JPH0518662A - Refrigerator with thawing device - Google Patents

Abstract

PURPOSE:To achieve a fair finish in thawing frozen food in a refrigerator with a thawing device even when the weight and shape of the food vary, and keep the food fresh in an atmosphere suitable for preserving fish and meat even when the food is left in the thawing device after thawing. CONSTITUTION:Two or more temperature sensors 30 and 31 are in heat- conductible close contact with a bottom plate 26, and the first step is defined as a time period required for one of the temperature sensors 30 and 31 to rise up to a specified temperature. A controller controls the energizing time period and energizing ratio that are automatically determined according to the time period of the first step, a finish setting input, and a temperature difference between the two temperature sensors 30 and 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerator with a thawing chamber for thawing frozen food.

[0002]

2. Description of the Related Art Conventionally, an example of using a heater for thawing frozen food is known. For example, Japanese Patent Publication Sho 48
This is the example shown in Japanese Patent Publication No. 25414, which is shown in FIG.
0 will be described with reference to FIG. Reference numeral 1 denotes a thawing box, which includes an outer box 2 made of metal or synthetic resin, and an inner box 3 made of aluminum or the like having a large thermal conductivity and provided inside the outer box 2 with an appropriate interval. Has been formed. Reference numeral 4 denotes a linear heater, which is heat conductively adhered to the inner box 3 by an aluminum foil 5 such that the bottom surface of the thawing box 1 is sparse and the top surface is dense. 6 is a heat insulating material interposed between the outer box 2 and the aluminum foil 5. When the food to be thawed 7 is placed on the bottom surface of the thaw box in such a configuration and the thaw action is started, heat is applied from the entire circumference of the inner box 3 by the heating of the heating heater 4, and the food to be thawed 7 is heated and thawed. It is characterized by making it.

[0003]

However, in such a structure, although the bottom portion of the thawing box 1 is heat-conducted by the heat conduction to the bottom portion of the food 7 to be thawed, the bottom portion can be thawed. There is almost no radiant heating from the upper surface and the side surface of the thawing box 1, and heating is performed mainly by convection of warmed air in the thawing box 1.

For this reason, the thawing unevenness with the central portion of the food 7 to be thawed tends to become large, and the thawing time becomes long, and the weight and size of the food affect the thawing performance. In addition, if the food is left as it is after the thawing is completed, the quality of the raw fish such as fish meat is deteriorated because the ambient temperature is high.

Therefore, after the thawing is completed, the user needs to be careful and perform the processing, and there is also a problem that the user cannot use it at ease. In addition, there are problems that the finished state is not constant due to the thickness and weight of the food, and that the finished state of the user cannot be met.

The present invention is intended to solve the above-mentioned problems, and there is little thawing unevenness, thawing can be done in a short time and with peace of mind, and a thawing chamber that can be finished according to the user's request, especially in a refrigerator. It is intended to be given to.

[0007]

A refrigerator with a thawing chamber according to the present invention comprises a reflector having a curved reflecting surface, a radiant heater provided below the reflector at a predetermined distance, and the reflector. A bottom plate disposed opposite to the plate, a heater heater thermally conductively attached to the back surface of the bottom plate, and a plurality of temperature sensors thermally conductively attached to the back surface of the bottom plate. Thaw chamber, a cooling chamber provided with the thaw chamber at one corner, a blower for forcedly ventilating the cold air cooled by the cooler of the known refrigeration cycle into the thaw chamber, and a cold air inflow amount provided at the inlet of the thaw chamber It comprises a damper device for adjusting the temperature, a defrosting switch for starting the defrosting action, and a finish setting key for inputting the finish of the food to be defrosted desired by the user.

[0008]

According to the present invention, with the above-described structure, indirect radiation is performed through the upper surface and the reflecting surface of the food to be thawed, and the heat is absorbed almost uniformly from the upper surface of the food to be thawed, and at the same time, the heater for heating the bottom surface. Heat is also transferred and absorbed from.

During thawing, the damper device is forcibly opened,
With the blower forcedly operated and the time from the start of thawing until one of the temperature sensors rises to a predetermined temperature as the first step, the radiant heater and the heating heater are energized at a predetermined energization rate. The step is a setting input of the finish setting key, the temperature difference of the plurality of temperature sensors, and the food to be defrosted is heated at a duty factor that is automatically determined according to the time required for the first step, and is thawed. Except at times, the thaw chamber is maintained in a third temperature zone between refrigeration and freezing temperatures.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A refrigerator with a thawing chamber showing an embodiment of the present invention will be described below with reference to FIGS. Reference numeral 8 denotes a refrigerator body, which is composed of an outer box 9, an inner box 10 and a heat insulating material 11 filled between the boxes 9 and 10. Reference numeral 12 is a cooling chamber (hereinafter referred to as a refrigerating chamber 12), and 13 is a freezing chamber partitioned and formed on the refrigerating chamber 12. Reference numeral 15 denotes a compressor for a refrigeration cycle provided at the bottom of the refrigerator body 8,
Reference numeral 16 is a cooler provided on the back surface in the freezer compartment 13.
Reference numeral 17 denotes the cold air cooled by the cooler 16 in the refrigerating chamber 1
2, a blower for forcedly ventilating the freezing compartment 13 and the thawing compartment 14, and 18 is a damper device (hereinafter referred to as a damper thermostat 18) installed at the inlet of the thawing compartment 14 to adjust the cold air inflow amount by an electric input. The damper 20 is opened and closed by the driving force of the motor 19. Reference numeral 21 is a discharge duct for guiding the cool air from the blower 17 to the defrosting chamber 14, and 22 is a suction duct for returning the cool air that has cooled the defrosting chamber 14 to the cooler 16.

Next, the detailed structure of the thawing chamber 14 will be described. Reference numeral 23 is an outer box made of synthetic resin, 24 is an inner box made of metal such as aluminum, and has a curved reflecting plate 25, a bottom plate 26 disposed below the reflecting plate 25, and both plates 2.
5, 26 are formed by a side plate 27 having a substantially U-shape connected to three sides. Reference numeral 28 denotes a door that is openably and closably provided in the front opening of the inner box 24, and has a double structure made of synthetic resin that forms an air layer to improve heat insulation.

Reference numeral 29 denotes a radiant heater made of a quartz glass tube, which is provided facing the reflection plate 25 of the inner box 24 at a predetermined interval and radiates far infrared rays of about 5 μm or more by itself. A ceramic paint containing silicon as a main component may be baked and applied on the surface to further increase the radiation efficiency of far infrared rays.

Reference numeral 30 is a temperature sensor (1) such as a thermistor which is heat conductively adhered to the vicinity of the central portion of the back surface of the bottom plate 26. Reference numeral 31 is a thermistor which is thermally conductively adhered to the vicinity of the periphery of the bottom plate 26. Such as a temperature sensor (2).

Reference numeral 32 denotes a linear heater which is heat conductively adhered to the back surface of the bottom plate 26 with an aluminum foil or the like.
Reference numeral 3 denotes a thawing plate which is detachably installed on the bottom plate 26 and on which the food to be defrosted 34 is placed. Reference numeral 35 is a protective net for preventing burns which is attached so as to cover the radiant heater 29 at a constant interval.

Reference numeral 37 is a heat insulating material inserted between the outer box 23 and the inner box 24, and has a discharge air passage 38 communicating with the discharge duct 21 and the damper thermostat 18 at the upper portion and a suction duct 22 at the rear portion. The suction air passage 39 is formed.
A plurality of discharge ports 40 are formed in the reflection plate 25 of the inner box 24 so as to connect the inside of the thawing chamber 14 with the discharge air passage 38.
Reference numeral 1 denotes a suction port formed in the side plate 27 of the inner box 24 so as to connect the inside of the thawing chamber 14 and the suction air passage 39.

Reference numeral 42 denotes an operation plate provided on a part of the outer shell of the refrigerator body 8 for selecting a finish state (eg, "hard", "standard", "soft") desired by the user. A finish setting key 44 (in this case, "standard" if nothing is set) and a defrosting switch 45 for starting or stopping the defrosting operation are provided.

Next, the control relationship will be described. Reference numeral 46 denotes a control means (hereinafter referred to as a microcomputer 46) including a microcomputer and the like, which is composed of three stages. A timer 47 for counting the time of the first stage of the decompression control, a timer 48 for counting the extension time of the first stage, and a timer 4 for counting the time of the second stage.
9, a timer 50 that counts the time of the third stage, and, for example, intermittent energization rate X% (ON ... x1s, OFF ... x2
s) timer 51, intermittent duty ratio A% (ON ... a
1s, OFF ... a2s), a timer 51a for setting the intermittent duty ratio Y% (ON ... y1s, OFF ... y2s), a timer 52a, an intermittent duty ratio B% (ON ... b1s, OF)
The timer 52b for setting F ... b2s) is built in.

At the input terminal of the microcomputer 45, there are provided a freezer compartment temperature detecting means 53 for detecting the temperature in the freezer compartment 13 for controlling the operation of the compressor 15 and the blower 17, and the temperature sensor 30. Food temperature detecting means 54, defrosting room temperature detecting means 55 composed of the same temperature sensor 30, food temperature detecting means 43 having the temperature sensor 31, finish setting switch 44, defrosting switch 4
5, the compressor 15 and the blower 1 are connected to the output terminals.
7, damper thermo 18, radiant heater 29, heater 3
Driving means 56, 5 such as an electromagnetic relay for driving 1
7, 58, 59 and 60 are connected.

The operation of the above arrangement will be described with reference to the flow charts and time charts shown in FIGS.

First, the food to be thawed (for example, beef steak meat having a thickness of 20 mm) 34 to be thawed is placed on the thaw plate 33 substantially at the center and set on the bottom plate 26. First, in STEP 1, the defrosting finish state desired by the user is set and selected from three types of "hard", "standard", and "soft" by the finish setting key 44 (for example, "standard" in this case). Therefore, the finish setting key 44 is not operated).

Then, in STEP 2, the thawing operation is started by turning on the thawing switch 45. When the thawing control starts, the timer 47 of the first stage starts counting time in STEP3, and then STE
At P5, the radiant heater 29 (for example, 100 W) and the heating heater 32 (for example, 10 W) are continuously energized, the blower 17 is forcibly operated, and the damper 20 of the damper thermostat 18 is forcibly opened.

Therefore, far infrared rays having a size of 5 μm or more are continuously and directly radiated from the upper surface directly or indirectly through the reflecting plate 25 to the upper side surface of the food to be defrosted 34, so that far infrared rays are emitted. Far-infrared rays are efficiently absorbed by general foods having an absorption wavelength band in the wavelength range, and the food to be defrosted 3
The heat quickly penetrates into the inside of No. 4. In addition, for the bottom portion of the food to be defrosted 34 that cannot be sufficiently heated by the radiant heater 32, the heating heater 31 is provided via the defrosting plate 33.
In addition to the fact that the continuous heat transfer heating is performed, the temperature of the food to be defrosted 34 that was in the frozen state (for example, −20 ° C.) in the first stage can be quickly raised.

On the other hand, the cool air cooled by the cooler 16 is guided to the discharge air passage 38 in the thawing chamber 14 via the discharge duct 21 and the damper thermostat 18 in the refrigerator body by the forced air blowing action of the blower 17. Blow-down air is blown from a large number of the outlets 40. Therefore, the radiant heater 2 described above
Combined with the effect of heat permeation into the food by far-infrared radiation of 9, the food to be defrosted 34 while suppressing the temperature rise on the surface.
Thawing proceeds in a state where the temperature unevenness between the surface and the center of the is not large.

The air warmed by the heating action in the thawing chamber 14 is returned to the cooler 16 from the suction port 41 and the suction air passage 40 provided at the rear of the room through the suction duct 22 of the refrigerator body 8 and again. It is cooled and the circulation action is repeated. While the continuous heating action with such cooling action progresses, STE
At P5, the temperature T of the temperature sensor 30 is set to a set value T '(for example, 2
If it is lower than 0 ° C, if it is lower, then in STEP 5, wait until it becomes higher.

When it is judged in STEP 5 that the temperature is high (T ≧ 20 ° C.), it is judged that the first stage is completed, and S
In step TEP6, the timer 47 of the first stage stops counting the time, and the required time t1 (eg, 6 min) from the start of defrosting is stored in the microcomputer 46 as the time of the first stage.

The required time t1 is approximately proportional to the weight of the food. At the same time, the temperature difference T1 between the temperature sensors 30 and 31 is stored. Here, the temperature difference T1 largely changes depending on whether or not the food to be defrosted 34 hangs on the temperature sensor 31. That is, T1 indirectly detects the area of the food to be defrosted 34.

Following this, the flow proceeds to STEP 7,
The extension time timer 48 of the first stage starts counting time. The set time of the time timer 48, that is, the first
As shown in Table 1, the extension time t1 ′ of the stage is a constant a predetermined according to the finishing setting of the first stage time t1, T1, and STEP1 (for example, T1> 5 ° C., finishing “standard” is a = Time multiplied by 0 t1 ′ = a · t
1. In this case, 0x6 = 0 (min) is automatically set.

[0028]

[Table 1]

Then, at the same time when the timer 48 counts the time, the process proceeds to STEP 7, where the radiant heater 29 and the heater 32 are heated.
Is continuously energized, and then the blower 17 is forcibly operated and the damper 20 of the damper thermostat 18 is forcibly opened. Then, in STEP 9, the count time of the timer 48 is t1 ′.
It is determined whether or not (0 min) has been reached, and if it has not reached, it waits until it reaches in STEP 10. STEP9
Then, when the timer 48 counts t1 '(0 min), the extension of the first stage is completed and the process proceeds to STEP9. STEP
At 9, the second stage timer 49 starts counting time.

At this time, the set time of the timer 49, that is, the time t2 of the second stage is S at the time t1 of the first stage.
Predetermined constant b for each TEP1, finish, and temperature T1 (for example, finish “standard”, b at T2> 5 ° C.
= 2) time t2 = b · t1 (2 × 6 in this case)
= 12 min) is automatically set.

Then, at the same time as the timer 49 counts the time, the process proceeds to STEP 10, where the radiant heater 29 causes the timer 51 to have the intermittent energization rate X% = [x1s / (x1 + x2) s] × 100.
(For example, 80% ... x1 = 60 s, x2 = 15 s), the current is intermittently supplied. The heater 32 uses the intermittent duty ratio A% of the timer 51a = [a1s / (a1 + a2) s] × 100.
(For example, 80% x1 = 60 s, x2 = 15 s) is intermittently energized. The blower 17 and the damper 20 of the damper thermostat 18 are continuously operated or forcibly opened, so that cold air is continuously introduced.

In this way, in the second stage, the amount of heat suppressed is smaller than that in the first stage, and since the intermittent heating is performed from the upper surface and the lower surface, the heat is transferred from the surface of the food to be defrosted 34 to the center. In addition to being accelerated, the thawing proceeds while suppressing the rise in surface temperature due to cold air.

While the intermittent heating action including the cooling action proceeds, it is determined in STEP 12 whether the count time of the timer 49 has reached t2 (12 min). If not, until it reaches STEP 12 stand by. When the timer 49 counts t2 (12 min) in STEP 12, the second stage is ended and the process proceeds to STEP 13.

In STEP 13, the timer 5 of the third stage
0 starts time counting. At this time, the set time of the timer 50, that is, the time t3 of the third stage is set to the finish at STEP1 at the time t1 of the first stage, and the constant c determined for each temperature difference T1 (for example, this finish "standard", temperature difference T1> Time t3 = c · t1 multiplied by c = 1) at 5 ° C
(1 × 6 = 6 min in this case) is automatically set.

Then, at the same time when the timer 50 counts the time, the process proceeds to STEP 14, and the radiant heater 29 causes the intermittent duty ratio Y% of the timer 52 = [y1s / (y1 + y2) s] × 100.
(For example, 40% ... y1 = 20s, y2 = 30s), the current is intermittently applied. The heater 32 on the bottom is a timer 52.
Intermittent duty ratio B% of b = [b1s / (b1 + b2) s] ×
100 (for example, 40% ... y1 = 20s, y2 = 30
Although the power is intermittently supplied in s), the blower 17 and the damper 20 of the damper thermostat 18 are continuously forced to operate or forced to be opened so that cold air is continuously introduced.

In this way, in the third stage, the heating amount is further suppressed as compared with the second stage, and the heating action is performed by mixing cold air, so that the temperature rise of the surface of the food to be defrosted 34 is sufficiently suppressed. As a result, the temperature difference between the central portion and the surface portion is small, and thawing without uneven thawing can be realized.

While thawing proceeds in this way, STEP
At 15, it is judged whether the count time of the timer 50 has reached t3 (6 min), and if not, STEP1
Wait until it arrives at 5. In STEP15, timer 50
When t3 (6 min) is counted, the third stage is ended, and in STEP 16, the power supply to the radiant heater 29 is stopped, the forced operation of the blower 17 and the forced opening of the damper thermostat 18 are released, and the thawing is automatically completed.

Next, the case where "softening" is selected by the finish setting switch 44 will be described. In STEP 1, after setting "soft", the flow is "standard"
Based on the constants shown in Table 1 as in the case of
Go to P and defrost. In the "soft" setting, the central temperature of the food to be defrosted 34 is further increased by extending the first stage and increasing the heating amount in the second stage, compared with the "standard" setting.
At this time, the continuous introduction of cold air suppresses the temperature rise of the surface of the food to be defrosted 34 to proceed with the defrosting. Further, in the third stage, the amount of heating is further suppressed and the cold air is continuously introduced. Then, the temperature rise of the surface of the food 34 to be thawed is sufficiently suppressed, and the food is sufficiently thawed to the center without widening the temperature difference between the center and the surface.

The setting of "soft syrup" can make foods such as minced meat, which may be molded immediately after thawing due to cooking, easy to handle, and can be soft simmered as desired. It can also be adapted to the user's preference.

Next, "hardening" will be described. STEP
After setting the finish setting switch 44 to "hard" in No. 1, the flow is defrosted based on the constants shown in Table 1 as in the case of "standard". With the "hard" setting, the heating time of the second stage is shorter and the finish is harder than the "standard". It is also suitable for users who want a harder finish, such as when eating sashimi in the summer, or for users who prefer a harder taste.

If the weight of the food to be thawed 34 changes, the cold heat capacity of the food changes, so the temperature rise gradient of the temperature sensor 30 changes, and the time t1 required for the first stage changes. As a result, the thawing time automatically changes, so that appropriate thawing is performed according to the change in the weight of the food. Further, in the present embodiment, T1 is determined by the temperature sensor 30, but if the first stage is determined by the sensor having the longest rise time to a predetermined temperature among the plurality of temperature sensors, the food to be defrosted 34 can be further processed. The weight can be detected accurately. As described above, the temperature difference T2> 5 ° C. (when the target area is relatively small) is set here. However, when the temperature difference T2 ≦ 5 ° C., the area is determined to be relatively large, and based on various experiments shown in FIG. The fixed constant is automatically selected, and thawing with less unevenness is performed with proper heating control. Also, regarding the thawing time, the internal penetration effect of far-infrared radiation and heating from the top and bottom of the initial thawing. By control, relatively short time (for example, 200g weight, 20m thickness)
Beef steak meat of 20 to 25 min) can be thawed. After the thawing is completed, the temperature inside the thawing chamber 14 is controlled based on the temperature detected by the temperature sensor 30 as in the normal cooling. Therefore, the thawed food 34 after thawing is immediately cooled so as to stabilize at the partial freezing temperature of about -3 ° C, and the temperature does not rise further due to residual heat.

Even after being left as it is after being thawed, since it is kept cold at the partial freezing temperature suitable for preservation of living things such as fish and meat, the user immediately monitors the end of the thawing as in the conventional case. There is no need to process it, and you can safely decompress it. Further, the food to be defrosted 34 can be used at any time after the end, which is extremely convenient.

[0043]

As described above, according to the refrigerator with the thawing chamber of the present invention, the following effects can be obtained.

(1) Radiant heating mainly from far infrared rays by the radiant heater from the top surface, heat conduction heating by the heating heater from the bottom surface, and efficient heating from both sides, and moreover, heat generation of the radiant heater during defrosting The amount gradually decreases, and in combination with the effect of far-infrared rays penetrating into the inside of food, thawing with less temperature unevenness between the central portion and the surface portion becomes possible.

(2) During thawing, cold air is allowed to flow down into the food from the upper part of the room, so that the surface of the food is cooled uniformly, the temperature rise is further suppressed, and the deterioration of the food is prevented.

(3) The weight of food can be indirectly detected by the temperature rise gradient of the temperature sensor, and the area can be indirectly detected by the temperature difference T1 between the temperature sensors. Since the electric current of the heater is automatically set and the thawing proceeds, a good thawing finish can be obtained even if the shape of the food is changed.

(4) In the initial stage of thawing, both the radiant heater and the heating heater are energized to perform rapid heating from above and below, so that thawing can be performed in a short time while maintaining quality. Further, by inputting a desired finish setting, an appropriate heating time and a heater energization rate are automatically set to proceed the thawing, so that the thawing finish desired by the user can be obtained.

(5) After the thawing is completed, the inside of the thawing chamber is kept in the temperature zone between the freezing room temperature and the refrigerating room temperature (for example, the partial freezing temperature of about -3 ° C.), so that the residual heat immediately after the thawing finishes the food. The temperature does not rise, the freshness is maintained in an environment suitable for preserving living things such as fish meat even if it is left as it is, and the food can be used at any time, which is extremely convenient.

[Brief description of drawings]

FIG. 1 is a perspective view of a thawing chamber showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line A-A ′ of the thawing chamber of FIG.

FIG. 3 is a vertical cross-sectional view of a refrigerator with a thawing chamber including the thawing chamber of FIG.

FIG. 4 is an enlarged view of the thawing operation plate

FIG. 5 is a control block diagram.

FIG. 6 is a flowchart of defrosting control.

FIG. 7: Time chart during thawing with the finish setting “standard” and temperature characteristic diagram of the food to be thawed

FIG. 8: Time chart during thawing with the finish setting “Soft Kamame” and temperature characteristic diagram of the food to be thawed

FIG. 9 is a time chart during thawing with the finish setting “hard” and a temperature characteristic diagram of the food to be thawed.

FIG. 10 is a perspective view of a conventional thawing box.

11 is a sectional view taken along line B-B ′ of the defrosting box in FIG.

[Explanation of symbols]

12 Cooling chamber 14 Thaw room 16 Cooler 17 blower 18 Damper device 23 outer box 24 inner box 25 reflector 26 Bottom plate 27 side plate 28 doors 29 Radiant heater 30 Temperature sensor (1) 31 Temperature sensor (2) 32 heater 33 thaw plate 34 Thawed food 37 Insulation 38 Discharge air passage 39 Suction path 40 outlets 41 Suction port 44 Finish setting key 45 Defrost switch 46 control means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G05D 23/00 G 9132-3H 23/19 E 9132-3H 23/24 N 9132-3H

Claims (3)

[Claims] 1. A reflecting plate having a curved reflecting surface, a radiant heater provided below the reflecting plate at a predetermined interval, a bottom plate arranged to face the reflecting plate, and the bottom. A thaw chamber equipped with a heater that is heat conductively attached to the back surface of the face plate, a plurality of temperature sensors that are thermally conductively attached to the back surface of the bottom plate, and a cooling unit provided with the thaw chamber in one corner. Chamber, a blower for forcedly ventilating the cold air cooled by the cooler of the refrigeration cycle into the defrosting chamber, a damper device provided at the inlet of the defrosting chamber to adjust the amount of cold air flowing in, and a defrosting switch for starting the defrosting action. , A finish setting key for inputting the finish of the food to be defrosted desired by the user, forcibly opening the damper device during defrosting, forcing the blower to operate, and one of the temperature sensors from the start of defrosting to a predetermined value. Above the temperature of With the time until the temperature rises as the first step, the radiant heater and the heating heater are energized at a predetermined energization rate, and the subsequent steps are the setting input of the finish setting key and the temperature of the plurality of temperature sensors. Along with the difference, the food to be thawed is heated at a duty factor that is automatically determined according to the time required for the first step, and the thaw chamber is in a third temperature zone between the refrigerating and freezing temperatures except when thawing. Refrigerator with a thawing chamber equipped with a control means for maintaining the above. 2. The refrigerator with a defrosting chamber according to claim 1, further comprising control means for determining the first stage by a sensor having the longest rise time to a predetermined temperature among a plurality of temperature sensors. 3. The refrigerator with a thawing chamber according to claim 2, wherein one of the plurality of temperature sensors is arranged in the center of the bottom plate, and the other temperature sensors are arranged near the periphery of the bottom plate.