What is the difference between an electronic thermostat and a mechanical thermostat?

The mechanical thermostat works on the principle of thermal expansion and contraction of paraffin, and controls the opening and closing of the thermostat by the temperature of the coolant. The center of the electronic thermostat is also filled with paraffin, but a heating device is installed inside the paraffin. This heating device is controlled by the electronic control unit ECU. The electronic control unit captures signals based on the engine water temperature sensor and the water temperature sensor on the radiator tank. When these signals reach the values set by the electronic control unit ECU, a heating instruction will be sent to control the heating of the heating device and the heating temperature can be accurately controlled. This is the implementation principle of the electronic thermostat. The electronic thermostat is more advanced than the mechanical thermostat. The main point is that the electronic control unit can dynamically control the heating of the heating device based on the sensor data of various sensors of the engine. That is to say, when the coolant has not reached the melting temperature of the paraffin, the electronic control unit can also control the melting of the paraffin in advance. This control is determined by the engine based on the sensor data of each sensor. The mechanical thermostat cannot achieve this effect. It can only start working after the coolant reaches a certain temperature. The above is the difference between mechanical and electronic thermostats.

How does the thermostat control the flow of coolant?

In the engine cooling system, the element that controls the flow of coolant is called a thermostat. The thermostat is a temperature-controlled valve that can automatically adjust the opening and closing of the valve according to the engine load and the temperature of the coolant to control the flow of the coolant to achieve large and small cycles. In layman’s terms, the thermostat is a three-way valve, one side of which is connected to the engine water outlet, one side is connected to the water inlet of the water pump, and one side is connected to the radiator. It can adjust the direction of the water flow according to the water temperature. When the water temperature is low, the coolant flows downward to achieve a small cycle; when the water temperature is high, the coolant flows upward to achieve a large cycle. It is usually installed in the engine water circuit to control the engine temperature. The engine mainly uses paraffin thermostats, which use the thermal expansion and contraction characteristics of paraffin to open and close the valve. Paraffin thermostats are divided into two categories: mechanical and electronic. Their implementation principles are the same, but the difference lies in the different trigger mechanisms of paraffin heating. First, let’s look at the mechanical thermostat. Let’s look at its components. It is a container, and the substance inside is paraffin. At low temperatures, paraffin becomes solid. Under the action of the spring, the thermostat valve closes the coolant channel between the engine and the radiator. The coolant returns to the engine through the water pump for a small cycle in the engine. At high temperatures, the paraffin melts and expands and gradually becomes liquid. The volume increases and compresses the rubber tube to shrink. While the rubber tube shrinks, it pushes the push rod upward. The push rod pushes the valve downward to open the valve. At this time, the coolant passes through the radiator to the thermostat valve and then circulates through the water pump to the engine for a large cycle. The main valve, return spring, base, lower bracket, bypass valve spring, bypass valve and other components form a whole and are sealed in the thermostat air shell. The base and lower bracket are fixed and play a fixing role. They cannot move during operation.

The linkage effect of the mechanical thermostat: The thermostat is held upward by the return spring and fixed to the base by the push rod passing through the piston. At low temperatures, the main valve and the base are sealed, and the bypass valve below and the wall of the sewer pipe are open. At this time, the coolant enters and exits to form a small cycle. When the temperature rises, the paraffin begins to melt and expand, and the piston will be pushed upward under the action of the expansion tension. Since the piston is fixed by the push rod and cannot move, the thermostat will be forced to move downward under the action of the reverse thrust. The thermostat moves downward under the action of the reverse thrust. At this time, the main valve is separated from the base, resulting in a certain opening, and the bypass valve below is combined with the wall of the sewer pipe to produce a certain degree of closeness. Since the water temperature at this time has not reached the peak value of the thermostat, the main valve above and the bypass valve below are not fully opened and closed, so the coolant will flow in two directions. At this time, the large and small cycles work at the same time. When the water temperature continues to rise and exceeds the thermostat peak, the main valve will be fully opened and the bypass valve below will be fully closed. At this time, all the coolant will flow through the main valve to the radiator and enter a full circulation mode. The above is the implementation principle of the mechanical paraffin thermostat.

How does the drum brake system brake by external force?

The automobile brake system is a safety guarantee for vehicle driving. Currently, the widely used ones are mainly disc systems and drum brake systems. Although the drum brake system is gradually withdrawing from the mainstream market, it is still used in some economical cars because of its low cost and stable braking effect. It is mainly used in the rear wheels with small braking loads and the hand brake when parking. A typical drum brake system is mainly composed of a back plate assembly, a brake drum, a wheel, and a wheel nut. First, let’s look at the brake drum and the back plate assembly. The brake drum is generally cast from iron, which has high strength, wear resistance and heat resistance. The brake drum is connected to the wheel. When braking, its inner wall rubs against the brake pad to generate huge friction resistance, and the brake drum is forced to slow down and stop rotating. The back plate assembly is composed of a combination of various parts, and each component plays its unique role. The back plate base is also cast from iron. It has many concave and convex grooves and various holes on it. Its function is to provide a solid chassis support for other components. The two semicircular arc parts are brake shoes, also called brake blocks. It is two steel frames fixed on the back plate base, and high-density friction material brake pads are attached to their outer walls.

Let’s look at the wheel cylinder. There is a hydraulic piston at each end of the wheel cylinder. When the brake pedal is pressed, the hydraulic system applies pressure to the wheel cylinder. Under the action of the hydraulic pressure, the two pistons are forced to push to both ends. The brake shoes on both sides will also open outward under the influence of the piston thrust. At this time, the brake pads on the outer wall of the brake shoes are attached to the brake drum and produce friction to form braking resistance, and the wheels are forced to slow down. Let’s look at the two pressure springs, which are responsible for fixing the brake shoes to the back plate. The fixed spring, when the brake pedal is released, the fixed spring can return the brake shoes to their original position, so that the braking force disappears and the wheels can turn again. Next is the automatic brake clearance adjuster, which is an automatic device. When the brake pads are worn, the gap between the brake pads and the brake drum will increase. This device can automatically adjust the gap between the brake pads and the inner wall of the brake drum so that they always maintain a standard distance. This can solve the problem that the brake pedal must be stepped on to the bottom to work after the brake pads are worn and thinned. Next, let’s take a look at the working principle of the clearance adjuster. The adjuster can be divided into three sections. The black part in the middle is a gear shaft. When it rotates one circle, the adjuster will automatically increase a little. Every time the brake is applied, the adjuster will be linked to self-adjust, so there is no need to manually adjust the excess clearance.

Finally, let’s look at the braking principle of the handbrake. The brake cable is connected from the back of the backplate base and is connected to the brake handbrake. When the handbrake is pulled, the brake cable pulls the brake rod. Under the influence of the fulcrum, the brake rod will push the left brake shoe to the left through the clearance adjuster to open it. At this time, the brake pad on the shoe fits with the inner wall of the brake to form resistance, thus successfully locking the brake drum and the wheel.

How does the car air conditioning system turn hot air into cool air? Where does the power of the compressor come from?

The automobile air conditioning system is mainly composed of condenser, cooling fan, dryer, expansion valve, evaporator, blower, and compressor components. The working process of the automobile air conditioning system: The compressor is responsible for compressing the gas. It is driven by the engine crankshaft. When working, the gaseous refrigerant in the evaporator flows back into the compressor and becomes high-pressure steam after compression. The gaseous refrigerant flowing back from the evaporator will become high-temperature and high-pressure steam after compression. The refrigerant is always in gaseous state during this process. Next, the refrigerant flows to the condenser through the pipeline. The condenser is a heat converter. It is usually installed in front of the radiator water tank of the front of the car. The high-temperature and high-pressure gaseous refrigerant will condense into liquid after releasing heat through the condenser. The gaseous refrigerant enters through the pipe below the condenser and gradually flows upward. The gaseous refrigerant will absorb moisture through the dryer to improve the purity. At the same time, under the action of the cold wind coming in from the front of the car, the temperature drops rapidly and finally condenses into liquid and flows out from the pipe above the condenser. At this time, the refrigerant is in the form of high-pressure liquid. Then the high-pressure liquid refrigerant enters the expansion valve, which is a high-pressure valve. After the high-pressure liquid refrigerant is ejected through the expansion valve, it is converted into a low-pressure gas and pressed into the evaporator box. This is a pressure relief process. During the gasification conversion process, the high-pressure liquid will absorb the heat from the surrounding air, so the temperature of the air outside will become lower. At the same time, since the blower at the rear has been continuously pumping hot air into the car, a large amount of hot air will be absorbed when passing through the evaporator box, so there will be continuous cold air blowing into the car. At the same time, due to the absorption of heat from the air, the temperature of the refrigerant in the evaporator box will rise, and it will continue to flow to the compressor, and after being pressurized by the compressor, it will be pushed to the condenser again. This cycle repeats, and the temperature conversion work continues to cycle. The above is the working principle of the automotive air-conditioning system. Since the power of the compressor comes from the crankshaft of the engine, the fuel consumption of the automotive air-conditioning system will increase when it is working.

How does a disc brake system stop the wheels and stop the car? How do brake pads stop a car at high speed?

The disc brake system is controlled by hydraulic pressure. Its working principle is to convert mechanical power into liquid pressure, and then the hydraulic pressure creates a huge friction force to slow down the wheel. The friction force is converted into heat energy, which is finally dissipated into the air. At present, hydraulic disc brake systems are widely used in family cars.

A typical disc brake system consists of the following components: wheel hub assembly, brake disc, brake caliper, wheel, and wheel nut. The wheel hub assembly is connected to the chassis of the car and also serves to fix the brake disc and other components. There is a bearing in the wheel hub assembly, which can control the wheel to make it rotate smoothly. The brake disc is an important component. It consists of two metal discs, one of which is equipped with a heat dissipation system. Because when braking, the friction between the brake pad and it will generate huge friction, and the huge friction will generate high temperature, especially on a long downhill. If the downhill speed is not controlled, the brake disc is easy to burn red. The heat dissipation system can accelerate air circulation and play a role in cooling and exhaust. The brake caliper is the main braking component. It can squeeze the brake pad through pressure so that the brake pad can stop the brake disc. It generally consists of a hydraulic piston, a bracket and a brake pad component. When we step on the pedal, the brake oil flows into the hydraulic piston in the brake caliper through the brake pipe under the pressure of the hydraulic brake system. The piston is squeezed out, and when the brake pedal is released, the piston returns to its original position. There is a sealing ring on the outside of the piston, which can prevent dust and dirt and protect the piston. Let’s look at the bracket component. It is generally installed on the car wheel hub to fix the brake pad and the caliper body. The piston assembly can be moved after the sliding pin is inserted. The brake pad is composed of four parts. The gasket reduces vibration and noise. The back plate is the rigid basis of the friction material. The interlayer between the back plate and the friction material plays a bonding role, which is responsible for bonding the friction material and the back plate together, and can also play a role in heat insulation. Finally, there is the friction material made of various compounds. It must have the characteristics of wear resistance, heat resistance, high strength and long life. The two brake pads are installed on the bracket and fixed by spring cuts. The brake pads are used very frequently and need to be replaced in time after wear, otherwise it will affect the braking performance.

The working principle of the disc brake system: When the driver steps on the brake pedal, the mechanical force is converted into liquid pressure. The hydraulic pressure forces the brake oil to enter the piston assembly. The piston is pushed out to press the inner brake pad against the brake disc. Under the influence of friction, the brake disc begins to slow down. Since the inner brake pad can no longer move, no further pressure can be applied. When the hydraulic system continues to increase pressure, it will force the brake caliper body to move backward along the bearing. At this time, the outer brake pad begins to work. Under the joint action of the brake pads on both sides, the brake disc is stopped and the wheel stops rotating. When the brake pedal is released, the pressure is released and the piston returns to its original position.

Brake pads generally need to be replaced after 3-5 km for front brake pads and 6-8 km for rear brake pads, but each car owner has different braking habits, so it depends on the actual wear and tear. Generally, the thickness of a new brake pad is about 1-1.5 cm. As the number of times increases, the thickness of the brake pad gradually becomes thinner, and the limit of use is 3 mm. If the thickness of the brake pad is only about 1/3 of the original thickness (about 0.5 cm), the brake pad needs to be replaced. When stepping on the brake, it is obvious that the brake is weak and soft. It is necessary to step on the brake deeply to achieve the previous braking effect. At this time, the braking distance becomes longer, which seriously affects driving safety and requires the replacement of brake pads.

What is the function of the clock spring and what kind of faults will occur if it is damaged?

The clock spring, also known as the airbag hairspring, is mainly a section of wiring harness that connects the main airbag (located on the steering wheel) and the airbag, and connects the steering wheel switch and the control unit. This section of wiring harness is installed inside the steering wheel, especially at the horn position, to ensure that when the steering wheel turns, the main airbag wiring harness will not break due to frequent rotation and twisting, thereby ensuring that the airbag can work normally at any time.

Its main functions: First, it adapts to the rotation of the steering wheel. Because the main airbag rotates with the steering wheel, the hairspring is designed as a length of wire harness that can be wound around the steering shaft of the steering wheel. When it moves with the steering wheel, it can be loosened in the opposite direction or wound tighter in time to adapt to the rotation of the steering wheel. Secondly, it prevents the wire harness from being pulled apart. When connecting the wire harness, it is necessary to leave a margin because it also has a limit. It is necessary to ensure that the wire harness cannot be pulled apart when the steering wheel is turned to the left or right. The design of the hairspring ensures that the wire harness has enough length and flexibility to adapt to the rotation of the steering wheel. Under normal circumstances, the number of rotations of the clock spring will be half a circle more than the steering wheel. It is necessary to ensure that the steering wheel is turned to the extreme position to one side without being pulled apart. Finally, it ensures signal transmission. In addition to connecting the main airbag, the hairspring is also responsible for transmitting other functional signals on the steering wheel, such as the signal of the multi-function button, to ensure that these functions can be used normally when the steering wheel is turned. Pay special attention to keeping it in the middle position as much as possible during installation to ensure that it will not be over-stretched or compressed when the steering wheel is turned.

What kind of problems will generally occur when the clock spring is broken?
1. The horn does not sound: If the airbag spring is damaged, the horn may not work properly or fail completely. At this time, you can unplug the horn plug, ground the horn button at the lower end of the airbag spring, and then measure the horn wire below. If both measurements are audible, measure the horn wire at the upper end of the spring. If it does not sound, it proves that the airbag spring is faulty.
2. Steering wheel makes abnormal noises while driving: If the airbag spring is damaged, the steering wheel may make abnormal noises while the vehicle is driving. At this time, you can try to remove the airbag spring and observe whether the steering wheel has no abnormal noises while the vehicle is driving to determine whether it is an airbag spring fault.
3. The airbag fault light appears on the instrument panel. If the airbag spring is damaged, the airbag fault light on the instrument panel may light up.
4. The control buttons on the steering wheel are faulty. If the airbag spring is damaged, the control buttons on the steering wheel, such as the audio control phone answering, may fail.

When the horn of our vehicle sometimes sounds and sometimes does not, the airbag light is always on, the steering wheel buttons are out of control, or the cruise control cannot be turned on, it is usually because the cable inside the hairspring is broken. We should pay attention to several points when removing the hairspring. First, keep the wheel centered, then the steering wheel centered, and finally keep the key door closed during the removal process.

The structure and working principle of the suspension system

Let’s take independent suspension as an example to learn more about the structure and working principle of the suspension. The most typical independent suspensions are the McPherson suspension system, double wishbone suspension, and multi-link suspension. The suspension system includes the wheel hub assembly, suspension links, control arms and beams, springs, shock absorbers, lateral balance bars (anti-roll bars), suspension mounting elements and other components. First of all, the entire wheel hub assembly consists of the wheel hub, wheel hub bearing, and steering knuckle. The wheel hub is installed on the steering knuckle. The steering knuckle is also called the horn. It has a wheel hub bearing inside. After the three are connected, they are connected to the control arm through the steering knuckle. The wheel hub is connected to the brake disc and the wheel. The steering knuckle is connected to the tie rod in addition to the control arm. In addition, the brake caliper is also installed on the steering knuckle. When the steering wheel turns, it drives the steering knuckle to move, and then drives the tie rod to move. The tie rod drives the steering knuckle to move, so that the wheel rotates to realize the steering function. Next is the suspension link, control arm and beam. In order to enable the wheels to move within a controllable range, each link, control arm and beam are indispensable. These components can also transmit the horizontal and longitudinal forces from the road surface.

Let’s continue to look at the coil spring and shock absorber. The two of them are combined to form a shock absorber pillar, which supports the weight of the vehicle body. When there is an external force pressing down, it will compress and deform, and when the external force is released, it will return to its original state. Therefore, the role of the coil spring is to absorb the vertical force of the downward pressure during the compression stroke of the vehicle body to mitigate the impact. In addition to coil springs, there are torsion bar springs, leaf springs and air springs. The torsion bar spring is a metal rod that can be twisted. It is rare in modern cars, but it often appears in many tracked vehicles. It can achieve a torsion effect. The leaf spring should be very common. It is made of stacked multiple steel plates. It is often seen in many cars and trucks. Its characteristics are strong bearing capacity but very hard. The air spring is a compressed gas filled in a sealed container, and the compressible characteristics of the gas are used to achieve elasticity. The pneumatic suspension system with air springs has good ride comfort, but due to its complex design and high manufacturing cost, it is generally used in high-end cars. Let’s look at the shock absorber. The role of the shock absorber is to suppress the rebound of the vehicle body and play a damping role. When the coil spring is pressed down and the external force is released, the spring will rebound several times after returning to its original state. These rebound actions are the characteristics of the spring component itself. If shock absorbers are not used to prevent the coil spring from rebounding, the vehicle will continue to shake vertically up and down when passing through the shock absorber belt. Therefore, the role of the shock absorber is to suppress the rebound during the extension stroke of the suspension and allow the vehicle to quickly restore balance.

Let’s look at the lateral balance bar, also called the anti-roll bar. The function of the anti-roll bar is to prevent the vehicle from rolling when turning. It is a U-shaped metal rod. Its central part is fixed to the subframe by a rubber bushing, and its two ends are connected to the suspension through two connecting rods. When the wheels on both sides pass through uneven roads at the same time, the anti-roll bar will rotate up and down with the bushing as the axis. At this time, the amplitude of the left and right wheels is the same. If only one side of the wheel passes through a concave road, the anti-roll bar on the same side will be forced to twist and press down. Since the anti-roll bar has a certain toughness, it will drive the other side and there will be a tendency to press down synchronously. The same effect is also achieved when it bounces upward. In this way, when the left and right wheels pass through uneven roads, the two wheels will inhibit and rely on each other, which can play a role in suppressing vibration and stabilizing the vehicle body. Next are the components used for suspension installation, including rubber bushings, ball joints, upper support brackets, anti-roll bar bushings and sub-brackets. The rubber bushing is composed of two layers of metal bushings with rubber pads embedded inside. It is a common connecting element. The fixation of control arms, torsion beams, shock absorbers, etc. all rely on this component. In the middle of the ball joint is a ball stud, which is wrapped in a metal shell on the outside and filled with plastic on the inside. The ball stud can swing and rotate. The connection between the control arm and the steering knuckle is made of a ball joint. The ball joint can be an independent component or integrated with the control arm. The ball joint can also be seen in the anti-roll bar and steering system, such as the connection between the anti-roll bar and the control arm, and the connection between the outer tie rod and the steering knuckle. Next, let’s look at the installation of the shock absorber. The upper strut support is connected by a rubber pad. At the same time, since its bottom needs to rotate with the control arm, there is a strut bearing in the middle. Of course, in the double wishbone suspension, the shock absorber does not need to rotate with the control arm and only bears the longitudinal load, so the lateral stiffness is large and the operability is strong. The fixation of the lateral balance bar is relatively simple. It is first clamped with an open plastic bushing and then fixed by a metal bracket. The lateral balance bar can rotate freely in the bushing. Finally, let’s look at the subframe. The subframe is the installation base for other components. It is connected to the vehicle body, so it must be rigid enough. The subframe can be installed on both the front and rear axles of the vehicle. In addition to supporting the steering knuckle and suspension system, the front subframe also serves as the installation base for other mechanisms such as the engine, transmission, and steering system.

What sensors are there in the engine? (Part 2)

Below is the knock sensor, which is located outside the engine body, between the outer walls of the second and third cylinders. Its function is to detect the intensity of the combustion and explosion of the engine cylinders, so as to effectively suppress the occurrence of engine deflagration, which is often called cylinder explosion. What is cylinder explosion? The combustible mixture accumulated in the cylinder explodes and burns irregularly in advance, causing the pressure and temperature of the gas in the cylinder to suddenly increase several times, causing a sharp knocking sound, which will cause the engine to overheat and reduce power, and in severe cases, damage and deformation of the machine parts. This is cylinder explosion. After the electronic control unit recognizes the detonation data, if it exceeds the safety range, it will adjust the advance angle and ignition timing to suppress the occurrence of detonation.

The next one is the coolant temperature sensor, which is located near the coolant outlet on the engine cover. It is responsible for detecting the temperature of the coolant. When the coolant temperature is too low, it will affect the performance of the engine. After the electronic control unit recognizes it, it will adjust the idle speed and ignition timing as well as the concentration of the fuel to optimize combustion and help achieve the optimal operating temperature. If the water temperature is too high, the radiator of the coolant system will be opened to help the engine dissipate heat. At the same time, the coolant temperature will also be displayed on the dashboard.

The oxygen content sensor is located in the exhaust manifold of the exhaust system. It is divided into front oxygen and rear oxygen. In engines that use a three-way catalytic converter to reduce exhaust pollution, the oxygen sensor is an indispensable component. The function of the front oxygen is to detect the oxygen concentration in the exhaust system exhaust gas and send a feedback signal to the ECU, which then controls the increase and decrease of the injector nozzle, thereby controlling the air-fuel ratio of the mixer near the theoretical value. In addition, the function of the rear oxygen sensor is to detect the working condition of the unit catalyst and feed back to the ECU to ensure that the exhaust emissions meet the standards.

The speed sensor is used to detect the actual speed of the car. The electronic control unit can adjust the fuel injection amount according to the vehicle speed to ensure that the engine is in a high-speed working range. At the same time, the vehicle speed information will also be displayed on the dashboard.

The oil pressure sensor is located at the upper end of the oil filter. Its function is to detect the oil pressure value. When the pressure value is normal, the lubrication system can work normally. When the pressure value is normal, an alarm signal will be issued and the oil light on the dashboard will be lit.

These sensors must cooperate with each other and work closely together to complete the engine’s power conversion work. As long as one of them fails, it will affect the normal operation of the engine. Therefore, the sensor is the basis for the normal operation of the engine and is also a strong guarantee for the on-board computer ECU to control the overall situation.

What sensors are there in the engine? (Part 1)

An ordinary fuel engine has about 300-600 independent non-detachable parts. All the parts must work together efficiently and closely to complete the tasks of fuel injection ignition, fuel work and power transmission. Therefore, when the engine is working, there must be a general commander to observe, analyze and issue instructions. The general commander in the engine is the on-board computer ECU, that is, the electronic control unit. The electronic control unit summarizes the operating data collected by various sensors in the engine, analyzes and calculates new instructions, and then sends the instructions to each execution unit for execution. Therefore, the ECU is the brain of the engine, which is responsible for controlling the overall situation. In this process, the parts responsible for sensing various working conditions of the engine are our sensors.

First of all, the air flow sensor is located in the engine intake duct, after the air filter and before the throttle. Its function is to detect the engine’s intake volume and convert it into an electrical signal to transmit to the ECU, which serves as the basis for the ECU to control the amount of fuel injection. Here is a point of knowledge to add, which is the air-fuel ratio. The air-fuel ratio refers to the mixing ratio of fuel and air. The ideal air-fuel ratio is 1:14.7, which means that 14.7 kg of air is needed to burn one kilogram of fuel, so that it can be fully burned.

Next is the throttle, commonly known as the air valve, which can control the size of the air mass entering the engine. This is the throttle position sensor, which is responsible for identifying the opening of the throttle. The larger the throttle opening, the more air enters the engine and the higher the oxygen content, which can be mixed with more mist gasoline to form a more combustible mixture, which can get more power after explosion and combustion. Therefore, the foot-operated accelerator we often hear about refueling is not actually refueling, but increasing the throttle opening to increase air. The throttle position sensor is responsible for identifying the throttle opening information and sending it to the electronic control unit ECU. After analysis and calculation by the electronic control unit, it sends a fuel injection command to the injector. The throttle is generally divided into two types: pull-wire type and electronic type, and most of the throttles on the market are electronic.

Next is the crankshaft position sensor, which is located next to the crankshaft pulley. It is one of the most important sensors in the engine’s electronic control system. It is responsible for detecting the crankshaft’s rotation angle and the engine’s speed. The rotation angle can determine whether the piston is at the top dead center position. Combined with the data from the camshaft position sensor, the ECU can accurately identify when to inject fuel and ignite which cylinder. At the same time, the engine speed information can be displayed on the dashboard, making it easier for the driver to identify the engine speed.

The next one is the camshaft position sensor, which is used to collect the rotation angle of each cam on the camshaft. Based on the rotation angle, the electronic control unit can identify which working stroke the cylinder is in, and at the same time can accurately control the injection timing of the injector and the ignition timing of the spark plug.

Working principle and function of shock absorber

The shock absorber is an important component of the automobile suspension system. It can buffer the vibration of the vehicle, and at the same time it can effectively prevent rebound and improve the smoothness and stability of the vehicle. The shock absorber is also called a damper. It is an important buffer component. Technically speaking, it is a hydraulic pump that can absorb the kinetic energy of the suspension system and dissipate the kinetic energy into the atmosphere in the form of heat. Now the mainstream shock absorbers can be divided into strut shock absorbers and telescopic shock absorbers. Their structures are different, but the principles are exactly the same.

Take the strut shock absorber as an example to understand the working principle of the shock absorber: the top of the strut shock absorber is connected to the body, and its bottom is connected to the steering knuckle. The steering knuckle is connected to the lower arm, and the lower arm is connected to the subframe. This connection method allows the shock absorber to move only in the vertical direction, which is also the best way to achieve the shock absorption effect. Because the steering knuckle can rotate, the wheel can rotate within the limited rotation angle of the steering knuckle. The main components of the strut shock absorber are shock absorber, coil spring, top strut mounting seat, dust cover above the piston rod, and oil seal. The internal structure of the shock absorber includes a piston rod, a rebound block, a piston, a base, and hydraulic oil. There are two cylinders inside the shock absorber, a working cylinder and an oil storage cylinder. The working cylinder is always filled with hydraulic oil, and there is also some hydraulic oil in the oil storage cylinder. When working, the compression valve on the base will control the flow of hydraulic oil between the two cylinders. This shock absorber designed with two cylinders is called a double-cylinder shock absorber. In order for the shock absorber to perform at its best, no gas can enter the working cylinder, and it must be ensured that there is always hydraulic oil filling. At this time, the oil storage cylinder comes into play. The oil storage cylinder stores enough hydraulic oil. When the piston moves down, the excess hydraulic oil will be squeezed into the oil storage cylinder due to the pressure. When the piston moves upward, the volume of the working cylinder increases, and the hydraulic oil in the oil storage cylinder will be pulled back. In this way, the working cylinder is always filled with hydraulic oil. In this process, the oil storage cylinder is only half-filled, and the rest of the space is filled with nitrogen or liquid nitrogen that can be compressed and expanded. Since nitrogen has the characteristics of compression and expansion, it is just right to use it to fill.

The linkage details of the shock absorber when working, first of all, is the downward pressure process. When the external force presses down, the piston moves downward. At this time, the compression valve in the piston opens, and the hydraulic oil flows into the upper chamber through the valve. Because the valve is small, the hydraulic oil will be throttled, and the speed of upward flow will slow down. When the piston continues to press down, the oil pressure in the lower chamber begins to increase. When the pressure is greater than the bearing value of the base compression valve, the compression valve on the base will automatically open, and the hydraulic oil will flow to the oil storage cylinder. In this process, each valve throttles the hydraulic oil, forming a damping of the downward pressure. Simply put, it is the throttling speed limit of the valve, which realizes shock absorption and buffering. Next is the rebound process. When the rebound begins, the pressure in the lower chamber slowly recovers, and the compression valve on the base automatically closes. When the piston moves up, the volume of the lower chamber increases, the oil pressure begins to decrease, and the rebound valve on the base automatically opens. The hydraulic oil in the oil storage cylinder is pulled back. At the same time, the hydraulic oil in the upper chamber will flow into the lower chamber synchronously. This process will also be controlled by throttling and form a damping force. Since both the downward pressure and the rebound process are affected by the damping force, the two functions of shock absorption and rebound prevention are realized. This is the working principle of the automobile shock absorber.