Heat pump air conditioner

• US 6,314,750 B1
• Filed: 05/08/2000
• Issued: 11/13/2001
• Est. Priority Date: 05/13/1999
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Tanaka, Masaya, Ishikawa, Hiroshi, Iritani, Kunio, Kusano, Katsuya, Honda, Keita
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): Jones, Melvin
• Application Number:
  US09/567,495
• Time in Patent Office: 554 Days
• Field of Search: 621/763, 621/93, 622/281, 622/39, 623/241, 623/244, 623/246, 621/29, 621/74
• US Class Current: 62/324.1
• CPC Class Codes: B60H 1/00921 where the flow direction of the refrigerant does not change and there is an extra subcondenser, e.g. in an air duct
• CPC Class Codes: B60H 1/3205 Control means therefor
• CPC Class Codes: B60H 1/3213 for increasing the efficiency in a vehicle heat pump
• CPC Class Codes: B60H 1/3214 for improving the lubrication of a refrigerant compressor in a vehicle
• CPC Class Codes: B60H 1/3225 characterised by safety arrangements, e.g. compressor anti-seizure means or by signalling devices
• CPC Class Codes: B60H 2001/00961 comprising means for defrosting outside heat exchangers
• CPC Class Codes: B60H 2001/325 of the refrigerant at a compressing unit
• CPC Class Codes: B60H 2001/3257 of the refrigerant at a compressing unit
• CPC Class Codes: B60H 2001/3261 of the air at an evaporating unit
• CPC Class Codes: B60H 2001/3272 to control the revolving speed of a compressor
• CPC Class Codes: B60H 2001/3275 to control the volume of a compressor
• CPC Class Codes: B60H 2001/3285 related to an expansion unit
• CPC Class Codes: F25B 2500/26 characterised by the startup of the refrigeration cycle
• CPC Class Codes: F25B 2700/04 Refrigerant level
• CPC Class Codes: F25B 43/006 Accumulators
• CPC Class Codes: F25B 49/022 Compressor control arrangements

Abstract

A heat pump air conditioner has a heat exchanger, a separator for separating refrigerant discharged from the heat exchanger into gas refrigerant and liquid refrigerant, and a compressor. Gas refrigerant in the separator is sucked into the compressor through a gas suction pipe. Oil-dissolved liquid refrigerant in the separator is also sucked through an oil return hole formed at a bottom of the gas suction pipe into the compressor. At the time of starting the air conditioner, when it is judged that a surface of liquid refrigerant in the separator is rapidly lowered to the oil return hole, a rotational speed of the compressor is controlled so that an amount of refrigerant discharged from the compressor is decreased. As a result, the surface of liquid refrigerant is kept higher than the oil return hole, and oil shortage of the compressor is restricted.

Claims

1. A heat pump air conditioner through which a refrigerant flows, the heat pump air conditioner comprising:

a compressor for compressing and discharging the refrigerant;

a first heat exchanger for radiating heat of gas refrigerant discharged from the compressor;

a decompressing unit for decompressing the refrigerant having passed through the first heat exchanger;

a second heat exchanger for evaporating the refrigerant having passed through the decompressing unit; and

a separator for separating the refrigerant having passed through the second heat exchanger into gas refrigerant and liquid refrigerant and storing the liquid refrigerant therein, the separator having a gas suction pipe through which the gas refrigerant in the separator is sucked into the compressor, the gas suction pipe having an oil return hole through which at least oil is sucked and mixed with the gas refrigerant to be returned into the compressor, the oil return hole being formed at a bottom of the gas suction pipe; and

a control unit for controlling an operation of the compressor, the control unit having judging means for judging whether a specific condition that a surface of the liquid refrigerant in the separator is rapidly lowered toward the oil return hole is satisfied, wherein;

the control unit decreases an amount of the refrigerant discharged from the compressor to a value smaller than that in a normal state at the time of starting the compressor, when the judging means judges that the specific condition is satisfied.

2. The heat pump air conditioner according to claim 1, wherein the compressor is an electric compressor which adjusts an amount of the refrigerant discharged therefrom by adjusting a rational speed thereof.

3. The heat pump air conditioner according to claim 2, wherein the control unit decreases a deviation rate of the rational speed of the compressor to a value smaller than that in the normal state at the time of starting the compressor, when the judging means that the specific condition is satisfied.

4. The heat pump air conditioner according to claim 2, wherein the control unit temporarily restricts an increase of the rotational speed of the compressor when the judging means judges that the specific condition is satisfied.

5. The heat pump air conditioner according to claim 2, wherein:

the control unit restricts an increase of the rotational speed of the compressor when the judging means judges that the specific condition is satisfied to a first degree; and

the control unit decreases the rotational speed of the compressor when the judging means judges that the specific condition is satisfied to a second degree.

6. The heat pump air conditioner according to claim 1, wherein the compressor is a variable capacity compressor which adjusts an amount of the refrigerant discharged therefrom by adjusting a capacity thereof.

7. The heat pump air conditioner according to claim 1, wherein:

the first heat exchanger is an interior heat exchanger disposed inside an interior space, and the second heat exchanger is an exterior heat exchanger disposed outside the interior space; and

air heated by the first heat exchanger is blown into the interior space to heat the interior space.

8. The heat pump air conditioner according to claim 7, wherein the judging means judges that the specific condition is satisfied when a temperature of air outside the interior space is lower than a predetermined value.

9. The heat pump air conditioner according to claim 7, wherein the judging means judges that the specific condition is satisfied, when a temperature of air outside the interior space is lower than a predetermined value and the compressor is left for a period longer than a predetermined period after being stopped.

10. The heat pump air conditioner according to claim 7, wherein the judging means judges that the specific condition is satisfied, when a temperature of the compressor is lower than a predetermined value.

11. The heat pump air conditioner according to claim 7, wherein the judging means judges that the specific condition is satisfied when a temperature difference between a temperature of the compressor and a temperature of air outside the interior space is smaller than a predetermined value.

12. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied, when a supercooling degree of the refrigerant discharged from the separator continues to be higher than a predetermined value for a period longer than a predetermined period.

13. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied, when a supercooling degree of the refrigerant discharged from the second heat exchanger continues to be higher than a predetermined value for a period longer than a predetermined period.

14. The heat pump air conditioner according to claim 1, further comprising:

a pressure sensor for detecting a low pressure in a low pressure passage disposed between the second heat exchanger and the separator, wherein;

the judging means judges that the specific condition is satisfied when the low pressure detected by the pressure sensor continues to be lower than a predetermined value for a period longer than a predetermined period.

15. The heat pump air conditioner according to claim 14, wherein:

the first heat exchanger is an interior heat exchanger disposed inside an interior space, and the second heat exchanger is an exterior heat exchanger disposed outside the interior space; and

the predetermined value is decreased as a temperature of air outside the interior space is decreased.

16. The heat pump air conditioner according to claim 1, further comprising:

a pressure sensor for detecting a high pressure in a high pressure passage communicating with the first heat exchanger, wherein;

the judging means judges that the specific condition is satisfied, when the high pressure detected by the pressure sensor continues to be lower than a predetermined value which depends on a heat load condition and a rotational speed of the compressor for a period longer than a predetermined period.

17. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied, when a temperature of the refrigerant discharged from the compressor continues to be lower than a predetermined value which depends on a heat load condition and a rotational speed of the compressor for a period longer than a predetermined period.

18. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied when the surf ace of the liquid refrigerant in the separator is lower than a predetermined position.

19. The heat pump air conditioner according to claim 18, wherein the judging means judges that the specific condition is satisfied, when a value related to a torque of the compressor is lower than a predetermined value which depends on a rotational speed of the compressor.

20. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied when the surface of the liquid refrigerant in the separator is lowered at a speed higher than a predetermined value.

21. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied when the compressor is left for a period longer than a predetermined period after being stopped.

22. The heat pump air conditioner according to claim 1, wherein the judging means judges that the specific condition is satisfied, when an amount of the refrigerant sucked into the compressor continues to be larger than a predetermined value for a period longer than a predetermined period and then is decreased to become smaller than the predetermined value.

23. The heat pump air conditioner according to claim 1, wherein:

the compressor has a discharge side portion in which the liquid refrigerant is accumulated; and

the judging means Judges that the specific condition is satisfied when a surface of the liquid refrigerant accumulated in the discharge side portion of the compressor

is higher than a predetermined position.

24. A heat pump air conditioner through which a refrigerant flows, the heat pump air conditioner comprising:

a compressor for compressing and discharging a refrigerant;

a first heat exchanger for radiating heat of the gas refrigerant discharged from the compressor;

a decompressing unit for decompressing the refrigerant having passed through the first heat exchanger, the decompressing unit having a throttle portion with a fixed opening degree;

a second heat exchanger for evaporating the refrigerant having passed through the decompressing unit;

a separator for separating the refrigerant having passed through the second heat exchanger into gas refrigerant and liquid refrigerant and storing the liquid refrigerant therein, the separator having a gas suction pipe through which the gas refrigerant in the separator is sucked into the compressor, the gas suction pipe having an oil return hole through which at least oil is sucked and mixed with the gas refrigerant to be returned into the compressor, the oil return hole being formed at a bottom of the gas suction pipe; and

a control unit for controlling an operation of the compressor, the control unit having judging means for judging whether a specific condition that a surface of the liquid refrigerant in the separator is rapidly lowered toward the oil return hole is satisfied, wherein;

the control unit forces the refrigerant to flow bypassing the decompressing unit at the time of starting the compressor when the judging means judges that the specific condition is satisfied.

25. A heat pump air conditioner through which a refrigerant flows, the heat pump air conditioner comprising:

a compressor for compressing and discharging a refrigerant;

a first heat exchanger for radiating heat of the gas refrigerant discharged from the compressor;

a decompressing unit for decompressing the refrigerant having passed through the first heat exchanger, the decompressing unit having a throttle portion with a variable opening degree;

a second heat exchanger for evaporating the refrigerant having passed through the decompressing unit;

a separator for separating the refrigerant having passed through the second heat exchanger into gas refrigerant and liquid refrigerant and storing the liquid refrigerant therein, the separator having a gas suction pipe through which the gas refrigerant in the separator is sucked into the compressor, the gas suction pipe having an oil return hole through which at least oil is sucked and mixed with the gas refrigerant to be returned into the compressor, the oil return hole being formed at a bottom of the gas suction pipe; and

a control unit for controlling an operation of the compressor, the control unit having judging means for judging whether a specific condition that a surface of the liquid refrigerant in the separator is rapidly lowered toward the oil return hole is satisfied, wherein;

the control unit increases the opening degree of the throttle portion to a value larger than that in a normal state at the time of starting the compressor when the judging means judges that the specific condition is satisfied.