JPH04279741A - Control method of engine for ffv - Google Patents

Abstract

PURPOSE:To realize the fail-safe of an engine for FFV when a trouble occurs in a sensor to measure the alcohol concn. of a fuel. CONSTITUTION:When the output VM of an alcohol concn. sensor is VML<=VM<=VMH, and it is within a set scope, the alcohol concn. sensor is decided to be normal, the measuring alcohol concn. MS is calculated (S105) depending on the output VM of the alcohol concn. sensor, and the measuring alcohol concn. MS is made as the first alcohol parameter M1 to renew the value (S106). On the other hand, when the output VM of the alcohol concn. sensor is VM<VML or VM>VMH, and it is out of the set scope, the alcohol concn. sensor is decided to be abnormal, an alcohol concn. sensor abnormal discriminating flag FLAGM is set (S107), and the above first alcohol concn. parameter M1 is not renewed but maintained at the value immediately before the trouble. And depending on the above first alcohol concn. parameter M1, an object air-fuel ratio is set, and the fuel injection pulse width is set.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an FFV engine in which a control amount of the engine is set in accordance with the alcohol concentration of fuel.

0002

[Prior Art] In recent years, due to worsening fuel conditions and demands for exhaust gas purification, systems that can use alcohol as an alternative fuel in addition to conventional gasoline are being put into practical use. Vehicles such as automobiles (Flexible Fuel Vehicles (hereinafter referred to as FFV)) can run on not only gasoline, but also a mixture of alcohol and gasoline, or alcohol alone.
The alcohol concentration (content rate) of the fuel used in V is 0% (gasoline only) due to user circumstances when refueling.
and 100% (alcohol only).

Generally, the stoichiometric air-fuel ratio of alcohol fuel is approximately half that of gasoline fuel, so the engine installed in the above-mentioned FFV is equipped with a sensor to measure the alcohol concentration of the fuel, and the engine is controlled according to the alcohol concentration. For example, Japanese Patent Application Laid-Open No. 64-697
The prior art is disclosed in Publication No. 68 and the like.

0004

[Problem to be Solved by the Invention] However, if a failure occurs in the sensor for measuring the alcohol concentration of fuel, if the alcohol concentration based on the output of this sensor is adopted to set the engine control amount, it will naturally occur. This will cause malfunctions and make control difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control method for an FFV engine that achieves fail-safe in the event that a failure occurs in a sensor for measuring the alcohol concentration of fuel. It is said that

[0006]

[Means for Solving the Problems] A control method for an FFV engine according to the present invention includes a procedure for determining whether an alcohol concentration sensor for measuring the alcohol concentration of fuel is normal or not, and a procedure for determining whether or not an alcohol concentration sensor for measuring the alcohol concentration of fuel is normal. The present invention is characterized by comprising a procedure for setting an alcohol concentration parameter based on the determination result of the above-described determination procedure, and a procedure for setting an engine control amount based on the alcohol concentration parameter.

[0007]

[Operation] In the FFV engine control method according to the present invention, an alcohol concentration parameter is set based on the output of the alcohol concentration sensor according to the determination result as to whether the alcohol concentration sensor is normal or not. The engine control amount is set.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings show one embodiment of the present invention, FIGS. 1 to 3 are flowcharts showing procedures for setting fuel injection amount and ignition timing, FIG. 4 is a schematic diagram of the engine control system, and FIG. 5 is a front view of the crank angle sensor and crank rotor. 6 is a front view of the cam angle sensor and cam rotor, FIG. 7 is a circuit configuration diagram of the control device, FIG. 8 is a flowchart showing the cylinder discrimination and engine rotation speed calculation procedure, FIG. 9 is a conceptual diagram of the target air-fuel ratio map, Figure 10 is a conceptual diagram of a fuel evaporation rate map, Figure 11 is a conceptual diagram of a wall surface adhesion rate map, Figure 12 is a conceptual diagram of an injection start crank angle map, Figure 13 is a conceptual diagram of a basic ignition timing map, and Figure 14 is a conceptual diagram of ignition control. Flowchart showing the procedure, FIG. 15 is a flowchart showing the fuel injection control procedure, FIG. 16 is a time chart of fuel injection and ignition, FIG. 17 is a flowchart showing the maximum boost pressure control procedure, and FIG. 18 is the characteristic showing the maximum boost pressure. Figure, Figure 19
is a conceptual diagram of a maximum boost pressure map.

[Configuration of engine control system] In FIG. 4,
Reference numeral 1 denotes an FFV engine (horizontally opposed four-cylinder engine in the figure), and a cylinder head 2 of this engine 1 is formed with an intake port 2a and an exhaust port 2b. An intake manifold 3 is communicated with the intake port 2a, a throttle chamber 5 is communicated upstream of the intake manifold 3 via an air chamber 4, and an air cleaner 7 is attached upstream of the throttle chamber 5 via an intake pipe 6. It is being

On the other hand, an exhaust pipe 9 is communicated with the exhaust port 2b via an exhaust manifold 8, and a catalytic converter 10 is interposed in the exhaust pipe 9. Further, the throttle chamber 5 is provided with a throttle valve 5a, and the intake pipe 6 immediately upstream of the throttle chamber 5 is provided with a throttle valve 5a.
An intercooler 11 is interposed therein, and a resonator chamber 12 is further interposed in the intake pipe 6 on the downstream side of the air cleaner 7. In addition, an idle speed control valve (as an actuator that controls the engine speed) is installed in a bypass passage 13 that communicates the resonator chamber 12 and the air chamber 4 and bypasses the upstream and downstream sides of the throttle valve 5a. ISCV) 14 is interposed, and furthermore, this ISCV 1
A check valve 14a that opens when the intake pressure is negative is provided immediately downstream of the valve 4.

The ISCV 14 is composed of, for example, a rotary valve driven by a duty solenoid, and the amount of air in the bypass passage 10 is increased or decreased depending on the valve opening determined by the duty ratio of the drive signal of the ISCV 14, thereby controlling the idle rotation speed. be done. In addition, in this embodiment, when the duty ratio becomes large, the above-mentioned ISCV14
The valve opening becomes larger.

Reference numeral 15 designates a turbocharger as an example of a supercharger, and a turbine wheel 15a of the turbocharger 15 is housed in a turbine housing 15b interposed in the exhaust pipe 9. A compressor wheel 15d connected to the intake pipe 6 via a turbine shaft 15c is housed in a compressor housing 15e interposed in the intake pipe 6 on the downstream side of the resonator chamber 12.

Further, a waste gate valve 16 is interposed at the inlet of the turbine housing 15b, and a lever 17 connected to the waste gate valve 16 is connected to a diaphragm 18a of a diaphragm actuator 18 via a rod 19. There is. Furthermore, the pressure chamber 18b of the diaphragm actuator 18 is communicated with the intake pipe 6 on the downstream side of the turbocharger 15 via a pressure passage 20. A duty solenoid valve 21 is interposed, and a valve body 21a of the duty solenoid valve 21 is disposed opposite to a discharge port of a pressure reducing passage 22 communicating with the resonator chamber 12.

[0014] The duty solenoid valve 21 includes:
It is controlled by a duty signal supplied from a control device (ECU) 41, which will be described later, to regulate the pressure supplied to the pressure chamber 18b of the diaphragm actuator 18, and adjust the pressure inside the pressure chamber 18b and the diaphragm 18a of the diaphragm actuator 18 in the backward direction. Constantly biasing rod 19
The maximum supercharging pressure is controlled by controlling the opening area of the inlet of the turbine housing 15b by the wastegate valve 16 in balance with the diaphragm spring 18c that biases the wastegate valve 16 in the closing direction via the lever 17. . In this embodiment, as the duty ratio of the duty signal increases, the opening time per unit time of the pressure reducing passage 22 by the valve body 21a of the duty solenoid valve 21 increases, and the pressure is supplied to the pressure chamber 18b of the diaphragm actuator 18. Compressor wheel 15d
Since the leakage amount of the downstream positive pressure is increased, the supercharging pressure at which the waste gate valve 16 starts to open is relatively increased, and the maximum supercharging pressure by the turbocharger 15 is increased.

Further, each intake port 2a of each cylinder of the intake manifold 3 is provided with an intake port heater 23 for low-temperature starting. The injector 24 faces the cylinder head 2, and a spark plug 40 is attached to each cylinder of the cylinder head 2, the tip of which is exposed to the combustion chamber.

Each injector 24 is communicated with a fuel tank 26 through a fuel passage 25, and this fuel tank 26 contains a fuel consisting only of gasoline, a fuel consisting only of alcohol, or a predetermined alcohol concentration of alcohol and gasoline. Mixed fuel, ie, fuel whose alcohol concentration varies between 0% and 100% depending on the user's refueling circumstances, is stored.

Further, an in-tank type fuel pump 27 is provided in the fuel tank 26, and this fuel pump 27
The fuel is fed under pressure to the injector 24 and pressure regulator 30 through the fuel filter 28 and alcohol concentration sensor 29 installed in the fuel passage 25, and from the pressure regulator 30 to the fuel tank 26.
The fuel is returned and the fuel pressure is regulated to a predetermined pressure.

The alcohol concentration sensor 29 is composed of, for example, a pair of electrodes provided in the fuel passage 25, and detects the alcohol concentration by detecting a change in current based on a change in electrical conductivity of the fuel. . Note that this alcohol concentration sensor 29 is not limited to the type that utilizes changes in electrical conductivity, and may also be of a resistance detection type, a capacitance type, or an optical type.

Further, an air flow meter (a hot wire type air flow meter in the figure) 31 is installed in the intake pipe 6 immediately downstream of the air cleaner 7, and a throttle opening sensor 32a is connected to the throttle valve 5a.
An idle switch 32b for detecting fully closed throttle valve 5a is connected thereto. Furthermore, the engine 1
A knock sensor 33 is attached to the cylinder block 1a, a cooling water temperature sensor 34 faces a cooling water passage (not shown) formed in the cylinder block 1a, and an O2 sensor 35 faces the exhaust pipe 9. There is.

Further, a crank rotor 36 is pivotally attached to the crankshaft 1b supported by the cylinder block 1a, and a crank angle sensor 37 is disposed opposite to the outer periphery of the crank rotor 36. A cam angle sensor 39 for cylinder discrimination consisting of an electromagnetic pickup or the like is provided opposite to the cam rotor 38 connected to the cam rotor 1c.

As shown in FIG. 5, the crank rotor 36 has protrusions 36a, 36b, and 36c formed on its outer periphery, and these protrusions 36a, 36b, and 36c, for example, and #3, #4) before compression top dead center (BTDC) θ1, θ2, θ3 positions (for example, θ1
= 97°, θ2 = 65°, θ3 = 10°). That is, the protrusion 36a indicates the reference crank angle when setting the ignition timing and fuel injection timing, and the protrusions 36a, 36
The engine rotation period f is calculated from the transit time between b,
Further, the protrusion 36c serves as a reference crank angle indicating fixed ignition timing.

Further, on the outer periphery of the cam rotor 38, as shown in FIG.
8c is formed, and for example, the protrusion 38a is at the position θ4 after compression top dead center (ATDC) of #3 and #4 (for example, θ4 =
20°), and the protrusion 38b is composed of three protrusions, and the first protrusion is formed at the ATDC θ5 position of the #1 cylinder (for example, θ5 = 5°). Furthermore, protrusion 3
8c is formed of two protrusions, and the first protrusion is formed at the ATDC θ6 position of the #2 cylinder (for example, θ6 = 20°).

The crank angle sensor 37 and the cam angle sensor 39 are not limited to magnetic sensors such as electromagnetic pickups, but may also be optical sensors.

[Circuit configuration of control device] On the other hand, in FIG. 7, reference numeral 41 is a control device (ECU) consisting of a microcomputer, etc.
M44, backup RAM 44a, and I/O interface 45 are connected to each other via bus line 46, and a constant voltage circuit 47 supplies a predetermined stabilized voltage to each part.

The constant voltage circuit 47 includes an ECU relay 48
A relay coil of the ECU relay 48 is connected to the battery 49 via an ignition switch 50. Further, a starter motor 62 is connected to the battery 49 via a starter switch 60 and a relay contact of a starter motor relay 61, and a fuel pump 27 is connected to the battery 49 via a relay contact of a fuel pump relay 51.
Further, the intake port heater 23 of each cylinder is connected from the relay contact of the heater relay 52 via a current sensor 63.

[0026] Also, the I/O interface 45
Each of the above-mentioned sensors 29, 31, 32a,
33, 34, 35, 37, 39, 63, the idle switch 32b, and the starter switch 60 are connected, and the battery 49 is connected to monitor the battery voltage, while the I/O interface 45
The igniter 40a of the spark plug 40 is connected to the output port of the spark plug 40.
is connected, and furthermore, via the drive circuit 58, ISCV
14, a duty solenoid valve 21, an injector 24, each relay coil (fuel pump relay 51, heater relay 52, starter motor relay 61), and an LED 59 as a failure display means for indicating the occurrence of an abnormality.

A serial monitor 65, which is a vehicle diagnostic device, can be connected to the I/O interface 45 through an external connector 64, and can be connected to a serial monitor 65, which is a vehicle diagnostic device, by reading trouble codes stored in the backup RAM 44a. , it is possible to understand the details of the failure.

The ROM 43 stores fixed data such as control programs and various maps, and the RAM 44 stores data after processing the output signals of the sensors and switches, as well as the above data. Data processed by the CPU 42 is stored. Further, the backup RAM 44a stores trouble codes when a failure occurs, first and second alcohol concentration parameters to be described later, and the data is retained even when the ignition switch 50 is OFF.

In accordance with the control program stored in the ROM 43, the CPU 42 controls various parameters such as fuel injection amount, ignition timing, and the duty ratio of the signal for driving the duty solenoid valve 21, based on various data stored in the RAM 44. A control amount is set, and a corresponding signal is used to control the injector 24, igniter 40a, and air-fuel ratio, and a drive signal is output to the duty solenoid valve 21 to control the maximum boost pressure by the turbocharger 15.

[Operation] Next, the operation of the embodiment having the above configuration will be explained. (Cylinder discrimination, engine rotation speed calculation procedure) FIG. 8 shows a routine for cylinder discrimination and engine rotation speed calculation that starts interruptively in response to a crank pulse input from the crank angle sensor 37.
7 and the output signal of the cam angle sensor 39, the ignition target cylinder #i is determined, and in step S202, #i
(+2) Determine the cylinder to which fuel is to be injected.

That is, as shown in the time chart of FIG. 16, for example, when a cam pulse of θ5 (projection 38b) is output from the cam angle sensor 39, the next compression top dead center is cylinder #3, and this It can be determined that the #3 cylinder is the target cylinder for ignition and the #4 cylinder is the target cylinder for fuel injection.

Furthermore, after the cam pulse of θ5, θ
4 When the cam pulse (protrusion 38a) is output, the next compression top dead center is the #2 cylinder, and it can be determined that the #2 cylinder is the ignition target cylinder and the #1 cylinder is the fuel injection target cylinder. .

Similarly, the compression top dead center after the cam pulse of θ6 (protrusion 38c) is output is the #4 cylinder;
The 4th cylinder becomes the cylinder targeted for ignition, and the #3 cylinder becomes the cylinder targeted for fuel injection. Also, after the cam pulse of θ6 above, θ4
When the cam pulse of (protrusion 38a) is output, it can be determined that the subsequent compression top dead center is the #1 cylinder, the #1 cylinder is the ignition target cylinder, and the #2 cylinder is the fuel injection target cylinder.

Furthermore, after the cam pulse is output from the cam angle sensor 39, the crank pulse output from the crank angle sensor 37 is used to set the reference crank angle (θ1) for setting the ignition timing and fuel injection start timing of the corresponding cylinder.
).

That is, in the 4-cycle 4-cylinder engine 1 of this embodiment, the combustion stroke is in the order of cylinders #1 → #3 → #2 → #4, and if the cylinder to be ignited in the #i cylinder is the #1 cylinder. At this time, the fuel injection target cylinder is the #2 cylinder, and the next #i (+2) fuel injection target cylinder is the #4 cylinder. Then, ignition is performed in the order of cylinders #1 → #3 → #2 → #4, and fuel injection is performed sequentially once every 720° C.A (two engine revolutions) to the corresponding cylinders.

Next, in step S203, the engine rotation speed NE is calculated. For example, the crank angle sensor 3
7 to detect the BTDC θ1 and θ2 to find the period f (f=dt (θ1
-θ2)/d (θ1 -θ2)), calculate the engine rotation speed NE from this period f (NE ←60/f),
The rotation speed data is stored at a predetermined address in the RAM 44, and the routine exits.

(Fuel injection amount and ignition timing setting procedure) On the other hand,
According to the interrupt routine shown in FIGS. 1 to 3 at predetermined time intervals,
Ignition timing θIG, fuel pulse width T corresponding to fuel injection amount
i is set, first, in step S101, the output VM of the alcohol concentration sensor 29 is read, and then, in step S102, it is determined that the output VM of the alcohol concentration sensor 29 is within the setting range of the upper limit value VMH and the lower limit value VML. Determine whether or not.

In step S102, the output VM of the alcohol concentration sensor 29 satisfies VML≦VM≦VM.
H and within the set range, the alcohol concentration sensor 29 is determined to be normal and the process proceeds to step S102.
The process advances to step S103, where the alcohol concentration sensor abnormality determination flag FLAGM is cleared (FLAGM ←
0), in step S104, the LED as a failure indicator
59 is turned off. The alcohol concentration sensor abnormality determination flag FLAGM is stored in the backup RAM4.
4a, and by reading it on the serial monitor 65, it is possible to know if there is an abnormality in the alcohol concentration sensor 29. Next, when the process proceeds from step S104 to step S105, the measured alcohol concentration MS is calculated based on the output VM of the alcohol concentration sensor 29, and in step S106, the measured alcohol concentration MS is calculated based on the output VM of the alcohol concentration sensor 29.
is stored at a predetermined address in the backup RAM 44a as the first alcohol concentration parameter M1 (M1
←MS ) and update the already stored value (M
The initial set value of 1 is M1 = 0) Step S1
Proceed to 09.

On the other hand, in S102 above, when the output VM of the alcohol concentration sensor 29 is VM < VML or VM > VMH and is outside the setting range,
When it is determined that the alcohol concentration sensor 29 is abnormal, the process branches from step S102 to step S107, and when the alcohol concentration sensor abnormality determination flag FLAGM is set (FLAGM ←1), the LED 59 as a failure indicating means is turned on in step S108. , step S10
Proceed to 9. That is, when the alcohol concentration sensor 29 is abnormal, the first alcohol concentration parameter M1 is not updated and is held at the value immediately before the failure.

In step S109, the engine speed NE stored at a predetermined address in the RAM 44 is read out, and the engine speed is adjusted based on this engine speed NE.
The time per two rotations, time1/2, is calculated from the following equation (1).

[0041] time1/2 =30/NE
...(1) Equation (1) above calculates the time per stroke in a 4-cylinder engine.For an evenly spaced combustion engine with n cylinders, Equation (1) above is calculated as follows (
1) It can be calculated from the formula.

time1/n/2 = (60/n/2)/NE
...(1)'Next, the process proceeds to step S110, and the weighting coefficient (weighted average weight) TNnew per stroke is calculated from the following equation (2).

TNnew=time1/2×COF
...(2) COF: Fixed value Then, in step S111, the measured intake air flow velocity Q (g/sec) based on the output of the air flow meter 31 is read, and the weighting coefficient TNo set in the previous routine is read.
ld, and read out the corrected intake air flow rate Qaold. Note that in the first routine, TNold=0 and Qaold=0.

After that, the process advances to step S112, and the corrected intake air flow rate Qanew that compensates for the first-order delay is calculated using the following (3
) Calculated from the formula.

[0045] Then, in step S113, the amount of air Qp taken into one cylinder during the intake stroke is calculated from the following equation (4), thereby compensating for the first-order lag and correcting the overshoot during the transition.

Qp=Qanew×time1/2
(4) The theoretical formula for the above-mentioned corrected intake air flow rate Qanew is detailed in Japanese Patent Laid-Open No. 2-5745, which was previously filed by the present applicant.

Next, the process proceeds to step S114, and based on the output values of the throttle opening sensor 32a, the idle switch 32b, and the coolant temperature sensor 34, various increase amounts such as increase corrections are made at the time of starting, when the engine is cold, and when the throttle is fully open. Set the correction coefficient COEF. However, acceleration increase correction is not performed.

Thereafter, in step S115, the air-fuel ratio feedback correction coefficient α is set based on the output signal of the O2 sensor 35, and in step S116, the backup R
The target air-fuel ratio map MPA/F is referred to based on the first alcohol concentration parameter M1 read from AM44a, the amount of air taken into one cylinder in the intake stroke Qp, and the engine speed NE, and the target is determined with interpolation calculation. Set the air-fuel ratio A/F.

Next, when the process proceeds from step S116 to step S117, the fuel evaporation rate map MPβ is referred to with interpolation calculation based on the engine speed NE, the cooling water temperature Tw, and the first alcohol concentration parameter M1.
Intake port 2 during 2 revolutions (1 cycle) of the engine
The rate of evaporation of the fuel adhering to a, that is, the fuel evaporation rate β is set, and then, in step S118, the corrected intake air flow rate Qanew, the fuel injection pulse width Ti set in the previous routine, and the first alcohol concentration parameter are set. M
1 with reference to the wall adhesion rate map MPX with interpolation calculation based on Proceed to S119.

In the first routine, since the fuel injection pulse width Ti is not set, it is set to X=0.

The fuel evaporation rate β is controlled by the wall temperature, period, and alcohol concentration M. In other words, the higher the wall surface temperature, the greater the fuel evaporation rate β, and as the engine speed NE increases, the cycle becomes shorter, so the fuel adhesion time until the next intake stroke is shorter, and the fuel evaporation rate β increases accordingly. The value becomes smaller. Furthermore, the higher the alcohol concentration, the higher the latent heat of vaporization, which makes it difficult for fuel to evaporate, and the fuel evaporation rate β
The value of becomes smaller.

Further, the change in the wall surface adhesion rate X is controlled by the intake air flow rate Qanew, the fuel injection pulse width Ti (fuel injection amount), and the alcohol concentration. That is, as the intake air flow rate Qanew increases, the vaporization time becomes shorter and the wall surface adhesion rate X increases. In addition, the intake air flow rate Qanew
When constant, the fluctuation width of the wall surface adhesion amount is minute with respect to the change in fuel injection amount, and therefore the fuel injection pulse width Ti
When becomes large, the above-mentioned wall surface adhesion rate X becomes a relatively small value. Furthermore, as the alcohol concentration of the fuel increases, the latent heat of vaporization increases, making it difficult for the fuel to evaporate, so the wall surface adhesion rate X becomes a relatively large value.

Therefore, the fuel evaporation rate β can be captured as a function of the cooling water temperature Tw, the engine speed NE, and the alcohol concentration.
Engine speed NE and cooling water temperature TW as shown in 0
A fuel evaporation rate map MPβ is constructed based on the first alcohol concentration parameter M1 and the first alcohol concentration parameter M1, and a fuel evaporation rate β determined in advance through experiments or the like is stored in each region. Furthermore, Figure 1
1, the wall adhesion rate map MPX is the first
Alcohol concentration M1 and corrected intake air flow rate Qanew
The map is composed of a map based on the fuel injection pulse width Ti and the fuel injection pulse width Ti, and the wall surface adhesion rate X determined in advance through experiments is stored in each region.

Then, when the process proceeds from step S118 to step S119, the intake port residual fuel amount Mf4 set four strokes (one cycle) ago is read out, and the process proceeds to step S1.
20, the fuel injection amount Gf per injection is as follows (5)
Set from a formula. Note that Mf4=0 until the fuel injection routine is executed four times from the first time.

Gf = {(Qp/A/F)×COEF−βMf4}/
(1 - When fuel is injected into the intake port 2a of a cylinder, a portion of the fuel is not inhaled into the cylinder (combustion chamber) but adheres to the intake valve, intake port wall, etc. This adhering fuel evaporates appropriately while the engine rotates twice, and this evaporated fuel is taken into the cylinder together with the fuel injected in the next intake stroke.

Here, the amount of fuel actually supplied into the cylinder per injection Ge is the amount of fuel that does not adhere to the wall surface (1-
The sum of X) Gf and the evaporation amount Mf4·β, that is, the following equation (6) is obtained, and from this equation (6), the required fuel amount Gf per injection is determined by the following equation (7).

Ge = (1-X)Gf +Mf4·β
...(6) Gf = (Ge - Mf4・β)/
(1-X) ...(7) The actual amount of fuel supplied into the cylinder Ge is the target air-fuel ratio A/F and the air amount Qp.
This is the target value for fuel supply based on
) can be expressed by the formula (8) and (7)
When substituted into the equation, the above equation (5) is obtained.

Ge = Qp ・COEF/(A/F)
...(8) Next, step S
121, the current intake port residual fuel amount Mf is determined by the following (
9) Set from formula.

Mf = (1-β)×Mf4+X・Gf
...(9) In other words, the amount of residual fuel at the intake port Mf immediately after fuel injection is the remaining amount (1-β) x Mf4 obtained by subtracting the evaporation from the fuel adhering to the previous corresponding cylinder, and the amount of fuel injected this time. It is the sum of the attached amount X・Gf. In addition, from the first time until the fourth injection is executed, Mf=X
・Gf becomes.

Thereafter, in step S122, the voltage correction pulse width TS for correcting the invalid time is determined based on the battery voltage.
is set, and in step S123, the fuel injection pulse width Ti that actually drives the injector 24 is set to the following (10
) Set based on the formula.

[0061] Ti=K・Gf・α+Ts
...(10) K: Injector characteristic correction coefficient, that is, the above fuel injection amount Gf performs wall fuel adhesion prediction correction and evaporation correction for wall adhesion fuel,
This prevents the air-fuel ratio from becoming rich during transient times, especially at low rotational speeds, prevents sluggishness during transient times, and improves output responsiveness. Furthermore, acceleration increase correction becomes unnecessary, improving air-fuel ratio controllability and preventing wasteful consumption of fuel.

In this case, the latest alcohol concentration measured when the alcohol concentration sensor 29 is normal is used instead of using the air-fuel ratio correction coefficient according to the alcohol concentration of the fuel in the fuel injection pulse width calculation as in the conventional case. The target air-fuel ratio A/F is determined by the first alcohol concentration parameter M1, which is
is set, and the fuel injection pulse width Ti is set to achieve this target air-fuel ratio A/F. Therefore, even if the alcohol concentration sensor 29 becomes abnormal, feedback control by the O2 sensor 35 is performed as long as the alcohol concentration of the fuel does not suddenly change. acts effectively, preventing abnormalities in the air-fuel ratio and achieving failsafe.

Thereafter, in step S124, the injection start crank angle θINJST is set based on the injection start crank angle map MPθINJST using the engine speed NE and the fuel injection pulse width Ti as parameters.

As shown in FIG. 12, the injection start crank angle map MPθINJST is determined by the engine speed N
The map is composed of a map using E and the fuel injection pulse width Ti as parameters, and each region stores an optimal injection start crank angle θINJST obtained from calculations in advance. This injection start crank angle θINJST is
The larger the engine rotational speed NE and the fuel injection pulse width Ti are, the more advanced the angle is set.

Thereafter, the process advances to step S125, where the previous data TNold is updated using the weighting coefficient TNnew set in step S110 (TNold←TN
new). Further, in step S126, the step S
The previous data Qaold is updated with the corrected intake air flow rate Qanew set in step 112 (Qaold←Qan
ew), the process advances to step S127.

In step S127, the engine rotation speed N
Determine whether E has reached the perfect rotational speed NKAN,
When NE < NKAN, in step S128, the ignition timing θIG is fixed to the fixed ignition timing ADVS (θIG
←ADVS), exit the routine, while NE ≧NK
When AN, steps S127 to S1
Branch to 29 and alcohol concentration sensor abnormality determination flag F
Referring to the value of LAGM, it is determined whether the alcohol concentration sensor 29 is normal or not.

[0067] Then, in the above step S129, FLA
When GM = 0 and the alcohol concentration sensor 29 is normal, in step S130, the measured alcohol concentration MS is stored in the backup RAM 44a as the second alcohol concentration parameter M2 (M2 ← MS
) Proceeding to step S132, if FLAGM = 1 and the alcohol concentration sensor 29 is abnormal, then in step S131 the second alcohol concentration parameter M2 is set.
is cleared (M2←0) and the process proceeds to step S132. Note that the second alcohol concentration parameter M2 is
M2 is initially set to 0.

[0068] In step S132, the engine rotation speed N
The basic ignition timing map MPθBASE is referred to based on E, the amount of air taken into one cylinder Qp, and the second alcohol concentration parameter M2, and the basic ignition timing (angle) θBASE with interpolation calculation is referred to. As shown in FIG. 13, each address of the basic ignition timing map MPθBASE is set based on the engine speed NE, the amount of air taken into one cylinder Qp, and the second alcohol concentration parameter M2. If the calculated and optimal basic ignition timing θBASE (crank angle based on θ2) is stored, and the amount of air taken into one cylinder Qp and the engine speed NE are the same, the second alcohol concentration parameter M2 is A small value of basic ignition timing θBASE is stored so that the larger the amount of advance (the higher the alcohol concentration), the larger the amount of advance.

Thereafter, the process proceeds to step S133, where the knock control value (angle) θNK is set based on the signal from the knock sensor 33, and then the process proceeds to step S134, where this knock control value θNK is set in step S132. Calculate the ignition timing θIG by adding it to the basic ignition timing θBASE (θIG←θBASE+θ
NK) Exit the routine.

In calculating the ignition timing θIG, if the alcohol concentration sensor 29 is abnormal, the basic ignition timing θIG
Since BASE is set to the most retarded side with the second alcohol concentration M2 being "0", the occurrence of knocking is prevented and the engine 1 is controlled to the safe side.

(Ignition and fuel injection control procedure) When the ignition timing θIG and fuel injection pulse width Ti are set by the above procedure, an ignition signal and a fuel injection signal are output according to the flowcharts of FIGS. 14 and 15. .

In the ignition control procedure shown in FIG. 14, an interrupt occurs when the current crank angle calculated based on the crank pulse input reaches the ignition timing θIG set in the above-mentioned routine (steps S128 and S134).
Executed every 0°CA.

That is, in step S301, an ignition signal is output to the ignition target cylinder #i determined in the above-described cylinder determination and engine speed calculation procedure, and the routine exits.

In the fuel injection control procedure shown in FIG. 15, an interrupt occurs when the current crank angle calculated based on the crank pulse input reaches the injection start crank angle θINJST set in the above routine (step S124). , similarly executed every 180° CA.

First, in step S401, a drive pulse signal with a fuel injection pulse width Ti is output to the injector 24 of the fuel injection target cylinder #i (+2) determined in the above-described cylinder determination and engine rotation speed calculation procedure. . Next, the process advances to step S402, where the previous intake port residual fuel amount Mf1 is updated with the current intake port residual fuel amount Mf set in the above-described fuel injection amount setting procedure (Mf1
←Mf ), similarly update each data sequentially (Mf2←
Mf1, Mf3←Mf2, Mf4←Mf3).

As a result, the intake port residual fuel amount Mf4 read out in step S119 of the above-described fuel injection amount setting procedure is always the residual fuel of the previous cycle, that is, the residual fuel of the relevant cylinder. In the case of an n-cylinder engine, the intake port residual fuel amount Mfn one cycle before is equal to the previous intake port residual fuel amount M
It will be updated at fn-1.

(Maximum Boost Pressure Control Procedure) On the other hand, the boost pressure by the turbocharger 15 is controlled according to the procedure shown in FIG. 17, and the procedure will be explained below. First, in step S501, the second alcohol concentration parameter M2
, engine speed NE, and 1 in the intake stroke
The maximum boost pressure map MCHMAX is referred to using the air amount Qp taken into the cylinder as a parameter, and the duty ratio DUTYMAX is set with interpolation calculation.

Next, the process advances to step S502, and the duty ratio DUTYMAX set in step S501 is
The duty signal of D is output to the duty solenoid valve 21, and the energization time of this duty solenoid valve is set to the duty ratio D until the next routine is executed.
Keep it in UTYMAX.

That is, the octane number of alcohol (methanol, ethanol, etc.) is higher than that of gasoline, and when alcohol is mixed with gasoline, the mixed octane number increases as the alcohol concentration M increases, and the frequency of knock occurrence decreases. As the engine speed NE increases, the combustion chamber temperature increases and pre-ignition is more likely to occur, while when the alcohol concentration is low, the knocking frequency increases and pre-ignition is less likely to occur.

Therefore, as long as knocking and pre-ignition do not occur, it is possible to increase the maximum boost pressure of the engine 1 according to the alcohol concentration of the fuel, and it is possible to increase the maximum boost pressure of the engine 1 according to the alcohol concentration of the fuel. %) ~ M100 (alcohol concentration 100%)
The maximum boost pressure for changes with engine speed N, and when the amount of air taken into one cylinder Qp is constant, Fig. 1
The relationship is as shown in 8. As a result, for example, when the alcohol concentration M100 is set, the maximum supercharging pressure can be lowered in a high engine speed region, while when the alcohol concentration M0 is, the maximum supercharging pressure can be increased as the engine speed increases.

For this reason, the duty ratio for obtaining the maximum boost pressure corresponding to the alcohol concentration M and the engine speed N was found through experiments, and as shown in FIG. Number NE
Knocking and pre-ignition can be avoided by storing the corresponding duty ratio DUTYMAX in each address of the maximum boost pressure map MCHMAX, which is composed of parameters Qp and the amount of air taken into one cylinder. At the same time, it is possible to realize precise maximum boost pressure control according to the engine condition and alcohol concentration, and the output performance of the engine 1 can be improved.

Also in this boost pressure control, when the alcohol concentration sensor 29 is abnormal, the second alcohol concentration parameter M2 is "0", and the fuel is gasoline 10
Since the duty ratio DUTYMAX is set in the direction in which the maximum boost pressure is reduced as it is in the 0% state, engine 1 is controlled on the safe side, and damage caused by knocking and pre-ignition is avoided, achieving a fail-safe. It is possible.

(Operation of supercharging pressure control system) Next, the operation of the supercharging pressure control system for varying the maximum supercharging pressure will be explained. When the engine 1 operates, the exhaust gas pressure (exhaust pressure) flowing through the exhaust pipe 9 rotates the turbine wheel 15a of the turbocharger 15, and the compressor wheel 15d connected to the turbine wheel 15a via the turbine shaft 15c rotates. and supercharges the intake air.

[0084] Exhaust pressure is low when the engine is under low load and at low rotation speeds.
Therefore, the supercharging pressure at the compressor wheel 15d is also low. On the other hand, as the engine speed and load increase, the boost pressure also gradually increases. Here, according to the maximum boost pressure control procedure described above, the higher the alcohol concentration of the fuel, the greater the duty signal that is applied to the duty solenoid valve 21. The opening time per unit time of 22 is increased, and the amount of leakage of the supercharging pressure downstream of the compressor wheel 15d of the turbocharger 15 acting on the pressure chamber 18b of the diaphragm actuator 18 via the pressure passage 20 increases. minute, the supercharging pressure applied to the pressure chamber 18b of the diaphragm actuator 18 becomes lower, and the diaphragm 18a of the diaphragm actuator 18 resists the biasing force of the diaphragm spring 18c, and the waste gate valve is opened via the rod 19 and lever 17. The supercharging pressure by the turbocharger 15 until the valve 16 is opened is relatively increased, and the maximum supercharging pressure is increased.

Then, the supercharging pressure by the turbocharger 15 increases, and the pressure chamber 18 of the diaphragm actuator 18 is regulated by the duty solenoid valve 21 according to the duty signal of the duty ratio DUTYMAX.
When the supercharging pressure acting on the diaphragm actuator 18 increases and the supercharging pressure by the turbocharger 15 reaches the maximum supercharging pressure, the regulated supercharging pressure acting on the pressure chamber 18b of the diaphragm actuator 18 is applied to the diaphragm 18a. Overcoming the biasing force of the diaphragm spring 18c, the diaphragm 18
A rod 19 connected to the rod 19 is protruded, and the waste gate valve 16 is connected via a lever 17 connected to the rod 19.
rotates in the clockwise direction in FIG.

As a result, the waste gate valve 16 is gradually opened, and the opening area of the inlet of the turbine housing 15b housing the turbine wheel 15a is gradually expanded. A part of the exhaust gas passing through this inlet bypasses the turbine wheel 15a, and accordingly,
This reaction of the turbine wheel 15a becomes small, and the supercharging pressure by the turbocharger 15 is prevented from exceeding the maximum supercharging pressure, and is maintained at the maximum supercharging pressure.

[0087]

[Effects of the Invention] As explained above, according to the present invention, depending on the result of determining whether or not the alcohol concentration sensor is normal,
The alcohol concentration parameter is set based on the output of the alcohol concentration sensor, and the engine control amount is set based on this alcohol concentration parameter, so even if the alcohol concentration sensor is abnormal, a failsafe is performed and the engine is kept on the safe side. Excellent effects can be obtained, such as control over

[Brief explanation of the drawing]

[Figure 1] Flowchart showing fuel injection amount and ignition timing setting procedure

[Figure 2] Flowchart showing fuel injection amount and ignition timing setting procedure

[Figure 3] Flowchart showing fuel injection amount and ignition timing setting procedure

[Figure 4] Schematic diagram of engine control system

[Figure 5] Front view of crank angle sensor and crank rotor

[
Figure 6: Front view of cam angle sensor and cam rotor

[Figure 7] Circuit configuration diagram of control device

[Fig. 8] Flowchart showing cylinder discrimination and engine rotation speed calculation procedure

[Figure 9] Conceptual diagram of target air-fuel ratio map

[Figure 10] Conceptual diagram of fuel evaporation rate map

[Figure 11] Conceptual diagram of wall adhesion rate map

[Figure 12] Conceptual diagram of injection start crank angle map

[Figure 1
3] Conceptual diagram of basic ignition timing map

[Figure 14] Flowchart showing ignition control procedure

[Fig. 15] Flowchart showing fuel injection control procedure

[Figure 16] Fuel injection and ignition time chart

[Figure 17] Flowchart showing maximum boost pressure control procedure

[Figure 18] Characteristic diagram showing maximum boost pressure

[Figure 19] Conceptual diagram of maximum boost pressure map

[Explanation of symbols]

1 FFV engine 29 Alcohol concentration sensor M1 Alcohol concentration parameter M2 Alcohol concentration parameter

Claims (1)

[Claims] Claim 1: A procedure for determining whether an alcohol concentration sensor for measuring the alcohol concentration of fuel is normal or not, and an alcohol concentration parameter based on the output of the alcohol concentration sensor according to the determination result of the determination procedure. 1. A method for controlling an FFV engine, comprising: a procedure for setting an engine control amount based on the alcohol concentration parameter; and a procedure for setting an engine control amount based on the alcohol concentration parameter.