JP2011219019A - Vehicle, and method for control of internal combustion engine to be stopped - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the rotation speed of an internal combustion engine to stop the internal combustion engine at a target crank angle without causing control failure.SOLUTION: When an engine rotation speed Ne is within a range from a threshold Nref2 to less than a threshold Nref 1, as a range of the rotation speed including a resonance rotation speed zone in which a driving system composed of a power distribution and integration mechanism or a motor resonates, feedback control is performed so that the engine rotation speed Ne becomes a target rotation speed Ne* by use of a proportional gain kp of a value k2 that is smaller than a normal value k1 to be used when the engine rotation speed Ne is out of the above range (S220-S280). A difference between the engine rotation speed Ne and the target rotation speed Ne* is prevented from being larger or smaller than expected due to resonance of the driving system, while preventing hunting to be caused in motor output torque and the engine rotation speed Ne, which hinders the feedback control.

Description

  More particularly, the present invention relates to an internal combustion engine, an electric motor capable of inputting / outputting power to / from an output shaft of the internal combustion engine via a mechanical mechanism, and exchange of electric power with the electric motor. The present invention relates to an automobile provided with a secondary battery capable of operating and a control method at the time of operation stop of an internal combustion engine mounted on the automobile.

  Conventionally, as a control method when the operation of this type of internal combustion engine is stopped, a drive shaft connected to an axle, an output shaft of an engine, and a rotary shaft of a generator are connected to three rotary elements, and an electric motor is connected to the drive shaft. In a connected hybrid vehicle, an engine target rotational speed necessary to stop the engine at a target stop position and a crank angle at that time are acquired, and the engine target rotational speed is corrected based on the acquired crank angle. It has been proposed (see, for example, Patent Document 1). In this control method, by correcting the target engine speed based on the crank angle, the frictional force in the engine, the electric machine, etc. varies, and the temperature and viscosity of the lubricating and cooling oil vary. The engine can be stopped at the target stop position even if the vehicle is accelerated or decelerated during the reduction of the engine rotation speed.

  Also, in an automobile with a motor attached to the crankshaft of an engine that outputs power to the drive shaft via an automatic transmission, when the motor rotation speed becomes lower than a predetermined rotation speed during idling stop, control greater than the normal control gain is performed. There has also been proposed one that controls the drive of a motor using a gain (see, for example, Patent Document 2). In this control method, by using a large control gain when the rotational speed of the motor is smaller than the predetermined rotational speed, the responsiveness of the motor control in the low rotational speed region of the engine is improved to suppress engine vibration.

JP 2005-16505 A JP 2004-100504 A

  In the case of an automobile in which the output shaft of the engine is connected to the electric motor via a mechanical mechanism such as a planetary gear mechanism as in the former automobile, the electric motor is set so that the engine rotational speed becomes the target rotational speed when the engine is stopped. If the feedback control is performed, the motor torque and the engine speed may cause hunting, and the engine speed may not follow the target speed. Since a drive system including a mechanical mechanism and an electric motor has a unique resonance frequency band, when the engine speed falls within this resonance frequency band, resonance occurs in the drive system due to engine torque pulsation. Since the resonance of the drive system causes fluctuations in the engine speed, the difference between the engine speed and the target engine speed becomes larger or smaller than expected, thereby reducing the torque and rotation of the motor. Hunting occurs in the number, and good feedback control is hindered, and sometimes feedback control fails.

  The main purpose of the control method for stopping the operation of the automobile and the internal combustion engine of the present invention is to reduce the rotational speed of the internal combustion engine without causing a control failure and to stop the internal combustion engine at the target crank angle.

  In order to achieve the main object described above, the control method for stopping the operation of the automobile and the internal combustion engine of the present invention employs the following means.

The automobile of the present invention
When stopping the operation of the internal combustion engine, an electric motor capable of inputting / outputting power to / from the output shaft of the internal combustion engine via a mechanical mechanism, a secondary battery capable of exchanging electric power with the electric motor, A target rotational speed of the internal combustion engine is set according to a crank angle or an elapsed time of the internal combustion engine during which the rotational speed is being decreased to stop the internal combustion engine at a predetermined target crank angle; Until the engine speed reaches a predetermined speed, the engine speed is controlled to be reduced so that the speed of the internal combustion engine becomes the set target speed, and the engine speed is reduced. After reaching the predetermined number of revolutions, the vehicle is provided with a stop-time control means for executing a control immediately before stopping to control the generator so that the internal combustion engine stops at the target crank angle,
The stop-time control means, as the decrease-time rotation speed control, when the rotation speed of the internal combustion engine is larger than a predetermined rotation speed range including a resonance rotation speed band that resonates a drive system including the electric motor and the mechanical mechanism. Using the first gain, the generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine falls within the predetermined rotational speed range, the first gain The generator is controlled using a small second gain so that the rotational speed of the internal combustion engine becomes the target rotational speed, and the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed range and greater than or equal to the predetermined rotational speed. Means for controlling the generator so that the rotational speed of the internal combustion engine becomes the target rotational speed using a third gain that is sometimes larger than the second gain;
It is characterized by that.

  In the automobile according to the present invention, when the operation of the internal combustion engine is stopped, the engine speed is controlled so that the generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed until the rotational speed of the internal combustion engine reaches a predetermined rotational speed. After the control is executed and the rotational speed of the internal combustion engine reaches a predetermined rotational speed, the control immediately before stopping is executed to drive the generator so that the internal combustion engine stops at the target crank angle. Then, as the engine speed control at the time of decrease, the target engine speed of the internal combustion engine according to the crank angle or the elapsed time of the internal combustion engine that is reducing the engine speed to stop the engine at a predetermined target crank angle. Is set, and when the rotational speed of the internal combustion engine is larger than a predetermined rotational speed range including a resonance rotational speed band that resonates the drive system including the electric motor and the mechanical mechanism, the rotational speed of the internal combustion engine is set to a target by using the first gain. The generator is controlled so as to achieve the rotational speed, and when the rotational speed of the internal combustion engine falls within a predetermined rotational speed range, the rotational speed of the internal combustion engine becomes the target rotational speed using a second gain smaller than the first gain. The generator is controlled so that when the speed of the internal combustion engine is smaller than the predetermined speed range and equal to or higher than the predetermined speed, a third gain larger than the second gain is used so that the speed of the internal combustion engine becomes the target speed. Generator Control to. In other words, in a predetermined rotational speed range including the resonance rotational speed band of the drive system, the rotational speed of the internal combustion engine is set to the target rotational speed by using the first gain outside the range or the second gain smaller than the third gain. The generator is controlled so that As a result, even if the difference between the rotational speed of the internal combustion engine and the target rotational speed becomes larger or smaller than expected due to resonance of the drive system, it occurs in the motor torque and the rotational speed of the internal combustion engine. The obtained hunting can be suppressed, and the control failure due to this can be suppressed. Of course, the internal combustion engine can be accurately stopped at the target crank angle.

  In such an automobile of the present invention, the stop time control means uses the proportional term and the integral term to cancel the difference between the detected rotation speed and the target rotation speed as the decrease rotation speed control. Rotational speed feedback control for setting the torque of the electric motor is executed, and the first gain, the second gain, and the third gain may be proportional gains. In the automobile of the present invention, the first proportional gain and the third proportional gain may be the same. Here, the “proportional term” means a value obtained by multiplying the difference between the rotational speed of the internal combustion engine and the target rotational speed by a proportional gain, and the “integral term” means the difference between the rotational speed of the internal combustion engine and the target rotational speed. The time integral of is multiplied by the integral gain.

  In the automobile of the present invention, the mechanical mechanism is a planetary gear mechanism in which three rotating elements are connected to a driving shaft coupled to an axle, an output shaft of the internal combustion engine, and a rotating shaft of the electric motor, respectively. It can also be.

The control method at the time of operation stop of the internal combustion engine of the present invention,
In an automobile equipped with an internal combustion engine, an electric motor capable of inputting / outputting power to / from an output shaft of the internal combustion engine via a mechanical mechanism, and a secondary battery capable of exchanging electric power with the electric motor, When the operation is stopped, the target rotational speed of the internal combustion engine is set according to the crank angle of the internal combustion engine which is being reduced in order to stop the internal combustion engine at a predetermined target crank angle. Until the rotational speed of the internal combustion engine reaches a predetermined rotational speed, the engine speed of the internal combustion engine is controlled so that the rotational speed of the internal combustion engine becomes the set target rotational speed. A control method at the time of stoppage of operation of the internal combustion engine that executes control immediately before stopping to drive the generator so that the internal combustion engine stops at the target crank angle after the rotational speed reaches the predetermined rotational speed. ,
As the reduction speed control, the first gain is used when the rotational speed of the internal combustion engine is larger than a predetermined rotational speed range including a resonance rotational speed band that resonates a drive system including the electric motor and the mechanical mechanism. The generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine falls within the predetermined rotational speed range, a second gain smaller than the first gain is used. The generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and is larger than the second gain when the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed range and greater than or equal to the predetermined rotational speed. Controlling the generator so that the rotational speed of the internal combustion engine becomes the target rotational speed using a third gain;
It is characterized by that.

  In the control method of the internal combustion engine when the operation of the present invention is stopped, when the operation of the internal combustion engine is stopped, power generation is performed so that the rotational speed of the internal combustion engine becomes the target rotational speed until the rotational speed of the internal combustion engine reaches a predetermined rotational speed. Decrease speed control for controlling the machine is executed, and after the engine speed reaches a predetermined speed, control immediately before stopping is executed to drive the generator so that the engine stops at the target crank angle. Then, as the rotational speed control at the time of reduction, the target rotational speed of the internal combustion engine is set in accordance with the crank angle of the internal combustion engine that is decreasing in order to stop the internal combustion engine at a predetermined target crank angle. When the rotational speed of the internal combustion engine is larger than a predetermined rotational speed range including a resonance rotational speed band that resonates a drive system including an electric motor and a mechanical mechanism, the rotational speed of the internal combustion engine is set to the target rotational speed using the first gain. The generator is controlled so that the rotational speed of the internal combustion engine becomes a target rotational speed by using a second gain smaller than the first gain when the rotational speed of the internal combustion engine falls within a predetermined rotational speed range. And when the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed range and equal to or higher than the predetermined rotational speed, the generator is set so that the rotational speed of the internal combustion engine becomes the target rotational speed using a third gain larger than the second gain. Control. In other words, in a predetermined rotational speed range including the resonance rotational speed band of the drive system, the rotational speed of the internal combustion engine is set to the target rotational speed by using the first gain outside the range or the second gain smaller than the third gain. The generator is controlled so that As a result, even if the difference between the rotational speed of the internal combustion engine and the target rotational speed becomes larger or smaller than expected due to resonance of the drive system, it occurs in the motor torque and the rotational speed of the internal combustion engine. The obtained hunting can be suppressed, and the control failure due to this can be suppressed. Of course, the internal combustion engine can be accurately stopped at the target crank angle.

1 is a configuration diagram showing an outline of a configuration of a hybrid vehicle 20 as an embodiment of the present invention. 2 is a configuration diagram showing an outline of the configuration of an engine 22. FIG. 5 is a flowchart showing an example of an engine stop time control routine executed by a hybrid electronic control unit 70; 5 is a flowchart showing an example of a control routine for when the engine speed is reduced, which is executed by the hybrid electronic control unit 70; It is explanatory drawing which shows an example of the relationship between correction | amendment torque T (beta) and the crank angle CA of the engine 22. FIG. It is explanatory drawing which shows the mode of the time change of the rotation speed Ne of the engine 22, and the proportional gain kp. FIG. 11 is a configuration diagram showing an outline of a configuration of a hybrid vehicle 120 according to a modification.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of the configuration of a hybrid vehicle 20 as an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an outline of the configuration of an engine 22. As shown in the figure, the hybrid vehicle 20 of the embodiment includes an engine 22, a three-shaft power distribution / integration mechanism 30 connected to a crankshaft 26 as an output shaft of the engine 22 via a damper 28, and power distribution / integration. A motor MG1 capable of generating electricity connected to the mechanism 30, a reduction gear 35 attached to a ring gear shaft 32a as a drive shaft connected to the power distribution and integration mechanism 30, a motor MG2 connected to the reduction gear 35, And a hybrid electronic control unit 70 for controlling the entire vehicle.

  The engine 22 is configured as a four-cylinder internal combustion engine capable of outputting power using a hydrocarbon-based fuel such as gasoline or light oil. For example, as shown in FIG. The fuel is injected from the fuel injection valve 126, and the intake air and the gasoline are mixed. The mixture is sucked into the fuel chamber through the intake valve 128, and is generated by an electric spark by the spark plug 130. Explosive combustion is performed, and the reciprocating motion of the piston 132 pushed down by the energy is converted into the rotational motion of the crankshaft 26. Exhaust gas from the engine 22 is discharged to the outside air through a purification device (three-way catalyst) 134 that purifies harmful components such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

  The engine 22 is controlled by an engine electronic control unit (hereinafter referred to as an engine ECU) 24 having a CPU 24a, a ROM 24b, and a RAM 24c. Signals from various sensors that detect the state of the engine 22 are input to the engine ECU 24 via an input port (not shown). For example, in the engine ECU 24, the crank position from the crank position sensor 140 that detects the rotational position of the crankshaft 26, the coolant temperature from the water temperature sensor 142 that detects the temperature of the coolant in the engine 22, and the pressure attached to the combustion chamber. The pressure in the cylinder from the sensor 143, the cam position from the cam position sensor 144 that detects the rotational position of the intake valve 128 that performs intake and exhaust to the combustion chamber and the camshaft that opens and closes the exhaust valve, and the opening of the throttle valve 124 are detected. Throttle position from the throttle valve position sensor 146, intake air amount from the air flow meter 148 attached to the intake pipe, intake air temperature from the temperature sensor 149 also attached to the intake pipe, air-fuel ratio from the air-fuel ratio sensor 135a, Oxygen sensor 13 Such as oxygen signal from b are input via the input port. Further, various control signals for driving the engine 22 are output from the engine ECU 24 via an output port (not shown). For example, the engine ECU 24 sends a drive signal to the fuel injection valve 126, a drive signal to the throttle motor 136 that adjusts the position of the throttle valve 124, a control signal to the ignition coil 138 integrated with the igniter, and the intake valve 128. A control signal to the variable valve timing mechanism 150 whose opening / closing timing can be changed is output via the output port. Further, the engine ECU 24 communicates with the hybrid electronic control unit 70, controls the operation of the engine 22 by a control signal from the hybrid electronic control unit 70, and outputs data related to the operating state of the engine 22 as necessary. . The engine ECU 24 also calculates the rotation speed of the crankshaft 26, that is, the rotation speed Ne of the engine 22 based on the crank position from the crank position sensor 140, and calculates the crank position detected by the crank position sensor 140 from the reference angle. The crank angle CA is calculated as the angle.

  The power distribution and integration mechanism 30 includes an external gear sun gear 31, an internal gear ring gear 32 arranged concentrically with the sun gear 31, a plurality of pinion gears 33 that mesh with the sun gear 31 and mesh with the ring gear 32, A planetary gear mechanism is provided that includes a carrier 34 that holds a plurality of pinion gears 33 so as to rotate and revolve, and that performs differential action using the sun gear 31, the ring gear 32, and the carrier 34 as rotational elements. In the power distribution and integration mechanism 30, the crankshaft 26 of the engine 22 is connected to the carrier 34, the motor MG1 is connected to the sun gear 31, and the reduction gear 35 is connected to the ring gear 32 via the ring gear shaft 32a. When functioning as a generator, power from the engine 22 input from the carrier 34 is distributed according to the gear ratio between the sun gear 31 side and the ring gear 32 side, and when the motor MG1 functions as an electric motor, the engine input from the carrier 34 The power from 22 and the power from the motor MG1 input from the sun gear 31 are integrated and output to the ring gear 32 side. The power output to the ring gear 32 is finally output from the ring gear shaft 32a to the drive wheels 63a and 63b of the vehicle via the gear mechanism 60 and the differential gear 62.

  The motor MG1 and the motor MG2 are both configured as well-known synchronous generator motors that can be driven as generators and can be driven as motors, and exchange power with the battery 50 via inverters 41 and 42. The power line 54 connecting the inverters 41 and 42 and the battery 50 is configured as a positive electrode bus and a negative electrode bus shared by the inverters 41 and 42, and the electric power generated by one of the motors MG1 and MG2 It can be consumed by a motor. The motors MG1 and MG2 are both driven and controlled by a motor electronic control unit (hereinafter referred to as a motor ECU) 40. The motor ECU 40 detects signals necessary for driving and controlling the motors MG1 and MG2, such as signals from rotational position detection sensors 43 and 44 that detect the rotational positions of the rotors of the motors MG1 and MG2, and current sensors (not shown). The phase current applied to the motors MG1 and MG2 to be applied is input, and a switching control signal to the inverters 41 and 42 is output from the motor ECU 40. The motor ECU 40 is in communication with the hybrid electronic control unit 70, controls the driving of the motors MG1 and MG2 by a control signal from the hybrid electronic control unit 70, and, if necessary, data on the operating state of the motors MG1 and MG2. Output to the hybrid electronic control unit 70. The motor ECU 40 also calculates the rotational speeds Nm1 and Nm2 of the motors MG1 and MG2 based on signals from the rotational position detection sensors 43 and 44.

  The battery 50 is configured as, for example, a lithium secondary battery, and is managed by a battery electronic control unit (hereinafter referred to as a battery ECU) 52. The battery ECU 52 receives signals necessary for managing the battery 50, for example, a voltage between terminals from a voltage sensor (not shown) installed between terminals of the battery 50, and a power line 54 connected to the output terminal of the battery 50. The charging / discharging current from the attached current sensor (not shown), the battery temperature Tb from the temperature sensor 51 attached to the battery 50, and the like are input. Output to the control unit 70. Further, the battery ECU 52 calculates the remaining capacity (SOC) based on the integrated value of the charging / discharging current detected by the current sensor in order to manage the battery 50, and calculates the remaining capacity (SOC) and the battery temperature Tb. The input / output limits Win and Wout, which are the maximum allowable power that may charge / discharge the battery 50, are calculated based on the above. The input / output limits Win and Wout of the battery 50 are set to basic values of the input / output limits Win and Wout based on the battery temperature Tb, and are input to the output limiting correction coefficient based on the remaining capacity (SOC) of the battery 50. It can be set by setting a correction coefficient for restriction and multiplying the basic value of the set input / output restrictions Win and Wout by the correction coefficient.

  The hybrid electronic control unit 70 is configured as a microprocessor centered on the CPU 72, and in addition to the CPU 72, a ROM 74 for storing processing programs, a RAM 76 for temporarily storing data, an input / output port and communication not shown. And a port. The hybrid electronic control unit 70 includes an ignition signal from an ignition switch 80, a shift position SP from a shift position sensor 82 that detects the operation position of the shift lever 81, and an accelerator pedal position sensor 84 that detects the amount of depression of the accelerator pedal 83. The accelerator pedal opening Acc from the vehicle, the brake pedal position BP from the brake pedal position sensor 86 for detecting the depression amount of the brake pedal 85, the vehicle speed V from the vehicle speed sensor 88, and the like are input via the input port. As described above, the hybrid electronic control unit 70 is connected to the engine ECU 24, the motor ECU 40, and the battery ECU 52 via the communication port, and exchanges various control signals and data with the engine ECU 24, the motor ECU 40, and the battery ECU 52. ing.

  The hybrid vehicle 20 of the embodiment thus configured calculates the required torque to be output to the ring gear shaft 32a as the drive shaft based on the accelerator opening Acc and the vehicle speed V corresponding to the depression amount of the accelerator pedal 83 by the driver. Then, the operation of the engine 22, the motor MG1, and the motor MG2 is controlled so that the required power corresponding to the required torque is output to the ring gear shaft 32a. As operation control of the engine 22, the motor MG1, and the motor MG2, the operation of the engine 22 is controlled so that power corresponding to the required power is output from the engine 22, and all of the power output from the engine 22 is the power distribution and integration mechanism 30. Torque conversion operation mode for driving and controlling the motor MG1 and the motor MG2 so that the torque is converted by the motor MG1 and the motor MG2 and output to the ring gear shaft 32a, and the required power and the power required for charging and discharging the battery 50. The engine 22 is operated and controlled so that suitable power is output from the engine 22, and all or part of the power output from the engine 22 with charging / discharging of the battery 50 is the power distribution and integration mechanism 30, the motor MG1, and the motor. The required power is converted to the ring gear shaft 32 with torque conversion by MG2. Charge / discharge operation mode in which the motor MG1 and the motor MG2 are driven and controlled to be output to each other, and a motor operation mode in which the operation of the engine 22 is stopped and the power corresponding to the required power from the motor MG2 is output to the ring gear shaft 32a. and so on.

  Next, the operation of the hybrid vehicle 20 of the embodiment thus configured, particularly the operation when stopping the operation of the engine 22 will be described. FIG. 3 is a flowchart showing an example of an engine stop time control routine executed by the hybrid electronic control unit 70. In this routine, when an automatic stop condition for automatically stopping the operating engine 22 is satisfied, for example, the remaining capacity (SOC) of the battery 50 is greater than or equal to a predetermined remaining capacity that does not require charging of the battery 50, and the requested power is stopped. When the motor stop power set for the engine becomes less than the engine stop power or when a motor travel switch (not shown) is turned on to instruct the travel in the motor operation mode, the rotational speed Ne of the engine 22 becomes approximately the idle rotational speed. Executed when. When this engine stop control routine is executed, the fuel injection control and ignition control of the engine 22 are controlled by the engine ECU 24 to be stopped, and while the vehicle is running, the motor MG1 The motor MG2 is controlled to output a torque obtained by dividing the sum of the torque as a reaction force to the torque output from the torque (torque command Tm1 *) and the required torque Tr * by the gear ratio Gr of the reduction gear 35. That is, the torque command Tm2 * for the motor MG2 is calculated by the following equation (1). Here, the torque command Tm1 * of the motor MG1 is set in the engine speed reduction control or the engine stop adjustment control in the engine stop control routine. “Ρ” in Equation (1) is the gear ratio ρ (number of teeth of the sun gear / number of teeth of the ring gear) of the power distribution and integration mechanism 30.

  Tm2 * = (Tr * + Tm1 * / ρ) / Gr (1)

  When the engine stop control routine of FIG. 3 is executed, the CPU 72 of the hybrid electronic control unit 70 first executes a process of inputting the rotation speed Ne and the crank angle CA of the engine 22 (step S100). Here, as the rotational speed Ne of the engine 22, the rotational speed Ne calculated based on the crank position detected by the crank position sensor 140 is input from the engine ECU 24 by communication. In addition, the crank angle CA calculated from the crank position detected by the crank position sensor 140 as an angle from the reference angle is input from the engine ECU 24 by communication.

  When the data is input in this way, a target crank angle CAtag is set as a target value for stopping the engine 22 based on the input engine speed Ne and the crank angle CA (step S110), and the input engine 22 rotation is input. Based on the number Ne and the crank angle CA, the target rotational speed Ne * of the engine 22 as an initial value is set (step S120). Here, the target crank angle CAtag is set to a crank angle CA (for example, a compression stroke of a certain cylinder) set in advance as a crank angle CA at which the startability of the engine 22 becomes good, for example, a shock is reduced when the engine 22 is started next. In the embodiment, since the engine 22 has four cylinders, it can be set every 180 degrees out of 720 degrees as a cycle of the crank angle CA. In the embodiment, the relationship between the rotational speed Ne of the engine 22, the crank angle CA, and the four target values is determined in advance and stored in the ROM 74 as a map, and the map is obtained when the rotational speed Ne of the engine 22 and the crank angle CA are given. Is set as the target crank angle CAtag. In the embodiment, the target engine speed Ne * of the engine 22 is set by adding a correction term to the input engine speed Ne. Since one target value is set as the target crank angle CAtag for each range of 180 degrees out of 720 degrees as a cycle of the crank angle CA, an error of plus or minus 90 degrees occurs as the crank angle CA around the reference. Accordingly, a correction term is set so that the larger the rotational speed Ne of the engine 22 is, the larger the rotational speed Ne of the engine 22 is in the direction of canceling out the crank angle CA as an error from the reference, and the input rotational speed Ne is added thereto to add the target rotational speed Ne *. It is. In the correction term, the crank angle CA as an error from the reference, the rotational speed Ne of the engine 22 and the correction value are determined in advance by experiments and stored in the ROM 74 as a map, and the crank angle CA and the rotational speed Ne are calculated. Is given, the correction value is derived from the map and set.

  When the target crank angle CAtag and the target rotational speed Ne * as the initial value are set in this way, the engine speed reduction control is executed until the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3 or less (step S130). When the rotational speed Ne of the engine 22 reaches a torque output stop rotational speed Nref3 (for example, 100 rpm, 150 rpm, etc.) or less, the engine speed reduction control is stopped and the engine stop adjustment control is executed (step S140). End the routine. Hereinafter, the engine speed reduction control and the engine stop adjustment control will be described in order.

  FIG. 4 is a flowchart showing an example of an engine speed reduction control routine executed by the hybrid electronic control unit 70 as engine speed reduction control. When this routine is executed, the CPU 72 of the hybrid electronic control unit 70 first inputs the rotational speed Ne and the crank angle CA of the engine 22 (step S200), and is preset as a reduction amount of the rotational speed Ne of the engine 22. A value obtained by subtracting the rotation speed gradient dne from the previous target rotation speed Ne * (previous Ne *) is set as the target rotation speed Ne * of the engine 22 so that the rotation speed Ne of the engine 22 becomes smaller at the determined rotation speed gradient dne. (Step S210). Here, the rotation speed gradient dne is obtained when the rotation speed Ne of the engine 22 passes through the resonance rotation speed band (for example, 300 to 500 rpm) of the drive system including the power distribution and integration mechanism 30 and the motors MG1 and MG2 relatively quickly. The gradient is set to be small, and the gradient is set so that the crank angle CA when the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3 becomes the torque output stop crank angle CAref. . As described above, the torque output stop rotational speed Nref3 is a rotational speed at which the engine speed reduction control is stopped and the engine stop time adjustment control is executed. Basically, the torque output stop torque output from the motor MG1 is stopped. Is a number. The crank angle CAref at the time of torque output stop is stopped at the target crank angle CAtag set with a high probability when the output of the torque from the motor MG1 is stopped when the rotation speed Ne of the engine 22 is the torque output stop rotation speed Nref. The crank angle CA to be obtained is obtained in advance through experiments and analysis.

  Subsequently, it is determined whether or not the rotation speed Ne of the engine 22 is in a resonance content range (for example, 250 rpm to 600 rpm) that is greater than or equal to a threshold Nref2 including a resonance rotation speed band in which the drive system resonates and less than the threshold Nref1 (step 250 rpm). S220), when the rotational speed Ne of the engine 22 is outside the resonance containing range, the value k1 is set to the proportional gain kp (step S230), and when the rotational speed Ne of the engine 22 is within the resonance containing range, the proportional gain kp is set from the value k1. A small value k2 is set (step S240). Then, using the set proportional gain kp, target rotational speed Ne *, and rotational speed Ne, a torque Tα to be output from the motor MG1 is set by the following equation (2) (step S250), and based on the crank angle CA. The correction torque Tβ is set (step S260), the torque command Tm1 * of the motor MG1 is set as the sum of the set torque Tα and the correction torque Tβ (step S270), and the set torque command Tm1 * is transmitted to the motor ECU 40. (Step S280). Here, Expression (2) is a relational expression in feedback control in which the engine 22 is rotated at the target rotational speed Ne *, the first term on the right side is a proportional term, and the second term on the right side is an integral term. “Kp” in the proportional term is the proportional gain kp set in steps S230 and S240, and “ki” in the integral term is a gain in this integral term. As described above, as the proportional gain kp, the value k1 is used when the rotational speed Ne of the engine 22 is outside the resonance containing range, and the value k2 smaller than the value k1 is used when it is within the resonance containing range. This suppresses the difference between the rotational speed Ne of the engine 22 and the target rotational speed Ne * from becoming larger or smaller than expected due to resonance of the drive system caused by torque pulsation of the engine 22, This is because hunting is generated in the torque output from the motor MG1 and the rotational speed Ne, thereby preventing the favorable feedback control from being hindered. The correction torque Tβ is a torque that suppresses torque fluctuations associated with the rotation of the engine 22 based on the crank angle CA of the engine 22. In the embodiment, the relationship between the crank angle CA and the correction torque Tβ is previously set as a correction torque setting map. Stored in the ROM 74, and when the crank angle CA is given, the corresponding correction torque Tβ is derived from the map and set. An example of the correction torque setting map is shown in FIG. As shown in the figure, the correction torque Tβ is in a phase opposite to the torque fluctuation caused by the rotation due to the compression stroke or expansion stroke of the engine 22. The reason for considering the correction torque Tβ in setting the torque command Tm1 * of the motor MG1 is that the followability of the engine speed Ne to the target engine speed Ne * deteriorates due to torque fluctuations caused by the engine 22 rotation. Based on suppressing. The motor ECU 40 that has received the torque command Tm1 * performs switching control of a switching element (not shown) of the inverter 41 so that torque corresponding to the torque command Tm1 * is output from the motor MG1.

  Tα = kp ・ (Ne * -Ne) + ki ・ ∫ (Ne * -Ne) dt (2)

  When the torque command Tm1 * of the motor MG1 is thus transmitted to the motor ECU 40, it is determined whether or not the rotational speed Ne of the engine 22 is equal to or less than the torque output stop rotational speed Nref3 (step S290), and the rotational speed Ne of the engine 22 is the torque. When it is larger than the output stop rotational speed Nref3, the process returns to step S200, and the processes of steps S200 to S290 are repeated until the rotational speed Ne of the engine 22 becomes equal to or less than the torque output stop rotational speed Nref3. Since this routine is executed when the operation of the engine 22 is stopped, when the process of steps S200 to S290 is started repeatedly, the rotational speed Ne of the engine 22 is larger than the resonance inclusion range, so that the normal value k1 is Feedback control is performed with the set proportional gain kp, and when the rotational speed Ne of the engine 22 falls within the resonance inclusion range, feedback control is performed with the proportional gain kp set to a value k2 smaller than the value k1, and the engine 22 When the rotational speed Ne becomes smaller than the resonance inclusion range, feedback control is performed again with the proportional gain kp in which the normal value k1 is set.

  If it is determined in step S290 that the rotational speed Ne of the engine 22 is equal to or less than the torque output stop rotational speed Nref3, the control routine at the time of engine speed reduction is terminated, and the engine stop speed control routine of FIG. Stop adjustment control (step S140) is performed. The engine stop adjustment control basically stops the engine 22 naturally without performing torque output of the motor MG1. As described above, when the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3 by the rotational speed control of the motor MG1, the torque output stop crank angle CAref is controlled. The crank angle CAref at the time of torque output stop is a crank that stops at the target crank angle CAtag set with a high probability when the torque output of the motor MG1 is stopped when the rotation speed Ne of the engine 22 is the torque output stop rotation speed Nref3. Therefore, if the engine 22 is naturally stopped, the engine 22 is stopped at the target crank angle CAtag set with a high probability. However, depending on the state of the engine 22, the engine 22 may try to stop before the target crank angle CAtag, or conversely, the engine 22 may stop after exceeding the target crank angle CAtag. In the engine stop adjustment control, when the engine 22 is about to stop before the target crank angle CAtag, by outputting a torque for rotating the engine 22 from the motor MG1, the stop position of the engine 22 becomes the target crank angle CAtag. If, on the contrary, the engine 22 tries to stop after exceeding the target crank angle CAtag, the motor MG1 outputs a torque for stopping the rotation of the engine 22 and the engine 22 stops significantly exceeding the target crank angle CAtag. Do not. Since this engine stop adjustment control does not form the core of the present invention, further detailed description is omitted.

  FIG. 6 is an explanatory diagram showing how the engine speed Ne and the proportional gain kp change with time. As shown in the figure, until the time T1 when the engine speed Ne reaches the threshold value Nref1, which is the upper limit value of the resonance containing range, feedback control is performed with the proportional gain kp with the normal value k1 being set. From the time T1 when the number Ne reaches the threshold value Nref1 to the time T2 when the rotational speed Ne of the engine 22 reaches the threshold value Nref2 that is the lower limit value of the resonance containing range, the proportional gain kp is set to a value k2 smaller than the normal value k1. Feedback control is performed, and the normal value k1 is set again from time T2 when the engine speed Ne reaches the threshold value Nref2 to time T3 when the engine speed Ne reaches the torque output stop speed Nref3. Feedback control is performed using the gain kp. Then, after the time T3 when the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3, since the engine stop adjustment control is performed, the feedback control is not executed.

  According to the hybrid vehicle 20 of the embodiment described above, the rotation speed Ne of the engine 22 is the threshold value Nref2 as a rotation speed range including the resonance rotation speed band in which the drive system including the power distribution and integration mechanism 30 and the motors MG1 and MG2 resonates. When the rotational speed Ne of the engine 22 is within the resonance containing range less than the threshold value Nref1 as described above, the rotational speed of the engine 22 is set using the proportional gain kp set to a value k2 smaller than the normal value k1 used when the rotational speed Ne of the engine 22 is outside the resonant containing range. By executing feedback control by the motor MG1 so that Ne becomes the target rotational speed Ne *, a difference between the rotational speed Ne of the engine 22 and the target rotational speed Ne * is assumed due to resonance of the drive system caused by torque pulsation of the engine 22. To prevent the motor MG1 from becoming larger or smaller than the size to be output. It is possible to suppress the hunting by the engine speed Ne and the torque good feedback control is inhibited occurs. As a result, the rotational speed Ne of the engine 22 can be reduced and the engine 22 can be stopped at the target crank angle CAtag without causing a control failure.

  In the hybrid vehicle 20 of the embodiment, when the rotational speed Ne of the engine 22 is within a resonance containing range set as a range that is greater than or equal to the threshold value Nref2 and less than the threshold value Nref1 as a rotational speed range that includes a resonant rotational speed range in which the drive system resonates. The value k2 smaller than the normal value k1 is set to the proportional gain kp. However, when the rotational speed Ne of the engine 22 is in the resonance rotational speed band where the drive system resonates, the value k2 smaller than the normal value k1 is proportional gain. It may be set to kp.

  In the hybrid vehicle 20 of the embodiment, when the rotational speed Ne of the engine 22 is less than the threshold value Nref2 that is the lower limit value of the resonance containing range and is equal to or higher than the torque output stop rotational speed Nref3, the rotational speed Ne of the engine 22 is the upper limit value of the resonance containing range. The normal value k1 used when the value is larger than the threshold value Nref1 is set as the proportional gain kp, but a value k3 different from the value k1 may be set as the proportional gain kp. In this case, the value k3 is preferably smaller than the value k1 and larger than the value k2.

  In the hybrid vehicle 20 of the embodiment, the proportional term and the integral term are used as the relational expression of the feedback control using the proportional gain kp when setting the motor torque Tα. However, the integral term may not be used. Absent.

  In the hybrid vehicle 20 of the embodiment, the sum of the motor torque Tα and the correction torque Tβ is set as the torque command Tm1 * of the motor MG1, but the motor torque Tα is set as it is as the torque command Tm1 * of the motor MG1. It does n’t matter what you do. Further, the sum of the correction torque different from the correction torque Tβ and the motor torque Tα may be set as the torque command Tm1 * of the motor MG1, or another correction torque may be added to the motor torque Tα and the correction torque Tβ. The additionally obtained torque may be set as the torque command Tm1 * of the motor MG1.

  In the hybrid vehicle 20 of the embodiment, the rotational speed gradient dne set so that the crank angle CA when the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3 becomes the torque output stop crank angle CAref is set to the previous value. The new target rotational speed Ne * is set to be subtracted from the target rotational speed Ne *. However, when the engine stop control routine is started and the target crank angle CAtag is set, the crank until the engine 22 is stopped is set. The relationship between the angle CA and the target rotational speed Ne * may be set, and the target rotational speed Ne * may be set by applying the crank angle CA to the set relationship.

  In the hybrid vehicle 20 of the embodiment, when the rotational speed Ne of the engine 22 reaches the torque output stop rotational speed Nref3 or less, basically the torque output from the motor MG1 is stopped as the engine stop adjustment control. When the engine 22 is about to stop before the target crank angle CAtag, the stop position of the engine 22 is set to the target crank angle CAtag by outputting a torque for rotating the engine 22 from the motor MG1, and conversely the engine 22 However, when attempting to stop exceeding the target crank angle CAtag, a torque for stopping the rotation of the engine 22 is output from the motor MG1 so that the engine 22 does not significantly stop exceeding the target crank angle CAtag. The motor M is simply used as adjustment control when the engine is stopped. The torque for rotating the engine 22 from the motor MG1 only when the engine 22 is about to stop before the target crank angle CAtag is used as an engine stop adjustment control. For example, the engine MG1 outputs a torque for stopping the rotation of the engine 22 from the motor MG1 only when the engine 22 is about to stop after exceeding the target crank angle CAtag. Various types of control may be performed as adjustment control during engine stop.

  In the hybrid vehicle 20 of the embodiment, the power of the motor MG2 is shifted by the reduction gear 35 and output to the ring gear shaft 32a. However, as illustrated in the hybrid vehicle 120 of the modified example of FIG. May be connected to an axle (an axle connected to the wheels 64a and 64b in FIG. 7) different from an axle to which the ring gear shaft 32a is connected (an axle to which the drive wheels 63a and 63b are connected). Further, the mechanical mechanism for connecting the engine 22 and the motor MG1 is not limited to the power distribution and integration mechanism 30 configured as a planetary gear, but may be an engine that connects the engine and the motor by a gear mechanism other than the planetary gear. Any type of automobile may be used as long as it has a motor capable of inputting and outputting power via a mechanical mechanism on its output shaft.

  Further, in the embodiments, the present invention has been described as a form of the hybrid vehicle 20, but it may be a form of a control method when the operation of the internal combustion engine mounted on such a car is stopped.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problems will be described. In the embodiment, the engine 22 corresponds to the “internal combustion engine”, the motor MG1 that inputs and outputs power to the crankshaft 26 of the engine 22 via the power distribution and integration mechanism 30 corresponds to “electric motor”, and the battery 50 corresponds to “two”. Corresponds to “second battery”. When the rotational speed Ne of the engine 22 is greater than the resonance content range that is greater than or equal to the threshold Nref2 including the resonance rotational speed band in which the drive system including the power distribution and integration mechanism 30 and the motors MG1 and MG2 resonates is greater than the resonance content range that is less than the threshold Nref1, Feedback control of the motor MG1 with the proportional gain kp for which k1 is set is performed so that the rotational speed Ne of the engine 22 becomes the target rotational speed Ne *. When the rotational speed Ne of the engine 22 is within the resonance containing range, the normal value k1 Control is performed so that the rotational speed Ne of the engine 22 becomes the target rotational speed Ne * by feedback control of the motor MG1 with a proportional gain kp set with a smaller value k2, and torque output is performed when the rotational speed Ne of the engine 22 is less than the resonance inclusion range When the rotation speed is higher than the stop speed Nref3, the proportional gay with the normal value k1 is set. The engine speed reduction control shown in FIG. 4 is executed to control the engine speed Ne so as to be equal to the target engine speed Ne * by feedback control of the motor MG1 by kp, and the engine speed Ne is the torque output stop rotation. When the number Nref3 or less, the hybrid electronic control unit 70 that executes the adjustment control at the time of engine stop, the motor ECU 40 that receives the torque command Tm1 * and controls the drive of the motor MG1, and the “control unit at the time of stop”.

  Here, the “internal combustion engine” is not limited to an internal combustion engine that outputs power using a hydrocarbon fuel such as gasoline or light oil, and may be any type of internal combustion engine such as a hydrogen engine. The “motor” is not limited to the motor MG1 configured as a synchronous generator motor, and may be any type of motor as long as it can input and output power, such as an induction motor. The “secondary battery” is not limited to the battery 50 configured as a lithium ion secondary battery, and various secondary batteries such as a nickel hydride secondary battery, a nickel cadmium secondary battery, and a lead storage battery are used. Can do. The “stop-time control means” is not limited to the combination of the hybrid electronic control unit 70 and the motor ECU 40, and may be configured by a single electronic control unit. Further, as the “stop-time control means”, the rotational speed Ne of the engine 22 is equal to or higher than a threshold Nref2 including a resonance rotational speed band in which a drive system including the power distribution and integration mechanism 30 and the motors MG1 and MG2 resonates and is lower than the threshold Nref1. When it is larger than the resonance content range, the engine 22 is controlled so that the rotational speed Ne becomes the target rotational speed Ne * by feedback control of the motor MG1 with the proportional gain kp set to the normal value k1, and the rotational speed Ne of the engine 22 is resonant. When it is within the content range, the rotational speed Ne of the engine 22 is controlled to be the target rotational speed Ne * by feedback control of the motor MG1 with the proportional gain kp set to a value k2 smaller than the normal value k1, and the rotational speed of the engine 22 is controlled. When Ne is less than the resonance content range and greater than the torque output stop rotational speed Nref3, The engine speed reduction control is executed so that the rotational speed Ne of the engine 22 becomes the target rotational speed Ne * by feedback control of the motor MG1 with the proportional gain kp set with k1, and the rotational speed Ne of the engine 22 is When the torque output stop rotational speed Nref3 or less, the engine output adjustment control is not limited to that executed when the engine is stopped. When the rotational speed Ne of the engine 22 is less than the threshold value Nref2 that is the lower limit value of the resonance containing range, the torque output stop rotational speed is When Nref3 or more, an internal combustion engine is set such that the proportional gain kp is set to a value k3 different from the normal value k1 used when the rotational speed Ne of the engine 22 is larger than the threshold value Nref1 that is the upper limit value of the resonance containing range. Is stopped to stop the internal combustion engine at a predetermined target crank angle. The target rotational speed of the internal combustion engine is set according to the crank angle or elapsed time of the internal combustion engine while the number is decreasing, and the rotational speed of the internal combustion engine is the target until the rotational speed of the internal combustion engine reaches a predetermined rotational speed. Decrease speed control is performed to control the generator so that the engine speed becomes equal to the engine speed. After the engine speed reaches a predetermined value, the generator is driven and controlled so that the engine stops at the target crank angle. The first gain is obtained when the control immediately before stopping is executed and the rotational speed control at the time of decrease is greater than a predetermined rotational speed range including a resonance rotational speed range in which the rotational speed of the internal combustion engine resonates the drive system including the electric motor and the mechanical mechanism. Is used to control the generator so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine falls within a predetermined rotational speed range, the internal combustion engine is used with a second gain smaller than the first gain. Is the target speed The generator is controlled so that the engine speed becomes a number, and when the speed of the internal combustion engine is smaller than the predetermined speed range and equal to or higher than the predetermined speed, the engine speed is set to the target speed by using a third gain larger than the second gain. Any generator can be used as long as it controls the generator so that the number becomes the same.

  The correspondence between the main elements of the embodiment and the main elements of the invention described in the column of means for solving the problem is the same as that of the embodiment described in the column of means for solving the problem. Therefore, the elements of the invention described in the column of means for solving the problems are not limited. That is, the interpretation of the invention described in the column of means for solving the problems should be made based on the description of the column, and the examples are those of the invention described in the column of means for solving the problems. It is only a specific example.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention is applicable to the automobile manufacturing industry.

  20,120 Hybrid vehicle, 22 engine, 24 engine electronic control unit (engine ECU), 24a CPU, 24b ROM, 24c RAM, 26 crankshaft, 28 damper, 30 power distribution integrated mechanism, 31 sun gear, 32 ring gear, 32a ring gear Shaft, 33 Pinion gear, 34 Carrier, 35 Reduction gear, 40 Motor electronic control unit (motor ECU), 41, 42 Inverter, 43, 44 Rotation position detection sensor, 50 battery, 51 Temperature sensor, 52 Battery electronic control unit ( Battery ECU), 54 power line, 60 gear mechanism, 62 differential gear, 63a, 63b driving wheel, 64a, 64b wheel, 70 electronic control unit for hybrid, 72 CPU, 74 ROM, 7 6 RAM, 80 ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 brake pedal, 86 brake pedal position sensor, 88 vehicle speed sensor, 122 air cleaner, 124 throttle valve, 126 fuel injection Valve, 128 intake valve, 130 spark plug, 132 piston, 134 purification device, 136, throttle motor, 138 ignition coil, 140 crank position sensor, 142 water temperature sensor, 143 pressure sensor, 144 cam position sensor, 146 throttle valve position sensor, 148 Air flow meter, 149 Temperature sensor, 150 Variable valve timing mechanism, MG1, MG2 motor.

Claims (5)

When stopping the operation of the internal combustion engine, an electric motor capable of inputting / outputting power to / from the output shaft of the internal combustion engine via a mechanical mechanism, a secondary battery capable of exchanging electric power with the electric motor, A target rotational speed of the internal combustion engine is set according to a crank angle or an elapsed time of the internal combustion engine during which the rotational speed is being decreased to stop the internal combustion engine at a predetermined target crank angle; Until the engine speed reaches a predetermined speed, the engine speed is controlled to be reduced so that the speed of the internal combustion engine becomes the set target speed, and the engine speed is reduced. After reaching the predetermined number of revolutions, the vehicle is provided with a stop-time control means for executing a control immediately before stopping to control the generator so that the internal combustion engine stops at the target crank angle,
The stop-time control means, as the decrease-time rotation speed control, when the rotation speed of the internal combustion engine is larger than a predetermined rotation speed range including a resonance rotation speed band that resonates a drive system including the electric motor and the mechanical mechanism. Using the first gain, the generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine falls within the predetermined rotational speed range, the first gain The generator is controlled using a small second gain so that the rotational speed of the internal combustion engine becomes the target rotational speed, and the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed range and greater than or equal to the predetermined rotational speed. Means for controlling the generator so that the rotational speed of the internal combustion engine becomes the target rotational speed using a third gain that is sometimes larger than the second gain;
A car characterized by that. The automobile according to claim 1,
The stop-time control means uses the proportional term and the integral term to set the torque of the motor so as to cancel out the difference between the detected rpm and the target rpm as the reduction rpm control. Perform number feedback control,
The first gain, the second gain and the third gain are proportional gains,
Car. The automobile according to claim 1 or 2,
The first proportional gain and the third proportional gain are the same.
Car. The automobile according to any one of claims 1 to 3,
The mechanical mechanism is a planetary gear mechanism in which three rotating elements are respectively connected to a drive shaft coupled to an axle, an output shaft of the internal combustion engine, and a rotating shaft of the electric motor.
Car. In an automobile equipped with an internal combustion engine, an electric motor capable of inputting / outputting power to / from an output shaft of the internal combustion engine via a mechanical mechanism, and a secondary battery capable of exchanging electric power with the electric motor, When stopping the operation, the target rotational speed of the internal combustion engine according to the crank angle or the elapsed time of the internal combustion engine during which the rotational speed is decreasing to stop the internal combustion engine at a predetermined target crank angle. The engine speed is controlled so that the generator is controlled so that the speed of the internal combustion engine becomes the set target speed until the speed of the internal combustion engine reaches a predetermined speed. After the rotational speed of the internal combustion engine reaches the predetermined rotational speed, the control when the operation of the internal combustion engine is stopped is executed to perform the control immediately before stopping to drive the generator so that the internal combustion engine stops at the target crank angle. A law,
As the reduction speed control, the first gain is used when the rotational speed of the internal combustion engine is larger than a predetermined rotational speed range including a resonance rotational speed band that resonates a drive system including the electric motor and the mechanical mechanism. The generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine falls within the predetermined rotational speed range, a second gain smaller than the first gain is used. The generator is controlled so that the rotational speed of the internal combustion engine becomes the target rotational speed, and when the rotational speed of the internal combustion engine is smaller than the predetermined rotational speed range and greater than or equal to the predetermined rotational speed, the second gain is used. Controlling the generator so that the rotational speed of the internal combustion engine becomes the target rotational speed using a large third gain;
A control method when the operation of the internal combustion engine is stopped.

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