JP3865612B2 - Knock detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a knock detection device for an internal combustion engine that detects the occurrence of knock using an ignition plug provided in the internal combustion engine.
[0002]
[Prior art]
Conventionally, knocking is generated from a signal obtained by a knock sensor fixed to the cylinder block, assuming that the knocking frequency component of the vibration of the cylinder block of the internal combustion engine corresponds to the knocking frequency component in the combustion chamber pressure (pressure in the combustion chamber). 2. Description of the Related Art A knock detection device for an internal combustion engine that detects the engine is known. There is also known a knock detection device for an internal combustion engine that uses a spark plug disposed in a combustion chamber of the internal combustion engine and detects the occurrence of knock based on an ionic current flowing in the combustion chamber immediately after the occurrence of an ignition spark.
[0003]
In addition, in knock detection using a knock sensor, erroneous detection may occur if mechanical vibration that is not related to the occurrence of knock is superimposed as noise. However, in knock detection based on ion current, noise may not be superimposed due to mechanical vibration. Generally known.
[0004]
[Problems to be solved by the invention]
By the way, when knocking occurs during combustion of the internal combustion engine, it is known that the combustion chamber pressure and the signal including the knock frequency component obtained by extracting the combustion chamber pressure through the BPF change as shown in FIG .
[0005]
Here, at the time of combustion of the internal combustion engine, as shown by the symbol “+” in the circled white area in FIG. 4A, if there are abundant combustion ions in the vicinity of the spark gap between both electrodes of the spark plug, As indicated by a thick line in FIG. 5 , the ion current signal due to the change in combustion ion density appears as a large change, and the signal including the knock frequency component corresponding to the knock intensity detected based on this changes greatly.
[0006]
On the other hand, when the internal combustion engine is burning, if there are not many combustion ions in the vicinity of the spark gap between both electrodes of the spark plug, as shown by the “+ sign in the circle” in FIG. As shown by a thin line in FIG. 5 , the ion current signal due to the change in the combustion ion density appears as a small change, and the signal including the knock frequency component corresponding to the knock intensity detected based on this also changes slightly.
[0007]
In other words, in a knock detection device for an internal combustion engine that detects the occurrence of knock using an ignition plug, the variation in the combustion state of the internal combustion engine is based on a signal including a knock frequency component corresponding to the knock intensity detected based on the ion current signal. There is a problem that it is difficult to accurately detect the occurrence of knock because it affects the determination of whether knock has occurred or not.
[0008]
Accordingly, the present invention has been made to solve such a problem, and it is an object of the present invention to provide a knock detection device for an internal combustion engine that can improve the detection accuracy of knock occurrence by eliminating the influence of variations in the combustion state of the internal combustion engine. Yes.
[0009]
[Means for Solving the Problems]
According to the knock detection device for an internal combustion engine according to claim 1, the secondary winding side of the ignition coil that generates a high voltage by on / off control of a switching element connected in series to the primary winding side. The ion current is detected by the ion current detection means based on the combustion ions when the flame is generated by the generation of the discharge spark between the spark gaps of the spark plug connected to. The signal including the knock frequency component superimposed on the ion current is extracted by the signal extraction means made of BPF, and the output of the knock frequency component obtained by the signal extraction means is obtained by the ion current output obtained by the ion current detection means by the signal correction circuit. Is corrected based on the magnitude of the ion current. As a result, the corrected signal waveform corresponding to the knock intensity eliminates the influence of variations in the combustion state of the internal combustion engine, and the detection accuracy of knock occurrence is improved.
[0010]
In the knock detection device for the internal combustion engine according to the second aspect, since the signal correction means includes a division circuit, the waveform of the corrected signal corresponding to the knock intensity eliminates the influence of variations in the combustion state of the internal combustion engine. Thus, the effect that the detection accuracy of knock occurrence is improved can be obtained .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0012]
<Example 1>
FIG. 1 is a schematic configuration diagram showing a knock detection device for an internal combustion engine according to a first example of an embodiment of the present invention.
[0013]
In FIG. 1, a spark plug 10 is disposed at the top of a cylinder head of an internal combustion engine (not shown) toward the combustion chamber. One end of the secondary winding 11 b of the ignition coil 11 is connected to the center electrode of the spark plug 10. Also, one end of the primary winding 11a of the ignition coil 11 is connected to a battery power source 12 that is a DC power source, and the other end of the primary winding 11a of the ignition coil 11 is the collector side of an ignition power transistor 13 as a switching element. It is connected to the. An ignition signal IGt from an electronic control unit (hereinafter referred to as “ECU”) 20 is input to the base side of the power transistor 13, and the power transistor 13 is turned on, whereby the ignition coil 11 is turned on. A primary current I1 from the battery power source 12 is applied to the primary winding 11a.
[0014]
Further, the other end of the secondary winding 11b of the ignition coil 11 is connected in series with the Zener diodes 31, 32 so as to form a current path for circulating the secondary current I2 together with the secondary winding 11b of the ignition plug 10 and the ignition coil 11. It is connected to the. Here, the Zener diode 32 is connected in the forward direction with respect to the direction in which the secondary current I2 (secondary circulating current) flows. The Zener diode 31 is a diode for charging a capacitor 33 as an ion current detection power source connected in parallel to the direction in which the secondary current I2 flows and connected in parallel thereto. An ion current detection resistor 34 is connected in parallel with the Zener diode 32. The zener diodes 31 and 32, the capacitor 33, and the ion current detection resistor 34 form an ion current detection circuit 30.
[0015]
The ECU 20 includes a CPU as a central processing unit that executes various known arithmetic processes, a ROM that stores control programs, a RAM that stores various data, a B / U (backup) RAM, an input / output circuit, and a bus line that connects them. It is configured as a logical operation circuit made up of and the like. Various sensor signals such as a rotation angle signal that detects a crank angle (° CA (Crank Angle)) of a crankshaft (not shown) of the internal combustion engine are input to the ECU 20.
[0016]
The ion current signal SIION from the ion current detection circuit 30 is input to a signal processing circuit 40 including a BPF 41 that is a specific frequency band pass filter that passes a signal including a knock frequency component and a division circuit 42. The division circuit 42 includes a differential amplifier 423 to which signals from Log (logarithmic converters) 421 and 422 and Logs 421 and 422 are input. A signal from the signal processing circuit 40 is input to the ECU 20.
[0017]
Next, the operation will be described.
In FIG. 1, the power transistor 13 is turned on / off based on the ignition signal Igt output from the ECU 20 to the base side of the power transistor 13, and thus flows from the battery power source 12 to the primary winding 11 a side of the ignition coil 11. The primary current I1 is turned on / off. Here, when the power transistor 13 is turned off by the fall of the ignition signal IGt and the primary current I1 flowing on the primary winding 11a side of the ignition coil 11 is cut off, the counter electromotive force corresponding to the primary current I1 is cut off. Is generated on the primary side. The secondary current I2 flows to the secondary winding 11b side of the ignition coil 11 by being induced by the counter electromotive force. A high secondary voltage, which is a multiple of the turns ratio of the primary winding 11a and the secondary winding 11b of the ignition coil 11 generated by the secondary current I2, is applied to the spark plug 10, and between the spark gaps. A discharge spark is generated.
[0018]
When a discharge spark is generated between the spark gaps of the spark plug 10 at the previous discharge timing and a flame is generated, abundant combustion ions exist in the vicinity of the spark gap. At this time, since the spark gap of the spark plug 10 becomes conductive, the ion current IION flows from the capacitor 33 in the order between the secondary winding 11b of the ignition coil 11 and the spark gap of the spark plug 10. The voltage between the terminals of the ion current detection resistor 34 based on the magnitude of the ion current IION is input to the signal processing circuit 40 as the ion current signal SIION and subjected to signal processing, and then input to the ECU 20.
[0019]
At this time, if knocking occurs, the ion current IION is transitioned corresponding to the combustion chamber pressure. In the signal processing circuit 40 configured as described above, a signal including a knock frequency component superimposed on the ion current signal SIION from the ion current detection circuit 30 is extracted by the BPF 41 and then input to the Log 421 of the division circuit 42. Further, the signal SIION from the ion current detection circuit 30 is input to the Log 422 of the division circuit 42 as it is.
[0020]
Both these signals are logarithmically converted by Logs 421 and 422, respectively, and then subtracted by the differential amplifier 423 to obtain both. That is, as a result, the signal processing circuit 40 divides the signal passed through the BPF 41 of the ion current signal SIION from the ion current detection circuit 30 by the direct signal as it is from the ion current detection circuit 30. The Rukoto.
[0021]
Next, the operation of the internal combustion engine will be described with reference to specific signals when knocking occurs in the internal combustion engine.
As described above, it is assumed that the combustion chamber pressure is changed and the knock frequency component is changed due to the occurrence of knock in the internal combustion engine. At this time, as shown in FIG. 4 (a), if there are abundant combustion ions in the vicinity of the spark gap between the two electrodes of the spark plug 10, as shown by the bold line in FIG. The signal including the knock frequency component superimposed on the ion current signal SIION extracted from the BPF 41 is large, as is the ion current signal SIION from 30.
[0022]
On the other hand, as shown in FIG. 4 (b), if there are not many combustion ions in the vicinity of the spark gap between the two electrodes of the spark plug 10, the ion current detection circuit 30 starts as shown by a thin line in FIG. The ion current signal SIION as it is and the signal containing the knock frequency component superimposed on the ion current signal SIION extracted by the BPF 41 are both small.
[0023]
Therefore, a signal obtained by dividing the signal obtained by extracting the ion current signal SIION from the ion current detection circuit 30 via the BPF 41 by the signal as it is from the ion current detection circuit 30 is a value in the combustion state of the internal combustion engine. The variation of the combustion ion density is corrected regardless of the magnitude of these signals, and a waveform characteristic diagram as shown in FIG. 2 as a corrected signal corresponding to the knock intensity is obtained. Thus, the waveform of the corrected signal corresponding to the knock intensity corresponds well to the waveform shown in FIG. 3 as a signal including the knock frequency component obtained by extracting the combustion chamber pressure through the BPF. That is, the corrected signal corresponding to the knock intensity can be used instead of the signal from the knock sensor in the conventional knock control.
[0024]
As described above, the knock detection device for the internal combustion engine of this embodiment is connected in series to the spark plug 10 disposed on the cylinder head (not shown) forming the combustion chamber of the internal combustion engine and the primary winding 11a side. An ignition coil 11 that generates a high voltage on the secondary winding 11b side by turning on / off the power transistor 13 as a switching element, and an ignition plug connected to the secondary winding 11b side of the ignition coil 11 A spark plug 10 for detecting an ion current signal SIION based on combustion ions at the time of generation of a flame by discharge spark generation between 10 spark gaps, an ignition coil 11, a capacitor 33 forming an ion current detection circuit 30, and an ion current detection resistor 34 And a knock frequency component to be superimposed on the ion current signal SIION detected by the ion current detection means. A signal extraction means for extracting a signal, and and a signal correcting means for correcting, based signals extracted by said signal extracting means with the magnitude of the detected ion current by the ion current detecting means.
[0025]
Further, the signal extraction means of the knock detection device for the internal combustion engine of the present embodiment is composed of the BPF 41 forming the signal processing circuit 40. The signal correction means of the knock detection device for the internal combustion engine of the present embodiment comprises a division circuit 42 formed by logarithmic converters 421 and 422 and a differential amplifier 423 as arithmetic circuits including division.
[0026]
That is, a signal including a knock frequency component superimposed on the ion current signal SIION output from the ion current detection circuit 30 is extracted by the BPF 41 forming the signal processing circuit 40. Then, the ionic current signal SIION as it is and the signal via the BPF 41 are divided and corrected by the division circuit 42 formed by the logarithmic converters 421 and 422 and the differential amplifier 423. The corrected signal waveform corresponding to the knock intensity eliminates the influence of variations in the combustion state of the internal combustion engine, and can improve the detection accuracy of knock occurrence.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a knock detection device for an internal combustion engine according to a first example of an embodiment of the present invention;
FIG. 2 is a characteristic diagram showing a corrected signal corresponding to the knock intensity in the knock detection device for an internal combustion engine according to the first example of the embodiment of the present invention;
FIG. 3 is a characteristic diagram showing a signal including a combustion chamber pressure and a knock frequency component extracted via BPF during combustion of a general internal combustion engine.
FIG. 4 is an explanatory diagram showing the presence of combustion ions in the vicinity of a spark gap between both electrodes of a general spark plug.
FIG. 5 is a characteristic diagram showing an ion current signal corresponding to FIG. 4 and a signal including a knock frequency component.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Spark plug 11 Ignition coil 11a Primary winding 11b Secondary winding 13 Power transistor (switching element)
20 ECU (electronic control unit)

Claims (2)

A spark plug disposed in a cylinder head forming a combustion chamber of an internal combustion engine;
An ignition coil that generates a high voltage on the secondary winding side by switching on / off a switching element connected in series on the primary winding side;
An ion current detection means for detecting an ion current based on combustion ions at the time of flame generation by discharge spark generation between the spark gaps of the spark plug connected to the secondary winding side of the ignition coil;
A signal extraction unit comprising a BPF ( Band Pass Filter ) for extracting a signal including a knock frequency component superimposed on the ion current detected by the ion current detection unit;
Signal correcting means for correcting based on a signal obtained by dividing the ion current detected by the ion current detecting means and the signal containing the knock frequency component extracted by the signal extracting means ; A knock detection device for an internal combustion engine. The knock detection device for an internal combustion engine according to claim 1, wherein the signal correction means includes a division circuit and a differential amplifier.

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