GB2278157A

GB2278157A - Control at starting of a mixed fuel engine

Info

Publication number: GB2278157A
Application number: GB9413312A
Authority: GB
Inventors: Yoichi Saito
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1991-07-19
Filing date: 1992-07-17
Publication date: 1994-11-23
Anticipated expiration: 2012-07-17
Also published as: GB2278155A; GB2278156A; GB9413312D0; GB2278155B; GB9413311D0; GB2278157B; GB2278156B; GB9413310D0

Description

2278157 DESCRIPTION "A CONTROL METHOD AND AN APPARATUS FOR A FLEXIBLE FUEL

VEHICLE" The present invention relates to a starting control method and a starting assist apparatus for an engine for an FFV which enhance starting characteristics.

Recently, for such reasons as the worse situation of fuel and a demand for the purification of emission, systems capable of simultaneously using alcohol as substitute fuel in addition to the conventional fuel of gasoline are coming into practical use as disclosed in, for example, the official gazette of Japanese Patent Application Laid-open No. 69768/1989.

A vehicle such as automobile (FFV; Flexible Fuel Vehicle) equipped with the system can be driven, not only with the gasoline, but also with mixed fuel consisting of the alcohol and the gasoline or with only the alcohol. The alcohol concentration (content) of the fuel for use in the FFV changes between 0% (gasoline only) and 100% (alcohol only) in dependency on user conditions in the case oil fuel supply.

In general, the alcohol fuel has such properties as being more difficult to vaporize at low temperatures, exhibiting a larger amount of latent heat of vaDorization and exhibiting a higher inflammation point, when compared with the gasoline fuel. Accordingly, when the alcohol concentration changes, the starting characteristics vary largely in accordance with the temperature condition. in particular, when the alcohol concentration is hiah, the problem of ing characteristics arises in a degradation in the start cold engine state.

There have hitherto been known techniaues wherein, in order to cope with the problem, the vaporization of the fuel is promoted for enhancing the starting characteristics by a heater, a heating element or the like serving as a starting assist device. By way of example, the official gazette of Japanese Patent is Application Laid-open No. 5266511982 discloses a technique wherein a heating device for heating an intake passage is controlled in accordance with the output of an alcohol concentration sensor, and wherein the heat generating quantity cf& the heating device is increased when the alcohol concentration is a reference value or above. In addition, the official gazette of Japanese Patent Application Laid-open No. 35179/1980 discloses technique wherein a distributing value is provided for controlling the distributive amounts of a mixture to flow into main and subsidiary intake passages, while a heat generating element is disposed in the subsidiary intake passage so as to vaporize fuel droplets gathering in this passage at starting the cold engine.

At starting the engine, however, the temperature of the combustion chamber of the engine needs to be raised by the heating means, besides the promotion of the vaporization of the fuel. The prior art therefore necessitates a fuel quantity increasing correction after starting, or the like. The fuel quantity increase after starting produces a deterioration in emission control and an increase in fuel cost.

Further, at starting the engine, the initial knocking which is unpleasant is sometimes caused by the residual fuel in a cylinder or an intake manifold. It is has sometimes hammered the engine from smoothly shifting from. the starting into the ordinary operation state thereof.

Besides, at the low temperatures, the alcohol is liable to seDarate from the gasoline in a fuel tank or in piping. It is accordingly understood that the starting mode cont-rol based on the outmut of the alcohol concentration sensor will become inaccurate on account of a nonuniform alcohol concentration distribution. - Moreover, in promoting the vaporization of the fuel by the heating means such as heater, the vaporization depends upon the mounted position of the heating means, and the fuel is not always vaporized entirely. It is accordingly understood that the air fuel ratio of the mixture will become inappropriate due to the adhesion of the residual fuel to the inner wall of the intake port of the engine and the subsequent evaporation of the adhering fuel, resulting in inferior starting of the engine and an increase of the fuel cost.

ro The present invention has been made in view of the above circumstances, and has for its object to provide a starting control method and a starting assist apparatus for an engine of an FFV according to which, at starting the engine, a precise control is realized to,-ure at an appropriate air-fuel ratio and to hold a mixt I effectively promote the vaporization of fuel at low t ---heencine can be started smoothly L-emperatures, wherebv t and quickly. invention, a In the first asDect o. he mresent control method for a flexible fuel vehicle having an engine mounted on L-he -flexible fuel vehicle, a fuel injector provided in an intake manifold for injecting fuel into a cv!-4nder via a cv-",-'nder head, a throttle valve in a tillro--le chamber Connected with the intake fold, a temmerature sensor mounted on the engine for mani.

-emperature and for producing a detecting a coolant. temperature signal, and a concentration sensor interposed between a fuel tank and the injector for sensing a concentration of an alcohol in the fuel and for generating a concentration signal, comprises the steps of: setting an engine startable temperature in dependency on said concentration signal; judging whether it is possible to start said engine by comparing said 1-0 engine startable temperature with said coolant temperature; heating a heater for a predetermined time before injecting said fuel into said cylinder when said coolant temperature is lower than said engine startable temperature; comparing said coolant temperature with a heating stop temiDeratu-e when said coolant temperature is higher than said engine startable temnerature; injecting said fuel when said coolant temperature is lower than said heating stop temperature without heating said heater; activating said heater untill said coolant temperature reaches a predetermined temmerature; and deactivating said heater when said coolant temmerature reaches said heating stop temperature after repeating said comparing stem so as to e-f-E--cz-4ve-lv start said engine as soon as possible.

Besides, in the second aspect, a control method for -6a flexible fuel vehicle having an engine mounted on said flexible fuel vehicle, a fuel in-jector provided 4n an intake manifold for injecting fuel 4nito a cylinder via a cylinder head, a throttle valve in a throttle chamber connected with said intake manifold, a starter motor mounted on said engine for starting said engine with electric power, a fuel pump for supplying said fuel from a fuel tank to said fuel injector, a temperature sensor mounted on said engine for detecting a coolant Iro temperature and for producing a temperature signal, and a concentration sensor interposed between said fuel tank and said injector - for sensing a concentration of an alcohol in said -fuel and -or generating a concentration signal, comDrises the stems cf:

prohibiting actuation of said starter mnotor f or a mredetermined time when starting said encine; returninc said fuel from a mressure reaulator c said fuel tank, and homocenizing a concentration of said alcohol and a casoline in said fuel so as to contain an optimum.

control of said engine.

Further, in the third. aspect, a c=trol method for a flexible fuel having an enaine mounted on said flexibble fuell 4 4_ vehicle, a fuel -.-.-,eczor provided an intake man-J--Ec--d for n-j-cz-J.-.a fue-i a cv14nder via a cylinder head, a throttle valve in a throttle 1 chamber connected with said intake manifold, a starter motor mounted on said engine for starting said engine with electric power, a fuel pump for supplying said fuel from a fuel tank to said fuel injector, a temperature sensor mounted on said engine for detecting a coolant temperature and for producing a temperature signal, and a concentration sensor interposed between said fuel tank and said injector for sensing a concentration of an alcohol in said fuel and for generating a concentration LO signal, comprises the steps of:

setting an engine startable temperature in dependency on the concentration; judging whether it is possible to start the engine by comparing the engine startable temperature with the coolant temperature; and cranking the engine for a predetermined time without injecting the fuel when starting the engine is judged impossible,so as to enable an optimum starting of the engine.

Still -urther, in the fourth aspect, a control method JEor a flexible fuel vehicle having an engine mounted on the 'Llexible fuel vehicle, a fuel injector provided in an i.-.4L--ake manifold for injecting fuel into a cylinder via a cylinder head, a throttle valve in a throttle chamber connected with the intake manifold, a 25 starter motor mounted on the engine for starting said -8engine with electric power, a fuel pump for supplying the fuel from a fuel tank to the fuel injector, a temperature sensor mounted on the engine for detecting a coolant temperature and for producing a temperature signal, and a concentration sensor interposed between the fuel tank and the injector for sensing a concentration of an alcohol in the fuel and for generating a concentration signal, comprises the steps of:

l-0 setting a duration time for fixing ignition timing in dependency on the coolant temperature, and fixing an ignition timing at a predetermined ignition timing while the fixed ignition time elapses after starting the engine so as to effedtively start the engine as soon as is possible.

The fifth aspect of the present invention consists in that the activating step in the first aspect further comprises:

fixing an adhesive ratio of the fuel on an intake port of the cylinder head and an evaporating ratio of the fuel in the intake port between a present intake stroke and a next intake stroke per cylinder at predetermined values when activating the heater so as to attain an optimum control of the starting of the engine.

Yet further, in the sixth aspect of performance, a control method for a -0-1exible fuel vehicle having an engine mounted on the flexible fuel vehicle, a fuel injector provided in an intake manifold for injecting fuel into a cylinder via a cylinder head, a throttle valve in a throttle chamber connected with the intake manifold, a temperature sensor mounted on the engine for detecting a coolant temperature and for producing a temperature signal, and a concentration sensor interposed between a fuel tank and the injector for sensing a concentration of an alcohol in the fuel and for generating a concentration signal, comprises the steps of:

setting an engine startable temperature in dependency on the concentration; judging whether it is possible to start the engine by comparing the engine startable temperature with the coolant temperature; prohibiting a fuel injection and an ignition when it is decided to be impossible to start the engine; activating a heater; cranking the engine; and allowing the fuel injection and the ignition after a predetermined time so as to perform an effective and optimum engine starting.

In the seventh aspect c,' the present invention, a control system for a flexible fuel vehicle having an engine mounted on the flexible fuel vehicle, a fuel injector provided in an intake manifold for injecting fuel into a c- inder head, a throttle Iinder via a cv. valve in a throttle chamber connected with the intake manifold, a terrmera-.u-t-e sensor mounted on the engine for detectina a coolant temDerature and for producing a temperature signal, and a concentration sensor interposed between a fuel tank and the -4njector for sensing a concentration of an alcohol in the fuel and for generating a concentration signal, comprises:

a heater included in a heater unit and interposed between the intake manifold and the cv-1-4nder head for effectively heating the fuel so as to attain an optimum starting of the engine.

With the cont cl method for an FFV according to the first aspect of t-he present invention, in the first is place, the encine st-art-able temDerature is set on the basis of the alcohol concentration cl the fuel, and whether or not -he enaine is startable is Judged by comparing -he encrine startable temmerature with the coolant temverature. Herein, when the enzine has been judged -.c be unstartable, the heating means for ion of - is activated for promoting the vapo-rizat hhe fuel - the predetermined time period before the fuel injection.

r-i contrast, when the engine has been decided tc, be startable, the coolant temperature is compared with the heating stop temperature. When the coolant temperature is lower than the heatina stoi) temiDerature as the result -hout of the comparison, the fuel is injected wit previously activating the heating means, and the heating means is thereafter activated until the coolant temperature reaches the predetermined value. On the other hand, when the engine temperature is not lower than the heating stop temperature, the heating means is held deactivated.

With the control method for an FFV according to the second aspect, at starting the engine, the actuation of the starter motor is prohibited for the predetermined time period, while the fuel pump is driven to feed the fuel in the fuel tank to the pressure regulator. Then, the fuel fed under pressure returns to the fuel tank via is the pressure regulator, whereby the fuel is circulated and stirred. In consequence, the alcohol concentration distribution of the fuel is homogenized.

With the control method for an FFV according to the third aspect, the engine startable temperature is set on the basis of the alcohol concentration of the fuel, and whether or not the engine is startable is judged by comparing the engine startable temperature with the coolant temperature. Herein, when the engine has been judged to be unstartable, it is cranked for the predetermined time period with the fuel injection A z)rohibited.

With the control method for an FFV according to the 4ne, the ign4t.

fourth aspect, at start'na the enq- - Jon timing is fixed to the predetermined timing and is held while the fixed ignition time period se 4 n dependency on the coolant temDerature elavses.

With the control method for an FFV according to the fifth aspect, when the heating means for promoting the vaporization of the fuel has been activated as starting 10- the engine, the adhesive ratio of the injected fuel adhering on the inner wall of the intake port and the evaporating ratio of the fuel in the intake po-rt between -roke per L-he intake stroke and the next intake st -o the predetermined values.

cylinder are fixed t - With the control method for an FFV according to the sixth aspect, the encine startable temperature is set on the basis of the alcohol concentration of the fuel, and whether or not the engine is startable is Judged by comparing the engine startable temperature with the coolant temverat=e. Herein, when the encine has been judged to be unstartable, the engine is cranked under the conditions that the fuel injection and the ignition are prohibited and that the heating means for promoting the vaporization of the fuel is activar-ed. Thereafter, when the present period has elapsed, the fuel injection -13and the ignition are allowed, whereby the injected fuel with its vaporization promoted by the heating means is fed to the engine and is ignited.

The control system for an FFV according to the seventh aspect comprises the heater included in the heater unit and interposed between the cylinder head and the intake manifold for each cylinder, whereby the fuel injected from the injector is vaporized.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:

Figs. 1 - 4 are flow charts showing control steps in the mode of starting an engine in accordance with the present invention; Fig.5 is a schematic view of an engine control system in accordance with the present invention; Fig.6 is a detailed view of a heater mounting portion;.

Fig.7 is a sectional view taken along line A-A in Fig.6; Fig-8 is an explanatory diagram showing a fuel injection state in the vicinity of an intake port; Fig.9 is a front view of a crank rotor as well as a crank angle sensor; Fig.10 is a front view of a cam rotor as well as a cam angle sensor; Fig.11 is a circuit arrangement diagram of a control unit; Fig. 12 is an explanatory diagram showing a startable range and an unstartable range; Fig. 13 is a conceptual diagram of a coolant temperature map for judging if an engine is startable; Fig. 14 is a diagram of the characteristics of a heater; Fig. 15 is a conceptual diagram of an electric power map for judging if heating is to be finished; Fig. 16 is a conceptual diagram of a fixed ignition 10 time map; Fig. 17 is a flow chart showing steps for controlling a starter motor; Fig. 18 is a flow chart showing steps for discriminating cylinder No. and for calculating engine R.PM; Figs. 19 - 21 are flow charts showing steps for setting a fuel injection amount and an ignition timing; Fig. 22 is a conceptual diagram of a map for a desired air-fuel ratio; Fig. 23 is a conceptual diagram of a map for the adhesive ratio of fuel adhering on a wall; Fig. 24 is a conceptual diagram of a map for the evaporating ratio of the fuel; Fig. 25 is a conceptual diagram of a map for a basic ignition timing; -isFig. 26 is a conceptual diagram of a map for an injection starting crank angle; Fig. 27 is a flow chart showing ignition control steps; Fig. 28 is a flow chart showing fuel injection control steps; and Fig. 29 is a time chart of fuel injection and ignition operations.

Now, embodiments of the present invention will be described with reference to the drawings. [Construction of Engine Control System] Referring to Fig. 5, numeral 1 designates an engine for an FFV (a horizontal opposed type four-cylinder engine in the illustration), the cylinder head 2 of which is formed with intake ports 2a and exhaust ports 2b. An intake manifold 3 is held in communication with the intake iDorts 2a, a throttle chamber 5 is provided upstream of the intake manifold 3 through an air chamber therewith, and an air cleaner 7 is 4 in communication t mounted upstream of the throttle chamber 5 through an 4ntake vipe 6.

On the other hand, an exhaust pipe 9 is held in communication with the exhaust ports 2b through an exhaust manifold 8, and a catalytic converter 10 is -'. 6- disi:)osed in the exhaust pipe 9. In addition, valve Sa is provided in the throttle chamber 5, a throttle and an intercooler 11. is disposed in the intake pipe 6 directly upstream of the throttle chamber 5. Further, a resonator chamber 12 is provided in the intake pipe 6 downstream of the air cleaner 7.

Besides, a bypass 13 is provided for bringing the resonazor chamber 12 and the air chamber 4 into communication, thereby to bypass the upper stream side 10- of it-he throttle valve 5a from the lower stream side thereof, and an idle speed control valve (ISCV) 14 which is an actuator for the operation of controlling an engine speed is mounted in the bypass 13. Further, a check valve 14a which is oDened in response to a negative intake pressure is mounted directly downstream of the ISCV 14.

The 1SCV 14 is, for example, a rotary valve which is driven by a duty solenoid. in accordance with a valve opening degree which is determined by the duty ratio of a drive signal ffor the ISCV 14, the quantity of air in the bypass 13 is regulated to control the engine speed at engine idling. By the way, in this embodiment, '.he ozenina dearee c - I- &-he ISCV 14 is enlarged with the duty ratio.

Numeral 15 indicates a turbocharaer which is an -117- example of a supercharger. The turbine wheel 15a of the turbocharger 15 is housed in a turbine housing 15b which is formed midway of the exhaust pipe 9, while the compressor wheel 15d thereof connected to the above turbine wheel 15a through a turbine shaft 15c is housed in a compressor housing 15e which is formed in the - the resonator chamber 12.

intake pipe 6 downstream of Besides, a wastegate valve 16 is provided in the inlet port of the turbine housing 15b, and a lever 17 connected to the wastegate valve 16 is connected to the diaphragm 18a of a diaphragm actuator 18 through a rod 19. Further, the pressure chamber 18b of the diaphragm actuator 18 is held in communication with the intake pipe 6 downstream of the turbocharger 15, through a pressure passage 20, a duty solenoid valve 21 as an example of an actuator for controlling a supercharging pressure is mounted midway of the pressure passage 20, and the valve body 21a of the duty solenoid valve 21 is disposed in opposition to the drain port of a pressure reducing passage 22 communicating with the resonator chamber 12.

The duty solenoid valve 21 is controlled by a duty signal applied from an electronic control unit (ECU) 41 to be described later, and it, regulates a pressure to be supplied into the pressure chamber 18b of the diaphragm is M_ actuator 18. in this regard, a diaphragm spring 18c normally urges the diaphragm 18a of the diaphragm actuator 18 in the direction of retreating the rod 19 so as to close the wastegate valve 16 through this rod 19 as well as the lever 17. Thus the wastegate valve 16 is operated by the balance between the inner pressure of the pressure chamber 18b and the force of the diaphragm spring 18c. In turn, the opening area of the inlet port of the turbine housing 15b is controlled by the wastegate valve 16, thereby to control the maxim= supercharging pressure.

Here in this embodiment, as the duty ratio of the duty signal is increased more, the pressure reducing passage 22 is opened longer per unit time by the valve body 21a of the duty solenoid valve 21, and the leaking quantity of a positive pressure downstream of the compressor wheel 15d to be supplied into the pressure chamber 18b of the diaphragm actuator 18 is enlarged more. Consequently, the supercharging pressure is relatively raised to heighten the maxim= supercharging pressure based on the turbocharger 15.

Besides, an intake-port heater unit 23 as a starting assist device is provided in each of the intake ports 2a of respective cylinders co mmu nicating with the intake manifold 3, and an injector 24 is confronted to a 1 position opposing to the corresponding intake-port heater unit 23 directly upstream of the intake port 2a.

Further, a spark plug 40 whose fore end is exposed to a combustion chamber is mounted in each of the cvlinders in the cylinder head 2.

As shown in Fig. 6, the intake-port heater unit 23 includes a heating element 23a facing the interior of an intake passage. A mounting portion configured of an insulator 23b and a flange 23c is held between the intake manifold 3 and the cylinder head 2, and is fixed to the cylinder head 2 with bolts or the like, not shown. The heating element 23a has a built-in heater 23d made of a PTC ippsitive temperature coefficient) pill on a side corresponding to the fuel injecting direction of the injector 24.

Besides, as shown in Fig. 7, the heating element 23a is formed to be cylindrical. It is supported by the flange 23c through st-ays 23e so as to face the interior of the intake passage, and is substantially thermally insulated from the intake manifold 3 and the cylinder head 2 by the insulator 23b.

Herein, when the heater 23d is energized through a terminal 23f, fuel injected from the injector 24 is vaporized by the heating element 23a, and it is distributed to two intake valves 2c as shown in Fig. 8.

In addition, the injectors 24 are held in communication with a fuel tank 26 through a fuel feed passage 25. The fuel tank 26 stores therein fuel consisting of gasoline only, fuel consisting of alcohol only, or mixed fuel consisting of gasoline and alcohol at a predetermined alcohol concentration, that is, fuel whose alcohol concentration changes between 0% and 100% in dependency on user conditions in the case of fuel supply.

Besides, a fuel pump 27 is provided in the fuel tank 26. The fuel from the fuel pump 27 is fed to the injectors 24 and a pressure regulator 30 via a fuel filter 28 and an alcohol concentration sensor 29 which are inserted in the fuel feed passage 25. Then, the fuel is returned from the pressure regulator 30 into the fuel tank 26, thereby to have its pressure regulated to a predetermined value.

The alcohol concentration sensor 29 is constructed of, for example, a pair of electrodes which are provided in the fuel supply passage 25, and which detect the alcohol concentration by detecting a current variation based on the electric conductivity variation of the fuel. incidentally, the alcohol concentration sensor 29 is not restricted to the type utilizing the electric conductivity variation, but one of resistance detection type, capacitance type or optical type may well be employed alternatively.

Also, an intake air quantitly sensor (a hot wire type airflow meter in the illustration) 31 is provided in the intake pipe 6 directly downstream of the air cleaner 7. A throttle opening-degree sensor 32a, and an idle switch 32b for detecting the full closure of the throttle valve Sa are connected to this throttle valve Sa. Further, a knock sensor 33 is mounted on the cylinder block la of the engine. A coolant temperature sensor 34 is confronted to a coolant passage (not shown) formed in the cylinder block la, while an 0 2_ sensor 35 is installed to the exhaust pipe 9.

Further, a crank rotor 36 is secured to a crank is shaft lb supported in the cylinder block la, and a crank angle sensor 37 is provided in opposition to the outer periphery of the crank rotor 36. Also, a cam angle sensor 39 made of a maznet-c iDickup or the like for discriminating cylinder Nos. is mounted in opposition to a cam rotor 38 which is secu--ed to the cam shaft lc o.0 the engine 1.

As shown in Fig. 9, the crank rotor 36 is formed with projections 36, 36b and 36c at its outer periphery.

By way of example, the respective projections 36a, 36b and 36c are formed at positions el, e2 and e3 (for i 5 example, 61 = 970, e2 = 651 and 63 = 10') before the top dead centers (BTDC) of compression in the respective cylinders (#l, 42 and Q, 44).

More specifically, the projection 36a indicates a reference crank angle in the case of setting an ignition timing as well as a fuel injection timing. The rotational frequency f of the engine is calculated from a time period in which the section between the projections 36a and 36b passes. The projection 36c serves as a reference crank angle indicative of a fixed ignition timing.

Also, as shown in Fig. 10, the outer periphery of the cam rotor 38 is formed with projections 38a, 38b and 38c for discriminating the cylinder Nos. By way of example, the projections 38a are respectively formed at positions 64 (for example, 64 = 20') after the top dead centers (ATDC) of compression in the cylinders #3 and 44. Besides, the projection group 38b is configured of three projections, the first one of which is formed at a position V (for example, V = 5) after the top dead center (ATDC) of the cylinder R. Further, the projection group 38c is configured of two projections, the first one of which is formed at a position 86 (for example, 66 = 20') after the top dead center (ATDC) of the cylinder 42.

Incidentally, each of the crank angle sensor 37 and the cam angle sensor 39 is not restricted to the magnetic sensor such as magnetic pickup, but it may well be an optical sensor or the like. [Circuit Arrangement of Electronic Control Unit] Referring now to Fig. 11, numeral 41 designates an electronic control unit (ECU) constructed of a microcomputer or the like, in which a CPU 42, a ROM 43, a RAM 44, a backup RAM 44a and an 1/0 interface 45 are LD interconnected through a bus line 46, and in which each element is supplied with predetermined stabilized voltages by a voltage regulating circuit 47.

The voltage -regulating circuit 47 is connected to a -battery 49 through the relay contact of an ECU relay 48, is and the relay coil of the ECU relay 48 is connected to the batterv 49 through an ignition switch 50. Also, a starter motor 62 is connected to the above battery 49 through astarter switch 60 and the relay contact of a starter motor relay 61, while the fuel pump 27 is connected -hereto throuqh the relav contact of a fuel pump relay 51. Further, the intake-port heater unit 23 -ery of each cvlinder iS connected to -he same batt. -hrouah the relav contact of a heater relav 52 and a current sensor 63.

In addition, the various sensors 29, 31, 32a, 33, -2434, 35, 37, 39 and 63, the idle switch 32b and the starter switch 60 are connected to the input ports of the I/0 interface 45, while the battery 49 is connected to the input port thereof so as to monitor a battery voltage. On the other hand, the igniter 40a of the spark plug 40 is connected to the output port of the TO interface 45. Further, the ISCV 14, the duty solenoid valve 21, each injector 24, the relay coils (of the fuel pump relay 51, heater relay 52 and starter motor relay ID 61), and an ECS imp 59 which is indication means for indicating the occurrence of any abnormality or for indicating the state of heater energization are connected to the output ports of the i/0 interface 45 through a driver circuit 58.

The ROM 43 stores therein control programs, and the fixed data of various maps etc., while the RAM 44 stores therein data after processing the output signals of the various sensors and switches, and data arithmetically processed by the CPU 42. Besides, the backup = 44a stores therein a trouble code etc. at zhe occurrence of any fault, and the data are held even when the ignition switch 50 is OFF.

The CPU 42 sets varicus controlled variables such as a fuel injecticn quanzity, an ilniticn timing, and the duty ratio of a sipnal for actuating the duty 1-0 -25solenoid valve 21, in accordance with the control programs stored in the ROM 43 and on the basis of the various data stored in the RAM 44. Then, it delivers corresponding signals to the injector 24 and the igniter 40a, thereby to perform an airfuel ratio control and an ignition timing control, and it also delivers the actuation signal to the duty solenoid valve 21, thereby to control the maxim= supercharging pressure based on the turbocharger 15. [operation] Next, the operation of the embodiment constructed as stated above will be described. (Starting-mode Control Stems) Flow charts in Figs. 1 - 4 show the program of a is starting-mode control which starts upon the closure of the power source of the ECU 41. First, at a step S101, the program is initialized to tturn OFF the relays such as starter motor relay 61 and heater relay 52 and to set a timer and clear counters and flags.

Subsequently, at a stem S102, the starter motor actuation prohibition flag FLAG1 is set (FLAG1 - 1) to prohibit the actuation oil the starter motor 62. Then, at a stem S103, the 'Luel pump actuation allowance flag FLAG42 is set (FLAG2 - 1) tc allow the actuation of the fuel mumD 27.

Subsequently, at a step S104, the fuel injection prohibition flag FLAG3 is set (FLAG3 - 1) to prohibit fuel injection. Then, at a step S105, the ECS lamp 59 is lit up. Besides, at a step S106, a coolant temperature TW is read from the coolant temperature sensor 34, and whether or not the coolant temperature TW as the temperature of the engine is, at least, equal to a preset coolant temperature RCHE TW is decided.

When TWal RCHE TW holds at the step S106, the A control flow jumps to a step S110. On the other hand, when TW < RCHE TW holds, the control flow proceeds to a step S107, at which the timer is started counting. The loop of the next step S108 is iterated until the counted time period TIMER of the timer reaches a preset time period Ti. When TIMER > T1 has been met at the step S108, the loop is quitted to a step S109, at which the timer is cleared (TIMER - 0) and which is followed by the step S110.

More specifically, in such a case where alcohol and gasoline in the fuel tank 26 or the fuel feed passage 25 are separated at a low temperature or where only alcohol (or only gasoline) is supplied in a zcnditicn in which an alcchol ccncent=aticn M in =he fuel (high), the alcohol cank 26 is low fuel in =he fuel the alcohol content changes with time.

Accordingly, when the coolant temperature TW is lower than the preset coolant temperature RCHE TW, only the fuel pump 27 is actuated before cranking the engine so as to return the fuel from the pressure regulator 30 into the fuel tank 26, whereby the fuel in this fuel tank is circulated and stirred. Herein, the circulation of the fuel is continued for the preset time period Tl which is determined by the discharge capacity of the fuel pump 27 and the volume of the fuel contained between the alcohol concentration sensor 29 and the injector 24. Thus, the alcohol concentration distribution of the fuel is homogenized, and the temporal and special deviations of the alcohol is concentration M between the mounted position of the alcohol concentration sensor 29 and that of the injector 24 actually feeding t-he engine with the fuel are eliminated, so that the control characteristics of the system are enhanced.

SI-Subsequentlv, at -he step S110, a coolant temperature TWMET for judging if the engine is startable, is set in such a wav t.hat a startability judgement coolant temperature map MP TW is derived frcm an interpolative calculation by using the alcohol concentration M as a parameter. At a step Sill, the -28coolant temperature TW is compared with the startability judging coolant temperature TWIMET to judge if the engine is startable.

More specifically, as illustrated in Fig. 12, lying the experiments etc. are conducted for speci. temDeratu.-e condition ranae of the alcohol concentration M in which the engine is startable without heating the fuel to be injected from the injector 2-4, by means of the heater 23d, and the temperature condition range 1-0 thereof in which the enaine is not startable in that condition. The startability judgement coolant temperature man MP TW (refer to Fig. 13) corresponding to a series of addresses in the ROM 43 is prepared on y,-he basis of the specified ranges, and the startabilit Is set from this man judging coolant temperature TWMET.

by using the alcohol concentration M as the parameter.

Then, whether or not the engine is startable can be judged by comparing the cool-ant temmerature TSI with s-"arzabil-J-"v judging coolant temperature TWMET.

incidentally, as the engine temperature for judging temperatures of the fuel the star tabillity, any of the t u etc. mav well be adoDted Instead of tIne coolant '---cm the cOclant temmerazu- emmerature TW f- -e sensor 34.

in consequence, when T5q < 7i7MEET holds at the stem S111, it is judged that the encine is anstartable, and the -29control flow proceeds to a step S112. When TW > TWMET holds, it is judged that the engine is startable, and the control flow proceeds to a step S129.

Here shall be first explained steps in the case where the engine has been judged unstartable.

At the step S112 following the step Slll at which the unstartable condition has been judged, the fuel pump actuation allowance flag FLAG2 is cleared (FLAG2 - 0) to -he fuel pump 27. A flag FLAG4 for stop the drive of 4.

deciding a control for the unstartable condition is set (FLAG4 - 1) at a step S113, which is followed by a step S114. The unstartable condition control deciding flag FLAG4 is referred o at starter motor control steps to be described later, and the corresponding steps are executed upon deciding the unstartable condition control.

Subsequently, at the step S114, the ECS lamp 59 is changed-over from the lit-up state into a flashed state -he heater 23d is beina warmed 4n order to indicate that 4.

up. At a step S115, the heater relay 52 is turned ON to start the activation of the heater 23d and to warm up this heater.

Next, at a step S116, the so as to count the activation 23d. Besides, at a step Sll", started countina 1-ime neriod of the heater the count-ng operation c.E the timer is continued until a time period TIMER counted by the timer reaches, at least, a preset time period TSET (for example, TSET = 3 sec.).

Then, when TIMER > TSET has been met at the step S117, the control flow proceeds to a step S118, at which the timer is cleared (TIMER - 0). At the next step S119, heating finish judging power Wl is set in such a way that a heating finish judgment power map MP HW is derived from an interpolative calculation by using the coolant temperature TW and the alcohol concentration M as parameters. Thereafter, the control flow proceeds to a step S120.

At the step ShO, heater cons ump tion power W is calculated from a battery voltage VB and a heater cons ump tion current i detected by the current sensor 63 (W - I x VB), whereupon at a step S121, the heater consumption power W is compared with the heating finish judging power Wl having been set at the step S119.

More specifically, as illustrated in Fig. 14, when the heater 23d made up of the PTC pill has had its temperature raised up to its Curie point after the activation, the cons ump tion current 1 begins to decrease on account of a sudden rise in resistance. it is therefore impossible to decide the warmed-uz condition of the heater with the cons ump tion power only.

p 1 -31Accordingly, the heating finish of the heater 23d is judged after the lapse of the time period TSET by avoiding the initial starting stage of the heater activation, thereby to prevent a misjudgement.

The heating finish judging power Wl is the power which is consumed when the heater 23d has been warmed up to a sufficient temperature for promoting the vaporization of the fuel, after starting the fuel injection. As illustrated in Fig. 15, the heating A finish judgement power map MP HW includes the coolant temperature TW and the alcohol concentration M as the parameters. Herein, as the alcohol concentration M is higher, the amount of the latent heat of vaporization is larger, and as the coolant temperature TW is lower, the is heater 231d needs to be heated more sufficiently for vaporizing the injected fuel. 71herefore, the values of the heating finish judging power Wl stored in the resiDective addresses of the mam MP HW are smaller for the higher alcohol concentration and for the lower coolant 4-emDeratu--e.

Refer-ring back to Fig. 2, when W > Wl holds at the stem 5121, the loop of -reading the consumed current II cf: the heater 23d from the currenz sensor 63 and calculating the heater power consumption W and thereafter comparing the calculated power consumption W -32with the heating finish judging power W1 is iterated again. On the other hand, when W < W1 holds, the finish of the heating is decided, and the control flow proceeds to a step S122.

At the stem S122, the starter motor actuation prohibition -flag FLAG1 is cleared (FLAG1 - 0) to allow L-he actuation of the starter motor 62. At a stem S123, the fuel pump actuation allowance flag FLAG2 is set (FLAG2 - 1) to drive the fuel pumm 27 again. Then, the 1-0 ECS lamp 59 is changed-over from the flashed state into continuous lighting at a step S124, which is followed by a stem S125.

At the stem S125, a loom is iterated until the counter COUNTST reaches a mreset value TC. The counter COUNTST counts a cranking time Deriod at starter motor the preset control stems to be described later, and t value TC -4s previously set at a value, for exam-ple, 2 3 sec. On this occasion, since the -'fuel- injection prohibition -Olag FILAG3 is kept set, the engine undergoes idle cranking 4n which the starter motor 62 is driven without the fuel injection.

t.le combust4on chamber is Thus, the temmerature 'uel raised bv the idle cranking. Ac--ord-4na--v, when the I mixture -4s fed 4nto the combus-4on chamber '-,v performing the fuel injection, the fuell has its vapor za"--Jon promoted and becomes easy to ignite. Therefore, the warming-up time period of the engine 1 can be shortened.

Thereafter, when COUNTST > TC has been met at the step S125, the loop is quitted to a step S126 et seq. At the steps S126, S127 and S128, the unstartable condition control discrimination flag F4, the counter COUNTST and the fuel injection prohibition flag FLAG3 are respectively cleared (FLAG4 - 0, COUNTST - 0, FLAG3 - 0). Then, the processing in the case where the engine is not startable has been entirely done, and it is followed by a step S133.

Meanwhile, when TW > TWMET holds at the step S111 in Fig. 1, the control flow proceeds from this step to the stem S129 et sea. in Fig. 3, which execute processing in the case where the engine is startable. More specifically, at the step S129, the starter motor actuation mrchibition flag FLAIG1 is cleared (FLAG1 - 0) to allow the actuation of the starter motor 62, and at the step S130, the fuel injection prohibition flag FLAG3 is cleared (FLAG3 - 0) to allow the fuel injection. Whether or not the coolant temperature TW has reached a warmina-ur) fInishing temmerature TWLA4 (for exami:)1e, 50 - 60OC) is decided at the stem S131.

When TW > TWLA4 holds at ithe stem S131, the control flow jumps from this stem to a stem S147 in Fig. 4, at is which the ECS lamp 59 is nut out, and the program is quitted. On the other hand, when TW < TWLA4 holds, the step S131 is &followed by the step S132, at which the heater relay 52 is turned ON so as to start the -er, the control activation of the heater 1-3d. Thereaft flow proceeds to the stem S133.

Subsequently, at the stem S133 which follows the step S128 of the unstartable condition processing or the step S132 of the startable condition processing, a time r10 period for keeping an ignition tiMing -fixed at a specified timing, namely, a fixed ignition time TADV is set in such a way that a fixed ignition time map MP IGST is derived from an interzolative calculation by using the coolant temDerature TW as a marameter.

As illustrated in Fic. 16, values obtained by an experiment etc. be-forehand are stored in the respective addresses of the fixed ignition time mam MP!GST, and the stored values of the lanition time TADV are greater as the coolant temmerature TW is lower. Herein, until the --4xed ignition time MAW elapses, the igniltion t4 ming is fixed to the snec-J-E----d timing retarded with respect tc a usuall -ian- 4---4cn -J=ing, -,zcr example, to the timing c-E the in-mut of a.3 crank pulse -f-rom the anale sensor 37.

In this way, the 4-nition t-4.-,-tina Js retarded crank -35relative to the usual one in accordance with the engine temperature, and the temperature of the combustion chamber is raised, so that the mixture can be reliably ignited, and the starting characteristics of the engine can be enhanced.

Further, the control flow proceeds from the step S133 to a step S134, at which the counting operation of the timer is started. At a step S135, it is decided whether or not the engine speed Ne has reached a speed 1-0 NKAN which represents that the engine is completely started. When Ne < NKAN holds, that is, when the engine is not completely started yet, the control flow branches from the step S135 to a step S141, at which a count value COUNT is incremented (COUNT - COUNT + 1). Whether or not the count value COUNT has exceeded a preset value COUNTSET is decided at a step S142.

Wh en COUNT < COUNTSET holds at the step S142, this step is followed by a step S143, at which the timer is cleared (TIMER - 0). Further, the control flow returns from the step S143 to the foregoing step S133, at which the fixed ignition time TADV is reset, whereupon the steps stated above are iterated. On the other hand, when COUNT > COUNTSET holds, -Lt is decided that the enaine stalls, and the cc.ntrol flow branches.,:--om the step S142 to a step S144. Herein, the count value COUNT is cleared at the step S144 (COUNT - 0), and the timer is cleared at a step S145 (TIMER - 0). Subsequently, whether or not the coolant temperature TW has exceeded the startability judging coolant temperature TWMET is decided at a step S146.

Besides, when TW > TWMET holds at the step S146, the control flow returns to the step S133, and when 'LW s TWMET holds, it returns to the step S113 et seq. of the unstartable condition control. On the other hand, when r-0 Ne > NKAN holds at the stem S135, that is, when the engine has been commletely started, the step S135 is followed by a stem S136, at which whether or not the coolant temDerature TW has exceeded the warming-up finishing temperature TWLA4 is decided again. Subject to TW < TWLA4, the control _Elow branches from the step S136 to the stem S143, at which the timer is cleared (TIMER - 0) and from which the control flow returns to 4L-he stem S!-333, whereas subject to TW > TWLIA4, t-he control flow proceeds from the stem SI-36 to a stem S137. the stem S!_37, it is decided whether or not the time period TIMER counted by the timer has reached a preset time period TLE, in other...jords, whether or not the warmina-un c--P the enaine has been finished owing to the f'act. that the state in which the enaine speed Ne is k- not lower than the co=leteiv-szarted enaine speed NKAN -37and in which the coolant temperature TW is higher than the warming-up finishing temperature TWLA4 has continued for the preset time period TL. Subject to TIMER < TL, the control flow returns to the step S135 so as to iterate the judgement of the complete starting of the engine, whereas subject to TIMER > TL, it is decided that the engine warmingup has been finished after the start.Lng, and the step S137 is followed by a step S138. Herein, the count value COUNT is cleared (COUNT 4- 0) at the step S1.38, the timer is cleared (TIMER - 0) at a step S139, the heater relay 52 is turned OFF to deactivate the heater 23d at a step S140, and the ECS lamp 59 is put out at a step S147, whereupon the program.is ended. In this way, the fuel injected from the 13d till the is injector 24 is vaporized by the heater finish of the engine warming-up, and the injected fuel is vaporized by the heat of the engine itself after the finish of the engine warming-uz, wherebv the &fuel is favorably vaporized at all times.

Owing to the precise starting-mode control as stated above, the fuel quantity after starting the engine can be sharply reduced by quickly raising the temmerature of the combustion chamber of the engine, so that a shortened warming-up time period and an enhanced fuel cost can be accomplished.

(Starter Motor Control Steps) Meanwhile, the program of the starter motor control steps shown 4 terrup ng the -n Fig. 17 is executed in t14 program of the initial control every predetermined time period.

In the temporally-interrupting program, at the first step S201, the value of the starter motor actuation prohibition flag FLAGI is checked to decide whether or not the actuation of the starter motor 62 is 10 allowed.

When FLAGI = 0 holds at the step S201, that is, when the actuation of the starter motor 62 is allowed, L-he control flow =roceeds from the ste= S201 to a stev S202, which decides whether or not the starter switch 60 is turned ON. Subject to the ON state of the starter switch 60, the control flow proceeds to a step S203, at which the value of the unstartable condition control dj.SCr4Mi_ - "'ag FLAG4 is checked.

at4 J_ on When FTAG' 0 holds at the stem S203, the control flow Jumps to a step S205. When FLAG-4- = 11 holds, the coolant temperature TW is lower than the startability judai.-.a coolant temperature TWMEET, and the enaine is in,the state of the unstartable condition control. Th ..erefore, the control flow proceeds from the step S203 to a step S204, at which the cou.nt- value COUNTST for 1 -39 measuring the idle cranking time period cranking without injecting the fuel as the before-mentioned starting-mode -ed (COUNTST - COUNTST + 1).

control steps is increment Then, at the step S205, the starter motor relay 61 is turned ON to drive the starter motor 62, whereupon the program is quitted. Thus, the engine 1 is cranked.

On the other hand, when FLAG1 = 1 holds at the step S201, so the actuation of the starter motor 62 is prohibited, or when it --s decided at the step S202 that the starter switch 60 is turned OFF, the control flow branches from the pertinent step to a step S206, at which the starter motor relay 61 is turned OFF to hold the starter motor 62 stopped, whereupon the program is quitted.

is (Steps for Discriminating Cylinder Nos. and for Calculating Engine R.P. M.) Fig. 18 shows a routine for discriminating cylinder Nos. and for calculatina encine R.P.M. which is Jnterrunt-Jvely started on the basis of the input of a crank pulse from the crank angle sensor 37. At a step S301, cylinder No. Iri for ignition is discriminated on the basis of the output signals of the crank angle sensor 37 and the cam anale sensor 39. Subseauently, at a stem S302, cylinder No. -'i -2 for fuel injection is discriminated.

i 5 More specifically, as illustrated in a time chart of Fig. 29, in a case where the cam pulses of the position 65 (projection group 38b) have been output from the cam angle sensor 39 by way of example, the next top dead center of compression is of the cylinder No. W. It is accordingly possible to discriminate that the cylinder No. 43 becomes the cylinder for ignition and that the cylinder No. #4 becomes the cylinder for fuel injection.

Further, in a case where the cam pulse of the position 64 (projection 38a) has been output after the cam pulses of the position eS, the next top dead center of compression is of the cylinder No. #2. It is accordingly possible to discriminate that the cylinder No. #2 becomes the cylinder for ignition and that the cylinder No. #1 becomes the cylinder for fuel injection.

Likewise, the top dead center of compression after the output of the cam pulses of the position 66 (projection group 38c) is of the cylinder No. 4. Thus, the cylinder No. 0 becomes the cylinder for ignition, and the cylinder No. #3 becomes the cylinder for fuel injection. Besides, in a case where the cam pulse of the position e4 (projection 3Sa) has been output after the cam pulses of the position e6, the subsequent top dead center of compression is of the cylinder No. Q.

is It is accordingly possible to discriminate that the cylinder No. #1 becomes the cylinder for ignition and "2 becomes the cylinder that the cylinder No. for fuel injection.

Further, it is seen from Fig. 29 that the crank pulse which is output J_rom the crank angle sensor 37 after the output of the cam pulse(s) from the cam angle sensor 39 indicates the reference crank angle (el) in the case of setting the ignition timing and fuel injection start timing of the corresponding cylinder.

More specifically, in the four-cycle four-cylinder engine 1 in this embodiment, the combustion strokes proceed in the sequence of the cylinders Nos. #1 - #3 ir 2 - Arr 4. Assuming the cylinder No. '7ri for ignition is the cylinder No. #1, the cylinder No. Irri(+2) I i- for fuel injection at this time is the cylinder No.:E2, and the next cyinder No. 4i(+2) for fuel injection becomes the cylinder No. 14. hus, the ignition operations are performed in the sequence of the cylinders Nos. 17rl - 73 42 - #4, and the fuel injection operations are performed in such a sequential manner that the fuel is injected into the corresponding cylinder once every 720CA (every two engine -revolutions).

Subsequently, the engine R.P.M. Ne is calculated at a step S303 in Fig. 18. By wav of example, the time is interval between the output pulses of the crank angle ' sensor 37 for detecting the positions ETDC el and e2 is measured to obtain a period f, and the engine R.P.M. Ne is calculated from the period ' (Ne - 60/f). The :L - calculated engine speed is stored as R.P.M. data in the predetermined address of the RAM 44, whereupon the routine is quitted. (Steps for Setting Fuel Injection Quantity and Ignition Timing) Meanwhile, a fuel injection quantity and an ignition timing are set by an interrupt routine of every predetermined time as shown in Figs. 19 - 21. First, at a stem S401, the vlue of the fuel injection prohibition flag FLAG3 is checked. When FLAG3 = 1 holds, that is -enresentina that the fuel injection is prohibited in the starting mode control, the control flow proceeds to a stem S402. At the stem S402 a fuel injection pulse width T-1 is set to "0" (Ti - 0). Besides, the ignition...s prohibited at a ster) S403, after which the routine is 20 auitted.

Thus, the initial knocking of comparatively great macni--Ude is mrevented from occurrina 4=edia-elv after the cranking under the influence of the low-boiling commonents of the fuel -remaining in 25 engine, in the intake no--t 2a or in c" 4 v i -nder o.E the intake manifold 3 or the residual fuel heated by the heater 23d. This avoids an unpleasant feeling to the driver of the vehicle or a situation in which the driver turns OFF the starter switch 60 at the first knocking, and makes it impossible to start the engine.

On the other hand, when FLAG3 = 0 holds at the step S401, in other words, when the fuel injection is allowed, the control flow proceeds from the step S401 to a step S404, which decides whether or not the engine R.P.M. Ne is "0", that is, whether or not the engine is at a stop. Subject to Ne = 0, the routine is quitted via the steps S402 and S403 stated above, whereas subject to Ne 0 0, the step S404 is followed by a step S405.

At the step S405, t-he engine R.P.M. Ne stored in the predetermined address of the RAM 44 is read out, and a time period TIME1/2 per 1/2 rotation of the crankshaft of the engine is calculated on the basis of the engine R.P.M. Ne from the following:

TIME112 = 30/Ne .. (1) The above equation (1) gives the time period per stroke in the four- cylinder engine. As regards an engine of equal-interval combustion operations having cylinders, the corresponding time period can be calculated from the following:

TIME1/n/2 = (60/n/2)/Ne... (1) 1 licient Thereafter, at a step S406, a weighting coef. (the weight of a weighted average) per stroke TNnew is calculated from:

TNnew = TIME1/2 x COF (2) where COF: fixed value.

Subsequently, at a step S407, an induced air quantity Q (gr./sec.) based on the output of the intake air quantity sensor 31 is read, and a weighting coefficient TNold and a corrected induced air quantity Qaold having been set in the last routine are read out. incidentally, TNold = 0 and Qaold = 0 are set in the first routine.

Thereafter, at a step S408, a compensated induced is air quantity Qanew with the first-order lag compensated is calculated from:

Qanew = (Qaold-TNold + QM1 + TNnew) Also, at a stem S409, an air quantity Qp which is h.n.duced 4n one cylinder at the intake st-roke is calculated from:

QP - Qanew x TIME1/2... (4) Thus, the first-order lac is compensated, whereby an overshoot in a szate can be corrected.

J:

By the way, the theoretical formula c. the comr)ensated induced air auantity Qanew is elucidated in .. (3) detail in the official gazette of Japanese Patent Application Laid-open No. 5745/1990, the application of which was filed by the same Applicant before.

Subsequently, at a step S410, a correction coefficient COEF which corresponds to the enrichment components of e.g. enrichment corrections at the starting of the engine, in a cold engine state and in the fully open state of the throttle valve is set on the basis of the output values of the throttle opening 1-0 sensor 32a, idle switch 32b and coolant temperature sensor 34. However, an acceleration enrichment correction is not made.

Thereafter, a a steD S411, an air-fuel ratio feedback correction coefficient a is a set on the basis is of the output signal of the 0 2_ sensor 35. Besides, at a step S412, a desired air-fuel ratio A/F is set by referring to a desired air-fuel ratio map MP A/F with an interpolative calculation, on the basis of the alcohol concentration M, Ithe air quantity Qp which is induced in one cylinder at the intake stroke, and the engine R.P.M. Ne.

Regarding the desired air-fuel ratio A/F, the air fuel ratio varies demendinc unon the alcohol 2 2, - concentration M. AS illustrated in Fig. herefore, the optimum air-fuel ratios (in general, theoretical -46air-fuel ratios) are stored in the map of the ROM 43 beforehand in accordance with the alcohol concentration M, the induced air amount Qp per cylinder at theintake stroke, and the engine R.P.M. as parameters.

Subsequently, the step S412 is followed by a step S413, which decides whether or not the heater is under activation. Subject to the activated state of the heater, the control flow proceeds to a step S414 et sea., whereas subject to the deactivated state, it -10 proceeds to a step S425 et sea. First, the steps for the activated heater will be explained. At the stem S414 of these stems, a rate at which fuel having adhered to the wall of the intake port 2a evaporates during two revolutions (one cycle) of' the engine is fixed to "1" (a fuel.

is 1). The rate is the evaporating ra-l--;o B oil the Further, at the stem S415, an adhesive rate at which the =el injected from the Mjector 24 adheres to the wall of the intake mort 2a is '&---4xed to "0" (X - 0). The adhesive rate is the adhesive ratio X cf the fuel adhering on the wall.

More spec-J-':-4cal-!v, -he fuel injeczed from the 4niector 24 is enzi-rely struck against the heating element 223a of the -4---ake-morz heater unit 21. During he heater activation, accor-r-.-4nciv, the fuel is instantly vaporized by the heater 23d without adhering 1 is to the wall, and hence, the evaporation of the adhering fuel does not occur. Therefore, the fuel evaporation ratio 0 is fixed to "1", and the wall adhesion ratio X is fixed to "0". Thus, -he air -fuel ratio can be set appropriate, and an overrich mixture can be prevented, thereby the fuel consumption is improved together with the enhancements of the starting characteristics.

When the control flow proceeds from the step S415 to a step S416, the engine R.P.M. Ne is compared with the explosion R.P.M. NKAN representing the completely- started state of the engine, thereby to judge the explosion of the engine. Subject to Ne < NKAN, at a stem S417, the enalne starting judgement flag FLAGS indicating the started state of engine before the explosion is set (FLAGS - 1) At a step S424, the ignition timing eIG is set at a fixed ignition timing (angle) ADVCS which is synchronized with, for example, the crank pulse of the position B= 63 (100CA) delivered from the crank angle sensor 37. This stem S424 is followed bv a stem S430.

On the other hand, when Ne > NKAN has been met at low mroceeds from this stem the step S416, the cont-rcl I.

to a step S418, at which the value of -he enaine starting judgement flag FLAGS is checked. FLAGS = 1 represents that the engine was not completely started at is the last routine, and that it has first come into the completely-started state this time. Therefore. the control flow proceeds to a stem S419, at which the timer -he fixed ignition is for counting the elapsed time of t cleared (TIMER2 - 0). The counting operation of this timer is started at a step S420, and the engine starting judgement flag FLAGS is cleared (FLAGS - 0) at a step S421, which is followed by the step S424 stated above.

In addition, when FLAGS = 0 holds at the step S418, U ithe control flow branches from this stem to a step S422, which decides whether or not the time period TIMER2 of the elapsed time of the fixed ignition as counted by the L-imer has reached a fixed-ignition time TADV. Herein, subject to TIMER2 < TADV, the stem S422 is followed by the fo-regoing stem S4424. Subject to TIMER2 > TADV, the stem S422 is followed by a stem S423, at which the timer is cleared (TIMER2 - 0) and which is followed by a stem S427.

Next, there will be exmiained stems in the case of heater deactivation where the routine zroceeds from the sten S413 to the stem S425 et sea.

At the stem S425 of these stems, the fuel evaporation rate 5 correspondina to two revolutions c= :- of the encine is set in such a wav -hat a he cranksha4L_ fuel evamoration rate maz MP is --e4-------ed to with an 1 49interpolative calculation in according with the engine speed Ne, the coolant temperature TW and the alcohol concentration M as 13arameters.

The fuel evaporation rate 0 is governed by a wall temperature, the period and the alcohol concentration M. More specifically, as the wall temperature is higher, the fuel evaporation rate S becomes larger. Besides, as the engine speed Ne heightens, the period shortens, and hence, a time period till the next intake stroke shortens, so that the fuel adhesion lower and the value of the fuel evaporation rate C decreases accordingly. Further, as the alcohol concentration M is higher, the latent heat of evaporation increases more, and hence, the fuel is more difficult to evaporate, so that the is value of the fuel evaporation rate S decreases more.

Accordingly, the fuel evaporation rate 6 can be grasped as a function of the coolant temperature TW, the engine R.P.M. Ne and the alcohol concentration M. In this embodiment, as -,-!-!us-L-rated in Ficr. 24, the fuel evaporation rate map MP 5 is formed in accordance with the engine R.P.M. Ne, the coolant temperature TW and the alcohol concentration M as parameters, and the values of the fuel evaporation rate 5 obtained by an experiment etc. beforehand are Stored in the individual areas of this map.

-so- Referring back to Fic. 20, at the steD S426, the adhesive ratio X of the fuel adhering to the wall is in such a way that a wall adhesion ratio map MP X is referred to with an interDolative calculation in accordance with the alcohol concentration M, the compensated induction air quantity Qanew, and the fuel injection pulse width Ti set at the last routine, as parameters. By the way, at the first routine, X = 0 is set because the fuel injection pulse width Ti has not been set.

Variation in the adhesive ratio X of the fuel adherina to the wall is governed by the induced air auantitv Qanew, the fuel injection pulse width Ti (the of the 4niected fuel) and the alcohol concentration M. More smec-4-4i--a-l-lv, when the induced air quantity Qanew enlarges, a time zeriod for atomizing the fuel shortens, and the wall adhesion ratio X enlarges. Besides, assuming the induced air quantity Qanew tc be constant, the -fluctuation cf the quantity of the fuel adhering -.c -he wall is slight relatJve to the change of -he fuel injection cuant4--.-, so that the wall adhesion ratio X becomes a rellativeiv small value when the fuell -.-.jec---Jcr pulse width when the alcohol concentraticon 2 the 4f'ue-i becomes more -=_ e,,=-z--rat-e due to a 1 -51higher latent heat of evaporation, so that the wall adhesion ratio X becomes a relatively large value in relation of alcohol concentration.

As illustrated in Fig. 23, the wall adhesion ratio map MP X is formed in accordance with the alcohol concentration M, the compensated induced air quantity Qanew and the fuel injection pulse width Ti as parameters, and the values of the wall adhesion ratio X obtained by an experiment etc. beforehand are stored in the individual areas of this man.

Subsequently, when the control flow proceeds to the step S427 from the step S426 or from the step S423 of the processing during the heater activation as stated.before, a basic ignition timing eBASE is set in such a way that a basic ignition timing map mp eBASE is referred to with an inter.Dolative calculation in accordance with engine R.P.M. Ne, the induced air amount Qp per cylinder at the intake stroke and the alcohol concentration M as parameters.

As illustrated in Fig. 25, the optimum values of the basic ignition timing eBASE (the crank angle with reference to el) obtained bv an experiment etc. beforehand with the paramezers cf the engine R.P.M. Ne, the induced air amount Qp per cylinder at the intake stroke and the alcohol concentration M are stored in the resmective addresses of the basic ignition timing map MP eBASE. Under the conditions of the same values of the parameters Qp and Ne, the stored values of the basic ignition timing (angle) eBASE are smaller for the higher alcohol concentration M in order to attain greater advanced angles.

Thereafter, at a stem S428, a knock control value (angle) eNK is set on the basis of a signal from the knock sensor 33, and at a step S429, the knock control 1D value eNK is added to the basic ignition timing eBASE set at the above step S427, thereby itc calculate the ignition timing (angle) eIG (eiG - eBASE + eNK), where uDon this stem S429 is followed bv the stem S430.

n ow proceeds to t.ke Subsequently, when the control -E is stem S430 from the stem S429 or from the stem S424 of the heater activation, the the processing in the case of t amount Mf4 of fuel remaininc in the intake mort which was set four strokes (one cvc-le) be-fore is read out.

Besides, at a stem S431, a fuel injection amount GfL corresponding to one -njec-1-4--n operation is set in accordance with an equation given below. By the way, Mf4 = 0 holds until the fuel -4niect-4cn routine is iterated four times.

Gf = { (Qp/A/F) x COEF - E - Mf 4 1, / (1 - X)... (5) As described before, wit.h th.e enaine 1 in this -53embodiment, one fuel injection operation is done for the corresponding cylinder every 7200CA (every two revolutions of the engine). When the fuel is injected from the injector 24 of the corresponding cylinder into the intake port 2a thereof, part of the injected fuel adheres to the intake valve, the wall of the intake port, etc. without being drawn into the cylinder (combustion chamber). The fuel having adhered evaporates properly during the two revolutions of the engine, and the fuel having evaporated is drawn into the cylinder together with the fuel injected at the next intake stroke.

Here, a fuel feed amount Ge which is actually fed into the cylinder by one injection operation becomes the sum of an evaporative amount Mf4-a and a fuel amount (1 - X)-G'L which does not adhere to the wall, that is:

.. (6) Ge = (1 - X).Gif + Mf4.6 From Ea. (6), the fuell amount Gif required for one injection operation is evaluated as follows:

G'E = (Ge - Mf4-eM1 - X)... i The fuel amount Ge to be actually fed into the cylinder is the desired value of fuel feed based on the desired air-fuel ratio A/F and the air quantity Qp, and. it becomes the followinc because the air fuel ratio subjected to the enrichment correction is denoted by (A/F)/COEF:

Ge = QP-COEF/A/F) (8) The substitution of Eq. (8) into Eq. (7) results in Eq. (5) mentioned before.

Subsequently, at a step S432 in Fig. 21, the fuel amount Mf remaining in the intake port at this time is set in accordance with the following equation:

Mf = (1 - 5) x MN + X-Gf... (9) That is, the fuel mount Mf remaining in the intake M port immediately after the fuel injection becomes the sum of the remaining amount (1 - 6) x M& obtained by subtracting the evaporative component from the adhering fuel amount of the corresponding cylinder at the last injection, and the adhesive component X-Gf in the fuel mount injected this time. By the way, Mf = X-Gf holds until the injection is performed four times from starting Vhis procedure.

Thereafter, at a step S433, a voltage pulse width Ts for compensating an invalid is set on the basis of the battery voltage. a step S434, the fuel injection pulse width correction time period Besides, at Ti for actually driving the injector 24 is set in accordance with the following equation:

Ti = K.Gf-a + Ts CO) where K: coefficient for compensating the characteristics of the injector.

:uel injection amount Gf has The aforementioned 1. been calculated with the predictive correction of the adhesion of the fuel to the wall and the correction of the evaporation of the fuel adhering to the wall. Therefore, the air fuel ratio is prevented from becoming rich in a transient state, particularly in a low engine speed state, so that any slow operation in the transient state is avoided to enhance the output response of the 1-0 control system.

Further, an enrichment correction for acceleration is dispensed with, so that a controllability for the air fuel ratio is enhaAced, and the wasteful consumption of L.he fuel is prevented.

Subsequentlv, at a step S435, an injection starting crank angle 6INJST is set on the basis of an injection starting crank anale man MP eINJST in accordance with the engine R.P.M. Ne and the fuel injection pulse width Ti as parameters.

As illustrated in Fig. 26, the injection starting crank anale man mP eINJST is -'formed in accordance with the engine R.P.M. Ne and the fuel injection pulse width as the parameters, and the ontimum values of the injection starting crank angle eINu-S-. obtained by a computation etc. beforehand are stored in the respective t -56areas of this map. The injection starting crank angle eINJST is set at a more advanced angle as the engine R.P.M. Ne and the fuel injection pulse width Ti are greater.

Thereafter, the control flow proceeds to a step S436, at which the last data TNold of the weighting coefficient is renewed with the data TNnew set at the step S406 (TNold - TNnew). Besides, at a step S437, the last data Qaold of the compensated induction air U quantity is renewed with the data Qanew set at the step S408 Qaold - Qanew), whereupon the routine is quitted. (Steps for Controlling Ignition and Fuel Injection) When the igniCon timing e1G and the fuel injection pulse width Ti have been set by the above steps, an ignition signal and a fuel injection signal are output in accordance with the charts shown in Fig. 27 and Fig. 28, respectively.

ignition conzrcl steps shown in Fig. 27 are executed every 1801CA interruptingly when the current crank angle calculated on the basis of the crank pulse input becomes the ignition timing (angle) 6IG set by the foregoing routine (steps S424, S429).

More specifically, at the step S501, the ignition signal is output to the correspcnding cylinder K for ignition as discriminated by the foregoing steps for 1 discriminating cylinder No. and calculating engine R.P.M., whereupon the routine is quitted. Meanwhile, fuel injection control steps shown in Fig. 28 are similarly executed every 180'CA interruptingly when the current crank angle calculated on the basis of the crank pulse input becomes the injection starting crank angle eINJST set by the foregoing routine (step S435).

Herein, at the first step S601, the driving pulse signal having the fuel injection pulse width Ti is output to the injector 24 of the corresponding cylinder #i(+2) for fuel injection as discriminated by the foregoing steps for discriminating cylinder No. and calculating engine R.P.M.

At the next steD S602, the fuel quantity Mfl remaining in the intake port at the last time is renewed with the -fuel quant_ity Mf remaining in the intake port at this time as has been set by the foregoing steps for ty and the ignition setting the fuel injection quantit timing (Mf l - Mf). Likewise, the data items of -he remaining fuel quantity are successively renewed (Mf2 Mfl, Mf3 - Mf2, M. E4 - Mf3).

As a result, the fuel amount Mf4 remaining in the intake port which is read out at the step S430 of the foregoing steps for setting the fuel injection quantity and the ignition timing becomes the fuel amount of the -58corresponding cylinder having existed one cycle before, at all times.

By the way, in case of an engine having cylinders, the fuel quantity MM remaining in the intake port one cycle before is renewed with the fuel quantity Mfn-1 remaining in the intake port at the preceding cycle.

As described above, according to the present invention, a precise starting-mode control dependent LO upon the temperature of an engine makes it possible to attain an appropriate air-fuel ratio and to sharply reduce the amount of fuel after the starting of the engine. Moreover, at starting the engine, the is temperature of a combustion chamber can be quickly raised without incurring unpleasant initial knocking immediately after cranking due to the residual components of fuel, and a warming-up time period can be shortened.

Accordingly, the engine starting can be shifted into an ordinary running state smoothly and quickly, and the enhancements of starting characteristics and the reduction of a fuel cost can be simultaneously accomplished.

Furthermore, a heater for vaporizing the fuel can be effectively arranged, and the fuel injected from an -59injector can be reliably vaporized to enhance the starting characteristics. The invention brings forth such excellent effects.

Claims

-60,CLAIMS

1. A control method for a flexible fuel vehicle having an engine mounted on said flexible fuel vehicle, a fuel injector provided in an intake manifold for injecting fuel into a cylinder via a cylinder head. a throttle valve in a throttle chamber connected with said intake manifold, a starter motor mounted on said engine for starting said engine with electric power, a fuel pump for supplying said fuel from a fuel tank to said fuel injector. a temperature sensor mounted on said engine for detecting a coolant temperature and for producing a temperature signal, and a concentration sensor interposed between said fuel tank and said injector for sensing a concentration signal of said fuel and for generating a concentration signal, the control method comprising the steps of:

setting an engine startable temperature in dependency on said concentration; judging whether it is possible to start said engine by comparing said engine startable temperature with said coolant temperature; and cranking said engine for a predetermined time without injecting said fuel when starting said engine is judged impossible so as to enable an opt' -61starting of said engine.

2. A control method for a flexible fuel vehicle having an engine mounted on said flexible fuel vehicle, a fuel injector provided in an intake manifold for injecting fuel into a cylinder via a cylinder head, a throttle valve in a throttle chamber connected with said intake manifold, a temperature sensor mounted on said engine for detecting a coolant temperature and for producing a temperature signal, and a concentration sensor interposed between a fuel tank and said injector for sensing a concentration of said fuel and for generating a concentration signal. the control method comprising the steps of: setting an engine startable temperature in dependency on said concentration; judging whether it is possible to start said engine by comparing said engine startable temperature with said coolant temperature; prohibiting a fuel injection and an ignition when it is decided to be impossible to start said engine; activating a heater; cranking said engine; and allowing said fuel injection and said ignition after a predetermined time so as to perform an effective and optimum engine starting.

3. A control method for a flexible fuel vehicle, substantially as herein described, with reference to, and as illustrated in, the accompanying drawings.

4. A control system for a flexible fuel vehicle, comprising means for carrying out the control method as claimed in any of claims 1 to 3. -

5. A flexible fuel vehicle comprising a control system as claimed in claim 4.