Abstract:
An method of operating a multiple speed (gear ratio) mechanical transmission and engine combination to optimize (reduce) fuel consumption comprises the steps of determining a fuel efficiency map for an engine, providing a multiple speed mechanical transmission controller having data and program storage capabilities, providing data regarding the fuel efficiency map to the controller and providing a control algorithm in the controller whereby operation of the engine/transmission combination is optimized for fuel economy in accordance with the fuel efficiency map.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates generally to a method of efficiently operating a multiple speed transmission and engine combination and more specifically to a method of operating a multiple speed mechanical or automated mechanical transmission and engine combination which utilizes the fuel map of the particular type or brand of engine to optimize fuel consumption of the engine/transmission combination. 
       BACKGROUND 
       [0002]    An unwavering goal of contemporary vehicle designers is the achievement of increased fuel efficiency, i.e., reduced fuel consumption. Designers of passenger cars, light trucks and long haul tractor trailers continually strive to improve the fuel efficiency of their vehicles while addressing other operating and performance parameters. While recent fuel consumption reductions stated in percent of hybrid vehicles are impressive, much smaller percentage fuel consumption reductions when applied to long haul tractor trailers typically represents much larger actual savings in fuel consumption because such vehicles consume more fuel on a miles per gallon basis and are driven many miles farther during any given period of time, for example, a year. 
         [0003]    One of the improvements to long haul tractor trailers in recent years is the automated mechanical transmission. In this device, a relatively conventional multiple speed (gear ratio) heavy duty transmission includes an actuator assembly which is controlled by a master controller or microprocessor. The microprocessor includes a plurality of inputs which receive signals from various sensors such as speed sensors, a throttle position sensor, brake and ABS sensors, a shift selector, an operator controlled mode selector and other devices and, through the use of algorithms, computational routines, look-up tables and the like, controls operation of the master clutch and selection and engagement of transmission gears. Because such systems will consistently command upshifts and downshifts based upon the sensed conditions and established shift rules, fuel efficiency of such devices is generally good. 
         [0004]    The fuel efficiency (consumption) of a particular engine, i.e., a particular size or output engine from a particular manufacturer, may be presented in a fuel efficiency map. This map relates fuel consumption as a function of engine speed, delivered torque and delivered horsepower. The fuel map includes a plurality of isograms or isolines of constant fuel consumption which are roughly arranged about a single value of speed and torque, i.e., a point, of maximum fuel efficiency. Stated somewhat differently, a single, vehicle operator or a single shift program when used with two engines having distinct fuel efficiency maps will be unable to achieve optimum fuel efficiency with both and may perform at a fuel efficiency well below that which could be obtained by commanding shifts based upon the fuel efficiency map of the given engine to achieve optimum fuel efficiency. 
         [0005]    Different styles and designs of internal combustion engines and engines from different manufacturers have different fuel efficiency maps. Accordingly, if a truck or tractor manufacturer utilizes two or more different engines in a particular truck, the experience and habits of one operator utilizing a manual transmission or an automated mechanical transmission with the same control algorithm and operating logic will not provide optimum fuel efficiency in both trucks. 
         [0006]    Such automated mechanical transmissions often have multiple control modes such as fully automatic and manual. The fully automatic mode may include several sub-modes that emphasize, that is, more heavily weight, one control variable or parameter over others. For example, one automatic control mode may emphasize performance, while another may provide improved control at very low vehicle speeds while a third may seek to minimize shifting by utilizing more widely separated upshift and downshift values. 
         [0007]    The present invention is directed to further improving the fuel efficiency of multiple speed mechanical and automated mechanical transmission engine combinations. 
       SUMMARY 
       [0008]    An method of operating a multiple speed mechanical transmission and engine combination to optimize (reduce) fuel consumption comprises the steps of determining a fuel efficiency map for an engine, providing a multiple speed transmission controller having program and data storage capabilities, providing and storing data regarding the fuel efficiency map in the controller and a providing a control algorithm in said controller whereby operation of the engine/transmission combination is optimized for fuel economy in accordance with the fuel efficiency map. 
         [0009]    Thus it is an object of the present invention to provide a method of operating a multiple speed transmission and engine combination which provides improved fuel efficiency. 
         [0010]    It is a further object of the present invention to provide a method of operating an automated mechanical transmission (AMT) and engine combination which provides improved fuel efficiency. 
         [0011]    It is a still further object of the present invention to provide a method of operating a conventional manual transmission and engine combination which provides improved fuel efficiency. 
         [0012]    It is a still further object of the present invention to provide a method of operating an automated manual transmission and engine combination which utilizes the fuel efficiency (consumption) map of a particular type of engine to maximize fuel efficiency. 
         [0013]    It is a still further object of the present invention to provide a method of operating a conventional mechanical transmission and engine combination which utilizes the fuel efficiency (consumption) map of a particular type of engine to maximize fuel efficiency. 
         [0014]    It is a still further object of the present invention to provide a method of operating an automated mechanical transmission and engine combination wherein the operation of the transmission is adjusted to match the fuel efficiency map of a particular engine. 
         [0015]    Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred embodiment and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a diagrammatic, plan view of a motor vehicle driveline utilizing an automated mechanical transmission and controller incorporating the present invention; 
           [0017]      FIG. 2  is a typical or representative fuel efficiency map of a first particular type or brand of internal combustion engine; 
           [0018]      FIG. 3  is a typical or representative fuel efficiency map of a second particular type or brand of internal combustion engine; 
           [0019]      FIG. 4  is a block diagram of a computer program for use with an automated mechanical transmission which embodies the present invention; and 
           [0020]      FIG. 5  is a block diagram of a computer program for use with a conventional mechanical transmission which embodies the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Referring now to  FIG. 1 , a diagrammatic, plan view of a typical truck tractor incorporating the present invention is illustrated and generally designated by the reference number  10 . The truck tractor  10  includes a prime mover  12  which may be an internal combustion gas or Diesel engine having an output provided directly to a master friction clutch  14 . The master friction clutch  14  selectively and positively engages the output of the prime mover  12  to an input of a multiple speed, gear change transmission  16 . The transmission  16  is preferably of the type currently designated as an automated mechanical transmission (AMT) wherein gear or speed ratio changes of a splitter, a main transmission, and a planetary gear assembly, for example, are all achieved by an automated, i.e., electric, hydraulic or pneumatic, shift actuator assembly  18 A connected through a data or control link  19  to a master microprocessor or controller  20 . Alternatively, the transmission  16  may be a conventional operator (manually) shifted multiple speed ratio transmission having a gear shift lever (not illustrated) extending into the cab of the truck tractor  10 . 
         [0022]    The master microprocessor or controller  20  includes data input ports, memory, one or more processors and data and control outputs driving, for example, the shift actuator assembly  18 A or a visual or audible indicator  18 B. 
         [0023]    The master microprocessor or controller  20  is preferably coupled by a data and control link  21  to an engine controller  22 . The engine controller  22  is an integral component of the prime mover  12  and will typically include a processor or controller which receives data from an engine speed sensor and other sensors or devices and controls (not illustrated), for example, a fuel control or metering device capable of adjusting and terminating the flow of fuel to the prime mover  12  and thus its speed. The master friction clutch  14  also includes a master friction clutch operator assembly  24  which controls the engagement and disengagement of the master friction clutch  14 . Once again, as an alternative, the manual transmission  16  may be paired with a manual, i.e. vehicle operator actuator friction clutch. A throttle position sensor  26  senses the position of a vehicle throttle or accelerator pedal  28  and provides real time data regarding the position of the throttle pedal  28  to the master controller  20 , which, in turn, typically will provide such data to the engine controller  22 . 
         [0024]    The output of the transmission  16  is provided to a rear driveline assembly  30  which includes a rear propshaft  32  which drives a conventional rear differential  34 . The rear differential  34  provides drive torque to a pair of rear axles  36  which are in turn coupled to left and right rear tire and wheel assemblies  38  which may be either a dual configuration illustrated or a single left and right tire and wheel assembly. Suitable universal joints  42  may be utilized as necessary with the rear propshaft  32  to accommodate static and dynamic offsets and misalignments thereof. 
         [0025]    Also disposed in the cab of the truck tractor  10  is an operator adjustable gear selector lever or assembly  44  having an output which is provided to the master controller  20 . The gear selector lever assembly  44  defines a shift pattern  46  through which the vehicle operator may select, for example, whether the master controller  20  will automatically select and shift between available gears of the transmission  16  or defeat or override such automatic selection and manually select and engage a desired gear. One or more push buttons or toggle switches  48 , for example, may be utilized to receive commands from the operator to select or de-select an operating mode or condition such as the fuel economy mode of the present invention. A stationary front axle  50  pivotally supports a pair of front tire and wheel assemblies  52  which are controllably pivoted by a steering linkage  54  which is coupled to and positioned by a steering wheel  56 . 
         [0026]    Reference to  FIGS. 2 and 3  will clarify two important aspects of the invention.  FIGS. 2 and 3  present two fuel (efficiency) maps  60  and  70  which set forth the fuel consumption (efficiency) of two different brands, types or models of internal combustion truck engines as a function of engine speed and engine torque output. Engine speed in revolutions per minute (RPM) is presented along the X axis of  FIGS. 2 and 3  and engine torque output (lb.ft) is presented along the Y axis of  FIGS. 2 and 3 . Curved dashed lines superimposed on the isograms of the graphs represent various levels of horsepower output of an engine or prime mover  12 . The irregular lines or curves of the graph are isograms (isolines) of constant fuel consumption. 
         [0027]    The fuel maps  60  and  70  may also be viewed as three dimensional, i.e., topologic, maps with surfaces sloping down and away from a point (peak) disposed with a closed, oblong region or isogram  62 . The fuel map  60  represents the operational characteristics of a first, particular engine or prime mover  12 . It should be understood, however, that the fuel map  60  is presented by way of example and illustration only. The closed, oblong region or isogram  62  generally disposed in the middle of the fuel map  60  represents a region of substantially optimum, i.e., maximum, fuel efficiency or minimum fuel consumption relative to maximum energy output. The condition of optimum fuel efficiency is, as noted, a point within the region  62 . Each isogram or isoline  64  more distant from this closed, oblong isogram  62  represents operating conditions having increased but constant fuel efficiency. All of the isograms or isolines  62  and  64  represent varying operating conditions of engine speed and load having constant fuel efficiency or consumption measured, for example, by brake specific fuel consumption (BSFC). 
         [0028]    Referring now to  FIG. 3 , a fuel (efficiency) map  70  for a second, distinct brand, type or model of internal combustion engine or prime mover  12  is illustrated. Here, the oblong region or isogram  72  likewise represents a region of substantially optimum fuel efficiency. As noted, the best fuel efficiency is represented by a point within the isogram  72 . The surrounding isograms or isolines  74  represent lines of constant fuel efficiency; the farther away from the isogram  72 , the poorer the fuel efficiency. 
         [0029]    Through inspection and study of the fuel maps  60  and  70  of  FIGS. 2 and 3 , it will become apparent that from the standpoint of the engines or prime movers  12 , maximum fuel efficiency, i.e., minimum fuel consumption, occurs within relatively small operating regions of the engines or prime movers  12 , in  FIG. 2 , between 1400 and 1500 rpm and in  FIG. 3 , between 1350 and 1450 rpm when the engines or prime movers  12  are developing between about 900 and 1100 pounds feet of torque which is approximately 300 horsepower. 
         [0030]    Second of all, study and inspection of  FIGS. 2 and 3  reveals that the two graphs or fuel maps  60  and  70  and the respective sets of isograms  62 ,  64 ,  72  and  74  are distinct. They are distinct because they represent two distinct internal combustion engines. Because the engines or prime movers  12 , their operation and fuel maps  60  and  70  are distinct, a shift program optimized for a given variable, such as fuel efficiency for one, will not provide optimization of the same parameter for the other. Stated somewhat differently, a single or common operating shift program for one prime mover  12  having, for example, a fuel map  60  such as illustrated in  FIG. 2  will not provide, with only random exceptions, optimum operation with another prime mover  12  having a different fuel map such as the fuel map  70  illustrated in  FIG. 3 . 
         [0031]    Thus, the present invention utilizes the data contained in the fuel map of a particular engine or prime mover  12  which may be stored in the master controller  20  to influence the shift program of the master controller  20 . Specifically, when an economy mode has been engaged, operation of the prime mover  12  and the transmission  16 , are adjusted within limits, to operate within, or as near as possible to, the closed, oblong isograms  62  and  72  representing that operation providing the best fuel economy associated with a specific manufacturer, design or type of engine or prime mover  12 . 
         [0032]    Accordingly, the first aspect of the invention is to read and store the fuel map data  60  or  70 , for example, for a particular manufacturer and design or type of engine or prime mover  12  such as a Diesel engine within the memory of the master microprocessor controller  20 . The data designating the closed, oblong region or isogram  62  such as the engine speed and engine load, and horsepower if desired, as discussed above, is the most critical with corresponding data more distant the closed, oblong isogram  62  of increasingly less significance. That is, data regarding the isogram  64  most removed from the closed, oblong isogram  62  is of negligible importance whereas those isograms  64  more proximate the closed, oblong isogram  62  are more important. Similarly, while it is apparent that both engine speed and engine load cooperatively determine the fuel efficiency, engine speed is the controllable variable whereas engine load is a function of primarily the speed of the vehicle and the currently selected operating gear ratio. Thus, even though, for example, in  FIG. 2 , engine speed may be between 1400 and 1500 rpm, if the engine load is low, engine efficiency may be significantly below that enjoyed when the engine is operating at a design load and horsepower, for example, 1000 pound feet and 300 horsepower. In other words, only when the engine or prime mover  12  is operating in the vicinity of its nominal rated torque output and horsepower will it achieve optimum fuel efficiency. This, in turn, means that defining and operating a prime mover  12  such as a gas or Diesel engine in an economy mode is most significant in the higher number (lower actual numerical) gear ratios. 
         [0033]    Referring now to  FIG. 4 , once data from a fuel map such as the fuel maps  60  or  70  referring to a particular engine or prime mover  12  is stored in the master microprocessor or controller  20 , an economy mode program or subroutine  80  may be executed. The program  80  starts with an initialization step  82  and moves to a first decision point  84  which determines whether an operator manipulatable switch or push button  48  or a certain motion of the gear selector lever assembly  44  has established that the driver wishes to engage the economy mode of the transmission  16 . If the economy mode of the transmission  16  has not been activated, the decision point  84  exits at NO and the program  80  terminates at an end point  86 . 
         [0034]    If the economy mode of the transmission  16  has been activated, the decision point  84  is exited at YES and a second decision point  90  is entered which inquires whether the transmission  16  is in its highest number (lowest numerical ratio) gear. If it is not, the program  80  moves to a third decision point  92  which inquires whether the transmission assembly  16  is in its next highest gear. If it is not, the third decision point  92  is exited at NO and a process step  94  is entered which activates and counts down a short duration timer. The timer may define a delay of typically between two and ten seconds or more or less depending upon the dynamic performance of the vehicle, the specific type of the vehicle and other operating and mechanical parameters. Once the delay timer times out its predetermined period, the program  80  returns to the input of the decision point  90 . If the transmission is in the highest gear, the decision point  90  is exited at YES and a fourth decision point  96  next inquires whether the speed of the engine or prime mover  12  is less than, for example 1150 rpm. If it is not, the decision point is exited at NO and the program  80  terminates at the end point  86 . If the speed of the engine or prime mover  12  is less than 1250 rpm, a process step  98  is entered which commands a downshift to increase the speed of the engine or prime mover  12  and move it closer to the maximum efficiency closed isogram  62 . Again, the program  80  terminates at the end point  86 . 
         [0035]    Returning to the decision point  92 , if the transmission  16  is in the next to the highest gear, the decision point  92  is exited at YES and a decision point  102  is entered which inquires whether the speed of the engine or prime mover  12  is greater than 1650 rpm. If it is, the decision point  102  is exited at YES and the program  80  enters a process step  104  which commands an upshift of the transmission assembly  16  to the highest gear in order to slow the speed of the engine or prime mover  12  and move the operating point to the left in  FIG. 2 , closer to the isogram  62 . 
         [0036]    Returning to the decision point  102 , if the speed of the engine or primer mover  12  is not greater than 1650 rpm, the decision point  102  is exited at NO and the program  80  enters a decision point  106  which inquires whether the speed of the engine or prime mover  12  is less than 1150 rpm. If it is not, the decision point  106  is exited at NO and the program concludes at the end point  86 . If the speed of the engine or prime mover is less than, for example, 1150 rpm, the decision point  106  is exited at YES and the program  80  enters a process step  108  which commands a downshift of the transmission  16  to increase the rpm of the engine or prime mover  12  and move the operating point to the right, more proximate the isogram  62 . 
         [0037]    It will be appreciated that the fuel maps  60  and  70  and the upshift and downshift values presented in  FIG. 4  and the above text are illustrative and utilized by way of example only. As stated previously, inasmuch as each type or configuration of engine or prime mover  12  from each particular manufacturer will define a distinct fuel (efficiency) map, the numerical shift r.p.m. values will be adjusted to match such fuel maps and provide optimum fuel efficiency consistent with established automated mechanical transmission shift protocols while maintaining the required power output of the engine/transmission combination. 
         [0038]    It will also be appreciated that the foregoing economy mode program  80  has discussed operation only in the highest two gears (lowest numerical ratios) of the transmission  16 . It should be appreciated that certain vehicles, performance and service requirements may encourage or necessitate operation in the economy or fuel efficiency mode of the present invention in lower gears, for example, ninth and tenth gears of a twelve speed transmission. To enable such operation in, for example, the four highest gears, the decision points  90  and  92  must be augmented or modified to inquire regarding additional gear ratios or selections. 
         [0039]    Referring now to  FIG. 5 , operation of an engine/transmission combination wherein the transmission and clutch are manually, i.e. by the vehicle operator, controlled will now be described. Again, it is first necessary to load data from a fuel map such as the fuel maps  60  or  70  referring to a particular engine or prime mover  12  into the master microprocessor or controller  20 . Then, a manual transmission economy mode program or subroutine  110  may be selected and executed. The program  110  starts with an initialization step  112  and moves to a decision point  114  which determines whether an operator controlled switch or push button  48  has been activated to indicate that the vehicle operator wishes to drive or operate in the economy mode. If the economy mode has not been selected, the first decision point  114  exits at NO and the program  110  terminates at an end point  116 . 
         [0040]    If the economy mode has been selected, the decision point  114  is exited at YES and a second decision point  120  is entered which inquires whether the transmission  16  is in its highest number (lowest numerical ratio) gear. If it is not, the program  110  moves to a third decision point  122  which inquires whether the transmission  16  is in its next highest gear. If it is not, the third decision point  122  is exited at NO and a process step  124  is entered which activates and counts down a short duration timer. The timer of the process step  124  may define a delay of typically between two and ten seconds or more or less depending upon the dynamic performance of the vehicle, the specific type of the vehicle and other operating and mechanical parameters. Once the delay timer of the process step  124  times out its predetermined period, the program  110  returns to the input of the second decision point  120 . If the transmission is in the highest gear, the second decision point  120  is exited at YES and a fourth decision point  126  next inquires whether the speed of the engine or prime mover  12  is less than, for example, 1200 rpm. If it is not, the fourth decision point  126  is exited at NO and the program  110  terminates at the end point  116 . If the speed of the engine or prime mover  12  is less than 1200 rpm, a process step  128  is entered which illuminates an indicator light, or provides another graphic, audible or tactile signal to the vehicle operator to downshift the transmission  16  to increase the speed of the engine or prime mover  12  and move such speed closer to the maximum efficiency closed isogram  62 . Again, the program  110  terminates at the end point  116 . 
         [0041]    Returning to the third decision point  122 , if the transmission  16  is in the next to the highest gear, the decision point  122  is exited at YES and a fifth decision point  132  is entered which inquires whether the speed of the engine or prime mover  12  is greater than 1600 rpm. If it is, the decision point  132  is exited at YES and the program  110  enters a process step  134  which illuminates an indicator light or provides another graphic, audible or tactile signal to the vehicle operator to upshift the transmission  16  to the highest gear in order to slow the speed of the engine or prime mover  12  and move the operating point to the left in  FIG. 2 , closer to the isogram  62 . 
         [0042]    Returning to the fifth decision point  132 , if the speed of the engine or primer mover  12  is not greater than 1600 rpm, the decision point  132  is exited at NO and the program  110  enters a sixth decision point  136  which inquires whether the speed of the engine or prime mover  12  is less than 1200 rpm. If it is not, the decision point  136  is exited at NO and the program  1110  concludes at the end point  116 . If the speed of the engine or prime mover is less than, for example, 1200 rpm, the fifth decision point  136  is exited at YES and the program  110  enters a process step  138  which illuminates an indicator light or provides other graphic, audible or tactile signal to the vehicle operator to downshift the transmission  16  to increase the rpm of the engine or prime mover  12  and move the operating point to the right, more proximate the isogram  62 . 
         [0043]    It will be appreciated that the fuel maps  60  and  70  and the upshift and downshift values presented in  FIG. 5  and the above text are illustrative and utilized by way of example only. As stated previously, inasmuch as each type or configuration of engine or prime mover  12  from each particular manufacturer will define a distinct fuel (efficiency) map, the numerical shift rpm values of the program  110  will be adjusted to match such fuel maps and provide optimum fuel efficiency consistent with established mechanical transmission operation while maintaining the required power output of the engine/transmission combination. 
         [0044]    It will also be appreciated that the foregoing economy mode program  110  has discussed operation only in the highest two gears (lowest numerical ratios) of the transmission  16 . It should be appreciated that just as with the program  80 , the program  110  may be augmented to function with the three or four highest gears of a manual transmission  16 . 
         [0045]    The foregoing disclosure is the best mode devised by the inventor for practicing this invention. It is apparent, however, that apparatus incorporating modifications and variations will be obvious to one skilled in the art of automated mechanical transmissions. Inasmuch as the foregoing disclosure is intended to enable one skilled in the pertinent art to practice the instant invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the spirit and scope of the following claims.