JP2004183502A - Fuel injection controller of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain good starting performance by suitably controlling air-fuel ratio at start-up and implement the reduction in exhaust emission and improvement in fuel consumption. <P>SOLUTION: On starting an engine, at first, in a first combustion cycling, a first combustion injection amount TSTAF is set based on a cooling water temperature Tw with a table check (S2 to S4). The air fuel ratio can be prevented from making lean, because fuel adhered to a wall face is added to the first combustion injection amount TSTAF. When it is moved to a second combustion cycle, a second fuel combustion amount TSTAN is set based on a cooling water temperature Tw with the table check (S5). In the second fuel injection amount TSTAN, the fuel adhered to the wall face at the first combustion cycling is subtracted, then the air fuel ratio can be prevented from making lean. As a result, the air fuel ratio at starting is suitably controlled to obtain good starting performance. The exhaust emission can be reduced, and the fuel consumption can be improved. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection control device for an engine that can obtain a good startability by appropriately controlling a fuel injection amount at the time of starting and after starting the engine.
[0002]
[Prior art]
The required fuel injection amount at the time of starting is affected by the external environment of the engine (outside air temperature, cooling water temperature as engine temperature, fuel temperature, etc.), but is generally set based only on the cooling water temperature. . In the case of a cold start or the like in which the temperature of the cooling water is low, the fuel adhering to the wall surface of the intake port or the like is unlikely to evaporate, so the fuel injection amount at the start is set to an increased value. On the other hand, in a restart or the like in which the cooling water temperature is relatively high, the fuel adhering to the wall surface of the intake port or the like is liable to vaporize, so the fuel injection amount at the time of starting is set to a reduced value. Then, after the start, the start-up fuel injection amount is changed to the normal operation with an increase in the cooling water temperature or with a gradual decrease.
[0003]
For example, in Japanese Patent No. 3050680 (Japanese Unexamined Patent Publication No. 5-214986), when the starter switch is turned on, first, the basic injection amount at the start is calculated by referring to a table based on the coolant temperature, and the basic injection amount at the start is calculated. A technique is disclosed in which the amount of fuel is compensated for temperature to compensate for the influence of temperature such as fuel temperature, intake air temperature, fuel evaporation at the time of starting, and the like, and the fuel injection amount at starting is set.
[0004]
[Patent Document 1]
Japanese Patent No. 3050680 (Japanese Unexamined Patent Publication No. 5-214986)
[Problems to be solved by the invention]
By the way, the wall sticking coefficient of the starting basic injection amount injected at the time of the first combustion cycle (crank angle 720 ° CA) at the start is the wall sticking coefficient of the basic fuel injection amount at the time of starting injected at the time of the second combustion cycle. Therefore, when the starting basic injection amount set during the first combustion cycle is applied to the starting basic injection amount during the second combustion cycle, the starting basic injection amount during the second combustion cycle becomes However, since the residual amount of the fuel injected during the first combustion cycle (the amount of fuel adhering to the wall surface) is added, there is a disadvantage that the air-fuel ratio becomes rich.
[0006]
It is also conceivable to compensate for the increase due to the residual fuel by temperature correction. However, since the coefficient used for this temperature correction is set based on the cooling water temperature, the first combustion cycle with little temperature change and the second combustion cycle In the cycle, the coefficient does not change significantly, and it is difficult to effectively avoid enrichment of the air-fuel ratio.
[0007]
In view of the above circumstances, the present invention provides an engine capable of appropriately controlling an air-fuel ratio at the time of starting to obtain good starting performance, reducing exhaust emissions, and improving fuel efficiency. It is an object to provide a fuel injection control device.
[0008]
[Means for Solving the Problems]
To achieve the above object, the present invention provides an initial fuel injection amount setting means for setting a starting fuel injection amount in a first combustion cycle based on an engine temperature, and a starting fuel injection amount in a second combustion cycle based on the engine temperature. A second fuel injection amount setting means for setting the amount, wherein the starting fuel injection amount at the time of the second combustion cycle set by the second fuel injection amount setting means is obtained from the required injection amount set based on the engine temperature. It is characterized by being set to a value obtained by subtracting the amount of fuel adhered to the wall surface remaining during the first combustion cycle.
[0009]
In this case, the fuel injection amount at the start of the first combustion cycle set by the first fuel injection amount setting means preferably includes a fuel amount attached to the wall surface.
[0010]
In such a configuration, the fuel amount adhering to the wall surface is added to the fuel injection amount at the start of the first combustion cycle, and the fuel amount adhering to the wall surface remaining during the first combustion cycle is subtracted from the fuel injection amount at the start of the second combustion cycle. Thus, during the first combustion cycle, the air-fuel ratio does not become lean, and during the second combustion cycle, the air-fuel ratio does not become rich, so that good starting performance can be obtained from the initial stage of cranking. Not only is it possible to reduce exhaust emissions and improve fuel efficiency.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overall schematic diagram of the engine control system.
[0012]
Reference numeral 1 in the figure denotes an engine body, which in the figure indicates a four-cylinder horizontally opposed engine. An intake manifold 3 is communicated with an intake port 2 a formed in a cylinder head 2 of the engine body 1, and a throttle chamber 5 is communicated upstream of the intake manifold 3 via an air chamber 4. An air cleaner 7 is mounted upstream via an intake pipe 6.
[0013]
An intake air amount sensor 8 is interposed immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5 a provided in the throttle chamber 5 is provided with a throttle opening sensor 9 a and an idle sensor for detecting that the throttle valve is fully closed. The switch 9b is connected in series.
[0014]
Further, an idle speed control (ISC) valve 11 is interposed in a bypass passage 10 that connects the upstream side and the downstream side of the throttle valve 5a. An injector 12 is disposed immediately upstream of each intake port 2a of each cylinder of the intake manifold 3. An ignition plug 13 whose tip is exposed to the combustion chamber is attached to each cylinder of the cylinder head 2, and an igniter 30 is connected to the ignition plug 13.
[0015]
A knock sensor 20 is attached to a cylinder block 1a of the engine body 1, and a cooling water temperature for detecting a cooling water temperature representative of the engine temperature is provided in a cooling water passage (not shown) formed in the cylinder block 1a. A sensor 21 is exposed, and further, an O2 sensor 23 is exposed to a gathering portion of the exhaust manifold 22 communicating with the exhaust port 2b of the cylinder head 2. Reference numeral 24 denotes a catalyst such as a three-way catalyst.
[0016]
A crank rotor 26 is axially mounted on a crankshaft 1b supported by the cylinder block 1a, and includes an electromagnetic pickup or the like on the outer periphery of the crank rotor 26 for detecting a projection (or slit) corresponding to a predetermined crank angle. A crank angle sensor 27 is provided opposite to the cam rotor 28 connected to the cam shaft 1c of the cylinder head 2, and a cam angle sensor 29 comprising an electromagnetic pickup or the like is provided oppositely.
[0017]
On the other hand, in FIG. 2, reference numeral 31 denotes a control device (ECU) including a microcomputer or the like, in which a CPU 32, a ROM 33, a RAM 34, a backup RAM 34a, and an I / O interface 35 are connected via a bus line 36, and a constant voltage circuit 37. A predetermined stabilized power is supplied from the power supply.
[0018]
The constant voltage circuit 37 is connected to a battery 39 via a relay contact of an ECU relay 38, and a relay coil of the ECU relay 38 is connected to the battery 39 via an ignition switch 40, and via a starter switch 42. A starter motor 43 is connected.
[0019]
The input ports of the I / O interface 35 are connected to the sensors 8, 9a, 20, 21, 23, 27, 29 and the idle switch 9b, and are connected to the output terminals of the battery 39 and the starter switch 42. Then, the battery voltage and the operation state of the starter switch 42 are monitored. On the other hand, the igniter 30 is connected to the output port of the I / O interface 35, and further, the ISC valve 11 and the injector 12 are connected via the drive circuit 45.
[0020]
The ROM 33 stores a control program and fixed data such as various control tables, and the RAM 34 stores data obtained by processing output signals of sensors and switches, and data processed by the CPU 32. Etc. are stored. The backup RAM 34a stores various learning correction values and the like, and retains data even when the ignition switch 40 is turned off.
[0021]
In accordance with the control program stored in the ROM 33, the CPU 32 calculates the engine speed NE based on the crank pulse from the crank angle sensor 27, and calculates the fuel injection start timing based on a specific crank pulse. Based on the cam pulse from the cam angle sensor 29 interposed between the pulse and the next crank pulse, the cylinder of the fuel injection target cylinder is determined.
[0022]
During normal operation, the fuel injection amount TAUGn is obtained based on the engine load Gn, and the fuel injection amount TAUGn is corrected by various correction values set based on various operation state parameters detected by the sensors and switches. Then, the final fuel injection amount TAU is calculated.
[0023]
When the engine is started, a fuel injection amount TSTAF during the first combustion cycle (hereinafter, referred to as an “initial fuel injection amount”) TSTAF is set based on the cooling water temperature Tw at this time, and subsequently, during the second combustion cycle. A fuel injection amount (hereinafter, referred to as a “second fuel injection amount”) TSTAN is set.
[0024]
The above-mentioned first fuel injection amount TSTAF and second fuel injection amount TSTAN are specifically set according to the flowcharts shown in FIGS.
[0025]
When the ignition switch 40 is turned on, the drive power is supplied to the ECU 31 and the system is initialized.
[0026]
Then, the starting fuel injection control routine shown in FIG. 3 is started. First, in step S 1, a crank pulse is output based on the crank pulse output from the crank angle sensor 27 and the cam pulse output from the cam angle sensor 29. The cylinder discrimination of the fuel injection target cylinder is performed from the cam pulse interrupted between the next crank pulse.
[0027]
Therefore, after the ignition switch 40 is turned on and the starter switch 42 is turned on to start cranking, the program is in a standby state until the crank pal and the cam pal are input.
[0028]
Then, when the crank pulse and the cam pulse are input to the ECU 31 and the cylinder discrimination is performed, the process proceeds to step S2, and based on the cooling water temperature Tw which is a representative of the engine temperature, the first fuel injection amount (TSFAF) table is interpolated with interpolation calculation. The first fuel injection amount TSTAF is set with reference to the reference value.
[0029]
The TSTAF table is composed of a series of addresses in the ROM 33, and in each area, a fuel injection amount for ensuring the starting performance in a cold state is obtained in advance through experiments or the like and stored, and includes the amount of fuel adhering to the wall surface. It is set as the total amount of the required injection amount.
[0030]
As shown in FIG. 5, the initial fuel injection amount TSTAF is set to a higher value as the cooling water temperature Tw is lower. That is, not all of the fuel injected from the injector 12 is vaporized and supplied to the combustion chamber, and a part of the fuel adheres to the intake port 2a and the peripheral wall surface and remains. In particular, at the time of a cold start, since the wall surface temperature of the intake port to the combustion chamber and the like is low, the fuel wall adhesion coefficient increases, and the initial fuel injection amount TSTAF increases accordingly.
[0031]
Since the amount of fuel adhering to the wall surface has a causal relationship with the engine temperature, the initial fuel injection amount TSTAF is set based on the cooling water temperature Tw, which is a representative of the engine temperature, so that appropriate fuel injection considering the amount of fuel adhering to the wall surface is performed. The quantity can be set.
[0032]
Then, the process proceeds to step S3, in which the fuel injection amount TAU for the injector 12 of the fuel injection target cylinder is set by the initial fuel injection amount TSTAF. Then, a drive signal corresponding to the fuel injection amount TAU is output to the injector 12 of the fuel injection target cylinder at a predetermined timing via the drive circuit 45, and the predetermined metered fuel is injected from the injector 12.
[0033]
Thereafter, the process proceeds to step S4 to determine whether or not the first combustion cycle has been completed. If the first combustion cycle has not been completed, the process returns to step S2, and the first fuel injection amount TSTAF for the injector 12 of the next cylinder to be fuel injected. Set. On the other hand, when the first combustion cycle is completed, the process proceeds to step S5. In this case, whether or not the first combustion cycle has ended is determined by comparing the count value of the number of times of fuel injection with the set value. Since the engine employed in the present embodiment is a four-cylinder engine, the set value is set to four, and when the number of fuel injections becomes four, it is determined that the first combustion cycle has ended. In this case, the number of times of ignition may be counted instead of the number of times of fuel injection.
[0034]
In step S5, the second fuel injection amount TSTAN is set based on the coolant temperature Tw with reference to the second fuel injection amount (TSTAN) table with interpolation calculation.
[0035]
The TSTAN table is made up of a series of addresses in the ROM 33, similar to the TSTAF table. In each area, the second combustion is performed mainly to secure the starting performance in a cold state and to reduce exhaust emissions and improve fuel efficiency. The amount of fuel remaining on the wall surface during the first combustion cycle is subtracted from the required fuel injection amount set based on the cooling water temperature Tw during the cycle, and the total amount obtained by adding the fuel amount on the wall surface this time is the second fuel It is stored as the injection amount TSTAN.
[0036]
As a result, as shown in FIG. 5, the second fuel injection amount TSTAN stored in the TSTAN table is set to a higher value as the cooling water temperature Tw is lower, and is higher than the first fuel injection amount TSTAF. Since the fuel amount adhering to the wall surface during the first combustion cycle has been subtracted, a low value is shown.
[0037]
Then, when the operation proceeds to step S6, the fuel injection amount TAU for the injector 12 of the fuel injection target cylinder is set as the second fuel injection amount TSTAN. Then, a drive signal corresponding to the fuel injection amount TAU is output to the injector 12 of the fuel injection target cylinder at a predetermined timing via the drive circuit 45, and the predetermined metered fuel is injected from the injector 12.
[0038]
Thereafter, the process proceeds to step S7 to determine whether or not the engine has completely exploded by comparing the engine speed NE with a complete explosion determination engine speed TSTJDG (for example, 500 rpm). At that time, the second combustion cycle is completed. It is determined whether or not the number of fuel injections counted from the initial stage has reached the end of the second combustion cycle.
[0039]
If the complete explosion determination rotation speed TSTJDG is TSTJDG> NE and the engine is not exploded, the process returns to step S5. Alternatively, since the engine employed in the present embodiment is a four-cylinder engine, the number of times the second combustion cycle has ended is eight. If the number of times of fuel injection <8, the second combustion cycle is not completed, and the process returns to step S5. Then, the second fuel injection amount TSTAN for the injector 12 of the next fuel injection target cylinder is set. In this case, the number of times of ignition may be counted instead of the number of times of fuel injection.
[0040]
On the other hand, when the complete explosion determination rotation speed TSTJDG is an engine complete explosion satisfying TSTJDG ≦ NE, and when the number of fuel injections is equal to or greater than 8, the routine ends.
[0041]
As described above, in the present embodiment, during the period from the start of the engine to the complete explosion, the initial fuel injection amount TSTAF in the first combustion cycle having the highest fuel adhesion coefficient on the wall surface is set to a value obtained by adding the fuel amount on the wall surface. Also, the second fuel injection amount TSTAN in the second combustion cycle was set to a value obtained by subtracting the amount of fuel adhering to the wall surface during the first combustion cycle and adding the amount of fuel adhering to the wall surface this time. The air-fuel ratio at the time of the cycle does not lean more than necessary, and the air-fuel ratio at the time of the second combustion cycle does not become more rich than necessary, so that a good startability can be obtained with an appropriate air-fuel ratio. Reduction of exhaust emissions and improvement of fuel efficiency can be realized.
[0042]
Further, since the first fuel injection amount TSTAF during the first combustion cycle and the second fuel injection amount TSTAN during the second combustion cycle are stored in separate tables each having the cooling water temperature as a parameter of the engine temperature as a parameter, Since the fuel injection amounts TSTAF and TSTAN can be set relatively freely for each cooling water temperature region, the fuel injection amounts TSTAF and TSTAN can be set more accurately.
[0043]
When the start-time fuel injection control routine is completed, a post-start fuel injection control routine shown in FIG. 4 is started. First, in step S11, the TSTAN table is referred to with the interpolation calculation based on the cooling water temperature Tw for the second time. The fuel injection amount TSTAN is set, and subsequently, in step S12. Based on the cooling water temperature Tw, the wall adhesion coefficient TAUSTM is set by referring to the fuel wall adhesion coefficient (TAUSTM) table with interpolation calculation. The wall surface adhesion coefficient TAUSTM indicates a ratio of fuel injected from the injector 12 to the wall surface such as an intake port, and is set between 1.5 and 1 according to, for example, the cooling water temperature Tw. When TAUSTM = 1, the amount of fuel adhering to the wall surface becomes zero. Therefore, as the elapsed time after starting the engine becomes longer, the wall surface adhesion coefficient TAUSTM gradually becomes a value approaching 1 from 1.5.
[0044]
Next, the routine proceeds to step S13, where the fuel injection amount TAUST is set from the second fuel injection amount TSTAN and the wall surface adhesion coefficient TAUSTM based on the following equation.
TAUST = TSTAN TAUSTM
[0045]
In step S14, the fuel injection amount (TAUGn) table is referred to with interpolation calculation based on the engine load Gn, or the fuel injection amount TAUGn is set by calculation. The engine load Gn may be set based on, for example, the engine speed NE and the intake air amount Qa, instead of directly measuring the engine load Gn.
[0046]
Then, the process proceeds to step S15, where the fuel injection amounts TAUST and TAUGn set in steps S13 and S14 are compared. (TAU ← TAUST), and exits the routine.
[0047]
On the other hand, when TAUST <TAUGn, the routine proceeds to step S17, in which the fuel injection amount TAUGn set in step S14 is corrected by various correction values set based on various operation state parameters detected by the sensors and switches. , The final fuel injection amount TAU is calculated.
[0048]
Next, an example of the fuel injection control according to the present embodiment will be described with reference to a time chart shown in FIG.
[0049]
When the starter switch 42 is turned on (t2) after the ignition switch 40 is turned on (t1), in the first combustion cycle (t2 to t3), the fuel injection amount TAU is reduced to the first fuel injection amount TSTAF stored in the TSTAF table. Is set. The initial fuel injection amount TSTAF includes the amount of fuel attached to the wall surface, so that the air-fuel ratio does not become lean and good startability can be obtained.
[0050]
Thereafter, in the second combustion cycle (t3 to t4), the fuel injection amount TAU is set by the second fuel injection amount TSTAN stored in the TSTAN table. In the second fuel injection amount TSTAN, since the amount of fuel adhering to the wall surface during the first combustion cycle is subtracted, the air-fuel ratio does not become rich, and good startability can be obtained.
[0051]
Then, when the second combustion cycle (t3 to t4) is completed, or when the engine completely explodes in the middle of the second combustion cycle, the process proceeds to the fuel injection control after starting, and the second fuel injection amount TSTAN is calculated by the wall adhesion coefficient TAUSTM. The fuel injection amount TAUST is set with the corrected value. The second fuel injection amount TSTAN becomes lower as the coolant temperature Tw increases, and the wall adhesion coefficient TAUSTM also approaches 1 as the coolant temperature Tw rises. The amount TAUST decreases as the coolant temperature Tw increases with each fuel injection. Further, at that time, the fuel injection amount TAUGn is set based on the engine load Gn, and while TAUST ≧ TAUGn (t4 to t5), the final fuel injection amount TAU is set by the fuel injection amount TAUST. . When TAUST <TAUGn, thereafter, the final fuel injection amount TAU is set based on the fuel injection amount TAUGn.
[0052]
【The invention's effect】
As described above, according to the present invention, it is possible to appropriately control the air-fuel ratio at the time of starting to obtain good startability, to realize reduction of exhaust emission, and to improve fuel efficiency. it can.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram of an engine control system. FIG. 2 is a circuit configuration diagram of a control device. FIG. 3 is a flowchart showing a fuel injection control routine at startup. FIG. 4 is a flowchart showing a fuel injection control routine after startup. FIG. 6 is an explanatory diagram of an initial fuel injection amount table and a second fuel injection amount table. FIG. 6 is a time chart showing an example of fuel injection control.
TSTAF Initial fuel injection amount (starting fuel injection amount)
TSTAN Second fuel injection amount (starting fuel injection amount)
Tw Cooling water temperature (engine temperature)

Claims (2)

An initial fuel injection amount setting means for setting a starting fuel injection amount during a first combustion cycle based on the engine temperature;
Second fuel injection amount setting means for setting a starting fuel injection amount during a second combustion cycle based on the engine temperature;
With
The starting fuel injection amount at the time of the second combustion cycle set by the second fuel injection amount setting means is a value obtained by subtracting the amount of fuel adhering to the wall surface remaining at the time of the first combustion cycle from the required injection amount set based on the engine temperature. A fuel injection control device for an engine, characterized in that: 2. The fuel injection control device for an engine according to claim 1, wherein the fuel injection amount at the start of the first combustion cycle set by the first fuel injection amount setting means includes a fuel amount attached to a wall surface.

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