JP2007151852A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems wherein conventionally the base material surface of a pot for a rice cooker is coated with fluororesin for improving non-viscosity, the fluororesin coat is thickened for improving abrasion resistance, and a large amount of substances with high hardness are mixed in a top coat; however, air bubbles generated in boiling are hardly separated from the fluororesin coat surface and liable to grow largely due to the high water-shedding quality of the fluororesin coat, so that the transmission of boiling heat to the water in the pot is insufficient to lower the contact opportunities between the rice and the air bubbles, and nonuniform heating of the rice causes cooking nonuniformity of the boiled rice. <P>SOLUTION: This rice cooker comprises a pot in which the fluororesin coat is formed on the base material inside and a plurality of polygonal-pyramid-shaped micropores are formed on the top coat surface layer side of the fluororesin coat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rice cooker including a pan having a fluororesin coat formed on the inner surface of a base material.

  Conventionally, pans used in cooking equipment such as rice cookers that are widely available to the general public are made of aluminum alone, or a laminate of aluminum and stainless steel or a laminate of aluminum, stainless steel and copper, etc. The mainstream is a composite material. In these metal rice cooker pans, a fluororesin coat is treated on the inner surface in order to prevent the rice that is normally cooked from sticking strongly, thereby improving the non-adhesiveness to the rice. The fluororesin coat is usually a one-layer structure to a two-layer or three-layer structure, but is preferably a two-layer or more fluororesin coat from the viewpoint of obtaining good non-adhesiveness, high durability, and appearance. In the two-layer fluororesin coating, the surface of the substrate is made to have an appropriate surface roughness by sandblasting or the like, and then a primer adhesive layer is formed on the substrate so that the film thickness is about 10 μm after film formation. A top coat is formed on the upper layer so as to have a film thickness of about 50 μm, and the film is baked at about 400 ° C. for about 20 minutes to form a fluororesin coat. It is necessary to assume that the fluororesin coat is placed in a severe wear environment due to a friction load between the rice and the fluororesin coat by washing the rice in the pan, or a friction load such as nylon scrubbing when the pan is washed. In general, as a means of improving the abrasion resistance of a fluororesin coat used for frying pans, a technique such as adding a large amount of inorganic fillers such as ceramic particles to the top coat to improve the hardness of the top coat is taken. However, it has been difficult to adopt the same method from the viewpoint of ensuring non-adhesiveness and visibility of the water level line display part in the fluororesin coat of the rice cooker pan (for example, see Patent Document 1). Therefore, in conventional rice cooker pans and the like, as a means for improving the wear resistance of the fluororesin coat, the top coat has been made as thick as possible to improve the wear resistance. For the two-layer structure, the fluororesin powder coating is applied as thick as possible in the two-layer structure, or in the three-layer structure, the intermediate coat between the primer adhesive layer and the top coat is thickened to increase the thickness of the top coat. Some have added film and additive effect. With the above thickening, a fluororesin coat having a thickness of about 30 to 50 μm can usually be made about 100 μm, and an improvement in wear resistance can be expected.

  Moreover, in order to improve rice cooking performance, the role which a pot plays is large, and when considering the thermal influence especially, the heat conduction to the rice in boiling heat transfer accounts for the largest ratio. Therefore, it is expected that the uniform heat transfer performance to the rice will differ depending on how bubbles are generated during nucleate boiling in boiling heat transfer. Therefore, it is considered that more uniform heat conduction can be realized by making the heat flux passing through the rice uniform at an arbitrary place. For this purpose, a state where bubbles as uniform as possible are always generated is ideal.

However, since the fluororesin coat has a strong water repellency, bubbles generated during nucleate boiling when water is kept in the pan and kept heating tend to grow large without easily leaving the fluororesin coat surface. For this reason, the boiling heat transfer to the water in the pan is not sufficient, and the strong convection necessary for achieving a uniform temperature hardly occurs. In the first place, in rice cooking, rice is heated uniformly by boiling heat transfer and strong convection of water in the pan. If this is insufficient, uneven cooking of rice occurs due to uneven heating of the rice.
JP 2003-144308 A

  However, in the conventional configuration, as described above, if the functions such as high non-stickiness, good visibility of the water level line, and high wear resistance are imparted to the fluororesin coat of the rice cooker pan, the top coat is made of ceramics, etc. The fluororesin coat must be a 100 μm thick film. Fluororesin is an expensive material, and considering the mass production of rice cookers, which are industrial products, it is desirable to reduce the amount of use and minimize the thickness.

  In order to keep the thickness of the fluororesin coat thin, it is possible to add a large amount of a high hardness substance to the top coat. However, if an additive is added to the top coat to a certain extent to improve the wear resistance, As described above, the non-adhesiveness is deteriorated and the visibility of the water level line is also deteriorated, so that the function as a pan for the rice cooker is not sufficiently performed.

  In addition, as described above, since the fluororesin coat has strong water repellency, bubbles generated at the time of nucleate boiling when water is put in the pan and heated continuously grows easily without detaching from the surface of the fluororesin coat. For this reason, the boiling heat transfer to the water in the pan is not sufficient, and the strong convection necessary to achieve a uniform temperature is unlikely to occur, so uneven cooking of rice occurs due to uneven heating of the rice.

  The present invention solves the above-described conventional problems, and can improve wear resistance while maintaining non-stickiness to rice without increasing the film thickness. Further, visual recognition of a display printed on a primer adhesive layer is possible. In addition, the bubble size is fine because bubbles generated during nucleate boiling are easily detached from the surface of the fluororesin coat, and the opportunity for contact between the bubbles and rice increases. The purpose is to cook delicious rice without uneven cooking by improving and heating rice uniformly with strong convection in the pot.

  In order to solve the above-mentioned conventional problems, the rice cooker of the present invention forms a fluororesin coat on the inner surface of the base material, and forms a plurality of polygonal pyramid-shaped fine holes on the top coat surface layer side of the fluororesin coat Rice cooker with a cooked pot.

  This ensures high abrasion resistance while maintaining the non-stickiness of rice without significant film thickness, ensuring sufficient visibility of the printed display on the primer adhesive layer, and coating with fluororesin when boiling Boil heat transfer efficiency is improved by the fine bubbles that are easily detached from the surface, and it is possible to uniformly heat the rice with strong convection of water in the pot, and to make a pot for rice cookers that improves the taste of rice Can do.

  The pan provided in the rice cooker of the present invention has high wear resistance while maintaining the non-stickiness of rice, sufficiently ensuring the visibility of the printed display on the primer adhesive layer, and improving the boiling heat transfer efficiency. The rice can be uniformly heated together with the strong convection of the water in the pot, and the rice cooker can be improved in the taste of rice.

  1st invention makes a rice cooker provided with the pot which formed the fluororesin coat in the substrate inner surface, and formed the plurality of polygonal pyramid-shaped fine holes in the top coat surface layer side of the fluororesin coat It is possible to improve the wear resistance while maintaining the non-stickiness to rice without increasing the film thickness, and also ensure sufficient visibility of the display printed on the primer adhesive layer. The bubble size is fine because the generated bubbles are easily detached from the surface of the fluororesin coat, which improves the efficiency of boiling heat transfer from the surface of the fluororesin coat to water, and makes the rice even with strong convection of water in the pan. By heating, it becomes possible to cook delicious rice without uneven cooking.

  According to a second aspect of the present invention, a fluororesin coat is formed on the inner surface of the base material of the bottom surface portion and the curved surface portion on a curved surface connected to the bottom surface, starting from an arbitrary outer periphery from the substantially middle of the overall height to the bottom surface. On the surface of the topcoat layer, a plurality of polygonal pyramid-shaped micropores are formed, and the bottom surface portion has a pan characterized by having a smaller exit area than the curved surface portion. By using a rice cooker, when the nucleate is boiled, the bottom part has a very fine air bubble compared to the curved part, thereby achieving uniform boiling heat transfer to the rice in the pan. By creating strong convection from the side of the pan to the inside by generating bubbles larger than the part, it is possible to heat the rice in the pan uniformly, heating the rice uniformly by more uniform boiling heat transfer and convection By improving the taste, Igohan it is possible to cook.

  According to a third aspect of the present invention, a fluororesin coat is formed on the inner surface of the base material of the bottom surface portion and the curved surface portion on the curved surface connected to the bottom surface, starting from an arbitrary outer periphery from the substantially middle of the overall height to the bottom surface. A rice cooker provided with a pan, wherein a plurality of polygonal pyramid-shaped micropores are formed on a top coat surface layer side, and the number of micropores in the curved surface portion is smaller than the number of micropores in the bottom surface portion. By using a vessel, a lot of very fine bubbles are generated at the bottom surface compared to the curved surface during nucleate boiling, realizing uniform boiling heat transfer to the rice in the pan, and at the curved surface Although the number is smaller than that of the bottom part, large bubbles are generated, causing strong convection from the side of the pan to the inside, enabling uniform convection heat transfer to the rice in the pan, and more uniform boiling heat transfer. And evenly heating the rice by convection heat transfer, Ri it is possible to cook a delicious rice with improved taste.

  The fourth invention is particularly a rice cooker provided with a pan in which at least one of silicon carbide or diamond is unevenly distributed as additive particles at the bottom of the micropores of the first to third inventions. In addition, since the additive particles are only present in a part of the fine pores inside the top coat, non-adhesiveness to rice can be maintained, and wear resistance can be improved by silicon carbide and diamond unevenly distributed on the top coat surface layer. In addition, since the visible light transmittance of the top coat is high, the visibility of the display portion printed on the primer adhesive layer is not impaired, and furthermore, the corrosion resistance can be maintained.

  Also, since fluororesin is a material with low thermal conductivity, diamond has extremely high thermal conductivity, so when diamond particles are used as additive particles, heat from the pan is easily transferred to the diamond particles. , It becomes easy to induce the generation of bubbles from fine pores where diamonds are unevenly distributed, and fine bubbles are generated uniformly and uniformly from the surface of the fluororesin coating in the pan 2, so that the rice is made uniform by uniform boiling heat transfer It becomes possible to cook delicious rice that has been heated and improved in taste.

  In a fifth aspect of the present invention, in particular, a pan in which powder coating material in which at least one of silicon carbide or diamond is microencapsulated as an additive particle is unevenly distributed at the bottom of the micropores of the first to third aspects of the invention. By making the rice cooker equipped, the additive particles are encased in the fluororesin powder by microencapsulation, so that they do not separate when painting the fluororesin powder paint, In addition, it is possible to obtain a uniform coating film containing additive particles at a constant concentration at all times, and to prevent the additive particles from falling off during actual use because the additive particles are also covered with a fluororesin in the coating film. Can do.

  In the sixth invention, in particular, the additive particles of the first to third inventions are unevenly distributed in the topcoat surface layer, and the rice cooker is provided with a pan that is present most in the lowest part of the fine holes. Fluorine resin coat has high wear resistance against wear loads such as sharpening of the rice, induces the generation of bubbles from fine pores where diamonds are unevenly distributed, and fine bubbles are uniformly stabilized from the surface of the fluorine resin coat. Therefore, the rice can be heated uniformly by uniform boiling heat transfer, and it is possible to increase the wear resistance of the fluororesin coat and to cook delicious rice with improved taste.

  According to a seventh aspect of the present invention, there is provided a rice cooker having a pan in which at least one of silicon carbide and diamond is unevenly distributed at the bottom of the micropore in the bottom surface portion of the first or second aspect of the invention. When boiling, a lot of very fine bubbles are generated at the bottom surface compared to the curved surface portion, realizing uniform boiling heat transfer to rice in the pan, and the curved surface portion is less in number than the bottom surface portion. However, by generating strong convection from the side of the pan to the inside due to the formation of large bubbles, it is possible to achieve uniform convection heat transfer to the rice in the pan, and the rice is fed by more uniform boiling heat transfer and convection heat transfer. By heating evenly, it becomes possible to cook delicious rice with improved taste.

  In the eighth aspect of the invention, in particular, the top coat surface layer of the bottom part of the first or second aspect of the invention has at least one of silicon carbide and diamond unevenly distributed, and a pan that is present most frequently at the lowermost part of the fine hole. By using a rice cooker equipped, the fluorine resin coat on the bottom surface where the load is most applied against wear loads such as rice sharpening has high wear resistance, and bubbles are generated from fine holes where diamonds are unevenly distributed. Inducing fine bubbles uniformly from the surface of the fluororesin coat, the rice can be heated uniformly by uniform boiling heat transfer, improving the wear resistance of the fluororesin coat and improving the taste. It becomes possible to cook improved delicious rice.

(Embodiment 1)
1 is a cross-sectional view of a rice cooker provided with a rice cooker pan in Embodiment 1 of the present invention, FIG. 2 is an enlarged cross-sectional view of the rice cooker pan, and FIG. 3 is an enlarged cross-sectional view of the main part of the rice cooker pan. 4 shows an enlarged perspective perspective view of the surface of the rice cooker pan.

  In FIG. 1, 1 shows the main body of a rice cooker. The main body 1 includes a detachable pot 2. The main body 1 is provided with a lid 3 covering its upper surface so as to be freely opened and closed. The rice cooker of Embodiment 1 induction-heats the pot 2 by the method mentioned later, and cooks the rice and water in the pot 2 by heating. The main body 1 includes a pot heating means 4 (which is an induction heating coil) for induction heating the bottom of the pot 2, a pot temperature detection means 5 for detecting the temperature of the pot 2, and a control means 6. The lid 3 further includes a heating plate 7 covering the opening of the pan 2, a heating plate heating means 8 (which is an induction heating coil) for induction heating the heating plate 7, and a heating plate temperature detection means 9 for detecting the temperature of the heating plate 7. And a detachable steam cylinder 10. The heating plate 7 is a detachable heating plate with a heating plate seal packing 11 attached to the lower surface of the lid 3. The heating plate 7 has a vapor hole 12 in the center. The heating plate temperature detecting means 9 is pressed against the heating plate 7. A lid seal packing 13 is provided between the lower surface of the lid 3 and the heating plate 7. The steam cylinder 10 is a float hole 14 at a portion facing the steam hole 12, a float 15 that is movably housed inside, and a float detection means 16 that detects the movement of the float 15. The float 15 is made of a cylindrical or spherical magnet, and a recessed groove 17 for guiding the movement of the float 15 is provided on the lower surface of the steam cylinder 10. Further, a reed switch is used for the float detecting means 16 to detect the movement of the float 15. Reference numeral 18 denotes a steam discharge port.

  Here, as shown in FIG. 2, the pan 2 is made of a clad material obtained by joining an aluminum 21 having a thickness of 1.0 mm to a ferrite stainless steel 20 having a thickness of 0.5 mm. It is molded by pressing so that the 20 side is the outer surface.

  A two-layer fluororesin coat 22 is formed on the surface of the aluminum 21 on the inner surface of the pan 2.

  Hereinafter, the treatment of the fluororesin coat 22 will be described with reference to FIGS. 3 and 4 in the case where concave fine holes are formed on the surface layer inside the top coat and diamonds are unevenly distributed as the additive particles at the bottom. To do.

  After the base material is press-molded into a pan shape and washed, sand blasting is applied to the surface of the aluminum 21 on the inner surface of the pan, and the surface roughness Ra is adjusted to 3 to 5 μm. Thereafter, the fluororesin, the adhesive component, the pigment, A liquid primer coating containing a glittering material as a coating film component was applied to a film thickness of about 10 μm after film formation, and dried at 100 ° C. for 20 minutes to form a primer adhesive layer 23.

  When drying of the primer adhesive layer 23 is completed and the substrate temperature is sufficiently lowered, a water level line display is printed on the primer adhesive layer 23 on the side of the pan using a color different from the color of the primer adhesive layer 23. After that, as a top coat treatment, a fluororesin powder coating containing no additives such as pigments and glittering materials is formed on the primer adhesive layer 23 and the water level line so that the film thickness becomes 40 μm. The top coat layer 24 was formed by coating. At this time, the used fluororesin is a mixed powder of PTFE: PFA = 2: 8.

  Next, a PFA powder coating material 26 in which fine holes 25 having a quadrangular pyramid shape (□ 0.05 × 0.05 mm depth) are formed in the lower topcoat layer 25 and at the same time, diamond having an average particle diameter of 5 μm is microencapsulated. The fluororesin coat 22 was formed by injecting into the apex of the fine hole 25 and then baking at 380 ° C. for 20 minutes.

  The control means 6 has a microcomputer mounted on a circuit board (not shown). The control means 6 (microcomputer) is a software operation command input by the user via an operation panel (not shown), a signal input from the pan temperature detection means 5, the hot plate temperature detection means 9, and the float detection means 17. On the basis of the above, the heating control of the pan 2 and the heating plate 7 is performed by the rice cooking program stored in the microcomputer in advance. The control means 6 controls the heating amount of the pan heating means 4 and the heating plate heating means 8 according to the energization rate and / or energization amount of each heating means.

  Operation | movement of the rice cooking process of the rice cooker in Embodiment 1 of this invention comprised as mentioned above is demonstrated.

  A user puts rice to be cooked and water corresponding to the amount of the rice into the pan 2 and decorates the main body 1. Further, when the user operates a rice cooking start switch (not shown), a rice cooking process is performed. The rice cooking process is largely divided into pre-cooking, cooking, boiling maintenance, and steaming in order of time. In the pre-cooking step, the pot heating means 4 is controlled so that the temperature of the pot 2 becomes a temperature (50 ° C.) suitable for water absorption of rice, and the rice and water in the pot 2 are heated. Next, in the cooking step, the pan 2 is heated with a predetermined amount of heat by the pan heating means 4 until the temperature of the pan 2 reaches a predetermined value (100 ° C.). The amount of cooked rice is determined based on the temperature rise rate at this time. In the boiling maintenance process, the pot heating means 4 and the heating plate heating means 8 are energized to heat the rice and water until the water in the pot 2 runs out and the temperature of the pot 2 reaches a predetermined value exceeding 100 ° C. Finally, in the steaming step, the heating (cooking) by the pan heating means 4 and the heating plate heating means 8 according to the amount of cooked rice and the stop (pause) of heating are repeated a plurality of times during a fixed time.

  In the cooking to boiling maintaining step, the temperature of the water in the pan 2 rises rapidly from 50 ° C. to 100 ° C. by continuous energization to the pan heating means 4. At this time, the water in the pan gradually (2) from the initial (1) non-boiling natural convection to the (2) nucleate boiling state where the bubbles generated on the surface of the fluororesin coat 22 do not reach the water surface. ) Nucleate boiling occurs in which bubbles generated on the surface of the fluororesin coat 22 reach the water surface.

  Next, natural convection and nucleate boiling will be described using the above (1) to (3) as specific examples. The surface heat flux q = Q / A of the pan 2 is obtained by dividing the Joule heating amount Q by the pan heating means 4 by the heat generating part surface area A of the pan 2, and saturation from the surface temperature T of the pan 2 to the pressure in the pan 2 A value obtained by subtracting the temperature Tsat is defined as a degree of superheat ΔTsat = T−Tsat.

  (1) While the pan 2 is heated by the pan heating means 4 and ΔTsat is small, the surface of the fluororesin coat 22 generates heat due to heat transfer, and the water in the pan 2 in contact with the surface of the fluororesin coat 22 is locally When heated, density differences occur in the water. A local buoyancy based on this density difference is generated, and a flow is induced in the water in the pan 2. Such local non-uniform density causes unboiled natural convection in the water in the pot 2. The heat transfer from water to rice at this time is natural convection heat transfer.

  (2) As ΔTsat increases, nucleate boiling occurs when small bubbles are generated on the surface of the fluororesin coat 22 and are separated. In the initial nucleate boiling, the amount of heat contained in the bubbles is not sufficient, so as the temperature rises toward the water surface, the temperature of the bubbles approaches the water temperature, liquefies as a result of recondensation, and the bubbles disappear (the bubbles are on the water surface). Nucleate boiling not reached). The heat transfer from water to rice at this time is natural convection heat transfer and boiling heat transfer.

  (3) Further, when Q is increased, the generation point of bubbles becomes dense and frequently leaves and bubbles reach the surface of the water, and the whole water in the pot 2 is vigorously stirred (core) boiling). The heat transfer from water to rice at this time is boiling heat transfer.

  Next, the phenomenon actually occurring in the pan 2 will be described below.

  In the state (1), natural convection heat transfer is dominant in the heat conduction from water to rice, and a large difference in the heat flux q due to the difference in the surface state of the fluororesin coat 22 is not recognized.

  In the state of (2), heat conduction from water to rice is divided into a case where natural convection heat transfer is dominant and a case where boiling heat transfer is dominant depending on how bubbles are generated on the surface of the fluororesin coat 22. . That is, the former is a case where bubbles grow large on the surface of the fluororesin coat 22, and most of the Joule heating value Q is spent on the growth of bubbles, so that heat transfer from water to the rice is from the surface of the fluororesin coat 22 Heat transfer from the water in the pan 2 and heat transfer from the bubbles to the water, both of which are transferred to the rice by natural convection heat transfer. On the other hand, the latter is a case where bubbles are easily detached from the surface of the fluororesin coat 22, and as described above, the bubbles are fine and the bubbles rise toward the water surface by buoyancy, but the amount of heat contained in the bubbles is small. Since it is not sufficient, the temperature of the bubbles approaches the water temperature as it rises, liquefies as a result of recondensation, and the bubbles disappear. However, the bubbles frequently rise toward the water surface, so that forced convection occurs in the water in the pan 2, and heat is transferred to the rice by boiling heat transfer and forced convection heat transfer. In forced convection heat transfer, natural heat transfer is more uniform than in natural convection heat transfer, so uniform heat transfer to rice can be achieved. Therefore, the rice can be heated uniformly by making the surface of the fluororesin coat 22 into a surface state in which air bubbles are easily detached.

  In the state of (3), the bubbles frequently leave and reach the water surface, and the entire water in the pan 2 is vigorously stirred. However, depending on how bubbles are generated on the surface of the fluororesin coat 22, the rice is not always heated uniformly in boiling heat transfer. That is, when bubbles are easily detached from the surface of the fluororesin coat 22, the opportunity for heat transfer to the rice is increased by increasing the contact opportunities between the bubbles and the rice as compared with the case where the bubbles grow large. . Therefore, the rice can be heated uniformly by making the surface of the fluororesin coat 22 into a surface state in which air bubbles are easily detached.

  As described above, in the nucleate boiling, by making the surface of the fluororesin coat 22 a surface in which bubbles are easy to be released, the opportunity for contact between the bubbles and rice increases, so the chance of heat transfer to the rice increases. The rice can be heated uniformly.

  The surface state in which bubbles are easy to detach is described below.

  When observing boiling from the surface of the fluororesin coat 22, it can be seen that the generation and detachment of bubbles due to boiling always occur from the same point. This is because when the bubbles are released, water cannot enter the fine concave and convex dents on the surface (the bottom of the dents is the boiling nucleus), and some of the bubbles are constantly left behind. This is considered to be the initial group of vapor molecules, where water evaporates and bubbles grow. In other words, in boiling from a heated surface, water evaporates with a small degree of superheat toward the vapor phase in the heated surface cavity without the formation of vapor molecules in the volume by homogeneous nucleation processes. Perform and generate bubbles.

  Next, regarding the bubble growth, how the curvature 1 / R of the bubble changes as the bubble trapped in the conical depression with the exit radius R grows will be described. Assuming that the contact angle of the bubble to the heating surface is 90 °, the curvature of the bubble accompanying the growth of the bubble takes the minimum value in a state where the bubble just touches the outlet and keeps 90 ° with the side of the cone. After that, it is in contact with the area around the outlet, but continues to increase until it shows a contact angle of 90 ° with the heated surface (stable equilibrium state). After reaching the maximum value, the contact position moves away from the area around the outlet again. It will decrease. As the volume of the bubble increases, the curvature decreases, becomes unstable and continues to grow towards bubble detachment.

  As described above, in order to easily remove bubbles from the heating surface, how to place the bubbles in an unstable state is important. To that end, it is conceivable to optimize the material of the heating surface and the shape of the recess, but for the reasons described above, it is desirable to use a fluororesin, so we decided to optimize the shape of the recess. . As shown in FIGS. 3 and 4, the concave cross-sectional shape is preferably a shape in which peaks and valleys are continuous in order to promote the detachment of the bubbles by applying pressure to each other, and the outlet shape is to maintain the shape of the bubbles. It is desirable to use a polygon because of the instability.

  The indentation in the present embodiment has a shape in which square pyramids having the same shape satisfying the above two points in a balanced manner are continuously arranged. As a result, during the nucleate boiling in the cooking-boiling maintenance process, the bubbles are easily released, so the bubble size is fine, and the opportunity for contact between the bubbles and the rice increases, so there is an opportunity for heat transfer to the rice. Increased, it will be possible to heat the rice evenly, it will be possible to cook delicious rice without uneven cooking.

  In addition, since the diamond particles are unevenly distributed at the bottom of the recess, heat from the pan 2 is easily transferred to the diamond particles, so that it is easy to induce the generation of bubbles from fine holes where diamonds are unevenly distributed. 2 is generated evenly and stably from the surface of the fluororesin coat 22 in 2, so that it becomes possible to cook delicious rice with improved taste by uniformly heating the rice by more uniform boiling heat transfer.

  In addition, by making the surface of the fluororesin coat 22 into the above shape, the contact part is sharp, so it has high wear resistance against wear loads such as rice sharpening and improved durability against peeling of the fluororesin coat, etc. can do. In addition, the number of rice sharpening operations can be reduced accordingly.

  Further, the additive resin particles are unevenly distributed on the surface of the fluororesin coat 22 and are present at the lowest part of the fine holes 25, so that the fluororesin coat has a high wear resistance against wear load such as rice sharpening. It has the property to induce the generation of bubbles from the boiling nuclei where diamonds are unevenly distributed, and fine bubbles are generated uniformly and stably from the surface of the fluororesin coat, so the rice is heated uniformly by uniform boiling heat transfer It is possible to increase the abrasion resistance of the fluororesin coat and to cook delicious rice with improved taste.

  In the present embodiment, the diamond particles are microencapsulated in the powder coating material, but the diamond particles may be dispersed in the liquid coating material. In this case, the fluororesin coating does not contain additive particles. The clear layer may be painted and fired, and then a liquid paint added with diamond particles may be injected into the fine holes and fired.

(Embodiment 2)
5 is a cross-sectional view of the rice cooker pan in Embodiment 2 of the present invention, FIG. 6 is an enlarged cross-sectional view of the rice cooker pan, FIG. 7 is an enlarged cross-sectional view of the main part of the rice cooker pan, and FIG. 8 is for the rice cooker. The surface expansion cross-section perspective view of a pan is shown.

  The rice cooker according to the second embodiment is the same as the rice cooker according to the first embodiment except for the pot for the rice cooker.

  Here, as shown in FIGS. 5 and 6, the pan 30 is made of a clad material in which an aluminum 32 having a thickness of 1.0 mm is bonded to a ferrite-based stainless steel 31 having a thickness of 0.5 mm. It is formed by pressing so that the stainless steel 31 side is the outer surface.

  The pan 30 takes the maximum value (point B) while the curvature increases as it goes down from the height (point A) from about the middle position to about 1/3 of the pot height, and the bottom (point C). It has a shape whose curvature decreases toward The lowest point C is a point on the outermost periphery that touches the table surface when the pan 30 is placed on a flat surface such as a table surface. In this embodiment, the diameter of the pan 30 including the handle is 220 mm, the outer diameter not including the handle is 195 mm, the pan height is 118 mm, the height of the point A is 55 mm, and the diameter of the outer periphery of the bottom including the point C is 120 mm. It was.

  A two-layer fluororesin coat 33 is formed on the surface of the aluminum 32 on the inner surface of the pan 30. Hereinafter, with respect to the treatment of the fluororesin coat 33, in the case where a concave fine hole is formed on the surface layer inside the top coat and diamond is unevenly distributed as additive particles at the lowermost part to form a boiling nucleus, FIGS. Will be described with reference to FIG.

  After the base material is press-molded into a pan shape and washed, sand blasting is applied to the surface of the aluminum 32 on the inner surface of the pan, and the surface roughness Ra is adjusted to 3 to 5 μm. Thereafter, the fluororesin, the adhesive component, the pigment, A liquid primer coating containing a glittering material as a coating film component was applied to a film thickness of about 10 μm after film formation, and dried at 100 ° C. for 20 minutes to form a primer adhesive layer 34.

  When drying of the primer adhesive layer 34 is completed and the substrate temperature is sufficiently lowered, a water level line display is printed on the primer adhesive layer 34 on the side of the pan using a color different from the color of the primer adhesive layer 34 by pad printing. After that, a fluororesin powder coating material that does not contain additives such as pigments and glittering materials as a top coat treatment is formed on the primer adhesive layer 34 and the water level line display so that the film thickness becomes 40 μm. The top coat layer 35 was formed by painting. At this time, the used fluororesin is a mixed powder of PTFE: PFA = 2: 8.

  Next, a fine hole 36 having a quadrangular pyramid shape (□ 0.1 × 0.05 mm depth) is formed on the curved surface passing through the line segment AC of the topcoat layer 35, and a circle passing through the point C of the topcoat layer 35 is A fine hole 37 having a quadrangular pyramid shape (□ 0.05 × 0.05 mm depth) is formed on the bottom surface, and a PFA powder coating 38 in which diamond with an average particle diameter of 5 μm is microencapsulated is formed in the fine hole 25 at the same time. The fluorine resin coat 33 was formed by injecting into the apex portion and then baking at 380 ° C. for 20 minutes.

  Although the operation | movement of the rice cooking process of the rice cooker in Embodiment 2 of this invention comprised as mentioned above is equivalent to Embodiment 1, since the boiling state differs in a cooking-boiling maintenance process, it is below. Explain.

  In the cooking to boiling maintaining step, the temperature of the water in the pot 30 rises rapidly from 50 ° C. to 100 ° C. by continuous energization of the pot heating means 4. At this time, the water in the pan gradually (2) from the initial (1) non-boiling natural convection to the (2) nucleate boiling state where the bubbles generated on the surface of the fluororesin coat 22 do not reach the water surface. ) Nucleate boiling occurs in which bubbles generated on the surface of the fluororesin coat 33 reach the water surface.

  Hereinafter, phenomena actually occurring in the pan 30 will be described below.

  In the state of (1), natural convection heat transfer is dominant in heat conduction from water to rice, and temperature distribution is observed in the rice in the pan 30.

  In the state of (2), boiling heat transfer is dominant in heat conduction from water to rice, and bubbles generated on the surface of the fluororesin coat 22 frequently rise toward the water surface, so that the water in the pot 30 Forced convection occurs, and heat is evenly transferred to the rice. In addition, since the exit area of the micro hole on the bottom part is smaller than the micro hole on the curved part, many fine bubbles are generated from the bottom part, realizing uniform boiling heat transfer to the rice in the pan, Larger bubbles are generated from the curved surface, so that strong convection from the side of the pan to the inside causes a uniform heating of the rice in the pan.

  In the state of (3), bubbles frequently come off and reach the surface of the water, and the entire water in the pot 30 is vigorously stirred, so that forced convection occurs in the water in the pot 30 and heat is uniformly applied to the rice. Reportedly. In addition, since the exit area of the micro hole on the bottom part is smaller than the micro hole on the curved part, many fine bubbles are generated from the bottom part, realizing uniform boiling heat transfer to the rice in the pan, Larger bubbles are generated from the curved surface, so that strong convection from the side of the pan to the inside causes a uniform heating of the rice in the pan.

  As described above, in nucleate boiling, by making the surface of the fluororesin coat 33 a combination of a bottom surface portion where fine bubbles are generated and a curved surface portion where relatively large bubbles are generated, uniform boiling heat transfer and inner side from the side of the pan By causing strong convection toward the sea, the opportunity for contact between the bubbles and the rice increases, so the opportunity for heat transfer to the rice increases and the rice can be heated uniformly.

  In the present embodiment, the exit area of the micro holes is determined so that the curved surface portion is larger than the bottom surface portion, but the number of micro holes on the curved surface portion is smaller than the number of micro holes on the bottom surface portion. Even if it makes it like, the same effect is acquired. That is, as described in the first embodiment, in this case, since the micropores are not close to each other in the curved surface portion, the contact position of the bubbles is relatively stable and away from the periphery of the outlet, so that the bubbles are sufficiently It can grow and breaks up after it becomes a relatively large bubble. Therefore, the same effect can be expected by uniform boiling heat transfer from the bottom surface portion and strong convection from the side surface of the pan from the curved surface portion to the inside.

  As described above, the pan provided in the rice cooker of the present invention can uniformly heat rice, can improve the taste of rice, and is useful as a domestic or commercial rice cooker.

Sectional drawing of the rice cooker provided with the pot for rice cookers in Embodiment 1 of this invention. The expanded sectional view of the pan for rice cookers in Embodiment 1 of this invention The principal part expanded sectional view of the pan for rice cookers in Embodiment 1 of this invention. The surface expansion cross-section perspective view of the rice cooker pan in Embodiment 1 of this invention Sectional drawing of the pan for rice cookers in Embodiment 2 of this invention The expanded sectional view of the pan for rice cookers in Embodiment 2 of this invention The principal part expanded sectional view of the pan for rice cookers in Embodiment 2 of this invention. The surface expansion cross-section perspective view of the rice cooker pan in Embodiment 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main body 2,30 Pan 3 Lid 4 Pan heating means 5 Pan temperature detection means 6 Control means 7 Heating plate 8 Heating plate heating means 9 Heating plate temperature detection means 10 Steam cylinder 11 Heating plate seal packing 12 Steam hole 13 Cover seal packing 14 Vapor hole 15 Float 16 Float detection means 17 Groove 18 Vapor discharge port 20, 31 Ferritic stainless steel 21, 32 Aluminum 22, 33 Fluororesin coat 23, 34 Primer adhesive layer 24, 35 Top coat layer 25, 36, 37 Fine hole 26 38 PFA powder coating

Claims (8)

A rice cooker provided with a pan in which a fluororesin coat is formed on the inner surface of a substrate, and a plurality of polygonal pyramid-shaped fine holes are formed on the topcoat surface layer side of the fluororesin coat. Starting from an arbitrary outer circumference from the middle to the bottom of the overall height, on the curved surface connected to the bottom, a fluororesin coat is formed on the inner surface of the base of the bottom and the curved surface, and on the top coat surface side of the fluororesin coat A rice cooker provided with a pan, wherein a plurality of polygonal pyramid-shaped micropores are formed, and the bottom surface portion has a smaller exit area than the micropores of the curved surface portion. Starting from an arbitrary outer circumference from the middle to the bottom of the overall height, on the curved surface connected to the bottom, a fluororesin coat is formed on the inner surface of the base of the bottom and the curved surface, and on the top coat surface side of the fluororesin coat A rice cooker provided with a pan, wherein a plurality of polygonal pyramid-shaped micropores are formed, and the number of micropores in the curved surface portion is smaller than the number of micropores in the bottom surface portion. The rice cooker of any one of Claims 1-3 provided with the pan in which at least any one of silicon carbide or diamond was unevenly distributed as additive material particle | grains in the lowest part of the said micropore. 4. The pan according to claim 1, further comprising a pan in which a powder coating material in which at least one of silicon carbide and diamond is microencapsulated is unevenly distributed as an additive material particle at a lowermost portion of the fine hole. Rice cooker. 4. The rice cooker according to claim 1, wherein the additive particles are unevenly distributed in the top coat surface layer and have a pan that is present most frequently at a lowermost portion of the fine holes. The rice cooker according to claim 2 or 3, further comprising a pan in which at least one of silicon carbide and diamond is unevenly distributed at a lowermost portion of the fine hole in the bottom portion. The rice cooker according to claim 2 or 3, further comprising a pan in which at least one of silicon carbide and diamond is unevenly distributed on the top coat surface layer of the bottom surface portion and is present most frequently at a lowermost portion of the fine holes.