JPH02178813A - Temperature controller using temperature detecting element - Google Patents

Abstract

PURPOSE:To improve the supply hot water temperature characteristic by performing the differential control in the feedback control and quickly changing the extent of combustion based on the change of the supply hot water temperature. CONSTITUTION:A temperature estimating part 51 to estimate the actual supply hot water temperature and a differential value estimating part 52 to estimate the differential value of the supply hot water temperature are provided as the function part which processes the detected temperature detected by a supply hot water thermistor (temperature detecting element) 19. Since the differential control is performed in the feedback control based on this estimated differential value, this controller quickly reacts on the change of temperature to change the controlled variable of the fuel control operation without being affected by the detection delay of the temperature detecting element 14. Thus, an excellent supply hot water temperature characteristic is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a temperature control device that is provided with a temperature detection element and controls the amount of heating based on a detection signal from the temperature detection element, and is mainly applied to a microcomputer (microcomputer). This invention relates to improving response delays in water heaters and water heaters that feedback control the amount of heat from a heating device.

[Prior Art] For example, in a combustion water heater such as a gas water heater, a thermistor is installed as a temperature detection element to detect the hot water temperature in order to obtain the hot water temperature desired by the user. The amount of heat generated by combustion is controlled through feedback control based on the deviation between the hot water temperature and the set temperature using an electronic circuit centered on an operational amplifier.

This feedback control not only controls the proportional operation based on the deviation between the hot water outlet temperature and the set temperature, but also prevents the hot water outlet temperature from becoming unstable due to residual deviation (or steady deviation) caused by the heat capacity of the heat exchanger, etc. Therefore, the PI operation (proportionalist integral operation) is controlled in which integral operation is performed in addition to proportional operation. In order to ensure that there is little change in the tapping temperature and no response delay, excellent hot water tapping temperature characteristics can be obtained by controlling by PID operation (proportionalist-integrator-differential operation) combined with differential operation.

On the other hand, recently, microcomputers (hereinafter referred to as microcomputers) have been introduced into various control devices, making it possible to freely set the control amount, and microcomputers have also been introduced into temperature control devices in gas water heaters, etc. It is being done.

For this reason, it is conceivable to replace the feedback differential control conventionally performed by an operational amplifier or the like with a microcomputer.

[Problems to be Solved by the Invention] However, when the detected temperature signal of the thermistor that detects the hot water temperature is AD converted into a digital signal and inputted to the microcomputer, for example, 0. When read at l5eC period,
In P operation and ■ operation, the temperature to be measured detected by a temperature detection element such as a thermistor is 0.5℃ when the hot water temperature is 0.5℃.
It is sufficient if the temperature can be detected by a difference in degree, but in order to reliably perform the D operation, the temperature detected by the thermistor must be set to 0, for example.
It is necessary to subdivide the temperature down to about 0.03°C and detect the difference.

Therefore, in order to subdivide the temperature signal and input it to the microcontroller, the temperature signal detected by the thermistor must be converted into a digital signal by AD.
A large number of input boats are required to convert and input,
The burden on the microcomputer hardware increases. Furthermore, as the number of boats increases, the program becomes more complex, resulting in longer development times and increased development costs.

The present invention enables rapid temperature adjustment in response to temperature changes, provides excellent temperature characteristics, and enables reliable feedback differential control using only a microcomputer, reducing development costs and time. An object of the present invention is to provide a temperature control device that can reduce the temperature.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a temperature detection element for detecting a temperature to be measured, and detects the temperature based on a detection signal detected by the temperature detection element. In a temperature control device that performs feedback control of an adjustment means, a temperature difference calculation unit that calculates a temperature difference in a predetermined time period between detected temperatures detected by the temperature sensing element, and estimates a differential value of the measured temperature based on the temperature difference. The present invention has a differential value estimating section that performs feedback differential control, and a differential control section that performs feedback differential control, and the technical means is to perform feedback differential control based on the differential value.

[Operation] In the temperature control device of the present invention, the temperature difference between the temperatures detected by the temperature detection element that detects the temperature to be measured is calculated for each predetermined time period.

Furthermore, a differential value of the measured temperature is estimated based on the calculated difference in the detected temperatures, and feedback differential control is performed based on the differential value.

[Effects of the Invention] In the present invention, the differential value of the measured temperature is estimated based on the difference in detected temperatures over a predetermined period of time.

For this reason, it is only necessary to subdivide the temperature in the input device for reading the temperature detected by the temperature sensing element to the extent that changes in the detected temperature can be discerned when the temperature is read after a predetermined period of time. Temperature control using a microcomputer with responsive feedback differential control can be achieved by simply subdividing the integral control.

Therefore, when converting the detected temperature signal detected by the temperature detection element into a digital signal by AD converting it, there is no need to increase the number of ports, so the burden on the hardware of the microcomputer can be reduced. Furthermore, since the program for processing it is simplified, the system development period can be shortened and development costs can be reduced.

In addition, since differential control is performed in feedback control based on the above estimated differential value, the control amount can be changed by quickly responding to temperature changes without being affected by the detection delay of the temperature sensing element. can do.

[Example] Next, a temperature control device using a temperature sensing element of the present invention will be described based on an example.

In the gas water heater 1, the outline of which is shown in FIG. A blower 12 is provided below the case 10 to supply combustion air.

The blower 12 includes an impeller 12b inside a scroll casing 12a, and a motor (not shown) drives the impeller 12b.
drive the rotation.

The scroll casing 12a is provided with a nozzle 13 for ejecting fuel scum, and the water heater case 1° and the burner plate 11 form a total air combustor that burns only with the primary air supplied by the blower 12. The combustion gas is discharged to the outside of the water heater case 10 from an exhaust port (not shown).

In the combustion chamber 10a, a sparker electrode 14 for generating spark discharge and a flame rod 15 for flame detection are provided near the burner plate 11.

Further, a heat exchanger 16 connected to a water supply source and a hot water inlet (not shown) is provided in the combustion chamber 10a, and upstream of the heat exchanger 16, the flow rate and water temperature of water flowing into the heat exchanger 16 are provided. The first stream of the heat exchanger 16 is equipped with a flow rate sensor 17 and an inlet water temperature thermistor 18 for detecting the temperature of heated hot water, respectively, and an outlet water temperature thermistor 19 for detecting the temperature of heated hot water.

In addition, in the mixing chamber 10b, a rectifying plate 10c provided with a large number of holes is disposed in order to uniformly supply the air-fuel mixture supplied by the blower 12 to the burner plate 11.

The fuel pipe 20 that supplies fuel gas to the nozzle 13 includes, in order from the tenth flow side, a main solenoid valve 21, a main solenoid valve 22, and a governor proportional valve 23 that adjusts the pressure on the downstream side of the fuel gas according to the current value.
, a solenoid valve 24 for shutting off fuel gas is provided, and the upstream and downstream sides of the solenoid valve 24 are communicated through a bypass pipe 20a having an orifice 25. The orifice 25 is provided to improve the aperture performance.
When the electromagnetic valve 24 is in the closed state, the amount of fuel supplied is limited by the orifice 25 instead of the nozzle 13, and a small combustion amount is obtained.

As shown in FIG. 1, the control device 40 includes a central processing unit (CPU) 5 as a microcomputer.
0, ROM4], RAM42, an input interface 43 having a multiplexer for processing analog signals from each sensor and thermistor, an AD converter for converting into digital signals, etc., and an output interface 4
4 is the main configuration, and includes a controller 40a operated by the user to set the desired hot water temperature and a safety circuit (not shown), and performs ignition control and combustion control.

The CPU 50 performs each necessary control operation according to the program in the ROM 41, and the input interface 43
It performs arithmetic processing based on each input of the controller, and drives and controls each part as follows via the output interface 44 according to the arithmetic results.

In the ignition control, when a water flow signal is transmitted from the flow rate sensor 17, the air blower 8!12, the sparker electrode 14, the main solenoid valve 21, and the main solenoid valve 22 are controlled respectively in a preset sequence to ignite.

In combustion control, the combustion amount Q is determined based on a temperature signal obtained from the resistance value of each thermistor, a pulse signal from the flow rate sensor 17 generated according to the amount of water passing through the heat exchanger 16, and the temperature set by the controller 40a. Based on the determined combustion amount Q, the blower 12 and the solenoid valve 2
4. Control the governor proportional valve 23.

Here, as shown in Fig. 1, as a functional unit for processing the detected temperature detected by the hot water temperature thermistor 1,
It includes a temperature estimation section 51 that estimates the actual hot water temperature, and a differential value estimation section 52 that estimates the differential value of the hot water temperature, and performs combustion control operations based on these estimated differential values. Therefore, when the amount of hot water supplied is changed, the change is kept as small as possible so that the hot water temperature does not become unstable due to the response delay of the hot water temperature thermistor 19.

Generally, there is a response delay in the detected temperature detected by a thermistor with respect to the temperature to be measured.

Therefore, in the temperature estimating section 51, the hot water temperature thermistor 19
The actual hot water temperature is estimated by using changes in the detected temperature.

That is, the detected temperature T(t) detected and read by the outlet hot water temperature thermistor 19 has a response delay with respect to the actual hot water temperature "rout" flowing out from the heat exchanger 16, and due to changes in the amount of hot water supplied, etc. In FIG. 3, if hot water temperature Tout changes from hot water temperature TO to Ta as shown by broken line A at time t1, the response delay of the outlet hot water temperature thermistor 19 shown by solid line B is generally expressed as Ta-T (t) = (Ta-T
o) eXp -" (τ is the time constant of the thermistor) Here, when each value is converted into a recurrence formula of time step t, the actual hot water temperature 'rout is... 'l”out n-2, Tout n-1, T
The out n detected temperature T'(t) is..., 'l'n-2, 'l'n-1, Tn, and the temperature difference Δ1 due to the temperature detected by the outlet hot water temperature thermistor 19
Since 'n is ΔT n = 'rn - Tn-1, rearranging the previous equations with respect to the water temperature 't'out n, Tout n = Tn-1+ (exp ' -1)
-1xΔTn, where r13XI) t/v-I J is usually a constant larger than 1, and the time step t is t=
In the case of 0.1 seconds, constant r=(expゝ/'-1)-
1 is about r-10, so ``'t'out n ='l'Q-i + t ox
The relationship of ΔTn is obtained, and this is determined as the current water temperature TOut n
The estimated value is as follows.

Therefore, in this embodiment, instead of using the detected temperature 1'b at time tn as the hot water temperature, the estimated temperature TOutn obtained from the detected temperature Tn-1 at the previous time step t and the temperature difference ΔTn is actually used. It is assumed that the water temperature is

Further, the differential value estimating unit 52 calculates the differential value of the outlet hot water temperature, which is difficult to calculate from the detected temperature of the outlet hot water temperature thermistor 19, which is normally read at a fixed time step t (0, 1 second), based on the above-mentioned detected temperature. This is calculated using the difference ΔTn.

That is, when the hot water temperature TOut n , the detected temperature Tn, and the temperature difference Δ]n between the detected temperatures between steps, the hot water temperatures TOut n and Tout n for the time step t.
-1,... is 'rout n ==Tn-1+ (r XΔTn)-
・・■'1'Out n-1='l'n-2+ (r
It can be estimated as described above based on the relationship:

Therefore, from the difference (■・-■) in each of the above equations, the differential value Δ'x'outn of the water temperature is: ΔTout n = Tout n - Tout n-1
='l'n-1+ (r XΔTn)-('l'n-2
+(r×ΔTn-1) )...■Here, Tn-1=Tn-2+ΔTn-1, -...■So, by substituting 2〇 into the formula ■, Δ'routn=rΔTn
+(1-r)ΔTn-1.

In this way, the differential value Δ'rout n can be obtained as a function of the temperature difference ΔTn between the detected temperatures at each time step (every predetermined time).

The combustion control operations of the CPU 50 for determining the combustion amount Q include a feedforward operation (FF operation) 53 as feedforward control, a proportional operation (P operation) 55 as feedback control, and an integral operation (I operation) 5.
6 and a differential operation (D operation) 57 are performed.

The FF operation 53 is a control operation that is performed after the start of operation until the hot water 1Toutn estimated by the temperature estimating section 51 reaches a predetermined condition with respect to the set temperature Tset, and is a control operation that is performed until the hot water 1Toutn estimated by the temperature estimating section 51 reaches a predetermined condition with respect to the set temperature Tset. 'set, the inlet water temperature Tin detected by the inlet water temperature thermistor 18, the water amount W detected by the flow rate sensor 17, and the heat exchange rate 1/eff, Q (FF) = (TSet - Ti11) XW/ef.
The combustion amount Q (FF) is determined by f.

The proportional action 55 and the integral action 56 are based on the water temperature TOLItn.
This is a combustion amount correction control operation that is performed after the set temperature TSet reaches a predetermined condition.
P=E (Tset −T
out n ) W. Here E is a constant of proportionality.

Also, the integral correction amount ■ by the integral operation 56 is determined by the set temperature TS.
(From the deviation between !t and the hot water temperature TOut n and the water volume W n, I n = I n-1 + bWn - (Tsct - T
out n ). Here, In is the integral correction amount found this time, In-1 is the integral complement 1 scene found last time, Wn is the current amount of water, and b is the integral constant.

Furthermore, the differential compensation iE weighing by the differential operation 57 is D:Δ
'l'0LIj n X d. Here C
ΔTOut n is the differential value of the tapping temperature estimated by the differential value estimating section 52, and d is a negative constant.

These proportional operation 55, integral operation 56, and differential operation 57 are operations that add each correction amount to the combustion amount Q ([F) by the above-mentioned FF operation 53, and the combustion amount (1ffiQ( FB) is Q(FB)=Q(
FF) 10Pf I +D.

In combustion control, R corresponding to the combustion amount Q obtained in this way is
The blower 12 is controlled based on the data in the OM 41.

Here, the control voltage data of the blower 12 corresponding to the determined combustion amount Q is stored in the ROM 41, and when the combustion amount Q is given, the corresponding data is controlled by the CPU 50 according to the type of gas used. The voltage is read out through arithmetic processing, and a voltage based on it is applied to the blower 12.

Further, the value of current applied to the governor proportional valve 23 is determined based on the detected rotational speed of the blower 12.

The waste water heater 1 of this embodiment having the above configuration operates as follows.

When the user sets the hot water temperature using the controller 40a and operates a faucet (not shown) to start hot water supply, ignition is performed in a predetermined sequence.

When a famous dog is detected by the flame rod 15, the combustion amount Q (FF) of the FF operation 53 is calculated based on the signals of the controller 40a, each sensor, and the thermistor, and the blower 12 and governor proportional valve 23 are controlled based on it. Ru.

After that, when the hot water temperature TOutn reaches a predetermined condition, the hot water temperature "
Feedback control is performed based on '+''out n, each correction value by the proportional action 55, integral action 56, and differential action 57 is determined, the combustion amount Q (FB) in the feedback control is determined, and the required temperature] It is heated to 0.

During hot water supply, for example, as shown by the solid line C in FIG.
1, when the amount of hot water supplied is changed by the user and the amount of hot water supplied decreases, the actual hot water temperature increases as shown by the solid line.

At this time, the detected temperature T (t) detected by the outlet hot water temperature thermistor 19 cannot follow the hot water temperature, and as shown by the broken line E, increases gradually.

In this embodiment, the differential value ΔTout n indicating the change in the hot water temperature is calculated not from the hot water temperature but based on the amount of change in the detected temperature 'i'' (t), so as shown by the solid line C,
A differential value corresponding to the actual change in water temperature is obtained, and there is no delay in the differential value as in the conventional case shown by the broken line G. Therefore, from time t1 to time t2, the solid line H
As shown in , the differential correction amount D1 is obtained, and the differential operation 57 in the feedback control is quickly performed.

As a result, unlike in the conventional case shown by the broken line I, the differential correction value D1 is not delayed, the combustion amount can be quickly corrected, and the tapping temperature can be stabilized.

As described above, in this embodiment, differential control is performed in the feedback control, and the combustion amount is quickly changed based on a change in the tapped water temperature, so that the tapped hot water temperature can be reliably brought close to the set temperature.

In addition, since the differential value of the hot water outlet temperature for this differential control is estimated based on the change value of the detected IMt degree detected by the thermistor, it is necessary to input the detected temperature detected by the hot water outlet temperature thermistor into the microcontroller. Since it is only necessary to subdivide the number of input ports to the extent necessary for proportional control or integral control, the number of input ports can be set to a small number, and the burden on the microcomputer's hardware can be reduced. Furthermore, since the program for processing it is simplified, the development period can be shortened and development costs can be reduced.

In this example, a gas water heater is shown, but hot water heaters,
Floor heating or central heating may also be used. Further, the heating source is not limited to a combustion device using gas, oil, etc., and may be an electric heating source.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the functional configuration of a control device for a gas water heater according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the configuration of a gas water heater according to this embodiment, and FIG. FIG. 4 is a time chart showing the relationship between measured temperature and detected temperature. FIG. 4 is a time chart for explaining the operation of the present invention. In the figure, 19... Hot water temperature thermistor (temperature detection element),
23... Governor proportional valve (temperature control means), 40...
Control device (temperature control device), 51... Temperature estimation section (temperature difference calculation section), 52... Differential value estimation section, 57... Differential operation (differential control section).

Claims (1)

[Claims] 1) A temperature detection element for detecting the temperature to be measured;
A temperature control device that performs feedback control of a temperature adjusting means based on a detection signal detected by the temperature detection element, comprising: a temperature difference calculation unit that calculates a temperature difference in a predetermined time period between the detected temperatures detected by the temperature detection element; Temperature detection comprising a differential value estimating section that estimates a differential value of the temperature to be measured based on a temperature difference, and a differential control section that performs feedback differential control, and performs feedback differential control based on the differential value. Temperature control device using elements.