Method for controlling the combustion of a burner in a booster for a dishwasher, booster for a dishwasher

Abstract

This design effectively prevents combustion vibrations from occurring even when the burner ignition control is performed in a cold state where the enclosure temperature is low. [Solution] The controller for the dishwasher booster operates the igniter until a predetermined operating time Tig has elapsed when igniting the burner, and uses a proportional valve to supply fuel gas at a predetermined low input to ignite the burner in a slow ignition control. After the slow ignition control, once a predetermined slow ignition time T has elapsed since the flame of the burner was detected by the flame rod, it uses a proportional valve to supply fuel gas at a predetermined high input greater than the low input to ignite the burner in a normal control. In addition, a predetermined waiting time T2 is added to the slow ignition time T1 to continue the combustion of the burner 11, and the normal control is executed after the total time T of the slow ignition time T1 and the waiting time T2 has elapsed.

Description

Technical Field

[0001] The present disclosure relates to a method for controlling the combustion of a burner and a booster for a dishwasher installed to supply hot water to a commercial dishwasher, and to a booster for a dishwasher that executes the method.

Background Art

[0002] A commercial dishwashing system is known to include a dishwasher that washes dishes carried into a washing chamber and a booster for a dishwasher that is installed beside the dishwasher to supply rinsing hot water to the dishwasher. The booster for a dishwasher includes, for example, an instantaneous heating type heat source unit having a burner, a tank unit for storing hot water, and a circulation path having a circulation pump for circulating hot water between the heat source unit and the tank unit, and enables the hot water in the tank unit maintained at a predetermined temperature by the heat source unit via the circulation path to be supplied to a dishwasher-side tank provided in the dishwasher.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described conventional booster for a dishwasher, at the time of ignition of the burner, the supply amount of fuel gas to the burner controlled by a proportional valve provided in the gas pipe is set as a predetermined low input set in advance for ignition, and the rotational speed of the fan is also set accordingly, and a slow ignition control for ensuring reliable ignition is executed. The time of this slow ignition control is, for example, 0.3 seconds, and after confirmation of ignition, the fuel gas is switched to high input and the rotational speed of the fan is also increased to execute normal control. However, when the burner is ignited while the heat source unit's casing is cold, such as during the first use of the day, and the control switches from slow ignition to normal ignition, the casing may resonate with the combustion frequency of the burner flame, causing combustion vibrations. This is thought to be a phenomenon that occurs when the combustion frequency of the burner flame matches the natural frequency of the casing before its temperature rises.

[0005] Therefore, the present disclosure aims to provide a burner combustion control method and a dishwasher booster that can suitably prevent the occurrence of combustion vibrations even when the burner ignition control is performed in a cold state where the temperature of the housing is low. [Means for solving the problem]

[0006] To achieve the above objective, the first configuration of this disclosure is a method for controlling the combustion of a burner in a dishwasher booster, the dishwasher booster comprising an instantaneous heating type heat source unit having a burner, a heat exchanger, a fan for supplying combustion air to the burner, an ignition means for the burner, a flame detection means for the burner, and a housing that at least houses the burner and the heat exchanger, A tank for storing hot water, A circulation path equipped with a circulation pump for circulating hot water between the heat exchanger and the tank, A gas control means for controlling the amount of fuel gas supplied to the burner, The system includes a controller that controls the combustion of the burner and the operation of the circulation pump. The controller, when igniting the burner, operates the ignition means until a predetermined operating time has elapsed, and uses the gas control means to supply fuel gas at a predetermined low input to ignite the burner, performing slow ignition control. After the slow ignition control, when the flame of the burner is detected by the flame detection means and a predetermined slow ignition time has elapsed, the gas control means performs normal control, which involves supplying fuel gas at a predetermined high input greater than the low input to ignite the burner. On the other hand, the controller can heat the hot water in the tank to a predetermined temperature by operating the circulation pump while the burner is burning, and can also supply the heated hot water in the tank to a dishwasher-side tank provided in an external dishwasher. Furthermore, the controller adds a predetermined waiting time to the slow ignition time to allow the burner to continue burning, and performs the normal control after the total time of the slow ignition time and the waiting time has elapsed. Another aspect of the first configuration is characterized in that, in the above configuration, the controller sets the waiting time such that the end of the total time coincides with the end of the operating time of the ignition means or the end of the operating time. Another aspect of the first configuration is characterized in that, in the above configuration, the controller controls the gas control means and / or the fan during the standby time such that the air-fuel ratio, which is the ratio of the amount of combustion air supplied by the fan to the amount of fuel gas supplied by the gas control means, becomes more gas-rich or air-rich than when the normal control is being performed. Another aspect of the first configuration is characterized in that, in the above configuration, the total time is at least 20 seconds.

[0007] To achieve the above objective, a second configuration of the present disclosure is a booster for a dishwasher, comprising an instantaneous heating type heat source unit having a burner, a heat exchanger, a fan for supplying combustion air to the burner, an ignition means for the burner, a flame detection means for the burner, and a housing that at least houses the burner and the heat exchanger, A tank for storing hot water, A circulation path equipped with a circulation pump for circulating hot water between the heat exchanger and the tank, A gas control means for controlling the amount of fuel gas supplied to the burner, The system includes a controller that controls the combustion of the burner and the operation of the circulation pump. The controller, when igniting the burner, operates the ignition means until a predetermined operating time has elapsed, and uses the gas control means to supply fuel gas at a predetermined low input to ignite the burner, performing slow ignition control. After the slow ignition control, once a predetermined slow ignition time has elapsed since the flame of the burner was detected by the flame detection means, the controller performs normal control by supplying fuel gas at a predetermined high input greater than the low input using the gas control means, thereby igniting the burner. On the other hand, the controller can heat the hot water in the tank to a predetermined temperature by operating the circulation pump while the burner is burning, and can also supply the heated hot water in the tank to a dishwasher-side tank provided in an external dishwasher. Furthermore, the controller adds a predetermined waiting time to the slow ignition time to allow the burner to continue burning, and performs the normal control after the total time of the slow ignition time and the waiting time has elapsed. Another aspect of the second configuration is characterized in that, in the above configuration, the controller sets the waiting time such that the end of the total time coincides with the end of the operating time of the ignition means or the end of the operating time. Another aspect of the second configuration is characterized in that, in the above configuration, the controller controls the gas control means and / or the fan during the standby time such that the air-fuel ratio, which is the ratio of the amount of combustion air supplied by the fan to the amount of fuel gas supplied by the gas control means, becomes more gas-rich or air-rich than when the normal control is being performed. Another aspect of the second configuration is characterized in that, in the above configuration, the total time is at least 20 seconds. [Effects of the Invention]

[0008] According to this disclosure, the temperature of the housing rises during the added waiting time, reaching a warm state. Therefore, even when switching to normal control, the housing resonates with the combustion frequency of the burner flame, suppressing the generation of combustion vibrations. Thus, even when ignition control of the burner is performed in a cold state with a low housing temperature, the generation of combustion vibrations can be effectively prevented. According to another aspect of this disclosure, in addition to the above effects, the controller sets the waiting time so that the end of the total time coincides with the end of the operating time of the ignition means or the end of the operating time, making it easy to set the waiting time required for the housing to become warm. According to another aspect of this disclosure, in addition to the above effects, the controller controls the gas control means and / or fan during standby time so that the air-fuel ratio is more gas-rich or air-rich than when normal control is being performed, thereby unbalancing the air-fuel ratio and effectively shifting the burner frequency to a frequency that does not resonate with the housing. According to another aspect of this disclosure, in addition to the above effects, the total time is at least 20 seconds, so that the temperature can be raised to 200°C to 300°C, which is a temperature at which the enclosure does not resonate. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a booster for dishwashers. [Figure 2] This is a diagram illustrating the burner's slow ignition control sequence. [Figure 3] This is a graph showing the air-fuel ratio. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a booster for a dishwasher according to a first configuration (hereinafter simply abbreviated as "booster"). This booster 1 is installed in the lower part inside the casing 2 of the dishwasher, and includes an instantaneous heating type heat source unit 3, a tank 4 for storing hot water, a circulation path 5 for circulating hot water between the heat source unit 3 and the tank 4, and a controller 6 for controlling the operation of the booster 1.

[0011] The heat source unit 3 includes a burner 11 at the lower part inside the casing 10, and a fin-tube type heat exchanger 12 through which the combustion exhaust of the burner 11 passes above the burner 11. The gas pipe 13 for supplying fuel gas to the burner 11 is provided with a raw gas solenoid valve 14, a proportional valve 15, and a main gas solenoid valve 16 from the upstream side. The proportional valve 15 is an example of the gas control means of the present disclosure. In addition, the casing 10 is provided with a fan 17 for supplying combustion air to the burner 11. An exhaust pipe 18 for discharging the combustion exhaust of the burner 11 that has passed through the heat exchanger 12 is connected to the upper part of the casing 10. The exhaust pipe 18 penetrates the casing 2 and protrudes upward, and is open to the outside through an exhaust duct not shown. The heat source unit 3 is provided with an igniter 20 having an ignition electrode 19 for igniting the burner 11, and a flame rod 21 for detecting the flame of the burner 11. The ignition electrode 19 and the igniter 20 are an example of the ignition means of the present disclosure. The flame rod 21 is an example of the flame detection means of the present disclosure.

[0012] Inside the tank 4, a float switch 25 for detecting a predetermined water level in the tank 4 and a tank thermistor 26 for detecting the temperature of the hot water in the tank 4 are provided. A water supply pipe 27 connected to an external water pipe is connected to the upper part of the tank 4. The water supply pipe 27 is provided with a water solenoid valve 28, and water can be supplied into the tank 4 by the opening and closing operation of the water solenoid valve 28. In addition, a hot water outlet pipe 29 is connected to the lower part of the tank 4. The circulation path 5 includes a forward pipe 30, a return pipe 31, and a circulation pump 32. The forward pipe 30 is connected between the upstream end of the heat transfer pipe of the heat exchanger 12 and the tank 4. The return pipe 31 is connected between the downstream end of the heat transfer pipe and the tank 4. The circulation pump 32 is provided in the forward pipe 30. In the forward pipe 30, an inlet thermistor 33 for detecting the temperature of the hot water supplied from the tank 4 is provided. In the return pipe 31, an outlet thermistor 34 for detecting the temperature of the hot water discharged from the heat source unit 3 is provided.

[0013] On the upper side inside the casing 2, a dishwasher-side tank 40 for storing the hot water for washing used in the dishwasher is provided. Above the dishwasher-side tank 40, a washing chamber (not shown) is installed. The hot water discharge pipe 29 of the tank 4 is piped to the washing chamber via a rinsing pump 41, enabling the supply of rinsing hot water from above and below the washing chamber. Also, a washing pipe 43 for supplying the hot water for washing from above and below the washing chamber is connected to the dishwasher-side tank 40 via a washing pump 42.

[0014] The controller 6 is composed of a CPU and a memory connected to the CPU. The controller 6 performs combustion control of the burner 11. Also, the controller 6 can control the circulation pump 32 and the water solenoid valve 28 based on the detected temperatures from the respective thermistors 26, 33, 34 and the detection signal of the float switch 25, and execute tank water supply control for supplying a predetermined amount of water into the tank 4 and heat retention control for operating the heat source unit 3 to maintain the hot water in the tank 4 at a predetermined temperature. In the tank water supply control, the controller 6 checks the detection signal of the water level with the float switch 25. If the detection signal is obtained, it is assumed that the tank 4 is at the predetermined water level and enters a standby state. When rinsing is performed in the dishwasher and the hot water in the tank 4 is supplied from the hot water discharge pipe 29 by driving the rinsing pump 41, the water level in the tank 4 drops and the detection signal of the water level by the float switch 25 cannot be obtained. Then, the controller 6 opens the water solenoid valve 28 to supply water into the tank 4 until the float switch 25 detects the water level.

[0015] In the temperature control function, when the dishwasher is operated and the controller 6 receives a wash start signal, the controller 6 turns on the circulation pump 32 and determines whether the detected temperature obtained from the tank thermistor 26 is below the set temperature (e.g., 80°C). If it is below the detected temperature, the controller 6 ignites the burner 11 to heat the hot water in the tank 4 to the set temperature. When performing this temperature control, the controller 6 executes a slow ignition control sequence when igniting the burner 11 to prevent combustion oscillations from occurring during subsequent normal control. This slow ignition control sequence will be explained with reference to Figure 2. This sequence is an example of a burner combustion control method according to the second configuration of this disclosure.

[0016] At time t1, after confirming that the detected temperature from the tank thermistor 26 is below the set temperature, the controller 6 controls the opening of the proportional valve 15 to achieve slow ignition combustion with a predetermined low input, and rotates the fan 17 at a predetermined slow ignition rotation speed to confirm that the flame is not detected (OFF) by the flame rod 21. If the flame is not detected at this point, at time t2, the controller 6 activates the igniter 20 to open the source gas solenoid valve 14 and the main gas solenoid valve 16 in that order, and performs slow ignition control to ignite the burner 11. In this slow ignition control, the controller 6 controls the opening of the proportional valve 15 and / or the rotation speed of the fan 17 so that the air-fuel ratio, which is the ratio of the amount of fuel gas supplied to the amount of combustion air supplied, becomes gas-rich (graph B shown as a dotted line in Figure 3) or air-rich (graph C shown as a dashed line in Figure 3) relative to the ideal air-fuel ratio (graph A shown in Figure 3) that is set in the subsequent normal control.

[0017] When the flame is detected by the flame rod 21 at time t3 and a predetermined slow ignition time T1 has elapsed to time t3', the controller 6 counts a predetermined waiting time T2 from time t3' while maintaining the combustion of the burner 11, before performing normal control. This waiting time T2 is set until time t5, after the operation of the igniter 20 is stopped at time t4. During this waiting time T2, the combustion of the burner 11 and the rotation of the fan 17 are controlled to be gas-rich or air-rich compared to the ideal air-fuel ratio, with low input and slow ignition rotation speed, similar to the slow ignition time T1. Then, when time t5 is reached, the controller 6 controls the opening of the proportional valve 15 to achieve high combustion, which is a preset high input, and controls the fan 17 to a predetermined high combustion rotation speed corresponding to the high combustion, and then switches to normal control. The time from time t3 when the flame is detected to time t5 when the high combustion is activated (slow ignition time T1 + waiting time T2 = total time T) is set to be after time t4, which is the end of the operation time Tig of the igniter 20.

[0018] In conventional slow ignition control, as shown by the dotted lines in the input and fan sequence, the system switches to high combustion and high combustion speed at time t3', which is before time t4 when the igniter 20 stops operating, and the slow ignition time T1 is set to 1 second or less (for example, 0.3 seconds). In contrast, in this example, the addition of a waiting time T2 to the slow ignition time T1 makes the time until full combustion begins longer than in the conventional method. As a result, the flame of the burner 11 stabilizes and the temperature of the housing 10 rises during the total time T. Therefore, even when switching to normal control, the combustion frequency of the flame of the burner 11 and the natural frequency of the housing 10 are less likely to match, and the occurrence of combustion vibrations is suppressed. The total time T varies depending on the capacity of the burner 11 (for example, if the burner 11 has a capacity of 24 kW, a total time T of 25 seconds will raise the temperature to a point where the housing 10 does not resonate). However, verification results showed that if the total time T is at least 20 seconds, the temperature will rise to 200°C to 300°C, which is the temperature at which the housing 10 does not resonate.

[0019] In the above configuration, the booster 1 includes an instantaneous heating type heat source unit 3, a tank 4 for storing hot water, a circulation path 5 for circulating hot water between the heat exchanger 12 and the tank 4, a proportional valve 15 for controlling the amount of fuel gas supplied to the burner 11, and a controller 6 for controlling the combustion of the burner 11 and the operation of the circulation pump 32. When the burner 11 is ignited, the controller 6 operates the igniter 20 until a predetermined operating time Tig has elapsed, and uses the proportional valve 15 to supply fuel gas at a predetermined low input to ignite the burner 11, which is called slow ignition control. After the slow ignition control, once a predetermined slow ignition time T has elapsed since the flame of the burner 11 was detected by the flame rod 21, the controller 6 uses the proportional valve 15 to supply fuel gas at a predetermined high input greater than the low input to ignite the burner 11, which is called normal control. Meanwhile, the controller 6 can heat the hot water in the tank 4 to a predetermined temperature by operating the circulation pump 32 while burning the burner 11, and can also supply the heated hot water in the tank 4 to the dishwasher-side tank 40 located in an external dishwasher. The controller 6 adds a predetermined waiting time T2 to the slow ignition time T1 to allow the burner 11 to continue burning, and performs normal control after the total time T of the slow ignition time T1 and the waiting time T2 has elapsed.

[0020] With this configuration, the temperature of the housing 10 rises during the added waiting time T2, reaching a warm state. Therefore, even when switching to normal control, the housing 10 resonates with the combustion frequency of the burner 11 flame, preventing combustion vibrations from occurring. Thus, even when ignition control of the burner 11 is performed while the housing 10 is cold, the occurrence of combustion vibrations can be effectively prevented.

[0021] Controller 6 sets the waiting time T2 such that the end of the total time T (time t5) coincides with the end of the operating time Tig of igniter 20. Therefore, the waiting time T2 required for the enclosure 10 to reach a warm state can be easily set. During the standby time T2, the controller 6 controls the proportional valve 15 and / or the fan 17 so that the air-fuel ratio, which is the ratio of the amount of combustion air supplied by the fan 17 to the amount of fuel gas supplied by the proportional valve 15, becomes richer in gas or air than when normal control is being performed. Therefore, by creating an unbalanced air-fuel ratio, the frequency of the burner 11 can be effectively shifted to a frequency that does not resonate with the housing 10. The total time T is at least 20 seconds. Therefore, the temperature can be raised to 200°C to 300°C, which is the temperature at which the enclosure 10 does not resonate.

[0022] The following describes examples of changes to this disclosure. In the above configuration, the end of the total time is defined as the end of the igniter's operating time; however, the end of the total time may also be defined as the same as the end of the igniter's operating time (time t4 = time t5 in Figure 2). In the above configuration, the air-fuel ratio is set to be either gas-rich or air-rich during both the slow ignition time and the standby time, but this is not the only configuration. For example, the air-fuel ratio during the standby time may be changed to match that of the slow ignition time, or the air-fuel ratio during both the slow ignition time and the standby time may be set to the same air-fuel ratio as in normal control. The ignition means and flame detection means are not limited to the above-described forms. The gas control means is not limited to proportional valves; for example, solenoid valves may be provided in multiple branch pipes branched from the gas pipe, and the input may be controlled by switching the opening and closing of each solenoid valve. [Explanation of Symbols]

[0023] 1. Dishwasher booster, 2. Casing, 3. Heat source unit, 4. Tank, 5. Circulation path, 6. Controller, 10. Housing, 11. Burner, 12. Heat exchanger, 13. Gas pipe, 14. Main gas solenoid valve, 15. Proportional valve, 16. Main gas solenoid valve, 17. Fan, 19. Ignition electrode, 20. Igniter, 21. Flame rod, 27. Water supply pipe, 29. Hot water outlet pipe, 30. Supply pipe, 31. Return pipe.

Claims

1. An instantaneous heating type heat source unit comprising a burner, a heat exchanger, a fan for supplying combustion air to the burner, an ignition means for the burner, a flame detection means for the burner, and a housing that at least houses the burner and the heat exchanger, A tank for storing hot water, A circulation path equipped with a circulation pump for circulating hot water between the heat exchanger and the tank, A gas control means for controlling the amount of fuel gas supplied to the burner, Includes a controller that controls the combustion of the burner and the operation of the circulation pump, The controller, when igniting the burner, operates the ignition means until a predetermined operating time has elapsed, and uses the gas control means to supply fuel gas at a predetermined low input to ignite the burner, performing slow ignition control. After the slow ignition control, when the flame of the burner is detected by the flame detection means and a predetermined slow ignition time has elapsed, the gas control means performs normal control, in which the fuel gas is supplied at a predetermined high input greater than the low input to ignite the burner. A dishwasher booster that can heat the hot water in the tank to a predetermined temperature by operating the circulation pump while the burner is burning, and can supply the heated hot water in the tank to a dishwasher-side tank provided in an external dishwasher, wherein the controller controls the combustion of the burner, A method for controlling the combustion of a burner in a booster for a dishwasher, wherein the controller adds a predetermined waiting time to the slow ignition time to continue the combustion of the burner, and the normal control is performed after the total time of the slow ignition time and the waiting time has elapsed.

2. The method for controlling the combustion of a burner in a booster for a dishwasher according to claim 1, wherein the controller sets the waiting time such that the end of the total time coincides with the end of the operating time of the ignition means or the end of the operating time.

3. The method for controlling the combustion of a burner in a booster for a dishwasher according to claim 1 or 2, wherein the controller controls the gas control means and / or the fan during the standby time so that the air-fuel ratio, which is the ratio of the amount of combustion air supplied by the fan to the amount of fuel gas supplied by the gas control means, becomes more gas-rich or air-rich than when the normal control is being performed.

4. The method for controlling the combustion of a burner in a booster for a dishwasher according to claim 1 or 2, wherein the total time is at least 20 seconds.

5. An instantaneous heating type heat source unit comprising a burner, a heat exchanger, a fan for supplying combustion air to the burner, an ignition means for the burner, a flame detection means for the burner, and a housing that at least houses the burner and the heat exchanger, A tank for storing hot water, A circulation path equipped with a circulation pump for circulating hot water between the heat exchanger and the tank, A gas control means for controlling the amount of fuel gas supplied to the burner, Includes a controller that controls the combustion of the burner and the operation of the circulation pump, The controller, when igniting the burner, operates the ignition means until a predetermined operating time has elapsed, and uses the gas control means to supply fuel gas at a predetermined low input to ignite the burner, performing slow ignition control. After the slow ignition control, when the flame of the burner is detected by the flame detection means and a predetermined slow ignition time has elapsed, the controller performs normal control by supplying fuel gas at a predetermined high input greater than the low input using the gas control means to ignite the burner, while A dishwasher booster that can heat the hot water in the tank to a predetermined temperature by operating the circulation pump while the burner is burning, and can supply the heated hot water in the tank to a dishwasher-side tank provided in an external dishwasher, The controller adds a predetermined waiting time to the slow ignition time to allow the burner to continue burning, and the booster for the dishwasher executes the normal control after the total time of the slow ignition time and the waiting time has elapsed.

6. The booster for a dishwasher according to claim 5, wherein the controller sets the waiting time such that the end of the total time coincides with the end of the operating time of the ignition means or the end of the operating time.

7. The booster for a dishwasher according to claim 5 or 6, wherein the controller controls the gas control means and / or the fan during the standby time so that the air-fuel ratio, which is the ratio of the amount of combustion air supplied by the fan to the amount of fuel gas supplied by the gas control means, becomes more gas-rich or air-rich than when the normal control is being performed.

8. The booster for a dishwasher according to claim 5 or 6, wherein the total time is at least 20 seconds.

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