Patent Publication Number: US-2002003344-A1

Title: Occupant protection apparatus

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to an occupant protection apparatus. More specifically, the present invention relates to an occupant protection apparatus that can selectively control deployment of an air bag based on whether a child seat is being used.  
       [0003] 2. Background Information  
       [0004] An air bag is an occupant protection device that is often used in conjunction with a seatbelt for protecting the occupant at the time of a vehicle collision. An occupant protection device is disclosed in Japanese Laid Open Patent Application No. H11-11153 that relates to the technology of controlling an air bag. According to this publication, the air bag apparatus has a load sensor that detects the weight of the occupant seated on the vehicle seat. If the weight detected by the load sensor is small, a relatively small amount of gas is supplied to inflate the air bag. If the weight is large, a relatively large amount of gas is supplied to inflate the air bag. In this manner, the air bag apparatus can function properly regardless of the weight of the occupant.  
       [0005] However, in the aforementioned airbag apparatus, the occupant&#39;s weight is detected by a weight sensor that is fixed to the vehicle body. Therefore, although it is possible to distinguish between a heavy adult and a light child, it is difficult to tell apart an adult and a child seat. This difficulty occurs because a child seat is fixed to a seat by a seatbelt. Particularly, a child seat has to be secured to the seat by the seatbelt so that the child seat is stable. Since the tension of the seatbelt applies a downward force on the seat, the load on the seat as detected by the weight sensor can be comparable to the weight of an adult, depending on the amount of tension in the seatbelt.  
       [0006] In view of the above, there exists a need for an occupant protection apparatus which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.  
       SUMMARY OF THE INVENTION  
       [0007] An object of the present invention is to provide an occupant protection apparatus that can accurately distinguish between a child seat installed on a seat and an adult sitting on the seat such that the deployment of an air bag can be accurately controlled.  
       [0008] The aforementioned object can be attained by providing an occupant protection apparatus that comprises a weight sensor, an air bag, a child seat detector, a load sensor control unit and an air bag controller. The weight sensor is configured to detect an object&#39;s weight that is sitting on a seat. The air bag is configured to deploy at time of a collision. The child seat detector is configured to detect whether a child seat is installed on the seat by a seatbelt. The load sensor control unit is configured to determine deployment and restriction of the air bag based on a comparison between the object&#39;s weight detected by the weight sensor and a predetermined threshold load value. The load sensor control unit determines restriction in the deployment of the air bag if the child seat detector detects a child seat being installed on the seat. The air bag controller is operatively coupled to the air bag to deploy the air bag based on the determination result of the load sensor control unit.  
       [0009] These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled, in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010] Referring now to the attached drawings which form a part of this original disclosure:  
     [0011]FIG. 1 is a partial diagrammatic, lateral cross sectional view of a vehicle interior, which includes an occupant protection apparatus in accordance with a first embodiment of the present invention;  
     [0012]FIG. 2 is a top schematic plan view of the occupant protection apparatus in accordance with the first embodiment of the present invention;  
     [0013]FIG. 3 is a flowchart of an operation of the occupant protection apparatus in accordance with the first embodiment of the present invention;  
     [0014]FIG. 4 is a graph showing load adjustment performed by the occupant protection apparatus in accordance with a second embodiment of the present invention;  
     [0015]FIG. 5 is a flowchart of an operation of the occupant protection apparatus in accordance with the second embodiment of the present invention;  
     [0016]FIG. 6 is a partial internal front elevational view of the seatbelt retractor in accordance with selected embodiments of the present invention and with certain parts removed for explaining the structure and operation of the seatbelt retractor with a retractor state detection switch as child seat detection means;  
     [0017]FIG. 7 is a cross sectional view the seatbelt retractor in accordance with selected embodiments of the present invention as viewed along section line A-A′ of FIG. 6 and with certain parts removed for explaining the structure and operation of the seatbelt retractor with a retractor state detection switch as child seat detection means;  
     [0018]FIG. 8 is an enlarged bottom plan view of selected parts of the seatbelt retractor with retractor state detection switch in accordance with selected embodiments of the present invention;  
     [0019]FIG. 9 is a partial internal front elevational view of the seatbelt retractor in accordance with selected embodiments of the present invention and with certain parts removed for showing a state (A-ELR stopper lock state) in which the webbing is fully drawn out from the seatbelt retractor;  
     [0020]FIG. 10 is an enlarged bottom plan view of selected parts of the seatbelt retractor in accordance with selected embodiments of the present invention, showing a state (A-ELR stopper lock state) in which the webbing is fully drawn out from the seatbelt retractor; and  
     [0021]FIG. 11 is a partial internal front elevational view of the seatbelt retractor in accordance with selected embodiments of the present invention and with certain parts removed for showing a state (A-ELR stopper lock release state) in which the webbing is halfway retracted by the seatbelt retractor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0022] Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.  
     First Embodiment  
     [0023] Referring initially to FIGS.  1 - 3 , an occupant protection apparatus is illustrated in accordance with a first embodiment of the present invention. FIG. 1 is a partial diagrammatic lateral cross sectional view of a vehicle interior showing the structure of the occupant protection apparatus in accordance with the first embodiment. FIG. 2 is a top schematic plan view of the structure of the occupant protection apparatus of the first embodiment. In this embodiment, the occupant protection apparatus is provided in a front passenger&#39;s seat on a left-hand side of the vehicle. However, it is obvious that the occupant protection apparatus of the present invention can be provided in the front passenger&#39;s seat on a right-hand side of the vehicle or in either of the rear seats. A child seat CS is diagrammatically illustrated on a seat  5  of the vehicle. The child seat CS is a conventional device that is well known in the art. Since child seats are well known in the art, the child seat CS will not be discussed or illustrated in detail herein. The child seat CS is held in the seat  5  in a conventional manner by a seat belt that applies a downward force to press the child seat CS against the seat  5 .  
     [0024] In FIG. 1, the occupant protection apparatus of the first embodiment has a seatbelt webbing  2 , a seatbelt retractor  3  with an A-ELR switch  3   a , a seatbelt outer side anchor  4 , a seatbelt buckle  6 , a seatbelt inner side anchor  7 , a plurality of load sensors  12 , a load sensor controller or control unit  13 , and an air bag controller or control unit  15 . The seatbelt retractor  3  is equipped with an A-ELR (automatic lock and emergency lock) function. The A-ELR switch  3   a  is located within the seatbelt retractor  3 , and indicates whether the seatbelt retractor  3  is in the automatic lock state or in the emergency lock state. The A-ELR switch  3   a  is a conventional component that is well known in the art. Since the A-ELR switch  3   a  is well known in the art, the A-ELR switch  3   a  will not be discussed or illustrated in detail herein. The A-ELR switch  3 a functions as both a child seat detection mean and a retractor detection means for indicating whether the child seat CS is installed in the seat  5 . Moreover, “child seat detection mean and retractor detection means” as utilized in the claims should include any structure that can be utilized to carry out the function of detecting the presents of the child seat CS on the seat  5  in accordance with the present invention.  
     [0025] The load sensors  12  detect a load or weight, which is the weight of the seat  5  plus the weight of any object sitting on the seat  5 . The load sensors  12  are conventional components that are well known in the art. Since load sensors are well known in the art, the load sensors  12  will not be discussed or illustrated in detail herein. Moreover, “weight sensing means” as utilized in the claims should include any structure that can be utilized to carry out the function of the load sensors  12  of the present invention.  
     [0026] The load sensor control unit  13  functions as a sitting object determination means that determines based on the load detected by the load sensors  12  whether the object or occupant sitting on the seat  5  is an object for which an air bag should be deployed, or an object for which the deployment of the air bag should be restricted. The air bag control unit  15  functions as an air bag control means that controls deployment of the air bag(s) of the air bag module M that is diagrammatically shown in FIG. 2, based on the determination by the load sensor control unit  13 .  
     [0027] The control units  13  and  15  can be a single unit or a pair of units that are operatively coupled together. One or both of the control units  13  and  15  includes or is controlled by a microcomputer with a control program that controls the occupant protection apparatus as discussed below. One or both of the control units  13  and  15  can also include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The memory circuit stores processing results and control programs for operation of the air bag module M. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the control units  13  and  15  can be any combination of hardware and software that will carry out the functions of the present invention. In other words, “means plus function” clauses as utilized in the specification and claims should include any structure or hardware and/or algorithm or software that can be utilized to carry out the function of the “means plus function” clause.  
     [0028] As shown in FIG. 1, the seatbelt retractor  3  is preferably installed at an inner bottom of a vehicle pillar (center pillar)  1  for the front seat  5 . The seatbelt retractor  3  retracts the webbing  2  from an inner end of the webbing  2  that is attached thereto. Further underneath the seatbelt retractor  3 , the other or outer end of the webbing  2  is fixed to the pillar  1  via the seatbelt outer side anchor  4 .  
     [0029] The seatbelt inner side anchor  7  has the seatbelt buckle  6  coupled thereto. The seatbelt inner side anchor  7  is disposed on an inner side of front passenger&#39;s seat  5 , such that a tongue plate  8  through which the webbing  2  passes can be coupled to and detached from the seatbelt buckle  6  in a conventional manner.  
     [0030] The seatbelt retractor  3  has the A-ELR switch  3   a  that indicates either the auto-lock state or the emergency lock state. The auto-lock state occurs after the webbing  2  is fully drawn out. During the auto-lock state, the seatbelt retractor  3  can only retract the webbing  2  until after the webbing  2  is fully retracted. The seatbelt retractor  3  is in a different state while in the emergency lock state.  
     [0031] The seat  5  is typically slidable in a front-rear direction of the vehicle by a pair of rails  9  that are disposed on inner and outer sides of the seat  5 . Each of the rails  9  is attached to a vehicle body  11  via a bracket  10 . In between the rails  9  and the brackets  10 , a total of four load sensors  12  are disposed. The load sensors  12  detect the weight or load of seat  5  and the weight or load of an object sitting on the seat  5 . The load sensor control unit  13  is disposed on a lower side opposite of a sitting surface  5   a  of the seat  5 . The load sensor control unit  13  determines whether the weight or load of the object or occupant is greater or smaller than a predetermined weight or load.  
     [0032] The air bag control unit  15  is disposed on top of a floor tunnel  14  of the vehicle body  11  in a conventional manner. The air bag control unit  15  controls the deployment of the air bag or air bags, based on the determination by the load sensor control unit  13  and signals from the A-ELR switch  3   a  operatively coupled to the seatbelt retractor  3 .  
     [0033] As seen in FIG. 2, the seatbelt retractor  3 , the four load sensors  12 , the load sensor control unit  13 , the air bag control unit  15 , and the air bag module are operatively connected to each other by a wire harness  16 , such that the necessary electric signals can be sent to and received from each other.  
     [0034] The seatbelt retractor  3  of the present embodiment functions as an A-ELR seatbelt device, having both ELR function and ALR function. In other words, during normal use, the seatbelt retractor  3  functions as an ELR (emergency lock-type retractor device). For instance, when the speed changes suddenly due to a vehicle collision or a collision from rear, or by turning upside down, a lock mechanism is activated to lock the drawing out of the webbing  2 . In the meantime, when a child seat is installed, the seatbelt retractor  3  can be switched from the ELR function to the ALR function (automatic lock-type retractor device) automatically by fully drawing the webbing  2  out of the seatbelt retractor  3 .  
     [0035] Once the seatbelt retractor  3  shifts to the ALR function, the seatbelt retractor  3  only functions for retraction. Thus, even if the occupant tries to draw the webbing  2  out of the seatbelt retractor  3 , the webbing  2  cannot be drawn out because it is locked. In this manner, the child seat can be fixedly installed in seat  5  due to this ALR function. Also, the seatbelt retractor  3  can be switched back to the ELR-functioning state from the ALR-functioning state by fully retracting the webbing  2  to its normal resting position as seen in FIG. 1.  
     [0036] The A-ELR switch  3   a  is a switch that outputs signals indicating whether the ALR function or the ELR function is in operation. For instance, the A-ELR switch  3   a  can be configured to be “OFF” when the ALR function is in operation, and “ON” when the ELR function is in operation.  
     [0037] Operation of the occupant protection apparatus in accordance with the first embodiment will now be described referring to the flowchart shown in FIG. 3. First in step S 10 , the four load sensors  12  detect the load from the combined weight of the sitting occupant and the seat  5 . Then in step S 12 , the load sensor control unit  13  reads the detected load value from the load sensors  1 - 2 , and determines whether the detected load is greater or smaller than the predetermined load that is a preset value based on the weight of the seat  5  plus a preselected weight of a child. If the detected load is smaller than the predetermined load, it is determined that a child is sitting in the seat  5 . Accordingly, in step S 20 , the load sensor control unit  13  sends an air bag operation restriction command to the air bag control unit  15 . Upon receiving the air bag operation restriction command, the air bag control unit  15  executes a control to restrict the deployment of the air bag such that the occupant sitting on the seat  5  is protected, in the event the air bag has to be deployed.  
     [0038] If the detected load is greater than the predetermined load in the determination at step S 12 , then the state of the A-ELR switch  3   a  is inputted to the load sensor control unit  13  in step S 14 . Then in step S 16 , it is determined whether the A-ELR switch  3   a  is in the ALR state or in the ELR state. If the A-ELR switch  3   a  is in the ALR state, it is determined that a child seat is being used. Then, the system proceeds to step S 20 .  
     [0039] If the A-ELR switch  3   a  is in the ELR state in step S 16 , a child seat is not being used. Therefore, the load detected by the load sensors  12  is that of an adult sitting on the seat  5 . Thus, the load sensor control unit  13  outputs an air bag operation “ok” command to the air bag control unit  15  in step S 18 . Upon receiving the air bag operation “ok” command, the air bag control unit  15  executes a control to deploy the air bag in the event the air bag has to be deployed, the air bag being provided to protect the occupant sitting on the seat  5 .  
     [0040] Therefore, when a child under the preselected weight is sitting on the seat  5 , the deployment of the air bag can be controlled, e.g., reduced inflation and/or no inflation of the air bag. Furthermore, the deployment of the air bag can be restricted even if the load sensors  12  detect a load that is comparable to an adult&#39;s weight because of the child seat that is installed in the seat  5  with a seatbelt.  
     [0041] Furthermore, in this embodiment, the A-ELR switch  3   a  functions as the retractor detection means and the child seat detection means. Since the A-ELR switch  3   a  can have a simple structure, the child seat detection means/ retractor detection means can be manufactured at a low cost.  
     Second Embodiment  
     [0042] Now, a second embodiment of the present invention will be described referring to FIGS. 4 and 5. In view of the similarity between the first and second embodiments, the parts of the second embodiment that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the second embodiment that are identical to the parts of the first embodiment may be omitted for the sake of brevity.  
     [0043] The structure of the second embodiment is similar to that of the first embodiment shown in FIGS.  1 - 3 . The difference between the first and second embodiments is that the load sensor control unit  13  operates differently in the second embodiment from the first embodiment. In the second embodiment, when the A-ELR switch  3   a  indicates the ALR state, the load sensor control unit  13  adjusts the detected load or the predetermined threshold value to take in to account the load due to the force of the seat belt applied to the child seat CS. More specifically, the occupant protection apparatus in the second embodiment has three factory settings W 1 , W 2 , W 3  for the threshold load value depending on the arrangement of the seat belt relative to the seat  5  as explained below. Then, the system determines whether the object or occupant sitting on the seat  5  is an object for which the air bag should be deployed, or an object for which the air bag should not be deployed or deployed with a reduced inflation, based on either the adjusted load if in the ALR state or the detected (non-adjusted) load if in the ELR state.  
     [0044] Now referring to FIG. 4, the manner in which the load detected by the load sensors  12  is adjusted will be explained. First of all, assuming that the sum of the child&#39;s weight and child seat&#39;s weight (referred to as CRS in Figures) is equal to W 1 , then an adjustment may be necessary depending on the manner in which the seatbelt is arranged. If both of the outer and inner side anchors  4  and  7  of the seatbelt are fixed to the seat  5 , then the load detected by the load sensors  12  on the seat  5  is the constant value W 1 , regardless of the magnitude of the tension applied to the webbing  2  of the seatbelt. In this situation, the occupant protection apparatus has a predetermined threshold load value for activating the air bag, which is set as W 2 , regardless of the magnitude of the tension applied to the webbing  2  of the seatbelt.  
     [0045] However, if one of the outer and inner side anchors  4  and  7  of the seatbelt is fixed to the seat  5 , the load detected by the load sensors  12  on the seat  5  becomes greater if the tension applied to the webbing  2  of the seatbelt is greater. However, its gradient is not as large if as both of the outer and inner side anchors  4  and  7  of the seatbelt are fixed to the vehicle body  11 . In this situation, the occupant protection apparatus adjusts the predetermined threshold load value for determining whether the air bag should be activated such that the adjusted predetermined threshold load value is set at W 3 , which is greater than the non-adjusted threshold load value W 2 . Instead of changing the predetermined threshold load value W 2 , the detected load can be decreased by an adjustment valve equal to the value W 3  minus the value W 2 .  
     [0046] If both of the outer and inner side anchors  4  and  7  of the seatbelt are fixed to the vehicle body  11  (such as to the floor), the load to seat  5  as detected by the load sensors  12  on the seat  5  becomes significantly greater if the tension applied to the webbing  2  of the seatbelt is greater. In this situation, its gradient is also larger than if only one of the outer and inner side anchors  4  and  7  of the seatbelt is fixed to the seat  5 . In this situation, the occupant protection apparatus adjusts the predetermined threshold load value for determining whether the air bag should be activated such that the adjusted predetermined threshold load value is set at W 4 , which is greater than the threshold load value W 3  and the non-adjusted threshold load value W 2 . Instead of changing the predetermined threshold load value W 2 , the detected load can be decreased by an adjustment valve equal to the value W 4  minus the value W 2 .  
     [0047] Next, the operation of the occupant protection apparatus in accordance with the second embodiment will be described referring to the flowchart shown in FIG. 5. First in step S 30 , the four load sensors  12  detect the load from the combined weight of the sitting occupant and the seat  5 . Then in step S 32 , the state of A-ELR switch  3   a  is inputted to the load sensor control unit  13 . The occupant protection apparatus then determines in step S 34  whether the A-ELR switch  3   a  indicates the ALR state or the ELR state.  
     [0048] If the A-ELR switch  3   a  indicates the ALR state, an adjusted load or an adjusted predetermined threshold load value is obtained in step S 36  by decreasing the detected load or by increasing the predetermined threshold value. The load sensor control unit  13  can perform this function, and thus, act as an adjustment means for making an adjustment when a child seat has been detected and for determining the seat arrangement. The amount of adjustment can be stored in the load sensor control unit  13 , which is then preset for the particular seat arrangement at the time of installation of the occupant protection apparatus. In other words, the load sensor control unit  13  can have a predetermined adjustment value for each of the three different seat arrangements, as discussed above. Thus, at the time of installation of the occupant protection apparatus, the predetermined adjustment value can be set by the installer for making the correct amount of adjustment in step S 36 . Then, the system proceeds to step S 38 . If the A-ELR switch  3   a  indicates the ELR state, the system proceeds to step S 38 , skipping step S 36 , which is the step for adjusting the detected load.  
     [0049] In step S 38 , the system determines whether the adjusted load or the detected load (if the detected load has not been adjusted) is greater than the predetermined load. If the adjusted load is smaller than the predetermined load, it is determined that a child is sitting on the seat  5  or a child seat is being used. Then in step S 42 , the load sensor control unit  13  sends an air bag operation restriction command to the air bag control unit  15 . Upon receiving the air bag operation restriction command, the air bag control unit  15  executes a control to restrict the deployment of the air bag such that the object or occupant sitting on the seat  5  is protected, in the event an incident occurs in which the air bag should be deployed.  
     [0050] In the determination step S 38 , if the adjusted load is greater than the predetermined load, it is determined that an adult is sitting. Then, the system proceeds to step S 40 . In step S 40 , the load sensor control unit  13  outputs an air bag operation “ok” command to the air bag control unit  15 . Upon receiving the air bag operation “ok” command, the air bag control unit  15  executes a control to deploy the air bag(s) in the event an incident occurs in which the air bag(s) should be deployed occurs, such that the air bag protects the object or occupant sitting on the seat  5 .  
     [0051] Therefore, when a child seat is being installed, the detected load from the load sensors  12  can be adjusted using a sum of the weight of the child seat and a weight equivalent to the fastening force of the seatbelt. Accordingly, even if the apparent load as detected by the load sensors  12  increases due to the child seat being tightly secured with the seatbelt, it is less possible that the child seat will be mistaken for an adult. Thus, the deployment control of the air bag can be more properly performed.  
     Sealtbelt Retractor  
     [0052] Next, referring to FIGS.  6 - 11 , the details of the structures of the seatbelt retractor  3  and A-ELR switch  3   a  that can be used in the occupant protection apparatus in accordance with the first and second embodiments will be explained.  
     [0053]FIG. 6 is a partial internal front elevational view of the seatbelt retractor  3  in with certain parts removed for explaining the structure and operation of the seatbelt retractor  3  with the retractor state detection (A-ELR) switch  3   a  as a child seat detection means. FIG. 7 is a cross sectional view the seatbelt retractor  3  as viewed along section line A-A′ of FIG. 6 and with certain parts removed for explaining the structure and operation of the seatbelt retractor  3  with the retractor state detection (AELR) switch  3   a . FIG. 8 is an enlarged bottom plan view of selected parts of the seatbelt retractor  3  in with the retractor state (A-ELR) detection switch  3   a.    
     [0054]FIG. 9 is a partial internal front elevational view of the seatbelt retractor  3  with certain parts removed for showing a state (A-ELR stopper lock state) in which the webbing  2  is fully drawn out from the seatbelt retractor  3 . FIG. 10 is an enlarged bottom plan view of selected parts of the seatbelt retractor  3 , showing a state (A-ELR stopper lock state) in which the webbing  2  is fully drawn out from the seatbelt retractor  3 . FIG. 11 is a partial internal front elevational view of the seatbelt retractor  3  with certain parts removed for showing a state (A-ELR stopper lock release state) in which the webbing  2  is halfway retracted by the seatbelt retractor  3 .  
     [0055] This seatbelt retractor  3  basically includes a case  301 , a wall  302 , a seatbelt retraction drum rotational axis  303 , a small gear  304 , a medium gear  305 , a large gear  306 , a seatbelt lock gear  308 , a guide  313 , an A-ELR stopper lock release rotary body  307 , a cutout  307   a , an A-ELR stopper  309 , a coil spring  310 , an electric conductor  311 , and a spring terminal  312 . The case  301  is fixedly attached to the pillar  1  of the vehicle body  11  in a conventional manner and accommodates the A-ELR lock mechanism. The wall  302  divides the inside of the case  301  from a seatbelt retraction drum portion, which is not shown in Figures. The seatbelt retraction drum rotational axis  303  passes through the wall  302 . The small gear  304  is fixed to the seatbelt retraction drum rotational axis  303 . The medium gear  305  is a two-level gear. The medium gear  305  is rotatable about a medium gear axis  314  that is fixed to the case  301 . A large diameter portion of the medium gear  305  meshes with the small gear  304 . The seatbelt lock gear  308  is rotatable about the seatbelt retraction drum rotational axis  303 . The guide  313  is a cylindrical protrusion formed within the case  301 . The A-ELR stopper lock release rotary body  307  is rotatably coupled to the guide  313 . The cutout  307   a  is formed on an outer peripheral portion of the A-ELR stopper lock release rotary body  307 . The A-ELR stopper  309  can be inserted into the cutout  307   a . The coil spring  310  biases the A-ELR stopper  309  toward the A-ELR stopper lock release rotary body  307 . The electric conductor  311 , such as a copper plate, is fixedly attached to a coil spring side of the A-ELR stopper  309 . The spring terminal  312  is disposed opposite the electric conductor  311 . When the A-ELR stopper  309  is inserted to cutoff  307   a , the spring terminal  312  separates from the electric conductor  311 . When the A-ELR stopper  309  is not inserted into the cutoff  307   a , the spring terminal  312  contacts the electric conductor  311 .  
     [0056] Now, the operation of the seatbelt retractor  3  will be explained. The small gear  304 , the medium gear  305 , and the large gear  306  are gears for adjusting the number of rotations. The gears  304 - 306  transmit and adjust rotations by reducing the number of rotations of the seatbelt retraction drum rotational axis  303 . In other words, the seatbelt retraction drum, which is not shown in Figures and to which the webbing  2  is wound, rotates when the webbing  2  is drawn out from the seatbelt retractor  3 . Accordingly, the seatbelt retraction drum rotational axis  303  also rotates when the webbing  2  is drawn out from the seatbelt retractor  3 . Then, the small gear  304  that is fixedly attached to the seatbelt retraction drum-rotational axis  303  rotates when the webbing  2  is drawn out from the seatbelt retractor  3 . This rotary force is subsequently transmitted from the small gear  304  to the medium gear  305 , and then from the medium gear  305  to the large gear  306 .  
     [0057] While the webbing  2  is fully drawn out from the seatbelt retractor  3 , the number of rotations of the seatbelt retraction drum rotational axis  303  is reduced in two levels and transmitted to the large gear  306 . Accordingly, the large gear  306  slowly rotates in the counterclockwise direction once, while the webbing  2  is fully drawn out. Once the webbing  2  is fully drawn out, a protrusion  306   a  formed on an outer peripheral portion of the large gear  306  contacts a protrusion  307   b  formed inside the A-ELR stopper lock release rotary body  307 . Then, the protrusion  306   a  pushes the protrusion  307   b  in the counterclockwise direction.  
     [0058] In this manner, the cutoff  307   a  of the A-ELR stopper lock release rotary body  307  comes to a position that opposes the A-ELR stopper  309 . Then, the A-ELR stopper  309  is pushed to the left hand side of FIG. 10 by the coil spring  310 . Accordingly, the A-ELR stopper  309  engages the cutoff  307   a . At this time, a bottom portion of the A-ELR stopper  309  meshes with the seatbelt lock gear  308 . Thereafter, as seen in FIG. 9, rotation of the seatbelt retraction drum rotational axis  303 , which is fixedly attached to the seatbelt lock gear  308 , is restricted from operating in the direction to draw out the webbing  2 .  
     [0059] The ALR state shown in FIG. 9. In the ALR state, the A-ELR switch  3   a  that includes the electric conductor  311  and the spring terminal  312  is in an open (OFF) state. Conversely, in the ELR state in which the webbing  2  is halfway retracted, the A-ELR stopper  309  is separated from the cutoff  307   a  of the A-ELR stopper lock release rotary body  307 , as seen in FIG. 10. Accordingly, the A-ELR switch  3   a  that includes the electric conductor  311  and the spring terminal  312  is in a closed (ON) state.  
     [0060] In this manner, the A-ELR switch  3   a  can report to the load sensor control unit  13  whether the seatbelt retractor  3  is in the ALR state or in the ELK state by sending either an OFF or an ON signal. Therefore, a retractor state detection signal can be obtained as a signal from a low-cost and reliable switch.  
     [0061] As used herein, the following directional terms “forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of a vehicle equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the present invention.  
     [0062] The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms should be construed as including a deviation of ±5% of the modified term if this would not negate the meaning of the word it modifies.  
     [0063] This application claims priority to Japanese Patent Application No. 2000-202148. The entire disclosure of Japanese Patent Application No. 2000-202148 is hereby incorporated herein by reference.  
     [0064] While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.