Abstract:
A multiplexed electromechanical shift mechanism includes a single linear actuator with multiple independently selectable linkages actuating a clutch and multiple gears for use in motor vehicle transmissions such as a dual clutch transmission. The linear actuator may be a ball screw, a planetary roller screw or hydraulic or pneumatic operator capable of controlling bi-directional linear motion of an output member. A plurality of linear clutches selectively couple the output member to one of a plurality of linkages adapted to transfer the bi-directional motion of the output member. One of the linkages is coupled to and engages an input (main) clutch of the transmission and the remaining linkages are coupled to and bi-directionally translate shift forks and synchronizer clutches which achieve gear selection and engagement.

Description:
FIELD 
     The present disclosure relates to a multiplexed electromechanical mechanism for clutch and gear actuation in a motor vehicle transmission and more particularly to a multiplexed electromechanical mechanism having a single actuator with multiple independently selectable linkages actuating a clutch and multiple gears in a motor vehicle transmission. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     Gear shift assemblies for motor vehicle transmissions take several forms. In a typical manual transmission, a plurality of parallel shift rails are acted upon by an operator manipulated shift lever and include shift forks which engage and translate synchronizers and clutches which engage a desired gear. In automatic transmissions, hydraulically operated clutches and brakes controlled by a plurality of logic and control valves engage, disengage and brake elements of planetary gear assemblies. In a newer transmission type, the dual clutch transmission (DCT), a plurality of synchronizer clutches on two countershafts are translated into and out of engagement by associated actuators and two input clutches alternately drive the countershafts. 
     Such dual clutch transmissions typically provide five, six or seven forward gears or speeds and reverse. In a dual clutch transmission having five forward gears and reverse, at least three actuators, three shift linkages and three double synchronizers will be required. The actuators which will typically be bi-directional, electric or hydraulic devices will generally be the most expensive components of the shift assembly. In a typical six speed dual clutch transmission, at least four actuators, four shift linkages, three double synchronizers and one single synchronizer will be required. Again, the actuator devices will generally be the most expensive components of the shift assembly. 
     Because of their excellent fuel economy and sporty performance, including the ability to complete rapid shifts which parallels that of a manual transmission, dual clutch transmissions are gaining recognition and acceptance in the marketplace. Given this trend, activity directed to improving all aspects of dual clutch transmission design and operation is ongoing and the present invention is the result of such activity. 
     SUMMARY 
     The present invention provides a multiplexed electromechanical mechanism having a single linear actuator with multiple independently selectable linkages actuating a clutch and engaging multiple gears for use in motor vehicle transmissions such as a dual clutch transmission. The linear actuator may be a ball screw, a planetary roller screw or hydraulic or pneumatic operator capable of controlling bi-directional linear motion of an output member. A plurality of linear clutches selectively couple the output member to one of a plurality of linkages adapted to transfer the bi-directional motion of the output member. One of the linkages is coupled to and engages an input (main) clutch of the transmission and the remaining linkages are coupled to and bi-directionally translate shift forks and synchronizer clutches which achieve gear selection and engagement. 
     This arrangement exploits the fact that, in a dual clutch transmission, odd gears are typically selected while the even clutch is engaged after which the odd clutch is engaged and a new even gear is selected. Stated somewhat differently, in a dual clutch transmission, it is never necessary (or desirable) to undertake gear changes and engage the input clutch on the same countershaft at the same time. This results from the configuration of a typical dual clutch transmission wherein all odd numbered gears are grouped together on one countershaft and associated with an odd gear input clutch and the even numbered gears and an even gear clutch are similarly disposed on the other countershaft. 
     Thus it is an aspect of the present invention to provide an actuator and linkage assembly for selecting certain gears and engaging one clutch of a motor vehicle transmission. 
     Thus it is a further aspect of the present invention to provide a multiplexed actuator and linkage assembly for selecting certain gears and engaging one clutch of a dual clutch transmission. 
     It is a still further aspect of the present invention to provide a ball screw, a planetary roller screw or hydraulic or pneumatic operator and a linkage assembly for selecting certain gears and engaging one clutch of a motor vehicle transmission. 
     It is a still further aspect of the present invention to provide a ball screw, a planetary roller screw or hydraulic or pneumatic operator and linkage assemblies for selecting certain gears and engaging one clutch of a dual clutch transmission. 
     It is a still further aspect of the present invention to provide a multiplexed actuator having a linear output member and a plurality of linkage assemblies for selecting certain gears and engaging one clutch of a dual clutch transmission. 
     It is a still further aspect of the present invention to provide a multiplexed actuator having a linear output member and linkage assemblies including linear clutches for selecting certain gears and engaging one clutch of a dual clutch transmission. 
     It is a still further aspect of the present invention to provide a multiplexed actuator and a plurality of linkage assemblies to be utilized in pairs for selecting gears and engaging clutches in a dual clutch transmission. 
     Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic, top plan view of an exemplary dual clutch transmission incorporating the present invention; 
         FIG. 2  is an enlarged side elevational view of a linear actuator output member including two linear clutch collars according to the present invention; and 
         FIG. 3A  is an schematic end view of a linear actuator output member and linear clutch collar according to the present invention in a first, disengaged position; 
         FIG. 3B  is an schematic end view of a linear actuator output member and linear clutch collar according to the present invention in a second, engaged position; and 
         FIG. 4  is a diagrammatic view of a planetary roller screw actuator and clutch linkage according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     With reference to  FIG. 1 , a typical dual clutch transmission is illustrated and generally designated by the reference number  10 . The transmission  10  includes a housing  12  having a plurality of openings, bores and flanges that receive, locate and support as well as provide protection to, the various components disposed within the transmission  10 . The transmission  10  includes an input shaft  14  which is coupled to and driven by the output of a gasoline, flex fuel or Diesel engine, hybrid power plant or electric motor (not illustrated). The input shaft  14  is connected to an input structure or drive housing  18  of a dual clutch assembly  20 . 
     The dual clutch assembly  20  includes a first main or input clutch  22  associated with the odd numbered gears of the transmission  10  and having a first clutch output shaft  24  that drives components within the transmission  10  and a second main or input clutch  26  associated with the even numbered gears and reverse of the transmission  10  and having a second clutch output quill, drive tube or member  28  that also drives components within the transmission  10 . A first countershaft  30  which is associated with the first main clutch  22  includes a first plurality of gears  32 ,  34 ,  36  and  38  freely rotatably disposed thereupon. The gears  32 ,  34 ,  36  and  38  may correspond to, for example, all of the odd numbered gears, namely, first, third, fifth and seventh in a seven speed transmission. A second countershaft  40  which is associated with the second main clutch  26  includes a second plurality of gears  42 ,  44 ,  46  and  48  which are freely rotatably disposed thereupon. The gears  42 ,  44 ,  46  and  48  may correspond to, for example, reverse and all of the even numbered gears, namely, second, fourth and sixth. 
     Disposed about the first countershaft  30  and between the gears  32  and  34  is a first synchronizer clutch  52 . The first synchronizer clutch  52  may be bi-directionally translated along the first countershaft  30  to first synchronize and then couple one of the gears  32  or  34  to the first countershaft  30 . A second synchronizer clutch  54  is disposed about the first countershaft  30  between the gears  36  and  38 . The second synchronizer clutch  54  may be bi-directionally translated along the first countershaft  30  to first synchronize and then couple one of the gears  36  or  38  to the first countershaft  30 . 
     Disposed about the second countershaft  40  and between the gears  42  and  44  is a third synchronizer clutch  56 . The third synchronizer clutch  56  may be bi-directionally translated along the second countershaft  40  to first synchronize and then couple one of the gears  42  or  44  to the second countershaft  40 . A fourth synchronizer clutch  58  is disposed about the second countershaft  40  between the gears  46  and  48 . The fourth synchronizer clutch  58  may be bi-directionally translated along the second countershaft  40  to first synchronize and then couple one of the gears  46  or  48  to the second countershaft  40 . 
     The first synchronizer clutch  52  is engaged and translated by a first shift fork and rail assembly  62 ; the second synchronizer clutch  54  is engaged and translated by a second shift fork and rail assembly  64 ; the third synchronizer clutch  56  is engaged and translated by a third shift fork and rail assembly  66  and the fourth synchronizer clutch  58  is engaged and translated by a fourth shift fork and rail assembly  68 . 
     Referring now to  FIGS. 1 ,  2  and  3 A and  3 B, the dual clutch transmission  10  also includes a pair of multiplexed shift actuator assemblies  70 A and  70 B which are essentially identical. The first multiplexed shift actuator assembly  70 A is associated with the first countershaft  30 , the odd numbered gears  32 ,  34 ,  36  and  38 , the first and second synchronizer clutches  52  and  54 , the first and second shift fork and rail assemblies  62  and  64  and the first input clutch  22 . The second multiplexed shift actuator assembly  70 B is associated with the second countershaft  40 , reverse and the even numbered gears  42 ,  44 ,  46  and  48 , the third and fourth synchronizer clutches  56  and  56 , the third and fourth shift fork and rail assemblies  66  and  66  and the second input clutch  26 . Accordingly, only the first multiplexed shift actuator assembly  70 A will be fully described. 
     The first multiplexed shift actuator assembly  70 A includes a bi-directional linear actuator  72 , which will be more fully described below, and may be, for example, a ball screw or planetary roller screw device or a hydraulic or pneumatic piston and cylinder assembly preferably having a linear output position sensor or transducer. The bi-directional linear actuator  72  includes an elongate output shaft or member  74 . The elongate output member  74  defines circumferentially interrupted male threads  76  along its length. The male threads  76  may have any conveniently formed, preferably symmetrical profile such as American Standard or knuckle, for example. The male threads  76  have no lead, that is, they are straight, not helical. As best illustrated in  FIG. 3 , the male threads  76  are circumferentially discontinuous, that is, they extend over three discontinuous circumferential regions of slightly less than 60° which alternate with three circumferential regions  78  of approximately 60° which are not threaded. The ends of the threads  76  adjacent the open (unthreaded) regions  78  are preferably beveled or chamfered to present oblique surfaces to assist thread engagement and avoid thread butt. 
     At axially spaced apart locations along the output member  74  are a plurality of linear clutches including a first shift collar  82 , a second shift collar  84  and a third clutch collar  86 . The first shift collar  82  is connected to and bi-directionally translates the first shift fork and rail assembly  62  through a first coupling  92  which allows relative rotation between the first shift collar  82  and the first shift fork and rail assembly  62 . The second shift collar  84  is connected to and bi-directionally translates the second shift fork and rail assembly  64  through a second coupling  94  which allows relative rotation between the second shift collar  84  and the second shift fork and rail assembly  64 . The third clutch collar  86  is connected to and bi-directionally translates a first clutch linkage assembly  88  which engages and disengages the first input clutch  22  through a third coupling  96  which allows relative rotation between the third clutch collar  86  and the first clutch linkage assembly  88 . 
     Each of the shift and clutch collars  82 ,  84  and  86  includes discontinuous internal (female) threads  102  which are configured in an arrangement complementary to the male threads  76  on the output shaft or member  74 . That is, the female threads  102  are preferably a symmetrical profile such as American Standard or knuckle, for example, with no lead. They must, of course, be the complementary to and engageable with the male threads  76 . They are also arranged in an internal, discontinuous arrangement having three regions of threads  102  of slightly less than 60° equally spaced with three approximately 60° regions  104  without threads. In a like manner, the ends of the threads  102  adjacent the open (unthreaded) regions  104  are preferably beveled or chamfered to present oblique surfaces to assist thread engagement and avoid thread butt. 
     Associated with each of the shift and clutch collars  82 ,  84  and  86  is a two position actuator such as an electric solenoid or hydraulic or pneumatic piston and cylinder assembly. A first shift actuator  112  rotates the first shift collar  82  through approximately 60° through a linkage  114  to fully engage or release the threads  76  and  102  within the first shift collar  82  and axially couple or uncouple it to the output member  74 . A second shift actuator  116  rotates the second shift collar  84  through approximately 60° through a linkage  118  to fully engage or release the threads  76  and  102  within the second shift collar  84  and axially couple or uncouple it to the output member  74 . A third clutch actuator  122  rotates the third clutch collar  86  through approximately 60° through a linkage  124  to fully engage or release the threads  76  and  102  within the third clutch collar  86  and axially couple or uncouple it to the output member  74 . 
     While three alternating threaded and unthreaded regions have been found to provide excellent operation and service life, it is acknowledged that more or fewer threaded regions in the collars  82 ,  84  and  86  and the output member  74  may be utilized with corresponding adjustment of the rotation of the collars  82 ,  84  and  86 . Fewer regions, for example, two alternating threaded and unthreaded regions each extending over approximately 90° would require greater (approximately 90°) rotation of the collars  82 ,  84  and  86  whereas more threaded regions, for example four alternating threaded and unthreaded regions would require lesser (approximately 45°) rotation of the collars  82 ,  84  and  86  whereas six alternating threaded and unthreaded regions would require even less (approximately 30°) rotation of the collars  82 ,  84  and  86 . 
     Finally, the transmission  10  includes an output shaft  128  which directly drives a final drive assembly  130  which may include a prop shaft, a differential, axles and wheels and tires (all not illustrated). 
     Operation is straightforward. To select, for example, fifth gear which for purposes of illustration and explanation will be assumed to be the gear  36  on the first countershaft  30 , the second actuator  116  is energized to rotate the second shift collar  84  from the position illustrated in  FIG. 3A  to the position illustrated in  FIG. 3B . With the female threads  102  engaged by the male threads  76 , the second shift collar  84  is connected to the output member  74  and actuation of the bi-directional linear actuator  72  translates the output member  74 , the second shift collar  84 , the second shift fork and rail assembly  64  and the second synchronizer clutch  54  to the left in  FIG. 1  to first synchronize and then couple the gear  36  to the first countershaft  30 . Then, the second shift actuator  116  is de-energized to uncouple the second shift collar  84  from the output member  74  and the third clutch actuator  122  is energized to rotate the third clutch collar  86 , engage the male threads  76  and the female threads  102  and couple the output member  74  to the first input clutch linkage assembly  88 . Bi-directional motion of the output member  74  may then be utilized to engage and disengage the first input clutch  22 . It will be appreciated that while the foregoing fifth gear selection process is occurring, the transmission  10  may be operating in fourth gear, for example, the gear  46  of the second countershaft  40  which has been selected through a similar series of steps by the second multiplexed shift actuator assembly  70 B and engagement of the second input clutch  26 . 
     Referring now to  FIG. 4 , a preferred bi-directional linear actuator and clutch linkage assembly is illustrated and generally designated by the reference number  150 . The bi-directional linear actuator and clutch linkage assembly  150  includes a planetary roller screw linear actuator  152  preferably including a bi-directional, three phase, brushless direct current (DC) motor  154  which directly drives a planetary roller screw assembly  156 . An electromagnetic brake  158  is coupled to the output of the electric motor  154  and may be energized to inhibit rotation of the motor  154  and a change in the position of the output member  74  of the planetary roller screw linear actuator  152 . A transducer  162  such as a Hall effect sensor may be included in the linear actuator  152  and utilized to provide data to a controller  164 , illustrated in  FIG. 1 , such as a transmission control module (TCM) regarding the present position of the output member  74 . Further details of the planetary roller screw linear actuator  152  may be obtained from U.S. Pat. No. 5,557,154 which is hereby incorporated by reference. 
     The output member  74 , as described above, receives the third clutch collar  86  which is operably connected to one end of a second class lever  166  which forms a portion of the first clutch linkage assembly  88 . The other end of the second class lever  166  is supported in a stationary pivot  168  which may be attached to the housing  12 . A first clutch actuator link  172  connects an intermediate point of the second class lever  166  to the first input clutch  22 . Translation of the output member  74  to the right in  FIG. 4  translates the clutch linkage assembly  88  to the right and compresses the discs of the first input clutch  22 , thereby transmitting torque from the input shaft  14  to the first clutch output shaft  24 . 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.