JP3783633B2 - Ground fault detection device for vehicles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ground fault detection apparatus.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as a technique for detecting a ground fault between a high-voltage power supply provided in an electric vehicle and a vehicle body, a technique described in Japanese Patent Laid-Open No. 8-70503 (hereinafter referred to as a conventional example) is known.
[0003]
In the above conventional example, a rectangular wave pulse with a duty ratio of 50% is input to an impedance converter connected to a positive bus of a DC power supply via a coupling capacitor and a resistor, and the output of this rectangular wave pulse is compared with a reference voltage. A ground fault is detected.
[0004]
[Problems to be solved by the invention]
However, in the ground fault detection apparatus described in the above-described conventional example, 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 impedance generated by the capacity of the vehicle body itself is also detected. That is, there is a drawback that the impedance component for detecting the ground fault and the impedance due to the capacity of the vehicle are detected, and the detection cannot be performed with high accuracy.
[0005]
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a vehicle ground fault detection device capable of detecting a ground fault with high accuracy.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a positive terminal of a DC power source is connected to one end side of a coupling capacitor, and a rectangular wave pulse is applied to a measurement point on the other end side of the coupling capacitor. applying a signal, the detecting the that voltage signals be generated in the measuring point, the vehicle site fault sensing device for detecting a ground fault of the DC power source, when the rectangular wave pulse signal is the first phase The second voltage measured at the measurement point when the first voltage value measured at the measurement point and the rectangular wave pulse signal are in a second phase different from the first phase. A difference between the voltage and the voltage value is obtained, and a ground fault of the DC power supply is detected based on the difference voltage.
[0007]
According to the second aspect of the present invention, a positive terminal of a DC power supply is connected to one end side of the coupling capacitor, a rectangular wave pulse signal is applied to a measurement point on the other end side of the coupling capacitor, and the measurement point to detect to that voltage signals occurs, the vehicle site fault sensing device for detecting a ground fault of the DC power source, an oscillation circuit for outputting a rectangular wave pulse signal to the measurement point, the rectangular wave pulse signal is first When the phase becomes 1, the first voltage value measured at the measurement point and the point when the rectangular wave pulse signal becomes the second phase different from the first phase A voltage measuring means for measuring a second voltage value measured in accordance with the first voltage value and obtaining a difference between the first voltage value and the second voltage value; and based on the differential voltage measured by the voltage measuring means. Detecting means for detecting a ground fault of the DC power supply , When the ground fault by said detecting means is detected, characterized in that anda informing means for informing them.
[0008]
According to a third aspect of the present invention, the rectangular wave pulse has a duty ratio of 50%, the first phase is a point in time when the rectangular wave pulse is at H level, and the second phase is a rectangular wave The pulse is at an L level. According to a fourth aspect of the present invention, the first phase is a phase immediately before the point in time when the rectangular wave pulse changes from H level to L level, and the second phase is that the rectangular wave pulse is L It is a phase immediately before the time point when the level changes to H level. The invention according to claim 5 is characterized in that the first phase and the second phase are phases when a voltage signal generated at the measurement point is not affected by a change in vehicle capacity. .
[0009]
According to a sixth aspect of the present invention, in the rectangular wave pulse, when the capacity of the vehicle exceeds 90% of the maximum capacity value, the differential voltage between the first voltage and the second voltage becomes small. Thus, the frequency of the rectangular wave pulse signal, the first phase, and the second phase are set.
[0011]
【The invention's effect】
In the invention of claim 1, a differential voltage between the first voltage measured when the rectangular wave pulse becomes the first phase and the second voltage measured when the square wave pulse becomes the second phase is obtained, A ground fault is detected based on the magnitude of the differential voltage. Therefore, it is possible to reliably detect the occurrence of a ground fault or an increase in vehicle capacity.
[0012]
In the invention of claim 2, the first voltage measured when the rectangular wave pulse output from the oscillation circuit becomes the first phase and the second voltage measured when the second phase becomes the second phase are obtained. taking measurement. The voltage measuring means measures these differential voltages and detects a ground fault based on the magnitude of the differential voltage. Therefore, it is possible to reliably detect occurrence of a ground fault or increase in vehicle capacity and notify the operator.
[0013]
According to the third to fifth aspects of the present invention, the duty ratio of the rectangular wave pulse is set to 50%, the first phase is set to the H level of the rectangular wave pulse, and the second phase is set to the L level of the rectangular wave pulse. Therefore, highly accurate ground fault detection becomes possible.
[0014]
In the invention of claim 6 , when the capacity of the vehicle exceeds 90% of the maximum capacity value, the frequency of the rectangular wave pulse so that the differential voltage between the first voltage and the second voltage becomes small, and Since the first phase and the second phase are set, it is possible to reliably detect the occurrence of a ground fault or an increase in vehicle capacity.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a ground fault detection apparatus according to an embodiment of the present invention. As shown in the figure, the ground fault detection device 10 detects a ground fault when a DC power source 1 for supplying a voltage to an inverter 2 for driving a motor 3 for an electric vehicle has a ground fault. A ground fault detection circuit 4 and an indicator (notification means) 5 for notifying the operator when a ground fault is detected are provided.
[0017]
The ground fault detection circuit 4 has a coupling capacitor C1, a control circuit 6, a voltage measurement circuit 7, and a resistor R1, which are connected to the positive output terminal of the DC power supply 1.
[0018]
The voltage measurement circuit 7 measures a voltage generated on one end side (measurement point A) of the coupling capacitor C1, and is connected in parallel to the series connection circuit of the resistor R2 and the capacitor C2 and the capacitor C2. Zener diode D1. A connection point between the resistor R2 and the capacitor C2 is connected to the control circuit 6.
[0019]
The control circuit 6 outputs a rectangular wave pulse signal to the measurement point A, detects a voltage generated at the measurement point A, and detects a ground fault in the DC power source 1 and outputs a rectangular wave pulse. An output unit (oscillation circuit) 11 for performing A / D conversion on a voltage signal output from the voltage measurement circuit 7 (voltage signal generated at a connection point between the resistor R2 and the capacitor C2); A CPU (voltage measuring means, detecting means) 13 serving as a control center, a RAM 14, a ROM 15, a timer 16, and a counter 17 are provided.
[0020]
As will be described later, the CPU 13 sets the frequency and duty ratio of the rectangular wave pulse signal output from the output unit 11, and based on the voltage signal output from the A / D conversion unit 12, Detect a ground fault.
[0021]
The ROM 15 stores data indicating the correspondence between the voltage value (voltage amplitude value) measured by the voltage measurement circuit 7 and the insulation resistance value of the DC power supply 1.
[0022]
Next, the operation of the present embodiment configured as described above will be described with reference to the flowchart shown in FIG.
[0023]
First, in step S10, the counter 17 is reset. Next, counting by the counter 17 is started in step S20.
[0024]
After that, in step S30, the output unit 11 outputs a signal having an “H” level of a rectangular wave pulse signal having a preset cycle T and a duty ratio (for example, 50%). Then, when the time Tc timed by the counter 17 is just before ½ of the period T, that is, immediately before the time T / 2 has elapsed, YES is determined in step S40, and voltage measurement is performed in step S50. The voltage value at the measurement point A detected by the circuit 7 is read into the CPU 13 via the A / D converter 12. The voltage value at this time is assumed to be VH (first voltage value).
[0025]
Next, in step S60, a signal of “L” level of the rectangular wave pulse signal is output. When the time Tc counted by the counter 17 is immediately before the cycle T, YES is determined in step S70, and the voltage value of the measurement point A detected by the voltage measurement circuit 7 is converted to the A / D conversion unit in step S80. 12 is read into the CPU 13 via The voltage value at this time is VL (second voltage value).
[0026]
Thereafter, in step S90, the CPU 13 calculates a difference (VH−VL) between the voltage value VH measured in the above-described process and VL. This differential voltage is VP-P.
[0027]
In step S100, the difference voltage VP-P is compared with the first threshold value V1, and if the difference voltage VP-P is larger than the threshold value V1, there is no abnormality (ie, a ground fault occurs). The process from step S10 is repeated.
[0028]
On the other hand, if it is smaller than the threshold value V1, the second threshold value V2 (where V2 <V1) is compared with the differential voltage VP-P in step S110. If V2 is smaller, it is determined that either a slight ground fault or an increase in vehicle capacity is detected, and a warning is displayed on the indicator 5 in step S130.
[0029]
If V2 is larger, it is determined that either a severe ground fault or an increase in vehicle capacity is detected (that is, it is determined that it is not good to continue driving the vehicle any more), and step In S120, a display indicating that the motor 3 is to be stopped is displayed.
[0030]
In this way, the voltage value of the measurement point A is detected, and based on the detection result, it is determined whether a ground fault or an increase in vehicle capacity has occurred, and the indicator 5 displays a warning or prompting stoppage. It can be done.
[0031]
Next, the voltage waveform generated at the measurement point A will be described with reference to the timing chart shown in FIG.
[0032]
FIG. 3A shows a rectangular wave pulse signal (period T) output from the output unit 11, and S1, S2,... Indicate sampling timings. As shown in the figure, sampling timings S1, S2,... Are set slightly before the trailing edge (falling point) of the rectangular wave pulse signal and slightly before the leading edge (rising point). That is, the sampling timings S1, S2,... Are set for each T / 2, and the rectangular wave pulse signal is sampled alternately at the “H” level and “L” level. Then, the voltage VH is measured at timings S1, S3,... (Odd number; first phase), and the voltage VL is measured at timings S2, S4,. Is measuring.
[0033]
FIG. 5B shows a voltage waveform generated at the measurement point A when it is normal, that is, when a ground fault has not occurred. As shown in the drawing, the voltage waveform at the measurement point A is measured at the voltage VH measured at the timing S1 and at the timing S2, although it is slightly rounded at the leading and trailing edges of the rectangular wave pulse. The difference VP-P (= VH−VL) with respect to the voltage VL is a large value. Therefore, NO is determined in step S100 described above (FIG. 2), and no ground fault is detected.
[0034]
FIG. 3C shows a voltage waveform generated at the measurement point A when a ground fault occurs. When a ground fault occurs, the insulation resistance of the DC power source 1 decreases. Therefore, the voltage value VH measured at the timings S1, S3,... (Odd number) is a low value. Accordingly, the differential voltage VP-P (= VH-VL) becomes a low value, and when the voltage VP-P is equal to or lower than the first threshold value V1 and larger than the second threshold value V2, an alarm is issued. When it is output and is smaller than the second threshold value V2, a display for prompting the vehicle to stop is displayed.
[0035]
Further, FIG. 3D shows a voltage waveform generated at the measurement point A when the capacity of the vehicle is increased. In this case as well, when the ground fault occurs, the DC power source 1 Since the insulation resistance decreases, the voltage VH becomes a low value. Accordingly, an alarm or a display prompting the stop is displayed.
[0036]
And the driver | operator of a vehicle can take an appropriate response by seeing this display.
[0037]
That is, in the conventional example, the effective value of the voltage generated at the measurement point A is obtained, and the ground fault is detected based on the effective value. Therefore, as shown in FIG. The effective voltage value for detecting the ground fault is affected by the vehicle capacity (2πfC), but in this embodiment, as shown in FIG. Since there is an area, high-accuracy ground fault detection can be performed in this area.
[0038]
Thus, in the ground fault detection apparatus 10 according to the present embodiment, the rectangular wave pulse signal is applied to one end side (measurement point A) of the coupling capacitor C1, and measurement is performed when the rectangular wave pulse signal is at the H level. The voltage VH and the measurement voltage VL at the L level are obtained, and the occurrence of the ground fault or the increase in the vehicle capacity is detected based on the difference VP-P. Therefore, reliable ground fault detection or increase in vehicle capacity can be detected.
[0039]
In addition, as shown in FIG. 3D, it is understood that when the vehicle capacity increases, the pulse waveform changes greatly near the leading edge and does not change much near the trailing edge. Therefore, if the sampling timings S1, S2,... Are set near the trailing edge of the pulse waveform, the influence of the vehicle capacity can be reduced. However, on the contrary, this makes it difficult to detect changes in vehicle capacity. Therefore, in order to remove the influence of the vehicle capacity and to detect the change in the vehicle capacity with high accuracy, the value of the differential voltage VP-P becomes small when exceeding 90% of the designed maximum vehicle capacity. By setting the frequency of the rectangular wave pulse signal output from the output unit 11, it is possible to detect the ground fault with higher accuracy.
[0040]
Further, correspondence data between the voltage amplitude and the insulation resistance is stored in advance in the ROM 15 shown in FIG. 1, and the insulation resistance is obtained by applying the voltage value measured at the measurement point A to the correspondence data. Based on this, it is also possible to configure to detect a ground fault.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a ground fault detection apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a processing procedure of the ground fault detection apparatus according to the embodiment of the present invention.
FIG. 3 is a timing chart showing a voltage signal generated at a measurement point A in the ground fault detection device according to the embodiment of the present invention.
FIG. 4 is a characteristic diagram showing a relationship between insulation admittance and a measured voltage value.
[Explanation of symbols]
1 DC power supply 2 Inverter 3 Motor 4 Ground fault detection circuit 5 Indicator (notification means)
6 Control Circuit 7 Voltage Measurement Circuit 10 Ground Fault Detection Device 11 Output Unit (Oscillation Circuit)
12 A / D converter 13 CPU
14 RAM
15 ROM
16 Timer 17 Counter C1 Coupling capacitor

Claims (6)

Connect the positive terminal of the DC power source to one end of the coupling capacitor, the measuring point as a second end of the coupling capacitor, by applying a rectangular pulse signal, detect to that voltage signals generated in the measuring point In the vehicle ground fault detection device for detecting the ground fault of the DC power supply,
When the rectangular wave pulse signal becomes the first phase, the first voltage value measured at the measurement point and the rectangular wave pulse signal become the second phase different from the first phase. A vehicle ground fault detection device characterized in that, at the time, a difference from the second voltage value measured at the measurement point is obtained, and a ground fault of the DC power supply is detected based on the difference voltage. Connect the positive terminal of the DC power source to one end of the coupling capacitor, the measuring point as a second end of the coupling capacitor, by applying a rectangular pulse signal, detect to that voltage signals generated in the measuring point In the vehicle ground fault detection device for detecting the ground fault of the DC power supply,
An oscillation circuit that outputs a rectangular pulse signal to the measurement point;
When the rectangular wave pulse signal becomes the first phase, the first voltage value measured at the measurement point and the rectangular wave pulse signal become the second phase different from the first phase. A voltage measuring means for measuring a second voltage value measured at the measurement point and obtaining a difference between the first voltage value and the second voltage value;
Detecting means for detecting a ground fault of the DC power supply based on the differential voltage measured by the voltage measuring means;
When a ground fault is detected by the detection means, a notification means for notifying this,
A ground fault detection device for a vehicle, comprising:   The rectangular wave pulse has a duty ratio of 50%, the first phase is when the rectangular wave pulse is at H level, and the second phase is when the rectangular wave pulse is at L level. The vehicular ground fault detection device according to claim 1, wherein the ground fault detection device is used.   The first phase is a phase immediately before the time when the rectangular wave pulse changes from the H level to the L level, and the second phase is a phase immediately before the time when the rectangular wave pulse changes from the L level to the H level. The ground fault detection device for a vehicle according to claim 3, wherein   5. The vehicle ground fault according to claim 4, wherein the first phase and the second phase are phases when a voltage signal generated at the measurement point is not affected by a change in vehicle capacity. Detection device.   The rectangular wave pulse has a frequency of the rectangular wave pulse signal so that a difference voltage between the first voltage and the second voltage becomes small when the capacity of the vehicle exceeds 90% of the maximum capacity value. And the first phase and the second phase are set, and the ground fault detection device for a vehicle according to any one of claims 1 and 2.

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