Abstract:
The present invention relates to a system for controlling loading of an internal combustion engine based on a an adjusted load bias signal produced by an engine control computer. The engine control computer is responsive to engine speed and commanded fueling to produce a load bias signal, is responsive to engine speed, engine intake air pressure and the load bias signal to produce an acceleration-adjusted load bias value, and is responsive to engine speed, a reference engine speed and the load 10 bias signal to produce a deceleration-adjusted load bias value. The engine control computer is thereafter operable to compare the load bias value, the acceleration-adjusted load bias value and the deceleration-adjusted load bias value and produce the adjusted load bias signal as one of these three signals based on a comparison therebetween. The adjusted load bias signal is provided to an external load generator operable to control loading of the engine based thereon. Improper loading of the engine is avoided with the present invention by accounting for transient engine operation involving engine acceleration and deceleration conditions.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to systems for controlling engine operation toward an optimum operating point, and more particularly to such systems operable to modify such control during vehicle acceleration and deceleration conditions. 
     BACKGROUND OF THE INVENTION 
     It is known in the control of internal combustion engines, particularly in industrial applications, to control engine load via an external generator. Such generators are typically electronically controlled and are responsive to at least a so-called “load bias” signal produced by electronic engine control circuitry to apply a corresponding load to the engine. 
     An example of a portion of a prior art control circuit  3  producing a steady state load bias signal (LB) is shown in FIG.  1 . Control circuit  3  includes a load bias calculation block  5  receiving a commanded fueling (CF) signal and an engine speed (ES) signal, wherein block  5  is operable to produce the load bias signal LB as a function thereof. Conventionally, the load bias signal is determined by comparing ES with CF and producing LB as a signal proportional to where the current engine operation point is (typically in relation to an engine output power or torque curve or map) relative to an optimal operating point. The optimal rating point is typically determined as the most efficient engine power generated at a given engine speed. 
     While the prior art load bias signal LB provides for accurate and effective engine load control during steady state operating conditions, this accuracy and efficacy diminishes during transient operating conditions. For example, during engine acceleration conditions, if the load bias signal LB is directly followed it results in less than optimal or sluggish engine performance. Optimal engine acceleration is dependent on the amount of air (boost pressure) and fuel available to the engine at any given engine speed. 
     Likewise, during deceleration of the engine, if the load bias curve is directly followed it results in less than optimal engine performance. The load bias signal in this case will request more load as the engine is decelerating, as the requested fueling is very low during deceleration conditions (i.e. the operator lets up on the throttle). The engine accordingly decelerates at the same time that the load bias signal is requesting more loading, which results in excessive loading on the engine when the target engine RPM is reached. This typically results in the target RPM being overshot, which is an undesirable engine response. 
     What is therefore needed is a system for improving the load bias signal LB to provide optimal engine performance not only during steady state engine operating conditions, but also during transient engine operating conditions such as during engine acceleration and deceleration. 
     SUMMARY OF THE INVENTION 
     The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for producing an adjusted load bias signal to provide for optimal acceleration conditions for an internal combustion engine comprises means for sensing engine rotational speed and producing an engine speed signal corresponding thereto, means for sensing intake air pressure of an internal combustion engine and producing a boost pressure signal corresponding thereto, means for determining a load bias signal as a function of the engine speed signal, and means for producing an adjusted load bias signal as one of the load bias signal and an acceleration-adjusted load bias signal, wherein the acceleration-adjusted load bias signal is based on the boost pressure signal and the engine speed signal. 
     In accordance with another aspect of the present invention, a method of producing an adjusted load bias signal to provide for optimal acceleration conditions for an internal combustion engine comprises the steps of sensing engine rotational speed, sensing engine intake air pressure, determining a load bias signal as a function of the engine rotational speed, determining an acceleration-adjusted load bias signal based on the engine rotational speed and the engine intake air pressure, and producing an adjusted load bias signal as one of the load bias signal and the acceleration-adjusted load bias signal. 
     In accordance with a further aspect of the present invention, a system for producing an adjusted load bias signal to provide for optimal deceleration conditions for an internal combustion engine comprises means for sensing engine rotational speed and producing an engine speed signal corresponding thereto, means for determining a reference engine speed, means for determining a load bias signal as a function of the engine speed signal, and means for producing an adjusted load bias signal as one of the load bias signal and a deceleration-adjusted load bias signal, wherein the deceleration-adjusted load bias signal is based on the engine speed signal and the reference engine speed. 
     In accordance with yet another aspect of the present invention, a method of producing an adjusted load bias signal to provide for optimal deceleration conditions for an internal combustion engine comprising the steps of sensing engine rotational speed, determining a reference engine speed, determining a load bias signal as a function of the engine rotational speed, determining a deceleration-adjusted load bias signal based on the engine rotational speed and the reference engine speed, and producing an adjusted load bias signal as one of the load bias signal and the deceleration-adjusted load bias signal. 
     In accordance with still another aspect of the present invention, a system for producing an adjusted load bias signal to provide for optimal acceleration and deceleration conditions for an internal combustion engine comprises means for sensing engine rotational speed and producing an engine speed signal corresponding thereto, means for sensing intake air pressure of an internal combustion engine and producing a boost pressure signal corresponding thereto, means for determining a reference engine speed, and a control computer computing a load bias signal as a function of said engine speed signal, the control computer computing an acceleration-adjusted load bias value as a function of the engine speed and boost pressure signals and computing a deceleration-adjusted load bias value as a function of the engine speed signal and the reference engine speed, the control computer producing an adjusted load bias signal as one of the load bias signal, the acceleration-adjusted load bias value and the deceleration-adjusted load bias value. 
     In accordance with still a further aspect of the present invention, a method of producing an adjusted load bias signal to provide for optimal acceleration and deceleration conditions for an internal combustion engine comprising the steps of sensing engine rotational speed of an internal combustion engine, sensing engine intake air pressure, determining a reference engine speed based on operator requested torque, determining a load bias signal as a function of the engine rotational speed, determining an acceleration-adjusted load bias signal based on the engine rotational speed and the engine intake air pressure, determining a deceleration-adjusted load bias signal based on the engine rotational speed and the reference engine speed, and producing an adjusted load bias signal as one of the load bias signal, the acceleration-adjusted load bias signal and the deceleration-adjusted load bias signal. 
     One object of the present invention is to optimize the performance of the engine and improve responsiveness and driveability of the vehicle in which the engine is placed. 
     Another object of the present invention is to provide such optimization by modifying the load bias signal for optimum engine performance during engine acceleration conditions. 
     Yet another object of the present invention is to provide such optimization by modifying the load bias signal for optimum engine performance during engine deceleration conditions. 
     These and other objects of the present invention will become more apparent from the following description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a prior art engine control system producing a load bias signal. 
     FIG. 2 is a block diagram of an engine control system producing an improved load bias signal in accordance with the present invention. 
     FIG. 3 is a block diagram of one preferred embodiment of at least a portion of the control computer  12  of FIG. 2 illustrating some of the concepts of the present invention.. 
     FIG. 4 is a block diagram illustrating one preferred embodiment of the load bias signal modification block of FIG.  3 . 
     FIG. 5 is a block diagram illustrating an alternative embodiment of the load bias signal modification block of FIG.  3 . 
     FIG. 6 is a flowchart illustrating one preferred embodiment of a software algorithm for executing the adjusted load bias signal feature illustrated in FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to a number of preferred embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated embodiments, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring to FIG. 2, one preferred embodiment of an engine control system  10 , in accordance with the present, is shown. System  10  includes as its central component a control computer  12  having a memory  15  and operable to control and manage the overall operation of an internal combustion engine  14 . In one embodiment, control computer is a known engine control computer that is sometimes referred to in the industry as an electronic control module (ECM), electronic control unit (ECU), or the like. 
     System  10  includes a number of sensors and/or actuators, wherein control computer  12  is responsive to signals supplied by such sensors and/or actuators to control the operation of engine  14  as is known in the art. For example, system  10  includes a throttle  16  electrically connected to an input IN 1  of control computer  12  via signal path  18  and producing a requested torque (RT) signal thereon. Throttle  16  may be any known mechanism for producing a requested torque signal RT corresponding to driver requested fueling, and in one embodiment, throttle  16  is an accelerator pedal of known construction. Alternatively, throttle  16  may be a known cruise control system, hand actuated throttle mechanism, or the like. 
     Engine  14  includes an engine speed sensor (ESS)  20  electrically connected to an input IN 2  of control computer  12  via signal path  22  and producing an engine speed signal (ES) thereon corresponding to engine rotational speed. In one embodiment, the engine speed sensor  20  is a known Hall effect sensor operable to produce an engine speed and position signal, although the present invention contemplates using other known sensors or sensing systems for providing the engine speed signal ES such as a variable reluctance sensor, or the like. Engine  14  also includes a turbocharger  24  and a boost pressure sensor  26  electrically connected to an input IN 3  of control computer  12  via signal path  28 . Boost pressure sensor  26  is preferably located within an air intake port or manifold (not shown) of the engine  14  and is operable to sense a pressure of intake air entering engine  14 , as is known in the art, and produce a boost pressure signal (BP) corresponding thereto. 
     Control computer  12  includes an output OUT 1  electrically connected to a fuel system  30  of engine  14  via signal path  32 . In accordance with known techniques, computer  12  is operable to determine fueling requirements for engine  14 , typically based on a number of engine operating parameters, and produce a corresponding commanded fueling (CF) signal on signal path  32 . Fuel system  20  is, in turn, responsive to the commanded fueling signal CF to supply fuel to engine  14  as is known in the art. 
     Control computer  12  also includes an output OUT 2  electrically connected to an electronic controller  36  of a known load generator  34  via signal path  38 . In accordance with the present invention, control computer  12  is operable to produce an adjusted load bias signal (ALB) on signal path  38  corresponding to the load bias signal (LB) described with respect to FIG. 1 modified to account for engine acceleration and deceleration conditions. The electronic controller  36  is responsive to the adjusted load bias signal ALB to control the load generator  34 , as is known in the art, to effectuate load control of engine  14  via process path  40 . 
     Referring now to FIG. 3, one preferred embodiment of at some of the internal features of control computer  12 , as they relate to the present invention, are shown. It is to be understood that while the features illustrated in FIG. 3 are shown as blocks, such blocks are not necessarily intended to represent physical structure but rather functional blocks that are typically executed via software. In any case, computer  12  includes a load bias calculation block  5 , which is preferably identical in structure and function to the load bias calculation block  5  of FIG. 1, wherein block  5  is responsive to the commanded fueling (CF) and engine speed (ES) signals on signal paths  32  and  22  respectively, to produce a load bias signal LB value on path  48 . For example, load bias calculation block  5  preferably uses the engine speed signal ES on signal path  22  and the commanded fueling signal CF on signal path  32 , in a known manner, to determine a current engine operating point relative to an optimal operating point (most efficient engine power generated at a given engine speed). Block  5  is then operable to produce the load bias value LB on path  48  that is proportional to the current operating point relative to the optimal operating point. Alternatively, block  5  may be responsive to CF and ES, and/or any other engine operating parameter signals, to produce LB in accordance with any other known technique therefore. 
     In any case, computer  12  further includes a reference speed calculation block  47  responsive to the requested torque signal RT to compute a reference engine speed ES REF  in accordance with known techniques therefore, and to provide the ES REF  value on path  49 . Computer  12  further includes a load bias adjustment or modification block  50  receiving the reference engine speed value ES REF  on path  49 , the load bias value LB on path  48 , the engine speed signal ES on signal path  22 , and the boost pressure signal on signal path  28 , and producing an adjusted load bias signal (ALB) on signal path  38 . As shown in FIG. 3, load bias adjustment block  50  preferably includes an engine acceleration adjustment block  52  and an engine deceleration adjustment block  54  coupled to a selection block  56 , wherein block  50  is operable to compute respective engine acceleration adjusted load bias and engine deceleration adjusted load bias values, and selectively produce an appropriate load bias value on signal path  38 . 
     Referring now to FIG. 4, one preferred embodiment  50 ′ of the load bias adjustment or modification block  50  of FIG. 3, in accordance with the present invention, is shown. Block  50 ′ includes an optimal ΔRPM calculation block  60  receiving as inputs the boost pressure BP and engine speed ES signals on signal paths  28  and  22  respectively, and producing on path  64  an optimal ΔRPM value. Block  60  may be implemented as a look-up table, graph or one or more equations relating current engine speed and boost pressure to an optimum rate of change of engine RPM for such operating conditions, wherein block  60  supplies the optimum rate of change of RPM (ΔRPM) value to an acceleration adjustment block  62  via path  64 . Acceleration adjustment block  62  is operable to receive the load bias signal LB on path  48  and the optimum ΔRPM value on path  64  and produce an acceleration-adjusted load bias value LB A  on path  72  as a function thereof. Block  62  may be implemented as a look-up table, graph or one or more equations relating LB and the optimal ΔRPM value to an appropriate LB A  value. 
     Block  50 ′ further includes a ΔES calculation block  66  receiving as inputs the reference engine speed value ES REF  and engine speed ES signal on signal paths  49  and  22  respectively, and producing on path  70  a ΔES value. Block  66  is preferably implemented as a comparison or subtraction function operable to compute ΔES as a difference between ES REF  and ES. A Deceleration adjustment block  68  is operable to receive the load bias signal LB on path  48  and the ΔES value on path  70  and produce a deceleration-adjusted load bias value LB D  on path  74  as a function thereof. Block  68  may be implemented as a look-up table, graph or one or more equations relating LB and the ΔES value to an appropriate LB D  value. 
     Block  50 ′ further includes a load bias selection block  56  receiving the load bias value LB, the acceleration-adjusted load bias value LB A , and the deceleration-adjusted load bias value LB D  from paths  48 ,  72  and  74  respectively, and producing an adjusted load bias signal ALB on signal path  38  as a function thereof. In one preferred embodiment, block  56  is operable to compare the two adjusted load bias values LB A  and LB D  with the load bias signal LB, and select an appropriate one of the three to supply on signal path  38  as the adjusted load bias signal ALB based on this comparison. In this embodiment, block  56  is operable to produce the acceleration-adjusted load bias value LB A  as the adjusted load bias signal ALB if the acceleration-adjusted load bias value LB A  is significantly different than the other two load bias values LB D  and LB. Conversely, if the deceleration-adjusted load bias value LB D  is significantly different than the other two load bias values LB A  and LB, block  56  is operable to produce the  25  deceleration-adjusted load bias value LB D  as the adjusted load bias signal ALB. Finally, if all three load bias values LB, LB A  and LB D  are nearly the same, then block  56  is operable to produce the original load bias signal LB as the adjusted load bias signal ALB. 
     Referring now to FIG. 5, an alternate embodiment  50 ″ of the load bias adjustment or modification block  50  of FIG. 3, in accordance with the present invention, is shown. Block  50 ″ is similar in many respects to block  50 ′ of FIG. 4, and like reference numbers are therefore used to identify like components. Block  50 ″ differs from block  50 ′ in that the optimal ΔRPM value produced on path  64  by block  60  and the ΔES value produced on path  70  by block  66  are fed directly into an adjusted load bias determination block  78 . Block  78  is responsive to the load bias signal LB and the optimal ΔRPM and ΔES values to determine, and produce on signal path  38 , an appropriate adjusted load bias signal ALB. In this embodiment, block  78  may be implemented as a look-up table, graph, one or more equations, or algorithm operable to directly determine an appropriate adjusted load bias signal ALB, as described above, based on the load bias signal LB and the optimal ΔRPM and ΔES values. 
     Referring now to FIG. 6, one preferred embodiment of a software algorithm  80  for executing the adjusted load bias signal feature illustrated in FIG. 3 is shown. Algorithm  80  is preferably stored within memory  15  and is executable by control computer  12  to effectuate the process illustrated therein. Algorithm  80  begins at step  82  and at step  84 , control computer  12  is operable to compute load bias signal LB, the acceleration-adjusted load bias value LB A  and the deceleration-adjusted load bias value LB D , all as described hereinabove. Thereafter at step  86 , control computer  12  is operable to determine, preferably based on a comparison between LB, LB A  and LB D , whether the engine  14  is accelerating, decelerating or neither. If control computer  12  determines that the engine  14  is accelerating, algorithm execution advances to step  88  where control computer  12  is operable to produce as the adjusted load bias signal ALB the acceleration-adjusted load bias value LB A . Algorithm  80  returns thereafter to its calling routine at step  90 . If, on the other hand, control computer  12  determines at step  86  that the engine  14  is decelerating, algorithm execution advances to step  92  where control computer  12  is operable to produce as the adjusted load bias signal ALB the deceleration-adjusted load bias value LB D . Algorithm  80  returns thereafter to its calling routine at step  94 . Finally, if control computer  12  determines at step  86  that the engine  14  is neither accelerating nor decelerating, algorithm execution advances to step  96  where control computer  12  is operable to produce as the adjusted load bias signal ALB the original (unadjusted) load bias signal LB. Algorithm  80  returns thereafter to its calling routine at step  98 . 
     In operation the electronic controller  36  (FIG. 1) will receive an unadjusted load bias signal LB, an acceleration-adjusted load bias signal LB A , or a deceleration-adjusted load bias signal LB D  depending on whether the engine is running at a steady rate, accelerating, or decelerating condition, respectively. The unadjusted load bias signal LB generally corresponds to the lowest fuel consumption point for a given engine speed and is preferably calculated in a conventional manner from an engine speed signal and a fueling command signal. The acceleration-adjusted load bias signal LB A  is determined using the engine speed signal, a boost pressure signal, and the unadjusted load bias signal LB. The deceleration-adjusted load bias signal LB D  is determined using the engine speed signal, a reference engine speed value, and the unadjusted load bias signal LB. 
     While the invention has been illustrated and described in detail in the foregoing drawings and description thereof, the same is to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.