JP2010164471A - Water level detection device and heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life and superior water level detection device in which a signal value is small in the case where the light does not reach a light receiving element, when the output signal value of the light receiving element in the case where light reaches thereto is decreased by deterioration with the lapse of time, and gradually approaches the signal value in the case where the light does not reach thereto. <P>SOLUTION: The water level detection device includes: a light emitting means emitting light toward a reflection/transmission part in a water tank including the reflection/transmission part in which the amount of reflection and the amount of transmission of the light are varied depending upon the presence of liquid; a water level detection means including a light receiving means receiving light through the reflection/transmission part, generating and outputting a signal in response to the amount of light; a water level determination part determining the water level of water stored in the water tank on the basis of the signal from the water level detection means; and a tank cover fixed to and in contact with a surface of the water tank other than the water level detection part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water level detection device for detecting a water level in a water tank and a cooking device provided with the water level detection device.

  Conventionally, as a water level detection device for detecting the water level in a tank, for example, “the prism 20 of the ink tank reflects the light incident from the outside when there is no liquid in the liquid chamber, but there is liquid in the liquid chamber. Has the function of not reflecting the light incident from the outside, and transmits all light when measuring the optical characteristics of a rectangular parallelepiped having a square cross section of 40 mm on one side and a thickness of 1.7 mm according to the standard according to JIS K7136. The ratio is 80% or more, and the haze value is 75% or more and 85% or less.

The conventional optical sensor has a water tank formed of a transparent resin so that the light beam of the optical sensor can be transmitted or reflected, and detects the presence or absence of liquid inside the water tank. At this time, when the light beam is irregularly reflected around the water tank and the light beam accidentally reaches the light receiving element through a complicated path regardless of the condition that the light emitted by the light emitting element does not reach, the light receiving element receives the light. There is a problem that even if the signal is weak, the detection performance is lowered.
The output signal value of the light receiving element decreases when light arrives due to aging, and when it approaches the signal value when light does not reach gradually, the smaller the signal value when light does not reach, the longer the service life. It can be said that it is an excellent water level detection device.

  A water level detection device according to the present invention includes: a light emitting unit that emits light toward the reflection / transmission unit in a water tank including a reflection / transmission unit whose light reflection amount and transmission amount change depending on the presence or absence of liquid; A water level detection unit including a light reception unit that receives light through the reflection / transmission unit and generates and outputs a signal corresponding to the amount of light, and covers the outer surface of the water tank at a position facing the water level detection unit across the water tank. And a tank cover.

  According to the present invention, disturbance light reaching the water level detecting means can be prevented, and light projected by the light emitting means is prevented from being reflected and reaching the light receiving means, so that the detection performance can be improved as compared with the conventional water level detecting device.

It is a side view of the heating cooker which concerns on Embodiment 1 of this invention. It is a block diagram of the water level detection apparatus which concerns on Embodiment 1 of this invention. It is a perspective view of the water tank and water level detection means of the water level detection apparatus which concerns on Embodiment 1 of this invention. It is a block diagram of the water level detection means 8 of the water level detection apparatus which concerns on Embodiment 1 of this invention. It is a cross-sectional view around a water level detection device in a heating cooker body according to Embodiment 2 of the present invention. It is a cross-sectional view around a water level detection device in a heating cooker body according to Embodiment 2 of the present invention. It is a cross-sectional view around a water level detection device in a heating cooker body according to Embodiment 2 of the present invention. It is a cross-sectional view around a water level detection device in a heating cooker body according to Embodiment 2 of the present invention. It is a longitudinal cross-sectional view of the water level detection apparatus periphery in the heating cooker main body which concerns on Embodiment 2 of this invention. It is a longitudinal cross-sectional view of the water level detection apparatus periphery in the heating cooker main body which concerns on Embodiment 2 of this invention.

Embodiment 1
FIG. 1 is a side view showing a state in which the internal configuration of heating cooker 100 according to Embodiment 1 of the present invention is viewed from the side.
The heating cooker 100 cooks the heated object by heating the inner pot containing the heated object (rice, water, etc.) with a heating means such as an induction heating coil, and collects the steam generated at that time in a water tank. To do. In the following drawings including FIG. 1, the relationship between the sizes of the constituent members may be different from the actual one.

  The cooking device 100 is covered with a lid 3 so that the top surface thereof can be freely opened and closed, and a main body 1 in which the rice cooker 2 and the water tank 7 are detachably stored, and a heated object to be cooked are placed. A rice cooker 2 that is detachably stored in the lid, a lid 3 that covers the upper surface of the main body 1 through a hinge portion (not shown) pivotally supported on the upper rear portion of the main body 1, and the inside of the lid 3 Is attached detachably and covers the upper opening of the rice cooker 2 so as to be openable and closable, the heating body 5 such as an induction heating coil for heating the rice cooker 2, and a predetermined amount of water are stored, and steam is stored. It is composed of a water tank 7 that recovers steam by cooling and condensing water, and a steam pipe 6 that connects the rice cooker 2 and the water tank 7 and conducts steam.

  The main body 1 has an opening on the upper surface, and stores the heating body 5 in addition to the rice cooker 2 and the water tank 7. The rice cooker 2 has an opening on the top surface, and the opening is covered with the inner lid 4 so that the inside is sealed. The lid 3 covers the upper surface of the main body 1 so as to be freely opened and closed when a user operates an open / close switch or the like (not shown). In addition, a vapor pipe 6 is detachably attached to the lid 3. The inner lid 4 closes the inside of the rice cooker 2 by closing the upper opening of the rice cooker 2 during cooking. The heating body 5 is disposed on the bottom surface side of the rice cooker 2 and heats the rice cooker 2 to cook or keep warm by being energized.

The steam pipe 6 is connected to a steam introduction pipe 13 having one end (the right end portion on the paper surface) inserted into the substantially central portion of the inner lid 4 and the other end (the left end portion on the paper surface) inserted into the water tank 7. The pot 2 and the water tank 7 are connected. The water tank 7 stores a predetermined amount of water therein, and cools and collects the steam circulated through the steam pipe 6. The water tank 7 is stored beside the position where the rice cooker 2 is stored. The water tank 7 has an upper surface formed with an opening, and has a tank lid 12 that detachably covers the opening. Further, a steam introduction pipe 13 is fixed to the tank lid 12 so as to penetrate therethrough.

  One end (upper end) of the steam introduction pipe 13 is detachably connected to the steam pipe 6 and the other end (lower end) thereof is located inside the water tank 7 in a state where the tank lid 12 is attached to the water tank 7. It is like that. That is, the steam pipe 6 is separated from the steam introduction pipe 13 when the lid 3 is opened, and the steam pipe 6 is connected to the steam introduction pipe 13 when the lid 3 is closed. The steam pipe 6 and the steam introduction pipe 13 function as a steam guide path that guides the steam generated during rice cooking into the water tank 7, and the water tank 7 uses the water that has flowed in via the steam introduction pipe 13 as water. Condensation is performed and the recovered water 9 is stored, and these constitute a steam recovery device.

  Also, in the main body 1, a determination control means 11 that determines the water level of the water tank 7 and controls the energization of the heating body 5, and a water level detection that detects the water level of the recovered water 9 stored in the water tank 7. Means (water level detection sensor) 8 are provided. The determination control means 11 is arranged on the bottom surface of the main body 1 and below the heating body 5, determines the water level based on a signal output from the water level detection means 8, and based on the determination result, the heating body 5. It controls the energization to the. The water level detection means 8 is provided to face the side surface of the water tank 7 and detects whether or not the water level of the recovered water 9 in the water tank 7 has reached a preset water level. This water level detection means 8 is provided with three sets of light emitting elements and light receiving elements so as to detect three water levels (details will be described later), and outputs the output signal to the determination control means 11 for determination. Based on the output of the water level detection means 8, the control means 11 determines whether or not the water level of the recovered water 9 has reached a certain set water level. Thus, the water level detection means 8 and the determination control means 11 constitute the water level detection device 20 of the present invention, and details thereof will be described with reference to FIG.

FIG. 2 is a block diagram showing the configuration of the water level detection device 20. The water level detection device 20 includes the water level detection means 8 and the determination control means 11 as described above. The water level detecting means 8 includes a light emitting means 21 and a light receiving means 22 for emitting and receiving light via the water tank 7 (details of the arrangement of both will be described in detail in FIG. 3 and the like). In the first embodiment, the light emitting means 21 and the light receiving means 22 are provided with three sets of light emitting elements and light receiving elements in the height direction.
Further, the determination control means 11 includes, as a configuration of the water level detection device 20, an amplifier 23 that amplifies the output of the light receiving means 22 and a control / signal processing circuit 24 that performs signal processing on the output of the amplifier 23. This control / signal processing circuit 24 corresponds to the water level determination means of the present invention, and is constituted by, for example, a microcomputer. The water level detection means 8 further includes a display 25 for displaying the calculation result by the control / signal processing circuit 24. The display 25 is composed of, for example, a lamp or a liquid crystal display, and is installed at a position above the water tank 7 like the lid 3, so that water may be spilled when the water tank 7 is taken in and out. Even so, the water is kept away.

In the water level detection device 20 having such a configuration, the control / signal processing circuit 24 supplies a light emission command signal to the light emitting means 21 and outputs a light reception command signal to the light receiving means 22. As a result, the light emitting means 21 emits light, and the light receiving means 22 receives light through the water tank 7. The amount of light received by the light receiving means 22 differs depending on whether or not there is recovered water in the water tank 7 at a position corresponding to the part where the light emitting means 21 and the light receiving means 22 are installed (when water is present). Light reception amount is small, and when there is no water, light reception amount is large). The output of the light receiving means 22 is amplified by the amplifier 23 and then supplied to the control / signal processing circuit 24. The control / signal processing circuit 24 determines whether or not the signal from the amplifier 23 corresponds to a predetermined water level, for example, stops cooking rice according to the water level or prompts the drainage of the recovered water 9 Is displayed to notify the user. For this notification, a buzzer or the like may be provided and sounded.

  Next, the mounting structure of the water level detection means 8 of the water level detection device 20 will be described.

FIG. 3 is an explanatory view showing the relationship between the water tank 7 and the water level detecting means 8 (however, the casing portion of the main body 1 is not shown in the figure), and FIG. FIG. The water tank 7 is made of a light-transmitting material (for example, polystyrene), and a concave portion 71 is formed on a part of the side surface (the side surface on the main body 1 side in the longitudinal direction of the water tank 7). Yes. The concave portion 71 is configured to have a predetermined depth along the height direction of the water tank 7 (trapezoidal in a plan view), two bent portions (incident surface, outgoing surface) 71a, 71b, and The transmission part 71c to tie is provided. The recess 71 functions as the reflection / transmission part 72 of the present invention. Note that the reflection / transmission unit 72 is not limited to the above-described form, and may be, for example, a triangular shape in a plan view.
The water tank 7 is configured in this way, and when the light is projected onto the bent portion 71a outside the water tank 7, the difference in refractive index (water and air) due to the presence or absence of water is detected inside the water tank 7. It is formed so that light is reflected or transmitted and the optical path is changed. When there is no water, reflected light is obtained from the bent portion 71b. As an example of the shape of the recess 71, a tank thickness of 2.0 mm, a bent part angle of 45 degrees (inside), 10 degrees (outside), a transmission part distance of 20 mm, and a transmission part thickness of 3.0 mm are configured.

  Water level detection means 8 (8a to 8c) are arranged at a position facing the recess 71 of the water tank 7 and corresponding to the measured water level. In the water level detection means 8, three sets of light emitting elements 21a to 21c and light receiving elements 22a to 22c are attached to a substrate 31 (see FIG. 4), and each set is connected to water level detection means 8a, 8b, 8c as necessary. Called.

  FIG. 4 is a view showing a mounting structure of the water level detecting means 8. Here, the water level detection means 8a will be described. Window members 33 and 34 are provided in the casing 1a of the main body 1 interposed between the water level detection means 8a (for example, the light emitting element 21a and the light receiving element 22a) and the water tank 7. For example, the window members 33 and 34 transmit 80% or more of light in a wavelength band of light used for at least water level detection of the light emitting element 21a and the light receiving element 22a. A window material having a light transmittance of 20% or less in other wavelengths, particularly in the visible light wavelength band, may be used. By using such window members 33 and 34, the user can enter the main body 1 from the inside. The installed water level detection means 8 cannot be seen and the design is improved.

A support 35 is interposed between the water level detection means 8 and the housing 1a. The support 35 serves to support the water level detection means 8 and to be attached to the housing 1a. In addition, the support 35 also serves to accurately guide or correct the light emitting element and the light receiving element to predetermined positions when the light emitting element and the light receiving element are soldered to the water level detecting means 8.
Openings 36a and 37a are formed in the support 35 at positions facing the light emitting element 21a and the light receiving element 22a. A light absorbing member or paint made of a carbon material such as carbon black is applied to the inner walls of the openings 36a and 37a and the periphery of the window members 33 and 34. In the following description, an example in which a paint is applied will be described, and it will be referred to as a light absorbing coating film 51. In this way, by providing the light absorbing coating film 51 on the inner walls of the openings 36a and 37a and the periphery of the window members 33 and 34, it is possible to suppress the reflected light at the place where light hits other than for detecting the members around the optical path. This reduces stray light and reduces false positives.

Next, the reflection and transmission of light in the water level detection means 8 and the water tank 7 will be described with reference to FIG.
The light emitting element 21 a emits light upon receiving a light emission command signal from the control / signal processing circuit 24, which enters the bent portion 71 a through the opening 36 a and the window member 33 of the support 33, and collects recovered water in the water tank 7. When there is no 9, there is a reflection at the inner surface of the bent portion 71a and the bent portion 71b is reached via the transmitting portion 71c, and an outer surface of the bent portion 71b is reflected and exits from the bent portion 71b. The light reflected from the bent portion 71 b is received by the light receiving element 22 a via the window member 34 and the opening 37 a of the support 33, and transmitted to the control / signal processing circuit 24 via the amplifier 23. When the recovered water 9 is present in the water tank 7, the infrared light from the light emitting element 21a is transmitted through the bent portions 71a and 71b, and the amount of light received by the light receiving element 22a is small. It is grasped that it has reached.

As described above, in the first embodiment, when the water level detection unit 8 is provided, the positional deviation and bending of the light emitting unit 21 and the light receiving unit 22 are efficiently corrected on the substrate to suppress the installation variation. A water level detection device with high detection accuracy is realized.
Moreover, in this Embodiment 1, said water level detection apparatus 20 is integrated in the heating cooker 100, As mentioned above, the water level of the water tank 7 can be detected with a sufficient precision, Therefore For this water level Appropriate control based on this is possible.
Embodiment 2

  In the first embodiment, the basic configuration and operation of the water level detection device and the heating rice cooker provided with the water level detection device are described. In the second embodiment, the structure, function and effect of the tank cover will be described.

  FIG. 5 shows a cross-sectional view of the main body of the heating cooker when the water level detecting means 20, the water tank 7 and the tank cover 15 are installed. As described above, when there is no water in the water tank 7, the light projected from the light emitting means 21 passes through a predetermined optical path in the water tank, reaches the light receiving means 22, and the light receiving means 22 receives the received light. A signal corresponding to the strength is output. As described above, when there is water in the water tank 7, the light projected from the light emitting means 21 once enters the water tank, but does not reflect on the bent portion 71 b and enters the tank filled with water. proceed. Therefore, most of the light projected from the light emitting means 21 does not reach the light receiving means 22, and the signal output from the light receiving element 22a is close to zero, but not completely zero. This is mainly due to the fact that the light projected from the light emitting means 21 is reflected and received by the path shown by the dotted arrow in the drawing, that is, the light projected inside the tank cover.

  Therefore, by reducing the intensity of the light that is reflected by this tank cover and reaches the light receiving element, the difference between the output signals of the light receiving means 22 when there is water in the water tank 7 and when there is no water is increased. A water level detection device 20 having the capability is obtained.

As shown in FIG. 6, an antireflection layer is formed on the inner side of the tank cover by applying a paint having a low reflectance in the wavelength band of light used for the water level detecting means 8 to absorb the light projected from the light emitting means 21. By suppressing reflection, a water level detection device with high detection performance can be obtained.
For example, when the light emitting means 21 and the light receiving means 22 using optical characteristics in the near-infrared wavelength region are used, an example of a paint having low reflectance is a paint containing carbon black having an absorption wavelength from visible to near infrared. is there.

  FIG. 10 is a cross-sectional view of the support 35 on the light receiving element side. The cylindrical portion of the support tool 35 is designed so that the thickness of the support tool is reduced at the tip and thinned inward, and the diameter of the cylindrical portion of the support tool 35 increases toward the tip. If it is not such a shape, the light to be incident is blocked and the detection accuracy is lowered.

As shown in FIG. 7, the resin material forming the tank cover 15 is mixed with a paint having a low reflectance in the light wavelength band used for the water level detection means 8, thereby reducing the reflectance of the tank cover itself and suppressing the reflection. By doing so, a water level detection device with high detection performance can be obtained.
For example, the above-mentioned effect can be obtained by mixing the carbon black with the resin and molding the tank cover 15 as described above.

  As described above, the use of carbon black as a material having a low reflectivity can achieve the above effect. However, the inside of the cover is black, which is not desirable in design. Therefore, when the wavelength band of the light used for the water level detection means is visible to near infrared as described above, for example, red is higher in absorption than white, so that reflection can be suppressed. The above effect is obtained more strongly in red. In this way, the paint is selected while looking at the balance with the design.

  FIG. 8 shows that the same effect can be obtained by increasing the surface roughness of the surface of the tank cover 15 facing the water level detection means 8 to make the surface rough. When there is water in the water tank 7, the light projected from the light emitting means 21 passes through a predetermined path, reaches the tank cover 15, and is reflected by the tank cover surface. Thus, the ratio of light reaching the light receiving element is reduced, and the light intensity is reduced. Accordingly, the apparent reflectivity of the tank cover surface when viewed from the light receiving element 22a is lowered, whereby the above-described effect can be obtained and a water level detecting device with high detection performance can be provided.

  FIG. 9 shows a longitudinal sectional view of the main body of the heating cooker when the water level detection device 20, the water tank 7 and the tank cover 15 are installed. Since the inner surface of the tank cover 15 is inclined not 90 degrees with respect to the optical axis of the water level detecting means, the light reflected from the light emitting means 21 is reflected upward or downward. . FIG. 9 shows an example in which the inner surface of the tank cover is inclined in the direction opposite to the water level detecting means 8 as it goes upward. In this case, the light reflected by the tank cover is reflected upward of the water level detection device 20 to reduce the light reaching the light receiving means 22. By forming such a tank cover, the above-described effects can be obtained, and a water level detection device with high detection performance can be provided.

  FIG. 10 shows a longitudinal sectional view of the main body of the heating cooker when the water level detection device 20, the water tank 7 and the tank cover 15 are installed. When the surface of the water tank 7 in contact with the tank cover 15 has a concave lens portion 17 that becomes thin with a certain thickness at the height position in the optical axis of the water level detection device 20 and serves as a plano-concave lens. The light projected from the light emitting means 21 is diffused by the concave lens portion 17 and reflected by the tank cover, so that the light reaching the light receiving means 22 is reduced. By forming such a tank cover, the above-described effects can be obtained, and a water level detection device with high detection performance can be provided.

  For example, when the water tank is made of polymethylpentene having a refractive index of 1.59 and the optical path from the light emitting element 21a to the inside of the tank is 40 mm, the concave lens has a curvature of 23.6 mm, and the concave lens having a gentle curvature has the above-mentioned shape. Has the greatest effect.

  The plano-concave lens shape of the concave lens portion 17 may be formed so as to function as a cylindrical plano-concave lens by spreading in the horizontal direction of the water tank 7.

1 body, 1a housing, 2 rice cooker, 3 lid, 4, inner lid, 5 heating body, 6 steam pipe, 7 water tank, 8 water level detection means, 9 recovered water, 11 determination control means, 12 tank lid, 13 steam introduction pipe, 20 water level detection device, 21 light emitting means, 21a light emitting element, 22 light receiving means, 22a light receiving element, 23 amplifier, 24 control / signal processing circuit, 25 display, 26 electrode section, 31 substrate, 33 window material , 34 window material, 35 support, 36a opening, 37a opening, 38a support, 39a support, 40 cylindrical part, 41 convex part, 42 concave part, 43 magazine jig, 44 convex part, 45 top lid fastener, 51 light absorption film, 52 film, 71 recessed part, 71a bending part, 71b bending part, 71c transmission part, 72 reflection transmission part.

Claims (8)

Out of a water tank having a reflection / transmission part in which the amount of reflection and transmission of light changes depending on the presence or absence of liquid, light is received through the reflection / transmission part and light emitting means for emitting light toward the reflection / transmission part. A water level detection unit including a light receiving unit that generates and outputs a corresponding signal, a water level determination unit that determines a water level stored in a water tank based on a signal from the water level detection unit, and the water tank A water level detection device comprising a tank cover fixed in contact with a surface other than the water level detection unit. The water level detection device according to claim 1, wherein a reflectance is reduced in a wavelength band of light used for the water level detection means in the tank cover. The water level detection device according to claim 1, wherein a surface roughness of the tank cover with respect to the water level detection means is increased in the tank cover. 2. The water level detection device according to claim 1, wherein the inclination angle of the surface with respect to the water level detection means is continuously changed in the tank cover as it goes upward from the bottom surface. 2. The water level detection device according to claim 1, wherein a surface of the water tank that is in contact with the tank cover is thinned in a spherical shape at a wall surface and a height of the water tank with respect to the water level detection means. In the water level detection device according to claim 1, in the wall surface and height of the water tank facing the water level detection means, the thickness of the surface in contact with the tank cover is reduced to a spherical shape in the cross section in the height direction, and in the horizontal direction A water level detection device characterized by being thinned continuously, that is, in a cylindrical shape. A steam recovery device comprising the water level detection device according to claim 1. A cooking device comprising the steam recovery device according to claim 11.

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