Car Window Regulator
This document describes the components and function of a car window lifting
mechanism. It is a mechanism that many of us use on a daily but rarely see or notice;
usually using it without any thought of how it works. This mechanism consists of set of
gears powered by a small electric motor or by hand crank, a lifting arm and the window
itself. It is used to raise and lower the windows of a car in and out of the door on a set of
tracks in the window frame. Pictured below is the entire mechanism.
Window Regulator Assembly
Source: http://www.m-99.co.uk/Electric_Windows/window_regulator.jpg
The power needed to lift the weight of the window is provided by either an
electric motor or hand crank. In each case this power is used to turn the gear assembly
which begins with a worm gear. A worm gear is a cylindrical gear with angled grooves
cut into it that looks similar to a screw or drill bit. This worm gear interlocks with a spur
gear, which is a circular disc with evenly spaced teeth protruding about its
circumferences. Here is an image of a worm gear linked with a spur gear.
Worm Gear with Spur Gear
Source: http://science.howstuffworks.com/gear5.htm
The use of the worm gear is very important for two reasons. First it greatly increases the
torque of the mechanism allowing it to lift the window easily by hand or with a small
electric motor. Second it works as a locking mechanism because while turning the worm
gear turns the spur gear, turning the spur gear will not turn the worm gear. This will
prevent the window from being pushed up or down by any other forces. The gear
assembly is linked with the teeth at the base of one of the regulator arms; the base of the
other arm is fixed to the door or in a small slide depending on the model. These 2 arms
are constructed of thin metal. Each is 2-3 feet long and they joined by a hinge in their
centers creating an ‘x’ shape. Both regulator arms have a square knob on their end that is
closest to the base of the window. These fit in a slide that is attached to the base of the
window. It is here that the arms apply forces to the window to raise it up or down while
sliding along its base to keep it level. All of these components are attached to the central
mount base which where the assembly is fixed to the inside of the car door.
To raise or lower the window power must be applied to the gear assembly by the electric
motor or hand crank. The power is used to turn the worm gear which causes the spur
gear to rotate, which directly cause the rotation of the regulator arms. The regulator arms
rotate in opposite directions in a scissor motion. At any point the ends of the arms will
always be at the same; this keeps the window balanced and level. Here is a link that
provides an animation of this mechanism: http://auto.howstuffworks.com/powerwindow1.htm
Sources:
http://auto.howstuffworks.com/power-window.htm
http://science.howstuffworks.com/gear.htm