JP6518430B2 - Insulation status detection device - Google Patents

Description

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

  For example, in vehicles such as electric vehicles that use electric power as propulsion energy, 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, the vehicle 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 power supply line of the negative electrode of the power supply that outputs high voltage.

  In such a vehicle, it is necessary to detect and confirm that the wiring between the high voltage DC power output and the vehicle body is sufficiently electrically insulated in order to ensure safety and the like. The prior art of the insulation state detection apparatus used when performing such a detection is disclosed by patent document 1, patent document 2, and patent document 3, for example.

  This kind of insulation state detection device uses a flying capacitor. That is, a detection capacitor (referred to as a flying capacitor) is connected for a fixed time between the high voltage positive and negative power supply lines and the ground line (vehicle body) via the switching elements. The charging voltage of the flying capacitor is monitored, and from this charging voltage, the ground resistance, that is, the insulation resistance between the power supply line and the ground line is calculated.

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

  By the way, the noise generated from various devices and the noise invaded from the outside propagate to other devices via the power supply line and cause various malfunctions. Therefore, for example, also in the case of a high voltage power supply for vehicles, it is necessary to use a line bypass capacitor connected between each electrode of the power supply and the ground line in order to reduce common mode noise. In addition, stray capacitance exists between the power supply line and the ground line. They are collectively referred to as Y capacitors.

  However, in the case of using the above-described insulation state detection device, when the flying capacitor is charged, the flying capacitor and the Y capacitor are connected in parallel. Therefore, at the same time charge flows into the flying capacitor from the high voltage power supply of the vehicle via the ground resistance, the charge stored in the Y capacitor also flows into the flying capacitor due to the potential difference. Therefore, the influence of the Y capacitor appears on the charging voltage of the flying capacitor.

  Also, there are actually Y capacitors on the positive side and Y capacitors on the negative side, and the potential at these connection points is normally stable in a balanced state, but the balance is achieved by the flow of charge from one Y capacitor. Crumble. Even if the balance of the potentials of these two Y capacitors is broken due to charge outflow, after measurement of the positive side ground fault resistance measurement voltage VC1p and the negative side ground fault resistance measurement voltage VC1n, the ground of the power supply charging voltage V0 is measured. Since charge flows from the high voltage power supply to the low voltage side Y capacitor via the junction resistor, the potentials of the two Y capacitors naturally return to a balanced state after a certain amount of time has elapsed. Further, when the potentials of the two Y capacitors are stable in a balanced state, the influence of the Y capacitor on the charging voltage of the flying capacitor can be calculated in advance, so that the ground resistance can be determined by correction.

  However, in order to reduce the time required to measure the ground resistance, it is necessary to shorten the cycle from the charging of the flying capacitor to the next measurement. In this case, the next measurement is performed in a state in which the potentials of the two Y capacitors are not balanced, but it is unclear to what extent the balance is broken. There is a problem that it does not fall. In other words, if the measurement cycle is short, as described above, the capacitance of the Y capacitor is large (for example, about 0.5 [μF]), and at the start of the next measurement of the ground resistance, two Y capacitors Of the initial charge transfer from the Y capacitor to the flying capacitor, which is generated to return to the balanced state, is superimposed on the charge transfer from the high voltage power supply to the flying capacitor. Become.

  Then, the higher the ground fault resistance, the longer it takes for the Y capacitor to balance, so when the Y capacitor's capacitance is large and the measurement cycle is short, the higher the ground fault resistance, the initial state. The degree of unbalance of the Y capacitor in the above becomes large, the amount of movement of initial charge from the Y capacitor to the flying capacitor increases, and the charging voltage of the flying capacitor is greatly increased.

By the way, measurement of ground fault resistance is performed using that the charging voltage of a flying capacitor becomes high, so that ground fault resistance is low. On the other hand, when the capacitance of the Y capacitor is large and the measurement cycle is short, as described above, the higher the ground fault resistance, the greater the degree of unbalance of the Y capacitor and the charging of the flying capacitor. The voltage rises more. Therefore, when the capacitance of the Y capacitor is large, if the measurement cycle is shortened, even if the charging voltage of the flying capacitor is measured, whether the voltage is due to the ground resistance or the Y capacitor is not It can not be distinguished whether it is due to balance, and it becomes difficult to correctly determine the value of the ground fault resistance.
Therefore, in the conventional insulation state detection device, when the capacitance of the Y capacitor is large, if the measurement cycle is shortened, the value of the ground fault resistance can not be correctly measured, and it is difficult to accurately detect the reduction in the ground fault resistance There was a problem that it was.

  The present invention has been made in view of the above situation, and it is desirable to extend the time required for measurement even in the situation where the charging voltage of the flying capacitor is greatly affected by the charge of the Y capacitor connected to the high voltage power supply. It is an object of the present invention to provide an insulation state detection device capable of correctly measuring the ground fault resistance.

The above object of the present invention is achieved by the following constitution.
(1) A positive side input terminal and a negative side input terminal respectively connected to a positive side power line and a negative side power line of a predetermined high voltage DC power output, between the positive side power line and the ground, and the negative side power A Y capacitor connected between the line and the ground, and based on the charging voltage of the flying capacitor, grasps the insulation state between the positive side power line and the negative side power line and the ground as a ground fault resistance Insulation state detection device,
The flying capacitors at a first time and a second time different in timing within one charging section when charging the flying capacitors via a predetermined conduction path affected by the ground resistance, respectively. A charge voltage measurement unit that measures the charge voltage of the
A ground fault resistance value calculation unit that calculates the value of the ground fault resistance based on the voltage measurement value at the first time measured by the charge voltage measurement unit and the voltage measurement value at the second time;
And the like.

(2) The insulation state detection device according to (1), wherein
The ground fault resistance value calculation unit is configured to associate a plurality of constant data in a state in which the ratio of the voltage measurement value at the first time and the voltage measurement value at the second time is associated with the resistance value of the ground fault resistance. Ground resistance map, which holds
And the like.

(3) The insulation state detection device according to (1) or (2), wherein
The ground fault resistance value calculation unit calculates the value of the ground fault resistance based on the voltage measurement value at the first time measured by the charge voltage measurement unit and the voltage measurement value at the second time. Measurement mode,
The charge voltage measurement unit measures the charge voltage of the flying capacitor at a third time in the single charge section, and the ground fault resistance calculation unit measures the third measured by the charge voltage measurement unit. A normal measurement mode in which the value of the ground fault resistance is calculated based on a voltage measurement value of time;
It is characterized by having.

(4) The insulation state detection device according to (1), wherein
The charge voltage measurement unit measures, as a negative measurement value, a voltage of the flying capacitor when charging the flying capacitor in a conduction path affected by a ground fault resistance between the negative electrode side power supply line and the ground electrode. And measuring the voltage of the flying capacitor at the time of charging the flying capacitor in the conduction path affected by the ground fault resistance between the positive electrode side power supply line and the ground electrode as a positive side measurement value,
When the difference between the negative side measurement value and the positive side measurement value is greater than or equal to a predetermined value, the ground fault resistance value calculation unit calculates only the smaller one of the negative side measurement value and the positive side measurement value. Then, correction is applied using a predetermined constant, and the value of the ground fault resistance is calculated based on the negative measurement value and the positive measurement value after correction.
It is characterized by

(5) The insulation state detection device according to (1), wherein
In a situation where the first time is earlier than the second time, the voltage measurement value of the first time is determined in advance immediately after the charge voltage measurement unit measures the voltage measurement value of the first time. A measurement control unit for reducing the maximum value of the charging voltage by shortening the time length of at least the charging section more than usual when the voltage measurement value at the first time exceeds the upper limit value in comparison with the upper limit value;
And the like.

  According to the insulation state detection device of the present invention, even in the situation where the charging voltage of the flying capacitor is greatly affected by the charge of the Y capacitor connected to the high voltage power source, the ground resistance can be increased without increasing the measurement required time. The correct measurement of

  The present invention has been briefly described above. Further, the details of the present invention will be further clarified by reading the modes for carrying out the invention described below with reference to the attached drawings.

FIG. 1 is a time chart showing the operation of a basic measurement cycle including the features of the present invention. FIG. 2 is an electric circuit diagram showing a configuration example of the insulation state detection device of the embodiment and its peripheral circuit. 3 (A) and 3 (B) show the operation of the basic measurement cycle not including the feature of the present invention, and FIG. 3 (A) is a state transition diagram showing operation state transition, and FIG. It is a wave form diagram showing change of voltage between terminals of a flying capacitor. FIG. 4 is an electric circuit diagram showing a state in which a part of the circuit shown in FIG. 2 is extracted, and showing a charge state at the time of V0 measurement operation. FIG. 5 is an electric circuit diagram showing a state in which a part of the circuit shown in FIG. 2 is extracted, and showing a state at the time of charge voltage measurement. FIG. 6 is an electric circuit diagram showing a state in which a part of the circuit shown in FIG. 2 is extracted, and showing a charging state at the time of VC1n measurement operation. FIG. 7 is an electric circuit diagram showing a state in which a part of the circuit shown in FIG. 2 is extracted, and showing a charging state at the time of VC1p measurement operation. 8A and 8B show a state in which a part of the circuit shown in FIG. 2 is extracted, and FIG. 8A shows the charge of the Y capacitor Yp at the time of charging for VC1n measurement. FIG. 8 (B) is an equivalent circuit diagram showing the influence of the ground fault resistance RLn at the time of charging for measuring VC1n. FIG. 9 is a waveform chart showing a specific example of the variation of the voltage across terminals of C1 and the balance potential of Yp and Yn. FIG. 10 is a waveform diagram showing a specific example of the charge / discharge voltage of the detection capacitor C1 in the case of measuring VC1n or VC1p under two types of conditions in which the resistance value of the ground resistance is different. FIG. 11 is a waveform diagram showing a change in the maximum value of the charging voltage when the length of the charging time is shortened. FIG. 12A and FIG. 12B are flowcharts showing the characteristic operation (2) and the modification thereof in the embodiment of the present invention.

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

<Overview of Overall Configuration and Operation>
The structure of the insulation state detection apparatus 10 mounted in the vehicle and its periphery circuit is shown in FIG.

  The insulation state detection apparatus 10 shown in FIG. 2 can be used by being mounted on a vehicle such as an electric car or a hybrid car having an engine and an electric motor as a drive source. The on-vehicle DC high voltage power supply 50 outputs DC power of high voltage of about 200 V, for example. The electric motor M that generates the propulsive force of the vehicle can be driven by the electric power output from the on-vehicle DC high voltage power supply 50.

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

  Further, to reduce common mode noise, as shown in FIG. 2, a Y capacitor Yp is connected between the positive power supply line 111 and the ground line 103, and between the negative power supply line 112 and the ground line 103. Y capacitor Yn is connected to. The Y capacitors Yp and Yn also include stray capacitances.

  By mounting the insulation state detection device 10 shown in FIG. 2 on a vehicle, it is possible to monitor the insulation state of the vehicle as needed. 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 on-vehicle DC high voltage power supply 50 and to grasp the insulation state.

  Therefore, as shown in FIG. 2, the positive electrode side input terminal 13 and the negative electrode side input terminal 14 of the insulation state detection device 10 are connected to the positive electrode side power supply line 111 and the negative electrode side power supply line 112, respectively. The ground point 15 of the insulation state detection device 10 is connected to the ground line 103.

  An output terminal 21 is provided as shown in FIG. 2 in order to output the measurement result of the insulation state detection device 10 and information of the alarm. The output terminal 21 can be connected to, for example, an electronic control unit (ECU) on the vehicle side.

<Configuration Example of Insulated State Detection Device 10>
As shown in FIG. 2, 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 adopted as the detection capacitor C1 in consideration of being for vehicle use.

  In addition, four switching elements S1 to S4 are provided in the periphery to control charging and discharging of the detection capacitor C1. Each of the switching elements S1 to S4 is a switch that can switch the open / close (off / on) state of the contact by controlling the isolated signal, for example, like an optical MOSFET.

  One end of the switching element S1 is connected to the positive electrode side input terminal 13 via the resistor R01, and the other end is connected to the wiring 31. One end of the switching element S2 is connected to the negative electrode side input terminal 14 via the resistor R02, and the other end is connected to the wiring 32 via the resistor R2.

  One end of the switching element S3 is connected to the wiring 33, and the other end is connected to the wiring 35. One end of the switching element S4 is connected to the wiring 32, and the other end is connected to the ground point 15 via the resistor R4.

  The negative terminal of the detection capacitor C 1 is connected to the wiring 32. The positive terminal of the detection capacitor C1 is connected to the wiring 31 via 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 through a series circuit including a diode D3 and a resistor R3, and is further connected to the wiring 33 through the diode D2. The diode D2 is connected in such a polarity as to permit conduction in the direction from the wiring 33 toward the wiring 34, and the diode D3 is connected in such a polarity as to permit conduction in the direction from the wiring 34 toward the wiring 33.

  The microcomputer (CPU) 11 executes various controls necessary for the insulation state detection apparatus 10 by executing a program incorporated in advance. Specifically, the microcomputer 11 individually controls the switching elements S1 to S4 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 through the wiring 36, performs calculation based on this input level, and performs ground fault resistance RLp and Understand RLn.

  The input circuit 20 is connected between the wire 35 and the wire 36. The input circuit 20 performs signal processing for converting a signal appearing on the wiring 35 into a signal suitable for processing by the microcomputer 11. Although various functions and configurations can be considered for the input circuit 20, a sample and hold circuit is assumed as the representative 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 point 15. When the microcomputer 11 temporarily turns on the analog switch at a specific timing (conductive state), 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.

<Measurement of ground fault resistance>
<Description of basic measurement cycle>
Changes in the operating state transition and the voltage between the terminals of the flying capacitor are shown in FIGS. 3 (A) and 3 (B). In order to facilitate the understanding of the basic operation, the description of the characteristic operation of the present invention is omitted in FIGS. 3 (A) and 3 (B).

  As shown in FIG. 3A, the basic measurement cycle of the insulation state detection apparatus 10 is “V0 measurement section” A1, “VC1n measurement section” A2, “V0 measurement section” A3, and “VC1p measurement section” A4. The basic measurement cycle is repeatedly executed.

  In "V0 measurement section" A1 and A3, charge voltage V0 which changes according to power supply voltage is measured. The charge voltage V0 is independent of the resistance value of the ground fault resistance.

  In the “VC1 n measurement section” A2, the charging voltage VC1 n that changes under the influence of the resistance value of the ground fault resistor RL n on the negative electrode side is measured. Further, in the “VC1p measurement section” A4, the charging voltage VC1p that changes under the influence of the resistance value of the ground fault resistor RLp on the positive electrode side is measured.

  In each of the sections A1, A2, A3 and A4, the “charging operation” for charging the detection capacitor (flying capacitor) C1 and the voltage between the terminals of the detection capacitor C1 are measured. The “measurement operation” and the “discharge operation” for discharging the charge accumulated in the detection capacitor C1 are included.

  The voltage across the terminals of the detection capacitor C1 rises according to an exponential function (exp) curve determined by the time constant of the charge circuit when charging starts in each section as shown in FIG. It descends according to an exponential curve determined by the time constant of the circuit. When the basic measurement cycle of FIG. 3A is performed, charging and discharging of the detection capacitor C1 are repeated, so that the voltage of the detection capacitor C1 changes as shown in FIG. 3B.

  In the “V0 measurement section” A1 and A3, the voltage when the charging of the detection capacitor C1 is finished is measured as V0.

  Further, in the “VC1 n measurement period” A2, the voltage before the charging of the detection capacitor C1 is completed and the discharge is started is measured as VC1 n. In the “VC1p measurement section” A4, the charging of the detection capacitor C1 is completed, and the voltage before shifting to the discharge is measured as VC1p.

  In practice, the microcomputer 11 shown in FIG. 2 can control the on / off of the switching elements S1 to S4 to execute the operation of the basic measurement cycle shown in FIG. 3 (A). And ground fault resistance can be computed based on V0, Vc1n, and Vc1p of a measured value obtained as a result of this basic measurement cycle.

<Description of the state of each section>
<State of charge of “V0 measurement section” A1, A3>
A part of the circuit shown in FIG. 2 is extracted, and a portion related to the charging state of “V0 measurement section” A1, A3 is shown in FIG.

  In the charging state of the “V0 measurement section” A1, A3, the switching elements S1 and S2 are turned on (contacts are closed), and the other switching elements are turned off (contacts are opened). Therefore, a conduction path as shown in FIG. 4 is formed, and current flows as indicated by arrows in FIG.

  That is, since the contact point of the switching element S1 is closed, the positive electrode side power supply line 111 passes through the positive electrode side input terminal 13, the switching element S1, the wiring 31, the diode D1, and the resistor R1 to the positive terminal of the detection capacitor C1. A current flows. Further, since the contact point of the switching element S2 is closed, 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 supply line 112. Accordingly, the detection capacitor C1 is charged by this current. The charging voltage of the detection capacitor C1 at this time is determined according to the output voltage of the in-vehicle DC high voltage power supply 50, the time constant of the charging circuit, and the charging time, but is not affected by the ground resistors RLn and RLp.

<State at the time of charge voltage measurement>
A part of the circuit shown in FIG. 2 is extracted, and a portion related to the state at the time of charge voltage measurement is shown in FIG.

  At the time of charge voltage measurement in each of the sections A1 to A4, the contacts of the switching elements S3 and S4 are closed, and the other switching elements are turned off (contact open). Therefore, a conduction path as shown in FIG. 5 is formed. That is, as shown in FIG. 5, the negative terminal of the detection capacitor C1 is connected to the ground point 15 via the resistor R4. The positive terminal of the detection capacitor C1 is connected to the analog input port of the microcomputer 11 through the diode D3, the resistor R3, the switching element S3, the wiring 35, the input circuit 20, and the wiring 36. Therefore, the microcomputer 11 can detect an analog level proportional to the charging voltage of the detection capacitor C1.

  Also in the discharging operation of the detection capacitor C1, the same state as in FIG. 5 is obtained except that the input circuit 20 is turned off. That is, the charge on the positive electrode side stored in the detection capacitor C1 passes through the diode D3 and the resistors R3 and R5, and the charge on the negative electrode side naturally discharges over time through the resistor R4.

<Charge status of “VC1n measurement section” A2>
A part of the circuit shown in FIG. 2 is extracted, and a portion related to the charge state of the “VC1n measurement section” A2 is shown in FIG.

  In the charging state of the “VC1 n measurement section” A2, the contacts of the switching elements S1 and S4 are closed, and the other switching elements are turned off (contact open). Therefore, a conduction path as shown in FIG. 6 is formed.

  That is, as indicated by an arrow in FIG. 6, 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. Flows. Further, since the contact point of the switching element S4 is closed, the negative electrode side power supply line passes through the switching element S4, the resistor R4, the grounding point 15, the grounding line 103, and the grounding resistor RLn from the negative terminal of the detection capacitor C1. A current flows in 112. This current charges the detection capacitor C1. The charging voltage at this time reflects the influence of the ground fault resistance RLn.

<Charge status of “VC1p measurement section” A4>
A part of the circuit shown in FIG. 2 is extracted, and a portion related to the charge state of the “VC1p measurement section” A4 is shown in FIG.

  In the charging state of the “VC1p measurement section” A4, the contacts of the switching elements S2 and S3 are closed, and the other switching elements are turned off (contact open). Therefore, a conduction path as shown in FIG. 7 is formed.

  That is, as indicated by an arrow in FIG. 7, the positive side power supply line 111 passes the ground resistance RLp, the ground line 103, the ground point 15, the resistor R5, the switching element S3 and the diode D2 to form the detection capacitor C1. Current flows to the positive terminal. Further, current flows from the negative electrode side terminal of the detection capacitor C1 to the wiring 32, the resistor R2, the switching element S2, the negative electrode side input terminal 14, and the negative electrode side power supply line 112. This current charges the detection capacitor C1. The charging voltage at this time reflects the influence of the ground fault resistance RLp.

<Basic ground resistance measurement operation>
The operation of the insulation state detection device 10 shown in FIG. 2 basically has the following relationship.

(RLp + RLn) / (RLp × RLn) = f [{(Vc1p) + (Vc1n)} / V0] (1)
However,
V0: Charge voltage Vc1n of detection capacitor C1 according to output voltage of vehicle DC high-voltage power supply 50: Charge voltage Vc1p of detection capacitor C1 affected by ground fault resistor RLn on the negative side: ground fault resistor RLp on the positive side Charging voltage RLp and RLn of detection capacitor C1 affected by

  Therefore, the microcomputer 11 grasps each charging voltage "V0", "Vc1 n", "Vc1 p" from the signal level input to the analog input port (AD1) in each state, and the ground fault resistance based on the above relational expression It is possible to calculate RLp and RLn.

<Description of the influence of Y capacitors Yp and Yn>
Y capacitors Yp and Yn are connected between the positive power supply line 111 and the negative power supply line 112 of the output of the on-vehicle DC high voltage power supply 50 shown in FIG. 2 and the ground line 103. Although these Y capacitors Yp and Yn are for reducing common mode noise, they may have a large effect when the insulation state detection device 10 detects an insulation state. Specifically, for example, when the resistance value of the ground resistances RLn and RLp becomes about 1 [MΩ] or more, the change of the measured values “Vc1n” and “Vc1p” which changes under the influence of the ground resistances RLn and RLp is Y Since the situation is difficult to distinguish from the effects of the capacitors Yp and Yn, it is not possible to measure the ground fault resistances RLn and RLp having a large resistance value. In particular, the influence becomes significant when the capacitances of the Y capacitors Yp and Yn are relatively large (for example, 0.5 [μF]).

<Description of charge transfer>
The influence of the Y capacitors Yp and Yn in FIG. 2 will be described with reference to the equivalent circuit diagrams of FIGS. 8 (A) and 8 (B). FIG. 8A shows a movement path of charges of the Y capacitor Yp at the time of charging the detection capacitor C1 for “VC1 n” measurement in the circuit shown in FIG. Further, FIG. 8B shows a path through which a charging current, which changes due to the influence of the ground fault resistance RLn, flows when the detection capacitor C1 for “VC1 n” measurement is charged.

  That is, in the state of charge shown in FIG. 6, as shown in FIG. 8B, the path through which charging current IRLn flows in the path including ground resistor RLn, and as shown in FIG. 8A, the charge of Y capacitor Yp. It can be considered as a combined circuit with the path through which the current Iyp flows.

  In the state shown in FIG. 8A, the voltage between the terminals of the Y capacitor Yp is large at the initial stage of charging start and the voltage between the terminals of the detection capacitor C1 is small. Therefore, the charge stored in the Y capacitor Yp has a low voltage In order to move to the detection capacitor C1, the current Iyp flows. Then, at the same time, as shown in FIG. 8B, the charging current IRLn influenced by the ground fault resistance RLn also flows.

  Therefore, the current for charging the detection capacitor C1 is the result of adding Iyp of FIG. 8 (A) and IRLn of FIG. 8 (B). That is, the measured value "Vc1 n" of the charging voltage of the detection capacitor C1 is influenced not only by the influence of the ground resistor RLn (IRLn) but also by the influence of the Y capacitor Yp (Iyp). When the influence of the Y capacitor Yp is large compared to the influence of the ground fault resistance RLn, it becomes difficult to calculate the ground fault resistance RLn from the measured value.

  Further, although not shown, when “Vc1p” is measured, the charge moves from the Y capacitor Yn to the detection capacitor C1, and the current Iyn flows accordingly. Then, the detection capacitor C1 is charged by a current obtained by adding the charging current IRLp affected by the ground fault resistance RLp and the current Iyn. Therefore, when the influence of the Y capacitor Yn is large compared to the influence of the ground fault resistance RLp, the influence of the Y capacitor Yn included in the measured value “Vc1p” becomes large, and it is difficult to calculate the correct ground fault resistance RLp become.

<Description of voltage balance of Yp, Yn>
In the circuit shown in FIG. 2, since the Y capacitors Yp and Yn have the same electrostatic capacitance, the Y capacitors Yp and Yn are in a balanced state in a steady state before starting measurement. That is, the voltage output from the on-vehicle DC high-voltage power supply 50 is divided in accordance with the ratio of the electrostatic capacitances of Yp and Yn, and the voltage across the Y capacitor Yp and the voltage across the Y capacitor Yn substantially match. It is a state (for example, 100 [V]). Further, the potential of the ground line 103 is stable at a median value of the potential of the positive power supply line 111 and the potential of the negative power supply line 112.

(1) On the other hand, when “VC1n” is measured, the charge of the Y capacitor Yp flows as the current Iyp as in the equivalent circuit shown in FIG. 8A, so that the balance is broken. That is, since the charges of the Y capacitor Yp flow out and the inter-terminal voltage of the Y capacitor Yp decreases, the balance of the voltages of the Y capacitors Yp and Yn is lost, and the potential of the ground line 103 fluctuates.

  When the voltage balance is broken in this way, in the “V0 measurement section” after “VC1n” measurement, the charge that has flowed out of the Y capacitor Yp is recharged again from the on-vehicle DC high voltage power supply 50 via the ground resistor RLn. So you will be back in a balanced state. However, if the capacitor of the Y capacitor is large and the measurement cycle is short, the next measurement will be started before returning to the balanced state.

(2) Further, when “VC1p” is measured, the charge of the Y capacitor Yn flows to the detection capacitor C1 as the current Iyn, and the balance is broken. That is, since the charges of the Y capacitor Yn flow out and the inter-terminal voltage of the Y capacitor Yn decreases, the balance of the voltages of the Y capacitors Yp and Yn is lost, and the potential of the ground line 103 fluctuates. Furthermore, when it is going to measure "VC1p" in the state which remains in the influence of the collapse of the balance which generate | occur | produced when measuring "VC1n", since the voltage between terminals of Y capacitor Yn is larger than usual, The amount of charge flowing to the detection capacitor C1 side further increases.

(3) When executing the second and subsequent basic measurement cycles, try to measure "VC1n" with the influence of balance imbalance occurring when measuring "VC1p" of the previous cycle still remaining. Then, since the voltage across the terminals of the Y capacitor Yp is larger than usual, the amount of charge flowing to the detection capacitor C1 side further increases.

  That is, since the above states (1), (2) and (3) are repeated, the charging current of the detection capacitor C1 increases more than usual due to the influence of the imbalance of the Y capacitors Yp and Yn. And in the measurement value of "VC1n" and "VC1p", it becomes impossible to distinguish the influence of ground fault resistance RLn and RLp, and the influence of Y capacitor Yp and Yn. A specific example of the fluctuation of the balance potential is shown in FIG.

  With regard to the correspondence relationship between the ground fault resistance detection value and the true value when the measurement is performed according to the normal procedure using the insulation state detection device 10 shown in FIG. 2, the relationship between Y capacitors Yp and Yn (Ycon) The simulation was performed while changing the capacitance and the ground condition. As a result, when the electrostatic capacitances of the Y capacitors Yp and Yn were about 0.3 [μF], it was impossible to determine a high resistance value of 1000 [kΩ] or more.

<Description of characteristic operation>
<Measurement operation of ground fault resistance using two-point measurement>
The operation of the basic measurement cycle including the features of the present invention is illustrated in FIG. Similar to the basic measurement cycles shown in FIGS. 3A and 3B, the basic measurement cycle shown in FIG. 1 is “V0 measurement section” A1, “VC1n measurement section” A2, “V0 measurement section” A3, It is comprised by continuation of each measurement area of "VC1p measurement area" A4, and this basic measurement cycle is repeatedly performed.

  In the “VC1n measurement section” A2 of FIG. 1, the first VC1n measurement value (a) is measured when a predetermined time TCna (for example, 0.1 second) elapses from the charging start time t3, and the fixed time is from the charging start time t3. When TCnb (for example, 0.4 seconds) has elapsed, the second VC1 n measurement value (b) is measured.

  In addition, in the “VC1p measurement section” A4 of FIG. 1, the first VC1p measurement value (a) is measured when a predetermined time TCpa (for example, 0.1 second) elapses from the charge start time t8, and from the charge start time t3. The second VC1p measurement value (b) is measured when a predetermined time TCpb (for example, 0.4 seconds) has elapsed.

  Moreover, in the ground fault resistance calculation processing unit 41 that calculates the ground fault resistance, the ratio of the two VC1 n measured values (a) and (b) and the ratio of the two VC1 p measured values (a) and (b) Based on the resistance value of ground fault resistance RLn, RLp is calculated. The V0 measurement may not be used. Further, the ground fault resistance calculation processing unit 41 uses the ground fault resistance map holding unit 42 when calculating the ground fault resistance.

  The ground fault resistance map held by the ground fault resistance map holding unit 42 is configured by a large number of predetermined constant data, and is different from the ratio of the measurement values of two points (a, b) of VC1 n and VC 1 p It hold | maintains in the state which matched one of many ground fault resistance values. That is, the resistance value of the ground resistor RLn can be obtained from the ratio of measured values of two points (a, b) of VC1 n by the ground resistance map, and the ratio of measured values of two points (a, b) of VC1 p The resistance value of the ground fault resistance RLp can be obtained from the ground fault resistance map.

  In the region (for example, 400 [kΩ] or less) in which the resistance value of the ground resistors RLn and RLp is relatively small, the ground resistance is obtained from the measured values of V0, VC1n, and VC1p using the equation (1). You may calculate a value.

<The advantage of two-point measurement>
A specific example of the waveform of the charge / discharge voltage of the detection capacitor C1 in the case of measuring VC1n or VC1p under two types of conditions in which the resistance values of the ground resistors RLn and RLp are different is shown in FIG.

  In the example shown in FIG. 10, it is assumed that the voltage at point a1 or a2 is measured when time ta passes from the start of charging, and the voltage at point b is measured when time tb passes further. As shown in FIG. 10, even if there is no significant change in the charging voltage at point b, the rising speed of the charging voltage waveform fluctuates due to the influence of the time constant including the ground fault resistance. That is, at the points a1 and a2 where the time from the start of charging is short, the influence of the difference in the resistance value of the ground fault resistance appears larger. Therefore, by using the voltages measured at two points (a1 + b or a2 + b) whose timings are different from each other, detection of the ground fault resistance is possible even in a region where the resistance value is large.

  When using the ratio (b / a1, b / a2) of the measured values of two points, the ground resistance value can be calculated without being affected by the applied voltage V0, as described below.

The change in the voltage Vc across the terminals of the detection capacitor C1 from the start of charging in the charging operation is expressed by the following equation.
Vc = V0 (1-exp ^{(-t / C. (R + RL))} ) (2)
V0: Applied voltage C: Capacitance of C1 R: Resistance value of charging circuit RL: Resistance value of ground fault resistance t: Elapsed time from the start of charging

Further, the charging voltage Vc (ta) at the timing of ta and the charging voltage Vc (tb) at the timing of tb are respectively expressed by the following equations.
Vc (ta) = V0 (1-exp ^{(-ta / C. (R + RL))} ) (3)
Vc (tb) = V0 (1-exp ^{(-tb / C. (R + RL))} ) (4)

Therefore, the ratio of two points is expressed by the following equation.
Vc (tb) / Vc (ta) = exp ^{(-tb / C. (R + RL))} / exp ^{(-ta / C. (R + RL))} (5)

  That is, by using Vc (tb) / Vc (ta), the influence of the applied voltage V0 can be eliminated. Further, since the capacitance C of C1 and the resistance value R of the charging circuit are known constant values, the ratio of Vc (tb) / Vc (ta) depends on the charging time t and the ground resistance value RL. Change. Therefore, when the charging times ta and tb are determined in advance, the ratio Vc (tb) / Vc (ta) can be associated with the ground fault resistance value RL.

  A ground fault resistance map representing such a correspondence relationship is held in the ground fault resistance map holding unit 42 shown in FIG. Therefore, in the operation shown in FIG. 1, based on the ratio between the Vc1 n measurement value (a) obtained at time t4 and the Vc1 n measurement value (b) obtained at time t5, the ground resistance calculation processing unit 41 The resistance value of the ground fault resistance RLn can be acquired from the ground fault resistance map. Further, the resistance value of the ground fault resistance RLp can be obtained from the ground fault resistance map based on the ratio of the Vc1p measurement value (a) acquired at time t9 and the Vc1p measurement value (b) acquired at time t10. Also, if the resistance values of the ground resistors RLn and RLp are known, it is possible to estimate the applied voltage on the secondary side of the circuit.

<Reduction process of charge time>
The characteristic operation (2) and its modification in the embodiment of the present invention are shown in FIGS. 12 (A) and 12 (B).

  The charging voltage (Vc1n, Vc1p) at each time point of the detection capacitor C1 largely changes according to the magnitude of the resistance value of the ground resistors RLn and RLp and the elapsed time. For example, when the ground resistance value is very small, the voltage rapidly increases even when the elapsed time from the start of charging is short. Therefore, when selecting the parts of each circuit of the insulation state detection apparatus 10 shown in FIG. 4, assuming the voltage rise of the worst case where the ground fault resistance is very small (for example, 0 [.OMEGA.]), The parts and circuits It is necessary to fully consider the pressure resistance characteristics of each part so that breakage or deterioration of the component does not occur. This inevitably increases the cost of the apparatus.

  On the other hand, in the operation shown in FIG. 1, since the measurement values are acquired at two points whose timings are shifted from each other, it is possible to detect an abnormality at an early time before the charging operation is completed. For example, when the voltage of the measurement value detected at time t4 in the Vc1n measurement section A2 of FIG. 1 is abnormally large, it can be recognized that the ground fault is apparent at that time. However, if the charging operation is continued as it is even after detecting an abnormality at time t4, a very high voltage may be reached at time t5 when charging is completed.

  Each of the operation shown in FIG. 12A and the operation shown in FIG. 12B is for suppressing an abnormally high voltage appearing in the secondary side circuit of the insulation state detection device 10 in the worst case. Help. For example, in the charging voltage Vc of the detection capacitor C1 shown in FIG. 11, the maximum value of the voltage under the worst condition can be lowered from Vmax to Vm2 or Vm3. As a result, it is possible to reduce the pressure resistance required for each component and to suppress the cost of the component.

<Operation of FIG. 12 (A)>
When the Vc1n measurement section A2 shown in FIG. 1 is reached, the process proceeds from step S21 to step S22 in FIG. Then, for example, when Vc1n (a) is acquired at time t4 in FIG. 1, the process proceeds from S22 to S23 immediately after that.

  In step S23, Vc1n (a) acquired in S22 is compared with a predetermined upper limit value Vcmax. The upper limit value Vcmax may be determined based on the estimated voltage when TCna is elapsed from the start of charging under the condition that the ground resistance value is less than the allowable value (for example, 300 [kΩ]). If the condition of "Vc1 n (a)> Vcmax" is satisfied, the ground fault is a certainty, so the process proceeds to the next step S24. If the condition is not satisfied, the process proceeds to step S25.

  In step S24, the charging operation of the section concerned is immediately terminated. Therefore, in this case, the measurement value Vc1 n (b) is not acquired. Further, since it is not possible to calculate the correct ground fault resistance only by the measurement value Vc1 n (a) of one point, an abnormal value is output as the ground fault resistance value.

  Further, when the Vc1p measurement section A4 shown in FIG. 1 is reached, the process proceeds from step S25 to S26 in FIG. Then, for example, when Vc1p (a) is acquired at time t9 in FIG. 1, the process proceeds from S26 to S27 immediately after that.

  In step S27, Vc1p (a) acquired in S26 is compared with a predetermined upper limit value Vcmax. The upper limit value Vcmax may be determined based on the estimated voltage at the time of TCpa, which is the elapsed time from the start of charging under the condition that the ground resistance value is less than the allowable value (for example, 300 kΩ). If the condition of "Vc1p (a)> Vcmax" is satisfied, the ground fault is a certainty, so the process proceeds to the next step S28. If the condition is not satisfied, the process returns to step S21.

  In step S28, the charging operation of the section concerned is immediately terminated. Therefore, in this case, the measurement value Vc1p (b) is not acquired. Further, since it is not possible to calculate the correct ground fault resistance only by the measurement value Vc1p (a) of one point, an abnormal value is output as the ground fault resistance value.

<Operation of FIG. 12 (B)>
The operation shown in FIG. 12B is different from that of FIG. 12A only in steps S24B and S28B. An operation different from that in FIG. 12A in FIG. 12B will be described below.

  In step S24B, the time length TCnb and the charging time length of the section are reduced from those in the normal state, for example, when the normal TCna and TCnb are 0.1 seconds and 0.4 seconds, respectively, the TCnb is 0.1. It will be shortened to 2 seconds and the charging time length will be shortened according to the shortened TCnb. Further, when the timing of the measured value Vc1 n (b) changes, it is necessary to switch the condition (constant) of the calculation formula for calculating the ground fault resistance, so a flag indicating that the TCnb has been shortened is set.

  In step S28B, the time length TCpb and the charging time length of the section are reduced from those in the normal state, for example, when the normal time TCpa and TCpb are 0.1 seconds and 0.4 seconds, respectively, TCpb is set at 0. It is shortened to 2 seconds and the charging time length is shortened according to the shortened TCpb. Further, when the timing of the measured value Vc1p (b) changes, it is necessary to switch the condition (constant) of the calculation formula for calculating the ground fault resistance, so a flag indicating that the TCpb has been shortened is set.

  In addition to the two-point measurement mode described above, the normal measurement mode in which the value of the ground fault resistance is calculated based on the voltage measurement value obtained by measuring only one point (third time) in a situation where the measurement cycle can be extended It is also possible to switch between the two-point measurement mode and the normal measurement mode.

  As described above, according to the insulation state detection device according to the present embodiment, the ground resistance value calculation unit calculates the voltage measurement value at the first time obtained by measurement and the voltage measurement value at the second time. , Calculate the value of ground fault resistance. When charging the flying capacitor, the voltage across the flying capacitor rises according to an exponential curve determined by the time constant of the charging circuit. The exponential curve includes the influence of the charge flowing out of the Y capacitor. Further, in the exponential curve, the voltage rises with a large slope immediately after the start of charging, and changes to a gentle slope after a certain amount of time has elapsed. Then, at a relatively early timing after the start of charging, a change in the charging voltage appears notably according to the change in the resistance value of the ground fault resistor. Further, with respect to the charging voltage when a certain time has elapsed from the start of charging, the influence of the power supply voltage becomes large, and the influence of the resistance value of the ground fault resistance and the influence of the charge flowing out from the Y capacitor become relatively small. Therefore, in the difference or ratio of the voltage measurement value at the first time and the voltage measurement value at the second time, the influence of the magnitude of the resistance value of the ground fault resistance appears relatively large. That is, even in the region where the resistance value of the ground fault resistance where the influence of the Y capacitor is large is large, the correct ground fault resistance can be grasped by using the voltage measurement value at the first time and the voltage measurement value at the second time. It will be possible.

  Moreover, according to this insulation state detection device, by using constant data of the ground fault resistance map prepared in advance, the ratio between the voltage measurement value at the first time and the voltage measurement value at the second time is simple. The resistance value of the ground fault resistance can be calculated by any conversion.

  Further, according to this insulation state detection device, even in a region where the resistance value of the ground fault resistance is large, it is possible to calculate a relatively correct ground fault resistance value. For example, if the difference between the ground fault resistance (RLp) between the positive side power supply line and the ground electrode and the ground fault resistance (RLn) between the negative side power supply line and the ground electrode is large, positive side measurement The difference between the value and the negative measurement value increases. The smaller the value of the positive side measurement value and the negative side measurement value, the larger the factor of the error due to the large ground fault resistance. Therefore, the detection error of the ground resistance can be reduced by correcting the smaller one of the positive side measurement value and the negative side measurement value and using the value after the correction.

  Further, according to this insulation state detection device, it is possible to prevent the charging voltage applied to the flying capacitor from being abnormally increased due to any cause. Therefore, it is not necessary to prepare a specially high withstand voltage component of the component of the flying capacitor, and the cost of the component can be reduced.

DESCRIPTION OF SYMBOLS 10 insulation state detection apparatus 11 microcomputer 13 positive electrode side input terminal 14 negative electrode side input terminal 15 earthing | grounding point 20 input circuit 21 output terminal 31-37 wiring 41 ground fault resistance calculation processing part 42 ground fault resistance map holding part 50 vehicle DC high voltage power supply 103 Grounding line 111 Positive power supply line 112 Negative power supply line C1 Detection capacitor (flying capacitor)
D1, D2, D3 Diodes R01, R02, R1, R2, R3, R4, R5 Resistor RLp, RLn Grounding Resistance Yp, Yn Y Capacitor S1, S2, S3, S4 Switching Element

Claims (3)

A positive side input terminal and a negative side input terminal respectively connected to a positive side power line and a negative side power line of a predetermined high voltage DC power output, between the positive side power line and the ground, and a negative side power line and the ground And an Y capacitor connected between the two, and an insulation state in which the insulation state between the positive side power supply line and the negative side power supply line and the ground is grasped as a ground fault resistance based on the charging voltage of the flying capacitor. A detection device,
The flying capacitors at a first time and a second time different in timing within one charging section when charging the flying capacitors via a predetermined conduction path affected by the ground resistance, respectively. A charge voltage measurement unit that measures the charge voltage of the
A ground fault resistance value calculation unit that calculates the value of the ground fault resistance based on the voltage measurement value at the first time measured by the charge voltage measurement unit and the voltage measurement value at the second time;
An insulation state detection device comprising: The insulation state detection device according to claim 1, wherein
The ground fault resistance value calculation unit is configured to associate a plurality of constant data in a state in which the ratio of the voltage measurement value at the first time and the voltage measurement value at the second time is associated with the resistance value of the ground fault resistance. Ground resistance map, which holds
An insulation state detection device comprising: The insulation state detection device according to claim 1 or 2, wherein
The ground fault resistance value calculation unit calculates the value of the ground fault resistance based on the voltage measurement value at the first time measured by the charge voltage measurement unit and the voltage measurement value at the second time. Measurement mode,
The charge voltage measurement unit measures the charge voltage of the flying capacitor at a third time in the single charge section, and the ground fault resistance calculation unit measures the third measured by the charge voltage measurement unit. A normal measurement mode in which the value of the ground fault resistance is calculated based on a voltage measurement value of time;
An insulation state detection device characterized by having.

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