JP2002289334A - Magnetic field generator for electromagnetic induction heating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field generator for electromagnetic induction heating useful to homogeneously heat food materials while eliminating roasting unevenness, which is different from a traditional coil wherein electroconductive wires are spirally wound. SOLUTION: Load dispatching terminals composed of an electroconductive material are installed at both ends, and plural electroconductive materials for induction field generation are arranged in straight lines in parallel between the load dispatching terminals, and this is comprised so that the electroconductive materials are mutually connected in electrically parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field generator for electromagnetic induction heating useful for uniformly heating a baked surface in, for example, baking and cooking food.

[0002]

2. Description of the Related Art The electromagnetic induction heating method is characterized in that a metal object to be heated can be directly heated, (i) a large amount of heat can be supplied to the object to be heated, and (ii) heat loss due to exhaust gas or the like. (Iii) there is an advantage that temperature control can be performed promptly because a heat medium does not pass between the initial heat source and the object to be heated, and a heating apparatus of a scale used in household cooking utensils and kitchens;
It is also widely used for larger industrial equipment.

[0003] Conventionally, a portion for performing electromagnetic induction heating includes:
In general, a coil is used in which a spiral wire is wound using an electric wire made up of a number of enamel wires called litz wires, and this coil is commonly used in household electric kettles, table-top plate-type heaters, and the like. Used. Other than the coil using the litz wire, those described in JP-A-6-236794 and JP-A-8-45654 are known.

[0004] Regarding the coils for heating an electromagnetic induction according to the prior art, regardless of whether a litz wire is used as a conductive material or not, a coil for generating an induction magnetic field has a required length. The common point is that the conductive material is spirally wound. This is because, for the alternating current applied to the conductive material, the length of the conductive material necessary for matching the impedance is necessary. It is necessary to collect the materials in a concentrated manner, and if the conductive material is reciprocated without being spirally wound, the directions of the magnetic fields generated from the forward and return conductive materials are reversed. Are unable to cancel each other to generate an effective magnetic field.

[0005] Therefore, the electromagnetic induction heating coil is characterized in that a conductive wire such as a litz wire having a predetermined length is spirally wound. Was wrapped around.

However, the coil of this type has a feature that a magnetic field strongly appears near the center of the conductive wires arranged in the same direction. For example, as seen in the example of a tabletop heating plate used for home use, the litz wire wound inside starts from the center and is uniformly wound up to the outer periphery, but the center is Heat generation was weak at the part and the peripheral part, and strong heat was generated at a substantially intermediate part between the center and the periphery, and as a result, a donut-shaped strong part was generated on the plate plane.

[0007] Such non-uniformity of heating is often preferred in the case of cooking with a pot or for the purpose of promoting convection by temperature distribution as in the case of rice cooking. Has a drawback that causes uneven printing.

[0008] The above-mentioned uneven grilling is the same when it is used in a continuous grilling machine using a metal conveyor. That is,
Even when a spiral electromagnetic induction heating coil is arranged side by side at the bottom of the conveyor for heating the metal conveyor, the conveyor surface heated by the induction heating coil with uneven heating is not necessarily uniform in the width direction orthogonal to the running direction Does not become
It was difficult to uniformly bake in the width direction without eliminating the baking unevenness of the foods baked by the conveyor.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a baking cooker, particularly a continuous baking cooker using a metal belt conveyor, which is useful for uniformly heating in a width direction orthogonal to the running direction. An object of the present invention is to provide a magnetic field generator for electromagnetic induction heating.

[0010]

The inventor of the present invention has made intensive studies to solve the above-mentioned problems, and as a result, unlike the conventional electromagnetic induction heating coil wound up in a spiral shape, a conductive material which generates an induction magnetic field is provided. Have been found to be able to be uniformly heated in the width direction by arranging them in a straight line in parallel in the same direction, and have completed the present invention.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the magnetic field generator for electromagnetic induction heating according to the present invention, conductive materials for generating an induction magnetic field are not spirally wound, but are arranged linearly and in parallel. By connecting both ends of the conductive material in parallel to the power supply terminal, a current is passed in parallel to the arranged conductive materials, and a uniform induction magnetic field is generated in the axial direction of the conductive material.

The conductive material for generating an induction magnetic field and the power supply terminals attached to both ends of the conductive material are treated as a set of magnetic field generating units. The magnetic field generating units may be arranged side by side in the axial direction of the members and electrically connected in series. This is effective when impedance matching is performed by adjusting the number of magnetic field generating units connected in series when the impedance of the circuit does not match with only one set of magnetic field generating units.

The term "conductive material for generating an induced magnetic field" as used in the present invention refers to a material constituting a portion for generating an induced magnetic field by supplying electric power of an appropriate frequency to the conductive material.

Usually, a special electric wire called a litz wire in which a thin enamel wire is twisted is often used as the conductive material. In the case of electromagnetic induction heating, high frequency is mainly used, but this is because the higher the frequency, the more the current tends to concentrate on the surface of the conductive material, and the narrower the surface area is. A method of bundling wires is used.

Therefore, a litz wire, a single wire, or a copper plate can be properly used according to the frequency of the power supply used.

[0016]

Next, the present invention will be described with reference to examples.

Embodiment 1 FIG. 1 shows a basic unit of a magnetic field generator for electromagnetic induction heating according to the present invention. A litz wire Ri is used as a conductive material, and crimp terminals Pt are attached to both ends thereof. Then, a plurality of litz wires Ri to which the crimp terminals Pt are attached are linearly extended and arranged in a line, and the crimp terminals Pt are sequentially supplied to the power supply terminals. Ft
(Fig. 1-a). A predetermined number of power supply terminals and a group of litz wires attached to the power supply terminals are fixed by sandwiching ceramic plates from both sides to maintain the shape, thereby forming a magnetic field generating unit U (FIG. 1-b).

Embodiment 2 FIG. 2 shows an example in which a plurality of magnetic field generating units U are connected in series and combined. The magnetic field generating unit U is as shown in the first embodiment. In this example, four magnetic field generating units U
₁ , U ₂ , U ₃ , and U ₄ are arranged in a direction orthogonal to the direction in which current flows, and the power supply terminals are sequentially connected by bridges B ₁ , B ₂ , and B ₃ . In this example, the feed terminal Ft ₁ and feeding of the inverter between the feeding terminal Ft ₄ (not shown)
Is supplied with the electric power generated in step (1).

In this example, since current flows in opposite directions in adjacent units, an aluminum shielding material is provided between the adjacent units so that no magnetic field interference occurs therebetween.

Embodiment 3 FIG. 3 shows an example in which a plurality of magnetic field generating units U are combined so that current flows in the same direction in each magnetic field generating unit U. The four magnetic field generation units U ₁ , U ₂ ,
U _3, in _{U 4} and the feeding terminal Ft ₁ of _{U 1,} which the the power supply terminal Ft ₂ adjacent magnetic field generating unit _{U 2} connected by wires E having flexibility, less Likewise feeding terminal Ft
Between ₂ and power supply terminals Ft _3, and connects the power supply terminal Ft ₃ and the feeding terminal Ft _4. In this example, a current in the same direction can flow through each magnetic field generating unit U.

Embodiment 4 FIG. 4 shows an example of a baking conveyor in which a magnetic field generator of the present invention is attached to a steel belt conveyor and induction heating is performed. Under the belt surface of the steel belt conveyor S, a deflection prevention receiving roller Ro is provided. The magnetic field generating unit U is manufactured to have a width that fits between the receiving rollers Ro, and the surface of the conductive material made of the litz wire is one distance from the belt material.
Attach it so that it is 0mm away. In each of the magnetic field generating units U, the power supply terminals are sequentially connected by the flexible electric wire E, and both ends thereof are connected to the induction heating inverter I by the method described in the third embodiment to supply power. Thereby, it is possible to bake foodstuffs uniformly on the conveyor.

Example 5 Fifty litz wires having an outer diameter of 5 mm were arranged in a straight line and the length was 1
m, a magnetic field generating unit having a width of 300 mm is arranged side by side, and the power supply terminal at the right end of the magnetic field generation unit is connected to the next unit to the power supply terminal on the left side. By supplying power to the magnetic field generating units from the inverter I for electromagnetic induction heating, a circuit is configured so that current flows in the same direction in any magnetic field generating unit.

A steel belt conveyor having a width of 1 m and a span length of 15 m between pulleys is formed by using a magnetic stainless steel (equivalent to SUS 630) having a belt thickness of 1 mm. The magnetic field generating unit group is installed in the section. A 7 m long hood is provided at the entrance side of the conveyor, and a steam blowing mechanism is provided in the hood to form a steamed and heated section of a dumpling steamed conveyer.

When power is supplied from the inverter to the electromagnetic induction heating unit while the belt is stopped, and the rate of temperature rise on the surface of the belt is measured. In each electromagnetic induction heating unit section, in the direction orthogonal to the litz wire, that is, in the running direction of the belt. The
Although heating tends to be strong near the center of each electromagnetic induction heating unit and weak at the ends, there is almost no difference in heating power in the direction parallel to the litz wire, that is, in the width direction of the belt, and 250 ° C. from the start of heating. The temperature difference in the width direction until the temperature is raised falls within 10 ° C.

Next, the temperature distribution of the surface of each part of the belt was measured while the belt was running at a speed of 1.8 m / min. As a result, the belt surface was almost 10 ° C. while passing through the 20 electromagnetic induction heating units. Raise the temperature by a constant temperature, and
Although the temperature can be raised to 60 ° C., the temperature distribution in the width direction at this time falls within approximately 5 ° C.

Next, dumplings formed by a dumpling molding machine are loaded at the entrance of the conveyor, steaming and heating are performed while blowing steam into the steaming section, and baking is performed by heating the belt with an electromagnetic induction heating unit. In this way, uniform baking and heating can be performed in the width direction of the belt, and the gyoza stacked at any location in the width direction can obtain favorable baking.

[0027]

According to the induction heating method of the present invention, unlike a conventional coil in which a conductive wire is wound in a spiral shape, the belt is used in an apparatus requiring uniform heating in the width direction, such as a metal belt conveyor. Uniform heating can be performed in the width direction of the surface. As a result, when the baked food is baked by a baking device using the belt conveyor, the food materials arranged in the width direction of the belt can be uniformly heated, and uniform baking can be obtained.

[Brief description of the drawings]

FIG. 1 shows a basic unit of a magnetic field generator for electromagnetic induction heating according to the present invention.

FIG. 2 shows an example in which basic units of a magnetic field generator according to the present invention are connected in series and combined.

FIG. 3 shows another example in which basic units of the magnetic field generator according to the present invention are connected in series and combined.

FIG. 4 shows an example of a baking conveyor for performing induction heating by attaching the magnetic field generator for electromagnetic induction heating according to the present invention to a steel belt conveyor.

[Explanation of symbols]

Ri ... litz wire Pt ... crimp terminal _{Ft, Ft 1, Ft 2,} Ft 3, Ft 4 ... feeding terminals _{U, U 1, U 2,} U 3, U 4 ... magnetic field generating unit _{B 1, B 2, B 3} ... Bridge E ... Electric wire S ... Steel belt conveyor Ro ... Deflection prevention receiving roller I ... Inverter for induction heating

Claims (3)

[Claims] 1. A power supply terminal made of a conductive material is provided at both ends, a plurality of conductive materials for generating an induced magnetic field are linearly arranged in parallel between the power supply terminals, and the conductive materials are electrically connected in parallel. A magnetic field generator for electromagnetic induction heating. 2. A magnetic field generating device for electromagnetic induction heating according to claim 1, wherein a plurality of magnetic field generating devices are arranged in parallel to a direction in which conductive materials for generating an induction magnetic field are arranged, and the devices are electrically connected in series. Magnetic field generator for electromagnetic induction heating. 3. The magnetic field generator for electromagnetic induction heating according to claim 1, wherein the conductive material for generating an induction magnetic field is a litz wire.