Compressed air system for a motor vehicle

Abstract

A compressed air system for a motor vehicle with an air supply system includes an electric drive motor, which can be controlled for variable speed, an air compressor coupled to be driven by the electric drive motor, an electric power supply for supplying electric power to the electric drive motor, at least one air reservoir connected with the air compressor to receive air from the air compressor, an air utilization system connected to the air reservoir to receive air from the air reservoir, and a controller to control the speed of the electric drive motor. The controller controls the electric drive motor to determine its speed depending upon at least one of the following signals: a signal representing the activation status of an accelerator pedal of the vehicle, a signal representing the speed of the vehicle, a signal representing the temperature of the power supply, a signal representing the temperature of the electric drive motor, a signal representing the wetness level of the air compressed by the air compressor, a signal representing the load of the air compressor, a signal representing the running time of the air compressor, or a signal representing the status of the electric power supply.

What is claimed is: 
     
         1 . A compressed air system for a motor vehicle with an air supply system, an internal combustion engine and a passive parking brake which is activated by decreasing pressure in parking spring brake cylinders and is released by increasing pressure in the parking brake cylinders to a parking brake release pressure, comprising:
 an electric drive motor, which is controllable for variable speed;   an air compressor coupled to be driven by the electric drive motor;   an electric power supply for supplying electric power to the electric drive motor;   at least one air reservoir connected with said air compressor to receive air from the air compressor;   an air utilization system connected to said at least one air reservoir to receive air from said at least one air reservoir; and   a controller to control the speed of the electric drive motor,   wherein
 the controller is configured to control the electric drive motor to determine the speed of the electric drive motor depending upon at least one of the following signals:
 a) a signal representing the activation status of an accelerator pedal of the vehicle, 
 b) a signal representing the speed of the vehicle, 
 c) a signal representing the temperature of the power supply, 
 d) a signal representing the temperature of the electric drive motor, 
 e) a signal representing the wetness level of the air compressed by the air compressor, 
 f) a signal representing the load of the air compressor, 
 g) a signal representing the running time of the air compressor, or 
 h) a signal representing the status of the electric power supply, and 
 
 the speed of the electric drive motor is controlled by the controller such that if the power stage of the electric power supply is below a set power stage limit, or if the temperature of the electric drive motor exceeds a critical temperature limit, or if the actual speed of the electric drive motor is not equal to a demanded speed, then the electric drive motor will be stopped. 
   
     
     
         2 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if the compressor is switched offload and the actual speed of the electric drive motor of the compressor is higher than zero, then the electric drive motor is operated in a generator mode to charge the electric power supply until a set or predetermined charge level of the electric power supply is reached.   
     
     
         3 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if an accelerator pedal of the drive engine of the vehicle is kicked down and the charge status of the electric power supply exceeds a set charge limit and the consumption of electric power is above a set consumption limit, then the electric drive motor of the compressor is controlled to operate with a calculated speed lower than its maximum speed until the pressure in the air system reservoir reaches a set cut off pressure level.   
     
     
         4 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if the ambient temperature is below a set ambient temperature, then the electric drive motor is controlled to operate with a set calculated speed until the pressure level in the air system reservoir reaches a cut off pressure level.   
     
     
         5 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if the temperature of the electric drive motor is above a set temperature limit, a reduced first speed (n calc1 ) of the drive motor of the compressor is calculated, reducing the load of the electric drive motor, which then is controlled to operate with said first calculated speed (n calc1 ), and if, additionally, the temperature of the electric power supply is above a set temperature limit, then, said first calculated speed (n calc1 ) of the electric drive motor is recalculated to a second calculated speed (n calc2 ) which is lower than first calculated speed (n calc1 ) and the electric drive motor is controlled to operate with said second calculated speed (n calc2 ), until the pressure in air system reservoir reaches a set cut off pressure level.   
     
     
         6 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if the electric drive motor is in an offload mode for a time period longer than a set or predefined time period, then the electric drive motor is started and controlled to operate with a set or calculated speed until the pressure in the air system reservoir reaches a cut off pressure level.   
     
     
         7 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if a wetness level in the air system reservoir is above a predefined or set wetness level limit, then the electric drive motor of the compressor is stopped.   
     
     
         8 . The compressed air system for a motor vehicle according to  claim 1 , wherein the electric drive motor is controlled by the controller such that:
 if the ambient temperature is below a set or predefined temperature, then the electric drive motor is controlled to start and run at a set or calculated speed until the pressure level in air system reservoir has reached a cut off pressure level.