Proportional valve control device and water heater

Abstract

To provide a proportional valve control device capable of accurately controlling a flow rate of fluid, and to provide a water heater excellent in temperature control performance by using the proportional valve control device.SOLUTION: The proportional valve 3 controls the flow rate of the fluid by sliding the plunger 45 in the guide cylinder 44 in accordance with the energization amount and changing the opening degree of the valve hole 34, and the control unit 205 controls the energization amount to the proportional valve 3, and the control unit 205 periodically energizes the proportional valve 3 with at least one of the high specific energization amount higher than the reference energization amount and the low specific energization amount lower than the reference energization amount for the predetermined specific energization time while energizing the proportional valve 3 with the reference energization amount corresponding to the predetermined target flow rate of the fluid.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a proportional valve control device and a water heater using the same. [Background technology]

[0002] Conventionally, proportional valves are used to control the flow rate of gas or liquid fluids. For example, in a water heater, a target combustion amount of a burner required to match the set temperature and the outlet temperature of hot water detected by an outlet temperature sensor is calculated, and combustion air and gas at a flow rate corresponding to the target combustion amount are supplied to the burner. To achieve this, the rotation speed of a combustion fan that supplies combustion air is controlled according to the target combustion amount, and the aperture of a proportional valve provided in a gas supply line is controlled according to the target combustion amount or the rotation speed of the combustion fan.

[0003] This type of proportional valve has a solenoid, a guide tube that penetrates the center of the solenoid, a plunger that slides within the guide tube due to the electromagnetic force of the solenoid, and a valve element that moves as the plunger slides.The plunger slides within the guide tube depending on the amount of current flowing through it, changing the opening of the valve orifice and thereby controlling the flow rate of fluid passing through the valve orifice (for example, Patent Document 1 and Patent Document 2).

[0004] Figure 7(a) shows the change in secondary pressure (gas flow rate) when the amount of current applied is gradually reduced while the plunger is sliding normally within the guide tube. As shown in Figure 7(a), there is a fixed relationship between the amount of current applied and the secondary pressure. Therefore, when controlling the flow rate of a fluid using a proportional valve, the secondary pressure can be controlled by controlling the amount of current applied using a control means such as a microcomputer. For example, when the set temperature of a water heater is changed, the amount of current applied to the proportional valve is determined based on control data such as a data table or an arithmetic formula preset from the target combustion amount. Then, by applying current to the proportional valve according to the determined amount of current applied, the valve hole opening is controlled to achieve the target gas flow rate.

[0005] In water heaters, the outlet water temperature can fluctuate due to external disturbances. For example, the amount and temperature of water supplied to the water heater can fluctuate due to water usage by other external devices, or the combustion fan's airflow can fluctuate due to outside air entering the exhaust port or temporary blockage of the exhaust port. Therefore, even when the same set temperature is set, temperature control is performed to maintain the outlet water temperature at the set temperature. Typically, the change in target gas flow rate during temperature control to maintain the set temperature is smaller than the change in target gas flow rate when the set temperature is changed, so the change in power supply during temperature control is smaller than the change in power supply when the set temperature is changed. As a result, if the sliding resistance of the plunger within the guide tube is higher than the electromagnetic force applied to the plunger by current application during temperature control, even if the proportional valve is energized with a power supply corresponding to the target gas flow rate, the plunger will become stuck in the guide tube, preventing it from sliding and preventing the gas flow rate from being properly adjusted.

[0006] Figure 7(b) shows the change in secondary pressure when the amount of current is gradually reduced, as in Figure 7(a), in a state where the plunger is stuck on the guide tube. As shown in Figure 7(b), even if the amount of current is reduced to reduce the gas flow rate, the secondary pressure hardly changes until the amount of current is reduced by a certain amount, and when the amount of current is further reduced, the secondary pressure drops suddenly. This is because the plunger does not slide in accordance with the amount of current due to the plunger being stuck as described above, and when the electromagnetic force applied to the plunger by the current becomes large enough to release the plunger from its stuck state, the plunger slides, causing a sudden change in the opening of the valve hole. As described above, since the change in the amount of current is small in temperature control to maintain the set temperature, the gas flow rate does not reach the intended level when the amount of current is changed until the plunger is released from its stuck state. The temperature deviates significantly from the target gas flow rate. As a result, the outlet water temperature after the plunger is released differs from the set temperature, and it is necessary to apply an amount of current corresponding to the target gas flow rate to the proportional valve so that the outlet water temperature returns to the set temperature. As a result, the outlet water temperature fluctuates significantly, and temperature control performance deteriorates. This phenomenon also occurs when the amount of current is increased. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-186958 [Patent Document 2] Japanese Patent Application Publication No. 2023-69629 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a proportional valve control device that can control the flow rate of a fluid with high precision. [Means for solving the problem]

[0009] According to a first aspect of the present technology, a proportional valve that controls the flow rate of the fluid by sliding a plunger within a guide tube and changing the opening of a valve hole according to the amount of current flow; a control unit that controls the amount of current supplied to the proportional valve, A proportional valve control device is provided in which, when the control unit is supplying a reference current amount corresponding to a predetermined target flow rate of the fluid to the proportional valve, the control unit periodically supplies at least one specific current amount to the proportional valve for a predetermined specific current time, the specific current amount being higher than the reference current amount or the specific current amount being lower than the reference current amount.

[0010] According to the first aspect, when a reference current corresponding to a target flow rate is applied to the proportional valve, a large electromagnetic force is periodically applied to the plunger, thereby preventing the plunger from getting stuck. This improves response to the current flow rate and enables accurate control of the flow rate of the fluid according to the current flow rate.

[0011] According to a second aspect of the present technology, in the first aspect, The control unit controls the amount of current supplied to the proportional valve by PWM (Pulse Width Modulation) control.

[0012] According to the second aspect, minute vibrations can be applied to the plunger, which further reduces the likelihood of the plunger getting stuck.

[0013] According to a third aspect of the present technology, in the first or second aspect, The high specific energization amount is 15% or more higher than the standard energization amount, and the low specific energization amount is 15% or more lower than the standard energization amount.

[0014] According to the third aspect, by energizing the proportional valve with the high specific energization amount or the low specific energization amount, a large electromagnetic force is applied to the plunger, so that it is possible to reliably prevent the plunger from getting stuck.

[0015] According to a fourth aspect of the present technology, in any one of the first to third aspects, the control unit controls the amount of current supplied to the proportional valve between a predetermined minimum reference current supply amount and a predetermined maximum reference current supply amount, When the reference energization amount corresponding to the target flow rate of the fluid is energized to the proportional valve, if the reference energization amount is equal to or less than a predetermined upper reference energization amount that is lower than the maximum reference energization amount, energizing the proportional valve for the specific energization time and the high specific energization amount; When the reference energization amount corresponding to the target flow rate of the fluid is being energized to the proportional valve, if the reference energization amount is higher than the upper limit reference energization amount, the reference energization amount is maintained.

[0016] According to the fourth aspect, the proportional valve can be stably operated.

[0017] According to a fifth aspect of the present technology, in any one of the first to fourth aspects, the control unit controls the amount of current supplied to the proportional valve between a predetermined minimum reference current supply amount and a predetermined maximum reference current supply amount, When the reference energization amount corresponding to the target flow rate of the fluid is being energized to the proportional valve, if the reference energization amount is equal to or greater than a predetermined lower limit reference energization amount that is higher than the minimum reference energization amount, energizing the proportional valve periodically for the specific energization time and the low specific energization amount; When the reference energization amount corresponding to the target flow rate of the fluid is being energized to the proportional valve, if the reference energization amount is lower than the lower limit reference energization amount, the reference energization amount is maintained.

[0018] According to the fifth aspect, the proportional valve can be stably operated.

[0019] According to a sixth aspect of the present technology, in any one of the first to fifth aspects, the fluid is a gas; When the control unit is energizing the proportional valve at the reference energization amount corresponding to a predetermined target gas flow rate of the gas, the control unit periodically energizes the proportional valve for the specific energization time and the high specific energization amount.

[0020] According to the sixth aspect, the gas flow rate is periodically increased while preventing the plunger from getting stuck. Furthermore, the amount of current is periodically increased, preventing the amount of current from falling below a reference value, thereby preventing gas from misfiring.

[0021] According to a seventh aspect of the present technology, A water heater equipped with the proportional valve control device of the sixth aspect, The control unit is provided with a water heater that periodically applies the high specific current amount to the proportional valve for the specific current amount while applying the standard current amount corresponding to the target gas flow rate of the gas to the proportional valve so that the outlet temperature of the hot water matches a predetermined set temperature.

[0022] According to the seventh aspect, it is possible to prevent the plunger from getting stuck during temperature regulation control, so that the gas flow rate can be controlled with high precision, and the temperature regulation performance of the water heater can be improved. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a water heater according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a proportional valve control device according to an embodiment of the present invention. [Figure 3] Figure 3 is an explanatory diagram for explaining the current conduction pattern of the specific current amount by the proportional valve control device according to an embodiment of the present invention, where (a) is an explanatory diagram of the current conduction pattern in which a high specific current amount is conducted to the proportional valve, (b) is an explanatory diagram of the current conduction pattern in which a low specific current amount is conducted to the proportional valve, and (c) is an explanatory diagram of the current conduction pattern in which a high specific current amount and a low specific current amount are conducted alternately to the proportional valve. [Figure 4] FIG. 4 shows the results of evaluation showing the number of times the plunger is caught when the specific amount of current is changed using the proportional valve control device according to the embodiment of the present invention. [Figure 5] Figure 5 shows the measurement results of the outlet hot water temperature during temperature control of a water heater according to an embodiment of the present invention, where (a) shows an example of the measurement results of the outlet hot water temperature when a high specific current is periodically applied to the proportional valve, (b) shows an example of the measurement results of the outlet hot water temperature when a low specific current is periodically applied to the proportional valve, and (c) shows an example of the measurement results of the outlet hot water temperature when no specific current is applied to the proportional valve. [Figure 6] FIG. 6 is a flowchart showing an example of a control operation in temperature regulation control of a water heater according to an embodiment of the present invention. [Figure 7] FIG. 7 is a correlation diagram showing the relationship between the amount of current supplied and the secondary pressure in a conventional proportional valve control device, where (a) is a correlation diagram when the plunger does not get stuck, and (b) is a correlation diagram when the plunger gets stuck. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, a proportional valve control device and a water heater according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing an example of a gas water heater equipped with a proportional valve control device according to this embodiment. As shown in Fig. 1, water heater 100 has a water heater casing 101. A water heater body 102 is housed within water heater casing 101. A heat exchanger 10 and a burner 11 for heating heat exchanger 10 are disposed within water heater body 102.

[0025] A combustion fan 13 for supplying combustion air into the can body 102 is connected to the bottom wall of the can body 102. The combustion fan 13 is driven to rotate by a fan motor 14. The fan motor 14 is provided with a rotation speed sensor 15, such as a Hall IC, that detects the rotation speed of the combustion fan 13. The rotation speed of the combustion fan 13 is changed by controlling the drive of the fan motor 14 in response to a command from a control unit 20, which will be described later. The rotation speed of the combustion fan 13 is detected by the rotation speed sensor 15 provided in the fan motor 14, and the drive current of the fan motor 14 for operating the combustion fan 13 at a predetermined target rotation speed is detected by a current detection unit (not shown).

[0026] An exhaust port 105 is formed at the top end of boiler body 102 for exhausting combustion exhaust gas to the outside of hot water heater casing 101. Exhaust port 105 is in communication with the interior of boiler body 102 via exhaust passage 106. Gas supply pipe 16 for supplying gas to burner 11 penetrates the bottom wall of boiler body 102. On-off valves 2a and 2b for controlling the supply of gas in response to commands from control unit 20, and a gas proportional valve 3 with a governor are disposed in gas supply pipe 16. Note that only one of on-off valves 2a and 2b may be provided.

[0027] Heat exchanger 10 is disposed above burner 11 within boiler body 102. One end of heat exchanger 10 is connected to water supply pipe 81, and the other end is connected to hot water outlet pipe 82. Water flow sensor 17 is disposed in water supply pipe 81, and hot water temperature sensor (outlet hot water temperature detection unit) 18 is disposed in hot water outlet pipe 82. Thus, for example, when a hot water supply terminal such as a faucet (not shown) is opened and water flow sensor 17 provided on water supply pipe 81 detects a water supply amount equal to or greater than a predetermined minimum operating water amount, combustion fan 13 starts rotating, and on-off valves 2a and 2b and gas proportional valve 3 are opened to supply combustion air and gas to burner 11. Then, an igniter (not shown) is activated to ignite burner 11, which burns the gas and starts combustion operation in which the heat exchanger 10 is heated by the combustion exhaust. When combustion operation starts, the rotation speed of the combustion fan 13 and the opening degree of the gas proportional valve 3 are adjusted to control the combustion of the burner 11 so that the hot water outlet temperature detected by the hot water outlet temperature sensor 18 becomes the predetermined set temperature set by the user.

[0028] The control unit 20 is electrically connected to the on-off valves 2a and 2b, the gas proportional valve 3, the fan motor 14, the operation unit 19, various sensors such as the rotation speed sensor 15, the water flow sensor 17, and the outlet hot water temperature sensor 18, as well as an igniter (not shown). As shown in FIG. 2, the control unit 20 is a microcomputer equipped with a CPU, ROM, RAM, and a timer. The gas proportional valve driving circuit 302 includes a microcomputer 200 (hereinafter referred to as "microcomputer 200"), an on-off valve driving circuit 301 that drives on-off valves 2a and 2b in accordance with commands from microcomputer 200, a proportional valve driving circuit 302 that drives gas proportional valve 3 in accordance with commands from microcomputer 200, a fan driving circuit 303 that drives fan motor 14 in accordance with commands from microcomputer 200, and an igniter driving circuit 304 that drives an igniter in accordance with commands from microcomputer 200. As will be described later, when energizing gas proportional valve 3, the command given by microcomputer 200 to proportional valve driving circuit 302 is the amount of current to be applied (more precisely, a PWM signal indicating the amount of current).

[0029] Although not shown, the on-off valves 2a and 2b are solenoid valves having a valve body, a plunger, and an electromagnet. When current is applied to the on-off valves 2a and 2b, the on-off valves 2a and 2b open, and when current is cut off, the on-off valves 2a and 2b close.

[0030] The gas proportional valve 3 is equipped with a casing 3a having an inlet-side primary pressure chamber 31 that communicates with the upstream gas supply pipe 16 via a gas inlet 30, an outlet-side secondary pressure chamber 32 that is located above the primary pressure chamber 31 and communicates with the downstream gas supply pipe 16 via a gas outlet (not shown), and a valve seat 33 between the primary pressure chamber 31 and the secondary pressure chamber 32. A valve hole 34 that connects the primary pressure chamber 31 and the secondary pressure chamber 32 is opened in the valve seat 33. The upper surface of the secondary pressure chamber 32 is covered by a top lid attached to the casing 3a.

[0031] The gas proportional valve 3 further includes a diaphragm 35 that covers the underside of the primary pressure chamber 31, a valve element 36 that faces the surface of the valve seat 33 on the secondary pressure chamber 32 side, and a solenoid 3b that slides the plunger 45 to move the valve element 36 upward and varies the electromagnetic force applied to the plunger 45.

[0032] The outer peripheral portion of the diaphragm 35 is clamped and fixed to the outer peripheral portion of the lower surface of the primary pressure chamber 31 by a presser plate 37 fastened to the underside of the casing 3a. A back pressure chamber 38 that is open to the atmosphere is defined between the diaphragm 35 and the presser plate 37. In addition, a cylindrical valve holder 40 is provided below the diaphragm 35 and has a flange portion 40a at its upper end that contacts the underside of the diaphragm 35 via a washer 39.

[0033] The valve element 36 has a valve stem 36a that extends vertically. A small-diameter shaft portion 36b is formed at the lower end of the valve stem 36a and protrudes downward from a shoulder surface that contacts the upper surface of the diaphragm 35. The small-diameter shaft portion 36b is passed through a hole formed in the center of the diaphragm 35 and fitted and fixed to the valve holder 40, thereby connecting the valve stem 36a to the diaphragm 35.

[0034] The solenoid 3b has a yoke 41 attached to the underside of the retainer plate 37, a coil 43 wound around a bobbin 42 in contact with the yoke 41, a guide tube 44 provided on the inner periphery of the yoke 41, a plunger 45 inserted into the guide tube 44 so as to be slidable in the vertical direction, and a spring 46 that urges the plunger 45 upward to cancel the weight of the plunger 45. The upper end of the plunger 45 abuts against the lower end of the small diameter shaft portion 36b of the valve shaft 31.

[0035] As described above, the electromagnetic force applied to the plunger 45 changes depending on the amount of current flowing through the solenoid 3b, causing the plunger 45 to slide up and down within the guide tube 44, thereby moving the valve element 36. In this gas proportional valve 3, as the amount of current flowing increases, the valve element 36 is displaced upward toward the opening side, increasing the secondary pressure (gas flow rate) in the secondary pressure chamber 32. On the other hand, as the amount of current flowing decreases, the valve element 36 is displaced downward toward the closing side, decreasing the secondary pressure in the secondary pressure chamber 32. Therefore, the gas flow rate of the gas supplied to the burner 11 changes in proportion to the amount of current flowing. Note that, when the primary pressure in the primary pressure chamber 31 fluctuates, the valve element 36 is displaced via the diaphragm 35, suppressing fluctuations in the gas pressure in the secondary pressure chamber 32. Therefore, this gas proportional valve 3 maintains the secondary pressure in the secondary pressure chamber 32 at a predetermined pressure corresponding to the amount of current flowing, even if gas pressure fluctuations occur in the primary pressure chamber 31. It has a governor function.

[0036] Microcomputer 200 includes a memory unit 210 storing a control program and control data. By executing the control program, microcomputer 200 functions as an operation control unit 201 that controls the overall operation of water heater 100, a temperature adjustment control unit 202 that sets a target combustion amount and performs temperature adjustment control so that the outlet hot water temperature matches the set temperature, a fan control unit 203 that controls the amount of power supplied to fan motor 14, an on-off valve control unit 204 that controls the amount of power supplied to on-off valves 2a and 2b, a proportional valve control unit 205 that controls the amount of power supplied to gas proportional valve 3, and an igniter control unit 206 that controls the operation of the igniter. Therefore, in this embodiment, proportional valve control unit 205 constitutes a control unit that controls the amount of power supplied to gas proportional valve 3. Furthermore, the proportional valve control device is comprised of gas proportional valve 3, temperature adjustment control unit 202, and proportional valve control unit 205.

[0037] The temperature adjustment control unit 202 sets a target combustion amount for the burner 11 based on the set temperature set by the user via the operation unit 19, the amount of water flowing through the water supply pipe 81 detected by the water flow sensor 17, and the actual hot water outlet temperature detected by the outlet hot water temperature sensor 18. The fan control unit 203 sets a target rotation speed for the combustion fan 13 in accordance with the target combustion amount set based on the control data, and determines the amount of power supplied to the fan motor 14 corresponding to the target rotation speed.

[0038] The proportional valve control unit 205 calculates a target gas flow rate based on the set target combustion amount or target rotation speed, and determines a reference energization amount or a specific energization amount (described later) corresponding to the target gas flow rate based on the control data. The proportional valve control unit 205 then generates a PWM signal (for example, frequency: 500 Hz) with a duty ratio corresponding to the energization amount, and controls the ON / OFF of the switching element using the PWM signal. As the duty ratio increases, the amount of electrical energy supplied to the solenoid 3b per unit time increases, increasing the electromagnetic force applied to the plunger 45. As a result, the opening of the valve hole 34 increases, and the gas flow rate increases. Conversely, as the duty ratio decreases, the amount of electrical energy supplied to the solenoid 3b per unit time decreases, decreasing the electromagnetic force applied to the plunger 45. As a result, the opening of the valve hole 34 decreases, and the gas flow rate decreases. The proportional valve control unit 205 controls the duty ratio within a predetermined range (e.g., 0 to 100%) so that a reference current ranging from a predetermined minimum reference current (e.g., 0 mA) to a predetermined maximum reference current (e.g., 500 mA) is applied to the solenoid 3b.

[0039] FIG. 3 is an explanatory diagram showing current conduction patterns of specific current amounts. Note that FIG. 3 is a schematic diagram for explaining current conduction patterns, and each current conduction pattern does not represent actual time or current amount. FIG. 3(a) shows a current conduction pattern in which, when a predetermined reference current amount (CmA) is conducted to the solenoid 3b, a high specific current amount Cu (e.g., 1.15 CmA) higher than the reference current amount is conducted to the solenoid 3b at a predetermined cycle Pa (e.g., 1 sec cycle) for a predetermined specific current conduction time Ta (e.g., 8 msec). FIG. 3(b) shows a current conduction pattern in which, when a predetermined reference current amount (CmA) is conducted to the solenoid 3b, a low specific current amount Cd (e.g., 0.85 CmA) lower than the reference current amount is conducted to the solenoid 3b at a predetermined cycle Pb (e.g., 1 sec cycle) for a predetermined specific current conduction time Tb (e.g., 8 msec). 3(c) shows a current pattern in which, when a predetermined reference current (CmA) is applied to solenoid 3b, a high specific current Cu (e.g., 1.15 CmA) higher than the reference current is applied to solenoid 3b at a predetermined cycle Pc (e.g., 1 sec) for a predetermined specific current time Tc1 (e.g., 8 msec). Then, a low specific current Cd (e.g., 0.85 CmA) lower than the reference current is applied to solenoid 3b at the same cycle Pc for a predetermined specific current time Tc3 (e.g., 8 msec). The cycle, specific current time, and time interval for the specific current can be selected as appropriate depending on the desired characteristics.

[0040] When the reference current corresponding to the target gas flow rate is applied to the solenoid 3b as described above, applying at least one of a high specific current higher than the reference current and a low specific current lower than the reference current to the solenoid 3b results in a change in current greater than the change in current during temperature control. This allows a greater electromagnetic force to be applied to the plunger 45 than the electromagnetic force during temperature control. Therefore, even when the plunger 45 slides less during temperature control and is more likely to jam, jamming of the plunger 45 can be prevented. Furthermore, because a large electromagnetic force is applied to the plunger 45, the specific current durations for the high and low specific currents can be significantly shorter than the current duration for the reference current. The high and low specific currents are each set according to the reference current. Furthermore, when a reference current equal to or greater than a predetermined value is applied, at least one of the high and low specific currents may be applied. The increase or decrease amount may be changed so that the larger the reference current amount, the larger the increase or decrease amount of the high specific current amount relative to the reference current amount.

[0041] Figure 4 shows the results of an evaluation of the number of times plunger 45 gets stuck within a specified measurement time while varying the high or low specific current amount at the same cycle (1 second cycle) and the same specific current duration (8 msec) during temperature control with a specified set temperature (85°C) using water heater 100. In the figure, the increase or decrease in the specific current amount is the percentage increase or decrease relative to the reference current amount (300 mA). The number of times plunger 45 gets stuck can be detected by changes in the current amount and the temperature of the hot water being discharged.

[0042] As shown in FIG. 4, when temperature control is performed by energizing solenoid 3b with only the reference current, the number of times plunger 45 gets stuck is very high, at 50. In contrast, the number of times plunger 45 gets stuck decreases as the high-specific current is increased relative to the reference current, and as the low-specific current is decreased relative to the reference current. In particular, when solenoid 3b is periodically energized with a high-specific current that is 15% or more higher than the reference current, or a low-specific current that is 15% or more lower than the reference current, the plunger 45 does not get stuck, and sticking of plunger 45 can be reliably suppressed during temperature control. Preferably, the high-specific current is set to a value equal to or less than the maximum reference current, and the low-specific current is set to a value equal to or greater than the minimum reference current.

[0043] Figure 5 shows the measurement results of the outlet hot water temperature during temperature control under conditions where the target combustion amount is decreasing. Figure 5(a) shows the measurement results when temperature control is performed while energizing solenoid 3b at a high specific current amount (current amount 15% higher than the reference current amount) for a specific specific current time (8 msec) at a predetermined cycle (1 sec cycle). Figure 5(b) shows the measurement results when temperature control is performed while energizing solenoid 3b at a low specific current amount (current amount 15% lower than the reference current amount) for a specific specific current time (8 msec) at a predetermined cycle (1 sec cycle). Figure 5(c) shows the measurement results when temperature control is performed using only the reference current amount.

[0044] As shown in Figure 5(c), when temperature control is performed using only the reference current, if the outlet hot water temperature deviates from the set temperature toward the higher side, a lower reference current begins to be applied to solenoid 3b to reduce the target gas flow rate so that the outlet hot water temperature matches the set temperature. However, as mentioned above, because the change in this reference current is small, if plunger 45 is stuck, the gas flow rate supplied to burner 11 is maintained, temperature control does not function, and the outlet hot water temperature further rises. Therefore, a lower reference current is applied to solenoid 3b to reduce the target gas flow rate. Then, if the reference current is reduced to the extent that the electromagnetic force applied to plunger 45 overcomes the sliding resistance of plunger 45 within guide tube 44, the sliding of plunger 45 reduces the opening of valve hole 34, causing a sudden decrease in gas flow rate and a drop in the outlet hot water temperature below the set temperature. Furthermore, if the outlet hot water temperature drops significantly below the set temperature, This causes a large reference current corresponding to the target gas flow rate to be applied to solenoid 3b so that the outlet hot water temperature rises to the set temperature, causing the gas flow rate to increase suddenly and the outlet hot water temperature to rise in a short period of time. This causes the outlet hot water temperature to fluctuate significantly during temperature control.

[0045] In contrast, as shown in Figures 5(a) and 5(b), when temperature control is performed while periodically energizing solenoid 3b with either a high or low specific current, the outlet hot water temperature remains stable without any significant drop in temperature. This is because periodically energizing solenoid 3b with either a high or low specific current suppresses the plunger 45 from jamming during temperature control, improving its ability to respond to changes in current flow. This allows for precise control of the gas flow rate according to the current flow rate, resulting in excellent temperature control performance. While not shown, similar jamming of plunger 45 can also be suppressed when energizing solenoid 3b alternately and periodically at predetermined time intervals between high and low specific current flows.

[0046] Next, in the water heater 100 of this embodiment, the control operation for energizing the gas proportional valve 3 with a high specific current amount during temperature adjustment control will be described with reference to the flowchart of Fig. 6. The control operation for energizing the gas proportional valve 3 with a low specific current amount and the control operation for energizing the gas proportional valve 3 with the high specific current amount and the low specific current amount alternately are the same as the control operation shown in Fig. 6.

[0047] When the burner 11 is ignited and the outlet hot water temperature rises to the set temperature, temperature control is initiated to maintain the outlet hot water temperature at the set temperature. When temperature control is initiated, a power-on cycle timer is started (step S1), measuring a predetermined cycle for supplying a high specific current. Next, when the power-on cycle arrives (Yes in step S2), a determination is made as to whether the reference current to the gas proportional valve 3 during temperature control is equal to or less than a predetermined upper reference current (e.g., 80% of the maximum reference current), which is lower than a predetermined maximum reference current (step S3). If the reference current is equal to or less than the upper reference current, the load on the plunger 45 is suppressed, even when a high specific current is supplied to the gas proportional valve 3, allowing stable operation of the gas proportional valve 3. Although not shown, when a low specific current is supplied to the gas proportional valve 3, a determination is made as to whether the reference current is equal to or greater than a predetermined lower reference current (e.g., 20% of the maximum reference current), which is higher than a predetermined minimum reference current. As long as the reference energization amount is equal to or greater than the lower reference energization amount, the gas proportional valve 3 can be stably operated even when a low specific energization amount is applied to the gas proportional valve 3. This prevents the absolute value of the gas flow rate from falling below the predetermined reference value, preventing misfires in the burner 11 and suppressing sticking of the plunger 45.

[0048] If the reference energization amount is equal to or less than the upper limit reference energization amount (Yes in step S3), a specific energization time measurement timer is started (step S4), and a high specific energization amount higher than the reference energization amount is energized to the gas proportional valve 3 for the specific energization time (steps S5 to S6). As a result, a large electromagnetic force is applied to the plunger 45 periodically for a short period of time during temperature control. After the specific energization time has elapsed (Yes in step S6), the energization amount is returned to the reference energization amount (step S7). Therefore, a large electromagnetic force is applied to the plunger 45 even when the energization amount returns from this high specific energization amount to the reference energization amount, further suppressing sticking of the plunger 45. Although not shown, when the set temperature is changed, a high specific energization amount higher than the new reference energization amount is periodically energized to the gas proportional valve 3.

[0049] If the reference current amount is higher than the upper limit reference current amount (No in step S3), the reference current amount is maintained, and temperature control is performed so that the outlet heated water temperature matches the set temperature (step S8).

[0050] As described above in detail, according to this embodiment, when the reference energization amount corresponding to the target gas flow rate is energized to the gas proportional valve 3, a specific energization time is periodically set to a value less than the reference energization amount. At least one of a high specific current amount and a low specific current amount lower than the reference current amount is applied to the gas proportional valve 3. Therefore, when the reference current amount corresponding to the target gas flow rate is applied to the gas proportional valve 3, a large electromagnetic force is periodically applied to the plunger 45, which prevents the plunger 45 from getting stuck. This improves response to the current amount and allows the gas flow rate to be accurately controlled according to the current amount.

[0051] Furthermore, according to this embodiment, the amount of current supplied to gas proportional valve 3 is controlled by PWM control, so that minute vibrations can be applied to plunger 45. This further reduces sticking of plunger 45. Furthermore, by supplying current to gas proportional valve 3 at a high specific current that is 15% or more higher than the reference current, or a low specific current that is 15% or more lower than the reference current, it is possible to reliably reduce sticking of plunger 45.

[0052] Furthermore, according to this embodiment, if the reference energization amount is equal to or less than an upper reference energization amount that is lower than the maximum reference energization amount, a high specific energization amount is applied to the gas proportional valve 3, and if the reference energization amount is higher than the upper reference energization amount, the reference energization amount is maintained, thereby enabling stable operation of the gas proportional valve 3. Furthermore, according to this embodiment, if the reference energization amount is equal to or greater than a lower reference energization amount that is higher than the minimum reference energization amount, a low specific energization amount is applied to the gas proportional valve 3, and if the reference energization amount is lower than the lower reference energization amount, the reference energization amount is maintained, thereby enabling stable operation of the gas proportional valve 3.

[0053] Furthermore, according to this embodiment, by using the proportional valve control device, it is possible to obtain the water heater 100 having excellent temperature control performance.

[0054] (Other embodiments) (1) In the above embodiment, a gas proportional valve for controlling the flow rate of gas and a gas water heater using the same are used. However, the present invention can also be applied to proportional valves and devices for controlling the flow rate of other gases or liquids.

[0055] (2) In the above embodiment, a proportional valve having a governor function is used. However, the present invention can also be applied to a proportional valve without a governor function.

[0056] (3) In the above embodiment, the specific energization amount is set as an increase or decrease rate relative to the reference energization amount. However, the specific energization amount may be set as a predetermined increase or decrease amount relative to the reference energization amount. [Explanation of symbols]

[0057] 100 Water Heater 3 Gas Proportional Valves 34 Valve orifice 44 Guide tube 45 Plunger 205 Proportional valve control section

Claims

1. a proportional valve that controls the flow rate of the fluid by sliding a plunger within a guide tube and changing the opening of a valve hole in accordance with the amount of current flow; a control unit that controls the amount of current supplied to the proportional valve, The control unit, when energizing the proportional valve with a reference current amount corresponding to a predetermined target flow rate of the fluid, periodically energizes the proportional valve with at least one specific current amount higher than the reference current amount or a specific current amount lower than the reference current amount for a predetermined specific current time.

2. The proportional valve control device according to claim 1, The control unit is a proportional valve control device that controls the amount of electricity supplied to the proportional valve by PWM control.

3. The proportional valve control device according to claim 1 or 2, A proportional valve control device in which the high specific current amount is 15% or more higher than the standard current amount, and the low specific current amount is 15% or more lower than the standard current amount.

4. The proportional valve control device according to claim 1 or 2, the control unit controls the amount of current supplied to the proportional valve between a predetermined minimum reference current supply amount and a predetermined maximum reference current supply amount, When the reference energization amount corresponding to the target flow rate of the fluid is being energized to the proportional valve, if the reference energization amount is equal to or less than a predetermined upper reference energization amount which is lower than the maximum reference energization amount, energizing the proportional valve periodically for the specific energization time and the high specific energization amount; a proportional valve control device that maintains the reference energization amount, if the reference energization amount corresponding to the target flow rate of the fluid is higher than the upper reference energization amount, when the reference energization amount is energized to the proportional valve;

5. The proportional valve control device according to claim 1 or 2, the control unit controls the amount of current supplied to the proportional valve between a predetermined minimum reference current supply amount and a predetermined maximum reference current supply amount, When the reference energization amount corresponding to the target flow rate of the fluid is being energized to the proportional valve, if the reference energization amount is equal to or greater than a predetermined lower limit reference energization amount that is higher than the minimum reference energization amount, energizing the proportional valve periodically for the specific energization time and the low specific energization amount; a proportional valve control device that maintains the reference energization amount, if the reference energization amount is lower than the lower limit reference energization amount, when the reference energization amount corresponding to the target flow rate of the fluid is energized to the proportional valve;

6. The proportional valve control device according to claim 1 or 2, the fluid is a gas; The control unit, when energizing the proportional valve at the reference energization amount corresponding to a predetermined target gas flow rate of the gas, periodically energizes the proportional valve at the high specific energization amount for the specific energization time.

7. A water heater equipped with the proportional valve control device according to claim 6, The control unit periodically energizes the proportional valve at the high specific current amount for the specific current amount while energizing the proportional valve at the standard current amount corresponding to the target gas flow rate of the gas so that the outlet temperature of the hot water matches the set temperature.

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