For the all the advances that have taken place over the last 100 or so years of cars, there's one area that doesn't seem to have progressed much at all. Now - just as then - raindrops are cleaned from the windscreen by the mechanical scraping action of rubber blades. Where is the ultrasonic shaking off of the water droplets, or the use of aerodynamic airflows allowing water to stream off, vision completely unimpaired? Well, nowhere! However, at least the technologies of those rubber blades - and the mechanisms which drive them - are undergoing changes.
Twin motor systems that control the two wipers independently, new designs of wiper blades and the automatic detection of how much water there is on the windscreen are just some of the changes. It's a bit like the technology of dampers - incremental change after change, until suddenly you realise that the shock absorbers in today's cars are really nothing like those found in cars the cars of 30 years ago. You just never noticed the changes occurring.
So here's why when you walk into a new car showroom in 5 years' time it's very likely that a good hard look at the wiper/washer system will reveal a lot of surprises.
Blade Design
In 1994 Bosch developed the so-called twin wiper, the first wiper to be made of two-component synthetic rubber. It consisted of a particularly hard, abrasion-resistant wiper lip, which changed into the extra-soft wiper back. The wiper lip - only ten to fifteen thousandths of a millimetre wide on both sides of its micro-double edge - ensured long term smear-free wiping. The softer back guaranteed optimum reversing behaviour at all temperatures, which meant smooth running without squeaking or juddering.
In 1999 the Bosch Aerotwin wiper was released, the first joint-free wiper. Instead of having a clip system with articulated parts - with which the wiper rubber is secured by means of claws - the joint-free wiper consists of a one-piece rubber profile with an integrated spoiler. Two spring bars distribute the contact pressure evenly over the entire length of the wiper blade.
The Aerotwin is only half as high as conventional wiper blades. The flat design improves the aerodynamics of the wiper blade and reduces wind noises. Furthermore, there is less blockage of the driver's view of the road when the wipers are in action. Parking of the wipers beneath the bonnet line is also facilitated because of the wipers' low height.
The Aerotwin was first used by Daimler-Chrysler on the Mercedes-Benz CL, with Volkswagen, Audi, Renault, Ford, Skoda and Seat since adopting the system. Bosch expects that in the next six years more than 80 percent of all new cars in Europe will be equipped with this type of wiper system.
Independent testing was carried out on the Aerotwin wiper blades by two masters students at Volvo in Sweden. Whereas an ordinary wiper blade showed wide wear stripes after 33,000 cycles in the test rig, the Bosch blades showed no stripes at all, even after 119,500 cycles.
Another approach to wiper blade design has been taken by the manufacturer that made the very first wiper blades - Trico. Together with DuPont, they have designed the Teflon™ brand wiper blade. The blades are said to reduce friction to give a smoother, cleaner wipe with less chattering. The Teflon™ coating is extruded at the same time as the rubber blade, being laminated to the wiping lip.
Intelligent Drive Units
Conventional wipers use an electric motor to drive a crank mechanism that reverses the wipers as they reach the end of their sweeps. However, wipers which are driven by one or more reversing motors are now being implemented. The mechanism is more compact and there are other advantages.
A sensor system in the motor reads the actual wiper arm position and provides a maximum wipe pattern independent of wiper rate, friction value or wind velocity Due to the accuracy that can be maintained in the wiper angle, the distance to the edge of the windscreen can be reduced to an absolute minimum. The electronic control also detects obstacles (like snow) packed in the turning points. In these cases, an automatic reduction of the wipe pattern prevents the system from locking or being damaged. A reduction of the motor speed before each change in direction results in quieter running and reduces wear on the wiper blade. In dry weather, the wiper arm rests below the bonnet line, reducing view blockage, improving the aerodynamics and lowering the risk of injuries in case of collisions with pedestrians and bicycle riders. A 'service' wiper position allows the easy changing of wiper rubbers.
The Renault Vel Satis uses a Bosch single motor reversing system, while the Volkswagen Phaeton uses the pictured system which comprises two electric motors, one controlling each blade. In the system fitted to the Phaeton the wiper arms are synchronized fully electronically and without any mechanical linkage.
Auto Sensing
The automatic triggering of wipers and appropriate changes in their wiping speeds can be implemented with electronic control. The Bosch rain sensor - mounted inside the windscreen - uses an optical principle. A LED emits light in such a way that when the windshield is dry almost the entire amount of light is reflected onto a light sensor. When the windshield is wet, the reflective behaviour changes: the more water there is on the surface, the less light is reflected. New rain sensors use infrared light instead of conventional visible light. This means that the sensor can be mounted in the black area at the edge of the windshield and cannot be seen from outside.
Depending on the quantity of rain detected, the sensor varies the speed of the wiper system. In conjunction with electronically controlled wiper drive units, the wiping speed can be continuously adjusted in intermittent operation. In the event of splash water - as when overtaking a truck - the system switches immediately to the highest speed.
The rain sensors offer further options. For example, they can be used to automatically close windows and sunroofs. Bosch suggests that it is even conceivable that the signals of the rain sensor could in future be used for modern traffic telematic systems, with each rain-sensing unit reporting to a central base the current weather situation on a certain section of the road.
US components supplier Valeo has developed a sensor that is multipurpose - it is dubbed a Rain/Light/Tunnel sensor. It is capable of detecting light variations (daylight, dusk, darkness, etc.) and interpreting them in an intelligent manner.
Equipped with three light-analysis sensors, it can differentiate the seven following modes: day, night, tunnel, pre-tunnel, rain, garage, trees. It can therefore detect and anticipate a tunnel and actuate the lighting function before entering the tunnel. It can also differentiate a bridge from a tunnel thanks to a diode designed to distinguish ahead into the tunnel.
Valeo's R&D teams are now working on a rear-window dust sensor as well as a multiple-function sensor based on a mini-camera.
Washing
So the scraping of water off the glass is improving in technology, but what about window washing?
Valeo has recently developed Opti-Wash™, a heated wash system. By heating a small amount of washer fluid to approximately 65 degrees C as it travels to the washer nozzles, the Opti-Wash™ improves visibility by enhancing the cleaning of most contamination from the vehicle windscreen. In addition, since the system has a very short initial heating time (typically less than 60 seconds after the ignition is switched on), hot washer fluid is readily available to assist in the de-frosting of the windscreen.
The components of the Opti-WashTM system are packaged into a small unit weighing less than 500 grams. This unit is self-contained, including its electronic controls. Compared to current wash systems, the Opti-WashTM saves as much as half the volume of washer fluid to clean the windscreen.
Hydrophobic Glazing
If the rain can stream off the sloped windscreen without needing to be scraped off, things would become a lot simpler. It's the same principle that the aftermarket Rain-X coating uses - but what if such behaviour could be built into the glass? Windscreen manufacturers are developing just such glass, which is called hydrophobic (literally, fear of water!).
Pilkington's hydrophobic coating is designed more for application on side windows than the windscreen. It works by changing the way in which the water droplet sits on the surface of the glass - in effect, the droplet has less contact area with the glass (it beads), allowing it to slide off more easily. The coating can be subjected to boiling water, acid and alkalis without being substantially degraded, and it is also rated for thousands of 'flannel rubs'.
Conclusion
Not all advances in car technology are major breakthroughs. Instead some are the incremental step-by-step alterations and refinements of current technologies. Maybe have a close look at the windscreen wipers on the next new car you see....
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