JP3247325B2 - Thermal relay and control circuit using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents electrical devices such as hot water heaters, water heaters and heaters from operating even when a physical quantity such as temperature exceeds a set value. And a control circuit using a thermal relay .

[0002]

2. Description of the Related Art Conventionally, when controlling a hot water temperature by a hot water storage tank of a hot water storage type water heater, a liquid expansion type thermostat, an analog electronic temperature controller, a microcomputer type temperature controller and the like have been used.

[0003] However, depending on the load of a heater or the like to be controlled, the opening and closing capability of the temperature controller itself is insufficient, so that a large capacity electromagnetic relay or electromagnetic contactor may be used in some cases.

In any case, an overheating prevention device is generally provided in preparation for a failure of the temperature control device.

Normally, a system different from the temperature controller, for example, a bimetallic thermal relay is used for the overheat prevention device, and the device is selected so as to operate at a temperature higher than the maximum controllable temperature of the temperature controller. Is done. This operating temperature is usually set to a temperature higher by 3 ° C. to 10 ° C. in consideration of the respective variations and error ranges of the temperature controller and the excessive temperature rise prevention device.

[0006]

However, when the set temperature of the temperature controller is near the boiling point, it is no longer possible to set an interval of 3 ° C. to 10 ° C. as described above. Therefore, conventionally, a rise in temperature due to steam generated, not the hot water temperature, is detected, and when the hot water temperature is equal to or higher than the set temperature, an abnormality is determined and the excessive temperature rise prevention device is operated.

[0007] Even if the set temperature is not near the boiling point, in order to operate the excessive temperature rise prevention device reliably, the temperature distribution on the surface of the hot water storage tank is measured. It has been necessary to fix the excessive temperature rise prevention device so as to specify the portion where the temperature rises when the occurrence occurs, and to make contact with the hot water storage tank in as large an area as possible.

The present invention has been made in view of such a problem, and can be manufactured at a low cost with a small number of parts, operates quickly and reliably when a failure occurs in a temperature control device, and aims to improve the safety of electric devices. In addition, an object of the present invention is to improve the ease of maintenance without sticking to the surface of the hot water storage tank, and also to provide an inexpensive and robust temperature control device, not limited to an excessive temperature rise prevention device.

[0009]

In order to solve the above problems SUMMARY OF THE INVENTION The control circuit using a thermal relay according to claim 1, set
Thermal relay for intermittent bimetal contact at constant temperature
In the vicinity of the bimetal contact,
The bimetal contact is energized by a circuit other than the
Uses a thermal relay with a heating element that makes the point non-conductive.
Control circuit for supplying power to the electrical equipment.
The normally open contact and the bimetal contact of the thermal relay
Connected to a column to form a first circuit;
A first relay that closes the contacts and conducts, and a predetermined physical quantity
Control element that detects conduction and shuts off conduction after reaching the set physical quantity
Are connected in series, and with respect to the first relay
A second circuit is configured by connecting the second relay in parallel,
The heating element of the thermal relay and the excitation of the second relay
Opened by magnetism, closed by de-energization of the second relay
A third circuit formed by connecting a first normally closed contact in series with
A sensor connected in parallel with the electric device.
Control circuit using a normal relay .

A control circuit using the thermal relay according to the second aspect is a control circuit using the thermal relay according to the first aspect.
It, the heating element is characterized by a heater comprising a PTC element.

A control circuit using the thermal relay according to claim 3.
The road uses the thermal relay according to any one of claims 1 and 2.
In the above control circuit , the physical quantity is a temperature, and the electric device is a heater.

[0012]

[0013]

Next, a control circuit and a thermal relay according to a preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a control circuit for a heating device according to this embodiment. In FIG. 1, a pair of conducting wires 1 and 2 are provided for convenience.
The first circuit 3 and the second circuit 4 are connected between them, but the first circuit 3 and the second circuit 4 may not be connected to each other. An energizing main switch (not shown) is provided on one of the pair of conducting wires 1 and 2. In the first circuit 3, a heater 5 (electric device) for heating a hot water storage tank (not shown), a normally open contact R1, and a thermal relay 6 having a bimetal contact composed of a normally closed contact are connected in series. ing. The normally open contact R1 is operated by the relay R1 of the second circuit 4, and closes the normally open contact R1 to energize the heater 5 when the relay R1 is excited by energization.

The heater 5 is arranged near the bottom of a hot water storage tank (not shown) of the water heater. The thermal relay 6 is provided at a position away from the hot water storage tank and at a position where the reset switch 7 can be easily operated, and presses the reset switch 7 from outside the water heater to return the contact to the normally closed side again. You can do it.

The thermal relay 6 is provided with a reset switch 7 as shown in FIG. 2. When the reset switch 7 is pressed, the contacts come into contact with each other in a separable manner to prevent welding.

An overheat prevention circuit 8 (separate circuit) for turning off the thermal relay 6 is connected to the heater 5 in parallel. The overheat prevention circuit 8 includes a heater 9 composed of a PTC element that generates heat by conduction and a relay R of the second circuit 4.
2 and a normally-closed contact R2 operated by the switch 2.

The bimetal contact 6 of the thermal relay 6 is fixed on a mounting plate 11, and the heater 9 is fixed on a mounting plate 12. The heater 9 is attached to the mounting plate 1 by the insulating material 13.
1 and 12 are electrically insulated. When the heater 9 is heated by energization of the overheat prevention circuit 8, the bimetal contact inside the thermal relay 6 is deformed and the terminals 14 connected to the first circuit 3 are cut off. The reset switch of the thermal relay 6 connects the terminals 14 and 14 to each other so that the terminals 14 and 14 are non-conductive, as in the case of the bimetal contact.

The second circuit 4 includes a thermostat 10 that is shut off when the temperature of the hot water in the hot water storage tank overheated by the heater 5 reaches a set temperature, and relays R1 and R2 that are connected in series to the thermostat 10. And the relays R1 and R2 are connected in parallel. Thermostat 1
0 detects the water temperature of the hot water storage tank of the water heater, and when the water temperature of the hot water storage tank becomes equal to or higher than the set temperature, the contact is opened to be in a non-conductive state.

Next, the operation of the circuit in the heating device of this embodiment will be described.

When a main switch (not shown) of the water heater is turned on, the thermostat 10 is normally closed and conductive, so that the second circuit 4 is conductive and the relays R1 and R2 are excited. Thereby, the normally open contact R1 is closed, and the normally closed contact R2
Opens. Due to the conductive connection of the normally open contact R1, the heater 5 generates heat, and the water in the hot water storage tank of the water heater is heated. When the water temperature of the hot water storage tank reaches the set temperature of the thermostat 10, the thermostat 10 operates to turn off the second circuit 4, the excitation of the relay R1 is released, and the normally open contact R1 is released.
Are turned off. When the normally open contact R1 is welded,
Even if the thermostat 10 is activated, the heating of the heater 5 is continued. However, since the excitation of the relay R2 is canceled, the normally closed contact R2 of the heating prevention circuit 8 is closed, the heater 9 is heated, and the thermal relay is heated. 6 operates to open the bimetal contacts of the thermal relay 6. As a result, the power supply to the heater 5 is stopped and the heating of the heater 5 is prevented, so that even if the normally open contact R1 is welded, overheating can be reliably prevented.

Although the control circuit 8 of the above embodiment is effective for welding of all contacts, especially when the hot water temperature is set to the boiling point, a timer is provided in the overheat prevention circuit 8 of FIG. Further, the boiling time can be controlled. Further, a heater is used as the electric device in this embodiment, but the electric device is not limited to the heater and may be used for a machine tool.

The thermal relay according to claim 1 of the present invention is used.
According to the control circuit, the bimetal contact
In a thermal relay that performs intermittent operation,
Near the point, energized by a circuit different from the bimetal contact
To provide a heating element that renders the bimetal contact non-conductive.
A control circuit using the digit thermal relay, electromechanical
A first normally open contact for supplying power to the
Are connected in series to form the first circuit.
The first normally open contact to close and conduct.
After detecting the relay and the specified physical quantity and reaching the set physical quantity
And a control element that interrupts conduction is connected in series and
The second relay is connected in parallel to the first relay.
And a heating element of the thermal relay.
Is opened by the excitation of the second relay, and the second relay is opened.
Series connection with the first normally closed contact that closes when the
A third circuit connected in parallel with the electrical equipment.
Since it is, even when the first normally open contact is no longer able to disconnect the power supply by contact welding, bimetal contact of the thermal relay is overheated by the heating elements, because they are reliably cut, stopping the abnormal driving of the electrical device Can be done.

The thermal relay according to claim 2 of the present invention is used.
According to the control circuit described above, since the heating element is a heater made of a PTC element, it is easy to control energization with a small current.

The thermal relay according to claim 3 of the present invention is used.
According to the control circuit , since the physical quantity is a temperature and the electric device is a heater, overheating of the heater due to welding of the first normally open contact can be reliably prevented.

According to the control circuit of the fourth aspect, in the control circuit of the third aspect, the physical quantity is a temperature, and the electric device is a heater. Overheating can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a control circuit of a heating device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement state of a bimetal switch and a PTC element in a thermal relay provided in the control circuit of FIG. 1;

[Explanation of symbols]

 Reference Signs List 3 first circuit 4 second circuit 5 heater 6 thermal relay 8 third circuit 9 PTC element

Claims (3)

(57) [Claims] A bimetal contact is switched on and off according to a set temperature.
In the thermal relay, near the bimetal contact
And the bimetal contact is energized by another circuit.
A heater provided with a heating element for making the bimetal contact non-conductive.
A control circuit using a thermal relay, wherein a first normally open contact for supplying power to an electric device and a bimetal contact of the thermal relay are connected in series to form a first circuit; A first relay that closes an open contact and conducts, and a control element that detects a predetermined physical quantity and cuts off conduction after reaching a set physical quantity are connected in series, and the first relay is connected to the first relay.
A second circuit is formed by connecting a second relay in parallel to the second relay, and a heating element of the thermal relay and the second relay are opened by excitation of the second relay and closed by the excitation release of the second relay. A control circuit using a thermal relay , wherein a third circuit formed by connecting a first normally closed contact in series is connected to the electric device in parallel. 2. A control circuit using the thermal relay according to claim 1.
A control circuit using a thermal relay , wherein the heating element is a heater composed of a PTC element. 3. The thermal relay according to claim 1, wherein :
In the control circuit using , the physical quantity is temperature,
A control circuit using a thermal relay, wherein the electric device is a heater.