JPS6154155B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water heater having a control device that detects the temperature of hot water discharged from a heat exchanger and controls the temperature of hot water to an arbitrarily set temperature, and particularly relates to a water heater for instantaneous gas hot water. It concerns boilers.

Conventionally, when using an instantaneous gas water heater to supply hot water and use a shower, etc., the flow rate of hot water supply to obtain the appropriate temperature is constant, and when the water volume is changed, the hot water temperature changes as shown in A in Figure 1. To move on the curve,
The temperature of the water varied greatly, making it difficult to use.

Additionally, a gas proportional control valve has been developed, and proportional control water heaters are now on the market that detect the temperature at the outlet of the water heater and control the amount of gas burned to maintain a constant temperature. . As a result, when the water heater is used at less than its maximum capacity, a nearly constant water temperature can be obtained even if the flow rate changes. However, even with this, the temperature changes as a drooping characteristic due to deviation.
This situation is shown in B, B', and B'' in Figure 1.Especially when using a shower, even a 1°C temperature increase makes the human body feel hot, so the performance could not be said to be sufficient.

Therefore, in order to eliminate the drooping characteristic, it is possible to use a proportional-integral control method. in this case,
As shown in Figure 2, when the water heater capacity is below A, the set temperatures C, C', and C'' remain constant regardless of the hot water supply flow rate Q. However, when the integral method is used, a new transient response characteristic For example, in Figure 2, if the set temperature is set to C' and the capacity is A', the outlet temperature will change depending on the capacity of the water heater.
It does not become C′. Here, the hot water supply amount Q is reduced to the control range D.
When used at , there is a phenomenon in which the temperature does not reach C' immediately, but once rises to D' on curve A, and then reaches C' after a certain period of time. In this case, if a person uses a shower or the like, it will be extremely dangerous. The cause of this will be explained with reference to FIG. In FIG. 3, T indicates the outlet temperature characteristic, and I indicates the driving current characteristic of the proportional control valve. Currently, when A' is in use, it is the capacity of the water heater, so the current I continues to increase due to integral action, and increases to the maximum current value determined by the power supply voltage (X area in the diagram). . Next, when the hot water supply amount is changed to D, the current I starts to be reduced little by little depending on the integral time, but until it enters the control region, the combustion amount is at its maximum, so the temperature becomes D', and the current reaches the control region. When the temperature drops
This returns us to C'. As described above, the vehicle may move on the performance curve by the delay of the integration time, resulting in an uncontrolled state. The above are disadvantages when using an integrating circuit.

Another idea is to drive a timer to discharge the integral amount when the water temperature rises, and then start from a lower value than the set value, but this would actually lengthen the time it takes for the temperature to drop, which would be uncomfortable, especially when using a shower. . This situation will be explained with reference to FIG. FIG. 7 shows the transient response characteristics, where T indicates the hot water supply temperature, I indicates the control current of the proportional control valve, and in the above example, the time indicated by V becomes longer. Therefore, if the integrated discharge amount is partially limited, the temperature drop can be improved to some extent. Ideally, it would be best to match the integrated discharge amount with '' in FIG. 7, but since ' varies more than the supply water temperature, the above method could not always provide the best conditions all year round.

The present invention improves these drawbacks and provides comfortable hot water supply throughout the year.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 4 shows a system diagram of an instantaneous gas water heater.
In Figure 4, water enters from water inlet 1 to heat exchanger 2.
It passes through to the hot water faucet 3. Gas enters through a gas inlet 4 and passes through an electromagnetic proportional control valve 5 to reach a gas burner 6. Reference numeral 7 denotes a temperature sensor for detecting the hot water temperature, which is composed of a negative temperature sensitive resistance element (hereinafter referred to as a thermistor), and sends a temperature signal to a control circuit 8, which sends a drive signal to the proportional control valve 5.

FIG. 5 shows a specific example of a conventional control circuit 8. As shown in FIG. 9
is a DC power supply, which applies a potential D divided by a thermistor 7 and a resistor 10 to a negative input terminal of an operational amplifier 12 via a resistor 11. On the other hand, a reference potential E is applied to the positive input terminal of the operational amplifier 12. Operational amplifier 1
2 compares the two potentials, inverts and amplifies the difference, and inputs it to the base of the transistor 13;
Controls the current value leading to the proportional control valve 5. For example, when the hot water temperature increases, the resistance value of the thermistor 7 decreases, so the divided potential D increases, and the potential of the negative input terminal 12a of the amplifier 12 also increases. The difference potential between this and the reference potential E, that is, the potential of the positive input terminal 12b, is R ₁₄ /R ₁₁ (R ₁₄ : resistance value of the resistor 14,
R ₁₁ :resistance value of the resistor 11) and output to the output terminal 12c, the potential of the output terminal 12c decreases. The potential of the output terminal 12c is the resistor 15,1
6, and the midpoint is connected to the base of the transistor 13, so as the potential of the output terminal 12c decreases, the base potential also decreases, causing the collector current of the transistor 13, that is, the current flowing to the proportional control valve 5. It acts to reduce the value and throttle the gas amount. In this case, the potential difference of DE due to the capacitor 17 is determined by the resistor 11 and the capacitor 17, and the output 12c becomes an integrated output, and D
Stop at the point where =E. In other words, since the sensor 7 changes to the point where it returns to its original resistance value (temperature), the hot water supply temperature can obtain a curve as shown in FIG. 2 with respect to the load. However, in this case, as mentioned above, there are problems shown in FIG. 3.

FIG. 6 shows an embodiment of the present invention, and since the control circuit operates in the same way as in FIG. 5, the same numbers are marked and the explanation thereof will be omitted here. Here, the capacitor 18 inputs the change in potential D to the positive input terminal of the operational amplifier 19 . In this case, the amplifier 19 functions as a comparator, and when the change value of the potential D output from the capacitor 18 exceeds a potential point F which is set to a value higher than the normal potential D, the output of the amplifier 19 is inverted. In the case of the figure, the output of the amplifier 19 is normally low, and when a change in the potential D occurs on the positive side, that is, when the temperature of the sensor 7 rises, the output of the amplifier 19 becomes high.
become. This output is the diode 2 of the timer circuit.
2 to the positive input terminal of the operational amplifier 23. The operational amplifier 23 functions as a comparator, and resistors 24, 27, 28 and a capacitor 25 constitute a monostable multivibrator. Now, when the output of the amplifier 19 becomes high, the output of the amplifier 23 also becomes high because it is connected to the negative input terminal of the amplifier 23 via the diode 26 and exceeds the preset potential G lower than the power supply voltage 9. Become. At this time, the potential divided by the resistors 27 and 28 is applied to the positive input terminal, so even if the output potential of the amplifier 19 instantaneously becomes low, the output of the amplifier 23 continues to be held. At the same time, the resistor 24 starts charging the capacitor 25, and the negative input terminal of the amplifier 23 starts to rise. Eventually, when the negative input terminal exceeds the positive input potential divided by resistors 27 and 28, amplifier 23 returns to low again.

Further, the output of the operational amplifier 23 is voltage-divided by resistors 35 and 36, and is applied to the positive input terminal of the operational amplifier 41 of the discharge limiting circuit. A potential obtained by dividing the power supply voltage by a second thermistor 37 and a resistor 38 is applied to its negative input terminal via a resistor 39, and at the same time, the output is fed back through a resistor 40, and the amplifier 41 is an inverting amplifier circuit. It consists of That is, the difference between the potential L at the midpoint of the resistors 35 and 36 and the midpoint potential K between the sensor 37 and the resistor 38 is amplified by a factor of amplification (resistance 40/resistance 39). amplifier 4
The output of transistor 45 is divided by resistors 42 and 43 and applied to the base of transistor 45.
The emitter is connected to the negative terminal of the DC power supply 9 via the emitter resistor 44, and the collector is connected to the base of the transistor 13.

When the water supply temperature is high, the resistance value of the sensor 37 is small, so the potential of K is low. Therefore, the output of the amplifier 41 is high and the transistor 45 is conductive.
The base current of transistor 13 is reduced. When the water temperature is low, the sensor 37 is large, the amount of conduction of the transistor 45 is small, and therefore the amount of decrease in the base potential of the transistor 13 is also small. Since the charge in the capacitor 17 is discharged through the resistors 14 and 33, the amount of discharge changes in proportion to the base potential of the transistor 13. Therefore, when the water supply temperature is low, the amount of discharge is small, and when the temperature is high, the amount of discharge is large. All of the above occurs while the timer is operating, and when the timer does not operate, the amplifier 23
Since the output of is low, the potential of L becomes zero, the output of amplifier 41 also becomes zero regardless of the resistance value of sensor 37, and transistor 45 continues to be off.

As explained above, according to the present invention, the following effects can be obtained. That is, if the water supply temperature is low, the load required to obtain a certain set temperature is large, so the current ' in FIG. 8 becomes large. Therefore, it becomes possible to reduce the integrated discharge amount and immediately shift to ''. On the other hand, if the water supply temperature is high, the load is small, so `` is small. Accordingly, it is possible to increase the integrated discharge amount so as to approach ``.

FIG. 9 is an example of a circuit for varying temperature settings. When the temperature setting value is varied, the load changes and '' in FIG. 8 changes even if the water supply temperature is constant. For example, the higher the temperature setting, the greater the load.
′ is also large, and the lower the setting, the smaller ′ is. In the circuit shown in Figure 9, the difference between the supply water temperature and the set temperature is taken,
The configuration is such that the integrated discharge amount is controlled according to the value. A power supply 9 is connected to the positive input terminal of the operational amplifier 12.
A potential K obtained by dividing the voltage of 1 by a resistor 45 and a setting resistor 46 is applied, the potentials K and D are compared, and the difference is output. Now, if the setting resistor 46 is large, the potential K will rise and the output of the amplifier 12 will also rise.
As a result, the transistor 13 becomes conductive and the current that can pass to the proportional control valve 5 increases. As a result, the temperature of the water increases and the resistance value of the sensor 7 decreases, so the potential D increases and stops at a stable point. Further, in the operational amplifier 41, the potential K is applied to the negative input terminal via the resistor 39, the M potential at the midpoint between the second temperature sensor 37 and the resistor 38 is applied to the positive input terminal, and the set temperature is set at the K potential. The supply water temperature is detected at the M potential, and the difference is amplified by a gain (R ₄₀ /R ₃₉ ) and applied to the base of the transistor 45. Further, when the timer is not operating, the output of the operational amplifier 23 is low, so the base of the transistor 45 is pulled negative through the diode 47, so it is turned off regardless of the potentials of K and M.

With the above circuit configuration, the integrated discharge amount can be controlled regardless of whether the water supply temperature or the set temperature changes.

FIG. 10 shows a configuration in which the integral discharge amount can be controlled even when the amount of hot water supplied is varied. The control potential ′ of the valve is proportional to the load of the water heater. Also, it can be calculated as load L=(T ₂ −T ₁ )×Q.

T ₂ = Water heater set temperature T ₁ = Water heater inlet temperature Q = Hot water supply flow rate From the above, it is ideal to control the integral discharge amount in proportion to the load L. Therefore, in Figure 10, 4
A variable resistor 8 is attached to the hot water faucet and operates in proportion to the degree of opening of the faucet, and the resistance becomes smaller as the faucet is opened. In other words, the more the faucet is opened and the amount of hot water increases, the gain R ₄₈ /R ₄₉ of the operational amplifier 41 increases.
becomes higher. Since the output is (potential K−potential M)×gain, it is equivalent to the equation for the load L described above.

The method of detecting the amount of hot water supplied may be a method other than that shown in FIG.

As explained above, according to the present invention, load fluctuations in one direction (increasing water temperature) are detected in a control system with an integral element, and the integral capacitor is charged by a timer driven by this. By installing a circuit that forcibly shifts the charge to the optimum charge amount for the load, it is possible to suppress the rise in water temperature due to load fluctuations and also limit the temperature drop due to overdischarge, making it possible to obtain a comfortable hot water temperature. Moreover, it has great industrial value as it eliminates the danger of burns and improves safety.

[Brief explanation of the drawing]

Figure 1 shows the hot water supply characteristics of a proportional control type water heater.
Figure 2 is a water supply characteristic diagram of a proportional-integral water heater, and Figure 3 is a transient response characteristic diagram of hot water temperature and load current when the present invention is not used, especially from the water heater capacity range to the control range. Indicate the case. Fig. 4 is a diagram of a water heater control system, Fig. 5 is a diagram showing a conventional proportional-integral control circuit, Fig. 6 is a diagram showing a circuit in an embodiment of the present invention, and Fig. 7 is a diagram showing key points of the present invention. This is a transient response characteristic diagram when a discharge amount control circuit is not provided, and shows when the load changes from a large load to a small load. FIG. 8 is a diagram showing transient response characteristics when the present invention is implemented, FIG. 9 is a circuit diagram of another embodiment of the present invention, and FIG.
FIG. 0 is a circuit diagram of still another embodiment of the present invention. 1...Water inlet (water channel), 2...Heat exchanger, 5...
...Proportional control valve (proportional controller), 6...Burner, 7
...Hot water temperature detection sensor (first temperature sensor),
37... Water supply temperature detection sensor (second temperature sensor), 46... Variable resistor for hot water temperature setting (temperature setting device), 48... Flow rate sensor for detection of water supply flow rate,...
...control circuit, ...timer circuit, ...discharge limit circuit.

Claims (1)

[Scope of Claims] 1. A water channel having a heat exchanger in the middle, a burner that heats the heat exchanger, a proportional controller that proportionally controls the combustion amount of the burner according to the amount of current, and A first temperature sensor that detects the hot water temperature, a second temperature sensor that detects the water supply temperature of the heat exchanger, and control that performs proportional integration according to the output signal of the first temperature sensor and drives the proportional controller. a timer circuit that detects the output signal of the first temperature sensor and discharges the electric charge of the integrating capacitor of the control circuit for a certain period of time; and an amount of electric charge discharged from the integrating capacitor according to the output signal of the second temperature sensor. A water heater characterized by comprising a discharge limiting circuit for controlling. 2. The control circuit has a temperature setting device that sets the temperature of the hot water, and the discharge limiting circuit controls the amount of discharged charge based on the difference between the temperature setting signal and the output signal from the second temperature sensor. water heater. 3 The discharge limiting circuit has a flow rate sensor for detecting the amount of water supplied, and controls the amount of discharged charge based on the value obtained by multiplying the difference between the temperature setting signal and the output signal from the second temperature sensor by the signal from the flow rate sensor. A water heater according to claim 2.