JPS5824889B2 - Anzen Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a safety device that automatically checks each time the device starts operating, and if the check is normal, the device is operated.

Conventional configuration and its problems As a conventional general safety device, for example, if the equipment becomes abnormally high temperature despite the presence of a temperature controller,
Some water heaters are equipped with a safety device that detects abnormally high temperatures using a temperature-sensitive element closely attached to the device and activates a cutoff relay to turn off the power and stop combustion in the combustion section. Unless the device reaches an abnormally high temperature, it will not operate at all, and in some cases, the device may end its life without operating even once during use.

However, the operational reliability of the safety device decreases in a natural logarithmic manner, even during periods of inactivity, according to reliability theory.

If the safety device fails in this way, the following two types of failure will occur.

The first is a safety device that activates and stops combustion even though there is no abnormality, and although the equipment cannot function, it is not dangerous to humans.

The second is that the safety device does not operate at all even in abnormal situations.
Therefore, this is a failure where combustion continues and the equipment becomes even more abnormally hot.

This is the same as not having safety equipment, and can easily lead to dangers such as fire.

In the first case, the safety device operates immediately when the equipment malfunctions, and from the perspective of the safety device, it can be said that it operated normally.
In the second case, even if the safety device fails before an abnormality occurs in the device, there is no problem in the normal operation of the device, and therefore, it is impossible to discover the failure of the safety device.

In order to improve this drawback, a configuration has been considered in which a safety device having a cutoff relay is automatically checked each time the device starts operating.

The one shown in Figure 1 shows an automatic check type safety device such as a water heater that detects abnormal temperature of the equipment and stops operation in case of abnormality.In other words, 1 is the power supply, 2 is the power switch, and 3 is the inspection. A signal generator, 4 an anomaly detector, 5 a transistor that is turned on by the output of the anomaly detector 4, 6 a cutoff relay, and 7 a pulse storage circuit, in this example a thyristor that is triggered by a pulse and remains on; 8 is a gate resistance of the thyristor 7, 9 is a device, and 10 is a normally closed contact that opens when the cutoff relay 6 is energized.

In the configuration shown in FIG. 1, when the power switch 2 is closed by a command to start operation of the device 9, the inspection signal generator 3 also outputs a pulse-like inspection signal to forcibly operate the abnormality detector 4. .

The width of the inspection signal is set within the dead time of the cutoff relay 6 in which the normally closed contact 10 is not opened even when the cutoff relay 6 is energized.

If the abnormality detector 4 is normal, an output corresponding to the inspection signal width is generated and the transistor 5 is turned on instantaneously.

During that time, the cutoff relay 6 is energized, but the cutoff relay 6
Since it is within the dead time, the normally closed contact 10 is not opened, and moreover, its output reaches the gate of the thyristor 7 and turns it on.

As a result, the equipment 9 starts operating.

If the outputs of the inspection signal generator 3, the abnormality detector 4, and the transistor 5 are not generated, or if the cutoff relay 6 is disconnected, the inspection signal will not reach the gate of the thyristor 7. Even if an operation start command is issued, the thyristor 7 is not turned on, and the device 9 is not operated.

When the power switch 2 is opened in response to an operation stop command, the thyristor 7 is turned off and waits for the next operation start command.

When the actual equipment 9 is abnormal, the abnormality detector 4 outputs a continuous output.

Accordingly, the cutoff relay 6 is activated, its normally closed contact 10 is opened, and the operation of the device 9 is stopped.

Although the above configuration can ensure extremely high safety, the dead time of the cutoff relay 6 is usually about several mS, although it varies depending on its rating and shape, and therefore the inspection signal generated from the inspection signal generator 3 The time width must be set to several milliseconds or less, and the shorter the time, the more sensitive the thyristor 7, which is a pulse memory circuit, must be so that it can operate even with a short inspection signal, so it is more likely to malfunction due to noise. Therefore, even when the device 9 is normal, the cutoff relay 6 operates and stops the operation of the device.

OBJECTS OF THE INVENTION The present invention has been made to overcome these conventional drawbacks, and it is an object of the present invention to provide a safety device that can be inspected using inspection signals over a long period of time, has high safety, and is less likely to malfunction.

Structure of the Invention In order to achieve this object, the present invention connects a direct thermal characteristic temperature-sensitive resistance element in series with a cutoff relay.

With this configuration, even if the cut-off relay is energized by an inspection signal having a time width longer than the dead time of the cut-off relay, the current is limited by the temperature-sensitive resistance element with direct heat characteristics, so the cut-off relay does not operate. Furthermore, the equipment can be operated by transmitting inspection signals to the pulse memory circuit, and when a continuous output occurs in the event of an abnormality or failure, the directly heated type negative temperature sensitive resistance element only heats up and its resistance increases. When the amount decreases, the cut-off relay can be operated to stop the operation of the equipment.

Description of examples An embodiment of the present invention will be described below with reference to the circuit diagram shown in FIG.

The same members as in FIG. 1 are given the same numbers, and the difference from FIG. 12 is connected to the gate of the thyristor 7.

Therefore, the pulses from the inspection signal generator 3 are transmitted to the thyristor 7, which is the pulse storage circuit, through a series circuit with the cutoff relay 6 and the direct heat characteristic temperature sensitive resistance element 11.
A pulse transmission path is constructed such that the direct heat characteristic temperature sensitive resistance element 15 is self-heated and its resistance value becomes small, and the pulse duration is set to be the time required for the direct heat characteristic temperature sensitive resistance element 15 to self-heat and reduce its resistance value, and to operate the cutoff relay 6. Therefore, even if the transistor 5 is turned on by the inspection signal at the time of inspection, the cutoff relay 6 will not operate because the resistance value of the direct heat characteristic temperature sensitive resistance element 15 is large. ,
Only the thyristor 7, which is the pulse storage circuit, is turned on and the device 9 starts operating.

In addition, in response to a continuous signal during an abnormality, after a certain period of time, the resistance value of the direct heating type negative temperature sensitive resistance element 15 suddenly decreases due to self-heating, and the current value increases, and the current reaches the current of the cutoff relay 6. At this point, the cutoff relay 6 operates to open the normally closed contact 10 and stop the operation of the device 9.

In this configuration, the capacitance of the capacitor 14 is determined to obtain a time constant necessary for noise prevention, and the inspection signal generator 3 is set so as to output an inspection signal pulse with a time width longer than the number of points in time. By selecting an element having a time constant longer than the inspection signal pulse time width as the direct heat characteristic temperature sensitive resistance element 15, design becomes possible easily.

Effects of the Invention As described above, the present invention connects a direct heat characteristic temperature sensitive resistance element in series with a cutoff relay, and a pulse from an inspection signal generator connects the cutoff relay and the direct heat characteristic temperature sensitive resistance element. Each time the pulse is transmitted to the pulse storage circuit that operates the device during storage through a series circuit of Since the time is set to be shorter than the activation time of the cut-off relay, the cut-off relay is not activated during inspection, and the inspection signal generator and the direct heat characteristic temperature sensitive resistance element are not opened. It is possible to start operation of the equipment after checking that there is no short-circuit failure or open failure of the cutoff relay, and to check whether the equipment is operated without pulses being transmitted to the pulse storage circuit when the above-mentioned failure occurs. Or, due to continuous output, the direct heat characteristic temperature sensitive resistance element self-heats and its resistance value decreases, operating a cutoff relay and cutting off the operation of the device.

Therefore, it is possible to ensure high safety, and at the same time, it is possible to use a long-width inspection pulse that can clearly distinguish the difference from noise, so there are fewer malfunctions due to noise, and the purpose can be achieved simply by adding a direct heat characteristic temperature-sensitive resistance element. It has features such as a simple structure.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional safety device, and FIG. 2 is a circuit diagram showing an embodiment of the safety device of the present invention. 3... Inspection signal generator, 4... Abnormality detector, 6... Cutoff relay, 7... Pulse memory circuit (thyristor), 9... ...Equipment, 10
・・・・・・Normally closed contact, 14・・・・Capacitor,
15... Direct heating characteristic temperature sensitive resistance element.

Claims (1)

[Claims] 1. An inspection signal generator that generates a pulsed inspection signal;
A cutoff relay that connects a normally closed contact in series with the device and opens the normally closed contact to cut off the operation of the device when the coil is energized, and a direct heat characteristic that limits the current flowing through the cutoff relay to below the electric current. a temperature resistance element, and a pulse storage circuit that activates the device during storage, and the pulse from the inspection signal generator is connected to the temperature resistance element through a series circuit with the cutoff relay and the direct heat characteristic temperature resistance element. When transmitted to the pulse storage circuit,
The pulse duration is set to be shorter than the time required for the direct heat characteristic temperature sensitive resistance element to self-heat and reduce its resistance value to operate the cutoff relay.