Pressure sensor malfunction detection device

An external impact avoiding part makes a sensor failure detection part withhold from determining that a right or left door pressure sensor has failed when a right-left detection difference calculated at first time is a threshold value or larger, and makes a detection value comparison part calculate the right-left detection difference again after a calming time has elapsed. An effect of closing operation of a right door on the right door pressure sensor or an effect of closing operation of a left door on the left door pressure sensor reduces during the calming time. The avoiding part subsequently makes the detection part compare the right-left detection difference calculated again with the threshold value. As a result of the comparison, when the right-left detection difference is the threshold value or larger, the avoiding part makes the detection part determine that the right or left door pressure sensor has failed.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2014-232905 filed on Nov. 17, 2014, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a pressure sensor malfunction detection device that detects a failure of a pressure sensor provided at a door of a vehicle.

BACKGROUND ART

Conventionally, a pressure sensor is attached in the door of a vehicle mainly to detect a collision with the side surface of the vehicle (hereinafter referred to as a side collision) thereby to detect a pressure change in the door. When a side collision occurs with the vehicle, the volume of the inside of the door changes, and its pressure change is detected by the pressure sensor attached. Consequently, the side collision with the vehicle is detected, and an occupant protection device such as an airbag device or a seat belt pretensioner is actuated to protect an occupant. The detection result by the above pressure sensor serves as a trigger for actuating the occupant protection device, and thus it should be an accurately-detected pressure change in the door. Thus, when the pressure sensor has failed, it has been necessary to detect this failure with precision, thus preventing the erroneous operation of the occupant protection device.

Regarding this issue, there is a conventional art relating to the method of detecting the failure of pressure sensors whereby to compare the detection values from a pair of pressure sensors provided in the right and left doors of a vehicle with each other and to determine that either one of the pressure sensors has failed when both the detection values are different beyond a predetermined degree (see, for example, Patent Document 1). In view of extremely rare failures of both the pressure sensors at the same time, the failure of either one of the pressure sensors can be detected by this conventional art. When the vehicle is located at high altitudes, both the pressure sensors detect abnormal values due to the change of the surrounding atmospheric pressure. Thus, the above conventional art can detect whether either one of the pressure sensors has failed or not separately from the abnormality of the pressure sensor due to the elevation where the vehicle is located.

PRIOR ART DOCUMENT

Patent Document

When the door of a vehicle is closed with great force, a pressure sensor provided in the door may detect a pressure change due to an impact made on the door. The abnormal value from the pressure sensor caused by the closing operation of the door has been often erroneously determined as the failure of the pressure sensor. If the pressure sensor is erroneously determined to have failed, the operation of the occupant protection device is prohibited, and the occupant cannot be protected from the collision of the vehicle.

SUMMARY OF INVENTION

The present disclosure addresses the above issues. Thus, it is an objective of the present disclosure to provide a pressure sensor malfunction detection device that can accurately determine whether a pressure sensor provided in a door of a vehicle has failed or not.

To achieve the objective, a pressure sensor malfunction detection device in an aspect of the present disclosure includes: a right door pressure sensor that is provided in a right door of a vehicle to detect a pressure change in the right door; a left door pressure sensor that is provided in a left door of the vehicle to detect a pressure change in the left door; a detection value comparison part that calculates a difference between a detection value by the right door pressure sensor and a detection value by the left door pressure sensor to calculate a right-left detection difference; a sensor failure detection part that determines that the right door pressure sensor or the left door pressure sensor has failed when the right-left detection difference calculated by the detection value comparison part is equal to or larger than a predetermined threshold value; and an external impact avoiding part that makes the sensor failure detection part withhold from determining that the right door pressure sensor or the left door pressure sensor has failed when the right-left detection difference calculated at first time by the detection value comparison part is equal to or larger than the threshold value. The external impact avoiding part makes the detection value comparison part calculate the right-left detection difference again after a predetermined calming time has elapsed. An effect of a closing operation of the right door on the right door pressure sensor or an effect of a closing operation of the left door on the left door pressure sensor reduces during the calming time. The external impact avoiding part subsequently makes the sensor failure detection part compare the right-left detection difference calculated again with the threshold value. As a result of the comparison, when the right-left detection difference is equal to or larger than the threshold value, the external impact avoiding part makes the sensor failure detection part determine that the right door pressure sensor or the left door pressure sensor has failed.

As a consequence of this configuration, the pressure sensor malfunction detection device includes an external impact avoiding part that makes the sensor failure detection part withhold from determining that the right door pressure sensor or the left door pressure sensor has failed when the right-left detection difference calculated at first time by the detection value comparison part is equal to or larger than the threshold value. After a predetermined calming time, during which an effect of a closing operation of the right door on the right door pressure sensor or an effect of a closing operation of the left door on the left door pressure sensor reduces, has elapsed, the external impact avoiding part makes the sensor failure detection part compare the right-left detection difference calculated again with the threshold value. As a result of the comparison, when the right-left detection difference is equal to or larger than the threshold value, the external impact avoiding part makes the sensor failure detection part determine that the right door pressure sensor or the left door pressure sensor has failed. Thus, it can be accurately determined whether the right door pressure sensor or the left door pressure sensor has failed or not based on the right-left detection difference calculated after the effect of the closing operation of the right door or the left door on the right door pressure sensor or the left door pressure sensor has reduced.

EMBODIMENTS FOR CARRYING OUT INVENTION

An occupant protection device1for a vehicle (corresponding to a pressure sensor malfunction detection device) in accordance with a first embodiment will be described with reference toFIGS. 1 to 4. As illustrated inFIG. 1, the occupant protection device1for a vehicle according to the present embodiment includes a right-front acceleration sensor2aand a left-front acceleration sensor2b, which are a pair of acceleration sensors. The right-front acceleration sensor2aand the left-front acceleration sensor2bare provided respectively at the right and left parts of the front surface of a vehicle8to detect the magnitude of the impact applied in a front-rear direction of the vehicle8(seeFIG. 2). The right-front acceleration sensor2aand the left-front acceleration sensor2bare hereinafter collectively referred to as acceleration sensors2a,2b. The acceleration sensors2a,2bmay be capacitance acceleration sensors, piezoresistance acceleration sensors, or acceleration sensors of a heat detection method.

A right door pressure sensor3ais attached to the inside of a driver's seat-side door8a(corresponding to “in a right door”) of the vehicle8, which is a right-hand drive vehicle. A left door pressure sensor3bis attached to the inside of a front passenger seat-side door8b(corresponding to “in a left door”) of the vehicle8. The right door pressure sensor3aand the left door pressure sensor3brespectively detect the pressure changes in the driver's seat-side door8aand the front passenger seat-side door8b, which are hinge doors to detect the impact applied in a right-left direction of the vehicle8. The right door pressure sensor3aand the left door pressure sensor3bmay be semiconductor strain gauge type pressure sensors, capacitance type pressure sensors, or other pressure sensors. The right door pressure sensor3aand the left door pressure sensor3bare hereinafter collectively referred to as pressure sensors3a,3b. The occupant protection device1for a vehicle includes an ignition switch4. The ignition switch4is provided for the vehicle8, and is a device for actuating an ignition device of an engine (not shown).

The acceleration sensors2a,2b, the pressure sensors3a,3b, and the ignition switch4are connected to an airbag controller5. The airbag controller5will be described later. An airbag device6(corresponding to an occupant protection part) is connected to the airbag controller5. The airbag device6is similar to a device of a prior and existing type, and is formed by an inflator, a bag, and an ignition device, which are not shown. The airbag device6includes a driver's seat airbag, a front passenger seat airbag, a pillar airbag accommodated in a front pillar (A-pillar)8c, and curtain airbags accommodated in a right lateral part and a left lateral part of the vehicle8(all these airbags are not shown). The airbag device6is deployed at the time of a collision of the vehicle8to protect an occupant's body against the impact applied to the vehicle8.

The airbag controller5is a control device formed by an input/output device, a CPU, a RAM, and so forth, and is attached to the lower part of a dashboard on a front side of the driver's seat (seeFIG. 2). The airbag controller5includes a detection value determination part5a, an airbag drive part5b, a right-left detection difference operation part5c, a sensor failure detection part5d, a disturbance avoiding part5e, a floor acceleration sensor5f, and an initial check part5g. Based on the accelerations detected by the acceleration sensors2a,2bor the pressure changes detected by the pressure sensors3a,3b, the detection value determination part5a(corresponding to a collision detection part) determines whether such a collision as to actuate the airbag device6of the vehicle8has occurred. If the detection value determination part5adetermines that such a collision as to actuate the airbag device6of the vehicle8has occurred, the airbag drive part5b(corresponding to a protection drive part) applies a squib current for actuating the airbag device6to the airbag device6. The right-left detection difference operation part5c(corresponding to a detection value comparison part) calculates the difference between the detection value by the right door pressure sensor3aand the detection value by the left door pressure sensor3bto calculate a right-left detection difference |PSR−PSL| (≥0). If the right-left detection difference |PSR−PSL| calculated by the right-left detection difference operation part5cis equal to or larger than a predetermined threshold value Dif, the sensor failure detection part5d(corresponding to a sensor failure detection part) determines that the pressure sensor3a,3bhas failed.

If the right-left detection difference |PSR−PSL| calculated at the first time by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif, the disturbance avoiding part5e(corresponding to an external impact avoiding part) makes the sensor failure detection part5dwithhold from determining that the pressure sensor3a,3bhas failed. Then, after a predetermined individual calming time Tdm (corresponding to a calming time), during which the effect of the closing operation of the driver's seat-side door8aon the right door pressure sensor3aor the effect of the closing operation of the front passenger seat-side door8bon the left door pressure sensor3breduces, has elapsed, the right-left detection difference operation part5cis made to calculate the right-left detection difference |PSR−PSL| again. Subsequently, as a result of the comparison between the right-left detection difference |PSR−PSL| calculated again and the threshold value Dif by the sensor failure detection part5d, it is determined that the pressure sensor3a,3bhas failed if the right-left detection difference |PSR−PSL| is equal to or larger than the threshold value Dif. The floor acceleration sensor5fis formed to be capable of detecting the acceleration of the vehicle8in the front-rear direction and in the right-left direction. The floor acceleration sensor5fmay include independently a sensor that can detect the acceleration of the vehicle8in the right-left direction, and a sensor that can detect the acceleration of the vehicle8in the front-rear direction. The initial check part5g(corresponding to an operation check part) checks (initial check) whether the airbag device6can be driven normally by the airbag controller5after the ignition switch4is turned on.

As illustrated inFIG. 3, when the driver's seat-side door8aor the front passenger seat-side door8bof the vehicle8, which is a hinge door, is closed, the pressure sensor3a,3bthat is integrated in one of the driver's seat-side door8aand the front passenger seat-side door8bfor which this closing operation is carried out detects a sharp pressure rise (time point indicated by t0inFIG. 3) due to the impact. After that, a pressure fluctuation continues to be detected by the pressure sensor3a,3b. Thus, the above-described determination that the pressure sensor3a,3bhas failed based on the right-left detection difference |PSR−PSL| cannot be accurately made while this pressure fluctuation is continuing. However, when the above individual calming time Tdm elapses after the driver's seat-side door8aor the front passenger seat-side door8bis closed, the pressure fluctuation reduces, so that the determination that the pressure sensor3a,3bhas failed can be made. A specific value for the above individual calming time Tdm can be obtained through a repeated experiment using an actual vehicle.

The flow of the method of detecting the failure of the pressure sensors3a,3bby the airbag controller5of the present embodiment will be described with reference toFIG. 4. Firstly, when the ignition switch4of the vehicle8is turned on (S101), the initial check part5gdetermines whether the airbag device6can be driven normally (S102). If it is determined by the initial check that there is anything abnormal with the occupant protection device1for a vehicle and that the airbag device6is not driven normally, control proceeds to S111. At S111, the operation of the airbag device6by the airbag drive part5bis prohibited to end this flow. On the other hand, if it is determined at S102that the occupant protection device1for a vehicle is not abnormal and that the airbag device6can be driven normally, a timer in the airbag controller5is started after a count time is reset (S103). After that, a pressure PSR in the driver's seat-side door8ais detected by the right door pressure sensor3a(S104), and then a pressure PSL in the front passenger seat-side door8bis detected by the left door pressure sensor3b(S105). In this flow, the pressure PSL is detected by the left door pressure sensor3bafter the detection of the pressure PSR by the right door pressure sensor3a, but actually, both the pressures PSL are assumed to be detected at the same time point without trouble, since a time difference between both the detections is very small.

Then, the right-left detection difference operation part5ccalculates the first-time right-left detection difference |PSR−PSL| using the detected pressures PSR, PSL. The sensor failure detection part5ddetermines whether the right-left detection difference |PSR−PSL| calculated by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif (S106). If the right-left detection difference |PSR−PSL| is smaller than the threshold value Dif (corresponding to “smaller than a threshold value”), it is determined that the pressure sensors3a,3bare normal to end this flow (S109). On the other hand, if it is determined at S106that the right-left detection difference |PSR−PSL| is equal to or larger than the threshold value Dif, the disturbance avoiding part5edetermines whether the detection of the pressure PSR in the driver's seat-side door8aand the pressure PSL in the front passenger seat-side door8bat this time is the first detection (S107). If the detection of the pressures PSR, PSL at this time is the first detection, the disturbance avoiding part5edoes not make the sensor failure detection part5ddetermine that the pressure sensor3a,3bhas failed (withholds from the determination that the pressure sensor3a,3bhas failed).

Subsequently, the disturbance avoiding part5econfirm with the timer that the individual calming time Tdm has elapsed, and then returns to S104again to perform the detection of the pressures PSR, PSL at the second time (S108). After that, the right-left detection difference operation part5cagain calculates the right-left detection difference |PSR−PSL| using the detected pressures PSR, PSL. The sensor failure detection part5ddetermines whether the right-left detection difference |PSR−PSL| calculated by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif (S106). If it is determined by the sensor failure detection part5dthat the right-left detection difference |PSR−PSL| is equal to or larger than the threshold value Dif, it is again determined at S107whether the detection of the pressure PSR in the driver's seat-side door8aand the pressure PSL in the front passenger seat-side door8bat this time is the first detection. If it is determined that the detection of the pressures PSR, PSL at this time is not the first detection, the sensor failure detection part5ddetermines that the pressure sensor3a,3bhas failed (S110). Then, the operation of the airbag device6by the airbag drive part5bis prohibited at S111to end this flow.

In the present embodiment, if the right-left detection difference |PSR−PSL| calculated at the first time by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif, the disturbance avoiding part5eof the occupant protection device1for a vehicle withholds from the determination by the sensor failure detection part5dthat the pressure sensor3a,3bhas failed. Subsequently, after the predetermined individual calming time Tdm, during which the effect of the closing operation of the driver's seat-side door8aon the right door pressure sensor3aor the effect of the closing operation of the front passenger seat-side door8bon the left door pressure sensor3breduces, has elapsed, the disturbance avoiding part5emakes the comparison between the right-left detection difference |PSR−PSL| calculated again and the threshold value Dif. As a consequence, if the right-left detection difference |PSR−PSL| is equal to or larger than the threshold value Dif, it is determined that the pressure sensor3a,3bhas failed. Thus, it can be accurately determined whether the pressure sensor3a,3bhas failed or not based on the right-left detection difference |PSR−PSL| calculated after the effect of the closing operation of the driver's seat-side door8aor the front passenger seat-side door8bon the pressure sensor3a,3bhas reduced. When the ignition switch4of the vehicle8is turned on, the right-left detection difference operation part5ccalculates the right-left detection difference |PSR−PSL| at the first time. Consequently, the failure of the pressure sensors3a,3bis not constantly detected, so that the loads on the airbag controller5and the entire occupant protection device1for a vehicle due to the failure detection can be reduced.

The occupant protection device1for a vehicle includes the detection value determination part5athat detects the collision of the vehicle8based on the detection values by the acceleration sensors2a,2band the pressure sensors3a,3b, the airbag device6that protects the occupant's body against the impact applied to the vehicle8, the airbag drive part5bthat actuates the airbag device6when the detection value determination part5adetects the collision of the vehicle8, and the initial check part5gthat determines whether the airbag device6is driven normally. After the initial check part5gdetermines that the airbag device6is driven normally, the detection value determination part5acalculates the right-left detection difference |PSR−PSL| at the first time. Consequently, the abnormal condition of the occupant protection device1for a vehicle can be eliminated before the failure of the pressure sensors3a,3bis detected. Thus, the abnormal condition due to the failure of the pressure sensors3a,3bcan be detected accurately. When it is determined by the sensor failure detection part5dthat the pressure sensor3a,3bhas failed, the airbag drive part5bprohibits the operation of the airbag device6. Consequently, the erroneous operation of the airbag device6due to the failure of the pressure sensors3a,3bcan be prevented to provide the safe and highly reliable occupant protection device1for a vehicle.

Only the differences of an occupant protection device1A for a vehicle in accordance with a second embodiment (corresponding to a pressure sensor malfunction detection device) from the first embodiment will be described below with reference toFIGS. 5 to 7. As illustrated inFIG. 5, an airbag controller5A of the present embodiment includes an average value operation part5h(corresponding to an average value calculation part) in addition to the configuration of the airbag controller5of the first embodiment. The average value operation part5haverages the detection values by a right door pressure sensor3aat two points (corresponding to a plurality of points) at which their detection time points are mutually different to calculate a right detection average value Rav. The average value operation part5haverages the detection values by a left door pressure sensor3bat the two points to calculate a left detection average value Lav. A right-left detection difference operation part5cof the present embodiment calculates the difference between the right detection average value Rav and the left detection average value Lav calculated by the average value operation part5hto calculate a right-left detection difference |Rav−Lav| (≥0).

The specific explanation will be given below. As illustrated inFIG. 6, the right door pressure sensor3aof the present embodiment detects a pressure Data (nR) in a driver's seat-side door8aeach time a time Tde ((Tde×2) corresponds to a predetermined period) elapses. The left door pressure sensor3bdetects a pressure Data (nL) in a front passenger seat-side door8beach time the time Tde elapses (corresponding to “the predetermined period elapses”). “n” in the pressure Data (nR), Data (nL) represents a detection time number. The pressures at mutually the same time point are detected for the pressures Data (nR), Data (nL). At the first time, the above average value operation part5haverages the detection values Data1R, Data2R by the right door pressure sensor3afor the pressure Data (nR) in the driver's seat-side door8ato calculate the right detection average value Rav at that time. The average value operation part5haverages the detection values Data1L, Data2L by the left door pressure sensor3bfor the pressure Data (nL) in the front passenger seat-side door8bto calculate the left detection average value Lav at that time. Based on the right detection average value Rav calculated by averaging the detection values Data1R, Data2R, and the left detection average value Lav calculated by averaging the detection values Data1L, Data2L, the right-left detection difference operation part5ccalculates the right-left detection difference |Rav−Lav|. Based on the right-left detection difference |Rav−Lav| which is the difference between the right detection average value Rav calculated by averaging the detection values Data1R, Data2R, and the left detection average value Lav calculated by averaging the detection values Data1L, Data2L, a sensor failure detection part5dmakes the first (first time) determination of the failure of the pressure sensors3a,3b.

If the right-left detection difference |Rav−Lav| calculated at the first time is equal to or larger than a threshold value Dif, a disturbance avoiding part5emakes the sensor failure detection part5dwithhold from determining that the pressure sensor3a,3bhas failed. After that, the average value operation part5his made to average the detection values Data3R, Data4R and to calculate the right detection average value Rav at that time, and the average value operation part5his made to average the detection values Data3L, Data4L and to calculate the left detection average value Lav at that time. Next, the right-left detection difference operation part5cis made to calculate the right-left detection difference |Rav−Lav| obtained by the difference between the right detection average value Rav calculated by averaging the detection values Data3R, Data4R, and the left detection average value Lav calculated by averaging the detection values Data3L, Data4L, and the sensor failure detection part5dis made to perform the second determination of the failure of the pressure sensors3a,3b. Similarly in the process thereafter, the disturbance avoiding part5emakes the right-left detection difference operation part5ccalculate the right-left detection difference |Rav−Lav| repeatedly each time a time (Tde×2) that is shorter than the calming time elapses until a mutual calming time {(Tdm×2)+(Tde×2)} (corresponding to the calming time) elapses, unless the pressure sensors3a,3bare determined to be normal halfway through the process. At the time of each calculation of the right-left detection difference |Rav−Lav|, the disturbance avoiding part5emakes the sensor failure detection part5dcompare the right-left detection difference |Rav−Lav| with the threshold value Dif. If the right-left detection difference |Rav−Lav| calculated before the mutual calming time {(Tdm×2)+(Tde×2)} elapses is equal to or larger than the threshold value Dif, the disturbance avoiding part5ewithholds from the determination by the sensor failure detection part5dthat the pressure sensor3a,3bhas failed. At the time when the right-left detection difference |Rav−Lav| calculated before the mutual calming time {(Tdm×2)+(Tde×2)} elapses is smaller than the threshold value Dif the disturbance avoiding part5emakes the sensor failure detection part5ddetermine that the pressure sensors3a,3bare normal.

In the present embodiment, the disturbance avoiding part5esimulates the strictest condition to set the mutual calming time {(Tdm×2)+(Tde×2)} that needs to elapse to avoid the effect of the closing operation of the driver's seat-side door8aon the right door pressure sensor3aor the effect of the closing operation of the front passenger seat-side door8bon the left door pressure sensor3b. Specifically, the present embodiment considers the case where the front passenger seat-side door8bis closed and the driver's seat-side door8ais closed immediately after its effect on the left door pressure sensor3bis reduced (the order of the closing operations of the driver's seat-side door8aand the front passenger seat-side door8bmay be switched). The condition simulated to calculate the mutual calming time {(Tdm×2)+(Tde×2)} in the present embodiment will be described in detail below with reference toFIG. 6. Similar to the case of the first embodiment, the present embodiment also requires the above individual calming time Tdm respectively to reduce the effect of the closing operation of the driver's seat-side door8aon the right door pressure sensor3aor the effect of the closing operation of the front passenger seat-side door8bon the left door pressure sensor3b. The configuration is set to be capable of detecting the pressures in the driver's seat-side door8aand in the front passenger seat-side door8b(n−2) times by the pressure sensors3a,3bwhile the individual calming time Tdm elapses (Tdm/(n−2)=Tde).

First, the front passenger seat-side door8bis assumed to be closed after the detection value Data1L is detected before the detection value Data2L is detected by the left door pressure sensor3b. In this case, the closing operation of the front passenger seat-side door8bhas an effect on the left door pressure sensor3bfrom the detection value Data2L to the detection value Data(n−1)L. Thus, the first to Nth determinations of the failure of the pressure sensors3a,3bcannot be performed accurately by the sensor failure detection part5d. Subsequently, the driver's seat-side door8ais assumed to be closed after the detection value Data(n+1)R is detected before the detection value Data(n+2)R is detected by the right door pressure sensor3a. In this case, the closing operation of the driver's seat-side door8ahas an effect on the right door pressure sensor3afrom the detection value Data(n+2)R to the detection value Data(2n−1)R. Thus, the (N+1)th to 2 Nth determinations of the failure of the pressure sensors3a,3bcannot be performed accurately by the sensor failure detection part5d. For those hatched of the symbols representing the detection values Data(nR), Data(nL) by the pressure sensors3a,3binFIG. 6, the closing operation of the driver's seat-side door8aor the front passenger seat-side door8bhas an effect on their detection values. For these reasons, it is found that the (2N+1)th determination of the failure of the pressure sensors3a,3bcan also be performed accurately by the sensor failure detection part5din the case where the front passenger seat-side door8bis closed and the driver's seat-side door8ais closed immediately after its effect on the left door pressure sensor3bis reduced. Therefore, the mutual calming time of the present embodiment, during which the effect of the closing operation of the driver's seat-side door8aor the closing operation of the front passenger seat-side door8bon the pressure sensor3a,3breduces, is expressed by {(Tdm×2)+(Tde×2)} (seeFIG. 6).

The flow of the method of detecting the failure of the pressure sensors3a,3bby the airbag controller5A of the present embodiment will be described with reference toFIG. 7. “Ntr” in the flow chart illustrated inFIG. 7represents the number of times of the determination of the failure of the pressure sensors3a,3bindicated inFIG. 6. Firstly, when an ignition switch4of a vehicle8is turned on (S201), an initial check part5gdetermines whether an airbag device6can be driven normally by the airbag controller5(S202). If it is determined by the initial check that there is anything abnormal with the occupant protection device1A for a vehicle and that the airbag device6is not driven normally, control proceeds to S211. At S211, the operation of the airbag device6by an airbag drive part5bis prohibited to end this flow.

On the other hand, if it is determined at S202that the occupant protection device1A for a vehicle is not abnormal and that the airbag device6can be driven normally, Ntr is incremented by one (S204) after setting: Ntr=0 (S203). Then, the right door pressure sensor3adetects the pressures Data1R, Data2R in the driver's seat-side door8a(S205). Next, the left door pressure sensor3bdetects the pressures Data1L, Data2L in the front passenger seat-side door8b(S206). The average value operation part5haverages the detection values Data1R, Data2R to calculate the right detection average value Rav, and averages the detection values Data1L, Data2L to calculate the left detection average value Lav (S207). After that, using the detected right detection average value Rav and the detected left detection average value Lav, the right-left detection difference operation part5ccalculates the right-left detection difference |Rav−Lav|, and the sensor failure detection part5ddetermines whether the right-left detection difference |Rav−Lav| calculated by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif (S208). If the right-left detection difference |Rav−Lav| is smaller than the threshold value Dif, it is determined that the pressure sensors3a,3bare normal to end this flow (S212).

On the other hand, if it is determined at S208that the right-left detection difference |Rav−Lav| is equal to or larger than the threshold value Dif, the disturbance avoiding part5edetermines whether the number Ntr of times of the determination of the failure of the pressure sensors3a,3bat this time is equal to or larger than Npd (S209). As will be appreciated from the foregoing, Npd is set at (2N+1). If the number Ntr of times of the failure determination at this time does not reach (2N+1)th determination, the disturbance avoiding part5emakes the sensor failure detection part5dwithhold from determining that the pressure sensor3a,3bhas failed. The disturbance avoiding part5ereturns to S204again to increment Ntr by one, and then carries out the detection of the pressures Data(nR), Data(nL) again. Using the right detection average value Rav and the left detection average value Lav, which are obtained respectively by averaging the detected pressures Data(nR), Data(nL), the right-left detection difference operation part5ccalculates again the right-left detection difference |Rav−Lav|, and the sensor failure detection part5ddetermines whether the right-left detection difference |Rav−Lav| calculated by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif (S208). If it is determined at S209that the number Ntr of times of the determination of the failure of the pressure sensors3a,3bat this time is equal to or larger than Npd (=2N+1), it is determined that the pressure sensor3a,3bhas failed (S210), and then the operation of the airbag device6by the airbag drive part5bis prohibited at S211to end this flow.

In the present embodiment, the occupant protection device1A for a vehicle includes the average value operation part5hthat averages the detection values Data(nR) by the right door pressure sensor3aat two points, at which their detection time points are mutually different, to calculate the right detection average value Rav, and that averages the detection values Data(nL) by the left door pressure sensor3bat these two points to calculate the left detection average value Lav. The right-left detection difference operation part5ccalculates the difference between the right detection average value Rav and the left detection average value Lav calculated by the average value operation part5hto calculate the right-left detection difference |Rav−Lav|. Consequently, the pressure detection values Data(nR), Data(nL) at two points at which their detection time points are mutually different are averaged respectively to calculate the right detection average value Rav and the left detection average value Lav. Thus, the variation of the pressure detection values can be reduced, so that the accuracy in detecting the failure of the pressure sensors3a,3bcan be improved.

If the right-left detection difference |Rav−Lav| calculated at the first time by the right-left detection difference operation part5cis equal to or larger than the threshold value Dif, the disturbance avoiding part5emakes the right-left detection difference operation part5ccalculate the right-left detection difference |Rav−Lav| repeatedly each time the time (Tde×2) that is shorter than the mutual calming time {(Tdm×2)+(Tde×2)} elapses until the mutual calming time {(Tdm×2)+(Tde×2)} elapses, and makes the sensor failure detection part5dcompare the calculated right-left detection difference |Rav−Lav| with the threshold value Dif for each calculation. If the right-left detection difference |Rav−Lav| calculated before the mutual calming time {(Tdm×2)+(Tde×2)} elapses is equal to or larger than the threshold value Dif, the disturbance avoiding part5ewithholds from the determination by the sensor failure detection part5dthat the pressure sensor3a,3bhas failed. At the time when the right-left detection difference |Rav−Lav| calculated before the mutual calming time {(Tdm×2)+(Tde×2)} elapses is smaller than the threshold value Dif the disturbance avoiding part5emakes the sensor failure detection part5ddetermine that the pressure sensors3a,3bare normal. Consequently, if the pressure sensors3a,3bare normal, the failure detection can be ended quickly to mitigate the loads on the airbag controller5A and the occupant protection device1A for a vehicle. The disturbance avoiding part5esets the mutual calming time {(Tdm×2)+(Tde×2)} on the assumption that: after the effect of the closing operation of one of the driver's seat-side door8aand the front passenger seat-side door8bon the right door pressure sensor3aor the left door pressure sensor3bhas reduced, the other one of the driver's seat-side door8aand the front passenger seat-side door8bis closed. As a result, it can be accurately determined whether the right door pressure sensor3aor the left door pressure sensor3bhas failed or not even in the situation where the closing operations of the driver's seat-side door8aand the front passenger seat-side door8bare continuously performed to cause a long mutual calming time {(Tdm×2)+(Tde×2)}.

The present disclosure is not limited to the above embodiments, and can be modified or expanded as follows. In the present disclosure, a seat belt device with a pretensioner may be used for the occupant protection part to give tension to a seat belt, thus protecting the occupant when the detection value by one of the acceleration sensors2a,2band the pressure sensors3a,3bis equal to or larger than a predetermined threshold value. The regions to which the pressure sensors3a,3bare attached are not only the driver's seat-side door8aand the front passenger seat-side door8b, but may be the rear seat doors of the vehicle8. The pressure sensors3a,3bmay be attached to slide doors of the vehicle8. In addition to the acceleration sensors2a,2band the pressure sensors3a,3b, a gyro sensor may be used to determine whether to actuate the airbag device6or not in the vehicle8In the second embodiment, the detection values Data(nR), Data(nL) by the pressure sensors3a,3bat three or more points at which their detection time points are mutually different may be averaged respectively to calculate the right detection average value Rav and the left detection average value Lav. In the second embodiment, each time the time Tde elapses, the right-left detection difference |PSR−PSL| may be calculated using the detection values PSR, PSL by the pressure sensors3a,3b(without calculating the right detection average value Rav or the left detection average value Lav), for the comparison between the right-left detection difference |PSR−PSL| and the threshold value Dif to detect the failure of the pressure sensors3a,3b.