JPS5899618A - Combustion control device for water heater - Google Patents

Abstract

PURPOSE:To suppress overchute and underchute by increasing or decreasing a gain of a control circuit within the combustion control device in accordance with the change of takeout rate of hot water. CONSTITUTION:A fluid state detecting device 10 detects changes in water flow rate in a heat exchanger 9 and provides a detection signal. A gain changeover circuit 19, in response to the detection signal, decreases the gain of a PID operation circuit 18 when the water amount is on a low water level side and increases when the water amount is on a high water level side. That is, before the takeout water temperature changed by the increase or decrease in the water amount is detected by a temperature sensor 12, the change in the water amount is directly detected by the fluid state detecting device 10, and the gain of the PID operation circuit 18 is changed based on the detection results, so that a flow rate control valve 5 is adjusted to have a predetermined opening degree. Accordingly, the combustion of a burner 2 is controlled in accordance with the increase and decrease in the water amount, and the change in the temperature of the takeout water is suppressed to its minimum, thereby improving largely a control response delay and suppressing the overchute and underchute effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in combustion control devices for combustion equipment such as water heaters.

In recent years, water heaters have been used to detect the output/drainage mixture from the heat exchanger, to determine the deviation from an arbitrarily set target mFm, and to control the flow rate control valve installed in the fuel supply path according to the deviation. As a result, devices equipped with a combustion control device that operates to maintain the S temperature at a target temperature regardless of the temperature of hot water used or changes in water temperature have appeared.

In this way, this type of water heater performs feedback control so that the detected water temperature matches the set temperature. Unlike a boiler, it has the great effect of consistently providing hot water at the desired temperature regardless of changes in water temperature or amount of hot water.

However, this type of water heater is used with frequent changes in the output sI, and the output temperature changes accordingly.In such cases, the combustion control device of this type of water heater is used to The flow rate control valve is actuated based on the deviation caused by the change in the outlet temperature. That is, in principle, there is a response delay in the control operation of this combustion control device. Changes in the hot water output level during this response delay time can be practically ignored if the change in the hot water output rate is slow, but if the change in the hot water output rate is rapid, a sudden temperature rise (overshoot) occurs. In particular, the above-mentioned overshoot that occurs when changing from a high hot water output side to a low hot water output side has become a problem that cannot be ignored in practice.

This invention was made focusing on the above problems,
The purpose of this is to significantly improve the response delay mentioned above, suppress overshoot and undershoot, and achieve relatively stable and uniform hot water temperature over the entire range of hot water output. The purpose of the present invention is to provide a control device.

In order to achieve the above object, the present invention is characterized in that the gain of the control circuit within the combustion control device is increased or decreased in accordance with changes in the amount of hot water dispensed.

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

FIG. 1 is a diagram showing the basic configuration of a water heater equipped with a combustion control device according to the present invention.

In the figure, the fuel supply path leading to the burner 2 in the main body 1 of the water heater includes an electromagnetic switching valve 3 that turns on and off the supply of fuel. A governor 4 and a flow control valve 5 that adjusts the fuel flow rate are provided, and an igniter 6 that generates an ignition spark in relation to the burner 2 and a flame detector 7 that detects whether or not the ignition is normally ignited by the ignition operation are provided. It is also equipped with an alarm device 8 that issues an alarm at all times, such as when normal ignition has not been achieved.

At the water inlet leading to the heat exchanger 9, there is a flow state detection device 11 for detecting the flow state of the water flow passing through the heat exchanger 9.
0, and a temperature sensor 12 such as a thermistor for detecting the mm temperature of the tap is provided on the outlet side.

The flow state detection device f10 detects that when the faucet is opened, the amount of water passing through the heat exchanger 9 has reached the minimum operating amount necessary for the water heater to operate, and also detects that the amount of water passing through the heat exchanger 9 has reached the minimum operating amount required for the water heater to operate. This is a device that detects in stages when the amount of water used has reached a predetermined amount of water that is equal to or higher than the minimum operating water amount.

The combustion control device 13 that controls the outlet temperature of the water heater to be constant is composed of a combustion sequence control circuit 14 and an S temperature control circuit 15, and the combustion sequence control circuit 14 includes an electromagnetic switching valve 3° Vessel 6. Flame detector7. Each element such as the alarm device 8 is connected. Further, each element such as a flow control valve 5', a temperature sensor 12, a temperature setting device 16, etc. is connected to the mm control circuit 15, and the minimum operating water amount detection signal of the flow state detection device @10 is used as a starting signal for combustion. The sequence control circuit 14 receives a change water amount signal at 1112.
g! Each is input to the control circuit 15.

The hot water temperature control circuit 15 includes a deviation detection circuit 17 that generates a deviation signal from a temperature signal detected by the temperature sensor 12 and a target temperature signal from the target temperature setting device 16, and a PID calculation circuit that outputs a predetermined control amount from this deviation signal. circuit 18 , a gain switching circuit 19 that switches the gain of the PID calculation circuit 18 based on the changed water amount signal that passes through the heat exchanger 9 and is detected by the flow state detection device 10 , and the PID calculation circuit 18
The valve drive circuit 20 adjusts the valve opening of the flow control valve 5 to a predetermined opening according to the output of the flow control valve 5.

What should be noted here is that a change in the amount of water passing through the heat exchanger 9 is detected by the flow state detection device [10, and based on this detection signal, the gain switching circuit 19 changes the gain of the PID calculation circuit 18 to the side where the water amount is low. It changes in response to increases and decreases in water volume, so that it is small when it is on the high water volume side and large when it is on the high water volume side. That is, before the temperature sensor 12 detects the temperature of the hot water that has changed due to an increase or decrease in the amount of water, an increase or decrease in the amount of water is immediately detected by the flow state detector *io and the PI
Since the gain of the D calculation circuit 18 is changed and the flow rate control valve 5 is adjusted to a predetermined valve opening degree, the combustion of the burner 2 is controlled as the amount of water increases or decreases, and the curve of the output S temperature is minimized. suppressed. Therefore, control response delay is significantly improved, and the above-mentioned overshoot and undershoot are also suppressed.

This will be explained next.

Now, when one faucet is opened and water flow is detected by the flow state detection device 10, the combustion sequence control circuit 14 is driven and the electromagnetic switching valve 3 is opened. At the same time P
The gain of the ID calculation circuit 18 is set to a predetermined value according to the amount of water by the gain switching circuit 19, and the deviation between the water temperature detected by the temperature sensor 12 and the target humidity determined by the target temperature setting device 16 is determined by the deviation detection circuit 17'. PI required by
It is output to the D calculation circuit 18. As a result, the PID calculation circuit 18 outputs a predetermined control amount to the flow rate control valve 5 via the valve drive circuit 20, and the valve opening degree of the flow rate control valve 5 is adjusted.
Since a predetermined flow rate of fuel is supplied to the burner 2, the combustion sequence 1 control circuit 14 operates the igniter 6 to generate an ignition spark. As a result, if the burner 2 is ignited normally, this is detected by the flame detector 7, and if there is an ignition error, the alarm 8 is activated.

As the burner 2 is normally ignited and enters a normal combustion state, heat exchange in the heat exchanger 9 progresses and hot water is dispensed from the faucet, but this WA version is detected by the temperature sensor 12.
The deviation between this temperature and the target temperature is again determined by the deviation detection circuit 17. Based on this newly determined deviation, the PID calculation circuit 18 outputs a predetermined control amount to the flow control valve 5 via the valve drive circuit 20 in order to reduce the deviation, and the valve opening of the flow control valve 5 is adjusted. .

Thereafter, the above-described operation is repeated, and feedback control is performed so that the detected hot water matches the set temperature, ii
The desired hot water with stable s can be obtained.

Here, when the remaining two faucets are opened at the same time, the amount of water passing through the heat exchanger 9 rapidly increases, and the temperature of the hot water dispensed from the faucets rapidly drops. At this time, the rapid increase in the amount of water is immediately detected by the flow state detection device 10 and input to the gain switching circuit 19, so that the gain of the PIDo11 circuit 18 is changed to the gain switching circuit before the rapidly decreasing hot water is detected by the temperature sensor 12. 19, and thereby the valve opening degree of the flow rate control valve 5 is adjusted to a predetermined opening degree.

As a result, the above-mentioned sudden drop in temperature is suppressed to a negligible level.
1, and this suppressed temperature change is detected by the temperature sensor 12. Thereafter, the steady-state control operation described above is performed, and the temperature of the hot water dispensed from the three faucets is quickly maintained at the desired temperature.

In addition, when initially opening and using three faucets, P (
The gain of the D calculation circuit 18 is increased, and a sudden decrease in the amount of water passing through the heat exchanger 9 when two faucets are turned on at the same time is immediately detected by the flow state detection device 10, and the water temperature is changed as described above. Rapid rises are suppressed to a negligible extent.

As described above, since changes in the amount of hot water dispensed are detected by the flow state detection device 10 and the gain of the PID calculation circuit 18 is changed accordingly, the above-mentioned overshoot and undershoot can be effectively suppressed. In addition, a relatively stable and uniform tapping temperature can be obtained over the entire range of hot water output. If the flow state detection device 10 detects changes in the amount of hot water dispensed continuously, ideal hot water temperature characteristics can be obtained, but even if the detection is performed in stages, good hot water temperature characteristics can be obtained.

Further, specific embodiments of the present invention are shown in FIGS. 2 to 4.

2 and 3 are cross-sectional views showing the above-mentioned flow state detection device. A holder 33 is protruded from a lid 32 provided above the flow path 31 of the device body 30.
Two operating plates 34, 35 are provided such that one end is rotatably supported by the bottle 36 and the other end closes the flow path 31.

Magnets 37, 38 are attached to the surface of the operating plate 34, 35 in the direction in which it rotates when urged by the water flow passing in the direction of the illustrated arrow, and the main body 30 is driven by the magnets 37, 38, respectively. A reed switch 39,40 is provided. The actuating plates 34 and 35 are regulated by springs (not shown) wound around the bottle 36 so that the rotation thereof differs depending on the amount of water. In other words, the actuating plate 34 easily rotates at low water flow rates and operates the reed switch 39 as shown in the figure at the minimum operating water flow level, and the actuating plate 35 rotates small as shown in the figure at the minimum operating water flow levels to a predetermined state. The reed switch 40 is configured to rotate significantly when the water reaches a high amount of water to activate the reed switch 40. As a result, reed switch 39
constitutes a freeze detector, and the reed switch 40 constitutes a flow rate detector. The output of the reed switch 39 is input to the combustion sequence control circuit 14, and the output of the reed switch 40 is input to the gain switching circuit 19. In addition, a magnetic shielding plate 41 is provided between the reed switches 39 and 40, and magnets 38 and 40 of different partners are provided.
37 so that it doesn't work.

Note that the method of regulating the rotation of the actuating plates 34, 35 is not limited to this embodiment, and can be realized by known techniques such as changing the mass of the actuating plates 34, 35, for example.

Next, FIG. 4 is a diagram showing a specific configuration of the hot water temperature control circuit, in which the deviation detection circuit 17 is connected to the target temperature setting device 16.
and the temperature sensor 12 on one side.
The output voltage V1 to v2 of this bridge circuit 45
is input to the PID calculation circuit 18 as the deviation signal. Further, the gain switching circuit 19 is composed of constant voltage diodes 46 and 47 that supply power to the bridge circuit 45, and the reed switch 40 is connected in parallel to the constant voltage diode 47. This reed switch 40 operates as described above, closing when the water flow is low and opening when the water flow is high.

With this configuration, when the amount of water passing through the heat exchanger 9 is low, the reed switch 40 is closed, and the power supply voltage supplied to the bridge circuit 45 is determined by the constant voltage diode 46, so that it is lower than VCC. The input voltages v1 to 2 of the PID calculation circuit 18 decrease accordingly, so the control output to the flow rate control valve 5 via the valve drive circuit 20 controls the valve opening of the flow rate control valve 5. The amount is such that it decreases. In other words, the gain of the PIDm calculation circuit 18 is reduced in accordance with the decrease in flow rate.

Further, when the flow rate increases and the reed switch 40 is opened, the power supply voltage supplied to the bridge circuit 45 becomes approximately Vcc due to the voltage regulator diodes 46 and 47, so contrary to the above, the gain of the PID calculation circuit 18 increases. It will be done.

Therefore, it is an object of the present invention to simply change the gain of the PID arithmetic circuit 18 into two stages by setting the high water volume at which the reed switch 40 operates to an appropriate water volume between the minimum operating water volume and the maximum water volume of the water heater. Overshoot and undershoot can be effectively suppressed, and the output Ii temperature characteristics can be made so good that they do not cause any practical problems.

The operating point of the reed switch 40 is determined by adjusting the sensitivity of the operating plate 35 of the flow state detection device 10 to the amount of water; however, in the above-described specific embodiment, only the spring force of the spring regulating rotation is adjusted. It's easy to do.

As described in detail above, if the water heater is equipped with the combustion control device according to the present invention, overshoot or undershoot will not occur even if there is a sudden change in the amount of hot water dispensed, and the water heater will not cause overshoot or undershoot even if there is a sudden change in the amount of hot water dispensed. The hot water temperature can be made stable and uniform.

Furthermore, since the flow state detection device can be realized with a simple configuration, it is easy to manufacture and easy to integrate into the main pipeline.

In addition, the flow switch conventionally used to detect the minimum operating water amount can be omitted, and the gain of the hot water temperature control circuit can be changed in stages, so the gain changing means is simplified and the combustion control device is less expensive. It has the advantage that there is no possibility of the image becoming too high.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a water heater showing an embodiment of the present invention, and FIGS. FIG. 4 is a schematic diagram showing a specific example of the hot water temperature control circuit according to the present invention. 2... Burner 5...8! Trowel control valve 9... Heat exchanger 10... Fluid state detection device 12... M-eating sensor 13... Combustion control device 14... ... Combustion sequence control circuit 15 ...
... Hot water temperature control circuit 19 ... Gain switching circuit 34.35 ... Actuation plate 37.38 ... Magnet 39.40 ... Reed switch 41 ...・・・・・・
・Magnetic shielding plate 46.47... Constant voltage diode Figure 1

Claims (3)

[Claims] (1) A 1 degree sensor that detects the balustrade flowing out from the heat exchanger, a target temperature setting device, and a control amount that outputs a control amount according to the deviation between the temperature detected by the temperature sensor and the target temperature by the target temperature setting device. A hot water temperature control circuit, a flow rate control valve that is driven in accordance with the output of the hot water temperature control circuit to vary the amount of fuel supplied to the burner, and a flow rate control valve that is provided in the middle of the water inflow pipe or the hot water outflow pipe of the heat exchanger. , a first actuating plate that is displaced by a minute flow in the conduit to activate the flow detector, and a second actuating plate that is displaced to activate the flow rate detector when the flow rate of hot water in the conduit exceeds a predetermined value. a flow state detection device having at least an actuating plate; a combustion sequence control circuit for starting a combustion sequence in response to the output signal of the flow sensor; and a combustion sequence control circuit for starting a combustion sequence in response to the output of the flow rate sensor; A combustion control device for a water heater, comprising gain switching means for switching the gain stepwise so that the gain increases when the flow rate is large. (2) The flow detector and the flow rate detector are respectively connected to the first one. The combustion control device for a water heater according to claim 1, comprising a reed switch operated by a magnet attached to the second actuating plate. (3) The combustion control 111 device for a water heater according to claim 2, wherein the two reed switches are separated by a magnetic shielding plate.