JP2010014071A - Engine start control device for hybrid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology enabling a smooth engine start by suitably inhibiting the overshoot of rotation speed and an increase of vibration in the engine start in a hybrid system. <P>SOLUTION: When a demand for starting the engine 1 in a stop state is raised, motoring start control for accelerating the rotation speed of the engine 1 by motoring the engine 1 by an MG 1 without injecting fuel by an injector 29 is executed at first. Then, fuel injection start control is performed for stopping engine motoring by the MG 1, starting fuel injection by the injector 29, and accelerating the rotation speed of the engine 1 by combustion energy of the fuel at a point time when the rotation speed of the engine 1 reaches a prescribed reference rotation speed NE1. The start control of the engine 1 is completed at a point of time when the rotation speed of the engine 1 is accelerated to target rotation speed NE2 at which it can be determined that start of the engine 1 completed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an engine start control device for a hybrid system.

When starting the engine of a hybrid system, cranking is performed by a motor up to a predetermined number of revolutions, fuel injection is started at a predetermined number of revolutions or more, and when engine complete explosion is judged, cranking by the motor is stopped to facilitate engine starting A technique for achieving this is described in Patent Document 1.
Japanese Patent Laid-Open No. 10-331749 JP-A-11-200191 JP 2005-256732 A JP 2006-233841 A

  Thus, when fuel injection is performed simultaneously with cranking by the motor at the time of engine start in the hybrid system, the increase in rotation due to motoring and the increase in rotation due to the combustion energy of fuel act synergistically, and the engine speed is reduced. There was a possibility of overshoot or increased vibration.

  The present invention has been made in view of such circumstances, and provides a technology that enables a smooth engine start by suitably suppressing an increase in rotational overshoot and vibration during engine start in a hybrid system. The purpose is to do.

In order to achieve the above object, the present invention provides:
An internal combustion engine;
A first power source that is a power source other than the internal combustion engine;
A power source other than the internal combustion engine, wherein the second power source outputs a driving force for operating the internal combustion engine without depending on the combustion energy of the fuel;
An engine start control device for a hybrid system that outputs a driving force to a driving system by at least the first power source,
A fuel injection device for injecting fuel into the internal combustion engine;
When starting the internal combustion engine,
Motoring start control for driving the internal combustion engine by the second power source without increasing the number of revolutions of the internal combustion engine without performing fuel injection by the fuel injection device;
Fuel injection start control for increasing the rotational speed of the internal combustion engine by performing fuel injection by the fuel injection device without driving the internal combustion engine by the second power source;
Starting control means for switching and executing,
It is characterized by providing.

  According to the above configuration, when the internal combustion engine is started, the driving of the internal combustion engine by the second power source and the driving of the internal combustion engine by the combustion energy of the fuel are suppressed. As a result, when the internal combustion engine is started, excessive drive energy is supplied to the internal combustion engine to increase vibrations, or the rotational speed of the internal combustion engine is excessively increased to overshoot the target rotational speed at the completion of startup. Can be suppressed.

  In the present invention, the start control means may switch between motoring start control and fuel injection start control based on the rotational speed of the internal combustion engine. That is, the start control means performs motoring start control during a period from the start of the internal combustion engine until the rotational speed of the internal combustion engine reaches a predetermined rotational speed, and the rotational speed of the internal combustion engine is set to the predetermined rotational speed. The fuel injection start control may be performed during a period from when the rotation speed is reached until the target rotation speed at the completion of the start is reached.

  Here, the predetermined number of rotations can be arbitrarily set according to the purpose as long as the number of rotations is not more than the upper limit value of the number of rotations that can be reached only by the second power source.

  For example, there is a large amount of fuel consumed when the rotational speed of an internal combustion engine in a low speed state is increased by the combustion energy of fuel. Therefore, in the low speed region, if the rotational speed of the internal combustion engine is increased by the second power source so as not to be the combustion energy of the fuel, the fuel efficiency characteristics at the start of the internal combustion engine can be improved. In this case, the upper limit value of the rotational speed that can be reached only by the second power source can be set to the “predetermined rotational speed” in the above configuration.

  Further, in the low speed region of the internal combustion engine, there is a rotational speed region where the magnitude of resonance between the internal combustion engine and the drive system becomes large. The rotation speed region in which the resonance becomes large is a specific rotation speed range determined by specifications such as the structure and weight of the internal combustion engine and the drive system. When fuel injection is performed in such a rotational speed region where resonance is large (hereinafter referred to as “resonance region”), vibration generated due to resonance tends to increase. Therefore, when the rotational speed of the internal combustion engine is included in the resonance region, if the rotational speed of the internal combustion engine is increased by the second power source so as not to be the combustion energy of the fuel, vibration at the start of the internal combustion engine is suppressed. it can. In this case, the resonance region can be obtained in advance by experiments or the like, and the upper limit value of the resonance region can be set to the “predetermined rotational speed” in the above configuration.

  Further, the vibration at the time of starting the internal combustion engine or an amount correlated with the vibration is measured, the resonance region is learned based on the measurement result, and the motoring start control is performed in the resonance region based on the learning result. Also good. For example, the present invention further includes a measuring means for measuring the rotational fluctuation and / or torque fluctuation of the internal combustion engine, and the rotational speed of the internal combustion engine is included in the resonance region based on the measured rotational fluctuation or torque fluctuation of the internal combustion engine. It may also be determined whether or not. Then, while executing the motoring start control, the fuel injection start control is switched at an arbitrary timing after it is determined that the rotational speed has exceeded the resonance region based on the measurement result of the rotation fluctuation or torque fluctuation. Also good.

  In particular, in the hybrid system of the present invention, when a motor is provided as the second power source, the rotational fluctuation or torque fluctuation of the internal combustion engine motored by the motor is used to control the motor torque or the motor rotational speed of the motor. The above configuration is particularly effective because the measurement can be performed with high accuracy.

  In the present invention, an intake throttle valve provided in the intake passage of the internal combustion engine is further provided, and the start control means opens the intake throttle valve when performing the motoring start control as compared with the case of performing the fuel injection start control. The degree may be set to the opening on the closing side. By doing so, the compression work in the internal combustion engine is reduced, so that the vibration of the internal combustion engine when the motoring start control is executed can be further reduced. When performing the motoring start control, it is not necessary to burn the fuel, so it is not necessary to supply air to the internal combustion engine. Accordingly, the intake throttle valve can be closed to the fully closed position or close to the fully closed position.

The present invention further includes a turbocharger having a compressor provided in an intake passage of an internal combustion engine and a turbine provided in an exhaust passage, and the turbocharger includes a nozzle vane having a variable opening degree, and the nozzle vane is opened. In the case of a variable capacity turbocharger that can reduce the supercharging efficiency by setting the opening degree to the opening side, the start control means performs the fuel injection start control when performing the motoring start control. Compared with the case where it performs, you may make it set the opening degree of a nozzle vane to the opening degree of an opening side. By doing so, the compression work in the internal combustion engine is reduced, so that the vibration of the internal combustion engine when the motoring start control is executed can be further reduced.

  In the hybrid system of the present invention, the second power source may be configured by surplus power of the first power source. That is, the hybrid system of the present invention is configured as a hybrid system that includes an internal combustion engine and a first power source as a power source, and outputs a driving force to the driving system by at least the driving force of the first power source. Of the driving force that can be output from the power source, the remaining surplus power that outputs the required driving force of the driving system may be used to operate the internal combustion engine regardless of the combustion energy of the fuel. For example, under conditions where the required driving force of the drive system is zero, such as when the internal combustion engine is started when the vehicle is stopped, the entire power of the first power source is used as the power for performing the motoring start control. It can also be used. By doing so, the hybrid system according to the present invention can have a simple configuration including only the first power source as a power source other than the internal combustion engine.

  According to the present invention, when the engine is started in the hybrid system, an increase in vibration and an overshoot of the rotational speed are suppressed, and a smooth engine start is possible.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a hybrid system to which an engine start control device of a hybrid system according to the present invention is applied.

  This hybrid system has an engine 1, a first motor generator (hereinafter referred to as “MG1”), and a second motor generator (hereinafter referred to as “MG2”) as power sources. The power of the engine 1 is distributed and output to the MG 1 and the output unit 4 by the power split mechanism 3. The power split mechanism 3 is configured by a known planetary gear mechanism. The power of MG2 is output to the output unit 4. The power of the engine 1 and the MG 2 output to the output unit 4 is transmitted to the drive wheels 40 as a driving force for driving the drive wheels 40 of the vehicle on which the hybrid system is mounted via the transmission unit 8. The transmission unit 8 has a known configuration such as a drive shaft or a differential gear.

  MG1 is a synchronous motor generator that functions as a motor or a generator.

  MG1 can operate as a motor by electric power supplied from battery 25 and / or electric power generated by MG2 when operated as a generator. The power of MG 1 when operated as a motor is output to the output shaft (crankshaft) of engine 1 as a driving force for motoring engine 1 via power split mechanism 3.

  Here, motoring the engine 1 means that the engine 1 is mechanically rotationally driven by an external force without depending on the internal combustion energy due to fuel combustion. In the hybrid system of the present embodiment, the engine 1 can be motored by the power of the MG1, so that the fuel injection is not performed in the engine 1 or the injection amount necessary for the engine 1 to rotate independently is less than The engine 1 can be operated even in a state where a small amount of fuel is injected.

  Further, even in a state where normal fuel injection is performed in the engine 1, that is, in a state where the engine 1 is in a load operation, the operating state of the engine 1 can be defined from the outside by the power of the MG1. Thereby, it is possible to maintain the engine 1 which carries out load driving | running | working in the state which operate | moves stably with a fixed rotational speed, for example. In this embodiment, it is assumed that controlling the operating state of the engine 1 under load operation from the outside by the power of the MG 1 includes motoring the engine 1.

  MG1 is driven by the power of engine 1 distributed to MG1 via power split mechanism 3, and can operate as a generator. The electric power generated by MG1 when operating as a generator is consumed as electric power for charging battery 25 and / or electric power for operating MG2 as a motor.

  MG2 is also a synchronous motor generator that functions as a motor or a generator.

  MG2 can operate as a motor by the electric power supplied from battery 25 and / or the electric power generated by MG1 when operated as a generator. The power of the MG 2 when operating as a motor is transmitted to the driving wheel 40 as a driving force for driving the driving wheel 40 via the output unit 4.

  The MG 2 is driven by the kinetic energy of the drive wheel 40 transmitted via the transmission unit 8 and the output unit 4 and can operate as a generator. The electric power generated by MG2 when operating as a generator is consumed as electric power for charging battery 25 and / or electric power for operating MG1 as a motor. In this case, regenerative power generation is performed by the kinetic energy of the drive wheels 40, and a braking force is applied to the drive wheels 40.

  The inverter 24 converts DC power supplied from the battery 25 into AC power and supplies it to MG1 and MG2, and also converts AC power supplied from MG1 and MG2 into DC power when operating as a generator. The battery 25 is supplied.

  The engine 1 is a diesel engine. FIG. 2 shows a schematic configuration of the intake / exhaust system and the control system of the engine 1.

  The engine 1 is a four-cylinder engine, and each cylinder 49 is provided with an injector 29 that directly injects fuel into the combustion chamber of the engine 1. Connected to the engine 1 are an intake passage 42 for supplying air into the combustion chamber and an exhaust passage 43 for discharging burned gas in the combustion chamber. A throttle valve 22 that adjusts the flow rate of intake air in the intake passage 42 is provided in the middle of the intake passage 42. A compressor 11 of the turbocharger 13 is provided downstream of the throttle valve 22. A turbine 12 of the turbocharger 13 is provided in the middle of the exhaust passage 43. The turbocharger 13 is a variable capacity turbocharger that includes the nozzle vane 5 having a variable opening degree in the turbine 12 and can change the supercharging efficiency by changing the opening degree of the nozzle vane 5. Specifically, the supercharging efficiency of the turbocharger 13 decreases as the opening degree of the nozzle vane 5 is increased.

  The control system of this hybrid system will be described with reference to FIGS.

  This hybrid system includes an ECU 26 that is a computer unit that controls the operation of the entire hybrid system. The ECU 26 is an electronic control computer having a known configuration such as a CPU, a ROM, and a RAM.

  The ECU 26 includes a water temperature sensor 48 that measures the temperature of the cooling water of the engine 1, an in-cylinder pressure sensor 50 that measures the in-cylinder pressure of the engine 1, a crank angle sensor 30 that measures the rotation angle of the crankshaft of the engine 1, and an accelerator pedal 52. An accelerator opening sensor 27 that measures the amount of depression of the vehicle, a vehicle speed sensor 28 that measures the vehicle speed of a vehicle equipped with a hybrid system, an SOC sensor 51 that acquires the state of charge of the battery 25, and an MG1 rotational speed that measures the rotational speed of MG1. A sensor 31, an MG2 rotational speed sensor 32 that measures the rotational speed of the MG2, and other sensor devices that measure various state quantities of the hybrid system and the vehicle are connected. Information on the state quantities measured by each sensor is sent to the ECU 26. Entered.

  Further, the ECU 26 is connected to the nozzle vane 5, the throttle valve 22, the injector 29, the inverter 24, other actuators for driving various hybrid systems and vehicles, and the like. Based on information input from the sensors. A control signal for driving and controlling the operation of each device is output.

  The ECU 26 has, for example, fuel efficiency based on the vehicle speed information from the vehicle speed sensor 28, the required driving force calculated from the accelerator opening information from the accelerator opening sensor 27, and the battery charge state information from the SOC sensor 51. The optimum operation mode is selected, and the engine 1, MG1, and MG2 are controlled so as to transition from the currently selected operation mode to the selected operation mode. Depending on the selected operation mode, operation / stop of the engine 1 (execution / stop of fuel injection) and power running / power generation of MG1 / MG2 are switched.

  When the engine 1 is started, the MG 1 operates as a motor by the electric power of the battery 25, and the engine 1 is started by motoring (cranking) the engine 1. When the rotational speed of the engine 1 reaches a predetermined rotational speed, fuel injection is started by the injector 29 and motoring of the engine 1 by MG1 is stopped. There is a feature of this embodiment in the control at the time of starting the engine. Details of the engine start control will be described later.

  When the vehicle starts, the engine 1 performs an operation for warming up, and outputs a required driving force for traveling the vehicle by the MG2. When the charged state of the battery 25 is lowered, the engine 1 performs an operation for driving the MG 1 as a generator, and charges the battery 25 with the electric power generated by the MG 1.

  During low load traveling, fuel injection in the engine 1 is stopped and the engine 1 is stopped. The requested driving force for traveling the vehicle is output by MG2. When the charged state of the battery 25 is lowered, the engine 1 performs an operation for driving the MG 1 as a generator, and charges the battery 25 with the electric power generated by the MG 1.

  During normal traveling, the required driving force for traveling the vehicle is mainly output by the engine 1. Moreover, MG1 is operated as a generator by the power split mechanism 3 in the power of the engine 1, MG2 is operated as a motor by the electric power generated by MG1, and the engine 1 is assisted by the power of MG2. A part of the electric power generated by MG1 is used for charging the battery 25.

  When the braking is requested, the rotational energy of the drive wheel 40 is transmitted to MG2, and MG2 is operated as a generator to perform braking by regenerative power generation. When the charged state of the battery 25 is high and the electric power generated by the regenerative power generation cannot be consumed, the rotational energy of the drive wheels 40 is transmitted to the engine 1 and braking by the engine brake is performed.

The ECU 26 grasps the current engine load and engine speed based on the accelerator opening information input from the accelerator opening sensor 27 and the crank angle information input from the crank angle sensor 30. The required driving force for driving the vehicle determined according to the driving state, the charging state information of the battery 25 from the SOC sensor 51, the required power of auxiliary equipment such as an air conditioner, etc. Based on the required driving force, the required output of the engine 1 is calculated. Then, based on the required output of the engine 1, a control signal for devices such as the throttle valve 22 and the injector 29 is output.

  The ECU 26 obtains the required operating state of power running / power generation of MG1 / MG2, the required output rotational speed and the required output torque of MG1 and MG2 according to the operating state, and outputs a command for independently controlling MG1 and MG2 to the inverter 24. To do. Inverter 24 generates a three-phase alternating current to be supplied to MG1 and MG2 from a direct current voltage supplied from battery 25 in accordance with a command from ECU 26.

  Here, the start control of the engine 1 in the hybrid system of the present embodiment will be described.

  In the present embodiment, when a request for starting the engine 1 in a stopped state occurs, first, the engine 1 is motored by the MG 1 without performing the fuel injection by the injector 29, thereby increasing the rotational speed of the engine 1. Perform motoring start control. When the rotational speed of the engine 1 reaches a predetermined reference rotational speed NE1, engine motoring by the MG1 is stopped, fuel injection by the injector 29 is started, and the rotational speed of the engine 1 is reduced by fuel combustion energy. The fuel injection start control to raise is performed. Then, when the rotational speed of the engine 1 increases to the target rotational speed NE2 that can be determined that the start of the engine 1 has been completed, the start control of the engine 1 is terminated, and the subsequent load operation mode is entered.

  The execution procedure of the start control of the engine 1 in the present embodiment described above will be described based on the flowchart of FIG. The engine start control routine represented by this flowchart is repeatedly executed during operation of the hybrid system.

  In step S101, the ECU 26 determines whether or not a request for starting the stopped engine 1 has occurred. For example, when the hybrid system transitions from an operation mode (EV travel mode) in which a required driving force for vehicle travel is output only by MG2 to a travel mode in which the engine 1 is loaded, the stopped engine 1 is started. Request to be generated. If it is determined in step S101 that an engine start request has been generated (Yes), the ECU 26 proceeds to step S102. If it is determined in step S101 that there is no engine start request (No), the ECU 26 once exits this routine.

  In step S102, the ECU 26 enters a non-injection state in which the fuel is not injected by the injector 29, and starts motoring start control for increasing the number of revolutions of the engine 1 by motoring the engine 1 with MG1. At this time, the throttle valve 22 is further closed, and the opening degree of the nozzle vane 5 is set to the opening degree ON1 on the opening side with respect to the opening degree ON2 of the nozzle vane 5 when the fuel injection start control described later is executed.

  In step S103, the ECU 26 acquires the rotational speed NE of the engine 1 based on the crank angle information from the crank angle sensor 30.

In step S104, the ECU 26 determines whether or not the rotational speed NE of the engine 1 acquired in step S103 is equal to or higher than a predetermined reference rotational speed NE1. Here, the reference rotational speed NE1 is set to the upper limit value NEsup of the rotational speed of the engine 1 that can be reached by MG1. When it is determined in step S104 that the engine speed NE has become equal to or higher than the reference speed NE1 (Yes), the ECU 26 proceeds to step S105. If it is determined in step S104 that the engine speed NE is not equal to or higher than the reference speed NE1 (No), the ECU 26 returns to step S103.

  In step S105, the ECU 26 stops the motoring of the engine 1 by the MG1, starts the fuel injection of the idle injection amount by the injector 29, and performs the fuel injection start control for increasing the rotational speed of the engine 1 by the combustion energy of the fuel. Start. At this time, since it is necessary to supply air for burning the fuel, the throttle valve 22 is opened, and the opening degree of the nozzle vane 5 is set from the opening degree ON1 of the nozzle vane 5 when the motoring start control is executed. Set the opening to ON2 on the closing side.

  In step S106, the ECU 26 acquires the rotational speed NE of the engine 1 based on the crank angle information from the crank angle sensor 30.

  In step S107, the ECU 26 determines whether or not the rotational speed NE of the engine 1 acquired in step S106 is equal to or higher than the target rotational speed NE2 at the time of starting the engine. If it is determined in step S107 that the engine speed NE has become equal to or higher than the target speed NE2 (Yes), the ECU 26 proceeds to step S108. If it is determined in step S107 that the engine speed NE is not equal to or higher than the target speed NE2 (No), the ECU 26 returns to step S106.

  In step S108, the ECU 26 determines that the engine 1 has been started.

  The hybrid system operation mode, the fuel injection amount by the injector 29, the operating state of the MG1, the rotational speed of the engine 1, the opening degree of the throttle valve 22 and the nozzle vane 5 when the engine start control of the present embodiment described above is executed. An example of the time change of the opening is shown in FIG.

  FIG. 4A shows the operation mode of the hybrid system. Here, the engine 1 is stopped at time t1 from the state in which the hybrid system is operating in the operation mode (EV travel mode) in which the operation of the engine 1 is stopped and the required driving force for vehicle travel is output only by MG2. A case where the hybrid system transitions to a state to be started will be described as an example.

  When a request to start the engine 1 is given to the ECU 26 at time t1, the MG 1 operates as a motor with the electric power of the battery 25 and motorizes the engine 1 as shown in FIG. Further, as shown in FIG. 4B, a fuel cut state in which fuel injection by the injector 29 is not performed is achieved. That is, at time t1, motoring start control for increasing the rotational speed of the engine 1 by motoring by MG1 is started regardless of the combustion energy of fuel.

  At this time, as shown in FIG. 4 (E), the throttle valve 22 is closed, and as shown in FIG. 4 (F), the nozzle vane 5 is set to the large opening degree ON1. By doing so, the amount of air taken into the engine 1 is reduced, so that the compression work in the engine 1 can be reduced. Thereby, it becomes possible to suppress suitably the vibration of the engine 1 at the time of motoring start control.

At the time (time t1) when the rotation speed of the engine 1 is increased by the motoring start control and reaches the reference rotation speed NE1, the motoring of the engine 1 by the MG1 is stopped as shown in FIG. Further, as shown in FIG. 4B, the fuel injection of the idle injection amount is performed by the injector 29, and the fuel injection start control for increasing the rotational speed of the engine 1 by the combustion energy of the fuel is started.

  At this time, as shown in FIG. 4 (E), the throttle valve 22 is opened, and as shown in FIG. 4 (F), the nozzle vane 5 is set to the small opening degree ON2. By doing so, sufficient air is supplied to burn the fuel injected and supplied to the engine 1.

  It is determined that the start of the engine 1 has been completed at the time (time t2) when the speed of the engine 1 is further increased by the fuel injection start control and reaches the target speed NE2 at the time of engine start. Transits to the normal load operation mode.

  As described above, in the starting control of the engine 1 in the present embodiment, the driving force of the MG 1 and the combustion energy of the fuel injected and supplied by the injector 29 are used as the energy source for increasing the rotational speed of the engine 1. They are not used at the same time. That is, in the low rotation range from the start of the engine 1 to the reference rotation speed NE1, the rotation speed of the engine 1 is increased only by motoring by the MG1, and at this time, fuel injection is not performed. On the other hand, in a high engine speed range where the engine speed is equal to or higher than the reference speed NE1 and cannot be reached by the motoring driving force of the MG1, the engine 1 is injected with an idle injection amount and the combustion energy of the engine 1 The rotational speed is increased, and at this time, motoring by MG1 is not performed.

  As a result, the driving force of the MG 1 and the combustion energy of the fuel act synergistically to suppress the vibration of the engine 1 from increasing or the engine speed from exceeding the target engine speed to overshoot.

  Further, in the present embodiment, at the time of motoring start control, the intake air amount sucked into the engine 1 is reduced by closing the throttle valve 22 and setting the large opening of the nozzle vane 5, so that it is also preferable to generate vibration due to compression work. It is possible to suppress it.

  In general, the amount of fuel consumed is high when the engine speed in a stopped state or in a low speed state is increased by the combustion energy of the fuel. Therefore, immediately after the start of the engine, if the rotational speed of the engine 1 is increased by motoring by MG1 rather than the combustion energy of the fuel as much as possible, the fuel consumption at the time of starting the engine can be reduced.

  In this respect, in the present embodiment, the reference rotational speed NE1 for switching from the motoring start control to the fuel injection start control is set to the upper limit value NEsup of the engine speed that can be reached only by MG1, so that the fuel consumption at the time of engine start Can be suitably reduced.

  The reference rotational speed NE1 can be arbitrarily set according to the purpose as long as the rotational speed is lower than the upper limit value NEsup of the engine rotational speed that can be reached only by MG1. For example, the low-speed region of the engine 1 includes a rotational speed region in which the magnitude of resonance between the engine 1 and the drive system such as the transmission unit 8 and the drive wheels 40 increases. The rotation speed region where the resonance increases is a range of a specific rotation speed determined by specifications such as the structure and weight of the engine 1 and the drive system. When fuel injection is performed in such a rotational speed region where resonance is large (hereinafter referred to as “resonance region”), vibration generated due to resonance tends to increase. Therefore, when the rotational speed of the engine 1 is included in the resonance region, if the rotational speed of the engine 1 is increased by motoring by MG1 instead of fuel combustion energy as much as possible, vibration at the time of engine start can be reduced. Can do.

  When determining the reference rotational speed NE1 for such a purpose, the rotational speed higher than the upper limit value of the resonance region and lower than the upper limit rotational speed NEsup that can be reached by MG1 is set as the reference rotational speed. It can also be set to NE1. By doing so, in a situation where the rotational speed of the engine 1 is included in the resonance region, the rotational speed is increased by the motoring start control, and the control is switched to the fuel injection start control with the engine rotational speed exceeding the resonance region. It will be. Therefore, it is possible to suitably suppress the occurrence of a large vibration due to fuel injection when the engine speed is included in the resonance region.

  FIG. 4D shows an example of this resonance region. In FIG. 4D, the rotational speed region satisfying NEk1 ≦ NE ≦ NEk2 is the resonance region. The resonance region is obtained by experiments or the like as a rotation speed range in which the vibration of the engine 1 exceeds a predetermined allowable level. In the case of the first embodiment, switching from the motoring start control to the fuel injection start control is performed at the time t2 when the engine speed NE reaches the reference speed NE1 (NEsup in the case of the first embodiment). When the reference rotational speed NE1 is set to the upper limit value NEk2 of the resonance region, the switching from the motoring start control to the fuel injection start control is performed at the time t2 ′ when the engine speed NE reaches the upper limit value NEk2 of the resonance region. Become.

  As described in the above embodiment, in order to reduce the vibration at the time of starting the engine, a resonance region is obtained in advance based on the structure of the vehicle and the engine so that the fuel injection start control is not executed in the obtained resonance region. The reference rotational speed NE1 can also be set. On the other hand, even if the resonance region is not obtained in advance, vibrations at the time of engine start-up and state quantities correlated with vibration are monitored, and the engine speed region and operating conditions where resonance increases are learned. It is also possible to switch between the motoring start control and the fuel injection start control.

  For example, when the motor (MG1) is used as a power source for operating the engine 1 regardless of the combustion energy of the fuel as in the above embodiment, the MG1 is motored based on the motor torque of the MG1 and the motor rotation speed control. The engine torque of the engine 1 and the fluctuation of the engine speed can be monitored accurately. Since fluctuations in the engine torque and engine speed are considered to correlate with the vibration of the engine 1, it can be estimated whether or not the engine speed is in the resonance region based on fluctuations in the engine torque and engine speed. .

  Therefore, when executing the motoring start control at the time of starting the engine, the engine torque of the engine 1 and the fluctuation of the engine speed are measured by the MG1, and based on the measurement result, it is determined that the speed of the engine 1 has exceeded the resonance region. It is also possible to switch from the motoring start control to the fuel injection start control at the timing or at a later timing.

  FIG. 5 is a flowchart showing an engine start control routine when such engine start control is performed. During operation of the hybrid system, this engine start control routine may be executed instead of the routine of FIG. 3 described in the above embodiment.

  In step S201, the ECU 26 determines whether or not a request for starting the stopped engine 1 has occurred. If it is determined in step S201 that an engine start request has occurred (Yes), the ECU 26 proceeds to step S202. If it is determined in step S201 that there is no engine start request (No), the ECU 26 once exits this routine.

  In step S202, the ECU 26 performs motoring start control. That is, the engine 29 is brought into a non-injection state in which fuel injection by the injector 29 is not performed, and the engine 1 is motored by the MG 1 to increase the rotational speed of the engine 1. Further, the throttle valve 22 is closed and the opening degree of the nozzle vane 5 is set to ON1.

  In step S203, the ECU 26 measures fluctuations in the engine torque or engine speed of the engine 1 motored by the MG1, based on the motor torque control or motor speed control of the MG1.

  In step S204, the ECU 26 determines whether or not the rotational speed of the engine 1 has exceeded the resonance region based on the fluctuation of the engine torque or the rotational speed of the engine 1 measured in step S203. When the engine speed is in the resonance region, the fluctuation of the engine torque and the engine speed increases, but when the engine speed exceeds the resonance area, the fluctuation of the engine torque and the engine speed decreases. Therefore, when the engine speed and the engine torque are monitored and it is estimated that the engine speed has exceeded the resonance region (Yes), the ECU 26 proceeds to step S205. On the other hand, when it is estimated that the engine speed is still within the resonance region or not exceeding the resonance region (No), such as a situation where fluctuations in the engine torque and the engine speed are gradually increasing, the ECU 26 The process returns to step S203.

  In step S205, the ECU 26 stops the motoring of the engine 1 by the MG1 to end the motoring start control, and starts the fuel injection start control by starting the fuel injection of the idle injection amount by the injector 29. At this time, the throttle valve 22 is opened and the opening degree of the nozzle vane 5 is set to ON2.

  In step S206, the ECU 26 acquires the rotational speed NE of the engine 1 based on the crank angle information from the crank angle sensor 30.

  In step S207, the ECU 26 determines whether or not the rotational speed NE of the engine 1 acquired in step S206 is equal to or higher than the target rotational speed NE2 at the time of engine start. When it is determined in step S207 that the engine speed NE has become equal to or higher than the target speed NE2 (Yes), the ECU 26 proceeds to step S208. If it is determined in step S207 that the engine speed NE is not equal to or higher than the target speed NE2 (No), the ECU 26 returns to step S206.

  In step S208, the ECU 26 determines that the engine 1 has been started.

  In the routine of FIG. 5 described above, the example of measuring the torque or the rotational speed of the engine 1 based on the control of the MG 1 has been described, but the method for measuring the torque or the rotational speed of the engine 1 is not limited to this. For example, the engine torque can be calculated based on a change in the in-cylinder pressure of the engine 1 measured by the in-cylinder pressure sensor 50.

  The above-described embodiment is an example for explaining the present invention, and various modifications can be made to the above-described embodiment without departing from the gist of the present invention. For example, in the above-described embodiment, an example in which the present invention is applied to a hybrid system including MG2 that outputs a driving force for driving a vehicle and MG1 that outputs a driving force for motoring the engine 1 as separate devices. As described above, the MG 2 that outputs the driving force for driving the vehicle is configured to motor the engine 1 with the remaining surplus power that outputs the driving force for driving the vehicle, and only MG 2 is used as a power source other than the engine 1. The present invention can also be applied to a provided hybrid system.

In that case, for example, when the engine is started from the EV traveling state, the electric power supplied to MG2 is increased, and in addition to the driving force for causing the vehicle to EV travel, the driving force for further motoring engine 1 is output to MG2. As a result, the motoring start control is started. Then, when the engine speed exceeds the reference speed NE1 or when it is determined from the measurement of the engine torque or the engine speed that the engine speed has exceeded the resonance region, the power supplied to the MG2 is returned to the original state. The MG 2 is brought into a state in which a driving force for causing the vehicle to EV travel is output, and fuel injection by the injector 29 is started to start fuel injection start control.

  The engine 1 in the above embodiment corresponds to the internal combustion engine of the present invention. MG1 corresponds to the second power source. MG2 corresponds to the first power source. The injector 29 corresponds to a fuel injection device. The ECU 26 that executes the engine start control shown in FIG. 3 or 5 corresponds to the start control means. MG1 in the case of estimating the engine torque or the engine speed of the engine 1 motored by the MG1 based on the control of the motor torque or the motor speed of the MG1 corresponds to the measuring means. The throttle valve 22 corresponds to an intake throttle valve.

It is a block diagram which shows schematic structure of the hybrid system in an Example. It is a figure which shows schematic structure of the intake-exhaust system of an engine in an Example, and a control system. It is a flowchart showing the engine starting control routine in an Example. The figure which shows an example of the time change of the operation mode of the hybrid system at the time of performing engine starting control in an Example, the fuel injection amount by an injector, the operating state of MG1, the engine speed, the opening degree of a throttle valve, and the opening degree of a nozzle vane It is. It is a flowchart showing the engine starting control routine in an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 3 Power split mechanism 4 Output part 5 Nozzle vane 8 Transmission part 11 Compressor 12 Turbine 13 Turbocharger 22 Throttle valve 24 Inverter 25 Battery 26 ECU
27 Accelerator opening sensor 28 Vehicle speed sensor 29 Injector 30 Crank angle sensor 31 MG1 rotational speed sensor 32 MG2 rotational speed sensor 40 Drive wheel 42 Intake passage 43 Exhaust passage 48 Water temperature sensor 49 Cylinder 50 In-cylinder pressure sensor 51 SOC sensor 52 Accelerator pedal

Claims (7)

An internal combustion engine;
A first power source that is a power source other than the internal combustion engine;
A power source other than the internal combustion engine, wherein the second power source outputs a driving force for operating the internal combustion engine without depending on the combustion energy of the fuel;
An engine start control device for a hybrid system that outputs a driving force to a driving system by at least the first power source,
A fuel injection device for injecting fuel into the internal combustion engine;
When starting the internal combustion engine,
Motoring start control for driving the internal combustion engine by the second power source without increasing the number of revolutions of the internal combustion engine without performing fuel injection by the fuel injection device;
Fuel injection start control for increasing the rotational speed of the internal combustion engine by performing fuel injection by the fuel injection device without driving the internal combustion engine by the second power source;
Starting control means for switching and executing,
An engine start control device for a hybrid system, comprising: In claim 1,
The start control means performs the motoring start control until the rotational speed of the internal combustion engine reaches a predetermined rotational speed, and thereafter performs the fuel injection start control. Start control device. In claim 1,
The start control means is configured to rotate the motor until the rotational speed of the internal combustion engine reaches a predetermined rotational speed that is faster than a rotational speed region where the magnitude of resonance between the internal combustion engine and the drive system is larger than a predetermined reference. An engine start control device for a hybrid system, which performs ring start control and thereafter performs the fuel injection start control. In claim 3,
Measuring means for measuring rotational fluctuations and / or torque fluctuations of the internal combustion engine,
The start control means is configured so that the rotational speed of the internal combustion engine is in a rotational speed region in which the magnitude of the resonance is larger than a predetermined reference based on the rotational fluctuation or torque fluctuation of the internal combustion engine measured by the measuring means. The engine start control device for a hybrid system is characterized by determining whether or not it is included. In any one of Claims 1-4,
An intake throttle valve provided in the intake passage of the internal combustion engine,
The start control means is configured to start the engine of the hybrid system, when performing the motoring start control, and opening the intake throttle valve at a closing side as compared with when performing the fuel injection start control. Control device. In any one of Claims 1-5,
A turbocharger further comprising a compressor provided in an intake passage of the internal combustion engine and a turbine provided in an exhaust passage of the internal combustion engine, the turbocharger comprising a nozzle vane having a variable opening degree, It is a variable capacity turbocharger that can reduce the supercharging efficiency by opening the opening to the opening side,
The engine of the hybrid system characterized in that the start control means sets the opening of the nozzle vane to an opening on the open side when performing the motoring start control compared to when performing the fuel injection start control. Start control device. In any one of Claims 1-6,
The engine start control device for a hybrid system, wherein the second power source is surplus power of the first power source.

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