JPH0626414A - Start control for engine for ffv - Google Patents

Abstract

PURPOSE:To make alcohol density in fuel to be detected and alcohol density actually injected coincide with each other by furnishing a process to preliminarily mix fuel in the case when fuel is separated at the time of starting and a process to carry out starting control at the normal time. CONSTITUTION:A surge tank 36 is formed at a part adjacent to the inflow side of an injector 23 of a fuel passage 34 from a fuel tank 32. An alcohol density sensor 37 to detect alcohol density in fuel is installed in this surge tank 36. In the case when it is judged that alcohol density in fuel at the time of starting is changed in comparison with alcohol density at the time when an engine stops previously, firstly fuel is preliminarily mixed and homogenized, and thereafter, normal time starting control is carried out in accordance with alcohol density in this fuel uniformly mixed. Consequently, it is possible to acquire favourable strating control performance and to improve exhaust emission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, when the fuel at the time of starting is separated, stirs and mixes this fuel before starting it.
The present invention relates to a start control method for an FV engine.

[0002]

2. Description of the Related Art In recent years, due to deterioration of fuel conditions and demand for exhaust gas cleaning, a system that can simultaneously use alcohol as an alternative fuel in addition to conventional gasoline has been put into practical use. Vehicles such as automobiles (Flexible Fuel Vehicles, hereinafter,
In "FFV"), it is possible to run not only with gasoline but also with a mixed fuel of alcohol and gasoline, or only with alcohol, and the fuel alcohol concentration (content ratio) used in this FFV is , 0% (gasoline only) to 1 depending on the user situation when refueling
Varies between 00% (alcohol only).

In this type of FFV engine, the target air-fuel ratio and MBT advance angle (Minimu
m Spark Advance for Best Torque) is determined, so accurate detection of this alcohol concentration is important in order to improve engine operating performance and exhaust emission. As a technique for variably setting the target air-fuel ratio depending on the alcohol concentration in the fuel, for example, as disclosed in Japanese Patent Laid-Open No. 3-253746, a correction coefficient corresponding to the target air-fuel ratio set based on the alcohol concentration. There is a method of correcting the basic fuel injection amount when the gasoline fuel is 100% to set an appropriate fuel injection amount.

[0004]

By the way, when the alcohol concentration in the fuel is low, the alcohol in the fuel is likely to be separated at a low temperature, and when the fuel contains a large amount of water, the fuel is separated. It is known to become more prominent.

When a predetermined time has passed after the engine was started, the fuel is circulated by the fuel pump, so that the fuel is in a uniform mixed state. However, at the time of starting, the fuel pump is just driven and the alcohol in the fuel is completely mixed. Since it is not uniform, the alcohol concentration detected by the alcohol concentration detection means is not constant, and there is a gap between the alcohol concentration in the fuel actually injected from the injector and the air-fuel ratio controllability and ignition timing control. However, there is a problem in that good starting performance cannot be obtained and the exhaust emission is deteriorated.

It is considered that such a problem can occur because the alcohol concentration suddenly changes due to the refueling fuel even when the fuel cell is restarted after refueling.

The present invention has been made in view of the above circumstances, and the alcohol concentration in the fuel to be detected matches the alcohol concentration actually injected, so that not only good start control performance can be obtained, but also exhaust gas is exhausted. It is an object of the present invention to provide a starting control method for an FFV engine that can improve emissions.

[0008]

In order to achieve the above object, an FFV engine start control method according to the present invention compares the alcohol concentration in the fuel when the engine is started with the alcohol concentration in the fuel when the engine was last stopped. However, if the alcohol concentration is changing, the procedure of premixing the fuel,
After completion of the premixing, a procedure for performing normal-time start control based on the alcohol concentration in the fuel is provided.

[0009]

[Operation] In the present invention, when it is determined that the alcohol concentration in the fuel at the time of starting changes as compared with the alcohol concentration at the time when the engine was stopped last time, first, the fuel is premixed to a uniform state, and then, Normal-time start control is performed based on the alcohol concentration in the fuel mixed uniformly.

As a result, since the mixed fuel is always made uniform in the normal start, the alcohol concentration in the detected fuel and the alcohol concentration in the actually injected fuel match, and good starting control performance is obtained. Thus, the exhaust emission can be improved.

[0011]

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

The drawings show an embodiment of the present invention, and FIGS. 1 and 2 are flowcharts showing a starting initial control routine, and FIG.
4 is a flow chart showing a heater normal time control routine, FIG. 4 is a flow chart showing a starter motor control routine, FIG. 5 is a flow chart showing a fuel injection control routine, FIG. 6 is a schematic diagram of an engine control system, and FIG. 7 is a schematic diagram of a control device. FIG. 8 is a conceptual diagram showing a startable region and a non-startable region, which are determined by the alcohol concentration and temperature conditions.
FIG. 9 is a conceptual diagram of a startable determination water temperature map, FIG. 10 is a heater characteristic diagram, and FIG. 11 is a time chart showing the control operation of the fuel pump and the PTC heater.

In FIG. 6, reference numeral 1 is an engine body,
In the figure, a horizontally opposed engine is shown. An intake port 2a and an exhaust port 2b are formed in the cylinder head 2 of the engine body 1. An intake manifold 3 is connected to the intake port 2a, and a throttle passage 5 is connected to an upstream side of the intake manifold 3 via an air chamber 4. An air cleaner 7 is attached to the upstream side of the throttle passage 5 via an intake pipe 6,
The air cleaner 7 is communicated with an air intake chamber 8 which is an intake port for intake air.

An exhaust pipe 10 is connected to the exhaust port 2b via an exhaust manifold 9, and a catalytic converter 11 is inserted in the exhaust pipe 10 and connected to a muffler 12. On the other hand, a throttle valve 5a is provided in the throttle passage 5, and an intercooler 13 is provided in the intake pipe 6 immediately upstream of the throttle passage 5,
Further, a resonator chamber 14 is interposed downstream of the air cleaner 7 in the intake pipe 6.

In addition, an idle speed control valve (IS) is provided in a bypass passage 15 that connects the resonator chamber 14 and the intake manifold 3 and bypasses the upstream side and the downstream side of the throttle valve 5a.
CV) 16 is interposed. Furthermore, this ISCV1
A check valve 17 which is opened immediately downstream of 6 when the intake pressure is negative and which is closed when the intake pressure becomes positive by supercharging by a turbocharger 18 described later is interposed. .

Reference numeral 18 denotes a turbocharger, which connects an exhaust side turbine wheel 18a and an intake side compressor wheel 18b through a turbine shaft 18c. A wastegate valve actuating actuator 20 is connected to a wastegate valve 19 provided on the exhaust side of the turbocharger 18. This wastegate valve actuating actuator 20 is partitioned into two chambers by a diaphragm, one of which forms a pressure chamber that communicates with a wastegate valve control duty solenoid valve 21 which is an example of supercharging pressure control means, and the other of which forms the pressure chamber. A spring chamber is formed in which a spring for urging the waste gate valve 19 is closed.

The waste solenoid valve controlling duty solenoid valve 21 includes the compressor wheel 18 of the resonator chamber 14 and the turbocharger 18.
It is provided in a passage communicating with the downstream side of b, and the pressure on the resonator chamber 14 side and the compressor wheel 18b according to a duty ratio r of a control signal output from a control device (ECU) 50 described later. The pressure on the downstream side is regulated and supplied to the pressure chamber of the wastegate valve operating actuator 20, and the wastegate valve operating actuator 20 is operated to generate the wastegate valve 19
Is adjusted to control the supercharging pressure by the turbocharger 18.

An absolute pressure sensor 22 is connected to the intake manifold 3 via a passage 22a, and an intake pipe pressure / atmospheric pressure switching solenoid valve 22b is provided in the passage 22a. The intake pipe pressure / atmospheric pressure switching solenoid valve 22b selectively connects the absolute pressure sensor 22 to the intake manifold 3 side and the atmosphere side. The absolute pressure sensor 22 communicates with the intake manifold 3 to intake air. The pipe pressure (supercharging pressure when supercharging) can be detected.

Further, an injector 23 is provided immediately upstream of each intake port 2a of each cylinder of the intake manifold 3.
And a PTC (Posi) which is an example of heating means for low temperature starting in the fuel injection direction of the injector 23.
live Temperature Coeffici
ent) The heater 3a is provided oppositely. Further, an ignition plug 24 whose tip is exposed to the combustion chamber is attached to each cylinder of the cylinder head 2, and an igniter 31 is connected to the ignition plug 24.

The injector 23 is a bottom feed type which is less affected by fuel separation, and fuel is pumped from an in-tank type fuel pump 33 provided in the fuel tank 32 through a fuel filter 34a interposed in a fuel passage 34. The pressure is regulated by the pressure regulator 35. In the fuel tank 32, a gasoline only fuel, an alcohol only fuel, or a mixed fuel of alcohol and gasoline, that is, an alcohol concentration M of 0% to 100% depending on a user's refueling situation. It is stored between varying.

A surge tank 36 is formed in a portion of the fuel passage 34 adjacent to the inflow side of the injector 23, and an alcohol concentration sensor 37 for detecting the alcohol concentration M in the fuel is attached to the surge tank 36. There is. In the figure, the surge tank 36 has a relatively small capacity and is formed in a shape that allows fuel to be easily mixed. Further, the alcohol concentration sensor 37 is of a capacitance type.

An intake air amount sensor (a thermal air flow meter in the figure) 41 is provided in the intake pipe 6 immediately downstream of the air cleaner 7, and a throttle opening sensor 42 is connected to the throttle valve 5a. It is set up.
Further, a knock sensor 43 is attached to the cylinder block 1a of the engine body 1 and a cooling water passage 4 for communicating both left and right banks of the cylinder block 1a.
4, a water temperature sensor 45 is exposed, and an O2 sensor 46 is exposed in the collecting portion of the exhaust manifold 9 of the exhaust pipe 10.

A crank rotor 25 is mounted on a crank shaft 1b supported by the engine body 1,
A crank angle sensor 26 including an electromagnetic pickup and the like is provided on the outer periphery of the crank rotor 25. Further, a cam rotor 27 connected to the cam shaft 1c of the engine body 1 is provided with a cam angle sensor 28 for cylinder discrimination, which is composed of an electromagnetic pickup and the like. The crank angle sensor 26 and the cam angle sensor 28 are
Not limited to a magnetic sensor such as an electromagnetic pickup, an optical sensor or the like may be used.

Protrusions (or slits) are formed on the outer periphery of the crank rotor 25 at predetermined intervals corresponding to the respective cylinders, and the ECU 50 described later detects the protrusions (or slits) detected by the crank angle sensor 26. The engine speed NE is calculated from the interval time, and the specific protrusion (or slit) serves as a reference crank angle when setting the ignition timing and the fuel injection start timing.

On the other hand, a protrusion (or slit) for cylinder discrimination is formed on the outer periphery of the cam rotor 27,
The ECU 50 determines the cylinder from the interruption of the pulse for detecting the protrusion (or slit) from the cam angle sensor 28.

Further, in FIG. 7, reference numeral 50 is a control unit (ECU) including a microcomputer, which is a CPU.
51, ROM 52, RAM 53, backup RAM 5
4, and the I / O interface 55 is a bus line 56.
Are connected to each other via.

Further, the constant voltage circuit 5 is provided in the ECU 50.
9 is built in, and this constant voltage circuit 59 is connected to the battery 57 via the relay contact of the ECU relay 60,
The relay coil of the ECU relay 60 is connected to the battery 57 via the ignition switch 61. When the ignition switch 61 is turned on, the contact of the ECU relay 60 is turned on, and the battery 57
Is supplied to the constant voltage circuit 59, and the stabilized voltage is supplied from the constant voltage circuit 59 to each part of the ECU 50. On the other hand, the backup voltage is constantly applied to the backup RAM 54 from the constant voltage circuit 59. Further, the fuel pump 33 is connected to the battery 57 via a relay contact of the fuel pump relay 62.

Further, the battery 57 is connected to relay contacts of a starter switch 63 and a heater relay 64. Further, a starter motor 66 is connected to the starter switch 63 via a relay contact of a starter motor relay 65.
On the other hand, the PTC heater 3a is connected to the relay contact of the heater relay 64 via the current sensor 67.

On the other hand, the starter switch 6 is connected to the input port of the I / O interface 55 of the ECU 50.
3, current sensor 67, alcohol concentration sensor 37, intake air amount sensor 41, crank angle sensor 26, cam angle sensor 28, throttle opening sensor 42, water temperature sensor 45,
O2 sensor 46, absolute pressure sensor 22, knock sensor 4
3. The vehicle speed sensor 47 is connected, the battery 57 is further connected, and the battery voltage is monitored.

An igniter 31 is connected to the output port of the I / O interface 55, and further,
ISCV16, injector 2 via drive circuit 58
3, relay coil of fuel pump relay 62, relay coil of heater relay 64, relay coil of starter motor relay 65, waste gate valve control duty solenoid valve 21, intake pipe pressure / atmospheric pressure switching solenoid valve 22
b, and the instrument panel (not shown),
ECS (El) showing the premixed state of fuel and heater warm-up state
An electronic control system lamp 48 is connected.

The ROM 52 stores fixed data such as control programs and various maps, and the RAM 53 stores the above-mentioned sensors after data processing.
The output signals of the switches and the data processed by the CPU 51 are stored. In the CPU 51, when the ignition switch 61 is turned on, the ROM 5
According to the control program stored in No. 2, first, the energization of the starter motor 66 is prohibited, while the fuel pump 3
3 is energized to circulate the fuel. Further, the alcohol concentration M in the fuel immediately after the ignition switch 61 is turned on is compared with the alcohol concentration MOLD when the engine was stopped last time, and when the alcohol concentration changes, the circulation of fuel by the fuel pump 33 is set. Continue for time T1 and premix the fuel before shifting to the normal start control.

When the normal start control is started after the set time T1 has elapsed, it is determined from the present alcohol concentration and temperature conditions whether the engine can be started.

If it is determined that the engine cannot be started, P
After heating the PTC heater 3a to a temperature sufficient to vaporize the fuel by energizing the TC heater 3a, the starter motor 66 is driven to enable the engine to start, and when the engine completes an explosion and rises to a predetermined rotation speed, normal control is performed. Move to.

In the normal control, in addition to the fuel injection control and the ignition timing control based on the output signals from the respective sensors, the duty ratio r for the waste gate valve control duty solenoid valve 21 for controlling the supercharging pressure and the like are set. Calculate

Next, the starting control and fuel injection control by the ECU 50 will be described with reference to the flow charts of FIGS.

The flowchart of FIG. 1 is a start initial control routine which is started at the same time when the ignition switch 61 is turned on and the power is supplied to the ECU 50. First, at step (hereinafter abbreviated as "S") 101, the system is initialized (clear each flag). , The count value is cleared, the output value of each I / O port is set to 0), the interrupt of the heater normal control routine is prohibited in S102, the process proceeds to S103, and the starter motor energization prohibition flag F1 is set (F1 ← 1), and then , S104, the I / O port output value G1 for the relay coil of the fuel pump relay 62 is set to 1, the fuel pump relay 62 is turned on, and the fuel pump 33 is driven.

After that, the process proceeds to S105 and the key switch is turned on.
Sometimes, the absolute value of the difference between the alcohol concentration M (%) in the fuel detected by the alcohol concentration sensor 37 and the alcohol concentration MOLD immediately before the engine stop (stored in the backup RAM 54) and the set value Ms (alcohol at the time of starting) (Determined from experiments etc. with a value that determines whether the change in the concentration M is within the allowable range), and if | M-MOLD |> Ms,
Premixed fuel (fuel circulation by driving only the fuel pump), judging that the alcohol concentration M suddenly changed due to the separation of gasoline and alcohol in the fuel or the replenishment of fuel with different alcohol concentration after the engine was stopped. Therefore, the process proceeds to S106, and if | M-MOLD | ≦ Ms, there is no separation between gasoline and alcohol in the fuel, or there is no sudden change in the alcohol concentration. Therefore, the process jumps to S111 to proceed to the normal start control. .

When the process proceeds from S105 to S106, the ECS lamp 48 provided on the instrument panel is flickered to indicate that the fuel is being premixed, and in S107 a timer is started in order to elapse the premixing time. S108
Go to.

At S108, the time measured by the timer TIM
And a set time T1 sufficient for premixing (sufficient time for the fuel in the fuel circulation system to be uniformly mixed, which is obtained from experiments, etc.)
Is compared, and the loop is repeated until the measured time TIM becomes TIM> T1. When TIM> T1, it is judged that premixing has ended, the process exits the loop and advances to S109, and after resetting the time measurement of the above timer, advances to S110. move on. When the timer count is reset, the blinking of the ECS lamp 48 is also cancelled.

While the loop is repeated in S108,
In the fuel system, the fuel stored in the fuel tank 32 is circulated through the fuel passage 34 by driving the fuel pump 33, returned to the fuel tank 32, and stirred to become a uniform mixed fuel.

When the process proceeds from S109 to S110, the alcohol concentration M in the fuel at the end of the premixing is detected from the output value of the alcohol concentration sensor 37, and the process proceeds to S111 to shift to the normal start control.

From S105 or S110 to S11
When the process proceeds to 1, the startable determination water temperature map MPTs is searched based on the alcohol concentration M, and the startable determination water temperature Tes is set directly or by interpolation calculation.

As shown in FIG. 8, this startable determination water temperature map MPTs has two regions specified by experiments,
That is, the fuel injected from the injector 23 is supplied to the PTC.
It is divided into a region that can be started without being heated by the heater 3a and a region that cannot be started as it is, and indicates the boundary temperature of these regions. As shown in FIG. 9, it is composed of a series of addresses in the ROM 52. Startable judgment water temperature map M
The alcohol concentration M is stored as a parameter in PTs in advance.

As a result, it is determined whether the engine can be started by determining whether the cooling water temperature Tw, which is representative of the engine temperature detected by the water temperature sensor 45, is less than or equal to the startable determination water temperature Tes set according to the alcohol concentration M at that time. In S112, the cooling water temperature Tw is compared with the startable determination water temperature Tes set in S111 to determine whether the engine can be started.

In S112, if Tw> Tes, it is determined that the PTC heater 3a can start without heating, and S113
In step S114, the starter motor energization prohibition flag F1 is cleared to permit energization of the starter motor relay 65, and then the interruption of the heater normal time control routine is permitted in step S114, after which the routine ends.

On the other hand, if Tw ≤ Tes in S112, it is determined that the engine cannot be started, and the process proceeds to S115 in order to warm up the heater, and the I / O port output value G for the ECS lamp 48 is set.
2 is set to 1 and the ECS lamp 48 is turned on to display the heater energization state. In S116, the I / O port output value G3 to the relay coil of the heater relay 64 is set to 1 to turn on the heater relay 64 and energize the PTC heater 3a. To start.

Then, in S117, a timer is started in order to measure the heater energization time, and the process proceeds to S118, and the loop is repeated until the measured time TIM becomes the set time T2 or more,
When TIM> T2, the process exits the loop and proceeds to S119, resets the time measurement of the timer, and then at S120, the consumption current I of the PTC heater 3a detected by the current sensor 67 is compared with the set current ISET.

In S120, when I ≧ ISET, the procedure of reading the consumption current I of the PTC heater 3a from the current sensor 67 again and comparing it with the set current ISET is repeated, and I <
In the case of ISET, it is determined that the heater warm-up is completed and the process proceeds to S121, where the I / O port output value G for the ECS lamp 48 is
2 is set to 0, the EC lamp 48 is extinguished, and the driver is informed of the completion of warming up the heater. Then, the program proceeds to S113, the starter motor energization prohibition flag F1 is cleared to permit energization to the starter motor relay 65, and the heater is heated in S114. After enabling the interrupt of the normal-time control routine, the routine ends.

Here, as shown in FIG. 10, in the PTC heater 3a, when the heater consumption current I rises after energization and the temperature rises to reach the Curie point, the resistance value sharply rises and the consumption current I increases. Starts to decrease, and then the temperature of the PTC heater 3a becomes substantially saturated and the consumption current I becomes a substantially constant value. Therefore, it is impossible to judge the heater warm-up completion state only by the consumption current I.

Therefore, the heater current consumption I and the set current ISE are set after the lapse of the set time T2, avoiding the beginning of the heater energization.
By comparing with T to determine the completion of heater warm-up, erroneous determination is prevented.

As a result, at the time of proceeding from S120 to S121, the PTC heater 3a is heated to the temperature at which the fuel can be vaporized, and the starter motor energization prohibition flag F1 is cleared in S113 to starter motor relay. Even if 65 is turned on and the starter motor 66 is driven to inject fuel from the injector 23 at the same time,
Since the fuel vaporization is promoted by the PTC heater 3a, the engine can be started even at a low temperature.

When the heater normal time control routine interrupt is permitted in S114 of the start initial control routine, the heater normal time control routine shown in FIG. 3 is started every predetermined time.

In this heater normal time control routine, first in S201, the cooling water temperature Tw and the set value TLA4 (cooling water temperature corresponding to the wall surface temperature at which the fuel adhering to the wall surface can be vaporized,
For example, at 25 ° C, but Tes <TLA4) is compared, and Tw
In the case of> TLA4, even if the fuel drops from the PTC heater 3a, it is determined that the wall surface temperature can vaporize, and the process proceeds to S202. In the case of Tw ≦ TLA4, it is determined that the vaporization of the droplet fuel is difficult and the process proceeds to S203. Then, the I / O port output value G3 for the relay coil of the heater relay 64 is set to 1 and the heater relay 64 is turned on to continue heating the PTC heater 3a from the start initial control routine and exit the routine. Also, S2
When it is determined that Tw> TLA4 in 01 and the process proceeds to S202, it is determined whether the current operating state is idle. The idle determination condition is determined based on, for example, the throttle opening and the vehicle speed,
When the throttle is fully closed and the vehicle speed sensor 47 detects the vehicle speed V = 0, it is determined that the vehicle is idle.

When it is determined that the vehicle is idle in S202, S
In step 203, the PTC heater 3a is heated in the same manner as above, and the routine is exited. The amount of fuel injected during idle operation is small, and when this fuel collides with the PTC heater 3a, the surface of the PTC heater 3a is cooled by latent heat of vaporization, and a large amount of fuel is liquefied and irregularly supplied to each cylinder. It may cause instability, so when idle, PTC
The heater 3a is heated to prevent fuel liquefaction.

If it is determined in S202 that the heater is not idle, the process proceeds to S204, in which the heater relay 64 I
/ O port output value G3 is set to 0 and heater relay 64 is turned off.
Then, the heater is de-energized to exit the routine.

Further, the flow chart shown in FIG. 4 is a starter motor control routine which is started every predetermined time. First, in S301, it is determined whether or not the starter switch 63 is turned on. If it is determined that the starter switch 63 is turned on, the process proceeds to S302. The process proceeds to refer to the value of the starter motor energization prohibition flag F1 to determine whether energization to the starter motor 66 is permitted.

In step S302, if F1 = 0, that is, if energization of the starter motor 66 is permitted,
In step 303, the I / O port output value G4 for the relay coil of the starter motor relay 65 is set to 1, the starter motor relay 65 is turned on, engine cranking by the starter motor 66 is enabled, and the routine exits. On the other hand, when the starter switch 63 is OFF in S301 or when F1 = 1 in S302 and the energization of the starter motor 66 is prohibited, the process branches to S304 from each step and the starter motor relay 65 I / O port output value G for relay coil
When 4 is set to 0, the starter motor relay 65 is turned off, the starter motor 66 cannot be driven, and the routine is exited.

Further, the flow chart shown in FIG. 5 is a fuel injection control routine which is started every predetermined time.
At 01, whether the engine speed NE is "0", that is,
Determine if the engine is running. And N
E = 0, that is, when the engine is stopped,
In S402, the fuel injection pulse width Ti is set to 0 (T
i ← 0), exits the routine, and if NE ≠ 0, S40
From 1 to S403, the fuel injection pulse width calculation routine is called, and the optimum fuel injection is performed from the target air-fuel ratio set according to the intake air amount Q, the engine speed NE, the alcohol concentration M, the air-fuel ratio feedback correction coefficient, and the like. The pulse width Ti is calculated and the fuel injection pulse width Ti is set and output at a predetermined timing in S404, and the alcohol concentration M in the fuel detected this time in S405 is stored in a predetermined address of the backup RAM 54 at the previous time. Update the alcohol concentration MOLD (MOLD ← M) and exit the routine.

Since the updating of the alcohol concentration MOLD is stopped when the engine is stopped (the ignition switch is turned off), the alcohol concentration M read at the next start is reduced.
OLD indicates the detected value immediately before the engine was stopped.

FIG. 11 is a time chart showing an example of the starting control.

First, turn on the ignition switch 61.
Then (elapsed time t0), the fuel pump 33 is turned on and the fuel in the fuel tank 32 is circulated through the fuel passage 34. The start control is performed by using the absolute value of the difference between the alcohol concentration M in the fuel when the ignition switch 61 is turned on and the alcohol concentration MOLD when the engine was last stopped (| M-MOL
D |) and also the cooling water temperature Tw.

As shown in FIG. 11B, | M-MOLD
If |> Ms, it is considered that gasoline and alcohol in the fuel are separated, and the ignition switch 61 is used.
From when the switch is turned on (elapsed time t0) to the set time T1,
Only the fuel pump 33 is driven to premix the fuel before shifting to the normal start control. Meanwhile, even if the starter switch 63 is turned on (elapsed time t1), the starter motor 66 is not driven and the engine is not started.

After the elapse of the set time T1, the cooling water temperature T
If w is Tw ≤ Tes, energization to the PTC heater 3a is started and PT is started as shown in FIG. 11 (b) (i).
The C heater 3a is warmed up, and the drive of the starter motor 66 is stopped during that time (elapsed time t2 to t4).

After the heater has been warmed up, the energization of the starter motor 66 is permitted and the engine is started (elapsed time t4).

Then, when the cooling water temperature Tw reaches Tw> TLA4 (however, in the non-idle state), the above PTC
The power supply to the heater 3a is stopped (elapsed time t5).

On the other hand, the cooling water temperature Tw at the end of fuel premixing
Is Tw> Tes, and this cooling water temperature Tw is Tw ≦ TLA
4 Or in idle operation, (b) (i)
As indicated by the solid line in i), the energization of the PTC heater 3a is started and the starter motor 66 is driven to start the engine (elapsed time t2). Then, when the cooling water temperature Tw reaches Tw> TLA4 (however, in the non-idle state), the power supply to the PTC heater 3a is stopped (elapsed time t5).

Further, in FIG. 6B and FIG. 6B, when the cooling water temperature Tw at the end of premixing is Tw> TLA4 and the non-idle operation is performed, the PTC heater 3a is not energized as indicated by the broken line. .

As shown in FIG. 7C, the absolute value of the difference between the alcohol concentration M in the fuel when the ignition switch 61 is turned on (elapsed time t0) and the alcohol concentration MOLD at the previous engine stop (| M -MOLD |) is | M
-MOLD | ≦ Ms, it is considered that gasoline and alcohol in the fuel are not separated, and the cooling water temperature Tw is Tw ≦
In case of Tes, as shown in (c) and (i) of FIG.
The energization of the heater 3a is started, the heater is warmed up for a predetermined time, and the energization of the starter motor 66 is stopped during that time (elapsed time t0 to t3).

After the heater has been warmed up, energization of the starter motor 66 is permitted and the engine is started (elapsed time t3).

The energization of the PTC heater 3a is stopped (elapsed time t5) when the cooling water temperature Tw reaches Tw> TLA4 (however, in the non-idle state).

Further, as shown by the solid line in (c) and (ii) of the figure, the cooling water temperature Tw when the ignition switch 61 is turned ON is Tw> Tes, and this cooling water temperature Tw is Tw ≤TLA4 or idle. When driving,
Energization of the PTC heater 3a is started, and energization of the starter motor 66 is permitted (elapsed time t
0). Therefore, thereafter, the engine is started at the same time when the starter switch 63 is turned on (elapsed time t1).

When the cooling water temperature Tw reaches Tw> TLA4 (however, in a non-idle state), the PTC
The power supply to the heater 3a is stopped (elapsed time t5).

Further, when the ignition switch 61 is turned on in (c) and (ii) of the figure (elapsed time t0)
When the cooling water temperature Tw is Tw> TLA4 and the non-idle operation is performed, the PTC motor 3a is not energized as indicated by the broken line.

[0074]

As described above, according to the present invention,
If the alcohol concentration in the fuel at the engine start changes compared to the alcohol concentration at the previous stop, the fuel is premixed before shifting to the normal start control, so the engine is always started in a homogeneous mixture state. The detected alcohol concentration in the fuel and the alcohol concentration in the actually injected fuel match, good start control performance is obtained, and in addition, exhaust emission can be improved. The effect is played.

[Brief description of drawings]

FIG. 1 is a flowchart showing a start initial control routine.

[Fig. 2] Same as above

FIG. 3 is a flowchart showing a heater normal control routine.

FIG. 4 is a flowchart showing a starter motor control routine.

FIG. 5 is a flowchart showing a fuel injection control routine.

FIG. 6 is a schematic diagram of an engine control system.

FIG. 7 is a schematic diagram of a control device.

FIG. 8 is a conceptual diagram showing a startable region and a non-startable region determined by an alcohol concentration and a temperature condition.

FIG. 9 is a conceptual diagram of a startable determination water temperature map.

FIG. 10 is a heater characteristic diagram.

FIG. 11 is a time chart showing a control operation of a fuel pump and a PTC heater.

[Explanation of symbols]

M: alcohol concentration in fuel MOLD: alcohol concentration in fuel (when the engine last stopped)

Claims (1)

[Claims] 1. A procedure for premixing the fuel when the alcohol concentration in the fuel when the engine is started and the alcohol concentration in the fuel when the engine was last stopped are compared, and the premixing is completed. And a procedure for performing normal-time start control based on the alcohol concentration in the fuel.
V engine start control method.