JPS61167840A - Measuring instrument for smoke density of internal-combustion engine - Google Patents

Abstract

PURPOSE:To reduce the size of a measuring instrument by arranging the front end of an optical fiber for laser light incidence and the front end of an optical fiber for photodetection in parallel at one side of a passage through which exhaust gas is passed and then guiding scattered light obtained at a measurement point through the optical fiber for photodetection. CONSTITUTION:The front end part 2a of the optical fiber 2 for laser light incidence and the front end part 3a of the optical fiber 3 for photodetection are arranged in a measuring instrument body 1 closely in parallel; and the other end of the optical fiber 2 extends from the main body 1 and is connected to a laser light source and laser light incident from the front end part 2a is focused on the measurement point P through a convex lens 5 and a prism 6. Then, light scattered when graphite particles in the exhaust gas flow at the measurement point P is converged on the pinhole of a pinhole shield plate 17 through the window 14 of the main body 1, an interference filter 15, and a convex lens 16 and only the scattered light from the measurement point P is passed and guided to the optical fiber 3 through a convex lens 18. The photodetected laser light is guided to a photodetector through the optical fiber 3 and a signal from the photodetector is processed by a smoothing circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a smoke concentration measuring device that optically detects the concentration of smoke emitted from an internal combustion engine such as a diesel engine.

Conventional ■ A variety of devices for optically detecting smoke concentration have been proposed in the past (for example, Japanese Patent Laid-Open No. 53-97886, Japanese Patent Laid-open No. 56-129842), and these conventional smoke concentration measurement devices The method adopted here is to measure the concentration of smoke by guiding light emitted from a light source into a container or passage through which smoke passes and detecting the amount of light absorbed by a light receiver.

According to this method, the light incident side and the light receiving side must be placed at opposite positions across the smoke path, so it is necessary to align the optical axes of both, and the measuring device (light injector) must be placed at opposing positions. There was a problem in that the structure of the mounting portion of both the light receiver and the light receiver became complicated.

In view of these conventional problems, the present invention integrates the light incident side and the light receiving side by arranging them on the same side with respect to the passage of exhaust gas containing smoke. The objective is to miniaturize the smoke concentration measuring device so that it can be incorporated into the device. Also, it should not protrude into the exhaust gas passage and be less likely to be contaminated by exhaust gas.

. In order to solve these problems, in the present invention, an example of a passage through which exhaust gas from an internal combustion engine passes is provided with a tip of an optical fiber for introducing laser light and a tip of an optical fiber for light reception. are arranged in parallel and close to each other, and means for condensing the laser beam irradiated from the tip of the introducing optical fiber onto a measurement point on the optical axis of the tip of the light receiving optical fiber and within the exhaust gas passage. There is provided a smoke concentration measuring device for an internal combustion engine, which is configured to guide the scattered light at the measurement point to a photodetector through the light receiving optical fiber.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the distal end 2a of the laser beam introducing optical fiber 2 and the distal end 3a of the light receiving optical fiber 3 are installed in the measuring instrument main body l so that they are located parallel to each other and close to each other. .

The other end of the introduction optical fiber 2 is as shown in FIG.
It extends from the measuring instrument main body 1 and is connected to a laser light source 4, and the laser light that has passed through the optical fiber 2 is made to enter from the tip 2a located inside the main body 1. There is a convex lens 5 in front of the tip 2a, and further in front of the convex lens 5, a wedge prism 6 is arranged at the front end of the main body l. Therefore, the laser light incident from the tip 2a of the optical fiber 2 is focused by the convex lens 5 and refracted slightly toward the light receiving fiber 3 by the prism 6, thereby converging the fish at the measurement point P.

In FIG. 2, exhaust gas discharged after combustion in an internal combustion engine 10 flows from an exhaust manifold 11 through an exhaust pipe 12, and the measuring instrument body 1 is attached to the wall of this exhaust pipe 12, and there are no measuring points. P is located within the exhaust pipe 12.

Further, the second measurement point P is located on the optical axis of the light-receiving fiber 3, as shown in FIG. In the illustrated embodiment, the measurement point P is located on an extension of the center line of the tip 3a of the light-receiving optical fiber 3.

Therefore, the light scattered when the black smoke particles in the exhaust gas pass through the measurement point P passes through the window 14 at the tip of the measuring instrument body 1 and the interference filter 15 that transmits only the wavelength of the incident laser light, and passes through the convex lens 16. The light is focused onto the pinhole of the pinhole shielding plate 17, and this pinhole allows only the scattered light from the measurement point P to pass through, and the parallel light is converted by the convex lens 18 and guided to the light receiving optical fiber 3, where the light is received. The laser beam is guided to a photodetector 19 through this light-receiving optical fiber 3, and a signal from this photodetector 19 is processed by a smoothing circuit 20.

The amount of black smoke particles passing through a measurement point P at a predetermined position in the exhaust pipe 12, that is, the count of scattered light.

The value is correlated with the black smoke concentration of the exhaust gas, and therefore an accurate black smoke concentration can be determined.

In the above embodiment, the prism 6 was placed on the side of the incident system, and the measurement point P was set on the extension of the center line of the tip 3a of the light receiving fiber 3. It is also possible to provide the measurement point on the center line extension of the tip 2a of the fiber 2 for introducing laser light. Furthermore, by appropriately combining optical means such as prisms and lenses, the measurement point can be set at any position.

■According to the present invention, since the optical devices of the incident system and the detection system can be integrated, once the optical adjustment is performed, there will be no errors due to subsequent installation and removal, making it easy to handle. It can be made smaller and can be installed in any position. Furthermore, since the measuring point can be set at a desired position within the exhaust pipe and the measuring instrument does not need to protrude into the exhaust pipe, the measuring instrument can be prevented from becoming contaminated by exhaust gas.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the main parts of a smoke concentration measuring device for an internal combustion engine according to the present invention, and FIG. 2 is a schematic diagram showing the entirety of the device according to the present invention. 1... Measuring instrument body, 2... Optical fiber for introducing laser light, 3... Optical fiber for receiving light, 5.16.18... Convex lens, 6... Prism, 10... Internal combustion engine, 12 ...Exhaust pipe, 14...Window, 15...Filter, 17...Pinhole plate, 19...Photodetector.

Claims (1)

[Claims] 1. On one side of the passage (12) through which the exhaust gas of the internal combustion engine passes, attach the tip (2a) of the optical fiber (2) for introducing laser light.
) and the tip (3a) of the light-receiving optical fiber (3) are arranged in parallel and close to each other, and the laser beam incident from the introduction optical fiber tip (2a) is transferred to the light from the light-receiving optical fiber tip (3a). An internal combustion engine comprising means for converging light at a measuring point (P) on the shaft and in the exhaust gas passage, and for guiding scattered light at the measuring point to a photodetector (19) through the light-receiving optical fiber. smoke concentration measuring device.