JPH02223761A - Temperature control device for hot water supply equipment - Google Patents

Abstract

PURPOSE:To obtain a stabilized hot water supply characteristic by compensating a heating value based on a differentiating value of temperature information transmitted from a temperature sensor of a heat exchanger outflow section, and reducing the compensation rate in proportion to the lapse of compensation time. CONSTITUTION:A temperature conditioning control means 37 decides a heating value under feed forward control based on an initial water capacity induced by a water entry temperature and water measurement section 32 stored in a memory 31a estimated by a target temperature and water entry estimation section 31 preset by a controller 40 and controls the heating value by way of a drive section 32 and a governor proportional valve 23. It obtains a proportional compensation rate and a differentiating compensation rate at a proportional compensation section 37a in conformity with the deviation between a detected value and a target value of an output hot water temperature thermistor 25, and performs feedback control which compensates the heating value of feedforward and reduces the differentiating compensation rate in proportion to the lapse of time. It is, therefore, possible to stabilize the temperature of output hot water after the change in the flow rate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects the temperature of hot water flowing out from a heat exchanger without providing an incoming water temperature sensor to detect the temperature of water flowing into the heat exchanger. Regarding a temperature control device for a water heater that is equipped with only an outflow temperature sensor and performs feedback control, it is particularly effective in a temperature control device for a water heater that has a simple structure that does not include a flow rate sensor for detecting the flow rate of water passing through a heat exchanger. It is true.

[Conventional technology] The structure of the water heater has been made into a sake tank! In order to simplify the II manufacturing process and reduce manufacturing costs, there is a temperature control device that performs feedback control to control the amount of heating using only a hot water exit temperature thermistor. In such a feedback control temperature control device, a reference heating amount is determined according to a temperature difference between a target temperature set by a temperature setting device or the like and a hot water outlet temperature detected by a hot water outlet temperature thermistor. Also,
In such a temperature control device, when the flow rate changes during hot water supply and the hot water outlet temperature changes accordingly, in order to quickly correct the heating amount, the correction is made in proportion to the differential value of the temperature detected by the hot water outlet temperature thermistor. Equipped with a function to correct the flow rate, it reduces the influence of changes in flow rate, etc., and improves the temperature characteristics of the hot water.
is planned.

[Problem to be solved by the invention] In such conventional feedback control, for example, the sixth
As shown by the solid line L1 in the figure, when the flow rate decreases,
As shown by the solid line L2, the hot water temperature gradually changes with a time delay, so the reference heating amount by proportional control of the feedback control is changed as shown by the broken line L8 in accordance with the change in the hot water tap temperature. Also, at this time, the differential value of the hot water temperature is
While the tapping temperature is changing, it continues to appear as a substantially constant value as shown by the solid line L3, and in the differential correction, a constant differential correction amount proportional to the constant is given, as shown by the broken line L9. For this reason, the final heating amount in the feedback control is corrected, for example, as shown by the broken line L7, even though it is originally desired to provide the heating amount according to the flow rate, as shown by the dashed line L6.

Therefore, when the conventional differential correction amount is corrected in proportion to the differential value, for example, when the flow rate change is small, as shown by the broken line Lll in FIG. 7, the heating amount is appropriate at the beginning of the flow rate change. If a heating amount is differentially corrected by setting a constant so that However, as the duration of the change increases, a differential correction amount that is more than necessary is gradually applied.For this reason, even a slight change in the flow rate results in an excessive correction of the heating amount. The hot water temperature changes greatly and becomes unstable.

At this time, conversely, if the flow rate change is large, as shown by the broken line L13 in FIG. Since an excessive amount of correction is given at the end of the correction, it takes time for the tapping temperature to stabilize.

In order to avoid such excessive correction, if the constant used to determine the differential correction amount is made smaller, the amount of correction will be further insufficient if there is a large change in flow rate; Further, even for large flow rate changes, an excessive amount of correction will be applied at the end of the correction.

In this way, as long as the differential correction amount proportional to the differential value of the tapped water temperature is continuously applied while the differential value is obtained, it is not possible to improve both the excess and deficiency of the heating amount.

Therefore, it is not possible to continuously apply the amount of heating corresponding to the changed flow rate while the outlet temperature is changing, so the outlet temperature becomes unstable when the flow rate changes, and excellent outlet temperature characteristics cannot be achieved. The problem is that it cannot be done.

An object of the present invention is to reduce the influence of flow rate changes and obtain stable hot water temperature characteristics in a temperature control device for a water heater that performs feedback control based on the temperature detected by a hot water tap temperature thermistor.

[Means for Solving the Problems] The present invention provides feedback control of the heating amount of the heating means that heats the heat exchanger based on temperature information detected by a temperature sensor provided at the outflow portion of the heat exchanger. A temperature control device for a water heater that includes a differential correction means for correcting the heating amount based on a differential value of the temperature information, and the differential correction means corrects the correction amount based on the differential value.
The technical means is that it gradually decreases depending on the correction duration.

[Function] In general, in water heaters, the flow rate change from one flow rate to another occurs only for a short period of time, for example when operated by the user, and once the flow rate has stabilized after the change, the flow rate continues. be done. In this case, assuming that the amount of heating is constant, the change in outlet temperature due to the change in flow rate will appear at a certain time after the change in flow rate, will be completed with a time delay, and will remain in an almost constant state of change during that time. shows.

At this time, in proportional feedback control, the amount of heating is determined according to the temperature difference between the hot water temperature and the target temperature, so
While the outlet temperature is changing, an inappropriate heating amount is determined for the changed actual flow rate. This inappropriate heating amount error appears greatly immediately after the flow rate changes, and then gradually decreases.

On the other hand, in the differential control of the present invention, a differential value is obtained only while the tapping temperature is changing, and the heating amount is corrected based on this differential value. At this time, the correction amount based on the differential value is gradually decreased according to the correction duration time.

Therefore, the amount of correction by differential control changes over time in accordance with changes in the error in the amount of heating caused by proportional control, and in order to exactly cancel out the error, overall feedback control, which is a combination of proportional control and differential control, With change,
The amount of heating can be determined according to the change, and an appropriate amount of heating can be given according to the flow rate.

[Effects of the Invention] According to the present invention, when the tapping temperature changes due to a change in the flow rate, the heating amount of the heating means can be controlled to an appropriate heating amount according to the changed flow rate.

Therefore, the tapping temperature is less likely to fluctuate greatly due to a change in the flow rate, and the stability of the tapping temperature after changing the flow rate can be improved.

[Example] Next, a temperature control device for a water heater according to the present invention will be described based on an example shown in the drawings.

A burner group 11 including a plurality of burners is provided in a combustor case 10 of the gas combustion water heater 1 shown in FIG. A burner group 11 is located below the combustor case 10.
A blower 12 is provided for supplying combustion air to the combustion chamber. A wood-tube heat exchanger 13 is provided above the burner group 11 in the combustor case 10, and water passing through the interior is heated by combustion heat from the burner group 11. A sparker 14 for igniting the burner group 11 and a flame rod 15 for detecting ignition of the burner group 11 are provided near the burner group 11 in the combustor case 10 . Furthermore, an exhaust port 2 is provided on one side of the combustor case 10 for discharging combustion exhaust gas to the outside.

A nozzle pipe 16 for supplying fuel gas is provided below the burner group 11.
A plurality of fuel injection ports 16a for ejecting fuel gas are provided corresponding to each burner.

The fuel pipe 20 that guides the fuel gas to the nozzle pipe 16 includes two electromagnetic valves 21 and 22 that allow the fuel gas to pass when energized, and a governor that adjusts the amount of fuel gas supplied by controlling the supply pressure according to the energized current. Proportional valves 23 are provided in order from the upstream side.

A water supply pipe 17 that leads water from a water supply source (not shown) to the heat exchanger 13 includes an electric water flow control bag W for adjusting the amount of hot water supply, 18, and a water flow switch that detects water passing through the heat exchanger 13. 19 are provided in order from the upstream side, and the hot water supply pipe 17a downstream of the heat exchanger 13 is provided with a hot water outlet temperature thermistor 25 that detects the outlet temperature 'rout of hot water flowing out from the heat exchanger 13.

The control device 30 has a control circuit centered on a microcomputer, starts and stops combustion in a predetermined sequence, and has a functional configuration shown in FIG. , performs feedback control temperature control.

The control device 30 also includes an inlet water temperature estimator 31 and a water amount estimator as functional units for respectively estimating the inlet water temperature Tin and water amount W to the heat exchanger 13 based on the temperature detected by the outlet hot water temperature thermistor 25. 32.

As shown in FIG. 3, the inlet water temperature estimation unit 31 calculates the inlet water temperature Ttn as follows according to the detected temperature T and its change state.
is estimated and stored in the memory 31a.

When the start of hot water supply is detected by the water flow switch 19 (YES in step 1), the hot water temperature thermistor 2
If the detected temperature in step 5] is changing, it is possible that hot water is being reheated. Therefore, if there is a temperature gradient of detected temperature] (No in step 2), the inlet water temperature Tin is not estimated.

If the temperature gradient of the detected temperature T is not detected when the start of hot water supply is detected (YES in step 2)
, the temperature detected by the outlet hot water temperature thermistor 25] is compared with the stored temperature Tie-, which has already been stored as the inlet water temperature in the memory 31a as 10, and according to the comparison result, a new value is stored in the memory 31a as follows. Inlet water temperature T for memorization
Estimate in.

If the detected temperature T is less than or equal to the stored temperature T men (YE, S in step 3), the detected temperature] is used as the new inlet water temperature Tin (step 4), and the detected temperature T is stored in the memory 31a, The stored contents are updated (step 5).

Conversely, if the detected temperature] is higher than the storage temperature Tff1el (No in step 3), the storage temperature Tm
A part of the temperature information of the detected temperature T is incorporated into en to estimate a new water inlet temperature Tin (step 6), and this is set as the stored temperature 'l'1ell (step 5).

In step 6, the new estimated temperature Tin is the stored temperature 1
From part of the temperature information of "me-" and part of the temperature information of "detected temperature", Tin = (ax'l'mem +b X '1'
)/(a+b), the new water inlet temperature Tin
is calculated.

The water amount estimating section 32 includes a heating amount calculation section 33 and a heating amount storage section 3.
4. It has a heating time calculating section 35 and a water amount calculating section 36, and estimates the amount of water W passing through the heat exchanger 13.

The temperature of the hot water flowing out from the heat exchanger 13 is the result of the water being heated by the heating means from the time the water flows into the heat exchanger 13 until the water flows out. Now, if water with a flow rate W per unit time requires time to pass through the heat exchanger 13, at this time, the temperature of the hot water flowing out from the heat exchanger 13 - the total amount involved in the increase ΔT The amount of heat dissipation QT is generally
For example, it can be expressed as the product of the heating amount Qu per unit time and the heating time t (time t required for passing through the heat exchanger 13). That is, it is expressed as Q7=QuXt --. (2).

Here, QuXt indicates the integration of the heating amount Qu per unit time during the heating time.

Therefore, if we express the total heating IQT, including the case where the amount of heating changes during the heating time from time t1 to time tn and the amount of heating per unit time is not constant, we get: -t+Qn-2+---F
Qi +Qt=Σ? Qj...
■It becomes.

Here, Qn, Qn-=, Qn-z, =・Q2, Qt are each unit time tn, tn-,, tn-z, ..., t2
, t, indicates the amount of heating.

In addition, the total amount of heat dissipated by the heating means QT is the temperature of the total amount of water U in the heat exchanger 13 according to the volume of the heat exchanger 13 - increase Δ
1゛, so Qa=Δ]゛×U ■. Therefore, from formula ■ and formula ■, Δ]' X U−Σ? Qt =Qn+Qn, t+Qn, 10-10Qz +Q1...
■ As a result, when going back in time and integrating the heating amount for each unit time, the heating amount is equivalent to the total heat dissipation amount QT that gives a temperature rise of ΔT to the surplus water UU in the heat exchanger 13. By calculating the total unit time until the heating time is obtained, it can be set as the heating time t.

Furthermore, this heating time t is the time required for water to pass through the heat exchanger 13, and the surplus water J in the heat exchanger 13 is
Between iU and stream iW, u=wxt...
・Since there is the relationship ①, the flow rate W can be determined by W=U/l... ②.

In this case, a delay time constant due to a heating response delay may be taken into consideration.

The heating amount calculating unit 33 calculates the temperature rise ΔT from the temperature T detected by the outlet hot water temperature thermistor 25 and the incoming water temperature Tln estimated by the incoming water temperature estimating unit 31 and stored in the memory 31a, and further calculates the temperature rise ΔT of the heat exchanger 13. The total amount of heat dissipated QT is calculated from the total amount of water U in the heat exchanger 13 based on the capacity, and the total amount of heat dissipated by 2㎜.

The heating amount storage unit 34 sequentially stores the heating amount output information ΔQ for each predetermined unit time Δ by the temperature adjustment control unit 37, which will be described later, in area E1, area E2, . . . area Ex shown in FIG. The information is stored and accumulated for a predetermined period of time, and the information after the predetermined period of time is sequentially deleted each time new information is provided.

That is, for example, as shown in FIG. 5, the heating amount output information ΔQ for each predetermined unit time Δ by the temperature adjustment control unit 37G changes over time as shown in FIG.
s, ΔQ n −2, ΔQ 11-1, ΔQ1】4, Δ
When changing like Qn+2, ΔQ n+2,...

At time Δtn, the heating amount storage unit 34 is set to A in FIG.
As shown in , area E1 has ΔQ at time Δtn.
n, and ΔQn-i at time Δtn1 in area E2.
However, in area E3, ΔQn,2 at time Δtn-2
In area E4, ΔQn-i at time Δtn is stored, and each heating amount output information ΔQ before time Δtn is stored in association with each area E up to area Ex.

Then, at the next time Δtn, as shown in B in FIG.
rl 14 is stored in area E1, ΔQll is stored in area E2, ΔQ n −+ is stored in area E3, ΔQn2 is stored in area E4, etc., and so on until area Ex, each area at each time Δt. E heating amount output information ΔQ
are respectively shifted and stored.

Thereafter, similarly, the newest heating amount output information ΔQ is always stored in area E1, and the stored information in area Ex is deleted, so that the heating amount output information ΔQ for every predetermined unit time Δ is continuously stored. Memory is stored.

The heating time calculation section 35 integrates the heating amount output information ΔQ stored in the heating amount storage section 34 in order of the latest information every predetermined unit time Δ, and calculates the heating amount output information ΔQ stored in the heating amount storage section 34 from the latest information using the above formula 〇. The sum of the predetermined unit time Δt when the total heat dissipation amount QT becomes equal to the total amount of heat dissipated is determined as the heating time t of the water flowing out from the heat exchanger 13.

The water layer calculation unit 36 calculates the water ff1W of the water passing through the heat exchanger 13 from the above formula 〇 based on the heating time t calculated by the heating time calculation unit 35. Note that the water amount W calculated here is a numerical value as the average water amount W at the heating time t before each time, and if the water amount W is changed (moss, water iW at each time cannot be expressed, However, the estimated water amount W is sufficiently effective in, for example, determining the amount of water to be supplied and the degree of thirst, and determining the time constant of the feedback control system in the temperature control control section 37.

Further, the water amount estimating unit 32 estimates the water amount W at the initial stage of hot water supply from the state of change in temperature 1'' detected by the outlet hot water temperature thermistor 25 at the start of hot water supply, and calculates the initial water ff1Wp to be 1.

The onsen 1 control unit 37 controls the target temperature 'rset set by the controller 40, the outlet hot water temperature TouI detected by the outlet hot water temperature thermistor 25, and the inlet water temperature estimation unit 3.
The inlet water temperature Ti stored in the memory 31a estimated in step 1
The heating IQ is determined from n and the water amount W estimated by the water amount estimating section 32.

Here, at the start of combustion, the heating amount FF in the feedforward control is determined based on the target temperature 'rset, the memory temperature "l'llem, and the initial water amount Wp by the water amount estimating section 32, and thereafter the hot water temperature thermistor 25 detects the heating amount FF. Feedback control is performed to correct the feedforward heating amount FF based on the temperature T and the target temperature Tset.

As a functional part in feedback control, the proportional correction amount P is determined based on the temperature difference between the detected temperature T and the target temperature 'rset.
There are a proportional correction section 37a for determining the differential correction ff1D based on the differential value of the detected temperature 1'', and a differential correction section 37e for determining the differential correction ff1D based on the differential value of the detected temperature 1.
is determined by Q = FF + P +.

In particular, in this embodiment, differential correction by the differential correction section 37c,
fltD is determined to gradually decrease depending on the time that the differential correction is continued, that is, the time that has elapsed since a change of 1° in the detected temperature appeared.

As a result, the amount of water changes as shown, for example, by the solid line L1 in FIG.
When the temperature changes as shown in 2, the differential value d of the detected temperature T shows a nearly constant value as shown in Figure 1! Because it gradually decreases with the elapsed time after the change in temperature T,
The heating amount Q is determined as shown by the solid line L5. For this reason, the heating ff1Q has less error from the ideal heating amount Qi according to the change in water amount shown in 6, as indicated by the dashed line, and is more responsive to the water amount W than the conventional differential correction. An appropriate differential correction amount is given, and compared to the conventional heating amount shown by the broken line L7, it is possible to provide a heating amount that corresponds more to the water amount W.

Therefore, when the change in water 1W is small, the fluctuation in the hot water temperature does not become large, and when the change in the water amount W is large, it takes less time for the hot water temperature to stabilize. There is.

In this embodiment, when there is a change in the water amount W, the water amount estimating section 32 calculates, as shown by the broken line L10, based on the hot water outlet temperature Tout, which changes as shown by the solid line L2 in FIG.
Regardless of the water volume W after the change, the water volume W changes at the same slope.
is estimated, until the change in the hot water temperature T ends,
Although the water volume W cannot be specified, and therefore it is not possible to respond to changes in the water volume W using the water volume W estimated by the water volume estimating unit 32, the differential correction unit 37
By using the differential correction scale based on C, the amount of heating can be changed in response to changes in the amount of water, and an appropriate amount of heating can be given.

In this feedback control, the time constant of the feedback control system can be set based on the water volume W estimated by the water volume estimating section 32 described above, so stable temperature control is performed and hunting etc. do not occur. There is. Therefore, even if the time constant of the feedback control system changes due to a change in the amount of water, stable temperature control can be achieved.

Note that the heating amount Q of the temperature control section 37 is based on the heating amount output information Δ
As Q, the above-mentioned heating amount storage unit 3 is
4 are sequentially stored.

The drive unit 38, based on the heating amount Q of the temperature control unit 37,
The blower 12 and the governor proportional valve 23 are driven and controlled. Here, a voltage based on the heating amount Q by the temperature control unit 37 is applied to the blower 12 to drive it, and the blower 12 is detected.
The current value to the governor proportional valve 23 is controlled based on the rotation speed of the governor proportional valve 23.

Furthermore, in order to prevent the water supply amount from exceeding the heating capacity, the control unit W, 30 adjusts the opening degree of the electric water flow control device 18 based on the temperature detected by the outlet hot water temperature thermistor 25. Limit flow.

Note that the controller 40, which allows the user to arbitrarily set the target temperature TSet, is installed according to the specifications of the water heater, and when the controller 40 is installed, the target temperature TSet can be set according to the user's operation. is set and the controller 40 is not installed, a constant temperature (for example, 60° C.) is set as the target temperature TSet.

Next, temperature control in the gas combustion water heater 1 of this embodiment having the above configuration will be explained.

When the user opens a hot water tap (not shown) provided downstream of the hot water supply pipe 17a and one or more working waters of the gas combustion water heater l pass through the water supply pipe 17, the water flow switch 19 detects hot water supply. , ignition control is performed in a predetermined sequence, and combustion is started. Further, the inlet water temperature Tin is estimated according to the temperature 1' detected by the outlet hot water temperature thermistor 25, and the stored temperature 'l'el in the memory 31a is updated.

When the flame rod 15 detects the ignition of the burner group 11, the temperature control section 37 determines the heating amount FF in the feedforward control, and the air blower Ia12 and the governor proportional valve 23 are controlled based on it.

When the temperature of the water flowing out of the heat exchanger 13 rises to a certain extent due to heating, the amount of water W is estimated based on the temperature 1' detected by the outlet hot water temperature thermistor 25, and the heating 1tQ is corrected by feedback control.

When the amount of water W changes during hot water supply, the amount of heating Q is corrected by feedback control. At this time, the differential correction section 3
The heating amount Q corresponding to the changed water amount is given by the differential correction amount (■) of 7c. For example, when there is a small change in water amount, as shown by the solid line L15 in FIG.
If a heating amount close to the ideal heating amount shown in L12 is given, and there is a similar large change in the amount of water, as shown by the solid line 16 in FIG. 8, the ideal heating amount shown in the -dotted chain line L14 Because the amount of heating is close to that of the previous one, there is little chance of overheating or underheating. Therefore, the hot water temperature "i' due to the change in water volume
Changes in out are reduced, and stable hot water temperature characteristics can be obtained.

In addition, since the water tray W determined by the water amount estimating unit 32 is used as a time constant for each predetermined unit time Δ in feedback control, for example, when the hot water temperature changes due to a change in flow rate, the water tray W determined by the water amount estimation unit 32 is Since the heating amount Q can be corrected using a corresponding time constant, hunting and the like associated with the heating amount correction are less likely to occur.

When you close the hot water tap and stop the hot water supply. Combustion stops.

As described above, according to this embodiment, when there is a change in the amount of water, the amount of heating is changed according to the changed amount of water.
The amount of heating that is just the right amount for the amount of water is given. As a result, fluctuations in the tapping temperature can be reduced, and stable tapping temperature characteristics can be maintained. Furthermore, since the amount of water is estimated, the time constant in feedback control can be set according to the amount of water, and the amount of heating can be corrected with appropriate responsiveness depending on the amount of water.

As a result, excellent hot water temperature characteristics can be obtained and stable hot water supply can be achieved.

In addition, in this embodiment, only the outlet hot water temperature thermistor is provided as a sensor, and no flow rate sensor or inlet water temperature sensor is provided at the inflow part of the heat exchanger, which further simplifies the structure of the water heater and reduces manufacturing costs. [The process can be simplified, and
Although it has the same structure as a water heater with simple feedback control, it provides extremely stable hot water temperature characteristics.

Further, in the above embodiment, correction without using the integral value of the outlet hot water temperature thermistor was shown in the feedback control, but a correction equivalent to the integral correction may be performed using the integral value.

In the above embodiments, a water heater using a burner that uses gas as fuel was shown, but a water heater that uses a burner that uses other fuels such as petroleum may also be used. It may also be done by heating or the like.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the functional configuration of the control device for the gas combustion water heater of this embodiment, Fig. 2 is a schematic configuration diagram showing the outline of the gas combustion water heater of this embodiment, and Fig. 3 is a flowchart for explaining the process of calculating the inlet water temperature in the control device of this embodiment, FIG. 4 is an area map showing the storage contents of the storage area of the heating amount storage unit in the control device of this embodiment, and FIG. A time chart showing changes in the heating amount output information in the control device of the embodiment, FIG. 6 is a timer 1 for explaining the temperature control of the present invention, and FIGS. 7 and 8 are the heating amount of the present embodiment. 2 is a time chart showing changes in . In the figure, 25... Hot water temperature thermistor (temperature sensor), 3
0...Control device (water heater temperature control device), 37...
- Temperature control control section (feedback control), 37c... differential control section (differential correction means). Figure 3

Claims (1)

[Scope of Claims] 1) A temperature of a water heater that feedback-controls the amount of heating of a heating means that heats the heat exchanger based on temperature information detected by a temperature sensor provided at an outlet of the heat exchanger. The control device includes a differential correction means for correcting the heating amount based on a differential value of the temperature information, and the differential correction means gradually decreases the correction amount based on the differential value according to a correction duration time. A water heater temperature control device characterized by: