JPS6410659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition timing control method for an internal combustion engine,
In particular, the present invention relates to an ignition timing control method for an internal combustion engine having an air-fuel ratio feedback control system.

In an internal combustion engine that detects intake pipe negative pressure or intake air amount and rotational speed as engine operating condition parameters, and controls ignition timing according to these detected operating condition parameters, atmospheric pressure When the intake air pressure decreases, phenomena such as the detected intake pipe negative pressure becomes apparently smaller, or the detected intake air amount becomes apparently larger than the true intake air amount due to a decrease in air density, occur, causing the ignition timing to change. The ignition timing is controlled to be later than the optimum ignition timing required by the engine. Further, the ignition timing may also be erroneously controlled when variations, errors, etc. occur in the intake pipe negative pressure sensor or the intake air amount sensor.

The present invention aims to solve the above-mentioned problems of the prior art. According to the present invention, the ignition timing can be controlled to the optimum value even if a change in the environment such as atmospheric pressure occurs or a detection error occurs in a sensor for operating condition parameters.

A feature of the present invention that achieves the above-mentioned object is to detect the concentration of a specific component in the exhaust gas, increase or decrease the air-fuel ratio correction value according to the detected value, and control the air-fuel ratio correction value to increase or decrease the air-fuel ratio correction value in accordance with the increased or decreased air-fuel ratio correction value. In an internal combustion engine having an air-fuel ratio feedback control system that controls the amount of fuel to be supplied, an operating state including at least a load state and a rotational speed of the engine is detected, and the system detects the operating state according to the detected operating state and the air-fuel ratio correction value. The purpose of this is to control the engine's ignition timing.

The present invention will be explained in detail below using the drawings.

FIG. 1 schematically shows an example of an electronically controlled fuel injection type internal combustion engine having an air-fuel ratio feedback control function as an embodiment of the present invention. In the figure, 10 is an air flow sensor that detects the intake air amount of the engine and generates a voltage corresponding to the detected value, and 12 is an air flow sensor that detects the engine's intake pipe negative pressure and generates a voltage according to the detected value. a negative pressure sensor; 14, a fuel injection valve that intermittently injects fuel according to a drive signal from the control circuit 16; 18, a spark plug; 2;
0 indicates an O ₂ sensor that detects the concentration of oxygen components in exhaust gas and generates a voltage according to the detected value, and 22 indicates a catalytic converter. Air flow sensor 10, negative pressure sensor 12 and _O2 sensor 2
The zero output voltage is sent to the control circuit 16. Ignition energy is sent to the spark plug 18 from an ignition coil 26 via a distributor 24 . The ignition coil 26 includes an igniter, to which an ignition signal is sent from the control circuit 16. The distributor 24 is provided with a rotation angle sensor 28 that generates an angular position signal each time the distributor shaft rotates through a predetermined angle, for example, 30° and 360° in terms of crank angle. The above two types of angular position signals from the angle sensor are sent to the control circuit 16, respectively.

FIG. 2 is a block diagram showing an example of the control circuit 16 of FIG. 1. The output voltages of the O ₂ sensor 20, air flow sensor 10, and negative pressure sensor 12 are:
A/D converter 30 including an analog multiplexer
and is sequentially converted into a binary signal at a predetermined conversion cycle.

Every 30° crank angle from the rotation angle sensor 28 and
The angular position signal every 360 degrees is applied to a timing signal forming circuit 32, which generates various timing signals for a fuel injection control circuit 34 and an ignition control circuit 36, which will be described later, as well as for calculating fuel injection time and ignition timing. This is a well-known circuit for forming an interrupt request signal for calculation, a gate control signal for the speed signal forming circuit 38, etc., and can be easily constructed by combining flip-flops, logic elements, etc.

The speed signal forming circuit 38 counts the number of gates that are opened and closed by a gate control signal having a pulse width corresponding to a crank angle of 60 degrees sent from the timing signal forming circuit 32, and the number of clock pulses that pass through these gates. It has a known configuration with a counter and forms a binary speed signal having a value depending on the rotational speed of the engine.

The fuel injection control circuit 34 controls the fuel injection valve 14 calculated by a central processing unit (CPU) 40.
and a down counter for forming an injection signal having a duration corresponding to the injection time τ. This type of circuit configuration is also well known, and the injection signal obtained thereby is sent to the injection valve 14 via the drive circuit 42.

The ignition control circuit 36 includes two registers that each receive output data regarding the start timing of energization of the ignition coil and output data regarding the energization end time, that is, the ignition timing, calculated by the CPU 40, and a register that receives the output data regarding the ignition timing, which are calculated by the CPU 40, and registers at the time point indicated by each output data. It comprises two down counters, each for generating pulses, and a flip-flop which is set and reset by the above-mentioned pulses from the down counters and generates an ignition signal representing the period during which the ignition coil is to be energized. This type of ignition control circuit is also well known, and the generated ignition signal is sent to an ignition device 44 comprising the spark plug 18, distributor 24, ignition coil 26, etc. shown in FIG.

The A/D converter 30, the speed signal forming circuit 38, the fuel injection control circuit 34, and the ignition control circuit 36,
CPU, each component of a microcomputer
40, a read only memory (ROM) 46, a random access memory (RAM) 48, and a clock generation circuit 50 via a bus 52, through which input/output data is transferred.

Although not shown in FIG. 2, the microcomputer is usually provided with an input/output control circuit, a memory control circuit, etc. using a well-known method.

The ROM 46 contains a main processing routine program, an interrupt processing program for calculating the air-fuel ratio correction amount, an interrupt processing program for calculating the ignition timing, an interrupt processing program for calculating the fuel injection time, and other interrupt processing programs, as well as for their calculation processing. Various necessary data are stored in advance.

Although both the air flow sensor 10 and the negative pressure sensor 12 are provided in FIGS. 1 and 2, in order to carry out the present invention, only one of these sensors is provided. It's fine as long as it's there.

Next, the processing contents and operation of the above-mentioned microcomputer will be explained using the flowcharts shown in FIGS. 3 and 4. Note that the following description will be made regarding the case where the air flow sensor 10 is used without using the negative pressure sensor 12.

The CPU 40 executes the processing routine shown in FIG. 3 in response to interrupt requests that occur at predetermined intervals. First, in step 60, the A/D converter 3
At 0, the A/D converted detection signal of the O ₂ sensor 20 is taken in. Then, in step 61,
This detected data is compared with a predetermined reference value to determine whether the oxygen concentration in the exhaust gas is lower than the value corresponding to the stoichiometric air-fuel ratio. It determines whether it is on the lean side or on the rich side, and if it is on the rich side or lean side, the rich flag is turned on or off depending on whether it is on the rich side or lean side. In the next step 62, this rich flag is determined, and if it is on, the process proceeds to step 63, where the air-fuel ratio correction coefficient (correction amount) f(A/
F) is the correction coefficient f in the previous calculation cycle
(A/F) by a constant value α. That is,
In step 63, f(A/F)=f(A/F)-α is calculated. If the rich flag is not on, the program proceeds to step 64, where the air-fuel ratio correction coefficient f(A/F) is calculated by increasing f(A/F) by a constant value β.
get. That is, in step 64, f(A/F)
Calculate =f(A/F)+β. The air-fuel ratio correction coefficient f(A/F) thus obtained is stored in a predetermined area of the RAM 48 in step 65. Note that if the rich flag was on in the previous calculation cycle but turned off in the current calculation cycle, or vice versa, the increase or decrease in f(A/F) this time may be significantly changed. Processing to increase the size (step processing) may also be performed.

On the other hand, when an interrupt request is generated from the timing signal forming circuit 32, for example every 360 degrees of crank angle, the CPU 40 executes a processing routine for calculating the fuel injection time. Since this processing routine is well-known, it will not be explained in detail, but the basic injection time τ _O is calculated from τ _O =K・Q/N from the data regarding the intake air amount Q and rotational speed N, and the constant K. The injection time τ is obtained by multiplying the calculated τ _O by the air-fuel ratio correction coefficient f (A/F) obtained in the processing routine of FIG. 3 and other coefficients R, and the data regarding the calculated τ is sent to the fuel injection control circuit. 34 registers. Feedback control of the air-fuel ratio is performed by controlling the amount of fuel supplied to the engine in accordance with the injection time τ calculated in this manner. Note that this processing routine for calculating the fuel injection time may be executed by interrupting every predetermined time.

Furthermore, the CPU 40 performs the ignition timing calculation shown in FIG. 4 in accordance with an interrupt request generated from the timing signal forming circuit 32 at every predetermined crank angle, for example, at every 120° crank angle in the case of a 4-stroke, 6-cylinder engine. Execute the processing routine. First, in step 70, data regarding the detected intake air amount Q and rotational speed N are taken in, and in the next step 71, the detected intake air amount data Q
, is corrected using the air-fuel ratio correction coefficient f (A/F) obtained in the processing routine of FIG. The simplest method for this correction is Q′=Q・f
(A/F) calculation, but other than that
Calculations such as Q'=Q・(a・f(A/F)+b) may be performed, and the average value F(A/F) of f(A/F) may be performed.
F) and then perform the calculation Q'=Q·F(A/F). Next, in step 72, the ignition advance angle θ _O is calculated from the corrected intake air amount data Q' and the detected rotational speed data N. Various methods are known for calculating this ignition advance angle θ _O. For example, as shown in FIG _. A method of determining θ _O by mapping using relationships may also be used. In the next step 73, warm-up correction, EGR correction, etc. are performed on the ignition advance angle _θO obtained as described above. For example, if these correction coefficients are γ, then in step 73, the calculation θ=θ _O +γ is performed. Next, in step 74, the crank angle between the corrected ignition advance angle θ and the reference angular position is calculated, the time required for the crankshaft to rotate by that angle is calculated, and then this calculated value is calculated. It is converted to the count number of the counter. Next, in step 75, the ignition timing data converted in this way is set in the ignition timing register of the ignition control circuit 36, thereby ending this interrupt processing routine. Further, the CPU 40 calculates data regarding the energization start timing of the ignition coil from the above-mentioned ignition timing data using a well-known method, and sets it in the other register of the ignition control circuit 36.

With the ignition timing data calculated in this way,
By controlling the ignition timing, even if the amount of intake air detected by the air flow sensor 10 differs from the amount of air actually taken in, the ignition timing can be correctly controlled to the optimum value. In other words, in the air-fuel ratio feedback control system, when the intake air amount detected by the air flow sensor is larger than the true intake air amount, the air-fuel ratio becomes rich, so the air-fuel ratio correction coefficient f (A/F) becomes smaller. As a result, an operation is performed to reduce the fuel injection amount to bring the air-fuel ratio closer to the stoichiometric air-fuel ratio. Therefore, Q・f(A/
By performing the calculation in F), the corrected intake air amount Q' will come closer to or match the true intake air amount, and if ignition timing control is performed based on this, optimal control will be achieved. This is possible.

Note that in the above embodiment, the detected intake air amount Q is corrected by f(A/F);
This may be performed for the detected rotational speed N, and in a system that performs ignition timing control from the intake pipe negative pressure and the rotational speed, f(A/F) for the detected intake pipe negative pressure. You may also make corrections.
Furthermore, in the above embodiment, f(A/F) is corrected for the detected intake air amount Q.
It is clear that this correction of f(A/F) may be performed on the finally calculated ignition advance angle θ or θ _O , and the effect in that case is the same as in the above embodiment. It is.

As explained in detail above, according to the present invention,
Even if a change in the environment such as a change in atmospheric pressure occurs or an error occurs in the sensor itself and the detected operating condition parameters differ from the true parameters, the ignition timing can be controlled to the optimal value. A special effect can be obtained in that there is no need to provide new special sensors.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an embodiment of the present invention, Fig. 2 is a block diagram of the control circuit, Figs. 3 and 4 are flowcharts explaining the operation of the control circuit, and Fig. 5 is ignition advance angle calculation. It is a map diagram for. 10... Air flow sensor, 12... Negative pressure sensor, 14... Fuel injection valve, 16... Control circuit, 1
8... Spark plug, 20... O ₂ sensor, 24...
...Distributor, 26...Ignition coil, 2
8...Rotation angle sensor, 36...Ignition control circuit, 4
0...CPU, 44...Ignition device, 46...
ROM, 48...RAM.

Claims (1)

[Claims] 1. Detecting the concentration of a specific component in exhaust gas, increasing or decreasing an air-fuel ratio correction value according to the detected value, and controlling the amount of fuel to be supplied to the engine according to the increased or decreased air-fuel ratio correction value. In an internal combustion engine having an air-fuel ratio feedback control system for controlling the engine, detecting the operating state including at least the load state and rotation speed of the engine,
A method for controlling ignition timing of an internal combustion engine, comprising controlling ignition timing of the engine according to the detected operating state and the air-fuel ratio correction value. 2 Calculating an ignition timing control value according to the detected operating state, correcting the calculated ignition timing control value according to the air-fuel ratio correction value, and matching the ignition timing of the engine to the corrected ignition timing control value. The ignition timing control method according to claim 1, wherein: 3 Correcting a load state parameter among the detected operating state parameters according to the air-fuel ratio correction value, calculating an ignition timing control value according to the operating state parameter including the corrected load state parameter, and calculating the ignition timing control value according to the operating state parameter including the corrected load state parameter. The ignition timing control method according to claim 1, wherein the ignition timing of the engine is made to match the ignition timing control value.