JPH0740903B2 - Defroster - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a defrosting device for defrosting an object to be defrosted by controlling the on / off of a heater based on temperature detection of the object to be defrosted. .

(Prior Art) Conventionally, in a defrosting apparatus such as a refrigerator, a defrosting chamber is provided in the refrigerator, and a heater for heating the object to be thawed and cold air to the object to be thawed are provided inside the thawing chamber. A fan is provided for spraying, a temperature sensor is provided for detecting the temperature of the object to be defrosted, and a heater drive control circuit is provided for performing on / off control of the heater based on the temperature detected by the temperature sensor. Is provided.

In this case, after the object to be thawed is housed in the thaw chamber, the thawing set switch is turned on to start thawing the object to be thawed. In this case,
While driving the fan, the temperature sensor detects the temperature of the object to be defrosted, and when the detected temperature is below the lower limit temperature reference value set in the heater drive control circuit, the heater is energized and reaches the upper limit temperature reference value. , Control to turn off the heater.

In this case, since the object to be thawed is heated by the heater in addition to blowing the cool air by the fan, the thaw time is short unlike the thaw method by the fan alone, but there was the following problem. . That is, when the object to be thawed is heated by the heater, there is a risk that the heater is continuously energized due to instability in temperature detection such as variations in the detection operation of the temperature sensor and changes in the ambient temperature. The temperature of (1) becomes too high with respect to the internal temperature and the surface of the object to be defrosted may be thawed so much that the surface of the object to be thawed may deteriorate. In order to prevent such alteration of the surface of the object to be thawed, conventionally, the lower limit temperature reference value and the upper limit temperature reference value in the heater drive control circuit are set low to increase the chances of the heater being cut off. However, this leaves a problem that the effect of shortening the thawing time by using the heater is not so remarkable.

(Problems to be Solved by the Invention) As described above, in the case of using a heater for thawing an object to be thawed, the problem that the time required for the thawing does not decrease so much if the surface portion alteration of the object to be thawed is eliminated was there.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a defrosting device capable of shortening the required time while eliminating deterioration of the surface portion of the object to be thawed.

[Structure of the Invention] (Means for Solving Problems) The present invention relates to a heater for heating an object to be defrosted contained in a defrosting chamber, and a temperature sensor for detecting the temperature of the object to be defrosted,
And a heater drive control circuit for energizing the heater to drive and control the heater when the temperature detection value based on the temperature sensor rises to the upper limit temperature reference value and the heater is cut off and drops to the lower limit temperature reference value. In the thing which comprises
The heater drive control circuit has a plurality of temperature determination circuits having different upper limit temperature reference values and lower limit temperature reference values, and the upper limit temperature reference value and the lower limit temperature are set with the lapse of time after the start of thawing the plurality of temperature determination circuits. It is characterized in that it has a timer circuit for enabling the reference values in descending order.

(Operation) When the object to be thawed in the freezing temperature state is housed in the thaw chamber and then thawed, the temperature of the object to be thawed is lower than the lower limit temperature reference value at the beginning of the thaw, so that the heater is Is energized to generate heat. The object to be thawed is heated by the heat generated by this heater, and its temperature rises. However, the timer circuit has a higher upper limit temperature reference value and a lower limit temperature reference value with the passage of time after starting the thawing of multiple temperature determination circuits. The temperature detection value based on the temperature sensor is
The temperature is significantly lower than the lower limit temperature reference value, and therefore, the opportunity to cut off the electric power to the heater is small, the electric power is supplied to the heater exclusively, and the electric power is cut off for a short time. In this case, since the temperature of the object to be thawed is low in the initial stage of thawing, even if the amount of heat applied to the object to be thawed is large, the surface and the inside of the object to be thawed to a temperature at which the surface portion does not deteriorate. Rise in a short time.

After that, the upper limit temperature reference value and the lower limit temperature for the detected temperature value are activated due to the activation of the temperature determination circuit with the lower upper limit temperature reference value and the lower limit temperature reference value and the temperature increase of the temperature of the object to be defrosted from the beginning of the defrosting. The temperature difference of the reference value becomes smaller, the chances of power interruption to the heater increase, the energization time decreases and the power interruption time becomes longer, and the temperature rise of the entire surface of the object to be thawed is suppressed while the temperature rise of the surface of the thawed object is suppressed. As a result, the object to be thawed is thawed in a short time without deteriorating the surface portion.

(Embodiment) An embodiment in which the present invention is applied to a refrigerator thawing apparatus will be described below with reference to the drawings.

First, in FIG. 2, reference numeral 1 is a cabinet body, and inside the cabinet body 1, a thawing chamber 3 and a refrigerating chamber 4 are provided by a partition wall 2.
Is divided into upper and lower partitions. A freezing chamber (not shown) is formed above the thawing chamber 3. Defrost room 3 above
Further, cold air is supplied to the refrigerating chamber 4 from a cold air supply duct (not shown). Vents 5 and 6 are formed in the front and rear of the partition wall 2 so as to connect the thawing chamber 3 and the refrigerating chamber 4, and a chilled case 7 is arranged above the thawing chamber 3.

Now, 8 is a thawing plate arranged at the bottom of the thawing chamber 3,
As shown in FIG. 3, a heater 9 is attached to the back surface of the thawing plate 8 and a temperature sensor 10 composed of a negative characteristic thermistor is attached. Reference numeral 11 is a fan arranged in the defrosting chamber 3, and 12 is a fan drive motor for driving the fan 11. The heater 9 is driven and controlled on the basis of the temperature detection of the temperature sensor 10 and the heater drive control circuit 13 (see FIG. 1) during defrosting, and the fan drive motor.
12 is also driven at the time of thawing.

Next, the heater drive control circuit 13 will be described with reference to FIG. 1. Reference numeral 14 is a temperature detection circuit having the temperature sensor 10, which is a temperature detection value Ek corresponding to the temperature detected by the temperature sensor 10. Is output at the voltage level. 15, 16 and 17 are respectively
The first, second, and third temperature determination circuits, and the first temperature determination circuit
Reference numeral 15 includes a reference voltage generation circuit 18 that generates a reference voltage as a temperature reference value E ₁₈ , and a comparator 19. The non-inverting input terminal (+) of the comparator 19 has a reference voltage generation circuit 18 The temperature reference value E ₁₈ is given, and the temperature detection value from the temperature detection circuit 14 is applied to the inverting input terminal (-).
Ek is given. Further, the comparator 19 has hysteresis in rising and falling of its output, that is, the temperature reference value E ₁₈ of the reference voltage generating circuit 18 is given the upper limit temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l. It has been done. Therefore, the comparator 19 changes its output signal S ₁₅ to a low level when the temperature detection value Ek from the temperature detection circuit 14 rises to the upper limit temperature reference value E ₁₅ h, and when it falls to the lower limit temperature reference value E ₁₅ l. The output signal S ₁₅ is changed to high level. The second temperature determination circuit 16 and the third temperature determination circuit 17 also have the same configuration as the first temperature determination circuit 15, and the second temperature determination circuit 16 sets the reference voltage as the temperature reference value E _20. The third temperature determination circuit 17 includes a reference voltage generation circuit 20 for generating a reference voltage and a comparator 21 having a hysteresis, and the third temperature determination circuit 17 has a reference voltage generation circuit 22 for generating a temperature reference value E ₂₂ and a comparator 23 having a hysteresis. It consists of and. However, each temperature judgment circuit
The temperature reference values E ₁₈ , E ₂₀ and E _{22 at} 15, 16 and 17 are E
_18> E _20> is defined as E becomes _22, i.e., the maximum temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l of definitive the first temperature determination circuit 15, the second temperature determining circuit 16 upper limit temperature reference value E ₁₆ h and lower limit temperature reference value ₁₆ l,
As can be seen from FIG. 4, the upper limit temperature reference value E ₁₇ h and the lower limit temperature reference value ₁₇ l in the third temperature determination circuit 17 are as follows.
It is set to lower in that order. Further, in this case, the temperature range between the upper limit temperature reference value and the lower limit temperature reference value (hysteresis width of each comparator) in each of the temperature determination circuits 15, 16 and 17 is made smaller in that order, as can be seen from FIG. Is set. Reference numeral 25 is an input circuit configured by including a decompression set / reset switch 26 composed of an automatic reset type push switch, a Schmitt trigger inverter 27, etc. This is a decompression set / reset switch.
The output signal S ₂₅ (inverter 27
Output signal) is changed to a high level, and the output signal is applied to the clock terminals CK of the D flip-flop circuits 28, 29 and 30. The D flip-flop circuits 28, 29 and 30 are set at the rising edge of the reset terminal when the signal applied to the clock terminal CK changes to the high level while the reset terminal is in the high level state, and the set output terminal Q is set to the data terminal. Change to D level. When the signal applied to the reset terminal changes from the high level to the low level, the signal is reset by the fall and the installed set output terminal Q is changed to the low level. Reference numeral 31 is a reset circuit including a resistor and a capacitor, and a Schmitt trigger inverter, which changes the output signal S ₃₁ to a low level when the power is turned on to change the flip-flop circuits 28, 29 and 3
The reset terminal of 0 is set to the high level, and each flip-flop circuit 28, 29 and 30 is reset when the power is turned off, and it is also used for instantaneous power failure compensation. 32 is an oscillator circuit which outputs a reference frequency pulse. Reference numeral 33 is a timer circuit configured to have a frequency dividing function. This is a reference provided by the oscillator circuit 32 to the clock terminal CK by its rising when the signal applied to the reset terminal changes from low level to high level. Counting is started based on the frequency pulse. And as can be seen from FIG. 5, the timer circuit 33 starts counting at that time.
The output terminal Q _T1 in the T _C0 time T ₁ has passed since the beginning T _C1 is changed from the low level to the high level, the high level from the low level to the output terminal Q _T2 at T _C2 were further time T ₂ elapses from the elapsed time T _C1 The output terminal Q _T3 is changed from the low level to the high level at the time T _C3 when the time T _{3 has} elapsed from the time T _C2 . Furthermore, this timer circuit 33
When the signal applied to the reset terminal changes from the high level to the low level, it is reset by the fall. 34 is a relay coil for turning on and off the heater, which is turned on and off by turning on and off the NPN transistor 35 which is a switching element. Incidentally, 36 is a diode for protecting the transistor 35. 37 is a relay coil for connecting / disconnecting the fan drive motor, 38 is a light emitting diode for displaying the defrosted set, and these are controlled to be switched on / off by turning on / off a switching element NPN transistor 39. Incidentally, 40 is a diode for protecting the transistor 39. Thus, each temperature determination circuit 15, 16, 17, flip-flop circuit 28, 29, 30, reset circuit 31, timer circuit 33, base of transistor 35, 3
The bases of 9 are connected as shown via the AND circuits 41, 42, 43, the OR circuit 44, the inverters 45, 46, and the NOR circuits 47, 48, 49.

Now, the operation of the above configuration will be described. Now, in the state of FIG. 1, the output signal S ₃₁ of the reset circuit ₃₁ is low level, and the timer circuit 33 is in the reset state (each output terminal Q _T1 , Q _T2
And Q _T3 are at a low level) and therefore each NOR circuit 47, 48
The outputs of 49 and 49 are in the high level state, and the reset terminals of the flip-flop circuits 28, 29 and 30 are in the high level state. When the object to be thawed (in the freezing temperature state) is placed on the thaw plate 8 and the thaw set / reset switch 26 is turned on, the output signal S ₂₅ of the input circuit 25 changes to a high level, The high level output signal S ₂₅ is the clock terminal CK of each flip-flop circuit 28, 29 and 30.
Given to. Now each flip-flop circuit 28,29
And 30 change each set output terminal Q to a high level and set its output signals S ₂₈ , S ₂₉ and S ₃₀ to a high level. Thus, the high-level output signal S _{30 of} the flip-flop circuit 30 is given to the base of the transistor 39, so that it is turned on, and the relay coil 37, that is, the fan drive motor 12 is energized and the defrosting set display is displayed. The light emitting diode 38 is turned on. The output signal S ₃₀ of the high level from the flip-flop circuit 30 because also applied to the reset terminal of the timer circuit 33, the timer circuit 33 starts counting. On the other hand, AND circuit 41, 42
And 43, the high-level output signal S ₂₈ is applied to one input terminal of the two-input AND circuit 41, and its output is applied to the other input terminal. changes according to the output signal S ₁₅ from the temperature judging circuit 15, also, 3 since the output signal S ₂₈ to one input terminal of the input type of the aND circuit 42 is given as the low level signal inverted by the inverter 45 , Its output goes to a low level regardless of the signal given to the other input terminal (in particular, the output signal S ₁₆ from the second temperature judgment circuit ₁₆ ), and further to one input terminal of the 3-input AND circuit 43. Is given as a low level signal obtained by inverting the output signal S ₂₉ by the inverter 46, so that its output is a signal given to another input terminal (particularly the third temperature judgment circuit).
It goes low regardless of the output signal S 17 from ₁₇ ). As a result, the first temperature determination circuit 15 is activated and its output signal S ₁₅ is given to the base of the transistor 35 via the AND circuit 41 and the OR circuit 4. As a result, the relay coil 34, that is, the heater 9 is turned on and off by the output signal S ₁₅ of the first temperature determination circuit 15. In other words, the first temperature determination circuit 15 has the upper limit temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l which are slightly higher than the upper limit temperature reference value and the lower limit temperature reference value of the other temperature determination circuits 16 and 17. Since the level of the output signal S ₁₅ is changed based on the above, the on / off control is eventually performed based on the upper limit temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l. At the start time T _C0 of thawing,
As shown in FIG. 6, since the temperature of the object to be defrosted is considerably low, the temperature detection value Ek is considerably lower than the upper limit temperature reference value E ₁₅ h in the first temperature judgment circuit 15, and therefore the heater 9
Is being energized to generate heat, which heats the object to be thawed through the thaw plate 8. In this case, since the fan 11 is driven, the fan 11 also blows cold air onto the object to be defrosted. After this, the temperature detection value Ek based on the temperature sensor 10 of the temperature detection circuit 14 becomes the upper limit temperature reference value E ₁₅ h.
When the temperature rises to, the heater 9 is cut off. After that, the temperature of the thawing plate 8 is lowered by heat exchange with the object to be thawed, and the detected temperature value Ek is the lower limit temperature reference value E ₁₅ l.
When the temperature drops to, the heater 9 is energized again. By repeating such a process, the object to be thawed is thawed at time T _{1 at the} initial stage of the start of the thawing. At this time T ₁ , since the upper limit temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l are slightly high, and the temperature of the object to be thawed is low, there are many opportunities to energize the heater 9, in other words, The energization time is long, but the disconnection time is short. As a result, the amount of heating by the heater 9 becomes large, and the temperature of the object to be thawed is raised from its initial low temperature (freezing temperature) in a short time. In this case, the amount of heat applied to the object to be thawed is large, but since the initial temperature of the object to be thawed is low, the surface of the object to be thawed is not altered.

Next, when the time T ₁ in the timer circuit 33 has elapsed, the output terminal Q _T1 changes to the high level at the time T _C1 . This timer circuit 33 maintains its output state (Q _T1 is at high level, Q _T2 is at low level, and Q _T3 is at low level) from this point in time T ₂ . Thus, the output terminal Q _{T1 of the} timer circuit 33
The high-level signal from the flip-flop circuit 28
Resets the set output terminal Q to low level (reset output terminal is high level). And Thus, by the output signal S ₂₈ of the flip-flop circuit 28 is changed to the low level, the output of the AND circuit 41 is set to the low level irrespective of the output signal S _15, also an inverter 45 supplied to the AND circuit 42 From the high level (the output signal S16 from the flip-flop circuit 29 given to the other input terminal is high level), the output of the AND circuit 42 is eventually the output signal from the second temperature determination circuit 16. It becomes S ₁₆ . Thus, the transistor 35 is turned on / off, that is, the heater 9 is turned on / off, by the second temperature determination circuit 16
In response to changes in the output signal S ₁₆ from. That is, the second temperature determination circuit 16 is activated. The output signal S ₁₆ from the second temperature determination circuit ₁₆ is the second temperature determination circuit 16
Upper limit temperature reference value E ₁₆ h and lower limit temperature reference value E ₁₆ l at
Change based on. The upper limit temperature reference value E ₁₆ h and the lower limit temperature reference value E ₁₆ l are set to be lower than the upper limit temperature reference value E ₁₅ h and the lower limit temperature reference value E ₁₅ l at the time T ₁ , respectively. As can be seen from FIG. 6, the heater 9 is turned on / off in a temperature region where the detected temperature value Ek is low. Therefore, the chances of the heater 9 being cut off are increased, the continuous energization state is effectively prevented, the heating amount of the heater 9 for the object to be thawed becomes small, and the bottom portion, which is the surface portion of the object to be thawed, becomes so high in temperature. Therefore, the thawed product is thawed while the internal temperature and the surface temperature of the thawed product come close to each other and become a temperature state. In this case, since the temperature range between the upper limit temperature reference value E ₁₆ h and the lower limit temperature reference value E ₁₆ l is small,
It is even more effective in preventing the temperature of the bottom of the thawed object from rising.

Then, when the time T ₂ in the timer circuit 33 elapses, the time T
_When it becomes _C2 , at this time T _C2 , the output terminal Q _T2 changes to high level, and the output state of this timer circuit 33 (Q _T1 is high level, output terminal Q _T2 is high level, output terminal Q _T3 is low level). Is maintained at time T ₃ . Then the timer circuit
The flip-flop circuit 29 is reset by the high level signal from the output terminal Q _{T2 of} 33, and its set output terminal Q
To low level. This flip-flop circuit
Since the output signal S ₂₉ from the set output terminal Q of ₂₉ changes to the low level, the output of the AND circuit 42 is set to the low level regardless of the output signal S ₁₆ from the second temperature determination circuit 16, while the ant circuit 43 Inverter given to 46
From the high level (the output signal S ₃₀ from the flip-flop circuit 30 given to the other input terminal is high level), the output of the AND circuit 43 is eventually the output from the third temperature determination circuit 17. It becomes signal S ₁₇ . Thus, the transistor 35 is turned on / off, that is, the heater 9 is turned on / off in accordance with the change of the output signal S ₁₇ from the third temperature determination circuit 17. That is, the third temperature determination circuit 17 is activated. Temperature determination signal S ₁₇ from the second temperature determining circuit 17 is changed on the basis of the maximum temperature reference value E ₁₇ h and the lower limit temperature reference value E ₁₇ l. The upper limit temperature reference value E ₁₇ h and the lower limit temperature reference value E
_{Since 17} l is set to be lower than the upper limit temperature reference value and the lower limit temperature reference value at the time T ₁ and the time T ₂ described above, the heater 9 is set to the temperature as shown in FIG. Electricity is cut off in a temperature range in which the detected value Ek becomes lower. Therefore, the opportunity of energization of the heater 9 is further increased, the heating amount of the heater 9 with respect to the object to be thawed is further reduced, and the object to be thawed is thawed while more effectively preventing the temperature rise of the bottom of the object to be thawed. It is possible to effectively prevent excessive thawing on the surface portion of the, and thus to prevent deterioration of the surface portion of the object to be thawed. In this case, since the temperature range between the upper limit temperature reference value E ₁₇ h and the lower limit temperature reference value E ₁₇ l is even smaller, it is more effective in preventing the temperature of the bottom of the thawed object from rising.
Surface alteration can be eliminated more reliably.

After that, when the time T ₃ in the timer circuit 33 elapses, the output terminal Q _T3 of the timer circuit 33 changes to the high level at the time T _C3 . As a result, the flip-flop circuit 30 in the set state is reset, that is, all of the flip-flop circuits 28, 29 and 30 are reset, so that the transistor 35 is turned off and the heater is cut off, and The transistor 39 is also turned off, the fan motor 12 and the light emitting diode 38 for displaying the defrosting set are cut off, and the timer circuit 33 is reset because its reset terminal changes to low level, and the defrosting is completed.

As described above, according to the present embodiment, the temperature determination circuits 15, 16 and 17 having different upper limit temperature reference values for disconnecting the heater 9 and different lower limit temperature reference values for energizing the heater 9 are connected to the timer circuit 33.
By activating the heater drive control circuit 13 by selectively activating it from the beginning of the thawing start, the upper limit temperature reference value and the lower limit temperature reference value are increased at the beginning of the thawing start, for example, at time T ₁ , and then at the time T Since the temperature is lowered in sequence at ₂ and time T ₃ , the chances of the heater 9 being cut off can be reduced at the initial stage of thawing, where the temperature of the object to be thawed is low and there is no risk of surface deterioration. The energization time of the heater 9 can be lengthened, and the amount of heat for the object to be thawed can be increased, so that the upper limit temperature reference value and the lower limit temperature reference value are set lower from the start point of the defrosting, compared to the conventional method. In such a short time, the temperature of the object to be thawed can be raised to such an extent that surface alteration does not occur, so that the thaw time can be shortened. Moreover,
After that, since the upper limit temperature reference value and the lower limit temperature reference value are sequentially lowered in two steps, it is possible to proceed with thawing without causing continuous energization, in other words, without causing surface portion alteration.

Incidentally, in the above-mentioned embodiment, with respect to setting the upper limit temperature reference value and the lower limit temperature reference value to be low, it was lowered in two steps, but this may be sequentially and successively lowered. Further, it may be lowered in one step.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, for example, it can be widely applied not only to the defrosting device of the refrigerator but also to the defrosting device in general, and various modifications can be made without departing from the scope of the invention. It can be implemented.

[Effects of the Invention] As is apparent from the above description, the present invention provides a heater drive control circuit with a plurality of temperature determination circuits having different upper limit temperature reference values and lower limit temperature reference values, and the plurality of temperature determination circuits. Since it has a timer circuit that activates the upper limit temperature reference value and the lower limit temperature reference value in descending order with the passage of time after the start of thawing, the temperature of the object to be thawed is quickly raised in the short time at the beginning of thawing. You can
Moreover, after that, it is possible to eliminate the occurrence of the continuous energization state of the heater which causes the surface of the object to be thawed to be deteriorated, and thus it is possible to greatly reduce the thawing time while eliminating the surface deterioration of the object to be thawed. Play.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is an electric circuit diagram,
2 is a vertical cross-sectional side view of a main part of the refrigerator, FIG. 3 is a perspective view of a thawing plate portion, and FIG. 4 is a diagram for explaining an upper limit temperature reference value and a lower limit temperature reference value of each temperature determination circuit, Fifth
FIG. 6 is a diagram showing the output operation of the timer circuit, and FIG. 6 is a diagram showing the temperature control characteristics and the temperature change of the object to be defrosted. In the figure, 3 is a thaw chamber, 8 is a thaw plate, 9 is a heater, 10 is a temperature sensor, 11 is a fan, 12 is a fan drive motor, 13 is a heater drive control circuit, 14 is a temperature detection circuit, 15, 16 and 17 Is a temperature judgment circuit, 26 is a decompression set / reset switch, 28, 2
9 and 30 are flip-flop circuits, 33 is a timer circuit, 34
Is a relay coil for connecting and disconnecting the heater, and 37 is a relay coil for connecting and disconnecting the fan drive motor.

Claims (1)

[Claims] 1. A heater for heating an object to be thawed contained in a thaw chamber, a temperature sensor for detecting the temperature of the object to be thawed, and a temperature detection value based on the temperature sensor raised to an upper limit temperature reference value. A heater drive control circuit for energizing the heater to drive and control the heater when the heater is cut off and the temperature drops to the lower limit temperature reference value. A timer that has a plurality of temperature determination circuits with different values and lower limit temperature reference values, and that activates the plurality of temperature determination circuits in descending order of the upper limit temperature reference value and the lower limit temperature reference value with the passage of time after the start of defrosting. A decompressing device comprising a circuit.