What are the structural forms of throttle position sensor?

An engine is a machine that can convert other forms of energy into mechanical energy, including internal combustion engines (gasoline engines, etc. ), external combustion engine (Stirling engine, steam engine, etc. ), motor, etc. For example, internal combustion engines usually convert chemical energy into mechanical energy. The engine is suitable for both power generation devices and complete machines (such as gasoline engines and aero-engines) including power devices. The engine was first born in Britain, so the concept of engine also originated in English. Its original meaning refers to "a mechanical device that generates power".

The engine block is the skeleton of the engine and the installation foundation of various mechanisms and systems of the engine.

It is equipped with all main parts inside and outside the engine and bears various loads. Therefore, the car body must have sufficient strength and rigidity. Engine cylinder block is mainly composed of cylinder block, cylinder liner, cylinder head and cylinder gasket.

cylinder block

The cylinder block and upper crankcase of water-cooled engine are often cast into a whole, which is called cylinder block-crankcase or cylinder block. The cylinder block is usually made of gray cast iron. The cylindrical cavity in the upper part of the cylinder block is called the cylinder, the lower part is the crankcase supporting the crankshaft, and its inner cavity is the space for the crankshaft to move. Many reinforcing ribs, cooling water jackets and lubricating oil passages are cast in the cylinder block.

The cylinder block should have sufficient strength and rigidity. According to the different installation plane positions of the cylinder block and the oil pan, the cylinder block is usually divided into the following three forms.

1. General cylinder block: characterized in that the installation plane of oil pan is at the same height as the rotation center of crankshaft. The advantages of this cylinder block are small height, light weight, compact structure, convenient processing and convenient disassembly and assembly of crankshaft; But its disadvantages are poor rigidity and strength.

2. Gantry cylinder block: characterized in that the installation plane of oil pan is lower than the rotation center of crankshaft.

Its advantages are good strength and rigidity, and it can bear large mechanical load. But its disadvantages are poor manufacturability, heavy structure and difficult processing.

3. Tunnel cylinder block: The main bearing hole of the crankshaft of this type of cylinder block is integral with rolling bearings, and the main bearing hole is larger, and the crankshaft is loaded from the back of the cylinder block. Its advantages are compact structure, good rigidity and strength, but its disadvantages are high machining accuracy, poor manufacturability and inconvenient disassembly and assembly of crankshaft.

In order to make the inner surface of the cylinder work normally at high temperature, it is necessary to properly cool the cylinder and cylinder head. There are two cooling methods, one is water cooling and the other is air cooling. Cooling water jackets are processed around the cylinder and cylinder head of water-cooled engine, and the cylinder block and cylinder head are communicated with each other. The cooling water continuously circulates in the water jacket, taking away some heat and cooling the cylinder and cylinder head.

crank case

The lower part of the cylinder used to install the crankshaft is called crankcase, which is divided into upper crankcase and lower crankcase. The upper crankcase is integrated with the cylinder block, and the lower crankcase is used to store lubricating oil and seal the upper crankcase, so it is also called oil pan diagram. The oil pan bears little force and is generally stamped from thin steel plate. Its shape depends on the overall layout of the engine and the oil capacity. An oil stabilizing baffle is installed in the oil pan to prevent the oil level from fluctuating too much when the car bumps. There is also an oil drain plug at the bottom of the oil pan. A permanent magnet is usually installed on the oil drain plug to absorb the metal chips in the lubricating oil and reduce the wear of the engine. The gasket is installed between the joint surfaces of the upper crankcase and the lower crankcase to prevent the lubricating oil from leaking.

cylinder head

The cylinder head is installed on the cylinder block to seal the cylinder from the upper part to form a combustion chamber. It is often in contact with high temperature and high pressure gas, so it bears great thermal load and mechanical load. A cooling water jacket is arranged in the cylinder head of the water-cooled engine, and the cooling water hole at the lower end face of the cylinder head is communicated with the cooling water hole of the cylinder block. Circulating water is used to cool high-temperature components such as combustion chambers.

The cylinder head is also equipped with intake and exhaust valve seats, valve guide holes for installing intake and exhaust valves, and intake and exhaust passages. The cylinder head of gasoline engine has holes for installing spark plugs, and the cylinder head of diesel engine has holes for installing fuel injectors. There are also camshaft bearing holes on the cylinder head of overhead camshaft engines for installing camshafts.

Generally, the cylinder head is made of gray cast iron or alloy cast iron, and the aluminum alloy has good thermal conductivity, which is conducive to improving the compression ratio, so the use of aluminum alloy cylinder heads is increasing in recent years.

The cylinder head is an integral part of the combustion chamber, and the shape of the combustion chamber has a great influence on the work of the engine. Because of the different combustion modes of gasoline engine and diesel engine, the parts of cylinder head that make up the combustion chamber are also very different. The combustion chamber of gasoline engine is mainly on the cylinder head, and the combustion chamber of diesel engine is mainly in the pit at the top of piston. Only the combustion chamber of gasoline engine is introduced here, and the combustion chamber of diesel engine is introduced in the diesel supply system.

Three common types of combustion chambers in gasoline engines.

1) hemispherical combustion chamber

The hemispherical combustion chamber is compact in structure, and the spark plug is arranged in the center of the combustion chamber, which has short flame stroke, high combustion rate, low heat dissipation and high thermal efficiency. The structure of this combustion chamber also allows the valves to be arranged in two rows, and the diameter of the air inlet is larger, so the charging efficiency is higher. Although the valve train has become more complicated, it is beneficial to exhaust purification and is widely used in automobile engines.

2) Wedge combustion chamber

The wedge-shaped combustion chamber has simple and compact structure, small heat dissipation area and small heat loss, which can ensure the mixture to form a good vortex motion in the compression stroke, which is beneficial to improve the mixing quality of the mixture, with small intake resistance and improved charging efficiency. The valves are arranged in a row, which makes the valve train simple, but the spark plug is placed at the height of the wedge-shaped combustion chamber, and the flame propagation distance is longer. This type of combustion chamber is used in Cherokee automobile engines.

3) Basin-shaped combustion chamber

The pot-shaped combustion chamber has good cylinder head manufacturability and low manufacturing cost, but the intake and exhaust effect is worse than that of the hemispherical combustion chamber because the valve diameter is easily limited. Jetta engine and Audi engine use basin combustion chamber.

Cover pad sheet

The cylinder gasket is installed between the cylinder head and the cylinder block, and its function is to ensure the sealing of the contact surface between the cylinder head and the cylinder block and prevent air leakage, water leakage and oil leakage.

The material of the cylinder gasket should have certain elasticity, which can compensate the unevenness of the joint surface and ensure sealing. At the same time, it should have good heat resistance and pressure resistance, and it will not burn or deform under high temperature and high pressure. At present, the cylinder gasket with copper cotton structure is widely used. Because there are three layers of copper skin at the flanging of copper skin-cotton cylinder pad, it is not easy to deform when pressed compared with asbestos. Some engines also use cylinder pads made of asbestos with woven steel mesh or perforated steel plate as the skeleton and asbestos and rubber adhesive pressed on both sides.

When installing the cylinder gasket, first check the quality and integrity of the cylinder gasket, and all the holes in the cylinder gasket should be aligned with the holes in the cylinder block. Secondly, the cylinder head bolts should be installed in strict accordance with the requirements of the manual. When tightening the cylinder head bolts, they must be expanded symmetrically from the center to the periphery for 2 ~ 3 times, and finally tightened to the specified torque.

Top valve

The camshaft layout of the engine is divided into OHC (overhead camshaft) and OHV (bottom camshaft). At present, Japanese and European automobile manufacturers prefer the design of overhead camshaft; The bottom camshaft is usually only visible on American cars.

OHC (Overhead Camshaft), after development, is now divided into SOHC (single overhead camshaft) and DOHC (Double Overhead Camshaft). Single overhead camshaft relies on camshaft to control the opening and closing of intake valve and exhaust valve. Generally speaking, the single top is designed with a two-valve engine. Because the intake and exhaust efficiency of two-valve engine is lower than that of multi-valve engine, the angular arrangement between valves is limited. Double overhead camshafts can optimize these problems, because one camshaft only controls one group of valves (intake valve or exhaust valve), eliminating the rocker arm of the valve and simplifying the transmission mechanism between the camshaft and the valve. Generally speaking, the double overhead camshaft has fewer transmission parts and high intake and exhaust efficiency, which is more suitable for the dynamic performance of the engine at high speed. For Japanese and European manufacturers who pursue high power, the overhead design of camshaft is of course the most suitable.

The design of the bottom camshaft engine is generally characterized by large displacement, low speed and high torque output. Because the bottom camshaft is driven by the crankshaft, and then the cam is connected with the valve rocker arm through a metal rod, that is, the cam lifts the connecting rod, and the connecting rod pushes the rocker arm to open and close the engine valve. Therefore, if the speed is too high, the ejector rod will be broken due to excessive pressure. However, this design with ejector pin also has its advantages, such as simple structure, high reliability, heavy engine center and low cost. Because the engine speed is low and torque performance is emphasized, the design of the bottom camshaft is enough to meet this demand.

Because these two designs have different biases, the former is for maximum power and the latter is for large torque. We know that the speed of a car is fast, the traction is large, it depends on torque, and the highest speed depends on power. There is also a simple formula: power = speed x torque. The simplest way to increase engine power when naturally inhaling is to increase the speed. The higher the speed, the higher the power naturally.

Knock sensor

When the engine is working, the engine will knock due to the influence of excessive ignition advance time (ignition advance angle), engine load, temperature, fuel quality and other factors. When knocking happens, because the gas burns before the piston moves to the top dead center, it will produce noise and reduce the power of the engine, and it will damage the mechanical parts of the engine in the worst case. In order to prevent the occurrence of knocking, the knock sensor is an essential component, so that the ignition advance time can be adjusted by the electronic control system.

When the engine knocks, the knock sensor converts the mechanical vibration of the engine into signal voltage and sends it to ECU. According to the pre-stored ignition data, ECU calculates and corrects the ignition advance angle in time to adjust the ignition timing and prevent knocking.

Platinum spark plug

There are many kinds of spark plugs, the main materials are: nickel alloy, platinum and so on. These materials themselves have good electrical conductivity. The heat dissipation forms of cremation plugs are cold spark plugs and hot spark plugs, and the electrode structures of spark plugs are mainly unipolar, bipolar and quadrupole. In order to improve the ignition performance of vehicles, many people will think of replacing their unipolar spark plugs with multipolar ones or replacing their nickel alloy spark plugs with platinum ones.

Spark plug consists of insulator and metal shell. The metal shell is threaded and screwed on the engine cylinder. There is a center electrode in the metal shell, which is insulated from the metal shell by insulating material. There is a connecting nut at the upper end of the center electrode for connecting the high-voltage line from the distributor, and a grounding electrode is welded under the metal shell. There is a small gap between the center electrode and the grounding electrode, and the air between the two electrodes is broken down by pulse high voltage electricity. Generate sparks to ignite the mixture to do work. Because the spark plug works in the harsh environment of high temperature and high pressure, it requires very high materials and manufacturing technology. However, most economical cars often use nickel alloy spark plugs, and platinum spark plugs or platinum spark plugs are only used in mid-to high-end cars.

Overhead camshaft

Camshaft is called overhead camshaft in English, or OHC for short. There are three installation positions of camshaft in general engines: lower, middle and upper. Overhead camshaft is to put the camshaft in the cylinder head and above the combustion chamber, and directly drive the rocker arm and valve without a long push rod. Compared with the pushrod engine with the same number of valves (i.e., overhead valve structure), the overhead camshaft structure requires far fewer parts to reciprocate, thus greatly simplifying the valve train structure, significantly reducing the engine weight, improving the transmission efficiency and reducing the working noise. Although the overhead camshaft makes the structure of the engine more complicated, it brings better comprehensive performance of the engine (especially the significant improvement of ride comfort) and a more compact engine structure, which makes the engine manufacturers widely adopt this design in their products soon. The driving modes of overhead camshaft and overhead valve structure are not necessarily different. Power can be transmitted to overhead camshaft through timing belt, chain and even gear set.

Distributor block

In the ignition system of gasoline engine, high voltage current is delivered to the spark plugs of each cylinder at regular intervals according to the ignition sequence of each cylinder. In the battery ignition system, the distributor and igniter are usually installed on the same shaft and driven by the camshaft. At the same time, it also has an ignition advance angle adjusting device and a capacitor.

The contact of the igniter power-off arm is closed with a spring leaf, and the camshaft drives the power-off cam to open the contact. The opening clearance is about 0.30 ~ 0.45 mm. The number of protrusions of the power closing cam is the same as that of the cylinders. When the contact is opened, the distributor arm of the distributor is just aligned with the corresponding side electrode, and the induced high-voltage electricity is transmitted from the secondary coil to the spark plug of the corresponding cylinder through the distributor arm, the side electrode and the high-voltage line.

Cylinder pipeline

Cylinder pipeline is an important part of the traditional ignition system, and it is the medium for the ignition coil to transfer energy to the spark plug. Cylinder pipeline is roughly divided into four parts. The first one is conductive material, the second one is insulating rubber, the third one is ignition coil connector, and the fourth one is spark plug connector (some cylinder pipes are wrapped with a layer of heat insulation material to prevent burning out).

The number of cylinder lines is the same as that of engine cylinders. With the development of science and technology, many cars now have no cylinder line. The cylinder line and ignition coil are combined into one, and each cylinder has one ignition coil, which greatly reduces the volume and provides more convenient conditions for each cylinder to ignite independently.

piston

The engine is like the "heart" of a car, and the piston can be understood as the "center" of the engine. In addition to being in a harsh working environment, it is also the busiest one in the engine, constantly reciprocating from bottom dead center to top dead center and from top dead center to bottom dead center, inhaling, compressing, doing work, exhausting and so on. The piston is hollow inside, more like a hat, and the round holes at both ends are connected by piston pins.

There are three wrinkles on the skirt of each piston, so as to install two gas rings and an oil ring, with the gas ring at the top. When assembling, it is necessary to stagger the openings of the two gas rings to play a sealing role. The function of the oil ring is mainly to scrape off the excess lubricating oil splashed on the cylinder wall and scrape the lubricating oil evenly. At present, the piston ring materials widely used mainly include high-quality gray cast iron, nodular cast iron and alloy cast iron.

Spark plug

The discharge phenomenon between electrodes produces sparks, and gasoline engines generate electricity through timely combustion of fuel and mixture. As a fuel, gasoline is difficult to spontaneously ignite even in a high temperature environment, and it needs to be ignited with a "fire" to make it burn in time. The spark ignition mentioned here is the function of "spark plug". The overall performance of the engine depends entirely on whether the spark plug flashes. We often compare the engine to "the heart of the car", but we can compare the spark plug to "the heart of the engine".

Machine filter

The full name of mechanical filter is oil filter. Its function is to remove dust, metal particles, carbon deposits, soot particles and other impurities in engine oil and protect the engine.

During the operation of the engine, metal chips, dust, carbon deposits oxidized at high temperature, colloid deposits and water are constantly mixed into the lubricating oil. The function of oil filter is to filter out these mechanical impurities and colloids, keep the lubricating oil clean and prolong its service life. The oil filter should have strong filtering ability, small circulating resistance and long service life.

The function of the oil cooler is to cool the lubricating oil and keep the oil temperature within the normal working range. It is necessary to install an oil cooler on a high-power intensified engine due to the large thermal load. When the engine is running, because the viscosity of engine oil becomes thinner with the increase of temperature, the lubricating ability decreases. Therefore, some engines are equipped with oil coolers, whose function is to reduce the oil temperature and keep the lubricating oil at a certain viscosity. The oil cooler is arranged in the circulating oil circuit of the lubrication system.

throttle valve

Throttle is a controllable valve that controls air to enter the engine. After the air enters the intake pipe, it will be mixed with gasoline to form a combustible mixture, which will be burned. It connects the air filter and the engine block, and is called the throat of the automobile engine. There are two kinds of throttles: traditional cable throttle and electronic throttle. The traditional engine throttle control mechanism works by pulling a cable (soft steel wire) or a pull rod. One end of the cable is connected with the accelerator pedal, and the other end is connected with the accelerator linkage plate. The electronic throttle mainly uses the throttle position sensor to control the throttle opening according to the energy required by the engine, so as to adjust the intake air.

thermostat

The thermostat automatically adjusts the amount of water entering the radiator according to the temperature of cooling water, changing the circulating range of water, thus adjusting the cooling capacity of the cooling system and ensuring the engine to work in a suitable temperature range. The thermostat must be kept in good technical condition, otherwise it will seriously affect the normal work of the engine. If the thermostat main valve is opened too late, it will lead to overheating of the engine; If the main valve is opened too early, the engine warm-up time will be prolonged and the engine temperature will be too low.

cooling system

The main function of the cooling system is to dissipate part of the heat absorbed by the heated parts in time to ensure that the engine works at the most suitable temperature. The cooling system can be divided into air cooling and water cooling according to different cooling media. If the heat of high-temperature parts in the engine is directly radiated to the atmosphere, this cooling device is called an air cooling system.

The device that transfers this heat to cooling water first and then diffuses into the atmosphere for cooling is called water cooling system. At present, water cooling system is widely used in automobile engines because of its uniform cooling, good effect and low noise of engine operation.

fuel nozzle

The fuel injector is actually a simple solenoid valve. When the electromagnetic coil is energized, the suction force is generated, the needle valve is sucked up, the nozzle hole is opened, and the fuel is ejected at high speed through the annular gap between the shaft pin at the head of the needle valve and the nozzle hole, forming mist, which is beneficial to full combustion.

The injector itself is a normally closed valve. When the ECU sends the fuel injection instruction, its voltage signal will make the current flow through the coil in the fuel injector, generate a magnetic field to attract the valve needle, open the valve, and make the fuel spray from the fuel injection hole. The biggest advantage of jet fuel supply is that the control of fuel supply is very accurate, so that the engine can have the correct air-fuel ratio in any state, which not only keeps the engine running smoothly, but also conforms to the norms of environmental protection laws and regulations.

balance shaft

The balance shaft makes the engine work more smoothly. Balanced axle technology is a simple and practical engine technology, which can effectively slow down the vibration of the whole vehicle and improve the driving comfort.

When the engine is in working condition, the movement speed of the piston is fast and uneven. When the piston is at the top and bottom dead center, its speed is zero, but it reaches the highest when it is in the middle of the top and bottom dead center. Because the piston makes repeated high-speed linear motion in the cylinder, it will inevitably produce greater inertia force on the piston, piston pin and connecting rod. Although the counterweight on the connecting rod can effectively balance these inertial forces, only a part of the moving mass participates in linear motion and the other part participates in rotation. Therefore, except for the top and bottom dead center positions, other inertial forces can't completely reach the equilibrium state, and the engine will vibrate at this time.

Starting enrichment system

In order to make the stationary engine enter the working state, the engine crankshaft must be rotated by external force to make the piston move up and down, and the combustible mixture is sucked into the cylinder, and then enters the subsequent working cycle in turn. The external force system is the starting system.

At present, almost all automobile engines are started by electric starters. When the driving gear on the motor shaft meshes with the ring teeth on the circumference of the flywheel of the engine, the electromagnetic torque generated when the motor rotates is transmitted to the crankshaft of the engine through the flywheel, so that the engine can be started. Electric starter is called starter for short. It uses storage battery as power supply, with simple structure, convenient operation and fast and reliable start.

blowhole

The valve is responsible for inputting fuel to the engine and discharging exhaust gas. In the traditional engine, each cylinder has only one intake valve and one exhaust valve. This design has the advantages of simple structure, low cost, convenient maintenance and good low speed performance. The disadvantage is that the power is difficult to improve, especially at high speed, the charging efficiency is low and the performance is weak. In order to improve the efficiency of intake and exhaust, multi-valve technology is often used. It is common that each cylinder is equipped with four valves (there are also three or five valves in a single cylinder, and the principle is the same, such as the engine of Audi A6). One of the four cylinders is 16 valve, and "16V" often seen in automobile data is * * 65438+. This multi-valve structure is easy to form a compact combustion chamber, and the fuel injector is arranged in the center, so that the fuel-air mixture burns faster and more evenly, and the weight and opening of each valve can be reduced appropriately, so that the valves can be opened or closed faster.

Crank train

Crank-connecting rod mechanism is the main moving part of engine to realize working cycle and complete energy conversion. The main parts of crank-connecting rod mechanism can be divided into three groups: body group, piston connecting rod group and crankshaft flywheel group.

The engine has four strokes: intake, compression, work and exhaust. In the power stroke, the crank-connecting rod mechanism converts the reciprocating motion of the piston into the rotating motion of the crankshaft and outputs power to the outside. In the other three strokes, due to inertia, the rotary motion of the crankshaft is converted into reciprocating linear motion of the piston. Generally speaking, the crank-connecting rod mechanism is the mechanism that the engine generates and transmits power. Through it, the thermal energy released by fuel combustion is converted into mechanical energy.

boss rod

Crankshaft is the main rotating mechanism of engine.

It is responsible for converting the up-and-down reciprocating motion of the piston into its own circular motion, and what we usually call the engine speed is the speed of the crankshaft.

Due to unclean engine oil and uneven stress on the journal, the crankshaft will wear the contact surface between the big end of the connecting rod and the journal. If there are large particles of hard impurities in the oil, there is also the danger of scratching the surface of the journal. If the wear is serious, it is likely to affect the stroke length of the piston moving up and down, reduce the combustion efficiency and naturally reduce the power output. In addition, the crankshaft may burn the surface of the journal due to insufficient lubrication or too thin oil, which will seriously affect the reciprocating motion of the piston. Therefore, it is necessary to use lubricating oil with proper viscosity and ensure the cleanliness of the oil.

lubrication system

When the engine is working, all moving parts act on another part with a certain force, resulting in high-speed relative motion. With relative motion, the surface of parts will inevitably produce friction and accelerate wear. Therefore, in order to reduce wear, reduce friction resistance and prolong service life, the engine must have a lubrication system.

The function of lubrication system is to continuously deliver enough clean engine oil with proper temperature to the friction surfaces of transmission parts when the engine is working, and form oil film between the friction surfaces to realize liquid friction, thus reducing friction resistance, power consumption and parts wear, and improving the reliability and durability of the engine. There are three kinds of lubrication methods: pressure lubrication, splash lubrication and grease lubrication.

air cooler

Generally, only turbocharged cars can see the intercooler. Because the intercooler is actually a supporting component of turbocharging, its function is to improve the air exchange efficiency of the engine. For supercharged engines, intercooler is an important part of supercharging system. Whether it is a supercharged engine or a turbocharged engine, it is necessary to install an intercooler between the supercharger and the engine intake manifold. Because this radiator is located between the engine and the supercharger, it is also called intercooler.