion.

[0018] According to the above configuration, the outer support portion interferes with the outer surface, making it less likely to shift in either the up or down direction from the support area, and the inner support portion interferes with the inner surface, making it less likely to shift in the other direction from the support area. [Effects of the Invention]

[0019] According to the present invention, the mounting structure for mounting the lumbar support on the backrest support can be made less noticeable. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a perspective view of a chair in a first embodiment, seen from the front side. [Figure 2] FIG. 2 is a rear view of the chair in the first embodiment. [Figure 3] FIG. 2 is a side view of the chair in the first embodiment. [Figure 4] 1 is an exploded perspective view of a chair backrest structure according to a first embodiment, seen from the front side. FIG. [Figure 5] FIG. 2 is a perspective view of a lumbar support used in a chair in the first embodiment. [Figure 6] FIG. 2 is an exploded perspective view of the lumbar support according to the first embodiment, as viewed from the front side. [Figure 7]FIG. 2 is an exploded perspective view of the lumbar support as viewed from the rear side in the first embodiment. [Figure 8] 8 is a cross-sectional view taken along line 8-8 of FIG. 5. [Figure 9] 9 is a cross-sectional view taken along line 9-9 of FIG. 5. [Figure 10] FIG. 2 is a side view of the backrest structure showing the support area of ​​the lumbar support in the first embodiment. [Figure 11] FIG. 2 is a perspective view of a main part illustrating a support area of ​​a lumbar support in a support column in the first embodiment. [Figure 12] FIG. 3 is a cross-sectional view illustrating an engagement portion in the first embodiment. [Figure 13] FIG. 10 is a cross-sectional view illustrating a modification of the engaging portion according to a second embodiment, which is a modification of the first embodiment. [Figure 14] FIG. 10 is a perspective view of a main part of a fourth embodiment, illustrating a support area of ​​a lumbar support in a support column. [Figure 15] FIG. 10 is a perspective view of a fifth embodiment. [Figure 16] 10(a) is a cross-sectional view illustrating that the support body in the fifth embodiment does not shift downward from the support area, and FIG. 10(b) is a cross-sectional view illustrating that the support body does not shift upward from the support area. [Figure 17] 10 is a cross-sectional view of a support part in which a V-shaped opening is formed by a first plate part and a second plate part. FIG. [Figure 18] 10 is a cross-sectional view of a support part in which the first plate part and the second plate part each have a thickness deviation shape. FIG. [Figure 19] 18 is a cross-sectional view showing a state in which a first support member and a second support member are attached to the support region of the support column shown in FIG. 17 from the opening side of the support column. FIG. [Figure 20] 19 is a cross-sectional view showing a state in which a first support member and a second support member are attached to the support region of the support column shown in FIG. 18 from the opening side of the support column. FIG. [Figure 21] 18 is a cross-sectional view showing a state in which a first support member and a second support member are attached to the support region of the support column shown in FIG. 17 from the base end side of the support column. FIG. [Figure 22]19 is a cross-sectional view showing a state in which a first support member and a second support member 67 are attached to the support region of the support column shown in FIG. 18 from the base end side of the support column. [Figure 23] 19 is a cross-sectional view showing a state in which a first support member and a second support member are attached to a support region of a support column having a thickness deviation shape different from that of the support column in FIG. 18 from the opening side of the support column. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, one embodiment of a chair will be described with reference to FIGS. 1 to 23. FIG. (First embodiment) (Overall chair configuration) As shown in Figures 1 and 2, chair 1 includes leg members 11, a seat structure 12, and a backrest structure 13. In this embodiment, chair 1 has seat 22 of seat structure 12 open to allow sitting. This open side is the front side, and the side of seat structure 12 on which backrest structure 13 is located is the rear side. In this embodiment, the left and right directions when viewing seat structure 12 from the front side are the right and left sides, the seat side relative to leg members 11 is the upper side, and the leg member 11 side relative to seat 22 is the lower side.

[0022] The leg member 11 is a leg member with casters. The leg member 11 is provided with a leg post 11a. Leg portions 11b extend radially from the lower end of the leg post 11a. Casters 11c are attached to the tips of the leg portions 11b. A gas spring is built into the leg post 11a. This gas spring adjusts the height of the support base 21 in response to operation of a first operating lever 16 provided on the seat structure 12. In addition, a second operating lever 17 is provided near the first operating lever 16. The second operating lever 17 has a knob for adjusting the backrest reaction force when reclining.

[0023] The seat structure 12 includes a support base 21 and a seat 22. The seat 22 is attached to the top of the support base 21. The seat 22 is configured by layering a cushioning material such as urethane foam on a seat plate and covering it with cloth or the like.

[0024] (Backrest structure) 2 and 3, the backrest structure 13 has a symmetrical shape when viewed from the front-to-rear direction. The backrest structure 13 includes a backrest support 31 and a backrest main body 32. The backrest main body 32 includes a back support member 33.

[0025] (Backrest support) As shown in Figures 2 to 4, the backrest support 31 is connected to the seat structure 12 by a connecting member 39. The backrest support 31 includes a lower support portion 42, a support column 43, and an upper support portion 46. The connecting member 39 connects the seat structure 12 and the lower support portion 42, and extends below the pedestal 21 from the rear to the front, reaching close to the leg column 11a. The connecting member 39 is fixed to the lower support portion 42 by a fixing member such as a screw. The connecting member 39 and the lower support portion 42 may be formed as a single, integral part.

[0026] The lower support part 42 extends in the left-right direction behind the seat part 22. The length of the lower support part 42 in the longitudinal direction extending left-right is approximately the same as or shorter than the rear edge of the seat part 22. As shown in FIG. 3, the surface of the lower support part 42 facing the leg post 11a is fixed to the connecting member 39. In addition, a swing support mechanism 45 that supports the backrest main body 32 so that it can swing is formed on the rear surface of the lower support part 42. The swing support mechanism 45 is formed on the opposite side of the connection part of the connecting member 39.

[0027] The support column 43 includes a pair of left support column 43l and right support column 43r. The pair of left support column 43l and right support column 43r extends upward from the lower support column 42 while gently curving. Specifically, the pair of left support column 43l and right support column 43r extend upward from below, diagonally rearward, with a gap between them (first gap C1). Next, the pair of left support column 43l and right support column 43r extend upward toward the front while the gap between them narrows (second gap C2). After that, the pair of left support column 43l and right support column 43r extend linearly upward at approximately the same gap (third gap C3). Then, the pair of left support column 43l and right support column 43r open in the left-right direction to form the upper support column 46. That is, the portion that defines the first interval C1 defines a first curved portion 47a that bulges diagonally rearward to widen the gap. The portion that defines the second interval C2 defines a second curved portion 47b that bulges forward. The pair of left and right support columns 43l, 43r curve toward each other from the first curved portion 47a to the second curved portion 47b, narrowing the gap between them at the upper second interval C2 from the lower first interval C1. As a result, the portion above the second curved portion 47b defines a linear portion 47c that is linear and narrower than the first curved portion 47a. A support region 48b for attaching a lumbar support 61 is defined in a portion of the second curved portion 47b in the vertical direction.

[0028] The upper support portion 46 connects the upper ends of the left support portion 43l and the right support portion 43r and protrudes outward in the left-right direction. That is, the upper support portion 46 includes a connecting portion 46a connecting the upper end of the left support portion 43l with the upper end of the right support portion 43r, a left extension portion 46l extending leftward from the upper end of the left support portion 43l, and a right extension portion 46r extending rightward from the upper end of the right support portion 43r.

[0029] The upper part of the backrest main body 32 is fixedly supported by a left connection part 49l, which is an inner corner formed by the connecting part 46a and the left support part 43l. The upper part of the backrest main body 32 is also fixedly supported by a right connection part 49r, which is an inner corner formed by the connecting part 46a and the support part 43r.

[0030] (Backrest body) As shown in FIG. 4, the backrest main body 32 has, for example, an annular frame shape. The backrest main body 32 includes an upper fixing portion 51, a lower connecting support portion 52, and left and right vertical frame portions 53l and 53r that connect the left and right sides of the upper fixing portion 51 and the left and right sides of the lower connecting support portion 52. The upper fixing portion 51 has a curved shape that follows the curve of the upper support portion 46 of the backrest support body 31. The vertical frame portions 53l and 53r extend diagonally forward from the upper fixing portion 51 toward the lower connecting support portion 52. The lower connecting support portion 52 has a U-shape, and both sides of the lower connecting support portion 52 protrude forward beyond the left and right sides of the upper fixing portion 51, and is curved so that the center protrudes rearward. The left and right sides of the lower connecting support portion 52 are connected to the lower sides of the vertical frame portions 53l and 53r. In the curved lower connection support part 52, a protrusion 54 constituting the swing support mechanism 45 protrudes downward from the central part located at the rearmost part.

[0031] A back support member 33 is tensioned across the backrest body 32. The back support member 33 is, for example, a tension member. The back support member 33 has, for example, a mesh shape, and is tensioned across the upper fixing portion 51, the lower connecting support portion 52, and the vertical frame portions 53l and 53r so as to be able to suitably receive a load from the front.

[0032] Both the backrest support 31 and the backrest main body 32 are made of reinforced plastic, for example, made of synthetic resin such as nylon containing glass fiber, but the backrest main body 32 is made to be more flexible than the backrest support 31 to improve sitting comfort.

[0033] (swinging support mechanism) The swing support mechanism 45 supports the protrusion 54 at the center of the lower support part 42 so that it can swing left and right. As an example, a through hole is formed in the protrusion 54. A shaft provided on the lower support part 42 is inserted into the through hole. As a result, the upper part of the backrest main body 32 is fixed to the backrest support body 31, and the lower part is supported by the swing support mechanism 45 so that it can swing left and right.

[0034] (lumbar support) Incidentally, a lumbar support 61 is arranged in the backrest structure 13, and the lumbar support 61 supports an ideal sitting posture of the user. Specifically, the lumbar support 61 is attached to the support pillars 43l, 43r in a space 60 (see FIG. 3) between the support pillars 43l, 43r and the backrest main body 32.

[0035] As shown in FIG. 4, the lumbar support 61 includes a support body 62 that supports the user's lower back and surrounding areas, and left and right support bodies 63l, 63r that are disposed on both left and right ends of the support body 62.

[0036] (Support unit) The support body 62 is a long plate member having a length that spans between the support pillars 43l and 43r. That is, the support body 62 extends in the left-right direction of the backrest structure 13. The support body 62 includes a resin plate. The support body 62 also includes a cushioning material, and is composed of, for example, a high-resilience cushion, a low-resilience cushion, or a cushion that combines high-resilience cushions and low-resilience cushions in multiple layers. The support body 62 may be composed of only a resin plate, or may have a configuration in which a cushion is supported on a resin plate.

[0037] The support body 62 is provided with mounting pieces 64l, 64r at both left and right ends for mounting to the supports 63l, 63r. The mounting pieces 64l, 64r are made of rigid resin moldings, metal pieces, or the like. The mounting pieces 64l, 64r have rough or uneven surfaces, which provide high friction with the contact surfaces of the supports 63l, 63r. This makes it difficult for the mounting pieces 64l, 64r to shift in position relative to the supports 63l, 63r in the vertical direction. Hereinafter, the mounting pieces 64l, 64r will be collectively referred to as mounting pieces 64.

[0038] In this embodiment, the distance between the left support pillar 43l and the right support pillar 43r, to which the supports 63l and 63r are attached, is narrower than the distance between the left vertical frame portion 53l and the right vertical frame portion 53r of the backrest main body 32. The longitudinal length of the support main body 62 can also be configured to match the distance between the left vertical frame portion 53l and the right vertical frame portion 53r. In this case, the positions of the mounting pieces 64l and 64r are aligned with the distance between the support pillars 43l and 43r. In other words, the positions of the mounting pieces 64l and 64r are located inward in the longitudinal direction relative to both left and right ends of the support main body 62. The ends of the support main body 62 protrude beyond the mounting pieces 64l and 64r.

[0039] (Support) As shown in Figures 4 and 5, the supports 63l and 63r are bilaterally symmetrical and have the same configuration. Hereinafter, the supports 63l and 63r will be collectively referred to simply as the support 63. Figures 6 and 7 show the support 63l, and are exploded perspective views of the support 63l. The support 63 includes a first support member 66, a second support member 67, and an attachment member 68. When the first support member 66 and the second support member 67 sandwich the support column 43, the first support member 66 is located inside and close to the center between the support columns 43l and 43r. The second support member 67 is located outside the support columns 43l and 43r.

[0040] (Support area of ​​the support column) As shown in FIGS. 4, 6, and 7, the support pillars 43l and 43r to which the lumbar support 61 is attached include a first plate portion 56 and a second plate portion 57, and are configured to have a V-shaped cross section in the vertical direction. As an example, the first plate portion 56 and the second plate portion 57 have the same constant thickness. The first plate portion 56 includes a first outer surface 56a and a first inner surface 56b. The second plate portion 57 includes a second outer surface 57a and a second inner surface 57b. The first inner surface 56b and the second inner surface 57b are surfaces that face each other. In addition, the V-shaped opening of the support pillars 43l and 43r is formed by the tip of the first plate portion 56 and the tip of the second plate portion 57, and these are connected at the base end. The support pillars 43l, 43r are configured such that the tip-side outer surface width (W1) of the tip portion of the first outer surface 56a and the tip portion of the second outer surface 57a is wider than the base-side outer surface width (W2), and serve as engagement portions that are gripped by the supports 63l, 63r (see FIGS. 8 and 9). The V-shaped opening of the support pillars 43l, 43r faces the front of the chair 1, and the base end side faces the rear of the chair 1. The first plate portion 56 is located on the inside and close to the center between the support pillars 43l, 43r. The second plate portion 57 is located on the outside, farther away from the center between the support pillars 43l, 43r than the first plate portion 56. The first plate portion 56 is shorter than the second plate portion 57.

[0041] The support pillars 43l and 43r are thickest at their bases in relation to the lower support member 42, followed by the first curved portion 47a. The support pillars 43l and 43r gradually become thinner toward the second curved portion 47b, with the straight portion 47c being thinner than the second curved portion 47b. As shown in FIG. 11 , the second curved portion 47b includes a constant-shape region 48a, for example. The constant-shape region 48a is a region with a constant shape, including a constant direction of curvature, thickness, and other characteristics. In the second curved portion 47b, the constant-shape region 48a includes a support region 48b that supports the lumbar support 61. The lower portion closer to the first curved portion 47a than the constant-shape region 48a differs in shape, including a different direction of curvature, thickness, and other characteristics, compared to the second curved portion 47b. The upper portion closer to the straight portion 47c than the constant-shape region 48a also differs in shape, including a different direction of curvature, thickness, and other characteristics, compared to the second curved portion 47b. Here, the lower portion closer to the first curved portion 47a than the shape-constant region 48a is thicker, and the upper portion closer to the straight portion 47c than the shape-constant region 48a is thinner.

[0042] Engagement portions 88 are provided at the upper and lower ends of the support region 48b defined within the shape-constant region 48a to regulate vertical displacement of the support body 63. The engagement portions 88 are ribs provided integrally with the first inner surface 56b and the second inner surface 57b (see FIGS. 11 and 12).

[0043] The base of the rib that constitutes the engagement portion 88 relative to the first inner surface 56b is at the same height as the tip of the first plate portion 56. Note that the base of the rib relative to the first inner surface 56b may be lower than the tip of the first plate portion 56. Also, the base of the rib that constitutes the engagement portion 88 relative to the second inner surface 57b is at the same height as the tip of the second plate portion 57. Note that the base of the rib relative to the second inner surface 57b may be lower than the tip of the second plate portion 57. The rib that constitutes the engagement portion 88 is substantially perpendicular to the first inner surface 56b and the second inner surface 57b of the second plate portion 57. The height of the rib is set so that it does not protrude above an imaginary plane connecting the tip of the first plate portion 56 and the tip of the second plate portion 57. As a result, the engagement portion 88 is hidden by the first plate portion 56 and the second plate portion 57 and is therefore inconspicuous.

[0044] The engagement portions 88 are provided at the upper and lower ends of the support region 48b, and the support body 63 is disposed between the upper and lower engagement portions 88. The support region 48b is between the upper and lower engagement portions 88. This restricts the support body 63 from shifting in the up-down direction relative to the support region 48b.

[0045] The backrest support 31 is formed by injection molding. The molding die has a first die that forms the front side of the backrest support 31 and a second die that forms the rear side. The backrest support 31 is formed by clamping the first die and the second die together, filling the cavity with molten resin, and then releasing the die. When molding the engagement portion 88, the engagement portion 88 is a rib that extends in the mold removal direction, so it can be molded without adding a new die.

[0046] (First support member) As shown in Figures 6 and 7, the first support member 66 is a member located inside the support column 43 in the left-right direction of the backrest support body 31, and has a main body 71 that follows the shape of the first plate 56. The front surface of the main body 71 is provided with an attachment groove 72 into which the attachment piece 64 engages. The attachment groove 72 has a length that allows the attachment piece 64 to move in the up-down direction. The groove bottom surface 72a of the attachment groove 72 is formed with a rough or uneven surface so that it can engage with the rough or uneven surface on the back surface of the attachment piece 64.

[0047] The mounting groove 72 is defined between an inner groove wall 72b and an outer groove wall 72c, which extend in the vertical direction. The inner groove wall 72b is a wall lower than the outer groove wall 72c. The inner groove wall 72b is a wall closer to the center between the support columns 43l and 43r. The support body 62 extends from one support column 43 to the other support column 43, climbing over the tip of the inner groove wall 72b. Mounting portions 73 for mounting the mounting piece 64 to the mounting groove 72 are provided in areas above the upper end of the mounting groove 72 and below the lower end of the mounting groove 72. The surface of the outer groove wall 72c opposite the mounting groove 72 forms the abutment surface 70 against which the abutment wall 78 of the second support member 67 abuts. The upper and lower ends of the mounting member 68 are attached to the mounting portions 73 by fixing members 87.

[0048] The main body 71 has a first outer support wall 74 on the surface opposite to the surface on which the mounting groove 72 is provided. The first outer support wall 74 is a first outer support portion 74a that abuts against the first outer surface 56a of the first plate 56. The first outer support portion 74a has a shape that follows the shape of the first outer surface 56a in the support region 48b. The surface of the main body 71 on which the first outer support wall 74 is provided is an abutment surface 71a against which the tip of the first plate 56 abuts. The end of the abutment surface 71a is an inner support portion 71b against which the second inner surface 57b of the second plate 57 abuts. The inner support portion 71b is configured as an inclined surface that follows the shape of the second inner surface 57b.

[0049] The main body 71 has an attachment protrusion 75 for attaching the second support member 67 to its side surface. The attachment protrusion 75 is fixed by a fixing member 86 in a state where it is engaged with an engagement recess 79 of the second support member 67. By engaging the attachment protrusion 75 with the engagement recess 79, the second support member 67 is positioned relative to the first support member 66.

[0050] (Second support member) The second support member 67 is a member located outside the support column 43 in the left-right direction of the backrest support 31 and includes a main body 76 conforming to the shape of the second curved portion 47b. The main body 76 includes a second outer support wall 77 that abuts against the second outer surface 57a of the second plate 57. The second outer support wall 77 is a second outer support portion 77a that abuts against the second outer surface 57a of the second plate 57. The second outer support portion 77a has a shape conforming to the second outer surface 57a in the support region 48b. The main body 76 also includes an abutment wall 78 on the opposite side from the second outer support wall 77 that abuts against the abutment surface 70 of the outer groove wall 72c. The outer groove wall 72c and the abutment wall 78 are fixed by a fixing member in an overlapping state. Specifically, the main body 76 includes an engagement recess 79 into which the mounting protrusion 75 engages.

[0051] (Mounting parts) The mounting member 68 is a member that is placed on the mounting groove 72 to prevent the mounting piece 64 from coming off the mounting groove 72. The mounting member 68 includes a long retaining portion 81 that prevents the mounting piece 64 from coming off the mounting groove 72, and fixing pieces 82 that are placed at the upper and lower ends of the retaining portion 81. The fixing pieces 82 are fixed to the mounting portion 73 by a fixing member 87. When the fixing pieces 82 are fixed to the mounting portion 73, the mounting piece 64 and the support main body 62 extend from a gap formed below the retaining portion 81. The back surface of the retaining portion 81 is the surface that faces the mounting piece 64, and like the groove bottom surface 72a, can be formed with a rough or uneven surface so that it can engage with a rough or uneven surface formed on the surface of the mounting piece 64.

[0052] (How to install lumbar support) As shown in FIG. 10 , the support body 62 is inserted into the space 60 between the support pillars 43l, 43r and the backrest body 32. Furthermore, in each of the support pillars 43l, 43r, the support regions 48b of the second curved portions 47b are attached to the support members 63l, 63r. At the same time, an attachment piece 64l is attached to the support member 63l, and an attachment piece 64r is attached to the support member 63r. The lumbar support 61 is attached to the support pillars 43l, 43r, which are part of the backrest support member 31 that has the relatively higher strength than the backrest support member 31 and the backrest body 32. The lumbar support 61 can be attached in a more stable state than when attached to the backrest body 32.

[0053] Specifically, as shown in FIG. 8 , the first support member 66 is disposed along the first outer surface 56 a. The second support member 67 is disposed along the second outer surface 57 a. The mounting protrusion 75 of the first support member 66 is engaged with the engagement recess 79 of the second support member 67. The first support member 66 and the second support member 67 are disposed so as to cover the support portion 43 from the open end formed by the tip of the first plate portion 56 and the tip of the second plate portion 57. The fixing member 86 connecting the first support member 66 and the second support member 67 is composed of a nut and a bolt. A nut is disposed on the mounting protrusion 75. The bolt is inserted into a through hole formed in the engagement recess 79 and fastened to the nut. This joins the first support member 66 and the second support member 67. The first outer support portion 74a and the second outer support portion 77a have a V-shape corresponding to the first outer surface 56a and the second outer surface 57a in the support region 48b.

[0054] As shown in FIG. 8, the mounting piece 64 of the support body 62 is engaged with the mounting groove 72 of the first support member 66. Then, a mounting member 68 is placed in the mounting groove 72 so as to cover the mounting groove 72. Then, the fixing piece 82 is placed on the mounting portion 73. A fixing member 87 that connects the first support member 66 and the mounting member 68 is made up of a nut and a bolt. The nut is placed on the mounting portion 73. Then, the bolt is inserted into a through hole formed in the fixing piece 82 and fastened to the nut (see FIG. 9). This joins the first support member 66 and the mounting member 68.

[0055] As an example, the first support member 66 and the second support member 67 are fixed to the support region 48b of the support columns 43l and 43r by fixing members 86. The support region 48b is a region between engaging portions 88, which are shape-changing portions provided above and below the support region 48b, and its position can be easily identified visually. Even when the fixing members 86 are fully tightened, the first outer support portion 74a of the first support member 66 and the second support member 67 is not pressed against the first outer surface 56a, nor is the second outer support portion 77a pressed against the second outer surface 57a. The first outer support portion 74a is supported by abutting against the first outer surface 56a, and the second outer support portion 77a is supported by abutting against the second outer surface 57a. Vertical displacement of the support member 63 relative to the support region 48b is restricted by the engaging portions 88 provided above and below the support region 48b.

[0056] In the support region 48b, the support columns 43l and 43r have their V-shaped openings facing forward and their base ends facing rearward. The first support member 66 and the second support member 67 attached to the support region 48b are attached so as to cover the opening ends defined by the tips of the first and second plate portions 56 and 57. That is, the first support member 66 and the second support member 67 sandwich the support columns 43l and 43r from the front. The support member opening width (W3) of the opening ends defined by the tips of the first and second outer support portions 74a and 77a is narrower than the tip-side outer surface width (W1) of the tip portions of the first and second outer surfaces 56a and 57a. The first and second plate portions 56 and 57 are covered on the outside by the first and second outer support walls 74 and 77. In this state, the first outer support portion 74a and the first outer surface 56a come into contact with each other, and the second outer support portion 77a and the second outer surface 57a come into contact with each other. This makes it difficult for the support body 63 to fall off from the front sides of the support pillars 43l and 43r.

[0057] The range (engagement portion) over which the first outer support wall 74 overlaps with the first outer surface 56a does not cover the entire first outer surface 56a, but extends from the tip of the first plate portion 56 that forms the open end to the center between the tip and base ends, or to any position between the tip and center. Similarly, the range over which the second outer support wall 77 overlaps with the second outer surface 57a does not cover the entire second outer surface 57a, but extends from the tip of the second plate portion 57 to the center between the tip and base ends, or to any position between the tip and center.

[0058] (Lumbar support effect) 11, if the vertical length of the shape-constant region 48a is longer than the vertical lengths of the first outer support portion 74a and the second outer support portion 77a, there is a risk that the support 63 will be displaced vertically from the support region 48b within the shape-constant region 48a. Note that the support 63 is shown in a simplified form in FIGS. 11 to 13.

[0059] 11 and 12, the first inner surface 56b of the first plate portion 56 and the second inner surface 57b of the second plate portion 57 are provided with engagement portions 88. The engagement portions 88 are provided above and below the support region 48b, and the support body 63 is disposed between the upper and lower engagement portions 88. In this case, the support region 48b is between the upper and lower engagement portions 88. As a result, when the support body 63 attempts to shift up or down, for example, the inner support portion 71b and the engagement portions 88 interfere with each other, thereby restricting the shift in the up or down direction relative to the support region 48b.

[0060] The lumbar support 61, maintained in the support region 48b, can fine-tune its vertical position by moving the support body 62 up and down relative to the support member 63. That is, when no load is applied to the backrest structure 13, the attachment piece 64 of the support body 62 is not pressed against the groove bottom surface 72a or the back surface of the retaining portion 81. Therefore, even though the support body 62 is difficult to move due to friction, it can still be manually moved up and down within the range of the attachment groove 72. Even when the user determines the position, the support body 62 does not move up and down under its own weight due to friction. When the user sits on the chair 1 and applies a load to the backrest structure 13, the load presses the support body 62, causing the back surface of the attachment piece 64 to press against the groove bottom surface 72a. Furthermore, the retaining portion 81 is pressed against the surface of the support body 62. As a result, while the user is applying a load up and down to the backrest structure 13, the increased friction makes the support body 62 more difficult to move than before the load was applied.

[0061] (Effects of the first embodiment) According to the first embodiment, the following effects can be obtained. (1) The lumbar support 61 can be retrofitted to the backrest structure 13. That is, the lumbar support 61 can be inserted into the space 60 between the support pillars 43l, 43r and the backrest body 32 and attached to the support pillars 43l, 43r.

[0062] (2) Even when the lumbar support 61 is not attached to the chair 1, the only structure for the lumbar support 61 is the engagement portion 88 as a shape-changing portion. The engagement portion 88 is disposed between the first plate portion 56 and the second plate portion 57 that constitute the support portions 43l and 43r. This position is inconspicuous from the outside. Moreover, the opening formed by the tip of the first plate portion 56 and the tip of the second plate portion 57 is not noticeable because the backrest main body 32 is located nearby. Therefore, even when the lumbar support 61 is not attached to the chair 1, the engagement portion 88 is inconspicuous, and the design of the chair 1 is not impaired.

[0063] (3) By sandwiching the support pillars 43l and 43r between the first support member 66 and the second support member 67, the lumbar support 61 can also be easily attached to the support region 48b. Specifically, the support opening width (W3) defined by the tip of the first outer support wall 74 and the tip of the second outer support wall 77 is narrower than the tip-side outer surface width (W1) of the tip portion of the first outer surface 56a and the tip portion of the second outer surface 57a. This makes it less likely that the support pillars 43l and 43r will fall off from the front sides of the support pillars 43l and 43r.

[0064] (4) The supports 63l, 63r, which sandwich the support pillars 43l, 43r between the first support member 66 and the second support member 67, are less likely to shift vertically from the support region 48b because the inner support portion 71b engages with the engagement portion 88. As a result, the lumbar support 61 is also less likely to shift vertically from the support region 48b.

[0065] (5) The supports 63l, 63r sandwich the first plate portion 56 and the second plate portion 57 from the direction of the tip of the first plate portion 56 and the tip of the second plate portion 57, which are spaced apart widely, making them less likely to fall off from the direction of the tip of the first plate portion 56 and the tip of the second plate portion 57.

[0066] (6) The first support member 66 includes the inner support portion 71b. Therefore, the second outer surface 57a of the second plate portion 57 is supported by the second outer support portion 77a, and the second inner surface 57b is supported by the inner support portion 71b. This makes it difficult for the supports 63l and 63r to shift vertically relative to the support region 48b.

[0067] (7) The engaging portion 88 is lower than the tip of the first plate portion 56 and the tip of the second plate portion 57. Therefore, the engaging portion 88 can be made less noticeable. (8) The rib that constitutes the engaging portion 88 is a wall that extends in the mold removal direction and has a simple structure. The engaging portion 88 can be molded without complicating the mold.

[0068] (Second embodiment) 13, the engaging portions 88 may be configured so that the engaging portions 88 provided in the support region 48b engage with engaging grooves 89 provided in the first support member 66 and the second support member 67. Even with this configuration, the support body 63 is restricted from shifting in the up-down direction relative to the support region 48b.

[0069] (Third embodiment) When the vertical length of the constant-shape region 48a and the length of the support region 48b are the same, the upper adjacent region adjacent to the upper side of the support region 48b is configured to differ from the support region 48b in shape, such as the direction of curvature, thickness, etc. Furthermore, the lower adjacent region adjacent to the lower side of the support region 48b is also configured to differ from the support region 48b in shape, such as the direction of curvature, thickness, etc. In such a case, the boundary between the constant-shape region 48a, which coincides with the range of the support region 48b, and the upper adjacent region is a shape-changing portion. Furthermore, the boundary between the constant-shape region 48a and the lower adjacent region is also a shape-changing portion. The greater the degree of shape change of the shape-changing portion, the less likely the support 63 is to be displaced in the vertical direction from the support region 48b.

[0070] In the third embodiment, the support body 63 supported by the support region 48b is prevented from shifting in the up and down direction by the upper and lower shape-changing portions. In the third embodiment, the up and down shifting of the support body 63 can be prevented by simply changing the shape of the support column 43 due to a change in curvature, etc., without the need to provide the engagement portion 88 or engagement groove 89. As a result, it is no longer necessary to provide the engagement portion 88 or the like for attaching the lumbar support 61 to the support column 43, and the shape can be simplified.

[0071] (Fourth embodiment) As shown in FIG. 14, the support columns 43l and 43r have a constant-shape region 48a at the position of the second curved portion 47b. Note that FIG. 14 shows a simplified view of the support 63. In the fourth embodiment, the support 63 also includes a first support member 66, a second support member 67, and an attachment member 68. The upper adjacent region 48c, which is adjacent to the upper side of the constant-shape region 48a, is configured to differ from the constant-shape region 48a in terms of the direction of curvature, thickness, and other characteristics of the curve. The lower adjacent region 48d, which is adjacent to the lower side of the constant-shape region 48a, is also configured to differ from the constant-shape region 48a in terms of the direction of curvature, thickness, and other characteristics of the curve. The boundary between the constant-shape region 48a and the upper adjacent region 48c is a shape change point, which is an upper shape-changing portion 48e. The boundary between the constant-shape region 48a and the lower adjacent region 48d is a shape change point, which is a lower shape-changing portion 48f.

[0072] In the fourth embodiment, support region 48b is a position that includes upper shape changing portion 48e or a position that includes lower shape changing portion 48f. Upper support region 48b is a region that spans constant shape region 48a, which includes upper shape changing portion 48e, and upper adjacent region 48c. Support body 63 has a shape that corresponds to the shape of upper shape changing portion 48e. When support body 63 is attached to upper support region 48b, it is sandwiched between first support member 66 and second support member 67 so as to include upper shape changing portion 48e, thereby preventing vertical displacement (position of support body 63 indicated by solid lines).

[0073] Lower support region 48b is a region that spans constant-shape region 48a, which includes lower-shape-changing portion 48f, and lower adjacent region 48d. Support body 63 has a shape that corresponds to the shape of lower-shape-changing portion 48f. When support body 63 is attached to lower support region 48b, it is sandwiched between first support member 66 and second support member 67 so as to include lower-shape-changing portion 48f, thereby preventing vertical displacement (position of support body 63 indicated by the dashed-dotted line).

[0074] In the fourth embodiment, it is possible to prevent the support body 63 from shifting up and down simply by changing the shape of the support column 43, without the need to provide the engagement portion 88 or engagement groove 89. As a result, it is no longer necessary to provide the engagement portion 88 or the like for attaching the lumbar support 61 to the support column 43, and the shape can be simplified.

[0075] (Fifth embodiment) As shown in Fig. 15, in the fifth embodiment, the support column 43 is configured to gradually become thinner from top to bottom. That is, the support column 43 includes a first plate portion 56 and a second plate portion 57, and is configured so that the cross section is V-shaped and the distance between the tip of the first plate portion 56 and the tip of the second plate portion 57 gradually becomes wider from top to bottom. Specifically, the first plate portion 56 is linear in the up-down direction, whereas the second plate portion 57 is configured to be curved so as to gradually move away from the first plate portion 56 as it extends downward. In addition, the plate thicknesses of both the first plate portion 56 and the second plate portion 57 are, for example, constant and the same.

[0076] The support body 91 used in this type of support column 43 includes a first outer support wall 92a and a first inner support wall 92b in the support region 48b for sandwiching the tip of the first plate portion 56. The first outer support wall 92a has a shape that follows the first outer surface 56a in the support region 48b. The first inner support wall 92b has a shape that follows the first inner surface 56b. Furthermore, the support body 91 includes a second outer support wall 93a and a second inner support wall 93b in the support region 48b for sandwiching the tip of the second plate portion 57. The second outer support wall 93a has a shape that follows the second outer surface 57a in the support region 48b. The second inner support wall 93b has a shape that follows the second inner surface 57b. Like the support body 63, the support body 91 also includes a first support member 66, a second support member 67, and an attachment member 68. The first support member 66 has a first inner support wall 92b, and the second support member 67 has a second inner support wall 93b.

[0077] As shown in Figure 16(a), when the support body 91 attempts to descend from the support region 48b, the second outer support wall 93a interferes with the second outer surface 57a. Note that the first inner support wall 92b and the second inner support wall 93b are omitted from Figure 16(a). This prevents the support body 91 from shifting downward from the support region 48b. The outer contact surface of the second outer surface 57a that serves as the outer interference portion with the second outer support wall 93a is the shape-changing portion 94a.

[0078] 16(b), when the support body 91 attempts to rise from the support region 48b, the second inner support wall 93b interferes with the second inner surface 57b. Note that the first outer support wall 92a and the second outer support wall 93a are omitted from FIG. 16(b). This prevents the support body 91 from shifting upward from the support region 48b. The inner contact surface of the second inner surface 57b, which serves as the inner interference portion with the second inner support wall 93b, is the shape-changing portion 94b.

[0079] In the fifth embodiment, the vertical displacement of the support body 63 can be suppressed by simply changing the shape of the support pillar 43, without the need to provide the engagement portion 88 or engagement groove 89. As a result, it is no longer necessary to provide the engagement portion 88 or the like for attaching the lumbar support 61 to the support pillar 43, and the shape can be simplified.

[0080] (Variation) The first to fifth embodiments can be modified as follows.

[0081] In the fifth embodiment (see FIGS. 15 and 16), the support body 91 may be provided with only the second outer support wall 93a, and the second inner support wall 93b may be omitted. In this case, the support body 91 only serves to prevent the support body 91 from shifting downward from the support region 48b. Alternatively, the support body 91 may be provided with only the second inner support wall 93b, and the second outer support wall 93a may be omitted. In this case, the support body 91 only serves to prevent the support body 91 from shifting upward from the support region 48b.

[0082] In the fifth embodiment, the configuration of the support column 43 is not limited to the example shown in FIGS. 15 and 16 . For example, the first plate 56 and the second plate 57 may both be curved so that the distance between them gradually increases from top to bottom. In this case, too, the first outer support wall 92a and the first inner support wall 92b, and the second outer support wall 93a and the second inner support wall 93b, conforming to the first outer surface 56a, can prevent the support column 43 from shifting vertically relative to the support region 48b. Furthermore, the second plate 57 may be curved so that it gradually moves away from the first plate 56 as it extends upward. In other words, the support column 43 may be configured to gradually become thicker or thinner toward the bottom.

[0083] In the fourth embodiment, the upper shape-changing portion 48e and the lower shape-changing portion 48f may only change in curvature, may only change in thickness, may only change in direction of curvature, or may be a shape-changing portion configured by combining these elements.

[0084] In the first and second embodiments, the rib constituting the engagement portion 88 may be provided only on the first inner surface 56b of the first plate portion 56, or may be provided only on the second inner surface 57b of the second plate portion 57. Furthermore, the rib may be higher than the tip of the first plate portion 56 and the tip of the second plate portion 57. For example, in the first embodiment, the rib is configured so as not to protrude from an imaginary plane connecting the tip of the first plate portion 56 and the tip of the second plate portion 57, but the rib may have at least a portion that protrudes from the imaginary plane.

[0085] The engaging portion 88 may have any configuration as long as it interferes with the support body 63 when the support body 63 attempts to move up and down from the support region 48b, and may have the shape of a protrusion, pin, piece, or the like. The location on the support body 63 that engages with the engaging portion 88 is not limited to the inner support portion 71b. For example, it may be a protrusion or piece protruding from the edge of the first support member 66 or the second support member 67.

[0086] The engaging portion 88 may be provided only at a position corresponding to the lower end of the support region 48b. In this case, downward movement caused by the weight of the lumbar support 61 or the load when the user leans on it can be restricted. Alternatively, the engaging portion 88 may be provided only at a position corresponding to the upper end of the support region 48b. In this case, upward movement caused by the load when the user leans on it can be restricted.

[0087] In the description of the first embodiment, the inner support portion 71b is provided on the first support member 66 and is configured to support the second inner surface 57b of the second plate portion 57. In this regard, the inner support portion 71b may be configured so that the first support member 66 supports the first inner surface 56b of the first plate portion 56. Alternatively, the second support member 67 may be configured to support the second inner surface 57b of the second plate portion 57. Alternatively, the second support member 67 may be configured to support the first inner surface 56b of the first plate portion 56. Alternatively, the first support member 66 and the second support member 67 may each be provided with the inner support portion 71b to support the first inner surface 56b and the second inner surface 57b.

[0088] The inner support portion 71b may be omitted from the first support member 66 and the second support member 67. The mounting member 68 may be provided integrally with the second support member 67.

[0089] The connection between the first support member 66 and the second support member 67 is not limited to the use of the fixing member 86 consisting of a nut and bolt, but may be made using fixing means such as a snap, hook, or fastener.

[0090] The connection between the first support member 66 and the mounting member 68 is not limited to the fixing member 87 consisting of a nut and bolt, but may be made using fixing means such as a snap, hook, or fastener.

[0091] The configuration for finely adjusting the vertical position by moving the support body 62 up and down relative to the support 63 can also be configured as follows. For example, the mounting groove 72 is provided with a rack member having a rack portion. The rack portion is configured with teeth aligned in the vertical direction so as to have a sawtooth shape. The teeth that make up the rack portion are elastic. The longitudinal length of the rack member corresponds to the fine adjustment range of the support body 62 in the vertical direction.

[0092] On the other hand, the mounting piece 64 is equipped with an engaging member. The engaging member has one or more engaging claws that engage with the rack portion. The engaging claws are configured to be more rigid than the rack portion and engage with the rack portion. When the support body 62 is moved up or down, the engaging claws bend the elastic tooth portions and move to the next position. The position of the support body 62 is difficult to move as the engaging claws engage with the tooth portions of the rack portion, and the adjusted position is maintained. The support body 62 can be moved little by little in the pressing direction by being pressed in either the up or down direction. Specifically, fine adjustments can be made by the size of one tooth portion. This allows fine adjustments to be made to the up or down position of the support body 62.

[0093] The support pillar 43 is not limited to a V-shape, but may have an H-shaped cross section with two plate portions connected by a connecting plate at their midpoints in the height direction, or may have a concave or U-shaped cross section with two plate portions connected at one end by a connecting plate. Support pillars with an H-shaped or U-shaped cross section preferably have the widest spacing at their tips. Furthermore, the support pillars may have a cylindrical cross section with no open ends, such as a rectangular or circular shape.

[0094] The support column 43 may have a solid structure without an internal cavity or recessed portions. The shape of the support column 43 and the first support member 66 and second support member 67 corresponding to that shape can also be configured as follows.

[0095] 17, the support pillar 43 has a V-shaped opening formed by the first plate 56 and the second plate 57, as in the above-described example. As an example, the first plate 56 and the second plate 57 have the same constant thickness. The support pillar 43 has a wider gap at the distal end than at the proximal end. That is, the support pillar 43 has a distal outer surface width (W1) at the distal end of the first outer surface 56a and the distal end of the second outer surface 57a that is wider than the proximal outer surface width (W2). The open end is the apex, which is the engagement portion where the first outer support wall 74 and the second outer support wall 77 engage.

[0096] As shown in FIG. 18 , the support column 43 has a V-shaped opening formed by the first plate portion 56 and the second plate portion 57, but each of the first plate portion 56 and the second plate portion 57 has a non-uniform thickness. That is, the inner surfaces of both the first plate portion 56 and the second plate portion 57 are flat. The outer surfaces include first inclined portions 56x, 57x that gradually increase in thickness from the distal end toward the proximal end, and second inclined portions 56z, 57z that gradually decrease in thickness toward the proximal end after passing the apexes 56y, 57y. Each outer surface has a mountain shape. In this support column 43, the base-side outer surface width (W2) of the apex 56y of the first outer surface 56a and the apex 57y of the second outer surface 57a is wider than the tip-side outer surface width (W1). The portion of the base end side outer surface width (W2) serves as an engagement portion where the first outer support wall 74 and the second outer support wall 77 engage with each other.

[0097] FIG. 19 shows an example in which the first support member 66 and the second support member 67 are attached to the support region 48b of the support column 43 shown in FIG. 17 from the opening side of the support column 43. The support opening width (W3) defined by the tip of the first outer support wall 74 and the tip of the second outer support wall 77 is narrower than the tip-side outer surface width (W1). Here, the range (engagement portion) in which the first outer support member 74a overlaps with the first outer surface 56a does not cover the entire first outer surface 56a, but extends from the tip that constitutes the opening end to the center between the tip and base ends, or to any position between the tip and center. Similarly, the range in which the second outer support member 77a overlaps with the second outer surface 57a does not cover the entire second outer surface 57a, but extends from the tip that constitutes the opening end to the center between the tip and base ends, or to any position between the tip and center. This makes it difficult for the support body 63 to fall off from the front side of the support pillars 43l and 43r even if the overlapping area with the outer surface of the support pillar 43 is small.

[0098] 20 shows an example in which the first support member 66 and the second support member 67 are attached to the support region 48b of the support column 43 shown in FIG. 18 from the opening side of the support column 43. In this case, the first outer support portion 74a and the second outer support portion 77a have shapes that conform to the first outer surface 56a and the second outer surface 57a, and their respective tips extend beyond the apexes 56y and 57y and are positioned at the second inclined portions 56z and 57z. Therefore, the first outer support wall 74 and the second outer support wall 77 are furthest apart at the positions of the apexes 56y and 57y and then narrow at the positions of the second inclined portions 56z and 57z. In other words, the support opening width (W3) defined by the tip of the first outer support wall 74 and the tip of the second outer support wall 77 is narrower than the base-end outer surface width (W2). The first outer support portion 74a and the second outer support portion 77a do not entirely cover the first outer side surface 56a and the second outer side surface 57a. Even with this configuration, the support body 63 is less likely to fall off from the front side of the support pillars 43l, 43r even if the overlapping area with the outer side surfaces of the support pillars 43 is small.

[0099] FIG. 21 shows an example of attaching a first support member 66 and a second support member 67 to the support region 48b of the support column 43 shown in FIG. 17. In FIG. 21, the first support member 66 and the second support member 67 are placed on the base ends of the first plate portion 56 and the second plate portion 57. In this case, the first outer support portion 74a and the second outer support portion 77a entirely cover the first outer surface 56a and the second outer surface 57a. The tips of the first outer support portion 74a and the second outer support portion 77a include first locking pieces 74x and second locking pieces 77x that are bent inward. As an example, the support opening width (W3), which is the distance between the tips of the first locking pieces 74x and the second locking pieces 77x, is narrower than the tip-side outer surface width (W1). As a result, the first locking piece 74x is locked to the tip of the first plate portion 56, and the second locking piece 77x is locked to the tip of the second plate portion 57. Therefore, even with this configuration, the support body 63 is less likely to fall off rearward from the support portions 43l, 43r.

[0100] FIG. 22 shows an example of attaching the first support member 66 and the second support member 67 to the support region 48b of the support column 43 shown in FIG. 18. In FIG. 22, the first support member 66 and the second support member 67 are placed over the base ends of the first plate portion 56 and the second plate portion 57. In this case, the first outer support portion 74a and the second outer support portion 77a are furthest apart at the apexes 56y and 57y and then narrow at the first inclined portions 56x and 57x. The first outer support portion 74a and the second outer support portion 77a cover the second inclined portions 56z and 57z and the first inclined portions 56x and 57x beyond the apexes 56y and 57y up to the middle of the first inclined portions 56x and 57x. In other words, the support opening width (W3) defined by the tip of the first outer support wall 74 and the tip of the second outer support wall 77 is narrower than the base-end outer surface width (W2). The first outer support portion 74a and the second outer support portion 77a do not entirely cover the first outer side surface 56a and the second outer side surface 57a. Even with this configuration, the support body 63 is less likely to fall off from the front side of the support pillars 43l, 43r even if the overlapping area with the outer side surfaces of the support pillars 43 is small.

[0101] As a modified example of the support 43 shown in FIG. 18 , a plurality of apexes 56y, 57y may be provided on the first outer surface 56a and the second outer surface 57a. For example, the apexes 56y, 57y may be provided at positions on the first outer surface 56a and the second outer surface 57a that are the same distance from the tip. The apexes 56y, 57y provided at corresponding positions in this manner have the same height. Furthermore, for example, when apexes 56y, 57y are provided at three locations on the first outer surface 56a and the second outer surface 57a, the apexes 56y, 57y at a first position on the tip side, the apexes 56y, 57y at a second intermediate position, and the apexes 56y, 57y at a third position on the base end side may be at different heights. Furthermore, the apexes 56y, 57y may be provided at different distances from the tip on the first outer surface 56a and the second outer surface 57a.

[0102] As shown in FIG. 23 , the support column 43 has a first plate portion 56 and a second plate portion 57 each having a thickness-varying shape. Both the first plate portion 56 and the second plate portion 57 have flat inner surfaces. The outer surfaces include first inclined portions 56o, 57o that are inclined so that the distance therebetween narrows from the opening edge, and second inclined portions 56q, 57q that are connected via valleys 56p, 57p. The second inclined portions 56q, 57q are inclined in the opposite direction to the first inclined portions 56o, 57o. Furthermore, the outer surfaces include third inclined portions 56s, 57s that are inclined in the same direction as the first inclined portions 56o, 57o through peaks 56r, 57r. That is, the support column 43 is configured such that the tip-side outer surface width (W1) of the tip portion of the first outer surface 56a and the tip portion of the second outer surface 57a is wider than the base-side outer surface width (W2). The open end portion serves as an engaging portion where the first outer support wall 74 and the second outer support wall 77 engage with each other.

[0103] The first outer support portion 74a and the second outer support portion 77a have shapes that follow the first outer surface 56a and the second outer surface 57a, and their respective tips are located in the valleys 56p and 57p. The support opening width (W3) defined by the tips of the first outer support wall 74 and the second outer support wall 77 is narrower than the tip-side outer surface width (W1). Even with this configuration, the support 63 is less likely to fall off from the front sides of the support posts 43l and 43r, even if the overlap with the outer surfaces of the support posts 43 is small.

[0104] The number of support pillars 43 may be one or three or more. For example, when there is one support pillar 43, the lumbar support 61 is supported by the one support pillar 43. When there is one support pillar 43, there is one support body 63, and when there are three support pillars 43, support bodies may be provided on all support pillars 43, or support bodies (two) may be provided on the support pillars on both sides.

[0105] The chair 1 does not have to be equipped with the swing support mechanism 45. That is, the chair 1 may be configured so that the backrest main body 32 is attached to the backrest support 31 on both the upper and lower sides so as not to swing.

[0106] The chair 1 may have legs that do not include casters 11c. The seat 22 may also be provided with armrests. [Explanation of symbols]

[0107] 12...Seat structure 13...Backrest structure 31...Backrest support 32...Backrest body 33...Back support member 39...Connecting member 43(43l,43r)...Strut part 47a...First curved section 47b...Second curved section 47c…Straight section 48a…Constant shape area 48b…Support area 56…1st plate part 56a...first outer surface 56b…First inner surface 57…Second plate part 57a…Second outer surface 57b…Second inner surface 60…Space part 61...Lumbar support 62...Support body 63(63l,63r)...Support 64(64l,64r)...Mounting piece 66...First support member 67...Second support member 68...Mounting member 71b…Inner support part 72...Mounting groove 74...First outer support wall 74a...First outer support part 77…Second outer support wall 77a…Second outer support part 81...Retaining part 88...Engagement part

Claims

1. A chair having a backrest structure, The backrest structure is a backrest support connected to the seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support supported by the support pillar and disposed between the support pillar and the backrest body, The lumbar support includes a support body extending in the left-right direction of the backrest body, and a support body that supports the support body on the support column, The support pillar portion includes a first plate portion having a first outer surface and a second plate portion having a second outer surface facing in a direction different from the first outer surface, and includes an engaging portion configured such that the first plate portion and the second plate portion are connected at a base end side and that the outer surface widths of the tip portions of the first outer surface and the second outer surface are wider than the base end side, the support body includes a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface; the outer surface width is larger than a support opening width between a tip end of the first outer support wall and a tip end of the second outer support wall in the support body, In the support region of the support body in the support column, the first support member and the second support member are connected, so that the first outer support wall and the second outer support wall cover the engaging portion from the distal end side or the proximal end side of the first plate portion and sandwich the first outer surface and the second outer surface of the support column. chair.

2. A chair having a backrest structure, The backrest structure is a backrest support connected to the seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support supported by the support pillar and disposed between the support pillar and the backrest body, The lumbar support includes a support body extending in the left-right direction of the backrest body, and a support body that supports the support body on the support column, the support portion comprises a first plate portion having a first outer surface and a second plate portion having a second outer surface facing in a direction different from the first outer surface, and the first plate portion and the second plate portion are connected at a base end side, and the support portion comprises an engaging portion configured so that the outer surface width of an apex on the base end side of each tip of the first outer surface and the second outer surface is wider than the outer surface width of a tip portion of the first outer surface and a tip portion of the second outer surface, the apex being the engaging portion, the support body includes a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface; an outer surface width of the top portion is larger than a support opening width between a tip end of the first outer support wall and a tip end of the second outer support wall in the support; In the support region of the support body in the support column, the first support member and the second support member are connected to each other to cover the engaging portion from the distal end side or the proximal end side of the first plate portion and sandwich the first outer surface and the second outer surface of the support column. chair.

3. A chair having a backrest structure, The backrest structure is a backrest support connected to the seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support supported by the support pillar and disposed between the support pillar and the backrest body, The lumbar support includes a support body extending in the left-right direction of the backrest body, and a support body that supports the support body on the support column, The support portion includes a first plate portion having a first outer surface and a second plate portion having a second outer surface facing in a direction different from the first outer surface, the support body includes a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface; In a support region of the support body in the support column, the first outer support wall and the second outer support wall sandwich the support column, the support column includes a shape-changing portion for restricting vertical displacement of the support body relative to the support region, The support column includes a shape-constant region having a constant shape in the vertical direction, and the support region is included within the shape-constant region, The shape-changing portion is an engaging portion that is provided on at least one of the inner surfaces of the first inner surface of the first plate portion and the second inner surface of the second plate portion and that engages with the support body, and is the engaging portion that is located corresponding to at least one of the upper end and the lower end of the support area. chair.

4. The engaging portion is a rib integral with at least one of the first inner surface and the second inner surface, and a tip of the rib is lower than at least one of the tip of the first plate portion and the tip of the second plate portion.

4. The chair of claim 3.

5. A chair having a backrest structure, The backrest structure is a backrest support connected to the seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support supported by the support pillar and disposed between the support pillar and the backrest body, The lumbar support includes a support body extending in the left-right direction of the backrest body, and a support body that supports the support body on the support column, The support portion includes a first outer surface and a second outer surface facing in a direction different from the first outer surface, the support body includes a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface; In a support region of the support body in the support column, the first outer support wall and the second outer support wall sandwich the support column, the support column includes a shape-changing portion including a shape-changing point for restricting vertical displacement of the support body relative to the support region, the support portion includes a shape-constant region having a constant shape in the up-down direction, and an upper adjacent region and a lower adjacent region adjacent to the shape-constant region, at least one of the upper adjacent region and the lower adjacent region has a shape different from that of the constant-shape region; The boundary between the shape-constant region and the adjacent region is the shape-changing portion, and the region spanning the shape-constant region and the adjacent region, including the boundary, is the support region. chair.

6. A chair having a backrest structure, The backrest structure is a backrest support connected to the seat structure, the backrest support having a support pillar extending upward from a lower portion thereof, a backrest body supported by the backrest support, and a lumbar support supported by the support pillar and disposed between the support pillar and the backrest body, The lumbar support includes a support body extending in the left-right direction of the backrest body, and a support body that supports the support body on the support column, The support portion includes a first plate portion having a first outer surface and a second plate portion having a second outer surface facing in a direction different from the first outer surface, the support body includes a first support member having a first outer support wall supported on the first outer surface, and a second support member having a second outer support wall supported on the second outer surface; In a support region of the support body in the support column, the first outer support wall and the second outer support wall sandwich the support column, the support column includes a shape-changing portion for restricting vertical displacement of the support body relative to the support region, The support portion gradually becomes thicker or thinner from top to bottom, one of the first support member and the second support member includes an inner support portion that supports an inner surface on the back side relative to one of the first outer surface and the second outer surface, The shape change portion is at least one of an outer interference portion where at least one of the outer support portion of the first outer support wall and the second outer support wall interferes with an outer surface facing the outer support portion, and an inner interference portion where the inner support portion interferes with an inner surface facing the inner support portion. chair.

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