TWI842902B - Cooking device - Google Patents

Abstract

The present disclosure provides a cooking device which can improve a heating performance of a pot. The cooking device (rice cooker (10)) includes: a receiving portion (22) for receiving the pot (15), and a plurality of coils (25A, 25B). Each of the coils (25A, 25B) is ring-shaped and includes: a first portion (26), which is curved with a first curvature radius (r1) to protrude toward an axis (A) of the receiving portion (22) and then extends along a bottom wall (24a) to pass through the bottom wall; a second portion (27), which is curved with a second curvature radius (r2) smaller than the first curvature radius (r1) and extends along an outer peripheral wall (24b); an arc-shaped third portion (28), which is connected to a first end (26a) of the first portion (26) and a first end (27a) of the second portion (27); and an arc-shaped fourth portion (29), which is connected to a second end (26b) of the first portion (26) and a second end (27b) of the second portion (27).

Description

Cooking equipment

The present invention relates to a cooking device.

Patent document 1 discloses an electric rice cooker, in which three coils are arranged at intervals along the circumferential direction at the bottom of a bottomed cylindrical rice cooker. In the electric rice cooker, one of the three coils is energized while the remaining coils are de-energized, and the energized state is switched in a prescribed order, while the rice cooker is inductively heated by the coils.

Existing technical literature Patent Literature

Patent document 1: Japanese Patent Publication No. 2018-61573

In view of this, we inventors have devoted ourselves to further research and development and improvement, hoping to find a better invention to solve the above problems. After continuous testing and modification, the present invention was born.

The heating device of Patent Document 1 states that a portion of the rice cooker is heated centrally by switching the energization state of the coil, but there is room for improvement in the heating performance of the coil on the rice cooker.

The subject of the present invention is to improve the heating performance of a pot in a cooking device having multiple coils.

One embodiment of the present invention provides a cooking device, comprising: a housing portion having a bottom wall and a cylindrical outer peripheral wall rising from the outer periphery of the bottom wall, and housing a bottomed cylindrical pot; and a plurality of coils arranged in a circumferential direction around the axis of the housing portion on the outer surface side of the housing portion, wherein the plurality of coils are respectively annular and respectively have: a first portion curved with a first radius of curvature so as to protrude toward the axis of the housing portion when the housing portion is observed from the direction in which the axis of the housing portion extends; The first part is curved and extends along the bottom wall in a manner of crossing the bottom wall; the second part is curved with a second curvature radius smaller than the first curvature radius and extends along the outer peripheral wall; the arc-shaped third part is connected to the first end of one side of the first part and the first end of the one side of the second part in the circumferential direction of the receiving portion; and the arc-shaped fourth part is connected to the second end of the other side of the first part and the second end of the other side of the second part in the circumferential direction of the receiving portion.

In the cooker, the first part locally heats the bottom of the pot, the second part locally heats the side of the pot, and the third and fourth parts locally heat the bottom to the side of the pot. Since the first curvature radius of the first part is larger than the second curvature radius of the second part, the heating area of the bottom of the pot can be ensured to be wider. Therefore, the heating performance of the bottom side of the pot, which is more important in heating cooking, can be improved.

The first to fourth parts are all arc-shaped, and there is no straight line part in the coil. When manufacturing the coil, if there is a straight line part in the coil, the tension becomes too little in the straight line part, and on the other hand, the tension becomes too much at both ends of the straight line part. However, in this method, since there is no straight line part, a given tension can be applied to a specified part to wind a single wire or a twisted wire. As a result, a coil of a specified shape can be reliably manufactured, and the productivity of the coil can be improved.

The ratio of the first radius of curvature to the second radius of curvature is greater than 100% and less than 160%. According to this method, the heating area of the bottom of the pot by the first part can be effectively ensured.

In the direction in which the axis of the accommodating portion extends, the thickness of the inner periphery of the third portion is thicker than the thickness of the outer periphery of the third portion, and the thickness of the inner periphery of the fourth portion is thicker than the thickness of the outer periphery of the fourth portion. Specifically, the thickness of the third portion and the thickness of the fourth portion gradually become thinner from the inner periphery to the outer periphery, respectively. According to this method, on the bottom surface side of the pot, the number of single wires per unit area is greater than the number of single wires per unit area on the side surface side, so that the heating amount can be ensured. In addition, on the side surface side of the pot, although the number of single wires per unit area becomes smaller, the range in which the coil can be configured can be expanded, so the heating area can be ensured. Furthermore, on the side of the pot, the flexibility of the coil is improved due to the reduction in the number of single wires, thereby improving the fit relative to the outer surface shape from the bottom wall to the outer peripheral wall.

Only two of the coils are provided. In addition, a sensor is provided, the sensor passes through the outer peripheral wall and detects the temperature of the pot, and when the receiving portion is observed from the direction in which the axis of the receiving portion extends, the two coils are arranged symmetrically with respect to the center of the bottom wall and the reference line of the sensor. According to this method, the bottom side of the pot can be heated unbiasedly by the two coils. In addition, the heating temperature of the pot by the two coils can be detected unbiasedly by one sensor.

The gap between the third part or the fourth part closest to the sensor and the sensor is less than 20 mm. As described above, by making the thickness of the outer periphery of the third part and the fourth part thinner than the thickness of the inner periphery, the heating area of the side surface can be expanded and brought closer to the sensor. Furthermore, if the third part or the fourth part and the sensor are configured in this way, the responsiveness when the temperature of the pot heated by the coil is detected by the sensor can be improved.

The thickness of the first part and the thickness of the second part in the direction in which the axis of the housing extends are uniform from the inner periphery to the outer periphery, and the density of the single wire constituting the first part is higher than the density of the single wire constituting the second part. According to this method, the heating amount per unit area of the bottom surface of the pot can be ensured, and the heating area of the side surface of the pot can be ensured.

In the cooker of the present invention, since the first curvature radius of the first part is larger than the second curvature radius of the second part, the heating performance of the bottom surface side of the pot by the plurality of coils can be improved. In addition, since there is no straight line portion in the coil, the productivity of the coil can be improved.

[The present invention]

10: Rice cooker (cooker)

15: Rice cooker (pot)

16: Bottom part

17: Lateral face

17a: Part 1

17b: Part 2

17c: Part 3

20: Rice cooker body

21:External body

22: Containment Department

23: Inner body

24: Protective frame

24a: Bottom wall

24b: Outer wall

24c: Part 1

24d: Part 2

24e: Installation Department

24f:Through hole

24g: protrusion

24h: Ribs

24i: Boss

25A, 25B: Coil

25a: Single line

25b: Inner circumference

25c: Periphery

25d: Connecting cable

25e:Connecting cable

26: Part 1

26a: First end

26b: Second end

27: Part 2

27a: First end

27b: Second end

28: Part 3

28a: Central part

29: Part 4

29a: Central part

30: Ferrite core

31: Retaining parts

35: Cover

36: Hinge connection part

37: Heat sink

38: Inner cover

39: Cover the heater

41:Sensor

42:Sensor

44: Control board

45: Retaining parts

A: Axis of the protective frame (housing unit)

L: Baseline

S: Gap

r1: first radius of curvature

r2: Second radius of curvature

r3: third radius of curvature

r4: fourth radius of curvature

Ta: thickness of the first part

Tb: thickness of the second part

Tc1, Tc2: thickness

W1, W2: Width

[Figure 1] is a cross-sectional view of a cooking device according to an embodiment of the present invention; [Figure 2] is an exploded perspective view of a protective frame and a coil; [Figure 3] is a bottom view of the protective frame and the coil; [Figure 4] is a bottom view of a coil; [Figure 5] is a V-V line cross-sectional view of Figure 4; [Figure 6] is a VI-VI line cross-sectional view of Figure 4; [Figure 7] is a partial enlarged view of Figure 5; [Figure 8] is a partial enlarged view of a portion of Figure 5 that is different from Figure 7; [Figure 9] is an enlarged view of Figure 6; [Figure 10] is a bottom view of a comparative example in which the curvature of the first portion of the coil is changed.

Regarding the technical means of our inventors, several preferred embodiments are described in detail below with accompanying drawings, so that you can have a deeper understanding and recognize the present invention.

The following is an explanation of the implementation of the present invention according to the attached drawings.

FIG1 shows a rice cooker 10 as an example of a cooking device according to an embodiment of the present invention. The rice cooker 10 includes a rice cooker body 20 equipped with a rice cooker (pot) 15 and a lid 35 mounted on the rice cooker body 20 in an openable and closable manner. The rice cooker body 20 is a multi-coil type in which a plurality of (two in this embodiment) coils 25A and 25B are arranged. In this embodiment, the heating performance of the rice cooker 15 is improved by optimizing the shapes of the coils 25A and 25B.

(Overview of rice cooker)

As shown in FIG1 , the rice cooker 15 is made of magnetic material and is an integrated structure formed by stamping or casting. The rice cooker 15 is a bottomed cylinder having a disc-shaped bottom portion 16 and a side portion 17 rising from the outer periphery of the bottom portion 16. The side portion 17 is a cylinder having an axis passing through the center of the bottom portion 16.

The rice cooker body 20 has a bottom cylindrical housing 22 for housing the rice cooker 15 in the outer body 21 in a detachable manner. The rice cooker 15 is housed on the inner surface of the housing 22, so that the axis A of the protection frame 24 (housing portion 22) coincides with the axis of the rice cooker 15. The housing 22 is provided at the lower part of the opening formed on the upper surface of the outer body 21. The housing 22 has an inner body 23 located at a position spaced apart from the upper part of the side surface 17; and a protection frame 24 located at a position spaced apart from the lower part of the bottom surface 16 and the side surface 17. The inner body 23 is made of metal and has a cylindrical shape with a uniform diameter. The protective frame 24 is made of resin (non-conductive material) and is in the shape of a tray arranged at the lower end of the inner body 23.

Referring to Figures 2 and 3, in the protective frame 24, on the outer surface side opposite to the inner surface side accommodating the rice cooker 15, two coils 25A and 25B are arranged circumferentially with the axis A of the protective frame 24 as the center. Referring to Figure 1, on the outer sides of the coils 25A and 25B, retainers 31 for retaining the ferrite core 30 are respectively arranged, and the coils 25A and 25B are retained (fixed) between the retainers 31 and the protective frame 24. The coils 25A and 25B generate eddy currents by passing high-frequency currents, and the rice cooker 15 is inductively heated.

As shown in FIG1 , the cover 35 is rotatably mounted on the hinge connection portion 36 of the back of the rice cooker body 20 located on the right side in FIG1 . The cover 35 has a heat sink 37 on the inner surface side facing the rice cooker 15 (the lower side in FIG1 ). An inner cover 38 is provided on the lower side of the heat sink 37 to close the upper end opening of the rice cooker 15 . Relative to the cover 35 , the inner cover 38 can be a detachable structure or a non-detachable structure. A cover heater 39 is provided on the upper surface of the heat sink 37 , and the cover heater 39 heats the inner cover 38 through the heat sink 37 to evaporate the dew attached to the inner cover 38 .

Next, referring to FIG. 1 , in the rice cooker 10 , two sensors 41 and 42 are arranged as a detection unit for detecting the temperature inside the rice cooker 15 . The first sensor 41 is arranged in the rice cooker body 20 , and the second sensor 42 is arranged in the cover 35 . The sensor (side sensor) 41 is arranged to pass through the protective frame 24 and contact the outer surface of the rice cooker 15 , and detect the temperature of the rice containing water or the rice temperature inside the rice cooker 15 through the rice cooker 15 . The sensor 42 is arranged to contact the heat sink 37 , and detect the temperature inside the rice cooker 15 (the space between the heat sink 37 and the inner cover 38 ) through the heat sink 37 .

The rice cooker 10 is provided with a control substrate 44 having a control unit (not shown). The control substrate 44 of the present embodiment is arranged on the front side of the rice cooker body 20 through a retainer 45, but may also be arranged on the back side of the rice cooker body 20, or may be arranged in the lid 35. The control unit is composed of a single or multiple microcomputers and other electronic devices. The control unit controls the coils 25A, 25B and the lid heater 39 based on the detected temperature of the sensors 41 and 42 to perform the rice cooking process including the preheating process, the high-fire heating (temperature increase) process, the boiling maintenance process and the stewing process.

When executing the rice cooking process, the control unit switches the power-on state alternately in such a way that one of the two coils 25A and 25B is energized and the power-on of the other is cut off. That is, the first power-on state of electrically connecting coil 25A and cutting off coil 25B and the second power-on state of electrically connecting coil 25B and cutting off coil 25A are repeated alternately. Their switching cycles may be different for each process or the same for all processes. However, it is preferred that in the high-fire heating process that rapidly heats the rice cooker 15, the switching cycle is made longer than in the process other than the high-fire heating process that maintains (adjusts) the temperature in the rice cooker 15 at a specified temperature.

Generally speaking, the power distribution boards installed in Japanese households are mostly 20 amps, and the sockets are mostly 15 amps. Therefore, in the case of the electric appliances including the electric rice cooker 10, the maximum rated power that can be input per unit time is 1500W. In the case of the electric rice cooker using a coil covering the entire bottom surface 16, the entire rice cooker 15 is inductively heated with a heating amount corresponding to the rated power. In contrast, in the electric rice cooker 10 of the present embodiment, since the rated power is input to one of the two coils 25A and 25B at the maximum, the corresponding heating area of 1/2 of the rice cooker 15 is inductively heated at the maximum and concentrated amount corresponding to the rated power. Therefore, compared with a rice cooker using one coil, the rice cooker 10 of this embodiment can increase the maximum heating capacity per unit area of the rice cooker 15. As a result, in this embodiment, a part of the rice cooker 15 can be heated with a larger heat.

The heating area of the rice cooker 15 is a portion located in the magnetic field generated by energizing the coils 25A and 25B, and its shape corresponds to the shape of the coils 25A and 25B. In addition, the heating amount of the rice cooker 15 corresponds to the magnetic flux of the coils 25A and 25B, and the magnetic flux corresponds to the number of single wires 25a (refer to Figures 7 to 9) constituting the coils 25A and 25B. The non-heating area outside the heating area in the rice cooker 15 is heated due to heat transfer from the heating area. As the non-heating area increases, the heating efficiency of the coils 25A and 25B for the rice cooker 15 decreases. That is, in order to improve the heating efficiency of the rice cooker 15, in addition to inputting electricity, it is also important to improve the heating property of the bottom surface 16 side of the rice cooker 15. Therefore, in this embodiment, the coils 25A and 25B arranged in the protective frame 24 are constructed as follows.

(Overview of protective frame and coil)

As shown in FIG. 2 and FIG. 3 , the plurality of coils 25A and 25B have the same structure and are arranged at a predetermined position of the protective frame 24. Since there are two coils 25A and 25B in this embodiment, they are arranged symmetrically with respect to the reference line L extending along the radial direction of the protective frame 24. The protective frame 24 has a shape corresponding to the outer surface shape of the lower part of the rice cooker 15.

Specifically, as shown in FIG. 1 , the rice cooker 15 has a bottom portion 16 and a side portion 17 as described above. Among them, the side portion 17 generally has a first portion 17a, a second portion 17b, and a third portion 17c. The first portion 17a is connected to the outer periphery of the bottom portion 16 and is a curved surface with a diameter gradually increasing from the lower side to the upper side. The second portion 17b is connected to the upper end of the first portion 17a and is a conical cylinder with a diameter gradually increasing from the lower side to the upper side. The third portion 17c is connected to the upper end of the second portion 17b and is a cylindrical shape with a uniform diameter from the lower side to the upper side.

Referring to Figures 1 to 3, the protective frame 24 has: a circular bottom wall 24a located at a distance from the bottom surface 16; and an outer peripheral wall 24b located at a distance from the side surface 17. The outer peripheral wall 24b is a cylindrical shape rising from the outer periphery of the bottom wall 24a, and has a first part 24c corresponding to the first part 17a and a second part 24d corresponding to the second part 17b. The first part 24c is connected to the outer periphery of the bottom wall 24a and is a curved surface with a gradually increasing diameter from the lower side to the upper side. The second part 24d is connected to the upper end of the first part 24c and is a conical tube with a gradually increasing diameter from the lower side to the upper side.

The protective frame 24 has a mounting portion 24e for mounting the sensor 41. The mounting portion 24e is provided in the second portion 24d in the outer peripheral wall 24b, and has a circular through hole 24f and a cylindrical protrusion 24g protruding outward from the periphery of the through hole 24f. As most clearly shown in FIG. 3 , the mounting portion 24e is formed in the outer casing 21 which is roughly rectangular in plan view, and protrudes toward one of the four corners when viewed from the direction extending from the axis A of the protective frame 24. By mounting the sensor 41 on the mounting portion 24e, as shown in FIG. 1 , the detection portion that penetrates the protective frame 24 abuts against the second portion 17b of the side surface 17. In addition, the sensor 41 is arranged on the rear side of the outer casing 21 in the present embodiment, but may also be arranged on the front side of the outer casing 21.

As most clearly shown in FIG. 2 , the protective frame 24 has ribs 24h for positioning the coils 25A and 25B, respectively, and bosses 24i for fixing the retainer 31. Referring to FIG. 3 , the ribs 24h and bosses 24i for the coil 25A, and the ribs 24h and bosses 24i for the coil 25B are symmetrically arranged with respect to a reference line L passing through the center of the bottom wall 24a (axis A of the protective frame 24) and the mounting portion 24e (sensor 41). The ribs 24h are provided at one end (inner side) of the two ends in the short axis direction, two ribs 24h are provided at the other end (outer side), and one rib 24h is provided at each of the two ends in the long axis direction in the inner circumference 25b of the substantially elliptical coils 25A and 25B. In addition, two ribs 24h are also provided between the pair of coils 25A and 25B. Two bosses 24i are provided on the outer side in the short axis direction and one boss 24i is provided at each end in the long axis direction in the inner circumference 25b of the coils 25A and 25B.

As shown in Figures 2 to 4, each coil 25A, 25B is formed by winding a plurality of single wires 25a (see Figures 7 to 9) into an asymmetric elliptical ring shape. Coils 25A, 25B have a substantially elliptical inner periphery 25b and a substantially semicircular outer periphery 25c. A first connecting wire 25d is extended from the inner periphery 25b, and a second connecting wire 25e is extended from the outer periphery 25c. The connecting wires 25d, 25e are respectively covered with insulating tubes and pass between adjacent coils 25A, 25B to be electrically connected to the control substrate 44.

The coils 25A and 25B are respectively arranged in the area from the bottom wall 24a to the first part 24c of the outer peripheral wall 24b of the protection frame 24, so as to heat the area from the bottom surface 16 to the first part 17a of the side surface 17 of the rice cooker 15. As shown most clearly in FIG. 3, when the storage portion 22 is observed from the direction in which the axis A of the storage portion 22 extends, the two coils 25A and 25B are arranged in the circumferential direction with the axis A of the protection frame 24 as the center, and are arranged symmetrically with respect to the reference line L.

More specifically, as shown in FIG3 and FIG4, each coil 25A, 25B has: a first portion 26 extending along the bottom wall 24a; a second portion 27 extending along the peripheral wall 24b; and a third portion 28 and a fourth portion 29 connected thereto. In FIG3 and FIG4, their boundary portions are shown by a single-point line (imaginary line). They are all formed into an arc shape with a given curvature, but are not limited to a strict arc shape, as long as they are substantially arc-shaped from one end to the other.

When the housing portion 22 is observed from the direction in which the axis A of the housing portion 22 extends, the first portion 26 protrudes inward toward the axis A of the housing portion 22 and is bent at a predetermined radius of curvature (first radius of curvature) r1. The first portion 26 extends along the reference line L in a manner that crosses the bottom wall 24a. The outer periphery 25c of the first portion 26 in the coil 25A and the outer periphery 25c of the first portion 26 in the coil 25B are located at a predetermined interval (e.g., 10 mm) apart.

The second portion 27 is located on the opposite side of the first portion 26 in the minor axis direction of the inner circumference 25b, and is bent with a radius of curvature (second radius of curvature) r2 smaller than the first radius of curvature r1 in a manner that protrudes in the opposite direction (outward) to the first portion 26. The second portion 27 extends along the first portion 24c of the outer circumferential wall 24b with the axis A of the protective frame 24 as the center.

The third portion 28 is connected to the first end 26a of one side of the first portion 26 and the first end 27a of one side of the second portion 27 in the circumferential direction of the housing portion 22, and is bent with a radius of curvature (third radius of curvature) r3 smaller than the second radius of curvature r2 in a manner protruding radially outward from the protective frame 24. The first end 26a of the first portion 26 and the first end 27a of the second portion 27 are portions located on the same side (one side) in the front-rear direction of the outer housing 21.

The fourth portion 29 is connected to the second end 26b of the other side of the first portion 26 and the second end 27b of the other side of the second portion 27 in the circumferential direction of the housing portion 22, and is bent with a radius of curvature (fourth radius of curvature) r4 smaller than the second radius of curvature r2 in a manner protruding radially outward of the protection frame 24. The second end 26b of the first portion 26 and the second end 27b of the second portion 27 are portions located on the side (the other side) opposite to the first ends 26a and 27a in the front-rear direction of the outer body 21.

The ratio of the first radius of curvature r1 of the first portion 26 to the second radius of curvature r2 of the second portion 27 is set to be 100% or more and 160% or less, and more preferably 140% or more and 150% or less. As shown by the dotted line in FIG. 10 , if the ratio of the radius of curvature is set too small, the third portion 28 and the fourth portion 29 are far from the reference line L, so that the heating area of the coils 25A and 25B cannot be ensured, and the non-heating area between the adjacent coils 25A and 25B becomes too wide. As shown by the dotted line in FIG. 10 , if the ratio of the radius of curvature is set too large, the first portion 26 is close to a straight line, so that, as described later, the single wire 25a cannot be wound with a predetermined tension when manufacturing the coils 25A and 25B. Therefore, in order to ensure that the first part 26 heats the rice cooker 15 and improve the productivity of the coils 25A and 25B, the ratio of the first curvature radius r1 to the second curvature radius r2 is preferably set within the above range.

The third curvature radius r3 of the third portion 28 and the fourth curvature radius r4 of the fourth portion 29 are set to be the same. As a result, as shown in FIG. 4 , the coils 25A and 25B have shapes that are symmetrical with respect to the center line C extending along the minor axis direction of the inner circumference 25b. Therefore, it is possible to prevent the heating area from being different at one end and the other end in the direction along the reference line L, so that the rice cooker 15 can be heated uniformly.

Referring to Fig. 3 and Fig. 5, the first portion 26 extends along the bottom wall 24a and is formed into a substantially planar shape having a thickness. The second portion 27 extends in the circumferential direction of the protective frame 24 along the first portion 24c of the peripheral wall 24b and is formed into a curved surface having a thickness. The thickness Ta of the first portion 26 in the direction in which the axis A of the protective frame 24 extends is uniform from the inner peripheral portion 25b to the outer peripheral portion 25c. The thickness Tb of the second portion 27 in the direction in which the axis A of the protective frame 24 extends is also uniform from the inner peripheral portion 25b to the outer peripheral portion 25c. The thickness Ta of the first portion 26 of this embodiment is the same as the thickness Tb of the second portion 27.

The width W1 of the first portion 26 from the inner circumference 25b to the outer circumference 25c is smaller than the width (creeping distance) W2 of the second portion 27 from the inner circumference 25b to the outer circumference 25c. Referring to FIG7 , a large number of single wires 25a constituting the first portion 26 are densely wound by applying tension. Referring to FIG8 , a large number of single wires 25a constituting the second portion 27 are wound with more gaps than the first portion 26 by applying tension weaker than that of the single wires 25a of the first portion 26. That is, the density of the single wires 25a constituting the first portion 26 is higher than the density of the single wires 25a constituting the second portion 27. Therefore, even if the thicknesses Ta and Tb are the same and the number of single wires 25a is the same, the width W1 of the first portion 26 and the width W2 of the second portion 27 are different. In addition, due to the difference in width W1 and W2, the amount of heat added per unit area of the first portion 26 is greater than the amount of heat added per unit area of the second portion 27.

Referring to FIG. 4 , the third part 28 and the fourth part 29 are formed into a line-symmetrical top view shape. Referring to FIG. 6 , they extend in the radial direction of the protective frame 24 along the first part 24c of the peripheral wall 24b and are formed into a curved surface with thickness. In the direction in which the axis A of the protective frame 24 extends, the thickness Tc1 of the inner peripheral part 25b of the third part 28 is thicker than the thickness Tc2 of the outer peripheral part 25c of the third part 28. Similarly to the third part 28, the thickness Tc1 of the inner peripheral part 25b of the fourth part 29 is thicker than the thickness Tc2 of the outer peripheral part 25c of the fourth part 29. Their thicknesses Tc1 and Tc2 gradually become thinner from the inner peripheral part 25b to the outer peripheral part 25c, respectively.

The thickness Tc1 of the inner circumference 25b of each of the third part 28 and the fourth part 29 is thinnest in the central part 28a, 29a between the first end 26a of the first part 26 and the first end 27a of the second part 27. That is, the thickness Tc1 of the inner circumference 25b of the third part 28 and the fourth part 29 gradually becomes thinner as it moves away from the first part 26 and the second part 27. The thickness Tc2 of the outer circumference 25c of each of the third part 28 and the fourth part 29 also gradually becomes thinner as it moves away from the first part 26 and the second part 27, and is thinnest in the central part 28a, 29a. Referring to FIG. 9, the density of the large number of single wires 25a constituting the third part 28 and the fourth part 29 is higher than the density of the single wire 25a constituting the second part 27.

In this way, the thickness of the third part 28 and the thickness of the fourth part 29 gradually decrease from the inner side of the coil 25A, 25B in the circumferential direction and the radial direction toward the outer side. Therefore, even if the number of single wires 25a is the same, the surface area of the third part 28 and the surface area of the fourth part 29 can be expanded to be larger than the surface area of the first part 26 and the surface area of the second part 27. As a result, the outer peripheral part 25c of the third part 28 and the outer peripheral part 25c of the fourth part 29 can be close to the sensor 41. In other words, as shown in FIG. 3, the gap S between the outer peripheral part 25c of the third part 28 and the outer peripheral part 25c of the fourth part 29 and the mounting part 24e (sensor 41) can be set within a range where the detection responsiveness of the sensor 41 is good.

Specifically, the gap S between the third part 28 and the fourth part 29 and the sensor 41 is less than 20 mm, and is preferably set to the shortest possible distance. However, considering the assembly of the coils 25A and 25B relative to the protective frame 24, it is preferably set to a range of 8 mm or more and 17 mm or less. If the gap S is set too small, the assembly of the coils 25A and 25B relative to the protective frame 24 may be deteriorated due to the manufacturing error of the coils 25A and 25B. If the gap S is set too large, the detection responsiveness of the sensor 41 may be deteriorated. In order to prevent these adverse conditions, the gap S is preferably set within the above range.

Next, an example of a method for manufacturing coils 25A and 25B is described. However, the method for manufacturing coils 25A and 25B is not limited to this.

The coils 25A and 25B are manufactured by a coil manufacturing machine having a bobbin and a feeder. The bobbin has: a first die having a first surface corresponding to the inner surface shape of the coils 25A and 25B; and a second die having a second surface corresponding to the outer surface shape of the coils 25A and 25B. The feeder feeds out a twisted wire formed by twisting together a plurality of (for example, 32) single wires 25a (see FIGS. 7 to 9).

The bobbin is rotated around a rotating shaft extending in the vertical direction, and the twisted wire is wound on the bobbin while applying a given tension through a feeder. Thus, coils 25A and 25B of thickness and shape corresponding to the space between the first die and the second die are wound. The portion protruding from the bobbin where the winding starts constitutes the connecting wire 25d, and the portion protruding from the bobbin where the winding ends constitutes the connecting wire 25e. When the winding of the twisted wire is completed, the temperature of the single wire 25a is raised by energizing. Thus, the welding layer of the outer peripheral portion of the single wire 25a is melted, and the adjacent single wires 25a are welded to each other. As a result, coils 25A and 25B of a prescribed shape corresponding to the space of the bobbin are formed.

Here, when the coil is D-shaped when viewed from the direction in which the axis A of the protection frame 24 extends, that is, when the first portion 26 is a straight line, when the braided wire is wound around the first portion 26, tension toward the second portion 27 cannot be applied to the braided wire. Moreover, when the braided wire of the first portion 26 is wound, excessive tension is applied to the first wound third portion 28 or fourth portion 29. That is, since a predetermined tension cannot be applied to a predetermined portion, the productivity of the coil is deteriorated.

In this embodiment, the first part 26 to the fourth part 29 are all arc-shaped, and there is no straight line part in the coils 25A and 25B. Therefore, there will be no situation where the tension becomes too little at the straight line part (the first part 26) or the tension becomes too much at both ends of the straight line part (the third part 28 or the fourth part 29). Therefore, it is possible to apply a specified tension to a specified part and wind the twisted wire (single wire 25a). As a result, the coils 25A and 25B of a specified shape can be reliably manufactured, and the productivity of the coils 25A and 25B can be improved.

The rice cooker 10 of the present invention constructed in the above manner has the following characteristics.

The first part 26 partially heats the bottom part 16 of the rice cooker 15, the second part 27 partially heats the side part 17 of the rice cooker 15, and the third part 28 and the fourth part 29 partially heat the bottom part 16 to the side part 17 of the rice cooker 15. Since the first curvature radius r1 of the first part 26 is larger than the second curvature radius r2 of the second part 27, the heating area of the bottom part 16 of the rice cooker 15 can be ensured to be wider. Therefore, the heating performance of the bottom part 16 side of the rice cooker 15, which is more important in heating cooking, can be improved. In addition, since there is no straight line portion in the coils 25A and 25B, productivity can be improved.

The thickness Tc1 of the inner peripheral portion 25b of each of the third portion 28 and the fourth portion 29 is thicker than the thickness Tc2 of the outer peripheral portion 25c of each of the third portion 28 and the fourth portion 29. In addition, the thickness of each of the third portion 28 and the fourth portion 29 gradually decreases from the inner peripheral portion 25b to the outer peripheral portion 25c. Therefore, on the bottom portion 16 side of the rice cooker 15, the number of single wires 25a per unit area is greater than the number of single wires 25a per unit area on the side portion 17 side, so that the heating amount can be ensured. In addition, on the side portion 17 side of the rice cooker 15, although the number of single wires 25a per unit area is reduced, the range in which the coils 25A and 25B can be arranged can be expanded, so that the heating area can be ensured. Moreover, on the side surface 17 of the rice cooker 15, the flexibility of the coils 25A and 25B is improved due to the reduction in the number of single wires 25a, so that the fit with the outer surface shape from the bottom wall 24a to the outer peripheral wall 24b can be improved.

It has two coils 25A and 25B, which are arranged symmetrically with respect to the reference line L passing through the center of the bottom wall 24a and the sensor 41. Therefore, the bottom portion 16 side of the rice cooker 15 can be heated unbiasedly by the two coils 25A and 25B. In addition, the heating temperature of the rice cooker 15 by the two coils 25A and 25B can be detected unbiasedly by one sensor 41.

The gap S between the third part 28 or the fourth part 29 closest to the sensor 41 and the sensor 41 is less than 20 mm. Therefore, the responsiveness of the sensor 41 when detecting the temperature of the rice cooker 15 heated by the coils 25A and 25B can be improved.

The thicknesses Ta and Tb of the first portion 26 and the second portion 27 are uniform from the inner circumference 25b to the outer circumference 25c, and the density of the single wire 25a constituting the first portion 26 is higher than the density of the single wire 25a constituting the second portion 27. Therefore, the heating amount per unit area in the bottom portion 16 of the rice cooker 15 can be ensured, and the heating area in the side portion 17 of the rice cooker 15 can be ensured.

In addition, the electric rice cooker (cooker) 10 of the present invention is not limited to the structure of the above-mentioned embodiment, and various modifications can be made.

For example, the thickness Ta of the first part 26 and the thickness Tb of the second part 27 may be different, or different at the inner circumference 25b and the outer circumference 25c. The thickness of the third part 28 and the thickness of the fourth part 29 may be different, or the same at the inner circumference 25b and the outer circumference 25c.

The radius of curvature of the first part 26 to the fourth part 29 and the density of the single wires 25a constituting them can be changed as needed. In particular, the radius of curvature of the third part 28 can also be different from the radius of curvature of the fourth part 29.

The number of coils is not limited to two, and three or more coils may be arranged circumferentially with the axis A of the protective frame 24 as the center. In this case, the sensor 41 is preferably arranged in the center of the bottom wall 24a of the protective frame 24.

In the above embodiment, the electric rice cooker 10 is used as an example for explanation, but any cooking device having a bottom cylindrical storage portion and a plurality of coils arranged on the outer surface of the storage portion can be applied and the same function and effect can be obtained.

In summary, the technical means disclosed in this invention can effectively solve the problems of knowledge and achieve the expected purpose and effect. It has not been seen in publications before the application, has not been publicly used, and has long-term progress. It is truly an invention as defined in the Patent Law. Therefore, I have filed an application in accordance with the law and sincerely pray that the Supreme Court will give a detailed review and grant the invention patent. I will be very grateful.

However, the above are only several preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention. In other words, all equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the invention specification should still fall within the scope of the present invention patent.

21:External body

22: Containment Department

24: Protective frame

24a: Bottom wall

24b: Outer wall

24c: Part 1

24d: Part 2

24e: Installation Department

24h: Ribs

25A, 25B: Coil

25b: Inner circumference

25c: Periphery

26: Part 1

26a: First end

26b: Second end

27: Part 2

27a: First end

27b: Second end

28: Part 3

29: Part 4

A: Axis of the protective frame (housing unit)

L: Baseline

S: Gap

r1: first radius of curvature

r2: Second radius of curvature

r3: third radius of curvature

r4: fourth radius of curvature

Claims (8)

A cooking device comprises: a housing portion having a bottom wall and a cylindrical outer peripheral wall rising from the outer periphery of the bottom wall, and housing a bottomed cylindrical pot; and a plurality of coils arranged in a circumferential direction around the axis of the housing portion on the outer surface side of the housing portion, the plurality of coils being ring-shaped and respectively composed of a first portion, a second portion, an arc-shaped third portion, and an arc-shaped fourth portion, the first portion protruding toward the axis of the housing portion when the housing portion is viewed from the direction in which the axis of the housing portion extends. The first portion is bent with a first curvature radius and extends along the bottom wall in a manner of crossing the bottom wall, the second portion is bent with a second curvature radius smaller than the first curvature radius and extends along the outer peripheral wall, the arc-shaped third portion is connected to the first end of one side of the first portion and the first end of the one side of the second portion in the circumferential direction of the receiving portion, and the arc-shaped fourth portion is connected to the second end of the other side of the first portion and the second end of the other side of the second portion in the circumferential direction of the receiving portion. A cooking device as described in claim 1, wherein the ratio of the first radius of curvature to the second radius of curvature is greater than 100% and less than 160%. A cooking device as described in claim 1 or 2, wherein, in the direction in which the axis of the receiving portion extends, the thickness of the inner peripheral portion of the third portion is thicker than the thickness of the outer peripheral portion of the third portion, and the thickness of the inner peripheral portion of the fourth portion is thicker than the thickness of the outer peripheral portion of the fourth portion. The cooking device as described in claim 3, wherein the thickness of the third part and the thickness of the fourth part gradually become thinner from the inner peripheral part toward the outer peripheral part. A cooking device as described in claim 1 or 2, wherein the cooking device only has two of the coils. A cooking device as described in claim 5, wherein the cooking device is provided with a sensor, the sensor passes through the outer peripheral wall and detects the temperature of the pot, and when the receiving portion is observed from the direction in which the axis of the receiving portion extends, the two coils are arranged symmetrically with respect to the center of the bottom wall and the reference line of the sensor. The cooking device as described in claim 6, wherein the gap between the third part or the fourth part closest to the sensor and the sensor is less than 20 mm. A cooking device as described in claim 1 or 2, wherein the thickness of the first part and the thickness of the second part in the direction in which the axis of the receiving portion extends are uniform from the inner periphery to the outer periphery, and the density of the single wire constituting the first part is higher than the density of the single wire constituting the second part.