JPH04278443A - Liquid mixing ratio sensor - Google Patents

Abstract

PURPOSE:To obtain the mixing ratio sensor capable of enhancing compensation accuracy and always obtaining high detection accuracy by providing a means capable of selectively supplying only the signal component of the light from a light emitting element and cutting off the incidence of light becoming noise to a monitor. CONSTITUTION:The optical liquid mixing ratio sensor is constituted by combining a prism 4 having a reflecting surface 42 coming into contact with a liquid to be measured, a light emitting element 53 irradiating the prism with light and a measuring photodetector 55 measuring the reflected light from the reflecting surface 42. A compensating photodetector monitoring the quantity of the light emitted from the light emitting element and a cut-off means 8 allowing monitor light to be selectively incident to the compensating photodetector 54 and cutting off the incidence of light other than the monitor light are provided to compensate the measuring photodetector 55.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a liquid mixture ratio sensor that measures the mixture ratio of a liquid to be measured in which two or more types of translucent liquids are mixed, using the difference in the refractive index of light. Especially regarding the improvement of detection accuracy.

0002

[Prior Art] As a liquid mixture ratio sensor, light emitted by a light emitting element placed near the glass (prism) whose surface is partially in contact with the liquid to be measured is incident on a surface other than the surface. A system has been developed in which the light is reflected off a part of the surface, received by a measuring light-receiving element placed opposite the light-emitting element, and the amount of light is used to detect the mixture ratio of a mixed fuel such as gasoline and alcohol. There is.

0003

[Problems to be Solved by the Invention] In this fuel mixture ratio sensor, the amount of light emitted by the light emitting element changes depending on the temperature, and the amount of light emitted decreases as the element deteriorates over time, so it is difficult to maintain detection accuracy. A compensating light receiving element is required to monitor the amount of light emitted from the light emitting element from this viewpoint. However, in addition to the signal component that is the light from the light emitting element to be monitored, this compensating light receiving element also receives the diffusely reflected light as a noise component when, for example, the liquid to be measured undergoes phase separation and diffuse reflection occurs on the reflective surface. incident, making accurate monitoring impossible. An object of the present invention is to selectively supply only the signal component of the light from the light emitting element to the compensation light receiving element, and to provide compensation by providing means for blocking the incidence of light that causes noise on the monitor, such as diffused reflection. An object of the present invention is to provide a liquid mixture ratio sensor that can improve accuracy and always obtain high detection accuracy.

0004

[Means for Solving the Problems] A liquid mixture ratio sensor of the present invention includes a prism having a reflective surface that is in contact with a liquid to be measured, a light emitting element that irradiates light onto the prism, and measures the light reflected by the reflective surface. In an optical liquid mixture ratio sensor that combines a measuring light-receiving element, a compensation light-receiving element is provided to monitor the amount of light emitted by the light-emitting element, and a monitor light is selectively made incident on the compensation light-receiving element, so that the light other than the monitor light is A shielding means for shielding the incident light is provided to compensate for the measurement light receiving element.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show a gasoline-alcohol mixed fuel mixture ratio sensor 100 according to an embodiment of the present invention, which is installed in a fuel supply path 200 of an engine through which the mixed fuel flows, and is installed to detect the fuel mixture ratio. To detect. The sensor 100 has a sensor body 300 made of resin, the upper part of which is an installation chamber for a sensor circuit board, and a sensor unit 1 in which an optical liquid mixture ratio sensor is integrated, and a measurement chamber C for a liquid to be measured. It is integrally molded with a metal housing 2.

The sensor unit 1 includes a cylindrical metal shell 3 and a fused glass 41 at the tip (lower end in the figure) of the metal shell 3.
The cylindrical element holder 5 is fitted into the metal shell 3 and holds a light emitting element and a light receiving element. The housing 2 is made of stainless steel and has a cylindrical shape with a bottom, and has a bottom 21 whose lower surface bulges downward in the shape of a truncated cone, and a cylindrical body 22. The main metal fitting 3 is
It consists of a lower part 32 whose lower end is an inner peripheral edge 31, and an upper part 33 having a large diameter. The inner periphery of the inner peripheral edge 31 is a prism fusion wall 34, and when the lower part 32 is fitted into the body 22, the lower end face faces the measurement chamber C.

The prism 4 is made of cylindrical optical glass,
The outer periphery of the lower end is fused to the prism fusion wall 34 by the annular fused glass 41 and fixed to the metal shell 3. With this configuration, the prism 4 is located at the lower part 32 of the metal shell, and the bottom surface 42 is a reflective surface (42) that contacts the fuel to be measured.
An annular space 43 is formed between the inner circumferential wall of the lower portion 32 and the outer circumferential wall of the prism.

In this embodiment, the element holder 5 has two upper and lower parts.
It consists of a divided lower holder 6 and upper holder 7,
It is integrally fixed within the metal shell by caulking the upper end of the metal shell. The lower holder 6 is connected to the annular space 4
3, and a flange 62 provided at its upper end. The inner circumferential wall of the cylindrical portion 61 has an axially I-shaped groove 63 in cross section for inserting an element substrate to be described later.
64 are formed in parallel to each other. Upper holder 7
has a disc shape with a recess 71 on the lower surface, and the I
A large number of tapered small holes 73 are opened at positions corresponding to the character-shaped grooves 63 and 64, and serve as lead pin extraction ports.

A light-emitting element substrate 51 and a light-receiving element substrate 52 made of ceramic strips are inserted into the I-shaped grooves 63 and 64, respectively. On the surface of the light-emitting element substrate 51, a light-emitting element 53, which is a small-area light source similar to a point light source, is formed at the lower part, a compensation light-receiving element 54 is provided at the upper part, and the leads thereof are printed. On the surface of the light-receiving element substrate 52, a measuring light-receiving element 55 having a vertically long strip shape is formed, and its leads are printed.

The substrates 51 and 52 are attached to the lower holder 6.
The upper holder 7 is sandwiched between the lower end of each I-shaped groove and the recess wall of the upper holder 7 and fixed in the vertical direction. These substrates 51, 5
The upper end of 2 protrudes into the recess 71, and a lead pin 56 is brazed to this portion. Lead pin 56
is inserted through the small hole 73 and taken out at the top,
The recess 71 and the small hole 73 are filled with epoxy resin, and the upper end of the small hole 73 is covered with silicone resin. Between the upper half of the substrate 51 and the prism 4, a metal shielding plate 8 whose one side is a reflective surface 81 is connected to the upper holder 7.
It is attached by screwing to the bottom surface of the.

The side of the cylindrical surface 44 of the prism 4 facing the light emitting element 53 serves as an incident surface 45 for light emitted from the element 53. The light emitting element 53 is installed at the lower end of the prism 4 so that light can efficiently enter the reflective surface 42 from the incident surface 45, and the light that has entered the cylindrical surface 44 has a critical value when the mixed fuel is all gasoline. A reflective surface 42 is formed between the angle and the critical angle when the mixed fuel is all alcohol.
and reaches the measurement light receiving element 55.

In the present invention, a shielding plate 8 is provided as a shielding means for selectively allowing monitor light to enter the compensating light receiving element 54 and blocking light other than the monitor light from entering the light emitting element 54.
The light of No. 3 is reflected by the reflective surface 81 of this shielding plate and is incident on the compensation light receiving element 54. Thereby, the light from the light emitting element 53 can directly enter the compensation light receiving element 54 without passing through the prism 4. The shielding plate 8 also includes a compensation light receiving element 54.
Second, the incidence of light other than the reflected light that is a signal component, such as diffusely reflected light that becomes noise, is blocked.

[0013] Therefore, it is possible to eliminate the influence of tolerances that occur in the manufacture and installation of the prism, making it possible to receive stable light and to perform accurate monitoring (compensation). This accurate compensation ensures that the detection accuracy of the sensor is always kept high. On the other hand, when monitoring with light transmitted through the prism 4, the amount of light incident on the compensation light-receiving element is more likely to vary than when using direct incident light, resulting in lower monitoring accuracy. The reflective surface 81 may be provided on the surface of the prism 4, and the reflective plate may be formed of a material other than metal.

FIG. 3 shows another embodiment. In this embodiment, the compensation light-receiving element 54 is installed on the upper part of the measurement light-receiving element substrate 52, and the upper part of the prism 4 is obliquely truncated.
A shielding plate 9 with transparent holes 91 is attached above the reflecting surface 42 in parallel with the reflecting surface 42. With this configuration, the light from the light emitting element 53 passes through the truncated part and the light transmitting hole 91 to the compensation light receiving element 54.
The same effect as above can be obtained.

In addition to the embodiments described above, the monitor light may be incident on the compensation light receiving element 54 through the prism 4, and the compensation light receiving element may be mounted on a separate substrate.

[0016]

[Effects of the Invention] As explained above, since the mixture ratio sensor of the present invention is provided with a shielding plate that prevents noise light from entering the compensation light receiving element, compensation accuracy can be improved.
This makes it possible to maintain high liquid mixture ratio detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a fuel mixture ratio sensor according to the present invention.

FIG. 2 is an enlarged view of the main part of FIG. 1;

FIG. 3 is a longitudinal sectional view of another embodiment of the fuel mixture ratio sensor according to the present invention.

[Explanation of symbols]

1 Sensor unit 2 Metal housing 3 Cylindrical main metal fitting 4 Prism 5 Cylindrical element holder 8 Shielding plate 9 Shielding plate 42 Reflective surface 45　Incidence plane 53 Light emitting element 54 Compensation light receiving element 55 Light receiving element for measurement

Claims (1)

[Claims] 1. An optical liquid mixing ratio that combines a prism having a reflective surface in contact with a liquid to be measured, a light emitting element that irradiates light to the prism, and a measuring light receiving element that measures the light reflected by the reflective surface. In the sensor, a compensation light-receiving element is provided for monitoring the amount of light emitted by the light-emitting element, and monitor light is selectively made incident on the compensation light-receiving element,
A shielding means is provided to block the incidence of light other than the monitor light,
A liquid mixture ratio sensor that compensates for the measurement light receiving element.