JPH0230954A - Fuel control device - Google Patents

Abstract

PURPOSE:To prevent the outflow of unburnt fuel by detecting the flameout state of an engine based on the change quantity or the like of the information corresponding to the rotating speed of the engine calculated from the interval between optional preset crank angles and stopping the fuel feed at the time of an engine flameout. CONSTITUTION:In an engine provided with solenoid type fuel injection valves 51-56 on individual cylinders, a control circuit 20 controlling the fuel injection valves 51-56 has a CPU calculating the fuel injection quantity based on outputs of an intake air quantity sensor 8, an intake air temperature sensor 9, a water temperature sensor 10 and a crank angle sensor 11. The CPU calculates the information corresponding to the rotating speed of the engine based on the interval between optional preset crank angles and detects the flameout state of the engine based on the change quantity or change rate of the information corresponding to the rotating speed, when the flameout state is detected, the CPU executes the control to stop the fuel feed to the engine. The outflow of unburnt fuel is prevented, the deterioration or the like of a catalyst device is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control device that detects a misfire in an internal combustion engine and stops fuel supply to a misfiring cylinder.

[Conventional technology]

Electronically controlled fuel injection devices, which have rapidly become installed in automobiles in recent years, are devices that create the air-fuel mixture that is supplied to the engine's combustion chamber. This is processed by a microcomputer to generate a signal representing the optimal air-fuel ratio, and this signal controls the opening time of the electromagnetically driven fuel injector to adjust the air-fuel ratio and optimize the operating condition of the engine. It is something that should be maintained.

This type of electronically controlled fuel injection device is generally equipped with an exhaust purification device (catalyst device) in the exhaust passage, for example, a three-way catalyst device that simultaneously oxidizes Co and Hc and reduces Nox. When using
The set air-fuel ratio is set to a value near the stoichiometric air-fuel ratio to efficiently reduce harmful components in the exhaust gas.

[Problem to be solved by the invention]

By the way, in the above-mentioned electronically controlled fuel injection system, if combustion does not occur normally in the cylinder due to component failure, poor wiring contact, malfunction, etc., and a misfire occurs, the mixture of unburned fuel and air may be When the gas flows to the catalyst device, a rapid chemical reaction occurs in the catalyst device, causing the temperature of the catalyst device to rise significantly, deteriorating the catalyst device, and emitting harmful components in the exhaust gas into the atmosphere. Otherwise, there was a risk of fire if dry grass etc. came into contact with the catalyst device which had an abnormally high fA when the car was stopped.

This invention was made to solve the above-mentioned problems, and provides a fuel control device that can accurately detect a misfiring cylinder in an engine, stop fuel supply, and prevent catalyst deterioration and fire hazards. The purpose is to obtain.

[Means to solve the problem]

The fuel control device according to the present invention calculates information equivalent to the rotational speed from the cycle of each predetermined crank angle corresponding to each cylinder of the engine, and calculates the misfire state of the engine from the amount or rate of change of the information equivalent to the rotational speed. The engine is equipped with a misfire detection means for detecting a misfire, and a control circuit for stopping the supply of fuel to a cylinder in which a misfire has been confirmed.

[For production]

The misfire detection means in this invention calculates information equivalent to the engine rotational speed from the period between arbitrary predetermined crank angles, detects a misfired cylinder of the engine based on the amount or rate of change of the information equivalent to the rotational speed, and detects the misfired cylinder of the engine. When a cylinder is detected, the control circuit acts to stop the supply of fuel to the misfiring cylinder.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows its overall configuration. In the figure, 1 is a four-stroke spark ignition engine installed in a car, and combustion air is transferred to an air cleaner 2. Intake pipe 3. slot valve 4
Inhale after.

The output of the control circuit 20 causes the electromagnetic fuel injection valves 51 to 5 to
6 is opened to supply fuel to each cylinder.

The exhaust gas after combustion is released into the atmosphere through an exhaust manifold 6, an exhaust pipe 7, etc.

An intake air amount sensor 8 is installed in the intake pipe 3 to detect the amount of intake air taken into the engine 1 and output an analog voltage corresponding to the amount of intake air.

Further, a thermistor-type intake temperature sensor 9 is installed that detects the temperature of intake air and outputs an analog voltage according to the intake air temperature.

A thermistor-type water temperature sensor 10 that detects the coolant temperature and outputs an analog voltage (analog detection signal) according to the coolant temperature is installed in the engine 1, and a crank angle sensor 11 detects the rotation of the crankshaft of the engine 1. It detects the speed and outputs a pulse signal with a frequency corresponding to the rotation speed.

Further, an idle switch 12 is installed on the throttle valve to detect that the throttle valve opening degree is less than or equal to a set value.

The control circuit 20 includes an intake air amount sensor 8. Intake temperature sensor 9, water temperature sensor 10. Crank angle sensor 11. The fuel injection amount is adjusted by controlling the opening time of the %i1 type fuel injection valves 51 to 56 using a circuit that calculates the fuel injection amount based on the detection signal of the idle switch 12.

The control circuit 2o will be explained with reference to FIG.

200 is a microprocessor C (hereinafter referred to as CPU) that calculates the fuel injection amount, 2o1 is a revolution counter,
This is a rotation number counter that counts the period between predetermined crank angles based on the signal from the crank angle sensor 11.

Further, the rotation number counter 201 sends an interrupt command signal to the interrupt control section 202 periodically with the engine rotation.

Upon receiving this signal, the interrupt control unit 202 outputs an interrupt signal to the CPU 200 via the common bus 212.

The digital input port 203 transmits digital signals such as a starter signal from the starter switch 13 that turns on and off the operation of a starter (not shown) to the CPU 200.

The analog input board 204 consists of an analog multiplexer and an A-D converter, and converts each signal from the intake air amount sensor 8 and the intake air temperature sensor 9 into analog/digital (hereinafter referred to as A/D) converters.
It has the function of converting the data into the computer and sequentially reading it into the cPu 200.

These rotation number counter 2o11 interrupt control unit 202,
Digital input port 203. Analog input port 20
4 output information is sent to the CPU 200 through the common bus 212.
transmitted to.

A power supply circuit 205 is connected to the battery 14 through the key switch 15.

206 is a random access memory (hereinafter referred to as RAM) that can be read and written.

Reference numeral 207 is a read-only memory (hereinafter referred to as ROM) that stores programs and various constants.

The 20th is a fuel injection time control counter including a register, which is composed of a down counter, and converts the digital signal representing the opening time of the electromagnetic fuel injection valves 51 to 56 calculated by the CPU2O5, that is, the fuel injection amount, into the actual electromagnetic signal. type injection valve 5
It is converted into a pulse signal with a pulse time width giving a valve opening time of 1 to 56.

209 is a power amplifying section that drives the electromagnetic fuel injection valves 51 to 56. A timer 210 measures the elapsed time and transmits it to the CPU 200.

The rotation number counter 201 measures the cycle time at every predetermined crank angle of the engine based on the output of the crank angle sensor IO, and supplies an interrupt command signal to the interrupt control section 202 when the measurement is completed.

The interrupt control unit 202 generates an interrupt signal in response to the signal, and causes the CPU 200 to execute an interrupt processing routine for calculating the fuel injection amount.

FIG. 3 (al) shows a schematic flowchart of the CPU 200, and is used to explain the functions of the CPU 200 based on this flowchart, as well as the operation of the entire configuration.

When the key switch 15 and the starter switch 13 are turned on and the engine 1 is started, the calculation process of the main routine is started at the start of step SO, the initialization process is executed at step S1, and the process of initialization is executed at step S2. , reads the digital value corresponding to the cooling water temperature from the analog input port 204.

In step S3, a fuel correction amount K is calculated based on the result, and the result is stored in the RAM 206. When step S3 ends, the process returns to step S2.

Normally, the CPU 200 performs steps 82 to S in FIG.
The processing of the main routine No. 3 is repeatedly executed according to the control program.

When an interrupt signal from the interrupt control unit 202 is input manually, the CPU 200 immediately interrupts the main routine processing even if it is in progress, and moves to the interrupt processing routine of step 340 shown in FIG. 3 fbl.

In step S41, the period between the predetermined crank angles read by the rotation number counter 201 is read.

In this embodiment, the predetermined crank angle is set every 120 degrees. Then, in step S42, the rotational speed is calculated in the rotation example and stored in the RAM 206.

Next, in step S43, it is checked whether the operating state is such that a misfire is detected. This includes, for example, a steady state detection means that detects whether or not the engine is in a rapid acceleration state based on the amount of change in the amount of intake air, an output signal from the idle switch 12, a neutral switch signal (not shown here), and a vehicle speed signal. The output of the idle state detection means is checked, and misfire detection is performed only when the engine is in a steady state or in an idle state.

If it is determined in step 343 that the misfire detection operating state is present, the process proceeds to step 344, and if it is determined that the misfire detection operating state is not present, the process proceeds to step 347.

In step 344, step 3 of the previous interrupt processing is performed.
At step 42, the amount of change between the previous rotation speed stored in the RAM 206 and the current rotation speed is calculated.

Then, in step S45, the amount of change is compared with a preset determination value.

If the amount of change is larger than the judgment value on the rotation reduction side, the process advances to step 346, and the current cylinder misfire flag is stored in the RAM 206.
If the amount of change is smaller than the determination value or larger on the rotation increasing side, step S346 is not processed and the process directly proceeds to step S47.

The contents of steps 344 to S46 will be explained in more detail with reference to FIG. For example, at the time of interrupt timing A, the amount of change in the rotational speed (
The current rotation number - the previous rotation number) and the determination value are compared in magnitude.

Now, if a misfire occurs during combustion in the #2 cylinder, the engine will not be able to output torque, and the current rotational speed will be significantly lower than the previous rotational speed, exceeding the determination value.

As shown in Fig. 4fa+, for example, the crank angle sensor corresponding to the #l cylinder has a longer H level period than the one corresponding to the #2 to #6 cylinders, so that each cylinder can be identified. If this is done, the cylinder in which the misfire has been detected can be identified in the interrupt routine, so step S
46 sets the misfire flag for that particular cylinder and stores it in the RAM.
206. A misfire detection means is configured as an abnormality.

In addition, FIG. 4(f) to FIG. 4(h) (electromagnetic injection valve 51 to
53), the electromagnetic injection valve 5
1 to 56 are shown in Figure 4 (as shown in C1 to Figure 4 te+,
The cylinder identification signal causes the valve to open during the exhaust stroke of each cylinder.

Next, in step 347 of FIG. 3 (bl), a signal representing the amount of intake air is input from the analog input port 204.

Next, in step 348, a basic fuel injection amount determined from the engine speed and intake air amount is calculated.

Next, in step S49, the fuel injection correction amount determined in the main routine is read from the RAM 206, and a correction calculation for the injection amount (injection time width) that determines the air-fuel ratio is performed.

Next, in step 350, the presence or absence of a misfire flag for the cylinder to be injected this time is checked. If the misfire flag is set, the process advances to step S52; if the misfire flag is not set, the injection amount is set in the counter in step 551. Then, the electromagnetic injection valve of the cylinder undergoing the exhaust process is opened, and the process returns to the main routine in the next step 352. The general functions of the microprocessor 200 are as described above.

Note that in this embodiment, step 344 in FIG.
In step S46, the amount of change in the rotational speed (current rotational speed -
Although we calculated the previous rotation speed) and compared the magnitude with the judgment value, it is also possible to use the amount of change in the information equivalent to the rotation speed related to the inverse calculation of the period, or instead of the amount of change, change rate = (current rotation speed) The same effect can be obtained by calculating (-previous rotation number)/current rotation number and comparing the result with the determination value.

Further, in the above embodiment, the rotation speed is calculated from the cycle of every 120 degrees of crank angle, but in a narrow range of the combustion process where the generation of torque during combustion is very noticeable (for example, TD
It goes without saying that a misfire can be detected more clearly if the calculation is performed based on the period from C (top dead center) to ATDC (30 degrees after top dead center).

〔Effect of the invention〕

As described above, according to the present invention, the crank angle of the engine is detected by the crank angle sensor, information corresponding to the rotation speed is calculated from the period of each predetermined crank angle corresponding to each cylinder of the engine, and the information corresponding to the rotation speed is calculated. The engine misfire condition is detected based on the amount or rate of change of corresponding information, and the fuel supply is stopped to the cylinder where the misfire is confirmed. This prevents unburned fuel from flowing out and prevents the catalytic converter from flowing out. This has the effect of preventing the deterioration of cars, the emission of harmful exhaust gases, and fires in vehicles.

Further, since misfires can be detected only when the engine is in a steady state or when the engine is idling, erroneous detection of misfires can be prevented and misfires can be detected accurately.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a fuel control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a control circuit in the same embodiment, FIG. 3 (δ) and FIG. FIG. 4 is a flowchart showing the operation of the CPU shown in FIG. ...Crank angle sensor, 20
...Control circuit, 51-56...Fuel injection valve, 2-
00...Microprocessor (CPU). In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] a crank angle sensor that detects the engine crank angle;
A misfire detection means that calculates information equivalent to the engine rotational speed from a period between arbitrary predetermined crank angles of the crank angle sensor, and detects a misfire state of the engine based on the amount or rate of change of the information equivalent to the rotational speed. and a control circuit that stops fuel supply to the engine when the misfire detection means detects a misfire in the engine.