JPH0555708B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an ignition timing control device for an internal combustion engine.
In particular, the present invention relates to a device that can perform ignition timing control suitable for two types of fuels having different octane numbers.

Prior Art In engines where two types of fuel with different octane numbers, normal octane fuel (hereinafter referred to as regular fuel) and high octane fuel (hereinafter referred to as high-octane fuel), are likely to be used, two types of fuel suitable for each fuel are used. One of the ignition timing characteristics is selected depending on the fuel used, and the ignition timing is controlled accordingly. Determination as to whether the fuel currently being used is regular fuel or high-octane fuel is automatically performed according to the detection output of the knock sensor. The problem with such a system that automatically determines the octane number is which ignition timing characteristic should be used for control until the determination is complete.
If relatively retarded ignition timing control for regular fuel is performed until the determination is completed, engine performance will suffer if high-octane fuel is used until the determination is completed. Furthermore, if relatively advanced ignition timing control for high-octane fuel is performed until the determination is completed, a large amount of knocking will occur if regular fuel is used and a high rotational speed is reached. At high rotational speeds, engine vibrations other than knocking become large, making it difficult to control knocking, resulting in significantly large knocking.
In the worst case, the engine may be damaged.

OBJECT OF THE INVENTION The present invention therefore solves the above-mentioned problems of the prior art, and its object is to avoid knocking and consequent engine damage when fuels with different octane ratings are used. Moreover, it is an object of the present invention to provide an ignition timing control device that can maintain engine performance as high as possible.

Structure of the Invention The structure of the present invention that achieves the above-mentioned object will be explained using FIG. ignition timing is calculated by selectively using the ignition timing characteristic for normal octane fuel or the ignition timing characteristic for high octane fuel according to the determination result; and means e for detecting that the engine a is in a high rotational speed state.
If it is detected that the engine a has reached a high rotational speed before the judgment by the judgment means c is completed, the ignition timing calculation means d calculates the ignition timing using the ignition timing characteristic for normal octane fuel. The present invention is characterized in that it includes a means f for forcing the user to perform the following steps.

Example The present invention will be explained in detail below with reference to Examples.

FIG. 2 shows an internal combustion engine in which ignition timing is controlled by a microcomputer as an embodiment of the present invention. In the figure, 10 is a cylinder block of the engine, and 12 is a knock sensor attached to the cylinder block 10. The knock sensor 12 is a well-known device that is composed of, for example, a piezoelectric element or an electromagnetic element, and converts mechanical vibrations into electrical amplitude fluctuations. The distributor 14 is provided with crank angle sensors 16 and 18. The crank angle sensor 16 generates 24 pulses every revolution of the distributor shaft, ie, every 30 degrees of crank angle. The crank angle sensor 18 is for cylinder discrimination, and every time the distributor shaft rotates once, that is, the crankshaft
Generates one pulse every time it rotates (every 720° CA). For example, this occurs at a position slightly before the compression top dead center of the first cylinder. Electrical signals and pulses from the knob sensor 12 and crank angle sensors 16 and 18 are sent to an electronic control unit (ECU) 20.

The ECU 20 further includes an engine intake passage 22.
A voltage signal corresponding to the intake air flow rate Q of the engine is sent from an air flow sensor 24 provided in the engine.

On the other hand, the ECU 20 outputs an ignition signal to the igniter 26, and the igniter 26 thereby controls the primary current of the ignition coil 28 intermittently. The high voltage current generated by the ignition coil 28 is passed through the distributor 14 to the spark plug 30 of each cylinder.
As a result, an ignition spark is formed at the ignition timing according to the ignition signal.

Engines are typically equipped with various other sensors that detect operating condition parameters, and
The ECU 20 also controls the opening and closing of the fuel injection valve 32 and controls the injection amount of pressurized fuel from a fuel system (not shown), but since these are not directly related to the present invention, they will be omitted in the following explanation. .

FIG. 3 shows an example of the configuration of the ECU 20 shown in FIG. The voltage signal from the airflow sensor 24 is sent to an analog multiplexer (MPX) 20b via a buffer 20a, selected according to instructions from a microcomputer, and applied to an analog-to-digital (A/D) converter 20c. . Input data representing the intake air flow rate Q converted into a binary signal by the A/D converter 20c is input into the microcomputer via the input/output port 20d.

Pulses at every 30° crank angle from the crank angle sensor 16 and pulses at every 720° crank angle from the crank angle sensor 18 are waveform-shaped in the waveform shaping circuit 20e and then input into the microcomputer via the input/output port 20f. be taken in.

The output signal of the knock sensor 12 is sent to an A/D converter 20h via an input circuit 20g consisting of a buffer for impedance conversion and a bandpass filter whose pass band is the frequency band (7 to 8 kHz) specific to knocking. After being converted into a binary signal, it is taken into the microcomputer via the input/output port 20f.

On the other hand, an ignition signal is output from the microcomputer to the igniter 26 via the input/output port 20f and the drive circuit 20i, thereby performing the above-mentioned ignition process.

The microcomputer has the aforementioned input/output ports 20d and 20f and a central processing unit (CPU) 2.
0j and random access memory (RAM) 20
k, 20l of read-only memory (ROM),
It mainly consists of a clock generation circuit (not shown), a memory control circuit, and a bus 20m connecting these circuits, and executes the ignition timing control process described later in accordance with a control program stored in advance in the ROM 20l.

Note that the engine of this embodiment is normally set to inject high-octane fuel, and controls the ignition timing to deal with the accidental injection of regular fuel.

The operation of the microcomputer will be explained below using a flowchart.

FIG. 4 shows part of the processing executed in the initial routine. When the engine's ignition switch is turned on, the CPU 20j goes to step
Execute processes 100 and 101. In step 100, a determination completion flag is set when the determination operation of whether or not regular fuel has been injected is completed.
Reset F _JCOM to “0”. At step 101, count values C ₁ and C ₃ used in the processing routines of FIGS. 5 and 6 are reset to "0".

FIG. 5 shows a portion of the TDC interrupt routine that is executed for knocking control at each compression top dead center of each cylinder and at each ignition. step
In step 200, it is determined whether or not the driving range is such that knocking control is to be performed, for example, a medium or low speed driving range. In the case of the knocking control region, the count value _C1 is increased by one in step 201. If it is not the knocking control area, step 201 is skipped and the process proceeds to the next step 202. In step 202, it is determined whether the count value _C1 is 500 or more. C ₁ ≧
500, that is, when the engine rotates for more than 500 ignitions in the knocking control region after the ignition switch is turned on, the count value C1 is set to 500 in step 203, and the count value _C1 is set to 500 in step 204.
Set the determination completion flag F _JCOM to "1".
Next, proceed to step 205. Also, if the rotation does not reach 500 ignitions (when C ₁ < 500), the step
Proceed directly from step 202 to step 205. Step 205 is a part that performs regular fuel injection determination processing,
This determination process is performed by the processing routine shown in FIG. 6 or 7. As described above, according to the processing routine shown in FIG. 5, the regular fuel injection determination is performed for 500 ignitions after the engine is started.

Next, the regular fuel injection determination process shown in FIG. 6 will be explained. First, in step 300, the CPU
20j is a flag that is set when the ignition timing advance correction value θ _k based on knocking control is retarded to the minimum value θ _KMIN , which is the limit on the retard side.
Determine whether F _MIN is "1" or not. _FMIN =0
If so, proceed to step 301 and check the knob sensor 12.
A check is made to see if it is determined that knocking has occurred using a well-known method based on the signal from the controller.
If knocking does not occur, the process proceeds to step 302, where the advance angle correction value θ _K is increased by α. That is, processing is performed in the advance direction.

If knocking has occurred, the process proceeds to step 303, where it is determined whether the advance angle correction value θ _K is greater than or equal to the minimum value θ _KMIN , which is the limit on the retard side. If θ _K ≧θ _KNIN , the process jumps to step 306, where the advance angle correction value θ _K is decreased by β, and retard processing is performed. If θ _K <θ _KMIN , the process proceeds to step 306 after steps 304 and 305, and retard processing is performed. In step 304, the aforementioned flag F _MIN is set to "1", and in step 305, the initial value "100" is set to the count value _C2 used in later processing.

In this way, even if knocking occurs and the advance angle correction value θ _K is decreased to control the ignition timing in the retarded direction, knocking still occurs and when θ _K is reduced to its retarded limit, The advance angle correction value θ _K is no longer adjusted, and the processing in steps 307 to 314 exclusively determines whether or not regular fuel has been injected.

In step 307, the count value _C2 is decreased by "1", and in the next step 308, this count value is
Determine whether C ₂ is greater than or equal to "0". C ₂ ≧
If it is 0, the process advances to step 309 to determine whether or not large knocking is occurring. This determination is made in accordance with the output of the knock sensor 12 using a well-known method. Step each time large knocking occurs
Proceed to 310 and increment the count value _C3 by one. The initial value of C ₂ is “100”, so θ _K <
After θ _KMIN is reached, the determination in step 309 is performed 100 times (100 ignitions), and the number of times large knocking occurs during that time becomes the count value _C3 . After 100 ignitions, C ₂ <0, so proceed to step 311.
It is determined whether the count value _C3 exceeds "10". If C ₃ > 10, it is determined that regular fuel has been injected and the process proceeds to step 312.
A flag F _R indicating this is set to "1".
Next, in step 313, the flag F _MIN is set to “0”.
and reset the count value _C3 to "0". If C ₃ ≦10, skip step 312 and proceed to step 313. In this way, the steps
According to the processing in steps 307 to 314, the number of times C ₃ of large knocking has occurred is detected during the 100 ignitions after the advance angle correction value θ _K has been retarded to the retard limit θ _KMIN , and this is When the predetermined value is "10" or more, it is determined that regular fuel is being injected.

Next, the regular fuel injection determination device shown in FIG. 7 will be explained. The processing routine of FIG. 7 is the processing routine of FIG. 6 with steps 400 and 401 added. That is, if it is determined in step 301 that knocking has occurred, the process proceeds to step 400, in which it is determined whether the engine rotational speed N is less than 4000 rpm, and
The process in step 303 is performed when the rotation speed is <4000 rpm, that is, when the rotation speed is in the medium to low rotation speed region. If N≧4000 rpm, proceed to step 302.
Furthermore, even when it is determined in step 308 that C ₂ ≧0, the process proceeds to step 401 to determine whether N<4000rpm, and only when the rotation speed is in the medium and low rotational speed region, the step is executed.
I am trying to proceed to 309. Step like this
By adding 400 and 401, the regular fuel injection determination operation is performed only in the medium and low rotational speed region where S/N is good for knocking control. If this judgment operation is performed in a high rotational speed region, non-knocking noise such as valve tapping may cause an erroneous judgment that regular fuel is being injected even though high-octane fuel is being injected. There isn't.

FIG. 8 shows processing that may be performed in place of steps 309 and 310 of the processing routines of FIGS. 6 and 7. In step 500, in exactly the same way as step 309, it is determined whether or not large knocking has occurred. If large knotting occurs, check whether or not the knotting occurs continuously.
Determine by 501. If there is continuous knocking, the count value is increased by "2" in step 502,
If there is no continuous knocking, the count value is increased by "1" in step 503. In this way, by changing the amount of increase in the count value _C3 depending on the presence or absence of continuous knocking, more accurate regular fuel injection determination processing can be performed.

FIG. 9 is a processing routine for calculating ignition timing. The CPU 20j executes the process shown in FIG. 9 during the main routine. First, in step 600, the rotational speed N and Q/K calculated in advance from this N and the intake air flow rate Q and stored in the RAM 20k are read from a predetermined position in the RAM 20k. In the next step 601, it is determined whether or not the determination completion flag F _JCOM described above is set to "1" to determine whether the regular fuel injection determination operation has been completed. If the judgment operation has been completed (F _JCOM = 1), proceed to step 602.
It is known whether regular fuel is being injected by checking whether the flag F _R is set to "1".

If F _R =1, it is regular fuel injection, so the process proceeds to step 603, and the basic ignition advance angle θ _BSE is determined using the ignition timing characteristics for regular fuel. If F _R =0, regular fuel is not injected, so the process proceeds to step 604, and the basic ignition advance angle θ _BSE is determined using the ignition timing characteristics for high-octane fuel. That is, in the ROM 20l, there is a function table suitable for high-octane fuel of θ _BSE for N and Q/N as shown in Figure 10a, and a function table suitable for regular fuel of θ _BSE for N and Q/N as shown in Figure 10b. A suitable function table is stored in advance.
In step 603, the regular fuel function table shown in FIG. 10b is used, and in step 604, the first function table is used.
Determine θ _BSE using the high-octane fuel function table shown in Figure 0a. Of course, in that case interpolation methods are used. The one for high-octane fuel in Figure 10a is the first
It is well known that θ _BSE is set to be on the more advanced side than the one for regular fuel shown in Figure 0b.

Now, if it is determined in step 601 that the regular fuel injection judgment operation has not been completed (if F _JCOM = 0), that is, if the engine has not rotated from engine start to 500 ignitions in the knocking control region. , proceed to step 605. In step 605, it is determined whether or not the rotational speed N exceeds 5000 rpm. Step if N≦5000rpm
Proceeding to 604, θ _BSE is determined using the function table for high-octane fuel. However, N>
When the rotation speed is as high as 5000 rpm,
Proceeding to step 603, θ _BSE is determined using the regular fuel function table.

In this way, if a high rotational speed state occurs before the regular fuel injection determination operation is completed, the basic ignition advance angle θ _BSE is determined using the relatively retarded ignition timing characteristic for regular fuel.

In the next step 606, the lead angle correction value θ _K obtained in the processing routine of FIG. 6 or 7 is stored in the RAM 2.
In step 607, the final ignition advance angle θ is determined from θ _BSE and θ _K by θ=θ _BSE +θ _K. The ignition advance angle θ obtained in this way
is stored at a predetermined location in the RAM 20k in step 608. This ignition advance angle θ is read by an interrupt processing routine executed at a predetermined crank angle position, and an ignition signal representing the start timing and end timing (ignition timing) of energization to the ignition coil 28 is determined according to this θ. Since the method for determining such an ignition signal is well known, the explanation thereof will be omitted in this specification.

In addition, in the embodiment described above, the engine is set to be compatible with high-octane fuel, and the determination is made when regular fuel is used in this engine, but which fuel is compatible is not set in advance. The present invention can also be applied to an engine in which the ignition timing characteristics adapted to the injected fuel are used after determining the fuel to be injected.

Effects of the Invention As explained in detail above, according to the present invention, if a high rotational speed state is reached before the determination as to whether normal octane fuel or high octane fuel is being used, normal octane fuel is used. Since we are trying to use the ignition timing characteristics of
It is possible to prevent knocking and engine damage that would occur if fuels with different octane numbers were used. Furthermore, engine performance can be improved as much as possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the present invention, Fig. 2 is a schematic diagram of an embodiment of the present invention, Fig. 3 is a block diagram showing the structure of the ECU shown in Fig. 2, and Figs. 4 to 9 are a block diagram of the ECU. Flowchart of part of control program, No. 10
FIG. 10A and FIG. 10B are diagrams showing function tables of basic ignition advance angle. DESCRIPTION OF SYMBOLS 10... Cylinder block, 12... Knock sensor, 14... Distributor, 16, 18... Crank angle sensor, 20... ECU, 24... Air flow sensor, 26... Igniter, 28... Ignition coil, 30... Spark plug.

Claims (1)

[Scope of Claims] 1. A means for detecting the occurrence of knocking in an engine, a means for determining whether normal octane fuel or high octane fuel is used depending on the output of the knocking detection means, and the determination result. means for calculating the ignition timing by selectively using the ignition timing characteristic for normal octane fuel or the ignition timing characteristic for high octane fuel according to the conditions; means for detecting that the engine is in a high rotational speed state; and the determining means. control means for controlling the ignition timing calculation means to calculate the ignition timing using the ignition timing characteristics for normal octane fuel when it is detected that the engine has reached a high rotation speed state before the determination is completed; An ignition timing control device for an internal combustion engine, characterized in that: 2. Claim 1, wherein the determining means includes means for detecting that the engine is in a medium-low rotational speed state, and performs the determination operation only when the engine is in a medium-low rotational speed state. ignition timing control device.