Abstract:
A seat belt system for a vehicle includes a collision predicting device, an occupant sensing device, a seat belt, a seat belt drive device and a seat belt control device. The collision predicting device senses an imminent collision of the vehicle before the collision actually takes place. The occupant sensing device determines an occupant state on a seat of the vehicle. The seat belt restrains an occupant to the seat. The seat belt drive device retracts and extends the seat belt. The seat belt control device drives the seat belt drive device to retract the seat belt and thereby to achieve a corresponding tension of the seat belt, which corresponds to the occupant, based on a signal outputted from the collision predicting device and occupant information outputted from the occupant sensing device.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and incorporates herein by reference Japanese Patent Application No. 2004-75010 filed on Mar. 16, 2004.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a seat belt system, which protects an occupant of a vehicle by restraining the occupant, more specifically, to a pre-crash seat belt, which retracts a seat belt prior to an unavoidable vehicle collision after the unavoidable vehicle collision is predicted.  
         [0004]     2. Description of Related Art  
         [0005]     One known vehicle occupant protective system is called a pre-crash seat belt system, which retracts a seat belt prior to an unavoidable vehicle collision after the unavoidable vehicle collision is predicted based on corresponding information, such as a following distance relative to a front vehicle or a brake operation by a vehicle driver (see, for example, Japanese Unexamined Patent Publication No. H06-286581 corresponding to U.S. Pat. No. 5,552,986).  
         [0006]     The above seat belt system restrains the occupant by the seat belt with a fixed tension regardless of a body size and a weight of the occupant on a vehicle seat when it is determined that the vehicle collision is unavoidable. However, at the time of fastening the seat belt, a contact position of the seat belt relative to the body of the occupant and a restraining force of the seat belt vary from occupant to occupant depending on the body size of the occupant. Thus, even when the seat belt is retracted prior to the collision, the restraining force of the seat belt may be too weak for some occupants or may be too strong for some other occupants. In each of these cases, the occupant has uncomfortable feeling, and the sufficient occupant protection cannot be achieved.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention addresses the above disadvantage. Thus, it is an objective of the present invention to provide a seat belt system, which addresses the above disadvantage.  
         [0008]     To achieve the objective of the present invention, there is provided a seat belt system for a vehicle. The seat belt system includes a collision predicting device, an occupant sensing device, a seat belt, a seat belt drive device and a seat belt control device. The collision predicting device senses an imminent collision of the vehicle before the collision actually takes place. The occupant sensing device determines an occupant state on a seat of the vehicle. The seat belt restrains an occupant to the seat. The seat belt drive device retracts and extends the seat belt. The seat belt control device drives the seat belt drive device to retract the seat belt and thereby to achieve a corresponding tension of the seat belt, which corresponds to the occupant, based on a signal outputted from the collision predicting device and occupant information outputted from the occupant sensing device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:  
         [0010]      FIG. 1  is a block diagram showing a seat belt system according to a first embodiment of the present invention;  
         [0011]      FIG. 2  is a block diagram showing a seat belt system according to a second embodiment of the present invention;  
         [0012]      FIG. 3A  is a diagram showing a state of a buckle moving device of the seat belt system of the second embodiment before movement of a buckle; and  
         [0013]      FIG. 3B  is a diagram showing another state of the buckle moving device of the seat belt system of the second embodiment after the movement of the buckle. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
       [0014]     A seat belt system for a vehicle according to a first embodiment of the present invention will be described.  FIG. 1  is a block diagram showing the seat belt system of the present embodiment installed in the subject vehicle. As shown in  FIG. 1 , the seat belt system  1  includes a buckle switch  20 , an occupant sensing device  3 , a collision predicting device  4 , a seat belt control device  5 , a motor  6  and a seat belt  7 .  
         [0015]     The buckle switch  20  is received in a buckle, which is installed to a seat frame. The buckle is connected to a tongue, which is, in turn, connected to the seat belt  7  (described latter). When the tongue is connected to the buckle, the buckle switch  20  is turned on.  
         [0016]     The occupant sensing device  3  includes a CCD camera  30  and an occupant sensing electronic control unit (ECU)  31 . The CCD camera  30  is installed to a corner of a room mirror. The CCD camera  30  captures an image of an occupant on a seat. The occupant sensing ECU  31  is received in a front passenger seat side end of an instrument panel. The occupant sensing ECU  31  senses and determines a locus of transition points of pixel gray scale based on the image data of the captured image, which is captured by the CCD camera  30 . Based on the locus, the occupant sensing ECU  31  determines whether the occupant is seating on the seat. Furthermore, in the case where the occupant is seating on the seat, the occupant sensing ECU  31  also determines a body size (e.g., a sitting height) of the occupant (occupant information) based on the locus.  
         [0017]     The collision predicting device  4  includes a millimeter wave radar  40  and a master cylinder pressure sensor  41 . The millimeter wave radar  40  is embedded at an ornament rear side of a front grille of the vehicle. The millimeter wave radar  40  senses a front vehicle or a front obstacle, which is located in front of the subject vehicle in a traveling direction of the vehicle. Furthermore, the millimeter wave radar  40  senses, for example, a distance between the subject vehicle and the front vehicle and/or a relative speed between the subject vehicle and the front vehicle. The master cylinder pressure sensor  41  is arranged in an engine room and senses a master cylinder pressure, which varies in connection with a change in an applied pressing force on a brake pedal.  
         [0018]     The seat belt control device  5  includes a constant voltage power source  50 , a seat belt central processing unit (CPU)  51 , a motor drive circuit  52  and an electric current sensing circuit  53 . The constant voltage power source  50  is connected to a vehicle battery  9  through a power supply line L 1 . An ignition switch  90  is inserted in the power supply line L 1 . The constant voltage power source  50  converts the high voltage of the vehicle battery  9  to a corresponding low voltage. The constant voltage power source  50  is connected to the seat belt CPU  51  through a power supply line L 2 .  
         [0019]     The seat belt CPU  51  is connected to the buckle switch  20 , the occupant sensing device  3 , the millimeter wave radar  40  and the master cylinder pressure sensor  41  through signal lines S 1 -S 4 , respectively. A signal of the buckle switch  20  is transmitted to the seat belt CPU  51  through the signal line S 1 . Body size data of the occupant is transmitted to the seat belt CPU  51  through the signal line S 2 . The data, which indicates the distance between the subject vehicle and the front vehicle and/or the relative speed between the subject vehicle and the front vehicle, is transmitted to the seat belt CPU  51  through the signal line S 3 . Furthermore, the data, which indicates the master cylinder pressure, is transmitted to the seat belt CPU  51  through the signal line S 4 . Based on the occupant body size data, which is received from the occupant sensing device  3 , the seat belt CPU  51  determines a corresponding tension of the seat belt  7  at the time of retracting the seat belt  7 . Furthermore, based on the data of the millimeter wave radar  40  and the data of the master cylinder pressure sensor  41 , the seat belt CPU  51  determines whether the imminent collision is unavoidable. When the seat belt CPU  51  determines that the imminent collision is unavoidable, the seat belt CPU  51  transmits a drive signal to the motor drive circuit  52  through a signal line S 5 .  
         [0020]     The motor drive circuit  52  is connected to the motor  6  through a power supply line L 3 . The motor drive circuit  52  drives the motor  6  based on the drive signal, which is transmitted from the seat belt CPU  51 . Through rotation of the motor  6 , the seat belt  7  is retracted. The motor  6  is included in a seat belt drive device of the present invention. The current sensing circuit  53  is connected to the motor drive circuit  52  through a signal line S 6  and is also connected to the seat belt CPU  51  through a signal line S 7 . The current sensing circuit  53  senses the value of the electric current in the motor drive circuit  52  and outputs current data, which indicates the sensed value of the electric current, to the seat belt CPU  51  through the signal line S 7 . The seat belt CPU  51  computes the tension of the seat belt  7  based on the transmitted current data. The seat belt CPU  51  controls the tension of the seat belt  7  to coincide with a predetermined corresponding value.  
         [0021]     Next, operation of the seat belt system of the present embodiment will be described. When the ignition switch  90  is turned on, the high voltage is supplied from the vehicle battery  9  to the constant voltage power source  50  through the power supply line L 1 . The voltage, which is converted in the constant voltage power source  50 , is supplied to the seat belt CPU  51  through the power supply line L 2 . In this way, the seat belt system  1  is activated.  
         [0022]     First, an image, which indicates an occupant state on the seat (including presence/absent of the occupant on the seat and/or a size of the occupant on the seat), is captured by the CCD camera  30  of the occupant sensing device  3 . The image data of the image, which is captured by the CCD camera  30 , is transmitted to the occupant sensing ECU  31 . The occupant sensing ECU  31  determines presence of the occupant on the seat based on the image data. When it is determined that the occupant is present on the seat, the occupant sensing ECU  31  determines the body size of the occupant on the seat based on the image data. The determined result of the occupant state on the seat is transmitted to the seat belt CPU  51  through the signal line S 2 . When an ON signal is transmitted from the buckle switch  20  to the seat belt CPU  51 , the seat belt CPU  51  determines the tension of the seat belt  7  at the time of retracting the seat belt  7  based on the occupant body size data, which is transmitted from the occupant sensing device  3 .  
         [0023]     The distance between the subject vehicle and the front vehicle and/or the relative speed between the subject vehicle and the front vehicle are transmitted from the millimeter wave radar  40  to the seat belt CPU  51 . The master cylinder pressure is transmitted from the master cylinder pressure sensor  41  to the seat belt CPU  51 . Based on at least one of the data of the millimeter wave radar  40  and the data of the master cylinder pressure sensor  41 , the seat belt CPU  51  determines whether the imminent collision is unavoidable. When the seat belt CPU  51  determines that the imminent collision is unavoidable, the seat belt CPU  51  transmits the drive signal to the motor drive circuit  52  through the signal line S 5 . The motor drive circuit  52  drives the motor  6 . In this way, the seat belt  7  is retracted. At this time, the seat belt CPU  51  controls the tension of the seat belt  7  to coincide with the predetermined corresponding value based on the current data, which is sensed by the current sensing circuit  53 .  
         [0024]     Next, advantages of the seat belt system  1  of the present embodiment will be described. In the seat belt system  1  of the present embodiment, the occupant sensing device  3 , which includes the CCD camera  30 , is used. The body size of the occupant can be easily determined by obtaining the occupant information through the image recognition process of the captured image. Based on the body size data of the occupant, the tension of the seat belt  7  at the time of retracting the seat belt  7  is determined. Thus, in the case where it is determined that the imminent collision is unavoidable, even when the seat belt  7  is retracted, the occupant is restrained by the seat belt with the corresponding tension, which corresponds to the body size of the occupant. Thus, the occupant has less uncomfortable feeling. Furthermore, the occupant is restrained by the seat belt with the suitable tension, which is suitable to the individual occupant. Thus, safety of the occupant is relatively high.  
       Second Embodiment  
       [0025]     A second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in the following points. That is, a fastening state of the seat belt  7  is sensed by the occupant sensing device  3 , and a buckle moving device  8  is added in the second embodiment. Thus, in the following discussion, these differences are mainly discussed.  
         [0026]      FIG. 2  is a block diagram of the seat belt system  1  of the second embodiment.  FIGS. 3A and 3B  are schematic diagrams showing the buckle moving device  8  of the seat belt system  1 . More specifically,  FIG. 3A  shows a state of the buckle moving device  8  before movement of the buckle  2 .  FIG. 3B  shows another state of the buckle moving device  8  after the movement of the buckle  2  toward the front end of the seat. In FIGS.  2  to  3 B, components similar to those of  FIG. 1  will be indicated by the same numerals. As shown in FIGS.  2  to  3 B, the buckle moving device  8  is connected to the seat belt CPU  51  thorough a signal line S 8 .  
         [0027]     Based on the image data of the image captured through the CCD camera  30 , the occupant sensing ECU  31  of the occupant sensing device  3  senses and determines the seat belt fastening state in addition to the body size of the occupant. In addition to the occupant body size data, the occupant sensing device  3  transmits the seat belt fastening state data (seat belt fastening state information) indicative of the fastening state of the seat belt to the seat belt CPU  51 . The seat belt fastening state information indicates a state of the seat belt, such as a contact position of the seat belt relative to the occupant.  
         [0028]     The buckle moving device  8  includes a buckle control device  80 , a motor  81 , a pinion  82  and a rack  83 . The buckle control device  80  and the motor  81  are connected to each other through a power supply line L 4 . The buckle control device  80  receives an operation command from the seat belt CPU  51  and drives the motor  81  based on the operation command. The pinion  82  is connected to the motor  81  through a rotatable shaft. Furthermore, the rack  83  is arranged along the seat frame (not shown) of the seat  10  to mesh with the pinion  82 . The rack  83  is movable relative to the seat  10  in a fore-and-aft direction of the seat  10 . The buckle  2  is connected to a top of the rack  83 . The buckle  2  is connected to the buckle control device  80  through a signal line S 9 . A buckle switch (not shown) is received in the buckle  2 . An ON signal of the buckle switch is transmitted to the buckle control device  80  through the signal line S 9 . Then, the ON signal of the buckle switch is transmitted from the buckle control device  80  to the seat belt CPU  51  through the signal line S 8 .  
         [0029]     The seat belt CPU  51  transmits a drive signal to the motor drive circuit  52  through the signal line S 5  when the seat belt CPU  51  determines that the imminent collision is unavoidable. In addition, based on the seat belt fastening state data received from the occupant sensing device  3 , the seat belt CPU  51  outputs an operation command to the buckle moving device  8  through the signal line S 8 . Based on this operation command, the buckle control device  80  drives the motor  81 . When the motor  81  is driven, the pinion  82  is rotated. When the pinion  82  is rotated, the rack  82  is moved from the position shown in  FIG. 3A  toward the front end of the seat  10 , as shown in  FIG. 3B . Due to the movement of the rack  83 , the buckle  2  is also moved toward the front end of the seat  10 . In this way, the position of the seat belt  7  is changed.  
         [0030]     The seat belt system  1  of the present embodiment achieves the same advantages as those of the seat belt system of the first embodiment in terms of adjusting the tension of the seat belt  7  based on the occupant body size. In addition, in the seat belt system  1  of the present embodiment, the position of the buckle  2  is moved based on the fastening state of the seat belt  7 . For example, when the occupant leans on a door arm rest to laterally tilt his/her body, or when the occupant seats shallowly in the seat and rests his/or her back on a seat back, the fastening state of the seat belt differs from that of the normal seating state of the occupant. In such a case, when the direction of the tension of the seat belt is changed according to the seating state of the occupant, the occupant can be more effectively restrained. Accordingly, the seat belt system  1  of the present embodiment can apply the tension of the seat belt  7  from the appropriate direction based on the seating state of the occupant on the seat  10  by moving the position of the buckle  2  according to the fastening state of the seat belt  7 . As a result, the seat belt system  1  of the present embodiment can effectively restrain the occupant to improve the safety of the occupant. Furthermore, the operational reliability of the seat belt system  1  is improved.  
         [0031]     The present invention has been described with reference to the first and second embodiments. However, it should be noted that the seat belt system of the present invention is not limited to those described in the first and second embodiments. That is, the seat belt systems of the above embodiments can be modified without departing the scope of the present invention.  
         [0032]     For example, in each of the above embodiments, the occupant sensing device obtains the occupant information through the image recognition of the image captured by the camera (an image capture sensor)  30 . However, the sensor used in the occupant sensing system is not limited to any particular one. Besides the above described image capture sensor, any other sensor, such as a load sensor, a pressure sensor or a distance sensor, can be used in the occupant sensing device. Also, any combination of two or more of the above sensors can be used in the occupant sensing device. For example, the image capture sensor and the load sensor can be advantageously used in combination in the occupant sensing device to obtain the occupant body size information and the occupant weight information (occupant information).  
         [0033]     Furthermore, in the above embodiments, the collision predicting device includes the millimeter wave radar and the master cylinder pressure sensor. However, the type of the collision predicting device is not limited to any particular one. For example, the collision predicting device may include an ultrasonic radar (or a sensor) in order to sense a front vehicle, which is present in front of the subject vehicle. Also, in order to sense abrupt braking, the collision predicting device may include an antilock brake system (ABS) operation signal sensor for sensing an ABS operation signal or a vehicle speed sensor. The collision predicting device may include anyone of or both of the sensor for sensing the front vehicle and the sensor for sensing the abrupt braking.  
         [0034]     In the above embodiments, the seat belt CPU determines whether the imminent collision is unavoidable based on the data transmitted from the millimeter wave radar and the data transmitted from the master cylinder pressure sensor. However, in the case where the collision predicting device includes the sensor and a collision determining ECU, the collision predicting device can determine whether the imminent collision is unavoidable. In this case, the result of this determination may be transmitted from the collision predicting device to the seat belt CPU. Then, the seat belt CPU drives the seat belt drive device based on the result of the determination.  
         [0035]     Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.