JPH0367035A - Fuel injection controller of alcohol engine - Google Patents

Abstract

PURPOSE:To perform stable fuel injection with an injector for a normal gasoline engine by providing fuel injection time set means which sets a fuel injection time of the injector based on a fuel pressure set value which is set by a fuel pressure adjusting means. CONSTITUTION:Fuel pressure is set in response to alcohol concentration by a fuel pressure adjusting means of an controller 31, and a pressure control value of an fuel pressure regulator 18 is varied in response to a fuel pressure set value. The fuel pressure is controlled by the fuel pressure regulator 18 in response to alcohol concentration, and a fuel injection time of an injector 10 is set by a fuel injection time set means inside a device 31 based on he pressure set value set by a fuel pressure adjusting means. As a result, fuel is injected for the fuel injection time from the injector 10 under the fuel pressure in response to the alcohol concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fuel injection control device for an alcohol engine that varies fuel pressure based on alcohol level and obtains a stable fuel injection angle.

[Conventional technology and issues to be solved by Komei] In recent years, due to worsening fuel conditions and demands for exhaust purification, in addition to conventional gasoline, alcohol has been used as an alternative fuel.
A system that can be used for
Fuel Vehicles (hereinafter referred to as rFFVJs) can run not only on gasoline, but also on a mixed fuel of alcohol and gasoline, or on alcohol alone.

The engine of this FFV is, for example, JP-A-58-285
As disclosed in Publication No. 57, the alcohol concentration in the mixed fuel of alcohol and gasoline is detected by an alcohol sensor, and the fuel injection amount is corrected based on the alcohol concentration to maintain the stoichiometric air-fuel ratio. ing.

However, the stoichiometric air-fuel ratio when using alcohol is approximately 1/2 of that when using gasoline, and the higher the alcohol concentration of the fuel, the lower the stoichiometric air-fuel ratio.

Therefore, in the above-mentioned FFV engine, under the same engine operating conditions as a conventional gasoline engine, when the fuel alcohol engine is 100% (gasoline 0%), when the alcohol level is O% (gasoline 100%), On the other hand, approximately twice the amount of fuel injection is required, and the capacity of the injector must be approximately twice as large.

In this case, for example, simply enlarging the nozzle diameter of a conventional injector to roughly double its capacity would result in an increase in the injection pulse width, that is, the opening of the injector, in a low-load operating range with an alcohol concentration of 0% (100% gasoline). The valve time becomes shorter than before, and not only does the injector in mm vary, but also fuel atomization deteriorates and engine combustion becomes unstable.

In addition, when using a conventional injector for a gasoline engine and approximately doubling the injection pulse width, the fuel injection timing is generally adjusted within the intake pipe and into the intake air in order to promote vaporization and stabilize combustion. Since it is set to complete before the start of injection, when the engine is running at high speeds and under high load, the time per engine revolution is short and the calculation cannot be completed in time for the injection start timing, and even if the injector is fully opened, There is a risk that the injection amount will be insufficient. Therefore, the injection amount varies, which not only significantly deteriorates combustion, but also causes a decrease in engine output.

In other words, the above FFV engine uses 100% gasoline.
Alcohol 1 from the minimum injection amount during fitting
The dynamic range required for the injector up to the maximum injection δ1 near the maximum output of 00% is approximately twice that of a conventional gasoline engine, and such an injector is not only difficult to develop in reality, but also It becomes a special product and causes a significant increase in cost.

[Object of the Invention] The present invention has been made in view of the above circumstances, and provides stable fuel injection that satisfies the fuel injection requirements required for alcohol engines by using an injector for a normal gasoline engine. It is an object of the present invention to provide a fuel injection control device for an alcohol engine that can be obtained.

[Means and effects for solving the problem] The fuel injection control device for an alcohol engine according to the present invention sets the fuel pressure according to the alcohol concentration, and adjusts the pressure control value of the fuel pressure regulator in accordance with this fuel pressure setting value. and a fuel injection period setting means for setting the fuel injection period of the injector based on the fuel pressure setting value set by the fuel pressure adjustment means.

113 That is, the fuel pressure adjustment means sets the fuel pressure according to the alcohol concentration, and the pressure control value of the fuel pressure regulator is changed in accordance with this fuel pressure setting value.

The fuel pressure is controlled by the fuel pressure regulator according to the alcohol concentration, and the fuel injection period of the injector is set by the fuel injection period setting means based on the pressure setting value set by the fuel pressure adjustment means. . As a result, fuel is injected from the injector during the fuel injection period under a fuel pressure that corresponds to the alcohol concentration.

[Embodiments of the invention] The present invention will be described in detail below with reference to the 19 drawings.

The drawings show an embodiment of the present invention, in which Fig. 1 is a functional block diagram of a control device, Fig. 2 is a schematic diagram of an engine control system, and Fig. 3 is a schematic diagram of an engine control system.
The figure is a front view of the crank rotor and crank angle sensor.
The figure is a front view of the cam rotor and cam angle sensor, Figure 5 is a front cross-sectional view of the fuel pressure pot 1: urator, Figure 6 is an explanatory diagram showing fuel pressure settings for alcohol concentration, Figure 7 is an explanatory diagram of a fuel pressure map, FIG. 8 is an explanatory diagram of a fuel injection period map, FIG. 9 is a time chart of fuel injection timing, and FIG. 10 is a flowchart showing a fuel injection timing setting procedure.
FIG. 11 is a flowchart showing the fuel injection interrupt process, and FIG. 12 is a flowchart showing the fuel pressure adjustment means.

(Configuration of Engine Control System) In FIG. 2, symbol 1 is an Alcor engine for FFV, and the figure shows a horizontally opposed four-cylinder engine. An intake manifold 3 is communicated with an intake boat 2a formed in the cylinder head 2 of the engine 1, and a throttle chamber 5 is communicated with the upstream side of the intake manifold 3 via an air chamber 4. An air cleaner 7 is attached to the upstream side of the air cleaner 7 via an intake pipe 6.

Further, an intake air skewer sensor (in the figure, a hot wire air flow meter) 8 is installed immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5a provided in the throttle lever 5 is connected to A throttle opening sensor 9a and an idle switch 9b for detecting a fully open throttle valve are connected.

Further, an injector 10 is disposed immediately upstream of each intake boat 2a of each cylinder of the intake manifold 3, and an ignition valve whose tip is exposed to the combustion chamber is provided for each cylinder of the cylinder head 2. A plug 17 is attached.

Further, the injector 10 is communicated with a fuel tank 12 via a fuel supply path 11, and the fuel tank 12
In the fuel tank, fuels with different alcohol levels A (%) are stored depending on the user's refueling situation, such as alcohol only, a mixed fuel of alcohol and gasoline, or only gasoline.

A fuel pump 13 and an alcohol m degree sensor 14 are installed in the fuel supply path 11 from the fuel tank 12 side, and a variable fuel pressure regulator 18 is installed in the return path 16.

The variable fuel pressure regulator 18 is composed of, for example, a regulator body 19, a stepping motor 20, and a cam 21. A pressure regulating chamber 19b separated from the fuel chamber 19a by a diaphragm 19d on the right side of the valve 19C is communicated with the intake manifold 3 as shown by a point gm in the figure. Then, the differential pressure between the fuel pressure of the injector 10 and the pressure inside the intake manifold 3 is kept constant, and the l11 control is performed so that the amount of fuel injected from the injector 10 does not vary due to fluctuations in the pressure inside the intake manifold 3. do.

Furthermore, the variable fuel pressure regulator 18 has a receiving portion of a spring 19e that biases the diaphragm 19d at the tip, and a seal 19g is interposed between the spring 19e and the regulator main body 19, so that the spring 19e is connected to the outside of the pressure regulating chamber 19b. The extended shaft 19f is in contact with a cam 21 driven by a stepping motor 20, as shown in FIG.
By displacing the shaft 19f from the single wall position on the base circle of the cam 21 to the maximum displacement position,
The leakage valve 19c, ie, the fuel return valve, is variable so that the fuel pressure can be varied.

Further, a crank rotor 21 is pivotally attached to the crankshaft 1b of the engine 1, and a crank angle sensor 22 consisting of a 1 m pickup or the like for detecting the crank angle is provided on the outer periphery of the crank rotor 21. Furthermore, 1/2 times for the crankshaft 1b? /
A cam rotor 23 is pivotally attached to the camshaft 1C, and a cam angle sensor 24 is provided on the outer periphery of the cam rotor 23.

As shown in FIG. 3, projections 21a, 21b, and 21c are formed on the outer periphery of the crank claw 921. These protrusions 21a, 21b, 21c are located before the compression top dead center of each cylinder (
BTDC) θ1. θ2. It is formed at the position θ3,
The protrusion 21a indicates the reference crank angle for setting the ignition timing.

The angular velocity ω is calculated from the transit time between 2Ib and the protrusion 21c indicates the heavy wall crank angle when setting the fixed ignition timing and the fuel injection start rank angle θ static.

Further, as shown in FIG. 4, cylinder discrimination protrusions 23a, 23b, and 23C are formed on the outer periphery of the cam rotor 23. The protrusion 23a is #3. It is formed at the position θ4 after the compression top dead center (ATDC) of the #4 cylinder, and the protrusion 23b
consists of three protrusions, the first of which is formed at the position θ5 after compression top dead center (ATDC) of the #1 cylinder, and furthermore, the protrusion 23c consists of two protrusions, the first of which is formed at a position θ6 after compression top dead center (ATDC) of #2 cylinder.

In the example shown in the figure, 01 = 97°, θ2 - 65°
θ3=10'', θ/I=20', θ5
= 5° θ6 = 20', and as shown in the time chart of FIG. It can be determined that the crank pulse is a signal indicating the crank angle of the #3 cylinder.

Also, after the cam pulse of θ5, θ4 (protrusion 23a
> is detected, it can be determined that the subsequent crank pulse detected by the crank angle sensor 22 indicates the crank angle of the #2 cylinder. Similarly 06
The crank pulse after detecting the cam pulse of (protrusion 23C) indicates the crank angle of the #4 cylinder, and
When the cam pulse of θ4 (protrusion 23a) is detected after the cam pulse of 06, it can be determined that the crank pulse detected thereafter indicates the crank angle of the #1 cylinder.

Further, after the cam pulse is detected by the cam angle sensor 24, the crank pulse detected by the crank angle sensor 22 is detected by the crank angle sensor 22 (of the corresponding cylinder). It can be determined that it indicates ti (crank angle <θ1).

Additionally, the cold water Wbner 25 is faced to one cooling passage (not shown) forming the lie lf formed in the intake manifold 3, and the exhaust boat 2 of the cylinder head 2 is
An 02 sensor 27 faces the exhaust pipe 26 communicating with the exhaust pipe 26. Note that the symbol 28 is a catalytic converter.

(Circuit configuration of control device) On the other hand, reference numeral 31 is a control device, and the CP of this control device 31 is
U (Central Enfeng Processing Sohoku) 32. ROM33, RAM3
4, and an I10 interface 35 are connected to each other via a pass line 36, and the input ports of the I10 interface 35 are connected to the respective sensors 8.9a,
14, 22, 24, 25, 27, and an idle switch 9b are connected.

Further, the spark plug 17 is connected to the output port of the I10 interface 35 via an Eve knife 29, and the stepping motors of the injector 10, fuel pump 13, and variable fuel pressure regulator 18 are connected via a drive circuit 37. 20 are connected.

In the above It OM 33, t R11l If [l program, and the fuel pressure map MPF, which will be described later, are fixed.
Fixed data such as rA end crank angle 08N are stored, and the RAM 34 also stores output signals of the sensors after data processing and data processed by the CPLI 32.

Further, the CPU 32 calculates the alcohol concentration A of the fuel and sets the control profile of the stepping motor 20 based on various data stored in the RAM 34 and according to the control program stored in the ROM 33. In addition to setting the fuel pressure, the pulse width for driving the injector 10 and the time of ignition of the spark plug 17! Performs gI etc.

(Functional configuration of control device) As shown in FIG. 1, the function of the control device 31 related to fuel injection (air-fuel ratio) 1.1
, crank pulse discriminator 8242, angular velocity calculation means 43
, engine rotation number calculation means 44, intake air adjustment means 4
5. Rumoto fuel injection! 8-leg setting means Pero, each weight increase 61 minute correction coefficient setting means 47, air-fuel ratio feedback correction coefficient setting means 4B, alcohol 8: Kodo Fengdashi Dingdan-19, alcohol content correction coefficient setting means 50, fuel injection copper rat Setting means 51
, fuel pressure adjustment means 52, fuel rfjjjvj setting means 5
3. It is composed of a fuel injection period map MPING, a fuel injection side end timing determining means 54, a fuel injection start 0\191 e'f output means 55, a timer means 56, and an injector selection/driving means 57.

Further, the fuel pressure adjusting means 52 includes a fuel pressure setting means 52a1.
Fuel pressure map MPF, switching motor drive means 52
It is composed of b.

In the cylinder 7+1 separate means 41, based on the cam pulses that detect the protrusions 23a to 23c of the force unevenness 23 of the cam angle sensor 24, the crank pulses detected by the subsequent crank angle sensor 22 determine the crank angle of which cylinder. Determine whether it is shown.

In the crank pulse discrimination means 42, the cam angle sensor 2
It is determined which protrusion 21a to 21c corresponds to the crank pulse output from the crank angle sensor 22 after the cam pulse output from the crank angle sensor 22.

The angular velocity calculating means 43 measures the elapsed time t between the crank pulses for detecting θ1 (protrusion 21a) and θ2 (protrusion 21b) determined by the crank pulse discriminating means 42, and calculates the elapsed time t and (θ1− The angular velocity ω is calculated from the included angle of 02> (ω=d(θ1-θ2)/dt).

The engine speed calculation means 44 calculates the engine speed N based on the angular speed ω calculated by the angular speed calculation means 43 (N=60Xω/2π).

The intake air amount calculation means 45 calculates the intake air AtQ from the output signal of the intake air amount sensor 8.

The basic fuel injection power setting means 46 calculates (Tp = KxQ/ The basic fuel injection 1ffiTp is set by NK: the reciprocal of a constant based on the stoichiometric air-fuel ratio, the number of cylinders, etc.) or by a map search using the engine speed N and intake air Q%Q as parameters.

Incidentally, here, the basic fuel injection 1st T p is the alcohol 'aO!' of the fuel. A is 0% (gasoline 100
%).

The various increase correction coefficient setting means 47 reads the throttle opening (0) signal of the throttle opening sensor 9a, the ON/OFF signal of the idle switch 9b, and the cooling water temperature (Tw) signal of the g1 cooling water temperature sensor 25, and performs acceleration/deceleration correction. , various increment correction coefficients CO[F related to full-open accumulation correction, idle rear rotation correction, cooling water temperature correction, etc. are set.

In the air-fuel ratio feedback correction coefficient setting means 48, 02
The output voltage of the sensor 27 is read, the output voltage of the 02 sensor 27 is compared with a preset slice level, and the air-fuel ratio feedback correction coefficient α is set by proportional-integral control.

Note that when the 02 sensor 27 is inactive, the air-fuel ratio feedback correction coefficient α is fixed at α=1.0, and the air-fuel ratio feedback control is stopped.

The alcohol cJ degree calculating means 49 reads the output signal of the alcohol temperature sensor 14 and calculates the alcohol concentration A of the fuel to be supplied to the injector 10.

The alcohol content correction coefficient setting means 50 sets an alcohol content correction coefficient KAL for correcting the deviation in the theoretical air-fuel ratio due to the difference in the alcohol concentration A, corresponding to the alcohol concentration A calculated by the alcohol WJ degree calculation means 49. Set.

For example, the theoretical air-fuel ratio is 14.9 when the fuel is 100% gasoline, and 6.45 when the fuel is 100% alcohol (methanol) (9.9% when the fuel is ethanol).
01). Therefore, as the alcohol concentration of the fuel increases, the stoichiometric air-fuel ratio decreases, and under the same engine operating conditions, it is necessary to increase the fuel injection rate.

In this embodiment, the basic fuel injection riJfil T
Since p is set as alcohol content A = O% as mentioned above, when the alcohol concentration A = O%, the above alcohol content correction coefficient is set as K AL = 1.0, and the alcohol concentration A increases. Is it so continuous that it goes up? (K^L=f(^)), and the deviation in the stoichiometric air-fuel ratio due to alcohol 81 degrees A is corrected by this alcohol fraction correction coefficient KAL.

In this case, if the stoichiometric air-fuel ratio in the case of 100% gasoline is 14.9, the alcohol content correction coefficient aKAL is the I! in the case of 100% alcohol (methanol). I
``Assuming the stoichiometric air-fuel ratio is 6.45, KAL = 2.3 (KAL = 1.7 in the case of ethanol), and under the same operating conditions, the fuel injection led in the case of 100% alcohol.
is approximately twice the fuel injection q in the case of 100% gasoline.

The fuel injection amount setting means 51 converts the basic fuel injection 1st set by the basic fuel injection semi-setting means 46 into various incremental correction coefficients C0FF set by the various increase correction coefficient setting means 47 and the Alcor Minute correction coefficient setting means 5
The air-fuel ratio is corrected using the alcohol correction coefficient set at 0, and the air-fuel ratio is corrected using the air-fuel ratio feedback correction coefficient α set by the air-fuel ratio feedback correction coefficient setting means 48 to calculate the fuel injection ITi.
=TpxcOEFxαxKAL).

The fuel pressure setting means 52a of the fuel pressure adjusting means 52 uses the alcohol temperature A calculated by the alcohol concentration calculating means 49 as a parameter to search for a fuel pressure setting value P corresponding to the alcohol concentration A from the fuel pressure map MP, and sets this fuel pressure. [
The pressure 11i control value ΔP is obtained by subtracting the fuel pressure setting 1fip FO previously stored at a predetermined address in the RAM 34 from PF.
F is calculated as ΔPF=PF-PFO>, and this pressure control value ΔPF is output to the stepping motor drive means 52b, and the fuel pressure setting IIIPF is output to the fuel injection period setting means 53.

The pressure t, 1ltll value ΔpF is a control 1ffl that drives the stepping motor 20 by the number of steps ST from the current step position, and the stepping motor 2
0 is driven, the cam 21 of the variable fuel pressure regulator 18 rotates, the shaft 19f is displaced, and the spring 1
9e compression ship changes. As a result, the position of the valve 19c changes, and the valve leakage, that is, the fuel return flow from the return passage 16 changes, and as shown in FIG. The fuel pressure is changed from ↑ to the maximum fuel pressure when the alcohol concentration A=100% (10,000 Solin O%).

In general, the pressure of fuel injection from a nozzle such as the injector 10 is proportional to the 1/2 power of the fuel pressure, so if the opening time of the injector 10 is constant, the fuel injection ff1Ti
In order to double the fuel pressure, the fuel pressure should be set to 4 (8).Actually, the above fuel pressure map MPF C, the change in the input time of the injector 10 depending on the fuel pressure, the characteristics of the variable fuel pressure regulator 18, etc. In consideration of this, as shown in FIG. 7, the fuel pressure setting IPF determined through experiments using alcohol level II as a parameter is stored.

Fuel injection ill r'! + The setting means 53 sets the fuel 111 injection ff1Ti calculated by the fuel injection amount setting means 51.
A fuel injection JI11 map M P using the fuel pressure setting value PF set by the fuel pressure setting means 52a as a parameter
Search INJ and set the fuel injection period P-.

As shown in FIG. 8, the fuel injection period map M P INJ is based on the fuel pressure set value PF and the fuel injection
Injector 1 at the address of the lattice with parameters
0 is stored, and this fuel injection period TP- during tJ4wJ is determined from the fuel pressure set value PF1.0. : Stored as data on the valve opening period vI of the injector 10 that injects the fuel injection jftTi with the pressure-regulated fuel [, that is, the drive pulse width.

The fuel injection end time calculation means 54 reads out the fixed injection end crank angle θAN stored in advance as fixed data in the ROM 33, and uses this fixed injection split end rank angle θ.
The injection end time T END is calculated from ^N and the angular velocity ω calculated by the angular velocity calculation means 43 (T END-
θ^N/ω〉.

The fuel injection start timing locking means 55 determines the injection rA end time 111TEN calculated by the fuel feeding end timing calculating means 54.
The fuel injection period TP- set by the fuel injection period setting means 53 is subtracted from D to calculate the fuel injection period start time TING@ (TING=TEND-TPW).

The timer means 56 calculates the fuel injection start time 1;Ir! calculated by the fuel injection interval start time 1lJ1 calculation means 55. III
Set T ING and set the above crank pulse discrimination stage 1 to 4.
Timing is started using the crank pulse that detects θ3 (protrusion 21C) determined in step 2 as a trigger.

The injector selection/driving means 57 receives a trigger pulse indicating the end of time measurement from the timer means 56, and the fuel injection period setting means 53 sets the fuel injection period to the injector 10 of the corresponding cylinder determined by the cylinder determination means 41. A drive signal having a pulse width of the fuel supply period TP- is output.

<Operation> Next, the operation of the embodiment with the above configuration is shown in FIGS. 10 to 12.
The explanation will be based on the flowchart shown in the figure.

<Fuel injection timing setting> In the interrupt routine for setting the fuel injection timing shown in FIG. 10, first, in step 5101, crank pulses and cam pulses are read from the crank angle sensor 22 and cam angle sensor 24, respectively, and the process proceeds to step 5102. Perform cylinder discrimination.

Next, in step 5103, a crank pulse is determined from the interruption of the cam pulse, and in step 5104, θ
1. The angular velocity ω is calculated from the time during which the crank pulse of θ2 is detected (ω=d(θ1−θ2)/dt).

Next, in step 5105, the engine rotation speed N is calculated from the angular velocity ω calculated in step 5104 (N=
(60/2π)×ω).

After that, in step 8106, intake air ff1Q is calculated from the output signal of the intake air amount sensor 8, and in step 510
7, the engine speed calculated in step 5105 above &
Based on N and the intake air amount Q calculated in step 8106 above, set the basic fuel injection ff1Tp.Tp=Kx
Q/N K: reciprocal of constant depending on stoichiometric air-fuel ratio, number of cylinders, etc.), proceed to step 8108.

In step 3108, the cooling water temperature TW, throttle angle θ, and idle switch output are read, and step 5109
Based on the engine operating state information read in step 8108, various increase correction coefficients C0FF related to cooling water temperature correction, acceleration/deceleration correction, full-throttle increase correction, post-idle increase correction, etc. are set.

Thereafter, the process proceeds to step 5110, where the air-fuel ratio feedback correction coefficient α is set based on the output signal of the 02 sensor 27, and in step 5111, the alcohol concentration
Based on the output signal of 4, the fuel alcohol 118aA is
and proceeds to step 5112.

In step 5112, an alcohol extraction coefficient KA is calculated based on the alcohol concentration A calculated in step 5111.
Set L, and proceed to step 5113 with /v, set in step 5107 above) B wood fuel injection 04 spear Tp
1 Based on the various increase correction coefficients C0FF set in step 5109 above, the air-fuel ratio feedback correction coefficient α set in step 5110 above, and the alcohol extraction coefficient KAL set in step 5112 above, fuel injection f
Calculate f1T+ (Ti = Tp XC0EFxαX
KAL).

Then, the process advances to step 5114, and the process proceeds to step 511 described above.
The fuel pressure setting value PF is searched from the fuel pressure map MPF using the alcohol concentration A calculated in step 1 as a parameter, and the process proceeds to step 5115.

In step 5115, the fixed injection split end rank angle θAN is read from a predetermined address in the ROM 33, and in step 5115, the fixed injection split end rank angle θAN is read.
At step 116, the fixed injection end crank angle θ^N is divided by the angular velocity ω calculated at step 5104 to calculate the fuel feeding end time T END (T END - θIV
/ω) Proceed to step 5117.

Proceeding to step 5117, the fuel injection period map M P TNJ is searched using the fuel injection ff1Ti calculated in step 5113 and the fuel pressure setting value PF set in step 5114 as parameters, and the injector 10 is searched.
Step 81
Proceed to 18.

When the process proceeds to step 3118, the fuel injection end time T END calculated in step 5116 is changed to step 5.
The fuel injection start timing TING is calculated by subtracting the fuel injection interval TP- set in step 117 (TING = TEN
[1TpII4>.

Then, in step 5119, the fuel injection start time ff1TING calculated in step 8118 is set to the timer means 5.
Set to 6 and end the routine.

(Fuel injection) Fig. 11 shows θ3 (BTDCloo in the embodiment)
) is a routine showing a fuel injection interrupt process activated by a crank pulse that detects
1, the timer means 56 set in the above-described fuel injection timing setting interrupt routine is triggered by the θ3 pulse and starts counting time.

Then, when the fuel injection start timing reaches 1” ING,
In step 5152, a drive signal having a pulse width of the fuel injection period Tpw set in the above-described fuel injection timing setting interrupt routine is output to the injector 10 of the corresponding cylinder, and fuel is injected.

(Fuel Pressure IIL Control) On the other hand, in the fuel pressure control routine shown in FIG.
Proceed to step 2.

In step 5202, the fuel alcohol 113ffA is
The fuel pressure map MPF is searched using pF as a parameter, and the fuel pressure set value pF is set.

Next, the process advances to step 5203 and the step 520 described above is performed.
The previous fuel pressure setting value PFO read in step 1 and step 5 above
At step 202, a pressure control value ΔPF is calculated from the fuel pressure set value PF set this time (ΔPF = PF - PFO).

Then, in step 5204, the stepping motor 20
is the pressure control 11w1Δ calculated in step 5203 above.
The fuel pressure is regulated to a predetermined level by driving the drive step number ST corresponding to the PF, and in step 5205, the above-mentioned R
The previous fuel pressure setting value PFO stored at the predetermined address of ΔM34 is updated with the current fuel pressure setting 1aPF.

Incidentally, when the routine is performed for the first time, the stepping motor 20 is initialized and set to the reference position.

As a result, as shown in FIG. 9, when the engine operating conditions are the same, the alcohol concentration A=O% (gasoline 100%
%>, the fuel injection length 1Ti is approximately 2 (8), and when the alcohol concentration A = 100% (gasoline 0%), the fuel injection period TPW of the injector 10 is
As shown by the dashed line in the figure, the fuel injection period TP14 is approximately doubled, and in the case of small-capacity injectors, the fuel injection period TP14 becomes abnormally long in accordance with the rotation period in the high engine speed range, and in the case of human-powered injectors, the fuel injection period TP14 becomes abnormally long. The fuel injection period TP- in the load range becomes short, and fuel injection becomes unstable. In the present invention, the fuel pressure is varied according to the alcohol concentration 11 degrees A, and the fuel pressure is increased as the alcohol level of the engine becomes higher. Using an injector for a normal gasoline engine, it is possible to achieve stable fuel injection at all times from the required minimum injection rate to the required maximum injection rate, and the dynamic range can be greatly expanded. can.

[Effects of the Invention] As explained above, according to the present invention, there is provided a fuel pressure adjusting means that sets the fuel pressure according to the alcohol concentration and changes the pressure control tIIlIrN of the fuel pressure regulator in accordance with the fuel pressure setting value. , and a fuel injection period setting means for setting the fuel injection period of the injector based on the fuel pressure setting value set by the fuel pressure adjustment means, so that the necessary fuel for an alcohol engine can be obtained by using an injector for a normal gasoline engine. Injection 61 can be satisfied, and stable fuel injection can always be obtained.

Therefore, excellent effects such as improvement in engine stability and exhaust gas purification performance and cost reduction are achieved.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, and FIG.
1'6Ai functional block diagram, Figure 2 is engine tiI
A schematic diagram of the III system, Figure 3 is a front view of the crank rotor and crank angle sensor, Figure 4 is a front view of the cam rotor and cam angle sensor, Figure 5 is a front sectional view of the fuel pressure converter, Figure 6 Figure 7 is an explanatory diagram showing fuel pressure settings relative to alcohol concentration, Figure 7 is an explanatory diagram of a fuel pressure map, Figure 8 is an explanatory diagram of a fuel injection time map, Figure 9 is a time chart of fuel injection timing, and Figure 10 is an explanatory diagram of a fuel injection time map. FIG. 11 is a flowchart showing the injection timing setting procedure, FIG. 11 is a flowchart showing the fuel injection valve interrupt processing, and FIG. 12 is a flowchart showing the fuel pressure adjusting means. 10... Injector 18... Variable fuel pressure regulator 52... Fuel pressure adjustment means 53... Fuel injection period setting means A... Alcohol concentration PF... Fuel pressure set value ΔPF... Pressure control value TP-...Fuel l111t14 period 5 Fig. 0% Alcohol raw hide 100% Pressure installation PF ICζ Small-♂Net ejection amount T → ri

Claims (1)

[Claims] a fuel pressure adjusting means for setting the fuel pressure according to the alcohol concentration and changing the pressure control value of the fuel pressure regulator in accordance with the fuel pressure setting value; 1. A fuel injection control device for an alcohol engine, comprising: fuel injection period setting means for setting a fuel injection period.