CN111182819A - Heating cooker - Google Patents

Abstract

The invention provides a heating cooker, which can efficiently heat the inner side wall of the heating cooker. The cooking device is formed in a bottomed tubular shape and has a double-wall structure having a sealed space therein, and the cooking device includes: a bottomed cylindrical inner container constituting an inner portion of the heating cooker; a bottomed cylindrical outer container constituting an outer portion of the heating cooker; and a working fluid that is injected into the sealed space, wherein the amount of the working fluid in the sealed space is set to an amount that does not cover the entire bottom surface of the sealed space.

Description

Heating cooker

Technical Field

The present invention relates to a heating cooker.

Background

Patent document 1 listed below describes a heating-tube type heating cooker. The heating cooker has a double-wall structure having a closed space therein, and the working fluid is injected into the closed space. When the bottom of the heating cooker is heated, the working fluid boils, and the vapor vaporized in the working fluid rises along the side of the sealed space. Thereby, the inner side wall of the heating cooker is heated by the steam. Further, the vapor heated in the side wall condenses, and becomes liquid as the working fluid. The liquid working fluid which has been changed into liquid descends by its own weight and returns to the bottom of the closed space. The cooking device is heated by repeating the phase change cycle of the working fluid.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 2713008

Disclosure of Invention

Problems to be solved by the invention

However, the heating cooker described above has room for improvement in the following respects. That is, in the heating cooker, the amount of the working fluid in the closed space for efficiently heating the inner side wall of the heating cooker is not defined.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heating cooker capable of efficiently heating the inner side wall of the heating cooker.

Means for solving the problems

Form 1: one or more embodiments of the present invention provide a heating cooker having a double-wall structure formed in a bottomed tubular shape and having a sealed space therein, the heating cooker including: a bottomed cylindrical inner container constituting an inner portion of the heating cooker; a bottomed cylindrical outer container constituting an outer portion of the heating cooker; and a working fluid that is injected into the sealed space, wherein the amount of the working fluid in the sealed space is set to an amount that does not cover the entire bottom surface of the sealed space.

Form 2: one or more embodiments of the present invention provide a heating cooker, wherein a volume ratio of the working fluid to the bottom portion in the closed space is set to 4 vol% to 80 vol%.

Form 3: one or more embodiments of the present invention provide a heating cooker in which a height dimension of the sealed space at a bottom portion of the heating cooker is set to be equal to or greater than a width dimension of the sealed space at a side portion of the heating cooker and is set to be equal to or greater than 2mm when viewed in a vertical direction.

Form 4: one or more embodiments of the present invention provide a cooking device in which a negative pressure or vacuum of 0.01atm or less is maintained in the sealed space.

Form 5: one or more embodiments of the present invention provide a heating cooker in which a plurality of pipes used when the working fluid is injected into the sealed space and when the inside of the sealed space is brought into a negative pressure or a vacuum are provided in an inner side wall portion of the inner container or an outer side wall portion of the outer container.

Form 6: one or more embodiments of the present invention provide a heating cooker in which a plurality of pipes are arranged at equal intervals in a circumferential direction of the heating cooker, and a pipe cover that covers the pipes is attached to the pipes.

Form 7: one or more embodiments of the present invention provide a cooking device in which an inner corner portion curved convexly toward an outer side of the inner container is formed between an inner bottom wall portion and an inner side wall portion of the inner container, and a radius of the inner corner portion is set to: the radius of the inside corner portion gradually decreases from the inside bottom wall portion toward the inside side wall portion.

Form 8: one or more embodiments of the present invention provide a heating cooker in which a surface of the inner container constituting the closed space and a surface of the outer container constituting the closed space are mirror-finished.

Effects of the invention

According to one or more embodiments of the present invention, the inner side wall of the heating cooker can be efficiently heated.

Drawings

Fig. 1 is a longitudinal sectional view of an inner pot according to a first embodiment (an enlarged sectional view taken along line 1-1 in fig. 2).

Fig. 2 is a plan view of the inner pot of the first embodiment viewed from the upper side.

Fig. 3 is an enlarged cross-sectional view showing a half of the inner pot shown in fig. 1 in an enlarged manner.

Fig. 4 is a partially cut-away plan view of the cover shown in fig. 1, as viewed from above.

FIG. 5 is a longitudinal sectional view of the rice cooker to which the inner pot shown in FIG. 1 is applied.

Fig. 6 is a graph showing temperature data of the inner pot and the rice when the inner pot shown in fig. 1 is used to cook the rice.

Fig. 7 is a graph showing temperature data of the inner bottom wall portion and the outer side wall portion of the inner pot when rice is cooked using the inner pot shown in fig. 1, and is a graph showing a case where a volume ratio of the working fluid to the bottom portion of the closed space is changed. Fig. 7 (a) shows a case where the volume ratio of the working fluid is set to 3 vol%, fig. 7 (B) shows a case where the volume ratio of the working fluid is set to 10 vol%, and fig. 7 (C) shows a case where the volume ratio of the working fluid is set to 85 vol%.

Fig. 8 is an explanatory diagram for explaining the rising of the vapor at the side of the closed space when the inner pot shown in fig. 1 is heated.

Fig. 9 is a longitudinal sectional view corresponding to fig. 1 showing a modification of the inner pot shown in fig. 1.

Fig. 10 (a) is a perspective view showing an example of a modification of the connection between the inner bottom wall portion and the outer bottom wall portion shown in fig. 1, and fig. 10 (B) is a perspective view showing another modification of the connection between the inner bottom wall portion and the outer bottom wall portion.

Fig. 11A is a longitudinal sectional view of the inner pot according to the second embodiment (a sectional view taken along line 11A-11A in fig. 11B), and fig. 11B is a bottom view of the inner pot shown in fig. 11A.

Fig. 12 is an explanatory view for explaining a method of manufacturing the inner pot shown in fig. 11.

Fig. 13 is a longitudinal sectional view of an inner pot of the third embodiment.

Fig. 14 (a) is a vertical sectional view of the inner pot for explaining the modification 1 of the tube shown in fig. 11 (a sectional view taken along line 14A-14A in fig. 14 (B)), and fig. 14 (B) is a bottom view of the inner pot shown in fig. 14 (a).

Fig. 15 is a vertical cross-sectional view of the inner pot for explaining modification 2 of the tube shown in fig. 11.

Fig. 16 (a) is a vertical sectional view showing an example in which a notch is formed in the inner pot shown in fig. 11, and fig. 16 (B) is an enlarged sectional view of the notch shown in fig. 16 (a) (an enlarged sectional view taken along line 16B-16B in fig. 16 (a)). Fig. 16 (C) is a partial vertical cross-sectional view of an example in which the slit of fig. 16 (a) is formed in the tube.

Fig. 17 is a longitudinal sectional view corresponding to fig. 1 of another modification of the inner pot shown in fig. 1, in which the coupling pin is omitted.

Fig. 18 is a partial vertical cross-sectional view showing a modification of the first flange of the inner container and the second flange of the outer container shown in fig. 1.

Detailed Description

(first embodiment)

Next, an inner pot 30 as a "heating cooker" according to a first embodiment will be described with reference to fig. 1 to 8. The inner pot 30 is a pot for cooking rice and constitutes a part of the rice cooker 10. Therefore, in the following description, the structure of the rice cooker 10 will be described first, and the structure of the inner pot 30 will be described next. Note that an arrow UP shown appropriately in the drawings indicates the upper side of the electric cooker 10 and the inner pot 30. In the following description, when the vertical direction is shown, the vertical direction of the rice cooker 10 and the inner pot 30 is shown unless otherwise specified.

(about electric cooker 10)

As shown in fig. 5, the rice cooker 10 is an IH (induction Heating) type rice cooker, and includes a rice cooker main body 12 and a lid 24.

< about the electric cooker main body 12 >

The rice cooker main body 12 has an inner pot housing part 14 for housing an inner pot 30 described later. The inner pot accommodating portion 14 has a concave shape that is open to the upper side, and is formed in a substantially circular shape in a plan view from the upper side. A heating part 16 for heating the inner pot 30 is provided under the inner pot accommodating part 14. The heating section 16 is formed by an induction coil wound in a substantially spiral shape below the inner pot housing section 14.

A power supply unit 18 is provided below the heating unit 16, and a high-frequency current is applied to the heating unit 16 (induction coil) via the power supply unit 18. Thus, by applying a high-frequency current to the heating portion 16 (induction coil), an eddy current is generated in the inner pot 30, which will be described later, and the inner pot 30 starts to generate heat by the resistance in the inner pot 30. Further, a temperature sensor 20 is provided below the center of the inner pot accommodating portion 14. The temperature sensor 20 is configured as a sensor for measuring the bottom temperature of the inner pot 30. Further, a control unit 22 electrically connected to the power supply unit 18 and the temperature sensor 20 is provided on the upper portion of the rice cooker main body 12. The control unit 22 controls the power supply unit 18 based on the output signal from the temperature sensor 20.

< with respect to the cover portion 24 >

The lid portion 24 is rotatably coupled to the upper portion of the rice cooker main body 12 by a hinge mechanism 26, and covers the opening of the inner pot housing portion 14. Then, the lid portion 24 is rotated from this state to open and close the opening of the inner pot accommodating portion 14, whereby the inner pot 30 described later can be accommodated in the inner pot accommodating portion 14.

(about inner pot 30)

As shown in fig. 1 to 3, the inner pot 30 is formed in a substantially bottomed cylindrical shape open to the upper side, and has a double-walled structure having a closed space 36 inside. Specifically, the inner pot 30 includes: an inner container 32 constituting an inner portion of the inner pot 30, and an outer container 34 constituting an outer portion of the inner pot 30. In addition, the working fluid 40 is injected into the closed space 36 of the inner pot 30. Further, the inner pot 30 includes: a coupling pin 42 (broadly, an element known as a "coupling part") for coupling the inner container 32 and the outer container 34, and a cover 50 for covering a flange formed at the opening of the inner pot 30. Next, the respective structures of the inner pot 30 will be explained.

< with respect to the inner container 32 >

The inner container 32 is formed of a magnetic material (stainless steel in the present embodiment, for example), and is formed in a substantially bottomed cylindrical shape that is open to the upper side. Specifically, the inner container 32 includes: an inner bottom wall 32A forming the bottom of the inner container 32, a cylindrical inner side wall 32B forming the side of the inner container 32, and an inner corner 32C connecting the inner bottom wall 32A and the inner side wall 32B. The inner bottom wall portion 32A is formed in a substantially circular plate shape whose vertical direction is the plate thickness direction. In addition, the inner bottom wall portion 32A is inclined downward to some extent as it goes radially outward from its central portion when viewed in vertical section. In other words, the inner bottom wall portion 32A is formed by being bent to some extent so that the center portion of the inner bottom wall portion 32A is convex upward.

The inner corner portion 32C is curved in a substantially 4-fold elliptical shape so as to be convex toward the outside of the inner container 32 (toward the radially outer and downward sides of the inner container 32) when viewed in vertical section, and smoothly connects the outer peripheral end portion of the inner bottom wall portion 32A and the lower end portion of the inner side wall portion 32B. Specifically, the radius R of the inner corner portion 32C is set to gradually decrease from the outer peripheral end of the inner bottom wall portion 32A toward the lower end of the inner side wall portion 32B in vertical cross section. That is, the radius R1 of the radius R corresponding to the outer peripheral end portion of the inner bottom wall portion 32A is set larger than the radius R2 of the radius R corresponding to the lower end portion of the inner side wall portion 32B.

A first flange 32D that extends radially outward of the inner container 32 is formed in the opening of the inner side wall portion 32B, and the first flange 32D extends over the entire circumference of the inner side wall portion 32B in the circumferential direction. The first flange 32D is formed by hemming or the like, and is bent into a substantially U-shape that is open to the inside in the radial direction of the inner container 32. Specifically, the first flange 32D includes: an upper flange portion 32D1 formed by bending the opening end portion of the inner side wall portion 32B substantially 90 degrees to the radial outside of the inner container 32, and a lower flange portion 32D2 formed by bending the tip end portion of the upper flange portion 32D1 downward and substantially 180 degrees to the radial inside of the inner container 32. Further, a second flange 34D of the outer container 34 described later is disposed between the upper flange portion 32D1 and the lower flange portion 32D2, and the second flange 34D is joined to the first flange 32D.

Further, a layer made of a heat-resistant fluororesin work, teflon (registered trademark) in this case, is formed on the inner peripheral surface of the inner container 32. On the other hand, the outer surface of the inner container 32 (specifically, the surface constituting the sealed space 36) is mirror-finished.

< with respect to the outer container 34 >

The outer container 34 is formed of a magnetic material (stainless steel in the present embodiment, for example) in a substantially bottomed cylindrical shape that is open to the upper side, as in the inner container 32. Specifically, the outer container 34 includes: an outer bottom wall portion 34A constituting the bottom of the outer container 34, a cylindrical outer side wall portion 34B constituting the side portion of the outer container 34, and an outer corner portion 34C connecting the outer peripheral end portion of the outer bottom wall portion 34A and the lower end portion of the outer side wall portion 34B. In the present embodiment, the plate thicknesses of the inner container 32 and the outer container 34 are set to be the same, and the plate thicknesses of the inner container 32 and the outer container 34 are set to be uniform (constant) as a whole.

The outer side wall portion 34B is formed in a cylindrical shape having a larger diameter than the inner side wall portion 32B of the inner container 32, and is arranged coaxially with the inner container 32 on the radially outer side of the inner side wall portion 32B. The outer bottom wall portion 34A is formed in a circular flat plate shape whose vertical direction is the plate thickness direction, and is disposed below the inner bottom wall portion 32A of the inner container 32. That is, when the inner pot 30 is accommodated in the inner pot accommodating portion 14 of the rice cooker 10, the outer bottom wall portion 34A is in close contact with the bottom surface of the inner pot accommodating portion 14. Similarly to the inner bottom wall portion 32A of the inner container 32, the outer bottom wall portion 34A may be curved to some extent so that the central portion of the outer bottom wall portion 34A is convex upward.

The outer corner portion 34C is curved into a substantially 4-fold elliptical shape so as to be convex toward the outside of the outer container 34 (toward the lower side and radially outward of the outer container 34) in a longitudinal sectional view, similarly to the inner corner portion 32C, and smoothly connects the outer peripheral end portion of the outer bottom wall portion 34A and the lower end portion of the outer side wall portion 34B. Specifically, the radius of the inner corner portion 32C is set to gradually decrease from the outer peripheral end of the outer bottom wall portion 34A toward the lower end of the outer side wall portion 34B in vertical cross section.

A second flange 34D that extends radially outward is formed at the opening end of the outer side wall portion 34B. The second flange 34D is bent by approximately 90 degrees outward in the radial direction of the outer container 34 at the opening end of the outer side wall portion 34B, and extends over the entire circumference of the outer side wall portion 34B in the circumferential direction. The second flange 34D is disposed between the upper flange portion 32D1 and the lower flange portion 32D2 of the first flange 32D of the inner container 32, and is crimped with the first flange 32D to join the two. That is, at the time of molding the first flange 32D, the first flange 32D is bent and molded so that the upper flange portion 32D1 and the lower flange portion 32D2 of the first flange 32D press-contact the second flange 34D vertically. Thus, the outer container 34 is assembled to the inner container 32, and a substantially U-shaped closed space 36 that is open upward in a vertical cross-sectional view is formed between the inner container 32 and the outer container 34. The tip end of the first flange 32D is joined to the second flange 34D by arc welding or the like. In addition to the joining of the distal end portion of the first flange 32D and the second flange 34D, the overlapping portions of the first flange 32D and the second flange 34D that overlap in the vertical direction may be joined together by spot welding, seamless welding, laser welding, or the like. This ensures airtightness of the sealed space 36. Further, the inner surface of the outer container 34 (the surface constituting the sealed space 36) is mirror-finished.

Here, the closed space 36 will be explained.

As described above, the closed space 36 is formed in a substantially U-shape that is hollow when viewed in vertical section. In the present embodiment, the bottom portion 36A of the closed space 36 is defined as a region (space) below the inner surface of the inner bottom wall portion 32A of the inner container 32 (see a region below the position indicated by the two-dot chain line L1 in fig. 1 and 3). Thus, in the present embodiment, the inner surface of the outer container 34 constituting the bottom portion 36A of the closed space 36 is defined as a bottom surface 36B of the closed space 36, and the bottom surface 36B includes: the inner surface of the outer bottom wall 34A and a part of the inner surface of the outer corner 34C of the outer container 34.

As will be described later, the working fluid 40 is stored on the bottom surface 36B, and when a high-frequency current is applied to the heating portion 16 (induction coil), the outer bottom wall portion 34A, which is a magnetic body, starts to generate heat, and the working fluid 40 is heated.

In the sealed space 36, a height dimension H of a bottom portion 36A of the sealed space 36 (a vertical dimension between the inner bottom wall portion 32A and the outer bottom wall portion 34A, see fig. 3) is set to be not less than a width dimension W of a side portion 36C of the sealed space 36 (a radial dimension of the inner pot 30 between the inner side wall portion 32B and the outer side wall portion 34B, see fig. 3), and is set to be not less than 2 mm. In the present embodiment, the height dimension H of the bottom portion 36A is set to 4mm, and the width dimension W of the side portion 36C is set to 2 mm. In consideration of the increase in size of the inner pot 30 and the practical level of the inner pot 30 as a pot, the height H of the bottom 36A is preferably set to 10mm or less. Further, since the inner bottom wall portion 32A is curved to some extent such that the central portion thereof is convex upward as described above, the height dimension H varies in the radial direction of the inner pot 30. Therefore, in the present embodiment, the height H is set to the minimum value of the vertical dimension between the inner bottom wall 32A and the outer bottom wall 34A. In the drawings, the width of the side portion 36C of the sealed space 36 is exaggerated for convenience.

In the explanation of the outer container 34, a circular through hole 34E is formed in an upper portion of the outer side wall portion 34B of the outer container 34 and in a lower position of the second flange 34D. Further, a vacuum-pumping pipe 38 for injecting the working fluid 40 and the sealed space 36 into the sealed space 36, which will be described later, is provided in the outer side wall portion 34B of the outer container 34 at a position corresponding to the through hole 34E. The tube 38 is disposed coaxially with the through hole 34E, and the proximal end portion of the tube 38 is joined to the outer side wall portion 34B by arc welding or the like. Thus, the inside of the sealed space 36 and the outside of the inner pot 30 are communicated with each other by the pipe 38 protruding radially outward from the outer side wall portion 34B of the inner pot 30.

In the present embodiment, the working fluid 40 is injected into the sealed space 36 from the pipe 38. After the working fluid 40 is injected into the sealed space 36, a vacuum pump (not shown) is attached to the pipe 38, and the air in the sealed space 36 is exhausted by the vacuum pump, so that the inside of the sealed space 36 is maintained at a negative pressure of less than 0.1atm (more preferably, a negative pressure of 0.01atm or less) or a vacuum setting. Further, the pipe for injecting the working fluid 40 and the pipe for vacuum evacuation do not need to be commonly used, and may be separately provided.

A caulking portion 38A is formed at the distal end portion of the tube 38, and the distal end portion of the tube 38 is closed by the caulking portion 38A. Specifically, the caulking process is performed on the tip end portion of the tube 38 while the air in the sealed space 36 is discharged by the vacuum pump, and the caulked portion 38A is molded by cutting the portion after the caulking process. The caulking portion 38A is flattened in the vertical direction and is formed into a substantially plate shape having a plate thickness direction in the vertical direction. Further, the tip end of the caulking portion 38A is sealed by arc welding or the like. Thereby, the airtightness of the closed space 36 is ensured.

< about working fluid 40 >

In the present embodiment, water is used as the working fluid 40. The working fluid 40 is injected into the sealed space 36 from the pipe 38 and is stored in the bottom 36A of the sealed space 36. The volume ratio of the working fluid 40 in the closed space 36 to the bottom 36A is set to 4 vol% to 80 vol%. That is, in the stored state of the working fluid 40, the entire bottom portion 36A of the sealed space 36 is not immersed in the working fluid 40, but a gap is formed between the working fluid 40 and the inner bottom wall portion 32A at the upper portion of the bottom portion 36A of the sealed space 36. More specifically, in the present embodiment, the amount of the working fluid 40 in the sealed space 36 is set so that the working fluid 40 does not cover the entire bottom surface 36B of the bottom portion 36A of the sealed space 36. Thus, in a state where the working fluid 40 is disposed on the bottom surface 36B of the closed space 36, a plurality of working fluids 40 in the form of droplets are disposed on the bottom surface 36B in a dispersed manner. In the present embodiment, as described above, the volume ratio of the working fluid 40 in the closed space 36 to the bottom 36A is set to 4 to 80 vol%, but the volume ratio is preferably set to 5 to 20 vol%, more preferably 7 to 15 vol%, and particularly preferably 8 to 12 vol%.

< about the connecting pin 42 >

The coupling pin 42 is made of a magnetic material (stainless steel in the present embodiment, for example). The coupling pin 42 is formed in a substantially cylindrical shape having an axial direction in the vertical direction, and couples the inner bottom wall 32A and the outer bottom wall 34A of the inner pot 30 together. Specifically, the coupling pin 42 includes: a center pin 44 that connects the central portion of the inner bottom wall portion 32A and the central portion of the outer bottom wall portion 34A, and a plurality of (4 in the present embodiment) outer peripheral pins 46 that connect the outer peripheral portion of the inner bottom wall portion 32A and the outer peripheral portion of the outer bottom wall portion 34A. The outer circumferential pins 46 are spaced apart at equal intervals (at intervals of 90 degrees) in the circumferential direction of the inner pot 30.

In the present embodiment, the upper end portion of the connecting pin 42 is joined to the inner bottom wall portion 32A of the inner container 32 by arc welding or the like. On the other hand, after the inner container 32 and the outer container 34 are assembled, the lower end portion of the connecting pin 42 is joined to the outer bottom wall portion 34A of the outer container 34 by laser welding or the like from the outside of the outer container 34. In the present embodiment, the coupling pin 42 includes the center pin 44 and the outer peripheral pin 46, but the outer peripheral pin 46 may be omitted from the coupling pin 42, and only the coupling pin 42 may be the center pin 44.

< about the cover 50 >

As shown in fig. 1, 3, and 4, the cover 50 is formed in a circular ring shape, and covers the first flange 32D of the inner container 32 and the pipe 38 from the radially outer side of the inner pot 30. The cover 50 is made of a heat-resistant resin (in the present embodiment, heat-resistant ABS, for example). The cover 50 is divided into two parts in a plan view, and is configured by a pair of cover members 52. The pair of cover members 52 are formed in a semicircular shape (substantially C-shaped) that opens toward the center of the inner pot 30 in plan view, and are formed in a concave shape that opens toward the inside in the radial direction of the inner pot 30 when viewed in cross section in the circumferential direction (longitudinal direction). Specifically, the cover member 52 includes: an outer peripheral wall 52A constituting an outer peripheral portion of the cover member 52, an upper wall 52B extending radially inward of the cover member 52 from an upper end portion of the outer peripheral wall 52A, and a lower wall 52C extending radially inward of the cover member 52 from a lower end portion of the outer peripheral wall 52A. A pair of upper and lower intermediate walls 52D extending radially inward from a vertically intermediate portion of the outer peripheral wall 52A are formed between the upper wall 52B and the lower wall 52C, and the intermediate walls 52D are arranged parallel to the upper wall 52B and the lower wall 52C and extend in the circumferential direction of the cover member 52.

An upper portion of the inside of the cover member 52 (a space between the upper intermediate wall 52D and the upper wall 52B) is a first housing portion 52E. The first flange 32D of the inner pot 30 is fitted into the first receiving portion 52E, and the cover member 52 is fixed to the inner pot 30. In other words, the cover member 52 covers the first flange 32D (including the second flange 34D) of the inner pot 30 from the radially outer side. A lower portion of the inside of the cover member 52 (a space between the lower intermediate wall 52D and the lower wall 52C) is a second housing portion 52F. The tube 38 of the inner pot 30 is accommodated in the second accommodation portion 52F. Thus, the pipe 38 is covered from the radially outer side of the inner pot 30 by the cover member 52.

In addition, a clasp 52G (see fig. 4) protruding radially outward is formed on the outer peripheral wall 52A of the one cover member 52 at both longitudinal end portions. Further, an engaging piece 52H (see fig. 4) protruding toward the one cover member 52 is formed at both longitudinal end portions of the outer peripheral wall 52A of the other cover member 52, and an engaging hole 52J (see fig. 4) for engaging with the catch 52G is formed at a distal end portion of the engaging piece 52H. Thus, in the engaged state of the pair of cover members 52, the cover 50 covers the first flange 32D and the pipe 38 from the radially outer side of the inner pot 30.

As the cover member 52 is fixed to the inner pot 30, the above-described hook 52G and the engaging piece 52H may be omitted, and only the first flange 32D may be fitted into the first receiving portion 52E. The cover member 52 may be fixed to the inner pot 30 by fastening the cover member 52 to the first flange 32D with screws, rivets, or the like. Further, the cover 50 is not limited to being divided into two, and the cover 50 may be divided into 3 or more pieces.

(action and Effect)

Next, the operation and effect of the present embodiment will be described.

When cooking rice using the inner pot 30 and the rice cooker 10 configured as described above, the inner pot 30 is accommodated in the inner pot accommodating portion 14 of the rice cooker 10, and the bottom of the inner pot 30 is heated by the heating portion 16 of the rice cooker 10. Specifically, by applying a high-frequency current to the heating portion 16 (induction coil), an eddy current is generated in the inner pot 30. Thereby, the bottom of the inner pot 30 starts to generate heat, and the working fluid 40 in the closed space 36 is heated.

When the temperature of the heated working fluid 40 reaches the boiling point, the working fluid 40 boils, and a part of the working fluid 40 is vaporized. The vaporized vapor instantaneously diffuses into the sealed space 36, and heats the inside side wall portion 32B of the inner pot 30. Then, the vapor heated in the inside side wall portion 32B of the inner pot 30 starts to condense, and the vapor turns into liquid as the working fluid 40. The working fluid 40 that has become liquid returns to the bottom 36A of the sealed space 36 by its own weight. Then, by repeating the cycle of the phase change in the working fluid 40, the inner side wall portion 32B of the inner pot 30 is heated, and the cooked material (rice) in the inner pot 30 is heated. Since the vapor of the working fluid 40 makes the entire wall surfaces of the inner container 32 and the outer container 34 surrounding the sealed space 36 at the same temperature, the inner bottom wall portion 32A, the inner side wall portion 32B, and the inner corner portion 32C of the inner container 32 are heated substantially uniformly without time lag, and the temperature of the inner container 32 rises.

Fig. 6 is a graph showing an example of temperature data of the inner pot 30 and the rice when the inner pot 30 of the present embodiment is used to cook rice. In the graph, the horizontal axis represents time (minutes) from the start of cooking, and the vertical axis represents temperature (. degree. C.). In addition, a solid line shown in fig. 6 is measurement data of an upper portion of the inner side wall portion 32B of the inner pot 30, a broken line is measurement data of a central portion of the inner bottom wall portion 32A of the inner pot 30, a chain line is measurement data of an upper portion of the rice in the inner pot 30, and a two-dot chain line is measurement data of a lower portion of the rice in the inner pot 30.

As shown in the figure, at the start of the "rice cooking zone" from the start of rice cooking to approximately 20 minutes later, the temperature of the inner side wall portion 32B of the inner pot 30 rises to 100 ℃ as high as the temperature of the inner bottom wall portion 32A of the inner pot 30. It is noted that even in the "rice cooking zone" and the "rice steaming zone" after the temperature of the inner pot 30 reaches 100 ℃, the inner pot 30 is heated with the temperature difference between the inner side wall portion 32B and the inner bottom wall portion 32A negligible.

Further, at the beginning of the "rice cooking zone", the temperatures of the upper and lower portions of the rice are increased as the temperatures of the inner side wall portion 32B and the inner bottom wall portion 32A of the inner pot 30 are increased. In other words, it is understood that the temperature difference between the inner side wall portion 32B and the inner bottom wall portion 32A of the inner pot 30 and the upper and lower portions of the rice can be reduced, and the rice can be cooked.

In addition, the present embodiment has been found that rice can be cooked in a short time even in so-called fast rice cooking in which a "soaking zone" during rice cooking is omitted and rice is cooked as a "rice cooking zone" immediately after the start of rice cooking. That is, in the case of fast rice cooking in general, in order to prevent excessive evaporation of water for soaking rice (hereinafter, referred to as "soaking water") during fast rice cooking, control is performed to reduce the output to the heating part 16 (induction coil) of the rice cooker 10 with respect to the output at the beginning of rice cooking during rice cooking. Therefore, the output is temporarily lowered during the cooking process, and the time until the cooking is finished is correspondingly prolonged during the rapid cooking.

In contrast, it has been found that, in the case of the rapid rice cooking using the inner pot 30 of the present embodiment, excessive evaporation of the steepwater in the rapid rice cooking can be suppressed. Therefore, it has been confirmed that even if the inner pot 30 is heated by setting the output to the heating part 16 (induction coil) of the rice cooker 10 to a constant output from the beginning to the end of cooking, cooked rice that is not inferior to that cooked by normal cooking is cooked. Thus, the time for rapid rice cooking can be further shortened by setting the output to the heating part 16 (induction coil) of the rice cooker 10 to a constant output from the start to the end of rice cooking.

Here, in the inner pot 30 of the present embodiment, the volume ratio of the working fluid 40 in the closed space 36 to the bottom 36A is set to 4 vol% to 80 vol%. Specifically, the plurality of working liquids 40 are dripped on the bottom surface 36B of the sealed space 36 so as not to cover the entire bottom surface 36B of the sealed space 36. This enables the inside side wall portion 32B of the inside container 32 to be heated efficiently.

This point will be described with reference to a graph shown in fig. 7. Fig. 7 is a graph showing an example of data obtained by measuring the temperature of the inner pot 30 when the volume ratio of the operating fluid 40 to the bottom portion 36A is changed during cooking of the inner pot 30. In each graph of fig. 7, the horizontal axis represents time (minutes) from the start of cooking, and the vertical axis represents temperature (deg.c). In each graph, the solid line represents measurement data of the upper portion of the inner side wall portion 32B of the inner pot 30, the broken line represents measurement data of the lower portion of the inner side wall portion 32B, the one-dot chain line represents measurement data of the central portion of the inner bottom wall portion 32A of the inner pot 30, and the two-dot chain line represents measurement data of the outer peripheral portion of the inner bottom wall portion 32A. Further, in fig. 7 a, the volume ratio is set to 3 vol%, in fig. 7B, the volume ratio is set to 10 vol%, and in fig. 7C, the volume ratio is set to a value larger than 80 vol% (approximately 85 vol%).

As shown in fig. 7 a, it has been found that when the volume ratio is set to 3 vol% or less, a phase transition period of the working fluid 40 (a cycle period in which the working fluid is vaporized from the liquid to become vapor and the working fluid is condensed from the vapor to return to the liquid) occurs, but the behavior of the temperature rise of the entire inner pot 30 is unstable.

As shown in fig. 7 (C), it is found that when the volume ratio exceeds 80 vol%, the efficiency of the phase transition cycle of the vapor decreases, the temperature difference between the inner bottom wall portion 32A and the inner side wall portion 32B of the inner pot 30 increases, and the temperature uniformity of the entire inner pot 30 cannot be obtained.

On the other hand, as shown in fig. 7 (B), it has been found that when the volume ratio is set to 10 vol%, the entire inner pot 30 is heated substantially uniformly while the phase transition cycle of the steam is favorably performed and the temperature difference between the inner bottom wall portion 32A and the inner side wall portion 32B of the inner pot 30 is suppressed.

As described above, by setting the volume ratio of the working fluid 40 to the bottom 36A of the closed space 36 to 4 vol% to 80 vol%, the inner side wall portion 32B of the inner container 32 can be efficiently heated, and the entire inner pot 30 can be substantially uniformly heated.

In the inner pot 30, the height H of the bottom 36A of the closed space 36 is set to be not less than the width W of the side 36C and not less than 2 mm. Therefore, the inside side wall portion 32B of the inside container 32 can be heated more efficiently.

That is, it has been found that when the height H is set to be smaller than the width W and smaller than 2mm, the efficiency of returning the working fluid 40, which is condensed and returned to a liquid state, from the side portion 36C to the bottom portion 36A of the closed space 36 is lowered in the phase transition period of the working fluid 40, and the effect of uniformly heating the inner pot 30 is lowered. Therefore, as described above, by setting the height H to the width W or more and 2mm or more, it is possible to suppress a decrease in the return efficiency of the working fluid 40, which has been condensed and returned to a liquid, from the side portion 36C to the bottom portion 36A of the closed space 36, and to improve the effect of uniformly heating the inner pot 30. As described above, the inner side wall portion 32B of the inner container 32 can be heated more efficiently.

Further, the inside of the sealed space 36 is set to be maintained at a negative pressure of less than 0.1atm (more preferably, a negative pressure of 0.01atm or less) or a vacuum. Therefore, the inside side wall portion 32B of the inside container 32 can be heated more efficiently.

That is, as shown in fig. 8, the steam generated in the sealed space 36 rises along the inner side wall portion 32B of the inner pot 30 (see the arrow in fig. 8). At this time, when the inside of the sealed space 36 is made to be a negative pressure exceeding 0.1atm, the residual air a (see the portion indicated by the two-dot chain line) in the sealed space 36 is pushed toward the upper end side of the sealed space 36 by the vapor rising along the inner side wall portion 32B. That is, in this case, the residual air a in the sealed space 36 becomes a resistance layer against the vapor when the vapor rises, and tends to inhibit the rise of the vapor. Further, by setting the inside of the sealed space 36 to a negative pressure state of less than 0.1atm, resistance of the residual air a to the rising vapor can be reduced, the vapor can be raised toward the upper end side of the sealed space 36, and the inside side wall portion 32B can be heated by the vapor favorably. Further, by maintaining the inside of the sealed space 36 at a negative pressure or vacuum of 0.01atm or less, the inside side wall portion 32B can be heated by the vapor more favorably. Therefore, by setting the inside of the sealed space 36 to be maintained at a negative pressure of less than 0.1atm (more preferably, a negative pressure of 0.01atm or less) or vacuum, the inside side wall portion 32B of the inside container 32 can be heated more favorably.

The radius R of the inner corner 32C of the inner pot 30 is set so as to gradually decrease from the outer peripheral end of the inner bottom wall 32A toward the lower end of the inner side wall 32B. That is, the radius R1 of the radius R corresponding to the outer peripheral end portion of the inner bottom wall portion 32A is set larger than the radius R2 of the radius R corresponding to the lower end portion of the inner side wall portion 32B. This makes it possible to efficiently raise the steam generated in the sealed space 36 toward the inner side wall portion 32B along the inner corner portion 32C of the inner pot 30 while suppressing a decrease in the capacity of the inner pot 30 (the amount of rice that can be cooked). This point will be explained below.

That is, if the radius R of the inner corner portion 32C is set to be constant as the radius R1 corresponding to the outer peripheral end portion of the inner bottom wall portion 32A without changing the size in the radial direction of the inner pot 30 (hereinafter, this case will be referred to as a comparative example), the lower portion of the inner corner portion 32C enters radially inward of the present embodiment. That is, the diameter of the inner bottom wall portion 32A is reduced in size. Thus, in the comparative example, the capacity of the inner pot 30 tends to be reduced.

In the comparative example, the inclination angle of the tangent line to the inner corner portion 32C with respect to the horizontal direction gradually increases toward the radially outer side of the inner container 32 in the vertical cross section.

In contrast, in the present embodiment, the radius R of the inner corner portion 32C of the inner container 32 is set so as to gradually decrease from the outer peripheral portion of the inner bottom wall portion 32A toward the lower end portion of the inner side wall portion 32B. Therefore, in a vertical cross-sectional view, the inclination angle of the tangent line to the inner corner portion 32C with respect to the horizontal direction increases more sharply than in the comparative example as it goes radially outward of the inner container 32. In other words, the inside corner portion 32C is formed so as to rise more sharply than the comparative example. Thus, the resistance to the steam rising along the inner corner portion 32C of the inner pot 30 can be reduced as compared with the comparative example, and the steam can be efficiently raised toward the inner side wall portion 32B.

In the present embodiment, the lower end portion of the inner corner portion 32C can be disposed radially outward of the comparative example. That is, the diameter of the inner bottom wall portion 32A can be made larger than that of the comparative example. This makes it possible to increase the capacity of the inner pot 30 as compared with the comparative example.

As described above, according to the inner pot 30 of the present embodiment, while suppressing a decrease in the capacity of the inner pot 30, the steam in the sealed space 36 can be efficiently raised toward the inner side wall portion 32B along the inner corner portion 32C of the inner container 32.

Further, the surface of the inner pot 30 constituting the closed space 36 is mirror-finished. Therefore, in the sealed space 36, resistance of the inner corner portion 32C and the inner side wall portion 32B of the inner pot 30 to the steam when the steam rises along these wall surfaces can be reduced. This enables the vapor in the sealed space 36 to satisfactorily rise toward the upper end of the sealed space 36. As a result, the entire inner container 32 can be efficiently heated.

Further, the resistance of the wall surfaces against the working fluid 40 when the working fluid 40 condensed and changed into a liquid falls can be reduced. This enables the working fluid 40 to be satisfactorily returned to the bottom 36A of the sealed space 36.

Further, a connecting pin 42 is provided in the closed space 36 of the inner pot 30, and the connecting pin 42 connects the inner bottom wall portion 32A and the outer bottom wall portion 34A of the inner pot 30 together. When the inner pot 30 is heated, the air pressure in the sealed space 36 rises, and the inner bottom wall 32A and the outer bottom wall 34A expand vertically. At this time, since the inner bottom wall portion 32A and the outer bottom wall portion 34A are connected by the connecting pin 42, the inner bottom wall portion 32A and the outer bottom wall portion 34A act to be stretched by the connecting pin 42. This can suppress the expansion of the inner bottom wall portion 32A upward and the expansion of the outer bottom wall portion 34A downward during heating of the inner pot 30 by the connecting pin 42, and can suppress the deformation of the bottom of the inner pot 30.

Further, the coupling pin 42 is formed of a pin having an axial direction in the vertical direction. Therefore, the inner bottom wall portion 32A and the outer bottom wall portion 34A can be connected by the connecting pin 42 in the bottom portion 36A of the sealed space 36 without obstructing the flow of the working fluid 40 and the vapor that becomes the gas.

The connecting pin 42 has a center pin 44, and the center pin 44 connects the center portion of the inner bottom wall portion 32A and the center portion of the outer bottom wall portion 34A of the inner pot 30. Therefore, the vertical displacement of the central portions of the inner bottom wall portion 32A and the outer bottom wall portion 34A can be suppressed by the connecting pin 42. This can suppress displacement of the portion where the displacement amount is the largest in the inner bottom wall portion 32A and the outer bottom wall portion 34A during inflation. Therefore, the expansion of the inner bottom wall portion 32A and the outer bottom wall portion 34A can be effectively suppressed.

Further, a pipe 38 protruding radially outward of the inner pot 30 is provided on the outer side wall portion 34B of the inner pot 30. Before the caulking portion 38A of the pipe 38 is formed, the inside of the sealed space 36 of the inner pot 30 and the outside of the inner pot 30 communicate with each other through the pipe 38. Thus, the working fluid 40 can be easily injected into the sealed space 36 by the pipe 38. Further, by attaching a vacuum pump to the pipe 38, the air in the sealed space 36 can be discharged from the pipe 38, and the inside of the sealed space 36 can be brought into a negative pressure or a vacuum state. Therefore, the workability in manufacturing the inner pot 30 can be improved.

Further, in the inner pot 30, the first flange 32D (second flange 34D) of the inner pot 30 and the tube 38 are covered by the cover 50 from the radially outer side of the inner pot 30. Therefore, even if the pipe 38 for improving workability in manufacturing the inner pot 30 is provided on the outer side wall portion 34B, the pipe 38 cannot be recognized through the cover 50. In addition, the cover 50 can be used as a handle of the inner pot 30. As can be seen from the above, it is possible to improve the design feeling of the inner pot 30 and the convenience of the user.

Further, in the inner pot 30, the first flange 32D of the inner container 32 is pressed against the second flange 34D by hemming or the like so as to be wound around the second flange 34D of the outer container 34 above and below the flange. That is, the overlapping portion of the inner container 32 and the outer container 34 is closed in a so-called labyrinth structure (labyrinth structure). This ensures airtightness in the sealed space 36 formed by the inner container 32 and the outer container 34.

In the present embodiment, as described above, the inner pot 30 has a double-walled structure having the sealed space 36 therein, and the inside of the sealed space 36 is in a negative pressure or vacuum state. Therefore, the heat retaining property of the inner pot 30 after cooking can be improved.

(modification of inner pot 30)

Next, an inner pot 60 according to a modification will be described with reference to fig. 9.

The inner pot 60 of the modification has the same structure as the inner pot 30 of the first embodiment except for the following points. In fig. 9, the same reference numerals are given to the same components as those of the first embodiment.

That is, in the inner pot 60 of the modified example, a part of the bottom of the inner pot 60 is formed in a solid shape. Specifically, the inner bottom wall portion 32A of the inner container 32 is omitted, and the inner container 32 is formed in a substantially cylindrical shape. In the outer container 34, the outer bottom wall portion 34A is omitted, and the outer container 34 is formed in a substantially cylindrical shape. Further, a substantially solid disk-shaped bottom plate 62 is provided on the radial inner side of the inner pot 60 with respect to the inner corner 32C of the inner container 32 and the outer corner 34C of the outer container 34. The bottom plate 62 is made of a magnetic material (stainless steel in this embodiment) as in the case of the inner container 32 and the outer container 34. The outer peripheral portion of the base plate 62 is joined to the inner corner 32C and the outer corner 34C by arc welding or the like.

Thus, in the inner pot 60, the sealed space 36 becomes a space between the inner corner 32C and the inner side wall 32B and between the outer corner 34C and the outer side wall 34B. Further, a part of the inside corner of the inner pot 60 (a part between the inside corner 32C and the outside corner 34C) constitutes a bottom 36A of the closed space 36. In the inner pot 60, the bottom of the inner pot 60 is formed by the bottom plate 62, and therefore the coupling pin 42 of the inner pot 30 of the present embodiment is omitted.

In the inner pot 60 of the modified example, when the bottom (bottom plate 62) of the inner pot 60 is heated, the working fluid 40 injected into the sealed space 36 is also heated. When the temperature of the heated working fluid 40 reaches the boiling point, the working fluid 40 boils, and a part of the working fluid 40 starts to vaporize. The vaporized vapor then rises toward the side portion 36C in the sealed space 36 along the inside corner portion 32C and the inside side wall portion 32B in the sealed space 36. Thereby, the inside side wall portion 32B of the inner pot 60 is heated by the steam. The vapor that heats the inside side wall portion 32B condenses, and the gas changes into a liquid as the working liquid 40. Further, the working fluid 40 changed into a liquid descends by its own weight and returns to the bottom 36A of the closed space 36. Then, the cycle of the phase change is repeated in the working fluid 40, so that the inside side wall portion 32B of the inner pot 30 is heated. As described above, in the inner pot 60 according to the modification, the inner side wall portion 32B of the inner pot 60 can be efficiently heated as in the first embodiment.

In the inner pot 60 of the modified example, the bottom 36A of the sealed space 36 is set in the corner of the inner pot 60. Therefore, when the working fluid 40 is vaporized into steam, the steam can be immediately moved (lifted) toward the side portion 36C of the sealed space 36 along the inner corner portion 32C. Therefore, the vaporized vapor can be efficiently moved (lifted) toward the side portion 36C of the closed space 36, and the inside side wall portion 32B of the inner pot 60 can be heated.

In the inner pot 60 of the modified example, the sealed space 36 of the inner pot 60 is a space between the inner corner 32C and the inner side wall 32B and between the outer corner 34C and the outer side wall 34B, but the sealed space 36 may be a space between the outer corner 34C and the outer side wall 34B. In other words, the sealed space 36 only needs to include at least the space between the outside corner 34C and the outside side wall 34B. In this case, the lower portion of the inner pot 60 with respect to the two-dot chain line L2 in fig. 9 is formed in a solid shape.

(modification of the method for connecting the inner bottom wall 32A and the outer bottom wall 34A of the inner pot 30)

Next, two modifications of the method of connecting the inner bottom wall portion 32A and the outer bottom wall portion 34A of the inner pot 30 will be described.

(modification 1 of the joining method)

Next, a modification 1 of the connection method will be described with reference to fig. 10 (a). In modification 1, the configuration is the same as that of the first embodiment except for the following points. In fig. 10 (a), the same reference numerals are given to the same components as those of the first embodiment.

That is, in modification 1, the coupling pin 42 is omitted, and the coupling plate 70 (broadly, an element known as a "coupling portion") is provided between the inner bottom wall portion 32A and the outer bottom wall portion 34A of the inner pot 30. The connecting plate 70 is formed in a substantially cross shape in a plan view. Specifically, the connecting plate 70 includes a first connecting plate 72 and a pair of second connecting plates 74. The first connecting plate 72 and the second connecting plate 74 are formed in a substantially elongated plate shape, and the length of the first connecting plate 72 in the longitudinal direction is set to be substantially 2 times the length of the second connecting plate 74 in the longitudinal direction. Further, one longitudinal end portion of the second linking plate 74 is joined to the longitudinal center portion of the first linking plate 72, and the second linking plate 74 projects from the longitudinal center portion to both sides in the plate thickness direction of the first linking plate 72. Thus, the connecting plate 70 is formed with 4 connecting pieces 70A, and the connecting pieces 70A radially protrude from the central portion of the connecting plate 70.

In addition, the connecting plate 70 is disposed between the inner bottom wall portion 32A and the outer bottom wall portion 34A such that the central portion of the connecting plate 70 overlaps the central portions of the inner bottom wall portion 32A and the outer bottom wall portion 34A of the inner pot 30 in a plan view. The upper end of the connecting plate 70 is joined to the inner bottom wall 32A, and the lower end of the connecting plate 70 is joined to the outer bottom wall 34A. Thereby, the inner bottom wall 32A and the outer bottom wall 34A are connected by the connecting plate 70. In this state, the bottom 36A of the sealed space 36 is partitioned by the connecting plate 70.

Further, a plurality of communication holes 70B are formed in the lower end portion of each coupling piece 70A of the coupling plate 70. Thus, the bottom portions 36A of the closed spaces 36 partitioned by the connecting plate 70 are configured to communicate with each other through the communication holes 70B, and the working fluid 40 in the bottom portions 36A can flow through the bottom portions 36A of the partitioned closed spaces 36.

In addition, in modification 1, as described above, the inner bottom wall portion 32A and the outer bottom wall portion 34A are coupled together by the coupling plate 70. Therefore, as in the present embodiment, expansion of the inner bottom wall portion 32A and the outer bottom wall portion 34A when the inner pot 30 is heated can be suppressed.

In addition, in modification 1, the connecting pieces 70A of the connecting plate 70 radially extend from the central portions of the inner bottom wall portion 32A and the outer bottom wall portion 34A, and connect the inner bottom wall portion 32A and the outer bottom wall portion 34A together. Therefore, when the inner pot 30 is heated, the heat transferred to the coupling plate 70 can be transferred across the radial direction of the inner bottom wall portion 32A by the coupling piece 70A. Thus, the inner bottom wall 32A can be heated substantially uniformly by the connecting piece 70A in the radial direction of the inner bottom wall 32A.

Further, a plurality of communication holes 70B are formed in the lower end portion of each coupling piece 70A of the coupling plate 70. Therefore, even if the connecting plate 70 is disposed so as to partition the bottom portion 36A of the sealed space 36, the working fluid 40 in the bottom portion 36A can flow in the bottom portion 36A of the sealed space 36 partitioned by the connecting plate 70.

In addition, in the modification 1, 4 connecting pieces 70A are formed on the connecting plate 70, but the number of the connecting pieces 70A may be arbitrarily set.

(modification 2 of the joining method)

Next, a modification 2 of the connection method will be described with reference to fig. 10 (B). In modification 2, the configuration is the same as that of the first embodiment except for the following points. In fig. 10 (B), the same reference numerals are given to the same components as those of the first embodiment.

That is, in modification 2, a substantially disc-shaped intermediate plate 80 is provided between the coupling pin 42 and the inner bottom wall portion 32A of the inner pot 30, and the intermediate plate 80 is made of a magnetic material (stainless steel in this modification, for example) similarly to the coupling pin 42. That is, in modification 2, the intermediate plate 80 is interposed between the connecting pin 42 and the inner bottom wall portion 32A of the inner pot 30, and the intermediate plate 80 is joined to the connecting pin 42 and the inner bottom wall portion 32A. Therefore, when the inner pot 30 is heated, the heat transmitted from the connecting pins 42 is dispersed by the intermediate plate 80 and transmitted to the entire inner bottom wall portion 32A of the inner pot 30. Thus, in modification 2, the expansion of the inner bottom wall portion 32A and the outer bottom wall portion 34A during heating can be suppressed while uniformly heating the inner bottom wall portion 32A of the inner pot 30 in the radial direction.

(second embodiment)

Next, an inner pot 90 as a "heating cooker" according to a second embodiment will be described with reference to fig. 11 and 12.

The inner pot 90 of the second embodiment has the same structure as the inner pot 30 of the first embodiment except for the following points. In fig. 11, the same reference numerals are given to the same components as those of the first embodiment. In fig. 11, the cover 50 is not shown in the inner pot 90.

As shown in fig. 11 (a) and (B), in the inner pot 90, the inner bottom wall portion 32A of the inner container 32 is arranged substantially horizontally (substantially parallel to the outer bottom wall portion 34A of the outer container 34) along a plane orthogonal to the vertical direction. In the inner pot 90, the coupling pins 42 of the first embodiment are omitted, and a plurality of coupling recesses 34F (broadly, elements known as "coupling portions") are formed at the outer bottom wall portion 34A of the outer container 34 (at 3 points in the present embodiment). The coupling recess 34F is formed in a substantially inverted U-shaped concave shape that opens downward when viewed in vertical section, and protrudes upward from the outer bottom wall portion 34A. The 3-point connecting recessed portions 34F are disposed radially outward of the inner pot 90 with respect to the center portion of the outer bottom wall portion 34A, and are disposed at equal intervals (every 120 degrees) in the circumferential direction of the inner pot 90. The top of the coupling recess 34F is disposed adjacent to the lower surface of the inner bottom wall 32A of the inner container 32, and is joined to the inner bottom wall 32A by spot welding. Thereby, the inner bottom wall 32A and the outer bottom wall 34A are coupled together by the coupling recess 34F. Further, as described above, in the second embodiment, the inner bottom wall portion 32A of the inner container 32 is disposed substantially horizontally along the plane orthogonal to the vertical direction, but similarly to the first embodiment, the inner bottom wall portion 32A may be curved to a certain extent so as to be convex upward.

In addition, in the first flange 32D of the inner container 32, the lower flange portion 32D2 of the first embodiment is omitted. The first flange 32D (the upper flange portion 32D1) of the inner container 32 and the second flange 34D of the outer container 34 are arranged so as to overlap each other in the vertical direction, and the tip end portion of the first flange 32D and the tip end portion of the second flange 34D of the outer container 34 are joined together by laser welding or the like. In addition to the joining of the distal end portion of the first flange 32D and the distal end portion of the second flange 34D, spot welding, seamless welding, laser welding, or the like may be performed on the overlapped portion of the first flange 32D and the second flange 34D that are overlapped in the vertical direction, and the both may be joined together.

Further, in the inner pot 90, a sealing material 92 containing glass frit is provided inside the distal end portion of the tube 38, and the opening portion of the tube 38 is sealed by the sealing material 92, thereby ensuring airtightness in the sealed space 36.

Next, a method for manufacturing the inner pot 90 according to the second embodiment will be described with reference to fig. 12.

As shown in fig. 12 (a), in the method of manufacturing the inner pot 90, first, the inner container 32 and the outer container 34 are molded by press working (drawing working) (press step). In this pressing step, the coupling recess 34F is also formed in the outer bottom wall portion 34A of the outer container 34.

After the pressing step, as shown in fig. 12 (B), a hole is formed in the upper portion of the outer side wall portion 34B of the outer container 34, and a through hole 34E is formed in the outer container 34 (drilling step).

After the drilling step, as shown in fig. 12 (c), the inner container 32 is disposed inside the outer container 34. Specifically, the inner bottom wall portion 32A of the inner container 32 is placed on the top of the coupling recess 34F of the outer container 34, and the first flange 32D of the inner container 32 is arranged to overlap the upper side of the second flange 34D of the outer container 34. Then, the front end portion of the first flange 32D of the inner container 32 and the front end portion of the second flange 34D of the outer container 34 are laser welded to join the front end portions of the two (flange joining step). Thereby, the inner container 32 and the outer container 34 are coupled together, and the closed space 36 is formed inside the inner pot 90.

In the flange joining step, in addition to joining of the distal end portion of the first flange 32D and the distal end portion of the second flange 34D, spot welding, seamless welding, laser welding, or the like may be performed on the overlapped portion of the first flange 32D and the second flange 34D that are overlapped in the vertical direction, and the both may be joined (in fig. 12 (c), an example of spot welding is illustrated). In the case of laser welding, laser welding is performed from the upper side of the first flange 32D or the lower side of the second flange 34D, and both are joined. In this case, when considering the design feeling of the inner pan 90, it is preferable to perform laser welding from the lower side of the second flange 34D.

As shown in fig. 12 (d), after the flange joining step, a pair of upper and lower spot welding guns are disposed above the inner bottom wall 32A of the inner container 32 and in the coupling recess 34F of the outer container 34, and the top of the inner bottom wall 32A and the top of the coupling recess 34F are joined by spot welding (pot bottom joining step). Thereby, the inner bottom wall portion 32A of the inner container 32 and the outer bottom wall portion 34A of the outer container 34 are coupled together.

As shown in fig. 12 (E), after the pan bottom joining step, the base end portion of the tube 38 is inserted into the through hole 34E of the outer container 34, and the base end portion of the tube 38 is joined to the edge portion of the through hole 34E by arc welding (vacuum inlet joining step). Thus, the pipe 38 is provided in the outer container 34, and the inside of the closed space 36 and the outside of the inner pot 90 communicate with each other through the pipe 38.

As shown in fig. 12 (f), after the vacuum mouthpiece joining step, the inner peripheral surface of the inner container 32 is subjected to a fluorine treatment to form a layer made of a fluororesin (teflon), and the outer peripheral surface of the outer container 34 is subjected to a coating treatment to form a layer made of a heat-resistant paint (surface treatment step).

As shown in fig. 12 (g), after the surface treatment step, the working fluid 40 is injected into the sealed space 36 from the pipe 38. After the working fluid 40 is injected into the sealed space 36, the air in the sealed space 36 is discharged by using a vacuum sealing apparatus, and the pipe 38 is sealed by using the sealing material 92. Specifically, the air in the sealed space 36 is discharged by a vacuum pump of the vacuum sealing apparatus, and when the air pressure in the sealed space 36 becomes a predetermined value or less, the sealing material 92 is filled into the tube 38 by the vacuum sealing apparatus. Further, the vacuum sealing apparatus has a spiral induction coil, and the tube 38 is inserted into the induction coil. Then, a high-frequency current is applied to the induction coil to locally inductively heat the tube 38, thereby melting the sealing material 92. Thereafter, the tube 38 is cooled, and the tube 38 is sealed with the sealing material 92 (vacuum sealing step).

As shown in fig. 12 (h), after the vacuum sealing step, the longitudinal intermediate portion of the tube 38 is cut (cutting step).

After the cutting step, as shown in fig. 12 (i), the pair of cover members 52 (covers 50) are assembled to the first flange 32D of the inner container 32 and the second flange 34D of the outer container 34 (cover assembling step).

As can be seen from the above, the inner pot 90 is manufactured.

The manufacturing process of the inner pot 90 may be performed in a vacuum environment (in a vacuum chamber) after the evacuation by the vacuum apparatus. In this case, all the steps shown in fig. 12 (a) to (i) may be performed in a vacuum atmosphere, and the steps after the press step shown in fig. 12 (a) and the drilling step shown in fig. 12 (b) are performed may be performed in a vacuum atmosphere. Accordingly, in the vacuum sealing step shown in fig. 12 (g), the inner pot 90 is already in a vacuum environment, and therefore, the step of evacuation can be omitted. In this case, the outer container 34 may be vacuum-sealed by omitting the vacuum-pumping pipe and welding a metal plate material covering (closing) the through hole 34E from the outside to the outer container 34. Glass frit may also be used as a vacuum sealing material. In this case, since the working fluid 40 can be introduced into the sealed space 36 in a solid (ice) state from the through hole 34E, a pipe for injecting the working fluid can be omitted.

Thus, the inner pot 90 having no protrusion such as a pipe on the inner container 32 or the outer container 34 can be manufactured. Therefore, the inner pot 90 has a tubeless structure, so that the inner pot 90 can be easily cleaned, the inner pot 90 can be more conveniently used, and the design of the inner pot 90 can be further improved.

In the second embodiment, when the bottom of the inner pot 90 is heated, the working fluid 40 injected into the sealed space 36 is also heated. When the temperature of the heated working fluid 40 reaches the boiling point, the working fluid 40 boils, and a part of the working fluid 40 is vaporized. The vaporized vapor then rises toward the side portion 36C in the sealed space 36 along the inside corner portion 32C and the inside side wall portion 32B in the sealed space 36. Thereby, the inside side wall portion 32B of the inner pot 90 is heated by the steam. The vapor that heats the inside side wall portion 32B condenses, and the gas changes into a liquid as the working liquid 40. Further, the liquid working fluid 40 descends by its own weight and returns to the bottom 36A of the closed space 36. Then, the phase change cycle is repeated in the working fluid 40, thereby heating the inside side wall portion 32B of the inner container 32. As is apparent from the above description, in the inner pot 90 according to the second embodiment as well, the inner side wall portion 32B of the inner pot 90 can be efficiently heated as in the first embodiment, and the entire inner pot 90 can be heated substantially uniformly.

In the inner pot 90 according to the second embodiment, a plurality of coupling recesses 34F are formed in the outer bottom wall portion 34A of the outer container 34, and the coupling recesses 34F are joined to the inner bottom wall portion 32A of the inner container 32 by spot welding or the like. Thus, the inner bottom wall 32A and the outer bottom wall 34A can be connected to each other with a simple structure. In addition, the number of components can be reduced and the number of manufacturing man-hours can be reduced as compared with the first embodiment.

In addition, in the inner pot 90 of the second embodiment, the front end portion of the first flange 32D of the inner container 32 and the front end portion of the second flange 34D of the outer container 34 are joined together by laser welding or the like. Further, the overlapped portions of the first flange 32D and the second flange 34D, which are overlapped in the vertical direction, are joined together by spot welding, seamless welding, laser welding, or the like. This can increase the joining strength between the first flange 32D and the second flange 34D, and can increase the rigidity of the opening of the inner pan 90. As a result, deformation of the inner container 32 can be suppressed when the inner pot 90 is heated.

That is, for example, in the joining (welding) of only the distal end portion of the first flange 32D and the distal end portion of the second flange 34D, there is a possibility that the inner container 32 is deformed so as to be lifted up from the distal end portion of the first flange 32D by the increase in the internal pressure of the sealed space 36 when the inner pot 90 is heated. On the other hand, the rigidity of the opening of the inner pan 90 is increased by joining the overlapping portions of the first flange 32D and the second flange 34D. As a result, deformation of the inner container 32 during heating of the inner pot 90 can be suppressed, and the joined state of the first flange 32D and the second flange 34D can be maintained satisfactorily.

In the second embodiment, a plurality of coupling recesses 34F are formed in the outer bottom wall portion 34A of the outer container 34, but one coupling recess 34F may be formed in the outer bottom wall portion 34A. In this case, the coupling recess 34F may be disposed at the center portion of the outer bottom wall 34A, and the top portion of the coupling recess 34F and the center portion of the inner bottom wall 32A may be joined together.

(third embodiment)

Next, an inner pot 100 as a "heating cooker" according to a third embodiment will be described with reference to fig. 13.

The inner pot 100 of the third embodiment has the same structure as the inner pot 30 of the first embodiment except for the following points. In fig. 13, the same reference numerals are given to the same components as those of the first embodiment. In fig. 13, the cover 50 is not shown in the inner pot 100.

In the third embodiment, the coupling pin 42 of the first embodiment is omitted from the inner pot 100. Further, a drawn portion 32G bulging upward is formed in the inner bottom wall portion 32A of the inner container 32. The drawn portion 32G is formed in a substantially disk shape concentric with the inner bottom wall portion 32A, and an outer peripheral portion of the drawn portion 32G is smoothly curved and connected to the inner bottom wall portion 32A. In addition, as an example, the diameter of the drawn portion 32G is set to 60% of the diameter of the inner bottom wall portion 32A, and the drawing height of the drawn portion 32G is set to 3 mm.

Further, a drawn portion 34G having the same configuration as the drawn portion 32G is formed in the outer bottom wall portion 34A of the outer container 34. That is, the drawn portion 34G is formed in a substantially disk shape concentric with the outer bottom wall portion 34A, and rises upward from the outer bottom wall portion 34A. The outer peripheral portion of the drawn portion 34G is smoothly curved and connected to the outer bottom wall portion 34A. Further, as an example, the diameter of the drawn portion 34G is set to 60% of the diameter of the outer bottom wall portion 34A, and the drawing height of the drawn portion 34G is set to 3 mm.

In the third embodiment, the lower flange portion 32D2 of the first embodiment is omitted from the first flange 32D of the inner container 32, as in the second embodiment. The first flange 32D (upper flange 32D1) of the inner container 32 and the second flange 34D of the outer container 34 are arranged so as to overlap each other in the vertical direction, and the tip end of the first flange 32D and the tip end of the second flange 34D of the outer container 34 are joined by laser welding or the like. The overlapped portions of the first flange 32D and the second flange 34D, which are overlapped in the vertical direction, are joined by spot welding or the like.

In the third embodiment, when the bottom of the inner pot 100 is heated, the working fluid 40 injected into the sealed space 36 is also heated, and the phase change cycle of the working fluid 40 is repeated. Thus, also in the inner pot 100 of the third embodiment, as in the first embodiment, the inner side wall portion 32B of the inner pot 100 can be efficiently heated, and the entire inner pot 100 can be heated substantially uniformly.

In the third embodiment, the drawing portion 32G bulging upward is formed in the inner bottom wall portion 32A, and the drawing portion 34G bulging upward is formed in the outer bottom wall portion 34A. Therefore, the drawn portion 32G (drawn portion 34G) functions as a reinforcing drawing of the inner bottom wall portion 32A (outer bottom wall portion 34A). Thus, even if the internal pressure of the sealed space 36 increases when the bottom of the inner pot 100 is heated, the deflection (deformation) of the inner bottom wall 32A and the outer bottom wall 34A can be suppressed.

Hereinafter, this point will be described by the amount of vertical deflection (deformation) of the inner bottom wall 32A and the outer bottom wall 34A when the internal pressure in the sealed space 36 is set to 5atm, which is the assumed maximum pressure at the time of heating. That is, it has been found that in a pot in which the drawn portion 32G and the drawn portion 34G are omitted from the inner bottom wall portion 32A and the outer bottom wall portion 34A, when the internal pressure in the closed space 36 is set to 5atm, the amount of deflection (deformation) in the vertical direction of the inner bottom wall portion 32A and the outer bottom wall portion 34A is 2.4 mm. In contrast, it was confirmed that when the internal pressure in the sealed space 36 of the pot 100 of the third embodiment was set to 5atm, the amount of vertical deflection (deformation) of the inner bottom wall 32A and the outer bottom wall 34A was 0.3 mm. Thus, according to the inner pot 100 of the third embodiment, the inner bottom wall portion 32A and the outer bottom wall portion 34A can be suppressed from being bent (deformed) when the bottom portion is heated.

In the third embodiment, the connecting pins 42 are omitted as compared with the first embodiment, and therefore, the deflection (deformation) of the inner bottom wall portion 32A and the outer bottom wall portion 34A during heating of the pan 100 can be suppressed while reducing the number of components.

(variants on the tube 38)

Next, a modification of the tube 38 used in the inner pots 30, 60, 90, and 100 of the first to third embodiments (including the modification) will be described with reference to the inner pot 90 of the second embodiment.

(modification 1 of tube 38)

As shown in fig. 14 (a) and (B), in modification 1 of the tube 38, a plurality of (2 in modification 1) tubes 38 are provided in the inner pot 90. One of the 2 tubes 38 is a tube for injecting the working fluid 40 into the sealed space 36, and the other tube 38 is a tube for evacuating the sealed space 36. That is, in modification 1, the tube 38 is provided for each manufacturing process (injection process and evacuation process of the working fluid 40) of the inner pot 90. This can improve the efficiency of the step of injecting the working fluid 40 into the sealed space 36 and the step of evacuating the sealed space 36.

In addition, in modification 1, 2 tubes 38 are arranged at equal intervals (180 degrees apart) in the circumferential direction of the inner pot 90. That is, 2 tubes 38 are disposed facing each other in the radial direction of the inner pot 90. Further, as a cover for the modification 1 of the tube 38, a pair of tube covers 110 covering only the tubes 38 are provided on the inner pot 90 instead of the cover 50. The pipe cover 110 is formed in a substantially rectangular plate shape having a thickness direction in the vertical direction. Further, a concave portion 110A that opens to the inside in the radial direction of the inner pot 90 is formed in the pipe cover 110, and the concave portion 110A is formed in a circular shape when viewed in the radial direction of the inner pot. The tube 38 is fitted into the recess 110A, and the tube cover 110 is attached to the inner pot 90. This enables the tube cover 110 covering the tube 38 to be used as a handle of the inner pot 90, and the tube 38 to be used flexibly as a mounting portion (core portion) of the handle (tube cover 110). Further, as described above, by arranging the 2 tubes 38 at equal intervals in the circumferential direction of the inner pot 90, the tube cover 110 as the handle can be arranged in a balanced manner. Therefore, the ease of grasping the inner pot 90 can be improved, and the convenience for the user can be improved.

In addition, in modification 1, 2 tubes 38 are provided in the inner pot 90, but 3 or more tubes 38 may be provided in the inner pot 90. In this case, the number of the tubes 38 provided in the inner pot 90 may be set in consideration of the operation time of using the tubes 38 (the operation time of injecting the working fluid 40 and the operation time of evacuating). For example, when the evacuation operation time is longer than the injection time of the working fluid 40, the number of evacuation pipes 38 may be larger than the number of injection pipes 38 of the working fluid 40. For example, the number of the pipes 38 for injecting the working fluid 40 may be 1, and the number of the pipes 38 for evacuating may be 2. This can shorten the working time using the pipe 38, and thus shorten the manufacturing time of the inner pot 90.

In addition, in modification 1, the plurality of tubes 38 are set to have the same diameter size, but the plurality of tubes 38 may be set to have different diameter sizes. In this case, as described above, the diameter of the pipe 38 provided in the inner pot 90 may be changed in consideration of the operation time using the pipe 38. For example, when the evacuation operation time is longer than the injection time of the working fluid 40, the diameter of the evacuation pipe 38 may be larger than the diameter of the injection pipe 38 of the working fluid 40. This can reduce the operation time as described above.

In addition, in modification 1, the plurality of (2) tubes 38 are arranged so as to be spaced 180 degrees apart in the circumferential direction of the inner pot 90, but the positions of the plurality of tubes 38 in the circumferential direction of the inner pot 90 may be set arbitrarily. For example, the plurality of tubes 38 may be disposed at adjacent positions in the circumferential direction of the inner pot 90. This can reduce the size of the working space when connecting the respective pipes for injecting and evacuating the working fluid to the pipe 38, for example. Further, for example, dragging work of the pipes connected to the respective pipes 38 can be suppressed, and reduction of the number of man-hours for manufacturing the inner pot 90 can be facilitated.

(modification 2 concerning the tube 38)

In modification 2, the configuration is the same as in modification 1 except for the following points.

That is, as shown in fig. 15, in modification 2, the tube 38 is provided to the inner container 32. Specifically, the tube 38 projects (protrudes) from the inner side wall portion 32B of the inner container 32 toward the radially inner side of the inner pan 90. Further, the inner side wall portion 32B is formed with a communication hole that communicates the inside of the tube 38 with the inside of the closed space 36. Thus, in modification 2, the pipe 38 does not protrude outward in the radial direction of the inner pot 90, so that the reduction in the design feeling of the outer appearance of the inner pot 90 can be suppressed. Further, the inner pot 90 can be easily applied to the conventional electric rice cooker by preventing the pipe 38 from protruding radially outward of the inner pot 90. Therefore, the versatility of the inner pot 90 can be improved. In modification 2, as in modification 1, a plurality of tubes 38 may be provided in the inner container 32.

In modification 2, the vertical position of the pipe 38 is set so that the pipe 38 is located above the cooked rice (the rice of the maximum rice cooking amount of the inner pot 90). Therefore, even if the pipe 38 is configured to be provided on the inner side wall portion 32B of the inner container 32, contact between the cooked rice and the pipe 38 can be suppressed.

In the inner pots 30, 60, 90, and 100 of the first to third embodiments (including the modifications), water is used as the working fluid 40, but the type of the working fluid 40 to be injected into the closed space 36 is not limited to this. For example, the working fluid 40 may be ethylene glycol, silicone oil, propylene glycol, or the like.

In the first to third embodiments, the height dimension H of the bottom portion 36A of the closed space 36 is set to 4mm, but from the viewpoint of increasing the capacity of the inner pot 30 without changing the size of the inner pot 30, it is conceivable to lower the inner bottom wall portion 32A to further lower the height dimension H. When the height H is further reduced (for example, when the height H is 3mm or less), the volume ratio of the working fluid 40 to the bottom 36A in the sealed space 36 is preferably 10 to 80 vol%, and particularly preferably 30 to 80 vol%.

On the other hand, in order to heat the inner side wall portion 32B of the inner pot 30 more efficiently, when the height dimension H is set to be higher than 4mm in the present embodiment, the volume ratio of the working fluid 40 to the bottom portion 36A of the closed space 36 is preferably set to 5 vol% to 80 vol%, and particularly preferably set to 8 vol% to 30 vol%.

In the inner pots 30, 60, 90, and 100 of the first to third embodiments (including the modifications), since the internal pressure of the sealed space 36 increases when the inner pots 30, 60, 90, and 100 are heated, a safety mechanism for preventing an abnormal increase in the internal pressure of the sealed space 36 may be provided in the inner pots 30, 60, 90, and 100. Next, this point will be described with reference to fig. 16 using the inner pot 90 of the second embodiment.

As shown in fig. 16 (a) and (B), a notch 32H constituting a safety mechanism is formed in an inner peripheral surface of an inner corner portion 32C of the inner container 32, and the notch 32H is formed linearly in a direction perpendicular to a circumferential direction of the inner container 32. The notch 32H is formed in a substantially V-shaped groove that opens inward in the radial direction of the inner container 32, and the portion of the inner container 32 where the notch 32H is formed is a thin portion 32I (broadly, an element that is grasped as a "weak portion"). Therefore, the strength of the thin portion 32I is lower than the strength of the other portions of the inner container 32.

The shape (depth and width) of the notch 32H is set so that the thin portion 32I is broken when the internal pressure of the sealed space 36 is greater than a predetermined value. Accordingly, when the internal pressure of the sealed space 36 is greater than a predetermined value during heating of the inner pot 90, the thin portion 32I is broken, and the steam in the sealed space 36 is ejected from the broken portion toward the lower portion (more specifically, the portion where rice is arranged) of the inner pot 90. Therefore, the steam can escape from the steam tower of the lid portion 24 of the rice cooker 10 through the opening portion of the inner pot 90. Therefore, the abnormal rise of the internal pressure of the closed space 36 can be suppressed, and the safety of the rice cooker 10 can be improved.

In the example shown in fig. 16 (a) and (B), the slit 32H linearly extends in a direction orthogonal to the circumferential direction of the inner pot 90, but the extending direction of the slit 32H may be set arbitrarily. For example, the notch 32H may be formed to extend in the circumferential direction of the inner pot 90, or the notch 32H may be formed to extend obliquely with respect to the circumferential direction of the inner pot 90.

In the example shown in fig. 16 (a) and (B), 1 slit 32H is formed in the inner pot 90, but the number of slits 32H may be plural.

Further, in the example shown in fig. 16 (a) and (B), the cross-sectional shape of the notch 32H is formed in a substantially V-shaped groove shape, but the cross-sectional shape of the notch 32H may be appropriately changed. For example, the cross-sectional shape of the notch 32H may be formed into a substantially semicircular groove shape.

In the safety mechanism, the thin portion 32I is formed in the inner container 32, but the position where the thin portion 32I is formed may be set arbitrarily.

For example, the slit 32H may be formed in the tube 38, and the thin portion 32I may be formed in the tube 38. That is, as shown in fig. 16C, a single or a plurality of (2 in the example shown in fig. 16C) notches 32H may be formed in the outer peripheral portion of the tube 38, and the thin portion 32I may be formed in the tube 38.

For example, the thin wall portion 32I may be formed at an upper portion of the inner side wall portion 32B (preferably, at a position above the maximum rice cooking amount of the inner pot 90). In this case, the thin wall portion 32I is disposed at a position of the inner pot 90 away from the bottom portion (i.e., the portion in the inner pot 90 that is heated). This can suppress deterioration of the thin portion 32I. In particular, by disposing the thin portion 32I above the maximum rice cooking amount of the inner pot 90, contact with the thin portion 32I after cooking can be suppressed.

In the above-described safety mechanism, the thin portion 32I is formed in the inner container 32 (inner side wall portion 32B), but the thin portion 32I may be formed in the outer container 34 (outer side wall portion 34B) instead of the inner container 32. The thin portion 32I may be formed in the inner container 32 and the outer container 34. In addition, when the thin portion 32I is formed in the inner container 32 and the outer container 34, for example, when the internal pressure of the sealed space 36 abnormally increases, even if one thin portion 32I is not broken, the other thin portion 32I is broken, and the steam can escape to the outside of the sealed space 36. This can further improve the safety of the rice cooker 10.

In addition, in the case where the inner container 32 is formed to have a thin portion 32I by reducing the thickness of the inner container 32, a portion of the inner container 32 (inner side wall portion 32B) may be crushed to form the thin portion 32I during the press working of the inner container 32. For example, although not shown, a circular recess crushed inward in the plate thickness direction may be formed in the inner peripheral surface or the outer peripheral surface of the inner side wall portion 32B, and the portion where the recess is formed may be the thin portion 32I.

In the press working of the inner container 32, a part of the inner container 32 (inner side wall portion 32B) may be half-blanked to form the thin portion 32I. For example, although not shown, a part of the inner side wall portion 32B may be half-blanked radially inward or radially outward, and a boundary portion of the half-blanked part may be the thin portion 32I.

This makes it possible to easily form the thin portion 32I and to manufacture the inner pot 90 at a low cost. In addition, similarly to the above, the concave portion or the half die cut portion may be formed in at least one of the inner container 32 and the outer container 34, and the position of the concave portion or the half die cut portion may be arbitrarily set.

In addition, in the case where the internal pressure of the sealed space 36 abnormally increases, and steam is allowed to escape to the outside of the sealed space 36, a safety valve (for example, a spring-type safety valve) may be provided in the inner container 32 or the outer container 34. In this case, when the internal pressure of the sealed space 36 abnormally increases, the steam can escape to the outside of the sealed space 36 without breaking the inner pot 90.

In the first embodiment, the inner pot 30 is provided with the coupling pin 42, and the inner bottom wall portion 32A and the outer bottom wall portion 34A are coupled together by the coupling pin 42. Alternatively, as shown in fig. 17, the inner pot 30 may be configured such that the coupling pins 42 (the center pin 44 and the outer peripheral pin 46) are omitted and the inner bottom wall portion 32A and the outer bottom wall portion 34A are not coupled to each other.

Although not shown in the drawings, in the inner pots 30, 60, 90, and 100 of the first to third embodiments (including the modifications), the coupling pin 42 may be provided between the inner side wall portion 32B of the inner container 32 and the outer side wall portion 34B of the outer container 34, and the inner side wall portion 32B and the outer side wall portion 34B may be coupled by the coupling pin 42. In this case, the coupling pins 42 are disposed with the radial direction of the inner pots 30, 60, 90, 100 as the axial direction, and the inner side wall portion 32B and the outer side wall portion 34B are coupled by the coupling pins 42. This can suppress deformation of the inner side wall portion 32B and the outer side wall portion 34B when the inner pots 30, 60, 90, and 100 are heated.

Further, in this case, the plurality of coupling pins 42 may be provided between the inner side wall portion 32B of the inner container 32 and the outer side wall portion 34B of the outer container 34 and arranged at equal intervals in the circumferential direction of the inner pots 30, 60, 90, and 100. This can suppress deformation of the inner side wall portion 32B and the outer side wall portion 34B during heating of the inner pots 30, 60, 90, and 100, and can make the gap between the inner side wall portion 32B and the outer side wall portion 34B of the sealed space 36 uniform. As a result, variation in the amount of steam that rises between the inner side wall portion 32B and the outer side wall portion 34B in the circumferential direction of the inner pots 30, 60, 90, 100 can be suppressed. Therefore, the inner side wall portion 32B can be uniformly heated in the circumferential direction of the inner container 32.

In the first to third embodiments (including the modifications), the inner pots 30, 60, 90, and 100 are configured to include the cover 50, but the inner pots 30, 60, 90, and 100 may be configured to omit the cover 50.

The cover 50 according to the first embodiment (including the modifications) to the third embodiment is formed in an annular shape in both the portion covering the first flange 32D and the second flange 34D of the inner pot 30, 60, 90, 100 and the portion covering the pipe 38. Instead, the cover 50 may be formed in a shape in which an annular portion covering the entire circumference of the first flange 32D and the second flange 34D and a portion covering only the pipe 38 (i.e., the pipe cover 110 described above) are integrated. In this case, the welded portion of the first flange 32D and the second flange 34D and the pipe 38 can be covered so as to be invisible.

In the inner pot 30(60) according to the first embodiment (including the modified example), the first flange 32D of the inner container 32 is folded back so as to be wound around the second flange 34D of the outer container 34 at the opening of the inner pot 30(60) to ensure airtightness of the sealed space 36, but the structure for ensuring airtightness of the sealed space 36 is not limited to this.

For example, as shown in fig. 18, the second flange 34D may be formed so as to be folded back 180 degrees inward in the radial direction of the inner pot 30, 60, and the first flange 32D of the inner container 32 may be formed so as to be wound around the folded-back second flange 34D. That is, in this case, the second flange 34D assumes an overlapping configuration in which it overlaps up and down. Further, the upper flange portion 32D1 and the lower flange portion 32D2 of the first flange 32D press-contact the second flange 34D, which has an overlapping structure, vertically. This can improve the rigidity of the opening of the inner pot 30(60) while ensuring the airtightness of the sealed space 36.

In the first embodiment (including the modifications) to the third embodiment, the inner peripheral surface of the inner container 32 is subjected to the teflon processing, but the surface treatment of the inner peripheral surface of the inner container 32 is not limited thereto. For example, the inner peripheral surface of the inner container 32 may be formed in an uneven shape by roughening all or a part of the inner peripheral surface of the inner container 32 (for example, only the inner bottom wall portion 32A or only the inner side wall portion 32B). For example, the inner circumferential surface of the inner container 32 may be diamond-coated. For example, the inner peripheral surface of the inner container 32 may be sandblasted and then subjected to teflon processing. This forms irregularities on the inner peripheral surface of the inner container 32. Therefore, when rice is cooked, relatively fine bubbles are generated in the inner pot due to the irregularities. As a result, the rice in the inner pot can be uniformly heated by the generation of the bubbles.

In the first embodiment (including the modifications) to the third embodiment, the outer surface of the inner container 32 and the inner surface of the outer container 34 are mirror-finished in order to satisfactorily raise the steam generated in the sealed space 36, but in a point of view that the steam is likely to be generated in the sealed space 36 during heating of the inner pot, the outer surface of the inner container 32 and the inner surface of the outer container 34 may be roughened. For example, the outer surface of the inner container 32 and the inner surface of the outer container 34 may be formed in an uneven shape by performing sand blasting on the outer surface of the inner container 32 and the inner surface of the outer container 34.

In the inner pots 30, 60, 90, and 100 of the first to third embodiments (including the modifications), the plate thickness of the inner container 32 and the plate thickness of the outer container 34 are set to be the same, but the plate thickness of the inner container 32 and the plate thickness of the outer container 34 may be set to be different. For example, the inner container 32 may be configured to have a plate thickness smaller than that of the outer container 34 to facilitate heating of the inner container 32. Further, by setting the thickness of the inner container 32 to be thinner than the thickness of the outer container 34, the heat of the vapor vaporized from the working fluid 40 in the closed space 36 can be efficiently dissipated to the inside of the inner pot 30, 60, 90, 100 through the inner side wall portion 32B of the inner pot 30, 60, 90, 100.

In the first embodiment (including the modifications) to the third embodiment, the plate thicknesses of the inner container 32 and the outer container 34 are set to be uniform (constant) as a whole, but the plate thicknesses of the inner container 32 and the outer container 34 may be set to be non-uniform. For example, in the inner container 32, the thickness of the inner side wall portion 32B may be set to be thinner than the thickness of the inner bottom wall portion 32A, so that heating of the inner side wall portion 32B is promoted. In this case, the thickness of the inner corner portion 32C of the inner container 32 may be set so as to become gradually thinner from the inner bottom wall portion 32A toward the inner side wall portion 32B.

In the first embodiment (including the modifications) to the third embodiment, the inner container 32 and the outer container 34 are made of a magnetic material (stainless steel). Alternatively, the inner container 32 may be made of a high thermal conductor such as copper or aluminum. In this case, the inner container 32 can be efficiently heated also at the time of heating the inner pots 30, 60, 90, and 100.

The inner container 32 may be molded using a precoated steel sheet or the like with a surface precoated with a fluorine-based resin. This can shorten the manufacturing process of the inner pots 30, 60, 90, and 100.

In the first embodiment (including the modified examples) to the third embodiment, the inner pots 30, 60, 90, and 100 are applied to the IH type electric rice cooker 10, but the electric rice cooker to which the inner pots 30, 60, 90, and 100 are applied is not limited thereto. For example, the heating part 16 of the rice cooker 10 may be changed to a heater, and the inner pots 30, 60, 90, and 100 may be heated by the heater.

(remarks)

As described above, the present invention has been explained from the viewpoint of efficiently heating the inner side wall of the heating cooker in the heating cooker having the double-wall structure having the closed space therein, but from other viewpoints, it can be understood as follows.

That is, in the heating cooker described in the background art, when the working fluid is injected into the sealed space and the bottom of the heating cooker is heated, the working fluid boils and vapor vaporized from the working fluid rises along the side portion of the sealed space. Thereby, the inner side wall of the heating cooker is heated by the steam. Further, the vapor that has heated the side wall condenses to become liquid as the working fluid, and the working fluid that has become liquid descends by its own weight and returns to the bottom of the closed space. Further, the side portion of the heating cooker is heated by repeating the phase change cycle described above in the working fluid.

However, the heating cooker described above has room for improvement in the following respects. That is, in the heating cooker, when the bottom portion of the heating cooker is heated as described above, the vapor vaporized from the working fluid rises along the side portion of the sealed space. Further, by continuing to heat the heating cooker, the air pressure (pressure) in the closed space rises. Therefore, the bottom portion in the closed space expands, and the bottom portion of the heating cooker may deform. Therefore, in a heating cooker having a closed space inside, it is desirable to have a structure capable of suppressing deformation of the heating cooker due to expansion.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a heating cooker capable of suppressing expansion during heating.

A first aspect of the present invention to solve the above problems provides a heating cooker having a double-wall structure formed in a bottomed tubular shape and having a sealed space therein, the heating cooker including:

a bottomed cylindrical inner container constituting an inner portion of the heating cooker;

a bottomed cylindrical outer container constituting an outer portion of the heating cooker;

a working fluid injected into the sealed space;

and a connecting portion provided in the sealed space and connecting an inner bottom wall portion of the inner container and an outer bottom wall portion of the outer container.

A second aspect for solving the above problems is a heating cooker of the first aspect,

the connecting portion is formed by a connecting pin extending in the axial direction of the heating cooker.

A third aspect for solving the above problems is a heating cooker of the second aspect,

the connecting pin is disposed at a center portion of the heating cooker in a plan view from an opening side of the heating cooker.

A fourth aspect for solving the above problems is the heating cooker of the first aspect,

the connecting portion radially extends from the center of the heating cooker in a plan view when viewed from the opening side of the heating cooker.

A fifth aspect for solving the above problems is a heating cooker of the fourth aspect,

a communication hole for communicating the sealed space defined by the connection portion is formed at a lower end portion of the connection portion.

Description of the reference symbols

30 inner pan (heating cooker)

32 inner side container

32A inner bottom wall portion

32B inner side wall part

32C inside corner

32 inside corner

34 outer container

36 closed space

38 tube

36A bottom

36B bottom surface

40 working fluid

60 inner pan (heating cooker)

90 inner pan (heating cooker)

100 inner pan (heating cooker)

110 pipe cover

Height dimension of the bottom of the H-shaped closed space

Radius of R inside corner

W the width of the closed space.

Claims (8)

1. A heating cooker is characterized in that,

the cooking device is formed in a bottomed tubular shape and has a double-wall structure having a sealed space therein, and the cooking device includes:

a bottomed cylindrical inner container constituting an inner portion of the heating cooker;

a bottomed cylindrical outer container constituting an outer portion of the heating cooker; and

a working fluid injected into the closed space,

the amount of the working fluid in the sealed space is set to an amount that does not cover the entire bottom surface of the sealed space.

2. The heating cooker according to claim 1,

the volume ratio of the working fluid to the bottom in the closed space is set to 4 vol% to 80 vol%.

3. The heating cooker according to claim 1 or 2,

the height dimension of the sealed space at the bottom of the heating cooker is set to be not less than the width dimension of the sealed space at the side of the heating cooker, and is set to be not less than 2mm when viewed in vertical section.

4. The heating cooker according to any one of claims 1 to 3,

the closed space is maintained at a negative pressure or vacuum below 0.01 standard atmospheric pressure.

5. The heating cooker according to claim 4,

a plurality of pipes used when the working fluid is injected into the sealed space and when the inside of the sealed space is brought into a negative pressure or a vacuum are provided in an inner side wall portion of the inner container or an outer side wall portion of the outer container.

6. The heating cooker according to claim 5,

the plurality of pipes are arranged at equal intervals in the circumferential direction of the heating cooker, and pipe covers for covering the pipes are attached to the pipes.

7. The heating cooker according to any one of claims 1 to 6,

an inner corner portion that is convexly curved outward of the inner container is formed between the inner bottom wall portion and the inner side wall portion of the inner container,

the radius of the inside corner is set as follows: the radius of the inside corner portion gradually decreases from the inside bottom wall portion toward the inside side wall portion.

8. The heating cooker according to any one of claims 1 to 7,

the surface of the inner container constituting the closed space and the surface of the outer container constituting the closed space are mirror-finished.

Images