Friday, 13 September 2013

WINDSHIELD WASHER


          A windshield washer system for an automotive vehicle includes a fluid reservoir, a pump mounted within the fluid reservoir and a heater mounted in proximity to the pump so as to provide heat to fluid contained within the reservoir. The system further includes a nozzle operatively associated with the pump for applying fluid from the reservoir to an outside surface of an automotive vehicle. The heater may comprise an electric resistance element, such as a positive temperature coefficient element mounted about a pumping chamber of the pump. In any event, the heater provides sufficient heat to the fluid contained within the reservoir to prevent water in the fluid from freezing at ambient temperatures normally encountered by automobiles.
          According to another aspect of the present invention, a nozzle incorporated in the present system may be of the telescoping variety such that it has a first position for spraying and a second, or retracted, position when it is not spraying. In this fashion, a neat, uncluttered appearance may be achieved, while protecting the nozzle from damage. In any event, the nozzle is close-coupled to the pump, so as to minimize the fluid volume between the pump and nozzle. This promotes drain back of fluid from the nozzle to the pump, while allowing heat to flow from the pump to the nozzle, thereby further inhibiting freezing of water within the nozzle.




WINDSHIELD WASER FLUID
          Windshield washer fluid is sold in many formulations, and some may require dilution before being applied, although most solutions available in North America come premixed with no diluting required. The most common washer fluid solutions are given labels such as "All-Season", "Bug Remover", or "De-icer", and usually are a combination of solvents with a detergent. Dilution factors will vary depending on season, for example in winter the dilution factor may be 1:1, whereas during summer the dilution factor may be 1:10. It is sometimes sold as sachet of crystals, which is also diluted with water. Distilled water is the preferred diluent, since it will not leave trace mineral deposits on the glass. Anti-freeze, or methylated spirits, may be added to a mixture to give the product a lower freezing temperature. But methanol vapor is harmful when breathed in, so more popular now is an ethanol winter mix, e.g. PAV, water, ethanol (or isopropanol), and ethylene glycol.
          Concerns have been raised about the overall environmental aspects of washer fluid. Widespread, ground-level use of wiper fluid (amounting to billions of liters each year) can lead to cumulative air pollution and water pollution. Consumer advocacy groups and auto enthusiasts believe that the alcohols and solvents present in some, but not all, windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components on paint, rubber, car wax, and plastics, and groups propose various alternatives and homemade recipes so as to protect the finish and mechanics of the motor vehicle.

WINDSHIELD WASHER NOZZLE(S)
          This model is equipped with two hood mounted washer nozzles. Each nozzle emits two streams into the wiper pattern. If the nozzle performance is unsatisfactory they can be adjusted. To adjust insert a pin into the nozzle ball and move to proper pattern. The right and left nozzles are identical. It is an advantage of the present system that separated fluid lines and nozzles are eliminated, with the entire system being contained in a single assembly, so as to allow the protection of the fluid and the entire system from freezing with a single heat source.




WINDSHIELD WASHER SYSTEM

All models are equipped with electrically operated windshield washer pumps. The wash function can be accessed in the OFF position of the wiper control switch. Holding the wash button depressed when the switch is in the OFF position will operate the wipers and washer motor pump continuously until the washer button is released. Releasing the button will stop the washer pump but the wipers will complete the current wipe cycle. Followed by an average of two more wipe cycles before the wipers park and the module turns off.

The electric pump assembly is mounted directly to the reservoir. A permanently lubricated motor is coupled to a rotor type pump. Fluid, gravity fed from the reservoir, is forced by the pump through rubber hoses to the hood mounted nozzles which direct the fluid streams to the windshield. The pump and reservoir are serviced as separate assemblies.





ADVANTAGES
o   It is an advantage of the present system that the use of hydrocarbon-based freezing point depressants may be eliminated with the present system.
o   It is another advantage of the present system that the nozzle included with the system is self-draining so as to allow the nozzle to purge itself of fluid when the system is not being energized and therefore to further protect the system against freezing.

DISADVANTAGES
o   Windshield washer fluid can damage the vehicle. These critics point to the corrosive effects of ethanol, methanol, and other components.



          In conclusion, it can be said that windshield washer is one of the most important parts of a vehicle’s equipment and that, despite the fact that most people do not pay much attention to this, they are really helpful when it comes to keeping the windshield clean and ensuring that visibility levels are as high as possible.

Tuesday, 10 September 2013

Anti-Lock Braking System (ABS)


It is a safety system in automobiles. It prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).


How Do Wheels Lock?

During braking, wheels lock if the brake force applied is more than the friction between the road and tyre. This often happens in a panic braking situation, especially on a slippery road. When the front wheels lock, the vehicle slides in direction of motion. When the rear wheels locks, the vehicle swings around. It is impossible to steer around an obstacle with wheels locked. Locked wheels can thus result in accident. Skidding also reduce tyre life.



What Does ABS Do?

The system detects when the wheel are about to lock and momentarily release the pressure on locking wheel. The brakes are reapplied as soon as the wheels have recovered.
A toothed wheel (pole wheel) is fitted to the rotating wheel hub. A magnetic sensor mounted on each wheel in close in close proximity to the teeth, generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated (frequency) is a measure of wheel speed. This signal is read by electronic control unit (ECU). When a wheel is lock, the ECU sends an electrical signal to the modulator valve solenoid, which release pressure from the brake chamber. When the wheel recovers sufficiently, the brake pressure is reapplied again by the switch off signal to the modulator valve.
The modulator valve has an addition ‘hold’ state which maintains pressure. In break in the chamber, thus optimizing the braking process. The cycling of modulator valve (5 to 6 times per second) is continued till the vehicle comes to a controlled stop.
With ABS, the vehicle remains completely stable even when the driver continues to press the brake pedal during braking, thus avoiding accidents.




Components:

The anti-lock braking system consists of following components.


Wheel Speed Sensor
    The wheel speed sensor consists of a permanent magnet and coil assembly. It generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated is a measure of wheel speed. The voltage induced increases with the speed of rotation of the wheel and reduces with increasing gap between the pole wheel and the sensor.

Pole Wheel
    Pole Wheel is a toothed wheel made of ferrous material. It normally has teeth on the face. In some cases where it is not possible to install the sensor parallel to the axle, the pole wheels are designed with teeth on periphery. The pole wheel fitted on standard 9-20, 10-20 tires has normally 100 evenly spaced teeth. 80 evenly spaced teeth pole wheels are used for the vehicles having the tyre diameter less than 9mm.

Sensor Extension Cable
    The sensor extension cable is a two core cable which connects the wheel speed sensor to the Electronic Control Unit. The inner core sheathing is of EPDM rubber and the outer sheathing is polyurethane which provide abrasion resistance to the cable. The cable has a module plug with two pins is connected to the control assembly. The cable has two cores-brown and black in colour.

Electronic Control Unit

    The ECU is the core component of the ABS system. Wheel speed sensor signal are the input to the Electronic Control Unit. The ECU computers wheel speeds, wheel deceleration and acceleration. If any wheel tends to lock, the ECU actuates the corresponding Modulator valve to prevent wheel lock. The ECU is normally mounted in driver's cabin.

    The ECU consists of 7 major circuits,
> Input circuit
> Master circuit
> Slave circuit
> Driver circuit
> Feedback circuit
> Power supply circuit
> Fail safe circuit

The functions of ECU,
> It receives wheel speed signal from the sensor. The wheel speed signals are processed and appropriate output signals are sent to the modular valves in the event of a wheel lock.
> It continuously monitors the status and operation of ABS components and wiring.
> It alerts the driver in the event of occurrence of any electrical fault in the ABS system by actuating a warning lamp.
> It disconnects the exhaust brakes during ABS operations.
> It enables the service technician to read the faults in the system either through a diagnostic controller or a blink code lamp.

Modulator Valve Cable
    The Modulator valve cable has thee cores. There are two solenoid interface lines and a common ground line. The inner core sheathing is of EPDM type and the outer sheathing is polyurethane which provide abrasion resistance to the cable.
    The cable has a three pin moulded socket is connected to the modulator valve solenoid at one and an interlock connector with locking feature at the other end. The cores are brown, blue and green.

Modulator Valve

    ABS Modulator valve regulate the air pressure to the brake chamber during ABS action. During normal braking it allows air to flow directly from inlet to delivery. Modulator valve cannot automatically apply the brakes, or increase the brake application pressure above the level applied by the driver through the dual brake valve.

    There is an inlet port, Delivery port and Exhaust passage.
> The inlet port is connected to the delivery of quick release valve or relay valve.
> The delivery port is connected to the brake chamber.
> The exhaust passage vents air from the brake chambers.

    The modulator valve has two solenoids. By energizing the solenoids, the modular valve can be switched to any of the following modes.
> Pressure
> Pressure hold
> Pressure release

Quick Release Valve

    Quick release valve are fitted in air braking system to release the air from the brake chamber quickly after release of brake pedal. This prevents delay in brake release due to long piping runs or multiples of brake chamber being exhausted through the brake valve.

Relay Valve
    Relay valve provides a means of admitting and releasing air to and from brake chamber quickly, in accordance with the signal pressure from the delivery of the dual brake valve.
    Air from the reservoir passes through the valve into the brake chamber. The pressure applied to the brake is equal to the signal pressure from the dual brake valve. When the brake pedal is released the signal pressure is released. The pressure in the brake chamber is released directly through the exhaust port of the relay valve.

Warning Lamp

     Vehicle are fitted with an ABS warning lamp. It is a LED indicator lamp amber in colour and lights up when the system has detected any electrical fault. ABS warning lamp is located on the instrument panel in form of a driver.

Blink Code Lamp

    This lamp is green in colour and is used to indicate the stored faults in the system to the service technician on operating a blink code switch. The nature of fault in the system can be diagnosed by the number of flashes.

Off Highway Switch
    This is an optional switch in front of the driver which can be switched ON when the vehicle is operating off highway. In this mode, ABS control will; allow higher wheel slip to achieve shorter stopping distance than with normal ABS control.

Blink Code Switch
    A momentary switch that grounds the ABS Indicator Lamp output is used to place the ECU into the diagnostic blink code mode and is typically located on the vehicle's dash panel.

Share This Content