JP2006010581A - Passenger detection device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a passenger detection device for a vehicle capable of detecting the passenger on the car seat accurately by detecting the load on the car seat without impairing the noise-proof property. <P>SOLUTION: The passenger detection device is provided with: the load detector 2 for detecting the load on the car seat; and the controller 1 for discriminating the passenger on the basis of the load data input from the load detector 2. The load detector 2 comprises: the measurement part 3 for measuring the load; the memory part 5 for storing the reference value determined for the standard of the measurement part 3. The memory part 5 is provided with a rewritable and nonvolatile memory means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a vehicle occupant detection device that detects a load on a vehicle seat and discriminates an occupant on the vehicle seat based on detected load data.

As a device as described above, for example, Patent Document 1 discloses a technique of a vehicle occupant detection device capable of adjusting a determination threshold value after a load sensor is assembled to a vehicle seat. This comprises at least one threshold value storage means for storing a discrimination threshold value for discriminating the state of the vehicle occupant based on a load measurement result from a load sensor for detecting a load on the vehicle seat. At least a part of the threshold value storage means is constituted by a rewritable nonvolatile memory. Then, the determination threshold value is easily and reliably adjusted by rewriting the contents of the nonvolatile memory by communication from the outside using a calibration inspection tool or the like. As a result, the determination threshold value can be adjusted after the load sensor is attached to the vehicle seat or after the vehicle seat to which the load sensor is attached is attached to the vehicle. Further, it is disclosed that this determination threshold value is an occupant determination threshold value for determining the type of vehicle occupant and a zero point load threshold value indicating a load when a vehicle seat is empty.
Patent Documents 2 and 3 disclose techniques for measuring a signal output from a load sensor and calibrating (calibrating) a signal output in a situation where it can be determined that an occupant is not sitting as a zero value.

JP 2004-125595 A (page 3-4) JP 2000-283834 (paragraphs 0019 to 0020) JP 2001-21411 (paragraphs 0072-0073)

  However, in the techniques disclosed in Patent Documents 1 to 3, the controller corrects the output value of the load sensor. Specifically, for example, the output range of the load sensor is 0 to 100, and the value of the load sensor is 20 in a vacant seat state after the vehicle seat to which the load sensor is attached is attached to the vehicle. Then, the threshold value is corrected so that the technique described in Patent Document 1 regards this as a zero point. As a result, the output range of 0 to 100 becomes 20 to 100, and the measurement range becomes narrow.

  In order to deal with this problem, for example, if an attempt is made to ensure 100 output regions even after correction, a method such as setting the output of the load sensor itself to 0 to 120 can be adopted. However, if the detection range of the load sensor is extended to a portion that is discarded by the correction, the measurement accuracy of the load sensor is deteriorated. That is, for example, when the output voltage range of 6 V (volts) is set to an output range of 0 to 100, the output changes by 1 with respect to the output voltage of 6 mV. When the output range is 0 to 120, the output changes 1 for 5 mV. In the case where noise or the like is assumed, the output voltage of 6 mV is more resistant. In recent vehicles, there are many noise sources such as navigation systems, ETC (automatic toll collection system) cabin units, and audio equipment. Therefore, improving noise resistance from various viewpoints is indispensable for building a stable vehicle system, and the techniques described in Patent Documents 1 to 3 are not sufficient.

  In view of the above problems, an object of the present invention is to provide a vehicle occupant detection device that can accurately detect a load on a vehicle seat and detect an occupant on the vehicle seat without impairing noise resistance. .

  The characteristic configuration of the vehicle occupant detection device according to the present invention for achieving this object includes a load detection device that detects the load on the vehicle seat, and occupant discrimination based on load data input from the load detection device. The load detection device includes a measurement unit that measures a load, and a storage unit that stores a measurement reference value that determines a reference for measurement by the measurement unit. The unit is configured to have rewritable and nonvolatile storage means.

According to this characteristic configuration, for example, the load of the vehicle seat is detected and the load data is input to the control device, not the part that stores the determination threshold value used for determining the occupant by the control device. A storage unit provided in the load detection device includes a rewritable and nonvolatile storage unit. The storage unit stores a measurement reference value that defines a measurement reference by a measurement unit included in the load detection device, for example, a strain gauge that measures a load. Therefore, if the load data input to the control device deviates from the design value or product assembly and so-called deviation occurs, the load data and the threshold value for determining the occupant are corrected in the control device. It is not necessary, and this deviation can be improved by correcting the measurement reference value inside the load detection device that generates load data.
Further, in order to improve the deviation on the load detection device side, all of the input load data can be used as effective data on the control device side. Therefore, the effective data range is not unintentionally narrowed on the control device side. Further, in view of the fact that the effective data range is narrowed from the load detection device side, it is not necessary to output load data including originally unnecessary portions. Therefore, the load detection device can output the load data in the range of the effective data, can maintain the accuracy of the load data, and can enhance the noise resistance.

  Further, in the above configuration, the measurement reference value is a value that determines an output of the load detection device in a no-load state where no occupant is present on the vehicle seat.

  According to this characteristic configuration, the measurement reference value is a value that determines the output of the load detection device in a no-load state in which no occupant is present on the vehicle seat, that is, the output at the so-called zero point. The deviation of the load data can be confirmed without having to put on the vehicle seat.

  Moreover, you may comprise so that the said measurement reference value may be a value which determines the range which needs to be transmitted to the said control apparatus among the load which can be measured by the said measurement part.

  According to this configuration, for example, a value that defines a range that needs to be transmitted as load data from the load detection device to the control device among the loads that can be measured by a measurement unit including a strain gauge or the like is used as the measurement reference value. Even when the deviation of the load data is confirmed, the measurement reference value can be updated while maintaining the range, that is, the effective data width. As a result, it is not necessary to output load data from the load detection device side including the unnecessary portion in anticipation of correction of deviation in the control device. Therefore, the load detection device can output the load data by limiting the range of the effective data, and can maintain the accuracy of the load data.

  Furthermore, in the above configuration, it is preferable that the load detection device executes a measurement reference value update process and updates the measurement reference value in accordance with an instruction from the control device.

  According to this, since the load detection device executes the measurement reference value update process and updates the measurement reference value according to the instruction from the control device, for example, even without connecting an inspection machine or the like, Correction can be performed. In addition, even when an inspection machine is connected to perform adjustment and inspection, execution programs such as a measurement reference value update instruction and a measurement reference value update process are stored in the control device and the load detection device in the vehicle. Therefore, the inspection machine only needs to give an opportunity to start the execution program, and there is no need to prepare an inspection machine corresponding to each vehicle type.

[System Overview]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an arrangement of each part of a vehicle occupant detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a system configuration of the vehicle occupant detection device according to an embodiment of the present invention. .

  As shown in FIG. 1, in the present embodiment, a sensor 2 as a load detection device is assembled to the lower part of the vehicle seat 20 and is configured to measure a load by an occupant seated on the vehicle seat 20. . The sensors 2 are provided on the seat rail 26 of the vehicle seat 20 as sensors 21 to 24 at four locations, a right front portion, a right rear portion, a left front portion, and a left rear portion, respectively. The sensors 21 to 24 are connected to an ECU (Electronic Control Unit) 1 as a control device via a transmission line 25.

  In the present embodiment, the sensor 2 is configured using a strain gauge. As shown in FIG. 2, the sensor 2 includes a gauge 3 as a measurement unit and a signal processing unit 4. The signal processing unit 4 includes an analog signal processing unit 12, an analog / digital conversion unit (hereinafter referred to as A / D conversion unit) 13, a digital signal processing unit 14, and a communication interface unit (hereinafter referred to as communication I / F unit) 15. And a signal processing control unit 6 for controlling them and a storage unit 5 for storing information and data necessary for processing in the signal processing unit 4.

  Next, the signal flow of the sensor 2 will be described. The gauge 3 outputs a gauge voltage proportional to the magnitude of strain caused by the weight applied to the vehicle seat 20 (gauge output voltage). The analog signal processing unit 12 includes an amplifier, and the input gauge output voltage is amplified here. The amplified signal is then converted into a digital signal by the A / D converter 13. The signal converted into the digital signal is subjected to digital signal processing such as correcting the signal as necessary or adjusting the format so as to match the communication specifications in the digital signal processing unit 14. . Next, the communication I / F unit 15 performs signal processing such as adding a code for determining a communication error and outputs the signal to the ECU 1. Since the sensor 2 and the ECU 1 perform two-way communication, the communication I / F unit 15 also has a role of receiving a communication signal input from the ECU 1 and transmitting it to the signal processing control unit 6. It should be noted that the bidirectional communication between the ECU 1 and the sensor 2 can be configured so that the communication speed can be changed.

  The signal processing control unit 6 controls each unit of the signal processing unit 4. For example, setting or changing the amplification factor of the amplifier included in the analog signal processing unit 12, setting or changing the upper and lower reference voltages of the A / D conversion unit 13, correction or format designation to the digital signal processing unit 14, communication I / O This is a transmission instruction to the F unit 15. The storage unit 5 is configured to include a nonvolatile memory and the like, and stores values such as an execution program of the signal processing control unit 6 and amplification factors used in each signal processing and upper and lower reference voltages. Yes. These amplification factors, upper and lower reference voltages, etc. function as measurement reference values as will be described later. The storage unit 5 does not need to be configured using a single non-volatile memory. For example, an execution program is stored in a ROM that cannot be rewritten, and a work area used for digital signal processing is provided in a volatile RAM. Values such as the upper and lower limit voltages may be stored in a rewritable flash memory.

  Next, the ECU 1 will be described. The ECU 1 receives the load data output from the sensor 2 via the communication I / F unit 7. As described above, the communication I / F unit 7 also plays a role of transmitting a control command or the like to the signal processing control unit 6 via the communication I / F unit 15 of the sensor 2. In the present embodiment, since the sensor 2 has four sensors 21 to 24, the ECU 1 receives four load data. The ECU 1 calculates the total load data by performing calculations such as addition and bias correction on the received load data by the calculation unit 10. The determination unit 11 detects the occupant state on the vehicle seat 20 from the total load data. Here, the detection of the occupant state includes, for example, a vacant seat state, an adult seated state, a child seated state, and the like.

  The detection result in the determination unit 11 is transmitted to other control devices in the vehicle via the communication I / F unit 7. Other control devices in the vehicle are, for example, a seat belt retractor, an ECU that controls an airbag, and the like. In the present embodiment, as shown in FIG. 2, the passenger state on the vehicle seat 20 detected by the airbag ECU 30 is transmitted. In the airbag ECU 30, based on the detection result at the time of a collision, for example, the airbag is not inflated if the seat is empty, the airbag is inflated to the maximum for adults, or the inflation of the airbag is suppressed for children. Control such as stopping.

  The ECU 1 is configured to be connectable to the inspection machine 40 via the communication I / F unit 7. The inspection machine 40 is an apparatus that is connected to the ECU 1 and performs inspection and calibration (adjustment) of the sensor 2 in, for example, a store or a repair factory. The program for executing the inspection and calibration does not need to be installed in the inspection machine 40, and may be stored in the storage means possessed by the ECU 1 or the sensor 2 itself. The inspection machine 40 may be configured to give a start instruction so as to execute a program included in the ECU 1 or the sensor 2 or to display or record an inspection result.

  As described above, the vehicle occupant detection device according to the present embodiment is configured to determine the occupant based on the sensor 2 as the load detection device that detects the load of the vehicle seat 20 and the load data input from the sensor 2. The sensor 2 includes a gauge 3 as a measurement unit that measures a load, and a storage unit 5 that stores a measurement reference value that defines a measurement reference by the gauge 3. The storage unit 5 includes rewritable and nonvolatile storage means.

[Standard operation of the system]
Next, an outline of the operation of the vehicle occupant detection device configured as described above will be described. First, the standard operation of the ECU 1 will be described. FIG. 3 is a flowchart for explaining a standard operation of the ECU of FIG. The ECU 1 requests the sensor 2 to acquire load information (load data) at regular time intervals (process # 10) (process # 20). When load information is acquired from the sensor 2 (each sensor 21 to 24) (process # 60), the calculation unit 10 calculates the load (process # 70), and determines the occupant on the vehicle seat 20 (process # 80). ).

  Next, the standard operation of the sensor 2 will be described. FIG. 4 is a flowchart for explaining the standard operation of the sensor of FIG. The sensor 2 receives the sensor load information request from the ECU 1 (see process # 20 in FIG. 3), and determines whether there is a sensor load information request (process # 30). If there is no request, the process ends, and this process # 30 is repeated until there is a request. Of course, control may be performed so as to receive a sensor load information request from the ECU 1 as an interrupt. When there is a sensor load information request in process # 30, signal processing such as amplification of the output of the gauge 3 is activated for the signal processing unit 4 (process # 40), and the communication I / F unit 15 of the sensor 2 is activated. Sensor load information is output (process # 50). In this example, the signal processing by the signal processing unit 4 is driven each time. However, this is for ease of explanation, and of course, the electronic circuit is steadily operated. The latest signal at that time may be extracted. In this way, the sensor load information output from the sensor 2 is acquired by the ECU 1 (see process # 60 in FIG. 3).

[Change of measurement standard value]
The outline and the standard operation of the present embodiment have been described above. Hereinafter, the configuration and operation for changing the measurement reference value will be described with reference to the drawings. FIG. 5 is a flowchart for explaining the measurement reference changing operation by the ECU of FIG. 2, and FIG. 6 is a flowchart for explaining the measurement reference changing operation of the sensor of FIG. Here, the measurement reference value is a value that determines the output of the sensor 2 as the load detection device in a no-load state where no occupant is present on the vehicle seat 20. The change of the measurement reference value will be described using an example of adjusting a so-called zero (zero) point reference when no occupant is seated on the vehicle seat 20.

  As shown in FIG. 5, the ECU 1 confirms whether or not there is a request for adjusting the zero point reference and a zero point reset request (processing # 1). This 0-point reset request is input from the inspection machine 40 connected to the ECU 1 at the time of vehicle inspection, for example. Alternatively, the ECU 1 may execute a self-diagnosis program or the like, and issue a 0-point reset request according to the result. This self-diagnosis program has no load on the target vehicle seat 20 in cooperation with other systems in the vehicle, for example, when the vehicle is stopped and the occupant gets off and locked. It can be done by recognizing that. In this embodiment, for ease of explanation, a zero-point reset request is input from the inspection machine 40, and based on this request, the ECU 1 as the control device and the sensor 2 as the load detection device update the measurement reference value. The operation will be described below as the process is executed.

  When there is no zero point reset request in the process # 1, the ECU 1 performs a standard operation as usual. That is, the processing # 20, # 60, # 70, and # 80 are sequentially executed in the same manner as the operation described in FIG. 3 to determine the occupant on the vehicle seat 20. When this operation is performed only for inspection, as shown in FIG. 5, the determination of the occupant on the vehicle seat 20 is performed without confirming the passage of a fixed time (the process # 10 is omitted). You may do it. When the zero point reset request is confirmed in the process # 1, a command is issued to the sensors 21 to 25 to adjust the deviation from the zero point (process # 5).

  Subsequently, the operation of each of the sensors 21 to 25 (hereinafter represented by the sensor 2) will be described. As shown in FIG. 6, first, the presence / absence of a sensor load information request is confirmed (processing # 30). When there is a request for sensor load information, the sensor 2 performs standard operation as usual. That is, the processes # 40 and # 50 described with reference to FIG. 4 are sequentially executed. If there is no request for sensor load information, the presence / absence of a displacement adjustment command from the ECU 1 is confirmed (processing # 35). If there is a deviation adjustment command, the current output position of the gauge 3 is set as the output reference position of the sensor 2 (process # 36). This operation is performed for zero point adjustment, and at this time, the vehicle seat 20 is in an empty seat state. Therefore, the zero point adjustment can be realized by setting the output of the gauge 3 at this time to the zero output reference position of the sensor 2. Thus, according to the instruction from the ECU 1 as the control device, the sensor 2 as the load detection device executes the measurement reference value update process, and updates the measurement reference value.

[Example of measurement reference value change 1]
A specific example in which the measurement reference value is changed will be described below. FIG. 7 is a block diagram illustrating signal processing from the gauge of FIG. 2 to the A / D converter, and FIG. 8 is a diagram illustrating A / D conversion by the A / D converter of FIG.

  The output of the gauge 3 is not large enough to be input to the A / D converter 13 or the like as it is. In the present embodiment, as shown in FIG. 7, the output of the gauge 3 is amplified using an amplifier (amplifier circuit) 12 a provided in the analog signal processing unit 12, and the output is supplied to the A / D conversion unit 13. The signal is input and is analog / digital converted (hereinafter referred to as A / D conversion) by the A / D converter 13a or the like. The A / D converter 13a digitally converts a voltage between an upper limit reference voltage (refH) and a lower limit reference voltage (refL) of an input analog voltage that is an A / D conversion target with a predetermined resolution.

  As shown in FIG. 8, if the upper and lower reference voltages are set to 1V and 3V, respectively, and the A / D converter 13a has a 6-bit resolution, the linearly changing amplified voltage When the output voltage of the gauge 3 is 1V, the digital value is 0 (zero). When the output voltage is 3V, the digital value is 63. The resolution per bit is 31.25 mV. Here, when the digital reference value is 16 when the measurement reference value change command is issued (process # 35 in FIG. 6), the gauge 3 after amplification when the vehicle seat 20 is in an empty seat state. The output voltage is 1.5V. Accordingly, since the voltage width of the A / D converter 13a up to the upper limit reference voltage 3V is 1.5V, only a digital value up to 48 can be obtained with a resolution of 31.25 mV.

  Therefore, the lower limit reference voltage of the A / D converter 13a is changed to 1.5V that is the output voltage of the gauge 3 after amplification when the seat 20 is in an empty seat state, and the upper limit reference voltage is changed to the changed lower limit reference voltage. Change to 3.5V with input width of 2V. Then, the upper and lower reference voltages of the A / D converter 13a stored in the storage unit 5 are changed to the new upper and lower reference voltages and stored. The upper and lower reference voltages of the A / D converter 13a are generated by a voltage generation circuit (not shown) based on the values stored in the storage unit 5 and input to the A / D converter 13a. As a result, it is possible to adjust the state when the vehicle seat 20 is empty while maintaining the resolution, that is, while maintaining the load measurement system using the gauge 3.

  Since the measurement reference value is a value that determines the output of the sensor 2 as the load detection device in a no-load state where no occupant is present on the vehicle seat 20, in the above-described embodiment, the lower limit reference voltage (refL) is It corresponds to this. Further, since the upper limit reference voltage (refH) is changed with the change of the lower limit reference voltage, both of these reference voltages correspond to measurement reference values.

  Further, the measurement reference value may be a value that defines a range that needs to be transmitted to the ECU 1 as the control device among the loads that can be measured by the gauge 3 as the measurement unit. In the above-described embodiment, the upper limit reference Since the range that needs to be transmitted to the ECU 1 is determined by the voltage and the lower limit reference voltage, these both reference voltages correspond to the measurement reference values. That is, as shown in FIG. 8, the effective data width of the load data to be transmitted to the ECU 1 is set to be W before and after the adjustment.

  Further, if the input voltage range converted by the A / D converter 13a is widened, for example, the lower limit reference voltage is 1V and the upper limit reference voltage is 4V, the effective data width of the load data to be transmitted to the ECU 1 is increased. Can do. Since the maximum value of the digitally converted value remains 63, the resolution is degraded, but a wide range of loads (in this example, 1.5 times) can be included in the effective load data. Conversely, if the input voltage range converted by the A / D converter 13a is narrowed such that the lower limit reference voltage is 1V and the upper limit reference voltage is 2V, the effective data width of the load data to be transmitted to the ECU 1 can be reduced. it can. Since the maximum value of the digitally converted value remains 63, the resolution increases, and only a narrow range of loads (in this example, 1/2 times) can be used as effective load data, but the accuracy is improved. Thus, the range which needs to be transmitted to ECU1 as a control device among loads measurable by gauge 3 as a measurement part can be defined by a measurement reference value.

[Example 2 of changing measurement reference value]
Another specific example for changing the measurement reference value will be described below. 9 is a diagram for explaining the signal processing of the gauge output in the analog signal processing unit of FIG. 7, and FIG. 10 is a diagram for explaining another example of the signal processing shown in FIG.

  As shown in FIG. 9B, the output of the gauge 3 is a low voltage to be used as it is. For example, as a value immediately after the first adjustment or a design value (hereinafter referred to as an initial value), it is 0.1 V when the vehicle seat 20 is a vacant seat and a load W0 in a no-load state, and load data to be transmitted to the ECU 1 When the maximum load W1 of the effective data is, it is 0.3V. The width between the loads W0 and W1 is the effective data width of the load data to be transmitted to the ECU 1. The output of the gauge 3 is amplified by about 10 times in the case of this example based on the amplification factor (gain) determined by the gain resistors 12b and 12c by the amplifier 12a of the analog signal processing unit 12 shown in FIG. Is done. The initial value of the virtual ground VG that serves as a reference for amplification is ground (= 0 V), and the input to the A / D converter 13 is 1 V to 3 V in the effective data width W. The amplified gauge output voltage is A / D converted and transmitted to the ECU 1 as digital data.

  Here, a deviation occurs in the output voltage of the gauge 3, which is 0.15 V when the load W0 is in a no-load state, and the gain is 10 times with respect to 0 V, which is the initial value of the virtual ground VG, as described above. Is amplified, the effective data width W of the amplified gauge output voltage is between 1.5V and 3.5V. As a result, as shown in FIG. 9C, the upper limit reference voltage and the lower limit reference voltage of the A / D converter 13a and the effective data width W of the amplified gauge output voltage become mismatched.

  Therefore, in the present embodiment, the value of the virtual ground VG of the amplifier 12a of the analog signal processing unit 12 shown in FIG. 9A can be set as the measurement reference value. The virtual ground VG, which is a reference for amplification, is obtained by calculating the output voltage of the gauge 3 at the load W0 in the initial state or the no-load state at the latest adjustment and the output voltage of the gauge 3 at the current load W0. Change to a value based on the difference. In this example, since it is 0.1V and 0.15V as described above, the difference is 0.05V. Therefore, the value of the virtual ground VG of the amplifier 12a is set to 0.05V. By doing so, the effective data width W of the amplified gauge output voltage is changed from 1 V to 3 V, and the upper and lower reference voltages of the A / D converter 13a and the effective data width of the amplified gauge output voltage W is matched.

  Since the measurement reference value is a value that determines the output of the sensor 2 as the load detection device in a no-load state where no occupant is present on the vehicle seat 20, in this specific example, the value of the virtual ground VG of the amplifier 12a. Corresponds to this.

  Furthermore, as shown in FIG. 10A, the gain resistors 12b and 12c can be made variable, and the amplification factor determined by the gain resistors 12b and 12c can be used as the measurement reference value. A waveform A shown in FIG. 10B is the same as the waveform example having no deviation in the waveform example shown in FIG. 9C, and the output voltage of the gauge 3 in which no deviation occurs is obtained from the amplifier 12a. This is a case where the value of the virtual ground VG is amplified to about 10 times with 0V. Therefore, the gauge output voltage after amplification is obtained so that the effective data width W is between the output loads W0 and W1. A waveform B is obtained by amplifying the output voltage of the gauge 3 in which the deviation is not generated at a gain of about 20 times, and a waveform C is amplified by a gain of about 5 times. All of the waveforms A to C have a load W0 which is an unloaded state when the amplified voltage is 1V.

  In the waveform B, it reaches 3V that is the upper limit reference voltage of the A / D converter 13a at the time of the load W2 located substantially at the center of the effective data width W of the waveform A. On the contrary, in the waveform C, at the time of the maximum load W1 of the effective data width W of the waveform A, the upper limit reference voltage of the A / D converter 13a has not yet reached 3V, and the load W3 that is twice the load W1. At this point, the upper limit reference voltage of 3V is reached. Thus, by making the amplification factor of the analog signal processing unit 12 variable, it is possible to determine the range of the load that needs to be transmitted to the ECU 1. That is, the amplification factor of the analog signal processing unit 12 corresponds to a measurement reference value that is a value that determines a range that needs to be transmitted to the ECU 1 as the control device, among the loads that can be measured by the gauge 3 as the measurement unit. It is. In the example described with reference to FIG. 10, when obtaining the waveform B and the waveform C, it is necessary to appropriately set the value of the virtual ground VG of the amplifier 12a. In this case, the value of the virtual ground VG also corresponds to the measurement reference value. Become. Values such as the amplification factor and virtual ground VG used in the analog signal processing unit 12 are stored in the storage unit 5 and appropriately updated as described above.

  In the above example, the initial value of the virtual ground VG value of the amplifier 12a has been described as being ground = 0V. Then, for example, the value of the virtual ground VG for obtaining the waveform B is 0.05 V, the value of the virtual ground VG for obtaining the waveform C is minus 0.1 V, and a minus power supply is required. Conceivable. However, this is only an example used for ease of explanation, and there is no problem. For example, if a clamp circuit that applies a constant voltage to the output voltage of the gauge 3 is provided in the analog signal processing unit 12 and the constant voltage (clamp voltage) applied uniformly is set as the initial value of the virtual ground VG, Since there is a section having a positive potential with the ground, a negative power source is not required.

  In the description of the embodiment, the sensor 2 has the A / D converter 13 as the load detection device, and the digital data is used when the load data is output to the ECU 1 as the control device. Load data may be output. As described in the measurement reference value change example 2, when the value used in the analog signal processing unit 12 is configured as the measurement reference value, the load data may be output to the ECU 1 as analog data. The present invention is applicable.

  As described above, according to the present invention, it is possible to provide a vehicle occupant detection device that can detect a load on a vehicle seat with high accuracy and detect an occupant on the vehicle seat without impairing noise resistance.

The schematic diagram which shows arrangement | positioning of each part of the passenger | crew detection apparatus of the vehicle which concerns on embodiment of this invention. 1 is a block diagram showing a system configuration of a vehicle occupant detection device according to an embodiment of the present invention. Flowchart explaining the standard operation of the ECU of FIG. Flowchart explaining the standard operation of the sensor of FIG. The flowchart explaining the measurement reference change operation by ECU of FIG. Flowchart for explaining measurement reference changing operation of the sensor of FIG. Block diagram for explaining signal processing from the gauge of FIG. 2 to the A / D converter The figure explaining the A / D conversion by the A / D conversion part of FIG. The figure explaining the signal processing of the gauge output in the analog signal processing part of FIG. The figure explaining other examples of the signal processing shown in FIG.

Explanation of symbols

1 ECU
2 Sensor 3 Gauge 5 Memory

Claims (4)

A vehicle occupant detection device including a load detection device that detects a load of a vehicle seat and a control device that determines an occupant based on load data input from the load detection device,
The load detection device includes a measurement unit that measures a load, and a storage unit that stores a measurement reference value that determines a measurement reference by the measurement unit,
The storage unit is a vehicle occupant detection device configured to include rewritable and nonvolatile storage means.   The vehicle occupant detection device according to claim 1, wherein the measurement reference value is a value that determines an output of the load detection device in a no-load state where no occupant is present on the vehicle seat.   2. The vehicle occupant detection device according to claim 1, wherein the measurement reference value is a value that defines a range that needs to be transmitted to the control device among loads measurable by the measurement unit.   The vehicle occupant detection device according to any one of claims 1 to 3, wherein the load detection device executes measurement reference value update processing and updates the measurement reference value according to an instruction from the control device.

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