JP2000039212A - Hot water supply apparatus with heat insulation function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform reliable detection of normal water presence by a method wherein when a circuit trouble occurs to an energization control circuit, the second threshold of the heat generation state of a heat-sensitive element is further set and a heat generating state detected during self-heat generation of a heat-sensitive element is compared with the second threshold, and the circuit trouble of the energization control circuit is decided. SOLUTION: A hot water supply apparatus 1 is connected to a hot water supply pipe 6, and by opening a faucet, water flows through an apparatus. When flow-through of water is detected by a water quantity sensor 8, a controller 10 causes respective opening of a main solenoid valve 11 and a solenoid valve 13, a proportional control valve 12 is opened at a given opening, and an ignition electrode 16 is continuously sparked to ignite a burner 4. The controller 10 computes a necessary heating amount from an initial water quantity obtained from an initial water temperature obtained by an incoming water temperature sensor 7, so that hot water is supplied at a set temperature set by a regulation button of a remote control 14. Further, the controller performs correction control of the opening of the proportional control valve 12, based on a detecting temperature obtained from a hot water supply temperature sensor 9, so that a hot water supply temperature coincides with a set temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater with a heat retaining function capable of performing heat retention control to burn a burner in a water stopped state and maintain a water temperature in an appliance within a predetermined temperature range.

[0002]

2. Description of the Related Art At the start of use of a water heater, first, water stored in the appliance is sent out, and it takes time to rise the tap water temperature. Therefore, the burner is heated to a predetermined temperature without using the water heater. Combustion in quantity, water temperature in the appliance is maintained in a predetermined temperature range, and when using a water heater, a warming function is provided to obtain hot water at the set temperature with a quick rise and improve usability. It has been known. However, the above-mentioned heat retention function works even when there is no water inside the appliance due to, for example, drainage for preventing freezing.When heated in this state, the interior of the appliance becomes an abnormally high temperature due to empty heating, and the inner body deteriorates. This can cause damage to the equipment. Therefore, the applicant has determined the presence or absence of water in the appliance before performing the heat retention control,
An invention for detecting presence of water without performing heat retention control when there is no water is provided earlier. This is done by installing a temperature-sensitive element such as a thermistor in the water pipe inside the appliance, and energizing the thermistor to generate heat by itself, and configuring an energization control circuit that detects the change in the heat generation state with a transistor or a microcomputer, etc. Is stored in advance the threshold value of the change in the heat generation state when the environment around the thermistor is water,
By causing the thermistor to self-heat before the burner burns in the heat retention control, and comparing the change in the detected heat generation state with the threshold, if it is larger than the threshold, there is no water in the appliance, and if the temperature rise is smaller than the threshold Is to judge that there is water in the appliance.

[0003]

However, in the above invention, there is a possibility of erroneous detection due to a failure of the power supply control circuit. For example, if the transistor for energizing the thermistor is O
Even when the thermistor cannot self-heat due to FF failure or the like, the temperature rise does not occur and the temperature falls below the threshold, so that it is determined that there is water, and in this case, if the heat retention control is executed, it results in idle heating. If the thermistor self-heats excessively due to a short-circuit failure of a resistor placed on the input side of the thermistor, it is determined that there is no water because the temperature rises and exceeds the threshold value. Nevertheless, the heat retention control is not executed. Further, even if the thermistor is constantly generating heat due to the ON failure of the transistor, the temperature rise is fixed at a value exceeding the threshold value. Will not be done.

[0004] Therefore, an object of the present invention is to provide a highly reliable water heater with a heat retaining function that can reliably detect normal water presence except when such a circuit failure occurs. It was done.

[0005]

In order to achieve the above object, according to the present invention, a second threshold value of a heat generation state of the temperature sensing element when a circuit failure occurs in the conduction control circuit. Is further set, and a heat generation state detected at the time of self-heating of the temperature-sensitive element is compared with the second threshold value, so that a circuit failure of the energization control circuit can be determined. is there. The invention according to claim 2 provides, in addition to the object of claim 1, a water-free state in the appliance or an energization control circuit in order to appropriately cope with the determination of the absence of water in the appliance or a circuit failure of the energization control circuit. If it is determined that the circuit has failed, the heat retention control is prohibited. According to a third aspect of the present invention, in addition to the object of the first or second aspect, in order to appropriately cope with a circuit failure when the temperature-sensitive element is also used as an incoming water temperature sensor, the temperature-sensitive element is controlled by an energization control circuit. While the amount of current supplied to the temperature control element can be switched to the amount of current that can be used to detect the temperature of the water pipe, the circuit failure of the power supply control circuit prevents the temperature sensitive element from being used to detect the temperature of the water pipe. If, the normal combustion control is prohibited.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a water heater with a heat retention function (hereinafter abbreviated as “water heater”). The water heater 1 is configured to supply water from a water supply pipe 3 connected to a combustion chamber 2 to heat generated by a burner 4. A heat exchanger 5 for heating the hot water is provided, and a tapping pipe 6 for feeding the heated hot water is connected to the heat exchanger 5. Water pipe 3
Is provided with an incoming water temperature sensor 7 for detecting the temperature of the water passing through the water supply pipe 3 and a water quantity sensor 8 for detecting the flow rate of the water, while the tapping pipe 6 detects the temperature of the water passing through the tapping pipe 6. A hot water temperature sensor 9 is provided, and a detection signal of each sensor is input to a controller 10. A main solenoid valve 11, a proportional control valve 12, and a main solenoid valve 13 are provided in the gas flow path to the burner 4 from the upstream side, and these valves are also opened and closed by the controller 10. Further, the controller 10 includes a remote controller 14 including an operation switch, a button for adjusting a set temperature, an insulation switch 15 for insulation control, an ignition electrode 16 for ignition of the burner 4, and a frame rod 17 for flame detection. It is connected.

Therefore, in the water heater 1, when the water flow sensor 8 detects the water flow through the appliance by opening a faucet (not shown) connected to the tapping pipe 6, the controller 10 returns to the original solenoid valve. 11 and the main solenoid valve 13 are each opened, and the proportional control valve 12 is opened at a predetermined opening to continuously spark the ignition electrode 16 and ignite the burner 4. Thereafter, the controller 10 calculates the required heating amount from the initial water temperature obtained from the incoming water temperature sensor 7 so that the hot water is discharged at the set temperature set by the adjustment button of the remote controller 14, and the opening of the proportional control valve 12. Is adjusted, and the opening of the proportional control valve 12 is corrected and controlled based on the detected temperature obtained from the tapping temperature sensor 9 so that the tapping temperature matches the set temperature.

The water temperature sensor 7 provided in the water supply pipe 3 uses an NTC thermistor, which is also used as a temperature sensing element for detecting the presence or absence of water in the water supply pipe 3. This incoming water temperature sensor (hereinafter, simply referred to as a "thermistor" because it has a plurality of functions) 7
As shown in FIG. 2, a PNP having a base connected to a microcomputer 21 via a transistor 22 for protecting a microcomputer port in an energization control circuit 20 in the controller 10.
The controller 1 is connected to the emitter side of the
The power supply V ₁ generated in the circuit 0 is connected in series with the resistor 24 on the output side of the transistor 23, and the terminal voltage of the thermistor 7 is input to the A / D conversion port of the microcomputer 21.
That is, the microcomputer 21 can control the energization of the thermistor 7 and detect the terminal voltage (temperature detection signal) accompanying the energization. On the other hand, the thermistor 7 is lower power V ₂ than V ₁ produced by the controller 10 within the resistor 25
Through the transistor 23, and the OF of the transistor 23
At the time of F, a voltage determined by a voltage dividing ratio based on V ₂ of the resistor 25 and the thermistor 7 is input to the A / D conversion port of the microcomputer 21. The input side of the A / D conversion port has a Zener diode 26 for protecting the A / D conversion port.
Is arranged.

When the heat retention switch 15 provided on the remote control 14 is turned on, the microcomputer 21 ignites the burner 4 in a water-stopped state, performs heating with water stored in the appliance, and outputs the hot water temperature sensor 9. Monitoring the detected temperature obtained from
Insulation control that keeps the water in the appliance at a constant temperature, and detects the presence or absence of water in the appliance before performing the insulation control.Water detection control that does not perform the insulation control when there is no water in the appliance And running. Hereinafter, this water detection control will be described with reference to the flowchart of FIG. First, the thermal insulation switch 15
Are not turned on, the transistors 22 and 23 are set in S1.
Are turned off, the thermistor 7 functions as an incoming water temperature sensor for detecting the water temperature in the water supply pipe 3 when the power supply V ₂ is supplied. That is, the self-heating amount is extremely reduced. Therefore, the microcomputer 21 performs normal hot water supply control based on the temperature detection signal obtained by the thermistor 7. When the ON warmth switch 15 is obtained in S2, after detecting the temperature T ₁ of the thermistor 7 first in S3, the transistors 22 and 23 is turned ON in S4, with energizing the thermistor 7, Arimizu detection for Timer (here 5
Seconds). When the timer times up in S5, detects the temperature T ₂ of the thermistor 7 at S6, S7
In the temperature rise from temperatures T ₁ to T ₂ is either in a second range below 5 ° deg least 15 ° deg as a threshold whether determined, if here outside the range, S8 To judge that a circuit failure has occurred.

This is because, as shown in the graph of FIG.
When the FF failure or the resistor 24 is an open failure, the thermistor 7 cannot generate heat by itself, and the temperature rises 5 as shown in the graph a.
° deg or less, a threshold A (10
° deg), and there is a risk of being erroneously detected as having water. Similarly, when the resistor 24 is short-circuited, the thermistor 7 generates too much heat and the temperature rises by 15 ° as shown in graph b. If the transistor 22 and 23 both have an ON failure, the thermistor 7 will generate heat by itself, and the temperature will exceed the threshold value A. 15 ° de as in c
g is fixed at a high temperature rise of not less than the threshold value A, and there is a possibility that it is erroneously detected that there is no water, that is, the hatched portion in the figure is a range excluded by the second threshold value. .

In this case, however, it is further determined in S9 whether or not the range excluded by the second threshold is an abnormality due to the constant self-heating in the graph c. In addition to prohibiting combustion only, a buzzer, lamp, etc. will be used to notify the user. On the other hand, if it is determined in S9 that the abnormality is always caused by self-heating, in S11,
The normal combustion control as well as the insulated combustion is prohibited and the notification is performed. This is because the transistors 22 and 23 in the graph c are turned on.
This is because the temperature of the water supply pipe 3 cannot be detected by the thermistor 7 in a self-heating state due to a failure, which hinders normal hot water temperature control. It is desirable that the notification in S10 and the notification in S11 be distinguished by how the buzzer sounds, the color of the lamp, blinking, and the like.

On the other hand, in the determination of S7, the temperature rise is 5
If it is within the range of not less than ° deg and not more than 15 ° deg, the transistors 22 and 23 are turned off in S12, and it is determined in subsequent S13 whether or not the temperature rise is equal to or more than the threshold value A (here, 10 ° deg). This is because, when a current is passed through the thermistor 7 to cause self-heating, a thermal equilibrium is reached in about 5 seconds, and the current and resistance are also stabilized. However, depending on whether the surrounding environment is air or water, the thermal equilibrium is reached as shown in FIG. This is based on the fact that there is a difference in the temperature rise when the temperature rise is performed. This temperature rise is determined by the heat dissipation constant δ (mw / ° C.) of the thermistor, and the following equation 1 holds.

[0013]

(Equation 1) T: temperature when thermal equilibrium is reached, Ta: ambient temperature,
I: current (mA) flowing through the thermistor at temperature T,
R: Resistance value of thermistor at temperature T (kΩ)

Δ differs between water and air, and is usually 4 mw / ° C. in water and 2 mw / ° C. in air. Therefore,
If the power consumption of the thermistor 7 is 20 mW, 5
° deg., And 10 ° deg. In air, and the difference in temperature rise shown in FIG. 4 appears. Therefore, here, the microcomputer 21
10 ° deg is set as a threshold value A for distinguishing between a temperature rise in water and a temperature rise in air.
The temperature rise from the start of energization to
Thus, it is possible to determine whether the environment around the thermistor 7 is water or air, that is, whether there is water in the water supply pipe 3.

Therefore, in the determination of S13, the temperature rise is 10
If it is not less than ° deg, it is determined in S14 that the environment around the thermistor 7 is in the air, that is, that there is no water in the appliance, and in S10, the heat-retaining combustion is prohibited and a notification is given by a lamp, a buzzer, or the like. On the other hand, if the temperature rise is less than 10 ° deg, S1
At 5, it is determined that the environment around the thermistor 7 is underwater, that is, there is water in the appliance, and the heat retention control is executed at S16. In this heat retention control, for example, intermittent combustion in which the burner 4 is burned for 7 seconds with a minimum input of the proportional control valve 12 at intervals of 10 minutes is performed during a predetermined heat retention timer started by turning on the heat retention switch 15. Control in S17
When the heat retention timer expires, the heat retention control is stopped until the heat retention switch 15 is turned on again at S1, and the thermistor 7 is used as a water temperature sensor.

As described above, according to the above-described embodiment, the presence or absence of water in the appliance can be determined by monitoring the temperature rise due to energization of the thermistor 7 before the heat retention control is performed. It is possible to effectively prevent the occurrence of damage to the body and the like and a decrease in durability. Also, here
Since the configuration is such that the self-heating of the thermistor 7 is used to detect the presence of water, the heat exchanger 5 and the like are not affected at all, and when the burner 4 is used, there is an effect such as deterioration of the inner body due to empty heating. Because there is not, we can use in peace. Further, since the incoming water temperature sensor is also used as the thermistor for detecting water presence, the components and circuit configuration can be shared, and a reasonable configuration with lower cost can be obtained. Then, at the first stage of the water presence detection, the temperature rise at which the water presence detection is performed is limited to a certain range after comparison with the second threshold value, and when the temperature is outside the range, the heat retention control is not performed. In addition, erroneous detection due to a rise in temperature due to a circuit failure can be eliminated, and reliable water detection can be performed. In particular, if the temperature rise outside the range is always caused by self-heating, normal combustion is also prohibited in addition to warm combustion,
Normal combustion can be prevented in a state where the thermistor 7 cannot be used as an incoming water temperature sensor due to an ON failure of the transistors 22 and 23, and the reliability of the appliance is further improved.

The configuration of the power supply control circuit is not limited to the above-described embodiment, and can be changed as appropriate as long as the self-heating of the thermistor 7 can be compared with a threshold value. The threshold value A and the threshold value A for detecting presence of water may be changed or increased or decreased in accordance with the thermistor or the energization control circuit to be employed. In particular, the threshold value is determined by the resistance value of the thermistor 7 before self-heating. It is preferable to increase or decrease. This is because, for example, when the water temperature is low, the resistance value of the thermistor is large, and the amount of current supplied to the thermistor is small.
This is because the self-heating value becomes small and the threshold value may not be exceeded when there is no water. In the opposite case (when the water temperature is high and the resistance value of the thermistor is low), the amount of self-heating increases, and there is a possibility that it is determined that there is no water.

[0018]

According to the first aspect of the present invention, if water is not present in the appliance by detecting presence of water, it is possible to take a precautionary measure such as not performing a notification or performing a heat retention control. Accordingly, it is possible to effectively prevent the occurrence of damage such as deterioration of the inner body, a decrease in durability, and the like. In addition, by setting the second threshold value, in addition to the detection of water presence, a circuit failure of the power supply control circuit can be determined, so that the presence or absence of water in the appliance can be reliably known without erroneous detection. According to the second aspect of the present invention, in addition to the effect of the first aspect, when it is determined that there is a circuit failure of the power supply control circuit or that there is no water in the appliance, the heat retention control is prohibited, thereby preventing a circuit failure or an internal appliance failure. We can cope appropriately without water. According to the invention described in claim 3, in addition to the effect of claim 1 or 2, the amount of current supplied to the temperature-sensitive element by the power supply control circuit is changed to the amount of current that can be used by the temperature-sensitive element to detect the temperature of the water pipe. On the other hand, if the circuit failure of the current supply control circuit is such that the temperature-sensitive element cannot be used for detecting the temperature of the water pipe, normal combustion control is prohibited. The reliability of the appliance can be increased by appropriately coping with a circuit failure that hinders control.

[Brief description of the drawings]

FIG. 1 is a schematic view of a water heater with a heat retaining function.

FIG. 2 is a circuit diagram of an energization control circuit.

FIG. 3 is a flowchart of water presence detection control.

FIG. 4 is a graph showing a change in temperature rise of a thermistor.

[Explanation of symbols]

1. Water heater with heat retention function, 2. Combustion chamber, 3. Water supply pipe, 4. Burner, 7. Water temperature sensor, 10. Controller, 14. Remote controller, 15. Heat switch,
20 .. energization control circuit, 21 .. microcomputer, 22, 23
..Transistors, 24, 25 .. resistors.

Claims (3)

[Claims] 1. A burner is burned in a water-stop state, and a heat retention control for maintaining a water temperature in an appliance within a predetermined temperature range is possible. While having a temperature-sensitive element that changes the heat generation state depending on the environment, an energization control circuit capable of detecting a change in the heat generation state by energizing the temperature-sensitive element is provided, and further, the environment around the temperature-sensitive element is water. In this case, a threshold value of a change in the heat generation state of the temperature sensing element is stored, and before the burner is burned in the heat retention control, the temperature control element causes the temperature sensing element to self-heat, and the detected heat generation state is determined by the threshold value. A water heater with a heat retention function that can determine the presence or absence of water in the appliance as compared with the second threshold value of the heat generation state of the thermosensitive element when a circuit failure occurs in the energization control circuit. Is further set, and The heating condition is detected during the self-heating of the temperature sensing element as compared with the second threshold value, the water heater with heat insulating function, characterized in that to enable determining circuit failure of the conduction control circuit. 2. The heat retention control is prohibited when it is determined that there is no water in the appliance or a circuit failure of the power supply control circuit.
Water heater with heat retention function as described in. 3. An electric power supply to the temperature-sensitive element by the electric power supply control circuit can be switched to an electric power supply amount that can be used for detecting the temperature of the water sensitive element by the temperature-sensitive element. The normal combustion control is prohibited when the temperature element cannot be used for detecting the temperature of the water pipe.
Or the water heater with a heat retention function described in 2.