JP2005121246A - Freezer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a freezer enlarging a capacity adjusting range of a compressor, and capable of preventing a damage accident and an abnormal drop of its delivery temperature. <P>SOLUTION: The freezer 1A is provided with a refrigerant circulation passage I interposed with the capacity-adjustable oil injection type compressor 11, an oil recovery unit 12, a condenser 13, a supercooler 14, a main expansion valve 16, and an evaporator 17. A branch passage II branching from the refrigerant circulation passage I and passing through an opening/closing valve 23 for supercooling and an expansion valve 24 for supercooling passes through the supercooler 14, and the branch passage II is communicated with an intermediate pressure part of the compressor 11. A control part 22 is provided for carrying out control of controlling a rotational frequency of a motor 18 for the compressor via an inverter 21, closing the opening/closing valve 23 for supercooling when the rotational frequency in a dropping process reaches a first threshold that is larger than a value causing an abnormal phenomenon in the oil recovery unit 12, and opening the opening/closing valve 23 for supercooling when the rotational frequency in a rising process reaches a second threshold that is larger than the first threshold not causing punching of opening/closing change-over of the opening/closing valve 23 for supercooling. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a capacity-adjustable oil-cooled compressor and a refrigeration apparatus using a supercooler.

Conventionally, a refrigeration apparatus using an oil-cooled compressor and a supercooler with adjustable capacity is known (see, for example, Patent Document 1).
JP 2003-021089 A

  The refrigeration apparatus described in Patent Document 1 includes a refrigerant circulation channel in which an oil recovery unit, a condenser, a supercooler, a main expansion valve, and an evaporator are provided following an oil-cooled compressor capable of adjusting capacity. The subcooler is branched from a portion between the condenser and the supercooler in the refrigerant circulation flow path, and a branch flow path via a supercooling expansion valve passes through the branch flow. A refrigerating apparatus is disclosed in which the passage is provided so as to communicate with the intermediate pressure portion of the compressor. In this refrigeration apparatus, the capacity adjustment is performed by controlling the rotation speed of the compressor driving motor through an inverter under the condition of using the supercooler.

  For the capacity adjustment of the compressor, in addition to the above, a piston valve, a slide valve, or a lift valve that changes the volume of the gas compression space in the compressor may be used. Assuming that the total load capacity with the maximum volume is 100%, capacity adjustment was performed between 100% and 50%. However, in recent years, with the increasing demand for expanding the capacity adjustment range, capacity adjustment using the inverter has been attracting attention. For this reason, capacity adjustment of 50% or less, which is outside the range of capacity adjustment by the piston valve, slide valve or lift valve, has been made by the inverter, and a new problem described below has arisen.

In the case of the conventional refrigeration apparatus described above, the use of the subcooler is continued during the capacity adjustment, and as a result of the capacity adjustment, the load on the subcooler decreases, so that the intermediate pressure used for this subcooler is reduced. The temperature of the return gas to the section decreases, and the discharge temperature of the compressor also decreases. Along with this, a large amount of refrigerant dissolves in the oil in the oil collector, causing the oil collected in the oil collector to form or abnormally rise in the oil level, resulting in a compressor damage accident. Occurs.
The present invention has been made in order to eliminate such a conventional problem, and it is possible to prevent an abnormal decrease in the discharge temperature of the compressor and the occurrence of a compressor damage accident while expanding the capacity adjustment range of the compressor. It is intended to provide a refrigeration apparatus.

  In order to solve the above-described problems, the present invention provides a refrigerant circulation in which at least an oil recovery unit, a condenser, a supercooler, a main expansion valve, and an evaporator are interposed after an oil-cooled compressor capable of adjusting capacity. A flow path, and the subcooling section branches from a portion between the condenser and the main expansion valve in the refrigerant circulation flow path, and branches via a supercooling on-off valve and a supercooling expansion valve In the refrigeration system provided so as to communicate with the intermediate pressure part of the compressor, the branch flow path is a control unit that controls the rotation speed of the motor that drives the compressor via an inverter. When the rotational speed in the lowering process reaches the first threshold value, the supercooling on-off valve is closed. On the other hand, when the rotational speed in the rising process reaches the second threshold value larger than the first threshold value, the supercooling is stopped. The control part that controls to open the on-off valve is provided.

  Further, the present invention includes a refrigerant circulation passage in which at least an oil recovery unit, a condenser, a supercooler, a main expansion valve, and an evaporator are interposed following an oil-cooled compressor capable of adjusting capacity. The subcooler branches from a portion between the condenser and the main expansion valve in the refrigerant circulation flow path, and a branch flow path through the supercooling on-off valve and the supercooling expansion valve passes through. In the refrigeration apparatus provided so that the branch flow path communicates with the intermediate pressure portion of the compressor, a pressure detector that detects the discharge pressure of the compressor, and a temperature detector that detects the discharge temperature of the compressor A control unit for controlling the rotational speed of a motor for driving the compressor via an inverter, receiving a pressure signal indicating a detected pressure from the pressure detector and a temperature signal indicating a detected temperature from the temperature detector; The discharge pressure saturation temperature corresponding to the above discharge pressure The temperature difference obtained by subtracting the discharge pressure saturation temperature from the discharge temperature is obtained. When the temperature difference in the decreasing process reaches the first threshold value, the overcooling on-off valve is closed while the temperature difference in the increasing process is closed. When the temperature difference reaches a second threshold value that is larger than the first threshold value, a control unit is provided that controls to open the supercooling on-off valve.

  Furthermore, in addition to the structure of the said invention, this invention set it as the structure whose said 1st threshold value is larger than the value which begins to cause the abnormal phenomenon in the said oil recovery device.

  Furthermore, in addition to the configuration of the present invention, the present invention has a configuration in which the second threshold value is larger than the first threshold value to such an extent that hunting for opening / closing switching of the overcooling on / off valve does not occur.

According to the refrigeration apparatus according to the present invention having the above-described configuration, the capacity of the compressor is increased, and even when the capacity is adjusted to 50% or less, an abnormal drop in the discharge temperature of the compressor does not occur. In addition, it is possible to prevent the occurrence of the formation of the recovered oil, the occurrence of an abnormal oil level rise, and the accompanying damage accident of the compressor.
In addition, by adopting control based on the discharge pressure and discharge temperature of the compressor, there is an effect that the capacity of the compressor can be adjusted by making the best use of the capacity of the subcooler.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a refrigeration apparatus 1A according to the present invention. The refrigeration apparatus 1A has an oil-cooled compressor 11, an oil-cooled compressor 12, a condenser 13, a supercooler 14, and a main on-off valve. 15, a refrigerant circulation flow path I in which a main expansion valve 16 and an evaporator 17 are interposed is provided. The compressor 11 is, for example, a screw compressor, and an inverter 21 is interposed between a motor 18 that drives the compressor 11 and a power source 19. The rotational speed of the motor 18 is controlled by the control unit 22 via the inverter 21. The subcooler 14 branches from the portion between the supercooler 14 and the main expansion valve 16 in the refrigerant circulation channel I, and passes through the supercooling on-off valve 23 and the supercooling expansion valve 24. II passes, and this branch channel II communicates with the intermediate pressure portion of the compressor 11. Further, an oil separation element 12a is provided in the oil recovery unit 12, and a lower part thereof is an oil reservoir 12b. An oil cooler 25 is interposed from the lower part of the oil reservoir 12b, and the compressor The oil flow path III which extends to oil supply locations, such as the compression space part in 11 and a bearing and a shaft seal part, is extended.

  In the refrigeration apparatus 1A having the above-described configuration, the refrigerant gas sucked into the compressor 11 is compressed under the injection of the gas-liquid mixed refrigerant from the branch flow path II and the oil from the oil flow path III, The oil is discharged to the oil collector 12 with accompanying oil. In the oil recovery device 12, oil is separated from the refrigerant gas by the oil separation element 12a, and the refrigerant gas is sent out toward the condenser 13, while the separated oil is once stored in the oil reservoir 12b, It is led to the oil supply point in the compressor 11 cooled by the oil cooler 25 in the path III.

  The refrigerant gas led to the condenser 13 is deprived of heat here and condensed to become a refrigerant liquid and reach the supercooler 14. Further, after passing through the supercooler 14, the refrigerant liquid is divided into a refrigerant liquid that flows from the main on-off valve 15 to the main expansion valve 16, and a refrigerant liquid that diverts to the branch flow path II. The refrigerant liquid divided into the branch channel II is adiabatically expanded through the supercooling on-off valve 23 and the supercooling expansion valve 24 to lower the temperature, and is in a gas-liquid mixed state and passes through the supercooler 14. . As a result of heat exchange between the refrigerant circulation channel I and the branch channel II while passing through the supercooler 14, the divided refrigerant takes heat away from the refrigerant in the refrigerant circulation channel I. Is brought into a supercooled state, exits the supercooler 14 and joins the intermediate pressure portion. The intermediate pressure part means a refrigerant working space in a pressure state between the suction pressure and the discharge pressure in the compressor 11, and the compressor 11 is a type including a compressor body arranged in multiple stages. The intermediate pressure portion also includes a refrigerant working space between the compressor bodies.

  The refrigerant liquid in the supercooled state that has passed through the supercooler 14 passes through the main on-off valve 15 and the main expansion valve 16 to lower the temperature by adiabatic expansion and enters a vapor-liquid mixed state to reach the evaporator 17. Further, the refrigerant evaporates by taking heat from the surroundings in the evaporator 17, returns to the compressor 11, and repeats the circulation as described above.

  By the way, in this refrigeration apparatus 1A, the rotational speed of the motor 19 is controlled by the control unit 22 via the inverter 21, and thereby the capacity of the compressor 11 is adjusted and, as will be described in detail below, this capacity adjustment Depending on the degree, the subcooler 14 can be switched between an operating state and a stopped state.

  When the rotational speed of the motor 19 is large and the compressor 11 is maintained in a relatively large capacity state, the supercooler 14 may be in an operating state, but the capacity of the compressor 11 is reduced. In such a case, a problem occurs if the supercooler 14 is left in an operating state. Assuming that the compressor 11 is in the state of maximum capacity with the rotation speed of the motor 19 being the maximum, the capacity is adjusted within a range of 100 to 50% under the operating state of the subcooler 14, for example. Even if there is no problem as long as the operation is performed, when the capacity is 50% or less under the operation state of the subcooler 14, the discharge temperature of the compressor 11 is abnormally decreased, and the oil recovered in the oil recovery device 12 Forming phenomenon and abnormal oil level rise may occur.

  Therefore, in this refrigeration apparatus 1A, as shown in FIG. 2 (horizontal axis: motor rotation speed r, vertical axis: operating state of the supercooling on-off valve), when the rotation speed of the motor 19 is in a decreasing process, When the first threshold value r1 larger than the value at which the forming phenomenon due to the abnormal drop of the discharge temperature, the abnormal rise of the oil level and the abnormal phenomenon in the oil recovery unit 12 starts to occur is reached, the controller 22 causes the supercooling on-off valve. 23 is controlled to be closed, and the supercooler 14 is stopped. Thereby, the abnormal drop of the discharge temperature of the compressor 11 is prevented, and the occurrence of the abnormal phenomenon is avoided. On the other hand, when the rotational speed of the motor 19 is in an increasing process, the control is performed when the motor reaches a second threshold value r2 that is larger than the first threshold value r1 at which the hunting for opening / closing switching of the overcooling on / off valve 23 does not occur. The supercooling on / off valve 23 is controlled to be opened by the section 22 so that the supercooler 14 is in an operating state. As a result, the occurrence of a damage accident of the compressor 11 due to the occurrence of the abnormal phenomenon is avoided, the range in which the capacity of the compressor 11 can be adjusted is expanded, and the capacity can be adjusted up to about 25%.

FIG. 3 shows another refrigeration apparatus 1B according to the present invention, and portions in FIG. 3 that are common to the refrigeration apparatus 1A shown in FIG.
In the refrigeration apparatus 1B, the discharge pressure of the compressor 11 is detected, the pressure signal 26 indicating the detected pressure is input to the control unit 22, the discharge temperature of the compressor 11 is detected, and the temperature signal indicating the detected temperature. And a temperature detector 27 for inputting the signal to the control unit 22.

  Then, the control unit 22 obtains a discharge pressure saturation temperature corresponding to the discharge pressure based on the input pressure signal, and a temperature difference Δt (= discharge temperature−discharge pressure) obtained by subtracting the discharge temperature from the discharge pressure saturation temperature. As shown in FIG. 4 (horizontal axis: temperature difference Δt, vertical axis: operating state of the supercooling on-off valve), when this temperature difference Δt is decreasing, the temperature difference is When a first threshold value Δt1, which is larger than a value at which an abnormal phenomenon in the recovery device 12 starts to occur, for example, 10 ° C., is reached, the control unit controls the supercooling on-off valve 23 to be closed, and the supercooler 14 is stopped. It is supposed to do. Thereby, the abnormal drop of the discharge temperature of the compressor 11 is prevented, and the occurrence of the abnormal phenomenon is avoided. On the other hand, when the temperature difference Δt is increasing, the second threshold value Δt2, for example, 15 ° C., which is larger than the first threshold value Δt1 at which the hunting for switching of the overcooling on / off valve 23 does not occur. Then, the control part 22 is controlled to open the supercooling on-off valve 23, and the supercooler 14 is put into an operating state. As a result, in addition to avoiding the occurrence of a damage accident of the compressor 11 and expanding the range in which the capacity can be adjusted, control using the capacity of the subcooler 14 to the maximum is possible.

In the present invention, as shown in FIGS. 1 and 2, a branch flow path II passing through the supercooler 14 is provided between the supercooler 14 and the main expansion valve 16, as shown by being surrounded by a square frame by a two-dot chain line. It is not limited to the refrigeration apparatuses 1A and 1B branched at, but also includes a refrigeration apparatus where the branch channel II is branched between the condenser 13 and the subcooler 14, as shown in FIG.
In FIG. 5, parts that are the same as those in FIGS. 1 and 2 are given the same reference numerals.

It is a block diagram which shows the whole structure of the freezing apparatus which concerns on this invention. It is a figure which shows the relationship between the motor rotation speed of the compressor in the freezing apparatus shown in FIG. 1, and the operating state of the on-off valve for supercooling. It is a block diagram which shows the whole structure of another freezing apparatus which concerns on this invention. It is a figure which shows the relationship between the temperature difference (= discharge temperature-discharge pressure saturation temperature) by the side of discharge of the compressor in the freezing apparatus shown in FIG. 2, and the operating state of the on-off valve for supercooling. It is a block diagram which shows the other structure of the branch flow path which passes the subcooler in this invention.

Explanation of symbols

1A, 1B Refrigeration apparatus 11 Compressor 12 Oil recovery unit 12a Oil separation element 12b Oil reservoir 13 Condenser 14 Supercooler 15 Main on / off valve 16 Main expansion valve 17 Evaporator 18 Motor 19 Power supply 21 Inverter 22 Control unit 23 Supercooling Open / close valve 24 Supercooling expansion valve 25 Oil cooler 26 Pressure detector 27 Temperature detector
I Refrigerant circulation flow path
II Branch channel
III Oil flow path

Claims (4)

Following the oil-cooled compressor whose capacity can be adjusted, a refrigerant circulation passage having at least an oil recovery unit, a condenser, a supercooler, a main expansion valve, and an evaporator,
The supercooling section branches from a portion of the refrigerant circulation passage between the condenser and the main expansion valve, and a branch passage through the supercooling on-off valve and the supercooling expansion valve passes. ,
In the refrigeration apparatus provided so that this branch flow path leads to the intermediate pressure part of the compressor,
A control unit that controls the rotational speed of a motor that drives the compressor through an inverter, and closes the overcooling on-off valve when the rotational speed in the decreasing process reaches a first threshold, while A refrigeration apparatus comprising: a control unit configured to control to open the overcooling on-off valve when a certain number of rotations reaches a second threshold value greater than the first threshold value. Following the oil-cooled compressor whose capacity can be adjusted, a refrigerant circulation passage having at least an oil recovery unit, a condenser, a supercooler, a main expansion valve, and an evaporator,
The subcooler branches from a portion of the refrigerant circulation passage between the condenser and the main expansion valve, and a branch passage through the supercooling on-off valve and the supercooling expansion valve passes. ,
In the refrigeration apparatus provided so that this branch flow path leads to the intermediate pressure part of the compressor,
A pressure detector for detecting the discharge pressure of the compressor;
A temperature detector for detecting the discharge temperature of the compressor;
A control unit for controlling the rotational speed of a motor for driving the compressor via an inverter, receiving a pressure signal indicating a detected pressure from the pressure detector and a temperature signal indicating a detected temperature from the temperature detector; A discharge pressure saturation temperature corresponding to the discharge pressure is obtained, a temperature difference obtained by subtracting the discharge pressure saturation temperature from the discharge temperature is obtained, and when the temperature difference in the decreasing process reaches a first threshold value, the overcooling opening / closing is performed. A refrigeration apparatus comprising: a control unit that controls to open the supercooling on-off valve when the temperature difference in the increasing process reaches a second threshold value that is larger than the first threshold value while closing the valve. .   The refrigeration apparatus according to claim 1 or 2, wherein the first threshold value is larger than a value at which an abnormal phenomenon starts in the oil recovery unit. The said 2nd threshold value is larger than the said 1st threshold value to the extent that the hunting of the opening-and-closing switching of the said on-off valve for supercooling does not arise, The any one of Claim 1 to 3 characterized by the above-mentioned. Refrigeration equipment.

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