JP2022189292A - Reaction force adjustment mechanism for chair backrest reaction force mechanism - Google Patents

Abstract

To enable materialization of weight saving and down-sizing of a main frame part, for example, reaction adjustment of a chair.SOLUTION: A chair backrest reaction force mechanism 60 generates, by compression of a reaction force spring 65, a force for pushing back a backrest linked with backward tilting of the backrest. In connection with this mechanism, a reaction force adjustment mechanism adjusts the initial compression amount of the reaction force spring 65, by providing displacement in a stretching direction for the reaction force spring 65 by including a reaction force adjustment operation shaft 7 and operating this shaft 7. The reaction force adjustment operation shaft 7 is composed of synthetic resin, with the left and right restrained by a main frame 2 for supporting a back seat, with one end of the reaction force spring 65 supporting in the intermediate position. In the main frame 2, there is installed an intermediate bearing part 11 which receives and supports, in the expansion direction of the reaction force spring 65, the reaction force adjustment operation shaft 7 on the opposite side of a part that supports one end of the reaction force spring 65 of the reaction force adjustment operation shaft 7.SELECTED DRAWING: Figure 3

Description

The present invention relates to a reaction force adjusting mechanism for a backrest reaction force mechanism of a chair. More specifically, the present invention is a chair backrest reaction force mechanism that obtains a force (reaction force) that compresses a spring and pushes the backrest back to its initial position. The present invention relates to a reaction force adjusting mechanism that adjusts the initial amount of compression of a force spring.

Conventionally, a spring (reaction spring) has been used in a locking mechanism for a backrest of a chair. The rocking function is a function that allows the backrest to tilt backward, and when you put your weight on the backrest, it tilts with a moderate repulsive force. When the backrest tilts backward, a force (reaction force) is obtained to compress the spring and push the backrest back to the initial position.

Therefore, since a large force is applied to the reaction spring, a rotating shaft that receives the reaction spring is required to have rigidity. Alternatively, the surface that receives the reaction spring is provided with a wall portion, and has a rigid structure that can withstand the load from the spring (for example, Patent Literature 1 and Patent Literature 2).

JP 2008-125561 A Japanese Unexamined Patent Application Publication No. 2012-10938

However, in recent years, the reaction force mechanism for locking the backrest of the chair, the reaction force adjustment mechanism, and the main frame part including the back seat support structure (generally called the mechanism) A simple configuration is desired from the viewpoint of lightening and miniaturization of the conventional equipment).

For example, by using a metal member for the reaction force adjustment operation shaft of the reaction force adjustment mechanism, the weight becomes heavy and it becomes difficult to separate and dispose. In addition, increasing the size of the spring receiving wall that receives the reaction force spring results in an increase in the size of the reaction force adjustment mechanism, the mechanical portion, and the main frame portion.

It is an object of the present invention to provide a reaction force adjusting mechanism for a backrest reaction force mechanism of a chair, which has a structure capable of realizing reduction in weight and size of the main frame portion of the chair, for example, reaction force adjustment. aim.

To achieve this object, the present invention provides a backrest reaction force mechanism for a chair that generates a force to push back the backrest by compressing a reaction spring in conjunction with the backward tilting of the backrest. The reaction force adjustment mechanism includes a force adjustment operation shaft, and by operating the reaction force adjustment operation shaft, provides displacement in the expansion and contraction direction to the reaction force spring to adjust the initial compression amount of the reaction force spring, and adjusts the reaction force. The operating shaft is made of synthetic resin, and is restrained on the left and right sides by the main frame that supports the seat back. An intermediate bearing portion is provided on the opposite side of the supporting portion for receiving and supporting the reaction force adjusting operation shaft in the expansion direction of the reaction force spring.

Further, in the reaction force adjusting mechanism of the backrest reaction force mechanism of the chair of the present invention, a cam is interposed between the reaction force adjusting operation shaft and the reaction force spring, and the reaction force adjusting operation shaft is operated to adjust the reaction force spring. It is preferable to adjust the initial compression amount of the reaction spring by changing the amount of cam displacement applied to .

Further, in the reaction force adjusting mechanism of the backrest reaction force mechanism of the chair of the present invention, the reaction force adjusting mechanism rotates the reaction force adjusting cam that displaces the reaction force spring in the extension/contraction direction, and the reaction force adjusting cam. and a reaction force adjustment operation shaft for switching the cam displacement amount applied to the reaction force spring, and by rotating the reaction force adjustment operation shaft, the cam displacement amount applied by the reaction force adjustment cam is switched, and the reaction force spring It is preferable to adjust the initial compression amount of .

Further, in the reaction force adjustment mechanism of the backrest reaction force mechanism of the chair of the present invention, the reaction force adjustment cams are provided at two locations on the reaction force adjustment operation shaft with an interval therebetween. It is preferable that the reaction force adjusting operation shaft and the reaction force spring are arranged in a positional relationship orthogonal to each other between and and the intermediate bearing portion is arranged on the side opposite to the reaction force spring.

Further, in the reaction force adjusting mechanism of the backrest reaction force mechanism of the chair of the present invention, it is preferable that the intermediate bearing portion rises from the bottom wall portion of the main frame.

Further, the chair of the present invention preferably comprises the reaction force adjusting mechanism for the backrest reaction force mechanism of the chair according to any one of claims 1 to 5.

According to the reaction force adjustment mechanism of the backrest reaction force mechanism of the chair of the present invention, by configuring the reaction force adjustment operation shaft with a synthetic resin, it is possible to reduce the weight of the reaction force adjustment and promote the sorting and disposal. A support structure in which the reaction force adjustment operation shaft is less likely to bend by supporting the reaction force adjustment operation shaft in the expansion direction of the reaction force spring at an intermediate bearing portion on the opposite side of a portion of the reaction force adjustment operation shaft that supports one end of the reaction force spring. can be Therefore, it is possible to provide a reaction force adjusting mechanism that achieves a lighter and smaller chair.

It is a perspective view which shows one Embodiment of the chair to which this invention is applied from the bottom. 1 is an exploded perspective view showing an embodiment of a seat, a back, a backrest reaction force imparting mechanism, and the like; FIG. FIG. 4 is a central vertical cross-sectional view showing an embodiment of a backrest reaction force mechanism, its reaction force adjustment mechanism, and a locking range adjustment mechanism that regulates the locking range of the backrest. 1 is a perspective view showing an embodiment of a backrest reaction force mechanism, its reaction force adjustment mechanism, and a locking range adjustment mechanism that regulates the locking range of the backrest; FIG. FIG. 3 is a vertical cross-sectional view showing one embodiment of the reaction force adjusting mechanism along the axial center (the cross-section is shown in color). FIG. 4 is a partial longitudinal cross-sectional perspective view showing the relationship between the reaction force adjusting operation shaft of the reaction force adjusting mechanism, the operating shaft holder, and the main frame, centering on the restricting protrusion (the cross section is shown in color). FIG. 4 is a partial vertical cross-sectional perspective view showing the relationship between the reaction force adjusting operation shaft of the reaction force adjusting mechanism, the operation shaft holder, and the main frame, centering on the intermediate bearing portion (the cross section is shown in color). FIG. 4 is a perspective view showing the relationship between the backrest reaction force mechanism and the reaction force adjustment mechanism with the operation shaft holder removed; FIG. 4 is a perspective view showing the relationship between a backrest reaction force mechanism and a reaction force adjustment mechanism; It is a perspective view which shows an operating shaft presser from the bottom. FIG. 4 is a perspective view showing a partial cross-section of the operating shaft presser along the shaft center; FIG. 5 is an explanatory diagram showing the relationship between the reaction force adjusting cam of the reaction force adjusting operation shaft and the slider; FIG. 4 is a perspective view showing one embodiment of a reaction force adjusting operation shaft; FIG. 10 is a side view of the reaction force adjusting operation shaft as viewed from the tip shaft portion side; FIG. 4 is a perspective view showing an embodiment of a main frame from diagonally upper left rear; FIG. 4 is a perspective view showing an embodiment of a main frame from diagonally upper right rear; FIG. 10 is a perspective view showing an embodiment of a backrest support member from diagonally above the front; FIG. 4 is a perspective view showing an embodiment of the outer shell of the seat from obliquely downward and rearward. Fig. 2 is a perspective view showing the relationship between the outer shell of the seat, the main frame, and the seat rotation shaft, partly in section along the axis (the section is shown in color). FIG. 10 is a perspective view showing one embodiment of a mechanism for preventing the seat rotation shaft from coming off (cross-sectional portions are shown in color). Fig. 10 is a partially sectioned perspective view showing a state before the retaining member is inserted into the vertical hole of the outer shell (the section is shown in color); FIG. 10 is a perspective view showing an embodiment of a backrest locking range adjusting mechanism from obliquely downward and rearward. FIG. 4 is a perspective view showing one embodiment of a locking block that constitutes the locking range adjustment mechanism; It is the perspective view which looked at the locking block from the axial end of the opposite side. FIG. 4 is a perspective view showing one embodiment of a fixed block that constitutes the locking range adjustment mechanism; It is the perspective view seen from the surface of the opposite side of the fixed block. FIG. 4 is a perspective view showing one embodiment of a rotation axis of a locking block; FIG. 5 is a perspective view showing another embodiment of the reaction force adjusting mechanism of the backrest reaction force mechanism of the chair according to the present invention; It is the perspective view which looked at the reaction force adjustment operation shaft of the same reaction force adjustment mechanism from the handle|steering-wheel side. It is the perspective view which looked at the reaction force adjustment operation shaft of the same reaction force adjustment mechanism from the front end side. It is a perspective view which shows the main frame of the same reaction force adjustment mechanism from diagonally upper right rear. It is the longitudinal cross-sectional view which looked at the peripheral wall part side of the same main frame (the cross-sectional part is colored and shown).

Hereinafter, the configuration of the present invention will be described in detail based on the embodiments shown in the drawings. In this specification, the term "front or front" refers to the front or front of the chair and the seat of the chair in the seat and the backrest, respectively, and the term "rear or rear" similarly refers to the direction of the chair. and rearward or backward facing to the occupant. Moreover, the direction orthogonal to the front-rear direction in the horizontal plane is the left-right direction or the width direction for the seated person or the chair in each of the seat and the backrest. In addition, in the seat and backrest, the inner side is the side facing the seated person or the side facing the vertical plane in the front-back direction passing through the center of the chair, and the outer side is the side away from the seated person or the front-back direction passing through the center of the chair. This is the side away from the vertical plane. Further, "top" and "bottom" are above and below for the chair and occupant in the armrests, seat and backrest, respectively, and above and below in a vertical plane.

1 and 2 show an embodiment of a chair to which the present invention is applied. This chair comprises, for example, legs 1 equipped with casters, a main frame (support base) 2 supported by the legs 1, a seat 3 and a back that are swingably supported on the main frame 2 and interlocked with each other. It has a reclining 4. On the front side of the main frame 2, there is a reaction force adjustment mechanism 6 that can adjust the initial reaction force of the backrest reaction force mechanism 5, and on the rear side, there is a reaction force adjustment operation shaft 7 that regulates the locking range of the backrest 4. A locking range adjusting mechanism 8 and an operating shaft for switching the locking range (hereinafter referred to as a locking range switching operating shaft 9) are provided so as to protrude from the sides of the main frame 2, respectively. A cover member 10 is provided between the back frame of the backrest 4 and the main frame 2. - 特許庁

Here, the main frame 2 is molded from a synthetic resin in the case of this embodiment. As the synthetic resin, it is preferable to use a rigid synthetic resin such as glass-fiber-reinforced nylon such as PA6-GF (polyamide 6) in order to ensure the mechanical rigidity of the structure. Of course, the main frame 2 is not particularly limited to this, and the main frame 2 may be configured by molding an aluminum die-cast or steel material into a box shape or other shape with welding.

For example, the main frame 2 of the present embodiment has a front and rear structure, as shown in FIGS. It has a box shape having left and right peripheral wall portions 2A, a bottom wall portion 2B, intermediate partition walls 2C arranged in the front-rear direction, and reinforcing ribs 2D connecting them. The rear side of the main frame 2 is further provided with a rear-side pedestal support cylindrical portion 2E into which the gas spring of the pedestal is fitted, and a recess 19 for mounting the buffer block 41 .

An intermediate bearing portion 11 is provided on the front side of the main frame 2 to support the intermediate shaft portion 52 of the reaction force adjusting operation shaft 7 at least in the expansion direction of the compression coil spring 65 between the left and right partition walls 2C. It is Since a large force is applied to the reaction force spring of the backrest reaction force mechanism 5, that is, the compression coil spring 65, rigidity is required for the shaft that receives the compression coil spring 65, that is, the reaction force adjustment operation shaft 7 of the present embodiment. . For this reason, metal members such as iron are usually used, but from the viewpoint of reducing the weight of the chair and promoting sorted disposal, there is a demand for using resin for the parts. However, in order to ensure mechanical rigidity as a structure, even if it is molded with a synthetic resin with rigidity such as glass fiber reinforced nylon such as PA6-GF (polyamide 6), it is more flexible than a metal shaft. A problem arises. Therefore, by providing the intermediate bearing portion 11 that receives and supports the intermediate shaft portion 52 of the reaction force adjusting operation shaft 7 at least in the expansion direction of the compression coil spring 65, the intermediate shaft portion 52 of the reaction force adjusting operation shaft 7 is supported by the bearing portions at both ends. It is preferable to make it difficult to bend by supporting three points together.

The intermediate bearing portion 11 receives and supports at least the force of the compression coil spring 65, and in the case of this embodiment, is configured as a semi-circular open bearing that opens toward the compression coil spring 65 side. . For example, it is composed of left and right standing walls 11A and front walls 11B that serve as both bearing portions and ribs, and an overhang portion 11C projecting rearward from the main frame. A bearing portion 11D is formed by forming a shape in which the left and right vertical walls 11A are hollowed out in a semicircular shape. The overhang portion 11C receives and supports the force of an upward compression coil spring 65 applied to the reaction force adjusting operation shaft 7. As shown in FIG. In this embodiment, the upright wall 11A, the front wall 11B, and the overhang portion 11C are formed integrally with the bottom wall portion 2B of the main frame 2 so as to stand up from the bottom wall portion 2B. Of course, the intermediate bearing portion 11 may be formed separately from the main frame 2 and fixed to the bottom wall portion 2B by screwing or welding.

The left and right side wall portions 2A of the front portion of the main frame 2 are provided with elongated holes 12 inclined rearward when viewed from below, and the seat rotation shaft 42 rotatably connects the outer shell 71 and the main frame 2. is provided so as to penetrate the

Further, one peripheral wall portion 2A of the main frame 2, for example, the right peripheral wall portion 2A, has a circular through hole (referred to as a round hole 13) for inserting the reaction force adjustment operation shaft 7 of the reaction force adjustment mechanism 6 from the side. A semicircular open bearing portion 14 having a gouged upper edge is provided on the inner partition wall 2C. Further, a semicircular open bearing portion 14 with a gouged upper edge is also provided on the partition wall 2C on the opposite side. Therefore, the reaction force adjusting shaft 7 inserted into the main frame 2 is supported by the round hole 13 and the semicircular open bearing portion 14 of the partition wall 2C. At the same time, the upper half of the reaction force adjustment operation shaft 7 is supported by the operation shaft retainer 43 shown in FIG. and is held so as not to come off in the axial direction.

10 and 11, semicircular bearing portions (open bearing portions 44) for supporting the shaft portions 55 and 59 of the reaction force adjusting operation shaft 7 are provided at both ends of the operating shaft retainer 43. By pressing the shaft portion 56 and the shaft portion 59 of the reaction force adjustment operation shaft 7 from above, the reaction force adjustment operation shaft 7 is held between the semicircular open bearing portion 14 of the partition wall 2C. is rotatably supported. In addition, the inner peripheral surface of the operation shaft retainer 43 is in contact with a restricting projection (stopper) 54 of the reaction force adjustment operation shaft 7 to allow the reaction force adjustment operation shaft 7 to rotate within a certain range (for example, approximately 270°). ) is provided with a restricting projection (stopper) 49 (see FIG. 6). Thereby, the reaction force adjusting operation shaft 7 is attached to the main frame 2 so as to be able to swing within a certain range.

Further, in the case of this embodiment, the operation shaft retainer 43 is provided with a slider housing 50 that accommodates the slider 66 so as to face the reaction force adjustment cam 51 of the reaction force adjustment operation shaft 7 and guides it in the spring axial direction. It is The slider housing 50 is, for example, a rectangular cylindrical case, and is integrally formed with the operating shaft retainer 43 so as to straddle between portions covering the left and right partition walls 2C. Of course, the slider housing 50 is not limited to being molded integrally with the operating shaft retainer 43 , but may be separately molded and assembled to the operating shaft retainer 43 , assembled to the main frame 2 or integrally molded with the main frame 2 . Needless to say, it is possible to do so.

In addition, the operating shaft retainer 43 is provided with a pair of projections 45 at positions where the left and right partition walls 2C of the main frame 2 are covered, respectively, with an interval substantially equal to the thickness of the partition wall 2C. , a recess 48 in which the partition wall 2C is sandwiched. A U-shaped mounting seat portion 47 is also fitted on the base end side (side of the seat rotating shaft 42) of the operating shaft retainer 43 so as to surround the boss portion provided with the screw hole 15 of the main frame 2 from above. is formed. Therefore, the mounting seat portion 47 is placed over the boss portion provided with the screw hole 15, and the partition wall 2C is fitted between the pair of projections 45, that is, the recess portion 48, so as to fit the four through holes on the front, back, left, and right. By screwing a screw from 46 into the screw hole 15, it can be fixed without rattling.

Further, as shown in FIG. 16, a round hole 16 through which the locking range switching operation shaft 9 of the locking range adjusting mechanism 8 passes is formed in one of the rear side walls of the main frame 2, for example, the left side wall 2A. The right side wall portion 2A and the partition wall 2C, which are the other side wall portions, are provided with a semicircular bearing portion receiver 17 for receiving and supporting the tip portion of the locking range switching operation shaft 9, and a round hole 18 through which the tip end penetrates. It is A recess 19 that accommodates the buffer block 41 (resin damper) is a recess surrounded by the side walls of the main frame 2 and has a bottom surface provided with a hole 20 for fitting the pin portion 41a of the buffer block 41 . The buffer block 41 is fixed to the main frame 2 by fitting the recess 19 and fitting the pin portion 41a into the hole 20 on the bottom.

Inside the main frame 2, more specifically, inside the left and right partition walls 2C, there is formed a space 2F in which the reaction force mechanism 60 including the compression coil spring 65 is housed, and is supported on the main frame 2 so as to be swingable. A spring bearing arm 21B of a backrest support member (also called a backrest rod) 21, a reaction force adjustment shaft 7 rotatably supported by the main frame 2, and a rear arm of the backrest 4 disposed between them. Means for generating a force to push back the backrest 4 in conjunction with tilting, such as a compression coil spring 65, can be accommodated.

Here, in the case of the present embodiment, the main frame 2 is connected to the pedestal (in other words, gas spring) by the pedestal support tube portion 2E at the rear portion and is rotatably supported in the horizontal plane, while the front is It is rotatably connected to the outer shell 71 of the seat 3 via the seat rotation shaft 42, and is attached to the seat support shaft 21D of the backrest support member 21 behind the portion of the seat 3 connected by the seat rotation shaft 42. By being engaged, the seat 3 and the backrest 4 are interlocked and supported by the main frame 2 so as to be swingable. That is, the seat 3 is supported so as to be pulled obliquely rearward and lifted in association with the swinging of the backrest supporting member 21 via the backrest rotating shaft 25 . As a result, a weight-sensing (or sensory) reaction force application mechanism 61 is formed, in which the resistance to back rocking is proportional to the weight of the user by linking the seat 3 so as to lift it when the backrest 4 is tilted backward. be.

(reclining back)
In the case of this embodiment, the backrest 4 is, for example, as shown in FIGS. It is composed of a mesh fabric (not shown) that forms a backrest surface, and is swingably mounted on the main frame 2 via a backrest support member 21 . The back frame 4a is preferably made of rigid synthetic resin such as glass fiber reinforced nylon such as PA6-GF (polyamide 6) in order to ensure mechanical rigidity as a structure.

The back frame 4a in this embodiment has, for example, a concave portion 90 on the front side of the bottom side for accommodating the rear portion of the backrest support member 21. The rear plate 21C is connected to the backrest support member 21 by screwing it to the nut 24 of the back plate 21C so as to pass through the bottom of the back frame 4a from behind. As a result, the back frame 4a is fixed to the backrest support member 21 in the front, rear, left, right, up and down directions without rattling.

The backrest support member 21 is swingably attached to the main frame 2 by a backrest rotating shaft 25 that penetrates the main frame 2 in the lateral direction. The backrest support member 21 is attached to the backrest 4 on the rear side of the backrest rotation shaft 25 and is linked to the seat 3 on the front side of the backrest rotation shaft 25 so that the backrest 4 is tilted backward. It has a structure that pulls up the seat 3. Specifically, for example, the plate member 21A of the backrest support member 21 is positioned forward of the through-hole 21F with respect to the rear side of the through-hole 21F with respect to the through-hole 21F through which the backrest rotating shaft 25 passes. In the initial position state (the state in which there is no seated person), the seat 3 and the backrest 4 are each held in the initial position. , the positional relationship is set such that a force for lifting the seat 3 is applied to the seat 3 when the backrest 4 tilts backward.

Specifically, in the case of this embodiment, as shown in FIG. 17, the backrest support member 21 includes a pair of plate members 21A arranged on both sides of the main frame 2 and a seat support shaft connecting them in front. 21D, a back attachment plate 21C connected at the rear, and a spring receiving arm 21B that receives and supports one end of the compression spring mechanism of the reaction mechanism. In the present embodiment, the spring receiving arm 21B has, for example, a generally triangular (v-shaped) shape, and the seat support shaft portion 21D is passed through the corner portion of the apex, and the end of one side in the hanging state (the apex ), the spring support shaft 21E for engaging the rear spring mount 63 is located at the end of the other side (the position corresponding to the vertex) which is tilted toward the rear and downward. A through hole 21F through which the shaft 25 is passed is provided. In other words, the backrest supporting member 21 and the spring receiving arm 21B are rotatably supported on the main frame 2, and simultaneously rock around the backrest rotating shaft 25 while maintaining a constant angular relationship. set to move.

The portion of the backrest support member 21 to which the back frame 4a is attached (that is, the back attachment seat) is arranged across the plate members 21A on both sides of the backrest support member 21, as shown in FIG. A screw hole is provided by fixing a nut 24 to the horizontal connecting plate 21C by welding. The rear portions of the plates 21A on both sides of the backrest support member 21, including the lateral connection plate 21C, are fitted into recesses (backrest support member mounting seats) 90 opened forward in the bottom of the back frame 4a, thereby connecting the lateral connection plate 21C and the lateral connection plate 21C. The backrest support member 21 and the back frame 4a are integrated by screwing the fastening screw from the back of the back frame 4a while the backrest support member mounting seat is attached. A hole (not shown) for inserting a fastening screw that appears on the rear surface of the bottom portion of the back frame 4a is closed by fitting a blind plate 91 after fastening the fastening screw so that it does not appear on the outside. are considered. The blindfold plate 91 has, for example, an engaging claw, which can be easily attached and detached by hooking the engaging claw on a notch of a recess on the back surface of the bottom side of the back frame.

(seat structure)
The seat 3 is not limited to a specific structure and shape, but in the case of this embodiment, as shown in FIG. By connecting the outer shell 71 and the main frame 2 via the seat rotation shaft 42 , it is mounted on the main frame 2 so as to be swingable about the seat rotation shaft 42 . The seat 3 can move up and down within a certain range through the outer shell 71 by making the hole 12 of the main frame 2 that supports the front seat rotation shaft 42 a long hole that is slanted rearward when viewed from below. It is mounted on the main frame 2 so that it can swing while moving in the direction and the front-rear direction.

For example, as shown in FIG. 18, the outer shell 71 of the present embodiment is provided with a U-shaped peripheral wall portion 74 surrounding the main frame 2 so as to protrude downward. and the backrest supporting member 21 are accommodated therein. A longitudinally cut slit 76 is provided in the backrest side surface of the peripheral wall portion 74 , and the backrest support member 21 and the outer shell 71 are separated by passing the backrest support member 21 through the slit 76 . Care is taken to prevent interference. The outer shell 71 is rotatably connected and supported with respect to the main frame 2 by arranging the seat rotating shaft 42 so as to pass through the main frame 2 and the peripheral wall portion 74 housed in the recess 75 and the peripheral wall portion 74 . . In the outer shell 71 , bearing portions are formed on the peripheral wall portion 74 to support both ends of the seat rotation shaft 42 . In the case of this embodiment, the peripheral wall portion 74 has a double-walled structure of, for example, an inner wall portion and an outer wall portion that are continuously formed so as to be folded back at the bottom, and the seat rotating shaft 42 is straddled therebetween. A bearing portion is formed to support both ends. The bearing portion has, for example, a blind round hole 77 formed in one of the peripheral wall portions and a penetrating round hole 78 formed in the other peripheral wall portion.

An outer wall portion of the peripheral wall portion 74 at the position of the round hole 78 is provided with a window-like opening (hereinafter referred to as an opening 80) into which the seat rotating shaft 42 is inserted. This opening 80 is closed by a retaining member 81 after the seat rotating shaft 42 is inserted so as to straddle the main frame 2 and the outer shell 71 . The shape and structure of the outer shell 71 are appropriately designed as required, but at least the outer shell 71 overlaps with the left and right peripheral wall portions 2A of the main frame 2 on one axis, for example, in the horizontal direction (horizontal direction) and is connected to each other via the seat rotation shaft 42. An opening 80 for inserting the seat rotation shaft 42 into the bearing from the side, and a retaining member for preventing the seat rotation shaft 42 from coming off. It is preferable to have a structure for installing 81 . In the present embodiment, one of the bearings is a blind hole, but the present invention is not limited to this. You can block it.

Outside the through hole 78 that supports the seat rotation shaft 42, that is, between the through hole 78 of the peripheral wall portion 74 of the outer shell 71 and the opening 80, as shown in FIGS. A retaining member insertion hole 79 to be attached is formed. The retaining member insertion hole 79 is, for example, a vertical hole that is arranged to intersect the seat rotation shaft 42 and opens to the upper surface of the outer shell 71 (that is, the surface on which the inner shell and urethane foam are placed). A stepped portion (overhang) 83 is formed on the inner surface of the outer wall portion of the peripheral wall portion 74 above the opening portion 80 so as to be caught against coming off. On the other hand, the retainer member 81 abuts on the end surface of the seat rotating shaft 42 inserted so as to straddle the main frame 2 and the outer shell 71 to prevent axial movement. In the case of this embodiment, the retainer member 81 has the rigidity and spring elasticity that realize the retaining of the seat rotating shaft 42. For example, as shown in FIG. It is made of a resin plate, and when the barb 82 is inserted into the retaining member insertion hole 79, the barb 82 part at the tip bends inward, and when it gets over the stepped part 83, it restores and fits in the recessed part under the stepped part 83. At the same time, it is structured to be caught on the stepped portion 83 . In the case of this embodiment, the barb 82 is composed of an inclined surface portion 86 fitted in the opening 80 and a locking portion 87 that rises vertically and abuts against the stepped portion 83 . Therefore, when the barb (bark) 82 portion of the retaining member 81 approaches the stepped portion 83, the locking portion 87 of the barb 82 enters due to the spring elasticity and is caught by the stepped portion 83, whereby the retaining member 81 is is engaged so as not to slip out of the retaining member insertion hole 79 . Further, the rear end of the retaining member 81 is provided with a hooking portion 85 that abuts against the edge of the retaining member insertion hole 79 so as not to sink into the retaining member insertion hole 79 . Although the planar shape of the retaining member insertion hole 79 is not particularly limited, in the case of this embodiment, it is a rectangular hole when viewed from above.

Since the retaining member insertion hole 79 communicates with the opening 80 of the peripheral wall portion 74, the inclined surface portion 86 of the barb 82 is exposed to the surface when the retaining member 81 is inserted. In this embodiment, the area of the inclined surface portion 86 of the barb 82 of the retaining member 81 is set slightly smaller than the opening area of the opening 80, and the retaining member 81 is pushed into the retaining member insertion hole 79. At the same time, the locking portion 87 of the barb 82 is fitted under the stepped portion 83 of the inner surface of the outer wall, and the inclined surface portion 86 of the barb 82 is fitted into the opening 80 to block it. As a result, the inclined surface portion 86 of the barb 82 exposed in the opening 80 from the outside of the peripheral wall portion 74 of the outer shell 71 can be pushed with a finger to be disengaged from the stepped portion 83 .

Further, as shown in FIG. 3 , the seat 3 is positioned rearward of the seat rotation shaft 42 and forward of the backrest rotation shaft 25 in the front-rear direction of the seat 3 . A hook-shaped engaging portion 84 is hooked on and supported by the seat support shaft portion 21D of the backrest support member 21 .

Here, the rear connection position of the outer shell 71 with respect to the backrest support member 21 is provided at the seat support shaft portion 21D forward of the rotation shaft of the backrest support member 21 (backrest rotation shaft 25). It is at a position where the seat 3 can be lifted by the seat support shaft portion 21D on the tip side of the backrest support member 21 when the backrest support member 21 tilts backward. That is, the seat 3 is lifted as the backrest 4 tilts backward, and a part of the weight of the seated person acts as resistance to the rearward tilting movement of the backrest 4 (locking resistance reacts to weight). It is provided to constitute an application mechanism. Therefore, when the seated person leans against the backrest 4, the backrest support member 21 rotates so as to tilt backward around the backrest rotation shaft 25, so that the seat 3 is pulled up obliquely rearward. A reaction force proportional to the weight of the seated person is applied to the backrest 4 via the backrest support member 21 by lifting the rear side of the seat 3 .

The outer shell 71 is not limited to a specific material and structure, but in the case of the present embodiment, it is molded from a rigid synthetic resin such as glass-fiber reinforced nylon, and has an appropriate rib structure. It is reinforced by employing The connection structure between the outer shell 71 and the inner shell is known, so it is not shown in detail. is engaged with a T-shaped slit extending in the front-rear direction as seen from above the inner shell, that is, the head of the T-shaped locking claw is passed through the T-shaped slit and then slid in the front-rear direction. are fixed to each other.

To assemble the seat 3 and the main frame 2, the outer shell 71 is put on the concave portion 75 of the outer shell 71 so as to accommodate the main frame 2, and the long hole 12 of the main frame 2 and the rotary shaft hole (opening) of the outer shell 71 are assembled. With the portion 80, the through hole 78 and the blind round hole 77) aligned, the seat rotating shaft 42 is inserted through the opening 80 from the outside of the outer shell 71. As shown in FIG. Then, the seat rotating shaft 42 is pushed in until the tip side hits the blind round hole 77 of the outer shell 71 . After that, the retaining member 81 is inserted into the retaining member insertion hole 79 from the upper surface of the outer shell 71 and pressed until the barb 82 is accommodated under the stepped portion 83 while abutting the rear end surface of the seat rotating shaft 42 . When the retainer member 81 is attached to the retainer member insertion hole 79 , the shaft end surface of the seat rotating shaft 42 abuts against the retainer member 81 and is fixed. After that, the inner shell 72 and the cushion 73 are put on the outer shell 71 and then wrapped with the covering material. Next, the claw-shaped bearing portion 84 in the middle of the outer shell 71 is placed on the seat support shaft 21D of the backrest support member 21 and pushed in from above, thereby engaging the claw-shaped bearing portion 84 and the seat support shaft 21D. rotatably fitted. As a result, the seat 3 is supported so as to be pulled obliquely rearward and lifted in association with the swinging of the backrest supporting member 21 about the backrest rotating shaft 25 .

In the case of this embodiment, for example, after the outer shell 71 is rotatably connected to the front of the main frame 2 via the seat rotation shaft 42, the retainer member 81 is inserted and then the inner shell is placed, and the cushion is placed thereon. It is designed to be fixed by wrapping it with an upholstery after putting it on. Therefore, after the seat 3 is assembled to the main frame 2 and the seat 3 is assembled, the seat rotating shaft 42 will not come off. On the other hand, when it becomes necessary to separate the seat 3 and the main frame 2, the outer shell 71 is exposed through the opening 80 of the outer peripheral wall of the outer shell 71 with the urethane foam cushion and inner shell removed. If the barb 82 of the retaining member 81 is pushed in to remove the barb 82 from the stepped portion 83, the retaining member 81 can be removed upward from the outer shell. can be separated. In the present embodiment, the retainer member insertion hole 79 is a vertical hole, and the retainer member 81 is inserted from the upper surface of the outer shell 71. However, the present invention is not limited to this. The retaining member insertion hole 79 and the stepped portion 83 may be formed laterally so that the retaining member 81 is inserted through. It is sufficient that the retaining member insertion hole 79 is provided in a direction intersecting with the shaft 42 . In this case as well, if the barb 82 of the retaining member 81 exposed in the opening 80 is pushed in to remove the barb 82 from the stepped portion 83, the retaining member 81 can be removed upward from the outer shell. The seat 3 and the main frame 2 can be separated by removing the axle 42 .

(Backrest reaction force mechanism)
The backrest reaction force mechanism 5 is not limited to a particular style, but in the case of this embodiment, as shown in FIG. A reaction force mechanism 60 using a spring that obtains a force (reaction force) to push back to the initial position and a resistance against back rocking are used by linking the backrest 4 so as to lift the seat 3 when the backrest 4 is tilted backward. A weight-sensitive (or sensing) reaction force application mechanism 61 is also used, which is proportional to the weight of the person. Of course, depending on the embodiment, only one of the reaction force mechanisms may be adopted.

Specifically, a weight-sensitive reaction force application mechanism 61 and a reaction force mechanism 60 using a spring are incorporated on the front side of the backrest rotation shaft 25 of the backrest support member 21 . It is provided between the main frame 2 and the reaction force adjustment operation shaft 7 so as to generate a force (reaction force) to push back the backrest 4 in conjunction with the backward inclination of the backrest 4 .

Here, the reaction force mechanism 60 using a spring is a reaction force adjustment operation, which is a fixed shaft attached to the spring support shaft 21E of the backrest support member 21 and the main frame 2, for example, one compression coil spring 65. A spring-type reaction force mechanism 60 including a compression coil spring 65 is interposed between the shaft 7 and the backrest supporting member 21 supported swingably by the main frame 2 and the front side of the main frame 2 . and a fixed shaft such as a reaction force adjustment operation shaft 7 so as to generate a force to push back the backrest 4 in conjunction with the backward inclination of the backrest 4 .

The compression coil spring 65 is mounted between a fixed shaft such as the reaction force adjustment operation shaft 7 and the spring support shaft 21E of the arm portion 21B of the backrest support member 21 via the front spring mount 62 and the rear spring mount 63 . A mount pin 64 is inserted between the front and rear spring mounts 62 and 63 to prevent the compression coil spring 65 from buckling.

The front spring mount 62 and the rear spring mount 63 are well-known mechanical elements and will not be described in detail. It is provided with means for engaging with the force adjusting operating shaft 7 or the movable shaft such as the spring support shaft 21E, such as a concave portion, a convex portion, or a hook portion. In the case of this embodiment, since the initial reaction force adjusting mechanism 6 of the reaction force mechanism is provided, the reaction force adjusting operation shaft 7 which is a fixed shaft is abutted via the slider 66 . Therefore, on the surfaces of the slider 66 and the front spring mount 62 that contact each other, a projection 62a and a recess 66b having a semi-circular cross section and having an axis (horizontal axis) parallel to the backrest rotation shaft 25 are formed. By fitting the concave portion 66b and the convex portion 62a, a universal joint is formed in which the angle (formed by the slider 66 and the front spring mount 62) can be varied in a plane orthogonal to the backrest rotation shaft 25. A front spring mount 62 is pivotally supported with respect to 66 .

The rear spring mount 63 is provided with a hook hooked on the spring support shaft 21E on the rear side and a shaft portion projecting to the side of the hook and functioning as a spacer between the arm portions 21B. It is swingably supported by being hooked on the support shaft 21E so as to prevent lateral (widthwise) movement.

Therefore, when the backrest 4 tilts backward and the arm portion 21B rotates around the backrest rotation shaft 25 and is pushed forward, the compression coil spring 65 is compressed via the rear spring mount 63. . At the same time, the seat support shaft 21D at the tip of the backrest support member 21 is lifted to lift the rear portion of the seat 3. As shown in FIG. Since the front end of the seat 3 is accommodated in the rearwardly inclined elongated hole 12 of the main frame 2 via the rotation shaft, the seat 3 is lifted so as to be pulled up slightly obliquely rearward. Therefore, the seat support shaft 21</b>D at the tip of the backrest support member 21 bears the weight of the seated person on the seat 3 . That is, a force proportional to the weight of the seated person is applied to the tip of the backrest support member, and a reaction force is applied to the backrest 4 via the arm portion 21B of the backrest support member 21 .

(Initial reaction force adjustment mechanism of reaction force mechanism)
The backrest reaction force application mechanism 5 is provided with a reaction force adjustment mechanism 6 that can adjust the initial reaction force (the reaction force of the compression coil spring 65 applied in the initial position state).

The reaction force adjustment mechanism 6 changes the position at which one end of the compression coil spring 65 abuts on a fixed member on the main frame 2 side, thereby adjusting the compression amount of the compression coil spring 65 at the initial position (that is, the initial compression amount). is adjusted. As shown in FIG. 8, the reaction force adjusting mechanism 6 of the present embodiment uses a cam mechanism to apply displacement in the expansion and contraction direction of the compression coil spring 65, thereby changing the amount of compression of the compression coil spring 65 at the initial position. It is composed of a reaction force adjusting cam 51 rotated by the reaction force adjusting operation shaft 7 and a slider 66 as a follower.

In the present embodiment, the reaction force adjusting cam 51 is integrally molded with the reaction force adjusting operation shaft 7 from rigid synthetic resin such as glass fiber reinforced nylon such as PA6-GF (polyamide 6). As shown in FIG. 14, the reaction force adjusting cam 51 has a cam base circle 51f having a smaller diameter than the minimum shaft diameter of the reaction force adjusting operation shaft 7, for example, the shaft diameter of the tip shaft portion 55 in the case of this embodiment. , with the position of the cam base circle 51f as the starting point or ending point. In the case of the reaction force adjusting cam 51 of the present embodiment, the swinging range of the reaction force adjusting operation shaft 7 (the swinging range regulated between the restricting protrusion 49 of the operating shaft retainer 43 and the restricting protrusion 54 of the reaction force adjusting operating shaft 7). It is configured as a planar cam having a polygonal cam contour that allows the cam displacement amount to be switched in a plurality of steps, for example, about four steps within a movable range).

Here, the cam surface 51a, which is the starting point or the terminal point, is a flat surface that is tangential to the cam base circle 51f having a diameter smaller than the minimum shaft diameter of the reaction force adjustment operation shaft 7. The cam surfaces 51b, 51c, and 51d, which are switched with rotation, increase or decrease the displacement given to the slider 66 stepwise. Therefore, the cam displacement can be set in multiple stages while the reaction force adjusting cam itself is made compact, and the cam can be operated with a light force due to the relationship between the moment of force and the torsional moment. In addition, when in a state other than the switching operation, the force from the compression coil spring 65 acts perpendicularly to the flat surfaces due to the contact between the flat surfaces, so there is a sense of stability, and the initial compression amount of the compression coil spring can be reduced. At the time of switching, a click feeling is generated by crossing over the switching section 51e while the displacement gradually increases.

Of course, the cam contour surface of the reaction force adjusting cam 51 is not limited to the intermittent polygonal flat end surface as shown in the figure, and the reaction force adjusting operation shaft 7 may be a continuous curved cam contour that provides stepless displacement. , the displacement applied to the compression coil spring 65, that is, the initial amount of compression may be steplessly increased or decreased. In this case as well, by making the cam base circle 51f smaller in diameter than the shaft diameter of the minimum shaft portion of the reaction force adjusting operation shaft 7, the reaction force adjusting cam itself can be made compact and the cam displacement can be set in multiple steps. The cam can be operated with a light force due to the relationship between force moment and torsional moment.

In this embodiment, as shown in FIG. 13, a pair of the reaction force adjusting cams 51 are provided on the reaction force adjusting operation shaft 7 with a space therebetween. In this case, as shown in FIG. 9, the reaction force adjusting cam 51 pushes the slider 66 at two points separated from each other. Parallel movement is easily possible.

As shown in FIG. 13 , an intermediate shaft portion 52 supported by the intermediate bearing portion 11 is formed between the pair of reaction force adjusting cams 51 . Axial portions 53 having a circular cross section are provided outside the reaction force adjusting cams 51 (in a direction away from the central intermediate shaft portion 52). The shaft portion 53 and the intermediate shaft portion 52 are, for example, shafts of a circle (that is, shaft diameter) that includes the apex of the contoured portion that gives the maximum displacement amount of the reaction force adjustment cam 51, and the slider 66 in contact with the reaction force adjustment cam 51 is It is provided so as to prevent deviation by swinging outward or inward (horizontal direction). Further outside each shaft portion 53, a restricting protrusion (stopper) 54 that restricts the rotation of the reaction force adjusting operation shaft 7, and a restricting protrusion (stopper) 54 that protrudes from the inner peripheral surface of the operating shaft presser 43 toward the shaft center ( A shaft portion 56 having a diameter that enables relative circumferential movement (rotation) of the stopper 49 is provided. It is provided so as to restrict the rotation of the adjustment operation shaft 7 within a certain range (approximately 270 degrees) (see FIG. 6).

On the further outside of each shaft portion 56, there is provided a tip end that is received and supported by the semicircular open bearing portion 14 of the partition wall 2C on the far side when viewed from the round hole 13, which is the insertion hole for the reaction force adjustment operation shaft 7. A shaft portion 55 and a front side shaft portion 57 supported by the semicircular open bearing portion 14 of the front side partition wall 2C are provided. Here, the restriction projection 54 on the far side has the same height (that is, the same diameter) as the shaft portion 53 , and the restriction projection 54 on the front side has the same height (that is, the same diameter) as the shaft portion 57 . Further, on the outside of the shaft portion 57 supported by the open bearing portion 14 of the partition wall 2C, a groove into which the open bearing portion 44 of the edge of the operating shaft retainer 43 is fitted is formed in the round hole 13 of the peripheral wall portion 2A. A shaft portion 59 having a diameter similar to that of the shaft portion 56 formed between the supported shaft portion 58 is provided.

That is, the reaction force adjustment operation shaft 7 of the present embodiment has a tip shaft portion (referred to as a tip shaft portion 55) formed to have the smallest diameter among the shaft portions to be inserted into the main frame. The shaft portion 52 is a circle (that is, the shaft diameter) that encompasses the apex of the contoured portion that gives the maximum displacement of the reaction force adjustment cam 51, and the shaft portions 57 and 58 are larger in diameter than the shaft portion 53 and are circular. It is formed as a shaft portion having a diameter that allows it to pass through the hole 13 with a sufficient clearance. In other words, the reaction force adjustment operation shaft 7 of the present embodiment is formed so that the shaft diameter gradually increases from the tip, and the reaction force adjustment operation shaft 7 is moved to the round hole 13 using an assembly robot or the like. It can be inserted straight.

As shown in FIG. 5, the reaction force adjusting operation shaft 7 is supported by the distal end shaft portion 55 and the shaft portion 57 at the semicircular open bearing portions 14 of the inner partition wall 2C and the front (left and right) partition walls 2C. At the same time, the shaft portion 59 and the tip shaft portion 55 are pressed from above by the open bearing portion 44 at the edge of the operating shaft retainer 43, thereby being rotatably supported while being prevented from moving in the axial direction. Further, since the shaft portion 58 is supported in the round hole 13 of the peripheral wall portion 2A and the outer flange 7B abuts against the peripheral wall portion 2A, the insertion of the reaction force adjusting shaft 7 into the main frame 2 is positioned correctly. It is

On the other hand, the slider 66 in contact with the reaction force adjusting cam 51 is accommodated in the slider housing 50 integrally formed with the operating shaft retainer 43 in this embodiment, so that the reaction force adjusting operation shaft 7 The backrest support member 21 is held so as to be linearly movable along a single axis connecting with the spring support shaft 21E at the tip of the spring receiving arm 21B of the backrest support member 21 in the position state (the state in which no occupant is present). Therefore, the slider 66 imparts the same amount of compression to the compression coil spring 65 via the front spring mount 62 behind it as the cam displacement imparted by the reaction force adjustment cam 51 .

As shown in FIG. 9 , the slider 66 has cam receiving surfaces (contactors) 66 a that protrude forward at both left and right ends and come into contact with the reaction force adjusting cams 51 . Here, the cam receiving surface (contactor) 66a of the slider 66 that comes into contact with the reaction force adjusting cam 51 is a flat surface (that is, a flat end contactor). A substantially H-shaped block is formed from which cam receiving surfaces 66 a at both left and right ends protrude so as to face the reaction force adjusting cam 51 . A slight height projection 66c that functions as a rail is formed on the side surface of the slider 66, and is fitted into a groove on the inner side surface of the slider 66 so as to be slidably supported in the front-rear direction, i.e., in the expansion and contraction direction of the spring. be. In this embodiment, the cam receiving surface (contactor) 66a has a flat end, but depending on the situation, it may have a pointed end or a circular end.

According to the initial reaction force adjustment mechanism of the reaction force mechanism described above, by rotating the reaction force adjustment operation shaft 7 , the cam surface of the reaction force adjustment cam 51 abutting against the slider 66 is switched and applied to the compression coil spring 65 . The initial compression amount of the compression coil spring 65 is switched by increasing or decreasing the amount of displacement applied. Moreover, since the reaction force adjusting cam 51 has a starting point or an end point at the position of the cam base circle 51f having a smaller diameter than the minimum shaft diameter of the reaction force adjusting operation shaft 7, the handle 7A of the reaction force adjusting operation shaft 7 When turning the , the switching operation can be performed with a light force due to the short diameter. Moreover, by turning the handle/grip 7A capable of adjusting the initial reaction force of the spring, the sensed condition of the reaction force mechanism can be switched step by step so as to be lighter or heavier. In particular, in the case of a chair that also uses a weight-sensitive reaction force application mechanism as the backrest reaction force mechanism, as in this embodiment, the load of the seated person is used as part of the reaction force of the backward tilting of the backrest. Therefore, the compression coil spring 65 as a spring that applies a reaction force can be a spring with a small reaction force. As a result, when the backrest 4 is tilted backward, the force applied to the reaction force adjusting operation shaft 7 is less than that of the backrest reaction force mechanism consisting only of the reaction force mechanism 60 using a spring that compresses the spring to obtain a reaction force. Sufficient durability can be obtained even with the reaction force adjusting operation shaft 7 made of resin without being large. That is, by turning the handle 7A of the reaction force adjustment operation shaft 7, the feeling that enables the adjustment of the hardness of the reaction force of the weight sensing mechanism can be changed.

28 to 32 show another embodiment of the initial reaction force adjusting mechanism. This initial reaction force adjustment mechanism rotates the reaction force adjustment operation shaft 70 between the intermediate bearing portion 11 and the outer bearing portion 67 provided on the bottom wall portion 2B of the main frame 2 using the biasing force of the reaction force spring 65. While freely supporting, the rotation between the main frame 2 and the reaction force adjusting shaft 70 is restricted. In other words, the reaction force adjusting operation shaft 70 has an outer bearing portion 67 that supports the outer shaft portion of the reaction force adjusting cam 51 and an inner bearing portion that supports the inner shaft portion of the reaction force adjusting cam 51 (that is, an intermediate bearing). 11), both sides of the reaction force adjusting cam 51 are rotatably supported by both end supports, and the vicinity of each reaction force adjusting cam 51 is rotatably supported. That is, the reaction force adjusting cam 51 is supported at both ends over a short distance. For this reason, even if the peripheral shaft including the reaction force adjusting cam 51 of the reaction force adjusting operation shaft 70 is thin, the both sides adjacent to the reaction force adjusting cam 51 are supported, so that the structure is hard to bend.

29 and 30, the reaction force adjustment operation shaft 70 includes a handle (also called a grip) 70A, a flange portion 70B, a shaft portion 93, a reaction force adjustment cam 51, an intermediate shaft portion 92, A left-right vibration preventing portion 94, a reaction force adjusting cam 51, and a tip shaft portion 95 are provided. 95 is the minimum shaft diameter. Also in the present embodiment, the reaction force adjusting operation shaft 70 and the reaction force adjusting cam 51 are integrally formed of rigid synthetic resin such as glass fiber reinforced nylon such as PA6-GF (polyamide 6). However, depending on the circumstances, it may be made of metal, or it may consist of two members, a metal shaft and a plastic cam member.

On the other hand, in the case of the present embodiment, the outer bearing portion 67 is integrally formed to rise from the bottom wall portion 2B of the main frame 2 in the same manner as the standing wall 11A of the intermediate bearing portion 11, for example. A semicircular open bearing portion 69 is provided concentrically with the semicircular open bearing portion 11D. The open type bearing portion 69 is opened toward the compression coil spring 65 side. Therefore, the front half of the reaction force adjusting operation shaft 70 inserted into the main frame 2 consists of the semicircular open bearing portion 11D of the intermediate bearing portion 11 and the semicircular open bearing portion 69 of the outer bearing portion 67. supported by. Further, the force of the reaction force spring of the backrest reaction force mechanism 5 , that is, the force of the compression coil spring 65 is always urged to the reaction force adjusting operation shaft 70 via the slider 66 . As a result, the reaction force adjusting operation shaft 70 is always pressed against the intermediate bearing portion 11 and the outer bearing portion 67 and supported at four points. For this reason, the reaction force adjusting operating shaft 70 is sandwiched between the operating shaft retainer 43 and the semicircular open bearing portions 14 of the left and right partition walls 2C, as in the embodiments shown in FIGS. It is held rotatably even if it does not. The intermediate bearing portion 11 and the outer bearing portion 67 may be formed separately from the main frame 2 and fixed to the bottom wall portion 2B by screws or welding.

As shown in FIGS. 29 and 30, the reaction force adjusting operation shaft 7 is formed by a semicircular open bearing portion 69 of an outer bearing portion 67 on the far side and a distal end shaft portion 95 and an outer bearing portion on the near side. While the shaft portions 93 are supported by the semicircular open bearing portions 69 of 67, the flange portion 70B abuts against the edge of the insertion hole 98 (that is, the peripheral wall portion 2A) to prevent axial movement. It is rotatably supported and positioned for insertion into the main frame 2 .

Although not shown, the slider 66 arranged to face the reaction force adjusting cam 51 of the reaction force adjusting operation shaft 70 is movable in the expansion and contraction direction of the reaction force spring at the initial position of the reaction force applying mechanism. should be retained at Therefore, although not shown, for example, as in the embodiments shown in FIGS. Fixed. Of course, the slider housing 50 is not limited to being molded integrally with the operating shaft retainer 43 , but may be separately molded and assembled to the operating shaft retainer 43 , assembled to the main frame 2 or integrally molded with the main frame 2 . Needless to say, it is possible to do so.

The reaction force adjusting operation shaft 70 of the present embodiment has a shaft portion 93 ahead of the flange portion 70B and a portion whose diameter is larger than the shaft diameter of the shaft portion 92, for example, the reaction force adjusting cam 51 and the lateral vibration prevention portion 94. Therefore, it cannot be inserted into a circular hole having a shaft diameter slightly larger than the shaft diameters of the shaft portions 93 and 92 . Further, if the outer bearing portion 67 and the bearing portions 11D and 69 of the intermediate bearing portion 11 are to be inserted concentrically, the reaction force adjusting cam 51 and the lateral vibration prevention portion 94 interfere with the outer bearing portion 67 and the intermediate bearing portion 11. It will be done. Therefore, a through hole (referred to as an insertion hole 98) for inserting the reaction force adjustment operation shaft 70 of the reaction force adjustment mechanism 6 is formed in one peripheral wall portion 2A of the main frame 2, for example, the right peripheral wall portion. In the case of the embodiment, it is formed in an elliptical shape in which the long axis is generally arranged in the front-rear direction. At the same time, the diameter of the insertion hole 98 on the side surface of the main frame in the minor axis direction is the maximum dimension of the portion to be inserted into the main frame 2 (the shaft diameter of the left-right anti-vibration part 94 or the maximum contour position of the reaction force adjustment cam 51). distance from the axis). As a result, the reaction force adjustment shaft 70 can be inserted once at a position away from the bearing center (original installation position) of the outer bearing portion 67 and the intermediate bearing portion 11, and then shifted to the original installation position for setting. (called shift insertion). Therefore, it is possible to insert the reaction force adjusting cam 51 and the lateral vibration preventing portion 94 into a predetermined position while avoiding interference with the outer bearing portion 67 and the intermediate bearing portion 11 .

Further, in the case of this embodiment, the insertion hole 98 also functions as a means for restricting the swinging range of the reaction force adjusting operation shaft 70 . A protrusion 97 corresponding to the restriction protrusion 49 of the operation shaft retainer 43 of the above-described embodiment is formed so as to protrude rearward from the front end side of the insertion hole 98 in the longitudinal direction. On the other hand, the reaction force adjustment operating shaft 70 is formed with projections 96 corresponding to the regulation projections 54 of the above-described embodiment. As a result, the reaction force adjusting shaft 70 is allowed to swing until the projection 96 of the reaction force adjusting shaft 70 comes into contact with the projection 97 of the insertion hole 98 of the main frame 2 . The reaction force adjustment operation shaft 70 is provided with a flange 70B, and the flange 70B abuts against the peripheral edge of the hole 98 (that is, the peripheral wall portion 2A), thereby positioning the insertion position into the main frame 2. is provided as follows. In the present embodiment, the reaction force adjusting operation shaft 70 is pivotable within a certain range, and the cam surface 51A that provides the minimum amount of cam displacement is used as the starting point or the terminal point. Instead, it may be provided such that it rotates one or more times as necessary, that is, the cam displacement amount is switched cyclically. This also applies to the embodiments shown in FIGS. 3-16.

As described above, the reaction force adjusting cam 51 has a cam base circle 51f having a diameter smaller than the minimum shaft diameter of the reaction force adjusting operation shaft 70, for example, the shaft diameter of the tip shaft portion 95 in the case of the present embodiment. The starting point or ending point is the position of the cam base circle 51f (see FIG. 14).

Here, the cam surface 51a, which is the starting point or the terminal point, is a flat surface that is tangential to the cam base circle 51f having a smaller diameter than the minimum shaft diameter of the reaction force adjustment operation shaft 70. It is configured as a planar cam having a polygonal cam contour that allows the cam displacement amount to be switched in a plurality of steps, for example, about four steps within the swing range. Therefore, the cam surfaces 51b, 51c, and 51d, which are switched with the rotation of the reaction force adjusting operation shaft 70, increase or decrease the displacement given to the slider 66 stepwise. Therefore, the cam displacement can be set in multiple stages while the reaction force adjusting cam itself is made compact, and the cam can be operated with a light force due to the relationship between the moment of force and the torsional moment.

Of course, the cam contour surface of the reaction force adjusting cam 51 is not limited to the intermittent polygonal flat end surface as shown in the figure, and the reaction force adjusting operation shaft 70 may be a continuous curved cam contour that provides stepless displacement. , the displacement applied to the compression coil spring 65, that is, the initial amount of compression may be steplessly increased or decreased. In this case as well, by making the cam base circle 51f smaller in diameter than the shaft diameter of the minimum shaft portion of the reaction force adjusting operation shaft 7, the reaction force adjusting cam itself can be made compact and the cam displacement can be set in multiple steps. The cam can be operated with a light force due to the relationship between force moment and torsional moment.

As shown in FIG. 28, a pair of the reaction force adjusting cams 51 are provided on the reaction force adjusting operation shaft 70 with a space therebetween, and are provided so as to press the slider 66 at two points separated from each other to provide cam displacement. It is As a result, the movement of the slider 66 is less likely to be biased, and parallel movement can be easily performed without twisting.

As shown in FIG. 28, an intermediate shaft portion 92 supported by the intermediate bearing portion 11 is formed between the pair of reaction force adjusting cams 51 . Further, inside the region supported by the left and right standing walls 11A of the intermediate bearing portion 11, for example, at the central portion of the intermediate shaft portion 92, a lateral vibration preventing portion 94 having a diameter larger than that of the intermediate shaft portion 92 is formed. . This lateral vibration preventing portion 94 is axially engaged with a projection 68 protruding upward from the intermediate shaft portion 92 from a member on the side of the main frame 2, such as the tip edge of the overhang portion 11C of the intermediate bearing portion 11. This prevents the reaction force adjusting shaft 70 and thus the reaction force adjusting cam 51 from moving in the left-right direction (width direction), i.e., prevents the reaction force adjusting cam 51 from slipping from the contact surface 66a of the slider 66 as a follower. A structure for preventing lateral vibration is constructed.

In the case of this embodiment, the shaft diameter of the reaction force adjustment operation shaft can be made smaller, so that the reaction force adjustment operation can be performed with a smaller force. In particular, in the case of a chair that also uses a weight-sensitive reaction force application mechanism as the backrest reaction force mechanism, the load of the sitter can be used as part of the reaction force of the backward tilting of the backrest. The compression coil spring 65 as a spring that applies force can be a spring with a small reaction force. As a result, when the backrest 4 is tilted backward, the force applied to the reaction force adjusting operation shaft 7 is less than that of the backrest reaction force mechanism consisting only of the reaction force mechanism 60 using a spring that compresses the spring to obtain a reaction force. Sufficient durability can be obtained even with the reaction force adjusting operation shaft 7 made of resin without being large.

(Backrest locking range adjustment mechanism)
Between the main frame 2 and the backrest 4, for example, as shown in FIGS. A locking range adjustment mechanism 8 is provided for adjusting the rearward tilt position.

The locking range adjusting mechanism 8 regulates and adjusts the maximum rearward tilt position at which the backrest 4 can be locked by changing the position at which a member interlocking with the backrest 4, such as a backrest support member 21, contacts the main frame 2. A locking block (so-called backward tilting range restricting member) 26 that prevents the backrest 4 from tilting backward by moving together with the backrest 4 and coming into contact with the main frame 2 , and the locking block 26 for the backrest 4 . It is composed of a fixed block 34 for fixing the position. At least one of the locking block 26 as the movable member and the fixed block 34 as the fixed member is preferably made of a resin member such as polyacetal resin (POM) having high slidability. A buffer block 41 is provided on the side of the main frame 2 as required to reduce impact and collision noise when the locking block 26 abuts.

In the case of this embodiment, as shown in FIG. 22, the locking block 26 is fixed to the locking range switching operation shaft 9 attached to the backrest support member 21 and provided to swing together with the backrest support member 21. It is provided so as to rotate about the same axis as the locking range switching operation shaft 9 rotates. The locking block 26 has a plurality of stepped portions that abut on the buffer blocks 41 of the main frame 2 at different positions from the center of the locking range switching operation shaft 9 in order to change the maximum rearwardly tilted position at which the backrest can be locked in stages. It has stepped portions 28A to 28D with four stages of length. For example, as shown in FIG. 24, the locking block 26 is a half-fan-shaped lever-shaped locking portion having stepped portions 28A to 28D with a length of a plurality of steps, for example, four steps from the center of the locking range switching operation shaft 9, that is, the center of rotation. 28.

Specifically, as shown in FIGS. 23 and 24 , the locking block 26 includes a cylindrical portion 27 through which the locking range switching operation shaft 9 passes, and a lever-like locking member projecting radially outward from the cylindrical portion 27 . part 28, a spring accommodating part 32 for containing a compression coil spring (not shown) that always urges the locking block 26 toward the other end at one end of the cylindrical part 27, and the other end of the cylindrical part 27. It has a convex portion 30 that fits into the concave portion 36 of the block 34, and the locking range switching operation shaft 9 is fixed to the main frame 2 on the other end side by the spring force of a compression coil spring (not shown) built in one end. It is provided to be fixed (positioned) by being pressed against the fixed block 34 .

The shapes of the recesses and projections 30 and 36 of the fixed block 34 and the locking block 26 are such that they mesh with each other in the axial direction of the locking range switching operation shaft 9 and can be overcome in the circumferential direction when a constant amount of rotation is applied. Although it is not limited to a specific shape, in the case of the present embodiment, for example, it is formed by a combination of projections and recesses of a semi-cylindrical shape (having a half-moon shape in cross section). In the case of this embodiment, one semicylindrical projection 30 is provided on the other end side of the cylindrical portion 27 of the locking block 26 . On the other hand, as shown in FIG. 25, the fixed block 34 has a plurality of, for example, four, semicylindrical recesses 36 centered around the locking range switching operating shaft 9 (strictly speaking, the hole 38 through which the locking range switching operating shaft 9 passes). arranged in a fan shape.

That is, the locking range adjusting mechanism 8 in this embodiment is provided so as to be switchable in four stages at arbitrary intervals, for example, at intervals of 6° from the reference position (0°). At both ends (outside the area where the recesses 36 are continuously formed) of the group of recesses 36 arranged in a fan shape on the fixed block 34 at the same intervals, regulation blocks 35 are provided to regulate the swing range. are formed respectively. The restricting block 35 prevents movement of the locking block 26 by coming into contact with the side surface of the fixed base 29 of the locking block 26 . The fixed base portion 29 and the lever-shaped engaging portion 28 are provided with ribs to increase their rigidity. In addition, on the other end surface of the cylindrical portion 27 of the locking block 26, a sliding convex portion 31 is provided which is lower than the convex portion 30 and contacts the surface 37 of the fixed block 34 surrounding the concave portion 36, and is locked with the fixed block 34. The contact area with block 26 is reduced to reduce the force required to rotate lock block 26 .

For example, the lever-shaped engaging portion 28 is divided into four stages at arbitrary intervals around the central axis of the cylindrical portion 27, for example, at intervals of 6° from the reference position (0°), and the length from the rotation center is gradually shortened. In the case of the present embodiment, levers of four stages of length are continuously formed to form stepped portions of four stages of length. A semi-fan-shaped lever-like locking portion 28 is formed. In this embodiment, a pair of lever-shaped engaging portions 28 are provided at, for example, an intermediate portion of the tubular portion 27 with a gap therebetween and are connected to each other by ribs to increase rigidity, thereby increasing mechanical rigidity. It has a structure that can be raised and is hard to twist. Of course, the lever-shaped engaging portion 28 may be provided at one location, for example, in the center of the tubular portion 27 . Further, the lever-shaped engaging portion 28 is not particularly limited to a fan-shaped stepped portion having four steps of length on the same plane. You may make it form a part.

A shaft hole 33 having a key groove is provided in the cylindrical portion 27 . On the other hand, the locking range switching operation shaft 9 is also provided with a key 9A, and when the locking range switching operation shaft 9 is passed through the cylindrical portion 27, it is supported so as to be axially movable and rotates together. arranged to rotate.

As shown in FIG. 27, the locking range switching operation shaft 9 has a short first shaft portion 9G having a cylinder receiving portion 9E and a flange 9F, and a long second shaft portion 9G having a key portion 9A and a flange 9D. The second shaft portion 9H is passed through one plate 21A of the backrest support member 21 from the outside and is inserted to the vicinity of the other plate 21A, and the first shaft portion 9G is inserted into the backrest support member 21. The other plate 21A of the leaning support member 21 is penetrated from the outside, and the tip of the second shaft portion 9H is fitted into the cylinder receiving portion 9E near the other plate 21A for connection. As a result, the two flanges 9D and 9F are placed in contact with the outer surfaces of the plates 21A on both sides of the backrest support member 21, respectively. The two-part locking range switching operation shaft 9 is integrated by press-fitting or caulking after assembly. An operation lever 9B is fitted and screwed to the second shaft portion 9H protruding to the outside of the backrest support member 21 . The operation lever 9B and the locking range switching operation shaft 9 are connected in the rotational direction by fitting a key 9A and a key groove (not shown). A flange 9D made of a washer is provided so as not to come off by a retaining projection 9C formed by partially crushing the shaft portion.

Through-holes 22 of plates 21A on both sides of backrest support member 21 are provided with grooves through which keys 9A pass. Thereby, the second shaft portion 9H may be inserted from the plate 21A on either side.

As shown in FIG. 25, the fixing block 34 has, on the surface opposite to the surface (the so-called surface) on which the recessed portions 36 are arranged in a fan shape, protruding claws 39 that engage with the holes 23 of the plate 21A, and the plate 21A. A plate-like claw 40 is provided that is applied and hooked to the lower edge of 21A. The protruding claw 39 is a claw member with a barb that deforms so as to narrow when penetrating through the hole 23, returns to its original state after penetrating, and engages with the plate 21A. As a result, the fixing block 34 presses the claw portions 39 into the pair of holes 23 formed around the through holes 22 of the backrest support member 21, and attaches the claw portions 40 to the lower edge of the plate 21A. , easy to install. At the same time when the fixed block 34 is attached to the backrest support member 21, the hole 38 through which the locking range switching operation shaft 9 passes is aligned with the hole 22 of the plate 21A.

The recessed portion 36 of the fixed block 34 is formed by continuously arranging the recessed portions 36 forming a semi-cylindrical shape in a fan shape at the same pitch as the protruding portions 30 of the locking block 26, so that the boundary portion between the recessed portions 36 is small. The convex portion 30 of the locking block 26, which becomes the top of the radius of curvature and is pressed by a spring (not shown), cannot stop near the top and falls to one of the bottoms. Therefore, the switching becomes reliable. However, the concave portion 36 of the fixing block 34 and the convex portion 30 of the locking block 26 are not limited to the above-described semi-cylindrical unevenness, and may be, for example, hemispherical unevenness or other shapes. .

In this embodiment, the buffer block 41 provided on the main frame 2 side is, for example, a kiln-shaped resin block exhibiting rubber elasticity, and is a recess surrounded by the side wall formed at the rear end of the main frame 2. Housed in 19. A push-in pin portion 41 a is integrally formed on the bottom surface of the resin block 41 , and is fixed to the main frame 2 by fitting the push-in pin portion 41 a into the hole 20 on the bottom surface of the recess 19 . The shock-absorbing block 41 reduces the impact and noise when the lever-shaped locking portion 28 of the locking block 26 collides with the main frame 2, and may be omitted in some cases, or the lever-shaped locking portion Each of the 28 steps themselves may be provided.

According to the locking range adjusting mechanism 8 of the present embodiment configured as described above, the stepped portion of the lever-shaped locking portion 28 that abuts on the buffer block 41 of the main frame 2 is moved by the rotation of the locking range switching operation shaft 9 . When one of the plurality of stepped portions 28A to 28D is selected, the convex portion 30 of the locking block 26 is fitted into the recessed portion 36 at the corresponding position of the fixed block 34, and the inclination angle of the lever-shaped locking portion 28 is fixed. be. Therefore, when the backrest 4 is about to be tilted backward, the stepped portion (any one of 28A to 28D) of the lever-shaped locking portion 28 at the corresponding angle abuts on the buffer block 41 of the main frame 2, causing the backrest to move further. Reclining rocking can be prevented.

Although the above embodiment is an example of the preferred embodiment of the present invention, the present invention is not limited to this, and can be modified in various ways without departing from the gist of the present invention. For example, in the case of the above-described embodiment, a pair of reaction force adjusting cams 51 are provided on the reaction force adjusting operation shafts 7 and 70 with a gap therebetween. However, it is not limited to such a cam support structure. One reaction force adjusting cam 51 is provided and a pair of backup portions, that is, an intermediate portion, is provided on both sides of the reaction force adjusting cam 51 so as to sandwich the reaction force adjusting cam 51 therebetween. The shaft portion 52 and the intermediate bearing portion 11 may be provided. For example, the reaction force adjusting cam 51 may be arranged between the left and right standing walls 11A of the intermediate bearing portion 11, or a pair of independent bearing portions such as the outer bearing portion 97 shown in FIG. 31 may be provided. In this case, the front surface of the slider 66, for example, at the center thereof, is formed with a flat surface that contacts the reaction force adjusting cam 51. As shown in FIG.

In the above-described embodiment, the reaction force adjusting operation shaft 7 and the reaction force adjusting cam portion 51 are integrally formed of synthetic resin. It may be composed of a processed product, or in some cases, it may be composed of two or more members.

In the above-described embodiment, the backrest is composed of a frame-like back frame and a mesh-like upholstery stretched thereon, but the structure of the backrest is not particularly limited. A backrest structure in which a perforated shell is fixed to the back frame or a backrest structure in which a cushion is fixed to a back plate and wrapped with upholstery may be used.

In the above-described embodiment, the backrest reaction force application mechanism 5 is provided with the reaction force adjustment mechanism 6 that can adjust the initial reaction force (the reaction force of the compression coil spring 65 applied in the initial position state). However, when there is no need to provide the reaction force adjusting mechanism 6, it may be constructed between the fixed shaft of the main frame 2. FIG.

In the above-described embodiment, the compression coil spring acting in the axial direction of the cylindrical portion 27 is used as the means for constantly urging the locking block 26 toward the fixed block 34. For example, a plate spring may be incorporated, or a ball plunger or the like may be used as the convex portion 30 of the locking block 26 instead.

Furthermore, in the above-described embodiment, the backrest 4 can be locked by restraining the movement of a member that interlocks with the backrest 4, such as the backrest support member 21, as a mechanism for fixing the position between the two members that rotate relatively. An example of application as a positioning member for the rocking range switching operation shaft of the rocking range adjusting mechanism 8 that allows adjustment of the maximum backward tilt position has been mainly described, but the present invention is not limited to this, and an operating member that exerts the function of the chair. If so, it can be implemented, and can be applied to, for example, a positioning member between the back frame and the headrest.

In the above-described embodiment, the retaining member 81 is arranged at one end of the seat rotating shaft 42, but it is not limited to this. It is also possible to insert retaining members 81 into both ends of the seat rotating shaft 42 as through holes to prevent the seat from detaching.

Further, in the above-described embodiment, as an example of the structure for preventing the shaft from coming off that connects two members that rotate relatively, an example of application to the seat rotation shaft 42 that connects between the seat outer shell and the main frame is mainly given. However, it is not particularly limited to this, and a connection structure between other components of the chair, such as a connection structure between the seat outer shell 71 and the backrest support member 21, and a connection between the headrest and the back frame. It is also possible to apply it to a structure, or a retaining structure for a shaft that connects two members that do not rotate with each other.

1 legs 2 main frame 3 seat 4 backrest
5 Backrest reaction force mechanism 6 Reaction force adjustment mechanism 7 Reaction force adjustment operation shaft 8 Locking range adjustment mechanism 9 Locking range switching operation shaft 10 Cover member 11 Intermediate bearing portion 12 Long hole 13 Round hole 14 Open type bearing portion 15 Screw hole 16 Round hole 17 Bearing portion 18 Round hole 19 Recess 20 Pin hole 21 Backrest support member 22 Hole 23 Hole 24 Nut 25 Backrest rotating shaft 26 Locking block 27 Cylindrical portion 28 Lever-like locking portion 29 Fixed base 30 Projection 31 Slide Moving convex portion 32 Spring accommodating portion 33 Operation shaft hole with keyway 34 Fixed block 35 Regulation block 36 Recess 37 Edge 38 Hole 39 Claw 40 Claw 41 Buffer block 42 Seat rotation shaft 43 Operation shaft holder 44 Bearing 45 Projection (middle sandwich the partition wall)
46 Through hole 47 Fixed portion 48 through which screws pass Groove (through partition wall)
49 regulation projection (stopper)
50 Slider housing 51 Reaction force adjusting cam 51f Cam base circle 51a, 51b, 51c, 51d Cam surface 52 Intermediate shaft portion 53 Shaft portion 54 Regulating projection (stopper)
55 tip shaft portion 56 shaft portion 57 shaft portion 58 shaft portion 59 shaft portion 60 spring type backrest reaction force mechanism 61 weight sensitive reaction force applying mechanism 62 front spring mount 63 rear spring mount 64 mount pin 65 compression coil spring 66 slider 66a Cam receiving surface (contactor)
67 Outer bearing 68 Protrusion 69 protruding toward the intermediate shaft Semicircular open bearing 70 Reaction force adjusting shaft 71 Outer shell 72 Inner shell 73 Cushion 74 Outer shell bottom peripheral wall 75 Recess 76 Slit 77 Blind Round hole (bearing of seat rotation axis)
78 through hole (bearing of seat rotation shaft)
79 vertical hole 80 opening (for inserting the seat rotation axis)
81 Retaining member 82 Return 83 Stepped portion 84 Claw-shaped bearing portion 85 Retaining member hook 86 Inclined surface portion (Retaining member)
87 Locking portion 90 Recessed portion 91 Blindfold plate 92 Intermediate shaft portion 93 Shaft portion 94 Left/right anti-vibration portion 95 Tip shaft portion 96 Reaction force adjusting shaft projection 97 Insertion hole projection 98 Insertion hole

Claims (6)

A backrest reaction force mechanism for a chair that generates a force to push back the backrest by compressing a reaction force spring in conjunction with the backward tilting of the backrest,
A reaction force adjustment mechanism including a reaction force adjustment operation shaft, and for adjusting an initial compression amount of the reaction force spring by operating the reaction force adjustment operation shaft to apply a displacement in an expansion and contraction direction to the reaction force spring. ,
The reaction force adjusting operation shaft is made of a synthetic resin, and is restrained on the left and right sides by a main frame that supports the backrest, and supports one end of the reaction force spring at an intermediate position thereof,
An intermediate bearing portion is provided on the opposite side of a portion of the reaction force adjustment operation shaft that supports one end of the reaction force spring, and supports the reaction force adjustment operation shaft in an expansion direction of the reaction force spring;
A reaction force adjustment mechanism for a backrest reaction force mechanism of a chair characterized by: A cam is interposed between the reaction force adjustment operation shaft and the reaction force spring, and the reaction force adjustment operation shaft is operated to change a cam displacement amount applied to the reaction force spring, thereby adjusting the reaction force spring. 2. The reaction force adjusting mechanism for the backrest reaction force mechanism of a chair according to claim 1, wherein the initial compression amount of is adjusted. The reaction force adjusting mechanism includes a reaction force adjusting cam that applies a displacement to the reaction force spring in an expansion/contraction direction, and the reaction force that rotates the reaction force adjusting cam to switch a cam displacement amount applied to the reaction force spring. and an adjustment operation shaft, and by rotating the reaction force adjustment operation shaft, the amount of cam displacement applied by the reaction force adjustment cam is switched to adjust the initial compression amount of the reaction force spring. The reaction force adjusting mechanism of the backrest reaction force mechanism of the chair according to claim 1. The reaction force adjustment cams are provided at two locations on the reaction force adjustment operation shaft with an interval therebetween, and the reaction force adjustment operation shaft and the reaction force spring are located between the two reaction force adjustment cams. 4. The reaction force adjusting mechanism of the chair back reaction force mechanism according to claim 3, wherein the intermediate bearing portion is arranged on the side opposite to the reaction force spring while being arranged in an orthogonal positional relationship. . 5. The reaction force adjusting mechanism for the backrest reaction force mechanism of a chair according to claim 1, wherein the intermediate bearing portion is erected from the bottom wall portion of the main frame. A chair comprising a reaction force adjusting mechanism for the backrest reaction force mechanism of the chair according to any one of claims 1 to 5.

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