Water heater

Abstract

To provide a water heater having an instant water boiling function which can accurately detect a start of the use of the heated water during an instant water heating operation.SOLUTION: When a fluid temperature decreases during water heating stop, an instant water heating operation is executed for heating the fluid in an instant hot water circulation path formed by an operation of a circulation pump 80 using a heat exchanger 40. During an instant water heating operation, a controller 10 executes a flow rate constant control for adjusting a rotational speed of a circulation pump 80 so as to maintain a total flow rate Qt of a water heater 1A at a constant level based on a flow rate detection value Qf by a flow rate detector 75. During an instant water heating operation, the controller 10 detects the use of hot water at a hot water destination according to a decrease in rotation speed of the circulation pump 80 under the flow rate constant operation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a water heater, and more particularly to a water heater having an instant hot water operation function.

Background Art

[0002] As one type of water heater, there is a so-called one having an instant hot water operation function that outputs hot water at an appropriate temperature immediately after the start of hot water supply even after the hot water supply has been stopped for a long time. In order to realize the instant hot water operation, it is necessary to operate the circulation pump even during the hot water supply stop (standby) to form a circulation flow path via the heat source.

[0003] In a water heater having an instant hot water operation function, when the use of hot water is started by opening a hot water tap or the like during the instant hot water operation, it is required to stop the circulation pump and return to the normal hot water supply operation. That is, a problem is how to detect the use of hot water in a state where a flow rate is generated in the water heater by the operation of the circulation pump.

[0004] Japanese Patent No. 3171979 (Patent Document 1) describes a technique for determining the hot water discharged from a hot water tap based on the detected flow rate of a flow rate detector provided in a circulation circuit excluding the return pipe in a circulation heat-insulating type water heater having an instant hot water operation function. In particular, it is described that the hot water discharged during the instant hot water operation is detected by setting different flow rate values (determination flow rates) for determining the use of hot water between the operating state and the stopped state of the circulation pump.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the hot water supply device in Patent Document 1 only describes the operation of the circulation pump during instant hot water operation as being controlled to start and stop. Therefore, there is concern that the flow rate may be higher or lower than the appropriate value depending on the influence of individual differences in the circulation pump, differences in conditions (piping resistance, etc.) at the installation location of the hot water supply device, changes in the pipe condition over time, etc. In such cases, the method in Patent Document 1, which directly compares the flow rate detection value with the judgment value, may reduce the accuracy of detecting hot water use during instant hot water operation.

[0007] The present invention has been made to solve such problems, and an object of the present invention is to accurately detect the start of hot water use during instant hot water operation in a hot water supply device having an instant hot water operation function. [Means for solving the problem]

[0008] In one aspect of the present invention, a water heating device for supplying hot water to a hot water supply destination is provided. The water heating device includes a heating mechanism, a first path, a second path, an instantaneous hot water circulation path, a flow detector, and a controller. The heating mechanism heats a flowing fluid. The first path introduces the fluid into the heating mechanism in response to hot water use at the hot water supply destination. The second path outputs the fluid heated by the heating mechanism to the hot water supply destination. The instantaneous hot water circulation path is formed in response to operation of a circulation pump during instantaneous hot water operation executed to increase the temperature of the fluid while hot water supply at the hot water supply destination is stopped. The instantaneous hot water circulation path includes a third path connected to the first path at a first connection point and connected to the second path at a second connection point, and a path from the first connection point to the second connection point, via the heating mechanism, of the first path and the second path. The flow detector is disposed at a portion of the first path closer to the heating mechanism than the first connection point, or at a portion of the second path closer to the heating mechanism than the second connection point. The controller performs constant flow control to adjust the rotation speed of the circulation pump so as to maintain the total flow rate of the hot water supply device at the flow command value based on the flow rate detection value of the flow rate detector during the instant hot water supply operation. Furthermore, the controller detects the use of hot water at the hot water supply destination when the rotation speed falls below a judgment value under the constant flow rate control. Effect of the Invention

[0009] According to the present invention, during the instant hot water operation, by controlling the total flow rate to be constant by adjusting the rotational speed of the circulation pump, it is possible to detect the use of hot water at the hot water supply destination based on the decrease in the rotational speed of the circulation pump.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

[0012] FIG. 1 is a block diagram for explaining the configuration of the hot water supply apparatus 1A according to the present embodiment. Referring to FIG. 1, the water heater 1A has a water inlet port 11 connected to the water inlet pipe 110, a hot water outlet port 12 connected to the hot water outlet pipe 120, and a circulation port 13 connected to the circulation pipe 130. Further, the water heater 1A includes a controller 10, a water inlet path 20, a check valve 21, a bypass path 22, a circulation path 23, a hot water outlet path 25, a combustion mechanism 30, a heat exchanger 40, a circulation pump 80, and a flow rate adjustment valve 90, which are housed in the housing 100.

[0013] The water inlet path 20 is formed between the water inlet port 11 and the input side (upstream side) of the heat exchanger 40 via the check valve 21. The combustion mechanism 30 is typically composed of a burner that generates heat by burning gas, oil, or the like.

[0014] The heat exchanger 40 uses the heat generated by the combustion mechanism 30 to heat the low-temperature water (fluid) flowing through the water inlet path 20 and raise its temperature. The combustion mechanism 30 and the heat exchanger 40 constitute an embodiment of the "heating mechanism".

[0015] The hot water outlet path 25 is formed between the output side (downstream side) of the heat exchanger 40 and the hot water outlet port 12. The bypass path 22 connects between the water inlet path 20 and the hot water outlet path 25 without passing through the heat exchanger 40. The bypass path 22 is arranged to connect a part downstream of the connection point 27 with the circulation path 23 on the upstream side (input side) of the heat exchanger 40 (the arrangement part of the flow rate adjustment valve 90 in FIG. 1) and a part upstream of the connection point 125 on the downstream side (output side) of the heat exchanger 40 (connection point 26). By controlling the opening degree of the flow rate adjustment valve 90 by the controller 10, the ratio of the flow rate of the heat exchanger 40 to the flow rate of the bypass path 22 (bypass flow rate ratio) is adjusted.

[0016] In such a bypass configuration, a part of the low-temperature water bypasses the heat exchanger 40 and remains unheated. It is mixed downstream of the heat exchanger 40, and thus hot water at an appropriate temperature is supplied from the hot water outlet port 12. As a result, the output temperature from the heat exchanger 40 (heating mechanism) can be increased, which is advantageous for suppressing the drain generated when the exhaust gas of the combustion mechanism 30 is cooled on the surface of the heat exchanger 40. Also, by controlling the bypass flow rate ratio, it is possible to control the hot water temperature to the set hot water supply temperature, thereby improving the responsiveness of the temperature control.

[0017] The circulation path 23 is formed between the circulation port 13 and the water inlet path 20 (connection point 27). A circulation pump 80 is inserted and connected to the circulation path 23. Alternatively, the circulation pump 80 may be inserted and connected to the circulation pipe 130 outside the housing 100. The operation and stop of the circulation pump 80 are controlled by the controller 10.

[0018] In the hot water supply device 1A of FIG. 1, the water inlet pipe 110 and the water inlet path 20 form a "first path" for introducing the fluid into the heating mechanism (heat exchanger 40), and the connection point 27 with the circulation path 23 corresponds to the "first connection point". Similarly, the hot water outlet path 25 and the hot water outlet pipe 120 form a "second path" for leading the fluid heated by the heating mechanism (heat exchanger 40) to a hot water supply destination such as the hot water supply destination 200, and the connection point 125 with the circulation pipe 130 corresponds to the "second connection point". Also, the circulation path 23 and the circulation pipe 130 form a "third path".

[0019] A temperature detector 71 is arranged in the water inlet path 20. The temperature detector 71 detects the water inlet temperature Tw before heating by the heat exchanger 40. On the other hand, temperature detectors 72 and 73 are arranged in the hot water outlet path 25. The temperature detector 72 is arranged downstream of the connection point 26 with the bypass path 22 in the hot water outlet path 25 to detect the hot water temperature Th. Meanwhile, the temperature detector 73 is arranged upstream of the connection point 26 to detect the can body temperature Tb corresponding to the output temperature from the heat exchanger 40. Each fluid temperature detected by the temperature detectors 71 to 73 is input to the controller 10.

[0020] The hot water supply device 1A is provided with a flow rate detector 75. For example, the flow rate detector 75 is arranged on the downstream side of a flow rate adjustment valve 90 corresponding to a branch point with the bypass path 22 in the water inlet path 20 so as to detect the flow rate (cylinder body flow rate) to be heated by the heat exchanger 40. The flow rate detection value Qf by the flow rate detector 75 is input to the controller 10.

[0021] When the hot water supply faucet 200 is opened and the hot water supply destination executes hot water supply use, cold water is introduced into the water inlet path 20 by the supply pressure of the cold water. Accordingly, when a flow rate (i.e., cylinder body flow rate) exceeding the minimum operating flow rate (MOQ) is detected by the flow rate detector 75 during the operation switch of the hot water supply device 1A being on, the controller 10 operates the combustion mechanism 30 to start the hot water supply operation. Note that the hot water supply faucet 200 is shown as a representative example of the "hot water supply destination" of the hot water supply device 1A. The hot water supply destination may include a solenoid valve for turning on and off the hot water discharged to a bathtub or the like, and is not limited to a device that is directly opened and closed by a user operation.

[0022] During the hot water supply operation, the high-temperature water heated by the combustion mechanism 30 and the heat exchanger 40 is mixed with the cold water passing through the bypass path 22 and then output from the hot water outlet pipe 120 to the hot water supply faucet 200 via the hot water outlet port 12. During normal hot water supply operation, the controller 10 stops the circulation pump 80 and controls the fluid temperature (hot water outlet temperature Th) detected by the temperature detector 72 to the hot water supply set temperature Tr input to the remote controller 92 (Fig. 2). Specifically, hot water outlet temperature control can be performed by combining control of the heating amount (generated heat amount) by the combustion mechanism 30 and control of the bypass flow rate ratio by the flow rate adjustment valve 90.

[0023] When the hot water supply operation is stopped due to the closing of the hot water tap 200 or the like, the temperature of the fluid remaining in the hot water outlet path 25 and the hot water supply pipe 120 decreases. Therefore, there is a concern that it will take time to supply hot water at an appropriate temperature to the hot water tap 200 after the start of the next hot water supply operation. For this reason, the hot water supply device 1A is provided with an instant hot water operation function for quickly supplying hot water at an appropriate temperature after the start of the hot water supply operation.

[0024] The instant hot water operation is realized by forming an instant hot water circulation path including the heat exchanger 40 (heating mechanism) by operating the circulation pump 80 while the hot water supply use from the above-described hot water tap 200 or the like is stopped. For example, the instant hot water operation can be started in response to the fluid temperature (for example, the can body temperature Tb and / or the hot water outlet temperature Th detected by the temperature detectors 72 and 73) dropping below the instant hot water start determination temperature (for example, set a predetermined temperature lower than the hot water supply set temperature) without hot water supply use during the period when the instant hot water operation mode is turned on by a switch operation or a timer setting.

[0025] The instant hot water circulation path is configured by a loop that returns from the circulation port 13, passes through the circulation path 23, the water inlet path 20 (downstream of the connection point 27), the heat exchanger 40, the hot water outlet path 25, the hot water outlet port 12, and the hot water supply pipe 120 (upstream of the connection point 125), and then returns to the circulation port 13. In this way, the instant hot water circulation path is formed to include the "third path (the circulation path 23 and the circulation pipe 130)" and the path from the connection point 27 to the connection point 125 via the heat exchanger 40 (heating mechanism) among the "first path (the water inlet pipe 110 and the water inlet path 20)" and the "second path (the hot water outlet path 25 and the hot water supply pipe 120)".

[0026] When the above instant hot water circulation path is formed by the operation of the circulation pump 80, the combustion mechanism 30 operates when the flow rate detection value Qf of the flow rate detector 75 (i.e., the can body flow rate) exceeds the MOQ. As a result, the hot water in the instant hot water circulation path is circulated and heated. The instant hot water operation ends when the heating by the combustion mechanism 30 is stopped and the circulation pump 80 is stopped in response to the fluid temperature in the instant hot water circulation path (for example, the incoming water temperature Tw or the outgoing water temperature Th detected by the temperature detector 71 or 72) reaching the instant hot water end determination temperature (for example, the hot water supply set temperature).

[0027] Hereinafter, for the sake of simplicity, it is assumed that during the instant hot water operation, the flow rate adjustment valve 90 is controlled to make the bypass flow rate ratio zero. In this case, it is understood that the total flow rate Qt of the hot water supply device 1A during the instant hot water operation, which is indicated by the sum of the circulation flow rate Qcr of the circulation path 23 due to the operation of the circulation pump 80 and the flow rate Qin introduced into the incoming water path 20 according to the use of hot water supply, passes through the flow rate detector 75 and the heat exchanger 40. Therefore, hereinafter, the flow rate detection value Qf during the instant hot water operation directly indicates the total flow rate Qt of the hot water supply device 1A.

[0028] Even when the bypass flow rate ratio is controlled to be non-zero by the flow rate adjustment valve 90, the total flow rate Qt of the hot water supply device 1A during the instant hot water operation can be calculated using the bypass flow rate ratio obtained from the opening degree of the flow rate adjustment valve 90 and the flow rate detection value Qf (flow rate detector 75).

[0029] If the hot water supply operation is continued with the circulation pump 80 operating, a part of the hot water flow rate from the hot water outlet port 12 will not be supplied to the hot water supply destination. Therefore, during the instant hot water operation, when the use of hot water supply is started by opening the hot water supply faucet 200 or the like, it is preferable to promptly stop the circulation pump 80 and stop the instant hot water operation. For this reason, it is necessary to detect and determine the start of hot water supply during the instant hot water operation.

[0030] As an example, in the water heater 1A, as described in Patent Document 1, after fixing the driving conditions of the circulation pump 80 during the instant hot water operation, the flow rate (circulation flow rate) of the instant hot water circulation path under the driving conditions is estimated, and a determination value for determining the use of hot water in the circulation pump operation state is provided corresponding to the estimated flow rate. However, as described above, there is a concern that the setting accuracy of the determination value may affect the determination accuracy of hot water use.

[0031] On the other hand, as in the comparative example of FIG. 2, it is also possible to add a flow rate detector to detect the use of hot water during the instant hot water operation.

[0032] FIG. 2 is a block diagram for explaining the configuration of the water heater 1♯ according to the comparative example. As shown in FIG. 2, the water heater 1♯ is different from the water heater 1A in FIG. 1 in that it is arranged in the circulation path 23 and further includes a flow rate detector 76 for detecting the circulation flow rate Qcr. The flow rate detection value (circulation flow rate Qcr) of the flow rate detector 76 is input to the controller 10.

[0033] In the water heater 1♯, when there is no hot water use during the instant hot water operation (while the circulation pump 80 is operating) (Qin = 0), the flow rate detection value Qf of the flow rate detector 75 (that is, the total flow rate Qt) and the flow rate detection value Qcr of the flow rate detector 76 are equal. On the other hand, when hot water use occurs during the instant hot water operation (while the circulation pump 80 is operating) and fluid is introduced from the water inlet port 11 (Qin>0), the flow rate detection value Qf (total flow rate Qt) of the flow rate detector 75 becomes larger than the flow rate detection value Qcr of the flow rate detector 76.

[0034] Therefore, it is understood that in the water heater 1♯ according to the comparative example, by comparing the difference (Qf - Qcr) between the flow rate detection values Qf and Qcr of the flow rate detectors 75 and 76 with a predetermined determination value, the presence or absence of hot water use during the instant hot water operation can be determined. On the other hand, in the water heater 1♯, there is a concern about the cost increase due to the additional arrangement of the flow rate detector 76.

[0035] In the water heater 1A according to the present embodiment, in order to accurately detect the use of hot water during the instant hot water operation without the need to additionally arrange a flow rate detector 76 as in FIG. 2 (water heater 1#), the control and determination described below are executed.

[0036] FIG. 3 shows a block diagram for explaining an example of the hardware configuration of the controller 10. Referring to FIG. 3, the controller 10 is typically composed of a microcomputer. The controller 10 includes a CPU (Central Processing Unit) 15, a memory 16, an input / output (I / O) circuit 17, an electronic circuit 18, and a timer 19 for timing. The CPU 15, the memory 16, the I / O circuit 17, and the timer 19 can exchange signals with each other via a bus 14. The electronic circuit 18 is configured to execute predetermined arithmetic processing by dedicated hardware. The electronic circuit 18 can exchange signals with the CPU 15 and the I / O circuit 17.

[0037] The CPU 15 receives output signals (detection values) from each sensor including the temperature detectors 71 to 73 and the flow rate detector 75 through the I / O circuit 17.

[0038] In addition, the CPU 15 receives a signal indicating an operation instruction input to the remote controller 92 through the I / O circuit 17. The operation instruction includes, for example, on / off operations of the operation switch of the water heater 1A, the set hot water temperature, and various time reservation settings (also referred to as "timer settings").

[0039] The CPU 15 generates an operation command for controlling each component device including the combustion mechanism 30 and the circulation pump 80 so that the water heater 1A operates according to the operation instruction. In the present embodiment, the controller 10 receives a detection value of the rotation speed Npm from the circulation pump 80 while outputting a control voltage Vpm for controlling the rotation speed.

[0040] The circulation pump 80 can be configured by a DC motor capable of controlling the rotational speed Npm according to the control voltage Vpm. As an example, by applying a pulse voltage whose pulse width is controlled according to the control voltage Vpm to the circulation pump 80, the rotational speed Npm can be increased or decreased.

[0041] In the water heater 1A, during the instant hot water operation, the use of hot water is detected based on the rotational speed behavior of the circulation pump 80 under the condition of performing constant flow rate control by the circulation pump 80 described below.

[0042] FIG. 4 is a block diagram for explaining the flow rate control by the circulation pump applied during the instant hot water operation of the water heater 1A.

[0043] Referring to FIG. 4, the flow rate control unit 50 includes a change rate learning unit 55 and a pump rotational speed control unit 60. The functions of each of the change rate learning unit 55 and the pump rotational speed control unit 60 can be realized, for example, by software processing in which the controller 10 executes a predetermined program, but it is also possible to use hardware processing by an electronic circuit or a digital circuit in part or in whole.

[0044] Input to the pump rotational speed control unit 60 are the flow rate deviation ΔQt (ΔQt = Qt* - Qt), which is the difference between the total flow rate Qt (Qt = Qf) and the flow rate command value Qt* during the instant hot water operation, and the rotational speed Npm of the circulation pump 80.

[0045] The change rate learning unit 55 learns a change rate Kp defined as the ratio of the change amount (ΔNpm) of the rotational speed Npm of the circulation pump 80 to the change amount (ΔQt) of the total flow rate Qt (flow rate detection value Qf) using the actual values of the rotational speed Npm and the total flow rate Qt of the circulation pump 80.

[0046] FIG. 5 shows a graph showing the relationship between the rotational speed of the flow rate pump and the total flow rate during the instant hot water operation for explaining the change rate learned by the change rate learning unit 55. The horizontal axis of FIG. 5 indicates the rotational speed Npm of the circulation pump 80, and the vertical axis indicates the total flow rate Qt based on the flow rate detection value Qf of the flow rate detector 75 (Qt = Qf).

[0047] In FIG. 5, the relationship between the rotational speed Npm and the total flow rate Qt when there is no hot water supply (Qin = 0) is plotted. Each of the symbols "circle (white)", "circle (black)", and "square (black)" plots the relationship between the rotational speed Npm and the total flow rate Qt in each of the three hot water supply devices 1A with different diameters of the circulation pipe 130 as installation conditions.

[0048] As understood from FIG. 5, in each hot water supply device 1A, the plotted points of the rotational speed Npm and the total flow rate Qt are substantially located on the characteristic lines 101 to 103 indicated by a linear function. That is, it is understood that the ratio (change rate Kp) of the change amount (ΔNpm) of the rotational speed Npm of the circulation pump 80 to the change amount (ΔQt) of the total flow rate Qt, which corresponds to the reciprocal of the slope of the linear function passing through the reference point (Npm0, Qt0), is determined for each hot water supply device 1A depending on installation conditions and the like.

[0049] For example, as part of the operation test during construction at the time of installation of the hot water supply device 1A, the measured values of the change rate Kp and the reference point (Npm0, Qt0) can be obtained from the rotational speed Npm and the total flow rate Qt (flow rate detection value Qf) measured when the circulation pump 80 is operated to perform constant flow rate control (total flow rate Qt). Note that, as understood from the fact that the reference point (Npm0, Qt0) is common among the characteristic lines 101 to 103, it can also be handled as a unique parameter value for each model of the hot water supply device 1A.

[0050] Therefore, in the rate-of-change learning unit 55, during the period when there is no hot water usage during the instant hot water operation, every time the rotational speed Npm is detected, the measured value Kp0 of the rate of change Kp is calculated according to the following formula (1) using the flow rate detection value Qf (total flow rate detection value) at that time and the reference point (Npm0, Qt0) described in FIG. 5.

[0051] Kp0 = (Npm - Npm0) / (Qt - Qt0) …(1) Furthermore, when Kp0 is calculated by formula (1), the rate-of-change learning unit 55 performs learning by exponential smoothing calculation or the like shown in formula (2) to update the rate of change Kp.

[0052] Kp = Kp1 + α(Kp0 - Kp1) …(2) In formula (2), Kp1 represents the current value of the rate of change Kp, and Kp on the left side represents the updated value after learning. The coefficient α (smoothing constant) is set in the range of 0 < α < 1.

[0053] Note that the learned value of the rate of change Kp is not cleared even when the instant hot water operation is once terminated. Therefore, at the start of the instant hot water operation, the value of the rate of change Kp at the end of the previous instant hot water operation is maintained and applied as the initial value.

[0054] Referring to FIG. 4 again, the pump rotational speed control unit 60 controls the total flow rate Qt (flow rate detection value Qf) to the flow rate command value Qt* by adjusting the control voltage Vpm of the circulation pump 80 so that the flow rate deviation ΔQt becomes zero.

[0055] At this time, the pump rotational speed control unit 60 can obtain the rotational speed change amount Npmc of the circulation pump 80 according to the multiplication value of the rate of change Kp from the rate-of-change learning unit 55 and the flow rate deviation ΔQf (Npmc = Kp·ΔQf). Furthermore, the control voltage Vpm can be calculated according to the rotational speed command value Npm* indicated by the sum of the current rotational speed Npm and the rotational speed change amount Npmc.

[0056] Note that the correspondence between the rotation speed command value Npm* and the control voltage Vpm can be determined in advance in the pump rotation speed control unit 60 by a table or a calculation formula. Regarding the table or the calculation formula, an offset or the like may be learned using the error between the rotation speed command value Npm* and the actually detected rotation speed Npm.

[0057] With the control configuration shown in FIG. 4, during the instant hot water supply operation, feedback control for maintaining the total flow rate Qt (flow rate detection value Qf of the flow rate detector 75) at a constant flow rate (flow rate command value Qt*) is executed through adjustment of the rotation speed Npm of the circulation pump 80. Thereby, the total flow rate during the instant hot water supply operation can be optimized without being affected by the solid difference of the circulation pump 80, the condition difference (such as piping resistance) at the installation location of the water heater, the change in the piping state over time, etc. For example, when the total flow rate becomes excessive, there are concerns about problems such as the occurrence of erosion in the piping and the insufficient temperature rise even when maximizing the capacity of the heating mechanism, but such problems can be solved.

[0058] FIG. 6 is a flowchart for explaining the control process related to the instant hot water supply operation in the water heater according to the present embodiment. The control process shown in FIG. 6 is repeatedly activated by the controller 10 when the hot water supply operation stops.

[0059] Referring to FIG. 6, in step (hereinafter simply referred to as "S") 110, the controller 10 determines the start condition of the instant hot water supply operation. S110 includes S111 to S114.

[0060] In S111, it is determined whether the instant hot water supply operation mode is on. The instant hot water supply operation mode is turned on and off, for example, according to the user's switch operation. Alternatively, the on period of the instant hot water supply operation mode may be provided by the user's timer setting or learning of past history. S111 is determined as YES when the instant hot water supply operation mode is on, while it is determined as NO when it is off.

[0061] In S112, it is determined whether or not the hot water supply is stopped by comparing the detected flow rate value Qf with the MOQ. If Qf < MOQ due to the closing of the hot water tap 200 or the like, S112 makes a YES determination and determines that there is no hot water supply (stopped). On the contrary, when hot water or water is output from the hot water supply device 1A and the detected flow rate value Qf ≧ MOQ, S112 makes a NO determination.

[0062] In S113, the detected value of the fluid temperature in the instant hot water circulation path, for example, the hot water outlet temperature Th which is the detected value by the temperature detector 72, is compared with the instant hot water start determination temperature T1. The instant hot water start determination temperature T1 is set lower than the hot water supply set temperature Tr by α [°C] (T1 = Tr - α). For example, α can be set to about 10 [°C]. S113 makes a YES determination if Th < T1, while making a NO determination when Th ≧ T1. Alternatively, the can body temperature Tb may also be compared with a separate determination temperature.

[0063] In S114, the interval time Tint of the instant hot water operation, that is, the elapsed time from the end of the previous instant hot water operation (the change from the operation to the stop of the circulation pump 80), is compared with the determination time Trst. Trst can be set to about 15 minutes, for example. S114 makes a YES determination if Tint > Trst, while making a NO determination when Tint ≦ Trst.

[0064] When all of S111 to S114 make a YES determination, the controller 10 makes a YES determination for S110 and starts the instant hot water operation. On the other hand, when any one of S111 to S114 makes a NO determination, S110 makes a NO determination and the instant hot water operation is not started. Since the determination of S112 is performed, it is understood that the hot water supply is in the "none" state at the start of the instant hot water operation.

[0065] When the instant hot water operation is started, the controller 10 activates the circulation pump 80 by S120. When the instant hot water circulation path is formed by the operation of the circulation pump 80, the controller 10 activates the combustion mechanism 30 in response to the flow rate detection value Qf (cylinder body flow rate) exceeding the MOQ. As a result, for example, the combustion of the burner is turned on and the fluid in the instant hot water circulation path is heated.

[0066] Furthermore, while the circulation pump 80 is operating, the controller 10 executes, by S130, the constant flow rate control (Qf(Qt)=Qt*) by adjusting the rotational speed Npm, which was described with reference to FIG. 4. During the constant flow rate control by S130, the learning (update) of the change rate Kp by the change rate learning unit 55 (FIG. 4) is executed in parallel.

[0067] In S140, the controller 10 monitors the rotational speed Npm of the circulation pump 80 for detecting the use of hot water during the instant hot water operation, and in S150, the controller 10 executes the hot water use determination using the monitored rotational speed Npm.

[0068] In the configuration of FIG. 1, when the use of hot water is started while the constant flow rate control (S130) is being executed during the instant hot water operation, the rotational speed Npm of the circulation pump 80 is adjusted so as to maintain the total flow rate Qt, which is the sum of the flow rate Qin introduced from the water inlet port 11 and the circulation flow rate Qcr passing through the circulation pump 80, at the flow rate command value Qt*. By this constant flow rate control, the rotational speed Npm of the circulation pump 80 is controlled so that the circulation flow rate Qcr decreases as compared with before the start of the use of hot water.

[0069] Therefore, in S150, it is possible to detect the start of the use of hot water based on whether or not the rotational speed of the circulation pump 80 has decreased due to the use of hot water exceeding a predetermined amount Nth while the constant flow rate control during the instant hot water operation is being applied. For example, the predetermined amount Nth can be set to Nth = Kp·Qth using the flow rate Qth (for example, a predetermined flow rate where Qth > MOQ), which is the threshold for detecting the use of hot water, and the change rate Kp.

[0070] For example, the determination in S150 can be executed by comparing the determination value set by the control process shown in FIG. 7 with the rotational speed Npm monitored in S140.

[0071] Referring to FIG. 7, the controller 10 sets, in S200, the determination value used in the previous instant hot water supply operation as the determination value in the current instant hot water supply operation. The initial value of the determination value can be set based on the rotational speed Npm of the circulation pump 80 and the change rate Kp measured in the operation test during construction described above. Specifically, the determination value can be initially set by subtracting a predetermined amount Nth calculated using the change rate Kp measured during the operation test from the actual value of the rotational speed Npm during the operation test. Thereby, the determination value can be set to be lower by a predetermined amount Nth corresponding to the decrease in the rotational speed corresponding to the hot water supply use of the flow rate Qth than the rotational speed Npm when there is no hot water supply use during the instant hot water supply operation.

[0072] Furthermore, the controller 10 waits in S210 until the elapsed time from the start of the instant hot water supply operation (startup of the circulation pump 80) reaches a predetermined time Tini. The predetermined time Tini is set corresponding to the required time until the rotational speed Npm stabilizes under the constant flow rate control after the startup of the circulation pump 80 (for example, Tini = about 20 [seconds]). Alternatively, in the determination of S210, the elapsed time since the flow rate detection value Qf (detection value of the total flow rate Qt) of the flow rate detector 75 reaches the flow rate command value Qt* may be used.

[0073] When the predetermined time Tini has elapsed (YES determination in S210), the controller 10 reads, in S220 and S230, the rotational speed Npm of the circulation pump 80 over a certain time Tset. In S240, it is determined whether the fluctuation of the read rotational speed Npm is within a certain range or less. For example, when the difference between the maximum value and the minimum value of the rotational speed Npm within the certain time Tset is smaller than a predetermined reference value, S240 is determined as YES.

[0074] When the fluctuation of the rotational speed Npm is small (when the determination in S240 is YES), the controller 10 calculates, by S250, the average value of the rotational speed Npm (for a fixed time Tset) read in S220. The calculated average value is used, by S260, for updating the determination value used in the determination of S150. On the other hand, when the fluctuation of the rotational speed Npm is large (when the determination in S240 is NO), the determination value is maintained, by S270, as the current determination value, that is, the determination value (previous value) used in the previous instant hot water supply operation.

[0075] Thereby, the determination value for detecting hot water supply use can be updated according to the actual rotational speed Npm under stable behavior. Specifically, the updated determination value can be set by subtracting the above-mentioned Nth = Kp·Qth from the rotational speed Npm calculated in S250. In this way, the determination value can be updated reflecting the transition of the actual value of the rotational speed Npm when there is no hot water supply use during the instant hot water supply operation. Also, by monitoring the change over time of the determination value or the change rate Kp (learning value) over time, it becomes possible to detect the occurrence of clogging in the instant hot water circulation path and the like.

[0076] Referring again to FIG. 6, when the rotational speed Npm monitored in S140 drops below the determination value set in FIG. 7, the controller 10 determines that there is hot water supply use and makes a YES determination in S160. Thereby, by S190, the instant hot water supply operation is terminated by stopping the circulation pump 80 in response to the start of hot water supply use.

[0077] When it is determined that there is no hot water supply use (when the determination in S160 is NO), the controller 10 further performs a temperature rise determination by S170. For example, in S170, it is determined whether or not the temperature detection value (inlet water temperature) Tw by the temperature detector 71 has reached the hot water supply set temperature Tr* (Tw≧Tr).

[0078] When the temperature detection value (inlet water temperature) Tw reaches the hot water supply set temperature Tr* (when the determination in S170 is YES), the instant hot water supply operation is terminated by S190, similar to when the determination in S160 is YES.

[0079] On the other hand, when the temperature detection value (inlet water temperature) Tw is lower than the hot water supply set temperature Tr* (when the NO determination is made in S170), the instant hot water operation is continued by S180, and the process returns to S130. As a result, when the instant hot water operation is started, the processes of S130 to S180 are repeatedly executed until hot water supply use is detected (when the YES determination is made in S160) or until the fluid temperature in the instant hot water circulation path reaches the hot water supply set temperature Tr* (when the YES determination is made in S170).

[0080] FIG. 8 shows a waveform diagram for explaining an operation example of the instant hot water operation in the hot water supply apparatus according to the present embodiment. The horizontal axis in FIG. 8 is a time axis, and an operation example is shown when the instant hot water operation is started at time t0 and hot water supply use is started at time tx.

[0081] In FIG. 8, the rotation speed Npm (reference numeral 111: dotted line) of the circulation pump 80, the flow rate detection value Qf (reference numeral 112: solid line), the control voltage Vpm (reference numeral 113) of the circulation pump 80, and the flow rate Qcr (reference numeral 114) of the circulation path 23 are shown with respect to the passage of time. Note that the flow rate Qcr was experimentally obtained by arranging a flow rate detector 76 similar to that in the comparative example (FIG. 2). Also, as described above, the flow rate detection value Qf corresponds to the total flow rate Qt.

[0082] As shown in FIG. 8, before time tx, the rotation speed Npm (reference numeral 111) is controlled so that Qf = Qt* while the flow rate detection value Qf (reference numeral 112) and the circulation flow rate Qcr (reference numeral 114) are equal.

[0083] When hot water supply use is started at time tx by opening the hot water supply faucet 200 or the like, the flow rate detection value Qf instantaneously increases due to the introduction of low-temperature water from the water inlet port 11. After time tx, since the Qf constant control (S130) is continuously executed, the control voltage Vpm (reference numeral 113) is decreased to decrease the circulation pump Npm (reference numeral 114) so that the flow rate detection value Qf decreases toward the flow rate command value Qt* equal to the value before time tx.

[0084] Accordingly, the circulation flow rate Qcr (reference numeral 114) will decrease according to the hot water supply usage amount after time tx. As a result, at time ty, the rotational speed Npm of the circulation pump 80 drops below the determination value by dropping below the predetermined amount Nth described above. Thereby, when S160 (FIG. 6) is determined to be YES, hot water supply usage can be detected. Note that, regarding the change rate Kp (Equation (1)) obtained at the time of determination at time ty, the learning error is suppressed by not using it for learning by Equation (2).

[0085] Note that, in FIG. 6, an example of detecting hot water supply usage by directly monitoring the rotational speed Npm of the circulation pump 80 has been described. On the other hand, when the flow rate passing through the circulation pump 80 decreases with the use of hot water supply, it is understood that in Equation (1), the change amount (ΔQt) of the total flow rate Qt with respect to the change amount (ΔNpm) of the rotational speed Npm, that is, the change rate Kp also becomes smaller.

[0086] Therefore, the determination of the presence or absence of hot water supply usage described with reference to FIGS. 6 and 7 can be similarly executed using the calculated value of the change rate Kp by the change rate learning unit 55 at each timing instead of the rotational speed Npm. That is, in S140 (FIG. 6), by monitoring the calculated value of the change rate Kp at that timing, hot water supply usage can be detected when the change rate Kp drops below the predetermined amount Kth.

[0087] In this case, the predetermined amount Kth can be calculated as Kth = Npm0 / Qth using the flow rate Qth which is the above-described threshold value and the rotational speed Npm0 when there is no water supply usage. Also, in the process of FIG. 7, the determination value can be updated using the calculated value of the change rate Kp by the change rate learning unit 55. Regarding the initial setting of the determination value, it can be performed using the rotational speed Npm0 (no hot water supply usage) of the circulation pump 80 and the actually measured value of the change rate Kp during the above-described operation test.

[0088] Then, in S150 (Fig. 6), in response to the change rate Kp monitored in S140 falling below the determination value set in the process of Fig. 7, it can be determined that there is hot water supply use and the hot water supply use can be detected. That is, even by using the change rate Kp, it is possible to indirectly determine the presence or absence of a decrease in the rotation speed of the circulation pump 80 exceeding the above-mentioned predetermined amount Nth, and similarly detect the hot water supply use during the instant hot water operation.

[0089] As described above, according to the hot water supply apparatus according to the present embodiment, during the instant hot water operation, by adjusting the rotation speed Npm of the circulation pump 80, the total flow rate Qt (in Fig. 1, the flow rate detection value Qf of the flow rate detector 75) that reflects the increase in the flow rate due to the hot water supply use can be controlled to be constant. And under the constant flow rate control, based on the decrease in the rotation speed Npm between before and after the hot water supply use at the hot water supply destination, the hot water supply use at the hot water supply destination can be accurately detected. In particular, it is possible to detect the hot water supply use during the instant hot water operation without requiring a flow rate detector 76 additionally arranged exclusively for the instant hot water circulation path as in the comparative example (Fig. 2).

[0090] In the present embodiment, an example in which the flow rate adjustment valve 90 is controlled so that the flow rate of the bypass path 22 is zero, that is, the bypass ratio is zero, during the instant hot water operation has been described. However, as described above, it is possible to calculate the total flow rate Qt during the instant hot water operation using the bypass ratio obtained from the opening degree of the flow rate adjustment valve 90 and the flow rate detection value Qf of the flow rate detector 75. Therefore, even if the bypass flow rate ratio is not zero, or even if the bypass flow rate ratio is not a constant value, it is possible to similarly execute the constant flow rate control of the total flow rate Qt. Therefore, based on the rotation speed Npm (or the change rate Kp) of the circulation pump 80 under which the constant flow rate control is executed without restricting the control of the flow rate adjustment valve 90, the same detection of the hot water supply use is possible.

[0091] Regarding the flow rate detector 75, it can be understood that by arranging it at any location between the connection point 27 (inlet water path 20) and the heat exchanger 40 (heating mechanism), or between the heat exchanger 40 and the connection point 125 (hot water supply pipe 120), the total flow rate Qt that reflects the increase in flow rate (Qin>0) due to hot water usage during the instant hot water operation can be detected.

[0092] Next, a modification of the configuration of the hot water supply device according to the present embodiment will be further described. FIG. 9 shows a block diagram for explaining the configuration of a hot water supply device 1B according to a modification of the present embodiment.

[0093] Referring to FIG. 9, different from the hot water supply device 1A in FIG. 1, the hot water supply device 1B is provided with only an inlet port 11 and an outlet port 12, and a circulation port 13 is not arranged.

[0094] The inlet water pipe 110 that receives the supply of low-temperature water is connected to the inlet port 11 of the hot water supply device 1B and is also connected to the circulation pipe 130. That is, in the hot water supply device 1B, the circulation pipe 130 is connected between the inlet water pipe 110 and the hot water supply pipe 120.

[0095] The circulation pump 80 is, for example, inserted and connected to the circulation pipe 130. The circulation pump 80 may be arranged outside the housing 100 as illustrated in FIG. 9, or may be inserted and connected to the inlet water path 20 inside the housing 100.

[0096] During the hot water supply operation, by stopping the circulation pump 80, a fluid path similar to that of the hot water supply device 1A in FIG. 1 can be formed inside the hot water supply device 1B. Therefore, in the hot water supply device 1B as well, a hot water supply operation similar to that of the hot water supply device 1A can be performed.

[0097] On the other hand, by operating the circulation pump 80, in the hot water supply device 1B as well, an instant hot water circulation path including the heat exchanger 40 (heating mechanism) can be formed in the same manner as the hot water supply device 1A.

[0098] Specifically, a loop that returns to the water inlet port 11 via the water inlet port 11, the water inlet path 20, the heat exchanger 40, the hot water outlet path 25, the hot water outlet port 12, and the hot water outlet pipe 120 (upstream of the connection point 125), the circulation pipe 130, and the water inlet pipe 110 (downstream of the connection point 127) can form an instant hot water circulation path.

[0099] In the water heater 1B of FIG. 9, the water inlet pipe 110 and the water inlet path 20 form a "first path" for introducing fluid into the heating mechanism (heat exchanger 40), and the connection point 127 corresponds to the "first connection point". Similarly, the hot water outlet path 25 and the hot water outlet pipe 120 form a "second path" for leading the fluid after heating in the heating mechanism (heat exchanger 40) to a hot water supply destination such as the hot water faucet 200, and the connection point 125 corresponds to the "second connection point". Also, in FIG. 9, a "third path" is formed by the circulation pipe 130.

[0100] In FIG. 9 as well, it is understood that the instant hot water circulation path is formed to include the "third path (circulation pipe 130)" and the path from the connection point 127 to the connection point 125 via the heat exchanger 40 (heating mechanism) among the "first path (water inlet pipe 110 and water inlet path 20)" and the "second path (hot water outlet path 25 and hot water outlet pipe 120)".

[0101] In FIG. 9 as well, the bypass path 22 is arranged to connect a portion downstream of the connection point 127 with the circulation pipe 130 on the upstream side (input side) of the heat exchanger 40 (the location where the flow rate adjustment valve 90 is arranged in FIG. 1) and a portion upstream of the connection point 125 on the downstream side (output side) of the heat exchanger 40.

[0102] In the water heater 1B as well, since the flow rate detector 75 and the temperature detectors 71 to 73 are arranged in the instant hot water circulation path in the same manner as in the water heater 1A, by performing flow rate constant control of the total flow rate Qt based on the flow rate detection value Qf of the flow rate detector 75, it is possible to detect the use of hot water during instant hot water operation in the same manner as in the water heater 1A.

[0103] Note that, as in the configuration examples of FIGS. 1 and 9, by arranging the flow rate detector 75 between the path bypassed by the bypass path 22, that is, between the water inlet path 20 and the branch point of the bypass path 22 (the location where the flow rate adjustment valve 90 is arranged) and the connection point 26 between the hot water outlet path 25 and the bypass path 22, while the passing flow rate (cylinder body flow rate) of the heat exchanger 40 necessary for MOQ determination can be directly detected, the total flow rate of the entire water supply apparatus can be calculated using the bypass ratio obtained from the opening degree of the flow rate adjustment valve 90.

[0104] On the other hand, when the flow rate detector 75 is arranged between the connection point 27 and the above-mentioned branch point (the location where the flow rate adjustment valve 90 is arranged), or between the connection point 26 and the connection point 125, while the total flow rate of the entire water supply apparatus is directly detected, the cylinder body flow rate can be calculated using the above bypass ratio. In this way, by arranging the flow rate detector 75 between the connection point 27 of the "first path (the water inlet pipe 110 and the water inlet path 20)" and the heat exchanger 40 (heating mechanism), or between the connection point 125 of the "second path (the hot water outlet path 25 and the hot water outlet pipe 120)" and the heat exchanger 40, the total flow rate Qt can be obtained based on the flow rate detection value Qf of the flow rate detector 75 both during the hot water supply operation and the immediate hot water supply operation.

[0105] Note that in the present embodiment, the heat source in the heating mechanism is not limited to the combustion mechanism 30 that heats by fuel combustion, and any heat source can be applied.

[0106] Also, in the present embodiment and its modified examples, although the configuration of the water supply apparatus provided with the bypass path 22 is exemplified, even in a configuration where the bypass path 22 and the flow rate adjustment valve 90 are not arranged, by detecting the same total flow rate Qt by the flow rate detector 75 arranged between the connection point 27 (first path) or the connection point 125 (second path) and the heat exchanger 40 (FIG. 1), or between the connection point 127 (first path) or the connection point 125 (second path) and the heat exchanger 40 (FIG. 9), the detection of water supply usage during the immediate hot water supply operation can be similarly executed.

[0107] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Signs

[0108] 1A, 1B, 1♯ Water supply device, 10 Controller, 11 Water inlet port, 12 Hot water outlet port, 13 Circulation port, 18 Electronic circuit, 20 Water inlet path, 21 Check valve, 22 Bypass path, 23 Circulation path, 25 Hot water outlet path, 26, 27, 125, 127 Connection points, 30 Combustion mechanism, 40 Heat exchanger, 50 Flow control unit, 55 Rate of change learning unit, 60 Pump speed control unit, 71, 72, 73 Temperature detectors, 75, 76 Flow detectors, 80 Circulation pump, 90 Flow regulating valve, 92 Remote controller, 100 Housing, 110 Water inlet pipe, 120 Hot water outlet pipe, 130 Circulation pipe, 200 Water supply faucet, Kp Rate of change, Qcr Circulation flow rate, Qf Flow detection value, Qt* Flow command value, Tb Tank body temperature, Th Hot water outlet temperature, Tini Predetermined time, Tint Interval time, Tr Hot water supply set temperature, Trst Judgment time, Tset Constant time, Tw Water inlet temperature.

Claims

1. A hot water supply device for supplying hot water to a hot water supply destination, A heating mechanism for heating the flowing fluid; A first passage for introducing the fluid into the heating mechanism in response to hot water supply at the hot water supply destination; A second path for leading the fluid heated by the heating mechanism to the hot water supply destination; During an instant hot water operation executed to raise the temperature of the fluid while the hot water supply destination is stopped, an instant hot water circulation path is formed in response to the operation of a circulation pump; The hot water circulation path is a third path connected to the first path at a first connection point and connected to the second path at a second connection point; a path from the first connection point to the second connection point via the heating mechanism, of the first path and the second path; The hot water supply device includes: a flow rate detector disposed at a portion of the first path closer to the heating mechanism than the first connection point, or at a portion of the second path closer to the heating mechanism than the second connection point; The hot water supply device further comprises a controller that performs constant flow rate control during instant hot water operation, adjusting the rotation speed (Npm) of the circulation pump so as to maintain the total flow rate of the hot water supply device at a flow rate command value based on the flow rate detection value of the flow rate detector, and detects the use of hot water at the hot water supply destination when the rotation speed falls below a judgment value under the constant flow rate control.

2. The controller includes: a change rate learning unit that learns a change rate, which is a ratio of an amount of change in the total flow rate to an amount of change in the rotation speed of the circulation pump when the rotation speed of the circulation pump changes during the constant flow rate control; The hot water supply device of claim 1, further comprising a circulation pump control unit that adjusts the rotation speed based on the rate of change obtained by the rate of change learning unit and the deviation between the flow rate detection value and the flow rate command value during the constant flow rate control.

3. The controller includes: Under the constant flow rate control, when the change rate obtained by the change rate learning unit drops below the determination value, it is determined that the rotational speed has dropped, and hot water usage at the hot water supply destination is detected. The hot water supply apparatus according to claim 2.

4. Inside the casing of the hot water supply apparatus, a bypass path is formed so as to bypass the heating mechanism between a portion downstream of the first connection point of the first path and a portion upstream of the second connection point of the second path. The hot water supply apparatus further includes an adjustment valve that controls a ratio between a first flow rate introduced from the first path into the heating mechanism and a second flow rate introduced into the bypass path. The adjustment valve is controlled such that the second flow rate becomes zero during the instant hot water operation. The hot water supply apparatus according to any one of claims 1 to 3.

Images