Abstract:
A load-detecting device for an object on a seat of an automobile comprises a plurality of load sensors for generating output signals corresponding to an object on the seat, a plurality of signal processing circuits for processing the output signals so as to provide load signals with unique IDs corresponding to each of the sensors, and a control unit including a plurality of ports communicated with the signal processing circuits so as to load the load signals in the control unit, wherein the control unit executes an initialization process so that the ports is assigned in relation to the signal processing circuits based on the unique IDs included in the load signals.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent Application No. 2004-020297 filed on Jan. 28, 2004, the entire content of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a load-detecting device for an object on a seat. More particularly, the present invention pertains to a load-detecting device for an object on a seat, comprising a plural load-detecting sensors and control unit for processing output signals of the sensors.  
       BACKGROUND  
       [0003]     It is a necessary in the automobile industry to improve safety performance of a driver, a co-driver and guests in an automobile. Conventionally so-called air bag system is used for protecting them as occupant on a seat at a traffic accident. Blowing volume, power and/or speed of the air bag is controlled since occupants&#39; physique is different between an adult and a child. It is, therefore, significant to correctly judge whether an adult or a child occupies the seat, especially co-drivers&#39; seat.  
         [0004]     According to the device described in US2002/0118104A1, four load-detecting sensors (eg. thick film sensor and/or strain gauges) are fixed on a supporting member to support a seat on an interior floor of the automobile. Each of the four sensors is fixed at right and left side of forward and backward portion of the supporting member so as to correctly detect the occupants&#39; weight (load) on the seat.  
         [0005]     A strain gauge is usually employed as load-detecting sensor because of its low cost. Output signal of the strain gauge is generally weak while a control unit is installed or located far from the strain gauge under the seat. An amplifier is necessary to amplify the output signal so as to surely transmit the weak signal to the control unit. A signal-processing unit is installed nearby the strain gauges to amplify the output signal. In addition, the unit controls and removes a possible noise on the output signal. Finally the unit transmits the signal to the control unit.  
         [0006]     When the occupant sits on the seat, a load is not uniformly applied on the entire seat. Each load received at the four sensors is also not uniform. A load-detecting sensor for high load is used at a position on the seat where a relative high load is applied while a load-detecting sensor for low-load is used at a position on the seat where a relative low load is applied, so as to reduce a cost. In consideration of load distribution on the entire seat, first identical load-detecting sensors for low load are used at the right and left side of the forward portion of the seat (the supporting member) while second identical load-detecting sensors for high load are used at the right and left side of the backward portion of the seat (the supporting member). The first and second load-detecting sensors are different each other in specific character but are same each other in shape. It has to be avoided to incorrectly install the first and second load-detecting sensors on the seat. Incorrect install of the sensors brings incorrect judgment of the occupant at the control unit.  
         [0007]     A pair of connectors is arranged between the signal processing unit and the control unit. Each of the connector corresponding to four sensors is able to comprise a unique lib for discrimination of the connectors. Indeed it is useful to avoid the incorrect install of the sensors, but it brings higher cost.  
       SUMMARY OF THE INVENTION  
       [0008]     In light of the foregoing, the present invention provides load-detecting device for an object on a seat of an automobile comprising a plurality of load sensors for generating output signals corresponding to an object on the seat, a plurality of signal processing circuits for processing the output signals so as to provide load signals with unique IDs corresponding to each of the sensors, and a control unit including a plurality of ports communicated with the signal processing circuits so as to load the load signals in the control unit, wherein the control unit executes an initialization process so that the ports is assigned in relation to the signal processing circuits based on the unique IDs included in the load signals. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description when considered with reference to the accompanying drawings, wherein:  
         [0010]      FIG. 1  is a perspective view of a seat for an automobile;  
         [0011]      FIG. 2  is a over view of the seat with a load-detecting device for an object on the seat;  
         [0012]      FIG. 3  is a perspective view of a front bracket applied on the seat;  
         [0013]      FIG. 4  is a perspective view of a rear bracket applied on the seat;  
         [0014]      FIG. 5  is block diagram of the load-detecting device;  
         [0015]     FIGS.  6  is a flowchart showing a program executed by a central processing unit in the load-detecting device; and  
         [0016]      FIG. 7  shows port arrangement of the central processing unit; and  
         [0017]      FIG. 8  shows another port arrangement of the central processing unit.  
     
    
     DETAILED DESCRIPTION  
       [0018]     Embodiments of the present invention will be explained with reference to illustrations of the drawing figures as follows.  
         [0019]     As shown in  FIGS. 1 and 2 , a seat  1  is fixed on an inside room floor  11  of an automobile via a pair of supporting frames  2 , 2 , supporting brackets  3 , 3 , 3 , 3 , a pair of lower rails  4 , 4  and a pair of upper rails  6 , 6 . The frames  2 , 2 , the lower rails  4 , 4 , and the upper rails  6 , 6  extend in forward and backward direction (X-direction) of the automobile. A pair of the supporting brackets  3 , 3  is fixed on the supporting frames  2 , 2  at forward and backward portions of the frames  2 , 2 , respectively. The lower rails  4 , 4  are fixed on the supporting brackets  3 , 3 , 3 , 3  so as to extend along the supporting frames  2 , 2 . Each of the lower rails  4 , 4  forms U-shaped in cross section and opens at the upper portion. Each opening of the lower rails  4 , 4  forms a slide channel or slide race extending along the X-direction.  
         [0020]     The upper rails  6 , 6  are slidably arranged in the openings of the lower rails  4 , 4 , respectively. The upper rails  6 , 6  are connected with the lower arms  16 , 16  via a pair of front brackets  7 , 7  and a pair of rear brackets  8 , 8  at both right and left side of the seat  1 .  
         [0021]     As shown in  FIG. 3 , the front bracket  7 , 7  comprises an upper fixing portion  7   a  and a lower fixing portion  7   b  at the upper and lower ends of the bracket  7 , 7 , respectively. A curved portion  7   c  of the bracket  7  is formed by presswork between the portions  7   a  and  7   b . The fixing portion  7   a  is fixed at the forward portion of the lower arm  16  by a fixing member, while the fixing portion  7   b  is fixed at the forward portion of the upper rail  6  by a fixing member. Front-right and front-left load-detecting sensors  21  and  22  are fixed on the curved portion  7   c  of the front bracket  7 , 7 , respectively.  
         [0022]     As shown in  FIG. 4 , the rear bracket  8 , 8  comprises an upper fixing portion  8   a  and a lower fixing portion  8   b  at the upper and lower ends of the bracket  8 , 8 , respectively. A curved portion  8   c  of the bracket  8 , 8  is formed by presswork between the portions  8   a  and  8   b . The fixing portion  8   a  is fixed at the backward portion of the lower arm  16  by a fixing member, while the fixing portion  8   b  is fixed at the backward portion of the upper rail  6  by a fixing member. Rear-right and rear-left load-detecting sensors  23  and  24  are fixed on the curved portion  8   c  of the front bracket  8 , 8 , respectively.  
         [0023]     Consequently, the seat  1  is equipped with four load-detecting sensors  21  through  24  at forward and backward portion on both right and left side of the seat  1 . As shown in  FIG. 5 , strain gauges (or thick film sensor)  21  through  24  are employed as sensors  21  through  24 , respectively, because of its lower cost. The strain gauges electrically detects deflection amount of the curved portions  7   c , 7   c  and  8   c , 8   c , respectively, due to the load applied on the seat cushion  9 . Signal processing circuits  31  through  34  are integrally installed nearby the strain gauges  21  through  24 , respectively. Each of the circuit  31  through  34  comprises a noise filter circuit (not shown) and an amplifier circuit (not shown). The noise filter circuit controls and/or removes a noise on each analog output signal of the strain gauges  21  through  24 . The amplifier circuit amplifies the amplitude of the analog output signal and transforms the analog signal into a digital signal (a load signal) with a unique ID corresponding to each of the strain gauges  21  through  24 . In consideration of load distribution on the entire seat  1 , the load-detecting sensors  21 , 22  are identical in shape and in character for low load while the load-detecting sensors  23 , 24  are identical in shape and in character for high load.  
         [0024]     The control unit  25  is driven by a battery  35  (eg. 12V) of the automobile. The unit  25  comprises Input/Output (I/O) circuits  19  and  29 , a central processing unit (CPU)  26 , a constant voltage circuit  27  and an output circuit  28 . The I/O circuit  19  establishes both-way communication between ports P 1 , P 2 , P 3  and P 4  of the CPU  26  and the signal processing circuits  31 ,  33 ,  34  and  32  while the I/O circuit  29  establishes both-way communication with a test apparatus  40 . Each digital load signal of the signal processing circuit  31 ,  33 ,  34  and  32  is outputted to ports P 1 , P 2 , P 3  and P 4  of the CPU  26 , respectively. The CPU  26  comprises ROM and RAM (not shown) as well as a timer (not shown). The ROM stores a program and the RAM temporally stores a necessary data for processing the program. The constant voltage circuit  27  generates a constant voltage (eg. 5V) so as to be supplied to the CPU  26 . The output circuit  28  outputs control signal to an air-bag control unit  30 .  
         [0025]     In order to initialize the control unit  25 , the test apparatus  40  is employed so as to be electrically connected with the CPU  26  through the I/O circuit  29 . The initialization of the unit  25  is executed when the unit  25  is firstly booted by electrical connection between the unit  25  and the battery  35 , when an apparatus including the unit  25  is shipped from a factory and/or when the strain gauges  21  through  24  and/or the unit  25  are replaced due to its malfunction. The test apparatus  40  provides the CPU  26  with an initialization request through the circuit  29  so that memorized contents in the CPU  26  is able to be re-written. The re-writable contents in the CPU  26  is port arrangement or port sequence for assigning the ports P 1  through P 4  corresponding to the circuit  31  through  34 .  
         [0026]     The output circuit  28  is electrically connected with the air-bag control unit  30  that controls the air-bag actuation for safely protecting the occupant in the automobile at a traffic accident. The CPU  26  judges whether the occupant is adult or child based on the digital load signal of the signal processing circuit  31  through  34 . The air-bag control unit  30  controls air-bag actuation as well as blowing volume, power and/or speed of the air bag. The controller  30  allows use of the air bag when the occupant is adult, while the controller  30  prohibits the use of the air bag when the occupant is child.  
         [0027]     Referring to  FIG. 6 , the operation of the control unit  25  carried out by the software in the CPU  26  is described, as follows:  
         [0028]     When the automobile is switched on, the CPU  26  is booted at the step S 0  and processes initial check at the step S 1 . Namely, the CPU  26  checks possible error of the ROM and RAM in the CPU  26  as well as outside devices connected to the control unit  25 . At the step S 2 , the CPU  26  judges whether an initialization request is executed by the test apparatus  40 . Namely, it is judged whether the test apparatus  40  is connected with the control unit  25  so as to make an initialization request of the control unit  25 . If the initialization request is not confirmed at the step S 2 , the CPU  26  processes the step S 6 .  
         [0029]     If the initialization request is confirmed, the CPU  26  processes the step S 3 . At the step S 3 , the CPU  26  provides the circuits  31  through  34  with a signal output request. The digital load signals of the output circuits  31 ,  33 ,  34  and  32  are loaded into the CPU via the ports P 1 , P 2 , P 3  and P 4 , respectively and stored in pre-determined address in the RAM of the CPU  26  based on the unique IDs. The ports P 1 , P 2 , P 3  and P 4  are assigned in relation to the circuits  31 ,  33 ,  34  and  32 , as shown in  FIG. 7 . The port P 1  of the CPU  26  is provided with the load signal of the circuit  31  corresponding to the front-right load-detecting sensor  21 . The port P 2  of the CPU  26  is provided with the load signal of the circuit  33  corresponding to the rear-right load-detecting sensor  23 . The port P 3  of the CPU  26  is provided with the load signal of the circuit  34  corresponding to the rear-left load-detecting sensor  24 . The port P 4  of the CPU  26  is provided with the load signal of the circuit  32  corresponding to the front-left load-detecting sensor  22 . Each of the digital load signals of the circuits  31  through  34  comprises a frame with  15  bits (a start bit, two unique ID bits, 10 load data bits, a parity bit and a stop bit).  
         [0030]     At the step S 4 , the CPU  26  checks the unique IDs from the load signals of the circuits  31 ,  33 ,  34  and  32 , so that the unique IDs included in the load signals provided to the ports P 1 , P 2 , P 3  and P 4  of the CPU  26 . A unique ID No. 1 is applied to the signal processing circuit  31  for the front-right load-detecting sensor  21 . A unique ID No. 2 is applied to the signal processing circuit  33  for the rear-right load-detecting sensor  23 . A unique ID No. 3 is applied to the signal processing circuit  34  for the rear-left load-detecting sensor  24 . A unique ID No. 4 is applied to the signal processing circuit  32  for the front-left load-detecting sensor  22 .  
         [0031]     Next, at the step S 5 , the port arrangement of the port P 1 , P 2 , P 3  and P 4  are assigned in consideration of the unique IDs included in the load signals of the signal processing circuits  31 ,  33 ,  34  and  32 , which is inputted into the port P 1 , P 2 , P 3  and P 4  of the CPU  26 , at the step S 5 . Namely, if a load signal having the unique ID No.1, a corresponding connected port is assigned as port P 1  so that the port is used for inputting and outputting a signal between the front-right load-detecting sensor  21  and control unit  25 . If a load signal having the unique ID No.2, a corresponding connected port is assigned as port P 2  so that the port is used for inputting and outputting a signal between the rear-right load-detecting sensor  23  and control unit  25 . If a load signal having the unique ID No.3, a corresponding connected port is assigned as port P 3  so that the port is used for inputting and outputting a signal between the rear-left load-detecting sensor  24  and control unit  25 . If a load signal having the unique ID No.4, a corresponding connected port is assigned as port P 4  so that the port is used for inputting and outputting a signal between the front-left load-detecting sensor  22  and control unit  25 . These port assignments are achieved since the port arrangement corresponding to the unique IDs is pre-memorized in the CPU, as shown in  FIG. 7 .  
         [0032]     At the step S 6 , the CPU  26  provides the circuits  31  through  34  with a signal output request. The digital load signals of the output circuits  31 ,  33 ,  34  and  32  are loaded into the CPU via the ports P 1 , P 2 , P 3  and P 4 , respectively and stored in pre-determined address in the RAM of the CPU  26  based on the unique IDs. At the step S 7 , the CPU  26  calculates a total load value based on the digital load signals of the signal-processing circuits  31  through  34 , for example. Namely, the total load value is calculated by a sum of load values corresponding to the digital load signals of the signal-processing circuits  31  through  34  for the sensors  21  through  24 .  
         [0033]     Usually, the signal processing circuits  31 ,  33 ,  34  and  32  are electrically connected with the ports P 1 , P 2 , P 3  and P 4 , respectively, as shown in  FIG. 5 . Even if the sensors  21  and  23  are incorrectly installed so that the circuit  31  is connected with the port P 2  and the circuit  33  is connected with the port P 1 , the CPU  26  assigns the port P 2  as port P 1  and the port P 1  as port P 2  at the step S 5 , as mentioned the above. The port arrangement is corrected, as shown in  FIG. 8 , so that the CPU  26  appropriately corrects the calculation.  
         [0034]     At the step S 8 , the CPU  26  judges whether the occupant is adult or child according to the total load value. So-called filter processing is used for removing unusual load value during the judgment. If the total load value exceeds a pre-determined value Y at the step S 8 , the occupant is judged as adult at the step S 9  and the CPU  26  processes the step S 2 . Meanwhile, if the total load value is less than a pre-determined value Y at the step S 8 , the occupant is judged as child at the step S 10  and the CPU  26  processes the step S 2 . The CPU  26  repeats from the step S 2  through S 10  at a pre-determined interval.  
         [0035]     The above embodiment shows four sensors  21  through  24 , but the number of the sensors applied to a seat is not restricted to four but decided to arbitrary according to necessary design. If the output signals of the sensors  21  through  24  are not so weak or the output signals have high tolerance, the signal processing circuits  31  through  34  are able to be omitted or separately located from the sensors  21  through  24 . On the former occasion, the unique IDs are appropriately added to the output signals. Meanwhile, even if the test apparatus  40  is not used, the port assignment for the load signals of the signal processing circuits  31  through  34  and the ports P 1  through P 4  is able to be automatically achieved when the control unit  25  is firstly connected with the battery  35 .  
         [0036]     The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents that fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.