JP2015083939A - Detector using ac signal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detector capable of accurately detecting a state of a detecting object even when a voltage value of an AC signal varies.SOLUTION: A leak detector 100 includes: a control unit 1 having an AC signal generation section 4 and a voltage detection section 5; and a coupling capacitor C1 disposed between the control unit 1 and a DC power supply B2. The voltage detection section 5 detects a voltage, at one end of the coupling capacitor C1, varying depending on the presence/absence of an electric leak of the DC power supply B2. The control unit 1 converts a voltage V2 detected by the voltage detection section 5 at the timing when the voltage at one end of the coupling capacitor C1 becomes a minimum value into information indicating a leak state of the DC power supply B2 and outputs the information.

Description

  The present invention relates to an apparatus for detecting a state of a detection target using an AC signal.

  For example, in an electric vehicle, a high-voltage DC power source for driving a motor or a vehicle-mounted device is mounted. This DC power supply is electrically insulated from the vehicle body that is grounded. However, when an insulation failure or a short circuit occurs between the DC power source and the vehicle body for some reason, a current flows in a path from the DC power source to the ground, resulting in leakage. Therefore, a leakage detection device for detecting this leakage is attached to the DC power supply.

  As such a leakage detection device, an AC signal output from the AC signal generator is applied between the DC power source and the vehicle body, and a voltage at a predetermined portion between the AC signal generator and the DC power source is measured. There is known an AC type leakage detection device that detects leakage (for example, Patent Documents 1 to 3).

  In the leakage detection device of Patent Document 1, a coupling capacitor is provided between the AC signal generator and the DC power supply, and the voltage at the connection point between the capacitor and the DC power supply is detected. Then, the resistance component of admittance is obtained from the amplitude and phase difference between the voltage and the current flowing through the coupling capacitor, and leakage between the DC power source and the vehicle body is detected based on the comparison result between the resistance component and the threshold value. .

  In the leakage detection device of Patent Document 2, a resistor and a coupling capacitor are connected in series between an AC signal generation unit and a DC power source, and a voltage ratio and a phase difference between voltages at both ends of the resistor are detected. Then, the insulation resistance is calculated from the voltage ratio and the phase difference, and the leakage between the DC power source and the vehicle body is detected based on the comparison result between the calculated insulation resistance and the threshold value.

  In the leakage detection device of Patent Document 3, a resistor and a coupling capacitor are connected in series between an AC signal generation unit and a DC power supply, and the voltage at these connection points is detected. And based on the comparison result of this voltage and a threshold value, the electrical leakage between DC power supply and a vehicle body is detected.

  In such a detection device using an AC signal, for example, when the ambient temperature changes, the voltage value of the AC signal output from the AC signal generator varies due to the temperature drift characteristics of the AC signal generator. . For this reason, the detected voltage value also fluctuates, thereby reducing the detection accuracy.

  Patent Documents 4 and 5 describe a torque detector that compensates for temperature drift and improves detection accuracy. In patent document 4, the output signal which compensated the temperature drift is produced | generated by outputting an alternating current signal from the middle point of two coils connected in series. In Patent Document 5, an output signal compensated for temperature drift is generated by connecting a temperature characteristic compensating resistor element to a coil.

Japanese Patent Laid-Open No. 11-218554 JP 2012-37278 A JP 2007-57490 A JP2012-103003A Table 2010/119958

  The subject of this invention is providing the detection apparatus which can detect the state of a detection target accurately, even when the voltage value of an alternating current signal fluctuates.

  The detection apparatus according to the present invention determines the state of the detection target based on the AC signal generation means for generating the AC signal, and the level of the AC signal of the predetermined part in the detection target when the AC signal is applied to the detection target. Detecting means for detecting. The detection means converts the level of the minimum value detected at the timing when the level of the AC signal becomes the minimum value into information indicating the state of the detection target, and outputs the information.

  The level fluctuation amount due to the temperature change increases as the AC signal level increases, and decreases as the AC signal level decreases. Therefore, when the detection target state is detected from the signal level at the timing when the AC signal level reaches the maximum value, the variation in the signal level increases and the detection accuracy decreases. However, in the present invention, since the state of the detection target is detected from the signal level at the timing when the level of the AC signal becomes the minimum value, the variation in the signal level is reduced and the detection accuracy is improved.

  In the present invention, the detection means is the level of the minimum value detected at a predetermined timing before the timing when the level of the AC signal becomes the minimum value and after the timing when the level of the AC signal becomes the maximum value. May be converted into information indicating the state of the detection target, and the information may be output.

  In the present invention, the detection device may be a leakage detection device that detects a leakage of a DC power source to be detected. In this case, the detection means includes a coupling capacitor and a voltage detection unit. The coupling capacitor is provided between the AC signal generating means and the DC power source, and an AC signal is given to one end, and the other end is connected to one pole of the DC power source. The voltage detection unit detects a voltage at one end of the coupling capacitor that changes depending on whether or not the DC power supply has a leakage. The detecting means converts the minimum voltage detected by the voltage detection unit at the timing when the voltage at one end of the coupling capacitor reaches the minimum value, and outputs the information indicating the leakage state of the DC power supply.

  In the present invention, the voltage detection unit has a predetermined timing before the timing at which the voltage at one end of the coupling capacitor reaches a minimum value and after the timing at which the voltage at one end of the coupling capacitor reaches a maximum value. The voltage of the minimum value detected by the voltage detection unit may be converted into information representing the leakage state of the DC power supply, and the information may be output.

  In the present invention, the conversion to the information may be performed by referring to a predetermined table or based on a predetermined arithmetic expression.

  In the present invention, the AC signal generated by the AC signal generating means may be a rectangular wave, a triangular wave, a sawtooth wave, or a sine wave.

  ADVANTAGE OF THE INVENTION According to this invention, even when the voltage value of an alternating current signal fluctuates, the detection apparatus which can detect the state of a detection target accurately can be obtained.

It is a circuit diagram of a leak detection device concerning an embodiment of the present invention. It is a wave form diagram of the voltage output from the alternating current signal generation part, and the voltage detected by the voltage detection part. It is a wave form diagram which showed the fluctuation | variation of the voltage by a temperature change. It is the wave form diagram which showed the timing of the conventional leakage detection. It is the wave form diagram which showed the timing of the electric leakage detection in this invention. It is a principle figure for demonstrating the magnitude | size of a voltage fluctuation. It is the wave form diagram which showed the other example of the timing of a leak detection. It is a circuit diagram of the earth-leakage detection apparatus which concerns on other embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the following, a leakage detection device for a vehicle is taken as an example of a detection device using an AC signal.

  In FIG. 1, a leakage detection device 100 is a device that detects a leakage of a DC power supply B2, and includes a control unit 1, an amplifier 2, a filter circuit 3, a resistor R1, and a coupling capacitor C1.

  The DC power supply B2 is a high-voltage vehicle battery. The negative electrode of the DC power supply B2 is connected to the leakage detection device 100, and the positive electrode of the DC power supply B2 is connected to a load (not shown) such as a motor or an in-vehicle device. R3 is a leakage resistance between the negative electrode of the DC power supply B2 and the ground G, and R4 is a leakage resistance between the positive electrode of the DC power supply B2 and the ground G. In the present embodiment, the ground G is a vehicle body.

  In the leakage detection device 100, the control unit 1 includes a microcomputer and includes an AC signal generation unit 4 and a voltage detection unit 5. For example, a driving power of 5 volts is supplied to the control unit 1 from the DC power supply B1. The control unit 1 communicates with a host device 10 such as an electronic control unit (ECU). The host device 10 includes a leakage determination unit 11.

  The AC signal generation unit 4 includes a D / A converter (digital / analog converter) or the like, and generates an analog AC signal having a predetermined period based on a digital command value. This AC signal is superimposed with a DC offset voltage so that the lower peak value of the waveform is 0 volts or more. In the present embodiment, the AC signal generated by the AC signal generation unit 4 is a pulse signal composed of a rectangular wave. The amplifier 2 amplifies the pulse signal output from the AC signal generation unit 4.

  The resistor R1 and the coupling capacitor C1 are connected in series. The coupling capacitor C1 is a capacitor for separating the DC power supply B2 and the leakage detection device 100 in a DC manner. One end of the resistor R1 is connected to the output side of the amplifier 2, and the other end of the resistor R1 is connected to one end of the coupling capacitor C1. The other end of the coupling capacitor C1 is connected to the negative electrode of the DC power supply B2.

  A connection point (point P) between the resistor R1 and the coupling capacitor C1 is connected to the control unit 1 via a filter circuit 3 for noise removal. The filter circuit 3 is a known circuit including a resistor R2 and a capacitor C2. The voltage detector 5 detects the voltage at one end (point P) of the coupling capacitor C1 based on the voltage taken into the controller 1 from the filter circuit 3.

  In the above configuration, the AC signal generation unit 4 is an example of the “AC signal generation means” in the present invention. The coupling capacitor C1 and the voltage detection unit 5 are examples of the “detection unit” in the present invention. The DC power supply B2 is an example of the “detection target” in the present invention.

  Next, the operation of the above-described leakage detection device 100 will be described.

  The AC signal generator 4 generates and outputs a rectangular wave having a predetermined period. Thus, the output voltage V1 (FIG. 1) output from the control unit 1 becomes a pulse signal as shown in FIG. This pulse signal is amplified by the amplifier 2 and then applied to the resistor R1 and the coupling capacitor C1. As a result, the coupling capacitor C1 is charged by the pulse signal, and the voltage at the point P rises. The voltage at the point P is input to the control unit 1 as the detection voltage V2 through the filter circuit 3. Although illustration is omitted, a stray capacitance exists between the DC power supply B2 and the ground G, and a charging current flows through the coupling capacitor C1 and the stray capacitance.

  When there is no leakage between the DC power supply B2 and the ground G (when there is no leakage), since the leakage resistances R3 and R4 do not exist, the coupling capacitor C1 is charged in a short time, and the voltage at the point P is It rises in a short time. For this reason, the detection voltage V2 rises steeply as shown by the thick solid line in FIG. When the pulse signal is no longer applied, the detection voltage V2 falls steeply due to the rapid discharge of the coupling capacitor C1.

  On the other hand, when a leakage occurs between the DC power supply B2 and the ground G (at the time of leakage), the leakage capacitor R3, the leakage resistor R4, or both exist, so that the coupling capacitor C1 is charged. Takes time, and the voltage at point P rises slowly. For this reason, the detection voltage V2 rises gently as shown by the thin solid line in FIG. When no pulse signal is applied, the detection voltage V2 gradually falls due to the slow discharge of the coupling capacitor C1.

  Therefore, the leakage of the DC power supply B2 can be detected by utilizing the level difference between the detection voltage V2 at the time of non-leakage and the detection voltage V2 at the time of leakage. The leakage detection in the present invention is not limited to the case where the leakage detection device 100 itself determines the presence or absence of leakage, but also includes the case where the leakage detection device 100 only detects a physical quantity generated due to leakage. In the present embodiment, the latter method is adopted.

  Specifically, for example, leakage detection is performed by the following method. The control unit 1 calculates an insulation resistance value between the DC power supply B2 and the ground G based on a detection voltage V2 detected by the voltage detection unit 5 at a predetermined timing (described later). There are a method of referring to the table and a method of calculation. When referring to the table, a table (not shown) in which the insulation resistance value corresponding to the detected voltage value is stored in advance is provided in the control unit 1, and the insulation resistance value corresponding to the detected voltage V2 is read from the table. In the case of calculation, the insulation resistance value is calculated using a predetermined calculation formula. Patent Document 2 describes an example of an arithmetic expression for obtaining an insulation resistance value.

  Thereafter, the control unit 1 transmits (outputs) the calculated insulation resistance value to the host device 10. The leakage determination unit 11 of the host device 10 compares the insulation resistance value received from the control unit 1 with a threshold value, determines that there is no leakage if the insulation resistance value is equal to or greater than the threshold value, and leaks if the insulation resistance value is less than the threshold value. Judge that there is. In this example, the leakage detection device 100 only detects the voltage V2 that is a physical quantity and calculates the insulation resistance value, and the presence / absence of leakage is determined in the host device 10.

  Here, the insulation resistance value is an example of “information indicating the state of the detection target” and “information indicating the leakage state of the DC power supply” in the present invention. Moreover, the calculation of the insulation resistance value using a table or an arithmetic expression is an example of “conversion” in the present invention.

  The above is the operation when the output voltage V1 does not vary due to temperature changes. Next, an operation when the output voltage V1 fluctuates due to a temperature change will be described.

  When the ambient temperature changes, the output voltage V1 output from the AC signal generator 4 varies due to the temperature drift characteristics of the controller 1 and the DC power supply B1. FIG. 3A shows a state where the output voltage V1 has increased by ΔV as indicated by a broken line due to a change in ambient temperature. When the output voltage V1 rises in this way, this rise is amplified by the amplifier 2, and the detection voltage V2 rises accordingly. FIG. 3B shows a state in which each detection voltage V2 at the time of non-leakage and at the time of leakage is increased as indicated by a broken line.

  Conventionally, as shown in FIG. 4, the leakage is detected at the timing t <b> 2 when the detection voltage V <b> 2 reaches the maximum value, that is, at the timing when the output voltage V <b> 1 in FIG. However, this method has the following problems.

  At timing t2 in FIG. 4, it is assumed that the detection voltage V2 at the time of non-leakage increases by ΔVu1 and the detection voltage V2 at the time of leakage increases by ΔVu2 due to a change in ambient temperature. These increases ΔVu1 and ΔVu2 are larger than the increases (ΔVd1 and ΔVd2 in FIG. 5) at the timing t3 when the detection voltage V2 becomes the minimum value. For this reason, the insulation resistance value for leakage detection calculated based on the detection voltage V2 varies greatly due to a temperature change. As a result, when the leakage determination unit 11 of the host device 10 compares the insulation resistance value with the threshold value to determine the presence / absence of leakage, it can be erroneously determined that there is no leakage (yes) despite the presence of leakage (no). The leakage detection accuracy is reduced.

  Therefore, in the present invention, as shown in FIG. 5, the leakage is detected at the timing t3 when the detection voltage V2 becomes the minimum value, that is, at the timing when the output voltage V1 of FIG. Specifically, based on the detection voltage V2 detected by the voltage detection unit 5 at the timing t3, the control unit 1 calculates an insulation resistance value for determining leakage and transmits this to the host device 10.

  Here, the increase ΔVd1 of the detection voltage V2 at the time of non-leakage at timing t3 is sufficiently smaller than the increase ΔVu1 of the detection voltage V2 at the time of non-leakage at timing t2. Further, the increase ΔVd2 of the detection voltage V2 at the time of leakage at timing t3 is also sufficiently smaller than the increase ΔVu2 of the detection voltage V2 at the time of leakage at timing t2. The reason why the voltage increase at the minimum value (timing t3) of the detection voltage V2 is smaller than the voltage increase at the maximum value (timing t2) of the detection voltage V2 will be described with reference to FIG.

  FIG. 6 schematically shows the level of the detection voltage V2. Now, it is assumed that the level after the fluctuation of the detection voltage V2 is 1.2 times the level before the fluctuation due to the temperature change. At this time, 1 volt before the fluctuation is 1.2 volt after the fluctuation, and the increase is +0.2 volts. Further, 2 volts before the fluctuation becomes 2.4 volts after the fluctuation, and the increase is +0.4 volts. Furthermore, 5 volts before the fluctuation is 6 volts after the fluctuation, and the increase is +1 volts. Thus, even if the rate of increase in voltage level is the same, the amount of increase in voltage level increases as the voltage level increases and decreases as the voltage level decreases.

  Thus, as shown in FIG. 5, at the timing t3 when the detection voltage V2 becomes the minimum value, the increments ΔVd1 and ΔVd2 of the detection voltage V2 become smaller than the increments ΔVu1 and ΔVu2 at the timing t2. Therefore, even if the ambient temperature changes, the variation in the insulation resistance value calculated based on the detection voltage V2 can be suppressed to a small value. As a result, when the leakage determination unit 11 of the host device 10 determines the presence / absence of leakage from the comparison result between the insulation resistance value and the threshold value, there is no possibility of making an erroneous determination, and the detection accuracy of leakage is improved.

  The above describes the case where the detection voltage V2 increases due to a temperature change. Even when the detection voltage V2 decreases due to a temperature change, the amount of decrease in the voltage level increases as the voltage level increases according to the same principle. The lower the voltage level, the smaller. Therefore, the detection accuracy is improved by detecting the leakage at the timing t3 when the detection voltage V2 becomes the minimum value.

  As described above, in the present embodiment, the insulation resistance value for leakage determination is calculated based on the detection voltage V2 detected at the timing t3 when the detection voltage V2 becomes the minimum value. For this reason, the dispersion | variation in the insulation resistance value by the change of ambient temperature is suppressed, and the presence or absence of an electrical leakage can be determined correctly. Further, a temperature characteristic compensating resistor element (such as a thermistor) for compensating for the temperature drift is not required, and it is possible to cope with the problem by simply changing the software of the control unit 1.

  In the present invention, various embodiments other than those described above can be adopted. For example, in the above-described embodiment, the leakage is detected at the timing t3 when the detection voltage V2 becomes the minimum value, but the present invention is not limited to this. As shown in FIG. 7, even if a leak is detected at a predetermined timing t3 ′ before the timing t3 when the detection voltage V2 becomes the minimum value and after the timing t2 when the detection voltage V2 becomes the maximum value. Good. This timing t3 'can be determined by a timer that starts measuring time from timing t2 (timing when the output voltage V1 in FIG. 3A falls). T in FIG. 7 represents the time measured by the timer. Note that the timer may start timing from timing t1 (timing when the output voltage V1 rises).

  Moreover, in the said embodiment, although the leakage determination part 11 of the high-order apparatus 10 determined the presence or absence of leakage, this invention is not limited to this. As shown in FIG. 8, the leakage determination unit 6 having the same function as the leakage determination unit 11 may be provided in the control unit 1 of the leakage detection device 100. In this case, the leakage determination unit 6 determines the presence / absence of leakage based on the comparison result between the insulation resistance value obtained based on the detection voltage V2 and the threshold value, and transmits (outputs) the determination result to the host device 10. Alternatively, the determination leakage determination unit 6 may determine the presence / absence of leakage based on the comparison result between the voltage value of the detection voltage V2 and the threshold value at the timing t3, and transmit (output) the determination result to the host device 10. . In the case of FIG. 8, the determination result of whether or not there is a leakage by the leakage determination unit 6 is an example of “information indicating the state of the detection target” and “information indicating the leakage state of the DC power supply” in the present invention.

  Moreover, in the said embodiment, although the rectangular wave was mentioned as an example as an alternating current signal produced | generated by the alternating current signal production | generation part 4, this invention is not limited to this. The AC signal generated by the AC signal generation unit 4 may be a triangular wave, a sawtooth wave, a sine wave, or the like.

  In the above embodiment, one end of the coupling capacitor C1 is connected to the negative electrode of the DC power supply B2, but one end of the coupling capacitor C1 may be connected to the positive electrode of the DC power supply B2.

  Moreover, in the said embodiment, although the earth-leakage detection apparatus 100 mounted in a vehicle was mentioned as an example, this invention is widely applied to the earth-leakage detection apparatus mounted not only in a vehicle but in various apparatuses provided with DC power supply. Can be applied.

  Furthermore, the present invention can be applied not only to a leakage detection device but also to all devices that detect the state of a detection target using an AC signal, such as a torque detection device or a resolver that detects the rotation angle of a motor.

DESCRIPTION OF SYMBOLS 1 Control part 4 AC signal generation part 5 Voltage detection part 100 Leakage detection apparatus B2 DC power supply C1 Coupling capacitor V1 Output voltage V2 Detection voltage

Claims (7)

AC signal generating means for generating an AC signal;
Detecting means for detecting the state of the detection target based on the level of the AC signal of a predetermined part in the detection target when the AC signal is applied to the detection target;
The detecting means converts the level of the minimum value detected at a timing when the level of the AC signal becomes a minimum value into information representing the state of the detection target, and outputs the information. Detection device using signals. In the detection apparatus using the alternating current signal according to claim 1,
The detection device is a leakage detection device that detects a leakage of a DC power source that is the detection target,
The detection means includes
A coupling capacitor provided between the AC signal generating means and the DC power source, the AC signal is given to one end, and the other end is connected to one pole of the DC power source;
A voltage detector that detects a voltage at one end of the coupling capacitor, which varies depending on whether or not the DC power supply has a leakage,
Converting the voltage of the minimum value detected by the voltage detection unit at a timing when the voltage at one end of the coupling capacitor reaches a minimum value into information indicating a leakage state of the DC power supply, and outputting the information. A detection device using a characteristic AC signal. AC signal generating means for generating an AC signal;
Detecting means for detecting the state of the detection target based on the level of the AC signal of a predetermined part in the detection target when the AC signal is applied to the detection target;
The detection means is a level of the minimum value detected at a predetermined timing before the timing at which the level of the AC signal becomes the minimum value and after the timing at which the level of the AC signal becomes the maximum value. Is converted into information representing the state of the detection object, and the information is output, and a detection apparatus using an AC signal. In the detection apparatus using the alternating current signal according to claim 3,
The detection device is a leakage detection device that detects a leakage of a DC power source that is the detection target,
The detection means includes
A coupling capacitor provided between the AC signal generating means and the DC power source, the AC signal is given to one end, and the other end is connected to one pole of the DC power source;
A voltage detector that detects a voltage at one end of the coupling capacitor, which varies depending on whether or not the DC power supply has a leakage,
The voltage detection unit is at a predetermined timing before the timing at which the voltage at one end of the coupling capacitor becomes the minimum value and after the timing at which the voltage at one end of the coupling capacitor becomes the maximum value. A detection apparatus using an AC signal, wherein the voltage of the minimum value detected by the voltage detection unit is converted into information indicating a leakage state of the DC power supply and the information is output. In the detection apparatus using the alternating current signal according to any one of claims 1 to 4,
The detection device using an AC signal, wherein the conversion into the information is performed by referring to a predetermined table. In the detection apparatus using the alternating current signal according to any one of claims 1 to 4,
The detection device using an AC signal, wherein the conversion to the information is performed based on a predetermined arithmetic expression. In the detection apparatus using the alternating current signal according to any one of claims 1 to 6,
The AC signal generated by the AC signal generation means is a rectangular wave, a triangular wave, a sawtooth wave, or a sine wave, and a detection device using an AC signal.

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