What parts does the chassis of a car refer to?

As we all know, a car has "three big pieces" : engine, gearbox and chassis. These three parts have the highest technology content, are the core parts of the car, and the highest price, accounting for more than 60% of the total price of the car. Their advanced technology, reliability and manufacturer's ability to adjust directly determine the performance of the vehicle.

The engine and gearbox are familiar to us. You can see them when you open the engine compartment. They are usually grouped together and collectively referred to as the car's powertrain. But a lot of people are very vague about what a case is. Some say that the suspension of a car is the chassis, some say that the iron plate at the bottom of the car is the chassis, and some say that everything except the gearbox of the engine belongs to the chassis. Who's right? Let's discuss in detail what the chassis of the car is, what the so-called chassis tuning is.

First of all, to be clear, the so-called "car chassis" is not a single component or assembly, but a larger system on the car, is a combination of transmission, ride, steering, braking system. It has the functions of supporting and installing the automobile engine and other components assembly, bearing and transferring the engine power, supporting the weight of the vehicle and realizing walking, controlling the direction and speed of the car, manipulating and controlling the body attitude and running state, etc. Automobile chassis is the basis of the automobile, the overall shape of the automobile is also determined by the type of chassis.

The body structure can be divided into two kinds: load-bearing body and non-load-bearing body, and their chassis structure is different. Early cars and now trucks and so on. All the non-load-bearing body structure, with a huge and strong frame, in the frame almost installed all the parts of the car, is the basis of the car chassis. The chassis refers to all parts of the car except the engine and body. Today's cars and SUVs basically adopt non-load-bearing body structure, all the parts of the car are directly or indirectly installed on the body of the car. The so-called chassis, more refers to the suspension system, steering system and braking system.

Let's look at the specific parts of the chassis.

1. Transmission system: transmission system is mainly composed of clutch (or torque converter), transmission (manual and automatic), universal transmission and drive axle. It can also be said that everything from the clutch (or torque converter) to the middle of the drive wheel belongs to the drivetrain. Its main function is to decelerate and increase the torque, change the speed and change the torque, realize the commutation, interrupt the power transmission of the transmission system, the difference between the wheels.

For rear-wheel drive cars, they're arranged like this; For a front-wheel-drive vehicle, the transmission and the drive axle are combined into one and collectively referred to as the transmission, and usually the engine and transmission are collectively referred to as the car's powertrain. Here's a paradox: the three main components of a car are the engine, the gearbox and the chassis, but the gearbox is contained in the drivetrain and is part of the chassis. According to this classification, the car should have only two main parts: the engine and the chassis. So when we talk about the structure of the car, it is generally said that the car is composed of the engine, chassis, body, electrical and electronic equipment. The idea that the big three are actually based on trucks is a little outdated.

2. Driving system: The driving system of the car is composed of the frame, axle, suspension, wheels and tires. Its function is to receive engine torque from the transmission system and generate driving force to drive the car; Bear the total weight of the car, transfer and bear the road acting on the wheel in all directions of the reaction force and torque; Bear the impact and vibration of various forces and moments given by the outside world, and make it buffer and reduce the vibration, so as to ensure the ride comfort and handling stability of the car; Coordinate with the steering system to control the driving direction of the vehicle; Coordinate with the braking system to ensure the safety and stability of the vehicle.

As for the non-load-bearing body, it has a huge and strong frame, the car in the process of driving all kinds of forces are ultimately borne by the frame. The suspension system can use very stiff leaf springs, which are less comfortable but can bear a lot of weight, or rigid independent suspension; For load-bearing cars and SUVs, there is no frame. All the parts in the driving system are eventually installed on the body of the car, and all the forces that the car is subjected to during the driving process are ultimately borne by the body. The suspension system mostly uses comfortable independent suspension. To enhance the rigidity of the chassis system, the suspension system and the body are usually connected by the subframe.

The driving quality or handling of a car is mainly determined by its driving system, in which the suspension system plays a crucial role. Most cars use independent suspension, such as McPherson type, double - arm type, multi - link type and so on. With different cushioning springs and shock absorbers, the car's handling is completely different. In particular, the support and deformation of the suspension system have a great influence on the car's handling. So it makes sense to say that the chassis of a car mainly depends on the suspension.

3. Steering system: The special mechanism used to change the direction of the car is generally called the vehicle steering system, which is mainly composed of steering control mechanism (steering wheel, steering column, etc.). Steering gear, steering transmission mechanism (bar, steering ball, etc.) Steering assist mechanism (steering pump, steering motor, etc.) The function of the car steering system is to ensure that the car can go straight or turn according to the driver's wishes. It is coordinated with the suspension system of the automobile and directly affects the handling performance of the automobile.

Now most of the steering systems of automobiles have power devices, generally including hydraulic power devices and electric power devices. Electric power steering systems are mostly used in passenger cars. It has the feature of steering at speed, which gives the car better handling, but it has the disadvantage of less power. And trucks and off-road vehicles mostly use hydraulic power steering system, more power, more stable and reliable performance. The disadvantage is to increase the engine load, can not change the power with the speed.

4. Braking system: Automobile braking system refers to a series of special devices that can produce braking force on automobiles. It is mainly composed of brake pedals and brakes

The main pump, brake pump, brake line, wheel brake and other components. Its main function is: according to the need to make the car slow down or stop in the shortest distance, in order to ensure driving safety, and make the driver dare to play the car's high-speed driving ability, so as to improve the productivity of automobile transportation; It can also make the car park reliably on the ramp.





The braking system is undoubtedly the most important active safety device in the automobile. It can be roughly divided into hydraulic braking system and pneumatic braking system two types. More hydraulic braking systems are used in light vehicles and passenger vehicles. In order to enhance the braking effect or maintain the body stability during braking, a variety of brake assist systems have been developed on automobiles, such as ABS, ESP, EBD, ASR, TCS, HAC, AUTOHOLD, HDC, BOS and so on. They are instrumental in keeping cars safe.







Therefore, the chassis of the car refers to the general term of a series of parts that support the car running and control the car running state. In our most common cars, all parts except the engine, body and electrical system can be classified as chassis. In this regard, people are most likely to misunderstand that the bottom of the car as a large piece of iron plate as the car chassis, in fact, it is a part of the car body, not the chassis. And we usually say scraping chassis, chassis rust, etc., all refer to this bottom plate.







Generally, the chassis structure of different models is different, some of the so-called use of the same chassis with a certain model, in fact, the use of the same transmission, suspension, steering and braking system with a certain model; Some models are developed on the basis of some chassis. Based on the original chassis, some changes have been made in the local area, such as the chassis suspension of the car, which can be developed into an SUV model.







But there is also a sense that even different models on the same chassis have different driving sensations, such as the stiffness of the suspension, the feel and precision of the steering, the height of the brake pedal, the height of the clutch pedal, the roll of the car through a corner...... Wait, why is that? This involves a very important technical process in the process of automobile design and manufacture: chassis adjustment.







The so-called chassis adjustment usually refers to the setting of the chassis system such as suspension system, steering system and braking system. Its ultimate purpose is to make the various components of the automobile chassis achieve relative unity, so that it has a certain correlation and integrity. Chassis adjustment is a very complex system engineering, which is not just a tinkering adjustment after the automobile manufacturing and forming, but a full participation in the automobile design and manufacturing process, which can be divided into three stages: early development, middle development and late development. Adjust the parameters of each system according to the positioning of the model, the environment of use and the habit of the target customers.







For example, now the ordinary family car, the basic is the pursuit of comfort, so that its suspension system adjustment is soft, better vibration filtering, road sense is not very clear, steering system adjustment is light, with good safety inadequate steering characteristics, brake system adjustment is slow; As for the performance car, it pursues good handling, so the suspension system needs to be harder, the steering system feels heavier and more accurate, the braking system is more responsive, and so on. And some more advanced models, in order to achieve the unity of comfort and good control, will also use the active suspension system, according to the speed of the high and low and road conditions, automatic adjustment of the soft and hard suspension system and steering system feel.







It can be said that chassis adjustment is the most test of the strength of the vehicle factory, even if it is the same structure of the chassis, different manufacturers will adjust out of different styles and driving characteristics, and different chassis adjustment will produce different personality models. It requires rich experience and accumulation of a large number of original data, as well as various feedback data during the use of cars, so it is not a technology that can be formed in a short period of time, but the accumulation of dozens or even hundreds of years of technology by automobile enterprises. As a result, some established car companies are very good at chassis tuning, such as Citroen, which uses torsion beam suspension system even better than some multi-link suspension system performance.







It should be said that the chassis of an automobile is a very complex system in automobile technology, and its structure and adjustment technology are even more complex than the engine and gearbox. For domestic independent brands at the present stage, they may be able to manufacture their own engines and research and develop their own transmission, but no car company can completely research and develop and adjust a set of chassis system. Even if it can completely reverse the chassis of a certain model, the performance of the chassis is far from that of the prototype due to the lack of late adjustment skills. Therefore, the current independent brands are more direct use of some joint venture vehicle chassis system, independent research and development of the road is far and heavy.