JPS5899619A - Combustion control device for water heater - Google Patents

Abstract

PURPOSE:To suppress overchute and underchute by increasing and decreasing the gain of a control circuit within the combustion control device in accordance with changes of takeout rate of hot water. CONSTITUTION:A gain adjusting circuit 19, in response to an increase and decrease of water amount, 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 a water amount sensor 11, 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 boilers have been developed to detect the temperature of the hot water coming out of the heat exchanger, find the deviation from an arbitrarily set target temperature, and control the flow rate control valve installed in the fuel supply path according to the deviation. Some models have appeared that are equipped with a combustion control device that operates to maintain the water at a target temperature regardless of changes in temperature or water temperature.

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 lit amount.

However, this type of water heater is used with frequent changes in the amount of hot water that comes out, and the temperature of the hot water that comes out changes accordingly. The flow rate control valve is operated based on the deviation caused by the change in the output S temperature. That is, in principle, there is a response delay in the braking operation of this combustion control device. Changes in the hot water temperature 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, there may be a sudden temperature rise (overshoot) or a temperature drop. In particular, the above-mentioned overshoot that occurs when changing from a high hot water output side to a low hot water output side is 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 provide a relatively stable and uniform hot water temperature over the entire range of hot water output. The purpose of this invention is to provide an ill 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.

Figure 1 shows the combustion system according to this invention! [1I] It is a diagram showing the basic configuration of a water heater equipped with a water heater.

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 in the event of an abnormality such as when normal ignition has not been achieved.

A flow switch 10 for detecting the water flow is installed at the water inlet leading to the heat exchanger 9, and a water sensor 11 and a temperature sensor 1 such as a thermistor for detecting the temperature of hot water at the outlet.
2 are provided respectively.

The combustion control device 13 that controls the hot water output temperature of the water heater to be constant is composed of a combustion sequence control circuit 14 and a hot water 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 an alarm device 8 and a flow switch 10 is connected. The wA sub-control circuit 15 also includes a flow rate control valve 5. Water level sensor 11, fj! degree sensor 12 and temperature setting device 1
The hot water temperature control circuit 15 is connected to a deviation detection circuit 17 that generates a deviation signal from the temperature signal detected by the temperature sensor 12 and the target temperature signal from the target humidity setting device 16, and P that outputs a predetermined control amount
PI is determined by the ID calculation circuit M18 and the changed water amount signal that passes through the heat exchanger 9 detected by the water amount sensor 11.
Gain adjustment circuit 19 that changes the gain of the D calculation circuit 18
and a valve drive circuit 20 that adjusts the valve opening of the flow control valve 5 to a predetermined opening according to the output of the PID calculation circuit 18.

What should be noted here is that the gain adjustment circuit 19 is PID
The gain of the arithmetic circuit 18 is changed according to the increase or decrease in the water amount so that it is small when the amount of water passing through the heat exchanger 9 is on the low water amount side and becomes large when it is on the high water amount side. That is, before the temperature sensor 12 detects the temperature at which the outflow temperature changes due to an increase or decrease in the amount of water, the increase or decrease in the amount of water is immediately detected by the water sensor 11, the gain of the PID calculation circuit 18 is changed, and the flow rate control valve 5 is detected. Since the valve opening 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 changes in the temperature of the hot water are suppressed to a minimum. Therefore,
As a result of the significant improvement in control response delay, the above-mentioned overshoot and undershoot are also suppressed.

This will be explained next.

Now, when one faucet is opened, the flow switch 10 detects the water flow, and the water amount sensor 11 detects the amount of water passing through the heat exchanger 9. As a result, the combustion sequence control circuit 14 is driven, and the electromagnetic switching valve 3
open. At the same time, the gain of the PID calculation circuit 18 is set to a predetermined value according to the amount of water by the gain adjustment circuit 19, and the water temperature detected by the temperature sensor 12 and
The deviation from the target m degree determined by the s degree setter 16 is determined by the deviation detection circuit 17 and outputted to the PID calculation circuit 18. Is this a PID? jl [11 circuit 18 is a predetermined control 1m
is output to the flow rate control valve 5 via the valve drive circuit 20, the valve opening of the flow rate control valve 5 is adjusted, and a predetermined flow rate of fuel is supplied to the burner 2. Therefore, the combustion sequence control circuit 14
The igniter 6 is operated 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 hot water is detected by the temperature sensor 12, and -
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 opening of the flow control valve 5 is adjusted. .

Thereafter, the above-described operation is repeated, and feedback IIJ# is performed so that the detection M[ matches the set temperature, and the desired water with stable mm is obtained.

Now, if you open the remaining two faucets at the same time, heat exchanger 9
The amount of water passing through the faucet increases rapidly, and the temperature of the hot water that comes out of the faucet drops rapidly. At this time, the sudden increase in cloudy weather is due to water flow sensor 1.
1 is immediately detected and input to the gain adjustment circuit 19. Therefore, before the rapidly dropping water temperature is detected by the temperature sensor 12, the gain of the PID sieve circuit 18 is increased by the gain adjustment circuit 19. By flow control valve 5
The valve opening degree is adjusted to a predetermined opening degree. As a result, the sudden drop in the lli temperature is suppressed to a negligible level, and this suppressed temperature change is caused by the temperature sensor 12.
Detected in 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 concentration.

In addition, if you initially open and use three faucets, please use the PI
The gain of the D arithmetic 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 water amount sensor 11, and the i
The rapid rise in temperature is suppressed to a negligible level.

As described above, it is ideal if the gain of the PID calculation circuit 18 is changed continuously, in addition to effectively suppressing the above-mentioned overshoot and undershoot when the amount of hot water is suddenly changed. However, even if it is changed in stages, it is relatively stable over the entire range of the amount of hot water, and a uniform mixture can be obtained.

Furthermore, specific embodiments of the present invention are shown in FIGS. 2 and 3.

FIG. 2 is a cross-sectional view showing the water amount sensor, which is attached to the outlet side of the heat exchanger 9 (as shown in FIG. 1) or to the water inlet side. A holder 33 is protruded from a lid 32 provided above the channel 31 of the main body 30, and a water amount detection plate 34 is rotatably supported on the holder 33 at one end by a bottle 35, and at the other end. is provided so as to close the flow path 31. Water flow detection plate 3 indicated by the broken line in the figure
The state 4 is when there is no water flow, and as the flow rate passing through the flow path 31 increases in the direction shown in the figure, it rotates and finally reaches the state shown by the solid line in the figure.

A magnet 36 is attached to the surface in the direction in which the water amount detection plate 34 rotates, and the main body 30 is provided with a reed switch 37 driven by the magnet 36.

As is clear from the above configuration, in this water flow sensor, when the flow rate exceeds a certain level, the magnet 36 comes to the position shown by the solid line in the figure and operates the reed switch 37. In other words,
The water flow sensor according to this specific embodiment detects a low water flow and an arbitrary high water flow that has increased to some extent.

Next, FIG. 3 is a diagram showing a specific configuration of the S temperature control circuit, in which the deviation detection circuit 17 is connected to the target mi setting device 16.
and the temperature sensor 12 on one side, and the output voltages v1 to v2 of this bridge circuit 39
is input to the PID performance circuit 18 as the deviation signal. Further, the gain adjustment circuit 19 is composed of constant voltage diodes 40 and 41 that supply power to the bridge circuit 39, and the reed switch 37 is connected in parallel to the constant voltage diode 41. This reed switch 37 operates as described above, closing when the amount of water is low and opening when there is fresh water.

With this configuration, when the amount of water passing through the heat exchanger 9 is low, the reed switch 37 is opened, and the power supply voltage supplied to the bridge circuit 39 is determined by the constant voltage diode 40, so it is lower than VCC. Since the input voltages v1 to v2 of the PID calculation circuit 18 decrease accordingly, the control amount outputted to the flow rate control valve 5 via the valve drive circuit 20 is equal to the valve opening of the flow rate control valve 5. The amount is such that it decreases. In other words, the gain of the PID calculation circuit 18 is reduced in accordance with the decrease in flow rate.

Further, when the flow rate increases and the reed switch 37 is opened, the power supply voltage supplied to the flicker circuit 39 becomes approximately vCC due to the voltage regulator diodes 40 and 41, 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 calculation circuit 18 into two stages so that the fresh water trowel operated by the reed switch 37 has an appropriate amount of water between the minimum operating water amount and the maximum water amount of the water heater. Overshoot and undershoot can be effectively suppressed, and the output Fm temperature characteristics can be made good to the extent that there is no problem in practical use.

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.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of a water heater showing an embodiment of the present invention, Fig. 2 is a schematic sectional view showing a specific example of a water flow sensor according to the invention, and Fig. 3 is an Ii water heater control according to the invention. FIG. 2 is a schematic diagram showing a specific example of a circuit. 2...Burner 5...Flow control valve 9...Heat exchanger 11...Water flow sensor 12... ... Temperature sensor 13 ... Combustion control device 15 ... - Temperature control circuit 16 ... Target hot water temperature setting device 17 ... Deviation detection Circuit 19... Gain adjustment circuit 37... Reed switch 39... Bridge circuit 40.41... Constant voltage diode Patent applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Kazu 1) Figure 1 of the Rules

Claims (2)

[Claims] (1) A temperature sensor that detects the salt water discharged from the heat exchanger, a target temperature setter, and the temperature detected by the temperature sensor and the target temperature setter! The water passes through a hot water temperature control circuit that outputs a control amount according to the deviation from the temperature, a flow rate control valve that is driven according to the output of this 1m control circuit and changes the amount of fuel supplied to the burner, and the heat exchanger. The present invention is characterized by comprising: a water flow sensor that outputs a signal corresponding to the water flow rate, and a gain adjustment circuit that changes the gain of the control circuit so as to increase on the high water flow side in accordance with the output of the water flow sensor. Combustion control device for single boiler. (2) The deviation detection circuit in the water temperature control circuit Ii is composed of a bridge circuit including the temperature sensor and the target attitude setting device, and the gain adjustment circuit adjusts the power supply voltage applied to the bridge circuit to the water flow sensor. The combustion control device for a water heater according to claim 1, characterized in that the combustion control device is configured to change depending on the output.