JP3031642U - Water temperature sensor with liquid level detection element - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a water temperature sensor with a liquid level detecting element that operates accurately in a long life without taking up a large space, as a sensor section that can be said to be a command tower of a heater heating prevention device. SOLUTION: A case in which one surface also serves as a prism reflection surface,
A thermistor chip, a photoreflector, a thermistor chip and a photoreflector are mounted side by side, and the thermistor chip is covered in the gap between the wiring board and the case, on the surface of which the electronic circuit that guides these outputs is formed. As described above, the liquid-tightly filled resin excellent in thermal conductivity and the liquid-tightly filled optical system resin so as to cover the photo reflector are provided in the gap between the wiring board and the case. ..

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

 This invention belongs to a water temperature sensor with a liquid level detecting element. This water temperature sensor can be suitably used as a part of a water temperature control device for an ornamental fish tank or a part of a toilet hot water tank such as a washlet.

[0002]

[Prior art]

 The water temperature control device for the aquarium that houses ornamental fish such as tropical fish and goldfish is a temperature sensor that detects the water temperature, a submersible heater that raises the water temperature, and a control that controls the heat generation amount of the submersible heater based on the output from the temperature sensor. It consists of a substrate.

By the way, in the previous Great Hanshin Earthquake, the water tank was damaged by an unexpected external force due to the earthquake, the heater was in an unheated state, and the heat was abnormally generated, resulting in many accidents leading to a fire. Therefore, recently, a technique for preventing the heater from being heated empty has been developed. For example, the following four types are known as technologies for preventing the heater from being heated in the air. First, a thermostat is built in the heater, and when the heater abnormally generates heat, the thermostat operates and turns off the heater power.

Second, the liquid level sensor is arranged near the heater, and when the liquid level sensor detects that the liquid level has dropped to the extent that the heater is exposed from the water surface, the detection signal is output. The heater power is turned off. In this case, as the liquid level sensor, a fixed electrode type, a float type and an optical type are known. In the fixed electrode type, one electrode made of a conductive resin is attached to the tip of a thin electric wire, and the other electrode is further attached via an insulating resin to the tip of the thin electric wire to check the presence or absence of water depending on the conduction between these electrodes. Detect. The float type is equipped with a cylindrical stem with a pair of reed switches inside and a float with two magnets inside. The float is normally rising, but it is synchronized with the lowering of the liquid level along with the float. When the magnet comes out of the drive magnetic field range of the reed switch, the contact of the reed switch is turned off and the liquid level is detected. The optical type is, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 64-8636, a bag-shaped case in which one surface also serves as a prism reflecting surface, and a light emitting portion and a light receiving portion face the prism reflecting surface, respectively. As described above, the photoreflector housed in the case and the cap that liquid-tightly seals the opening of the case are provided, and when the prism reflection surface is out of the liquid, light is emitted between the light emitting unit and the light receiving unit. A coupling path is formed, and when immersed in liquid, the optical coupling path is opened by the change in the refractive index and a liquid level detection signal is output.

Third, a temperature sensor is arranged near the heater, and when the temperature sensor is removed from the water, the temperature drop caused by the heat of vaporization of the water adhering to the sensor element surface is detected to turn on the heater power supply. It turns it off.

[0006]

[Problems to be solved by the device]

 However, in the first technique described above, the thermostat does not operate until the heater heats up to a certain degree, so a flammable substance may cause a fire if it is near the heater. Among the second techniques, the fixed electrode type has a short life because the conductive resin forming the electrode is easily deteriorated. In the float type, if it is used for a long period of time, the float will stick to the stem due to stains such as mold and moss and will not move and will not operate. The optical system requires a liquid level detection unit including an amplifier circuit to be connected to the water temperature control device, so the volume occupied by the liquid level detection unit is increased and it is not suitable for a small Japanese house. In the third technology, an error is likely to occur when the temperature difference between water temperature and air temperature is small, and there is a large time lag until vaporization heat detection.

[0007] Therefore, an object of the present invention is to provide a water temperature sensor with a liquid level detection element that operates accurately in a long life without taking up a large space as a sensor section that can be said to be a command tower of an underwater heater dry heating prevention device. It is in.

[0008]

[Means for Solving the Problems]

 In order to achieve the object, a case whose one surface also serves as a prism reflection surface, a thermistor chip housed in the case, and a light emitting part and a light receiving part which are housed in the case An optical coupling path is formed between the light emitting part and the light receiving part when the surface is removed from the liquid, and when the surface is immersed in the liquid, the optical coupling path is opened by the change in the refractive index and a liquid level detection signal is output. A thermistor and a thermistor chip and photoreflector that are housed in the case side by side, and the wiring board on which the electronic circuit that guides these outputs is formed, and the thermistor in the gap between the wiring board and the case. A resin that is liquid-tightly filled to cover the chip and has excellent thermal conductivity, and an optical resin that is liquid-tightly filled to cover the photo reflector in the gap between the wiring board and the case. Characterized by comprising a.

In the sensor of the present invention, a thermistor chip as a temperature detecting element and a photo reflector as a liquid level detecting element are mounted on one wiring board. Therefore, it is not necessary to separately protect the thermistor chip and the photo reflector. Also, some of the circuits connected to them can be shared on the wiring board. For this reason, it does not occupy too much space. Furthermore, since each sensing element is covered with a case and the gap is liquid-tightly filled with resin, the element portion is hardly deteriorated. Since it detects the liquid level, it accurately outputs a signal regardless of the difference between the water temperature and the air temperature to prevent the heater from becoming empty. If the case itself is made of fluororesin or other resin that does not easily adhere to dirt, or is coated, there is no risk of malfunction due to dirt on the prism reflection surface.

[0010]

[Embodiment of device]

 An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a water temperature sensor with a liquid surface detecting element (hereinafter, simply referred to as “sensor”) of the embodiment, FIG. 2 is a right side view of the same, FIG. 3 is an axial front sectional view, and FIG. FIG. 5 is a front view showing a wiring board housed inside the case and components mounted therein, FIG. 5 is a right side view of the same, and FIG. 6 is an XY sectional view of FIG.

The sensor 1 includes a case 2 whose one surface parallel to the axial direction also serves as the prism reflection surface 21, and a wiring board 3 housed in the case. The wiring board 3 has a shape in which the width of the tip is smaller than that of the other portion, the thermistor chip 4 is mounted on the tip portion, and the photoreflector 5 is mounted at a position as close to the tip as the wide portion that follows. The wiring board 3 is further provided with an electronic circuit on its surface for guiding the output of the thermistor chip 4 and the photoreflector 5 to the outside. These electronic circuits are connected to the leads 31 via terminals (not shown) formed at the rear end of the wiring board 3. The leads 31 are bound together by a cabtire cord 32.

The case 2 includes a cup-shaped front end portion 22 having a small diameter and a body portion 23 having a large diameter continuously connected to the cup-shaped front end portion 22 corresponding to a small width portion of the wiring board 3. It is formed on the body portion 23. An epoxy resin 6 is liquid-tightly filled in a gap between the tip portion 22 and the wiring board 3 so as to cover the thermistor chip. The epoxy resin 6 contains ceramic powder such as alumina so as to have excellent heat conduction. Further, an optical epoxy resin 7 is liquid-tightly filled in a gap between the body portion 23 and the wiring board 3 so as to cover the photo reflector 5.

The material of the case 2 is selected according to the environment in which the sensor 1 is used. In this example, assuming that the tip portion 22 is used in seawater, the tip portion 22 is made of stainless steel that is hard to rust and has good thermal conductivity, and the body portion 23 is made of a fluorine-based hard resin, and both are bonded. The adhesive portion is sealed with the silicone resin 24. The tip portion 22 may be made of hard resin instead of stainless steel, instead of stainless steel. In this case, the tip portion 22 and the body portion 23 can be integrally molded. If it is assumed that the tip 22 is used in fresh water, the tip 22 may be made of inexpensive brass and the surface may be plated. Silicon resin 8 is further filled in the rear portion of the resin 7 so as to surround terminals (not shown) and leads 31.

The photo-reflector 5 integrally includes a light-emitting portion made of a light-emitting diode and a light-receiving portion made of a phototransistor. Then, it is normally immersed in the liquid and opens the optical coupling path between the light emitting part and the light receiving part to output the liquid level detection signal.However, when the prism reflection surface is removed from the liquid, that is, the water in the water tank is When the liquid level decreases and falls below the sensor 1, the optical coupling path is formed by the change in the refractive index, and the non-liquid level detection signal is output.

Since the sensor 1 detects the liquid surface based on the photoelectric effect of the photo reflector 5 as described above, the liquid surface can be detected accurately and quickly. Further, since the distance between the thermistor chip 4 and the outer surface of the tip portion 22 of the case 2 is short, and the resin having excellent thermal conductivity is interposed between them, the heat of water in the tank can be quickly generated. It is transmitted to chip 4. Therefore, the water temperature can also be measured accurately. Moreover, since the thermistor chip 4 and the photo reflector 5 are mounted on one wiring board 3 and housed in one case 2, the sensor occupies a smaller volume than individually housing them.

Moreover, since the spaces inside the case 2 are filled with the resins 6, 7, and 8, dew condensation inside the case 2 due to changes in the outside temperature is prevented. Therefore, parts such as the thermistor chip 4 and the photo reflector 5 are not destroyed by rusting of each metal terminal or short circuit. Therefore, the life of the sensor 1 is long.

When the water tank is placed indoors, light from a fluorescent lamp or the like may enter the light receiving portion of the photo reflector 5 and erroneously output the non-liquid level detection signal. For this, as shown in FIG. 7, a cover 9 made of a light shielding material is put on the outside of the case. The cover 9 is in the shape of a box with a circular cross section that surrounds the entire case 2, but water inlets / outlets 91, 92, 93 are provided at a total of three locations, namely, two locations above and below the photoreflector 5 and a bottom location. And a water channel 94 communicating with these entrances and exits in front of the prism reflection surface 21. By doing so, the light outside the cover 9 is blocked, so that the light receiving section of the photoreflector 5 receives only the light emitted from the light emitting section, and malfunction does not occur.

[0018]

[Effect of device]

 As described above, according to the water temperature sensor with a liquid surface detecting element of the present invention, it is possible to prevent the heating of the heater in the water tank or the tank from being burnt accurately and in advance, without occupying too much space. Moreover, the sensor has a long life.

[Brief description of drawings]

FIG. 1 is a front view showing a water temperature sensor with a liquid surface detecting element according to an embodiment.

FIG. 2 is a right side view of the same.

FIG. 3 is an axially normal sectional view of the sensor.

FIG. 4 is a front view showing a wiring board housed in a case of the sensor and components mounted thereon.

FIG. 5 is a right side view of the same.

6 is an XY sectional view of FIG.

FIG. 7 is a right side view showing a place where a cover is attached to the sensor.

[Explanation of symbols]

 1 Water temperature sensor with liquid level detection element 2 Case 21 Prism reflection surface 3 Wiring board 4 Thermistor chip 5 Photoreflector 6 Resin with excellent thermal conductivity 7 Optical resin 8 Silicon resin 9 Cover

Claims (6)

[Scope of utility model registration request] 1. A case, one surface of which also serves as a prism reflecting surface, a thermistor chip housed in the case, and a light emitting portion and a light receiving portion which are housed in the case, and the prism reflecting surface is made of liquid. A photoreflector that forms an optical coupling path between the light emitting part and the light receiving part when it is removed, and opens the optical coupling path due to the change of the refractive index when it is immersed in the liquid, and outputs a liquid level detection signal. The thermistor chip and the photo reflector are housed side by side, and the wiring board on which the electronic circuit that guides these outputs is formed is placed in a liquid-tight manner so that the gap between the wiring board and the case covers the thermistor chip. It is equipped with a resin with excellent thermal conductivity filled in the optical system and an optical system resin that is liquid-tightly filled in the gap between the wiring board and the case so as to cover the photo reflector. The liquid level sensing device with a water temperature sensor for a. 2. The water temperature sensor with a liquid surface detecting element according to claim 1, wherein the case has an outer diameter around the thermistor smaller than an outer diameter around the photo reflector. 3. The water temperature sensor with a liquid surface detecting element according to claim 2, wherein the case has a closed front end, and the thermistor chip and the photo reflector are arranged in that order from the front end. 4. The water temperature sensor with a liquid surface detecting element according to claim 1, wherein the resin having excellent thermal conductivity is an epoxy resin containing ceramic. 5. A cover for enclosing the case so as to block light outside the case that is about to enter the photoreflector and to form a water channel communicating with the outside in front of the prism reflection surface. A water temperature sensor with a liquid level detecting element according to any one of 1 to 4. 6. The water temperature sensor with a liquid level detecting element according to claim 1, which is mounted on an aquarium for aquarium fish or a hot water tank for cleaning a toilet.