JPH0647986B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ignition timing control device for controlling a knocking level of an internal combustion engine of an automobile or the like within a predetermined range.

(Prior Art) The ignition timing of an internal combustion engine must be determined according to the state of the engine so that the engine operates optimally. It is generally known that it is best to ignite in the vicinity of a so-called MBT (Minmum ad-vace for Beat Torque), which is the minimum advance angle at the time of maximum torque, considering the efficiency and fuel efficiency of the engine. Need to change.

However, in a certain engine state, knocking occurs as the ignition timing is advanced, and stable engine operation cannot be performed. For example, MBT at low speed and low load
The knocking limit has come earlier. Further, the knocking limit is easily affected by atmospheric conditions such as temperature and humidity.

Therefore, a device has been developed in which the ignition timing is retarded depending on the presence or absence of knocking. For example, there is a device described in Japanese Patent Laid-Open No. 82074/58.

In this device, the pressure in the combustion chamber is detected by the in-cylinder pressure sensor, the detection signal is processed by an averaging circuit such as an amplifier, a bandpass filter, an envelope circuit, etc., and the knocking level is detected by its magnitude. The ignition timing is controlled so that the knocking level becomes equal to or lower than a predetermined value.

(Problems to be Solved by the Invention) However, such a conventional ignition timing control device for an internal combustion engine has a configuration in which an output signal of the in-cylinder pressure sensor is processed by a predetermined method to detect knocking. Therefore, many circuit elements are required to detect knocking.

For this reason, it becomes a high-cost device, and it is difficult to realize it with the conventional control unit generally used for electronic control of the engine.

(Object of the invention) Therefore, the present invention detects a knocking peak position by detecting the combustion peak position where the combustion pressure becomes maximum, and comparing this peak position with the knock limit θpmax corresponding to the operating condition at that time. An object of the present invention is to provide an ignition timing control device capable of performing knock suppression control with the ability of a conventional system by simplifying the system configuration required for knock detection.

(Structure of the Invention) As shown in the basic conceptual diagram of the ignition timing control device for an internal combustion engine according to the present invention, a pressure detecting means a for detecting combustion pressure of the engine and an operation for detecting an operating state of the engine are provided. State detection means b, peak position detection means c for detecting the crank angle at which the combustion pressure is maximum from the output of the pressure detection means a as the combustion peak position, and limit for setting the knock peak combustion peak position according to the operating state. Value setting means d
And a knock determination means e for comparing the actual combustion peak position with the combustion peak position at the knock limit to determine the presence or absence of knocking, and setting the ignition timing based on the operating state, and setting the ignition timing to the presence or absence of knocking. An ignition timing setting means f for making a corresponding correction, and an ignition means g for igniting the air-fuel mixture based on the output of the ignition timing setting means f.
This simplifies the system configuration required for knock detection.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 10 are views showing an embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 1 denotes an in-cylinder pressure sensor (pressure detecting means), and the in-cylinder pressure sensor 1 converts the combustion pressure in the cylinder into an electric charge by a piezoelectric element and outputs an electric charge output S ₁ . Specifically, the in-cylinder pressure sensor 1 is screwed to the cylinder head 2 and formed as a washer for the ignition plug 3, as shown in detail in FIGS. 3 (A) and 3 (B).
The ignition plug 3 is pressed and fixed in the outer recess of the cylinder head 2 by the tightening portion 3a of the ignition plug 3.

The sensor output S ₁ is input to the charge amplifier 4,
The charge amplifier 4 has operational amplifiers OP1 and OP2, resistors R1 to R8, and a capacitor C, as shown in detail in FIG.
1 and the so-called charge composed of diodes D1 to D3
A voltage conversion amplifier is configured, and the sensor output S ₁ is converted into a voltage signal S
_It is converted to ₂ and output to the control unit 5.

The control unit 5 further includes operating state detection means 6
Is inputted, and the operating state detecting means 6 comprises a crank angle sensor 7 and an air flow meter 8. The crank angle sensor 7 has an explosion interval (a crank angle of 120 ° for a 6-cylinder engine and 180 for a 4-cylinder engine).
At each predetermined position before the compression top dead center (TDC) of each cylinder,
For example, the reference position signal Ca that becomes a [H] level pulse at BTDC 70 ° is output, and the unit signal C ₁ that becomes a [H] level pulse is output for each unit angle (for example, 2 °) of the crank angle. The engine speed can be known by counting the pulses of the signal Ca. Further, the air flow meter 8 detects the intake air amount Qa of the engine and outputs an analog signal Sa.

The control unit 5 has a function as a peak position detecting means, a limit value setting means, a knock determination means, and an ignition timing setting means, and has a CPU 11, a ROM 12, a RAM 13, an A /
It is composed of a D converter 14 and an I / O port 15. C
The PU11 fetches the external data required from the I / O port 15 according to the program written in the ROM12, and exchanges the data with the RAM13 to calculate the processing value required for the ignition timing control. Then, the data processed as necessary is output to the I / O port 15.
The I / O port 15 receives signals from the operating state detecting means 6 and the charge amplifier 4, and the I / O port 15 outputs an ignition signal Sp. A / D converter 14
Performs A / D conversion of the external signal input to the I / O port 15 according to the instruction of the CPU 11. Further, the ROM 12 is the CPU 11
The RAM 13 stores the calculation program in, and the RAM 13 stores the data used for the calculation in the form of a map or the like.

The ignition signal Sp is input to the ignition means 16 and
Reference numeral 16 is composed of an ignition coil, a distributor, an ignition plug, etc., and generates a high voltage based on the ignition signal Sp to ignite the air-fuel mixture.

Next, the operation will be described. First, the basic principle of the present invention will be described.

In general, the knocking phenomenon refers to abnormal combustion due to early ignition of unburned air-fuel mixture in the cylinder, which is caused by the pressure in the cylinder having multiple natural vibrations determined by the cylinder size (especially bore diameter) and combustion gas temperature. Appears as damped vibration. This pressure vibration is transmitted to the air through the cylinder wall, the cylinder block, etc., and an unpleasant high-frequency sound that reaches the human sense of hearing is what is called a knocking sound.

FIG. 5 shows the relationship between the crank angle (hereinafter referred to as the combustion peak position) θpmax when the in-cylinder pressure becomes maximum and the knocking level by the sensitivity evaluation. This is one
This is an example of an engine of a model, but other models also show a similar tendency. As is clear from FIG. 6, there is a large difference between θpmax when knocking occurs and when it does not knock. Therefore, by detecting this θpmax, it is possible to detect a knocking level that is faithful to human sensitivity evaluation.

Further, as shown in FIG. 6 which shows the relationship between θpmax and the ignition timing, the position of θpmax can be changed by modifying the ignition timing. Therefore, knocking can be suppressed by detecting θpmax and correcting the ignition timing based on the difference from θpmax that provides a desired knocking level.

Next, the ignition timing control based on the above basic principle will be described according to the program shown in FIG.

This program uses the reference position signal Ca of the crank angle sensor 7.
When the [H] pulse is detected, the counting of the [H] pulse of the unit signal C ₁ is started, a predetermined number of times is counted, and the crank angle θ is started at a predetermined value (for example, BTDC 40 °).

First, the voltage signal S ₂ (corresponding to the in-cylinder pressure waveform) corresponding to the in-cylinder pressure changing at P ₁ as shown in FIG.
/ D start an A / D converter 14 for converting, A with _{P 2}
The count value CC ₁ of the unit signal C ₁ when the / D converter 14 is activated is stored in the RAM 13. Next, in P ₃ , it is determined whether or not the A / D conversion of the signal S ₂ is completed, and when it is not completed, the process waits, and when it is completed, the A / D conversion value is counted in P ₄ to count the unit signal C ₁ . RAM paired with value CC ₁
Store at 13. Then, the count value CC ₁ of the unit signal _{C 1} at _{P 5} is compared with a predetermined value _{C 0,} when the CC 1 _{<C 0} repeated flow of _P 1 to P ₅ by return to _{P 1.}
Then, when CC ₁ ≧ C ₀ , the process proceeds to P ₆ . Therefore, the in-cylinder pressure waveform S ₂ is converted into an A / D conversion value in a predetermined section as shown in FIG. 8 (b).

At P ₆ , the maximum value P among the A / D converted values of the cylinder pressure waveform S ₂
θpmax is obtained from max and the count value CC ₁ corresponding to this Pmax. These are stored in a one-to-one correspondence as shown in FIG. 8 (b), and the count value CC _{1 at} Pmax is the combustion P position θpmax. Next, in order to obtain the knock limit θpmax (hereinafter, referred to as knock limit value) θ _K corresponding to the operating state at that time, the intake air amount Qa and the rotation speed N are calculated as parameters indicating the operating state. That is, at P ₇ , the output Sa of the air flow meter 8 is A / D converted to obtain the intake air amount Qa, and each time the reference position signal Ca is input from the crank angle sensor 7, the [H] pulse of the unit signal C ₁ is input. Is repeatedly counted for a fixed time interval to obtain the engine speed N.

At P ₈ , from these Qa and N, the basic injection amount Tp (Tp
= K · Qa / N, where K: constant)
The knock limit value θ _K corresponding to the operating state at that time is looked up from the data table shown in FIG. 9 using these Tp and N as parameters. The data table of FIG. 9 is an example of a predetermined model (2000cc, 6-cylinder engine). N =
At 4000 rpm, there is a discrepancy in the overall trend of the data, which is due to the inertia supercharging effect. Further, the higher the load, the more the knocking occurs, and the lower the rotation speed, the lower the stability of the combustion state as compared with the high rotation speed region. Therefore, when trying to bring the knock to a desired level, the knock limit value θ _K becomes as shown in FIG. 9.

Next, at P ₉ , the combustion peak position θpmax is set to the knock limit value θ.
Compare with _K. ? pmax <calculates a present correction amount M for correcting the retard side the basic ignition timing N in P ₁₀ it is determined that knocking has occurred when the theta _K according to the following equation to correct the ignition timing is retarded.

M = M '+ ΔM ₁ ...... However, M': the last of the correction amount ΔM _1: retard correction amount The correction amount of this time in the P ₁₁ it is determined that the knock does not occur when the θpmax ≧ θ _K M is calculated according to the following equation, and the ignition timing is advanced and corrected.

M = M'-ΔM ₂ ...... However, .DELTA.M _2: advance angle correction amount thus detects a? Pmax, whether knocking simple process as compared with the conventional of comparing the detected value theta _K Can be determined. Therefore, knock suppression control can be performed easily and at low cost with the conventional system capability. In other words, the knock detection system can be sufficiently configured with a microcomputer used for ordinary engine electronic control with a small number of circuit elements required for knock detection.

After a P _10, P ₁₁ alternatively may (expressed in advance value in the figure) the basic ignition timing from a table map shown in FIG. 10 according to the operation state at P ₁₂ looks up the N, P This N at ₁₃
From the above M, the final ignition timing D is calculated according to the following equation,
This D is stored in RAM ₁₃ at P ₁₃ .

D = N + M ... And the final ignition timing D is obtained by counting the unit signal C _1.
At the timing corresponding to, the ignition signal Sp is output to ignite the mixture. Therefore, when knock occurs, the ignition timing is retarded, while when it does not occur, the ignition timing is advanced. As a result, it is possible to improve the combustion efficiency of the engine and improve the torque characteristics, and it is possible to achieve improvements in fuel consumption and driving performance.

(Effect) According to the present invention, the configuration of the system required for knock detection can be simplified, and knock suppression control can be performed easily and at low cost with the capability of the conventional control unit.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 10 are diagrams showing an embodiment of the present invention, and FIG. 2 is a block configuration diagram thereof.
3 (A) is a sectional view showing the mounting state of the cylinder pressure sensor, FIG. 3 (B) is a plan view of only the cylinder pressure sensor, and FIG. 4 is a detailed circuit diagram of the charge amplifier. FIG. 6 is a diagram showing the relationship between θpmax and knock level, FIG. 6 is a diagram showing the relationship between θpmax and ignition timing, FIG. 7 is a flowchart showing a program for ignition timing control, and FIG. FIG. 9 is a signal waveform diagram for explaining the above, FIG. 9 is a diagram showing an example of a data table of the knock limit value θ _K ,
FIG. 10 is a diagram showing the characteristic of the basic ignition timing. 1 ... In-cylinder pressure sensor (pressure detection means), 5 ... Control unit (peak position detection means, limit value setting means, knock determination means, ignition timing setting means), 6 ... Operating state detection means, 16 ... Ignition means.

Claims (1)

[Claims] 1. A) pressure detecting means for detecting combustion pressure of the engine; b) operating state detecting means for detecting operating state of the engine; and c) crank angle at which combustion pressure becomes maximum from output of the pressure detecting means. Peak position detecting means for detecting the combustion peak position as a combustion peak position, d) limit value setting means for setting a combustion peak position at the knock limit according to the operating state, and e) an actual combustion peak position as a combustion peak position for the knock limit. Knock determination means for comparing the presence or absence of knocking; f) setting the ignition timing based on the operating state, and
Ignition of an internal combustion engine, comprising: ignition timing setting means for correcting the ignition timing depending on whether knocking is present, and g) ignition means for igniting an air-fuel mixture based on the output of the ignition timing setting means. Timing control device.