JPH0213774A - Frosting/defrosting detecting device and refrigerator - Google Patents

Abstract

PURPOSE:To permit the outputting of a frosting confirmation signal and a defrosting confirmation signal with a correct timing by a method wherein one set of air capacitor is employed to discriminate the confirmation of frosting from the confirmation of defrosting utilizing different phenomena generated in the air capacitor. CONSTITUTION:When the adhering amount of frost 41 to the surface of a refrigerant circulation pipe 17 is increased, the electrostatic capacity of an air capacitor 27 is increased and the oscillating frequency of an oscillating circuit 29 is reduced. A judging circuit 30 responds oscillating frequency at that time and rises up outputting signals P1, P2 while outputting a frosting confirmation signal. Then, precooling is effected for a given period of time T1 and a compressor 1 as well as fan are stopped while conductions of a glass tube heater 15 and a vacuum heater 16 are started. When the melting of the frost 41 is advanced, a pool 42 contacts with an electrode plate 22 to short-circuit the refrigerant circulation pipe 17 and the electrode plate 22 electrically and the oscillating operation of an oscillating circuit 29 is stopped. As a result, outputting signals P1, P2 rise up and a defrosting confirmation signal is outputted.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a frosting/defrosting detection device and a refrigerator.

(Prior Art) As is well known, a refrigerator is provided with a cooler (evaporator) inside the refrigerator, and at least a compressor, a radiator (condenser), an expansion mechanism, and the above-mentioned cooler.

It is equipped with a refrigeration cycle that circulates in the path of the compressor. In such a refrigerator, the surface of the cooler is kept at the lowest temperature inside the refrigerator.

Therefore, water vapor generated from foods stored in the refrigerator becomes frost and adheres to the surface of the cooler. If the amount of frost on the surface of the cooler increases, the cooling efficiency will drop significantly. For this reason, conventional refrigerators are equipped with a detection device that detects the amount of frost on the surface of the cooler, and when a certain amount of frost is detected, the compressor stops operating and is cooled using a heating source. The container is heated to defrost it.

By the way, how do you perform this kind of defrosting operation?

A frost/defrost detection device is required that sends a signal when the amount of frost on the surface of the cooler reaches a certain level and also sends a signal when defrosting is completed. Conventionally, this frost/defrost detection device has a pair of electrodes facing each other so that one electrode has the same temperature as the surface temperature of the cooler, and depending on the amount of frost on one electrode, the temperature between both electrodes is Two types are considered: a capacitive type that utilizes the phenomenon in which capacitance changes, and a conductive type that utilizes the fact that a pair of electrodes becomes electrically conductive due to frost formation.

However, the conventional frost formation/defrost detection device configured as described above has the following problem. In other words, when the amount of frost exceeds a certain value.

Since the capacitance between the two electrodes changes or becomes conductive, the timing to switch to defrosting operation can be detected relatively well. but.

When water generated during defrosting operation remains between both electrodes, the @frost/defrost detection device outputs an output signal that is almost the same as at the start of defrosting, even though defrosting has already finished. Sent out. For this reason, there was a problem that the timing to stop the defrosting operation could not be accurately detected. Therefore, in order to solve this problem, a temperature detection element such as a thermistor is installed near the frosting/defrosting detection device 9, and it is determined that defrosting has finished when the temperature in the vicinity exceeds a certain value. A method is being considered in which the refrigeration operation is restarted. However, if this is done, an extra circuit, that is, a circuit for detecting temperature, must be specially incorporated, which is unavoidable in terms of cost and construction.

(Problem to be solved by the invention) As mentioned above, with conventional frost formation/defrost detection devices.

It is not possible to clearly know when defrosting has finished.

As a result, there is a risk that the defrosting operation will be carried out for a longer period than necessary, and in order to prevent this, there is a problem that a separate circuit must be specifically installed.

Therefore, the present invention can be achieved without complicating the configuration.

A frosting system that can reliably send out a defrost confirmation signal when a certain amount of frost has formed, and can also reliably send out a defrost confirmation signal to that effect when defrosting is complete.・The objective is to provide a defrost detection device and a refrigerator that can be operated efficiently using the defrost detection device.

[Configuration of the Invention (Means for Solving the Problems) The frosting/defrosting detection device according to the present invention has a first surface in which one surface is in contact with air and the other surface is in direct or indirect contact with a refrigerant. and the first electrode, the first electrode is disposed opposite to the first electrode in a relationship such that at least a part of the natural fall channel extending in a direction non-parallel to the direction of gravity is formed between the electrode and the first electrode. a second electrode forming an air capacitor with the electrode;
When the capacitance of the air capacitor formed between the second electrode and the first electrode exceeds a certain value, a frost formation confirmation signal is sent and the insulation level of the air capacitor is set to a certain value. and signal sending means for sending out a defrosting confirmation signal when the defrosting temperature drops below.

In addition, the refrigerator according to the present invention has the above-mentioned relationship in which a natural fall passage extending in a direction non-parallel to the direction of gravity can be formed at least in part between the refrigerator and the refrigerant flow pipe of the cooler that cools the inside of the refrigerator. an electrode that is disposed opposite to the refrigerant flow pipe and forms an air condenser with the refrigerant flow pipe; Signal sending means for sending out a frosting confirmation signal when the insulation level of the air capacitor exceeds a certain value and sending out a defrosting confirmation signal when the insulation level of the air capacitor falls below a certain value; and means for controlling the compressor and heating source to perform a defrosting operation.

(Function) When frost forms on the surface of the first electrode or refrigerant flow pipe, the gap between the two electrodes forming the air condenser narrows in inverse proportion to the amount of frost formed.

As the gap between the electrodes narrows, the capacitance of the air capacitor increases. When the value of this capacitance exceeds a certain value, a frost formation confirmation signal is sent out from the signal sending means.

Now, if the defrosting operation is started based on this frost formation confirmation signal, the frost adhering to the first electrode or the refrigerant flow pipe will start to melt. As this dissolution progresses, water droplets generated by the dissolution move downward. in this case.

Since at least a portion of the natural fall channel extending in a direction non-parallel to the direction of gravity is formed between the two electrodes, the moving speed of water in this channel is slow.

Therefore, in the flow path, water droplets move while contacting the picture electrode, and this contact causes a gap between the two electrodes.

This is called a short circuit. Therefore, the air condenser is
This results in what is called a poor insulation condition. in this way.

When the air capacitor becomes insulated, a defrosting confirmation signal is sent from the signal sending means, and the defrosting operation is stopped. In other words, in this frost formation/defrost detection device, frost detection uses the phenomenon in which the capacitance of the air capacitor changes due to frost formation, and defrost detection uses the phenomenon that the capacitance of the air capacitor changes due to frost formation. It takes advantage of the phenomenon. Both phenomena are completely different and therefore easy to distinguish. Therefore, it is possible to accurately know when defrosting starts and when defrosting ends. Therefore, a refrigerator incorporating this frosting/defrosting detection device can operate efficiently.

(Example) An embodiment will be described below with reference to one drawing.

Fig. 1 shows a refrigeration cycle system of an electric refrigerator incorporating a frost formation/defrost detection device according to an embodiment, and Fig. 2 shows a schematic arrangement of each component of the refrigerator. has been done.

In FIG. 1, 1 indicates a compressor. The refrigerant gas compressed by the compressor 1 is heated by the refrigerant gas in the compressor 1 after passing through the pipe 3 that heats the defrosting water tray 2, and then sent to the radiator (condenser) 4. I was guided. The refrigerant liquefied by the radiator 4 is then transferred to the clean pipe 5. Dryer 6, differential pressure valve 7. Main capillary tube 8
．． First cooler (evaporator) 1 for cooling cooling plate 9
0, intermediate capillary tube 11. Second cooler (evaporator)12. Accumulator 13. It is guided to the suction port of the compressor 1 via the check valve 14. That is, this refrigeration cycle system is similar to a known one built into an electric refrigerator. The cooling plate 9 is arranged horizontally in the freezing chamber and is cooled by the first cooler 10.

Further, the second cooler 12 is arranged above the cooling plate 9 with a partition wall interposed therebetween. The air inside the refrigerator is controlled by a fan (not shown) so as to circulate while contacting the second cooler 12. Further, a glass tube heater 15 is attached to the cooling plate 9.

Further, the accumulator 13 is also provided with an accumulator heater 16 for selectively heating the accumulator 13.

As shown in FIG.
An electrode plate 22 constituting a part of 1 is arranged. As shown in FIGS. 4 and 5, this electrode plate 22 is placed near the upper surface of a substantially horizontal portion of the refrigerant flow pipe 17, that is, a portion extending non-parallel to the direction of gravity, and between the above upper surface. It is formed of semi-cylindrical metal plates arranged concentrically and facing each other with an interval 23 of 3 to 5 m. This electrode plate 2
2, both ends thereof are insulating plates 24a.

It is fixed to the refrigerant flow pipe 17 via 24b.

That is, both ends of the electrode plate 22 are insulating plates 24a and 24b.
The insulating plates 24a and 24b are fastened to the outer peripheral surface of the refrigerant flow pipe 17 by metal screws 25a and 25b that are attached to these plates with a phase difference of 180 degrees. . One ends of sheathed lead wires 26a and 26b are connected to the screw 25a and the electrode plate 22. As can be seen from the above configuration, the refrigerant,
The outer peripheral surface of the flow pipe 17 and the electrode plate 22 formed in a semi-cylindrical shape have a gap such that a natural fall channel extending in a direction non-parallel to the direction of gravity is formed at least in part. This forms an air condenser 27.

The other ends of the lead wires 26a, 26 are connected to a defrosting control device 28 shown in FIG. This defrosting control device 28 includes an oscillation circuit 29 and an oscillation circuit 2 as shown in FIG.
The heater control circuit 31 is comprised of a determination circuit 30 that operates based on one output, and a heater control circuit 31 that operates based on the output of this determination circuit 30. The oscillation circuit 29 has an OP amplifier 32 and an OP
The other end of the lead wires 26a and 26b, that is, the air capacitor 27 is interposed in the feedback circuit of the OP amplifier 32, and a resistor 34 is interposed in the feedback circuit from the OP amplifier 33 to the OP amplifier 32. let me,
It is configured to oscillate at an oscillation frequency determined by the value of the resistor 34 and the capacitance of the air capacitor 27.

On the other hand, the 1 determination circuit 30.

When the oscillation frequency of the oscillation circuit 29 falls below a certain predetermined value, the output signal p1. Launch p2.

When the oscillation circuit 29 stops oscillating, the output signal P 1 +
It is configured to bring down P2. and.

The output signal P1 is given to the heater control circuit 31.

In addition, the output signal P2 turns on the compressor 1 according to the temperature inside the refrigerator.
It is given to the control device 35 for off-control.

When the output signal P1 rises, the heater control circuit 31 controls the glass tube heater 15 and the accumulation heater 16 described above from a certain period T1 after the rise of the output signal P1.
Start energizing. and.

When the output signal P1 falls, the power supply to each of the heaters is stopped. Further, when the output signal P2 rises, the control device 35 forcibly operates the compressor 1 and the fan for a certain period T1 even if an off control signal is introduced from the internal temperature detection system at this point, After that, the operation of the compressor 1 and the fan is stopped. Then, when the output signal P2 falls, the operation of the compressor 1 is restarted at the time when the output signal P2 falls, and the fan is started to be driven after a certain period of time T2 has elapsed.

With such a configuration, the second cooler 1
When the amount of frost on the surface of No. 2 increases, the following operation occurs. That is, at the start of the refrigeration operation, no frost is formed on the surface of the second cooler 12, that is, the surface of the refrigerant flow pipe 17. therefore.

As shown in FIG. 8(a), there is no frost between the refrigerant flow pipe 17 and the electrode plate 22 either. At this time, it is assumed that the capacitance of the air capacitor 27 is, for example, 180 (PF), as shown in FIG. The oscillation circuit 29 oscillates at a frequency determined by the capacitance of the air capacitor 27 at that time.

After a certain period of time has elapsed from the start of operation, moisture in the refrigerator forms frost 41 on the surface of the refrigerant flow pipe 17, as shown in FIG. 8(b). As a result.

The gap length between the refrigerant flow pipe 17 and the electrode plate 22 becomes narrower, and the capacitance of the air capacitor 27 increases as shown in FIG. As the capacitance of the air capacitor 27 increases, the oscillation frequency of the oscillation circuit 29 also decreases.

As shown in FIG. 8(c), as the amount of frost 41 attached further increases, the capacitance of the air capacitor 27 further increases. Therefore, the oscillation frequency of the single oscillation circuit 29 also becomes low. Then, when the capacitance of the air capacitor 27 increases to, for example, 200 (PI'), the 2 determination circuit 30 raises the output signals P, . . . P2 in response to the oscillation frequency at that time. In other words, the determination circuit 30 sends out a frost formation confirmation signal.

In this way, the output signal P 1 +P2 from the 2 determination circuit 30
When T is output, as shown in FIG.
Only one pre-cool will be held. next.

The compressor 1 and the fan are stopped, and the glass tube heater 15 and the accumulation heater 16 are started to be energized. By this energization.

The frost 41 adhering to the surface of the cooler 9 and the surface of the refrigerant flow pipe 17 of the second cooler 12 begins to melt. In this case, the following phenomenon occurs between the refrigerant flow pipe 17 and the electrode plate 22. Namely.

A portion of the refrigerant flow pipe 17 facing the electrode plate 22 extends substantially horizontally, and the electrode plate 22 faces the upper surface of the refrigerant flow pipe 17 concentrically. Therefore, on the surface of the refrigerant flow pipe 17 facing the electrode plate 22,
When the frost, especially on the top edge, melts, the generated water droplets slowly move horizontally. However, at this point, it does not flow down in the direction of gravity due to surface tension. Therefore, when the water generated by melting the frost adhering to the uppermost end moves horizontally, the refrigerant flow pipe 17
A water puddle is formed on the circumferential surface of the electrode plate 22 except for the vicinity of the top end, and this puddle is sufficiently close to the electrode plate 22 . When the water pool approaches the electrode plate 22 sufficiently in this way, the capacitance of the air capacitor 27 increases rapidly. As the frost 41 melts further, the above-mentioned water puddle grows and eventually falls.
2, the water puddle 42 comes into contact with the electrode plate 22 before falling, as shown in FIG. 8(d). When the water puddle 42 contacts the electrode plate 22, the refrigerant flow pipe 17 and the electrode plate 22 are electrically short-circuited by the water puddle 42, and the air condenser 27
The capacitor no longer functions as a capacitor and becomes equivalent to dielectric breakdown. When the air capacitor 27 enters a dielectric breakdown state, the eight oscillation circuit 29 stops its oscillation operation. As a result, the sending of the output signals P1 and P2 from the 1 determination circuit 30 is stopped. That is, the output signal p1. p2 falls and a defrost confirmation signal is sent.

Signal P1. When P2 falls, the glass tube heater 15.
The power supply to the accumulation heater 16 is stopped, and the operation of the compressor 1 is restarted. Then, after a certain period of time T2 has elapsed, the operation of the fan is restarted and the operation shifts to steady operation. Even after the operation of the compressor 1 is restarted, the temperature is maintained at a high temperature for a certain period due to thermal inertia, so water droplets on the surface of the refrigerant flow pipe 17 fall or evaporate during this period. therefore.

Good defrosting will occur here. In addition.

During defrosting, it is difficult to completely remove water droplets from the surface of the refrigerant flow pipe 17, and as shown in FIG. 8(e), water droplets remain slightly attached even after defrosting. These water droplets gradually freeze. Therefore, air condenser 27
The capacitance is close to that of a frost-free state, and the defrost control circuit 28 will not malfunction due to the few remaining water droplets.

In this way, the detection of frost formation utilizes the capacitance of the air capacitor 27, and the detection of the end of defrosting utilizes the poor insulation of the air capacitor 27.

Since both phenomena are very different, it is easy to distinguish between them.

Therefore, frost formation and the end of defrosting can be reliably detected with a simple circuit like the embodiment. Therefore, it is possible to prevent the defrosting operation from being performed for an unnecessarily long time.
It can contribute to realizing efficient operation.

In the embodiment described above, a part of the refrigerant flow pipe 17 also serves as one electrode of the air condenser 27, but an electrode plate cooled to approximately the same temperature as the refrigerant flow pipe serves as one electrode of the air condenser 27. may be configured. Further, the gap between the air condensers may be any gap that can at least partially form a natural falling flow path extending in a direction non-parallel to the direction of gravity.

[Effects of the Invention] As detailed above, according to the frosting/defrosting detection device according to the present invention, one air condenser is used.

Since frost formation confirmation and defrost confirmation discrimination are performed using different phenomena that occur in the air condenser,
Identification can be facilitated, and as a result, the frosting confirmation signal and the defrosting confirmation signal can be sent out at accurate timing without complicating the configuration. Furthermore, according to the refrigerator according to the present invention, the defrosting operation is performed by incorporating the above-mentioned frosting/defrosting detection device, so that it is possible to prevent the defrosting operation from becoming longer than necessary, and to improve efficiency. Achieves good driving performance.

[Brief explanation of the drawing]

Fig. 1 is a refrigeration cycle system diagram of the refrigerator according to the embodiment, Fig. 2 is a schematic layout diagram of each element constituting the refrigeration cycle system, and Fig. 3 is an air condenser that is part of the frosting/defrosting detection device. Figure 4 is an external view of the air condenser, Figure 5 is a view taken along the line A-A in Figure 4, and Figure 7 is the remainder of the frosting/defrosting detection device. The configuration diagram of the defrosting control device, which is the part shown in Figures 7 and 8, shows the frost formation and
FIG. 9 is a diagram for explaining the operation of the defrosting detection device, and FIG. 9 is a diagram for explaining the operation mode during defrosting operation of the refrigerator according to the embodiment. 1...Compressor, 4...Radiator (condenser), 8...
Main capillary tube (expansion mechanism), 9...Cooling plate. DESCRIPTION OF SYMBOLS 10... First cooler (evaporator), 11... Intermediate capillary tube (expansion mechanism), 12... Second cooler (evaporator), 15... Glass tube heater, 16...・
・Accumulation heater, 17... Refrigerant flow pipe, 21
...frost formation/defrost detection device, 22...electrode plate, 27.
...Air condenser, 28...Defrosting control device, 29.
... Oscillation circuit, 30... Judgment circuit, 3]... Heater control circuit. 41...Frost, 42...Water drops. Applicant's representative Patent attorney Takehiko Suzue Figure 3 Figure 1- Figure 6 (a) (bXCXd) (e)
Q Figure 7

Claims (4)

[Claims] (1) A first electrode whose one surface is in contact with the air and the other surface is in direct or indirect contact with the refrigerant, and a natural structure extending in a direction non-parallel to the direction of gravity between the first electrode and the first electrode. a second electrode that is disposed opposite to the first electrode in a relationship capable of forming at least a portion of a falling flow path, and that forms an air condenser with the first electrode; A frost formation confirmation signal is sent when the capacitance of the air capacitor formed between the air capacitor and the electrode exceeds a certain value, and defrosting is confirmed when the insulation level of the air capacitor falls below a certain value. 1. A frosting/defrosting detection device comprising a signal sending means for sending a signal. (2) The first electrode is formed by a part of a cylindrical refrigerant flow pipe, and the second electrode is arranged concentrically with the refrigerant flow pipe on the outside of the refrigerant flow pipe. 2. The frost formation/defrost detection device according to claim 1, wherein the frost formation/defrost detection device is formed by a semi-cylindrical metal plate arranged in the. (3) The signal sending means includes an oscillation circuit that performs an oscillation operation at a frequency corresponding to the capacity of the air capacitor and stops the oscillation operation when the insulation level of the air capacitor drops below a certain level; The frosting/defrosting detection device according to claim 1, further comprising a circuit that sends out a frosting confirmation signal when the oscillation frequency is outside a predetermined range and sends out a defrosting confirmation signal when the oscillation operation stops. . (4) A cooler is provided to cool the inside of the refrigerator, and at least a compressor, a radiator, an expansion mechanism, the cooler,
In a refrigerator equipped with a refrigeration cycle that circulates in the path of the compressor, and also equipped with a heating source that selectively heats the cooler, the refrigerator has a refrigerant flow pipe that is located between the cooler and the refrigerant flow pipe that is non-parallel to the direction of gravity. an electrode that is disposed opposite to the refrigerant flow pipe in a relationship capable of forming at least a portion of a natural fall flow path extending in the direction, and that forms an air condenser with the refrigerant flow pipe; this electrode and the refrigerant flow pipe; A frosting confirmation signal is sent when the capacitance of the air capacitor formed between the air capacitor and 1. A refrigerator comprising: a signal transmitting means; and a means for controlling the compressor and the heating source to perform a defrosting operation in accordance with the output signal of the signal transmitting means.