With the rapid development of automobile industry, the requirements of fuel economy and emission standards are becoming more and more stringent. More and more systems are applied to automobiles, such as intake/exhaust gas management system, fuel steam management system, brake power assist system, diesel particle filtration system and so on. All of these systems need to determine the state of the system and the next action by the pressure information obtained quickly and accurately by the pressure sensor.
1. Intake/tail gas management system
The automobile engine management system needs to inject the appropriate amount of fuel into the cylinder at the appropriate time, so as to make the fuel burn fully and effectively, achieve the best combustion efficiency and reduce pollution. The engine manager's ECU makes decisions based on a number of sensor signals, such as crankshaft position, camshaft position, air flow, intake manifold temperature, intake manifold pressure, etc. The intake manifold pressure sensor is a pressure sensor working in the absolute pressure mode. The ECU calculates the amount of fuel to be injected according to the pressure signal, so that the optimal air-fuel ratio can be obtained in the combustion process.
To reduce NOx emissions, some vehicles are equipped with EGR(Exhaust Gas Recirculation) systems. The EGR system introduces a small amount of exhaust gas into the intake manifold. Due to the inertia of the exhaust gas, the combustion process is delayed. The combustion rate is slowed down, the maximum combustion temperature is lowered, and the pressure formation process in the combustion chamber is slowed down, thus reducing the generation of nitrogen oxides. Due to high exhaust gas temperatures and the presence of a variety of corrosive substances, vehicles equipped with EGR systems require higher media compatibility for intake manifold pressure sensors.
2. Fuel steam management system
Since the volatilization of fuel oil is one of the main causes of carbon and hydrogen emissions, the regulation of automobile fuel steam is mandatory in some US states. When filling up a car at a gas station, the fuel vapor is released directly into the atmosphere, which is not only environmentally friendly but also a waste of fuel. The oil tank steam of the vehicle equipped with the fuel steam management system enters the activated carbon tank through the pipeline through the separation valve. The activated carbon in the activated carbon tank is porous and has a large surface area, which can absorb a large number of fuel steam molecules. Activated carbon tank is connected to the engine intake manifold, when the engine running in the intake stroke, the piston movement make the intake manifold produces low pressure, low pressure suction in the intake manifold, air pass through activated carbon tank, activated carbon adsorption of fuel tank vapor molecules into engine combustion, make it fully application of activated carbon tank adsorption ability of active carbon restoration. In the fuel steam management system, a micro pressure sensor (gauge pressure mode) is needed to detect whether there is leakage of fuel steam.
3. Brake power system
The vacuum brake booster is the core component of the vacuum assisted servo braking system. It uses the vacuum of the engine intake manifold and the pressure difference of atmosphere to help the brake. When the brake is not pressed down, the chamber diaphragm separator connects the two chambers of the vacuum booster to the intake manifold of the engine through the vacuum check valve. Both chambers are vacuum. When the brake pedal is stepped on, the diaphragm diaphragm of the air chamber moves, the air valve is opened and the vacuum valve is closed. The front chamber of the air chamber is vacuum, and the back chamber is connected with the atmosphere. The pressure difference between the two cavities acts on the diaphragm diaphragm of the chamber, which is equivalent to increasing the braking braking force. The braking force is transmitted to the braking master cylinder through the push rod of the braking master cylinder to realize the braking function.
If the brake power system appears air leakage phenomenon, will cause the pressure difference between the front and back of the air chamber is very small or even disappear when braking, the brake power system failure, resulting in increased braking distance, braking difficulties, etc. In addition, the installation of direct fuel injection system and start-stop system reduces the vacuum degree of the intake manifold, so it is necessary to install a vacuum pump to provide a vacuum source to meet the requirements of the brake power assist system. In both cases, it is necessary to add a pressure sensor to monitor whether the pressure difference between the front and rear chambers is appropriate, to activate the corresponding warning system in case of air leakage, and to notify the ECU to activate the vacuum pump to provide additional vacuum if vacuum is insufficient.
4. Diesel exhaust filter system
Due to the physical characteristics of diesel engines, their exhaust gas in addition to carbon monoxide, hydrocarbons, nitrogen oxides and some small particulate matter, these particulate matter is the main cause of black smoke. In order to meet emissions requirements and reduce environmental pollution, more and more Diesel engines are equipped with a Diesel Particulate Filter (DPF). When the exhaust gas produced by diesel engine combustion passes through the diesel particle filter, the porous system of the filter will capture the particles in it. When the diesel exhaust particles continue to accumulate in the filter, the filter will be saturated or even blocked, so it is necessary to regenerate the filter. A differential pressure sensor is used to detect the pressure difference between the inlet and outlet of the filter. When the pressure difference is higher than the set threshold, the filter is considered to reach saturation. The ECU control increases the engine temperature, and the engine emits high temperature exhaust gas to burn the particles stored in the filter, thus completing the regeneration of the filter. Because the exhaust gas temperature is high and contains a variety of corrosive gases and particles, the issue of medium compatibility needs to be considered.
5. Natural Gas/LPG fueled systems
Due to its relatively cheap price, low exhaust pollution, safety and reliability, and easy vehicle modification, natural gas/liquefied petroleum gas (LPG) is increasingly being used as a fuel in some countries and regions producing natural gas/LPG. A dedicated natural gas/liquefied petroleum gas (LPG) unit is added to form a "dual-fuel vehicle" while retaining the original vehicle fuel supply system. Compressed natural gas/liquefied petroleum gas is stored in a cylinder, and the high-pressure gas in the cylinder is sent to the combustion chamber through a pressure reducing valve and pressure regulator to be fully mixed with air and burned to power the vehicle. The air fuel ratio can be better controlled by monitoring the pressure of the gas and the air in the intake manifold through two pressure sensors, so as to achieve the best combustion state, improve the fuel economy and reduce pollution.
