JP2008157256A - Control device for cylinder direct injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein a variable valve train is used for an exhaust valve in order to improve startability and engine speed is raised to complete explosion rotation speed by using only torque provided by combustion, but it is difficult to provide good startability since torque provided by combustion is unstable in a very low speed region at an early stage of start in the conventional technology. <P>SOLUTION: A control device for an engine for injecting fuel directly into a cylinder is provided with: a means for discriminating a stroke of each cylinder in start of the engine; a means for discriminating piston stop positions; and a mechanism for controlling the piston stop positions, and executes control making a motor start cranking after initial explosion in start of the engine, injecting fuel to two or more cylinders during strokes in start, and executing ignition within crank angle 180° from start in two or more cylinders. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine control device, and more particularly to an engine start control device that reduces power consumption in a starter at the time of starting.

  In recent years, for the purpose of reducing engine fuel consumption and exhaust gas, the number of vehicles that perform idle stop tends to increase, and the power consumed by the starter and motor generator during startup tends to increase. Various start control methods are being developed for the purpose of reducing the power consumption of the starter and motor generator at the start.

  Further, when the engine is stopped, fuel is injected and ignited into the cylinders in the expansion stroke, and the engine is started by combustion. Furthermore, by changing the opening timing of the exhaust valve of the cylinder in the expansion stroke, the expansion ratio is increased, the work generated by the combustion is increased, and the startability is improved (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2002-4985

  In the prior art, a variable valve mechanism is used for the exhaust valve for the purpose of improving startability, and only the torque obtained by combustion is used to increase the complete explosion speed. However, in a very low rotation region at the beginning of start-up, the torque obtained by combustion is unstable, and it may be difficult to obtain good startability.

  Therefore, in the present invention, cranking is performed by a motor that engages with the crankshaft after the first explosion occurs. The torque obtained from the initial explosion can reduce the inrush current of the motor required at the initial stage of cranking, and cranking by the motor torque can ensure stable startability. Furthermore, since the starter is not used for starting, a quiet start can be realized.

In an engine control device that can inject fuel directly into a cylinder,
Means for determining the stroke of each cylinder when starting the engine;
Means for determining the piston stop position;
A motor that is directly or indirectly engaged with the starter and the crankshaft and is different from the starter;
It has a mechanism that can control the piston stop position,
When starting the engine after warming up,
A control apparatus for a direct injection type in-cylinder engine, wherein torque is generated by the motor so that the engine can be cranked during a period from the time when the engine first explosion occurs to a time when a complete explosion occurs.

More preferably, when starting the engine,
The motor starts cranking after the first explosion,

  A start control device characterized in that fuel injection is performed for two or more cylinders during a start stroke, and ignition is performed for two or more cylinders within a crank angle of 180 ° from the start.

  The torque obtained from the initial explosion can reduce the inrush current of the motor required at the initial stage of cranking, and cranking by the motor torque can ensure stable startability.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a powertrain system diagram of an in-cylinder direct injection engine showing a first embodiment of the invention. In FIG. 1, an engine 1, a transmission 2, a motor 3 that drives or brakes the engine 1, a powertrain control unit 4 that comprehensively controls the operation modes of the engine 1 and the motor 3, and an engine that controls the engine 1 A control unit 5, a motor control unit 6 for controlling the motor 3, an inverter 7 for supplying electric power to the motor 3 based on a command value of the motor control unit 6, a crank angle sensor 8, and a cylinder for discriminating a cylinder of the engine 1 A discrimination sensor 9, a starter switch (not shown), a vehicle speed sensor, a water temperature sensor, a fuel pressure sensor, a brake switch, a transmission gear position sensor, and a brake negative pressure sensor are provided. Signals from these sensors and switches are sent from the cylinder discriminating sensor 9 and an intake air temperature sensor (not shown) to the engine control unit 5, starter switch, vehicle speed sensor, water temperature sensor, fuel pressure sensor, brake switch, transmission gear position. Signals from the sensor, the brake negative pressure sensor, and the crank angle sensor 8 are output to the powertrain control unit 4 and the motor control unit 6. The motor 3 may be a motor generator (motor generator).

  The powertrain control unit 4 includes an engine automatic stop control unit 41, an engine start control unit 42, and a crankshaft acceleration calculation unit 43. The crankshaft acceleration calculation unit 43 includes an engine torque calculation unit 44. In order to perform normal engine start and idle stop according to the input signals from the brake switch, starter switch, brake negative pressure, fuel pressure, water temperature and vehicle speed sensor, the engine control unit 5 and the motor Output to the control unit 6.

  The engine control unit 5 includes a fuel injection amount / injection timing control unit 51, an ignition timing control unit 52, a stroke determination unit 53, and a starter control unit 54. The fuel injection amount, injection timing, and ignition timing are controlled by the engine speed calculated from the water temperature, fuel pressure, and crank angle. Further, when a starter operation command is output from the starter control unit 54 by the starter switch ON, the fuel injection amount, the injection timing, and the ignition timing are the water temperature and the fuel injection amount until the complete explosion is determined from the engine speed calculated from the crank angle. Controlled by fuel pressure.

  The motor control unit 6 includes a start control unit 61 that controls the motor 3 at the start time, and a stop position control unit that controls the motor 3 to be driven to stop at the desired stop position when the engine 1 is stopped. 62. An example of the stop position control unit 62 is described in “Japanese Patent Laid-Open No. 2001-304080”, and the piston can be stopped at an arbitrary position of an arbitrary cylinder. As for, other stop position control methods may be used.

  The signal output from the fuel injection amount / injection timing control unit 51 is amplified by the fuel injection valve drive circuit 10, and fuel is injected from the fuel injection valve 11 arranged so that fuel can be directly injected into the cylinder of the engine 1. Is done. The signal output from the ignition timing control unit 52 is boosted by an ignition coil (not shown) installed above the spark ignition device 12 and ignited by the spark ignition device 12 to the fuel / air mixture injected into the cylinder. The When a starter switch ON signal is output from the starter control unit 54, a starter gear (not shown) is engaged with a flywheel (not shown) and is cranked by the starter 13. The engine 1 and the motor 3 are engaged by a crankshaft and a belt 14 that restrains the motor 3, and cranking by the motor 3 can be performed. Cranking in the present invention means that the motor generates torque and drives the crankshaft.

  It is desirable that the crank angle sensor 8 described in the present embodiment is capable of measuring forward and reverse rotation angles like a resolver used for motor rotation control.

  In this embodiment, the stroke of each cylinder is determined by the stroke determination unit 53 as follows. For example, the cylinder discrimination sensor 9 is set in advance so as to output a signal in accordance with the top dead center of a specific stroke of a specific cylinder. Further, the engine control unit 5 counts and stores the signal from the crank angle sensor 8 between the output signals of the cylinder discrimination sensor, whereby the stroke and piston position of each cylinder can be discriminated. When the engine 1 is stopped, the stroke of each cylinder is stored by the stroke discriminating means of each cylinder immediately before the engine 1 is stopped, whereby the stroke of the specific cylinder and the piston stop position when the engine is stopped can be discriminated. With the above operation, it is possible to determine the expansion stroke cylinder and the piston position.

  Next, the operation of this embodiment will be described.

  FIG. 2 shows a control flow of the engine automatic stop routine. In S110, it is determined whether or not the engine 1 has been warmed up. In this embodiment, it is determined that the water temperature is 80 ° C. or higher and the warm-up is completed, and the temperature of 80 ° C. or lower is determined as the cold state. If it is determined in S110 that the warm-up is completed, it is determined in S120 whether or not the vehicle is stopped. If the vehicle is stopped, it is determined in S130 whether a predetermined time has elapsed since the vehicle stopped. When a predetermined time has elapsed since the vehicle stopped, execution of idle stop is determined in S140, and execution of idle stop is commanded in S150. In this embodiment, since the piston stop position control mechanism is provided, the piston stop position is controlled in S160. As shown in FIG. 3, the piston stop position control is performed so that the piston position of the cylinder in the expansion stroke falls within a predetermined range. In this embodiment, the stop position is controlled in the range of 80 ° to 130 ° after the top dead center in the expansion stroke, and the starter is not operated. This is because it has been experimentally confirmed that sufficient torque sufficient for starting can be obtained within the range of the piston position. Even when the vehicle is moved by the power obtained from other than the engine 1 after the engine 1 is stopped and the piston stop position of the expansion stroke cylinder is moved, the powertrain control unit 4, the engine control unit 5 and the motor control unit 6 are in the idle stop state. Since power is supplied from the battery, the piston stop position of the expansion stroke cylinder can be determined. Thereafter, before the engine start condition is satisfied, fuel may be injected into the expansion stroke cylinder detected by the stroke determination means in the arbitrary cylinder. Due to this operation, the fuel is sufficiently vaporized in the combustion chamber when the engine is started, so that a homogeneous air-fuel mixture can be formed. Thereby, startability can be improved. Other conditions may be added as conditions for performing the idle stop.

  FIG. 4 shows a control flow of the engine start routine. In S210, it is determined whether or not to start the engine based on at least the brake switch, water temperature, fuel pressure, and brake negative pressure. When the brake switch is OFF, it is determined that the driver has started the acceleration operation, and it is determined that the engine is to be started. In addition, the starter is started when the water temperature is lower than the predetermined water temperature and fuel pressure. This is because when the water temperature is lower than the predetermined value, fuel vaporization is hindered and exhaust gas deteriorates. Furthermore, when the fuel pressure is lower than a predetermined value, the particle size of the fuel spray becomes large, so that fuel vaporization is hindered and exhaust gas deteriorates. When the brake negative pressure falls below a predetermined value, the engine is started by a starter or other means to ensure the brake negative pressure.

  In S220, it is determined whether or not to operate the starter based on the piston position of the expansion stroke cylinder at least when starting. When entering the piston stop position range shown in FIG. 3, the starter is deactivated. If the remaining battery level is smaller than a predetermined value, the starter may be deactivated. Further, in addition to the piston position, the starter may be activated or deactivated depending on the water temperature and the fuel pressure. The starter is deactivated when the water temperature is higher than the specified temperature. This is because when the water temperature is lower than a predetermined value, fuel vaporization is hindered. In addition, when the fuel pressure is lower than a predetermined value, the particle size of the fuel spray becomes large, and fuel vaporization is hindered. Further, whether to start the starter may be determined based on any of the map information from the GPS, the steering angle of the steering wheel, the blinker, and the time from brake release to accelerator pedal depression. This is a safety function for avoiding a starting failure when starting from an idle stop when turning right at, for example, an intersection. When it is determined that the driver is going to turn right based on the map information from the GPS, the steering angle, the blinker, and the time from the release of the brake to the depression of the accelerator pedal, measures such as always operating the starter may be taken.

  If the starter non-operation is selected in S220, the amount of air charged in the expansion stroke cylinder and the compression stroke cylinder in S230 depending on the piston stop positions, the water temperature, and the intake air temperature of the expansion stroke cylinder and the compression stroke cylinder when starting. To decide. The amount of air charged in the expansion stroke cylinder is written in advance as a map of each of the water temperature, the intake air temperature, and the piston position at the time of starting. 5, 6 and 7 show the relationship between the water temperature, the intake air temperature, and the piston stop position with respect to the amount of air charged in the expansion stroke cylinder and the compression stroke cylinder. In addition, the amount of air charged in the intake stroke cylinder may be calculated from the intake air temperature and the water temperature at the start of the first explosion with the in-cylinder pressure as atmospheric pressure.

  Next, in S240, based on the air amount determined in S230, the fuel injection amount to each cylinder is determined so as to achieve the target air-fuel ratio. Thereby, it becomes possible to select an optimal fuel injection amount according to the engine state at the time of starting, and it is possible to avoid exhaust deterioration due to the adhesion of the fuel spray piston and the like while improving the startability.

  In S240, the fuel injection amount is determined, and the divided injection ratio of the combustion injection amount determined in S250 is determined. Since the spray penetration can be shortened by performing the divided injection, it is possible to avoid adhesion of the fuel spray to the combustion chamber wall surface. In S250, the divided injection ratio of the combustion injection amount is determined based on at least one of the fuel injection amount at the time of starting and the piston position of the expansion stroke cylinder and the compression stroke cylinder. Furthermore, in addition to the piston position and the fuel injection amount, the division ratio of the fuel injection amount may be determined by the water temperature and the fuel pressure. In the present embodiment, a map of the division injection ratio of the combustion injection amount is written as a map of each of the water temperature at the start, the fuel injection amount, the fuel pressure, and the piston stop position of the expansion stroke cylinder and the compression stroke cylinder. By dividing the fuel injection, the air utilization rate of the fuel spray can be improved, and vaporization can be promoted.

  Next, in S260, a time interval from fuel injection to ignition (hereinafter referred to as vaporization time) is determined based on at least the fuel injection amount at the start and the divided injection ratio of the fuel injection amount. Further, the vaporization time may be determined by the water temperature and the fuel pressure in addition to the fuel injection amount and the divided injection ratio of the fuel injection amount. In this embodiment, the vaporization time map is written as each map of the water temperature, fuel pressure, fuel injection amount, and split injection ratio at start-up. The optimum value of the vaporization time depends on the vaporization characteristics of the fuel spray, the in-cylinder flow induced by the fuel spray and the air-fuel ratio around the spark plug. Therefore, the water temperature, the fuel pressure, the fuel injection amount, and the split injection are highly sensitive to them. It can be determined by percentage. This makes it possible to select an optimal vaporization time depending on the engine state at the time of starting and improve the starting torque.

  As described above, the amount of air charged in the expansion stroke cylinder, the compression stroke cylinder and the intake stroke cylinder, the fuel injection amount to the expansion stroke cylinder, and the vaporization time are determined, and the expansion stroke cylinder and the compression stroke cylinder are determined in S270 and S280. An ignition command is issued to the fuel injection and expansion stroke cylinders. Next, in S290, it is determined whether or not the initial explosion occurring in the expansion stroke cylinder has been successfully performed. In this embodiment, if the acceleration of the predetermined crankshaft is not reached within a certain time after the ignition command is output, it is determined that the initial explosion has ended abnormally and the starter is operated. Since time elapses until the predetermined acceleration is reached, a dead time until a torque command is given to the motor can be provided. Thereafter, the motor start control routine is started in S300. When the starter operation is selected in S220, the starter is operated by the output from the starter control unit 54 in S400, and the engine 1 is started.

  In this embodiment, the split injection ratio of the fuel is determined in S250, but the split injection may not be performed. In S290, the sound pressure sensor and the in-cylinder pressure sensor may be used to determine whether the initial explosion has been successfully performed.

  FIG. 8 shows a control flow of a motor control routine at the time of engine start performed in the start control unit 61 in the motor control unit 6 of FIG. After the motor torque command is output in S310, in S320, the difference between the crankshaft acceleration calculated from the sum of the shaft torque obtained by combustion and the motor torque and the target crankshaft acceleration is calculated, and the difference value is calculated. In S330 and S340, the fuel injection amount and the ignition timing are determined so as to be zero or more. The fuel injection amount determined in S330 is determined as described above with reference to FIG. 4 for the cylinders from the engine start command output to the third ignition. When the number of ignitions is the fourth or later, the fuel injection amount and the ignition timing are determined in S330 and S340 so that the difference value calculated in S320 is zero or more. In S350 and S360, fuel injection and ignition commands are output. In S370, the difference between the engine speed and the target engine speed is calculated. If the difference value is zero or more, it is determined that the explosion is complete, and in S375, the motor torque is set to zero or less, and this control flow ends. .

In this embodiment, the motor torque command is output after the first explosion occurs, but the motor torque command may be output simultaneously with the first explosion. In this case, the motor start control routine (S300) in FIG. 4 is started simultaneously with the ignition of the expansion stroke cylinder, and the motor torque command (S310) in FIG. 8 is output. The control routine after S310 is the same as in FIG.

The powertrain system figure of 1st Embodiment of this invention. The figure which shows the control flow of the engine automatic stop routine of 1st Embodiment of this invention. The figure which shows the starter non-operation area | region by the piston position of 1st Embodiment of this invention. The figure which shows the control flow of the engine starting routine of 1st Embodiment of this invention. The figure which shows the relationship of the charge air quantity in the expansion stroke cylinder and compression stroke cylinder with respect to the water temperature of 1st Embodiment of this invention. The figure which shows the relationship of the charge air quantity in the expansion stroke cylinder and the compression stroke cylinder with respect to the intake air temperature of 1st Embodiment of this invention. The figure which shows the relationship of the charge air quantity in the expansion stroke cylinder and the compression stroke cylinder with respect to the piston stop position of 1st Embodiment of this invention. The figure which shows the control flow of the motor control routine at the time of engine starting of 1st Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Transmission, 3 ... Motor, 4 ... Powertrain control unit, 5 ... Engine control unit, 6 ... Motor control unit, 7 ... Inverter, 8 ... Crank angle sensor, 9 ... Cylinder discrimination sensor, 10 ... Fuel injection valve drive circuit, 11 ... Fuel injection valve, 12 ... Spark ignition device, 13 ... Starter, 14 ... Belt.

Claims (13)

In an engine control device that can inject fuel directly into a cylinder,
Means for determining the stroke of each cylinder when starting the engine;
Means for determining the piston stop position;
A motor that is directly or indirectly engaged with the starter and the crankshaft and is different from the starter;
It has a mechanism that can control the piston stop position,
When starting the engine after warming up,
A control device for a direct injection type in-cylinder engine, wherein torque is generated by the motor so that the engine can be cranked after the first engine explosion until the complete explosion. In the in-cylinder direct injection engine control device according to claim 1, when starting the engine,
A control apparatus for an in-cylinder direct injection engine characterized in that fuel injection is performed for two or more cylinders during a stroke when starting, and ignition is performed for two or more cylinders within a crank angle of 180 ° from the start. In the in-cylinder direct injection engine control device according to claim 1, when starting the engine,
A control apparatus for a direct injection type engine, wherein fuel is injected into at least an expansion stroke cylinder and a compression stroke cylinder detected by means capable of discriminating the stroke of each cylinder, and the expansion stroke cylinder is ignited. . In the in-cylinder direct injection engine control device according to claim 1, when starting the engine,
A control apparatus for an in-cylinder direct injection type engine, wherein an engine starting method is switched according to a starting environment parameter when starting the engine. In the control apparatus for a direct injection type engine according to claim 4,
The in-cylinder direct injection type engine control device, wherein the starting environment parameter is at least one of water temperature, fuel pressure, piston stop position, and remaining battery level. In the direct injection type engine control device according to claim 1,
When starting the engine,
A control device for a direct injection type in-cylinder engine, wherein the fuel injection amount is controlled by at least a starting environment parameter when starting the engine. In the control unit for a direct injection type engine according to claim 6,
An in-cylinder direct injection type engine control device characterized in that a starting environment parameter when starting an engine is at least one of a water temperature, a fuel pressure, and a piston position of a cylinder in an expansion stroke. In the direct injection type engine control device according to claim 1,
When starting the engine,
A control apparatus for a direct injection type in-cylinder engine, characterized in that a time from fuel injection to ignition is controlled at least by a starting environment parameter when starting the engine. In the control unit for a direct injection type engine according to claim 8,
A control apparatus for an in-cylinder direct injection engine, characterized in that a starting environment parameter when starting the engine is at least one of a water temperature, a fuel pressure, and a piston position of a cylinder in an expansion stroke. In the direct injection type engine control device according to claim 1,
When starting the engine,
A control device for a direct injection type in-cylinder engine, characterized in that the time from the ignition timing at which an initial explosion occurs until the motor starts cranking is controlled by at least a starting environment parameter when starting the engine. In the control apparatus for a direct injection type engine according to claim 10,
The in-cylinder direct injection type characterized in that the starting environment parameter when starting the engine is at least one of water temperature, fuel pressure, battery voltage, piston position of the cylinder in the expansion stroke, and crankshaft acceleration after the initial explosion Engine control device. In the direct injection type engine control device according to claim 1,
In-cylinder direct injection engine characterized in that fuel is injected into an expansion stroke cylinder detected by at least the stroke determination means of each cylinder from the stop of the engine to the start of the engine to vaporize the fuel. Control device. In the direct injection type engine control device according to claim 1,
A control apparatus for a direct injection type in-cylinder engine, wherein torque generated on the crankshaft by a motor different from the starter and the starter engaged with the crankshaft is equal to or less than torque generated on the crankshaft by the starter. .

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