JP3120265B2 - Knock detection device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting knocking of an internal combustion engine, and more particularly to an apparatus for determining the presence or absence of knocking vibration from a detection signal of engine vibration.

[0002]

2. Description of the Related Art In an internal combustion engine, when knocking of a predetermined level or more occurs, not only does the output decrease, but also
Some shock absorbers have an ignition timing control device that adversely affects the intake / exhaust valves and pistons, so that when knocking occurs, the ignition timing is corrected to avoid knocking immediately.

[0003] As an apparatus for detecting the knocking,
There is one that performs frequency analysis on a detection signal of engine vibration using a digital filter or Fourier transform (see Japanese Patent Application Laid-Open No. 4-295729). That is, since knocking vibration is considered to be prominent in a frequency range of, for example, 7 to 9 kHz, the presence or absence of knocking is determined by obtaining the intensity (amplitude) of the component in the frequency range by analyzing the frequency of engine vibration. Things.

[0004]

However, in a knocking detection device that performs frequency analysis using a digital filter or a Fourier transform, the complexity of the operation logic causes a problem.
There is a problem that the cost is increased with respect to the performance of the knocking detection, and it has been desired to provide a knocking detection device that can exhibit a knocking detection performance equivalent to that of digital filtering with a simple configuration.

[0005] The present invention has been made in view of the above circumstances, and can perform frequency analysis of engine vibration with a simple configuration.
It is an object of the present invention to provide a device that can easily and accurately detect knocking.

[0006]

Therefore, a knocking detecting device for an internal combustion engine according to the present invention is configured as shown in FIG. In Figure 1, the vibration sensor is a sensor that detects the engine vibration is attached to the engine body, off
The filter is the frequency component of the detection signal of the vibration sensor.
Passes the predetermined frequency range including the frequency component of knocking vibration
The period measuring means measures the period of the detection signal of the vibration sensor passing through the filter .

The cycle classifying means classifies the cycle of the component in the predetermined frequency range into a plurality of cycles based on a comparison between the cycle measured by the cycle measuring means and a preset reference cycle.
Then, the classified cycle counting means, said plurality of categorical
The number of occurrences is counted. Here, the knocking determination unit determines that when any of the count numbers for each of the classifications within a predetermined time by the classification-specific cycle counting unit exceeds a threshold value,
Knocking is determined .

[0008] In the knocking detection apparatus for an internal combustion engine according to the second aspect of the present invention, the period measuring means includes a detection signal.
Time from the rise to the fall of
The period from the fall of the output signal to the rise is half cycle
And a latch circuit for latching the time measured by the timer .

[0009]

[Action] According to knock detecting apparatus for an internal combustion engine according to the invention of claim 1, knocking detection signal of the engine vibration damping
Classify frequency components of motion into multiple
The number of occurrences is separately counted, and the number of occurrences (frequency) of the corresponding frequency band component within a predetermined time is calculated based on the counted number.
The calculated, to determine the knocking when the mosquitoes c <br/> cement number either by knocking vibration becomes larger than the threshold value.

[0010] In the detection device according to the invention of claim 2 detects the rising and falling of the detection signal, the time from the rising of the detection signal to the rising from the fall or the fall was measured as a half period, the measurement result is latched in the latch circuit, the row I causes knocking determination by processing the half period obtained by the latch.

[0011]

Embodiments of the present invention will be described below. In FIG. 2 showing an embodiment, a knock sensor (vibration sensor) 1 attached to a cylinder block of an internal combustion engine (not shown) has a built-in piezoelectric element, and detects a waveform (voltage) according to engine vibration.
Output a signal.

A detection signal from the knock sensor 1 is amplified by an amplifier 2 and then input to an analog bandpass filter 3. The band-pass filter 3 is a filter that passes a predetermined frequency range including a frequency component of knocking vibration among frequency components of the detection signal. The detection signal filtered by the bandpass filter 3 is pulse-shaped by a pulse shaper 4. Then, the timer 5 detects the rise and fall of the pulse signal output from the pulse shaper 4, and measures a half cycle time from the rise to fall of the pulse signal. Incidentally, the measurement interval of the half cycle may be rising or Detoshi falling.

The half cycle time measured by the timer 5 is latched by a latch circuit 6. The timer 5 and the latch circuit 6 constitute a period measuring means of the present embodiment. The period classifiers 7a to 7c (period classification means) determine whether the half-period time latched by the latch circuit 6 corresponds to any of the three predetermined period classifications and the reference time as the reference time. The determination is made based on a comparison with a half cycle. Each of the cycle classifiers 7a to 7c is provided with a counter 8a to 8c (classified cycle counting means).

That is, different time widths (frequency ranges) are preset in the cycle classifiers 7a to 7c. For example, the time latched by the latch circuit 6 is determined by the cycle classifier 7b.
, The count value of the counter 8b attached to the cycle classifier 7b is increased. With this configuration, the frequency classifiers 7a to 7c separate the period (frequency) of the detection signal of the engine vibration into three types, and further, the counters 8a to 8c.
The number of occurrences can be determined for each cycle based on the count value of c.

FIG. 3 shows the operation of the period classifiers 7a to 7c and the counters 8a to 8c, and how knocking is detected by a microcomputer (not shown) based on the count values of the counters 8a to 8c. And the flowchart of FIG.
The flowchart of FIG. 3 is executed in synchronization with the fall of the pulse signal output from the pulse shaper 4, that is, in synchronization with the end timing of the cycle measurement, and is executed in step 1 (S1 in the figure). The same applies below.)
The half cycle TL which is measured most recently and latched by the latch circuit 6 is read.

In step 2, the read half cycle T
L is whether it is time length corresponding to the period classifier 7a shown in FIG. 2, the half period TL is the period classifier 7
The determination is made based on whether or not the time is equal to or longer than the reference time TL1 in a. In the present embodiment has a configuration of classifying the half period TL into three large, medium and small, the reference time TL1 or more half cycles
TL is the corresponding cycle of the cycle classifier 7a, and the reference time TL
A half cycle TL that is less than 1 and equal to or longer than the reference time TL2 (<TL1)
Is a corresponding cycle of the cycle classifier 7b, and a half cycle TL shorter than the reference time TL2 is a corresponding cycle of the cycle classifier 7c.

Therefore, in the step 2, the half period TL
Is longer than the reference time TL1, the latest measured half cycle TL belongs to the cycle range of the cycle classifier 7a, so the process proceeds to step 3, and the counter corresponding to the cycle classifier 7a 8a is counted up. On the other hand, in step 2, the half cycle TL is equal to the reference time TL1.
If it is determined that the above is not the case, the process proceeds to step 4,
It is determined whether or not it is longer than the reference time TL2 (<TL1).

[0018] Here, when the half cycle TL is judged to be the reference time TL2 or more, half period which is measured in the most recent
Since TL belongs to the cycle range of the cycle classifier 7b, the process proceeds to step 5, and the counter 8b corresponding to the cycle classifier 7b is counted up. If it is determined in step 4 that the half cycle TL is less than the reference time TL2, the latest measured half cycle TL belongs to the cycle range of the cycle classifier 7c. The counter 8c corresponding to the cycle classifier 7c is counted up.

As described above, when the half cycle TL is measured,
The number of times that the half cycle TL corresponding to each cycle classification is measured by discriminating to which of the preset cycle categories this half cycle TL corresponds and counting up a counter corresponding to the corresponding cycle category. Is counted. The half period TL is a half period from the rise of the pulse to fall, deer, because to perform the processing shown in the flowchart of FIG. 4 in synchronism with the falling timing of the pulse, the non-measurement of the half period TL The classification and count-up processing of the half cycle TL and the knocking determination processing to be described later can be reliably performed in the section, and processing with a simple configuration can be performed.

The flowchart of FIG.
A routine for determining whether knocking has occurred based on the count values a to 8c is shown. First, in step 11, it is determined whether a predetermined time has elapsed since the start of counting. When it is determined in step 11 that the predetermined time has elapsed, the process proceeds to step 12, where the value of the counter 8a is set to the threshold S.
It is determined whether or not L1 has been exceeded. If the value of the counter 8a has exceeded the threshold value SL1, the routine proceeds to step 15, where knocking is determined.

On the other hand, the value of the counter 8a is equal to the threshold SL1.
When it is determined that the following is satisfied, the process proceeds to step 13,
Similarly, it is determined whether or not the value of the counter 8b exceeds the threshold value SL2.
If it exceeds 2, the process proceeds to step 15 to determine the occurrence of knocking. If it is determined that the value of the counter 8b is equal to or less than the threshold value SL2, step 14 is executed.
Then, it is determined whether or not the value of the counter 8c exceeds the threshold value SL3. Here, if the value of the counter 8b exceeds the threshold value SL2, the process proceeds to step 15 to determine the occurrence of knocking.

When it is determined that all of the counters 8a to 8c are equal to or smaller than the threshold value, it is determined that knocking has not occurred, and the process proceeds to step 16. In step 16, the counters 8a to 8c are reset, and the counters 8a to 8c are newly counted up within the predetermined time determined in step 11.

The count values of the counters 8a to 8c indicate the number of times a predetermined frequency component is detected, and the threshold value is set in advance so that the count value exceeds only when knocking occurs. Therefore, when a specific frequency component is detected the number of times equal to or greater than the threshold value within a predetermined time, it is considered that the count value has exceeded the threshold value due to knocking occurrence, and knocking occurrence is determined. Since knocking occurrence is determined when any of the count values exceeds the threshold value, knocking determination can be reliably performed in response to a change in frequency at which knocking vibration appears.

In the above-described embodiment, the configuration is such that the half cycle TL is determined into three types. However, it is clear that the configuration may be such that the half period TL is classified into four types or more. What is necessary is just to provide the structure provided with the same number of counters as the number of classification.

[0025]

As described in the foregoing, according to the device for detecting knocking in an internal combustion engine according to the invention of claim 1, Nokki
The frequency components of the knocking vibration are classified into a plurality of cycles from the cycle, and the presence / absence of knocking is determined based on the cycle count number of each category within a predetermined time, so that knocking detection by frequency analysis can be performed with a simple configuration. This has the effect.

In the knocking detection device according to the second aspect of the present invention, the half cycle is measured by detecting the rise and fall of the detection signal, and the measurement result is latched by the latch circuit, so that the processing can be performed with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the invention according to claim 1;

FIG. 2 is a system block diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart illustrating a state of period classification in the embodiment.

FIG. 4 is a flowchart illustrating a state of knocking determination in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Knock sensor (vibration sensor) 2 Amplifier 3 Bandpass filter 4 Pulse shaper 5 Timer 6 Latch circuit 7a-7c Period classifier 8a-8c Counter

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01M 15/00 F02D 45/00 368 G01H 17/00 G01L 23/22

Claims (2)

(57) [Claims] 1. A vibration sensor attached to an engine main body for detecting engine vibration, and a knocking portion of a frequency component of a detection signal of the vibration sensor.
To pass a predetermined frequency range including the frequency
A filter, a cycle measuring means for measuring a cycle of the detection signal passed through the filter , and a component of the predetermined frequency range based on a comparison between the cycle measured by the cycle measuring means and a preset reference cycle . a periodic classification means for classifying a period into a plurality, and the classified cycle counting means for counting the number of occurrences for each of the plurality of classification, before in a predetermined time period by該分classification cycle counting means
When any of the counts by classification exceeds the threshold
A knocking detection device for an internal combustion engine, comprising: knocking determination means for determining occurrence of knocking. 2. The method according to claim 1, wherein the period measuring means is configured to detect a rising edge of the detection signal.
Time from rising to falling, or the detection signal
Time from fall to rise as half cycle
2. The knocking detection device for an internal combustion engine according to claim 1, comprising a timer for measuring, and a latch circuit for latching a time measured by the timer .