JP4079564B2 - Refrigeration equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a refrigeration apparatus that uses a refrigerant mainly composed of hydrofluorocarbon to operate a compressor and cool a commodity storage.
[0002]
[Prior art]
A can vending machine that sells can beverages is provided with a product storage that can store various beverages, an evaporator is provided in the product storage, and a plurality of product storages are provided. The product can be cooled and stored by controlling the refrigerant solenoid valve connected to the inlet side of the evaporator provided in the product storage and the refrigeration cycle (compressor, temperature sensor, expansion valve, fan motor, etc.) Yes.
[0003]
Conventionally, in a refrigerating apparatus using CFC 12 or HCFC 22 as a refrigerant, a refrigerating machine oil such as mineral oil or alkylbenzene oil has been used for the compressor. Mineral oils and alkylbenzene oils are mutually soluble with CFC12 and HCFC22, so refrigeration oil does not stay excessively in the refrigeration cycle and is returned to the compressor, which has a high level of reliability and durability. A refrigeration system could be realized.
[0004]
However, since CFC12 and HCFC22 destroy the ozone layer when released into the atmosphere, refrigerants mainly composed of hydrofluorocarbons that are less likely to destroy the ozone layer have been used in refrigerators. If a refrigerating machine oil with almost no mutual solubility such as mineral oil or alkylbenzene oil is used for the refrigerant mainly composed of hydrofluorocarbon, the refrigerating machine oil discharged together with the refrigerant from the compressor may stay in the refrigerating cycle. is there. If the refrigerating machine oil stays in the refrigeration cycle, there is a problem that the oil level in the compressor is lowered to cause problems such as wear of sliding parts.
[0005]
Therefore, various methods have been tried in order to reliably return the refrigeration oil in the refrigeration apparatus using the refrigerant mainly composed of hydrofluorocarbon. The refrigerating machine oil discharged from the compressor has a low flow rate in an accumulator having a large cross-sectional area, and tends to stay with high viscosity in an evaporator having the lowest temperature. However, it has been confirmed that even if the refrigeration oil has a high viscosity and a low temperature, it moves along the inner surface of the refrigerant pipe and returns to the compressor if the refrigerant flow rate exceeds a certain level. For example, in Japanese Patent Laid-Open No. 7-174439, by setting the inner diameter of the refrigerant pipe constituting the refrigeration cycle to a predetermined value or less, the refrigerant flow rate is maintained at a certain level or more, and the refrigeration oil stays in the refrigeration cycle. Techniques for preventing this are disclosed.
[0006]
It is effective if the stroke volume of the compressor and the inner diameter of the refrigerant pipe can be configured so that the refrigerant flow rate becomes a certain level or more. However, for example, as in the above can vending machine that requires a wide variety of models. In addition, when the capacity ratio is about 3 to 6 times from the small capacity to the large capacity, the compressor can be used to obtain the refrigeration capacity for maintaining the temperature in the product storage at the set value. It is desirable to prepare several types of stroke volumes according to the internal volume of the product storage, and to configure the refrigerant pipes with several types of inner diameters according to the stroke volume of the compressor. However, the use of several types of inner diameters in accordance with the stroke volume of the compressor for the refrigerant pipe requires production equipment with the same number of kinds of inner diameter of the refrigerant pipe due to the structure of the condenser and evaporator currently used. , Productivity is greatly reduced, and the cost increases. Therefore, in order to minimize production costs, several types of stroke volume compressors that can obtain the minimum refrigerating capacity necessary to maintain the temperature in the product storage at the set value, and limited types of internal diameters It uses a combination of refrigerant piping and condenser, evaporator, and other parts.
[0007]
[Problems to be solved by the invention]
However, the refrigerant pipe uses a refrigerant pipe having an inner diameter capable of obtaining a refrigerant flow rate required for cooling a large-capacity product storage and obtaining a refrigerant flow rate higher than a certain level. For this reason, since the vending machine with a large product storage capacity uses a refrigerant pipe with an inner diameter that can obtain a refrigerant flow rate above a certain level, mineral oil or alkylbenzene can be used as a refrigerant mainly composed of hydrofluorocarbon. Even if refrigeration oil that has little mutual solubility such as system oil is used, the refrigeration oil will not stay in the refrigerant line, but a small-volume can vending machine uses a compressor with a small stroke volume. In some cases, the flow rate of the refrigerant flowing in the refrigerant pipe decreases and becomes less than the oil return limit refrigerant flow rate. If the refrigeration cycle is operated while the refrigerant flow rate is below the oil return limit refrigerant flow rate, the refrigeration oil will stay in the refrigerant pipeline, and the appropriate amount of refrigeration oil will not be returned to the compressor. In some cases, the oil level in the compressor is lowered to cause problems such as wear of the sliding portion. In general, various parts are arranged in the refrigeration cycle, and the cross-sectional area of the pipe through which the refrigerant flows changes in a complicated manner. For this reason, the malfunction that refrigeration oil stays in components (parts) with the largest cross-sectional area and refrigeration oil is not returned.
[0008]
The present invention has been made in order to solve the above-described problems, and uses a refrigerating machine oil having almost no mutual solubility such as mineral oil or alkylbenzene oil as a refrigerant mainly composed of hydrofluorocarbon, and stores products. In a refrigeration system that cools a refrigerator, a compressor with a stroke volume that can obtain the minimum refrigeration capacity required to maintain the temperature in the product storage of a small-capacity can vending machine at a set value, and a large-capacity product It is an object to prevent the refrigeration oil from staying in the refrigerant pipe when the refrigerant pipe having an inner diameter suitable for use in the can vending machine of the storage is used in combination.
[0009]
[Means for Solving the Problems]
The present invention according to claim 1 comprises a compressor, a condenser, an expansion valve whose valve opening degree can be adjusted, an evaporator, and a refrigerant pipe that connects these to form a closed circuit, and the compressor oil of the compressor In the steady operation of the cooling unit that executes a refrigeration cycle using a refrigerant having a low mutual solubility with the refrigerant and the cooling unit having a constant valve opening, the expansion valve is stationary for a predetermined time. A control unit that controls the valve opening of the expansion valve so as to have a valve opening different from that during operation, and varies the pressure of the refrigerant in the condenser and the evaporator, and the control unit includes: The valve of the expansion valve is set so that the expansion valve has a valve opening smaller than that during steady operation for a first time, and then the valve opening is larger than that during steady operation for a second time. The opening degree is controlled.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a configuration diagram of a refrigeration apparatus according to an embodiment of the present invention, which includes a compressor 1, a condenser 2, a dryer 3, an expansion valve 4, an evaporator 6, and a check valve 8 that function to change the flow rate of refrigerant. And an accumulator 9 and a refrigerant pipe 10 connecting them. The evaporator 6 is connected by piping and is provided in a commodity storage (not shown). Further, 11 is a condenser blower driven by a condenser fan motor 11M, and 12 is an evaporator blower driven by an evaporator fan motor 12M. Reference numeral 7 denotes a temperature sensor, for example, a thermistor, which detects the temperature in the product storage and outputs a detected temperature signal to the control unit 13 which will be described later. The refrigerant is mainly composed of hydrofluorocarbon, and the refrigerating machine oil is made of mineral oil or alkylbenzene oil that is not mutually soluble with hydrofluorocarbon. When the inside of the product storage is cooled, the refrigerant compressed by the compressor 1 is condensed by the condenser 2 together with the refrigerating machine oil, passes through the dryer 3 and the expansion valve 4, is vaporized by the evaporator 6, and is blower for the evaporator. The cool air circulates in the product storage by the operation of 12, and the product storage is cooled. The refrigerant that has passed through the evaporator 6 returns to the compressor 1 via the check valve 8 and the accumulator 9.
[0012]
FIG. 3 is a control block diagram of the refrigeration system of the refrigeration apparatus according to the embodiment of the present invention. The control unit 13 controls the compressor 1, the expansion valve 4, the refrigerant electromagnetic valve 5, the condenser fan motor 11M, and the evaporator fan motor 12M based on the ON / OFF signal of the start switch 14 and the detection signal of the temperature sensor 7. Yes. In the case of the configuration described in FIG. 1, the refrigerant solenoid valve 5 is not necessary.
[0013]
FIG. 4 is a time chart illustrating a first operation state of the refrigeration apparatus according to the embodiment . In the state where the start switch 14 is ON and the temperature in the product storage is equal to or higher than the cooling temperature set value, the temperature sensor 7 is ON and a detected temperature signal is output to the control unit 13. Based on this detected temperature signal, a control signal is output from the control unit 13, the compressor 1 is operated (ON), and the expansion valve 4 is opened at a normal valve opening. For this reason, the refrigerant compressed by the compressor 1 is condensed by the condenser 2 together with the refrigerating machine oil, passes through the expansion valve 4, is sent to the evaporator 6, and the inside of the product storage is cooled. When the time T1 is reached from this state, a control signal is output from the control unit 13 to the expansion valve 4, and the low-pressure side pressure of the expansion valve 4 is reduced by reducing the valve opening of the expansion valve 4. When time t1 elapses from time T1 and time T2 is reached, a control signal is output from the control unit 13, and by increasing the valve opening of the expansion valve 4, the refrigerant is accelerated by the reaction that has been delayed for time t1, As the flow rate rapidly increases, the refrigerant flow rate increases, and the refrigerant flows in the pipe line of the evaporator 6 at a high speed. When time t2 elapses from time T2 and time T3 is reached, the expansion valve 4 is set to a normal valve opening.
[0014]
FIG. 5 is a time chart illustrating a second operation state of the refrigeration apparatus according to the embodiment . When the start switch 14 is ON and the temperature in the product storage is equal to or higher than the cooling temperature set value, when the time T4 comes from this state, a control signal is output from the control unit 13 to the expansion valve 4 to expand the expansion. By reducing the valve opening degree of the valve 4, the low pressure side pressure of the expansion valve 4 decreases. When time t3 elapses from time T4 and time T5 is reached, the expansion valve 4 is set to a normal valve opening, whereby the refrigerant is accelerated by the reaction that has been delayed for time t3, and the refrigerant flow rate increases, resulting in a large refrigerant flow rate. Therefore, the refrigerant flows in the pipe line of the evaporator 6 at a high speed.
[0015]
FIG. 6 is a time chart illustrating a third operation state of the refrigeration apparatus according to the embodiment . When the start switch 14 is ON and the temperature in the product storage is equal to or higher than the cooling temperature set value, when the time T6 is reached from this state, a control signal is output from the control unit 13 to the expansion valve 4 and the expansion is performed. Increasing the valve opening degree of the valve 4 increases the refrigerant flow rate, increases the refrigerant flow velocity, and the refrigerant flows in the pipe line of the evaporator 6 at high speed. When time t4 elapses from time T6 and time T7 is reached, the expansion valve 4 is set to a normal valve opening.
[0016]
FIG. 2 is a configuration diagram of a refrigeration apparatus according to a reference example in the case where a plurality of product storages are provided, and the same parts as those in FIG. A compressor 1, a condenser 2, a dryer 3, an expansion valve 4, a refrigerant electromagnetic valve 5, a plurality of evaporators 6, a check valve 8, an accumulator 9, and a refrigerant pipe 10 connecting these components. The evaporators 6 are connected in parallel, and the refrigerant solenoid valves 5 are connected in series on the inlet side of the evaporators 6, and are provided in different product storages (not shown). When the inside of the product storage is cooled, the refrigerant compressed by the compressor 1 is condensed by the condenser 2 together with the refrigerating machine oil, passes through the dryer 3 and the expansion valve 4, then passes through the refrigerant electromagnetic valve 5, and the evaporator 6. Then, the vapor is circulated by the operation of the blower 12 for the evaporator, and the inside of the product storage is cooled. The refrigerant that has passed through the evaporator 6 returns to the compressor 1 via the check valve 8 and the accumulator 9. Also in the reference example , the same effect as the embodiment can be obtained by controlling two or three of the refrigerant solenoid valves 5 simultaneously as shown in the time charts showing the first to third operating states.
[0017]
FIG. 7 is a time chart showing a fourth operation state of the refrigeration apparatus according to the reference example . When the start switch 14 is ON and the temperature in the product storage is equal to or higher than the cooling temperature set value, a control signal is output from the control unit 13 to the refrigerant solenoid valve 5 at time T8 from this state. The refrigerant solenoid valve 5 is fully closed (OFF) to stop the refrigerant flow. When time t5 elapses from time T8 and time T9 is reached, the refrigerant solenoid valve 5 is released (ON), whereby the refrigerant is accelerated by the reaction that has stopped at time t5, and the refrigerant flow rate suddenly increases, thereby increasing the refrigerant flow rate. Therefore, the refrigerant flows in the pipe line of the evaporator 6 at a high speed.
[0018]
By controlling the refrigeration cycle as described above, the refrigerant can flow at a high speed to the evaporator. As a result, the minimum refrigerating capacity required to maintain the temperature in the product storage of a small-capacity can vending machine using a refrigerating machine oil that is not mutually soluble with a refrigerant mainly composed of hydrofluorocarbon. Refrigerating machine oil stays in the refrigerant line for a long time even when used in combination with a stroke volume compressor capable of obtaining a high-capacity product storage can vending machine with an inner diameter suitable for use in a vending machine As a result, it is possible to prevent the oil from returning to the compressor from becoming insufficient and the oil level in the compressor from being lowered to cause problems such as wear of the sliding portion.
[0019]
The predetermined refrigeration cycle operation times t1 to t5 in the time charts showing the first to fourth operation states are times (for example, several seconds to several minutes) set in advance by grasping the oil return characteristic numerical value and taking into account the safety factor. Yes, the optimum time is determined in consideration of evaporative temperature change characteristics due to changes in the outside air temperature, compressor characteristics, refrigerant flow rate change characteristics due to the refrigerant pipe inner diameter, and the like. The predetermined times t1 to t5 are desirably as short as possible within a time range in which the refrigeration oil in the refrigerant pipe is reliably returned to the compressor. The can vending machine controls the refrigeration cycle to keep the temperature in the product storage box at an appropriate temperature of, for example, 1 to 5 ° C. If the predetermined time t1 to t5 is too long, 1 If it deviates from the temperature range of ˜5 ° C., it will not be possible to keep the commercial product (cooling load) at an appropriate temperature.
[0020]
Also, the interval at which the refrigerant pressure of the condenser 2 and the evaporator 6 is changed by changing the valve opening of the expansion valve 4 or opening and closing the refrigerant electromagnetic valve 5 is obtained by grasping the oil return characteristic value in advance. The time is set taking into account the rate (for example, several hours to several tens of hours), taking into account evaporative temperature change characteristics due to changes in outside air temperature, compressor characteristics, refrigerant flow rate change characteristics due to refrigerant pipe inner diameter, etc. To determine the optimal time.
[0021]
【The invention's effect】
As described above, according to the first aspect of the present invention, in the refrigeration apparatus that cools the commodity storage using the refrigerant mainly composed of hydrofluorocarbon and the refrigerating machine oil such as mineral oil or alkylbenzene oil. , Compressor, condenser, condenser blower that blows to condenser, expansion valve that changes the flow rate of refrigerant, evaporator provided in product storage, evaporator blower that works to send cool air of evaporator The valve opening of the expansion valve is set so that the expansion valve has a valve opening different from that during the normal operation for a predetermined time during the steady operation of the refrigerant pipe and the cooling unit having a constant valve opening. And a control unit for controlling, when the compressor and condenser blower are operated based on a signal from the control unit, the expansion valve is opened at a certain valve opening, and the product storage is cooled, the expansion valve The predetermined time After making the valve opening different from that during steady operation, the flow rate of the refrigerant is set to a certain level or more by changing the valve opening as a constant valve opening, so that there is no mutual solubility with the refrigerant mainly composed of hydrofluorocarbon. Even if the refrigeration oil is used, the refrigeration oil in the refrigerant pipe can be reliably returned to the compressor, so that the refrigeration oil does not stay in the refrigerant pipe.
[0022]
In addition, the expansion valve is set to a valve opening smaller than that during steady operation for a predetermined time, and then the change in the valve opening is further increased as the valve opening is larger than during steady operation, so that the flow rate of the refrigerant exceeds a certain level. This makes it possible to return the refrigerating machine oil in the refrigerant pipe line to the compressor more reliably even when using a refrigerating machine oil that is not mutually soluble with the refrigerant mainly composed of hydrofluorocarbon. There is no stagnation.
[0023]
Accordingly, the oil level of the compressor can be prevented from being lowered, the oil film of the sliding portion of the compressor can be prevented from being cut off, the refrigerating capacity can be prevented from being lowered, and the refrigeration system can be stably operated over a long period of time.
[0024]
In addition, the conventional refrigeration apparatus using the CFC 12 or HCFC 22 as a refrigerant can be modified to a refrigeration apparatus using a refrigerant mainly composed of hydrofluorocarbon with a minimum change.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a refrigeration apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a refrigeration apparatus according to a reference example when a plurality of commodity storages are provided.
FIG. 3 is a control block diagram of the refrigeration system of the refrigeration apparatus according to the embodiment of the present invention.
FIG. 4 is a time chart showing a first operation state of the refrigeration apparatus according to the embodiment .
FIG. 5 is a time chart showing a second operation state of the refrigeration apparatus according to the embodiment .
FIG. 6 is a time chart showing a third operation state of the refrigeration apparatus according to the embodiment .
FIG. 7 is a time chart showing a fourth operation state of the refrigeration apparatus according to the reference example .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Dryer 4 Expansion valve 5 Refrigerant solenoid valve 6 Evaporator 7 Temperature sensor 8 Check valve 9 Accumulator 10 Refrigerant line 11 Condenser fan 11M Condenser fan motor 12 Evaporator fan 12M Evaporator fan motor 13 Control part 14 Start switch

Claims (1)

  A refrigerant comprising a compressor, a condenser, an expansion valve whose valve opening can be adjusted, an evaporator, and a refrigerant pipe that connects these together to form a closed circuit, and that has a low mutual solubility with the refrigerating machine oil of the compressor. During the steady operation of the cooling unit that uses and executes the refrigeration cycle and the cooling unit with the expansion valve at a constant valve opening, the expansion valve has a valve opening that is different from that during steady operation for a predetermined time. And a control unit for controlling the valve opening degree of the expansion valve, and fluctuates the pressure of the refrigerant in the condenser and the evaporator, and the control unit keeps the expansion valve steady for a first time. The valve opening of the expansion valve is controlled so that the valve opening is smaller than that during operation, and then the expansion valve is made larger during the second time than during normal operation. Refrigeration equipment.

Images