JPH0444713A - Water boiling device - Google Patents

Abstract

PURPOSE:To improve safety by providing a dry burning preventing control means to turn OFF a heater if a time when a heater is turned ON by a first temperature deciding means after the heater is turned OFF by a second temperature deciding means is below a given time. CONSTITUTION:A control device 13 is provided with a first temperature deciding means 14 to compare a temperature signal from a temperature detector 12 with a first reference temperature signal and a second temperature deciding means 15 to compare a temperature with a second reference temperature signal higher than the first reference temperature signal. A dry burning preventing control means 17 to turn OFF a heater 3 if a time when the heater 3 is turned ON by the first temperature deciding means 14 after the heater 3 is turned OFF by the second temperature deciding means 15 is below a given time is provided. When a power source is turned ON in a state that a dry burning state occurs as a result of a user leaving a tank 2 in a state not to feed water therein and a heater being turned ON though there is no water, this state is detected to forcibly turn OFF the heater 3, an alarm is displayed to report it to the user and a fire can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a water boiling device used in a tea dispenser for dispensing tea.

2. Description of the Related Art In recent years, tea dispensers that store hot water in a tank and supply a predetermined amount of hot water to sweets to brew tea have become widely used in offices, restaurants, and the like. For example, this is
It is shown in Publication No. 90.

The hot water stored in the tank of this tea dispenser is kept at 85-90°C by detecting the temperature of the water in the tank with a thermistor and controlling the heater so that tea is always ready for drinking.

A conventional tea dispenser will be described below with reference to FIG.

1" is a tea dispenser, 2' is a hot water tank covered with a heat insulating material such as class wool, and a heater 3' is installed on the bottom. 4' is a hot water supply vibrator, and the hot water supply control is installed in the dark. A hot water supply valve 5' is provided. 6' is a hot water supply port provided at the tip of the hot water supply pipe 4'. 7' is a tea strainer located directly below the hot water supply port, and 8' is a tea cup. It is 9°
10 is a hopper for supplying new tea leaves, and 10' is a tea leaf exchanging device which has a built-in gear motor 11'. 12' is a temperature sensor installed in the tank 2'. 13,'
is a control device that controls the hot water temperature by turning off the heater 7 when the temperature signal from the temperature sensor 12' is lower than the set temperature, and turns off the heater when it is higher, and also controls the entire tea dispenser 1'. be.

The operation of the conventional tea dispenser configured as described above will be explained. The temperature of the hot water in the tank 2' is maintained at 85-90°C by measuring the temperature with a temperature sensor 12' and controlling the heater 3'. Then, when the user turns on the tea switch (not shown), the hot water supply valve 5' is activated, and the hot water in the tank 2' is poured into the tea strainer 7' from the hot water supply port 6' and stored in the tea strainer 7'. The tea is supplied to the teacup 8'' through the tea confectioner.

Problems to be Solved by the Invention However, with the above configuration, if the user forgets to turn on the water supply to the tank and turns on the power, Peter will turn ON even though there is no water, resulting in dry cooking and a fire. There was a danger that

In view of the above 881, the present invention provides safe control of a heater.

I! ! ! Means for Solving the Problems In order to achieve this object, the water heating device of the present invention provides a water heating apparatus of the present invention, in which the time from when the second temperature determining means turns off the heater to when the first temperature determining means turns on the heater is less than or equal to a predetermined time. It consists of a dry cooking prevention control means that turns off the heater t in the case of .

Effect: With this configuration, if the user forgets to supply water to the tank and turns on the power, and the heater turns on even though there is no water, causing dry cooking, this will be detected and the heater will be forced to 0F.
FL/, to prevent fire.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a water boiler V device in an embodiment of the present invention. This example shows a case where the device is used in a tea dispenser. 1 is a tea dispenser, 2 is a hot water tank covered with an insulating material such as glass wool, and is equipped with a heater 3t''. 4 is a hot water supply vibrator, and behind it is a hot water supply valve that controls hot water supply. 5 is provided. 6 is a hot water supply port provided at the tip of the hot water supply vibrator 4. 7 is a tea strainer located directly below the hot water supply port and stores tea leaves, 8 is a tea cup. 9 is a hopper for supplying new tea leaves. , 10 is a tea and confectionery exchanging device which incorporates a geared motor 11. 12 is a temperature detector provided in the hot water tank 2, and 13 is a control device for controlling the entire tea dispenser.

The control device ff113 includes a first temperature determination means 14 that compares the temperature signal from the temperature sensor 12 and a first reference temperature signal, and compares the temperature signal and a second reference temperature signal higher than the first reference temperature signal. When the temperature signal is lower in the second temperature determining means] 5 and the first temperature determining means 14, the heater 3t! : ON, and the second temperature determination means 15
a heat retention control means 16 that turns off the heater 3 when the temperature signal is higher than the temperature signal;
and a dry cooking prevention control means 17 which turns off the heater 3 when the time required to turn on the heater 3 is less than a predetermined time.

Next, the electric circuit shown in FIG. 2 will be explained.

18 is a power switch, the heater 3 and temperature fuse 21 are connected in series via the normally open contact 20 of the first relay 19, the hot water supply valve 5 is connected via the tea switch 22, and the second relay 23 is normally open. The gear motor 11 of the tea leaf exchanging device 10 is connected through the contact point 247, and the control device 13
The primary side of the power transformer 25 inside is connected. A power circuit 26 is connected to the secondary side of the power transformer 25. The control device 13 has the temperature sensor 12 as an input. The temperature sensor 12 is an NTC thermistor, and has a negative temperature characteristic in which the electrical resistance decreases as the temperature of the object to be detected increases and the electrical resistance increases as the temperature decreases. One end of the temperature sensor 12 is connected to a DC power supply Vec, and the other end is grounded via a resistor R1. A node A between the temperature sensor 12 and the resistor R1 is connected to an inverting input terminal of the comparator 27. A resistor R is connected to the non-inverting input terminal of the comparator 27.
2, a resistor R3 and a resistor R4 are connected, the other end of the resistor R2 is connected to the DC power supply Vcc, and the resistor R3
The other end of the resistor R4 is grounded, and the other end of the resistor R4 is connected to the output terminal of the comparator 27. The resistors R2 and R3
, R4 generates a first reference voltage (first reference temperature signal) and a second reference voltage (second reference temperature signal) for heat retention control.

The first reference voltage is higher than the second reference voltage. The output terminal of the comparator 27 is connected to the input terminal a of the microcomputer 28.

Output terminals c, d and e of the microcomputer 28 are connected via buffers 29, 30 and 31 to a first relay 19 having a normally open contact 20 and a second relay 2 having a normally open contact 24.
3. Connected to LED 32 for warning display.

The water heating device configured as described above will be explained using the flowchart of FIG. 3 and the timing chart of FIG. 4.

First, when the power is turned on, the water in the tank 2 is at room temperature, the electrical resistance of the temperature detector 12 is R (25), and the voltage at point A is V (25). Therefore, in step 33, the voltage at point A is Since is lower than the first reference voltage V (87') for heat retention control, the output of the comparator 27 becomes H, and H is input to the input terminal a of the microcomputer 28. In step 34, H is outputted to the output terminal C, the first relay 19 is turned on via the buffer 29, the normally open contact 20 is closed, and the heater 34 is turned on. Water in tank 2 goes to heater 8
When the temperature rises to 98C' or higher, the electrical resistance of the temperature sensor 12 becomes smaller than R(93), and in step 35, the potential at point A becomes equal to the second reference voltage v(98C).
), so the a power of the comparator 27 becomes L. The microcomputer 28 outputs L to the output terminal C and turns off the first relay 19 via the buffer 29.
to open the normally open contact 20, and in step 36, the heater 3 is turned off. In step 87, the O of the heater 3 is
Timing is started at the same time as FF, and the process returns to step 33 again. The temperature of the hot water in tank 2 decreases due to heat radiation, reaching 87°C.
Below, the electrical resistance of the temperature sensor 12 is R(87)
In step 33, the voltage at point A becomes lower than the first reference voltage V (87), so the output of the comparator 27 becomes H. Microcomputer-28
outputs H to the output terminal C, and the first
The relay 19 is turned on and the normally open contact 20t is closed, and in step 34, the heater 3 is turned on. In step 38, time measurement is stopped at the same time as the heater 3 is turned on. 0 Normally, if the tank 2 contains hot water from the maximum amount to the minimum amount, heat radiation from turning off the heater 3 in step 36 until turning on the heater 3t in step 34 The opening time is about several tens of minutes.

Therefore, in step 39, since the time from turning off the heater 8 in step 36 to turning on the heater 3 in step 34 is longer than the predetermined time (10 minutes), the process proceeds to step 35 to perform heat retention control. .

When the user turns on the tea switch 24, the hot water supply valve 5 operates, and the hot water in the hot water tank 2 is poured from the hot water supply port 6 into the tea strainer 7, passes through the tea confectionery stored in the tea strainer 7, and makes tea. is poured into a container such as a teacup. Here, since the tea confectionery in the tea strainer 7 becomes 8 twigs when an appropriate amount of tea is supplied, the microcomputer 28 is programmed in advance so that the confectionery is automatically supplied from the hopper 9 after a certain amount of tea is supplied. This is what is being done.

Next, a case will be described in which the user forgets to supply water to the hot water tank 2 and turns on the power switch 18 of the tea dispenser 1, resulting in empty cooking.

First, when the power is turned on, the tea dispenser 1 is at room temperature, the electrical resistance of the temperature detector 12 is R(25), and the voltage at point A is V(25).
5). Therefore, in step 33, since the voltage at point A is lower than the first reference voltage V (87) for heat retention control, the output of the comparator 27 becomes H, and H is input to the input terminal a of the microcomputer 28. . In the state 34, He is outputted to the output terminal C, and the first relay 19 is turned on via the buffer 29, the normally open contact 20 is closed, and the heater 3 is turned on and dry heating starts. Tank 2 is heater 3
When the temperature rises and becomes 93C or more, the electrical resistance of the temperature sensor 12 becomes smaller than R(93), and in step 35, the voltage at point A becomes equal to the second reference voltage V(93).
), so the output of the comparator 27 becomes L. The microcomputer 28 has an output terminal e! i
l: Connect l-, open the normally open contact 20 by turning the first relay 19 to 0FFL/through the buffer 29, and proceed to step 3.
At step 6, turn off the heater 3. In step 37, timing is started at the same time as the heater 3 is turned off, and the process returns to step 33 again. The temperature of tank 2 decreases due to heat radiation,
When the temperature falls below 87C, the electrical resistance of the temperature sensor 12 becomes R.
(87), and in step 38, the voltage at point A becomes lower than the first reference voltage V(87), so the output of the comparator 27 becomes H. The microcomputer 28 outputs H to the output terminal C, turns on the first relay 19 via the buffer 29, closes the normally open contact 20, and turns on the heater 8 in step 34. Step 38
At this time, timing is stopped at the same time as the heater 3 is turned off. In the case of dry cooking, turn the heater 3t OFF in step 36.
Since there is no hot water and only the temperature of the tank 2 is lowered, the time from when the heater 3 is turned on in step 34 is very short, and the heat is dissipated in about a few minutes. Therefore, in step 39, all heaters are turned off in step 36.
Since the time from when the heater 3 is turned on in step 84 is shorter than the predetermined time (10 minutes), the process proceeds to step 40, and the dry cooking prevention side @ is started. The microcomputer 28 outputs L to the output terminal C, turns the first relay 19 OFFFL/OFF via the buffer 29, opens the normally open contact 20, and forcibly turns off the heater 3. In step 41, the microcomputer 28 outputs the Lt ratio to the output terminal e and displays a warning Lt via the buffer 31.
Turn on ED32.

As described above, according to the present embodiment, dry cooking is performed in which the heater is turned off when the time from turning off the heater by the second temperature determining means to turning the heater on by the first temperature determining means is less than or equal to a predetermined time. By providing a prevention control means, if the user forgets to supply water to the tank and turns on the power, and the heater turns on/off even though there is no water, this will be detected and the heater will be forced to turn OFF. /, a warning is displayed to notify the user and prevent a fire.

In addition, costs can be rationalized by using a temperature sensor for both heat retention control and dry cooking prevention control.

As described above, the present invention provides a temperature sensor for detecting the temperature of hot water in a tank, a first temperature determination means for comparing a temperature signal from the temperature sensor with a first reference temperature signal, and a temperature sensor for detecting the temperature of the water in the tank. a second temperature determination means that compares the signal with a second reference temperature signal that is higher than the first reference temperature signal; and a heater is turned on when the temperature signal is lower in the first temperature determination means, and the second temperature determination is performed. a heat retention control means for turning off the heater when the temperature signal is higher than the temperature signal; By comprising a dry cooking prevention control means that turns off the heater in the case of F, the user forgets to supply water to the tank and turns on the power, causing the heater to turn on even though there is no water, resulting in dry cooking. When this is detected, the heater e is forced to 0FFL/,
It prevents fires and has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a water heating device according to an embodiment of the present invention, Fig. 2 is an electric circuit diagram of the device, Fig. 3 is a flowchart showing the operation of the device, and Fig. 4 is a flowchart showing the operation of the device. The timing chart shown in FIG. 5 is a configuration diagram of a conventional water heating device. 2...Tank, 3...Heater, 12...Temperature detector, 1
4..First temperature determination means, 15..Second temperature determination means,
16. Heat retention control means, 17. Dry cooking prevention control means. Name of agent: Patent attorney Shigetaka Awano and 1 other person -ta〉ri3-heaterl? -3 act 1 (!

Claims (1)

[Claims] A tank for storing hot water, a heater provided in the tank, a temperature sensor for detecting the temperature of the water in the tank, and a first temperature determination means for comparing a temperature signal from the temperature sensor with a first reference temperature signal. , a second temperature determination means for comparing the temperature signal and a second reference temperature signal higher than the first reference temperature signal, and a heater is turned on when the temperature signal is lower in the first temperature determination means; a heat retention control means for turning off the heater when the temperature signal is higher in the two temperature determination means; and a time period from when the heater is turned off by the second temperature determination means to when the heater is turned on by the first temperature determination means. A water boiling device comprising an empty cooking prevention control means that turns off the heater when the time is less than a predetermined time.