RU2476033C1 - Method for manufacture of multi-electrode composite electric heater - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: method for manufacture of a multi-electrode composite electric heater (MECEH) relates to resistive heating elements with application of electrically conductive composite materials and may be used for manufacture of composite electric heaters applied in industrial and agricultural productions. The manufacture method consists in shaping a package including a heat-emitting (electrically conductive) layer 1, positioned between the insulation layers 2. Placed inside the electrically conductive layer 1 is a system of electrodes 3 made of metal (e.g. copper or brass) grid; preliminarily soldered to the electrodes 3 are flexible contact leads 4 projecting outside the electric heater structure in the insulating jacket 5. The targeted change of the MECEH electrically conductive layer composition and the heater manufacture technological mod parameters has resulted in MECEHs with a negative temperature resistance coefficient α_p, which corresponds to decrease of the electrically conductive layer volume resistivity p_v combined with increase of temperature on the MECEH surface.

EFFECT: method for manufacture of a multi-electrode composite electric heater allows to ensure an energy efficient mode of the electric heater functioning with automatic adjustment of surface temperature without loss of the required operational and electrophysical characteristics.

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Description

The invention relates to the field of electrical engineering, in particular to a technology for producing heating elements, and can be used in the manufacture of electric heaters for local heating in technical and domestic conditions.

A known method of manufacturing a composite electric heater (Pat. RF No. 2037895, class. НСС 7/00, publ. 06/19/95), including the manufacture of insulating layers and a heat-releasing layer of an electrically conductive material consisting of a carbon filler in the form of carbon black, bonding to based on butyl rubber, a plasticizing ingredient in the form of stearin and additional functional ingredients, the placement of a heat-generating layer with electrodes and flexible current leads between the insulating layers and subsequent vulcanization is assembled package in the following ratio of components, wt.%:

Butyl rubber 51-57.73 Carbon black 21.17-28.04 Stearin 1.54-1.64 Additional functional ingredients 16.86-19.46,

moreover, additional functional ingredients are selected in the following ratio, wt.%:

Zinc oxide 1.54-1.64 Barite Concentrate 7.75-8.10 Hexachlor-p-xylene 0.22-0.52 n-tert-Alkyl-phenol-formaldehyde resin 5.75-7.10 Staboil 1.6-2.1.

The disadvantage of this method is that it does not provide a mode of self-regulation of temperature on the surface of a multi-electrode composite electric heater (FEM).

The closest in technical essence is the method of manufacturing FEM, including the manufacture of insulating layers and a heat-releasing layer of an electrically conductive material consisting of a carbon filler in the form of carbon black, a binder based on butyl rubber, a plasticizing ingredient in the form of stearin and additional functional ingredients, the placement of a heat-releasing layer with electrodes and flexible current leads between the insulating layers and the subsequent two-stage vulcanization of the assembled pack eta (Pat. RF №2075836, class H05B 3/28, publ. 03.20.97)

The disadvantage of this method, as well as in the known analogues, is that it does not provide a mode of self-regulation of temperature, which leads to inefficient use of electricity.

The technical result of the invention is the development of such a method of manufacturing FEM, which would allow, along with wide functional and operational capabilities, to provide a mode of self-regulation of temperature on the surface without losing the necessary electrical and physical characteristics.

The problem is solved in that in a method for manufacturing a multi-electrode composite electric heater, including the manufacture of insulating layers and a heat-releasing layer of an electrically conductive material consisting of a carbon filler in the form of carbon black, a binder based on butyl rubber, a plasticizing ingredient in the form of stearin and additional functional ingredients; placement of the heat-generating layer with electrodes and flexible current leads between the insulating layers and the subsequent vulcanization of the assembled package in two stages, characterized in that the manufacture of the electrically conductive material is carried out by mixing butyl rubber, carbon black, stearin and additional functional ingredients in the following ratio of components, wt.%:

Butyl rubber 59-60 Carbon black 19.50-21.10 Stearin 1.44-1.53 Additional functional ingredients 16.86-19.46.

Additional functional ingredients are selected in the following ratio, wt.%:

Zinc oxide 1.54-1.64 Barite Concentrate 7.75-8.10 Hexachlor-p-xylene 0.22-0.52 n-tert-Alkyl-phenol-formaldehyde resin 5.75-7.10 PM oil 1.6-2.1.

Moreover, the vulcanization of the collected package is carried out at the first stage for 0.5-1 minutes at a pressure of 12-13 MPa, and at the second stage - for 30-35 minutes at a pressure of 11-11.5 MPa.

In modern industrial production of butyl mixtures, PM brand paraffin-naphthenic oil is used as the vulcanizing ingredient as the most environmentally friendly component in comparison with previously used stableoil. Therefore, instead of stabiloil (Pat. RF No. 2037895, class Н01С 7/00, publ. 06/19/95), PM oil was introduced as an additional functional ingredient without changing the ratio of wt.%.

The invention is illustrated in figure 1.

Figure 1 presents a method of manufacturing a multi-electrode composite electric heater. The heat-releasing layer 1 is placed between the insulating layers 2, a system of electrodes 3 of a metal mesh, for example, copper or brass, is placed in the electrically conductive layer 1, flexible current leads 4 preceding the structure of the electric heater in the insulating sheath 5 are pre-soldered to the electrodes 3. The assembled package is vulcanized in two stages at a temperature of 172-174 ° C, at the first stage - for 0.5-1 minutes at a pressure of 12-13 MPa, and at the second stage - for 30-35 minutes at a temperature of 165-167 ° C and a pressure of 11-11 5 MPa.

A decrease in pressure below the specified limit (below 12 MPa) and a decrease in vulcanization time at the first stage (less than 0.5 min) do not allow to obtain the required electrical parameters of the electric heater.

A decrease in pressure at the second stage of the vulcanization process (below 11 MPa) and a decrease in time (less than 30 minutes) do not allow to obtain a product that meets the requirements of GOST R 52161.1-2004 (IEC 60335-1: 2001).

Thus, by a directed change in the composition of the electrically conductive layer of the FEM and the parameters of the technological mode of its manufacture, FEM electric heaters with a negative temperature coefficient of resistance α _ρ were obtained, which corresponds to a decrease in the specific volume resistance of the conductive layer ρ _v with an increase in temperature on the surface of the FEM.

To study the dependence of ρ _v on the temperature change T FEM, a batch of 5 electric heaters was selected, made in accordance with the proposed method.

The measurements were carried out at an ambient temperature of 18–20 ° C, the sample was placed on a wooden base, and an electric heater was supplied with voltage of 220 V at a frequency of 50 Hz every five minutes during the first hour and every ten during the second; measured voltage, current and temperature on the surface of the electric heater.

The nature of the given dependences ρ _v = f (T) after entering the operating mode (Fig. 2) indicates a negative temperature coefficient inherent in polymer semiconductor materials, and shows the predominance of the conductive filler - conductive filler bonds with respect to the polymer - conductive filler bonds in the resistive CM phase, resulting from an increase in the thermal emission of electrons in a butyl rubber matrix, an increase in their mobility, and the movement of charges in places where the conductive circuits rupture EC due to the tunnel effect. This circumstance makes possible the operation of the FEM in an energy-efficient self-regulation mode. It was found that the nature of the dependence ρ _v = f (T) is similar for samples of the entire batch, the average deviation was not more than 7% of the measured value.

The operation of the FEM in the technological mode of self-regulation allows you to adjust the energy consumption for local heating, for example, young animals, depending on the conditions of heat transfer. The principle of operation of the self-regulating FEM is that, in the absence of animals, the heater is heated to a temperature sufficient to attract them. When the young animals are on the electric heater, the heat transfer at the point of contact decreases, which leads to an increase in temperature and a decrease in its resistance. The decrease in resistance ρ _v in the contact zone of animals with the fuel surface of the FEM is accompanied by an additional increase in power and the establishment of the required temperature. To implement the FEM self-regulation mode, the electrically conductive layer must have a negative α _ρ . The use of self-regulating FEM allows significantly reducing the consumption of electric energy for local heating of young animals. In addition, since the regulation process occurs due to the self-organization of the structure of the electrically conductive layer with changing heat transfer conditions, there is no need for additional automation elements and communication lines to control the temperature.

Thus, in comparison with known analogues, the inventive method of manufacturing a multi-electrode composite electric heater allows you to provide an energy-efficient mode of operation of the electric heater with self-regulation of temperature on the surface without losing the necessary operational and electrophysical characteristics.

Claims (1)

A method of manufacturing a multi-electrode composite electric heater, including the manufacture of insulating layers and a heat-releasing layer of an electrically conductive material consisting of a carbon filler in the form of carbon black, a binder based on butyl rubber, a plasticizing ingredient in the form of stearin and additional functional ingredients; placing a heat-generating layer with electrodes and flexible current leads between the insulating layers, characterized in that the preparation of the electrically conductive material is carried out by mixing butyl rubber, carbon black, stearin and additional functional ingredients in the following ratio of components, wt.%:
Butyl rubber 59-60 Carbon black 19.50-21.10 Stearin 1.44-1.53 Additional functional ingredients 16.86-19.46;
moreover, the collected package is vulcanized at the first stage for 0.5-1 min at a temperature of 172-174 ° C and a pressure of 12-13 MPa, and at the second stage for 30-35 min at a temperature of 165-167 ° C and a pressure of 11- 11.5 MPa.

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