JP3960642B2 - Abnormal load current detection method for automobiles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an abnormal load current detection method for automobiles.
[0002]
[Prior art]
In general, a large number of loads such as lamps exist in an automobile, and it is monitored whether or not a predetermined current flows through the loads.
[0003]
Conventionally, as a load current monitoring method for monitoring whether or not a predetermined current is flowing through a load, as shown in FIG. 4, the voltage across the shunt resistor 10 is applied to a differential amplifier circuit 12 via an input protection circuit 11. The signal from the differential amplifier circuit 12 is input to the control unit 15 through the low-pass filter 13 and the analog output circuit 14, and the control unit 15 monitors the load current with the voltage value, as shown in FIG. The Hall element 16 is used, the output is input to the differential amplifier circuit 12, and the signal from the differential amplifier circuit 12 is input to the control unit 15 through the low-pass filter 13 and the analog output circuit 14, and the control unit 15 There are methods for monitoring the load current.
[0004]
[Problems to be solved by the invention]
By the way, when the electric wire connected to the load is short-circuited, the current waveform fluctuates in an AC manner. However, the conventional method for monitoring the load current has a problem that the AC load current due to a short circuit cannot be monitored because a low-pass filter is used as a countermeasure against noise and the like. If the state in which the electric wire is short-circuited is left unattended, it may lead to a vehicle fire. Therefore, there has been a demand for an abnormal load current detection method for automobiles that can easily detect the short-circuit state.
[0005]
[Means for Solving the Problems]
The present invention provides a method for detecting an abnormal load current for an automobile that solves the above-described problems. A voltage drop or an electromotive force generated by the load current is amplified by an amplifier circuit, and a voltage value is controlled via a low-pass filter. In the method for detecting an abnormal load current for an automobile in which the control unit measures the normal load current from the voltage value, the control unit further observes the AC component load current and the switch fluctuation, An abnormal load current detection method for an automobile, wherein an abnormality of a load system is detected from the observation results of the normal load current, the load current of the AC component, and the switch fluctuation.
[0006]
Also, when there is a fluctuation in the AC component load current, the fluctuation timing of the AC component load current and the switch fluctuation timing are collated, and if these occur at the same timing, A method for detecting an abnormal load current for an automobile, wherein the load system is determined to be abnormal when the time or the number of times is equal to or greater than a variation range associated with switch variation.
[0007]
In addition, when the AC component load current fluctuates, the fluctuation timing of the AC component load current and the switch fluctuation timing are collated. An abnormal load current detection method for an automobile, wherein the load system is determined to be abnormal when it occurs for a predetermined time or a predetermined number of times.
[0008]
Moreover, the control part is provided with the memory | storage part which memorize | stores normal load current, It is an abnormal load current detection method for motor vehicles characterized by the above-mentioned.
[0009]
Generally, when the switch is turned on / off, the load current of the AC component varies. The fluctuation of the AC component load current based on the switch fluctuation and the fluctuation of the AC component load current due to an abnormality in the load system are difficult to distinguish by simply monitoring the AC component load current. Therefore, in the present invention, the normal load current, the AC component load current, and the switch fluctuation are observed, and by using these three observation results, the load current is caused by the fluctuation of the load current due to the switch fluctuation or the abnormality of the load system. The load system abnormality is detected at an early stage.
[0010]
When an AC component load current fluctuates, the AC component load current fluctuation timing and the switch fluctuation timing are collated, and an error in the load system is discriminated from the result of the collation, thereby eliminating a discrimination error. it can.
[0011]
By providing a storage unit for storing the normal load current in the control unit, it is possible to store the value when a predetermined normal load current is passed at the time of inspection after the assembly of the automobile. In addition, the memory can be rewritten.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram for carrying out the method for detecting an abnormal load current for automobiles according to the present invention.
[0013]
In the present invention, the voltage across the shunt resistor 10 is input to the differential amplifier circuit 12 via the input protection circuit 11, and the signal from the differential amplifier circuit 12 is input to the low-pass filter 13, the level limiter 17, and the analog output circuit 14. Is output to the control unit 15 and is input to the control unit 15, and the control unit 15 monitors the normal load current with the voltage value, which is substantially the same as the conventional configuration. In the present invention, the differential amplifier circuit is further provided. 12 is AC-coupled by the capacitor 18 to extract only the AC component, and its waveform is input to the control unit 15 through the high-pass filter 19, the level limiter 17, and the waveform shaping circuit 20. The input to the control unit 15 is input to an interrupt port of the control unit 15, for example. In FIG. 1, reference numeral 21 denotes a detection power source.
[0014]
Although not shown, the control unit 15 observes switch fluctuation when the switch is turned ON / OFF.
[0015]
When an abnormality occurs in the load system, the waveforms shown in A, B, C, and D in FIG. 2 are generated in the respective parts A, B, C, and D in FIG.
[0016]
The control unit 15 determines, based on the normal load current, the AC component load current, and the switch fluctuation, whether the load current fluctuates due to the switch fluctuation or the load current fluctuation due to a load system abnormality.
[0017]
An example of the determination procedure in the control unit 15 will be described with reference to FIGS. In the main program, the normal load current is constantly observed, and it is confirmed whether or not a current corresponding to the switch ON / OFF switch state is flowing.
When a change occurs in the normal load current, it is determined whether or not there is a change in the switch state. If there is a change in the normal load current despite the fact that there is no change in the switch state, it is detected that an abnormal current is flowing, counts for a predetermined time or a predetermined number of times, and exceeds a predetermined time or a predetermined number of times. At that time, the load current is cut off. On the other hand, when a change occurs in the normal load current and the switch state also fluctuates, it is determined whether or not the change in the normal load current is a change commensurate with the switch fluctuation. If the change in the normal load current is commensurate with the switch fluctuation, there is no problem, but if the change in the normal load current is not commensurate with the switch fluctuation, the predetermined time or number of times is counted and The load current is cut off when the time has elapsed or the predetermined number of times has elapsed.
[0018]
Next, a case where an AC component load current is input from the interrupt port of the control unit will be described.
When the AC component load current is input from the interrupt port of the control unit and the AC component load current varies, the load current timing of the AC component is compared with the switch variation timing.
[0019]
As a result, when the fluctuation timing of the AC component load current and the switch fluctuation timing occur at the same timing, it is determined whether the fluctuation of the AC component load current is caused by the switch fluctuation, and the AC component If it is determined that the load current fluctuation is caused by switch fluctuation, it is considered that there is no problem, but the time or number of fluctuations of the AC component load current is counted, and these values are within the fluctuation range accompanying the switch fluctuation. When it is above, it is determined that the load system is abnormal.
[0020]
On the other hand, as a result of collating the fluctuation timing of the AC component load current and the switch fluctuation timing, if both are not generated at the same timing, it is determined whether or not the fluctuation of the AC component load current is caused by the switch fluctuation. However, if it is determined that the fluctuation of the AC component load current is due to the switch fluctuation, there is no problem, but the fluctuation of the AC component load current is counted and counted for a predetermined time or a predetermined number of times. In this case, it is determined that the load system is abnormal.
[0021]
As described above, when the fluctuation timing of the load current of the AC component and the fluctuation timing of the switch input load current are collated, if they do not occur at the same timing, the load system does not immediately determine that the load system is abnormal. By determining that the load system is abnormal when the fluctuation of the load current for the minute occurs for a predetermined time or a predetermined number of times, it is possible to distinguish it from the power fluctuation that may occur in the vehicle.
[0022]
Note that when a load system abnormality is determined by comparing the fluctuation timing of the load current of the AC component with the fluctuation timing of the switch input load current, the change of the normal load current that is constantly observed is also taken into consideration. .
[0023]
Further, the control unit 15 includes a storage unit that stores a normal load current. In this way, by storing the storage unit for storing the normal load current in the control unit, it is possible to store the value when a predetermined normal load current is passed at the time of inspection after the assembly of the automobile. Can do. It is preferable from the viewpoint of ensuring detection accuracy that the storage unit can be rewritten.
[0024]
The detection circuit configuration used in the method for detecting an abnormal load current for automobiles according to the present invention is not limited to the configuration shown in FIG.
[0025]
【The invention's effect】
As described above, the method for detecting an abnormal load current for an automobile according to the present invention observes the normal load current, the load current of the AC component, and the switch fluctuation, and uses these three observation results to change the load current due to the switch fluctuation. The load system abnormality is detected by discriminating between the load system and the load current fluctuation due to the load system abnormality, so that the load system abnormality can be detected easily and early. .
[0026]
Further, since the fluctuation timing of the AC component load current and the fluctuation timing of the switch input load current are collated and the abnormality of the load system is discriminated from the result of the collation, the discrimination error can be eliminated.
[0027]
Furthermore, by providing a storage unit for storing the normal load current in the control unit, it is possible to store the value when a predetermined normal load current is passed at the time of inspection after the assembly of the automobile. Therefore, the normal load current can be used as a reference. If the memory of the storage unit can be rewritten, the normal load current can be set to an optimum value.
[Brief description of the drawings]
FIG. 1 is a block diagram for carrying out an abnormal load current detection method for automobiles according to the present invention.
FIG. 2 is a waveform diagram at portions A, B, C, and D in FIG. 1;
3A is a flowchart of a main program in the control unit, and FIG. 3B is a flowchart of interrupt processing in the control unit.
FIG. 4 is an explanatory diagram of a conventional method for detecting an abnormal load current for an automobile.
FIG. 5 is an explanatory diagram of a conventional method for detecting an abnormal load current for automobiles.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Shunt resistance 11 Input protection circuit 12 Operational amplifier 13 Low pass filter 14 Analog output circuit 15 Control part 18 Capacitor 19 High pass filter 20 Waveform shaping circuit 21 Power supply for detection

Claims (4)

For automobiles, a voltage drop or electromotive force generated by a load current is amplified by an amplifier circuit, a voltage value is input to a control unit via a low-pass filter, and a normal load current is measured from the voltage value by the control unit In the abnormal load current detection method, the control unit further observes the load current of the AC component, and also observes the switch fluctuation related to the switch for turning on / off the load current, and the normal load current, the load current of the AC component, and An abnormal load current detection method for an automobile, wherein an abnormality of a load system is detected from an observation result of the switch fluctuation. When there variation of the load current of the AC component, against the fluctuation timing of the load current of the AC component and said switch change timing, if they are generated at the same timing, the time variation of the load current of the AC component Alternatively automotive abnormal load current detection method of claim 1, wherein the number of the load system in the case where more than the variation range associated with the switch change determined to be abnormal. When there variation of the load current of the AC component, collates the said switch change timing and variable timing of the load current of the AC component, if these do not occur at the same timing, variations in the load current of the AC component is predetermined 2. The method for detecting an abnormal load current for an automobile according to claim 1, wherein the load system is determined to be abnormal when it occurs for a time or a predetermined number of times. The method for detecting an abnormal load current for an automobile according to any one of claims 1 to 3, wherein the control unit includes a storage unit for storing a normal load current.

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