JPS59157433A - Method of controlling water temperature - Google Patents

Abstract

PURPOSE:To provide a method of controlling the water temperature capable of measuring the flow quantity of water as well as the temperature thereof by use only of a temperature sensor. CONSTITUTION:Water flows within a water feed pipe 1 via a flowing water switch 2 and reaches a heat exchanger 3 wherein water is subjected to a heat exchange. Thereafter, hot water is supplied through a water plug 4. Reference numeral 12 designates a temprrature detecting thermistor which is provided in the vicinity of the heat exchanger 3. The thermistor 12 detects the temperature of supply hot water and supplies a detected value to a microcomputer (MPU) 13. The MPU carries out an operational processing by a water temperature signal to PID control a proportional control valve 10. When the increment of the reference value is set at 10%, for example, with respect to the step temperature output in a time TS produced from the MPU, differences in time t1 and t2 required for reaching this reference value are introduced depending on the flow quantity. In the case of the time t2(curve b), the flow speed is slow (small flow quantity). In the case of the time t1, the flow speed is large (large flow quantity). Accordingly, when the inner diameter of the water pipe is set at a predetermined value, the flow quantity can be obtained indirectly by measuring the above described times.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control method, and particularly to a temperature control method in which flow rate measurement is also performed using only a temperature sensor.

Temperature control for water heaters, etc. uses m-differential and integral methods (hereinafter referred to as PID control) using a microcomputer.
is commonly used.

This will be explained using the conventional device shown in FIG. That is, the first
As shown in the figure, water travels through a water supply pipe 1 via a water flow switch 2 to a heat exchanger 3, where it is heat exchanged and then supplied from a faucet 4.

On the other hand, gas is passed through the gas pipe 5, through the main valve 6, and then through the pilot flame 7.
It is configured to combust the gas, reach the main burner 11 via the hot water supply valve 8, the gas pressure regulator 9, and the proportional control valve 1O, and combust there. Reference numeral 12 denotes a thermistor for temperature detection, which is installed near the heat exchanger 3, detects the hot water temperature, and sends it to a microcomputer (MPU).
3.

Then, the MPU performs arithmetic processing based on the water temperature signal from the temperature sensor 12, and operates the proportional control valve 10 (hereinafter referred to as PCV).
is controlled by PID.

Figure 2 shows a block diagram of a typical temperature control system.
Igl and the detected 'process variable X. (water temperature)
is compared with the set value S, to derive the difference eI+, and using this, the differential element e 1 T! An intermediate variable n θ consisting of 2(en-en-1) is obtained.

The conventional method described above uses only a temperature sensor (thermistor) as a sample value sensor, performs arithmetic processing only from this temperature signal, and is famous for its method of feeding back the results. When controlling the temperature of fluids found in hot water heaters, etc., sufficiently accurate temperature control is possible by adding not only temperature but also flow rate as sample values. However, from a cost standpoint, temperature control has conventionally been performed using only temperature sample values, so high accuracy cannot be expected.

The present invention has been made to solve the above problems, and aims to provide a temperature control method that can measure not only temperature but also flow rate using only a temperature sensor.

In the present invention, it is known that there is a constant relationship with a time delay in the response from the thermistor that detects the step temperature output output from the MPU when the inner diameter of the water pipe is constant. The starting point is profit,
A reference value is established by setting the temperature rise caused by the thermistor as a constant value, and the flow velocity is indirectly measured by measuring the time until the response signal from the thermistor reaches this reference value. This method attempts to control temperature using signals and indirectly measured flow rates.

Examples will be described below with reference to the drawings. FIG. 3 is a diagram showing the relationship between the step temperature output from the MPU, which is the gist of the present invention, and the response output from the thermistor that detects the step temperature output.

Note that the vertical axis in FIG. 3 represents temperature, and the horizontal axis represents time. What is shown by 3 in the figure is the step temperature output output from the MPU, and what is shown by b and b' are the responses from the thermistor that detected this in response to the step temperature output from the MPU. It's a signal.

In other words, for the 1-hour step temperature output output from MI)U, for example, when the reference value is set as an increase of 10%, there is a difference of 11.12 in the time it takes to reach this reference value, and the time It can be seen that in the case of time t2 (curve b), the flow rate is slow (small flow rate), and in the case of time t1, the flow rate is fast (large flow rate). Therefore, considering that the inner diameter of the water pipe is constant, it is possible to indirectly determine the flow rate by setting 4111 between each L1:Il-.

Therefore, if the constant is changed by performing a correction calculation that takes into account the flow rate for the process output y, which is conditioned only on the temperature, temperature control that takes into account the flow rate with high υ accuracy is possible.

FIG. 4 is a flowchart for explaining the arithmetic processing. First, the temperature is detected by the thermistor 12 in the Stella f41, and then the temperature is moved to the Stella f42 to compare and judge the detection result with the set value.

If it is determined that there is a difference, the MPU proceeds to step 43 and generates a step temperature output with an arbitrary pulse width T8, and in step 44 calculates the time t until the temperature detected by the thermistor reaches the reference value. measure. At this time, since the measured time and the flow rate have a constant relationship as described above, the flow rate Q is calculated in the next step 45, and the process moves to step 46, where a constant K e T that takes the flow rate into account is calculated.
Calculate 1 + TD. Next, move on to Stella f47 and P
An ID control calculation is performed, and based on the control calculation, 1) is output to the CV in step 48, and then the process returns to repeat the above operation.

In addition, in the embodiments described above, the temperature sensor is explained as one, but it is needless to say that the temperature sensor is not limited to this and a plurality of temperature sensors may be used.

As explained above, according to the present invention, since temperature detection and indirect flow rate measurement are performed using only a temperature sensor, not only control accuracy can be greatly improved, but also an inexpensive temperature control method can be provided. Can be done.

[Brief explanation of the drawing]

Fig. 1 shows a conventional temperature control method, Fig. 2 shows a normal temperature control system, and Fig. 3 shows the step temperature output from the MPU, which is the gist of the present invention, and a thermistor that detects this. FIG. 4 is a flowchart for explaining the arithmetic processing. 1...Water pipe 2...Water flow switch 3...
・Heat exchanger 4... Faucet 5... Gas pipe
6... Main valve 7... Pilot fire 8... Hot water supply valve 9... Gas pressure regulator 10... Proportional control valve (P
CV) 11... Main burner ] 2... Thermistor 13... MPU Patent applicant Mikuni Kogyo Co., Ltd. Agent Patent attorney Norio Ishii Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a temperature control method that detects the hot water temperature with a temperature sensor and controls the hot water temperature while comparing it with a set temperature, the hot water temperature can be controlled by indirectly detecting the flow rate from the response temperature signal detected by the temperature sensor. A temperature control method characterized by controlling