JPH01145550A - Prism for discriminating fluid - Google Patents

Abstract

PURPOSE:To enable the reliable detection of the kind of a fluid with a high signal ratio, by providing the title prism with a plurality of reflecting surfaces and by setting each reflecting surface to form a critical angle substantially for the fluid to be detected. CONSTITUTION:Reflecting surfaces 3, 4, 5 and 6 of a prism 1 are so set as to form critical angles for light oil, gasoline, water and kerosene respectively, and the prism 1 is fitted to the fore end of a nozzle of a lorry and inserted into a tank together with a hose. When a modulated 21 light from a light- emitting element 20 is made to enter the prism 1 through a light-conductive member 11, it is reflected by the reflecting surfaces 3, 4, 5 and 6 and returns to an incidence/emission surface 2 and then enters a light-sensing element 22 through a light-conductive member 12. In the state wherein the prism 1 is immersed in water in the tank, on the occasion, the incident light is transmitted through the reflecting surface 5 by about 90% of the quantity of the incident light, and the element 22 outputs a signal of a level of about 10% of the one of a gas. In this way, a liquid to be discriminated is brought into contact, and the kind of the liquid can be discriminated on the basis of the quantity of the return light being varied in relation to be quantity of the incident light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a prism used in snow making that brings a liquid to be determined into contact with the prism and discriminates the type of liquid based on a change in the amount of reflected light relative to the amount of incident light.

(Prior Art) For example, at a gas station, gasoline, kerosene, and light oil are stored in separate tanks, and when they are depleted, they are replenished using a trowel. During this replenishment, it is necessary to replenish the same type of oil, but there is a possibility that the type of oil may be misjudgedNote.

In order to solve this problem, we used a liquid type discriminator M, which consists of a prism attached to maintain the incident and exit relationship with the light guiding material. I am trying to determine the type of liquid in the tank (
(Japanese Patent Application Laid-Open No. 60-251094). According to this device, it is possible to determine the type of liquid without running the risk of fire, etc., but since it uses the difference in reflectance based on the change in the critical angle on a single liquid contact surface, The approximate reflectance on reflective surfaces below the critical angle is 10% for gasoline, 0.09% for kerosene, and 0 for light oil.
．． 08%) There is a problem in that the change in reflectance between liquid types is small, resulting in detection errors.

(Objective) The present invention has been made in view of the above problems, and its purpose is to provide a fluid discrimination prism that can detect a fluid with a high signal ratio based on the ratio of the amount of reflected light to the amount of incident light. It's about doing.

(Summary of the Invention) That is, the present invention is characterized in that it has a plurality of reflecting surfaces, and each reflecting surface forms approximately a critical angle with respect to each fluid to be detected, and the critical angle of the fluid to be detected is In the following reflection, the change in the amount of returning light is increased by substantially transmitting the light through the structure.

(Example) The details of the present invention will be described below based on illustrated examples.

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 indicates a light receiving section that receives light from a light emitting section via a light guiding material 11 such as an optical fiber, and a light receiving section that receives light via a light guiding material 12. (This is a prism that sends out one person exit surface 2 and four reflection surfaces 3.4
．． 5.6, it is formed into a piece-shaped cross section so that the light 11 incident from the person exit surface 2 is sequentially reflected on each surface and returns to the original person exit surface 2, and the first reflection The surface 3 is arranged at an angle of incidence θ1 having a critical angle for the first fluid, e.g. β2 has a critical angle of incidence θ with respect to the second fluid, for example gasoline, and a third
The reflective surface 5 is the light β3 reflected by the second reflective surface 4 or the third
Roughly speaking, at an incident angle θ3 having a critical angle with respect to a fluid such as water, the fourth reflective surface 6 is such that the light ρ4 reflected by the third reflective surface 5 is transmitted to the fourth fluid, such as water. The angle of incidence is set to θ4, which is a critical angle for kerosene, and the angle of incidence is set so that it returns to the exit surface.

FIG. 2 shows an example of fluid discrimination drawing using the above-mentioned prism, and the reference numeral 20 in the figure indicates the light guide material 1.
This is a light-emitting element that allows light to enter the prism 1 through the prism 1, and emits light at a wavelength that is not easily affected by the surrounding environment, for example, a wavelength in the near-infrared region. It emits light. 22 is a light receiving element that receives the light returned by the prism 1 via the light guiding material 12, and the signal from this is demodulated by the synchronous rectifier circuit 23 which receives the signal from the modulation circuit 2], and then is demodulated by the synchronous rectifier circuit 23 which receives the signal from the modulation circuit 2]. A signal based on a small amount of liquid is amplified until it becomes detectable, and then compared by a comparison circuit 24 having a level determined for each type of fluid.
5, the type of fluid is determined.

In this embodiment, for example, a prism is used in which the critical angle of the reflecting surface 3.4.5.6 of No. 1.2.3.4 is approximately the same angle for light oil, gasoline, water, and kerosene, respectively. (Fig. 3), attach it to the tip of the supply nozzle at the mouth, and insert it into the tank together with the hose.

When the detection device M is operated in this state, the light emitting element 20
Modulator 2] causes the light to flicker at a constant frequency and whose peak value is adjusted to be constant, and enters the prism 1 via the light guide member 11. This light is reflected on the reflective surface 3.4.5.6
The light guide member 12 returns to the person exit surface 2 while being reflected by the light guide member 12.
The light enters the light receiving element 22 via the light receiving element 22 .

At this time, if there is gas such as air or gasoline vapor in the tank, the light incident on the reflective surfaces 3.4.5.6 will have an angle greater than the critical angle, so all the reflective surfaces 3.4.5. 4.
5.6, approximately 100% of the amount of incident light is totally reflected and enters the light receiving element 22. The signal from the light-receiving element 22 is selectively extracted by a synchronous rectifier circuit 23 to only the component synchronized with the driving signal of the light-emitting element 20 and amplified to a predetermined level. The liquid is compared with a reference value for determining the type of liquid present, and since it does not meet any of the reference levels, it is determined that it is a gas.

When there is water in the tank and prism 1 is immersed in water,
Since the first and second reflecting surfaces 3.4 are set at a critical angle with respect to the liquid having a higher refractive index than water, the critical angle is exceeded and the third reflecting surface 3.4 is totally reflected. is incident on the reflective surface 5 of.

On the other hand, since the third reflective surface 5 has a critical angle with respect to water, only about 90% of the light incident on this surface is transmitted, and only about 10% of the remaining light is reflected. is incident on the fourth reflecting surface 6, or since this reflecting surface is set at a critical angle with respect to a liquid with a higher refractive index than water, it is totally reflected and enters the light receiving element 22.As a result, , the light receiving element 22 outputs a signal having a level of approximately 10% of the output in the case of gas, and the determination circuit 24 determines that it is a fluid or water.

When there is gasoline in the tank and the prism 1 is immersed in gasoline, the second and third reflecting surfaces are below the critical angle, so the light is totally reflected by the first reflecting surface. Approximately 10% of the light is reflected by the second reflecting surface 4, about 9% is reflected by the third reflecting surface 5 in proportion to the incident angle, and then it is totally reflected by the fourth reflecting surface 6. It returns to the light receiving element 22. As a result, the amount of incident light is O, l0X0.09=O
, O○9, that is, only about 0.9% is incident on the light-receiving element 22, so the determination circuit 24 determines that it is Ganlin.

When kerosene is present in the tank and the prism 1 is immersed in kerosene, the second and third reflecting surfaces 3.4 will be less than the critical angle. 8% of the light is reflected on the third reflecting surface, and about 10% is reflected on the fourth surface, which is roughly at the critical angle to the kerosene, so the amount of incident light is 0.09x0.08x0.1 =0.00072
That is, approximately 0.072% of the light is incident on the light receiving element.

If light oil is present in the tank and the prism is immersed in light oil, the first reflecting surface will have a critical angle of 3, so about 10% will be reflected here. Approximately 8 rays are reflected on the reflective surface of , 7% and 9% are reflected, making the total
, Ix O,08x 0.07x 0.09= 0.0
0005, that is, about 0.005% of the light returns.

In other words, each time the type of fluid that comes into contact with the prism differs, the amount of returning light changes by one order of magnitude, and the difference in signal level between the types of fluids differs greatly, so that detection can be ensured.

In addition, in the above example, in the case of light oil, the amount of light returned is extremely small, but since it is amplified electrically,
It will not become undetectable.

FIG. 4 shows a second embodiment of the present invention, in which reference numeral 30 denotes a prism formed with a rectangular cross section, and a prism with a person exit surface 31, a first, a second, and a third prism. Reflective surface 32.33
．． 34, and the first reflective surface 32 has a refractive index of 1.429.
The second reflecting surface 33 has a refractive index of 1.1 or more, such as gasoline vapor, at an incident angle θ5 that is equal to or greater than the critical angle for the above-mentioned fluid, for example, gasoline.
Further, the third reflecting surface 34 is set at an incident angle θ7 with respect to a fluid having a refractive index of 1.446, for example, kerosene.

According to this embodiment, when air is present in the tank, the light is totally reflected at the reflective surfaces 32, 33, 34, and when gasoline vapor is present, the light incident from the incident reflective surface 31 is The critical angle becomes less than the critical angle at the reflecting surface 33 of 2, and the angle becomes approximately 1
0% is reflected, and the other reflective surfaces 32, 34 are reflected H.

For gasoline, the second and third reflective surfaces 33.34
is below the critical angle, while total reflection occurs at the first reflecting surface 32, so 0.09X0.1=O0○09, that is, approximately 0.
9% of the light returns.

In addition, in the case of kerosene or light oil with a higher refractive index than this, all the reflecting surfaces 32, 33, 34 are below the critical angle, so 01 x 0.09X O,08 = 0.0007
2, that is, 0.072% of the light is returned, and it is possible to obtain signals that differ by an order of magnitude for each type of fluid.

In addition, if the type of fluid to be detected is limited,
Among these types, the surface with the smallest critical angle or less, for example, in the first embodiment, the reflective surface 5 is used when it is not necessary to discriminate water, and in the second embodiment, it is unnecessary to discriminate gasoline vapor. In some cases, by mirror-finishing the reflective surface 33, the amount of returning light can be increased, thereby reducing the cost of the signal amplification circuit and simplifying the discrimination.

(Effects) As explained above, according to the present invention, there is a plurality of reflecting surfaces, and each reflecting surface forms approximately a critical angle with respect to the fluid to be detected. It is possible to create a change in light intensity that differs by one order of magnitude for each liquid type without attenuation due to the following reflectance, and it is possible to reliably detect the liquid type with a high signal ratio.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a prism showing an embodiment of the present invention, Fig. 2 is a configuration diagram showing an embodiment of a fluid discrimination device using the same prism, and Fig. 3 is a specific example of the same prism. The explanatory diagram, FIG. 4, is a sectional view showing another embodiment of the present invention. 1...Fluid type discrimination prism 2...Person exit surface 3.4.5.6...Reflection surface 11, ]2...Light guiding material

Claims (1)

[Claims] A fluid discriminating prism having a plurality of reflective surfaces, each reflective surface forming approximately a critical angle with respect to each liquid to be detected.