Abstract:
The automatic transmission with improved efficiency combines the advantages of existing standard transmissions with new features that allow fully automatic operation. The transmission uses two or more lay shafts and non-constant mesh gears to allow continuous power transfer even during shifting between gears. The non-constant mesh gears are synchronized during shifting through the use of servo motors and position sensors.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     FEDERALLY SPONSORED RESEARCH 
     Not Applicable 
     SEQUENCE LISTING OR PROGRAM 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to improving the efficiency of automatic transmissions used in motor vehicles. 
     2. Prior Art 
     There have been a number of inventions in the history of vehicle transmissions. Ford&#39;s famous Model A used a 3 speed manual transmission and a foot operated clutch. This transmission changed gear ratios by sliding different gears into engagement. There was no automatic method for insuring that the gears were turning at a matching speed as they were engaged. This required the driver to carefully synchronize the speed of the gears before shifting. Failure to do this well would result in grind the gears and a shorter transmission life. A driver had to learn a complicated process called double clutching. This entailed pressing the clutch pedal two times while at the same time changing engine speed to bring the gears into synchronization. 
     This was difficult for most people to master. The solution was a transmission with automatic synchronizers. This eliminated the need for double clutching. The synchronizers acted between the gears to eliminate any speed difference. Thus, the transmission could be shifted without worrying about grinding gears. 
     In a synchromesh transmission all gears were engaged at all times, a feature called constant mesh. The transmissions gear ratio is changed by using shifter rings that lock the desired gear to its shaft. This design combines two features; constant mesh gears and synchronizers. All modern standard transmission cars have synchromesh transmissions. 
     Unfortunately, in a constant mesh transmission all gears remain engaged and turning even when not carrying the load thereby causing drag and reducing energy efficiency. Furthermore, the synchronizer rings for those gears not engaged also cause drag wasting more power and additional reductions in efficiency. 
     But people did not want to worry about shifting at all. Thus was born the fully automatic transmission. This removed the chore of shifting the transmission completely. Gear changes were entirely managed by engaging clutches which were controlled by a computer. 
     Early designs had a hydraulic computer that controlled the clutches. More recently, the management of the transmission is left to an electronic computer. Automatic transmissions are also constant mesh gearboxes but are shifted by means of friction clutches. The transmission has series of clutches that allow a particular set of planetary gears to rotate or to be locked together. 
     In any particular gear some clutches would be engaged and others would be relaxed. The relaxed clutches also spin resulting in drag which reduces efficiency. 
     Each of these inventions solved some problems but exacerbated other problems. The Model A transmission was simple and very efficient. No gears were engaged unless they were being used to carry power. This reduced friction and wear. However, it was difficult to use and gears could be damaged by improper shifting. 
     The synchromesh transmission was much easier to use but had many moving parts all contributing to drag. All gears were engaged at all times with only some of the gears being used to carry power. The synchronizer clutches dragged for all the gears except the one currently selected. 
     The fully automatic transmission was even easier to use but had even more moving parts all contributing to wear and drag. In any particular gear, multiple clutches would not be engaged but were rotating thereby adding to drag. 
     PRIOR PATENT ART 
     The idea of a transmission with multiple lay shafts and multiple clutches is not new. U.S. Pat. No. 2,386,540 by John J. Campodonico describes a transmission with two lay shafts and two clutches. This patent describes a feature where the next gear ratio is selected before the transmission is actually shifted. The actual shifting is accomplished by releasing one clutch and then engaging the other clutch. This transmission incorporated constant mesh gears and grinding is avoided by using mechanical synchronizers. 
     U.S. Pat. No. 4,461,188 describes a dual lay shaft transmission configured for a transverse engine in a front wheel drive vehicle. It too uses two clutches to select between sets of gears. The constant mesh gears are synchronized using mechanical synchronizers. 
     U.S. Pat. No. 6,463,821 illustrates a method of using the dual clutches to control the shifting of the transmission. The engagement and release of the clutches is changed as the load on the transmission is changed. 
     PRIOR ART IN PRODUCTS 
     Chrysler motors introduced dual lay shaft and dual clutch transmissions in both automobile and truck versions. These are the 79REM and 62TEM transmissions. These transmissions are constant mesh designs that use mechanical synchronizers to prevent gear grinding during shifting. 
     OBJECTS AND ADVANTAGES 
     The present invention improves on previous designs in these ways; 
     1. Reduced drag from unnecessary moving parts. 
     2. Fewer parts. 
     3. More compact design. 
     4. Fully automatic shifting. 
     5. Only two clutches are necessary to shift all gears. 
     6. The clutches are separate from the gear mechanism allowing easy maintenance. 
     SUMMARY 
     The automatic transmission with improved efficiency combines the best features of early transmission designs with an innovative synchronizing mechanism. This provides a simpler and more compact automatic transmission. The compact structure supports a design with many possible gear ratios. The external clutch feature allows easier maintenance. 
    
    
     
       DRAWINGS 
         FIG. 1  This shows the arrangement of the gears, clutches and motors. 
         FIG. 2  This chart shows the steps taken to shift from one gear ration to another. 
     
    
    
     DETAILED DESCRIPTION 
     List of Drawing Elements 
     
         
         
           
               10  Input shaft. 
               11  First lay shaft. 
               12  Second lay shaft. 
               13  Output shaft. 
               20  Input drive gear. 
               21  First lay shaft drive gear. 
               22  Second lay shaft drive gear. 
               30  Input shaft bearing. 
               31  Output shaft bearing. 
               32  First lay shaft bearing. 
               33  First lay shaft bearing. 
               34  Second lay shaft bearing. 
               35  Second lay shaft bearing. 
               36  Output shaft bearing. 
               40  First lay shaft servo motor. 
               41  Second lay shaft servo motor. 
               42  First lay shaft speed and position sensor. 
               43  Output shaft speed and position sensor. 
               44  Second lay shaft speed and position sensor. 
               45  Transmission controller. 
               60  First and third shifter. 
               61  Second and forth shifter. 
               62  Fifth and seventh shifter. 
               63  Sixth and eighth shifter. 
               70  First gear, movable. 
               71  Second gear, movable. 
               72  Third gear, movable. 
               73  Forth gear, movable. 
               74  Fifth gear, movable. 
               75  Sixth gear, movable. 
               76  Seventh gear, movable. 
               77  Eighth gear, movable. 
               80  First and third gear, fixed. 
               81  Second and forth gear, fixed. 
               82  Fifth and seventh gear, fixed. 
               83  Sixth and eighth gear, fixed. 
               90  First lay shaft clutch. 
               91  Second lay shaft clutch. 
               100  Decision step. 
               101  Release idling clutch in anticipation of shift step. 
               102  Measure speed and gear phasing step. 
               103  Bring idling lay shaft to correct speed and phasing step. 
               104  Command actuator to bring movable gear into engagement step. 
               105  Release load carrying clutch and engage idling clutch step. 
               106  Command actuator to disengage previous load carrying gear step. 
               107  Engage clutch on now idling lay shaft step. 
               108  Gear shift complete step. 
           
         
       
    
     DETAILED DESCRIPTION 
     FIG.  1   
       FIG. 1  shows the layout of all the major components of the transmission. The input shaft  10  will connect to an engine possibly through a torque converter. This optional torque converter is not shown for simplicity sake. The input shaft  10  is solidly attached to the input drive gear  20 . The input shaft  10  rides in a bearing  30 . Power is transmitted through the input drive gear  20  to the two lay shaft drive gears  21  and  22 . 
     The lay shaft drive gears  21  and  22  are not rigidly attached to the lay shafts but are able to spin on the shaft. The lay shaft drive gears  21  and  22  may be coupled to the lay shafts by the two clutches  90  and  91 . These clutches  90  and  91  are controlled by the transmission controller  45 . There is no connection shown in  FIG. 1  between the clutches  90  and  91  and the transmission controller  45  to avoid cluttering the drawing. 
     Each lay shaft  11  and  12  have a set of movable gears  70 ,  71 ,  72 ,  73 ,  74 ,  75 ,  76 , and  77 . These movable gears are able to slide on the lay shafts but not rotate due to the splined lay shafts. The position of the movable gears is controlled by 4 actuators  60 ,  61 ,  62 , and  63 . These actuators are connected to the transmission controller  45  but the connections are not shown for simplicity in the drawing. 
     The actuators can move each of the movable gears to one of three positions. The center position is shown in  FIG. 1 . For example, actuator  61  is able to move the gear pair  71  and  73  to the left in  FIG. 1 . This would result in gear  71  engaging with gear  80 . When the clutch  91  is actuated power will pass from the input shaft through gear  20  to gear  22  into the second lay shaft  12 . The lay shaft will pass power to gear  71  which is engaged with gear  80 . Gear  80  is permanently attached to the output shaft  13 . This power passes from gear  80  to the output shaft then to the final load. The connection from the output shaft  13  to the load is not shown for simplicity. This is the situation when the transmission is in first gear. 
     When in first gear the actuators  60 ,  62  and  63  hold their gear pairs  70 ,  72  and  74 ,  76 , and  75 ,  77  in the center which is the not engaged position. Clutch  90  is engaged and the lay shaft  11  spins freely. Clutch  90  is left engaged when the lay shaft  11  is not in use so as to avoid dragging friction and wear. 
     When the transmission controller determines that it wants to shift into second gear it prepares lay shaft  11 . First the lay shaft  11  must be brought to the correct speed. The clutch  90  is released which allows the shaft to spin freely. The controller  45  measures the speed of the output shaft  13  using the output shaft position sensor  43 . The controller  45  also measures the speed of the lay shaft  11  using the lay shaft position sensor  42 . The controller  45  compares the two speeds and its knowledge of the number and position of the teeth on the two gears  70  and  80  which are to be engaged. If the speed and position of the lay shaft  11  is not correct, the controller commands the lay shaft motor  40  to bring the lay shaft to the correct speed and phasing so that the gears  70  and  80  can be engaged without grinding. 
     When the controller  45  determines that the two gears  70  and  80  are in proper alignment a command is issued to the actuator  60  to move the gear pair  70 ,  72  to the left resulting in gear  70  engaging with gear  80 . This completes the preparatory steps necessary before the transmission can be shifted to the next higher gear ratio. 
     The actual change from first gear to second gear is accomplished by disengaging clutch  91  at the same time as clutch  90  is engaged. During this process power is removed from lay shaft  12  and applied to lay shaft  11 . At the completion of the shift clutch  91  is disengaged. 
     The post shift process is to disengage gear  71  from gear  80 . When the controller determines that the clutch  91  is fully disengaged it will issue a command to the actuator  61  to move the gear pair  71 ,  73  to the center position. This allows the lay shaft  12  to spin freely. To avoid drag in the clutch  91  the controller will command the clutch  91  to engage. This has completed the shift from first gear to second gear. 
     The next shift up to third gear proceeds similarly and results in gear  73  being engaged with gear  81 . In each step the controller manages the preparatory process where the next set of gears are moved into position. The controller first synchronizes the freely spinning lay shaft using the position sensors and the motors to obtain correct speed and phasing of the gear teeth. 
     The actual shift is accomplished by releasing one clutch at the same time as engaging the second clutch. After the shift is complete then the controller disengages the now unused gear and engages the idling lay shaft&#39;s clutch. The process of shifting up to the next gear or down shifting are essentially the same. 
     Since one or both lay shafts are turning at all times that the engine is running the servo motors can do double duty and act as generators when they are not needed for shifting. 
     The speed and position sensors  42 ,  43 ,  44  are shown as magnetic resolver devices. This is only one possible choice. Another choice would be optical encoders. Alternatively magnetic pickups that sensed the teeth of the gears could be used. All of these are well known devices. 
     Alternatively the speed and position sensors  42 ,  44  can integral to the servo motors  40 ,  41 . This is accomplished by measuring the back EMF of the motors windings. This indicates the relative position of the rotor to the stator. This technique is well known in the industry. 
     The servo motors  40 ,  41  are shown as separate units attached to their respective lay shafts  11 ,  12 . Alternatively they can be integrated into other elements of the transmission. For example, they could act directly of the gears by using the gear as the rotor. Another example it that the servo motors could be integrated with the clutch. 
     Detailed Description 
     FIG.  2   
       FIG. 2  illustrates the step by step process of shifting the transmission from one gear ratio to the next. The first block  100  determines if a shift will occur in the near future. This is likely to be less than one second before the actual shift. If the decision is made to begin the anticipatory moves, but the conditions change, the shift process can be aborted. The decision to begin the anticipatory shifting process can be based on a number of factors; 
     1. Is the speed changing and the engine is nearing a RPM limit? 
     2. Is the speed constant and the engine needs to run at a more efficient RPM? 
     3. Has the engine&#39;s controller commanded a gear ratio change? 
     4. Has the driver commanded a gear change? 
     The information that the decision block  100  may need to perform its task can come from a number of sources. It may read the speed of the output shaft from the output shaft position sensor  43 . It may get the engine speed and torque from the engine controller. The engine controller is not part of the present invention and is not shown. The decision block  100  may make the decision when to anticipate a gear shift or it may simply respond to commands from the engine controller or even from some other device controlled by the driver. 
     The next step  101  is to release the idling lay shaft clutch. During constant speed driving the transmission may not anticipate a shift. In this case the lay shaft not carrying power is spinning in an idle state. If, for example, we assume that we are shifting from first gear to second gear then the idling shaft is lay shaft  11 . Its clutch  90  is engaged to reduce wear but it is not transferring power. Because the clutch  90  is engaged the lay shaft  11  is spinning, driven by the engine. It is not carrying power because its gears  70 ,  72 ,  74 ,  76  are not engaged. The first step in the shift process is to allow the idling lay shaft  11  to spin freely and not to be coupled to the engine. 
     After the idling lay shaft  11  is released to spin freely, the next step  102 , is for the controller to measure the speed of the idling shaft  11  and the speed of output shaft  13 . The controller will read this information from the two relevant speed and position sensors  42 ,  43 . The controller will calculate any error in speed and position of the lay shaft  11  taking into account the number of and position of the teeth of two gears  70 ,  80  that will be engaged. 
     At block  103  the controller will use the speed and position error to drive the servo motor  40  to bring the lay shaft  11  to the proper speed and position so that the two gears  70 ,  80  are in alignment and can be engaged without grinding. This will be an iterative process where the speed and position will be monitored and servo motor  40  driven to reduce the errors. 
     In this step  104 , when the error is reduced sufficiently the first and third shifter  60  will be commanded to move gear  70  into engagement with gear  80 . The shifter has three positions; left, center, and right. The center position has the gear pair  70 ,  72  is the disengaged position. Moving left or right engages one gear of the gear pair. 
     Now the load is ready to me moved from the currently loaded lay shaft  12  to the new lay shaft  11 , step  105 . Now the state of the two clutches  90 ,  91  will be reversed. The currently loaded clutch  91  will be release while the other clutch  90  will be engaged. This transfer must be carefully orchestrated. The torque to the output shaft  13  should be smoothly changed from the previous value to the new value. The engine speed should likewise be smoothly changed as well. When clutch  91  is fully disengaged the power transfer is complete. 
     The next step  106  is to complete the post shift process. This entails disengaging the previous running gear set  71 ,  80  so that the lay shaft  12  can idle. The controller will issue a command to shifter  61  to move gear pair  71 ,  73  to the center position. The lay shaft  12  can now spin freely. 
     The final step  107  is to engage the clutch  91 . This causes the lay shaft  12  to be locked to the engine through gears  20 ,  22 . This results in the lowest wear for the transmission. The clutch is not moving with respect to the shaft so the clutch plates will not wear. No power is transmitted because no gear is engaged. This is the normal running and most efficient condition. 
     Block  108  indicates that the shift from one gear ratio to the next gear ratio has been completed. The transmission is now running in the lowest wear state and in the lowest drag state. In this state the running efficiency will be the highest.