JP2001289083A - Method of controlling internal combustion engine for hybrid vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of defectiveness such as a misfire caused by the difference between engine speed used for computing a fuel injection quantity and engine speed in actually injecting fuel in the case of starting an internal combustion engine constituting a power source in a hybrid vehicle. SOLUTION: In the power source of the hybrid vehicle provided with an internal combustion engine and an electric rotating machine and starting the internal combustion engine by the electric rotating machine serving as a motor for starting the internal combustion engine, a current is applied to the electric rotating machine in starting, to rotatory-drive the internal combustion engine. A current quantity to the electric rotating machine is controlled to reduce the increase rate of engine speed after the engine speed of the internal combustion engine reaches a value not smaller than a specified value VT near the injection authorized rotating speed N1 preset to determine fuel injection start timing, and the injection of fuel is started in an engine speed area of the injection authorized rotating speed N1 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an internal combustion engine for a hybrid vehicle having an internal combustion engine and an electric rotating machine used for running and starting.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine for a vehicle such as an automobile, the internal combustion engine is rotationally driven by a starter at the time of starting, and at the same time, an increased amount of fuel is supplied (injected) to facilitate starting. The feedback control of the air-fuel ratio is not performed until the air-fuel ratio is not gradually reduced, and thereafter the air-fuel ratio is controlled so as to obtain an optimal operation state.
On the other hand, in a so-called hybrid vehicle power source that includes an internal combustion engine and an electric motor and operates one or both of them to drive the vehicle, the internal combustion engine is started without depending on the running state of the vehicle. The fuel is supplied (injected) when the rotational speed of the rotationally driven internal combustion engine reaches a preset certain rotational speed. In a hybrid vehicle, it is necessary to charge a battery as a power source of an electric motor. Therefore, when an electric motor is used, the internal combustion engine is started to charge when the remaining capacity of the battery becomes low regardless of a running state. .

[0003] In such an internal combustion engine as a power source of a hybrid vehicle, a generator provided for charging a battery is energized to function as a motor, that is, a starter. Further, in the internal combustion engine of this power source, unlike the normal startup of the internal combustion engine, the fuel injection is started after the internal combustion engine is rotated to a relatively high speed (near the idle speed) by the generator. The internal combustion engine is started without increasing the amount of fuel.
In this case, for example, as described in Japanese Patent Application Laid-Open No. 11-153075, the engine is driven by a motor to perform cranking, and the engine rotation speed becomes equal to or higher than an injection permission rotation speed set in advance for performing fuel injection. When the engine is started, the engine is started by injecting fuel and igniting, and when cold, the maximum value of the target torque of the motor output is suppressed, and the injection permitted rotation speed is reduced to reduce the power consumption of the motor. It has been known.

[0004]

By the way, in the above-mentioned system, fuel is injected when the engine rotation speed becomes equal to or higher than the injection permission rotation speed, and the engine is driven by the electric motor until starting is determined. The engine speed differs between the time when the fuel amount is calculated and the time when the fuel is injected. That is, since the fuel injection is started while the engine speed during motoring, in which the engine is not running by itself, is rising, the engine speed at the time of fuel injection is higher than that at the time of calculating the fuel amount. For this reason, the amount of fuel injected does not correspond to the actual engine speed, and a gap occurs between the two, and the amount of fuel injected is smaller than the fuel injection amount corresponding to the actual engine speed. Failure occurs. For this reason, there is a concern that a misfire or the like may occur at the time of starting, or that the air-fuel ratio is not maintained near the target air-fuel ratio and the emission increases. On the other hand, if the motor torque is reduced and the increase in the engine speed is reduced in the above-described method in order to reduce the deviation, it takes time to reach the target engine speed, and a quick start is achieved. There may be a problem that is said to be difficult.

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, the method for controlling the internal combustion engine for a hybrid vehicle according to the present invention uses an electric rotating machine in a power source including the internal combustion engine for a hybrid vehicle and an electric motor in order to reduce an increase in emissions at the time of starting. When the engine is driven and started, after the engine speed of the internal combustion engine becomes equal to or higher than a predetermined value near a preset injection permission speed, the electric rotating machine is driven so as to reduce the rate of increase of the engine speed. It is a configuration for controlling.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a power source for a hybrid vehicle that includes an internal combustion engine and an electric rotating machine, and uses the electric rotating machine as a starting motor for the internal combustion engine. The internal combustion engine is rotationally driven by energizing the engine, and after the engine rotation speed of the internal combustion engine becomes equal to or higher than a predetermined value near an injection permission rotation speed set in advance to determine a fuel injection start timing, an increase rate of the engine rotation speed A method for controlling an internal combustion engine for a hybrid vehicle, characterized in that the amount of electricity supplied to an electric rotating machine is controlled so as to reduce the engine speed, and fuel injection is started in an engine rotation speed range equal to or higher than an injection permission rotation speed.

With such a configuration, the engine speed in a state where the internal combustion engine does not rotate by itself is smaller than a predetermined value near the injection permission speed from the start of driving of the internal combustion engine by the electric rotating machine. Thus, in the region above the predetermined value, the rate of increase of the engine speed is small. Therefore, the amount of fuel to be injected is calculated when the engine speed becomes equal to or higher than a predetermined value near the injection-permitted rotation speed. Therefore, the deviation between the actual engine speed and the amount of fuel to be injected is minimized. For this reason, it is necessary to prevent the occurrence of a problem that the air-fuel ratio becomes lean when the fuel amount at the start is smaller than the required amount based on the actual engine speed at the time of injection, or that a misfire occurs. Becomes possible. In addition, the rate of increase of the engine speed is large in a region below a predetermined value.
The starting is performed quickly, and since it is small at the time of fuel injection, overshoot of the engine speed is suppressed, and the target speed at the time of starting can be reached with good responsiveness.

The electric rotating machine may include a motor for driving a vehicle and a generator.

[0010]

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

A power source 100 for a hybrid vehicle charges an engine 1 as an internal combustion engine, a running electric motor 2 as an electric rotating machine, and a battery 3 electrically connected to the electric motor 2 and starts the engine 1. And a generator 4 which is an electric rotating machine functioning as an electric motor in a case where the power is transmitted from the engine 1 and the electric motor 2 by a power split mechanism 5 having a planetary gear. I have. The power source 100 includes an electronic control unit 6
Is controlled by Engine 1 is, for example, 4
It is a cylinder fuel injection type, and may be structurally equivalent to that mounted on a normal vehicle other than a hybrid vehicle. In order to perform feedback control of the air-fuel ratio, the exhaust system 11 of the engine 1 includes an O ₂ sensor 7 serving as an exhaust sensor for measuring the oxygen concentration in the exhaust gas.
Is installed at a position upstream of the three-way catalyst provided in the pipeline leading to the muffler. A fuel injection valve 8 is provided for each cylinder near the end of the intake manifold of the intake system 12 on the cylinder head side. The electric motor 2 is, for example, of a three-phase AC type, is connected to the battery 3 via an inverter 9, and is energized when the vehicle starts or accelerates. The generator 4 is connected to a crankshaft (not shown) of the engine 1 via a power split mechanism 5, charges the battery 3 with electric power generated via an inverter 9, and supplies electric power for driving via the inverter 9 to the electric motor. 2.

The electronic control unit 6 is mainly composed of a microcomputer system including a central processing unit, a storage device, an input interface, and an output interface. The input interface of the electronic control unit 6 includes, for example, an intake pressure signal corresponding to a pressure (intake pipe pressure) in a surge tank and an engine speed NE for detecting data necessary for controlling the engine 1. rotational speed signal, cam position signal corresponding to the crank angle, a throttle opening signal corresponding to the opening degree of the throttle valve, a water temperature signal according to the coolant temperature of the engine 1, the air-fuel ratio output from the O ₂ sensor 7 as described above , A current and voltage signal for detecting the remaining capacity of the battery 3, a power signal for detecting the power generated by the generator 4, and a current and voltage when the generator 4 functions as the motor 2. Starter current and voltage signals to be detected are input. on the other hand,
From the output interface, a fuel injection signal is output to each fuel injection valve 8 and an ignition signal is output individually to the spark plug of each cylinder at a predetermined timing.

The electronic control unit 6 uses the intake pressure signal, the rotation speed signal, and the air-fuel ratio signal as main information, and calculates the basic injection time, that is, the basic injection amount, with various correction coefficients determined according to the operating state of the engine 1. The fuel injection amount is corrected and the final injection time, that is, the fuel injection valve opening time, that is, the fuel injection amount is determined. The fuel injection valve 8 is controlled based on the determined time, and the fuel injection amount corresponding to the operating state of the engine 1 is injected. Valve 8 to intake system 1
2 and a program for maintaining the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio. Also, in this engine control program, the generator 4 is energized at the time of start to drive the engine 1 to rotate, and the engine speed NE of the engine 1 is increased.
The generator 4 reduces the increase rate of the engine speed NE after the engine speed reaches a predetermined value near the injection permission speed N1 set in advance for determining the fuel injection start timing.
The amount of power supplied to the engine is controlled so that fuel injection is started in an engine rotation speed range equal to or higher than the injection permission rotation speed.

The engine control at the time of starting will be described with reference to FIG.

First, in step S1, the generator 4 is energized. As a result, the generator 4 rotates, and its driving force is transmitted to the engine 1 via the power split device 5, and the engine 1
Rotates without injecting fuel. In this case, the rotation speed of the generator 4 is, as shown in FIG.
Until, the rate of increase is set to be high. When the generator 4 rotates, the engine 1 also does not rotate by itself, but is driven to rotate. However, the fuel injection is not performed until the injection permission rotation speed N1 is reached, and the engine 1 continues the idling state in which the engine 1 does not rotate by itself. . In step S2, it is determined whether or not the engine speed NE of the idle engine 1 has reached a predetermined value VT set near the injection permission speed N1. The injection permission rotation speed N1 is set lower than the start determination rotation speed N2, as shown in FIG. The predetermined value VT is set to be lower than the injection permission rotation speed N1, for example, in the vicinity of the injection permission rotation speed N1. Thus, the predetermined value V
If T is set, the fuel injection is executed in a state where the engine rotation speed NE is smaller than the rate of increase at a rotation speed lower than the injection permission rotation speed N1 at the injection permission rotation speed N1.

In step S2, the engine speed N
If it is determined that E is equal to or greater than the predetermined value VT, step S
The process proceeds to step S3, and if not, step S2 is repeated. In step S3, the amount of fuel to be injected is calculated based on, for example, the intake pressure signal and the engine speed NE at the time when the predetermined value VT or more is reached. In step S4,
The amount of electricity supplied to the generator 4 is reduced. That is, the generator 4
When the engine speed NE is less than the predetermined value VT, the energization amount is large, and the rate of increase in the engine speed NE is high (large). Becomes smaller (small) than a region smaller than the predetermined value VT. That is, from the predetermined value VT, the start determination rotation speed N2
In the meantime, the amount of electricity to the generator 4 is reduced,
This is to lower the rate of increase. In step S5, fuel injection is executed based on the calculated fuel amount. While the fuel injection is being performed, the engine speed NE increases, but the rate of increase does not increase as in the region below the predetermined value VT because the amount of electricity supplied to the generator 4 is decreasing. In other words, it does not significantly change from the engine speed at the time of calculating the amount of fuel to be injected.

In step S6, it is determined whether or not the engine rotational speed NE has become equal to or higher than the start determination rotational speed N2. If the engine rotational speed NE is equal to or greater than the start rotational speed N2, the process proceeds to step S7. The start determination rotation speed N2 may be set to the idle engine rotation speed. Usually, in this step S6, it is difficult to determine whether or not the engine 100 has completely exploded if the determination is made based on the engine speed NE in one cycle. Therefore, the determination confirmation time T1 of several cycles, for example, 10 to 100 ms. Is set, and the determination is made during that time. In step S7,
Since the engine 100 has completely exploded, the power supply to the generator 7 is stopped. Thereby, the engine 1 rotates by itself and the start is completed.

As described above, when the engine 1 is started, the rate of increase of the injection permission rotational speed N1 for judging the engine rotational speed at which fuel can be injected is changed with a predetermined value VT near the boundary as a boundary, that is, Specifically, in the region above the predetermined value VT, the rate of increase is smaller than before, so that the fuel is injected at the engine speed NE that does not greatly change from the engine speed NE at the time when the amount of fuel to be injected is calculated. Can be. For this reason, the actual engine speed N
The deviation between E and the amount of fuel to be injected is small, so that misfire or the like can be prevented beforehand, and increase in emission due to deviation of the air-fuel ratio can be reliably prevented. Further, since the rate of increase of the engine speed NE is reduced at the time of injecting the fuel, it is possible to suppress an overshoot in which the engine speed NE increases to a start determination speed N2 or more, and to reduce idling operation. The set target idle speed can be reached in a short time.

The present invention is not limited to the embodiment described above. The amount of fuel to be injected is well-known in the art, such as the opening amount of the throttle valve of the intake system and the engine speed, the amount of intake air and the engine speed, in addition to the one based on the intake pressure and the engine speed described above. Can be widely used.

The predetermined value VT is determined by the injection permission rotational speed N1.
And the rotation speed may be set slightly higher than that. By setting the predetermined value VT in this manner, it is possible to shorten the time required to reach the injection permission rotation speed N1, and if the predetermined value VT or more, the engine rotation speed NE is set.
, The deviation between the amount of fuel to be injected and the engine speed NE is small, and the occurrence of misfire and an increase in emissions can be prevented.

In the above embodiment, the electric rotating machine including the electric motor and the generator has been described. However, the electric rotating machine may be constituted by only the electric motor. In such a configuration, when not used as a motor during traveling, the motor is rotated by the engine and functions as a generator. With such a configuration, the generator can be omitted, so that the vehicle weight can be reduced.

In addition, the configuration of each section is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0023]

As described above, according to the present invention, the engine speed in a state where the internal combustion engine does not rotate by itself is less than a predetermined value near the injection permission speed from the start of driving of the internal combustion engine by the electric rotating machine. Since the rate of increase of the engine speed is reduced in a region equal to or higher than a predetermined value as compared with the region, the amount of fuel to be injected is calculated when the engine speed becomes equal to or higher than a predetermined value in the vicinity of the injection permission speed. Even if the injection is performed with the amount, the difference between the actual engine speed and the injected fuel amount is minimized because the engine speed does not greatly change from the calculation point of the injected fuel amount. Can be suppressed. For this reason, it is necessary to prevent the occurrence of a problem that the air-fuel ratio becomes lean when the fuel amount at the start is smaller than the required amount based on the actual engine speed at the time of injection, or that a misfire occurs. Can be. In addition, since the rate of increase of the engine speed is large in a region less than a predetermined value, the engine is started quickly, and since it is small at the time of fuel injection, overshoot of the engine speed is suppressed. The rotational speed can be reached with good responsiveness.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall schematic configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the embodiment.

FIG. 3 is an operation explanatory view of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Electric motor 4 ... Generator 6 ... Electronic control device

Continued on the front page F-term (reference) 3G093 AA07 BA14 BA20 CA01 DA01 DA03 DA05 DA06 DA07 DA11 DB19 DB20 DB28 EA05 EB09 3G301 HA00 JA03 JA21 JA23 KA01 MA18 NB11 PA07Z PA11Z PD03Z PE01Z PE03Z PE08Z PG01Z 5H16 PC23 PU01 PI01 QH01 RE01 RE02 RE04 RE05 SE04 SE05 TB01 TE02 TO12 TO13 TU01 TU04 TU07 TU11

Claims (2)

[Claims] A power source for a hybrid vehicle comprising an internal combustion engine and an electric rotating machine, wherein the electric rotating machine is used as a starting motor of the internal combustion engine for starting the internal combustion engine. The engine is driven to rotate, and after the engine speed of the internal combustion engine becomes equal to or higher than a predetermined value near an injection permission speed set in advance to determine the fuel injection start timing, the electric motor is driven so as to reduce the increase rate of the engine speed. A method for controlling an internal combustion engine for a hybrid vehicle, comprising: controlling an amount of electricity supplied to a rotating machine; and starting fuel injection in an engine speed range equal to or higher than an injection permission speed. 2. The method for controlling an internal combustion engine for a hybrid vehicle according to claim 1, wherein the electric rotating machine comprises a motor for driving the vehicle and a generator.