US 6,672,844 B2Granted

Apparatus and method for controlling variable displacement compressor

AssigneeKabushiki Kaisha Toyota Jidoshokki

InventorsTetsuhiko Fukanuma, Atsuyuki Morishita, Tomohiko Yokono

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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.

Claims19

Dependent claims

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.

9 more elements

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.

7 more elements

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.

5 more elements

Dependencies are inferred from the claim text.