JPH0511251B2 - - Google Patents

Description

[Detailed description of the invention] [Field of application of the invention] The present invention relates to a flame light detection device.

[Background of the invention]

In order to maintain optimal combustion in boilers, kerosene stoves, spark ignition type or compression ignition type internal combustion engines, etc., it is necessary to optimally control combustion temperature, pressure, air-fuel ratio, ignition timing, injection timing, etc. figure,
In an internal combustion engine, it is advantageous in terms of output and economy to operate near the limit where no knock occurs.

Many methods for detecting any of these various parameters and performing closed-loop control have been published so far, and in particular, a flame light detection device for detecting the physical process of combustion using combustion flame light has been proposed. For example, JP-A-57-108734 and JP-A-Sho.
In Japanese Patent No. 57-108735, a quartz glass rod is placed on the combustion chamber side in the screw casing, and an optical fiber is placed on the other end side to detect flame light. In such a case, in order to sufficiently guide the flame light to the optical fiber, it is necessary to increase the cross-sectional area of the quartz glass rod, which increases the cost and makes it difficult to make the device compact. Further, since the metal part and the quartz glass part are arranged in close contact with each other in the high temperature part on the side of the combustion chamber, the thermal expansion coefficients of the two parts are greatly different, which is not preferable from the viewpoint of heat resistance.

Furthermore, in Japanese Patent Application Laid-Open No. 57-163842, a center electrode is inserted into the axial center of the quartz glass rod of the above-mentioned detection device,
A device has been proposed that uses a screw casing portion as a ground electrode and also functions as a spark plug. However, this device also has a flame introduction section that is almost the same in structure as the above-mentioned one, and has the same drawbacks as the above-mentioned one.

[Purpose of the invention]

The present invention has been made in view of the above points,
The object of the present invention is to provide a flame light detection device that is compact and has a flame light introduction section that is capable of improving heat resistance and airtightness.

[Summary of the invention]

That is, the present invention provides a device for detecting combustion flame light in a combustion chamber, which includes a screw casing, a flame light introduction section disposed within the screw casing, and having at least one light guide for inputting and propagating the flame light; A flame light detection unit having a screw casing external optical fiber connected to the light guide and disposed outside the screw casing, and a photoelectric conversion unit connected to the optical fiber and photoelectrically converting the incident and propagated flame light. and a quartz-based optical fiber whose outer periphery is covered with a metal pipe through a predetermined distance, and whose core and cladding are quartz; and an output end of the silica-based optical fiber. A heat-resistant insulator is provided between the metal pipe and the threaded casing with a predetermined distance between them, and the output of the silica-based optical fiber is A metal body for joining is provided around the end side and the multi-component optical fiber on the output end side via a predetermined distance, and a metal body for joining is provided between the screw casing and the insulator, between the insulator and the metal pipe, and between the metal pipe and the metal pipe. The metal bodies are bonded to each other with a predetermined width, the multi-component optical fiber and the bonding metal body are sealed, and the input end of the silica optical fiber has a protruding part, This input end is characterized by protruding from the screw casing toward the combustion chamber, so that each constituent member of the flame light introducing section is airtightly joined by adhesive and sealing. At the same time, elongation due to thermal expansion of each constituent member is allowed to escape through the predetermined gap provided between the members, and there is no need for the silica optical fiber to have a large cross-sectional area.

[Embodiments of the invention]

The present invention will be explained below based on the illustrated embodiments. An embodiment of the present invention is shown in FIGS. 1-6. As shown in FIG. 1, a device for detecting combustion flame light in a combustion chamber (not shown) is disposed in a screw casing 1 and inside the screw casing 1, and is configured to receive and propagate flame light. a flame light introduction part 3 having at least one light guide 2 which is connected to the light guide 2 and arranged outside the screw casing 1;・
The flame light detection section 6 includes a photoelectric conversion section 5 that photoelectrically converts the propagated flame light. In the figure, 5a and 5b constitute the photoelectric conversion section 5, where 5a is a photoelectric conversion element, 5b is a signal processing circuit, and 7 is a connector. In this embodiment of the flame light detection device configured as described above, as shown in FIGS. 2 to 4, the light guide 2 is covered with a metal pipe 8 on its outer periphery, and is connected to a core 2c and a cladding. 2d is a quartz optical fiber 2a made of quartz;
A multi-component optical fiber 2b is connected to the output end of the silica optical fiber 2a, and the input end of the silica optical fiber 2a is connected to a screw casing 1.
It was made to protrude from the side toward the combustion chamber. By doing so, the light guide 2 is formed of a silica optical fiber 2a covered with a metal pipe 8 and a multi-component optical fiber 2b, and the input end of the silica optical fiber 2a is connected from the screw casing 1 to the combustion chamber. It is possible to obtain a flame light detection device having a flame light introduction part 3 which is compact and can improve heat resistance and airtightness by projecting to the side.

In other words, the threaded casing 1 includes a hexagonal nut part 1a for tightening, and a threaded part 1 required for attachment to the combustion chamber.
b. The screw casing has a threaded portion 1c for a connecting connector to which the external optical fiber 4 is connected.
Inside this screw casing 1, a quartz-based optical fiber 2a (about φ1 mm) is arranged on its central axis,
The outer periphery is guarded with a pipe 8 made of a metal with relatively low thermal expansion (for example, an alloy of F.-N. mixed with C.), and the outer periphery is further covered with an insulator 9 with excellent heat resistance such as ceramic. I tried to cover it. The input end of this silica-based optical fiber 2a opened into the combustion chamber, and the other output end was joined to the multi-component optical fiber 2b via a joining metal body 10. By doing so, the flame light introducing section 3 can be made compact and excellent in heat resistance and airtightness, which will be described below.

Particular attention should be paid to the flame light introduction section 3 of this type of flame light detection device to prevent the pressure inside the combustion chamber from leaking, that is, to ensure high airtightness.
In a spark ignition engine, the combustion rate is 10 to 20 kg/
cm ² , and compression ignition engines have high pressures of about 100 to 150 kg/cm ² . It is also necessary to prevent thermal breakdown in an atmosphere with a sharp temperature gradient between the high temperature atmosphere inside the combustion chamber and the outside air (low temperature). This is because the gas temperature during combustion instantaneously reaches a high temperature of about 2000 to 2500°C. Therefore, it is necessary to use a material with a sufficiently high melting point for the parts that come into contact with the combustion gas.
The melting point of quartz glass is 1,760℃, and that of ceramics is about 2,000℃, but the temperature distribution of conventional general spark plugs is about 500 to 700℃ at the center electrode and 250 to 350℃ at the ground electrode. Therefore, due to its heat capacity and heat dissipation properties, the temperature is below 700℃,
Quartz glass and ceramics can bear well. The reason why I mentioned the spark plug is that it is best to incorporate the flame light introduction part 3 of the flame light detection device into the spark plug and install it in the combustion chamber of the engine because it is the easiest product to manufacture and is desirable from the standpoint of compactness. It is.

First, ensuring airtightness will be explained. Second
4 and 6, the screw casing 1 and the ceramic insulator 9 have some kind of metal (Mn-M.) at the joint A on the outer periphery of the insulator 9. This part is welded (metallized), and this part and the inner circumferential surface of the screw casing 1 are joined by silver brazing. The metal pipe 8 and the insulator 9 are joined by metallizing the joint part B on the inner circumferential surface of the insulator 9, and silver brazing this part to the metal pipe 8. Since it is difficult to directly join the silica-based optical fiber 2a and the metal pipe 8, the joining metal body 10
It was done through. That is, the metal body 10 for bonding and the metal pipe 8 are silver-brazed at the joint portion C shown in the figure, and the multi-component optical fiber 2b provided at the other end of the metal body 10 for bonding is connected to the metal body 10 for bonding as shown in the figure. The joint D is sealed with glass. The rear end 2e of the silica optical fiber 2a is made as large as the outer diameter of the metal pipe 8 to prevent it from coming off in the X direction. By doing so, the space between the combustion chamber and the atmosphere can be sufficiently closed, and high airtightness of the flame light introducing section 3 can be ensured. That is, the gas and combustion pressure flowing between the quartz optical fiber 2a and the metal pipe 8 are cut off at the joints C and D.

Next, heat resistance was to be ensured, and in addition to using heat-resistant materials as described above, we also took measures as described below. A joint A between the screw casing 1 and the insulator 9 and a joint B between the insulator 9 and the metal pipe 8 are formed locally as shown in the figure, and a joint between the casing 1, the insulator 9 and the metal pipe 8 is formed. A slight gap was provided except for joints A and B. As a result, both the axial and radial directions of the respective members become free ends, allowing elongation due to differences in thermal expansion of the respective members to escape.

For compactness, use silica optical fiber 2a.
As shown in FIG. 4, the input end of the quartz-based optical fiber 2a and the multi-component optical fiber are used to make the input end of the quartz-based optical fiber 2a and the multi-component optical fiber sufficiently incident and direct the flame light.
Since it is made to propagate, it is no longer necessary to have a large cross-sectional area unlike conventional quartz glass rods, making it possible to make it more compact. That is, the quartz-based optical fiber 2a has a core 2c and a cladding 2d both made of quartz (however, the cladding 2d has a certain additive added thereto so that the refractive index of the cladding 2d is n ₂ relative to the refractive index n ₁ of the core 2c). (n ₁ > n ₂ ), and the diameter ratio thereof is approximately 9/10. In order to enlarge the field of view, it is desirable to form the input end (opening end) of the silica-based optical fiber 2a on the combustion chamber side with a wide-angle lens with a predetermined radius R as shown in the figure. However, as shown in FIG. 5, various shapes can be arbitrarily selected depending on workability, object to be measured, etc. The shape a in the figure is the easiest to process, and the metal pipe 8 and the quartz optical fiber 2a are cut at the same cross section. Therefore, its field of view is the smallest among those shown in FIG. 5, making it suitable for introducing and propagating localized flame light. In FIG. 1B, the quartz-based optical fiber 2a is slightly protruded from the metal pipe 8, and the end face is cut at a right angle. The field of view is almost the same as a, but if you peel off the protruding portion of the cladding 2d in b and make the cladding 2d and the metal pipe 8 on the same surface as shown in c, the field of view becomes b.
significantly improved compared to that of . The end face of the quartz-based optical fiber 2a is formed into a hemispherical shape in d of the figure, and conical in the shape of e in the same figure.

FIG. 6 shows the condensing state of the light guide 2, and as shown in the same figure, the arrow mark in the figure indicates that the multi-component optical fiber 2b is connected to the multi-component optical fiber 2b between the distance _X1 and _X2 . It has a lens function that focuses the flame light Q. By doing this, the optical fiber outside the screw casing at the rear end of the multi-component optical fiber _2b can be converted into a general communication optical fiber cable 4a, as shown in FIG.
(φ50 to φ125μm) can be used, and this optical fiber cable 4a transmits strong flame light,
A flame light detection device for detecting the flame light can be constructed. In other words, as shown in FIG. 1, the optical fiber cable 4a performs photoelectric conversion in a location separated from the harsh electrical, thermal, and mechanical environment around the combustion chamber, but in the case of an internal combustion engine, Combustion flame light from one representative cylinder or each cylinder is transmitted through optical fibers 4b, 4c, 4d, 4 of optical fiber cable 4a.
The light is collected into a bundle at e, and converted into an electric quantity by a photoelectric conversion element 5a (for example, a phototransistor, a photodiode, or a PIN photodiode) connected to this end. The output signal of the photoelectric conversion element 5a is sent to the signal processing circuit 5b, where necessary signal processing is performed and the target detection parameter is output. Therefore, by configuring the flame light detection device in this way, it is possible to not only obtain the flame light introduction section 3 which is compact and has improved heat resistance and airtightness as described above, but also solves the problem in spark ignition engines. It is possible to detect flame signals that are free from the effects of electromagnetic noise, mechanical vibration noise, etc. that occur in general internal combustion engines.

Other embodiments of the invention are shown in FIGS. 7-9. In this embodiment, the flame light detection device is attached to the band fiber 4 on the external optical fiber 4 of the screw casing.
It was constructed using f. By doing so, it becomes possible to couple with a plurality of photoelectric conversion elements 5a ₁ and 5a ₂ , and it is possible to detect a plurality of pieces of information simultaneously compared to the case described above. i.e. core 2
A multi-component optical fiber 2b' having a cladding 2d' and a cladding 2d' is arranged so that the parallel light of the flame light Q incident on _X1 becomes parallel light even when exiting at _X2 , as indicated by the arrow in the figure. The rear end of the multi-component optical fiber 2b' having such a function is constituted by a bundle fiber 4f. In the bundle fiber 4f, a large number of optical fibers 4g are bundled and housed inside the jacket 11. This bundle fiber 4f
is connected to the multi-component optical fiber 2b' via a connector 7a provided in the flame light introducing section 3. Then, the bundled optical fibers 4g of the bundle fiber 4f are twisted several by one to form a branch part 12,
By combining the branched optical fibers with a plurality of photoelectric conversion elements 5a ₁ and 5a ₂ having different detection characteristics,
Multiple pieces of information can be detected simultaneously. In this case, the flame light detection section 6 is configured to perform photoelectric conversion at a position away from the combustion chamber, as in the case described above. Further, as in the case described above, the optical fiber cables of each cylinder can be guided to the respective photoelectric conversion elements 5a ₁ and 5a ₂ for signal processing.

A further embodiment of the invention is shown in FIGS. 10 and 11. In this embodiment, the flame light introduction section 3a of the flame light detection device is integrated with the spark plug. By doing this, the flame light introducing section 3
a is formed integrally with the spark plug, making it easier to attach the flame light introducing portion 3a to the combustion chamber than in the case described above. The basic configuration of the flame light introduction section 3a in this case is almost the same as that described above. In other words, silica-based optical fiber 2
A multi-component optical fiber 2b is joined to the output end of the quartz optical fiber 2b via a joining metal body 10, and the input end of the silica optical fiber 2a is made to protrude toward the combustion chamber.
A metal pipe provided around the outer periphery of the quartz-based optical fiber 2a is used as the center electrode 8a, and a screw casing is used as the ground electrode 13. Therefore, in order to position the ground electrode 13 part and the center electrode 8a part with a predetermined gap, the electrode part P at the tip of the ground electrode 13 is bent toward the center electrode 8a side as shown in the figure. The ground electrode 13, the center electrode 8a, and the quartz optical fiber 2a, which are screw casings, are constructed using a heat-resistant ceramic insulator 9 (preferably having properties similar to those of a spark plug insulator) with excellent electrical insulation properties. The insulator 9, the ground electrode 13, the center electrode 8a, and the silica optical fiber 2a were bonded in the same manner as described above. That is, the insulator 9 and the ground electrode 13 are metallized and silver soldered at the joint E, the center electrode 8a and the insulator 9 are metalized and silver soldered at the joint F, and the quartz-based optical fiber 2a and the center electrode 8a are is silver soldered at the joint G at one end of the metal body 10 for joining, and the multi-component optical fiber 2b and the other end of the metal body 10 for joining are bonded by glass sealing at the joint H. . The multi-component optical fiber 2b penetrates through the auxiliary insulator 9a made of heat-resistant ceramics, and an optical fiber connector 7b is provided at its end. The auxiliary insulator 9a and the insulator 9 were metalized at the joint I and then silver-brazed.

By doing so, the space between the combustion chamber and the atmosphere can be sufficiently closed as in the case described above, and high airtightness of the flame light introducing section 3a can be ensured. Further, an electrical signal from the power distributor is guided from a high voltage terminal 14 formed protruding from a part of the insulator 9 to the joining metal body 10 via a leaf spring 15, and further to the center electrode 8a. As is well known, optical fibers such as the quartz optical fiber 2a and the multi-component optical fiber 2b have excellent electrical insulation properties, so even if they are in close proximity to a conductive path with a high voltage of several tens of kV. Not affected by any electrical influence. Furthermore, the flame light detecting section provided in connection with this flame light introducing section 3a may be selected from any of the above-mentioned ones.

As the electrode portion P of the spark plug, in addition to the shapes shown in the figure, various shapes can be selected as shown in FIGS. 11a, b, and c. In the figure a, the ground electrode 13 is extended to the tip of the center electrode 8a to form an electrode part P, and the spark discharge between the center electrode 8a and the ground electrode 13 always attaches to the input end of the silica optical fiber 2a. The cleaning effect is promoted by burning the dust. Figure b shows the ground electrode 1 relative to the center electrode 8a.
A plurality of electrodes 3 are installed to form the electrode portion P, thereby avoiding the directionality of spark discharge. Figure c considers the position function of the center electrode 8a and the ground electrode 13, incorporates the advantages of Figures a and b, and simultaneously achieves the cleaning effect of firework discharge and avoids the directionality caused by the plurality of ground electrodes 13. It is something. By forming these electrode portions P as shown in a and c in the figure, it is possible to eliminate the problem of damage to the quartz-based optical fiber 2a during engine installation work. This is because, as is clear from the figure, the silica optical fiber 2a is covered with the ground electrode 13.

FIG. 12 shows yet another embodiment of the invention. In this embodiment, a flame light introduction section 3b of a flame light detection device is integrated into a commercially available general spark plug. By doing this, the flame light introducing section 3
b is formed integrally with a commercially available spark plug, making it easier to attach the flame light introducing portion 3b to the combustion chamber than in the case described above. That is, although the flame light introduction part 3b is configured with the threaded casing 16 of the spark plug as a threaded casing, the metal pipe 8 of the quartz optical fiber 2a inserted into the J part and the threaded casing 16 are joined by silver brazing or the like. . The input side of the silica-based optical fiber 2a is made to protrude toward the combustion chamber, and the other end, the output end K, has a stepped shape as shown in the figure to prevent it from coming off in the X direction in the figure. . That is, this output end K is processed so that it is perpendicular to the Y direction indicated by the arrow in the figure, and the first multi-component optical fiber 2b ₁ (a silica optical fiber may be used) is inserted and connected here. . The flame light incident on this first multi-component optical fiber _2b1 is transmitted as parallel light. Next, a second multi-component optical fiber 2b ₂ is connected to the first multi-component optical fiber 2b ₁ .
is constructed as a lens having a light condensing function, and the output end 17 condenses the light to about φ50 to φ200 μm. A common optical fiber 18 used for communication, having a core diameter of about 50 to 200 μm, was connected to the output end 17 to form the flame light introduction section 3b. An optical fiber cable 4a having a connector 19 connected to the optical fiber 18 is connected to the screw casing 16 via a cushioning material 20 such as rubber. In this case, the silica optical fiber 2
Gas and pressure leakage from the space between the first multi-component optical fiber 2b1 and the screw casing 16 can be easily prevented by glass-sealing the joint L between the first multi-component optical fiber _2b1 and the screw casing 16. , the airtightness of the flame light introducing section 3b can be maintained.

〔Effect of the invention〕

As described above, the present invention provides a flame light detection device having a flame light introduction part which is compact and has improved heat resistance and airtightness. can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view of the essential parts of an embodiment of the flame light detection device of the present invention, FIG. 2 is a longitudinal sectional side view of the flame light introducing section of the embodiment, and FIG.
P. Arrow view, FIG.
Figures a, b, c, d, and e are longitudinal cross-sectional side views showing different shapes of the input end of a silica-based optical fiber according to an embodiment, and Figure 6 is a state of convergence by a multi-component optical fiber according to an embodiment. FIG. 7 is a longitudinal cross-sectional side view of the main part of another embodiment of the flame light detection device of the present invention, and FIG. FIG. 9 is a sectional view of the handle fiber of another embodiment, and FIG. 10 is a longitudinal sectional side view of the flame light introduction part of still another embodiment of the flame light detection device of the present invention. Figures a, b, and c are longitudinal sectional side views showing different configurations of the electrode portions of the center electrode and the ground electrode in still another embodiment, and Fig. 12 is still another embodiment of the flame light detection device of the present invention. FIG. 1... Screw casing, 2... Light guide, 2a...
...silica-based optical fiber, 2b, 2b'...multi-component optical fiber, 2b ₁ ...first multi-component optical fiber,
2b ₂ ... second multi-component optical fiber, 2c, 2
c'... Core, 2d, 2d'... Clad, 3, 3
a, 3b... Flame light introduction part, 4... Screw casing external optical fiber, 4a... Optical fiber cable,
4b, 4c, 4d, 4e...optical fiber, 4f...
...Bundle fiber, 4g...Optical fiber, 5
...Photoelectric conversion section, 5a, 5a ₁ , 5a ₂ ... Photoelectric conversion element, 5b ... Signal processing circuit, 6 ... Flame light detection section, 7, 7a, 7b ... Connection connector, 8 ... Metal pipe, 8a...Center electrode (metal pipe), 9
...Insulator, 9a...Auxiliary insulator, 10...Metal body for joining, 11...Outer cover, 13...Ground electrode (screw casing), 14...High voltage terminal, 16...Screw casing, 18... ...Optical fiber, 20...Cushioning material.

Claims (1)

[Scope of Claims] 1. A device for detecting combustion flame light in a combustion chamber, comprising a screw casing and a flame light introduction part disposed in the screw casing and having at least one light guide for incident and propagating the flame light. , a flame light having a screw casing external optical fiber connected to the light guide and disposed outside the screw casing, and a photoelectric conversion unit connected to the optical fiber and photoelectrically converting the incident and propagated flame light. and a detection unit, the outer periphery of the light guide is covered with a metal pipe with a predetermined distance therebetween,
The core and cladding are formed of a quartz-based optical fiber made of quartz, and a multi-component optical fiber connected to the output end of the silica-based optical fiber, and between the metal pipe and the threaded casing, a A heat-resistant insulator having a predetermined distance between the quartz-based optical fiber and the multi-component optical fiber on the output end side is provided with a heat-resistant insulator, and a bonding metal body is provided around the output end of the silica-based optical fiber and the multi-component optical fiber on the output end side via a predetermined distance. The threaded casing and the insulator, the insulator and the metal pipe, and the metal pipe and the joining metal body are each bonded with a predetermined width, and the multi-component optical fiber and the joining metal body are sealed. A flame light detection device characterized in that the input end of the silica-based optical fiber has a protruding portion, and the input end protrudes from the screw casing toward the combustion chamber. 2. The flame light detection device according to claim 1, wherein the flame light introducing section is configured to have the function of a spark plug with the metal pipe as a center electrode and the screw casing as a ground electrode. . 3. The flame light detection device according to claim 1, wherein the threaded casing is formed of a threaded casing of a general spark plug. 4. The flame light detection device according to claim 1, wherein the screw casing external optical fiber is formed of an optical fiber cable or a bundle fiber.