JPS5953450B2 - electric instant water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric instantaneous water heater used for purposes such as hot water supply and space heating.

Conventionally, most electric instant water heaters use a heating element to heat the water flowing into the water heater, detect the temperature of the water flowing out from the water heater, and set the water temperature based on the detection signal. The electric power supplied to the heating element was controlled by a power control device, and the water temperature was adjusted so as to maintain the same temperature.

Generally, the configuration of such flowing water heating control is shown in FIG.

In the figure, L is the distance from the heater to the temperature sensor A, and ■ is the flow rate when water flowing in at temperature T1 is heated in the container and flows out at temperature T2.

Usually, the transfer function G (S) of such a control system has a gain element (capacity of the heater) as P, a time constant (time from when water flowing in at temperature T1 is heated until it flows out at temperature T2) as T. When the Laplace operator is S, it is expressed as the following equation.

That is, equation (1) here is an equation when the distance from the heating element to the temperature detector is not taken into account.

However, in reality, this distance cannot be ignored, and the dead time τ=
Since L/V occurs, the transfer function G (S) is as follows.

That is, as can be seen from equation (2), when the gain element P (capacity of the heater) is increased in order to improve control accuracy, the stability of the control system deteriorates.

Furthermore, the longer the distance from the heating element to the temperature detector, the greater the dead time τ and the worse the control accuracy.

By the way, in such a control system, conventionally, the power supplied to the heating element was controlled by simply turning on or off a control switch according to the change in water temperature.
A method such as FF control or step control that controls the supplied power by dividing it into about 2 to 10 steps has been adopted.

However, with such ON-OFF control and step control,! Precise temperature control was impossible because it could not be controlled.

Therefore, a semiconductor power control device may be used to perform continuous control, but as mentioned above, dead time τ occurs due to the distance from the heating element to the temperature sensor, so there is a delay in response to the temperature sensor output. occurred, making it impossible to perform precise control.

In order to further improve control accuracy, it is necessary to narrow the allowable range between the upper and lower limits of the set temperature, but due to the response delay described above, the control temperature may exceed the proportional band, making precise temperature control impossible. It was possible.

In other words, in conventional electric instantaneous water heaters, the temperature detector was installed at a point far away from the heating element, so there was a delay in the thermal response from the heating element at that detection point, and the detection at point B was delayed. When the temperature reaches the target value, the temperature of the heating element and the water in its vicinity has already exceeded the target value.

In such conventional control, the control characteristics are as shown in (2) in FIG. 2, and only control with a large control error including a large ripple component (pulsation component) can be performed.

The present invention has been made in view of the above-mentioned circumstances, and includes a mixing section for stirring the heated fluid near the outlet in the container, and further detecting the temperature of the heated fluid in the mixing section. An object of the present invention is to provide an electric instantaneous water heater that can perform highly accurate temperature control with less control error by providing a temperature detector close to a heating element and improving thermal response. .

Hereinafter, one embodiment of the invention will be described with reference to the drawings.

FIG. 3 shows the configuration of an electric instantaneous water heater.

Reference numeral C denotes a container, and the container C houses a substantially U-shaped heating element H in which heating coils HR, H5°Hl provided corresponding to each of the three phases are connected in delta.

An inlet for supplying water is provided on the lower side wall of the container C, and an outlet E for discharging water heated by the heating element H is further provided at the upper end.

A pipe-shaped outflow pipe J is attached to the outflow port E outside the container C, and flow rate detectors F and C for detecting the amount of water flowing through the outflow pipe J are provided in the path of the outflow pipe J.

In addition, mixing parts M and C for stirring the heated water are provided near the outlet E in the container C, and a heating element H near the outlet E is provided.
Temperature detectors T and C consisting of a thermistor or the like for detecting the water temperature near the heating element H are attached to the side wall of the container C nearby.

On the other hand, the outputs of the flow rate detectors F and C and the temperature detectors T and C are respectively applied as control condition signals to a semiconductor power control device whose details will be described later.

Further, the outputs of the three-phase AC power supplies A and C are applied as control power to the heating element H via this semiconductor power control device.

FIG. 4 shows the configuration of the semiconductor power control device.

HR, H5, and HT are the heating coils, and HR, H5°, and H□ are connected in delta and connected to the U phase, ■ phase, and W phase of the three-phase AC power supplies A and C, respectively.

Triacs Tu, Tv, and Tw for controlling the power supplied to the heating coils HR, H5, and HT are connected to fuses Fu and Fv, respectively, to the heating coils HR, H5, and H, respectively.

Connect in series via Fw.

Zu, Zv, and Zw are “on” only at the zero point of the signal.
This is a zero-cross switch that operates in the "off" state, and its output signal controls the firing of the gates 1 to 3, Tu, Tv, and Tw.

Also zero cross switch Zu. Zv and Zw are connected between the U phase, ■ phase, and W phase of the three-phase AC power supplies A and C, respectively.

On the other hand, K is a temperature control circuit whose details will be described later, and its input terminals are connected to a transformer Tr and a fuse F A1. AC power supplies A and C1 for operation are connected via F A2.

Further, one terminal Tu1. Connect the setting volume U and R for setting the temperature set value between Tu2,
Other terminal Th1. Connect the thermistor TH between Th2.

Furthermore, one terminal Th2 is connected to one output terminal Tp2 of the temperature control circuit via a fuse Fh.

Also, Pu, Pv, Pw are zero cross switches Zu,
A photocoupler consisting of a light emitting diode and a phototransistor corresponding to Zv and Zw, and the flow rate detectors F and C
When the switches S and W that respond to this operate, and a signal is output from one output terminal Tp1 to the temperature control circuit, the respective light emitting diodes emit light and the signal is sent to the zero cross switches Zu and Zv, respectively, via the phototransistor. , is added to Zw.

In addition, the anode side of the light emitting diode is connected to the positive side of the DC power supplies P and C that drive the photocouplers Pu, Pv, and Pw via an LED that emits green light when the light emitting diode emits light, and the negative side is connected to the above output. Terminal T
Connect to p2.

FIG. 5 shows a block configuration of the temperature control circuit.

1 is a buffer amplifier to which the setting volume U, R is connected to its input terminal, and 2 is the thermistor TH to its input terminal.
are connected to the buffer amplifiers 1 and 2, and apply the respective outputs of buffer amplifiers 1 and 2 to the comparator 3.

Comparator 3 compares these 100 outputs and generates a deviation output, which is applied to pulse width modulator 4.

The pulse width modulator 4 changes the pulse width of the pulse wave output from the oscillator 5 in accordance with the deviation output from the comparator 3.

The output of this pulse width modulator 4 is applied to the base B of a transistor 6 and is led through its collector C and emitter E to output terminals TP1 and Tv2, respectively.

In the above, setting volume U, R and thermistor TH
are set to be negative and positive, respectively, and when the resistance value R of the thermistor TH is larger than the setting value R6 of the setting volume, a positive deviation signal is output from the comparator 3, and when it is small, a negative deviation signal is output from the comparator 3. When they are equal, no signal is output.

Further, within the proportional band range, the pulse width modulator 4 has a long "on" time as shown in FIG. 6 (a) when R>Ro.

In addition, when R=Ro, as shown in (b), the "on" time and "off" time are equal, and when R<R6, as shown in (C), a pulse is generated with a short "on" time. It is.

Next, the operation of the electric instantaneous water heater configured as above will be explained.

First, if the water faucet (not shown) is closed, water will not flow into the container C and will not flow out of the container C, so the flow rate detectors F and C installed in the outflow pipe J will detect the flow rate. The switches S and W do not operate and are in the "off" state.

Therefore, even though a signal is being output from the temperature control circuit K, no signal is applied to the photocoupler Pu, Pv, Pw and the zero cross switches Zu, Zv, Zw, and the triacs Tu, Tv, Tw are non-conducting. be.

Therefore, no power is supplied to the heating coils HR, H5, and HT, and the heating element H is not heated.

Next, when the tap is opened, water flows from the inlet through the container C and flows out from the outlet E.

Then, the flow rate is detected by the flow rate detectors F and C, and the switches S and W are operated by the detection signals and turned on.

At this moment, since the inside of the container C is still water and the temperature is low, the detection signals of the temperature detectors T and C, that is, the resistance value R of the thermistor TH, are very large compared to the set resistance value R6 of the set volumes U and R.

Therefore, the comparator 3 outputs a positive deviation signal.

The pulse width modulator 4 outputs a pulse signal that remains "on" until the water temperature detected by the temperature detectors T and C reaches the lower limit value ta of the proportional band shown in FIG. Output.

Therefore, the green LED emits light and each photocoupler P
The light emitting diodes u, Pv, and Pw emit light at the same time,
Each zero cross switch Zu from hole l-1 ~ transistor,
The above pulse signal is added to Zv and Zw.

The signals from these zero cross switches Zu, Zv, and Zw are the river/Liac Tu.

When applied to the gates of Tv and Tw, the triac remains conductive.

Therefore, from the initial time (when switches S and W are on'') to the lower limit value ta, power is continuously supplied to each heating element HR, R5, and HT, and the heat capacity of the heating element H is 100% in the container C. water is heated.

When the water temperature in the container C rises in this manner and exceeds the lower limit ta, the water temperature is controlled as follows until it reaches the set value.

That is, as the water temperature rises, the resistance value R of the thermistor TH becomes smaller than the initial value, but the set value t remains the same.

Until then, it is still larger than the set value R6, so the comparator 3 continues to output a positive deviation signal.

Also, this deviation signal causes the pulse width modulator 4 to output the sixth
As shown in Figure a, a pulse signal is output whose 8 "on" times are longer than "off" times.

Through the same process as described above, when this pulse signal is applied to the zero cross switches Zu, Zv, and Zw, the triacs Tu, Tv, and Tw become conductive in response to the ``on'' and 9-off times of this pulse signal. "and non-conducting" are repeated cyclically.

Therefore, power is cyclically supplied to each heating element (R, R5, HT) according to the operation of the triacs Tu, Tv, and Tw.

For example, as shown in FIG. 7, when t somewhat exceeds the lower limit ta,
At time a1, as shown in (at), the ratio (tenity ratio) of the ON time (24 seconds in this example) to one period of the pulse signal (30 seconds in this example) is 0.
．． When a pulse signal such as 8 is applied, each heating element HR, H5, H, is supplied with power during the "on" time, and is not supplied with power during the "off" time, and this is done cyclically, resulting in the following: As a result, the water in the container C will be heated by 80% of the heat capacity of the heating element H.

Next, the water temperature rises in this way to the set value t.

When this value is reached, the resistance value R of the thermistor TH becomes equal to the set value R6.

Therefore, the comparator 3 does not output a deviation signal, and the output signal from the oscillator 5 is added as is.

That is, as shown in Fig. 6, the pulse signal has the same "on" time and "off" time, in other words, the duty ratio α is 0.5.
Figure 7a.

A pulse signal such as is applied.

Then, power is cyclically supplied to each heating element HR, H5, and H0 for the 9-on period of the pulse signal as described above, and as a result, the water in the container C is heated by 50% of the heat capacity of the heating element H. .

However, in this way, even when the water temperature reaches the set point t, due to a slight delay in the thermal response, the water temperature remains at the set point t.

It exceeds. The period from the set value to the upper limit value tb of the proportional band is controlled as follows.

That is, when the water temperature exceeds the set price tag, the resistance value R of the thermistor TH becomes smaller than the set value R6.

Therefore, the comparator 3 outputs a negative deviation signal.

Based on this deviation signal, the pulse width modulator 4 outputs the signal shown in FIG.
A pulse signal whose ON time is shorter than the OFF time as shown in FIG. 9 is output until the upper limit value tb is reached.

However, in this case, taking into account that there is actually a slight delay in thermal response, the final temperature detection in the high temperature range is performed at the upper limit value tb of the proportional band, and a pulse signal is applied to each heating element H.
R.

H5, rather than controlling the power supplied to HT, the upper limit value t
This is done at a certain point before point b, that is, at point tb1 in FIG. 7, to control the water temperature so that it does not exceed the upper limit of the proportional band.

At time tb1, the duty ratio α is 0.2.
A pulse signal is applied such that .

Therefore, through the same process as above, each heating element HR, H5
, H□ are supplied with power during the "on" time (6 seconds in this example) and are not supplied with power during the "off" time (24 seconds in this example), which occurs cyclically, resulting in: The water in the container C will be heated by the heating element H's heat capacity of 20%.

In this way, when the water temperature exceeds the set price tag, the proportional band upper limit t
Until b, the water temperature is gradually lowered and returned to the set value t.

controlled so that At this point, that is, at point to, the heating element H is heated again at 50% of its heat capacity as described above, so that the heating is harmonized and the set value t is achieved.

However, even here, due to a slight delay in the thermal response, the water temperature will be lower than the set price tag.

and the set value t. When it exceeds the lower limit value ta of the proportional band, up to ta1 near the lower limit ta of the proportional band, heating is performed again in the same process as described above to reach the set value t.

controlled so that

In this way, the set price tag is reached and, due to a slight delay in the thermal response, the set value t is also reached.

If the value exceeds 100, the same process as above is performed again.

By repeatedly performing the above-described operations on the cycler, the water temperature can be controlled to be substantially constant.

The control state as described above is shown in FIG. 2 (■).

In the present invention, as shown in FIG. 3, temperature detectors T and C for detecting the water temperature in the container C are provided very close to the tip of the heating element H.

Furthermore, the water near the heating element H is stirred between the tip of the heating element H near the temperature detectors T and C and the outlet E to uniformly exchange heat between the heating element H and the water phase tile. Mixing section M for
, C are provided.

Therefore, the water temperature near the heating element H can be detected more quickly by the temperature detectors T and C, and since the mixing sections M and C are provided, most of the ripples are removed, allowing control with fewer control errors. .

That is, in the present invention, the positions of the temperature detectors T and C are changed from the conventional positions, and the mixing sections M and C are further provided.
By using the semiconductor power control device as described above, it is possible to perform almost constant temperature control that does not exceed the proportional band range as shown in FIG. 2 (2).

It should be noted that the present invention is not limited to the embodiments described above, and it goes without saying that the present invention can be modified and implemented in a wide variety of ways without changing the gist of the invention.

As described above, according to the present invention, a mixing section for stirring the heated fluid to be heated is provided near the outlet in the container, and a temperature sensor for detecting the temperature of the fluid to be heated in this mixing section is provided close to the heating element. Since the thermal response is improved, an electric instantaneous water heater can be provided that can perform highly accurate control with few control errors.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of running water heating control, Fig. 2 is a diagram showing the state of temperature control of electric instantaneous water heaters of the conventional and the present invention, and Fig. 3 is an embodiment of the electric instantaneous water heater of the present invention. 4 is a circuit diagram showing the structure of the semiconductor power control device, FIG. 5 is a block diagram showing the structure of the temperature control circuit, and FIGS. 6 and 7 are the electric instantaneous water heater of the present invention. FIG. 1.2...Buffer amplifier, 3...Comparator, 4...Pulse width modulator, 5...
Oscillator, 6... register, HR, H5, H□
...Heating element, Tu. Tv, Tw・・・Triac, Zu, Zv
, Zw...Zero cross switch, Pu, P
v, Pw...Photocoupler, LED...
・Light emitting diode (green), K...Temperature control circuit, Tr...Transformer, TH...Thermistor, U, C...Setting volume, S , W...
...Switch, FAl, FA2. Fh, Fu,
Fv, Fw...Fuse, A, C1...
・・Re-operation AC power supply, D, C・・・・DC power supply, T
ul, TH2, Th1. Th2... Each input terminal of the temperature control circuit, Tpl, Tp2... Output terminal of the temperature control circuit, C... Container, D...
・Inlet, E... Outlet, A, C...
3-phase AC power supply, J...outflow pipe, F, C...
...Flow rate detector, M...Mixing section, T, C...
...Temperature detector.

Claims (1)

[Claims] 1. A container having an inlet for supplying water and an outlet for discharging water, a heating element stored in the container to heat the guided water, and a heating element provided near the outlet in the container to heat the heated water. a mixing section for stirring; a temperature detector disposed close to the heating element to detect the temperature of the water in the mixing section; a flow rate detector for detecting the amount of water flowing out from the outlet of the container; Input each detection signal from the detector and flow rate detector, compare the detected temperature value and the set temperature value, and turn on the triac according to the deviation value on the condition that the detected flow rate value is above a predetermined value. 1. An electric instantaneous water heater comprising: a semiconductor power control device that controls the power supplied to the heating element so as to maintain the deviation value at zero through arc control.