Control apparatus for vehicle

A control apparatus for a vehicle that is capable of enhancing fuel efficiency of an internal-combustion engine. The vehicle is provided with at least one electronically controllable vehicle-mounted accessory that can be driven by the engine, and energy storage means for storing energy generated by the at least one vehicle-mounted accessory being driven by the engine. The apparatus includes regenerative control means for performing regenerative control during deceleration of the vehicle according to a deceleration instruction from a driver, and drive-control means for performing drive-control of the at least one vehicle-mounted accessory during a vehicle running period other than a regenerative control period so that the energy storage means has a margin in energy storage capacity for storing energy to be generated by the at least one vehicle-mounted accessory being driven by the engine during the regenerative control.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2010-259681 filed Nov. 22, 2010, the description of which is incorporated herein by reference.

BACKGROUND

This invention relates to a control apparatus for a vehicle provided with an electronically controllable vehicle-mounted accessory to be driven by an internal-combustion engine and energy storage means for storing energy generated by driving the vehicle-mounted accessory, which apparatus is capable of conducting regenerative control to convert kinetic energy of the vehicle into drive energy of the vehicle-mounted accessory during deceleration of the vehicle according to (or in response to) a driver's instruction.

A known control apparatus, as disclosed in Japanese Patent Application Publication No. 2009-196457, performs regenerative control by driving vehicle-mounted accessories to convert kinetic energy of the vehicle into drive energy of the vehicle-mounted accessories during a fuel-cut period of time when the vehicle is decelerating. More specifically, a vehicle battery is charged with electrical energy generated by driving a generator, which is a vehicle-mounted accessory, during the regenerative control. This can reduce a subsequent frequency at which the generator is driven to charge the battery, thereby enhancing fuel efficiency of the internal-combustion engine.

In the conventional apparatus as described above, however, when a state of charge (SOC) of the battery is already at an adequately high level before the regenerative control, kinetic energy of the vehicle cannot be effectively used as electrical power output of the generator through the regenerative control, which may reduce the fuel efficiency of the internal-combustion engine.

In general, the generator and other vehicle-mounted accessories to be driven by the internal-combustion engine cannot effectively use kinetic energy of the vehicle as drive energy of the vehicle-mounted accessories through the regenerative control, which may reduce fuel efficiency of the internal-combustion engine.

In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a control apparatus for a vehicle capable of effectively using kinetic energy of the vehicle as drive energy of the vehicle-mounted accessories through the regenerative control, thereby enhancing the fuel efficiency of the internal-combustion engine.

SUMMARY

In accordance with an exemplary aspect of the present invention, there is provided a control apparatus for a vehicle. The vehicle is provided with at least one electronically controllable vehicle-mounted accessory that can be driven by an internal-combustion engine, and energy storage means for storing energy generated by the at least one vehicle-mounted accessory being driven by the engine. The apparatus includes: regenerative control means for performing regenerative control during deceleration of the vehicle according to a deceleration instruction from a driver of the vehicle by driving the at least one vehicle-mounted accessory to convert kinetic energy of the vehicle into drive energy of the at least one vehicle-mounted accessory; and drive-control means for performing drive-control of the at least one vehicle-mounted accessory during a vehicle running period other than a regenerative control period so that the energy storage means has a margin in energy storage capacity for storing energy to be generated by the at least one vehicle-mounted accessory being driven by the engine during the regenerative control.

With this configuration, the regenerative control is performed to convert the kinetic energy of the vehicle into the drive energy of the vehicle-mounted accessory. The vehicle-mounted accessory is drive-controlled during a vehicle running period other than the regenerative control period so that the energy storage means has a margin in energy storage capacity for storing energy to be generated by the vehicle-mounted accessory being driven during the regenerative control. This enables the energy storage means to properly store energy generated by the regenerative control, which leads to enhancement of fuel efficiency of the internal-combustion engine.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention will be described more fully hereinafter with reference to the accompanying drawings. Like numbers refer to like elements throughout.

FIG. 1is a schematic view showing a collection of an engine system, an air-conditioning system and a power generation system, to which a control apparatus for a vehicle can be applied in accordance with one embodiment of the present embodiment.

As shown inFIG. 1, each cylinder of an engine10is provided with a fuel injection valve12from which an air-fuel mixture is supplied into a combustion chamber (not shown) of the engine10for combustion. Energy generated in the combustion of the air-fuel mixture is used as rotary power for an output shaft (crankshaft14).

The air-conditioning system includes a compressor16that suctions and discharges a refrigerant to circulate the refrigerant in a refrigerating cycle, a condenser18, and an evaporator20.

The compressor16, which is also rotationally driven by the rotating crankshaft14via the belt22, is a continuously variable displacement type compressor including an electromagnetically-driven control valve therein (not shown). Power supply to the valve is controlled so as to variably set a discharge capacity of refrigerant in a continuous manner during rotationally driving of the compressor16. More specifically, as the refrigerant discharge capacity of the compressor16becomes larger, a drive torque (also referred to as a compressor torque) of the compressor16is increased.

In the following, it is assumed that the compressor16is in operation when the discharge capacity is larger than 0 and is in a suspended state when the discharge capacity is equal to 0.

The condenser18performs heat exchange between the refrigerant discharged from the compressor16and air blown against the condenser18while the vehicle is running and/or air fed from a compressor fan (not shown) rotationally driven by a DC-motor or the like. The receiver24separates a liquid refrigerant from the refrigerant fed from the condenser18via vapor-liquid separation, and temporarily stores the liquid refrigerant therein (in the receiver) to supply only the liquid refrigerant to the downstream side. The liquid refrigerant stored in the receiver24is rapidly expanded through the thermal expansion valve26to be nebulized. The nebulized refrigerant is supplied to an evaporator20that cools air in the passenger compartment. In the evaporator20, some or all of the nebulized refrigerant is vaporized through heat exchange between air fed from an evaporator fan28rotationally driven by a DC-motor and the nebulized refrigerant. This allows air fed from the evaporator fan28to be cooled and then supplied to the passenger compartment via the air blowoff port (not shown) provided in the compartment.

The evaporator20serves as a heat accumulator having a cold-storage agent30(e.g., paraffin) encapsulated therein for storing heat of the refrigerant, which stores a surplus of heat for air conditioning produced in the refrigeration cycle during driving of the compressor16. The heat stored is used for air-conditioning in a period of time when the compressor16is suspended, such as a period of time when the vehicle is automatically stopped by idle stop control (which will be described later). More specifically, heat of the refrigerant is stored in the evaporator20through heat exchange between the refrigerant fed to the evaporator20by driving the compressor16and the cold-storage agent30. Subsequently, when the compressor16is suspended, air fed from the evaporator fan28is cooled through heat exchange between the air fed from the evaporator fan28and the cold-storage agent30, and then supplied to the passenger compartment via the air blowoff port, thereby cooling the passenger compartment while the compressor16is suspended. A refrigerant-temperature sensor32that detects a refrigerant temperature is provided in proximity to an inlet port of the evaporator20. The refrigerant discharged from the evaporator20is suctioned into the compressor16via an inlet port of the compressor16.

The power generation system includes an alternator34and a battery36. The alternator34includes a regulator (not shown) and a rotor coil (not shown), and is rotationally driven by the rotating crankshaft14via the belt22to generate electrical power. More specifically, a power output of the alternator34is adjusted by the regulator adjusting an electrical current flowing through the rotor coil. As the power output of the alternator34becomes larger, a drive torque (alternator torque) for the alternator34increases. An output voltage of the alternator34is set to a voltage larger than a voltage (electromotive force) of the battery36.

The alternator34is electrically connected to the battery36, which in turn is electrically connected to the compressor fan, the evaporator fan28, and other electrical loads38in parallel with each other. The battery36is charged with the power output of the alternator34. The battery36is also a power supply source for the vehicle electrical load38. In the present embodiment, it is assumed that the battery36is a lithium ion battery which is a high energy density battery. This configuration can increase a maximum charging power allowable for the battery36and the power output of the alternator34through the regenerative control which will be described later. As shown inFIG. 1, the battery36is provided with a voltage sensor40that detects a voltage of the battery36and a current sensor42that detects an input/output current of the battery36.

An ECU (hereinafter referred to as an engine-control ECU44) that controls the engine system is composed of a microcomputer including well-known CPU, ROM, and RAM. The engine-control ECU44receives output signals of an accelerator-pedal sensor46that detects an accelerator-pedal depression amount, a brake-pedal sensor48that detects a brake-pedal depression amount, and a vehicle speed sensor50that detects a travelling speed. The engine-control ECU44performs various control programs stored in the ROM or the like in response to the inputs to perform combustion control of the engine10, such as fuel injection control of the fuel injection valve12, and idle stop control.

The idle stop control is such that the engine10is automatically stopped upon stop of fuel injection from the fuel injection valve12when a predetermined stopping condition is met, and then the engine10is restarted by drive control of a starter (not shown) when a predetermined restarting condition is met. The stopping condition may be, for example, that a value of logical AND operation on values of the following two propositions is 1 (true), where one of the two propositions is that a travelling speed derived from an output value of the vehicle speed sensor50is 0 and the other one of the two propositions is that the brake pedal is being depressed. Whether or not the brake pedal is being depressed can be determined on the basis of whether or not the brake-pedal depression amount derived from an output value of the brake-pedal sensor48is 0.

The engine-control ECU44performs fuel-cut control for stopping supply of fuel from the fuel injection valve12as the above fuel injection control. The fuel-cut control is performed, for example, when it is determined that the engine revolution speed becomes equal to or larger than a prescribed revolution speed during the accelerator pedal not being depressed. Whether or not the accelerator pedal is not being depressed may be determined, for example, on the basis of whether or not the accelerator-pedal depression amount derived from an output value of the accelerator-pedal sensor46is 0.

An ECU (hereinafter referred to as an accessory-control ECU52) that controls vehicle-mounted accessories, such as the alternator34and the compressor16, is composed of a microcomputer including well-known CPU, ROM, and RAM. The accessory-control ECU52receives output signals of the air conditioning switch54, the refrigerant-temperature sensor32, the voltage sensor40, and the current sensor42. The output signal of the air conditioning switch54includes a drive command for the compressor16to cool the passenger compartment. The accessory-control ECU52performs various control programs stored in the ROM or the like according to the output signals to perform air-conditioning control of the passenger compartment, such as drive control of the compressor16and air volume control of the evaporator fan28, and drive control of the alternator34.

The engine-control ECU44and the accessory-control ECU52communicate information with each other. More specifically, the engine-control ECU44receives the output signal of the air conditioning switch54and information on the compressor torque through the accessory-control ECU52. The accessory-control ECU52receives the output signals of the accelerator-pedal sensor46, the brake-pedal sensor48, and the vehicle speed sensor50through the engine-control ECU44. Practically, the compressor16and the alternator34are controlled by respective ECUs, which are collectively designated as the accessory-control ECU52inFIG. 1.

The drive control of the alternator34is performed by controlling power supply to the alternator34so that an actual SOC of the battery36can reach a target value of SOC (target SOC) under feedback control. The actual SOC is calculated, for example, on the basis of a battery voltage derived from an output value of the voltage sensor40and a battery current derived from an output value of the current sensor42.

The drive control of the compressor16is performed by controlling power supply to the compressor16so that an actual heat quantity stored in the evaporator20(actual cold storage capacity of the evaporator) can reach a target value (target cold storage capacity) under feedback control. The actual cold storage capacity is calculated, for example, on the basis of a refrigerant temperature derived from an output value of the refrigerant-temperature sensor32.

In the present embodiment, the regenerative control is performed, during deceleration of the vehicle (i.e., during braking by the driver) under the fuel-cut control, to drive the alternator34and the compressor16to convert the kinetic energy of the vehicle into drive energy of the alternator34and the compressor16. The regenerative control may reduce, for example, a subsequent frequency at which the alternator34is driven to charge the battery36, which leads to enhancement of the enhance fuel efficiency of the engine10.

However, when the SOC of the battery36and the cold storage capacity of the evaporator20are already at or around a target level before activation of the regenerative control, kinetic energy of the vehicle cannot be effectively used as drive energy of the alternator34and others through the regenerative control, which may reduce the fuel efficiency of the engine10.

In consideration of the above, in the present embodiment, a target SOC of the battery36and a target cold storage capacity of the evaporator20are set during a vehicle running period of time other than a regenerative control period of time so that the battery36has a margin for storing electrical power and the evaporator20has a margin for storing heat during the regenerative control period of time. This allows kinetic energy of the vehicle to be effectively used as drive energy of the alternator34and other accessories through the regenerative control, which leads to enhancement of the enhance fuel efficiency of the engine10.

There will now be explained the drive control of the alternator34and the compressor16with reference toFIG. 2.

FIG. 2shows a functional block diagram for the drive control of the alternator34and the compressor16to be performed by the accessory-control ECU52. In particular, the drive control of the compressor16is preceded by turn-on of the air conditioning switch54.

A target SOC calculator B1calculates the target SOC of the battery36on the basis of current electrical power supplied from the alternator34to the vehicle electrical load38and the evaporator fan28and others (actual power consumption) and a travelling speed V of the vehicle. More specifically, as actual power consumption becomes larger, the target SOC is set to a larger value. This is because there has to be ensured the power to be supplied to the vehicle electrical load38and others during automatic stop of the engine10under idle stop control. The actual power consumption may be calculated on the basis of a current drive state of the vehicle electrical load38and others.

In addition, as the travelling speed V of the vehicle becomes higher, the target SOC is set to a smaller value. This is because kinetic energy of the vehicle can be effectively used as drive energy of the alternator34without the brake system converting kinetic energy of the vehicle into thermal energy during deceleration of the vehicle due to braking operation by the driver, thereby preventing deterioration in drivability.

In other words, as the travelling speed V of the vehicle becomes higher, the kinetic energy of the vehicle becomes larger, which leads to a larger amount of electrical power that the alternator34can generate during deceleration of the vehicle under the regenerative control. Therefore, setting of the target SOC to a smaller value for a higher travelling speed V of the vehicle allows the battery36to have a margin corresponding to an amount of electrical power that the alternator34can generate under the regenerative control. This allows the kinetic energy of the vehicle to be effectively used as power generation energy of the alternator34during the regenerative control, thereby enhancing fuel efficiency of the engine10.

Further, setting of the target SOC to a larger value for a lower travelling speed V of the vehicle can also prevent deterioration in drivability. This is because, for example, when the regenerative control is performed to drive the alternator34with a predetermined alternator torque and the actual SOC then reaches the target SOC before the end of the regenerative control, electrical power to be subsequently produced by driving the alternator34decreases rapidly, which may lead to reduction in alternator torque and thus to deterioration in drivability. In particular, in the present embodiment where the battery36is a lithium ion battery, since the battery36needs a relatively large maximum charging power, the alternator torque tends to become larger, which may lead to a significantly large degree of rapid decrease in alternator torque and thus to significant deterioration in drivability. As described above, setting of the target SOC to a larger value for a lower travelling speed V during deceleration of the vehicle allows the target SOC to increase gradually during the regenerative control, which may lead to prevention of the actual SOC reaching the target SOC before the end of the regenerative control and thus to suppression of the drivability deterioration.

There will now be explained in more detail a setting process of the target SOC. The target SOC may be calculated on the basis of a map defining a correspondence relation between the travelling speed V of the vehicle and the target SOC. For example, in the present embodiment, the target SOC may be set to an upper limit of a use range which is considered to be the SOC of the battery36at the time that the running vehicle stops without braking and accelerating operations by the driver while the alternator34is being driven with a predetermined torque to charge the battery36.

The above map may be prepared by dividing a use range of the travelling speed V of the vehicle into a plurality of intervals to reduce a workload for setting the target SOC as a function of the travelling speed V of the vehicle, where the target SOC takes a constant value over each interval (see a dotted line of an upper block B1inFIG. 2). That is, the target SOC takes discrete values.

The SOC deviation calculator B2calculates a deviation Δa between the actual SOC and the target SOC. More specifically, the deviation Δa is a value obtained by subtracting the actual SOC from the target SOC.

The alternator FB-controller B3calculates a command value for the alternator torque (hereinafter referred to as an alternator command value Ta) such that the actual SOC of the battery36can reach the target SOC under feedback control. More specifically, the alternator command value Ta is calculated by performing the proportional-integral control (PI-control) on the basis of the deviation Δa between the actual SOC and the target SOC. In the present embodiment, a proportional gain Kap used in the feedback control is set larger for a larger absolute value of the deviation Δa, which leads to enhancement of controllability of the actual SOC.

In this scheme, the proportional gain Kap is set smaller for a smaller absolute value of the deviation Δa between the actual SOC and the target SOC, which can suppress a fluctuation in alternator torque caused by a fluctuation of the actual SOC around the target SOC. On the other hand, the proportional gain Kap is set larger for a larger absolute value of the deviation Δa, which allows the actual SOC to reach the target SOC more rapidly.

The target cold storage capacity calculator B4calculates the target cold storage capacity on the basis of a cooling load and a travelling speed V of the vehicle. More specifically, the target cold storage capacity is set larger for a larger cooling load, and is set smaller for a higher travelling speed V of the vehicle. A reason why the target cold storage capacity is set larger for a larger cooling load is to ensure a larger heat quantity for cooling the passenger compartment during automatic stop of the engine10under the idle stop control. The cooling load may be calculated, for example, on the basis of a temperature difference between a temperature inside the passenger compartment and its target temperature, and an amount of air fed from the evaporator fan28.

Similarly to the process performed by the target SOC calculator B1, setting the target cold storage capacity to a smaller value for a higher travelling speed V of the vehicle is for effectively using kinetic energy of the vehicle as drive energy of the compressor16and for suppressing the drivability deterioration.

Similarly to the setting of the target SOC as described above, the target cold storage capacity may be calculated on the basis of another map defining a correspondence relation between the travelling speed V of the vehicle and the target cold storage capacity. Also similarly to the setting of the target SOC, the above map may be prepared by dividing a use range of the travelling speed V of the vehicle into a plurality of intervals to reduce a workload for setting the target cold storage capacity as a function of the travelling speed V of the vehicle, where the target cold storage capacity takes a constant value over each interval (see a dotted line of a lower block B4inFIG. 2). That is, the target cold storage capacity takes discrete values.

The cold storage capacity deviation calculator B5calculates a deviation Δc between the target cold storage capacity and the actual cold storage capacity. More specifically, the deviation Δc is calculated by subtracting the actual cold storage capacity from the target cold storage capacity.

The compressor FB-controller B6calculates a command value for the compressor torque (hereinafter referred to as a compressor command value Tc) such that the actual cold storage capacity can reach the target cold storage capacity under feedback control. Similarly to the calculation of the alternator command value Ta, the compressor command value Tc is calculated by performing the proportional-integral control (PI-control) on the basis of the deviation Δc between the target cold storage capacity and the actual cold storage capacity. A proportional gain Kcp used in the feedback control is set larger for a larger absolute value of the deviation Δc.

The deceleration requirement calculator B7calculates a deceleration requirement for the vehicle. The deceleration requirement is calculated to be larger as an accelerator-pedal depression amount is decreased and/or a brake-pedal depression amount is increased. A reason why the accelerator-pedal depression amount is used to calculate the deceleration requirement is for taking into account the fact that the vehicle can also be decelerated by decreasing the accelerator-pedal depression amount. More specifically, the deceleration requirement may be calculated by using a map defining a correspondence relation between the decreased amount of accelerator-pedal depression, the brake-pedal depression amount, and the deceleration requirement. The map may be previously determined by experiment.

The torque limiter B8calculates the alternator command value Ta and the compressor command value Tc such that a sum of the alternator command value Ta and the compressor command value Tc is equal to or smaller than an allowable upper limit Tmax for the sum, thereby suppressing drivability deterioration caused by increase in alternator torque and/or compressor torque. The allowable upper limit Tmax is set larger for a larger deceleration requirement, which maximizes a conversion rate of kinetic energy of the vehicle into drive energy of the alternator34and the compressor16through the regenerative control while suppressing the drivability deterioration.

In other words, in the case of an increasing deceleration requirement for the vehicle, since the driver intends to decelerate the vehicle even when the alternator torque and the compressor torque are increased through the regenerative control, it can be assumed that the driver is given as little discomfort as possible. Therefore, setting of the allowable upper limit Tmax to a larger value for a larger deceleration requirement allows the sum of the alternator command value Ta and the compressor command value Tc to increase so that drive energy of the alternator34and the compressor16is increased prior to an amount of kinetic energy of the vehicle being decreased through braking of the vehicle.

Further in the present embodiment, the sum of the alternator command value Ta and the compressor command value Tc is limited to or under the allowable upper limit Tmax while maintaining a ratio of the compressor command value Tc to the alternator command value Ta. This enables the alternator34and the compressor16to be properly driven as a function of a degree of demand for charging the battery and a degree of demand for air-conditioning the passenger compartment.

A resultant alternator command value Ta and a resultant compressor command value Tc are calculated in the torque limiter B8as follows. In the torque limiter88, when it is determined that the sum of the alternator command value Ta calculated by the alternator FB-controller B3and the compressor command value Tc calculated by the compressor FB-controller B6is equal to or smaller than the allowable upper limit Tmax, the alternator command value Ta calculated by the alternator FB-controller B3and the compressor command value Tc calculated by the compressor FB-controller B6are outputted as the resultant alternator command value Ta and the resultant compressor command value Tc, respectively. On the other hand, when it is determined that the sum of the alternator command value Ta calculated by the alternator FB-controller B3and the compressor command value Tc calculated by the compressor FB-controller B6exceeds the allowable upper limit Tmax, the resultant alternator command value Ta to be outputted from the torque limiter B8is given by dividing the alternator command value Ta calculated by the alternator FB-controller B3by the sum of the alternator command value Ta calculated by the alternator FB-controller B3and the compressor command value Tc calculated by the compressor FB-controller B6and then multiplying the quotient by the allowable upper limit Tmax, and the resultant compressor command value Tc to be outputted from the torque limiter B8is given by dividing the compressor command value Tc calculated by the compressor FB-controller B6by the sum of the alternator command value Ta calculated by the alternator FB-controller B3and the compressor command value Tc calculated by the compressor FB-controller B6and then multiplying the quotient by the allowable upper limit Tmax.

In the present embodiment, the allowable upper limit Tmax is set to zero when the deceleration requirement is equal to or smaller than a predetermined value below zero (where the predetermined value may be zero). This allows the power generation of the alternator34to be ceased and the generated torque of the engine10to be efficiently used for driving the vehicle when a degree of acceleration of the vehicle is large.

There will now be explained with reference toFIG. 3a drive control process for the vehicle-mounted accessories in accordance with the present embodiment. This process is performed repeatedly by the accessory-control ECU52at a predetermined time interval.

This process starts with calculation of the target SOC and the target cold storage capacity in step S10in a manner as described above.

Subsequently, in step512, the alternator command value Ta and the compressor command value Tc are calculated by the alternator FB-controller B3and the compressor FB-controller B6, respectively. In step S14, in the torque limiter88, the sum of the alternator command value Ta and the compressor command value Tc is limited to or under the allowable upper limit Tmax to obtain the resultant alternator command value Ta and the resultant compressor command value Tc.

In step S16, the drive control of the alternator34is performed on the basis of the resultant alternator command value Ta, and the drive control of the compressor16is performed on the basis of the resultant compressor command value Tc.

The process in this cycle is ended after the operation of step S16is completed.

FIG. 4shows a timing chart for the drive control of the alternator34in accordance with the present embodiment. More specifically,FIG. 4shows (a) changes in travelling speed V of the vehicle, (b) changes in braking state where “OFF” indicates that the brake-pedal depression amount is zero and “ON” indicates that the brake-pedal depression amount is above zero, (c) changes in SOC of the battery38, (d) changes in alternator command value Ta, and (e) changes in fuel-cut control state.

As shown inFIG. 4, the engine10is restarted at the time t1under the idle stop control. The feedback control on the basis of the deviation Δa between the target SOC and the actual SOC is commenced immediately after the vehicle has started to accelerate. In the feedback control, the target SOC is set smaller for a higher travelling speed V of the vehicle. Subsequently, the accelerator pedal depression amount becomes zero (i.e., the accelerator pedal is released by the driver) at the time t2, which leads to increase in deceleration requirement and thus to increase in allowable upper limit Tmax. At the same time, the fuel-cut control and the regenerative control are started, and the target SOC is increased as the travelling speed V of the vehicle decreases. During a time period from t3to t4, the torque limiting process as described above with reference toFIG. 2is performed for limiting the alternator command value Ta on the basis of the allowable upper limit Tmax. Subsequently, the braking operation is performed at the time t4, which also leads to increase in deceleration requirement and thus to further increase in allowable upper limit Tmax. This allows the alternator command value Ta to be increased at the time t4.

Summary of the Embodiment

There will now be explained advantages of the present embodiment.

(1) In the drive-control of the alternator34and the compressor16, the target SOC of the battery36and the target cold storage capacity of the evaporator20are set during a vehicle running period of time other than a regenerative control period of time so that the battery36has a margin for storing electrical power and the evaporator20has a margin for storing heat. This allows energy generated through the regenerative control to be stored (or accumulated) adequately in the battery36and the evaporator20, which leads to desired enhancement of the fuel efficiency of the engine10.

(2) The target SOC is set smaller for a higher travelling speed V of the vehicle. This can increase a conversion rate of kinetic energy of the vehicle into drive energy of the alternator34and the compressor16and others through the regenerative control while suppressing the drivability deterioration due to rapid decrease in alternator torque or the like during the regenerative control.

It should be noted that in general, as the travelling speed V of the vehicle becomes higher, kinetic energy of the vehicle becomes larger, which leads to a larger amount of energy (electrical energy and/or thermal energy) to be generated by the vehicle-mounted accessories (alternator and/or compressor) through the regenerative control.

(3) The proportional gain Kap used in the feedback control is set larger for a larger absolute value of the deviation Δa between the target SOC and the actual SOC and the proportional gain Kcp used in the feedback control is set larger for a larger absolute value of the deviation Δc between the target cold storage capacity and the actual cold storage capacity, which allows the SOC of the battery36and the cold storage capacity of the evaporator20to be controlled properly.

(4) The sum of the alternator command value Ta and the compressor command value Tc is limited to or under the allowable upper limit Tmax that is set larger for a larger deceleration requirement. This enables the alternator34and the compressor16to be driven with the driver being given as little discomfort as possible during accelerating and/or braking of the vehicle, thereby suppressing the drivability deterioration. In addition, the kinetic energy of the vehicle can be effectively used as drive energy of the alternator34and others before the kinetic energy of the vehicle is decreased due to deceleration of the vehicle.

(5) The sum of the alternator command value Ta and the compressor command value Tc is limited to or under the allowable upper limit Tmax while maintaining a ratio of the compressor command value Tc to the alternator command value Ta. This enables the battery36to be properly charged as a function of a degree of battery charge request and the evaporator20to properly store (or accumulate) heat as a function of a degree of cold storage request.

Without such a torque limiting process, when the sum of the alternator command value Ta and the compressor command value Tc exceeds the allowable upper limit Tmax, a surplus of torques will be discarded without being used as drive energy of the alternator and the compressor and others (vehicle-mounted accessories).

Other Embodiment

In the above embodiment, the allowable upper limit Tmax is set larger for a larger deceleration requirement. Alternatively, the allowable upper limit Tmax may be set larger for a larger brake-pedal depression amount.

In the above embodiment, the battery36is a lithium ion battery. Alternatively, the battery36may be a lead battery.

In the above embodiment, the compressor16is a continuously variable displacement type compressor. Alternatively, the compressor16may be a fixed-displacement type compressor whose discharge capacity is kept constant while being driven, where there is provided for performing drive control of the compressor16an electromagnetic clutch that transfers (in an ON-state) and interrupts (in an OFF-state) rotary power of the crankshaft14from the crankshaft14to the drive shaft of the compressor16through control of power supply to the electromagnetic clutch. More specifically, an operation rate, which is given by dividing an ON-period of time by a prescribed period of time, is adjusted so that an actual cold storage capacity can reach a target cold storage capacity, where the operation rate of 1 may be defined such that the compressor16is driven at a maximum discharge capacity.

In the above embodiment, the evaporator20also serves as a heat accumulator that includes a cold-storage agent30encapsulated therein. Alternatively, the evaporator20may not serve as a heat accumulator.

In the above embodiment, the target SOC and/or the target cold storage capacity are set smaller for a higher travelling speed V of the vehicle. Additionally or alternatively, the target SOC and/or the target cold storage capacity may be set smaller when it is determined that the vehicle is traveling downhill than when it is determined that the vehicle is traveling on level ground on the basis of an output value of a sensor that detects a pavement gradient. With this configuration, rapid decrease in alternator torque which occurs when the actual SOC reaches the target SOC due to increase in kinetic energy of the vehicle when the vehicle is traveling downhill may be suppressed as much as possible.

In the above embodiment, the vehicle supports the idle stop control. Alternatively, the vehicle may not support the idle stop control.

In the above embodiment, the alternator command value Ta and the compressor command value Tc are calculated by means of the PI control. Alternatively, the alternator command value Ta and the compressor command value Tc may be calculated by means of the proportional-integral-derivative control (PID-control) or the proportional control (P-control).

Alternatively to the drive control of the vehicle-mounted accessories in the above embodiment, the drive control of the vehicle-mounted accessories may be performed with drive torque being fixed at a predetermined torque during the regenerative control. With this configuration, fluctuations in drive torque of the vehicle-mounted accessories during the regenerative control can be suppressed, which leads to desirable suppression of the drivability deterioration.

In the above embodiment, the target SOC of the battery36and the target cold storage capacity of the evaporator20are set during a vehicle running period of time other than a regenerative control period of time so that the battery36has a margin for storing electrical power and the evaporator20has a margin for storing heat. Alternatively, the SOC of the battery36and the cold storage capacity of the evaporator20may be controlled during a vehicle running period of time other than a braking period of time so that the actual SOC is kept smaller than an upper limit of the SOC of the battery36by a predetermined amount of SOC and the actual cold storage capacity of the evaporator20is kept smaller than an upper limit of the cold storage capacity of the evaporator20by a predetermined amount of cold storage capacity.

In the above embodiment, the torque limiting process is performed on the basis of the allowable upper limit Tmax, where the alternator command value Ta and the compressor command value Tc are calculated such that a sum of the alternator command value Ta and the compressor command value Tc is equal to or smaller than the allowable upper limit Tmax. Alternatively, the sum of the alternator command value Ta and the compressor command value Tc may be limited to or under the allowable upper limit Tmax while maintaining a ratio of a compressor torque requirement to an alternator torque requirement. The alternator torque requirement is a ratio of an actual alternator torque to an alternator maximum drive torque which is an alternator torque when the alternator34is driven to output maximum power as a function of a revolution speed of the alternator34. The power output of the alternator34becomes larger as the alternator torque requirement increases. The compressor torque requirement is a ratio of an actual compressor torque to a compressor maximum drive torque which is a compressor torque when the compressor16is driven at a maximum discharge capacity. The discharge capacity of the compressor16becomes larger as the compressor torque requirement increases. In the alternative torque limiting procedure on the basis of the ratio of the compressor torque requirement to the alternator torque requirement, the actual alternator torque is normalized by the alternator maximum drive torque and the compressor torque, is normalized by the compressor maximum drive torque. Therefore, even in the case of a large difference between the alternator maximum drive torque and the compressor maximum drive torque, this allows the battery36to be charged to properly reflect a degree of demand for charging the battery36and the evaporator20to store heat to properly reflect a degree of demand for air-conditioning the passenger compartment.