JP2009150779A - Insulation detector for non-grounded circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation detector for a non-grounded circuit which is capable of accurately detecting insulation between the non-grounded circuit and a grounding potential section mounted onto a vehicle. <P>SOLUTION: The detector comprises a first resistor 21 which is connected to positive-electrode wiring of a DC power supply 12 and has a resistance higher than the insulation criterion for maintaining insulation between the non-grounded circuit 10 and the grounding potential section BE of the vehicle; a second resistor 22 which is connected to negative-electrode wiring of the DC power supply 12 and has a resistance higher than the insulation criterion; a third resistor 23 which is connected between the first resistor 21 and the second resistor 22, grounding wiring which connects a connection of the second resistor 22 and the third resistor 23 to the grounding potential section BE of the vehicle; and an insulation level detecting means 31 which inputs an inter-terminal voltage V<SB>in</SB>of the third resistor 23 via a differential amplifier 26 and detects the insulation level between the non-grounded circuit 10 and the grounding potential section BE of the vehicle, based on the voltage V<SB>in</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an insulation detection device for a non-ground circuit that is insulated from a ground potential portion of a vehicle and a non-ground circuit that detects an insulation level between the ground potential portion of the vehicle.

  In vehicles such as battery-powered vehicles, hybrid vehicles, and fuel cell vehicles equipped with a DC power source that outputs high voltage, the DC power source and a circuit connected to the DC power source are insulated from the ground potential portion of the vehicle body and are not grounded Generally, it is a circuit.

  In this way, insulation deterioration between the non-ground circuit arranged insulated from the ground potential portion of the vehicle and the ground potential portion of the vehicle and a ground fault (non-ground circuit and ground potential portion of the vehicle) A configuration shown in FIG. 9 has been proposed as a configuration for detecting a short circuit between the non-ground circuit and the resistance between the non-ground circuit and the ground potential portion of the vehicle that has decreased to near 0Ω (for example, Patent Document 1). 1).

  In the configuration shown in FIG. 9, the positive-side wiring of the high-voltage DC power supply 100 mounted on the vehicle is connected to the vehicle ground potential BE via the series circuit 110 including the switching element 111, the resistor 112, and the capacitor 113. Has been. Then, based on the change in potential at the measurement point 120 on the positive side of the capacitor 113 when the switching element 111 is turned on, the insulation between the non-ground circuit including the DC power supply 100 and the ground potential portion BE is detected. Yes.

Here, when the resistance 130 between the non-ground circuit and the ground potential portion BE is high and the insulation between the non-ground circuit and the ground potential portion BE is maintained, the DC power supply 100 can be used even if the switching element 111 is in a conductive state. Since the current I ₅₀ from the capacitor to the capacitor 113 hardly flows, the rise in the potential at the measurement point 120 is very small.

On the other hand, the insulation between the non-ground circuit and the ground potential portion BE is deteriorated and a ground fault occurs between the non-ground circuit and the ground potential portion BE, so that the resistance 130 between the non-ground circuit and the ground potential portion BE is low. When this happens, the current I ₅₀ supplied from the direct current 100 to the capacitor 113 increases and the capacitor 113 is rapidly charged. Therefore, the potential at the measurement point 120 increases rapidly. Therefore, the insulation between the non-ground circuit and the ground potential portion BE can be detected from the degree of increase in the potential at the measurement point 120 when the switching element 111 is switched from the cutoff state to the conductive state.

However, generally, so-called Y capacitors 101 and 102 are provided between the output terminal of the DC high-voltage power supply 100 and the ground potential portion BE for noise countermeasures. When the switching element 111 is switched from the cut-off state to the conduction state, the current I ₅₁ due to the charge charged in the Y capacitor 101 is supplied to the capacitor 113, and the voltage across the terminals of the capacitor 113 increases.

As described above, in the case of the configuration shown in FIG. 9, the potential at the measurement point 120 rises also by the current supplied from the Y capacitor 101 to the capacitor 113, so that the insulation between the non-ground circuit and the ground potential portion BE is achieved. There is a disadvantage that it cannot be detected with high accuracy.
JP-A-8-226950

  The present invention has been made in view of the above background, and provides an insulation detection device for a non-ground circuit that can accurately detect insulation between a non-ground circuit mounted on a vehicle and a ground potential portion. With the goal.

  The present invention has been made to achieve the above object, and includes a DC power supply, a positive wiring connected to the positive electrode of the DC power supply, and a negative wiring connected to the negative electrode of the DC power supply. The present invention relates to an insulation detection device for a non-ground circuit that detects an insulation level between a non-ground circuit disposed on a vehicle and insulated from a ground potential portion of the vehicle.

  A first resistor having one end connected to the positive-side wiring and having a resistance higher than an insulation reference value for maintaining insulation between the non-grounded circuit and the ground potential portion of the vehicle; A second resistor connected to the negative wiring and having a resistance higher than the insulation reference value, and a third resistor connected between the other end of the first resistor and the other end of the second resistor Any one of a connecting portion between the first resistor and the third resistor and a connecting portion between the second resistor and the third resistor is connected to a ground potential portion of the vehicle. Grounding wiring, and an insulation level detection means for detecting an insulation level between the non-grounding circuit and the ground potential portion of the vehicle based on a voltage reference value that changes in accordance with the voltage across the terminals of the third resistor. It is characterized by that.

  According to this invention, since the first resistor and the second resistor have a resistance higher than the insulation reference value, they are connected to the positive electrode of the DC power source of the first resistor. Even if the terminal on the side not connected or the terminal not connected to the negative electrode of the DC power source of the second resistor is connected to the ground potential part of the vehicle by the ground wiring, the non-ground circuit and the ground potential of the vehicle The insulation level between the parts is maintained above the insulation reference value. If the insulation level between the non-ground circuit and the ground potential portion of the vehicle is not lowered, the voltage between the terminals of the third resistor is equal to the output voltage of the DC power source and the second resistor. However, if the insulation level between the non-grounded circuit and the ground potential portion of the vehicle decreases, the voltage drop in the first resistor will be described in detail later. As a result, the voltage drop in the second resistor changes, and the voltage across the terminals of the third resistor also changes. Therefore, with the simple configuration that is not affected by other elements such as a Y capacitor, the insulation level detection means is configured to perform the non-reduction based on the voltage reference value that changes according to the voltage across the third resistor. It is possible to accurately detect the insulation level between the ground circuit and the ground potential portion of the vehicle.

  Further, the ground wiring connects a connection portion between the second resistor and the third resistor to a ground potential portion of a vehicle, and the insulation level detection means uses the ground potential portion of the vehicle as a reference. When the voltage reference value is equal to or greater than a predetermined negative-side ground fault determination value, it is determined that a ground fault has occurred between the negative-side wiring and the ground potential portion of the vehicle.

  According to the present invention, when a ground fault occurs between the negative wiring and the ground potential portion of the vehicle, the voltage between the terminals of the second resistor becomes substantially zero, and the voltage generated by the second resistor until then. Since there is no drop, the voltage between the terminals of the third resistor rises and the voltage reference value increases. Therefore, the insulation level detection means determines that a ground fault has occurred between the negative side wiring and the ground potential portion of the vehicle when the voltage reference value is equal to or greater than the negative side ground fault determination value. can do.

The ground wiring connects a connection portion between the second resistor and the third resistor to a ground potential portion of a vehicle.
When the voltage reference value with respect to the ground potential portion of the vehicle is equal to or less than a predetermined positive ground fault determination value, the insulation level detection means is configured to connect between the positive side wiring and the vehicle ground potential portion. It is characterized by determining that a ground fault has occurred.

  According to the present invention, when a ground fault occurs between the positive wiring and the ground potential portion of the vehicle, the terminal voltage of the series circuit including the first resistor and the third resistor becomes substantially zero. As a result, the voltage between the terminals of the third resistor also becomes almost zero, and the voltage reference value decreases. Therefore, the insulation level detection means determines that a ground fault has occurred between the positive side wiring and the ground potential portion of the vehicle when the voltage reference value is equal to or less than the positive side ground fault determination value. be able to.

  Further, a fourth resistor and a switching element are connected in series, and a resistance switching circuit connected in parallel with the first resistor or the second resistor is provided. Based on the voltage reference value when the switching element is in a conductive state, it is determined whether or not there is a ground fault between the non-ground circuit and the ground potential portion of the vehicle, and the voltage when the switching element is in a cutoff state Based on the reference value, it is determined whether or not there is a ground fault between the non-ground circuit and the ground potential portion of the vehicle.

  In the present invention, as will be described in detail later, when the ground fault between the positive side wiring and the ground potential portion of the vehicle and the ground fault between the negative side wiring and the ground potential portion of the vehicle occur at the same time, Depending on the insulation level in the ground fault of the side wiring and the ground fault of the negative side wiring, there is no difference in the voltage reference value between when the ground fault occurs and when no ground fault occurs. There is. In this case, a short circuit between the positive side wiring and the negative side wiring and the ground potential portion cannot be detected. Therefore, when the insulation level detecting means changes the resistance between the positive side wiring or the negative side wiring and the ground potential portion of the vehicle by switching the switching element between the conductive state and the cutoff state by the resistance switching circuit. Based on the voltage reference value, it is determined whether or not there is a ground fault between the non-ground circuit and the ground potential portion of the vehicle. As a result, even if a ground fault occurs between the positive side wiring and the ground potential portion of the vehicle and between the negative side wiring and the ground potential portion of the vehicle at the same time, the non-ground circuit and the ground potential portion of the vehicle. The presence or absence of a ground fault can be determined.

  The non-grounding circuit includes a motor and an inverter connected between the motor and the DC power source and supplying a multiphase driving voltage to the motor, and the resistance value of the first resistor and the first resistance The resistance value of the two resistors is set to a different value, and includes a smoothing capacitor connected in parallel with the third resistor, the insulation level detecting means based on the voltage reference value, It is characterized by determining the presence or absence of a ground fault between the wiring between the motors and the ground potential part of the vehicle.

  According to the present invention, when a ground fault occurs between the wiring between the inverter and the motor and the ground potential portion of the vehicle, the ground potential portion passes through the ground potential portion according to the switching timing by the inverter. A multiphase drive voltage is superimposed on the positive side wiring or the negative side wiring. The driving voltage superimposed in this way is smoothed by the smoothing capacitor, but the resistance value of the first resistor and the resistance value of the second resistor are set to different values. The voltage obtained by smoothing the drive voltage does not become zero, and the voltage across the terminals of the smoothing capacitor is obtained by dividing the output voltage of the DC power supply by the first resistor, the second resistor, and the third resistor. The smoothed voltage is superimposed on the pressed voltage.

  Therefore, when a short circuit occurs between the wiring between the inverter and the motor and the ground potential portion of the vehicle, the voltage between the terminals of the third resistor changes accordingly, and the voltage reference value also changes. Therefore, the insulation level detection means can detect the presence or absence of a ground fault between the wiring between the inverter and the motor and the ground potential portion of the vehicle based on the voltage reference value.

  The voltage reference value is a value obtained by dividing the voltage across the third resistor by the output voltage of the DC power supply.

  According to the present invention, as will be described in detail later, the voltage reference value is a value obtained by dividing the voltage between the terminals of the third resistor by the output voltage of the DC voltage, thereby affecting the influence of fluctuations in the DC voltage. And the insulation level between the non-ground circuit and the ground potential portion of the vehicle can be detected.

  Further, the insulation level detecting means has an input circuit for inputting a voltage across the third resistor, acquires the voltage reference value based on the input voltage to the input circuit, and The resistance value of the resistor, the second resistor, and the third resistor is such that when a ground fault occurs between the non-ground circuit and the ground potential portion of the vehicle, the voltage across the third resistor is It is set so that it may become below the upper limit of the allowable input voltage range of an input circuit.

  According to the present invention, when a ground fault occurs between the non-ground circuit and the ground potential portion of the vehicle, a voltage exceeding the upper limit of the allowable input voltage range is input to the input circuit, and the input circuit is damaged. Can be prevented.

  An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a configuration diagram of an insulation detecting device for a non-grounded circuit according to the present invention. The insulation detection device for a non-grounded circuit according to the present embodiment includes a DC power source 12 that outputs a high voltage V _m (for example, several hundreds V) such as a fuel cell stack, and a DC power source connected between the DC power source 12 and the motor 40. By switching the voltage V _m output from the power supply 12 to the positive side transistors Q ₁₁ , Q ₂₁ , Q ₃₁ and the negative side transistors Q ₁₂ , Q ₂₂ , Q ₃₂ , the motor 40 has three phases (U phase, And an inverter 11 that outputs a drive voltage of V phase and W phase), and detects insulation between the non-ground circuit 10 arranged insulated from the ground potential portion BE and the ground potential portion BE of the vehicle. And is configured as a part of an ECU (Electronic Control Unit) 20.

  The insulation detection device includes a differential amplifier 26, a first wiring connected between the positive amplifier connected to the positive electrode of the DC power supply 12 (wiring connected to POG in the drawing) and the differential amplifier 26. , The second resistor 22 connected between the negative wiring (connected to NEG in the figure) connected to the negative electrode of the DC power source 12 and the differential amplifier 26, and the differential amplifier 26 A third resistor 23 connected between the input terminals of the two, a ground wiring connecting the connection portion of the second resistor 22 and the third resistor 23 to the ground potential portion BE of the vehicle, and a third resistor 23 in parallel. And a microcomputer 30 connected to the output terminal of the differential amplifier 26.

  The input section of the differential amplifier 26 corresponds to an input circuit that inputs the voltage across the terminals of the third resistor 23 of the present invention.

The microcomputer 30 functions as an insulation level detection means 31 that detects an insulation level between the non-ground circuit 10 and the ground potential portion BE by executing a predetermined control program. Incidentally, the microcomputer 30 and the differential amplifier 26, the output voltage is provided separately from the DC power source 12 is activated by the output power from the DC power supply is lower V _d than V _m (not shown).

Here, the resistance value R1 of the first resistor 21 and the resistance value R2 of the second resistor 22 are not less than a reference value (for example, 500 Ω / V or more) of the insulation resistance with respect to the ground potential portion BE of the non-ground circuit 10. In order to ensure the insulation level, the MΩ level is set. Here, when a ground fault between the ungrounded circuit 10 ground unit BE is not generated, V _in (inter-terminal voltage of = the third resistor 23) the input voltage to the differential amplifier 26 has the following formula It is approximated by (1).

Where V _in is the input voltage to the differential amplifier 26, R 1 is the resistance value of the first resistor 21, R 2 is the resistance value of the second resistor 22, R 3 is the resistance value of the third resistor 23, and V _{m is} : The output voltage of the DC power supply 12.

Then, the input voltage V _in to the differential amplifier 26 becomes maximum when the resulted ground fault of the negative-side wiring to be described later, V _in this case is approximated by the following equation (2).

Therefore, the resistance value R1 of the first resistor 21 and the resistance of the third resistor 23 are set so that V _in according to the above equation (2) does not exceed V _d that is the upper limit of the allowable input voltage range of the differential amplifier 26. The value R3 is set. Then, insulating level detection means 31 inputs the amplified output V _ref of V _in output from the differential amplifier 26, recognizes the level of V _in.

Next, detection of a ground fault between the negative side wiring of the non-ground circuit 10 and the ground potential part BE (hereinafter referred to as a negative side ground fault) will be described with reference to FIG. Referring to FIG. 2A, when a ground fault occurs between the negative wiring of the non-ground circuit 10 and the ground potential portion BE due to the resistor 50 (the resistance value Rt of the resistor 50 << the resistance value R2 of the second resistor 22). The input voltage V _in to the differential amplifier 26 is approximated by the following equation (3).

  Rt: resistance value between the negative wiring of the non-ground circuit 10 and the ground potential portion BE.

From the equation (3), in accordance with the resistance value Rt of the resistor 50 between the negative-side wiring and the ground potential portion BE ungrounded circuit 10 is reduced, it can be seen that the input voltage V _in to the differential amplifier 26 becomes high. Then, V _in the case of Rt ≒ 0 .OMEGA becomes a voltage shown by the formula (2).

2 (b) is the resistance value Rt of the resistor 50 between the negative-side wiring and the ground potential portion BE of ungrounded circuit 10, the relationship between the input voltage V _in to the differential amplifier 26, a resistance value Rt horizontal It is an approximate graph which made the input voltage Vin _{in the} axis | shaft and showed the input voltage Vin. Insulation level detecting means 31, as shown in FIG. 2 (b), the input voltage V _in to the differential amplifier 26, corresponding to the reference value Rth_1 the insulation resistance between the ungrounded circuit 10 ground potential portion BE When the voltage becomes equal to or higher than the voltage Vth_1 (corresponding to the negative side ground fault determination voltage of the present invention), it is determined that a ground fault occurs between the negative side wiring of the non-ground circuit 10 and the ground potential portion BE.

Next, detection of a ground fault between the positive wiring of the non-ground circuit 10 and the ground potential part BE (hereinafter referred to as a positive ground fault) will be described with reference to FIG. Referring to FIG. 3A, when a ground fault occurs between the positive wiring of the non-ground circuit 10 and the ground potential portion BE due to the resistor 51 (the resistance value Rt of the resistor 51 << the resistance value R1 of the first resistor 21). The input voltage V _in to the differential amplifier 26 is expressed by the following equation (4).

From the equation (4), in accordance with the resistance value Rt of the resistor 51 between the positive-side wiring and the ground potential portion BE ungrounded circuit 10 is reduced, it can be seen that the input voltage V _in to the differential amplifier 26 is lowered. Then, when the resistance value Rt ≒ 0Ω, V _in becomes 0V.

FIG. 3 (b), the resistance value Rt of the positive-side wiring and the ground potential portion BE resistance between 51 ungrounded circuit 10, the relationship between the input voltage V _in to the differential amplifier 26, a resistance value Rt horizontal It is an approximate graph which made the input voltage Vin _{in the} axis | shaft and showed the input voltage Vin. Insulation level detecting means 31, as shown in FIG. 3 (b), the input voltage V _in to the differential amplifier 26, corresponding to the reference value Rth_2 the insulation resistance between the ungrounded circuit 10 ground potential portion BE When the voltage becomes equal to or lower than the voltage Vth_2 (corresponding to the positive side ground fault determination voltage of the present invention), it is determined that a ground fault occurs between the positive side wiring of the non-ground circuit 10 and the ground potential portion BE.

Next, referring to FIG. 4, a ground fault between the DC midpoint of the power supply 12 (the point of dividing the output voltage V _m of the DC power supply 12 to the V _m / 2) and the ground potential portion BE ungrounded circuit 10 (hereinafter The detection of the midpoint ground fault) will be described. Referring to FIG. 4A, a ground fault occurs between the middle point of the DC power supply 12 and the ground potential portion BE due to the resistor 52 (the resistance value Rt of the resistor 52 << the resistance value R1 of the first resistor 21, the second resistance 22), the input voltage V _in to the differential amplifier 26 is expressed by the following equation (5).

The above equation (5), in accordance with the resistance value Rt of the resistor 52 between the ground potential portion BE and the midpoint of the DC power supply 12 is small, it can be seen that the input voltage V _in to the differential amplifier 26 becomes high. Then, when the resistance value Rt ≒ 0Ω, V _in is represented by the following equation (6).

FIG. 4 (b), the resistance value Rt of the resistor 52 between the midpoint of the DC power source 12 ground unit BE, the relationship between the input voltage V _in to the differential amplifier 26, the resistance value Rt and the horizontal axis a proximity graph showing the input voltage V _in the vertical axis. Insulation level detecting means 31, as shown in FIG. 4 (b), the differential input voltage V _in to the amplifier 26, the DC power source 12 midpoint between the reference value of insulation resistance between the ground potential portion BE Rth_3 more Then, it is determined that a ground fault has occurred between the midpoint of the DC power supply 12 and the ground potential portion BE.

  Next, with reference to FIGS. 5 and 6, detection of a ground fault (hereinafter referred to as a three-phase ground fault) between the wiring of the non-ground circuit 10 between the inverter 11 and the motor 40 and the ground potential portion BE will be described. . FIG. 5 shows a state where the wiring between the inverter 11 and the W phase of the motor 40 is grounded to the ground potential portion BE via the resistor 53.

5, for the W phase, when the transistor Q ₃₂ transistors Q ₃₁ of inverter 11 is a ON (conductive state) is OFF (disconnected state), the positive-side wiring transistor Q ₃₁ ungrounded circuit 10 Through the ground potential portion BE. The transistor Q ₃₁ transistors Q ₃₂ of inverter 11 is a turned ON when it is OFF, the negative side wiring ungrounded circuit 10 is a ground fault to the ground potential portion BE through the transistor Q _32. The same applies to the U phase and the V phase.

FIG. 6A shows a case where R1 = R2 (>> R3), the resistance value Rt of the resistor 53 Rt≈0Ω, and the capacitance C1 of the smoothing capacitor 25 is 0 pF, which is large (the drive voltage for the motor 40 is smoothed). Therefore, the change _in the input voltage Vin to the differential amplifier 26 is set according to the frequency of the drive voltage.

In this case, when the capacitance C1 of the smoothing capacitor 25 is 0pF, when the transistor Q ₃₁ is a transistor Q ₃₂ is OFF in ON, the ground potential positive side wiring through the transistor Q ₃₁ of ungrounded circuit 10 A ground fault occurs in the portion BE, and the input voltage Vin _in the differential amplifier 26 becomes 0V. When the transistor Q ₃₂ is ON and the transistor Q ₃₁ is OFF, the negative side wiring of the non-ground circuit 10 is grounded to the ground potential part BE via the transistor Q ₃₂ , and the input voltage to the differential amplifier 26 V _in is twice the voltage V _typ when no ground fault occurs (V _tpy × 2).

When the capacitance C1 of the smoothing capacitor 25 is increased, the input voltage V _in to the differential amplifier 26 is smoothed near the voltage V _typ , and the wiring between the inverter 11 and the motor 40 and the ground potential portion BE are reduced. The situation is the same as when no ground fault has occurred. Therefore, the insulation level detection means 31 cannot detect that a ground fault has occurred between the wiring between the inverter 11 and the motor 40 and the ground potential portion BE.

  Therefore, by setting the resistance value R1 of the first resistor 21 and the resistance value R2 of the second resistor 22 to different values, a ground fault occurs between the wiring between the inverter 11 and the motor 40 and the ground potential portion BE. The occurrence can be detected separately from the case where the ground fault does not occur.

FIG. 6B shows the resistance value Rt of the resistor 53 when the resistance value R2 of the second resistor 22 is three times the resistance value R1 of the first resistor 21 (R2 = 3 × R1). the change in the input output voltage V _in to the differential amplifier 26 when a 0 .OMEGA, similarly to FIG. 6 (a), the time the capacity C1 of the smoothing capacitor 25 is 0pF and large (drive voltage to the motor 40 Is set according to the frequency of the drive voltage in order to smooth the signal.

In FIG. 6B, when the capacitance of the smoothing capacitor 25 is 0 pF, when the transistor Q ₃₁ is ON and the transistor Q ₃₂ is OFF, the positive-side wiring of the non-ground circuit 10 passes through the transistor Q ₃₁ . grounded to a ground potential portion bE Te, the input voltage V _in to the differential amplifier 26 is 0V. When the transistor Q ₃₂ is ON and the transistor Q ₃₁ is OFF, the negative side wiring of the non-ground circuit 10 is grounded to the ground potential part BE via the transistor Q ₃₂ , and the input voltage to the differential amplifier 26 V _in is, it is four times the normal voltage at the time of a ground fault has not occurred _{(V typ = R3 / (R3} + 4R1) ≒ R3 / 4R1) (4 × V typ).

When the capacitance C1 of the smoothing capacitor 25 is increased, the input voltage V _in to the differential amplifier 26 becomes twice (2 × V _typ ) the steady-state voltage V _typ . Therefore, the insulation level detecting means 31 can determine that a three-phase ground fault has occurred when the input voltage V _in to the differential amplifier 26 has increased to about twice the steady-state voltage V _typ .

  Next, as shown in FIG. 7A, a ground fault occurs between the positive wiring of the non-ground circuit 10 and the ground potential portion BE through the resistor 54, and the negative wiring of the non-ground circuit 10 and the ground potential. It will be described that the ECU 20 does not fail when a ground fault occurs between the parts BE via the resistor 55 (hereinafter referred to as a bipolar ground fault).

Referring to FIG. 7B, when a ground fault occurs between the positive side wiring of the non-ground circuit 10 and the ground potential portion BE, the input 1 and the input 2 to the ECU 20 have the same potential. or without a ground fault between parts bE, the input voltage V _in to the differential amplifier 26 becomes 0V.

When a ground fault occurs between the negative wiring and the ground potential portion BE, the current I ₁₀ flows from the positive electrode (POG side) of the DC power supply 12 to the negative electrode (NEG side) through the resistor 54 and the resistor 55. Thus, even if a bipolar ground fault occurs, the current I ₁₀ flows through a path outside the ECU 20, and therefore no overcurrent flows through the ECU 20, so that the ECU 20 does not fail.

Next, with reference to FIG. 8, a description will be given of a configuration for avoiding the detection of the ground fault when a bipolar ground fault occurs. The resistance value of the resistor 54 between the positive side wiring of the non-ground circuit 10 and the ground potential portion BE is Rt1, and the resistance value of the ground fault resistor 55 between the negative side wiring of the non-ground circuit 10 and the ground potential portion BE is Rt2. In some cases, the input voltage V _in to the differential amplifier 26 is expressed by the following equation (7).

  However, (R1 + R3) // Rt1: Resistance value when (R1 + R3) and Rt1 are connected in parallel, R2 // Rt2: Resistance value when R2 and Rt2 are connected in parallel.

  If, for example, Rt1 = R1 + R3 and Rt2 = R2 in the above equation (7), the following equation (8) is obtained, and the voltage is the same as in the normal state. Therefore, the insulation level detecting means 31 indicates that a bipolar ground fault has occurred. It cannot be detected.

  Thus, when Rt1 = A.times. (R1 + R3) and Rt2 = A.times.R2 (A is a variable), that is, when the relationship of the following equation (9) is established, a ground fault cannot be detected.

Therefore, as shown in FIG. 8, it is possible to detect a bipolar ground fault by connecting a switching circuit in which a fourth resistor and a switching element 27 are connected in series in parallel with the first resistor 21. It becomes. An input voltage V _in to the differential amplifier 26 when the switching element 27 is turned on (conductive state) is expressed by the following equation (10).

  However, R1 // R4: resistance value when R1 and R4 are connected in parallel, (R1 // R4 + R3) // Rt1: resistance value when (R1 // R4 + R3) and Rt1 are connected in parallel, R2 // Rt2 in parallel Resistance value when connected.

  In the above formula (9), the ratio of Rt1 and Rt2 in which the detection of the bipolar ground fault is impossible is as shown in the following formula (11), which is a ratio different from the above formula (9).

Therefore, the insulating level detection unit 31, the input voltage V _in to the differential amplifier 26 when the ON the switching element 27, the input voltage V _in to the differential amplifier 26 when the OFF the switching element 27, By determining the ground fault, it is possible to avoid the detection of the ground fault when a bipolar ground fault occurs.

Further, the input voltage V _in to the differential amplifier 16 changes according to the level of the output voltage V _m of the DC power supply 12. Therefore, due to the influence of fluctuations in the output voltage V _m of the DC power source 12, detection accuracy of the ground fault based on the input voltage V _in to the differential amplifier 16 may deteriorate.

Therefore, as shown in the following equation (12), by dividing the input voltage V _in to the differential amplifier 26 by the output voltage V _m of the DC power source 12, the voltage reference value At calculated only by the resistance By adopting and determining the ground fault based on this voltage reference value At, it is possible to prevent the ground fault detection accuracy from deteriorating due to the influence of the fluctuation of the output voltage V _m and causing the false detection of the ground fault. Can do.

  In this embodiment, the negative side ground fault, the positive side ground fault, the midpoint ground fault, the three-phase ground fault, and the bipolar ground fault are determined, but at least one of the ground faults is detected. Thus, the effects of the present invention can be obtained.

  Further, in the present embodiment, as shown in FIG. 1, the connecting portion between the second resistor 22 and the third resistor 23 is connected to the ground potential portion BE of the vehicle. 3 is connected to the ground potential BE of the vehicle, and the insulation level between the non-ground circuit 10 and the ground potential BE is detected based on the voltage across the third resistor 23. May be.

The block diagram of the insulation detection apparatus of the non-grounding circuit of this invention. Explanatory drawing of a negative side ground fault detection. Explanatory drawing of a positive side ground fault detection. Explanatory drawing of a midpoint ground fault detection. Explanatory drawing of a three-phase ground fault detection. Explanatory drawing of a three-phase ground fault detection. Explanatory drawing of the state where a bipolar ground fault occurred. The block diagram for responding to a bipolar ground fault. The block diagram of the conventional insulation detection apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Ungrounded circuit, 11 ... Inverter, 12 ... DC power supply, 20 ... ECU, 21 ... 1st resistance, 22 ... 2nd resistance, 23 ... 3rd resistance, 24 ... 4th resistance, 25 ... Smoothing Capacitor, 26 ... Differential amplifier, 27 ... Switching element, 30 ... Microcomputer, 31 ... Insulation level detection means

Claims (7)

A non-grounded circuit having a DC power source and a positive side wiring connected to the positive electrode of the DC power source and a negative side wiring connected to the negative electrode of the DC power source and arranged on the vehicle insulated from the ground potential portion of the vehicle An insulation detection device for a non-ground circuit that detects an insulation level between a circuit and the ground potential portion,
A first resistor having one end connected to the positive side wiring and having a resistance higher than an insulation reference value for maintaining insulation between the non-grounded circuit and the ground potential portion of the vehicle;
A second resistor having one end connected to the negative wiring and having a resistance higher than the insulation reference value;
A third resistor connected between the other end of the first resistor and the other end of the second resistor;
A ground wiring for connecting one of the connection portion between the first resistor and the third resistor and the connection portion between the second resistor and the third resistor to a ground potential portion of the vehicle. When,
Insulation level detection means for detecting an insulation level between the non-ground circuit and the ground potential portion of the vehicle based on a voltage reference value that changes in accordance with the voltage across the terminals of the third resistor. A non-grounded circuit insulation detector. The ground wiring connects a connection portion between the second resistor and the third resistor to a ground potential portion of a vehicle,
When the voltage reference value based on the ground potential portion of the vehicle is equal to or greater than a predetermined negative ground fault determination value, the insulation level detection means is configured to be between the negative wiring and the ground potential portion of the vehicle. 2. The non-grounded circuit insulation detection device according to claim 1, wherein a ground fault is determined in step 1. The ground wiring connects a connection portion between the second resistor and the third resistor to a ground potential portion of a vehicle,
When the voltage reference value with respect to the ground potential portion of the vehicle is equal to or less than a predetermined positive ground fault determination value, the insulation level detection means is configured to connect between the positive side wiring and the vehicle ground potential portion. 3. The non-grounded circuit insulation detection device according to claim 1, wherein it is determined that a ground fault has occurred. A fourth resistor and a switching element connected in series, and a resistance switching circuit connected in parallel with the first resistor or the second resistor;
The insulation level detection means determines the presence or absence of a ground fault between the non-ground circuit and the ground potential portion of the vehicle based on the voltage reference value when the switching element is in a conductive state, and the switching element The presence or absence of a ground fault between the non-grounded circuit and the ground potential portion of the vehicle is determined based on the voltage reference value in the cut-off state. Insulation detecting device for non-grounded circuit of item. The non-grounded circuit has a motor and an inverter connected between the motor and the DC power source to supply a multiphase drive voltage to the motor,
The resistance value of the first resistor and the resistance value of the second resistor are set to different values,
A smoothing capacitor connected in parallel with the third resistor;
The said insulation level detection means judges the presence or absence of the ground fault between the wiring between the said inverter and the said motor, and the grounding potential part of a vehicle based on the said voltage reference value. Item 5. The non-grounded circuit insulation detection device according to any one of Items 4 to 5.   6. The non-grounding according to any one of claims 1 to 5, wherein the voltage reference value is a value obtained by dividing a voltage across the third resistor by an output voltage of the DC power supply. Circuit insulation detector. The insulation level detection means has an input circuit for inputting the voltage across the third resistor, acquires the voltage reference value based on the input voltage to the input circuit,
The resistance values of the first resistor, the second resistor, and the third resistor are between the terminals of the third resistor when a ground fault occurs between the non-ground circuit and the ground potential portion of the vehicle. The insulation detection device for a non-grounded circuit according to any one of claims 1 to 6, wherein the voltage is set to be equal to or lower than an upper limit of an allowable input voltage range of the input circuit. .

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