JPH07122514B2 - Water heater temperature control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a water heater that stabilizes the temperature of hot water supply.

Conventional technology This type of conventional temperature control device uses a method that uses feedforward control and feedback PID control together, but when the tapping starts, the ratio of feedback control becomes high and the excess amount (over (Shoot) becomes large, and good temperature control becomes difficult. As a means for solving these problems, the feed-forward output is controlled at the start of tapping, and the feedback output is combined after a predetermined time has elapsed. For example, the actual Kaisho 61-18
There is 351 publication.

Problems to be Solved by the Invention However, in the configuration as described above, when the feedforward output amount is out of the proper amount, it may take a long time to reach the set temperature or the set temperature may be exceeded. There was a problem that it took a long time to stabilize at the set temperature.

This prosperity solves such conventional problems and aims to shorten the time required to reach the set temperature and the recovery time.

Means for Solving the Problems In order to solve the above problems, the temperature control device of the present invention has an integral switch for prohibiting the integral calculation of the feedback PID control at the start of tapping until the tapping temperature reaches a predetermined range value of the set value. The control means and the integral switch limiting timer for limiting the time during which the integral operation is prohibited by the integral switch control means are provided.

Effect The present invention can eliminate the time delay of the set temperature due to the feedforward output error by the above configuration.

Embodiment One embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a temperature control block diagram in an embodiment of the present invention, FIG. 2 shows a schematic configuration diagram of a water heater, and FIG. 3 shows a flowchart for explaining the operation of the embodiment of the present invention.

In FIG. 2, 1 is a hot water supply tap, 2 is a heat exchanger, 3 is a burner for heating the heat exchanger 2, 4 is a proportional control valve, which is a combustion amount adjuster for adjusting the combustion amount of the burner 3, 5 detecting the hot water supply amount Q _L in a flow rate sensor provided in the water supply path of the second heat exchanger. Reference numeral 6 denotes the same feed water temperature sensor that detects the feed water temperature Ti supplied to the heat exchanger 2. Reference numeral 7 is a hot water outlet temperature sensor for detecting a hot water outlet temperature To which is heated by the heat exchanger 2 and comes out. 8 is a temperature setting device that sets the hot water temperature to a desired temperature.
Set Ts. Reference numeral 9 is a controller of the water heater including the hot water temperature control block shown in FIG.

Next, the hot water temperature control will be described with reference to FIG. 11 is a feed-forward control means, the hot water supply amount Q _L and enter the feed water temperature Ti and the set temperature Ts, determine the amount of heating QF by the following formula from the efficiency W.

QF = QL (Ts-Ti) / W 12 is a feedback control means, which constitutes a PID law as a control law. The feedback PID control means 12 sets the established temperature Ts.
And the proportional term P and the integral term I to correct the deviation amount of the hot water temperature To.
And the calculated output value of the differential term D are combined and summed to obtain the feedback output value QB. PV value obtained by combining the feedforward output value Qf and the feedback output value QB, that is, PV = QF ±
The control operation amount value of QB is given to the combustion controller 4 to control the outlet heated water temperature To to the set temperature Ts. 13 is a water heater. The control operation amount value PV is the deviation amount between the set temperature Ts and the hot water temperature To at the start of hot water supply.
Since TER is large, the ratio of feedback PID output QB is high. When the general PID control law is expressed by the following equation, QB = K ・ TER + TD / τ ・ △ TER + τ / TIΣTER, where K is a proportional constant, TD is a differential time constant, TI is an integral time constant, and τ is a sampling time.

The integral switch control means 12A is configured to prohibit the integral term calculation of the above equation at the start of tapping, and to start the integral calculation when the deviation amount TER reaches a predetermined threshold value Tk (for example, within 5 ° C. of the set temperature). ing.

However, the feedforward output QF deviates from the optimum value,
When the hot water temperature does not reach the predetermined temperature range, the integral switch limit timer 14 releases the integral calculation prohibition.

The integral switch limiting timer 14 is started at the time of starting hot water, and the integral switch control means 12A is set in the integral calculation prohibited state.
Or the output of the integral switch limiting timer 14 is released.

FIG. 3 is a flowchart showing the above operation. That is, the integral switch limiting timer 14 is started at the same time when the hot water is started. Thereafter, the feedforward control means calculates the combustion amount QF. Then, it is determined whether the integral switch limit timer 14 has passed a predetermined time. If it has not yet passed, it is determined whether the deviation amount TER has reached a predetermined value Tk, and if | TER | ≧ Tk, the calculation of the combustion amount QB by the feedback PID control means has no integral term, That is, it is calculated by PD calculation. The integration switch limit timer 14 has not yet passed the specified time, and | TER | <Tk
Then, the calculation of the combustion amount QB by the feedback PID control means has an integral term, that is, it is obtained by PID calculation.
Further, if the integral switch limit timer 14 has passed a predetermined time, the calculation of the combustion amount QB by the feedback PID control means has an integral term, that is, PI regardless of the deviation amount TER.
Calculated by D calculation. The combustion amount QF and feedback PID obtained by the feedforward control means obtained in this way
The control operation amount PV is output by adding the combustion amount QB by the control means. In this way, the operation of the integral term of the feedback PID control means is prohibited after the start of tapping, and the deviation amount TER
Reaches the specified value Tk or the integral switch limit tire
This prohibition is released when 14 has passed a predetermined time or whichever comes first, and the combustion amount QB by the feedback PID control means is obtained by PID calculation with an integral term. Until then, the operation of the integral term is prohibited, and the combustion amount QB by the feedback PID control means is obtained by PD calculation.

FIG. 4 is a diagram showing hot water discharge performance by the temperature control device having the configuration of FIG.

At the start of tapping, the integral switch limiting timer IT starts at time to. Characteristic A is the case where the prohibition of the integral calculation is released by the output of the integral switch control means 12A at the time when the hot water temperature To reaches the predetermined threshold value Tk, and characteristic B is the case where the hot water temperature To has not reached the predetermined threshold value Tk. , Output from the integral switch limit timer IT, which is released at time t ₁ .

With the above configuration, it is possible to reliably reach the set temperature.

Effects of the Invention As described above, the temperature control device of the present invention has the following effects.

(1) At the start of tapping, the overshoot can be suppressed by providing the control means for prohibiting the integral calculation of the feedback PID control until the tapping temperature reaches a predetermined range value of the set temperature. Moreover, by providing the integral switch limiting timer, the time required to reach the set temperature can be shortened.

(2) The error in the feedforward control amount can be repaired, and the feedforward control and the feedback control can be optimized.

In addition, the hot water temperature control performance is improved even with repeated operations such as re-entering.

[Brief description of drawings]

FIG. 1 is a temperature control block diagram of a water heater temperature control device according to an embodiment of the present invention, FIG. 2 is a schematic view of temperature control of the water heater, FIG. 3 is a flowchart of the water heater, and FIG. It is a hot water discharge performance diagram of the water heater. 2 ... Heat exchanger, 3 ... Burner, 4 ... Combustion amount controller,
5 ... Flow rate sensor, 6 ... Water supply temperature sensor, 7 ... Hot water temperature sensor, 8 ... Temperature setting device, 11 ... Feedforward control means, 12 ... Feedback PID control means, 12A
...... Integral switch control means, 14 …… Integral switch limit timer.

Claims (1)

[Claims] 1. A heat exchanger, a burner for heating the heat exchanger, and a combustion amount controller for adjusting the combustion amount of the burner,
A flow rate sensor provided in the water supply passage of the heat exchanger, a feed water temperature sensor, a hot water temperature sensor, a temperature setting device for setting the hot water temperature, a hot water supply amount detected by the flow rate sensor, and water supply detected by the water temperature sensor. A feedforward control means for calculating a combustion amount from a temperature, a set temperature set by the temperature setting device, and a heat exchange efficiency; a hot water temperature detected by the hot water temperature sensor; and a set temperature set by the temperature setting device. Feedback PID control means for calculating the combustion amount to correct the deviation amount, while energizing the combustion regulator with both output values of the feedforward control means and the feedback PID control means, the feedback PID control means at the start of tapping Until the hot water temperature detected by the hot water temperature sensor reaches a predetermined range of the set temperature set by the temperature setting device. And integrating the switch control means for inhibiting, water heater temperature controller having an integration switch restriction timer to limit the time for prohibiting the integral operation by the integrating switch control means.