JPS6058531A - Apparatus for detecting smoke density in exhaust air - Google Patents

Abstract

PURPOSE:To prevent the decrease in accuracy of detection due to contamination, by constituting a light receiving device, wherein a ceramics sintered body forms a light source, and a light sensitive element, a protecting film that is provided in front of the light sensitive element, and a heater that heats th protective plate are provided. CONSTITUTION:A light source 4 is provided in a light emitting device 4 and emits light. A heating resistor 6 is conducted so that the temperature in the vicinity of the resistor becomes 900 deg.C or more. The light emitted from the light source 4 is projected from a window 9 and transmitted through exhaust air. Then the light is transmitted through a protective plate 25 of a light receiveing device and projected on a light sensitive element 17. The smoke density in the exhaust air is obtained by detecting the transmittance of the light, which is projected on the light sensitive element 17. A ceramic sintered body having the heating resistor is used as the light source. Therefore, the light source itself has a high temperature. Even though smoke is attached, it is immediately oxidized and disappears. Since the protective plate 25 is provided in front of the light sensitive element 17, the light sensitive element 17 is not contaminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust smoke concentration detection device that optically detects particulate carbon (hereinafter referred to as "smoke") remaining in the exhaust gas of an internal combustion engine.

Conventionally, various methods for detecting the smoke concentration in exhaust gas have been known, such as optical, filter paper adsorption, and resistance methods, but the optical method is being studied most actively because of its good responsiveness. However, all conventional optical detection devices have the disadvantage that light sources such as lamps, light emitting diodes, and transistors, as well as photosensitive elements such as diodes and transistors, are contaminated by exhaust gas. Contaminants had to be removed periodically.

Possible ways to remove contaminants include brushing them off or blowing them with clean air, but they cannot be expected to be completely removed without damaging the equipment, and the overall size of the equipment has increased due to recent miniaturization. Does not follow the trend of weight reduction.

The present invention was made to overcome the drawbacks of Kogyoku.
The gist is a light-emitting device whose light source is a ceramic sintered body provided with a heating resistor inside or on its surface, a photosensitive element that is sensitive to the light emitted from the light-emitting device,
Smoke concentration in exhaust gas comprising a protective plate made of quartz glass or transparent alumina provided in front of the photosensitive element toward the light emitting device, and a light receiving device equipped with a heater for heating the protective plate. It exists in the detection device.

This will be explained below based on the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the detection device of the present invention. A light emitting device 2 and a light receiving device 3 are attached to an exhaust pipe 1 of a diesel engine.

The smoke concentration is determined by detecting the change in light transmittance when the light emitted from the light emitting device 2 passes through the smoke-containing exhaust gas and is irradiated toward the light receiving device 3 (in the direction marked in the figure) using the light receiving device 3. You will be rewarded by doing so. The internal structure of the light emitting device 2 is shown in FIGS. 2 and 3. FIG. 2 is a partially cutaway sectional view of a light source fixed inside the light emitting device 2. FIG. 4 is a light source, and a heating resistor 6 is formed in a meandering shape at one end of the outer surface of a hollow cylinder 5 made of heat-resistant insulating ceramic such as alumina or silicon nitride, and is connected to terminals 7a and 7b at the other end. . In order to prevent the heating resistor 6 on the outer surface of the hollow cylinder 5 from being contaminated by exhaust gas, a covering plate 8 made of the same material as that of the hollow cylinder 5 is provided.
covered with. FIG. 3 is a vertical sectional view of the main part of the light emitting device 2. FIG. The light source 4 shown in FIG. 2 is inserted into a hollow fully curved boulder 10 having a window 9 on the side surface and fixed with a heat-resistant inorganic adhesive 11. Terminals 7a and 7b of the light source 4 are connected to insulated lead wires 12. ．． The other ends of the insulated lead wires 12 and 13 pass through a heat-resistant rubber plug 14 inserted near the opening of the holder 10, and are connected to a power source (not shown). A flange 16 having screw holes 15a and 15b is welded or brazed to the boulder 10 for attachment to an exhaust pipe.

Next, the internal structure of the light receiving device 3 is shown in FIGS. 4 and 5.

Fig. 4 is a vertical sectional view of the main part of the light receiving device 3, and Fig. 5 is Fig. 4V.
It is an enlarged view of the vicinity of the part. It is inserted into a metal tube 19 together with a phototransistor element mounting table 18 . The photosensitive element 17 is connected to a detection circuit (not shown) through a heat-resistant rubber stopper 22 fixed to the tail of the tube 19 through insulated lead wires 20 and 21. The diameter of the inner side 23 of the head end of the tube 19 is increased by cutting, and a ring-shaped banking 24 made of copper or aluminum, a disk-shaped protection plate 25 made of quartz glass or transparent alumina, a ring-shaped heater 26, and copper or aluminum are installed in this part. After sequentially loading the ring-shaped bankings 27, the four types of loading parts are fixed by caulking and reducing the diameter of the tip 28 of the tube I9. The heater 26 is connected to a power source (not shown) via sheathed wires 29 and 30. Tube 19 also has flange 1
A flange 32 having screw holes 31a and 31b is welded or brazed for the same purpose as 6.

Next, the functions of the detection device of the present invention shown in the above embodiments will be explained.

First, the light source 4 provided in the light emitting device 2 is energized to emit light so that the temperature near the heating resistor 6 becomes 900° C. or higher. The light emitted by the light source 4 exits through the window 9, passes through the exhaust air, and then passes through the protection plate 25 of the light receiving device, and then is irradiated onto the photosensitive element 17. As described above, the smoke concentration in the exhaust gas can be determined by detecting the change in the transmittance of the light irradiated onto the photosensitive element 17. If a light emitting device and a light receiving device are used while being directly exposed to exhaust gas, there is a risk that the light source and photosensitive element will be contaminated by the exhaust gas, but in the present invention, a ceramic sintered body having a heating resistor is used as the light source. Since the light source itself is at a high temperature during use, even if smoke adheres to it, it oxidizes and disappears immediately, so there is no need to worry about contaminating the light source.

In addition, since the protective plate 25 is installed in front of the photosensitive element 17, there is no fear that the photosensitive element 17 will be contaminated. If electricity is applied so that the temperature of the protective plate 25 is 500° C. or more, smoke adhering to the protective plate 25 can be oxidized, so that the protective plate 25 will not be contaminated. However, if the temperature of the protection plate 25 exceeds 600°C, it will emit light from itself and cause the detection circuit to malfunction, so the temperature of the protection plate 25 must be maintained at 500 to 600°C. The heater 26 that heats the protection plate 25 is preferably a ceramic heater, but the present invention is not limited to this. For example, platinum paste may be applied directly to the protection plate 25 and then energized and used as a heater. In short, it is sufficient if the temperature of the belly retaining plate 25 can be maintained within the above range.

Since the detection device of the present invention uses a ceramic sintered body having a heating resistor as a light source, it has various advantages such as the above-mentioned accuracy is stable. Regarding power consumption, about 10 W is sufficient to heat the length of the tip 811 of the light source made of a 2Φ×701 alumina sintered body to 900° C., for example.

In the above embodiment, the light source and the photosensitive element are installed on the same optical axis, and the light emitted from the light source is transmitted to the exhaust gas, and then the transmittance is measured. However, how to use the detection device of the present invention The method is not limited to this, but it can also be used in a method in which a photosensitive element is installed offset from the optical axis to detect light scattered by smoke in the exhaust gas, and the smoke concentration is determined from the amount of the scattered light. .

As described above, the exhaust smoke concentration detection device of the present invention is useful for accurately detecting smoke concentration over a long period of time with low power.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of the exhaust smoke concentration detection device of the present invention, FIG. 2 is a partially cutaway cross-sectional view of a light source fixed inside the light emitting device in the detection device, 3 is a cross-sectional view of the main part of the light emitting device in the above-mentioned detection device, FIG. 4 is a longitudinal cross-sectional view of the main part of the light-receiving device in the above-mentioned detection device, and FIG.
It is an enlarged view of the vicinity of section V in the figure.

Claims (1)

[Claims] A light emitting device whose light source is a ceramic sintered body having a heating resistor provided inside or on the surface thereof, a photosensitive element sensitive to the light emitted from the light emitting device, and a photosensitive element in front of the photosensitive element facing the light emitting device. A smoke concentration detection device in exhaust gas, comprising a protective plate made of quartz glass or transparent alumina, and a light receiving device equipped with a heater for heating the protective plate.