Seat for motor vehicles

A seat for motor vehicle includes a seat cushion whose rear or front section or both are coupled via a link mechanism with a base frame in a manner that can be lifted and lowered, whereby through joining of the link mechanism to a control shaft for height adjustment that can be rotated without any limitation, coupling of one of the rocking ends of a bell crank which repeats a rocking motion, interlocked with the rotation of the control shaft, to the seat cushion, and joining of the other rocking end to the control shaft via a crank, it is possible to adjust the height of the rear section, front section, or both, of the cushion seat between the lowest position and the highest position, for every rocking operation of the bell crank.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a seat for motor vehicles, and more 
particularly, to a link mechanism which governs the lifting and lowering 
portion in the height adjustment mechanism for the seat cushion. 
2. Description of the Prior Art 
In a seat for a motor vehicle, there is incorporated a height adjusting 
mechanism for the seat cushion. By the use of the mechanism it is possible 
to adjust the overall height of the seat cushion to match the seated 
height or the leg length of the user, and raise the rear end or lower the 
front end of the seat cushion. By so doing, the seat may be made to fit 
the user, permitting the user to put his feet at a proper position or 
secure a forward field of vision during driving. 
A seat for a motor vehicle equipped with a height adjusting mechanism of 
the above kind includes an elevating mechanism of the seat cushion and an 
actuating mechanism for driving the elevating mechanism. As to the 
elevating mechanism of the above type, various techniques as disclosed in 
Japanese publications of unexamined utility model applications No. 
57-194842, No. 58-49864, No. 60-90030 have been known. In addition, 
various kinds of techniques similar to the above have also been developed. 
An elevating mechanism that is employed commonly in these techniques is 
mainly a parallel link mechanism. Namely, in these techniques, the upper 
parts of a pair of links that constitutes the parallel link mechanism are 
coupled with the front and rear of the seat cushion so as to have the 
height of the front section, rear section, or both of the seat cushion 
variably adjustable in response to the changes in the tilting angle of 
each link. 
In a height adjusting means of the above kind, the rocking ends, namely, 
the upper portion, of the links are coupled directly with the seat 
cushion, and a control shaft is coupled with the turning center of the 
cushion so that the turning range of the control shaft is restricted. 
In other words, in such a structure, the turning range of the control shaft 
is limited to the range of from 0.degree. to 90.degree. since the position 
of the maximum height corresponds to the state in which the links are 
upright and the position of the lowest height corresponds to the state in 
which the links are in the horizontal position. Accordingly, it is 
necessary to turn the control shaft in the reverse direction in order to 
readjust the seat cushion from either one of these states. 
Further, as the operating system for the above kind of height adjustment 
mechanism, there are a manual type in which the control shaft is turned by 
the hand of the adjuster who grasps a knob which is provided on one end of 
the shaft, and a motor driven type, called power lift, in which the 
control shaft is linked via a reduction mechanism to the output shaft of a 
power motor which is rotated by the operation of a button, therefore power 
of the motor being transmitted to the link mechanism. 
Accordingly, when the control shaft of the elevating mechanism that adopts 
the conventional parallel link mechanism is turned manually, there arises 
a possibility of applying an unreasonable force to the mechanism itself in 
an attempt to adjustment a range beyond the allowed limit of the operating 
range. On the other hand, it should be noted that the manual operation 
system may be advantageous to those who are accustomed to the system. This 
is because, due to the limitation on the turning of the control shaft, the 
operator is able to have a feel that suggests the limiting conditions of 
the rotation that is transmitted directly to his hand. 
In contrast, the motor driven system requires a sensor and a device which 
can give the same kind of feel that the hand receives in the manual 
operation. These are a limit switch for detecting the stopping position of 
the motor rotation and a mechanism that carries out a control on the 
reverse rotation of the motor in response to the detected output of the 
switch. Consequently, the motor driven system becomes complicated in 
proportion to the added portion of the mechanism for controlling the 
rotation. 
Therefore, it has to be concluded that neither the manual system nor the 
motor driven system is a desirable system in the sense that the necessity 
of regulating the range of rotation may adversely affect the rigidity of 
the mechanism itself or requires an addition of a mechanism for preventing 
such an undesirable effect. 
SUMMARY OF THE INVENTION 
Accordingly, the principal object of the present invention is to provide a 
seat for motor vehicles having a control shaft for actuating the elevating 
that can be rotated manually or by the driving of a motor in an 
unrestricted manner, and that the elevating mechanism can position the 
height of the seat cushion on an arbitrary level between the lowest 
position and the highest position, during one rotation of the crank that 
corresponds to the rotation of the control shaft. 
Another object of the present invention is to provide a seat for motor 
vehicles which can provide miniaturization, a reduction in size, and a 
reduction in the cost, for the actuating mechanism by an unrestricted 
rotation of the control shaft. 
Still another object of the present invention is to provide a seat for 
motor vehicles which makes it possible to drive the elevating mechanism in 
the rear end section of the seat cushion of the seat by an unrestricted 
rotation of the control shaft. 
Still further object of the present invention is to provide a seat for 
motor vehicles which makes it possible to drive the elevating mechanism in 
the front end section of the seat cushion of the seat by an unrestricted 
rotation of the control shaft. 
Still another object of the present invention is to provide a seat for 
motor vehicles which makes it possible to drive the elevating mechanism in 
the front end section and in the rear end section of the seat cushion of 
the seat by an unrestricted rotation of a pair of respectively independent 
control shafts. 
Still another object of the present invention is to provide a seat for 
motor vehicles which makes it possible to drive the elevating mechanism in 
the front end section and in the rear end section of the seat cushion of 
the seat by an unrestricted rotation of a single control shaft. 
Still another object of the present invention is, to provide a seat for 
motor vehicles having a system which can drive the elevating mechanism in 
the front and rear end sections of the seat cushion by an unrestricted 
rotation of one control shaft, where in the system makes the operations of 
lifting and lowering of the front end section, quasi-parallel lifting, and 
lifting and lowering of the rear end section, to be carried out 
continuously during one rotation of the crank that corresponds to the 
rotation of the control shaft. 
Still another object of the present invention is to provide a seat for 
motor vehicle which will not suffer from undesirable effects such as 
twisting to the cushion frame during the lifting or lowering operation. 
Still another object of the present invention is to provide a seat for 
motor vehicles which makes it possible to incorporate a reclining device 
for adjusting the angle of the seat back and the control portion of the 
elevating mechanism in one seat without undue effort. These and other 
objects and advantages of the present invention will become more apparent 
in connection with the description of several embodiments to be 
hereinafter described in greater detail. These and other objects and 
advantages of the present invention will become more apparent in 
connection with the description of several embodiments to be hereinafter 
described in greater detail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to the drawings for each embodiment, the present invention will 
be described in detail. 
FIG. 1 and FIG. 2 show a first embodiment of the present invention. 
In the figures, a vehicle seat 10 consists in the main of a base frame 14 
which is fixed on sliding rails 12, a cushion frame 16 which is arranged 
on the inner upper part of the base frame 14, and a seat back frame which 
is coupled, as can be tilted forwardly and backwardly, to the rear end 
section of the base frame 14 via a reclining device that is not shown. 
Below the tip of the cushion frame 16, there is fixed a bearing bracket 20, 
and coupled thereto via a pivotally supporting pin 24 is the upper end of 
a flat link lever 22. 
The lower end of the flat link lever 22 is coupled via a coupling pin 26 to 
the inner section of the tip of the base frame 14. The flat link lever 22 
supports pivotally the tip of the cushion frame 16 turnably, in a state 
which is approximately perpendicular to the base frame 14 and can rock 
slightly back and forth. 
Further, another bearing bracket 20 is fixed to the lower part of the rear 
end of the cushion frame 16, and the bracket 20 is linked to the upper 
rocking end of a bell crank 28 via another coupling pin 26. 
The rocking center of the bell crank 28 is pivotally supported by a 
pivotally supporting pin 30, and the lower rocking end is linked via a 
linking pin 34 to the rear end of a linking rod 32. 
The coupling rod 32 is arranged substantially parallel to the bottom 
surface of the cushion frame 16, and the tip thereof is coupled to a crank 
pin 38 which is provided on an end surface of a flat gear 36 that is used 
commonly as a crank arm. 
The flat gear 36 is supported pivotally as turnably to the inside section 
on the tip of the base frame 14, and it is engaged with a pinion gear 42 
provided on a control shaft 40 which is supported by the base frame 14 
penetrating through the inner and outer sides of the base frame. 
In the above-construction, the flat gear 36 is rotated at a reduced speed 
via the pinion gear 42 by means of the unidirectional rotational power of 
the control shaft 40 that is operated from outside. 
During one rotation of the flat gear 36, the coupling rod 32 completes one 
stroke, thereby the bell crank 28 carries out a reciprocating motion in 
response to the stroke of the coupling rod 32. By this rocking motion, the 
rear end section of the cushion frame 16 repeats a continuous cycle which, 
starting from the lowest position shown in FIG. 1, is lifted to the 
highest position indicated by the imaginary line shown in FIG. 2, with the 
pivotally supporting pin 24 as the center of turning, and is lowered back 
again to the lowest position. 
Here, a slight back-and-forth motion of the cushion frame 16 during the 
operation is absorbed by the back-and-forth motion of the flat link lever 
22. 
The amount of the up-and-down adjustment of the rear end of the cushion 
frame during its forward tilting is determined by the eccentricity ratio 
of the crank pin 38 that is provided on the flat gear 36 and the lever 
length of the bell crank 28. 
Accordingly, the control shaft 40 during adjustment can be rotated 
continuously in an arbitrary direction of rotation along, so that the 
cushion frame can be fixed at an arbitrary angle of forward tilt by 
providing an irreversible mechanism for preventing the reverse rotation. 
In addition, in the case of driving the control shaft 40 with a motor, 
angle adjustment becomes possible by the mere provision of a switch along 
which can drive and stop the motor. 
As in the foregoing, according to the first embodiment of the present 
invention, it is possible to realize a cycle in which the rear end section 
of the seat cushion is moved continuously between the highest position and 
the lowest position during one rotation of the flat gear that constitutes 
the crank arm, by an unrestricted unidirectional rotation of the control 
shaft. Therefore, there is no need of providing a mechanism for bringing 
the rotation to a stop as was required in the existing system In 
particular, in the case of adjusting the forward tilt with the motor 
power, the entire mechanism can be made simpler with no need for providing 
a position detection switch and a reverse rotation control. 
FIG. 3 and FIG. 4 show a second embodiment of the present invention. 
In describing the embodiment, members that are common to the first 
embodiment are given identical symbols and only the parts that are 
different from those in the first embodiments are assigned different 
symbols. 
In the figures, the vehicle seat 10 is constructed, similar to the first 
embodiment, mainly of the base frame 14 that is fixed on the sliding rails 
12, the cushion frame 16 that is arranged on the top portion of the base 
frame 14, and the seat back frame 18 that is coupled as tiltable forwardly 
and backwardly, via a reclining device (not shown), to the rear end 
section of the base frame 14. 
On the bottom of the rear end of the cushion frame 16, there is fixed a 
bearing bracket 20, and a pivotally supporting pin 50 which is attached on 
the inner side surface in the rear of the base frame 14 is inserted 
therethrough. The rear end section of the cushion frame 16 is supported as 
may be rocked by the base frame 14 with the pivotally supporting pin 50 as 
the center of turning. 
Further, on the inner side surface in the front of the base frame 14, there 
is supported pivotally the turning center of the bell crank 52 via a shaft 
54a, as rockably. 
On the inner surface of the base frame 14, in the proximity of the rear 
section of the bell crank 52, there are arranged a pinion gear 58 which is 
provided on the control shaft 56 that is supported by penetrating through 
the inner and outer peripheries of the frame 14, and a flat gear 60 that 
engages the pinion gear 58. The flat gear 60 serves also as a crank arm, 
and on its end surface there is provided a crank pin 62 with a 
predetermined eccentricity, projecting from the center of turning. 
One end of a first flat link lever 64 is coupled with the crank pin 62 
while the other end is joined via a coupling pin 66 to the upper rocking 
end of the bell crank 52. 
Further, the lower rocking end of the bell crank 52 is coupled with the 
lower end of a second flat link lever 68 via a coupling pin 66. 
The upper end of the flat link lever 68 is coupled similarly via a coupling 
pin 66 to a bracket 70 which is fixed to the lower front end of the 
cushion frame 16, with the link levers 64 and 68 crossing each other in 
the form of the letter X. 
It should be noted that, although the bell crank 52, pinion gear 58, flat 
gear 60, and flat link levers 64 and 68 are depicted as if they lie in a 
same plane, they are arranged adjacently so as not to obstruct their 
mutual rotations or rocking motion. 
With the construction as in the above, the flat gear 60 is rotated at a 
reduced speed via the pinion gear 58 by a rotational power of the control 
shaft 56 given by an operation from the outside. By this motion, the bell 
crank 52 is rocked and repeats a cycle in which, during one rotation of 
the flat gear 60, the front end section of the cushion frame 16 is lifted 
from the lowest position shown in FIG. 3 to the highest position that is 
shown by the chained line in FIG. 4 with the pivotally supporting pin 50 
as the turning center, and is lowered again to the lowest position. 
The amount of the adjustment is determined by the eccentricity ratio of the 
crank pin 60, the length of the levers, and so forth. 
Therefore, the control shaft 56 can be rotated toward an arbitrary 
unidirection continuously, so that by providing a mechanism for preventing 
the reverse rotation on the control shaft 56, it is possible to fix the 
cushion 16 at an arbitrary height. 
Further, in the case of driving the control shaft 56 with a motor, height 
adjustment can be realized by the mere use of a switch for driving and 
stopping the motor, without requiring a checking mechanism for reverse 
rotation. 
According to the second embodiment, it is possible to realize, in one 
rotation of the crank arm, a cycle which moves continuously between the 
highest and the lowest positions of the front end section of the cushion 
during one rotation of the flat gear, by an unrestricted unidirectional 
rotation of the control shaft. Therefore, similar to the first embodiment, 
there is no need for providing a mechanism for stopping the rotation, and 
in particular, in the case of height adjustment with motor power, the 
mechanism can be simplified without requiring a position detection switch 
or a control for preventing reverse rotation. 
FIG. 5 to FIG. 7 show a third embodiment of the present invention. 
The embodiment has a construction in which, by a combination of the first 
and the second embodiments, the height of the front end and the rear end 
of the seat cushion can be adjusted by a pair of control shafts. 
Consequently, the present embodiment consists mostly of members that are 
common to the first and the second embodiments. The principal difference 
from the first embodiment is the positions of the coupling rod 32 and the 
control shaft 40 which is interlocked to the rod 32. For that reason, only 
the important part of the present invention will be described, and 
explanation of the other part is omitted by showing the most part in 
thereof figures with symbols that are common to these embodiments. 
Namely, in the present embodiment, the mechanism which includes the control 
shaft 56 on the front side has a construction similar to the second 
embodiment, and the position of the control shaft 40 on the rear side is 
receded to the center of the base frame. The main point of modification in 
the present embodiment is the reduction in length of the coupling rod 32. 
Accordingly, in the present embodiment, the rear side is displaced as shown 
in FIG. 6 from the lowest position to the highest position by the 
rotational operation of the control shaft 40, and the front side is 
displaced in response to the rotation of the control shaft 56 as shown in 
FIG. 7. 
In the third embodiment, it is possible to move cushion frame up and down 
parallel to the floor and fix the front on the rear at a predetermined 
height, by rotating independently the front and the rear control shafts in 
the same direction. Therefore, the adjustment range can be expanded and 
the selection range of the angular position can also be widened. 
FIG. 8 and FIG. 9 show a fourth embodiment of the present invention. 
The construction of the embodiment shown in the figure looks at a glance 
like a modification of the third embodiment. In other words, in the 
present embodiment, the difference is that the pinion gear 42 and flat 
gear 36 that are interlocked with the bell crank 28 on the rear side are 
removed, and the coupling rod 32 is prolonged toward the front as in the 
first embodiment and is axially linked to the crank pin 62 of the flat 
gear 60 on the front side as shown in the second embodiment. 
However, the action of the present embodiment is very much different from 
those of the first to the third embodiments, and represents a very 
peculiar form. Accordingly, the present embodiment will be described with 
special emphasis on the action during the lifting or lowering of the 
cushion frame. 
The rear side of the cushion frame 16 is raised and lowered to the height 
that corresponds to the eccentricity ratio of the crank pin 62 and the 
lever ratio of the bell crank 28 on the rear side, by the rotation of the 
flat gear 60 that corresponds to the rotational operation of the control 
shaft 56. 
In addition, the front side of the cushion frame 16 moves up and down 
synchronized with the bell crank 28 on the rear side, within the range of 
a certain predetermined turning angle .alpha..sub.1 .degree. of the crank 
pin 62, with the lowest height as the starting position as shown in FIG. 9 
(a), by the pushing up of the bell crank 52 by the flat link 64. 
Consequently, within the range of 0.degree. to .alpha..sub.1 .degree., the 
front and the rear of the cushion frame 16 are raised and lowered 
substantially parallel to the floor as shown by the imaginary lines by a 
quasi-parallel link motion, so that it is possible to carry out a parallel 
adjustment with 0.degree. as the lowest and .alpha..sub.1 .degree. as the 
highest height positions. 
In the state that exceeds the angle .alpha..sub.1 .degree., the bell crank 
28 on the rear side is still in the process of ascent whereas the raised 
amount of the front side bell crank 52 is small as shown in FIG. 9 (b), 
and as a result, the cushion frame 16 is tilted forwardly as in the 
imaginary lines. 
In other words, the difference in the lever ratios between the front and 
the rear cranks is made conspicuous. The above state continues to exist 
within the range .alpha..sub.2 .degree. of angle until the bell crank 28 
on the rear side is rocked to the descending side. 
Next, in the range of angle .alpha..sub.3 .degree. which covers the region 
from the state of exceeding the angle .alpha..sub.2 .degree. to the 
original reference position, the rear side bell crank 28 is about to pass 
the maximum rocked condition, as shown in FIG. 9 (c), with little change 
in the height. In contrast, the front side bell crank 52 is pushed up 
further toward the ascending side so that the cushion frame 16 is tilted 
backward with its front end pushed up till a maximum height. 
Following that, the front end of the cushion frame 16 descends later than 
the rear end and returns to its lowest height position shown by the solid 
line in each figure, while regaining slowly the posture which is parallel 
to the sliding rails. 
Accordingly, the present embodiment enables the cushion frame 16 to carry 
out continuously three operations of quasi-parallel lifting, front section 
tilting, and rear section tilting, during one rotation of the control 
shaft 56. 
The amount of height adjustment and the forward and backward tilting angles 
in the above operations can be set appropriately in response to the lever 
ratios of the bell cranks 28 and 52, the eccentricity of the crank pin 62, 
and the lengths of the flat links 64 and 68. 
Further, an ordinary seat back carries out adjustment mainly of the amount 
of the parallel lifting and the amount of the backward tilting, so that 
the adjustment of the parallel lifting and the backward tilting may be 
carried out by a clockwise and a counterclockwise rotations, respectively, 
of the control shaft 56, by locking the range of angle .alpha..sub.2 that 
is needed for the intermediate forward tilting. 
Moreover, in the case of carrying out mainly the quasi-parallel lifting of 
the cushion frame 16, for example, it can be achieved by giving a 
construction in which the point of the pivotal support (pivotally 
supporting pin 54) of the front side bell crank 52 by the base frame 14, 
and the point of pivotal support (coupling pin 66) of the flat link 68 by 
the front side bracket 70, are shifted toward the lower side, namely, 
toward the sliding rails 12. 
Furthermore, in the case of carrying out mainly the two operations of 
tilting of the front section and tilting of the rear section, for example, 
they can be achieved by giving a construction in which the point of the 
pivotal support (coupling pin 66) of the flat link 64 by the front side 
bracket 70 is shifted to the crank pin 62 side. 
According to the fourth embodiment, the three operations of the 
quasi-parallel lifting, tilting of the front section, and tilting of the 
rear section, mainly the two operations of quasi-parallel lifting and 
tilting of the front section, mainly the two operations of tilting of the 
front section and tilting of the rear section, or mainly the operation of 
quasi-parallel lifting, can be carried out selectively by the use of a 
single mechanism. As a result, the entire mechanism can be simplified, and 
moreover, the adjustment operations can be accomplished by the use of a 
single control knob or lever or by means of motor driving, so that the 
adjustment work can also be simplified. 
FIG. 10 and FIG. 11 show a fifth embodiment of the present invention. 
The embodiment may even be said to be a modification of the fourth 
embodiment. The reason for this is that the lifting and lowering operation 
of the front and the rear ends and the quasi-parallel lifting of the seat 
cushion can be carried out by means of a single control shaft. 
However, a feature of the embodiment is that although the mechanism for 
lifting and lowering the seat cushion is being simplified markedly, the 
above-mentioned three operations can be accomplished. 
The important part of the present embodiment is as follows. 
In the FIGS. 10 and 11, the lower end of a flat link 80 is joined axially 
to the crank pin 62 of the flat gear 60. The upper end of the flat link 80 
is coupled via a coupling pin 66 with the bracket 70 that is provided 
below the cushion frame 16. 
Further, between the flat gear 60 and the rear side bell crank 28, there is 
hung a pulling coil spring 84, with its one end engaged with an attaching 
pin 82 that is provided projectingly from the flat gear 60, and its the 
other end engaged with the coupling pin 34. By means of the biasing force 
of the pulling coil spring 84, the cushion frame 16 is biased all the time 
toward the lifting side, by the pulling of the bell crank 28 and the flat 
gear 60 in the directions to bring them closer. 
Next, the lifting and lowering operation of the above structure will be 
described. 
By the rotation of the flat gear 60 that corresponds to the rotational 
operation of the control shaft 56, the rear side of the cushion frame 16 
is lifted or lowered to the height position that corresponds to the 
eccentricity ratio of the crank pin 62 and the lever ratio of the bell 
crank 28. 
Further, the front side of the cushion frame 16 is lifted or lowered to the 
height position that corresponds similarly to the eccentricity ratio of 
the crank pin 62 and the lever ratio of the flat link 80. 
Then, the front side of the cushion frame carries out an ascending and 
descending motion with a predetermined delay with respect to the ascending 
and descending motion of the rear side that accompanies the rocking motion 
of the bell crank 28 that is caused by the difference between the two 
lever ratios and eccentricity ratios. These conditions are illustrated in 
FIGS. 11 (a) and 11 (b). 
Both figures show the see-saw motion of the front and rear sides of the 
cushion frame, from the position marked (a) to each of the positions (b) 
through (h) that correspond to the rotational angles .alpha..sub.1 
.degree. through .alpha..sub.8 .degree. that cover 360.degree.. 
Corresponding to these angular positions, the cushion frame 16 covers the 
ranges of the rising of the front end in the forward tilted state, the 
parallel lifting, and the lowering of the rear end in the backward tilted 
state. Accordingly, by adjusting the rotational angle of the flat gear 60, 
it is possible to realize the three kinds of states of parallel lifting 
motion and the forward and backward tilted motions. 
Further, in the foregoing embodiments, the bell crank 28 was arranged on 
the rear side while the flat gear 60 and the flat link 80 that is coupled 
with the gear 60 were arranged on the front side. Needless to say, 
however, the arrangement of these components may be reversed. Moreover, as 
the driving power for the control shaft 56, an exclusive driving motor may 
be employed instead of a control knob or lever that is joined to the 
control shaft with an axis. 
According to the fifth embodiment, the mechanism be simplified than in the 
fourth embodiment. 
FIG. 12 through FIG. 14 show a sixth embodiment which applies the present 
invention in a way that is suited for practical uses. 
In other words, in the first through fifth embodiments, description was 
presented by focusing the attention only the mechanism that is related to 
the principle of the present invention. In contrast, in the present 
embodiment, description will be given by mentioning the forms and 
combinations of the members that constitute the height adjustment 
mechanism which is close to the reality that is suited for the mounting on 
the seat, and even referring to the configurational relationship to the 
reclining device that is provided along with the seat height adjustment 
mechanism. Further, in the present embodiment, illustrations will be given 
having in mind the driver's seat which is mounted on the right-hand side 
of the vehicle. However, it will be easy to imagine that, for a driver's 
seat on the left-hand side of the vehicle, the relevant figures will be 
those that are symmetric to the figures that will be shown in the 
following. 
In the figures, a vehicle seat 10 is constructed roughly with a pair of 
base frames 14 fixed on a pair of sliding rails 12 that are arranged on 
the vehicle floor, back frames 18 which are supported turnably by the rear 
end section of the base frames 14, and a cushion frame 16 which is 
supported on the inner upper side of the base frame 14 in a manner which 
is possible to be raised or lowered and tilted forwardly or backwardly. 
The cushion frame 16 is a press-molded body made of steel plate or the like 
formed in the shape of a rectangular frame. A seat cushion is completed by 
placing springs or the like that are not shown over the frame, and 
assembling pads and surface decorating material. In addition, each of the 
back frames 18 has a similar rectangular frame form, and a seat back is 
completed by assembling members mentioned above. 
Accordingly, what is of concern is a distortion phenomenon due to imbalance 
of loads that may be applied on the left and right sides of the frames 16 
and 18 during ascent or descent of the cushion frame 16 or during forward 
or backward tilting of the back frames 18. In the embodiments that follow, 
a structure is employed which will equalize the loaded states on the left 
and the right sides, when a force is applied to the height adjustment 
mechanism or the reclining device that is provided on one of the side 
surfaces of the frame 16 or 18. 
On one side in the rear section of the base frames 14, there is arranged a 
latch type or a swash plate type reclining device 90, with its latch lever 
92 extending toward the front side. In addition, a reclining knob 94 is 
projected from the side in the rear end of the base frame 14. 
The lower ends of the back frames 18 are connected to connecting shaft 96 
that is supported axially between the base frames 14. One end of the 
connecting shaft 96 is turned interlocked with a revolving lever 94a of 
the reclining device 90 and transmits the power to the other back frame 
18, to equalize the loads on both sides of the back frames 18. Joining the 
other side of the back frame 18 and the connecting shaft 96, there is 
interposed a wound spring 98 which energizes the back frame 18 to its 
forward falling side all the time. 
Because of this, by setting the reclining device 90 to the free state 
through the operation on the latch lever 92, the back frames 18 tend to 
fall forward with the connecting shaft 96 as the center of turning. 
By applying a load to the back frames 18 in order to cope with the above 
trend, the back frames 18 are tilted backwardly, and by releasing the 
lever 92 at an arbitrary angle, the reclining device 90 is latched and the 
back frames 18 are held at that angular posture. Here, the load is applied 
via the connecting shaft 96 to the back frames 18 uniformly to the left 
and the right sides so that the distortion phenomenon can be prevented. 
The cushion frame 16 is held on the base frames 14 according to the 
following mechanism. 
Namely, in the front and the rear on the inner section of one of the base 
frames 14, a pair of bell cranks 52 and 28 are mounted pivotally as 
rockable via pivotally supporting shafts 54 and 30. One of the racking 
ends of the rear side bell crank 28, of the two bell cranks 52 and 28, is 
coupled via the coupling pin 26 with the bracket 20 that is provided on 
the rear bottom surface of the cushion frame 16. 
Further, the lower rocking end of the front side bell crank 52 and the 
bracket 70 that is provided on the front bottom of the cushion frame 16 
are coupled by a flat link 68 which has its both ends joined with coupling 
pins 66. 
In addition, the other ends of the pivotally supporting shafts 54 and 30 
are supported axially by the base frame 14 on the other side as shown in 
FIG. 12, and are coupled with the crank levers 102 and 104 that are 
provided on the frame 14 directly and via a flat link 106, respectively. 
On one of the base frame 14, there is supported axially a control shaft 56, 
and a pinion 58 which is formed as a united body on the periphery of the 
control shaft 56 is engaged with the flat gear 60. 
On an end surface of the flat gear 60, there is provided a crankpin 62 
projecting from the surface with a predetermined eccentricity ratio. The 
crankpin 62 and the coupling pin 66 provided in the upper rocking end of 
the front side bell crank 52 are coupled with a flat link 64. 
Moreover, the crank pin 62 and a coupling pin 34 which is provided in the 
lower rocking and of the rear side bell crank 28 are coupled with a 
coupling rod 32. In a manner described in the above, the rear side bell 
crank 28 and the front side bell crank 52 are interlocked with the 
rotation of the flat gear 60. 
Furthermore, between both bell cranks 28 and 52, there is hung a pulling 
coil spring 84. The spring absorbs the looseness in the relative positions 
between the cranks as well as biases the cushion frame 16 to the side of 
upper position all the time, facilitating the lifting operation. 
In addition, a control knob 110 is joined axially to the end of the control 
shaft 56 that projects outwardly from the base frame 14. 
Next, the lifting function and the forward and backward tilting function of 
a vehicle seat 10 with the above construction will be described. 
First, the state shown in FIG. 13 corresponds to that in which the cushion 
frame 16 is at its lowest position and the flat gear 60 is at its original 
position. In this state, by rotating the control knob 110 in the clockwise 
direction in the figure, the front side of the cushion frame 16 is raised 
corresponding to the range of turning with an angle of A.degree. in FIG. 
14. 
Next, in the turning range of B.degree., the front side of the cushion 
frame 16 tends to descend somewhat from its highest position and the frame 
is raised as a whole, achieving a quasi-parallel lifted state. 
Next, in the turning range of C.degree., the front side descends from the 
lifted position, followed by a descent of the entire frame, and the 
cushion frame 16 returns again to the lowest position which is the 
original position. 
In other words, the operational modes during one rotation of the flat gear 
60 are, a forwardly tilted state of the cushion frame 16 in the range from 
the origin to A.degree., a parallel lifted state of the cushion frame in 
the range of angle B.degree., and the return to the original position 
while tilted backward of the cushion frame in the range of angle 
C.degree.. 
Accordingly, it is possible to position the cushion frame 16 to a posture 
that corresponds to the purpose, depending upon the height or preferred 
posture of the user, securing the field of vision, and so on, by the 
turning of the control knob 110. Further, the power for the above purpose 
can be applied uniformly to the cushion frame 16 for the left and right 
sides through the pivotally supporting shafts 30 and 54, preventing the 
left-right distortion of the cushion frame 16. 
Needless to say, the amount of displacement of the cushion frame and the 
turning points of the various postures can be set to the values 
corresponding to the various lever ratios and the eccentricity ratios. 
Next, FIG. 15 shows a modification of the sixth embodiment. 
In the figure, the construction of the mechanism for lifting the cushion 
frame 16 and for the forward and backward tilting of the back frames 18, 
is the same as in the first embodiment. Note, however, that the control 
shaft is joined to the output terminal of a lifter motor unit M.sub.1 
which incorporates an electrical motor and a reduction mechanism into a 
united body so that operations mentioned above can be realized by means of 
the driving of the motor. 
Further, the reclining device 90 makes use of a swash plate type mechanism 
alone, and the driving axis of the reclining device 90 is driven by a 
motor unit M.sub.2. 
In other words, in the present embodiment, reclining of the seat back, and 
the lifting and forward and backward tiltings of the seat cushion, are 
arranged to be accomplished by the switch driving in place of the manual 
operation. 
In the sixth embodiment and its modification, the three functions of seat 
back reclining, lifting and forward and backward tiltings of the seat 
cushion can be incorporated into the seat, without accompanying 
complication of the mechanism or without accompanying problems involving 
rigidity of the component parts. 
The present invention has been described in detail in conjunction with the 
various embodiments. However, the spirit and advantages of the present 
invention will not be limited to these embodiments, and needless to say 
various modifications and applications will become possible without 
deviating from the scope of the claims that will be presented in what 
follows.