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.

What is the automobile suspension system?

The suspension system is located between the wheels and the vehicle body, with the wheels connected at the bottom and the vehicle body connected at the top, playing the role of connecting the upper and lower parts and absorbing shock and buffering. The suspension system between the wheels and the vehicle body will automatically compress and straighten to help buffer and prevent rebound, so that the vehicle body can be kept as horizontal as possible, which can greatly improve driving comfort. Common suspension systems on the market are divided into independent suspension, non-independent suspension and semi-independent suspension. The left and right wheels are installed on the same rigid crossbeam, forming a whole. When the right wheel encounters an obstacle and jumps, the left wheel will also jump. This is a non-independent suspension. This type of suspension is simple, reliable and low in cost, but because the two wheels are fixed together, when one wheel is impacted by the road surface, the other wheel will also be affected, so the comfort of the non-independent suspension is poor. It is now mainly used in trucks, buses and some SUV models.

Independent suspension, the two wheels are connected to the body through movable control arms, they can move independently without interfering with each other, so when one wheel is impacted and bounced by the road, it will not affect the other wheel, so the stability of the independent suspension system will be better, and it can absorb the vibration and impact of the road, so its driving comfort will be higher, and at the same time, because the independent suspension system removes the middle rigid axle, it frees up more space, so its cabin space will be larger. At present, the McPherson suspension system is widely used on the market.

The semi-independent suspension system improves the middle rigid beam on the basis of the non-independent suspension system, so that the original rigid beam becomes a torsion beam with a certain elasticity. The torsion beam can withstand a certain degree of deformation. When the right wheel is impacted and bounced, part of the impact force will be consumed by the deformation of the torsion beam, so the left wheel will be affected less, which plays a role in lateral stability. This semi-independent suspension system is what we often call the torsion beam suspension system. Its stability and comfort are generally used in the rear suspension of mid-range cars.

Why can AT transmission shift automatically?

The core logic of AT transmission automatic shifting is that it has a transmission control module. AT transmission consists of three parts: torque converter, transmission control module and speed change mechanism. The torque converter is a power component, which is responsible for flexibly transmitting the power of the engine to the transmission. Since it relies on the hydraulic oil filled inside to transmit power, when the brake wheel stops rotating, the drag force will not be fed back to the engine, and the engine will not be stalled.

The transmission control module is the core of the AT transmission, which can automatically identify and automatically send shift instructions. The controller control module is located at the bottom of the gearbox. It consists of a large number of integrated circuits and oil channels. When it collects engine speed information, the opening information of the driver’s accelerator pedal and the current vehicle speed information, it can identify the driver’s operating intention to decide whether to shift up or down, and then control the locking of the clutch plate in the speed change mechanism by adjusting the pressure of the oil in the oil channel in the shift valve body, and finally realize the shifting and speed change through the planetary gear. Among them, each of the densely packed oil channels has its specific function. For example, the clutch plate can be pressed to close by the pressure of the oil in the oil channel. By locking and releasing these clutches, different combinations of planetary gears can be realized and different speeds can be output, thus realizing the automatic switching of different gears.

The speed change mechanism in the transmission is commonly known as the planetary gear and multi-plate clutch plate. The planetary gear set is responsible for completing the conversion of different transmission ratios. The multi-plate clutch plate is responsible for locking and releasing the engagement of different mechanisms in the planetary gear set. The gear combinations of different planetary sets are also different, and the speeds obtained are also different. The speed change mechanism is a specific command executor. They are only responsible for switching the corresponding gear and outputting the corresponding speed. They do not have their own thinking and consciousness and do not have automatic control capabilities.

Why do we need Brake Pad Wear Sensor?

1. Improved safety: By monitoring the wear degree of the brake pad in real time, the Brake Pad Wear Sensor can ensure that enough braking force is provided at critical moments, thus improving the safety of driving.
2. Prevent accidents: If the driver fails to detect the condition of the brake pad is too thin in time, it may lead to the loss of control of the vehicle or the increase of braking distance, and then cause traffic accidents. With the warning function of the Brake Pad Wear Sensor, this kind of risk can be greatly reduced.
3. Extended service life of the brake system: timely replacement of the brake pad not only ensures the safety of driving, but also helps to extend the overall service life of the brake system and save maintenance costs.

What is the Brake Pad Wear Sensor?

The Pad Wear Sensor is a device used to monitor the wear degree of brake pads. When the thickness of the brake pad is lower than a preset value, the sensor will send a signal to the vehicle’s electronic control system to remind the driver to replace the brake pad in time, so as to avoid the safety hazards caused.