JPS63189672A - Knocking detecting device for engine - Google Patents

Abstract

PURPOSE:To improve the precision in knock control by shifting the crank angle division for judging knocking according to the operation state of an engine. CONSTITUTION:A knock slice setting means sets the knock slice level as the standard for the knock judgement on the basis of the signal supplied from a knock sensor which is outputted from the detection of the vibration of an engine. A comparing means outputs a signal for judging if the signal of the knock sensor exceeds a knock slice level or not. A knock judgement division setting means sets the crank angle division for judging knocking in the optimum range corresponding to each number of revolution, on the basis of the operation state detected by an operation state detecting means. The knocking judging means judges the existence of knocking on the basis of the output signal of the comparing means in the crank angle division set as described in the above. With such constitution of the knocking detecting means, knocking can be correctly detected even if the operation state of the engine is changed, and the precision of knocking control can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine knocking detection device, and more particularly to an engine knocking detection device that detects knocking only in a certain crank angle section.

(Prior Art) An engine knock detection device is used to determine a control amount of a knob king control unit in an engine having a knock control system. This knock control system, for example, compares the knock sensor output and the knock slice level, generates a pulse when the knock sensor output exceeds the knock slice level, and then adjusts the ignition advance angle value according to the number of pulses. This is to suppress knobking by retarding. Furthermore, since the crank angle range in which knocking occurs in an engine is limited to a certain extent, if knock detection were performed constantly, mechanical vibrations (back noise) would also be detected as knob king. Japanese Patent Application Publication No. 5
As described in Japanese Patent No. 6-69532, a knocking detection device has been proposed that extracts the output of a vibration detector only in a predetermined section near top dead center.

By the way, spark ignition engines usually have an advance mechanism in their ignition system, which shifts the ignition point according to fluctuations in engine speed and load so that the maximum pressure point is within a predetermined crank angle range. However, the time from ignition to the time when maximum pressure is reached and knocking actually occurs is almost constant even if the engine speed changes, so the crank angle at which knocking occurs will vary as the engine speed changes. It's going to change. However, conventional knocking detection devices
As mentioned above, knocking is determined in a predetermined section near top dead center, and the knocking determination section is expanded to cover the region where knocking occurs at any rotation speed. Therefore, it is not possible to sufficiently eliminate back noise, and there is a great risk of erroneous control.

(Object of the Invention) In view of the problems of the conventional knocking detection device as described above, the present invention provides an engine knocking device that can accurately detect knocking without detecting mechanical noise as knocking even if the operating state of the engine changes. The object of the present invention is to provide a knocking detection device.

(Structure of the Invention) As shown in FIG. 1, the engine knocking detection koji production according to the present invention includes a knock sensor that detects engine knocking, and a knock slice that sets a knock slice level based on the output of the knock sensor. a level setting means, a comparison means for comparing the output of the knock slice level setting means and the output J of the knock sensor, an operating state detecting means for detecting the operating state of the engine, and an output of the operating state detecting means. a knock determination section setting means for setting a knock determination section based on the knock determination section, and a knocking determination means for determining knocking based on the output of the comparison means in the crank angle section set by the knock determination section setting means,
The crank angle section for determining knocking is configured to be moved depending on the operating state of the engine.

(Operation) The knock sensor detects engine vibration, and the knock slice level setting means sets a knock slice level that is a reference for knock determination based on the knock sensor signal. The comparison means compares the knock slice level and the knock sensor signal, and outputs a signal indicating whether the knock sensor signal exceeds the knock slice level. The operating state detection means detects the operating state of the engine from the rotational speed and the like. The knock determination interval setting means sets a crank angle interval in which knocking is to be determined based on the operating state of the engine.

The knocking determination means determines the presence or absence of knob king based on the output signal of the comparison means in the set crank angle interval.

(Example) Embodiments of the present invention will be described below based on the drawings.

This embodiment is an example of a knocking detection device that changes the knock judgment interval according to changes in engine speed, and this knocking detection device is applied to correct knocking by retarding the ignition timing. An outline of the knock control system designed to suppress knocking is shown in Figure ≠2. A functional block diagram showing the main parts is shown in FIG. An intake valve 3 and an exhaust valve 4 are provided at an intake port and an exhaust port opening into a combustion chamber 2 of the engine 1, respectively, and an ignition plug 5 is provided at the top of the combustion chamber. An intake passage 6 connected to the intake port communicates with an air cleaner 7, and an air flow sensor 8 is provided downstream of the air cleaner 7. A throttle valve 9 is provided downstream of the air flow sensor 8, and further downstream of the throttle valve 9, a fuel injection valve 10 is provided close to the intake port. Furthermore, fuel injection valve 1
An assist air passage 11 that guides assist air for atomizing fuel ejected from the throttle valve 9 is provided so as to bypass the throttle valve 9. Fuel to the fuel injection valve 10 is supplied from the fuel tank 12 to the fuel pump 13. The fuel is supplied through a fuel filter 14, and the fuel pressure is adjusted by a pressure regulator 15. The exhaust passage 16 is provided with an oxygen sensor 17 that detects the oxygen concentration in the exhaust gas. The engine is also provided with a crank angle sensor 18 that detects a crank angle based on the rotation of the crankshaft, and a knock sensor 19 that detects knocking from vibrations of the cylinder block. The control unit 20 receives an intake air amount signal from the air flow sensor 8, a crank angle signal from the crank angle sensor 18, a knock signal from the knock sensor 19, and 0.
It receives an air-fuel ratio signal from a sensor, calculates the fuel injection amount, outputs a fuel injection pulse to the fuel injection valve 10, calculates the ignition timing, and outputs an ignition signal to the ignition coil 21 connected to the ignition plug 5. do.

As shown in FIG. 3, the knock sensor signal that has passed through the filter (BPF) is rectified and amplified in a knock slice level setting circuit to create a slice level. The knock slice level thus set is compared with the knock sensor output, and when the knock sensor output exceeds the knock slice level, a knock pulse is output to the knock pulse counter circuit. The knock pulse counter circuit counts knock pulses only in the knock setting period set by the knock judgment period setting circuit. The knock determination section setting circuit calculates the engine rotation speed from the waveform-shaped signal of the crank angle sensor, and sets the crank angle section for determining knocking to an optimal range according to each rotation speed. For example, as shown in the table below, the starting crank angle and ending crank angle for knock detection are changed according to the engine speed, and the knock detection section is made faster at low engine speeds.
High rpm is slow. That is, the determination interval is shifted so that the knock determination state can be covered.

The pulse count value thus obtained is output to the ignition timing calculation circuit, and ignition retardation correction is performed. The ignition timing calculation circuit also uses the crank angle signal and the injection pulse width signal from the fuel injection time calculation circuit to perform ignition advance correction based on the ignition map expressed in terms of engine speed and load. A final ignition timing calculation is performed by adding the angle correction and advance angle correction, and an ignition signal is output to the ignition coil.

FIG. 4 shows a flowchart for detecting knocking and performing knock control based on the knocking detection. In the figure, Sl to S1. indicates each step.

When starting (Sl), first the intake air amount Qa is called in (S,), and the signal of the crank angle sensor is input (s).
s) L, which measures the engine speed Ne (
S4). Then, the basic fuel injection time T E t is calculated from these Qa and Ne.

In S8, engine speed Ne and basic fuel injection time IE
, (corresponding to the engine load), reads the ignition map value IGMAP.

Next, a knock determination section is set by reading it from the table based on the engine speed Ne read in S7 (S,
), clear the counter value with S.

After that, when there is a knock sensor rising force (S tO), the knock slice level is set (S, ), and it is determined whether the sensor input is greater than the slice level (S, ).
t).

If the sensor input is larger (YES), it means that knocking is occurring, and in this case (YES), the number of pulses is counted (S, , ).

Then, check again whether it is within the judgment interval (
s +4). If it is still within the determination period (YES), the process returns and the comparison between the knock sensor input and the slice level is repeated. Then, if the determination interval has passed (No), S3. , add all the pulse count values during the knock judgment period, completely add them up, and calculate that value (how many times the slice level has been exceeded).
In step S16, an ignition retard correction value (IGK) is determined. This is an operation in which, for example, the retard amount per l pulse is set as a constant, such as retarding 1 degree (crank angle) per l pulse, and the retard angle correction value is determined according to the number of pulse counts. It is.

Next, Sl? The ignition map value IGMAP, which is the basic ignition timing, and the retardation correction value IG due to knock.
Calculate the final ignition timing IG by adding
S II outputs the ignition signal to the ignition coil.

In S11, if the knock sensor input is smaller than the slice level (NO), it is not determined that there is a knock,
It simply takes in the ignition map value IGNAP (S, S) and outputs it to the ignition coil as an ignition signal.

FIG. 5 schematically shows the determination of knob king in this embodiment.

By the way, in the above embodiment, the knock judgment interval is set only based on the engine rotation speed, but the crank angle at which knocking occurs depends not only on the rotation speed but also on external conditions such as intake air temperature and engine temperature. It also changes depending on changes in internal conditions.

In other words, when external conditions change and combustion conditions change,
The combustion rate changes, which affects the crank angle at which knocking occurs. For example, the higher the intake air temperature, the faster knocking occurs, and the higher the engine temperature (coolant temperature), the faster knocking occurs. Therefore, it is also possible to detect not only the engine speed but also these external conditions as the operating state of the engine, and set the knock determination section based on them.

In the above embodiment, a knock control system that retards the ignition advance value was explained.
The knock control system is not limited to this, but can also be applied to systems that control knocking by increasing the air-fuel ratio, for example. Further, the knock sensor is not limited to the one described in the above embodiments, and for example, a finger pressure detector that detects pressure vibrations in the combustion chamber can also be used.

Moreover, the present invention can be implemented in various other embodiments.

(Effects of the Invention) Since the present invention is configured as described above, even if the crank angle at which knocking occurs changes depending on the operating state of the engine, it is possible to accurately detect knobking. Therefore, by using this, the accuracy of knock control can be improved.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of the present invention, Fig. 2 is a schematic diagram showing an embodiment of the invention, Fig. 3 is a functional block diagram showing main parts of the embodiment, and Fig. 4 is a diagram of the embodiment. A flowchart for executing the control, and FIG. 5 is an explanatory diagram of the operation of the same embodiment. l: Engine, 18: Crank angle sensor, 19: Knock sensor, 20: Control unit.

Claims (1)

[Claims] (1) a knock sensor for detecting engine knock; a knock slice level setting means for setting a knock slice level; a comparison means for comparing the output of the knock slice level setting means with the output of the knock sensor; A driving state detecting means for detecting a driving state, a knock judgment period setting means for setting a knock judgment period based on the output of the driving state detecting means, and the comparison in the crank angle period set by the knock judgment period setting means. What is claimed is: 1. A knocking detection device for an engine, comprising: knocking determining means for determining knocking based on the output of the means; and a crank angle section for determining knocking is moved according to the operating state of the engine.