JPH0128405B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a temperature control device for an electric water heater.

(Prior Art) Conventionally, many devices of this type are controlled using a bimetal as a temperature sensor.

(Problem to be Solved by the Invention) Therefore, there is an inconvenience in that the boiling temperature cannot be continuously varied and adjusted to a desired temperature, and the display of the amount of remaining hot water also depends on the temperature sensor and its control circuit. Another problem was that a dedicated sensor and its display driving circuit had to be provided separately.

The present invention has been made in view of the above circumstances, and its purpose is to display the amount of remaining hot water at a desired boiling temperature and control the water temperature in the tank continuously and accurately using two temperature sensors. An object of the present invention is to provide a temperature control device for an electric water heater that can be quickly controlled.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a water tank having substantially the same length as the tank height of a hot water storage tank, and having a positive resistance value change with respect to a rise in hot water temperature. A first temperature sensor is fixed in the height direction of the outer wall of the hot water storage tank, and the output value of the first temperature sensor is determined by the boiling temperature set by the first variable resistance element through an amplifier in the next stage. The output is amplified in a negative linear relationship with respect to the temperature, and the amount of hot water remaining in the hot water storage tank is displayed as 100% when the output value is the maximum value.
The second type has a negative resistance value change as the water temperature rises.
A temperature sensor is disposed near a heating heater provided at a lower position inside the hot water storage tank, and a second variable resistance element sets the output value of the second temperature sensor and the magnitude of the boiling temperature. The divided voltage divided by the resistance value is led to the other input of a comparator whose one input is given the reference voltage, and compared, and the result of the comparison determines that the divided voltage is equal to the reference voltage. the second variable resistance element is configured to operate the warming heater when the voltage is higher than the reference voltage, and to stop the operation of the warming heater when the divided voltage becomes lower than the reference voltage; The resistance value of the first variable resistance element is changed such that the maximum output value of the amplifier is always a constant value for any boiling temperature that is set by changing the resistance value of the amplifier. This is how it was done.

(Function) By setting the boiling temperature using the first variable resistance element, the output value of the first temperature sensor is adjusted to the magnitude of the boiling temperature set by the resistance value of the variable resistance element. The output signal from the amplifier amplified in a negative linear relationship becomes a signal indicating the amount of remaining hot water. In other words, when the value of this signal reaches the maximum value, the remaining amount of hot water in the hot water tank will be displayed as 100%.

On the other hand, when the boiling temperature is set by the second variable resistance element, the resistance value of the second variable resistance element and the second temperature sensor, which has a negative resistance value change with respect to a rise in water temperature, are The divided voltage divided by the output value is led to the other input of a comparator whose one input is given a reference voltage, and compared, and the comparison output is used to control the operation of the heating heater. It becomes a signal. In other words, when the divided voltage is higher than the reference voltage, the comparison output goes to "H" level and activates the heating heater, and when the divided voltage becomes lower than the reference voltage, the comparison output goes to "L" level. As a result, the operation of the heating heater is stopped.

The first variable resistance element and the second variable resistance element, which control the display of the amount of remaining hot water and the operation of the heating heater in this way, adjust the resistance value of the second variable resistance element. The maximum output value of the amplifier is always a constant value (for example, 5V) for any boiling temperature that is set by changing the temperature.
The resistance value of the first variable resistance element is interlocked so that the resistance value of the first variable resistance element changes as follows.

That is, when the resistance value of the second variable resistance element is changed to set the boiling temperature of hot water in the hot water storage tank to a certain temperature (for example, 90 degrees), the heating heater is activated and the temperature of the hot water in the hot water storage tank is When the temperature of the hot water inside reaches 90 degrees, the resistance value of the first variable resistance element changes so that the output value of the amplifier becomes 5V based on the relationship with the output value of the first temperature sensor.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an electric water heater equipped with a temperature control device of the present invention.

In the figure, 1 is a hot water storage tank having a water supply port 2 at the bottom and a hot water discharge port 3 at the top;
A heating heater 4 is inserted into the tank, and a temperature sensor (first temperature sensor) 5 for displaying the amount of remaining hot water is installed on the outer wall and has approximately the same length as the tank height in the height direction.
a is fixed. Further, a temperature sensor (second temperature sensor) 5b for temperature control is fixed to the lower part of the hot water storage tank. Temperature sensor 5a for displaying amount of remaining hot water
For example, a copper wire, nickel wire, platinum wire, etc., whose resistance value changes depending on the temperature of the water in the tank, is used, and a thermistor is used as the temperature sensor 5b for temperature control. As is well known, this thermistor is a resistor with a negative temperature coefficient, and unlike ordinary metals, its resistance value decreases as the temperature rises.
This resistance value changes exponentially with temperature changes. Reference numeral 6 denotes a control section that performs the required functions of the present invention based on the resistance value changes of each of the sensors 5a and 5b, including a remaining hot water amount display circuit 15 consisting of an amplifier 7, a set temperature adjustment section 8a, and a remaining hot water amount display section 9; Temperature control circuit 1 consisting of a comparison circuit 10, a set temperature adjustment section 8b, an electromagnetic switch drive control section 11, and an electromagnetic switch drive section 12
It's more familiar than 6. 13 is an electromagnetic switch controlled by the electromagnetic switch drive section 12. Also,
The set temperature adjustment section 8a of the remaining hot water amount display circuit 15 and the set temperature adjustment section 8b of the temperature control circuit 16 are interlocked with each other (described later).

FIG. 2 shows a specific example of the control section 6, in which the amplifier 7 and the comparison circuit 10 are mainly composed of operational amplifiers OP ₁ and OP ₂ , respectively. However, OP ₁ is used for amplification and OP ₂ is used for comparison. The set temperature adjustment section 8a of the remaining hot water amount display circuit 15 is composed of a general variable resistor (first variable resistance element) VR, which is connected to the operational amplifier.
By connecting between the negative input terminal and output terminal of OP ₁ and adjusting the resistance value, the amplification factor of the amplifier 7 can be changed. That is, if the voltage across the temperature sensor 5a is _Vs , the voltage value of the output signal of the operational amplifier _OP2 is _Vp , and the resistance value of _R3 is ignored, the amplification factor A can be expressed by the following equation.

V _s = V _p (R ₂ / R ₂ + VR) ... (1) Therefore, A = V _p / V _s = 1 + VR / R ₂ ... (2) In other words, the amplification factor A depends on the resistance value of VR. It varies linearly based on However, by setting the set temperature scale on the VR display board (not shown) so that it is inversely proportional to the VR resistance value, the higher the set temperature, the lower the amplification factor A, and the lower the set temperature, the lower the amplification factor. Rate A
is set to be high. Therefore, the voltage V _p appearing at the output terminal of the amplifier 7 has a physical meaning of the value obtained by dividing the hot water temperature in the hot water storage tank 1 by the set temperature. In other words, even if there is no change in the water temperature in the hot water tank 1,
If the set temperature is high, the output signal voltage V _p will be a small value, and if the set temperature is low, the output signal voltage V _p will be a small value.
is a large value. In this case, the output signal voltage V _p
The maximum value of is when the water temperature in the hot water tank 1 becomes equal to the set temperature due to the operation of the electromagnetic switch 13, which will be described later, but this maximum value is set to 5V in the embodiment.

The remaining hot water amount display section 9 is mainly composed of a voltmeter M, and displays the output signal voltage V _p . This voltmeter M is graduated in percentages with its full scale (for example, 5V) as 100%. Therefore, the voltmeter M will display the ratio of the hot water temperature in the hot water storage tank 1 to the set temperature as a percentage. however,
As will be described later, this display value is equal to the amount of hot water remaining in the hot water storage tank 1 at the set temperature.

The set temperature adjustment section 8b of the temperature control circuit 16 is composed of a general variable resistor (second variable resistance element) VR', which is connected between the DC input terminal and the positive input terminal of the operational amplifier OP ₂ to adjust the resistance value. By changing , the timing of switching the output level of the comparator circuit 10 can be adjusted. That is, the voltage level at the positive terminal of the operational amplifier OP ₂ is determined by the voltage division ratio between the combined resistance value of the variable resistor VR' and the resistance value of the resistor Rg, and the resistance value of the thermistor which is the temperature sensor 5b. will be determined. In this case, if the voltage gain of the operational amplifier OP ₂ is D, the voltage across the thermistor V _s ' and the reference voltage V _b applied to the negative terminal of the operational amplifier OP ₂ obtained by dividing the DC voltage +V, The following equation holds between the output signal voltage V _p ′ of the operational amplifier OP ₂ and the output signal voltage V p ′.

V _p ′=D(V _s ′−V _b ) ……(3) As a result, the output signal voltage of operational amplifier OP ₂
V _p ′ becomes an “H” level output when V _s ′>V _b ,
When V _s ′≦V _b , the output changes to “L” level.

The electromagnetic switch drive control section 11 is composed of a grounded emitter transistor Tr and a relay Ry. When the output of the comparison circuit 10 is at the "H" level, the transistor Tr is turned on and the relay and Ry are energized. Electromagnetic switch drive unit 1 is activated by energizing relay Ry.
The relay contact ry constituting 2 is switched on, and the electromagnetic switch 13 is energized. This causes the heating heater 4 to generate heat and heat the hot water in the hot water storage tank 1.
The heating is stopped when the output of the operational amplifier _OP2 changes to the "L" level.

In other words, when the resistance value of VR' is decreased, V _s ' = V _b when the resistance value of the thermistor is larger than before, so the temperature of the water in the hot water tank 1 is lower than before. As a result, the operation of the heating heater 4 is stopped, and the boiling temperature is set low. Conversely, when the resistance value of VR' is increased, V _s ' = V _b when the thermistor's resistance value is smaller than before, and the water temperature in the hot water tank 1 becomes lower than before. As a result, the operation of the heating heater 4 stops at a high temperature, resulting in a high boiling temperature.

Incidentally, the remaining hot water amount display circuit 15 and the temperature control circuit 16 are controlled by interlocking the variable resistors VR and VR' as described above.

In other words, by changing the resistance value of the variable resistor VR', the boiling temperature of hot water in the hot water storage tank 1 can be set to a desired temperature (for example, 90°C), and the heating heater 4 is activated to store hot water. The hot water in tank 1 is 90℃
(that is, when the output signal voltage V _p ' of the operational amplifier OP ₂ changes from the "H" level to the "L" level), the output value of the operational amplifier OP ₁ changes from the relationship with the output value of the temperature sensor 5a. The resistance value of the variable resistor VR is designed to change so that V _p is always at the maximum value (5V).

Next, the operation of the temperature control device having the above configuration will be explained using a specific example.

Now, the length of the temperature sensor 5a for displaying the tank height and remaining hot water amount of the hot water storage tank 1 is 1 m, and the temperature sensor 5a has a resistance value of 1000Ω at 20°C and a temperature coefficient.
Use a material with a characteristic of 4000PPM/℃.
Then, the boiling temperature is adjusted to 90°C by operating the set temperature adjustment units 8a and 8b. However, it is assumed that the voltmeter M is uniformly adjusted so that it displays 0% when the temperature sensor 5a detects a water temperature of 20°C.

Under these conditions, the hot water in the hot water tank 1
When the hot water is heated to 90°C and the heating heater 4 is in the heating stop state, 30% of the total hot water storage capacity is used,
If water at 20°C corresponding to 30% of the water is supplied from the water supply port 2, the inside of the hot water storage tank 1 is not stirred, so it is separated into a water tank, a hot water mixed layer, and a hot water layer. In this case, assuming that the hot water mixed layer is 20% of the total hot water storage capacity, and if water and hot water are mixed in equal amounts, the ratio of each layer is 20% for the water layer and 20% for the hot water mixed layer.
(Water temperature 55℃), the hot water layer becomes 60%. Temperature sensor 5a
detects the temperature of the layer corresponding to the length corresponding to each layer, so the water layer part is 200Ω, the hot water mixed layer part is 228Ω, the hot water layer part is 768Ω, and the resistance value of the entire length is It becomes 1196Ω. boiling temperature
The resistance value of the temperature sensor 5a at 90°C is 1280Ω, and at 20°C it is 1000Ω, so if the boiling temperature is 100% and 20°C is 0%, the resistance value of 1196Ω becomes 70%. Similarly, if 60% hot water is used and the equivalent amount of water is supplied, the resistance value of the temperature sensor 5a will be 1112Ω, and the ratio will be 40%. Such ratio calculation is possible because the amplification factor A of the amplifier 7 is adjusted based on the set temperature as described above.
A hot water temperature detection signal based on the change in the resistance value of a is sent to the amplifier 7.
The result is an output signal voltage V _p corresponding to said ratio. Therefore, the voltmeter M indicates that the resistance value of the temperature sensor 5a is
The amount of unused hot water remaining in the hot water tank 1, that is, the amount of remaining hot water, is displayed, which is 70% when the resistance is 1196Ω and 40% when the resistance is 1112Ω.

On the other hand, the output signal voltage V _p of the amplifier 7 based on the change in water temperature changes in response to the change in the output signal voltage V _p ' of the comparator circuit 10 based on the change in the water temperature, but the output signal Until the voltage V _p reaches the maximum value (=5V), the voltage V _s across the temperature sensor 5b is
Since V _s ′>V _b (that is, the output V _p ′ of the operational amplifier OP ₂ is at “H” level), the electromagnetic switch drive control section 11 and the electromagnetic switch drive section 12 are operated, and the electromagnetic switch 13 is activated. When excited, the heating heater 4 generates heat. This heat generation continues until the water temperature in the hot water storage tank 1 reaches 90°C, and when it reaches 90°C, the voltage V _s across the temperature sensor 5b changes to V _s ′≦V _b (that is, the operational amplifier
Since the output V _p ′ of OP ₂ is “L” level),
Electromagnetic switch drive control section 11, electromagnetic switch drive section 1
2 stops operating, and the heating heater 4 stops. Furthermore, when the temperature reaches 90° C., the output V _p of the operational amplifier OP ₁ reaches its maximum value (5 V), so the voltmeter M displays 100%.

For convenience of explanation, the boiling temperature has been explained as 90°C, but by operating the set temperature adjustment section 8b, the value of the set temperature adjustment section 8a changes in conjunction with this as described above. Therefore, the desired temperature can be set, and even in that case, the remaining amount of hot water is displayed based on the set boiling temperature as 100%. Further, the heating of the hot water in the hot water tank 1 is controlled to the boiling temperature.

(Effects of the Invention) As explained above, according to the present invention, two temperature sensors fixed to the outer wall of the hot water storage tank can display the amount of remaining hot water at a desired boiling temperature and continuously monitor the boiling temperature. Since it is possible to perform adjustments, high measurement accuracy can be obtained, and a simple configuration with a small number of parts can be achieved. Further, there are effects such as a significant cost reduction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a circuit diagram showing a specific example of FIG. 1. 1...Hot water tank of electric water heater, 5a, 5b...Temperature sensor, 7...Amplifier, _Vp , _Vp '...Output signal, V _a , _Vb ...Reference signal.

Claims (1)

[Scope of Claims] 1. A first temperature sensor having approximately the same length as the tank height of the hot water storage tank and having a positive resistance value change with respect to a rise in hot water temperature is arranged in the height direction of the outer wall of the hot water storage tank. The output value of the first temperature sensor is amplified in a negative linear relationship with respect to the boiling temperature set by the first variable resistance element through an amplifier in the next stage. The remaining hot water amount in the hot water storage tank is set to be displayed as 100% when the output value is the maximum value. A temperature sensor is disposed near a heating heater provided at a lower position inside the hot water storage tank, and a resistance of a second variable resistance element is configured to set the output value of the second temperature sensor and the magnitude of the boiling temperature. The divided voltages divided by the values are compared by being led to the other input of a comparator whose one input is given a reference voltage, and the result of the comparison shows that the divided voltage is lower than the reference voltage. The second variable resistance element is configured to operate the heating heater when the voltage is higher than the reference voltage, and to stop the operation of the heating heater when the divided voltage becomes lower than the reference voltage. The resistance value of the first variable resistance element is changed such that the maximum output value of the amplifier is always a constant value for any boiling temperature that is set by changing the resistance value. A temperature control device for an electric water heater.