Insulation abnormality detection apparatus

A controller (1) forms an insulation measurement path and turns on a third switch connected in parallel to a capacitor, (2) after a lapse of a first time period turns off the third switch, and (3) detects an insulation abnormality based on a voltage of the capacitor measured after a lapse of a second time period after the turning off of the third switch.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention relates to an insulation abnormality detection apparatus and an insulation abnormality detection method.

Description of the Background Art

Recently, in a vehicle, the number of mounting ECUs (Electric Control Units) that require a power supply is increasing in association with complicated control systems. Along with the increased number of ECUs, for example, a stray capacitance stored in a vehicle body that serves as a ground tends to increase, and when an abnormality that a resistance value of an insulation resistance of the vehicle body decreases occurs, a malfunction of a load may be caused by the stray capacitance that is supplied to the load via a battery.

On the other hand, conventionally, there is a technology that detects an insulation abnormality of a vehicle based on a voltage of a flying capacitor charged in a state in which a battery, the flying capacitor, a vehicle insulation resistance, and a vehicle body ground are connected (for example, refer to Japanese Published Unexamined Patent Application No. 2017-133965).

However, there is a room for further improvement in accurately detecting the insulation abnormality of the vehicle.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an insulation abnormality detection apparatus includes: a voltage detecting circuit that has (i) a battery, (ii) a capacitor connected in parallel to the battery and having first and second electrodes, (iii) two first switches respectively connected to the first and second electrodes of the capacitor on an input side of the voltage detecting circuit, (iv) two second switches respectively connected to the first and second electrodes of the capacitor on an output side of the voltage detecting circuit, and (v) a third switch connected in parallel to the capacitor; and a controller that (a) forms an insulation measurement path either by turning on a first one of the two first switches connected to the first electrode of the capacitor and a second one of the two second switches connected to the second electrode of the capacitor or by turning on a second one of the two first switches connected to the second electrode of the capacitor and a first one of the two second switches connected to the first electrode of the capacitor, (b) measures a voltage of the capacitor charged through the insulation measurement path, and (c) detects an insulation abnormality based on the voltage that is measured, wherein the controller (1) forms the insulation measurement path and turns on the third switch, (2) after a lapse of a first time period turns off the third switch, and (3) detects the insulation abnormality based on the voltage of the capacitor measured after a lapse of a second time period after the turning off of the third switch.

It is an object of the invention to provide an insulation abnormality detection apparatus and an insulation abnormality detection method capable of accurately detecting an insulation abnormality of a vehicle.

These and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS

An insulation abnormality detection apparatus and an insulation abnormality detection method disclosed in this application will be described in detail below with reference to the drawings. This invention is not limited to an embodiment described below.

FIG.1illustrates one example of an in-vehicle system according to the embodiment. An in-vehicle system1, for example, is mounted on a vehicle, such as a hybrid electric vehicle (HEV), an electric vehicle (EV), or a fuel cell vehicle (FCV). The in-vehicle system1performs control including charging and discharging of a power supply that supplies power to a motor that is a power source of the vehicle.

The in-vehicle system1includes a battery2, a system main relay (SMR)3a, a SMR3b, a motor4, a compressor5, a battery ECU (one example of the insulation abnormality detection apparatus)10, a PCU20, an air conditioner ECU30, a motor generator ECU (MG_ECU)40, and a hybrid ECU (HV_ECU)50. An electrical component, such as the motor4, the compressor5, the PCU20, the air conditioner ECU30, or the MG_ECU40, is one example of a load circuit. “ECU” is an abbreviation of an Electric Control Unit.

The battery2is the power supply (battery) insulated from a vehicle body (not shown) and is configured to include a plurality of, for example, two cell stacks2A and2B that are connected in series. The cell stacks2A and2B are respectively configured to include a plurality of, for example, three battery cells2aand three battery cells2bthat are respectively connected in series. That is, the battery2is a high voltage DC power supply.

Numbers of cell stacks and battery cells are not limited to those described above or illustrated in the drawings. Moreover, for example, a lithium ion secondary battery, a nickel hydride secondary battery, and the like, may be used for the battery cell, but the battery cell is not limited to those batteries.

The SMR3ais controlled by the HV ECU50to be turned on and off. While being turned on, the SMR3aconnects the PCU20to a highest voltage side of the battery2. The SMR3bis controlled by the HV ECU50to be turned on and off. While being turned on, the SMR3bconnects the PCU20to a lowest voltage side of the battery2.

The battery ECU10is an electronic control apparatus that monitors a state of the battery2and that controls the battery2. The battery ECU10includes a monitor IC (integrated circuit)11a, a monitor IC11b, a voltage detecting circuit12, an A/D (analog/digital) converter13, a controller14and a power supply IC15. The power supply IC15supplies power to the monitor IC11a, the monitor IC11b, the voltage detecting circuit12, the A/D converter13and the controller14.

The monitor IC11ais connected to each of the plurality of the battery cells2a(a connection line is omitted) so as to monitor a voltage of each battery cell2a. Moreover, the monitor IC11ais connected to a highest voltage side and a lowest voltage side of the cell stack2A so as to monitor a voltage of the cell stack2A. The monitor IC11bis connected to each of the plurality of the battery cells2b(a connection line is omitted) so as to monitor a voltage of each battery cell2b. Moreover, the monitor IC11bis connected to a highest voltage side and a lowest voltage side of the cell stack2B so as to monitor a voltage of the cell stack2B.

A monitor IC may be provided to each battery cell or a monitor IC may be provided to the battery2. In a case where one monitor IC is provided to each battery cell, the controller14uses, as a total voltage of the battery2, a sum of voltages of the cell stacks each of which is monitored by each monitor IC. Moreover, in a case where one monitor IC is provided to the battery2, the controller14uses the total voltage of the battery2monitored by the monitor IC. The monitor ICs11aand11bare external units of the controller14.

Configurations and operations of the voltage detecting circuit12, the A/D (analog/digital) converter13, and the controller14of the battery ECU10will be described inFIG.2.

The PCU20boosts a voltage of the power supply to be supplied to the motor4and other electrical equipment of the vehicle, and also converts the voltage from DC voltage to AC voltage. As illustrated inFIG.1, the PCU20is connected to positive and negative electrode sides of the battery2. The PCU20includes a DCDC converter21, a three-phase inverter22, a low pressure-side smoothing capacitor23a, and a high pressure-side smoothing capacitor23b.

The air conditioner ECU30includes a control apparatus (not shown), and also includes an inverter31that converts the voltage of the power supply to be supplied to the compressor5from DC voltage to AC voltage.

The MG_ECU40is an electronic control apparatus that monitors a state of the PCU20and that controls the PCU20. More specifically, the MG_ECU40monitors operation states of the DCDC converter21and the three-phase inverter22, and also monitors charged states of the low pressure-side smoothing capacitor23aand the high pressure-side smoothing capacitor23b. The MG_ECU40obtains information on a presence or absence of boosting in the PCU20and the boosted voltage, and then informs the HV_ECU50that is an upper apparatus of the MG_ECU40of the information. Moreover, the MG ECU40controls operations of the PCU20based on a command from the HV ECU50.

Next, the voltage detecting circuit12according to the embodiment will be described with reference toFIG.2.FIG.2illustrates one example of the voltage detecting circuit12according to the embodiment.FIG.2illustrates a configuration of the voltage detecting circuit12to be connected to the cell stack2A of the battery2. However, when being connected to the cell stack2B, the voltage detecting circuit12has the same configuration as inFIG.2. In the description ofFIG.2, the cell stack2A is referred to as the battery2.

As illustrated inFIG.2, the voltage detecting circuit12includes a switch SW1to a switch SW5, a capacitor C1, and a resistor R1to a resistor R6. Solid state relays (SSR) may be used as the switch SW1to the switch SW5, for example. However, the switch is not limited to the solid state relay.

Among the switch SW1to the switch SW5, each of the switch SW1and the switch SW2is a first switch, each of the switch SW4and the switch SW5is a second switch, and the switch SW3is a third switch.

As illustrated inFIG.2, on a positive electrode side of the battery2(cell stack2A), the switch SW1, the resistor R1, the switch SW4, and the resistor R3are connected in series in order of proximity to the battery2. Moreover, on a negative electrode side of the battery2(cell stack2A), the switch SW2, the resistor R2, the switch SW5, and the resistor R4are connected in series in order of proximity to the battery2.

The capacitor C1is connected in parallel to the battery2and serves as a flying capacitor. Specifically, one electrode of the capacitor C1is connected between the resistor R1and the switch SW4, and the other electrode is connected between the resistor R2and the switch SW5. In other words, one electrode of the capacitor C1is connected to the switch SW1on an input side and is connected to the switch SW4on an output side. The other electrode of the capacitor C1is connected to the switch SW2on the input side and is connected to the switch SW5on the output side. That is, both electrodes of the capacitor C1are respectively connected to the switch SW1and the switch SW2as a plurality of the first switches on the input side and the both electrodes of the capacitor C1are respectively connected to the switch SW4and the switch SW5as a plurality of the second switches on the output side. Moreover, the switch SW3is connected in parallel to the capacitor C1.

One side of the resistor R5is connected to the switch SW4in parallel with the resistor R3, and the other side is grounded to the vehicle body, and the like. Moreover, one side of the resistor R6is connected to the switch SW5in parallel with the resistor R4, and the other side is grounded to the vehicle body, and the like.

An insulation resistance Rn and a stray capacitance C2exist in parallel between the negative electrode side of the battery2and one end of each of the resistor R5and the resistor R6. Moreover, an insulation resistance Rp and a stray capacitance C3exist in parallel between the positive electrode side of the battery2and the one end of each of the resistor R5and the resistor R6. The stray capacitance C2and the stray capacitance C3have substantially the same value. The stray capacitance is also referred to as a common capacitance.

The resistor R3is connected to a positive terminal of the A/D converter13that is configured as an amplifier, and the resistor R4is connected to a negative terminal of the A/D converter13. The A/D converter13converts an analog voltage input from the voltage detecting circuit12into a digital voltage, and then outputs the converted digital voltage to the controller14.

The controller14is a processing apparatus that is a microcomputer and the like including, for example, a central processing unit (CPU), a random access memory (RAM) and a read only memory (ROM).

The controller14detect an insulation abnormality of the insulation resistances Rp and Rn by executing the insulation abnormality detection method according to the embodiment.

Here, a circuit operation of the voltage detecting circuit12executed by the insulation abnormality detection method according to the embodiment will be described with reference toFIG.2. In the insulation abnormality detection method according to the embodiment, four processes (1) to (4) described below are performed.

(1) Battery voltage measurement process

(2) VRp measurement process

(4) Insulation abnormality detection process

In the insulation abnormality detection method according to the embodiment, especially, by devising a measurement method in (2) VRp measurement process and (3) VRn measurement process, it becomes possible to measure a voltage of the capacitor C1from which an influence of the stray capacitances C2and C3is eliminated. As a result, it is possible to accurately detect the insulation abnormality.

(1) Battery Voltage Measurement Process

The battery voltage measurement process is a process of measuring a battery voltage of the battery2. Specifically, the controller14, first, turns on the switch SW1and the switch SW2, and turns off the switch SW3, the switch SW4and the switch SW5.

As a result, since a charging path is formed in order of the battery2, the switch SW1, the resistor R1, the capacitor C1, the resistor R2, and the switch SW2, the capacitor C1is charged by the battery2.

Subsequently, after a lapse of a predetermined time, that is, after a completion of charging the capacitor C1, the controller14turns off the switch SW1and the switch SW2, and turns on the switch SW4and the switch SW5. As a result, since electricity is conducted from the capacitor C1to a ground (vehicle body), a charge stored in the capacitor C1is discharged through the resistors R5and R6. Moreover, at this time, an analog voltage of the capacitor C1is output to the A/D converter13through resistor R3and R4, and is converted into a digital voltage by the A/D converter13. The controller14measures the voltage of the capacitor C1, i.e., the battery voltage of the battery2based on a value of the digital voltage to be output from the A/D converter13.

After measuring the battery voltage of the battery2, the controller14completely discharge the charge of the capacitor C1by turning on the switch SW3and ends the battery voltage measurement process.

(2) VRp Measurement Process

After the battery voltage measurement process, the VRp measurement process is performed. The VRp measurement process may also be performed prior to the battery voltage measurement process. The VRp measurement process is a process of measuring a VRp as a voltage value for calculating a resistance value of the insulation resistance Rp on the positive electrode side of the battery2by forming an insulation measurement path by turning on the switch SW2connected to an input side of the capacitor C1and the switch SW4connected to an output side of the capacitor C1. That is, the insulation measurement path in the VRp measurement process is formed by the negative electrode side of the battery2, the switch SW2, the resistor R2, the capacitor C1, the switch SW4, the resistor R5, the insulation resistance Rp and the stray capacitance C3, and the positive electrode side of the battery2. By forming this insulation measurement path, the voltage (VRp) according to the resistance value of the insulation resistance Rp is charged in the capacitor C1. In this embodiment, since an elimination operation for eliminating the stray capacitance C3flowing through the capacitor C1is performed prior to a measurement operation of this VRp, it becomes possible to measure the VRp from which the influence of the stray capacitance C3is eliminated.

Specifically, the controller14, as the elimination operation, turns on the switch SW2, the switch SW3, and the switch SW4. Since the switch SW3is turned on in a discharge process that has been performed at an end of the battery voltage measurement process, the switch SW3continues to be turned on in the elimination operation.

The controller14maintains a state in which the switch SW2, the switch SW3, and the switch SW4are turned on for a predetermined time period (a first time period). That is, the controller14forms the insulation measurement path by turning on the switch SW2as the first switch and the switch SW4as the second switch and performs the elimination operation in which the switch SW3as the third switch is turned on only for the first time period.

As a result, since the insulation measurement path passes through not the capacitor C1but the switch SW3, a charge of the stray capacitance C3is discharged (eliminated) without being charged in the capacitor C1.

After the elimination operation, the measurement operation of the VRp is performed. Specifically, after a lapse of the first time period, after the controller14controls the A/D converter13to convert the voltage of the capacitor C1by turning on the switch SW4and the switch SW5, the controller14turns off the switch SW3. Subsequently, the controller14forms the insulation measurement path by turning on the switch SW2and switch SW4and maintains a state in which the switch SW3is turned off for a predetermined time period (a second time period). In this case, when the insulation resistance Rp is normal (the resistance value is sufficiently large), since the insulation measurement path does not conduct the electricity through the insulation resistance Rp, the capacitor C1is not charged. When the resistance value is lowered due to the abnormality of the insulation resistance Rp, such as a deterioration, since the insulation measurement path conducts the electricity through the insulation resistance Rp, the capacitor C1is charged.

Since the controller14, after a lapse of the second time period, turns off the switch SW2and turns on the switch SW4and the switch SW5, the controller14controls the A/D converter13to A/D convert the voltage of the capacitor C1and measures the A/D converted voltage as the VRp. The measured VRp is used in the insulation abnormality detection process as a subsequent step.

That is, the controller14detects the insulation abnormality based on the VRp that is the voltage of the capacitor C1measured after the lapse of the second time period after turning off the switch SW3as the third switch.

After measuring the VRp, the controller14completely discharges the charge of the capacitor C1by turning on the switch SW3and ends the VRp measurement process. That is, the switch SW3as the third switch serves as both a switch for eliminating the charge of the stray capacitance C3and a discharge switch for discharging the charge of the capacitor C1. As a result, since it is not necessary to provide each switch, it is possible to reduce costs.

After the VRp measurement process, the VRn measurement process is performed. The VRn measurement process is a process of measuring a VRn as a voltage value for calculating a resistance value of the insulation resistance Rn of the battery2on the negative electrode side by forming the insulation measurement path by turning on the switch SW1connected to the input side of the capacitor C1and the switch SW5connected to the output side of the capacitor C1. That is, the insulation measurement path in the VRn measurement process is formed by the positive electrode side of the battery2, the switch SW1, the resistor R1, the capacitor C1, the switch SW5, the resistor R6, the insulation resistance Rn, the stray capacitance C2, and the negative electrode side of the battery2. By forming this insulation measurement path, the voltage (VRn) according to the resistance value of the insulation resistance Rn is charged in the capacitor C1. In this embodiment, in the same manner as the VRp measurement process, since an elimination operation for eliminating the stray capacitance C2flowing through the capacitor C1is performed prior to a measurement operation of the VRn, it becomes possible to measure the VRn from which the influence of the stray capacitance C2is eliminated.

Specifically, the controller14, as the elimination operation, turns on the switch SW1, the switch SW3, and the switch SW5. Since the switch SW3is turned on in the discharge process that has been performed at an end of the VRp measurement process, the switch SW3continues to be turned on in the elimination operation.

The controller14maintains a state in which the switch SW1, the switch SW3, and the switch SW5are turned on for a predetermined time period (the first time period). That is, the controller14forms the insulation measurement path by turning on the switch SW1as the first switch and the switch SW5as the second switch and performs the elimination operation in which the switch SW3as the third switch is turned on only for the first time period.

As a result, since the insulation measurement path passes through not the capacitor C1but the switch SW3, a charge of the stray capacitance C2is discharged (eliminated) without being charged in the capacitor C1.

After the elimination operation, the measurement operation of the VRn is performed. Specifically, since the controller14, after the lapse of the first time period, turns on the switch SW4and the switch SW5, the controller14controls the A/D converter13to convert the voltage of the capacitor C1and then turns off the switch SW3. Subsequently, the controller14forms the insulation measurement path by turning on the switch SW1and switch SW5and maintains a state in which the switch SW3is turned off for a predetermined time period (the second time period). In this case, when the insulation resistance Rn is normal (the resistance value is sufficiently large), since the insulation measurement path does not conduct the electricity through the insulation resistance Rn, the capacitor C1is not charged. When the resistance value is lowered due to the abnormality of the insulation resistance Rn, such as a deterioration, since the insulation measurement path conducts the electricity through the insulation resistance Rn, the capacitor C1is charged.

Since the controller14, after the lapse of the second time period, turns off the switch SW1and turns on the switch SW4and the switch SW5, the controller14controls the A/D converter13to A/D convert the voltage of the capacitor C1and measures the A/D converted voltage as the VRn. The measured VRn is used in the insulation abnormality detection process as the subsequent step.

That is, the controller14detects the insulation abnormality based on the VRn that is the voltage of the capacitor C1measured after the lapse of the second time period after turning off the switch SW3as the third switch.

After measuring the VRn, the controller14completely discharges the charge of the capacitor C1by turning on the switch SW3and ends the VRn measurement process. That is, the switch SW3as the third switch serves as both a switch for eliminating the charge of the stray capacitance C2and a discharge switch for discharging the charge of the capacitor C1. As a result, since it is not necessary to provide each switch, it is possible to reduce costs.

Here, the voltage value of VRp and VRn to be measured by the VRp measurement process and the VRn measurement process will be described with reference toFIG.3.FIG.3illustrates the voltage value of VRp and VRn to be measured.FIG.3shows a total sum of the VRp and the VRn on a vertical axis and shows a charging time of the capacitor C1on a horizontal axis. Although the total sum of the VRp and VRn is shown inFIG.3, the VRp and the VRn may be shown respectively and separately.

Moreover, a “common elimination period” shown inFIG.3is the first time period, and an “insulation resistance calculation period” is the second time period.FIG.3shows, as a reference example, the total sum of the VRp and the VRn to be detected in the voltage detecting circuit that does not include the switch SW3as the third switch.

As illustrated inFIG.3, in the reference example, since a charge of a stray capacitance is charged in a capacitor, in the common elimination period between a time t1and a time t2, charges of a battery and the stray capacitance are stored in the capacitor. As a result, for example, when the stray capacitance increases, since the charges stored in the capacitor increase, there is a possibility that a battery voltage is not accurately measured depending on the capacitance of the capacitor.

Therefore, in this embodiment, since the controller14forms the insulation measurement path and turns on the switch SW3in the common elimination period (period between the time t1and the time t2) that is influenced by the charges of the stray capacitances C2and C3, the charge of the stray capacitance C2is not stored in the capacitor C1. As a result, as illustrated inFIG.3, in the common elimination period, since the switch SW3is turned on, the capacitor C1is not charged, and thus, the voltage of the capacitor C1becomes substantially zero.

After a lapse of the common elimination period, that is, at the time t2after completely discharging the charges of the stray capacitances C2and C3, since the controller14forms the insulation measurement path and turns off the switch SW3after controlling the A/D converter13to A/D convert the voltage of the capacitor C1, the controller14starts charging of the capacitor C1. That is, if the voltage detecting circuit12does not include the switch SW3, the common elimination period as the first time period is a time required from formation of the insulation measurement path to a completion of charging the stray capacitance C2. As a result, it is possible to store only the charge of the battery2in the capacitor C1by eliminating the influence of the stray capacitances C2and C3.

In the insulation resistance calculation period (period between the time t2and a time t3) as the second time period, the controller14charges the capacitor C1by continuing to turn off the switch SW3. That is, the second time period is a time required for a completion of charging the capacitor C1by the battery2.

The controller14, at the time t3after a lapse of the insulation resistance calculation period, controls the A/D converter13to A/D convert the voltage of the capacitor C1and detects the abnormality of the insulation resistances Rp and Rn in the (4) insulation abnormality detection process as described later based on the A/D converted voltage of the capacitor C1.

As described above, in the insulation abnormality detection method according to the embodiment, by turning on the switch SW3in the common elimination period, it becomes possible to measure the voltage of the capacitor C1from which the influence of the stray capacitances C2and C3is eliminated. That is, according to the insulation abnormality detection method according to the embodiment, it is possible to accurately detect the abnormality of the insulation resistances Rp and Rn.

As described above, in the insulation abnormality detection method according to the embodiment, since the charge of the stray capacitance C2is not stored in the capacitor C1, the capacitance of the capacitor C1is reduced by the stray capacitance C2. In other words, the capacitance of the capacitor C1is set as the capacitance from which the stray capacitance C2is eliminated. As a result, it is possible to reduce the cost of the capacitor C1.

(4) Insulation Abnormality Detection Process

The insulation abnormality detection process is a process of detecting the abnormality of the insulation resistance Rn based on the measured VRp and the VRn. Specifically, the controller14calculates a voltage (Vt2) of the capacitor C1A/D converted at the time t2and an increase rate (inclination) of a voltage (Vt3) of the capacitor C1A/D converted at the time t3, as shown inFIG.3. That is, the increase rate is calculated by (Vt3−Vt2)/(t3−t2). When the increase rate is less than a predetermined threshold value, the controller14determines that the insulation resistances Rp and Rn are normal. When the increase rate is the predetermined threshold value or more, the controller14determines that the insulation resistances Rp and Rn are abnormal. That is, the controller14detects the insulation abnormality based on the inclination of the VRp and the VRn in the insulation resistance calculation period (period between the time t2and the time t3) illustrated inFIG.3.

The controller14may detect the insulation abnormality by calculating the increase rate of the sum of the VRp and VRn or by calculating the increase rate of each of the VRp and the VRn.

The controller14does not necessarily determine the insulation abnormality by the increase rate and may determine the insulation abnormality depending on whether or not the sum (or each value) of the VRp and the VRn is the predetermined threshold value or more.

The controller14may detect the insulation abnormality without A/D converting the voltage of the capacitor C1at the time t2. In this case, the controller14may calculate the increase rate described above as Vt2=0.

The controller14may detect that a stuck-open abnormality of the switch SW3has occurred based on the voltage of the capacitor C1. Specifically, the controller14measures the voltage of the capacitor C1after the lapse of the first time period (common elimination period shown inFIG.3). When the voltage has a predetermined value or more, the controller14detects that the stuck-open abnormality of the switch SW3as the third switch has occurred.

That is, when the voltage that is supposed to be zero after the lapse of the common elimination period is not zero, the controller14determines that the capacitor C1is unintentionally charged due to the abnormality that the switch SW3is not turned on and detects that the stuck-open abnormality of the switch SW3has occurred. As a result, it is possible to accurately detect that the stuck-open abnormality of the switch SW3has occurred.

The controller14, prior to the common elimination period as the first time period, may perform a process of measuring the stray capacitance C2and determine a length of the common elimination period according to the stray capacitance C2. Specifically, the controller14, in the process (2) or (3) described above, forms the insulation measurement path before turning on the switch SW3as the third switch for the first time period, and measures the voltage of the capacitor C1that is charged by turning off the switch SW3for the first time period. Since such a voltage is charged in the stray capacitance C2, the first time period is determined according to the stray capacitance C2expected based on the voltage.

As a result, since the length of the common elimination period as the first time period is accurately determined, it is possible to accurately prevent the charge of the stray capacitance C2from remaining in the insulation resistance calculation period due to the length of the first time period that is longer than necessary or that is too short, for example.

Next, a process executed by the battery ECU10as the insulation abnormality detection apparatus according to the embodiment will be described with reference toFIG.4toFIG.6.FIG.4is a flowchart illustrating a processing procedure of an overall process executed by the battery ECU10according to the embodiment.FIG.5is a flowchart illustrating a processing procedure of the VRp measurement process executed by the battery ECU10according to the embodiment.FIG.6is a flowchart illustrating a processing procedure of the VRn measurement process executed by the battery ECU10according to the embodiment.

First, the processing procedure of the overall process will be described with reference toFIG.4.

As illustrated inFIG.4, the controller14of the battery ECU10controls the voltage detecting circuit12to measure the battery voltage of the battery2(a step S101). Subsequently, the controller14performs the discharge process of discharging the charge of the capacitor C1after the battery voltage measurement process (a step S102).

Subsequently, the controller14controls the voltage detecting circuit12to perform the VRp measurement process (a step S103). Subsequently, the controller14performs the discharge process of discharging the charge of the capacitor C1after the VRp measurement process (a step S104).

Subsequently, the controller14controls the voltage detecting circuit12to perform the VRn measurement process (a step S105). Subsequently, the controller14performs the discharge process of discharging the charge of the capacitor C1after the VRn measurement process (a step S106).

Subsequently, the controller14performs the insulation abnormality detection process of detecting the insulation abnormality of the insulation resistance Rn based on the measured VRp and VRn (a step S107) and ends the process.

Next, the processing procedure of the VRp measurement process will be described with reference toFIG.5.

As illustrated inFIG.5, the controller14turns on the switch SW2, the switch SW3and the switch SW4in the voltage detecting circuit12(a step S201). Since the switch SW3has already been turned on in the discharge process as a previous step (the step S102illustrated inFIG.4), the switch SW3continues to be turned on in the step S201.

Subsequently, the controller14determines whether or not the first time period has elapsed after turning on the switch SW2, the switch SW3and switch SW4(a step S202). When the first time period has not elapsed (No in the step S202), the controller14repeatedly executes the step S202until the first time period elapses.

When the first time period has elapsed (Yes in the step S202), the controller14controls the A/D converter13to A/D convert the voltage of the capacitor C1and turns off the switch SW3(a step S203). As a result, charging of the capacitor C1is started (a step S204).

Subsequently, the controller14determines whether or not the second time period has elapsed after turning off the switch SW3(a step S205). When the second time period has not elapsed (No in the step S205), the controller14repeatedly executes the step S205until the second time period elapses.

When the second time period has elapsed (Yes in the step S205), the controller14controls the A/D converter13to carry out an AD sampling to obtain the VRp (a step S206) and ends the process.

Next, the processing procedure of the VRn measurement process will be described with reference toFIG.6.

As illustrated inFIG.6, the controller14turns on the switch SW1, the switch SW3and the switch SW5in the voltage detecting circuit12(a step S301). Since the switch SW3has already been turned on in the discharge process as a previous step (the step S104illustrated inFIG.4), the switch SW3continues to be turned on in the step S301.

Subsequently, the controller14determines whether or not the first time period has elapsed after turning on the switch SW1, the switch SW3and the switch SW5(a step S302). When the first time period has not elapsed (No in the step S302), the controller14repeatedly executes the step S302until the first time period elapses.

When the first time period has elapsed (Yes in the step S302), the controller14controls the A/D converter13to A/D convert the voltage of the capacitor C1and turns off the switch SW3(a step S303). As a result, charging of the capacitor C1is started (a step S304).

Subsequently, the controller14determines whether or not the second time period has elapsed after turning off the switch SW3(a step S305). When the second time period has not elapsed (No in the step S305), the controller14repeatedly executes the step S305until the second time period elapses.

When the second time period has elapsed (Yes in the step S305), the controller14controls the A/D converter13to carry out the AD sampling to obtain the VRp (a step S306) and ends the process.

As described above, the insulation abnormality detection apparatus (battery ECU10) according to the embodiment includes the voltage detecting circuit12and the controller14. The voltage detecting circuit12has the battery2, the capacitor C1connected in parallel to the battery2and having first and second electrodes, two first switches (switches SW1and SW2) respectively connected to the first and second electrodes of the capacitor C1on the input side of the voltage detecting circuit12, two second switches (switches SW4and5) respectively connected to the first and second electrodes of the capacitor C1on the output side of the voltage detecting circuit12, and the third switch (switch SW3) connected in parallel to the capacitor C1. The controller14forms the insulation measurement path either by turning on a first one of the two first switches connected to the first electrode of the capacitor C1and a second one of the two second switches connected to the second electrode of the capacitor C1or by turning on a second one of the two first switches connected to the second electrode of the capacitor and a first one of the two second switches connected to the first electrode of the capacitor C1, measures the voltage of the capacitor C1charged through the insulation measurement path, and detects the insulation abnormality based on the voltage that is measured. The controller14forms the insulation measurement path and turns on the third switch, after the lapse of the first time period turns off the third switch, and detects the insulation abnormality based on the voltage of the capacitor C1measured after the lapse of the second time period after the turning off of the third switch. As a result, it is possible to accurately detect the insulation abnormality of the vehicle.

It is possible for a person skilled in the art to easily come up with more effects and modifications. Thus, a broader modification of this invention is not limited to specific description and typical embodiments described and expressed above. Therefore, various modifications are possible without departing from the general spirit and scope of the invention defined by claims attached and equivalents thereof.

While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous other modifications and variations can be devised without departing from the scope of the invention.