JP2013245895A - Water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable undershoot in resupplying hot water to be properly suppressed.SOLUTION: In a water heater 1 including a heat exchanger 5 heated by a burner 2 in a combustion chamber, a water inlet pipe 3 connected with the heat exchanger 5 and supplying tap water, a hot water outlet pipe 4 connected with the heat exchanger 5 and supplying heated hot water, a bypass pipe 10 connected between the water inlet pipe 3 and the hot water outlet pipe 4 and bypassing the heat exchanger 5, a mixing motor 14 capable of controlling a flow rate in the bypass pipe 10, an internal drum thermistor 15 detecting an internal drum temperature at an outlet from the combustion chamber, in the hot water outlet pipe 4, and a controller controlling motion of the mixing motor 14 according to an internal drum temperature obtained by the internal drum thermistor 15, the controller reduces the flow rate in the bypass pipe 10 by the mixing motor 14 according to decrease gradient of the internal drum temperature obtained by the internal drum thermistor 15.

Description

  The present invention relates to a bypass mixing hot water supply apparatus in which a bypass pipe that bypasses a heat exchanger is connected between a water inlet pipe and a hot water outlet pipe.

The bypass mixing type hot water supply apparatus connects a heat exchanger heated by a burner with a water inlet pipe for supplying tap water and a hot water outlet pipe for discharging hot water heated by heat exchange with the combustion exhaust of the burner, A bypass pipe that bypasses the heat exchanger is connected between the water inlet pipe and the hot water outlet pipe, and the hot water discharged from the heat exchanger is mixed with the water from the bypass pipe to obtain hot water at the set temperature. It has become.
In such a hot water supply device, when re-bathing is performed after a predetermined time has elapsed after stopping the hot water supply, the water from the bypass pipe is mixed with the hot water in the appliance whose temperature has dropped due to the flow of hot water during fire extinguishing. This causes a drop in hot water temperature. Therefore, as disclosed in Patent Document 1, when the temperature of the hot water from the heat exchanger becomes equal to or lower than the reference temperature (set temperature), the bypass valve provided in the bypass pipe is closed while the hot water is discharged from the heat exchanger by re-heating. When the temperature of the hot water reaches or exceeds the first reference value, the bypass valve is opened, and when the temperature of the hot water from the hot water pipe becomes lower than or equal to the second reference value, the bypass valve is closed again to perform opening / closing control. An invention has been proposed in which the hot water temperature fluctuation at the time of tapping is suppressed.

JP-A-6-249504

  However, in the invention of Patent Document 1, a normally open bypass valve is used to open the bypass pipe when hot water is stopped, and the opening / closing control is also simply performed during re-watering. Undershoot cannot be avoided even if the temperature is controlled so that the tapping temperature is much lower than the set temperature.

  Therefore, an object of the present invention is to provide a bypass mixing type hot water supply apparatus that can suitably suppress undershoot during re-heating.

In order to achieve the above object, the invention described in claim 1 is a heat exchanger heated by a burner in a combustion chamber, an inlet pipe connected to the heat exchanger for supplying tap water, and a heat exchanger. A hot water outlet pipe connected to the heated hot water pipe, a bypass pipe connected between the incoming water pipe and the hot water outlet pipe to bypass the heat exchanger, and a flow rate control means capable of controlling the flow rate through the bypass pipe; The inner cylinder temperature detecting means for detecting the inner cylinder temperature, which is the temperature at the exit from the combustion chamber in the tapping pipe, and the operation of the flow rate control means according to the inner cylinder temperature obtained by the inner cylinder temperature detecting means. A hot water supply apparatus comprising: a control means for controlling, wherein the control means reduces the flow rate flowing through the bypass pipe by the flow rate control means in accordance with a predetermined decrease gradient of the inner trunk temperature. is there.
According to a second aspect of the present invention, in the configuration of the first aspect, when the control means reduces the flow rate flowing through the bypass pipe and then the inner cylinder temperature starts to rise, the control means bypasses with a time constant. The flow rate flowing through the pipe is gradually increased.

According to the first aspect of the present invention, since the flow rate flowing through the bypass pipe is reduced by the flow rate control means in accordance with the predetermined lowering gradient of the inner cylinder temperature, the undershoot at the time of re-bathing is suitably performed. It becomes possible to suppress.
According to the second aspect of the present invention, in addition to the effect of the first aspect, a rapid increase in the amount of bypass water when the inner trunk temperature rises is suppressed, and a decrease in the hot water temperature is suppressed.

It is the schematic of a hot-water supply apparatus. It is a flowchart of mixing control. It is a flowchart of the calculation method of a differential FB bypass rate. It is a graph which shows the change of the position of the inner trunk temperature at the time of re-bathing, a tapping temperature, and a mixing motor, respectively.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing an example of a bypass mixing type hot water supply apparatus. The hot water supply apparatus 1 forms a combustion chamber with an air supply fan (not shown) in the appliance body, and a fuel is formed inside the combustion chamber. A burner 2 that combusts a mixed gas of gas and primary air from an air supply fan is provided, and a heat exchanger 5 that is heated by the combustion of the burner 2 and that connects a water inlet pipe 3 and a hot water outlet pipe 4 is provided. The gas pipe 6 to the burner 2 is provided with an original solenoid valve 7, a gas proportional valve 8, and a main solenoid valve 9, and each valve can be controlled by a controller (not shown) as control means.

  Further, a bypass pipe 10 that bypasses the heat exchanger 5 is connected between the water inlet pipe 3 and the hot water outlet pipe 4, and the water inlet pipe is located upstream of the connection portion of the water inlet pipe 3 with the bypass pipe 10. 3, a water throttle motor 11 that controls the amount of water flowing through the water inlet 3, a water flow sensor 12 that detects the water flow in the water inlet pipe 3, and a water inlet thermistor 13 that detects the water temperature in the water inlet pipe 3. A mixing motor 14 is provided as a flow rate control means for controlling the amount of water to the bypass pipe 10 and is electrically connected to each controller. On the other hand, the hot water discharge pipe 4 has hot water on the downstream side of the connection portion between the inner pipe thermistor 15 serving as an inner cylinder temperature detecting means for detecting the inner cylinder temperature, which is the temperature at the exit from the combustion chamber, and the bypass pipe 10. A hot water thermistor 16 for detecting the temperature is provided, and each is electrically connected to the controller.

  When the hot water supply device 1 configured as described above opens a hot water tap (not shown) connected to the hot water discharge pipe 4 and allows water to pass through the appliance, and the signal obtained from the water flow sensor 12 confirms the water passing through the appliance. When the difference between the incoming water temperature obtained from the incoming water thermistor 13 and the set temperature set by a remote controller (not shown) is equal to or higher than a predetermined temperature (for example, 10 ° C.), the controller operates the water throttle motor 11 from the specified water amount. The position is reduced by a predetermined amount. If the temperature difference between the two does not exceed the predetermined temperature, the water squeezing motor 11 is set to the position of the specified water amount. Thereafter, the air supply fan is rotated to perform pre-purge, the original solenoid valve 7, the gas proportional valve 8 and the main solenoid valve 9 are opened to supply gas to the burner 2, and the igniter (not shown) is operated to ignite the burner 2. Take control.

  Thereafter, the controller continuously changes the gas amount by controlling the opening of the gas proportional valve 8 according to the difference between the hot water temperature detected by the hot water thermistor 16 and the set temperature set by the remote controller. The hot water temperature control is performed so that the temperature coincides with the set temperature, and the target bypass rate is set by controlling the mixing motor 14 so that the inner cylinder temperature detected by the inner cylinder thermistor 15 becomes a predetermined target temperature. The mixing control for setting the target bypass rate will be described based on the flowchart of FIG.

First, this mixing control is performed every 0.25 seconds (S2) after the water flow sensor 12 is turned on and water passing through the appliance is confirmed (S1).
Next, in S3, the FF bypass rate is calculated. This FF bypass rate is calculated by the following equation (1).
FF bypass rate = (inner trunk target temperature−set temperature) / (inner trunk target temperature−incoming water temperature) (1)

  Next, in S4, an offset bypass rate is calculated. This offset bypass rate is a correction value of the bypass rate that corrects the difference when there is a difference between the default center value and the actual value in the relationship between the step position of the mixing motor 14 and the bypass rate. The aim is to obtain an appropriate bypass rate when both the bypass rate and the differential FB bypass rate are zero.

Next, in S5, the FB bypass rate is calculated. This FB bypass rate is a correction value of the bypass rate based on the tapping temperature, and is calculated by the following equation (2). α is a constant.
FB Bypass Rate (Tempered Water Temperature-Set Temperature) x α / (Inner Body Target Temperature-Incoming Water Temperature) (2)
In S6, the differential FB bypass rate is calculated. This differential FB bypass rate is determined as described later in accordance with the change (slope) of the inner trunk temperature.
Finally, in S7, the target bypass rate is calculated by adding the calculated FF bypass rate, offset bypass rate, FB bypass rate, and differential FB bypass rate.

FIG. 3 is a flowchart showing a method for calculating the differential FB bypass rate. First, in S10, the inclination of the inner body temperature is obtained. This inclination is obtained by obtaining the difference between the detected inner cylinder temperature and the previous inner cylinder temperature stored in the previous control. The inner cylinder temperature obtained in this way is stored in S11 as the previous inner cylinder temperature to be used next time.
Next, in S12, it is determined whether or not the inclination of the inner body temperature obtained in S10 exceeds −0.1 ° C., that is, whether or not there is a tendency to decrease. Here, if the inclination exceeds −0.1 ° C., the inclination of the inner trunk temperature is set to 0 in S13 because it is not a decreasing tendency. On the other hand, if the inclination does not exceed −0.1 ° C., the differential FB bypass rate is calculated by the following equation (3) in S14 because it is in a decreasing tendency.
Differential FB bypass rate = Inner trunk temperature gradient x 30 / (Inner trunk target temperature-Incoming water temperature) (3)

In the determination in S15, it is determined whether or not the previous differential FB bypass rate calculated and stored last time is lower than the current differential FB bypass rate obtained in S14. If the previous differential FB bypass rate is not lower than the current differential FB bypass rate, the current differential FB bypass rate is set as the differential FB bypass rate and stored as the previous differential FB bypass rate to be used next time in S17. On the other hand, if the previous differential FB bypass rate is lower than the current differential FB bypass rate, the differential FB bypass rate is corrected by the following equation (4) in S16. This is to obtain a smoothed differential FB bypass rate using the previous differential FB bypass rate and the current differential FB bypass rate.
Differential FB bypass rate = (previous differential FB bypass rate × m + differential FB bypass rate × n) / (m + n) (where m> n) (4)
Thus, the differential FB bypass rate obtained in S14 or S16 is used for calculation of the target bypass rate in FIG.

Here, m = 14 and n = 1 will be described specifically with numerical values. The set temperature is 40 ° C., the tapping temperature is 42 ° C., the incoming water temperature is 10 ° C., the inner trunk target temperature is 60 ° C., the inner trunk temperature slope is −0. Assuming that the previous differential FB bypass rate is −0.18 at 2 ° C., first, the FF bypass rate is (60−40) / (60−10) = 0.40 from the above equation (1).
The offset bypass rate is assumed here to be 0, assuming that the relationship between the step position of the mixing motor 14 and the bypass rate does not differ between the default center value and the actual value.
Next, the FB bypass rate is (42−40) × 0.5 / (60−10) = 0.02 from the above equation (2).

Then, the differential FB bypass rate is −0.2 × 30 / (60−10) = − 0.12 from the above equation (3). However, since this value exceeds the previous differential FB bypass rate (−0.18), the differential FB bypass rate is −0.18 × 14 + (− 0.12) × 1 from the above equation (4). /15=−0.176.
Therefore, the target bypass rate is 0.40 + 0.00 + 0.02 + (− 0.176) = 0.244.

FIG. 4 is a time chart showing changes in the inner trunk temperature, the tapping temperature, and the position of the mixing motor 14 during re-bathing. A is the inner trunk temperature, B is the tapping temperature, and C is the position of the mixing motor 14. Yes. Note that the position of the mixing motor 14 is the valve closing side and the bottom is the valve opening side.
In FIG. 4, when the hot-water tap is opened at time point t1 and the hot water is discharged again, the inner trunk temperature A suddenly rises during the post-boiling time t1-t2. Since the differential FB bypass rate is also 0, the target bypass rate calculated in FIG. 2 is increased.

Thereafter, when the inner cylinder temperature A decreases from the time point t2, the slope of the inner cylinder temperature A is detected, so that the differential FB bypass rate is obtained in S6 of FIG. 2, and the target bypass rate gradually decreases (t2-t3). In the meantime, the mixing motor 14 is gradually throttled). Accordingly, the amount of water in the bypass pipe 10 mixed with the water in the tap water pipe 4 is reduced, and a decrease in the hot water temperature is suppressed.
In addition, since the differential FB bypass rate becomes smaller than the previous value as the gradient of the inner body temperature gradually increases, the differential FB bypass rate is a numerical value calculated in S14 of FIG.

  Next, when the inner body temperature A starts to increase from time t3 and the differential FB bypass rate calculated in S14 exceeds the previous differential FB bypass rate in the determination of S15 in FIG. 3, it is smoothed in S16. A differential FB bypass rate is calculated. That is, even if the differential FB bypass rate is suddenly opened, the value changes at a ratio of 14: 1. Therefore, the mixing motor 14 does not open suddenly, and the time constant between t3 and t4 is set. It will gradually open with you. Therefore, a rapid increase in the amount of bypass water is suppressed, and a decrease in the hot water temperature B is suppressed.

  Thus, according to the hot water supply apparatus 1 of the said form, the heat exchanger 5 heated by the burner 2 within a combustion chamber, the inlet pipe 3 connected to the heat exchanger 5, and supplying tap water, and heat exchange A hot water outlet pipe 4 connected to the water heater 5 for discharging heated water, a bypass pipe 10 connected between the incoming water pipe 3 and the hot water outlet pipe 4 to bypass the heat exchanger 5, and a flow rate flowing through the bypass pipe 10 A mixing motor 14 capable of controlling the inner cylinder, an inner cylinder thermistor 15 for detecting the inner cylinder temperature at the exit from the combustion chamber in the tapping pipe 4, and the mixing motor 14 according to the inner cylinder temperature obtained by the inner cylinder thermistor 15. And a controller for controlling the operation of the bypass pipe 1 by the mixing motor 14 in accordance with the decreasing gradient of the inner cylinder temperature obtained by the inner cylinder thermistor 15. And to reduce the flow rate through the. Therefore, the undershoot at the time of re-heating can be suitably suppressed.

  In particular, here, the controller reduces the flow rate through the bypass pipe 10 and then gradually increases the flow rate through the bypass pipe 10 with a time constant when the inner cylinder temperature starts to rise. Therefore, a rapid increase in the amount of bypass water when the inner body temperature rises is suppressed, and a decrease in the tapping temperature is suppressed.

  The calculation of each bypass rate is not limited to the above-described form, and the design can be changed as appropriate. The present invention can be applied even if the structure of the hot water supply device itself is provided with a bath tub (bath heat exchanger). is there.

  1 .... Hot water supply equipment, 2 .... Burner, 3 .... Inlet pipe, 4 .... Hot water pipe, 5 .... Heat exchanger, 6 .... Gas pipe, 7 .... Original solenoid valve, 8 .... Gas proportional valve, 9 .... Main solenoid valve, 10 .... Bypass pipe, 13 .... Water-filled thermistor, 14 .... Mixing motor, 15 .... Inner body thermistor, 16 .... Hot water thermistor.

Claims (2)

A heat exchanger heated by a burner in the combustion chamber, a water inlet pipe connected to the heat exchanger for supplying tap water, a hot water outlet pipe for discharging hot water connected to the heat exchanger, A bypass pipe connected between the entry water pipe and the hot water pipe and bypassing the heat exchanger; flow rate control means capable of controlling a flow rate flowing through the bypass pipe; and an outlet of the hot water pipe from the combustion chamber An inner cylinder temperature detecting means for detecting an inner cylinder temperature, which is a temperature at the same time, and a control means for controlling the operation of the flow rate control means in accordance with the inner cylinder temperature obtained by the inner cylinder temperature detecting means. A water heater,
The said control means reduces the flow volume which flows through the said bypass pipe by the said flow volume control means according to the predetermined fall gradient of the said inner trunk temperature, The hot water supply apparatus characterized by the above-mentioned.   The control means reduces the flow rate flowing through the bypass pipe and then gradually increases the flow rate flowing through the bypass pipe with a time constant when the inner cylinder temperature starts to rise. The hot water supply apparatus according to claim 1.

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