JPS6022046A - Fuel injection controlling method for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent consumption of superfluous fuel, by detecting combustion pressure in a combustion chamber, judging complete combustion of an engine from the detected signal, and stopping fuel increasing for starting the engine when it is judged that the engine has caused complete combustion during the while when the fuel supply rate is increased for starting the engine. CONSTITUTION:In an engine, in which the injection quantity of fuel is calculated by an electronic control unit 20 according to the operational conditions of the engine and correction is made to increase the injection quantity of fuel at the time of starting the engine, a pressure detecting sensor 13 is attached in the manner that it is exposed in a combustion chamber 3, and a voltage signal proportional to combustion pressure P is produced. When the crank angle detected by a crank-angle sensor 15 is within the range of 360 deg. CA, the differential value DELTAV of the stroke volume at the intervals of a predetermined crank angle (5 deg.) is calculated and DELTAPi(=PXDELTAV) is stored in a RAM24. Then, the mean effective pressure Pi is detected by integrating DELTAPi and compared with a reference value. In case that the mean effective pressure Pi thus detected has exceeded a reference value, judgement is made that the engine has caused complete combustion, and fuel increasing for starting the engine is stopped, for instance, by stopping operation of a cold starting injector 12.

Description

TECHNICAL FIELD The present invention relates to a fuel injection control method for an internal combustion engine, and more particularly to a method for controlling fuel injection at startup using combustion pressure of an internal combustion engine.

In conventional electronically controlled fuel injection internal combustion engines for automobiles, in order to improve engine startability, the amount of fuel injected is increased at startup compared to during regular operation. Some also include a separate cold start injector to increase the amount of fuel at low temperatures. The determination at the time of starting is generally made based on a starter signal.

There is a delay of several seconds between when the driver decides to start the engine, that is, when it is a complete explosion, and when he turns off the starter. and carbon monoxide emissions will also increase. It is also a cause of smoldering when starting at low temperatures. Also, there are individual differences in the time it takes to turn off the starter.

Purpose of the Invention The purpose of the present invention is to determine complete explosion of an engine based on combustion pressure,
The purpose of this is to immediately stop the start-up fuel increase and prevent excess fuel consumption.

Structure of the Invention In the present invention, the combustion pressure in the engine combustion chamber is detected,
The engine is characterized in that a complete combustion of the engine is determined from the detected combustion pressure, and when it is determined that the engine has completely exploded during the fuel increase at the time of startup, the increase in fuel at the time of startup is stopped.

Referring to FIG. 1 of the embodiment, ■ is the engine body, 2 is the piston, and 3 is the engine body.
is a combustion chamber, 4 is an intake valve, 5 is an intake boat, 6 is a surge tank, 7 is a branch pipe connecting the intake boat 5 and the surge tank 6 of each cylinder, 8 is an intake duct, 9 is inside the intake duct 8 The throttle valve 10 is an air cleaner.

A fuel injector 11 is arranged in each branch pipe 7 and a cold start injector 12 is arranged in the surge tank 6.

Fuel injection from the fuel injector 11 and the cold start injector 12 is controlled by an electronic control unit 20. A pressure detection sensor 13 faces the engine combustion chamber 3, a cooling water temperature sensor 14 is attached to the engine and the main body 1, and the output signals of these sensors are sent to AD converters 21 and 22.
It is connected to the input port 23 of the electronic control unit 20 via. Signals from the crank angle sensor 15, crank reference position sensor 16, and starter switch 17 are directly input to the input port 23. Naturally, a signal indicating the amount of intake air from an air flow meter (not shown) and a signal indicating the engine speed are also input to the input boat 23.
These are basically well known and are omitted from FIG. 1 to simplify the explanation.

The electronic control unit 20 consists of a digital computer, and includes a random access memory RAM 24, a read-only memory ROM 25, and a central processing unit CPU 2G. Each of these means is coupled to each other by a bidirectional bus 27 and also to an input port 23 and an output port 28. From the output port 28, the drive circuit 2
9 and '30 to the fuel injector 11 and cold start injector 12.

The average effective pressure Pi is generally calculated using the following formula.

1'i= Sl"d Shiba h (1) (If formula 11 is rewritten using the crank angle θ, Pi=
Sp, dθ・dshi/dθ/shih (2). however,
P: pressure, v: volume, Vh: stroke volume. In the example shown below, the average effective pressure Pi is calculated as an integrated value every 605 degrees.

The combustion pressure sensor 13 shown in FIG. 1 is attached to a specific cylinder and generates a voltage proportional to the pressure inside the combustion chamber 3. As shown in FIG. 2, the crank reference position sensor 16 generates a reference position signal at the bottom dead center of compression every 720 degrees of the crankshaft. The crank angle sensor 15 generates a signal every 5 degrees.

FIG. 3 shows a routine for calculating the average effective pressure in the δ1 calculation performed by the electronic control unit 20.
This is done by interrupt every time. First, in step 31, it is determined whether the crank reference position signal is ONL. The crank reference position signal is assumed to turn ON at compression bottom dead center before combustion pressure is measured. If it is determined that the position is the reference position, the crank angle counter (crank CL) is reset (step 32); if not, 1 is added to the counter CL (step 33). That is, the counter CL is zero at the reference position, and is counted up by one every 5 degrees of the crank angle. Next, the A/D conversion value of the combustion pressure at that time is taken in from the dedicated register, and the RA? +24 (step 34). Subsequently, the next A/D conversion is started (step 35).

Referring also to FIG. 2, in step 36, it is determined whether the crank CL is within 360° CA. Y
If ES, proceed to step 37 and calculate the average effective pressure Pi.
If the answer is NO, no further calculation is performed. In step 37, the ROM 23
Differential value ΔV of stroke volume for every 5 degrees of crank angle stored in
Then, in step 38, ΔPi=PXΔV is calculated and stored in the RAM 24. By integrating this ΔPi, the average effective pressure Pi can be determined, but the processing differs depending on whether the piston is in the compression stroke or the expansion stroke.

If it is in the compression stroke, it means that it is doing negative work, and the integrated value of ΔPi during this stroke is stored as Piθ, and if it is in the expansion stroke, it is doing positive work.
It is integrated as Pi■. The process during this time is step 39.
From step 41, "0" is executed.

Next, in step 42, it is determined whether the crank angle has passed 360 degrees, and only when YES, that is, when the crank angle is at the 360 degree position, the average effective pressure Pi is ai calculated, and R
AM 24 (step 43).

Therefore, the average effective pressure calculated in this way is
When the engine temperature becomes larger than the set value, it is determined that the engine has completely exploded (31'), and the operation of the cold start injector 12 shown in FIG. In order to control the operation of the cold start injector I2, it is also possible to configure a circuit using a conventional start injector time switch, and as shown in FIG.
A switch 32 is provided between the cold start injector 12 and the electronic control unit 20.
It is designed to be opened and closed by a control signal. The start injector time switch 31 operates the cold start injector 12 only at the time of starting when the engine cooling water temperature is low, and when the start switch 17 is turned off, the operation of the cold start injector 12 is stopped. However, even before the scooter switch 17 is turned off, as shown in FIG. 5, the switch 32 opens when the average effective pressure Pi calculated by δ4 becomes larger than the set value, and the cold start injector 12 is no longer energized. The fuel injection from the cold start injector 12 is stopped. From now on, only energized fuel injection will be performed from the fuel injector 11 arranged for each cylinder.

In the case of an engine not equipped with a cold start injector 12 or even in the case of an engine equipped with a cold start injector, the amount of fuel injected from the fuel injector 11 is generally controlled by the valve opening time of the fuel injector 11. The basic injection amount is calculated mainly as a function of the intake air amount and the rotational speed, and corrections such as an increase during starting, an after-start amount, and an increase during acceleration are performed on this basic injection amount. The feature of the present invention shown in the sixth example is that the time to switch from the increased amount at startup to the increased amount after startup, that is, the time when the engine has completely exploded, is determined based on whether the average effective pressure Pi has become larger than a predetermined value. An example of the amount increased at startup and the amount increased after startup is shown in FIG.

The solid line shows the amount increased at startup, and the starting line shows the amount added after startup.

In the above embodiment, the determination of complete engine explosion is made by calculating the average effective pressure. Alternatively, it is also possible to determine complete engine explosion based on the maximum value of combustion pressure' during one cycle. - Effects As explained above, according to the present invention, the increase in starting fuel is stopped immediately after the engine has completely exploded, so that fuel consumption of more than 20 n1 more than necessary can be saved.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an internal engine to which the present invention is applied, Fig. 2 is an explanatory diagram for calculating the average effective pressure, Fig. 3 is a flowchart for calculating the average effective pressure, and Fig. 4 is a cold Control circuit diagram of the start injector, Figure 5 is a flowchart for controlling the cold start injector, Figure 6 is a flowchart for controlling the cold start injector.
The figure is a flowchart for stopping the amount increase at the time of starting, and FIG. 7 is a graph for showing the amount increase at the time of starting. ■...Engine body, 3...Combustion chamber, 11...Fuel injector, 12...Cold star 1-injector, 13...Pressure sensor, 17'-...Starter switch, 20... Electronic control unit, 31...Stark injector time switch, 32...Switch. Patent Applicant Toyota Motor Corporation Patent Application Agent Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Kyosuke Donakayama Patent Attorney Akira Yamaguchi 2nd No. Isujlr −m−□−−−−−−− -1-!
l Oo 360° 720° Angle 1" 1 5 Figure 01 7 ■ I1 Cooling water temperature ->

Claims (1)

[Claims] In an internal combustion engine that has an electronic control unit that calculates the fuel injection amount and increases the fuel injection amount at startup,
An internal combustion engine characterized by detecting combustion pressure in an engine combustion chamber, determining complete combustion of the engine from the detected combustion pressure, and stopping the increase in fuel consumption at startup when it is determined that the engine has completely exploded during fuel increase at startup. fuel injection control method.