JPH0624983Y2 - Step-up transformer for high-frequency heating device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a step-up transformer that is provided in a high-frequency heating device for heating cooking materials and supplies high-voltage power to a magnetron that generates high-frequency waves. Is.

[Conventional technology]

The high-frequency heating device is provided with a step-up transformer 11 in order to obtain high-voltage power for supplying to a magnetron that generates a high frequency, based on a commercial power supply. In the step-up transformer 11, in the ferrite core having high magnetic permeability, the primary coil 12 and the secondary coil 12 are provided with secondary leakage for the purpose of controlling the magnetron current peculiar to magnetron control.
In order to transmit power between the secondary coil 13 and the secondary coil 13, for example, as shown in FIG.
3 and 3 are provided adjacent to each other.

Since the secondary coil 13 generates a considerably high voltage,
The reliability of the step-up transformer 11 is improved by suppressing the voltage generated by each coil 13a ... Which is formed by the coils 13a ... Which are divided into a plurality of blocks having the same number of windings and the same coil diameter. Can be improved.

Further, the coils 13a, which are adjacent to each other, respectively, as shown in FIG. 8 and FIG.
It was designed to be connected via 5a.

[Problems to be solved by the device]

When a current flows through the primary coil 12 of the step-up transformer 11, a magnetic circuit as shown by the chain double-dashed line in FIG. 7 is formed, and the magnetic flux passes through the secondary coil 13. In addition, a part of the magnetic flux generated by the primary coil leaks and crosses the winding 15, and the eddy current causes heat generation in the winding 15.

However, the step-up transformer 1 of the conventional high-frequency heating device described above.
1, the plurality of coils 13a in the secondary coil 13 ...
However, since all of them are formed with the same number of windings and the same coil diameter, heat is significantly generated in the coil 13a provided in a position adjacent to the primary coil 12 with the largest leakage flux, and the winding 15 is burned out. However, there is a problem that it tends to cause deterioration of the insulating coating.

In addition, as shown in FIG. 10, for example, a gap having a length of 1 is provided between the primary coil 12 and the secondary coil 13, and the winding 1
Although the heat generation amount of 5 is reduced, the strength of the magnetic field is inversely proportional to the distance from the primary coil 12, so the length of the winding 15 is set to 1 so that heat generation is suppressed. Then, the efficiency of the step-up transformer 11 is reduced.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, a step-up transformer of a high-frequency heating device according to the invention of claim 1 is provided with a primary coil and a secondary coil adjacent to each other, and a high voltage is applied to a magnetron that generates a high frequency. In a step-up transformer that supplies electric power, the number of windings in a portion of at least one of the primary coil and the secondary coil, which is adjacent to the other coil, is greater than the number of windings in a portion that is distant from the other coil. It is characterized in that it is configured to be less.

In order to solve the above-mentioned problems, a step-up transformer of a high-frequency heating device according to a second aspect of the present invention is provided with a primary coil and a secondary coil adjacent to each other, and applies a high voltage to a magnetron that generates a high frequency. In a step-up transformer for supplying electric power, a coil diameter of a portion of at least one of the primary coil and the secondary coil which is close to the other coil is larger than a coil diameter of a portion which is distant from the other coil. It is characterized by being configured as follows.

[Action]

According to the structure of claim 1, the number of windings is reduced in a portion of one coil adjacent to the other coil, that is, a portion located in a position where the leakage magnetic flux is the largest. Even if the gap between the primary coil and the secondary coil is not increased, the total amount of heat generated by the eddy current can be reduced.

Therefore, it is possible to reduce the amount of heat generated by the coil and prevent burnout of the winding and deterioration of the insulating coating without lowering the efficiency of the step-up transformer.

According to the configuration of claim 2, the coil diameter of the portion of one coil adjacent to the other coil, that is, the portion of the portion located at the position where the leakage magnetic flux is the largest is the coil diameter of the portion separated from the other coil. Since it is configured to be larger than that, the leakage magnetic flux is not concentrated on the relevant portion of the coil.

Therefore, like the step-up transformer of the high-frequency heating device according to the first aspect of the present invention, the heat generation amount of the coil is reduced without causing a decrease in the efficiency of the step-up transformer, and the burnout of the winding and the insulation coating are prevented. It is possible to prevent deterioration.

[Embodiment according to the first aspect of the invention] The following will describe one embodiment of the present invention with reference to FIGS. 1 to 3.

In the high frequency heating device 21, for example, as shown in FIG.
A rectifying / smoothing circuit 26 including a bridge rectifying circuit 22, a choke coil 23, and a smoothing capacitor 24 is provided, and a rectifying / smoothing circuit 26 that rectifies and smoothes a commercial power supply 25 into a DC power supply.

The rectifying / smoothing circuit 26 includes a step-up transformer 31 that supplies high-voltage power to a magnetron 51, which will be described later, a resonance capacitor 32, a diode 33, and a switching element 34 that are connected in series to the step-up transformer 31 to form a resonance circuit. The inverter circuit 35 is connected. The resonance circuit is not limited to the one configured by connecting the boosting transformer 31 and the resonance capacitor 32 in series as described above, but may be configured by connecting in parallel.

In the switching element 34 of the inverter circuit 35,
A drive circuit 36 that drives the switching element 34 is connected. Further, the control circuit 3 is provided at both ends of the drive circuit 36 and the primary coil 41 in the step-up transformer 31.
7 is connected to the primary coil 4 in the step-up transformer 31.
The drive circuit 36 is controlled on the basis of the voltage between both ends of 1, and the switching element 34 is turned ON / OFF, whereby an appropriate heating operation is performed.

The secondary coil 42 in the step-up transformer 31 prevents a high frequency current from flowing through the high voltage diode 52 for driving the magnetron 51, the high voltage capacitor 53, and the filter capacitor connected to the filament terminal inside the magnetron 51. A diode 54 for driving the magnetron 51 is connected to a magnetron drive circuit 55 that drives the magnetron 51 to generate a high frequency.

The specific structure of the step-up transformer 31 is, for example, as shown in FIG. 1, the bobbin 4 mounted on the magnetic core 43.
4 is wound around a primary coil 41 and a secondary coil 42.

That is, on the bobbin 44, the groove 44 a for winding the primary coil 41, the groove 44 b for providing a gap between the primary coil 41 and the secondary coil 42, and the secondary coil 42 are divided into four blocks. Groove 4 for splitting and winding
4c ... Is formed. The primary coil 41 is wound around the groove 44a formed in the bobbin 44, while the same number is provided in the three grooves 44c of the grooves 44c, which are located away from the primary coil 41. The coils 42a are wound with the number of turns, and the grooves 42c closest to the primary coil 41 are wound with the coils 42b with a number of turns smaller than that of the coils 42a. Has been formed.

In the above configuration, when the switching element 34 of the inverter circuit 35 is in the ON state due to the driving of the drive circuit 36 based on the control of the control circuit 37, the resonance between the primary coil 41 of the step-up transformer 31 and the resonance capacitor 32. As a result, a resonance current flows in the primary coil 41 and a high voltage is generated in the secondary coil 42.

When a high voltage is generated in the secondary coil 42, the magnetron 5
1 oscillates to generate a high-frequency heating output, and the object to be heated is heated. The switching element 34 is controlled by the control circuit 37 to repeat the ON state for a time determined according to the heating state of the object to be heated and the OFF state for a preset time to maintain an appropriate heating state. .

By the way, when the resonance current flows through the primary coil 41 due to the resonance between the primary coil 41 of the step-up transformer 31 and the resonance capacitor 32, a magnetic circuit as shown by a chain double-dashed line in FIG. It passes through the coil 42. A high voltage is generated in the secondary coil 42 due to the change of the magnetic flux, while a part of the magnetic flux generated by the primary coil 41 leaks and crosses the winding of the secondary coil 42 to generate heat by an eddy current.

Here, the coil 4 provided at the position with the largest leakage magnetic flux
2b is formed so as to have a smaller number of windings than the coils 42a. The temperature rise of the coil 42b does not increase as the number of windings decreases, as shown in FIG. 3, for example. Therefore, the heat generated by the eddy current does not cause burnout of the winding or deterioration of the insulating coating. Further, since it is not necessary to increase the length l of the gap provided between the primary coil 41 and the secondary coil 42 so much, the efficiency of the step-up transformer 31 does not decrease.

In the present embodiment, an example in which the number of windings in the portion of the secondary coil 42 closest to the primary coil 41 is reduced has been described, but conversely, the primary coil 41 is
Even if the number of turns of the portion closest to the secondary coil 42 is reduced, the same effect can be obtained.

[Embodiment according to the invention of claim 2] The following will describe one embodiment of the present invention with reference to FIG. 2 and FIGS. 4 to 6.

The high-frequency heating apparatus according to this embodiment has the configuration shown in FIG. 2 and operates in the same manner as the high-frequency heating apparatus described above.

Further, a step-up transformer 31 used in the high frequency heating device.
For example, as shown in FIG. 4, a primary coil 41 and a secondary coil 42 are wound around a bobbin 44 attached to a magnetic core 43.

That is, the primary coil 41 is wound around the bobbin 44 once the groove 44a is formed. Further, on the other end side of the bobbin 44, the outer diameter of the groove bottom in the portion close to the primary coil 41 is made larger than the outer diameter of the groove bottom in the portion distant from the primary coil 41 in a stepwise manner. Three grooves 4
4c are formed, and the secondary coil 42 is divided and wound around the coils 42a of three blocks.

The secondary coil 42 is formed by winding a winding 45 in order from the groove 44c on the side farther from the primary coil 41. That is, as shown in FIG. 5 and FIG.
The winding wire 45 forming the outermost layer in the coil 42a farther from the next coil 41 forms the innermost layer in the coil 42a closer to the primary coil 41 via the crossover portion 45a.

In the above configuration, the portion of the secondary coil 42 adjacent to the primary coil 41, that is, the coil 42a provided at the position where the leakage magnetic flux in the magnetic flux generated by the primary coil 41 is the largest, is separated from the primary coil 41. The coil diameter is larger than that of the coil 42a in the portion.

Therefore, since the leakage magnetic flux does not concentrate on the coil 42a adjacent to the primary coil 41, the temperature rise of the coil 42a does not rise so much, and the winding 45 is not burned or the insulating coating is deteriorated.

Further, since the secondary coil 42 is configured such that the coil diameter of the portion close to the primary coil 41 is larger than the coil diameter of the portion remote from the primary coil 41, as shown in FIG. And the crossover portion 45a of the winding 45
However, the winding 45 of a portion having a greatly different potential, such as the winding 45 on the inner layer side of the coil 42a far from the primary coil 41, the winding 45 on the outer layer side of the coil 42a near the primary coil 41, and the like. Never come into contact with.

In particular, step l ₂ of the groove 44c ... while adjacent the bobbin 44, - the set to be larger than (the thickness l ₁ of the coil 42a ... diameter direction of the winding layers of the diameter d of the winding 45) The crossover portion 45a of the winding wire 45 can be prevented from coming into contact with the winding wire 45 at a portion of the winding wire 45 having a different potential.

Therefore, the insulating coating of the winding is destroyed by corona discharge or the like due to the potential difference generated in the secondary coil 42,
It is possible to prevent the secondary coil 42 from burning.

[Effect of device]

As described above, the step-up transformer of the high-frequency heating device according to the first aspect of the present invention is provided with the primary coil and the secondary coil adjacent to each other, and supplies high-voltage power to the magnetron that generates a high frequency. In the step-up transformer, the number of windings of at least one of the primary coil and the secondary coil adjacent to the other coil is smaller than the number of windings of the portion away from the other coil. It is a configuration configured in.

As a result, it is possible to reduce the amount of heat generated by the coil and prevent burnout of the winding and deterioration of the insulating coating without lowering the efficiency of the step-up transformer.

As described above, in the step-up transformer of the high-frequency heating device according to the second aspect of the present invention, the primary coil and the secondary coil are provided adjacent to each other, and high-voltage power is supplied to the magnetron that generates a high frequency. In the step-up transformer, a coil diameter of a portion of at least one of the primary coil and the secondary coil which is close to the other coil is larger than a coil diameter of a portion of the step-up transformer which is distant from the other coil. It is the configured configuration.

As a result, like the step-up transformer of the high-frequency heating device according to the first aspect of the present invention, the heat generation amount of the coil is reduced without causing a decrease in the efficiency of the step-up transformer, and the burnout of the winding and the insulation coating are reduced. Can be prevented from deteriorating. Moreover,
It is also possible to prevent the insulation coating from being destroyed by the potential difference generated in the secondary coil.

[Brief description of drawings]

FIG. 1 shows an embodiment of the invention of claim 1, and FIG. 1 is a longitudinal sectional view showing the structure of a step-up transformer, and FIG. 2 shows one embodiment of the invention of claims 1 and 2. FIG. 4 is an example showing a circuit diagram showing a configuration of a high-frequency heating device, FIG. 3 is a graph showing the relationship between the number of windings of a step-up transformer according to the invention of claim 1 and the temperature rise, FIG. 1 to 6 show an embodiment of the invention of claim 2; FIG. 4 is a longitudinal sectional view showing the structure of a step-up transformer, and FIG. 5 is an enlarged view of the arrow A in FIG. , FIG. 6 is BB in FIG.
FIG. 7 to 10 show a conventional example, and FIG. 7 is a vertical sectional view showing the structure of a conventional step-up transformer, and FIG.
7 is an enlarged view taken along arrow C in FIG. 7, FIG. 9 is a sectional view taken along arrow DD of FIG. 8, and FIG. 10 is a longitudinal sectional view showing the structure of another conventional step-up transformer. 21 is a high frequency heating device, 31 is a step-up transformer, 41 is 1
A secondary coil, a secondary coil 42, a winding 45, and a magnetron 51.

Claims (2)

[Scope of utility model registration request] 1. A step-up transformer in which a primary coil and a secondary coil are provided adjacent to each other and supplies high-voltage power to a magnetron that generates a high frequency, and at least one of the primary coil and the secondary coil is used. A step-up transformer for a high-frequency heating device, wherein the number of windings in a portion of one of the coils close to the other coil is smaller than the number of windings in a portion of the coil away from the other coil. 2. A step-up transformer in which a primary coil and a secondary coil are provided adjacent to each other and supplies high-voltage power to a magnetron that generates a high frequency, and at least one of the primary coil and the secondary coil is used. A step-up transformer for a high-frequency heating device, characterized in that a coil diameter of a portion of one of the coils which is close to the other coil is larger than a coil diameter of a portion of the coil which is distant from the other coil.