JP7663417B2 - Rice cooker - Google Patents

Description

The present invention relates to a rice cooker that can detect abnormal temperatures in the lid that covers the opening of a pot that contains food to be cooked.

There have been many rice cookers of this type in the past, and the applicant of the present application has also proposed, for example in Patent Document 1, a rice cooker equipped with a thermistor-type lid sensor that detects the temperature of the inner lid. During cooking and keeping rice warm, the lid heater that heats the inner lid is controlled based on the temperature detected by the lid sensor, thereby controlling the temperature of the heat sink and, by extension, the inner lid.

JP 2008-295493 A

In conventional technologies including Patent Document 1, the inner lid is removably attached to the lid body, and the inner lid is kept clean by being easily cleaned. However, since the lid sensor detects the temperature of the inner lid by contacting the inner lid, if the inner lid is removed, the lid sensor cannot detect the temperature of the inner lid, and therefore, even if there is a temperature abnormality in the lid body at that time, it cannot be detected.

Figure 10 shows a front view of a conventional rice cooker 100 with the lid body 101 open and the inner lid removed. In a conventional rice cooker 1, if the drive circuit for the lid heater that heats the inner lid shorts out for some reason, the lid heater will remain ON, and there is a risk that the heat sink 103 on which the lid heater is installed and the outer lid cover 102 will become hot. If a contact-type lid sensor 104 such as a thermistor that comes into contact with the inner lid to detect the temperature of the inner lid detects an abnormality at this time, the user is notified of the temperature abnormality by, for example, a display such as an LCD or LED or an alarm such as a buzzer.

However, because the temperature of the inner lid was detected by the contact-type lid sensor 104, it was not possible to detect a temperature abnormality, for example, when the inner lid was removed from the lid body 101 to clean it. In such a case, the user could not be notified even if the heat sink 103 or outer lid cover 102 became too hot, and there was a risk that the user would come into contact with the hot heat sink 103 or outer lid cover 102.

The present invention aims to provide a rice cooker that can effectively detect when the lid has become abnormally hot.

The present invention comprises a pot for containing the food to be cooked, a lid body that can be opened and closed freely to cover the opening of the main body that contains the pot, an inner lid that is attached to the lid body and covers the opening of the pot when the lid body is closed, a lid temperature detection means that is attached inside the lid body without contacting the inner lid , and a display unit that displays various information, wherein the display unit is attached to a substrate disposed inside the lid body, the lid temperature detection means is attached to the substrate, and the lid temperature detection means detects and estimates the temperature of the inner lid by detecting the ambient temperature of the substrate .

According to the present invention, regardless of whether or not there is an inner lid, it is possible to detect the temperature of the part forming the lower part of the lid body, and it is possible to detect when the part forming the lower part of the lid body becomes too hot.

1 is an external perspective view of a rice cooker showing one embodiment of the present invention; FIG. FIG. 11 is a perspective view of the inner lid assembly unit as viewed from above. FIG. 11 is a perspective view of the inner lid assembly unit as viewed from the bottom side. FIG. 2 is a front view showing the rice cooker with the lid open. FIG. 13 is a block diagram showing the electrical configuration of the first embodiment. 11 is a graph showing the correlation between the temperature detected by the chip sensor and the temperature of the inner lid. FIG. 13 is an explanatory diagram of the rice cooker with the lid open. Same as above, (A) is a front view showing the rice cooker with the lid open and the inner lid assembly unit removed, (B) is a top view of the rice cooker and a plan view from the back of the control PC board. FIG. 11 is a front view showing a conventional rice cooker with the lid body open and the inner lid removed.

Each embodiment of the rice cooker of the present invention will be described with reference to the attached drawings. Note that the embodiments described below do not limit the contents of the present invention described in the claims. Furthermore, all of the configurations described below are not necessarily essential requirements of the present invention. The directions indicated by the arrows (up, down, front, rear, right, left) in Figure 1 will be described as the upper, lower, front, rear, right, and left sides of the rice cooker, respectively. Furthermore, common symbols will be used for common parts throughout these drawings.

1 to 9 show an embodiment of the present invention. The overall configuration of the rice cooker in this embodiment will be described with reference to Figs. 1 and 2. 1 is a rice cooker, and is generally rectangular with a front and rear, left and right sides facing each other when viewed from above, and the rice cooker 1 has an open top. The entire unit is made up of a main body 2 of the rice cooker 1 and a lid 3 that can be opened and closed to cover the top opening of the main body 2. The main body 2 has a pot housing 4 that is open at the top, and when the lid 3 is opened, a bottomed pot 5 that serves as a container for holding water or rice to be cooked is detachably housed in the pot housing 4. The outer shell of the main body 2 is formed by an upper frame 6 that constitutes the upper and side parts, an outer frame 7 that constitutes a part of the upper part, and a bottom plate 8 that covers the lower part of the upper frame 6. In this case, the upper frame 6 and the bottom plate 8 are formed of a synthetic resin such as PP, and the outer frame 7 is formed of a metal member such as stainless steel. The pot storage section 4 is formed integrally with the upper frame 6, and the bottom is formed by combining a bowl-shaped inner frame 9 made of resin such as PET, etc., so that the whole is formed into a cylindrical shape with a bottom.

The pot 5 is mainly made of aluminum, which has good thermal conductivity, and a heating element made of a magnetic metal plate such as ferritic stainless steel is joined to the outer surface of the main material from the lower side to the bottom. In addition, the outer surface of the inner frame 9, which faces the lower side of the pot 5 to the bottom, is equipped with a heating coil 11 as a heating means for electromagnetic induction heating of the heating element of the pot 5. A thermistor-type pot sensor 15 is disposed in the center of the bottom of the inner frame 9 as a pot temperature detection means so as to come into elastic contact with the outer bottom of the pot 5. In this embodiment, the pot sensor 15 is configured to detect the temperature of the pot 5 and mainly control the temperature of the heating of the bottom of the pot 5 by the heating coil 11.

A cord heater 16 (see FIG. 6) is provided at the top end of the pot housing 4, and this cord heater 16 is covered with a metal plate 12 made of a material such as aluminum that has good thermal conductivity. This metal plate 12 is provided in a position facing the gap 13 between the main body 2 and the lid 3 as a heat dissipation part, and these cord heater 16 and metal plate 12 constitute a flange heater as a heat generating means. The lower surface of the flange 14 extending from the upper end of the pot 5 to the entire outer periphery direction is placed on the upper surface of the metal plate 12, and the pot 5 is housed in the pot housing 4 in a suspended state. Therefore, in this state, there is almost no gap between the pot 5 and the upper end of the pot housing 4. However, by forming a partial gap 13 in a plan view of the metal plate 12 so that the handle portion formed on the flange 14 of the pot 5 is not in contact with the metal plate 12, steam is discharged from this gap 13 when cooking rice with water attached to the outer surface of the pot 5. Furthermore, the flange portion 14 of the pot 5 is formed with an outer shape that is equal to or larger than the cord heater 16 so as to cover the cord heater 16, which is the heat generating portion.

When cooking rice or keeping it warm, the pot 5 is heated by the heating means, while when keeping it warm, the heating coil 11 is heated and adjusted according to the temperature detected by the pot sensor 15 to keep the pot 5 at a constant temperature. After cooking, the cord heater 16, which serves as the heating means, is heated until the temperature of the rice in the pot 5 drops from the freshly cooked temperature of approximately 100°C to the keeping temperature of approximately 73°C. Even when the temperature is stable at approximately 73°C, the cord heater 16 is heated and radiates heat from the metal plate portion 12 to the gap 13 between the main body 2 and the lid 3, suppressing cooling caused by outside air entering through the gap 13 and heating the pot 5. Furthermore, during keeping it warm, the cord heater 16 is heated to heat the pot 5 during the period when hot reheating is being performed to reheat the rice in the pot 5, and prevents moisture generated by reheating from condensing on the upper inner surface of the pot 5.

A lid-opening button 17 is provided in an exposed state on the front upper surface of the lid body 3. When this lid-opening button 17 is pressed, the engagement between the main body 2 and the lid body 3 is released, and the lid body 3 is automatically opened around a hinge shaft 19 by a hinge spring 18 provided at the upper rear of the main body 2. A steam vent unit 21 is detachably attached to the rear upper surface of the lid body 3, forming an exhaust path for exhausting steam generated from the food being cooked in the pot 5 to the outside of the rice cooker 1.

In addition to the lid opening button 15 and steam vent unit 21, the top surface of the lid 3 is provided with an operation panel 22 for displaying button names and the like, which serves as the display and operation unit of the rice cooker 1. This operation panel 22 is provided with an LCD 23 that displays the time and the selected cooking course as a display section for displaying various information, and an LED 24 (see Figure 6) that displays the current process, and a switch 25 that starts and stops cooking rice, selects the cooking course, and the like as an operation section. The LCD 23, LED 24, and switch 25 are provided on a control PC (Printed Circuit) board 26 provided inside the lid 3. The control PC board 26 is equipped with a display/operation control means 27 (see FIG. 6) which is the control means for the operation panel 22, a chip sensor 28 as a lid temperature detection means, and a buzzer 30 as an alarm means. It also has a patterned conductive circuit portion, and by mounting a control IC 61 related to operation and display on the control PC board 26, the display/operation control means 27 linked to the heating control means 31 described later is formed. In addition, since the chip sensor 28 is arranged on the control PC board 26, which is a board on which the LCD 23, LED 24, and display/operation control means 27 are arranged, the number of parts can be reduced, and since wiring can be performed within the control PC board 26, the circuit configuration can be simplified and costs can be reduced. The operation panel 29 also prevents dust and water from adhering to the electronic components LCD 23, LED 24, switch 25, and control PC board 26.

The lid body 3 is provided with a lid heating means 29, such as a cord heater, which is used as a lid heater, and this lid heating means 29 is mainly used to manage the temperature of the inner lid 39, which will be described later.

31 is a heating control means for controlling the temperature of the pot 5 and the inner lid 39 by detecting the temperature from the pot sensor 15 and the chip sensor 28 during cooking and keeping warm. The heating control means 31 receives detection signals from the pot sensor 15 and the lid temperature sensor 17 and adjusts the heating of the heating coil 11, the cord heater 16, and the lid heating means 29 as heating means. The heating control means 31 is provided with an element 32 that drives and controls the heating coil 11, which drives the heating coil 11 to heat the heating element of the pot 5 by electromagnetic induction. This element 32 has a usage condition temperature and needs to be operated at a certain temperature or lower, so a radiator 33 made of a material with good thermal conductivity, such as aluminum, is attached to the element 32, and is cooled by the wind from a cooling fan 34 as a cooling means, so that it is operated within the usage condition temperature. This cooling fan 34 is arranged below or to the side of the radiator 33 attached to the heating control means 31.

A hole is provided on the bottom or side of the rice cooker, which is the product, for discharging to the outside the air that has been blown from the cooling fan 34 and heated by the radiator 33. The heating control means 31 is housed inside the main body 2, which is the inside of the product, but may be disposed in any position relative to the pot 5, and the hole may also be disposed in any position. However, in recent years, there has been a demand for more compact product designs, and it is preferable that the heating control means 31 and the cooling fan 34 are disposed in approximately opposite directions to the hole for discharging the air, with the pot 5 in between.

The lid body 3 is composed of an outer lid 36, which is an outer shell part, and an outer lid cover 37 that forms the lower part of the outer lid 36. The outer lid cover 37 is provided with a metal heat sink 38 made of stainless steel or aluminum that has been anodized (anodized), and the heat sink 38 is provided with a lid heating means 29. As shown in FIG. 2, an inner lid 39 made of metal and anodized stainless steel or aluminum is provided below the heat sink 38. The outer periphery of the inner lid 39 that forms the lower surface of the lid body 3 is provided with a lid packing 41 as a sealing member that seals the gap between the pot 5 and the inner lid 39 when the lid body 3 is closed. The lid packing 41 is made of silicone rubber or fluororubber, and is configured to abut against the upper surface of the flange portion 14 of the pot 5 when the lid body 3 is closed. The inner lid 39 and the lid packing 41 are integrated with a packing base 42, and an inner lid assembly unit 43 mainly composed of these parts is detachably attached to the inner surface of the outer lid cover 37. Therefore, when the lid body 3 is closed to the main body 2 with the inner lid assembly unit 43 attached, the lid gasket 41 abuts against the upper surface of the flange portion 14, and the inner lid assembly unit 43 is configured to completely cover the upper opening of the pot 5.

Next, the configuration of the inner lid assembly unit 43, which essentially corresponds to the inner lid of this embodiment, will be described with reference to Figures 3 to 5. The inner lid assembly unit 43 has a steam exhaust hole 45 and a pressure reduction hole 46, which are opened in the inner lid 39. In addition, a convex insertion part 47 that partially protrudes in the outer circumferential direction is formed in the resin packing base 42 formed in a substantially annular shape. With the lid body 3 open, the insertion part 47 is inserted into a recess 48 formed on the base end side near the hinge part 31 on the inner surface of the lid body 3, and the packing base 42 is fitted to the outer lid cover 37, so that the inner lid assembly unit 43 can be attached to a predetermined position on the inner surface side of the lid body 3 as shown in Figure 5. Above the pressure reduction hole 46, a cylindrical pressure reduction packing 49 (see Figure 9) that protrudes downward from the heat sink 38 is arranged.

Next, the internal structure of the lid 3 will be further described with reference to FIG. 2. The lid 3 is formed with a steam exhaust passage 51 that connects the steam port unit 21 and the pressure adjustment section 53 as a passage that connects with the inside of the pot 5 and allows steam generated from the pot 5 to be exhausted to the outside of the rice cooker. The pressure adjustment section 53 is provided with a pressure adjustment valve 54 that opens and closes the steam exhaust passage 51 between the inside of the pot 5 and the steam port unit 21. The pressure adjustment valve 54 is, for example, a solenoid valve and can be driven up and down. When steam in the pot 5 is to be released to the outside, the pressure adjustment valve 54 is driven upward to open the steam exhaust passage 51, and when the pressure inside the pot 5 is reduced, the pressure adjustment valve 54 is driven downward to close the steam exhaust passage 51.

55 is a decompression pump for lowering the pressure inside the pot 5 below normal atmospheric pressure when the lid 3 is closed on the main body 2. The decompression pump 55 lowers the internal pressure of the sealed pot 5 through a path (not shown) that connects the decompression pump 55 and the decompression hole 46 when the pot 5 is housed in the pot container 4 and the lid 3 is closed and the pressure regulating valve 54 is driven downward to block the steam exhaust path 51. When the pressure inside the pot 5 drops below atmospheric pressure by a certain value, the decompression pump 55 is operated to keep the inside of the pot 5 in a decompressed state. Furthermore, when the inside of the pot 5 is to be returned from the decompressed state to the same pressure as the outside air, the operation of the decompression pump 55 is stopped and the pressure regulating valve 54 is driven upward to open the steam exhaust path 51. In other words, the decompression pump 55 and the path that connects the decompression pump 55 and the decompression hole 46 act as a decompression means for lowering the pressure inside the pot 5 below normal atmospheric pressure, and also serve as a pressure return means for returning the inside of the pot 5 from the decompressed state to the same pressure as the outside air. In addition, a valve that can open and close the path connecting the decompression pump 55 and the decompression hole 46 may be provided.

Next, the control system of the heating control means 31 and the display/operation control means 27 will be described with reference to Fig. 6. In the figure, the heating control means 31 equipped in the main body 2 includes an element 32 as a control IC constituting a microcomputer, a memory means 57, a timer means (not shown), etc., and receives a temperature detection signal from the pot sensor 15, a control signal from the display/operation control means 27, and a temperature detection signal from the chip sensor 28 via the display/operation control means 27, to control the heating coil 11 that heats the pot 5 during cooking and keeping warm, the lid heating means 29 that heats the inner lid 39, and the cord heater 16 that heats the flange portion 14 of the pot 5, respectively, and also controls the operation of the pressure regulating valve 54 and the pressure reducing pump 55 mentioned above. In particular, the heating control means 31 mainly controls the heating coil 11 based on the temperature detected by the pot sensor 15 to control the temperature of the bottom of the pot 5, controls the cord heater 16 to control the temperature of the flange portion 14 of the pot 5, and mainly controls the lid heating means 29 based on the temperature detected by the tip sensor 28 to control the temperature of the inner lid 39. The heating coil 15, lid heating means 29, and cord heater 16 correspond to the heating means that heat the food to be cooked placed in the pot 5.

The heating control means 31 has a rice cooking control means 58 and a warming control means 59 in the element 32 as functions in the control sequence of the program read from the storage means 57. The rice cooking control means 58, upon receiving an instruction to start cooking rice from, for example, the rice cooking key of the switch 25 as the operation unit, sequentially executes each of the following processes: a soaking cooking process to promote the absorption of water by the rice put into the pot 5, a boiling heating process to raise the temperature of the food to boiling in a short time, a boiling continuing process to keep the food boiling, and a steaming process to keep the rice at a high temperature but not so high that it burns, thereby cooking and heating the food inside the pot 5 at the desired pressure. The warming control means 59 also controls the warming process to keep the rice inside the pot 5 at a predetermined warming temperature.

On the other hand, the display/operation control means 27 includes a control IC 61, a storage means 62, a timer means (not shown), and the like that constitute a microcomputer, and receives an operation signal from the switch 25 and a control signal from the heating control means 31 to control the display operation of the LCD 23 and the LED 24 as a display unit, controls the operation of the buzzer 30 as an alarm means, and transmits a control signal to the heating control means 31. As a function of the control sequence of the program stored in the storage means 62, the display/operation control means 27 includes an operation unit control means 63 that generates various control signals based on the operation signal from the switch 25, a display operation control means 64 that controls the display operation of the LCD 23 and the LED 24, and a condition setting means 65 that cooperates with the operation unit control means 63 and the display operation control means 64 to select and set conditions that can be selected by the switch 25, for example, to select and set a desired cooking course or rice cooking course from a plurality of cooking courses or rice cooking courses.

Next, the operation of the rice cooker 1 configured as above in the rice cooking process will be described. First, rice and water are placed in the pot 5 as the food to be cooked, and then this is placed in the pot housing 4 of the main body 2, and the lid 3 is closed. Around the same time, when the power plug (not shown) of the rice cooker 1 is inserted into an outlet to turn on the power, the rice cooker 1 goes into its initial off (standby) state, where no rice is being cooked or kept warm. Here, each time the switch 25 is operated, the operation signal is received by the operation unit control means 63, and the cooking course setting is changed by the condition setting means 65. The changed setting is displayed on the LCD 23 by the display operation control means 64 each time, and the user can visually confirm this.

When the switch 25, for example the rice cooking key, is operated after the rice cooking course is set, the operation signal is received by the operation unit control means 63, and the condition setting means 65 stores the setting currently displayed on the LCD 23 in the memory means 62 as the setting for this rice cooking course, and sends information on the heating pattern corresponding to the set rice cooking course to the heating control means 31. In response to this, the heating control means 31 performs each of the cooking operations of the soaking cooking process, boiling heating process, continued boiling process, and steaming process for the food in the pot 5 according to the heating pattern of the set rice cooking course, using the rice cooking control means 58 built into the element 32.

In more detail, when the heating control means 31 receives information sent from the display/operation control means 27, it transitions to the soaking process, and the rice cooking control means 58 controls the operation of the pressure regulating valve 54 and the pressure reducing pump 55 so that the pressure inside the pot 5 is reduced below atmospheric pressure during the soaking process. Specifically, when the soaking process starts, the rice cooking control means 58 closes the steam exhaust path 51 with the pressure regulating valve 54. In this state, the rice cooking control means 58 operates the pressure reducing pump 55 continuously, and performs a vacuum by removing the air inside the sealed pot 5 with the pressure reducing pump 55. After that, the rice cooking control means 58 controls the pressure reducing pump 55 so that the pressure inside the pot 5 is maintained at a reduced pressure below a certain value. In this way, the inside of the pot 5 is kept in a reduced pressure state throughout the entire soaking process.

The rice cooking control means 58 controls the heating of the pot 5 by controlling the power on/off of the heating coil 11 based on the temperature detection of the bottom of the pot 5 by the pot sensor 15, promoting the water absorption of the rice while calculating the amount of rice to be cooked in the pot 5 from the time and amount of heat required to reach a specified temperature. After the specified time has elapsed and the soaking process is completed, the process moves to the next boiling and heating process.

When the process moves to the boiling heating process, the rice cooking control means 58 controls the heating coil 11 to be continuously energized, so that the food in the pot 5 is heated more strongly than in the soaking cooking process, and the food is heated to the boiling temperature in a short time. The rice cooking control means 58 also controls the operation of the pressure reducing pump 55 to be stopped, while controlling the pressure regulating valve 54 to keep the steam exhaust path 51 closed, so that the inside of the pot 5 is maintained in a reduced pressure state lower than atmospheric pressure after the soaking cooking process. Therefore, even after the process moves from the soaking cooking process to the boiling heating process, the pressure inside the pot 5 gradually increases due to heating to the pot 5 and slow leaks, but the reduced pressure state can be maintained for a while without operating the pressure reducing pump 55. If a valve capable of opening and closing the path is provided in the path connecting the pressure reducing pump 55 and the pressure reducing hole 46, the valve may be closed to block the path. In this way, the food inside the pot 5 is kept in a reduced pressure state even during the heating process after the soaking process, so the water boils at a temperature of 100°C or less during the heating process. Therefore, by boiling the food under reduced pressure at 60°C to 100°C, which is the gelatinization temperature of rice, the bubbles caused by the boiling make the rice dance, eliminating uneven heating, and by placing the food under reduced pressure, the rice can absorb water all the way to the core in a short time.

Next, the rice cooking control means 58 takes in the temperature detection signal from the pot sensor 15, and when the detected temperature at the bottom of the pot 5 reaches the predetermined temperature of 100°C, it determines that the food inside the pot 5 has boiled under reduced pressure, and controls the pressure adjustment valve 54 to open without operating the pressure reduction pump 55. This causes the steam exhaust path 51 to be in an open state, connecting the inside and outside of the pot 5 without sealing it, and the inside of the pot 5 immediately returns to normal pressure, the same as the outside air. In this way, when the rice cooking control means 58 determines that the food inside the pot 5 has boiled under reduced pressure during the boiling heating process, it controls the operation of the pressure adjustment valve 54 to instantly switch the inside of the pot 5 from a reduced pressure state to atmospheric pressure, and opens the steam exhaust path 51.

Then, the rice cooking control means 58 detects that the temperature of the pot 5 has reached a predetermined temperature or higher, for example 90°C or higher, based on a temperature detection signal from the pot sensor 15, and when it also detects that the temperature of the inner lid has reached a predetermined temperature or higher, for example 90°C or higher, based on a temperature detection signal from the chip sensor 28, it starts controlling the boiling detection to detect the boiling of the food being cooked.

The lid heating means 29 heats the inner lid 39 that is in contact with the heat sink 38 by directly heating the heat sink 38. Therefore, when the lid heating means 29 heats the heat sink 38, the heat inside the heat sink 38 moves into the outer lid cover 37 and then moves to the periphery of the control PC board 26. In the rice cooker 1 of this embodiment, the chip sensor 28 detects the ambient temperature of the control PC board 26, which is the temperature around the control PC board 26, and the rice cooking control means 58 estimates and detects the temperature of the inner lid 39.

7 is a graph showing the correlation between the temperature detected by the chip sensor 28 and the temperature of the inner lid 39. The memory means 57 stores the graph in FIG. 7, and the rice cooking control means 58 calculates the temperature of the inner lid 39 using the graph in FIG. 7. For example, point a indicates the temperature detected by the chip sensor 28 when the temperature of the inner lid 39 is 90° C., and the temperature detected by the chip sensor 28 at this time is t ₁ , that is, approximately 37° C. Therefore, when the rice cooking control means 58 detects from the temperature detection signal from the chip sensor 28 that the temperature detected by the chip sensor 28 has reached t ₁ or higher, for example, 37° C. or higher, the rice cooking control means 58 is configured to determine that the temperature of the inner lid 39 has reached 90° C. or higher.

When the rice cooking control means 58 starts the control of boiling detection, it continues to control the heating coil 11 and the cord heater 16 to continuously energize and strongly heat the food inside the pot 5, while calculating the slope of the detected temperature, i.e., how much the detected temperature of the pot sensor 15 and the detected temperature of the chip sensor 28 rise in a specified time. Specifically, when the rice cooking control means 58 calculates that the rise in the temperature of the pot 5, which is the temperature of the bottom of the pot 5, from the detected temperature of the pot sensor 15 has become equal to or less than a specified temperature rise rate, such as 3°C or less in 120 seconds, it determines that boiling due to a change in the temperature rise rate of the pot 5 has been detected. Also, when the rice cooking control means 58 calculates that the rise in the temperature of the inner lid 39 from the detected temperature of the chip sensor 28 has become equal to or less than a specified temperature rise rate, such as 1°C or less in 60 seconds, it determines that boiling due to a change in the temperature rise rate of the inner lid 39 has been detected. When the rice cooking control means 58 detects boiling due to a change in the rate of temperature rise of the pot 5 and also detects boiling due to a change in the rate of temperature rise of the inner lid 39, it transitions to the next boiling continuation process.

When the process moves to the continuing boiling process, the rice cooking control means 58 controls the energization of the heating coil 11 and the cord heater 16 so that the temperature of the pot 5 based on the temperature detected by the pot sensor 15 is maintained at a predetermined temperature, for example 98°C or higher, and also controls the lid heating means 29 to be continuously energized so that the temperature detected by the chip sensor 28 is maintained at a predetermined temperature, for example 45°C or higher at _t2 at point b in Figure 7, i.e., the temperature of the inner lid 39 is maintained at a predetermined temperature, such as 98°C or higher, thereby maintaining the boiling state of the cooked food.

When the water inside pot 5 runs out during the continuing boiling process and the pot sensor 15 calculates that the temperature rise at the bottom of pot 5 exceeds a predetermined temperature rise rate, such as 0.5°C or more in 10 seconds, the rice cooking control means 58 determines that it has detected a change in the rate of temperature rise of pot 5. Here, when the temperature detected by pot sensor 15 reaches the predetermined dry-up temperature, it detects that the food inside pot 5 is done, the continuing boiling process ends, and the process moves to the next steaming process.

During the steaming process, the rice cooking control means 58 controls the temperature by turning on and off the lid heating means 29 based on the temperature detected by the chip sensor 28 to prevent condensation on the inner lid 39, and controls the temperature of the bottom of the pot 5 by turning on and off the heating coil 11 so that the temperature is kept high enough that the rice inside the pot 5 does not burn. When the steaming process ends after a predetermined time has passed, the rice cooking process is complete, and the display and operation control means 27 receives a control signal from the heating control means 31 to control the display of the LCD 23 and LED 24, and also controls the buzzer 30 to perform an alarm operation to notify the user that the rice cooking process is complete, and the process proceeds to the keep-warm process by the keep-warm control means 59.

Figure 8 shows the state where the user's finger touches the inner lid 39 with the lid body 3 open. Burns (burns) depend on the temperature of the contacted object and the contact time. When the temperature of the contacted object is 120°C, 5 seconds of contact time is required to cause a second-degree burn (see TED Y538C). Here, a second-degree burn is a burn in which a blister appears at the contacted area, and in severe cases, water may accumulate under the skin. If the blisters, which are the water that accumulates under the skin, do not suppurate, it can heal without leaving a significant scar. Since a first-degree burn is a burn in which the skin is only reddened, a second-degree burn is described here. Here, the contact time, which is the time from when a person feels "hot" to when they remove the part of their finger or other contacted object, is usually about 0.2 to 0.3 seconds, less than 1 second, and if the contacted object is less than 150°C, it usually does not cause a second-degree burn.

In the rice cooker 1 of the present invention, a triac is used in the drive circuit of the lid heating means 29, and this drive circuit controls the ON/OFF of the lid heating means 29 by receiving a control signal from the heating control means 31. If the triac of the drive circuit that controls the lid heating means 29 as a lid heater shorts for some reason, such as when the triac becomes a defective part due to initial failure or aging, when solder is shorted on the control PC board 26, or when other parts such as transistors used in the drive circuit fail due to static electricity, the lid heating means 29 cannot be turned ON/OFF by the control signal from the heating control means 31, and the lid heating means 29 is kept ON, and the heat sink 38 on which the lid heating means 29 is provided and the inner lid 39 in contact with this heat sink 38 may become so hot that they can cause second-degree burns if touched. Therefore, in this embodiment, a chip sensor 28, which is a temperature detection means that does not come into contact with the inner lid 39, is provided inside the lid body 3, so that the temperature of the outer lid cover 37 that forms the lower part of the lid body 3 can be detected regardless of whether the inner lid 39 is present or not.

Referring to Figures 9(A) and 9(B), as shown in Figure 9(A), the rice cooker 1 of this embodiment does not have a lid sensor on the heat sink 38, and does not have a temperature sensor that directly detects the temperature of the inner lid 39. On the other hand, as shown in Figure 9(B), in the rice cooker 1 of this embodiment, a chip sensor 28 is provided as a lid temperature detection means on the control PC board 26 inside the lid body 3, on which the LCD 23, LED 24, and switch 25 are provided, and the heating control means 31 estimates the temperature of the inner lid 39 based on the detection signal from the chip sensor 28, thereby detecting the temperature of the inner lid 39 without contacting the inner lid 39.

Next, the operation of the rice cooker 1 configured as above will be described. When a temperature detection signal is received from the chip sensor 28 via the display/operation control means 27, the heating control means 31 calculates the temperature of the inner lid 39 by applying this information to the correlation graph of the temperature detected by the chip sensor 28 and the temperature of the inner lid 39 shown in FIG. 7, which is stored in the memory means 57. The heating control means 31 also has time and temperature thresholds, such as the temperature detected by the chip sensor 28 being 85°C or higher for 10 minutes or more continuously, and the temperature value Th of this threshold is a value that is not reached during the normal rice cooking process or warming process.

Here, when the heating control means 31 receives a notification via the display/operation control means 27 that the temperature detected by the chip sensor 28 has reached or exceeded the threshold temperature of 85°C, the heating control means 31 uses the timer to measure the time during which the temperature remains above the threshold temperature Th. As shown in FIG. 7, in the rice cooker 1 of this embodiment, the temperature detected by the chip sensor 28 rises to approximately 81.5°C during the normal rice cooking process and warming process, i.e., the temperature of the inner pot 39 rises to approximately 125°C. In order to avoid the risk of false detection during normal use, the temperature threshold Th is set to 85°C, i.e., the temperature of the inner pot 39 is approximately 130°C, and a predetermined time is also set to determine whether the temperature remains above the temperature threshold Th for the predetermined time or longer.

After that, when the heating control means 31 receives from the timer that the time the temperature is above the threshold value measured by the timer has exceeded the threshold time, the heating control means 31 determines that the temperature of the inner pot 39 is abnormal and sends a control signal to the display/operation control means 27, which controls the LCD 23 and LED 24 to display an error message indicating the temperature is abnormal, and also controls the buzzer 30 to sound an alarm to notify the user that the lid temperature is abnormal. Therefore, regardless of whether the inner lid 39 is present or not, the temperature of the outer lid cover 37 that forms the lower part of the lid body 3 can be detected, and the user can be notified of the abnormality in the lid temperature by the display of the LCD 23 and LED 24 and the alarm operation of the buzzer 30, to call attention to the abnormality in the lid temperature.

In this embodiment, the temperature of the lid of the inner pot 39 is detected as abnormal by the temperature detected by the chip sensor 28, but the chip sensor 28 may also be configured to detect temperature abnormalities inside the lid 3 to which the inner pot 39 is attached, or to detect temperature abnormalities in the control PC board 26 on which the chip sensor 28 is provided. The correlation graph between the temperature detected by the chip sensor 28 and the temperature of the inner lid 39 in FIG. 7, as well as the time and temperature thresholds, are stored in the storage means 62 of the display/operation control means 27, and the display/operation control means 27 may use a timing means to measure the time that the temperature is equal to or higher than the threshold temperature Th, control the LCD 23 and LED 24 to display an error message, and control the buzzer 30 to sound an alarm to alert the user of the abnormal temperature.

As described above, the rice cooker 1 of this embodiment includes a pot 5 for containing the food to be cooked, a lid 3 that can be opened and closed to cover the opening of the main body 2 that contains the pot 5, an inner lid 39 that is attached to the lid 3 and covers the opening of the pot 5 when the lid 3 is closed, and a chip sensor 28 that is attached inside the lid 3 and serves as a lid temperature detection means for detecting the temperature of the inner lid 39 without contact. Therefore, regardless of whether the inner lid 39 is present or not, the temperature of the outer lid cover 37, which is the part that forms the lower part of the lid 3, can be detected. For example, even if the inner lid 39 is removed, it can be detected that the outer lid cover 37 or the heat sink 38 has become too hot, and it can be detected that the temperature of the lid 3 has become abnormal.

The rice cooker 1 of this embodiment further includes an LCD 23 and an LED 24 as a display unit that displays various information. The LCD 23 and the LED 24 are provided on a control PC board 26, which serves as a substrate disposed inside the lid 3, and the chip sensor 28 is provided on the control PC board 26. This configuration allows for a reduction in the number of components, and wiring can be done within the control PC board 26, simplifying the circuit configuration and reducing costs.

In addition, in the rice cooker 1 of this embodiment, the chip sensor 28 is a chip element, making it easy to mount on the control PC board 26 and reducing costs.

The rice cooker 1 of this embodiment is further equipped with a heating control means 31 as a determination means for determining whether the temperature of the inner lid 39 is equal to or higher than a threshold temperature Th, which is a predetermined temperature, and is capable of determining whether the temperature of the inner lid 39 is abnormal.

In addition, in the rice cooker 1 of this embodiment, the heating control means 31 measures the time that the temperature of the inner lid 39 is equal to or higher than the threshold temperature Th and determines whether the time is equal to or higher than a predetermined time, thereby avoiding the risk of false detection during normal use.

In addition, the rice cooker 1 of this embodiment is further equipped with an LCD 23, an LED 24, and a buzzer 30 as notification means that notify when the heating control means 31 determines that the temperature is equal to or higher than a predetermined temperature Th or for a predetermined time, and the LCD 23 and LED 24 and the buzzer 30 can be used to notify the user that the lid temperature is abnormal and call their attention.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. Furthermore, the numerical values given in the embodiment are merely examples, and may be modified as appropriate according to the specifications of the rice cooker.

1 Rice cooker 2 Main body 3 Lid 5 Pot 23 LCD (display unit, notification means)
24 LED (display section, notification means)
26 Control PC board (substrate)
28 Chip sensor (lid temperature detection means)
29 Lid heating means
31 Heating control means (determination means)
36 Outer lid
37 Outer cover
38 Heat sink
39 Inner lid

Claims (6)

A pot for containing food to be cooked;
A lid that can open and close the opening of the main body that houses the pot;
An inner lid is provided on the lid body and covers the opening of the pot when the lid body is closed;
A lid temperature detection means is provided inside the lid body in a non-contact manner with the inner lid;
A display unit that displays various information ,
the display unit is provided on a substrate disposed inside the lid,
The lid temperature detection means is provided on the substrate,
The rice cooker is characterized in that the lid temperature detection means detects the temperature of the inner lid by detecting the ambient temperature of the substrate . The lid body includes an outer lid, an outer lid cover forming a lower portion of the outer lid, and a heat sink provided below the outer lid cover,
The inner lid is provided below the heat sink,
A lid heating means for heating the inner lid is provided between the outer lid cover and the heat sink,
2. The rice cooker according to claim 1, wherein the lid temperature detection means is provided between the outer lid and the outer lid cover . The rice cooker according to claim 1 or 2, characterized in that the lid temperature detection means is a chip element. The rice cooker according to any one of claims 1 to 3, further comprising a determination means for determining whether the temperature of the inner lid is equal to or higher than a predetermined temperature. The rice cooker according to claim 4, characterized in that the determination means measures the time during which the temperature of the inner lid is equal to or higher than a predetermined temperature and determines whether the time is equal to or higher than the predetermined time. 6. The rice cooker according to claim 5 , further comprising an alarm means for alarming when the determination means determines that the temperature is equal to or higher than the predetermined temperature or the time is equal to or higher than the predetermined time.

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