JP2008032305A - Refrigeration apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly control a gas temperature in a compression chamber by properly supplying the liquid injection quantity at a good timing in starting the other stopped compressor in such a state that at least one compressor is operated. <P>SOLUTION: The plural compressors 1a, 1b having liquid injection circuits are loaded in a refrigeration apparatus. When the stopped compressor 1b is started while operating one compressor 1a, a liquid injection flow rate control valve 5b is controlled to an opening to be the same as that of a flow rate control valve 5a corresponding to the compressor 1a, so that the initial liquid injection quantity in starting the compressor 1b becomes the same as the liquid injection quantity of the compressor 1a already operated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plurality of compressors and a liquid injection circuit for controlling a gas temperature in the compression chamber by injecting a part of the liquid refrigerant exiting the condenser into a compression chamber (intermediate pressure portion) in the compression process of the compressor. Is particularly suitable when a scroll compressor is used as the compressor.

  For example, an abnormal rise in the gas temperature in the compression chamber of a scroll compressor not only accelerates the deterioration of the refrigerant and the refrigeration oil contained in the compressor, but also causes abnormal wear and seizure due to poor lubrication and thermal deformation of the components that make up the compression chamber. And greatly affects reliability. Therefore, it is important to always properly control the gas temperature in the compression chamber in order to improve the reliability of the compressor. For this reason, some scroll compressors employ a liquid injection method in which a liquid refrigerant is injected into a gas during a compression stroke to cool the compression chamber gas.

  However, in a scroll compressor that employs a liquid injection method, excessive injection of liquid refrigerant will cause a large amount of refrigerant to melt into the lubricating oil, resulting in poor lubrication due to a decrease in the viscosity of the lubricating oil, and discharge due to liquid compression. There was a problem that the valve was damaged. Therefore, it is important for maintaining the reliability of the equipment to appropriately control the liquid injection amount and keep the gas temperature in the compression chamber properly.

  The control of the liquid injection amount in the compressor generally detects the temperature of the gas discharged from the compression chamber and controls the liquid injection amount in accordance with the temperature so that the gas temperature in the compression chamber becomes an appropriate temperature. It has been known.

  However, when the evaporation temperature is −30 ° C. or lower and the evaporation pressure (ie, the compressor suction pressure) is low, the pressure ratio is high, so the gas temperature in the compression chamber is high, but the density of the sucked gas is low, and the mass flow rate of the gas is Since the temperature of the discharged gas is high, the heat capacity is small, and the peripheral components are deprived of heat in the process of being discharged, and the temperature tends to decrease. For this reason, when the temperature suddenly rises at the time of starting the compressor, the gas discharged from the compression chamber is in the middle of reaching the temperature detection sensor section even though the temperature of the gas in the compression chamber is high. Heat is taken away by the components of the path, and the temperature decreases, and the difference between the temperature detected by the sensor and the actual temperature in the compression chamber increases. The temperature of the parts that have deprived heat from the discharge gas gradually increases, and it takes time for the discharge gas temperature from the compression chamber to approach the same value as the temperature detected by the temperature sensor. There is a problem that a delay occurs and the gas temperature in the compression chamber rises abnormally.

  For this reason, as described in Patent Document 1, the liquid injection amount is controlled by changing the compressor suction pressure, or as described in Patent Document 2, the liquid injection amount is increased by increasing the detected change amount of the discharge gas temperature. In some cases, the control amount is increased to follow the change in the gas temperature in the compression chamber.

JP-A-8-313074 Japanese Patent Laid-Open No. 8-200247 JP 2005-282972 A

  In a refrigeration system having only one compressor, when the compressor is stopped and restarted, the high pressure side pressure during the stop is lower than the pressure during the normal operation, and the low pressure side pressure during the stop is also during the normal operation. Since the pressure is higher than the pressure and gradually approaches the pressure during operation after starting operation, the operation can be started from a place where the gas compression ratio is relatively small. Therefore, the discharge gas temperature is unlikely to rise suddenly. However, in the case of a refrigeration apparatus including a plurality of compressors, when one unit is in operation and the second and subsequent compressors are started, the first compressor is already in operation. The side pressure is high and the low pressure side pressure is also low. For this reason, since the operation is immediately started at a high pressure ratio, the gas temperature in the compression chamber rapidly increases. Therefore, in the conventional method of detecting the gas temperature discharged from the compression chamber and adjusting the liquid injection amount, there is a problem that the control delay becomes large and the gas temperature in the compression chamber temporarily becomes abnormally high.

  For this reason, when one unit is in operation and the second and subsequent compressors are started, it is important to grasp in advance an appropriate liquid injection amount without excess or deficiency and to control the flow rate.

  However, in a refrigeration system operated in a wide range of evaporation temperatures, there is a large difference in the appropriate liquid injection amount, and it is difficult to set the appropriate amount in advance. Control is needed.

  Therefore, as described in Patent Document 3, there is a method in which the liquid injection amount is estimated from the suction pressure, the discharge pressure, and the suction temperature, and the amount is flowed in advance. However, there is a means for measuring each pressure and temperature. It is necessary and the estimation method becomes complicated.

  An object of the present invention is to provide an appropriate amount of liquid injection in a timely manner when starting another stopped compressor while at least one compressor is in operation with simple control. The object is to obtain a refrigeration apparatus capable of appropriately controlling the gas temperature in the compression chamber.

  To achieve the above object, the present invention provides a plurality of compressors, a condenser that condenses the refrigerant gas discharged from the plurality of compressors, and an expansion valve that expands the liquid refrigerant that has exited the condenser, A liquid injection circuit that sequentially connects a vaporizer that vaporizes the liquid refrigerant that has exited the expansion valve by a closed circuit, and injects a part of the liquid refrigerant that has exited the condenser into a compression chamber in the compression process of the compressor. And at least one of the plurality of compressors in a refrigeration apparatus comprising: a flow control means for controlling a liquid injection amount provided in the liquid injection circuit; and a control device for controlling the number of operating compressors. When at least one of the remaining compressors is started during operation, the amount of liquid injection that flows to the compressor at the initial start of the compressor to be started is set to the liquid injection to the already operating compressor. It is characterized in that to control the tio emission amount and close the flow.

  Here, as the compressor, it is preferable to employ a scroll compressor suitable for liquid injection. Further, the flow rate control means for controlling the liquid injection amount provided in the liquid injection circuit may be configured by providing a plurality of flow paths in combination of capillary tubes and electromagnetic valves in parallel, or an expansion capable of adjusting the flow rate. It can consist of valves.

  When one compressor starts up at least one of the remaining compressors during operation, the amount of liquid injection that flows to the compressor at the start of the startup of the compressor is constant from the start of the compressor. Until the time elapses, control is performed so as to maintain the initial liquid injection flow rate unless the discharge gas temperature from the compressor exceeds a predetermined constant value. It is preferable to control the injection amount.

  In addition, when three or more compressors are mounted and two or more compressors are already in operation, the initial control of the liquid injection amount for the compressor to be started next is liquid injection in the starting compressor. The compressor having the largest amount may be selected, and the flow rate may be the same as the liquid injection amount, or may be the same flow rate as any one liquid injection amount in the activated compressor.

  The compressor that is started next while one or more compressors are in operation is almost the same as the operating state of the compressor that is already in operation immediately after the start, so that the initial liquid injection amount for the compressor to be started is The appropriate value is the same as the liquid injection amount of the compressor already in operation. Therefore, according to the present invention, the liquid injection amount at the initial start of the compressor to be started next is substantially the same as the liquid injection amount flowing to the compressor that is already in operation regardless of the state of the discharge gas temperature. To control.

  According to the present invention, in a refrigerating apparatus including a plurality of compressors, when at least one of the plurality of compressors starts at least one of the remaining compressors during operation, the start of the compressor to be started Since the liquid injection amount that flows to the compressor in the initial stage is controlled to a flow rate that is close to the liquid injection amount to the compressor that is already in operation, the appropriate liquid injection amount for the compressor to be started Therefore, it is possible to prevent a delay in controlling the liquid injection amount, and to appropriately control the gas temperature in the compression chamber. Accordingly, it is possible to prevent the deterioration of the refrigerant and the refrigerating machine oil due to the abnormal increase in the refrigerant gas temperature, and it is possible to prevent the seizure due to the deterioration of the lubricating oil, thereby obtaining the effect of improving the reliability of the compressor.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of the refrigeration apparatus of the present invention. FIG. 1 shows a refrigeration cycle configuration diagram of a scroll refrigeration apparatus equipped with two scroll compressors. Numerals 1a and 1b are scroll compressors, 2 is a condenser, 3 is an expansion valve, 4 is an evaporator, and these devices are sequentially connected by refrigerant piping to form a refrigerant main circuit (first circuit) 8 of the refrigeration cycle. ing. As a refrigerant, R404A (an HFC refrigerant in which R125 is 44% by weight, R143a is 52%, and R134a is 4%), R410A (an HFC refrigerant in which R32 is 50% and R125 is 50% by weight), or R22 Etc. are used. The refrigerant discharged from the scroll compressors 1a and 1b is cooled and liquefied by the condenser 2, and a liquid injection circuit (second circuit) 7 is branched from the first circuit 8 on the downstream side of the condenser 2. The liquid injection circuit 7 is branched into two refrigerant pipes 7a and 7b. One refrigerant pipe 7a is an intermediate pressure part in the compression process of the compressor 1a, and the other refrigerant pipe 7b is an intermediate pressure part in the compression process of the compressor 1b. Are connected to each. The refrigerant pipes 7a and 7b are provided with liquid injection flow control valves (liquid injection flow control means) 5a or 5b, respectively. These flow control valves 5a and 5b are composed of, for example, electronic expansion valves to control liquid injection. It is controlled by the device 9. The liquid injection control device 9 detects the discharge gas temperature from each compressor with the discharge gas temperature sensors 10a and 10b, and the discharge gas temperature discharged from each compressor becomes an appropriate temperature (for example, 90 ° C.). The liquid injection amount is adjusted by controlling the opening degree of the flow rate control valves 5a and 5b.

  The refrigerant flowing through the first circuit 8 cools the evaporator 4 through the expansion valve 3 and is then introduced into the suction port of the compressor 1. The refrigerant branched to the second circuit 7 is adjusted in flow rate by the liquid injection flow control valve 5 and injected (liquid injection) into the intermediate pressure part (compression chamber) in the compression process of the scroll compressor 1, and is in the compression stroke. Cool down. In the case of a scroll refrigeration apparatus equipped with three or more scroll compressors, a refrigerant pipe branched by the liquid injection circuit 7 may be added according to the number of compressors.

  After starting the first scroll compressor 1a, the control device 9 controls the flow rate control valve 5a according to the discharge gas temperature detected by the discharge gas temperature sensor 10a so that the discharge gas temperature becomes an appropriate temperature. Adjust the liquid injection volume. This liquid injection amount is a value that is optimally controlled among various factors such as the high pressure side pressure, the low pressure side pressure, the suction gas temperature, and the ambient temperature in the compressor currently in operation. It is also an optimum value as the liquid injection amount at the time of starting with the compressor that is started next during the operation of the eye compressor. Therefore, the present embodiment is made based on this finding.

  In the conventional refrigeration system, when the second compressor is started, an intermediate liquid injection amount is made to flow as an initial flow rate in the same manner as when the first compressor is started, and the temperature of the gas discharged from the compression chamber is liquid injection. Control is performed to increase the liquid injection amount when the increase value is equal to or higher than the set value (for example, 90 ° C.), and to decrease the liquid injection amount when the value is equal to or less than the set value for liquid injection decrease (for example, 60 ° C.). For this reason, there is a possibility that control delay occurs and the gas temperature in the compression chamber abnormally overheats.

  On the other hand, in this embodiment, based on the above knowledge, the flow rate control valve 5b is controlled as shown in the control flow diagram of FIG. When the second compressor 1b is activated while the first compressor 1a is activated (step 11), the initial liquid injection flow rate of the compressor 1b is set to the first unit just before the compressor 1b is activated. The flow rate is the same as the liquid injection amount in the compressor 1a (step 12). Even if the discharge gas temperature is less than the set value for liquid injection reduction (for example, 60 ° C.), the initial flow rate is maintained at the initial liquid injection flow rate for a certain period of time (3 minutes in the present embodiment) in anticipation of temperature rise after startup Control is performed (step 13). However, when the detected discharge gas temperature becomes 90 ° C. or higher (step 14), it is considered that the liquid injection amount is insufficient. In this case, the process proceeds to step 15, and the normal discharge gas temperature is reached. Since the liquid injection control is performed, the amount of liquid injection is increased.

  In a scroll refrigerator equipped with three or more compressors, when two or more compressors are already in operation, the initial control of the liquid injection amount for the next compressor to be started is Among them, it is preferable to select a compressor having the largest liquid injection amount and control the flow rate to be the same as the liquid injection amount. Alternatively, a representative one of a plurality of compressors can be determined in advance, and the liquid injection amount of the compressor can be controlled to be the liquid injection amount of the compressor to be started next. In some cases, control can be made easier.

FIG. 2 shows another embodiment of the present invention. In the embodiment of FIG. 1, the liquid injection amount is controlled by a flow control valve such as an electronic expansion valve, but in this embodiment, the electromagnetic valves 6a, 6b, 6c, 6d and the capillary tubes 6A, 6B, 6C, 6D are controlled. A description will be given of an example in which the liquid injection amount can be controlled in four stages for each of the compressors 1a and 1b. That is, when the sizes of the two capillaries 6A and 6B and 6C and 6D for each compressor are different, for example, when the liquid injection flow rate from the first capillary tubes 6A and 6C is 1, the second capillary tube 6B The liquid injection flow rate from 6D is selected to be 2. For each of these compressors, two capillary tubes 6A and 6B, 6C and 6D, first electromagnetic valves 6a and 6c connected thereto, and second electromagnetic valves 6b and 6d are opened and closed to Thus, the liquid injection flow rate control of 4 steps is performed.
First step: Liquid injection amount 0 (all solenoid valves 6a, 6b, 6c, 6d closed)
Second step: Liquid injection amount 1 (solenoid valves 6a, 6c open, solenoid valves 6b, 6d closed)
Third step: Liquid injection amount 2 (solenoid valves 6a, 6c closed, solenoid valves 6b, 6d opened)
Fourth step: Liquid injection amount 3 (all solenoid valves 6a, 6b, 6c, 6d open)
The initial liquid injection amount when starting the first compressor 1a is the second step in which only the first electromagnetic valve 6a is opened, and the discharge gas temperature of the compressor 1a has risen to a predetermined value of 90 ° C. or higher. Time, the process proceeds to the third step (the second electromagnetic valve 6b is opened and the first electromagnetic valve is closed).

  In this embodiment, when the second compressor 1b is started during the operation of the compressor 1a, the liquid injection amount of the first compressor 1a during operation, that is, the first electromagnetic valve 6a and the second electromagnetic valve 6b. The first electromagnetic valve 6c and the second electromagnetic valve 6d corresponding to the compressor 1b to be started next are opened and closed so that the compressor 1b is started.

  Thus, even when the stopped compressor 1b is started in a state where the refrigeration cycle is operated, an appropriate liquid injection amount is supplied to the started compressor 1b from the start of the compressor 1b. The indoor gas temperature can be controlled to an appropriate temperature without control delay.

  In the embodiment shown in FIG. 2, the scroll refrigerator having two compressors is described. However, the present invention can be applied to a scroll refrigerator having three or more compressors in the same manner as in the embodiment shown in FIG. That is, when starting the next compressor while two or more compressors are already in operation, the amount of liquid injection into the compressor having the largest liquid injection amount is set to the same amount or to a predetermined compressor. What is necessary is just to control the initial amount of liquid injection to the compressor to start next so that it may become the same amount as this liquid injection amount.

The refrigeration cycle block diagram which shows one Example of the freezing apparatus of this invention. The refrigeration cycle block diagram which shows the other Example of the freezing apparatus of this invention. The control flowchart which shows an example of the liquid injection amount control in a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b ... Scroll compressor, 2 ... Condenser, 3 ... Expansion valve, 4 ... Evaporator, 5a, 5b ... Liquid injection flow control valve (flow control means), 6a, 6b, 6c, 6d ... Solenoid valve, 6A , 6B, 6C, 6D ... capillary tube (flow rate control means), 7 ... liquid injection circuit (second circuit), 8 ... refrigerant main circuit (first circuit), 9 ... liquid injection control device, 10a, 10b ... discharge gas Temperature sensor.

Claims (7)

A plurality of compressors, a condenser that condenses the refrigerant gas discharged from the plurality of compressors, an expansion valve that expands the liquid refrigerant that exits the condenser, and a liquid refrigerant that exits the expansion valve is vaporized A liquid injection circuit that sequentially connects the evaporator with a closed circuit and injects a part of the liquid refrigerant that has exited the condenser into a compression chamber in the compression process of the compressor; and a liquid injection provided in the liquid injection circuit In a refrigeration apparatus comprising flow control means for controlling the amount and a control device for controlling the number of operating compressors,
When at least one of the plurality of compressors is activated and at least one of the remaining compressors is activated, the liquid injection amount to be supplied to the compressor at the initial activation of the activated compressor is already in operation. A refrigeration apparatus controlled to a flow rate close to the amount of liquid injection into the compressor.   2. The refrigeration apparatus according to claim 1, wherein the compressor is a scroll compressor.   3. The flow rate control means for controlling a liquid injection amount provided in the liquid injection circuit according to claim 1 or 2, wherein a plurality of flow paths combining capillary tubes and electromagnetic valves are provided in parallel. Refrigeration equipment.   3. The refrigeration apparatus according to claim 1, wherein the flow rate control means for controlling a liquid injection amount provided in the liquid injection circuit is an expansion valve capable of adjusting a flow rate.   In any one of Claims 1-4, when at least 1 compressor starts at least 1 of the remaining compressors in operation | movement, the liquid injection amount which flows into the compressor at the initial stage of starting of the said compressor to start Is controlled so as to maintain the initial liquid injection flow rate until the discharge gas temperature from the compressor does not exceed a predetermined constant value until a predetermined time has elapsed since the start of the compressor. When it exceeds, the refrigeration apparatus characterized by controlling the liquid injection amount by the discharge gas temperature.   In any one of Claims 1-5, when the said compressor is mounted three or more and two or more compressors are already driving | running, the initial control of the liquid injection amount with respect to the compressor to start next is starting. A compressor having the largest liquid injection amount is selected from among the compressors, and the flow rate is the same as the liquid injection amount. In any one of Claims 1-5, when the said compressor is mounted three or more and two or more compressors are already driving | running, the initial control of the liquid injection amount with respect to the compressor to start next is starting. The refrigeration apparatus is characterized in that the flow rate is the same as the liquid injection amount of any one of the compressors.

Images