JPS6080019A - Burning control device of water heater - Google Patents

Abstract

PURPOSE:To enable to monitor the condition of each device such as a temperature sensor, a water quantity sensor and the like, also contrive to improve the stability of hot- water temperature. CONSTITUTION:In case when one faucet in opened and a water flow signal is inputted from a water flow switch 6, an electromagnetic change-over valve 13 is opened, a gas flow rate adjusting valve 11 is slightly opened while an ignitor 14 is operated, the burning of a burner 2 is started. Based on an inflow (e) detected by a water quantity sensor 5, a water temperature (f) detected by an inflow water temperature sensor 7 and a setting temperature (b) set by a temperature setting device 17, an objective control quantity F1 for regulating a necessary burning quantity in the burner 2 is calculated in an objective control quantity calculating part 311. A deviation (c) between a hot-water temperature (a) detected by a temperature sensor 9 and a setting temperature (b) set by the temperature setting device 17 is calculated in a temperature deviation detecting part 312. A designated control quantity F2 is calculated based on the deviation (c) in PID calculating part 313. A deviation F between the objective control quantity F1 and the designated control quantity F2 is calculated in a control quantity deviation detecting part 314, the burning quantity in the burner 2 is adjusted in a burning control part 315 according to the valve opening degree of the gas flow rate adjusting valve 11 based on said control quantity deviation F.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a combustion control device for a water heater that controls and maintains the temperature of hot water at a target temperature, and particularly to one that is capable of monitoring the status of each device.

(Background of the Invention) A water heater combustion control device currently under development (unpublished) by the applicant is implemented by a microcomputer.
Which deviation is the target control product F+ (corresponding to the target combustion amount) determined from the target temperature, the inlet water temperature of the heat exchanger, and the inflow water amount, and the predetermined control amount F2 determined by epx'o calculation according to the deviation between the hot water outlet temperature and the target temperature. F is used to control the combustion amount of the burner, thereby making the outlet hot water temperature match the target temperature.

Therefore, the hot water temperature control operation performed here is F=F+ +
F2...(1) It can be expressed as: Here, Fl is given by the following equation.

F+=W·(SPn −WPn) (2) W: Inflow water amount SPn: Set temperature WPn: Inlet water temperature Further, F2 is given by the following formula (PID*formula).

Δ[:i = SPi - MPi Kp: Proportional gain Ti: Integral gain Td: Differential gain θ: Sampling time ΔEi: Deviation SPi: Set temperature MPi: Output temperature Note that the subscript n is the current sampling value, and the subscript n
-1 is the previous sampling value.

From the above equation (1), it is understood that this 'lam control operation modifies the target control amount using the P■D calculation value. This is due to the following reason.

FIG. 1 shows the hot water temperature control characteristics when the set temperature is changed from 40'C to 80C. In the figure, each device, such as a temperature sensor that detects the concentration of hot water and a water flow sensor that detects the amount of inflow water, usually has a certain variation. Therefore, if the combustion amount is controlled only by the target control amount, the hot water temperature may exceed the target temperature (curve A in the diagram) or may not reach the target temperature (curve B in the diagram). The control characteristics vary from curve to curve B within the range of curve B.Therefore, the outlet hot water temperature is fed back, an integral operation is performed based on the deviation between this and the target temperature, and corrections are sequentially made using this calculated value. As shown in curve C, the hot water temperature is controlled and maintained at the target temperature regardless of variations in the equipment.In other words, the corrective action can be performed by integral calculation alone.However, if only the integral calculation operation is used, the response characteristics Since it is bad, PID that adds proportional calculation operation and differential calculation operation to this
It was used as a control (curve D in the diagram).

Incidentally, the integral calculation operation continues as long as there is a deviation, but since it is a correction operation for the target control amount, if the variation exceeds a predetermined range, there is a risk of over-integration. This becomes a cause of impairing the stability of the tapped water temperature at saturation.

However, even if a situation in which the hot water temperature becomes unstable actually occurs, the cause of the situation cannot be detected with the above-described configuration.

(Object of the Invention) The object of the invention is to provide a combustion control device for a water heater that can monitor the status of each device such as a temperature sensor and a water flow sensor, and improve the stability of water temperature. It is about providing.

(Structure and Effects of the Invention) In order to achieve the above object, the combustion control device for a water heater according to the present invention determines the required combustion amount in the burner based on the target temperature, the inlet water temperature of the heat exchanger, and the inflow water amount. A means for calculating a target control amount, and a PID that follows changes in hot water outlet temperature and calculates a predetermined control amount according to changes in hot water outlet temperature and target temperature.
and means for calculating the combustion amount in the burner according to the deviation between the target control I amount and the predetermined control I amount, and in the integral calculation operation of the PIDI sieve means, the integral range is It is characterized in that it is limited within a predetermined range determined by the target control amount.

According to this configuration, the integral calculation range is limited to a predetermined range determined by the target control amount. Therefore, in the integral calculation operation,
Over-integration is eliminated, and the stability of hot water extraction is improved. Further, if the 5-integral calculation operation is to be performed beyond the limit range, it can be seen that the variations in each device such as the temperature sensor and the water amount sensor are larger than the predetermined value.

In other words, it is possible to monitor the condition of each device, such as changes over time.

(Description of Embodiments) FIG. 2 is a basic configuration diagram of a water heater equipped with a combustion control device according to an embodiment of the present invention. In the figure, the main body 1 of the water heater is formed into a vertical cylindrical shape, and a burner 2 is disposed at the bottom side, and a heat exchanger 3 is disposed at the top thereof. Note that an exhaust fan (not shown) is attached to the upper exhaust port of the heat exchanger 3.

A water supply pipe 4 is provided on the water inlet side of the heat exchanger 3, and a water flow sensor 5. A water flow switch 6 and an inlet water temperature sensor 7 are each attached. Further, on the outlet side of the heat exchanger 3, there is provided a hot water supply pipe 8 which is branched and connected to a plurality of channels (three in this embodiment), and a water temperature sensor 9 is installed at the branch point of the hot water supply pipe 8. The mounting number is listed.

6- In the gas supply pipe 10 leading to the burner 2, a gas flow rate adjustment valve 11 is installed from the burner 2 side. A gas governor 12 and an electromagnetic switching valve 13 are respectively provided.

and igniter 14 in connection with burner 2. A flame detector 15 is provided respectively.

The water amount sensor 5 continuously detects water stones in the water supply pipe 4 and outputs this to the controller 16.

The water flow switch 6 is connected to the water supply pipe 4 by opening and closing the switch.
In response to the occurrence/disappearance of the water flow inside the controller 16, a signal indicating whether there is a water flow or no water flow is output to the controller 16. controller 16
receives a water flow/no water flow signal from the water flow switch 6 and starts or stops a predetermined operation.

The inlet water temperature sensor 7 is composed of, for example, a thermistor,
The water temperature is detected and output to the controller 16.

The temperature sensor 9 is composed of, for example, a thermistor, and is connected to the processing circuit in the controller 16 together with the humidity setting device 17.

The gas flow rate adjustment valve 11 is driven by the controller 16,
The valve opening changes continuously from fully open to fully open, and burner 2
Adjust the amount of gas supplied to the

The gas governor 12 has a function of mixing fuel gas and air at an appropriate ratio.

The electromagnetic switching valve 13 is driven by the controller 16, and performs full open and full open operations.

The igniter 14 is driven by the controller 14 and the burner 2
Attempt to ignite the gas spewing out.

The flame detector 15 receives the flame generated in the burner 2, converts the flame current into a binary signal, and outputs this to the controller 16.

The controller 16 is composed of a sequence circuit that controls the sequence from the start to the stop of combustion, and an lfiIIIm circuit that maintains the hot water temperature at a target temperature, and each circuit operation is performed by a microcomputer.

FIG. 3 is a block diagram showing the configuration of the hot water temperature control circuit in the configuration of the controller 16 as an operation system diagram for controlling the hot water temperature. The hot water temperature control circuit 31 includes a target control amount calculation section 311, a temperature deviation detection section 312, and a PID calculation section 3.
13, a control amount deviation detection section 314, and a combustion control section 315.
It consists of

Now, when one bell is opened and a water flow signal is input from the water flow switch 6, the electromagnetic switching valve 13 is opened and the gas flow rate adjustment valve 11 is slightly opened by the operation of the sequence circuit. The igniter 14 is driven, and the burner 2
combustion begins.

Thereafter, the 2I concentration control circuit 31 operates to control the outlet temperature so as to reach the target humidity.

The target control amount calculation unit 311 calculates a target that defines the required combustion amount in the burner 2 based on the inflow water amount e detected by the water amount sensor 5, the water temperature f detected by the inlet water temperature sensor 7, and the set temperature S by the concentration setting device 17. A control amount F1 is calculated. This arithmetic expression is the second expression.

In the temperature deviation detection unit 312, the detection m by the temperature sensor 9
A deviation of 0 between ma and the m degree set by the temperature setting device 17 is found.

The PID calculation unit 313 calculates a constant control amount F2 based on the deviation C. The calculation formula for this PID calculation corresponds to the third formula, and the difference is that the integral range is limited in the integral term (second term).

That is, as described above, there is a predetermined variation in the detection values of each device such as the water amount sensor 5, the water inlet temperature sensor 7, and the temperature sensor 9, and this variation usually falls within a certain range. Therefore, the target system III amount calculation unit 31
The target control amount F1 calculated in step 1 will vary within a predetermined range, but this range can be known in advance.

On the other hand, since the integral calculation operation is to modify the target control amount as described above, the operation range of the integral calculation operation only needs to be within the range in which the target control amount varies. Specifically, a limit is placed on the number of bits in the register for integral calculations. This not only greatly reduces the number of bits in the arithmetic register, but by monitoring the state of the arithmetic register, it is possible to check the operating state of the integral arithmetic operation and the state of each device, such as changes over time.

10- The control amount deviation detection unit 314 calculates the deviation F between the target control amount F1 and the predetermined control amount Fz. That is, the calculation of the first equation is performed.

In the combustion control section 315, based on this control amount deviation F,
The amount of combustion in the burner 2 is adjusted according to the opening degree of the gas flow rate adjustment valve 11.

The above-mentioned operations are repeated to control and maintain the dry and dry temperature at the set temperature.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram illustrating the hot water temperature control characteristics of a warm-hearted type combustion control device currently being developed by the present applicant (unpublished), and FIG. 2 is a characteristic diagram illustrating the combustion control characteristics of a water heater according to an embodiment of the present invention. FIG. 3 is a block diagram showing the operation system for controlling the hot water temperature of the apparatus according to the above embodiment. 2...Burner 3...Heat exchanger 5...Water flow sensor 6...Water flow switch 7...Incoming water temperature sensor 9...Temperature sensor 11...・Gas flow rate adjustment valve 14...Igniter 16...Controller 17...Temperature setting device 31...Hot water temperature control circuit 311...Target control amount Calculation unit 312...Temperature deviation detection unit 313...PID calculation unit 314...Control I amount width deviation detection unit 15...Combustion control unit Patent applicant Tateishi Electric Co., Ltd. Fig. 2 j ty Needle 3 figure

Claims (1)

[Claims] (1) A means for calculating a target control amount that determines the required combustion amount in the burner based on the target temperature, the water inlet temperature of the heat exchanger, and the amount of water flowing in, and
Combustion control for a water heater, comprising: PID calculation means for calculating a predetermined control amount according to a deviation of temperature, and means for calculating a combustion amount in a burner according to a deviation between the target control amount and the predetermined control amount. A combustion amount n device for a water heater, wherein in the integral calculation operation of the PID calculation means, an integral range is limited within a predetermined range determined by the target control amount.