JPH08277768A - Method of controlling start of engine - Google Patents

Abstract

PURPOSE: To prevent an error in judgment of start caused by the fuel left within an intake system combusting within a cylinder, by judging whether to make idle cracking or not without injecting fuel, based on the temperature of an engine, at start of the engine, and inhibiting the ignition together with the injection of fuel. CONSTITUTION: In case that an ignition switch 52 is turned on and that ECU 40 judges it to be control at start, this judges whether idle cracking is necessary or not from the output of a cooling water temperature sensor 24. Here, in case that it is judged that it is the time of idle cracking besides being at the time of cooling of an engine, the setting time of a timer to clock the execution time of the idle cracking, based on the temperature of an engine, is set. Then, with the fuel injection stopped, and besides with the ignition stopped, a starter motor 55 is driven to make the engine cracked idly for the setting time of a timer. Hereby, the erroneous judgment of the start of an engine can be removed by surely preventing the combustion caused by the remaining fuel of an intake system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine start control method for improving startability by blanking an engine without injecting fuel.

[0002]

2. Description of the Related Art Generally, when the temperature is low, the vaporized state of the fuel deteriorates and the startability of the engine deteriorates. In particular, in the case of an engine using heavy gasoline, the heavy component of gasoline is difficult to vaporize, and therefore it is necessary to improve startability at low temperatures.

In order to deal with the deterioration of the engine startability at such a low temperature, for example, Japanese Patent Laid-Open No. 4-23166.
As disclosed in Japanese Patent Publication No. 7, when the engine is cranked at the time of engine start, the fuel injection is temporarily stopped to execute an empty crank without fuel to reduce the friction of each part and increase the temperature in the cylinder. There is known a technique for improving startability.

[0004]

However, conventionally,
Since empty cranking considers only fuel injection stop and does not particularly consider ignition, the fuel remaining in the intake system, such as the fuel adhering to the wall of the intake port when the engine was stopped the last time, remains in the cylinder during empty cranking. It may enter the fuel cell and ignite this fuel to cause combustion. For this reason, the driver may turn off the starter switch and stop cranking, with the illusion that the engine has started.

Further, in an engine having a fuel heating means such as a heater in the intake system, the fuel adhering to the heater portion is vaporized by the warming up of the heater when the engine is started, and this vaporized fuel is subjected to empty cranking. The cylinder may be ignited, causing the driver to make a mistake in determining the initial or complete explosion and failing to start.

The present invention has been made in view of the above circumstances, and prevents an erroneous start determination due to combustion of the fuel remaining in the intake system in the cylinder when the engine is started and the engine is blanked without being injected. However, it is an object of the present invention to provide a starting control method for an engine, which can reduce the friction of each part due to empty cranking and reliably increase the temperature in the cylinder to improve the startability.

[0007]

According to the present invention, when the engine is started, it is determined whether or not to blank the engine without injecting fuel based on the engine temperature, and it is determined that the engine is to be blanked. At this time, the execution time of the empty cranking is set based on the engine temperature, and during the execution time of the empty cranking, the ignition is prohibited together with the fuel injection.

[0008]

According to the present invention, when it is judged that the engine temperature requires the air cranking at the time of starting, the fuel injection and the ignition are prohibited for the time set based on the engine temperature to execute the air cranking.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, FIG. 1 is a flowchart of a start-up control routine, FIG. 2 is a flowchart of a starter switch ON → OFF interrupt routine, FIG. 3 is a schematic configuration diagram of an engine system, and FIG. 4 is an electronic control system. 2 is a circuit configuration diagram of FIG.

In FIG. 3, reference numeral 1 is an engine,
In this embodiment, a horizontally opposed four cylinder engine is shown. An intake manifold 3 is connected to each intake port 2a formed in a cylinder head 2 of the engine 1,
A throttle chamber 5 is connected to the intake manifold 3 via an air chamber 4. Further, an air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6, and a hot wire type or hot film type intake air amount sensor 8 is provided immediately downstream of the air cleaner 7. .

A throttle valve 5a is provided in the throttle chamber 5, and the throttle valve 5a is provided.
Further, a throttle sensor 9 having a built-in throttle opening sensor for detecting the throttle opening and an idle switch which is turned on when the throttle valve is fully closed is provided in series. Further, an idle speed control valve (ISCV) 11 is provided in a bypass passage 10 that connects the upstream side and the downstream side of the throttle valve 5a.

An injector 12 is disposed immediately upstream of each intake port 2a of each cylinder of the intake manifold 3, and a spark plug 13a is provided for each cylinder of the cylinder head 2 whose tip is exposed to the combustion chamber. Is installed. An ignition coil 13b is connected to the ignition plug 13a, and an igniter 14 is connected to the ignition coil 13b.

The injector 12 is communicated with a fuel tank 17 via a fuel supply passage 16, and an in-tank type fuel pump 18 is provided in the fuel tank 17. The fuel from the fuel pump 18 is pressure-fed to the injector 12 and the pressure regulator 21 via the fuel filter 19 provided in the fuel supply passage 16.
From the pressure regulator 21 to the fuel tank 1
The surplus fuel is returned to 7, and the fuel pressure to the injector 12 is adjusted to a predetermined pressure.

A knock sensor 22 is attached to the cylinder block 1a of the engine 1, and a cooling water temperature sensor 24 is exposed to a cooling water passage 23 that connects the left and right banks of the cylinder block 1a. Further, the O2 sensor 2 is provided at the collecting portion of the exhaust manifold 25 communicating with the exhaust port 2b of the cylinder head 2.
6 is coming. Reference numeral 27 is a catalytic converter.

A crank rotor 28 is rotatably mounted on the crank shaft 1b supported by the cylinder block 1a, and a magnet for detecting a protrusion (or slit) corresponding to a predetermined crank angle on the outer circumference of the crank rotor 28. A crank angle sensor 29 including a sensor (electromagnetic pickup or the like) or an optical sensor is provided oppositely. Further, a cam rotor 30 is connected to the camshaft 1c of the cylinder head 2, and a cam angle sensor 31 for discriminating a cylinder, which is also composed of a magnetic sensor or an optical sensor, is provided opposite to the cam rotor 30.

On the other hand, in FIG. 4, reference numeral 40 is an electronic control unit (ECU), which includes a CPU 41, a ROM 42, and an RA.
The M43, the backup RAM 44, and the I / O interface 45 are mainly configured by a microcomputer connected to each other via a bus line 46, and a constant voltage circuit 47 that supplies a stabilizing voltage to each unit, the I / O described above. A drive circuit 48 that drives actuators by a signal from an output port of the interface 45, an A / D that converts analog signals from sensors to digital signals
Peripheral circuits such as the converter 49 are incorporated.

The constant voltage circuit 47 includes an ECU relay 50.
Is connected to the battery 51 via the relay contact of
A relay coil of the CU relay 50 is connected to the battery 51 via an ignition switch 52. Further, a starter motor 55 is connected to the battery 51 from a starter switch 53 via a relay contact of a starter motor relay 54, and the fuel pump relay 5
The fuel pump 18 is connected via the relay contact 6 of FIG.

The constant voltage circuit 47 is connected to the battery 51 via a relay contact of the ECU relay 50, and is also directly connected to the battery 51.
When the ignition switch 52 is turned on and the relay contact of the ECU relay 50 is closed, power is supplied from the constant voltage circuit 47 to each part, while the ignition switch 52 is constantly turned on or off. Power for backup is supplied to the backup RAM 44.

A knock sensor 22, a crank angle sensor 29, a cam angle sensor 31, a starter switch 53, etc. are connected to the input port of the I / O interface 45, and an intake air amount sensor 8 and a throttle sensor 9 are also provided. , The cooling water temperature sensor 24, the O 2 sensor 26, etc. are connected via the A / D converter 49, and the voltage V from the battery 51 is connected to the A / D converter 49.
B is input and monitored.

On the other hand, the igniter 14 is connected to the output port of the I / O interface 45, and the ISCV 11, the injector 12, the relay coil of the starter motor relay 54, and the fuel pump are connected via the drive circuit 48. A relay coil or the like of the relay 56 is connected.

The ROM 42 stores fixed data such as an engine control program and various maps, and the RAM 43 stores data after processing output signals of the sensors and switches, and CPU4 above
The data processed in 1 is stored. The backup RAM 44 has various maps, control data,
Trouble data or the like corresponding to the failed portion detected by the self-diagnosis function is stored, and the data is retained even when the ignition switch 52 is OFF.

When the engine is started, the CPU 41 follows the control program stored in the ROM 42.
By temporarily stopping fuel injection and performing empty cranking, it is judged based on the engine temperature whether or not it is necessary to raise the temperature in the cylinder to ensure startability, and empty cranking is necessary. If it is determined that the fuel injection is prohibited, the ignition is prohibited, and the air cranking is performed. Then, various controls such as normal air-fuel ratio control, ignition timing control, and idle speed control are performed.

The control at the time of starting by the ECU 40 will be described below with reference to the flowcharts of FIGS. 1 and 2.

In the flow chart shown in FIG. 1, the ignition switch 52 is turned on and the power of the ECU 40 is turned on to be initialized (fuel pump relay 56 → ON, starter motor relay 54 → OFF, timer reset, various flags cleared, etc.). After that, when the starter switch 53 is turned on, a start-up control routine that is executed is shown.
In step S101, the fuel injection prohibition flag F1 is set (F1 ← 1), and in step S102, the ignition prohibition flag F2 is set (F2 ← 1).

The fuel injection flag F1 and the ignition prohibition flag F2 are referred to in the programs of the fuel injection control and the ignition control, respectively. When F1 = 1, the fuel injection is stopped, and F1 =
When 0, fuel injection is performed, when F2 = 1, ignition is stopped, and when F2 = 0, ignition is performed. Since well-known techniques can be applied to the fuel injection control and the ignition timing control, description thereof will be omitted.

Next, in step S103, the cooling water temperature TW is detected by the cooling water temperature sensor 24 as a parameter representing the engine temperature, and in step S104, it is determined whether or not the air cranking is necessary based on the cooling water temperature TW. to decide. As the engine temperature, a fuel temperature, a lubricating oil temperature or the like may be adopted instead of the cooling water temperature TW.

That is, when the engine is at room temperature or higher, the lubrication condition of each part is relatively good, and even if the fuel is injected together with the cranking, the fuel is smoothly vaporized and a relatively good mixture is obtained. Although reliable ignition and combustion can be expected in the cylinder, at low temperatures, the friction of each part is large and the temperature inside the cylinder is low, so when fuel is injected during cranking, the fuel is not vaporized and spark plug fogging etc. It may occur and it may be difficult to start. For this reason,
Immediately after the starter switch 53 is turned on, it is determined based on the engine temperature whether it is an empty crank without fuel injection or a normal crank with fuel injection.

When it is determined that the cranking is normal in step S104, the steps from step S104 to
Proceed to S105 to clear the fuel injection prohibition flag F1 (F1 ←
At the same time, the ignition prohibition flag F2 is cleared in step S106 (F2 ← 0), and in step S107, the state of the starter switch 53 is detected and it is confirmed whether or not it is turned off.

In step S107, the starter switch 5
When OFF of 3 is detected, the routine exits, and when the starter switch 53 is still ON, the process proceeds to step S108 to set the I / O port output value G for the starter motor relay 54 (G ← 1 ) Turn on the starter motor relay 54 to exit the routine. As a result, the starter motor 55 is driven to crank the engine, fuel is injected at the time of starting, and the air-fuel mixture is introduced into the cylinder and ignited. Then, after the initial explosion and the complete explosion, the control shifts to normal control.

In this case, when the starter switch 53 is turned from ON to OFF, the starter switch shown in FIG. 2 is turned ON.
→ The OFF interrupt routine is started, and in step S201,
When the I / O port output value G for the starter motor relay 54 is cleared (G ← 0), the starter motor relay 5
4 is turned off.

On the other hand, if it is determined in step S104 that there is empty cranking, the process proceeds from step S104 to step S109, and a set value TC of a timer for measuring the execution time of empty cranking based on the engine temperature (cooling water temperature TW). To set. This set value TC is the entire empty cranking time period in which the temperature in the cylinder is increased, fuel is injected, and even if the air-fuel mixture is introduced into the cylinder, it is possible to reliably ignite and obtain a stable combustion state. Is a value obtained in consideration of the relationship with the starting time, and is obtained, for example, by storing an optimum value obtained in an experiment or the like using the cooling water temperature TW as a parameter in a map and referring to this map.

After the execution time of this empty cranking is set, the routine proceeds to step S110, where the starter switch 53 is
Check if is turned off, and starter switch 53
Is ON, the I / O port output value G for the starter motor relay 54 is set (G ← 1) in step S111, the starter motor relay 54 is turned ON, and the timer is counted in step S112. The number TM is incremented (TM ← TM + 1).

As a result, the starter motor 55 is driven, and the engine is blanked while the fuel injection is stopped. Since the ignition is also stopped at the same time during this blanking, the engine is stopped after the last stop. When the fuel remaining in the intake system, for example, the fuel adhering to the wall surface of the intake port 2a enters the cylinder, combustion does not occur, and the driver feels that the engine has started and the starter switch 53 is turned off.
Therefore, it is possible to prevent the start-up failure in advance without stopping the cranking.

Then, the above steps S112 to S1
In step 13, it is checked whether the count value TM of the timer has reached the set value TC. If TM <TC, the process returns to step S110 to check whether the starter switch 53 is turned off. If it is turned off during the process, the process branches from step S110 to step S114 to clear the count value TM of the timer (TM ← 0) and exit the routine, and the starter switch ON → OFF interrupt routine of FIG. 54 is turned off. When the starter switch 53 remains ON, empty cranking is continued.

After that, when the blank count is continued and the count value TM of the timer reaches the set value TC (TM ≧ TC),
The process proceeds from step S113 to step S115, the count value TM is cleared (TM ← 0), the fuel injection prohibition flag F1 is cleared (F1 ← 0) at step S116, and fuel injection is permitted. The prohibition flag F2 is cleared (F2 ← 0) to permit ignition and the routine is exited.

That is, in the present invention, the fuel injection and the ignition are permitted after the empty cranking is executed for the set time according to the engine temperature, and the combustion of the residual fuel in the intake system at the time of the empty cranking is performed. While preventing it, improve the lubrication condition of each part to reduce friction, raise the temperature in the cylinder, and ensure that the air-fuel mixture injected after empty cranking does not cause spark plug fogging in the cylinder. Can be ignited. And, not only can the combustion after the initial explosion be made into a stable combustion state and the rise of rotation after the initial explosion can be accelerated, but when the normal control is performed after the complete explosion after the initial explosion, It is possible to suppress the occurrence and shorten the entire starting time.

The present invention is effective even when the engine 1 is provided with a fuel heating means such as a heater in the intake system, and the fuel adhering to the heater portion evaporates due to the warm-up of the heater when the engine is started. It is possible to prevent the start failure from occurring by eliminating the mistake of determining the initial explosion or the complete explosion due to the vaporized fuel being ignited in the cylinder during the empty cranking.

[0038]

As described above, according to the present invention, when the engine is started, it is determined whether or not the engine is to be blanked without injecting fuel, based on the engine temperature, and the engine is blanked. When it is determined that the empty cranking execution time is set based on the engine temperature,
During this empty cranking execution time, ignition is prohibited along with fuel injection, so it is possible to prevent mistakes in the starting decision due to combustion of fuel remaining in the intake system in the cylinder, to reduce friction in each part due to empty cranking, It is possible to obtain an excellent effect such that the temperature rise can be surely made and the startability can be improved.

[Brief description of drawings]

FIG. 1 is a flowchart of a startup control routine.

FIG. 2 is a flowchart of a starter switch ON → OFF interrupt routine.

FIG. 3 is a schematic configuration diagram of an engine system.

FIG. 4 is a circuit configuration diagram of an electronic control system.

[Explanation of symbols]

 1 ... Engine TW ... Cooling water temperature (engine temperature) TC ... Set value (set time) F1 ... Fuel injection prohibition flag F2 ... Ignition prohibition flag

Claims (1)

[Claims] 1. When starting the engine, it is determined whether or not to blank the engine without injecting fuel based on the engine temperature, and when it is determined to blank the engine, the empty temperature is determined based on the engine temperature. A starting control method for an engine, wherein a cranking execution time is set, and during the empty cranking execution time, ignition is prohibited together with fuel injection.