Patent ID: 7398653
Filing Date: 2008-07-15
Classification: B60H,F25B

Abstract:
1. An air conditioner for a vehicle, comprising: an electric compressor having a compression mechanism for sucking and compressing a refrigerant, an electric motor for diving the compression mechanism, and a motor drive unit for controlling and driving the electric motor and being arranged so as to be cooled by the refrigerant, the electric compressor constituting a refrigerating cycle together with an evaporator for evaporating the refrigerant; evaporator discharge temperature detection means for detecting the temperature of the air having passed through the evaporator; pressure detection means for detecting refrigerant pressure at a high pressure side in the refrigerating cycle; and an air conditioning control unit for issuing a rotational speed specifying value that specifies a rotational speed of the electric motor or directs the electric motor to stop, to the motor drive unit, wherein: the electric motor operates in a protection-against-overheat mode for protecting the motor drive unit from being overheated, when the motor drive unit is in a state of overheat; in the protection-against-overheat mode, the motor drive unit is cooled by the refrigerant by rotating the electric motor at a rotational frequency for protection against heat specified by the motor drive unit, separately from the rotational frequency specifying value, to drive the compression mechanism to suck and compress the refrigerant; the air conditioning control unit judges whether the protection-against-overheat mode should be stopped during the operation in the protection-against-overheat mode and when the result of the judgment is that the mode should be stopped, the air conditioning control unit outputs a stop signal to the motor drive unit to stop the rotation of the electric motor rotating at the rotational speed for protection against heat; when the stop signal is not output, the air conditioning control unit outputs a start signal to the motor drive unit and when the start signal is output from the air conditioning control unit, and the motor drive unit drives the electric motor in accordance with the rotational speed specifying value or in the protection-against-overheat mode; the motor drive unit judges whether to operate in the protection-against-overheat mode and when result of the judgment is affirmative, the motor drive unit transmits a protection-against-overheat mode flag to the air conditioning control unit as well as driving the electric motor at the rotational speed for protection against heat regardless of the rotational speed specifying value from the air conditioning control unit; when the protection-against-overheat mode flag is transmitted, the air conditioning control unit judges whether refrigerant pressure detected by the pressure detection means exceeds a predetermined value or whether the temperature detected by the evaporator discharge temperature detection means falls below a predetermined value; when the protection-against-overheat mode flag is transmitted, if the air conditioning control unit judges that refrigerant pressure detected by the pressure detection means exceeds a predetermined value or that temperature detected by the evaporator discharge temperature detection means falls below a predetermined value, the air conditioning control unit judges that the protection-against-overheat mode should be stopped and outputs the stop signal; when the protection-against-overheat mode flag is transmitted, if the air conditioning control unit judges that refrigerant pressure detected by the pressure detection means falls below a predetermined value and that temperature detected by the evaporator discharge temperature detection means exceeds a predetermined value, the air conditioning control unit judges that the protection-against-overheat mode should not be stopped and outputs the start signal; and when the protection-against-overheat mode flag is not transmitted, the air conditioning control unit does not judge whether refrigerant pressure detected by the pressure detection means exceeds a predetermined value and whether temperature detected by the evaporator discharge temperature detection means falls below a predetermined value and outputs the start signal.