JPH0466754A - Knocking detecting device - Google Patents

Abstract

PURPOSE:To simplify the circuit composition by deciding that a knocking is generated when the detecting values of the inner pressures of cylinder in a compression stroke, or the inner pressures prior to the upper dead center in an explosion stroke are at a specific value or higher. CONSTITUTION:A pressure detecting means M2 to detect the inner pressure of a cylinder of an engine M1, and a crank angle detecting means M3 to detect the crank angle are provided, and the output signals of them are input to a knocking detecting means M4. And when the pressure difference between two points of specific crank angles, ore between two points of specific times in a compression stroke or in an explosion stroke is at a specific value or higher, it is decided that the engine is in a knocking condition. By such a knocking detecting method, no analog circuit is necessary, and as a result, the filter frequency regulation regulated at every engine is now unnecessary,a nd the cost of parts and the number of process can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a knocking detection device for detecting knocking in an internal combustion engine.

[Prior Art] Various methods for detecting knocking have been proposed in the past. For example, a bandpass filter that passes only high-frequency components of the knock sensor output signal and an analog gate that masks ignition noise are provided, and further back-up detection is performed. Some devices use an integrator to integrate only the knock signal after ground noise has been removed by a comparator.

FIG. 6 shows an example of this, where 51 is an acceleration sensor attached to the engine and detects the vibration acceleration of the engine, and 52 is a signal component of the output signal of the acceleration sensor 1 that has a high frequency that is sensitive to knocking. frequency filter, 53
54 is an analog gate that blocks noise that becomes an interference wave for knocking detection from the output signal of the frequency filter 2; 54 is a gate timing controller that instructs the analog gate 53 to open or close in accordance with the timing of occurrence of the interference noise; 55
56 is a noise level detector that detects the mechanical vibration noise level of the engine other than knocking; 56 is a comparator that compares the output voltage of the analog gate 53 with the output voltage of the noise level detector 55 and generates a knock detection pulse; 57 is a comparator that generates a knock detection pulse; Comparator 5
This is an integrator that integrates the output pulses of 6 and generates an integrated voltage according to the knocking intensity.

FIG. 7 shows the frequency characteristics of the output signal of the acceleration sensor 1. In this Fig. 7, A is when there is no knocking, B is
is the case where knocking occurs.

The output signal of the acceleration sensor 51 includes a knock signal (a signal generated due to knocking), mechanical noise from other engines, and various noise components on the signal transmission path, such as ignition noise. Comparing A and B in FIG. 7, it can be seen that the knock signal has unique frequency characteristics.

Although this distribution differs depending on the engine or the mounting position of the acceleration sensor 51, there is a clear difference in the distribution depending on the presence or absence of knocking at each location. Therefore, by passing the frequency component of the knock signal, the noise of other frequency components can be suppressed and the knock signal can be detected.

8 and 9 show the operating waveforms of each part in FIG. 6,
The same reference numerals indicate the waveforms of the same parts, and FIG. 8 shows a mode in which engine knocking does not occur, and FIG. 9 shows a mode in which engine knocking occurs.

If engine knocking is not occurring now, engine vibration due to knocking will not occur, but due to other mechanical vibrations, the output signal of acceleration sensor 1 will be affected as shown in Figure 8 (a).
), mechanical noise and ignition noise that rides on the signal transmission path occur at the ignition timing F. This signal passes through the frequency filter 52, as shown in FIG.
), the mechanical noise part is suppressed considerably, but
Since the ignition noise portion is strong, it may be output at a high level even after passing through the frequency filter 2.

If this continues, the ignition noise will be mistakenly recognized as a knock signal, so the analog gate 53 closes the gate for a certain period from the ignition timing according to the output of the gate timing controller 4 (FIG. 8 (C)) to cut off the ignition noise. . Therefore, only low-level mechanical noise remains in the output of the analog gate 53, as shown by symbol A in FIG. 8(d).

On the other hand, the noise level detector 55 responds to changes in the peak value of the output signal of the analog gate 53, and in this case, has the characteristic of being able to respond to relatively slight changes due to the peak value of normal mechanical noise. A DC voltage slightly higher than the peak value of the noise is generated (the part indicated by the symbol in FIG. 8(d)).

Therefore, as shown in FIG. 8(d), the analog gate 3
Since the output of the noise level detector 55 is larger than the average peak value of the output signal of
6, nothing is output as shown in FIG. 8(e), and all noise signals are eventually removed. Therefore, the output voltage of the integrator 57 becomes zero as shown in FIG. 8(f).

In addition, when knocking occurs, the output of the acceleration sensor 1 includes a knock signal around a certain time delay from the ignition timing as shown in FIG. 9(a), and after passing through the frequency filter 2 and analog gate 3, As shown in FIG. 9(d), the signal becomes a mechanical noise largely superimposed with a knock signal.

Among the signals that have passed through the analog gate 53, the rise of the knock signal is steep, so the noise level detector 5
5, the response to the knock signal is delayed. As a result, the inputs of the comparators 56 are respectively shown in FIG.
), a pulse is generated at the output of the comparator 56 as shown in FIG. 9(e). integral 57
integrates the pulse and generates an integrated voltage as shown in FIG. 14(f).

[The story that the invention attempts to solve] However, this method requires an analog circuit to detect knocking, which is disadvantageous in terms of cost, and the knocking frequency varies depending on the shape of the engine, exhaust cover, number of cylinders, etc. Therefore, it is necessary to set the passing frequency of the bandpass filter for each engine, which poses a problem in that it requires a lot of man-hours.

[Means for Solving the Problems] In order to solve such problems, the present invention provides a first pressure detection means for detecting the pressure inside the cylinder during the compression process, and a first pressure detection means for detecting the pressure inside the cylinder before the top dead center during the explosion process. A second pressure detection means detects the internal pressure, and knocking occurs when it is detected that the pressure detected by the first pressure detection means and the pressure detected by the second pressure detection means are equal to or higher than a predetermined value. and a determination means for determining that a problem has occurred.

[Operation] The first pressure detection means detects the pressure inside the cylinder during the compression process, the second pressure detection means detects the pressure inside the cylinder before top dead center during the explosion process, and the first pressure detection means When it is detected that the pressure detected by the second pressure detection means and the pressure detected by the second pressure detection means are equal to or higher than a predetermined value, the determination means determines that knocking has occurred.

[Embodiment] FIG. 1 is a block diagram showing the constituent elements of the present invention, and FIG. 2 shows an embodiment of the present invention. In Figure 1, M
1 is an engine, and M2 is a pressure detection means for detecting the pressure inside the cylinder, for example, the pressure sensor M2 shown in FIG. 2 corresponds thereto. M3 is a crank angle detecting means for detecting the crank angle, and M4 is a knocking detecting means for detecting knocking from the output signals of both of the means.
If the pressure difference between the points is greater than or equal to a predetermined value, it is determined that the engine is in a knocking state.

Next, one embodiment of the present invention will be described. In general, knocking reduction refers to abnormal combustion due to early ignition of unmixed mixture in the cylinder, and as shown in FIG. 3, the rising slope of the pressure waveform becomes steeper when compared to normal combustion. Therefore, the pressure difference between two points at a given crank angle during the compression or explosion process is higher when knocking occurs (pressure difference between points B1 and B2) than during normal combustion (pressure difference between points A1 and A2). growing. In this embodiment, if this pressure difference exceeds a predetermined value, it is determined that the engine is in a knocking state.

FIG. 4 is a flowchart showing the operation of this device.

The process shown in FIG. 4 is performed at every predetermined crank angle.
0, when it is determined that the crank angle is at a predetermined angle at point A1 during the compression process, for example, an angle θ1 sufficiently before top dead center, the first pressure detection means, step 1
As shown in 01, the pressure P1 at angle θ1 is measured and the process ends. However, if the crank angle is not B1, then in step 102, the crank angle is in the explosion process and is at point A2 before top dead center. It is determined whether the angle θ2 corresponds to the angle θ2. At this time, if the angle is not the same, the process is immediately terminated, and if the angle is reached, the second pressure detecting means measures the pressure P2 at the angle θ2 as shown in step 103.

Thereafter, the difference P between the pressure P2 measured in step 103 and the pressure P1 measured in step 101 is determined, and if it is determined in step 105 that the differential pressure P is greater than a predetermined value, the occurrence of knocking is indicated as shown in step 106. A signal is output, and if the value is less than a predetermined value, a signal representing normal combustion is output as shown in step 107, and the process ends. Note that steps 104 and 105 constitute determination means.

FIG. 5 shows an example in which a pressure difference between two points for a predetermined period of time is used instead of a pressure difference between two points at a predetermined crank angle. This example is processed at predetermined time intervals, and first, in step 150, if a predetermined time T1 is determined from a reference signal (for example, the TDC signal of the intake stroke), the pressure P1 at that time TI is measured as shown in step 151. The process ends. However, if the predetermined time T is not reached, it is determined in step 152 whether or not the time is T2, and the time T2 (TI<
T2), the process ends immediately.

If it is time T2 in step 152, step 1
As shown in 53, the pressure P2 at time T2 is measured, and in step 154, the differential pressure P between the pressure P2 in step 153 and the pressure P1 in step 151 is determined, and in step 15
In step 5, it is determined whether the differential pressure P is greater than or equal to a predetermined value.

At this time, if it is above a predetermined value, a signal indicating the occurrence of knocking is output as shown in step 156, and if it is below a predetermined value, a signal indicating normal combustion is output, and the process ends.

[Effects of the Invention] As explained above, the present invention detects the cylinder pressure using a pressure sensor and detects knocking from that value, so there is no need for an analog circuit as in the past, and as a result, adjustments can be made for each engine. This eliminates the need to adjust the filter frequency, which has the effect of reducing both component costs and man-hours.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the components of the present invention, Fig. 2 is a configuration diagram showing an embodiment of the invention, Fig. 3 is a graph showing the relationship between crank angle and cylinder pressure, and Fig. 4 is a diagram showing the invention. 5 is a flowchart showing another embodiment, FIG. 6 is a block diagram showing an example of the conventional device, FIG. 7 is a graph showing its characteristics, and FIGS. 8 and 9 show each part. FIG. Ml...engine, M2...-pressure detection means, M
3... Crank angle detection means, M4... Knocking detection means.

Claims (1)

[Claims] A first pressure detection means for detecting the pressure inside the cylinder during the compression process, and a second pressure detection means for detecting the pressure inside the cylinder before top dead center during the explosion process.
and determines that knocking has occurred when it is detected that the pressure detected by the first pressure detection means and the pressure detected by the second pressure detection means are equal to or higher than a predetermined value. A knocking detection device comprising a determination means.