JP6303900B2 - Liquid detection sensor - Google Patents

Description

  The present invention relates to a liquid detection sensor that detects a liquid present in a detection target region.

  Conventionally, a liquid detection sensor is mounted on an electronic device or a manufacturing apparatus that handles liquid. For example, Patent Document 1 describes a configuration in which a part of a washing tub is formed with a transparent wall surface, and a light emitting element and a light receiving element are arranged on an outer tub wall facing the wall surface. Light from the light emitting element is transmitted when the water level reaches the transparent wall surface, and when it does not reach, it is reflected and incident on the light receiving element, and the water level can be detected by changing the light quantity of the light receiving element. Patent Document 1 also describes that the transparent wall surface is constituted by a prism.

  In Patent Document 2, light that is formed inside an ink tank and reflects from the outside when no liquid is present in the liquid chamber is reflected to the outside. When liquid is present in the liquid chamber, the light that is incident from the outside is reflected to the outside. In the prism having the function of not reflecting, a configuration is described in which the shape is a specific shape and the total light transmittance and the haze value are specific values. This makes it possible to detect the remaining amount of ink with stable operation at low cost.

  Patent Document 3 describes a configuration in which an exposure apparatus that irradiates a substrate with exposure light through a liquid to expose the substrate optically detects a liquid leak using a detector including a prism. The detector is attached to a prism, a light projecting unit that is attached to the first surface of the prism and projects light onto the prism, and a second surface of the prism (a surface that is substantially perpendicular to the first surface). And a light receiving unit that receives the light reflected from the third surface of the prism of the light emitted from the light projecting unit. The light from the light projecting unit is totally reflected by the third surface when the liquid is not attached to the third surface and received by the light receiving unit, and when the liquid is attached to the third surface, the liquid is It is possible to detect the presence of the liquid by changing the amount of light at the light receiving portion (see FIGS. 14 and 15 of Patent Document 3).

Japanese Patent Laid-Open No. 54-58465 (published on May 11, 1979) Japanese Patent Laying-Open No. 2005-41183 (released on February 17, 2005) JP 2007-5830 A (published January 11, 2007)

  However, the conventional technology as described above has a problem that it is not possible to detect a liquid having a slight layer thickness (a small amount of liquid) of, for example, 1.5 mm or less. This will be specifically described.

  Since Patent Document 1 is a liquid level sensor that detects a liquid level of a washing tub, it does not have a concept of detecting a liquid having a slight layer thickness. Therefore, even if the liquid level sensor is provided in the vicinity of the bottom surface of the washing tub, it is not possible to detect a slightly thick liquid existing on the bottom surface.

  In the configuration of Patent Document 2, a prism having a height of 3.2 mm is exemplified, but in the case of a liquid having a slight layer thickness intended to be detected by the present invention, the prism has such a height. Protrudes from the liquid. For this reason, the light is reflected by the portion of the prism slope that is not in contact with the liquid, and the light enters the light receiving element. Therefore, it is conceivable to reduce the height of the prism to, for example, about 1.5 mm in order to detect a liquid having a slight layer thickness. However, if the prism is so small, the light emitting element and the light receiving element must be small, and the distance between them must be small. Furthermore, in order to secure the amount of light entering the light receiving element, it is necessary to use a high power light emitting element with a large light emission amount. Therefore, it becomes impossible to use a light-emitting element and a light-receiving element that are easy to manufacture and inexpensive.

  On the other hand, in the configuration of Patent Document 3, by providing the third surface on the bottom surface of the liquid container, the liquid existing on the bottom surface can be detected regardless of the height from the bottom surface. However, in the case of a liquid with a slight layer thickness intended to be detected by the present invention, since the layer thickness is thin, even the light reflected by the liquid surface enters the light receiving unit, and the liquid exists but does not exist. There is a risk of false detection. In order to avoid such erroneous detection, it is necessary to devise the optical system and the light receiving unit so that only the light reflected by the third surface enters the light receiving unit.

  The present invention has been made in view of the above problems, and an object of the present invention is to detect a liquid having a slight layer thickness, which has not been conventionally detected, using a light-emitting element and a light-receiving element that are easy to manufacture and inexpensive.

  In order to solve the above problems, the liquid detection sensor of the present invention irradiates the optical member with light from the light emitting element, receives the reflected light with the light receiving element, and the presence or absence of liquid in contact with the optical member due to a change in the amount of light In the liquid detection sensor for detecting the light, the light emitting element and the light receiving element are arranged along the mounting surface on the back side of the mounting surface on which the liquid is placed, and the optical member includes the light emitting element and the light receiving element. A plurality of prisms arranged side by side in the arrangement direction, and each prism protrudes upward from the placement surface so that the two sloped portions that face each other are in contact with the liquid on the placement surface. It is characterized by being provided as follows.

  According to the above configuration, it is possible to detect whether or not the liquid is present on the mounting surface based on whether the light emitted from the light emitting element is reflected by the plurality of prisms and reaches the light receiving element. In addition, since the prism is provided so as to protrude upward from the mounting surface, it is reflected by the liquid surface as compared with the configuration of Patent Document 3 in which the prism protrudes downward from the mounting surface. Thus, the detection accuracy can be improved by reducing the influence of the light returning to the prism again.

  Since a plurality of prisms are arranged, each prism can be made smaller than the conventional prism, and a liquid with a slight layer thickness that cannot be detected conventionally can be detected. Also, by arranging a plurality of prisms, it is not necessary to reduce the light emitting element and the light receiving element, and the distance between them even if the individual prisms are made smaller than before, and the light emitting element and the light receiving element that are easy to manufacture and inexpensive. An element can be used. Furthermore, since the reflected light from the plurality of prisms is incident on the light receiving element, the amount of received light necessary for detection can be ensured without using a high power element with a large light emission amount as the light emitting element.

  Further, even if the device on which the sensor is mounted is slightly inclined, it is difficult for all of the plurality of prisms to come out of the liquid surface, and the structure is strong against inclination. Moreover, when a plurality of prisms are used, even if some prisms have a shape abnormality from the time of manufacture or a shape abnormality due to aging, they can be used, so the prism shape has a long life and a high molding yield. It can be configured with high robustness.

  The liquid detection sensor of the present invention may further include at least one spare prism provided in parallel with the plurality of prisms.

  Even if the position of the plurality of prisms and the light emitting element shifts and light does not enter a part of the plurality of prisms, it functions as an alternative by providing a spare prism provided alongside the plurality of prisms. Can be made. Since the spare prism can be manufactured in the same process as the plurality of prisms, the manufacturing cost does not increase.

  In the liquid detection sensor of the present invention, the placement surface may be a bottom surface of the liquid storage container, and the liquid stored in the liquid storage container may be a detection target.

  In this case, the plurality of prisms may be provided in recesses formed on the bottom surface.

  According to this, the liquid accumulated in the concave portion on the bottom surface of the liquid container becomes a detection target. Therefore, even if a very small amount of liquid spreads over the entire bottom surface of the liquid container and cannot be detected by the configuration in which the prism is provided directly on the bottom surface, the same prism height can be obtained by accumulating in the recess to ensure the layer thickness. It can be detected. In addition, since the prism is provided in the recess formed on the bottom surface, there is an effect that the thickness of the bottom surface portion of the liquid container can be reduced.

  In the liquid detection sensor of the present invention, the placement surface may be a bottom of a tubular member through which the liquid flows, and the liquid flowing inside the tubular member may be a detection target.

  In the liquid detection sensor of the present invention, the height from the placement surface of the plurality of prisms may be 1.5 mm or less.

  By setting it to such a height, it is possible to reliably detect a liquid having a slight layer thickness.

  An inclination detection sensor according to the present invention is mounted on an object and detects the inclination of the object. The liquid detection sensor according to claim 1 and the plurality of prisms of the liquid detection sensor are formed at the bottom. And a predetermined amount of liquid sealed inside the liquid sealed container, the predetermined amount of liquid from the liquid surface of the plurality of prisms according to the inclination of the liquid sealed container It is characterized in that the amount is set so that the number of exposed prisms changes.

  An inclination detection sensor for detecting the inclination of an object can be provided using the liquid detection sensor of the present invention.

  The present invention has an effect that a liquid having a small layer thickness can be detected using a light-emitting element and a light-receiving element that are easy to manufacture and inexpensive.

It is a schematic diagram which shows the principal part structure of the apparatus which mounts the liquid detection sensor based on one Embodiment of this invention. It is drawing explaining the path | route of the light irradiated from the light emitting element in the said liquid detection sensor, and shows the path | route when a liquid does not exist. It is drawing explaining the path | route of the light irradiated from the light emitting element in the said liquid detection sensor, and shows the path | route in case a liquid exists. It is a schematic diagram which shows the relationship between the optical member and liquid level in the liquid detection sensor mounted in the apparatus of the inclined state, (a) shows the case of the said liquid detection sensor, (b) is the conventional liquid detection sensor. This case is shown. It is drawing which shows the result of having simulated the course of the light irradiated from the light emitting element in case the inclined surface of a some prism is an interface with air. It is explanatory drawing which shows the positional relationship in the case of arrange | positioning a some prism with respect to a light emitting element and a light receiving element. It is explanatory drawing which shows the course of the light which injected into the prism at the angle near horizontal from the bottom face. FIG. 9 shows the result of simulating the path of light emitted from the light emitting element, assuming that the setting angle of the plurality of prisms and the slopes of the plurality of prisms are interfaces with air in a light emitting element with a half-value angle θ _LED of 30 °. It is a drawing. FIG. 6 shows the result of simulating the path of light emitted from the light emitting element, assuming that the setting angle of the plurality of prisms and the slopes of the plurality of prisms are the interfaces with air in the light emitting element having a half-value angle θ _LED of 80 °. It is a drawing. FIG. 6 shows the result of simulating the path of light emitted from the light emitting element, assuming that the setting angle of the plurality of prisms and the slopes of the plurality of prisms are interfaces with air in the light emitting element having a half-value angle θ _LED of 20 °. It is a drawing. It is drawing explaining the path | route of the light irradiated from the light emitting element in the liquid detection sensor of a modification, and shows a path | route when a liquid does not exist. It is a figure which shows the modification and shows the structure provided with the reserve prism in addition to the some prism. FIG. 25 is a schematic diagram illustrating a configuration in which a plurality of prisms of a liquid detection sensor are arranged inside a pipe that is a tubular member according to another embodiment of the present invention. It is a schematic diagram which shows the structure by which the single prism in the conventional liquid detection sensor is arrange | positioned inside the pipe which is a tubular member. The other form of implementation of this invention is shown and it is a schematic diagram of an inclination detection sensor. FIG. 24 is a perspective view showing a configuration in which a plurality of prisms of a liquid detection sensor are arranged in a recess formed on the bottom surface of a liquid container, showing another embodiment of the present invention. It is explanatory drawing which shows the effect of the structure which provided the several prism in the recessed part of the bottom face. FIG. 10 is a perspective view showing a configuration in which a plurality of prisms of a liquid detection sensor are arranged in a recess formed on the bottom surface of a liquid container, showing a modification.

  Hereinafter, embodiments of the present invention will be described in detail.

[Embodiment 1]
FIG. 1 is a schematic diagram illustrating a configuration of a main part of a device 1 on which a liquid detection sensor 10 is mounted. The device 1 includes a liquid storage container 3 that stores the liquid 5 and a liquid detection sensor 10 that detects the presence or absence of the liquid 5 stored in the liquid storage container 3.

  The liquid detection sensor 10 irradiates the optical member 12 with light from the light emitting element 13, receives the reflected light with the light receiving element 15, and detects the presence or absence of the liquid in contact with the optical member 12 by changing the light amount.

  The light emitting element 13 and the light receiving element 15 are arranged along the bottom surface 3 a on the back side of the bottom surface (mounting surface on which the liquid is placed) 3 a of the liquid container 3. Here, “the light emitting element 13 and the light receiving element 15 are arranged along the bottom surface 3a” means that the light emitting element 13 and the light receiving element 15 are aligned in the normal direction of the bottom surface 3a. Any arrangement is possible except in some cases. The light emitting element 13 and the light receiving element 15 are located outside the liquid container 3 below.

The optical member 12 is provided on the bottom surface of the liquid container 3 so as to face the inside of the liquid container 3. The optical member 12 includes a plurality of prisms 11 ₁ , 11 ₂ ... 11 _n (n is an integer indicating the number of prisms). The plurality of prisms 11 _{1 to} 11 _n are triangular prisms having a triangular cross section, and are provided so as to protrude from the bottom surface 3 a so that two butted slopes (slope portions) are in contact with the liquid 5 on the bottom surface 3 a. Yes. The plurality of prisms 11 _{1 to} 11 _n are juxtaposed in the direction in which the light emitting element 13 and the light receiving element 15 are arranged. In the example of FIG. 1, a configuration including _three prisms 11 _{1 to} 11 ₃ is illustrated as n = 3. However, the number of prisms is not limited to three, and may be two or more. .

The plurality of prisms 11 _{1 to} 11 _n have a minute height of at least 1.5 mm or less from the bottom surface 3a in order to detect a liquid having a slight layer thickness of 1.5 mm or less, for example. .

  2 and 3 are diagrams for explaining the path of light emitted from the light emitting element 13 in the liquid detection sensor 10.

Light from the light emitting element 13 is incident on the plurality of prisms 11 _{1 to} 11 _n from below the liquid storage container 3. Here, when the liquid 5 does not exist, the liquid 5 does not contact the surfaces of the plurality of prisms 11 _{1 to} 11 _n . Therefore, as shown in FIG. 2, the light incident on the plurality of prisms 11 _{1 to} 11 _n is reflected by the inclined surface that becomes the interface with the air 6 of each prism 11 _{1 to} 11 _n , and the optical path (1) → the optical path ( 2) → It reaches the light receiving element 15 through the optical path (3).

On the other hand, even a slight layer thickness of the liquid, if the degree of the liquid 5 that the liquid level is at the respective apexes of the plurality of prisms 11 ₁ to 11 _n exist, the plurality of prisms 11 ₁ to 11 _n surface Liquid 5 contacts. Therefore, as shown in FIG. 3, the light incident on the plurality of prisms 11 _{1 to} 11 _n follows the path of the optical path (1) → the optical path (4), and is absorbed in the liquid 5. Is not reached.

As described above, whether the liquid is present in the liquid container 3 is detected based on whether the light emitted from the light emitting element 13 is reflected by the plurality of prisms 11 _{1 to} 11 _n and reaches the light receiving element 15. can do. In addition, since the plurality of prisms 11 _{1 to} 11 _n are provided so as to protrude upward from the bottom surface 3a, the prisms 11 _{1 to} 11 _n have a liquid surface as compared with a configuration in which the prism protrudes downward from the bottom surface 3a. The detection accuracy can be improved by reducing the influence of the light reflected and returning to the prism.

Since the plurality of prisms 11 _{1 to} 11 _n are arranged, the individual prisms can be made smaller than conventional ones, and a liquid having a slight layer thickness that could not be detected conventionally can also be detected.

Further, since the plurality of prisms 11 _{1 to} 11 _n are arranged, it is not necessary to reduce the light emitting element 13 and the light receiving element 15 and the distance between them even if the individual prisms are made smaller than the conventional prism, and the manufacturing is easy. Inexpensive light emitting elements and light receiving elements can be used.

Further, since the reflected light from the plurality of prisms 11 _{1 to} 11 _n is incident on the light receiving element 15, the amount of received light necessary for detection can be secured without using a high power element with a large light emission amount for the light emitting element 13. it can.

Moreover, as shown in FIG. 4 (a), that was small plurality of prisms ₁₁ 1 to 11 _n, the degree to which device 1 is tilted slightly, all of the plurality of prisms ₁₁ 1 to 11 _n is the liquid surface It is possible to have a structure that is resistant to tilting. On the other hand, in the case of a conventional liquid detection sensor using a single prism 112, as shown in FIG. 4B, the prism 112 protrudes from the liquid surface even when the device 111 is tilted to the same degree. The liquid 5 cannot be detected.

In addition, when a plurality of prisms 11 _{1 to} 11 _n are used, some prisms can be used even if they have a shape abnormality from the time of manufacture or a shape abnormality due to secular change. Thereby, it can be set as the structure with high robustness with a long lifetime of a prism shape, and a high molding yield.

Hereinafter, the relationship between the plurality of prisms 11 _{1 to} 11 _n and the light emitting element 13 and the light receiving element 15 will be described.

FIG. 5 simulates the path of light emitted from the light emitting element 13 _{assuming that} the slopes of the plurality of prisms 11 _{1 to} 11 _n are interfaces with the air 6. Of the plurality of prisms 11 _{1 to} 11 _n , the lower end of the slope L of the _first prism 11 ₁ closest to the light emitting element 13 is positioned at the center of the divergent light emitted from the light emitting element 13.

Of the light emitted from the light emitting element 13 and diverging and traveling, the light that has reached the slope L on the light emitting element 13 side (left side slope in the drawing) of each of the prisms 11 _{1 to} 11 _n is reflected by the slope L. The light reaches the light receiving element 15 side inclined surface R (right inclined surface in the figure), is reflected by the inclined surface R, and reaches the light receiving element 15. On the other hand, of the light that diverges and travels, the light that has reached the slope R (right slope in the drawing) of each of the prisms 11 _{1 to} 11 _{n on} the light receiving element 15 side passes through the slope R.

As shown in FIG. 5, the plurality of prisms 11 _{1 to} 11 _n are minute prisms having a height of 1.5 mm or less, but a plurality of prisms 11 _{1 to} 11 _n are arranged in accordance with the arrival area of light emitted from the light emitting element 13 and diverging. Since the reflected light from each of the prisms 11 _{1 to} 11 _n reaches the light receiving element 15, the amount of light received by the light receiving element 15 can be ensured. Arranging the plurality of prisms 11 _{1 to} 11 _n together with the arrival region of the light emitted from the light emitting element 13 and diverging in other words, by arranging the prisms 11 _{1 to} 11 _n together with the half-value angle (directivity) of the light emitting element 13. is there. The half-value angle is a value indicating an angle at which the light intensity of the front surface of the light emitting element 13 is 100% and the light intensity is 50% of the half.

Further, as shown in FIG. 5, in the plurality of prisms 11 _{1 to} 11 _n , the angle of the inclined surface L on the light emitting element 13 side is the largest at the _first prism 11 ₁ closest to the light emitting element 13, and the light emitting element The structure set so that it may become small as it leaves | separates from 13 is preferable. In this way, the amount of light reaching the light receiving element 15 can be increased and light can be used more effectively than in a configuration in which the angle of the inclined surface L is the same in all the plurality of prisms. The slope R on the light receiving element 15 side is set to an angle at which the light reflected by the slope L and reaching the slope R can be reflected to reach the light receiving element 15.

FIG. 6 is an explanatory diagram showing a positional relationship when a plurality of prisms 11 _{1 to} 11 _n are arranged with respect to the light emitting element 13 and the light receiving element 15.

When the half-value angle of the light-emitting element 13 is θ _LED , the distance between the light-emitting element 13 and the prism bottom surface is L _dis , and the distance from the _first prism 11 ₁ to the apex of the n-th prism 11 _n farthest is L _pri It is preferable that the following relational expression (1) is satisfied between the element 13 and the plurality of prisms 11 _{1 to} 11 _n .

  By satisfying the relational expression (1), it is possible to effectively use the light that travels to the right located on the light receiving element 15 side among the divergent light emitted from the light emitting element 13.

Further, among the plurality of prisms ₁₁ 1 to 11 _n, in the first prism 11 ₁ light enters the vertical than the prism bottom surface of the light emitting element 13, the angle of the slope L of the light emitting element 13 side theta _{Lpri (1 )} , When the refractive index of the transparent resin constituting the plurality of prisms 11 _{1 to} 11 _n is about 1.5, it is preferable that the relational expression (2) is satisfied.

When the prism 11 ₁ of the refractive index is about 1.5, the first prism 11 _first angle of slope L theta _{Lpri (1)} is at 70 ° or more, the slant surface reaches the inclined surface L of the prism 11 ₁ Even if it is reflected by L, the light does not reach the slope R on the light receiving element 15 side. For this reason, the light cannot be reflected by the slope R and reach the light receiving element 15. By satisfying the relational expression (2), strong light entering vertically from the light emitting element 13 can surely reach the light receiving element 15.

Further, among the plurality of prisms ₁₁ 1 to 11 _n, the light from the light emitting element 13 enters a parallel state close than the prism bottom surface, in the farthest prism 11 _n from the light emitting element 13, the slope of the light emitting element 13 side L _Is the angle θ _{Lpri (n)} , it is preferable that the relational expression (3) is satisfied when the refractive index of the transparent resin constituting the plurality of prisms 11 _{1 to} 11 _n is about 1.5.

When the prism 11 ₁ of the refractive index is about 1.5, the final n th prism 11 _n slope L angle theta _{Lpri (n)} is 50 ° or more, incident at an angle close to the horizontal than the prism bottom surface As shown in FIG. 7, the emitted light does not reach the slope L. FIG. 7 is an explanatory diagram showing the path of light that has entered the prism at an angle closer to the horizontal than the bottom surface. Therefore, the light cannot be reflected on the slope L and the slope R and reach the light receiving element 15. By satisfying the relational expression (3), light that enters from the light emitting element 13 at the most horizontal angle can also reach the light receiving element 15.

When the angle of the slope R on the light receiving element 15 side of the plurality of prisms 11 _{1 to} 11 _n is θ _Rpri , the angle θ _Rpri and the half-value angle θ _LED of the light emitting element 13 satisfy the relational expression (4). Is preferred.

As described above, in the plurality of prisms 11 _{1 to} 11 _n , the slope R on the light receiving element 15 side reflects the light reflected by the slope L and reaches the slope R to reach the light receiving element 15. Designed at an angle that can. In the plurality of prisms 11 _{1 to} 11 _n , when the angle of the inclined surface L on the light emitting element 13 side is set so as to decrease as the distance from the light emitting element 13 increases, the inclined surface R increases as the distance from the light emitting element 13 increases. Set to

For example, in the case of the light emitting element 13 having a half-value angle θ _LED of 30 °, the plurality of prisms 11 _{1 to} 11 _n are arranged on the slope L of the _first prism 11 ₁ closest to the light emitting element 13 as shown in FIG. The angle is 45 °, the angle of the inclined surface R is 27 °, the angle of the inclined surface L of the _second prism 112 is 43.30 °, the angle of the inclined surface R is 27.50 °, and so on. (One case). 8, in the light-emitting element 13 of the half-value angle theta _LED is 30 °, the setting angles of a plurality of prisms ₁₁ 1 to 11 _n, as the slope of the plurality of prisms ₁₁ 1 to 11 _n is the interface with air, the light emitting The result of having simulated the course of the light irradiated from the element 13 is shown.

Further, for example, if the half-value angle theta _LED is 80 ° of the light emitting element 13, as shown in FIG. 9, the plurality of prisms ₁₁ 1 to 11 _n, 1 th prism 11 ₁ in the most light-emitting element 13 side the angle of slope L 40.50 °, the angle of slope R is 28 °, the angle of the second prism 11 _{and second} inclined surfaces L the subsequent 39 °, the angle of the slope R is 28.20 °, ... and so on Set (example). 9, in the light-emitting element 13 of the half-value angle theta _LED is 80 °, the setting angles of a plurality of ₁₁ 1 to 11 _n, as the slope of the plurality of prisms ₁₁ 1 to 11 _n is the interface with air, the light emitting element 13 shows the result of simulating the path of light emitted from 13.

As shown in the examples of FIGS. 8 and 9, when the half-value angle θ _LED is 30 ° or more, the relationship between the angle θ _Rpri and the half-value angle θ _LED of the light emitting element 13 in the plurality of prisms 11 _{1 to} 11 _n . Equation (4) can be satisfied.

In contrast, if the half-value angle theta _LED is smaller than 30 °, in the light-emitting element 13, for example 20 °, when satisfying the relation (4), as shown in FIG. 10, a plurality of ₁₁ 1 to 11 _n is the most angle of the first prism 11 ₁ slope L in the light-emitting element 13 side is 45 °, the angle of the slope R is 18 °, the angle of the second prism 11 _{and second} inclined surface L that persists 43.30 ° The angle of the slope R is set to 17 °, etc. (an example). 10, in the light-emitting element 13 of the half-value angle theta _LED is 20 °, the setting angles of a plurality of prisms ₁₁ 1 to 11 _n, as the slope of the plurality of prisms ₁₁ 1 to 11 _n is the interface with air, the light emitting The result of having simulated the course of the light irradiated from the element 13 is shown.

As shown in FIG. 10, when the angle θ _Rpri of the slope R is smaller than 20 °, when the refractive index of the transparent resin constituting the plurality of prisms 11 _{1 to} 11 _n is about 1.5, the slope R The incident angle of light reflected and incident on the bottom surface of the prism exceeds the critical angle and is not emitted from the bottom surface of the prism.

That is, when the relational expression (4) is satisfied, in order to reflect the reflected light from the slope L on the slope R and reach the light receiving element 15, a relatively wide light emitting element having a half-value angle θ _LED of 30 ° or more. 13 should be used. In other words, by satisfying the relational expression (4), the light emitting element 13 is suitable for a configuration in which a plurality of prisms 11 _{1 to} 11 _n having a large divergence angle such that the half-value angle θ _LED is 30 ° or more are arranged. It can be limited.

(Modification 1)
In the liquid detection sensor 10 described above, the perpendicular light emitted from the light emitting element 13, that is, the light at the center of the divergent light, is incident on the slope L of the _first prism 11 ₁ among the plurality of prisms 11 _{1 to} 11 _n. It was configured to be incident. However, in this configuration, only half of the light emitted from the light emitting element 13 is guided to the plurality of prisms 11 _{1 to} 11 _n and the remaining half is not guided.

Therefore, as shown in FIG. 11, in the liquid detection sensor 104 of the modification, the light emitting element 13 is tilted, and the center light of the divergent light emitted from the light emitting element 13 is out of the plurality of prisms 11 _{1 to} 11 _n . The light is incident on the inclined surface L of the prism (prism 11 _{2 in} the example of FIG. 11) located in the central portion. FIG. 11 is a diagram for explaining the path of light emitted from the light emitting element 13 in the liquid detection sensor 104 of the modification, and shows the path when no liquid is present.

This structure generates a may direct the entire light emitted from the light emitting element 13 into a plurality of prisms 11 ₁ to 11 _n, it can be effectively utilized light.

(Modification 2)
As shown in FIG. 12, the liquid detection sensor according to the modification has a configuration in which n + 1-th and n + 2-th spare prisms 11 _{n + 1} , 11 _{n + 2} are further provided in the plurality of prisms 11 _{1 to} 11 _n . FIG. 12 shows a modified example and is a drawing showing a configuration in which a spare prism is provided in addition to a plurality of prisms.

Light does not enter the spare prisms 11 _{n + 1} and 11 _{n + 2} when the plurality of prisms 11 _{1 to} 11 _n are appropriately disposed with respect to the light irradiation region of the light emitting element 13. However, when the set position with respect to the liquid container 3 in which the plurality of prisms 11 _{1 to} 11 _n are formed is shifted and the positions of the plurality of prisms 11 _{1 to} 11 _n and the light emitting element 13 are shifted, light enters. become. The spare prisms 11 _{n + 1} and 11 _{n + 2} function as an alternative to a part of the plurality of prisms 11 _{1 to} 11 _n that cannot receive light.

If the direction of deviation is determined, the spare prism may be provided only in the direction of deviation. If the direction of displacement is not determined, it may be provided on both sides of the arrangement of the plurality of prisms 11 _{1 to} 11 _n as in the example of FIG. The number of spare prisms may be provided in consideration of the shift amount. In consideration of a large shift, a plurality of prisms 11 _{1 to} 11 _n may be provided.

[Embodiment 2]
FIG. 13 is a schematic diagram showing a configuration in which a plurality of prisms 11 _{1 to} 11 _n of the liquid detection sensor 10 are arranged inside a pipe (tubular member) 20. By making the height of the plurality of prisms 11 _{1 to} 11 _n minute, the plurality of prisms 11 _{1 to} 11 _n are also arranged inside the thin pipe 20 with a part of the lower part made of a transparent resin material. By doing so, it is possible to detect the liquid having a slight thickness remaining inside the pipe 20 without obstructing the flow of the liquid. Moreover, since it is a minute prism, it is difficult to have bubbles (bubbles).

  FIG. 14 is a schematic diagram showing a configuration in which a single prism 112 in a conventional liquid detection sensor is arranged inside a pipe 20. In this case, not only the liquid with a small layer thickness cannot be detected, but also the flow path of the liquid becomes narrow due to the presence of the single prism 112, which obstructs the flow and easily causes clogging.

[Embodiment 3]
FIG. 15 is a schematic diagram of an inclination detection sensor 50 according to the present embodiment. The tilt detection sensor 50 is mounted on an object and detects the tilt of the object. The liquid detection sensor 10 described above, the liquid enclosure 30 in which the plurality of prisms 11 _{1 to} 11 _{n of} the liquid detection sensor 10 are formed at the bottom, and a predetermined amount of the liquid 5 enclosed in the liquid enclosure 30. Prepare. The predetermined amount of the liquid 5 is set such that the number of prisms exposed from the liquid surface of the plurality of prisms 11 _{1 to} 11 _n changes according to the inclination of the liquid enclosure 30. Specifically, the liquid amount is adjusted so that the liquid level is positioned at the apexes of the plurality of prisms 11 _{1 to} 11 _n in a state where the liquid enclosure 30 is installed on a horizontal plane.

Since a liquid with a slight layer thickness can be detected, the amount of light received by the light receiving element 15 changes when any of the prisms 11 _{1 to} 11 _n comes out of contact with the liquid due to the inclination of the liquid enclosure. The inclination of the object can be detected by associating the change amount and the inclination of the received light amount in advance.

[Embodiment 4]
FIG. 16 is a perspective view showing a configuration in which a plurality of prisms 11 _{1 to} 11 _n of the liquid detection sensor 10 are arranged in the recess 3 b formed in the bottom surface 3 a of the liquid container 3. In such a configuration, the liquid present on the bottom surface 3a of the liquid container 3 is accumulated in the recess 3b, and the liquid accumulated in the recess 3b is a detection target.

Therefore, as shown in FIG. 17B, in the configuration of FIG. 1 in which the plurality of prisms 11 _{1 to} 11 _n are provided directly on the bottom surface 3a of the liquid storage container 3, it is spread over the entire bottom surface 3a and is necessary for detection. Even if it is a trace amount of liquid 5 that does not reach the layer thickness, as shown in FIG. 17A, it is stored in the recess 3b to secure the layer thickness, thereby increasing the height of the plurality of prisms 11 _{1 to} 11 _n . It can be detected while the same.

  Further, by providing the prism in the recess 3b formed on the bottom surface 3a, the thickness h of the bottom surface portion of the liquid container 3 can be made thinner than the configuration of FIG.

(Modification 3)
FIG. 18 is a perspective view showing another configuration in which the plurality of prisms 11 _{1 to} 11 _n of the liquid detection sensor 10 are arranged in the recess 3 b formed in the bottom surface 3 a of the liquid container 3. In the configuration of FIG. 18, the recess 3 b is provided only in the formation region of the plurality of prisms 11 _{1 to} 11 _n .

Therefore, it is possible to concentrate more liquid 5 in the recess 3b than in the configuration of FIG. 16, and the amount of the plurality of prisms 11 _{1 to} 11 _n is kept the same, and a smaller amount than in the configuration of FIG. The liquid 5 can be detected.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Since the present invention can detect a very small amount of liquid, it can be suitably used for liquid leak detection, equipment that may be installed in an inclined place, equipment that needs to store liquid compactly without waste, and the like. .

1 Device 3 Liquid container 3a Bottom surface (mounting surface)
3b Concave portion 5 Liquid 6 Air 10 Liquid detection sensors 11 _{1 to} 11 _n Prism 12 Optical member 13 Light emitting element 15 Light receiving element 20 Pipe (tubular member)
30 Liquid Enclosed Container 50 Tilt Detection Sensor 104 Liquid Detection Sensor

Claims (9)

In the liquid detection sensor that irradiates the optical member with light from the light emitting element, receives the reflected light with the light receiving element, and detects the presence or absence of the liquid in contact with the optical member by the change in the amount of light,
The light emitting element and the light receiving element are arranged side by side along the mounting surface on the back side of the mounting surface on which the liquid is placed,
The optical member is a plurality of prisms juxtaposed in the direction in which the light emitting element and the light receiving element are arranged, and each prism has two abutted butted surfaces in contact with the liquid on the mounting surface. Provided so as to protrude upward from the placement surface ,
The mounting surface is a bottom portion of a tubular member through which liquid flows, and a liquid flowing through the tubular member is a detection target .   The liquid detection sensor according to claim 1, further comprising at least one spare prism arranged in parallel with the plurality of prisms. In the liquid detection sensor that irradiates the optical member with light from the light emitting element, receives the reflected light with the light receiving element, and detects the presence or absence of the liquid in contact with the optical member by the change in the amount of light,
The light emitting element and the light receiving element are arranged side by side along the mounting surface on the back side of the mounting surface on which the liquid is placed,
The optical member is a plurality of prisms juxtaposed in the direction in which the light emitting element and the light receiving element are arranged, and each prism has two abutted butted surfaces in contact with the liquid on the mounting surface. Provided so as to protrude upward from the placement surface ,
A liquid detection sensor comprising: at least one spare prism arranged in parallel with the plurality of prisms, the spare prism having the same height as the plurality of prisms . Placing surface is a bottom of the liquid container, the liquid detection according to any one of claims 1 to 3, characterized in that the liquid contained inside the liquid container and the detection target Sensor. The liquid detection sensor according to claim 4 , wherein the plurality of prisms are provided in a recess formed in the bottom surface. The liquid detection sensor according to claim 3 , wherein the placement surface is a bottom portion of a tubular member through which the liquid flows, and the liquid flowing inside the tubular member is a detection target. Liquid sensor according to any one of claim 1 to 6, wherein the height from the mounting surface of the plurality of prisms is 1.5mm or less. In an inclination detection sensor mounted on an object and detecting the inclination of the object,
The liquid detection sensor according to claim 1 or 3 ,
A liquid sealed container in which the plurality of prisms of the liquid detection sensor are formed at the bottom;
A predetermined amount of liquid enclosed in the liquid enclosure,
The predetermined amount of liquid is set to such an amount that the number of prisms exposed from the liquid surface of the plurality of prisms changes according to the inclination of the liquid enclosure. . In an inclination detection sensor mounted on an object and detecting the inclination of the object,
A liquid detection sensor that irradiates an optical member with light from a light emitting element, receives the reflected light with a light receiving element, and detects the presence or absence of liquid in contact with the optical member by a change in light amount, wherein the light emitting element and the light receiving element are The optical member is a plurality of prisms arranged side by side along the placement surface on the back side of the placement surface on which the liquid is placed, and arranged in the direction in which the light emitting element and the light receiving element are arranged. Is a liquid detection sensor provided so as to protrude upward from the placement surface, so that the two sloped portions that face each other are in contact with the liquid on the placement surface ,
A liquid sealed container in which the plurality of prisms of the liquid detection sensor are formed at the bottom;
A predetermined amount of liquid enclosed in the liquid enclosure,
The predetermined amount of liquid is set to such an amount that the number of prisms exposed from the liquid surface of the plurality of prisms changes according to the inclination of the liquid enclosure. .

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