Water heater

Abstract

To enhance temperature control accuracy in a bypass mixing type water heater.SOLUTION: High-temperature water flowing in can body piping 55 and low-temperature water flowing in bypass piping 60 are mixed and supplied. A hybrid valve 80 is configured to have a first section in which a flow ratio between a flow rate Q1 of the high-temperature water and a flow rate Q2 of the low-temperature water is changed and a second section in which the flow ratio is fixed and a total flow rate Qt is changed, relative to an opening control value. When the total flow rate Qt is a restriction flow rate or less, temperature control in which the hybrid valve 80 is operated in the first section is executed. When the total flow rate Qt is more than the restriction flow rate, flow rate control in which the hybrid valve 80 is operated in the second section is executed. In the temperature control, a heating amount by using a combustion burner 30 is regulated to control a can body temperature Tb to a can body set temperature set so as to lower along with an increase in the total flow rate Qt.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water heater, and more particularly to a water heater of a bypass mixing type that mixes high-temperature water and low-temperature water. [Background technology]

[0002] A bypass mixing type hot water heater is used, which adjusts the outlet hot water temperature by controlling the flow rate ratio between high-temperature water that has passed through a heat exchanger and low-temperature water that has bypassed the heat exchanger.

[0003] Japanese Patent No. 3067498 (Patent Document 1) describes a configuration in which the valve opening of a bypass valve (distribution valve) for controlling the flow ratio of high-temperature water and low-temperature water is controlled by the number of steps of a stepping motor. Patent Document 1 also describes that the number of steps of the stepping motor is set by correcting the target number of steps calculated back from the target flow ratio using a correction number of steps according to a previously obtained reference characteristic relationship between the number of steps (valve opening) in the bypass valve and the flow ratio. The correction number of steps is calculated based on the deviation between the actual flow ratio calculated from the detected temperature and the target flow ratio.

[0004] Furthermore, Japanese Patent No. 4823149 (Patent Document 2) describes an embodiment of a mixing valve that mixes hot water and cold water to output hot water, which also has a function of restricting only the amount of hot water when the water inlet is fully closed. Specifically, the mixing valve in Patent Document 2 has the characteristic of having a first section in which the opening areas of the water inlet and the hot water inlet gradually decrease and increase in conjunction with each other according to the valve opening degree of the mixing valve, and a second section in which the opening area of ​​the hot water inlet changes from a maximum value to a minimum value when the water inlet is fully closed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3067498 [Patent Document 2] Patent No. 4823149 Summary of the Invention [Problem to be solved by the invention]

[0006] It is understood that the mixing valve described in Patent Document 2 has a first section in which the flow rate ratio (mixing ratio) changes depending on the valve opening without affecting the output flow rate from the mixing valve (i.e., the total flow rate of cold water and hot water), and a second section in which the output flow rate from the mixing valve changes depending on the valve opening while the mixing ratio of cold water and hot water is fixed (total amount is hot water).

[0007] Here, assuming a configuration in which the mixing valve of Patent Document 2 is applied to the bypass valve of the hot water heater of Patent Document 1, in temperature control when the mixing valve operates in the first section, the outlet hot water temperature can be controlled by adjusting the flow rate ratio, so the temperature of the high-temperature water does not directly affect the outlet hot water temperature. In contrast, in temperature control when the mixing valve operates in the second section, the flow rate ratio is fixed, so the temperature of the high-temperature water directly affects the outlet hot water temperature. This raises concerns that the accuracy of temperature control may decrease when switching from temperature control in which the mixing valve operates in the first section to temperature control in which the mixing valve operates in the second section.

[0008] The present invention has been made to solve these problems, and an object of the present invention is to improve the accuracy of temperature control in a water heating apparatus using a bypass mixing type that uses a control valve having a region in which the flow rate ratio does not change in response to changes in the control value. [Means for solving the problem]

[0009] In one aspect of the present invention, a hot water supply device is provided. The hot water supply device mixes low-temperature water and high-temperature water and includes a heating section, a first flow path, a second flow path, a flow detector, a control valve, and a control device. The heating section heats low-temperature water and outputs high-temperature water. The first flow path passes low-temperature water through the heating section. The second flow path passes low-temperature water without passing through the heating section. The flow detector is disposed in the first flow path or the second flow path. The control valve is connected to the first flow path and the second flow path and controls the flow rates of the first flow path and the second flow path. The control device sets a control value of the control valve and an amount of heating by the heating section in order to control the outlet temperature of the hot water after mixing of the low-temperature water and the high-temperature water to a hot water supply setting temperature. The control valve is configured so that there are a first section in which the flow rate ratio of the first flow path and the second flow path changes without affecting the total flow rate of the first flow path and the second flow path, and a second section in which the flow rate ratio is fixed while the total flow rate decreases in response to a change in the control value. When the total flow rate obtained based on the detected flow rate of the flow detector is greater than a limit flow rate set corresponding to the maximum heating amount of the heating section, the control device sets the control value of the control valve within a second interval so that the total flow rate is equal to or less than the limit flow rate and controls the heating amount of the heating section to control the outlet temperature to the hot water supply set temperature, while when the total flow rate obtained based on the detected flow rate of the flow detector is equal to or less than the limit flow rate, the control device controls the heating amount of the heating section to control the high-temperature water temperature to the boiler body set temperature and sets the control value of the control valve within a first interval corresponding to the flow rate ratio for controlling the outlet temperature to the hot water supply set temperature. The boiler body set temperature is set so that there is a flow rate range in which the boiler body set temperature decreases as the total flow rate increases and approaches the limit flow rate. Effect of the Invention

[0010] According to the present invention, it is possible to improve the accuracy of temperature control in a hot water supply device of a bypass mixing type that employs a control valve having a region in which the flow rate ratio does not change in response to a change in the control value. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a water heater according to an embodiment of the present invention. [Diagram 2] 2 is a conceptual diagram illustrating input and output of a hybrid valve applied to the hot water supply device of FIG. 1. [Diagram 3] FIG. 2 is a conceptual diagram showing the characteristics of a hybrid valve applied to the hot water supply device of FIG. [Figure 4] 10 is a flowchart illustrating a control process for a hybrid valve in a water heating apparatus according to an embodiment of the present invention. [Diagram 5] 5 is a flowchart illustrating combustion control of a heating section in a water heater according to an embodiment of the present invention. [Figure 6] FIG. 13 is a conceptual diagram illustrating a comparative example of setting the can body set temperature. [Figure 7] FIG. 11 is a conceptual diagram illustrating an example of setting a can body set temperature in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 given the same reference characters, and their description will not be repeated in principle.

[0013] FIG. 1 is a schematic diagram of a water heating apparatus 100 according to an embodiment of the present invention. Referring to FIG. 1, the water heating apparatus 100 includes a combustion can body (hereinafter also simply referred to as "can body") 5 which houses a heat exchanger 10 and a combustion burner 30 etc., a blower fan 40, a water inlet passage 50, can body piping 55, a bypass piping 60, a water outlet passage 70, a hybrid valve 80, and a controller 200.

[0014] The inlet passage 50 is connected to the boiler body piping 55 and the bypass piping 60 via a hybrid valve 80. Low-temperature water such as tap water is supplied to the inlet passage 50. The low-temperature water in the inlet passage 50 is distributed to the boiler body piping 55 and the bypass piping 60 via the hybrid valve 80. In this embodiment, a "control valve" for controlling the flow rate ratio of high-temperature water and low-temperature water in the bypass mixing method is configured using a hybrid valve 80 having characteristics described later.

[0015] The boiler body piping 55 passes low-temperature water through the heat exchanger 10. The low-temperature water introduced from the water inlet 50 into the boiler body piping 55 is heated by the heat generated by the combustion burner 30 as it passes through the heat exchanger 10. As a result, high-temperature water is output from the heat exchanger 10.

[0016] A main gas solenoid valve 32, a gas proportional valve 33, and capacity changeover valves 35a to 35c are arranged in a gas supply pipe 31 to the combustion burner 30. The main gas solenoid valve 32 has a function of turning on and off the supply of fuel gas to the combustion burner 30. The gas flow rate in the gas supply pipe 31 is controlled according to the opening degree of the gas proportional valve 33.

[0017] The capacity switching valves 35a to 35c are controlled to open and close in order to switch the number of burners to which fuel gas is supplied among the multiple combustion burners 30. The amount of heat generated in the boiler body 5 is proportional to the amount of gas supplied from all of the combustion burners 30, which is determined by a combination of the number of burners and the gas flow rate. Therefore, a setting map can be created in advance that determines a combination of the opening / closing pattern of the capacity switching valves 35a to 35c (number of burners) and the opening degree of the gas proportional valve 33 (gas flow rate) in accordance with the amount of heat required for the combustion burners 30.

[0018] In the can body 5, the fuel gas output from the combustion burner 30 is mixed with the combustion air from the blower fan 40. The amount of air blown by the blower fan 40 is controlled so that the air-fuel ratio with respect to the amount of gas supplied from the entire combustion burner 30 becomes a predetermined value (for example, an ideal air-fuel ratio). Since the amount of air blown by the blower fan 40 is proportional to the fan rotation speed, the rotation speed of the blower fan 40 is controlled according to a target rotation speed that is set according to changes in the amount of gas supplied. The blower fan 40 is provided with a rotation speed sensor 45 for detecting the fan rotation speed.

[0019] The mixture of fuel gas and combustion air is ignited by an ignition device (not shown), and the fuel gas is burned to generate a flame. Combustion heat generated by the flame from the combustion burner 30 is provided to the heat exchanger 10 in the boiler body 5.

[0020] The high-temperature water heated by the heat exchanger 10 is output toward the hot water outlet 70. An exhaust path 15 for exhausting the combustion exhaust gas after heat exchange is provided downstream of the boiler body 5 in the flow direction of the combustion gas. The heat exchanger 10 may be configured to include both a primary heat exchanger and a secondary heat exchanger.

[0021] The bypass piping 60 and the boiler body piping 55 are connected at a junction 75. Hot water at an appropriate temperature, adjusted by mixing high-temperature water from the boiler body piping 55 and low-temperature water from the bypass piping 60, is supplied to the hot water outlet path 70 downstream of the junction 75. The hot water in the hot water outlet path 70 is supplied to a predetermined hot water supply point, such as a hot water tap (not shown) in the kitchen or bathroom, or a hot water supply circuit to a bathtub (not shown).

[0022] In this way, water heating apparatus 100 has a so-called bypass mixing type configuration in which high-temperature water that has passed through heat exchanger 10 and low-temperature water that has bypassed heat exchanger 10 are mixed via hybrid valve 80. As will be described later, the flow rate ratio (mixing ratio) of high-temperature water and low-temperature water is controlled by an opening control value (described later) of hybrid valve 80 from controller 200.

[0023] 1, the boiler body piping 55 forms a "first flow path," and the bypass piping 60 forms a "second flow path." Furthermore, the heat exchanger 10 that receives heat from the combustion burner 30 forms an embodiment of a "heating section."

[0024] In the following, the flow rate of boiler body piping 55 (first flow path) is denoted as Q1, and the flow rate of bypass piping 60 (second flow path) is denoted as Q2. The flow rate of hot water discharged from outlet piping 70 corresponds to the total flow rate Qt (Qt=Q1+Q2) of hot water supply device 100, which is the sum of flow rates Q1 and Q2. Each flow rate is a flow rate per unit time, and the unit is, for example, liters / minute.

[0025] The temperature sensor 110 is provided on the boiler body piping 55 upstream of the heat exchanger 10 in order to detect the temperature of the low-temperature water. The temperature sensor 110 may be provided in the water inlet passage 50 or the bypass piping 60.

[0026] Temperature sensor 120 is disposed downstream of heat exchanger 10 in boiler body piping 55 in order to detect the temperature of the high-temperature water. That is, temperature sensor 120 is disposed upstream of junction 75. Temperature sensor 130 is disposed in hot water outlet passage 70 downstream of junction 75 in order to detect the temperature of the hot water at the outlet after the high-temperature water and the low-temperature water are mixed.

[0027] In the following, the temperature detected by temperature sensor 110 is referred to as inlet water temperature Tw, the temperature detected by temperature sensor 120 is referred to as boiler body temperature Tb, and the temperature detected by temperature sensor 130 is referred to as outlet water temperature Th.

[0028] A flow rate sensor 150 is further disposed in the can body pipe 55. The flow rate sensor 150 can be typically configured by an impeller type flow rate sensor. The flow rate sensor 150 detects a flow rate Q1 in the can body pipe 55. The flow rate sensor 150 corresponds to one embodiment of a "flow rate detector."

[0029] Controller 200 can be configured, for example, by a microcomputer. Controller 200 receives detection values ​​from each sensor and user operations, and generates control commands to each device in order to control the overall operation of water heating apparatus 100. User operations include on / off commands for the operation switch of water heating apparatus 100, and designation of a hot water supply setting temperature Tr, which corresponds to a target value for the outlet hot water temperature.

[0030] When the operation switch of water heating apparatus 100 is turned on, controller 200 turns on the combustion operation in boiler body 5 in response to flow rate Q1 detected by flow sensor 150 exceeding the minimum operating flow rate (MOQ). When the combustion operation is turned on, main gas solenoid valve 32 is opened, and the supply of fuel gas to combustion burner 30 begins, and is ignited by an ignition device (not shown). In response, water heating apparatus 100 starts a hot water supply operation. During the hot water supply operation, controller 200 controls the outlet hot water temperature in accordance with the hot water supply set temperature Tr.

[0031] When the operation switch of the water heating device 100 is turned off, or when the flow rate Q1 falls below the minimum operating flow rate (MOQ) during hot water heating operation, the supply of fuel gas to the combustion burner 30 is stopped, thereby terminating the hot water heating operation.

[0032] Next, the characteristics of hybrid valve 80 applied to water heating apparatus 100 according to the present embodiment will be described in detail.

[0033] 2, the hybrid valve 80 has a first port 81 connected to the boiler body piping 55, a second port 82 connected to the bypass piping 60, and a third port 83 connected to the inlet passage 50. The hybrid valve 80 is configured to control the flow rates Q1 and Q2 by controlling the aperture of one or more valve bodies (not shown) according to an aperture control value X from the controller 200, thereby changing the opening areas of at least a portion of the first port 81, the second port 82, and the third port 83. For example, the valve bodies are driven to open and close by a stepping motor (not shown). In this case, the aperture control value X is represented by the number of steps of the stepping motor.

[0034] As an example, the opening areas of the first port 81 and the second port 82 each change according to the opening of the first valve element (not shown), while the sum of the two is controlled to maintain a constant value. On the other hand, the opening area of ​​the third port 83 is controlled according to the opening of the second valve element (not shown).

[0035] While the flow rate Q1 of the boiler body piping 55 changes according to the opening area of ​​the first port 81 and the flow rate Q2 of the bypass piping 60 changes according to the opening area of ​​the second port 82, the sum of the opening areas of the first port 81 and the second port 82 is constant, so the flow rate ratio k (defined as k = Q2 / Q1) of the flow rate Q1 and the flow rate Q2 changes according to the opening degree of the first valve body described above.

[0036] Furthermore, since the sum of the opening areas of the first port 81 and the second port 82 is constant, the total flow rate Qt (Q1+Q2) changes according to the opening area of ​​the third port 83 which depends on the opening degree of the second valve element described above.

[0037] FIG. 3 shows a characteristic diagram of the hybrid valve 80 with respect to the opening control value X. 3, the hybrid valve 80 is configured to have a first section (X=X1 to Xt) in which the flow rate ratio k changes without affecting the total flow rate Qt with respect to the opening control value X that changes between a minimum value X1 and a maximum value X2, and a second section (X=Xt to X2) in which the total flow rate Qt changes while the flow rate ratio k is kept constant. Hereinafter, the first section will also be referred to as the "temperature control region 91," and the second section will also be referred to as the "flow rate control region 92."

[0038] The total flow rate Qt is maintained at a maximum flow rate Qmax in the temperature control region 91 (X=X1 to Xt), while in the flow rate control region 92 (X=Xt to X2), it is controlled to decrease from the maximum flow rate Qmax to a minimum flow rate Qmin as the opening control value X increases.

[0039] In contrast, in the temperature control region 91 (X=X1 to Xt), the flow rate ratio k is controlled to gradually decrease from a maximum value kmax to a minimum value kmin in response to an increase in the opening control value X, while in the flow rate control region 92 (X=Xt to X2), the flow rate ratio k is maintained at the minimum value kmin at X=Xt.

[0040] For example, in the temperature control region 91, the opening area of ​​the first port 81 and the opening area of ​​the second port 82 are changed in conjunction with each other so that the opening area of ​​the first port 81 gradually increases while the opening area of ​​the second port 82 gradually decreases as the opening control value X increases from the minimum value X1 to the boundary value Xt, while the opening area of ​​the third port 83 is maintained at a maximum value independent of the opening control value X in the temperature control region 91. This realizes the characteristics of the flow rate ratio k and the total flow rate Qt relative to the opening control value X in the temperature control region 91 shown in Fig. 3. The maximum flow rate Qmax is determined by the pressure of the low-temperature water introduced into the water inlet 50 (for example, the water pressure of the waterworks) and the opening of a hot water tap (not shown) at the hot water supply destination.

[0041] Furthermore, in the flow rate control region 92, the hybrid valve 80 can be configured so that as the opening control value X increases from the boundary value Xt to the maximum value X2, the opening area of ​​the third port 83 gradually decreases, while the opening areas of the first port 81 and the second port 82 are maintained in the state when X=Xt. This realizes the characteristics of the flow rate ratio k and the total flow rate Qt versus the opening control value X in the flow rate control region 92 shown in Fig. 3. The hybrid valve 80 controls the flow rate Q1 (high temperature water) and the flow rate Q2 (low temperature water) according to the characteristics of the flow rate ratio (Q2 / Q1) and the total flow rate (Q1+Q2) shown in Fig. 3.

[0042] The flow rate ratio kmin may be set so that a flow rate occurs in the bypass piping 60 even in the flow rate control region 92 (Q2>0, kmin>0), and the flow rate ratio kmin=0 (i.e., Q2=0) in the flow rate control region 92 may be set by fully closing the second port 82 at X=X2.

[0043] Furthermore, the minimum flow rate Qmin of the total flow rate Qt at the maximum value X2 of the opening control value X can be set to Qmin=0 by fully closing the third port 83. On the other hand, it is also possible to make Qmin>0 by not fully closing the third port 83 at X=X2. However, as described above, when the flow rate Q1 falls below the minimum operating flow rate (MOQ), the combustion in the combustion burner 30 is stopped.

[0044] Therefore, in temperature control region 91, water heating apparatus 100 can control outlet hot water temperature Th to hot water supply set temperature Tr by adjusting flow rate ratio k by means of opening control value X of hybrid valve 80. It will be understood that when the "heating section" in water heating apparatus 100, i.e., the maximum heating amount Pmax when the amount of heat generated by combustion burner 30 is set to a maximum value (for example, maximum gas flow rate and combustion by all burners), is equal to or greater than the required heating amount Prq (Prq=Qt·ΔT) according to the product of total flow rate Qt and amount of temperature rise ΔT=Tr-Tw (Prq≦Pmax), it is possible to control the outlet hot water temperature by adjusting flow rate ratio k in temperature control region 91.

[0045] On the other hand, when the required heating amount Prq becomes greater than the maximum heating amount Pmax (Prq>Pmax), the hot water outlet temperature Th cannot be raised to the hot water supply set temperature Tr unless the total flow rate Qt is reduced from the maximum flow rate Qmax. For this reason, it is necessary to control the hot water outlet temperature by adjusting the total flow rate Qt in the flow rate control region 92.

[0046] The relationship between the required heating amount Prq and the maximum heating amount Pmax described above can also be expressed by the total flow rate Qt. If the maximum value of the total flow rate Qt that can raise the inlet water temperature Tw to the hot water supply setting temperature Tr when the maximum heating amount Pmax is generated is defined as the limiting flow rate Qlm, the limiting flow rate Qlm can be expressed by the following formula (1) using the thermal efficiency η (η≦1.0). In the following, to simplify the explanation, η will be treated as 1.0. Qlm = η Pmax / (Tr-Tw) … (1)

[0047] Therefore, by comparing the flow rate limit Qlm with the total flow rate Qt, it is possible to determine that when Qt≦Qlm, outlet hot water temperature control is performed by adjusting the flow rate ratio k in temperature control region 91, while when Qt>Qlm, outlet hot water temperature control is performed by adjusting the total flow rate Qt (Qt≦Qlm) in flow rate control region 92. In other words, it can be understood that a determination based on a comparison of the flow rate limit Qlm and the total flow rate Qt is equivalent to a determination based on a comparison of the required heating amount Prq and the maximum heating amount Pmax.

[0048] In addition, even when the flow rate Q1 of the boiler body piping 55 is the upper limit flow rate (the boiler body maximum flow rate Q1max) in terms of durability performance of the heat exchanger 10, it is possible to further combine flow rate control for making Q1≦Q1max by operating the hybrid valve 80 in the flow rate control region 92. In this case, when the flow rate value obtained by converting the boiler body maximum flow rate Q1max into a total flow rate using the flow rate ratio k is smaller than the flow rate value obtained by the above-mentioned formula (1), the flow rate value converted from the boiler body maximum flow rate Q1max is set to the limited flow rate Qlm, so that flow rate control can be performed to limit Q1≦Q1max.

[0049] Here, the relationship of the following formula (2) is established among the flow rate Q1 of the boiler body piping 55, the flow rate Q2 of the bypass piping 60, the boiler body temperature Tb, the inlet water temperature Tw, and the outlet hot water temperature Th. Q2·(Th-Tw)=Q1·(Tb-Th) …(2)

[0050] From equation (2), the flow rate ratio k (k=Q2 / Q1) can be expressed by equation (3) using the boiler body temperature Tb, the inlet water temperature Tw, and the outlet water temperature Th. k=Q2 / Q1=(Tb-Th) / (Th-Tw) …(3)

[0051] Therefore, the flow rate ratio k* for controlling the outlet hot water temperature Th to the hot water supply setting temperature Tr can be calculated by the following equation (4) by replacing the outlet hot water temperature Th with the hot water supply setting temperature Tr in equation (2). k*=Q2 / Q1=(Tb-Tr) / (Tr-Tw) …(4)

[0052] Theoretically, by setting the flow rate ratio by hybrid valve 80 according to the flow rate ratio k* calculated by equation (4), it is possible to control outlet hot water temperature Th to set hot water supply temperature Tr.

[0053] On the other hand, during hot water supply operation, the actual flow rate ratio k can be calculated back from the actual temperature value by substituting the temperatures detected by the temperature sensors 110, 120, and 130 into equation (3). Hereinafter, the flow rate ratio calculated in this manner is referred to as the actual flow rate ratio ktm.

[0054] For example, by measuring the actual flow rate ratio ktm relative to the opening control value X of the hybrid valve 80 based on the results of a prior actual test, it is possible to determine the correspondence relationship between the opening control value X (number of steps) and the flow rate ratio k in the hybrid valve 80. This makes it possible to predetermine the reference correspondence relationship between the opening control value X and the flow rate ratio k for the hybrid valve 80 as a reference characteristic line (Xk) for the flow rate ratio.

[0055] Therefore, the controller 200 can execute outlet hot water temperature control by controlling the hybrid valve 80 by back-calculating the opening control value X from the flow rate ratio k* calculated by the formula (4).

[0056] Similarly, by using the flow rate detection value by the flow rate sensor 150 when the opening control value X of the hybrid valve 80 is changed in the flow rate control region 92, the correspondence between the opening control value X of the hybrid valve 80 and the total flow rate Qt, i.e., the reference characteristic line (X-Qt) for the total flow rate Qt in the flow rate control region 92, can be determined in advance based on the results of actual equipment tests, etc.

[0057] Fig. 4 is a flowchart explaining the control process of the hybrid valve in the hot water supply device of Fig. 1. The process of the flowchart shown in Fig. 4 can be periodically executed by controller 200 during hot water supply operation. Although not shown in Fig. 4, controller 200 can acquire the detection values ​​(Tw, Tb, Tw, Q1) of each sensor for each control cycle in which the process shown in Fig. 4 is executed.

[0058] 4, in step (hereinafter also simply referred to as "S") 100, the controller 200 calculates the total flow rate Qt from the flow rate Q1 detected by the flow rate sensor 150. At this time, the calculation can be performed according to equation (5) using the flow rate ratio k back-calculated from the current opening control value X of the hybrid valve 80 according to the above-mentioned reference characteristic line (Xk). Qt = Q1 + Q2 = (1 + k) · Q1 … (5)

[0059] In S200, controller 200 sets the limit flow rate Qlm according to formula (1) using the detected value of inlet water temperature Tw (temperature sensor 110), hot water supply setting temperature Tr, and maximum heating amount Pmax which is a specification value of water heating apparatus 100. Alternatively, in S200, the limit flow rate Qlm may be set in a manner further combined with flow rate control that limits the limit flow rate Qlm to equal to or less than the boiler body maximum flow rate Q1max, as described above.

[0060] In S300, the controller 200 compares the total flow rate Qt calculated in S100 with the restricted flow rate Qlm calculated in S200. When the total flow rate Qt is equal to or less than the restricted flow rate Qlm (YES in S300), the controller 200 advances the process to S400 and executes temperature control by setting the opening control value X of the hybrid valve 80 within the temperature control region 91 (FIG. 3) in the corresponding control cycle.

[0061] On the other hand, when the total flow rate Qt is greater than the restriction flow rate Qlm (NO in S300), the controller 200 advances the process to S500, and in the corresponding control cycle, the opening control value X of the hybrid valve 80 is set within the flow control region 92 (FIG. 3) to perform flow control.

[0062] When performing temperature control (S400), the controller 200 calculates a target flow rate ratio kst, which is a target value of the flow rate ratio k for temperature control, using the detected values ​​of the inlet water temperature Tw and the boiler body temperature Tb in the control cycle and the hot water supply set temperature Tr in accordance with the flow rate ratio k* in the above-mentioned equation (4) in S410. That is, kst is set to k*=(Tb-Tr) / (Tr-Tw).

[0063] In S420, controller 200 calculates flow ratio k[i] for the current control cycle according to the target flow ratio kst calculated in S410. In S420, the target flow ratio kst may be set as the flow ratio k[i] as is, or the flow ratio k[i] may be set by further reflecting a feedback control term based on the deviation between the hot water outlet temperature Th and the hot water supply setting temperature Tr.

[0064] Furthermore, in S430, the controller 200 sets the opening control value X[i] of the hybrid valve 80 in the i-th control cycle from the flow ratio k[i] calculated in S420 in accordance with the reference characteristic line (Xk) for the flow ratio k, within the temperature control region 91.

[0065] On the other hand, when the flow control is executed (S500), the controller 200 sets a target total flow rate Qst in the flow control in S510. The target total flow rate Qst in S510 is set to be equal to or less than the limit flow rate Qlm. This allows the amount of heat generated by the heating section (combustion burner 30) to be set within a range equal to or less than the maximum heating amount Pmax. Also, by setting the limit flow rate Qlm reflecting the boiler body maximum flow rate Q1max, the flow rate Q1 can be limited to be equal to or less than the boiler body maximum flow rate Q1max under the flow rate ratio kmin (FIG. 3) in the flow control region 92.

[0066] In step S520, the controller 200 calculates the total flow rate Qt[i] in the current control cycle according to the target total flow rate Qst set in step S510. For example, in step S520, the target total flow rate Qst can be set directly as the total flow rate Qt[i].

[0067] Furthermore, in S530, the controller 200 sets the opening control value X[i] of the hybrid valve 80 in the i-th control cycle from the total flow rate Qt[i] calculated in S520 in accordance with the reference characteristic line (X-Qt) for the total flow rate Qt, within the flow rate control region 92.

[0068] The outlet hot water temperature control is performed by combining the control of the hybrid valve 80 shown in FIG. 4 with the control of the amount of heat provided by the heating section (combustion burner 30).

[0069] FIG. 5 shows a flowchart illustrating the combustion control of the combustion burner in water heating apparatus 100.

[0070] 5, in step S600, controller 200 branches the combustion control process according to whether hybrid valve (HV) 80 is performing temperature control or flow rate control. The determination in step S600 can be performed in the same manner as in step S300 in FIG.

[0071] When temperature control is performed (YES in S600), the controller 200 sets the can body set temperature Tb*, which is the target temperature for the can body temperature Tb, in S610. Then, in S620, combustion control is performed to adjust the amount of heat generated by the combustion burner 30 so that the can body temperature Tb (temperature sensor 120) becomes the can body set temperature Tb*.

[0072] For example, in S620, the amount of heat generated by the combustion burner 30 can be set according to the product of the temperature difference between the boiler body set temperature Tb* and the inlet water temperature Tw and the total flow rate Qt (S100). Alternatively, the amount of heat generated by the combustion burner 30 can be set by further reflecting a feedback control term for compensating for the deviation between the boiler body temperature Tb (temperature sensor 120) and the boiler body set temperature Tb*.

[0073] As described above, the amount of heat generated by the combustion burner 30 can be adjusted by a combination of the opening and closing pattern of the capacity switching valves 35a to 35c (the number of burners) and the opening degree of the gas proportional valve 33 (gas flow rate).

[0074] On the other hand, when flow control is executed (NO in S600), controller 200 executes combustion control in S630 to adjust the amount of heat (i.e., gas amount) by combustion burner 30 according to a comparison between outlet hot water temperature Th (temperature sensor 130) and hot water supply set temperature Tr. This makes it possible to execute temperature control to set outlet hot water temperature Th to hot water supply set temperature Tr even when flow rate ratio k by hybrid valve 80 is constant.

[0075] As described above, when the limiting flow rate Qlm is set so that the flow rate Q1 is equal to or less than the boiler body maximum flow rate Q1max, in the flow rate control region 92, the flow rate is controlled so that Q1≦Q1max at the flow rate ratio kmin (FIG. 3), while the amount of heating by the combustion burner 30 is controlled so that the hot water outlet temperature Th becomes the hot water supply set temperature Tr within a range in which the amount of heating by the combustion burner 30 is equal to or less than the maximum amount of heating Pmax.

[0076] Next, we will explain the setting of the can body set temperature Tb* during temperature control of the hybrid valve 80. Fig. 6 shows a comparative example of the setting of the can body set temperature Tb*, and Fig. 7 shows an example of the setting of the can body set temperature Tb* according to this embodiment.

[0077] Considering the boiler body temperature Tb, if the boiler body temperature Tb is low, condensation is likely to occur on the surface of the heat exchanger 10. In addition, if a situation is assumed in which the outlet hot water temperature Th is to be maintained when the flow rate is increased, it can be understood that maintaining the outlet hot water temperature Th by adjusting the flow rate ratio k provides higher control responsiveness than maintaining the outlet hot water temperature Th by increasing the amount of heating.

[0078] Therefore, when the hybrid valve 80 operates within the temperature control region 91 (when controlling temperature), the boiler body temperature Tb is set high, and the outlet hot water temperature Th is controlled to the hot water supply set temperature Tr by adjusting the flow rate ratio k.

[0079] On the other hand, when the hybrid valve 80 operates within the flow rate control region 92 (during temperature control), the flow rate ratio k is fixed to kmin in Fig. 3, and the tapping temperature Th is controlled to the hot water supply set temperature Tr by adjusting the amount of heat in the combustion burner 30. Therefore, the boiler body temperature Tb is determined by the tapping temperature Th and the flow rate ratio kmin, and is no longer directly controlled by the combustion control.

[0080] For this reason, in the comparative example of Fig. 6, when the temperature control is performed such that Qt≦Qlm, the boiler body set temperature Tb* is set to a temperature T1 (T1=Tr+α) obtained by adding a fixed value α (for example, α=approximately 15 to 20°C) to the hot water supply set temperature Tr. In this case, the boiler body set temperature Tb* is set to a constant value (T1) regardless of changes in the total flow rate Qt.

[0081] In contrast, for flow control where Qt>Qlm, the boiler body set temperature Tb* is not set, and the actual boiler body temperature Tb becomes the temperature T2 determined from the tapping water temperature Th and the flow rate ratio kmin in the flow control region 92 (Tb=T2).

[0082] However, when the can body set temperature Tb* during temperature control is set according to the comparative example of FIG. 6, it is feared that the following problems may occur in the control of the hot water temperature Th when switching from temperature control to flow rate control in response to an increase in the total flow rate Qt.

[0083] During temperature control, the flow rate ratio k does not directly depend on the total flow rate Qt, but is controlled by the relationship between the can body temperature Tb (can body set temperature Tb*), the hot water temperature Th (hot water supply set temperature Tr), and the incoming water temperature Tw, as described by equations (2) and (3). For this reason, there is a possibility that the difference between the flow rate ratio k during temperature control and the flow rate ratio (minimum value kmin) in the flow rate control region 92 may be relatively large.

[0084] In such a state, if the control is directly switched from temperature control to flow rate control, there is a risk that the hot water temperature Th may become higher than the hot water supply set temperature Tr due to the difference between the can body temperature Tb controlled to the can body set temperature Tb* and the can body temperature (T2) during flow rate control. For this reason, it is not possible to immediately start limiting the total flow rate Qt, and it is necessary to start flow rate control for limiting the total flow rate Qt after providing a transition period in which the heating amount of the combustion burner 30 is adjusted to lower the can body temperature Tb while continuing the temperature control by the flow rate ratio k. During such a transition period, since a total flow rate Qt larger than the limiting flow rate Qlm occurs, the temperature control accuracy will temporarily decrease due to the decrease in the hot water temperature Th.

[0085] On the other hand, in the example of setting the can body set temperature according to the embodiment of the present invention, in the flow rate range of Qt < Qlm to which temperature control is applied, a flow rate range is provided in the vicinity of the limiting flow rate Qlm where the can body set temperature Tb* decreases as the total flow rate Qt increases.

[0086] As shown in Fig. 7, by multiplying the restricted flow rate Qlm by a coefficient β (0 < β < 1.0), the boundary flow rate Qx is set. In the first flow rate range 101 where Qt ≤ Qx, the can body set temperature Tb* is set to Tb* = T1 (T1 = Tr + α), similar to the comparative example in Fig. 6. That is, in the first flow rate range 101, the can body set temperature Tb* is constant with respect to the change in the total flow rate Qt.

[0087] On the other hand, in the second flow rate range 102 where Qx < Qt ≤ Qlm, the can body set temperature Tb* is set to decrease from a constant value T1 as the total flow rate Qt increases.

[0088] For example, using the hot water supply set temperature Tr and the flow rate ratio kmin in the flow rate control region 92, the calculated temperature T2r of the can body temperature Tb during flow rate control can be calculated. Therefore, at Qt = Qx, Tb* = T1, and at Qt = Qlm, Qb* = T2r. Between Qx < Qt < Qlm, the can body set temperature Tb* in the second flow rate range 102 can be set to decrease at a constant rate with respect to the increase in the total flow rate Qt.

[0089] The calculated temperature T2r can be set according to Equation (7) obtained by transforming the following Equation (6) using, for example, the flow rates Q1, Q2, the hot water supply set temperature Tr, and the inlet water temperature Tw (detected temperature), and setting the flow rate ratio k (k = Q2 / Q1) = kmin (flow rate control region 92). The calculated temperature T2r corresponds to the "lower limit set value" of the can body set temperature Tb*. Q1·T2r + Q2·Tw = (Q1 + Q2)·Tr …(6) T2r = Tr + kmin·(Tr - Tw) …(7)

[0090] That is, in the present embodiment, the setting of the can body set temperature Tb* during temperature control in S610 of FIG. 5 can be executed according to FIG. 7. Note that the boundary flow rate Qx in FIG. 7 may be set according to the difference in a predetermined flow rate from the limiting flow rate Qlm. By doing so, the rate at which the can body set temperature Tb* changes with respect to the increase in the total flow rate Qt can be fixed. In any case, the first flow rate range 101 (Qt ≦ Qx) is located on the lower flow rate side than the second flow rate range 102 (Qx < Qt ≦ Qlm).

[0091] Accordingly, in the water heater according to the present embodiment, when shifting from temperature control to flow rate control as the total flow rate Qt increases, the temperature difference between the can body temperature Tb during the temperature control before the shift and the can body temperature Tb (corresponding to T2 in FIG. 6) after the shift to flow rate control can be suppressed. As a result, in response to the increase in the total flow rate Qt, the flow rate control for restricting the total flow rate Qt to be equal to or less than the limiting flow rate Qlm can be started without providing the "transition period" described in FIG. 6. Therefore, by suppressing a temporary decrease in the temperature control accuracy during the switching from temperature control to flow rate control, the temperature control accuracy can be improved.

[0092] In FIG. 1, a configuration example in which the flow rate sensor 150 is arranged in the can body pipe 55 to detect the flow rate Q1 has been described. However, even in a configuration in which the flow rate sensor 150 is arranged in the bypass pipe 60 to detect the flow rate Q2, the control processes of FIGS. 4 and 5 according to the present embodiment can be similarly applied. Alternatively, even in a configuration in which the flow rate sensor 150 is arranged in the water inlet pipe 50 to detect the total flow rate Qt (Q1 + Q2), by calculating the flow rates Q1 and Q2 using the flow rate ratio k, the same control process can be applied.

[0093] Further, in FIG. 1, an example in which the heat source of the "heating unit" is the combustion heat of gaseous fuel has been shown. However, the fuel is not limited to gas, and the hot water outlet temperature control according to the present embodiment can be applied to a water heater in which the "heating unit" is configured by a mechanism that generates the combustion heat of any fuel.

[0094] In the present embodiment, the hybrid valve 80 is connected between the inlet passage 50 and the boiler body pipe 55 and the bypass pipe 60 to control the distribution ratio of the low-temperature water from the inlet passage 50 to the boiler body pipe 55 and the bypass pipe 60. However, the hybrid valve 80 may be disposed at the junction 75 and connected between the outlet passage 70 and the boiler body pipe 55 and the bypass pipe 60. In this case, at the junction 75 in FIG. 2, the third port 83 is connected to the outlet passage 70, and the flow direction at each port is reversed. Then, the mixture ratio of the high-temperature water in the boiler body pipe 55 and the low-temperature water in the bypass pipe 60 is controlled by controlling the flow rates Q1 and Q2 according to the flow rate ratio (Q2 / Q1) and the total flow rate (Q1+Q2) shown in FIG. 3.

[0095] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0096] 5 boiler body, 10 heat exchanger, 15 exhaust path, 30 combustion burner, 31 gas supply pipe, 32 main gas solenoid valve, 33 gas proportional valve, 35a to 35c capacity switching valve, 40 blower fan, 45 rotation speed sensor, 50 water inlet passage, 55 boiler body piping, 60 bypass piping, 70 hot water outlet passage, 75 junction, 80 hybrid valve, 81 first port, 82 second port, 83 third port, 91 temperature control area, 92 flow rate control area, 100 hot water supply device, 101 first flow rate area, 102 second flow rate area, 110, 120, 130 temperature sensor, 150 flow rate sensor, 200 controller, Q1, Q2 flow rate, Q1max boiler body maximum flow rate, Qlm limit flow rate, Qmax maximum flow rate, Qst target total flow rate, Qt total flow rate, Qx Boundary flow rate, T1 constant value, T2r calculated temperature (boiler body temperature), Tb boiler body temperature, Tb* boiler body set temperature, Th outlet water temperature, Tr hot water supply set temperature, Tw inlet water temperature, X opening control value (hybrid valve), X1 minimum value (opening control value), X2 maximum value (opening control value), Xt boundary value (opening control value), k flow rate ratio, kst target flow rate ratio

Claims

1. A hot water supply device that mixes low temperature water and high temperature water, A heating unit that heats the low-temperature water and outputs high-temperature water; A first flow path for passing the low-temperature water through the heating section; a second flow path through which the low-temperature water flows without passing through the heating section; a flow rate detector disposed in the first flow path or the second flow path; a control valve connected to the first flow path and the second flow path for controlling a flow rate of the first flow path and the second flow path; a control device that sets a control value of the control valve and an amount of heating by the heating unit in order to control a hot water outlet temperature after mixing the low temperature water and the high temperature water to a hot water supply setting temperature; the control valve is configured to have a first section in which a flow rate ratio of the first flow path and the second flow path changes without affecting a total flow rate of the first flow path and the second flow path, and a second section in which the flow rate ratio is fixed while the total flow rate decreases, in response to a change in the control value; The control device includes: When the total flow rate acquired based on the detected flow rate of the flow detector is greater than a restriction flow rate set corresponding to a maximum heating amount of the heating unit, the control value of the control valve is set within the second range so that the total flow rate is equal to or less than the restriction flow rate, and the heating amount of the heating unit is controlled so that the hot water outlet temperature is controlled to the hot water supply setting temperature, When the total flow rate acquired based on the detected flow rate of the flow rate detector is equal to or less than the restricted flow rate, the heating amount of the heating unit is controlled so as to control the temperature of the high-temperature water to a boiler body set temperature, and the control value of the control valve is set within the first interval in correspondence with the flow rate ratio for controlling the outlet hot water temperature to the hot water supply set temperature, and A hot water supply device, wherein the boiler body set temperature is set so that there is a flow rate region in which the boiler body set temperature decreases as the total flow rate increases and approaches the restricted flow rate.

2. The water heating device of claim 1, wherein the tank body set temperature is set to a constant value higher than the hot water supply set temperature in a first flow rate range on the lower flow rate side of a boundary flow rate set lower than the limiting flow rate, while in a second flow rate range between the boundary flow rate and the limiting flow rate, the tank body set temperature is set to decrease from the constant value as the total flow rate increases.

3. The water heater device of claim 2, wherein the tank body set temperature set in the second flow rate range is set to gradually decrease from the constant value to a lower limit set value corresponding to the temperature of the high-temperature water for setting the outlet temperature to the hot water supply set temperature under the flow rate ratio in the second section of the control valve as the total flow rate increases.

4. The hot water supply apparatus according to claim 2 , wherein the constant value is set according to a sum of the hot water supply setting temperature and a predetermined fixed value.

5. A water heating device as described in any one of claims 1 to 4, wherein the limiting flow rate is set according to a second value corresponding to the total flow rate when the flow rate of the first flow path becomes the maximum allowable flow rate of the heating section under the flow rate ratio in the second section of the control valve, when the second value is smaller than a first value corresponding to the total flow rate at which the outlet water temperature can be the water heating set temperature when the maximum heating amount of the heating section occurs.

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