Windscreen wipers description (Wipers & washers)

WINDSCREEN WIPERS DESCRIPTION

The windscreen wiper functions are controlled from the wash/wipe stalk located on the right hand side of the steering column. The wash/wipe stalk is a multi-function switch which controls the windscreen wiper, intermittent and washer operation. The Central Control Unit (CCU) is responsible for the operation of the intermittent wipe facility and the park facility when the wipers are turned off.

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.

The two speed operation is achieved by three brushes in the motor. One brush is the common earth. The slow speed is initiated by a brush positioned 180° to the common brush. The fast speed is initiated by a brush positioned at approximately 45° to the common brush. The fast speed operates by the brushes transferring direct current to a smaller portion of the armature coils, which causes the armature to rotate faster, but with a lower torque than the slow speed.

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 airfoil, 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.