JP3225782B2 - Electric water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric water heater used in ordinary households.

[0002]

2. Description of the Related Art In recent years, electric water heaters have become widespread in general households, and their use has been various. In a conventional electric water heater, as a method of discharging hot water from the electric water heater, there is a method of increasing the pressure in a container containing water of the electric water heater by an air pump. The method of pumping out is also common. In general, an electric water heater using this electric water tapping method generally has a configuration in which a power supply for an electric motor is separately provided in addition to a power supply for an electronic control circuit for controlling a heat retaining temperature and the like.

FIG. 5 is a block diagram showing a configuration of a conventional general electric water heater. In FIG. 5, reference numeral 21 denotes a container for storing the liquid, 22 denotes a temperature detecting unit for measuring the temperature of the container 21, and 23 denotes a heating unit for heating the liquid stored in the container 21, and includes a heater 23a and a relay 23b.
It is composed of a relay power supply 23c and the like. 24 is container 2
This is a heat retaining means for keeping the liquid stored in 1 at an arbitrary temperature, and includes a heat retaining heater 24a, a triac 24b, a gate resistor R30, and the like. Reference numeral 25 denotes a tapping means for discharging the liquid in the container 21 to the outside of the container 21, and includes a pump 25a, a motor 25b, a tapping switch 25c, a motor power supply circuit 25d, a photocoupler 25e, and the like.

[0004] The control circuit 26 includes a temperature detecting means 22.
When the detection of the boiling of the liquid in the container 21 in response to the input from the controller 21, the relay output of the control circuit 26 is changed from HIGH to LO.
W is set to W to turn off the relay 23b, and the power supply to the heater 23a is stopped. After that, the triac 24b of the heat retaining means 24 is turned on by setting the heat retaining output of the control circuit 26 to LOW, and the triac 24b of the heat retaining means 24 is turned off by turning the heat retaining output HIGH, so that the liquid in the container 21 is brought to a predetermined temperature. I keep it.

A DC power supply 2 for operating this control circuit 26
Reference numeral 7 includes a transformer T, diodes D27 and D28, an electrolytic capacitor C22, a Zener diode ZD22, a transistor Tr23, and a resistor R31.

In the above configuration, when the user tries to discharge the liquid in the container 21, the release output of the control circuit 26 is set to LOW, the operation of the photocoupler 25e is stopped, and the transistor Tr21 is turned off. Later, by switching the contact of the switch 25c from the NC side to the NO side, the power supply to the motor power supply circuit 25d is started, and the motor 2
5b rotates, and the liquid in the container 21 is discharged out of the container 21 by the pump 25a.

The motor power supply circuit 25d turns on / off the charging of the smoothing capacitor C21 by the operation of the operational amplifier IC21, and energizes the motor 25b while smoothing the current flowing through the heat retaining heater 24a to DC.

[0008]

In such a conventional electric water heater, a tapping switch 25c and a heater 2 are provided.
The circuit has a complicated configuration including three power supply circuits, that is, a relay power supply 23c for driving a relay 23b for controlling the energization of the motor 3a, and a DC power supply 27 for the control circuit 26. Since the on / off operation is performed by turning on / off the AC input of the hot water switch 25c, the hot water switch 25c must be able to withstand the application of the commercial power supply voltage, and there is a problem in that the hot water switch 25c becomes large.

The present invention solves the above-mentioned problems, and comprises a power supply circuit having a simple configuration and operating stably.
An object of the present invention is to provide an electric water heater in which a small operation switch for a motor can be used.

[0010]

According to one aspect of the present according to claim 1 invention measures a vessel for containing a liquid, the temperature of the container
A temperature detecting means for heating or heating the liquid contained in the container;
And heating Heater and kept the heater used for the thermal insulation, the pressure
Either or both of the heat heater and the heat retention heater
Rectifying means for rectifying commercial power supply through
The smoothed capacitor is charged with the rectified current,
When the voltage reaches the voltage VH, the charging is stopped and the predetermined voltage is stopped.
When the predetermined voltage VL lower than VH is reached,
The DC power is applied to both ends of the capacitor by
DC power supply that generates voltage and controls the operation of the entire device
Comprising a control circuit, when the temperature of the container measured by the temperature detecting means is lower than a predetermined heat retaining temperature, even after stopping charging the smoothing capacitor by the DC power supply,
The current path is switched so as to bypass the charging current path, and the commercial power is continuously supplied to the heater in series with the rectifier. If the charging voltage becomes equal to or less than a predetermined value during the continuous supplying, the bypass is opened. In particular, the present invention according to claim 2 is characterized in that when the voltage of the smoothing capacitor drops to a predetermined voltage VL, the instantaneous voltage of the output of the rectifying means becomes equal to or lower than a predetermined voltage VON. This is an electric water heater that is set to be a charging start point again from a certain point.

[0011]

According to the first aspect of the present invention, the DC power supply charges the current rectified by the rectifier to the smoothing capacitor, and stops charging the smoothing capacitor when the voltage reaches a predetermined voltage VH. When the voltage drops to the predetermined voltage VL lower than the predetermined voltage VH, the charging of the smoothing capacitor is started again, so that a DC voltage having a ripple from the voltage VL to the voltage VH at both ends of the smoothing capacitor. Generate.

Further, DC power source, the temperature of the vessel measured by the temperature sensing means, when lower than a predetermined insulation temperature, even after the stop of charging of the smoothing capacitor by the DC power source, charging The current path is switched so as to bypass the path to continue supplying the commercial power to the heater via the rectifier, and the voltage of the smoothing capacitor of the DC power supply falls below VL even while the heater is supplied to the heat retaining means. Switch the current path to start charging,
When the voltage exceeds VH, the current path is switched again to energize the heat retaining heater.

In the power supply circuit according to the second aspect of the present invention, when the voltage of the smoothing capacitor decreases to a predetermined voltage VL, the instantaneous voltage of the output of the rectifying means may be a predetermined voltage VO
The charging of the smoothing capacitor is started again from the point of time N or less, and the timing of starting the charging of the DC power supply to the smoothing capacitor is limited to a predetermined time before and after the zero volt point of the rectified voltage of the commercial power supply. I have.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electric water heater according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. In FIG. 1, reference numeral 1 denotes a container for storing a liquid, 2 denotes a temperature detecting unit for measuring the temperature of the container 1, and 3 denotes a heating unit for heating the liquid stored in the container 1, and a heater 3a
And a relay 3b. Reference numeral 4 denotes a heat retaining means for keeping the liquid stored in the container 1 at an arbitrary temperature, and is constituted by a heat retaining heater 4a. Reference numeral 5 denotes a tapping means for discharging the liquid in the container 1 out of the container 1, and includes a pump 5a, a motor 5b, a tapping switch 5c, and a transistor Tr.
6 and the like. Reference numeral 6 denotes a DC power supply, which includes rectifier diodes D1 to D4, a thyristor SCR, and a gate resistor R.
3, an operational amplifier IC, a smoothing capacitor C, and the like. Reference numeral 7 denotes a second DC power supply, which includes a transistor Tr4, a Zener diode ZD4, and a resistor R9.

Reference numeral 8 denotes a control circuit which operates using the second DC power supply 7 as a power supply, and receives an input from the temperature detecting means 2 to control the relay 3b of the heating means 3. At this time, the transistor Tr5 is turned on by setting the relay output of the control circuit 8 to HIGH, the current flows through the coil of the relay 3b, the relay 3b is turned on, and the current flows through the heater 3a to heat the container 1. Conversely, when the relay 3b is turned off, when the relay output of the control circuit 8 is set to LOW, the transistor Tr5 is turned off and the relay 3b is also turned off.

In order to drive the motor 5b of the tapping means 5, first, the release output of the control circuit 8 is set to HIGH, the transistor Tr6 is turned on, and then the tapping switch 5c is closed by the user, so that the DC power is supplied to the motor 5b. 6, the motor 5b rotates to drive the pump 5a to discharge the liquid in the container 1 to the outside of the container 1.

The operation of the above configuration will be described. First, the operation of the DC power supply 6 will be described. FIG. 2 is a timing chart showing the operation of the DC power supply 6 in the present embodiment. In FIG. 2, the voltage Vu of the smoothing capacitor C
First, when the voltage falls below the predetermined voltage VL at the time A1, the voltage V
The positive input (+) to the operational amplifier IC obtained by dividing u by the resistors R7 and R8 is lower than the negative reference voltage input (−) to which a constant voltage is input, and the output of the operational amplifier IC is LO.
W. When the output of the operational amplifier IC becomes LOW, supply of the base current to the transistor Tr2 is stopped, and the transistor Tr2 is turned off. When the transistor Tr2 is on, the gate of the thyristor SCR is connected to the ground to cut off the gate current from the gate resistor R3 to the thyristor SCR. Therefore, when the transistor Tr2 is turned off, the gate current is supplied to the thyristor SCR. Then, the thyristor SCR is turned on at the point A1 in FIG. 2, and charging of the smoothing capacitor C via the diode D5 is started.

Next, when the voltage Vu exceeds the predetermined voltage VH at the time A2, a constant voltage is input to the positive input (+) to the operational amplifier IC obtained by dividing the voltage Vu by the resistors R7 and R8. Exceeds the negative reference voltage input (-)
The output of the operational amplifier IC becomes HIGH. At this time, the positive input (+) to the operational amplifier IC dividing the voltage Vu is performed by the action of the resistor R6 connected to the output of the operational amplifier IC.
Operates at a predetermined voltage V
L and the predetermined voltage VH, there is a voltage difference between them, so that the voltage of the smoothing capacitor C, that is, the output voltage V
As for u, a DC voltage having a ripple of the voltage VH from the voltage VL is obtained.

Further, once the thyristor SCR is turned on, it does not turn off while the holding current continues to flow, so that the thyristor SCR at the point A3 when the voltage of the full-wave rectified output by the diodes D1 to D4 becomes zero volts next time. Until it disappears, the current through the heat retaining heater 4a continues to flow. At this time, the charging of the smoothing capacitor C is continued as it is, and therefore, as shown in FIG.
, The transistor Tr3 is turned on to stop charging the smoothing capacitor C from the time A2 to the time A3. Also, at this time, even if the transistor Tr3 is turned on, even if the transistor Tr3 is turned on, the charge charged in the smoothing capacitor C does not flow toward the transistor Tr3, and the voltage Vu is consumed by the output of the DC power supply 6. Only the amount of current that falls.

At this time, the average voltage value of the DC power supply 6 is
The voltage is about 10 V necessary for operating the motor 5b, and the ripple voltage, which is the difference between the voltage VH and the voltage VL, is
It is preferable to set the voltage to about 1.5 V so as not to impose a burden on the device.

Next, the operation of the DC power supply 6 when the power is turned on will be described. In the configuration of FIG. 1, the Zener voltage of the Zener diode ZD2 is set to a predetermined voltage VOP. When the commercial power is turned on, the voltage Vu is zero,
Since the transistor Tr2 is off, first, a full-wave rectified voltage is applied to the gate resistor R3, the thyristor SCR is turned on, charging of the smoothing capacitor C is started, and the voltage rises. At this time, the output voltage of the operational amplifier IC also increases, but until the voltage exceeds the voltage VOP, regardless of whether the output of the operational amplifier IC is LOW or HIGH.
The transistor Tr2 and the transistor Tr3 are off without receiving a base current.

Therefore, the output voltage Vu of the DC power supply 6
That is, until the charging voltage to the smoothing capacitor C becomes VOP, the smoothing capacitor C is forcibly charged regardless of the control operation of the operational amplifier IC.

At this time, the voltage of the predetermined voltage VOP, that is, the voltage of the Zener diode ZD2 is equal to or higher than the operation guarantee voltage of the general operational amplifier of 3 V and the negative reference voltage (-−) of the operational amplifier IC according to the circuit configuration of the present invention. 5V
It is reasonable to set it to less than.

Next, the operation of the DC power supply 6 at the time of warming will be described with reference to the drawings. FIG. 3 is a timing chart showing the operation during warming. In the figure, B
At one point in time, when it is determined from the result measured by the input of the temperature detecting means 2 that the temperature of the liquid in the container 1 has become equal to or lower than the heat retention temperature set at that time, the control circuit 8 sets the heat retention output to LOW. Controlling. By this operation,
Since the base and the emitter of the transistor Tr2 shown in FIG. 1 have the same potential and are turned off, a gate current is supplied to the gate of the thyristor SCR by the resistor R3, and the thyristor SCR keeps on. However, since the voltage Vu of the smoothing capacitor C is higher than the voltage VL, the operational amplifier I
The output of C remains HIGH, the transistor Tr3 remains ON, and charging of the smoothing capacitor C is not started. Therefore, the current supplied to the DC power supply 6 via the heat retaining heater 4a does not flow to the smoothing capacitor C, but returns to the commercial power supply through the full-wave rectifier circuits of the diodes D1 to D4, the thyristor SCR, and the transistor Tr3. When the commercial power supply is applied, the rated current flows and the heater 4a generates heat, heats the container 1, and raises the temperature of the liquid in the container 1 to a predetermined temperature.

If the voltage of the smoothing capacitor C falls below the voltage VL at the time B2 during this period, the output of the operational amplifier IC becomes LOW, so that the transistor Tr3 is turned off.
The current returning from the thyristor SCR to the commercial power supply through the transistor Tr3 is used for charging the smoothing capacitor C. When the charging to the voltage VH is completed, the output of the operational amplifier IC becomes HIGH again, so that the transistor Tr3 is turned on, and the current path is switched from the operation of charging the smoothing capacitor C to the operation of returning to the commercial power supply through the transistor Tr3.

At time B4 in FIG. 3, when it is determined from the result measured by the input of the temperature detecting means 2 that the temperature of the liquid in the container 1 has become equal to or higher than the heat retention temperature set at that time, the control circuit 8 Sets the heat retention output to HIGH. By this operation, the transistor Tr shown in FIG.
Since the switch 2 is turned on, the thyristor SCR which has lost the holding current at the next zero volt point B5 is turned off, the power supply to the heat retaining heater 4a is stopped, and the heating of the liquid in the container 1 is completed.

Hereinafter, an operation for suppressing noise generated from the power supply circuit will be described. FIG. 4 is a timing chart showing the noise suppression operation.

In FIG. 1, when the output voltage of the full-wave rectifier circuit of the diodes D1 to D4 exceeds the Zener voltage of the Zener diode ZD1 when the thyristor SCR is off, a Zener current starts to flow through the resistor R1. When the voltage increases and reaches a predetermined voltage VON, the Zener current increases, and the transistor Tr1 is turned on by the current. Then, since the gate of the thyristor SCR is connected to the ground, no gate current flows through the thyristor SCR, and the thyristor SCR cannot be turned on. That is, the thyristor SCR can be turned on from the off state only in the range where the output of the full-wave rectifier circuit by the diodes D1 to D4 is equal to or lower than the voltage VON.

In FIG. 4, normally, when the voltage Vu of the smoothing capacitor C decreases to a predetermined VL, such as at time C1, the thyristor SCR is turned on and the transistor Tr is turned on.
3 is turned off, and charging of the smoothing capacitor C is started.
When the charging is completed at the time point, Tr3 is turned on again to stop the charging, and the thyristor SCR also turns off Tr2 to turn off the gate current at the time point C3 because the gate current is stopped flowing at the time point C2. Next,
When the voltage Vu of the smoothing capacitor C decreases to the voltage VL at the time point C4, the output of the full-wave rectifier circuit is equal to or higher than VON, and since the transistor Tr1 is in the ON state, no gate current flows and the thyristor SCR is turned ON. Can not be.
Next, the thyristor SCR is turned on only when the output of the full-wave rectifier circuit becomes VON or less at the time C5 and the transistor Tr1 is turned off.

That is, the thyristor SC is used only during the period when the transistor Tr1 and the transistor Tr2 are simultaneously turned off.
R can be turned on, and in FIG. 4, the thyristor SCR can be turned on only from the time point C1 to the time point C6 and only from the time point C5 to the time point C7.

Since the voltage VON is about 10 V, it is appropriate to set the voltage VON to about 20 V, which is higher than the voltage Vu.

The protection operation when the SCR fails will be described below. As shown in FIG. 1, a Zener diode ZD3 is connected in parallel with the smoothing capacitor C between the positive output and the negative output of the DC power supply 6 so that the positive output side is the cathode. At this time, in the event that the thyristor SCR fails and is continuously turned on and the transistor Tr3 remains off without operating, the voltage Vu of the DC power supply 6 continues to increase, and eventually the withstand voltage of the smoothing capacitor C And the smoothing capacitor C may burst,
Due to the presence of the Zener diode ZD3, when the voltage Vu of the DC power supply 6 exceeds the Zener voltage of the Zener diode ZD3, the charging current flows through the Zener diode ZD3, and the rise of the voltage Vu stops at the Zener voltage.
Furthermore, a large amount of charging current flows and the Zener diode ZD
When the rating exceeds 3, the zener diode is generally short-circuited and destroyed.
D3 shorts the positive and negative outputs of the DC power supply 6.

Hereinafter, the second DC power supply 7 will be described. In FIG. 1, a transistor Tr4, a resistor R9, and a Zener diode ZD4 constitute a second DC power supply 7 used as a power supply for a control circuit 8.

Since the second DC power supply 7 absorbs the ripple of the DC power supply 6 by the Zener diode ZD4, a substantially flat voltage is obtained, and is used as a power supply for a microcomputer constituting the control circuit 8. Generally, the Zener diode ZD4 has a Zener voltage of about 5 to 6 V, and a voltage of about 5 V obtained by subtracting a voltage between the base and the emitter of the transistor Tr4 of about 0.6 V is applied to the second DC power supply 7. Output voltage.

Hereinafter, the power consumption will be described. FIG. 2 shows a case where the charging / discharging cycle of the smoothing capacitor C is one cycle of the commercial power supply, and the thyristor SCR is turned on once every half-wave of the commercial power supply, and the transistor is maintained even after the charging is completed. Heater heater 4a by the action of Tr3
Will continue to flow current. At this time, the electric power consumed is 7 in a warming heater of a general electric water heater.
Since the power is about 5 W, an average power of about 37.5 W is consumed.

Therefore, the smoothing capacitor C is selected to have a large capacity, and the ripple of the voltage Vu of the DC power supply 6 is made large within a range that does not impose a load on the motor 5b, that is, the interval between VH and VL is widened. Accordingly, the charge / discharge cycle can be extended, and the average power consumption can be suppressed to a predetermined power W0 or less.

At this time, the predetermined power W0 does not prevent the boiling liquid in the container 1 from lowering to the selected heat retaining temperature, for example, 60 ° C., and is left without putting the liquid in the container 1. It is appropriate to set the temperature to about 2 W so that the temperature of the container 1 does not rise to a dangerous temperature even when the temperature is increased. That is, it is appropriate to set the capacitance of the smoothing capacitor C and the values of the voltage VH and the voltage VL so that the thyristor SCR is turned on about once every 40 half-waves of the commercial power supply.

In the above embodiment, as shown in FIG. 1, a full-wave rectifier circuit of diodes D1 to D4 is used. However, there is no problem with half-wave rectification.
Although the heater for heating the water heater and the heat retaining heater are divided, it goes without saying that there is no problem if the same heater is used.

[0040]

As described above, according to the electric water heater of the present invention, it is possible to realize a DC power supply for a motor for tapping a liquid in a container to the outside of the container with a simple configuration. The hot water outlet switch is a DC output on / off switch, so that a small one can be used and an inexpensive electric water heater can be provided.

Further, an electric water heater having an inexpensive power supply circuit with a simple configuration in which the operation of keeping the liquid contained in the container warm and the operation of charging the smoothing capacitor of the DC power supply by the heater of the heat retaining means is combined. Can be provided.

Further, the timing of the start of charging is limited to a predetermined time before and after the zero volt point of the rectified voltage of the commercial power supply, the noise generated from the DC power supply when the thyristor is turned on can be suppressed, and a safe electric water heater can be provided. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an electric water heater according to the present invention.

FIG. 2 is a timing chart showing the operation of the power supply circuit according to one embodiment of the present invention.

FIG. 3 is a timing chart showing a heat retaining operation in one embodiment of the present invention.

FIG. 4 is a timing chart showing a noise suppression operation in one embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional electric water heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Container 2 Temperature detection means 3a Heater 4a Heat retention heater 6 DC power supply 7 2nd DC power supply 8 Control circuit D1-D4 Diode (rectification means) C Smoothing capacitor

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Saori Fujita 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-45224 (JP, A) JP-A-1- 117688 (JP, A) JP-A-8-280539 (JP, A) JP-A-8-224172 (JP, A) JP-A-6-133865 (JP, A) JP-A-1-122324 (JP, A) JP-A-3-268797 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A47J 27/21

Claims (2)

(57) [Claims] 1. A container for accommodating a liquid, a temperature detecting means for measuring the temperature of the container, a heater and a heater for heating or keeping the liquid contained in the container, the heater and the heat insulator A rectifier for rectifying the commercial power supply through one or both of the heaters; charging the current rectified by the rectifier to the smoothing capacitor; stopping the charging when the voltage reaches a predetermined voltage VH; A DC power supply for generating a DC voltage across the capacitor by restarting charging when a predetermined voltage VL lower than the predetermined voltage VH is reached, and a control circuit for controlling the operation of the entire apparatus. If the temperature of the container measured by the means is lower than a predetermined temperature, the charging path is stopped even after the charging of the smoothing capacitor by the DC power supply is stopped. The current path is switched so as to bypass the rectifier, and the commercial power supply is continuously supplied to the heater in series with the rectifier. During the continuous supply of electricity, the bypass is opened when the charging voltage falls below a predetermined value. Electric water heater. 2. A container for accommodating a liquid, temperature detecting means for measuring the temperature of the container, a heater and a heater for heating or keeping the liquid contained in the container, the heater and the heat insulator. A rectifier for rectifying the commercial power supply through one or both of the heaters; charging the current rectified by the rectifier to the smoothing capacitor; stopping the charging when the voltage reaches a predetermined voltage VH; A DC power supply for generating a DC voltage across the capacitor by starting charging again when the voltage reaches a predetermined voltage VL lower than the voltage VH, and a control circuit for controlling the operation of the entire apparatus. When the instantaneous voltage drops to the predetermined voltage VL, charging is started again from the point in time when the instantaneous voltage of the output of the rectifier becomes equal to or lower than the predetermined voltage VON. Electric water heater.