JP3115437B2 - Water heater combustion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater combustion control method based on PID calculation.

[0002]

2. Description of the Related Art FIG. 4 shows a system configuration of a general water heater. In FIG. 1, a burner 2 is provided in a combustion chamber 1, a combustion fan 3 for supplying and exhausting air is provided below the burner 2, and a heat exchanger 4 is provided above the burner 2.
Is provided. A gas supply passage 5 communicating with the burner 2 is provided with a main solenoid valve 6 and a proportional valve 8 for controlling a gas supply amount by an opening amount. A water supply pipe 10 is provided on the inlet side of the heat exchanger 4. The water supply pipe 10 is provided with a water supply temperature sensor 11 such as a thermistor, and a flow rate sensor 13 for detecting the flow of water and the amount of supplied water (flow of hot water). Also,
A hot water supply pipe 14 is connected to the outlet side of the heat exchanger 4, and a water faucet 15 is provided on the outlet side of the hot water supply pipe 14. And
Near the outlet of the heat exchanger 4, there is provided a tapping temperature sensor 16 for detecting tapping temperature of the tapping water such as a thermistor.

The feed water temperature sensor 11 and the flow rate sensor 13
And the respective detection signals from the tapping temperature sensor 16 are applied to the control device 17, and the control device 17 receives these detection signals and performs the combustion operation of the water heater.

That is, when the faucet 15 is opened and the flow sensor 13 detects the feedwater flow,
The combustion fan 3 is rotated. Subsequently, the main solenoid valve 6 is opened,
The fuel gas is supplied to the burner 2 to drive the igniter electrode 18 to ignite the gas. Then, the frame rod electrode 20
The ignition is confirmed by receiving the flame detection signal added from the controller, the opening amount of the proportional valve 8 is controlled in accordance with the difference between the set temperature and the tapping temperature, and the tapping water temperature is set by the proportional control including the PID calculation. That is, the amount of combustion is controlled so as to approach.

In recent years, it has been desired to improve the tapping temperature characteristics of hot water heaters, and precise control of combustion operation has been performed in order to tap out stable tapping water with small temperature fluctuations. The flow rate (water supply flow rate) is detected, and when a predetermined hot water supply flow rate (water supply flow rate) is reached, PI
A method of switching the PID constant of the D operation stepwise has been proposed.

FIG. 3 shows an example of switching PID constants in the proposed method. When the hot water supply flow rate (water supply flow rate) exceeds a preset switching reference flow rate in a rising direction during the tapping operation of the water heater, the PID calculation is performed. a PID constants from a _1
2 and the PID constant is changed from A ₂ to A ₁ when the tapping flow rate (water supply flow rate) exceeds the switching reference flow rate in the decreasing direction.
And depending on the size of tap water flow (water supply flow),
By switching the PID constant stepwise, precise control of the combustion operation is attempted.

[0007]

However, in this type of combustion control method, when a plurality of hot water heaters are used at the same time, the number of used hot water outlets and the state of use thereof change, or the water supply pressure applied to the water inlet of the hot water heater changes. Due to such factors, the tap water flow rate (water supply flow rate) fluctuates near the switching reference flow rate,
When the tap water flow rate (water supply flow rate) exceeds the switching reference flow rate vertically, the PID constant is frequently switched each time. At this time, since the PID is subtracted for a smaller state than tapping flow (water flow rate) switching the reference flow Q is controlled using the A _1, the drive current of the proportional valve 8 with respect to the variation of hot water flow (water flow) Although the operation amount is small, when the hot water flow rate (water supply flow rate) exceeds the switching reference flow rate, P
ID constants switches to A _2, the operation amount of the driving current of the proportional valve 8 with respect to the variation of hot water flow (water flow) increases. For this reason, for example, when the supply water pressure temporarily rises and the tap water flow rate (water supply flow rate) exceeds the switching reference flow rate, the proportional valve 8 is driven with a large operation amount, so that the change in the gas supply amount to the burner 2 is also large. And overshoot from steep follow-up to the set temperature,
When the feed water pressure returns to the original state again, the proportional valve 8 is driven and controlled with a small operation amount, so that the change in the gas supply amount to the burner 2 is also small, and the follow-up is slow, adversely affecting the stability of following the set temperature. Had the problem of

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to make it possible to frequently switch the PID constant even when the tap water flow rate (water supply flow rate) fluctuates near the switching reference flow rate. An object of the present invention is to provide a combustion control method for a water heater that has excellent tapping temperature characteristics without causing a change in hot water temperature.

[0009]

The present invention is configured as follows to achieve the above object. That is, the present invention detects the tap water flow rate (water supply flow rate) of the water heater, and when the tap water flow rate (water supply flow rate) reaches the switching reference flow rate,
In the combustion control method for a water heater in which a PID constant of combustion control by PID calculation is switched, the switching reference flow rate is set to a first PID when an outlet flow rate (water supply flow rate) increases.
A first switching reference flow rate for switching from the constant to the second PID constant, and a second switching reference flow rate when the tapping flow rate (water supply flow rate) decreases.
The first PID constant is switched from the ID constant to the first PID constant.
A predetermined flow rate difference serving as a switching dead zone is provided between the switching reference flow rate and the second switching reference flow rate.

[0010]

In the present invention having the above-described structure, the flow rate of hot water (water supply flow rate) changes in the increasing direction during the combustion operation of the water heater, and
When the switching reference flow rate is exceeded, the PI
The D constant is switched from the first PID constant to the second PID constant, and the combustion control by the PID calculation is performed. The tapping flow rate (water supply flow rate) fluctuates near the first switching reference flow rate, and does not reach the second switching reference flow rate of the tapping flow rate (water supply flow rate) even if it exceeds the first switching reference flow rate in the vertical direction. At this time, the second PID constant is still used for the PID operation. When the hot water flow (water supply flow) exceeds the switching dead zone in the decreasing direction and reaches the second switching reference flow, the PID constant is changed from the second PID constant to the first PI.
Switch to D constant. After the switching of the PID constant, even if the tap water flow rate (water supply flow rate) fluctuates up and down around the second switching reference flow rate, the first flow rate does not reach the first switching reference flow rate beyond the switching dead zone. The PID constant is used for the PID calculation as it is.

As described above, since the switching dead zone is provided between the first switching reference flow rate and the second switching reference flow rate, the tapping flow rate (water supply flow rate) can be changed to the first switching reference flow rate or the second switching reference flow rate. Even if the PID constant fluctuates in the vicinity of the switching reference flow rate, the PID constant is not frequently switched, and the instability of the tap water temperature due to the frequent switching of the PID constant is suppressed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In the description of this embodiment, the same parts as those of the system shown in FIG. 4 are denoted by the same reference numerals, and the description thereof will not be repeated. The water heater to which the method of the present embodiment is applied has the same configuration as that shown in FIG. 4, and the characteristic of the present embodiment is that the P
The switching control method of the ID constant has a unique configuration, and the rest is the same as the conventional example.

FIG. 1 shows a configuration of a control part using a characteristic PID calculation of this embodiment. This control part is composed of a flow rate calculation part 21, a PID constant switching selection part 22, and a combustion control part 23. And The flow rate calculation unit 21 calculates the tap water flow rate (water supply flow rate) by calculation based on the flow rate detection signal supplied from the flow rate sensor 13, and adds the flow rate calculation result to the PID constant switching selection unit 22. PID constant switching selector 22
As shown in FIG. 2, a value of a first switching reference flow rate and a value of a second switching reference flow rate are given in advance, and the discharge flow rate (water supply flow rate) increases in the increasing direction. when exceeding the flow rate is switched to select the PID constants from the first PID constants a ₁ in the second PID constants a _2. On the other hand, when the tap water flow rate (water supply flow rate) decreases and exceeds the second switching reference flow rate, the PID
The PID constant of the operation is changed from the second PID constant A ₂ to the first PID constant.
To switch selects the ID constants A _1. Then, the selected PID constant is added to the combustion control unit 23. Combustion control unit
Reference numeral 23 controls the valve opening amount of the proportional valve 8 by PID calculation using the PID constant switched and selected by the PID constant switching selection unit 22, and performs the combustion operation of the water heater by proportional control.

Next, the switching operation of the PID constant in this embodiment will be described. As shown in FIG. 2, a switching dead zone corresponding to a predetermined flow rate difference is provided between the first switching reference flow rate and the second switching reference flow rate, and the tapping flow rate (water supply flow rate) increases. To C ₆
In position, when it exceeds the first switching reference flow in an increasing direction, PID constants switches from the first PID constants A ₁ in the second PID constants A _2, using a PID constants of the A ₂ combustion The control unit 23 controls the combustion of the burner 2 by proportional control based on PID calculation. After switching of the PID constants, tapping flow (water flow rate) is varied in the vicinity of the first switching reference flow, the first switching reference flow at the position of the C ₇ -C ₁₀ tapping flow (water flow rate) in the vertical direction even beyond, since hot water flow (water flow) does not exceed the second reference flow rate in the decreasing direction is maintained subsequently the value of a ₂ never PID constant is changed.

The tapping flow (water flow rate) is varied in the decreasing direction, when it exceeds in terms of C ₁₁ in the decreasing direction of the second switching reference flow rate across the switch dead band, PID constant is second PID constants It switches from a ₂ to the first PID constants a _1, PID calculation is performed using the PID constants a _1. Tapping flow (water flow rate) is varied in the vicinity of the second switching reference flow rate, even beyond the second changeover reference flow rate at the position of C ₁₂ -C ₁₆ in the vertical direction varies within a range of switching dead band As long as the PID constant is kept at the value of A ₁ .

As described above, according to this embodiment, the switching reference flow rate is constituted by two types of reference flow rates, the first switching reference flow rate and the second switching reference flow rate, and the first reference flow rate and the second switching reference flow rate are set. A predetermined flow rate difference is provided between the reference flow rate and the reference flow rate to make the switching dead zone, so that the tap water flow rate (water supply flow rate) fluctuates near the first switching reference flow rate or the second switching reference flow rate. However, the PID constant does not change frequently each time, thereby suppressing the fluctuation of the tap water temperature, so that the tap water temperature characteristic of the water heater can be further stabilized.

The present invention is not limited to the above embodiment, but can take various embodiments. For example, in the above embodiment, a single function water heater has been described, but the present invention is also applicable to a combined water heater having a reheating function and a hot water supply function.

Further, the setting of the switching dead zone given by the first switching reference flow rate and the second switching reference flow rate of the present invention can be set to an arbitrary width according to the magnitude of the tapping flow rate. The magnitudes of the first switching reference flow rate and the second switching reference flow rate may be different from each other, and the switching reference flow rate may be 1 to the tapping flow rate.
You may apply to what is set more than one place or continuously.

[0019]

According to the present invention, a first switching reference flow rate for switching a PID constant switching reference flow rate from a first PID constant to a second PID constant, and a second PID constant.
A predetermined flow rate which is provided by two kinds of reference flow rates, ie, a second switching reference flow rate for switching from a constant to a first PID constant, and is a switching dead zone between the first switching reference flow rate and the second switching reference flow rate. Since the difference is provided, even if the outlet flow rate (water supply flow rate) of the water heater fluctuates in the vicinity of the first switching reference flow rate or the second switching reference flow rate, the variation exceeds the switching dead band. As long as the PID constant does not change unless the other switching reference flow rate is exceeded, the PID constant is frequently changed each time the hot water flow rate (water supply flow rate) changes near the switching reference flow rate as in the conventional example.
It is possible to prevent the problem that the tap water temperature fluctuates due to switching of the constant, and it is possible to further stabilize the tap water temperature of the water heater.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a control part for executing a method of the present invention.

FIG. 2 is an explanatory diagram of a PID constant switching operation of a PID operation in the present embodiment.

FIG. 3 is an explanatory diagram of a switching operation of a PID constant according to a conventional combustion control method.

FIG. 4 is an explanatory diagram of a general water heater system.

[Description of Signs] 13 Flow rate sensor 17 Control device 21 Flow rate calculation unit 22 PID constant switching selection unit 23 Combustion control unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F23N 1/08 101 F24H 1/10 302

Claims (1)

(57) [Claims] 1. A hot water heater of a system in which a hot water supply flow rate (water supply flow rate) of a water heater is detected and a PID constant of combustion control by PID calculation is switched when the hot water flow rate (water supply flow rate) becomes a switching reference flow rate. In the control method, the switching reference flow rate may be set to a first value when the hot water flow rate (water supply flow rate) increases.
A first switching reference flow rate for switching from the PID constant to the second PID constant and a second switching reference flow rate for switching from the second PID constant to the first PID constant when the tapping flow rate (water supply flow rate) decreases. A combustion control method for a water heater, characterized in that a predetermined flow rate is provided between the first switching reference flow rate and the second switching reference flow rate, which is a switching dead zone.