Abstract:
A method and system for controlling an automotive internal combustion engine having NVH feedback uses NVH signals which are processed and compared with human threshold values to determine whether an engine control parameter such as idle speed needs to be adjusted so as to mitigate unwanted noise, vibration, and harshness.

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for controlling an internal combustion engine, in which the speed of the engine and other operating parameters are governed according to the presence of noise, vibration, or harshness (“NVH”) conditions which are sensed by appropriate sensors and processed by the vehicle&#39;s engine controller. It should be noted in this regard that the presence of an NVH condition does not necessarily indicate that the vehicle or engine is running improperly. For example, as noted below, certain objectionable engine vibrations may occur without knocking operation. 
     2. Background Information 
     As vehicle powertrains and body structures become increasing refined, it has become necessary to treat engine-related vibrations more carefully. Particularly with premium automobiles, it is imperative that minimum objectionable vibration and noise be evidenced by the vehicle&#39;s power plant. U.S. Pat. No. 6,167,860 illustrates a system in which failure of a electroelastic vibration isolator engine mount is masked by the use of an idle speed control; there is no attempt to determine whether any particular vibration has sufficient strength to be objectionable to a person occupying the vehicle. 
     The present invention is very different from the &#39;860 patent, by making the control of idle speed or other engine operating parameters a function of noise, vibration, harshness or other objectionable NVH conditions which may be sensed by the human operator or other occupants of a motor vehicle. In essence, a system and method according to present invention allows engine idle speed control to be a function of the driver&#39;s projected physical response. 
     SUMMARY OF INVENTION 
     A system for controlling the idle speed or other operating parameter of an internal combustion engine in a motor vehicle includes an engine controller for receiving a plurality of engine operating parameters and for providing an idle speed control signal in response to the values of the parameters. At least one sensor is operatively connected with the controller for the purpose of sensing an NVH condition capable of being sensed by an occupant of the vehicle. The sensor produces an NVH signal in response to the sensing of the NVH condition. A signal processor operatively associated with controller receives the NVH signal. The signal processor also comprises a comparator for comparing characteristics of the NVH signal with a predetermined human threshold value. The controller uses the result of the comparison by the processor as one of a plurality of operating parameters for providing an idle speed control signal. 
     According to an aspect of the present invention, an NVH condition may comprise a vibration which may be sensed by the occupants of the vehicle, such as vibration of a vehicle structure such as a floor pan or other body panel or a seating component such as a seat track. Alternatively, the NVH condition may comprise a noise which may be sensed by occupants of the vehicle. 
     According to another aspect of the present invention, the signal processor, which may be housed within the engine controller itself, may comprise a filter operating in the time domain or filter operating in the frequency domain or both. 
     According to yet another aspect of the present invention, a method for controlling the idle speed or other operating parameter of an internal combustion engine installed in an automotive vehicle comprises the steps of sensing a NVH condition which is sensible by an occupant of the vehicle, producing an NVH signal corresponding to the sensed NVH condition, processing the NVH signal, and comparing the value of a characteristic of the processed NVH signal with a predetermined threshold value. 
     A method according to the present invention will alter idle speed or other controlled engine operating parameter in the event the value of a characteristic of the signal generated by an NVH sensor exceeds a threshold value. As before, an NVH condition according to present method may be a vibration which may be sensed by an occupant of the vehicle. Processing may comprise filtering of the NVH signal in the time domain or frequency domain followed by the comparison of the filtered signal with a threshold value, and correction of the idle speed or other operating parameter in the event that the threshold value is exceeded. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic representation of a internal combustion engine having an idle speed control with NVH feedback according to the present invention. 
     FIG. 2 is a flow chart illustrating a method according to present invention. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIG. 1, engine controller  110  which may comprise any of the plurality of electronic engine controllers known to those skilled in the art and suggested by this disclosure, receives inputs from a variety of sensors  112 . These sensors, which are of the type known to those skilled in the art, may include sensors for determining crankshaft position, EGR valve position, engine speed, crankshaft speed, camshaft position and other sensors. Moreover, according to the present invention, sensors  112  may comprise sensors capable of sensing an NVH condition. Such sensors include, without limitation, accelerometers, strain gauges applied to moving parts and microphones and other devices capable of sensing vibration and audible and sub-audible sound pressure level variation. 
     NVH signals arising from sensors  112  are communicated to controller  110 , and then processed by signal processor  114 . Signal processor  114  may comprise a filter which could be of the time or frequency domain variety or both, or another type of signal processor, digital and/or analog. In any event, according to FIG. 2, once an NVH condition has been sensed at block  212 , an NVH signal is produced at step  214  and processed at step  216  by filtering, as noted above. At step  218 , a character of the NVH signal, such as sound pressure level as a function of time, is compared with a human threshold value. For example, at step  218 , a processed signal relating to noise within vehicle&#39;s cabin may be compared with a sound pressure level or noise threshold value at which humans will have an adverse response. If the value of the processed NVH signal exceeds the predetermined human threshold value at step  218 , the program moves to step  220 , wherein the idle speed may be adjusted either up or down to reduce the perceived noise within the vehicle&#39;s cabin. Controller  110  will adjust the idle speed based not only upon the value of the processed NVH signal, but also upon the values of the other engine operating parameters reported by other of sensors  112 . 
     If the NVH condition being sensed is vibration of the seat track of the vehicle upon which the driver or passengers of the vehicle is seated, or for that matter, any other vibration, the filtered vibration signal may be compared with a human threshold value at step  218  and the engine speed increased or decreased accordingly at step  220  so as to move operation of the engine out of the regime within which the seat track is excited so as to either reduce or eliminate an objectionable vibration. 
     If the answer to the question posed in step  218  regarding the threshold comparison is “no”, then step  218 , the routine continues to loop, beginning once again with block  212 . 
     According to another aspect of the present invention, step  220  may comprise adjustment of not only engine idle speed, but other engine output parameters as well. Thus, if the engine exhibits, for example, the phenomenon termed “dominant cylinder firing”, which is characterized by one cylinder having a statistically greater firing pressure than the other cylinders, an unwanted vibration may result. This vibration may be corrected by retarding the spark timing for the particular cylinder which exhibits the greater firing pressure. And, this adjustment may be needed to achieve a desired level of NVH even though the cylinder exhibiting the dominant firing characteristic is not operating in a knocking condition. Those skilled in the art will appreciate in view of this disclosure that dominant cylinder firing may be sensed by, and be objectionable to, the driver or passengers of a vehicle even without knocking operation. 
     Dominant cylinder firing may be sensed by including within the array of sensors  112  a crankshaft position sensor and a related program in controller  110  for determining crankshaft acceleration. Such programs, which are known to those skilled in the art and suggested by this disclosure, are useful for detecting a cylinder exhibiting abnormally high or low firing pressure, so that a system and method according to the present invention may be implemented to address any resultant unacceptable NVH condition. 
     Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention. It is intended that the invention be limited only by the appended claims.