Abstract:
A method of controlling a device having restricted movement. A controller is provided for controlling the operation of the device using a control algorithm. A normal operation control method is programmed onto the controller and is selectively activated by the controller to generate a normal control signal. A forcing control method is also programmed into the controller and selectively activates a forcing control signal. The normal operation control signal provides regular operation of the device, while the forcing control signal causes the device to operate in a manner that will correct the operation of the device when a restricted motion of the device is detected.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/833,172, filed Jul. 25, 2006. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a valve control algorithm for freeing a stuck valve. 
       BACKGROUND OF THE INVENTION 
       [0003]    Federal and State legislation require control of vehicle exhaust emissions. Oxides of Nitrogen (NOx) are one of the exhaust gas emissions that must be controlled. 
         [0004]    Formation of NOx will occur at higher combustion temperatures. In order to reduce the occurrence of the formation of NOx gasses, exhaust gas recirculation systems have been developed which effectively reduce combustion temperatures and control emissions. Exhaust gas recirculation systems work by re-circulating a portion of the exhaust gas from an engine back to the intake manifold where it can combined with incoming air. When the mixture is compressed and ignited in the cylinder the result is a lower combustion temperature and the reduction of NOx. In order to make the recirculation of exhaust gas possible, exhaust gas recirculation systems use exhaust gas recirculation (EGR) valves to open and close the conduits that recirculate the exhaust gas back to the intake manifold of the engine. 
         [0005]    The composition of exhaust gas includes substances that can effect the operation of the EGR valve. These substances typically adhere to the EGR valve components and restrict movement of the poppet valve, valve stem and other associated valve components. Also, it is particularly important to avoid exposing the actuator component of an EGR valve to the exhaust gas. In general contamination of an EGR valve impedes the movement of the valve and may require higher actuating force to achieve a desired valve position and exhaust gas flow. The operation of the EGR valve can be controlled in order to provide valve freeing force movements when a stuck valve situation is detected. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is directed to a method of controlling a device having restricted movement. A controller is provided for controlling the operation of the device using a control algorithm. A normal operation control method is programmed onto the controller and is selectively activated by the controller to generate a normal control signal. A forcing control method is also programmed into the controller and selectively activates a forcing control signal. The normal operation control signal provides regular operation of the device, while the forcing control signal causes the device to operate in a manner that will correct the operation of the device when a restricted motion of the device is detected. The method is carried out by the controller activating a first initial learn sequence where the operation of the device is checked to see if a restricted motion condition exists. If a restricted motion condition is detected, then the forcing control signal is activated by the controller causing the device to operate in a forcing mode. After the forcing mode has occurred for a given period of time, then the controller will cause the device to perform a device function test where the device will move a predetermined amount of its range of motion in order to make an evaluation of whether or not a restricted motion condition exists. After the device function test has occurred, the controller will activate a second initial learn sequence wherein the device is checked to see if it is functioning properly. If the device is functioning properly, then the controller will activate the normal control signal and the device will operate along its normal course. 
         [0007]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0009]      FIG. 1  depicts a flow chart outlining the steps of the control algorithm for freeing a device from contamination adhesion. 
           [0010]      FIGS. 2   a  and  2   b  depict a partially broken away perspective view of the exhaust gas recirculation valve moving between the stuck and free positions; 
           [0011]      FIG. 3  depicts a graph of the forcing control signal, and 
           [0012]      FIG. 4  depicts a graph of two variations of the forcing control signal having variations on duration and amplitude. 
       
    
    
       [0013]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 
         [0015]      FIG. 1  depicts a flow chart outlining the steps of a control algorithm  10  for freeing a device, such as an electromagnetic device, from contamination adhesion. The control algorithm  10  has a first step  12  where an initial learn sequence is executed. The initial learn sequence can occur at engine start up or at any suitable time when the sequence can occur so that it will not effect the operation of the device. As shown in  FIG. 2 , the electromagnetic device can be an exhaust gas recirculation valve (EGR) valve, however, it is possible to use this method in other types of applications where there is sticking of a device as a result of environmental factors. 
         [0016]    When the initial learn sequence of the first step  12  begins, the electromagnetic device will move through its entire range of motion or a portion of its range of motion and at a second step  14 , a determination is made as to whether or not the electromagnetic device is experiencing restricted motion. 
         [0017]    If it is determined that a restricted motion condition does exist, then at a third step  16 , a forcing sequence signal is transmitted to the device. The forcing sequence sends motor outputs of varying intensity that act on the electromagnetic device to cause rapid movement in order to free the valve from a restricted motion condition. The restricted motion can be caused by several different factors which include environmental conditions such as contamination or coking of a valve member that causes a sticking condition. The forcing function is a series of pulses that are directed to a bi-directional or uni-directional actuator. The pulses can vary in duration as well as intensity and frequency. For a given application, it is possible for some frequencies to be more ideal than others. 
         [0018]    At a fourth step  18  of the control algorithm  10 , a device function test signal will be transmitted to the electromagnetic device where it is determined whether or not the restricted motion condition still exists. At a step  20 , a determination is made of whether or not a restricted motion condition still exists. If a restricted motion condition still exists, then the third step  16  and fourth step  18  will be repeated and another device function test will be performed. 
         [0019]    If at step  20  it is determined that no restricted motion condition exists then at a step  22  a second initial learn sequence is activated. If any errors are detected then at a step  26  an error signal will be transmitted/logged and the device will not function. If there is no failure of the device, then at a step  26  the normal control method will be used and the device will operate normally. If at step  14  it is determined that there is no restricted motion then steps  16 - 26  will be skipped completely and the device will operate normally using a normal control method at step  28 . 
         [0020]    Referring now to  FIGS. 2   a  and  2   b  perspective views of a device  30  having a stuck valve that is freed using the control algorithm  10  are shown. The valve  30  in this particular application is an exhaust gas recirculation valve that is experiencing restricted motion as a result of contamination. The device  30  has a valve seat  32  which in this case has soot or particulate coked around its surface. A valve member  34  as shown in  FIG. 2   a  is stuck against the valve seat  32 . In  FIG. 2   a  the device  30  has experienced restricted motion. Therefore, a forcing control signal is activated and the valve member  34  rapidly rotates and pulls upward away from the valve seat  32 . The rapid application of intermittent load of the valve member  34  in relation to the seat  32  breaks the valve member  34  free from the coking material on the valve member  34  and the valve seat  32 . In  FIG. 2   b  the valve member  34  has broken away from the valve seat  32  and some of the coking material has been removed from the valve member and valve seat as a result of the forcing control signal. 
         [0021]      FIG. 3  shows a graph of the forcing control signal that performs on the device  30  in  FIGS. 2   a  and  2   b,  and described at step  16  in  FIG. 1 . The forcing control signal has a first phase  36  that varies in frequency and intensity. The negative intensity represents the device  30  moving the valve member  34  in one direction, while the positive intensity represents the device  30  moving the valve member  34  in an opposite direction. The intensity of the signal can vary between 0% and 100% maximum achievable motor force as well as the frequency or number of pulses can be any number. Also it is possible for the intensity levels to go in one direction for a period of time and then in a second direction for a period of time. After a first forcing phase  36 , the forcing function will perform a device function test  38  and a determination is made whether or not restricted motion of the valve is still occurring. This is done by moving the valve member  34  a distance from the valve seat  32 . If restricted motion is still detected (step  20  on  FIG. 1 ) then a second forcing phase cycle  40  will be performed on the valve  30  (step  16  on  FIG. 1 ). After the second forcing phase cycle  40 , a second device function test  42  will be performed. The number of forcing phases and device function tests performed can vary and are not limited to two. The process will keep repeating until it is determined that the valve is no longer sticking or a maximum number of cycles has occurred. Once it is determined that the restricted motion condition no longer exists, a normal control method  44  will be applied. 
         [0022]    The amount of coking material  33  removed from the valve member  35  and valve seat  32  can be enhanced by the composition of the forcing control signal. For example, certain frequencies or intensity levels of the motor output have been determined to remove contamination better than other frequencies or intensities. In the case of an EGR valve a frequency range of about 10-500 Hertz have been found to be effective. 
         [0023]    Referring to  FIG. 4 , two variations of the forcing motor output are shown. A forcing control signal  46  shown in  FIG. 4  has an output signal that varies in duration. The forcing control signal  46  can be a sweeping frequency having a duration that can be predetermined or random. The forcing control signal  46  of this type can be, for example, a pulse width modulated. A forcing control signal  48  is a signal that has varying amplitude over a period of time. The forcing control signal of this type can be, for example, an amplitude modulation signal. 
         [0024]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.