JPS6258055A - Ignition timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To detect the knocking with a simple device, by detecting a combustion peak position where a combustion pressure is maximum, and comparing the peak position with a combustion peak position at the knock limit according to an operational condition at this time. CONSTITUTION:There is provided a peak position detecting means (c) for detecting a combustion peak position corresponding to a crank angle at a maximum combustion pressure according to an output from a pressure detecting means (a) for detecting the combustion pressure of an engine. There is further provided a limit setting means (d) for setting the combustion peak position at the knock limit according to an engine operational condition detected by an operational condition detecting means (b). The combustion peak position at the knock limit is compared with an actual combustion peak position by a knock determination means (e) to thereby determine whether or not the knocking has been generated. According to the result of the determination, an ignition timing set according to the operational condition is corrected by an ignition timing setting means (f), and the operation of an ignition means (g) is controlled according to the corrected ignition timing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an ignition timing control device for controlling the knocking level of an internal combustion engine such as an automobile within a predetermined range.

(Prior Art) The ignition timing of an internal combustion engine needs to be determined depending on the state of the engine so that the engine can be operated optimally.

Generally speaking, when considering engine efficiency and fuel consumption, the minimum advance angle at maximum torque, so-called MBT (Minimum a
It is known that it is best to ignite near the d-vace for Be5t Torque), and it is necessary to change the ignition timing to MBT depending on the engine condition.

However, in certain engine conditions, when the ignition timing is advanced, non-king occurs and stable engine operation cannot be performed. For example, at low speeds and low loads, MBT
The knocking limit was reached earlier. Furthermore, the non-king limit is easily influenced by atmospheric conditions such as temperature and humidity.

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

In this device, the pressure inside the combustion chamber is detected by an in-cylinder pressure sensor, and the detected signal is processed by an averaging circuit such as an amplifier, a bandpass filter, and an envelope circuit, and the non-king level is determined based on the magnitude of the signal. To detect. Then, the ignition timing is controlled so that the knocking level is below a predetermined value.

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

This results in an expensive device and is difficult to implement with conventional control units commonly used for electronic control of engines.

(Objective of the Invention) Therefore, the present invention detects the combustion peak position where the combustion pressure is maximum and compares this peak position with the knock limit θpmax corresponding to the operating conditions at that time to detect non-king. It is an object of the present invention to provide an ignition timing control device that can sufficiently suppress knock control using the capabilities of conventional systems by simplifying the configuration of the system necessary for knock detection.

(Structure of the Invention) The ignition timing control device for an internal combustion engine according to the present invention, as shown in the basic conceptual diagram in FIG. The state detecting means includes a peak position detecting means C which detects the crank angle at which the combustion pressure is maximum from the output of the pressure detecting means a as the combustion peak position, and a
Limit value setting means d for setting the combustion peak position of the limit
and a knock determination means e that compares the actual combustion peak position with the combustion peak position of the knock limit to determine whether there is knocking. The ignition timing setting means f corrects the ignition timing according to the output of the ignition timing setting means f, and the ignition means g ignites the air-fuel mixture based on the output of the ignition timing setting means f.
This simplifies the configuration of the system required for knock detection.

(Example) Hereinafter, the present invention will be explained based on the drawings.

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

First, the configuration will be explained. In FIG. 2, reference numeral 1 denotes a cylinder pressure sensor (pressure detection means), and the cylinder pressure sensor 1 converts the combustion pressure in the cylinder into a charge using a piezoelectric element, and outputs a charge output S. The cylinder pressure sensor l is specifically shown in Figure 3 (
As shown in detail in λ) and (B), it is screwed onto the cylinder head 2 and is formed as a washer for the ignition plug 3, and the ignition plug 3 is tightened in the outer recess of the cylinder head 2 by the part 3.
It is pressed and fixed by a.

The sensor output S1 is input to the charge amplifier 4,
Charge amplifier 4 includes operational amplifiers OPI and OF2, resistors R1 to R8, and capacitor C, as shown in detail in FIG.
I and the so-called charge consisting of diodes D1 to D3 -
A voltage conversion amplifier is configured, and the sensor output S is converted into a voltage signal S.
2 and output to control unit 5.

The control unit 5 further includes an operating state detection means 6.
The operating state detection means 6 is composed of a crank angle sensor 7 and an air flow meter 8. The crank angle sensor 7 detects the (H) level at a predetermined position before compression top dead center (TDC) of each cylinder at every explosion interval (120'' crank angle for a 6-cylinder engine, 180'' for a 4-cylinder engine), for example, at 70° BTDC. It outputs a reference position signal Ca that is a pulse of
The engine speed can be determined by counting the pulses. Further, the air flow meter 8 detects the intake air lQa of the engine and outputs an analog signal Sa.

The control unit 5 has functions as a peak position detection means, a limit value setting means, a knock discrimination means, and an ignition timing setting means, and includes a CPU Ull, a ROM 12, and a RAM 1.
3, an A/D converter 14 and an I10 port 15. The CPU II takes in necessary external data from the I10 boat 15 according to the program written in the ROM 12, and processes values necessary for ignition timing control while exchanging data with the RAM 13. I10 processes the data as necessary.
Output to port 15. Signals from the operating state detection means 6 and charge amplifier 4 are input to the I10 port 15, and an ignition signal Sp is output from the I10 port 15. The A/D converter 14 converts the external signal input to the I10 port 15 according to the command from CP Ull into an A/D converter.
Convert. Further, the ROM 12 stores calculation programs for the CPU Ull, and the RAM 13 stores data used in calculations in the form of a map or the like.

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

Next, the operation will be explained, but 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, and this is caused by the pressure inside the cylinder, which has multiple natural vibrations determined by the cylinder dimensions (particularly the bore diameter) and the combustion gas temperature. Appears as damped vibration. This pressure vibration is transmitted through the cylinder wall, cylinder block, etc. into the air, and the unpleasant high-frequency sound that reaches the human auditory sense is called a knocking sound.

FIG. 5 shows the relationship between the crank angle θpmax (hereinafter referred to as the combustion peak position) when the cylinder pressure reaches its maximum and the knocking level based on a sensitive evaluation. Although this is an example of one model of engine, substantially the same tendency is shown in other models as well. As is clear from Fig. 6, θpma when knocking occurs and when knocking does not occur.
There is a big difference between x. Therefore, this θpma
By detecting x, it becomes possible to detect the knocking level faithfully to human sensitivity evaluation.

Furthermore, as shown in FIG. 6 showing the relationship between θpmax and ignition timing, it is possible to change the position of θρll1ax by correcting the ignition timing. Therefore, by detecting θpmax and correcting the ignition timing based on the difference between θpmax and the desired knocking level, it is possible to suppress knocking.

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

This program is based on the reference position signal Ca of the crank angle sensor 7.
When the [H] pulse of unit signal C1 is detected, counting of (H) pulses of unit signal C1 is started, and counting is performed a predetermined number of times, and the count starts when the crank angle θ reaches a predetermined value (for example, BTDC40').

First, a voltage signal St corresponding to the cylinder pressure changing as shown in Fig. 8(a) at P (corresponding to the cylinder pressure waveform)
The A/D converter 14 is activated to A/D convert P.
The count value CC7 of the unit signal C1 when the A/D converter 14 is activated in step 2 is stored in the RAM 13. Then,
At P3, it is determined whether or not the A/D conversion of the signal S2 has been completed. If it has not been completed, it waits. When it is completed, at P4, the A/D conversion value is paired with the count value CC+ of the unit signal CI. Store in RAM13. Next, in P5, the count value CC1 of the unit signal C3 is compared with a predetermined value C8, and cc
When t<co, the process returns to Pl and repeats the flow from P to P. Then, when CC1≧00, P6
Proceed to. Therefore, a predetermined section of the cylinder pressure waveform S2 is converted into an A/D converted value as shown in FIG. 8(b).

P, the maximum value P of the A/D converted values of the cylinder pressure waveform S2
max and the above count value C corresponding to this Prmax
Determine θpmax from C1. These are stored in one-to-one correspondence as shown in FIG. 8(b), and P m
The count value CCI at the time of ax is the combustion P position θpmax
becomes. Next, the knock limit θpmax (hereinafter referred to as knock limit value) θK corresponding to the operating state at that time is determined.
In order to obtain this, intake air 1iQa and rotational speed N are calculated as parameters representing the operating state. That is, in P7, 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 unit signal C1 ()(
) The engine speed N is determined by repeatedly counting the pulses during a fixed time interval.

At pH, basic injection 1Tp (Tp
= -Qa /N, where: constant) is calculated, and the knock limit value θ8 corresponding to the operating state at that time is looked up from the data table shown in FIG. 9 using Tp and N as parameters. The data table in FIG. 9 is an example of a predetermined model (2000cc, 6-cylinder engine). At N=400 Orpm, there is a shift in the overall trend of the data, but this is due to the inertial supercharging effect. In addition, knock is more likely to occur under high loads, and because the stability of the combustion state is less in the low rotation range than in the high rotation range, knock is more likely to occur. Therefore, when attempting to bring the knock to a desired level, the knock limit value θa is as shown in FIG.

Next, the combustion peak position θpmax is compared with the knock limit value θya at P. When θpmax <θ, it is determined that a knock has occurred and Pl is set. The current correction amount M for correcting the basic ignition timing N to the retarded side is calculated according to the following equation (2), and the ignition timing is retarded.

M=M'+ΔM1 ・・・・・・■However, M'
: Previous correction amount ΔMI : Retardation correction amount Also, when θpmax≧θ, it is determined that knocking has not occurred, and at P, the current correction amount M is calculated according to the following formula 〇, and the ignition timing is advanced. Correct the angle.

M=M'-ΔM2 ・・・・・・■ However, 6M2
:Advance angle correction amount In this way, the presence or absence of a knock can be determined by a simpler process than the conventional method of detecting θpmax and comparing the detected value with 08.

Therefore, knock suppression control can be performed easily and at low cost using conventional system capabilities. That is, by reducing the number of circuit elements necessary for knock detection, the knock detection system can be sufficiently constructed using a microcomputer used for ordinary engine electronic control.

After selectively passing through PIO1pH, look up the basic ignition timing (represented by advance value in the figure) N from the table map shown in Fig. 10 according to the operating condition using pat, and set PI3pH.
Then, from this N and the above M, the final ignition timing is calculated according to the following formula (2), and this D is stored in the RAM 13 in terms of pH.

D:N+M...■Then, when the timing corresponding to the final ignition timing is reached by counting the unit signal CI, the ignition signal Sp is output to ignite the air-fuel mixture. Therefore, when knock occurs, the ignition timing is retarded, whereas when knock does not occur, the ignition timing is advanced. As a result, it is possible to increase the combustion efficiency of the engine, improve torque characteristics, and achieve improvements in fuel efficiency and driving performance.

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

[Brief explanation of the drawing]

Figure 1 is a basic conceptual diagram of the present invention, Figures 2 to 10 are diagrams showing an embodiment of the present invention, Figure 2 is a block diagram thereof, and Figure 3 (A) is a diagram of the cylinder pressure sensor. A cross-sectional view showing the installed state, FIG. 3(B) is a plan view of only the cylinder pressure sensor,
FIG. 4 is a detailed circuit diagram of the charge amplifier, FIG. 5 is a diagram showing the relationship between θpmax and non-free level, and FIG.
Figure 7 shows the relationship between θpmax and ignition timing.
Figure 8 is a flowchart showing the ignition timing control program, Figure 8 is a signal waveform diagram for explaining its operation, Figure 9 is a diagram showing an example of a data table of the knock limit value θ, and Figure 10 is a diagram showing an example of a data table for the knock limit value θ. It is a figure showing the characteristic of the basic ignition timing. 1... Cylinder pressure sensor (pressure detection means), 5...
... Control unit (peak position W detection means, limit value setting means, knock discrimination means, ignition timing setting means), 6 ... Operating state detection means, 16 ... Ignition means.

Claims (1)

[Scope of claims] a) pressure detection means for detecting the combustion pressure of the engine; b) operating state detection means for detecting the operating state of the engine; and c) a crank whose combustion pressure is maximized based on the output of the pressure detection means. d) limit value setting means for setting the knock limit combustion peak position according to the operating condition; and e) detecting the actual combustion peak position as the knock limit combustion peak position. f) a knock determination means for determining the presence or absence of knocking by comparing with the engine; f) setting the ignition timing based on the operating condition;
ignition timing means for correcting the ignition timing according to the presence or absence of knocking; and g) ignition means for igniting the air-fuel mixture based on the output of the ignition timing setting means. Timing control device.