Abstract:
A control system for a vehicle comprises a throttle control module and a diagnostic module. The throttle control module controls a position of a throttle of the vehicle and compensates for changes in effective opening area of the throttle due to coking. The diagnostic module reports a coking value to a user based upon an amount of compensation performed by the throttle control module. A method comprises controlling a position of a throttle of a vehicle; compensating for changes in effective opening area of the throttle due to coking; and reporting a coking value to a user based upon an amount of compensation performed.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/918,612, filed on Mar. 16, 2007. The disclosure of the above application is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to throttle area control in motor vehicles. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Referring now to  FIG. 1 , a functional block diagram of a vehicle powertrain  100  according to the prior art is presented. The vehicle powertrain  100  includes an engine  102  that generates drive torque. Air is drawn into an intake manifold  104  of the engine  102  through a throttle  106 . Operation of the engine  102  is monitored and controlled by a control module  110 . 
         [0005]    The control module  110  receives signals from a MAP (Manifold Absolute Pressure) sensor  112  in the intake manifold  104 , a throttle position sensor  114 , a MAF (Mass Air Flow) sensor  116 , and other sensors (not shown). The control module  110  controls various functions of the engine  102 , including opening and closing the throttle  106 . The control module  110  receives driver input from, for example, an accelerator pedal position sensor  120 . 
         [0006]    The control module  110  also receives input from vehicle control systems, such as a cruise control module  122 , a stability control system (not shown), a traction control module (not shown), etc. The control module  110  determines the desired engine torque based upon the inputs. The control module  110  instructs the throttle  106  to open to a specified position to allow a desired airflow into the engine  102  to produce that desired engine torque. 
         [0007]    The control module  110  may use a mapping from desired airflow to throttle area opening to determine the desired throttle area opening. The control module  110  may then use a mapping from throttle area opening to throttle position to determine where to position the throttle  106 . The relationship between desired throttle area opening and throttle position may change over time. For example, deposits may accumulate on the throttle  106 , especially in applications where vehicle drive times are short. 
         [0008]    The accumulation of deposits on the throttle  106  is sometimes referred to as coking. To compensate for such changes, a Learned Airflow Variation Algorithm (LAVA) has been disclosed in commonly assigned U.S. Pat. Nos. 7,024,305 and 6,957,140, the disclosures of which are hereby incorporated by reference in their entirety. In various implementations, the LAVA provides for two tables that each include a mapping from uncompensated throttle area to throttle area correction factor. 
         [0009]    The throttle area correction factor may be added to the uncompensated throttle area to produce a compensated throttle area. The compensated throttle area can then be mapped to a throttle blade position for the throttle  106 . The throttle area correction factor may be negative when an empirically determined throttle area opening is larger than expected for a given throttle position. The two tables may be an upper table and a lower table, corresponding to larger uncompensated area values and smaller uncompensated area values, respectively. 
         [0010]    The upper and lower tables may include mutually exclusive ranges of uncompensated throttle area or may overlap at one or more uncompensated throttle area values. The upper and lower tables may each have a predetermined upper limit for the amount of throttle area correction. The control module  110  may update the upper and lower tables to reflect changes in effective throttle area opening based upon airflow data from the MAP sensor  112  and the MAF sensor  116 . 
       SUMMARY 
       [0011]    A control system for a vehicle comprises a throttle control module and a diagnostic module. The throttle control module controls a position of a throttle of the vehicle and compensates for changes in effective opening area of the throttle due to coking. The diagnostic module reports a coking value to a user based upon an amount of compensation performed by the throttle control module. 
         [0012]    In other features, the coking value is based upon the amount of compensation performed with respect to an amount of compensation allowed. The coking value is based upon dividing the amount of compensation performed by the amount of compensation allowed. The throttle control module maintains a first table of throttle area compensation factors. The first table is indexed by uncompensated throttle area. 
         [0013]    In further features, the throttle control module applies a first upper limit to the throttle area compensation factors and the diagnostic module reports a relation between the throttle area compensation factors and the first upper limit. The diagnostic module reports a percentage calculated by dividing a maximum one of the throttle area compensation factors by the first upper limit. 
         [0014]    In still other features, the throttle control module maintains a second table of throttle area compensation factors, applies a second upper limit to the throttle area compensation factors of the second table, determines a first relation between the throttle area compensation factors of the first table and the first upper limit, determines a second relation between the throttle area compensation factors of the second table and the second upper limit, and reports a maximum one of the first and second relations. The diagnostic module selectively instructs the throttle control module to clear the first and/or second tables based upon user input. 
         [0015]    In other features, the control system further comprises a visual display module. The diagnostic module reports the coking value to the visual display module when the coking value exceeds a threshold. The diagnostic module reports the coking value to a scan tool operated by the user. The control system further comprises a remote diagnostic module. The remote diagnostic module transmits the coking value to a service provider. The service provider includes a satellite service provider. 
         [0016]    A method comprises controlling a position of a throttle of a vehicle; compensating for changes in effective opening area of the throttle due to coking; and reporting a coking value to a user based upon an amount of compensation performed. 
         [0017]    In other features, the method further comprises determining the coking value based upon the amount of compensation performed with respect to an amount of compensation allowed. The method further comprises determining the coking value by dividing the amount of compensation performed by the amount of compensation allowed. The method further comprises maintaining a first table of throttle area compensation factors. 
         [0018]    In further features, the first table is indexed by uncompensated throttle area. The method further comprises applying a first upper limit to the throttle area compensation factors; and reporting a relation between the throttle area compensation factors and the first upper limit. The method further comprises reporting a percentage calculated by dividing a maximum one of the throttle area compensation factors by the first upper limit. 
         [0019]    In still other features, the method further comprises maintaining a second table of throttle area compensation factors; applying a second upper limit to the throttle area compensation factors of the second table; determining a first relation between the throttle area compensation factors of the first table and the first upper limit; determining a second relation between the throttle area compensation factors of the second table and the second upper limit; and reporting a maximum one of the first and second relations. 
         [0020]    In other features, the method further comprises selectively clearing the first and/or second tables based upon user input. The method further comprises visually reporting the coking value to the user when the coking value exceeds a threshold. The method further comprises reporting the coking value to a scan tool operated by the user. The method further comprises transmitting the coking value to a service provider. The method further comprises transmitting the coking value to a service provider via satellite. 
         [0021]    Further areas of applicability of the present disclosure 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 disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0023]      FIG. 1  is a functional block diagram of a vehicle powertrain according to the prior art; 
           [0024]      FIG. 2  is a functional block diagram of an exemplary vehicle powertrain system according to the principles of the present disclosure; 
           [0025]      FIG. 3  is an exemplary functional block diagram of the reporting control module according to the principles of the present disclosure; 
           [0026]      FIG. 4  is flowchart depicts exemplary steps performed by the reporting control module according to the principles of the present disclosure; and 
           [0027]      FIG. 5  is a flowchart depicts exemplary steps performed in determining maximum upper and lower values according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0029]    As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
         [0030]    Referring now to  FIG. 2 , a functional block diagram of an exemplary vehicle powertrain system  200  according to the principles of the present disclosure is presented. The powertrain system  200  includes the engine  102  and a reporting control module  202 . The reporting control module  202  determines the amount of correction applied to uncompensated throttle area values to correct for changes in effective opening area of the throttle  106 , such as by accumulation of deposits (i.e., coking). 
         [0031]    When the correction being applied becomes too large, the reporting control module  202  can report this highly coked condition. For example, the reporting control module  202  may display a warning message on a vehicle information system or may transmit the message, such as by satellite, to a service provider, which can then contact the driver. 
         [0032]    In addition, the reporting control module  202  may be configured to report the amount of throttle area correction to scan tools, such as are employed by vehicle service technicians. The throttle  106  can then be cleaned preemptively before accumulation of deposits affects the performance of the vehicle. The amount of throttle area correction may be measured as a percentage. The percentage may be determined by dividing the maximum throttle area correction applied by the maximum throttle area correction allowed. The reporting control module  202  may signal the highly coked condition when the percentage is greater than a predetermined value. 
         [0033]    Referring now to  FIG. 3 , an exemplary functional block diagram of the reporting control module  202  according to the principles of the present disclosure is presented. The reporting control module  202  includes a processing module  210 , a diagnostic access port  211 , and nonvolatile memory  214 . The processing module  210  may include a throttle control module  212  and a diagnostic module  213 . The throttle control module  212  may update a lower table  216  and an upper table  218  within nonvolatile memory  214 . The lower and upper tables  216  and  218  may include throttle area correction factors indexed by uncompensated throttle opening area. 
         [0034]    Nonvolatile memory  214  may also include limits  220  that determine the maximum amount of correction that can be applied by the lower table  216  and the upper table  218 . The limits  220  may be different for the lower and upper tables  216  and  218  and may be established by a calibrator. The diagnostic module  213  may receive data requests from the diagnostic access port  211 . The diagnostic module  213  may respond to these requests with a percentage. 
         [0035]    The percentage may indicate how much of the allowed correction is currently being applied to throttle opening area values. The percentage may be the larger of percentages calculated for the lower table  216  and the upper table  218 . The diagnostic module  213  may periodically calculate percentages for the lower and upper tables  216  and  218  and store these percentages in volatile memory  230  and/or nonvolatile memory  214 . The percentages for the lower and upper tables  216  and  218  may be calculated by taking the maximum value from the table and dividing it by the limit for the table. 
         [0036]    To respond to data requests from the diagnostic access port  211 , the diagnostic module  213  may transmit the larger of the percentages for the lower and upper tables  216  and  218  to the diagnostic access port  211 . The diagnostic access port  211  may also receive an instruction commanding the throttle control module  212  to clear the lower and/or upper tables  216  and  218 . Such an instruction may be issued after the throttle  106  has been cleaned. 
         [0037]    When the vehicle is in for service, the service technician can connect to the diagnostic access port  211  to determine the state of the throttle  106 . The service technician may then be able to recommend preventative maintenance to the vehicle owner. In addition, throttle restriction information may be used in troubleshooting drivability concerns reported by the owner. 
         [0038]    The diagnostic module  213  may output the selected percentage to an optional display  240 . The diagnostic module  213  may wait to transmit the selected percentage to the display  240  until the percentage has crossed a threshold, such as 80%. The diagnostic module  213  may also transmit the percentage to a remote diagnostic access port  250 . 
         [0039]    The remote diagnostic access port  250  may include satellite communication capability to relay service information, such as correction percentages, to a remote service provider. The remote service provider can then contact the owner of the vehicle to indicate that the throttle  106  may need to be serviced. In various implementations, the diagnostic module  213  may wait until the selected percentage has crossed a threshold before transmitting the percentage to the remote diagnostic access port  250 . For purposes of example only, the threshold may be 70%. 
         [0040]    Additionally, the remote diagnostic access port  250  may be configured to receive remote data requests, which the diagnostic module  213  can service in the same way as data requests from the diagnostic access port  211 . In this way, the remote service provider may be able to periodically query the vehicle to determine the state of the throttle  106 . In addition, the remote service provider may be able to issue a clear instruction to clear the lower and/or upper tables  216  and  218  when troubleshooting vehicle operation. 
         [0041]    Referring now to  FIG. 4 , a flowchart depicts exemplary steps performed by the reporting control module  202  according to the principles of the present disclosure. Control begins in step  302 , where lower and upper values are determined, corresponding to the lower and upper tables  216  and  218 , respectively. This process is discussed in more detail to  FIG. 5 . Control continues in step  304 , where control determines if a predetermined time period has expired. This period determines how often the lower and upper values are calculated. This period may correspond to a preexisting vehicle control loop, which may be a 250 millisecond loop. 
         [0042]    If the period has expired, control returns to step  302  to calculate new lower and upper values; otherwise, control transfers to step  306 . In step  306 , control determines whether a data request has been made for the correction percentage. If so, control transfers to step  308 ; otherwise, control transfers to step  310 . In step  308 , control determines the correction percentage, such as by selecting the maximum of the lower and upper values. Alternatively, the lower and upper values may also be determined when a data request has been made. In various other implementations, the maximum of the lower and upper values may be selected once the lower and upper values are determined. Control continues in step  312 , where the maximum is reported as the correction percentage. Control then returns to step  304 . 
         [0043]    In step  310 , control determines whether a reset request has been received. If so, control transfers to step  314 ; otherwise, control returns to step  304 . In step  314 , the lower and upper tables  216  and  218  are reset and control returns to step  302 . The lower and upper tables  216  and  218  may be reset to all zeroes or to predetermined values, which may be set by a calibrator. 
         [0044]    Referring now to  FIG. 5 , a flowchart depicts exemplary steps performed by step  302  of  FIG. 4  in determining maximum upper and lower values according to the principles of the present disclosure. Control begins in step  402 , where two variables, lower and upper, are set to zero. Control continues in step  404 , where the first entry in the lower and upper tables  216  and  218  is selected. 
         [0045]    Control continues in step  406 . If the selected entry in the upper table  218  is greater than the variable upper, control transfers to step  408 ; otherwise, control transfers to step  410 . In step  408 , the variable upper is set to the value of the selected entry in the upper table  218  and control continues in step  410 . In step  410 , if the selected entry in the lower table  216  is greater than the variable lower, control transfers to step  412 ; otherwise, control transfers to step  414 . 
         [0046]    In step  412 , the variable lower is set to the value of the selected entry in the lower table  216 , and control continues in step  414 . In step  414 , if a selected entry is the last entry in the lower or upper tables  216  and  218 , control transfers to step  416 ; otherwise, control transfers to step  418 .  FIG. 5  could be easily modified to allow for upper and lower tables of different sizes, or for a single combined table. 
         [0047]    In step  416 , the next entry in the lower and upper tables  216  and  218  is selected and control returns to step  406 . In this way, each entry in the lower and upper tables  216  and  218  is evaluated and the largest entry is stored in the lower and upper variables, respectively. In step  416 , the lower and upper variables are converted to percentages. 
         [0048]    For example, the lower variable may be divided by the maximum correction value for the lower table  216  as indicated by the limits  220 . The upper value may be divided by the maximum correction value for the upper table  218  as indicated by the limits  220 . Control continues in step  418 , where the lower and upper variables are stored. Control then ends. 
         [0049]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.