JP2007024825A - Fault diagnostic system for current sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fault diagnostic system for a current sensor which can easily and surely diagnose output fixing abnormality in a current sensor detecting the charging/discharging current of a battery and easily avoid false diagnosis at output clamping, when the output range of the current sensor is provided. <P>SOLUTION: When the difference between the present value and the previous value of the current sensor output represents the predetermined value A or smaller, it is decided that there is a possibility of output fixing, and the present value is stored. Whether the difference between the stored value and the detected output value of the current sensor is the predetermined value A or smaller is decided. When it is the predetermined value or smaller, a timer is made to count. When the timing by the timer has continued for a predetermined time period, it is decided that there is an output fixing abnormality in the current sensor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a failure diagnosis device for a current sensor, and more particularly to a failure diagnosis device for a current sensor for diagnosing an output sticking abnormality in which an output of a current sensor for detecting a charge / discharge current of a battery is fixed.

Conventionally, as a fault diagnosis device for a current sensor for detecting a charge / discharge current of a battery, the output voltage of the current sensor is fixed to a certain value in an intermediate region between the upper limit value and the lower limit value of the output range of the current sensor. There is one that diagnoses an output sticking abnormality (see, for example, Patent Document 1).
In this case, when the amount of battery voltage fluctuation from an arbitrary time detected by the voltage sensor exceeds the reference fluctuation amount, the fluctuation amount of the detected current value of the current sensor corresponding to the reference fluctuation amount is less than the reference value. And, when the state continues for a predetermined time, it is determined that the current sensor has caused the output fixing failure.
JP-A-10-253682

  However, when the output fixation diagnosis is performed using the relationship between the battery voltage and the current fluctuation amount as in the diagnosis method of Patent Document 1 described above, the internal resistance in which the battery voltage changes according to the remaining capacity and temperature of the battery. Since it depends on the value, the relationship between the voltage of the battery and the amount of fluctuation of the current also changes depending on the battery state. For this reason, there is a problem that it is difficult to set the reference value because it is necessary to change the reference value of the voltage fluctuation amount and the current fluctuation amount by estimating the battery state. Also, if the harness between the battery and the control unit is long, or if power is being supplied to another electrical load between the battery and the control unit, the battery may be offset by a harness drop or a voltage drop when driving the load. Since voltage signal information varies, there is a possibility of erroneous diagnosis.

  In addition, in order to determine disconnection or short-circuit, if an output range is defined by setting an upper limit value (upper clamp value) and a lower limit value (lower clamp value) for the output of the current sensor, the sensor output will remain in the clamped state. Since the behavior of the sensor output voltage is the same as that at the time of sticking abnormality, the clamp state and the sensor output sticking abnormality are distinguished from each other, and it is avoided that the current sensor is normal but erroneously judged as an output sticking abnormality. There is a need.

  The present invention has been made by paying attention to the above problems, and it is easy to diagnose an abnormality in the output sticking of the current sensor, and even when the output range of the current sensor is defined, erroneous determination at the time of sensor output clamping is easy. An object of the present invention is to provide a current sensor failure diagnosis apparatus that can be avoided.

  For this reason, the present invention is a current sensor failure diagnosis device that detects a charging / discharging current of a battery and diagnoses an output sticking abnormality in which an output of a current sensor that outputs a voltage value corresponding to the detected current value is fixed. Storage means for storing the output voltage value of the current sensor when the fluctuation of the output voltage value of the current sensor falls within a predetermined value range, and the output of the current sensor with respect to the stored value stored in the storage means And a determination unit that determines that the output of the current sensor is abnormally fixed when the voltage value variation is within the predetermined value range for a predetermined time.

  According to the present invention, since it is determined that the output sticking abnormality is detected when the current sensor output continues substantially the same value for a predetermined time, the battery state is estimated and the reference value is set as in the prior art. Therefore, it is possible to reliably and easily diagnose output sticking abnormality. In addition, if the clamping time of the sensor output is grasped in advance, by appropriately setting the predetermined time, it is possible to easily distinguish between the clamped state and the output fixing abnormality, and prevent erroneous determination at the time of sensor clamping.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a first embodiment of a failure diagnosis device for a current sensor according to the present invention, and shows an example of application to a current sensor for detecting a charge / discharge current of an in-vehicle battery.
In FIG. 1, a battery 1 is connected to an alternator (not shown) and an on-vehicle electric load. The current sensor 2 is provided in a current line near the terminal of the battery 1 and detects a discharge current discharged from the battery 1 when supplying electric power to the in-vehicle electric load and a charging current when being charged by the alternator. The output voltage of the current sensor 2 is input to the failure diagnosis unit 3, and the failure diagnosis unit 3 performs output fixing diagnosis based on the output state of the current sensor 2.

  The current sensor 2 has, for example, the characteristics shown in FIG. That is, when the current is not flowing, the output voltage is set to 2.5 V, for example, and the output voltage increases as the charging current (positive current) increases, and the discharge current (negative current) increases. In response, the output voltage decreases, and a voltage value in the range of 0V to 5V is output. Then, in order to enable determination of disconnection or short circuit (short circuit) of the current line, an upper limit value (for example, 4.5 V) and a lower limit value (for example, 0.5 V) are set for the output voltage, and changes according to the detected current. The output voltage range is defined (0.5V to 4.5V). Therefore, the output voltage is clamped at 4.5V when a charging current equal to or greater than 4.5V (100A in FIG. 2) flows, and the current corresponding to 0.5V (−100A in FIG. 2). The output voltage is clamped to 0.5 V when the above negative discharge current flows. Thereby, when the output of the current sensor 2 becomes 0V, it can be determined that it is a disconnection, and when the output of the current sensor 2 becomes 5V, it can be determined that it is a short circuit. Note that a range may be provided for the upper and lower limit values in consideration of fluctuations in the output of the current sensor 2. For example, a range of 4.25 to 4.75 V is set as the upper limit value and 0.25 is set as the lower limit value. A voltage range of ˜0.75V may be set.

  The failure diagnosis unit 3 determines that the output is stuck abnormally when the output of the current sensor 2 continues substantially the same value for a predetermined time, and the fluctuation of the output voltage value of the current sensor 2 is within a predetermined value range. The output voltage value of the current sensor 2 when the current value is reached is stored, and when the state in which the fluctuation of the output voltage value of the current sensor 2 with respect to the stored value is within the predetermined value range continues for a predetermined time, the output of the current sensor Determined as sticking abnormality. Therefore, the failure diagnosis unit 3 has functions of a storage unit and a determination unit.

Next, a specific adhesion diagnosis operation of the failure diagnosis unit 3 of the first embodiment will be described with reference to the flowcharts of FIGS. Hereinafter, the upper limit value is referred to as an upper clamp value (4.5V), and the lower limit value is referred to as a lower clamp value (0.5V).
FIG. 3 is an operation flowchart for estimating output sticking. For example, when a key switch is turned on, the operation is started and executed at a constant cycle.

In step 1 (indicated by S1 in the figure, the same applies hereinafter), the output voltage of the current sensor 2 is read.
In step 2, it is determined whether or not the difference between the current value and the previous value is equal to or less than a predetermined value A. If the determination is YES, the output voltage value of the current sensor 2 does not vary and the output is fixed. Proceed to Step 3 assuming that there is a possibility. In the first time, for example, 2.5 V in which no current flows may be calculated as the previous value.

In step 3, the current value is stored in the memory as a reference value for sticking determination. Note that the previous value may be stored instead of the current value.
In step 4, the sticking determination operation is started.
FIG. 4 is a flowchart of the sticking determination operation started in step 4.
In step 11, the timer is activated.

In step 12, each time the output value of the current sensor 2 is read in the flowchart of FIG. 3, it is determined whether or not the difference between the read detection value and the stored value is equal to or less than the predetermined value A. If the determination is YES, the count value of the timer is counted up in step 13.
In step 14, it is determined whether a predetermined time has elapsed from the count value of the timer. If the predetermined time has elapsed, the determination is YES, and it is determined that the output of the current sensor 2 does not continuously change for a predetermined time. Then, the process proceeds to step 15 to notify the sensor sticking abnormality.

If the difference between the detected value and the stored value exceeds the predetermined value A in step 12 and the determination is NO, it is determined that the output of the current sensor 2 has fluctuated and the output is not fixed, and the process proceeds to step 16. Advance and clear the count value of the timer.
According to the first embodiment, since the output sticking abnormality of the current sensor 2 is determined from the output state of the current sensor 2, it is not necessary to estimate the battery state and set the reference value as in the prior art, and the output Diagnosis of sticking abnormality can be made reliably and easily. In the case of the in-vehicle battery 1, the large current that clamps the current sensor 2 flows mainly when the engine is started. Therefore, the time for the battery current to return to the normal state when the engine is started is determined in advance. By properly setting, it is possible to distinguish between the clamped state and the output sticking abnormality, and to diagnose erroneously as an output sticking abnormality even when the current sensor 2 is normal when the current sensor 2 is clamped. Can be prevented.

By detecting the failure of the current sensor 2 in this way, it is possible to prevent malfunctions in correcting the engine air amount for the alternator load, erroneous detection of the charge amount of the battery 1, and the like.
Next, a second embodiment of the present invention will be described.
In the second embodiment, an output fixing abnormality in the clamped state of the current sensor 2 can be diagnosed more reliably.

In the second embodiment, although not shown, a voltage sensor for detecting a battery terminal voltage is added between the positive and negative terminals of the battery 1 in the configuration of FIG.
With reference to the flowchart of FIG. 5, the output fixing abnormality diagnosis operation according to the second embodiment will be described. The flow chart of FIG. 5 corresponds to the operation of FIG. 4 of the first embodiment, and the output fixation can be fixed when the difference between the current value and the previous value is less than or equal to the predetermined value A by the output fixation estimation operation flow of FIG. It is an operation flow when it is determined that there is a sex.

In step 21, a timer is activated.
In step 22, it is determined whether or not lower clamp value <stored value <upper clamp value, and the intermediate output region in which the output voltage changes according to the detected current value between the lower clamp value and the upper clamp value If YES, the determination is YES and the process proceeds to step 23. If the stored value is an upper clamp value or a lower clamp value that is not the intermediate output region, the determination is NO and the process proceeds to step 28.

The operations of Steps 23 to 27 are the same as Steps 12 to 16 of the flowchart of FIG. 4, and an output fixing abnormality is notified when a state where the difference between the detected value and the stored value is not more than the predetermined value A continues for a predetermined time.
If the stored value is the upper clamp value or the lower clamp value and the process proceeds to step 28, it is determined in step 28 whether or not the difference between the detected value and the stored value is equal to or less than a predetermined value A. If the determination is yes, the process proceeds to step 29, and if the determination is no, the process proceeds to step 34.

  In step 29, it is determined whether the stored value is the upper clamp value and the battery terminal voltage VB detected by the voltage sensor is equal to or lower than a predetermined voltage (for example, 9V) lower than the electromotive force (for example, 11.8 to 12.8V) of the battery 1. judge. If the determination is NO, the process proceeds to step 33, where it is determined whether the stored value is the lower clamp value and the battery terminal voltage VB is equal to or higher than a predetermined voltage (for example, 14V) higher than the electromotive force of the battery 1. If the determination of either step 29 or step 33 is YES, the process proceeds to step 30, and if both are NO, the process proceeds to step 34.

If the process proceeds to step 30, as in steps 24-26, the timer count value is incremented in step 30, and it is determined in step 31 whether or not a predetermined time has elapsed. In step 32, an output fixing abnormality is diagnosed and notified.
When the routine proceeds to step 34, the count value of the timer is cleared.
According to the second embodiment, the output voltage value of the current sensor 2 indicates the charged state with the upper clamp value even though the battery terminal voltage VB is lower than the predetermined voltage lower than the electromotive force of the battery 1 and the battery is in the discharged state. On the contrary, the output voltage value of the current sensor 2 indicates a discharge state with a lower clamp value even though the battery terminal voltage VB is in a charged state at a predetermined voltage higher than the electromotive force of the battery 1. When the current state continues for a predetermined time, the current sensor 2 diagnoses the sticking abnormality. Therefore, as compared with the configuration in which the diagnosis is performed only with the lapse of time as in the first embodiment, the diagnosis accuracy of the output sticking abnormality of the current sensor 2 in the output clamp region can be improved.

Next, a third embodiment of the present invention will be described.
With reference to the flowchart of FIG. 6, the output fixing abnormality diagnosis operation of the third embodiment will be described.
In step 41, it is detected that the starter switch has been turned on, the start timer is activated, and the elapsed time from the start of the engine is started.
In step 42, it is determined whether or not the stored value is within the output region where the output voltage changes according to the detected current value between the lower clamp value and the upper clamp value, and the lower clamp value <stored value <upper side. If it is a clamp value, the determination is YES and the process proceeds to step 43. If the stored value is greater than or equal to the upper clamp value or less than or equal to the lower clamp value, the determination is NO and the process proceeds to step 49. Here, normally, since the battery 1 is discharged as the engine starts and a large discharge current flows, if the current sensor 2 is normal, for example, a lower clamp value is stored as a stored value. Therefore, if the determination in step 42 is YES, the sticking determination operation is prohibited in step 49. Then, in step 50, it is determined whether or not the time measured by the start timer has passed a predetermined time, and the sticking determination operation is prohibited until the predetermined time has passed. If the predetermined time has passed, the sticking is determined in step 51. The prohibition of the determination operation is canceled and the sticking determination operation is started.

On the other hand, if the value of the intermediate output region is stored as a stored value when the engine is started, there is a possibility that the current sensor 2 has an output fixing abnormality. In this case, similarly to steps 11 to 16 in FIG. 4, the operations of steps 43 to 48 are executed to determine whether or not the output is fixed.
According to the third embodiment, since the output of the current sensor 2 is normally in the clamped state when the engine is started, the clamping diagnosis is prohibited until a predetermined time elapses after the engine is started. Avoid misdiagnosis in Also, if the output value of the intermediate output area is stored between the time when the key switch is turned on and the time when the starter switch is turned on, the current sensor 2 may be stuck abnormally. In this case, the fixation of the current sensor 2 can be detected early by executing the fixation diagnosis.

  A battery having a large capacity tends to have a long charge / discharge time, and therefore the clamp state becomes long. Therefore, when performing the sticking diagnosis of the current sensor used for such battery current detection, the predetermined time for sticking determination in the intermediate output region may be different from the predetermined time for sticking judgment in the clamp region. For example, in the first and third embodiments described above, a step of determining whether the stored value is the value of the intermediate output region or the clamp value and changing the predetermined time according to the determination result may be added. Then, the predetermined time of step 25 and the predetermined time of step 31 may be set to different values.

  Needless to say, the fault diagnosis apparatus of the present invention can be applied not only to in-vehicle current sensors but also to fault diagnosis of other current sensors.

1 is a schematic configuration diagram of a first embodiment of a current sensor failure diagnosis apparatus according to the present invention. Current sensor characteristics Flowchart explaining output sticking estimation operation The flowchart explaining the diagnostic operation of 1st Embodiment Flowchart for explaining diagnosis operation of the second embodiment Flowchart explaining the operation at the time of engine start of the third embodiment

Explanation of symbols

1 Battery 2 Current sensor 3 Fault diagnosis unit

Claims (6)

A current sensor failure diagnosis device for diagnosing an output sticking abnormality in which a charge / discharge current of a battery is detected and an output of a current sensor that outputs a voltage value corresponding to a detected current value is fixed,
Storage means for storing the output voltage value of the current sensor when the fluctuation of the output voltage value of the current sensor falls within a predetermined value range;
A determination unit that determines that the output sticking abnormality of the current sensor is abnormal when a change in the output voltage value of the current sensor with respect to the stored value stored in the storage unit is within the predetermined value range for a predetermined time;
A fault diagnosis device for a current sensor, comprising:   The determination unit determines whether the stored value is an upper limit value or a lower limit value of a predetermined current sensor output region. If the stored value is the upper limit value, a change in the output voltage value of the current sensor with respect to the stored value is the predetermined value. If the state within the value range continues for the predetermined time and the battery terminal voltage is equal to or lower than the predetermined voltage lower than the electromotive force of the battery, it is determined that the current sensor output is stuck abnormally. When the state in which the fluctuation of the output voltage value of the current sensor with respect to the value is within the predetermined value range continues for the predetermined time, and the battery terminal voltage is equal to or higher than the predetermined voltage higher than the electromotive force of the battery, the current sensor output sticking abnormality The current sensor failure diagnosis device according to claim 1, wherein the current sensor failure diagnosis device is configured to determine that   The determination means is configured so that when the stored value is an upper limit value and a lower limit value of a predetermined current sensor output region, an output voltage value in the output region between the upper and lower limit values that changes according to a detected current value. The failure diagnosis device for a current sensor according to claim 1 or 2, wherein the predetermined time is set to a different value depending on whether the value is a value.   4. The structure according to claim 1, wherein the storage unit is configured to store the previous value or the current value when the difference between the previous value and the current value of the voltage output value of the current sensor falls within the predetermined value range. The fault diagnosis apparatus of the current sensor as described in any one.   The current sensor failure diagnosis device according to any one of claims 1 to 4, wherein the current sensor is used for detecting a charge / discharge current of an in-vehicle battery.   The diagnosis prohibiting means for prohibiting the determination operation of the determination means until a predetermined time elapses after the engine is started when the stored value is the upper limit value or the lower limit value when the engine is started. Current sensor failure diagnosis device.

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