Wipers and washers (Description): Description and operation

Description

Windscreen Wipers

Two front windscreen wipers are operated by a single electric motor. The motor and a link assembly are located below the plenum grill at the base of the windscreen.

The link assembly is handed for left and right hand drive vehicles. All other wiper components remain common to both versions. The component descriptions and operation are the same for both left and right hand drive.

The parallel coupled link assembly comprises a curved galvanized tube which has a cast wheel box pushed into each end of the tube and crimped for retention. A galvanized link arm is attached to a lever at the base of each wheel box.

Each link is attached by a spherical bearing which is permanently attached to the lever and the link. The opposite end of each link also has a spherical bearing, which are both attached to a spigot which in turn is attached to a lever. The lever has a splined bore and mates with a splined shaft from the motor. A spring washer and nut secure the lever to the shaft.

Each wheel box comprises a cast housing, through which a splined shaft is located on bearings. The outer end of each shaft has splines which provide positive location for the wiper arms. The link assembly is a sealed unit and is not serviceable. The motor is attached to the link assembly with three bolts. The motor can operate at two speeds for fast and slow wiper operation. The motor is a DC motor with permanent magnets. The central shaft of the motor is fitted with a worm drive which in turn rotates a gear connected to the splined drive shaft.

A wiper arm is located on the splined shaft of each wheel box and secured with a nut. The wiper arm attachment to the splined shaft has a pivot to which the remainder of the arm is attached. The two parts of the arm are connected by a spring which controls the pressure of the blade on the screen to a predetermined amount.

Each wiper blade is attached to its wiper arm with a clip that allows the blade to pivot. Each wiper blade comprises a number of levers and yokes to which the rubber wiper is fitted. The levers and yokes ensure that the pressure applied by the arm spring is distributed evenly along the full length of the blade. The rubber wiper is held in the yokes by a pair of stainless steel strips, which also distribute the spring pressure evenly. The driver's side wiper blade is fitted with an aerofoil, which presses the wiper blade onto the windscreen at high speed. This prevents the wiper blade from lifting off the screen and maintains the wiping performance.

Rear Screen Wiper

The rear screen wiper is attached to a splined shaft which is driven by an electric motor via an eccentric drive mechanism.

The motor is a single speed dc motor with permanent magnets. The motor shaft is fitted with a worm drive which rotates a gear wheel. The gear wheel has an offset spigot to which an eccentric cam is fitted which can rotate through 180° in each direction. A coil spring is located around the cam and operates as a simple friction clutch to enable the cam to be rotated when the motor is driven in reverse. A connecting link is attached to the cam and drives two gears located in a link. The connecting link converts the rotary motion of the gear wheel into linear movement of the link. The linear movement is converted back into rotary movement of the splined shaft which moves the wiper arm in an arc in two directions across the rear screen.

The wiper motor has the ability to park the wiper arm off the rear screen when the wiper is selected off. When the motor is operating to wipe the rear screen, the motor shaft is rotating in a clockwise direction. When the rear screen wiper is selected off, the Central Control Unit (CCU) allows the wiper arm to reach the vertical position on the screen. A microswitch, actuated by a slip ring on the underside of the gear wheel, signals that the wiper arm has reached this position. The CCU then reverses the polarity of the supply to the motor which causes the motor shaft to rotate in an anti-clockwise direction.

When the motor changes direction, the eccentric cam is rotated through 180° which effectively lengthens the linear movement of the connecting link. This causes the wiper arm to sweep across the screen to its park position. The longer linear movement of the connecting link, causes the wiper arm to rotate further than during normal wiping, parking the wiper arm and blade off screen. A second slip ring operated microswitch, on the underside of the gear wheel, signals the CCU that the wiper arm has reached the off screen position and the CCU removes the supply to the rear screen wiper motor.