Car chassis basic knowledge!

The chassis of the vehicle consists of four parts: drive train, driving train, steering system and brake system. The role of the chassis is to support and install the automobile engine and its parts and assemblies, to shape the overall shape of the car, and to receive the power of the engine so that the car can produce movement and ensure normal driving.

Main components

Drive Train

The drive train is generally composed of clutches, transmissions, universal transmissions, final drives, differentials, and axle shafts.

1 function

The power generated by the engine of the car is transmitted to the drive wheels by the drive train. The drive train has the functions of deceleration, speed change, reverse parking, interrupted power, wheel-to-wheel differential and differential between shafts. It cooperates with the engine to ensure normal running of the vehicle under various working conditions and has good dynamic performance. Economical.

2 types of composition

Drive trains can be divided into mechanical transmissions, hydraulic transmissions, hydraulic transmissions, electric transmissions, etc., depending on the type of energy transfer.

The following describes the working principle and role of each subassembly of a small drive train separately:

Clutch: The clutch is located in the flywheel housing between the engine and the transmission. The clutch assembly is fixed to the rear plane of the flywheel with screws. The output shaft of the clutch is the input shaft of the transmission. During driving of the vehicle, the driver may depress or release the clutch pedal as required to temporarily and gradually engage the engine and the transmission to cut off or transfer the power input from the engine to the transmission.

Clutch engaged state Clutch closed state

The function of the clutch is mainly:

1 Ensure that the car starts smoothly:

Before the start, the car is at a standstill. If the engine and the transmission are rigidly connected, once the file is hung up, the car will suddenly rush forward due to sudden power. Not only will it cause damage to the machine, but the driving force will not be enough to overcome the car's rush. The enormous inertial force generated causes the engine speed to drop sharply and extinguishes. If the clutch is used to temporarily separate the engine from the transmission at the start and then the clutch is gradually engaged, the slipping torque between the active part and the driven part of the clutch can cause the torque transmitted from the clutch to gradually increase from zero. The driving force of the car also gradually increases, so that the car starts smoothly.

2 easy to shift:

During the driving of a car, different transmission gear positions are frequently used to adapt to changing driving conditions. If there is no clutch to temporarily disengage the engine from the transmission, the meshing force transmission gear in the transmission will not be removed due to the load, and the pressure between the meshing tooth surfaces is large and difficult to separate. Another gear to be engaged will be difficult to mesh due to the difference in peripheral speeds. Even if it is forcibly engaged, it will have a large tooth end impact and will easily damage the parts. When the clutch is used to temporarily disengage the engine and the transmission from the shift, the previously meshed pair of gears are removed by the load, and the pressure between the engagement surfaces is greatly reduced and it is easy to separate. For the other pair of gears to be meshed, since the moment of inertia of the pair of driving gears and the engine is small, proper gear shifting action can make the circumferential speeds of the gears to be meshed equal or nearly equal, thus avoiding or reducing the impact between the gears.

3 to prevent the driveline overload:

When the car is in emergency braking, the wheels suddenly abruptly decelerate, and the drive train connected to the engine still maintains the original rotation speed due to the inertia of rotation, which often generates a moment of inertia much larger than the engine torque in the transmission system. The parts are easily damaged. Because the clutch transmits torque by friction force, when the load in the driveline exceeds the torque that can be transmitted by the friction force, the main and driven parts of the clutch will automatically slip, thus preventing overload of the drive train. .

Transmission: Automotive transmission: By changing the transmission ratio, changing the engine crankshaft's turn-rejection, it can meet the requirements of different driving conditions such as starting, acceleration, driving and overcoming various road obstacles, etc. Popularly divided into manual transmission (MT), automatic transmission (AT), manual / automatic transmission, stepless transmission.

Driveshaft: The driveshaft assembly consists of outer universal joint (RF section), inner universal joint (VL section) and splined shaft. Both RF section and VL section are ball cage constant velocity joints. The VL section is bolted to the flange of the drive shaft of the differential. The RF section is connected to the front wheel through the spline shaft at the end of the outer star wheel. The left and right front wheels are respectively driven by a constant velocity joint drive shaft. .

Main reducer: The main reducer is the main component that reduces the speed and increases the torque in the automotive powertrain. For cars with a vertical engine, the final drive also uses a bevel gear drive to change the direction of power.

When the car is running normally, the engine speed is usually around 2000 to 3000r/min. If such a high speed is only reduced by the gearbox, then the gear ratio of the gearbox in the gearbox must be large, and the gear pair must be driven. The larger the ratio, the larger the ratio of the radii of the two gears. In other words, the larger the gearbox size will be. In addition, the rotation speed decreases, and the torque must increase, which increases the transmission load of the transmission mechanism behind the transmission and the transmission. Therefore, if a main reducer is installed before the power is diverted to the right and left drive wheels, the torque transmitted by the transmission components in front of the main reducer such as the gearbox, transfer case, and universal transmission can be reduced. The gearbox's size and quality are reduced, making it easy to operate. Modern car's main reducer is widely used spiral bevel gears and hypoid gears. When the hyperboloid gear is working, the pressure and sliding between the tooth surfaces are large, and the oil film on the tooth surface is easily damaged. The gear must be lubricated with a double-curve gear and must not be replaced with a common gear oil. Otherwise, the tooth surface will be rapidly scratched and worn. Greatly reduces the service life.

Differential: If the drive wheels on both sides of the transaxle are rigidly connected with a single shaft, the two wheels can only rotate at the same angular speed. In this way, when the car turns to travel, because the distance of the outer wheel is larger than the distance of the inner wheel, the outer wheel will cause a slip while rolling, while the inner wheel will slide while rolling. Even if the car is running straight, the wheels may slip due to uneven roads or flat roads with different tire rolling radius (tire manufacturing errors, wear, uneven load, or air pressure). When the wheels slide, they not only increase tire wear, increase power and fuel consumption, but also make the steering of the vehicle difficult and the braking performance deteriorate. In order to keep the wheels from slipping as much as possible, it must be structurally ensured that the vehicles can rotate at different angular velocities. The driven wheel bearing is usually supported on the spindle so that it can rotate at any angular velocity, and the drive wheels are rigidly connected to the two half axles, respectively, and a differential is provided between the two axles. This kind of differential is also called inter-wheel differential. Multi-axis drive off-road vehicles, in order to make each drive axle can rotate at different angular speeds, to eliminate the sliding of the drive wheels on each bridge, and some interaxle differentials are installed between the two drive axles. Differentials on modern cars are generally classified into gear type differentials and non-slip differentials according to their operating characteristics. Gear differential When the left and right drive wheels have a difference in speed, the torque assigned to the slow drive wheel by the differential is greater than the torque of the fast drive wheel. This differential torque sharing feature can meet the car's normal driving on a good road. However, when a car is driving on a bad road, it seriously affects its ability to pass. For example, when one driving wheel of a car is stuck in a muddy road, the car often cannot advance (commonly known as skid), although the other driving wheel is on a good road surface. At this time, the driving wheels on the muddy road slipped in place, but the wheels on the good road surface were stationary. This is because the adhesion between the wheel and the road surface on the muddy road surface is small, and the road surface can only react with a small reaction torque to the axle shaft, so the torque assigned to this wheel by the differential is also small. Although the adhesion between the other drive wheel and a good road surface is relatively large, due to the characteristics of even distribution torque, this drive wheel can only be assigned to the same amount of torque as the slide drive wheel, so that the driving force is insufficient. Overcoming the driving resistance, the car cannot move forward, and the power is consumed on the slip drive wheel. At this time, increasing the throttle not only does not make the car go forward, but also wastes fuel and accelerates the wear of the parts, which in particular makes the tire wear worse. The effective solution is to dig out the mud under the sliding drive wheel or dry soil, gravel, branches, hay, etc. under this wheel. In order to improve the car's ability to pass through bad roads, certain off-road vehicles and limousines are equipped with a slip differential. The feature of the slip differential is that when one side drive wheel slides on a bad road, most or all of the torque can be transmitted to a drive wheel on a good road surface to fully utilize the adhesion of this drive wheel to produce Sufficient driving force to make the car start or continue.

Axle shaft: Axle shaft is a solid shaft that transmits torque between the differential and the drive wheel. The inner end is generally connected to the axle gear via a spline and the outer end is connected to the hub.

The semi-axes commonly used in modern automobiles have two types, full-floating and semi-floating, depending on the type of support.

The full-floating axle shaft only transmits torque and does not bear any reaction force and bending moment, so it is widely used in various types of automobiles. Full-floating half shafts are easy to disassemble and remove. Only by unscrewing the bolts on the flanges of the axle shafts, the axles can be pulled out. However, the wheels and axle housings can still support the car, thus bringing convenience to vehicle maintenance.

Semi-floating axle shafts transmit both torque and all reaction and bending moments. Its support structure is simple and its cost is low, so it is widely used in various types of cars with smaller reaction moments. However, such semi-axial support is difficult to remove, and if the semi-axle breaks during driving of the vehicle, it is easy to cause the wheel to fly off.

Brake system

Overview

A series of special devices on the car to apply external forces (mainly pavements) to certain parts of the car (mainly the wheels) to apply a certain amount of force to them are collectively referred to as brake systems.

Its role is: to make the car in motion according to the driver's requirements for forced deceleration or even stop; the parked car in a variety of road conditions (including on the slope) to stabilize the parking; so that downhill car speed to maintain stable.

The brake on the car can only be the external force that acts on the car and the direction is opposite to the direction of the car. These external forces are random and uncontrollable. Therefore, a series of special devices must be installed on the car to achieve The above functions.

classification

1 Press the brake system

The brake system can be divided into service brake system, parking brake system, emergency brake system and auxiliary brake system. The braking system for reducing the speed or even stopping the vehicle while it is moving is referred to as a service braking system; the braking system for parking the parked vehicle in situ is called a parking brake system; In the event of a failure of the service brake system, the brake system that ensures that the vehicle can still achieve deceleration or stop is called an emergency brake system; in the course of driving, the auxiliary service brake system reduces the vehicle speed or keeps the vehicle speed stable, but it cannot make the vehicle emergency. The stopping brake system is called the auxiliary braking system. In each of the above brake systems, the service brake system and the parking brake system are required for every car.

2 press brake to manipulate energy

Braking system can be divided into manpower braking system, dynamic braking system and servo braking system. The braking system that uses the driver's body as the only source of braking energy is called the manpower braking system; a system that brakes completely by the potential energy of air pressure or hydraulic pressure converted from the power of the engine is called a dynamic braking system; Braking systems that use human and engine power for braking are called servo brake systems or assisted brake systems.

3 Press brake energy transmission

Braking system can be divided into mechanical, hydraulic, pneumatic, electromagnetic and so on. At the same time, two types of brake systems with upload energy are called combined brake systems.

composition

The brake system is generally composed of two main parts: brake control mechanism and brake.

1 brake operating mechanism

Generates the braking action, controls the braking effect and transmits the braking energy to the various parts of the brake, as well as the brake wheel cylinder and brake line.

2 brake

A component that generates a force (braking force) that impedes the movement or movement of the vehicle. Commonly used brakes on automobiles are brake torques generated by the friction between the fixed element and the rotating surface of the rotating element, called friction brakes. It has two types of drum brakes and disc brakes.

Driving Department

The driving system consists of the car's frame, axles, wheels and suspension. The frame, axle, wheels, and suspension of the automobile constitute the driving system. The functions of the driving system are:

1, to accept the power of the drive shaft, through the role of the drive wheel and the road to produce traction, so that the normal driving of the car;

2, withstand the car's total weight and ground reaction;

3, ease the impact of uneven road on the body, attenuate the vibration of the car, keep the ride smooth;

4, with the steering system to ensure the stability and stability of the car.

Common injuries

Drag the bottom, foreign bodies hit the chassis

The speed of domestic road construction is very fast. Today, the road that has just been repaired will be “opened up again” tomorrow. When road repairs are done, most of the time, there will be more large stones or pits. This time our car is When you open up to such a road, you can make a big stone or other protruding object make intimate contact with the chassis of your own vehicle, which is what we often call the bottom.

Due to the uncertainty of the dragging bottom situation, it is easy to cause damage to the parts located on the chassis, such as the crushing of the three-way catalytic converter housing, the crack of the engine oil pan, the crack of the transmission case, or the deformation of the suspension system. The occurrence of these problems will bring fatal damage to your car.

corrosion

With the worsening of the environment, even the rain is acid rain, and in this environment our car may increase the possibility of damage. Because the chassis is often in contact with sewage, greasy substances and other substances, and the chemical composition of these substances will slowly corrode the chassis and parts on the chassis, so we must pay more attention to the anti-corrosion of the chassis.

In addition to the dangers of rain and sludge that may cause corrosion of the chassis, the snow melting agent and seawater used to melt the snow in winter can corrode our chassis, especially seawater. If your own car goes to the sea, you must not drive it to the sea. Seawater is very corrosive to the chassis. If you do not pay attention to the chassis and sea water contact, as soon as possible with a large amount of fresh water or neutral detergent to wash the chassis.

How to avoid

Generally, in order to prevent the occurrence of two chassis damages, the 4S shop will advise the owner to install engine guards or chassis protection, which is commonly known as “chassis armored”. The suggestion of installing engine guards is highly recommended because some economical cars will not install protective devices below the engine and transmission in order to save costs. This will allow the engine and transmission to come in direct contact with the road surface. With the engine guard installed, it is possible to artificially protect the engine and transmission as well as the important parts located on the undercarriage part of the front, so that even if the undercarriage really occurs, it will be in contact with the guard before the damage will not occur. Components.

Conservation Rules

In the winter, it is necessary to thoroughly clean the chassis and prevent rust. First of all, the chassis should be thoroughly cleaned. If there is too much mud in the chassis, it must be washed again with an oil-removing detergent to expose the chassis to the original “natural” color so that the rust preventive care can be started. In a professional beauty shop, the car can be lifted to a lifting rack for chassis cleaning, wiping, and rust prevention. In the middle of this should pay attention to, after the cleaning must be sure to wait until the water on the plate after the dry, in order to carry out anti-rust care. When performing care, be sure to maintain a uniform spray coating to form a durable layer of uniform anti-rust coating. After the completion of all the natural air drying 5-10 minutes, the chassis rust treatment is completed.

Vehicle Chassis Parts Damage First Aid Method

When the vehicle is damaged in the chassis in the field or far from the vehicle repair location, the following emergency methods can be used to drive the vehicle to the conditions for repairing the vehicle in response to different fault conditions.

Brake cylinder leakage brake fluid or the branch pipeline broken, can be used in the branch of the pump pipe with tin, copper skin to be a small mat, block the pipeline, and then tighten the screws, or the fracture flat, The curling is blocked, so that the wheel can not be used as a brake. However, doing so may cause unilateral braking, and should pay attention to safety when driving.

The brake master cylinder lacks brake fluid and can be replaced with alcohol or liquor. In special cases, fresh water can be used instead. Brake cups rise and the soaked skin cups are soaked in hot water for 10 minutes to 20 minutes to remove the oily components from the bowl so that the cups can be restored to their original size.

The clutch friction plate is ablated and slippery, and the friction plate that is less severe for ablation can be turned over. If the ablation is severe, use several layers of cotton cloth or canvas (the thickness of which should be the same as the original friction plate), and use steel wire or wire to pass through the hole in the steel plate to fix it. When driving a vehicle, it should be done steadily and the gear shifts quickly.

The tie rod ball joint is broken. In the bumper or other places that do not affect the driving, remove a screw with a total length similar to the ball joint to replace the broken ball joint. After installing the knuckle arm and nut, expose the screw. Partially riveted with a hammer. Damage to the triaxial automobile differential gear, such as damage to the differential in the rear axle and the rear axle, can remove the driveshaft and the axle from the axle and continue driving. If the front differential is damaged, the hub splint can be removed and continued.

Troubleshooting

First, the tie rod ball section breaks. In the bumper or other places that do not affect the driving, remove a screw with a similar overall length to the ball joint, replace the broken ball joint, install the knuckle arm and nut, and then rivet the exposed part of the screw.

Second, the three-axle differential gears are damaged. If any of the middle and rear axle differentials is damaged, the axle and half shaft of the axle can be removed and continued. If the front differential is damaged, the hub splint can be removed and continued.

Third, the brake master cylinder lacks brake fluid. Instead of alcohol or liquor, special water can be used instead. Brake cups rise and the soaked cups are soaked in hot water for 10-20 minutes to remove the oily components from the cups. This will allow the cups to return to their original size.

Fourth, the brake cylinder leak brake fluid or pump line break. When this happens in the suburbs, you can use the tin and copper skin as a small mat at the branch of the branch pump, block the pipeline, and then tighten the screw, or flatten and crimp the fracture to make the round Can not afford braking effect. This only serves as a temporary emergency. After the owner takes measures, he must immediately seek a professional shop for repairs.

Fifth, clutch friction plate ablation slip. The clutch of the car can make the car start steadily. In the changing road conditions, it is convenient to use different transmission gear positions. If the clutch friction plates have ablation, the friction plates that are not severely ablated can be turned over. If the ablation is serious, use several layers of cotton cloth or canvas (the thickness of which should be the same as the original friction plate), and use steel wire or iron wire to pass through the hole in the steel plate to fix it. Once the friction plate fails, if you do not take timely measures, it may pose a threat to traffic safety.

Fuel consumption

There are the following points regarding the maintenance and fuel consumption of the vehicle chassis:

(1) The front wheel toe adjustment is appropriate. Unprecedented beams will increase the rolling resistance of the car and increase fuel consumption. Check the toe value regularly and compare it with the normal value. If the value is different, adjust it.

(2) Wheel Yi bearings are well lubricated and properly adjusted. Poor wheel grease and improper adjustment of the bearing gap will increase the running resistance.

(3) Pay attention to changes in front and rear axles and frames. The front and rear axles and the frame are displaced or bent so that the vehicle body cannot be kept vertical or horizontal. When the car is driving, it is biased toward one side. The tires and the ground are subject to sliding friction, which increases the driving resistance and greatly increases the fuel consumption. .

(4) Note whether the leaf spring is damaged. The damage of the leaf spring causes poor balance of the vehicle's driving, increases the running resistance, and the fuel consumption also increases.

(5) The brake clearance is adjusted properly. If the brake clearance is too small and the resistance increases, you must open a large throttle to run, which will increase the fuel consumption. If the clearance is too large, the brake will not work and the safety will be affected. Adjusting the braking gap to avoid brake drag and gaps that are too large or too small has an important effect on the gliding performance of the car.

(6) Pay attention to the working condition of the clutch. The clutch is in poor working condition. In the process of transmitting torque, there are phenomena such as “shaking”, “slipping”, “bottom separation”, etc., which results in lower transmission efficiency and increased fuel consumption.

(7) Pay attention to whether the tire pressure is normal. The tire type should be the same. According to statistics, tire pressure decreased by 30% from the specified value, the tire service life was reduced by 33%, and fuel consumption increased by 6%.

Chassis inspection

From the point of view of the inspection project, it can be summarized as follows:

1Whether the automobile chassis is rusty or not

The chassis is exposed to a very harsh working environment for a long time, and the damage and erosion thereof are also the greatest. Driving in rainy weather, the chassis is in direct contact with rain; driving in snow; the chassis is directly in contact with the icy snow; while the rugged mountain roads have to withstand gravel and other harsh environments. These special road conditions are very damaging to the chassis. Therefore, checking the degree of corrosion of the chassis in time is one of the important items to effectively protect the chassis.

2 Chassis equipment equipment inspection

The chassis is loaded with many important body parts. Total exhaust performance is one of the important items for chassis inspection. Although a part of the exhaust assembly is located in the engine compartment, most of it is loaded on the chassis of the vehicle. Therefore, the safety of the relevant components must also be taken into consideration when conducting chassis inspections. The inspection of automobile exhaust pipe is mainly to determine if there is a leak.

The inspection of the chassis of the car focuses on “diligentness”, and the savvy owner must be a diligent owner. The role of the chassis cannot be ignored. Checking the working status often is also a necessary guarantee for driving safety.