JP3956790B2 - Ground fault detection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground fault detection device that detects a ground fault between a vehicle body of an electric vehicle equipped with a high voltage power source and a high voltage power source.
[0002]
[Prior art]
Conventionally, for example, a technique disclosed in Japanese Patent Application Laid-Open No. 8-70503 is known as a technique for detecting a ground fault between a high-voltage power supply provided in an electric vehicle and a vehicle body.
[0003]
In this conventional electric vehicle ground fault detection circuit, a rectangular wave pulse having a duty ratio of 50% is input to an impedance converter connected to a positive bus of a DC power source via a coupling capacitor and a resistor. The output is compared with the reference voltage to detect a ground fault between the high voltage power source and the vehicle body.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional ground fault detection circuit, since the impedance at one end of the coupling capacitor connected to the positive bus of the high voltage power supply is compared with a predetermined threshold value, the vehicle body itself has The impedance caused by the capacitance is also detected. In other words, it detects the total impedance of the impedance component for detecting the ground fault and the impedance due to the vehicle's capacitance, and it detects the ground fault even though it is not ground fault. There was a possibility of doing.
[0005]
Therefore, the present invention has been proposed in view of the above-described circumstances, and provides a ground fault detection device that can accurately detect a ground fault without erroneous detection.
[0006]
[Means for Solving the Problems]
In the present invention, the output terminal of the power source is connected to one end side of the capacitor, a pulse is applied to the other end side of the capacitor, and the voltage value generated on the other end side of the capacitor is detected and connected to the power source. In the ground fault detection device for determining the ground fault of the circuit, the pulse generating means for applying a pulse to the other end of the capacitor, and the pulse generating means for applying a pulse to the other end of the capacitor The voltage detection means for detecting the voltage amplitude value generated at the other end of the capacitor is compared with the threshold value and the voltage amplitude value detected by the voltage detection means to detect the occurrence of a ground fault in the circuit. A ground fault detection means; a capacitance estimation means for estimating the capacitance of the vehicle; and a threshold setting for setting a threshold based on the vehicle capacitance estimated by the capacitance estimation means. and means The frequency is set based on the vehicle capacitance estimated by the capacitance estimation means, and the pulse generation means applies a pulse of the set frequency to the other end of the capacitor, The occurrence of a ground fault in the circuit is detected by the ground fault detection means.
[0007]
【The invention's effect】
In the present invention, since the threshold for ground fault detection is set based on the capacitance of the vehicle, the ground fault can be detected without being affected by the capacitance of the vehicle (vehicle body) itself. Therefore, it is possible to accurately detect the ground fault without erroneous detection.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
The present invention is applied to, for example, an electric vehicle configured as shown in FIG.
[0010]
[Configuration of electric vehicle]
In the electric vehicle (hereinafter also referred to as a vehicle) of the present embodiment, the DC power discharged from the assembled battery 4 is converted into three-phase AC power by the inverter 1 and supplied to the motor 2. Drive. The driving force of the motor 2 is transmitted to the tire 7 via the speed reducer 5 and the drive shaft 6 to drive the vehicle.
[0011]
Further, the regenerative power generated by the motor 2 when the vehicle decelerates is supplied to the assembled battery 4 via the inverter 1, whereby the assembled battery 4 is charged.
[0012]
The electric power of the assembled battery 4 is also supplied to an air conditioner fan motor 8 mounted as an auxiliary machine of the vehicle, and the air conditioner fan motor 8 is rotationally driven by this electric power.
[0013]
The air conditioner fan motor 8 is provided with a current sensor 14 for detecting a current flowing through the air conditioner fan motor 8, and a current value detected by the current sensor 14 is output to a battery controller 9 described later. The
[0014]
The inverter 1 and the motor 2 described above are controlled by the vehicle controller 3 so that the motor 2 generates the required driving force based on the operation of an accelerator pedal and a brake pedal (not shown).
[0015]
The vehicle controller 3 includes peripheral components such as a CPU 21, ROM 22, RAM 23, and an input / output interface (not shown), and performs various calculations. The vehicle controller 3 is connected to the indicator 10 to notify various information by the indicator 10 and is connected to the battery controller 9 to communicate various information with the battery controller 9.
[0016]
11 is an outside air temperature sensor that detects the outside air temperature, 12 is a body temperature sensor that is provided on the right door of the vehicle and detects the body temperature, and 13 is an auxiliary machine temperature sensor that detects the temperature of the air motor fan motor 8. The outside air temperature by the outside air temperature sensor 11, the body temperature by the car body temperature sensor 12, and the temperature of the air conditioner fan motor 8 by the auxiliary machine temperature sensor 13 are output to the battery controller 9.
[0017]
Reference numeral 15 denotes an auxiliary machine operation switch for turning on and off the operation of the air conditioner. Reference numeral 16 denotes a temperature setting switch for setting the temperature of the air conditioner. The temperature set by the on / off signal 15 and the temperature setting switch 16 by these auxiliary machine operation switches. Is output to the battery controller 9.
[0018]
The battery controller 9 includes peripheral components such as a CPU 31, a ROM 32, a RAM 33, a timer 34 and an input / output interface (not shown), and performs an abnormality detection process described later based on various input information.
[0019]
Reference numeral 17 denotes a ground fault detection circuit, and one end of an insulation resistance Ri is connected to the plus bus of the assembled battery 4, and the assembled battery 4 and the vehicle body B are insulated by the insulation resistance Ri. Further, the capacitance of the vehicle body B is shown as vehicle body capacitance Ci.
[0020]
One end of the capacitor C is connected to one end of the insulation resistance Ri, and a resistor R1 and a buffer 41 are connected in series to the other end of the capacitor C. The buffer 41 is connected to the output terminal OUT and the input terminal IN1 of the battery controller 9. Connected. A buffer 42 is connected to the other end of the capacitor C via a resistor R2. The buffer 42 is connected to the input terminal IN2 of the battery controller 9.
[0021]
The ground fault detection circuit 17 captures a rectangular wave pulse output from the output terminal OUT of the battery controller 9 at the input terminal IN1 of the battery controller 9 and applies it to the resistors R1, R2 and the capacitor C via the buffer 41. After that, the data is taken into the input terminal IN2 through the buffer 42.
[0022]
[Electric vehicle abnormality detection processing]
Next, the abnormality detection process in the above-described electric vehicle will be described with reference to the flowcharts of FIGS.
[0023]
The control program based on this flowchart is executed by the battery controller 9.
[0024]
In this abnormality detection process, first, in step S1, the state of an ignition switch (not shown) (hereinafter referred to as an IGN switch) is detected, it is determined whether or not the IGN switch is on, and the IGN switch is on. If so, the process proceeds to step S2.
[0025]
In steps S2 to S4, in order to estimate the vehicle body capacitance Ci from the vehicle body temperature, the outside air temperature, and the auxiliary machine temperature, the vehicle body temperature is detected by reading the sensor signal from the vehicle body temperature sensor 12 (step S2). The sensor signal from the outside air temperature sensor 11 is read to detect the outside air temperature (step S3), and the sensor signal from the auxiliary machine temperature sensor 15 is read to detect the auxiliary machine temperature (step S4). Proceed with the process.
[0026]
In step S5, the vehicle body capacitance Ci with respect to the vehicle body temperature detected in step S2 is calculated with reference to the map data describing the change in the vehicle body capacitance Ci according to the vehicle body temperature in FIG. The process proceeds to S6. The map data shown in FIG. 5 is stored in the ROM 32 by obtaining a change in the vehicle body capacitance Ci with respect to the vehicle body temperature in advance through experiments or the like when designing an electric vehicle.
[0027]
In step S6, the correction coefficient for the auxiliary machine temperature detected in step S4 is calculated with reference to the correction table data describing the correction coefficient corresponding to the auxiliary machine temperature in FIG. The correction table data shown in FIG. 6 includes a correction coefficient for correcting the vehicle body capacitance Ci calculated in step S5 from the change in the vehicle body capacitance Ci according to the auxiliary machine temperature as shown in FIG. It is set for each and stored in the ROM 32. Then, by correcting the calculated correction coefficient by multiplying the vehicle body capacitance Ci detected in step S5, correction according to the auxiliary machine temperature is performed, and the process proceeds to step S7.
[0028]
In step S7, the state of the auxiliary machine operation switch 15 is detected to determine whether or not the auxiliary machine operation switch 15 is in the on state. If it is determined that the auxiliary machine operation switch 15 is not in the on state, the auxiliary machine operation switch 15 is turned on. The process proceeds to step S11 without correcting the vehicle body capacitance Ci according to the state of the machine (air conditioner fan motor 8), and if it is determined that the accessory operation switch 15 is in the ON state, the process proceeds to step S8. Proceed with the process.
[0029]
In step S8, the set temperature set by the temperature setting switch 16 is detected, and the process proceeds to step S9.
[0030]
In step S9, a temperature difference between the outside air temperature detected in step S3 and the set temperature detected in step S8 is calculated, and the process proceeds to step S10.
[0031]
In step S10, the correction coefficient for the temperature difference calculated in step S9 is calculated with reference to the correction table data describing the correction coefficient corresponding to the temperature difference in FIG. The correction table data shown in FIG. 8 includes, for each temperature difference, a correction coefficient for correcting the vehicle body capacitance Ci corrected in step S6 from the change in the vehicle body capacitance Ci according to the temperature difference as shown in FIG. It is set and stored in the ROM 32. Then, by correcting the calculated correction coefficient by multiplying the vehicle body capacitance Ci corrected in step S6, correction according to the auxiliary machine situation is performed, and the process proceeds to step S11.
[0032]
In step S11, the sensor signal is read from the current sensor 14, the current value flowing through the air conditioner fan motor 8 is detected, and the process proceeds to step S12.
[0033]
In step S12, the vehicle body capacitance Ci calculated in step S10 or step S6 is referred to the correction table data shown in FIG. 10, the output frequency corresponding to the vehicle body capacitance Ci is set, and the process proceeds to step S13. To proceed.
[0034]
In step S13, a rectangular wave pulse having the frequency set in step S12 is generated and output from the output terminal OUT. At the same time as the output timing, the timer 34 starts timing, and the process proceeds to step S14.
[0035]
In step S14, the rising time of the rectangular wave pulse input from the input terminal IN2 of the rectangular wave pulse output in step S13 is measured by the timer 34, and the process proceeds to step S15.
[0036]
In step S15, with reference to the correction table data describing the allowable range of the rise time with respect to the output frequency shown in FIG. 11, it is determined whether or not the rise time of the rectangular wave pulse measured in step S14 is within the allowable range. judge. If it is determined that the rise time is within the allowable range, the process proceeds to step S16. If it is determined that the rise time is not within the allowable range, the process proceeds to step S17.
[0037]
In step S16 and step S17, the amplitude of the rectangular wave pulse input in step S14 is detected, and the process proceeds to step S18 in FIG. 3 and step S19 in FIG.
[0038]
In steps S18 and S19, it is determined whether or not the amplitude of the rectangular wave pulse detected in steps S16 and S17 is equal to or less than a preset threshold value. This threshold value is obtained by referring to the correction table data describing the change of the determination threshold value with respect to the vehicle body capacitance Ci as shown in FIG. 12 by the battery controller 9 and calculating the vehicle body electrostatic capacitance calculated in step S6 or step S10. A value corresponding to the capacity Ci is set.
[0039]
If it is determined in step S18 and step S19 that the amplitude of the rectangular wave pulse is equal to or less than the threshold value, the process proceeds to step S20 and step S21, respectively, and a ground fault occurs between the assembled battery 4 and the vehicle body B. The vehicle controller 3 is notified that the ground fault has occurred by proceeding to step S22 and step S23, respectively. Then, the vehicle controller 3 drives the indicator 10 so as to notify the operator that a ground fault has occurred between the assembled battery 4 and the vehicle body B, and ends the process.
[0040]
If it is determined in step S18 that the amplitude of the rectangular wave pulse is not equal to or smaller than the threshold value, the process proceeds to step S24, the sensor signal from the current sensor 14 is read, and the current value flowing in the air conditioner fan motor 8 is detected. To do. Then, by comparing the current value detected this time with the current value detected in step S11, it is determined whether or not the current value has changed from the current value at the time of step S11. It is determined whether or not the operating state of the fan motor 8 has changed. If it is determined that the operating state of the accessory has changed, the process returns to step S1 and the above processing is repeated. If it is determined that the operating state of the accessory has not changed, the process proceeds to step S25. Proceed.
[0041]
In step S25, it is determined whether or not the time measured by the timer 34 that has started measuring time in step S13 has passed a fixed time. If it is determined that the fixed time has passed, the process returns to step S1 to return to a fixed time. If it is determined that the time has not elapsed, the process returns to step S16, and the processes after step S16 are repeated.
[0042]
If it is determined in step S19 in FIG. 4 that the amplitude of the rectangular wave pulse is not less than or equal to the threshold value, the process proceeds to step S26, where it is determined that the vehicle body capacitance Ci is an abnormal value. The vehicle controller 3 is notified. Then, the vehicle controller 3 drives the indicator 10 so as to notify the operator that the vehicle body capacitance Ci is an abnormal value, and ends the process.
[0043]
In the above-described example, the case where the vehicle body capacitance Ci corresponding to the vehicle body temperature is first obtained and the vehicle body capacitance Ci is corrected according to the auxiliary device temperature and the auxiliary device state has been described. After obtaining the vehicle body capacitance Ci according to the auxiliary machine temperature and the situation of the auxiliary machine, for example, a correction coefficient according to the vehicle body temperature as shown in FIG. 13 may be obtained to correct the vehicle body capacitance Ci.
[0044]
[Effect of the embodiment]
As described above in detail, according to the electric vehicle according to the present embodiment, the vehicle body capacitance Ci is increased by the operation of the auxiliary machine, and the insulation resistance Ri of the assembled battery 4 with respect to the vehicle body B is affected. Even in this case, the threshold value for the vehicle body capacitance Ci is detected by detecting the amplitude of the rectangular wave pulse, and the ground fault is detected using this threshold value. Even when the value of the insulation resistance changes by affecting the capacitance of the ground, the ground fault can be detected accurately.
[0045]
Further, according to this electric vehicle, the state of the auxiliary machine (air conditioner fan motor 8) in the vehicle is detected, and processing is performed in step S1 at regular intervals or when the operating state of the air conditioner fan motor 8 changes. Since the electrostatic capacitance between the vehicle body B and the plus bus 4A is detected, the vehicle body capacitance Ci changes depending on the operation state such as on / off of the auxiliary machine and the driving amount. Even if it exists, a ground fault can be detected correctly.
[0046]
Furthermore, according to this electric vehicle, the decrease in the insulation resistance Ri is detected by determining the vehicle body capacitance Ci based on the vehicle body temperature and the auxiliary machine temperature and changing the frequency of the rectangular wave pulse output to the ground fault detection circuit 17. Even when the vehicle body temperature or the auxiliary machine temperature changes, the ground fault can be accurately detected.
[0047]
Furthermore, according to this electric vehicle, when the vehicle body capacitance Ci is out of the predetermined range, it is determined that the vehicle body capacitance is abnormal, so that the operator is notified in distinction from the decrease in the insulation resistance Ri. be able to.
[0048]
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.
[0049]
The correspondence relationship between the embodiment of the above-described invention and the claims will be described below.
[0050]
The battery controller 9, the outside air temperature sensor 11, the vehicle body temperature sensor 12, the auxiliary machine temperature sensor 13, the auxiliary machine operation switch 15, the temperature setting switch 16, and steps S2 to S10 in FIG. The ground fault detection circuit 17 and steps S2 to S10 in FIG. 2, steps S18 to S21 in FIGS. 3 and 4 are ground fault detection means, and the battery controller 9 and steps S18 and S19 in FIGS. Threshold setting means is configured. Further, the battery controller 9 and steps S6, S10, and S12 of FIG. 2 constitute frequency setting means. Further, the battery controller 9 and step S26 in FIG. 4 constitute an abnormality determining means. Further, the battery controller 9 and step S24 of FIG.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an electric vehicle to which the present invention is applied.
FIG. 2 is a flowchart showing a processing procedure of abnormality detection processing by an electric vehicle to which the present invention is applied.
FIG. 3 is a flowchart showing a processing procedure of abnormality detection processing by an electric vehicle to which the present invention is applied.
FIG. 4 is a flowchart showing a processing procedure of abnormality detection processing by an electric vehicle to which the present invention is applied.
FIG. 5 is a diagram showing changes in vehicle body capacitance according to vehicle body temperature.
FIG. 6 is a diagram showing correction table data of correction coefficients for auxiliary machine temperatures.
FIG. 7 is a diagram showing a change in the vehicle body capacitance with respect to the auxiliary machine temperature.
FIG. 8 is a diagram showing correction table data of correction coefficients for a temperature difference between an outside air temperature and a set temperature of an air conditioner.
FIG. 9 is a diagram showing a change in the vehicle body capacitance with respect to the temperature difference between the outside air temperature and the set temperature of the air conditioner.
FIG. 10 is a diagram showing correction table data of the frequency of a rectangular wave pulse with respect to the vehicle body capacitance.
FIG. 11 is a diagram illustrating correction table data of a rise time of a rectangular wave pulse with respect to a frequency of the rectangular wave pulse.
FIG. 12 is a diagram showing a change in the determination threshold value with respect to the vehicle body capacitance.
FIG. 13 is a diagram showing correction table data of correction coefficients for vehicle body temperature.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inverter 2 Motor 3 Vehicle controller 4 Battery pack 5 Reducer 6 Drive shaft 7 Tire 8 Air conditioner fan motor 9 Battery controller 10 Indicator 11 Outside temperature sensor 12 Body temperature sensor 13 Auxiliary temperature sensor 14 Current sensor 15 Auxiliary equipment operation switch 16 Temperature setting switch 17 Ground fault detection circuit 21 CPU
22 ROM
23 RAM
31 CPU
32 ROM
33 RAM
34 Timer 41 Buffer 42 Buffer

Claims (5)

Connect the output terminal of the power supply to one end of the capacitor, apply a pulse to the other end of the capacitor, detect the voltage value generated at the other end of the capacitor, and In the ground fault detection device for determining the ground fault,
Pulse generating means for applying a pulse to the other end of the capacitor;
Voltage detecting means for detecting a voltage amplitude value generated on the other end side of the capacitor when a pulse is applied to the other end side of the capacitor by the pulse generating means;
A ground fault detection means for comparing the voltage amplitude value detected by the voltage detection means with a threshold value to detect the occurrence of a ground fault in the circuit;
Capacitance estimation means for estimating the capacitance of the vehicle;
Threshold setting means for setting a threshold based on the capacitance of the vehicle estimated by the capacitance estimation means ,
The frequency is set based on the vehicle capacitance estimated by the capacitance estimating means, and the pulse generating means applies a pulse of the set frequency to the other end side of the capacitor, and A ground fault detection device characterized by detecting the occurrence of a ground fault in the circuit by a fault detection means.   The said electrostatic capacity estimation means estimates the electrostatic capacity of a vehicle based on the temperature of the vehicle body and the temperature of the auxiliary machine mounted in the vehicle at least, The Claim 1 or Claim 2 characterized by the above-mentioned. Ground fault detection device.   The ground fault detection means compares the voltage amplitude value detected by the voltage detection means with a threshold value when it is determined that the rise time after outputting the pulse of the set frequency is not within an allowable range. If the voltage amplitude value is less than or equal to the threshold value, it is determined that there is a ground fault in the circuit. If the voltage amplitude value is not less than or equal to the threshold value, the capacitance is determined to be an abnormal value. The ground fault detection device according to claim 1. Auxiliary machine state detection means for detecting the operating state of the auxiliary machine mounted on the vehicle,
The ground fault detection means starts a process of detecting a ground fault between a vehicle body and a power source when an operation state of the auxiliary machine is changed by the auxiliary machine state detection means. The ground fault detection apparatus according to any one of claims 3 to 4. The ground fault detection device according to any one of claims 1 to 3 , wherein the ground fault detection by the ground fault detection means is performed at regular intervals.

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