JPH03528Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

The present invention relates to an ignition timing sensor for an internal combustion engine,
In particular, the light guide includes a light guide rod made of a light guide such as quartz glass, the tip of which is arranged so as to face into the combustion chamber of the engine, and a light receiving element arranged so as to face the rear end of the light guide rod. The present invention relates to an improvement in an ignition timing sensor for an internal combustion engine for detecting ignition timing from the state of combustion light guided by a light rod via the light receiving element.

[Conventional technology]

In recent years, improvements in output, fuel efficiency, or exhaust gas purification performance have become important issues, particularly in diesel engines and gasoline engines for automobiles. As one means to achieve this, when controlling the fuel injection timing, an ignition timing sensor is provided to detect combustion light in the engine combustion chamber, and the ignition timing is detected from the output of the ignition timing sensor. Accordingly, it has been proposed, for example, to perform feedback control on timing control valves. When detecting the ignition timing in such fuel injection timing control, as a means for extracting the state of combustion light from the engine combustion chamber to the outside, for example, a light guide rod made of a quartz glass rod is used to isolate the inside of the combustion chamber from the outside air. It is conceivable to attach and hold it to the cylinder head of the engine, etc. in this state. Here, the combustion light extracted from the combustion chamber through the light guide rod is transmitted through a light receiving element mounted facing the rear end of the light guide rod, or via an optical fiber, and is placed at a distance. The light is received by a light-receiving element, where it is converted into an electrical signal. The quartz glass as the material of the light guiding rod is
Although it is used for its heat resistance, cost, and chemical resistance, it is easily corroded by alkali components such as P and Ca in the combustion gas in the engine combustion chamber, causing optical devitrification, which impairs the performance of the ignition timing sensor. There is a problem in that the value decreases significantly.

[Problem that the invention attempts to solve]

This idea was made in view of the above problems, and is designed to prevent the part of the tip of the light guiding rod that faces the combustion gas in the engine combustion chamber from being corroded or eroded by the alkaline components in the combustion gas. An object of the present invention is to provide an ignition timing sensor for an internal combustion engine.

[Means to solve the problem]

This device has a light guide rod consisting of a light guide arranged so that its tip faces into the engine combustion chamber,
In an ignition timing sensor for an internal combustion engine for detecting ignition timing from the state of combustion light guided by the light guide rod via a light receiving element, an alkali corrosion-resistant metal film is coated on the tip of the front light guide rod. The above purpose is achieved by coating.

[Effect]

According to this invention, by coating the tip of the light guide rod with a substance that is not corroded by alkaline components in the combustion gas, such as metal such as Cr, corrosion of the tip of the light guide rod can be prevented. Optical devitrification can be prevented.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the ignition timing sensor of the present invention is applied to a diesel engine will be described in detail below with reference to the drawings. In this embodiment, as shown in FIG. 1, an ignition timing sensor 12 is inserted and fixed into a cylinder head 10B of a diesel engine 10 for detecting combustion light in a combustion chamber 10A of a diesel engine 10.
and detects the ignition timing by processing the output of the ignition timing sensor 12 inputted via the signal line 16,
It has an electronic control unit (hereinafter referred to as ECU) 20 that controls, for example, fuel injection timing according to the detected ignition timing. In Figure 1,
22 is a fuel injection nozzle, 24 is a globe lug, and 26 is a piston. As shown in detail in FIG. 2, the ignition timing sensor 12 includes a light guide rod 30 made of, for example, a quartz glass light guide, which is disposed so that its tip 30A faces into the engine combustion chamber 10A, and a light guide rod 30 that is made of a light guide made of quartz glass, for example. A cylindrical case 32 made of highly heat-resistant metal or ceramics holds the light guide rod 30 in a state where the inside is shielded from the outside air, and a cylindrical case 32 is disposed facing the rear end 30B of the light guide rod 30, Rod 30
and a light receiving element 34 made of, for example, a silicon phototransistor, for receiving the combustion light guided by the light guiding rod 30 and converting it into an electric signal. The ignition timing is detected through the light receiving element 34, and the tip of the light guide rod 30 has a
It is coated with an alkali corrosion-resistant metal film 36 made of Cr. Reference numeral 40 in the figure indicates the bulge 30C for preventing the light guide rod 30 from coming off, and the cylindrical case 32 surrounding the bulge 30C in front and rear thereof.
The adhesive used to adhere to the inside of each is shown. Here, the tip of the cylindrical case 32 is attached to the cylinder head 10B as shown in FIG.
3 to 5 mm from the inner peripheral wall of the cylinder head 10B
It is installed so that it can be recessed into the wall of the building. Here, as the alkali corrosion resistant metal film 36,
Cr was selected based on the fact that it was found to be most compatible with the light guide rod 30 made of quartz glass through experiments. As mentioned above, when Cr is coated with a film thickness of 100 to 200 Å as the alkali corrosion-resistant metal film 36, the mileage of the automobile and the ignition timing sensor 1
The relationship with the sensor light amount ratio of 2 (1.0 when the traveling distance is 0), that is, the deterioration characteristics of the sensor, is now shown by the solid line in FIG. The broken line shows the case of a conventional ignition timing sensor without coating. Here, if a metal film such as Cr is coated on the tip of the light guide rod 30, the absolute value of the combustion light in the engine combustion chamber 10A that passes through the light guide rod 30 will be as shown on the horizontal axis in FIG. When the Cr film thickness is 200 Å, it decreases to about 0.5, and when it is 100 Å, it decreases to about 0.7. However, even if the amount of input light is small,
Since the waveform of the light does not change, sufficient responsiveness and reliability can be obtained by increasing the gain of the amplifier of the processing circuit for the output signal from the light receiving element 34 from the beginning. However, in order to obtain sufficient responsiveness and reliability, a light transmittance of 40% or more is required. On the other hand, when the light intensity attenuates due to sensor deterioration, the rise of the input light itself is distorted, and it is difficult to accurately detect and correct the attenuation amount, making it impossible to accurately detect the ignition timing. . Here, the reason why the Cr coating film thickness was set to 100 to 200 Å is as shown in FIG.
If the film is too thick, it will peel off due to thermal stress.
For this reason, the coating amount ratio at the tip of the glass decreases, and the decrease in the absolute value of the light amount becomes excessive.Also, if the film thickness is too thin, the tip of the light guiding rod 30 will be easily corroded due to deterioration over time. . Furthermore, in the above embodiment, the tip of the cylindrical case 32 is attached at a position 3 to 5 mm away from the inner circumferential wall surface of the engine combustion chamber 10A, so the average temperature at the tip of the light guiding rod 30 is The temperature was lower than when it was installed protruding into the engine combustion chamber 10A, and the maximum value was approximately 500°C. Therefore, the Cr coating can sufficiently withstand this temperature of 500° C., and has sufficient adhesion to the tip of the light guiding rod 30 made of quartz glass. Here, the relationship between the amount of Cr deposited on the tip of the glass and the distance traveled by the vehicle is shown by the solid line in FIG. In the figure, the dashed-dotted line indicates the case of the C film, and the broken line indicates the case of the Au film. In the above embodiment, the alkali corrosion-resistant metal film 36 is a Cr film, but the present invention is not limited to this. Combustion chamber 10
It is sufficient if it has corrosion resistance against the alkaline components of the combustion gas in A. Therefore, other metal films, such as Au films, may be used. However, as shown in Figure 6, in the case of Au film, the adhesion performance to the tip of quartz glass is inferior to that of Cr, so in this case, for example, as shown in Figure 7, quartz glass It is preferable to first coat the tip of the light guide rod 30 with a Cr film, and then coat it with an Au film. The film thickness in these cases is preferably about 100 Å. In the case of the embodiment shown in FIG. 7, the Cr film has a high adhesion performance to the light guide rod 30 made of quartz glass, and the Au film has high corrosion resistance against combustion gas, so that the light guide rod 30 can be attached more reliably. Loss of clarity at the tip can be prevented. Further, in the above embodiments, the Cr film or the Au film was simply described as coating, but the coating means may be sputtering, ion beam, vacuum evaporation, or the like. Further, it is preferable that the film thickness be uniform. If the film thickness becomes non-uniform, it will easily peel off due to thermal stress.

[Effect of the idea]

Since the present invention is configured as described above, it is possible to suppress corrosion of the tip of the light guide rod of the ignition timing sensor due to alkaline components in the combustion gas without impairing the responsiveness and reliability of the sensor. It has this excellent effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the overall configuration of an ignition timing detection device in which an embodiment of the ignition timing sensor for an internal combustion engine according to the present invention is used, and FIG. 2 is a sectional view of the ignition timing sensor according to the embodiment. 3 is an enlarged cross-sectional view showing the tip of the light guiding rod of the same embodiment; FIG. 4 is a diagram showing the sensor deterioration characteristics in the same embodiment; FIG. A diagram showing the relationship between Cr film thickness and adhesion force in the same example,
FIG. 6 is a diagram showing the deterioration characteristics of the alkali corrosion-resistant metal film in the same example in comparison with other coating materials, and FIG. 7 is the same as FIG. 3 showing the second example of the present invention. FIG. 10A...Engine combustion chamber, 12...Ignition timing sensor, 30...Light guide rod, 30A...Tip,
30B... rear end, 34... light receiving element, 36... alkali corrosion resistant metal film.

Claims (1)

[Scope of utility model registration request] An internal combustion engine having a light guide rod made of a light guide arranged so that its tip faces into the engine combustion chamber, and for detecting ignition timing from the state of combustion light guided by the light guide rod via a light receiving element. An ignition timing sensor for an internal combustion engine, wherein the tip of the light guide rod is coated with an alkali corrosion-resistant metal film.