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  Method for controlling compressor clutchUSPTO Application #: 20070253839Title: Method for controlling compressor clutch Abstract: A control method for an electromagnetic clutch of a variable capacity compressor in a refrigeration cycle includes: setting an electric current of an electromagnetic control valve to zero; when a predetermined time pass after setting step, calculating a load torque based on a discharge pressure and a rotation speed of the variable capacity compressor; determining whether or not the load torque is greater than the power of the electromagnetic clutch; engaging the electromagnetic clutch when the load torque is smaller than the power of the electromagnetic clutch; and when the load torque is greater than the power of the electromagnetic clutch, increasing air flow from a fan to a condenser in the refrigeration cycle and returning to the calculating step. (end of abstract)
Agent: Foley And Lardner LLP Suite 500 - Washington, DC, US Inventor: Shinichiro Higashihara USPTO Applicaton #: 20070253839 - Class: 417317000 (USPTO) Related Patent Categories: Pumps, Correlated Pump And Motor Or Clutch Control, Pump Distributor Control The Patent Description & Claims data below is from USPTO Patent Application 20070253839. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-007598, filed on Jan. 16th, 2006; the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates a method for controlling an electromagnetic clutch of a variable capacity compressor. [0004] 2. Description of the Related Art [0005] An electromagnetic clutch of a variable capacity compressor has been put to actual use. The electromagnetic clutch is configured to be turned on to transmit driving force from a vehicle engine to the compressor and to be turned off to disconnect the driving force of the vehicle engine from the compressor. The electromagnetic clutch includes an armature, a rotor, and an electromagnetic coil. The armature is fixed to a drive shaft of the compressor so that the armature and the drive shaft rotate together. The rotor is a pulley that is configured to be rotated by the vehicle engine. When the clutch is turned on, the electromagnetic coil is energized to connect the armature to the rotor so that driving force is transferred from the engine to the compressor to drive the compressor. When driven, the compressor inducts and compresses refrigerant and discharges the compressed refrigerant. Therefore, the compressor serves as a pump in a refrigeration cycle. [0006] Japanese Patent Application Laid-Open No. 57-73877 discloses a control method for a variable capacity compressor. The control method firstly operates the compressor at 50% capacity within a predetermined time after starting the compressor, and then, operates the compressor at 100% capacity. SUMMARY OF THE INVENTION [0007] Load torque of a variable capacity compressor (that is, torque required to rotate the drive shaft of the compressor) changes according to operating conditions of the compressor. Accordingly, power of the electromagnetic clutch of the compressor is set to be larger than a maximum load torque of the compressor so as to positively engage the clutch even when the load torque is at a maximum value. [0008] Conventionally, the power of the electromagnetic clutch is constant regardless of the operating conditions of the compressor. [0009] An object of the present invention is to provide a method for controlling an electromagnetic clutch of a variable capacity compressor so as to allow downsizing of the electromagnetic coil of the electromagnetic clutch and to reduce power consumption of the electromagnetic clutch. [0010] A first aspect of the present invention is a control method for an electromagnetic clutch of a variable capacity compressor working in a refrigeration cycle. The method includes: setting an electric current of an electromagnetic control valve to zero; when a predetermined time has pass after the setting step, calculating a load torque of the variable capacity compressor based on a discharge pressure and a rotational speed of the variable capacity compressor; determining whether or not the load torque is greater than the power of the electromagnetic clutch; engaging the electromagnetic clutch when the load torque is smaller than the power of the electromagnetic clutch; and when the load torque is greater than the power of the electromagnetic clutch, increasing air flow rate from a fan to a condenser in the refrigeration cycle and then returning to the calculating step. [0011] A second aspect of the present invention is a control method for an electromagnetic clutch of a variable capacity compressor working in a refrigeration cycle. The method includes: calculating a load torque of the variable capacity compressor based on an electric current of an electromagnetic control valve, a discharge pressure and a rotational speed of the variable capacity compressor; determining whether the load torque is larger than the power of the electromagnetic clutch; engaging the electromagnetic clutch when the load torque is smaller than the power of the electromagnetic clutch; and when the load torque is greater than the power of the electromagnetic clutch, increasing air flow rate from a fan to a condenser in the refrigeration cycle and then returning to the calculating step. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIG. 1 is a diagrammatic view showing a vehicular air conditioner according to a first embodiment of the present invention; [0013] FIG. 2 is a cross-sectional view showing an electromagnetic clutch used for a variable capacity compressor in the vehicular air conditioner according to the first embodiment of the present invention; [0014] FIG. 3 is a flow chart showing a method for controlling the electromagnetic clutch of the variable capacity compressor according to the first embodiment of the present invention; [0015] FIG. 4 is a diagram showing a characteristic of load torque of the variable capacity compressor; and [0016] FIG. 5 is a flow chart showing a method for controlling an electromagnetic clutch of a compressor according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0017] An air conditioner having a refrigeration cycle according to embodiments of the present invention will be explained. First Embodiment [0018] FIG. 1 is a schematic diagram of the vehicular air conditioner according to a first embodiment. As shown in FIG. 1, the air conditioner of the present embodiment is a vehicle air conditioner installed in a vehicle and includes a refrigeration cycle 100 that circulates refrigerant and conducts heat exchange between the refrigerant and air. Continue reading... Full patent description for Method for controlling compressor clutch Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method for controlling compressor clutch patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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