Auto Questions: How Windshield Wipers Work

Windsheild wipers are an important safety component to your car when rain, fog, sleet, mud or snow impairs visibility. This article will explain just how they work to keep you windshield clear.

The windshield wiper is an important safety device developed to improve a driver's visibility when rain, snow or mud restricts their view of the road. When windshield wipers were first introduced, the driver operated the entire mechanism by turning a small handle back and forth. Through the technological advancements made in automotive industry over the years, modern cars use windshield wipers powered by an electric motor. The modern windshield wiper system consists of wiper blades, an electric motor, and a reduction worm gear along with several rods that form a linkage between these different moving components. Let's take a look at how they work.

The actual windshield wiper blades are made out of thin rubber strips with a straight edge, designed to effectively clear water, snow and mud off of the windshield surface. Each wiper blade is attached to a single pivoting wiper arm through a series of V shaped connections, resulting in over six to eight separate connections between the blade and the arm. The purpose of this design is to allow for pressure from the wiper arm to be applied evenly to the windshield across the entire length of the blade. If this pressure was stronger in one region of the blade compared to another, streak marks would occur in the area(s) with the least pressure.

The wiper arm(s) that moves the blades from side to side is connected through a series of linkages to a small cam that revolves around a central point. This revolving cam is connected on one end to a horizontal rod in the linkage system. As the cam revolves, the horizontal rod is moved back and forth in a side-to-side motion. This motion is transmitted directly through the linkages to the wiper arms and blades, causing them to move in a similar fashion.



As you may imagine, the force needed to move two wiper blades back and forth across a windshield at varying speeds requires a significant amount of torque. However, a relatively small electric motor is used to power this entire mechanism. Manufacturers were able to accomplish this feat by utilizing the mechanical advantage gained through the use of a reduction worm gear, which work by reducing the output speed from the power source to increase torque. If an electric motor produces one horsepower and one foot-pound of torque, reducing the output speed by a factor of twenty (through a reduction worm gear) will effectively decrease power to one twentieth of a horsepower, but increase torque to twenty foot-pounds! In this way, the relatively weak electric motor is able to have the power to move the wiper blades back and forth.

The wiper controls available to the driver typically offer varying settings ranging from an intermittent to a high-speed operation. These different modes are achieved by varying the speed at which the electric motor runs. The faster the motor runs, the faster the blades will move. When the blades move intermittently, power is cut to the electric motor momentarily, causing the wiper blades to pause.

This is in essence how windshield wipers work on the modern automobile. As automotive innovation continually progresses, the technology available in the windshield wiper system will continue to improve as well. Already, several luxury vehicle manufacturers such as Lexus and Mercedes-Benz offer rain-sensing wipers which use infrared light to detect the amount of moisture falling on your windshield and automatically varies the speeds at which the wipers move to effectively keep the driver's vision of the road clear at all times!

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