Heating equipment and roasters

Abstract

To provide a heating device capable of taking measures against harmonics and flicker without deteriorating the performance of baking foodstuffs by simple temperature control. [Solution] According to the present invention, there is provided a heating device for heating food ingredients, comprising a heating unit and a control unit, wherein the heating unit is configured to be driven by an AC power source, and the control unit is configured to control a duty ratio, which is the ratio of the time that current is applied to the heating unit within a predetermined control period, and the control period is 15 seconds or more.

Description

[Technical Field]

[0001] The present invention relates to a heating device for cooking foodstuffs such as meat and vegetables, and a roaster equipped with the heating device. [Background technology]

[0002] Gas burners have been widely used in heating devices for cooking, but in recent years, heating devices that use electric heaters have been on the rise. These heating devices are often driven by AC power and consume a certain amount of power, so just like other home appliances that consume a lot of power, it is important to take measures against harmonics and flicker.

[0003] Patent Document 1 discloses a digital power supply for electric grills that uses phase angle control technology to cut the AC waveform at a desired phase angle, causing voltage changes at frequencies beyond human perception, thereby reducing harmonics and flicker. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6890166 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the level at which humans experience discomfort from flickering varies depending on the illuminance of the lighting and individual differences, but it is known that the frequency of illuminance changes is approximately 8.8 times per second (i.e., a frequency of 8.8 Hz). (Figure 11 of Patent Document 1 doubles the count to count on and off, and the graph is per minute, so the minimum value of the graph appears around 8.8 x 2 x 60 = 1056.) Therefore, in the above-mentioned conventional technology, even a slight increase in the control period due to improvements in the accuracy of temperature adjustment (e.g., by dividing the heater output setting step into smaller steps) can easily cause voltage changes in a frequency range that is easily perceived by humans. Furthermore, increasing the frequency at which the heater conduction state is switched would complicate temperature control.

[0006] The present invention has been made in consideration of these circumstances, and provides a heating device that can take measures against harmonics and flicker through simple temperature control without compromising the ability to grill food. [Means for solving the problem]

[0007] According to the present invention, the following inventions are provided. [1] A heating device for heating food ingredients, comprising a heating unit and a control unit, wherein the heating unit is configured to be driven by an AC power source, and the control unit is configured to control a duty ratio, which is the ratio of the time that current is applied to the heating unit within a predetermined control period, and the control period is 15 seconds or more. [2] A heating device as described in [1], further comprising a heat-reflecting member, wherein the heating section has an electric heater, and the heat-reflecting member is configured to cover the underside of the electric heater and has a support section configured to support a food placement member on the upper part. [3] A roaster for heating and cooking food, comprising the heating device described in [2] and a food placement member placed on the support part, and configured to heat and cook food on the food placement member using the heating device. [4] The roaster according to [3], further comprising a switching unit configured to be able to switch on and off the power supply to the heating unit, the switching on and off of the power supply to the heating unit being performed in accordance with the timing of the arrival of a zero cross point of the AC of the AC power supply, and performing at least one of power control in which the power supply to the heating unit is turned on at the beginning of the control period and turned off after a power supply time corresponding to the duty ratio has elapsed, and power control in which the power supply to the heating unit is turned off at the beginning of the control period and turned on after a predetermined time corresponding to the duty ratio has elapsed. [5] The roaster according to [3] or [4], wherein the control period is 15 seconds or more and 60 seconds or less. [6] The roaster according to [3] or [4], further comprising a detection unit configured to detect the temperature of the heating unit, and the control unit configured to control the duty ratio based on the detection result of the detection unit. [Effects of the Invention]

[0008] In the heating device of the present invention, the temperature of the heating element driven by an AC power source is controlled by the ratio of the time that current is applied to the heating element (duty ratio) within a long control period of 15 seconds or more (usually 1 second or less). This results in voltage changes at an extremely low frequency beyond human perception, resulting in almost no flicker. Furthermore, since there is no need to cut the AC voltage waveform at a desired phase angle and the AC voltage waveform is easily turned on and off at zero-crossing points (also known as zero-crossing points), repetitive waveforms other than sine waves are unlikely to occur. This means that harmonics are also unlikely to occur. Furthermore, the applicant's experiments have shown that food-supporting components such as grills and grates do not experience a sudden drop in temperature that would affect grilling performance for a considerable period of time, even when a long control period of 15 seconds or more is adopted. This allows for optimal heating of ingredients such as meat and vegetables while also providing simple temperature control to combat harmonics and flicker. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a roaster 1 according to one embodiment of the present invention. [Figure 2] FIG. 2A is a perspective view showing the appearance of the heating device 3, and FIG. 2B is an exploded perspective view of the heating device 3 seen from a different angle. [Figure 3] FIG. 3A is a perspective view showing the configuration of heater unit 33, food placement member 34, and heat reflecting member 35, and FIG. 3B is a perspective view showing the state in which food placement member 34 has been separated from heater unit 33 and heat reflecting member 35. [Figure 4] FIG. 4A is a schematic configuration of the temperature control section of the first electric heater 33A and the second electric heater 33B, and FIG. 4B is a waveform diagram showing an example of temperature control of the first electric heater 33A and the second electric heater 33B. [Figure 5] FIG. 10 is a diagram showing the short-term flicker value (Pst) when the drive voltage, control period, and duty ratio are changed. [Figure 6] 10 is a diagram showing a modified example of the temperature control section of the first electric heater 33A and the second electric heater 33B. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

[0011] <Outline of Roaster 1> As shown in FIG. 1, roaster 1 is equipment for cooking ingredients such as meat and vegetables, and includes a table 2 and a heating device 3. Table 2 includes a top plate 21 and a support portion 22. Top plate 21 has an opening 21A in the center, and the top of heating device 3 is exposed through this opening 21A. Support portion 22 has a hollow structure, and is configured so that the internal space can be opened by removing the side panel. This internal space houses a power unit that supplies power to heating device 3, a control unit that comprehensively controls the operation of roaster 1, various wiring, etc.

[0012] The table 2 is also provided with an operation unit 23. The operation unit 23 has a volume controller 23A that allows the user to adjust the heating power (also referred to as the amount of heat generated) of the heating device 3. The volume controller 23A may be configured, for example, so that the desired heating power can be obtained by the user turning a knob for adjusting the heating power. The position of the knob may be detected by the resistance value of an internal variable resistor. However, the means for adjusting the heating power of the heating device 3 is not limited to the volume controller 23A, and other known adjustment means may be used as appropriate.

[0013] <Heating device 3> 2A and 2B, the heating device 3 has a casing 31 and a top cover 32. The casing 31 contains a heater unit 33, a food placement member 34, a heat reflecting member 35, a drain pan 36, a filter 37, etc. The heater unit 33, the food placement member 34, and the heat reflecting member 35 will be described later.

[0014] The drain pan 36 is supported on the inner periphery of the casing 31 and also functions as an inner casing that surrounds the area where ingredients are cooked. The lower part of the drain pan 36 in the casing 31 is connected to an exhaust unit (not shown) via a filter 37. The exhaust unit has a connecting tube and an exhaust duct, and is configured to suck in smoke, oil droplets, etc. generated in the heating device 3, for example, by using the suction force of an exhaust fan in the exhaust duct. Therefore, smoke, oil droplets, etc. generated when ingredients are cooked are discharged to the outside of the roaster 1 through the through-holes in the top cover 32 and the exhaust flow path formed in the casing 31. It is preferable that a fire damper, a fall prevention net, etc. be provided on the connecting tube.

[0015] <Heater unit 33: heating section> As shown in FIGS. 3A and 3B, the heater unit 33 includes a first electric heater 33A and a second electric heater 33B of a resistance heating type. The first electric heater 33A and the second electric heater 33B are, for example, sheathed heaters having a heating element such as a nichrome wire, and each is rod-shaped. However, the shape of the electric heaters mounted in the heater unit 33 is not limited to a rod shape. For example, a U-shaped heater consisting of a continuous straight portion and an arc-shaped portion (e.g., a semicircular portion) can be used. It is also possible to use a shape consisting of multiple continuous U-shaped portions, a shape consisting only of curved portions, or other complex shapes. The heater unit 33 radiates heat from the first electric heater 33A and the second electric heater 33B to heat the air and the heat-reflecting member 35 of the first electric heater 33A and the second electric heater 33B, generating hot air. Furthermore, radiant heat from first electric heater 33A and second electric heater 33B reaches food placement member 34 and food directly, and indirectly after being reflected by heat reflecting member 35. As a result, food placement member 34 and food are heated by hot air and radiant heat.

[0016] In this embodiment, the food placement member 34 is a stainless steel grate (also called a grill). However, a grate or other material can also be used instead of a grate. Also, iron materials can be used instead of stainless steel. It is preferable to use a food placement member 34 with as high a heat capacity as possible, so that the temperature of the food placement member 34 does not change easily even when a relatively long control period (e.g., 15 seconds or more) is used.

[0017] The heat-reflecting member 35 is configured to cover the underside of the first electric heater 33A and the second electric heater 33B, and has a support portion 35A configured to support the food placement member 34 on its upper portion. Because the heat-reflecting member 35 surrounds the first electric heater 33A and the second electric heater 33B on the side opposite the food placement member 34, heat can be efficiently transferred to the food placement member 34. Furthermore, even when a relatively long control cycle is adopted, as described below, a decrease in temperature of the food placement member 34 is suppressed. In this embodiment, the heat-reflecting member 35 is made of stainless steel with a No. 2B surface finish, but this is not limited to this. To minimize temperature changes in the food placement member 34 even when a relatively long control cycle (e.g., 15 seconds or longer) is adopted, it is preferable to use a heat-reflecting member 35 with as high a heat capacity as possible.

[0018] <Power Control of First Electric Heater 33A and Second Electric Heater 33B> 4A and 4B, power control for the first electric heater 33A and the second electric heater 33B will be described. The first electric heater 33A and the second electric heater 33B are each driven by an AC power supply 5. More specifically, the first electric heater 33A and the second electric heater 33B are configured to receive AC current from the AC power supply 5 via a semiconductor relay 4.

[0019] The semiconductor relay 4 is, for example, a solid-state relay (SSR), and in this embodiment is configured to operate based on a control signal from the control unit 6. The semiconductor relay 4 has a triac 41 and a zero-cross detection circuit 42. The triac 41 is configured to be able to switch on and off the power supply to the first electric heater 33A and the second electric heater 33B based on a control signal (gate output) from the control unit 6. In this embodiment, the triac 41 corresponds to the switching unit of the present invention. The zero-cross detection circuit 42 is configured to send a zero-cross pulse to the control unit 6 when it detects a zero-cross point of the AC power supply 5.

[0020] The control unit 6 is configured to control the ratio (duty ratio) of the time during which power is supplied to the first electric heater 33A and the second electric heater 33B within a predetermined control period. The control period is preferably 15 seconds or more, and more preferably approximately 15 to 60 seconds. Specific examples of the control period include 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 seconds, and may be within a range between any two of the values ​​exemplified here (e.g., 15 to 40 seconds, 20 to 35 seconds, etc.).

[0021] For example, if the control period shown in FIG. 4B is 20 seconds, the energization time is set to 10 seconds when the duty ratio is 50%, and to 16 seconds when the duty ratio is 80%. The duty ratio is appropriately determined by the control unit 6 according to the setting value of the volume-type controller 23A. Here, the control unit 6 performs power control by turning on the gate output at the beginning of the control period to conduct the triac 41, and then turning off the gate output after a period of energization corresponding to the duty ratio has elapsed, thereby cutting off the power supply to the first electric heater 33A and the second electric heater 33B. However, the control unit 6 may also perform power control by turning off the gate output at the beginning of the control period to make the triac 41 non-conductive, and then turning on the gate output to start the power supply to the first electric heater 33A and the second electric heater 33B after a predetermined period of time corresponding to the duty ratio (the control period minus the energization time) has elapsed. These power control methods may also be used in combination. In either case, the on / off switching of the power supply to the first electric heater 33A and the second electric heater 33B is minimized (to once per control period).

[0022] Furthermore, the control unit 6 switches the triac 41 on and off (switches the power supply to the first electric heater 33A and the second electric heater 33B on and off) in accordance with the timing of the arrival of the zero-crossing point of the AC of the AC power supply 5. As a result, there is no need to cut the voltage waveform of the AC power supply 5 at a desired phase angle, making it less likely that a repetitive waveform other than a sine wave will occur, and therefore less likely that harmonics will occur. Furthermore, by switching the triac 41 on and off only at the zero-crossing points of the AC of the AC power supply 5, it is possible to use the power supply voltage as a sine wave, which is also a great advantage in terms of reducing power loss.

[0023] Figure 5 shows the measurement results of the short-term flicker value (Pst) of the international standard (IEC61000-3-3) for voltage fluctuations and flicker when the drive voltage, control period (also called drive period), and duty ratio (duty) are changed. In the experiment, an electric heater with a 1700W output driven by an AC voltage of 240V was used. Note that at a duty ratio of 100%, no on / off control is performed, so the control frequency was set to 0. In other cases, the reciprocal of the control period was used as the control frequency (also called drive frequency).

[0024] As shown in Figure 5, when the duty ratio is 100%, no on / off control is performed, resulting in a fairly small short-term flicker value (Pst) (less than 0.03). Furthermore, when the duty ratio was varied between approximately 30% and 80%, no correlation was observed between the drive voltage and duty ratio and the short-term flicker value (Pst). The applicant then discovered a strong correlation between the control period and the short-term flicker value (Pst). Specifically, the short-term flicker value (Pst) was found to be 1 or less when the control period was 15 seconds or longer, i.e., when the drive frequency was 0.067 or less, and 0.9 or less when the control period was 20 seconds or longer, i.e., when the drive frequency was 0.05 or less. IEC 61000-3-3 specifies the short-term flicker value (Pst) as 1, so it is important to keep the short-term flicker value (Pst) below 1.

[0025] Considering the short-term flicker value (Pst), the control period of the first electric heater 33A and the second electric heater 33B is preferably 15 seconds or more, more preferably 20 seconds or more, and even more preferably 30 seconds or more. However, since uneven browning when grilling foodstuffs (meat, etc.) is undesirable, the upper limit of the control period is preferably set appropriately taking into consideration the heat capacity of the foodstuff placing member 34, the heat reflecting member 35, etc. Even when using a stainless steel grill, which has a relatively small heat capacity, among the foodstuff placing members 34 used in the roaster 1, a control period of about 40 to 60 seconds did not result in uneven browning when grilling foodstuffs (meat, etc.).

[0026] In experiments evaluating grilling performance, not only were the food items' doneness visually inspected, but thermocouples were also soldered to nine locations on the stainless steel grill to measure the grill temperature. Even when the grill temperature was approximately 240-320°C and on / off control was performed with a control period of 40-60 seconds and a duty cycle of 50%, the temperature at each location on the grill did not drop by more than 20°C. In Roaster 1, even when the first electric heater 33A and the second electric heater 33B were driven at a duty cycle of 100%, the grill temperature may fluctuate by approximately 20°C. Therefore, a control period of approximately 60 seconds can be said to be comparable in terms of food grilling performance to a 100% duty cycle. Of particular note is that the temperature fluctuations on the grill were nearly identical when the control period was 40-60 seconds and when the control period was 0.5 seconds. Therefore, if the control cycle is within the range of 15 to 60 seconds, good grilling performance can be achieved regardless of the configuration and materials of foodstuff placing member 34 and heat reflecting member 35.

[0027] <Modification of Power Control of First Electric Heater 33A and Second Electric Heater 33B> In the above embodiment, an example has been described in which the control unit 6 appropriately determines the duty ratio based on the setting value of the volume-type controller 23A, etc., but this is not limiting. For example, as shown in FIG. 6, a temperature detection unit 6A may be further provided. The temperature detection unit 6A is configured to detect the surface temperatures of the first electric heater 33A and the second electric heater 33B. In this case, the control unit 6 may control the duty ratio taking into account the detection result of the temperature detection unit 6A in addition to the setting value of the volume-type controller 23A, etc.

[0028] <Other embodiments> In the above-described embodiment, since the first electric heater 33A and the second electric heater 33B are switched on and off infrequently, it is possible to use, for example, a mechanical relay instead of the semiconductor relay 4. [Explanation of symbols]

[0029] 1: Roaster 2: Table 3: Heating device 4: Semiconductor relay 5: AC power supply 6: Control section 6A: Temperature detection unit 21: Top plate 21A: Opening 22: Support part 23:Operation unit 23A: Volume controller 31: Casing 32: Top cover 33: Heater unit 33A: First electric heater 33B: Second electric heater 34: Food placing member 35: Heat reflecting material 35A: Support part 36: Drain pan 37: Filter 41: Triac 42: Zero cross detection circuit

Claims

1. A heating device for heating food materials, comprising a heating unit and a control unit, The heating unit is configured to be driven by an AC power source, the control unit is configured to control a duty ratio, which is a ratio of a time during which current is applied to the heating unit within a predetermined control period; A heating device, wherein the control period is 15 seconds or longer.

2. The heating device according to claim 1, further comprising a heat reflecting member, the heating unit has an electric heater, The heat reflecting member is configured to cover the underside of the electric heater and has a support portion configured to support a food placing member on top of the heat reflecting member.

3. A roaster for cooking food ingredients, The heating device according to claim 2; A food material placing member placed on the support portion; Equipped with A roaster configured to heat and cook food on the food placement member by the heating device.

4. The roaster according to claim 3, further comprising a switching unit, the switching unit is configured to be able to switch on and off the supply of electricity to the heating unit, The power supply to the heating unit is switched on and off in accordance with the timing at which a zero cross point of the AC power supply arrives, and A roaster that performs at least one of power control in which power supply to the heating unit is turned on at the beginning of the control cycle and power supply to the heating unit is turned off after a power supply time corresponding to the duty ratio has elapsed, and power control in which power supply to the heating unit is turned off at the beginning of the control cycle and power supply to the heating unit is turned on after a predetermined time corresponding to the duty ratio has elapsed.

5. The roaster according to claim 3 or claim 4, A roaster in which the control period is 15 seconds or more and 60 seconds or less.

6. The roaster according to claim 3 or claim 4, further comprising a detection unit, the detection unit is configured to detect a temperature of the heating unit, The control unit is configured to control the duty ratio based on the detection result of the detection unit.

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