Power supply degradation determination apparatus

A power supply degradation determination apparatus which is mounted to the vehicle includes a controller and a DC-DC converter that control execution of a charge phase in which a capacitor capable of accumulating regenerative energy of the vehicle is charged and execution of a discharge phase in which the capacitor is discharged. The controller detects the internal resistance of the capacitor using the difference between the terminal voltage and the open circuit voltage of the capacitor during the execution of the discharge phase and the discharge current thereof, determines whether the internal resistance is a predetermined value or more, and delays the execution start of the discharge phase for a predetermined time when the internal resistance is determined to be the predetermined value or more.

CROSS-REFERENCE TO RELATED APPLICATION

Priority is claimed on Japanese Patent Application No. 2012-102593, filed on Apr. 27, 2012, the content of which is incorporated herein by reference.

BACKGROUND

Field of the Invention

The present invention relates to a power supply degradation determination apparatus.

Description of Related Art

Hitherto, apparatuses have been known in which, for example, an open circuit voltage measured at the time of charge interruption during pulse charging of a secondary battery, or the like is used as a nonresistance voltage, and the amount of charge of the secondary battery is estimated based on the nonresistance voltage (see, for example, Japanese Unexamined Patent Application, First Publication No. H9-139236).

SUMMARY

Incidentally, according to the above-mentioned apparatus in the related art, since an open circuit voltage is measured during the charge interruption, charging is required to be interrupted.

For this reason, for example, when the apparatus is mounted to a vehicle capable of recovering regenerative energy, regenerative energy capable of being recovered is reduced by interrupting charging, and thus a problem of a drop in the fuel efficiency of a vehicle occurs.

Aspects according to the invention is contrived in view of such circumstances, and an object thereof is to provide a power supply degradation determination apparatus which is capable of determining the degradation of a power supply with a high level of accuracy while preventing energy loss.

An aspect according to the present invention includes the following means for achieving the object related to solving the problems.

(1) A power supply degradation determination apparatus according to an aspect of the present invention which is mounted to a vehicle, includes: a battery which is capable of accumulating regenerative energy of the vehicle; a charge and discharge control unit which controls execution of a charge phase in which the battery is charged and a discharge phase in which the battery is discharged; a standby unit which delays an execution start of the discharge phase by the charge and discharge control unit for a predetermined time; and an internal resistance determination unit which determines an internal resistance of the battery, wherein the internal resistance determination unit detects the internal resistance of the battery using a difference between a terminal voltage and an open circuit voltage of the battery during the execution of the discharge phase, and a discharge current of the battery during the execution of the discharge phase, and determines whether the internal resistance is a predetermined value or more, and the standby unit delays the execution start of the discharge phase by the charge and discharge control unit for the predetermined time when the internal resistance is determined to be the predetermined value or more by the internal resistance determination unit.

(2) In the aspect of (1), the standby unit may delay the execution start of the discharge phase for the predetermined time only when the execution of the discharge phase is started within the predetermined time after the execution of the charge phase is terminated in a case where the discharge phase is executed subsequent to the execution of the charge phase by the charge and discharge control unit.

(3) In the aspect of (1) or (2), the standby unit may increase the predetermined time with an increase in the internal resistance detected by the internal resistance determination unit.

(4) In any one of aspects (1) to (3), the standby unit may make the predetermined time when the discharge phase is executed subsequent to the execution of the discharge phase by the charge and discharge control unit longer than the predetermined time when the discharge phase is executed subsequent to the execution of the charge phase by the charge and discharge control unit.

(5) Any one of aspects (1) to (4) may further include a standby prohibition unit which prohibits the execution start of the discharge phase by the charge and discharge control unit from being delayed for the predetermined time by the standby unit until the internal resistance is determined to be the predetermined value or more by the internal resistance determination unit.

(6) In the aspect of (5), the vehicle may be equipped with an internal combustion engine that drives the vehicle, an electric load, and a battery capable of supplying power to the electric load with a predetermined depth of discharge, the charge and discharge control unit may supply power from the battery to the electric load during the execution of the discharge phase, and the charge and discharge control unit may supply power from the battery to the electric load with a depth of discharge smaller than the predetermined depth of discharge, when the internal resistance is determined to be the predetermined value or more by the internal resistance determination unit in a state where standby prohibition by the standby prohibition unit is not executed.

(7) In the aspect of (6), the vehicle may further include an idle stop unit which temporarily stops the internal combustion engine when stop conditions are satisfied and starts the internal combustion engine in a temporary stop state when return conditions are satisfied, the battery may hold power required for starting the internal combustion engine, the idle stop unit may supply the power from the battery to a start-up device of the internal combustion engine based on a return request, and the charge and discharge control unit may make a supply of power from the battery to the electric load smaller when the internal resistance is determined to be the predetermined value or more by the internal resistance determination unit than when the internal resistance is determined to be less than the predetermined value by the internal resistance determination unit.

(8) A power supply degradation determination apparatus according to an aspect of the present invention which is mounted to a vehicle, includes: a battery which is capable of accumulating regenerative energy of the vehicle; a charge and discharge control unit for controlling execution of a charge phase in which the battery is charged and a discharge phase in which the battery is discharged; and an internal resistance determination unit for determining an internal resistance of the battery, wherein the internal resistance determination unit detects the internal resistance of the battery using a difference between a terminal voltage and an open circuit voltage of the battery during the execution of the discharge phase and a discharge current of the battery during the execution of the discharge phase, only when the execution of the discharge phase is started within the predetermined time after the execution of the charge phase is terminated in a case where the discharge phase is executed subsequent to the execution of the charge phase by the charge and discharge control unit and determines whether the internal resistance is the predetermined value or more.

According to the aspect of (1), the execution start of the discharge phase is delayed for the predetermined time with respect to the internal resistance determination unit which detecting the internal resistance of the battery using the difference between the terminal voltage and the open circuit voltage of the battery during the execution of the discharge phase and the discharge current thereof, thereby allowing the internal resistance to be detected with a high level of accuracy in a state where the terminal voltage of the battery is stable.

Furthermore, since the internal resistance is detected by delaying the execution start of the discharge phase, energy (for example, regenerative energy or the like) of the vehicle capable of being recovered as electric energy is prevented from being reduced, for example, as compared to the case where the internal resistance is detected by delaying the execution start of the charge phase, and thus the fuel efficiency of the vehicle can be prevented from dropping.

According to the aspect of (2), in a state where switching from the charge phase to the discharge phase is performed, the difference between the terminal voltage and the open circuit voltage of the battery is large, and the time required for the terminal voltage to stabilize lengthens. Thereby, the internal resistance is easily detected as a higher value than in reality in addition to an increase in a detection error of the internal resistance, and thus the degradation of the battery can be determined too early.

On the other hand, the execution start of the discharge phase is delayed for at least the predetermined time, and standby is performed until the terminal voltage stabilizes so that the difference between the terminal voltage and the open circuit voltage of the battery is made to be small, thereby allowing the detection accuracy of the internal resistance and the reliability of the degradation determination of the battery to be improved.

According to the aspect of (3), the execution start of the discharge phase is prevented from being excessively delayed when the internal resistance is small. Thereby, it is possible to secure a desired supply of power and to prevent the detection accuracy of the internal resistance from dropping when the internal resistance is large.

According to the aspect of (4), it is possible to accurately determine the degradation of the battery.

That is, when the predetermined time required for standby before the execution start of the discharge phase is insufficient in a case where the discharge phase is executed subsequent to the execution of the charge phase, the difference between the terminal voltage and the open circuit voltage of the battery is easily detected as a higher value than in reality, and thus it is easily determined that the battery is degraded.

On the other hand, when the predetermined time required for standby before the execution start of the discharge phase is insufficient in a case where the discharge phase is executed subsequent to the execution of the discharge phase, the difference between the terminal voltage and the open circuit voltage of the battery is easily detected as a lower value than in reality, and thus it is easily determined that the battery is not degraded.

Therefore, when the discharge phase is executed subsequent to the execution of the discharge phase, the degradation of the battery can be prevented from not being detected by making the predetermined time required for standby longer than when the discharge phase is executed subsequent to the execution of the charge phase.

According to the aspect of (5), the execution of standby is omitted with respect to the battery in a low temperature state, for example, during the start of the vehicle, or the like. Thereby, it is possible to perform the execution start of the discharge phase and the determination of the internal resistance early and to prevent the execution start of the discharge phase and the determination of the internal resistance from being delayed unnecessarily.

According to the aspect of (6), the depth of discharge of the battery is reduced with an increase in the internal resistance of the battery, thereby allowing the battery to be prevented from being degraded.

According to the aspect of (7), it is possible to secure the supply of power to the electric load over a desired idle stop time while securing power for starting the internal combustion engine in a stop state.

According to the aspect of (8), in a state where switching from the charge phase to the discharge phase is performed, the difference between the terminal voltage and the open circuit voltage of the battery is large, and the time required for the terminal voltage to stabilize lengthens. Thereby, the internal resistance is easily detected as a higher value than in reality in addition to an increase in a detection error of the internal resistance, and thus the degradation of the battery can be determined early.

DESCRIPTION OF THE EMBODIMENT

Hereinafter, a power supply degradation determination apparatus according to an embodiment of the invention will be described referring to the accompanying drawings.

For example, as shown inFIG. 1, a power supply degradation determination apparatus10according to the present embodiment is mounted to a vehicle1, and the vehicle1is configured to include a capacitor (a battery)11and a battery12as a secondary battery, a DC-DC converter (a charge and discharge control unit)13, a controller (the charge and discharge control unit, an internal resistance determination unit, a standby unit, a standby prohibition unit)14, a contactor15, a contactor relay16, an FI-ECU (an idle stop unit)17, a starter magnet switch18, a starter relay19, a starter motor (a start-up device)20, a generator21, an internal combustion engine22, and an electric load23.

The power supply degradation determination apparatus10according to the present embodiment is configured to include, for example, the capacitor11, the battery12, the DC-DC converter13, the controller14, the contactor15, and the contactor relay16.

The capacitor11is, for example, an electric double-layer capacitor, an electrolytic capacitor, a lithium ion capacitor or the like, and is connected to the starter magnet switch18.

In addition, the capacitor11is connected to an input and output terminal13aon one side (for example, high-voltage side) of the DC-DC converter13, and is capable of being electrically connected to the generator21and the electric load23through the DC-DC converter13.

The battery12is, for example, a lead battery of a predetermined low voltage (for example, 12 V) or the like, and is connected to the generator21, the electric load23, the contactor relay16, and the FI-ECU17.

In addition, the battery12is connected to an input and output terminal13bon the other side (for example, low-voltage side) of the DC-DC converter13, and is capable of being electrically connected to the starter magnet switch18through the DC-DC converter13.

Further, the capacitor11and the battery12are connected to terminals15aand15bof the contactor15and are configured to be capable of switching electrical connection and cut-off therebetween by the contactor15.

The DC-DC converter13can be stepped up and stepped down bi-directionally between input and output terminals13aand13b, for example, by control of the controller14.

For example, the DC-DC converter13charges the capacitor11by supplying generative power generated by the generator21to the capacitor11during the operation of the internal combustion engine22or regenerative power generated by the generator21during the braking of the vehicle1.

In addition, for example, the DC-DC converter13discharges the capacitor11by supplying power electrically accumulated in the capacitor11to the electric load23.

The controller14controls for example, the bi-directional step-up/step-down operation of the DC-DC converter13and the operation of the connection and cut-off of the contactor15by the contactor relay16.

In addition, the controller14controls, for example, the execution permission and execution prohibition of an idle stop by the FI-ECU17and outputs a control command instructing the FI-ECU17to permit or prohibit execution of the idle stop.

In addition, the controller14detects, for example, the internal resistance and capacitance of the capacitor11. The controller determines whether the internal resistance is a predetermined value or more, and determines the degradation of the capacitor11based on the internal resistance.

For this reason, the controller14includes, for example, a voltage sensor that detects the terminal voltage of the capacitor11, a current sensor that detects the charge current and discharge current of the capacitor11, and a temperature sensor that detects the temperature of the capacitor11.

In addition, the controller14controls, for example, the discharge of the battery12and the depth of discharge of the battery12caused by the supply of power from the battery12to the electric load23.

The contactor15switches, for example, the connection and cut-off between terminals15aand15bof the contactor15based on the “On”/“Off” operation of the contactor relay16, and the “On”/“Off” operation of the contactor relay16are controlled, for example, by the controller14.

In addition, the one terminal15aof the contactor15is connected to, for example, a terminal on a positive electrode side of the capacitor11and the starter magnet switch18.

In addition, the other terminal15bof the contactor15is connected to, for example, a terminal on a positive electrode side of the battery12.

Thereby, in the connection state of the contactor15, the capacitor11and the battery12are connected in parallel with the starter magnet switch18and the starter motor20which are connected in series with each other.

The FI-ECU17is, for example, an ECU (Electronic Control Unit) constituted by electronic circuits such as a CPU (Central Processing Unit) and performs various types of control on the operations of the internal combustion engine22such as fuel supply and ignition timing.

For example, the FI-ECU17controls the start and stop of the internal combustion engine22by a start request and a stop request based on a signal which is output from an ignition switch operated by a driver. Further, the FI-ECU automatically temporarily stops the internal combustion engine22in an operating state when stop conditions are satisfied, and controls an idle stop for automatically restarting the internal combustion engine22in a temporary stop state when return conditions are satisfied.

In addition, the stop conditions correspond to, for example, a case where the vehicle speed of the vehicle1is zero, a case where the opening degree of an accelerator pedal is zero, and a case where a brake pedal switch is turned on, and the like, and the return conditions correspond to, for example, a case where the brake pedal switch is turned off, and the like.

In addition, the internal combustion engine22is started by, for example, a driving force of the starter motor (STM)20, and the starter motor20is rotationally driven by the application of a voltage from the capacitor11or the battery12through the starter magnet switch (STMGSW)18.

The starter magnet switch18switches, for example, the presence or absence of the supply of power to the starter motor20based on the “On”/“Off” operation of the starter relay19, and the “On”/“Off” operation of the starter relay19is controlled by, for example, the FI-ECU17.

For example, the FI-ECU17starts the internal combustion engine22by controlling the starter relay19so as to be turned on according to a start request based on a signal which is output from the ignition switch or a return request from a temporary stop state of the idle stop.

In addition, for example, the FI-ECU17controls a generation operation of the generator (ACG)21, and arbitrarily changes a generation voltage of the generator21.

In addition, the generator21is, for example, an AC generator coupled to a crank shaft of the internal combustion engine22through a belt or the like, and outputs regenerative power by generating power through motive power of the internal combustion engine22during the operation of the internal combustion engine22, and outputting generative power, or converting kinetic energy of a car body transmitted from driving wheels during the deceleration of the vehicle1, during running in a stop state for fuel supply, or the like, into electric energy (regenerative energy).

In addition, the generator21includes a rectifier that rectifies an AC output by generation and regeneration to a DC output.

The electric load23is, for example, various types of auxiliary equipment mounted to the vehicle1, and the like.

The power supply degradation determination apparatus10according to the present embodiment includes the above-mentioned configuration. Next, operations of the power supply degradation determination apparatus10will be described.

In the vehicle1, as shown in Table 1 below, for example, seven operating modes are set as charge and discharge operations of the capacitor11and the battery12based on the driving of the vehicle1.

TABLE 1Operating modeOperating detailM1: initial startStarter ONM2: I/S readiness chargeCharge to capacitor in preparation for I/SM3: regeneration chargeCharge to capacitor during regenerationM4: regeneration dischargeDischarge regenerative power and halt ACGM5: I/S supply of powerDischarge from capacitor to electric load(capacitor)during I/SM6: I/S supply of powerSupply of power from battery to electric loadM7: ENG restartDischarge from capacitor and restart

First, an operating mode M1of initial start is an operating mode in which the internal combustion engine22is started by a start request based on a signal which is output from the ignition switch. In this mode, the supply of power to the starter motor20through the starter magnet switch18is started by the “On” operation of the starter relay19, and the internal combustion engine22is started by a driving force of the starter motor20.

In this case, it is likely that power required for the start of the internal combustion engine22will not be able to be supplied, for example, due to a drop in the remaining capacity SOC of the capacitor11to less than a predetermined value, or a drop in the temperature of the capacitor11to less than a predetermined temperature.

For this reason, the contactor15is set to be in a connection state by the “On” operation of the contactor relay16, and the capacitor11and the battery12are connected in parallel with the starter magnet switch18and the starter motor20which are connected in series with each other. The starter motor20is then driven by the supply of power from the capacitor11and the battery12.

In addition, in the initial start, for example, as at time t1shown inFIG. 2, the terminal voltage (equivalent to, for example, a potential of a terminal on a positive electrode side with respect to a grounded terminal on a negative electrode side) of the capacitor11and the remaining capacity SOC drop due to the supply of power from the capacitor11to the starter motor20.

Next, an operating mode M2of I/S readiness charge is an operating mode in which power required for the restart of the internal combustion engine22is charged to the capacitor11in preparation for the execution of an idle stop. In this mode, for example, capacitor11is charged by supplying generative power, which is output from the generator21that generates power by motive power of the internal combustion engine22in an operating state, from the DC-DC converter13to the capacitor11.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and, for example, as in the period from time t1to time t2shown inFIG. 2, the capacitor11is charged until at least the terminal voltage of the capacitor11reaches a predetermined I/S readiness potential.

In addition, the predetermined US readiness potential is, for example, a terminal voltage corresponding to the remaining capacity SOC capable of executing the required supply of power to the electric load23or the like in a temporary stop state of the internal combustion engine22over a predetermined period of time due to an idle stop.

In addition, in the period from time t1to time t2shown inFIG. 2, for example, the vehicle1maintains constant speed running after the vehicle is accelerated up to a predetermined vehicle speed by motive power of the internal combustion engine22.

Next, an operating mode M3of regeneration charge is an operating mode in which regenerative power which is output from the generator21during the deceleration of the vehicle1or the like is charged to the capacitor11. In this mode, for example, the capacitor11is charged by supplying regenerative power, obtained by converting kinetic energy of a car body transmitted from driving wheels into electric energy (regenerative energy), through the DC-DC converter13to the capacitor11.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and, for example, as in the period from time t3to time t4shown inFIG. 2, the capacitor11is charged in a range in which at least the terminal voltage of the capacitor11becomes a predetermined upper limit potential or less.

In addition, the predetermined upper limit potential is, for example, a terminal voltage corresponding to a full charge state (that is, remaining capacity SOC=100%).

Next, an operating mode M4of regeneration discharge is an operating mode in which the capacitor11is discharged by supplying power, electrically accumulated in the capacitor11during constant speed running of the vehicle1, or the like, to the electric load23. In this mode, for example, the capacitor11is discharged by supplying regenerative power, electrically accumulated in excess of a predetermined I/S readiness potential, through the DC-DC converter13to the electric load23.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and, for example, as in the period from time t4to time t5shown inFIG. 2, the capacitor11is discharged while halting the generation and regeneration of the generator21until at least the terminal voltage of the capacitor11reaches the predetermined I/S readiness potential.

Next, an operating mode M5of I/S supply of power (capacitor) is an operating mode in which the capacitor11is discharged by supplying power, electrically accumulated in the capacitor11in a temporary stop state of the internal combustion engine22due to an idle stop of the vehicle1, to the electric load23. In this mode, for example, the capacitor11is discharged by supplying the power electrically accumulated in the capacitor11through the DC-DC converter13to the electric load23while securing power required for restarting the internal combustion engine22based on a return request.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and, for example, as in the period from time t6to time t7shown inFIG. 2, the capacitor11is discharged until at least the terminal voltage of the capacitor11reaches a predetermined VS lower limit potential.

In addition, the predetermined I/S lower limit potential is, for example, a terminal voltage corresponding to the remaining capacity SOC which is capable of executing an adequate supply of power required for restarting the internal combustion engine22in a temporary stop state by a driving force of the starter motor20.

In addition, the adequate supply of power by the capacitor11means that the capacitor11is discharged so that the terminal voltage of the capacitor11does not drops to less than a predetermined minimum security potential.

Next, an operating mode M6of I/S supply of power (BATT) is an operating mode in which the battery12is discharged by supplying power, electrically accumulated in the battery12in a temporary stop state of the internal combustion engine22due to an idle stop of the vehicle1, to the electric load23. In this mode, for example, discharge from the capacitor11in which minimum power required for restarting the internal combustion engine22based on a return request is secured is prohibited.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and, for example, as in the period from time t7to time t8shown inFIG. 2, the discharge of the capacitor11is prohibited so that at least the terminal voltage of the capacitor11maintains the predetermined I/S lower limit potential.

An operating mode M7of ENG restart is an operating mode in which the internal combustion engine22is restarted based on a return request from a temporary stop state of an idle stop. The supply of power to the starter motor20through the starter magnet switch18is started by the “On” operation of the starter relay19, and the internal combustion engine22is restarted by a driving force of the starter motor20.

In this case, the contactor15is set to be in a cut-off state by the “Off” operation of the contactor relay16, and the starter motor20is driven by the supply of power only from the capacitor11connected in parallel with the starter magnet switch18and the starter motor20which are connected in series with each other.

In this restart operation, for example, as at time t8shown inFIG. 2, the terminal voltage and the remaining capacity SOC of the capacitor11drop due to the supply of power from the capacitor11to the starter motor20, but the terminal voltage is set so as not to drop to less than the predetermined minimum security potential.

After the restart of the internal combustion engine22, for example, like that after time t8shown inFIG. 2, the above-mentioned operating mode M2of I/S readiness charge is executed, and the vehicle1is accelerated by motive power of the internal combustion engine22.

Incidentally, the above-mentioned predetermined I/S lower limit potential changes according to the state (for example, the internal resistance, the degree of degradation and the like depending on temperature) of the capacitor11.

For this reason, for example, as shown inFIG. 3, the controller14detects the internal resistance of the capacitor11, and updates the I/S lower limit potential based on the detection result.

The controller14detects the internal resistance of the capacitor11, for example, using the difference between the terminal voltage and the open circuit voltage of the capacitor11during the execution of a discharge phase in which the capacitor11is discharged, and the discharge current of the capacitor11during the execution of the discharge phase.

For example, referring to data or the like indicating a predetermined correspondence relationship between the internal resistance and the I/S lower limit potential which are stored in advance, the I/S lower limit potential based on the detected internal resistance is acquired, a current I/S lower limit potential is updated by the newly acquired I/S lower limit potential, and an updated result thereof is maintained until the next update.

First, for example, in the initial start of the internal combustion engine22concomitant with the “On” operation of the ignition switch (IGON) at time t1shown inFIG. 3, the controller14sets a predetermined lower limit potential initial value as the VS lower limit potential.

The lower limit potential initial value may be, for example, a value based on the temperature, the internal resistance, the degree of degradation and the like of the capacitor11ascertained at this point in time, and may be a predetermined fixed value. For example, when the internal resistance is high due to the low temperature of the capacitor11, the predetermined lower limit potential initial value becomes a high value in order to secure power required for starting the internal combustion engine22.

After time t2ofFIG. 3at which the discharge (for example, operating mode M4of regeneration discharge) of the capacitor11is started after the start of the internal combustion engine22, the controller14detects the terminal voltage and the discharge current of the capacitor11over a predetermined time. The internal resistance of the capacitor11is then detected based on a detection result thereof, and the I/S lower limit potential based on the detected internal resistance is acquired. For example, as shown in time t3ofFIG. 3, a current I/S lower limit potential is updated by the newly acquired I/S lower limit potential.

After time t4ofFIG. 3, for example, at which the execution of an idle stop and the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)) are started after the I/S lower limit potential is updated, the controller14detects the terminal voltage and the discharge current of the capacitor11over a predetermined time. The internal resistance of the capacitor11is then detected based on a detection result thereof, and the I/S lower limit potential based on the detected internal resistance is acquired. For example, as shown at time t5ofFIG. 3, a current I/S lower limit potential is updated by the newly acquired I/S lower limit potential.

After time t5ofFIG. 3at which the terminal voltage of the capacitor11reaches the I/S lower limit potential along with the continuation of the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)) during the execution of an idle stop after the update of the I/S lower limit potential, the controller14stops the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)), and starts the discharge of the battery12(for example, operating mode M6of I/S supply of power (BATT)).

For example, after time t8ofFIG. 3at which the discharge of the capacitor11(for example, operating mode M4of regeneration discharge) is started after the internal combustion engine22is automatically restarted based on a return request at time t7ofFIG. 3, the controller14detects the terminal voltage and the discharge current of the capacitor11over a predetermined time. The internal resistance of the capacitor11is then detected based on a detection result thereof, and the I/S lower limit potential based on the detected internal resistance is acquired. For example, as shown at time t9ofFIG. 3, a current I/S lower limit potential is updated by the newly acquired I/S lower limit potential.

After time t10ofFIG. 3, for example, at which the execution of an idle stop and the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)) are started after the I/S lower limit potential is updated, the controller14detects the terminal voltage and the discharge current of the capacitor11over a predetermined time. The internal resistance of the capacitor11is then detected based on a detection result thereof, and the I/S lower limit potential based on the detected internal resistance is acquired. For example, as shown at time t11ofFIG. 3, a current I/S lower limit potential is updated by the newly acquired I/S lower limit potential.

After time t12ofFIG. 3at which the terminal voltage of the capacitor11reaches the I/S lower limit potential along with the continuation of the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)) during the execution of an idle stop after the update of the I/S lower limit potential, the controller14stops the discharge of the capacitor11(for example, operating mode M5of I/S supply of power (capacitor)) and starts the discharge of the battery12(for example, operating mode M6of I/S supply of power (BATT)).

After the internal combustion engine22is automatically restarted based on a return request, for example, at time t13ofFIG. 3, and the internal combustion engine22is stopped along with the “Off” operation of the ignition switch (IGOFF) at time t14shown inFIG. 3, and further after time t15ofFIG. 3at which the discharge of the capacitor11is started, the controller14continuously detects the terminal voltage and the discharge current of the capacitor11. The internal resistance of the capacitor11is then detected based on a detection result thereof, and the degree of degradation of the capacitor11is determined based on the detected internal resistance.

For example, as shown inFIG. 3, when the internal resistance drops due to a rise in the temperature of the capacitor11after the start of the internal combustion engine22, the I/S lower limit potential is updated to a lower value, and the duration time (that is, time required for the terminal voltage of the capacitor11to drop from the predetermined I/S readiness potential to the I/S lower limit potential) of the discharge of the capacitor11(that is, operating mode M5of I/S supply of power (capacitor)) during the execution of an idle stop lengthens.

Therefore, for example, when the internal resistance of the capacitor11increases, the duration time of the discharge of the battery12(that is, operating mode M6of I/S supply of power (BATT)) lengthens within the period of duration of an idle stop over a predetermined time.

Thereby, for example, when the execution permission of an idle stop is output in a case where the internal resistance of the capacitor11is determined to be less than a predetermined value, the controller14supplies power from the battery12to the electric load23with a normal predetermined depth of discharge.

On the other hand, for example, when the execution permission of an idle stop is output in a case where the internal resistance of the capacitor11is determined to be a predetermined value or more, the controller supplies power from the battery12to the electric load23with a smaller depth of discharge than the normal predetermined depth of discharge.

In addition, for example, when the internal resistance of the capacitor11is determined to be a predetermined value or more, the controller14makes the supply of power from the capacitor11to the electric load23smaller than when the internal resistance of the capacitor11is determined to be less than the predetermined value.

In addition, when the internal resistance of the capacitor11is determined to be a predetermined value or more, the controller14delays the execution start of the next discharge phase for a predetermined time (predetermined standby time).

For example, as shown inFIG. 4, only when the execution of a discharge phase is started within a predetermined time after the execution of a charge phase is terminated in a case where the discharge phase is executed subsequent to the execution of the charge phase in which the capacitor11is charged, the controller14delays the execution start of the discharge phase for a predetermined time.

For example, when the internal resistance of the capacitor11is determined to be a predetermined value or more in a case where the execution start of the discharge phase is scheduled within a predetermined time after the execution of the charge phase at time t1shown inFIG. 4is stopped, the controller14delays the execution start of the discharge phase for a predetermined standby time.

In this standby time, since the charge and discharge of the capacitor11is stopped, the open circuit voltage of the capacitor11becomes a predetermined constant value, whereas the terminal voltage of the capacitor11changes so as to converge toward the open circuit voltage. Thus, the difference between the terminal voltage and the open circuit voltage of the capacitor11decreases.

Thereby, for example, when the execution of the discharge phase is started at time t3when the predetermined standby time elapses from time t1ofFIG. 4at which the execution of the charge phase is stopped, the controller14sets a terminal voltage V0of the capacitor11, detected at time t2immediately before the execution start of the discharge phase, to the open circuit voltage of the capacitor11.

The internal resistance of the capacitor11is detected using the difference between (that is, voltage drop ΔV(t)) between the terminal voltage of the capacitor11detected at an appropriate timing t during the execution of the discharge phase executed after time t3ofFIG. 4and the open circuit voltage (that is, terminal voltage V0) of the capacitor11detected in the standby time, and the discharge current of the capacitor11during the execution of the discharge phase.

In addition, for example, as shown inFIG. 5, the controller14increases the standby time for the execution start of the next discharge phase with an increase in the detected internal resistance of the capacitor11, based on an increase in the standby time of ta to te (that is, time required for the terminal voltage to be stabilized by causing the terminal voltage to converge toward the open circuit voltage when the charge and discharge of the capacitor11are stopped) required for the detection value of the internal resistance to stably converge, in addition to an increase in the internal resistance of the capacitor11with a decrease in the temperature of the capacitor11.

In addition, for example, the controller14prohibits the execution start of the discharge phase from being delayed for a predetermined time until the internal resistance of the capacitor11is determined to be a predetermined value or more.

For example, as shown inFIG. 6, when the detection value of the internal resistance is less than a predetermined value as in the initial state where the degradation of the capacitor11is not present, at the ordinary temperature of the capacitor11, or the like, the controller14prohibits (prohibits standby) the execution start of the discharge phase from being delayed for a predetermined time.

When the detection value of the internal resistance becomes a predetermined value or more in a state where standby prohibition is executed with an increase in the internal resistance due to the lengthening of the period of use of the capacitor11, for example, like that after the elapse of a period of use T1shown inFIG. 6, the controller14starts (starts standby) delaying the execution start of the next discharge phase for a predetermined time.

Even when the detection value of the internal resistance becomes less than the predetermined value along with the execution of the standby start, for example, like that after the elapse of a period of use T2shown inFIG. 6, the controller14continues the execution of the standby start.

In addition, the controller14prohibits the update of the I/S lower limit potential based on the internal resistance, for example, until the detection value of the internal resistance becomes the predetermined value or more in a state where the standby start is executed, and may execute the update of the I/S lower limit potential based on the internal resistance when the detection value of the internal resistance becomes the predetermined value or more in a state where the standby start is executed, for example, like that after the elapse of a period of use T3shown inFIG. 6.

As mentioned above, according to the power supply degradation determination apparatus10of the present embodiment, when the internal resistance of the capacitor11is determined to be the predetermined value or more, the execution start of the next discharge phase is delayed for the predetermined time, thereby allowing the internal resistance to be detected with a high level of accuracy in a state where the terminal voltage of the capacitor11is stable.

Furthermore, since the internal resistance is detected by delaying the execution start of the discharge phase, regenerative energy of the vehicle1capable of being recovered as electric energy is prevented from being reduced, for example, as compared to the case where the internal resistance is detected by delaying the execution start of the charge phase, and thus the fuel efficiency of the vehicle1can be prevented from dropping.

Further, in a state where switching from the charge phase to the discharge phase is performed, the difference between the terminal voltage and the open circuit voltage of the capacitor11is large, and the time required for the terminal voltage to stabilize lengthens. Thereby, the internal resistance is easily detected as a higher value than in reality in addition to an increase in a detection error of the internal resistance, and thus the degradation of the capacitor11can be determined early.

On the other hand, the execution start of the discharge phase is delayed for at least the predetermined time, and standby is performed until the terminal voltage stabilizes so that the difference between the terminal voltage and the open circuit voltage of the capacitor11is made to be small, thereby allowing the detection accuracy of the internal resistance to be improved.

Further, since the standby time for the execution start of the next discharge phase is increased with an increase in the internal resistance of the capacitor11, the execution start of the discharge phase is prevented from being excessively delayed when the internal resistance is small. Thereby, it is possible to secure a desired supply of power to the electric load23and the like and to prevent the detection accuracy of the internal resistance from dropping when the internal resistance is large.

Further, since the execution of standby that delaying the execution start of the discharge phase for at least a predetermined time is prohibited until the internal resistance of the capacitor11is determined to be a predetermined value or more, the execution of standby is omitted with respect to the capacitor11in a low temperature state, for example, during the start of the vehicle1, or the like. Thereby, it is possible to early perform the execution start of the discharge phase and the determination of the internal resistance, and to prevent the execution start of the discharge phase and the determination of the internal resistance from being delayed unnecessarily.

Further, the depth of discharge of the battery12is reduced with an increase in the internal resistance of the capacitor11, thereby allowing the battery12to be prevented from being degraded.

Further, since the supply of power from the capacitor11to the electric load23is made to be smaller when the internal resistance of the capacitor11is determined to be a predetermined value or more, than when the internal resistance thereof is determined to be less than the predetermined value, it is possible to secure the supply of power to the electric load23over a desired idle stop time.

In addition, in the above-mentioned embodiment, the controller14may make a predetermined time (predetermined standby time) when the discharge phase is executed subsequent to the execution of the discharge phase, for example, longer than a predetermined time (predetermined standby time) when the discharge phase is executed subsequent to the execution of the charge phase.

For example, as shown inFIG. 7A, in a case where the discharge phase is executed subsequent to the execution of the charge phase before time t1, an error occurs in which a voltage drop ΔVA(t) (that is, difference between the open circuit voltage and the terminal voltage) when the discharge is started after the elapse (for example, at time t2) of a short standby time TA becomes higher than a voltage drop ΔVB(t) when the discharge is started after the elapse (for example, at time t3) of a sufficiently long standby time TB.

For this reason, when the discharge is started before the sufficiently long standby time TB elapses, the internal resistance is easily detected as a higher value than in reality, and thus the degradation of the capacitor11can be determined early.

On the other hand, for example, as shown inFIG. 7B, in a case where the discharge phase is executed subsequent to the execution of the discharge phase before time t1, an error occurs in which the voltage drop ΔVA(t) (that is, difference between the open circuit voltage and the terminal voltage) when the discharge is started after the elapse (for example, at time t2) of the short standby time TA becomes lower than the voltage drop ΔVB(t) when the discharge is started after the elapse (for example, at time t3) of the sufficiently long standby time TB.

For this reason, when the discharge is started before the sufficiently long standby time TB elapses, the internal resistance is easily detected as a lower value than in reality, and thus it is difficult to determine the degradation of the capacitor11.

Therefore, when the discharge phase is executed subsequent to the execution of the discharge phase, the degradation of the capacitor11is prevented from not being detected by making the predetermined time required for standby longer than when the discharge phase is executed subsequent to the execution of the charge phase, and thus the degradation of the capacitor11can be determined accurately.

In addition, in the above-mentioned embodiment, the controller14may supply power from the capacitor11to the electric load23, for example, during the execution of the discharge phase, and may supply power from the battery12to the electric load23with the depth of discharge smaller than the predetermined depth of discharge when the capacitor11is determined to be degraded in a state where standby prohibition is not executed.

In addition, in the above-mentioned embodiment, for example, the controller14may determine that the capacitor11is degraded when the internal resistance is the predetermined value or more.

In addition, in the above-mentioned embodiment, for example, only when the execution of the discharge phase is started within the predetermined time after the execution of the charge phase is terminated in a case where the discharge phase is executed subsequent to the execution of the charge phase, the controller14detects the internal resistance of the capacitor11using the difference between the terminal voltage and the open circuit voltage of the capacitor11during the execution of the discharge phase and the discharge current of the capacitor11during the execution of the discharge phase, and may determine whether the internal resistance is the predetermined value or more.

In this case, in a state where switching from the charge phase to the discharge phase is performed, the difference between the terminal voltage and the open circuit voltage of the capacitor11is large, and the time required for the terminal voltage to stabilize lengthens. Thereby, the internal resistance is easily detected as a higher value than in reality in addition to an increase in a detection error of the internal resistance, and thus the degradation of the capacitor11can be determined early.

In addition, in the above-mentioned embodiment, for example, when an instruction is given to prohibit the execution of the idle stop of the vehicle1based on the operation or the like of a driver, or when the idle stop is not able to be executed due to an abnormality of an idle stop function of the vehicle1, or the like, the controller14may not execute a process of delaying the execution start of the discharge phase for the predetermined time in order to detect the internal resistance of the capacitor11.

In addition, in the above-mentioned embodiment, when the power supply degradation determination apparatus10includes, for example, a notification apparatus using a display or a sound output, and the controller14determines that the capacitor11is degraded, notification for promoting the replacement of the capacitor11may be performed by the notification apparatus together with the determination result.