Anti-tilt feature for torsion spring for default-to-park lever

Abstract

In a default-to-park system for a transmission, a lever member has a cylindrical hub configured to rotate about a spindle. The lever member has a transverse plate including a lever arm connected to a park release actuator and to a link to a park pawl of the transmission. Under normal operation, a transmission controller shifts the actuator to turn the lever arm and release the park pawl so the transmission can rotate. In an absence of a signal from the controller to the actuator, a bias spring restores the lever arm so that the transmission is locked. The bias spring comprises torsion coils disposed over the hub, a fixed end, and a drive end. The drive end has a heel segment bearing against a transverse surface of the transverse plate facing the torsion coils and a loading hook wrapped around an edge of the transverse plate.

What is claimed is: 
     
         1 . A return spring for a default-to-park lever, comprising:
 torsion coils receiving a cylindrical hub of the lever;   a fixed end for bearing on a transmission; and   a drive end having a heel segment bearing against a surface of the lever facing the torsion coils and a loading hook wrapping around an edge of the lever;   wherein the spring is counterbalanced against tilting when movement of the lever winds up the torsion coils.   
     
     
         2 . The return spring of  claim 1  further comprising:
 a bridge segment between the heel segment and the torsion coils; 
 wherein the lever includes the cylindrical hub and a transverse plate which are configured to rotate about a fixed spindle, wherein the transverse plate includes a lever arm engageable with a park release actuator and a receiver engageable with a link to a park pawl of a transmission brake; 
 wherein the cylindrical hub includes a guide slot proximate to the transverse plate configured to receive a guide pin projecting from the spindle; and 
 wherein the bridge segment is configured to extend in an axial direction of the spindle so that the guide slot is unobstructed by the torsion coils. 
 
     
     
         3 . The return spring of  claim 2  wherein the return spring applies an initial loading force against the link with the park pawl in an engaged position, wherein the actuator winds up the return spring when moving the park pawl to an unengaged position, and wherein the heel segment counterbalances a twisting force associated with the wind up. 
     
     
         4 . The return spring of  claim 2  wherein the transverse plate provides the surface of the lever bearing against the heel segment, and wherein the heel segment and the lever surface are flat. 
     
     
         5 . The return spring of  claim 4  wherein the transverse plate provides the edge for wrapping around the loading hook.