JP5182149B2 - Sensor failure detection device - Google Patents

Description

  The present invention relates to a sensor failure detection device that detects a failure of an in-vehicle sensor device.

  2. Description of the Related Art Conventionally, vehicle-mounted sensor devices that output analog and digital sensor signals are known. In addition, a sensor failure detection device that detects such a sensor failure is known. For example, a sensor failure detection device described in Patent Document 1 detects a failure of a yaw rate sensor that outputs analog and digital sensor signals. In this sensor failure detection device, the sensor values of the analog sensor signal and the digital sensor signal are compared, and if the sensor values do not match, it is detected that a failure has occurred in the yaw rate sensor.

JP 2008-116339 A

  Incidentally, the sensor failure detection apparatus described in Patent Document 1 acquires the sensor value of an analog sensor signal by digitizing the analog sensor signal with an AD converter. Therefore, even when a failure occurs in the AD converter, it is detected that a failure has occurred in the yaw rate sensor. Such a problem may also occur in a sensor failure detection device that detects a failure in an in-vehicle sensor device other than the yaw rate sensor.

  The present invention has been made in order to solve the above-described problems, and has as its main object to provide a sensor failure detection device capable of improving the failure detection accuracy of an in-vehicle sensor device.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The present invention is applied to an in-vehicle sensor device that outputs an output signal of a sensor unit as an analog first sensor signal via a resistor and outputs the output signal as a second sensor signal without passing through a resistor. An AD converter that digitizes the first sensor signal, acquires the sensor value of the second sensor signal and the sensor value of the first sensor signal digitized by the AD converter, and is mounted on the vehicle based on the sensor value It is a sensor failure detection device that detects a failure of a sensor device.

  In such a configuration, a signal of a predetermined failure detection level is output from the sensor unit in a state where a power short circuit or a ground short circuit has occurred in the resistor side of the AD converter in the signal path of the first sensor signal. Even if the in-vehicle sensor device is controlled so that the signal is output, the sensor value of the second sensor signal becomes a predetermined level according to the output current characteristic of the sensor unit and the resistance value of the resistor, and may not become a failure detection level. Conceivable. Specifically, a signal with a predetermined failure detection level is output from the sensor unit in a state where a power supply short-circuit failure has occurred in the resistor side of the signal path of the first sensor signal. When the on-vehicle sensor device is controlled, the current from the power source flows to the sensor unit via the resistor, so that the sensor value of the second sensor signal becomes a voltage level lower than the power source level by the voltage drop in the resistor. Conceivable. Further, a signal having a predetermined failure detection level is output from the sensor unit in a state where a ground level short-circuit failure has occurred in a portion of the signal path of the first sensor signal on the resistor side of the AD converter. Even if the vehicle-mounted sensor device is controlled, the sensor value of the second sensor signal becomes a voltage level higher than the ground level by the voltage drop in the resistor because the current flows from the sensor unit to the ground through the resistor. It is possible.

Therefore, in the first aspect of the present invention, the sensor value of the second sensor signal acquired in a state in which the in-vehicle sensor device is controlled so that a failure detection level signal is output from the sensor unit is When the level is a predetermined level corresponding to the output current characteristics and the resistance value of the resistor, it is detected that a failure has occurred in a portion of the signal path of the first sensor signal on the resistor side of the AD converter.
According to the first aspect of the present invention, a failure in a portion closer to the resistor than the AD converter in the signal path of the first sensor signal is detected separately from a failure in the AD converter of the sensor failure detection device. Can do. As a result, it is possible to improve the detection accuracy of the failure of the in-vehicle sensor device.

In addition, in the state where a failure has occurred in the resistor side of the AD converter in the signal path of the first sensor signal, there is a high probability that the sensor value of the first sensor signal does not reach the failure detection level.
Therefore, in the invention according to claim 2, as a detection condition for detecting that a failure has occurred in a portion of the signal path of the first sensor signal on the resistor side of the AD converter, in the output control state, This includes that the sensor value of the acquired first sensor signal is not at the failure detection level.
According to the invention described in claim 2, in addition to the failure detection condition of the invention described in claim 1, the in-vehicle sensor device is controlled so that a signal of a predetermined failure detection level is output from the sensor unit. The fact that the sensor value of the first sensor signal acquired in the state is not at the failure detection level is detected that a failure has occurred in the resistor side of the AD converter in the signal path of the first sensor signal. Since the detection condition is used, the failure can be detected with high accuracy.

On the other hand, even if a failure occurs in the AD converter of the sensor failure detection device, it is considered that the influence of the failure does not reach the sensor value of the second sensor signal.
Therefore, in the invention according to claim 3, the sensor value of the first sensor signal acquired in a state where the vehicle-mounted sensor device is controlled so that a signal of a predetermined failure detection level is output from the sensor unit is the sensor value. When the sensor value of the second sensor signal acquired in the same state is different from the failure detection level at the time of acquisition of the value and is at the failure detection level, it is detected that a failure has occurred in the AD converter.
According to the invention described in claim 3, it is possible to detect a failure of the AD converter of the sensor failure detection device.

  In the invention according to claim 4, the in-vehicle sensor device is controlled so that a power level or ground level signal is output from the sensor unit as a failure detection level. And the sensor value of the 1st sensor signal and the 2nd sensor signal which were acquired in the 1st output control state which is controlling the vehicle-mounted sensor apparatus so that the signal of a power supply level may be output from a sensor part, and ground from a sensor part Failure detection is performed based on the first sensor signal and the sensor value of the second sensor signal acquired in the second output control state in which the in-vehicle sensor device is controlled so that a level signal is output.

According to the fourth aspect of the present invention, even if any failure of the power supply short circuit or the ground short circuit occurs in the resistor side of the signal path of the first sensor signal, the failure is detected. can do. As a result, it is possible to further improve the detection accuracy of the failure of the in-vehicle sensor device.
That is, the fact that a power supply short-circuit failure has occurred in the resistor side of the AD converter in the signal path of the first sensor signal means that a ground level signal is output from the sensor unit. It can be detected by controlling. Specifically, the vehicle-mounted sensor is configured so that a ground level signal is output from the sensor unit in a state where a power supply short-circuit failure occurs in a portion of the signal path of the first sensor signal on the resistor side of the AD converter. When the device is controlled, a current flows from the power supply to the sensor unit via the resistor, so that the sensor value of the second sensor signal becomes a voltage level lower than the power supply level by the voltage drop in the resistor.
In addition, the fact that a ground short failure has occurred in the portion of the signal path of the first sensor signal between the AD converter and the resistor side means that a power level signal is output from the sensor unit. Detection is possible by controlling the sensor device. Specifically, the vehicle-mounted sensor is configured so that a power level signal is output from the sensor unit when a ground short failure occurs in a portion of the signal path of the first sensor signal on the resistor side of the AD converter. When the device is controlled, a current flows from the sensor unit to the ground via the resistor, so that the sensor value of the second sensor signal is higher than the ground level by the voltage drop in the resistor.

  Here, as described above, a ground level signal is output from the sensor unit in a state where a power supply short-circuit failure has occurred in the resistor side of the signal path of the first sensor signal. When the in-vehicle sensor device is controlled as described above, a current flows from the power source to the sensor unit via the resistor, and the current value is considered to be the maximum sink current value of the sensor unit. The vehicle-mounted sensor device outputs a power level signal from the sensor unit in a state where a ground short failure has occurred in a portion of the signal path of the first sensor signal closer to the resistor than the AD converter. Is controlled, a current flows from the sensor unit to the ground via a resistor, and the current value is considered to be the maximum source current value of the sensor unit.

Therefore, in the invention according to claim 5, the sensor value of the second sensor signal acquired in the first output control state is ground level by a voltage corresponding to the maximum source current value of the sensor unit and the resistance value of the resistor. When the voltage is higher than that of the first sensor signal, it is detected that a ground short fault has occurred in the resistor side of the signal path of the first sensor signal, and is acquired in the second output control state. When the sensor value of the second sensor signal is a voltage lower than the power supply level by a voltage corresponding to the maximum sink current value of the sensor unit and the resistance value of the resistor, AD conversion is performed on the signal path of the first sensor signal. Detects that a power supply short circuit has occurred in the resistor side of the resistor.
According to the fifth aspect of the present invention, it is possible to detect a failure mode (power supply short / ground short) in a portion of the signal path of the first sensor signal closer to the resistor than the AD converter.

  Furthermore, if the vehicle sensor device is controlled so that a ground level signal is output from the sensor unit in a state where the power supply level is fixed in the AD converter, the sensor value of the first sensor signal becomes the power level. The sensor value of the second sensor signal is considered to be the ground level. In addition, when the vehicle-mounted sensor device is controlled so that a power level signal is output from the sensor unit in a state where the ground level is fixed in the AD converter, the sensor value of the first sensor signal becomes the ground level. The sensor value of the second sensor signal is considered to be the power supply level.

Therefore, in the invention described in claim 6, the sensor value of the first sensor signal acquired in the first output control state is the ground level, and the sensor value of the second sensor signal acquired in the same state is the power source. When the level is the level, it is detected that a failure of fixing the ground level has occurred in the AD converter, the sensor value of the first sensor signal acquired in the second output control state is the power level, and in the same state When the sensor value of the acquired second sensor signal is the ground level, it is detected that a failure with a fixed power supply level has occurred in the AD converter.
According to the invention described in claim 6, it is possible to detect a failure mode (fixed power level / fixed ground level) of the AD converter.

The block diagram which shows the structure of an acceleration sensor and a sensor failure detection apparatus. The figure which shows the sensor value and parity check result of the analog sensor signal in the normal state and various failure states of a system, and a digital sensor signal. The flowchart which shows the flow of a system failure detection program.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, the present invention is embodied as an electronic control device (hereinafter referred to as an ECU) that detects a failure of an acceleration sensor mounted on a vehicle, and a detailed configuration thereof will be described below.

FIG. 1 is a block diagram showing configurations of the acceleration sensor 10 and the ECU 20.
The acceleration sensor 10 shown in FIG. 1 outputs an analog sensor signal and a digital sensor signal corresponding to the acceleration applied to the acceleration sensor 10. Specifically, the acceleration sensor 10 includes a sensor element 11. The sensor element 11 is formed with a capacitor including a fixed electrode and a movable electrode (not shown). The movable electrode is displaced with respect to the fixed electrode in accordance with the acceleration applied to the sensor element 11. An operational amplifier 12 that amplifies the output signal of the sensor element 11 is connected to the sensor element 11. An analog output terminal TS1 is connected to the operational amplifier 12 via a protective resistor 13 and a digital output terminal TS2 is connected via a LAN interface 15. The LAN interface 15 includes a signal conversion circuit 15a that converts an analog signal output from the operational amplifier 12 into a serial signal, and a parity circuit 15b that adds a parity bit to the serial signal.

  In this case, in the sensor element 11, the capacitance of the capacitor composed of the movable electrode and the fixed electrode changes according to the acceleration applied to the sensor element 11, and an analog signal corresponding to the capacitance change is output. This analog signal is output as an analog sensor signal via the operational amplifier 12, the protective resistor 13, and the analog output terminal TS1. The analog signal amplified by the operational amplifier 12 is converted to a serial signal with a parity bit by the LAN interface 15 and output as a digital sensor signal via the digital output terminal TS2.

  The acceleration sensor 10 has, as an internal state, a “first output control state” and a “second output control state” in addition to a “normal state” that outputs a sensor signal corresponding to the acceleration as described above. Here, the first output control state and the second output control state are states for outputting a signal of a failure detection level corresponding to each failure detection state from the operational amplifier 12. In the present embodiment, the first output control state is an internal state for outputting a power level signal from the operational amplifier 12, and the second output control state is an internal state for outputting a ground level signal from the operational amplifier 12. Is assumed. In the acceleration sensor 10, it is assumed that each internal state can be changed by applying a predetermined voltage to the control input terminal TS3.

  The acceleration sensor 10 corresponds to an “in-vehicle sensor device”, and the sensor element 11 and the operational amplifier 12 correspond to a “sensor unit”. Further, the analog sensor signal and the digital sensor signal correspond to a “first sensor signal” and a “second sensor signal”, respectively.

  The acceleration sensor 10 is connected to an ECU 20 as a sensor failure detection device. Specifically, the analog output terminal TS1 and the control input terminal TS3 of the acceleration sensor 10 are connected to the analog input terminal TE1 and the control output terminal TE3 of the ECU 20, respectively. The digital output terminal TS2 of the acceleration sensor 10 is connected to the digital input terminal TE2 of the ECU 20 via the in-vehicle LAN.

  The ECU 20 is mainly configured by a CPU 21, a ROM (not shown), and a RAM (not shown). In addition to the CPU 21 and the memory, the ECU 20 includes an AD converter 22 that digitizes an analog sensor signal input to the analog input terminal TE1. In addition to the sensor signal of the acceleration sensor 10, sensor signals of various sensor devices mounted on the vehicle are input to the AD converter 22. The CPU 21 has a serial interface unit 21a that receives a digital sensor signal input to the digital input terminal TE2.

  The ECU 20 controls various devices mounted on the vehicle based on the sensor signal of the acceleration sensor 10 and the like. Particularly in the present embodiment, the ECU 20 performs failure detection of the acceleration sensor 10 and also performs a self-diagnosis of the ECU 20.

  Next, failure detection of the acceleration sensor 10 and self-diagnosis of the ECU 20 (hereinafter referred to as “system failure detection”) will be described with reference to FIGS. 2 and 3. In the following description, the power supply voltage and the ground voltage are 5 V and 0 V, the output signal of the sensor element 11 is amplified to an analog signal of 0 V to 5 V in the operational amplifier 12, and the output current characteristics of the operational amplifier 12. When the output of the operational amplifier 12 is shorted to the ground, the current value flowing out from the operational amplifier 12 (maximum source current) and the current value flowing into the operational amplifier 12 when the output of the operational amplifier 12 is shorted to the power supply (maximum sink) Current) is assumed to be 0.1 A.

  FIG. 2 is a diagram illustrating analog sensor signals and digital sensor signals in the normal state and various failure states of the system, and parity check results.

(When the system is in a normal state)
As shown in FIG. 2, when the system is in a normal state, when the internal state of the acceleration sensor 10 is changed to the first output control state (a state for outputting a power level signal from the operational amplifier 12), an analog state is obtained. The sensor values of the sensor signal and the digital sensor signal are both 5V, and when the internal state of the acceleration sensor 10 is changed to the second output control state (a state for outputting a ground level signal from the operational amplifier 12), the analog sensor signal and Both sensor values of the digital sensor signal are 0V. Further, the parity check result is normal in both the first output control state and the second output control state.

(When a failure of a fixed power level occurs in the sensor element or operational amplifier)
When a failure of the power supply level fixing occurs in the sensor element 11 or the operational amplifier 12, even if the internal state of the acceleration sensor 10 is changed to the second output control state, the output of the operational amplifier 12 is fixed to 5V. The sensor value of the analog sensor signal and the sensor value of the digital sensor signal are both 5V.

(When a failure of a fixed ground level occurs in the sensor element or operational amplifier)
When a failure of fixing the ground level occurs in the sensor element 11 or the operational amplifier 12, the output of the operational amplifier 12 is fixed to 0V even if the internal state of the acceleration sensor 10 is changed to the first output control state. The sensor value of the analog sensor signal and the sensor value of the digital sensor signal are both 0V.

(When a failure of a fixed power level occurs in the signal conversion circuit of the LAN interface)
When a failure with a fixed power supply level occurs in the signal conversion circuit 15a of the LAN interface 15, even if the internal state of the acceleration sensor 10 is changed to the second output control state, the sensor value of the digital sensor signal becomes 5V. . In this case, the sensor value of the analog sensor signal is 0V.

(When a failure with a fixed ground level occurs in the signal conversion circuit of the LAN interface)
When a failure with a fixed ground level occurs in the signal conversion circuit 15a of the LAN interface 15, even if the internal state of the acceleration sensor 10 is shifted to the first output control state, the sensor value of the digital sensor signal is about 0V. Become. In this case, the sensor value of the analog sensor signal is 5V.

(When the digital output terminal or digital input terminal is shorted to the power supply)
When the digital output terminal TS2 or the digital input terminal TE2 is short-circuited to the power supply, the input voltage to the CPU 21 is fixed at the power supply level even if the internal state of the acceleration sensor 10 is changed to the second output control state. The sensor value of the digital sensor signal is 5V. Further, since all the parity bits are “1”, the result of the parity check is abnormal. In this case, the sensor value of the analog sensor signal is 0V.

(When digital output terminal or digital input terminal is shorted to ground)
When the digital output terminal TS2 or the digital input terminal TE2 is shorted to the ground, the input voltage to the CPU 21 is fixed to the ground level even if the internal state of the acceleration sensor 10 is changed to the first output control state. The sensor value of the digital sensor signal is 0V. Further, since all the parity bits are “0”, the result of the parity check is abnormal. In this case, the sensor value of the analog sensor signal is 5V.

(When analog output terminal or analog input terminal is shorted to power supply)
When the analog output terminal TS1 or the analog input terminal TE1 is short-circuited to the power supply, when the internal state of the acceleration sensor 10 is shifted to the second output control state, a current corresponding to the sink current value of the operational amplifier 12 is protected from the power supply by the protective resistor. 13 flows into the operational amplifier 12. As a result, a voltage drop (1 V) is generated in the protective resistor 13 according to the resistance value (10Ω) and the sink current value (0.1 A) of the operational amplifier 12, so that the input voltage to the LAN interface 15 is higher than the power supply level. The voltage level is fixed to be lower by the voltage drop. Therefore, the sensor value of the digital sensor signal is 4V (= 5V-1V). In this case, since the analog output terminal TS1 or the analog input terminal TE1 is short-circuited to the power source, the sensor value of the analog sensor signal is 5V.

(When analog output terminal or analog input terminal is shorted to ground)
When the analog output terminal TS1 or the analog input terminal TE1 is shorted to the ground, the current corresponding to the source current value of the operational amplifier 12 is protected from the operational amplifier 12 by changing the internal state of the acceleration sensor 10 to the first output control state. It flows into the ground through the resistor 13. As a result, a voltage drop (1 V) corresponding to the resistance value (10Ω) and the source current value (0.1 A) of the operational amplifier 12 occurs in the protective resistor 13, so that the input voltage to the LAN interface 15 is lower than the ground level. Is also fixed at a voltage level higher by the voltage drop. Therefore, the sensor value of the digital sensor signal is 1V (= 0V + 1V). In this case, since the analog output terminal TS1 or the analog input terminal TE1 is short-circuited to the ground, the sensor value of the analog sensor signal is 0V.

(When a failure with a fixed power level occurs in the AD converter)
When a failure with a fixed power supply level occurs in the AD converter 22, even if the internal state of the acceleration sensor 10 is shifted to the second output control state, the sensor value of the analog sensor signal is 5V. In this case, the sensor value of the digital sensor signal is 0V.

(When a fault with a fixed ground level occurs in the AD converter)
When a failure with a fixed ground level occurs in the AD converter 22, even if the internal state of the acceleration sensor 10 is changed to the first output control state, the sensor value of the analog sensor signal becomes 0V. In this case, the sensor value of the digital sensor signal is 5V.

  As described above, since the sensor value of the analog sensor signal and the digital signal and the parity check result differ depending on the failure location and failure mode of the system, the system failure detection is performed based on the sensor value and the parity check result. It can be carried out.

  FIG. 3 is a flowchart showing the flow of the system failure detection program. In the present embodiment, it is assumed that the CPU 21 executes this program at a predetermined cycle.

  In step S <b> 11 shown in FIG. 3, the CPU 21 applies a predetermined voltage to the control input terminal TS <b> 3 of the acceleration sensor 10 so that the acceleration sensor 10 outputs a 5 V sensor signal that is a power supply level. In subsequent step S12, the CPU 21 acquires the sensor value VAh of the analog sensor signal and the sensor value VDh of the digital sensor signal. In subsequent step S13, the CPU 21 performs a parity check based on the parity bit of the digital sensor signal.

  In step S <b> 14, the CPU 21 applies a predetermined voltage to the control input terminal TS <b> 3 of the acceleration sensor 10 so that the acceleration sensor 10 outputs a sensor signal of 0 V that is a ground level. In subsequent step S15, the CPU 21 acquires the sensor value VAl of the analog sensor signal and the sensor value VDl of the digital sensor signal. In subsequent step S16, the CPU 21 performs a parity check based on the parity bit of the digital sensor signal.

  In steps S17 to S28, the CPU 21 detects the failure location and failure mode of the system based on VAh, VDh, VAl, VD1 acquired in steps S12 and S15 and the result of the parity check performed in steps S13 and S16. Then, predetermined processing corresponding to the failure is performed.

Specifically, in step S17, the CPU 21
(1) VAh and VDh are about 5V (for example, a voltage of 4.5V or more), VAl and VDl are about 0V (for example, a voltage lower than 0.5V), and the parity check result is normal If so, it will detect that there is no failure in the system,
(2) When it is determined that VAh, VDh, VAl, and VDl are about 5 V and the parity check result is normal, it is confirmed that a failure with a fixed power supply level has occurred in the sensor element 11 or the operational amplifier 12. Detect
(3) When it is determined that VAh, VDh, VAl, and VDl are about 0 V and the parity check result is normal, a failure with a fixed ground level has occurred in the sensor element 11 or the operational amplifier 12. Detect
(4) When it is determined that VAh, VDh, VDl is about 5V, VAl is about 0V, and the parity check result is normal, the power conversion level is fixed to the signal conversion circuit 15a of the LAN interface 15. Detect that a failure has occurred,
(5) When it is determined that VAh is about 5V, VDh, VAl, VDl are about 0V and the parity check result is normal, the signal conversion circuit 15a of the LAN interface 15 is fixed to the ground level. Detect that a failure has occurred,
(6) When it is determined that VAh, VDh, VDl is about 5V, VAl is about 0V, and the parity check result is abnormal, the power supply short circuit is applied to the digital output terminal TS2 or the digital input terminal TE2. Detect that a failure has occurred,
(7) When it is determined that VAh is about 5V, VDh, VAl, VDl is about 0V, and the parity check result is abnormal, a ground short is connected to the digital output terminal TS2 or the digital input terminal TE2. Detect that a failure has occurred,
(8) When it is determined that VAh, VDh, and VAl are about 5V, VDl is about 4V (for example, a voltage not lower than 3.5V and lower than 4.5V), and the parity check result is normal , Detecting that a short circuit failure has occurred in the analog output terminal TS1 or the analog input terminal TE1,
(9) When it is determined that VAh, VAl, VDl is about 0 V, VDh is about 1 V (for example, a voltage not lower than 0.5 V and lower than 1.5 V), and the parity check result is normal , Detecting that a ground short failure has occurred in the analog output terminal TS1 or the analog input terminal TE1,
(10) When it is determined that VAh, VDh, and VAl are about 5V, VDl is about 0V, and the parity check result is normal, a failure of fixing the power supply level occurs in the AD converter 22. Detect that
(11) When it is determined that VAh, VAl, and VDl are about 0V, VDh is about 5V, and the parity check result is normal, a fault with a fixed ground level occurs in the AD converter 22. Detect that
(12) If none of the above (1) to (11) applies, it is detected that a failure with an unknown failure location and failure mode has occurred in the system.

  If the CPU 21 determines in step S17 that there is no abnormality in the system, the CPU 21 ends the execution of the current program. If it is determined in step S17 that there is an abnormality in the system, the abnormal part and abnormality mode are determined. After executing predetermined processing according to the above, the execution of the current program is terminated (see steps S18 to S28).

  Here, the following processes can be considered as the process according to the failure.

(Processing according to failure location and failure mode)
-Display the failure location and failure mode, or the urgency of repair based on this information. This can prompt the user of the vehicle to repair the system.
-The failure location and failure mode are stored as a failure history. As a result, the system failure can be repaired promptly.

(Processing according to failure location)
When the sensor element 11 or the operational amplifier 12 is out of order, the vehicle-mounted device is controlled based on output signals from various sensor devices other than the acceleration sensor 10. Even if the sensor element 11 or the operational amplifier 12 of the acceleration sensor 10 fails, since the AD converter 22 of the ECU 20 is normal, the vehicle-mounted device is controlled by the output signals of various sensor devices other than the acceleration sensor 10 to retreat the vehicle. Can be considered.
When the AD converter 22 is out of order, the in-vehicle device is controlled based on the digital sensor signal. Even if the AD converter 22 of the ECU 20 breaks down, the sensor value of the digital sensor signal of the acceleration sensor 10 indicates the acceleration applied to the vehicle. Conceivable.
When any of the digital output terminal TS2, the digital input terminal TE2, and the signal conversion circuit 15a is out of order, the in-vehicle device is controlled based on the analog sensor signal. Even if a failure occurs in the signal path of the digital sensor signal, the sensor value of the analog sensor signal indicates the acceleration applied to the vehicle. Therefore, it is conceivable that the vehicle-mounted device is controlled by the sensor value and the vehicle is evacuated. .

  In the system failure detection described above, the failure of the analog output terminal TS1 or the analog input terminal TE1 corresponds to “the failure of the portion of the signal path of the first sensor signal on the resistor side of the AD converter”.

(Other embodiments)
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.
-System failure detection may be performed based on the difference between the sensor value of the analog sensor signal and the sensor value of the digital sensor signal.
For example, when the difference between the analog sensor signal VAh (VA1) and the digital sensor signal VDh (VD1) is +5 V, it is determined that VAh (VA1) is 5 V and VDh (VD1) is 0 V, and analog When the difference between the sensor signal VAh (VAl) and the digital sensor signal VDh (VDl) is −5V, it may be determined that VAh (VAl) is 0V and VDh (VDl) is 5V. .
Further, the difference between the analog sensor signal VAl and the digital sensor signal VDl in the second output control state (a state for outputting a ground level signal from the operational amplifier 12) is about + 1V (for example, 0.5 <VAh−VDh ≦ 1). .5V), it is detected that a power supply short-circuit failure has occurred at the analog output terminal TS1 or the analog input terminal TE1, and a first output control state (a state for outputting a power level signal from the operational amplifier 12) When the difference between the analog sensor signal VAl and the digital sensor signal VDl is about −1V (for example, −1.5 <VAh−VDh ≦ −0.5V), the analog output terminal TS1 or the analog input terminal TE1 is grounded. It is conceivable to detect that a short circuit failure has occurred.

  In the embodiment described above, failures other than power level fixation (power supply short-circuit) and ground level fixation (ground short-circuit) are detected as other failures. However, it is possible to detect the other failures in more detail. For example, (i) when the sensor value of the analog sensor signal and the sensor value of the digital sensor signal are the same voltage that is not 5V, 4V, 1V, or 0V, the output signal of the sensor element 11 or the operational amplifier 12 is the power supply level. However, it is detected that a failure that is fixed at a voltage level other than the ground level has occurred, (ii) the sensor value of the analog sensor signal is the failure detection level (5 V or 0 V), and the sensor value of the digital sensor signal is 5 V, When it is not 4V, 1V, or 0V, it is detected that a failure has occurred in which the output signal of the LAN interface 15 is fixed at a voltage level that is neither the power supply level nor the ground level, and (iii) the sensor value of the digital sensor signal Is the failure detection level (5V or 0V), and the sensor value of the analog sensor signal is 5V, 4V, 1V, If neither and V, a fault output signal of the AD converter 22 is fixed at the voltage level nor ground level at the power level is considered to be detected that has occurred.

  In the above embodiment, the failure location and failure mode of the system are detected, but only the failure location may be detected. That is, the failure location is “sensor element 11 or operational amplifier 12”, “LAN interface 15”, “digital output terminal TS2 or digital input terminal TE2”, “analog output terminal TS1 or analog input terminal TE1”, and “AD converter 22”. Either of them may be detected. Even in this case, it is possible to execute processing according to the failure location.

  Only the failure of “analog output terminal TS1 or analog input terminal TE1” may be detected, or only the failure of “analog output terminal TS1 or analog input terminal TE1” and the failure of “AD converter 22” are detected. You may make it detect.

  The first failure detection state and the second failure detection state may be a state for outputting a voltage level signal that is neither the power supply level nor the ground level from the operational amplifier 12. Even in this case, depending on the setting values of the signal levels in both states, it is possible to detect a system failure as in the above embodiment. For example, the first failure detection state may be a state for outputting a 4.5V signal from the operational amplifier 12, and the second failure detection state may be a state for outputting a 0.5V signal from the operational amplifier 12. It is possible to detect system failures.

  In the above embodiment, a failure of the acceleration sensor 10 connected to the ECU 20 via the in-vehicle LAN is detected. However, the present invention is not limited to this, and a failure of the acceleration sensor 10 built in the ECU 20 may be detected. Even in this case, a system failure can be detected as in the above embodiment.

  The present invention can also be applied to an in-vehicle sensor device (for example, a yaw rate sensor or a pressure sensor) other than the acceleration sensor 10. Even in this case, a system failure can be detected in the same manner as in the above embodiment. The present invention is also applicable to an in-vehicle sensor device capable of transitioning to one of the first failure detection state and the second failure detection state. Even in this case, it is possible to detect the failure of either the power supply level fixing (power supply short circuit) or the ground level fixing (ground short circuit).

DESCRIPTION OF SYMBOLS 10 ... Acceleration sensor, 11 ... Sensor element, 12 ... Operational amplifier, 13 ... Protection resistor, 15 ... Interface, 15b ... Parity circuit, 15a ... Signal conversion circuit, 20 ... ECU, 21 ... CPU, 21a ... Serial interface part, 22 ... AD converter, TE1 ... analog input terminal, TE2 ... digital input terminal, TE3 ... control output terminal, TS1 ... analog output terminal, TS2 ... digital output terminal, TS3 ... control input terminal.

Claims (6)

The sensor unit outputs an output signal as an analog first sensor signal via a resistor, and is applied to an in-vehicle sensor device that outputs the output signal as a second sensor signal without going through the resistor,
An AD converter that digitizes the first sensor signal; and a sensor value acquisition unit that acquires a sensor value of the second sensor signal and a sensor value of the first sensor signal digitized by the AD converter. In the sensor failure detection device for detecting a failure of the in-vehicle sensor device based on the sensor value acquired by the sensor value acquisition means,
Output control means for controlling the in-vehicle sensor device so that a signal of a predetermined failure detection level is output from the sensor unit;
The sensor of the second sensor signal acquired by the sensor value acquisition means in an output control state in which the in-vehicle sensor device is controlled so that the signal of the failure detection level is output from the sensor unit by the output control means. When the value is a predetermined level corresponding to the output current characteristic of the sensor unit and the resistance value of the resistor, the signal path of the first sensor signal is closer to the resistor side than the AD converter. A failure detection means for detecting that a failure has occurred;
A sensor failure detection device comprising:   The failure detection means detects the output from the output control means as a detection condition for detecting that a failure has occurred in a portion of the signal path of the first sensor signal closer to the resistor than the AD converter. The sensor failure detection device according to claim 1, wherein a sensor value of the first sensor signal acquired by the sensor value acquisition unit in a control state includes not being the failure detection level.   The failure detection means has a sensor value of the first sensor signal acquired by the sensor value acquisition means in the output control state by the output control means that is different from a failure detection level at the time of acquisition of the sensor value, and in the same state 3. When the sensor value of the second sensor signal acquired by the sensor value acquisition unit is at the failure detection level, it is detected that a failure has occurred in the AD converter. Sensor failure detection device. The output control means controls the in-vehicle sensor device so that a signal of a power supply level or a ground level is output as the failure detection level from the sensor unit,
The failure detection means is acquired by the sensor value acquisition means in a first output control state in which the in-vehicle sensor device is controlled such that a power level signal is output from the sensor unit by the output control means. The sensor value of the first sensor signal and the second sensor signal, and the output control means in the second output control state in which the vehicle sensor device is controlled so that a ground level signal is output from the sensor unit. The sensor failure detection apparatus according to any one of claims 1 to 3, wherein the failure detection is performed based on sensor values of the first sensor signal and the second sensor signal acquired by a sensor value acquisition unit. .   In the failure detection means, the sensor value of the second sensor signal acquired by the sensor value acquisition means in the first output control state corresponds to a maximum source current value of the sensor unit and a resistance value of the resistor. When the voltage is higher than the ground level by the voltage, it is detected that a ground short-circuit failure has occurred in the resistor side of the AD converter in the signal path of the first sensor signal. The sensor value of the second sensor signal acquired by the sensor value acquisition means in the two-output control state is lower than the power supply level by a voltage corresponding to the maximum sink current value of the sensor unit and the resistance value of the resistor. 5, it is detected that a short circuit failure has occurred in a portion of the signal path of the first sensor signal that is closer to the resistor than the AD converter. Sensor failure detecting device. The failure detection means has the sensor value of the first sensor signal acquired by the sensor value acquisition means in the first output control state at a ground level, and the sensor value acquisition means acquired in the same state. When the sensor value of the second sensor signal is at the power supply level, it is detected that a failure with a fixed ground level has occurred in the AD converter, and the sensor value acquisition means acquires the failure in the second output control state. When the sensor value of the first sensor signal is the power level and the sensor value of the second sensor signal acquired by the sensor value acquisition means in the same state is the ground level, the power level is fixed to the AD converter. The sensor failure detection device according to claim 4, wherein the failure detection device detects that a failure has occurred.