JP2001189221A - Transformer having core with gap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce temperature increase in a transformer with a gap, which is mainly used in a high-frequency heating apparatus of an inverter type. SOLUTION: One side magnetic legs 6a, 7a of U-shaped core half bodies 6, 7, constituting a square shape core 8 with a gap are inserted in a center hole 5 of a bobbin 1 around which a primary winding 2 and a secondary winding 3 are wound isolated in the axial direction. A gap 10 between tip surfaces of the magnetic legs 6a, 7a is arranged between the primary winding 2 and the secondary winding 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer for driving a magnetron using an inverter.

[0002]

2. Description of the Related Art FIG. 7 shows an inverter-type high-frequency heating device disclosed in Japanese Patent Publication No. 7-40465. The current is converted into an alternating current and supplied to a primary winding 24p of a transformer 24 having a core with a gap. The high-frequency output voltage of the secondary winding 24s of the transformer 24 is rectified by a high-voltage rectifier circuit 25 to become a DC high voltage, and is supplied to a magnetron 26 in which a heater is driven by a heater winding 24h of the transformer 24 to generate a microwave. .

FIG. 8 is a view showing the structure of the transformer 24. A bobbin 30 in which a primary winding 24p, a secondary winding 24s, and a heater winding 24h are wound apart from each other in the axial direction is provided.
One of the magnetic legs of the U-shaped cores 31 and 32 is inserted, and the U-shaped core 34 having the gap 33 is opposed to the U-shaped cores 31 and 32 via a spacer 30 g having a thickness G formed in the cylindrical portion 30 s of the bobbin 30. The primary winding 24p and the secondary winding 24
By configuring the coupling coefficient of s to be 0.6 to 0.8, a leakage inductance is provided on the secondary side, and the high frequency choke on the secondary side, which was required in the conventional inverter circuit for magnetron, is not required. I have.

The transformer 24 is arranged at a position where the primary winding 24p surrounds the gap 33. The portion of the gap 33 of the square-shaped core 34 is the portion that generates the most heat during operation, but since the gap 33 exists inside the primary winding 24p, the heat from the gap 33 is
Thus, there is a problem that the temperature is transmitted to the primary winding 24p through the primary winding 24p to increase the temperature of the primary winding 24p and deteriorate the primary winding 24p. Further, the temperature of the heat generated from the gap 33 rises because the periphery is surrounded by the cylindrical portion 30s of the bobbin 30 and it is difficult to dissipate heat, so that the temperature of the bobbin 33 surrounding the gap 33 also becomes high. Worsen.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a transformer which suppresses an adverse effect on the winding due to heat from a core gap.

[0006]

In order to achieve the above object, a transformer according to the present invention has a primary winding and a secondary winding wound around a bobbin such that the primary winding and the secondary winding are axially separated from each other. A core is inserted and a core gap is located between the two windings. According to the above configuration, since the gap having a large calorific value is located between the primary winding and the secondary winding,
Thermal adverse effects on both windings are suppressed. Further, since the position of the gap can be set at the center of the core, when the core is formed by a pair of core halves, these core halves can have the same shape and the same dimensions. Accordingly, the productivity of the core is improved, and it is not necessary to distinguish the pair of core halves when inserting the core halves into the bobbin, so that the transformer assembling workability is also improved.

[0007] In a preferred embodiment of the present invention, the core has a square shape and one leg thereof is inserted into a center hole of the bobbin. According to the above configuration, the width of the transformer is smaller than when the primary winding and the secondary winding are separately wound around the two legs of the core.

In another preferred embodiment of the present invention, an air hole for facilitating the flow of air to the gap is formed in the bobbin at a position facing the gap so as to penetrate in the radial direction. According to the above configuration, the heat convection of the air into the gap is promoted through the air hole facing the gap, and the temperature rise around the gap of the core is reduced. As a result, the thermal adverse effect on both windings is further suppressed. it can.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a first embodiment of a transformer having a core with a gap according to the present invention, and FIG.
3 is a plan view thereof, and FIG. 3 is a sectional view taken along line III-III in FIG. The transformer provided with this core with a gap is used for the high-frequency heating device shown in FIG. 7, and as shown in FIG.
Are wound around the primary winding 2 and the divided secondary winding 3 and the heater winding 4 in the axial direction. One of the magnetic legs 6a, 7a of the U-shaped core halves 6, 7 is inserted into the center hole 5 of the bobbin cylinder 1a shown in FIG. 3 from opposite directions, and the tips of the magnetic legs 6a, 7a are inserted into the bobbin 1a. The two magnetic legs 6 are brought into contact with four gap forming pieces 9 which are formed in the center hole 5 at 90 ° intervals and protrude in the central axis direction.
A gap 10 having an interval G is formed between the opposed end faces a and 7a.

The distal ends of the other magnetic legs 6b and 7b are brought into contact with a gap forming rib 12 formed on the insulating member 11 to form a gap 10 having the same interval G. The two core halves 6 and 7 have the same shape and dimensions and form a square-shaped gapped core 8. The insulating member 11
As shown in FIG. 4, a pair of left and right side walls 11a and a bottom wall 1 are provided.
1b, a core fitting groove 11c for fitting the magnetic legs 6b, 7b of the core 8 in FIG. 3 is formed.

As shown in FIG. 2, a winding frame 13 around which the primary winding 2 of the bobbin 1 is wound and a winding frame 14 around which the secondary winding 3 is wound are separated in the axial direction. Double winding frame 1 shown in FIG.
A gap 15 is provided between the end walls 13a, 14a facing each other on the axially inner side of the end walls 13a, 13b, 14a, 14b of FIGS. The four gap forming pieces 9 are formed in the center hole 5, and eight air holes 17 penetrating the cylindrical portion 1a of the bobbin 1 in the radial direction and facing the groove 15 are formed at intervals of 45 °. Have been. The gap forming piece 9 is provided at a central position of the bobbin 1 in the axial direction. Secondary winding 3
Is wound around three divided grooves 20 divided by the partition wall 14c, and a groove 21 between the end wall 14a of the reel 14 near the primary reel 13 and the adjacent partition wall 14c.
Is wound around the first half turn of the secondary winding 3, from which a winding is introduced into the adjacent divided groove 20.

On the inner surface of the center hole 5, four guide ribs 16 extending in the axial direction are formed so as to protrude in the radial direction at 90 ° intervals. The guide rib 16 guides the magnetic legs 6a, 7a of the U-shaped core halves 6, 7 inserted into the center hole 5, and extends axially between the bobbin 1 and the magnetic legs 6a, 7a. Are formed. 19
Is a clip for fixing the core halves 6 and 7 from both ends.

The gap 10 of the core 8 generally generates a large amount of heat. On the other hand, in the above embodiment, the gap 10 of the square-shaped core 8 is disposed between the primary winding 2 and the secondary winding 3 of the bobbin 1, and both the windings 2 and 3 have the gap 10. , The adverse effect on the windings 2 and 3 due to the heat generated in the gap 10 is suppressed. Moreover, since the position of the gap 10 can be set at the center of the core 8, the core halves 6, 7 can have the same shape and the same dimensions. Therefore, the productivity of the core 8 is improved. Also, when inserting the pair of core halves 6, 7 into the bobbin 1, there is no need to distinguish between the two halves 6, 7, so that the transformer assembling workability is also improved.

Further, in the above embodiment, the gap 15 at a position radially opposed to the gap 10 has
A plurality of air holes 17 penetrating in the radial direction are formed.
As a result, the heat convection of the air in and around the gap 10 passing through the air hole 17 is increased, and heat radiation around the gap 10 is promoted, so that the temperature rise around the gap of the core 8 is reduced. With the primary windings 2 and 2
The adverse thermal effect on the secondary winding 3 is further suppressed. Further, the gap 10 of the core 8 is formed by providing a plurality of gap forming pieces 9 protruding in the axial direction of the center hole 5 between the adjacent air holes 17, 17. Are not displaced relative to each other, which facilitates assembly.

By the way, the air hole 17 is formed in the gap 1
It may be provided in the vicinity of a position radially opposed to zero and at a position slightly shifted in the axial direction of the bobbin 1 from this position. For example, in the second embodiment shown in FIG. 5, the gap 10 is provided at a position radially inwardly facing the groove 15 between the primary winding frame 13 and the secondary winding frame 14, while the air hole 17 is The bobbin 1 is formed in the cylindrical portion 1a so as to face the groove 21 around which the winding start wire 3a of the secondary winding 3 is wound. Here, the winding start wire 3a is wound around the secondary terminal 22 attached to the bobbin 1 as shown in FIG.
After being wound by 1/2 turn in 1, the partition wall 14c
5 is introduced into the adjacent dividing groove (the lowermost dividing groove) 20 in FIG. 5, and the air hole 17 does not face the winding start line 3a in the cylindrical portion 1a shown in FIG. In this example, two are formed so as to penetrate the cylindrical portion 1a at the positions. The groove 21 has a wall for increasing the creeping distance between the secondary winding 3 and the core 8 over the entire length in the depth direction of the groove 21 and over the entire width in the axial direction to enhance the electrical insulation. 24 are provided.

In each of the above six embodiments, four gap forming pieces 9 are provided at 90 ° intervals, and air holes 17 are provided at 45 ° intervals at 8 °.
However, the number of the gap forming pieces 9 and the number of the air holes 17 are not limited to this embodiment. The air holes 17 can be omitted.

[0017]

According to the present invention, since the gap generating a large amount of heat is located between the primary winding and the secondary winding, an adverse thermal effect on both windings is suppressed. Further, since the position of the gap can be set at the center of the core, when the core is formed by a pair of core halves, these core halves can have the same shape and the same dimensions. Accordingly, the productivity of the core is improved, and it is not necessary to distinguish the pair of core halves when inserting the core halves into the bobbin, so that the transformer assembling workability is also improved.

[Brief description of the drawings]

FIG. 1 is a side view of a transformer having a core with a gap according to a first embodiment of the present invention.

FIG. 2 is a plan view of the same embodiment.

FIG. 3 is a sectional view taken along line III-III of FIG. 1;

FIG. 4 is a perspective view showing the insulating member of the embodiment.

FIG. 5 is a sectional view corresponding to FIG. 3 of a transformer having a core with a gap according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a main part of the second embodiment.

FIG. 7 is a circuit diagram showing a high-frequency heating device using the transformer of the present invention.

FIG. 8 is a sectional view showing a conventional transformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Bobbin, 2 ... Primary winding, 3 ... Secondary winding, 4 ... Heater winding, 5 ... Center hole of bobbin, 6, 7 ... U-shaped core half, 6a, 7a, 6b, 7b ... magnetic leg, 8 ... square core with gap, 9 ... gap forming piece, 10 ... gap, 1
DESCRIPTION OF SYMBOLS 1 ... Insulating member, 12 ... Gap formation rib, 13 ... Primary winding frame, 14 ... Secondary winding frame, 15 ... Gap, 16 ...
Guide rib, 17: air hole, 18: air passage, 19: clip

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01F 31/00 EQ (72) Inventor Hideaki Soma 1-12-20 Motejima, Nishiyodogawa-ku, Osaka City Tabuchi Electronics F term in Industrial Co., Ltd. (reference) 3K086 AA02 AA06 BA08 DB11 FA02 FA06

Claims (3)

[Claims] 1. A primary winding and a secondary winding are wound around a bobbin while being spaced apart in an axial direction, a core is inserted into a center hole of the bobbin, and a core gap is arranged between the two windings. Transformer with a gapped core. 2. The transformer according to claim 1, wherein the core has a square shape, and one leg of the transformer has a gapped core inserted into a center hole of the bobbin. 3. The gap-equipped air conditioner according to claim 1, wherein an air hole for facilitating the flow of air to the gap is formed in the bobbin at a position facing the gap or in the vicinity thereof in a radial direction. Transformer with core.