Patent Description:
When the sitting posture of an occupant on a vehicle seat is not appropriate, the occupant may get deeply tired, for example. Thus, it has been proposed to inflate air bags of a seat back in accordance with the body type of the occupant, and keep the pelvis of the occupant at an appropriate position, so as to appropriately adjust the posture of the occupant and reduce tiredness (see, for example, <CIT> (<CIT>)).

It has also been proposed to detect the shape of the lumbar spine of an occupant seated on a vehicle seat, and adjust the position of a lumbar support so that the lumbar spine assumes a curved shape (see, for example, <CIT> (<CIT>)).

<CIT> discloses a personalized seat control device and method. The personalized seat control device includes an input unit that receives passenger information from a vehicle occupant, a human body modeling unit that generates a personalized human body model based on the passenger information, and generates a mode shape by simulating at least one vibration on the human body model. As a mode shape generating unit, the mode shape is a mode shape corresponding to a predetermined condition among the generated mode shapes based on the mode shape generation unit and the occupant information, which is the vibration shape information of the human body model according to the vibration. When a vibration corresponding to the high-risk mode shape is detected by detecting a high-risk mode shape extraction unit for extracting a high-risk mode shape for a passenger and a vibration state of the vehicle, the vehicle according to a predetermined method for avoiding the high-risk mode shape It includes a sheet control unit for controlling the sheet. Therefore, by generating a mode shape that is a response characteristic according to the vibration of the occupant, and extracting the high-risk mode shape, when the vibration corresponding to the high-risk mode shape is detected while driving, the seat is controlled to avoid the occurrence of the customized seat to the occupant.

<CIT> discloses a vehicle seat constituted so that a plate of monolithic plate shape made of synthetic resin capable of supporting the back part of a seat sitting person is attached to a back-rest frame of a back-rest seat in such a manner that it can be moved forward or backward through wire springs with a resilience adjustment plate of monolithic plate shape made of resilient synthetic resin arranged at the front surface of the plate in such a manner that it can be moved forward or backward in respect to the plate, wherein the resilience adjustment plate is constituted to enable a resilience force for pushing out the seat sitting person in a forward direction to be adjusted with a plurality of vertical protrusions protruded forwardly to which predetermined portions of the resilience adjustment plate abut arranged side by side in a lateral direction at predetermined locations in a front side of the plate.

The sitting posture of an occupant changes depending on oscillation of the vehicle during traveling, steering action, etc. However, it is difficult for the vehicle seats described in <CIT> and <CIT> to cope with change of the sitting posture of the occupant due to oscillation of the vehicle, for example.

This invention provides a technology for appropriately adjusting the posture of the upper body of an occupant, even when the sitting posture of the occupant changes due to oscillation of a vehicle, for example.

A first aspect of the invention is concerned with a vehicle seat. The vehicle seat is defined in claim <NUM>.

According to the first aspect as described above, the elastic force of the seat back in the longitudinal direction is made larger in the case where oscillation of the vehicle is large, than that in the case where oscillation of the vehicle is small. Thus, when oscillation of the vehicle is large, reaction force applied from the seat back to the occupant acts in such a direction as to curb movement of the upper body of the occupant, and oscillation of the head of the occupant can be reduced.

In the first aspect, the elastic force adjustment unit may be configured to make the elastic force of the lumbar spine support larger than those of portions of the seat back other than the lumbar spine support.

With the above arrangement, even when oscillation of the vehicle is large, and the sitting posture of the occupant changes, the posture of the upper body of the occupant can be appropriately adjusted by making a support load of the lumbar spine region of the occupant larger than support loads of the other regions.

In the first aspect, the elastic force adjustment unit is configured to adjust elastic force of a sacrum support included in the seat back and configured to support the sacrum located below the lumbar spine of the occupant, and elastic force of a thoracic spine support included in the seat back and configured to support the thoracic spine located above the lumbar spine of the occupant, in addition to the elastic force of the lumbar spine support. The elastic force adjustment unit is configured to make the elastic force of the lumbar spine support larger than the elastic force of each of the sacrum support and the thoracic spine support, when oscillation of the vehicle is large.

With the above arrangement, the elastic force of the sacrum support that supports the sacrum located below the lumbar spine, and that of the thoracic spine support that supports the thoracic spine located above the lumbar spine, in addition to that of the lumbar spine support, are adjusted, so that the elastic force of the lumbar spine support is made larger than those of the thoracic spine support and sacrum support located above and below the lumbar spine support, and the support load of the lumbar spine region of the occupant can be efficiently made larger than the support loads of the other regions. Thus, the posture of the upper body of the occupant can be efficiently and appropriately adjusted, and oscillation of the head of the occupant can be reduced.

In the first aspect, the case where oscillation of the vehicle is large may be at least one case selected from traveling on a bad road, cornering, lane change, and acceleration, and the controller may be configured to make the elastic force of the lumbar spine support larger than those of portions of the seat back other than the lumbar spine support, in at least one case selected from traveling on a bad road, cornering, lane change, and acceleration.

With the above arrangement, in a traveling condition in which the sitting posture of the occupant changes due to oscillation of the vehicle, the posture of the upper body of the occupant can be appropriately adjusted, and oscillation of the head of the occupant can be reduced.

In the first aspect, the elastic force adjustment unit may include a wire extended in a width direction of the seat back, and a tension adjustment mechanism configured to adjust tension of the wire. The elastic force adjustment unit may be configured to change the elastic force by causing the tension adjustment mechanism to adjust the tension of the wire.

With the above arrangement, the elastic force can be adjusted with a simple, lightweight arrangement.

In the first aspect, the seat back may be configured to rotate relative to the seat cushion.

In the first aspect, the vehicle seat may further include a frame that is mounted on the vehicle and supports the seat cushion and the seat back. The seat cushion may be configured to pivot in a roll direction and a yaw direction of the vehicle relative to the frame, and may be configured to support the buttocks and thighs of the occupant. The seat back may be configured to pivot in the roll direction and the yaw direction of the vehicle relative to the frame, and a pivot center axis of the seat cushion may pass the lumbar spine support of the seat back.

With the above arrangement, the elastic force adjustment unit is combined with the vehicle seat of which the seat cushion and the seat back are supported so as to rock. In the rocking seat, reaction force applied from the seat back to the occupant when the vehicle shakes acts in such a direction as to curb movement of the upper body of the occupant, and oscillation of the head of the occupant can be reduced.

According to the first aspect of the invention, the posture of the upper body of the occupant can be appropriately adjusted, even when the sitting posture of the occupant changes due to oscillation of the vehicle, for example.

A vehicle seat <NUM> of a first embodiment will be described with reference to the drawings. Arrow FR, arrow UP, and arrow RH shown in each of the drawings indicate the front direction (a vehicle traveling direction), upward direction, and right-hand direction, respectively, of the vehicle. The opposite directions of arrows FR, UP, RH are the rear direction, downward direction, and left-hand direction of the vehicle. When the front and rear, right-hand and left-hand, and upward and downward directions are simply used in the description below, they are supposed to indicate the vehicle front-rear direction (or vehicle longitudinal direction), vehicle right-left direction (or vehicle width direction), and vehicle upward-downward direction (or vehicle vertical direction), respectively, unless otherwise specified. In this embodiment, rotation about an axis extending in the vehicle longitudinal direction will be referred to as rotation in a roll direction, and rotation about an axis extending in the vehicle width direction will be referred to as rotation in a pitch direction, while rotation about an axis extending in the vehicle vertical direction will be referred to as rotation in a yaw direction, for the sake of convenience. While the vehicle seat <NUM> is a driver's seat in this embodiment, the vehicle seat <NUM> may be used as a vehicle seat, such as a passenger's seat, other than the driver's seat.

As shown in <FIG> and <FIG>, the vehicle seat <NUM> includes a seat cushion frame <NUM> (which will be called "C frame <NUM>"), seat cushion <NUM>, seat back frame <NUM> (which will be called "B frame <NUM>"), seat back subsidiary frame <NUM> (which will be called "S frame <NUM>"), and seat back <NUM>. The vehicle seat <NUM> has a moving mechanism, such as a reclining mechanism, and the seat back <NUM> can rotate relative to the seat cushion <NUM>. The seat cushion <NUM> may rotate relative to the seat back <NUM>, or both the seat back <NUM> and the seat cushion <NUM> may rotate relative to each other. The relative rotational movements of the seat back <NUM> and the seat cushion <NUM> as described above may not be strictly arc-like movements.

The C frame <NUM> is a rectangular framework member that consists of side members 12a that are disposed on the right and left sides and extend in the longitudinal direction, and pipes 12b, 12c that connect the side members 12a in the lateral direction, at front and rear portions of the side members 12a. The C frame <NUM> is mounted to a floor <NUM> of the vehicle, via slide rails <NUM>.

The seat cushion <NUM> that supports the buttocks <NUM> and thighs <NUM> of an occupant <NUM> is mounted on the upper side of the C frame <NUM>. Also, the B frame <NUM> as an inverted U-shaped framework member as seen in a front view is attached at its lower end portions to rear end portions of the C frame <NUM>.

The S frame <NUM> is mounted to the front side of the B frame <NUM>. The S frame <NUM> is a framework member that consists of right and left vertical members <NUM> that extend in the vertical direction, upper lateral member <NUM> that connects the right and left vertical members <NUM> at the slightly upper side of the middle of the vertical members <NUM> in the vertical direction, and lower lateral member <NUM> that connects the right and left vertical members <NUM> at the lower ends of the vertical members <NUM>. The vertical members <NUM> and the upper and lower lateral members <NUM>, <NUM> form a generally rectangular frame of parallel bars. The S frame <NUM> is mounted to the front side of the B frame <NUM>, via an upper bracket <NUM> and a lower bracket <NUM> provided on the vertical members <NUM>.

The seat back <NUM> is mounted to the front side of the S frame <NUM>. The seat back <NUM> is a rectangular bowl-shaped plate member that has substantially the same size as an upper portion of the B frame <NUM> located above the seat cushion <NUM>, and includes a middle portion that is recessed backward. The seat back <NUM> is formed from an elastic member made of resin, for example. Right and left end portions of the seat back <NUM> are mounted to the opposite vertical members <NUM> of the S frame <NUM>. An upper end portion of the seat back <NUM> is slidably supported by an upper end portion of the B frame <NUM>.

As shown in <FIG>, when the occupant <NUM> is seated on the vehicle seat <NUM>, a load applied backward from a portion of the occupant <NUM> including the sacrum <NUM> of the spine, a load applied backward from a portion of the occupant <NUM> including the lumbar spine <NUM> (hatched area) located above the sacrum <NUM>, and a load applied backward from a portion of the occupant <NUM> including the thoracic spine <NUM> located above the lumbar spine <NUM> are respectively supported by a sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM>.

Next, an elastic force adjustment unit <NUM> that adjusts elastic force will be described. As shown in <FIG>, the elastic force adjustment unit <NUM> consists of a load receiving wire assembly <NUM> that consists of a lower section <NUM>, middle section <NUM>, and upper section <NUM>, three tension adjustment mechanisms <NUM> that adjust tensions of respective wires <NUM>, 32Y, <NUM> of the sections <NUM>, <NUM>, <NUM>, three tension sensors <NUM> that detect the tensions of the respective wires <NUM>, 32Y, <NUM>, a traveling condition detecting unit <NUM> that detects traveling conditions of the vehicle, and a controller <NUM> that operates the tension adjustment mechanisms <NUM> based on data received from the respective tension sensors <NUM> and the traveling condition detecting unit <NUM>. The controller <NUM> is an example of a controller and the controller <NUM> is a microcomputer that processes data supplied, and outputs control signals, and a hardware, such as an electronic control unit (ECU), may be employed as the controller <NUM>. The controller <NUM> and the traveling condition detecting unit <NUM> may be provided with the inside of the vehicle seat <NUM>, and may be provided with the outside of the vehicle seat <NUM>.

As shown in <FIG> and <FIG>, the load receiving wire assembly <NUM>, which is disposed between the S frame <NUM> and the seat back <NUM>, has a plurality of lines of wires <NUM> extended between the vertical members <NUM> of the S frame <NUM> in the width direction of the seat back <NUM>.

The load receiving wire assembly <NUM> consists of three sections, i.e., the lower section <NUM>, middle section <NUM>, and upper section <NUM> corresponding to the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM>, respectively. Each of these sections <NUM>, <NUM>, <NUM> is formed by turning a single wire <NUM>, 32Y, <NUM> back and forth a plurality of times while looping it around a plurality of pulleys <NUM> rotatably mounted on the opposite vertical members <NUM> of the S frame <NUM>, so that a plurality of lines of wires <NUM>, 32Y, <NUM> is extended between the vertical members <NUM>. In the vehicle seat <NUM> of this embodiment, six lines of each wire <NUM>, 32Y, <NUM> are extended over a corresponding one of the sections <NUM>, <NUM>, <NUM>.

As shown in <FIG>, when the occupant <NUM> is seated on the vehicle seat <NUM>, and a load is applied backward to the seat back <NUM>, the seat back <NUM> elastically bows backward. Then, the load applied backward from the back <NUM> of the occupant <NUM> is transmitted to the respective wires <NUM>, 32Y, <NUM> of the lower, middle, and upper sections <NUM>, <NUM>, <NUM> located backward of the seat back <NUM>, and tensile force is applied to the respective wires <NUM>, 32Y, <NUM>. Then, the loads applied to the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM> are transmitted to the respective wires <NUM>, 32Y, <NUM> of the sections <NUM>, <NUM>, <NUM> corresponding to the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM>, and supported by the tensile forces of the wires <NUM>, 32Y, <NUM>.

Accordingly, it is possible to adjust elastic forces of the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM> supporting the sacrum <NUM>, lumbar spine <NUM>, and thoracic spine <NUM> of the occupant <NUM>, respectively, by adjusting the tensions of the respective wires <NUM>, 32Y, <NUM> of the lower section <NUM>, middle section <NUM> and upper section <NUM>. The occupant <NUM> senses the elastic force of each support of the seat back <NUM>, as a seating pressure.

As shown in <FIG>, each tension adjustment mechanism <NUM> is provided with a take-up mechanism <NUM> for taking up each wire <NUM>, 32Y, <NUM>. The take-up mechanism <NUM> consists of a casing <NUM>, a reel <NUM> around which the wire <NUM>, 32Y, <NUM> drawn into the casing <NUM> through an opening <NUM> of the casing <NUM> is wound, and a motor <NUM> that rotates/drives the reel <NUM>. A rotary shaft <NUM> attached to the reel <NUM> is rotatably mounted to the casing <NUM>, such that the motor <NUM> is connected to one end of the rotary shaft <NUM>, and the reel <NUM> rotates as the motor <NUM> rotates. One end of each of the wires <NUM>, 32Y, <NUM> is fixed to a wire fixing point <NUM> of the reel <NUM>. When the reel <NUM> rotates clockwise in <FIG>, the wire <NUM> is wound around the reel <NUM>, and the tension of each wire <NUM>, 32Y, <NUM> is increased. Also, when the reel <NUM> rotates counterclockwise in <FIG>, each wire <NUM>, 32Y, <NUM> is reeled out from the reel <NUM>, and the tension of the wire <NUM>, 32Y, <NUM> is reduced. The motor <NUM> is connected to the controller <NUM> shown in <FIG>, and rotates clockwise or counterclockwise, according to a command of the controller <NUM>.

The tension sensor <NUM> detects tension applied to each wire <NUM>, 32Y, <NUM>, by means of a strain gauge, or the like, mounted on the wire <NUM>, 32Y, <NUM>. The tension sensor <NUM> may not be directly mounted on each wire <NUM>, 32Y, <NUM>, but may be mounted on a portion of the S frame <NUM> over which each wire <NUM>, 32Y, <NUM> is extended, for example, so that the tension of the wire <NUM>, 32Y, <NUM> can be detected by detecting deformation of the corresponding portion of the S frame <NUM>.

The traveling condition detecting unit <NUM> consists of various sensors that detect traveling conditions of the vehicle. In <FIG>, as one example, the traveling condition detecting unit <NUM> consists of a millimeter-wave radar <NUM> that detects obstacles, vehicle speed sensor <NUM> that detects high-speed traveling, lateral G sensor <NUM> that detects turning, door pressure sensor <NUM> that detects a collision situation of the vehicle, and accelerating and decelerating conditions, G sensor <NUM>, and GPS device <NUM> that detects the traveling position of the vehicle.

Referring next to <FIG>, operation of the elastic force adjustment unit <NUM> of this embodiment will be described. As shown in step S101 of <FIG>, the controller <NUM> obtains traveling condition data of the lateral G sensor <NUM>, G sensor <NUM>, etc. of the traveling condition detecting unit <NUM>. Then, in step S102 of <FIG>, the controller <NUM> calculates the acceleration GX in the longitudinal direction of the vehicle, acceleration GY in the lateral direction, acceleration Gz in the vertical direction, acceleration GRol in the roll direction, acceleration GPic in the pitch direction, and acceleration GYaw in the yaw direction, and determines whether each acceleration exceeds a corresponding one of acceleration limits G0X, G0Y, G0Z, G0Rol, G0Pic, and G0Yaw in the respective directions. Then, when one or more accelerations exceed the corresponding one or more of the acceleration limits, namely, when any one or more conditions of GX>G0X, GY>G0Y, GZ>G0Z, GRol>G0Rol, GPic>G0Pic, and GYaw>G0Yaw are satisfied, an affirmative decision (YES) is obtained in step S102 of <FIG>. Also, when none of the above six conditions is satisfied, a negative decision (NO) is obtained in step S102 of <FIG>. When a negative decision (NO) is obtained in step S102 of <FIG>, the controller <NUM> determines that oscillation of the vehicle is not large, and returns to step S101, to repeatedly execute steps S101 and S102 of <FIG>.

On the other hand, when an affirmative decision (YES) is obtained in step S102 of <FIG>, the controller <NUM> determines that the vehicle shakes largely, during traveling on a bad road, cornering, lane change, or acceleration, for example, and proceeds to step S103 of <FIG>. In step S102, the controller <NUM> is not necessarily required to refer to the accelerations, but may make the above determination, referring to map information, steering information, or accelerator pedal information. In step S103, the controller <NUM> obtains wire tensions TS, TY, TK of the wire <NUM> that supports the sacrum <NUM> region of the occupant <NUM>, wire 32Y that supports the lumbar spine <NUM> region of the occupant <NUM>, and wire <NUM> that supports the thoracic spine <NUM> region of the occupant <NUM>, by means of the respective tension sensors <NUM>. Then, the controller <NUM> determines, in step S104 of <FIG>, whether the wire tension TY is larger than the wire tensions TK, TS. When an affirmative decision (YES) is obtained in step S104 of <FIG>, the controller <NUM> determines that the elastic force of the lumbar spine support 36Y of the seat back <NUM> is larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and finishes the routine without adjusting the tensions of the respective wires <NUM>, 32Y, <NUM>. Then, the controller <NUM> returns to step S101 of <FIG>.

On the other hand, when a negative decision (NO) is obtained in step S104 of <FIG>, the controller <NUM> determines that the sitting posture of the occupant <NUM> changes due to large oscillation of the vehicle, for example, and the elastic force of the lumbar spine support 36Y of the seat back <NUM> becomes smaller than the elastic force of the sacrum support <NUM> or thoracic spine support <NUM>. Then, the controller <NUM> proceeds to step S105 of <FIG>, to adjust the tension of each wire <NUM>, 32Y, <NUM>.

In step S105 of <FIG>, the controller <NUM> causes the take-up mechanism <NUM> to take up the wire 32Y extended over the middle section <NUM> that supports the lumbar spine <NUM> region of the occupant <NUM>, so as to increase the wire tension TY and increase the elastic force of the lumbar spine support 36Y. Also, the controller <NUM> causes the take-up mechanism <NUM> to reel out the wires <NUM>, <NUM> extended over the lower section <NUM> and upper section <NUM> that support the sacrum <NUM> and thoracic spine <NUM> regions of the occupant <NUM>, so as to reduce the elastic forces of the sacrum support <NUM> and thoracic spine support <NUM>. Then, the controller <NUM> returns to step S103 of <FIG>, to detect the respective wire tensions TS, TY, TK, and repeatedly executes step S103 to step S105 of <FIG>, until it determines in step S104 of <FIG> that the wire tension TY is larger than the wire tensions TK, TS.

Then, when an affirmative decision (YES) is obtained in step S104 of <FIG> the controller <NUM> determines that the elastic force of the lumbar spine support 36Y of the seat back <NUM> is larger than the elastic forces of the sacrum support <NUM> and thoracic spine support <NUM>, and finishes adjustment of the tensions of the wires <NUM>, 32Y, <NUM>. Then, the controller <NUM> returns to step S101 of <FIG>.

When the vehicle shakes largely, the elastic force of the lumbar spine support 36Y of the seat back <NUM> is made larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and the support load of the lumbar spine of the occupant <NUM> is made larger than those of the other regions, so that the posture of the upper body of the occupant <NUM> can be appropriately adjusted, and oscillation of the head <NUM> of the occupant <NUM> can be reduced, for reasons as will be described with reference to <FIG>. Each load distribution line <NUM> indicated in <FIG>, <FIG>, and <FIG> indicates a distribution in the vertical direction of the load applied forward (i.e., toward the front of the vehicle) from the seat back <NUM> to the occupant <NUM>.

When the sitting posture of the occupant <NUM> changes due to large oscillation of the vehicle, for example, and the support load of the sacrum <NUM> region of the occupant <NUM> becomes larger than those of the other regions, as indicated by the load distribution line <NUM> in <FIG>, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to the level of the sacrum <NUM>, or a lower end portion of the lumbar spine <NUM>, of the occupant <NUM>. In this case, a pivot central axis <NUM> of the lower body of the occupant <NUM> including the pelvis <NUM>, thighbones <NUM>, etc. in the roll direction is represented by a line that extends in substantially the horizontal direction, passing the vicinity of the pelvis <NUM> of the occupant <NUM>. Thus, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> is higher than the vertical level Pk of the pivot central axis <NUM>. In this case, when the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to oscillation of the vehicle, as shown in <FIG>, and the upper body is apt to move toward the left side of the vehicle, the occupant <NUM> receives reaction force FK applied from the seat back <NUM> in the vehicle right-hand direction, and rotation moment MK in the clockwise direction. In the case shown in <FIG>, the reaction force FK acts in such a direction as to curb movement of the upper body of the occupant <NUM> to the left of the vehicle, but the rotation moment MK is applied in such a direction as to incline the upper body of the occupant <NUM> to the left of the vehicle. Therefore, the upper body of the occupant <NUM> is inclined to the left of the vehicle; as a result, the head <NUM> of the occupant <NUM> is likely to move leftward.

At this time, if the sitting posture of the occupant <NUM> is corrected by making the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, as indicated by the load distribution line <NUM> in <FIG>, and making the support load of the lumbar spine region of the occupant <NUM> larger than those of the other regions, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to or a little higher than a middle portion of the lumbar spine <NUM> of the occupant <NUM>. In this case, the pivot central axis <NUM> of the lower body of the occupant <NUM> in the roll direction is represented by a slanting line passing the vicinity of the middle portion of the lumbar spine <NUM> of the occupant <NUM>. Then, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes substantially equal to the vertical level Pk of an intersection of the pivot central axis <NUM> and the lumbar spine <NUM>. In this case, when the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to oscillation of the vehicle, as shown in <FIG>, and the upper body is apt to move toward the left side of the vehicle, the occupant <NUM> receives reaction force FK applied from the seat back <NUM> in the vehicle right-hand direction, and rotation moment MK in the counterclockwise direction. In the case shown in <FIG>, the reaction force FK acts in such a direction as to curb movement of the upper body of the occupant <NUM> to the left of the vehicle. Also, the rotation moment MK acts in such a direction as to curb inclination of the upper body of the occupant <NUM> to the left of the vehicle. Therefore, the upper body of the occupant <NUM> is less likely or unlikely to be inclined to the left of the vehicle, and the head <NUM> of the occupant <NUM> is less likely or unlikely to be moved.

When the sitting posture of the occupant <NUM> changes due to large oscillation of the vehicle, for example, and the support load of the thoracic spine <NUM> region of the occupant <NUM> becomes larger than those of the other regions, as indicated by the load distribution line <NUM> in <FIG>, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to or a little lower than a middle portion of the thoracic spine <NUM> of the occupant <NUM>. Therefore, the pivot central axis <NUM> of the lower body of the occupant <NUM> in the roll direction is represented by a line that passes the vicinity of a middle portion of the thoracic spine <NUM> of the occupant <NUM> with a large inclination angle with respect to the horizontal direction. Then, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes lower than the vertical level Pk of an intersection of the pivot central axis <NUM> and the thoracic spine <NUM>. In this case, when the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to oscillation of the vehicle, as shown in <FIG>, and the upper body is apt to move toward the left side of the vehicle, the occupant <NUM> receives reaction force FK that moves the upper body to the left of the vehicle, and counterclockwise rotation moment MK that curbs inclination of the upper body of the occupant <NUM> to the left of the vehicle. Therefore, the upper body of the occupant <NUM> is more likely to be inclined to the left of the vehicle, and the head <NUM> of the occupant <NUM> is more likely to be moved leftward, as compared with the case as described above with reference to <FIG>.

For the reasons as described above, when the vehicle shakes largely, the vehicle seat <NUM> of this embodiment makes the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and makes the support load of the lumbar spine region of the occupant <NUM> larger than those of the other regions, so that the pelvis of the occupant <NUM> can be appropriately supported, and oscillation of the head <NUM> of the occupant <NUM> can be reduced or curbed.

In the vehicle seat <NUM> of the illustrated embodiment, the elastic forces of the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> can be respectively adjusted. However, the elastic force of the lumbar spine support 36Y may be made larger than those of the other portions of the seat back <NUM>, by making it possible to adjust the elastic force of only the lumbar spine support 36Y, and making the elastic force of the lumbar spine support 36Y larger than a predetermined elastic force.

In the illustrated embodiment, each of the wires <NUM>, 32Y, <NUM> is extended over the corresponding one of the lower section <NUM>, middle section <NUM>, and upper section <NUM>, such that six lines of each wire <NUM> are arranged in the vertical direction. However, the number of lines is not limited to six, but may be larger or smaller than six.

Two or more take-up mechanisms <NUM>, rather than a single take-up mechanism <NUM>, may be provided for each of the wires <NUM>, 32Y, <NUM>. Also, the take-up mechanism <NUM> may be provided with a latch mechanism for keeping a condition where the wire <NUM> is taken up or wound in the take-up mechanism <NUM>. This makes it possible to keep the tensions of the wires <NUM>, 32Y, <NUM> even while the take-up mechanism <NUM> is not energized. Further, the take-up mechanism <NUM> may be arranged to manually take up and reel out each wire <NUM>, 32Y, <NUM>.

Each of the wires <NUM>, 32Y, <NUM> may be in the form of a resin string, or may be formed of another material provided that it can keep tension. For example, each wire <NUM>, 32Y, <NUM> may be formed from an artificial muscle containing polyvinyl chloride. In this case, the artificial muscle may be arranged to be expanded and contracted, in response to a body pressure from the occupant <NUM>.

The tension of each wire <NUM>, 32Y, <NUM> may be controlled by predicting oscillation of the vehicle, based on various kinds of information obtained by the traveling condition detecting unit <NUM>.

The tension sensor <NUM> may be replaced with a pressure sensor that detects the elastic force of the occupant <NUM> against the seat back <NUM>, and the tension of each wire <NUM>, 32Y, <NUM> may be adjusted by means of the pressure sensor.

Referring next to <FIG>, a vehicle seat <NUM> of a second embodiment will be described. In <FIG>, the same reference numerals are assigned to the same components or portions as those of the vehicle seat <NUM> as described above with reference to <FIG>, and these components or portions will not be further described.

As shown in <FIG>, the vehicle seat <NUM> includes a back pad <NUM> located on the vehicle rear side of the seat back <NUM> and formed of urethane, spring, or the like, and air bags <NUM> located between the back pad <NUM> and the seat back <NUM>, in place of the load receiving wire assembly <NUM>. The air bags <NUM> serve to adjust elastic forces of the sacrum <NUM> region, lumbar spine <NUM> region, and thoracic spine <NUM> region of the occupant <NUM>, respectively.

As shown in <FIG>, the air bags <NUM> are disposed between a partition plate <NUM> provided in the back pad <NUM>, and the seat back <NUM>. Three air bags <NUM> corresponding to the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM>, respectively, are arranged in the vertical direction. Each of the air bags <NUM> is connected to an actuator <NUM> that adjusts the pressure of the corresponding air bag <NUM>. Also, pressure sensors <NUM> that detect elastic forces of respective regions of the occupant <NUM> are mounted on surfaces of the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM> of the seat back <NUM>. The pressure sensor <NUM> detects elastic force per given area, as a pressure.

The pressure sensors <NUM> and actuators <NUM> are connected to the controller <NUM>, and the controller <NUM> controls the pressures of the air bags <NUM>, based on the traveling conditions of the vehicle detected by the traveling condition detecting unit <NUM>, and the elastic forces detected by the pressure sensors <NUM>, so as to adjust elastic force of each of the sacrum support <NUM>, lumbar spine support 36Y, and thoracic spine support <NUM>.

Like the vehicle seat <NUM>, when the vehicle shakes largely, the vehicle seat <NUM> appropriately adjusts the posture of the upper body of the occupant <NUM>, and reduces oscillation of the head <NUM> of the occupant <NUM>, by making the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and making the support load of the lumbar support region of the occupant <NUM> larger than those of the other regions.

Referring next to <FIG>, a vehicle seat <NUM> of a third embodiment will be described. In <FIG>, the same reference numerals are assigned to the same components or portions as those of the vehicle seat <NUM> as described above with reference to <FIG>, and these components or portions will not be further described.

As shown in <FIG>, the vehicle seat <NUM> includes a back pad <NUM> located on the vehicle rear side of the seat back <NUM> and formed of urethane, spring, or the like, in place of the load receiving wire assembly <NUM>, and a lumbar support <NUM> provided on the vehicle rear side of the back pad <NUM> for adjusting the elastic force of the lumbar spine support 36Y. The lumbar support <NUM> consists of two screws 94a, 94b that extend in mutually orthogonal directions, a composite nut <NUM> into which the two screws 94a, 94b are screwed, and a motor <NUM> that drives the composite nut <NUM>. Also, a pressure sensor <NUM> is mounted at a position of the seat back <NUM> against which the lumbar spine <NUM> region of the occupant <NUM> abuts. The pressure sensor <NUM> and the motor <NUM> are connected to the controller <NUM>. The controller <NUM> adjusts the elastic force of the lumbar spine support 36Y, by driving the motor <NUM>, based on the traveling conditions of the vehicle detected by the traveling condition detecting unit <NUM>, and the elastic force detected by the pressure sensor <NUM>.

When the vehicle shakes largely, the vehicle seat <NUM> appropriately adjusts the posture of the upper body of the occupant <NUM>, and reduces oscillation of the head <NUM> of the occupant <NUM>, by making the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than a predetermined elastic force, and increasing the support load of the lumbar spine region of the occupant <NUM>.

Referring next to <FIG>, a vehicle seat <NUM> of a fourth embodiment will be described. In these figures, the same reference numerals are assigned to the same components or portions as those of the vehicle seat <NUM> as described above with reference to <FIG>, and these components or portions will not be further described. The vehicle seat <NUM> is provided by making the seat cushion <NUM> and seat back <NUM> of the vehicle seat <NUM> rotatable in the roll direction and yaw direction of the vehicle.

As shown in <FIG> and <FIG>, the seat cushion <NUM> is mounted on a cushion support <NUM>. The cushion support <NUM> consists of a cushion pan <NUM>, brackets <NUM>, <NUM>, bearing <NUM>, rotary shaft <NUM>, guide rail <NUM>, and sliders <NUM>. The cushion pan <NUM> is mounted rotatably relative to the C frame <NUM> in the roll direction and yaw direction of the vehicle, and the seat cushion <NUM> is mounted on the upper side of the cushion pan <NUM>.

The bracket <NUM> having an L shape is fixed to the front pipe 12b of the C frame <NUM>, and the bearing <NUM> is fixed to the bracket <NUM>. The bearing <NUM> is positioned such that its pivot central axis <NUM> shown in <FIG> is inclined to be raised at the rear side in the vehicle longitudinal direction, and extends in a slanting direction passing the vicinity of a middle portion of the lumbar spine <NUM> of the occupant <NUM>. The rotary shaft <NUM> is fixed to a lower surface of a front portion of the cushion pan <NUM>. The rotary shaft <NUM> is rotatably fitted in the bearing <NUM>.

As shown in <FIG> and <FIG>, the bracket <NUM> having a U shape is fixed to the rear pipe 12c of the C frame <NUM>, and the guide rail <NUM> curved in an arc shape is fixed to the bracket <NUM>. Two sliders <NUM> that slide in an arc-like fashion along the guide rail <NUM> are mounted on a lower surface of a rear portion of the cushion pan <NUM>.

When the rotary shaft <NUM> of the cushion pan <NUM> rotates about the pivot central axis <NUM> of the bearing <NUM>, the two sliders <NUM> move in an arc-like fashion along the guide rail <NUM>. In this manner, the cushion pan <NUM> can rotate in the roll direction and yaw direction of the vehicle about the pivot central axis <NUM>. Thus, as shown in <FIG> and <FIG>, the cushion pan <NUM> can rotate in the roll direction and yaw direction of the vehicle relative to the C frame <NUM>, and the seat cushion <NUM> mounted on the cushion pan <NUM> can also rotate in the roll direction and yaw direction of the vehicle relative to the C frame <NUM>.

As shown in <FIG> and <FIG>, the S frame <NUM> on which the seat back <NUM> is mounted is supported rotatably in the roll direction and yaw direction of the vehicle relative to the B frame <NUM>. As shown in <FIG> and <FIG>, brackets <NUM> that protrude rearward from the upper lateral member <NUM> are mounted to laterally opposite end portions of the upper lateral member <NUM> that is disposed slightly above the middle of the S frame <NUM> as viewed in the vertical direction and connects the opposite vertical members <NUM>. The rear end of each of the brackets <NUM> is connected to the B frame <NUM> via a leaf spring <NUM>. One face of one end of the leaf spring <NUM> is connected to the outer face (in the vehicle width direction) of a rear end portion of the bracket <NUM>, and the other face of the other end of the leaf spring <NUM> is connected to the B frame <NUM>. The leaf spring <NUM> is oriented such that its thickness direction corresponds to the vehicle lateral direction, and its longitudinal direction corresponds to the vehicle longitudinal direction. When the S frame <NUM> moves in the lateral direction relative to the B frame <NUM>, the leaf springs <NUM> are flexed in the vehicle lateral direction and absorb the amount of relative movement of the S frame <NUM> and the B frame <NUM>. Thus, the S frame <NUM> is supported laterally movably relative to the B frame <NUM> by means of the leaf springs <NUM>.

As shown in <FIG> and <FIG>, two or more wires <NUM> are hung between two or more mounting points of the B frame <NUM> via a wire through device <NUM>. As shown in <FIG>, the opposite ends of the wires <NUM> located on the right and left sides in the uppermost portion are attached to the vicinity of the laterally middle portion of the B frame <NUM>, and two points in the upper, opposite portions. Each of the wires <NUM> is extended between two points in a V shape that is open in an upward oblique direction, along a U-shaped wire groove <NUM> provided in the wire through device <NUM>. Thus, the wire through device <NUM> is hung from the B frame <NUM> by means of the upper wires <NUM>. Similarly, the wires <NUM> are attached to two points on right and left vertical frame portions of the B frame <NUM> which extend in the vertical direction, and each of the wires <NUM> is extended between two points in a V shape that is open in the lateral direction, along a U-shaped wire groove <NUM> of the wire through device <NUM>. Thus, the wire through device <NUM> is supported in the lateral direction by the right and left wires <NUM>, against the B frame <NUM>.

Also, as shown in <FIG>, two or more wires <NUM> are hung between two or more mounting points of the S frame <NUM> via the wire through device <NUM>. One end of each wire <NUM> is connected to the upper lateral member <NUM>, and the other end is connected to the lower lateral member <NUM>. The wire <NUM> is extended between two points in a V shape that is open in a downward oblique direction, along a U-shaped wire groove <NUM> provided in the wire through device <NUM>. Thus, the wire through device <NUM> hangs the S frame <NUM> by means of the right and left wires <NUM>.

As described above, the wire through device <NUM> is hung from the upper side of the B frame <NUM> by means of the wires <NUM>, and is supported in the lateral direction against the B frame <NUM>. The wire through device <NUM> also hangs the S frame <NUM> by means of the wires <NUM>. Accordingly, the S frame <NUM> is hung from and supported by the B frame <NUM> via the wires <NUM>, <NUM>, and wire through device <NUM>.

Thus, the S frame <NUM> is hung from the B frame <NUM> via the wires <NUM>, <NUM>, and wire through device <NUM>, and is laterally movably supported by the leaf springs <NUM>. Through the use of the wires <NUM>, <NUM> and wire through device <NUM> and deformation of the right and left leaf springs <NUM>, the S frame <NUM> can rotate in the roll direction and yaw direction of the vehicle, about a pivot central axis <NUM> that passes the center of the wire through device <NUM> and extends in the vehicle longitudinal direction as shown in <FIG>, and a pivot central axis <NUM> that extends in the vertical direction. With this arrangement, as shown in <FIG> and <FIG>, the S frame <NUM> can rotate in the roll direction and yaw direction of the vehicle relative to the B frame <NUM>, and the seat back <NUM> mounted on the S frame <NUM> can also rotate in the roll direction and yaw direction of the vehicle relative to the B frame <NUM>.

Referring next to <FIG> and <FIG>, operation of the vehicle seat <NUM> will be described. In the following description, it is assumed that the vertical level Pb of the center position of the total reaction force applied toward the front of the vehicle from the seat back <NUM> to the occupant <NUM> is located in a middle portion of the lumbar spine <NUM> of the occupant <NUM> or slightly above the middle portion, as described above with reference to <FIG>.

The seat back <NUM> mounted on the S frame <NUM> rotates in the roll direction of the vehicle about the pivot central axis <NUM> shown in <FIG>. As shown in <FIG>, the pivot central axis <NUM> is set to a level at which the thoracic spine <NUM> of the occupant <NUM> is located. Accordingly, the pivot central axis <NUM> is located above the level Pb of the center position of the total reaction force which the occupant <NUM> receives from the seat back <NUM>, and the center of gravity <NUM> of the upper body of the occupant <NUM>. In <FIG> and <FIG>, reference numerals <NUM>, <NUM> denote the center of gravity of the head <NUM> and that of the lower body, respectively.

Thus, when external force F1 (which will be called "lateral force F1", see <FIG>) is applied in the seat width direction to the upper body of the occupant <NUM>, due to turning of the vehicle or disturbance from a road surface, for example, a moment M of force having a distance between the pivot central axis <NUM> and the level Pb of the center position of the total reaction force as a moment arm length is generated. With the moment M thus generated, force (frictional force) is applied between the back <NUM> of the occupant <NUM> and the seat back <NUM>, in such a direction as to prevent the upper body of the occupant <NUM> from falling in the direction of application of the lateral force Fl. This force is applied to the entire area of a contact portion between the back <NUM> of the occupant <NUM> and the seat back <NUM>, and is particularly applied from a seating surface in the vicinity of the lumbar spine <NUM> having large elastic force to the back. As a result, the seat back <NUM> rotates counterclockwise about the pivot central axis <NUM> (see the S frame <NUM> of <FIG>).

As a result, the upper body of the occupant <NUM> rotates or displaces counterclockwise, and the spine of the occupant <NUM> is curved to project in the direction of application of the lateral force F1, as shown in <FIG>. At this time, the seat cushion <NUM> rotates about the pivot central axis <NUM> (see the cushion pan <NUM> of <FIG>), and the lower half of the occupant <NUM> rotates clockwise. As a result, the head <NUM> of the occupant <NUM> is inclined in a direction opposite to the direction of application of the external force; therefore, the posture of the head <NUM> can be stabilized, due to a balance between component force in the seat width direction of the force of gravity applied to the head <NUM>, and external force applied in the seat width direction to the head <NUM>.

Like the vehicle seat <NUM>, the vehicle seat <NUM> includes the elastic force adjustment unit <NUM> as shown in <FIG>. The operation of the elastic force adjustment unit <NUM> has been described above with reference to <FIG>.

When the vehicle shakes largely, the elastic force adjustment unit <NUM> operates to make the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and make the support load of the lumbar spine region of the occupant <NUM> larger than those of the other regions, so that the posture of the upper body of the occupant <NUM> can be appropriately adjusted, and oscillation of the head <NUM> of the occupant <NUM> can be reduced, for reasons as described below with reference to <FIG>.

As shown in <FIG>, in the vehicle seat <NUM>, the seat cushion <NUM> rotates in the roll direction and yaw direction of the vehicle, about the pivot central axis <NUM> that extends in a slanting direction passing the vicinity of the middle portion of the lumbar spine <NUM> of the occupant <NUM>. When the sitting posture of the occupant <NUM> changes due to large oscillation of the vehicle, for example, and the support load of the sacrum <NUM> region of the occupant <NUM> becomes larger than those of the other regions, as indicated by a load distribution line <NUM> in <FIG>, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to the level of the sacrum <NUM> of the occupant <NUM>, or the level of the lower end portion of the lumbar spine <NUM>. Therefore, the level Pb becomes lower than the vertical level Pk of an intersection of the pivot central axis <NUM> and the middle portion of the lumbar spine <NUM>. In this case, if the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to rotation of the seat cushion <NUM> as shown in <FIG>, and the upper body is apt to move toward the left side of the vehicle, the occupant <NUM> receives reaction force FK applied from the seat back <NUM> to the right of the vehicle, and rotation moment MK in the clockwise direction. In the case shown in <FIG>, the reaction force FK acts in such a direction as to curb movement of the upper body of the occupant <NUM> to the left of the vehicle, but the rotation moment MK is applied in such a direction as to incline the upper body of the occupant <NUM> to the left of the vehicle. Therefore, the upper body of the occupant <NUM> is inclined to the left of the vehicle; as a result, the head <NUM> of the occupant <NUM> is likely to move leftward.

At this time, if the sitting posture of the occupant <NUM> is corrected, by making the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and making the support load of the lumbar spine region of the occupant <NUM> larger than those of the other regions, as indicated by the load distribution line <NUM> in <FIG>, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to or a little higher than the middle portion of the lumbar spine <NUM> of the occupant <NUM>. Therefore, the vertical level Pb becomes substantially equal to the vertical level Pk of the intersection of the pivot central axis <NUM> and the middle portion of the lumbar spine <NUM>. In this case, if the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to rotation of the seat cushion <NUM>, and the upper body is apt to move to the left of the vehicle, as shown in <FIG>, the occupant <NUM> receives reaction force FK applied in the right-hand direction of the vehicle from the seat back <NUM>, and rotation moment MK in the counterclockwise direction. In the case shown in <FIG>, the reaction force FK acts in such a direction as to curb movement of the upper body of the occupant <NUM> to the left of the vehicle. Also, the rotation moment MK acts in such a direction as to curb inclination of the upper body of the occupant <NUM> to the left of the vehicle. Therefore, the upper body of the occupant <NUM> is less likely or unlikely to be inclined leftward of the vehicle, and the head <NUM> of the occupant <NUM> is less likely or unlikely to be moved.

When the sitting posture of the occupant <NUM> changes due to large oscillation of the vehicle, for example, and the support load of the thoracic spine <NUM> region of the occupant <NUM> becomes larger than those of the other regions as shown in the load distribution line <NUM> in <FIG>, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes equal to or a little lower than the middle portion of the thoracic spine <NUM> of the occupant <NUM>. Therefore, the vertical level Pb of the center position of the total reaction force applied forward from the seat back <NUM> to the occupant <NUM> becomes higher than the vertical level Pk of the intersection of the pivot central axis <NUM> and the lumbar spine <NUM>. In this case, if the lower body of the occupant <NUM> rotates clockwise by an angle θK about the pivot central axis <NUM>, due to rotation of the seat cushion <NUM>, as shown in <FIG>, and the upper body is apt to move toward the left side of the vehicle, the occupant <NUM> receives reaction force FK that moves the upper body in the vehicle left direction, and counterclockwise rotation moment MK that curbs inclination of the upper body of the occupant <NUM> to the left of the vehicle, as shown in <FIG>. Therefore, the upper body of the occupant <NUM> is more likely to be inclined to the left of the vehicle, and the head <NUM> of the occupant <NUM> is more likely to be moved leftward, as compared with the case as described above with reference to <FIG>.

For the reasons as described above, when the vehicle shakes largely, the vehicle seat <NUM> of this embodiment can appropriately support the pelvis of the occupant <NUM>, and reduce or curb oscillation of the head <NUM> of the occupant <NUM>, by making the elastic force of the lumbar spine support 36Y of the seat back <NUM> larger than those of the sacrum support <NUM> and thoracic spine support <NUM>, and making the support load of the lumbar spine region of the occupant <NUM> larger than those of the other regions.

In the illustrated embodiment, the elastic force adjustment unit <NUM> includes the load receiving wire assembly <NUM> that consists of the lower section <NUM>, middle section <NUM>, and upper section <NUM>, and the three tension adjustment mechanisms <NUM> that adjust tensions of the wires <NUM>, 32Y, <NUM> of the sections <NUM>, <NUM>, <NUM>, respectively. When oscillation of the vehicle is large, the elastic force adjustment unit <NUM> adjusts the tensions of the wires <NUM>, 32Y, <NUM>, so that the elastic force of the lumbar spine support 36Y for the occupant <NUM> becomes larger than those of the sacrum support <NUM> and the thoracic spine support <NUM>. However, the elastic force adjustment unit <NUM> is not limited to this configuration.

For example, as shown in <FIG>, the elastic force adjustment unit <NUM> may include one tension adjustment mechanism <NUM> that adjusts only the tension of the wire 32Y of the middle section <NUM>, so as to adjust the elastic force of only the lumbar spine support 36Y for the occupant <NUM>, in the longitudinal direction. The elastic force adjustment unit <NUM> may be configured to make the elastic force of the lumbar spine support 36Y for the occupant <NUM> larger in the case where oscillation of the vehicle is large, than that in the case where oscillation of the vehicle is small.

With this configuration, the controller <NUM> causes the tension adjustment mechanism <NUM> to adjust the tension of the wire 32Y in the following manner. In the following description, the same step numbers are assigned to steps that are identical with or similar to those of <FIG> as described above, and these steps will be briefly described.

As shown in step S101 of <FIG>, the controller <NUM> obtains traveling condition data of the lateral G sensor <NUM>, G sensor <NUM>, etc. of the traveling condition detecting unit <NUM>. Then, in step S102 shown in <FIG>, the controller <NUM> determines that oscillation of the vehicle is large when any one or more conditions of GX>G0X, GY>G0Y, GZ>G0Z, GRol>G0Rol, GPic>G0Pic, and GYaw>G0Yaw are satisfied, as in step S102 of <FIG> above, and proceeds to step S203 of <FIG>. Then, the controller <NUM> detects the wire tension TY of the wire 32Y in step S203, and proceeds to step S204 of <FIG>.

In step S204 of <FIG>, the controller <NUM> determines whether the wire tension TY is larger than wire tension TYNORMAL of the case where oscillation of the vehicle is small. Then, when a negative decision (NO) is obtained in step S204 of <FIG>, the controller <NUM> proceeds to step S205 of <FIG>, to take up the wire 32Y Then, the controller <NUM> returns to step S203 of <FIG>, to detect the wire tension TY of the wire 32Y. Then, when an affirmative decision (YES) is obtained in step S204 of <FIG>, the controller <NUM> finishes taking up the wire 32Y. Thus, the controller <NUM> increases the tension of the wire 32Y, until an affirmative decision (YES) is obtained in step S204 of <FIG>. Then, when the wire tension TY becomes larger than the wire tension TYNORMAL, the controller <NUM> determines that the elastic force of the lumbar spine support 36Y in the longitudinal direction becomes larger than that in the case where oscillation of the vehicle is small, and finishes adjustment of the wire 32Y.

According to this embodiment, when oscillation of the vehicle is large, the elastic force of only the lumbar spine support 36Y of the seat back <NUM> in the longitudinal direction can be made larger than that in the case where oscillation of the vehicle is small. Thus, it is possible to appropriately hold the pelvis of the occupant <NUM>, and reduce oscillation of the head <NUM>, when oscillation of the vehicle is large.

Claim 1:
A vehicle seat (<NUM>; <NUM>; <NUM>; <NUM>) comprising:
a seat cushion (<NUM>) configured to support buttocks (<NUM>) of an occupant (<NUM>);
a seat back (<NUM>) configured to support a back (<NUM>) of the occupant (<NUM>), the seat back (<NUM>) including a lumbar spine support (36Y) configured to support a lumbar spine (<NUM>) of the occupant (<NUM>);
an elastic force adjustment unit (<NUM>) configured to adjust elastic force of the lumbar spine support (36Y) in a longitudinal direction;
a controller (<NUM>) configured to operate the elastic force adjustment unit (<NUM>);
a unit having a sensor configured to detect a condition of a vehicle when it is travelling and being located in the elastic force adjustment unit, wherein:
the controller (<NUM>) is configured to cause the elastic force adjustment unit (<NUM>) to make the elastic force larger in a case where a detected oscillation of a vehicle by the sensor is above a threshold, than that in a case where oscillation of the vehicle is below the threshold,
characterized in that the elastic force adjustment unit (<NUM>) is further configured to:
adjust, in addition to the elastic force of the lumbar spine support (36Y), the elastic force of a sacrum support (<NUM>) configured to support a sacrum (<NUM>) located below the lumbar spine (<NUM>) of the occupant (<NUM>), and elastic force of a thoracic spine support (<NUM>) configured to support a thoracic spine (<NUM>) located above the lumbar spine (<NUM>) of the occupant (<NUM>) in the seat back, respectively; and
make the elastic force of the lumbar spine support (36Y) larger than the elastic force of each of the sacrum support (<NUM>) and the thoracic spine support (<NUM>), when oscillation of the vehicle is above the threshold.