JP2678097B2 - Humidity sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for automatic cooking control of a microwave oven, and more particularly to a humidity sensor provided with measures against high frequency noise.

[0002]

2. Description of the Related Art The appearance and structure of a conventional humidity sensor is shown in FIG.
5A and 5B, and the wiring of the humidity sensor is shown in FIG.

The above humidity sensor uses a glass-coated minute thermistor as a heat-sensitive element. An open container 81 made of metal and a closed container 82 made of metal containing dry air contain the thermistor.

The open container 81 and the closed container 82 are placed on a soaking holder 85 so as to be soaked. The open container 81 and the closed container 82 are covered with a metal sensor cover 83 and are electromagnetically shielded. Further, a shield wire 84 is used as a conductor wire connected to the thermistor.

Since the function of the humidity sensor to sense the humidity is well known, its explanation is omitted.

The sensor cover 83 and the shielded wire 84
Prevents the microwave leaking from the microwave generator, which is the heating source of the microwave oven, to the humidity sensor from entering the thermistor. Therefore, the microwave of the microwave generator can be prevented from directly heating the thermistor of the humidity sensor, and the microwave can be prevented from directly changing the resistance value of the thermistor. Thus, the humidity sensor prevents the output value of the humidity sensor from being changed by the microwave.

[0007]

However, in the above-mentioned conventional humidity sensor, it is necessary to use a shield wire as a conductor wire connected to the thermistor of the humidity sensor in order to cut off leaked microwaves, so that the cost is relatively high. There is a problem of becoming.

Therefore, an object of the present invention is to provide a humidity sensor which does not need to use a shield wire as a conductor wire connected to a thermistor as a heat sensitive element.

[0009]

In order to achieve the above object, the humidity sensor of the first invention comprises a first heat sensitive element housed in a metal airtight container containing dry air and a vent hole on the outer peripheral surface. A second heat-sensitive element housed in an open container made of metal and having one end fixed to one surface of the substrate, and supporting the closed container and the open container on the substrate with a gap between the substrate. A soaking holder made of metal having a terrace, a ground conductor formed on one surface of the substrate, lead wires of the first and second heat sensitive elements formed on the other surface of the board, and another lead wire. And a wiring pattern formed on one surface of the substrate, having one end connected to the wiring pattern and the other end open, and a filter pattern having a length of about ¼ wavelength of a high frequency noise component, Fixed to the other side of the board, It is characterized in that it comprises a metal sensor cover for covering the.

The humidity sensor of the second invention comprises a first thermosensitive element housed in a metal airtight container containing dry air, and a first heat sensitive element housed in a metal open container having a ventilation hole on its outer peripheral surface. A heat-sensitive element of No. 2 and a metal fixed to one surface of the substrate to cover the one surface of the substrate and have a terrace for supporting the closed container and the open container on the substrate with a gap between the substrates. Made of a uniform heat holder, a grounding conductor formed on the other surface of the substrate, and wiring formed on one surface of the substrate and connecting the lead wires of the first and second heat-sensitive elements to another lead wire. A pattern and a filter pattern formed on one surface of the substrate, having one end connected to the wiring pattern and the other end opened, and having a length of about ¼ wavelength of a high frequency noise component. There is.

Further, the humidity sensor of the third invention is such that the first heat-sensitive element housed in a metal airtight container containing dry air, and the first heat sensitive element housed in a metal open container having a ventilation hole on the outer peripheral surface. A heat sensitive element of No. 2 and a metal fixed to one surface of the substrate and covering the one surface of the substrate and grounded, and having a terrace for supporting the closed container and the open container on the substrate with a gap from the substrate. And a wiring pattern formed on the other surface of the substrate for connecting the lead wires of the first and second thermosensitive elements to another lead wire, and the other surface of the substrate. , One end is connected to the above wiring pattern and the other end is opened, and the high frequency noise component is approximately 1 /
A filter pattern having a length of four wavelengths and a sensor cover made of metal, which is fixed to the other surface of the substrate and covers the wiring pattern, are provided.

[0012]

According to the first invention, the substrate, the filter pattern connected to the wiring pattern formed on the other surface of the substrate, and the ground conductor formed on the one surface of the substrate form a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from another lead wire connected to the lead wires of the first and second thermosensitive elements via the wiring pattern.

Therefore, it is not necessary to use an expensive shield wire as the other lead wire to prevent microwaves from entering the other lead wire, and a normal lead wire may be used as the other lead wire. Therefore, the cost can be reduced. The wiring pattern formed on the substrate is electromagnetically shielded by a metal sensor cover that covers the wiring pattern. In this way, microwaves are prevented from entering the heat-sensitive element.

According to the second invention, the substrate, the filter pattern connected to the wiring pattern formed on the one surface of the substrate, and the ground conductor formed on the other surface of the substrate form a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from another lead wire connected to the lead wires of the first and second thermosensitive elements via the wiring pattern. Therefore, it is not necessary to use an expensive shielded wire as the other lead wire to prevent microwaves from entering the other lead wire, and a normal lead wire may be used as the other lead wire. You can go down. Further, the wiring pattern formed on the one surface of the substrate is electromagnetically shielded by a metal soaking holder that covers the one surface of the substrate. In this way, microwaves are prevented from entering the heat-sensitive element. Since the heat equalizing holder also serves as an electromagnetic shield for the wiring pattern, it is not necessary to provide a metal sensor cover dedicated to the electromagnetic shielding of the wiring pattern. Therefore, the humidity sensor of the present invention can be reduced in cost and downsized. Further, due to this miniaturization, the constraint condition when mounting the humidity sensor in a microwave oven or the like can be relaxed.

According to the third invention, the substrate, the filter pattern connected to the wiring pattern formed on the other surface of the substrate, and the one surface of the substrate fixed to cover the one surface of the substrate and are grounded. A soaking holder made of metal constitutes a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from another lead wire connected to the lead wires of the first and second thermosensitive elements via the wiring pattern.
Therefore, by using an expensive shielded wire as the other lead wire, it is not necessary to prevent the microwave from entering the other lead wire, and a normal lead wire may be used as the other lead wire, The cost can be reduced.

Further, since the heat equalizing holder also serves as a ground conductor, it is not necessary to form a ground conductor only for the microstrip on the substrate, and the cost can be reduced. The wiring pattern formed on the other surface of the substrate is electromagnetically shielded by a metal sensor cover that covers the wiring pattern. In this way,
Microwaves are prevented from entering the heat sensitive element.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments.

FIG. 1A shows the structure of the humidity sensor of the first embodiment of the invention. In this embodiment, an open container 1 made of metal having ventilation holes on the outer peripheral surface thereof and a closed container 2 made of metal containing dry air are provided, and the open container 1 and the closed container 2 are each provided as a heat sensitive element inside. Holds the thermistor.

The open container 1 and the closed container 2 are usually
It is equipped with a terminal block and a can. Then, as shown in FIG. 1 (D), in order to insulate the open container 1 from the thermistor lead 13 of the thermistor, an insulating glass 7 is fitted between the terminal block of the open container 1 and the thermistor lead 13. A hermetic structure is formed. Further, the closed container 2 also adopts the above hermetic structure. The insulating glass 7 is generally attached to the outside of the terminal block of the open container 1 at approximately 1
It is protruding about mm. Also, the thickness of the terminal block is approximately 0.3 mm.
It is about. In order to secure a space for the insulating glass 7 and the terminal block, the open container 1 and the closed container 2 are provided.
Is supported on the substrate 6 by a terrace portion of a soaking holder 5 made of metal fixed to the upper surface of the substrate 6 with a gap of about 2 mm from the substrate 6. A ground conductor 8 is formed on the upper surface of the substrate 6 as shown in FIG. Further, as shown in FIGS. 1A, 1B, and 1C, the thermistor lead 1 of the thermistor is formed on the lower surface of the substrate 6.
A wiring pattern 9 is formed to connect 3 and the lead wire 4 connected to the control unit (not shown). The thermistor lead 13 and the lead wire 4 are soldered to the wiring pattern 9. The wiring pattern 9 has approximately 1 high-frequency noise component.
/ 4 wavelength long open-ended filter pattern 11
Is succeeding. The substrate 6, the ground conductor 8, and the filter pattern 11 form a microstrip.

This microstrip serves as a filter for attenuating the microwaves that have entered from the lead wire 4. Therefore, even if a microwave enters from the lead wire 4, this microwave does not reach the thermistor. Therefore, it is not necessary to use an expensive shielded wire for the lead wire 4 to prevent microwaves from entering the lead wire 4, and a normal lead wire may be used as the lead wire 4, thus reducing the cost.

A metal sensor cover 3 covering the wiring pattern 9 is fixed to the lower surface of the substrate 6 to electromagnetically shield the wiring pattern 9. Thus,
The microwave is prevented from entering the thermistor as the heat sensitive element.

FIG. 4 shows the sensor output when the humidity sensor of the embodiment having the microstrip having the filter pattern 11 having a length of 9 mm receives high frequency noise.
It shows in (B). Further, FIG. 4A shows the sensor output when the humidity sensor obtained by removing the filter pattern 11 from the humidity sensor receives high frequency noise.

The filter pattern 11 shown in FIG.
The influence of the high frequency noise appearing on the sensor output of the humidity sensor having no temperature is almost not appearing on the sensor output of the humidity sensor having the filter pattern 11 shown in FIG.

Next, the structure of the humidity sensor of the second embodiment of the present invention is shown in FIG. In addition, in this embodiment, as shown in FIG.
The same parts as those of the embodiment of the first invention shown in FIG. In this embodiment, an open container 1 made of metal having ventilation holes on the outer peripheral surface thereof and a closed container 2 made of metal containing dry air are provided, and the open container 1 and the closed container 2 are each provided as a heat sensitive element inside. Holds the thermistor.

The open container 1 and the closed container 2 are usually
It is equipped with a terminal block and a can. Then, as shown in FIG. 1D, in order to insulate the open container 1 and the thermistor lead 13 of the thermistor, an insulating glass 7 is fitted between the terminal block of the open container 1 and the thermistor lead 13. A hermetic structure is formed. Further, the closed container 2 also adopts the above hermetic structure. The insulating glass 7 is generally attached to the outside of the terminal block of the open container 1 at approximately 1
It is protruding about mm. Also, the thickness of the terminal block is approximately 0.3 mm.
It is about. In order to secure a space for the insulating glass 7 and the terminal block, the open container 1 and the closed container 2 are provided.
Is supported on the substrate 6 by a terrace portion of a soaking holder 5 made of metal fixed to the upper surface of the substrate 6 with a gap of about 2 mm from the substrate 6. Further, a ground conductor 28 is formed on the lower surface of the substrate 6 as shown in FIG. 2 (B). As shown in FIGS. 2A, 2B, and 2C, the thermistor lead 13 of the thermistor is formed on the upper surface of the substrate 6.
And a wiring pattern 29 for connecting the lead wire 24 connected to a control unit (not shown). The thermistor lead 13 and the lead wire 24 are soldered to the wiring pattern 29. The wiring pattern 29 is connected with a filter pattern 31 having an open end and having a length of about ¼ wavelength of the high frequency noise component. The substrate 6 and the ground conductor 28
And the filter pattern 31 form a microstrip.

This microstrip serves as a filter for attenuating the microwaves that have entered from the lead wire 24. That is, even if microwaves enter from the lead wire 24, the microstrip serves as a filter that attenuates the microwaves. Therefore, even if the microwave enters from the lead wire 24, the microwave does not reach the thermistor. Therefore, using an expensive shield wire for the lead wire 24,
It is not necessary to prevent microwaves from entering the lead wire 24, and a normal lead wire may be used as the lead wire 24, so that the cost can be reduced.

Further, the metal soaking holder 5 covering the upper surface of the substrate 6 electromagnetically shields the wiring pattern 29 formed on the upper surface of the substrate 6. Further, since the space between the substrate 6 and the terrace portion of the soaking holder 5 is set to a minimum of about 2 mm, the electromagnetic shielding effect of the soaking holder 5 can be enhanced. As described above, since the heat equalizing holder 5 also serves as an electromagnetic shield for the wiring pattern 29, it is not necessary to provide a metal sensor cover dedicated to the electromagnetic shield of the wiring pattern 29. Therefore, it is possible to reduce the cost and the size of the humidity sensor. The miniaturization can alleviate the constraint condition when the humidity sensor is mounted on a microwave oven or the like.

Next, the structure of the humidity sensor of the third embodiment of the present invention is shown in FIG. In this embodiment, the first
The same parts as those in the embodiment of the invention are designated by the same reference numerals. In this embodiment, an open container 1 made of metal having ventilation holes on the outer peripheral surface thereof and a closed container 2 made of metal containing dry air are provided, and the open container 1 and the closed container 2 are each provided as a heat sensitive element inside. Holds the thermistor.

The open container 1 and the closed container 2 are usually
It is equipped with a terminal block and a can. Then, as shown in FIG. 1D, in order to insulate the open container 1 and the thermistor lead 13 of the thermistor, an insulating glass 7 is fitted between the terminal block of the open container 1 and the thermistor lead 13. A hermetic structure is formed. Further, the closed container 2 also adopts the above hermetic structure. The insulating glass 7 is generally attached to the outside of the terminal block of the open container 1 at approximately 1
It is protruding about mm. Also, the thickness of the terminal block is approximately 0.3 mm.
It is about. In order to secure a space for the insulating glass 7 and the terminal block, the open container 1 and the closed container 2 are provided.
Is supported on the substrate 6 by a terrace portion of a soaking holder 5 made of metal fixed to the upper surface of the substrate 6 with a gap of about 2 mm from the substrate 6. Further, the soaking holder 5 made of metal is grounded. As shown in FIGS. 3A, 3B, and 3C, the thermistor lead 13 of the thermistor and a lead wire 54 connected to a control unit (not shown) are connected to the lower surface of the substrate 6. The wiring pattern 59 is formed. The thermistor lead 13 and the lead wire 54 have a wiring pattern 59.
Soldered to. The wiring pattern 59 is connected to a filter pattern 61 having an open end and having a length of about ¼ wavelength of the high frequency noise component. The substrate 6;
The grounded soaking holder 5 and the filter pattern 6
1 and 1 form a microstrip.

This microstrip serves as a filter for attenuating the microwaves invading from the lead wire 54. Therefore, even if the microwave enters from the lead wire 54, the microwave does not reach the thermistor. Therefore, it is not necessary to use an expensive shielded wire as the lead wire 54 to prevent microwaves from entering the lead wire 54, and a normal lead wire may be used as the lead wire 54, which leads to cost reduction.

On the lower surface of the substrate 6, a metal sensor cover 3 covering the wiring pattern 59 is fixed,
The wiring pattern 9 is electromagnetically shielded. In this way, microwaves are prevented from entering the thermistor as the heat sensitive element.

Further, since the heat equalizing holder also serves as a ground conductor, it is not necessary to form a ground conductor only for the microstrip on the substrate, and the cost can be reduced.

[0033]

As is apparent from the above description, according to the first invention, the substrate, the filter pattern connected to the wiring pattern formed on the other surface of the substrate, and the filter pattern formed on the one surface of the substrate are formed. The ground conductor constitutes a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from another lead wire connected to the lead wires of the first and second thermosensitive elements via the wiring pattern.

Therefore, it is not necessary to use an expensive shield wire as the other lead wire to prevent microwaves from entering the other lead wire, and use a normal lead wire as the other lead wire. Because it is good, the cost can be reduced.

On the other hand, the wiring pattern formed on the substrate is electromagnetically shielded by a metal sensor cover that covers the wiring pattern. Therefore, microwaves can be prevented from entering the heat sensitive element.

According to the second invention, the substrate, the filter pattern connected to the wiring pattern formed on the one surface of the substrate, and the ground conductor formed on the other surface of the substrate form a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from the other lead wire connected to the lead wires of the first and second heat sensitive elements via the wiring pattern. Therefore, by using an expensive shielded wire as the other lead wire, it is not necessary to prevent the microwave from entering the other lead wire, and a normal lead wire may be used as the other lead wire, The cost can be reduced. Further, the wiring pattern formed on the one surface of the substrate is electromagnetically shielded by a metal soaking holder that covers the one surface of the substrate. Therefore, microwaves can be prevented from entering the heat sensitive element. Further, since the heat equalizing holder also serves as an electromagnetic shield for the wiring pattern, it is not necessary to provide a metal sensor cover dedicated to the electromagnetic shielding of the wiring pattern. Therefore, the humidity sensor of the present invention can be reduced in cost and downsized. Further, due to this miniaturization, the constraint condition when mounting the humidity sensor in a microwave oven or the like can be relaxed.

According to the third invention, the substrate, the filter pattern connected to the wiring pattern formed on the other surface of the substrate, and the metal which is fixed to the one surface of the substrate and covers the one surface of the substrate and is grounded. A soaking holder made of microstrip constitutes a microstrip. The microstrip serves as a filter for attenuating the microwaves that have entered from another lead wire connected to the lead wires of the first and second thermosensitive elements via the wiring pattern. Therefore, by using an expensive shielded wire as the other lead wire, it is not necessary to prevent the microwave from entering the other lead wire, and a normal lead wire may be used as the other lead wire, The cost can be reduced.

Further, since the heat equalizing holder also serves as a ground conductor, it is not necessary to form a ground conductor only for the microstrip on the substrate, and the cost can be reduced. The wiring pattern formed on the other surface of the substrate is electromagnetically shielded by a metal sensor cover that covers the wiring pattern. Therefore, microwaves can be prevented from entering the heat sensitive element.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a humidity sensor according to an embodiment of the first invention.

FIG. 2 is a structural diagram of a humidity sensor of an embodiment of the second invention.

FIG. 3 is a structural diagram of a humidity sensor of an embodiment of the third invention.

FIG. 4 is an output characteristic diagram of a humidity sensor that receives high frequency noise.

FIG. 5 is a diagram showing the appearance, structure, and wiring of a conventional humidity sensor.

[Explanation of symbols]

 1,81 Open container 2,82 Closed container 3,53 Sensor cover 4,24,54 Lead wire 5,85 Soaking holder 6 Substrate 8,28 Ground conductor 9,29,59 Wiring pattern 11,31,61 Filter pattern 13 Thermistor lead

Claims (3)

(57) [Claims] 1. A first heat-sensitive element housed in a metal airtight container containing dry air, a second heat-sensitive element housed in a metal open container having ventilation holes on the outer peripheral surface, and one surface of a substrate. A soaking container made of metal and having a terrace for supporting the closed container and the open container on the substrate with a gap between the substrate and a ground conductor formed on one surface of the substrate. And a wiring pattern that is formed on the other surface of the substrate and connects the lead wires of the first and second heat sensitive elements to another lead wire, and is formed on the one surface of the substrate, and one end of the wiring pattern is formed. And the other end is open,
A humidity sensor, comprising: a filter pattern having a length of about ¼ wavelength of a high frequency noise component; and a metal sensor cover fixed to the other surface of the substrate and covering the wiring pattern. 2. A first thermosensitive element housed in a metal airtight container containing dry air, a second thermosensitive element housed in a metal open container having ventilation holes on the outer peripheral surface, and one surface of a substrate. A soaking holder made of metal, which is fixed to and covers one surface of the substrate, and which has a terrace for supporting the closed container and the open container on the substrate with a gap between the substrate and the substrate; A ground conductor formed on the other surface of the substrate, lead wires of the first and second heat sensitive elements formed on one surface of the substrate,
A filter having a length of about ¼ wavelength of a high frequency noise component, which is formed on one surface of the substrate and has one end connected to the wiring pattern and the other end opened, which is formed on one surface of the substrate. Humidity sensor having a pattern for use. 3. A first thermosensitive element housed in a metal airtight container containing dry air, a second thermosensitive element housed in a metal open container having ventilation holes on the outer peripheral surface, and one surface of a substrate. A soaking holder made of metal having a terrace fixed on the one surface of the substrate while being covered with one surface of the substrate, and supporting the closed container and the open container on the substrate with a gap between the substrate and the substrate. A wiring pattern formed on the other surface of the substrate for connecting the lead wires of the first and second heat sensitive elements to another lead wire, and formed on the other surface of the substrate, and one end of which is connected to the wiring pattern. In addition, the other end is opened, and a filter pattern having a length of about ¼ wavelength of the high frequency noise component and a metal sensor cover fixed to the other surface of the substrate and covering the wiring pattern are provided. A characteristic humidity sensor.