In recent years, thanks to technological innovation, pressure sensors have achieved better vehicle driving.
If pressure sensors are not used in modern cars, our driving experience will be much worse.
In fact, most of the key 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 early failures of hydraulic brakes
The easy braking sensation you are used to, and the ability to react to the pedals under your feet, are composed of complex components, including pressure sensors. The in-car system detects the pressure you exert on the pedals and then amplifies it to make your efforts 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 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 releasing the brake pedal, a vacuum source can be used to restore the vacuum, which can be pumped out by a dedicated pump or from a 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 alert the driver or the engine management system when the pressure in the chamber is insufficient to be effective.
If there is no way to measure the pressure in the cabin, then the system may fail without the driver’s knowledge and cause the sudden loss of braking efficiency, which is when it is most needed.
Manufacturers use Manifold Absolute Pressure (MAP) sensors in this application, which are available in surface mount packages and can measure pressures in the range of 10 to 150 kPa (kilopascals) with an accuracy of 1% across the range.
2. Optimize the fuel mixture to suit the air pressure
Making the efficiency of the internal combustion engine as high as possible has a lot to do with making the fuel mixture fit the current conditions. Of course, this includes the actual speed and the desired speed, but it also includes adjustments to the current engine speed, engine and manifold temperature.
However, it is not only the air temperature that needs to be measured; the air pressure is also an important factor when 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 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 obtain the best efficiency, regardless of whether the car is on sea level or above 20,000 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. Automatically clean exhaust filter
Diesel is one of the most common forms of fuel for vehicles (especially large-scale transportation, construction and agricultural vehicles), and pressure sensors are essential to make diesel engines 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 the filter needs to be cleaned by burning off the particles.
This can be achieved by using an active system that heats the filter to the temperature at which soot is burned, or a passive system that uses a catalyst.
In an active system (see figure below), a pressure sensor is used to measure 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 the catalytic converter is sealed
In a passive system, the particulate matter in the exhaust gas is destroyed using a catalytic converter. In this case, a pressure sensor will be used to ensure that the system can work effectively even at lower engine temperatures.
Catalytic converters need to heat up quickly to work effectively. Usually, it needs to reach more than 300°C, but when the engine is cold, so does the catalytic converter. Supplying air to the exhaust manifold triggers an exothermic process, which helps increase the temperature of the catalytic converter.
When the temperature is reached, the auxiliary air valve pump is turned off 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 correctly and protects the rest of the system from harmful exhaust gases.
5. Monitor exhaust gas recirculation
Automakers are facing pressure to reduce overall engine emissions, and one possible way is to recirculate part of the exhaust gas.
This technology is effective in both gasoline and diesel engines. It reduces the temperature in the combustion chamber, thereby reducing the production and emissions of nitrogen oxides.
Controlling the engine gas recirculation (EGR) process involves the use of absolute pressure sensors to monitor the pressure at the valve. Without this control, the system may become unstable, causing too much or too little gas recirculation.
Sensor manufacturers have been working hard to improve their production processes to provide pressure sensors that can better withstand the harsh environments that exist in such applications.
6. Check the pressure of key fluids
The most common use of electronic pressure sensors may be to measure the pressure of key fluids in vehicles, such as engine oil, transmission and transmission oil, and hydraulic oil in the brake system, cooling system, and fuel system.
Part of the structure of electronic pressure sensors will be exposed to the measured fluid, so they must be durable and flexible. Typically, it will use the piezoresistive effect, which detects changes in the resistance of the material due to the deflection caused by the pressure applied by the fluid.
Pressure sensors for this application area will usually be able to withstand extreme environments, and are sealed to IP6k9k (dust-proof, high-pressure steam/jet clean), and can measure pressures from 0 bar to a maximum of 600 bar. The operating temperature range is -40 to +125°C.
7. Prevent fingers from being caught by the door
The electric door closure on a car is a great innovation, but if you (or someone with a smaller body size) enter between the door and the door frame at the wrong time, it may malfunction, but the pressure sensor will help.
Using the relative pressure sensor connected with the sealing hose and installed around the edge of the door frame, any obstacle can be detected quickly and reliably.
Any compression of the hose will cause the internal pressure to rise, and the pressure sensor will immediately receive the pressure and transmit it to the vehicle's safety system. If the door is electrically activated, it will stop closing; the same technique applies to windows.
Sensors designed for this emerging application usually conform to the PSI5 (Peripheral Sensor Interface 5) protocol, which was originally developed as a reliable interface between airbag sensors and ECUs and used twisted-pair cables to transmit power and data. The operating range of pressure sensors designed for this safety-critical application is approximately 50 to 110 kPa.
8. Detect leaking vapor
Part of the responsibility of car manufacturers is to protect the environment from the potentially harmful steam produced 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 the vapor to an evaporation system containing activated carbon. The air is mixed with steam so that they can be burned safely by the engine. Known as evaporative emission control (EVAP) systems, they have undergone rigorous testing.
The absolute pressure sensor monitors the integrity of the sealing system at any time, and alerts the car (and the driver) when a leak occurs. If there is no pressure sensor monitoring system, once a leak occurs, steam may escape, which not only releases harmful steam into the atmosphere, but also exposes the manufacturer to the risk of 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
Automakers are constantly innovating to improve passenger safety. Modern cars not only install airbags on the dashboard, they also have airbags inside, including airbags on the doors, to protect passengers in the event of a side collision.
Using relative pressure sensors can detect sudden pressure changes that occur in the door cavity during a side collision, which is usually much faster than using other technologies. Using the correct sensor in this application allows the car’s safety system to deploy the airbag in a few hundredths of a second, which is usually much faster than the front airbag system. This is necessary because, compared with the dashboard airbag system, the proximity of the door to the passenger can greatly shorten the available reaction time. In this case, milliseconds are counted.
10. Release pedestrian airbags
In the unfortunate incident 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 risk of pedestrians when they fall on the hood. The impact.
By installing a relative pressure sensor on the front bumper of the car, any deformation of the bumper can be detected immediately. If this happens, the car's safety system can activate the compressed air reserve in the engine compartment, thereby pushing the hood upwards and toward the front of the car.
The raised hood creates a barrier between pedestrians and the harder parts of the engine, reducing the severity of potential impacts.
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, so that the driving process is cleaner, smoother and safer.
At present, the automotive market is one of the largest markets for pressure sensors, and due to the diversity of usage methods, this market may continue.
From a series of safety functions 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.
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