HK1066855B

HK1066855B - Liquid level detecting device

Info

Publication number: HK1066855B
Application number: HK04109769.6A
Authority: HK
Inventors: 大缠直之
Original assignee: 大缠直之
Priority date: 2001-06-12
Filing date: 2002-06-12
Publication date: 2006-09-01

Description

Liquid level height detection device

Technical Field

The present invention relates to a device for detecting a liquid level of a liquid which is contained in a container such as a storage tank, a pipe, a tank, or the like and is not easily visible from the outside, and more particularly, to a device for detecting a liquid level using scattered light.

Background

Fig. 7 is a sectional view of an example of a conventional liquid level detection device using light reflection by a prism. The liquid level detection apparatus 100 shown in fig. 7 is constituted by the following various components: a columnar light-transmitting member 102 made of fluorine-based resin or glass or the like having one end (hereinafter referred to as a prism portion 101) cut into a predetermined shape; a light emitting device 103 facing the prism portion 101 and emitting light along a length direction of the light transmitting member 102; a light receiving device 104 for receiving the light reflected from the prism portion 101, the light being emitted from the light emitting device 103, and then reflected by the prism portion 101 and returning in the longitudinal direction of the light transmitting member 102; and an IC105 for measuring the amount of light received by the light receiving device 104 and outputting the measurement result.

In addition, a predetermined shape is set on the prism portion 101 so that the light receiving device 104 can efficiently receive the light emitted by the light emitting device 103. For example, the emitted light is totally reflected on the prism portion 101, and such totally reflected light is returned to the light-receiving device 104 all the way. That is, when the refractive index of the light-transmitting member 102 is n_tRefractive index of air n_s(n_s* 1) is the angle of illumination sin θ of the light emitted from the light emitting device 103₀＝n_s/n_tThereby, the prescribed shape of the lower end of the prism portion 101 and the arrangement positions of the light emitting device 103 and the light receiving device 104 are determined.

The part of the prism part 101 irradiated with light is contacted with the liquid surface 107 of the liquid 106In the above case, the refractive index of the outside of the prism portion 101 changes (normally, the refractive index of the outside becomes larger because the refractive index of the liquid 106 is larger than that of air), and the total reflection angle θ₀As well as variations. Thus, the light emitted from the light emitting device 103 is emitted into the liquid 106, and the amount of light returned to the light receiving device 104 is greatly reduced. By measuring the change in the amount of light, the liquid surface 107 in contact with the lower end can be detected.

However, in the liquid level detection device 100 in fig. 7, since the liquid level detection portion is present in the prism portion 101 at the lower end, when the liquid level of the liquid 106 is detected once, the liquid droplets continue to adhere to the liquid level detection portion, and the liquid level detection device malfunctions to detect the liquid level or fails to detect the liquid level. The liquid level detection device shown in fig. 8 below is one of liquid level detection devices as an improvement to this problem.

Fig. 8 is a cross-sectional view of an example of a conventional liquid level detection device using total reflected light. The liquid level detection device 200 shown in fig. 8 is constituted by the following components: a transparent member 201 made of fluorine resin or glass, etc., having a hollow interior; a light emitting device 202 and a light receiving device 203 which are provided in the hollow space and are constituted by optical fibers or the like; a light shielding wall 204 for preventing the light emitted from the light emitting device 202 from directly irradiating the light receiving device 203; and an IC205 for measuring the amount of light received by the light receiving device 203 and outputting the measurement result.

In the case where the liquid 206 does not exist outside (that is, in the case where the outside is air), the angles of the light emitting device 202 and the light receiving device 203 may be set so that the light is totally reflected on the outer wall of the side surface of the transparent member 201. That is, when the refractive index of the light-transmitting member 201 is n_tRefractive index of air n_s(n_s* 1) is set so that the incident angle of the light emitting device 202 is larger than the sin θ of the irradiation angle of the light from the light emitting device 202₀＝n_s/n_tSet critical angle theta₀The light receiving device 203 is also arranged at the same incident angle as the light emitting device 202The reflection angle is set so that the total reflection light from the outer wall of the light transmitting member 201 can be efficiently received.

As described above, when the outside is air, the light emitted from the light emitting device 202 is totally reflected on the outer wall of the transparent member 201, received by the light receiving device 203, and when the liquid surface 207 comes into contact with a portion where the light on the side surface of the transparent member 201 is totally reflected (hereinafter, referred to as a total reflection portion), the refractive index of the outside of the transparent member 201 changes, and the critical angle θ₀As well as variations. Then, the light emitted from the light emitting device 202 is emitted into the liquid 206, and the amount of light returned to the light receiving device 203 is greatly reduced. By measuring the change in the amount of light, it is possible to detect that the liquid surface 207 contacts the total reflection portion. In such detection of the liquid level by total reflection, when the liquid 206 is present at the total reflection site, total reflection of light does not occur, and the amount of reflected light changes dramatically. Therefore, the amount of change in the amount of light received by the light receiving device is large, and the liquid level height can be detected with high accuracy.

Further, japanese patent laid-open nos. 2000-329607 and 2000-321116 disclose liquid level height sensors that measure the attenuation of transmitted light by scattering of the transmitted light and detect the liquid level height. For example, japanese patent application laid-open No. 2000-329607 discloses a liquid level sensor 300 using scattered light obtained by scattering transmitted light, as shown in fig. 9.

In the liquid level sensor 300, the transmitted light is scattered by the light scattering member (granular particles) 301 to become scattered light, and the scattered light is emitted from the detection portion 302 to the outside, and the attenuation amount of the transmitted light after the attenuation is measured by the influence of the liquid existing outside, thereby detecting the level of the liquid level. Further, in addition to fig. 9, for example, as shown in fig. 10, a device in which light transmitting substances having different refractive indexes are arranged over the entire U-shaped portion is disclosed.

However, in the liquid level height detection device shown in fig. 8, since the liquid level height is detected by total reflection, for example, when the liquid level height of a liquid having a high viscosity is detected once and then the liquid level height is detected by using the liquid level detection device again, the liquid droplets adhere to the total reflection sites and total reflection does not occur at the total reflection sites, and therefore, there is a problem that the liquid level height cannot be detected without removing the liquid droplets. In addition, when an oil film or stain is adhered to the total reflection portion, there is also a problem that malfunction may occur.

In the liquid level height detection device shown in fig. 8, since a critical angle for determining total reflection is set in the prism portion and the total reflection portion, it is necessary to set various conditions such as an angle of the prism portion, positions and angles of the light emitting device and the light receiving device, a distance from the light emitting device to the light receiving device (i.e., a distance in a longitudinal direction of the light shielding wall), an angle of light emission, an angle of light reception, and the like. Further, there is a problem that the liquid level height detection device has a very short life, such as scratches and damages due to external impact, and deterioration of the performance of the liquid level height detection device due to various use conditions such as acidity and alkalinity. Further, since the above various conditions must be set, there is a problem that it is difficult to manufacture the liquid level height detection device precisely.

The liquid level detection device shown in fig. 8 is set such that total reflection occurs in an initial state where air is present outside the liquid level detection portion, and total reflection does not occur inside a predetermined detection target (liquid), for example. On the other hand, the detection target set in this way changes depending on the environment used. Thus, for example, according to a set critical angle θ₀There is a problem that although a liquid having a high refractive index can be detected, a liquid having a low refractive index cannot be detected. Further, the conventional liquid level height detecting device has a problem that a malfunction occurs when the detection target is a colored liquid.

Further, the liquid level detecting means shown in fig. 8 is capable of detecting, for example, a double-layer interface between air and liquid, but if it is intended to detect a 3-layer interface between air, oil and water, there is a problem that two kinds of liquid level detecting means must be provided, a liquid level detecting means for setting a change in whether or not total reflection occurs is provided on the interface between air and oil, and another kind of liquid level detecting means for setting a change in whether or not total reflection occurs is provided on the interface between oil and water. In this specification, the interface between a liquid phase and a gas phase and the interface between two different liquid phases are referred to as liquid level.

Further, the liquid level sensor shown in fig. 9 is structured such that the light emitted from the light emitting means directly enters the light receiving means, which has received a considerable amount of transmitted light even before the liquid level is detected. The light directly entering the light receiving device from the light emitting device is not only irrelevant to the detection of the liquid level height, but also greatly reduces the detection precision of the liquid level height. In particular, when the amount of scattered light emitted from the detection portion (i.e., the amount of attenuation of light transmitted by the light receiving device) is small at the time of detecting the liquid level, the rate of change of the amount of light received by the light receiving device (the rate of change is the amount of light received after the liquid level is detected/the amount of light received before the liquid level is detected) becomes extremely small, and it is very difficult, and currently, it is not realistic.

Therefore, particularly in the case where the distance L of the detection portion is shortened in order to improve the accuracy of liquid level height detection, the rate of change in the amount of light received by the light receiving device is further reduced because the amount of scattered light emitted from the detection portion to the outside is inevitably reduced. Therefore, if the distance L between the detection portions of the liquid level sensor is not set to be large, it is impossible to detect the height of the liquid level, and the detection accuracy of the liquid level is very low.

Further, as shown in fig. 10, since the light transmitting material having a different refractive index is provided over the entire U-shaped portion and the liquid level sensor for emitting light is used for the U-shaped portion, the light transmission path of the structure is very meandering, almost all of the transmitted light leaks to the outside as scattered light, and the amount of light received by the light receiving device is very small. Further, even when the liquid level is detected, since it is impossible to accurately specify a specific liquid level, only the liquid level with extremely low accuracy can be detected, and this does not actually work.

Disclosure of Invention

In view of the above-described problems, it is an object of the present invention to provide a liquid level height detection device which can be applied to various detection objects and use environments without sorting the detection objects, can continuously and reliably detect a liquid level even with a liquid having a high viscosity, and further has excellent durability and can be easily manufactured. Further, another object of the present invention is to provide a liquid level detecting apparatus which can irradiate light onto a liquid level detecting portion with high efficiency, and which has high sensitivity to a change in the amount of received light by a light receiving means at the time of detection, and can actually perform liquid level detection with high sensitivity.

The light receiving means is provided with a light shielding means for preventing the light emitted from the light emitting means from directly irradiating the light receiving means, and on the one hand, a part of the scattered light scattered by the light scattering means is emitted to the outside at the liquid level height detecting portion of the light emitting means, and on the other hand, the light receiving means receives the scattered light which is not emitted but returned after being reflected, and detects the change in the amount of the received light.

That is, according to the present invention, there is provided a liquid level detection device for detecting a liquid level of a liquid existing outside, the liquid level detection device including:

a light emitting device that emits light;

a light scattering means for scattering light emitted from the light emitting means;

a light emitting device for emitting a part of the scattered light scattered by the light scattering device to a liquid level detection portion outside the light scattering device;

a light receiving means for receiving not the light emitted from the light emitting means but the part of the scattered light scattered by the light scattering means and returned, or receiving not the light emitted from the light emitting means but the part of the light reflected by the interface between the light emitting means and the outside and returned; and

a light shielding device for shielding light so that the light emitted from the light emitting device does not directly irradiate the light receiving device;

when the liquid exists outside, the amount of light emitted to the outside of the light emitting device changes, and the level of the liquid is detected by detecting the change with the amount of light received by the light receiving device.

In addition, the preferred embodiment of the present invention also arranges the above-described light emitting device and light receiving device at a predetermined angle.

In addition, a preferred embodiment of the present invention is also provided with a plurality of the above-described light-receiving devices.

Further, the preferred embodiment of the present invention also arranges the plurality of light-receiving devices described above on a substantially horizontal plane.

In addition, in order to prevent the light shielding means from absorbing light, the preferred embodiment of the present invention covers the light shielding means with a thin film for reflecting light.

In a preferred embodiment of the present invention, a reference light receiving amount in the light receiving device may be set according to a type of the liquid, and a liquid level height of the liquid may be detected by comparing the light receiving amount of the light receiving device with the reference light receiving amount.

In addition, in a preferred embodiment of the present invention, the light scattering means is further disposed around a light emitting portion of the light emitting means.

In addition, in a preferred embodiment of the present invention, the light scattering means is further disposed around the liquid level height detection portion irradiated with the light emitted from the light emitting means.

Further, in a preferred embodiment of the present invention, the light scattering means is silicone rubber.

In addition, in a preferred embodiment of the present invention, the light emitting device is an alkoxy perfluoro compound.

In a preferred embodiment of the present invention, a tungsten lamp is used for the light emitting device, and a glass optical fiber is used for the light receiving device.

In addition, in a preferred embodiment of the present invention, the liquid level of the liquid is detected by immersing the light emitting device in the liquid.

In addition, in a preferred embodiment of the present invention, the light emitting device is further provided on an outer wall of a translucent container to detect a liquid level of the liquid contained in the container.

In addition, in a preferred embodiment of the present invention, the light emitting device further comprises a fixing device capable of fixing the light emitting device to an outer wall of the container.

Drawings

FIG. 1 is a schematic view showing a state of use of a liquid level detection device according to the present invention;

FIG. 2 is a sectional view of a first embodiment of the liquid level detection device of the present invention;

FIG. 3 is an enlarged schematic view of the vicinity of the liquid level detection portion of the liquid level detection device of the present invention shown in FIG. 2;

FIG. 4 is a schematic graph showing changes in the amount of light received by the light receiving device when the liquid level is detected by the liquid level detecting device of the present invention;

FIG. 5 is a sectional view of a liquid level detection device according to a second embodiment of the present invention;

FIG. 6 is a sectional view of a liquid level detection device according to a third embodiment of the present invention;

FIG. 7 is a sectional view showing an example of a conventional liquid level detecting device using light reflection from a prism;

FIG. 8 is a cross-sectional view of an example of a conventional liquid level detection device using total reflected light;

FIG. 9 is a sectional view showing an example of a conventional liquid level detecting apparatus using scattered light;

FIG. 10 is a cross-sectional view showing another example of a conventional liquid level detecting apparatus using scattered light;

FIG. 11 is a schematic view showing a first example of a state of use of the liquid level detection device according to the present invention;

FIG. 12(A) is a schematic view showing a first example of the liquid level detection unit of the liquid level detection apparatus of the present invention, the liquid level detection unit being provided at different levels;

FIG. 12(B) is a schematic view showing a second example of the liquid level detection device of the present invention, in which liquid level detection portions are provided at different heights;

FIG. 12(C) is a schematic view showing a third example of the liquid level detection device of the present invention, in which liquid level detection portions are provided at different heights;

FIG. 13 is a sectional view of a liquid level detection apparatus according to a fourth embodiment of the present invention;

FIG. 14 is a view of the liquid level detecting apparatus shown in FIG. 13 with a plurality of glass optical fibers provided, and is a cross-sectional view taken along line X-Y of FIG. 13;

fig. 15 is a schematic view showing a second example of a usage state of the liquid level detection device according to the present invention.

Detailed Description

< first embodiment >

Next, a liquid level detection device according to the present invention will be described with reference to the drawings. First, a first embodiment of the liquid level detection device of the present invention will be described. FIG. 1 is a schematic view showing a state of use of a liquid level detection device according to the present invention; fig. 2 is a sectional view of a liquid level detection device according to a first embodiment of the present invention. In addition, fig. 2 is an enlarged view of a dotted line portion in fig. 1. The liquid level detecting device 10 of the present invention detects the liquid level by inserting a column portion substantially vertically into a tank from above a container such as the tank, and bringing a liquid 17 into contact with a liquid level detection portion located below the column portion.

The liquid level detection apparatus 10 of the present invention shown in fig. 2 has an overall length of approximately several tens of centimeters, and is composed of the following parts: a columnar light-transmitting member (light emitting device, light transmitting device) 11 made of a fluorine-based resin, glass, or the like and having a hollow portion inside; a light emitting device 12 formed of an optical fiber, a Light Emitting Diode (LED), or the like, provided in the inner cavity portion; a light receiving device 13 for converting light energy into electric energy such as an electric signal; a light shielding wall (light shielding means) 14 for preventing the light emitted from the light emitting means from directly irradiating the light receiving means 13; an IC (integrated circuit) 15 that measures the amount of light received by the light receiving device 13 and outputs the measurement result; and a light scattering member (light scattering means, silicone rubber) 16 that covers the entire distal ends of the light emitting device 12 and the light receiving device 13 and gives scattering properties to the irradiated light. In addition, for example, when the light emitting device 12 is an optical fiber, it is connected to a light supplying device; when the light emitting device 12 is a light emitting diode, it is connected to a power source. Further, as the light scattering member 16, silicone rubber 16 having a property of being capable of being fixedly connected to the light emitting device 12 and the light receiving device 13 is preferable, and in particular, translucent soft silicone sealant having moisture absorption hardening property and heat resistance is preferable.

The wavelength of the light used for the liquid level detection is not particularly limited, and any light used in the visible field, the infrared field, the ultraviolet field, and other fields can be used. Further, a prism or the like is provided so that the light emitted from the light emitting device 12 and the light received by the light receiving device 13 have directivity, making it possible to efficiently emit and receive light. The light-transmitting member 11 is preferably made of a material having high durability against chemicals, and for example, a fluorine-based resin such as PTEE (polytetrafluoroethylene), PFA (alkoxy perfluorocompound), FEP (fluorescent ethylene propylene), ETFE (ethylene tetrafluoroethylene) or the like is used, and in particular, it is preferable to use PTFE which is stable and does not melt even at high temperatures, PFA which is inexpensive and easy to process, or the like. Since the light transmitting member 11 has light transmitting properties and serves as a liquid level detection site for emitting light to the outside environment, the light transmitting member 11 is also referred to as a light emitting device 11. Further, since the transparent member is only a device for protecting the external environment, the object of the present invention can be achieved even if the light scattering means 16 is directly exposed to the external environment (that is, the light emitting means 11 and the light scattering means 16 are formed as the same member) without providing the transparent member 11 in the vicinity of the liquid level detection portion.

FIG. 3 is an enlarged schematic view of the vicinity of the liquid level detection portion of the liquid level detection device of the present invention shown in FIG. 2. Next, the operation and the light flow when detecting the liquid level are described with reference to fig. 3. For example, the substance such as the silicone rubber 16 is a translucent substance in which many fine particles are irregularly scattered, and when light is irradiated on the silicone rubber 16, it is scattered inside the silicone rubber 16. Therefore, the light emitted from the light emitting device 12 is scattered by the fine particles in the silicone rubber 16, and spreads in any direction. Then, the scattered light is repeatedly scattered back and forth by the fine particles, and for example, again returns to the direction in which the light emitting device exists and strikes the inner wall of the transparent member 11. In addition, a substance or a member having a property of scattering irradiated light may be used instead of the silicone rubber 16.

Further, the light receiving device 13 can be prevented from directly receiving the light emitted from the light emitting device 12 by the light shielding wall 14. In this way, the light interfering with the detection of the liquid level can be blocked without directly irradiating the light emitted from the light emitting device 12 to the light receiving device 13. Further, the light receiving device 13 is not directly made to receive the light emitted from the light emitting device 12, which means that the light is not directly irradiated on the light receiving device 13 regardless of the presence or absence of the silicone rubber 16 by arranging the light emitting device 12 and the light receiving device 13 to face each other. Further, by arranging the light emitting device at a predetermined design angle, the average amount of light irradiated between the light emitting device 12 and the light receiving device 13 in the vicinity of a portion of the light transmitting member 11 that emits a part of scattered light to the outside (hereinafter referred to as a liquid level height detection portion) can be increased, and by arranging the light receiving device at a predetermined design angle, the efficiency of receiving light can be increased, and the accuracy of liquid level height detection can be improved.

Further, the light shielding wall 14 is inclined so as to function as a light reflecting plate, and if the light reflecting plate is provided separately, the accuracy of liquid level detection can be improved. Further, the length of the liquid level height detection portion is in the range of several millimeters. In addition, in order to prevent light from being absorbed by the light-shielding wall 14, the light-shielding wall 14 is made white or covered with a thin film of silver, aluminum, or the like, so that the light reflectance of the light-shielding wall 14 can be improved.

The light reaching the inner wall of the light-transmitting member 11, a part of which is reflected on the inner wall, passes through the inside of the light-transmitting member 11 to reach the outer wall of the light-transmitting member 11. In the case where the liquid 17 is not present outside (external environment) the light-transmitting member 11 (i.e., in the case where the outside is air), light incident at an angle smaller than the critical angle with respect to the normal line of the outer wall of the light-transmitting member 11 passes through the interface with the outside and is emitted to the outside (however, a part thereof is reflected off the outer wall); on the other hand, light incident at an angle equal to or greater than the critical angle is totally reflected by the outer wall. In addition, on the inner and outer walls of the light-transmitting member 11, the light travels following the laws of reflection and refraction at the interface. Further, a fluorine-based resin such as PFA is not strictly transparent (i.e., translucent) and has a property of scattering light, and the description of the effect thereof is omitted here for the sake of simplicity.

After being reflected on the inner wall and the outer wall of the transparent member 11, the light returning to the inside of the transparent member 11 is repeatedly scattered in the silicone rubber 16 existing inside the transparent member 11 and reflected on the light shielding wall 14. As a result, the light reaches the outer wall of the light-transmitting member 11 again, and there is also light emitted to the outside after passing through the outer wall. Thus, the light emitted from the light emitting device 12 is finally classified into two main types, one being light emitted to the outside of the light transmitting member 11 and the other being light returned to the inside of the light transmitting member 11. Then, part of the light repeatedly scattered inside the transparent member 11 is received by the light receiving device 13. Since the direction of the scattered light is arbitrary, the average light amount in the stationary state is fixed, and the amount of light radiated to the outside of the transparent member 11 (average radiated light amount) and the amount of light received by the light receiving device 13 (average received light amount) are also fixed.

As described above, in the case where the external environment is not changed, the amount of light received by the light receiving device 13 is fixed. However, for example, when the liquid surface 18 rises and the liquid surface approaches a liquid surface height detection portion (or the light-transmitting member 11 is inserted into the liquid 17 a little), the amount of light received by the light receiving device 13 changes due to a change in the external environment.

Further, the light receiving amount of the light receiving device is related not only to the refractive index of the external liquid 17 but also to a large extent to the spectral characteristics of absorption-reflection of such liquid 17. For example, white liquid such as milk, and metal liquid such as mercury have a property of reflecting light in a visible region. In this case, the liquid level height can be detected by selecting the wavelength range of the light to be used, based on the spectral characteristics of absorption and reflection of the liquid to be detected.

Fig. 4 is a schematic graph showing changes in the amount of light received by the light receiving device when the liquid level is detected by the liquid level detection device of the present invention. When the liquid 17 having a refractive index higher than that of air rises and the liquid surface 18 reaches the liquid surface height detection portion, a part of the scattered light reflected by the outer wall of the light-transmitting member 11 before that is emitted to the inside of the liquid 17. That is, the refractive index of the medium existing in the external environment increases, the reflection/transmission characteristics of light at the interface between the liquid 17 and the light-transmitting member 11 change, and the amount of light emitted into the medium increases. As a result, the amount of light returning to the inside of the light transmitting member 11 after being reflected on the interface between the liquid 17 and the light transmitting member 11 decreases, and the amount of light received by the light receiving device 13 also decreases. By measuring the change in the amount of light received attenuated during this transfer, the level of the liquid 17 can be detected.

As explained above, according to the first embodiment, the light emitted from the light emitting device 12 has the same effect as that of emitting light from most light sources in an arbitrary direction due to scattering in the silicone rubber 16. Thus, the range of the detected liquid surface height (the range in which light is emitted to the outside and the range in which light once emitted to the outside returns) is extremely large, and even when liquid droplets or a liquid film adheres to the vicinity of the liquid surface height detection portion, the influence thereof can be ignored, and the change in the amount of light accompanying the change in the liquid surface height can be measured, thereby accurately detecting the height of the liquid surface.

For example, when the amount of light received by the light receiving device 13 is equal to or less than a predetermined amount of light received (reference amount of light received), the preset IC 15 may output a signal indicating the detection of the liquid level height and report the detection of the liquid level height to the outside. Further, for example, a predetermined light receiving amount can be easily adjusted by an adjusting device such as a micro-actuator, and liquid surface heights of various liquids can be detected by previously defining different light receiving amounts according to the types of the liquids. Further, by setting a plurality of values for a predetermined amount of received light, each interface of the liquid 17 having a plurality of layers can be detected. For example, it may be preset that, after a change in the amount of light received by the light receiving device 13 is measured, if the change exceeds a predetermined value, the IC 15 outputs a signal indicating the detection of the liquid level.

In addition, when the liquid surface 18 of the liquid 17 having light reflection characteristics such as the white liquid reaches the liquid surface height detection portion, the light emitted to the outside of the light transmitting member 11 is totally returned, and the light receiving amount of the light receiving device 13 is increased. Therefore, for example, when the amount of light received by the light receiving device 13 exceeds a predetermined amount of light received, the IC 15 can be set to output a signal indicating the detected liquid level height, thereby reporting the detection of the liquid level height to the outside.

Since the change in the amount of light received by the light receiving device 13 is to be measured, it is not necessary to strictly define the installation positions of the light emitting device 12 and the light receiving device 13, and the light receiving device 13 may be installed at a position where it can receive the light emitted by the light emitting device 12. This is a detection device of the present invention, and is different from the conventional liquid level height detection device for measuring the presence or absence of total reflection as shown in fig. 8 in that the installation positions of the light emitting device 202 and the light receiving device 203 must be strictly defined according to the critical angle of total reflection. Further, in the preferred embodiment, the light emitting device 12 and the light receiving device 13 each have directivity toward the vicinity of the liquid level detection portion, and the light emitted from the light emitting device 12 can be efficiently irradiated to the vicinity of the liquid level detection portion, while the light receiving device 13 can efficiently receive the light emitted from the vicinity of the liquid level detection portion.

In the first embodiment, the silicone rubber 16 is added to the entire vicinity of the liquid level detection portion, and the light emitting device 12 and the light receiving device 13 are adhered thereto, so that the light emitting device 12, the light receiving device 13, the light shielding wall 14, and the like can be fixed by the silicone rubber 16. In particular, since the silicone rubber 16 has high adhesiveness to a fluorine-based resin such as PFA or PTFE, various devices can be stably attached near the liquid level height detection portion, and as a result, the operation of detecting the liquid level height can be stably performed.

< second embodiment >

Next, a second embodiment of the liquid level detection device of the present invention will be described. Fig. 5 is a sectional view of a liquid level detection device according to a second embodiment of the present invention. The liquid level detection device 10 of the present invention shown in fig. 5 is also composed of a light transmitting member 21, a light emitting device 22, a light receiving device 23, a light shielding wall 24, and silicone rubber 26, as in the liquid level detection device in fig. 2, but the silicone rubber 26 is present only in the vicinity of the light emitting device 22.

In the liquid level detection device 10 of the present invention shown in fig. 5, the light emitted from the light emitting device 22 is scattered by the silicone rubber 26, and such scattered light is irradiated to the liquid level detection portion. The light returned after being reflected by the liquid level height detection portion is transmitted in the direction of the light receiving device 23 while being repeatedly reflected by the gap between the light shielding wall 24 and the light transmitting member 21, for example, so that the liquid level height can be detected by the light receiving device 23. Therefore, as in the liquid level height detection device 10 described in the first embodiment shown in fig. 2, scattered light can be irradiated to the liquid level height detection portion, and the change in the amount of light received by the light receiving device 23 is measured, whereby the liquid level height of the liquid 17 can be detected.

As described above, according to the second embodiment, since light emitted from the light emitting device 22 is scattered in the silicone rubber 26 disposed in the light emitting device 22, the same effect as that of light emitted from a plurality of light sources in any direction is obtained. In this way, the range of the detected liquid surface height is very wide, and even when a droplet or a liquid film is attached near the detection portion of the liquid surface height, the influence thereof can be ignored, and the change in the light amount can be measured with the change in the liquid surface height, so that the height of the liquid surface can be accurately detected.

< third embodiment >

Next, a third embodiment of the liquid level detection device of the present invention will be described. Fig. 6 is a sectional view of a liquid level detection device according to a third embodiment of the present invention. The liquid level detection device 10 of the present invention shown in fig. 6 is also composed of a transparent member 31, a light emitting device 32, a light receiving device 33, a light shielding wall 34, and a silicone rubber 36, as in the liquid level detection device in fig. 2, but the silicone rubber 36 is present only on the entire inner wall of the transparent member 31 (in the vicinity of the liquid level detection portion).

In the liquid level detection device 10 of the present invention shown in fig. 6, light reaching the non-interface between the liquid 17 and the transparent member 31 also becomes scattered light by the silicone rubber 36. Therefore, as in the liquid level height detection devices described in the first and second embodiments shown in fig. 2 and 5, scattered light can be applied to the liquid level height detection portion, and the change in the amount of light received by the light receiving device 33 can be measured, whereby the liquid level height of the liquid 17 can be detected.

As described above, according to the third embodiment, since light emitted from the light emitting device 32 is scattered in the silicone rubber 36 disposed on the entire inner wall of the light transmitting member 31, the same effect as that of light emitted from a plurality of light sources in an arbitrary direction can be obtained. In this way, the range of the detected liquid surface height is very wide, and even when a droplet or a liquid film is attached near the detection portion of the liquid surface height, the influence thereof can be ignored, and the change in the light amount can be measured with the change in the liquid surface height, so that the height of the liquid surface can be accurately detected.

< fourth embodiment >

Next, a fourth embodiment of the liquid level detection device according to the present invention will be described. FIG. 13 is a sectional view of a liquid level detection device according to a fourth embodiment of the present invention. The liquid level detection device 10 of the present invention shown in fig. 13 is also composed of a transparent member 41, a light emitting device 42, a light receiving device 43, a light shielding wall 44, and silicone rubber 46, as in the liquid level detection device of fig. 2. Further, a glass fiber 51 is used as the light receiving device 13 shown in fig. 2. As described later, such a glass optical fiber 51 has an advantage of high strength at high temperature.

Further, FIG. 14 is a view showing the liquid level detecting apparatus shown in FIG. 13 when a plurality of glass optical fibers are provided, and is an X-Y sectional view in FIG. 13. As shown in the figure, a plurality of glass optical fibers 51 are provided, and the light reflected from the liquid level detection portion and returned therefrom can be received by these glass optical fibers 51.

When the area of the light receiving portion is small, a malfunction is likely to occur when a water droplet or the like remains on the liquid level height detection portion. On the other hand, when it is necessary to consider the miniaturization and weight reduction of the liquid level detection apparatus 10, the portion that receives light cannot be made too large. Therefore, in the fourth embodiment, as shown in fig. 14, for example, a plurality of glass fibers 51 (12 in fig. 14) having a diameter of 1mm are arranged. Thus, even when water droplets are attached near the liquid surface height detection portion, the influence of the water droplets can be ignored, and the change in the amount of light can be measured with the change in the liquid surface height, thereby accurately detecting the liquid surface height.

As described above, according to the fourth embodiment, since light emitted from the light emitting device 42 is scattered in the silicone rubber 46, the same effect as that of light emitted from a plurality of light sources in any direction can be obtained. In this way, the range of the detected liquid surface height is very wide, and even when a droplet or a liquid film is attached near the detection portion of the liquid surface height, the influence thereof can be ignored, and the change in the light amount can be measured with the change in the liquid surface height, so that the height of the liquid surface can be accurately detected.

In addition, as shown in fig. 14 in particular, since the light receiving portion composed of a plurality of glass optical fibers 51 is arranged on a substantially horizontal plane along the inner wall of the light transmitting member 41, the liquid level height of the substantially horizontal plane can be detected with high accuracy, and malfunction due to liquid droplets and a liquid film can be prevented. In fig. 14, a mode in which light receiving portions composed of a plurality of glass optical fibers 51 are arranged along the inner wall of the light transmitting member 41 is also shown, but the arrangement mode of the light receiving portions in the present invention is not limited to this arrangement mode. For example, the arrangement of the plurality of light receiving sections may be determined in accordance with the shape of the liquid level detection device 10. For example, as shown in fig. 15, the liquid level detection device 10 may be arranged in accordance with the shape of the pressure tank 91 so that the liquid level can be detected from the outside without being immersed in the liquid.

Next, an example of the liquid level detection device to which the present invention is applied will be described. FIG. 11 is a schematic view showing a first example of a state of use of the liquid level detection device of the present invention. The liquid level detection device 10 is connected to a controller 90 for controlling the operation and processing the measurement results, and the device of the present invention is inserted into the liquid 17 in the pressure tank 91. Since the length of the columnar portion having a portion for detecting the liquid level at the lower portion thereof can be freely set, the liquid level detection device 10 can be manufactured to be convenient to use in accordance with various situations. For example, in equipment such as medical gallon bottles, pressurized tanks, Peltier boilers, etc., the column section is about 330mm in length, and in equipment such as cylindrical boilers, the column section is typically about 800 mm.

Fig. 12 is a schematic diagram showing an example in which liquid level detection portions are provided at different heights in the liquid level detection device of the present invention. As shown in fig. 12(a) and 12(B), since a plurality of columnar portions having different lengths are provided, the height of the liquid surface can be detected at different heights. In addition, the liquid level height detection device 10 shown in fig. 12(a) can detect the height of the liquid level at two different points, whereas the liquid level height detection device 10 shown in fig. 12(B) can detect the height of the liquid level at four different points. Further, since such a case where a plurality of columnar portions are provided is somewhat difficult to use in a small tank, it is possible to provide a plurality of detection portions for liquid level at different heights in one columnar portion as shown in fig. 12(C), and it is possible to miniaturize the liquid level detection apparatus 10 capable of detecting liquid levels at a plurality of portions.

Fig. 15 is a schematic diagram showing a second example of the usage state of the liquid level detection device according to the present invention. In the example of use shown in fig. 11, the liquid level detection portion of the liquid level detection device 10 of the present invention is inserted directly into the liquid 17 to detect the height of the liquid level 18, while in the example of use shown in fig. 15, the liquid level detection portion is provided on a level gauge tube 93 of a pressure tank 91 whose liquid level is usually visually observed to detect the liquid level 18. Thus, in the case where it is difficult to immerse the liquid level detection portion in the liquid 17, or in the case where the liquid 17 is a dangerous substance (for example, a substance having a high reactivity, a high-temperature or low-temperature substance), the liquid level can be detected without directly immersing in the liquid 17. In addition, when the liquid level of the liquid placed in the container (pressure tank) 91 without the level vial 93 is to be detected, the liquid level detection portion may be provided directly in the container 91.

Further, it is preferable that a fixing means (tape) 92 for fixing the liquid level detection portion is provided on the outer wall of the liquid container 91. For example, a tape 92 of the type shown in FIG. 15 may be used to fix the liquid level detection portion at a prescribed position in the container 91 in such a manner that the tape 92 is wound around the outer circumference of the container. The fixing device 92 may be provided with an adhesive surface, and the liquid level detection portion may be attached to the container 91 by the adhesive surface.

Further, as shown in fig. 15, the silicone rubber 56 may be directly attached to the outer wall of the container 91. Thus, light does not leak from the gap (optical tightness), and the silicone rubber 56 does not fall off due to its adhesive property, and the silicone rubber can be attached to the outer wall of the container 9 without using the tape 92, thereby preventing liquid from penetrating into the outer wall between the silicone rubber 56 and the container 91, and preventing malfunction. Further, the liquid level detection portion and the container 91 can be bonded together by using the same silicone rubber hardening liquid.

In addition, there are cases where the liquid to be detected as the liquid level or the working environment is at a high temperature, and particularly, in the case where the liquid is oil, it is often necessary to detect the liquid level of the liquid at approximately 200 ℃. However, if semiconductor LED light sources are used as the light emitting devices 12, 22, 32, 42, the LED light sources are damaged beyond about 80 ℃, and monitoring becomes impossible. In consideration of the operation at such a high temperature, a small-sized precision lamp (tungsten lamp) can be used, and glass fibers are used as the light receiving means 13, 23, 33, which can normally operate at a high temperature of about 300 ℃, ensuring that the liquid level height detection operation can be performed even at a high temperature.

Industrial applicability of the invention

As described above, according to the present invention, since the light blocking means is provided so that the light emitted from the light emitting means does not directly irradiate the light receiving means, and on the other hand, part of the scattered light scattered by the light scattering means is emitted to the outside of the scattering means or the light transmitting means at the liquid level height detection portion of the light emitting means, and the scattered light which is not emitted and returned after being reflected is received by the light receiving means, the change in the amount of received light can be detected.

Claims

1. A liquid level detection device for detecting the liquid level of a liquid existing outside, comprising:

a light emitting device that emits light;

2. The liquid level detection apparatus according to claim 1, wherein the light emitting device and the light receiving device are arranged at a predetermined angle.

3. The liquid level detecting device according to claim 1 or 2, wherein a plurality of said light receiving means are provided.

4. The liquid level detecting apparatus according to claim 3, wherein the plurality of light receiving devices are arranged on a horizontal plane.

5. The liquid level detecting device according to claim 1, wherein the light shielding means is covered with a light reflecting film in order to prevent the light shielding means from absorbing light.

6. The liquid level detection apparatus according to claim 1, wherein a reference light receiving amount in said light receiving means is set in accordance with a type of said liquid, and the liquid level of said liquid is detected by comparing the light receiving amount of said light receiving means with said reference light receiving amount.

7. The liquid level detecting apparatus according to claim 1, wherein said light scattering means is disposed around a light emitting portion of said light emitting means.

8. The liquid level detection apparatus according to claim 1, wherein said light scattering means is disposed around said liquid level detection portion irradiated with said light emitted from said light emitting means.

9. The liquid level detecting apparatus according to claim 1, wherein said light scattering means is silicone rubber.

10. The liquid level detecting apparatus according to claim 1, wherein said light emitting means is an alkoxy perfluoro compound.

11. The liquid level detection apparatus according to claim 1, wherein a tungsten lamp is used for the light emitting device, and a glass optical fiber is used for the light receiving device.

12. The liquid level detecting device according to claim 1, wherein the liquid level of the liquid is detected by immersing the light emitting device in the liquid.

13. The liquid level detecting apparatus according to claim 1, wherein said light emitting means is provided on an outer wall of a container having light permeability to detect the liquid level of said liquid contained in said container.

14. The liquid level detecting device according to claim 13, further comprising a fixing means for fixing said light emitting means to an outer wall of said container.