Water heating system

Abstract

To provide a water heating system capable of appropriately preventing or suppressing an abnormality of high temperature hot water delivery while using a valve gear enabling flow rate control in a predetermined temperature control range mode and flow rate control range mode as hot water flow rate control means.SOLUTION: A valve gear A of a water heating system WH can sequentially execute flow rate control in a temperature control range mode capable of controlling a hot water delivery temperature to outside by changing a mixed flow rate of heated hot water from a heat exchanger 11 and bypass hot water and in a flow rate control range mode capable of controlling a total flow rate of hot water flowing in the valve gear so that a flow rate of the heated hot water is changed while a flow rate of bypass hot water is maintained to a predetermined minimum flow rate or lower as a control mode, in a process in which a rotating angle of a motor drive shaft 8 for valve motion changes between predetermined first angle α1 and second angle α2. When a first condition where an outlet side temperature Tout of the heat exchanger 11 is higher than a predetermined reference temperature Ta is satisfied, change from the temperature control range mode and a boundary between the temperature control range mode and the flow rate control range mode to the flow rate control range mode is prohibited.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hot water device such as a water heater. [Background technology]

[0002] A specific example of a water heating device is described in Patent Document 1. The hot water device described in this document is equipped with a heat exchanger capable of heating hot water using a burner, and the inlet and outlet channels connected to the inlet and outlet sides of the heat exchanger, respectively, are interconnected via a bypass channel. This makes it possible to flow heated hot water heated by the heat exchanger through the outlet channel, while mixing this heated hot water with unheated bypass hot water flowing through the bypass channel. The flow rates of the heated hot water and bypass hot water can be changed using, for example, two flow control valves (a heat exchanger flow control valve and a bypass flow control valve), making it possible to set the temperature of the mixed hot water to or approach a desired target hot water supply temperature (target hot water outlet temperature).

[0003] However, the above-mentioned conventional techniques have the following problems to be solved.

[0004] Specifically, specific examples of valve devices include the valve devices described in Patent Documents 2 and 3, which may be used in place of the two flow control valves of the hot water heater described above. More specifically, the valve devices described in Patent Documents 2 and 3 are so-called three-way valves. They can be used as a mixing valve, with heated hot water heated by a heat exchanger and unheated bypass hot water flowing into the first and second ports of the valve device, and with the mixed hot water flowing out of the third port. The control modes of the valve device include a temperature adjustment range mode and a flow control range mode. The temperature adjustment range mode is a control mode that adjusts the temperature of the hot water discharged to the outside by changing the mixed flow rate ratio of the heated hot water and the bypass hot water. The flow control range mode is a control mode that adjusts the flow rate of the heated hot water discharged to the outside by changing the flow rate of the heated hot water while maintaining the flow rate of the bypass hot water at a predetermined minimum flow rate. This configuration allows the total number of valve devices (flow control valves) used in the hot water heater to be reduced, thereby simplifying the overall configuration of the hot water heater and reducing manufacturing costs.

[0005] However, the above-mentioned valve device cannot simultaneously adjust the temperature of hot water and the overall flow rate. Therefore, if, for example, a post-boiling phenomenon occurs in the heat exchanger (a phenomenon in which hot water in the heat exchanger becomes hot due to residual heat after the hot water supply device is turned off), and high-temperature hot water flows out of the heat exchanger into the hot water outlet, or there is a risk of this happening, if the valve device is set to the flow rate adjustment range mode, it becomes difficult to appropriately and quickly lower the temperature of the high-temperature hot water. This could result in high-temperature hot water being discharged to the hot water supply destination. It is necessary to appropriately prevent this risk. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3674014 [Patent Document 2] Patent No. 5004674 [Patent Document 3] Patent No. 3812614 [Patent Document 4] Japanese Patent Application Publication No. 10-300208 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention was devised under the circumstances described above, and its objective is to provide a hot water device that can appropriately prevent or suppress the discharge of high-temperature hot water, while using a valve device that can control the flow rate in a predetermined temperature adjustment range mode and flow rate adjustment range mode as a hot water flow rate control means. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following technical solutions.

[0009] The hot water device provided by the present invention comprises a water inlet passage and a hot water outlet passage connected respectively to the inlet side and outlet side of a heat exchanger for heating hot water, a bypass flow path that bypasses the heat exchanger and connects the water inlet passage and the hot water outlet passage to each other, and is capable of mixing the hot water in the water inlet passage as bypass hot water with heated hot water flowing through the hot water outlet passage, and a valve device that can change the flow rate of the heated hot water flowing through the hot water outlet passage and the flow rate of the bypass hot water flowing through the bypass flow path, and a control mode of the valve device is to change the mixing flow rate ratio of the heated hot water and the bypass hot water as the rotation angle of a motor drive shaft for valve operation changes between a predetermined first angle and a second angle. and a flow rate adjustment range mode in which the total flow rate of hot water flowing through the valve device can be adjusted so that the flow rate of the heated hot water is changed while maintaining the flow rate of the bypass hot water at or below a predetermined minimum flow rate.This hot water device is capable of sequentially performing flow rate control in a temperature adjustment range mode in which the temperature of the hot water discharged to the outside can be adjusted, and a flow rate adjustment range mode in which the total flow rate of hot water flowing through the valve device can be adjusted so that the flow rate of the heated hot water is changed while maintaining the flow rate of the bypass hot water at or below a predetermined minimum flow rate.The hot water device is characterized in that a first condition is set such that the outlet temperature of the heat exchanger is higher than a predetermined reference temperature, and the valve device is configured to implement control mode change regulation in which, when the first condition is met, a change to the temperature adjustment range mode and from the boundary between the temperature adjustment range mode and the flow rate adjustment range mode to the flow rate adjustment range mode is prohibited.

[0010] This configuration provides the following effects. That is, when the first condition is met, that is, the outlet temperature of the heat exchanger is higher than a predetermined reference temperature, and high-temperature hot water is actually flowing out or is likely to flow out of the heat exchanger, the control mode of the valve device is not changed to the flow rate adjustment range mode. Therefore, it is avoided that it becomes difficult to lower the temperature of the hot water due to the valve device being in the flow rate adjustment range mode even though high-temperature hot water is flowing out of the heat exchanger. In the temperature adjustment range mode of the valve device, it is possible to reliably lower the temperature of the high-temperature hot water and appropriately prevent the inappropriate discharge of high-temperature hot water to the outside.

[0011] In the present invention, the predetermined reference temperature is preferably a target outlet hot water temperature, a target outlet temperature of the heat exchanger, or a temperature determined based on these temperatures.

[0012] This configuration is preferable in that it prevents or inhibits hot water that is significantly higher in temperature than the target hot water outlet temperature or the target temperature on the outlet side of the heat exchanger, etc., from being discharged from the hot water device.

[0013] In the present invention, preferably, the second condition is that the cumulative flow rate of the heated hot water in the hot water outlet path from the most recent start of hot water flow to the present time has not reached a predetermined standard cumulative flow rate, and when the second condition is met instead of or in addition to the first condition, the control mode change regulation is implemented, and when both the first and second conditions are no longer met, the control mode change regulation is released.

[0014] This configuration provides the following effects. That is, when the hot water device is turned off from on and the hot water in the heat exchanger is heated to a high temperature by residual heat (post-boiling phenomenon), the hot water device is restarted. When hot water in the heat exchanger flows out into the hot water outlet path due to a malfunction, there is a risk of high-temperature hot water flowing out until all of the hot water in the heat exchanger has flowed out (e.g., when high-temperature hot water remains in the most upstream part of the heat exchanger). With the above configuration, in such a case, when all of the hot water in the heat exchanger has not flowed out, the second condition is met, making it possible to prohibit the valve device from being set to the flow rate adjustment range mode. Therefore, it is possible to thoroughly prevent high-temperature hot water from being discharged due to the after-boiling phenomenon. Furthermore, even if the first condition is not detected to be met, for example due to a temperature sensor failure, there is also the advantage that the second condition can be met to accurately regulate the control mode change. The control mode change regulation is released when both the first and second conditions are not met, so that the control mode change regulation is appropriately avoided from being released inappropriately when there is a possibility of high-temperature hot water being discharged.

[0015] In the present invention, preferably, the third condition is that the time elapsed from the most recent start of hot water flow to the present time has not reached a predetermined reference time, and when the third condition is met instead of or in addition to the first condition, the control mode change restriction is implemented, and when both the first and third conditions are no longer met, the control mode change restriction is released.

[0016] This configuration provides the following effects. In other words, in a situation where the hot water in the heat exchanger is experiencing post-boiling when the hot water device is turned off, if not much time has passed since the hot water device was restarted, the third condition is deemed to be met, and control mode change restrictions can be implemented. Therefore, the valve device is prohibited from being set to the flow rate adjustment range mode before all of the high-temperature hot water in the heat exchanger has flowed out, making it possible to thoroughly prevent the discharge of high-temperature hot water caused by post-boiling. The control mode change regulation is released when both the first and third conditions are not met, so that the control mode change regulation is appropriately avoided from being released inappropriately when there is a possibility of high-temperature hot water being discharged. While the parameter to be measured for the second condition mentioned above is the cumulative flow rate, the parameter to be measured for the third condition is time. Therefore, it is possible to simplify the control.

[0017] In the present invention, preferably, a fourth condition is set as that the outlet temperature of the heat exchanger is in a predetermined unstable state, and when the fourth condition is met instead of or in addition to the first condition, the control mode change restriction is implemented, and when both the first and fourth conditions are no longer met, the control mode change restriction is released.

[0018] With this configuration, when the outlet temperature of the heat exchanger is unstable and there is a possibility that high-temperature hot water will flow out of the heat exchanger, the fourth condition will be met, making it more preferable in terms of preventing high-temperature hot water from flowing out. The control mode change regulation is released when both the first and fourth conditions are not met, so that the control mode change regulation is appropriately avoided from being released inappropriately when there is a possibility of high-temperature hot water being discharged.

[0019] Other features and advantages of the present invention will become more apparent from the following description of the preferred embodiments of the invention, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic explanatory diagram showing an example of a hot water device according to the present invention. [Figure 2] (a) is a side cross-sectional view of a main part showing the valve device of the hot water device of Figure 1, (b) is a side cross-sectional view of a main part of the valve device of the hot water device of Figure 1 at a different location from (a), and (c) is a bottom view of the valve device of the hot water device of Figure 1. [Figure 3] 3(a) is a side view of the main part of the valve body of the valve device shown in FIG. 2, and FIG. 3(b) is a bottom view thereof. [Figure 4] 3(a) is a plan cross-sectional view of a main part of the valve device shown in FIG. 2, (b) is a plan cross-sectional view of a main part of the valve device shown in FIG. 2 at a different location from (a), and (c) is a bottom view of the valve device corresponding to (a) and (b). [Figure 5]4(a) is a cross-sectional view of the valve body rotated by a predetermined angle in the portion shown in FIG. 4(a), (b) is a cross-sectional view of the valve body rotated by a predetermined angle in the portion shown in FIG. 4(b), and (c) is a bottom view of the valve device corresponding to (a) and (b). [Figure 6] 5(a) is a cross-sectional view of the valve body in the state where it has been further rotated by a predetermined angle in the portion shown in FIG. 5(a), (b) is a cross-sectional view of the valve body in the state where it has been further rotated by a predetermined angle in the portion shown in FIG. 5(b), and (c) is a bottom view of the valve device corresponding to (a) and (b). [Figure 7] 3 is an explanatory diagram showing control modes in the valve device of FIG. 2. FIG. [Figure 8] 2 is a flowchart showing an example of an operational processing procedure executed in the hot water device shown in FIG. [Figure 9] 10 is a flowchart showing another example of the operational processing procedure executed in the hot water device shown in FIG. [Figure 10] 10 is a flowchart showing another example of the operational processing procedure executed in the hot water device shown in FIG. [Figure 11] 10 is a flowchart showing another example of the operational processing procedure executed in the hot water device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

[0022] The hot water device WH shown in Figure 1 is configured as a hot water supply device and includes a premixing device 3, a combustion device C (premixing combustion device), a heat exchanger 11, hot and cold water flow paths 40 to 42 described below, a valve device A, a control unit 5, and an outer case 19 that houses these and has a water inlet 43 and a hot water outlet 44.

[0023] The combustion device C is configured by combining a premixing device 3 with a fan 1 and a burner unit 2. The premixing device 3 is a device that generates a mixture (combustible mixture) of air and fuel gas. The mixture is supplied to the burner unit 2 by driving the fan 1. The burner unit 2 is configured such that a perforated plate 21 with multiple vent holes 20 is housed in a case 10, and an ignition plug 22 is attached to it. The mixture passes through the multiple vent holes 20 and is combusted below the perforated plate 21. The combustion gas generated by the burner unit 2 acts on the heat exchanger 11, and hot water passing through this heat exchanger 11 is heated. The heat exchanger 11 includes, for example, primary and secondary heat exchange sections 11A and 11B for sensible heat recovery and latent heat recovery, but is not limited to this. For example, it may also be configured with only the heat exchange section 11A for sensible heat recovery. After passing through the heat exchanger 11, the combustion gas passes through the exhaust duct portion 10a of the case 10 and is discharged to the outside as exhaust gas.

[0024] The water inlet 43 is a portion to which, for example, a water pipe is connected, and unheated hot water is supplied from the outside. The hot water outlet 44 is a portion to which the hot water heated by the heat exchanger 11 is supplied to an external hot water supply destination.

[0025] The hot water flow paths of the water heater WH include a water inlet path 40, a hot water outlet path 41, and a bypass path . Here, the water inlet passage 40 is a hot and cold water flow path from the water inlet 43 to the inlet 11a of the heat exchanger 11. The water inlet passage 40 is provided with a valve device A, a flow rate sensor Sa, and a temperature sensor Sb for detecting the inlet water temperature. The water inlet passage 40 is divided into two flow paths 40a and 40b, located upstream and downstream of the valve device A, respectively.

[0026] The hot water outlet path 41 is a hot water flow path from the outlet 11b of the heat exchanger 11 to the hot water outlet 44. The hot water outlet path 41 is provided with a temperature sensor Sc for detecting the outlet temperature Tout of the heat exchanger 11 (hereinafter referred to as heat exchanger outlet temperature Tout), a temperature sensor Sd for detecting abnormally high temperatures, and a temperature sensor Se for detecting the hot water temperature (outlet hot water temperature) downstream of the connection point of the bypass flow path 42.

[0027] Bypass flow path 42 is a hot water flow path that connects a part of valve device A corresponding to an intermediate point in water inlet path 40 with intermediate point Pa in hot water outlet path 41 so as to bypass heat exchanger 11. A portion of the hot water flowing in water inlet path 40 can pass through bypass flow path 42 and flow into intermediate point Pa in hot water outlet path 41. This allows the heated hot water in hot water outlet path 41 to be mixed with the bypass hot water flowing through bypass flow path 42 to produce temperature-adjusted mixed hot water, which can be discharged from outlet 44.

[0028] The valve device A can change the flow rate Qa of heated water flowing through the hot water outlet passage 41 and the flow rate Qb of bypass hot water flowing through the bypass passage . In Figure 2, the valve device A includes a case 6 having first to third ports P1 to P3, a valve element 7 as a rotary valve element arranged in this case 6, and a drive shaft 8 (motor drive shaft 8) of a motor M for rotating this valve element 7. The motor M is, for example, a stepping motor, and is capable of controlling the rotation angle of the motor drive shaft 8 and the valve element 7.

[0029] In this embodiment, the valve device A is configured to be used as a distribution valve that directs hot water that flows into the third port P3 to flow out to the first and second ports P1 and P2 (see also FIG. 1). The third port P3 is connected to the upstream flow path 40a of the water inlet passage 40, and unheated hot water supplied to the water inlet 43 flows into it. The second port P2 is connected to the downstream flow path 40b of the water inlet passage 40, and the hot water that flows out from this second port P2 is sent to the heat exchanger 11. The first port P1 is connected to a bypass flow path 42, and the hot water that flows out from this first port P1 flows through the bypass flow path 42 and flows into a midpoint Pa of the hot water outlet passage 41.

[0030] In FIG. 2, partition walls 61a to 63a that form openings 61 to 63 for water passage are provided in the first to third ports P1 to P3 of the case 6 at positions close to the valve body 7 inside each of the ports. On the other hand, the valve body 7 is a combination of a first valve body 7A that is approximately cylindrical and has an opening on the side of the third port P3, and a second valve body 7B that is connected to the lower part of the first valve body 7A and rotates in conjunction with the rotation of the first valve body 7A. The peripheral wall of the first valve body 7A is provided with first and second openings 71, 72 extending in the circumferential direction for water passage. The second valve body 7B is provided with a third opening 73 for communication with the third port P3 and a sector-shaped blocking portion 74 in a bottom view (see also FIG. 3). Hot or cold water flows into the third port P3, passes through the third opening 63, and flows into the inside of the valve body 7, then flows from the first and second openings 71, 72 through the openings 61, 62 to the first and second ports P1, P2.

[0031] As shown in FIG. 7, the valve device A can sequentially perform flow control in the temperature adjustment range mode and flow control in the flow rate adjustment range mode by changing the rotation angle of the motor drive shaft 8 and the valve element 7. do.

[0032] More specifically, the rotation angle of the motor drive shaft 8 and the valve element 7 can be changed from a predetermined first angle α1 to a second angle α2 beyond a predetermined boundary angle α3. The angular arrangement of the valve element 7 shown in Figure 4 corresponds to the first angle α1. Figures 5 and 6 correspond to the boundary angle α3 and the second angle α2, respectively.

[0033] When the first angle α1 shown in FIG. 4 is set, the flow rate Qb of the bypass hot water is at a maximum, and the flow rate Qa of the heated hot water flowing through the hot water outlet passage 41 is zero. That is, in this state, the third opening 63 is not blocked by the valve body 7 (second valve body 7B), and hot water and cold water flow into the valve body 7. On the other hand, the communication area between the first opening 71 and the first port P1 is large, and a large amount of hot water and cold water flows from the first port P1 to the bypass flow path 42. The second opening 72 and the second port P2 are not connected, and hot water and cold water do not flow into the heat exchanger 11 from the second port P2.

[0034] The temperature adjustment range mode is between the first angle α1 and the boundary angle α3, and in this temperature adjustment range mode, as the rotation angle of the drive shaft 8 and the valve body 7 is increased, the flow rate Qb of the bypass hot water gradually decreases while the flow rate Qa of the heated hot water flowing through the hot water outlet path 41 gradually increases. That is, as the valve element 7 rotates from the state shown in FIG. 4 in the direction indicated by the arrow Da to the angle shown in FIG. 5, the communication opening area between the first opening 71 and the first port P1 gradually decreases. Therefore, the bypass hot and cold water flow rate Qb gradually decreases. As shown in FIG. 4(a), the first opening 71 extends circumferentially at an appropriate angle θ1, but its vertical width W1 (FIG. 3) narrows as it moves away from the one end 71a. In contrast, the communication area between the second opening 72 and the second port P2 gradually increases. As shown in FIG. 4(b), the second opening 72 extends circumferentially at an appropriate angle θ2, but its vertical width W2 widens as it moves away from the one end 72a. In the configuration shown in Figure 5(a), when the rotation angle of the valve body 7 (and motor drive shaft 8) is at the boundary angle α3, the bypass hot water flow rate Qb becomes zero, but instead it may be configured to be a small amount close to zero (the virtual line part in Figure 7).

[0035] The range from boundary angle α3 to second angle α2 is the flow rate adjustment range mode. In this flow rate adjustment range mode, as the rotation angle of motor drive shaft 8 and valve body 7 is increased, the total flow rate of hot water flowing through valve device A is changed so that the flow rate Qa of heated hot water flowing through hot water outlet path 41 gradually decreases while the flow rate Qb of bypass hot water is maintained below a predetermined minimum flow rate (zero or a small amount close to zero). Eventually, the flow rates Qa and Qb of bypass hot water and heated hot water both become zero. That is, when the valve element 7 reaches the angle shown in Figure 6, the water passage opening 63 is fully closed by the blocking portion 74 of the second valve element 7B, and hot water and cold water no longer flows into the third port P3. As a result, the flow rates Qa and Qb become zero. In the process of the valve element 7 changing from Figure 5 to Figure 6, although the second opening 72 and the second port P2 are connected, the opening area of ​​the water passage opening 63 gradually decreases, and the flow rate of hot water and cold water into the third port P3 and the inside of the valve element 7 decreases, so the flow rate Qa decreases. In the flow rate adjustment range mode, the total flow rate of hot water flowing through the valve device A may be changed while maintaining the ratio of the bypass hot water flow rate to the heated hot water flow rate at the boundary angle α3.

[0036] The control unit 5 is configured using a microcomputer or the like, and executes operation control and data processing of each part of the hot water device WH, as well as operation control of the valve device A. However, details thereof will be described later. A remote control (not shown) installed in the kitchen or bathroom is communicatively connected to the control unit 5. By using this remote control, the user can set the target hot water outlet temperature Ta1 (target hot water supply temperature), etc. can be set appropriately.

[0037] Next, an example of the operation processing procedure of the water heating device WH will be described with reference to the flowchart of Fig. 8. The action of the water heating device WH will also be described.

[0038] First, during normal operation when the hot water heater WH is not supplying hot water, the motor drive shaft 8 and valve element 7 of the valve device A are controlled to be at boundary angle α3 (S1). Next, the hot water supply terminal (not shown) connected to the hot water outlet 44 is opened to start the flow of hot water. When the hot water flow rate of the heat exchanger 11 reaches or exceeds a predetermined minimum operating flow rate (MOQ-ON), and this is detected based on the detection signal of the flow sensor Sa, the burner unit 2 is turned on (S2: YES, S3). This starts the heating of hot water using the heat exchanger 11, and hot water is dispensed from the hot water outlet 44.

[0039] During this hot water supply operation, the control unit 5 causes the valve device A to perform normal control, controlling the flow rate Qa of heated hot water and the flow rate Qb of bypass hot water, so that the temperature of hot water discharged from the outlet 44 reaches the desired target hot water discharge temperature Ta1 (target hot water supply temperature) (S4). The control for setting the discharge temperature to the desired target hot water discharge temperature Ta1 is basically performed in the temperature adjustment range mode. However, there are cases where it is difficult to generate hot water at the target hot water discharge temperature Ta1 even when the burner unit 2 is set to maximum combustion power or a power close to it, for example, because the target hot water discharge temperature Ta1 is significantly higher than the inlet water temperature. In such cases, the valve device A responds by switching to the flow rate adjustment range mode and reducing the overall flow rate.

[0040] Next, during the hot water supply operation, if at least one of the predetermined first and second conditions is met, the control mode change regulation of the valve device A is implemented (S5: YES, S6). Here, the control mode change restriction includes prohibiting a change from the temperature regulation range mode to the flow rate regulation range mode of the valve device A, and also prohibiting a change from the boundary between the temperature regulation range mode and the flow rate regulation range mode to the flow rate regulation range mode.

[0041] The first condition is that the heat exchanger outlet temperature Tout detected by the temperature sensor Sc is higher than a predetermined reference temperature Ta. The reference temperature Ta is, for example, a target outlet heated water temperature Ta1, a target temperature Ta2 on the outlet side of the heat exchanger 11, or a temperature Ta3 determined based on these temperatures Ta1 and Ta2. The outlet side target temperature Ta2 of the heat exchanger 11 is the heat exchanger outlet side temperature that is considered appropriate for making the actual hot water temperature the target hot water temperature Ta1, and is determined by the control unit 5 based on data on the target hot water outlet temperature Ta1 and the inlet water temperature. The temperature Ta3 corresponds to, for example, a temperature obtained by correcting the target hot water outlet temperature Ta1 or the outlet target temperature Ta2 of the heat exchanger 11. As shown by the imaginary line in Figure 7, if the bypass hot water flow rate Qb is not zero when it is at or near the boundary angle α3, a small amount of bypass hot water is mixed with the heated hot water flowing out of the heat exchanger 11, causing a drop in temperature. The outlet target temperature Ta2 and temperature Ta3 of the heat exchanger 11 are set to temperatures that take such circumstances into consideration.

[0042] The second condition is that the cumulative flow rate ΣQa of heated water in the hot water outlet passage 41 from the most recent start of hot water flow to the present time does not reach a predetermined reference cumulative flow rate ΣQth. Here, the integrated flow rate ΣQa is calculated as the cumulative value of the flow rate (flow rate per unit time) detected by the flow rate sensor Sa. The reference integrated flow rate ΣQth is, for example, the volume of the heat exchanger 11 or a value obtained by adding a margin to this volume, and is preferably a value equal to or greater than the volume of the heat exchanger 11.

[0043] The above-described operation control provides the following effects. That is, when the hot water supply device WH is switched from ON to OFF and the hot water in the heat exchanger 11 is heated to a high temperature by residual heat (post-boiling), the burner unit 2 may be driven ON in step S3 to restart the hot water supply device WH. In this case, if the valve device A is set to the flow rate adjustment range mode before all of the high-temperature hot water in the heat exchanger 11 has flowed out, the bypass hot water flow rate Qb cannot be increased to lower the outlet hot water temperature, and there is a risk that the high-temperature hot water in the heat exchanger 11 due to the post-boiling phenomenon will be discharged to the outside from the outlet 44. In contrast, according to this embodiment, when there is a possibility of post-boiling (the first condition is met) or when the entire amount of hot water or water in the heat exchanger 11 or a nearly entire amount of hot water has not yet flowed into the hot water outlet passage 41 (the second condition is also met), the valve device A is not changed to the flow rate adjustment range mode and is maintained in the temperature adjustment range mode. Therefore, it is possible to appropriately adjust the temperature of hot water that is high in temperature due to the post-boiling phenomenon and effectively prevent the discharge of high-temperature hot water caused by the post-boiling phenomenon. If either the first condition or the second condition is met, the control mode change regulation of the valve device A is attempted, thereby more thoroughly preventing the discharge of high-temperature hot water.

[0044] If neither the first nor the second condition is met, the control mode change restriction for the valve device A is released and the valve device A returns to the normal control state (S7: YES, S8). After that, if the inflow water flow rate falls below the minimum operating flow rate (MOQ-OFF), the burner unit 2 is turned off (S9: YES, S10).

[0045] Although not shown in the flowchart of FIG. 8, when at least one of the temperature sensors Sc and Sd detects an abnormally high temperature exceeding a predetermined additional reference temperature (higher than the aforementioned reference temperature Ta), the burner unit 2 is turned off and measures are taken to prevent or suppress the abnormally high temperature of the molten metal from being discharged from the tap port 44. For example, when the valve device A is in the temperature adjustment range mode, the rotational angles of the motor drive shaft 8 and the valve element 7 are set to a first angle α1, and when the valve device A is in the flow rate adjustment range mode, the rotational angles of the motor drive shaft 8 and the valve element 7 are set to a second angle α2. When the valve device A is at the boundary between the temperature adjustment range mode and the flow rate adjustment range mode (boundary angle α3), the rotational angles of the motor drive shaft 8 and the valve element 7 are set to the angle between the first and second angles α1 and α2, whichever is smaller in angle difference from the boundary angle α3.

[0046] The hot water device WH of this embodiment can be configured to execute the operation controls shown in Figures 9 to 11 instead of or in addition to the operation control already described and shown in Figure 8. Note that steps that are the same as or similar to the steps of the operation control shown in Figure 8 are given the same reference numerals, and duplicate explanations will be omitted.

[0047] The operation control shown in FIG. 9 differs from the operation control shown in FIG. 8 in steps S5a and S7a, and in step S5a, it is determined whether the third condition is met in addition to the first condition described above. The third condition is that the elapsed time Tp from the most recent start of hot water flow to the present time has not reached a predetermined reference time Tc. The reference time Tc is preferably the time required for all the hot water in the heat exchanger 11 to completely flow out into the hot water outlet 41, or a time with a margin added thereto.

[0048] In the operational control shown in FIG. 9, when at least one of the first and third conditions is satisfied, the control mode change regulation of the valve device A is attempted, and when both of the conditions are subsequently unsatisfied, the valve device A returns to normal control with the control mode change regulation released (S5a: YES, S6, S7a: YES, S8). According to such operation control, when the hot water in the heat exchanger 11 is in a state where the phenomenon of post-boiling occurs, the valve device A Therefore, as in the case shown in Figure 8, it is possible to effectively prevent high-temperature hot water from being discharged due to the after-boiling phenomenon. The third condition can be easily determined whether it is met or not by monitoring the time.

[0049] The operation control shown in FIG. 10 differs from the operation control shown in FIG. 8 in steps S5b and S7b, and in step S5b, it is determined whether a fourth condition is met in addition to the first condition described above. The fourth condition is that the heat exchanger outlet temperature Tout is in a predetermined unstable state, for example, when the fluctuation range and / or frequency of the heat exchanger outlet temperature Tout during the period from the present time to a predetermined time ago is not within a predetermined range.

[0050] In the operational control shown in FIG. 10, when at least one of the first and fourth conditions is satisfied, the control mode change regulation of the valve device A is attempted, and when at least one of the conditions subsequently fails to be satisfied, the valve device A returns to normal control with the control mode change regulation released (S5b: YES, S6, S7b: YES, S8). Repeated on-off operation of the hot water device WH in a short period of time generates high-temperature hot water in the heat exchanger 11 due to the after-boiling phenomenon, and when this hot water flows out into the hot water outlet passage 41, the heat exchanger outlet temperature Tout tends to become unstable. In such a case, the operational control shown in Figure 10 regulates the change in control mode of the valve device A, so that high-temperature hot water discharge due to the after-boiling phenomenon can be appropriately prevented, as in the cases of Figures 8 and 9. Furthermore, even when there is a risk of high-temperature hot water discharge due to a cause other than the after-boiling phenomenon, there is also the advantage that the high-temperature hot water discharge can be appropriately prevented.

[0051] The operational control shown in FIG. 11 does not judge the second to fourth conditions, but judges only whether the first condition is met, and if the first condition is met, the control mode change regulation of the valve device A is attempted (S5c: YES, S6). In this type of operational control, if the heat exchanger outlet temperature Tout is higher than the reference temperature Ta, the control mode change restriction of the valve device A is implemented. Therefore, it is possible to reliably implement the control mode change restriction of the valve device A not only in cases where there is a risk of high-temperature hot water being dispensed due to the after-boiling phenomenon but also in cases where there is a risk of high-temperature hot water being dispensed due to other phenomena. When the control mode change restriction is implemented and the first condition is no longer met, the valve device A returns to normal control (S7c: YES, S8).

[0052] The present invention is not limited to the above-described embodiment, and the specific configuration of each part of the hot water device according to the present invention can be freely modified in various ways within the intended scope of the present invention.

[0053] In the above-described embodiment, the valve device A is used as a distribution valve provided at the cross-connection point between the water inlet passage 40 and the bypass passage 42, but the present invention is not limited to this. For example, the valve device A can be provided at the cross-connection point (corresponding to intermediate point Pa) between the water outlet passage 41 and the bypass passage 42 and used as a mixing valve that mixes heated water and bypass water.

[0054] As the valve device, instead of the valve device A of the above-described embodiment, it is possible to use a valve device with another configuration, such as that described in Patent Document 2. Furthermore, the valve device is not limited to a rotary type. As for the valve device, there is also a type that can control the flow rate by sliding a spool valve in accordance with the rotation angle of the drive shaft of the motor, as described in Patent Document 3, for example, and such a valve device can also be used. In any case, the specific configuration of the valve device used in the present invention is not important, but the point is that it is configured to be able to sequentially perform flow control in a predetermined temperature adjustment range mode and flow control in a flow rate adjustment range mode. Any valve device may be used.

[0055] Although the water heating device described above is equipped with a premixing burner unit, the burner unit does not have to be of the premixing type. Also, an oil burner type may be used instead of a gas burner type. The hot water device referred to in the present invention is not limited to a hot water supply device, but also includes a concept that includes a device that generates hot water for purposes other than general hot water supply or hot water supply for baths, such as a hot water device for floor heating. [Explanation of symbols]

[0056] WH water heater A valve gear C. Combustion device 11 Heat exchanger 40 Inlet Channel 41 Hot water outlet 42 Bypass flow path 43 Water Inlet 44 Tap 5. Control section

Claims

1. a water inlet channel and a hot water outlet channel connected to the inlet side and the outlet side, respectively, of a heat exchanger for heating hot water; a bypass flow path that bypasses the heat exchanger and connects the water inlet and the hot water outlet, and allows the hot water in the water inlet to be mixed with the heated hot water flowing through the hot water outlet as bypass water; a valve device capable of changing the flow rate of the heated water flowing through the hot water outlet passage and the flow rate of the bypass hot water flowing through the bypass passage; It is equipped with A hot water device capable of sequentially performing flow rate control in the control modes of the valve device, which include a temperature adjustment range mode in which the temperature of hot water discharged to the outside can be adjusted by changing the mixed flow rate ratio of the heated hot water and the bypass hot water while the rotation angle of the motor drive shaft for valve operation changes between a predetermined first angle and a second angle, and a flow rate adjustment range mode in which the total flow rate of hot water flowing into the valve device can be adjusted so that the flow rate of the heated hot water is changed while maintaining the flow rate of the bypass hot water at or below a predetermined minimum flow rate, A first condition is that the outlet temperature of the heat exchanger is higher than a predetermined reference temperature, The valve device is configured to regulate control mode changes so that, when the first condition is met, changes to the temperature adjustment range mode and to the flow rate adjustment range mode from the boundary between the temperature adjustment range mode and the flow rate adjustment range mode are prohibited.

2. The hot water device according to claim 1, The predetermined reference temperature is a target hot water outlet temperature, a target temperature on the outlet side of the heat exchanger, or a temperature determined based on these temperatures.

3. The hot water device according to claim 1, As a second condition, it is determined that the cumulative flow rate of the heated hot water in the hot water outlet path from the most recent start of hot water flow to the present time does not reach a predetermined reference cumulative flow rate, When the second condition is satisfied instead of or in addition to the first condition, the control mode change restriction is implemented, and The hot water device is configured such that the control mode change restriction is released when both the first and second conditions are no longer met.

4. The hot water device according to claim 1, The third condition is that the time elapsed from the most recent start of hot water flow to the present time has not reached a predetermined reference time. When the third condition is satisfied instead of or in addition to the first condition, the control mode change restriction is implemented, and The hot water device is configured such that the control mode change restriction is released when both the first and third conditions are not met.

5. The hot water device according to claim 1, A fourth condition is that the outlet temperature of the heat exchanger is in a predetermined unstable state, When the fourth condition is satisfied instead of or in addition to the first condition, the control mode change restriction is implemented, and The hot water apparatus is configured such that the control mode change restriction is released when both the first and fourth conditions are not met.

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