JP2013061215A - Earth detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an earth detector capable of enhancing fault determination accuracy in a fault diagnosis as a first purpose and to correct a determination error due to aged deterioration and temperature characteristics in the fault diagnosis as a second purpose.SOLUTION: A pseudo insulation resistance deterioration in a high-voltage power supply system 40 is caused by a pseudo insulation resistance deterioration section 10 by electrically connecting the high-voltage power supply system 40 and a vehicle body 60 to each other via resistors R1 and R2 for a fault diagnosis. At the time of occurrence of the pseudo insulation resistance deterioration, a response when a predetermined signal is output from a signal outputting section 31 to a wiring route 12 connecting the high-voltage power supply system 40 and the resistors R1 and R2 to one another is acquired by a signal inputting section 32 as a detection signal. Then, a controller 30 determines whether or not the detection signal is included within a normal range set according to resistance values of the resistors R1 and R2 and, in a case where the detection signal is determined not to be included within the normal range, determines abnormality of the high voltage power supply system 40.

Description

  The present invention relates to a ground fault detection device for detecting a ground fault, and more particularly to a ground fault detection device having a fault diagnosis function.

  Conventionally, for example, Patent Document 1 proposes a ground fault detection system that can self-diagnose whether or not the system itself is operating normally. Specifically, in Patent Document 1, a ground fault trial circuit for simulating a ground fault by connecting a battery and a vehicle body via a resistor, and a predetermined rectangular wave on a battery bus connected to the battery There has been proposed a configuration including a ground fault detector that detects a ground fault by comparing a response voltage when a voltage is applied and a reference voltage.

JP-A-10-221395

  However, in the above conventional technique, since a ground fault is detected by comparison with a reference voltage, it is possible to detect a failure as to whether or not a ground fault can be detected, but due to errors due to aged deterioration or changes in temperature characteristics. There is a problem in that it is impossible to detect a deviation in accuracy and to correct it. Moreover, it is a pseudo ground fault at one reference voltage, and there is a problem that only the periphery of this ground fault judgment value (reference voltage) can be detected.

  In view of the above points, it is a first object of the present invention to provide a ground fault detection device capable of improving the accuracy of failure determination in failure diagnosis. A second object of the present invention is to correct determination errors due to aging and temperature characteristics in failure diagnosis.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a ground fault detection device for detecting a ground fault of a high voltage power supply system (40) mounted on a vehicle in an insulated state, for fault diagnosis. The high voltage power supply system (40) and the vehicle body (60) of the vehicle are electrically connected via the resistors (R1 to R3) to cause a decrease in pseudo insulation resistance in the high voltage power supply system (40). Pseudo-insulation resistance lowering means (10) is provided.

  In addition, a response when a predetermined signal is input to the wiring path (12) connecting the high voltage power supply system (40) and the resistors (R1 to R3) at the time of occurrence of the pseudo insulation resistance reduction is acquired as a detection signal. A determination means (30) for determining whether the detection signal is included in a normal range set according to the resistance values of the resistors (R1 to R3) and determining that the detection signal is abnormal if the detection signal is not included in the normal range It is characterized by having.

  According to this, since the determination value for determining abnormality is not a single value, but is set in a range that can be said to be normal, failure occurs if the detection signal is outside the design tolerance range that is the normal range. It can be determined that Therefore, the failure determination accuracy can be improved.

  The invention according to claim 2 is characterized in that the determination means (30) corrects a value indicated by the detection signal as a true value when the detection signal is included in a normal range.

  Thereby, the normal range can be corrected for errors due to temperature characteristics and deterioration characteristics. Such correction can improve the accuracy of failure determination.

  The invention according to claim 3 is characterized in that the pseudo insulation resistance lowering means (10) performs the pseudo insulation resistance reduction in a plurality of patterns by changing the resistance values of the resistors (R1 to R3). .

  According to this, since the failure is diagnosed by the detection signal at a level corresponding to the resistance value of the resistors (R1 to R3), the failure determination accuracy can be improved. In addition, since a plurality of detection signals are obtained, it is possible to determine a failure on a line connecting them, so that the reliability of the failure determination can be improved.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an overall system diagram including a ground fault detection device according to a first embodiment of the present invention. It is the figure which showed the waveform of the signal handled by a signal output part and a signal input part. It is a flowchart showing the contents of failure diagnosis. It is the figure which showed the correlation of the synthetic resistance value (pseudo ground fault resistance R) of two resistances, and a detection signal. It is a whole system figure containing the ground fault detection apparatus which concerns on 2nd Embodiment of this invention. It is the figure which showed the correlation of the synthetic resistance value (pseudo ground fault resistance R) of three resistances, and a detection signal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The ground fault detection device according to the present embodiment is a device for detecting a ground fault such as a high voltage battery, and is applied when detecting a ground fault of a high voltage power supply system of an electric vehicle such as a hybrid vehicle, for example. .

  FIG. 1 is an overall system diagram including a ground fault detection apparatus according to the present embodiment. As shown in this figure, the ground fault detection apparatus includes a pseudo insulation resistance lowering unit 10, a resistor 20, and a control unit 30.

  The pseudo insulation resistance lowering unit 10 is connected via a terminal 50 to a high voltage power supply system 40 (HV battery in FIG. 1) mounted on the vehicle in an insulated state. The high-voltage power supply system 40 is a battery group configured by connecting a plurality of rechargeable lithium ion secondary batteries in series. The high voltage power supply system 40 is used for generating a high voltage of, for example, about 300 V and operating a load.

  The pseudo insulation resistance lowering unit 10 includes a capacitor 11 connected to the terminal 50, two resistors R1 and R2, and two switches SW1 and SW2.

  The capacitor 11 serves to insulate the high voltage power supply system 40 from the ground fault detection device. One electrode of the capacitor 11 is connected to the terminal 50, and the other electrode is connected to the resistor 20.

  The resistor R1 and the switch SW1 are connected in series, and the resistor R1 is connected to the other electrode of the capacitor 11. Similarly, the resistor R2 and the switch SW2 are connected in series, and the resistor R2 is connected to the other electrode of the capacitor 11. Each switch SW1, SW2 is connected to the vehicle body 60.

  That is, the pseudo insulation resistance lowering unit 10 electrically connects the high voltage power supply system 40 and the vehicle body 60 via the resistors R1 and R2 when either of the switches SW1 and SW2 is turned on. The power supply system 40 is configured to generate a pseudo insulation resistance drop. ON / OFF of each switch SW1, SW2 is controlled by the control unit 30.

  The control unit 30 determines a ground fault of the high voltage power supply system 40. In addition to the signal output unit 31 and the signal input unit 32, the control unit 30 includes an A / D converter and a microcomputer (hereinafter referred to as a microcomputer) not shown.

  The signal output unit 31 is a circuit unit that generates and outputs a rectangular wave voltage signal. The rectangular wave is output via the resistor 20 to the wiring path 12 to which the resistors R1 and R2 are connected. The wiring path 12 is a wiring that connects the high-voltage power supply system 40 and the resistors R1 and R2, and more specifically is a wiring that connects the other electrode of the capacitor 11 and the resistor 20.

  FIG. 2 shows the waveforms of signals handled by the signal output unit 31 and the signal input unit 32. As shown in FIG. 2A, the signal output unit 31 outputs a rectangular wave.

  The signal input unit 32 is a circuit unit that acquires a response from the wiring path 12 as a detection signal. Specifically, the signal input unit 32 inputs a voltage at a connection point between the resistor 20 and the capacitor 11 as a detection signal. The signal input unit 32 outputs the acquired detection signal to the A / D converter.

  2B to 2D show signals input by the signal input unit 32. FIG. As shown in FIG. 2B, when the switches SW <b> 1 and SW <b> 2 of the pseudo insulation resistance lowering unit 10 are OFF, the rectangular wave output from the signal output unit 31 is input to the signal input unit 32.

  The A / D converter converts the detection signal detected by the signal input unit 32 into a digital signal and inputs it to the microcomputer. The microcomputer is a control circuit that determines the presence or absence of a ground fault based on the detection signal input from the A / D converter.

  The microcomputer also has a self-diagnosis function for determining an abnormality in ground fault detection based on a detection signal input from the A / D converter. As shown in FIG. 2C, when the rectangular wave acquired as the detection signal is included in the normal range (design tolerance range), the microcomputer determines that the device is functioning normally. The microcomputer includes a CPU, ROM, EEPROM, RAM, and the like (not shown), and is set to perform ground fault detection and self-diagnosis according to a program stored in the ROM.

  In the present invention, when the detection signal is included in the normal range, the microcomputer also has a function of correcting the normal range using the voltage value indicated by the detection signal as a true value. Ideally, the detection signal should always show the value at the time of shipment, but even if an error occurs due to temperature characteristics or deterioration characteristics, it does not change normally, so the value indicated by the current detection signal is true. The normal range is corrected (updated) as a value.

  Further, the microcomputer determines whether the detection signal is included in a normal range set in advance according to the resistance values of the resistors R1 and R2. If the detection signal is not included in the normal range, the microcomputer determines that an abnormality has occurred. As shown in FIG. 2D, when the rectangular wave acquired as the detection signal is out of the normal range, the microcomputer determines that the device is malfunctioning (failure).

  The microcomputer controls the switches SW1 and SW2 of the pseudo insulation resistance lowering unit 10 to change the combined resistance value of the resistors R1 and R2, thereby implementing the pseudo insulation resistance reduction in a plurality of patterns. Since the two switches SW1 and SW2 are provided in the pseudo insulation resistance lowering unit 10, the microcomputer can cause three patterns of pseudo insulation resistance reduction.

  As described above, when the pseudo insulation resistance is lowered in a plurality of patterns, a normal range is set for each pattern. Therefore, the microcomputer performs the normality determination shown in FIG. 2C and the abnormality determination shown in FIG.

  The above is the overall configuration of the ground fault detection device and system according to the present embodiment. In such a ground fault detection device, the rectangular wave generated by the signal input unit 32 is output to the wiring path 12, and the voltage at the connection point between the resistor 20 and the capacitor 11 is acquired by the signal input unit 32. The ground fault detection of the high voltage power supply system 40 is performed based on the voltage.

  Next, the fault diagnosis operation of the ground fault detection device will be described with reference to FIGS. FIG. 3 is a flowchart showing the contents executed by the microcomputer. FIG. 4 is a diagram showing the correlation between the combined resistance value (pseudo ground fault resistance R) of the two resistors R1 and R2 and the detection signal.

  Here, the resistance value of the resistor R1 is 200 kΩ, and the resistance value of the resistor R2 is 300 kΩ. Thereby, the pseudo ground fault resistance R of the pattern A when the switch SW1 is turned on and the switch SW2 is turned on becomes 120 kΩ. Further, the pseudo ground fault resistance R of the pattern B when the switch SW1 is turned on and the switch SW2 is turned off is 200 kΩ. Furthermore, the pseudo ground fault resistance R of the pattern C when the switch SW1 is turned off and the switch SW2 is turned on is 300 kΩ.

  The flowchart shown in FIG. 3 starts, for example, when the ground fault detection device is activated or according to a command from the host ECU.

  First, in step 100, it is determined whether self-diagnosis is possible. This is because, in a hybrid vehicle or the like, failure diagnosis in a situation where noise is generated in the high voltage power supply system 40 is not preferable. For example, it is preferable when the ignition is on or at the start. In this step, it is determined whether or not such a situation exists.

  If it is determined that self-diagnosis is not possible, step 100 is repeated until self-diagnosis is possible, and if it is determined that self-diagnosis is possible, the process proceeds to step 110.

  In step 110, a pseudo ground fault is generated. That is, the switches SW1 and SW2 are controlled by the microcomputer in the above three patterns. Thereby, the detection signal in each pattern is acquired.

  In step 120, it is determined whether or not the voltage value indicated by the detection signal acquired in step 110 is within the normal range. The “normal range” is a range that can be said to be within a component tolerance including deterioration within this range in terms of design. The data in the normal range is stored in advance in the microcomputer when the ground fault detection device is manufactured.

  When the voltage value indicated by the detection signal in at least one pattern is not included in the normal range, the process proceeds to step 130, and the abnormality determination of the ground fault detection device is performed. In this case, the microcomputer reports it to the host ECU or the like. In the case of abnormality determination, the voltage value indicated by the detection signal is not included in the normal range shown in FIG. Thus, the flowchart shown in FIG. 3 ends.

  In FIG. 4, the “safe area” of 300 kΩ or more is an area where there is no problem even if the user touches the system, and the “dangerous area” of 120 kΩ or less is an area where an electric shock is received when the user touches the system. The “intermediate area” is a gray zone between safety and danger, and the user should not touch the system.

  On the other hand, when the voltage value indicated by the detection signal in all patterns is included in the normal range in step 120, the process proceeds to step 140. This is the case shown in FIG. In FIG. 4, the voltage values indicated by the detection signals in all patterns A, B, and C are included in the normal range.

  In step 140, it is determined whether correction is possible. Whether or not correction is possible is determined by whether or not the line connecting the detection signals of each pattern is located within the normal range. As shown in FIG. 4, the line connecting the three points at the time of shipment is located within the normal range. In such a case, it can be corrected and the process proceeds to step 150. The connecting points may be two points instead of three.

  In step 150, correction is performed. “Correction” means correcting the voltage value indicated by the current detection signal as a true value.

  When an error due to temperature characteristics or aging occurs, the voltage value indicated by the detection signal deviates from the value at the time of shipment as in pattern A and pattern C in FIG. Even if such a deviation occurs, it is possible to cope with a deviation caused by temperature characteristics or aged deterioration by correcting the true value in this step. Thus, the flowchart shown in FIG. 3 ends.

  On the other hand, if it is determined in step 140 that the line connecting the three or two detection signals is out of the normal range, the process proceeds to step 160. In step 160, the diagnosis circuit abnormality is reported to the host ECU or the like without performing correction. The fact that the line connecting the detection signals is out of the normal range means that a circuit fault such as a characteristic failure of the ground fault detection circuit itself or a deviation in the resistance values of the resistance R1 and the resistance R2 of the pseudo insulation resistance lowering portion 10 occurs. Is considered to have occurred. Therefore, in such a case, an abnormality is reported without correcting the true value, and the flowchart shown in FIG. 3 ends.

  As described above, the present embodiment is characterized in that, in the fault diagnosis function of the ground fault detection device, it is determined that the detection signal is abnormal when the detection signal is not included in the normal range. Thus, since the determination value for determining abnormality is set in a range having a width, it can be determined that a failure has occurred if the detection signal is outside the normal range. Further, if the detection signal is included in the normal range, an error due to temperature characteristics or deterioration characteristics can be corrected by setting the detection signal to a true value. Therefore, the failure determination accuracy can be improved.

  In addition, since the combined resistance value of the resistor R1 and the resistor R2 can be changed into a plurality of patterns by switching the switches SW1 and SW2 of the pseudo insulation resistance lowering unit 10, it is possible to determine a failure on a line connecting a plurality of detection signals. Become. For this reason, the reliability of failure determination can be improved.

  As for the correspondence relationship between the description of the present embodiment and the description of the claims, the resistor R1 and the resistor R2 correspond to the “resistance for fault diagnosis” of the claims and include a microcomputer for determining an abnormality. The control unit 30 corresponds to “determination means” in the claims. The pseudo insulation resistance lowering unit 10 corresponds to “pseudo insulation resistance lowering means” in the claims.

(Second Embodiment)
In the present embodiment, parts different from the first embodiment will be described. In the first embodiment, the resistors R1 and R2 of the pseudo insulation resistance lowering unit 10 are connected in parallel, but in the present embodiment, they are connected in series. Hereinafter, the configuration will be described.

  FIG. 5 is an overall system diagram including the ground fault detection apparatus according to the present embodiment. As shown in this figure, the pseudo insulation resistance lowering unit 10 is connected in parallel to three resistors R1, R2, and R3 connected in series, a switch SW1 connected in parallel to the resistor R1, and a resistor R2. The switch SW2 and the switch SW3 connected to the resistor R3 are provided.

  Resistors R1 to R3 and a switch SW3 are connected in series. Further, the resistor R1 is connected to a connection point between the capacitor 11 and the resistor 20, and the switch SW3 is connected to the vehicle body 60.

  Since the switch SW3 needs to insulate the high voltage power supply system 40 side from the vehicle body 60 side as a single unit, a switch with a high breakdown voltage is used. Since the switch SW1 and the switch SW2 are divided by the resistors R1 to R3, the breakdown voltage is not as high as that of the switch SW3.

  The switches SW1 to SW3 are controlled by the microcomputer of the control unit 30. Further, the configuration other than the pseudo insulation resistance lowering portion 10 is the same as the configuration shown in FIG.

  FIG. 6 is a diagram showing a correlation between the combined resistance value (pseudo ground fault resistance R) of the three resistors R1 to R3 and the detection signal. In the present embodiment, the resistance values of the resistors R1 to R3 are each 100 kΩ. Thereby, the pseudo ground fault resistance R of the pattern A when all the switches SW1 to SW3 are turned ON becomes 100 kΩ. Further, the pseudo ground fault resistance R of the pattern B when the switch SW1 is turned off and the switch SW2 and the switch SW3 are turned on is 200 kΩ. Furthermore, when the switch SW1 and the switch SW2 are turned off and the switch SW3 is turned on, the pseudo ground fault resistance R of the pattern C is 300 kΩ.

  Thus, in the configuration in which the resistors R1 to R3 are connected in series, there is an advantage that it is easy to set the combined resistance value (pseudo ground fault resistance R) of the three resistors R1 to R3.

  As described above, even in the configuration in which the resistors R1 to R3 of the pseudo insulation resistance lowering unit 10 are connected in series, it is possible to improve the failure determination accuracy by determining whether or not the detection signal is within the normal range. Can do.

  Regarding the correspondence between the description of the present embodiment and the description of the claims, the resistors R1 to R3 correspond to the “resistance for failure diagnosis” in the claims.

(Other embodiments)
The configurations shown in the above embodiments are examples, and the present invention is not limited to the configurations described above, and other configurations that can realize the present invention may be employed. For example, the number of switches SW1 to SW3 in the pseudo insulation resistance lowering unit 10 may be one instead of two or three. In such a case, it is preferable that only one point in the dangerous area shown in FIGS. 4 and 6 is detected.

  Moreover, although the capacitor 11 is provided in the pseudo insulation resistance lowering portion 10, this is an example of the configuration, and the capacitor 11 may not be included in the pseudo insulation resistance lowering portion 10.

  Furthermore, the pattern of the combined resistance value (pseudo ground fault resistance R) is not limited to three patterns. A configuration that employs one pattern may be employed, or a configuration that employs four or more patterns.

10 Pseudo insulation resistance reduction part (Pseudo insulation resistance reduction means)
12 Wiring path 30 Control unit (determination means)
40 High-voltage power supply system 60 Car body R1-R3 Resistance

Claims (3)

A ground fault detection device for detecting a ground fault of a high voltage power supply system (40) mounted on a vehicle in an insulated state,
By electrically connecting the high voltage power supply system (40) and the vehicle body (60) of the vehicle via resistances (R1 to R3) for fault diagnosis, a pseudo insulation resistance is provided to the high voltage power supply system (40). Pseudo-insulation resistance lowering means (10) for generating a decrease;
A response when a predetermined signal is input to the wiring path (12) connecting the high-voltage power supply system (40) and the resistors (R1 to R3) when the pseudo-insulation resistance is reduced is acquired as a detection signal. It is determined whether or not the detection signal is included in a normal range set according to the resistance values of the resistors (R1 to R3), and it is determined that the detection signal is abnormal when the detection signal is not included in the normal range. A ground fault detection device comprising: means (30).   The ground fault detection device according to claim 1, wherein when the detection signal is included in the normal range, the determination unit (30) corrects a value indicated by the detection signal as a true value.   3. The pseudo insulation resistance lowering means (10) implements the pseudo insulation resistance reduction in a plurality of patterns by changing a resistance value of the resistors (R1 to R3). The ground fault detection apparatus of description.

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