JP6267866B2 - Insulation state detector - Google Patents

Description

  The present invention relates to an insulation state detection device that can be mounted on a vehicle.

  For example, in a vehicle that uses electric power as propulsion energy, such as an electric vehicle, a DC power supply device that outputs a high voltage of about 200 V may be mounted. In the case of a vehicle equipped with such a high-voltage DC power supply device, it is used in a state where the positive and negative power supply lines of the DC power supply device and the vehicle body are electrically insulated. That is, the vehicle body is not used as a ground for a power source that outputs a high voltage.

  In such a vehicle, it is necessary to inspect and confirm that the high-voltage DC power output wiring and the vehicle body are sufficiently electrically insulated in order to ensure safety. For example, Patent Literature 1, Patent Literature 2, and Patent Literature 3 disclose conventional techniques of an insulation state detection device used when performing such an inspection.

  This type of insulation state detection device uses a flying capacitor. That is, a detection capacitor (referred to as a flying capacitor) is connected between a high-voltage positive / negative power supply line and a ground electrode (vehicle body) for a certain period of time via a switching element. The charging voltage of the flying capacitor is monitored, and the ground fault resistance, that is, the insulation resistance between the power supply line and the ground electrode is calculated from the charging voltage.

  For example, a film capacitor or a ceramic capacitor may be used as a detection capacitor of such an insulation state detection device. However, while film capacitors are highly accurate, they are difficult to downsize and have low moisture resistance. Therefore, in the case of an in-vehicle insulation state detection device, it is assumed that a ceramic capacitor having a small size is used.

However, when using a ceramic capacitor, there is a problem in terms of accuracy. That is, there are the following problems.
(1) There is a large variation in capacitance among components.
(2) The capacitance when actually used varies due to the influence of a DC (direct current) bias voltage.
(3) Capacitance during actual use varies according to temperature changes.

  Therefore, Patent Document 1 discloses a technique for removing the influence of DC bias characteristics when a ceramic capacitor is used as a detection capacitor. Specifically, all charging voltages and charging time constants when the ground fault resistance RL is the alarm threshold value RLx are made the same. Thereby, in the vicinity of the alarm threshold value RLx, the influence of the DC bias characteristic can be reduced, and the measurement accuracy can be prevented from being lowered.

  In Patent Document 2, the measurement timing of the power supply charging voltage V0 and the negative side ground fault resistance measurement voltage VC1n and the measurement timing of the power supply charging voltage V0 and the positive side ground fault resistance measurement voltage VC1p are the same. . As a result, even when the voltage of the power supply fluctuates, the influence of the fluctuation can be reduced.

  Patent Document 3 discloses a technique for shortening measurement time while ensuring detection accuracy. Specifically, a sample hold circuit is connected in front of the analog input port of the CPU, and the timing for measuring the voltage is controlled to prevent a decrease in detection accuracy.

JP 2009-281986 A JP 2009-281987 A JP 2011-102788 A

  When a ceramic capacitor is used as a detection capacitor of an insulation state detection device, there are problems (1), (2), (3), etc., but since it is a special environment for measuring insulation resistance, These multiple factors affect each other and are intertwined in a complicated manner, which adversely affects measurement accuracy.

  Therefore, it is not easy to eliminate the influence of the temperature characteristic problem (3). For example, even if the temperature of the actual detection capacitor can be grasped using a temperature sensor, it is not easy to correctly correct the measurement result of the ground fault resistance by reflecting this temperature change.

  On the other hand, a vehicle equipped with a DC power supply device that outputs a high voltage is equipped with a special device for measuring a power supply voltage, and it is necessary to constantly monitor whether there is a voltage abnormality. However, since a trouble such as a failure may occur in the apparatus that measures the power supply voltage, it is also desired to prepare a backup of the apparatus that measures the power supply voltage.

  The insulation state detection device as described above charges the detection capacitor based on the high voltage supplied from the DC power supply device that outputs a high voltage, and measures the charging voltage of the detection capacitor. It is also possible to estimate the power supply voltage from the value. That is, if the power supply voltage detection function is installed in the insulation state detection device, the insulation state detection device can be used as a backup device instead of the original power supply voltage measurement device.

  However, in order to detect an accurate power supply voltage, the detection capacitor must be fully charged, so that the time required for charging becomes long. That is, the charging voltage between the terminals of the detection capacitor increases with time according to an exponential function curve corresponding to the capacitance of the detection capacitor, and the voltage increase stops when fully charged. If measurement is performed with the voltage increase stopped, the power supply voltage can be detected without being affected by the capacitance. Therefore, it is inevitable that the time period for measuring the power supply voltage becomes long.

  However, in a situation where backup is required, it is desirable to be able to measure the power supply voltage at as short a time interval as possible. However, if the voltage is measured in a state where the detection capacitor is not completely charged, a measurement error occurs depending on the difference in capacitance. In particular, when a ceramic capacitor is used as a detection capacitor, the capacitance changes due to various factors as described above, so it is difficult to accurately measure the power supply voltage when not fully charged. is there.

  The present invention has been made in view of the above-described circumstances, and its purpose is to provide temperature detection even when a component such as a ceramic capacitor whose characteristics are likely to change due to various factors is used as a detection capacitor. An object of the present invention is to provide an insulation state detection device that is less susceptible to changes and can output accurate measurement values.

In order to achieve the above-described object, an insulation state detection device according to the present invention is characterized by the following (1) to ( 4 ).
(1) A positive-side input terminal and a negative-side input terminal connected to a positive-side power line and a negative-side power line for a predetermined high-voltage DC power output, respectively, and a ground electrode, and based on the charging voltage of the flying capacitor An insulation state detection device for grasping an insulation state between the positive electrode side power line and the negative electrode side power line and the ground electrode,
A temperature detector for detecting a temperature in the vicinity of the flying capacitor;
A charging voltage measuring unit for measuring a charging voltage of the flying capacitor;
Based on a measurement value related to a charging voltage of the flying capacitor, a ground fault resistance value calculating unit that calculates an insulation resistance value between the positive power line and the negative power line and the ground electrode;
With
The charging voltage measuring unit changes a length of time for charging the flying capacitor according to the temperature detected by the temperature detecting unit.
(2) The insulation state detection device according to (1) above,
The charging voltage measuring unit has a constant table that holds each of a plurality of temperature ranges in association with information on a coefficient corresponding to a length of time for charging the flying capacitor, and the temperature detecting unit detects And determining a length of time for charging the flying capacitor using the constant table based on the measured temperature.
(3) The insulation state detection device according to (1) above,
Using the charging voltage measurement unit, further comprising a power supply voltage detection unit for detecting a power supply voltage appearing between the positive electrode side power supply line or the negative electrode side power supply line and the ground electrode,
The power supply voltage detection unit measures a voltage after charging the flying capacitor at a power supply voltage measurement cycle shorter than a required charging time required for fully charging the flying capacitor, and calculates an estimated value of the power supply voltage from the measured value. Calculate
The power supply voltage detection unit changes a length of time for charging the flying capacitor within a power supply voltage measurement cycle according to the temperature detected by the temperature detection unit.
(4) The insulation state detection device according to (3) above,
The power supply voltage detection unit has a voltage conversion constant table that holds information on a plurality of conversion coefficients for converting a voltage measurement value into the estimated value in association with each of a plurality of ranges of voltage measurement values. The estimated value is calculated based on one conversion coefficient acquired from the voltage conversion constant table .

According to the insulation state detection apparatus having the configuration (1), it is possible to calculate an accurate insulation resistance value even when the capacitance of the flying capacitor varies according to the temperature difference. . In other words, the change in capacitance according to the temperature difference can be compensated by adjusting the length of time for charging the flying capacitor.
That is, the charging voltage between the terminals of the flying capacitor changes exponentially according to each parameter including the power supply voltage applied to the input, the capacitance, and the elapsed time from the start of charging. The corresponding capacitance error can be compensated by adjusting the charging time.
According to the insulation state detection device having the configuration of (2) above, it is possible to easily obtain the parameter of the charging time necessary for correctly compensating for the capacitance error of the flying capacitor in accordance with the temperature fluctuation, and the control can be performed. It becomes easy.
According to the insulation state detection device having the configuration (3), not only the ground fault resistance value but also the power supply voltage can be measured. In addition, since the correction is performed according to the temperature, accurate measurement is possible even in a situation where the capacitance varies according to the temperature. That is, since the measurement can be performed before the flying capacitor is fully charged, the measurement cycle can be shortened.
That is, the charging voltage between the terminals of the flying capacitor changes exponentially according to each parameter including the power supply voltage applied to the input, the capacitance, and the elapsed time from the start of charging. The corresponding capacitance error can be compensated by adjusting the charging time.
According to the insulation state detection apparatus having the configuration (4), it is possible to easily obtain the conversion coefficient necessary for correctly compensating for the error in the capacitance of the flying capacitor in accordance with the fluctuation of the DC bias voltage, and easy control. Become .

  According to the insulation state detection device of the present invention, even when a component such as a ceramic capacitor whose characteristics are likely to change due to various factors is used as a detection capacitor, it is not easily affected by temperature changes and is accurate. Measurement values can be output.

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading through a mode for carrying out the invention described below (hereinafter referred to as “embodiment”) with reference to the accompanying drawings. .

FIG. 1 is an electric circuit diagram illustrating a configuration example of an insulation state detection device and its peripheral circuits according to the embodiment. FIG. 2 is a flowchart showing the main control contents of the insulation state detection apparatus shown in FIG. FIG. 3 is a time chart showing a specific example of the operation timing of the insulation state detection device shown in FIG. FIG. 4 is a schematic diagram showing a configuration example of a constant table that holds compensation values according to temperature. FIG. 5 is a graph showing a specific example of the relationship between the voltage applied to the capacitor, the charge charge, and the temperature. FIG. 6 is a graph showing a specific example of compensation characteristics corresponding to a temperature change. FIG. 7 is a schematic diagram illustrating a configuration example of a voltage conversion constant table. FIG. 8 is a time chart showing the operation timing of the basic measurement cycle.

  Specific embodiments relating to the insulation state detection device of the present invention will be described below with reference to the drawings.

<Overview of overall configuration and operation>
FIG. 1 shows the configuration of an insulation state detection device 10 mounted on a vehicle and its peripheral circuits.
The insulation state detection device 10 shown in FIG. 1 can be used by being mounted on a vehicle such as an electric vehicle or a hybrid vehicle including an engine and an electric motor as drive sources. The in-vehicle DC high-voltage power supply 50 outputs high-voltage DC power of about 200V, for example. The electric motor that generates the driving force of the vehicle can be driven by the electric power output from the in-vehicle DC high voltage power supply 50.

  The positive electrode side power supply line 111 of the output of the in-vehicle DC high voltage power supply 50 and the ground electrode 103 are electrically insulated. The negative power supply line 112 and the ground electrode 103 are also electrically insulated. The ground electrode 103 corresponds to an earth part such as a vehicle body. Here, the insulation state between the positive power line 111 and the ground electrode 103 can be expressed as a ground fault resistance RLp. Further, the insulation state between the negative power supply line 112 and the ground electrode 103 can be expressed as a ground fault resistance RLn.

  In order to reduce common mode noise, as shown in FIG. 1, a Y capacitor 101 is connected between the positive power line 111 and the ground electrode 103, and between the negative power line 112 and the ground electrode 103. A Y capacitor 102 is connected to this.

  By mounting the insulation state detection device 10 shown in FIG. 1 on a vehicle, the insulation state of the vehicle can be monitored at any time as necessary. That is, the insulation state detection device 10 can be used to detect the ground fault resistances RLp and RLn at the output of the in-vehicle DC high voltage power supply 50 and grasp the insulation state.

  Therefore, as shown in FIG. 1, the positive input terminal 13 and the negative input terminal 14 of the insulation state detection device 10 are connected to the positive power supply line 111 and the negative power supply line 112, respectively. The ground electrode 15 of the insulation state detection device 10 is connected to the ground electrode 103.

  An output terminal 21 is provided as shown in FIG. 1 in order to output the measurement result of the insulation state detection device 10 and alarm information. The output terminal 21 can be connected to, for example, a vehicle-side electronic control unit (ECU).

<Configuration Example of Insulation State Detection Device 10>
As shown in FIG. 1, the circuit of the insulation state detection device 10 is provided with a detection capacitor C1 that operates as a flying capacitor. A ceramic capacitor is employed as the detection capacitor C1 in consideration of being used in a vehicle.

  Further, in order to control charging and discharging of the detection capacitor C1, four switching elements S1 to S4 are provided in the vicinity thereof. Each of these switching elements S1 to S4 is a switch that can switch the open / close (off / on) state of a contact by controlling an insulated signal, such as an optical MOSFET.

  The switching element S <b> 1 is connected to the positive input terminal 13 and the other end is connected to the wiring 31. The switching element S2 has one end connected to the negative input terminal 14 and the other end connected to the wiring 32 via the resistor R2.

  The switching element S <b> 3 has one end connected to the wiring 33 and the other end connected to the wiring 35. The switching element S4 has one end connected to the wiring 32 and the other end connected to the ground electrode 15 via the resistor R4.

  The detection capacitor C <b> 1 has a negative terminal connected to the wiring 32. The positive terminal of the detection capacitor C1 is connected to the wiring 31 through a series circuit including a diode D1 and a resistor R1. The positive terminal of the detection capacitor C1 is connected to the wiring 33 via a series circuit including a diode D3 and a resistor R3, and is further connected to the wiring 33 via a diode D2. The diode D2 is connected with a polarity that allows energization in the direction from the wiring 33 to the wiring 34, and the diode D3 is connected with a polarity that allows energization in the direction from the wiring 34 to the wiring 33.

  Note that the wiring 34 may be grounded via a special switch and resistor (not shown) in order to discharge the electric charge accumulated in the detection capacitor C1. However, such a special discharge circuit can be omitted by using components having relatively small resistance values for the resistors R3, R4, and R5.

  As shown in FIG. 1, a thermistor 25 is disposed in the vicinity of the detection capacitor C1. Since the resistance value of the thermistor 25 changes according to the temperature of the detection capacitor C1, it is possible to output an electric signal whose level changes according to this temperature.

  The microcomputer (CPU) 11 executes various controls required for the insulation state detection device 10 by executing a program incorporated in advance. Specifically, the microcomputer 11 controls the switching elements S1 to S4 individually to control charging and discharging of the detection capacitor C1. Further, the microcomputer 11 inputs an analog level corresponding to the charging voltage of the detection capacitor C1 from one analog input port AD1 via the wiring 36, performs calculation based on this input level, and performs ground fault resistance RLp and Know RLn.

  The input circuit 20 is connected between the wiring 35 and the wiring 36. The input circuit 20 performs signal processing for converting a signal appearing on the wiring 35 into a signal suitable for the processing of the microcomputer 11. Although various functions and configurations are conceivable for the input circuit 20, a sample hold circuit is assumed as a typical input circuit 20.

  For example, an analog switch is connected between the wiring 35 and the wiring 36, and a capacitor (capacitor) that holds a signal level is connected between the wiring 36 and the ground electrode 15. When the microcomputer 11 temporarily turns on (conducts) the analog switch at a specific timing, the signal level input at that timing can be sampled and held by the capacitor in the input circuit 20. . Of course, the function of such a sample and hold circuit can be omitted.

  The other analog input port AD <b> 2 of the microcomputer 11 is connected to one end of the thermistor 25 via a wiring 37. Therefore, the microcomputer 11 can acquire the temperature information of the detection capacitor C1 detected by the thermistor 25 by measuring the input level of the analog input port AD2.

  In addition to the function of measuring the ground fault resistances RLp and RLn, the insulation state detection device 10 of the present embodiment is also equipped with a function of measuring the voltage (high voltage) of the in-vehicle DC high-voltage power supply 50 as an auxiliary.

  Normally, a vehicle equipped with the on-vehicle DC high-voltage power supply 50 is equipped with a dedicated measuring device for measuring the power supply voltage appearing on the positive power supply line 111 and the negative power supply line 112. However, since there is a possibility that such a dedicated measuring device may break down, it is desired to mount a backup device when a failure occurs.

  The insulation state detection apparatus 10 has a normal measurement mode and a backup mode as operation modes. As will be described later, the insulation state detection device 10 can measure the power supply voltage when the backup mode is selected. In order to designate this operation mode, the operation switch SWx is connected to the input port of the microcomputer 11. That is, the microcomputer 11 can select the normal measurement mode and the backup mode by identifying on / off of the operation switch SWx.

  In addition, you may change so that the operation mode of the insulation state detection apparatus 10 may be switched by the command from external apparatuses (ECU on the vehicle side, etc.). Further, it may be changed so that the microcomputer 11 automatically switches between the normal measurement mode and the backup mode when it is detected that a specific condition is satisfied during the measurement of the ground fault resistance.

<Measurement of ground fault resistance>
<Description of Charging / Discharging of Capacitor for Detection (Flying Capacitor) C1>
<Timing for switching>
A specific example of the switching timing of the switching elements S1 to S4 during measurement is shown in FIG. That is, when measuring the ground fault resistances RLp and RLn, the microcomputer 11 controls on / off of the switching elements S1 to S4 according to the schedule of the basic measurement cycle as shown in FIG. Get the necessary measurements.

  The basic measurement cycle shown in FIG. 8 includes “V0 charge”, “measurement”, “discharge”, “Vc1n charge”, “measurement”, “discharge”, “V0 charge”, “measurement”, “discharge”, “ It is composed of a series of sections of “Vc1p charge”, “measurement”, and “discharge”.

  In the “V0 charging” section at time t1-t2, the switching elements S1 and S2 are turned on (contacts closed), and the other switching elements are turned off (contacts open). In the “measurement” section at time t2-t3, the switching elements S3 and S4 are turned on, and the other switching elements are turned off.

  In the “discharge” section from time t3 to t4, the switching elements S3 and S4 are turned on, and the other switching elements are turned off. In the “Vc1p charging” section at time t4-t5, the switching elements S1 and S4 are turned on, and the other switching elements are turned off.

  The “measurement” section at time t5-t6 is the same as the “measurement” section at time t2-t3. Further, the “discharge” section at time t6-t7 is the same as the “discharge” section at time t3-t4. The “V0 charging” section from time t7 to t8 is the same as the “V0 charging” section from time t1 to t2. The subsequent “measurement” section from time t8 to t9 is the same as the “measurement” section from time t2 to t3. Further, the “discharge” section from time t9 to t10 is the same as the “discharge” section from time t3 to t4.

  In the “Vc1p charge” section from time t10 to t11, the switching elements S2 and S3 are turned on, and the other switching elements are turned off. The “measurement” section at time t11-t12 is the same as the “measurement” section at time t2-t3. The “discharge” section from time t12 to t13 is the same as the “discharge” section from time t3 to t4.

<Energization path and operation in each section of measurement cycle>
"V0 charge" section:
Since the contact of the switching element S1 is closed, a current flows from the positive power supply line 111 to the positive terminal of the detection capacitor C1 through the positive input terminal 13, the switching element S1, the wiring 31, the diode D1, and the resistor R1. Flowing. Further, since the contact of the switching element S2 is closed, a current flows from the negative terminal of the detection capacitor C1 to the wiring 32, the resistor R2, the switching element S2, the negative input terminal 14, and the negative power line 112. Therefore, the electric charge is charged in the detection capacitor C1 by this current.

“Measurement” section:
Since the contact of the switching element S4 is closed, the negative terminal of the detection capacitor C1 is connected to the ground electrode 15 via the resistor R4. Since the contact of the switching element S3 is closed, the positive terminal of the detection capacitor C1 is connected to the microcomputer 11 via the diode D3, the resistor R3, the switching element S3, the wiring 35, the input circuit 20, and the wiring 36. Connected to analog input port. Therefore, the microcomputer 11 can detect an analog level proportional to the charging voltage of the detection capacitor C1.

“Discharge” section:
Since the contact of the switching element S4 is closed, the negative terminal of the detection capacitor C1 is connected to the ground electrode 15 via the resistor R4. Since the contact of the switching element S3 is closed, the positive terminal of the detection capacitor C1 is connected to the ground electrode 15 via the diode D3, the resistor R3, the switching element S3, and the resistor R5. Accordingly, the charge accumulated in the detection capacitor C1 is naturally discharged.

"Vc1n charge" section:
Since the contact of the switching element S1 is closed, a current flows from the positive power supply line 111 to the positive terminal of the detection capacitor C1 through the positive input terminal 13, the switching element S1, the wiring 31, the diode D1, and the resistor R1. Flowing. Further, since the contact of the switching element S4 is closed, the negative power supply line from the negative terminal of the detection capacitor C1 passes through the switching element S4, the resistor R4, the ground electrode 15, the ground electrode 103, and the ground fault resistor RLn. A current flows through 112. This current charges the detection capacitor C1. The charging voltage at this time is a result reflecting the influence of the ground fault resistance RLn.

"Vc1p charge" section:
Since the contact of the switching element S3 is closed, the positive electrode of the detection capacitor C1 passes from the positive power supply line 111 through the ground fault resistance RLp, the ground electrode 103, the ground electrode 15, the resistor R5, the switching element S3, and the diode D2. Current flows through the side terminals. Further, since the contact of the switching element S2 is closed, a current flows from the negative terminal of the detection capacitor C1 to the wiring 32, the resistor R2, the switching element S2, the negative input terminal 14, and the negative power line 112. This current charges the detection capacitor C1. The charging voltage at this time is a result reflecting the influence of the ground fault resistance RLp.

<Basic grounding resistance measurement operation>
Regarding the operation of the insulation state detection device 10 shown in FIG. 1, the following relational expression is basically established.
(RLp + RLn) / (RLp × RLn) = {(Vc1p) + (Vc1n)} / V0
However,
V0: Charge voltage Vc1n of the detection capacitor C1 corresponding to the output voltage of the in-vehicle DC high-voltage power supply 50: Charge voltage Vc1p of the detection capacitor C1 affected by the negative ground fault resistance RLn: Positive ground fault resistance RLp Voltage RLp, RLn of the capacitor C1 for detection affected by the resistance: resistance value of the local resistance

  Therefore, the microcomputer 11 grasps each charging voltage “V0”, “Vc1n”, “Vc1p” from the signal level inputted to the analog input port (AD1) in each state, and the ground fault resistance based on the above relational expression. RLp and RLn can be calculated.

<Explanation of compensation of temperature characteristic of detection capacitor C1>
A specific example of the relationship between the voltage applied to the capacitor, the charge charged, and the temperature is shown in FIG. A specific example of compensation characteristics corresponding to temperature changes is shown in FIG.

  When using a ceramic capacitor, the characteristics change as shown in FIG. That is, when the charging time is constant, the capacitance decreases when the temperature of the capacitor itself (generally equivalent to the ambient temperature) becomes higher than the normal temperature (for example, 20 ° C.) (80 ° C.). Charge charge decreases. Further, when the temperature of the capacitor itself becomes lower than the normal temperature (−30 ° C.), the capacitance increases and the charge charge also increases.

  When a ceramic capacitor whose characteristics change in accordance with the temperature as described above is used as the detection capacitor C1 of the insulation state detection device 10, the charge charge, that is, the measured value of the voltage changes due to the influence of the temperature. It becomes a factor of resistance measurement error.

  Therefore, the insulation state detection apparatus 10 controls temperature compensation as shown in FIG. That is, when the capacitance decreases due to a temperature rise, the charging time of the detection capacitor C1 is changed to be shorter than usual, and when the capacitance increases due to a temperature drop, the charging time of the detection capacitor C1. The length of is changed to be longer than usual.

  By such control, even when a ceramic capacitor having the characteristics shown in FIG. 5 is used as the detection capacitor C1, a state close to the ideal characteristic F0 can be obtained as in the characteristic F1 shown in FIG. That is, the influence of temperature can be compensated by changing the length of the charging time according to the temperature. Further, by performing another compensation according to the difference in the DC bias voltage of the detection capacitor C1, it is possible to obtain a state closer to the ideal characteristic F0 than the characteristic F1 shown in FIG.

<Description of Constant Table Used for Temperature Compensation of Detection Capacitor C1>
FIG. 4 shows a configuration example of the constant table TB1 that holds a compensation value corresponding to the temperature. The constant table TB1 shown in FIG. 4 holds constants of the length of charging time associated with each of a plurality of temperature ranges.

  In the example shown in FIG. 4, the lowest temperature range (−A ° C. or lower),..., 0 to 10 [° C.], 10 to 20 [° C.], 20 to 30 [° C.], 30 to 40 [° C.] , 40 to 50 [° C.],..., Constants for the length of the charging time associated with the highest temperature range (+ B ° C. or higher) are held in the constant table TB1.

  The constant of the charging time length associated with each temperature range is determined as a result of multiplying the reference value (t1 [sec]) by a predetermined coefficient. For example, the constant in the temperature range of 0-10 [° C.] is 1.2 times the reference value (t1), and the constant in the temperature range of 30-40 [° C.] is 0.9 times the reference value (t1). is there.

  That is, the temperature range of 20-30 [° C.] is set as a reference state, the charging time is changed longer than the reference (t1) at a temperature lower than this range, and the charging time is changed shorter than the reference at a higher temperature. It means that.

  In the insulation state detection device 10 shown in FIG. 1, the constant table TB1 having the configuration shown in FIG. 4 is held in advance in an internal memory (ROM or nonvolatile memory) of the microcomputer 11. Therefore, the microcomputer 11 can easily obtain the optimum value of the charging time length necessary for temperature compensation using the constant table TB1.

<Measurement of power supply voltage (high voltage)>
The insulation state detection device 10 shown in FIG. 1 can measure not only the ground fault resistance but also the voltage of the power supply applied between the positive power supply line 111, the negative power supply line 112, and the ground electrode 103. .

  That is, basically, the charging voltage V0 in the case of measuring the ground fault resistance can be handled as a voltage corresponding to the output voltage of the in-vehicle DC high-voltage power supply 50. That is, if the contact of the switching elements S1 and S2 is closed and the detection capacitor C1 is completely charged, the charging voltage V0 between the terminals of the detection capacitor C1 matches the output voltage of the in-vehicle DC high-voltage power supply 50.

  However, it takes time to fully charge the detection capacitor C1. That is, the voltage between the terminals of the detection capacitor C1 is represented by a voltage | Vc | shown in FIG. 3 according to an exponential function from the relationship between the resistances of the resistors R1 and R2 and the capacitance of the detection capacitor C1. Gradually rises to saturation and becomes constant when fully charged.

  If the detection capacitor C1 is fully charged, it is easy to accurately measure the output voltage of the in-vehicle DC high-voltage power supply 50 using the insulation state detection device 10. However, in a situation where the original high-voltage measuring device provided on the vehicle side has failed, there is a high possibility that it is desirable to repeatedly measure the voltage in a short time period.

  However, in order to repeatedly measure the power supply voltage in a short time period, the measurement must be performed before the detection capacitor C1 is fully charged. That is, it is necessary to measure this voltage while the voltage gradually rises like the voltage | Vc | shown in FIG. 3, and to estimate the power supply voltage based on this measured value.

  Further, when a ceramic capacitor is used as the detection capacitor C1, the rising curve of the voltage | Vc | shown in FIG. 3 varies with the change in the characteristics of the detection capacitor C1. Therefore, it is not easy to estimate the accurate power supply voltage from the measured value of the voltage across the terminals of the detection capacitor C1.

  Therefore, even when the insulation state detection device 10 measures the output voltage of the in-vehicle DC high voltage power supply 50 in the backup mode, the temperature of the detection capacitor C1 is detected, and the charging time of the detection capacitor C1 is determined according to the detected temperature. Adjust the length automatically. That is, the charging time length necessary for temperature compensation is determined using a table equivalent to the constant table TB1 described above.

  Further, when the insulation state detection device 10 estimates the output voltage of the in-vehicle DC high-voltage power supply 50 from the measured value of the charging voltage of the detection capacitor C1, the calculation is performed using a predetermined conversion coefficient. In order to obtain the optimum conversion coefficient, the insulation state detection apparatus 10 uses a voltage conversion constant table TB2 as shown in FIG. This voltage conversion constant table TB2 is held in advance on the internal memory (ROM or nonvolatile memory) of the microcomputer 11.

  In the voltage conversion constant table TB2 shown in FIG. 7, conversion coefficients (converted values) associated with the respective ranges of the voltage measurement values of the detection capacitor C1 are held. This conversion coefficient includes a charging rate (a ratio to a fully charged state) of the detection capacitor C1 at the time of measurement, and a compensation value for characteristic change according to the DC bias voltage.

  That is, the voltage measurement value of the detection capacitor C1 is “a or less”,..., “Within the range of b to c”, “within the range of c to d”, “within the range of d to e”, “e or more "Is stored in the voltage conversion constant table TB2. For example, the conversion coefficient when the voltage measurement value of the detection capacitor C1 is “within the range of b to c” is “B”, and the conversion coefficient when the voltage measurement value is within the range of “c to d” is “C”. It is.

  Therefore, the microcomputer 11 can easily obtain from the voltage conversion constant table TB2 the optimum conversion factor corresponding to the charging rate (ratio to the fully charged state) of the detection capacitor C1 during measurement and the DC bias voltage. That is, the insulation state detection device 10 can estimate the output voltage of the in-vehicle DC high-voltage power supply 50 with high accuracy without setting the detection capacitor C1 to a fully charged state, and can shorten the measurement time period. .

<Control Operation in Insulation State Detection Device 10>
<Processing contents of microcomputer 11>
FIG. 2 shows the main control contents of the insulation state detection apparatus 10 shown in FIG. That is, the microcomputer 11 executes the process of FIG. A specific example of the operation timing of the insulation state detection device shown in FIG. 1 is shown in FIG.

The contents of the control shown in FIG. 2 will be described below.
When the power source of the insulation state detection apparatus 10 is turned on, the microcomputer 11 performs a predetermined initialization in step S11 and then proceeds to the process of S12.

  In step S12, the microcomputer 11 inputs the analog level of the signal output from the thermistor 25 from the analog input port AD2 via the wiring 37 and converts it into digital information. Thereby, the temperature information in the vicinity of the detection capacitor C1 can be grasped.

  In step S13, the microcomputer 11 obtains the correction coefficient for the charging time of the detection capacitor C1 according to the temperature measurement value from the constant table TB1 shown in FIG. 4, and determines the charging time. For example, when the temperature is 35 [° C.], a value of (0.9) is acquired as a correction coefficient from the constant table TB1, and the charging time is determined as (t1 × 0.9).

  In step S14, the microcomputer 11 identifies ON / OFF of the operation switch SWx with reference to the state of the input port to which the operation switch SWx is connected. That is, the normal measurement mode / backup mode is distinguished by the state of the operation switch SWx. In the case of the normal measurement mode, the process proceeds to S15, and in the backup mode, the process proceeds to S21.

  In step S15, the microcomputer 11 executes the schedule of the basic measurement cycle, and acquires the measured values of V0, Vc1n, and Vc1p. That is, the switching elements S1 to S4 are controlled as shown in FIG. 8, and the “control section” “V0 measurement section”, “Vc1n measurement section”, “V0 measurement section”, “ In the “Vc1p measurement section”, the measurement values of V0, Vc1n, and Vc1p are acquired.

  In this case, the absolute value of the voltage appearing between the terminals of the detection capacitor C1 has a waveform such as | Vc | shown in FIG. The charging time length Tc from the start of charging of the detection capacitor C1 in each section to the timing of measuring the voltage corresponds to the charging time determined in step S13. Therefore, the timing for actually measuring each voltage (V0, Vc1n, Vc1p) is automatically adjusted according to the temperature of the detection capacitor C1.

  In step S16, the microcomputer 11 acquires voltage compensation values corresponding to the measured voltages (V0, Vc1n, Vc1p) from the “voltage compensation value table” in order to compensate for the influence of the DC bias voltage of the detection capacitor C1. To do. Although this “voltage compensation value table” is not shown, it holds a list of compensation values for bringing the characteristic F1 shown in FIG. 6 closer to the ideal characteristic F0, and is prepared on the internal memory of the microcomputer 11. .

  In step S17, the microcomputer 11 calculates the resistance value RL of the ground fault resistance based on each voltage (V0, Vc1n, Vc1p) acquired in S15 and the voltage compensation value acquired in S16.

  In step S18, the microcomputer 11 compares the resistance value RL of the ground fault resistance acquired in S17 with a predetermined ground fault resistance alarm value (lower limit value) RLref. If the condition “RL <RLref” is satisfied, the process proceeds to S19. If the condition is not satisfied, the process proceeds to S20.

  In step S <b> 19, the microcomputer 11 outputs a ground fault resistance alarm to the output terminal 21 because the resistance value RL of the ground fault resistance detected by the insulation state detection device 10 is less than the ground fault resistance alarm value RLref.

  In step S20, the microcomputer 11 outputs information representing the resistance value RL of the ground fault resistance acquired in S17 to the output terminal 21.

  In step S <b> 21, the microcomputer 11 executes the schedule of “measurement cycle for high voltage measurement”, and acquires the measured values of V0, Vc1n, and Vc1p at each time point. In the “measurement cycle for high voltage measurement”, the V0 measurement cycle is shortened as in the “control section” of the backup mode shown in FIG.

  That is, since control is performed so that measurement is repeated a plurality of times within one “V0 measurement section”, in each measurement process, from the start of charging of the detection capacitor C1 to the timing of voltage measurement. The charging time length Tc2 is much shorter than the charging time length Tc in the normal measurement mode. Similarly to the charging time length Tc, the charging time length Tc2 is automatically adjusted according to the temperature of the detection capacitor C1 based on the constant table TB1. Therefore, errors due to temperature fluctuations can be reduced.

  In step S22, the microcomputer 11 obtains a voltage conversion coefficient for converting the measured charging voltage V0 into an estimated value of the power supply voltage (high voltage) from the voltage conversion constant table TB2. That is, when the measured charging voltage V0 is converted into the estimated power supply voltage, the charging rate at the time of measurement of the detection capacitor C1 and the influence of the DC bias voltage are taken into consideration, so that the cycle of the short charging time length Tc2 is achieved. Even when the measurement of the charging voltage V0 is repeated, an accurate power supply voltage (high voltage) can be estimated.

  In step S23, the microcomputer 11 determines the power supply voltage (high voltage) and the resistance of the ground fault resistance based on the voltage (V0, Vc1n, Vc1p) of each measurement value acquired in S21 and the voltage conversion coefficient acquired in S22. A value RL is calculated.

  In the backup mode, the charging time length Tc2 of the “V0 measurement section” is shorter than the charging time length Tc of the “Vc1n measurement section” and “Vc1p measurement section”. Can not handle. However, by converting using the voltage conversion coefficient of the voltage conversion constant table TB2, the resistance value RL of the ground fault resistance can be calculated based on the measured values of V0, Vc1n, and Vc1p as in the normal measurement mode. it can.

  In step S24, the microcomputer 11 compares the resistance value RL of the ground fault resistance acquired in S23 with a predetermined ground fault resistance alarm value (lower limit value) RLref. If the condition “RL <RLref” is satisfied, the process proceeds to S25. If the condition is not satisfied, the process proceeds to S26.

  In step S <b> 25, the microcomputer 11 outputs a ground fault resistance alarm to the output terminal 21 because the resistance value RL of the ground fault resistance detected by the insulation state detection device 10 is less than the ground fault resistance alarm value RLref.

In step S <b> 26, the microcomputer 11 outputs information representing the power supply voltage (high voltage) and the resistance value RL of the ground fault resistance obtained at S <b> 23 to the output terminal 21.
Although not shown in FIG. 2, steps S12 and S13 can be executed again every time a predetermined time elapses while steps SS14 to S26 are being executed. Thereby, the influence of the temperature change with time can also be compensated.

By performing the control as shown in FIG. 2, the following advantages can be obtained.
(1) Even when a ceramic capacitor is employed as the detection capacitor C1, improvement in detection accuracy of the ground fault resistance can be expected.

(2) By performing appropriate correction, not only the relative value but also the detection accuracy as an absolute value can be improved. Therefore, not only the ground fault resistance but also the power supply voltage (high voltage) can be detected with high accuracy.

(3) Since the charging time length (Tc, Tc2) of the detection capacitor C1 is automatically adjusted, correction can be made to increase the amount of charge under the condition that the charged charge is reduced. Thereby, measurement in a lower voltage region and a higher resistance region becomes possible. The noise margin can be improved by raising the threshold value for failure determination. Moreover, it can correct | amend so that the amount of electric charges may be reduced on the conditions in which charging charge is large. As a result, the voltage dividing ratio of the voltage dividing circuit constituted by the resistors R3, R4, and R5 can be increased, and the dynamic range of the A / D conversion input can be utilized more effectively.

  In addition, about the detailed circuit structure of the insulation state detection apparatus 10 shown in FIG. 1, various deformation | transformation can be considered as disclosed by patent document 3, for example. What is necessary is just to change about a detailed circuit structure as needed.

<Supplementary explanation>
(1) The insulation state detection device (10) shown in FIG. 1 is connected to the positive power supply line (111) and the negative power supply line (112) of a predetermined high-voltage DC power supply (50), respectively. A terminal (13), a negative-side input terminal (14), and a ground electrode (15), and the positive-side power line, the negative-side power line, and the ground electrode based on the charging voltage of the flying capacitor (C1); The insulation state (RLn, RLp) between the two is grasped. Moreover, it has the temperature detection part (25) which detects the temperature in the vicinity of the said flying capacitor. In addition, as shown in FIG. 2, the positive-side power line and the negative-side power line based on a measured value related to the charging voltage of the flying capacitor and a charging voltage measuring unit (S15) that measures the charging voltage of the flying capacitor A ground fault resistance value calculation unit (S17) for calculating an insulation resistance value between the grounding electrode and a temperature parameter detected by the temperature detection unit, and a control timing related to measurement of a charging voltage of the flying capacitor. And a measurement timing control unit (S13) that reflects the change.

  (2) Further, the measurement timing control unit (S13) reflects the temperature parameter on the difference in the length of time (Tc in FIG. 3) for charging the flying capacitor.

  (3) The measurement timing control unit has a constant table (TB1) that holds each of the plurality of temperature ranges in association with information on a coefficient corresponding to a length of time for charging the flying capacitor. Then, based on the temperature detected by the temperature detector, the length of time for charging the flying capacitor (Tc in FIG. 3) is automatically corrected using the constant table.

  (4) Further, as shown in FIG. 2, a power supply voltage detection unit that detects a power supply voltage that appears between the positive electrode side power supply line or the negative electrode side power supply line and the ground electrode using the charging voltage measurement unit ( S21, S23) are further provided. The power supply voltage detection unit measures the voltage after charging the flying capacitor in a power supply voltage measurement cycle (Tc2 in FIG. 3) shorter than the required charging time required for complete charging of the flying capacitor, and from the measured value The estimated value of the power supply voltage is grasped, and the temperature parameter detected by the temperature detection unit is used for correcting the estimated value.

  (5) In addition, the power supply voltage detection unit sets the temperature parameter detected by the temperature detection unit to the difference in the length of time (Tc2 in FIG. 3) for charging the flying capacitor within the power supply voltage measurement cycle. reflect.

  (6) In addition, the power supply voltage detection unit stores information on a plurality of conversion factors for converting a measured voltage value into the estimated value in association with each of a plurality of ranges of the measured voltage value. Having the constant table (TB2), the estimated value is calculated based on one conversion coefficient acquired from the voltage conversion constant table (S23).

DESCRIPTION OF SYMBOLS 10 Insulation state detection apparatus 11 Microcomputer 13 Positive electrode side input terminal 14 Negative electrode side input terminal 15 Ground electrode 20 Input circuit 21 Output terminal 25 Thermistor 31-37 Wiring 50 In-vehicle DC high voltage power supply 101, 102 Y capacitor 103 Ground electrode 111 Positive electrode side power supply Line 112 Negative power supply line C1 Capacitor for detection (flying capacitor)
D1, D2, D3 Diode R1, R2, R3, R4, R5 Resistor RLp, RLn Ground fault resistance S1, S2, S3, S4 Switching element SWx Operation switch TB1 Constant table TB2 Voltage conversion constant table

Claims (4)

A positive-side input terminal and a negative-side input terminal connected to a positive-side power line and a negative-side power line of a predetermined high-voltage DC power output, respectively, and a ground electrode, and the positive-side based on the charging voltage of the flying capacitor An insulation state detection device for grasping an insulation state between a power line and a negative side power line and the ground electrode,
A temperature detector for detecting a temperature in the vicinity of the flying capacitor;
A charging voltage measuring unit for measuring a charging voltage of the flying capacitor;
Based on a measurement value related to a charging voltage of the flying capacitor, a ground fault resistance value calculating unit that calculates an insulation resistance value between the positive power line and the negative power line and the ground electrode;
With
The said charge voltage measurement part changes the length of time which charges the said flying capacitor according to the temperature which the said temperature detection part detected. The insulation state detection apparatus characterized by the above-mentioned. The charging voltage measuring unit has a constant table that holds each of a plurality of temperature ranges in association with information on a coefficient corresponding to a length of time for charging the flying capacitor, and the temperature detecting unit detects The insulation state detection device according to claim 1, wherein a length of time for charging the flying capacitor is determined using the constant table based on the measured temperature. Using the charging voltage measurement unit, further comprising a power supply voltage detection unit for detecting a power supply voltage appearing between the positive electrode side power line or the negative electrode side power line and the ground electrode,
The power supply voltage detection unit measures a voltage after charging the flying capacitor at a power supply voltage measurement cycle shorter than a required charging time required for fully charging the flying capacitor, and calculates an estimated value of the power supply voltage from the measured value. Calculate
2. The insulation according to claim 1, wherein the power supply voltage detection unit changes a length of time for charging the flying capacitor within a power supply voltage measurement cycle in accordance with the temperature detected by the temperature detection unit. State detection device. The power supply voltage detection unit has a voltage conversion constant table that holds information on a plurality of conversion coefficients for converting a voltage measurement value into the estimated value in association with each of a plurality of ranges of voltage measurement values. The insulation state detection device according to claim 3, wherein the estimated value is calculated based on one conversion coefficient acquired from the voltage conversion constant table.

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