JPH0455690B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention allows the backrest and seat to easily follow the body movements of both heavy and light people. To provide a chair that allows one to easily take a resting position.

(Prior Art) When a user sits on a chair for a long time, such as an office chair, the user gets tired if he or she takes only one posture, so the user takes various postures. It is desirable that the seat, backrest, etc. move easily according to the movement of the seat. Furthermore, when resting, the user generally leans his or her back against the backrest, and it is desirable to have a chair with a deeper seat and backrest that can easily move to follow the user's movements.

Furthermore, there is a need for a chair that allows the seat and backrest to return to their original, standard positions when not in use.

In a conventional chair of this kind, for example, as shown in FIG. 12, the backrest and the seat are supported by springs 10, and the backrest and the seat are tilted backwards when the user leans on the backrest during rest. It has been known.

Further, as shown in FIG. 13, the backrest 25 and the seat 23 are
connected via a hinge joint 13 at the rear end,
Further, the backrest 25 is pivotally attached to the frame 15 at its vertical midway point by a horizontal support shaft 14 so as to be freely rotatable in the front and back direction, and both ends of a cross bar 16 fixed to the lower surface of the seat part 23 are attached to the front end side of the frame 15. A chair is known that is movably guided along a long hole 18 in a seat guide 17 (Japanese Patent Application Laid-Open No. 1983-1999).
247418). According to this chair, when you lean on the backrest 25 while resting, the backrest 25 tilts backward,
In conjunction with the rearward tilting of the backrest 25, the seat 23 moves forward and upward, allowing the user to take a resting position.

(Problems to be Solved by the Invention) However, the conventional chair described above has the following problems.

That is, in the case of the chair shown in FIG. 12, the backrest and seat tilt backward in response to the user's movements, but the angle between the backrest and the seat does not change even at that time. Furthermore, since the seat does not move forward, the degree of freedom in taking a working position or a resting position is limited accordingly.

Furthermore, when the backrest and seat part tilt, the center of gravity moves rearward, so there is a risk that the user may easily fall backwards.

Furthermore, in the case of the above-mentioned chair, since the load applied to the backrest varies depending on the user's weight, the springs should be adjusted according to the user's weight before use.
Initial adjustment to adjust the strength of 0 is essential. It is not always easy for the user to optimally perform this initial adjustment. In addition, since the strength of the spring 10 is set according to the weight of the user, it can generally only be used as a chair exclusively for that user, and can be used only for chairs used by an unspecified number of people, such as conferences. Not suitable as a room chair.

In the case of the chair shown in Fig. 13, the backrest 25
When tilting the backrest 25 backward, the upper side of the backrest 25 tilts backward, but the lower side of the backrest 25 moves forward. Therefore, when the user tries to take a resting posture by leaning his entire back on the backrest 25, there is a problem that the movement of the user's back and the movement of the backrest 25 do not match, resulting in a feeling of discomfort.

In addition, since the horizontal support shaft 14 is located midway in the vertical direction of the backrest 25, people who are light in weight or who sit at a low height cannot apply the necessary load to the backrest 25, causing the backrest 25 to tilt backwards. There are some problems that make it difficult.

Furthermore, since the seat 23 is connected to the lower end of the backrest 25, although the seat 23 can move forward, it does not extend to the depth of the seating space, making it difficult to take a comfortable resting position. There is a problem.

The present invention has been made to solve the above problems, and its purpose is to enable both heavy and light people to easily follow their body movements when working or taking a resting position. To provide a chair in which a backrest and a seat part can be moved and a comfortable resting posture can be taken.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes the following configuration.

In other words, it is a chair with a backrest, and a seat part,
a support base, a balance member that is supported by the support base below the seat in the front-rear direction of the seat and has the backrest at its rear; and a balance member that supports the seat so as to be movable in the front-rear direction. The balance member also includes a seat support part that divides the load on the seat part to a point of action that pinches the fulcrum part of the balance member, and when the backrest tilts rearward about the fulcrum part of the balance member. force transmitting means for converting a backward tilting motion of the seat into a forward motion of the seat via the seat support, and when the backrest tilts backward due to a load being applied to the backrest;
Regarding the load on the backrest, the load on the seat, etc.
It is characterized by comprising a mechanical elastic body that acts as a balancer to balance the moment around the fulcrum of the balance member via the force transmission means, and an adjustment means that adjusts the elastic force of the mechanical elastic body. do.

(effect) Next, the operation of this invention will be described.

When a user sits down on the seat, such as when working, the load applied to the seat is distributed to both application points of the balance member via the seat support and is canceled out.

The unbalanced load around the fulcrum of the balance member is small, and when no load is applied to the backrest, this unbalanced balance is suspended by the urging force of the mechanical elastic body or the like.

When taking various working postures during work, if a slight load is applied to the backrest, the above-mentioned unbalance increases, and the backrest and seat easily move to follow this body movement.

When taking a deeper resting position, lean back against the backrest and intentionally put more weight on it. This further increases the load imbalance,
The backrest tilts rearward about a fulcrum located below the seat of the balance member, and the seat moves forward via the force transmission means, expanding the seating space back and forth. Then, the increase in the load on the backrest caused by the backrest tilting backwards, the increasing biasing force of the mechanical elastic body, and the user's muscle strength combine to stop the backrest tilting backwards, and this position is reached. You can take a comfortable resting position. When attempting to tilt the backrest backwards, a heavier person will have a greater load on the backrest than a lighter person, but the load on the fulcrum in the opposite direction from the backrest side will also be relatively large. Both heavy and light weight people can tilt the backrest backwards by leaning on the backrest to the same degree.

When the load on the backrest is removed, the seat and backrest return to their original standard positions due to the biasing force of the mechanical elastic body.

The biasing force of the mechanical elastic body is varied by the adjusting means. This adjustment can be made in advance at the time of shipment from the factory, and after adjustment, there is almost no need to make adjustments taking into account differences in weight, etc., and the device is suitable for use by an unspecified number of people in a conference room or the like.

(Example) An example of the present invention will be described below in detail based on the accompanying drawings.

In FIGS. 1 and 2, reference numeral 20 denotes a pedestal, and a fixed frame 21 serving as a support base is fixed to the upper end. The front end of the fixed frame 21 rises gently toward the front, and the rear end rises rearward at a relatively steep angle. A pressure receiving plate 40 is provided on the front end side of the fixed frame 21 and extends further forward and upward, and an adjustment screw 41 is attached to this pressure receiving plate 40 as will be described in detail later. It goes without saying that the present invention can also be suitably applied to chairs without pillars.

Reference numeral 22 denotes a balance member, which extends along both sides of the fixed frame 21, below the seat 23, and in the front-back direction of the seat 23, and in the middle thereof, the fixed frame 21
It is rotatably attached to the shaft. 24 is its rotation axis.

25 is a backrest, and a back support rod 2 is provided integrally with the balance member 22 at the rear end of the balance member 22.
It is attached to 6.

Reference numeral 27 denotes an L-shaped link, which is rotatably attached to both sides of the front end of the fixed frame 21 by a shaft 28 at an L-shaped bent portion. One link end of the L-shaped link 27 is pivotally attached to the front side of the seat 23 by a shaft 29, and the other link end of the L-shaped link 27 is attached to the front end of the balance member 22. They are connected by a pin 30 and a long hole 31.
That is, a pin 30 protruding from one end of the L-shaped link 27 is loosely fitted into an elongated hole 31 provided at the front end of the balance member 22 and extending in the front-rear direction. It goes without saying that the pin may be provided on the balance member 22 and the elongated hole may be provided on the L-shaped link 27 side.

A helical spring 42 is mounted on the shaft 28, as clearly shown in FIG.
One end of 2 is locked to a shaft 29, and the other end extends in the direction of the pressure receiving plate 40. That is, this helical spring 42 is elastically loaded between the shaft 29 and the pressure receiving plate 40, and urges the L-shaped link 27 to rotate clockwise about the shaft 28 in FIG. are doing. In other words, the helical spring 42 applies a braking torque to the leftward rotation of the L-shaped link 27 about the shaft 28 . The magnitude of this braking torque is determined by the adjustment screw 4 provided on the pressure receiving plate 40.
1.

The rear side of the seat portion 23 is supported by a link plate 32 on the balance member 22 on the rear side of the rotation shaft 24 . That is, one end of the link plate 32 is pivoted to the rear of the seat portion 23 by a shaft 33, and the other end is pivoted to the balance member 22 on the rear side of the rotation shaft 24 by a shaft 34.

The L-shaped link 27 and the link plate 32 constitute a seat support. Further, by connecting the L-shaped link 27 to the tip of the balance member 22 through a pin 30 and a long hole 31, a force transmitting means for moving the seat portion 23 forward is configured.

35 is a tension spring for return and balance, which connects the shaft 29 of the L-shaped link 27 and the fixed frame 2.
1 and a fixed shaft 36 provided on the rear end side of the chair, and urges the seat 23 to its original standard position as a chair, and also supports the backrest 25 via the L-shaped link 27 and the balance member 22. It is biased to its original standard position (standing position) as a chair.

This tension spring 35 is set so that the spring constant is small at the initial stage of expansion and increases as the degree of expansion increases, so that the spring constant changes depending on the degree of expansion of the spring. There is. Such a spring can be formed, for example, by a coil spring in which the coil density is high at both ends of the spring and the coil density is low at the center of the spring.

This tension spring 35 acts as an elastic body for returning the seat 23 and backrest 25 to their original standard positions as described above, and as a load balancer as will be described in detail later.
As long as it acts as a returning elastic body and a balancer, its installation position is not particularly limited, and it can be installed between an appropriate movable part and a fixed part, or in some cases between a movable part and a movable part. .
Further, the type of the spring is not limited to a tension spring, but may be a compression spring, etc., and is appropriately selected depending on the mounting position and the like.

Note that when the seat portion 23 and the backrest 25 are biased to the standard position by the tension spring 35 and are stationary as described above, the line connecting the shafts 28 and 29 of the L-shaped link 27 and the link plate As is clear from FIG. 1, a line connecting the shafts 34 and 33 of 32 is set to slope rearward and upward. At this time, the shaft 28 of the L-shaped link 27
The line connecting the pin 30 and the pin 30 is slanted rearward and downward.

Next, its operation will be explained.

First, the seat 2 is placed in the standard position shown in Fig. 1.
3, the load is distributed to the application points in front and behind the rotating shaft 24 (fulcrum part) of the balance member 22.
The load due to this component force applies a clockwise moment to the balance member 22 around its rotation axis 24 via the link plate 32 on one side, and a counterclockwise moment via the L-shaped link 27 on the other side. Grant.

Furthermore, when the counterclockwise moment is larger,
The balance member 22 rotates counterclockwise about the rotation shaft 24, but a stopper (not shown) acts so that the seat portion 23 and the backrest 25 are located at the standard position.

Furthermore, when the clockwise moment is larger, the balance member 22 tries to rotate clockwise, but since the aforementioned tension spring 35 acts, the standard state is still maintained when no load is applied to the backrest. maintain.

In this case (also when taking a resting position as described later), in the present invention, the load is transferred to the balance member 2.
Since the force is applied around the fulcrum part 2, and the unbalanced part is canceled out by the balance, the clockwise moment, which is the unbalanced part, is relatively small.

Therefore, the above-mentioned tension spring 35 does not need to be a very strong spring in the initial state of extension.

The fact that the strength of the tension spring 35 does not need to be so large at the initial stage of extension has the following advantages.

In other words, even when working, the worker may take a posture of leaning slightly on the backrest 25, but in this case, the strength of the tension spring 35 is not very strong, so the backrest 25 is tilted slightly backwards. This allows the user to take a comfortable working posture (in this case, the seat 23 moves slightly forward).
Note that the biasing force of the helical spring 42 is also initially adjusted by the adjustment screw 41 so that the above-mentioned working posture can be taken. In this manner, even when working, the seat portion 23 and the backrest 25 can be easily moved to follow the movements of the user's body.

This can be done with little difference between heavy and light weight people. In other words, for both heavy and light people, the balance of the load around the fulcrum is offset by the balancing action of the balance member 22, so even for a light person, the tensile force of the tension spring 35, which is not as strong, can be offset. The backrest 25 can be easily tilted against the biasing force of the coiled spring 42.

Next, when transitioning to a resting state, the user intentionally leans against the backrest 25, applies a load to the backrest 25, and pushes the backrest 25 against the tensile force of the tension spring 35 and the resistance force due to the load described later. Rotation axis 2
It tilts backward around point 4.

In this case as well, both heavy and light people can tilt the backrest 25 backwards with almost no difference.

In other words, in the case of a heavy person, the backrest 2
5, a larger load will be applied to the backrest 25 in the case of a lighter person, and a relatively small load will be applied to the backrest 25. The amount of load that acts on a person who is heavy is greater than that of a person who is light, and this is offset by the balance action, so both people who are heavy and people who are light will lean to the same degree. This makes it possible to tilt the backrest 25 rearward.

When the backrest 25 is tilted backward, the tip side of the balance member 22 rotates upward in an arc around the rotation shaft 24, and this causes the L-shaped link 27 to move toward the shaft 28.
It rotates to the left in Fig. 1 about the center. That is, the link piece connecting the shafts 28 and 29 of the L-shaped link 27 gradually stands up from the backward tilted position shown by the solid line in FIG. 1, and rotates beyond the standing position to a slightly forward tilted position. . Therefore, the seat portion 23
moves forward as the L-shaped link 27 rotates. Further, at this time, the front side of the seat portion 23 rises slightly as shown by the broken line in FIG.

On the other hand, as the seat portion 23 moves forward, the link plate 32 also moves from the backward inclined position shown by the solid line in FIG.
It is further rotated about the shaft 34 beyond the standing position to a position slightly tilted forward as shown by the broken line. By the way, the shaft 34 rotates in an arc around the rotation shaft 24 due to the rotation of the balance member 22, and is slightly lowered from the standard position. Therefore, the rear side of the seat 23 moves forward and sinks slightly in conjunction with the rearward tilting of the backrest 25.

In this way, the seat 23 moves forward in conjunction with the rearward tilting of the backrest 25.
The front side of seat 23 will rise slightly, and the rear side of seat 23 will sink slightly.

By the way, the link piece of the L-shaped link 27,
When the link plate 32 rotates from the rearward tilted state to the upright position as described above, the load from the user applied to the link piece and the link plate 32 is a kind of load against the rearward tilting of the backrest 25. Acts as a resistance force. The resistance force due to the load at this time prevents the backrest 25 from falling all at once backwards when a load is applied to the backrest 25. In particular, as mentioned above, the tensile force of the tension spring 35 is small at the initial stage of extension, and the biasing force of the helical spring 42 is also small at the initial stage, so if a large load is applied to the backrest 25, the backrest Although there is a risk that the backrest 25 may fall backward all at once, the resistance force due to the above-mentioned load acts to effectively prevent the backrest 25 from tilting backward all at once.

Note that since the backrest 25 is in an upright position at the beginning of its tilting, the load moment on the backrest 25 side relative to the fulcrum of the balance member 22 is not so large.

Therefore, in order to allow the backrest 25 to tilt backward even during this initial load, the spring constant of the tension spring 35 is set to be small at the initial stage of extension, so that the resistance force from the tension spring 35 is reduced. This is what we are doing. On the other hand, helical spring 4
The biasing force No. 2 is also adjusted in advance using the adjustment screw 41 as described above. This helical spring 42
The biasing force can be uniformly adjusted at the time of shipment from the factory.

In other words, since the position of the fulcrum of the balance member 22 and the spring constants of various springs are known in advance, the initial settings can be made at the time of factory shipment so that both heavy and light people can use it with almost no difference. It can be done. Once this initial setting has been made, there will be little need for subsequent adjustments taking into account differences in user weight.

Next, the more the backrest 25 tilts backward, the more the user's load distribution moves backward, so the backrest 25 relative to the fulcrum of the balance member 22
The moment on the 5th side increases rapidly.

On the other hand, since the link pieces of the L-shaped link 27 and the link plate 32 stand up as shown by the broken lines in FIG. It becomes zero at the position.

Therefore, the force opposing the load on the backrest 25 is the biasing force of the tension spring 35 and the helical spring 42, the muscular strength of the user, etc., but as mentioned above, the load on the backrest 25 is As the tilting increases, the biasing force of both springs needs to be quite large. To this end, in this embodiment, the spring constant of the tension spring 35 is set to increase as the degree of extension of the spring increases, and when the load on the backrest 25 increases, the tension force of the tension spring 35 is reduced. By increasing the size, the load on the backrest 25 side is balanced with the biasing force of the helical spring 42, etc.

Therefore, in this balanced position, the backrest 25 stops tilting backwards, and a resting position is achieved. When taking this resting position, as mentioned above, the backrest 25
The seat tilts rearward about the pivot shaft 24 located below the seat 23, while the seat 23 moves forward, which expands the seating space back and forth, allowing a comfortable resting position. . Furthermore, when the seat 23 moves forward, the rear side of the seat 23 moves forward but sinks slightly as described above, so the movement of the buttocks when trying to take a resting position and the movement of the seat 23 are different. They almost match, and you can shift to the resting position without feeling any discomfort. Although not shown, a locking device for preventing the backrest 25 from tilting may be provided at the above-mentioned balance position or any position before shifting to the balance position.

Further, in the above embodiment, one tension spring 35 whose spring constant changes depending on the degree of extension is used in combination with the helical spring 42 to cope with changes in the load on the backrest 25. By using a plurality of springs, only one spring acts at the beginning of the tilting of the backrest 25, and as the tilting of the backrest 25 increases, the plurality of springs act sequentially, so that the increasing load on the side of the backrest 25 can be handled. You may try to deal with it.

Further, among the spring bodies that resist the load on the backrest 25 side, in the above embodiment, the biasing force of the helical spring 42 is adjustable, but the biasing force of the tension spring 35 may be adjustable.

FIG. 6 shows another embodiment of the force transmitting means. Although tension springs and other spring bodies are used in this embodiment as well, their illustrations are omitted to simplify the explanation. Note that illustration of the spring body is also omitted in other embodiments shown below.

In this embodiment, the link board 3 in the previous embodiment is
2, the balance member 22 behind the rotation shaft 24
A support arm 44 is erected from above, and a pin 45 provided at the upper end of the support arm 44 is loosely fitted into a long hole 46 provided on the rear side of the seat portion 23 and long in the front-rear direction. Also in this embodiment, the seat portion 23 is connected to the backrest 25.
It moves forward in conjunction with the backward tilting of the

FIG. 7 shows another embodiment of the seat support.

In this embodiment, a seat support plate 47 is pivotally attached to the front end of the fixed frame 21 by a pin 48 so as to be able to swing freely, and the rear part of the seat support plate 47 and the top of the balance member 22 behind the rotation shaft 24 are connected. They are connected by a link plate 49. The seat portion 23 is placed on a seat support plate 47 so as to be movable in the front-rear direction. Further, as shown in the figure, elongated holes 50, 50 are provided in the side portion of the seat portion 23, and pins 48, 48 provided on the seat support plate 47 are loosely fitted into the elongated holes 50, 50, respectively. , seat 2
3 is movable back and forth on the seat support plate 47 according to the restrictions of the long holes 50, 50 and the pins 48, 48. One end of the link piece of the L-shaped link 27 is pivoted to the seat portion 23.

In this embodiment as well, the load on the seat portion is distributed around the fulcrum portion of the balance member 22.

When the backrest 25 tilts backward, the L-shaped link 27 rotates and the seat 23 moves forward, and the link plate 49 moves the seat support plate 47 and therefore the seat 23
The rear part is pulled slightly downward and sinks. Therefore, the movement of the seat portion 23 is substantially the same as in each of the embodiments described above. Of course, the spring body (not shown) is used to return the seat 23 and the backrest 25 to their standard positions, and to balance each part at the rest position, as described above.

FIG. 8 again shows another embodiment of the force transmission means.

In this embodiment, the L-shaped link 27 and the balance member 2
The second tip is not connected by a pin and a long hole but by a cam, that is, the pin 52 provided at the tip of the balance member 22 is brought into contact with the lower surface of the L-shaped end of the L-shaped link 27. As a result, when the balance member 22 rotates around the rotation shaft 24, the pin 52 moves to the L position.
Since the letter-shaped link 27 is rotated about the shaft 28, substantially the same effect as in each of the embodiments described above is achieved.

FIG. 9 shows yet another embodiment of the force transmitting means.

In this embodiment, a gear 57 is formed at one end of the L-shaped link 27, and this gear 57 meshes with a gear 58 provided at the front end of the balance member 22.

This embodiment also provides the same effects as described above.

FIG. 10 shows another embodiment of the balance member 22.

In this embodiment, the rotation axis of the balance member 22 is formed with an elongated hole 53 extending in the front-rear direction as shown in the figure. That is, a pin 54 provided on the fixed frame 21 is loosely fitted into this elongated hole 53.

In this embodiment, when the front end side of the balance member 22 rotates upward in an arc to rotate the L-shaped link 27, the necessary play between the balance member 22 and the L-shaped link is set between the fixed frame 21 and the balance. It is provided between the member 22 and the member 22.

In the illustrated example, the L-shaped link 27 and the front end of the balance member 22 are simply rotatably connected to each other, but this side can also be engaged with a pin and a long hole. It becomes possible to move the balance member 22, and thus the backrest 25, back and forth relative to the seat, providing a chair that moves more closely following the movement of the user's body.

In FIG. 11, the rotation shaft 24 of the balance member 22 is suspended from the fixed frame 21 by a link 55.

This embodiment also provides substantially the same effects as the embodiment shown in FIG. 10.

Note that the rotation shaft portion of the balance member 22 may be supported from below by a link.

In the present invention, the fulcrum part of the balance member 22 is
It also includes a movable fulcrum as shown in FIGS. 10 and 11.

The present invention has been variously explained above with reference to preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

(Effects of the Invention) As described above, according to the chair according to the present invention, the load on the seat portion is distributed to the application point portions that sandwich the fulcrum portion of the balance member via the seat support portion. Since it is supported by the balance member and the seat is moved forward in conjunction with the rearward tilting of the backrest and the balance member, the load is offset around the fulcrum of the balance member, and when working, The seat and backrest can be easily moved to follow the movements of the body when taking various working postures, and the remarkable effect is that it is possible to easily take a working posture that does not cause fatigue even when sitting for long periods of time. play.

In addition, when transitioning to a resting position, both heavy and light people can tilt the backrest backwards with almost the same amount of leaning on the backrest, and the balance position with the mechanical elastic body can be adjusted. You can easily take a resting position. At this time, the backrest tilts backwards around a rotation axis located below the seat, while the seat moves forward, which expands the seating space back and forth, allowing a comfortable resting position.

Furthermore, when the load on the backrest is removed, the seat and backrest return to their original standard positions.

The biasing force of the mechanical elastic body can be adjusted in advance by adjusting means at the time of factory shipment, taking into account the position of the fulcrum of the balance member, etc., and thereafter, there is almost no need for adjustment taking into account differences in weight, etc. It can be extremely suitably used for chairs used by an unspecified number of people, such as in conference rooms.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing the connection between the balance member and the seat, and FIG. 2 is a plan view thereof. FIG. 3 is a side view of the L-shaped link with the link piece and link plate in the upright state, and FIG. 4 is a side view of the L-shaped link in a state where it is tilted forward beyond the upright state. Fifth
The figure is an explanatory diagram showing an adjustment means for adjusting the biasing force of the helical spring, FIG. 6 is a side view showing another embodiment, FIG. 7 is a side view showing another embodiment of the seat support, and FIG. 9 and 9 are explanatory diagrams showing other embodiments of the force transmitting means, and FIGS. 10 and 11 are explanatory diagrams showing other embodiments of the position of the fulcrum part of the balance member. FIGS. 12 and 13 are explanatory diagrams showing an example of a conventional chair. 20... Pillar, 21... Fixed frame, 22... Balance member, 23... Seat, 24... Rotating shaft, 25...
Backrest, 26...Back support rod, 27...L-shaped link, 28...Shaft, 29...Shaft, 30...Pin, 3
1... Long hole, 32... Link plate, 33... Shaft, 3
4... shaft, 35... tension spring, 40... pressure receiving plate,
41... Adjustment screw, 42... Spiral spring, 44...
...Support arm, 45...Pin, 46...Elongated hole, 4
7... Seat support plate, 48... Pin, 49... Link plate, 50... Long hole, 52... Pin, 53... Long hole, 54... Pin, 55... Link.

Claims (1)

[Scope of Claims] 1. A chair with a backrest, comprising a seat, a support base, and a seat supported by the support base in the front-rear direction below the seat, with the backrest provided at the rear. a balance member that is attached to the backrest; a force transmitting means for converting a backward tilting motion of the balance member into a forward motion of the seat portion via the seat support portion when the balance member tilts rearward about the fulcrum portion of the balance member; When the backrest tilts backward due to the load applied to the backrest, the load acting on the backrest, the load on the seat, etc. acts as a balancer that balances the moment around the fulcrum of the balance member through the force transmission means. A chair comprising: a mechanical elastic body; and an adjusting means for adjusting the elastic force of the mechanical elastic body.