JP5253844B2 - Reaction force adjustment device for chair reaction force mechanism - Google Patents

Description

  The present invention relates to a reaction force adjusting device for a chair reaction force mechanism. More specifically, the present invention relates to a reaction force adjusting device for adjusting the magnitude of the reaction force of a reaction force mechanism that generates a reaction force when the chair is tilted after the backrest of the chair by a reaction force spring.

  A chair having a locking mechanism that can tilt the seat and the backrest is provided with a reaction force mechanism that applies a reaction force to the backrest and returns the back support frame to the initial position, and a device that can adjust the reaction force. ing. As this reaction force mechanism, for example, a compression coil spring (hereinafter simply referred to as a coil spring) is used as a reaction force spring between a seat receiving frame fixed to a leg and a back support frame that can swing relative to the seat receiving frame. In other words, there is known a technique in which a reaction force is applied to the backrest by the spring force of the spring to return the back support frame to the initial position (Patent Document 1). In this reaction force mechanism, the reaction force is adjusted by converting the initial length of the coil spring 103 by converting the linear movement direction between the slider 101 and the retainer 102 using the linear motion cam as shown in FIG. The initial pressure is adjusted by changing the height. Here, the slider 101 and the retainer 102 constituting the reaction force adjusting device are constituted by blocks made of a resin having a small friction coefficient and good slidability in order to reduce the operating force. Then, the slider 101 is screwed with a threaded portion (not shown) cut in the metal reaction force adjusting rod 104, and linearly moves back and forth in the direction orthogonal to the compression / extension direction of the coil spring 103 by the rotation of the rod 104. It is provided to do. The slider 101 and the retainer 102 are supported so as to be in direct contact by a pair of partition walls 106 and 107 formed integrally with the seat receiving frame 105 and a retainer guide portion (hole) 108 provided in the partition walls 106 and 107. Has been. That is, the slider 101 and the retainer 102 made of resin slide in direct contact with the metal seat frame 105. The retainer 102 is also in direct contact with the edge of the hole 108 provided in the partition wall 106 protruding from the metal seat frame 105.

JP 2006-181101 A

  Therefore, in the above-described reaction force adjusting device, the resin slider 101 and the retainer 102 constituting the linear cam are formed of resin in order to improve sliding, but always receive the force from the coil spring 103. Since it is pressed against the metal seat frame 105 and the partition walls 106 and 107 that surround it, the frictional resistance at the time of sliding becomes large and smooth movement cannot be realized, and the movement becomes bad and a large operating force is required. There is a problem that the resin is scraped off due to friction and easily worn out.

  Further, the retainer 102 receives the thrust by the slope of the slider 101 except for the stroke end where the flange portion 109 of the spring mount abuts against the partition wall 107 of the seat receiving frame 105. Since it is pressed against the edge of the hole 108 of the partition wall 106 and the reinforcing rib 110, the frictional resistance at the time of sliding becomes large like the slider 101, so that a smooth movement cannot be realized, and the movement becomes worse. There is a problem that a large operating force is required and wears quickly.

  The feed screw mechanism configured between the reaction force adjusting rod 104 and the slider 101 includes a metal male screw cut from the metal rod 104 and a resin female screw cut into the resin slider 101 ( The screw hole of the resin slider 101 is severely worn, and the screw hole is quickly worn out by a small screw thread. Moreover, since the movement of the screw thread portion is not smooth due to the friction between the resin slider and the metal, a large force is applied to the screw thread portion, so that the screw thread portion needs to have high rigidity. For this reason, there is a problem that the feed amount has to be reduced, and since the change amount is small, the reaction force does not change unless the rod is rotated many times.

  Further, since the “thread” is formed by directly cutting the reaction force adjusting rod 104, the cost is increased.

  Further, when the slider 101 is further rotated from the state in which the slider 101 is in contact with the partition wall 107, thrust is generated in the rod 104 itself, which increases the burden on the washer 111 fitted to prevent the rod 104 from coming off. It is necessary to fit several 111 pieces. On the other hand, several washers are required so that the rod 104 does not enter more than necessary on the opposite standing wall. This also increases the cost.

  Then, an object of this invention is to provide the reaction force adjustment apparatus of the reaction force mechanism for chairs which can reduce the operation force required for reaction force adjustment.

In order to achieve this object, the invention according to claim 1 is directed to an initial length of a coil spring interposed between a seat receiving frame fixed to a leg and a back support frame swingable with respect to the seat receiving frame. in reaction force adjusting device for adjusting the reaction force applied to the backrest by adjusting the initial pressure by changing the of, of the coil spring while being movably arranged in a direction perpendicular to the compression and expansion direction of the coil spring A slider having a screw hole penetrating in a direction perpendicular to the compression / extension direction and a cam slope inclined on the axis of the screw hole, and supporting one end of the coil spring so as to be slidable with the cam slope of the slider A retainer disposed so as to be in contact with the coil spring so as to be able to advance and retreat in the compression / extension direction, and the slider is formed of a separate member and is screwed into a screw hole of the slider. A screw-making cylinder, a reaction force adjusting operation rod which penetrates the screw cylinder and engages the screw cylinder in the rotational direction but is slidable in the axial direction; and the slider provided on the seat receiving frame , A reaction force adjusting device accommodating recess that surrounds and supports the retainer, the resin screw cylinder, and the reaction force adjusting operation rod, a surface that slides on the slider and an inner surface of the reaction force adjusting device accommodating recess, and the screw And a resin casing that covers at least the abutting surface and the end surface of the cylinder that is pressed by the thrust applied to the slider, and linearly moves by the rotation of the screw cylinder that rotates in conjunction with the reaction force adjusting operation rod. The movement of the slider is converted into linear movement of the retainer to change the initial length of the coil spring.

  According to a second aspect of the present invention, in the reaction force adjusting device for a chair reaction force mechanism according to the first aspect, the screw cylinder has a length such that both ends thereof are in contact with opposite side walls of the resin casing. It is what.

  Further, the invention according to claim 3 is the reaction force adjusting device of the reaction force mechanism for a chair according to claim 1 or 2, wherein the retainer of the reaction force adjusting device housing recess is provided on the front wall portion through which the retainer passes. A rib for supporting the retainer pushed by the thrust acting on the resin, and the resin casing has a rib cover interposed at least between the rib and the retainer.

  Furthermore, the invention according to claim 4 is the reaction force adjusting device for the reaction force mechanism for a chair according to any one of claims 1 to 3, wherein the resin housing abuts the retainer and the retainer is made of resin. It has a retainer cradle that is lifted and supported from the bottom surface of the housing.

  According to the reaction force adjusting device for a reaction force mechanism for a chair according to claim 1, the resin slider and the retainer constituting the linear motion cam are made of resin between the standing wall of a metal seat frame surrounding the resin slider and the retainer. Since the casing is interposed and the force of the coil spring is received and supported by the standing wall of the metal seat receiving frame via the resin casing, not only the sliding between the slider and the retainer but also the metal surrounding it Smooth movement is realized by reducing the frictional resistance when sliding with the seat receiving frame. The feed screw mechanism configured between the reaction force adjusting rod and the slider is also composed of a resin screw cylinder and a female screw (screw hole) cut out inside the resin slider. Smooth resistance can be achieved by reducing the resistance. Therefore, the linear movement of the slider by the reaction force adjusting operation rod becomes smooth, and the operation force necessary for the rotation of the operation rod can be reduced. Moreover, since both the slider and the screw cylinder are made of resin, the frictional resistance is small and the wear does not occur quickly.

  Further, since the screw cylinder and the reaction force adjusting operation rod are formed as separate members and are provided so as to be slidable in the axial direction and engaged only in the rotational direction, the coil spring and the retainer are interposed. The spring force (mainly thrust force) transmitted to the slider is not applied to the reaction force adjusting operation rod at all. Therefore, even if the movement of the slider is prevented by coming into contact with the standing wall, the rod itself does not move in the axial direction by rotating the reaction force adjusting operation rod. For this reason, a great rigidity is not necessary for the washer for preventing the rod from coming off, and a large number of sheets is not required, so that the cost can be reduced.

  In addition, since the feed screw mechanism configured between the reaction force adjusting rod and the slider is composed of a resin screw cylinder and a screw hole, there is less wear on the threads of the male screw or female screw. It is possible to increase the feed amount per rotation by enlarging the screw lead, and the reaction force can be adjusted with a small amount of rotation of the reaction force adjusting rod. In addition, since the thread is not cut from a metal rod by turning or rolling, it is formed by molding or cutting using a resin material, so the degree of freedom of processing is high and the pitch of the screw is easily free Can be set.

  Further, according to the reaction force adjusting device of the second aspect, since both ends of the screw cylinder are in contact with opposite side walls of the resin casing, the thrust applied to the slider always passes through the screw cylinder and the resin casing. Since it is supported by the standing wall of the metal seat receiving frame and does not apply to the reaction force adjusting operation rod at all, the reaction force can be adjusted with a light operating force.

  Further, according to the reaction force adjusting device of the third aspect, the rib is provided for supporting the retainer that is pushed to the side by the thrust generated between the slider and the resin casing is provided at least between the rib and the retainer. Since the rib cover is interposed, deformation of the retainer can be prevented without being worn.

  Further, according to the reaction force adjusting device of the fourth aspect, the resin casing has a retainer receiving base that abuts and supports the retainer by floating from the bottom surface of the resin casing. Can slide while being supported by a small contact surface. Since the front end of the retainer is received and supported by the front end of the slider, the retainer is supported by a resin-made retainer pedestal with low friction and a relatively small area and can slide smoothly. Therefore, the operation force during reaction force adjustment is reduced.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  1 to 10 show an embodiment of a chair reaction force adjusting apparatus according to the present invention. The chair locking mechanism includes a seat support frame 2 fixed to the leg 1, a back support frame 3 swingable with respect to the seat support frame 2, and a back support frame interposed between the frames 2 and 3. And a reaction force device 4 that applies a force to return the frame 3 to the initial position. Here, in the chair of the present embodiment, the back frame 3 that supports the back of the back of the seat shell 33 while supporting the front of the seat shell 33 constituting the seat 32 to the front end of the seat receiving frame 2 via the pin 34. By attaching the seat 32 to the support pipe 35, the seat 32 is supported between the seat receiving frame 2 and the back support frame 3, and the seat 32 sinks the rear end side as the backrest 36 tilts in the front-rear direction. A synchro-rocking mechanism for returning to the position is configured. Further, as shown in FIG. 3, the seat receiving frame 2 has a reaction force adjusting device 11 on the distal end side of a pair of side plates 25 extending forward from a cylindrical portion 37 that is fixed by press-fitting to a gas spring serving as a support of the leg 1. Is provided with a recess (hereinafter referred to as a reaction force adjusting device accommodating recess) 17. Reference numeral 5 in the figure denotes a gas spring having a lock mechanism for fixing the movement of the back support frame 3, 6 denotes a connecting pin serving as a swing center of the back support frame 3 with respect to the seat receiving frame 2, and 7 denotes a coil spring. 8 is a pin fixed to the back frame 3 side for receiving and supporting the second spring mount 9 for receiving and supporting the other end side of 8.

  The reaction force device 4 includes a coil spring 8 that stores an axial elastic force, a first spring mount 10 and a second spring mount 9 that suspend both ends of the coil spring 8 on the seat receiving frame 2 and the back support frame 3, and between them. And a guide rod 38 that is fitted so as to straddle and prevent the coil spring 8 from buckling. The first spring mount 10 is supported by a standing wall 19 formed on the seat receiving frame 2, and the second spring mount 9 is engaged with and mounted on a pin 7 fixed to the back support frame 3 side. A reaction force adjusting device 11 capable of changing the initial length of the coil spring 8 is provided on the first spring mount 10 side. In the present embodiment, the compression coil spring 8 is used as a reaction force spring.

  The reaction force adjusting device 11 changes the initial length of the coil spring 8 to adjust the initial pressure. In the case of this embodiment, the reaction force adjusting device 11 is provided between the slider 12 and the retainer 13 constituting the linear motion cam. The initial pressure is adjusted by changing the initial length of the coil spring 8 by changing the linear movement direction. Specifically, the reaction force adjusting device 11 according to the present embodiment includes a resin slider 12 disposed so as to be movable back and forth in a direction orthogonal to the compression / extension direction of the coil spring 8, and sliding with respect to the slider 12. A resin retainer 13 disposed so as to be able to advance and retreat in the compression / extension direction while supporting the coil spring 8, and a resin screw cylinder 14 formed of a separate member from the slider 12 and screwed into the screw hole 39 of the slider 12. A reaction force adjusting operation rod 15 that penetrates the screw cylinder 14 and engages with the screw cylinder 14 in the rotational direction but is slidable in the axial direction, and a reaction force adjusting device housing recess 17 of the seat receiving frame 2. At least the surface of the upright wall that constitutes the reaction force adjusting device housing concave portion 17 that is in sliding contact with the slider 12 and the end surface of the screw cylinder 14 that is pressed by at least thrust applied to the slider 12. It is intended to include a resin housing covering the abutting surface. Here, the slider 12 and the retainer 13 and the resin casing 16 and the screw cylinder 14 that support the slider 12 and the retainer 13 so as to surround them are made of a resin having a small coefficient of friction and good slidability, for example, polyacetal or the like, in order to reduce the operating force. ing.

  The resin slider 12 has a screw hole 39 penetrating in a direction orthogonal to the compression / extension direction of the coil spring 8 and a cam inclined surface 40 obliquely intersecting with the axis of the screw hole 39, and is screwed into the screw hole 39. As the screw cylinder 14 rotates, the coil spring 8 linearly moves back and forth in a direction orthogonal to the compression / extension direction of the coil spring 8. In the present embodiment, the slider 12 is formed in a block having a substantially trapezoidal shape in plan view. A protrusion 41 extending in the direction of sliding contact with the retainer 13 is formed at the center of the cam slope 40, and a groove 43 at the center of the cam slope 42 of the retainer 13 is fitted into the protrusion 41 so that the retainer is perpendicular to the sliding direction. 13 and the slider 12 are provided so as not to slip.

  On the other hand, the retainer 13 is formed of the same resin material integrally with the first spring mount 10 of the reaction force mechanism in this embodiment. Between the retainer 13 and the first spring mount 10, a flange 44 that abuts against the front wall 19 of the reaction force adjusting device accommodating recess 17 is provided. Therefore, when the flange 44 comes into contact with the front wall 19, the force of the coil spring 8 does not act between the retainer 13 and the slider 14. Further, at the tip of the retainer 13, similarly to the slider 12, a cam slope 42 that obliquely intersects the traveling direction of the slider 12 is provided. The retainer 13 receives and supports one end of the coil spring 8 and is supported by the retainer guide hole 22 in the front wall 19 of the reaction force adjusting device accommodating recess 17 so as to be able to advance and retract in the compression / extension direction of the coil spring. In the present embodiment, the retainer 13 and the first spring mount 10 are integrally formed. However, the present invention is not limited to this, and depending on the case, the retainer 13 and the first spring mount 10 may be separated. good. Also in this case, the retainer 13 and the first spring mount 10 are interlocked in the moving direction of the retainer 13 by the elastic force of the coil spring 8, and the initial length of the coil spring 8 can be adjusted.

  In the case of the present embodiment, the screw cylinder 14 constituting the screw feed mechanism by screwing with the screw hole 39 provided in the slider 12 has such a length that both ends thereof are in contact with opposite side walls of the resin casing 16. Have. The center of the screw cylinder 14 has a hole 45 through which the reaction force adjustment operation rod 15 passes, and at least a key groove 46 into which the key portion 47 of the reaction force adjustment operation rod 15 is fitted. They are provided at positions and intervals corresponding to the key portions 47 of the reaction force adjusting rod 15. That is, the reaction force adjusting rod 15 and the screw cylinder 14 are connected by the spline groove and the sliding key so as to engage in the rotational direction and slide in the axial direction. In the case of this embodiment, four key grooves 46 of the screw cylinder 14 are provided at 90 ° intervals corresponding to the key portions 47 of the reaction force adjusting operation rod 15, and when inserting the reaction force adjusting operation rod 15. It is considered that the screw cylinder 14 is slightly rotated to be fitted into the nearest key groove 46. Of course, the key groove 46 of the screw cylinder 14 and the key portion 47 of the reaction force adjusting rod 15 are not necessarily provided at intervals of 180 °, and are provided as a combination of one key groove 46 and the key portion 47. Alternatively, a plurality of key grooves 46 may be prepared for one key portion 47. Furthermore, the plurality of key portions 47 and the corresponding key grooves 46 are not limited to being arranged at equal intervals. For example, two key portions 47 may be provided with an interval of 90 °, while two or four key grooves 46 may be provided every 90 °.

  In the case of the present embodiment, the key portion 47 of the reaction force adjusting rod 15 has a convex portion (referred to as a key portion) that functions as a sliding key by crushing a part of the rod 15 by forging or rolling. Try to form. A grip 30 is provided at one end of the reaction force adjusting operation rod 15 so as to easily apply a rotational force. Further, in order to prevent the seat receiving frame 2 from coming off, a washer-stopping projection 29 and a projection that engages with the groove of the screw cylinder 14 are integrally formed.

  The reaction force adjusting device accommodating concave portion 17 supports the first spring mount 10 and penetrates the retainer 13 so as to be slidably supported in the compression / extension direction of the coil spring 8 and the opposite of the cam inclined surface 40 of the slider 12. The rear wall 18 for supporting the force applied from the coil spring 8 on the side surface, the left and right side walls 20 for receiving the thrust load applied to the screw cylinder 14 and the bottom wall for preventing the rotation of the slider 12 and supporting the resin casing 16. 23. Here, the front wall 19 is provided with a hole 22 through which the retainer 13 passes, and a retainer guide portion for guiding the retainer 13 to advance and retreat in the compression / extension direction is configured. The front wall 19 has a reinforcing rib 21 for preventing the retainer 13 pushed by the force of the coil spring 8 from being pushed and deformed by the component force generated by the cam slope 42 of the slider 12 toward the side standing wall 20. Is provided. The left and right side standing walls 20 are each provided with a U-shaped notch 24 through which the reaction force adjusting operation rod 15 passes, and the side standing wall 20 on the side where the reaction force adjusting operation rod 15 is inserted. Further, a notch for allowing the key portion 47 to pass therethrough is also provided. The bottom wall 23 is provided with, for example, two nail hooking holes 48 for hooking the claws 49 formed on the bottom surface of the resin casing 16. The reaction force adjusting device accommodating recess 17 is provided with the above-mentioned standing walls 18, 19, 20, the bottom wall 23 and the reinforcing ribs integrally with the seat receiving frame 2 when the seat receiving frame 2 is molded by, for example, aluminum die casting. 21 is formed by molding, but is not particularly limited to this. When the seat frame 2 is formed by welding an iron plate or the like, it may be assembled by welding each standing wall or the like. is there.

  The resin casing 16 covers at least the periphery of the portion through which the rods of the rear standing wall 18 and the bottom wall 23 and the left and right side standing walls 20 of the reaction force adjusting device accommodating recess 17 pass, and covers the slider 12, the retainer 13, and the screw cylinder 14. It is provided so as to surround and abut against at least one end of the screw cylinder 14. In the present embodiment, as shown in FIG. 4, the resin casing 16 includes a rear standing wall 52, a bottom wall 54, and left and right side standing walls 54 that cover at least the periphery of the portion through which the rod 15 passes. The slider 12 is supported by the bottom wall 54 and the screw cylinder 14 is supported by the left and right side walls 54 so as to be in contact with both end faces thereof. The resin casing 16 covers at least a surface of the reinforcing rib 21 provided on the standing wall 19 on the side of the retainer 13, and at least a rib cover 51 interposed between the reinforcing rib 21 and the retainer 13. It is provided at the 19th edge. In the case of the present embodiment, the rib cover 51 has a hook-like shape that is vertically formed in a U shape so as to cover the entire circumference of the reinforcing rib 21, and the inside of the rib cover 51. The bottom wall 53 portion of the resin casing 16 is cut so as not to interfere with the reinforcing rib 21. Further, the resin casing 16 is provided with a retainer cradle 50 that lifts and supports the retainer 13 from the bottom wall 53 of the resin casing 16. The retainer receiving base 50 is formed at the front edge of the resin casing 16 so as to be disposed in the hole 22 of the retainer guide portion provided in the front wall 19, and is formed in the groove 43 of the cam slope 42 at the front end. The portion is provided so as to receive and support the proximal end side of the retainer 13 that is fitted with the protrusion 41 of the inclined surface 40 of the slider 12.

  A hole 55 having a diameter smaller than that of the screw cylinder 14 and slightly larger than that of the reaction force adjusting operation rod 15 is provided concentrically with the screw hole 39 of the slider 14 in the left and right side standing walls 54 of the resin casing 16. ing. At the edge of the hole 55, a notch 56 through which the key portion 47 of the reaction force adjusting rod 15 passes is formed at a position / interval corresponding to the key portion 47 of the rod 15, and the key of the rod 15 is formed in the notch 56. The rod 15 is provided so that the rod 15 can penetrate the hole 55 of the side standing wall 54 only when the portions 47 are matched. For example, two claws 49 are provided on the back surface side of the bottom wall 53 of the resin casing 16, and the claws 49 are inserted into the holes 48 for hooking the bottom wall 23 of the reaction force adjusting device accommodating recess 17. Thus, the resin casing 16 is provided so as to be locked in a state of being accommodated in the reaction force adjusting device accommodating recess 17.

  According to the reaction force adjusting device 11 configured as described above, the feed screw is rotated by the rotation of the screw cylinder 14 that rotates in conjunction with the rod 15 by grasping the grip 30 and rotating the reaction force adjusting operation rod 15. The slider 12, which is a counterpart member constituting the mechanism, is non-rotatably accommodated in the reaction force adjusting device accommodating recess 17 via the resin casing 16, and thus moves linearly. The initial length of the coil spring 8 is changed by converting it into a linear movement of the retainer 13 in a direction orthogonal to this via 40 and 42. Thereby, the initial pressure of the coil spring 8 is adjusted.

  At this time, the screw cylinder 14, the slider 12, and the retainer 13 that are rotated and linearly moved by the rotation of the rod 15 are each formed of synthetic resin, and the reaction force adjusting device housing recess 17 of the metal seat receiving frame 2. Since the resin casing 16 is interposed between them and the metal casing 16 does not slide in direct contact with the metal, the movement is smooth, and the length of the coil spring 8 is adjusted with a lighter operating force than before. Can do.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, in the case of the example given as an embodiment, a part 47 of the reaction force adjusting rod 15 is crushed by forging, rolling, or the like to form the convex portion 47 that functions as a sliding key. Alternatively, a shaft into which a sliding key as another member is driven may be used.

It is the schematic which shows the structure of the reaction force mechanism which uses one Embodiment of the reaction force adjustment apparatus of this invention, and a chair which mounts it. It is a bottom view of the reaction force adjusting device and the reaction force mechanism. It is an enlarged vertical sectional view showing a seat receiving member and a reaction force adjusting device. It is a section top view showing one embodiment of the reaction force adjusting device of the present invention. It is the longitudinal cross-sectional view seen from the side of the reaction force adjusting device. It is a longitudinal cross-sectional view which shows an example of a reaction force adjustment apparatus accommodation recessed part. It is a figure which shows one Embodiment of resin-made housing | casings, (A) is a center longitudinal cross-sectional view, (B) is a top view. It is a figure which shows one Embodiment of a slider, (A) is a front view, (B) is a top view. It is a figure which shows one Embodiment of resin screw cylinders, (A) is a fragmentary sectional top view, (B) is a front view. It is a figure which shows one Embodiment of a retainer, (A) is a front view, (B) is a top view. It is a bottom view which shows the conventional reaction force adjustment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Seat receiving frame 3 Back support frame 4 Reaction force mechanism 8 Coil spring 10 1st spring mount 11 Reaction force adjustment apparatus 12 Slider 13 Retainer 14 Screw cylinder 15 Reaction force adjustment rod 16 Resin case 17 Pressure adjustment apparatus accommodation Recessed portion 19 Front wall through which retainer of pressure adjusting device accommodating recessed portion penetrates 21 Rib for supporting retainer 39 Screw hole of slider 40 Slider cam inclined surface 42 Retainer cam inclined surface 46 Key cylinder of screw cylinder 47 Key of rod for reaction force adjusting operation Part 50 Retainer cradle 51 Rib cover 52 Rear wall of resin casing (surface in sliding contact with slider)
53 Bottom wall of resin casing (surface in sliding contact with slider)
54 Side wall of resin casing with which at least one end of screw cylinder contacts

Claims (4)

To lean back to adjust the initial pressure by changing the initial length of the coil spring interposed between the swingable Se支frame relative to the fixed seat support frame and said seat support frame legs A reaction force adjusting device for adjusting a reaction force to be applied, wherein the screw hole and the screw are disposed so as to be movable back and forth in a direction orthogonal to the compression / extension direction of the coil spring and penetrate in a direction orthogonal to the compression / extension direction of the coil spring. A resin slider having a cam slope inclined on the axis of the hole, and supports one end of the coil spring so as to slidably contact the cam slope of the slider, and can advance and retreat in the compression / extension direction of the coil spring. A resin retainer disposed on the slider, a resin screw cylinder configured to be a member different from the slider and screwed into a screw hole of the slider, and penetrating through the screw cylinder. The rod is a reaction force adjusting operation rod that engages in the rotational direction but is slidable in the axial direction, and the slider, the retainer, the screw cylinder, and the reaction force adjusting operation provided on the seat receiving frame. A reaction force adjusting device housing recess that surrounds and supports the working rod, a surface of the inner surface of the reaction force adjusting device housing recess that is in sliding contact with the slider, and an end surface that is pressed by thrust applied to the slider of the screw cylinder, A resin casing covering at least the abutting surface, and converting the movement of the slider that linearly moves by the rotation of the screw cylinder that rotates in conjunction with the reaction force adjusting operation rod into linear movement of the retainer. A reaction force adjusting device for a reaction force mechanism for a chair, which changes an initial length of the coil spring. The reaction force adjusting device for a reaction force mechanism for a chair according to claim 1, wherein both ends of the screw cylinder are in contact with opposite side walls of the resin casing. The front wall through which the retainer of the reaction force adjusting device accommodating recess penetrates includes a rib that supports the retainer that is pushed by thrust acting on the retainer, and the resin casing includes the rib and the retainer. The reaction force adjusting device for a reaction force mechanism for a chair according to claim 1 or 2, further comprising a rib cover interposed between the two. 4. The retainer base according to claim 1, wherein the resin casing includes a retainer base that abuts and supports the retainer while floating from the bottom surface of the resin casing. Reaction force adjustment device for the reaction force mechanism for chairs.

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