JPH042793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the ignition timing of an engine, and particularly to a method of controlling the ignition timing of an engine using high octane fuel.

In recent years, as air pollution regulations have been tightened, the use of high-octane fuels containing lead compounds such as tetraethyl lead has been restricted.

As a result, engines were designed to use so-called regular fuel with an unleaded normal octane rating (75-85), and had to be designed with relatively low compression ratios in order to suppress engine knock.

In addition, considering engine efficiency such as output, it is preferable to have a high compression ratio, and recently, high octane fuel without the addition of lead compounds has been developed, so engines that use high octane fuel are once again being provided. It's coming.

In addition, for engines designed to use high-octane fuel (hereinafter simply referred to as high-octane),
If you accidentally use normal octane fuel (hereinafter simply referred to as "regular"), or if you are forced to use regular because high-octane fuel is not available, engine knocks (hereinafter simply referred to as "knock") will occur frequently and the engine will not be able to maintain sufficient performance. In the worst case scenario, the engine may be damaged. Therefore, in order to solve this problem, prepare two ignition timings in advance, one for regular and one for high-octane, and when using a regular, specify the ignition timing for regular by operating a switch, and then set the ignition timing for regular. A method has been proposed to protect the engine by retarding the timing.

However, such methods require the driver to constantly be aware of the type of fuel being used. For example, if for some reason you use the regular mode and then use the high-octane mode, even if you forget to reset the switch to the high-octane mode, the knock will not occur and the driver will not notice the incorrect setting of the switch. In such cases, even if you are using a high-octane engine, you will not be able to take full advantage of the engine's performance.

An object of the present invention is to provide an ignition timing control method that eliminates the drawbacks of the conventional methods. This purpose is to control the ignition timing after starting the engine based on a preset required advance value for high-octane fuel, and to determine whether the fuel is normal octane fuel when engine knock is detected under predetermined engine conditions. This is achieved by determining that the ignition timing is corrected to the retarded side in accordance with the difference between the required advance value and the required advance value for normal octane fuel.

Hereinafter, the present invention will be explained by giving examples and referring to the drawings.

First, FIG. 1 is an explanatory diagram showing an engine and its peripheral equipment to which the method of the present invention is applied. In this figure, 1 is the engine, 2 is the piston, 3 is the exhaust manifold, 4 is the exhaust valve,
5 is a spark plug, 6 is an intake valve, 7 is an intake manifold, 8 is a fuel injection valve, 9 is a throttle valve, 10 is an air flow meter, 11
12 is an igniter, 13 is a distributor, 14 is a cylinder discrimination sensor provided in the distributor, 15 is a rotation angle sensor also provided in the distributor, 16 is a cooling water temperature sensor, 17 represents a knock sensor, and 18 represents a control circuit.

Next, FIG. 2 is a block diagram illustrating the configuration of the control circuit 18. 20, 21 and 22 in the figure
are air flow meter 10 and water temperature sensor 1, respectively.
6, a buffer connected to each sensor of the intake temperature sensor 11; 23, a multiplexer that selectively outputs the output signal of each buffer; 24, an A/D converter that digitizes the analog signal output from the multiplexer 23; 25 is a multiplexer 23,
Outputs a control signal for the A/D converter 24,
Each sensor 10,
Input/output port for inputting signals 16 and 11, 2
6 is a shaping circuit that shapes the waveform of the pulse signal output from the cylinder discrimination sensor 14 and the rotation angle sensor 15; 27 is a knock discrimination circuit that discriminates the presence or absence of a knock based on the signal output from the knock sensor 17; and 28 is a shaping circuit. The output signals of the cylinder discrimination sensor 14 and the rotation angle sensor 15 are sent via the circuit 26, and the knock sensor 1 is sent to the knock sensor 1 via the knock discrimination circuit 27.
7, and the knock discrimination circuit 27
The input and output ports to which the mask signals of are output are respectively shown. Note that here, the knock discrimination circuit 2
7 is a bandpass filter that passes only signals in the frequency band around 7kHz (none of which are shown below), a rectifier circuit that half-wave rectifies the output of the bandpass filter, and a reference value signal that integrates the output of the rectifier circuit and generates a comparison reference value signal. It consists of an integrator circuit that generates an integrator, and a comparator that compares the output of the rectifier circuit with the output of the integrator circuit, and outputs a knock detection signal when vibrations exceeding a certain amplitude are detected. In addition, the mask signal output from the input/output port 28 is designed to prevent the knock discrimination circuit 27 from malfunctioning due to noise such as vibration caused by the operation of the intake valve 6 and exhaust valve 4.
The knock discrimination circuit 27 is masked within a predetermined crank angle range.

29 is a drive circuit that operates the igniter 12 based on a signal output from the MPU 33, which will be described later; 30 is an output port that outputs a signal from the MPU 33 to the drive circuit 29; and 31 is a drive circuit that operates the igniter 12 based on a signal output from the MPU 33, which will be described later. Random access memory (hereinafter simply referred to as
32 is a read-only memory (hereinafter simply referred to as ROM) in which control programs and initial data necessary for control are stored; 33 is a ROM 32
input/output of various signals according to the control program in the
Microprocessor unit (hereinafter simply referred to as MPU) that performs data calculations and controls the drive circuit, 34
3 represents a clock circuit which outputs a clock signal which is a timing signal for each element including the MPU 33, ROM 32, RAM 31, etc., and 35 represents a bus line which connects each element and serves as a data transfer path.

Furthermore, FIGS. 3 and 4 are flowcharts representing control programs.

FIG. 3 shows the main program of this embodiment. Each step will be simply explained below.

101 represents a step for initially setting the input/output ports to a state necessary for starting the engine.

102 is a RAM in which the flag Fk etc. described later is stored.
31 and sets initial data in registers, etc. in the RAM 31.

Reference numeral 103 represents a step for defining a clock for an input/output counter, such as setting a timing cycle for A/D conversion.

Reference numeral 104 represents a step for performing interrupt linkage set processing, such as designating a save destination address for saving the contents of the program counter, registers, etc. when an interrupt occurs.

105 represents a step for performing processing for permitting an interrupt when an interrupt signal is detected.

Reference numeral 106 represents a step for calculating the intake air amount Q per engine unit time, the engine rotation speed N, and the intake air amount Q/N per engine rotation, which indicates the engine load, from the air flow meter 10 and the rotation angle sensor 15.

Reference numeral 107 represents a step for calculating the basic advance angle value θB from the data map based on the engine speed N and the engine load Q/N.

The main program composed of the steps described above performs the following processing.

First, when a key switch (not shown) is input, the control circuit 18 is activated, executes step 101 to set the input/output ports 25, 28, and 30 to the initial state, and then executes step 102 to set the RAM.
31 is cleared and initial data is set, and then, in step 103, the input/output counter clock is defined. After performing the processing necessary for interrupt processing in steps 104 and 105, in step 106, the engine speed N, the intake air amount Q necessary for ignition timing control, and the engine load Q/N are calculated from the above N and Q. Then, in step 107, a basic advance value θB is determined from the data map based on the engine speed N and the engine load Q/N. The processes of steps 103 to 107 are repeated until the key switch is turned off.

FIG. 4 shows a 90° BTDC (Befor Top Dead Center) interrupt routine for ignition timing control, which is the main part of this embodiment.
Each step will be explained below.

201 is based on the basic advance angle value θB obtained in the main routine, the intake temperature correction value θA calculated based on the intake temperature data obtained from the intake temperature sensor 11, and the water temperature data obtained from the water temperature sensor 16. This step represents the step of adding the water temperature correction value θW calculated in the above step to calculate the advance angle required by the engine when using a high-octane engine, that is, the required advance angle value θ.

202 represents a step for determining whether or not a flag Fk indicating that the ignition timing for the guillotine has been corrected has been set since the engine was started up to the present time.

203 represents a step for determining whether the engine rotation speed N is 1500 rotations or more.

204 represents a step for determining whether the engine rotation speed is 4000 rotations or less.

Reference numeral 205 represents a step for determining whether or not the knock detection signal is output from the knock determination circuit 27.

Reference numeral 206 represents a step in which processing is performed to further delay the required advance angle value θ calculated in step 201 by Δθ as a general purpose.

207 represents a step for setting or maintaining the flag Fk at "1".

The processing operation of this routine, which is composed of each step described above, will be explained below. At the timing of 90° BTDC of each cylinder determined by the cylinder discrimination sensor 14 and rotation angle sensor 15, the MPU 33 performs the processing shown in this routine. In step 201, the basic advance angle θB calculated in the main routine is corrected according to the intake air temperature TA and engine coolant temperature TW to obtain the required advance angle value θ. It is determined that the flag Fk is set. In this step 202, a knock signal is detected from the time the engine is started until the present time, and if the flag Fk is set, a determination is made to automatically switch to the ignition timing for the guiller.

If the determination result in step 202 is "YES", that is, flag Fk = 0, step 203 is executed to determine whether or not the engine speed N exceeds the lower limit. The result is "YES" and step 204 is subsequently executed. The reason for setting the lower limit in step 203 is that even if high octane is used,
In low engine speed ranges, especially under high loads, knocks are likely to occur, and in such low speed ranges, even if a knock is detected, it is better not to switch to the ignition timing for the guiller. The reason why the upper limit value is set in step 204 is that the vibration noise is large in the high engine speed range, making it impossible to accurately detect the knock signal 2. For example, from 1500 rpm to obtain an accurate knock detection signal.
Next step 2 only within the engine speed range of 4000rpm
05 is performed. Therefore, if the engine speed N deviates from the predetermined range in steps 203 and 204, the judgment result will be "NO" and the processing of this routine will be completed, and the judgment result will be "YES", that is, the engine speed If the number is within the predetermined range, the next step 205 is executed. In addition, during transient times such as acceleration or sudden load changes, or during high loads, knocking is likely to occur even at the normal advance angle, so it is more accurate to avoid knocking when the intake manifold negative pressure is below a predetermined value. Can detect knocks.

Then, in step 205, the knock discriminating circuit 2
It is determined whether or not a knock is detected by the knock sensor 17 via the knock sensor 7. If the knock is not detected, the determination result is "NO" and the processing of this routine is completed. If it has occurred, the process moves to step 206.

In step 206, processing is performed to delay the required advance value θ calculated in step 201 by Δθ, that is, processing to correct the ignition timing for the high-octane engine to the ignition timing for the high-octane engine. The value of the correction amount Δθ may be fixed to the average value or the maximum value of the difference between the required advance angle values in all driving ranges for the high-octane vehicle and the Guiller vehicle. The value may be calculated according to a function based on the engine speed N as shown in the broken line and in FIG. In this embodiment, in order to obtain a more appropriate ignition timing, for example, the high-octane and guillear ignition timings stored in the ROM 32 in accordance with the engine load Q/N and the engine speed N as shown in FIG. The correction amount Δθ is determined from a data map showing the difference between the required advance angle values.

Then, in step 207, the flag Fk
The value of is set to "1" and the processing of this routine ends. Once the ignition timing for the high-octane engine has been corrected to the ignition timing for the general engine in the above process, the required advance value θ is calculated in step 201 when the subsequent processing of this routine is performed. Then, in step 202, since the flag Fk is set to "1", the process in step 206 is immediately executed to maintain the correction of the ignition timing for the guiller, and in the following step 207, the flag Fk is set to "1".
is maintained, and the processing of this routine ends.

To summarize the processing of this routine described above,
The processing of this routine starts at the timing of 90 degrees BTDC, the ignition timing for high-octane engine is calculated in step 201, and then it is determined whether or not the ignition timing has been previously corrected using the flag Fk.
If it is determined that the correction has been made, step 206
Maintain the process of jump to the ignition timing for Guiller. If no correction has been made yet, it is determined in steps 203 and 204 whether the engine speed N is within a range suitable for detecting a knock, and then in step 205 it is determined whether or not there is a knock, and the engine Only when the engine speed is within a range suitable for detecting a knock and a knock is detected, the ignition timing for the high-octane engine is corrected to the ignition timing for the regular engine, and in the subsequent process, the flag Fk is set, and the engine speed is adjusted. If the knock is not suitable for detecting a knock, or if no knock is detected, the processing of this routine ends.

In this way, once the flag Fk is set to "1", control is performed based on the ignition timing for the regular engine until the engine is stopped, so the ignition timing for the regular engine and the high-octane engine are controlled as in the conventional method. There is no need to operate a switch, and there is no inconvenience that occurs when using high-octane fuel with the ignition timing set for the regular.

In the BTDC90° interrupt routine, a time counting step is provided which is set when Fk is first set in step 207 and reset after a predetermined period of time, for example, 1 to 2 hours has elapsed, and the flag Fk is reset when the predetermined period of time has elapsed. By doing so, even if for some reason, for example, a deposit occurs in the combustion chamber, or the air-fuel ratio suddenly becomes lean, and a knock occurs and the ignition timing is incorrectly corrected to the Guiller ignition timing, the predetermined period of time will still be maintained. Later, it becomes possible to determine again whether or not the ignition timing can be corrected depending on the fuel used.

As explained above, in the method of the present invention, after the engine starts, ignition timing is controlled based on a preset required advance value for high octane fuel, and when engine knock is detected under predetermined engine conditions, fuel is determined to be normal octane fuel, and the ignition timing is corrected to the retard side in accordance with the difference between the required advance value and the required advance value for normal octane fuel.

Therefore, when an engine knock is detected under specified engine rotation conditions, it automatically determines that the fuel in use is not for high-octane fuel without any troublesome manual operation, and sets the required advance angle value for regular. The ignition timing can be controlled, preventing frequent occurrence of harsh knocking noises and damage to the engine, and making it possible to control the ignition timing according to the fuel used.

Furthermore, if no engine knock is detected under predetermined engine conditions after the engine is started, ignition timing retardation correction will not be performed, and ignition timing control will only be performed using the required advance value for high-octane fuel.
There is no problem with retarding the ignition timing when using high octane fuel, and when using high octane fuel, the engine performance due to the high octane fuel can be fully demonstrated.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an engine and its peripheral equipment applied to an embodiment of the method of the present invention. Fig. 2 is a block diagram showing the control circuit, Fig. 3 is a flowchart showing the main program of the embodiment, Fig. 4 is a flowchart showing the BTDC90° interrupt routine, and Fig. 5 is a flowchart showing the BTDC90° interrupt routine. A graph showing the required advance angle according to the engine rotation speed, Fig. 6 is a graph showing the correction amount of the required advance angle according to the engine rotation speed, that is, a graph showing the difference between the required advance angle value for high-octane and regular use, Fig. 7 is a data map showing the required advance angle correction amount corresponding to engine load-engine speed. 1...Engine, 5...Spark plug, 10...
Air flow meter, 11... Intake temperature sensor, 14...
... Cylinder discrimination sensor, 15 ... Rotation angle sensor, 16
...Water temperature sensor, 17...Knock sensor, 18...
...Control circuit, 33...MPU.

Claims (1)

[Claims] 1. After starting the engine, the ignition timing is controlled based on a preset required advance value for high octane fuel, and when an engine knock is detected under predetermined engine conditions, the fuel is of normal octane value. An ignition timing control method comprising determining that the fuel is fuel and correcting the ignition timing to the retard side according to the difference between the required advance value and the required advance value for normal octane fuel.