CN104879798B - A kind of micro-wave oven for quickly heating weak wave absorbtion material - Google Patents

Abstract

The invention relates to a microwave oven which can be used for heating weak wave-absorbing substances, which can rapidly heat weak wave-absorbing substances, and even has a certain effect on heating difficult wave-absorbing substances. The microwave oven is characterized by an auxiliary electric field generating circuit, which is composed of an auxiliary electric field control circuit and positive and negative metal electrode plates. An auxiliary electric field, the auxiliary electric field makes the heated weak absorbing material undergo multiple polarizations, the electric dipole moment of the molecule further increases, and the polarized weak absorbing material can produce more Large combined electric field force and moment, more intense friction, extrusion, and collision between molecules, can quickly absorb microwave energy and convert it into self-heating energy, achieving the effect of rapid heating.

Description

A microwave oven for rapidly heating weak absorbing substances

technical field

The invention relates to a microwave oven for quickly heating weak wave-absorbing substances. Specifically, the microwave oven can quickly heat some weak wave-absorbing substances, and even works on heating difficult wave-absorbing substances, and belongs to the field of microwave heating.

Background technique

Microwave is a new technology that has emerged in recent decades. Compared with traditional heating, microwave has the advantages of internal heating, fast heating, clean and hygienic, easy automatic control, and energy saving. However, microwave heating is selective to materials, it is difficult to heat substances composed of weak polar molecules (weak absorbing substances), and it cannot heat substances composed of non-polar molecules (difficult to absorb waves), so it is difficult to achieve large-scale applications and limits development of the microwave industry.

In industry, auxiliary heating is generally used for weak absorbing materials, such as adding strong absorbing materials, Picket fence method, microwave absorber lined with silicon carbide, Patterson method, and adjustable microwave coupling window for single-mode cavity. These auxiliary heating methods have disadvantages: 1. The heating process is relatively complicated; 2. The energy loss is large, and it is necessary to do useless work to heat the strong absorbing material; 3. The weak absorbing material needs to be mixed with the strong absorbing material during the heating process. New impurities may be generated in weak absorbing substances.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the disadvantages of the auxiliary heating method, to apply microwaves widely in the industrial field, and to provide a microwave oven that can be used to rapidly heat weak absorbing substances by using the principle of dielectric polarization and microwave heating mechanism , the microwave oven also has a certain effect on the heating of difficult-to-absorb materials.

The technical solution of the present invention is: a microwave oven for rapidly heating weak wave-absorbing substances, comprising:

The main control circuit, the transformer circuit, the magnetron, the waveguide and the microwave cavity are characterized in that they also include: an auxiliary electric field generating circuit, which is used to generate an auxiliary electric field in the microwave cavity, so that the heated substance can be heated between the auxiliary electric field and the microwave cavity. Under the joint action of the microwave field generated by the magnetron, it can be heated rapidly.

The auxiliary electric field generating circuit includes: an auxiliary electric field control circuit and positive and negative metal electrode plates.

The auxiliary electric field generated by the auxiliary electric field generating circuit is a steady electric field.

The auxiliary electric field control circuit of the auxiliary electric field generating circuit is also used to control the intensity of the auxiliary electric field to be smaller than the electric field intensity of the microwave field generated by the magnetron.

The field strength of the auxiliary electric field is between 0.4 times and 0.6 times of the maximum value of the microwave electric field strength.

The positive and negative metal electrode plates of the auxiliary electric field generating circuit are symmetrically placed on two opposite sides of the microwave cavity, close to the inner surface of the microwave cavity.

The metal electrode plate is close to but not in contact with the inner cavity of the microwave cavity, and insulating ceramics are filled between the metal electrode plate and the inner cavity of the microwave cavity, and there is no space between the positive and negative metal electrode plates and the surface of the microwave cavity Insulating ceramic isolation over 2.5mm thickness.

The positive and negative metal electrode plates of the auxiliary electric field generating circuit are stainless steel electrode plates with a thickness between 3 mm and 12 mm. The higher the temperature, the larger the microwave cavity, and the thicker the positive and negative metal electrode plates.

The cavity of the microwave cavity is grounded.

The beneficial effects of the present invention are:

The invention utilizes the dielectric polarization principle and microwave heating mechanism to propose a rapid heating method under the joint action of the auxiliary electric field generated by the auxiliary electric field generating circuit and the microwave field generated by the magnetron. The heated substance undergoes the following polarizations: electronic displacement polarization, ion displacement polarization, ion relaxation polarization, and space charge polarization. The electric dipole moment of the polarized weak absorbing material and difficult absorbing material increases, which provides a prerequisite for the rapid heating of the microwave field.

According to the mechanism of microwave heating, when these substances with increased electric dipole moment are irradiated by microwave energy in the microwave cavity, they will obtain a larger combined electric field force and larger moment, and the collision and extrusion between molecules , The friction increases, the efficiency of converting microwave energy into heat energy further increases, and the microwave heating rate increases.

According to the microwave oven of the present invention, the heated weak absorbing material is placed under the double action of the auxiliary electric field and the microwave field, the auxiliary electric field mainly plays the role of polarization, and the microwave electric field plays the role of heating. Absorb microwave energy and convert it into its own heat energy, and the temperature increases rapidly. It not only has the advantages of conventional microwave ovens, but also overcomes the disadvantages of auxiliary heating methods, can heat weak absorbing substances that cannot be directly heated by conventional microwave ovens, and is also effective for heating difficult absorbing substances. The microwave oven of the invention can heat more substances and expand the application range of the microwave industry.

Description of drawings

The schematic block diagram of the circuit of Fig. 1 embodiment of the present invention;

The schematic diagram of the installation of the positive and negative metal electrode plates of Fig. 2 embodiment microwave oven of the present invention;

The difference between Fig. 3 kinds of nonpolar molecules, polar molecules with smaller dipole moment and larger polar molecules with electric dipole moment;

Figure 4 The force of polar molecules in the electric field;

Figure 5 Polarization of nonpolar molecules and weakly polar molecules in an electric field;

In the figure: 200-microwave oven for rapidly heating weak wave-absorbing material, 201-main display window, 202-control panel, 203-heated material (weak wave-absorbing material), 204-positive and negative metal electrode plates, 205-insulating ceramics.

detailed description

The present invention will be further described below in combination with the accompanying drawings and specific embodiments.

As shown in Figure 1, it is a schematic circuit diagram of a microwave oven for rapidly heating a weak absorbing material in this embodiment, specifically including:

Main control circuit 1 , transformer circuit 2 , magnetron 3 , waveguide 4 , microwave cavity 5 and auxiliary electric field generating circuit 6 . The auxiliary electric field generating circuit 6 is used to generate an auxiliary electric field in the microwave cavity, so that the material to be heated can be rapidly heated under the joint action of the auxiliary electric field and the microwave field generated by the magnetron 3 .

The auxiliary electric field generating circuit 6 includes: an auxiliary electric field control circuit and positive and negative metal electrode plates. The auxiliary electric field generated by the auxiliary electric field generating circuit 6 is a steady electric field.

The auxiliary electric field control circuit of the auxiliary electric field generating circuit 6 is also used to control the intensity of the auxiliary electric field to be smaller than the electric field intensity of the microwave field generated by the magnetron. If the field strength of the auxiliary electric field is greater than or equal to the electric field strength of the microwave field, then the microwave cannot heat the weakly absorbing substance.

The field strength of the auxiliary electric field is between 0.4 times and 0.6 times of the maximum value of the microwave electric field strength. If the field strength of the auxiliary electric field is too small, the polarization effect on the weak polar molecules is insufficient, and it is difficult to significantly increase the electric dipole moment of the molecules, then the effect of the auxiliary electric field is not very large, so the minimum magnification is selected as 0.4 times. The electric field intensity of described microwave field changes with time, in order to ensure that microwave field has sufficient heating time in one cycle, the intensity of auxiliary electric field should not be too large, consider the relation between peak value and effective value, so maximum magnification is selected as 0.6 times.

The positive and negative metal electrode plates of the auxiliary electric field generating circuit 6 are symmetrically placed on two opposite sides of the microwave cavity 5 , close to the inner surface of the microwave cavity 5 .

The positive and negative metal electrode plates of the auxiliary electric field generating circuit 6 are close to but not in contact with the cavity of the microwave cavity 5, and insulating ceramics are filled between the metal electrode plates and the cavity of the microwave cavity 5, and at the same time In order to prevent a small part of the microwave from leaking and losing from the insulating ceramics, the positive and negative metal electrode plates are isolated from the surface of the microwave cavity by insulating ceramics with a thickness not exceeding 2.5 mm.

The positive and negative metal electrode plates of the auxiliary electric field generating circuit 6 are stainless steel electrode plates. In addition to generating the auxiliary electric field, it can also reflect microwaves like a microwave cavity, so its thickness is between 3mm and 12mm. The higher the microwave cavity, the larger the thickness of the positive and negative metal electrode plates.

The cavity of the microwave cavity 5 is grounded.

220V, 50Hz alternating current flows into the microwave oven through the socket, first passes through the main control circuit 1 (fuse, switch, etc. will not be described in detail), and is supplied to the microprocessor, timing and power regulator, turntable circuit, lighting circuit, fan, and main display window, etc., then flows through the primary coil of the transformer and back to the outlet. Transformer circuit 2 divides 220V, 50Hz alternating current into three parts, the first part is auxiliary electric field generation circuit 6, after the process of voltage transformation, rectification and filtering, the voltage in the circuit is a stable voltage, and the auxiliary electric field control circuit then stabilizes After the power supply is processed, it is emitted into the microwave cavity through the positive and negative metal electrode plates; the second part of the commercial power is transformed into an alternating current of about 4V and applied to the cathode of the magnetron 3 to heat the filament of the magnetron 3, so that the cathode can Emitting electrons; the third part of the commercial power is boosted to a high voltage of about 4000V through high-voltage transformation, and after rectification, it is loaded on the anode of the magnetron 3, which is used to receive electrons. Under the joint action of the second part of the input and the third part of the input, after the hot electrons overflow from the cathode, under the joint action of the magnetic field force and the electric field force, they fly to the anode at high speed in a spiral shape, and also have the function of a resonant cavity, and the electrons oscillate into Microwaves are finally input into the furnace cavity through the waveguide 4 . In the microwave cavity 5, the heated substance quickly absorbs the microwave energy and converts it into its own heat energy under the double action of the microwave field generated by the magnetron 3 and the auxiliary electric field generated by the auxiliary electric field generating circuit 6, and the temperature rapidly rise.

As shown in FIG. 2 , a schematic diagram of the installation of the positive and negative metal electrode plates of the microwave oven according to the embodiment of the present invention. The microwave oven 200; the main display window 201 is located at the upper right corner, which can display heating time, power, heating mode, etc.; the control panel 202 is located at the lower right side, connected with the main control circuit, and can adjust the heating time, power, heating mode, etc.; The substance 203 is placed in the middle of the cavity of the microwave oven, which is a weak absorbing substance; the positive and negative metal electrode plates are marked as 204, through which a constant voltage is emitted into the cavity of the microwave oven to form a constant auxiliary electric field. Insulating ceramics 205 are filled between the inner cavity of the microwave cavity and the positive and negative metal electrode plates. In order to prevent microwave energy loss, the thickness of the insulating ceramics does not exceed 2.5mm.

From the perspective of the microstructure of matter, the molecules that make up matter can be divided into non-polar molecules and polar molecules. As shown in Figure 3, when there is no electric field, the molecules or atoms that make up the dielectric, in which the center of the positive charge of the nucleus coincides with the center of the negative charge of the electrons distributed around the nucleus, are neutral to the outside, which means Class molecules are called non-polar molecules; contrary to non-polar molecules, when there is no external electric field, the positive and negative centers of the molecules or atoms that make up the dielectric do not coincide, that is, the molecules have a dipole moment, and these molecules are called polar molecules. In the microwave field, dielectrics can generally be divided into non-polar dielectrics, weakly polar dielectrics, and polar dielectrics with large electric dipole moments. Non-polar dielectrics are composed of non-polar molecules. Since there is no electric dipole moment, they do not absorb microwave energy. We call them difficult or non-absorbing substances; weakly polar dielectrics are composed of polar molecules with small electric dipole moments. , although there is a certain electric dipole moment, but the electric dipole moment is very small, so it can absorb a small amount of microwave energy, and the heating rate is very slow when heated in a microwave field. We call this kind of material a weak absorbing material; Polar molecules with large dipole moments can quickly dissipate microwave energy in a microwave field due to their large electric dipole moments, and heat up quickly in a microwave field. We call them microwave-absorbing substances.

According to the polarization principle of dielectric physics, when the medium is affected by the electric field force, it will happen: 1. Electronic displacement polarization: the relative displacement of the positive and negative charge centers in each molecule or atom; 2. Ion displacement polarization: positive , Negative ions produce relative displacement, positive ions move along the direction of the electric field, and negative ions move against the direction of the electric field; 3. Ion relaxation polarization: This polarization occurs in a medium composed of ions or containing ionic impurities, and is a certain substance existing in the dielectric. 4. Space charge polarization: under the action of an electric field, the positive and negative free charges that were originally chaotically arranged tend to have a tendency The regular movement process leads to the accumulation of more negative charges near the positive plate, and the redistribution of space charges actually forms the space charge polarization of the medium. It occurs in inhomogeneous media and crystals with defects. For actual crystal media, the internal free charges move under the action of an electric field, which may be eliminated by the unavoidable defects in the crystal (such as lattice vacancies, impurity centers, Dislocations, etc.) are trapped and accumulated to cause local accumulation of charges, which makes the charge distribution uneven, thereby causing polarization. Most of the dielectric materials used in engineering are uneven and defective. Therefore, both the weak absorbing material and the non-absorbing material will be polarized after being put into the electric field, and the total polarization intensity is equal to the sum of the above polarizations.

Starting from the microstructure of matter, we briefly explain the mechanism of microwave heating from the force of electric dipoles in the electric field.

Figure 4 is a force situation of an electric dipole model in an electric field, , ,in The magnitude of is the distance between -q and +q , and the direction is from the positive charge to the negative charge. When the electric dipole is in the electric field, +q is subjected to a force along the direction of the electric field line, -q is subjected to a force against the direction of the electric field line, the resultant force of the two forces in the uniform electric field is 0, and in the non-uniform electric field The resultant force of each force is not 0, and the electric dipole will move along the direction of the resultant force; the electric dipole moment with electric field When there is an included angle not equal to 0, the electric dipole generates a torque under the action of a pair of forces , moment Make the positive charge in the electric dipole rotate in the direction of the electric field. If the direction of the electric field changes, the torque Make the direction of the electric dipole rotate with the change of the electric field. If the direction of the electric field changes billions of times per second (microwave frequency), the electric dipoles that make up the material rub, squeeze, and collide with each other during the rotation and movement, consuming a large amount of electric energy and converting it into its own heat energy , which is the principle of microwave heating of matter. From the above analysis, it can be seen that in order to improve the efficiency of microwave heating, a larger resultant external force or moment is required, so it is necessary to increase the dipole moment of the household appliance, so increase the spacing is a feasible way.

According to the above description, the microwave oven of the present invention is based on the principle of increasing the distance between positive and negative equivalent charges, and an auxiliary electric field generated by an auxiliary electric field generating circuit is added to the two opposite sides of the microwave oven. The auxiliary electric field includes an auxiliary electric field control circuit and Positive and negative metal electrode plates, the commercial power becomes a stable voltage after being transformed, rectified and filtered, then the required voltage value is output through the auxiliary electric field control circuit, and finally an auxiliary electric field is emitted in the microwave cavity through the positive and negative metal electrode plates. The auxiliary electric field control circuit of the auxiliary electric field generating circuit is used to control the intensity of the generated auxiliary electric field to be smaller than the intensity of the microwave field generated by the magnetron, and the field strength of the auxiliary electric field is 0.4 to 0.6 times the maximum value of the microwave field electric field intensity Between multiples, the auxiliary electric field and the microwave electric field are in the best coordination state, and the heating effect is the best, and the specific multiple depends on the material composition.

When the microwave oven is powered on, the heated substance is in a double-field environment (auxiliary electric field and microwave electromagnetic field). The function of the auxiliary electric field is to polarize the heated substance. The total polarization is electron displacement polarization, ion displacement polarization, The sum of several polarizations such as ion relaxation polarization or space charge polarization, and the distance between the positive and negative charges of the electric dipoles that constitute the supported atoms or molecules after polarization Further increase, which is a necessary condition for rapid heating of difficult or non-absorbing materials by microwave ovens. The function of the microwave field is heating, and the microwave field is an electromagnetic field. When the microwave electric field acts on the polarized substance, according to with ( is the angle between the auxiliary electric field and the microwave electric field vector), the atoms or molecules that make up these substances are subject to a greater combined electric field force and greater rotational torque , these resultant forces and moments will provide greater extrusion force, rotational power and rotational inertia, while the direction of the microwave electric field changes billions of times per second, the friction and extrusion between molecules in the polarized load And the collision is more severe, the efficiency of converting microwave energy into heat energy is further increased, and the heating rate of the load becomes larger.

The positive and negative metal electrode plates of the auxiliary electric field generating circuit can not only generate a stable electric field, play the role of polarized molecules, but also reflect microwaves like a microwave cavity.

The auxiliary electric field generated by the auxiliary electric field generating circuit is a steady electric field, which acts on the heated substance together with the microwave electric field generated by the magnetron, and works synchronously without interfering with each other.

When the microwave field acts on these polarized weak absorbing substances, when the angle between the auxiliary electric field vector generated by the auxiliary electric field generating circuit and the microwave electric field vector is 0, the auxiliary electric field does not contribute to the heating of the microwave electric field, but The direction of the microwave field changes hundreds of millions of times per second, so this state exists for a very short time and does not have much impact on the heating of the microwave oven, which can be ignored.

Therefore, the microwave oven in the present invention can quickly heat weak absorbing substances, and can also heat difficult absorbing substances to a certain extent. It overcomes the shortcomings of the auxiliary heating method, the heating process is simple, there is no additional energy loss, and it will not introduce new impurities into the heated substance and cause "pollution".

It can be understood that changes made to the auxiliary electric field generating circuit, such as the size, shape, position, and parameters of the positive and negative metal electrode plates, should all fall within the protection scope of the claims of the present invention.

The specific embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Variations.

Claims (6)

1. a kind of micro-wave oven for quickly heating weak wave absorbtion material, including main control circuit, transforming circuit, magnetron, waveguide and Microwave cavity, it is characterised in that：Also include that auxiliary electric field produces circuit, for producing an auxiliary electric field in microwave cavity, makes Heated material can be heated rapidly under the microwave field collective effect produced by auxiliary electric field and magnetron；

Described auxiliary electric field produces circuit to control circuit and positive and negative metal electrode board including auxiliary electric field；

It is steady electric field that described auxiliary electric field produces the auxiliary electric field produced by circuit；

Described auxiliary electric field produces the auxiliary electric field control circuit of circuit, and the intensity for controlling described auxiliary electric field is less than The electric-field intensity of the microwave field that the magnetron is produced.

2. the micro-wave oven for quickly heating weak wave absorbtion material according to claim 1, it is characterised in that：Described auxiliary electricity The field intensity of field is between 0.4 times to 0.6 times of microwave electric field maximum of intensity.

3. the micro-wave oven for quickly heating weak wave absorbtion material according to claim 1, it is characterised in that：Described auxiliary electricity Field produces the positive and negative metal electrode board of circuit to be symmetrically positioned two offsides of microwave cavity, near the inner surface of microwave cavity.

4. the micro-wave oven for quickly heating weak wave absorbtion material according to claim 3, it is characterised in that：Described metal electricity Pole plate is close to microwave cavity inner chamber but does not contact, and is filled between described metal electrode board and the microwave cavity inner chamber Insulating ceramics, is isolated between the positive and negative metal electrode board and microwave cavity surface with the insulating ceramics no more than 2.5mm thickness.

5. the micro-wave oven for quickly heating weak wave absorbtion material according to claim 1, it is characterised in that：Described auxiliary electricity Produce circuit positive and negative metal electrode board be stainless steel electrode plate, thickness between 3mm to 12mm, heating-up temperature microwave higher Cavity is bigger, and the thickness of the positive and negative metal electrode board is thicker.

6. the micro-wave oven for quickly heating weak wave absorbtion material according to claim 3 or 4, it is characterised in that：Described is micro- The inner chamber ground connection of ripple cavity.