JPS6314766B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a knocking control method for suppressing or avoiding knocking occurring in an engine.

It is known that in order to improve the fuel efficiency and performance of an engine, it is possible to increase the engine's compression ratio and advance the ignition timing, but this increases the likelihood of knocking, so it is difficult to detect Therefore, it is necessary to take appropriate measures such as controlling the ignition timing to be delayed (for example, see Japanese Patent Laid-Open No. 53-60430).

Conventional knocking detection methods for this purpose include
There are methods to detect knocking by measuring engine cylinder pressure, and methods to detect knocking by measuring engine vibration.

In other words, in the former case, when knocking does not occur, the cylinder pressure changes smoothly with respect to the engine rotation angle, as shown by the solid line in Figure 1, but when knocking occurs, it changes violently due to abnormal combustion, as shown by the broken line. This is a method to determine whether knocking has occurred by measuring the pressure change.The latter method measures the abnormal vibration of the engine caused by the sudden pressure change and detects the occurrence of knocking. This is a method to determine the presence or absence.

However, such conventional knocking detection methods require a pressure sensor that can withstand the high temperature and pressure inside the engine cylinder, and a highly sensitive vibration sensor that can detect minute engine vibrations, making it expensive. It had the disadvantage of becoming. In addition, in the case of pressure detection, it is difficult to ensure the permanence of the pressure sensor, and in the case of vibration detection, when trying to increase the detection signal level of the vibration sensor in order to accurately determine the vibration caused by knocking, the The amount of displacement of the vibration sensor must be increased, which also poses the problem of making it difficult to ensure the durability of the vibration sensor.

The purpose of this invention is to reliably detect the occurrence of knocking and to suppress or avoid the knocking without using pressure sensors or vibration sensors that are expensive and have durability problems. do.

Therefore, the knocking control method according to the present invention detects the amount of variation in the engine rotation speed in a predetermined rotation angle range near the top dead center of the engine, and delays the ignition timing when the amount of variation is larger than a predetermined value. .

Next, the operation of this knocking control method will be explained.

Generally, if knocking does not occur in the engine, the pressure inside the cylinder changes as shown by the solid line in Figure 1 with respect to the engine rotation angle, and the engine rotation speed changes accordingly as shown by the solid line in Figure 2. However, when knocking occurs, a sudden pressure change occurs as shown by the broken line in FIG. 1, and the change in engine speed becomes more rapid than normal, as shown by the broken line in FIG. 2.

The period during which the engine speed changes drastically due to the occurrence of knocking is the second
As can be seen from the figure, the engine rotation angle is limited to a certain range, which is immediately after ignition, that is, immediately after the start of combustion, and approximately near top dead center.

Therefore, according to the present invention, the amount of fluctuation in the engine is detected in a predetermined rotation angle range near the top dead center of the engine, and whether or not knocking has occurred is determined based on whether the amount of fluctuation is larger than a predetermined value. is determined reliably, and when it is larger than the predetermined value,
Although knocking occurs, the occurrence of knocking can be suppressed or avoided by delaying the ignition timing.

Furthermore, according to this method, it is possible to detect the amount of variation in engine rotation speed by using the engine rotation angle detection means conventionally used to generate angle pulses for determining ignition timing. Therefore, there is no need to use pressure sensors or vibration sensors that are expensive and have durability problems.

Hereinafter, an embodiment in which the knocking control method according to the present invention is applied to an ignition timing control device will be described with reference to FIG. 3 and subsequent figures of the accompanying drawings.

In FIG. 3, the engine rotation angle detection means 1 generates pulse signals a and b at every constant rotation angle of the engine.
occurs. For example, when the present invention is applied to a six-cylinder engine, as shown in FIG. 4, the pulse signal a rises and falls repeatedly every 1 degree of engine rotation angle, and the pulse signal b rises every 120 degrees.

Many engine rotation angle detection means 1 are already known, such as a combination of an electromagnetic pickup and a gear, a combination of a light emitting/light receiving device and a disk with a slit, a combination of a magnetic sensing element and a disk attached to a magnet, etc. .

As shown in FIG. 5, the period measuring means 2 consists of a clock oscillator 21, a counter 22, and a timing control circuit 23, and calculates and calculates the period of the pulse signal a.
The measurement is controlled by a microcomputer (hereinafter referred to as "microcomputer") 3 as a storage means.

That is, the timing control circuit 23 controlled by the microcomputer 3 outputs to the microcomputer 3 an interrupt request signal i that rises, for example, every 1 degree in synchronization with the pulse signal a, and the microcomputer 3 responds to this by changing the engine rotation angle 1. The counter 22 reads and stores the count data h obtained by counting the clock signal c from the clock oscillator 21 at every 100 degrees, and measures the period of the pulse signal a by calculating, for example, the difference between the data. .

As shown in FIG. 6, the microcomputer 3 includes a central processing unit (CPU) 31, a read-only memory ROM 32 that stores programs to be described later, and a random access memory that temporarily stores various calculation data.
It is composed of a memory RAM 32, etc., and can store measured cycle data, process the data to calculate the instantaneous value of the engine rotation speed, and operate the engine in a predetermined rotation angle range near the top dead center of the engine. Calculates the instantaneous value fluctuation amount of the rotation speed, determines the presence or absence of knocking based on the magnitude of the fluctuation amount, and outputs ignition timing data f and energization angle data e corresponding thereto to the ignition signal generating means 4; Further, a signal g corresponding to the amount of variation is outputted to the D/A converter 5 of the tick display system. Note that these details will be described later.

As shown in FIG. 8, the ignition signal generating means 4 includes a register 41 that receives ignition timing data f from the microcomputer and stores it, and a register 42 that receives energization angle data e from the microcomputer and stores it.
A counter 43 that is reset by the pulse signal b, counts the pulse signal a, and measures the current value of the engine rotation angle position based on the engine rotation angle at which the pulse signal b enters, and the measured value of the counter 43 and a register. A comparator 45 compares the values of 41 and resets the ignition signal j which is the output of the flip-flop 44 when they match, and a comparator 45 which compares the measured value of the counter 43 and the value of the register 42 and resets the ignition signal j which is the output of the flip-flop 44 when they match. - Consists of a comparator 46 that sets the ignition signal j that is the output of the flop 44, etc., and the engine is ignited at the engine rotation angle corresponding to the ignition timing data f. An ignition signal j is generated to start supplying the primary current to the ignition coil at an engine rotation angle corresponding to data e.

The D/A converter 5 converts the digital signal g corresponding to the amount of variation in the instantaneous value of the engine rotational speed output from the microcomputer 3 into an analog signal m, and uses the analog signal m to control a pointer-type meter, etc., for example. The display 6 is driven to display the magnitude of the variation, that is, the degree of occurrence of knocking. In addition, microcontroller 3
Instead of the digital signal g from the controller, an on/off signal indicating the presence or absence of knocking may be used to operate an indicator such as a lamp or buzzer, and the degree of knocking occurrence may be displayed in several stages. You can do it like this.

Next, the operation of the microcomputer 3 in the embodiment configured as described above will be explained with reference to the flowcharts shown in FIGS.

First, when the power is turned on, as shown in Figure 7 A,
Starts operation from the "reset" state and reads various input data. Although input data is not shown in Fig. 3, it includes signals indicating engine load conditions (e.g. intake air amount, intake pressure, throttle opening), engine coolant temperature, intake air temperature, power supply (battery) voltage, etc. This is the signal.

The ignition timing is determined based on these data, and first, the basic ignition timing is calculated in accordance with data of the engine rotational speed measurement results and data indicating the engine load state, which will be described later. Read cooling water temperature,
Ignition timing is corrected based on intake air temperature, etc. Next, the conduction angle of the primary current of the ignition coil is calculated in accordance with these factors so that the ignition energy is constant regardless of the engine rotational speed or power supply voltage. These calculations are repeated so that the newest data is always stored in the RAM 33 of the microcomputer 3.

Next, a method for determining the presence or absence of knocking will be explained. As mentioned above, the period of the pulse signal a is measured using the period measuring means 2, and the measured data is transmitted to the interrupt request signal i generated every 1° from the timing control circuit 23 shown in FIG. The interrupt processing program that is called by the CPU of the microcontroller 3
31 is executed and obtained.

When this interrupt request signal i is input, the 7th
CPU31 was repeatedly executing the calculation process shown in Figure A.
, temporarily interrupt it and use the "1° interrupt" in Figure B.
Processing starting from is executed preferentially.

First, count data h of the counter 22 is read. Calculate the period t from the rising edge to the falling edge or from the falling edge to the rising edge of the signal a from that data and the previously read data, and calculate the period t from the rising edge to the falling edge or from the falling edge to the rising edge.
Store it in RAM33. Next, similarly, the difference Δt between the periodic data calculated last time and stored in the RAM 33 and the periodic data calculated this time is calculated.

Note that since the period t is the reciprocal of the instantaneous value of the engine rotational speed, the larger the difference Δt between them, the greater the amount of variation in the rotational speed. Therefore, the amount of variation in the instantaneous value of the rotational speed can be determined by the size of this Δt. be able to.

Of course, the fluctuation amount may be directly determined by determining the instantaneous value of the engine rotational speed and then calculating the difference between the two values.

Therefore, Δt is compared with a predetermined reference value, and if it is larger than the reference value, it is determined that there is a knock, and if it is smaller, it is determined that there is no knock, and the determination result is
Store it in RAM33.

Note that this determination or the calculation of Δt corresponding to the variation amount of the engine rotational speed for making this determination is performed in a predetermined rotation angle range near the top dead center of the engine.

For example, the engine rotation angle detection means 1 is set so that the pulse signal b is generated near the top dead center, and the above-mentioned determination is performed only immediately after the pulse signal b is received.

Further, the reciprocal of the period t is calculated to obtain an instantaneous value of the engine rotation speed, which is used for calculating the basic ignition timing described above.

In addition, at the time when the difference Δt of period data is calculated,
A digital signal g corresponding to the magnitude is outputted to the D/A converter 5, and the magnitude of the rotational fluctuation, that is, the degree of occurrence of knocking, is displayed on the display 6 via it (see FIG. 3).

When the above arithmetic processing is completed, the arithmetic processing starting from "reset" in A of the figure is resumed again from where it was interrupted.

Next, a method for correcting the ignition timing according to the knock determination result will be explained.

When the pulse signal b, that is, the signal of the engine rotation angle of 120° is input to the CPU 31 of the microcomputer 3, the 7th
The arithmetic processing starts from the "120° interrupt" in Figure C. .

First, it is determined by the arithmetic processing shown in FIG.
3. Check the knock judgment result stored in step 3. If there is a knock, the calculated and corrected ignition timing is retarded using the arithmetic processing shown in A of the same figure. If there is no knock, the correction to delay the ignition timing has already been made. If the correction amount has been made, gradually reduce the correction amount to return it to zero, and if the correction has not been made, the ignition timing data f is left unchanged.
and energization angle data e are output to the ignition signal generating means 4. Then, the ignition signal generating means 4 generates an ignition signal j from these data f, e and the pulse signals a, b from the engine rotation angle detecting means 1, thereby controlling the energization of an ignition coil (not shown). ,
Ignition is performed via a power distributor or spark plug in a manner that suppresses or avoids the occurrence of knocking.

What has been described above is a basic embodiment of the present invention, and next, other embodiments will be described.

When applied to engines other than 6-cylinder engines, pulse signal b can be changed every 180° for a 4-cylinder engine, and every 90° for an 8-cylinder engine, that is, 720° ÷ ( A pulse is generated for each angle (number of cylinders).

Period measurement does not necessarily have to be performed every 1°. For example, if you want to do it every 2 degrees, the pulse signal a
It may be changed so that it changes every 2 degrees, or the period from one rising edge of the pulse signal a to the next rising edge may be measured.

Furthermore, in the arithmetic processing, Δt may be calculated for each result of two measurements. Slowing down the cycle in this way has the advantage of allowing the use of inexpensive microcomputers and their peripheral circuits that have slow processing speeds.

The presence or absence of knocking can be determined more accurately by changing the reference value depending on the operating state of the engine. For example, when the engine rotational speed is low, the absolute value of the amount of variation in the engine rotational speed due to knocking is small, but when the rotational speed is high, the absolute value of the variation becomes large. Therefore, it is preferable to change the reference value according to the change in rotational speed.

Note that the same effect can be obtained by multiplying the difference Δt in circumferential base data by a value corresponding to the rotation speed and comparing it with a constant reference value.

Further, the reference value may be changed or Δt may be corrected based on factors other than the engine rotation speed, such as cooling water temperature, engine load, vehicle speed, etc.

As explained above, according to the present invention, the presence or absence of knocking is determined based on the amount of variation in engine rotational speed in a predetermined rotation angle range near the top of the engine, and the amount of variation is determined to be a predetermined value. Since the ignition timing is delayed when the ignition timing is larger, the ignition timing is delayed, so instead of using conventional pressure sensors and vibration sensors that are expensive and have problems with durability, it is possible to generate the angular pulse to determine the ignition timing. By using the engine rotation angle detection means used, the presence or absence of knocking can be determined from the amount of variation in engine rotation speed, and the ignition timing can be controlled.
Thereby, the occurrence of knocking can always be reliably suppressed or avoided.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between engine cylinder pressure and engine rotation angle. FIG. 2 is a diagram showing the relationship between engine rotation speed and engine rotation angle. FIG. 3 is a block diagram showing an embodiment of the invention. FIG. 4 is a waveform diagram of the output pulse signal of the engine rotation angle detection means. FIG. 5 is a block diagram showing the structure of the period measuring means. FIG. 6 is a block diagram showing the basic configuration of the microcomputer. FIGS. 7A to 7C are flowcharts showing the operation of the microcomputer, respectively. FIG. 8 is a block diagram showing the configuration of the ignition signal generating means. 1...Engine rotation angle detection means, 2...Period measurement means, 3...Microcomputer (calculation/storage means), 4...Ignition signal generation means.

Claims (1)

[Claims] 1. A knocking control method comprising: detecting the amount of variation in the engine rotational speed in a predetermined rotational angle range near the top dead center of the engine; and retarding the ignition timing when the amount of variation is larger than a predetermined value.