JPH0243982B2 - - Google Patents

Description

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

[Conventional technology]

Figure 4 shows the schematic structure of the instant water heater. In the figure, a fin-type heat exchanger 2 is disposed in the upper part of a combustion cylinder 1, and three gun-type burners 3, 4, and 5 are usually disposed in the lower part. A flow switch 21 is provided in the water supply pipe to the heat exchanger 2, and a thermistor 6 as a water temperature sensor is provided in the middle of the water pipe in the main body of the heat exchanger 2. Solenoid valves 31 and 4 are installed in the oil supply pipes of burners 3, 4, and 5.
1 and 51 are provided, respectively. Signals from the thermistor 6, flow switch 21, etc. are sent to the control circuit 7. The control circuit 7 controls the opening and closing of the electromagnetic valves 31, 41, and 51 based on these signals, and also controls the combustion blower 8, ignition heater (not shown), and the like.

This water heater can supply hot water only while the flow switch 21 is on. That is, water supplied from the water supply pipe is heated by the burners 3, 4, and 5 while passing through the heat exchanger 2, becomes hot water, and is supplied to a predetermined location from the hot water supply pipe. The water temperature is burner 3,
The temperature is maintained at the set temperature by ignition and extinguishing control in steps 4 and 5. Of course, this set temperature is variable.

[Problem that the invention seeks to solve]

However, since this water heater ignites and extinguishes the burner based only on the temperature in the middle of the water piping of the heat exchanger, fluctuations in the outlet temperature cannot be ignored, especially when used with low water flow rates and low flow rates. Become.

The present invention aims to provide a water heater control device that eliminates these drawbacks.

[Means for solving problems]

The present invention is characterized in that, when the water temperature of the water temperature sensor section reaches a set value and a burner extinguishing signal is output, a delay circuit is provided to further maintain combustion for a predetermined period of time.

[Effect]

In the present invention, apart from the case where the burner is extinguished by a flow switch provided in the water supply pipe, when extinguishing the fire using a signal from the water temperature sensor, the extinguishing is always delayed for a certain period of time, thereby stabilizing the hot water temperature. That's what I do.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a block diagram of one embodiment of the present invention, and the case where it is applied to the water heater shown in FIG. 4 will be explained. Therefore, the same parts as in FIG. 4 are designated by the same reference numerals.

Solenoid valves 31, 41, and 51 are provided in the fuel oil supply pipes to the burners 3, 4, and 5, respectively.
Further, a thermistor 6 for detecting water temperature is provided in the intermediate piping of the heat exchanger. The solenoid valve 31 is controlled by the output of a comparator 32 which receives a signal from the temperature setting device 33 and a signal from the thermistor 6 as input. The solenoid valve 41 is controlled by the output of a comparator 42 which receives a signal from the temperature setting device 43 and a signal from the thermistor 6 as input. Similarly, the solenoid valve 51 is also controlled by the output of the comparator 52.

The following explanation assumes that the flow switch provided in the water supply pipe is on.

The control system of the solenoid valve 31 compares the signal corresponding to the first set temperature T ₁ set by the temperature setting device 33 and the water temperature detection signal obtained from the thermistor 6.
If the set temperature T ₁ is higher, the solenoid valve 31 is opened to continue combustion. Then, when the water temperature around the thermistor 6 reaches close to the set temperature, the solenoid valve 31 closes and extinguishes the fire.

In the control system of the electromagnetic valve 41, the second set temperature _T2 of the temperature setter 43 is set several degrees to several tens of degrees Celsius lower than the set value _T1 of the temperature setter 33.

Furthermore, in the control system of the solenoid valve 51, a temperature setting device 5
The third set temperature T ₃ of No. 3 is set lower than the set value T ₂ of the temperature setting device 43 by several degrees Celsius to several tens of degrees Celsius.

Therefore, according to this device, when the flow of water in the water supply piping is detected, the burners 3, 4, and 5 are all ignited and combustion begins. When the water temperature in the heat exchanger rises and first reaches the third set temperature T ₃ , the burner 5 is extinguished, and then when the second set temperature T ₂ is reached, the burner 4 is extinguished. When the temperature further increases and reaches the first set temperature _T1 , the burner 3 is also extinguished. After that, when hot water continues to be supplied and the low-temperature supplied water reaches the thermistor 6, the burners 3, 4,
5 is lit. Further, for example, if a large amount of hot water is supplied during combustion only in the burner 3, and the temperature of the hot water drops to near the set temperature _T2 , the burner 4 is ignited. In addition,
The comparators 32, 42, and 52 all have hysteresis, and a difference is given to the temperature when the burners 3, 4, and 5 are ignited and extinguished. Of course, if the flow switch is turned off, the solenoid valves 31, 41, 5, which are in the open state, will remain open regardless of the outputs of the comparators 32, 42, 52.
1 is closed and extinguishes the fire.

In the present invention, this device further includes a delay circuit 34,
44 and 45 are provided. FIG. 2 is a time chart of signal waveforms at various parts, and FIG. 3 is a diagram showing changes in hot water temperature in the device of the present invention (solid line) and the conventional device (broken line). Note that combustion is reflected in water temperature with a half-cycle delay in the waveform shown in the figure.

In order to make it easier to understand the effects of the device of the present invention, a conventional device that does not have the delay circuits 34, 44, and 45 will be explained first.

To explain from a state where the water temperature T is between set temperatures T ₃ and T ₂ and burners 3 and 4 are burning, when the water temperature rises and reaches the set temperature T ₂ , burner 4 starts combustion at time t ₁₁ . Stop. When the water temperature further increases and reaches the set temperature _T1 , the burner 3 is extinguished at time _t12 .
The water temperature rises further due to residual heat, but immediately begins to drop and at time t ₁₃ , when the water temperature has dropped to the set temperature T ₁ , burner 3 is turned on.
is reburned. The combustion of burner 3 is not immediately reflected in the water temperature, and the amount of heat from burner 3 alone is not sufficient, so when the water temperature further decreases to the set temperature _T2 , burner 4 is re-ignited at time _t14 . but,
Since this combustion in burner 4 is not immediately reflected in the water temperature, the water temperature further decreases to the set temperature _T3 , and after the burner 5 is ignited at time _t15 , it follows an upward trend. Then, immediately set the temperature
Burner 5 is extinguished at time t ₁ after rising to T ₃ , but this extinguishment is not immediately reflected in the water temperature and the water temperature continues to rise and burner 4 is extinguished at time t ₁₇ when the water temperature rises to the set temperature T ₂ . . This extinguishing of the burner 4 is not immediately reflected in the water temperature, and since there is residual heat from the combustion of the burner 5, the water temperature further rises, and at time _t18 when the water temperature rises to the set temperature _T1 , the burner 3 is extinguished. Even at this point, the extinguishing of burners 3, 4, and 5 is not reflected in the water temperature, and after the water temperature continues to rise for a while, the effect of extinguishing burner 5 appears and the water temperature begins to decrease.

As is clear from the above explanation, the conventional device performs control using control conditions based on the detection signal from the water temperature sensor, and there is a delay in the ignition and extinguishing of each burner reflected in the water temperature. As shown by the broken line in FIG. 3, the range of temperature fluctuation becomes wider. These drawbacks are particularly noticeable when using low water flow rates with low flow rates, and even though the heat of burners 3 and 4 is actually sufficient and there is no need to ignite burner 5, the water temperature increases due to burner ignition. This can be said to be caused by a delay in the reflection of

On the other hand, in the device of the present invention, the delay circuit 34 detects the fall of the output of the comparator 32 and outputs a high level signal to the driving section of the solenoid valve 31 for a time t ₀ from the time of this fall. Delay circuits 44, 45
detects the fall of the output of the comparator 42, and outputs high-level signals to the driving parts of the solenoid valves 31 and 41 for times t ₁ and t ₂ from the time of this fall, respectively.

In this manner, in the water heater according to the present invention, when extinguishing a fire based on the signal from the thermistor 6, the burner 3 always uses the delay circuit 34 or the
In the burner 4, the combustion is forcibly extended by a time t ₀ or t ₁ , whichever is longer, and in the burner 4, the combustion is forcibly extended by a time t ₂ by the delay circuit 45.

To explain this with reference to FIG. 3, the burner 3 is not extinguished at time t ₁₂ and is extended by time t ₀ , so its reflection appears after time t ₁₄ , as seen in the conventional device. The temperature does not follow the downward trend shown by the broken line, but shows an upward trend without decreasing to the set temperature T ₃ as shown by the solid line. As a result, burner 5 is not ignited, and there is no effect of burner 5 after time _t18 as seen in conventional devices, so the water temperature rise is a gentler solid line than the rising trend shown by the broken line. After reaching the peak with an upward trend shown, it starts to decline. The times t ₀ , t ₁ , and t ₂ vary depending on the thermistor installation position, water volume, time lag from starting combustion to rising water temperature, time lag from stopping combustion to falling water temperature, etc., but range from several seconds to tens of seconds. Set within a few seconds.

As described above, according to the device of the present invention, when the water flow rate is low and the flow rate is low, burner 3 performs additional combustion, so that the water temperature of only burners 3 and 4 can be controlled, and burner 5 is ignited. Therefore, the range of temperature fluctuation can be narrowed.

Note that since the comparators 32, 42, and 52 each have hysteresis, there is a difference between the temperature at the time of ignition and the temperature at the time of extinguishment in each burner. It is shown in temperature.

[Effects of the Invention] As explained above, compared to conventional devices that do not have such an extended combustion function, the boiling time from the start of hot water supply until reaching the set temperature is shortened by the extended combustion of burner 4. Ru. Furthermore, as is clear from FIG. 3, according to the present invention, the extended combustion function reduces the amplitude of temperature changes, making it possible to reduce fluctuations in the tapped water temperature.

In addition, in the embodiment, a device was described that uses three burners to switch the calorific value in three stages by ignition and extinguishing, but the present invention can not only control ignition and extinguishing with one burner, but also Alternatively, it can also be applied to several stages of heat generation switching control using four or more wires. Further, the delay circuit 45 for the burner 4 may be omitted.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a time chart of signal waveforms of each part, and Figure 4 is a schematic configuration diagram of a water heater to which the present invention is applied.
FIG. 3 is a diagram showing changes in hot water temperature to explain the difference between the device of the present invention and the conventional device. In the figure, 1 is a combustion tube, 2 is a heat exchanger, 3, 4, 5
is burna.

Claims (1)

[Claims] 1. A hot water supply system that is equipped with a plurality of burners and controls the ignition and extinguishing of each burner according to the difference between the water temperature and the set temperature using a signal from a water temperature sensor installed in the middle of the water pipe of the heat exchanger. In the machine, when a signal to extinguish a predetermined burner arrives based on a signal from the water temperature sensor, the burner is extinguished for a set time within a range of several seconds to more than ten seconds from the time of arrival. A control device for a water heater, characterized in that it is provided with a circuit that delays the time.