JPH0424286Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of the Invention) The present invention includes a fuel control valve installed in a fuel supply path to a burner, a target temperature setting means for the hot water outlet temperature, a hot water outlet temperature detection means, and a A PID (Proportional Integral Derivative) calculates the opening degree of the fuel control valve based on the deviation between the target temperature signal from the setting means and the detected temperature signal from the hot water temperature detection means and outputs a valve drive current to the fuel control valve. ) Control means for a water heater.

(Summary of the invention) The present invention is designed to prevent the I (integral
By devising the integral operation of the operation control means,
This is designed to improve the responsiveness of the hot water temperature.

(Prior art and its problems) An example of a conventionally known water heater is shown in FIG.

In FIG. 7, 1 is a burner, 1a is a pilot burner, 2 is a fuel supply path connected to the burner 1 and the pilot burner 1a, and the fuel supply path 2 includes a solenoid valve 3 that controls fuel supply to the burner 1, A solenoid valve (main valve) 3a that controls fuel supply to the pilot burner 1a, a gas governor 4, and a fuel control valve (proportional valve) 5 are interposed. Near the burner 1 are a spark plug 6 and a flame rod 7.
is located. The combustion chamber 8 is located above the burner 1.
is provided, and an exhaust passage 9 communicates with the upper end of the combustion chamber 8. 10 is a fan 1 provided in the exhaust path 9
This is a fan motor that drives 1. The fan motor 10 controls exhaust gas and also supplies combustion air to the burner 1.

12 is a heat exchanger installed in the combustion chamber 8;
The inlet of the heat exchanger 12 is connected to a water supply pipe 15 via an exhaust heat recovery device 13 installed in the combustion chamber 8 and a coiled pipe 14 surrounding the combustion chamber 8, and an outlet of the heat exchanger 12 is connected to a hot water outlet pipe. 16, it is connected to a plurality of outlets 17, such as taps and showers. The route from the water supply pipe 15 to the outlet 17 constitutes a water supply route 18.

The water supply pipe 15 in the water supply path 18 is equipped with a water flow switch 19 as a water flow detection means, and the hot water outlet pipe 16 is equipped with a hot water temperature detection means 2 such as a thermistor.
0 is inserted. Note that 21 is an air volume detection means installed in the exhaust path 9.

The operation of this combustion control device will be explained below based on the flowchart of FIG.

In the step, it is determined whether the water flow switch 19 is on or not, and if YES, the combustion chamber 8 is pre-purged in the step. This prepurge is
This is done by temporarily driving the fan motor 10.

At the same time as opening the solenoid valve 3a in step,
The spark plug 6 is sparked to ignite the pilot burner 1a. In step, the solenoid valve 3 is opened and the burner 1 is ignited. In the step, it is determined whether or not flame is detected by the flame rod 7, and if YES, the process moves to the step.

In step, the detected temperature Td from the outlet hot water temperature detection means 20 is read out, and in step, the target temperature Ts is read out from the target temperature setting means (not shown).
In step, the deviation e _o =Ts - Td is calculated, and in step, the PID control means (not shown) calculates the PID output M _o based on the deviation e _o .

In step, the opening control of the fuel control valve 5 is executed based on the PID output M _o , and in step 〓, the PID output is
The fan motor 10 is controlled by phase control based on M _o.
Execute rotation speed control. As a result, the outlet hot water temperature is adjusted to the target temperature, and the air-fuel ratio is maintained within a predetermined range.

Further, when the judgment of flame detection in step is NO, the process moves to step 〓 and outputs an alarm signal.

However, the conventional example having such a configuration has the following problems.

(b) In the conventional example, PID control is based on the calculation formula, M _o (%) = K _P・e _o + M _Io + K _D (e _o −e _o-1 ) + M _p (%) ...(1) It is being done. In equation (1), M _o is the fuel control valve 5 at the sampling timing t _o
The manipulated variable for opening control, e _o is the deviation between the target temperature Ts and the detected temperature Td at timing t _o , that is, e _o = Ts - Td... (2) In addition, the first term K _P e _o is a proportional term, K _P is a proportional constant, and the second term M _Io is an integral term, M _Io = _o 〓 ⁿ⁼⁰ K _I・e _o = M _Io-1 +K _I・e _o ……(3 ), M _Io-1 is the manipulated variable at timing t _o-1 ,
K _I is an integration constant. The third term K _D (e _o −e _o-1 ) is a differential term, and e _o-1 is the temperature deviation at timing t _o-1 .

Further, M _p is the initial value of the manipulated variable (basic manipulated variable), and is set to, for example, about 50%.

PID control based on equation (1) is feedback control based on sampling of the deviation e _o , so if the target temperature is changed rapidly, it will take a relatively long time for the outlet temperature to reach the target temperature. I need.

This point will be explained based on the time charts of FIGS. 9 and 10.

(b) [At the time of temperature rise] See Figure 9 As shown in Figure A, before time t ₀ , the outlet temperature matches the target temperature and is stable at a low temperature (30°C). At this time, the PID output is also stable.

At time t ₀ , the target temperature is suddenly increased to 60
When set to ℃, the differential term K _D (e _o −e _o-1 ) and the proportional term K _P ·e _o mainly function, and the PID output M _o rises rapidly.

From the peak of the rise of the PID output M _o to time t ₁ , the differential term K _D (e _o −e _o-1 ) and the integral term, _o 〓 ⁿ⁼⁰ K _I・e _o mainly function, and the differential term acts more strongly than the integral term, so the PID output M _o gradually decreases and reaches the lower limit at time t ₁ .

Between time t ₁ and time t ₂ , the integral term, _o 〓 ⁿ⁼⁰ K _I・_{e o} and the proportional term K _P・e _o mainly function, and the PID output
M _o increases gradually. Then, after time t ₂ ,
The proportional term K _P ·e _o mainly functions, and the PID output M _o becomes stable.

As a result of the above PID operation, the hot water temperature gradually rises from the initial temperature of 30°C to the target temperature of 60°C, as shown in Figure C.

As described above, it takes a long time T ₁ for the hot water outlet temperature to reach the target temperature, and the response speed of the hot water outlet temperature is slow, causing discomfort to the hot water user.

(c) [When the temperature falls] See Figure 10 For example, when the temperature drops from 60°C to 30°C, the response speed of the outlet temperature is slow as shown in the figure, causing discomfort to the hot water user.

The above also applies to cases where the temperature of hot water suddenly decreases as a result of changing the water flow.

(Purpose of the invention) The present invention was made in view of the above circumstances, and it is possible to adjust the temperature of the outlet water when the target temperature changes suddenly or when the outlet temperature suddenly changes as a result of changing the water flow. The purpose is to improve the responsiveness of hot water baths and avoid discomfort to users.

(Structure and effects of the invention) In order to achieve the above purpose, the invention has the following features:
It has the following structure.

That is, the combustion control device for a water heater according to the present invention includes a fuel control valve interposed in a fuel supply path to a burner, a target temperature setting means for the hot water outlet temperature, a hot water outlet temperature detecting means, and the target temperature setting means. A PID that calculates the opening degree of the fuel control valve based on the deviation between the target temperature signal and the detected temperature signal from the outlet hot water temperature detection means and outputs a valve drive current to the fuel control valve.
A combustion control device for a water heater, comprising: a storage means for storing integral data of the I operation control means in the PID control means; and a readout for reading the integral data from the storage means when the deviation occurs. and an arithmetic means for multiplying the integral data thus read by a coefficient corresponding to the deviation and inputting the arithmetic data to the PID control means, the I operation control means in the PID control means The device is configured to execute the I operation based on the calculation data in the calculation means.

The reason for adopting such a configuration will be explained below.

(b) An example of the calculation formula for PID control in the present invention is as follows: M _o (%) = K _P・e _o + {K _P・e _o・M _Io-1 +K _I・e _o } +K _D (e _o −e _o-1 ) +M _p (%) ...(4) is mentioned. In equation (4), M _Io-1 corresponds to the "integral data read out from the storage means by the reading means" in the structure of the invention, and K.e _o corresponds to the "deviation e _o" in the structure of the invention. corresponds to "coefficient corresponding to".

This calculation formula (4) shows that in the basic formula (1), in a steady combustion state, the deviation e o _{- 1 at timing t o-1} is 0, and the deviation e _o at timing t _o is also 0. Therefore, it takes advantage of the fact that M _o = M _Io-1 ...(5). That is, the integral data M _Io-1 during steady combustion is stored in the storage means, and when the deviation e _o occurs, the integral data M _Io-1 in the steady combustion state is calculated based on the magnitude of the deviation e _o . The responsiveness of PID output has been improved by adjusting accordingly.

When formula (4) is transformed using formula (3) _o 〓 ⁿ⁼⁰ K _I・e _o = M _Io-1 +K _I・e _o , the manipulated variable M _o for controlling the opening of the fuel control valve is obtained. The calculation formula is M _o (%) = K _P・e _o + {(K _P・e _o ) _o 〓 ⁿ⁼⁰ (K _I・e _o ) +K _I・e _o (1−K・e _o } +K _D (e _o −e _o-1 ) +M _p (%) ...(6).

In equation (6), 1-K.e _o >0, that is, K.e _o <1.

In equation (6), the terms bracketed by { } are integral terms, but the first term actually contributes to the integral action, and the second term carries the proportional action (e _o is negative). In this case, the digits are lowered).

The effect of carrying up and down will be explained based on the time charts of FIGS. 4 and 5.

() [When increasing temperature] See Figure 4 If the target temperature is suddenly raised from 30℃ to 60℃ at time _t3 as shown in Figure A, the differential term
K _D (e _o −e _o-1 ), the proportional term K _P・e _o and the second term of the integral term K _I・e _o (1−K・e _o ) mainly function, and the PID output M _o suddenly, and 1-K・e _o >
Since it is 0, it rises larger than the conventional example.

The period from the rising peak of the PID output M _o to time t ₄ is mainly the differential term K _D (e _o −e _o-1 ) and the first term of the integral term.

(K・e _o ) _o 〓 ⁿ⁼⁰ (K _I・e _o ) works, and the differential term works stronger than the integral term, so the PID output M _o gradually decreases and reaches the lower limit at time t ₄ . reach

From time t ₄ to time t ₅ , the first integral term (K・e _o ) _o 〓 ⁿ⁼⁰ (K _I・e _o ) functions, and the PID output M _o gradually increases. ,K・e _o
< 1, the rate of change is smaller than that of the conventional example, and the lower limit value at time _t4 is considerably higher than that of the conventional example. Therefore, the time it takes for the PID output M _o to reach a stable state (t ₅ −t ₄ ) is significantly shorter than in the conventional example.

As a result of the above PID operation, the outlet temperature rapidly rises from the initial 30°C to the target temperature of 60°C, as shown in Figure C.

In this way, the time required for the tapped water temperature to reach the target temperature is shorter than in the conventional example, and the response speed of the tapped hot water temperature is increased.

() [When temperature falls] See Figure 5 For example, when the temperature drops from 60°C to 30°C, the response speed of the outlet temperature becomes faster as shown in the figure.

The above also applies to cases where the temperature of hot water changes suddenly as a result of changing the water flow.

As described above, according to the present invention, when the target temperature is suddenly changed or the outlet temperature is suddenly changed as a result of changing the water flow, the integral of the I (integral) operation control means in the PID control means By optimizing the operation, the responsiveness of the hot water temperature can be improved, and the effect of not causing discomfort to the hot water user can be achieved.

(Description of Embodiments) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

<First Embodiment> FIG. 1 is a block circuit diagram of a combustion control device for a water heater according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a memory map.

〔composition〕

Although this combustion control device is applied to the water heater shown in FIG. 7, it goes without saying that it can also be applied to other water heaters having a similar configuration.

In FIG. 1, 20 is a hot water temperature detection means;
2 is a target temperature setting means for the hot water temperature, 23
is the detected temperature signal a from the hot water temperature detection means 20
This is a deviation detection section that generates a deviation signal c between the detected temperature signal b from the target temperature setting means 22 and the detected temperature signal b from the target temperature setting means 22. Further, 24 calculates the conduction phase of the drive current of the fan motor 10 based on the deviation signal c, and sends a trigger signal d to the fan motor drive means 25 for phase control.
The motor rotation speed control means 26 calculates the opening degree of the fuel control valve 5 by PID calculation based on the calculation formula (6) using the deviation signal c and the integral data M _Io-1 of the steady combustion state, and This is a PID control means that outputs an opening signal e to the fuel control valve driving means 27.

28, 29, and 30 are PID control means 2, respectively.
6, P (proportional) operation control means, I (integral) operation control means, and D (differential) operation control means.

Reference numeral 31 denotes a storage means for storing integral data M _Io-1 of the I operation control means 29 in the PID control means 26. As shown in FIG. 2, this storage means 31 contains, in addition to the integral data M _Io-1 , a proportional constant K _P , an integral constant K _I , a differential constant K _D , and information to be multiplied by the integral data M _Io-1. A constant K out of the coefficients K·e _o corresponding to the deviation e _o is stored in advance.

Reference numeral 32 denotes a determining means that determines whether the absolute value of the deviation e _o , which is the value of the deviation signal c, is greater than or equal to a predetermined value, and outputs a control signal f when it is greater than or equal to the predetermined value.
Reference numeral 33 denotes a readout means which operates based on the control signal f outputted from the determination means 32 when the deviation e _o is determined to be equal to or greater than a predetermined value, and reads out the data stored in the storage means 31. be.

34 multiplies the integral data M _Io-1 read out from the storage means 31 by the reading means 33 by a coefficient K.e _o corresponding to the deviation e _o , and obtains the calculated data K.
This is a calculation means that outputs e _o ·M _Io-1 to the PID control means 26.

The I operation control means 29 of the PID control means 26 executes the calculation of the integral term of calculation formula (4) based on the calculation data K・e _o・M _Io-1 , and the PID control means 26 as a whole calculates the calculation formula It is configured to output the PID output M _o to the fuel control valve driving means 27 based on (6).

〔motion〕

The operation of the fuel control device for the water heater configured in this manner is as described above with reference to FIGS. 4 and 5. To explain this based on the flowchart of Fig. 3, in step, detected temperature data and target temperature data are input, and in step, target temperature data at the previous sampling timing t _o-1, that is, PID output M Read _o-1 . Next, set the current sampling timing at step
The integral data M _Io at t _o is the previous integral data M _Io-1
Determine whether the change is more than a predetermined amount from
In the case of YES, the process moves to step and computation data K, e _o , and M _Io-1 are created. Then, the PID is carried up or down based on formula (6) in the step.
Perform calculations.

If NO at the step, jump to the step and perform normal PID calculations.

Due to the above-mentioned PID calculation with carry up or down, the time _T2 required for the fuel control valve 5 to open to the opening degree corresponding to the target temperature is significantly shortened compared to the time _T1 in the conventional case. Ru.

On the other hand, between times T ₃ and _{T 5} , the motor rotation speed control means 24 calculates the rotation speed of the fan motor 10 based on the deviation signal c, and controls the phase of the fan motor drive means 25 . As a result, the rotational speed of the fan motor 10 increases and stabilizes at time _T5 .

Therefore, the opening degree of the fuel control valve 5, ie, the amount of fuel supplied to the burner 1, becomes proportional to the rotational speed of the fan motor 10, ie, the amount of air supplied to the burner 1, and the air-fuel ratio is maintained within a predetermined range.

<Second Embodiment> Next, a second embodiment of the present invention will be described based on FIG. 6 showing a memory map.

That is, in place of the constant K used in the first embodiment, constants K ₁ , K _{2 , .} . . K _n corresponding to the magnitude and sign of the deviation e _o are stored in the storage means. Then, the reading means reads out a constant K _j (j is an integer from 1 to m) corresponding to the deviation e _o and outputs it to the calculation means. In the calculation means, PID based on M _o (%) = K _P・e _o + {K _j・M _Io-1 + K _I・e _o } + K _D (e _o −e _o-1 ) ...(7) The operation is executed.

As is clear from the above two examples, PID
The general formula for the calculation is, where K(e _o ) is a coefficient (function) corresponding to the deviation e _o , M _o (%) = K _P・e _o + {K(e _o )・M _Io-1 + K _I・e _o } +K _D (e _o −e _o-1 ) ...(8)

That is, in the case of the first embodiment, K(e _o )=K· _eo , and in the case of the second embodiment, K(e _o )=K _j .

[Brief explanation of the drawing]

1 to 5 relate to a combustion control device for a water heater according to a first embodiment of the present invention, FIG. 1 is a block circuit diagram of the combustion control device for a water heater, and FIG. 2 is a diagram showing a memory map. Figure 3 is a flowchart, Figure 4
5 and 5 are time charts for explaining the operation, FIG. 6 is a memory map according to the second embodiment, FIGS. 7 to 10 are related to the conventional example, and FIG. 7 is a schematic diagram showing an example of a water heater. 8 is a flowchart, and FIGS. 9 and 10 are time charts for explaining the operation. In the figure, numeral 1 is a burner, 2 is a fuel supply path, and 5 is a burner.
20 is a fuel control valve, 20 is a hot water temperature detection means, 22 is a target temperature setting means, 26 is a PID control means, 29 is an I operation control means, 31 is a storage means, 33 is a reading means, and 34 is a calculation means.

Claims (1)

[Scope of Utility Model Registration Claim] A fuel control valve installed in a fuel supply path to a burner, a target temperature setting means for the hot water outlet temperature, a hot water outlet temperature detection means, and a target temperature signal from the target temperature setting means. A combustion control device for a water heater, comprising: PID control means for calculating the opening degree of the fuel control valve based on a deviation from the detected temperature signal from the hot water temperature detection means and outputting a valve driving current to the fuel control valve. A storage means for storing the integral data of the I operation control means in the PID control means, a reading means for reading the integral data from the storage means when the deviation occurs, and a reading means for reading the integral data from the storage means when the deviation occurs; and a calculation means for multiplying by a coefficient corresponding to the deviation and inputting the calculated data to the PID control means, and the I operation control means in the PID control means performs the I operation based on the calculation data in the calculation means. A water heater combustion control device configured to perform.