Abstract:
A control apparatus provided in a hybrid vehicle having a combustion engine for outputting a driving force, an electric motor for generating a force for assisting the output from the engine, depending on the driving conditions, a power storage unit for storing electric energy generated by the motor acting as a generator using the output from the engine and electric energy regenerated by the motor when the vehicle decelerates. The control apparatus includes: a speed limiter for decreasing the driving force produced by the motor when the vehicle speed exceeds a first threshold value while the engine and the motor produce the driving force; a generation starter for starting generation by the motor when the vehicle speed exceeds a second threshold value which is higher than the first threshold value; and a generation amount setting device for setting the amount of generation, depending on the driving conditions of the vehicle, when the generation starter starts the generation. The motor generates the electric energy, depending on the amount of generation set by the generation amount setting device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control apparatus for a hybrid vehicle which can optimize energy management when the vehicle is driving at a high speed. 
     2. Description of the Related Art 
     Conventionally, hybrid vehicles are well-known which have electric motors as power sources for driving the vehicles in addition to engines. 
     In conventional hybrid vehicles, there are parallel hybrid vehicles which use motors as assisting driving sources for assisting the output from the engines. Parallel hybrid vehicles assist the output from the engine by the motor when the vehicle accelerates, charge the battery by deceleration regeneration when the vehicle decelerates, and perform various controls, to respond the driver&#39;s demands while maintaining the remaining charge (electric energy) of the battery (as disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 7-123509). 
     When a conventional hybrid vehicle is accelerating, the motor assists the output from the engine. The assistance of the output from the engine by the motor is maintained even when the vehicle is driving at a high speed when the fuel supply to the engine is stopped by a limiter. In this case, even though the engine is controlled to decelerate the vehicle, the motor is controlled to assist the driving power from the engine, thus causing inconsistencies in the controls. 
     The unnecessary assistance by the motor decreases the remaining charge of the battery, causing problems in energy management. 
     For example, the vehicle drives at a high speed while stopping the fuel supply, the vehicle then decelerates, and the motor enters a deceleration mode to perform regeneration. In this case, the deceleration may be excessive, and the driver may experience a feeling of unease. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a control apparatus for a hybrid vehicle which restricts the assistance of the engine by the motor, and which appropriately controls electric generation. 
     In a first aspect of the present invention, the control apparatus is provided in a hybrid vehicle with a combustion engine (E) for outputting a driving force, an electric motor (M) for generating a force for assisting the output from the engine, depending on the driving conditions, a power storage unit (battery  3 ) for storing electric energy generated by the motor acting as a generator using the output from the engine and electric energy regenerated by the motor when the vehicle decelerates. The control apparatus includes: a speed limiter (step S 100 A) for decreasing the driving force produced by the motor when the vehicle speed exceeds a first threshold value (assist trigger look-up upper limit vehicle speed #VMASTHG) while the engine and the motor produce the driving force; a generation starter (step S 100 B) for starting generation by the motor when the vehicle speed exceeds a second threshold value (the high vehicle speed VASTVHG, shown in FIG. 15, at which the assistance is zero) which is higher than the first threshold value; and a generation amount setting device (step S 250 ) for setting the amount of generation, depending on the driving conditions of the vehicle, when the generation starter starts the generation. The motor generates the electric energy, depending on the amount of generation set by the generation amount setting device. 
     When the vehicle speed exceeds the first threshold value, the unnecessary driving force is decreased. Further, when the vehicle speed exceeds the second threshold value, the motor starts the generation to restrict the increase of the vehicle speed. 
     That is, as compared with the case where the fuel supply to the engine is suddenly stopped, the feeling of unease felt by the driver is reduced. 
     In a second aspect of the present invention, the speed limiter decreases the driving force produced by the motor after the vehicle speed exceeds the first threshold value until the vehicle speed reaches the second threshold value, and makes the motor stop the production of the driving force when at the second threshold value. 
     When at the second threshold value, the motor stops producing the driving force, and can continuously start the generation. 
     That is, once the motor stops producing the driving force, the motor smoothly starts the generation, thereby preventing the driver from experiencing the feeling of unease. 
     In a third aspect of the present invention, the control apparatus includes a fuel supply stopper for repeating stopping of the supply of fuel at a predetermined interval when the vehicle speed reaches a fourth threshold value which is higher than the second threshold value. 
     The control apparatus can reliably decrease the vehicle speed even the braking by stopping the assistance for the engine while starting the generation by the motor is insufficient. 
     Therefore, the energy is not unnecessarily consumed when the vehicle is driving at a high speed, thereby reducing the fuel consumption. 
     In a fourth aspect of the present invention, the generation amount setting device sets the amount of generation, depending on the degree of throttle opening, when the vehicle speed exceeds a third threshold value which is higher than the second threshold value and lower than the fourth threshold value. 
     When decelerating the vehicle by the generation by the motor, the amount of generation can be adjusted by the generation amount setting device, depending on the degree of the throttle opening indicating the driver&#39;s intention. 
     Once the motor starts the generation, the amount of generation is set depending on the degree of throttle opening. Therefore, the vehicle decelerates depending on the depression of the accelerator pedal by the driver, and this prevents the driver from experiencing a feeling of unease. As the result, the energy management can be optimized, and the commercial value of the vehicle is increased. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing the structure of the hybrid vehicle with the control system of the present invention. 
     FIG. 2 is a graph showing the assistance, generation, and fuel supply cut operation when the vehicle of the present invention is driving at a high speed. 
     FIG. 3 is a flowchart showing the motor operation determination in the present invention. 
     FIG. 4 is a flowchart showing the motor operation determination in the present invention. 
     FIG. 5 is a flowchart showing the assist trigger determination in the present invention. 
     FIG. 6 is a flowchart showing the assist trigger determination in the present invention. 
     FIG. 7 is a graph for determining a cruise charging amount correction coefficient when at a high speed according to the present invention. 
     FIG. 8 is a graph for calculating the values in steps S 119  and S 131  according to the present invention. 
     FIG. 9 is a graph showing threshold values in a TH assist mode and in a PB assist mode in the present invention. 
     FIG. 10 is a graph showing a TH assist trigger upper limit in the present invention. 
     FIG. 11 is a graph showing threshold values for an MT vehicle in the PB assist mode in the present invention. 
     FIG. 12 is a graph for the calculation in steps S 120  and S 132  in the present invention. 
     FIG. 13 is a graph showing threshold values for a CVT vehicle in the PB assist mode in the present invention. 
     FIG. 14 is a flowchart showing the acceleration mode in the present invention. 
     FIG. 15 is a graph showing the upper limit value of the amount of assistance in the present invention. 
     FIG. 16 is a main flowchart of a cruise mode in the present invention. 
     FIG. 17 is a flowchart showing the calculation of the amount of cruise charging in the present invention. 
     FIG. 18 is a flowchart showing the calculation of the cruise charging amount in the present invention. 
     FIG. 19 is a flowchart showing the calculation of a cruise charging amount correction coefficient in the present invention. 
     FIG. 20 is a graph for obtaining a cruise charging amount correction coefficient #KVCRSRG in the present invention. 
     FIG. 21 is a graph for obtaining a cruise charging amount coefficient #KRGVELN in the present invention. 
     FIG. 22 is a graph for obtaining a cruise generation coefficient #KPACRSRN in the present invention. 
     FIG. 23 is a graph showing a table for looking up the degree of throttle opening, depending on the engine speed in the present invention. 
     FIG. 24 is a graph for interpolating the cruise charging correction coefficient depending on the present degree of throttle opening in the present invention. 
     FIG. 25 is a graph for looking up a cruise charging fully-opened throttle correction coefficient depending on the engine speed in the present invention. 
     FIG. 26 is a graph for interpolating a cruise charging fully-opened throttle correction coefficient depending on the present degree of throttle opening in the present invention. 
     FIG. 27 is a flowchart showing the determination for stopping the fuel supply in the present invention. 
     FIG. 28 is a flowchart showing the determination for stopping the fuel supply in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiment of the control apparatus for the hybrid vehicle of the present invention will be explained with reference to the figures. 
     The hybrid vehicle is a parallel hybrid vehicle. Driving forces from both an engine E and a motor M are transmitted via a transmission T of an automatic or manual transmission, to front wheels Wf which are the drive wheels. When the hybrid vehicle decelerates and the driving force is transmitted from the front wheels Wf to the motor M, the motor M acts as a generator to generate what is termed a regenerative braking force, so that the kinetic energy of the vehicle body is stored as electric energy. Reference symbol Wr denotes rear wheels. 
     A power drive unit  2  performs the driving and regeneration of the motor M in response to control commands from a motor ECU  1 . A high-voltage battery  3  for sending and receiving electric energy to and from the motor M is connected to the power drive unit  2 . The battery  3  includes a number of modules connected in series, each module having a number of cells connected in series. The hybrid vehicle includes a 12-volt auxiliary battery  4  for driving various accessories. The auxiliary battery  4  is connected to the battery  3  via a downverter  5 . The downverter  5 , controlled by an FIECU  11 , reduces the voltage from the battery  3  and charges the auxiliary battery  4 . 
     The FIECU  11  controls, in addition to the motor ECU  1  and the downverter  5 , a fuel supply amount controller  6  for controlling the amount of fuel supplied to the engine E, a starter motor  7 , an ignition timing, etc. Therefore, the FIECU  11  receives a signal from a speed sensor S 1  for detecting the vehicle speed V based on the rotation of the driving shaft of the transmission, a signal from an engine rotational speed sensor S 2  for detecting the engine rotational speed NE, a signal from a shift position sensor S 3  for detecting the shift position of the transmission T, a signal from a brake switch S 4  for detecting operation of a brake pedal  8 , a signal from a clutch switch S 5  for detecting operation of a clutch pedal  9 , a signal from a throttle valve opening sensor S 6  for detecting the degree of throttle opening TH (throttle opening state), and a signal from an air intake passage pressure sensor S 7  for detecting the air intake passage pressure PB. In FIG. 1, reference numeral  21  denotes a CVTECU for controlling the CVT (Continuous Variable Transmission), and reference numeral  31  denotes a battery ECU for protecting the battery  3  and calculating the state of charge (remaining charge) SOC of the battery  3 . 
     Motor Operation Mode Determination 
     The control modes of the hybrid vehicle are the “idle mode”, “idle stop mode”, “deceleration mode”, “acceleration mode”, and “cruise mode.” In the idle mode, the fuel supply is stopped, and is restarted to maintain the engine in the idling state. In the idle stop mode, the engine is stopped under specific conditions, e.g., when the vehicle stops. In the deceleration mode, the motor M performs the regenerative braking. In the acceleration mode, the motor assists the engine. In the cruise mode, the motor is not driven, and the vehicle is driven only by the driving force produced by the engine. 
     The motor operation determination mode for determining the mode will be explained with reference to the flowcharts of FIGS. 3 and 4. 
     In step S 001 , it is determined whether an MT/CVT determination flag F_AT is 1. When this determination is NO, that is, when the vehicle is an MT vehicle, the flow proceeds to step S 002 . When in step S 001  the determination is YES, that is, when the vehicle is a CVT vehicle, the flow proceeds to step S 010 , and it is then determined whether the CVT in-gear determination flag F_ATNP is 1. When in step S 010  the determination is NO, that is, when in the in-gear state, the flow proceeds to step S 010 A, and it is then determined, based on a switch back determination flag F_VSWB, whether the vehicle is being switched back (the shift lever is being operated). When the vehicle is being switched back, the flow proceeds to step S 022 , enters the idling mode, and the control terminates. In the idling mode, the fuel supply is stopped, and is then restarted, and the idling of the engine E is continued. When in step S 010 A the vehicle is not being switched back, the flow proceeds to step S 004 . 
     When in step S 010  the determination is YES, that is, when in the N-(neutral) or P-(parking) position, the flow proceeds to step S 014 , and it is determined whether the engine stop control execution flag F_FCMG is 1. When in step S 014  this determination is NO, the flow enters the idling mode in step S 022 , and the control terminates. When in step S 014  the flag is 1, the flow proceeds to step S 023 , and enters idling stop mode, and the control terminates. In the idling stop mode, the engine E is stopped under specified conditions e.g., when the hybrid vehicle is stopped. 
     In step S 002 , it is determined whether the neutral position determination flag F_NSW is 1. When in step S 002  the determination is YES, that is, when in the neutral position, the flow proceeds to step S 014 . When in step S 002  the determination is NO, that is, when in the in-gear state, the flow proceeds to step S 003 , and it is determined whether a clutch engagement determination flag F_CLSW is 1. When the determination is YES, that is, when the clutch is disengaged, the flow proceeds to step S 014 . When in step S 003  the determination is NO, that is, when the clutch is engaged, the flow proceeds to step S 004 . 
     In step S 004 , it is determined whether the IDLE determination flag F_THIDLMG is 1. When this determination is NO, that is, when the throttle is completely closed, the flow proceeds to step S 011 . When in step S 004  the determination is YES, that is, when the throttle is not completely closed, the flow proceeds to step S 005 , and it is determined whether the motor assistance determination flag F_MAST is 1. 
     When in step S 005  the determination is NO, the flow proceeds to step S 011 . When in step S 005  the determination is YES, the flow proceeds to step S 006 . 
     In step S 011 , it is determined whether the MT/CVT determination flag F_AT is 1. When the determination is NO, that is, when the vehicle is an MT vehicle, the flow proceeds to step S 013 . When in step S 011  the determination is YES, that is, when the vehicle is a CVT vehicle, the flow proceeds to step S 012 , and it is determined whether the reverse position determination flag F_ATPR is 1. When this determination is YES, that is, when in the reverse position, the flow proceeds to step S 022 . When the determination is NO, that is, when in other than the reverse position, the flow proceeds to step S 013 . 
     In step S 006 , it is determined whether the MT/CVT determination flag F_AT is 1. When this determination is NO, that is, when the vehicle is an MT vehicle, it is determined in step S 008  whether a final charging command value REGENF is equal to or below zero. When the value is equal to or below zero, the flow proceeds to the acceleration mode in step S 009 , and the control terminates. When in step S 008  the REGENF is above zero, the control terminates. 
     When in step S 006  the determination is YES, that is, the vehicle is a CVT vehicle, the flow proceeds to step S 007 , and it is determined whether a brake ON determination flag F_BKSW is 1. When in step S 007  this determination is YES, that is, when the driver is depressing the brake, the flow proceeds to step S 013 . When in step S 007  the determination is NO, that is, when the driver is not depressing the brake, the flow proceeds to step S 008 . 
     In step S 013 , it is determined whether the vehicle speed VP for the engine control is zero. When this determination is YES, that is, when the vehicle speed VP is zero, the flow proceeds to step S 014 . When in step S 013  the determination is NO, that is, when the vehicle speed VP is not zero, the flow proceeds to step S 015 . In step S 015 , it is determined whether an engine stop control execution flag F_FCMG is 1. When in step S 015  the determination is NO, the flow proceeds to step S 016 . When in step S 015  the flag is 1, the flow proceeds to step S 023 . 
     In step S 016 , the vehicle speed VP for the engine control is compared with a deceleration mode braking determination lower vehicle speed #VRGNBK. The #VRGNBK has hysteresis. 
     When in step S 016  the vehicle speed VP≦the deceleration mode braking determination lower vehicle speed #VRGNBK, the flow proceeds to step S 019 . When in step S 016  the VP&gt;#VRGNBK, the flow proceeds to step S 017 . 
     In step S 017 , it is determined whether the brake ON determination flag F_BKSW is 1. When in step S 017  the determination is YES, that is, the driver is depressing the brake, the flow proceeds to step S 018 . When in step S 017  the determination is NO, that is, the driver is not depressing the brake, the flow proceeds to step S 019 . 
     In step S 018 , it is determined whether the IDLE determination flag F_THIDLMG is 1. When this determination is NO, that is, when the throttle is completely closed, the flow proceeds to step S 024 , and enters the deceleration mode, and the control terminates. In the deceleration mode, the regenerative braking by the motor M is performed. When in step S 018  the determination is YES, that is, when the throttle is not completely closed, the flow proceeds to step S 019 . 
     In step S 019 , it is determined whether a deceleration fuel supply cut execution flag F_MADECFC is 1. The flag is used to determine whether to stop the fuel supply in a special mode in a high speed range described below. 
     When in step S 019  the determination is YES, that is, when the fuel supply is stopped because the vehicle is decelerating, the flow proceeds to step S 024 . When in step S 019  the determination is NO, the flow proceeds to step S 020 , a final assistance command value ASTPWRF is decreased, and in step S 021  it is determined whether the final assistance command value ASTPWRF is equal to or below zero. When the value is equal to or below zero, the flow proceeds to step S 025 , and enters the cruise mode. In the cruise mode, the hybrid vehicle travels by the driving force produced by the engine E without assistance by the motor M. Further, the motor M regenerates the power, or acts as a generator to charge the battery  3 , depending on the driving condition of the vehicle. When in step S 021  the ASTPWRF is above zero, the control terminates. 
     Zoning of State of Charge (SOC) 
     The zoning of the state of charge (also referred to as the “remaining charge” or SOC) (dividing the remaining charge into zones), which significantly affects the entry into the assist trigger determination, and the cruise mode, will be explained. The calculation of the SOC is carried out by the battery ECU  31  of the hybrid vehicle  10 , based on, i.e., the voltage, the discharged current, or the temperature. 
     In this example, zone A (from 40% to 80 or 90% of SOC), which is the normal use zone, is defined as the standard. Zone B (from 20% to 40% of SOC), which is a temporary use zone, is below zone A, and zone C (from 0% to 20% of SOC), which is an over-discharge zone, is below zone B. Zone D (from 80% or 90% to 100% of SOC), which is an overcharge zone, is above zone A. 
     The SOC is calculated by integrating the current when in zones A and B, and is calculated based on voltages when in zones C and D, taking into consideration the characteristics of the battery. The boundaries between zones A, B, C, and D have upper and lower threshold values. The threshold values when the SOC is increasing are chosen to differ from those when the SOC is decreasing so as to cause hysteresis. 
     Assist Trigger Determination 
     FIGS. 5 and 3 are flowcharts showing the assist trigger determination which specifically determines the acceleration/cruise mode based on zones. 
     In step S 100 , it is determined whether an energy storage zone C flag F_ESZONEC is 1. When this determination is YES, that is, when the battery remaining charge SOC is in zone C, it is determined in step S 136  whether a final assist command value ASTPWRF is equal to or below 0. When in step S 136  the determination is YES, that is, when the final assist command value ASTPWRF is equal to or below 0, a cruise charging subtraction coefficient KTRGRGN is set to 1.0 in step S 137 , a motor assist determination flag F_MAST is set to 0 in step S 122 , and the flow returns. 
     When in steps S 100  and S 136  the determination is NO, the flow proceeds to step S 100 A. In step S 100 A, the vehicle speed VP is compared with an assistance trigger look-up upper vehicle speed #VMASTHG. The #VMASTHG has hysteresis. 
     When in step S 100 A the vehicle speed VP is equal to or below the assistance trigger look-up upper vehicle speed #VMASTHG, the flow proceeds to step S 101 . The #VMASTHG is, for example, 170 km. 
     When in step S 100 A the vehicle speed VP is above the assistance trigger look-up upper vehicle speed #VMASTHG, the flow proceeds to step S 100 B. In step S 100 B, as shown in FIG. 7, a cruise charging amount correction coefficient KTRGRGN for high speed cruising is looked up in a #KVTRGRN table, based on the vehicle speed VP. The flow proceeds to step S 122 . The KTRGRGN is used as a coefficient in step S 365  in FIG.  19 . As the vehicle speed is increased, the coefficient is increased, and the cruise charging amount CRSRGN is gradually increased. Therefore, the motor is not suddenly switched from the driving operation to the charging operation, and is smoothly switched, preventing unstable behavior of the vehicle. 
     When in the determination in step S 100 A the vehicle speed VP is above the assist trigger look-up upper vehicle speed #VMASTHG, step S 100 A does not look up the assist trigger after step S 100 B, and does not enter the acceleration mode. Further, the motor assistance is gradually decreased as shown in FIG. 15 which is explained below. This prevents a shock due to variations in the driving power which are caused by suddenly stopping the motor assistance. 
     In step S 101 , a throttle assist trigger correction value DTHAST is calculated. The process increases the assist trigger threshold value, depending on the atmospheric pressure, when the consumed electric power consumption at 12 volts is high. 
     In step S 102 , a threshold value MTHASTN which is the standard for the throttle assist trigger is looked up in a #MTHAST throttle (assist trigger) table. The #MTHAST throttle assist trigger table, as shown with the solid line in FIG. 9, defines the threshold value MTHASTN of the degree of throttle opening depending on the engine speed NE. The threshold value MTHASTN is the standard for the determination of whether the motor assist is performed, and is based on the engine speed NE. 
     Subsequently, in steps S 103  and S 106 , the threshold value MTHASTN which is the standard for the throttle assist trigger obtained in step S 102  is added to the correction value DTHAST calculated in step S 101  to obtain an upper throttle assist trigger threshold MTHASTH. A difference #DMTHAST for setting the hysteresis is subtracted from the upper throttle assist trigger threshold value MTHASTH to obtain a lower throttle assist trigger threshold value MTHASTL. These upper and lower throttle assist trigger threshold values are shown with the dashed lines MSASTNH and MSASTNL in FIG. 9, overlapping the standard threshold value MTHASTN of the throttle assist trigger table. 
     In step S 104  after step  103 , a throttle assist trigger upper limit value MTHHASTN is looked up in a throttle assist trigger upper limit table, shown in FIG. 10, depending on the engine speed NE. In step S 105 , it is determined whether the upper throttle assist trigger threshold value MTHASTH obtained in step S 103  is equal to or above the MTHHASTN. When the MTHASTH is equal to or above the MTHHASTN, the flow proceeds to step S 105 A, the MTHASTH is then set to the MTHHASTN, and the flow proceeds to step S 106 . When in step S 105  the MTHASTH is below the MTHHASTN, the flow proceeds to step S 106 . 
     Thus, steps S 104 , S 105 , and S 105 A sets the assist trigger threshold value below the throttle assist trigger upper limit value MTHHASTN, regardless of the additional amount for the assist trigger threshold value when correcting the throttle assist trigger in step S 101  described below. The MTHASTH has an upper limit which depends on the engine speed NE, which avoids the situation in which the assistance is hard to start, and which improves the driveability. 
     In step S 107 , it is determined whether the present value THEM of the degree (extent, or state) TH of throttle opening is equal to or above the throttle assist trigger threshold value MTHAST calculated in steps S 105  and S 106 . The throttle assist trigger threshold value MTHAST, which includes the hysteresis mentioned above, refers to the upper throttle assist trigger threshold value MTHASTH when the degree TH of the throttle opening is increased, and refers to the lower throttle assist trigger threshold value MTHASTL when the degree TH of the throttle opening is decreased. 
     When in step S 107  the determination is YES, that is, when the present value THEM of the degree TH of throttle opening is equal to or above the throttle assist trigger threshold value MTHAST (which has the upper and lower hysteresis), the flow proceeds to step S 109 . When in step S 107  the determination is NO, that is, when the present value THEM of the degree TH of throttle opening is not equal to or above the throttle assist trigger threshold value MTHAST (which has the upper and lower hysteresis), the flow proceeds to step S 108 . 
     In step S 109 , the throttle motor assist determination flag F_MASTTH is set to 1. In step S 108 , the throttle motor assist determination flag F_MASTTH is set to 0. 
     In the above process, it is determined whether the motor assist is required according to the degree TH of the throttle opening. When in step S 107  the present value THEM of the degree TH of the throttle opening is equal to or above the throttle assist trigger threshold value MTHAST, the throttle motor assist determination flag F_MASTTH is set to 1. In the above-described acceleration mode, the flag is read and it is determined that the motor assist is required. 
     When in step S 108  the throttle motor assist determination flag F_MASTTH is set to 0, this indicates that the vehicle is outside the zone in which the motor assist determination is made based on the degree TH of throttle opening. The embodiment performs the assist trigger determination based on the throttle opening state TH or on the air intake passage pressure PB of the engine. When the present value THEM of the degree TH of the throttle opening is equal to or above the throttle assist trigger threshold value MTHAST, the assist determination is made based on the opening state TH of the throttle, while, when the present value THEM does not exceed the threshold value MTHAST, the determination is made based on the air intake passage pressure PB. 
     In step S 109 , the throttle motor assist determination flag F_MASTTH is set to 1. Then, the flow proceeds to step S 134 , separating from the normal assist determination, and the cruise generation subtraction coefficient KTRGRGN is set to 0. In the next step S 135 , the motor assist determination flag F_MAST is set to 1, and the flow returns. 
     In step S 110 , it is determined whether a MT/CVT determination flag F_AT is 1. When this determination is NO, that is, when the vehicle is an MT vehicle, the flow proceeds to step S 111 . When in step S 110  the determination is YES, that is, when the vehicle is a CVT vehicle, the flow proceeds to step S 123 . In step S 111 , an air intake passage assist trigger correction value DPBAST is calculated. This process increases the assist trigger threshold value, depending on the atmospheric pressure, when the 12-volt consumed electric power is high. 
     Subsequently, in step S 112 , threshold values MASTL and MASTH (for an MT vehicle) for the air intake passage pressure assist trigger are looked up in an air intake passage pressure assist trigger table. The air intake passage pressure assist trigger table, as shown with the two solid lines in FIG. 11, defines the upper air intake passage pressure assist trigger threshold value MASTH and the lower air intake passage pressure assist trigger threshold value MASTL for determining whether the motor assist is required depending on the engine rotational speed NE. In the process in step S 112 , when the air intake passage pressure PBA, as the PBA is increased or as the engine rotational speed NE is decreased, crosses the upper threshold value line MASTH from the lower area to the upper area in FIG. 11, the motor assist determination flag F_MAST is switched from 0 to 1. When the air intake passage pressure PBA, as the PBA is decreased or as the engine rotational speed NE is increased, crosses the lower threshold value line MASTL from the upper area to the lower area, the motor assist determination flag F_MAST is switched from 1 to 0. The process shown in FIG. 11 is changed depending on the stoichiometric or the lean-burn state. 
     In the next step S 113 , it is determined whether the motor assist determination flag F_MAST is 1. When this determination is 1, the flow proceeds to step S 114 . When the determination is not 1, the flow proceeds to step S 115 . In step S 114 , the air intake passage pressure lower threshold value MASTL calculated in step S 112  and the correction value DPBAST calculated in step S 111  are added to thereby obtain an air intake passage assist trigger threshold value MAST. In step S 116 , it is determined whether the present air intake passage pressure PBA is equal to or above the MAST obtained in step S 114 . When this determination is YES, the flow proceeds to step S 134 . When the determination is NO, the flow proceeds to step S 119 . In step S 115 , the air intake passage assist trigger upper threshold value MASTH looked up in step S 112  and the correction value DPBAST calculated in step S 111  are added to thereby obtain the air intake assist trigger threshold value MAST, and the flow proceeds to step S 116 . 
     In step S 119 , as shown in FIG. 8, a predetermined air intake passage pressure delta value #DCRSPB (e.g., 100 mmHg) is subtracted from the air intake passage pressure assist trigger threshold value MAST, to thereby obtain a final air intake passage pressure lower threshold value MASTFL. Then, in step S 120  as shown in FIG. 12, the threshold value is interpolated between MASTFL and MAST, based on the present air intake passage pressure PBA, to thereby obtain a cruise charging subtraction coefficient KPBRGN. In step S 121 , this KPBRGN is set as the cruise charging subtraction coefficient KTRGRGN. In step S 122 , the motor assist determination flag F_MAST is set to 0, and the flow returns. 
     In step S 123 , the air intake passage pressure assist trigger correction value DPBASTTH has been calculated. The process increases the assist trigger threshold value, depending on the atmospheric pressure, when the electric power consumption at 12 volts is high. 
     In step S 124 , the PB assist trigger threshold values MASTTHL and MASTTHH (for a CVT vehicle) are looked up in the PB assist trigger table. The PB assist trigger table, as shown in FIG. 13 with two solid lines, defines the upper PB assist trigger threshold value MASTTHH and the lower PB assist trigger threshold value MASTTHL for determining whether to perform the assist by the motor, depending on the vehicle speed VP. In the look-up process in step S 124 , when the degree TH of throttle opening, as it is increased or as the vehicle speed VP is decreased, crosses the upper threshold value line MASTTHH from the lower area to the upper area in FIG. 13, the motor assist determination flag F_MAST is switched from 0 to 1. When TH, as it is decreased or as VP is increased, crosses the lower threshold value line MASTTHL from the upper area to the lower area, the motor assist determination flag F_MAST is switched from 1 to 0. The process shown in FIG. 13 is changed depending on the position of the gear, and depending on the stoichiometric or lean-burn state. 
     In step S 125 , it is determined whether the motor assist determination F_MAST is 1. When the flag is 1, the flow proceeds to step S 126 . When it is not 1, the flow proceeds to step S 127 . In step S 126 , the lower PB assist trigger threshold value MASTTHL looked up in step S 124  is added to the correction value DPBASTTH calculated in step S 123 , to thereby obtain the PB assist trigger threshold value MASTTH. In step S 128 , it is determined whether the present value THEM of the degree TH of throttle opening is equal to or above the PB assist trigger threshold value MASTTH calculated in step S 126 . When the determination is YES, the flow proceeds to step S 134 . When the determination is NO, the flow proceeds to step S 131 . In step S 127 , the upper PB assist trigger threshold value MASTTHH, and the correction value DPBASTTH are added to the PB assist trigger threshold value MASTTH, and the flow proceeds to step S 128 . 
     In step S 131 , a predetermined delta value #DCRSTHV of the degree TH of throttle opening is subtracted from the PB assist trigger threshold value MASTTH, to thereby obtain a final PB assist trigger lower threshold value MASTTHFL. In the next step S 132 , the threshold value is interpolated between MASTTHFL and MASTTH, based on the present value THEM of the degree TH of throttle opening, to obtain a cruise charging subtraction coefficient table value KPBRGTH, and in step S 133  this KPBRGTH is set as the cruise charging subtraction coefficient KTRGRGN. In step S 122 , the motor assist determination flag F_MAST is set to 0, and the flow returns. 
     Acceleration Mode 
     FIG. 14 is a flowchart showing the acceleration mode. In the acceleration mode, the amount of assistance is calculated. 
     In step S 220 , it is determined whether the vehicle is in the acceleration mode. When the vehicle is not in the acceleration mode, the final assist command value ASTPWRF is set to 0 in step S 221 , and the flow proceeds to step S 223 . When in step S 220  the vehicle is in the acceleration mode, a normal assist final calculated value ACCASTF is set to the ASTPWRF, and the flow proceeds to step S 223 . 
     In step S 223 , the normal assist calculation process is performed, and, in the next step S 224 , the final assist command value ASTPWRF is set to the final normal assist calculated value ACCASTF. 
     When in step S 224  the final assist command value ASTPWRF is set to the predetermined amount of assistance, the normal assistance is started in step S 225 . Then, as shown in FIG. 15, in step S 226 , the assistance amount upper limit value ASTVHG is obtained from a table, depending on the vehicle speed VP for the engine control. In step S 227 , it is determined whether the ASTPWRF is equal to or above the ASTVHG. When this determination is YES, the final assist command value is set to the ASTVHG in step S 228 , the final generation amount is set to 0 in step S 229 , and the flow returns. 
     When in step S 227  the determination is NO, the flow proceeds to step S 229 . Therefore, when the vehicle speed reaches a high speed above a predetermined value (VMASTHG) in the above-described step S 100 A, the assistance is limited, based on the vehicle speed, as shown in FIG.  15 . Thus, the assistance is gradually decreased, and finally becomes zero. This process prevents unnecessary assistance, and is therefore advantageous in the terms of energy management. Further, the generation by the motor can be smoothly started, and therefore the drives does not experience a feeling of unease. 
     Cruise Mode 
     Next, the cruise mode will be explained with reference to FIGS. 16 to  26 . The main flowchart of the cruise mode in FIG. 16 will be explained. In step S 250 A, it is determined whether the vehicle is in the cruise mode. When in step S 250 A the vehicle is not in the cruise mode, the final cruise charging amount CRSRGNF is set to 0 in step S 250 C, and the flow proceeds to step S 250 . When in step S 250 A the vehicle is in the cruise mode, the final cruise charging amount CRSRGNF is set to the final charging command value REGENF in step S 250 B, and the flow proceeds to step S 250 . 
     Step S 250  performs a process for calculating the cruise charging amount which will be described with reference to FIGS. 17 and 18. The flow proceeds to step S 251 , and it is then determined whether a gradual addition/subtraction timer TCRSRGN is zero. When this determination is NO, a final charging command value REGENF is set to a final cruise charging amount CRSRGNF in step S 259 , the final assistance command value ASTPWRF is set to zero in step S 260 , and the control terminates. 
     When in step S 251  the determination is YES, the gradual addition/subtraction timer TCRSRGN is set to a predetermined value #TMCRSRGN in step S 252 , and the flow proceeds to step S 253 . In step S 253 , it is determined whether the cruise charging amount CRSRGN is equal to or above the final cruise charging amount CRSRGNF. 
     When in step S 253  the determination is YES, the flow proceeds to step S 257 , and a gradual addition factor #DCRSRGNP is added to the CRSRGNF. Then, in step S 258 , it is again determined whether the CRSRGN is equal to or above the CRSRGNF. When in step S 258  the CRSRGN is equal to or above the CRSRGNF, the flow proceeds to step S 259 . 
     When in step S 258  the cruise charging amount CRSRGN is below the final cruise charging amount CRSRGNF, the flow proceeds to step S 256 , the CRSRGNF is set to the CRSRGN, and the flow proceeds to step S 259 . 
     When in step S 253  the determination is NO, a gradual subtraction factor #DCRSRGNM is subtracted from the CRSRGNF in step S 254 , and it is determined in step S 255  whether the CRSRGNF is equal to or above the CRSRGN. When in step S 255  the CRSRGN is above the CRSRGNF, the flow proceeds to step S 256 . When in step S 255  the CRSRGNF is equal to or above the CRSRGN, the flow proceeds to step S 259 . 
     The process following step S 251  eliminates rapid variations in the amount of generation, and allows the vehicle to smoothly enter the cruise charging mode. 
     Next, the flowchart in step S 250  of FIG. 16 for calculating the cruise charging amount will be explained with reference to FIGS. 17 and 18. 
     In step S 300 , a cruise charging amount CRSRNM is looked up in a map. The map defines the cruise charging amount, depending on the engine speed NE and the air intake passage pressure PBGA. The map is changed, depending on the MT or the CVT. 
     Then, the flow proceeds to step S 302 , and it is determined whether an energy storage zone D determination flag F_ESZONED is 1. When this determination is YES, that is, when the battery remaining charge SOC is in zone D, the flow proceeds to step S 323 , the cruise charging amount CRSRGN is set to 0, and the flow proceeds to step S 328 . It is determined in step S 328  whether the final cruise charging command value CRSRGNF is 0. When in step S 328  the command value CRSRGNF is not 0, the flow proceeds to step S 329 , and enters the cruise charging stop mode, and the control terminates. When in step S 328  the command value CRSRGNF is zero, the flow proceeds to step S 330 , enters the cruise battery supply mode, and the control terminates. 
     When in step S 302  the determination is NO, that is, when the remaining battery charge SOC is outside zone D, the flow proceeds to step S 303 , and it is then determined whether the energy storage zone C determination flag F_ESZONEC is 1. When this determination is YES, that is, when the remaining battery charge SOC is within zone C, the flow proceeds to step S 304 , and a correction coefficient KCRSRGN for the cruise charging is set to 1 (for a high charging mode). Then, the flow proceeds to step S 316 . When in step S 303  the determination is NO, that is, when the remaining battery charge SOC is outside zone C, the flow proceeds to step S 305 . 
     In step S 305 , it is determined whether the energy storage zone B determination flag F_ESZONEB is 1. When this determination is YES, that is, when the remaining battery charge SOC is within zone B, the flow proceeds to step S 306 . In step S 306 , a correction coefficient KCRSRGN for the cruise charging is set to a cruise charging coefficient #KCRGNWK (for a low charging mode), and the flow proceeds to step S 313 . 
     When in step S 305  the determination is NO, that is, when the remaining battery charge SOC is outside zone B, the flow proceeds to step S 307 , and it is then determined whether a DOD limitation determination flag F_DODLMT is 1. When in step S 307  the determination is YES, the flow proceeds to step S 308 , the correction coefficient for the cruise charging amount KCRSRGN is set to the cruise charging amount coefficient #KCRGNDOD (for a DOD limited charging mode), and the flow proceeds to step S 313 . The DOD limited charging mode controls the amount of assistance and the amount of cruise charging to recover the remaining battery charge SOC when the initial remaining charge of the battery is decreased by a predetermined amount. 
     Therefore, the increased amount of generation quickly recovers the remaining battery charge SOC. 
     When in step S 307  the determination is NO, the flow proceeds to step S 309 , and it is then determined whether an air-conditioner ON flag F_ACC is 1. When the determination is YES, that is, when the air conditioner is turned on, the flow proceeds to step S 310 , the correction coefficient for the cruise charging amount KCRSRGN is set to the cruise charging amount coefficient #KCRGNHAC (for a HAC_ON charging mode), and the flow proceeds to step S 313 . 
     When in step S 309  the determination is NO, that is, when the air conditioner is turned off, the flow proceeds to step S 311 , and it is then determined whether a cruise mode determination flag F_MACRS is 1. When in step S 311  the determination is NO, that is, when not in the cruise mode, the cruise charging amount CRSRGN is set to 0 in step S 325 , and the flow proceeds to step S 326 . 
     When in step S 311  the determination is YES, that is, when in the cruise mode, the flow proceeds to step S 312 , the cruise charging amount CRSRGN is set to the cruise charging amount coefficient #KCRGN (for a normal charging mode), and the flow proceeds to step S 313 . 
     In step S 326 , it is determined whether the engine speed NE is equal to or below a cruise battery supply mode execution upper limit engine speed #NDVSTP. When this determination is YES, that is, when NE≦#NDVSTP, the flow proceeds to step S 328 . 
     When in step S 326  the determination is NO, that is, when the engine speed NE&gt;the cruise battery supply mode execution upper limit engine speed #NDVSTP, the flow proceeds to step S 329 . The #NDVSTP has hysteresis. 
     In step S 313 , it is determined whether the remaining battery charge QBAT (which is similar to the remaining battery charge SOC provided at the upper limit of zone A) is equal to or above a normal charging mode execution upper limit remaining charge #QBCRSRH. The #QBCRSRH has hysteresis. 
     When in step S 313  the determination is YES, that is, when QBAT≧#QBCRSRH, the flow proceeds to step S 325 . 
     When the remaining battery charge QBAT&lt;the normal charging mode execution upper limit remaining charge #QBCRSRH, it is determined in step S 314  whether a lean-burn determination flag F_KCMLB is 1. When this determination is YES, that is, when in the lean-burn state, the correction coefficient KCRSRGN for the cruise charging amount is multiplied by the cruise charging amount coefficient #KCRGNLB (for the lean-burn charging mode) in step S 315 , the calculated value is set as the correction coefficient KCRSRGN for the cruise charging amount, the flow proceeds to step S 316 . When in step S 314  the determination is NO, that is, when not in the lean-burn mode, the flow proceeds to step S 316 . 
     In step S 316 , a value for correcting the cruise charging amount (shown in FIG.  19 ), which is described below, is calculated, the mode enters the cruise charging mode in step S 322 , and the control terminates. 
     The process for calculating the cruise charging amount correction coefficient in step S 316  in the sub-routine for calculating the cruise charging amount in FIG. 18 will be explained with reference to the flowchart of FIG.  19 . 
     In step S 351 , a cruise charging amount subtractive coefficient KVCRSRG is looked up in a #KVCRSRG table in FIG. 20, depending on the vehicle speed VP for the engine control. The coefficient is used when starting and accelerating the vehicle at a low speed, and becomes 1 when the vehicle reaches a predetermined speed. The coefficient is multiplied by the cruise charging amount in step S 365 . 
     In step S 352 , the map value CRSRGNM value (obtained in step S 300 ) for the cruise charging amount is multiplied by the correction coefficient KCRSRGN (obtained in FIGS. 17 and 18) for correcting the cruise charging amount, and the calculated value is set as the cruise charging amount CRSRGN. 
     In step S 353 , a correction factor CRGVEL shown in FIG. 21 is looked up in a #CRGVELN table, depending on the average consumed current VELAVE, and the flow proceeds to step S 354 . 
     In step S 354 , the cruise charging amount CRSRGN is added to the correction additional factor CRGVEL, and the flow proceeds to step S 355 . This increases the cruise charging amount to make up for the power consumed by the 12-volt system. In step S 355 , a cruise charging amount PA correction coefficient #KPACRSRN, shown in FIG. 22, is looked up in a KPACRSRN table, depending on the atmospheric pressure PA, and the flow proceeds to step S 356 . 
     In step S 356 , it is determined whether the gear position NGR is equal to or above a #NGRKCRS cruise charging throttle correction execution lower limit gear position. When in step S 356  this determination is NO, that is, when the gear is high (above the second gear), the flow proceeds to step S 359 , a cruise charging TH correction coefficient #KTHCRSRN is set to 1.0, and the flow proceeds to step S 361 . Because the coefficient is 1.0, sudden variations in the cruise charging amount can be prevented in step S 365 . When in step S 356  the determination is YES, that is, when the gear is low, the flow proceeds to step S 357 , and it is determined whether the vehicle speed VP for the engine control is equal to or below a cruise charging throttle correction execution lower limit vehicle speed #VKCRS (e.g., 30 km/h at which the correction is conducted based on the throttle operation). The #VKCRS has hysteresis. When this determination is NO, that is, when at a high speed, the flow proceeds to step S 359 . When in step S 357  the determination is YES, that is, when at a low vehicle speed, the flow proceeds to step S 358 . In step S 358 , the look-up process in a #THCRSRNH/L table, shown in FIG. 23, is performed, depending on the engine speed NE, and the flow proceeds to step S 360 . In step S 360 , as shown in FIG. 24, the #KTHCRSRN between the two points is interpolated, depending on the present value THEM of the degree TH of throttle opening to obtain a cruise charging throttle correction coefficient KTHCRSRN, and the flow proceeds to step S 361 . 
     In step S 361 , the vehicle speed VP for the engine control is compared with a cruise charging fully-opened throttle correction execution upper limit vehicle speed #VCRCT. The #VCRCT has hysteresis, and the higher #VCRCT is, e.g., 180 km/h. 
     When in step S 361  the determination is NO, that is, when the throttle is fully opened while the vehicle is driving at a high speed, the cruise charging fully-opened throttle correction coefficient KTHCRCT is set to 1.0 in step S 362 , and the flow proceeds to step S 365 . Therefore, in this situation, the correction based on the throttle opening is not conducted, and the coefficient is fixed to 1.0. 
     When in step S 361  the determination is YES, that is, when at a low speed, the throttle opening degrees #THCRCTNH/L are looked up in a table in step S 363 , as shown in FIG. 25, depending on the engine speed NE, and the flow proceeds to step S 364 . 
     In step S 364 , as shown in FIG. 26, the cruise charging fully-opened throttle correction coefficient KTHCRCTN is obtained by the #KTHCRCTN interpolation depending on the present value THEM of the degree TH of throttle opening, and the flow proceeds to step S 365 . That is, the correction coefficient is determined based on the throttle opening. As the throttle opening is increased, the cruse charging amount is decreased. 
     In step S 365 , the cruise charging amount CRSRGN is multiplied by the cruise charging amount PA correction coefficient KPACRSRN obtained in step S 355 , the cruise charging amount subtraction coefficient KTRGRGN (set in step S 121  in the assistance trigger determination), the cruise charging amount subtraction coefficient KVCRSRG obtained in step S 351 , the cruise charging TH correction coefficient KTHCRSRN calculated in step S 360 , and the cruise charging fully-opened throttle correction coefficient KTHCRCT obtained in step S 364 , to thereby obtain the final cruise charging amount CRSRGN. 
     The fuel supply cut determination will be explained with reference to FIGS. 27 and 28. The determination determines the deceleration fuel supply cut execution flag F_MADECFC in step S 019  in FIG.  4 . In step S 401 , it is determined whether the engine speed NE is equal to or above a higher speed fuel cut engine speed NHFC 1 . When in step S 401  the determination is YES, that is, when the engine speed is high, the flow proceeds to step S 407 , a high engine speed fuel supply cut flag F_HIFC is set to 1, the deceleration fuel cut execution flag F_MADECFC is set to 0, and the flow proceeds to step S 408 . 
     In step S 408 , the fuel cut execution flag F_FC (the flag indicating that the fuel supply is being stopped) is set to 1, and the control terminates. The determination in step S 401  stops the supply of fuel (F_HIFC=1) to protect the engine when the engine speed is high, for example, when a rev-limiter is actuated. 
     According to the relationship with the F_MADECFC in step S 019  in the motor operation mode determination in FIG. 4, the F_MADECFC is set to 0 in step S 407 . When the supply of fuel is stopped (F_FC is set to 1) by the high engine speed fuel supply cut operation, the vehicle decelerates. In this situation, if the motor operation may enter the deceleration mode (step S 024 ), the vehicle decelerates excessively due to the fuel supply cut operation and to the motor deceleration mode, and the driver may experience a feeling of unease because of the jolt given to the vehicle. To avoid this, the present invention prevents the motor from entering the deceleration mode. 
     The higher speed fuel cut engine speed NHFC 1  corrects the threshold value, based on the vehicle speed, the water temperature, the operation of the air-conditioner, and the throttle opening. 
     When in step S 401  the determination is NO, that is, when the engine speed is low, the flow proceeds to step S 402 , and it is determined whether the vehicle speed VP for the engine control is equal to or above a vehicle speed #VHFC for a high vehicle speed limiter. The #VHFC is, e.g., 183 km/h. When in step S 402  the determination is YES, that is, when the vehicle speed is high, it is determined in step S 404  whether a high vehicle speed fuel supply cut delay timer TDFCON is 0. When it is 0, the flow proceeds to step S 406 . 
     In step S 406 , the high vehicle speed fuel supply cut restarting delay timer TDFCOFF is set to a predetermined value #TMDFCOFF (e.g., 0.2 sec.), and the flow proceeds to step S 407 . Step S 407  for setting F_MADECFC to 0 prevents the simultaneous actuation of the fuel supply cut operation and the deceleration mode of the motor (regenerative braking) when the vehicle speed is high, in order to prevent a strong jolt from being impacted to the vehicle as described above. 
     When in step S 404  the value is not 0, the flow proceeds to step S 409  in FIG.  28 . 
     The vehicle speed VP for the engine control is increased, and, while the VP is below the vehicle speed #VHFC for the high vehicle speed limiter, the high vehicle speed fuel supply cut delay timer TDFCON is set. When the VP exceeds the #VHFC, the fuel supply cut operation is not started until the TDFCON reaches 0. When the TDFCON becomes 0, the high vehicle speed fuel supply cut restarting delay timer TDFCOFF is set so as to start the fuel supply cut operation. 
     When in step S 402  the determination is NO, that is, when the vehicle speed is low, the flow proceeds to step S 403 , and it is determined whether the high vehicle speed fuel supply cut restarting delay timer TDFCOFF is 0. When the timer is 0, the flow proceeds to step S 405 . In step S 405 , the vehicle speed fuel supply cut delay timer TDFCON is set to a predetermined value #TMDFCON (e.g., 0.5 sec.), and the flow proceeds to step S 409 . When in step S 403  the timer is not 0, the flow proceeds to step S 407 . 
     As described in above step S 407  for setting F_MADECFC to 0, the simultaneous actuations of the fuel supply cut operation and the deceleration mode of the motor (regenerative braking) can be prevented when the vehicle speed is high, in order to prevent a strong jolt from being impacted to the vehicle as described above. 
     In step S 409 , it is determined whether an idling determination flag F_THIDLE is 1. When the determination is YES, that is, when the throttle is opened, the flow proceeds to step S 419 . In step S 419 , it is determined whether a fuel supply cut delay change determination flag F_FCDCRS is 1. 
     When in step S 419  the determination is YES, the fuel supply cut delay timer TFCDLY is set to a predetermined value #TMTCDCRS in step S 420 , and the flow proceeds to step S 422 . 
     In step S 422 , the high engine speed fuel supply cut flag F_HIFC is set to 0, the deceleration fuel supply cut execution flag F_MADECFC is set to 0, and the flow proceeds to step S 423 . In step S 423 , the fuel supply cut execution flag F_FC is set to 0, and the control terminates. When in step S 419  the determination is NO, the fuel supply cut delay timer TFCDLY is set to a predetermined value #TMFCD in step S 421 , and the flow proceeds to step S 422 . 
     When in step S 409  the idling determination flag F_THIDLE is 1, that is, when the throttle is closed, the flow proceeds to step S 410 , and a throttle fuel supply cut engine speed NFCT is calculated. The calculation appropriately sets the engine speed at which the fuel supply is to be stopped, depending on the driving condition, in order to respond to the demands from the fuel supply and from the driver. 
     In step S 411 , it is determined whether the engine speed NE is equal to or below the throttle fuel supply cut engine speed NFCT. When this determination is YES, that is, when the engine speed is high, the flow proceeds to step S 419 . When in step S 411  the determination is NO, that is, when the engine speed is low, the flow proceeds to step S 412 . 
     In step S 412 , it is determined whether the fuel supply cut execution flag F_FC is 1. When the flag value is 0, the flow proceeds to step S 413 . In step S 413 , it is determined whether the absolute value of a DPBACYL indicating the difference between the present PBA and the PBA in the previous cycle is equal to or above a predetermined value #DPBDLY. This determines whether the air intake passage pressure PB is stable. When the determination is YES (the pressure is stable), the flow proceeds to step S 419 . When in step S 413  the determination is NO (the pressure is not stable), the flow proceeds to step S 414 , and it is determined whether the fuel supply cut delay timer TFCDLY is 0. When this determination is YES, the flow proceeds to step S 422 . When in step S 414  the determination is NO, the flow proceeds to step S 415 , and it is determined whether a motor starting mode flag F_STMODMA is 1. 
     When in step S 415  the flag value is 1, that is, when the mode is the motor starting mode, the high engine speed fuel supply cut flag F_HIFC is set to 0, and the deceleration fuel supply cut execution flag F_MADECFC is set to 1 in step S 417 , and the flow proceeds to step S 418 . In step S 418 , the fuel supply cut execution flag F_FC is set to 1, and the control terminates. 
     When in step S 415  the flag value is 0, that is, when the mode is not the motor starting mode, the high engine speed fuel supply cut flag F_HIFC is set to 0, and the deceleration fuel supply cut execution flag F_MADECFC is set to 1 in step S 417 , and the flow proceeds to step S 418 . 
     In this embodiment, as shown in FIG. 2, when the vehicle speed exceeds the assistance trigger look-up upper limit vehicle speed #VMASTHG, which is the first threshold value, e.g., 170 km/h, the assistance is limited by the assistance amount upper limit value ASTVHG, and the amount of assistance is decreased as shown in FIG.  15 . Then, when the vehicle speed reaches the high vehicle speed point at which the amount of assistance is 0 as shown in FIG. 15, which is the second threshold value, e.g., 175 km/h, the cruise charging amount is gradually increased by the cruise charging amount correction coefficient KTRGRGN depending on the vehicle speed while the vehicle is driving at a high speed, and becomes a fixed generation amount (the cruise charging amount and the amount of energy consumed by the 12-volt system). Then, the vehicle speed exceeds the cruise charging fully-opened throttle correction execution upper limit vehicle speed #VCRCT, which is the third threshold value, e.g., 180 km/h. When 0.5 seconds have elapsed after the vehicle speed reaches the high vehicle speed limiter determination vehicle speed #VHFC, e.g., 183 km/h, the fuel supply is stopped by the high vehicle speed fuel supply cut delay timer TDFCON. When 0.2 seconds have elapsed after the vehicle speed becomes below the high vehicle speed limiter determination vehicle speed #VHFC, the fuel supply is restarted. 
     The driver&#39;s intentions can be sufficiently reflected by the control because, when calculating the cruise charging amount, the value looked up based on the engine speed NE and on the air intake passage pressure PB is multiplied by the correction value depending on the throttle opening. 
     Further, the control is suitable to the engine output characteristic because the variation (correction) is based on the engine speed NE. 
     When the vehicle is driving at a high speed and reaches the upper speed limit, the correction based on the throttle operation is prohibited, and the gradual decrease of the assistance, the gradual increase of the cruise charging, and the control of the fuel supply cut are effectively performed based on the vehicle speed, thereby optimizing the limitation in the vehicle speed, the maintenance of the vehicle speed, and the energy management in the high speed cruising range. 
     This invention may be embodied in other forms or carried out in other ways without departing from the spirit thereof. The present embodiments are therefore to be considered in all respects illustrative and not limiting, the scope of the invention being indicated by the appended claims, and all modifications falling within the meaning and range of equivalency are intended to be embraced therein.