Aparking pawlis a device fitted to amotor vehicle'sautomatic transmissionthat locks up thetransmissionwhen thetransmission shift leverselector is placed in thePark position. "Park" is the first position of the lever (topmost on a column shift, frontmost on a floor shift) in all cars sold in the United States since 1965 (when the order was standardised by theSociety of Automotive Engineers(SAE)) throughSAE J915,[1]and in most other vehicles worldwide.
Design and operation
editThe parking pawl locks the transmission'soutput shaftto the transmission casing by engaging apawl(a pin) that engages in a notched wheel on the shaft, stopping it (and thus the driven wheels) from rotating. The main components of a parking pawl mechanism are the parking gear, parking pawl, actuator rod, cam collar, cam plate, pivot pin, and parking pawl return spring. The mechanism assembly is designed so that the parking pawl tooth collides and overrides the parking gear teeth (ratchets) until a safe engagement speed for the vehicle is reached. Software controls are put in place to avoid this condition and engage the pawl only when the vehicle has come to a standstill.[2]
Applicable standards
edit- FMVSS 114 – Theft Protection and Rollaway Prevention, Keyless Ignition Systems
- SAE J2208 – Park Standard for Automatic Transmissions.
See also
editExternal links
editReferences
edit- ^"SAE International".
- ^Jeyakumaran, Jeku; Zhang, Nong (2008)."Dynamic Analysis of an Automatic Transmission Parking Mechanism".University of Adelaide, Australia.(subscription required)