JPH02223764A - Temperature control device for hot water supply equipment - Google Patents

Abstract

PURPOSE:To improve an output hot water temperature rise characteristic in an initial stage of hot water supply by estimating the flow rate of water which passes through a heat exchanger based on the time which is required until a temperature detected by a temperature sensor indicates a specified change from the start of hot water supply. CONSTITUTION:A control device 30 obtains time which is required until a detected temperature of an output hot water temperature thermistor shows a specified change in a timer section 33a and estimates the flow rate of water which passes through a heat exchanger based on the above information. A temperature conditioning control means 34 performs feed-forward control based on the estimated initial stage water opacity and the deviation between a preset temperature by a controller 40 and a selected temperature, and an input water temperature estimated in an input water temperature estimation section 31 and stored in a memory 31a. Then, a water capacity estimation section 32 estimates the capacity of water and performs feed-back control based on a total heating value obtained from the detected temperature and the integrated value of heating value output information in a memory section 32a.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature control device for a water heater that does not include a flow rate sensor for detecting the flow rate of water passing through a heat exchanger.
It is particularly effective for water heaters with a simple structure that does not include an inlet water temperature sensor that detects the temperature of water flowing into the heat exchanger, but only an outflow temperature sensor that detects the temperature of hot water flowing out from the heat exchanger. be.

[Prior Art] In order to simplify the structure of a water heater, simplify the manufacturing process, and reduce manufacturing costs, there is a temperature control device that performs feedback control using only a hot water outlet temperature thermistor. These temperature control devices do not have an inlet water temperature thermistor that detects the temperature of water entering the heat exchanger and a flow rate sensor that detects the flow rate of water passing through the heat exchanger, which improves the outlet temperature characteristics. Those with functions to achieve this are used.

In such a feedback control temperature control device, if the amount of heating is directly controlled based on the unheated outflow temperature at the beginning of hot water supply, when the amount of hot water to be supplied is small, the hot water output temperature will become too high due to excessive heating. To avoid danger, the amount of heating is set low based on the assumption that the amount of hot water supply is small.
Thereafter, the heating amount is gradually changed with a certain time delay due to the time constant of the feedback control system, depending on the temperature detected by the outlet hot water temperature sensor.

[Problems to be Solved by the Invention] As described above, in such conventional feedback-controlled water heaters, information for controlling the amount of heating is provided only by the hot water temperature sensor, and the flow rate of water passing through the heat exchanger is Because there is no information about Flow! There is inevitably a large response delay to changes, and especially when the amount of hot water supplied is large at the beginning of hot water supply, the amount of heating is insufficient, causing the hot water temperature to rise.
- There is a problem that the temperature of the hot water is slow to rise and it takes a long time for the temperature of the hot water to rise to the target temperature and stabilize.

The present invention provides a temperature control device for a water heater that performs feedpack control without a flow rate sensor, and which has good rising characteristics of the outlet temperature at the initial stage of hot water supply, and particularly has excellent rising characteristics when a large amount of hot water is being supplied. The purpose is to provide

[Means for Solving the Problems] A first aspect of the present invention is that when hot water supply is detected by a water flow detection means that detects water flowing into a heat exchanger, heating of the heat exchanger by a heating means is performed. In a temperature control device for a water heater that controls the heating amount of the heating means based on temperature information detected by a temperature sensor provided at an outflow portion of the heat exchanger, the time elapsed after the start of hot water supply is controlled. The flow rate estimating means includes a timer for measuring time and a flow rate estimating means for estimating the flow rate of water passing through the heat exchanger, and the flow rate estimating means is configured to measure the flow rate from the start of hot water supply until the temperature detected by the temperature sensor shows a predetermined change. The technical means is to estimate the flow rate based on the time of .

In a second aspect of the present invention, the technical means is that the flow rate estimating means estimates the flow rate based on a time until a flIX value of a change in temperature detected by the temperature sensor reaches a predetermined value.

In general, in water heaters, there is a time delay before the heating result appears in the hot water temperature, and if hot water is not reheated, the time from the start of hot water supply until a change in the hot water temperature appears is This is the time required for water to pass through the exchanger.

The passage time of this water varies depending on the flow rate through a water tube heat exchanger having a certain length, for example, and in the case of a large amount of water, the time from when it flows into the heat exchanger until it flows out is changed. The time is short, and the time becomes longer if the amount of water is small.

In view of these characteristics of the water heater, in the first invention, the temperature of the water flowing out from the heat exchanger is detected by a temperature sensor, and after hot water supply starts, the temperature of the flowing water rises, and the temperature detected by the temperature sensor reaches a predetermined level. The flow rate of water passing through the heat exchanger is estimated based on the time it takes to show a change in temperature, for example, the time it takes to detect a rise in the temperature of the outflowing water.

In addition, in the second invention, the cumulative value of the cumulative amount of heat given to the water passing through the heat exchanger and the cumulative value of the change in temperature detected by the 17 temperature sensors are calculated, and the cumulative value is determined based on the time until the cumulative value reaches a predetermined value. Since the flow rate is estimated, it is possible to clarify the difference in the amount of change in detected temperature due to the difference in flow rate.

[Effects of the Invention] In the first aspect of the present invention, since the flow rate is estimated at the time when a predetermined change appears in the outflow temperature after the start of hot water supply, it is possible to quickly control the heating amount of the heating means according to the flow rate. can.

In particular, the higher the flow rate, the faster the flow rate can be estimated, which greatly improves the temperature rise of the tapped water in the case of a large flow rate compared to the conventional method.

In the second invention, since the integrated value of the change in detected temperature is used as the cumulative value of the amount of heating to water, it is possible to clearly understand the difference in flow rate. Therefore, even if there is a slight difference in flow rate, each flow rate can be specified.

[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.

Gas-fired water heater shown in Figure 2 1. combustor case 10
A burner group 11 including a plurality of burners is provided inside. A burner group 1 is located below the combustor case 10.
A blower 12 is provided for supplying combustion air to 1. A water tube type 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 1-1. A five burner group 11 is located near the burner group 11 in the combustor case 10.
A flame rod 15 is provided to detect the ignition of the five-banner group 11. Furthermore, an exhaust port 2 is provided above 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 are provided, each corresponding to each burner 7, for ejecting fuel gas.

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. A water supply pipe 17 that leads water from a water supply source (not shown) to the heat exchanger 3 is provided with a proportional valve 23 in order from the upstream side. Dynamic water flow control device 18, heat exchanger 13
A water flow switch 19 for detecting water passing through the heat exchanger 1.
A hot water outlet temperature thermistor 25 for detecting the outlet temperature TOut of hot water flowing out from the hot water outlet 3 is provided.

The control device W30 has a control circuit centered on a microcomputer 17, starts and stops combustion in a predetermined sequence according to the water flow detection state of the water flow switch 1.9, and has a functional configuration shown in FIG. Accordingly, the temperature of the hot water is controlled by using only the hot water temperature thermistor 25 as a sensor.

Here, since a water inlet temperature thermistor to the heat exchanger 3 and a current sensor for detecting the amount of water passing through the heat exchanger 13 are not provided, the control device 30 controls the outlet water temperature thermistor 25. Inlet water temperature Tin based on detected temperature T
and the amount of water W are estimated respectively.

The incoming water temperature estimating unit 31 estimates the incoming water temperature Tin based on the temperature T detected by the outlet hot water temperature thermistor 25, and stores it in the memory 3Ia.

Next, a method for estimating the inlet water temperature group T will be explained based on FIG.

When the start of hot water supply is detected by the water flow switch 19 (YES in step 1) + hot water temperature thermistor 2
If the detected temperature T in No. 5 is changing, it is possible that hot water is being reheated. Therefore, if there is a temperature gradient in the detected temperature T (NO in step 2), the inlet water temperature'
No estimation of Hn is performed.

If the temperature gradient is not detected when the start of hot water supply is detected (YES in step), the detected temperature T of the outlet hot water temperature thermistor 25 and the inlet water temperature "["in] have already been stored in the memory 31a. Memory temperature “i”
If the detected temperature T is lower than the memory temperature TmeIl, then YES in step 3), the detected temperature is estimated as the new water inlet temperature Tin.Step 4), memory The memory contents of 31a are updated (step 5).

If the detected temperature T is higher than the stored temperature 'T''ta slope (NO in step 3), the stored temperature 'l''ll1cm
In step 6), a new inlet water temperature 1゛tn is estimated by incorporating part of the temperature information of the detected temperature 1゛ into the memory temperature TIIC! 1 (step 5).

In step 6, the new estimated temperature] 1n is calculated by 'rin= (aXTel +bxT)/(a-tb) from part of the temperature information of the stored temperature Tmei and part of the temperature information of the detected temperature T. , a new inlet water temperature 'l''in is calculated.

The water amount estimation unit 32 estimates the amount of water W passing through the heat exchanger 13.

Generally, the temperature rise ΔT of hot water flowing out from the heat exchanger 13
is the result of the water being heated by the burner group 11 from the time it flows into the heat exchanger 13 to the time it flows out. Now, if it is assumed that 11 W u of water per unit time requires an hour rIRt to pass through the heat exchanger 13, then the total amount of water involved in the temperature rise ΔT of the hot water flowing out from the heat exchanger 13 is The amount of heat dissipation Q can generally be expressed, for example, 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 Qt = Q u x t −■.

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

Therefore, if the total amount of heat dissipation Q is expressed including the case where the heating amount changes during the heating time from time t1 to time tn and the heating amount Qu per unit time is not constant, QT=Qn+Qn-, t+Qn-z+-+Qz +Q1
=Σ? Qt... becomes ■.

Here, Qn, Qn-, , Qn-i, -Q2, Q.

is each unit time tn, tn-x, tn, ..., t2
．． The amount of heating in 1 is shown.

In addition, the total amount of heat dissipated QT by the burner group 11 is
It can be considered that the temperature increase Δ1' of the total amount of water U in the heat exchanger 13 corresponds to the volume of the heat exchanger 13 according to the volume of the heat exchanger 13. Therefore, from formula ■ and formula ■, ΔTXU=Σ? Qt = Q n + Q n -1+ Q n -2+ -
＋ Q If the total unit time required to obtain a heating amount corresponding to QT can be determined as the heating time t.

Furthermore, this heating time Ht is the time required for water to pass through the heat exchanger 13, and between the total amount of water U in the heat exchanger 13 and the flow rate W, U=Wxt...
Since there is the relationship (2), the flow rate W can be determined by W=U/l (2).

Note that in this case, a constant of time delay due to passage of water may be taken into consideration.

The water amount estimating unit 32 calculates the temperature - rise ΔT from the temperature T detected by the outlet hot water temperature thermistor 25 and the incoming water temperature stored in the memory 31a of the incoming water temperature estimating unit 31, and further calculates the The total amount of heat disintegration QT is calculated from the surplus water itJ of .

On the other hand, the heating amount output information ΔQ for each predetermined unit time Δ by the temperature adjustment control unit 34, which will be described later, is stored in areas E1, E2, . . . , E of the heating amount storage unit 32a shown in FIG.
The information is sequentially stored in x 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, the heating amount output information ΔQ for each predetermined unit time Δ by the temperature control unit 34 is as shown in FIG.
With time......, ΔQn-4, ΔQn-t
, ΔQn-x, ΔQ n -t, ΔQn, ΔQ n and 8
, ΔQn+2,..., at time Δtn, in the heating amount storage unit 32a, as shown in A of FIG. In area E2, Δ at time Δtn,, i
Qn-t is in area E3 at time Δtn-2.
ΔQn-1 at time ΔtrL-3 is stored in area E4, and each heating amount output information ΔQ before time Δtn is stored in correspondence with each area E up to area Ex.

Then, at the next time Δtn+t, as shown in B in FIG. 4, the heating amount output information ΔQn+ at the time Δtn+t is
x is stored in area E1, and ΔQn is stored in area E2 below.
, ΔQn-t is in area E3, ΔQn-2 is in area E
4, . . . , the heating amount output information ΔQ of each area E at time Δtn is shifted and stored in the same manner up to area Ex.

Thereafter, similarly, the latest heating amount output information ΔQ is always stored in area E1, and the stored information in areas F and x is deleted, so that the heating amount output information ΔQ for every predetermined unit time Δ is continuously stored. and stored in memory.

The Mercury estimation unit 32 integrates the heating amount output information ΔQ stored in this way in order from the newest information, and calculates the predetermined unit time Δt when it becomes equal to the calculated total heat disintegration JiQ1 using the -L formula (■). The total is determined as the heating time t of the water flowing out from the heat exchanger 13.

Based on this heating time t, the heat exchanger 13
Calculate the water itw passing through.

Note that the water dispersion W p estimated here is the heating time t
It is a value based on the average water 1w in , and the amount of hot water supply W
If the is changed sequentially, 1w of water at each time
cannot be expressed.

Further, the water amount estimating unit 32 described in item 1 integrates the stored heating amount output information ΔQ in order from the newest information, and when
Total heat dissipation QT and heating time 1 that is effective only when it becomes cloudy
．． is what is required. Therefore, for example, at the beginning of hot water supply, the heating amount output information Δ
Even if an attempt is made to integrate Q, water cannot drip before hot water starts being supplied, so the estimated amount of water WP1 is much larger than the actual amount of water W. This situation is shown in FIG. 6. In this Fig. 6, for example, the solid line C indicates a large flow rate.
The solid lines indicate the case of small fisheries.

Here, the water amount Wp estimated by the water amount estimating section 32.

, is an effective water amount We as a substitute for the actual water amount W
, Wd are shown when time tc and time 1'tajtd have passed after the start of hot water supply, respectively. Therefore, from the start of hot water supply until the time tc and time td have elapsed, the water amount Wp remains constant.

Temperature control based on , it is not possible to determine an appropriate heating 11Q.

Therefore, in this embodiment, instead of the water amount Wp1 estimated by the water amount estimating section 32 described above only at the initial stage of hot water supply, the amount of water passing through the heat exchanger 13 is determined by the initial water amount estimating section 33 as the water amount estimating means of the present invention. Wri 2 is estimated.

1. In other words, the hot water outlet temperature 'rout after the start of hot water supply changes in accordance with the water volume W, as shown in Figure 7. ”
- In the case of a small amount of water, as shown by the solid line F, the rise is slower than in the case of a large amount of water.

The initial water amount estimating unit 33 calculates the water amount W based on the fact that the time required for the amount of heat given to the heat exchanger 13 to appear as a change in the hot water outlet temperature differs depending on the amount of water W passing through. The water jlW is estimated by measuring the elapsed time tm until a predetermined amount of heat due to heating is detected by the timer 33a.

Here, as an indication of the given predetermined amount of heat, the integrated value l) obtained by integrating the detected temperature T at the start of hot water supply minus the increase Δ (integrated value with respect to time for the detected temperature T)
is calculated, and the elapsed time tm until this integrated value P reaches a predetermined integrated value P0 is measured.

This predetermined integrated value Po is determined by the heat exchanger ]3 at the start of combustion.
In Fig. 7, for example, in the case of a large amount of water, it is shown as the amount of heat equivalent to the area S up to time te, and in the case of a small amount of water, , is shown as the amount of heat corresponding to the area S2 up to time tf. In particular, in order to clearly detect the difference in the amount of water W that actually passes through the heat exchanger 13, a value corresponding to the amount of heating for a relatively short time after the start of combustion is set.

According to the measured elapsed time tm, the amount of water W px is estimated, as shown in FIG. 8.

As a result, each time measurement can be completed at a relatively early stage before the tapped water temperature becomes stable for each water amount.

In particular, in the case of a large amount of water, as shown in Figure 7, the time measurement ends much earlier than the time td when the hot water temperature stabilizes in the case of a small amount of water, and as a result, it is possible to detect a large amount of water. Can be done.

Note that the times tc and td in FIG.
This shows the same time as times te and td in the figure.

Therefore, for reference, the times te and tf at which time measurement ends at each water volume in FIG. 7 are as follows:
The times t'mte and tf in FIG. - It can be seen that this is the time required to show a constant water amount value Wx.

The temperature control unit 34 controls the target temperature '1'Set set by the controller 40, the outlet hot water temperature TOut detected by the outlet hot water temperature thermistor 25, and the inlet water temperature estimation unit 3.
The inlet water temperature Tin estimated in step 1, the water amount w estimated by the water amount estimating section 32 and the initial water amount estimating section 33, respectively.
The heating amount Q is determined from p, , wp2.

Here, immediately after the start of hot water supply, the water flow rate Ws at which the water flow switch 19 starts operating is set to the water volume W passing through the heat exchanger 13, the estimated water inlet temperature Tin, and the target temperature ' of the controller 40.
The heating amount Q is determined based on I'Set.

Thereafter, when the integrated value reaches a predetermined integrated value P0, the heating amount Q is determined using the water JLWpi estimated by the initial water amount estimating unit 33 as the water amount W, and when the time determined based on this water amount Wp2 has elapsed, the water amount is estimated. The heating amount Q is determined by setting the water amount Wpl estimated by the unit 32 as the water amount W.

Furthermore, when the detected temperature T of the outlet hot water temperature thermistor 25 rises to a constant temperature, feedback control is performed based on the detected temperature T.

In this feedback control, by setting the time constant of the feedback control system each time based on the water tWp l estimated by the water amount estimating section 32 described above, stable temperature control is performed and hunting etc. are prevented from occurring. ing. 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 34 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 35, based on the heating amount Q of the temperature control unit 34,
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 34 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 device 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 to control the passing flow rate. Restrict.

Note that the controller 40, which allows the user to arbitrarily set the target temperature 'l''set, is installed according to the specifications of the water heater, and when the controller 40 is provided, the target temperature 'l''set can be set arbitrarily by the user. When the target temperature "+'set" is set and the controller 40 is not installed, a constant temperature (for example, 60° C.) is set as the target temperature "i"set.

Next, temperature control in the gas combustion water heater 1 of this embodiment having the above configuration will be explained with reference to FIG. 9, focusing on estimation of the water amount W.

When a user opens a hot water tap (not shown) provided downstream of the hot water supply pipe 17a, water passes through the water supply pipe 17 and flows into the heat exchanger 13.

When hot water supply is detected by the water flow switch 9 (YES in step 11), ignition control is performed in a predetermined sequence to start combustion, and at the same time, the timer 33a starts measuring the elapsed time tm (step 12). ),
At this time, only when the outlet water temperature 'i''out does not change, the inlet water temperature Tin is estimated according to the temperature T detected by the outlet hot water temperature thermistor 25, and the temperature stored in the memory 31a is '+'.
'mem is updated. Further, the temperature increase Δ]' for every predetermined unit time Δ of the temperature T detected by the outlet hot water temperature thermistor 25 is integrated to calculate an integrated value P (step 13).

When the integrated value P becomes greater than or equal to the predetermined integrated value Po (step 1
4), the time measurement by the time measurement section 33a ends (Step 15), water IWp2 is estimated based on the measured elapsed time tm (Step 16), and the water IWp
2, an initial time tp is set (step 17).

When the initial time tp has elapsed (step 18), control using the water Ji W p I estimated by the water amount estimating section 32 is started (step 19), and thereafter, the heating plate Q is determined based on the water amount W pl.

The water amount Wpl obtained here is used as a time constant in feedback control, so for example, when the outlet temperature changes due to a change in flow rate, it is possible to correct the heating amount Q using the time constant according to the change in flow rate. Therefore, hunting and the like associated with correction of the heating amount are less likely to occur.

When the hot water tap is closed and hot water supply is stopped (YES in step 20), combustion is stopped.

As described above, according to this embodiment, the amount of water is quickly estimated at the initial stage of hot water supply, so that an appropriate amount of heating is determined.

In particular, the larger the amount of water, the earlier the temperature control is started based on the estimated amount of water, so the temperature of the hot water rises faster than in the conventional case.

In the example described above, the amount of water was estimated based on the time it took for the detected temperature to show a predetermined amount of change, but the amount of water was estimated based on the time it took for the detected temperature to rise (indicate a change). Good too.

In addition, in this embodiment, only the outlet hot water temperature thermistor is provided as a sensor, and no sensor is provided at the inflow part of the heat exchanger, so the structure of the water heater is simplified and the manufacturing process can be simplified. At the same time, although the structure is equivalent to that of a simple feedback control water heater, extremely stable hot water temperature characteristics similar to feedforward control can be obtained.

In the above embodiment, a gas water heater that uses gas as fuel is shown, but water heaters that use other fuels such as oil may also be used.
The heat source is not limited to a burner, but may be a heating means such as electric heating.

[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 determining the inlet water temperature in the control device of this embodiment, FIG. 4 is an area map showing the storage area of the heating amount storage unit of this embodiment, and FIG. 5 is a flowchart of the control device of this embodiment. Figure 6 is a time chart showing changes in the estimated mercury by the water volume estimating section of this embodiment, and Figure 7 is a time chart showing changes in the output temperature of hot water in this embodiment. Time chart I shown for
-・, FIG. 8 is a characteristic diagram showing the relationship between the elapsed time measured by the timer in the initial water amount estimating section of this embodiment and the estimated water Jt W p 2, and FIG. 9 is the water amount estimation process in this embodiment. FIG. In the figure, one...Water flow switch (water flow detection means), 25
... Hot water temperature thermistor (temperature sensor), 30... Control device (temperature control device of water heater), 33... Initial water amount estimating section (flow rate estimating means), 33a... Timing section (time measuring means) . Figure 3

Claims (1)

[Scope of Claims] 1) When hot water supply is detected by the water flow detection means that detects the inflow of water into the heat exchanger, the heating means starts heating the heat exchanger, and the outflow portion of the heat exchanger is heated. A temperature control device for a water heater that controls the amount of heating by the heating means based on temperature information detected by a temperature sensor installed in the water heater, comprising: a timer for measuring the elapsed time after the start of hot water supply; A flow rate estimating means for estimating the flow rate of passing water is provided, and the flow rate estimating means estimates the flow rate based on the time from the start of hot water supply until the temperature detected by the temperature sensor shows a predetermined change. A water heater temperature control device featuring: 2) The water heater temperature control according to claim 1, wherein the flow rate estimating means estimates the flow rate based on a time until an integrated value of changes in temperature detected by the temperature sensor reaches a predetermined value. Device.