Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
  • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
  • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
  • B60R16/033—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for characterised by the use of electrical cells or batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
  • H01M10/44—Methods for charging or discharging
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/14—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
  • H02J7/1423—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle with multiple batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2220/00—Batteries for particular applications
  • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
  • H02J2310/40—The network being an on-board power network, i.e. within a vehicle
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
  • H02J2310/40—The network being an on-board power network, i.e. within a vehicle
  • H02J2310/46—The network being an on-board power network, i.e. within a vehicle for ICE-powered road vehicles
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

• the present invention relates to a vehicular electric power system that includes an electric generator capable of performing regenerative power generation using regenerative energy of a motor vehicle and first and second batteries both of which are configured to be charged with electric power generated by the electric generator.
• Electric power systems for motor vehicles that include an internal combustion engine as a propulsion source.
• Those electric power systems include: an automotive alternator (or electric generator) capable of performing regenerative power generation using regenerative energy of the vehicle; a lead-acid battery configured to supply electric power to various electrical loads such as a starter motor; and a regulator (or power generation controller) that regulates the output voltage of the alternator to a regulation voltage.
• variable voltage control under which the regulator regulates the output voltage of the alternator to: a lower regulation voltage (e.g., 12V) during operation of the alternator in a normal mode; and a higher regulation voltage (e.g., 15V) during operation of the alternator in a regenerative mode.
• a lower regulation voltage e.g., 12V
• a higher regulation voltage e.g., 15V
• the alternator In the normal mode, the alternator generates electric power upon being driven by the engine of the vehicle without using regenerative energy (or kinetic energy) of the vehicle.
• the alternator In the regenerative mode, the alternator generates electric power using regenerative energy of the vehicle.
• variable voltage control during operation of the alternator in the normal mode, it is possible to reduce the load imposed on the engine for driving the alternator, thereby improving the fuel economy of the vehicle.
• alternator in the regenerative mode it is possible to increase the amount of electric power obtained by the regenerative power generation performed by the alternator.
• some of the electrical loads of the vehicle require the voltage of the electric power supplied thereto to be constant.
• variation in the voltage of the supplied electric power may cause headlamps to blink and the operating speed of wipers to vary; therefore, the headlights and the wipers require the voltage of the supplied electric power to be constant.
• the change rate of the output voltage of the alternator is controlled so as to be not higher than a predetermined change rate limit. Consequently, the change rate of the voltage of the electric power supplied to the headlamps and the wipers is also kept not higher than the predetermined change rate limit.
• 2011-178384 discloses a vehicular electric power system which includes both a lead-acid battery and a lithium-ion battery so as to more suitably supply electric power to the various electrical loads of the vehicle. More specifically, in the vehicular electric power system, the lithium-ion battery is electrically connected to the alternator and the lead-acid battery via a switch. When the alternator operates in the normal mode, the switch is turned off, thereby allowing only the lead-acid battery to be charged with the electric power generated by the alternator. In contrast, when the alternator operates in the regenerative mode, the i switch is turned on, thereby allowing both the lead-acid battery and the lithium-ion battery to be charged with the electric power generated by the alternator.
• the regulation voltage of the alternator is changed from the higher regulation voltage to the lower regulation voltage.
• the output voltage of the alternator still remains high until the time instant at which the switch is actually turned from on to off (or until the output voltage of the lead-acid battery has been lowered to become not higher than the turn-off-allowable voltage)
• the output voltage of the lead-acid battery will be rapidly increased by the high output voltage of the alternator. Consequently, the voltage of the electric power supplied to those electrical loads i which require a constant supply voltage will be accordingly ; rapidly increased, thereby causing the operations of those , electrical loads to become unstable.
• an electric power system for a vehicle.
• the system includes an electric generator, first and second batteries, at least one electrical load, a switch, a first controller, a regulator, a second controller and a voltage detector.
• the electric generator is configured to selectively operate in either a regenerative mode or a normal mode. In the regenerative mode, the electric generator generates electric power using regenerative energy of the vehicle. In the normal mode, the electric generator generates electric power upon being driven by an engine of the vehicle without using regenerative energy of the vehicle. Both the first and second batteries are electrically connected in parallel to the electric generator.
• the at least one electrical load requires the voltage of electric power supplied thereto to be constant and is electrically connected to the first battery.
• the switch is provided to selectively electrically connect and disconnect the second battery to and from the electric generator and the first battery.
• the first controller controls the switch so as to hold the switch in an on-state during operation of the electric generator in the regenerative mode and turn the switch from on to off when the output voltage of the first battery has been lowered to become not higher than a predetermined turn-off-allowable voltage after stop of operation of the electric generator in the regenerative mode.
• the regulator regulates the output voltage of the electric generator to a regulation voltage.
• the second controller controls the output voltage of the electric generator by variably setting the regulation voltage.
• the voltage detector detects the output voltage of the first battery. Further, in the system, the second controller also variably sets a target output voltage of the first battery.
• the second controller variably sets the regulation voltage and thereby controls the output voltage of the electric generator so as to keep the difference between the target output voltage and the output voltage of the first battery detected by the voltage detector not greater than a predetermined allowed voltage deviation and keep the difference between the regulation voltage and the target output voltage of the first battery not greater than a predetermined threshold.
• the output voltage of the first battery is kept from deviating too much from the target output voltage.
• the regulation voltage and thus the output voltage of the electric generator are also kept from deviating too much from the target output voltage of the first battery. Consequently, it becomes possible to control the deviation of the output voltage of the electric generator from the output voltage of the first battery.
• the second controller sets the target output voltage of the first battery to a higher value when the electric generator operates in the regenerative mode and to a lower value when the electric generator operates in the normal mode.
• the second controller gradually changes the target output voltage of the first battery between the higher and lower values at a change rate lower than a predetermined voltage change rate limit.
• the second controller also computes a voltage drop between the electric generator and the first battery as the product of a wiring resistance between the electric generator and the first battery and electric current outputted from the electric generator.
• the predetermined threshold is set to the voltage drop so that during operation of the electric generator in the regenerative mode, the second controller variably sets the regulation voltage and thereby controls the output voltage of the electric generator so as to keep the difference between the regulation voltage and the target output voltage of the first battery not greater than the voltage drop.
• FIG. 1 is a schematic view illustrating the overall configuration of a vehicular electric power system according to an exemplary embodiment
• FIG. 2 is a flow chart illustrating a conventional process of setting a regulation voltage of an automotive alternator
• FIG. 3 is a timing chart illustrating the conventional process
• FIG. 4 is a functional block diagram illustrating the configuration of an ECU (Electronic Control Unit) of the vehicular electric power system for performing a process of setting a regulation voltage of an automotive alternator according to the exemplary embodiment;
• ECU Electronic Control Unit
• FIG. 5 is a flow chart illustrating the regulation voltage setting process according to the exemplary embodiment.
• FIG. 6 is a timing chart illustrating the regulation voltage setting process according to the exemplary embodiment.
• FIG. 1 shows the overall configuration of a vehicular electric power system according to an exemplary embodiment.
• This system is configured to be used in a motor vehicle that includes an internal combustion engine as a propulsion source.
• the engine is configured to be started by a starter motor provided on the vehicle.
• the vehicular electric power system includes an automotive alternator (or electric generator) 10, a lead-acid battery (or first battery) 20, a lithium-ion battery (or second battery) 30, various electrical loads 41, 42 and 43, a first switch 50, a second switch 60, a first ECU (Electronic Control Unit) 70 and a second ECU 80. All of the lead-acid battery 20, the lithium-ion battery 30 and the electrical loads 41-43 are electrically connected in parallel to the alternator 10 via electric supply lines (or connecting wires) 15. In other words, via the electric supply lines 15, there are formed electric supply paths between the electrical components of the vehicular electric power system.
• the alternator 10 has a regulator 10a built therein.
• the regulator 10a is configured to regulate the output voltage of the alternator 10 to a regulation voltage (or target voltage) Vreg.
• the lead-acid battery 20 is a well-known, general-purpose battery.
• the lithium-ion battery 30 is a battery which has higher charge-discharge energy efficiency, higher output density and higher energy density than the lead-acid battery 20.
• the lithium-ion battery 30 is implemented by a battery pack which consists of a plurality of battery modules connected in series with each other.
• the charge capacity of the lead-acid battery 20 is set to be higher than the charge capacity of the lithium-ion battery 30.
• the first switch 50 is implemented by, for example, an electronic switch that is configured with a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor).
• the first switch 50 is provided between the lithium-ion battery 30 and both the alternator 10 and the lead-acid battery 20.
• the first switch 50 functions to electrically connect and disconnect the lithium-ion battery 30 to and from both the alternator 10 and the lead-acid battery 20. More specifically, when the first switch 50 is turned on, the lithium-ion battery 30 is electrically connected to both the alternator 10 and the lead-acid battery 20. In contrast, when the first switch 50 is turned off, the lithium-ion battery 30 is electrically disconnected from both the alternator 10 and the lead-acid battery 20.
• the turn-on and turn-off of the first switch 50 is controlled by the first ECU 70.
• the second switch 60 is also implemented by, for example, an electronic switch that is configured with a MOSFET.
• the second switch 60 is provided between the lithium-ion battery 30 and a junction point X between the first switch 50 and the electrical loads 43.
• the second switch 60 functions to electrically connect and disconnect the lithium-ion battery 30 to and from the junction point X between the first switch 50 and the electrical loads 43. More specifically, when the second switch 60 is turned on, the lithium-ion battery 30 is electrically connected to the junction point X. In contrast, when the second switch 60 is turned off, the lithium-ion battery 30 is electrically disconnected from the junction point X.
• the turn-on and turn-off of the second switch 60 is also controlled by the first ECU 70.
• the second switch 60 is provided as an emergency switch. More specifically, the second switch 60 is normally held in the on-state by receiving an "ON" signal outputted from the first ECU 70. However, in emergency cases, the output of the "ON" signal from the first ECU 70 is stopped and thus the second switch 60 is turned from on to off, thereby preventing overcharge and over-discharge of the lithium-ion battery 30.
• the second switch 60 is turned from on to off, thereby preventing the i lithium-ion battery 30 from being overcharged.
• the lithium-ion battery 30 becomes unable to be charged with electric power generated by the : alternator 10 due to a failure of the alternator 10 or/and a failure of the first switch 50, there is a danger that the lithium-ion battery 30 will be over-discharged. Therefore, in this emergency case, the second switch 60 is turned from on to off, thereby preventing the lithium-ion battery 30 from being over-discharged.
• the second switch 60 may also be alternatively implemented by a normally-open electromagnetic relay.
• the first ECU 70 fails to control the turn-on and turn-off (i.e., the closing and opening) of the second switch 60
• the second switch 60 will be automatically turned off (i.e., opened), thereby electrically disconnecting the lithium-ion battery 30 from the junction point X between the first switch 50 and the electrical loads 43.
• the lithium-ion battery 30, the first and second switches 50 and 60 and the first ECU 70 are together received in a housing (or a receiving case) and thereby integrated into a battery unit U.
• the first ECU 70 which is included in the battery unit U and controls the turn-on and turn-off of the first and second switches 50 and 60, also detects the output current, output voltage and temperature of the lithium-ion battery 30.
• the first ECU 70 is connected, via a communication network such as LIN (Local Interconnect Network), to the second ECU 80 that is located outside of the battery unit U. Consequently, the first and second ECUs 70 and 80 can communicate with each other and share various data stored in them.
• LIN Local Interconnect Network
• the electrical loads 43 are such electrical loads that require the voltage of the supplied electric power to be almost constant or variation in the voltage to be kept stable within a predetermined range.
• the electrical loads 43 are electrically connected to the same side of the first switch 50 as the lithium-ion battery 30. Consequently, the electrical loads 43 are supplied with electric power mainly by the lithium-ion battery 30.
• the electrical loads 43 include, for example, a navigation system and an audio system.
• the voltage of the electric power supplied to the electrical loads 43 varies greatly so that variation in the voltage exceeds the predetermined range, the voltage may become lower than the minimum operating voltages of the navigation and audio systems, thereby causing those systems to be reset. Therefore, variation in the voltage of the electrical power supplied to the electrical loads 43 is required to be so stable that the voltage will not drop below the minimum operating voltages of the navigation and audio systems.
• the electrical loads 41 and 42 are electrically connected to the same side of the first switch 50 as the lead-acid battery 20. Consequently, the electrical loads 41 and 42 are supplied with electric power mainly by the lead-acid battery 20.
• the sole electrical load 41 is the starter motor for starting the engine of the vehicle.
• the electrical loads 42 include, for example, headlamps, wipers for the front windshield of the vehicle, a blower fan ; of an air-conditioning system and a defrosting heater for the rear windshield of the vehicle.
• some of the electrical loads 42 are constant voltage-requiring electrical loads which require the voltage of the supplied electric power to be constant.
• the constant voltage-requiring electrical loads 42 include, for example, the headlamps, the wipers and the blower fan. This is because variation in the voltage of the supplied electric power may cause the headlamps to blink, the operating speed of the wipers to vary and the rotating speed (thus the air-blowing noise) of the blower fan to vary.
• the expression "the voltage of the supplied electric power to be constant" used hereinafter means that the change rate of the voltage of the supplied electric power is not higher than a predetermined value.
• the alternator 10 is of a well-known type and therefore the configuration of the alternator 10 is not graphically shown.
• a rotor of the alternator 10 is driven by torque transmitted from a crankshaft of the engine to rotate.
• field current is supplied to a field coil of the rotor, thereby creating a rotating magnetic field.
• the rotating magnetic field induces AC power in a stator coil, and the AC power is then rectified into DC power by a rectifier.
• the regulator 10a regulates the voltage of the DC power outputted from the i alternator 10 to the regulation; voltage Vreg by controlling the supply of the field current to the field coil of the rotor.
• the regulation voltage Vreg is set by the second ECU 80.
• the electric power generated by the alternator 10 is supplied to the lead-acid battery 20 and the lithium-ion battery 30 as well as to the electrical loads 41-43.
• the electrical loads 41-43 are supplied with electric power by the lead-acid battery 20 and the lithium-ion battery 30. Further, both the amount of electric power discharged by the batteries 20 and 30 to the electrical loads 41-43 and the amount of electric power charged by the alternator 10 into the batteries 20 and 30 are controlled, by the first and second ECUs 70 and 80, so as to prevent overcharge and over-discharge of the batteries 20 and 30 and thereby keep the SOC (State of Charge) of each of the batteries 20 and 30 within a suitable range.
• the first ECU 70 controls the turn-on and turn-off of the first switch 50
• the second ECU 80 controls the output voltage of the alternator 10 by variably setting the regulation voltage Vreg of the alternator 10.
• the alternator 10 is configured to selectively operate in either a regenerative mode or a normal mode. Specifically, when regenerative braking is performed for the vehicle, the alternator 10 operates in the regenerative mode, in which it generates electric power using regenerative energy (or kinetic energy) of the vehicle, thereby charging both the batteries 20 and 30 (mainly the lithium-ion battery 30). Otherwise, the alternator 10 operates in the normal mode in which it generates electric power upon being driven by the engine of the vehicle without using regenerative energy of the vehicle.
• regenerative braking is performed for the vehicle only when several predetermined conditions are satisfied. Those predetermined conditions include, for example, that the vehicle is in a decelerating state and that fuel injection into the engine is cut off.
• the lead-acid battery 20 and the lithium-ion battery 30 are electrically connected in parallel with each other. Therefore, when both the first and second switches 50 and 60 are in the on-state, electric power generated by the alternator 10 will be preferentially charged into that one of the batteries 20 and 30 which has a lower output voltage than the other. In contrast, when no electric power is generated by the alternator 10 and both the first and second switches 50 and 60 are in the on-state, that one of the batteries 20 and 30 which has a higher output voltage than the other preferentially discharges electric power to feed the electrical loads 42 and 43.
• the open-circuit voltages and internal resistances of the batteries 20 and 30 are suitably set so as to allow the lithium-ion battery 30 to be preferentially charged with electric power generated by the alternator 10 than the lead-acid battery 20.
• the open-circuit voltage of the lithium-ion battery 30 is set by suitably selecting the cathode active material, anode active material and electrolytic solution of the lithium-ion battery 30.
• the vehicle is equipped with an engine automatic stop/restart system (also called idle stop system) which automatically stops the engine of the vehicle when predetermined automatic stop conditions are satisfied and then automatically restarts the engine when predetermined automatic restart conditions are satisfied.
• the second ECU 80 is also employed in the engine automatic stop/restart system to perform an automatic stop/restart control for the engine of the vehicle. Further, in automatically stopping the engine under the automatic stop/restart control by the second ECU 80, the first switch 50 is turned on by the first ECU 70, thereby allowing the lithium-ion battery 30 to be charged with electric power generated by the alternator 10 in the regenerative mode.
• the first switch 50 is turned off by the first ECU 70, thereby electrically disconnecting the lithium-ion; battery 30 from both the lead-acid i battery 20 and the starter motor (i.e., the sole electrical load 41). : Consequently, the starter motor is driven only by the electric i power discharged by the lead-acid battery 20, thereby restarting the engine.
• the first ECU 70 controls the first and second switches 50 and 60 so as to hold them respectively in the off-state and on-state. Consequently, the electrical loads 43 are electrically disconnected from the alternator 10 and the lead-acid battery 20, while remaining electrically connected to the lithium-ion battery 30. As a result, the electrical loads 43 are supplied with electric power only by the lithium-ion battery 30. Further, with the lithium-ion battery 30 having discharged during operation of the alternator 10 in the normal mode, when the alternator 10 turns to operate in the regenerative mode, it is possible to charge the lithium-ion battery 30 with more electric power generated by the alternator 10. As described previously, the lithium-ion battery 30 has higher charge-discharge energy efficiency than the lead-acid battery 20. Therefore, with the above control, it is possible to improve the total charge-discharge energy efficiency of the vehicular electric power system.
• the second ECU 80 sets the regulation voltage Vreg of the alternator 10 to a higher value in the regenerative mode than in the normal mode of the alternator 10. Consequently, during operation of the alternator 10 in the regenerative mode, it is possible to increase the amount of electric power generated by the alternator 10. On the other hand, during operation of the alternator 10 in the normal mode, it is possible to reduce the load imposed on the engine for driving the alternator 10, thereby improving the fuel economy of the vehicle.
• FIG. 2 shows the conventional process of setting the regulation voltage Vreg of the alternator 10. This process is repeatedly performed by the second ECU 80 at a predetermined time cycle.
• the second ECU 80 determines whether the alternator 10 operates in the regenerative mode.
• step S01 If the alternator 10 operates in the regenerative mode and thus the determination at step S01 produces a "YES" answer, then the process proceeds to step S02.
• the second ECU 80 sets the regulation voltage
• Vreg of the alternator 10 to a first value (e.g., 15V).
• the second ECU 80 commands the first ECU 70 to control the first and second switches 50 and 60, thereby holding both the switches 50 and 60 in the on-state. Thereafter, the process goes to the end.
• step S04 determines whether the alternator 10 operates in the normal mode and thus the determination at step SOI produces a "NO" answer. If the alternator 10 operates in the normal mode and thus the determination at step SOI produces a "NO" answer, then the process proceeds to step S04.
• the second ECU 80 sets the regulation voltage Vreg of the alternator 10 to a second value (e.g., 12V) that is lower than the first value.
• step S05 the second ECU 80 commands the first ECU 70 to control the first and second switches 50 and 60, thereby holding the first switch 50 in the off-state and the second switch 60 in the on-state. Thereafter, the process goes to the end.
• FIG. 3 shows the changes with time in the regulation voltage Vreg of the alternator 10 and the output voltage V(Pb) of the lead-acid battery 20, which are caused by performing the conventional process shown in FIG. 2.
• a Fuel-Cut (F/C) flag is in an on-state and the alternator 10 operates in the regenerative mode.
• the regulation voltage Vreg of the alternator 10 is set by the second ECU 80 to the first value (i.e., 15V); the regulator 10a regulates the output voltage of the alternator 10 to the first value.
• the first ECU 70 holds the first switch 50 in the on-state; thus the lead-acid battery 20 and the lithium-ion battery 30 are electrically connected with each other.
• the output voltage V(Pb) of the lead-acid battery 20 is kept at about 13V.
• the F/C flag is turned from on to off and operation of the alternator 10 is shifted from the regenerative mode to the normal mode.
• the second ECU 80 gradually lowers the regulation voltage Vreg of the alternator 10 from the first value to the second value (i.e., 12V) at a predetermined change rate.
• the first switch 50 is turned by the first ECU 70 from on to off, thereby electrically disconnecting the lithium-ion battery 30 from the alternator 10 and the lead-acid battery 20. Consequently, electric current flowing from the alternator 10 to the lithium-ion battery 30 comes to flow to the lead-acid battery 20, thereby rapidly increasing the output voltage V(Pb) of the lead-acid battery 20 to exceed the regulation voltage Vreg of the alternator 10.
• the output voltage V(Pb) of the lead-acid battery 20 is rapidly increased, for example, by 1.7V from 13.3V to 15V.
• the voltage of the electric power supplied to the electrical loads 42 is accordingly rapidly increased, thereby causing the operations of the constant voltage-requiring electrical loads 42 to become unstable.
• the second ECU 80 variably sets the regulation voltage Vreg of the alternator 10 in the regenerative mode so as to keep the regulation voltage Vreg close to the output voltage V(Pb) of the lead-acid battery 20 detected by the second ECU 80. Consequently, when operation of the alternator 10 is shifted from the regenerative mode to the normal mode, it is possible to suppress variation in the output voltage V(Pb) of the lead-acid battery 20 which is caused by the turning of the first switch 50 from on to off by the first ECU 70. As a result, it is possible to stabilize the operations of the constant voltage-requiring electrical loads 42.
• the ECU 80 variably sets a target output voltage of the lead-acid battery 20 so that the target output voltage is higher in the regenerative mode of the alternator 10 than in the normal mode of the alternator 10. Further, when operation of the alternator 10 is shifted from the normal mode to the regenerative mode, the second ECU 80 gradually increases the target output voltage of the lead-acid battery 20; in contrast, when operation of the alternator 10 is shifted from the regenerative mode to the normal mode, the second ECU 80 gradually lowers the target output voltage.
• the second ECU 80 sets the regulation voltage Vreg of the alternator 10 based on both the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20 so as to decrease the difference between the target output voltage and the detected output voltage V(Pb); then the regulator 10a regulates the output voltage of the alternator 10 to the thus set regulation voltage Vreg. Consequently, during operation of the alternator 10 in the regenerative mode, it is possible to increase the amount of electric power generated by the alternator 10. On the other hand, during operation of the alternator 10 in the normal mode, it is possible to reduce the load imposed on the engine for driving the alternator 10, thereby improving the fuel economy of ithe vehicle. ⁇
• FIG. 4 shows the configuration of the second ECU 80 according to the present embodiment for performing the process of setting the regulation voltage Vreg of the alternator 10.
• the second ECU 80 includes a voltage detecting unit A01, an allowed voltage deviation setting unit A02, a target output voltage upper limit setting unit B01, a target output voltage setting unit B02, a target output voltage modifying unit B03, a first integral upper limit setting unit B04, a second integral upper limit setting unit B05, a voltage deviation computing unit B06, an integral upper limit outputting unit B07, a voltage deviation integrating unit B08, a required regulation voltage setting unit B09, a required regulation voltage modifying unit B10 and a regulation voltage setting unit Bll.
• the voltage detecting unit A01 detects the actual output voltage V(Pb) of the lead-acid battery 20 and outputs the detected output voltage V(Pb) to the target output voltage upper limit setting unit B01.
• the allowed voltage deviation setting unit A02 sets an allowed voltage deviation (abbreviated to A. V. D. in FIG. 4) and outputs the set allowed voltage deviation to the target output voltage upper limit setting unit BOl.
• the target output voltage upper limit setting unit BOl sets a target output voltage upper limit (abbreviated to T. O. V. U. L. in FIG. 4) and outputs the set target output voltage upper limit to the target output voltage setting unit B02. Specifically, the target output voltage upper limit setting unit BOl sets the target output voltage upper limit to the sum of the actual output voltage V(Pb) of the lead-acid battery 20 detected by the voltage detecting unit A01 and the allowed voltage deviation set by the allowed voltage deviation setting unit A02. In addition, the target output voltage upper limit is an upper limit for the target output voltage of the lead-acid battery 20.
• the target output voltage setting unit B02 sets the target output voltage of the lead-acid battery 20 based on the target output voltage upper limit set by the target output voltage upper limit setting unit B01, a target output voltage lower limit (abbreviated to T. O. V. L. L. in FIG. 4) set by a target output voltage lower limit setting unit (not shown) and a required target output voltage (abbreviated to R. T. O. V. in FIG. 4) set by a required target output voltage setting unit (not shown).
• the required target output voltage is set by the required target output voltage setting unit to a higher value (e.g., 14V) when the alternator 10 operates in the regenerative mode and a lower value (E.G.
• the target output voltage setting unit B02 sets the target output voltage of the lead-acid battery 20 to: the target output voltage upper limit when the required target output voltage is higher than the target output voltage upper limit; the required target output voltage when the required target output voltage is not higher than the target output voltage upper limit and not lower than the target output voltage lower limit; and the target output voltage lower limit when the required target output voltage is lower than the target output voltage lower limit. Then, the target output voltage setting unit B02 outputs the set target output voltage to the target output voltage modifying unit B03.
• the target output voltage modifying unit B03 modifies, when the change rate of the target output voltage set by the target output voltage setting unit B02 is higher than a voltage change rate limit (abbreviated to V. C. R. L. in FIG. 4) set by a voltage change rate limit setting unit (not shown), the target output voltage set by the target output voltage setting unit B02 and outputs the modified voltage as the target output voltage (abbreviated to T. O. V. in FIG. 4) of the lead-acid battery 20. Specifically, the target output voltage modifying unit B03 modifies the target output voltage set by the target output voltage setting unit B02 so as to gradually change at a rate lower than the voltage change rate limit.
• a voltage change rate limit abbreviated to V. C. R. L. in FIG.
• the target output voltage modifying unit B03 directly outputs the target output voltage set by the target output voltage setting unit B02 as the target output voltage of the lead-acid battery 20 without modifying it.
• the voltage deviation computing unit B06 computes a voltage deviation (abbreviated to V. D. in FIG. 4) by subtracting the actual output voltage V(Pb) of the lead-acid battery 20 detected by the voltage detecting unit A01 from the target output voltage outputted from the target output voltage modifying unit B03.
• the first integral upper limit setting unit B04 sets a first integral upper limit to the result of subtracting the target output voltage outputted from the target output voltage modifying unit B03 from a regulation voltage upper limit (abbreviated to R. V. U. L. in FIG. 4) set by a regulation voltage upper limit setting unit (not shown).
• the regulation voltage upper limit is an upper limit for the regulation voltage Vreg of the alternator 10.
• the second integral upper limit setting unit B05 sets a second integral upper limit to the product of the wiring resistance between the alternator 10 and the lead-acid battery 20 and the maximum electric current outputted from the alternator 10 in the regenerative mode.
• the product of the wiring resistance between the alternator 10 and the lead-acid battery 20 and the maximum electric current outputted from the alternator 10 in the regenerative mode also represents the maximum voltage drop between the alternator 10 and the lead-acid battery 20 due to the wiring resistance.
• the integral upper limit outputting unit B07 compares the first integral upper limit set by the first integral upper limit setting unit B04 and the second integral upper limit set by the second integral upper limit setting unit B05 and outputs the lower one of the first and second integral upper limits as an integral upper limit (abbreviated to I. U. L. in FIG. 4).
• the voltage deviation integrating unit B08 integrates the voltage deviation computed by the voltage deviation computing unit B06 with respect to time. Further, when the result of the time integral of the voltage deviation is not higher than the; integral upper limit outputted from the integral upper limit outputting unit B07, the voltage deviation integrating unit B08 outputs the result as a voltage deviation integral value (abbreviated to V. D. I. V. in FIG. 4). In contrast, when the result of the time integral of the voltage deviation is higher than the integral upper limit outputted from the integral upper limit outputting unit B07, the voltage deviation integrating unit B08 outputs the integral upper limit as the voltage deviation integral value.
• the required regulation voltage setting unit B09 sets a required regulation voltage to the sum of the target output voltage outputted from the target output voltage modifying unit B03 and the voltage deviation integral value outputted from the voltage deviation integrating unit B08.
• the required regulation voltage modifying unit B10 modifies, when the change rate of the required regulation voltage set by the required regulation voltage setting unit B09 is higher than the voltage change rate limit, the required regulation voltage set by the required regulation voltage setting unit B09 and outputs the modified voltage as the required regulation voltage (abbreviated to R. R. V. in FIG. 4) of the alternator 10.
• the required regulation voltage modifying unit BIO modifies the required regulation voltage set by the required regulation voltage setting unit B09 so as to gradually change at a rate lower than the voltage change rate limit.
• the required regulation voltage modifying unit B10 directly outputs the required regulation voltage set by the required regulation voltage setting unit B09 as the required regulation voltage of the alternator 10.
• the regulation voltage setting unit Bll sets the regulation voltage Vreg of the alternator 10 based on the regulation voltage upper limit, a regulation voltage lower limit (abbreviated to R. V. L. L. in FIG. 4) set by a regulation voltage lower limit setting unit (not shown) and the required regulation voltage outputted from the required regulation voltage modifying unit B10.
• the regulation voltage setting unit Bll sets the regulation voltage Vreg of the alternator 10 to: the regulation voltage upper limit when the required regulation voltage outputted from the required regulation voltage modifying unit B10 is higher than the regulation voltage upper limit; the required regulation voltage when the required regulation voltage is not higher than the regulation voltage upper limit and not lower than the regulation voltage lower limit; and the regulation voltage lower limit when the required regulation voltage is lower than the regulation voltage lower limit.
• the regulation voltage setting unit Bll outputs the set regulation voltage Vreg to a commanding unit
• the commanding unit commands the regulator 10a to regulate the output voltage of the alternator 10 to the regulation voltage Vreg.
• FIG. 5 shows the process of setting the regulation voltage Vreg of the alternator 10 according to the present embodiment.
• This process is repeatedly performed by the second ECU 80 at a predetermined time cycle.
• step Sll the second ECU 80 determines whether the alternator 10 operates in the regenerative mode.
• step Sll determines whether the alternator 10 operates in the regenerative mode or not. If the alternator 10 operates in the regenerative mode and thus the determination at step Sll produces a "YES" answer, then the process proceeds to step S12.
• the second ECU 80 commands the first ECU
• the lithium-ion battery 30 is electrically connected to the alternator 10 and the lead-acid battery 20.
• the second ECU 80 determines whether the target output voltage (abbreviated to T. O. V. in FIG. 5) of the lead-acid battery 20 has increased to become not lower than the higher value (e.g., 14V) set for operation of the alternator 10 in the regenerative mode.
• the target output voltage abbreviated to T. O. V. in FIG. 5
• the higher value e.g. 14V
• step S13 If the determination at step S13 produces a "YES" answer, then the process directly proceeds to step S14.
• step S13 determines whether the target output voltage is gradually increased to the higher value. If the determination at step S13 produces a "NO" answer, then the process proceeds to step S16, at which the target output voltage is gradually increased to the higher value. Thereafter, the process goes on to step S14.
• the second ECU 80 sets, based on the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20, the regulation voltage Vreg for operation of the alternator 10 in the regenerative mode.
• the second ECU 80 commands the regulator 10a to regulate the output voltage of the alternator 10 (abbreviated to ALT. VOL. in FIG. 5) to the regulation voltage Vreg. Then, the process goes to the end.
• step Sll determines whether the alternator 10 operates in the normal mode and thus the determination at step Sll produces a "NO" answer. If the alternator 10 operates in the normal mode and thus the determination at step Sll produces a "NO" answer, then the process proceeds to step S17.
• the second ECU 80 determines whether the target output voltage of the lead-acid battery 20 has been lowered to become not higher than the lower value (e.g., 12.5V) set for operation of the alternator 10 in the normal mode.
• the lower value e.g. 12.5V
• step S17 If the determination at step S17 produces a "YES" answer, then the process directly proceeds to step S18.
• step S20 the target output voltage is gradually lowered to the lower value. Thereafter, the process goes on to step S18.
• the second ECU 80 sets, based on the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20, the regulation voltage Vreg for operation of the alternator 10 in the normal mode.
• the second ECU 80 commands the regulator 10a to regulate the output ivoltage of the alternator 10 to the regulation voltage Vreg. ⁇
• the second ECU 80 further determines whether the output voltage V(Pb) of the lead-acid battery 20 has been lowered to become not higher than a predetermined- turn -off-allowable voltage (e.g., 13V).
• a predetermined- turn -off-allowable voltage e.g. 13V
• the turn-off-allowable voltage is predetermined such that the first switch 50 is allowed to be turned from on to off only when the detected output voltage V(Pb) of the lead-acid battery 20 is not higher than the turn-off-allowable voltage.
• step S21 If the determination at step S21 produces a "NO" answer, then the process directly goes to the end.
• step S21 determines whether the determination at step S21 produces a "YES" answer. If the determination at step S21 produces a "YES" answer, then the process proceeds to step S22.
• FIG. 6 shows the changes with time in the regulation voltage Vreg of the alternator 10, the target output voltage (abbreviated to T. O. V. in FIG. 6) and the detected output voltage V(Pb) of the lead-acid battery 20, which are caused by performing the regulation voltage setting process of the present embodiment shown in FIG. 5.
• the change with time in the regulation voltage Vreg of the alternator 10 is designated by a twordot chain line; the change with time in the target output voltage of the lead-acid battery 20 is designated by a one-dot chain line; and the change with time in the detected output voltage V(Pb) of the lead-acid battery 20 is designated by a solid line.
• a Fuel-Cut (F/C) flag is in an off-state and the alternator 10 operates in the normal mode.
• the target output voltage of the lead-acid battery 20 is set by the second ECU 80 to the lower value (i.e., 12.5V).
• the regulation voltage Vreg of the alternator 10 is set by the second ECU 80 such that the difference between the regulation voltage Vreg and the target output voltage of the lead-acid battery 20 is equal to the maximum voltage drop caused by the wiring resistance between the alternator 10 and the lead-acid battery 20.
• the second ECU 80 commands the regulator 10a to regulate the output voltage of the alternator 10 to the above-set regulation voltage Vreg.
• the second ECU 80 commands the first ECU 70 to hold the first switch 50 in the off-state, thereby electrically disconnecting the lithium-ion battery 30 from the alternator 10 and the lead-acid battery 20. Consequently, the detected output voltage V(Pb) of the lead-acid battery 20 becomes close to the regulation voltage Vreg of the alternator 10.
• the second ECU 80 when operation of the alternator 10 is shifted from the normal mode to the regenerative mode, gradually increases the target output voltage of the lead-acid battery 20 to the higher value (i.e., 14V) at a predetermined change rate of, for example, lV/s. Further, with the increase in the target output voltage of the lead-acid battery 20, the regulation voltage Vreg of the alternator 10 set by the second ECU 80 is also according increased.
• the first switch 50 is turned by the first ECU 70 from off to on, thereby electrically connecting the lithium-ion battery 30 to the alternator 10 and the lead-acid battery 20. Consequently, the detected output voltage V(Pb) of the lead-acid battery 20 is once lowered to become close to the output voltage of the lithium-ion battery 30, and then increased with increase in the regulation voltage Vreg of the alternator 10.
• the voltage deviation i.e., the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20 has been increased to reach the allowed voltage deviation.
• the second ECU 80 sets the target output voltage of the lead-acid battery 20 by taking the sum of the detected output voltage V(Pb) and the allowed voltage deviation as the target output voltage upper limit. Further, the second ECU 80 increases the regulation voltage Vreg of the alternator 10 so as to decrease the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20.
• the target output voltage of the lead-acid battery 20 has increased to reach the higher value (i.e., 14V) set for operation of the alternator 10 in the regenerative mode. Then, the second ECU 80 further increases, based on the voltage deviation integral value, the regulation voltage Vreg of the alternator 10 so as to decrease the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20.
• the second ECU 80 sets the regulation voltage Vreg of the alternator 10 to the sum of the target output voltage of the lead-acid battery 20 and the maximum voltage drop. Consequently, during the time period from the time instant T14 to a time instant T15, the lead-acid battery 20 is charged with electric power generated by the alternator 10, thereby causing the detected output voltage V(Pb) of the alternator 10 to gradually increase.
• the F/C flag is turned from “ON” to "OFF” and operation of the alternator 10 is shifted from the regenerative mode to the normal mode.
• the second ECU 80 gradually lowers the target output voltage of the lead-acid battery 20 to the lower value (i.e., 12.5V) at a predetermined change rate of, for example, lV/s.
• the regulation voltage Vreg of the alternator 10 is set by the second ECU 80 as being equal to the sum of the target output voltage of the lead-acid battery 20 and the maximum voltage drop, the regulation voltage Vreg is also lowered at the same change rate as the target output voltage.
• the detected output voltage V(Pb) of the lead-acid battery 20 is also lowered.
• the detected output voltage V(Pb) of the lead-acid battery 20 has been lowered to become not higher than the turn-off-allowable voltage (i.e., 13V).
• the second ECU 80 commands the first ECU 70 to control the first and second switches 50 and 60, thereby holding the first switch 50 in the off-state and the second switch 60 in the on-state.
• the lithium-ion battery 30 becomes electrically disconnected from the alternator 10 and the lead-acid battery 20. Consequently, electric current flowing from the alternator 10 to the lithium-ion battery 30 comes to flow to the lead-acid battery 20.
• the electric current outputted from the alternator 10 and thus the voltage drop caused by the wiring resistance between the alternator 10 and the lead-acid battery 20 become zero immediately after the stop of operation of the alternator 10 in the regenerative mode at the time instant T15. Therefore, the detected output voltage V(Pb) of the lead-acid battery 20 is approximately equal to the regulation voltage Vreg of the alternator 10 immediately before and after the turning of the first switch 50 from on to off.
• the output voltage V(Pb) of the lead-acid battery 20 is prevented from being rapidly increased due to the turning of the first switch 50 from on to off. Consequently, the voltage of the electric power supplied to the constant voltage-requiring electrical loads 42 are also prevented from being rapidly increased, thereby ensuring stable operations of those electrical loads 42.
• the second ECU 80 variably sets the regulation voltage Vreg of the alternator 10 and thereby controls the output voltage of the alternator 10 so as to: keep the voltage deviation (i.e., the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20) not greater than the allowed voltage deviation; and keep the difference between the regulation voltage Vreg of the alternator 10 and the target output voltage of the lead-acid battery 20 not greater than a predetermined threshold (i.e., the maximum voltage drop caused by the wiring resistance between the alternator 10 and the lead-acid battery 20).
• a predetermined threshold i.e., the maximum voltage drop caused by the wiring resistance between the alternator 10 and the lead-acid battery 20.
• the output voltage of the lead-acid battery 20 is kept from deviating too much from the target output voltage.
• the regulation voltage Vreg and thus the output voltage of the alternator 10 are also kept from deviating too much from the target output voltage of the lead-acid battery 20. Consequently, it becomes possible to control the deviation of the output voltage of the alternator 10 from the output voltage of the lead-acid battery 20.
• the target output voltage of the lead-acid battery 20 is variably set by the second ECU 80 so as to be higher during operation of the alternator 10 in the regenerative mode than during operation of the alternator 10 in the normal mode.
• the second ECU 80 variably sets the regulation voltage Vreg and thereby controls the output voltage of the alternator 10 so as to keep the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20 not greater than the allowed voltage deviation. Consequently, the output voltage of the lead-acid battery 20 will be higher during operation of the alternator 10 in the regenerative mode than during operation of the alternator 10 in the normal mode.
• the difference between the output voltages of the alternator 10 and the lead-acid battery 20 is equal to the voltage drop caused by the wiring resistance between the alternator 10 and the lead-acid battery 20.
• the second ECU 80 makes the detected output voltage V(Pb) of the lead-acid battery 20 approach the target output voltage while keeping the difference between the regulation voltage Vreg of the alternator 10 and the target output voltage of the lead-acid battery 20 equal to the maximum voltage drop. Consequently, the difference between the regulation voltage Vreg of the alternator 10 and the detected output voltage V(Pb) of the lead-acid battery 20 is accordingly made to approach the maximum voltage drop.
• the difference between the regulation voltage Vreg of the alternator 10 and the target output voltage of the lead-acid battery 20 is kept not greater than the maximum voltage drop; the maximum voltage drop is computed as the product of the wiring resistance between the alternator 10 and the lead-acid battery 20 and the maximum electric current outputted from the alternator 10.
• the second ECU 80 integrates the voltage deviation, which is the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20, and sets the regulation voltage Vreg of the alternator 10 based on the obtained voltage deviation integral value.
• the second ECU 80 may also set the regulation voltage Vreg of the alternator 10 simply by adding the voltage deviation to the target output voltage of the lead-acid battery 20.
• the second ECU 80 variably sets the regulation voltage Vreg of the alternator 10 and thereby controls the output voltage of the alternator 10 so as to ⁇ keep the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20 not greater than the allowed voltage deviation.
• the second ECU 80 may also variably set the regulation voltage Vreg and thereby control the output voltage of the alternator 10 so as to . make the difference between the target output voltage and the detected output voltage V(Pb) of the lead-acid battery 20 zero.

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• 2012
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