JPH06147519A - Hot water-water mixture controller - Google Patents

Abstract

PURPOSE:To improve output hot water temperature characteristics by correcting a drive control quantity of a mixture valve based on factors since a mixture ratio change rate is varied by not only a lifting position of the mixture valve but also a differential pressure between a feed water passage and an output hot water passage when a constant-flow rate valve is provided at a heat exchanger side channel. CONSTITUTION:A differential pressure P is calculated from a hot water side flow rate QH and a lifting position L of a mixture valve (S11), a proportional term control constant kd and a differential term control constant kp are obtained from the pressure P and the position L by referring to a control constant calculating map (S12), and a motor drive control quantity is decided (S13).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot and cold water mixing control device for use in a mixing type hot water supply device that mixes hot water and water to produce hot water.

[0002]

2. Description of the Related Art Conventionally, there has been known a water heater which mixes hot water heated by a heat exchanger with water supplied by bypassing the heat exchanger in order to improve hot water discharge characteristics of the water heater. ing. In the hot water mixing control device used for such a water heater, the hot water temperature after hot water mixing is detected, and the mixing valve is drive-controlled so that the hot water temperature reaches a preset temperature. PID control (proportional integral derivative control), P
D control (proportional differential control), PI control (proportional integral control),
P control (proportional control) or the like is used.

For example, in PD control, the drive operation amount of the mixing valve is set according to the following equation. yn = kpen + kd (en-en-1) yn ... Driving operation amount en ... Deviation between hot water temperature and set temperature en-1 ... Enkp detected last time ... proportional term control constant kd ... differential term control constant In hot and cold water mixing control, one set of control constants (kp, kd) was set so as to satisfy the hot water discharge performance under various conditions.

[0004]

However, since the rate of change of the mixing ratio is not constant depending on the position of the mixing valve,
The proper hot water temperature control cannot be performed. For example, the lift amount of the mixing valve shown in FIG.
9), the change of the mixing ratio of the hot water with respect to the total flow rate has a curved characteristic.
In other words, the smaller the lift amount (the higher the mixing ratio of hot water), the smaller the amount of operation will change the mixing ratio. Conversely, the larger the lift amount, the smaller the change of the mixing ratio (Conversely, the same amount). The larger the lift amount is, the larger the manipulated variable is required to change the mixing ratio. In addition, it is not limited to the mixing valve shown in FIG. 2 that has such characteristics,
The same applies to a control valve provided on each of the hot water side and the water side, and a control valve provided on only the hot water side or the water side.

Therefore, in the conventional control method, if the linear characteristic as shown in FIG. 9B (the rate of change of the mixing ratio with respect to the lift amount is constant), the control constants (kp, kd ) May be constant, but in reality, the valve structure becomes very complicated to obtain such characteristics. Therefore, generally, the setting of the control constant is based on the point where the rate of change of the mixing ratio is high so that hunting of the tapping temperature does not occur, and the control speed must be slowed. In other words, although the control speed can be increased at the point where the mixture ratio change rate is low, the hot water temperature cannot be properly controlled because the control rate must be adjusted to the point where the change rate is high.

To make matters worse, in a water heater in which a constant flow valve is provided in the heating side water passage (passage passing through the heat exchanger), the change characteristic of the mixing ratio with respect to the lift amount is different between the water supply passage and the hot water passage. It changes as shown in FIG. 9C depending on the differential pressure.
In other words, in order to maintain the hot water temperature on the outlet side of the heat exchanger at a high temperature (to prevent excess capacity), in the water heater with a constant flow valve in the water passage on the heating side, The constant flow valve works to change the pressure difference between the water supply passage and the hot water passage, and the change characteristic of the mixing ratio changes accordingly.

Therefore, if the effect of such a differential pressure is also taken into consideration, the control coefficient that influences the drive operation amount must be further reduced. In other words, in order to prevent hunting from occurring even under the worst condition that the lift amount of the mixing valve is small and the differential pressure is large, such as the region A in FIG. 9C, the control coefficient must be reduced inevitably. is there. As a result, even in a situation where there is no problem even if the control coefficient is originally increased, the control speed becomes slow and a good tapping temperature characteristic cannot be obtained. An object of the hot water mixing control device of the present invention is to solve the above-mentioned problems and further improve the hot water temperature characteristic by correcting the drive operation amount according to the lift amount (valve position) and the differential pressure.

[0008]

The hot and cold water mixing control device of the present invention supplies hot water heated by a heat exchanger with a flow rate limited to a predetermined flow rate or less, and a bypass pipe branched from a water supply passage to the heat exchanger. Used in a water heater for mixing hot water mixed with hot water, adjusting a mixing ratio of the hot water and water, hot water temperature detecting means for detecting the hot water temperature of the hot water mixed, the above detection On the basis of the deviation between the tapping temperature and the set temperature, a hot water mixing control device comprising a mixing control means for driving and controlling the mixing valve device, a position determining means for determining the valve body position of the mixing valve device, and A differential pressure detecting means for detecting a differential pressure between the water supply passage and the hot water outlet for the mixed hot water, and a drive amount for correcting the drive control amount of the mixing control means according to the valve body position and the differential pressure. The gist is to have a correction means.

Also, in the hot and cold water mixing control device of the second invention, in the first invention, the drive amount correcting means corrects the drive control amount by using at least one of the valve body position and the differential pressure as a factor of fuzzy reasoning. Is the gist.

[0010]

In the hot and cold water mixing control device of the present invention having the above-mentioned structure, the mixing control means drives and controls the mixing valve device to adjust the mixing ratio based on the deviation between the outlet temperature of the mixed hot water and the set temperature. The drive control amount is corrected according to the pressure difference between the water supply passage and the hot water passage and the valve body position. Therefore, even if the rate of change of the mixing ratio fluctuates according to the valve body position, the pressure difference between the water supply channel and the hot water outlet channel also occurs due to the flow rate limitation of the heat exchanger side water channel (by the constant flow valve etc.). Even if the mixing ratio or the rate of change of the mixing ratio changes, the drive control amount is corrected in accordance with these two factors (valve position and differential pressure), so that a good hot water temperature characteristic can be obtained. For example, at the point where the rate of change of the mixing ratio, which is determined by the differential pressure and the valve position, is large,
It suffices to correct the valve body drive control amount to a smaller value, and conversely, to correct the valve body drive control amount to a larger value at a point where the mixing ratio change rate is small.

Further, in the hot and cold water mixing controller of the second invention,
Fuzzy inference is used to correct the drive control amount. In general, in proportional control such as PID control, a precise control amount is calculated by mathematical processing, but when control conditions are increased by dividing cases to cope with various situations, arithmetic processing is exponential. Will increase. On the other hand, the fuzzy control is not suitable for precise control, but is effective for control in various situations. Therefore, in the second aspect of the invention, by taking advantage of this advantage, the drive control amount is corrected by using at least one of the mixing ratio and the differential pressure as a factor for fuzzy reasoning, so that various situations can be dealt with and the correction calculation process becomes easy.

[0012]

EXAMPLES In order to further clarify the constitution and operation of the present invention described above, preferred examples of the hot and cold water mixing control apparatus of the present invention will be described below.

FIG. 1 is a schematic configuration diagram of a water heater provided with a hot and cold water mixing control device as one embodiment. This water heater
A water supply pipe 1 connected to the water supply, a heat exchanger 3 for heating the cold water guided from the water supply pipe 1 by the combustion heat in the burner 2, and a hot water supply pipe 4 for sending out the hot water heated by the heat exchanger 3. A bypass pipe 5 branched from the water supply pipe 1; a hot and cold water mixing control unit 20 that mixes cold water from the bypass pipe 5 with hot water from the hot water supply pipe 4 to control a mixing ratio so as to reach a set temperature;
A hot water outlet pipe 7 for guiding the mixed hot water to the hot water tap 6 is provided. Further, in the water supply pipe 1, a flow rate sensor 8 for detecting the water flow rate (hot water side flow rate) on the heat exchanger 3 side downstream from the branch point of the bypass pipe 5, and a constant flow rate valve for restricting inflow above a predetermined flow rate. 11 is provided, and an incoming water temperature sensor 9 that detects the incoming water temperature is provided upstream of the bypass branch point. Furthermore, hot water supply pipe 4
At the downstream side of the heat exchanger 3, there is provided a hot water temperature sensor 10 for detecting the hot water temperature (hot water temperature) before mixing. The combustion system, the air supply / exhaust system, the ignition system, etc. in the water heater are omitted because they are not the subject of the present invention.

The hot and cold water mixing control section 20 includes a mixing valve 21 provided at a confluence of the hot water supply pipe 4 and the bypass pipe 5, and a mixing valve 2.
A motor 13 (stepping motor in this embodiment) for driving the valve body 12 of No. 1 (schematically shown in FIG. 2) forward and backward, and a hot water temperature sensor 14 provided in the hot water pipe 7 for detecting hot water temperature.
And a controller 30 that controls the drive of the mixing valve 21.

As shown in FIG. 2, the mixing valve 21 uses hot water and hot water by a valve body 12 that advances and retracts between a valve seat 15 provided on the bypass pipe 5 side and a valve seat 16 provided on the hot water supply pipe 4 side. The rotation of the motor 13 is transmitted to the valve disc drive shaft 18 via the gear device 17, and the screw 19 formed on the valve disc drive shaft 18 causes the forward / backward movement. There is. Therefore, the position of the valve body 12 (that is, the mixing ratio) depends on the rotational position of the motor 13.

The controller 30 includes a CPU 31 which constitutes a well-known arithmetic and logic operation circuit, a ROM 32 which stores a control program and fuzzy inference, a RAM 33 which temporarily stores position data and various data of the motor 13, and each temperature. An input interface 34 that inputs signals from the sensors 9, 10, 14 and the flow rate sensor 8 and converts them into a digital signal that can be calculated, an output interface 35 that outputs a drive control signal to the motor 13, and these are mutually connected. It is composed of a bus 36 and the like.

Next, a first embodiment of the hot and cold water mixing control process will be described. FIG. 3 shows a hot and cold water mixing control routine executed by the controller, which is repeatedly executed at a predetermined cycle (in this embodiment, every 50 mm seconds).

First, the tapping temperature T from the tapping temperature sensor 14
M is read from the flow rate sensor 8 as the hot water flow rate QH, and the valve body position (lift amount) L of the mixing valve, that is, the motor 13 is read.
The control position of is read (S10). This lift amount L is
Since the stepping motor is used in this embodiment, it can be obtained by storing the total number of pulses from the origin position. Of course, a lift sensor may be obtained by providing a position sensor such as an encoder on the motor shaft.

Subsequently, the differential pressure P between the hot water outlet and the water supply passage (hereinafter simply referred to as differential pressure P) is calculated based on the read lift amount L and hot water flow rate QH (S11). This calculation method will be described below.

As shown in FIG. 4, the relationship between the lift amount L and the flow rate changes depending on the pressure difference. In this figure, the hot water flow rate Q
Not only H, but also the relationship between the water-side flow rate QB (flow rate through the bypass pipe 5) and the lift amount L is shown. Now, assuming that the detected hot water flow rate QH is 2 liters / minute and the lift amount L is 0.5 mm, the differential pressure P is 0.2 kgf from this characteristic diagram.
/ Cm2 can be judged. Therefore, in the present embodiment, the differential pressure P is calculated by referring to the calculation map in which such characteristics are stored in the ROM 32. When the bypass pipe 5 is provided with a flow rate sensor, the water side flow rate QB as shown in FIG.
The differential pressure P may be obtained from the relationship between the lift amount L and the lift amount L. Alternatively, the differential pressure may be directly detected by a diaphragm or a pressure sensor.

Next, based on the calculated differential pressure P and lift amount L, the control constants (kp, kd) used for PD control are determined by referring to the control constant calculation map (S12). 5 (A), (B), and (C) show, by way of example, the mixing ratio with respect to the lift amount L at differential pressures of 0.1 kgf / cm2, 1.0 kgf / cm2, and 3.0 kgf / cm2, respectively, and the corresponding appropriate ratio. In the present embodiment, the relationship between the lift amount L and the control constant for each of various differential pressure P conditions is stored as a control constant calculation map in the present embodiment. In this map, the control constant is set to a smaller value as the rate of change of the mixing ratio is larger, and conversely, the control constant is set to a larger value as the rate of change of the mixing ratio is smaller. Therefore, an appropriate control constant is set from the rate of change of the mixing ratio.

The control constants (kp, kd thus determined)
) And the deviation between the hot water temperature TM and the set temperature TS, the drive operation amount yn is calculated by the following PD control formula (S).
13). Note that en-1 is the deviation calculated last time, and RAM
This is the data temporarily stored in 23. yn = kpen + kd (en-en-1) Then, the motor 13 is driven by this operation drive amount yn (S14), and this control routine is once exited.

As a result, even if the rate of change of the mixing ratio fluctuates according to the lift amount, the constant flow valve 11 causes a pressure difference fluctuation between the water supply channel and the hot water outlet channel so that the mixing ratio and the rate of change of the mixing ratio vary. Even if it changes, since the operation drive amount is corrected according to the lift amount and the differential pressure, it is not necessary to reduce the operation drive amount according to the worst condition as in the conventional case, and the control speed is high. Therefore, excellent hot water temperature characteristics can be obtained. Further, since the stepping motor is used as the drive source of the mixing valve 21, the controllability is good, and a special sensor for position detection is unnecessary. Further, since a mechanical structure such as a diaphragm is not used for detecting the differential pressure, the number of parts can be reduced and the space can be saved.

Next, a second embodiment of the hot and cold water mixing control processing will be described with reference to the flowchart of FIG. In this embodiment, not only the differential pressure and the lift amount but also the hot water discharge amount and the temperature deviation are taken into consideration to correct the drive operation amount, and the fuzzy control in which these are used as factors for fuzzy reasoning is adopted.

First, the inlet temperature TC, the hot water temperature TH, and the hot water temperature TM are read from the temperature sensors 9, 10 and 14, and the hot water flow rate QH is read from the flow rate sensor 8, and the current mixture stored in the RAM 33 is read. The lift amount L of the valve 21 is read (S20). Then, similarly to the first embodiment, the differential pressure P between the hot water outlet and the water supply passage is calculated based on the lift amount L and the hot water flow rate QH (S21).

Subsequently, the incoming water temperature TC, the hot water temperature TH, the hot water temperature TM, and the hot water flow rate QH read in step 20.
From this, the hot water discharge amount QT, which is the total flow rate, is calculated by the following equation (S22). QT = QH (TH-TC) / (TM-TC) This is obtained from the relationship of QT * TM = TH * QH + TC (QT-QH). A flow rate sensor may be provided on the upstream side of the hot water discharge pipe 7 or the water supply pipe 1 to directly detect the hot water discharge amount QT, but if the influence of the pressure loss is taken into consideration, it is calculated as in this embodiment. Is preferable.

Next, the drive operation amount yn of the motor 13 is calculated according to the following equation based on the deviation en between the preset set temperature TS and the hot water discharge temperature TM (S23). yn = kpen + kd (en-en-1) The control constants kp and kd in this equation are constant values set in advance. Further, since this drive operation amount yn is corrected by the processing described later, it may be calculated together with the correction processing.

Next, the correction coefficient A for correcting the drive operation amount yn is calculated based on the lift amount L and the differential pressure P previously obtained. In this embodiment, the lift amount L and the differential pressure P are
Not only that, the correction coefficient A of the drive operation amount yn is obtained by fuzzy inference using the hot water discharge amount QT and the deviation en as control factors (S24).

Now, the condition part membership function, rule, and conclusion part membership function necessary for performing fuzzy control will be described. FIG. 7 (A) is a condition part membership function relating to the hot water discharge amount QT, FIG. 7 (B) is a condition part membership function relating to the absolute value of deviation | en |, and FIG. 7 (C).
Is a condition part membership function related to the lift amount L, and FIG. 7D is a condition part membership function related to the differential pressure P. Further, FIG. 8 (A) shows the hot water discharge amount QT and the deviation | en |
The conclusion part membership function relating to the above, and the same figure (B) is the conclusion part membership function relating to the lift amount L and the differential pressure P. The symbols PS, PM, PL and α mean the following respectively.

PS: Small in the positive direction PM: Medium in the positive direction PL: Large in the positive direction α: Weight

The preset rules are as follows. In this embodiment, the hot water discharge amount QT and the deviation | en |
The rule of the conclusion section (1) regarding the above is divided into the rule of the conclusion section (2) regarding the lift amount L and the differential pressure P. Rule for Conclusion Part (1) <Rule 1> | en | = PS and QT = PS α = PS <Rule 2> | en | = PS and QT = PL α = PM <Rule 3> | en | = PL and QT = PS, α = PM <Rule 4> | en | = PL and QT = PL, α = PL

Rule for Conclusion Part (2) <Rule 5> If L = PL and P = PS α = PL <Rule 6> L = PL and P = PL α = PM <Rule 7> L = PS and If P = PS α = PM <Rule 8> L = PS and P = PL α = PS

A specific example will be described here. now,
Hot water output QT = 2.5 (liter / min), deviation en = 3.
0 (deg), lift amount L = 0.5mm, differential pressure P = 2kgf / c
Consider the case of m2. From FIG. 7 (A), the goodness of fit of PS = 0.75 and the goodness of fit of PL = 0.25 in the amount of hot water discharge QT.
From the figure (B), the degree of conformity of PS at the deviation en = 0, the degree of conformity of PL = 1.0, and from the figure (C), the degree of conformity of PS at the lift amount L = 0.83, the conformity of PL. Degree = 0.17, and from the figure (D), P at the differential pressure P
The goodness of fit of S = 0.7 and the goodness of fit of PL = 0.3. On the other hand, if the above rules 1 to 8 are applied, from rule 1 PS = 0 from rule 2 PM = 0 from rule 3 PM = 0.75 from rule 4 PL = 0.25 from rule 5 PL = 0. 17 PM = 0.17 from rule 6 PM = 0.7 from rule 7 PS = 0.3 from rule 8

When the conclusion part membership function is corrected by using this conformity, it becomes as shown in FIGS. 8 (C) and 8 (D). Multiplying the weight α of each goodness of fit to find the center of gravity G that combines them, G = (0.75X1.0 + 0.25X1.5 + 0.3X0.2 + 0.17X1.0 + 0.7X1.0 +
0.17X1.8) / (0.75 + 0.25 + 0.3 + 0.7 + 0.17 + 0.17) = 1.
009. The center of gravity G is the correction coefficient A to be obtained.

When the correction coefficient A is obtained in this way, FIG.
In step 25, the driving operation amount yn is corrected to A · yn, the motor 13 is driven based on the corrected driving amount yn (S26), and the control routine is once exited. Then, these processes are repeated every 50 mm seconds.

As described above, in the hot and cold water mixing control process of the second embodiment, not only the lift amount and the differential pressure, but also the hot water discharge amount and the deviation are used as control factors to correct the drive operation amount by fuzzy inference to further improve the hot water discharge temperature. The characteristics are good. This is for the following reason.

That is, in the hot and cold water mixing control, it is desired to minimize the time delay from the time when the hot water is mixed with the water until the hot water temperature is detected. The time delay until it reaches is large. For this reason, in the past, in order to prevent hunting of the hot water discharge temperature due to such a time delay, the drive operation amount must be set small, and even when the drive operation amount is increased, there is no problem in controlling the flow rate. The speed was slowed down due to the small flow rate.

Therefore, in the second embodiment, by correcting the drive control amount using the amount of hot water discharged as a control factor, it is possible to cope with the time delay from the mixing of the hot water to the temperature detection, and the mixing in a wide range from a small flow rate to a large flow rate. The control is good and the tapping property is improved.

Further, when the correction is made only by the hot water discharge amount, the drive operation amount can be suppressed at a small flow rate, but in a situation where the deviation at this time is large, it is not necessary to suppress it so much, so the deviation is also added to the control factor. If the deviation is large, the degree of suppression of the drive operation amount can be reduced and the tapping characteristics can be further improved by the correction.

Moreover, since these correction processes are performed by using fuzzy inference, the advantages thereof are utilized to facilitate the control according to various conditions, and the calculation load of the PD control can be reduced.

The embodiment of the present invention has been described above.
The present invention is in no way limited to these examples,
Needless to say, the present invention can be implemented in various modes without departing from the scope of the present invention.

[0042]

As described above in detail, according to the hot and cold water mixing control device of the present invention, the drive control amount is corrected according to the pressure difference between the water supply passage and the hot water discharge passage and the valve body position. Even if the mixing ratio change rate changes depending on the body position, or if the constant flow valve or the like causes a differential pressure change between the water supply passage and the hot water discharge passage, the mixing ratio or the mixing ratio change rate changes. Even if there is, since the drive control amount is corrected according to these two elements (valve position, differential pressure), there is an excellent effect that good hot water temperature characteristics can be obtained. In addition, in the second invention in which the drive control amount is corrected using fuzzy inference, in addition to the above effects, control according to various situations is facilitated and the calculation load can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a water heater having a hot and cold water mixing control device according to an embodiment.

FIG. 2 is a schematic configuration diagram of a mixing valve.

FIG. 3 is a flowchart showing a hot and cold water mixing control routine as a first embodiment.

FIG. 4 is a graph showing a flow rate characteristic with respect to a lift amount shown for each differential pressure.

FIG. 5 is a graph showing a relationship between a mixing ratio characteristic and a control constant with respect to a lift amount shown for each differential pressure.

FIG. 6 is a flowchart showing a hot and cold water mixing control routine as a second embodiment.

FIG. 7 is a graph showing a membership function of a condition part.

FIG. 8 is a graph showing a conclusion part membership function.

FIG. 9 is a graph showing a mixture ratio characteristic with respect to a lift amount.

[Explanation of symbols]

8 ... Flow rate sensor, 11 ... Constant flow rate valve, 12 ... Valve body,
13 ... Motor, 14 ... Hot water temperature sensor, 20 ... Hot water mixing control part, 21 ... Mixing valve, 30 ... Controller.

Claims (2)

[Claims] 1. A water heater that mixes hot water heated by a heat exchanger with a flow rate limited to a predetermined flow rate or less and water supplied to a bypass pipe branched from a water supply path to the heat exchanger to discharge hot water. Based on the deviation between the detected hot water temperature and the set temperature, a mixing valve device used for adjusting the mixing ratio of the hot water and water, a hot water temperature detecting means for detecting the hot water temperature of the mixed hot water. A hot water mixing control device including a mixing control device that drives and controls the mixing valve device; a valve body position determining device that determines a valve body position of the mixing valve device; and a hot water discharge of the water supply passage and the mixed hot water. And a drive amount correction unit for correcting the drive control amount of the mixing control unit according to the valve body position and the pressure difference. Hot and cold water mixing control device. 2. The hot and cold water mixing control device according to claim 1, wherein the drive amount correction means corrects the drive control amount by using at least one of the valve body position and the differential pressure as a factor for fuzzy reasoning.