JP2012077714A - Failure detection device for voltage supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure detection device capable of determining failure of a voltage supply device more accurately.SOLUTION: A vehicle 10 includes: an idle stop ECU62 for automatically stopping an engine 20 and automatically restarting the engine 20 by a starter 21; a DC-DC converter 30 for raising a voltage supplied from a battery 23 on an automatic restart of the engine 20 by a step-up circuit 50; and an engine ECU for causing a fixed voltage to be supplied by an alternator 22 during execution of a fuel-cut of the engine 20. The converter 30 has a diode for lowering a voltage supplied from the alternator 22 to an electrical load 60 by a predetermined voltage. The ECU62, when a fixed voltage is supplied by the alternator 22, raises the voltage supplied from the alternator 22 by the step-up circuit 50, and on the basis of comparison between the voltage supplied from the alternator 22 and the voltage raised by the step-up circuit 50, determines failure of the converter 30.

Description

  The present invention relates to a voltage supply device that is applied to a vehicle that performs automatic stop and automatic restart of an engine and increases a voltage supplied to an electric load when the engine is automatically restarted.

  Conventionally, in this type of device, when the battery voltage drops below a set value during automatic restart of the engine, there is one that raises the voltage supplied to the electric load by a voltage compensation circuit (see, for example, Patent Document 1).

  Further, in the same device, there is a device that checks the boosting operation of the voltage supply device in response to the establishment of the automatic engine stop condition and prohibits the automatic engine stop if the boosting operation is abnormal. (For example, refer to Patent Document 2).

  In the one described in Patent Document 2, when the automatic engine stop condition is satisfied, a voltage drop corresponding to the forward voltage of the diode is generated between the input voltage and the output voltage of the voltage supply device, and the input voltage at that time And the output voltage are detected. Thereafter, the boosting operation is performed so that the voltage drop is compensated, and it is determined whether the boosting operation is normally performed based on the difference between the input voltage and the output voltage detected at that time. Specifically, if the difference between the detected input voltage and output voltage is less than or equal to a predetermined determination value, it is determined that the boost operation is being performed normally, and if it exceeds the predetermined determination value, the boost operation is performed. Is determined to be abnormal.

JP 2002-38984 A JP 2007-56728 A

  By the way, the input voltage of the voltage supply device always changes depending on the battery voltage at that time, the power generation state of the in-vehicle generator, and the like. For this reason, in the thing of the said patent document 2, the difference of the detected input voltage and output voltage will always change, and there exists a possibility that it cannot be determined correctly whether a pressure | voltage rise operation is normal.

  The present invention has been made in view of such circumstances, and a main object thereof is to provide a failure detection device that can more accurately determine a failure of a voltage supply device.

  The present invention employs the following means in order to solve the above problems.

  The invention according to claim 1 is an engine, a battery that can be charged and discharged, an electric load, a starter driven by a voltage supplied from the battery, and an automatic stop based on a predetermined condition. And an automatic stop / restart means for automatically restarting the engine by the starter, and a voltage supply circuit for increasing the supplied voltage and supplying the increased voltage to the electric load. A voltage supply device that raises the voltage supplied from the battery at the time of automatic restart by the voltage supply circuit; a generator that generates power by the driving force of the engine and supplies the voltage to the battery and the voltage supply device; Fuel cut means for performing fuel cut of the engine when the condition is satisfied, and the power generation state of the generator is controlled to control the fuel cut. Power generation control means for supplying a constant voltage by the generator during fuel cut by the means, and a voltage for dropping a voltage supplied from the battery and the generator to the electric load via the voltage supply device by a predetermined voltage A failure detection device for detecting a failure of the voltage supply device, applied to a vehicle equipped with a descent means, wherein when the power generation control means supplies the constant voltage by the generator, from the generator The supplied voltage is raised by the voltage supply circuit, and a failure of the voltage supply device is detected based on a comparison between the voltage supplied from the generator and the voltage raised by the voltage supply circuit. And

  According to the above configuration, the engine is automatically stopped and the engine is automatically restarted by the starter based on the predetermined condition. At this time, since the starter is driven by the voltage supplied from the battery, the voltage supplied from the battery to the electric load other than the starter decreases. On the other hand, when the engine is automatically restarted, the voltage supplied from the battery is raised by the voltage supply circuit, and the raised voltage is supplied to the electric load.

  Further, power is generated by the generator by the driving force of the engine, and the voltage is supplied to the battery and the voltage supply device. The engine fuel cut is executed when a predetermined condition is satisfied, and a constant voltage is supplied by the generator during the fuel cut. Thereby, power generation is performed without consuming fuel, and the battery is charged, so that the fuel efficiency of the engine can be improved.

  The constant voltage supplied from the generator to the electric load via the voltage supply device during the fuel cut is dropped by a predetermined voltage by the voltage drop means. In the failure detection of the voltage supply device, when a constant voltage is supplied from the generator, the voltage supplied from the generator is raised by the voltage supply circuit. For this reason, the failure of the voltage supply device can be detected by comparing the voltage supplied from the generator with the voltage raised by the voltage supply circuit.

  For example, when there is a difference between the voltage supplied from the generator and the voltage raised by the voltage supply circuit that corresponds to a predetermined voltage dropped by the voltage drop means, the voltage supplied to the electric load is the voltage It is not raised by the supply circuit, and it can be detected that the voltage supply device has failed. On the other hand, if there is almost no difference between the voltage supplied from the generator and the voltage raised by the voltage supply circuit, or if there is a difference smaller than the predetermined voltage dropped by the voltage drop means, The supplied voltage is raised by the voltage supply circuit, and it can be detected that the voltage supply device is operating normally.

  Here, the comparison between the voltage supplied from the generator and the voltage raised by the voltage supply circuit is performed when a constant voltage is supplied by the generator. Therefore, regardless of the voltage supplied from the battery at that time, the voltage can be compared in a state where a constant voltage is supplied to the voltage supply device. As a result, the failure of the voltage supply device can be detected more accurately.

  According to a second aspect of the present invention, as a change from the first aspect of the present invention, when the power generation control means supplies the constant voltage by the power generator, the power is supplied from the power generator. Comparison between the voltage supplied to the electric load before the voltage is raised by the voltage supply circuit and the voltage supplied to the electric load after the voltage supplied from the generator is raised by the voltage supply circuit Based on the above, a failure of the voltage supply device is detected.

  For example, if there is almost no difference between the voltage supplied to the electric load before the voltage is raised by the voltage supply circuit and the voltage supplied to the electric load after the voltage is raised by the voltage supply circuit, the electric load It can be detected that the voltage supply device is not raised by the voltage supply circuit and the voltage supply device is out of order. On the other hand, if the voltage supplied to the electric load after the voltage is raised by the voltage supply circuit is higher than the voltage supplied to the electric load before the voltage is raised by the voltage supply circuit, the voltage is supplied to the electric load. The voltage is raised by the voltage supply circuit, and it can be detected that the voltage supply device is operating normally.

  Here, a comparison between the voltage supplied to the electric load before the voltage is raised by the voltage supply circuit and the voltage supplied to the electric load after the voltage is raised by the voltage supply circuit is a constant voltage by the generator. Performed when supplied. Therefore, the voltage can be compared in a state where a constant voltage is supplied to the voltage supply device regardless of the voltage supplied from the battery at that time. As a result, the failure of the voltage supply device can be detected more accurately.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the automatic stop / restart means is configured so that the speed of the vehicle is lower than a determination speed in the process of decreasing the speed of the vehicle. As a condition, the engine is automatically stopped, and the fuel cut means executes the fuel cut until the rotational speed of the engine becomes a predetermined rotational speed or less in the process of decreasing the speed of the vehicle. Yes, the power generation control means supplies the constant voltage by the generator, and the failure of the voltage supply device is detected during execution of the fuel cut immediately before the vehicle speed drops to the determination speed. To do.

  According to the above configuration, the engine is automatically stopped on the condition that the vehicle speed is lower than the determination speed in the process of decreasing the vehicle speed. For this reason, even when the vehicle speed is not zero, the engine is automatically stopped when the vehicle speed is lower than the determination speed. Further, in the fuel cut of the engine, the fuel cut is executed until the rotational speed of the engine becomes equal to or lower than a predetermined rotational speed in the process of decreasing the speed of the vehicle. During the fuel cut of the engine, a constant voltage is supplied by the generator.

  Here, when the voltage supply device breaks down, the voltage supplied to the electric load cannot be increased at the time of automatic engine start, which may cause inconvenience in the operation of the electric load. Therefore, it is necessary to detect a failure of the voltage supply device before automatically stopping the engine, and to prohibit the automatic stop of the engine when a failure is detected. However, when the period from the detection of the failure of the voltage supply device to the operation of the voltage supply device is long, it is difficult to ensure reliability during operation of the voltage supply device.

  In this regard, according to the above configuration, a constant voltage is supplied by the generator, and during the fuel cut immediately before the vehicle speed is reduced to the determination speed, that is, immediately before the condition for automatically stopping the engine is established. A failure of the voltage supply device is detected. For this reason, it is possible to detect a failure of the voltage supply device before the engine is automatically stopped, and to shorten the period from the detection of the failure to the operation of the voltage supply device. As a result, the reliability of the operation of the voltage supply device can be improved. Furthermore, since the failure of the voltage supply device is detected immediately before the condition for automatically stopping the engine is established, the engine is automatically compared with the configuration for detecting the failure of the voltage supply device after the condition for automatically stopping the engine is established. It can suppress that the time to stop is delayed. Therefore, it is possible to suppress the period during which the engine is stopped from being shortened, and it is possible to suppress deterioration of the fuel consumption of the engine.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the power generation control means can supply the electric load during the fuel cut by the fuel cut means. The maximum constant voltage is supplied by the generator.

  According to the above configuration, since the maximum constant voltage that can be supplied to the electric load is supplied by the generator during the fuel cut, the amount of power generation can be increased to the maximum, and the fuel consumption of the engine is further improved. be able to. At this time, the constant voltage supplied from the generator to the electric load via the voltage supply device during execution of the fuel cut is dropped by a predetermined voltage by the voltage drop means. Therefore, even when the maximum constant voltage that can be supplied to the electric load is supplied by the generator, the voltage supplied from the generator can be raised by the voltage supply circuit. As a result, the failure of the voltage supply device can be detected in the same manner as in the first and second aspects of the invention.

The block diagram which shows a DC-DC converter and its periphery structure. The electric circuit diagram which shows the electric constitution of a DC-DC converter. The time chart which shows the aspect of charge control during fuel cut. The flowchart which shows the process sequence of failure detection control of a DC-DC converter. The time chart which shows the aspect of the failure detection control of a DC-DC converter. The flowchart which shows the process sequence about the modification of failure detection control of a DC-DC converter.

  Hereinafter, an embodiment will be described with reference to the drawings. The present embodiment is applied to a vehicle that automatically stops and restarts an engine even in a running state, and is specifically used as a failure detection device that detects a failure of a DC-DC converter that raises a voltage supplied from a battery. It has become.

  FIG. 1 is a block diagram showing a DC-DC converter and its peripheral configuration. As shown in the figure, a vehicle 10 includes an engine 20, a starter 21, an alternator 22, a battery 23, various sensors 25 to 28, a DC-DC converter 30, various electric loads 60, and an engine ECU (Electric Control Unit) 61. And an idle stop ECU 62.

  The engine 20 is a multi-cylinder gasoline engine, and includes an EFI (Electronic Fuel Injection) unit 20a, a spark plug, and the like. The battery 23 is a lead storage battery that can be charged and discharged.

  The EFI unit 20 a, starter 21, alternator 22, and DC-DC converter 30 are connected to the voltage input / output line of the battery 23. Engine ECU 61, idle stop ECU, and various electric loads 60 are connected to a voltage output line of DC-DC converter 30.

  The EFI unit 20 a injects fuel for each cylinder of the engine 20. The spark plug ignites the injected fuel for each cylinder of the engine 20. As a result, a driving force is generated in the engine 20.

  The starter 21 is driven by the power supply voltage VB supplied from the battery 23 and rotates the engine 20 when the engine 20 is started. When the engine 20 is automatically restarted, the starter 21 is driven based on the start signal START from the idle stop ECU 62.

  An alternator 22 (generator) generates a magnetic field in a built-in rotor based on a power supply voltage VB supplied from a battery 23, and rotates the rotor by the driving force of the engine 20, and a stator provided around the rotor. Generate AC voltage. Further, the alternator 22 rectifies the generated AC voltage with a built-in diode and converts it into a DC voltage. The alternator 22 supplies the converted DC voltage (generated voltage VG) to the DC-DC converter 30 and supplies the generated voltage VG to the battery 23 to charge the battery 23. The alternator 22 changes the magnitude of the generated voltage VG to be generated by changing the voltage supplied to the built-in rotor.

  The DC-DC converter 30 (voltage supply device) raises the supplied voltage (input voltage VIN) and sends the raised voltage (output voltage VOUT) to the engine ECU 61, the idle stop ECU 62, and various electric loads 60. A booster circuit 50 is provided. That is, the power supply voltage VB supplied from the battery 23 and the power generation voltage VG supplied from the alternator 22 are supplied to the engine ECU 61, the idle stop ECU 62, and various electric loads 60 via the DC-DC converter 30.

  The engine ECU 61 is an electronic control device including a known microcomputer or the like. Based on the detection results of the engine ECU 61 and various sensors 25 to 28, various engine controls such as fuel injection amount control by the EFI unit 20a, ignition control by the spark plug, and control of the power generation state by the alternator 22 are executed. The engine ECU 61 (power generation control means) transmits a power generation signal GEN to the alternator 22 to control the voltage supplied to the rotor built in the alternator 22 and to control the magnitude of the power generation voltage VG generated by the alternator 22. For details on the sensors, the engine ECU 61 includes an accelerator sensor 25 that detects the amount of depression of the accelerator pedal, a brake sensor 26 that detects the amount of depression of the brake pedal, a vehicle speed sensor 27 that detects the speed of the vehicle 10, and the engine 20. A rotation speed sensor 28 and the like for detecting the rotation speed are connected, and detection signals of these sensors are sequentially input to the engine ECU 61.

  The idle stop ECU 62 is an electronic control device including a known microcomputer or the like. When a predetermined automatic stop condition is satisfied during operation of the engine 20, the idle stop ECU 62 (automatic stop / restart means) transmits an engine stop signal EST to the EFI unit 20a to automatically stop the engine 20. Thereafter, when a predetermined automatic restart condition is satisfied, the idle stop ECU 62 transmits a start signal START to the starter 21 to automatically restart the engine 20. The idle stop ECU 62 and the engine ECU 61 are connected, and communication is performed between them.

  The automatic stop condition of the engine 20 includes, for example, at least one of the operation of depressing the brake pedal and the vehicle speed being lower than a predetermined engine stop vehicle speed (determination speed). The automatic restart condition of the engine 20 includes, for example, at least one of the fact that the brake pedal is not depressed and the accelerator pedal is depressed when the engine is stopped. . Such idle stop control is performed even when the speed of the vehicle 10 decreases, that is, even when the vehicle 10 is in a traveling state (a state where the vehicle speed is higher than 0).

  When the engine 20 is started by the starter 21, the voltage supplied from the battery 23 to the engine ECU 61, the idle stop ECU, and various electric loads 60 is raised by the DC-DC converter 30. For this reason, when the engine 20 is started, the voltage supplied from the battery 23 to the electric load other than the starter 21 can be suppressed from decreasing.

  FIG. 2 is an electric circuit diagram showing an electrical configuration of the DC-DC converter 30. As shown in the figure, the DC-DC converter 30 includes a booster circuit 50, voltage detection sensors 56 and 57, a CPU 38, and the like.

  The boost signal DDON of the idle stop ECU 62 is input to the CPU 38 through the boost signal input terminal 33. The CPU 38 is connected to the idle stop ECU 62, and communication is performed between the CPU 38 and the idle stop ECU 62.

  The booster circuit 50 (voltage supply circuit) includes capacitors 51 and 55, a coil 52, and output control relays 53 and 54.

  One electrode of the capacitor 51 is connected to the voltage input terminal 31 and the other electrode is grounded. One end of the coil 52 is connected to the voltage input terminal 31. The output control relay 53 includes a MOS transistor 53a and a diode 53b, and the output control relay 54 includes a MOS transistor 54a and a diode 54b. The other end of the coil 52 is connected to a portion between the drain of the MOS transistor 53a and the source of the MOS transistor 54a. A diode 53b that flows current from the source to the drain is connected to a portion between the source and drain of the MOS transistor 53a. A diode 54b that allows current to flow from the source to the drain is connected to a portion between the source and drain of the MOS transistor 54a.

  The source of the MOS transistor 53 a is grounded, and the drain of the MOS transistor 54 a is connected to the voltage output terminal 32.

  The booster circuit 50 boosts the voltage (input voltage VIN) supplied from the voltage input terminal 31 and supplies the boosted voltage (output voltage VOUT) to the voltage output terminal 32.

  The CPU 38 is connected to the gate of the MOS transistor 53a. The gate of the MOS transistor 54a is open. A signal PWM for switching control of the MOS transistor 53a is input from the CPU 38 to the gate of the MOS transistor 53a. The CPU 38 controls the gate potential so that the MOS transistor 53a is turned on / off according to the signal PWM. As a result, the input voltage VIN is boosted according to the period during which the MOS transistor 53 a is turned on by the signal PWM and is supplied to the output control relay 54.

  Since the gate of the MOS transistor 54a is open, the MOS transistor 54a is always off. For this reason, the voltage supplied to the output control relay 54 is lowered by the voltage corresponding to the forward voltage of the diode 54 b by the diode 54 b (voltage drop means) of the output control relay 54. At this time, the capacitor 55 smoothes the voltage supplied via the diode 54b, and supplies the smoothed voltage to the voltage output terminal 32 as the output voltage VOUT.

  The voltage detection sensor 56 detects the input voltage VIN supplied to the booster circuit 50 and outputs the detected input voltage VIN to the CPU 38. The voltage detection sensor 57 detects the output voltage VOUT supplied from the booster circuit 50 and outputs the detected output voltage VOUT to the CPU 38.

  Here, the CPU 38 causes the booster circuit 50 to increase the voltage supplied from the battery 23 when the engine 20 is automatically restarted. The CPU 38 receives the input voltage VIN from the voltage detection sensor 56 and receives the output voltage VOUT from the voltage detection sensor 57. The CPU 38 generates a signal PWM for switching control of the MOS transistor 53a based on the input voltage VIN and the output voltage VOUT, and outputs the signal PWM to the gate of the MOS transistor 53a.

  Specifically, the CPU 38 sets the voltage command value Vord to the constant voltage Vc. This voltage Vc is set to about the power supply voltage VB (for example, 12 V) supplied by the battery 23 during normal operation. Then, the CPU 38 calculates the on-duty D_ON of the MOS transistor 53a by the following equation (1).

D_ON = 1-VIN / Vord (1)
Then, the CPU 38 generates a signal PWM for turning on / off the MOS transistor 53a based on the calculated on-duty D_ON, and outputs the generated signal PWM to the MOS transistor 53a. The CPU 38 sets the voltage command value Vord to the input voltage VIN when the input voltage VIN is higher than the constant voltage Vc.

  Further, when the output voltage VOUT is input from the voltage detection sensor 57, the CPU 38 calculates a deviation Vord−VOUT between the voltage command value Vord and the output voltage VOUT, and the on-duty is set so that the calculated deviation Vord−VOUT becomes zero. D_ON is calculated. As described above, the CPU 38 performs feedback control using the input voltage VIN and the output voltage VOUT.

  In the present embodiment, the engine ECU 61 performs a fuel cut of the engine 20 when a predetermined condition is satisfied, and charges the battery 23 by supplying a constant voltage from the alternator 22 during the fuel cut.

  FIG. 3 is a time chart showing an aspect of charge control during fuel cut. As shown in the figure, when the speed of the vehicle 10 starts increasing at time t11, the engine ECU 61 controls the power generation voltage by the alternator 22 to a predetermined voltage VG1. Specifically, the engine ECU 61 transmits a power generation signal GEN to the alternator 22 to control the voltage supplied to the rotor built in the alternator 22 and to control the alternator 22 to generate the voltage VG1. This voltage VG1 is a voltage for suppressing power generation by the alternator 22. For this reason, charging of the battery 23 is suppressed after time t11. And even when the speed of the vehicle 10 becomes a constant speed, the engine ECU 61 continues to control the generated voltage to the voltage VG1.

  When the speed of the vehicle 10 starts to decrease at time t12, a condition for executing the fuel cut of the engine 20 is satisfied, and the engine ECU 61 transmits a fuel cut signal FCUT to the EFI unit 20a to execute the fuel cut of the engine 20. . The fuel cut execution conditions include, for example, that the accelerator pedal is not depressed, and that the rotational speed of the engine 20 is higher than a predetermined fuel cut rotational speed (for example, 1500 rpm). Here, the engine ECU 61 performs fuel cut until the rotation speed of the engine 20 becomes a predetermined resupply rotation speed (for example, 1200 rpm) that is slightly lower than the fuel cut rotation speed.

  When the fuel cut of the engine 20 is thus executed, the engine ECU 61 controls the power generation voltage by the alternator 22 to a predetermined voltage VG2. This voltage VG2 is the maximum voltage that can be supplied from the alternator 22 to various electric loads 60, and is set to 14.5 [V], for example. The voltage VG2 is set based on the power generation capability of the alternator 22 and the maximum voltage that can be input by various electric loads 60. For this reason, after time t12, the battery 23 is charged, and the capacity of the battery 23 increases. Accordingly, power generation is performed without consuming fuel, and the battery 23 is charged, so that the fuel efficiency of the engine 20 can be improved.

  Then, when the fuel cut of the engine 20 is completed at time t13, the engine ECU 61 reduces the voltage generated by the alternator 22 from the voltage VG2. For this reason, after time t13, charging of the battery 23 is suppressed.

  FIG. 4 is a flowchart showing a processing procedure for failure detection control of the DC-DC converter 30. This series of processing is repeatedly executed at a predetermined cycle by the idle stop ECU 62.

  First, it is determined whether the fuel of the engine 20 is being cut (S10). Specifically, the idle stop ECU 62 determines whether or not the fuel cut of the engine 20 is being executed based on communication with the engine ECU 61. At this time, if the fuel of the engine 20 is being cut, as described above, the power generation voltage by the alternator 22 is controlled to the predetermined voltage VG2.

  In the above determination, when it is determined that the fuel of the engine 20 is not being cut (S10: NO), this series of processing is temporarily ended (END). On the other hand, when it is determined that the fuel of the engine 20 is being cut (S10: YES), it is determined whether or not the speed of the vehicle 10 is lower than a predetermined failure detection vehicle speed (S11). Specifically, it is determined whether or not the speed detected by the vehicle speed sensor 27 is lower than the failure detection vehicle speed. This failure detection vehicle speed is set to be slightly higher than the engine stop vehicle speed described above.

  In the above determination, when it is determined that the speed of the vehicle 10 is not lower than the failure detection vehicle speed (S11: NO), this series of processing is temporarily ended (END). On the other hand, when it is determined that the speed of the vehicle 10 is lower than the failure detection vehicle speed (S11: YES), it is determined whether the speed of the vehicle 10 is equal to or higher than the engine stop vehicle speed (S12). Specifically, it is determined whether or not the speed detected by the vehicle speed sensor 27 is equal to or higher than the engine stop vehicle speed. At this time, when the speed of the vehicle 10 is equal to or higher than the engine stop vehicle speed, the automatic stop condition of the engine 20 is not satisfied, and the operation of the engine 20 is continued.

  In the above determination, when it is determined that the speed of the vehicle 10 is not equal to or higher than the engine stop vehicle speed (S12: NO), this series of processes is temporarily ended (END). That is, when the speed of the vehicle 10 is lower than the engine stop vehicle speed and there is a possibility that the engine 20 is automatically stopped, the failure determination of the DC-DC converter 30 is not executed. On the other hand, when it is determined that the speed of the vehicle 10 is equal to or higher than the engine stop vehicle speed (S12: YES), the input voltage VIN is increased by the booster circuit 50 (S13).

  Specifically, since the fuel cut of the engine 20 is being executed, the voltage VG2 is supplied as the input voltage VIN by the alternator 22. When the on-duty D_ON of the MOS transistor 53a is 0%, that is, when the MOS transistor 53a is off, a voltage drop corresponding to the forward voltage of the diode 54b occurs in the output control relay 54. Here, the idle stop ECU 62 increases the voltage corresponding to the voltage drop by the diode 54 b through the control of the CPU 38 of the DC-DC converter 30. That is, the input voltage VIN is raised by the booster circuit 50 so as to compensate for the voltage drop of the diode 54b.

  Specifically, the voltage command value Vord is set to the voltage VG2 through the control by the CPU 38, and the on-duty D_ON of the MOS transistor 53a is calculated by the above equation (1). Further, through the control by the CPU 38, the output voltage VOUT is input from the voltage detection sensor 57, the deviation Vord−VOUT between the voltage command value Vord and the output voltage VOUT is calculated, and the calculated deviation Vord−VOUT becomes 0. Perform feedback control.

  Subsequently, it is determined whether or not the deviation between the input voltage VIN and the output voltage VOUT is smaller than the determination value Vr (S14). Specifically, the idle stop ECU 62 receives the input voltage VIN from the voltage detection sensor 56 and the output voltage VOUT from the voltage detection sensor 57 through the control of the CPU 38, and whether the deviation is smaller than the determination value Vr. Judge whether or not. The determination value Vr is set to a value that can determine that the input voltage VIN and the output voltage VOUT are substantially the same.

  In the above determination, when it is determined that the deviation between the input voltage VIN and the output voltage VOUT is not smaller than the determination value Vr (S14: NO), it is detected that the DC-DC converter 30 has failed (S15). . Then, the automatic stop of the engine 20 is prohibited (S16), and this series of processing ends (END). That is, thereafter, even if the automatic stop condition for the engine 20 is satisfied, the automatic stop of the engine 20 is prohibited.

  On the other hand, in the above determination, when it is determined that the deviation between the input voltage VIN and the output voltage VOUT is smaller than the determination value Vr (S14: YES), it is detected that the DC-DC converter 30 is normal (S17). The series of processes is terminated (END). That is, thereafter, the engine 20 is automatically stopped based on the automatic stop condition of the engine 20, and the engine 20 is automatically restarted based on the engine automatic restart condition.

  FIG. 5 is a time chart showing an aspect of failure detection control of the DC-DC converter 30. As shown in the figure, the speed of the vehicle 10 starts to increase at time t21, and thereafter a constant speed is maintained. At time t22, the fuel cut execution condition of the engine 20 is satisfied, the fuel cut is executed, and the power generation voltage of the alternator 22 is controlled to the voltage VG2.

  At time t23, the speed of the vehicle 10 becomes lower than the failure detection vehicle speed (23 [km / h]) and higher than the engine stop vehicle speed (20 [km / h]). Therefore, the input voltage VIN is raised by the booster circuit 50, and a failure of the DC-DC converter 30 is detected based on the comparison between the input voltage VIN and the output voltage VOUT. At this time, since the constant voltage VG2 is supplied to the DC-DC converter 30 by the alternator 22, the input voltage VIN and the output voltage VOUT can be accurately compared. Furthermore, a failure of the DC-DC converter 30 can be detected immediately before the engine 20 is stopped, and it is possible to suppress a delay in the time for automatically stopping the engine 20. Here, it is assumed that the DC-DC converter 30 is detected to be normal.

  At time t24, the speed of the vehicle 10 becomes lower than the engine stop vehicle speed, and the engine 20 is automatically stopped. Thereafter, the automatic restart condition of the engine 20 is satisfied at time t25, the engine 20 is automatically restarted, and the input voltage VIN is raised by the booster circuit 50. Here, since the failure of the DC-DC converter 30 is detected immediately before the engine 20 is stopped, the period from the detection of the failure to the restart of the engine 20, that is, the boosting operation by the DC-DC converter 30 is shortened. be able to.

  At time t26, fuel cut is executed, and the power generation voltage of the alternator 22 is controlled to the voltage VG2. At time t27, the input voltage VIN is raised by the booster circuit 50, and a failure of the DC-DC converter 30 is detected. Here, it is assumed that the DC-DC converter 30 is detected to be normal, and the speed of the vehicle 10 is increased and maintained at a constant speed. That is, even if the vehicle 10 is not automatically stopped, a failure of the DC-DC converter 30 is detected when the speed of the vehicle 10 falls below the failure detection vehicle speed.

  Thereafter, at times t28, t29, and t30, processing similar to that at times t22, t23, and t24 is executed.

  The embodiment described above has the following advantages.

  -Electric power is generated by the alternator 22 by the driving force of the engine 20, and a voltage is supplied to the battery 23 and the DC-DC converter 30. When the predetermined condition is satisfied, the fuel cut of the engine 20 is executed, and a constant voltage VG2 is supplied by the alternator 22 during the fuel cut. Accordingly, power generation is performed without consuming fuel, and the battery 23 is charged, so that the fuel efficiency of the engine 20 can be improved.

  The constant voltage VG2 supplied from the alternator 22 to the various electric loads 60 through the DC-DC converter 30 during the fuel cut is dropped by the diode 54b by a voltage corresponding to the forward voltage. In the failure detection of the DC-DC converter 30, when the constant voltage VG2 is supplied from the alternator 22, the voltage (input voltage VIN) supplied from the alternator 22 is raised by the booster circuit 50. Therefore, a failure of the DC-DC converter 30 can be detected by comparing the input voltage VIN with the voltage (output voltage VOUT) raised by the booster circuit 50.

  Here, the comparison between the input voltage VIN and the output voltage VOUT is performed when the constant voltage VG2 is supplied by the alternator 22. Therefore, regardless of the voltage supplied from the battery 23 at that time, the voltage can be compared in a state where the constant voltage VG2 is supplied to the DC-DC converter 30. As a result, the failure of the DC-DC converter 30 can be detected more accurately.

  During the fuel cut execution immediately before the constant voltage VG2 is supplied by the alternator 22 and the engine speed decreases to a predetermined resupply speed, that is, immediately before the condition for automatically stopping the engine 20 is satisfied. A failure of the DC-DC converter 30 is detected. For this reason, it is possible to detect a failure of the DC-DC converter 30 before the engine 20 is automatically stopped. Further, it is possible to shorten the period from the detection of the failure until the DC-DC converter 30 is operated. As a result, the operation reliability of the DC-DC converter 30 can be improved.

  Since the failure of the DC-DC converter 30 is detected immediately before the condition for automatically stopping the engine 20 is established, the configuration is compared with the configuration for detecting the failure of the DC-DC converter 30 after the condition for automatically stopping the engine 20 is established. Thus, it is possible to suppress the delay of the time for automatically stopping the engine 20. Therefore, it is possible to suppress the period during which the engine 20 is stopped from being shortened, and to suppress the deterioration of the fuel consumption of the engine 20.

  Since the maximum voltage VG2 that can be supplied to the various electric loads 60 is supplied by the alternator 22 during the fuel cut, the power generation amount can be increased to the maximum, and the fuel consumption of the engine 20 can be further improved. Can do. At this time, the voltage VG2 supplied from the alternator 22 to the various electric loads 60 via the DC-DC converter 30 during the fuel cut is dropped by a predetermined voltage by the diode 54b. Therefore, even when the maximum voltage VG2 that can be supplied to the various electric loads 60 is supplied by the alternator 22, the voltage supplied from the alternator 22 can be raised by the booster circuit 50, and the DC A failure of the DC converter 30 can be detected.

  It is not limited to the said embodiment, For example, it can also implement as follows.

  As the boost signal DDON, the ignition switch start signal START may be input to the CPU 38 through the boost signal input terminal 33.

  Each relay may include a field effect transistor other than a MOS transistor or a junction transistor.

  Instead of the output control relay 54, a simple diode may be provided.

  When the booster circuit 50 supplies the output voltage VOUT, the CPU 38 may input the on-duty D_ON calculated by D_ON = VIN / Vord to the gate of the MOS transistor 54a of the output control relay 54. According to such a configuration, voltage loss in the diode 54b can be suppressed when the output voltage VOUT is supplied.

  The speed of the vehicle 10 can also be calculated based on the rotational speed of the engine 20 detected by the rotational speed sensor 28 and the gear ratio of the in-vehicle transmission.

  In the idle stop ECU 62, when the detection result of the input voltage VIN and the output voltage VOUT cannot be input from the CPU 38 of the DC-DC converter 30, it may be detected that the interface for inputting and outputting signals is broken.

  FIG. 6 is a flowchart showing a processing procedure for a modification of the failure detection control of the DC-DC converter 30. This series of processing is repeatedly executed at a predetermined cycle by the idle stop ECU 62. In the figure, the same processes as those in FIG. 4 are denoted by the same step numbers and the description thereof is omitted.

  The processing in S10 to S12 is the same as that in FIG. 4, and subsequently, the idle stop ECU 62 inputs the output voltage VOUTpre from the voltage detection sensor 57 by the CPU 38. That is, the output voltage VOUTpre is detected by the voltage detection sensor 57 before the boosting circuit 50 increases the input voltage VIN. Subsequently, the process of S13 for increasing the input voltage VIN is the same as that in FIG.

  Subsequently, the idle stop ECU 62 receives the output voltage VOUTaft from the voltage detection sensor 57 by the CPU 38. That is, after the input voltage VIN is raised by the booster circuit 50, the output voltage VOUTaft is detected by the voltage detection sensor 57. Then, it is determined whether or not the deviation between the output voltage VOUTafft and the output voltage VOUTpre is smaller than the determination value Vr (S22). This determination value Vr is set to a value that can determine that the output voltage VOUTpre and the output voltage VOUTafft are substantially the same.

  The process of S15-17 is the same as FIG. Even with such a configuration, it is possible to determine whether or not the input voltage VIN has been normally boosted by the DC-DC converter 30, that is, whether or not the DC-DC converter 30 has failed. As a result, the same effects as in the above embodiment can be obtained.

  In the above embodiment, the idle stop ECU 62 detects the failure of the DC-DC converter 30, but the CPU 38 of the DC-DC converter 30 may detect the failure of the DC-DC converter 30. In this case, as shown in FIG. 1, the CPU 38 may generate a warning signal WARN and output it to the idle stop ECU 62 when the DC-DC converter 30 is out of order.

  The engine 20 is not limited to a gasoline engine, and may be a diesel engine.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 20 ... Engine, 21 ... Starter, 22 ... Alternator (generator), 23 ... Battery, 30 ... DC-DC converter (voltage supply device), 50 ... Booster circuit (voltage supply circuit), 60 ... Electric load 61 ... Engine ECU (fuel cut means, power generation control means), 62 ... Idle stop ECU (automatic stop / restart means, failure detection device).

Claims (4)

Engine,
A battery that can be charged and discharged;
Electrical load,
A starter driven by a voltage supplied from the battery;
Based on a predetermined condition, the engine is automatically stopped and the engine is automatically restarted by the starter.
A voltage having a voltage supply circuit for increasing the supplied voltage and supplying the increased voltage to the electric load, and for increasing the voltage supplied from the battery when the engine is automatically restarted by the voltage supply circuit; A feeding device;
A generator for generating power by the driving force of the engine and supplying a voltage to the battery and the voltage supply device;
Fuel cut means for performing fuel cut of the engine when a predetermined condition is satisfied;
Power generation control means for controlling the power generation state of the generator and supplying a constant voltage by the generator during execution of fuel cut by the fuel cut means;
Voltage drop means for dropping a voltage supplied from the battery and the generator to the electric load via the voltage supply device by a predetermined voltage;
A failure detection device for detecting a failure of the voltage supply device,
When the power generation control means supplies the constant voltage by the generator, the voltage supplied from the generator is raised by the voltage supply circuit, and the voltage supplied from the generator and the voltage supply circuit A failure detection device for a voltage supply device, wherein a failure of the voltage supply device is detected based on a comparison with the voltage raised by the above. Engine,
A battery that can be charged and discharged;
Electrical load,
A starter driven by a voltage supplied from the battery;
Based on a predetermined condition, the engine is automatically stopped and the engine is automatically restarted by the starter.
A voltage having a voltage supply circuit for increasing the supplied voltage and supplying the increased voltage to the electric load, and for increasing the voltage supplied from the battery when the engine is automatically restarted by the voltage supply circuit; A feeding device;
A generator for generating power by the driving force of the engine and supplying a voltage to the battery and the voltage supply device;
Fuel cut means for performing fuel cut of the engine when a predetermined condition is satisfied;
Power generation control means for controlling the power generation state of the generator and supplying a constant voltage by the generator during execution of fuel cut by the fuel cut means;
Voltage drop means for dropping a voltage supplied from the battery and the generator to the electric load via the voltage supply device by a predetermined voltage;
A failure detection device for detecting a failure of the voltage supply device,
When the power generation control means supplies the constant voltage by the generator, the voltage supplied from the generator before the voltage supply circuit increases the voltage supplied to the electric load, and the power generation A failure of the voltage supply device, wherein the failure of the voltage supply device is detected based on a comparison with a voltage supplied to the electric load after the voltage supplied from the machine is raised by the voltage supply circuit Detection device. The automatic stop / restart means automatically stops the engine on the condition that the speed of the vehicle is lower than a determination speed in the process of decreasing the speed of the vehicle,
The fuel cut means performs the fuel cut until the rotational speed of the engine is equal to or lower than a predetermined rotational speed in a process in which the speed of the vehicle decreases.
The power generation control means detects the failure of the voltage supply device during execution of the fuel cut immediately before the constant voltage is supplied by the generator and the speed of the vehicle is reduced to the determination speed. Item 3. A failure detection device for a voltage supply device according to Item 1 or 2.   The said power generation control means supplies the largest fixed voltage which can be supplied to the said electrical load by the said generator during execution of the fuel cut by the said fuel cut means. The failure detection apparatus of the voltage supply apparatus of description.

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