JP2007240300A - Insulation detection method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation detection method and a device capable of detecting insulation in all vehicle traveling conditions. <P>SOLUTION: In a first voltage measuring means 10, ground fault resistance of a DC power supply V is calculated on the basis of a first voltage measurement value V<SB>RL-</SB>obtained by measuring a both end voltage of a capacitor C charged by closing control of first and fourth switches SW1, SW4 by a control means 10, a second voltage measurement value V<SB>RL+</SB>obtained by measuring a both end voltage of the capacitor C charged by closing control of second and third switches SW2, SW3, and a both end voltage V<SB>0</SB>' of the DC power supply V obtained by measurement by a second voltage measuring means 30 connected to both ends of the DC power supply V. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an insulation detection method and apparatus, and more particularly to an insulation detection method and apparatus for detecting a ground fault resistance of a DC power supply.

  For example, a flying capacitor type insulation detection device has been proposed as the above-described conventional insulation detection device. When detecting the insulation state of a DC high-voltage power supply, this insulation detection device charges the voltage of the high-voltage power supply to a capacitor (that is, a flying capacitor) floating from the ground, and measures the voltage at both ends. In the state where one of the capacitors is grounded via a resistor, the voltage of the high voltage power supply is similarly charged to the capacitor, and the ground fault resistance is calculated based on the measured value of the voltage across the capacitor, thereby isolating the high voltage power supply. The state is detected (see, for example, Patent Documents 1 and 2).

  FIG. 6 is a circuit diagram showing a configuration example of a conventional insulation detection device. In the figure, V is a high-voltage power supply (= DC power supply) in which N batteries are connected in series. This high-voltage power supply V is insulated from a ground potential G of a low-voltage system such as a microcomputer (hereinafter referred to as a microcomputer) 10. ing.

  As shown in the figure, the insulation detection apparatus includes a bipolar capacitor C, a first switch SW1 for connecting the positive electrode of the high voltage power source V insulated from the ground potential G to one end of the capacitor C, and the high voltage power source V. And a second switch SW2 for connecting the other negative electrode to the other end of the capacitor C. The first switch SW1 and the second switch SW2 function as first switch means and second switch means in the claims, respectively.

  The microcomputer 10 has a voltage measurement function for A / D converting and measuring the voltage supplied to the input port A / D (= input terminal). The insulation detection apparatus also includes a third switch SW3 for connecting one end of the capacitor C to the input port A / D, and a fourth switch SW4 for connecting the other end of the capacitor C to the ground potential G. Yes.

  The insulation detection device is provided between the first resistor R1 provided between the input port A / D side of the third switch SW3 and the ground potential G and between the ground potential G side of the fourth switch SW4 and the ground potential G. And a second resistor R2.

  Further, a voltage is supplied to the input port A / D via the protection circuit 11. The protection circuit 11 includes a protection resistor Rp1 provided between the third switch SW3 side of the first resistor R1 and the input port A / D side, and an input port A / D side of the protection resistor Rp1 and the ground potential G. The clamp diode Dc is provided.

  The protective resistor Rp1 functions as a current limiting resistor and prevents an overcurrent from flowing through the input port A / D of the microcomputer 10. The clamp diode Dc can prevent an excessive positive potential or negative potential from being applied to the input port A / D of the microcomputer 10 so as to damage the microcomputer 10.

  In addition, the insulation detection device includes a resistance switching circuit 12 provided between the connection line of the first switch SW1 and the third switch SW3 and the capacitor C. The resistance switching circuit 12 includes a series circuit including a first diode D1 and a first switching resistor Rc1 connected in a forward direction from the connection line of the first switch SW1 and the third switch SW3 toward the capacitor C. A series circuit composed of a second diode D2 and a second switching resistor Rc2 connected to be opposite to the first diode D1 is connected in parallel.

  The first to fourth switches SW1 to SW4 described above are, for example, optical MOSFETs, and can be controlled by the microcomputer 10 while being insulated from the high-voltage power supply V. Reference numeral 13 denotes a reset circuit. When the reset switch SWr is controlled to be closed, the charge accumulated in the capacitor C can be discharged quickly by the discharge resistor Rdc.

The operation of the insulation detection apparatus having the above-described configuration will be described with reference to the flowchart of FIG. First, the microcomputer 10 measures the high voltage V ₀ of the high voltage power supply (step S11). Specifically, this measurement is performed as follows. First, the microcomputer 10 controls the first switch SW1 and the second switch SW2 to be closed from the initial state where all the switches are open, and the voltage of the high-voltage power supply V is charged in the capacitor C.

Next, after the first and second switches SW1 and SW2 are controlled to open, the third and fourth switches SW3 and SW4 are controlled to close so that the voltage across the capacitor C, that is, the voltage V ₀ across the high-voltage power supply V. Is supplied to the input port A / D of the microcomputer 10. Thereby, the both-ends voltage V ₀ is read by the microcomputer 10 as the voltage of the high voltage power source V.

Next, the microcomputer 10 measures the voltage V _RL− according to the value of the negative side ground fault resistance RL− (step S12). Specifically, this measurement is performed as follows. That is, the microcomputer 10 closes the first switch and the fourth switches SW1 and SW4 after resetting by the reset circuit 13. As a result, a voltage corresponding to the value of the negative side ground fault resistance RL− is charged in the capacitor C.

Next, the microcomputer 10 controls the opening of the first switch SW1, and then controls the third and fourth switch means SW3 and SW4 to close. Thereby, the voltage V _RL− corresponding to the voltage across the capacitor C, that is, the value of the negative side ground fault resistance _RL− is read by the microcomputer 10.

Next, the microcomputer 10 measures the voltage V _{RL +} according to the value of the positive side ground fault resistance RL + (step S13). Specifically, this measurement is performed as follows. That is, after reset by the reset circuit 13, the microcomputer 10 controls the second switch and the third switches SW2 and SW3 to be closed. As a result, a voltage corresponding to the value of the positive side ground fault resistance RL + is charged in the capacitor C.

Next, the microcomputer 10 controls the opening of the second switch SW2, and then controls the third and fourth switch means SW3 and SW4 to close. As a result, the voltage across the capacitor C, that is, the voltage V _{RL +} corresponding to the value of the positive-side ground fault resistance _{RL +} is read by the microcomputer 10.
Become.

Then, microcomputer 10 measures a voltage corresponding measurement voltage V _{RL +} the sum of the corresponding to the measurement voltage V _RL- and the positive electrode side grounding resistor RL + corresponding to the negative electrode side grounding resistor RL- the voltage across the high-voltage power source V An operation of dividing by V ₀ (V _RL− + V _{RL +} / V ₀ ) is performed (step S14). Next, the microcomputer 10 calculates the ground fault resistance of the high-voltage power supply V with reference to the calculation value / ground fault resistance conversion table stored in advance in the internal memory based on the calculated value (step S15).

Thus, the microcomputer 10 are respectively controlling the first to fourth switches SW1 to SW4, the voltage across V ₀ which high voltage source V, the voltage V _{RL +,} the negative electrode side grounding resistor RL corresponding to the positive electrode side grounding resistor RL + Each time the capacitor C is charged with the voltage V _RL− according to −, the voltage _across the capacitor C at that time is read by the microcomputer 10, whereby the insulation state of the high-voltage power supply V can be detected.
JP 2004-170103 A JP 2004-245632 A

  By the way, in a vehicle having a high-voltage DC power source such as an EV vehicle, there is a demand for performing insulation detection between the high-voltage DC power source and the ground in all situations that are not affected by the traveling state of the vehicle from the viewpoint of safety. However, in a vehicle having a high-voltage DC power source such as an EV vehicle, the high-voltage voltage fluctuates depending on traveling conditions.

  FIG. 8 is a diagram showing a fluctuation image of the high voltage in the high voltage power source of the vehicle. As shown in the figure, the high voltage remains constant during the period from when the engine of the vehicle in the stopped state is turned on to the start of traveling, so this period is an area suitable for measurement for insulation detection. is there. After the start of traveling, the voltage decreases when the load is large (when the accelerator is on), and the voltage increases during regeneration (when braking). Further, during inertial traveling (during stable traveling), there is no voltage fluctuation and it is constant.

FIG. 9 is a diagram illustrating a change in the voltage across the capacitor C during the insulation detection cycle. As shown in the figure, when the voltage across the capacitor C has a high voltage fluctuation, during one insulation detection cycle, the charging waveform at the time of measuring the voltage V ₀ across the high voltage power source V starting at time t1 and the time t2 In the charging waveform at the time of measurement of the voltage V _RL− according to the value of the negative side ground fault resistance RL− starting from the time V 3 and the charging waveform at the time of measuring the voltage V _{RL +} according to the value of the positive side ground fault resistance RL + starting from the time t 3 There are cases where charging is performed by high voltage of different high voltage power sources V. Even if an attempt is made to detect insulation in a situation where there is a fluctuation of the high voltage in this way, the voltage V ₀ across the high voltage power supply V at the time of voltage measurement starting at each of the times t1, t2, and t3 becomes a different voltage. The calculation result of V _RL− + V _{RL +} / V ₀ ) is not a correct value, and accurate insulation detection cannot be performed. Therefore, while the voltage across the high-voltage power supply V is fluctuating, there is no choice but to stop the insulation detection. However, in this case, the insulation detection can hardly be performed.

  In this way, insulation detection can only be performed when there is no high voltage fluctuation, so in practice it can only be performed during the period from when the vehicle is stopped to when it starts running or when it is stable. Can not.

  However, a state where there is a possibility of electric shock due to a decrease in insulation resistance can always occur while the vehicle is running, so this is a safety problem, and countermeasures against fluctuations in high voltage in insulation detection devices have been a concern. It was.

  In view of the above problems, an object of the present invention is to provide an insulation detection method and apparatus capable of detecting insulation in all vehicle traveling states.

In order to solve the above-mentioned problem, the invention according to claim 1 is an insulation detection method for detecting a ground fault resistance of a DC power source insulated from a ground potential, wherein a capacitor is connected between the positive electrode of the DC power source and the ground potential. And measuring the voltage between both ends with a first voltage measuring means to obtain a first voltage measurement value V _RL− , and the capacitor between the negative electrode of the DC power source and the ground potential And a second measurement step for obtaining a second measured voltage value V _{RL +} by measuring the voltage at both ends by the first voltage measuring means, and a second voltage measuring means at both ends of the DC power supply. And a third measurement step for obtaining a voltage V ₀ ′ across the DC power source during the measurement period of the first and second measurement steps, and a first voltage measurement obtained in the first measurement step the value V _RL- and the second Calculating step and the second voltage measurement values obtained by measuring the step V _{RL +,} the third measured based on the voltage across V ₀ 'of the DC power source obtained step, to calculate the ground-fault resistance of the DC power supply Insulation detection method characterized by including.

In the first aspect of the present invention, a first voltage measurement value V _RL− is obtained by connecting a capacitor between the positive electrode of the DC power source and the ground potential, and measuring the voltage between both ends by the first voltage measuring means. The second voltage measurement value V _{RL +} is obtained by connecting a capacitor between the negative electrode of the DC power source and the ground potential and measuring the voltage across the capacitor with the first voltage measuring means. Further, the second voltage measuring means is connected to both ends of the DC power supply, and the both-ends voltage V ₀ ′ of the DC power supply during the measurement period of the first and second voltage measurement values by the first voltage measuring means is obtained. Then, the first voltage measurement value V _RL− and the second voltage measurement value V _{RL +} obtained by the first voltage measurement means, the both-ends voltage V ₀ ′ of the DC power source obtained by the second voltage measurement means 30, and Based on the above, the ground fault resistance of the DC power supply is calculated.

The invention according to claim 2, which has been made in order to solve the above problem, is an insulation detection device for detecting a ground fault resistance of a DC power source insulated from a ground potential, and measures a capacitor and a voltage across the capacitor. A first voltage measuring means; a first switch connected between the positive electrode of the DC power supply and one end of the capacitor; a second switch connected between the negative electrode of the DC power supply and the other end of the capacitor; A third switch connected between one end of a capacitor and the first voltage measuring means, a fourth switch connected between the other end of the capacitor and the ground potential, and the first to fourth switches are selectively used. In the control means for closing control, the second voltage measuring means connected to both ends of the DC power supply and measuring the voltage V ₀ ′ across the DC power supply, and the first voltage measuring means, the control means Yo Charged by the first switch and the fourth first voltage measurement value V obtained by measuring the voltage across the capacitor charged by closing control of the switch _RL-, and closing control of the second switch and the third switch Based on the second voltage measurement value V _{RL +} obtained by measuring the voltage across the capacitor, and the voltage V ₀ across the DC power source obtained by measurement in the second voltage measurement means, Calculation means for calculating a ground fault resistance of a DC power supply, wherein the second voltage measurement means includes the first voltage measurement value V _RL− and the second voltage measurement value V in the first voltage measurement means. _In the insulation detection device, the voltage V ₀ ′ of the DC power supply V is measured during the measurement period of _{RL +} .

According to a second aspect of the present invention, an insulation detection device for detecting a ground fault resistance of a DC power source insulated from a ground potential includes a capacitor, first voltage measuring means for measuring a voltage across the capacitor, and a DC power source. A first switch connected between the positive electrode and one end of the capacitor; a second switch connected between the negative electrode of the DC power supply and the other end of the capacitor; and a first switch connected between one end of the capacitor and the first voltage measuring means. 3 switches, a fourth switch connected between the other end of the capacitor and the ground potential, a control means for selectively closing and controlling the first to fourth switches, and both ends of the DC power supply. a second voltage measuring means for measuring the voltage V ₀ ', the first in the voltage measuring means 10, a capacitor which is charged by closing control of the first switch SW1 and the fourth switch SW4 by the control unit 10 The first voltage measurement value V obtained by measuring the voltage across _RL-, and the second switch and the third second voltage measurement values V obtained by measuring the voltage across the capacitor which is charged by closing the control switch Calculation means for calculating the ground fault resistance of the DC power supply based on _{RL +} and the voltage V ₀ ′ across the DC power supply obtained by the measurement by the second voltage measurement means 30 is provided. The second voltage measurement means measures the voltage V ₀ ′ across the DC power supply during the measurement period of the first voltage measurement value V _RL− and the second voltage measurement value V _{RL +} in the first voltage measurement means. .

  According to a third aspect of the present invention, there is provided an insulation detection device according to the second aspect, wherein the third switch and the first voltage measuring means are connected between a connection point and the ground potential. A first resistor, a second resistor connected between the fourth switch and the ground potential, and a first and second connected between a connection point of the first and third switches and one end of the capacitor. A switching resistor and one of the first and second switching resistors corresponding to the polarity direction of the capacitor are selected, and the selected one is connected to a connection point between the first switch and the third switch and the capacitor. The insulation detection apparatus further includes selection means for selectively connecting the one end.

  In the invention according to claim 3, the insulation detecting device is connected between the connection point of the third switch and the first voltage measuring means and the ground potential, and connected between the fourth switch and the ground potential. The second resistor, the first and second switching resistors connected between the connection point of the first and third switches and one end of the capacitor, and the polarity direction of the capacitor among the first and second switching resistors And selecting means for selecting one and selectively connecting the selected one between the connection point of the first switch and the third switch and one end of the capacitor.

According to the first aspect of the present invention, there is provided an insulation detection method for detecting a ground fault resistance of a DC power source insulated from a ground potential, wherein a capacitor is connected between the positive electrode of the DC power source and the ground potential, _Is measured by the first voltage measuring means to obtain a first voltage measurement value V _RL− , and the capacitor is connected between the negative electrode of the DC power source and the ground potential, and the voltage across the capacitor is measured. A second measurement step of obtaining a second voltage measurement value V _{RL +} by measuring with the first voltage measurement means; and a second voltage measurement means connected to both ends of the DC power supply V to The third measurement step for _{obtaining the} voltage V ₀ ′ across the DC power supply during the measurement period of the two measurement steps, the first voltage measurement value V _RL− obtained in the first measurement step, and the second measurement step The second measured voltage value V _{RL +} and the third meter And a calculation step for calculating the ground fault resistance of the DC power source based on the both-ends voltage V ₀ ′ of the DC power source V obtained in the measurement step. Insulation can be detected in all vehicle running conditions. In addition, since the high voltage fluctuation can be reflected in the calculation of the ground fault resistance, the detection accuracy of the ground fault resistance is improved. Moreover, the measurement of the both-ends voltage of the high voltage power supply V which was performed before measuring the voltage according to the negative electrode side ground fault resistance RL− and the voltage according to the positive electrode side ground fault resistance RL + is conventionally performed. Since the measurement is performed during the measurement period of the voltage according to the voltage and the voltage according to the positive side ground fault resistance RL +, the insulation detection cycle can be shortened compared to the conventional case, and the responsiveness is improved.

According to a second aspect of the present invention, there is provided an insulation detection device for detecting a ground fault resistance of a DC power source insulated from a ground potential, the capacitor, and a first voltage measuring means for measuring a voltage across the capacitor. A first switch connected between the positive electrode of the DC power supply and one end of the capacitor; a second switch connected between the negative electrode of the DC power supply and the other end of the capacitor; and between the one end of the capacitor and the first voltage measuring means. A third switch connected, a fourth switch connected between the other end of the capacitor and the ground potential, a control means for selectively closing and controlling the first to fourth switches, and both ends of the DC power supply; a second voltage measuring means for measuring the voltage across V ₀ 'of the DC power supply, the first voltage measuring means, the voltage across the capacitor which is charged by closing control of the first switch and the fourth switch by the control means The first voltage measurement V _RL-, and the second voltage measurement value V _{RL +} of the voltage across the second switch and the third capacitor is charged by closing the control switch obtained by measurement obtained by measuring, Calculation means for calculating a ground fault resistance of the DC power supply based on the both-ends voltage V ₀ ′ of the DC power supply measured by the second voltage measurement means, and the second voltage measurement means includes: high pressure in the first voltage measurement V _RL- and the second voltage measurements V _{RL +} the measurement period in the voltage measuring means, so measuring the voltage across V ₀ 'of the DC power supply and a conventional measurement impossible Insulation can be detected in all vehicle running states, including when the power supply voltage fluctuates. In addition, since the high voltage fluctuation can be reflected in the calculation of the ground fault resistance, the detection accuracy of the ground fault resistance is improved. Moreover, the measurement of the both-ends voltage of the high voltage power supply V which was performed before measuring the voltage according to the negative electrode side ground fault resistance RL− and the voltage according to the positive electrode side ground fault resistance RL + is conventionally performed. Since the measurement is performed during the measurement period of the voltage according to the voltage and the voltage according to the positive side ground fault resistance RL +, the insulation detection cycle can be shortened compared to the conventional case, and the responsiveness is improved.

According to the invention described in claim 3, the first resistor connected between the connection point of the third switch and the first voltage measuring means and the ground potential, and the second resistor connected between the fourth switch and the ground potential. And first and second switching resistors connected between the connection point of the first and third switches and one end of the capacitor, and one of the first and second switching resistors corresponding to the polarity direction of the capacitor is selected. And selecting means for selectively connecting the selected one between the connection point of the first switch and the third switch and one end of the capacitor, so that the measurement according to the negative side ground fault resistance RL− is provided. The ground fault resistance of the high voltage power source V is calculated based on the voltage V _RL− , the measured voltage V _{RL +} corresponding to the positive side ground fault resistance RL +, and the measured voltage V ₀ ′ corresponding to the voltage across the high voltage power source V. Can do.

  The insulation detection method and apparatus of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram showing an embodiment of an insulation detection apparatus for carrying out an insulation detection method according to the present invention. A high-voltage power source (= DC power source) V in which N batteries are connected in series is insulated from a low-voltage ground potential G such as the microcomputer 10. The microcomputer 10 functions as a first voltage measurement unit, a calculation unit, and a control unit in the claims.

  As shown in the figure, the insulation detection apparatus includes a bipolar capacitor C, a first switch SW1 for connecting the positive electrode of the high voltage power source V insulated from the ground potential G to one end of the capacitor C, and the high voltage power source V. And a second switch SW2 for connecting the other negative electrode to the other end of the capacitor C.

  The microcomputer 10 has a voltage measurement function for A / D converting and measuring the voltage supplied to the input ports (= input terminals) A / D1 and A / D2. Further, the microcomputer 10 has an alarm function for driving and alarming the alarm unit 20 when an insulation failure is detected. The insulation detection device includes a third switch SW3 for connecting one end of the capacitor C to the input port A / D1, and a fourth switch SW4 for connecting the other end of the capacitor C to the ground potential G.

  The insulation detection device is provided between the first resistor R1 provided between the input port A / D1 side of the third switch SW3 and the ground potential G and between the ground potential G side of the fourth switch SW4 and the ground potential G. And a second resistor R2.

  Further, a voltage is supplied to the input port A / D via the protection circuit 11. The protection circuit 11 is provided between the protection resistor Rp1 provided between the third switch SW3 side of the first resistor R1 and the input port A / D1, and between the input port A / D1 side of the protection resistor Rp1 and the ground potential G. And a clamp diode Dc.

  The protective resistor Rp1 functions as a current limiting resistor and prevents an overcurrent from flowing through the input port A / D1 of the microcomputer 10. Further, the clamp diode Dc can prevent an excessive positive potential or negative potential from being applied to the input port A / D1 of the microcomputer 10 so as to damage the microcomputer 10.

  In addition, the insulation detection device includes a resistance switching circuit 12 provided between the connection line of the first switch SW1 and the third switch SW3 and the capacitor C. The resistance switching circuit 12 includes a series circuit including a first diode D1 and a first switching resistor Rc1 connected in a forward direction from the connection line of the first switch SW1 and the third switch SW3 toward the capacitor C. A series circuit composed of a second diode D2 and a second switching resistor Rc2 connected to be opposite to the first diode D1 is connected in parallel.

  That is, the first and second diodes D1 and D2 function as a selection unit, select one of the first and second switching resistors Rc1 and Rc2 corresponding to the polarity direction of the capacitor C, and select the selected one as the first. The connection line between the 1 switch SW1 and the third switch SW3 and the capacitor C are electrically connected. The first to fourth switches SW1 to SW4 described above are, for example, optical MOSFETs, and can be controlled by the microcomputer 10 while being insulated from the high-voltage power supply V. Reference numeral 13 denotes a reset circuit. When the reset switch SWr is controlled to be closed, the charge accumulated in the capacitor C can be discharged quickly by the discharge resistor Rdc.

  Further, the insulation detection device includes a high voltage measuring circuit 30 whose input side is connected to the positive and negative electrodes of the high voltage power supply V and whose output side is connected to the input port A / D2 of the microcomputer 10. The high voltage measuring circuit 30 is for monitoring the voltage across the high voltage power supply V in real time. The high voltage measuring circuit 30 functions as a second voltage measuring means in the claims.

  FIG. 2 is a block diagram showing an example of the configuration of the high voltage measurement circuit 30. As shown in FIG. The high voltage measurement circuit 30 has a circuit configuration of a direct measurement system including a voltage dividing circuit 31, an insulation amplifier 32, and a buffer filter 33. The voltage dividing circuit 31 is connected to both ends of the high voltage power source V and divides the high voltage into a predetermined voltage. The insulation amplifier 32 amplifies the divided voltage divided by the voltage dividing circuit 31 by insulating the input side and the output side. The buffer filter 33 blocks the noise contained in the output of the insulation amplifier 32 and supplies it to the input port A / D2 of the microcomputer 10.

Next, the insulation detection operation of the insulation detection apparatus of the present invention having the above-described configuration will be described with reference to the flowchart of FIG. First, the microcomputer 10 measures the voltage V _RL− according to the value of the negative side ground fault resistance RL− (step S1). Specifically, this measurement is performed as follows. That is, the microcomputer 10 controls the first switch SW1 and the fourth switch SW4 to be closed during the charging time T1 from the initial state where all the switches are open. The charging time T1 is set to a time shorter than the time required to fully charge the capacitor C (for example, a fraction of the full charging time). Accordingly, the positive electrode of the high-voltage power source V, the first switch SW1, the first diode D1, the first switching resistor Rc1, the capacitor C, the fourth switch SW4, the second resistor R2, the ground potential G, and the negative electrode side ground of the high-voltage power source V. Tangle resistance RL- A closed circuit is formed by the negative electrode of the high-voltage power supply V, and the capacitor C is charged with a voltage corresponding to the value of the negative-side ground fault resistance RL−.

Next, after opening the first switch SW1, the microcomputer 10 controls the third and fourth switches SW3 and SW4 to close. Accordingly, a closed circuit is formed by the capacitor C, the second diode D2, the second switching resistor Rc2, the third switch SW3, the first resistor R1, the second resistor R2, and the fourth switch SW4. As a result, the voltage Vc across the capacitor C is divided by a voltage dividing ratio determined by the second switching resistor Rc2, the first resistor R1, and the second resistor R2, and supplied to the input port A / D1 of the microcomputer 10. The supplied divided voltage (∵Vc · R1 / (Rc2 + R1 + R2)) is converted into a digital value by A / D (analog / digital) conversion, and the value corresponds to the value of the negative side ground fault resistance RL−. The voltage V _RL− (first voltage measurement value) is read by the microcomputer 10.

Next, the microcomputer 10 measures the voltage V _{RL +} corresponding to the value of the positive side ground fault resistance RL + (step S2). Specifically, this measurement is performed as follows. That is, the microcomputer 10 closes the reset switch SWr of the reset circuit 13 to sufficiently discharge the voltage charged in the capacitor C. Next, after opening the reset switch SWr and the fourth switch SW4, the microcomputer 10 controls the second switch and the third switches SW2 and SW3 to close during the charging time T1. Accordingly, the positive electrode of the high-voltage power supply V, the positive-side ground fault resistor RL +, the ground potential G, the first resistor R1, the third switch SW3, the first diode D1, the first switching resistor Rc1, the capacitor C, the second switch SW2, and the high voltage A closed circuit is formed by the negative electrode of the power supply V, and the capacitor C is charged with a voltage corresponding to the value of the positive side ground fault resistance RL +.

Next, the microcomputer 10 controls the opening of the second switch SW2, and then controls the third and fourth switch means SW3 and SW4 to close. As a result, the voltage Vc across the capacitor C is divided by a voltage division ratio determined by the second switching resistor Rc2, the first resistor R1, and the second resistor R2, and supplied to the input port A / D1 of the microcomputer 10. . The supplied divided voltage is converted into a digital value by A / D conversion, and the value is read by the microcomputer 10 as a voltage V _{RL +} (second voltage measurement value) corresponding to the value of the positive side ground fault resistance RL +. It is.

  The first resistor R1 and the second resistor R2 described above are set to the same value (R1 = R2). As a result, the first and fourth switches SW1 and SW4 are closed and the charging resistance (Rc1 + R2) for charging the capacitor C with a voltage corresponding to the negative-side ground fault resistance RL−, and the second and third switches SW2 and SW3 are closed and the charging resistance (Rc1 + R1) when charging the capacitor C with a voltage corresponding to the positive side ground fault resistance RL + becomes equal. That is, if the negative side ground fault resistance RL− and the positive side ground fault resistance RL + have the same value, the voltage corresponding to the negative side ground fault resistance RL− charging the capacitor C and the positive side ground fault resistance RL + The voltage becomes equal.

On the other hand, as shown in FIG. 4, the microcomputer 10 outputs the output of the high-voltage measuring circuit 30 at a predetermined sampling timing (during a measurement period T _RL− of the voltage V _RL− according to the negative-side ground fault resistance RL−. For example, every several tens of milliseconds) (for example, dozens of times) are taken in the input port A / D2 and an operation is performed to average the obtained data, and the obtained average value is used as the negative side ground fault. The voltage V _RL− corresponding to the resistance RL− is read as the both-ends voltage V ₀₋ of the high voltage power source V during the measurement period T _RL− (step S3).

Next, as shown in FIG. 4, the microcomputer 10 outputs the output of the high voltage measurement circuit 30 to a predetermined sampling timing (for example, for example) during the measurement period T _{RL +} of the voltage V _{RL +} according to the above-described positive side ground fault resistance RL +. (Several tens of milliseconds) multiple times (for example, dozens of times) at the input port A / D2, and performs an arithmetic operation to average the multiple data, and the obtained average value is used as the positive side ground fault resistance RL + read as a voltage across V ₀₊ voltage V _{RL +} the measurement period T _{RL +} high-voltage power supply V medium corresponding to (step S4).

Next, the microcomputer 10 processes the voltage across V _0- capital and V ₀₊ of the high-voltage power source V which is measured in step S3 and S4 (e.g., averaging processing) to the voltage across V ₀ which the high-voltage power source V ' (Step S5).

Next, the microcomputer 10 measures the measurement voltage V _RL− (first voltage measurement value) corresponding to the negative side ground fault resistance RL− and the measurement voltage V _{RL +} (second voltage measurement) corresponding to the positive side ground fault resistance RL +. Value) is divided by the measurement voltage V ₀ ′ according to the voltage across the high-voltage power supply V (V _RL− + V _{RL +} / V ₀ ') is performed (step S6). Next, the microcomputer 10 calculates the ground fault resistance of the high-voltage power supply V based on the calculated value with reference to a calculation value / ground fault resistance conversion table stored in the internal memory in advance (step S7).

  In this way, the ground fault resistance of the high voltage power supply V can be calculated. After calculating the ground fault resistance, the microcomputer 10 compares the calculated ground fault resistance value with a threshold value stored in advance in the internal memory, and the calculated ground fault resistance value is smaller than the threshold value. If so, the alarm unit 20 can warn that an insulation failure has occurred.

  As described above, according to the present invention, since the high voltage measuring circuit 30 for measuring the voltage across the high voltage power supply V in real time is provided, the voltage fluctuation state of the high voltage power supply that has been impossible to measure in the past is included. Insulation detection is possible in all vehicle travel states.

  In addition, the measurement of the voltage at both ends of the high-voltage power supply V, which has been conventionally performed before the measurement of the voltage according to the negative side ground fault resistance RL− and the voltage according to the positive side ground fault resistance RL +, is performed. Since the voltage corresponding to the voltage and the voltage corresponding to the positive side ground fault resistance RL + are performed in parallel, the fluctuation of the high voltage can always be reflected in the calculated value, and the conventional measurement is impossible. The ground fault resistance can be measured even during high voltage fluctuations. In addition, since the high voltage fluctuation can be reflected in the calculation of the ground fault resistance, the detection accuracy of the ground fault resistance is improved. Moreover, since the measurement cycle for the conventional high-pressure measurement cycle can be shortened, the responsiveness is improved and the noise resistance is improved. Furthermore, the selection of processing methods such as noise countermeasures is expanded.

  Moreover, the noise tolerance of the whole apparatus can be improved conventionally. That is, when the capacitance of the noise removing capacitor (Y capacitor) between the high voltage and the ground potential G attached outside the insulation detection device (ground fault sensor) increases, the voltage corresponding to the negative side ground fault resistance RL− and the positive side ground Although there is a problem that accurate measurement cannot be performed unless the voltage measurement time corresponding to the resistance RL + is lengthened, this measurement time extension also corresponds to the conventional negative side ground fault resistance RL− in the present invention. Since it can be absorbed by omitting the voltage measurement time at both ends of the high-voltage power supply V, which was performed before the measurement of the voltage and the voltage corresponding to the positive side ground fault resistance RL +, the range of selection of the capacitor capacity for noise removal can be expanded more than before. And can contribute to the improvement of the noise tolerance of the entire apparatus.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various deformation | transformation and application are possible.

  For example, in the above-described embodiment, the high-voltage measuring circuit 30 has a configuration of a direct measurement method via the insulation amplifier 32. However, the configuration is not limited to this, and another configuration may be used.

  FIG. 5 is a circuit diagram illustrating another example of the configuration of the high-voltage measuring circuit 30. In FIG. 5, the high voltage measuring circuit 30 has a flying capacitor type configuration including a capacitor C30, a resistor circuit 35, a multiplexer 36, a sample switch circuit 37, and an interface circuit 38. The resistance circuit 35 is individually connected to the pole terminal of each battery of the high-voltage power supply V composed of N (here, N = 5) batteries V1 to V5, and protection resistors R11 to R16 that limit current for short circuit protection. Consists of. The multiplexer 36 includes switches SW11 to SW20 that are connected to both ends of the capacitor C30 via protective resistors R11 to R16, and are opened and closed under the control of the microcomputer 10. The sample switch circuit 37 includes switches SW21 and SW22 that supply a voltage across the capacitor C30 to the interface circuit 38. The interface circuit 38 converts the voltage across the capacitor C30 supplied via the sample switch circuit 37 into a voltage with respect to the ground potential G, and supplies it to the input port A / D2 of the microcomputer 10.

The high voltage measuring circuit 30 in FIG. 5 sequentially converts the voltages of the individual batteries V1 to V5 into the multiplexer 36 during the measurement period of the voltage corresponding to the negative side ground fault resistance RL− and the voltage corresponding to the positive side ground fault resistance RL +. by measuring the closing control of the closing control and the sampling switch circuit 37 that follows, performs arithmetic summing the measured value of the voltage of the individual battery V1~V5 the switch SW11～SW20, V ₀ a voltage across the high-voltage power source V Is read into the microcomputer 10 a plurality of times (for example, dozens of times) at a predetermined sampling timing, and an operation of averaging the plurality of read data is performed, and the obtained average value is read as the voltage V ₀ across the high-voltage power supply V.

  For example, when measuring the battery V1, the switches SW11 and SW16 of the multiplexer 36 are closed from the initial state where all the switches are open, and the voltage of the battery V1 is charged in the capacitor C30. Subsequently, the switches SW11 and SW16 are turned on. By controlling the opening and closing the switches SW21 and SW22 of the sample switch circuit 37, the voltage across the capacitor C30 is supplied to the input port A / D2 of the microcomputer 10 via the interface circuit 38. The supplied voltage across the capacitor C30 is A / D converted into a digital value, and is read by the microcomputer 10 as the voltage of the battery V1.

  Similarly, both-end voltages of the batteries V2 to V5 are sequentially read by the microcomputer 10 by the closing control of the combinations of the switches SW12 and SW17, SW13 and SW18, SW14 and SW19, SW15 and SW20 of the multiplexer 35.

In the above-described embodiment, the voltage V ₀ across the high-voltage power supply V is calculated as an average value. However, the present invention is not limited to this, and other calculation methods may be used. For example, an intermediate value between the maximum value and the minimum value of the high voltage fluctuation monitored during the measurement period of the voltage according to the negative side ground fault resistance RL− and the voltage according to the positive side ground fault resistance RL + was calculated. The intermediate value may be determined as the voltage V ₀ across the high-voltage power supply V. The average value of the high voltage monitored during the voltage measurement period according to the negative side ground fault resistance RL− and the average of the high voltage monitored during the voltage measurement period according to the positive side ground fault resistance RL + A weighted value calculated by appropriately weighting each value may be determined as the voltage V ₀ across the high-voltage power supply V. This weighted calculation value is calculated, for example, by weighting the difference between the measured ground fault resistance data at the time of a certain known ground fault resistance and when the model of the vehicle is running and the known ground fault resistance value.

It is a circuit diagram showing one embodiment of an insulation detection device which carries out an insulation detection method concerning the present invention. It is a block diagram which shows the structural example of the high voltage measuring circuit in the insulation detection apparatus of FIG. It is a flowchart for demonstrating operation | movement of the insulation detection apparatus of FIG. It is a wave form diagram for demonstrating operation | movement of the insulation detection apparatus of FIG. It is a circuit diagram which shows the other structural example of the high voltage measuring circuit in the insulation detection apparatus of FIG. It is a circuit diagram which shows the structure of the conventional insulation detection apparatus. It is a flowchart for demonstrating operation | movement of the insulation detection apparatus of FIG. It is a figure which shows the fluctuation image of the high voltage in the high voltage power supply of a vehicle. It is a figure which shows the change of the both-ends voltage of the capacitor | condenser C in the insulation detection cycle in the insulation detection apparatus of FIG.

Explanation of symbols

C capacitor D1 first diode (selection means)
D2 Second diode (selection means)
G ground potential R1 first resistor R2 second resistor Rc1 first switching resistor Rc2 second switching resistor SW1 first switch SW2 second switch SW3 third switch SW4 fourth switch V high voltage power source (DC power source)
A / D1 input port (input terminal)
A / D2 input port (input terminal)
10 Microcomputer (first voltage measurement means, control means, calculation means)
30 High voltage measurement circuit (second voltage measurement means)

Claims (3)

An insulation detection method for detecting a ground fault resistance of a DC power source insulated from a ground potential,
A first measurement step of _{obtaining a} first voltage measurement value V _RL− by connecting a capacitor between the positive electrode of the DC power source and a ground potential and measuring a voltage across the capacitor with a first voltage measurement means;
A second measuring step of obtaining a second voltage measurement value V _{RL +} by connecting the capacitor between the negative electrode of the DC power source and a ground potential and measuring the voltage across the capacitor with the first voltage measuring means;
A third measuring step of connecting a second voltage measuring means to both ends of the DC power supply to obtain a voltage V ₀ ′ of the DC power supply during the measurement period of the first and second measuring steps;
The first voltage measurement value V _RL− obtained in the first measurement step, the second voltage measurement value V _{RL +} obtained in the second measurement step, and the DC power source obtained in the third measurement step And a calculation step of calculating a ground fault resistance of the DC power source based on the both-end voltage V ₀ ′. An insulation detection device for detecting a ground fault resistance of a DC power source insulated from a ground potential,
A capacitor,
First voltage measuring means for measuring the voltage across the capacitor;
A first switch connected between a positive electrode of the DC power source and one end of the capacitor;
A second switch connected between the negative electrode of the DC power source and the other end of the capacitor;
A third switch connected between one end of the capacitor and the first voltage measuring means;
A fourth switch connected between the other end of the capacitor and the ground potential;
Control means for selectively closing the first to fourth switches;
A second voltage measuring means connected to both ends of the DC power source and measuring a voltage V ₀ ′ across the DC power source;
In the first voltage measurement means, a first voltage measurement value V _RL− obtained by measuring a voltage across the capacitor charged by closing control of the first switch and the fourth switch by the control means, and The second voltage measurement value V _{RL +} obtained by measuring the voltage across the capacitor charged by the closing control of the second switch and the third switch, and the second voltage measurement means obtained by the measurement. Calculating means for calculating a ground fault resistance of the DC power supply based on a voltage V ₀ ′ across the DC power supply;
The second voltage measurement unit is configured to measure the voltage V across the DC power source V during the measurement period of the first voltage measurement value V _RL− and the second voltage measurement value V _{RL +} in the first voltage measurement unit. An insulation detection device characterized by measuring ₀ '. The insulation detection apparatus according to claim 2,
A first resistor connected between a connection point of the third switch and the first voltage measuring means and the ground potential;
A second resistor connected between the fourth switch and the ground potential;
First and second switching resistors connected between a connection point of the first and third switches and one end of the capacitor;
One of the first and second switching resistors corresponding to the polarity direction of the capacitor is selected, and the selected one is selected between a connection point of the first switch and the third switch and one end of the capacitor. Insulation detection apparatus, further comprising selection means for connection to each other.

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