JPS5828645A - Knocking detecting method of internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting whether or not knocking occurs in an internal combustion engine.

In the knocking detection method, the mechanical vibrations that occur due to abnormal combustion in the engine, that is, knocking, are detected as mechanical amplitude fluctuations using a vibration detection element called a knock sensor. By comparing K with the comparison reference value, it is determined whether the detected vibration is actually caused by knocking or not. In this case, without fixing the comparison reference value to a constant value, by changing the comparison reference value according to an output signal that is considered to be unrelated to knocking of the knock sensor (hereinafter referred to as pack ground signal), it is possible to eliminate the variation in the knock sensor. It becomes possible to compensate for changes over time. Conventionally, an integration circuit with a large time constant applies the output signal of the knock sensor and integrates this at all times, that is, over the entire crank angle, thereby obtaining a pack ground signal. However, according to this type of method in which the output of the knock sensor is averaged over the entire crank angle, the crankshaft
The pack ground signal changes due to noise such as camshaft vibration and valve hitting noise, causing problems.

In order to solve the above-mentioned problems of the conventional floor technology, the present applicant has proposed a system that does not include valve tapping noise, ignition noise, etc.

A technique has already been proposed in which the knock sensor output is simulated within a predetermined crank angle range in which knocking does not occur, and this is used as a background signal. However, this method requires control to incorporate the knock sensor output within a predetermined crank angle range, and the control system becomes complicated. An object of the present invention is to easily control the detection of the background signal, to obtain an accurate background signal, and, as a result, to obtain a highly accurate and reliable background signal. It is an object of the present invention to provide a method for detecting knocking.

The mosquito vibration detecting element of the present invention that achieves the above-mentioned 90 targets is equipped with at least one vibration detection element that converts mechanical vibration into an amplitude fluctuation of an electric signal, and converts the electric signal from the mosquito vibration detection element into an electric signal. In the method of detecting the presence or absence of knocking according to the method, the average value of the amplitude value of the electric signal in a predetermined crank angle range after ignition of at least one cylinder is calculated over a plurality of ignition cycles, and The purpose is to detect whether or not knocking has occurred by comparing the average value with the amplitude value of the electric signal that falls within the predetermined crank angle range.

The present invention will be described in detail below with reference to the drawings. FIG. 1111 schematically represents the entire configuration of a knocking control system as an embodiment of the present invention.
0 is a cylinder block of the engine, and 12 is a knock sensor attached to the cylinder block 10. The knock sensor 12 is a well-known device that is composed of, for example, a piezoelectric element or an electromagnetic element, and converts mechanical vibrations into electrical amplitude fluctuations. In FIG. 1, 14 further indicates the distribution chorus 1-event 14.
Crank angle sensors 16 and 18 are installed in ○
The crank angle sensor 16a is for cylinder discrimination.If this engine has 6 cylinders, every time the distributor shaft makes one revolution, that is, every two revolutions of the crankshaft (720'C
One pulse is generated for each A). The occurrence position is set, for example, to the top dead center of the IEI cylinder. The crank angle sensor 18 generates 24 pulses each time the distributor shaft rotates, ie, every 30 degrees of crank angle.

Electric signals from knock sensor 12 and crank angle sensors 16 and 18 are sent to control circuit 20. The control circuit 20 is further fed with a signal representing the intake air flow rate from an air sensor 24 provided in the intake passage 22 of the engine. On the other hand, from the control circuit 20, the igniter 2
An ignition signal is output to 6, and the 9 spark current generated by the igniter 26 is distributed to each cylinder 0 spark plug 28 via the distributor 14.

Various other sensors are provided to detect the machine WAKa% normal operating state parameters, and also control the t&, control circuit 20, fuel injection valve 29, etc., but since these are not directly related to the present invention, they will be described below. In the explanation, these will be completely omitted.

FIG. 1B2 is a block diagram showing an example of the configuration of the control circuit 20 in FIG. The voltage signal from the air 70-sensor 24 is passed through a buffer 30 to an analog multiplexer 3.
The signal is sent to the microcomputer 2, selected in accordance with instructions from the microcomputer, applied to the A/D converter 34, converted into a 2-pass signal, and taken into the microcomputer via the input/output port 36.

Pulses for every 7200 crank angles from the crank angle sensor 16 are applied to the interrupt request signal forming circuit 40 via the buffer 381. On the other hand, pulses from the crank angle sensor 18 at every 30 degrees of crank angle are applied to the interrupt request signal forming circuit 40 and the speed signal forming circuit 44 via the buffer γ42. The interrupt request signal forming circuit 40 forms various interrupt request signals from each node at each crank angle of 7200 and 30'. These interrupt request signals are sent to the microphone I:I: 0: Applied to the input signal. Speed signal forming circuit 44 companies, engine rotation speed Ne from the period of pulse every 300 crank angles
Forms a two-over signal that praises the

The formed rotational speed signal is sent to the microcomputer via the input/output port 46.

The output of knock sensor 2 (No. 1 is a buffer for impedance conversion and a frequency band unique to knocking (7 to 8
KH) is sent to the peak hold circuit 50 via a circuit 48 consisting of a bandpass filter having a pass band. The peak hold circuit 50 monitors the output signal from the knock sensor 2 and holds its maximum amplitude only when a signal of 11 lb is applied to the micro combinatorial collar via the line 52 and the input/output port 46. perform an action. The output of the peak hold circuit 50 is sent to the A filter converter 54.
However, the A/
The A/D conversion of the LJ converter 54 starts at the input/output capo)
This is done by an A7D conversion activation signal applied from the micro combinator via the 46A and 56 lines. Also, A
/D゛When the conversion is completed, A7. Transducer 54 connects line 58
A4 conversion completion notification is sent to the microcomputer via the input/output board 46. On the other hand, when an ignition signal is output from the microcomputer to the drive circuit 60 via the input/output board 46, this is converted into a drive signal. The igniter 26 is energized, and nine ignition controls are performed depending on the duration and duration of the ignition signal.

The micro combinator includes the aforementioned input/output boats 36 and 46, a micro six processor (MPU) 62, a random access memory (RAM) 64, and a read only memory (R).
The ROM 66 mainly comprises a clock generation circuit (not shown), a memory control path, a bus 68 connecting these, and the like, and executes various processes according to control programs stored in the ROM 66.

I! 3 to 11L6 are flowcharts showing only nine parts of the control contents that are particularly relevant to the present invention. According to these processing routines, the peak hold operation of the knock sensor output is performed during the period c (knock detection period) in which the knocking signal is included in the signal from the knock sensor 12 when knocking occurs, and the final value thereof is 2.
It is included as a forward signal. Furthermore, the average value of the binary signals taken in each knocking detection period for a predetermined number of times is calculated, and the 0 comparison reference value for which this average value is recognized as the background value is determined. The comparison reference value is compared with the binary signal value taken in each knocking detection period to determine whether or not knocking has occurred. 110° CA @ ATDC in the explosion stroke of a specified O cylinder
~ Selected near 50° CA/ATDC
-The contents of the processing routines shown in Figs. 3 to 6 will be explained in detail below.0 From the interrupt request signal forming circuit 40, a predetermined crank angular displacement of each cylinder or a predetermined specific cylinder *eoC
For example, 300C at explosion top dead center or compression stroke
When a predetermined interrupt request signal is applied at A-BTDC, the MPU 62i@3 calculates the time t1 at which the knocking detection period starts at the point where the interrupt processing routine shown in FIG. 3 is executed, that is, at step 7O. This time t1 is the time of the timer on the software, and the crank angle position pupil at which the knocking detection period starts (for example, 10° CA @ ATDC)
), the current crank angular displacement 1i1 (θ0CA), the current time t0 of the timer, and the engine rotational speed N・, it is obvious that it can be easily calculated. , this interrupt routine ends, and the program returns to the main routine. When the soft timer reaches the end, a time interrupt request is generated, which causes the MPU 62 to issue an I! 4. Execute the interrupt processing routine shown in Figure 4. First, in step 71, the peak hold circuit 5
0, the peak hold operation of the output of the knock sensor 12 is started. This is done by sending a peak hold instruction signal of %1' level to the peak hold circuit 50 via the line 52.Next, in step 72, the knocking detection period O#I is calculated. do.

The crank angle position at which the knocking detection period ends (for example, 5
The calculation method in step 72 is the same as in step 70 since oOCA@ATDC) has been settled in advance. Then, in step 73, the fear converter'
After instructing s4 to start ~δ conversion, the process returns to the main routine.

When the female conversion by the A7o converter 54 is completed and an interrupt request signal due to completion of ~δ conversion is applied via line 58,
The MPU 62a executes the interrupt processing routine shown in FIG.

First, in step 74, the peak hold circuit 50
The output of is also converted to this time, and the 9-value IyDt is compared with the previous het-converted value width meter, and in the next steps 75 and 76, the larger radial conversion Ill t a K is substituted.

The contents of this a are stored in a predetermined Ω area of the RAM 64.

In the next step 77, it is determined whether or not the peak hold operation is currently in progress, and if the previous operation is in progress, then step 78
Go to and start VD conversion again. As described above, in this embodiment, the capital conversion is repeated a plurality of times during one peak hold operation period, and the maximum value thereof is detected. This is done because the peak hold value does not maintain the peak value t as time passes, but begins to sag. Note that an excellent peak hold circuit can be used to prevent the above-mentioned 1 sag. When prevented, the envy conversion operation only needs to be performed once at the end of each peak hold operation period.

When the time of the soft timer becomes negative, a time interrupt request is generated, and in response to this, the MPU 62 executes the interrupt processing routine shown in FIG. First, in step 79, the peak hold instruction signal f: is inverted to %O', and the peak hold operation is ended. Next, the process proceeds to step 80, in which the maximum value of the peak hold values detected during the knocking detection period, that is, the value a corresponding to the maximum amplitude of the output of the knock sensor 12 during this period stored in the RAM 64, and each past ignition Based on the average value C of the 6 values a in the cycle (that is, the background value) A and a constant value, it is determined whether K・A≧a or not.OK@A≧1, it is determined that no knocking has occurred. The process then proceeds to step 81, where the background value A is corrected by the current value a. That is, this formula is a rounding formula that calculates the average value A of the past values a by weighting so that the influence of the recent value a becomes stronger.Then, the MPU 62 performs step 82.
In steps 82 to 85, which execute the outer rings of steps 82 to 85, if no knocking has occurred in the past 10 consecutive ignition cycles, the ignition timing is advanced by Y.

That is, in step 82 it is determined whether n is 10 or more, and if it is less than 10, n is set to 1 in step 83.
After increasing the number by 1, this interrupt handling routine ends. On the other hand, if n is 10 or more, proceed to step 84;
After resetting to nt atmosphere, proceed to step 85.0 At step 85, processing is performed to increase the advance angle correction value θ of the ignition timing by Y.0 This advance angle correction value θ is determined by a well-known method that is executed at every predetermined crank angle position. This is used in the ignition timing calculation processing routine of o j! D. In the ignition timing calculation processing routine, the optimum ignition timing is calculated from the operating conditions such as the intake air flow rate Q detected by the second flow sensor 24 and the rotational speed Ne obtained from the rotational speed signal forming circuit 44. , the calculated ignition timing is further corrected using the advance angle correction value θ.Therefore, step 85
By performing the above processing, the ignition timing (ignition timing of the first ignition cycle) is advanced by Y712. When the process in step 85 is completed, the process returns to the main routine.
1 On the other hand, if it is determined in step 80 that K*A<'a, that is, if it is determined that knocking has occurred, the process proceeds to step 86, where the advance angle correction value θ is
As a result, the ignition timing in the next ignition cycle will be retarded by X. Next, in step 87, the program is reset to nt-atmosphere and returns to the main routine. It is well known that knocking can be suppressed by retarding the ignition timing when it is detected that knocking has occurred.

FIG. 7 is a diagram for explaining the present invention in detail, in which the horizontal axis represents the amplitude value of the knock sensor output, and the vertical axis represents the degree St of occurrence of the output of the amplitude value. In the same figure, the frequency distribution of the knock sensor output amplitude value when no knocking occurs is shown by the broken line, and when slight knocking (knocking to the extent that a human can hear the knocking sound after straining his/her ears) occurs. The frequency distribution of the knock sensor output amplitude values is shown by broken l1IC, and the frequency distribution of the knock sensor output amplitude values in the engine state where minute knocking occurs is shown by actual vId. In addition, if large knocking occurs, the knock sensor output amplitude value will also increase, so
The #J1 degree distribution will appear in the right margin of Figure 687. To obtain the pack ground ([,
[Since it is sufficient to obtain x, the frequency distribution of %b and C
The area of the part where the frequency distribution of If the knock sensor output amplitude value is used to update the average i when the sensor output amplitude value is smaller than K @ , that is, 116
The processes of steps 80 and 81 in the figure are an improvement to this.By performing such processes, it is possible to detect the background signal during the knocking detection period.

As is clear from the above 1 light, step 8 of the m6 diagram
0 simultaneously performs both processes of determining whether it is okay to create a pack ground signal and determining whether or not knob kinging has occurred.

However, in the present invention, the above-mentioned determination process 1! It is also possible to perform each separately. FIG. 8 shows the case where the ζ&+) determination process is performed separately. In other words, in step 80m, it is determined whether or not knocking has occurred, and in step 8Ub, step 81 for background value detection is performed. Processing mt--A determination is made as to whether it is okay to proceed. In this way, if K is used separately in steps 80a and 80b, when detecting whether or not knocking has occurred (steps 80 & ml), it is very advantageous because there is a large degree of freedom in the heat correction. It is.

9s is another example of the processing routine of FIG.

In this example, the calculation method of the average value A is for m6 diagram and 14
In other words, in this example, the equal average value of the knock sensor output amplitude values for the current and past nine ignition cycles is calculated.
At step 88, where areas 11 to an for storing input data of KIO knock sensor output amplitude values in the AM64 are prepared, the consecutive addresses of the ten areas mentioned above are incremented by one. The data corresponding to ato in the previous large point cycle is lost, and an empty area is created in the area corresponding to a in the previous ignition cycle. 1 for the ignition cycle
, ~Hatake, the data will be 0. Next step 89
In step 90, the average value of data 81 to B+6 is input in step 90, where 9 data a is stored in the empty area &1 of Jin! Calculated from. The subsequent steps are exactly the same as in the case of the m6 diagram.As explained in detail above, according to the knocking detection method of the present invention, the knocking ground signal is detected during the non-king detection period, so no knocking is actually detected. It is possible to accurately understand the knock sensor output without
Since this knocking detection period is often the crank angle range with the least amount of noise, it is possible to obtain an accurate and stable ground signal.As a result, highly accurate and reliable knocking detection can be achieved. In addition, the crank angle range in which the knock sensor output *D is applied is rounded only once per ignition cycle, and the control becomes simpler and the complication of the control system can be avoided. Can be done 0 6th f 7th Xi knock 7n V out JJ Shin'ei 1i [iL→

Claims (1)

[Claims] 11! At least one vibration detection element that converts mechanical vibration into an amplitude fluctuation of an electric signal is attached to an engine body, and the presence or absence of knocking is detected according to the electric signal from the vibration detection element. Calculating an average value of the amplitude value of the electric signal in a predetermined crank angle range after ignition of at least one cylinder over a plurality of ignition cycles, and combining the calculated average value and the amplitude value of the electric signal in the predetermined crank angle range. A method for detecting non-knocking in an internal combustion engine, in which the presence or absence of knocking is detected by comparing the size with K.