JP2000074546A - Defrosting control device for refrigerating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defrosting control device in which a completion time of defrosting operation is made to be most appropriate one during hot gas defrosting operation, defrosting of an evaporator is performed positively and at the same time an increasing in temperature of a freezer is restricted minimum. SOLUTION: A defrosting control device is comprised of a temperature measuring means 31 for measuring a temperature related to a temperature of refrigerant at an outlet of an evaporator 12, and an electrical resistance variable means 32 in which an electrical resistance value is varied due to adhesion of frost at the evaporator 12. After starting the hot gas defrosting operation, a temperature related to the temperature of refrigerant at the outlet becomes more than a predetermined temperature and when the electrical resistance value becomes a predetermined resistance value, the hot gas defrosting operation is released.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting control device for a refrigerator, and more particularly to a hot gas defrosting device in which high-temperature refrigerant gas (hot gas) flows into an evaporator to perform defrosting. The present invention relates to a defrost control device for optimizing a frost operation end time.

[0002]

2. Description of the Related Art Conventionally, in defrosting control of a refrigerator in a refrigerator car or the like, generally, hot gas defrosting is performed in which a high-temperature refrigerant gas (hot gas) is sent to an evaporator by bypassing a condenser. Frost is employed. In this hot gas defrosting, normally, when the refrigerant temperature at the evaporator outlet rises to a preset defrosting release temperature (usually 3 ° C.), this is sensed by a temperature sensor and the hot gas defrosting is released. ing.

[0003]

However, according to the study of the present inventor, the defrosting speed in the evaporator varies depending on the rotational speed of the vehicle engine for driving the compressor, the outside temperature, and the like. I do. Therefore, even when the refrigerant temperature at the outlet of the evaporator rises to the defrost release temperature of about 3 ° C. and the hot gas defrost is released, the frost does not partially melt and remains on the evaporator surface. Sometimes. In this case, there is a problem that the defrosting of the evaporator becomes insufficient and the refrigeration capacity cannot be sufficiently restored.

In order to solve this problem, it is conceivable to take measures to sufficiently defrost the evaporator by setting a high defrost release temperature at which hot gas defrost is released. However, in this case, the time for performing the hot gas defrosting is long, and in the hot gas defrosting, since the defrosting is performed using the high-temperature refrigerant gas, the heat during the defrosting causes the temperature inside the freezer compartment to decrease. Is excessively raised.

[0005] In view of the above, the present invention optimizes the defrosting operation end time in hot gas defrosting, thereby reliably performing defrosting of the evaporator and increasing the internal temperature of the refrigerator. It is an object of the present invention to provide a defrosting control device that minimizes defrosting.

[0006]

In order to solve the above-mentioned problems, an electric resistance variable means (32) is provided at a portion of the evaporator (12) where frost adheres, and a change in electric resistance value (R) due to frost formation. May be measured to determine whether frost is actually attached to the evaporator (12) and determine the end time of the defrosting operation. However, in this case, since the frost formation state can be detected only in the portion where the electric resistance variable means (31) is arranged in the entire evaporator (12), if the frost in this portion melts quickly, It is determined that the entire evaporator (12) has been defrosted, and the end time of the defrosting operation cannot be properly determined.

Therefore, according to the first aspect of the present invention, a temperature measuring means (31) for measuring a temperature (T) related to the outlet refrigerant temperature of the evaporator (12), and at least one electrode (3).
2a) is disposed with a gap (h) provided so as to oppose a portion of the evaporator (12) to which frost adheres, and the electric resistance (R) changes due to the adhesion of frost to the evaporator (12). A variable means (32), after the start of hot gas defrosting, the temperature (T) related to the outlet refrigerant temperature becomes equal to or higher than a predetermined temperature (Te), and the electric resistance value (R) is set to a predetermined resistance value (R).
It is characterized in that hot gas defrosting is released when the condition e) is reached.

Accordingly, the temperature measuring means (31) determines that the temperature of the entire evaporator (12) has risen to a temperature higher than the temperature at which the frost melts (defrost release temperature). By 32), it can be detected whether or not frost actually remains in the evaporator (12). That is, the evaporator outlet refrigerant temperature (T) of the temperature measuring means (31)
Is higher than the defrost release temperature (Te), the evaporator (1) is controlled by the electric resistance value R of the electric resistance variable means (32).
2) If it is determined that frost remains on the surface, the defrost operation is continued to perform the defrost reliably.

Then, the evaporator outlet refrigerant temperature (T) becomes higher than the defrost release temperature (Te) and the electric resistance value (R)
Is released when the resistance value reaches a predetermined resistance value (Re).
In this way, by combining the electric resistance value (R) with the evaporator outlet refrigerant temperature (T), it is possible to appropriately determine the end time of the defrosting operation before the internal temperature rises more than necessary, and the evaporator ( The defrosting of 12) can be reliably performed, and the rise in the internal temperature can be suppressed to a minimum.

[0010] Further, the invention according to claim 2 is characterized in that the electric resistance measuring means (32) is arranged on the refrigerant pipe (14) outlet side in the evaporator (12). During hot gas defrosting, the temperature of the refrigerant pipe outlet side rises most slowly in the entire evaporator (12), so that frost remains at the refrigerant pipe outlet side until the latest.

Therefore, by detecting the state of frost on the outlet side of the refrigerant pipe (14) of the evaporator (12) by the electric resistance measuring means (32), it is possible to more appropriately determine the defrosting operation end time. it can. According to the third aspect of the present invention, the temperature measuring means (31) and the electric resistance measuring means (3) are provided.
2) is characterized in that it is arranged on the windward side of the evaporator (12).

On the windward side of the evaporator (12), the air inside the refrigerator, which contains a large amount of water, comes into contact first, and the most frost adheres to the entire evaporator (12). Therefore, the evaporator outlet refrigerant temperature () on the windward side of the evaporator is measured by the temperature measuring means (31), and the electric resistance variable means (32) is measured.
By detecting the state of frost on the windward side of the evaporator,
The end time of the defrosting operation can be more appropriately determined.

The electric resistance varying means (32) of the defrost control device according to the present invention is characterized in that the frost adheres to the evaporator (12) to cause the electrode (32a) to evaporate. The electric resistance value (R) between the metal surface of the evaporator (12) and the metal surface of the evaporator (12) may be changed. Piping (1
4) It can be a fin (12b) joined to.

[0014] The invention according to claim 6 provides the electrode (32)
In (a), a heating means (40) is provided near the tip of the evaporator (12) on the side opposite to the portion to which frost adheres, and the heating means (40) melts the frost near the tip of the electrode (32a). It is characterized by: Thereby, when the frost is formed on the evaporator (12) and the frost reaches the electrode (32a), the frost near the tip of the electrode (32a) is melted and becomes water, so that the frost is more easily conducted. In addition, the electric resistance value (R) by the electric resistance variable means (32) can be more easily measured.

The reference numerals in parentheses of the above means indicate the correspondence with the specific means described in the embodiment described later.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. Figure 1
FIG. 2 shows a first embodiment in which the present invention is applied to a refrigerator for a freezing car. A freezing car 1 is provided with a freezing room (freezer) 2 at a rear portion of the cabin. For example, frozen products such as frozen foods are loaded. The freezer compartment 2 is provided with two opening / closing doors 4 and 5 for carrying a frozen product into the inside and for taking out the frozen product in the freezer compartment 2.
As shown in FIG. 1, a known refrigeration cycle device 3 is mounted on the refrigeration vehicle 1 at the front of the vehicle.

FIG. 2 shows a circuit configuration of the refrigeration cycle device 3 and a control device 6 for cycle control. The refrigeration cycle device 3 has a compressor 7 for compressing and discharging a refrigerant to a high temperature and a high pressure. Then, the gas refrigerant compressed to a high temperature and a high pressure by the compressor 7 is cooled and condensed by the condenser 9. A receiver 10 is provided at the outlet side of the condenser 9 to separate the refrigerant after condensation by the receiver 10 into a gas-phase refrigerant and a liquid-phase refrigerant, and store the liquid-phase refrigerant.

At the outlet side of the receiver 10, a pressure reducing device (temperature type expansion valve in this embodiment) 11 for reducing the pressure of the liquid-phase refrigerant from the receiver 10 is provided. Is evaporated in the evaporator 12. An evaporator 1 is provided between the evaporator 12 and the compressor 7.
An accumulator 13 is provided for storing the liquid-phase refrigerant among the refrigerants that have passed through the second refrigerant. These devices are connected by a refrigerant pipe 14.

The compressor 7 is driven by a vehicle driving engine (not shown) via a well-known electromagnetic clutch (power interrupting device) 15. When the driving force of the driving engine is transmitted to the compressor 7 and the compressor 7 is driven and the energization of the electromagnetic clutch 15 is cut off, the driving force from the running engine is cut off and the compressor 7 stops. I do.

An oil separator 8 is provided on the discharge side of the compressor 7 for separating oil for lubricating the compressor 7 from the refrigerant, which oil has passed through the compressor 7 together with the refrigerant. Is again circulated to the compressor 7 together with the refrigerant. In the refrigerating cycle device 3, the evaporator 1 is disposed on the discharge side of the compressor 7 and on the downstream side of the pressure reducing device 11.
2 is provided with a hot gas bypass passage 16 that directly communicates with the upstream side.
An electromagnetic valve (valve means) 17 for opening and closing the flow path is provided.

As shown in FIG. 1, the condenser 9 is installed at a position below the floor of the vehicle so as to easily receive the traveling wind of the vehicle. The traveling wind and the cooling air blown by the electric condensing fan 18 are provided. Thus, the internal refrigerant is cooled and condensed. The evaporator 12 cools the freezing compartment 2 by the latent heat of evaporation of the refrigerant, and is installed in an upper portion on the vehicle front side in the freezing compartment 2 as shown in FIG. First
The evaporator 12 in the embodiment is of a so-called plate fin tube type, in which a circular tubular refrigerant pipe 14 penetrates the laminated fins 12b, and both ends of the fins 12b in the refrigerant flow direction retain the shape of the evaporator 12. A thick side plate 12a is disposed on the side wall.

In the freezer compartment 2, an electric cooling fan 20 for blowing air toward the evaporator 12 is provided adjacent to the evaporator 12. The cooling fan 20 is
After sucking air in the refrigerator, passing through the evaporator 12 and cooling, the cooling air is blown into the freezing chamber 2 again.
Thereby, the entire inside of the freezing room 2 can be cooled with a uniform temperature distribution.

As shown in FIG. 3, the evaporator 12 has a thermistor 31 (temperature measuring means) for measuring the evaporator outlet refrigerant temperature T and a frost detection for detecting the state of frost on the evaporator 12. A sensor 32 (electric resistance variable means) is attached. The frost detection sensor 32 includes an electrode 32a. The thermistor 31 is connected to a control device 6 described later by lead wires 31a and 31b. The electrode 32a of the frost detection sensor 32 is connected to the control device 6 by a lead 32c, and the other lead 32d of the frost detection sensor 32 is connected to the side plate 12a.

Thermistor 31 and frost detection sensor 32
Is installed on the outlet side of the refrigerant pipe 14 of the evaporator 12 and on the windward side of the internal air of the evaporator 12 for a reason to be described later. As shown in FIG. 3, a sensor support 33 for fixing the thermistor 31 and the electrode 32 a is provided on the side plate 12 a on the refrigerant pipe 14 outlet side of the evaporator 12 with a screw 3.
3a. This sensor support 3
3 is made of metal.

The thermistor 31 is connected to the side plate 12a.
It is arranged in the sensor support 33 so as to be located above. The thermistor 31 is in contact with the side plate 12a and the sensor support 33 via an insulating member (not shown), and the lead wires 31a and 31b are in contact with the sensor support 33 via an insulating member (not shown). There is no conduction between them.

The electrode 32a is disposed so as to penetrate the side plate 12a from the sensor support 33 and face the fin 12b. At this time, the electrode 32a and the fin 12a
When the frost 35 attached to the fins 12b reaches a height h (for example, 2 mm) at which defrosting is required, the electrode 32
a Height h (2 mm above) so that frost 35 contacts the tip
Are provided. A lead wire 32c between the electrode 32a and the control device 6 comes into contact with the side plate 12a and the sensor support 33 via an insulating member (not shown), and is connected between the lead wire 32c and the side plate 12a and the sensor support 33. Does not conduct.

The side plate 1 of the evaporator 12 is used.
Since 2a, the refrigerant pipe 14, and the fin 12b are made of metal, there is conduction between the lead wire 32d and the fin 12b. When the frost is not formed on the evaporator 12, there is a gap h between the fin 12b and the electrode 32a, so that the fin 12b and the electrode 32a do not conduct with each other. At this time, the electric resistance value R between the fin 12b and the electrode 32a measured by the frost detection sensor 32 indicates infinity.

After the start of the freezing operation, when the frost adhering to the fins 12b reaches the height h where defrosting is required, the frost is removed from the electrode 32a.
And the fin 12b and the electrode 32a conduct through the frost. Since there is a correlation between the amount of frost and the electric resistance R as shown in FIG. 5, the electric resistance R gradually changes according to the amount of frost. Thus, the frost formation state on the evaporator 12 can be detected by measuring the electric resistance value R of the frost formation detection sensor 32.

In the freezer compartment 2, a refrigerator temperature sensor 22 for detecting the refrigerator temperature is provided. Control device 6
Is configured to include computer means such as a microcomputer, and to control the refrigeration cycle apparatus 3 by performing predetermined arithmetic processing pre-programmed based on an input signal from an input terminal. is there.

The input terminals of the control device 6 include the thermistor 31, the frost detection sensor 32, and the internal temperature sensor 22 described above.
Besides, a temperature setting device 23 for setting a set temperature in the freezer compartment, a refrigeration operation switch 25 for starting cooling of the freezer compartment 2
Etc. are connected. The temperature setter 23, the refrigeration operation switch 25, and the like are installed on a refrigerator operation panel in the cabin of the refrigerator car 1 and are manually operated by an occupant.
The temperature setter 23 is constituted by a variable resistor or the like, and the set temperature inside the refrigerator can be arbitrarily changed in a predetermined range, for example, in a range of $ 10C to $ 20C.

On the other hand, a drive circuit (not shown) for the electromagnetic clutch 15 and an electromagnetic valve 1 are connected to the output terminal of the control device 6.
7, a condensing fan 18, a cooling fan 20 and the like are connected. Next, the operation of the above configuration will be described. The control device 6 is configured to be supplied with electric power when an ignition switch (not shown) of a vehicle is turned on. When the occupant manually operates the refrigeration operation switch 25 in a state where the ignition switch is turned on, a signal for cooling the inside of the freezing room 2 is generated by the switch 25, and the control device 6 controls the freezing room. 2
Is automatically controlled so that the temperature in the inside becomes the set temperature (for example, $ 20 ° C.) set by the temperature setting device 23.

Specifically, when the refrigeration operation switch 25 is turned on, the control device 6 energizes the electromagnetic clutch 15 to connect the vehicle running engine and the compressor 7 to drive the compressor 7. (ON). Further, at this time, the control device 6
Starts the refrigeration cycle apparatus 3 in a normal refrigeration operation state by operating (ON) the condensing fan 18 and the cooling fan 20 to start cooling the freezing chamber 2.

Thereafter, when the cooling of the freezing room 2 proceeds and the freezing room temperature decreases to the set temperature (設定 20 ° C.), based on the detection signal of the freezing room temperature sensor 22, the control device 6 To the compressor 7, the compressor 7 is stopped (OFF), and the condensing fan 18 and the cooling fan 20 are stopped (OFF). Then, the cooling of the freezing compartment 2 is interrupted by the stop of the operation, and the temperature in the freezing compartment 2 is slightly higher than the set temperature, for example, # 1
When the temperature rises to 8 ° C., the compressor 7 is driven as described above, and the condensing fan 18 and the cooling fan 20 are driven.
Activate Thus, the compressor 7, the condensing fan 1
By intermittently operating the cooling fan 8 and the cooling fan 20 in accordance with the freezing room temperature, the freezing room temperature is maintained at the set temperature.

The solenoid valve 17 is always closed (OFF) except when hot gas defrosting described below is performed. By the way, as described above, in the freezing car 1, the freezing room temperature is extremely low, such as ─20 ° C., so that when the outside air containing moisture enters the freezing room 2 by frequent opening of the doors 4 and 5, the freezing is performed. Frost adheres to the vessel 12.
Due to the adhesion of the frost, the cooling capacity of the evaporator 12 is reduced. Therefore, in the refrigeration cycle apparatus 3, it is necessary to perform defrost control in order to remove frost attached to the evaporator 12.

Therefore, in the present embodiment, defrost control is performed according to the flowchart shown in FIG. In FIG.
Step 100 is a cooling operation start step.
The cooling operation is started by turning on the refrigeration operation switch 25. Next, after the start of the cooling operation, it is determined in step 101 whether or not the evaporator 12 needs to be defrosted as follows.

When no frost is formed on the fins 12b of the evaporator 12, there is a gap between the electrode 32a and the fins 12b.
Has an infinite value of electrical resistance R. When frost forms on the fins 12b, the frost 35 gradually increases from the fins 12b to the electrodes 32a.
And the fin 12b and the electrode 32a are electrically connected via frost.

Then, as shown in FIG. 5, the electric resistance R between the fin 12b and the electrode 31a conducted through the frost.
And the amount of frost, there is a correlation, and when the fin 12b is not frosted, the electric resistance value R indicating infinity is shown.
Changes gradually according to the amount of frost. That is, the fin 1
As the amount of frost on 2b increases, conduction between the fin 12b and the electrode 32a becomes easier, and the electric resistance R becomes smaller.

Therefore, in step 101, it is determined whether or not the electric resistance value R detected by the frost sensor 32 is equal to or less than a first predetermined resistance value Rs corresponding to the frost height h (2 mm above) that requires defrosting. . If the electrical resistance value R is larger than the first predetermined resistance value Rs, it is determined that the frost attached to the evaporator 12 has not reached the height h required for defrosting, and the defrosting operation is not started and cooling is not performed. Operation is continued. And, when the electric resistance value R is the first
When the resistance value becomes equal to or less than the predetermined resistance value Rs, the control device 6 generates a defrost start signal, and proceeds to step 102 to start a defrost operation.

As described above, by starting the defrosting based on the electric resistance value R, the defrosting is performed only when the frost is formed on the evaporator 12 as compared with the case where the defrosting is periodically started by the timer. It is possible to prevent unnecessary defrosting operation. In this step 102, the defrosting solenoid valve 17: O
N, condensing fan 18: OFF, cooling fan 20: O
FF is set, and the defrost mode by hot gas bypass is set. Thereby, the defrosting operation of the evaporator 12 by the hot gas bypass is started.

In hot gas defrosting, defrosting is performed with a high-temperature refrigerant gas. Therefore, when the defrosting operation is started, the temperature of the evaporator 12 rises, and the evaporator outlet refrigerant temperature T gradually rises.
Then, the frost adhering to the fins 12b is melted, and a gap is gradually formed between the fins 12b and the electrodes 32a, so that conduction between the fins 12b and the electrodes 32a is stopped, and the electric resistance value R shows infinity. become.

Therefore, in step 103, the evaporator outlet refrigerant temperature T is equal to or higher than the set temperature Te (for example, 3 ° C.) in order to determine whether to cancel the defrosting operation, and
It is determined whether the electric resistance value R of the electric resistance measuring means 32 is the second predetermined resistance value Re (infinity). Here, it is determined whether or not the temperature of the entire evaporator 12 has risen above the temperature at which the frost melts based on the evaporator outlet refrigerant temperature T, and the residual frost state in the evaporator 12 is detected based on the electric resistance value R.

Either one of the two conditions that the evaporator outlet refrigerant temperature T is equal to or higher than the set temperature Te (the above 3 ° C.) and the electric resistance value R is the second predetermined resistance value Re (infinity). If none of them is satisfied, it is determined that the frost adhering to the evaporator 12 is not completely melted.
Is not performed, and the defrosting operation of the evaporator 12 by the hot gas bypass in step 102 is continued.

When the evaporator outlet refrigerant temperature T rises above the set temperature Te (the above-mentioned 3 ° C.) and the electric resistance value R reaches the second predetermined resistance value Re (infinity), steps 102 to 103 are executed. To the defrosting solenoid valve 17
Is closed (OFF). The closing of the solenoid valve 17 stops the flow of the hot gas into the evaporator 12, thereby releasing the hot gas defrosting.

Then, the low-temperature and low-pressure gas-liquid two-phase refrigerant, which has been depressurized through the decompression device 11, is circulated to the evaporator 12, and the cooling action in the evaporator 12 is resumed, and the condensing fan 18 and The operation of the cooling fan 20 is resumed, and the operation returns to the normal freezing operation. According to the present embodiment, it is possible to appropriately determine the end time of the defrost operation in the defrost control device for the following reasons.

That is, when defrosting is released based only on the evaporator outlet refrigerant temperature T as in the prior art, even if the evaporator outlet refrigerant temperature T reaches the predetermined temperature Te, various factors cause the evaporator surface to defrost. In some cases, frost may remain, and in order to reliably perform defrosting, it is necessary to set the predetermined temperature Te to be high. In this case, the internal temperature of the refrigerator excessively increases.

The electric resistance R of the frost detection sensor 32
If the defrosting is released based only on the frost formation state, the frost formation state can be determined only at the portion of the entire evaporator 12 where the frost detection sensor 32 is disposed. However, there is a problem in that it is determined that defrost has been performed even if frost remains in other parts.

On the other hand, according to the present invention, it is determined by the thermistor 31 that the temperature of the entire evaporator 12 has risen to a temperature higher than the temperature at which the frost melts. It can be detected whether or not frost actually remains. Therefore, even if the evaporator outlet refrigerant temperature T rises above the predetermined temperature Te, if the electric resistance value R of the frost detection sensor 32 has not reached the predetermined resistance value Re, frost remains in the evaporator 12. It is determined that the defrosting operation has been performed, and the defrosting operation is continued without performing the defrosting operation. Then, the evaporator outlet refrigerant temperature T becomes equal to or higher than the predetermined temperature Te, and the electric resistance value R becomes equal to the predetermined resistance value R.
When it becomes e, the defrosting operation is canceled.

As described above, when the defrosting operation is canceled, the evaporator outlet refrigerant temperature T is determined by combining the evaporator outlet refrigerant temperature T with the electric resistance value R, as in the prior art.
In comparison with the case where the defrosting operation is canceled based only on the defrosting operation, the defrosting can be reliably performed at a lower defrosting cancellation temperature Te. Further, as described above, in the first embodiment,
The thermistor 31 and the frost detection sensor 32
2 is located on the outlet side of the refrigerant pipe and on the windward side of the air inside the refrigerator of the evaporator 12.

That is, at the time of hot gas defrosting, the hot gas is circulated inside the evaporator 12 and the temperature of the evaporator 12 is raised to melt the frost 35 attached to the evaporator 12. The hot gas gradually loses heat while circulating inside the evaporator 12, and the temperature at the refrigerant pipe outlet side in the entire evaporator 12 rises most slowly. Therefore, during hot gas defrosting, frost remains on the refrigerant pipe outlet side until the latest in the entire evaporator 12.

Further, since the windward side of the evaporator 12 first comes into contact with the air in the refrigerator containing a large amount of water, the evaporator 12 in the entire evaporator 12 during the freezing operation.
The windward side of No. 2 is the site where the frost adheres most. Therefore, even in the evaporator 12, the frost remains on the outlet side of the refrigerant pipe 14 and the windward side of the air in the refrigerator at the latest during the defrosting operation, so that the thermistor 31 and the frost formation detection sensor 32 are evaporated. By installing it on the outlet side of the refrigerant pipe 14 of the device 12 and on the windward side of the evaporator 12, it becomes possible to more appropriately determine the defrosting operation end time.

As described above, according to the present embodiment, it is possible to optimize the timing of ending the defrosting operation, prevent the residual frost state at the end of the defrosting operation, and ensure the defrosting of the evaporator 12. And the rise in the internal temperature can be minimized. (Second Embodiment) In the first embodiment, the fins 12b
Although the frost on the evaporator 12 is detected by measuring the electric resistance value R between the fin 12b and the electrode 32a, according to the experiments and studies by the present inventor, the frost simply adheres to the fin 12b. Therefore, if the frost only reaches the electrode 32a, the fins 12b
Between the electrode 32a and the frost detection sensor 3
It was confirmed that the measurement of the electric resistance value R by the method No. 2 was not easy in some cases.

Therefore, in the second embodiment, as shown in FIG. 6, an electric heater 35 is provided as a heating means for melting the frost in the vicinity of the side of the electrode 32a where the frost contacts. The electric heater 35 is operated periodically (for example, every hour) by a timer (not shown) to melt the frost near the electrode 32a. At this time, what is melted by the electric heater 35 is
There is only frost near the electrode 32a, and the water after melting does not flow out but stays there.

As a result, the frost in the vicinity of the electrode 32a is melted and turned into moisture, making it easier to conduct than the frost state, and the electric resistance R between the fin 12b and the electrode 32a can be easily measured. become. Note that other configurations and operations of the defrost control device according to the second embodiment are the same as those of the first embodiment, and a description thereof will be omitted. (Third Embodiment) In each of the above embodiments, the thermistor 31 is used.
Is installed on the side plate 12a of the evaporator 12 by the sensor support 33, and measures the temperature on the side plate 12a as the temperature related to the evaporator outlet refrigerant temperature.

On the other hand, in the third embodiment, as shown in FIG. 7, the thermistor 31 is disposed on the surface of the refrigerant pipe 14 immediately after the outlet of the evaporator 12 to measure the evaporator outlet refrigerant temperature T. I have. Even when the defrosting operation release timing is determined based on the evaporator outlet refrigerant temperature T measured in this way and the electric resistance value R measured in the same manner as in the first embodiment, the same result as in the first embodiment is obtained. Obtainable.

Note that other configurations and operations of the defrost control device according to the third embodiment are the same as those of the first embodiment, and thus description thereof is omitted. (Other Embodiments) In each of the above embodiments, the electric resistance R between the fin 12b, which is the metal surface of the evaporator 12, and the electrode 32a was measured. However, as shown in FIG.
Both a and 32b are arranged with a gap in opposition to the portion of the evaporator 12 where frost adheres, and the electric resistance value between these two electrodes 32a and 32b that are frosted and conducted by the frost is measured. However, as in the above embodiments, the evaporator 1
2 can be detected.

In each of the above embodiments, the frost detection sensor 32 detects the fin 12b of the evaporator 12 and the electrode 32a.
The frost on the evaporator 12 was detected by measuring the electric resistance R between the evaporator 12 and the evaporator 12 in the same manner as the above embodiment by measuring the voltage V instead of the electric resistance R. 12 can be detected. Further, in each of the above embodiments, the electrode 32a is arranged so as to face the fin 12b of the evaporator 12 to detect frost formation. However, the electrode 32a does not necessarily have to be arranged so as to face the fin 12b. If the frost adheres to the evaporator 12, it may be arranged, for example, so as to face the refrigerant pipe 14 of the evaporator 12.

In each of the above embodiments, the start of the hot gas defrosting operation is performed based on the change in the electric resistance value R of the frost detection sensor 32. However, the present invention is not limited to this.
May be started based on the change in the temperature T of the frost detection sensor 32.
May be started based on a combination of the changes in the temperature T, or may be started after a predetermined time has elapsed by the timer after the start of the freezing operation.

The present invention is not limited to the above embodiment, but can be variously modified, and can be widely applied to refrigerators for uses other than refrigeration vehicles.

[Brief description of the drawings]

FIG. 1 is a schematic installation diagram showing an entire configuration of a refrigerating car to which a first embodiment of the present invention is applied.

FIG. 2 is a refrigeration cycle diagram in the first embodiment.

FIG. 3 is an enlarged view of a thermistor and a frost detection sensor according to the first embodiment.

FIG. 4 is a flowchart of defrost control in the refrigeration cycle of FIG. 2;

FIG. 5 is a frost formation characteristic diagram showing a correlation between an electric resistance value, an evaporator outlet refrigerant temperature, and a frost formation amount.

FIG. 6 is an enlarged view of a thermistor and a frost detection sensor according to a second embodiment.

FIG. 7 is an enlarged view of a thermistor and a frost detection sensor according to a third embodiment.

FIG. 8 is an enlarged view of a thermistor and a frost detection sensor according to another embodiment.

[Explanation of symbols]

6 ... Control device, 12 ... Evaporator, 12a ... Side plate, 12b ... Fin, 14 ... Refrigerant pipe, 31 ... Thermistor (temperature measuring means), 32 ... Frosting detection sensor (electric resistance measuring means), 32a ... Electrode.

Claims (6)

[Claims] An evaporator (1) of a refrigeration cycle device (3).
A cooling room (2) is provided in which the room air cooled in 2) is blown by a cooling fan (20) and cooled, and is compressed to a high temperature and a high pressure by a compressor (7) of the refrigeration cycle device (3). A defrosting control device for a refrigerator that performs hot gas defrosting to defrost frost adhering to the evaporator (12) by flowing the separated gas refrigerant through the refrigerant pipe (14) into the evaporator (12). A temperature measuring means (31) for measuring a temperature (T) related to a refrigerant temperature at an outlet of the evaporator (12); and at least one electrode (32a) comprising the evaporator (12).
A gap (h) is provided so as to face a portion where frost adheres, and an electric resistance variable means (32) whose electric resistance value (R) changes due to the adhesion of frost to the evaporator (12). After the start of the hot gas defrosting, the temperature (T) related to the outlet refrigerant temperature becomes equal to or higher than a predetermined temperature (Te), and the electric resistance value (R) becomes a predetermined resistance value (Re).
A defrosting control device for a refrigerator, wherein the hot gas defrosting is released when the temperature becomes zero. 2. The defrosting control device for a refrigerator according to claim 1, wherein the electric resistance variable means (32) is arranged in a refrigerant outlet side region of the evaporator (12). . 3. The evaporator (12) according to claim 1, wherein the temperature measuring means (31) and the electric resistance variable means (32) are arranged on the windward side of the evaporator (12). Defrost control device for refrigerator. 4. The electric resistance variable means (32) is configured to cause the electrode (32a) to adhere to frost on an evaporator (12).
2. An electric resistance value (R) between a metal surface of the evaporator (12) and the metal surface of the evaporator (12) changes.
A defrosting control device for a refrigerator according to any one of claims 3 to 3. 5. The metal surface according to claim 1, wherein the metal surface is a fin (12b) joined to a refrigerant pipe (14) of the evaporator (12). A defrosting control device for a refrigerator according to the above. 6. The evaporator (1) of the electrode (32a).
A heating means (40) is provided near the tip on the side opposite to the part to which the frost adheres in 2), and the heating means (40) melts the frost near the tip of the electrode (32a). The defrosting control device for a refrigerator according to any one of claims 1 to 5.