JPS62125217A - Ignition timing sensor for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a devitrification of an optical conducting rod caused by a corrosion in its surface by a method wherein the surface of the optical extremity end being placed adjacent within a combustion chamber in order to detect a combustion light in the combustion chamber of an engine is covered by an anti-corrosion ceramic film. CONSTITUTION:An electrical control unit (ECU) 20 for use in controlling a time of fuel injection is provided. An extremity end of an optical conduction rod 30 to be arranged within an engine combustion chamber 10A is welded to an inner circumference at an extremity end of a cylindrical case 32 in an ignition time sensor 12 and it is covered by a tube 32A constituting a part of the cylindrical case up to its extremity end, resulting in that this covering may act to hold the optical conducting rod and restrict its removal in a direction toward its extremity end. The extremity end of the optical conducting rod 30 is formed as a semi-spherical shape and an anti-corrosion ceramic film composed of, for example, silicon nitride (Si3N4) is formed on the surface of it to show a thickness of about 2-3mum. A film of silicon nitride of which representing compound is Si2N4 can be formed with a sputtering process or a reduced pressure CVD process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ignition timing sensor for an internal combustion engine, and in particular has a light guide rod made of a light guide arranged so that its tip faces into the engine combustion chamber; The present invention relates to an improvement in an ignition timing sensor for an internal combustion engine that detects ignition timing from the state of combustion light thickened by the light guide rod via a light detection section.

[Conventional technology]

In recent years, improvements in output, fuel efficiency, or exhaust gas purification performance have become important issues, particularly in automotive diesel engines and gasoline engines.

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 a timing control valve.

When determining 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, Japanese Patent Application Laid-Open No. 58-25
As described in Japanese Patent No. 584, etc., it is conceivable to attach and hold a light guiding rod made of an optical fiber or a quartz glass rod to the cylinder head of an engine, etc., with the inside of the combustion chamber insulated from the outside air.

Combustion light in the engine combustion chamber taken out through this light guide rod is sent to a light receiving element mounted facing the rear end of the light guide rod, or to a light receiving element placed at a distance via an optical fiber. The light is received and converted into an electrical signal.

[Problem that the invention seeks to solve]

However, when the present inventors prototyped this conventional sensor, attached it to an actual vehicle, and conducted a durability test, the following problems became clear.

In other words, the surface of the light guide rod made of quartz rod exposed inside the combustion chamber became cloudy over time, and this exposed surface became extremely rough, reducing the light guide rate of light passing through the light guide rod. be.

In order to investigate the cause of this, we analyzed the cross section of the exposed surface of the quartz rod in the combustion chamber using EPMA, and found that the exposed surface of the quartz rod contains alkali metals such as Ca, Na, and Ba, or alkaline earth metal elements. It was found that devitrification occurs because it penetrates into the interior of the quartz rod through the exposed surface and corrodes the surface of the quartz rod.

Therefore, the present invention aims to prevent devitrification due to surface corrosion of the light guiding rod based on the above experimental observations.

[Means for solving problems]

In order to achieve the above object, the present invention employs an ignition timing sensor for an internal combustion engine in which the surface of the light guiding rod is coated with a corrosion-resistant ceramic coating.

[For production]

According to the above means, the corrosion-resistant ceramic coating prevents metal elements such as alkali metals or alkaline earth metals contained in the combustion gas from entering the light guide rod, and prevents devitrification of the light guide rod. .

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments in which the ignition timing sensor of the present invention is applied to a diesel engine will be described in detail with reference to the drawings.

In this embodiment, as shown in FIG. 2, a diesel engine 1
In order to detect combustion light in the combustion chamber 10A of the diesel engine 10, an ignition timing sensor 12 is inserted and fixed into the cylinder head IOB of the diesel engine 10, and the output of the ignition timing sensor 12 is inputted via a lead wire 16. It has an electronic control unit (hereinafter referred to as ECU) 20 that processes the ignition timing to detect the ignition timing and controls, for example, the fuel injection timing according to the detected ignition timing. In FIG. 2, 22 is a fuel injection nozzle, and 24 is a glow plug.

26 each indicates a piston.

As shown in detail in FIG. 1 (8), the ignition timing sensor 12 includes a light guide rod 30 made of, for example, a quartz glass light guide, disposed so that its tip 30A faces into the engine combustion chamber 10A; A cylindrical case 32 made of highly heat-resistant metal or ceramics holds the light guide rod 30 in a state where the inside of the combustion chamber 10A is isolated from the outside air, and the cylindrical case 32 is arranged facing the rear end 30B of the light guide rod 30. It has a light receiving element 34 made of, for example, a silicon phototransistor, for receiving the combustion light guided by the light guide rod 30 and converting it into an electric signal. Note that this phototransistor detects light with a wavelength of 600 to 1l100n.

□ Reference numeral 36 in FIG. 1 is an O-ring interposed between the outer periphery of the light guide rod 30 and the inner periphery of the cylindrical case 32 to seal between both. Reference numerals 38 and 40 indicate the first copper ring and the light guide rod 30 which are tightly fitted to the inner periphery of the cylindrical case 32 at the four-light rod tip end positions of the O-ring 36.
a second copper ring tightly fitted around the outer periphery of the ring. Reference numeral 42 denotes a backup ring arranged adjacent to the rear end side of the light guide rod of the O-ring 36 and between the outer periphery of the light guide rod 30 and the inner periphery of the cylindrical case 32; Fig. 7 shows the spars (S) 7 that constitute a stopper for preventing the rod from being pulled out toward the rear end.

A second copper ring is provided between the O-ring 36 and the first copper ring 38.
A backup ring 46 is interposed.

The second backup ring 46 is the O-ring 3
6 and the first copper ring 38 adjacent to this O-ring 36 in the axial direction of the light guide rod.

The backup rings 42 and 46 are made of fluororesin,
It is made of a material such as a sintered body of carbon, and the O-ring 36 is made of fluorine rubber.

Is the tip end of the light guide rod 30 on the inner periphery of the tip of the cylindrical case 32? The tip of the light guide rod 32A is covered with a tube 32A that forms a part of the cylindrical case 32, thereby holding the light guide rod 30 and preventing it from coming off in the direction of the tip.

A through hole 47 is formed in the cylindrical case 32 holding the light guide rod 30 so as to extend coaxially and continuously through the center of the cylindrical case 32 with the tube 32A. This through hole 47 is continuously formed up to a part of the front end side of an adapter 48 attached to the rear end of the cylindrical case 32 .

The light guide rod 30 has a cylindrical case 32 at its tip end.
It is inserted into the through hole 47 with a portion protruding from the tip thereof and is held with an adhesive 49 interposed therebetween.

A part of the distal end portion of the light guiding rod 30 protruding from the cylindrical case 32 is covered and protected by the tube 32A. The light guide rod 30 is positioned in the rear end direction and prevented from coming off by being pressed by an inner peripheral protrusion 48A formed at the upper end of the through hole 47 in the adapter 48 so as to contact the outer peripheral portion of the rear end 30B. . The adapter 48 is fixedly attached to the rear end of the cylindrical case 32 by caulking.

The adapter 48 is a cylindrical member having a hollow chamber 50 containing the light receiving element 34, and the light receiving element 34 is
It is supported by a base plate 52, and this base plate 52 is positioned and held by being inserted from the rear end direction of the adapter and abutting against a shoulder portion 54 of the adapter 48 that protrudes inwardly from the hollow chamber 50.

The rear end side of the adapter 48 is a connector body 58, and this connector body 58 is connected to the mating connector body 5.
When the mating connector body 59 is inserted from the rear end side, the terminal 60 is electrically connected to the terminal of the mating connector body 59.

This terminal 60 penetrates the substrate 52 and is connected to a lead wire 62 from the light receiving element 34 to derive an electrical output signal from the light receiving element 34.

Reference numeral 66 in the figure is an O-ring attached to the connector body 58 for sealing the gap between the two when the connector body 58 is connected to the mating connector body 59; The locking knobs for locking are shown respectively.

Further, reference numeral 32B connects the cylindrical case 32 to the cylinder head IO.
A screw portion 32C for screwing into B is the threaded portion 32C of the cylindrical case 3.
2 and which are used when screwing the cylindrical case 32 into or out of the cylinder head IOB are shown.

The tip 30A of the light guide rod 30 is formed into a hemispherical shape as shown in FIG. 1(b), which is an enlarged view of the tip.
The surface is covered with a coating rr111 which is a corrosion-resistant ceramic coating of the present invention made of silicon nitride (S t 2 Na).
is formed to have a thickness of 2 to 3 μm.

When the ignition timing sensor of the present invention configured as described above was installed in a diesel engine, a durability test was conducted and the amount of light passing through the light guide rod before and after durability was compared, and the light transmittance was 50% compared to the initial one. It was found that the above results were sufficient for practical use.

In addition, when a similar durability test was conducted on a conventional ignition timing sensor in which the N layer 11 was not strongly formed, the light transmittance was 20.
%, demonstrating the remarkable effect of the present invention. Here, the durability test was continued for 10 minutes at an engine speed of 1100Qrp.
This is a so-called up-down endurance mode that repeats a 10-minute wlvt at 500 rpm for 200 hours.

Next, the results of experiments conducted by the present inventors in selecting the ceramic coating will be described. As already explained, the inventors investigated the light guide rod after the durability test and found that the surface of the rod facing into the combustion chamber was extremely rough.
In addition, cloudiness was observed on the surface, and as a result of EPMA analysis, it was found that alkali metals and alkaline earth metals such as Ca, Ba, and Na, which were not observed initially, were attached to the surface. Therefore, we thought that the cause of rod devitrification was mainly corrosion of quartz caused by alkali metals or alkaline earth metals contained in fuel or oil, and decided to take countermeasures. Figure 3 shows various ceramic powders (average particle size 1.Q~2.0un) with NaoHIQ% and
This shows the results of examining the weight change rate after being immersed in a jtlO% solution for 50 hours. The @S i Oz powder is almost completely dissolved in the alkaline solution, indicating that quartz is extremely susceptible to alkali corrosion. Among the materials tested, the materials that are resistant to both alkali and acid corrosion are Si, Na, and SiC.

There are three types: TiC. Among these, the one whose thermal expansion coefficient is closest to quartz is (Si3N) as shown in the table below. Si3N is the most preferable as the corrosion-resistant ceramic coating of the present invention, but ceramic coatings such as SiC and Tic is also available.

Next, referring to the method for manufacturing this ceramic film, a silicon nitride film typified by 5isNn can be created using sputtering or low pressure CVD. Sputtering is more suitable in terms of adhesion to the quartz light guide rod.

The specific coating method is N! using pressure 1. Opa, the substrate temperature was 500°C. A high frequency magnetron sputtering device was used as the device. The 'I/AK of the formed film is 2 to 3 μm.

FIG. 4 shows the transmittance at each wavelength after applying the silicon nitride film. 600~1 which is the measurement wavelength of the phototransistor
It shows a transmittance of 70% or more at 100 mm, and there is no practical problem even if a film is formed.

FIG. 5 shows the results of investigating the alkali contact resistance of silicon nitride films. Since it was difficult to directly measure the decrease in the film thickness of S i 3 N-, 513N, B
At the same time, a part of the film is left unformed by a method such as masking, and the quartz glass and Si3N4
It was determined by measuring the height difference X. The test is NaOH
A 10% solution was heated to 70° C. for an accelerated corrosion test. It can be seen that the step X increases with time, and that the portions not covered with the Si and N4 films are more likely to be immersed in the alkaline solution. That is, it was found that S i 3N4 has excellent alkali contact resistance.

In the present invention, the effective thickness of the corrosion-resistant ceramic coating is about 200 to 5 μm, and if it is less than 200 Å, the durability will be poor, and if it is more than 5 μm, the durability will improve, but the light transmittance will decrease and the sensitivity will decrease. At the same time, sputtering time becomes longer and productivity deteriorates.

Furthermore, in the above embodiment, the ceramic coating was applied only to the surface of the hemispherical part at the tip as shown in Fig. In Figure 1 ta>, the tip 3 from the 0 ring 36
The entire surface of the 0A side may be coated.

In addition to the materials shown in the examples above, the material for the ceramic coating of the present invention may also be ceramic, which is resistant to peeling even when subjected to thermal shock and resistant to corrosion by alkali metals and alkaline earth metals. It can be anything.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to provide an ignition timing sensor for an internal combustion engine that has a simple configuration, prevents devitrification of a light guiding rod without increasing manufacturing cost, and has stable performance over a long period of time. This has an extremely practical effect.

[Brief explanation of drawings]

FIG. 1(a) is a sectional view showing the structure of an ignition timing sensor for an internal combustion engine according to the present invention, FIG. A cross-sectional view showing the ignition timing sensor installed in a diesel engine, Fig. 3 is a characteristic diagram showing the results of corrosion resistance tests of various ceramic materials, and Fig. 4 shows the light transmittance of the ignition timing sensor of the present invention. FIG. 5 is a characteristic diagram showing the wavelength change, and FIG. 5 is a characteristic diagram showing the results of the alkali corrosion resistance test of Si, N, and coatings. Representative patent attorney Takashi Okabe AIN Si3N4 Sic
TiCAl2O35io2 Figure 3 Figure 4

Claims (1)

[Claims] (1) It has a light guide rod made of a light guide arranged so that its tip faces into the engine combustion chamber, and a light detection section that detects output light from the rear end of the light guide rod, An ignition timing sensor for an internal combustion engine for detecting ignition timing from the state of guided combustion light via the light detection section, characterized in that the surface of the dim light rod is coated with a corrosion-resistant ceramic coating. Engine ignition timing sensor.