Transmission form

The transmission is used to change the torque and speed of the crankshaft of the engine to meet the requirements of different driving conditions such as starting, accelerating, driving and overcoming various road obstacles. It is used to change the engine crankshaft torque and speed, mainly: manual transmission (MT), automatic transmission (AT), manual / automatic transmission, continuously variable transmission (CVT).

Manual Transmission (MT)

Manual transmission, also known as manual transmission, that is, shifting the shift lever by hand can change the gear meshing position in the transmission, change the transmission ratio, so as to achieve the purpose of shifting speed. When the manual transmission is shifting gears, it is necessary to depress the clutch pedal before activating the shift lever. The working principle of the manual transmission is to replace the passive gears of different sizes to engage with the power output shaft. When downshifting, the passive gear is actually switched to a larger gear. According to the lever principle, the output speed of the transmission will be Relatively lower, but the torque increases; conversely, if it is upshift, it is actually the passive gear is switched to the pinion, then the output speed of the transmission will increase, but the torque will decrease. The manual transmission of a car usually has a synchronizer, which can facilitate shifting, direct power transmission, rapid power response, relatively low fuel consumption, and low noise.

Manual gear shift transmissions generally have 4 gears, 5 gears to 16 gears and other gears. This gear refers to the forward gear of the car and does not include reverse gears. Passenger cars, passenger cars and medium-sized freight cars commonly use 4 to 6-speed transmissions. Off-road vehicles and heavy-duty trucks often use 8-speed to 16-speed transmissions to meet a variety of complex conditions. The expression of manual transmission is: 6-speed manual transmission, or abbreviated as M6. [2]

Automatic transmission (AT)

The automatic transmission uses a planetary gear mechanism to shift gears. It can automatically shift gears according to the accelerator pedal level and the speed change. Drivers only need to use the accelerator pedal to control the speed.

In general, there are several types of automatic transmissions commonly used in automobiles: hydraulic automatic transmissions, hydraulic transmission automatic transmissions, electric transmission automatic transmissions, stepped mechanical automatic transmissions, and stepless mechanical automatic transmissions. Among them, the most common is the hydraulic automatic transmission. The hydraulic automatic transmission is mainly composed of a hydraulically controlled gear transmission system, and mainly includes two parts of an automatic clutch and an automatic transmission. It can automatically shift gears according to the throttle opening and speed changes.

At present, individual limousines have used 7-speed automatic transmissions. The expression of the automatic transmission is: 5-speed automatic transmission, or abbreviated as A5.

There are many clutch plates in an automatic transmission, and there is a clutch plate in almost every gear position. These clutch plates are driven and separated by a control mechanism to perform gear shifting. The control mechanism in the automatic transmission is basically hydraulic. Many valves are designed. When the oil pressure rises, some valves will be automatically opened, and then these oils will drive some clutch plates to move. The designer uses various information such as the vehicle speed and throttle opening as the input signal to control the increase or decrease of the hydraulic pressure. When the vehicle speed and the throttle opening change, it will automatically switch to a different gear. Nowadays, many automatic transmissions use solenoid valves instead of complicated hydraulic valves. They can use information such as the vehicle speed and throttle opening to directly control the action of multiple-disc clutches to achieve the purpose of automatic transmission. It is worth mentioning that the gears in automatic transmissions and the gears in manual transmissions are very different. They are combined using planetary gears. Different rotational speed outputs can be achieved by controlling the rotation of certain planetary gears. Of course, they also include reverse rotation. Each gear, either fixed or rotating, is automatically hydraulically actuated according to computer calculations or according to vehicle speed commands.

Manual/automatic transmission

The manual/automatic transmission was first introduced by the Porsche depot in Germany on the 911 model, called Tiptronic, which allows high-performance sports cars to not be constrained by the traditional automatic files, allowing drivers to enjoy manual shifting. This car has "+" and "-" selection gears on its gear. In the D position, the downshift (-) or upshift (+) can be freely changed, just like the manual gear.

Drivers can force downshifts like a manual gear before entering a corner, and can go out of a low mid-range corner when out of a corner.

The "+" and "-" shift buttons have been added to the steering wheel of the current automatic transmission so that the driver can move his hand off the steering wheel.

Continuously Variable Transmission (CVT)

The continuously variable transmission is composed of two sets of shifting discs and a transmission belt. Therefore, it has a simpler structure and a smaller volume than the conventional automatic transmission. Its speed change has exceeded the concept of number of gears. In addition, it can freely change the transmission ratio, thus achieving full-step infinitely variable transmission, so that the car's speed changes smoothly, without the traditional "transient" feel when shifting gears. The CVT is a kind of automatic transmission, but it can overcome the shortcomings of "abrupt shifting", slow throttle response, and high fuel consumption of an ordinary automatic transmission, but at the same time it lacks driving pleasure, and its maintenance cost is also relatively high.

The main components of a continuously variable transmission are two pulleys and a metal belt, and the metal belt is sleeved on two pulleys. The pulley is composed of two discs. The groove in the middle of the two discs forms a V-shape. One of the discs is controlled by a hydraulic control mechanism. It can be divided and closed according to different engine speeds. V-shaped concave The slot also becomes wider or narrower, and the metal strip is raised or lowered to change the diameter of the metal strip in contact with the pulley, which is equivalent to switching gears of different diameters during gear shifting. The two pulleys are adjusted in the opposite direction, that is, when one of the pulley grooves gradually widens, the other pulley groove gradually narrows, thereby quickly increasing the transmission ratio change. When the car is running at a slow speed, the groove width of the active pulley may be larger than that of the passive pulley, and the circumferential radius of the metal belt of the active pulley is smaller than the circumferential radius of the metal belt of the passive pulley, that is, the small round circle has a large circle, so it can transfer a larger turn. Moment; When the car gradually turns to high speed, one wheel of the active pulley moves closer inwards, and the width of the groove becomes smaller, forcing the metal belt to rise up to the highest point, while the one side of the passive pulley is just the opposite, and the outward movement is large. The groove width forces the metal belt to fall, that is, the circumferential radius of the active pulley metal band is greater than the circumferential radius of the passive pulley metal belt, and becomes a big circle with a small circle, thus ensuring the speed requirement of the car at a high speed.