We know that engine is only responsible for power output of car, but it does not directly affect wheels to drive car. Many motorists do not understand that sometimes a car can travel up to 100 km / h. H when engine is 2000 rpm, but sometimes engine speed reaches 4000 rpm or higher, but speed is only 50 km/h. It appears that final speed of vehicle is not entirely determined by engine speed, but is result of a series of complex and precise power transmission mechanisms based on actual load and road conditions. How does this power get to wheels? Has engine power output gone through transmission components? Today Kandy will briefly introduce you to car transmission system.
A car's engine can deliver a continuous stream of energy, like a human heart, and reach wheels that drive car through a series of power transmission devices. The mechanism for transmitting power between engine and driving wheels is called vehicle transmission, which is mainly composed of clutch (torque converter), transmission, universal transmission, transfer case, final reduction gear, differential and axle shafts, etc.
▌The role of transmission
(1) Transmission is a general term for all mechanisms that transfer engine power to drive wheels. Since engine produces limited torque and high speed, and drive wheels must operate at high torque and low speed, transmission must have a sufficiently large gear ratio (to increase torque).
(2) The direction of rotation of engine cannot be changed, and transmission must change direction of rotation of vehicle's drive wheels (forward and reverse).
(3) The power of engine through transmission system must also increase smoothly (balance power of engine) so that car starts in a balanced manner.
(4) Turn off engine power output so that engine can be started and engine does not need to be turned off when car is temporarily parked or slowed down.
(5) Make sure fuel consumption of power system is as low as possible (improve fuel economy).
(6) Sometimes changing transmission ratio is not necessary to improve use of engine power and reduce fuel consumption, but to meet certain vehicle speed requirements. For example, on a highway, required torque is small, but at this time gear ratio must be increased to obtain a very high speed. (increased practicality)
To protect engine and other transmission components, clutches (automatic transmission, dual clutch transmission and torque converter) are required to increase torque and cut off power when engine is running.
The gearbox is most complex part of entire transmission system, and most important function of transmission is to match power of engine to actual load on the road.
(1) Change gear ratio, widen torque range and drive wheel speed to accommodate frequently changing driving conditions, and at same time make engine run in favorable conditions (higher power and lower fuel consumption). consumption);< /p>
(2) Provided that direction of rotation of engine remains unchanged, vehicle can move backward;
(3) Use neutral to interrupt power transmission so that engine can start and idle, and transmission can conveniently shift gears or perform power output.
When vehicle is in motion, suspension and tires are constantly changing due to difficult road conditions, resulting in frequent changes in angle and distance between drive shaft and final drive input shaft. it is necessary to be able to adjust angle in several dimensions. Transmission is a universal joint.
It mainly consists of universal joints, transmission shafts and intermediate supports.
In a multi-wheel drive vehicle, a transfer case is required to distribute power output of transmission to each drive axle according to desired gear ratio. The structure of transfer case is also a gear transmission system. The input shaft is directly connected to output shaft of transmission, directly or through a universal transmission device. The output shafts differ according to number of drive axles. Connection.
Some transfer cases are designed to be used as an auxiliary transmission. Generally, there are low gears (gearboxes are also called overdrives) and high speed gears (also known as direct gears). In order not to overload rear drive axle and damage components of transmission system, a locking mechanism is often provided. usually 2.5~5 km/h).
5. Drive axle
Drive axle function: further change gear ratio, reduce speed, increase torque, change direction of rotation of power and transfer power from gearbox to left and right drive wheels.
Composition of drive axle: final drive, differential.
6. Last gear
The function of main gearbox is very simple, and structure is uncomplicated. There is only a simple gear mechanism, and small gear drives large gear to achieve deceleration and increase torque.
The function of main gearbox is to increase gear ratio, usually used to change direction of torque and transfer torque from vertical output shaft of transmission to final output shaft on both sides.
Kandy already talked about the differential device in detail in a previous article, if you are interested, you can go and have a look.
Differential function: Allows left and right drive wheels to rotate at different speeds and transmit power. This is not only a necessity for steering, but also requires that left and right drive wheels can be rotated at different speeds to reduce tire wear and power consumption when driving in a straight line, since actual tire radii cannot be completely equal.
Classification of differentials: The most widely used differentials with bevel teeth, which are divided into casing and frameless. The case differential has a special shell for mounting planetary gears and side gears. Its shell has high rigidity and a short bearing distance, which can improve meshing of center gear bevel gear. The entire differential is designed as a single unit. .
Differential lock. Typically, differential lock is only used as an emergency measure when vehicle is stuck. When rear wheel of vehicle slips to one side and cannot move forward, depress differential lock control pedal to make vehicle's two drive wheels rotate simultaneously to allow vehicle to pass through slip zone. The differential lock of medium power vehicles is of pin type.
Eight, axle shaft
The axle shaft is shaft that transmits torque between gearbox and drive wheel (it used to be mostly solid because hollow shaft is lighter and easier to steer, which is why many cars use hollow shafts), inner and outer ends of which, respectively, have a universal joint, and through splines on universal joint, one side is connected to gearbox, and other side is connected to inner ring of hub bearing, and power is transmitted to wheel.
The axle shafts commonly used in modern vehicles are of two types: fully floating and semi-floating, depending on type of bearing they support.
A fully floating axle shaft only carries torque when it is running, and a axle that does not carry any force and no bending moment at either end is called a fully floating axle. The outer flange of axle shaft is bolted to hub, and hub is mounted on axle shaft sleeve through two bearings located far from each other. Structurally, inner end of a fully floating axle shaft is equipped with a spline, and outer end with a flange, and flange has several holes. Widely used in commercial vehicles due to reliable performance.
The semi-floating axle shaft rests directly on a bearing located in inner bore of outer end of axle housing with trunnion close to outer end, and end of axle shaft is rigidly connected to hub. with a trunnion with a conical surface and a key or with a boss. The rim is directly connected to rim and brake hub. Therefore, in addition to transmitting torque, it also bears vertical force transmitted from wheel, bending moment caused by driving force, and lateral force. The semi-floating axle shaft is used in passenger cars and some similar vehicles due to its simple design, light weight and low cost.
▌Resume of Kandy
Although this is an era where looks and appearance are judged, many consumers are more interested in beautiful and exquisite appearance when buying a car, but Kandy reminds everyone that mechanical part of car is equally important, such as transmission. system introduced today. Cars have been in development for over 100 years, and every little progress embodies relentless pursuit of car performance by engineers. The quiet operation of transmission system inside car ensures car's stable operation, fuel economy and quietness, making driving easier. With ease, vehicle gradually transforms from a tool into a space of enjoyment, providing people with a standard of living.
For more exciting traffic and car news, visit official Daily Kanche WeChat account.