Abstract:
A clutch mechanism for coupling and decoupling a motor to a rack is disclosed herein. The clutch mechanism having: a clutch lever pivotally mounted to an axis for movement from a first position to a second position; a cam gear having a cam surface, wherein rotational movement of the cam gear causes the cam surface to move the clutch lever from the first position to the second position; and a gear train configured to cause linear movement of the rack in response to rotational movement of the motor, wherein movement of the clutch lever from the first position to the second position disconnects a pair of gears of the gear train.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/769,386 filed Feb. 26, 2013, the entire contents of which are incorporated herein by reference thereto. 
     This application also claims the benefit of U.S. Provisional Patent Application Ser. No. 61/769,388 filed Feb. 26, 2013, the entire contents of which are incorporated herein by reference thereto. 
     Reference is also made to the following U.S. patent application Ser. No. 13/862,074 filed Apr. 12, 2013, which claims priority to the following U.S. Provisional Patent Application Ser. No. 61/625,179 filed Apr. 17, 2012, the entire contents of each of the aforementioned applications are incorporated herein by reference thereto. 
    
    
     TECHNICAL FIELD 
     Exemplary embodiments of the present invention relate to an actuator for a shift by wire system and, more particularly, to a manual override system for an electronically controlled linkage. 
     BACKGROUND 
     Vehicles provide a number of controls allowing the driver of the vehicle to control various functions of the vehicle during operation. One control that is typically provided is a means for shifting the vehicle transmission. Automatic transmissions include a limited number of control selections such as park, reverse, neutral and drive as well as variants thereof. 
     In some automatic transmissions, a shift lever or mechanism is generally provided, wherein the driver operates the vehicle by moving the shift lever in a pattern in order to shift gears of the transmission. In some contemplated applications, the shifting of the transmission is achieved through an electronic system or shift by wire system wherein signals are provided to an electric motor coupled to the transmission via a button or actuator located within the vehicle compartment. 
     In an electronic system, an operator may not be able to shift the transmission if the vehicle loses power or there is a failure of one of the sensors and/or the motor of the electrical system. 
     Accordingly, it is desirable to provide an actuator for an electronic shift system wherein manual operation thereof is provided. 
     SUMMARY OF THE INVENTION 
     According to one exemplary embodiment of the present invention, an actuator for a shift by wire system is provided. The actuator having: a motor; a rack; a gear train configured to cause linear movement of the rack in response to rotational movement of the motor; a clutch mechanism for coupling and decoupling the rack to the motor; and a manual override for operating the clutch mechanism. 
     In another exemplary embodiment, a shift by wire system for a vehicle transmission is provided. The system having: an input device; a motor; a microcontroller operatively coupled to the motor and configured to receive signals from the input device to operate the motor; a sensor operatively coupled to the microcontroller and configured to receive signals from sensor, wherein the signals from the sensor are indicative of a position of the motor; a rack; a gear train configured to cause linear movement of the rack in response to rotational movement of the motor; a clutch mechanism for coupling and decoupling the rack to the motor; and a manual override for operating the clutch mechanism. 
     In yet another exemplary embodiment, a method for manually overriding a shift by wire system is provided. The method including the steps of: decoupling a rack of the shift by wire system from a motor by rotating a cam gear from a first position in a first direction to an intermediate position wherein a clutch spool is moved from a first position, wherein the clutch spool couples the motor to the rack to a second position, wherein the clutch spool decouples the rack from the motor; and further rotating the cam gear in the first direction from the intermediate position to a second position wherein a lever moves the rack after it has been decoupled from the motor, wherein the cam gear is spring biased into the first position and the clutch spool is spring biased into the first position. 
     In yet another embodiment, a clutch mechanism for coupling and decoupling a motor to a rack is provided. The clutch mechanism having: a clutch lever pivotally mounted to an axis for movement from a first position to a second position; a cam gear having a cam surface, wherein rotational movement of the cam gear causes the cam surface to move the clutch lever from the first position to the second position; and a gear train configured to cause linear movement of the rack in response to rotational movement of the motor, wherein movement of the clutch lever from the first position to the second position disconnects a pair of gears of the gear train. 
     In yet another embodiment, a method of decoupling and coupling a motor to a rack is provided. The method including the steps of: decoupling the rack from the motor by rotating a cam gear from a first position in a first direction to an intermediate position wherein a clutch spool is moved from a first position, wherein the clutch spool couples the motor to the rack to a second position, wherein the clutch spool decouples the rack from the motor; and further rotating the cam gear in the first direction from the intermediate position to a second position wherein a lever moves the rack after it has been decoupled from the motor, wherein the cam gear is spring biased into the first position and the clutch spool is spring biased into the first position and wherein the second direction is perpendicular to the first direction. 
     The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a view of an actuator in accordance with one non-limiting exemplary embodiment of the present invention; 
         FIG. 2  is a perspective view of the actuator illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view of the actuator illustrated in  FIG. 1  with portions of a clutch mechanism removed for illustration purposes; 
         FIGS. 4 and 5  are other perspective views of the actuator; 
         FIGS. 6-9  are views illustrating movement of the clutch mechanism in accordance with one exemplary embodiment; and 
         FIGS. 10 and 11  are cross-sectional views of components of the clutch mechanism illustrating movement of the clutch mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the FIGS., an actuator  10  for use in a shift by wire system is illustrated. In one non-limiting exemplary embodiment, the actuator is configured to be mounted under a console in the passenger compartment of the vehicle or directly on a transmission of the vehicle or in any other suitable location. For use in vehicular applications, the actuator  10  needs to move a vehicle transmission  12  (illustrated schematically) into a specific gear. In one exemplary embodiment, the actuator is directly coupled to the transmission or is coupled thereto by a cable attachment  14 . As mentioned above, there is a need to provide a manual override in order to move the transmission from one position to another in the event of a power failure or a failure of a component of the shift by wire system. For example, there may be a need to move the transmission out of a park position into a neutral or other position in order to allow for towing of the vehicle. 
     In the illustrated embodiment, a rack  16  is coupled to the transmission either directly or by the cable  14  and is driven by a gear train  18  powered by a single motor  20 . Input signals from a driver select device  22  are processed by a controller or microcontroller  24  operatively coupled to the motor  20  using feedback signals from the actuator to identify its position. In one embodiment, the driver select device  22  (illustrated schematically) may be any one of a push button, lever, sensor, switch or any other equivalent device capable of providing signals to the microcontroller in order to operate motor  20  and thus operate the transmission in a shift by wire process, wherein there is not actual physical link directly between device  22  and transmission  12 . 
     In one embodiment, an encoder  26  and sensor  28  are also operatively coupled to the controller or microcontroller  24  so that feedback signals are provided to the microcontroller. In one non-limiting exemplary embodiment, controller or microcontroller  24  comprises a microprocessor, microcontroller or other equivalent processing device capable of executing commands of computer readable data or program for executing a control algorithm that controls the operation of the actuator and/or shift by wire system. In order to perform the prescribed functions and desired processing, as well as the computations therefore (e.g., the execution of fourier analysis algorithm(s), the control processes prescribed herein, and the like), the controller may include, but not be limited to, a processor(s), computer(s), memory, storage, register(s), timing, interrupt(s), communication interfaces, and input/output signal interfaces, as well as combinations comprising at least one of the foregoing. For example, the controller may include input signal filtering to enable accurate sampling and conversion or acquisitions of such signals from communications interfaces. 
     In accordance with an exemplary embodiment of the present invention, a manual override is provided through the use of a clutch mechanism  30  configured to disengage the drivetrain of the vehicle from the rack  16  of the actuator  10 . As used herein, clutch mechanism  30  may refer to the components necessary to input a manually applied user action to decouple the rack from the motor and/or subsequently move the same or alternatively anyone of the components that performs the aforementioned actions or sub actions necessary to perform the aforementioned actions. 
     In one embodiment, the clutch mechanism  30  or a component thereof further comprises a lever  32  configured to move the rack independently by a pre-described amount. 
     During normal electrical operation (e.g. shift by wire) inputs via device  22  are provided to the microcontroller  24  which in turn operates motor  20 . As motor  20  is operated a worm  34  coupled to a shaft  36  of the motor  20  is rotated. Rotation of worm  34  causes rotation of worm gear  38 . Worm gear  38  is also coupled to a gear  40  which rotates with worm gear  38  about an axis  42 . Gear  40  is configured to mesh with a gear  44  coupled to a gear  46  that is configured to mesh with rack  16 . Accordingly rotation of worm gear  38  in the directions of arrows  48  causes linear movement of rack  16  in the direction of arrows  50  which in turn causes a corresponding movement of the gears of the transmission coupled thereto either directly or indirectly. 
     As mentioned above, encoder  26  is also coupled to shaft  36  so that the rotational movement and location of worm  34  as well as rack  16  can be fed back to microcontroller  24 . 
     As previously discussed, power loss to the vehicle or system or malfunction of one of the components of the shift by wire system may prevent operation of the vehicle transmission and more particularly, prevent the same from being shifted from one position to another position more suitable for operation during the above malfunction (e.g., vehicle towing, etc.). 
     In accordance with one exemplary embodiment of the present invention, clutch mechanism  30  is provided to achieve manual operation of the actuator in the event of such a failure mentioned above. Clutch mechanism  30  comprises a clutch lever  52  configured to move a clutch spool or clutch component  54  from a first position wherein gear  46  is coupled to gear  42  by for example, a plurality of pins  56  of the clutch spool which when are in the first position couple gear  46  to gear  42  by for example engaging portions or openings of gear  42  and gear  46  and thus the rack  16  is directly coupled to motor  20  to a second position wherein pins  56  no longer couple gear  46  to gear  42  (e.g., pins  56  are moved out of engagement with both gears  42  and  46  or pins only engage one of gears  42  and  46 ) thus rack  16  is no longer coupled to motor  20 . 
     The first position of the clutch lever  52  is illustrated in at least  FIGS. 8 and 10  and  FIG. 10  illustrates cross-sectional views of portions of the clutch mechanism  30  as well as gears  46  and  42 . As illustrated in at least  FIGS. 4 and 10  the clutch lever  52  and clutch spool  54  are spring biased into the first position by a spring  58 . 
     The second position of the clutch lever  52  is illustrated in at least  FIGS. 4, 7, 9 and 11 . The clutch mechanism  30  further comprises a cam gear  70  having a cam surface  72  configured to act upon a portion or one end  74  of clutch lever  52  such that rotation of cam gear  70  in the directions of arrows  48  causes portion  74  of clutch lever  52  two move along cam surface  72  and thus transition the clutch lever  52  from the first position to the second position and thus overcome the biasing force of spring  58  such that clutch spool or clutch component  54  can be moved into a position wherein gears  42  and  46  are decoupled from each other and thus rack  16  is uncoupled from motor  20 . 
     Cam gear  70  further comprises a plurality of teeth  76  configured to engage a gear  78  whose rotation facilitates movement of the cam gear  70  such that clutch lever  52  is moved from the first position to the second position. Alternatively, clutch lever  52  and/or cam gear  70  is coupled to a cable or other actuation device that can be manipulated by an operator in order to transition clutch lever  52  from the first position to the second position and provide the desired movements of the clutch mechanism as well as the rack. 
     In addition and in one non-limiting exemplary embodiment, the clutch mechanism  30  provides two features. The first one being movement of the clutch spool or clutch component  54  from the first position to the second position in order to disengage the motor  20  from the rack  16  and ultimately the drivetrain of the vehicle while the second one is to move the rack  16  linearly after it has been disengaged from the motor  24  gear train  18 . The linear movement of rack  16  by cam gear  70  is facilitated by lever  32  which is coupled to cam gear  70 . 
     Accordingly and as illustrated in the attached figures rotational movement of cam gear  70  in a direction from a first position via a gear  78  will cause portion  74  to slide along cam surface  72  and clutch lever  52  is pivoted about an axis  80  as it moves from the first position to the second position in order to move the clutch spool  54  from the first position to the second position so that gears  42  and  46  are decoupled from each other. At this point or at an intermediate position of cam gear  70 , lever  32  is now in contact with a surface  82  of rack  16  and further movement of cam gear  70  in the direction (e.g., from the intermediate position of the cam gear  70  to a second position of the cam gear  70 ) will cause linear movement of the rack in the direction of arrow  86  which will in turn move the transmission from one gear selection to another. 
     In one non-limiting embodiment, gear  78  is configured to be moved via a hand tool (e.g., screwdriver from an individual) with a minimal amount of rotating motion merely necessary to disengage motor  20  from rack  16  and then move rack  16  in order to change the vehicle transmission from one selected position to another selected position (e.g., from the first position to the intermediate position to the second position). In the illustrated embodiment, movement of the rack is in a direction 90° offset or perpendicular from movement of the clutch spool  54  or clutch lever  52 . Of course, other directions are contemplated to be within the scope of various embodiments of the present invention. Accordingly, the clutch and manual override system provides unique two-stage motion acting on sequential components and perpendicular axes. Of course, numerous other configurations (e.g., other than 90° offset) are contemplated to be within the scope of exemplary embodiments of the present invention. 
     In one embodiment, gear  78  or a portion thereof is accessible via an access panel in order to provide the rotational movement of gear  78  via a hand tool. See for example slot  79  which may be configured to receive a corresponding screw driver. Of course, numerous other types of configurations are contemplated. Alternatively, gear  78  is operatively coupled to a manual input device in order to provide the desired movement of gear  78  (e.g., cable, lever, etc.) Referring now to at least  FIG. 4 , cam gear  70  is spring biased into a first position by a spring  88  wherein gear  78  is configured to engage a first end of teeth  76  of cam gear  70  and cam surface  72  has not caused rotational movement of clutch lever  52 . Accordingly and as cam gear  70  is rotated via a rotational movement of gear  78  spring  88  will provide a biasing force to return cam gear  70  to the first position such that the clutch mechanism  30  we engages or re-couples motor  22  rack  16 . In other words once gear  78  is rotated in order to decouple the motor  20  from the rack  16  and rack  16  is moved via lever  32 , spring  88  will cause cam gear  72  rotate back to the first position such that clutch mechanism  30  can be couple motor  22  rack  16  via gear train  18  although rack  16  has now been repositioned via lever  32 . In addition and in order to assist in this process spring  58  will also bias the clutch spool  56  back into the first position. 
     In one non-limiting exemplary embodiment, a two-piece cam gear/lever driven by a separate driver is provided. The cam gear, when rotated, acts upon a clutch lever that is used to push the clutch spool with an initial part of its full rotation. The cam moves the lever through its travel to push the clutch spool to disengage the motor from the drivetrain. Continued rotation of the cam gear after this disengagement impacts an additional lever that pushes the rack a prescribed amount. At the end of this rotation the cam gear is acted upon by a return spring which will rotate the cam gear back to its initial position thereby rotating the lever away from the rack. Final rotation of the cam gear by the return spring will lower the clutch lever allowing a spring acting axially on the clutch spool to return the clutch spool to its original position engaging the motor to the drivetrain. The cam gear/lever can be acted upon by a separate driver either in direct connection by gear teeth or remotely by a cable. 
     In one non-limiting exemplary embodiment, the actuator  10  (gear train  18  and clutch mechanism  30 ) are configured such that rotational movement of cam gear  70  will only contact portion  74  of clutch lever  52  when the vehicle transmission is in a predetermined state (e.g., Park) and the two-step rotational movement of the clutch mechanism  30  will first disengage the gear train  18  from the rack and then move the rack via lever  32  to a another predetermined state (e.g., Park to neutral) in order to allow for towing of the vehicle. Of course, numerous other configurations are contemplated to be within the scope of exemplary embodiments of the present invention and the aforementioned movements are merely examples and the various embodiments of the present invention are not intended to be specifically limited to the examples provided herein. 
     It is, of course, that various configurations and alternatives are considered to be within exemplary embodiments of the present invention and it may or may not be necessary to spring bias cam gear  70  and clutch spool  54  back into their first positions. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.