JPH0449916A - Water heater - Google Patents

Abstract

PURPOSE:To obtain safety control of a heater by providing a waterless boiling preventing control means which turns the heater OFF when a time period from turning-ON of the heater by a first temperature deciding means to turning-OFF of the heater by a second temperature deciding means is shorter than a prescribed value. CONSTITUTION:A controller 13 is provided with a first temperature deciding means 14 for comparing temperature signal from a temperature detector 12 with a first reference temperature signal, a second temperature deciding means 15 for comparing the temperature signal with a second reference temperature signal which is higher than the first reference temperature signal, and further with a warmth retaining control means 16 for turning a heater 3 ON when the temperature signal is lower than the first reference temperature signal in the first temperature deciding means 14 and turning the heater 3 OFF when the temperature signal is higher than the second reference temperature signal in the second temperature deciding means 15, and a waterless boiling preventing control means 17 for turning the heater OFF when a time period from turning-ON of the heater 3 by the first temperature deciding means 14 to turning- OFF of the heater by the second temperature deciding means 15 is shorter than a prescribed value. Thus, safety control of the heater can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a water heating device used in a tea dispenser that supplies 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
This is shown in Publication No. 90, etc. The hot water stored in the tank of this tea dispenser is kept at a temperature of 85-90C 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 glass wool, and a heater 3' is provided on the bottom surface. 4' is a hot water supply pipe, and a hot water supply valve 5' for controlling hot water supply is provided between the pipes. 6″ is hot water supply vibe 4″
It is a hot water supply port installed at the tip of the 7' is a tea strainer located directly below the hot water supply spout for storing tea and sweets, and 8' is a tea cup. Reference numeral 9'' is a hopper for supplying fresh greens; 10' is a tea and confectionery exchanging device which incorporates a geared motor 11';12'' is a temperature sensor provided in the tank 2'. 13' turns on/off the heater when the temperature signal from the temperature sensor 12' is lower than the set temperature, and turns off the heater when it is higher than the set temperature.
This is a control device that not only controls the temperature of hot water but also controls the entire tea dispenser 1'.

The operation of the conventional tea dispenser configured as described above will be explained. The hot water in the tank 2' is kept at a temperature of 85-9000 by detecting 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''. Tea is supplied to the teacup 8' through the tea confectionery.

Problems to be Solved by the Invention However, with the above configuration, if the user forgets to supply water to the tank and turns on the power, the heater will turn on even though there is no water, resulting in dry cooking, which may lead to a fire. It was dangerous.

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

Means for Solving the Problems In order to achieve this object, the water boiling device of the present invention provides such that the time from when the heater is turned on by the first temperature determining means to when the heater is turned off by the second temperature determining means is less than or equal to a predetermined time. It consists of a dry cooking prevention control means that turns off the heater 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 heating 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 a heat insulating material such as class wool, and a heater 3 is provided on the bottom surface.

4 is a hot water supply pipe, and a hot water supply valve 5 for controlling hot water supply is provided between the pipes. 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 spout for storing tea and sweets, and 8 is a tea cup. Reference numeral 9 denotes a hopper for supplying new confectionery, and 10 denotes a confectionery exchange device, which incorporates a geared motor 11. 12 is a temperature sensor provided in the hot water tank 2, and 13 is a control device that controls the entire tea dispenser.

The control device 18 includes a first temperature determination means 14 that compares the temperature signal from the temperature sensor 12 with a first reference temperature signal.
and a second temperature determination means 15 that compares the temperature signal with a second reference temperature signal higher than the first reference temperature signal, and turns on the heater 3 when the temperature signal is lower in the first temperature determination means 14. A heat retention control means 16 turns off the heater 8 when the temperature signal is higher in the second temperature determination means 15, and a second temperature determination means turns on the heater 8 by the first temperature determination means 14. 15 to turn off the heater 3;

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 and snack exchanging device 10 is connected via the contact 24, and the control device 13
The primary side of the power transformer 25 inside is connected. A power supply circuit 26 is connected to the secondary side of the power supply system 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 Vcc, 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 R2, a resistor R3, and a resistor R4 are connected to the non-inverting input terminal of the comparator 27, and the other end of the resistor R2 is connected to the DC power supply Vcc, and the resistor R
The other end of the resistor R 3 is grounded, and the other end of the resistor R 4 is connected to the output terminal of the comparator 27 . The resistance R2, R
3 and R4 create 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 81 to a first relay 19 having a normally open contact 20 and a second relay 2 having a normally open contact 24.
8. Connected to the 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 sensor 12 is R (25'), and the voltage at point A is v (25).
Since the point voltage 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 output 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 8 is turned on. In step 35, timing is started at the same time as the heater 3 is turned on. When the water in the tank 2 is heated by the heater 3 and the temperature rises to 93°C or higher, the electrical resistance of the temperature sensor 12 becomes smaller than R(93), and in step 36, the potential at point A becomes the second reference voltage. Since it is higher than V(93), comparator 27
The output of becomes L. The microcomputer 28 outputs L to the output terminal C, and the first relay 19 is 0FFL/OFF via the buffer 29 to open the normally open contact 20, and step 3
At step 7, heater 3t' is turned off. In step 38, time measurement is stopped at the same time as the heater 3 is turned off. 0 Normally, if the tank 2 contains hot water from the maximum amount to the minimum amount, the time from turning on the heater 3t in step 34 until turning off the heater 3 in step 37 It takes about ten minutes.

Therefore, in step 39, since the time from turning on the heater 8 in step 34 to turning off the heater 3 in step 37 is longer than the predetermined time (2 minutes), the process returns to step 38 again.

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 waste 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. It is something that exists.

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(2
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 step 34, H is output to the output terminal C, the first relay 19t is turned ON via the buffer 29, the normally open contact 20e is closed, and the heater 3 is turned on/dry heating is started. In step 35, timing is started at the same time as the heater 8 is turned on. When the tank 2 is heated by the heater 3 and the temperature rises to 93°C or higher, the electrical resistance of the temperature sensor 12 becomes smaller than R(93), and in step 36, the potential at point A becomes equal to the second reference voltage V(93 ), so comparator 27
The output of becomes L. The microcomputer 28 outputs Lt- to the output terminal C, and outputs the first signal through the buffer 29'f:
The relay 19 is turned OFF to open the normally open contact 20, and in step 37, the heater 3t is turned off. In step 38, timing is stopped at the same time as the heater 3 is turned off. In the case of dry cooking, the time from turning on the heater 3 in step 34 until turning off the heater 3 in step 37 is as follows.
Since there is no water and only the temperature of the tank 2 is raised, it takes only a very short time and only one common charge. Therefore, in step 89, the time from turning on the heater 3 in step 34 until turning off the heater 3 in step 37 is a predetermined time (
2 minutes), so proceed to step 40. Then, dry cooking prevention control is started. Microcomputer-2
8 outputs L to the output terminal C, turns the first relay 19 to 0FFL/ through the buffer 29, opens the normally open contact 20, and forcibly turns off the heater 3. In step 41, the microcomputer 28 outputs L to the output terminal e and turns on the warning display LED 32 via the buffer 81.

As described above, according to this embodiment, when the time from when the heater is turned on by the first temperature determining means to when the heater is turned off by the second temperature determining means is less than or equal to a predetermined time, the heater is turned off. 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.

Effects of the Invention As described above, the present invention includes a temperature sensor that detects the temperature of hot water in a tank, a first temperature determination means that compares a temperature signal from the temperature sensor with a first reference temperature signal, and a temperature sensor that detects the temperature signal. and a second reference temperature signal higher than the first reference temperature signal, and when the temperature signal is lower in the first temperature judgment means, the heater t″ONL/, the second temperature judgment is performed. a heat retention control means for turning off the heater when the temperature signal is higher in the means; and a time from when the heater is turned on by the first temperature determining means to when the heater is turned off by the second temperature determining means is less than or equal to a predetermined time. By comprising a dry cooking prevention control means that turns off the heater when the user forgets to supply water to the tank and turns on the power, the heater turns on even though there is no water, resulting in dry cooking. detects this and forces the heater to 0FFL.
/ It prevents fires, and its practical effects are great.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a water heating device according to an embodiment of the present invention;
3 is a flowchart showing the operation of the device, FIG. 4 is a timing chart showing the operation of the device, and FIG. 5 is a configuration diagram of a conventional water boiling 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 2-・-
Tank 3-・To-ta/2- 45Lv pump Figure 1 Figure 2

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 that turns 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 on by the first temperature determination means until it is turned off by the second 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.