JPH05333074A - Microwave sensor - Google Patents

Abstract

(57) [Summary] [Purpose] It is easy to manufacture and can be easily attached to an object such as a microwave oven. It has high thermal response, excellent heat resistance, and is manufactured at relatively low cost. A radio wave absorber 12 having a front surface for receiving microwaves and capable of absorbing the microwaves, a metal body 14 bonded to a position on the back surface of the radio wave absorber that does not receive the microwaves, and the metal body. Held by the thermistor element 16 for sensing the temperature of the radio wave absorber through the metal body
With. Preferably, the electromagnetic wave absorber is formed in a flat plate shape and has a joint portion 18 for joining the metal body at the center of the back surface thereof, and the thermistor element has leads 22 covered with an insulating material 20 at both ends thereof. However, the metal body has a slit 24 for inserting the thermistor element with leads and a locking groove 26 for mounting the microwave sensor 10 to the mounted body 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave sensor suitable for detecting a heating condition or a finishing condition of an object to be heated in a microwave heating device such as a microwave oven.

[0002]

2. Description of the Related Art Microwave ovens are equipped with various functions such as a function for thawing frozen food by microwave heating and a function for warming cold food. The microwave oven automatically controls the output of the magnetron that generates microwaves by detecting the heating status or finishing status of this type of food with a sensor.
Conventionally, a microwave heating device is provided with a device for detecting a microwave transmitted or reflected without being absorbed by an object to be heated, as a sensor for controlling the magnetron (for example, Japanese Patent Laid-Open No. 59-59-59). 207595, 5
9-207596, 62-79394), and a humidity sensor for detecting water vapor generated from food in the exhaust duct (for example, Japanese Patent Laid-Open No. 62-123226).
Alternatively, one provided with a temperature sensor composed of a thermistor for detecting the temperature of the heating chamber (for example, JP-A-60-17018).
8, JP-A-61-263092) and the like have been proposed.

However, in the case of detecting by the above microwave detecting device, the detection circuit is complicated and expensive, and the sensor is attached to the heating chamber, so that it is easily destroyed thermally, and the directivity of the antenna is strong and the object to be heated is heated. There is a problem that the detection output is easily affected by the shape of the object. Further, when the humidity sensor is used for detection, there is a problem that the heating condition cannot be accurately detected when the object to be heated is wrapped with wraps or aluminum foil. Further, when the temperature sensor is used for detection, the temperature sensor is far from the object to be heated, so that the temperature of the object to be heated cannot be directly measured, and the temperature sensor has a drawback that it is only a guide for cooking. In order to solve the above-mentioned various problems, the applicant of the present invention has applied for a patent for a microwave sensor having a radio wave absorber in the temperature sensing portion of a thermistor element (Japanese Patent Application No. 4-100348). As shown in FIG.
The microwave sensor 40 includes a thermistor element 42 with a lead 41, a metal encapsulation body 43 encapsulating the thermistor element 42, and a radio wave absorption layer 44 formed on the surface of the metal encapsulation body 43. Are fixed with a filler 46 in the metal envelope. The microwave sensor 40 directly detects the amount of microwave energy by heat generation of the radio wave absorption layer 44 when microwaves arrive and the resistance value of the thermistor element 42 changes. In this microwave sensor 40, the sensor 4 is attached to the frame 48 of the microwave oven.
In order to attach 0, a flange 43a is formed on the metal envelope 43, the flange 43a is joined to the attachment plate 50, and then the attachment plate 50 is attached to the frame 48 with the screw 50a.

[0004]

However, the conventional microwave sensor shown in FIG. 10 still has the following points to be improved. First, in order to manufacture the microwave sensor 40,
The step of fixing the thermistor element 42 with the lead 41 in the metal encapsulation body 43, and the electromagnetic wave absorption layer 4 on the surface of the metal encapsulation body 43.
The manufacturing process becomes complicated because a process for forming the No. 4 is required. Secondly, in order to mount the microwave sensor 40 on the microwave oven, the mounting plate 50, the screw 50a, and the like are required, so that mounting is troublesome. An object of the present invention is to provide a microwave sensor which is easy to manufacture and can be easily attached to an attached object such as a microwave oven. Another object of the present invention is to provide a microwave sensor which has a high thermal response and excellent heat resistance and which is relatively low in cost.

[0005]

In order to achieve the above object, as shown in FIGS. 1 and 2, the microwave sensor 10 of the present invention has a surface that receives microwaves and can absorb the microwaves. Radio wave absorber 12; this radio wave absorber 1
And a thermistor element 16 held by the metal body 14 and sensing the temperature of the radio wave absorber 12 through the metal body 14. It is a thing. In addition, the electromagnetic wave absorber 12 of the microwave sensor 10 is formed in a flat plate shape and has a joint portion 18 for joining the metal body 14 in the center of the back surface thereof. The thermistor element 16 with the lead 22 has a lead 22 covered with 20.
Slit 24 for inserting and attaching microwave sensor 10
It is preferable to have a locking groove 26 for attaching the to.

[0006]

When the microwave reaches the microwave sensor 10, the radio wave absorber 12 absorbs the microwave and generates heat. This amount of heat generation changes according to the amount of microwave energy, and the electric resistance value of the thermistor element 16 that constitutes the microwave sensor 10 changes. The radio wave absorber 12 has a high thermal conductivity, that is, a high thermal response, and is excellent in heat resistance. This microwave sensor 1
In 0, the metal body 14 and the thermistor element 16 can be easily joined simply by inserting and crimping the thermistor element 16 in the slit 24. Further, the microwave sensor 10 can be easily attached to the attached body by engaging the attachment member of the attached body with the engagement groove 26.

An embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the radio wave absorber 12 constituting the microwave sensor 10 of the present invention is formed of radio wave absorber powder. This radio wave absorber powder is a ceramic powder having either or both magnetic properties and dielectric properties. As the electromagnetic wave absorber powder having magnetism, there is a ceramic powder containing ferrite or ferrite as a main component,
As the electric wave absorber powder having a dielectric property, SiC, Al ₂
One or more ceramic powders selected from the group consisting of O ₃ , B ₄ C, SrTiO ₃ , ZrO ₂ , Y ₂ O ₃ , PZT and PLZT can be mentioned. Further, as a radio wave absorber powder having both magnetism and dielectric property, there is disclosed in Japanese Patent Laid-Open No. 1-2914.
06, a magnetic material powder containing ferrite fine powder having a particle size of 50 μm or less and a dielectric material powder containing a perovskite type compound such as BaTiO ₃ having a particle size of 10 μm or more are mixed, and this mixture is mixed. 1000-150
A material fired at 0 ° C., which forms a reaction phase between ferrite particles or between ferrite particles and perovskite type compound particles, and powdered ceramics having both magnetic loss and extremely large dielectric loss. Is mentioned.

The radio wave absorber 12 is formed by compressing the ceramic powder of the magnetic material and the dielectric material described above together with the binder into a flat plate and firing the compact, or by kneading the ceramic powder with the binder and the solvent. It is prepared by preparing a slurry by molding the slurry into a sheet, punching it into a flat plate, and firing it. In this example, as shown in FIG. 2, the radio wave absorber 12 has a disk shape with a diameter of 10 to 30 mm and a thickness of about 1 to 3 mm, and the surface is a surface for receiving microwaves. In addition, a metal layer 18 serving as a joint for joining the metal body 14 is formed on the center of the back surface of the radio wave absorber 12.
Is formed. The metal layer 18 is made of Cu-Zn, Zn, A.
It is made of a metal such as g or Ag-Pd, and is formed by thermal spraying, vapor deposition, printing of a metal paste, or the like.

As shown in FIGS. 1 to 5, a slit 24 having a predetermined depth is formed in the metal body 14 through the center of its upper surface. In this example, the metal body 14 has a diameter of 5 to 10 m.
It has a cylindrical shape with a thickness of 3 to 5 mm. The slit 24 is formed from the upper surface of the metal body 14 to the center in the thickness direction, and the thermistor element 1 with the lead 22 is provided at the bottom of the slit 24.
A through hole wider than the slit 24 for inserting 6 is formed. The microwave sensor 1 is provided on the outer peripheral surface of the metal body 14.
Locking groove 2 for attaching 0 to an attached object such as a microwave oven
6 is formed. Further, it is desirable that the metal body 14 is made of a metal such as Cu—Zn alloy or aluminum that has good heat conductivity and high heat resistance.

The thermistor element 16 is preferably small and has heat resistance, and a glass-coated bead type coated with glass as shown in FIG. 6 has heat resistance of about 200 to 400 ° C., which is preferable. The glass-coated bead-type thermistor element is made by welding two leads 22 having a small diameter to both ends of the bead-type thermistor element 16, and then coating and welding the element portion with glass. In this example, the lead 22 is covered at its portion close to the thermistor element 16 with a heat-resistant insulating material 20 such as Teflon or polyimide.

In the method of manufacturing the microwave sensor 10, first, as shown in FIG. 7, a flat wave absorber 12 is prepared.
A metal layer 18 is formed at the center of the back surface of the radio wave absorber 12 to serve as a joint for joining the metal body 14. The metal body 14 is bonded onto the metal layer 18 using a bonding technique such as high temperature soldering or brazing. Next, the insulating material 20
The thermistor element 16 having the lead 22 covered with is inserted into the slit 24 of the metal body 14 (see FIGS. 1 to 5). At the time of this insertion, as shown in the drawing, a part of each lead 22 is bent in advance at a right angle so that the lead-out end portion of the lead 22 is hidden behind the radio wave absorber 12 after the insertion so as not to receive microwaves. After inserting the thermistor element 16 into the slit 24, a force is applied to the metal body 14 from the direction of the arrow A as shown in FIG. 2 to crimp the thermistor element 16 into the through hole at the bottom of the slit 24. Fix it. The microwave sensor 10 of the present invention is not limited to household microwave heating devices such as microwave ovens, but can also be applied to microwave detection in industrial microwave heating devices.

An example of attaching the microwave sensor 10 of the present invention to the microwave oven 30 to be attached will be described with reference to FIGS. 8 and 9. First, an opening 32 for mounting the microwave sensor 10 is provided on a part of the inner wall 31 of the microwave oven 30. In the vicinity of the opening 32 on the outer side of the inner wall 31, the base ends of the fittings 34, 34 made of a pair of leaf springs facing each other are bonded. The tip ends of the pair of fittings 34, 34 are provided outside the inner wall 31 so as to face the opening 32, and
There is an interval for engaging with the engaging groove 26. Also the fixture 3
Each of the tips of the inner walls 3 and 4 makes the surface of the electromagnetic wave absorber 12 flush with the surface of the inner wall 31 when locked in the locking groove 26.
Has a height from 1. In order to mount the microwave sensor 10 on the opening 32 of the microwave oven configured as described above, the opening 32 of the microwave sensor 10 is exposed from the heating chamber side of the microwave oven 30 so that the leads 22 are exposed to the outside of the inner wall 31. Each of the fixtures 34, 34 into the metal body 1.
4 is locked in the locking groove 26.

[0013]

As described above, according to the microwave sensor of the present invention, the amount of microwave energy is converted into heat energy by the radio wave absorber, and this is detected by the thermistor element. The amount of absorbed microwave energy can be detected directly and easily. Since this microwave sensor does not require an antenna or a waveguide as in the past, it has a simple structure and can be miniaturized. Further, since the thermistor element with leads can be attached to the metal body by simply inserting and crimping the thermistor element in the slit provided in the metal body, the microwave sensor can be easily manufactured. Further, the metal body is provided with a locking groove for mounting the microwave sensor to the mounted body, and the mounting member of the mounted body is locked in the locking groove to easily mount the microwave sensor on the mounted body. You can

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the microwave sensor of the present invention taken along the line II of FIG.

FIG. 2 is an external perspective view of a microwave sensor of the present invention.

FIG. 3 is a plan view of a metal body that constitutes the microwave sensor of the present invention.

FIG. 4 is a front view of the metal body.

FIG. 5 is a central longitudinal sectional view of the metal body.

FIG. 6 is a plan view of a thermistor element that constitutes the microwave sensor of the present invention.

FIG. 7 is a diagram showing a manufacturing process of the microwave sensor of the present invention.

FIG. 8 is a cross-sectional view showing a state in which the microwave sensor of the present invention is attached to a microwave oven of an attached body.

FIG. 9 is a plan view of the fixture.

FIG. 10 is a cross-sectional view of a conventional microwave sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Microwave sensor 12 Electromagnetic wave absorber 14 Metal body 16 Thermistor element 18 Joint part 20 Insulating substance 22 Lead 24 Slit 26 Locking groove 30 Attached body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Koshimura 2270 Yokose, Yokose-cho, Chichibu-gun, Saitama Sanryo Materials Co., Ltd.

Claims (2)

[Claims] 1. A radio wave absorber (12) having a front surface as a surface for receiving microwaves and capable of absorbing the microwaves, and a metal bonded to a back surface of the radio wave absorber (12) at a position not receiving the microwaves. A body (14) and a thermistor element (1) which is held by the metal body (14) and senses the temperature of the radio wave absorber (12) through the metal body (14).
6) Microwave sensor with and. 2. A radio wave absorber (12) is formed in a flat plate shape, and a joining portion (1) for joining a metal body (14) to the central portion of the back surface thereof.
8), the thermistor element (16) has a lead (22) covered with an insulating material (20) at both ends thereof, the metal body (14) is the thermistor element with the lead (22) (1)
The slit (24) for inserting the 6) and the microwave sensor (1
The microwave sensor according to claim 1, further comprising a locking groove (26) for mounting the (0) on the mounted body (30).