Driving would be an entirely different experience without all the pressure sensors used throughout the modern vehicle, helping to manage everything from braking to electric windows, exhaust emissions to power steering. In fact, most of the critical systems in a vehicle rely on pressure sensors to measure and monitor key parameters, which has become central factor in making our roads safer, lowering pollution and improving our driving experience.
But how exactly do pressure sensors enable better vehicles, and what do manufacturers need to know in order to do that?
- Detecting early faults in hydraulic brakes
That easy braking sensation you’re used to and the responsiveness of the pedal beneath your foot is down to a complex blend of components, including pressure sensors. In-car systems detect the pressure you’re applying to the pedal then amplify it to make your efforts more effective. These systems use an absolute pressure sensor to monitor the vacuum maintained in two separate chambers inside the brake servo. Under normal operating conditions, when the brake pedal is depressed it allows atmospheric pressure to flow into one of the chambers. This increases the pressure on a diaphragm, which, in turn, increases the effort applied to the master cylinder. When the brake pedal is released the vacuum is restored using a vacuum source, which may be via a dedicated pump or drawn from the manifold.
- Optimizeing the fuel mix to match the air pressure
Making internal combustion engines as efficient as possible has much to do with getting the fuel mixture just right for the prevailing conditions. This includes the actual and desired speed, of course, but also includes making adjustments for the current engine speed, and the engine and manifold temperature. It isn’t just the air temperature that needs to be measured though; the air pressure is also an important factor when adjusting the fuel mixture and ignition timing.
- Cleaning exhaust filters automatically
Diesel fuel is one of the most common forms of fuel for vehicles, especially large haulage, construction and agricultural vehicles, and pressure sensors are vital in making diesel engines as clean as possible. Particulate filters inside the engine are used to capture the soot and other particles present in the exhaust gas before it can escape into the atmosphere. The filters then need cleaning, which is done by burning off the particulates. This can either be achieved using an active system which heats the filter to a temperature where the soot combusts, or a passive system using.
- Ensuring the catalytic converter is sealed
In a passive system, particulates in exhaust gases are destroyed using a catalytic converter. In this case a pressure sensor is used to make sure the system can work efficiently even at low engine temperatures. The catalytic converter needs to get up to temperature quickly in order to work efficiently. Typically, it needs to reach in excess of 300°C but when the engine is cold so too is the catalytic converter. Feeding air into the exhaust manifold triggers an exothermic process, which helps raise the temperature of the catalytic converter.