JPS6343700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pre-ignition detection device that determines the presence or absence of pre-ignition by detecting light (heat rays) generated when air-fuel mixture burns in the cylinder of a spark-ignition engine. It is.

Preignition refers to the initiation and development of a flame before normal spark ignition. This phenomenon, caused by, for example, overheated spark plugs, valves, or other combustion chamber surfaces, or by compression ignition, is undesirable for engine operation. Therefore, in developing, designing, and prototyping new engines, it is extremely useful to use a device that detects the occurrence of preignition. Additionally, depending on the type of pre-ignition, it is possible to suppress its occurrence by controlling the ignition timing, air-fuel ratio, cooling water temperature, etc., and prevent serious engine overheating and structural damage. . By the way, conventional pre-ignition detection devices constantly observe the output of cylinder pressure sensors to detect abnormal or premature increases in cylinder pressure, or insert ion probes into the cylinder to detect ions in the flame. The presence or absence of pre-ignition was detected by detecting. However, with the former device, the cylinder pressure sensor is expensive, and it is not easy to record and observe the rise pattern of cylinder pressure to make a judgment, and requires a computer with extremely advanced judgment processing ability. There is a drawback. In addition, the latter device has the disadvantage that it has a low detection rate because it cannot be determined that it is preignition unless preignition occurs near the point where the ion probe is installed and is not detected.

In addition to the above, there are methods for detecting the presence or absence of preignition by detecting light from combustion of preignition (for example, U.S. Pat. No. 2,841,979), which are generally commercially available.
The sensitivity characteristics of small optical sensors (for example, phototransistors and photodiodes) that can be used even at room temperature with respect to the wavelength of light are as shown in FIG. 1, and are sensitive to visible light to near-infrared light. If you try to detect preignition light using such an optical sensor, it will also detect the light from spark discharge (this light has a relatively short wavelength and contains a lot of blue to yellow light). This results in false detection.

The present invention has been made in view of the above-mentioned drawbacks, and by providing an optical filter that selectively transmits only light with a wavelength longer than the wavelength of near-infrared rays out of the light detected by a light emission detector, it is possible to prevent spark discharge from occurring. It is an object of the present invention to provide a device that can remove optical noise and accurately detect the presence or absence of pre-ignition.

Therefore, the present invention provides a luminescence detector that detects light during combustion of an air-fuel mixture taken into a spark ignition engine, and an optical system that transmits only light with a wavelength longer than near-infrared rays among the light detected by the luminescence detector. A filter, a photoelectric converter that converts the light transmitted through the optical filter into an electrical signal, and a preignition determination circuit that determines the presence or absence of preignition based on the time difference between the signal of the photoelectric converter and the ignition timing signal. A pre-ignition detection device for a spark ignition engine is provided.

As a result, only light with a wavelength longer than near-infrared rays among the light detected by the light emission detector during combustion of the air-fuel mixture passes through the optical filter, and light with a short wavelength that is generated as noise during spark discharge is blocked. Ru. Then, the light that has passed through this optical filter is converted into an electrical signal by a photoelectric converter, and preignition is determined by a preignition determining circuit based on the time difference between this electrical signal and an ignition timing signal.

An embodiment of the present invention shown in the drawings will be described below. FIG. 2 shows the in-cylinder pressure of one cylinder and the light emission signal due to combustion when the four-cylinder, four-cycle engine is operating normally. a is an ignition timing signal, b is a piston top dead center signal, c is an in-cylinder pressure signal, and d is an in-cylinder light emission signal. In this in-cylinder light emission signal, the light emission of sparks during spark discharge is also detected and is included in the light emission signal as ignition noise. The present invention aims to obtain the waveform e by cutting only this ignition noise, accurately detect combustion light emission, and determine the presence or absence of pre-ignition.

This will be explained below using FIGS. 3 to 7. FIG. 3 is a sectional view of the combustion chamber of the engine, where 1 is a cylinder and 2 is a piston inserted into the cylinder 1. A cylinder head 3 is fastened to the upper part of the cylinder 1 via a gasket 4. Then, the top surface 5 of the piston 2 at the compression top dead center position and the inner surface 6 of the cylinder head
A combustion chamber 7 is formed by this. The intake port 8 opens on the inner surface 6 of the cylinder head near the outer periphery of the combustion chamber 7, and is arranged so that its central axis is directed toward the approximate center of the cylinder 1 near the opening in the combustion chamber, that is, near the intake valve 9. There is. An ignition plug 11 is attached to the upper part of the combustion chamber, and a light emission detector 10 according to the present invention is installed on the side of the ignition plug 11 facing toward the center of the combustion chamber. 12 is an exhaust valve, and 13 is a valve seat. 15 is an ignition device equipped with an ignition timing calculation circuit, an ignition coil, etc.; 16 is a crank angle detector; 18 is a photoelectric converter; 20 is a pre-ignition discrimination circuit; and other engine parameter detectors 17. This is a device that controls ignition timing and ignition energy based on the

Details of the luminescence detector 10 are shown in FIG. The tip of the light emission detecting section 101 exposed to the combustion chamber is hemispherical, allowing light from various parts of the combustion chamber to enter. This is because preignition is generally caused by hot spots such as spark plugs, valves, or deposits in the combustion chamber, so the light emission detector 10 requires a fairly wide field of view. The tip on the opposite side of the light emission detection section 101 has a brim shape and is made of a material such as quartz glass or sapphire. 102 is a light guide made of optical fiber made of quartz glass or the like; 103 is a housing made of heat-resistant metal such as stainless steel or nickel alloy;
04 is a sealing material made of a soft metal such as nickel or copper attached between the housing 103 and the light emission detecting section 101; 105 is a covering portion of the light guide section 102; and 106 is a seal material between the light guide section 102 and the housing 10.
107 is an optical filter that transmits only light with a wavelength longer than red out of the light detected by the light emission detector 101, and 108 is a gasket used when attaching the light emission detector 10 to the upper part of the combustion chamber. .

Light generated within the combustion chamber is guided by a light emission detection section 101, and its wavelength is selected by an optical filter 107. The wavelength characteristic of the transmittance of the optical filter 107 is as shown in FIG. 5, for example, and light of 6500 Å or less is blocked. Therefore, the light generated during spark discharge (mostly light with a wavelength of 3000 Å to 6000 Å) is cut out, and the light emission signal becomes as shown in FIG. 2e, making it possible to detect only light emission due to true combustion. Visible light is present in the light emitted by combustion, but because the combustion gas temperature is also high, a large amount of infrared rays is also emitted. Therefore, the light transmitted through the optical filter 107 represents a high temperature state due to combustion.

Next, details of the photoelectric converter 18 and the preignition discrimination circuit 20 will be explained using time charts shown in FIGS. 6 and 7. The combustion light guided by the light guide section 102 of the light emission detector 10 enters the photoelectric converter 18 and is irradiated onto the base of the phototransistor 181. As a result, the light is converted into a current, which flows through the resistor 182 and is detected as a voltage, resulting in a signal c as shown in FIG. 7c. Ignition noise has already been removed from this signal by an optical filter 107. By comparing this signal at a certain level by the comparator 201, FIG.
Make the signal D as follows. 202 is a differentiating circuit which extracts only the leading edge of the signal D and generates the signal E shown in FIG. 7E. On the other hand, FIG. 7B from the crank angle detector 16
Using the top dead center signal B as a reference, a monostable circuit 203 generates a pulse having a width of a certain time τ. 204 is τ from top dead center based on that pulse.
This is a differential circuit that generates differential pulses over time. The signals created by the differentiating circuits 202 and 204 are
It enters the OR circuit 205 and is added, and the NOR circuit 20
6,207 to one input of the RS flip-flop circuit.

The ignition timing signal A shown in FIG. 7A from the ignition device 15 is also input to another input of the RS flip-flop circuit composed of NOR circuits 206 and 207.
Depending on the time difference between these two inputs, the output F of the flip-flop circuit becomes as shown in FIG. 7F. That is, in FIG. 7, if it is assumed that normal combustion occurs at the time of ignition of A and C, combustion light will be detected after the ignition is delayed by the ignition delay time. Therefore, the output F of the RS flip-flop circuit goes to the "0" state due to the ignition timing signal, and returns to the "1" state due to the cylinder light emission signal. However, in the case of ignition (a) where pre-ignition occurs, the in-cylinder light emission signal enters the RS flip-flop circuit earlier than the ignition timing. Therefore, the output F of the RS flip-flop circuit changes to "0" state due to the ignition timing signal as in the normal state, but it returns to "1" state not due to the leading edge signal E of the in-cylinder light emission signal but This is performed using a signal from the differentiating circuit 204, which is a signal delayed by a time τ from the dead center signal. The presence or absence of preignition is determined by the monostable circuit 203.
FIG. 7 G where the output of is passed through the inverter circuit 208.
Using signal G shown in as a gate signal, NOR circuit 2
By 09, the output F of the RS flip-flop circuit
This is done by checking the "0" and "1" states of the signals. In other words, only when pre-ignition occurs, the signal G of the inverter circuit 208 is "0" and the output G of the RS flip-flop circuit is also "0".
Therefore, the output H of the NOR circuit 209 becomes "1" as shown in FIG. 7H, and preignition can be determined. In response to this pre-ignition detection signal, the ignition device 15 controls the ignition timing to suppress the occurrence of pre-ignition.

In this embodiment, the top dead center signal is used to calculate the τ
The presence or absence of pre-ignition is determined based on the time after which the ignition timing is delayed considerably depending on the engine, and the generation of the in-cylinder light emission signal may be delayed from top dead center. In this case, the time to test whether the output signal F of the RS flip-flop is "0" or "1" may be set at a time delayed by a certain period of time from the top dead center.

Further, the signal such as the constant time τ may be a predetermined angle signal using a crank angle signal.

Further, although an optical fiber is used as the light guiding section, the photoelectric converter or the entire preignition discrimination circuit may be miniaturized and installed within the light emission detector 10 using integrated circuit technology.

Furthermore, instead of controlling the ignition timing using the preignition detection signal, an alarm may be issued or a signal may be sent to another engine control device to suppress preignition.

Furthermore, the optical filter 107 is connected to the light emission detection section 101.
Although it is used by being inserted between the light guide member 102 and the phototransistor 181, it may also be used by inserting it between the light guide member 102 and the phototransistor 181. For this optical filter 107, in addition to a filter that absorbs light below the cutoff frequency, a glass with a reflection increasing film coated with a multilayer thin film on the glass surface to reflect light below the cutoff frequency may be used.

As described above, the present invention detects luminescence caused by combustion, passes this light through an optical filter that transmits only light with a wavelength longer than near infrared rays, and generates a photoelectrically converted signal and an ignition timing signal from the light transmitted through the optical filter. Since pre-ignition is detected based on the time difference between the pre-ignition and the pre-ignition, it is possible to block light with a short wavelength during spark discharge and has the excellent effect of being able to detect pre-ignition with high accuracy.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram showing an example of the sensitivity characteristics of an optical sensor, Fig. 2 is a time chart showing the relationship between an ignition timing signal, an in-cylinder pressure signal, and an in-cylinder light emission signal, which is used to explain the operation of the present invention. 4 is a sectional view of the main part showing an embodiment of the present invention, FIG. 4 is a sectional view of the light emission detector in FIG. 3, FIG. 5 is a characteristic diagram of the optical filter in FIG. 4, and FIG. FIG. 3 is a detailed configuration diagram of the photoelectric converter and preignition discriminating circuit, and FIG. 7 is a time chart showing the operation of the preignition discriminating circuit shown in FIG. 6. 7... Combustion chamber, 10... Luminescence detector, 15...
Ignition device, 18... photoelectric converter, 20... pre-ignition discrimination circuit, 101... light emission detection section,
107...Optical filter.

Claims (1)

[Claims] 1. A luminescence detector that detects light during combustion of the air-fuel mixture taken into a spark ignition engine, and of the light detected by this luminescence detector, only light with a wavelength longer than near-infrared rays is detected. An optical filter that transmits light, a photoelectric converter that converts the light that has passed through the optical filter into an electrical signal, and a pre-ignition determination that determines the presence or absence of pre-ignition based on the time difference between the signal of the photo-electric converter and the ignition timing signal. A pre-ignition detection device for a spark ignition engine, characterized by comprising a circuit. 2. The preignition detection device according to claim 1, wherein the optical filter is provided inside the light emission detector. 3. Claim 1, wherein the tip of the light emission detection portion of the light emission detector is semispherical.
The preignition detection device according to item 1 or 2.