Patent Publication Number: US-4727764-A

Title: Automotive transmission system

Description:
The invention concerns a multiple speed transmission, specifically for motor vehicles which transmission is broadly a split-speed type transmission with a main power transfer path and at least one auxiliary power transfer path. In transmissions of that type, the transmission of force occurs through form-fitting shifting elements. Absent are frictional shifting elements which are used in other transmissions and cause power losses in the disengaged condition. 
     To establish synchronism for shifting into another gear, other transmissions of this type feature frictional synchronization devices. With normally two such synchronizing devices needed on each sliding sleeve, these devices require a considerable axial space. Besides, the frictional synchronizing devices have an adverse effect on the efficiency of the transmission because the friction faces rotate constantly in oil. 
     The invention provides a multiple speed transmission of the split-speed type which is designed with a minimal length and without frictional synchronizing devices. In these split-speed transmissions shifting between gears is accomplished at a high shifting speed to reduce or minimize the interruption of the force transfer. Further, the transmission should be designed to be equipped with either a manual, semi automatic or fully automatic actuating device. 
     This problem is inventionally solved in that for creating synchronism, as another gear is shifted, an accelerating device and a retarding device are arranged on the auxiliary shaft (and/or on at least one of the auxiliary shafts). Additionally, an electrical control is provided which is capable of determining whether synchronism has been established on the sliding sleeve concerned as gears are shifted, and which controls the feeding of servoagent to the respective actuating cylinder based on the determined synchronism. In other words: A synchronizing device is provided which is common to all gears (including the above accelerating and the retarding device), and which upon disengagement of the previously engaged gear establishes synchronism on the sliding sleeve to be engaged next, by acceleration or retardation. The central synchronizing device is preferably actuated by a control signal emitted by the electrical control. 
     The inventional synchronizing device and the automatic engagement of each next gear (with the aid of the above electrical control) governed by its actuation makes it possible to achieve a high shifting speed, although no frictional synchronizing devices are provided on the sliding sleeves. Their elimination reduces the overall length of the transmission; or a greater number of gear groups can be provided at unchanged overall length, and the number of gears increased thereby. 
     Additional overall length can be saved by providing two auxiliary shafts on both sides of the central main shaft. This feature is previously known as such. The two auxiliary shafts being coplanar with the main shaft, the central main shaft need not transmit appreciable bearing forces to the two auxiliary shafts, due to power branching. Additionally, the torque distribution to two auxiliary shafts permits a relatively narrow design of the gear wheels, resulting in the above additional savings of overall transmission length. 
     Further embodiments of the invention include the following: a brake-actuated planetary gear sets in the accelerating device, an input pilot transmission component with a double shift clutch, which is also a starting clutch which may have a dual disk arrangement; and, a shift lever for a manual transmission which is operable in perpendicular directions for shifting the principal speeds or split speeds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows the longitudinal section of the transmission signified 1--1 in FIG. 3. 
     FIG. 2 shows the transmission in a partial longitudinal section of the shift elements, signified 2--2 in FIG. 3. 
     FIG. 3 illustrates the transmission as viewed from the output end, with a section through the selector fork along with the gear plan. 
     FIG. 4 shows the control diagram of the transmission featuring manual operation and electronic synchronization. 
     FIGS. 5 and 6 show the control diagrams of the semiautomatic and/or fully automatic transmission actuation. 
    
    
     In the figures, 1 indicates the crankshaft of the engine, 2 the flywheel, and 3 the starting and shifting clutch designed as a double clutch flanged to the flywheel. Moreover, the main multiple speed transmission is marked 11 while a pilot transmission component fashioned as a planetary gear is marked 27. The latter serves to split the gear sets of the main multiple speed transmission 11. The double clutch 3 features three clutch rings 3 1 , 3 2 , and 3 3  of which only the center ring is axially movable. It connects through extensions 3 4  with a dual disk spring 4 bearing on bolts 3 5  so that it causes either the clutch disk 6 or, in opposite direction, the clutch disk 7 to bear. Two pneumatically operable annular pistons 10 1  and 10 2  serve the clutch operation in starting and shifting the planetary transmission 27. These pistons are arranged in a two-part annular cylinder housing 5 1 , 5 2  (connected with the transmission housing 30). Each of the annular pistons 10 1 , 10 2  bears in the pressure space on prestressed springs 9. Located between the annular pistons is the thrust bearing 8, whose outer race is connected with the disk spring 4. To relieve the thrust bearing in coupled condition, the disk spring 4 is axially entrained by the outer race under play. Also provided for that purpose are the spacer rings 5 3 , 5 4  serving to seat the annular pistons in the annular cylinder housing. Compressed air is fed to the actuation spaces in the annular cylinder housing through the lines 42 4  and 42 5 . In the present illustration, the compressed air line 42 4  is pressurized; overcoming the tension of thesprings behind the annular piston 10 2  and moving it back to its stop on the ring 5 4 , the annular piston 10 1  has moved the disk spring in a position where the clutch disk 6, due to the torque introduced from the engine, powers the drive gear 16 of the main multiple speed transmission 11 via the drive shaft 13. If compressed air is supplied through the line 42 5  and the clutch 3 encompasses the clutch disk 7, the planetary transmission 27 is driven through the hollow shaft 14. The latter comprises a drive bell 27 1 , dual planetary gears 27 2 , 27 3  and a land (planetary support) 28 connecting with the shaft 13. 
     The main multiple speed transmission 11 comprises a main shaft 24 on which seven shift gears 17 through 23 are rotatably mounted. On its end supporting the output flange 24a, the main shaft is mounted in the transmission housing 30 and, on the clutch side, in the drive gear 16. The drive gear 16 drives the two auxiliary shafts 24 1  and 24 2  through gears 16 1  and 16 2 . Mounted rigidly on the two auxiliary shafts, the gears 17 1  through 23 1  and/or 17 2  through 23 2   form the countergears for the shift gears 17 through 23. Located between the shift gears are the sliding sleeves 24 3  through 24 6  which can be moved axially by means of selector forks 25 1  through 25 4 . The selector forks interlock axially with the double pistons 39 6  through 39 9  mounted in the servocylinder housing 39 (FIG. 2). The interior of the cylinder housing 39 is subdivided into four actuating double cylinders with eight pressure spaces 41 1  through 41 8 , through partitioning walls 39 1  through 39 5 . The feed lines to the pressure spaces are marked 41 11  through 41 81 . To avoid misshifting, each selector fork 25 1  through 25 4  connects with one of four rods 40 which in customary fashion permit only the movement of one selector fork, by interlocking. 
     If the gears of the multiple speed transmission component are helical gears, the drive gears 16, 16 1  and 16 2  are designed having a helix angle opposite to that of the shift gears. To obtain a maximally power branching on both auxiliary shafts and compensate for manufacturing tolerances, both the drive gears 16 2  of the one auxiliary shaft and the auxiliary shaft 24 2  itself are in this case mounted in axially movable fashion and stressed by springs 16 3  and 26 against the respective helix angle of the gears. 
     For synchronization when shifting up, the auxiliary shaft 24 1  features on its clutch-side end a retarding device in the form of a disk brake 36 which is pneumatically operated. Arranged on the opposite end is an accelerating device in the form of a planetary gear set 33 whose sun gear 33 1  is driven via the gear 31 arranged on the main transmission shaft 24 and by the gear 32. When shifting down, the central gear 24 8  of the planetary gear set 33 is accelerated to a higher speed of rotation, for acceleration of the auxiliary shafts, by braking the land (planetary support 33 2 ) of the planetary gears 34 by the pneumatically operated brake 35. Coordinated with the input end of the transmission is a rotational speed sensor 37 which is acted upon by the gear 21 1 . Another rotary speed sensor 38 is acted upon by the outer teeth of the sun gear 33 1  which is driven by the output end. Both sensors 37 and 38 transmit their rotary speed information through electrical lines 37 1  and 38 1  to an electrical control (for instance 61, FIG. 4), which will be described farther down and determines the synchronization for shifting. In shifting down, the brake 35 is then operated by compressed air, and the brake 36 in shifting up. 
     The transmission of the embodiment features the following gear ratio: 
     
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1.       Gear   11.15     4+          3.05                                
1+              9.29      5.     Gear 2.53                                
2.       Gear   7.72      5+          2.1                                 
2+              6.41      6.     Gear 1.75                                
3.       Gear   5.32      6+          1.45                                
3+              4.42      7.     Gear 1.2                                 
4.       Gear   3.67      7+          1.0                                 
______________________________________                                    
 
    
     The transmission is thus geometrically geared, the jump of the split gear being 1.2. The reverse gears R and R+ can have the same ratios as the 1. and 1+ gear. 
     Listed hereafter are the force-transmitting gears in the various speeds: 
     Gear 1/1+ 16, 16 1 , 16 2 , 22 1 , 22 2 , 22 
     Gear 2/2+ 16, 16 1 , 16 2 , 21 1 , 21 2 , 21 
     Gear 3/3+ 16, 16 1 , 16 2 , 20 1 , 20 2 , 20 
     Gear 4/4+ 16, 16 1 , 16 2 , 19 1 , 19 2 , 19 
     Gear 5/5+ 16, 16 1 , 16 2 , 18 1 , 18 2 , 18 
     Gear 6/6+ 16, 16 1 , 16 2 , 17 1 , 17 2 , 17 
     Gear 7/7+ direct from shaft 13 to shaft 24 
     In gears 1 through 7 and R, the planetary gear set 27 is engaged (flow of force through the clutch disk 7). In gears 1+ through 7+ and R+, the planetary gear set 27 is circumvented (flow of force through the clutch disk 6). In reverse gears R and R+, the gears 16, 16 1 , 16 2 , 22 1 , 22 2 , 23 1 , 23 2  and 23 in the main multiple speed transmission 11 share in the transmission of force. 
     The inventional transmission may be actuated either manually or semiautomatically or fully automatically. 
     In the manual transmission actuation according to the diagram in FIG. 4, a clutch pedal 57 is used for starting and shifting along with a manual operating device 43, 43 1 . The manually shifted transmission involves a greater expense than the semiautomatic and fully automatic solutions. However, its use offers presently the advantage that it continues to permit operation in the event of a defective or completely failing electronic system, and that the split group can be shifted without operating the clutch pedal. 
     In the semiautomatic actuation of the transmission according to the diagram in FIG. 5, no clutch pedal is needed for starting and shifting. In starting, the engagement operation of the clutch 3 is controlled in response to the engine speed and the accelerator position. The gears are shifted manually by means of electrical switches. 
     With the fully automatic transmission actuation according to the diagram in FIG. 6, starting and shifting occur as well without a clutch pedal. The electrical control (microprocessor) causes not only the synchronization but initiates also the shifting of the gears with the aid of speed sensors arranged in the transmission input and output. 
     1. Manual Transmission Actuation 
     In the diagram relative to FIG. 4, the compressed air tank 50 connects through the line 42 3 , branch lines 41 21  through 41 81 , and through electrically actuated 3/2-way valves 51 2  through 51 8  with respective pressure spaces 41 2  through 41 8  of the selector fork operating pistons. Only the 3/2-way valves 51 2  and 51 8  and the pressure spaces 41 2  and 41 8  of the operating pistons for speeds 7 and 1 are indicated in FIG. 4, while these elements are only symbolized by the respective numeral for speeds 2 through 6. (For the reverse gear they have been omitted). The valves 51 2  and 51 8  are presented in their inoperative position (solenoid not excited). Each of these valves connects in this position its pressure space 41 2 , 41 8  with the vent, so that the respective gears are disengaged. When exciting one of the solenoids (for instance 51 8 ), the respective gear is engaged. The valves 51 1  through 51 8  are preferably arranged directly on the cylinder housing 39 (FIG. 2). 
     Also, the tank 50 connects through the line 50 1  and the electrically switched 3/2-way valve 52 with the pressure space 35 1  of the brake 35 of the accelerating device 33. Another line 50 2  runs from the tank viat the 3/2-way valve 53 to the pressure space 36 1  of the disk brake 36 retarding the auxiliary shaft 24 1 . 
     For operating the double shift clutch 3, the following is provided: A line 50 3 , 56 1  with pressure control valve 54 runs to the reversing valve 55, which can be mechanically actuated by twisting the shift rod 43 (double arrow b). Depending on the position of the valve 55, compressed air proceeds from the tank through the lines 42 4  and/or 42 5  to the respective operating annular space of the double acting pneumatic cylinders 5 1 , 5 2  for acting upon the respective clutch disk 6 or 7. In starting, the compressed air pressure can be regulated with the aid of the clutch pedal 57 and the pressure control valve 54 (control line 42 8 ). As long as the clutch pedal is depressed, compressed air proceeds uncontrolled to the clutch 3. The 3/2-way valves 51 connect though electrical lines 58 1  through 58 7 , the 3/2-way valves 52 and 53 through electrical lines 59 and 60 with the electrical control (microprocessor 61). The microprocessor receives input signals through the line 38 1  from the sensor 38, and through the line 37 1   from the sensor 37. Both continually pick up the rotational speed of the output and/or input train. In addition, information concerning the desired speed (likewise also concerning the shift direction) are conveyed to the microprocessor. This takes place through the lines 62 1  through 62 7  for the forward speeds 7 through 1, and through the line 62 8  for the reverse gear R. By axial shifting (a) of the shift rod (43), which may assume nine positions, each of these lines can be connected alternately with the slip contact 43 6 . Shown in the drawing is only the gearshift rod 43 in idling position (between gears 1 and R). Moreover, the microprocessor receives the information--through the electrical switch 63 operated by the clutch pedal 57 and the line 63 1  --whether the connection between engine and transmission has been interrupted or established. 
     The shift operation in the multiple speed transmission 11 is initiated by the driver through operation of the clutch pedal 57 and shifting the gearshift rod 43 in the position of the desired speed. As the clutch pedal is depressed, the unregulated compressed air flow to the momentarily supplied pressure space of the pneumatic cylinder 5 1 , 5 2  is interrupted. Depending on the position of the 4/3-way valve 55, the pressurized annular cylinder space of the annular cylinder 5 1 , 5 2  is depressurized through the vent 56 2  of the pressure control valve 54. This interrupts the flow of force between engine and transmission, irrespective of whether or not a regular speed or a split speed is engaged. Controlling the electronic synchronization, the microprocessor 61 is informed of the flow of force interruption, through the switch 63 which is closed when the clutch pedal is depressed. As the driver now moves the gearshift rod 43 in axial direction, with the aid of the handle 43 1 , he informs the microprocessor 61 through one of the lines 62 1  through 62 8  which of the gears is to be engaged, with the microprocessor first deactivating the previously excited solenoid (one of 51 2  through 51 8 ). This causes the venting of the respective pressure space (one of 41 2  through 41 8 ) of the selector fork operating piston of the previously engaged gear. Thus, the sliding sleeve disengages from the entraining teeth of the selected gear, through the return compression spring acting on the operating piston and the selector fork. 
     During the axial movement (a) of the gearshift rod 43, the driver is informed of the momentary position, through a digital display 49 controlled by the processor 61, and thus the speed selected by him as the respective numeral appears on the display. A warning signal (for instance an indicator light 49a) informs the driver during the shift operation that the synchronization of the selected speed is not completed yet. 
     In order to avoid unnecessarily long synchronization times in shifting down and aid the driver in selecting the lower speed, the microprocessor can cause the blinking, on another digital display, of the number of the lowest possible gear in which the input end of the transmission will not overspeed or the vehicle must be slowed down using the operating brake. The microprocessor can determine this value from the engaged speed, the continually sensed speed of rotation of the output train and the fixed gear ratios. 
     Once the driver has moved the gearshift rod 43 is the intended position (and, as the case may be, the numerals of the two illuminated displays are in agreement), the command input to the microprocessor 61 is completed and the synchronization can take place. The microprocessor monitors the rotational speeds of the input and the output trains and, depending on shifting direction (up or down), actuates the solenoid 52 or 53. This causes either a connection of the pressure space 35 1  of the brake 35 or of the pressure space 36 1  of the brake 36 with the compressed air tank and the acceleration or retardation of the auxiliary shaft 24 1 , and thus of the gears to be shifted. Once synchronism has been established between the respective gear on the output shaft and the sliding sleeve, the microprocessor 61 deactivates the solenoid valve 52 or 53 by shutting off the current in the lines 59 and/or 60, i.e., the pressure chamber 35 1  and/or 36 1  is vented. The microprocessor actuates at the same time the 3/2-way valve 51 1  through 51 8  corresponding to the selected speed, by exciting the pertaining solenoid. This opens the compressed air supply to the pressure space 41 1  through 41 8  of the respective operating piston of the sliding sleeve, and the sleeve will engage. All of this occurs within the range of tenths of a second. The completion of the synchronizing process is indicated to the driver by extinction of the above warning signal 49a. He can now gradually release the clutch pedal, thereby building up controlled pressure in the respective operating annular space of the annular cylinder 5 1 , 5 2 , through the valve 54, thereby restoring the flow of force between the transmission and the engine. During the normal travel, the digital display 49 informs the driver of the gear which is engaged. 
     2. Semiautomatic Transmission Actuation 
     FIG. 5 shows a simplified shifting diagram. The moment of shifting and the speed are determined by the driver by operating the corresponding switches on the panel 70. To convey the shift intention and the intended speed, each switch connects through an electrical line 70 1  through 70 17  with the microprocessor 71. Information on the speeds of rotation in the input and output trains are transmitted to the microprocessor by the sensors 37 and 38 through lines 37 1  and 38 1 . The synchronization is controlled again by the microprocessor. It contacts for that purpose through electrical lines 72 1  through 72 8  with the solenoid valves 73 1  through 73 8  for regulating the pressure admission to the operating pistons of the sliding sleeves, and through lines 59 and 60 with the solenoid valves 52 and 53 which determine the shift condition of the brakes 35 and 36 for retardation and/or acceleration of the transmission shafts 24 1  and 24 2 . By actuating the reversing valve 74 via the line 74 1  and the 4/3-way valve 76 through one of the lines 76 1  and 76 2 , the microprocessor 71 establishes the flow of force connection or interruption between the engine and the transmission, and thus the activation of the planetary gear set 27 for the split gear ratio. The pressure condition in the operating spaces of the double-acting pneumatic clyinder 5 1 , 5.sub. 2 is determined through the solenoid valve 76, which can be switched into three positions. In the center position of the valve, both chambers are unpressurized and, thus, both clutch disks 6 and 7 disengaged, interrupting the flow of force between the engine and the transmission. In the other two valve positions, one chamber is always pressurized and, thus, either the clutch disk 6 or 7 engaged. To accomplish a controlled engaging when starting, the reversing valve 74 establishes the pressure connection from the compressed air tank 75 to the pressure spaces of the pneumatic cylinder 5 1 , 5 2  through a pressure control valve 77. Acting on the pressure control valve 77 as control variables are the engine speed (symbolically illustrated by the &#34;control&#34; 78) and the position of the accelerator 79. 
     Described hereafter are three different shift operations: 
     (2.1) If the flow of force must be interrupted between the engine and the transmission, the driver presses the key &#34;0&#34; on the panel 70. In response, the microprocessor 71 moves the valve 76 to its center position and vents the two chambers of the pneumatic cylinder 5 1 , 5 2  through the compressed air lines 42 4  and 42 5 . The microprocessor selects this position of the valve 76 also without command unit by the driver as soon as the sensor 37 reports a specific minimum speed of rotation, so as to prevent a stalling of the engine. Next, the microprocessor 71, by changeover of the valve 74, automatically connects the input line 74 2  of the 4/3-way valve with the output line 7 1  of the pressure control valve 77 so that a controlled pressure can be built up in the pneumatic cylinder 5 1 , 5 2  for the subsequent starting. 
     (2.2) If the driver instructs to changeover from the regular to the split gear or vise versa, the microprocessor actuates the 4/3-way valve 76 from the one limit position through the center position to the other limit position. This causes the pressure admission of the double-acting pneumatic cylinder to change from the one piston side to the other, and the planetary gear 27 is engaged or disengaged for producing the split ratio. 
     (2.3) If the driver selects another speed, the microprocessor 71 examines in down shifting, through the sensor 38, whether the intended gear can be shifted without overspeeding the input end. If this is not the case, the digital display 49 starts blinking the number of the lowest possible gear. The driver must then shift this gear anew, and the microprocessor moves the 4/3-way valve through the line 76 1  in center position, interrupts the flow of force between the engine and the transmission, and then switches, of the solenoid valves 73 1  through 73 8 , the valve coordinated with the selected gear through its line 72 1  through 72 8  in the position where the pressure space 41 1  through 41 8  of the selector fork operating piston coordinated with the engaged gear will be vented. This causes the sliding sleeve to disengage the entraining teeth of the selected gear wheel, due to the return compression spring force acting on the operating piston. 
     The solenoid valves 73 1  through 73 8  and the pressure spaces 41 1  through 41 8  of the selector fork operating pistons are shown in FIG. 5 for the 7th forward and the reverse gear, and are symbolized for the other speeds by the respective number. Each of the valves 73 1  through 73 8  can be switched in two positions. In the inoperative position presented in FIG. 5, which is assumed when the respective speed is not engaged, the valve vents the coordinated pressure space 41 1  through 41 8 . In the operating position, i.e., with the solenoid excited and the gear engaged, it connects the coordinated pressure space 41 1  or 41 2  through 41 8  through the line 80 with the compressed air tank 75. 
     Upon disengagement of the sliding sleeve of the previously engaged gear, the microprocessor determines the rotational speeds of the input and output trains by way of sensors 37 and 38 and, depending on shift direction, actuates the solenoid valve 52 or 53. In response, either the pressure space 35 1  of the brake 35 or the pressure space 36 1  of the brake 36 is being connected with the compressed air tank 75 and the auxiliary shafts 24 1  and 24 2  are accelerated or retarded. Once synchronism has been accomplished between the gear on the main shaft 24 to be shifted and the corresponding sliding sleeve, the microprocessor deenergizes again the solenoid valve 52 or 53, causing the pressure space 35 1  and/or 36 1  to be vented. At the same time, the pressure space 41 1  through 41 8  coordinated with the newly selected gear is pressurized through the microprocessor by actuation of the respective solenoid 73 1  through 73 8 , and the sliding sleeve is engaged through the operating piston. Next, the microprocessor switches the 4/3-way valve 76 from the center position to the selected limit position so that, by pressure admission to the respective operating space of the annular cylinder 5 1 , 5 2 , the clutch disk 6 or 7 restores the flow of force between the engine and transmission. The shift operation is completed and the digital display, blinking up to that point, displays now permanently the number of the newly engaged gear. 
     (2.4) If the driver selects the reverse gear by pressing the key R or R+, the shift operation proceeds as described under (3), but with the exception that the microprocessor, after switching the 4/3-way valve in the center position, will actuate the other valves only as the sensor reports an output speed of zero. 
     (2.5) In starting, i.e., when raising the engine speed for forward or reverse travel, the microprocessor switches upon driver input of the selected starting gear the 4/3-way valve 76 from its center position in the respective limit position. Up to a specific speed of rotation reported by the sensors 38, the driver leaves the reversing valve 74 in its position where the connected pressure space of the annular cylinder 5 1 , 5 2  makes connection with the compressed air tank 75 through the pressure control valve 77. This causes a controlled buildup of the clutch pressure based on the position of the accelerator and the engine speed, through the &#34;regulator&#34; 78. From a predetermined speed of rotation onward, the microprocessor switches the reversing valve in its home position, connecting the pressure space of the annular cylinder 5 1 , 5 2  directly with the compressed air tank 75. If the driver misshifts--for instance when traveling in direct gear and intending to engage gear 6+ and/or 6 but shifting into third gear--the display marked 49 in FIGS. 4 and 5, normally displaying the gear engaged, starts blinking the required gear as determined by the computer from the transmission output speed. This display may be corrected by another accelerator position information conveyed to the computer. 
     3. Fully Automatic Transmission Actuation 
     The diagram in FIG. 6 corresponds closely with the diagram of the semiautomatic transmission presented in FIG. 5. Identical elements in FIGS. 5 and 6 are therefore identified using identical reference numbers. 
     In contrast to the semiautomatic solution, the change of all forward speeds is initiated by the microprocessor 81. For that purpose, the microprocessor senses the engine load through an engine speed sensor through the line 83 1  ; the position of the accelerator 84 through the contact rail 85 and the line 85 1  ; and the vehicle speed through the sensor 38 of the output train. The processor compares these values with the programmed shifting points and initiates the respective gearshifting. The shift operation i.e., actuating the valves for synchronization, flow of force interruption between engine and transmission, and operation of the various elements, proceeds the same as in the semiautomatic transmission. In variation from it, only the pressure control valve 86 is as well actuated by the microprocessor through the line 86 1 , for controlled pressure buildup in the pressuce chambers of the annular cylinder5 1 , 5 2 , in starting. Variables used for that purpose are the engine speed and the accelerator position. The necessary connecting lines between panel 82 and microprocessor 81 are marked 82 1  through 82 18  in the diagram. Thus, the panel permits the driver to influence the shifting points programmed in the microprocessor. The panel of the fully automatic transmission features a cancel key 89 for changing the shift program. 
     The microprocessor 81 causes the gears to be shifted automatically up to the topmost gear, unless a lower speed has been selected on the panel 82. In normal level traffic, forward 7+ will be preselected causing the transmission to shift through the 1+ through 7+ column. If 7 is preselected, the transmission shifts according to this column. If both 7+ and 7 are preselected, the transmission will shift through all gears. When the vehicle is subjected to heavy loads and the driver is of the opinion that he should travel in the additionally geared speed 1 while thereafter he may change over to the 1+ to 7+ column, he will preselect 1 and 7+. As a result, gears 1, 1+ through 7+ will be shifted; if he feels that up to third gear he shoud drive at a finer graduation, he will select 3 and 7+, causing the transmission to shift 1, 1+, 2, 2+, 3, 3+, through 7+. If the driver wants to prevent the transmission from shifting below a specific gear, he must preselect the respective gear in column 1-7. Example: On a hilly stretch with a uniform climb the driver wants to prevent a continuous shifting between 4 and 3+ (with both columns preselected); this shifting can be prevented by preselecting the 4-key.