The present invention relates to a method for controlling an electric compressor, such as one suitable for a compressor in an air conditioning system for vehicles, into which an inverter for controlling an electric motor as a drive source is integrally incorporated.
In a conventional electric compressor as disclosed in patent document 1 or 2 into which an inverter for controlling an electric compressor is integrally incorporated, an inverter accessory such as a smoothing capacitor, and a coil or capacitor for EMC-filter, which means a filter for electromagnetic compatibility, is designed as capable of preventing failures even when used at such a condition as high temperature and maximum electric current. Therefore, used are accessory parts which are designed to cause no defect even when they are utilized under high temperature and the maximum electric current flows, as well as when they are utilized at a usual condition.
However, when the accessory parts are designed/selected so as to cause no defect in the accessories even if used under high temperature environment or the maximum electric current, the accessories have to grow in their own size. In addition, that accompanies that even a harness which connects each accessory part to compose an electric circuit grows in size. Therefore the electric circuit has to grow in cost and weight, and an electric compressor may grow in cost and size. Further, their freedom to be mounted in vehicles, etc., may be reduced.
Patent document 1: JP-2002-243246-A
Patent document 2: JP-2007-216818-A
Accordingly, an object of the present invention is to provide a method for controlling an electric compressor, which can prevent a defect of an accessory even during the usage under a condition such as high temperature, as preventing the electric compressor from growing in cost and size through avoiding the growth of inverter accessories in size.
To achieve the above-described object, a method for controlling an electric compressor according to the present invention is a method for controlling an electric compressor into which an inverter for controlling an electric motor as a drive source is integrally incorporated, comprising the steps of: acquiring a temperature of an accessory of the inverter; when the acquired temperature becomes or is already equal to or higher than a maximum rated temperature of the accessory, calculating a value of an electric current which can flow at the acquired temperature and restrictively controlling a rotational speed of the electric compressor such that an input electric current becomes equal to or less than a value of the electric current which can flow; and when the temperature of the accessory becomes lower than the maximum rated temperature, releasing the restrictive control. In such a control method, the value of the electric current that can flow electricity into the accessory is calculated depending on the temperature of the acquired accessory, and the rotational speed of the electric compressor is restrictively controlled so that an actual input current becomes equal to or less than a predetermined value. When the temperature of the accessory of the inverter of the electric compressor is more than, or equal to, the maximum rated temperature of the accessory in such a season as summer, because the rotational speed of the electric compressor is restrictively controlled, the temperature increase by the electricity flowed into the electric compressor is suppressed so as to avoid further temperature increase. Further, after the electric compressor starts to be operated, the accessory is cooled by sucked refrigerant and then becomes equal to or less than the maximum rated temperature, so that the restrictive control can be released and a usual control for the rotation speed can be performed. Therefore, even when the accessory is designed based on a value of electric current in a usual operation, defect generation can be prevented.
The accessory temperature can be acquired by a temperature sensor provided in the neighborhood of the accessory, for example. Furthermore, the accessory temperature may be estimated from a value of an electric current flowing in the accessory and a sensor value of a temperature sensor provided in a space to mount the inverter inside the electric compressor, and the estimated value may be deemed to be an accessory temperature which can be used for determination in the restrictive control.
As an example of the above-described accessory, a smoothing capacitor or, a coil or a capacitor for EMC-filter, etc., can be quoted.
An electric compressor to which the control method of an electric compressor according to the present invention is applied is particularly suitable for refrigeration cycle of an air conditioning system of vehicles.
In the control method of an electric compressor according to the present invention, when the temperature of the inverter accessory reaches or has reached the maximum rated temperature, the rotational speed of the electric compressor is controlled restrictively so that the input electric current becomes no more than the value at which the electricity can flow. Therefore, such a defect that the accessory is overheated over the maximum rated temperature for a long time can be surely prevented. Further, instead of the maximum electric current, an electric current during a usual operation may be sufficiently used as a standard electric current for designing and choosing the accessory. Therefore the growth in the accessory size can be avoided, so that the circuit and even the device can be reduced in weight and size.
Furthermore, as for a temperature of the accessory, a temperature data acquired by a temperature sensor provided near the accessory or a space temperature data measured by a temperature sensor provided in a space where the inverter is mounted inside the electric compressor can be utilized as determination information for the restrictive control, as well as a temperature data estimated from the present electric current in the accessory can be utilized. Therefore, necessary information for the determination in the restrictive control can be easily acquired, and the control method according to the present invention can be surely applied to an electric compressor into which an inverter is integrally incorporated.
Hereinafter, desirable embodiments of a control method of an electric compressor according to embodiments of the present invention will be explained referring to figures.
One end of rotating shaft 9 is connected to the back of movable scroll member 6 through crank mechanism 8. Rotating shaft 9 is connected to electric motor 10 as a drive source of electric compressor 1. Electric motor 10 has rotor 11 which rotates integrally with rotating shaft 9, and stator 12 which is provided outside of rotor 11.
The rotational speed of electric motor 10 is controlled by inverter 13, and inverter 13 is mounted in space 14 inside suction housing 4. Three pairs, which equal six in total, of switching elements 21 are provided in inverter 13, as shown in
In the above-described electric compressor 1, refrigerant which has been sucked from suction port 19 provided on suction housing 4 is delivered to compression mechanism 7 and compressed, and then, is discharged from discharge port 20 provided on discharge housing 2. Further, some of the refrigerant sucked inward from suction port 19 flows into space 14, so as to chill inverter 13 and smoothing capacitor 16 in filter circuit 15, etc.
In the above-described electric compressor 1, temperature of an accessory such as smoothing capacitor 16a of inverter 13, which is simply called “accessory” hereinafter, is acquired, and when the acquired temperature becomes or is already equal to or higher than the maximum rated temperature of the accessory, a value of an electric current which can flow at the acquired temperature is calculated, and a rotational speed of the electric compressor 1 is controlled restrictively so that an input electric current becomes equal to or less than a value of the electric current which can flow, and then, the restrictive control is released when the temperature of the accessory becomes lower than the maximum rated temperature.
In addition, when a vehicle is left under the scorching sun as in summer season, sometimes at the startup of electric compressor 1, accessory temperature T already becomes higher than maximum rated temperature T1. In such a case, the rotational speed of electric compressor 1 is controlled restrictively from the startup as being equal to, or less than, designated rotational speed, as shown in
Concretely, the restrictive control is performed by inverter control device 22 which is connected to inverter 13 as shown in
At first, the temperature determination flow will be explained with
Secondly, the rotational speed designation flow of electric compressor 1 will be explained with
In the control method of an electric compressor according to the present invention, the electric current value which can flow in the accessory is calculated depending on acquired accessory temperature T, and the rotational speed of the electric compressor is controlled restrictively so that the actual input electric current is equal to or less than the value of the calculated electric current. Therefore, when the accessory temperature of the electric compressor is equal to or more than maximum rated temperature T1 as in summer season, the rotational speed of electric compressor 1 is restrictively controlled, so as to suppress further increase of accessory temperature T. Further, after the operation of electric compressor 1 is started, the accessory is quickly chilled by sucked refrigerant so as to become equal or less than maximum rated temperature T1, so that the restrictive control can be released. Therefore, defects of the accessory from overheat can be surely prevented. Additionally, in such a control method an electric current in a usual operation can be set as a standard electric current value for designing and selecting the accessory, so as to contribute to the reduction in size and weight of the accessory and the whole electric compressor.
Though in the above-described embodiments the temperature of the smoothing capacitor as an accessory is acquired and controlled restrictively, the temperature such as of a capacitor and of a coil for EMC-filter can be acquired and controlled restrictively as well.
The control method of an electric compressor according to the present invention is applicable to an electric compressor having an integrally incorporated inverter, and is specifically suitable for a control method of an electric compressor in an air conditioning system for vehicles, which tends to be left under high temperature.
Number | Date | Country | Kind |
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2007-312168 | Dec 2007 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2008/070780 | 11/14/2008 | WO | 00 | 6/3/2010 |