Patent Publication Number: US-2006004501-A1

Title: Method of operating an engine cooling permanent magnet DC motor to increase motor life

Description:
This application claims the benefit of U.S. Provisional Application No. 60/585,335, filed on Jul. 2, 2004, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      When a motor for an engine cooling fan/motor assembly is ventilated (e.g., has ventilation holes in a housing thereof), contaminants such as mud, salt, etc., can enter the motor and contact the commutator interface surface and/or enter the brush tube and hamper the operation of brush springs and the brushes. The contaminants may not be removed when the motor is operated at low and medium speeds, which can reduce the life of the motor. In addition, extended amount of running at low or medium speed tends to wear the brushes in an undesirable way and does not create the much needed filming on the commutator.  
      Commutator film is developed by a chemical reaction between the copper surface of the commutator and the surface of the brush, together with the surrounding air. This film is required to have a good commutation and to have acceptable noise emissions from the motor. In vehicle conditions where a motor operates in a mixture of heat, water, mud, salt and vibration, the actual brush wear rates are much different from conditions under which lab testing can be performed.  
      Thus, there is a need to provide an algorithm in a vehicle Engine Control Unit (ECU) that turns on an engine cooling motor to high or full speed for a period of time in order to clean the commutator and to lay down a new film, and to shake loose any contaminants that may hinder operation of the brushes.  
     SUMMARY OF THE INVENTION  
      An object of the invention is to fulfill the need referred to above. In accordance with the principles of the present invention, this objective is achieved by providing method for cleaning a DC permanent magnet motor of a vehicle. The motor has a commutator and brushes and is capable of operating at, at least a low speed and a high speed. The method obtains certain operating data associated with the vehicle. The certain operating data is compared to a threshold. If the certain operating data is greater than the threshold, it is determined if a speed of the vehicle is greater than a certain value. If the speed of the vehicle is greater than the certain value, the motor is operated at high speed for a certain amount of time.  
      In accordance with another aspect of the invention, a computer readable medium has stored thereon sequences of instructions for cleaning a DC permanent magnet motor of a vehicle based on obtaining certain operating data associated with the vehicle. The motor has a commutator and brushes and is capable of operating at, at least a low speed and a high speed. The sequence of instructions include instructions for comparing the certain operating data to a threshold, if the certain operating data is greater than the threshold, determining if a speed of the vehicle is greater than a certain value, and if the speed of the vehicle is greater than the certain value, operating the motor at high speed for a certain amount of time.  
      Other objects, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which:  
       FIG. 1  is a schematic view of a vehicle&#39;s electronic control unit (ECU) shown for controlling a permanent magnet brush-type DC motor assembly in accordance with the principles of the present invention.  
       FIG. 2  is flow chart of a process of an embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT  
      With reference to  FIG. 1 , a vehicle&#39;s electronic control unit (ECU)  10  shown for controlling a DC fan/motor assembly, generally indicated at  12 , in accordance with the principles of the present invention. The fan/motor assembly  12  includes at least one fan  13  at least one motor  15  to operate the fan  13 . The motor  15  is preferably a ventilated permanent magnet, engine cooling motor for a vehicle having a commutator  16  and at least two brushes  18 . The motor  15  is capable of operating at, at least a low speed and a high speed.  
      In accordance an embodiment, an algorithm in the ECU  10  includes the following run pattern and dependencies:  
      A device  14  such as a timer, counter or distance switch is implemented in the ECU  10  to determine if or when there is some usage of the fan/motor assembly  12 . The device  14  is shown to be part of the ECU  10 , but it can be appreciated that the device  14  can be separate from the ECU but operatively associated therewith to provide certain vehicle operating data to the ECU  10 . For example, as soon as the usage exceeds the determined usage for the specific vehicle, the ECU  10  turns on the fan/motor assembly  12  to high or full speed for a certain amount of time in order to clean the commutator  16  and brushes  18  and to lay down a new film. With regard to the fan/motor assembly  12  operating noise, the noise is masked with normal driving noise. Therefore, the full speed operation of the fan/motor assembly  12  for cleaning thereof is preferably limited to when the speed of the vehicle is greater than a threshold, for example, at least 60 km/h. Thus, the driver cannot detect the cleaning operation of the fan/motor assembly  12 .  
      This cleaning mode of the fan/motor assembly  12  can be triggered by one of three basic types of comparisons while the vehicle&#39;s engine is on: 
          A) If a timer is implemented, after a certain amount of engine run time (e.g., threshold of at least 100 hrs), the fan/motor assembly  12  is turned on by the ECU  10  in order to clean the commutator  16  and brushes  18 .     B) If a counter is implemented, after a number (e.g., threshold of at least 30) of startups of the fan/motor assembly  12  at low speed without running at high speed, the fan/motor assembly  12  is turned on to high speed by the ECU in order to clean the commutator and brushes.     C) The cleaning mode could also be triggered by exceeding a pre-determined distance the vehicle is driven (e.g., threshold of a minimum of 5000 km).        

       FIG. 2  shows a flow chart of an embodiment of a process of cleaning the fan/motor  12 . In step  100 , the ECU  10  collects certain vehicle data from device  14 , such as kilometers the vehicle is driven, hours of vehicle operation, counting times when the fan/motor assembly  12  is on low speed without running at high speed, season of operation, and/or date the vehicle is driven.  
      In step  200 , the ECU  10  compares the certain vehicle data obtained in step  100  to a threshold such as one of the thresholds noted above. If the certain vehicle data is greater than the threshold, the ECU  10  in step  300  determines if the vehicle speed (as measured by, for example, a speedometer) is above a minimum level such as 60 km/hr. If so, in step  400 , the ECU  10  turns the fan/motor assembly  12  on at high speed for a certain amount of time (e.g., at least ten minutes). The operation of the fan/motor assembly  12  at high speed cleans the commutator  16  and brushes  18 , lays down a new film, and thus adds to the life of the fan/motor assembly  12 .  
      The steps described in of  FIG. 2  can be implemented as executable code stored on computer readable medium (e.g., a hard disk drive, a floppy drive, a random access memory, a read only memory, an EPROM, a compact disc, etc.). It is preferable that a processor  20  of the ECU  10  executes the steps of  FIG. 2 . The ECU  10  can be considered to be a controller. The processor  20  can be separate from the ECU, for example, provided as part of the fan/motor assembly  12  internally or externally thereof. More particularly, the processor  20  can be incorporated into a conventional pulse width modulated (PWM) speed control unit.  
      Although an engine cooling fan/motor assembly  12  is disclosed, the method described herein is applicable to cleaning any commutated motor used in a vehicle.  
      The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the spirit of the following claims.