Patent Publication Number: US-2022227274-A1

Title: Seat for vehicle

Description:
CLAIM OF PRIORITY 
     The present application claims priority from Japanese Patent Application JP 2021-006034 filed on Jan. 18, 2021, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a seat for vehicle and more particularly to a technique effectively applied to a vehicle seat having a massage function. 
     A proposal concerning a massage device is set forth in Japanese Unexamined Patent Application Publication No. 2003-38599. The massage device is configured to automatically detect a physical frame of a user and to provide massage at a proper area of a user&#39;s body. Further, Japanese Unexamined Patent Application Publication No. 2006-198307 discloses a massage seat for vehicle which is configured to change a pressure level of the massage according to the settings made by a seat occupant. 
     SUMMARY OF THE INVENTION 
     According to Japanese Unexamined Patent Application Publication No. 2003-38599, a sheet-like pressure sensor (physical frame detection sensor) is mounted on a seat surface in order to automatically detect the physical frame of the user. The physical frame of the user is estimated from a back area load distribution. A massaging position for a roller as a massage driver is decided so that the roller is moved to a proper position for the user. Therefore, the massage device requires the physical frame detection sensor in addition to the roller as the massage driver. This leads to the increase in the number of parts. 
     According to Japanese Unexamined Patent Application Publication No. 2006-198307, the seat for vehicle is equipped with a massage mechanism such as air unit covering a wide area from a back area to a lumbar area of the seat occupant. Therefore, the vehicle seat is expensive, involving a large number of parts and complicated control. 
     It is, accordingly, an object of the present invention to provide a technique that enables the reduction of fatigue of the seat occupant at low cost and without an increase in the number of parts. 
     Other problems and novel features of the present invention will become apparent from the description of the present invention and the accompanying drawings. 
     The following is a brief description of typical features of the present invention. 
     Without preparing the sensor in addition to a posture changing mechanism, the position of the lumbar vertebra or the thoracic vertebra of each occupant is estimated by controlling the operation of the posture changing mechanism. The posture changing mechanism is set to a position based the estimation results of relevant positions. Then, the posture changing mechanism is used to provide a fatigue reduction effect on the occupant. 
     According to the above-described seat for vehicle, the fatigue of the seat occupant can be reduced at low cost and without an increase in the number of parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a seat for vehicle according to an embodiment of the present invention; 
         FIG. 2  is a perspective view showing a seat back frame of the vehicle seat according to the embodiment hereof; 
         FIG. 3  is a diagram showing an exemplary configuration of a lumbar support portion, a driving portion, and a power transmission portion shown in  FIG. 2 ; 
         FIG. 4  is a plan view illustrating the power transmission portion; 
         FIG. 5  is a diagram showing a state where a wire B 62  is slidably moved downward relative to a wire A 61  and retained at place; 
         FIG. 6  is a diagram showing a state where the wire B 62  is slidably moved upward relative to the wire A 61  and retained at place; 
         FIG. 7  is a diagram showing a state where a resin plate  63  at a lower position pushes forward a urethane pad  38 ; 
         FIG. 8  is a diagram showing a state where the resin plate  63  at an upper position pushes forward the urethane pad  38 ; 
         FIG. 9  is a block diagram illustrating an exemplary circuit configuration of a control system according to the embodiment hereof; 
         FIG. 10  is a diagram explaining a method of estimating positions of the thoracic vertebra and the lumbar vertebra of an occupant PE seated on the vehicle seat; 
         FIG. 11  is a diagram explaining a case where each of the regions  3 P 1  to  3 P 3  of the urethane pad  38  is pushed by a back side support mechanism  63 ; 
         FIG. 12  is a flow chart showing the steps of an operation flow of an estimation system; 
         FIG. 13  is a diagram illustrating the operations of the back side support mechanism  63  during the operation flow of  FIG. 12 ; 
         FIG. 14  is a flow chart showing the steps of an operation flow of the estimation system succeeding the operation flow of  FIG. 12 ; 
         FIG. 15  is a diagram illustrating a first fatigue reduction mode; 
         FIG. 16  is a diagram illustrating a second fatigue reduction mode; 
         FIG. 17  is a flow chart showing the steps of an operation flow of a fatigue reduction system; and 
         FIG. 18  is a diagram illustrating an operation pattern of a fatigue reduction system according to a modification. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will hereinbelow be described with reference to the accompanying drawings. 
     It is noted that the disclosure is meant only for an example. For greater clarity, there are cases where the drawings provide more schematic illustrations of some parts than those in practical modes in terms of width, thickness, shape, and the like thereof. However, the drawings are not meant to limit the interpretation of the present invention. In the description and the individual drawings, components similar to those described with reference to the foregoing drawing will be referred to by like reference numerals and the detailed description thereof may be dispensed with as needed. In the drawings, an arrow pointing to the front indicates the front side of a vehicle, an arrow pointing to the back indicates the back side of the vehicle, an arrow pointing to the left indicates the left side of the vehicle, an arrow pointing to the right indicates the right side of the vehicle, an arrow pointing upward indicates the upper side of the vehicle, and the arrow pointing downward indicated the lower side of the vehicle. In the following description, the terms “front”, “back”, “up”, “down”, “left” and “right” are defined to mean the front, back, up, down, left and right with respect to the vehicle. 
     Embodiment 
       FIG. 1  is a perspective view showing a seat for vehicle according to an embodiment of the present invention. 
     A vehicle seat  1  includes: a seat cushion  2  on which an occupant is seated; a seat back  3  on which the occupant seated on the seat cushion  2  rests his/her back; a head rest  4  supporting a head of the occupant; and side supports  5 . The seat back  3  is tiltably connected to the seat cushion  2  by means of a reclining mechanism. A front-back direction adjustment switch  21  is disposed on a side surface of the seat cushion  2  for adjusting a position of a lumbar support portion  60  (described hereinlater) with respect to a front-back direction. Also, a vertical direction adjustment switch  22  is disposed on the side surface of the seat cushion for adjusting the position of the lumbar support portion  60  with respect to a vertical direction. 
       FIG. 2  is a perspective view showing a seat back frame which is removed of members on a front side of the seat back  3  (a side in contact with a back of the seated occupant) such as surface skin and urethane pad. A left back side frame is indicated at  31 . A right back side frame is indicated at  32 . An upper backside frame is indicated at  33 . An upper panel is indicated at  35  and a lower panel is indicated at  36 . The upper back side frame, the upper panel and the lower panel are connected to the left back side frame  31  and the right back side frame  32 , respectively. A support portion for supporting a pair of stays extended from the head rest  4  is indicated at  34 . The support portion is fixed to the upper back side frame  33  by welding. 
     The lumbar support portion is indicated at  60 , a lumbar support driving portion is indicated at  70  and a power transmission portion is indicated at  71 . An end of a shaft constituting the lumbar support portion  60  is indicated at  612 . 
       FIG. 3  corresponds to an enlarged view as seen along the line B-B in  FIG. 2 , showing an exemplary configuration of the lumbar support portion  60 , the lumbar support driving portion  70 , and the power transmission portion  71 . The driving portion  70  includes an electric motor ( 701  in  FIG. 9 ) equipped with a gearhead and is fixed to the right back side frame  32 . An output shaft of the driving portion  70  is indicated at  72 . The output shaft has a driving gear  73  secured thereto in the power transmission portion  71 . 
     A sector gear, which is meshed with the driving gear  73  is indicated at  74 . The sector gear  74  is supported by the right back side frame  32  and the power transmission portion  71  in a manner to be pivotable about a shaft  75 . The driving portion  70  oscillates the sector gear  74  by rotating the driving gear  73  fixed to the output shaft  72  in the forward direction and in the backward direction. An end of a wire A 61  constituting the lumbar support portion  60  is fixed to the sector gear  74  at place (decentered portion) away from the shaft  75 . 
       FIG. 4  corresponds to an enlarged view as seen along the line C-C in  FIG. 3 , illustrating the power transmission portion  71  in plan view. The sector gear  74  and the driving gear  73  are in meshing engagement. The sector gear  73  is configured such that a part of a circular gear is cut away, leaving a portion required for meshing engagement with the driving gear  73 . The output shaft  72  of the motor on which the driving gear  73  is mounted and the shaft  75  on which the sector gear  74  is mounted are each pivotally supported by the power transmission portion  71 . 
     The power transmission portion  71  is formed with a groove  76  for guiding the wire A 61  eccentrically secured to the sector gear  74 . The groove  76  is formed in a shape conforming to a trajectory of the wire A 61  oscillating relative to the shaft  75  supporting the sector gear  74 . 
     Returning to  FIG. 3 , the lumbar support portion  60  includes: the wire A 61 ; a wire B 62  supported on the wire A 61  by way of two blocks  64  at lateral portions thereof; a resin plate  63  secured to the wire B 62 ; and a vertical driving portion  65  secured to the wire A 61  for vertically driving the wire B 62 . The blocks  64  are fixed to the wire A 61  as slidably supporting the wire B 62 . 
     A left end of the wire A 61  extends through the groove  76  formed in the power transmission portion  71  and is fixed to the sector gear  74 . The wire A 61  has a right end portion which is once bent at a portion  611  and bent again to define an end portion  612  which is rotatably supported by the left back side frame  31 . The end portion  612  is formed such that a center axis thereof is aligned with a center axis of the shaft  75  supporting the sector gear  74 . 
     The lumbar support portion  60  configured in this manner provides for the following operation. The front-back direction adjustment switch  21  disposed on the side of the seat cushion  2  is operated to actuate the driving portion  70  so as to rotate the output shaft  72  a certain degree. Whereby the driving gear  73  fixed to the output shaft  72  oscillates the sector gear  74  about the shaft  75 . The oscillation of the sector gear  74  causes the wire A 61  having the end thereof fixed to the sector gear  74  to swing about the shaft  75  of the sector gear  74  and along the groove  76  formed in the power transmission portion  71 . 
     In conjunction with the oscillating movement of the wire A 61  along the groove  76 , the resin plate  63  secured to the wire B 62  oscillates about the shaft  75  of the sector gear  74 , so that the position of the resin plate  63  is changed with respect to the front-back direction (direction perpendicular to the drawing surface as seen in  FIG. 3 ). Thus, the amount of pressure on the back of the seated occupant via a member (e.g., the urethane pad covered with the surface skin) on the front side (surface on the side in contact with the back of the occupant seated on the vehicle seat  1 ) of the seat back can be varied. That is, the pressing force can be increased or decreased. 
     It is noted here that the wire B 62  is configured to be guided by the pair of blocks  64  secured to the wire A 61  and to be vertically (the vertical direction as seen in FIG.  3 ) movable relative to the wire A 61  as driven by the vertical driving portion  65 . A vertical position of the resin plate  63  can be changed by moving up or down the wire B 62  relative to the wire A 61 . Thus, the position to press on the back of the seated occupant via the member (e.g., the urethane pad covered with the surface skin) on the front side (surface on the side in contact with the back of the occupant seated on the vehicle seat  1 ) of the seat back  3  can be adjusted with respect to the vertical direction (height direction). 
       FIG. 5  and  FIG. 6  each correspond to a sectional view taken on the line A-A of the vehicle seat  1  in  FIG. 1 .  FIG. 5  is a diagram showing a state where the wire B 62  is slidably moved down relative to the wire A 61  and retained at position.  FIG. 6  is a diagram showing a state where the wire B 62  is slidably moved up relative to the wire A 61  and retained at position. Referring to  FIG. 5  and  FIG. 6 , the wire B 62  is retained by the blocks  64  secured to the wire A 61  in a manner to be slidably movable in the vertical direction. The wire A 61  is mounted with the vertical driving portion  65  for driving the wire B 62  with respect to the vertical direction. The vertical driving portion  65  is mounted in position by way of a gear  66  secured to an output shaft  67  of a motor  69  equipped with reducer. On the other hand, the wire B 62  is formed with a spur gear  68  meshed with the gear  66 . The gear  66  and the spur gear  68  jointly constitute rack and pinion gears. 
     With the wire A 61  and the wire B 62  configured in this manner, the following operations are provided. When the vertical direction adjustment switch  22  disposed on the side portion of the seat cushion  2  is operated to actuate the motor  69  with reducer of the vertical driving portion  65  secured to the wire A 61 , the gear  66  is rotated in the direction of an arrow in  FIG. 6 . The rotation of the gear causes the wire B 62  to move up relative to the wire A 61  as guided by the blocks  64  secured to the wire A 61 . Further, the wire B 62  is moved down relative to the wire A 61  by rotating the motor with reducer  69  backward so as to change a positional relation between the wire A 61  and the wire B 62  from that shown in  FIG. 6  to that shown in  FIG. 5 . 
       FIG. 7  is a diagram showing a state where the resin plate  63  at a lower position pushes forward the urethane pad  38 .  FIG. 8  is a diagram showing a state where the resin plate  63  at an upper position pushes forward the urethane pad  38 .  FIG. 7  shows a pushing state where the resin plate  63  at the lower position protrudes forward to push forward the urethane pad  38 . This pushing state corresponds to a state of the lumbar support portion  60  shown in  FIG. 5 . In this state, the resin plate presses on a lumbar area of the occupant seated on the vehicle seat  1  via the urethane pad  38  and a surface skin  37 . 
     On the other hand,  FIG. 8  shows a pushing state where the resin plate  63  protrudes forward to push forward the urethane pad  38  as located at a position higher than the position shown in  FIG. 7 . In this state, the lumbar support portion  60  corresponds to the state shown in  FIG. 6 . In this state, the resin plate presses on an area upward from the lumbar area of the occupant seated on the vehicle seat  1  via the urethane pad  38  and the surface skin  37 . 
     These positions of the resin plate  63  with respect to the height direction (vertical direction) and the front-back direction can be independently adjusted by operating the front-back direction adjustment switch  21  and the vertical direction adjustment switch  22 . 
     The present invention provides a fatigue reduction effect on the occupant by means of the vehicle seat  1  described with reference to  FIG. 1  to  FIG. 8 . In the following description, a posture changing mechanism  110  is defined to include, for example, the lumbar support portion  60 , the driving portion  70 , and the power transmission portion  71 . For example, a back side support mechanism ( 63 ) corresponds to the resin plate  63 . A support changing mechanism ( 65 ), for example, corresponds to the vertical driving portion  65  incorporating the motor  69 . A pushing amount adjusting motor ( 701 ), for example, corresponds to the electric motor incorporated in the driving portion  70 . 
       FIG. 9  is a block diagram illustrating an exemplary circuit configuration of a control system according to the embodiment. A control system  100  has two functions which include: an estimation system (also referred to as first system) for estimating the position of a thoracic vertebra and a position of a lumbar vertebra of the occupant; and a fatigue reduction system (also referred to as second system) for providing the fatigue reduction effect on the occupant. 
     The control system  100  is provided at the vehicle seat  1 . The control system includes: the posture changing mechanism  110 ; a control unit  120  for controlling the operations of the posture changing mechanism  110 ; a plurality of switches  21 ,  22 ,  23 ,  24  connected to the control unit  10 ; and the like. 
     The posture changing mechanism  110  includes: a motor (MT)  69  capable of vertically moving the back side support mechanism  63 ; and the pushing amount adjusting motor  701  capable of moving the back side support mechanism  63  in the front-back direction. The posture changing mechanism  110  further includes: a Hall IC (HIC)  80  as a sensor for detecting a work amount such as turnover number of the motor  69 ; and a Hall IC (HIC)  81  as a sensor for detecting a work amount such as turnover number of the pushing amount adjusting motor (MT)  701 . The motor  69  with reducer may also be referred to as “first motor”, and the pushing amount adjusting motor (MT)  701  may also be referred to as “second motor”. The Hall IC (HIC)  80  may also be referred to as “first Hall IC”, and the Hall IC (HIC)  81  may also be referred to as “second Hall IC”. 
     The control unit  120  is a seat ECU (electronic control unit) and includes: a motor driver MDR for driving the motors  69 ,  701 ; and a central processing unit CPU. The motor driver MDR is electrically connected to the motors  69 ,  701  via a harness. On the basis of control from the central processing unit CPU, the motor driver MDR controls the rotation of the individual motors  69 ,  701  by way of PWM (pulse width modulation). The central processing unit CPU is a general term for data processors incorporated in the central processing unit. The data processors receive data (values) of the turnover numbers of the motors  69 ,  701  detected or measured by the HICs  80 ,  81  and store the data in a memory circuit incorporated in the central processing unit CPU. The central processing unit CPU performs the data processing based on plural data pieces on the turnover numbers stored in the memory circuit. Based on the data processing results, the central processing unit controls the motor driver MDR, for example. The central processing unit CPU is electrically connected with the HICs  80 ,  81  by means of the harness. The central processing unit CPU is connected to a power source (PWR)  91  such as battery and supplied with an operating voltage from the PWR  91 . The central processing unit CPU is also electrically connected to another ECU  92  equipped on the vehicle via the harness, thus configured to perform communications. 
     Furthermore, the motor driver MDR and the central processing unit CPU are electrically connected to an electric motor of the reclining mechanism, an electric motor of a lift mechanism, an electric motor of a tilt mechanism, an electric motor of a slide mechanism, and a seat motor &amp; sensor  93  including a variety of sensors. Although not shown in  FIG. 1 , the vehicle seat  1  includes the electric motor of the reclining mechanism, the electric motor of the lift mechanism, the electric motor of the tilt mechanism, the electric motor of the slide mechanism, and the sensors. 
     The switch  21  is the front-back direction adjustment switch used for manual adjustment of the pushing amount of the motor  701  with respect to the front-back direction. The switch  22  is the vertical direction adjustment switch  22  used for manual adjustment the height of the motor  69  with respect to the vertical direction. 
     The switch  23  is an operation mode selector switch for determining whether or not to operate the control system  100  as the estimation system and the fatigue reduction system. The switch  23  in ON-state indicates that the control system  100  is operated as the estimation system and the fatigue reduction system. On the other hand, the switch  23  in OFF-state indicates that the occupant uses the switches  21 ,  22  for manually operating the posture changing mechanism  110 . 
     The switch  24  is a selector switch for switching the operation mode of the fatigue reduction system. As will be described hereinlater, the fatigue reduction system gives choices between an S-shape posture mode (first fatigue reduction mode) where a support position of the back side support mechanism  63  is set to a lumbar vertebra position and a C-shape posture mode (second fatigue reduction mode) where the support position of the back side support mechanism  63  is set to a thoracic vertebra position. The fatigue reduction system is configured for choices between the S-shape posture mode and the C-shape posture mode depending upon whether the switch  24  is in the ON-state (the first mode) or the OFF-state (the second mode). 
     An LED  25  is made of a plurality of light emitting diodes. The LED  25  is connected to the central processing unit CPU. Based on a signal from the central processing unit CPU, the LED  25  is adapted to indicate the operation mode of the control system  100  by way of combination of ON and OFF states of the light emitting diodes. 
     Next, the description is made on a case where the control system  100  operates as the estimation system for estimating the position of the thoracic vertebra or the lumbar vertebra of the occupant. The human body includes seven cervical vertebrae, twelve thoracic vertebrae, and five lumbar vertebrae in this order named from the head. Under these, a sacral vertebra and tailbone are contiguous thereto. 
     In the control system  100 , when the switch  23  is turned on, an estimation program related to the estimation system is first activated and executed by the central processing unit CPU. Thus, the positions of thoracic vertebra and lumbar vertebra of the occupant are estimated. After the estimation by the estimation system is completed, the system operation of the control system  100  is switched from the estimation system to the fatigue reduction system. In the fatigue reduction system, the system operation is switched from the estimation system to a fatigue reduction system. In the fatigue reduction system, a fatigue reduction program related to the fatigue reduction system is activated and executed by the central processing unit CPU. 
     When the estimation system is actuated, a vertical support position of a support changing mechanism  65  is shifted to the lowest stage as an initial state. Accordingly, the back side support mechanism  63  is also set to the lowest stage. The pushing amount adjusting motor  701  is driven from a reference position (also referred to as “N state”) at a certain torque for a given period of time (e.g., 3 to 5 seconds) so as to push forward the back side support mechanism  63 . In the meantime, a turnover number of the motor  701  is detected by means of the Hall IC  81  and recorded in a built-in memory circuit and the like by the central processing unit CPU. 
     Next, the vertical support position of the back side support mechanism  63  is shifted upward by the support changing mechanism  65  at a certain space interval (e.g., about 10 to 25 mm). At all of the support positions, the pushing amount adjusting motor  701  is operated under the same conditions as the above while the data (value) on the turnover number of the motor  701  is recorded by the central processing unit CPU. 
     The data pieces on the turnover number of the motor  701  recorded with respect to all the support positions are compared by the central processing unit CPU. Thus, the central processing unit CPU determines a support position exhibiting the largest turnover number of the motor  701  to be the lumbar vertebra area. A thoracic vertebra area is estimated by substituting the support position exhibiting the largest turnover number of the motor  701  in the following equation 1. 
     Next, the description is made on the fatigue reduction system. 
     The fatigue reduction system sets the support position of the back side support mechanism  63  based on the estimation results given by the estimation system. In a case where the S-shape posture mode is designated as an operation mode of the fatigue reduction system by turning on the switch  24 , the support position of the back side support mechanism  63  is set to the estimated thoracic vertebra position. In a case where the C-shape posture mode is designated as the operation mode of the fatigue reduction system by turning off the switch  24 , the support position of the back side support mechanism  63  is set to the estimated thoracic vertebra position. In the S-shape posture mode and the C-shape posture mode, the system may preferably provide control such that the pushing amount of the back side support mechanism  63  alternate between a pushing amount at the reference position (also referred to as “N state”) and the maximum pushing amount at a certain interval (e.g., 5 to 30 minutes). 
     Estimation System 
     Next, the description is made on a method of estimating the position of the thoracic vertebra or the lumbar vertebra of the occupant. 
     Heightwise positions of the thoracic vertebra and the lumbar vertebra of the seated occupant with respect to the vehicle seat  1  vary depending upon the physical frame of the occupant. For effective operation of the fatigue reduction system, therefore, the positions of the thoracic vertebra and the lumbar vertebra of each occupant need to be estimated with relatively high accuracy. Whether in upright position or seated position, the human body is characterized in that the lumbar vertebra area is curved forward due to the physiological bowing. In the case of seated position, the occupant need be deep-seated so as to bring the buttocks into contact with the back side surface of the seat. 
       FIG. 10  is a diagram explaining a method of estimating the positions of the thoracic vertebra and the lumbar vertebra of an occupant PE seated on the vehicle seat  1 .  FIG. 10  is a conceptual diagram of the seat back  3  of the vehicle seat  1  and the occupant PE seated on the seat cushion  2 . The urethane pad  38  of the seat back  3  and a back area PB of the occupant PE are shown in enlarged dimension. As to the urethane pad  38 , an area of contact with the back area PB is assumed to have a constant hardness. 
     In the enlarged illustration of  FIG. 10 , “ 3 P 1 ” denotes a region ranging from a first lumber vertebra area to a thoracic vertebra. The region  3 P 1  is characterized in that in a case where the urethane pad  38  is pushed toward the back area PB at its portion corresponding to the region  3 P 1 , the spine of the occupant PE is slightly less movable. “ 3 P 2 ” denotes a region ranging from a second to a fourth lumbar vertebra. The region  3 P 2  is characterized in that in a case where the urethane pad  382  is pushed toward the back area PB at its portion corresponding to the region  3 P 2 , the spine of the occupant PE is more movable. “ 3 P 3 ” denotes a region ranging from a fifth lumbar vertebra to a pelvis vertebra. The region  3 P 3  is characterized in that in a case where the urethane pad  38  is pushed toward the back area PB at its portion corresponding to the region  3 P 3 , the spine of the occupant PE is slightly less movable. The method of estimating the positions of the thoracic vertebra and the lumbar vertebra of the occupant utilizes such characteristics. 
       FIG. 11  is a diagram explaining a case where each of the regions  3 P 1  to  3 P 3  of the urethane pad  38  is pushed by the back side support mechanism  63 . According to  FIG. 11 , when the back side support mechanism  63  is pushed forward with a certain output (desired output) for a certain length of time, the pushing amount on the back side support mechanism  63  varies depending upon the regions  3 P 1  to  3 P 3  as supporting areas. The pushing amount is the largest at the region  3 P 2  (ranging from the second to the fourth lumbar vertebra) where the spine is more movable. The positions of the second to the fourth lumbar vertebrae of the occupant are searched for by taking the advantage of this characteristic. 
     When the region  3 P 1  is pushed forward, the spine of the occupant PE is less movable. Because of the large resistance, a three-second support pushing amount (a value of the turnover number of the pushing amount adjusting motor  701 ) is small. 
     When the region  3 P 2  is pushed forward, the spine of the occupant PE is more movable. Because of the small resistance, a three-second support pushing amount (a value of the turnover number of the pushing amount adjusting motor  701 ) is the largest. 
     When the region  3 P 3  is pushed forward, the spine of the occupant PE is slightly less movable. Because of the large resistance, a three-second support pushing amount (a value of the turnover number of the pushing amount adjusting motor  701 ) is small. 
     Next, the description is made on an operation flow of the estimation system which estimates the positions of the thoracic vertebra and the lumbar vertebra of the occupant.  FIG. 12  is a flow chart showing the operation flow of the estimation system.  FIG. 13  is a diagram illustrating the operations of the back side support mechanism  63  in the operation flow of  FIG. 12 .  FIG. 14  is a flow chart showing the steps of an operation flow of the estimation system succeeding the operation flow of  FIG. 12 . 
     As shown in  FIG. 12 , when the switch  23  is turned on, the operation of the estimation system is started. 
     Step S 1 : Determine whether or not the switch  24  is in ON-state or in OFF-state. With this, whether an operation mode of the fatigue reduction system is switched to the S-shape posture mode is determined. In a case where the S-shape posture mode is selected (Yes), the operation proceeds to Step S 2 . In a case where the operation is switched to the C-shape posture mode (No), the operation proceeds to Step S 3 . 
     Step S 2 : Set a mode flag provided in the central processing unit CPU to “0” (designate the S-shape posture mode). Subsequently, the operation proceeds to Step S 4 . 
     Step S 3 : Set the mode flag provided in the central processing unit CPU to “1” (designate the C-shape posture mode). Subsequently, the operation proceeds to Step S 4 . 
     Step S 4 : Determine whether the pushing amount of the back side support mechanism  63  is 0 mm (N state) or not. In a case where the pushing amount of the back side support mechanism  63  is 0 mm (Yes), the operation proceeds to Step S 6 . In a case where the pushing amount of the back side support mechanism  63  is not 0 mm (No), the operation proceeds to Step S 5 . 
     Step S 5 : Adjust the pushing amount adjusting motor  701  so as to set the pushing amount of the back side support mechanism  63  to 0 mm. Subsequently, the operation proceeds to Step S 6 . 
     Step S 6 : Determine whether or not the support position of the support changing mechanism  65  is at the lowest stage (B 100 ). Namely, whether or not the position of the back side support mechanism  63  is at the lowest stage is determined. In a case where the support position of the support changing mechanism  65  is at the lowest stage (B 100 ) (Yes), the operation proceeds to Step  8 . In a case where the support position of the support changing mechanism  65  is not at the lowest stage (B 100 ) (No), the operation proceeds to Step S 7 . 
     Step S 7 : Drive the motor  69  to shift the support position of the support changing mechanism  65  to the lowest stage (B 100 ). Thus, the position of the back side support mechanism  63  is set to the lowest stage. This state is illustrated by a fragmentary diagram S 7  in  FIG. 13 . Subsequently, the operation proceeds to Step S 8 . 
     Step S 8 : Drive the pushing amount adjusting motor  701  at a constant output for a certain length of time (3 to 5 seconds). Thus, an operation of pressing the back side support mechanism  63  against the region  3 P 3  is performed as illustrated by a fragmentary diagram S 8  in  FIG. 13 . In this operation, the pushing amount adjusting motor  701  is driven till resistance on the back side support mechanism  63  pressing on the urethane pad  38  reaches a predetermined threshold value. Subsequently, the operation proceeds to Step S 9 . 
     Step S 9 : When the back side support mechanism  63  pushes forward till the resistance thereon reaches the predetermined threshold value, the value (turnover number) of the pushing amount adjusting motor  701 , as detected by the Hall IC  81 , is recorded by the central processing unit CPU. Subsequently, the operation proceeds to step S 10 . 
     Step S 10 : Drive the pushing amount adjusting motor  701  and set the pushing amount of the back side support mechanism  63  to 0 mm (N state). This state is illustrated by a fragmentary diagram S 10  in  FIG. 13 . Subsequently, the operation proceeds to step S 11 . 
     Step S 11 : Determine whether or not the support position of the support changing mechanism  65  is at the highest stage (B 180 ). Namely, whether or not the back side support mechanism  63  is at the highest stage is determined. In a case where the support position of the support changing mechanism  65  is at the highest stage (B 180 ) (Yes), the operation proceeds to Step S 20  in  FIG. 14 . In a case where the support position of the support changing mechanism  65  is not at the highest stage (B 180 ) (No), the operation proceeds to Step S 12 . 
     Step S 12 : Drive the motor  69  to shift the support position of the support changing mechanism  65  to place 20 mm upward therefrom, for example. This state is illustrated by a fragmentary diagram S 12  in  FIG. 13 . An upward shift distance or a downward shift distance can be set to any value in the range of 10 mm to 25 mm, for example. 
     After Step S 12 , the operations of Steps S 8  to S 12  are repeated till the support position of the support changing mechanism  65  is shifted to the highest stage (B 180 ). 
     Next, an operation flow of  FIG. 14  is described. In this operation flow, the position of the thoracic vertebra or lumbar vertebra of each occupant is estimated from the turnover number values of the pushing amount adjusting motor  701  as detected by the Hall IC  81  at individual support positions and recorded in Step S 9 . According to the operation flow of  FIG. 14 , the turnover number values of the pushing amount adjusting motor  701  as recorded at the individual support positions are compared by the central processing unit CPU. In a case where the C-shape posture is applied by withdrawing the support on the S-shape posture or on the lumbar vertebra area, the support position of the back side support mechanism  63  is set to a position where the pushing amount adjusting motor  701  exhibits the largest turnover number. In a case where the C-shape posture is applied by pressing on the back area, the support position of the back side support mechanism  63  is set to a position derived from calculation using the following equation 1. The calculation is performed by the central processing unit CPU. 
       Support position of the back side support mechanism 63 in the  C -shape posture mode=190+( X −100)  (Equation 1),
 
     where “X” denotes a position out of the positions B 100  to B 180 , at which the motor exhibits the largest turnover number. It is noted that B 100  to B 180  are values representing the support positions of the support changing mechanism  65 . The lowest stage of the support position of the support changing mechanism  65  is expressed as B 100  (reference position). In a case where the support position of the support changing mechanism  65  is shifted L mm upward from the lowest stage, the shifted support position is expressed as B(100+L). In the case of estimating the position of the lumbar vertebra, B 100  and B 180  represent the lowest stage of the support position and the highest stage of the support position of the support changing mechanism  65 , respectively. 
     Each of the steps of the operation flow in  FIG. 14  is described as follows. 
     Step S 20 : Determine whether or not a support position at which the pushing amount adjusting motor  701  exhibits the largest turnover number value as detected by the Hall IC  81 , namely the back side support mechanism  63  exhibits the largest pushing amount (movement amount) is the lowest stage. In a case where the support position of the largest pushing amount (movement amount) is at the lowest stage B 100  (Yes), the operation proceeds to Step S 21 . In a case where the support position of the largest pushing amount (movement amount) is not at the lowest stage B 100  (No), the operation proceeds to Step  24 . 
     Step S 21 : Determine whether the mode flag is “0” or not (Determine whether the operation is in the S-shape posture mode or not). In the case of “Yes” (S-shape posture mode), the operation proceeds to Step S 22 . In the case of “No” (C-shape posture mode), the operation proceeds to Step S 23 . 
     Step S 22 : Set the support position of the back side support mechanism  63  to the lowest stage (B 100 ) and terminate the operation. 
     Step S 23 : Set the support position of the back side support mechanism  63  to B 290  and terminate the operation. 
     Step S 24 : Determine whether or not the support position of the largest turnover number value of the pushing amount adjusting motor  701  as detected by the Hall IC  81 , namely the support position of the largest pushing amount (movement amount) of the back side support mechanism  63  is B 120 . In a case where the support position of the largest pushing amount (movement amount) is B 120  (Yes), the operation proceeds to Step S 25 . In a case where the support position of the largest pushing amount (movement amount) is not B 120  (No), the operation proceeds to Step S 27 . 
     Step S 25 : Determine whether the mode flag is “0” or not (Determine whether the operation is in the S-shape posture mode or not). In the case of “Yes” (S-shape posture mode), the operation proceeds to Step S 26 . In the case of “No” (C-shape posture mode), the operation proceeds to Step S 27 . 
     Step S 26 : Set the support position of the back side support mechanism  63  to B 120  and terminate the operation. 
     Step S 27 : Set the support position of the back side support mechanism  63  to B 310  and terminate the operation. 
     Step S 28 : Determine whether or not the support position of the largest turnover number value of the pushing amount adjusting motor  701  as detected by the Hall IC  81 , namely the support position of the largest pushing amount (movement amount) of the back side support mechanism  63  is B 140 . In a case where the support position of the largest pushing amount (movement amount) is B 140  (Yes), the operation proceeds to Step S 29 . In a case where the support position of the largest pushing amount (movement amount) is not B 140  (No), the operation proceeds to Step S 32 . 
     Step S 29 : Determine whether the mode flag is “0” or not (Determine whether the operation is in the S-shape posture mode or not). In the case of “Yes” (S-shape posture mode), the operation proceeds to Step S 30 . In the case of “No” (C-shape posture mode), the operation proceeds to Step S 31 . 
     Step S 30 : Set the support position of the back side support mechanism  63  to B 140  and terminate the operation. 
     Step S 31 : Set the support position of the back side support mechanism  63  to B 330  and terminate the operation. 
     Step S 32 : Determine whether or not the support position of the largest turnover number value of the pushing amount adjusting motor  701  as detected by the Hall IC  81 , namely the support position of the largest pushing amount (movement amount) of the back side support mechanism  63  is B 160 . In a case where the support position of the largest pushing amount (movement amount) is B 160  (Yes), the operation proceeds to Step S 33 . In a case where the support position of the largest pushing amount (movement amount) is not B 160  (No), the operation proceeds to Step S 36 . 
     Step S 33 : Determine whether the mode flag is “0” or not (Determine whether the operation is in the S-shape posture mode or not). In the case of “Yes” (S-shape posture mode), the operation proceeds to Step S 34 . In the case of “No” (C-shape posture mode), the operation proceeds to Step S 35 . 
     Step S 34 : Set the support position of the back side support mechanism  63  to B 160  and terminate the operation. 
     Step S 35 : Set the support position of the back side support mechanism  63  to B 350  and terminate the operation. 
     Step S 36 : Determine whether the mode flag is “0” or not (Determine whether the operation is in the S-shape posture mode or not). In the case of “Yes” (S-shape posture mode), the operation proceeds to Step S 37 . In the case of “No” (C-shape posture mode), the operation proceeds to Step S 35 . 
     Step S 37 : Set the support position of the back side support mechanism  63  to B 180  and terminate the operation. 
     Step S 38 : Set the support position of the back side support mechanism  63  to B 370  and terminate the operation. 
     By way of modification, the position of the thoracic vertebra or the lumbar vertebra can also be estimated by using a method where time taken by the motor to reach a predetermined turnover number is recorded on a per-support position basis and these time data pieces are compared by the central processing unit CPU. 
     Fatigue Reduction System 
     The fatigue reduction system can be switched to any of three modes by operating mode selector switches  23 ,  24 . The modes include: an OFF-state of the fatigue reduction system (normal lumbar support mode); a first fatigue reduction mode (switching from the N-state to the S-shape posture); and a second fatigue reduction mode (switching from the N-state to the C-shape posture). The number of selectable modes is not limited to three. The system can be switched to any one of four or more modes (e.g., switched to a massage system or the like) or can be switched only between two modes (ON/OFF switching between two modes). 
     The following operations are performed when the switch  23  is switched from the OFF state to the ON state. 
     1. Switch the back side support mechanism  63  to the N state. 
     2. Determine an optimum support position. 
     3. Operate the posture changing mechanism at regular intervals (1 minute or more and less than 30 minutes) so as to change the seated posture of the occupant. The posture pattern and the operation interval vary depending upon the selected mode. 
     The fatigue reduction system is switched to the OFF state by the following operation and automatically returns to the N state. 
     1. When the switch  23  is operatively switched from the ON state to the OFF state. 
     2. When the central processing unit CPU receives from the vehicle ECU  92  a stop signal for the fatigue reduction system. 
     When the fatigue reduction system is in the ON state, the support strength of the posture changing mechanism  110  can be adjusted by the occupant at will (support strength in standard setting: maximum). When the fatigue reduction system is in the ON state, manual adjustment of the support strength of the posture changing mechanism  110  is allowed only when the posture changing mechanism  110  is in operation (S-shape posture, C-shape posture). When the fatigue reduction system is in the OFF state, the support position and the support strength of the posture changing mechanism can be adjusted according to the preference of the occupant operating the switch  21 ,  22  just as in the normal lumbar support mode. 
     A posture switching operation pattern can be configured in a manner to satisfy the following conditions. 
     1. The duration of one posture is a predetermined length of time between 5 minute or more and less than 30 minutes. 
     2. The same posture is not set consecutively. For example, it is impossible to make settings which include 15-minute S-shape posture, followed by 5-minute S-shape posture. 
       FIG. 15  is a diagram illustrating the first fatigue reduction mode.  FIG. 16  is a diagram illustrating the second fatigue reduction mode. In operation pattern graphs shown in  FIG. 15  and  FIG. 16 , the abscissa is the time and the ordinate is the support pushing amount. The graphs show the pushing amount (S) from the N state and the retracting amount (C) from the N state, respectively. 
     As shown in  FIG. 15 , the operation is switched between the N state and the S-shape posture (S) in the first fatigue reduction mode. According to the example, the posture switching operation pattern is configured as N state (N)→S-shape posture (S)→N state (N)→S-shape posture (S)→N state (N)→S-shape posture (S). In this example, one cycle (N state (N)→S-shape posture (S)) takes 30 minutes, of which 15 minutes is allotted to the N state and the remaining 15 minutes is allotted to the S-shape posture. 
     As shown in  FIG. 16 , the operation is switched between the N state and the C-shape posture (C) in the second fatigue reduction mode. The C-shape posture is varied by the mechanism and includes, for example, a C-shape posture C 1  where a blade bone area of the occupant is pushed forward; and a C-shape posture C 2  where a third lumbar vertebra area of the occupant is retracted. Hereinafter, the description is made by referring to the C-shape posture C 1  and the C-shape posture C 2  as “C-shape posture”. In the second fatigue reduction mode, the operation is switched between the N state and the C-shape posture. According to the example, the posture switching operation pattern is configured as N state (N)→C-shape posture (C)→N state (N)→C-shape posture (C)→N state (N)→C-shape posture (C). In this example, one cycle (N state (N)→C-shape posture (C)) takes 20 minutes, of which 15 minutes is allotted to the N state and 5 minutes is allotted to the C-shape posture. 
     Next, the description is made on an operation flow of the fatigue reduction system with reference to  FIG. 17 .  FIG. 17  is a flow chart showing the steps of an operation flow of the fatigue reduction system. When the fatigue reduction system is turned ON, Steps S 1  to S 38  described with reference to  FIG. 12  and  FIG. 14  are performed. Step S 38  is followed by Step S 40 . 
     Step S 40 : Set a support push-forward flag provided in the central processing unit CPU to “0”. The “0” of the support push-forward flag is defined to designate the N state. Subsequently, the operation proceeds to Step S 41 . 
     Step S 41 : Stand by for length of time (5 to 30 minutes) specified for each posture. Subsequently, the operation proceeds to Step S 42 . 
     Step S 42 : Determine whether the support push-forward flag is “0” or not. In a case where the support push-forward flag is “0” (Yes), the operation proceeds to Step S 43 . In a case where the support push-forward flag is not “0” (No), the operation proceeds to Step S 44 . 
     Step S 43 : Determine whether the mode flag is “0” or not. In a case where the mode flag is “0” (Yes), the operation proceeds to Step S 45 . In a case where the mode flag is not “0” (No), the operation proceeds to Step S 46 . 
     Step S 44 : Actuate the pushing amount adjusting motor  701  as a front-back direction adjusting motor so as to switch the operation mode from the S-shape posture to the N state or from the C-shape posture to the N state. Subsequently, the operation proceeds to step S 48 . 
     Step S 45 : Actuate the pushing amount adjusting motor  701  as the front-back direction adjusting motor so as to switch the operation mode from the N state to the S-shape posture. Subsequently, the operation proceeds to step S 47 . 
     Step S 46 : Actuate the pushing amount adjusting motor  701  as the front-back direction adjusting motor so as to switch the operation mode from the N state to the C-shape posture. Subsequently, the operation proceeds to step S 47 . 
     Step S 47 : Set the support push-forward flag to “1”. The operation proceeds to Step S 41 . 
     Step S 48 : Set the support push-forward flag to “0”. Subsequently, the operation proceeds to step S 41 . 
     Modification 
       FIG. 18  is a diagram illustrating an operation pattern of the fatigue reduction system according to a modification. Referring to  FIG. 15  to  FIG. 17 , the description has been made on the two patterns of switching the mode from the N state to the S-shape posture and from the N state to the C-shape posture. However, the present invention is not limited to these. As shown in  FIG. 18 , the fatigue reduction system is also adapted for a mode combining three postures (N state, S-shape posture, C-shape posture). A switching duty ratio can be set based on the same conditions for switching two postures. The posture switching operation pattern of  FIG. 18  is configured as N state (N)→C-shape posture (C)→S-shape posture (S)→N state (N)→C-shape posture (C)→S-shape posture (S)→N state (N). One cycle of this operation (N state (N)→C-shape posture (C)→S-shape posture (S)) of this example takes 30 minutes, of which 15 minutes is allotted to the N state, 5 minutes is allotted to the C-shape posture, and 10 minutes is allotted to the S-shape posture. 
     The order of the N state, the S-shape posture and the C-shape posture can be set arbitrarily under the following conditions. The fatigue reduction mode is always started with the N state (with the support push-forward flag “0”). The same posture is not set consecutively. For example, it is impossible to set a pattern including 10-minute S-shape posture followed by 10-minute S-shape posture. 
     The embodiments can offer the following effects. 
     1) Without preparing the sensor in addition to the posture changing mechanism, the positions of the lumbar vertebra and the thoracic vertebra of each occupant can be estimated only by controlling the operation of the posture changing mechanism. 
     2) The fatigue of the occupant can be reduced at low cost and by means of a small number of parts and simple control. 
     While the present invention made by the inventors has been specifically described by way of examples, it goes without saying that the present invention is not limited to the above-described embodiments and examples but may include a variety of changes and modifications.