JP2001272121A - Method of controlling two-stage compression refrigerating unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time required for attaining temperature stabilization of each part at the time of resuming operation, by enabling the adjustment of low pressure (evaporation temperature) and preventing a refrigerant from flowing into the low pressure side from high pressure side at stoppage of a compressor 12. SOLUTION: In a two-stage compression refrigerating unit 21 which constitutes a freezing cycle by connecting the two-stage compressive rotary compressor 12, a condenser, first and second electronic expansion valves 18 and 36, a middle cooler, a capillary 38, and an evaporator 40 by refrigerant pipes, the flow of a refrigerant to be supplied to the evaporator 40 is controlled by automatically adjusting the opening of a first electronic expansion valve provided on this side of the middle cooler and a second electronic expansion valve provided on this side of a capillary tube connected to the evaporator, based on each detection temperature and set reference temperature of a temperature sensor 52 provided on the inlet side of the capillary tube and temperature sensors 54 and 56 provided on the inlet side and outlet side of the evaporator, and also, controlling the revolution of the compressor 12 by means of an inverter circuit 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a two-stage compression refrigeration system, and more particularly to a method for controlling a two-stage compression refrigeration system using, for example, an electronic expansion valve and a capillary tube as a decompression device of a two-stage compression refrigeration cycle.

[0002]

2. Description of the Related Art In general, a two-stage compression refrigeration cycle using a two-cylinder two-stage compression type rotary compressor comprises
Since the temperature in front of the expansion valve that performs the depressurizing action can be lowered and supercooling can be increased, a sufficient cooling action can be exhibited in the evaporator.

However, at the start of operation, in order to expand the refrigerant in a gas state or a two-phase state of a gas and a liquid,
For example, when a capillary tube is used, the inner diameter of the tube increases. In addition, since the refrigerant is liquid refrigerant before the expansion valve at the time of steady operation, a length of several tens of meters is theoretically required. Conversely, if the inner diameter of the capillary tube is reduced, processing becomes difficult.

[0004]

Even when an electronic expansion valve is used instead of the capillary tube, the low pressure cannot be adjusted unless the diameter of the orifice is reduced, and it becomes difficult to machine a small diameter orifice. Furthermore, when the electronic expansion valve is closed after the compressor is stopped, the refrigerant flows from the high pressure side into the low pressure side evaporator, and the inside of the evaporator becomes high pressure,
For example, in the case of a refrigerator, there is a problem that it takes a considerable amount of time for the internal temperature to rise to a stable state at the time of restart, and the operating efficiency is deteriorated.

Therefore, the main object of the present invention is to
An electronic expansion valve and a capillary tube are used in combination as a decompression device in a two-stage compression refrigeration cycle, and the valve length of the electronic expansion valve is appropriately controlled to adjust the substantial length of the capillary tube to achieve a two-stage compression with good operating efficiency. An object of the present invention is to provide a method for controlling a refrigeration apparatus.

[0006]

SUMMARY OF THE INVENTION The present invention provides a two-stage compression type compressor having a low-stage compression section and a high-stage compression section, a condenser, first and second electronic expansion valves, an intercooler, and a capillary. In a two-stage compression refrigeration system in which a tube and an evaporator are connected by a refrigerant pipe to form a refrigeration cycle including an intermediate cooling cycle and a main cooling cycle, (a) a temperature detected by a temperature sensor for detecting an inlet side temperature of the evaporator And (b) set the operating frequency of the compressor by the inverter means according to the result, and start the operation of the compressor. (C) First and second after the start of the operation. The two-stage compression refrigeration wherein the opening of the electronic expansion valve is set to a predetermined opening, and (d) the operation of the compressor is continued for a certain period of time, and then the opening of the second electronic expansion valve is half-opened. It is a method of controlling the location.

[0007]

In the two-stage compression refrigeration system, the operation frequency is set according to the inlet-side temperature of the evaporator, and the operation of the compressor is started. Thereafter, the opening degrees of the first and second electronic expansion valves are set to 20%, respectively. After the compressor is fully operated (100%) and the operation of the compressor is continued for a certain period of time, the opening of the second electronic expansion valve is half-opened (50%). Therefore, when the compressor is started, the evaporation temperature of the refrigerant in the evaporator increases. (= Evaporation pressure increases), but a large amount of refrigerant can flow through the evaporator, so that the refrigerating capacity can be increased. Immediately after the start of the compressor, the refrigerant in the vicinity of the second electronic expansion valve is in a gas state without supercooling. However, since the expansion valve is fully opened, the flow rate of the refrigerant to the evaporator is insufficient. I will not do it.

[0008]

According to the present invention, a sufficient flow rate of refrigerant to the evaporator is ensured at the start of operation, so that a large refrigeration capacity can be obtained, and an efficient two-stage compression refrigeration cycle can be realized.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0010]

FIG. 1 shows a two-stage compression refrigeration system 10 in which a control method according to the present invention is implemented. The electric motor unit 12 that is rotated and driven to be shifted
c, a two-cylinder two-stage compression type rotary compressor 12, a condenser 14, and a third intercooler 1 described later.
6. First electronic expansion valve 18, first intercooler 2 described later
0 and the accumulator 22 as a merger are connected to refrigerant pipes 24 and 26, branch pipes 28, refrigerant pipes 30 and 3.
An intermediate cooling cycle configured by connecting the rotary compressor 12, the condenser 14, the third intermediate cooler 16, the second intermediate cooler 34, the second electronic expansion valve 36, and the first A main cooling cycle configured by connecting the intercooler 20, the capillary tube 38, and the evaporator 40 in an annular manner by the refrigerant pipes 24 and 26, the branch pipe 42, and the refrigerant pipes 44 and 46 is included. The discharge side of the low-stage compression section 12 a of the rotary compressor 12 and the accumulator 22 are connected by a refrigerant pipe 48.

A predetermined amount of HFC refrigerant or HC refrigerant such as R-134a is sealed in a refrigerant circuit constituting the two-stage compression refrigeration apparatus 10, and lubricating oil of the rotary compressor 12 is ester oil, ether oil, Alkyl benzene oil, mineral oil and the like are used. In this embodiment, R-134a is used as a refrigerant, and ester oil is used as a lubricating oil.

Next, an outline of the cooling operation in the two-stage compression refrigeration system 10 will be described.

In FIG. 1, when the rotary compressor 12 is driven by the electric motor section 12c, as shown by the solid arrow, the gas refrigerant sucked into the low-stage compression section 12a and compressed in the first stage is refrigerant. The refrigerant flows into the accumulator 22 through the pipe 48, where it joins with the low-temperature gas refrigerant that has passed through the third intercooler 16 and is sucked into the high-stage compression section 12 b.

The high-temperature and high-pressure gas refrigerant discharged at the second stage compression in the high-stage compression section 12b is supplied to the refrigerant pipe 2
4, flows into the condenser 14, where it is radiated and condensed to become a liquid refrigerant, exchanges heat with the third intercooler 16, passes through the refrigerant pipe 26, and branches off in two directions by branch pipes 28 and 42. Is done.

The liquid refrigerant flowing through one branch pipe 28 is then decompressed by the first electronic expansion valve 18 and removes heat from the surroundings while passing through the first intercooler 20 and the third intercooler 16. As a result, the refrigerant is vaporized into a low-pressure gas refrigerant, flows into the accumulator 22 from the refrigerant pipe 30, where the low-stage compression section 12 a of the rotary compressor 12 is formed.
Of the rotary compressor 12 from the refrigerant pipe 32 and into the high-stage compression section 12b of the rotary compressor 12.

The liquid refrigerant flowing through the other branch pipe 42 exchanges heat with the second intercooler 34, and then is decompressed by the second electronic expansion valve 36. After being supercooled by further exchanging heat with the refrigerant decompressed by the electronic expansion valve 18, the pressure is reduced by the capillary tube 38, flows into the evaporator 40, and evaporates there. At this time, the evaporator 40 exerts a cooling action by removing heat from the surroundings.

Further, the low-pressure low-temperature gas refrigerant that has exited from the evaporator 40 exchanges heat with the liquid refrigerant supplied from the third intercooler 16 while passing through the second intercooler 34, and the refrigerant pipe 46 And is sucked into the low-stage compression section 12a of the rotary compressor 12.

The first-stage compressed gas refrigerant discharged from the low-stage compression section 12a passes through the refrigerant pipe 48 and joins with the low-temperature gas refrigerant exiting the third intercooler 16 by the accumulator 22 as described above. High-stage compression section 1 from refrigerant pipe 32
2b, and further compressed at the second stage as described above. Thereafter, by repeating the same cycle, the two-stage compression refrigeration cycle operation is maintained.

As is apparent from the above description, the third intercooler 16 supercools the liquid refrigerant supplied from the condenser 14 and further converts the other refrigerant flowing through the capillary tube 38 and the evaporator 40 into the first refrigerant. Can be supercooled in the intercooler 20 and the second intercooler 34.

Here, an outline of the control operation of the two-stage compression refrigeration apparatus shown in FIG. 1 will be described.

First, the rotary compressor 12 is driven by an electric motor unit 1 whose rotation speed is controlled by an inverter circuit 50.
The drive is controlled by 2c.

Further, a first temperature sensor 52 is provided at the inlet side tube of the capillary tube 38, and the evaporator 4 is provided.
A second temperature sensor 54 is provided at the inlet and outlet side pipes.
And a third temperature sensor 56, respectively, and a first electronic expansion valve 18 and a second electronic expansion valve 18 are controlled by a control circuit 58 including a microcomputer to which detection signals detected by the temperature sensors 52, 54 and 56 are input. The opening degree of the expansion valve 36 is controlled, and the drive of the rotary compressor 12 is controlled by frequency control via the inverter circuit 50. Each of the electronic expansion valves 18 and 36 includes valve driving units 19 and 37 including a stepping motor (not shown), and the valve opening is automatically adjusted by the valve driving units 19 and 37.

The refrigerant flowing through the inlet tube of the capillary tube 38 must be in a supercooled liquid state. If not enough supercooling,
In the case of a two-phase state (a mixed state of liquid refrigerant and gas refrigerant), the inlet side temperature of the evaporator 40 becomes extremely low, and the temperature difference from the inlet side temperature of the capillary tube 38 increases.

Therefore, in the two-stage compression refrigeration cycle,
While the operation of the rotary compressor 12 is stopped, the refrigerant in the subcooling cycle is heated by the outside air (ambient temperature), and the liquid refrigerant existing in front of the second electronic expansion valve 36 also has a small degree of subcooling. The required length of the capillary tube 38 differs depending on the degree of supercooling of the refrigerant existing before the second electronic expansion valve 36. When the effect of supercooling gradually appears at the same time as the operation of the rotary compressor 12 is started, and the temperature of the refrigerant at the preceding stage of the second electronic expansion valve 36 decreases and supercooling can be obtained,
Accordingly, it is necessary to change the length of the capillary tube 38 (= change the aperture amount). In the present invention, this switching change is appropriately performed using the second electronic expansion valve 36.

When the rotary compressor 12 is stopped, the second electronic expansion valve 36 is fully closed to shut off the refrigerant circuit, thereby preventing the refrigerant from flowing from the high pressure side to the low pressure side of the evaporator 40.

That is, when the rotation speed of the rotary compressor 12 is controlled by the inverter circuit 50 according to the refrigeration load, the second temperature sensor 54 and the third temperature sensor 5
6, the inlet side temperature and the outlet side temperature of the evaporator 40 are respectively detected, and the degree of heating (superheat) of the refrigerant flowing through the evaporator 40 can be measured from the temperature difference. For example, when the heating degree is too large (there is a large amount of refrigerant gas), the second electronic expansion valve 36 is opened by a command from the control circuit 58 to open the evaporator 40.
Increase the amount of refrigerant flowing into the air. Conversely, if the degree of heating is too small (there is a large amount of refrigerant liquid), the second electronic expansion valve 36 is throttled by a command from the control circuit 58 including a microcomputer to reduce the amount of refrigerant flowing into the evaporator 40.

As described above, by controlling the second electronic expansion valve 36 to an optimum valve opening in accordance with the degree of heating of the refrigerant, a more balanced two-stage compression can be achieved in combination with the capillary tube 38. A refrigeration cycle can be performed.

Next, the above control operation will be described with reference to the flowcharts shown in FIGS.

First, the process is started, and in step S1, it is determined whether or not the detected temperature of the second temperature sensor 54 provided at the inlet side pipe of the evaporator 40 is higher than a set reference temperature T1, for example, -22.degree. If the result is "YES", the process proceeds to step S3, and if "NO", the process returns to the start.

In step S3, the second temperature sensor 54
It is further determined whether or not the detected temperature is higher than the set reference temperature T2, for example, −10 ° C., and if the result is “YES”, the flow proceeds to step S5 and the operating frequency 40 of the compressor 12 is determined.
Hz or more, and the compressor 1 is set in step S9.
The operation of No. 2 is started. If “NO” in the step S3, the operation frequency 40 of the compressor 12 is set in a step S9.
Hz is set and the process proceeds to step S9.

In step S11, it is determined whether or not 5 seconds have elapsed since the start of the operation of the compressor 12. If the result is "NO", the process returns to the original. If "YES", the process proceeds to step S13 and the first process is performed. 20% of the full opening of the electronic expansion valve 18 and the full opening of the second electronic expansion valve 36 (100%).
%).

Further, in step S15, it is determined whether or not the operation time of the compressor 12 has passed, for example, 120 seconds. If the result is "NO", the process returns to "YE".
If S ", the process proceeds to step S17, and the opening of the second electronic expansion valve 36 is set to half open (50%).

In step S19, it is determined whether or not the temperature detected by the third temperature sensor 56 provided at the outlet side pipe portion of the evaporator 40 is lower than a set reference temperature T1 (-22 ° C.).
If the result is "YES", the flow proceeds to step S21,
Based on the control command from the control circuit 58, the second electronic expansion valve 36 is closed by one step from the half-open state by the valve drive unit 37, and the process proceeds to the throttle step S25. If "NO" in the step S19, the second electronic expansion valve 36 is opened one step from the half-open state in the step S23 to increase the opening degree, and the process proceeds to the step S25.

In step S25, the third temperature sensor 5
If the outlet temperature of the evaporator 40 detected by Step 6 is equal to or lower than the set reference temperature T3, for example, −33 ° C., Step S27
Then, the operation of the compressor 12 is stopped, the first electronic expansion valve 18 and the second electronic expansion valve 36 are fully closed, and a series of control operations is completed. Thereafter, the same control operation is repeatedly executed.

On the other hand, if the decision result in the step S25 is "NO", a timer for 10 seconds is operated in a step S29, and the first temperature sensor 52 in a step S31.
The PID control is performed with the target being the inlet side temperature T4 of the capillary tube 38, for example, 9 ° C., and step S3
In step S3, the first electronic expansion valve 18 is opened and closed, and step S
19, the series of operations described above are performed.

The following is a brief description of an example in which the above control operation is applied to a freezer / freezer. 1) From start to step S17 While the operation of the compressor 12 is stopped, for example, the temperature of both the freezing room and the refrigerating room of the refrigerator-freezer is rising.
Immediately after starting, the cooling load is large. Therefore, the evaporation temperature need not be so low, but requires a large refrigeration capacity.

Then, by opening the second electronic expansion valve 36 widely, the evaporating temperature becomes high (= the evaporating pressure becomes high), but since a large amount of refrigerant can flow through the evaporator 40, the refrigerating capacity becomes large. The state of the refrigerant in the vicinity of the electronic expansion valve 36 is in a gas state without supercooling. However, since the expansion valve is greatly opened, the flow rate of the refrigerant does not become insufficient, and the refrigerant flow to the evaporator 40 is not increased. Sufficiently supplied. 2) From step 19 to the end In the above-mentioned "from start to step S17", cooling has been advanced to some extent in both the freezing room and the refrigeration room, and to further lower the temperature, the evaporation temperature is further lowered ( = Evaporation pressure must be further reduced).

Here, the second electronic expansion valve 36 is gradually closed (throttled). If the second electronic expansion valve 36 is closed too rapidly, the evaporation temperature decreases, but the flow rate of the refrigerant extremely decreases, and the refrigerating capacity is reduced. The temperature of the freezer / refrigeration compartment rises together with the temperature of the evaporator due to a shortage.

Therefore, the electronic expansion valve 36 is gradually and slowly closed while feeding back the state of the evaporator temperature (outlet temperature) (steps S19 to S23). 3) Step S31 to Step S33 In this step, the opening degree of the electronic expansion valve 18 of the intermediate cooling cycle (shunt circuit) is determined by the temperature sensor 52 in order to stably create the supercooling degree of the refrigerant flowing into the capillary tube 38.
Is controlled based on the temperature information.

As described above, according to the present invention,
Low pressure (= evaporation temperature) in a two-stage compression refrigeration cycle
Allows for adjustments. Further, it is possible to prevent the refrigerant from flowing into the evaporator from the high pressure part, and to shorten the time required for each part to reach a stable temperature at the time of re-operation. Further, when the two-stage compression refrigeration apparatus according to the present invention is applied to a refrigerator-freezer, the target temperature can be reached in the shortest time even if the internal temperature changes due to disturbance such as opening and closing of a door.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram including a control method of a two-stage compression refrigeration apparatus according to an embodiment of the present invention.

FIG. 2 is a partial flowchart showing a control operation of the two-stage compression refrigeration apparatus shown in FIG.

FIG. 3 is another partial flowchart showing a control operation of the two-stage compression refrigeration apparatus shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Two-stage compression refrigeration apparatus 12 ... Two-cylinder type two-stage compression type rotary compressor 12a ... Low stage compression part 12b ... High stage compression part 12c ... Electric motor part 14 ... Condenser 16 ... Third intermediate cooler 18 ... 1st electronic expansion valve 19 ... valve drive part 20 ... 1st intermediate cooler 34 ... 2nd intermediate cooler 36 ... 2nd electronic expansion valve 37 ... valve drive part 38 ... capillary tube 40 ... evaporator 50 ... Inverter circuit 52 First temperature sensor 54 Second temperature sensor 56 Third temperature sensor 58 Control circuit (including microcomputer)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Yamakawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Atsushi Oda 2-5-2 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A two-stage compression type compressor having a low-stage compression section and a high-stage compression section, a condenser, a first electronic expansion valve, an intercooler, a second electronic expansion valve, a capillary tube, and an evaporator. Are connected by a refrigerant pipe to form a refrigeration cycle including an intermediate cooling cycle and a main cooling cycle. (A) A temperature detected by a temperature sensor for detecting an inlet side temperature of the evaporator is set. (B) setting the operating frequency of the compressor by an inverter means according to the result and starting the operation of the compressor; and (c) starting the first and second operation after the start of the operation. Setting the opening of the electronic expansion valve to a predetermined opening, and (d) after continuing the operation of the compressor for a certain time,
The opening degree of the second electronic expansion valve is set to half open,
A control method for a two-stage compression refrigeration system. And (e) judging a temperature detected by a temperature sensor for detecting an outlet side temperature of the evaporator and the reference temperature, and adjusting an opening degree of the second electronic expansion valve according to the result. (F) when the temperature detected by the temperature sensor becomes equal to or lower than a predetermined reference temperature, the operation of the compressor is stopped and the two electronic expansion valves are fully closed. A control method for a two-stage compression refrigeration system. And (g) when the temperature detected by the temperature sensor does not reach the predetermined reference temperature, performs PID control targeting a predetermined temperature by a temperature sensor for detecting an inlet-side temperature of the capillary tube. , The first
3. The control method for a two-stage compression refrigeration system according to claim 2, wherein the electronic expansion valve is adjusted for opening and closing.