Apparatus and method for controlling variable displacement compressor

• US 6,672,844 B2
• Filed: 11/09/2001
• Issued: 01/06/2004
• Est. Priority Date: 11/10/2000
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Original Assignee: Kabushiki Kaisha Toyota Jidoshokki
• Inventors: Yokono, Tomohiko, Fukanuma, Tetsuhiko, Morishita, Atsuyuki
• Primary Examiner(s): Yu, Justine R.
• Assistant Examiner(s): Liu, Han L
• Application Number:
  US10/040,860
• Publication Number:
  US 20020094278A1
• Time in Patent Office: 788 Days
• Field of Search: 417/222.2, 417/269, 417/270, 417/213, 417/222.1, 914/99, 915/04, 915/05, 622/283, 622/285, 621/33, 251/129.02, 251/129.05, 251/129.15
• US Class Current: 417/222.2
• CPC Class Codes: F04B 2027/185 Discharge pressure
• CPC Class Codes: F04B 2027/1854 External parameters
• CPC Class Codes: F04B 27/1804 Controlled by crankcase pressure

Abstract

A variable displacement compressor has a control valve for controlling the displacement of the compressor. When the pressure in a discharge chamber of the compressor (discharge pressure) is equal to or higher than a first threshold value, a controller executes a limiting control for limiting the discharge pressure. During the limiting control, the controller gradually decreases a duty ratio, which is sent to the control valve, such that the displacement of the compressor is gradually decreased. When the duty ratio is decreased to a reference duty ratio, the controller sets the duty ratio to zero %. As a result, the compressor displacement is minimized and the discharge pressure is lowered. Therefore, the pipes of an external refrigerant circuit does not receive excessive load based on high discharge pressure.

Claims

1. A refrigerant circuit of an air conditioner, comprising:

a compressor, wherein the compressor includes;

a crank chamber having a pressure;

a drive shaft;

a reciprocating piston; and

a tiltable drive plate, which is located in the crank chamber and converts rotation of the drive shaft to reciprocation of the piston, the drive plate changes its inclination angle in accordance with the pressure in the crank chamber, and wherein the drive plate changes the stroke of the piston according to the inclination angle of the drive plate thereby changing the displacement of the compressor;

an external circuit, which is connected to the compressor, wherein the compressor compresses refrigerant sent from the external circuit and discharges the compressed refrigerant to the external circuit;

a high pressure zone, which is exposed to the pressure of refrigerant that is compressed by the compressor;

a pressure sensor for detecting the pressure in the high pressure zone;

a control valve, which adjusts the pressure in the crank chamber; and

a controller for controlling the control valve, wherein the controller sends a command value that corresponds to cooling performance required for the refrigerant circuit to the control valve, wherein the control valve operates to adjust its opening according to the sent command value, wherein, when the pressure in the high pressure zone is equal to or higher than a predetermined threshold value, the controller executes a limiting control for limiting the pressure in the high pressure zone, wherein, during the limiting control, the controller first gradually changes the command value, which is sent to the control valve, such that the displacement of the compressor is gradually decreased, and then, when the command value is equal to a predetermined reference value, the controller sends a command value that can minimize the displacement of the compressor to the control valve.

2. The refrigerant circuit according to claim 1, wherein the minimum displacement of the compressor is zero.

3. The refrigerant circuit according to claim 1, wherein the minimum displacement of the compressor is greater than zero, wherein the refrigerant circuit includes a circulation stopping device, which stops circulation of refrigerant in the refrigerant circuit when the compressor displacement is minimum, and wherein, when the circulation stopping device stops refrigerant circulation in the refrigerant circuit, refrigerant circulates within the compressor.

4. The refrigerant circuit according to claim 3, wherein the circulation stopping device is a shutoff valve, which prevents refrigerant from being discharged from the compressor.

5. The refrigerant circuit according to claim 3, wherein the compressor includes:

a suction chamber for receiving refrigerant from the external circuit;

a cylinder bore for accommodating the piston, wherein a compression chamber is defined in the cylinder bore, and wherein the piston compresses refrigerant that is drawn into the compression chamber from the suction chamber; and

a discharge chamber for receiving compressed refrigerant gas from the compression chamber, wherein the discharge chamber forms a part of the high pressure zone, wherein the compressed gas is sent to the external circuit from the discharge chamber, wherein, when the circulation stopping device stops circulation of refrigerant in the refrigerant circuit, an internal refrigerant circuit, which includes the discharge chamber, the crank chamber, the suction chamber, and the compression chamber, is formed in the compressor.

6. The refrigerant circuit according to claim 1, wherein the drive shaft is directly coupled to an external drive source so that the drive shaft is always rotated when the external drive source is running.

7. The refrigerant circuit according to claim 1, wherein the threshold value is a first threshold value, and wherein the controller continues the limiting control until the pressure in the high pressure zone is equal to or lower than a second threshold value, which is lower than the first threshold value, after the pressure in the high pressure zone is equal to or higher than the first threshold value.

8. The refrigerant circuit according to claim 1, wherein the controller changes the reference value in accordance with the speed of the drive shaft.

9. The refrigerant circuit according to claim 8, wherein the controller changes the reference value such that the compressor displacement, which corresponds to the reference value, is relatively increased as the speed of the drive shaft increases.

10. A refrigerant circuit of an air conditioner, comprising:

a compressor, wherein the compressor includes;

a drive shaft, which is coupled to an external drive source through a clutch mechanism; and

a compression mechanism, which is actuated by the drive shaft to compress refrigerant and changes the displacement of the compressor;

an external circuit, which is connected to the compressor, wherein the compressor compresses refrigerant sent from the external circuit and discharges the compressed refrigerant to the external circuit;

a high pressure zone, which is exposed to the pressure of refrigerant that is compressed by the compressor;

a pressure sensor for detecting the pressure in the high pressure zone;

an actuator for controlling the compression mechanism to change the displacement of the compressor; and

a controller for controlling the actuator and the clutch mechanism, wherein the controller sends a command value that corresponds to cooling performance required for the refrigerant circuit to the actuator, wherein the actuator actuates the compression mechanism according to the sent command value, wherein, when the pressure in the high pressure zone is equal to or higher than a predetermined threshold value, the controller executes a limiting control for limiting the pressure in the high pressure zone, wherein, during the limiting control, the controller first gradually changes the command value, which is sent to the actuator, such that the displacement of the compressor is gradually decreased, and then, when the command value is equal to a predetermined reference value, the controller disconnects the drive shaft from the external drive source by using the clutch mechanism.

11. The refrigerant circuit according to claim 10, wherein the compression mechanism includes:

a piston; and

a tiltable drive plate, which is located in a crank chamber of the compressor and converts rotation of the drive shaft to reciprocation of the piston, the drive plate changes its inclination angle in accordance with the pressure in the crank chamber, and wherein the drive plate changes the stroke of the piston according to its inclination angle thereby changing the displacement of the compressor.

12. The refrigerant circuit according to claim 11, further comprising a control valve for adjusting the pressure in the crank chamber, wherein the actuator is located in the control valve.

13. The refrigerant circuit according to claim 10, wherein the threshold value is a first threshold value, and wherein the controller continues the limiting control until the pressure in the high pressure zone is equal to or lower than a second threshold value, which is lower than the first threshold value, after the pressure in the high pressure zone is equal to or higher than the first threshold value.

14. The refrigerant circuit according to claim 10, wherein the controller changes the reference value in accordance with the speed of the drive shaft.

15. The refrigerant circuit according to claim 14, wherein the controller changes the reference value such that the compressor displacement, which corresponds to the reference value, is relatively increased as the speed of the drive shaft increases.

16. A method for controlling a variable displacement compressor used in a refrigerant circuit of an air conditioner, wherein the refrigerant circuit includes the compressor and an external circuit, which is connected to the compressor, the method comprising:

sending refrigerant from the external circuit to the compressor;

compressing the refrigerant by the compressor;

discharging the compressed refrigerant from the compressor to the external circuit;

adjusting the pressure in a crank chamber of the compressor by a control valve, wherein the control valve operates according to a command value, which represents cooling performance required for the refrigerant circuit;

changing the inclination angle of a drive plate located in the crank chamber in accordance with the pressure in the crank chamber, wherein the inclination angle of the drive plate determines the displacement of the compressor;

detecting the pressure in a high pressure zone, which is exposed to the pressure of refrigerant that is compressed by the compressor; and

executing a limiting control for limiting the pressure in the high pressure zone when the pressure in the high pressure zone is equal to or higher than a predetermined threshold value, wherein, during the limiting control, the command value, which is sent to the control valve, is first gradually changed such that the displacement of the compressor is gradually decreased, and then, when the command value is equal to a predetermined reference value, a command value that can minimize the displacement of the compressor is sent to the control valve.

17. The method according to claim 16, wherein the minimum displacement of the compressor is zero.

18. The method according to claim 16, wherein the minimum displacement of the compressor is greater than zero, the method further including:

stopping circulation of refrigerant in the refrigerant circuit when the compressor displacement is minimized; and

circulating refrigerant within the compressor when circulation of refrigerant in the refrigerant circuit is stopped.

19. A method for controlling a variable displacement compressor used in a refrigerant circuit of an air conditioner, wherein the refrigerant circuit includes the compressor and an external circuit, which is connected to the compressor, the method comprising:

sending refrigerant from the external circuit to the compressor;

compressing the refrigerant by a compression mechanism of the compressor, wherein the compression mechanism is actuated by a drive shaft, which is coupled to an external drive source through a clutch mechanism;

discharging the compressed refrigerant from the compressor to the external circuit;

controlling the compression mechanism by an actuator to change the displacement of the compressor, wherein the actuator operates according to a command value, which represents cooling performance required for the refrigerant circuit;

detecting the pressure in a high pressure zone, which is exposed to the pressure of refrigerant that is compressed by the compressor; and

executing a limiting control for limiting the pressure in the high pressure zone when the pressure in the high pressure zone is equal to or higher than a predetermined threshold value, wherein, during the limiting control, the command value, which is sent to the actuator, is first gradually changed such that the displacement of the compressor is gradually decreased, and then, when the command value is equal to a predetermined reference value, the clutch mechanism disconnects the drive shaft from the external drive source.