Abstract:
A device for measuring a weight of a seat, including the weight of an occupant sitting on the seat. The device includes a resilient member supported by at least one support point;  
     a load sensor supported by a sensor support. The load sensor is in communication with the resilient member to receive the weight of the seat; the weight of the seat is applied between the at least one support point and the sensor point.

Description:
BACKGROUND  
         [0001]    The present invention relates to seat weight measuring devices, which are mounted to a vehicle seat and measure seat weight including the weight of an occupant sitting on a vehicle seat.  
           [0002]    In an automobile, a seat belt device and an airbag device are provided as equipment for ensuring safety of an occupant. Recently, for the purpose of improving the performance of seat belts and airbags, efforts to control the operation of those safety devices have been made in a manner matched with the weight and posture of the occupant. For example, the amount of gas for expanding an airbag and the expansion speed of the airbag are adjusted or pretension of a seat belt is adjusted in match with the weight and posture of the occupant. Such an adjustment requires it to know the weight of the occupant sitting on a seat, and to know the position where the center of weight of the occupant locates on the seat.  
           [0003]    To be adapted for those requirements, a seat weight measuring device is proposed which can accurately measure the seat weight at the lowest possible cost.  
           [0004]    [0004]FIG. 4 is a side view conceptually showing the construction of a seat weight measuring device. FIG. 5 partially shows a front portion of the seat weight measuring device. FIG. 5(A) is an exploded perspective view, and FIG. 5(B) is a front sectional view of a pin bracket section. FIG. 6 partially shows the front portion of the seat weight measuring device shown in FIG. 5. FIG. 6(A) is a plan view, FIG. 6(B) is a sectional view as viewed in the lengthwise direction, FIG. 6(C) is a sectional view taken along the line C-C in FIG. 6(B), and FIG. 6(D) is a sectional view taken along the line D-D in FIG. 6(B). Note that the right-and-left direction on the drawing sheets of FIGS.  4 ,  6 (A) and  6 (B) corresponds to the back-and-forth direction of a vehicle, and that since the seat weight measuring device is substantially symmetrical in the back-and-forth direction, one half of the device is omitted from the drawings.  
           [0005]    As shown in FIG. 4, the seat weight measuring device  9  comprises a coupling mechanism  15  for coupling a seat  3  (including a seat frame and seat rails) to a seat mounting portion  13  of a vehicle body and for bearing seat weight, and a transmitting mechanism  16  for transmitting the seat weight acting on the coupling mechanism  15  to load sensors  54  of a load meter  50 .  
           [0006]    The coupling mechanism  15  comprises a bearing member (pin bracket)  25 , an arm (Z-arm)  23 , a base pin (corresponding to a fulcrum support in the present invention)  31 , a base  21 , etc. The bearing member  25  is a disposed in each of the front, rear, left and right sides of the seat  3  for transmitting the weight of the seat itself and the weight of an occupant sitting on the seat to the arm (corresponding to a resilient member in the present invention)  23 . The arm  3  is rotatable about the base pin  31 . The base pin  31  is coupled to the seat mounting portion  13  of the vehicle body through the base  21 .  
           [0007]    The load meter  50  is formed by attaching strain gauges  54 , serving as the load sensors, onto an upper flat surface of a sensor plate  51 . Support points or fulcrums (corresponding to a sensor support in the present invention)  41   b ,  42   b  are formed on the underside of the sensor plate  51  at its left end side. A vertical load is transmitted from an acting part  23   j  of the arm  23  to the sensor plate  51  through these support points. The transmitted load is measured by the strain gauges  54  on the sensor plate  51 .  
           [0008]    How a load is transmitted in the seat weight measuring device  9  will be described below. A load W of the seat  3  is transmitted from the bearing member  25  to the arm  23 . The load W includes a vertical component Wv and a horizontal component Wh. The vertical component Wv includes the weight of the seat  3  itself and a part of the weight of an occupant. Of these weights, the weight of the occupant transmitted from one bearing member  25  to the arm  23  differs depending on the weight and posture of the occupant, the acceleration of the vehicle, and so on. On the other hand, the horizontal component Wh of the load W varies primarily depending on the acceleration of the vehicle and forces applied from the occupant&#39;s legs stretched against a vehicle floor.  
           [0009]    Herein, the distance (span) between the position (coupling point) where the bearing member  25  acts upon the arm  23  and the center axis of the base pin  31  (fulcrum of rotation) is S 1 , and the distance (span) between the center axis of the base pin  31  and the acting part  23   j  of the load upon the load meter  50  is S 2 . Accordingly, a vertical component Wv 2  transmitted from the arm acting part  23   j  to the sensor plate  51  is given as follows: Wv 2 =Wv×S 1 /S 2 . A vertical component Wv 1  supported by the base pin  31  is given as follows: 
             Wv   1 = Wv+Wv   2 = Wv (1+( S   1 / S   2 )). 
           [0010]    On the other hand, the horizontal component Wh of W is borne by the base pin  31  and is hardly transmitted to the sensor plate  51 . Stated another way, the transmitting mechanism  16  of the seat weight measuring device  9  has a characteristic of selectively transmitting, to the load meter  50 , the vertical component of the load W applied from the seat  3  to the coupling mechanism  15 .  
           [0011]    As shown in FIGS.  5 (A) and  5 (B) and FIGS.  6 (A) and  6 (B), the known seat weight measuring device  9  is constructed by using the elongate base  21  as a base member. The base  21  is extended long in the back-and-forth direction when the seat weight measuring device  9  is mounted to the vehicle body. As shown in FIGS.  6 (C) and  6 (D), the base  21  is made of a stamped steel plate having a substantially C-shaped cross-section opened upward, and comprises a bottom plate  21   c  and side plates  21   a ,  21   a ′ bent 90° at left and right ends of the bottom plate  21   c  so as to rise upward from them.  
           [0012]    Each of the base side plates  21   a ,  21   a ′ has pin holes  21   e ,  21   g  opened at two positions spaced from each other in the back-and-forth (longitudinal) direction. The holes  21   e ,  21   g  are opened it the right and left side plates  21   a ,  21   a ′ in an opposite relation. The hole  21   e  nearer to the longitudinal end of the base  21  is opened at a location away from the longitudinal end toward the center of the base  21  by a distance that is substantially ⅛ of an overall length of the base  21 . As shown in FIG. 5(A), the holes  21   e  are each an elongate hole extending longer in the vertical direction. A shaft portion of a bracket pin (corresponding to a force acting point in the present invention)  27  is inserted in the elongate holes  21   e . A retainer  33  is attached to an end of the bracket pin  27  lying in the right-and-left direction. The retainer  33  serves to prevent the bracket pin  27  from slipping off from the elongate holes  21   e.    
           [0013]    Gaps are left between the bracket pin  27  and inner edges, i.e., upper, lower, left and right edges, of each elongate hole  21   e  so that the bracket pin  27  is usually kept out of contact with the inner edges of the elongate hole  21   e . However, when an excessive load is applied to the seat weight measuring device  9  (specifically a pin bracket  25  section), the bracket pin  27  descends and strikes against the lower edge of the elongate hole  21   e  to avoid the excessive load from being transmitted to the load sensor  50  (sensor plate  51 ). In other words, the bracket pin  27  and the elongate holes  21   e  constitute a part of a mechanism for restricting an upper limit of the load applied to the sensor plate  51 . Additionally, a main role of the bracket pin  27  is to transmit the seat weight imposed on the pin bracket  25  to the Z-arm  23 .  
           [0014]    The pin holes  21   g  are each opened at a location slightly closer to the center of the base  21  than the elongate hole  21   e  (by a distance substantially {fraction (1/10)} of the overall length of the base  21 ). A base pin  31  penetrates the pin holes  21   g . The base pin  31  is laid to bridge between the right and left base side plates  21   a ,  21   a ′. A retainer  33  is a attached to an end of the base pin  31  lying in the right-and-left direction such that the base pin  31  is fixed to the base  21 . Incidentally, the base pin  31  serves as an axis about which the Z-arm  23  rotates.  
           [0015]    The Z-arm  23  is disposed inside the base  21 . In a plan view of the Z-arm  23 , a portion closer to the center of the base  21  is bifurcated into right and left legs (bifurcated portion  23   h ), and a portion closer to the longitudinal end of the base  21  has a rectangular shape. Side plates  23   a ,  23   a ′ are formed by bending 90° upward right and left end portions of a half of the Z-arm  23 , which is located closer to the longitudinal end of the base  21 . The bifurcated portion  23   h  is in the form of a simple flat plate. The side plates  23   a ,  23   a ′ are positioned inside the side plates  21   a ,  21   a ′ of the base  21  to extend along them. A gap is left between both the side plates  23   a  (or  23   a ′) and  21   a  (or  21   a ′).  
           [0016]    Two pin holes  23   c ,  23   e  are opened in each of the Z-arm side plates  23   a ,  23   a ′. The bracket pin  27  penetrates the pin holes  23   c  positioned closer to the longitudinal end side. The bracket pin  27  hardly slides relative to each of the pin holes  23   c . The base pin  31  penetrates the pin holes  23   e  positioned closer to the center side. The base pin  31  serves as the center for rotation of the Z-arm  23 , and therefore the base pin  31  slides relative to the pin holes  23   e  corresponding to the rotation of the Z-arm  23 . A holed disk-shaped spacer  35  is fitted over an outer periphery of the base pin  31  at a position between the base side plate  21   a  (or  21   a ′) and the Z-arm side plate  23   a  (or  23   a ′).  
           [0017]    The bifurcated portion  23   h  of the Z-arm  23  has a length substantially equal to a half of the overall length of the Z-arm  23 . The bifurcated portion  23   h  is branched into the right and left legs, which are extended toward the center of the base in the longitudinal direction and have a width narrowing toward the center side. Acting parts  23   j  formed by fore ends of the Z-arm bifurcated portion  23   h  of the Z-arm  23  are interposed between wing portions  41   a ,  42   a  of upper and lower half arms  41 ,  42 .  
           [0018]    When a load is applied to the pin bracket  25 , the Z-arm  23  is slightly rotated (about 5° at maximum) and the acting parts  23   j  transmit the load to the sensor plate  51  through the upper and lower half arms  41 ,  42 . The strain gauges are attached onto the sensor plate  51  to measure the applied load. The pin bracket  25  has, as shown in FIG. 6(C), a substantially C-shaped cross-section opened downward. A length of the pin bracket  25  in the back-and-forth direction is not so large, i.e., about {fraction (1/20)} of the overall length of the base  21 . The pin bracket  25  has a flat upper surface  25   a  on which a seat rail  7  of the seat  3  is laid. The pin bracket  25  and the seat rail  7  are firmly coupled to each other by fastening bolts or the likes. Further, the sensor plate  51  is fixed to a column  63  provided in a central area of the base bottom plate  21   c  by a nut  68  and a screw  69 .  
           [0019]    Right and left side plates  25   b  of the pin bracket  25  are vertically extended downward from the right and left sides of the pin bracket  25 , and their lower ends are bent to project inward. The side plates  25   b  are disposed inside the Z-arm side plates  23   a ,  23   a ′ with plays left between them. Pin holes  25   c  are opened respectively in the side plates  25   b . The bracket pin  27  penetrates the pin holes  25   c . Each of the pin holes  25   c  has a size larger than the diameter of the bracket pin  27 . Gaps left between the pin holes  25   c  and the bracket pin  27  serve to absorb dimensional errors and accidental deformations of the seat and the vehicle body.  
           [0020]    A spring leaf  29  is interposed between the right and left side plates  25   b  of the pin bracket  25  and the right and left Z-arm side plates  23   a ,  23   a ′. The spring leaf  29  has spring washer-like portions having holes, which are fitted over an outer periphery of the bracket pin  27  with gaps left between them. The spring leaf  29  constitutes a centering mechanism for biasing the pin bracket  25  so as to centrally position. Such a centering mechanism serves to locate the pin bracket  25  as close as possible to the center of its slidable range.  
           [0021]    In the seat weight measuring device  9  thus constructed, the seat rail  7  of the seat  3 , the pin bracket  25 , the Z-arm  23 , the base  21 , a seat bracket  11 , etc. constitute a mechanism for coupling the seat and the vehicle body of each other.  
           [0022]    In the known seat weight measuring device  9 , however, the base pin  31  serving as the fulcrum for the arm  23  is positioned, as shown in FIG. 7(A), between the bracket pin  27 , which serves as a force acting point applied with the seat weight and supports the one end side of the arm  23 , and the support points  41   b ,  42   b  for the sensor plate  51 , which serve as a force acting point and support the acting part  23   j  at the other end side of the arm  23 . As shown in FIG. 7(B), therefore, when the seat load is applied to the bracket pin  27 , the bracket pin  27  descends while the position of the support points  41   b ,  42   b  and the position of the base pin  31  are both kept not changed, thereby causing the arm  23  to resiliently deflect upward in its portion between the support points  41   b ,  42   b  and the base pin  31 .  
           [0023]    Stated another way, with a descent of the bracket pin  27 , the seat rail  7  also descends while the arm  23  deflects upward as described above, whereby the seat rail  7  and the deflected portion of the arm  23  come closer to each other, thus resulting in a risk of interference between them. For that reason, it is required to maintain a sufficient spacing between the seat rail  7  and the arm  23 .  
           [0024]    To maintain the sufficient spacing, however, the height of the seat rail  7  relative to the arm  23  must be set so as to ensure a sufficient space between them, and the height of the seat weight measuring device  9  is necessarily increased  
         SUMMARY OF THE INVENTION  
         [0025]    An exemplary object of the present invention is to provide a seat weight measuring device that can be suppressed from increasing in height even when an arm for transmitting seat weight to a sensor deflects with the seat weight. According to an embodiment of the present invention, a seat weight measuring device is provided. The device includes a resilient member for transmitting, to a load sensor, seat weight including the weight of an occupant sitting on a vehicle seat, said resilient member is supported by a fulcrum support and a sensor support for said load sensor, the seat weight is applied to said resilient member, wherein a force acting point on said resilient member, to which the seat weight is applied, is set between said fulcrum support and said sensor support.  
           [0026]    According to another exemplary embodiment of the present invention a seat weight measuring device is provided in which the height of the seat weight measuring device can be suppressed from increasing even when an arm for transmitting seat weight to a sensor deflects with the seat weight. The seat weight measuring device may include a resilient member for transmitting, to a load sensor, seat weight including the weight of an occupant sitting on a vehicle seat, the resilient member is supported by a fulcrum support and a sensor support for the load sensor, the seat weight is applied to the resilient member, wherein a force acting point on the resilient member, to which the seat weight is applied, is set between the fulcrum support and the sensor support.  
           [0027]    According to the seat weight measuring device of an embodiment of the present invention, the device is constructed such that a deflected portion of a resilient member is caused to move away from a support member for a vehicle seat instead of coming closer to the support member for the vehicle seat. The support member for the vehicle seat and the deflected portion of the resilient member are hence prevented from interfering with each other.  
           [0028]    Consequently, the spacing between the support member for the vehicle seat and the resilient member is not required to be set so large, and the height of the seat weight measuring device can be suppressed from increasing.  
           [0029]    An exemplary embodiment of the present invention will be described below with reference to the drawings.  
           [0030]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    These and other features, aspects, and advantages of the present invention will become apparent from the following description, appended claims, and the accompanying exemplary embodiments shown in the drawings, which are briefly described below.  
         [0032]    [0032]FIG. 1 partially and schematically shows one embodiment of a seat weight measuring device according to the present invention, in which FIG. 1(A) is an illustration showing a state of an arm before application of a seat load, and FIG. 1(B) is an illustration showing a state of the arm after application of the seat load.  
         [0033]    [0033]FIG. 2 partially shows the front portion of one embodiment of the seat weight measuring device shown in FIG. 1, in which FIG. 2(A) is a plan view and FIG. 2(B) is a front view.  
         [0034]    [0034]FIG. 3 partially shows the front portion of another embodiment of a seat weight measuring device according to the present invention, in which FIG. 3(A) is a plan view and FIG. 2(B) is a front view.  
         [0035]    [0035]FIG. 4 is a side view conceptually showing the construction of a seat weight measuring device.  
         [0036]    [0036]FIG. 5 partially shows a front portion of the seat weight measuring device in which FIG. 5(A) is an exploded perspective view, and FIG. 5(B) is a front sectional view of a pin bracket section.  
         [0037]    [0037]FIG. 6 partially shows the front portion of the seat weight measuring device shown in FIG. 5, in which FIG. 6(A) is a plan view, FIG. 6(B) is a sectional view as viewed in the lengthwise direction, FIG. 6(C) is a sectional view taken along the line C-C in FIG. 6(B), and FIG. 6(D) is a sectional view taken along the line D-D in FIG. 6(B).  
         [0038]    [0038]FIG. 7 partially and schematically shows a seat weight measuring device of the prior art in which FIG. 7(A) is an illustration showing a state of the arm before application of a seat load, and FIG. 7(B) is an illustration showing a state of the arm after application of the seat load. 
     
    
     DETAILED DESCRIPTION  
       [0039]    [0039]FIG. 1 partially and schematically shows one embodiment of a seat weight measuring device according to the present invention, in which FIG. 1(A) shows a state of an arm before application of a seat load, and FIG. 1(B) shows a state of the arm after application of the seat load, and FIG. 2 partially and specifically shows the front portion of one embodiment of the seat weight measuring device shown in FIG. 1, in which FIG. 2(A) is a plan view and FIG. 2(B) is a front view. Note that the same components as those of the above-described seat weight measuring device, shown in FIGS.  4  to  7 , are denoted by the same symbols and a detailed description of those components is omitted here.  
         [0040]    In a seat weight measuring device  9  of this embodiment, as shown in FIG. 1(A), and FIG. 2(B), one end portion of an arm  23  is supported by a base pin  31  serving as a fulcrum support for the arm  23 . Also, between the base pin  31  and support points  41 (B),  42 (B) provided on a sensor plate  51 , which supports an acting part  23   j  formed by the other end portion of the arm  23  and is a sensor support, a bracket pin  27  is positioned to serve as a force acting point, to which seat weight is applied, and to support the arm  23 .  
         [0041]    Other components of the seat weight measuring device  9  of this exemplary embodiment may be the same as those of the above -described seat weight measuring device, shown in FIGS.  4  to  7 .  
         [0042]    In the seat weight measuring device  9  of this exemplary embodiment, as shown in FIG. 1(B), when the seat load is applied to the bracket pin  27 , the bracket pin  27  descends while the position of the support points  41 (B),  42 (B) and the position of the base pin  31  are both kept not changed, thereby causing the arm  23  to resiliently deflect downward in its portion between the support points  41 (B),  42 (B) and the base pin  31 .  
         [0043]    Stated another way, with a descent of the bracket pin  27 , the seat rail  7  of the seat  3  also descends, but at this time the arm  23  deflects downward as described above. Therefore, the deflected portion of the arm  23  is moved away from the seat rail  7  instead of coming closer to the seat rail  7 . The seat rail  7  and the deflected portion of the arm  23  are hence prevented from interfering with each other.  
         [0044]    Accordingly, the spacing between the seat rail  7  and the arm  23  is not required to be set so large, and the height of the seat weight measuring device  9  can be suppressed from increasing.  
         [0045]    The other operational and advantageous features of the seat weight measuring device  9  of this exemplary embodiment are the same as those of the above described seat weight measuring device, shown in FIGS.  4  to  7 .  
         [0046]    [0046]FIG. 3 partially shows the front portion of another embodiment of a seat weight measuring device according to the present invention, in which FIG. 3(A) is a plan view and FIG. 2(B) is a front view. Note that the same components as those of the known seat weight measuring device, shown in FIGS.  4  to  7 , denoted by the same symbols and a detailed description of those components is omitted here. Also, a sectional view taken along the line C-C in FIG. 3 is the same sectional view as those of FIG. 6(C), and a sectional view taken along the line D-D in FIG. 3 is the same sectional view as those of FIG. 6(D).  
         [0047]    In one embodiment shown in FIGS.  2 (A) and  2 (B), the same components as those of the above-described seat weight measuring device, shown in FIGS.  4  to  7 , the bifurcated portion  23   h  is formed on the arm  23 , and the arm  23  has two acting parts  23   j . However, alternatively in the seat weight measuring device  9  of the embodiment as shown in FIGS.  3 (A) and (B), the arm  23  does not have the bifurcated portion  23   h  and have a single acting part  23   j  at the tip of the arm  23 . This single acting part  23   j  is positioned between the upper and lower half arms  41 ,  42  mounted on the sensor plate  51  respectively, and seat weight is transmitted from the arm  23  to the sensor plate  51  through the upper and lower half arms  41 ,  42 .  
         [0048]    The other components of the arm  23  are as known in the art, such as of the above-mentioned prior art embodiment. The arm  23  is rotatably supported by the side plates  21   a ,  21   a ′ of the base  21  through the base pin  31 . Also, the bracket pin  27  passes through the side plates  23   a ,  23   a ′ of the arm  23  and passes through the side plates  21   a ,  21   a ′ of the base  21 . Accordingly, the seat weight from the pin bracket  25  is transmitted to the arm  23  through the bracket pin  27 , but is not transmitted to the base  21  through the bracket pin  27 .  
         [0049]    Also, the pin bracket of the present invention, unlike the pin bracket of the prior art is rotatably supported by the base pin  31  and transmits the seat weight to the bracket pin  27 .  
         [0050]    Other components of the seat weight measuring device  9  of this embodiment are the same as those of the above-described seat weight measuring device, shown in FIG. 2 and FIGS.  4  to  6 .  
         [0051]    Also, the state of the arm associated with the seat load in the seat weight measuring device of this embodiment is the same as those of FIGS.  1 (A) and  1 (B).  
         [0052]    In the seat weight measuring device  9  of this embodiment, the seat weight transmitted to the arm  23  is transmitted to the sensor plate  51  through the single acting part  23   j . As stated above, the arm  23  is not formed on the bifurcated portion and has the single acting part  23   j . Thus, accuracy in manufacturing the arm  23  can be lower than those of the bifurcated portion. As a result, the arm  23  can be easily and inexpensively manufactured.  
         [0053]    The other operational and advantageous features of the seat weight measuring device  9  of the present invention may be the same as those of the above-described seat weight measuring device, shown in FIGS. 5 and 6.  
         [0054]    A seat weight measuring device of the present invention can be suitably applied to a seat weight measuring device for a vehicle, installed below a vehicle seat, for measuring a seat load including the load of an occupant sitting on the vehicle seat.  
         [0055]    The priority applications, Japanese Patent Application No. 2003-184649, filed on Jun. 27, 2003 and Japanese Patent Application No. 2004-15710, filed on Jan. 23, 2004 are both incorporated herein by reference in its entireties.  
         [0056]    Given the disclosure of the present invention, one versed in the art would appreciate that there may be other embodiments and modifications within the scope and spirit of the invention. Accordingly, all modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is to be defined as set forth in the following claims.