JPH04242155A - Liquid mixing-ratio sensor - Google Patents

Abstract

PURPOSE:To keep the accurate relative positions of a prism, a light emitting element and a photodetector and to improve detecting accuracy by fusing and bonding glass prism to the tip of a tubular main-body metal fitting, and coupling and fixing an element holder made of ceramic in the inside. CONSTITUTION:A prism 4 comprises cylindrical block-shaped optical glass. A ring-shaped fusing glass is fused and bonded to a prism fusing and bonding wall 36 and fixed to a main-body metal fitting 3. The fuse bonding utilizes the difference between the melting point of the glass 41 and the melting point of the optical glass. The glass 41 becomes the fixing means as well as the gap sealing means between the metal fitting 3 and the prism 4. An element holder 5 comprises an assembly of front and rear holders 6 and 7. The front holder is made of ceramic whose main component is alumina. The element holder 5 is fitted into the metal fitting 3 and held and fixed between a caulking part 38 and a step 37. The difference in thermal expansions of the glass and ceramic is small at temperatures in use. The relative positions of the prism, the light emitting element and the photodetector are accurately maintained. Thus, the detection accuracy becomes high.

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, which is a mixture of two or more translucent liquids, using the difference in the refractive index of light. In particular, the present invention relates to the structure of a liquid (fuel) mixture ratio sensor suitable for installation in an engine that uses a mixed fuel of gasoline and alcohol.

0002

[Prior Art] As a mixture ratio sensor for liquid fuel, etc., a glass (prism) whose surface is partially in contact with a liquid to be measured is used, and light emitted by a light emitting element placed near the glass (prism) is emitted from a surface other than the surface of the glass (prism). A system has been developed in which the light enters from the surface, is reflected by the partial surface (reflective surface), is received by a light receiving element placed opposite to the light emitting element, and the mixing ratio of gasoline and alcohol is detected based on the amount of light. ing.

In this mixture ratio sensor for liquid such as fuel, the relative positions of the prism, light emitting element, and light receiving element are as follows:
It is required to be accurately maintained for a long period of time without being affected by the operating temperature. Also, since gasoline and alcohol are highly flammable and highly soluble liquids, it is necessary to ensure a secure seal, and it is inappropriate to use materials that are easily corroded, such as plastic or rubber, if they are in constant contact. It is.

0004

SUMMARY OF THE INVENTION An object of the present invention is to provide a mixture ratio sensor in which the relative positions of the prism and element change little due to operating temperature and can always maintain accurate detection accuracy. Another object of the invention as set forth in claim 2 is to provide a liquid mixture ratio sensor with improved sealing performance and high safety. Another object of the invention as set forth in claim 3 is to provide a liquid mixture ratio sensor having the configuration as set forth in claim 2, which can prevent the connection portion of the lead pin from peeling off.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the liquid mixture ratio sensor of the present invention includes a prism having a reflective surface in contact with a liquid to be measured in which two or more types of translucent liquids are mixed; In an optical liquid mixture ratio sensor that combines a light-emitting element that irradiates light to the surface and a light-receiving element that detects light reflected by a prism, a glass prism is fitted into the tip of a cylindrical main metal part, and a glass prism is fitted into the fused glass. A configuration was adopted in which a ceramic element holder holding the light-emitting element and the light-receiving element was fitted into the main metal fitting to fix the light-emitting element and the light-receiving element. To achieve other purposes,
The element holder consists of a front holder and a rear holder that are divided into two parts, the front holder being cylindrical and containing the prism, and a light emitting element substrate and a light receiving element substrate facing each other and fixed to the inner wall thereof. The rear holder has a disk shape, and is provided with a lid on the front holder, and has a small through hole that serves as an outlet for taking out the lead pins of the board, and the inner wall of the small hole is metallized and sealed with a brazing material. We adopted a configuration in which In order to achieve another objective, a structure in which a curved portion of the lead pin is provided between the substrate and the through hole is adopted.

[0006]

[Example] Figures 1 to 3 show one example of a liquid mixture ratio sensor.
A gasoline-alcohol mixed fuel mixture ratio detection device 100 is shown as an example, and is installed in a fuel supply path 200 of an engine through which the mixed fuel flows to detect the fuel mixture ratio.

This mixture ratio detection device 100 includes a fuel mixture ratio sensor 1 serving as a sensor unit, and a bottomed cylindrical sensor body 300 whose upper surface serves as an installation chamber 301 for a sensor circuit board. and sensor unit 1
The measurement chamber housing 2 into which the tip end of the measurement chamber is fitted and which forms a measurement chamber for the liquid to be measured is integrally molded by injection molding. In addition, the sensor body 300 has
Fuel pipes 201, 20 brazed to housing 2
2 are molded at the same time.

The sensor unit 1 includes a cylindrical metal shell 3 whose tip (lower part in the figure) is fitted into the rear part (upper part in the figure) of the housing 2, and a cylindrical metal shell 3 that is fused to the tip (lower end in the figure) of the metal shell 3. It consists of a prism 4 fused with a bonded glass 41 and a ceramic element holder 5 that 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 bottom 21 whose outer surface bulges forward in a truncated conical shape, and a cylindrical body 22. A fuel inlet 2 is provided at the front end of the body 22.
3 and the outlet 24 are opened, and the fuel pipe 201,
202. Moreover, the inside is a measurement chamber C, into which a mixed fuel of gasoline and alcohol flows in through the inlet 23 and flows out through the outlet 24 .

The main metal fitting 3 is made of a 50% Ni-Fe alloy, and has a small diameter tip portion 3 having a tip wall 31 serving as an inner edge.
2 and a large-diameter rear portion 34 with a thin rear end portion 33, and a flange 35 is provided protruding from the outer periphery of the intermediate portion. The inner peripheral wall of the tip wall 31 is a prism fused wall 36, and when the tip 32 is fitted into the housing 2, the tip surface faces the measurement chamber C, and the rear part 34 protrudes to the rear of the housing 2. , the flange 35 is connected to the body 22 of the housing.
It comes into contact with the rear end surface of. The inner periphery is formed with a small diameter at the tip and a large diameter at the rear, with the step 37 as a boundary.

In this embodiment, the prism 4 is made of optical glass in the form of a cylindrical block, and the prism fusion wall 3
6 is fused to an annular fused glass 41 and fixed to the metal shell 3. This fusing is performed by utilizing the difference in melting point between the fusing glass and the optical glass, and the fusing glass 41 serves as a fixing means and also as a means for sealing the gap between the metal shell and the prism. With this configuration, the prism 4 is located at the tip 32 of the metal shell, and an annular space 43 is formed between the inner circumferential wall of the tip 32 and the outer circumferential wall of the prism.

In this embodiment, the element holder 5 has two
It consists of an assembly of a divided front holder 6 and rear holder 7. The front holder 6 is made of ceramic mainly made of alumina, has a cylindrical shape, and has a cylindrical portion 61 inserted into the annular space 43, and extends outward from its rear end to come into contact with the step 37 of the metal shell. It has a flange portion 62 that is shaped like a flange. In the inner wall of the cylindrical portion 61, I-shaped grooves 63 and 64, which have an I-shaped cross section and extend in the axial direction and in the direction in contact with the cylindrical surface, are provided in parallel and opposite to each other.

The rear holder 7 is made of ceramic mainly made of alumina and has a disc shape, and has a recess 71 on the front surface.
An O-ring groove 72 is formed on the outer periphery of the tip, and a step 73 is provided on the outer periphery of the rear end. A predetermined number of small through holes 74 are drilled in the board surface at positions corresponding to the I-shaped grooves 63 and 64, and serve as openings for lead pins. The inner wall of each small hole 74 is metallized 75.

A light emitting element and a light receiving element 51, 52 are fixed to the I-shaped grooves 63, 64, respectively, and ceramic strip-shaped element substrates 53, 54 on which leads of these elements are printed are fitted. ing. The tips of lead pins 55 are brazed to the rear ends of these element substrates 53 and 54, respectively. The lead pin 55 is curved in a U-shape within the recess 71, and the rear portion is formed into the small hole 7.
4 is inserted and taken out to the outside. The small hole 74 is filled with a metal brazing material 56 such as solder or copper solder to fuse the metallization 75 and the lead pin, and to seal the small hole 74 for taking out the lead pin. The curved portion of the lead pin 55 has the function of preventing excessive thermal stress from being generated in the soldered portions of the element substrates 53 and 54 due to the difference in thermal expansion that occurs during this fusion bonding or insert molding.

This element holder 5 is fitted into the metal shell 3 in the assembled state, and is held between the caulking portion 38 and the step 37 by caulking the rear end portion 33 of the metal shell inward. and fixed inside the metal shell 3. Also, a buffer material 39 made of an O-ring with a metal ring is interposed between the step 73 of the upper holder and the caulking part 38, to cushion the impact during caulking and to reduce the difference in thermal expansion during use. Absorption is performed.

An O-ring 8 is attached to the O-ring groove 72, and together with the metal brazing material 56 filled in the small hole 74, cracks occur in the fused glass 41 or the prism 4, and the primary seal is destroyed. When this happens, it acts as a secondary seal to prevent the mixed fuel from leaking between the metal shell and the holder.

The prism may be a prism, a hemisphere, or the like, and the element holder 5 may be integrated instead of being divided into two parts. Also,
As a means for fixing the element holder into the metal shell, other than caulking the ends of the metal shell described above, various other fixing methods such as fastening, fusing, adhesion, etc. can be employed.

[0018]

[Effects of the Invention] In the liquid mixture ratio sensor of the present invention, a glass prism is fused to the tip of a cylindrical metal shell, and a ceramic element holder is fitted and fixed therein. Glass and ceramic have a small difference in thermal expansion in the radial and axial directions when the operating temperature changes (usually about -20 degrees to +100 degrees), and the relative positions of the prism, light emitting element, and light receiving element can be maintained accurately for a long period of time. Ru. This makes the detection accuracy accurate. In addition, the small through hole for taking out the lead pin of the element holder is sealed with a metal brazing material to provide a secondary seal, so there is high safety against leakage of the liquid to be measured such as fuel. Furthermore, since the lead pin has a curved part, brazing,
It absorbs the difference in expansion between parts caused by heat such as injection molding, and prevents lead pins from peeling off.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a fuel mixture ratio sensor.

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

FIG. 3 is an assembled perspective view of the ceramic element holder.

[Explanation of symbols]

1 Sensor unit (fuel mixture ratio sensor) 2 Housing 3 Metal shell 4 Prism 5 Ceramic element holder 6 Front holder 7 Rear holder 41 Fusing glass 55 Lead pin 56 Brazing material 74 Small through hole 75 Metallization

Claims (3)

[Claims] 1. A prism having a reflective surface in contact with a liquid to be measured in which two or more types of translucent liquids are mixed, a light emitting element that irradiates light to the prism, and a light receiving element that detects light reflected by the prism. In the optical liquid mixture ratio sensor, a glass prism is fitted into the tip of a cylindrical metal shell, and the gap is sealed by fusing glass, and the light emitting element is placed inside the metal shell. and a liquid mixture ratio sensor in which a ceramic element holder holding a light receiving element is fitted and fixed. 2. In claim 1, the ceramic element holder consists of a front holder and a rear holder that are divided into two parts at the front and rear, the front holder being cylindrical and containing the prism, and having a light-emitting device on the inner wall. The element substrate and the light-receiving element substrate are fixed to face each other, the rear holder has a disk shape, a lid is provided on the front holder, and a small through hole is drilled to serve as an outlet for the lead pin of the substrate, and the inner wall of the small hole is provided with a lid. is a liquid mixture ratio sensor that is metallized and sealed with a metal brazing material. 3. The liquid mixture ratio sensor according to claim 2, wherein the lead pin has a curved portion between the substrate and the through hole.