JP2006177840A - Earth fault detector and diagnosis method of earth fault detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine an earth fault in the state where connection to a high-voltage power supply side is secured surely, without providing a different diagnosis circuit. <P>SOLUTION: A positive terminal of the high-voltage power supply 2 is connected to one end side of a coupling capacitor C1, and a pulse signal is applied to a measuring point A on the other end side of the coupling capacitor C1, and the earth fault of the high-voltage power supply is determined by detecting a voltage value generated on the measuring point A. When determining the earth fault of the high-voltage power supply 2, a switch circuit SW of an external noise removing circuit 13 is switched to the ON-state to remove a high frequency noise. When diagnosing an earth detector 1, a high frequency noise removal function of the external noise removing circuit 13 is stopped. When a high frequency noise is included in the voltage value generated at the measuring point A, it is diagnosed that the connection state between the high-voltage power supply 2 and the earth detector 1 is normal, and if the high frequency noise is not included in the voltage value generated at the measuring point A, it is diagnosed that the connection state between the high-voltage power supply 2 and the earth detector 1 is abnormal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ground fault detection device that detects, for example, a ground fault between a high-voltage power supply provided in an electric vehicle and a vehicle body, and a diagnosis method for the ground fault detection device.

  Usually, in an electric vehicle such as an electric vehicle, a fuel cell vehicle, and a hybrid electric vehicle, a high voltage circuit connected to the high voltage battery and a vehicle electrical circuit with the vehicle body grounded are insulated. Conventionally, as a ground fault detection device that performs ground fault determination of a high-voltage power supply, a ground fault detection device as described in Patent Document 1 below is known.

In Patent Document 1, a circuit between the high voltage power supply and the ground fault detection device is provided between the negative terminal of the high voltage power supply and the vehicle body side GND, separately from the circuit that actually determines the ground fault of the high voltage power supply. A diagnosis circuit including a resistor and a relay for diagnosing the connection state of And before using the high voltage power supply to operate the high voltage load, the relay is turned on and the high voltage power supply and the vehicle body side GND are turned on to create a state where a ground fault has actually occurred. . Then, by determining whether or not a ground fault has been detected by the ground fault detection device, a connection diagnosis between the high voltage power source and the ground fault detection device or a diagnosis of the ground fault detection device itself has been performed.
JP-A-10-221395

  However, in the above-described conventional technology, since the ground fault detection device is diagnosed by creating a situation where the high voltage power supply is actually grounded, the ground fault detection is performed in a state where the high voltage load is operating. The device cannot be diagnosed. If a high-voltage power supply and the vehicle body side GND are brought into conduction at a timing when a certain high-voltage load is not operating, electric leakage occurs, which may affect the operation of other high-voltage loads.

  Therefore, in the technique described in Patent Document 1 described above, if the high voltage load is a drive motor of an electric vehicle, diagnosis cannot be performed when the vehicle travels, so whether it is an actual ground fault detection, It was necessary to stop the vehicle without being able to determine whether it was a fault in the ground fault detection device itself.

  Furthermore, in the technique described in Patent Document 1 described above, when the relay of the diagnostic circuit breaks down and the high voltage power supply and the vehicle body side GND are brought into conduction, the occurrence of a ground fault can be detected. There was also sex.

  Therefore, the present invention has been proposed in view of the above-described circumstances, and it is possible to determine a ground fault in a state where the connection with the high voltage power supply side is ensured without providing a separate diagnostic circuit. An object of the present invention is to provide a ground fault detection device and a diagnostic method for the ground fault detection device.

  The present invention connects the output terminal of the high voltage power supply to one end side of the coupling capacitor, applies a pulse signal to the measurement point on the other end side of the coupling capacitor, and detects the voltage value generated at the measurement point. In the ground fault detection device for determining the ground fault of the high voltage power source, noise removing means for removing an AC noise signal generated in a load circuit connected to the high voltage power source and operating at a frequency higher than the frequency of the pulse signal; The voltage detection unit detects the voltage value generated at the measurement point from the signal from which the noise has been removed by the noise removal unit, and the change in the voltage value detected by the voltage detection unit with respect to the pulse signal causes the ground fault of the high voltage power supply. And a ground fault detecting means for determining.

  In the present invention, the operation of removing the AC noise signal by the noise removing means is stopped, and when the AC noise signal is included in the voltage value detected by the voltage detecting means, the connection state with the high voltage power supply If the voltage value detected by the voltage detection means does not include an AC noise signal, the connection state with the high voltage power supply is diagnosed as abnormal, thereby Resolve.

  According to the present invention, when diagnosing the connection state between the ground fault detection means and the high voltage power source, the AC noise removal function is stopped, and when the AC noise cannot be detected, the ground fault detection device and the high voltage power source are connected. It can be determined that the state is abnormal. Therefore, according to the present invention, in order to diagnose the connection state between the ground fault detection device and the high voltage power source, a state where the connection to the high voltage power source side is reliably ensured without providing a separate diagnostic circuit. The ground fault can be determined.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The present invention is applied, for example, to a vehicle electrical system configured as shown in FIG.

[Configuration of vehicle electrical system]
In this vehicle electrical system, the ground fault detection device 1 determines that a ground fault has occurred in the high voltage power source 2. The ground fault detection device 1 is connected to a high voltage system circuit including a high voltage power source 2, an AC load circuit 3, a motor 4, a motor controller 5, and a relay 6 via a connection terminal 1a.

  The AC load circuit 3 switches the DC voltage from the high-voltage power supply 2 according to the control of the motor controller 5 and supplies the AC voltage to the motor 4 when the relay 6 is in a conductive state. The AC load circuit 3 supplies power to the motor 4 from the high-voltage power source 2 in response to a driving force generation request of the electric vehicle. This AC load circuit 3 is insulated from an electrical component which is a weak electric circuit in an electric vehicle by an insulation resistance.

  In such a vehicle electrical system, since the ground fault detection device 1 and the AC load circuit 3 are electrically connected, the AC load circuit 3 to the ground fault detection device 1 are connected to an inverter that is the AC load circuit 3. High-frequency noise such as switching noise flows in. In the case where the motor 4 is a three-phase AC motor, high-frequency noise on the order of 100 kHz to several 100 kHz usually flows into the ground fault detection device 1. Although not shown, the high voltage power supply 2 is also connected to an inverter of an air conditioner, which is another load circuit mounted on the electric vehicle.

  The ground fault detection device 1 detects the insulation resistance of the high voltage power source 2 in order to detect that the high voltage power source 2, the AC load circuit 3, and the high power system on the motor 4 side are completely grounded. Detect value. Specifically, the ground fault detection apparatus 1 includes a coupling capacitor C1, a resistor R1, a control circuit 11, a comparator 12, and an external noise removal circuit that are connected to the positive output terminal (+) of the high voltage power supply 2. 13 and a comparator 14. In the present embodiment, the coupling capacitor C1 is connected to the plus output terminal (+) of the high voltage power supply 2, but may be connected to the minus output terminal (−).

  The external noise removal circuit 13 functions as a voltage detection unit that measures a voltage generated at one end side (measurement point A) of the coupling capacitor C1 and has a function of removing high-frequency noise, and includes a resistor R2 and a capacitor C2. It is composed of a series connection circuit with a switch circuit SW. Further, the external noise removing circuit 13 is provided with a comparator 14 connected to the control circuit 11 at a connection point between the resistor R2 and the capacitor C2. Further, in the external noise removing circuit 13, the switch circuit SW has one end connected to the capacitor C2 and the other end grounded. A Zener diode that regulates the voltage value supplied to the comparator 14 may be provided in parallel with the capacitor C2.

  The control circuit 11 outputs a pulse signal to the measurement point A connected between the resistor R1 and the coupling capacitor C1 and connected to the external noise removal circuit 13. In addition, the control circuit 11 detects the voltage generated at the measurement point A and determines the ground fault of the high voltage power supply 2. The control circuit 11 outputs a voltage signal (voltage signal generated at a connection point between the resistor R2 and the capacitor C2) output from the short waveform pulse generating unit 21 that outputs a pulse signal and the external noise removing circuit 13 to an A / D. An A / D conversion unit 22 for conversion and a ground fault detection unit 23 such as a CPU serving as a control center are provided.

  The ground fault detector 23 oscillates a pulse signal from the short waveform pulse generator 21 when determining a ground fault of the high voltage power supply 2, and determines the voltage value output by the A / D converter 22 for the pulse signal. The ground fault of the high voltage power supply 2 is detected from the change. The ground fault detection signal detected by the ground fault detector 23 is transmitted to an alarm device (not shown). The ground fault detection unit 23 is provided with a memory (not shown), and the memory includes a threshold voltage that is a voltage value measured by the A / D conversion unit 22 and an insulation resistance value of the high-voltage power supply 2. Is stored.

  Here, when the insulation resistance of the high voltage power supply 2 is reduced or the vehicle capacity is increased, even if the pulse signal is generated by the short waveform pulse generator 21, the voltage value of the pulse signal is obtained. However, the voltage value input by the A / D converter 22 becomes small. Therefore, the ground fault detection unit 23 compares the voltage value input by the A / D conversion unit 22 with the predetermined threshold voltage stored in the memory, and a ground fault occurs in the high voltage power supply 2. It is determined whether or not.

  The frequency of the pulse signal oscillated from the short waveform pulse generator 21 may be any frequency that is lower than the switching frequency of the AC load circuit 3, and is lower than the AC circuits other than the AC load circuit 3. Any low frequency that is not used in the vehicle electrical system may be used.

  In such a vehicle electrical system, the external noise removal circuit 13 passes the coupling capacitor C1 from the AC load circuit 3 when the switch circuit SW is in a conductive state (ON state) as shown in FIG. Inflow high-frequency noise flows to the ground side. Thereby, it functions as a low frequency pass filter that passes a pulse signal having a frequency lower than the high frequency noise to the control circuit 11 side, in other words, functions as a high frequency cutoff filter.

  On the other hand, when the switch circuit SW is in an open state (off state) as shown in FIG. 3, the external noise removal circuit 13 allows not only the pulse signal but also high-frequency noise to flow to the A / D conversion unit 22. That is, when the switch circuit SW is turned off, the function as a low-frequency pass filter is stopped, in other words, the function as a high-frequency cutoff filter is stopped.

  Such switching between the ON state and the OFF state of the switch circuit SW is performed by a control signal of the ground fault detection unit 23 when diagnosing the connection state between the ground fault detection device 1 and the high voltage power supply 2. And the ground fault detection part 23 determines that a high frequency noise signal does not flow into the ground fault detection apparatus 1 in the state where the high voltage power supply 2 is not connected to the connection terminal 1a, as shown in FIG. .

  Further, the ground fault detection unit 23 performs an internal diagnosis process for determining whether or not an internal circuit including the comparator 12, the resistor R1, the coupling capacitor C1, and the external noise removing circuit 13 operates normally.

[Operation of vehicle electrical system]
Next, the operation of the vehicle electrical system configured as described above will be described with reference to the flowchart of FIG.

  This vehicle electrical system executes the process of step S1 not only when the vehicle is started but also when the vehicle is running, that is, when a high voltage system such as the AC load circuit 3 and the motor 4 is operating. To do.

  First, diagnosis of the connection state between the ground fault detection device 1 and the high voltage power supply 2 is started, and the switch circuit SW is turned off by the ground fault detection unit 23 in step S1, and the high frequency noise of the external noise removal circuit 13 is set. Put the removal function in a stopped state.

  Next, in step S2, the ground fault detector 23 oscillates a pulse signal from the short waveform pulse generator 21, measures the voltage value input after oscillating the pulse signal in the A / D converter 22, and step S3. , It is determined whether or not the connection state between the ground fault detection device 1 and the high voltage power supply 2 is abnormal. At this time, when the ground fault detection unit 23 does not include high-frequency noise in the voltage value A / D converted by the A / D conversion unit 22, the high voltage power supply 2 is not connected to the connection terminal 1a. On the other hand, if it contains high frequency noise, the high voltage power supply 2 is connected to the connection terminal 1a, and the high frequency noise signal from the AC load circuit 3 passes through the external noise removal circuit 13. It is determined that the input is normal.

  If the connection state is abnormal, the process proceeds to step S11, and the ground fault detection unit 23 has failed in the ground fault detection device 1, and cannot perform the ground fault determination of the high voltage power supply 2. A ground fault detection signal indicating the state is output to a warning device (not shown). Thereby, the vehicle electrical system notifies the user of an abnormality in the ground fault detection device 1.

  On the other hand, if the connection state is normal, the process proceeds to step S4 to start the ground fault determination of the high voltage power supply 2, and the ground fault detection unit 23 turns on the switch circuit SW in step S5. Then, the external noise removing circuit 13 is made to remove high frequency noise, the pulse signal is oscillated from the short waveform pulse generating unit 21, and the voltage value is detected by the A / D converting unit 22. If the voltage value detected by the A / D converter 22 is smaller than the threshold voltage, it is determined that a ground fault has occurred in the high voltage power supply 2, and the process proceeds to step S7, where the A / D conversion is performed. If the voltage value detected by the unit 22 is not smaller than the threshold voltage, it is determined that the high voltage power supply 2 is in a normal state where no ground fault has occurred, and the process is terminated.

  In step S7, the ground fault detection unit 23 determines that the diagnosis of the connection state between the ground fault detection device 1 and the high voltage power source 2 is performed again, and in step S8, the switch circuit SW is turned off, and external noise is detected. A pulse signal is oscillated from the short waveform pulse generator 21 with the high frequency noise removal function of the removal circuit 13 stopped. When the voltage value A / D converted by the A / D converter 22 does not include high-frequency noise, the ground fault detector 23 is in a connected state in which the high voltage power source 2 is not connected to the connection terminal 1a. It is determined that there is an abnormality, and a ground fault detection signal is output in step S11 to give a warning.

  On the other hand, when the ground fault detector 23 includes high frequency noise in the voltage value A / D converted by the A / D converter 22, the high voltage power source 2 is connected to the connection terminal 1a. It is determined that Thereby, it can be recognized that the determination result that the ground fault has occurred in step S6 is accurate, and the ground fault detection unit 23 can release a warning to stop the vehicle or the relay 6 in step S10. Then, the motor controller 5 is controlled so as to stop the operations of the AC load circuit 3 and the motor 4, and the process is terminated.

  In step S2, step S3, and step S9, the ground fault detection unit 23 changes the frequency of the pulse signal when it normally outputs a 10 Hz pulse signal when determining the ground fault of the high voltage power supply 2. Then, the internal diagnosis processing of various ground fault detection devices 1 may be performed.

  Specifically, when a pulse signal for diagnosis having a frequency of 1 Hz is output and the voltage value detected by the A / D converter 22 is a constant value of L (low) level and does not become H (high) level. It can be diagnosed that a failure has occurred in which a part of the circuit portion of the ground fault detection device 1 is short-circuited to GND. Further, when a pulse signal having a frequency of 100 Hz is output and the amplitude of the voltage value detected by the A / D converter 22 is smaller than a predetermined value different from the threshold value at the time of ground fault determination, the noise of the external noise removal circuit 13 When it is recognized that the resistance values of the removal capacitor C2 and the noise removal resistor R2 are normal and a voltage amplitude of a predetermined value or more is input to the A / D converter 22, the external noise removal circuit 13 It can be diagnosed that the resistance value of the resistor R2 and the resistance value of the capacitor C2 or the resistor R2 are abnormal. Further, when outputting a pulse signal having a frequency of 100 Hz, a change in voltage amplitude in the A / D converter 22 when the relay 6 is turned from the off state to the on state is detected, and the relay 6 is turned off. If it is determined that there is no amplitude change between the current voltage amplitude and the voltage amplitude after being turned on, it is possible to diagnose that there is an abnormality in the coupling capacitor C1.

  Thereby, after detecting that there is no abnormality in the connection state between the ground fault detection device 1 and the high voltage power source 2 and that there is no abnormality in the internal circuit of the ground fault detection device 1, the ground fault of the high voltage power source 2 is detected. The detected result can be output, and the reliability of the ground fault determination result can be improved.

[Effect of the embodiment]
As described above in detail, according to the vehicle electrical system to which the present invention is applied, when the connection state between the ground fault detection device 1 and the high voltage power supply 2 is diagnosed, the switch circuit SW is turned off to externally When the high frequency noise removal function of the noise removal circuit 13 is stopped and the high frequency noise cannot be detected by the control circuit 11, it can be determined that the connection state between the ground fault detection device 1 and the high voltage power supply 2 is abnormal. Therefore, according to this vehicle electrical system, in order to diagnose the connection state between the ground fault detection device 1 and the high voltage power source 2, the connection to the high voltage power source 2 side can be reliably performed without providing a separate diagnostic circuit. The ground fault can be determined in the secured state.

  Thereby, according to the vehicle electrical system, for example, the insulation between the high voltage power source 2 side and the low power side such as the ground fault detection device 1 is performed without diagnosing the connection state by actually grounding the high voltage power source 2. The connection state can be diagnosed without any influence on the vehicle, and the connection state can be diagnosed even when the vehicle is running and the AC load circuit 3 is operating. The ground fault determination result of 1 can be made more reliable.

  Specifically, as a configuration for stopping the high-frequency noise removal function of the external noise removal circuit 13, a switch circuit SW is provided, and the connection state can be diagnosed only by performing on / off control of the switch circuit SW.

  Moreover, according to this vehicle electrical system, during the operation of the AC load circuit 3, the high frequency noise removal function is stopped, the connection state between the ground fault detection device 1 and the high voltage power supply 2 is diagnosed, and the connection state is abnormal. If the connection state is normal, the high-frequency noise signal is removed, the ground fault of the high voltage power supply 2 is determined and the ground fault is detected. Since an alarm can be performed, a highly reliable ground fault determination result can be notified after the connection state is diagnosed while the vehicle is running.

  The above-described embodiment is an example of the present invention. For this reason, the present invention is not limited to the above-described embodiment, and various modifications can be made depending on the design and the like as long as the technical idea according to the present invention is not deviated from this embodiment. Of course, it is possible to change.

It is a block diagram which shows the structure of the vehicle electrical system which applied this invention. It is a block diagram which shows the structure at the time of removing a high frequency noise signal in the vehicle electrical system to which this invention is applied. It is a block diagram which shows a structure when the high frequency noise removal function is stopped in the vehicle electrical system to which this invention is applied. It is a block diagram for demonstrating a state when there exists abnormality in a connection state in the vehicle electrical system which applied this invention. It is a flowchart for demonstrating operation | movement of the vehicle electrical system which applied this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground fault detection apparatus 2 High voltage power supply 3 AC load circuit 4 Motor 5 Motor controller 6 Relay 11 Control circuit 12, 14 Comparator 13 External noise removal circuit 21 Short waveform pulse generation part 22 A / D conversion part 23 Ground fault detection part C1 Coupling capacitor C2 capacitor SW switch circuit

Claims (5)

Connect the output terminal of the high voltage power supply to one end side of the coupling capacitor, apply a pulse signal to the measurement point on the other end side of the coupling capacitor, detect the voltage value generated at the measurement point, In the ground fault detection device for determining the ground fault of the high voltage power supply,
Noise removing means for removing an AC noise signal generated in a load circuit connected to the high voltage power source and operating at a frequency higher than the frequency of the pulse signal;
Voltage detection means for detecting a voltage value generated at the measurement point from a signal from which noise has been removed by the noise removal means;
A ground fault detection means for determining a ground fault of the high voltage power supply from a change in the voltage value detected by the voltage detection means for the pulse signal;
The ground fault detecting unit stops the operation of removing the AC noise signal by the noise removing unit, and the high voltage power source when the AC noise signal is included in the voltage value detected by the voltage detecting unit. When the voltage value detected by the voltage detection means does not include the AC noise signal, the connection state with the high voltage power supply is diagnosed as abnormal. A ground fault detection device characterized by that. The noise removing means includes a resistor and a capacitor connected in series to the measurement point, and a switch circuit provided on the ground side of the capacitor,
The ground fault detection device according to claim 1, wherein the ground fault detection unit opens the switch circuit when diagnosing a connection state with the high voltage power source. The ground fault detection means, during operation of the load circuit,
Stop the operation of removing the AC noise signal by the noise removing means, diagnose the connection state with the high-voltage power supply, and if the connection state is abnormal, make an alarm,
When the connection state is normal, an operation of removing the AC noise signal by the noise removing unit is performed, and from the change in the voltage value detected by the voltage detecting unit with respect to the pulse signal, the high voltage power supply The ground fault detection device according to claim 1 or 2, wherein a ground fault is determined and an alarm is issued when a ground fault is detected. Connect the output terminal of the high voltage power supply to one end side of the coupling capacitor, apply a pulse signal to the measurement point on the other end side of the coupling capacitor, detect the voltage value generated at the measurement point, In the diagnostic method of the ground fault detection device for determining the ground fault of the high voltage power supply,
When determining the ground fault of the high voltage power supply,
The AC noise signal generated in the load circuit connected to the high voltage power supply and operating at a frequency higher than the frequency of the pulse signal is removed, and the voltage value generated at the measurement point is detected from the signal from which the noise has been removed. And determining a ground fault of the high-voltage power supply from a change in the detected voltage value with respect to the pulse signal,
When diagnosing the ground fault detection device,
When the operation for removing the AC noise signal is stopped and the AC noise signal is included in the voltage value generated at the measurement point, the connection state between the high-voltage power supply and the ground fault detection device is normal. When the voltage value generated at the measurement point does not include the AC noise signal, the connection state between the high-voltage power supply and the ground fault detection device is diagnosed as abnormal. A method for diagnosing a ground fault detection device characterized by the above. During operation of the load circuit,
Stop the operation of removing the AC noise signal by the noise removing means, diagnose the connection state with the high-voltage power supply, and if the connection state is abnormal, make an alarm,
When the connection state is normal, an operation of removing an AC noise signal by the noise removing unit is performed, and a ground of the high voltage power source is detected from a change in the voltage value detected by the voltage detecting unit with respect to the pulse signal. The ground fault detection device diagnosis method according to claim 4, wherein a fault is determined and an alarm is issued when a ground fault is detected.

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