In recent years, thanks to technological innovation, pressure sensors have achieved better vehicle driving.
If we don’t use pressure sensors in modern cars, our driving experience will be much worse.
In fact, most critical systems in vehicles rely on pressure sensors to measure and monitor key parameters to improve our driving experience, improve safety and reduce pollution.
In recent years, thanks to technological innovation, pressure sensors have achieved better vehicle driving.
1. Detect the early failure of hydraulic brake
The feeling of easy braking that you are used to, and the responsiveness of your pedals, are made up of complex components, including pressure sensors. The in car system detects the pressure you put on the pedal and amplifies it to make your effort more effective.
These systems use absolute pressure sensors to monitor the vacuum maintained in two separate chambers in the brake servo system.
Under normal operating conditions, depressing the brake pedal causes its atmospheric pressure to flow into one of the chambers. This increases the pressure on the diaphragm, which in turn increases the force applied to the master cylinder. After the brake pedal is released, the vacuum can be recovered by using a vacuum source, which can be extracted from a special pump or manifold.
If the vacuum in one or both chambers cannot be maintained or restored, a fault condition will occur. The absolute pressure sensor is used to monitor the pressure in the chamber and to alert the driver or the engine management system when the pressure in the chamber is not enough to be effective.
If there is no way to measure the pressure in the compartment, the system may fail without the driver’s knowledge and result in a sudden loss of braking efficiency, which is exactly when it is most needed.
Manufacturers use manifold absolute pressure (map) sensors in this application, which are available in surface mount packages and are capable of measuring pressures from 10 to 150 kPa (kPa) with an accuracy of 1% over the entire range.
2. Optimize the fuel mixture to adapt to the air pressure
Making the internal combustion engine as efficient as possible has a lot to do with making the fuel mixture just right for the current conditions. Of course, this includes the actual speed and the desired speed, but also the adjustment of the current engine speed, engine and manifold temperature.
However, it is not just the air temperature that needs to be measured; air pressure is also an important factor in adjusting the fuel mixture and ignition timing. Here, the absolute pressure sensor is used to provide the required information to the engine management system (EMS).
These sensors are used to measure the pressure inside the manifold, and since air is drawn in from the surrounding area, the external air pressure is also used to measure. Atmospheric pressure has a great influence on the fuel mixture, so by measuring the air pressure and compensating for changes, the EMS can adjust the engine to achieve optimum efficiency, whether the car is at sea level or above 20000 feet above sea level.
Map sensors are also used here, but in this case they need to be able to measure pressures up to 400 kPa.
3. Automatic cleaning of exhaust filter
Diesel is one of the most common fuel forms for vehicles (especially large transport, construction and agricultural vehicles). Pressure sensor is very important to make diesel engine as clean as possible.
The particulate filter inside the engine is used to capture soot and other particles present in the exhaust gas before it can be discharged into the atmosphere. Then you need to clean the filter by burning off the particles.
This can be achieved by using an active system that heats the filter to the temperature of the soot combustion, or by using a passive system of the catalyst.
In the active system (see figure below), the pressure sensor is used to measure the exhaust gas pressure. When the pressure on the diesel particulate filter (DPF) reaches a threshold, the cleaning process is triggered. This can be measured by using two absolute pressure sensors or differential pressure sensors.
4. Ensure that the catalytic converter is sealed
In the passive system, the particles in the exhaust gas are destroyed by catalytic converter. In this case, a pressure sensor will be used to ensure that the system works effectively even at lower engine temperatures.
Catalytic converters need to be heated up quickly to work effectively. Normally, it needs to be above 300 ° C, but when the engine is cold, so is the catalytic converter. Supplying air into the exhaust manifold triggers an exothermic process, which helps to raise the temperature of the catalytic converter.
When the temperature is reached, the pump for the auxiliary air valve is shut down and the system is sealed with the valve. The use of an absolute pressure sensor located between the pump and the valve ensures that the valve closes properly and protects the rest of the system from harmful exhaust gases.
5. Monitoring exhaust gas recirculation
Automobile manufacturers are faced with the pressure to reduce the overall emission of the engine, one of the feasible methods is to let partial exhaust gas recirculation.
This technology is effective in both gasoline and diesel engines. It reduces the temperature in the combustion chamber, thus reducing the generation and emission of nitrogen oxides.
Controlling the engine gas recirculation (EGR) process involves the use of an absolute pressure sensor to monitor the pressure at the valve. Without this control, the system may become unstable, resulting in excessive or insufficient gas recirculation.
Sensor manufacturers have been working to improve their manufacturing processes to provide pressure sensors that are better able to withstand the harsh environments that exist in such applications.
6. Check the pressure of critical fluid
The most common use of electronic pressure sensors may be to measure the pressure of key vehicle fluids, such as engine oil, transmission and transmission oil, as well as hydraulic oil in brake, cooling and fuel systems.
Some of the structures of electronic pressure sensors are exposed to the fluid being measured, so they must be robust and resilient. Typically, it will use piezoresistive effect, which detects changes in material resistance due to deflection caused by the pressure exerted by the fluid.
Pressure sensors for this application will normally be able to withstand extreme environments, sealed to ip6k9k (dust proof, high pressure steam / jet cleaning) and be capable of measuring pressures from 0bar to 600bar. Working range from – 40 ° C to + 125 ° C
7. Prevent the door from pinching fingers
Electric door closing in a car is a great innovation, but if you (or someone smaller) enters between the door and the door frame at the wrong time, there may be a problem, but the pressure sensor will help.
Any obstacle can be detected quickly and reliably by using a relative pressure sensor connected to the sealing hose and installed around the edge of the door frame.
Any compression of the hose will cause the internal pressure to rise, and the pressure sensor will immediately receive the pressure and transmit the pressure to the safety system of the vehicle. If the door is electrically activated, it stops closing; the same technique applies to windows.
Sensors designed for this emerging application usually conform to the PSI 5 (peripheral sensor interface 5) protocol, which was originally developed as a reliable interface between the airbag sensor and ECU, and uses twisted pair cables to transmit power and data. Pressure sensors designed for this safety critical application have an operating range of about 50 to 110 kPa.
8. Detect leaking steam
Part of the responsibility of car manufacturers is to protect the environment from potentially harmful vapors generated by internal combustion engines.
New gasoline vehicles now include a system to prevent these vapors from escaping from the sealed fuel system, usually by delivering steam to an evaporation system containing activated carbon. Air is mixed with steam so that they can be safely burned by the engine. Known as evaporative emission control (evap) systems, they are rigorously tested.
The absolute pressure sensor monitors the integrity of the sealing system at any time and alerts the vehicle (and driver) in case of leakage. Without a pressure sensor monitoring system, steam may escape in the event of a leak, not only releasing harmful vapor into the atmosphere, but also exposing the manufacturer to prosecution for non-compliance with regional regulations.
The air pressure sensor may be located in the fuel tank and can provide analog or digital output. The measured pressure range is about 40 to 115 kPa with an accuracy of 1.5 kPa or higher.
9 activate the airbag faster
Car manufacturers are constantly innovating to improve passenger safety. Modern cars don’t just have airbags on the dashboard, they all have airbags inside, including airbags on doors, to protect passengers in the event of a side impact.
The use of a relative pressure sensor can detect sudden pressure changes in the door cavity during a side impact, which is usually much faster than using other technologies. Using the right sensors in this app allows the car’s safety system to deploy the airbag in a few percent of a second, usually much faster than the front airbag system. This is necessary as the proximity of the door to the passenger significantly reduces the available reaction time compared to the instrument panel airbag system. In this case, the millisecond count.
10. Release the pedestrian airbag
In the unfortunate event of a car hitting a pedestrian, a recent innovation is the use of pressure sensors to deploy a safety mechanism (an active hood system) designed to reduce the impact on pedestrians when a pedestrian falls on the hood.
By installing a relative pressure sensor on the front bumper, any deformation of the bumper can be detected immediately. If this happens, the car’s safety system activates the reserve of compressed air in the engine compartment, pushing the hood up and towards the front of the car.
The raised hood forms a barrier between pedestrians and the harder parts of the engine, reducing the potential impact severity.
Some cars also deploy an airbag from the engine compartment to cover the windshield to further protect pedestrians.
Pressure sensors play a vital role in all these innovations, making driving cleaner, smoother and safer.
At present, the automotive market is one of the largest markets for pressure sensors and is likely to remain so due to the diversity of use methods.
From a range of safety features to reducing pollution and optimizing engine efficiency, pressure sensors are the core of the modern driving experience and are essential to the modern driving experience.