AIR CONDITIONER

TECHNICAL FIELD

The present disclosure relates to an air conditioner.

BACKGROUND ART

An air conditioner includes a compressor that discharges a high-temperature and high-pressure refrigerant to a refrigerant circuit. The compressor is filled with refrigeration oil for maintaining lubricity of a drive unit such as a motor. As a temperature of the refrigeration oil is decreased, viscosity of the refrigeration oil is increased.

When the viscosity of the refrigeration oil is increased, driving torque of the compressor is increased, and a current value of the motor may become excessive. PTL 1 discloses a technique of heating the refrigeration oil until the temperature of the refrigeration oil reaches the pour point in a case where the temperature of the refrigeration oil is lower than the pour point, for the purpose of maintaining appropriate viscosity of the refrigeration oil. Here, a temperature at which a liquid does not flow at all is referred to as solidification point, and a temperature immediately before the solidification point is referred to as pour point.

CITATION LIST
Patent Literature

- PTL 1: WO 2018/138796

SUMMARY OF INVENTION
Technical Problem

The refrigeration oil may be present in the compressor in a state of a mixture of the refrigeration oil and the refrigerant in a liquid state. As the amount of the refrigerant in the liquid state in the compressor is increased, a concentration of the refrigeration oil is decreased. In a constant temperature environment, the viscosity of the mixture is decreased as the concentration of the refrigeration oil is decreased. Therefore, even in a case where the temperature of the refrigeration oil is sufficiently high, in a case where the concentration of the refrigeration oil is too low, the refrigeration oil may not exhibit a function as a lubricant. In addition, even when the concentration of the refrigeration oil is not low, in a case where the temperature of the refrigeration oil is too low, the viscosity of the refrigeration oil is increased, which may abnormally increase the driving torque of the motor of the compressor.

Therefore, the necessity of heating the refrigeration oil should be determined in consideration of not only the temperature of the refrigeration oil but also the concentration of the refrigeration oil.

The technique in the related art decides the necessity of heating the refrigeration oil by using the temperature of the refrigeration oil as an index. However, the technique in the related art does not consider the concentration of the refrigeration oil. Therefore, according to the technique in the related art, even when the concentration and temperature of the refrigeration oil are in a range in which the refrigeration oil can exhibit a lubricating function in the compressor, the refrigeration oil is unnecessarily heated in a case where the temperature of the refrigeration oil does not reach the pour point.

Moreover, in the technique in the related art, in a case where the temperature of the refrigeration oil does not reach the pour point, a heating operation is continued until the temperature of the refrigeration oil reaches the pour point. In order to increase the temperature of the refrigeration oil by heating the refrigeration oil mixed with the refrigerant in the liquid state, it is necessary to vaporize the refrigerant having a lower boiling point out of the refrigeration oil and the refrigerant first. Therefore, in the technique in the related art, power for heating is excessively consumed.

The present disclosure has been made to solve such a problem, and an object of the present disclosure is to provide an air conditioner capable of appropriately maintaining lubricating performance of refrigeration oil in a compressor in consideration of a temperature and a concentration of the refrigeration oil.

Solution to Problem

The present disclosure relates to an air conditioner. The air conditioner includes a compressor; a first heat exchanger; a second heat exchanger; a decompression device; a circulation path through which a refrigerant circulates through the compressor, the first heat exchanger, the decompression device, and the second heat exchanger in this order; a temperature sensor to detect a temperature of refrigeration oil in the compressor; a concentration sensor to detect a concentration of the refrigeration oil in a mixture of the refrigerant in a liquid state and the refrigeration oil in the compressor; a heater to heat the refrigeration oil in the compressor; and a control device. In a case where a concentration of refrigeration oil detected by the concentration sensor is less than a first threshold value, the control device operates the heater such that a part of a refrigerant in a liquid state in the compressor is vaporized, and in a case where the concentration of the refrigeration oil detected by the concentration sensor exceeds a second threshold value greater than the first threshold value and a temperature of the refrigeration oil detected by the temperature sensor is less than a specified temperature, the control device operates the heater such that the refrigerant in the liquid state in the compressor is vaporized and the temperature of the refrigeration oil in the compressor is increased.

Advantageous Effects of Invention

According to an air conditioner of the present disclosure, it is possible to provide an air conditioner capable of appropriately maintaining lubricating performance of the refrigeration oil in the compressor in consideration of the temperature and the concentration of the refrigeration oil.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram illustrating a configuration of an air conditioner (first embodiment).

FIG. 2 is a diagram for describing a region where a heater is operated, from the viewpoint of a temperature Toil and a concentration αoil of refrigeration oil (first embodiment).

FIG. 3 is a diagram for describing control of the heater, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (first embodiment).

FIG. 4 is a flowchart illustrating control for setting heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (first embodiment).

FIG. 5 is a flowchart illustrating control for operating the heater according to the heating condition (first embodiment).

FIG. 6 is a diagram for describing control of a heater, from the viewpoint of a temperature Toil and a concentration αoil of refrigeration oil (second embodiment).

FIG. 7 is a flowchart illustrating control for setting heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (third embodiment).

FIG. 8 is a flowchart illustrating control for operating a heater according to the heating condition (third embodiment).

FIG. 9 is a diagram for describing a region where a heater is operated in a state where a refrigerant in a liquid state and refrigeration oil are separated into two layers in a compressor, from the viewpoint of a temperature Toil and a concentration αoil of the refrigeration oil (fourth embodiment).

FIG. 10 is a diagram for describing control of the heater, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (fourth embodiment).

FIG. 11 is a flowchart illustrating control for setting heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (fourth embodiment).

FIG. 12 is a flowchart illustrating control for operating the heater according to the heating condition (fourth embodiment).

FIG. 13 is a diagram illustrating an example in which a temperature sensor and a concentration sensor are provided in a vicinity portion of a shaft of a compressor (fifth embodiment).

FIG. 14 is a diagram illustrating an example in which a temperature sensor and a concentration sensor are provided at an end portion of a shaft of a compressor (sixth embodiment).

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described, but it is planned from the beginning of the application to appropriately combine the configurations described in each embodiment. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

First Embodiment

FIG. 1 is a refrigerant circuit diagram illustrating a configuration of an air conditioner 100 according to a first embodiment (first embodiment). Referring to FIG. 1, air conditioner 100 includes a compressor 1, a first heat exchanger 2, a decompression device 3, a second heat exchanger 4, and a control device 70. Compressor 1, first heat exchanger 2, decompression device 3, and second heat exchanger 4 constitute a refrigerant circuit that circulates a refrigerant. The refrigerant circuit includes a circulation path 5 through which the refrigerant circulates through compressor 1, first heat exchanger 2, decompression device 3, and second heat exchanger 4 in this order.

First heat exchanger 2 is located on a high pressure side in the refrigerant circuit. Therefore, first heat exchanger 2 functions as a condenser. Second heat exchanger 4 is located on a low pressure side in the refrigerant circuit. Therefore, second heat exchanger 4 functions as an evaporator. For example, by disposing first heat exchanger 2 indoors and disposing second heat exchanger 4 outdoors, air conditioner 100 functions as a heating unit that warms an indoor space. Air conditioner 100 may be provided with a switching valve that switches a discharge destination of the refrigerant from compressor 1 between first heat exchanger 2 and second heat exchanger 4.

The refrigeration oil is sealed in compressor 1. The refrigeration oil functions as a lubricant for a drive unit such as a motor in compressor 1. Compressor 1 is provided with a temperature sensor 50, a concentration sensor 51, and a heater 60. Temperature sensor 50 detects the temperature of the refrigeration oil in compressor 1, and transmits a detection value to control device 70. Concentration sensor 51 detects the concentration of the refrigeration oil in compressor 1, and transmits a detection value to control device 70. Heater 60 heats the refrigeration oil in compressor 1.

Temperature sensor 50 may be provided at any position in compressor 1 as long as the temperature of the refrigeration oil in compressor 1 can be detected at the position. Similarly, concentration sensor 51 may be provided at any position in compressor 1 as long as the concentration of the refrigeration oil in compressor 1 can be detected at the position.

Control device 70 includes a processor 71 and a memory 72. Memory 72 includes a read only memory (ROM) and a random access memory (RAM). Processor 71 develops a program stored in the ROM in the RAM or the like, and executes the program. The program stored in the ROM is a program in which a processing procedure of control device 70 is described.

Control device 70 controls each device of air conditioner 100 according to the program stored in memory 72. For example, control device 70 controls compressor 1, decompression device 3, and heater 60. As a result, the frequency at which compressor 1 is operated, the opening degree of a valve of decompression device 3, the timing of the operation of heater 60, and the like are adjusted.

In some cases, a refrigerant in a liquid state is present in compressor 1. For example, in a case where a part of the refrigerant returning from second heat exchanger 4 to compressor 1 is sucked into compressor 1 in a liquid state without being vaporized, or in a case where the temperature of the refrigerant in compressor 1 is decreased while the operation of air conditioner 100 is stopped, the refrigerant in the liquid state is generated in compressor 1.

The refrigerant in the liquid state and the refrigeration oil are mixed in compressor 1 according to the condition such as a temperature. At this time, a target of which the temperature is detected by temperature sensor 50 is more strictly a mixture of the refrigerant in the liquid state and the refrigeration oil. The target heated by heater 60 is more strictly a mixture thereof. The concentration detected by concentration sensor 51 corresponds to a proportion of the refrigeration oil included in the mixture.

That is, concentration sensor 51 detects a component ratio between the refrigeration oil and the refrigerant in the liquid state in compressor 1. In other words, the detection value of concentration sensor 51 is an index indicating how much the refrigeration oil is diluted by the refrigerant. Concentration sensor 51 is, for example, a capacitive sensor that detects the relative permittivity of the refrigeration oil to obtain the component ratio. Heater 60 is, for example, a heating winding.

The amount of the refrigerant in the liquid state in compressor 1 is changed depending on the operation status of air conditioner 100. A part of the refrigeration oil in compressor 1 is discharged to the refrigerant circuit together with the refrigerant discharged from compressor 1. Therefore, the concentration of the refrigeration oil in compressor 1 is not constant. The viscosity of the refrigeration oil in compressor 1 is changed depending on the temperature of the refrigeration oil.

In a case where the viscosity of the refrigeration oil is too high, the driving torque of the motor in compressor 1 is abnormally increased, and the current value of the motor is excessively increased. As a result, an overcurrent may flow in the motor. Further, the supply of the refrigeration oil to bearings and the like of compressor 1 becomes insufficient. In addition, in a case where the concentration of the refrigeration oil is too low, the refrigeration oil cannot exhibit a function as a lubricant, and lubrication failure occurs in compressor 1. Therefore, in order to cause the refrigeration oil to exhibit a function as a lubricant, it is important to control the concentration and the temperature of the refrigeration oil.

For example, when the temperature of the refrigeration oil in compressor 1 continues to be decreased, the temperature eventually reaches the solidification point at which the refrigeration oil does not flow. In the present specification, the temperature higher than the solidification point of the refrigeration oil and immediately before the solidification point is referred to as pour point.

In a case where the temperature of the refrigeration oil detected by temperature sensor 50 is lower than the pour point, it is conceivable to operate heater 60 until the temperature of the refrigeration oil becomes greater than or equal to the pour point. As a result, the fluidity of the refrigeration oil can be enhanced. However, the refrigeration oil may be present in compressor 1 in a state of being diluted to an appropriate concentration by the refrigerant in the liquid state.

Even in a case where the temperature detected by temperature sensor 50 is lower than the pour point, the refrigeration oil diffused in the mixture may function as a lubricant depending on the concentration of the refrigeration oil. Of course, in a case where the concentration of the refrigeration oil is too low, it is necessary to operate heater 60 in order to cause the refrigeration oil to exhibit a function as a lubricant.

However, in this case, it is sufficient to increase the concentration of the refrigeration oil until the refrigeration oil diluted by the refrigerant in the liquid state functions as a lubricant. In other words, it is not necessary to operate heater 60 until all of the refrigerant in the liquid state in the mixture is vaporized and further the temperature of the refrigeration oil is increased.

On the other hand, in a case where the temperature detected by temperature sensor 50 is less than the pour point of the refrigeration oil in a state where the concentration of the refrigeration oil is too high, it is necessary to increase the fluidity of the refrigeration oil by increasing the temperature of the refrigeration oil. In this case, it is necessary to operate heater 60 until all of the refrigerant in the liquid state included in the mixture is vaporized and further the temperature of the refrigeration oil is increased.

Control device 70 determines a state of the refrigeration oil in compressor 1 on the basis of the detection values of temperature sensor 50 and concentration sensor 51, and operates heater 60 appropriately.

FIG. 2 is a diagram for describing a region where heater 60 is operated, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (first embodiment). In FIG. 2, the horizontal axis represents temperature Toil of the refrigeration oil in compressor 1, and the vertical axis represents concentration coil of the refrigeration oil in compressor 1. Temperature Toil is a value detected by temperature sensor 50. Concentration αoil is a value detected by concentration sensor 51. Therefore, in a case where the refrigerant in the liquid state is present in compressor 1, temperature Toil illustrated in FIG. 2 is the temperature of the mixture of the refrigerant in the liquid state and the refrigeration oil.

In FIG. 2, Tp is the pour point of the refrigeration oil. In FIG. 2, X1 is a threshold value for determining whether or not the concentration of the refrigeration oil is a concentration that causes lubrication failure. In FIG. 2, X2 is a threshold value for determining whether or not the concentration of the refrigeration oil is a concentration that causes the overcurrent in the motor of compressor 1. In particular, X2 is a value designed assuming that the overcurrent flows in the motor of compressor 1 when the temperature of the refrigeration oil in compressor 1 corresponds to pour point Tp and the concentration of the refrigeration oil in compressor 1 is X2.

Appropriate values of Tp, X1, and X2 are selected by the designer in consideration of the types of the refrigeration oil and the refrigerant, the structure of compressor 1, and the like. These values are stored in memory 72 of control device 70. Note that “1” on the vertical axis means that the concentration of the refrigeration oil is 100%, that is, there is no refrigerant in the liquid state diluting the refrigeration oil in compressor 1.

As illustrated in FIG. 2, the graph with temperature Toil on the horizontal axis and concentration αoil on the vertical axis is divided into regions (1) to (6). Coordinates (Toil, αoil) specified by temperature Toil and concentration αoil belong to any of these regions.

FIG. 3 is a diagram for describing control of heater 60, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (first embodiment). (1) to (6) illustrated in FIG. 3 correspond to regions (1) to (6) illustrated in FIG. 2. Hereinafter, the contents of the control corresponding to each region will be described with reference to FIGS. 2 and 3.

(1) of FIG. 3 illustrates a region where temperature Toil is less than pour point Tp and concentration αoil is less than or equal to threshold value X1. (2) of FIG. 3 illustrates a region where temperature Toil is greater than or equal to pour point Tp and concentration αoil is less than or equal to threshold value X1. Since concentration αoil is less than or equal to threshold value X1 in both region (1) and region (2), lubrication failure may occur in compressor 1.

In a case where the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil belongs to region (1) or region (2), control device 70 operates heater 60 such that a part of the refrigerant in the liquid state in compressor 1 is vaporized. As a result, concentration αoil exceeds threshold value X1. In this case, control device 70 stops heater 60, for example, when concentration αoil detected by concentration sensor 51 exceeds threshold value X1.

As a result, (Toil, αoil) is moved from region (1) to region (3) or from region (2) to region (4).

An upward arrow extending from region (1) to region (3) in FIG. 2 indicates that the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil transitions from region (1) to region (3) by the heating operation. An upward arrow extending from region (2) to region (4) in FIG. 2 indicates that the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil transitions from region (2) to region (4) by the heating operation.

As illustrated in FIG. 3, heating condition 1 corresponding to region (1) and region (2) is to operate heater 60 until concentration αoil>X1 is satisfied (heating condition 1).

(3) of FIG. 2 illustrates a region where temperature Toil is less than pour point Tp and concentration αoil exceeds threshold value X1 and is less than threshold value X2. In region (3), temperature Toil is less than the pour point, but since concentration αoil is less than threshold value X2, there is no possibility that an overcurrent flows in the motor in compressor 1. In addition, in region (3), since concentration αoil exceeds threshold value X1, lubrication failure does not occur in compressor 1.

(4) of FIG. 2 illustrates a region where temperature Toil is greater than or equal to pour point Tp and concentration coil exceeds threshold value X1 and is less than threshold value X2. In region (4), since temperature Toil is greater than or equal to the pour point, there is no possibility that an overcurrent flows in the motor in compressor 1. In addition, in region (4), since concentration αoil exceeds threshold value X1, lubrication failure does not occur in compressor 1.

Therefore, in a case where temperature Toil detected by temperature sensor 50 and concentration αoil detected by concentration sensor 51 belong to region (3) or region (4), control device 70 does not operate heater 60 (refer to FIG. 3).

Here, the description has been given assuming that, in a case where the (Toil, αoil) belongs to region (1) or region (2), the operation of heater 60 is stopped when concentration αoil detected by concentration sensor 51 exceeds threshold value X1. However, the timing of stopping the operation of heater 60 is not limited thereto.

For example, in a case where (Toil, αoil) belongs to region (1) or region (2), control device 70 may stop heater 60 when concentration αoil detected by concentration sensor 51 reaches any value from threshold value X1 to threshold value X2. However, from the viewpoint of reducing power consumption, it is desirable to stop heater 60 when concentration αoil detected by concentration sensor 51 exceeds threshold value X1.

(5) of FIG. 2 illustrates a region where temperature Toil is less than pour point Tp and concentration αoil is greater than or equal to threshold value X2. In region (5), there is a possibility that an overcurrent flows in the motor in compressor 1. In a case where (Toil, αoil) belongs to region (5), control device 70 operates heater 60 so that the refrigerant in the liquid state in compressor 1 is vaporized and the temperature of the refrigeration oil in compressor 1 is increased. As the heating by heater 60 is continued, the refrigerant in the liquid state is vaporized, and concentration coil of the refrigeration oil eventually reaches “1”. Thereafter, temperature Toil of the refrigeration oil is increased, and eventually temperature Toil reaches pour point Tp. Control device 70 stops the operation of heater 60 when temperature Toil detected by temperature sensor 50 reaches pour point Tp.

As a result, (Toil, αoil) is moved from region (5) to region (6).

An arrow extending from region (5) to region (6) in FIG. 2 indicates that the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil transitions to region (6) in a state of concentration oil=1, by the heating operation.

As illustrated in FIG. 3, the heating condition corresponding to region (5) is to operate heater 60 until temperature Toil≥pour point Tp by vaporizing the refrigerant in the liquid state so that concentration αoil=1 (heating condition 2).

(6) of FIG. 2 illustrates a region where temperature Toil is greater than or equal to pour point Tp and concentration αoil is greater than or equal to threshold value X2. In region (6), concentration αoil is greater than or equal to threshold value X2. However, in region (6), since temperature Toil is greater than or equal to pour point Tp, there is no possibility that an overcurrent flows in the motor in compressor 1. In addition, in region (6), since concentration αoil exceeds threshold value X1, lubrication failure does not occur in compressor 1. Therefore, in a case where temperature Toil detected by temperature sensor 50 and concentration αoil detected by concentration sensor 51 belong to region (6), control device 70 does not operate heater 60 (refer to FIG. 3).

As described above, among regions (1) to (6), the regions as the targets where control device 70 operates heater 60 are (1), (2), and (5). Control device 70 operates heater 60 in a case where (Toil, αoil) belongs to either region (1) or region (2). Moreover, control device 70 stops the operation of heater 60 in a stage where concentration αoil of the refrigeration oil exceeds threshold value X1.

In other words, control device 70 does not operate heater 60 until all of the refrigerant in the liquid state for diluting the refrigeration oil is vaporized. Therefore, according to the present embodiment, it is possible to reduce the power consumption associated with the operation of heater 60 while increasing the concentration of the refrigeration oil until the refrigeration oil diluted by the refrigerant in the liquid state functions as a lubricant.

Further, in a case where (Toil, αoil) belongs to region (5), control device 70 operates heater 60. At this time, control device 70 operates heater 60 until the refrigerant in the liquid state is vaporized so that αoil=1 and further temperature Toil≥pour point Tp is satisfied. As a result, the fluidity of the refrigeration oil can be enhanced. As a result, according to the present embodiment, it is possible to prevent the driving torque of the motor in compressor 1 from being abnormally increased and an overcurrent from flowing in the motor.

As described above, according to the present embodiment, it is possible to provide the air conditioner capable of appropriately maintaining lubricating performance of the refrigeration oil in compressor 1 in consideration of the temperature and the concentration of the refrigeration oil.

FIG. 4 is a flowchart illustrating control for setting the heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (first embodiment). The processing based on this flowchart is executed by control device 70. A program corresponding to this flowchart is stored in memory 72 of control device 70.

First, control device 70 determines whether or not the power supply of compressor 1 is on (step S1). In a case where the power supply of compressor 1 is not on (NO in step S1), control device 70 ends the processing based on the present flowchart.

In a case where the power supply of compressor 1 is on (YES in step S1), control device 70 acquires temperature Toil and concentration αoil of the refrigeration oil in compressor 1 (step S2). Control device 70 acquires temperature Toil from temperature sensor 50. Control device 70 acquires concentration αoil from concentration sensor 51.

Next, control device 70 determines whether or not “concentration αoil≤threshold value X1” is satisfied (step S3). In a case where “concentration αoil≤threshold value X1” is satisfied, control device 70 sets heating condition 1 (step S4), and ends the processing. As a result, heating condition 1 is set corresponding to region (1) and region (2) illustrated in FIG. 2.

In a case where “concentration αoil≤threshold value X1” is not satisfied, control device 70 determines whether or not “temperature Toil<pour point Tp” and “concentration αoil≥threshold value X2” are satisfied (step S5). In a case where “temperature Toil<pour point Tp” and “concentration αoil≥threshold value X2” are satisfied, control device 70 sets heating condition 2 (step S6), and ends the processing. As a result, heating condition 2 is set corresponding to region (5) illustrated in FIG. 2.

In a case where “temperature Toil<pour point Tp” and “concentration αoil≥threshold value X2” are not satisfied, control device 70 decides not to perform heating (step S7), and ends the processing. As a result, the heating is not performed corresponding to region (3), region (4), and region (6) illustrated in FIG. 2.

FIG. 5 is a flowchart illustrating control for operating heater 60 according to the heating condition (first embodiment). The processing based on this flowchart is executed by control device 70. A program corresponding to this flowchart is stored in memory 72 of control device 70.

First, control device 70 determines whether or not heating condition 1 is set (step S11). In a case where heating condition 1 is set, control device 70 operates heater 60 (step S12). Control device 70 operates heater 60 until “concentration αoil>X1” corresponding to heating condition 1 is satisfied. When “concentration αoil>X1” is satisfied (YES in step S13), control device 70 stops the operation of heater 60 (step S14), and ends the processing based on the present flowchart.

In a case of determining NO in step S11, control device 70 determines whether or not heating condition 2 is set (step S15). In a case where heating condition 2 is set, control device 70 operates heater 60 (step S16). Control device 70 operates heater 60 until “concentration αoil=1” and “temperature Toil≥pour point Tp” corresponding to heating condition 2 are satisfied. When heating condition 2 is satisfied (YES in step S17), control device 70 stops the operation of heater 60 (step S14), and ends the processing based on the present flowchart.

Second Embodiment

Next, a second embodiment will be described. FIG. 6 is a diagram for describing control of heater 60, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (second embodiment). As illustrated in FIG. 6, the second embodiment is different from the first embodiment in that threshold value X1 is varied according to temperature Toil of the refrigeration oil. In other respects, the second embodiment is similar to the first embodiment.

When temperature Toil of the refrigeration oil is decreased, the viscosity of the refrigeration oil is increased. In a case where the viscosity of the refrigeration oil is appropriately high, the lubricating performance of the refrigeration oil can be secured even when concentration αoil of the refrigeration oil is small. Therefore, in the second embodiment, in consideration of the fact that the viscosity of the refrigeration oil is increased when temperature Toil of the refrigeration oil is decreased, threshold value X1 is made smaller as temperature Toil is decreased.

For example, FIG. 6 illustrates threshold value X11 corresponding to temperature T1 of the refrigeration oil and threshold value X12 corresponding to temperature T2 of the refrigeration oil. Control device 70 of air conditioner 100 according to the second embodiment stores a plurality of threshold values X1 including threshold value X11 and threshold value X12 in memory 72.

As is clear from the comparison between FIGS. 2 and 6, in the second embodiment, region (1) and region (2) are narrower than those in the first embodiment by an area A1 illustrated in FIG. 6. This means that there is less need to operate heater 60 in the second embodiment than in the first embodiment. As a result, according to the second embodiment, the power consumption associated with the operation of heater 60 can be further reduced as compared with the first embodiment.

Third Embodiment

Next, a third embodiment will be described. FIG. 7 is a flowchart illustrating control for setting the heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (third embodiment). FIG. 8 is a flowchart illustrating control for operating heater 60 according to the heating condition (third embodiment). The processing based on these flowcharts of FIGS. 7 and 8 is executed by control device 70. A program corresponding to these flowcharts is stored in memory 72 of control device 70.

As illustrated in step S1A of FIG. 7, control device 70 starts the control for setting the heating condition by detecting an activation signal. The activation signal is a signal for an instruction to start the operation of air conditioner 100. The activation signal is output from, for example, a remote controller of air conditioner 100.

As illustrated in step S18 of FIG. 8, control device 70 turns on the power supply of compressor 1 after operating heater 60 according to the set heating condition.

That is, in the third embodiment, control device 70 sets the heating condition before turning on the power supply of compressor 1, and operates heater 60 according to the set heating condition. According to the third embodiment, compressor 1 is activated after temperature Toil and concentration oil of the refrigeration oil are adjusted to appropriate values. Therefore, compressor 1 can be operated in an appropriate environment from an activation start time point. As a result, it is possible to more reliably prevent occurrence of a failure such as an overcurrent flowing in the motor of compressor 1.

The third embodiment is similar to the first embodiment except for the timing of turning on the power supply of compressor 1. For example, the processing in steps S2 to S7 in FIG. 7 is similar to the processing in steps S2 to S7 in FIG. 4 described as the first embodiment. In addition, the processing in steps S11 to S17 in FIG. 8 is similar to the processing in steps S11 to S17 in FIG. 5 described as the first embodiment. Therefore, the description of points common to the first embodiment including the flowchart will not be repeated here.

Fourth Embodiment

Next, a fourth embodiment will be described. The fourth embodiment realizes control in consideration of a case where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1. FIG. 9 is a diagram for describing a region where heater 60 is operated in a state where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (fourth embodiment).

As illustrated in FIG. 9, the graph with temperature Toil on the horizontal axis and concentration αoil on the vertical axis is divided into regions (7) to (9). Coordinates (Toil, αoil) specified by temperature Toil and concentration αoil belong to any of these regions.

FIG. 10 is a diagram for describing control of heater 60, from the viewpoint of temperature Toil and concentration αoil of the refrigeration oil (fourth embodiment). (1) to (6) illustrated in FIG. 10 are similar to (1) to (6) of FIG. 3 described as the first embodiment. These indicate heating conditions when the refrigerant in the liquid state and the refrigeration oil are not separated into two layers in compressor 1. (7) to (9) illustrated in FIG. 10 illustrate heating conditions when the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1. (7) to (9) correspond to regions (7) to (9) illustrated in FIG. 9.

Hereinafter, the contents of the control corresponding to regions (7) to (9) will be described with reference to FIGS. 9 and 10. Note that the contents of the control corresponding to regions (1) to (6) are similar to those in the first embodiment, and thus, the description thereof will not be repeated here.

(7) of FIG. 9 illustrates a region where temperature Toil is less than pour point Tp. In a case where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1, the refrigeration oil and the refrigerant are not mixed with each other and are present in a single state.

Therefore, even in a case where the concentration of the refrigeration oil satisfies αoil>X1, when temperature Toil is less than pour point Tp, the refrigeration oil maintains a high viscosity state. In general, the density of the refrigerant in the liquid state is higher than the density of the refrigeration oil. Therefore, in a case where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1, a state is obtained in which the refrigeration oil collects in an upper portion of compressor 1, and the refrigeration oil is not present at the end portion of the shaft in a lower portion of compressor 1. In this state, lubrication failure may occur in compressor 1.

Therefore, at this time, regardless of concentration αoil of the refrigeration oil, control device 70 operates heater 60 until the refrigerant in the liquid state present at the end portion of the shaft of compressor 1 is gasified (concentration αoil=1) and further temperature Toil≥pour point Tp is satisfied (heating condition 2). As a result, the refrigerant in the liquid state pushing the refrigeration oil upward is gasified. As a result, (Toil, αoil) is moved from region (7) to region (9). At this time, the end portion of the shaft in the lower portion of compressor 1 is thus moistened by the refrigeration oil.

An arrow extending from region (7) to region (9) in FIG. 9 indicates that the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil transitions from region (7) to region (9) by the heating operation. As indicated by the tip of the arrow, the transition destination is the position of concentration αoil=1.

(8) of FIG. 9 illustrates a region where temperature Toil is greater than or equal to pour point Tp and concentration αoil is less than or equal to threshold value X1. Since concentration αoil is less than or equal to threshold value X1 in region (8), lubrication failure may occur in compressor 1. In particular, in a case where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1, a state is obtained in which the refrigeration oil collects in an upper portion of compressor 1, and the refrigeration oil is not present at the end portion of the shaft in a lower portion of compressor 1. In order to prevent lubrication failure in compressor 1 in this state, it is necessary to gasify all of the refrigerant in the liquid state in compressor 1. Therefore, at this time, control device 70 operates heater 60 until αoil=1 is satisfied to gasify the refrigerant in the liquid state (heating condition 3).

As a result, (Toil, αoil) is moved from region (8) to region (9). At this time, the end portion of the shaft in the lower portion of compressor 1 is thus moistened by the refrigeration oil.

An arrow extending from region (8) to region (9) in FIG. 9 indicates that the position of coordinates (Toil, αoil) specified by temperature Toil and concentration αoil transitions from region (8) to region (9) by the heating operation. As indicated by the tip of the arrow, the transition destination is the position of concentration αoil=1.

(9) of FIG. 9 illustrates a region where temperature Toil is greater than or equal to pour point Tp and concentration coil exceeds threshold value X1. Under this condition, there is no possibility that lubrication failure occurs in compressor 1 in region (9). Therefore, in a case where temperature Toil detected by temperature sensor 50 and concentration oil detected by concentration sensor 51 belong to region (9), control device 70 does not operate heater 60 (refer to FIG. 10).

FIG. 11 is a flowchart illustrating control for setting the heating conditions in accordance with temperature Toil and concentration αoil of the refrigeration oil (fourth embodiment). The processing based on this flowchart is executed by control device 70. The processing based on the flowchart of FIG. 11 is executed by control device 70. A program corresponding to this flowchart is stored in memory 72 of control device 70.

The flowchart illustrated in FIG. 11 is different from the flowchart illustrated in FIG. 4 described as the first embodiment in the following two points. The first point is that step S48 of determining that the refrigeration oil and the refrigerant in the liquid state are separated into two layers is added. The second point is that steps S49 to S53 of setting the heating conditions in a case where the refrigeration oil and the refrigerant in the liquid state are separated into two layers are added.

Hereinafter, the flowchart illustrated in FIG. 11 will be described. Among the steps of the flowchart illustrated in FIG. 11, step S41 corresponds to step S1 of the flowchart illustrated in FIG. 4, and steps S42 to S47 correspond to steps S2 to S7 of the flowchart illustrated in FIG. 4, respectively. Therefore, the description of these steps will not be repeated here.

After acquiring temperature Toil and concentration αoil of the refrigeration oil in compressor 1 in step S42, control device 70 determines whether or not temperature Toil of the refrigeration oil is less than or equal to a separation temperature Ts (step S48). That is, control device 70 compares acquired temperature Toil of the refrigeration oil with the separation temperature Ts to determine whether or not the refrigeration oil and the refrigerant in the liquid state are separated into two layers in step S48.

Separation temperature Ts used for the determination in step S48 is stored in memory 72 of control device 70. Control device 70 may vary separation temperature Ts according to the concentration detected by concentration sensor 51.

In a case where it is determined that the refrigeration oil and the refrigerant in the liquid state are not separated into two layers, control device 70 proceeds to step S43. The processing in steps S43 to S47 is similar to that in steps S3 to S7 in FIG. 4 as described above.

In a case where it is determined that the refrigeration oil and the refrigerant in the liquid state are separated into two layers, control device 70 determines whether or not “temperature Toil<pour point Tp” is satisfied (step S49). In a case where “temperature Toil<pour point Tp” is satisfied, control device 70 sets heating condition 2 (step S50), and ends the processing. As a result, heating condition 2 is set corresponding to region (7) illustrated in FIG. 9.

In a case where “temperature Toil<pour point Tp” is not satisfied, control device 70 determines whether or not “concentration αoil≤threshold value X1” is satisfied (step S51). In a case where “concentration αoil≤threshold value X1” is satisfied, control device 70 sets heating condition 3 (step S52), and ends the processing. As a result, heating condition 3 is set corresponding to region (8) illustrated in FIG. 9. In a case where “concentration αoil≤threshold value X1” is not satisfied, control device 70 decides not to perform heating (step S53), and ends the processing. Accordingly, it is decided that heating is not performed corresponding to region (9) illustrated in FIG. 9.

FIG. 12 is a flowchart illustrating control for operating heater 60 according to the heating condition (fourth embodiment). The processing based on this flowchart is executed by control device 70. A program corresponding to this flowchart is stored in memory 72 of control device 70.

Hereinafter, the flowchart illustrated in FIG. 12 will be described. The flowchart shown in FIG. 12 is different from the flowchart illustrated in FIG. 5 described as the first embodiment in that control corresponding to heating condition 3 is added. The control corresponding to heating condition 3 is illustrated in steps S58 to S60 in FIG. 12. Steps S51 to S57 in FIG. 12 are similar to steps S11 to S17 in FIG. 5. Therefore, the description of steps S51 to S57 will not be repeated here.

In a case where it is determined in step S55 that heating condition 2 is not set, control device 70 determines whether or not heating condition 3 is set (step S58). In a case where heating condition 3 is not set, control device 70 ends the processing without operating heater 60.

In a case where heating condition 3 is set, control device 70 operates heater 60 (step S59). Control device 70 operates heater 60 until “concentration αoil=1” corresponding to heating condition 3 is satisfied. When heating condition 3 is satisfied (YES in step S60), control device 70 stops the operation of heater 60 (step S54), and ends the processing based on the present flowchart.

According to the fourth embodiment, the state of the refrigerant and the state of the refrigeration oil can be set to appropriate states according to each of a case where the refrigerant in the liquid state and the refrigeration oil are separated into two layers in compressor 1 and a case where the refrigerant in the liquid state and the refrigeration oil are not separated.

Fifth Embodiment

Next, a fifth embodiment will be described. FIG. 13 is a diagram illustrating an example in which temperature sensor 50 and concentration sensor 51 are provided in a vicinity portion of a shaft 53 of compressor 1 (fifth embodiment). Compressor 1 includes a compression unit 52, shaft 53, an oil reservoir 54, and a motor 55. Refrigeration oil is stored in oil reservoir 54. In FIG. 13, heater 60 is not illustrated. For example, heater 60 may be disposed between compression unit 52 and motor 55. Alternatively, heater 60 may be disposed at a lower portion of motor 55 and outside a housing of compressor 1.

As illustrated in FIG. 13, temperature sensor 50 and concentration sensor 51 are disposed in the vicinity portion of shaft 53 when shaft 53 is viewed from a vertical direction. For example, temperature sensor 50 and concentration sensor 51 are disposed in the vicinity portion of shaft 53 at a position close to a lower portion of compression unit 52. In particular, temperature sensor 50 and concentration sensor 51 are disposed at a lower portion of compression unit 52.

By disposing temperature sensor 50 and concentration sensor 51 at the positions illustrated in FIG. 13, temperature sensor 50 and concentration sensor 51 can respectively detect the temperature and the concentration for the refrigeration oil supplied when compressor 1 is activated. As a result, control device 70 can determine whether or not the refrigeration oil exhibits lubricating performance when compressor 1 is activated.

Sixth Embodiment

Next, a sixth embodiment will be described. FIG. 14 is a diagram illustrating an example in which the temperature sensor and the concentration sensor are provided at the end portion of shaft 53 of compressor 1 (sixth embodiment). As illustrated in FIG. 14, temperature sensor 50 and concentration sensor 51 are disposed at the lower portion of shaft 53 when shaft 53 is viewed from the vertical direction. In particular, temperature sensor 50 and concentration sensor 51 are disposed at positions close to the end of shaft 53.

By disposing temperature sensor 50 and concentration sensor 51 at the positions illustrated in FIG. 14, temperature sensor 50 and concentration sensor 51 can respectively detect the temperature and the concentration for the refrigeration oil present in the lower portion of shaft 53 before the activation of compressor 1. As a result, control device 70 can determine whether or not the refrigeration oil is sufficiently supplied before the activation of compressor 1 and the refrigeration oil exhibits lubricating performance.

In each embodiment described above, “exceeding” may be replaced with “greater than or equal to”, and “less than or equal to” may be replaced with “less than”. Conversely, “greater than or equal to” may be replaced with “exceeding”, and “less than” may be replaced with “less than or equal to”.

SUMMARY

Hereinafter, the present embodiment will be summarized.

(1) The present disclosure relates to an air conditioner (100). The air conditioner includes a compressor (1); a first heat exchanger (2); a second heat exchanger (4); a decompression device (3); a circulation path (5) through which a refrigerant circulates through the compressor, the first heat exchanger, the decompression device, and the second heat exchanger in this order; a temperature sensor (50) to detect a temperature of refrigeration oil in the compressor; a concentration sensor (51) to detect a concentration of the refrigeration oil in a mixture of the refrigerant in a liquid state and the refrigeration oil in the compressor; a heater (60) to heat the refrigeration oil in the compressor; and a control device (70). In a case where a concentration of refrigeration oil detected by the concentration sensor is less than a first threshold value, the control device operates the heater such that a part of a refrigerant in a liquid state in the compressor is vaporized (step S4 and steps S11 to S13), and in a case where the concentration of the refrigeration oil detected by the concentration sensor exceeds a second threshold value greater than the first threshold value and a temperature of the refrigeration oil detected by the temperature sensor is less than a specified temperature, the control device operates the heater such that the refrigerant in the liquid state in the compressor is vaporized and the temperature of the refrigeration oil in the compressor is increased (step S6 and steps S15 to S17).

According to the disclosure described in (1), it is possible to provide the air conditioner capable of appropriately maintaining lubricating performance of the refrigeration oil in the compressor in consideration of the temperature and the concentration of the refrigeration oil.

(2) In a case where the concentration of the refrigeration oil detected by the concentration sensor is less than the first threshold value, the control device ends heating of the refrigeration oil via the heater when the concentration of the refrigeration oil in the compressor exceeds the first threshold value (steps S13 and S14).

According to the disclosure described in (2), the power consumption of the heater can be reduced as compared with a case where the heater is continuously operated even when the concentration of the refrigeration oil in the compressor exceeds the first threshold value.

(3) The specified temperature is a temperature (Tp) corresponding to a pour point of the refrigeration oil (FIG. 2).

According to the disclosure described in (3), it is possible to prevent occurrence of a failure in the operation of the compressor due to the refrigeration oil having high viscosity.

(4) The second threshold value is a value designed assuming that an overcurrent flows in a motor of the compressor when the temperature of the refrigeration oil in the compressor is a temperature (Tp) corresponding to the pour point and the concentration of the refrigeration oil in the compressor is the second threshold value.

According to the disclosure described in (4), it is possible to prevent an overcurrent from flowing in the motor of the compressor.

(5) The air conditioner further includes a memory (72) to store the first threshold value, in which the first threshold value (X11) is a value corresponding to a first temperature (T1) of the refrigeration oil, and the memory further stores a third threshold value (X12) corresponding to a second temperature (T2) of the refrigeration oil (FIG. 6).

According to the disclosure described in (5), the power consumption of the heater can be reduced.

(6) The control device activates the compressor (step S18) after adjusting the concentration or the temperature of the refrigeration oil in the compressor by operating the heater.

According to the disclosure described in (6), the compressor can be operated in an appropriate environment from an activation start time point. As a result, it is possible to more reliably prevent occurrence of a failure in the operation of the compressor.

(7) The control device operates the heater (steps S48 to S50) regardless of the concentration of the refrigeration oil in the compressor in a case where the refrigerant and the refrigeration oil in the compressor are separated and the temperature of the refrigeration oil detected by the temperature sensor is less than the specified temperature.

According to the disclosure described in (7), the heater operates to gasify the refrigerant in the liquid state pushing the refrigeration oil upward in the compressor. As a result, it is possible to prevent occurrence of the lubrication failure in the compressor.

(8) The control device stops the operation of the heater (steps S57 and S54) in a case where the temperature of the refrigeration oil in the compressor exceeds the specified temperature.

According to the disclosure described in (8), the refrigerant in the liquid state can be sufficiently gasified.

(9) The control device operates the heater (steps S48, S49, S51, and S52) in a case where the refrigerant and the refrigeration oil in the compressor are separated, the temperature of the refrigeration oil detected by the temperature sensor exceeds the specified temperature, and the concentration of the refrigeration oil detected by the concentration sensor is less than the first threshold value.

According to the disclosure described in (9), the heater operates to gasify the refrigerant in the liquid state pushing the refrigeration oil upward in the compressor. As a result, it is possible to prevent occurrence of the lubrication failure in the compressor.

(10) The control device stops the operation of the heater (steps S60 and S54) in a case where the refrigerant in the liquid state in the compressor is vaporized.

According to the disclosure described in (10), the power consumption of the heater can be reduced as compared with a case where the heater is continuously operated even after the refrigerant is vaporized.

(11) The temperature sensor and the concentration sensor are provided in a vicinity of a shaft of the compressor (FIG. 13).

According to the disclosure described in (11), the control device can more appropriately maintain the lubricating performance of the refrigeration oil in the compressor in consideration of the temperature and the concentration of the refrigeration oil in a state where the compressor is activated.

(12) The temperature sensor and the concentration sensor are provided at an end portion of a shaft of the compressor (FIG. 14).

According to the disclosure described in (12), the control device can more appropriately maintain the lubricating performance of the refrigeration oil in the compressor in consideration of the temperature and the concentration of the refrigeration oil before the compressor is activated.

It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present disclosure is defined not by the above description in the above embodiments but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

REFERENCE SIGNS LIST

- 1: compressor, 2: first heat exchanger, 3: decompression device, 4: second heat exchanger, 5: circulation path, 50: temperature sensor, 51: concentration sensor, 52: compression unit, 53: shaft, 54: oil reservoir, 55: motor, 60: heater, 70: control device, 71: processor, 72: memory, 100: air conditioner, A1: area

AIR CONDITIONER

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CPC

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