JPH0335954Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an instantaneous water heater equipped with a temperature control device.

The temperature control device in this kind of instantaneous water heater is
A gas proportional valve control system is used, but a system that uses feed forward control and PID control in combination is effective and widely used. However, if hot water temperature control is always performed using both control methods, the ratio of PID control becomes too high during so-called feed-forward control transients such as at the start-up of hot water tap or when hot water is re-tapping, resulting in a slow settling time. It is difficult to properly control the temperature and the amount exceeding the set temperature (excess amount).

The present invention aims to solve the above problem, and an embodiment thereof shown in the drawings will be specifically described below.

FIG. 1 is a schematic sectional view showing the instantaneous water heater of this embodiment, and FIG. 2 is a sectional view taken along the - line in FIG. In these figures, 1 is the water heater main body, 2 is a burner, 3 is a heat exchanger, and 4 is a controller. This controller 4 controls a gas proportional valve 8 to supply gas to the burner 2. The amount is controlled. The controller 4 includes means for calculating a feed forward control amount based on a set temperature determined by a feed water temperature detector (not shown) and a water flow rate determined by a water flow rate detector;
A means for calculating a PID control amount based on the hot water temperature detected by a hot water tap temperature detector and a set temperature, a means for calculating a transition time from the internal volume of the heat exchanger and a flow rate of water, and a means for calculating a transition time from the internal volume of the heat exchanger and the flow rate of water; is characterized in that the feedforward control amount is output to the gas proportional valve 8, and after the transition time has elapsed, the PID control amount is added to the feedforward control amount and output to the gas proportional valve 8. . FIG. 3 is a characteristic diagram showing temperature changes from immediately after ignition to the controlled hot water temperature. In this figure, the transition time T until the control result value by feedforward control reaches a steady value is T
Calculated by ={V/(Q/60)}+a. However, V is the internal volume of the heat exchanger 3, Q is the water flow rate (/min), and a is the delay time (sec). In addition,
The internal volume V of the heat exchanger 3 is equal to the water inlet and outlet ports 5 and 6.
This is the volume between them (the shaded area in FIG. 2).

That is, the value of V is input into the controller 4 in advance, and when the fuel tap is opened, this transition time is first calculated. After the burner 2 is ignited, only the feed forward control amount is output to the gas proportional valve 8 until this transition time T has elapsed, and after the transition time T has elapsed,
The PID control amount is added and output to the gas proportional valve 8.
Note that the transition time T can also be approximately calculated from β×V/(Q/60). However, β is a coefficient set to a value greater than 1. These calculation processes can be easily performed by incorporating a microcomputer into the controller 4.

As described above, according to the present invention, only the feedforward control amount is output to the gas proportional valve 8 during the transition time until the control result value by the feedforward control reaches a steady value, and during this transition time, After the elapsed time, the PID control amount is added to the feedforward control amount and outputted to the gas proportional valve 8, so the disadvantages of PID control can be suppressed and the disadvantages of feedforward control can be suppressed. Since it is possible to eliminate the deviation from the set temperature, accurate control of the hot water temperature can be expected. Furthermore, since the transition time from operating only the feed forward control to adding PID control is calculated from the internal volume of the heat exchanger and the water flow rate, it is easily compatible with different models. It has the advantage of being able to

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention;
FIG. 2 is a cross-sectional view taken along the line - in FIG. 1, and FIG. 3 is a characteristic diagram of the temperature of tapped water. 2... Gas burner, 3... Heat exchanger, 4... Controller.

Claims (1)

[Scope of utility model registration request] A heat exchanger, a burner that heats the heat exchanger, a gas proportional valve that controls the amount of gas supplied to the burner, a water supply temperature detected by a water supply temperature sensor, a set temperature determined by an operator, and a water flow rate determined by a water flow rate detector. A means for calculating a feed forward control amount from a hot water outlet temperature sensor, a means for calculating a PID control amount based on a hot water outlet temperature detected by a hot water outlet temperature detector and a set temperature, and a means for calculating a transition time from an internal volume of a heat exchanger and a water flow rate. and a means for outputting the feedforward control amount to the gas proportional valve by combining the feedforward control amount and the PID control amount after the transition time has elapsed after the start of hot water dispensing and before the transition time has elapsed. An instantaneous water heater characterized by being equipped with a container.