Electronically-Controlled Cooling Systems
The cooling system of a car up until now has been based on mechanical thermostat valves and a mechanically-driven water pump. Except for the speed of the electric cooling fan, it has hardly been influenced by electronics at all. However, Bosch is currently developing electronically-controlled thermal management for the engine. This approach has the potential to decrease fuel consumption by up to five percent and also raises the heating comfort within the vehicle, controlling the temperature in the passenger area faster and more evenly.
Compared to traditional vehicles, an engine using electronic thermo management reaches its operating temperature faster after a cold start, thus reducing the emission of exhaust gases. At engine idle and in the part throttle range, electronic thermal management permits a higher engine temperature; the resulting lower oil viscosity reduces engine losses and leads to further fuel savings compared to traditional "over-cooled" engines frequently operated in these conditions.
In contrast, at high engine load, the coolant temperature drops faster and even with sudden wide-open throttle, temperature spikes do not occur. This is easier on the engine and may contribute to a longer service life of the oil. As a result, using thermal management also supports longer maintenance intervals.
Finally, the heating and climate systems of modern vehicles benefit from electronic thermal management. A constant heat power, which is independent from engine load, raises passenger comfort.
The key components of the thermal management system include:
- A cooling fan driven by an electric motor
- One or several electrically actuated proportional-opening water valves that replace the traditional thermostat valves
- A primary water pump, driven by a 14-volt or 42-volt electrical power supply.
All the cooling system components are controlled by the Bosch Motronic engine management system. With temperature sensors, fast and efficient control of the cooling circuit is achieved, regardless of the operating condition of the engine. The monitoring and diagnostics functions of the engine control unit assure a high degree of operating safety for the system, even under extreme conditions.
Stepless speed-variable cooling fans are already in production, while Bosch is developing the other key components. The first application in series-produced passenger vehicles is scheduled for 2004.
Figures from the USA prove the importance of passive safety in rollover accidents: in 1998, half of all fatal single-car accidents were the result of the vehicle overturning. The fact is that rollovers account for around 20 percent of all accidents.
Against this background, Bosch has developed a new concept in rollover sensing which detects at an early stage when a vehicle is about to overturn. This guarantees that safety devices such as seatbelt tensioners, head-protection airbags and safety bars are activated in good time, thus reducing the risk of injury.
The concept is based around the data provided by a yaw rate sensor and two acceleration sensors integrated into the central airbag control unit. The yaw rate sensor uses the gyro principle to determine the speed at which the vehicle is rotating about its longitudinal axis; the acceleration sensors additionally measure the horizontal and vertical acceleration of the vehicle.
The principal software algorithm evaluates the rate of rotation. The data from the acceleration sensors indicate the type of rollover to be expected, as well as providing a plausibility check (ie is a rollover reallyabout to happen?). Even when the rotation rate algorithm detects an imminent rollover, the safety devices are not triggered unless released by a simultaneous positive plausibility check.
The sensors manufactured using silicon surface micromachining. They are resistant to temperature variations as well as being both mechanically robust and offering a long service life. The small, plastic-packaged units are easily accommodated inside compact control devices. They are planned for introduction in production cars later this year.
Bosch has introduced a new generation of rain sensors: the new sensor has an extended range of functions to offer improved visibility and greater comfort - and thus even more safety. In addition, the new model is significantly smaller than its predecessor. It is barely larger than a matchbox and can be inconspicuously mounted on the inside of the windscreen.
The optical principle on which the rain sensor functions remains unchanged. An 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 behavior changes: the more water there is on the surface, the less light is reflected. In the new rain sensor, infrared light is used 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 controls 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 new rain sensor offers further options. For example, it can be used to close windows and sunroofs automatically if the vehicle is parked and it starts to rain. It can even be fitted with an additional light sensor to control the headlights - at night or at the entrance to a tunnel, the lights can be switched on without any intervention by the driver.
It is even conceivable that the signals of the rain sensor could in future be used as ininput in traffic telematic systems, used to automatically report the current weather situation on a certain section of road.
Bosch has developed a new wiper drive unit that uses a precise electronic controller. This concept integrates the electronics in a new type of reversing motor.
Conventional wiper drives have only one direction of rotation, and the direction of wiping is changed mechanically. The new electronically controlled motor reverses its direction of rotation at the turning point of the wiper - therefore, the mechanical components require less space.
The electronic controller ensures a maximum visibility area at all times, irrespective of wiping speed, coefficient of friction or wind force. Through exact adherence to the wiping angle, it is possible to reduce the tolerance distance to the edge of the windsscreen to a minimum and thus to enlarge the swept area. The controller can detect obstacles such as packed snow at the reversing points and automatically reduces the swept area to prevent the system from blocking. The speed of the motor is reduced before reversal to ensure quiet running.
The electronic speed controller is also very practical in conjunction with a rain sensor: depending on the quantity of water on the windshield, the drive unit can be operated at a continuously variable wiping speed.
The so-called extended parking position is available as an additional function: this means that when the wipers are switched off, the wiper arms are parked under the trailing edge of the bonnet. This improves the aerodynamics of the vehicle. Driving noise is reduced and the driver's field of vision is enlarged. At the same time, the risk of injury is reduced in the event of accidents with pedestrians and two-wheeled traffic.
The electronically controlled wiper motor also allows the use of two-motor wiper systems. Each wiper arm is moved by its own drive unit, and the electronic controller is responsible for the coordination of the movements. Since this system requires no connecting rods, it offers further advantages: reduced space requirements and significantly lower weight.