JPH04191464A - Method for controlling ignition time of engine for ffv - Google Patents

Abstract

PURPOSE:To avoid generation of pre-ignition by setting the ignition time correction quantity on the basis of a setting difference between the temperature inside of a combustion chamber, which is estimated on the basis of the operation condition of an engine, and a pre-ignition limit temperature, which is set on the basis of an alcohol concentration of the fuel. CONSTITUTION:During the operation of an engine; in a ECU 41, the standard ignition time is set by a standard ignition time map on the basis of the intake air weight Ga per one stroke, which is obtained on the basis of the output from an intake air quantity sensor 28, and an alcohol concentration M, which is obtained on the basis of the output of an alcohol concentration sensor 26, as parameter. Next, plug temperature is estimated by a map on the basis of the output of an intake air temperature sensor 39 and the intake pipe pressure sensor 40 and the engine speed N as parameter. Furthermore, pre-ignition limit temperature is set by a pre-ignition limit temperature map on the basis of the alcohol concentration M as parameter. A temperature difference between the plug temperature and the pre-ignition limit temperature is computed, and the pre-ignition correction spark-delay quantity is set by a map on the basis of that temperature difference as parameter, and the standard ignition time is corrected to compute the ignition time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ignition timing control method for an FFV engine that avoids pre-ignition by estimating the combustion chamber temperature.

[Prior art] In recent years, F engines that can be operated on gasoline fuel, alcohol fuel, or a mixed fuel of gasoline and alcohol have been developed.
F V (Flexible Fuel Vehicle
e) engine has been developed, and the alcohol concentration (content rate) in the fuel supplied to this FFV engine is:
0% depending on user circumstances when refueling (gasoline only)
and 100% (gasoline 0%).

Generally, alcohol fuel tends to cause pre-ignition at a relatively low temperature compared to gasoline fuel, so it is necessary to take measures such as increasing the heat value of the spark plug or retarding the ignition timing.

However, if a spark plug with a heat value matched to alcohol fuel is installed to prevent this pre-ignition, problems such as smoldering and deterioration of driving performance will occur when gasoline fuel is used, and the ignition timing will be When retarded, the optimum ignition timing (
The advantage of alcohol fuel, which is that it is easy to advance up to MBT), cannot be utilized.

To deal with this, for example, Japanese Patent Application Laid-Open No. 1-285662 discloses that the combustion pressure in the combustion chamber is detected and the ignition timing is advanced based on this combustion pressure, thereby adjusting the ignition timing in the pre-ignition generation region. A technology for improving engine efficiency by bringing the MBT closer to the vicinity has been disclosed, and
Publication No. 285663 discloses that by detecting the temperature in the combustion chamber and advancing the ignition timing based on the temperature in the combustion chamber,
Similarly, the ignition timing is set to MB in the pre-ignition generation area.
A technique has been disclosed for improving engine efficiency by bringing the temperature close to T.

[Problems to be Solved by the Invention] However, as described above, conventionally, when trying to avoid the occurrence of pre-ignition by controlling the ignition timing, it is difficult to detect the combustion pressure in the combustion chamber or the temperature in the combustion chamber. Requires hardware. Therefore, the hardware of the control system must be changed, which inevitably increases the system cost.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides an FFV engine that can perform ignition timing control without changing the hardware configuration of the control system and avoid the occurrence of pre-ignition. The purpose is to provide an ignition timing control method.

[Means for Solving the Problems] In order to achieve the above object, the ignition timing control method for an FFV engine according to the present invention includes a procedure for setting a basic ignition timing according to the operating state of the engine, and a method for controlling the ignition timing based on the operating state of the engine. A procedure for estimating the combustion chamber temperature based on the alcohol concentration of the fuel, a procedure for setting the pre-ignition limit temperature based on the alcohol concentration of the fuel, and a procedure for setting the ignition timing based on the difference between the estimated combustion chamber temperature and the pre-ignition limit temperature. The present invention is characterized by comprising a procedure for setting a correction amount, and a procedure for correcting the basic ignition timing using the ignition timing correction amount.

[Function] In the FFV engine ignition timing control method of the present invention, the pre-ignition limit temperature is determined based on the difference between the combustion chamber temperature estimated based on the operating state of the engine and the pre-ignition limit temperature set based on the alcohol concentration of the fuel. An ignition timing correction V is set, and the basic ignition timing is corrected by this ignition timing correction amount.

Therefore, ignition timing control to avoid pre-ignition can be executed without requiring hardware for detecting the combustion chamber temperature.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail based on the drawings.

The drawings show one embodiment of the present invention, and FIG. 1 is a flowchart showing the ignition timing control procedure, FIG. 2 is a schematic diagram of the engine control system, FIG. 3 is a front view of the crank rotor and crank angle sensor, and FIG. The figure is a front view of the cam rotor and cam angle sensor.
Fig. 5 is a conceptual diagram of the basic ignition timing map, Fig. 6 is a conceptual diagram of the estimated plug temperature map, Fig. 7 is a conceptual diagram of the pre-ignition limit temperature map, and Fig. 8 is a conceptual diagram of the pre-ignition correction retard amount. Explanatory drawings, Fig. 9 is a conceptual diagram of the pre-ignition correction retard violet map, Fig. 10 is a time chart showing the ignition timing, Fig. 11 is a flowchart showing the boost pressure control procedure, and Fig. 12 is a diagram showing the relationship between alcohol concentration. An explanatory diagram of the maximum boost pressure, and FIG. 13 is a conceptual diagram of a duty ratio table.

(Configuration of Engine Control System) In Fig. 2, the reference numeral 1 in the figure is a horizontally opposed four-cylinder engine in the FFV Effengin, and an intake boat 2a and an exhaust boat 2b are formed in the cylinder head 2 of this engine 1. has been done.

An intake manifold 3 is communicated with the intake boat 2a, a throttle chamber 5 is communicated upstream of the intake manifold 3 via an air chamber 4, and an air cleaner 7 is attached upstream of the throttle chamber 5 via an intake pipe 6. It is being

On the other hand, an exhaust manifold 8 is attached to the exhaust boat 2b.
An exhaust pipe 9 is communicated through the exhaust pipe 9, and a catalytic converter 10 is interposed in the exhaust pipe 9.

Also, a throttle valve 1 is installed in the throttle chamber 5.
1 is provided, an intercooler 12 is interposed in the intake pipe 6 immediately upstream of the throttle champara, and further,
A resonator chamber 13 is interposed in the intake pipe 6 on the downstream side of the air cleaner 7.

Reference numeral 14 designates a turbocharger as an example of a supercharger, and a turbine wheel 14a of the turbocharger 14 is housed in a turbine housing 14b interposed in the exhaust pipe 9.
A compressor wheel 14d connected to the compressor housing 1 via a turbine shaft 14c is interposed on the downstream side of the resonator chamber 13 of the intake pipe 6.
It is stored in 4e.

Further, a wastegate valve 15 is interposed at the inlet of the turbine housing 14b, and a lever 16 connected to the wastegate valve 15 is connected to a diaphragm 17a of a diaphragm actuator 17 via a rod 18.

Further, the pressure chamber 17b of the diaphragm actuator 17 is connected to the compressor housing 1 of the intake pipe 6.
4e through a pressure passage 19, and a duty solenoid valve 2 is connected in the middle of this pressure passage 19.
1 is interposed, and a valve body 21a of this duty solenoid valve 21 is disposed opposite to a discharge port of a pressure reducing passage 20 communicating with the resonator chamber 13.

The duty solenoid valve 21 is controlled by a duty signal supplied to a solenoid coil 21b from a control device (ECU) 41, which will be described later, and regulates the pressure supplied to the pressure chamber 17b of the diaphragm actuator 17. Internal pressure and a diaphragm spring 1 that constantly biases the diaphragm 17a of the diaphragm actuator 17 in the backward direction and biases the wastegate valve 15 in the closing direction via the rod 18 and lever 16.
7c, the maximum boost pressure is controlled by controlling the opening area of the inlet of the turbine housing 14b by the waste gate valve 15.

In this embodiment, as the duty ratio of the duty signal decreases, the valve body 21 of the duty solenoid valve 21 decreases.
The opening time per unit time of the decompression passage 20 due to a increases, and the amount of positive pressure leaked downstream of the compressor wheel 14d supplied to the pressure chamber 17b of the diaphragm actuator 17 increases, so that the turbine housing is relatively The supercharging pressure at which the waste gate valve 15 of 14b starts to open increases, and the maximum supercharging pressure increases.

Further, an intake air temperature sensor 39 and an intake pipe pressure sensor 40 are attached to the air chamber 4, and an injector 22 is placed directly upstream of the intake boat 2a of each cylinder of the intake manifold 3.

Each injector 22 is communicated with a fuel tank 23 via a fuel passage 24, and a fuel pump 25 and an alcohol concentration sensor 26 are interposed in the fuel passage 24 from the fuel tank 23 side.

Further, each of the injectors 22 is communicated with a pressure regulator 27, return fuel is returned to the fuel tank 23, and the fuel pressure is regulated to a predetermined pressure.

Further, the fuel tank 23 stores fuel having a predetermined alcohol concentration M of alcohol and gasoline, and this fuel is 100% gasoline when the alcohol concentration M is 0, and when the alcohol concentration M is 1.0. time gasoline 0
% (alcohol 100%), that is, the alcohol concentration M of the fuel varies between 0 and 1°0 depending on the user's refueling situation.

Further, the alcohol concentration sensor 26 includes, for example, a pair of electrodes provided in the fuel passage 24, and detects the alcohol concentration M by detecting a current change based on a change in electrical conductivity of the fuel. be done.

Note that the alcohol concentration sensor 26 is not limited to the type that detects changes in electrical conductivity as described above;
In addition, a resistance detection type, a capacitance type, and an optical type may be used.

Further, an intake air amount sensor 28 (a hot wire air flow meter in the figure) is installed in the intake pipe 6 immediately downstream of the air cleaner 7, and a throttle opening sensor 29a and a throttle opening sensor 29a are connected to the throttle valve 11. An idle switch 29b that detects whether the valve 11 is fully closed is connected thereto. Furthermore, the intake manifold 3
A cooling water temperature sensor 30 faces a cooling water passage (not shown) forming a riser formed in the exhaust pipe 9.
A sensor 31 is facing.

Further, a knock sensor 38 is attached to the cylinder block la of the engine 1, and a crank rotor 32 is attached to the crankshaft 1b supported by the cylinder block 1a. An angle sensor 33 is provided oppositely.

Furthermore, a cam angle sensor 35 consisting of an electromagnetic pickup or the like is provided opposite to a cam rotor 34 connected to the camshaft 1c of the engine 1.

As shown in FIG. 3, the crank rotor 32 has protrusions 32a, 32b, and 32c formed on its outer periphery.
#1. #2 and #3. #, 4) before compression top dead center (BTDC
) θ1. θ2. The position of θ3 (for example, θ1 =97@,
θ2=65°, θ3−10°).

That is, the protrusion 32a indicates the reference crank angle when setting the ignition timing, and the rotation period f of the engine is calculated from the passage time between the protrusions 32a and 32b.

Further, the protrusion 32c serves as a reference crank angle indicating fixed ignition timing.

Further, on the outer periphery of the cam rotor 34, as shown in FIG. 4, there are protrusions 34a and 34b for cylinder discrimination.

34c is formed, and for example, the protrusion 34a is at the position θ4 after compression top dead center (ATDC) of #3° #4 (for example, θ4=2
The protrusion 34b is composed of three protrusions, and the first protrusion is formed at the ATDC θ5 position of the #1 cylinder (for example, θ5=5°). Furthermore, the protrusion 34c is formed of two protrusions, and the first protrusion is the ATD of the #2 cylinder.
It is formed at a position Cθ6 (for example, θ6=20°).

Incidentally, the crank rotor 32 or the cam rotor 3
A slit may be provided on the outer periphery of the sensor 4 instead of a protrusion.Furthermore, the crank angle sensor 33 and the cam angle sensor 35 are not limited to magnetic sensors such as an electromagnetic pickup.
It could also be a light sensor.

(Circuit configuration of control device) On the other hand, reference numeral 41 is a control device (ECU) consisting of a microcomputer, etc., and CPtJ42, ROM43
, RAM 44, and I10 interface 45 are connected to each other via a path line 46.

The input port of the I10 interface 45 includes each of the sensors 26, 28.29a, 30, 31.33.3.
5.38.39.40 and idle switch 29b
The spark plug 36 attached to the cylinder head 2 is connected to the output boat of the 110 interface 45 via an igniter 37, and the injector 22 and fuel pump are connected via the drive circuit 47. 25 and the solenoid coil 21b of the duty solenoid valve 21 are connected.

On the other hand, the ROM 43 stores a control program and fixed data, and the fixed data includes a basic ignition timing map MPθ8AS[, an estimated plug temperature map M
P TPUL, pre-ignition limit temperature map M
There are P TLIM and a pre-ignition correction retard amount map M P RTD. In addition, the above RAM4
4 contains data obtained by processing the output signals from each of the above sensors,
Further, data processed by the CPU 42 is stored.

The CPU 42 calculates the pulse width for driving the injector 22, the ignition timing to be output to the igniter 37, etc. based on the various data stored in the RAM 44 according to the control program stored in the ROM 43,
The corresponding drive signal is sent to the injector 2 at a predetermined timing.
2. Calculates the duty ratio of the signal that is output to the igniter 37 and drives the duty solenoid valve 21, and controls the maximum boost pressure by the turbocharger 14.

(Ignition timing control procedure) Next, the ignition timing control procedure will be explained according to the flowchart of FIG.

The program shown in FIG. 1 is a routine that is executed at predetermined intervals. First, in step 5101, a crank pulse from the crank angle sensor 33 and a cam pulse from the cam angle sensor 35 are read, and in step 5102, cylinder discrimination is performed. Let's do it. Next, the process advances to step 5103, where the read crank pulse is θ1. It is determined which crank angle between θ2° and θ3 this corresponds to.

That is, as shown in FIG. 10, the cam angle sensor 3
5 to θ5 (protrusion 34b), it can be determined that the crank pulse subsequently output from the crank angle sensor 33 is a signal indicating the crank angle of the #3 cylinder, and after the cam pulse of θ5, θ4 (
When the cam pulse of the protrusion 34a) is output, it can be determined that the crank pulse subsequently output from the crank angle sensor 33 indicates the crank angle of the #2 cylinder.

Similarly, the crank pulse after the cam pulse of θ6 (protrusion 34C) is output indicates the crank angle of the #4 cylinder, and if the cam pulse of θ4 (protrusion 34a) is output after the cam pulse of θ6 described above It can be determined that the subsequent crank pulse indicates the #1 cylinder number and rank angle.

Furthermore, after the cam pulse is output from the cam angle sensor 35, the crank pulse output from the crank angle sensor 33 indicates a reference crank angle (θ1) for setting the ignition timing of the corresponding cylinder. Can be distinguished.

Next, the process proceeds from step 3103 to step 5104, where θ1 (for example, BTDC97@) and the next θ2 (
For example, the elapsed time t between crank pulses of BTDC 65°) is measured, and the period f is determined based on the crank angle θ1-02 (for example, θ1-θ2=32°) corresponding to these crank pulses and the elapsed time t. Calculate f=dt
/d(θ1-θ2)), and in step 5105, the engine rotation speed N is calculated by 1 based on this period f (N=60/
f).

Next, the process advances to step 8106, where the intake air amount sensor 28
The amount of intake air per unit time (mass flow rate) obtained from is divided by the number of combustion cycles to calculate the intake air weight per stroke G
a is calculated, and in step 5107, the alcohol concentration M of the fuel is calculated from the output signal of the alcohol concentration sensor 26, and the process proceeds to step 8108.

In step 8108, the basic ignition timing map MPθBASE is referred to with interpolation calculation using the engine speed N, intake air weight Ga per stroke, and alcohol concentration M as parameters, and the basic ignition timing (angle) θBASE is set.

As shown in FIG. 5, each address of the basic ignition timing map MPθBASE is set in advance by experiments, etc., using engine speed N, intake air weight per stroke Ga, and alcohol concentration M as parameters. The optimum basic ignition timing θBASE (crank angle based on θ2) according to the condition is stored, and if the intake air weight Ga per stroke and the engine speed N are the same, the higher the alcohol concentration M, the greater the advance. A small value of the basic ignition timing θBASE is stored to obtain the angle quantity.

Thereafter, in step 5109, the intake air temperature Ta from the intake air temperature sensor 39 and the intake pipe pressure p from the intake pipe pressure sensor 40 are determined.
s and proceeds to step 5110 to read the intake air temperature T.
The estimated plug temperature map MP-- TPUL is referred to with interpolation calculation using a, the intake pipe pressure ps, and the engine speed N as parameters, and the plug temperature TPU is estimated, and the process proceeds to step 5111.

As shown in FIG. 6, the estimated plug temperature map M P
In each address of TPUL, a plug temperature TPυ [obtained in advance through experiments etc. using intake air temperature Ta, intake pipe pressure ps, and engine speed N as parameters is stored. The combustion chamber temperature of the engine 1, represented by the plug temperature TPυ, is estimated based on the operating state indicated by the engine speed N and the like.

Then, when the process proceeds from step 5110 to step 5111, the pre-ignition limit temperature map M P TLIM is referred to with interpolation calculation using the alcohol concentration M calculated in step 5107 as a parameter, and the pre-ignition limit temperature TLIH is set. .

That is, it has been experimentally confirmed that the temperature at which pre-ignition occurs decreases as the alcohol concentration M increases, and as shown in FIG. The limit temperature at which pre-ignition occurs (plug temperature or combustion chamber temperature) T11M is stored at each address of the pre-ignition limit temperature map M P TLIH.

Next, the process proceeds from step 5111 to step 5112, where the plug temperature TP estimated in step 5110 is determined.
Calculate the temperature difference TDEC between UL and the pre-ignition limit temperature TLIH set in step 5111 above.
DEC=TPUL-TLIM), step 7'51
Step 5114: Using this temperature difference T DEC as a parameter, refer to the pre-ignition correction retard amount map M P RTD with interpolation calculation, and set the pre-ignition correction retard amount (ignition timing correction amount) RTD. Proceed to.

That is, as shown in FIG. 8, the estimated plug temperature T
The larger the temperature difference T DEC between PUL (estimated combustion chamber temperature) and the pre-ignition limit temperature TLIM is, the larger the pre-ignition retard correction amount RTD is. RT
By storing the pre-ignition retard correction amount RTD with the temperature difference T DEC as a parameter in each address of Pre-ignition can be avoided by lowering the temperature.

When the process proceeds from step 5113 to step 5114, a knock control value (angle) θNK is set based on the signal from the knock sensor 38, and then the process proceeds to step 5115, where the basic ignition timing θBASE set in step 8108 is set. , the preignition correction retard amount RTD set in step 5113 above, and
The ignition timing θIG is calculated by adding the knock control value θH set in step 5114 above (θIG←
θBASE+ RT D+θNK).

Next, proceeding from step 5115 to step $116,
The ignition time ADV is set by multiplying the ignition timing θIG calculated in the above step 5115 by the cycle f calculated in the above step 5104. ADV-(/IGx f ), and the process proceeds to step 5117, where a timer is set for this ignition time ADV. The process then proceeds to step 8118.

In step 8118, as shown in FIG. 10, a timer is driven using the θ2 crank pulse as a trigger, and the ADV
After the elapsed time, Stella 7S119 outputs an ignition signal to the corresponding cylinder and exits the routine.

In other words, pre-ignition can be avoided by estimating the combustion chamber temperature without changing the hardware, such as by adopting a thermometer plug embedded with a thermocouple, etc., to measure the combustion chamber temperature. Damage to the engine 1 can be prevented.

On the other hand, the boost pressure of the engine 1 is controlled to the maximum boost pressure according to the alcohol concentration M of the fuel, and the maximum boost pressure control procedure will be described below with reference to the flowchart shown in FIG. 11.

First, in step 5201, the alcohol concentration M is calculated, and in step 5202, the duty ratio table TB[)tl is calculated using this alcohol concentration M as a parameter.
TY with interpolation calculation, sets the duty ratio DUTY of the signal that drives the duty solenoid valve 21, proceeds to step 5203, outputs the duty signal to the duty solenoid valve 21, and executes the next routine. The energization time of the solenoid coil 21b is maintained at the duty ratio DUTY until the solenoid coil 21b is turned on.

i.e. alcohol (methanol, ethanol, etc.)
The octane number of is higher than that of gasoline, and the mixed octane number when alcohol is mixed with gasoline increases as the alcohol concentration M increases.
As shown in FIG. 2, as long as pre-ignition does not occur, it is possible to increase the maximum boost pressure of the engine 1 according to the alcohol concentration M of the fuel.

Therefore, the duty ratio DuTY of the drive signal of the duty solenoid valve 21 that provides the maximum boost pressure is determined in advance through experiments, and as shown in FIG. The higher the duty ratio D U becomes, the smaller the value becomes.
By storing TY, the maximum supercharging pressure of the engine 1 can be increased in accordance with the alcohol concentration M, and the output performance of the engine 1 can be fully brought out.

(Operation of supercharging pressure control system) Next, the operation of the supercharging pressure control system for varying the maximum supercharging pressure will be described.

When the engine 1 operates, the exhaust gas pressure (exhaust pressure) flowing through the exhaust pipe 9 rotates the turbine wheel 14a of the turbocharger 14, and the compressor wheel 14d connected to the turbine wheel 14a via the turbine shaft 14c rotates. and supercharges the intake air.

The exhaust pressure is low when the engine load is low and the engine speed is low, so the supercharging pressure at the compressor wheel 14d is also low. On the other hand, if the engine speed and load increase,
The supercharging pressure also gradually increases.

Here, according to the maximum boost pressure control procedure described above, the higher the alcohol concentration M of the fuel, the higher the duty ratio DUTY of the drive signal to the duty solenoid valve 21.
becomes smaller, the energization time of the solenoid coil 21b is shortened, and the opening time per unit time of the pressure reducing passage 20 by the valve body 21a of the duty solenoid valve 21 is increased. The turbocharger acting on the pressure chamber 17b of
The amount of leakage of supercharging pressure downstream of the compressor wheel 14d of the compressor wheel 14 increases.

Then, as the amount of leakage of the supercharging pressure acting on the pressure chamber 17b of the diaphragm actuator 17 increases, the supercharging pressure applied to the pressure chamber 17b of the diaphragm actuator 17 decreases, and the diaphragm 17a of the diaphragm actuator 17 decreases. resists the biasing force of the diaphragm spring 17c, and the supercharging pressure generated by the turbocharger 14 increases relatively until the waste gate valve 15 is opened via the rod 18 and lever 16, and the maximum supercharging pressure is raised.

Then, the supercharging pressure by the turbocharger 14 increases,
The supercharging pressure acting on the pressure chamber 17b of the diaphragm actuator 17, which is regulated by the duty solenoid valve 21, increases according to the duty signal of the duty ratio D uTY, and the supercharging pressure by the turbocharger 14 reaches the maximum supercharging pressure. When the diaphragm actuator 1 reaches
Diaphragm-spring 1' in which the regulated supercharging pressure acting on the pressure chamber 17b of No. 7 urges the diaphragm 17a.
7c, the rod 18 connected to the diaphragm 17a is projected, and the wastegate valve 15 is rotated clockwise in FIG. 2 via the lever 16 connected to the rod 18.

As a result, the waste gate valve 15 is gradually opened, and the opening area of the inlet of the turbine housing 14b that accommodates the turbine wheel 14a is gradually expanded. A part of the exhaust gas passing through this inlet bypasses the turbine wheel 14a, and the reaction of the turbine wheel 14a is reduced by that amount, causing the boost pressure by the turbocharger 14 to exceed the maximum boost pressure. This prevents this from occurring and maintains the maximum boost pressure.

Although this embodiment shows an example of an ignition timing control method using time control, it goes without saying that it is also applicable to an ignition timing control method using angle control, and the supercharger may be a supercharger or the like.

[Effects of the Invention] As explained above, according to the present invention, ignition timing control can be performed to avoid occurrence of pre-ignition without changing the hardware configuration of the control system.
The full potential of the engine can be brought out without increasing system costs.

As a result, excellent effects such as a significant improvement in engine output performance are achieved.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a flowchart showing the ignition timing control procedure, FIG. 2 is a schematic diagram of the engine control system, FIG. 3 is a front view of the crank rotor and crank angle sensor, and FIG. The figure is a front view of the cam rotor and cam angle sensor.
Fig. 5 is a conceptual diagram of the basic ignition timing map, Fig. 6 is a conceptual diagram of the estimated plug temperature map, Fig. 7 is a conceptual diagram of the pre-ignition limit temperature map, and Fig. 8 is a conceptual diagram of the pre-ignition correction retard amount. Explanatory drawings, Fig. 9 is a conceptual diagram of the pre-ignition correction retard amount map, Fig. 10 is a time chart showing the ignition timing, Fig. 11 is a flowchart showing the boost pressure control procedure, and Fig. 12 is a diagram showing the relationship between alcohol concentration. An explanatory diagram of the maximum boost pressure, and FIG. 13 is a conceptual diagram of a duty ratio table. θBASE...Basic ignition timing T PUL...Plug temperature (combustion chamber temperature) M...
Alcohol concentration TLIM... Pre-ignition limit temperature RTD...
・Pre-ignition correction retardation amount (ignition timing correction amount) Fig. 5 Fig. 6 (i￥b turbidity 1ζ (゛1 earth 0 Pre-ignition correction retardation amount RTD -←-T
D[Ct=TPU1. -TIIM+ Figure 13, DIITV Alcohol 1% M -1sa/

Claims (1)

[Claims] A procedure for setting the basic ignition timing according to the operating state of the engine, a procedure for estimating the combustion chamber temperature based on the operating state of the engine, and a procedure for setting the pre-ignition limit temperature based on the alcohol concentration of the fuel. A procedure for setting an ignition timing correction amount based on the estimated difference between the combustion chamber temperature and the pre-ignition limit temperature, and a procedure for correcting the basic ignition timing using the ignition timing correction amount. A method for controlling ignition timing of an FFV engine, characterized in that: