The function of the chassis is to support and install the car engine and its components and assemblies to form the overall shape of the car, and to receive the power of the engine to make the car move and ensure normal driving. The chassis consists of four parts: transmission system, driving system, steering system and braking system.
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Figure 1 Car chassis
Drive Train
The transmission system generally consists of clutch, transmission, universal transmission device, main reducer, differential and half shaft.
The function of the drive train
The power generated by the automobile engine is transmitted to the driving wheels through the transmission system. The transmission system has functions such as deceleration, speed change, reversing, power interruption, inter-wheel differential and inter-axle differential. It works in conjunction with the engine to ensure the normal driving of the car under various working conditions and has good power and performance. Economy.
Types and composition of drive trains
The transmission system can be divided into mechanical transmission, hydraulic transmission, hydraulic transmission, electric transmission, etc. according to different energy transmission methods.
1. General composition and layout of mechanical transmission system (see Figure 2).
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Figure 2 Schematic layout of front-mounted, longitudinal-mounted engine and rear-wheel drive
Schematic diagram of the layout of a 4×2 car with a traditional engine installed longitudinally at the front of the car and rear axle drive. The power generated by the engine is transmitted to the drive axle through the clutch, transmission, and universal transmission device. At the transaxle, power is transmitted to the drive wheels through the final reducer, differential and half shafts.
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Figure 3 Schematic layout of front-mounted, longitudinal-mounted engine and front-wheel drive
The engine is front-mounted, longitudinally mounted and front-axle driven, so that the transmission and the main reducer are connected together, eliminating the need for a universal transmission device between them, as shown in Figure 3.
2. Typical hydraulic mechanical transmission schematic diagram (shown in Figure 4).
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1-Torque converter 2-Automatic transmission 3-Universal transmission 4-Drive axle 5-Main reducer 6-Drive shaft
Figure 4 Schematic diagram of hydraulic mechanical transmission
Hydraulic transmission (here refers to hydrodynamic transmission only) uses the change in kinetic energy of the liquid medium during the cyclic flow between the active element and the driven element to transmit power. A hydraulic transmission device is connected in series with a stepped mechanical transmission. This transmission is called a hydromechanical transmission.
3. Schematic diagram of hydrostatic transmission system (shown in Figure 5).
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1-Clutch 2-Oil pump 3-Control valve 4-Hydraulic motor 5-Transmission axle 6-Oil pipe
Figure 5 Schematic diagram of hydrostatic transmission system
Hydraulic transmission, also called hydrostatic transmission, transmits energy through changes in the static pressure energy of the liquid transmission medium. It is mainly composed of engine-driven oil pump, hydraulic motor and control device.
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4. Electric transmission used in hybrid electric vehicles (as shown in Figure 6).
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1-Clutch 2-Generator 3-Controller 4-Motor 5-Transmission axle 6-Wire
Figure 6 Electric transmission used in hybrid electric vehicles
In the electric transmission, the engine drives the generator to generate electricity, and then the electric motor drives the transaxle or the electric motor directly drives the drive wheel with a reducer.
Drive train layout
The common layout of mechanical transmission systems is mainly related to the location of the engine and the drive type of the car. It can be divided into:
1. Front-engine and rear-wheel drive-FR: that is, front-engine and rear-wheel drive
This is a traditional arrangement. Most trucks, some cars and some buses at home and abroad adopt this type. It is front-wheel to rear-wheel drive. The engine output power is transmitted to the drive axle through the clutch-transmission-transmission shaft. After decelerating and increasing torque, it is transmitted to the rear left and right half-shafts to drive the rear wheels to make the car run. Each wheel performs its own duties, steering and driving are separated, and the load distribution is relatively even.
2. Rear-mounted and rear-wheel drive-RR: rear-mounted engine and rear-wheel drive
This layout is mostly used on large buses, and a small number of mini and light cars also use this layout. The rear-mounted engine makes the front axle less likely to be overloaded and makes full use of the trunk area. It can also effectively lower the height of the body floor or make full use of the space under the floor in the middle of the car to place luggage. It is also helpful in reducing the impact of high temperature and noise from the engine. Driver impact. The disadvantage is that the engine's cooling conditions are poor, and some faults during driving are not easily noticed by the driver. Remote control also makes the control mechanism complicated and maintenance and adjustment inconvenient. However, due to its outstanding advantages, it is increasingly used in large buses.
3. Front-engine-FF: front-engine, front-wheel drive
This type has a simple operating mechanism and good engine heat dissipation conditions. However, when going uphill, the mass of the car moves backward, which reduces the attached mass of the front drive wheels and makes the drive wheels prone to slipping; when braking downhill, the mass of the car moves forward, causing the front wheels to be overloaded and overturning at high speeds. Most cars now adopt this layout.
4. Transmission system of off-road vehicle
Off-road vehicles are generally all-wheel drive with a front-mounted engine and a transfer case behind the gearbox to transmit power to all wheels. At present, light off-road vehicles generally use 4×4 drive type, medium-sized off-road vehicles use 4×4 or 6×6 drive type; heavy off-road vehicles generally use 6×6 or 8×8 drive type.
