JPH0427460B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention adjusts the amount of fuel supplied by performing PID (proportional, integral, and differential) calculations based on the temperature deviation between the set temperature and the outlet temperature. Regarding hot water supply control equipment,
In particular, it is determined that the control is in a stable state by detecting that the temperature deviation has been essentially 0 for a predetermined period of time, and if the temperature deviation exceeds a certain value in this stable control state, the set temperature The present invention relates to a hot water supply control device that suppresses changes in the hot water outlet temperature due to fluctuations in the amount of hot water dispensed, etc. by increasing the gain of PID control until the magnitude relationship between the hot water outlet temperature and the outlet temperature is reversed.

(Prior art) Japanese Patent Laid-Open No. 61-228248 discloses that in a PID control type temperature control device, the proportional gain of the proportional control circuit is increased when the outlet temperature exceeds an overshoot detection temperature that is higher than the set temperature. A technique has been disclosed for suppressing a transient increase in the temperature of tapped water.

In addition, Japanese Patent Application Laid-Open No. 61-295457 describes a combustion control device for a water heater that performs PID calculation on the deviation between the hot water outlet temperature and the set temperature to control the opening degree of the fuel control valve. By providing a gain switching means that increases or decreases the gain of the PID control means accordingly, overshoot and hunting of the hot water temperature can be prevented even if the water volume changes without changing the target temperature. In addition, a technique for ensuring responsiveness of tapping temperature is disclosed.

(Problem to be Solved by the Invention) The temperature control device disclosed in Japanese Unexamined Patent Publication No. 61-228248 enters an overshoot state based on the outlet temperature being higher than the set temperature by a certain value. After determining that, the gain of the proportional control circuit is set to a sufficiently large value, and the output of the proportional control circuit is reduced to around the minimum level (reducing the amount of combustion heat to around the minimum level) to prevent overshoot of the hot water temperature. After the problem is resolved, the gain is returned to its original relatively small value and the proportional control operation is restarted from the lowest level of combustion amount.

Therefore, if an overshoot occurs when transitioning from hot water supply stop state to hot water supply state (hot water temperature rising state), hot water supply at the set temperature is started after sufficiently reducing the opening of the proportional solenoid valve for adjusting the fuel supply amount. The control returns the opening to the desired opening.

Therefore, although overshoot can be effectively suppressed, there is a risk that it will take a long time until the temperature of the hot water becomes stable.

Furthermore, since the combustion control device disclosed in JP-A-61-295457 is configured to switch the gain of the PID control means depending on the magnitude of the deviation, the transition from the hot water supply stop state to the hot water tap state (hot water rising In the (increasing) state, the deviation between the outlet hot water temperature and the set temperature becomes smaller as the outlet hot water temperature increases, so the gain of the PID control means is set to a smaller value as the hot water temperature increases.

Therefore, overshooting and hunting of the hot water temperature is prevented, but in the state where the hot water supply is stopped to the hot water supply state (hot water temperature is started), and in the hot water temperature fluctuation suppression control state due to fluctuations in the amount of hot water dispensed, There is a possibility that the time from the point when the hot water temperature approaches the set temperature until it reaches the set temperature becomes longer.

In this way, the conventional technology sets the gain of the PID control circuit based only on the temperature difference between the hot water outlet temperature and the set temperature, so even if a predetermined amount of deviation is detected, the deviation is not enough to increase the hot water temperature. Since there is no distinction between whether the hot water temperature is caused by the current state or whether it is caused by fluctuations in the output amount after the hot water temperature has reached a stable state, the optimal It was not possible to set the control gain.

This invention was made to solve these problems, and it starts the water temperature with a gain according to the set temperature, and after reaching the set water temperature, the water temperature changes as the hot water amount fluctuates. It is an object of the present invention to provide a hot water supply control device that can effectively suppress fluctuations in water levels.

(Means for Solving the Problems) In order to solve the above problems, a hot water supply control device according to the present invention includes (a) a piping system for distributing hot water heated by a heat exchanger, and (b) setting a desired hot water output temperature. (c) a hot water outlet temperature detection means for detecting the hot water outlet temperature in the piping system; (d) a hot water outlet temperature detecting means for detecting the outlet hot water temperature based on the set temperature set by the temperature setting means and the outlet hot water temperature detected by the outlet hot water temperature detecting means. (e) PID control means that performs PID calculation on the output temperature deviation to generate a signal for controlling the fuel supply amount; (f) PID control means that generates a signal for controlling the fuel supply amount based on the set temperature In addition to setting the control gain of the PID control means, the temperature deviation is virtually 0.
If this state continues for a predetermined period of time, it is determined that the control has shifted to a stable state, and if the temperature deviation exceeds a predetermined reference value set in advance in this stable control state, it is determined that a pressure fluctuation state is occurring. In this pressure fluctuation state, a control gain larger than the control gain set based on the set temperature is set to the PID control means, and when the magnitude relationship between the set temperature and the hot water temperature is reversed, the control gain is set to the original value. The present invention is characterized by comprising a PID control gain setting means for determining that the pressure fluctuation state has been resolved.

(Function) Since the PID control gain setting means is configured to set the control gain of the PID control means based on the set temperature set by the temperature setting means, it is possible to set the control gain according to the level of the set temperature.

Further, the PID control gain setting means is configured to perform combustion control with a control gain set according to the set temperature, and the temperature deviation becomes substantially 0, and this state continues for a predetermined period of time. Determine whether the control has reached a stable state.

Thereby, when transitioning from the hot water supply stop state to the hot water supply state, it can be determined that the hot water temperature rising state has entered the stable control state.

Then, the PID control gain setting means determines that the pressure fluctuation state is present when the temperature deviation becomes equal to or greater than the reference value after the control becomes stable.

In this pressure fluctuation state, the PID control gain setting means increases the control gain set based on the set temperature, and returns the increased gain to the original value when the magnitude relationship between the set temperature and the tapped water temperature is reversed.

Therefore, the control gain is increased when the temperature deviation exceeds the reference value (threshold), and the state where the control gain is increased is not the point at which the temperature deviation becomes less than the reference value (threshold). The control gain is maintained until the magnitude relationship between the set temperature and the hot water temperature is reversed, and then the original control gain is restored.

In this way, the amount of hot water output increases (decreases) in the hot water supply state (stable control state) other than the hot water temperature startup state.
If the hot water temperature drops (increases) by more than a certain value due to reasons such as this, the PID control gain is increased until the hot water temperature drops below (or above) the set temperature.
Fluctuations in hot water temperature can be suppressed in a short time.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the same reference numerals in each drawing indicate similar objects.

FIG. 1 is a system diagram showing a hot water supply control device according to an embodiment of the present invention. According to the piping system in the same figure,
Water supplied through the water supply pipe 1 is heated by a heat exchanger 2, and is supplied from each water supply pipe 4 through a hot water supply pipe 3. The heat exchanger 2 is heated with a burner 6 that ignites the gas supplied by the gas pipe 5. The amount of heating is controlled by a flow control valve 7 located in the middle of the gas pipe 5.

The control system that controls such a piping system includes a hot water temperature detection means 8, a temperature setting switch 10 on the operation panel, a temperature difference calculation means 11, a pressure fluctuation detection means 12, a gain calculation means 13, a PID control means 14,
and a main control circuit 15. Note that the pressure fluctuation detection means 12, the gain calculation means 13, and the main control circuit 15 constitute the PID control gain setting means described in the claims. These will be explained below.

The outlet hot water temperature detecting means 8 is arranged in the middle of the hot water supply pipe 3 to detect the outlet hot water temperature Tm, and uses a thermistor or the like, for example. The operation panel includes various switches such as a temperature setting switch 10 and a power switch. The temperature setting switch 10 is used, for example, to set a predetermined temperature to be obtained with the ring 4.

The temperature difference calculation means 11 includes a temperature setting switch 10
Set temperature signal Ts and hot water temperature detection means 8
Temperature difference △T= based on the hot water temperature Tm detected by
Calculate Ts−Tm. This temperature difference signal ΔT is input to the pressure fluctuation detection means 12.

When the temperature difference signal ΔT is equal to or higher than the standard value, the pressure fluctuation detection means 12 detects the pressure fluctuation, assuming that the temperature difference change has occurred because the pressure in the pipe has decreased due to the use of another cylinder. The gain calculation means 13 stores the optimum gain Go for each set temperature Ts, and is configured by, for example, a ROM.

The PID control means 14 executes PID calculation based on the optimum gain Go given by the gain calculation means 13, and opens or closes the flow rate regulating valve 7 by a predetermined amount. This calculation continues until the hot water temperature Tm detected by the hot water temperature detecting means 8 matches the temperature signal Ts set by the temperature setting switch 10 (actually, there is a certain tolerance range). Further, the above control is entirely managed by the main control circuit 15.

Next, the operation of the embodiment of the present invention will be described with reference to the flowcharts of FIGS. 2 and 3. In the following explanation, numbers 20 to 40 correspond to each block number in the flowchart. Also, for example, codes such as 25y and 25n are determined by judgment block 2.
Let us indicate that the judgments in Section 5 are positive and negative, respectively.

In Figure 2, when the system starts, 2
0, the registers of the main control circuit 15 are initialized 21, and the temperature setting 22 from the temperature setting switch 10 on the operation panel is accepted.

Here, in the initial setting 21, the flag F1 indicating whether the state is stable and the flag F2 indicating whether the pressure is fluctuating are set to F1=1, respectively.
Set F2=0.

When the set temperature Ts is selected by the temperature setting switch 10, the gain G based on the initial setting is set as a gain value 23, and hot water supply is started based on this. After this, first, the hot water outlet temperature Tm is read by the hot water outlet temperature detection means 8 (24a). Next, a fluctuation process 24b shown in detail in FIG. 3 is performed, and then PID control 24c is performed to discharge hot water at a set temperature.

Then, the process loops back to reading the hot water temperature until the hot water tap is stopped, and repeats the fluctuation process and PID control. When the start/stop 24d is reached, the series of controls ends.

Here, to explain the fluctuation processing in Fig. 3, since the status flag F1 = 1 by default, 25y,
Whether the deviation △T between the set temperature Ts and the hot water temperature Tm becomes 0 by the temperature difference calculation means 11, that is, △T=Ts−Tm=0 or whether Ts=Tm (actually, it is determined by a certain tolerance). The main control circuit 15 monitors 26. Here, Tm=Ts
If not, in step 26n, a timer is set 29 to count the time t of block 27, and the process returns to the original process 40 to continue control.

Next, a state in which the hot water temperature Tm matches the set temperature Ts (Tm=Ts) continues for a certain period of time, for example, 5 seconds, and it is confirmed whether this state is stable27. If the tapped water temperature Tm does not change from the set temperature Ts for a certain period of time (27y), the main control circuit 15 sets the flag F1=0 (28), assuming that the target has been achieved. Thereafter, the process returns to the original process 40 to continue control.

If hot water continues to be supplied in this state, the main control circuit 15
Since the flags F1=0 and F2=0, 25n,3
0n, detection by the pressure variation means 12 is performed 31 based on the output of the temperature difference calculation means 11; In this detection, when the temperature difference signal ΔT becomes larger than a certain reference value, it is determined that there is a pressure fluctuation 31y. After this, the sign of the temperature difference signal △T is determined and 3
2. After setting 33 the flag F2=1, the gain is increased 34 to a gain value several times the normal gain value stored in advance in the gain calculating means 13, and the process returns 40 to continue the process.

If hot water continues to be supplied in this state, the main control circuit 15
The flags are 25n, since F1=0 and F2=1.
30y, it is detected 35 whether the sign detected by the temperature difference calculating means 11 and the pressure fluctuation detecting means 12 along with the detection 31 of the pressure fluctuation, that is, the magnitude relationship between the tapping temperature Tm and the set temperature Ts has been reversed.
This is to confirm that as a result of executing PID control in which the gain was increased due to pressure fluctuations, the outlet temperature changed in the opposite direction to the temperature change accompanying the pressure fluctuations. If not reversed 3
5n is 4, which returns to continue processing.
0.

In the case of inversion, at 35y, the main control circuit 15
Set the flags to F1=1, F2=0, 36, 37,
After returning the gain to the normal gain value previously stored in the gain calculating means 13 (38) and setting the same timer as described above (39), the process returns to continue the process (40).

During this time, as mentioned above, as a result of executing PID control that increased the gain due to pressure fluctuations, the outlet temperature changed in the opposite direction to the temperature change accompanying the pressure fluctuations, and the gain was changed to the original value. By returning to the value, the hot water temperature will gradually settle to the set temperature.
Moreover, temperature changes caused by pressure fluctuations and PID
Since the temperature changes that occur as a result of the control are in opposite directions, these are canceled out and a temperature closer to the set temperature is obtained as the hot water temperature.

(Effects of the Invention) As explained above, in the hot water supply control device according to the present invention, the PID control gain setting means sets the control gain of the PID control means based on the set temperature set by the temperature setting means. , the control gain can be set according to the level of the set temperature.

Further, the PID control gain setting means is configured to perform combustion control with a control gain set according to the set temperature, and the temperature deviation becomes substantially 0, and this state continues for a predetermined period of time. Since the configuration is configured to determine when the control has reached a stable state,
When transitioning from the hot water supply stop state to the hot water supply state, it can be determined that the hot water temperature has changed from a rising state to a stable state.

Then, the PID control gain setting means determines that the pressure fluctuation state is present when the temperature deviation becomes equal to or higher than the reference value after the control becomes stable,
The control gain set based on the set temperature is increased, and the increased gain is returned to the original value when the magnitude relationship between the set temperature and the tapped water temperature is reversed.

Therefore, the control gain is increased when the temperature deviation exceeds the reference value (threshold), and the state where the control gain is increased is not the point at which the temperature deviation becomes less than the reference value (threshold). The control gain is maintained until the magnitude relationship between the set temperature and the hot water temperature is reversed, and then the control gain is returned to the original control gain.

In this way, the amount of hot water output increases (decreases) in the hot water supply state (stable control state) other than the hot water temperature startup state.
If the hot water temperature drops (increases) by more than a certain value due to reasons such as this, the PID control gain is increased until the hot water temperature drops below (or above) the set temperature.
Fluctuations in hot water temperature can be suppressed in a short time.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a hot water supply control device according to the present invention, Fig. 2 is a flowchart showing the overall operation of the hot water supply control device, and Fig. 3 is a flowchart showing control gain settings of the PID control circuit. . 2...Heat exchanger, 3...Hot water pipe, 4...Karan, 6...
Burner, 7... Gas flow rate adjustment valve, 9... PID control gain setting means, 10... Temperature setting means, 11... Temperature deviation calculation means, 12... Pressure fluctuation detection means, 13
...Gain calculation means, 14...PID control means, 14a
...Opening control signal, 15... Main control means, F1... Control state flag, F2... Pressure fluctuation state flag, G... Control gain, Tm... Hot water outlet temperature signal, Ts... Set temperature signal, △T... Temperature deviation signal.

Claims (1)

[Scope of Claims] 1. A piping system for distributing hot water heated by a heat exchanger, a temperature setting means for setting a desired hot water temperature, a hot water temperature detection means for detecting a hot water temperature in the piping system, and the above. temperature difference calculation means for outputting a temperature deviation based on the set temperature set by the temperature setting means and the hot water temperature detected by the hot water tap temperature detection means; PID control means that generates a signal to control the supply amount; and a control gain of the PID control means that sets a control gain of the PID control means based on the set temperature, and controls when the temperature deviation remains substantially 0 for a predetermined period of time. It is determined that the control has shifted to a stable state, and if the temperature deviation exceeds a predetermined reference value set in advance in this stable control state, it is determined that the pressure is fluctuating, and in this pressure fluctuating state, the set temperature is A control gain larger than the control gain set based on is set to the PID control means, and when the magnitude relationship between the set temperature and the hot water temperature is reversed, the control gain is set to the original value to eliminate the pressure fluctuation state. A hot water supply control device comprising a PID control gain setting means for determining that the problem has been resolved.