JPS6390670A - Ignition timing control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable prevention of unnecessary correction of a delay angle, by a method wherein an ignition timing is delayed for correction only in a knock occurring region discriminated from the value of an in-cylinder pressure maximum timing, based on a knock sensor signal. CONSTITUTION:In-cylinder pressure signals from in-cylinder pressure sensors 1a-1d are switched at each cylinder by means of a multiplexer 3 to extract a signal for a frequency component, equivalent to knock vibration, by means of a hand pass filter 4. A current value is held by means of a peak hold circuit 6, and a knock level is detected therefrom. Meanwhile, the in-cylinder signal is inputted to a control unit 7 through a hand pass filter 5 and an in-cylinder pressure maximum timing is calculated therein. As note above, based on detecting information on an in-cylinder pressure maximum timing, a knock level, running conditions, control of an ignition timing for preventing the occurrence of knocking is effected according to a program. The control causes accurate decision of the occurrence of knocking, and enables prevention of unnecessary correction of a delay angle.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a device that suppresses knocking by controlling the ignition timing of an internal combustion engine such as an automobile, and in particular, determines the authenticity of a knock sensor signal based on the timing of maximum cylinder pressure. The present invention relates to a device for controlling ignition timing.

(Prior art) In general, in order to efficiently extract the output of an engine,
Set the ignition timing to the timing when maximum torque can be generated M B T (
Minimum aavknce for Be5t
It is desirable to perform control to advance the angle up to (Torque). However, in certain engine conditions, advancing the ignition timing causes knocking, making it impossible to operate the engine stably. For example, at low speeds and low loads, the knocking limit is reached before the MBT. Also,
Knocking limits are also easily affected by atmospheric conditions such as temperature and humidity. Therefore, the ignition timing is controlled depending on the presence or absence of knocking.

Conventional ignition timing control devices for this type of internal combustion engine include:
For example, there is a method described in JP-A-60-197467. This device detects knocking by extracting the energy of high frequency components (6 to 8 KHz) from the output of vibration sensors attached to the cylinder block wall and sensors that detect cylinder pressure, and when it is determined that there is knocking, The ignition timing is retarded.

(Problem to be Solved by the Invention) However, in such a conventional ignition timing control device for an internal combustion engine, a predetermined high frequency component is extracted from the output of a knock sensor, and knocking is determined from this to determine the ignition timing. For example, even if the above-mentioned high-frequency component is a pseudo-knock signal caused by mechanical vibration or electrical noise rather than regular knocking, it will be incorrectly determined that knocking has occurred and the ignition timing will be delayed. be cornered.

In this case, knocking is not actually occurring, so there is no need to perform retardation processing.
The ignition timing is retarded, resulting in deterioration of drivability and fuel efficiency. Therefore, it is desirable to accurately determine knocking.

(Objective of the Invention) Therefore, the present invention focuses on the timing of maximum cylinder pressure (θPmax) that is correlated with the knock level, and determines whether or not the knock occurrence region is present from the value of θPmax, and when the knock occurrence region is present. By performing retardation correction based on the knock sensor signal, the purpose is to accurately determine the occurrence of knocking, avoid unnecessary retardation correction, and prevent deterioration of engine drivability and fuel efficiency.

(Means for Solving the Problems) In order to achieve the above object, the ignition timing control device for an internal combustion engine according to the present invention has a pressure detection system that detects the cylinder pressure of the engine, as shown in FIG. Means a, a knock detection means for detecting knocking of the engine, operating state detection means C for detecting the operating state of the engine, and maximum cylinder pressure at which the cylinder pressure becomes maximum based on the output of pressure detection means a. maximum timing detection means d for detecting the timing; area determination means e for determining whether or not the knock occurrence region is where knocking may occur based on the maximum cylinder pressure timing; and based on the operating state of the engine. When a knocking equivalent signal is detected by the knock detection means, the basic ignition timing is retarded so as to suppress knocking if the operating region at that time is in a knock occurrence region. It is provided with an ignition timing setting means f that stops the retard correction if the knock is not in the knock occurrence region, and an ignition means g that ignites the air-fuel mixture based on the output of the ignition timing setting means f.

(Function) In the present invention, it is determined whether or not the knock occurrence region exists based on the value of the maximum cylinder pressure timing, and the ignition timing is retarded based on the knock sensor signal only when the knock occurrence region is present. Therefore, even if the knock sensor signal includes a pseudo-knock signal such as vibration or electrical noise, unnecessary retardation correction is avoided, and deterioration of drivability and fuel efficiency is prevented.

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

2 to 4 are diagrams showing an embodiment of the present invention.

First, the configuration will be explained. In FIG. 2, 1a to ld are cylinder pressure sensors (pressure detection means), and cylinder pressure sensor 1
A to 1d are arranged for each cylinder, and convert the combustion pressure in the cylinder into an electric charge using a piezoelectric element, and output the electric charge signal to the charge amplifiers 2a to 2d.

Charge amplifiers 2a to 2d are similarly arranged for each cylinder,
It has a predetermined low frequency cutoff characteristic, amplifies the charge signal, converts it into a voltage signal, and outputs it to the multiplexer 3. The multiplexer 3 selectively switches each signal from the charge amplifiers 2a to 2d for each cylinder based on a switching signal from a control unit 7, which will be described later, and passes the switched signals to a bandpass filter (BPF) 4 and a low-pass filter ( LPF) 5. The bandpass filter 4 selectively passes only signals in a band of, for example, 6 to 8 kHz, which are particularly abundant when knocking occurs in the cylinder pressure signal, and outputs the signal to a peak hold circuit (PH) 6.

The peak hold circuit 6 holds the maximum amplitude value (peak value) in a predetermined crank angle section and outputs it to the control unit 7 as a value corresponding to knock energy.

This peak hold processing is performed based on a peak hold set/reset signal from the control unit 7, and is set, for example, to a range where knocking is expected to occur (about 50° from TDC to ATDC). The peak hold value is used as data for detecting the level of knocking.

Note that the holding of the peak value is not limited to the peak hold circuit 6, and may be performed using, for example, a rectifying integrator.

The above-mentioned cylinder pressure sensors 1a to 1d, charge amplifiers 23 to 2
d, the multiplexer 3, the bandpass filter 4, and the peak hold circuit 6 constitute a knock detection means 10 as a whole. Furthermore, the low-pass filter 5 passes the low frequency component of the cylinder pressure signal and outputs it to the control unit 7. The cylinder pressure maximum timing θp ax is determined from the cylinder pressure that has passed through the low-pass filter 5.

The control unit 7 further includes an operating state detection means 1.
The signal from 1 is input, and the operating state detection means 11
is composed of a crank angle sensor 12 and an air flow meter 13. The crank angle sensor 12 detects the explosion interval (4
For cylinder engines, the specified position before the compression top dead center TDC of each cylinder for every 180° crank angle)! , for example B T D C
A reference signal that becomes a [H] level pulse at 70 @, a unit signal that becomes an (H) level pulse for every unit angle of the crank angle (for example, 2 degrees), and a ( H) Output a cylinder determination signal that becomes a level pulse. Furthermore, by counting the pulses of the reference signal,
The engine rotation speed N can be known, and this process is performed by a control unit 7, which will be described later. Further, the air flow meter 13 detects the intake air amount Qa of the engine.

The control unit 7 has a function as a maximum timing detection means together with the low-pass filter 5, and also functions as a region determination means and an ignition timing setting means by itself.
It is composed of 0 votes 24.

The CPU 21 reads necessary external data from the I10 boat 24 according to the program written in the ROM 22, and while exchanging data with the RAM 23, detects the maximum cylinder pressure timing θρmax and controls the ignition timing. It calculates the processing values necessary for control, and outputs the processed data to the I10 port 24 as necessary.

Signals from the low-pass filter 5, knock detection means 10, and operating state detection means 11 are input to the I10 port 24, and a switching signal to the multiplexer 3 and a peak hold set to the peak hold circuit 6 are input from the I10 port 24. /Reset signal is output, and
The ignition signal Sp is output to the ignition means 25. ROM22
stores an arithmetic program for the CPU 21, and the RAM 23 stores data used in the arithmetic operations in the form of a map or the like. The ignition signal Sp is input to the ignition means 25, which is composed of a spark plug, an ignition coil, a distributor, etc., and generates a high pressure pulse based on the ignition signal Sp to ignite the air-fuel mixture.

Next, the effect will be explained.

To briefly describe the processing of the cylinder pressure signal, the control unit 7 sends a switching signal at a timing of 90 degrees before and after TDC of each cylinder based on the signal from the crank angle sensor 12, and the multiplexer 3 converts the cylinder pressure signal to each cylinder. Switch to The in-cylinder pressure signal that has passed through the multiplexer 3 is passed through a bandpass filter 4, where a signal with a frequency component corresponding to knock vibration (including a pseudo knock signal) is extracted.The peak value at that time is held by a peak hold circuit 6, and the knock level is then determined from this signal. is detected. On the other hand, the cylinder pressure signal is input to the control unit 7 through the bandpass filter 5, and the control unit 7 calculates the cylinder pressure maximum timing θpmax. As an example of a specific method, the in-cylinder pressure is sampled every 2 degrees of crank angle, A/D conversion is repeated, and the crank angle corresponding to the maximum value is set as θp+sax. Based on the detection information of θpmax, knock level, and operating conditions, ignition timing control for knock avoidance is performed according to the program shown in FIG. 3.

In Fig. 3, first, from a two-dimensional table map of two operating conditions as shown in Fig. 4 using engine speed N and intake air amount Qa as parameters in Pl, θ0 (determination level of θpmaX at which knocking hardly occurs) is determined. ). This table map uses engine speed N and engine load (intake air amount Qa as data),
For example, data based on load sensor output such as throttle valve opening or intake pipe internal pressure may be used). In addition, the optimum value of this 77 block has been determined in advance through experiments and is stored in ROM2.
2, but it is not limited to this, and for example, the correlation between the knock level and θpmax during driving may be learned and created for each driving condition, and in this way, even more effects can be obtained. Be expected.

Here, to describe the basic principle of this embodiment, θ0 is a judgment value of θpmax at which knocking hardly occurs, and this is due to the causal relationship that there is a specific correlation between the average value of θpmax and the knocking level. is set based on. In addition to the average value, the value of θpmax in one combustion cycle and the knock energy (6 to 8 KHz
The same applies to the signal power of According to this causal relationship, even if a knock-equivalent signal is detected by the knock detection system, if θpmax is smaller than the determination level θ0, the signal is in a region where there is essentially no possibility of knocking (not in the knocking region). Therefore, it can be determined that it is a pseudo knock signal. On the other hand, if θpmax is larger than θ0 when a knock-equivalent signal is detected, it is determined that the signal is a regular knock signal because it is in a region where knocking is possible (located in a knock occurrence region). In other words, in this embodiment, in addition to the conventional single determination element of knock level, a new determination element of whether or not it is in the knock occurrence area is added to strictly evaluate the validity of the knock equivalent signal and eliminate errors. This avoids unnecessary retardation correction based on judgment.

Based on the above basic principle, next, the energy KL (knock level) of the high frequency component of the cylinder pressure is compared with SL (slice level) at PS. SL is a determination value for determining the occurrence of knocking, and this is not limited to a constant value, but may be changed depending on the operating conditions.

When KL<SL, it is determined that knocking has not occurred, and the ignition timing is retarded with P. As a result, the ignition timing is advanced to near the MBT, thereby improving the output. On the other hand, when KL≧SL, it is determined that a knock-equivalent signal is output from the knock detection system, but this may also include a pseudo-knock signal, so in order to determine this, P4 The cylinder pressure maximum timing θpmax is compared with the determination level θ0. When θpmaX<00, that is, when θpmax is located before θO in terms of crank angle, it is determined that the current operating range is in the knock generation range based on the above-mentioned basic principle, and that a normal knock signal is being output. So, the amount of ignition timing retardation in PS? Do step 11. This suppresses knocking and provides stable operation.

On the other hand, when θpmax≧00, that is, when θpmaxχ is located after 00 in terms of crank angle, it is not in the knock generation region, so although a knock equivalent signal is output, it is determined that this is a pseudo-knock signal. Do not perform ignition timing retard control. Therefore, even if mechanical vibrations or electrical noise similar to knocking occur, the occurrence of knocking can be accurately determined unlike in the past, and unnecessary retardation processing can be avoided. As a result, deterioration in engine drivability and fuel efficiency can be prevented.

Note that, in the case of a pseudo knock signal, the method is not limited to not performing retard processing at all, but the retard amount may be reduced, for example. Also, from P2 through the YES command, θpma
There is a state where χ≧00! ! If this continues, it may be determined that there is an abnormality in the knock detection system or the θpmax detection system, and appropriate fail-safe measures may be taken.

(Effects) According to the present invention, it is determined from the value of the cylinder pressure maximum timing θpmax whether or not it is in the knock occurrence region, and the ignition timing is retarded based on the knock sensor signal only when it is in the knock occurrence region. This makes it possible to accurately determine the occurrence of knocking and avoid unnecessary retardation correction.
Deterioration of engine drivability and fuel efficiency can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a basic conceptual diagram of the present invention, Figs. 2 to 4 are diagrams showing an embodiment of the ignition timing control device according to the present invention, Fig. 2 is an overall configuration diagram thereof, and Fig. 3 is a diagram showing the ignition timing control device according to the present invention. A flowchart showing the timing control program, Fig. 4 shows its θpn+ax
FIG. 3 is a diagram showing the characteristics of the determination level θO. 1a to 1d...Cylinder pressure sensor (pressure detection means)
, 7... Control unit (area discrimination means, ignition timing setting means), 10... Knock detection means, 11... Operating state detection means, 25...・Ignition means.

Claims (1)

[Scope of Claims] a) Pressure detection means for detecting the cylinder pressure of the engine; b) Knock detection means for detecting knocking of the engine; c) Operating state detection means for detecting the operating state of the engine; d ) a maximum timing detection means that detects the timing when the cylinder pressure reaches its maximum based on the output of the pressure detection means, and e) a knock occurrence that may cause knocking based on the timing when the cylinder pressure reaches its maximum. f) setting the basic ignition timing based on the operating state of the engine, and determining whether the operating region is in the operating region at that time when a knocking equivalent signal is detected by the knock detection means; ignition timing setting means that retards the basic ignition timing so as to suppress knocking if it is in the knock occurrence region, and stops the retardation correction if it is not in the knock occurrence region; g) based on the output of the ignition timing setting means; An ignition timing control device for an internal combustion engine, comprising: ignition means for igniting an air-fuel mixture.