JPS6227812Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to preventing malfunction of a safety thermometer provided on a heater flange as a safety device in an electric water heater using an electric heater as a heating device.

A conventional electric water heater will be explained with reference to FIG. 1
This is a can body which has a water chamber 2 inside and whose inner surface is glass-lined. Reference numeral 7 designates a corrosion protection electrode of an externally powered corrosion protection device that prevents the glass lining surface of the can body 1 from rusting, and is installed so as to be electrically insulated from the can body 1. 8 is an electric heater installed so as to protrude into the water chamber 2, and 9 is a heater flange. Reference numeral 10 denotes a thermostat attached to the outer wall of the can body 1, which controls energization of the electric heater 8 by detecting temperature. A safety thermostat 11 is attached to the heater flange, and serves as a safety device when the thermostat 10 is not activated. Reference numeral 12 denotes a heater protection tube, one end of which is shaped like a collar, and the heater flange 9 is inserted between the heater seats 16 and attached. The other end protrudes into the water chamber 2 and has an open cylindrical shape. The heater protection tube 12 has such a structure that it protrudes into the water chamber in relation to the anticorrosion current generated by the anticorrosion electrode 7. 13 is a water retention area between the heater protection tube 12 and the electric heater 8. 14 is a heater core rod, and 15 is a heating wire connected from the tip of the heater core rod.

In this configuration, when the electric heater 8 is energized, the wall temperature of the thermostat 10 and the wall temperature of the safety thermostat 11 are as shown in FIG. A shows the temperature rise curve of the wall temperature of the thermostat 10, and b shows the temperature rise curve of the wall temperature of the safety thermostat 11. Each curve increases in proportion to the energization time of the electric heater 8, and the set value of the thermostat 10 (for example, 83
℃), the thermostat 10 is turned off and the electric heater 8 is de-energized. At this time, the temperature of the safety thermostat 11 is approximately 90°C, which is only a low temperature with a safety factor compared to the set value of the safety thermostat 11 (for example, 100°C).

However, under conditions such as when the quality of the water used is poor, rust water, scale, or air generated from the water accumulates in the water retention area 13 after several months of installation and use, causing water to flow from the electric heater 8. Heat conduction to the sides will deteriorate, and the temperature of the heater flange 9 will rise. As a result, a curve with a large temperature difference from the temperature rise curve of the thermostat 10, as shown in the curve C in FIG.
will exceed the set value (e.g. 100℃),
Safety thermo 11 operates earlier than thermo 10,
Stop energizing. Therefore, hot water at a predetermined temperature cannot be obtained.

The present invention eliminates the drawbacks of the above-mentioned conventional technology, and also solves the problem of the factors that inhibit heat conduction to the water side of the electric heater.
This invention provides a mounting structure for an electric heater in which a safety thermostat does not operate, and the present invention will be explained below with reference to an embodiment shown in FIG. 17 is a heater core rod, and the position where it is joined to the heat generating wire 18 is from the open cylindrical end of the heater protection tube 12 to the water chamber 2.
It is located on the side. The other configurations are the same as before.

According to this configuration, rust water,
Even if scale or air accumulates, the temperature of the heater flange 9 will not rise abnormally because there is no heating wire 18 inside the heater protection tube 12. To explain this with reference to FIG. 4, the curve a shows the temperature increase curve of the thermostat 10, and the curve b shows the temperature increase curve of the safety thermostat 11 during normal times.
Curve C shows the temperature rise curve of the safety thermostat 11 when rust water, scale, air, etc. accumulate in the water retention area 13, and it is almost on the same line as curve b during normal operation.

As mentioned above, by locating the heat generating wire of the electric heater closer to the water chamber than the tip of the open cylindrical part of the heater protection tube, factors that inhibit heat conduction on the water side of the heater (rust water, scale, air, etc.) It is possible to obtain a heater mounting structure that can normally control the energization to the electric heater even under usage conditions that are affected by (e.g.).

Furthermore, in order to further improve heat conduction to the water side of the heater, it goes without saying that the same effect can be achieved by providing a heat conductor such as a copper plate at the tip of the heater protection tube in contact with the heater.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of the heater mounting portion of a conventional electric water heater, Fig. 2 is a temperature rise characteristic diagram of the thermo section and safety thermo section when the conventional heater is energized, Fig. 3 is a vertical cross-sectional view of the heater mounting portion of an electric water heater according to one embodiment of the present invention, and Fig. 4 is a diagram equivalent to Fig. 2 in the case of Fig. 3. 1.... boiler body, 2.... water chamber, 7.... corrosion protection electrode, 8
……Electric heater, 9……Heater flange, 10…
...thermostat, 11...safety thermostat, 12...heater protection tube, 13...water retention area, 17...heater core rod, 18...heating wire.

Claims (1)

[Scope of utility model registration request] In an electric water heater having a can body whose water contact surface is glass-lined and an anti-corrosion electrode for protecting the can body, the starting position of the heating wire of the electric heater, which is the heating device, is arranged on the outer periphery of the electric heater. An electric water heater characterized in that the protective tube is located further toward the water chamber than the tip position on the water chamber side.