JP6411140B2 - Steam generator - Google Patents

Description

  The present invention relates to a steam generator and a heating cooker, and more particularly to a steam generator and a heating cooker capable of performing cooking using steam.

  As a heating cooker using steam, a heating device described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-176943) is provided. The heating device of Patent Document 1 controls water supply to the steam generation unit based on temperature information from a temperature detection unit provided in the steam generation unit.

Japanese Patent Laid-Open No. 2004-176943

  In Patent Document 1, water detection is performed by detecting the temperature of the steam generation unit. That is, the detection is performed by utilizing the property that the temperature is constant when water is present and the temperature further increases when water is exhausted. In the control, heating is stopped when the temperature of the steam generator rises to some extent.

  However, although the method using the detection temperature of Patent Document 1 can determine whether or not there is water, it is difficult to detect the water level of how much water is present inside the steam generation unit. Therefore, in Patent Document 1, when the heating is stopped based on the detected temperature, the water in the container may already be completely evaporated to be in a dry-up state. In this case, there is a problem that the scale (mineral component of tap water, calcium carbonate, etc.) generated by evaporation tends to adhere to the inner wall of the container, and the thermal efficiency decreases when the amount of attached scale increases.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a steam generator and a heating cooker that can perform operation control of steam generation in accordance with the amount of water in the steam generator.

  A steam generator according to an aspect of the present invention detects a water level in a housing, a steam generator having a housing capable of storing water, a heating unit for heating the housing to generate steam, and a water level in the housing A water level detection unit, a water supply unit for supplying water into the housing, and a control unit for controlling the heating unit and the water supply unit, and the control unit has a threshold level detected by the water level detection unit. When the period for determining that the detected water level does not exceed the threshold and thereafter determining that the detected water level does not exceed the first period continues, the supply of water into the housing is performed. The water supply unit is controlled to start, and the heating unit is controlled to stop heating of the housing when the period for which it is determined that the water supply unit does not exceed the second period is longer than the first period. Configured as follows.

  Preferably, the length of the second period indicates the length of the period required for the water level stored in the housing to change from a threshold value to a predetermined residual water level due to evaporation.

  Preferably, the control unit further controls the heating unit to start heating the housing when it is determined that the detected water level exceeds the threshold value, and then the period for determining that the detected water level exceeds the threshold value continues for the third period. And when the period which determines with exceeding is continued for the 4th period longer than a 3rd period, it is comprised so that a water supply part may be controlled to stop supply of the water into a housing.

  Preferably, the steam generator further includes a temperature detection unit that detects the temperature in the housing, and changes the length of the water supply period by the water supply unit based on the temperature detected by the temperature detection unit.

  Preferably, the length of the water supply period when the detected temperature is equal to or higher than a predetermined temperature is longer than the length of the water supply period when the detected temperature is lower than the temperature.

  Preferably, the heating cooker further includes a water tank for containing water, and the water supply unit has a pump for circulating water between the water tank and the inside of the housing.

  The control unit controls the pump so as to continue the supply operation of sending water from the water tank into the housing for a predetermined supply period from the start of water supply into the housing, or heating by the heating unit. When the pump is controlled so as to continue the supply operation for a predetermined period from the stop, when the determination unit determines that the detected water level does not exceed the threshold value, it is determined that there is no water in the water tank. Composed.

  Preferably, a control part controls a pump so that the water in a housing may be sent to a water tank.

  Preferably, the water level detection unit has an electrode that can be immersed in the water of the housing, and detects the water level in the housing by conduction between the electrodes.

  When the other aspect of this invention is followed, the cooking-by-heating machine provided with the steam generator as described above is further provided with a food storage room, and is constituted so that steam from a steam generator may be supplied into a storage room.

  ADVANTAGE OF THE INVENTION According to this invention, operation control of steam generation can be implemented according to the quantity of the water in a steam generation part.

It is a schematic front view at the time of the door closing of the heating cooker which concerns on Embodiment 1. FIG. It is a schematic front view at the time of door opening of the heating cooker of FIG. It is a schematic diagram for demonstrating the structure of the principal part of the heating cooker which concerns on Embodiment 1. FIG. It is a control block diagram of the heating cooker according to the first embodiment. FIG. 3 is a diagram illustrating a functional configuration and stored contents according to the first embodiment. 3 is a process flowchart relating to control of water supply and heating to the steam generator according to Embodiment 1; 3 is a timing chart regarding water supply and heating control according to the first embodiment. 3 is a timing chart regarding water supply and heating control according to the first embodiment. 3 is a timing chart regarding water supply and heating control according to the first embodiment. It is a figure which shows typically the signal waveform at the time of the normal driving | operation which concerns on Embodiment 1. FIG. It is a figure which shows typically the signal waveform in the case of stopping heating by detection temperature at the time of water supply abnormality. It is a figure which shows typically the signal waveform in the case of stopping heating by the detected water level at the time of abnormal water supply according to Embodiment 1. 6 is a timing chart for explaining water supply control according to Embodiment 2. 10 is a timing chart regarding water supply and heating control according to the third embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In each figure, the same reference numerals indicate the same or corresponding parts, and description thereof will not be repeated.

  With reference to FIGS. 1-3, the heating cooker provided with the steam generator which concerns on embodiment is demonstrated. In the following description, the left side refers to the left side toward the cooking device when the cooking device is viewed from the door side, and the right side refers to the cooking device when the cooking device is viewed from the door side. Point to the right side.

(Embodiment 1)
FIG. 1 is a schematic front view of the heating cooker according to Embodiment 1 when the door is closed. FIG. 2 is a schematic front view when the door of the cooking device of FIG. 1 is opened. As shown in the figure, the cooking device includes a rectangular parallelepiped casing 1, a heating chamber 2 provided in the casing 1 and having an opening 2a on the front side, and a door 3 for opening and closing the opening 2a of the heating chamber 2. And a magnetron 4 (shown in FIG. 4) for supplying microwaves to the heating chamber 2. The heating chamber 2 is an example of a “accommodating room” for accommodating foods to be cooked.

  An exhaust duct 5 is provided at the rear of the upper surface of the casing 1. A dew receptacle 6 is detachably attached to the lower part of the front surface of the casing 1. The dew receptacle 6 is located below the door 3 and is provided so as to receive water droplets from the rear surface of the door 3. Further, a water supply tank 26 described later is detachably attached to the lower part of the front surface of the casing 1. The water supply tank 26 stores water for generating steam, which will be described later.

  The lower part of the door 3 is rotatably attached to the front surface of the casing 1. A transparent outer glass 7 having heat resistance is provided on the front surface of the door 3 (the surface opposite to the heating chamber 2). The door 3 has a handle 8 positioned above the outer glass 7 and an operation panel 9 provided on the right side of the outer glass 7.

  The operation panel 9 has a color liquid crystal display unit 10 for displaying various information and a button group 11. The button group 11 includes a cancel key 12 that is operated when heating is stopped halfway, a start key 13 that is operated when heating is started, menu keys for designating various cooking modes, and the like. The operation panel 9 is provided with an infrared light receiving unit 14 that receives infrared rays from a smartphone or the like. The operation panel 9 is an example of an “operation unit” for accepting a user operation on the cooking device.

  FIG. 2 schematically shows the inside of the heating chamber 2 with the door 3 opened. In relation to the position where the foodstuff 15 is placed, air outlets 29, 30, 31, 37 and the like for sending steam into the cabinet are arranged. An air inlet 27 is also provided. Details of these will be described later.

  FIG. 3 schematically shows the configuration of the main part of the cooking device. In FIG. 3, the heating chamber 2 is shown as viewed from the left side.

  The heating cooker includes a circulation duct 18, an upper heater 20, an intermediate heater 21, a lower heater 22, a circulation damper 23, a steam generator 24, a tube pump 25, and a detachable water supply tank 26. Each of the upper heater 20, the middle heater 21, and the lower heater 22 is a sheathed heater, for example.

  The upper part 2e of the heating chamber 2 is connected to the rear part 2d of the heating chamber 2 through an inclined portion 2f. A plurality of suction ports 27 are provided in the inclined portion 2 f so as to face the circulation fan 19. A plurality of upper outlets 28 are provided in the upper part 2 e of the heating chamber 2. Moreover, the blower outlets 29, 30 and 31 are provided in the rear part 2d of the heating chamber 2, respectively.

  Cooking trays 91 and 92 are accommodated in the heating chamber 2. The cooking trays 91 and 92 are used for placing foods to be cooked. When the cooking trays 91 and 92 are accommodated in the cabinet, the placed foods are discharged from the outlets 29, 30, and 31. It is set at a position where steam can be delivered.

  The circulation duct 18 is provided outside the heating chamber 2 and communicates with the inside of the heating chamber 2 through the suction port 27 and the air outlets 28 to 31. A circulation fan unit 80 having a circulation fan 19 is provided for convection of air, saturated steam, and the like (hereinafter referred to as “air”) in the heating chamber 2. The “air etc.” is an example of a heat medium for cooking.

  The upper heater 20 heats air that flows to the air outlet 28. The middle heater 21 heats air or the like from the circulation fan 19 toward the upper heater 20, and heats air or the like from the circulation fan 19 toward the lower heater 22.

  The lower heater 22 is disposed in the circulation duct 18 and heats air flowing to the outlets 30 and 31.

  The steam generator 24 is an example of a “steam generator”. The steam generator 24 includes a metal container 32 having an open upper end, a resin lid 33 that closes the opening, and a steam generating heater 34 (hereinafter referred to as a heater) that is cast into the bottom of the container 32 and includes a sheathed heater. 34) and an in-housing temperature sensor 70 for detecting the temperature in the container 32. Water from the water supply tank 26 is stored on the bottom of the container 32, and the heater 34 heats the stored water through the bottom of the container 32. The saturated steam generated by heating flows through the resin steam tube 35 and the metal steam pipe 36 and is supplied into the connection portion of the circulation duct 18. At this time, if the circulation fan 19 is driven, the saturated steam from the steam generator 24 is sent into the circulation duct 18. On the other hand, if the circulation fan 19 is not driven, the saturated steam flows out into the heating chamber 2 through the plurality of steam supply ports 37.

  The saturated steam blown out from the steam pipe 36 or the saturated steam in the heating chamber 2 is sent to the upper heater 20, the middle heater 21 and the lower heater 22 by the circulation fan 19, and heated by these heaters to be 100 ° C. or higher. It can be steam.

  A water level sensor 38 including a pair of electrode bars 39A and 39B is attached to the lid 33. The electrode rods 39A and 39B are attached so as to be immersed in the stored water in the container 32. It is detected from the output of the water level sensor 38 whether or not the two electrodes are in a conductive state due to immersion. Based on this detection, it is determined whether or not the water level on the bottom of the container 32 is a predetermined water level. The water level sensor 38 is an example of a “water level detection unit” for detecting the water level in the container 32.

  The container 32 is an example of a “housing” capable of storing water. The heater 34 is an example of a “heating unit” for heating the housing. The housing internal temperature sensor 70 is an example of a “temperature detection unit” for detecting the temperature in the container 32.

  The tube pump 25 is an example of a “pump” for circulating water between the steam generator 24 and the water supply tank 26. Specifically, the tube pump 25 squeezes the elastically deformable water supply / drainage tube 40 made of silicon rubber or the like with a roller (not shown), and causes the water in the water supply tank 26 to flow to the steam generator 24. Then, the water in the steam generator 24 is caused to flow into the water supply tank 26.

  The water supply tank 26 has a water supply tank main body 41 and a communication pipe 42. One end of the communication pipe 42 is located in the water supply tank body 41, and the other end is located outside the water supply tank 26. When the water supply tank 26 is accommodated in the tank cover 43, the other end of the communication pipe 42 is connected to the water supply / drainage tube 40 via the tank joint part 44. That is, the inside of the water supply tank main body 41 communicates with the inside of the steam generator 24 via the communication pipe 42 and the like.

  FIG. 4 is a control block diagram of the heating cooker according to the first embodiment. Referring to FIG. 4, the cooking device includes a control device 100 including a microcomputer, an external circuit, and an input / output circuit that inputs and outputs signals on a circuit board (not shown). The control device 100 includes an upper heater 20, an intermediate heater 21, a lower heater 22, a steam generating heater 34, a circulation fan motor 56, an exhaust fan motor 57, an air supply fan motor 58, a circulation damper motor 59, an exhaust gas. The damper motor 60, the supply damper motor 61, the operation panel 9, the steam sensor 53, the water level sensor 38, the tube pump 25, the magnetron 4, the in-housing temperature sensor 70, and the like are connected.

  The control device 100 controls various heaters and various motors, the tube pump 25, and the like based on signals from the operation panel 9, the steam sensor 53, the water level sensor 38, the in-housing temperature sensor 70, and the like.

  The control device 100 includes a timer 1C for timekeeping, a CPU (Central Processing Unit) 1A, and a storage unit 1B including a volatile or nonvolatile memory, various registers, and the like.

  FIG. 5 shows a functional configuration and stored contents of the heating cooker according to the first embodiment. Referring to FIG. 5A, CPU 1 </ b> A is an example of a “control unit” that controls a heating unit including heater 34 and a water supply unit including tube pump 25.

  Referring to FIG. 5 (A), CPU 1A synchronizes with the timing of timer 1C, counter control unit 2A for controlling a counting operation using a counter, which will be described later, and steam generator 24 by means of tube pump 25. A water supply control unit 2B for controlling water supply and a heating control unit 2C for controlling heating by the heater 34 are included. Each of these units is stored in advance in the storage unit 1B as a program. The function of each unit is realized by the CPU 1A reading and executing these programs. Note that these units may be realized by a combination of a program and a circuit.

  Referring to FIG. 5B, storage unit 1B includes threshold values α, α1, β corresponding to control parameters for controlling area E1 for storing pump counter 3A and heater counter 3B and heating and water supply. And an area E2 for storing β1.

  The pump counter 3 </ b> A is count-up controlled in order to measure the length of the period related to the operation or stop of the tube pump 25 for supplying water to the container 32. The heater counter 3 </ b> B is count-up controlled to measure the length of the period related to the heating operation in the container 32 by the heater 34. The pump counter 3A and the heater counter 3B are realized using, for example, a register of the storage unit 1B, but are not limited thereto.

  The threshold values α, α1, β, and β1 are values that are compared with the count values of the pump counter 3A and the heater counter 3B in the region E1, and are used to determine the time (period) related to heating or the time (period) related to water supply. To be referenced. Details thereof will be described later.

  FIG. 6 is a process flowchart relating to water supply and heating control according to Embodiment 1 of the present invention. This flowchart is stored in advance in the storage unit 1B as a program. The CPU 1A reads out the program from the storage unit 1B and executes the program, thereby realizing processing. FIGS. 7-8 shows the timing chart regarding control of the water supply and heating which concern on Embodiment 1 of this invention. 7 to 8 show the elapsed time on the horizontal axis, the presence or absence of the water level in the container 32 in relation to the elapsed time in the direction of the vertical axis, ON (operation) or OFF (stop) of the tube pump 25, And a signal indicating ON (heating) or OFF (heating stop) of the heater 34 is shown.

  The water supply controller 2 </ b> B controls the supply of voltage to the tube pump 25. Specifically, the tube pump 25 rotates when a voltage is supplied, and the rotation operation acts to circulate water through the tube. Further, when the supply of voltage is stopped by the water supply control unit 2B, the rotation operation of the pump is stopped and the water flow is also stopped. Thus, supplying the voltage signal to the tube pump 25 by the water supply control unit 2B is referred to as “pump ON”, and stopping the output of the voltage signal is referred to as “pump OFF”.

  The heating control unit 2C supplies current to the heater 34 by duty control. The heater 34 generates heat when current is supplied, and stops heating when the current supply is stopped. Here, supplying a current signal to the heater 34 by duty control by the heating controller 2C is referred to as “heater ON”, and stopping the supply of the current signal is referred to as “heater OFF”.

  In the control according to the first embodiment, when steaming cooking mode is performed, cooking using steam from the steam generator 24 is performed. When this steaming cooking mode is performed, the CPU 1A controls the heater 34 and the tube pump 25 to be turned on and off so that a predetermined amount of water is stably stored in the container 32 while generating steam. Thereby, it becomes possible to make the finishing state of the foodstuffs by steam cooking using steam favorable.

  Control of water supply and heating to the steam generator will be described with reference to the timing charts of FIGS. The threshold value TH shown below is a stored water level from the bottom surface of the container 32, and indicates a water level at which the electrode rods 39A and 39B of the water level sensor 38 can be conducted. The determination unit of the CPU 1A determines that “there is water” based on the output of the water level sensor 38 in the conductive state, and “water” based on the output of the water level sensor 38 when the water level is less than the threshold TH in the non-conductive state. "None".

  First, it is assumed that the heater 34 and the tube pump 25 are ON / OFF controlled and the steam cooking mode is being performed.

  The normal operation of FIG. 7 will be described with reference to FIG. When “pump OFF” and “heater ON”, the CPU 1A determines whether or not “water present” changes to “water absent” based on the output of the water level sensor 38 (step S3). If this change is not determined (NO in step S3), step S3 is repeated.

  When determining the change from “with water” to “without water” (step S3), the counter control unit 2A initializes the pump counter 3A and the heater counter 3B (for example, sets 0) (step S5).

  Thereafter, the stored water level of the container 32 is detected based on the output of the water level sensor 38 (hereinafter also referred to as a detected water level). Then, it is determined whether or not the condition of (detected water level <threshold TH) is satisfied (step S7). If it is determined that it is not established (NO in step S7), the process returns to step S3. As described above, when it is determined that “water is present” based on the condition (detected water level <threshold value TH), that is, when it is determined that the water level of the container 32 has been recovered, the processing from step S9 described later is performed. Instead, normal ON / OFF control of the heater 34 and the tube pump 25 is performed.

  On the other hand, if it is determined that the condition of (detected water level <threshold TH) is satisfied (YES in step S5), it is determined as “no water”, that is, the water level is not recovered. In order to increase, more specifically, ON / OFF control for recovering the detected water level to the threshold value TH is performed.

  First, the counter control unit 2A starts counting up the pump counter 3A and the heater counter 3B (step S9). After the count-up starts, the count-up continues in synchronization with the timer 1C. Thereafter, the CPU 1A determines whether or not the condition (the count value of the pump counter 3A> the threshold value α) is satisfied (step S11). If it is determined that the condition is not satisfied (NO in step S11), the process returns to step S7, and the subsequent processing is similarly repeated.

  On the other hand, if it is determined that the condition is satisfied (YES in step S11), the water supply control unit 2B switches the tube pump 25 from “OFF control” to “ON control” (step S13). Then, it returns to step S3. Thereby, the supply of water from the water supply tank 26 is started into the container 32 so that the water level of the container 32 is recovered.

  As described above, when it is determined that the detected water level does not exceed the threshold value TH (when it is determined that the water level has changed from the presence of water to the absence of water), the period during which it is determined that the detected water level does not exceed the first threshold value α is then displayed. If this period continues (when the period of time t1 to t2 in FIG. 7 has elapsed), the ON control of the tube pump 25 is started so as to start the supply of water into the container 32. The threshold value α is a sufficiently short period, and is the length of time required to sufficiently absorb noise (including circuit noise) included in the output of the water level sensor 38 and obtain a stable detected water level. Equivalent to. The threshold value α is obtained in advance by experiments or the like.

  Further, the CPU 1A determines whether or not the condition (counter value of the heater counter 3B> threshold value β) is satisfied (step S15). If it is determined that the condition is not satisfied (NO in step S15), the process returns to step S7, and the subsequent processing is similarly repeated.

  On the other hand, if it is determined that the condition is satisfied (YES in step S15), the heating control unit 2C switches the heater 34 from “ON control” to “OFF control” (step S17). Then, it returns to step S3. Thereby, when the water level of the container 32 does not recover to the threshold value TH (the amount of water is small), the heating is stopped. As a result, the dry-up state can be avoided. Here, the dry-up state refers to a dry state in which the container 32 has no stored water and scale can adhere to the inner wall of the container 32.

  As described above, when it is determined that the detected water level does not exceed the threshold value TH, the heating of the container 32 is stopped when the period during which it is determined that the detected water level does not exceed thereafter continues for the second period indicated by the threshold value β. The heater 34 is controlled. That is, in the normal operation shown in FIG. 7, since water supply is normally performed by ON control (water supply) of the tube pump 25, the water level of the container 32 can be recovered between time t1 and t4. Therefore, during normal operation in which normal water supply is performed, switching of “ON control” → “OFF control” of the heater 34 by the heating control unit 2C is not performed. Therefore, steam generation can be continued stably.

  However, if there is an abnormality in the water supply of the tube pump 25 and the water level does not recover during time t1 to t4 (a period corresponding to the threshold value β) (see FIG. 8), the heating control unit 2C at time t4 in FIG. Thus, switching from “ON control” to “OFF control” of the heater 34 is performed (step S17). As a result, when the water level cannot be recovered even by the “ON control” of the tube pump 25, the heating by the heater 34 can be stopped to avoid the dry-up and prevent the scale from adhering.

  Here, there is a relationship of (threshold α> threshold β). The threshold value β indicates the length of time required for the water level stored in the container 32 to change from the threshold value TH to a predetermined residual water level by evaporation. For example, the threshold value TH is a water level corresponding to 25 to 30 ml, and the residual water level is a water level at which dry-up can be avoided, for example, a water level corresponding to 10 to 15 ml.

  Next, similarly, the operation at the time of temporary water supply abnormality of FIG. 9 while the steam cooking mode is being performed with the heater 34 and the tube pump 25 being controlled ON / OFF will be described with reference to FIG. To do.

  For example, in the case of “pump ON” and “heater OFF” after elapse of time t4 in FIG. 8, the CPU 1A determines whether or not it changes from “without water” to “with water” based on the output of the water level sensor 38. Determine (step S3). If this change is not determined (NO in step S23), step S23 is repeated.

  When it is determined that there is a change from “without water” to “with water” (YES in step S3), the counter control unit 2A initializes the pump counter 3A and the heater counter 3B (for example, sets 0) (step S25). .

  Thereafter, based on the output of the water level sensor 38, it is determined whether or not the water level is sufficient, that is, whether or not the condition (detected water level> threshold value TH) is satisfied (step S27). If it is determined that it is not established (NO in step S27), the process returns to step S23, and ON control of the tube pump 25 is performed. Thus, when the water level of the container 32 is not yet sufficient, the water supply by ON control of the tube pump 25 is implemented, without performing the process after step S29 mentioned later.

  On the other hand, if it is determined that the condition of (detected water level> threshold value TH) is satisfied (YES in step S27), the water level is recovered by the water supply, so that the water level of the container 32 is maintained at an appropriate amount. ON / OFF control for maintaining the threshold TH is performed.

  First, the counter control unit 2A controls the pump counter 3A and the heater counter 3B to start counting up (step S29). After the count-up starts, the CPU 1A determines whether or not the condition (count value of the heater counter 3B> threshold value β1) is satisfied (step S35). If it is determined that the condition is not satisfied (NO in step S35), the process returns to step S27, and the subsequent processing is similarly repeated.

  On the other hand, if it is determined that the condition is satisfied (YES in step S35), the heating control unit 2C switches the heater 34 from “OFF control” to “ON control” (step S37). Then, it returns to step S3.

  Even when the heater 34 is OFF-controlled due to the water supply abnormality in FIG. 8, when the period in which the detected water level exceeds the threshold value TH continues for the period indicated by the threshold value β1, the heater 34 is ON-controlled, By generating steam quickly, the steam can be stably supplied into the heating chamber 2.

  Further, the CPU 1A determines whether or not the condition (count value of the pump counter 3A> threshold value α1) is satisfied (step S31). If it is determined that the condition is not satisfied (NO in step S31), the process returns to step S27, and the subsequent processing is similarly repeated.

  On the other hand, if it is determined that the condition is satisfied (YES in step S31), the water supply control unit 2B switches the tube pump 25 from “ON control” to “OFF control” (step S33). Thereafter, the process returns to step S23. Thereby, the water supply from the water supply tank 26 stops so that the water level of the container 32 may be maintained at an appropriate amount.

  As described above, when it is determined that the detected water level exceeds the threshold value TH (time t1 in FIG. 9), and thereafter, the period determined to exceed the third period indicated by the threshold value β1 (time in FIG. 9). t <b> 1 to t <b> 2), the heater 34 is turned on to start heating in the container 32, and the period during which the detected water level is determined to exceed the threshold value TH is longer than the threshold value β <b> 1 (third period). When the period of 4 (the period indicated by the threshold value α1) continues, the tube pump 25 is controlled to be OFF so that the supply of water into the container 32 is stopped.

  Here, the threshold value β1 is a sufficiently short period, and corresponds to the length of time required until a stable detection water level is obtained by sufficiently absorbing circuit noise included in the output of the water level sensor 38. The threshold value β1 is obtained in advance through experiments or the like.

  Thus, when the water level of the container 32 is recovered, heating can be started at an early stage, and steam supply into the heating chamber 2 can be stably performed.

  10 to 12 are data obtained by experiments, and are diagrams for explaining the ON / OFF control for the tube pump 25 and the heater 34 according to the first embodiment. In each figure, the horizontal axis indicates the passage of time, and the detected water level A of the water level sensor 38, the detected temperature B of the in-housing temperature sensor 70, the ON / OFF of the tube pump 25, the ON / OFF of the heater 34 along the vertical axis. OFF and the change of the water quantity E in the container 32 are typically shown. The control according to the embodiment will be further described with reference to FIGS.

  In the case of the normal operation in FIG. 10, when “no water” is determined, the tube pump 25 is ON-controlled. Then, the water level recovers before the threshold β period for controlling the heater 34 to turn OFF. Therefore, the heater 34 can always be controlled to be ON, and steam can be generated stably.

  FIG. 11 and FIG. 12 show the operation when water supply is abnormal. Conventionally, as shown in FIG. 11, in the case of controlling the heater 34 based on the detected temperature, the heater 34 is stopped after the temperature rises. When the heater 34 is stopped, the inside of the container 32 may already be in a dry-up state, and scale adhesion cannot be avoided, resulting in a decrease in heating efficiency.

  On the other hand, in the control at the time of water supply abnormality according to Embodiment 1 shown in FIG. 12, even when the water level does not recover due to water supply abnormality, the heater 34 is turned off at an early stage thereafter (after the threshold β period has elapsed). Can be controlled. Thereby, the heater 34 can be OFF-controlled while leaving the amount of water that can avoid the dry-up state in the container 32. Therefore, scale adhesion as shown in FIG. 11 can be avoided and heating efficiency can be maintained.

(Embodiment 2)
The second embodiment shows a modification of the first embodiment.

  In the second embodiment, the time period from when the water level is detected during water supply to when the water supply is stopped differs between a boiling high temperature at which the water surface of the container 32 easily moves and a low temperature at which the water surface of the container 32 does not move relatively. By setting the length, water level control is performed to prevent pump ON / OFF hunting and maintain a stable water level.

  FIG. 13 is a timing chart for explaining the water level control according to the second embodiment. In FIG. 13, the horizontal axis indicates the passage of time, and the vertical axis indicates the detected water level of the container 32 and ON / OFF of the tube pump 25 in association with each other. FIG. 13 shows a case where the temperature in the container 32 is 100 ° C. or higher, for example, when the steam cooking mode is in operation, and a case where the temperature in the container 32 is 100 ° C. or lower, for example, the initial water supply at the start of the steam cooking mode. Is shown.

  In the present embodiment, the tube pump 25 is ON / OFF controlled so that the water level determined as “water present” based on the threshold value TH is maintained for stable steam generation. Therefore, it is desirable to accurately control the time period from the detection of the water level when water is supplied into the container 32 until the water supply is stopped. In the second embodiment, as shown in FIG. 13, the length of the water supply period by the ON control of the tube pump 25 is changed based on the temperature detected by the in-housing temperature sensor 70. Specifically, the water supply control unit 2B determines that the length of the water supply period Xα1 when the detected temperature is equal to or higher than a predetermined temperature (for example, 100 ° C.) is less than the temperature. Change to be longer than

  Accordingly, by performing “ON control” of the tube pump 25 until the water level is stabilized at the time of boiling when the water surface moves, hunting related to ON / OF control of the tube pump 25 can be prevented and the control can be stabilized. In a state where the temperature is low and the water surface is quiet, the water supply can be stopped immediately after the water level is detected, and heating by the heater 34 can be started.

(Embodiment 3)
In the third embodiment, a modification of the first or second embodiment will be described. In the present embodiment, the absence of water in the water supply tank 26 is determined based on the detected water level based on the output of the water level sensor 38. FIG. 14 is a timing chart for explaining the control according to the third embodiment. FIG. 14 shows the passage of time on the horizontal axis and the detected water level of the container 32, ON / OFF of the tube pump 25, and ON / OFF of the heater 34 on the vertical axis.

  The CPU 1 </ b> A has two timings for determining the absence of water in the water supply tank 26. First, when the tube pump 25 is ON-controlled so as to continue the supply operation of sending water from the water supply tank 26 into the container 32 for a predetermined period from the start of water supply into the container 32. (See period Xα2 in FIG. 13). The second time is when the water supply operation is continued by the ON control of the tube pump 25 during a predetermined period (period Yα2 in FIG. 13) from the OFF control (heating stop) of the heater 34. If it is determined that the detected water level has exceeded the threshold TH at the first or second timing, it is determined that the water level has recovered, that is, the water supply tank 26 has water. On the other hand, if it is determined that (detected water level <threshold TH) at any of the first and second timings, it is determined that there is no water in the water supply tank 26 because the water level cannot be recovered.

  The determination result is displayed via the color liquid crystal display unit 10 or output from an audio output unit (not shown). Thereby, it is possible to prompt the user to supply water to the water supply tank 26.

  According to the third embodiment, the absence of water in the water supply tank 26 can be determined without providing the water level detection function of the water supply tank 26.

(Embodiment 4)
The fourth embodiment shows a modification of the first to third embodiments. In the fourth embodiment, the CPU 1 </ b> A controls the tube pump 25 so as to send the water in the container 32 to the water supply tank 26. Thereby, for example, the tube pump 25 is reversely rotated so that the residual water after cooking in the container 32 is returned to the water supply tank 26 at the end of cooking in the steaming mode or when a predetermined time has elapsed since the end. Thereby, the water with a comparatively high calcium carbonate density | concentration at the time of completion | finish of the steaming cooking mode which remained in the container 32 can be discharged | emitted to the water supply tank 26 side.

  In the fourth embodiment, the discharge destination of the residual water in the container 32 is the water supply tank 26. However, the drainage path is not limited to this, and for example, a path for discharging to the dew receiver 6 side may be provided.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2A Counter Control Unit, 2B Water Supply Control Unit, 2C Heating Control Unit, 3A Pump Counter, 3B Heater Counter, 9 Operation Panel, 24 Steam Generator, 25 Tube Pump, 26 Water Supply Tank, 34 Steam Generator Heater, 38 Water Level Sensor, 39A, 39B Electrode rod, 70 Temperature sensor in housing, 100 Control device.

Claims (6)

A steam generating section having a housing capable of storing water, and a heating section for heating the housing to generate steam;
A water level detector for detecting the water level in the housing;
A water supply section for supplying water into the housing;
A control unit for controlling the heating unit and the water supply unit,
The controller is
A determination unit that determines whether or not the detected water level by the water level detection unit exceeds a threshold;
When the period for determining that the detected water level does not exceed the threshold value and thereafter not exceeding the threshold value continues for the first period, the water supply unit is controlled to start supplying water into the housing. And
The heating unit is configured to stop heating of the housing when the period that is determined not to exceed is continued for a second period longer than the first period .
The control unit further includes:
When it is determined that the detected water level exceeds the threshold value, and thereafter, when the period for determining that the detected water level exceeds is continued for the third period, the heating unit is controlled to start heating the housing, and
Period is determined that the excess is, when the continuing said third long fourth period than, Ru is configured to supply water into the said housing to control the water supply unit to stop, Steam generator. The length of the second period indicates a length of a period required for the water level stored in the housing to change from the threshold value to a predetermined residual water level due to the generation of the steam. The steam generator according to 1. A temperature detection unit for detecting the temperature in the housing;
The steam generator according to claim 1 or 2 , wherein a length of a water supply period by the water supply unit is changed based on a temperature detected by the temperature detection unit. The steam generator according to claim 3 , wherein a length of the water supply period when the detected temperature is equal to or higher than a predetermined temperature is longer than a length of the water supply period when the detected temperature is lower than the temperature. A water tank for containing water;
The water supply unit has a pump for circulating water between the water tank and the housing,
The controller is
When the pump is controlled so as to continue the supply operation of sending water from the water tank into the housing for a predetermined supply period from the start of water supply into the housing, or by the heating unit When the pump is controlled to continue the supply operation for a predetermined period from the heating stop,
The steam generation according to any one of claims 1 to 4 , wherein when the determination unit determines that the detected water level does not exceed the threshold value, it is determined that there is no water in the water tank. apparatus. The controller is
The steam generator according to claim 5 , wherein the pump is controlled so that water in the housing is delivered to the water tank.

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