JPH02295089A - Electric heater - Google Patents

Abstract

PURPOSE:To providing it with deflection resistance strength so as to enable free temperature design by arranging a resistor, which has a nonflat-plate-shaped or tubular section, meanderingly thereby forming a heater. CONSTITUTION:Inside a case, inner plates 5 and 5 are erected, and a water pan freely in mounting in and removal from the case is stored between these inner plates 5 and 5. A heater 7 is attached meanderingly through an insulator 8 above the inner plates 5 and 5, and relay terminal plates 9 are attached to the heater terminals 7a and 6b. Heater supporting bars 10 perform electrical connection of adjacent heaters 7, and do duties of supporting the heaters by the inner plates 5 and 5. In this case, by arranging resistors, which have nonflat- plate-shaped or tubular sections, meanderingly, the resistance value can be set freely as compared with a round line, and the degree of freedom in temperature design is great. Moreover, as compared with a belt line it can have deflection strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electric heater using a plate-shaped or cylindrical resistor as a heat source.

[Conventional technology]

Conventionally, in low-voltage resistance heaters using insulation transformers in electric heaters, nine wires made of nichrome alloy material have been used for the resistor. This method is particularly popular as a commercial heating cooker.

When a heat source is obtained directly by passing a current through a resistor, the surface temperature of the same resistor material is determined by the load per unit surface area of the resistor, the so-called surface load density (want density). However, nine wires have the same cross-sectional area and the smallest surface area, and this cross-sectional area directly determines the resistance value of the resistor.

Therefore, if you use something other than nine wires, such as a band wire, instead of nine wires, you can freely change the surface area with the same cross-sectional area, that is, the same resistance value, which means that you can freely design the temperature. . In other words, when looking at the same resistor paulownia with the same capacitance and the same surface area, that is, the same surface temperature, the increased resistance value leads to a reduction in the current value and the reduction in the cross-sectional area leads to a reduction in the weight of the resistor.

[Problem to be solved by the invention]

However, when a band wire is used instead of a nine-wire wire, its high-temperature strength decreases due to its shape, so conventionally it could not be used in industrial or other spaces.

The present invention was devised in view of such conventional problems, and an object of the present invention is to provide an electric heater equipped with a heater that can maintain strength at high temperatures.

[Failure to solve the problem]

In order to achieve this object, the electric heater of the present invention is characterized in that the heater is formed by arranging resistors having a non-planar plate-like or cylindrical cross-section in a meandering manner.

[Effect]

The present inventors applied simple processing to the band wire to give it strength against deflection, allowing for flexible temperature design, reducing costs by reducing the weight of the resistance material, and increasing the resistance value, thereby reducing the current flow. We have developed a heater that has the following advantages: the reduced cost of accessories and equipment brought about by the reduction in value.

The outline will be explained below.

1) According to Stefan-Bormann's law, emissivity ε
, the total radiation of a gray body with absolute temperature T E [W/m'
] is given by the following equation.

E=5.667 E (T/100)' [W/
m']...=... ■The temperature of an object with a surface load density of 5 [W/Ci] and an emissivity of 0.7 is given by the formula, T='J(5xltl')/(5.667x0.7)
XIOO'-]060K approx. 787℃ However, this assumes that there are no surrounding walls and the ambient temperature is not taken into account.In reality, the heater is placed inside the aircraft, and the heater is installed to a specified size. In this case, multiple heaters are arranged in parallel, so the value is larger than 787℃.2) The resistance value of a certain length of the resistive material is:
It is inversely proportional to the cross-sectional area S of the resistor. Resistivity 1.09 [Ω
mm'/rn] of the nichrome type resistance material is S[m
If m2:l, the resistance per 1m is R [Ω/ml
is R=1.09/S [Ω/m] 3) When the object is placed as shown in Figure 4, the deflection y due to gravity of the object is given by the following equation.

y l = -shiX "'゜p""...13fl4
E-I However, W is the weight per unit length of an object i1 [kg/
cm ] β Length of one object [cm] E Yank rate of one object [kg/c] ■ Moment of inertia of one object [cm ”] Using this, y was determined for each type. The results are shown in Figure 5 (
Shown in a) and (b). In addition, in the same figure, ■, ■,
In the examples (2) and (2), shrinkage and bending hardening due to bending are not considered.

Table 1 shows the numerical values when heaters of various shapes were installed on a 250 x 140 mm fire bed with a capacity of 2 KW, a surface load density of 5 W/cnt, and the material used was nichrome type 1.

Table 1-1 As can be seen from Table 1, when using nine lines, ■,■
The number of heater elements determined from the effective length is 8 to 10, which is 250 mm x 1.40 mm.
Too many to place on the fire pit. On the other hand, a half-round or pipe-shaped strip wire provides an appropriate effective length and a reasonable number of heater elements.

〔Example〕

Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings.

FIG. 1 is a front sectional view showing an embodiment in which the present invention is applied to a heating cooker, FIG. 2 is a partially cutaway side view, and FIG. 3 is a plan view.

In these figures, I is the case of the heating cooker,
It has side plates 2, 2, a top plate 3, and a bottom plate 4. Inside the case 1, inner plates 5.5 are erected, and between the inner plates 5.5, a water tray 6, which can be attached or detached from the outside of the case I, is housed. A heater 7 is attached to the upper portions of the inner plates 5, 5 in a meandering manner (see FIG. 3) via an insulator 8, and heater terminals 7a, 7b are attached to a relay terminal plate 9. 10 is a heater support rod, which electrically connects the routing portions of adjacent heaters 7;
The heater 7 is supported on the inner plates 5, 5.

The relay terminal board 9 is erected on the bottom plate 4 by an insulating plate 11, and is connected to a power supply wiring 12 and a power supply terminal 13.

In this embodiment, the heater 7 has a width of 12 mm,
Six 25cm long heater elements are made of 1.2mm thick nichrome single wire processed into a semicircle.
As shown in FIG. 3, the heater support rod 10 was connected and attached to the case 1. Electric power was supplied to this heater 7 from a low voltage transformer. The secondary voltage of this transformer is 15. 4V,
When heater 7 was heated, a current of 1295A flowed,
Heat generation with a surface load density of 5 W l cnl was observed. As a result of measurement using an optical thermometer, the surface temperature of the heater 7 was approximately 850° C., which was a necessary and sufficient temperature as a cooking device for grilled meat dishes, etc.

Also, this heater has a moment of inertia of 30. 2
X10-'[rm'], and there was little deflection at high temperatures.

In the above embodiments, the present invention is applied to a heating cooker, but it goes without saying that the present invention can also be applied to other electric heaters such as heaters, dryers, electric furnaces, etc.

〔Effect of the invention〕

As explained above, in the electric heater of the present invention, the heater is formed by arranging resistors having a non-planar plate shape or a cylindrical cross section in a meandering manner. By using a heater with such a cross-sectional shape, the resistance value can be set more freely than in the case of a nine-wire heater, and the degree of freedom in temperature design is greater. Moreover, it can have more bending strength than a band wire.

[Brief explanation of the drawing]

Fig. 1 is a front sectional view showing an embodiment of the present invention, Fig. 2 is a partially cutaway side view, Fig. 3 is a plan view, Fig. 4 is a diagram for explaining the deflection of the heater, and Fig. 5 ( (a) and (b) are comparison diagrams of various characteristics depending on the cross-sectional shape of the heater. 12 cases 2: Side plate 3: Top plate 4゛Bottom plate 5: Inner plate 6: Water tray 7: Heater 7a, 7b: Heater terminal 8: Insulator 9: Relay terminal plate 10: Heater support rod
11: Insulating plate 12/power wiring 13. power terminal

Claims (1)

[Claims] 1. An electric heater characterized in that a heater is formed by arranging resistors having a non-planar plate shape or a cylindrical cross section in a meandering manner.