How many types of automatic transmissions are there according to different control methods?

1. Electronically controlled hydraulic automatic transmission (AT).

It is formed by adding an electronic control system on the basis of the traditional hydraulic automatic transmission. The electronically controlled hydraulic automatic transmission can select the optimal speed ratio for different loads and vehicle speeds, so that the engine can work at the corresponding optimal speed. All gear changes are carried out by the transmission itself, and the driver only uses the accelerator pedal to express the intention of the vehicle to change the speed and select the required operating state via the gear selector.

2. Electronically controlled mechanical automatic transmission (AMT).

On the basis of the traditional dry clutch and manual gear transmission, an electronic control system is added, and the manual shift mechanism is transformed into an automatic shift mechanism, so as to realize the stepwise mechanical automatic transmission with automatic gear shifting.

3. Electronically controlled mechanical continuously variable automatic transmission (CVT).

The transmission belt and the main and driven wheels with variable working diameter are used to transmit power, and the continuous change of the transmission ratio can be realized, so as to obtain the best match between the drive train and the engine working conditions.

4. Dual-clutch transmission (DCT).

The clutch is located between the engine and the transmission, and is the "switch" for the power transmission between the engine and the transmission. Its main function is to ensure that the car can start smoothly, reduce the shock load of the transmission gear and prevent the drive train from overloading when shifting.

According to the mode of operation, the transmission can be divided into three types: forced operation, automatic operation and semi-automatic operation.

The transmission is a mechanism used to change the speed and torque from the engine, which can change the output shaft and input shaft transmission ratio in fixed or divided gears, also known as the gearbox. The transmission is composed of a transmission mechanism and a control mechanism, and some cars also have a power take-off mechanism. Most of the transmission mechanisms are driven by ordinary gears, and some are driven by planetary gears.

Ordinary gear transmission and transmission mechanism generally use sliding gears and synchronizers.

Transmission uses basic noun terms:

1) Drive gear, driven gear. The input shaft can be understood to be connected with the clutch and rotate under the engine drive, and the gear fixed on the input shaft rotates synchronously with it, and the gear is called the driving gear and is forced to rotate after being connected with the output shaft, so the gear is called the driven gear.

2) Gear ratio i. The ratio of the number of teeth of the driven gear to the number of teeth of the driving gear is defined as the transmission ratio.

When the relationship between the number of teeth of driven gear and the number of teeth of driving gear changes, the transmission ratio i changes, and under the condition that the engine speed does not change, the output shaft speed change is affected, that is, the wheel speed changes.

A pair of gears that mesh with each other will not change the number of teeth in use, so its gear ratio is fixed. If a plurality of gears with unequal number of teeth are installed on the input shaft and the gear meshing that the corresponding number of teeth on the output shaft is also variable, a group of step-by-step transmissions with different transmission ratios i can be obtained. It is according to this basic principle that the automobile transmission realizes the shift of gears.

There are three types, which are mandatory, automatic, and semi-automatic.

Commonly used automatic transmissions mainly include electronically controlled hydraulic automatic transmissions (AT), electronically controlled mechanical automatic transmissions (AMT), electronically controlled mechanical continuously variable automatic transmissions (CVT), and dual-clutch transmissions (DCT).

AT gearbox is what we often call automatic transmission, the gear of automatic transmission is divided into P, R, N, D or L, etc., this kind of gearbox is relatively stable technology, the disadvantage is mainly high cost, difficult to develop, but as the most mature technology in automatic transmission, AT automatic transmission still has a broad development trend.

How the transmission works.

Although the torque converter can transmit and increase the engine torque, the torque conversion ratio is not large, and the transmission range is not wide, which is far from meeting the needs of the automobile working conditions. In order to further increase the torque, expand its transmission range, and improve the adaptability of the car, an auxiliary transmission is installed behind the torque converter, and the planetary gear mechanism is mostly used.

The planetary gear transmission is composed of a planetary gear mechanism and actuators such as clutches, brakes and one-way clutches. The planetary gear mechanism is usually composed of multiple planetary rows, and the number of planetary rows is related to the number of gears.

The shift actuators of planetary transmissions include shift clutches, shift brakes, and one-way clutches.

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Automatic transmission: also known as automatic transmission, it is generally a kind of automobile transmission that can automatically change the gear ratio while the vehicle is moving, so that the driver does not have to manually change gears, and is also used in large equipment railway locomotives.

There are different classifications of automatic transmissions.

1. According to the form of variable speed.

It can be divided into two types: continuously variable transmission and continuously variable transmission.

A CVT is a transmission with a finite number of fixed-value ratios (typically 4 9 [2] forward gears and one reverse gear).

Continuously variable transmission is a transmission that can make the transmission ratio change continuously within a certain range, and the application of continuously variable transmission in automobiles has gradually increased.

2. According to the type of stepless torque change.

1) Hydraulic automatic transmission.

It is a planetary gear transmission system behind the torque converter.

2) Mechanical continuously variable transmission.

It is continuously variable by the clutch and the radius of the V-pulley depending on the change of vehicle speed and throttle opening.

3) "Electric motor" infinitely variable speed.

It does away with the traditional mechanism in mechanical transmission and instead uses an electric current to drive the wheels that are integrated with the motor.

3. According to the number of gears of the automatic transmission.

It can be divided into 2 forward gears, 3 forward gears, and 4 forward gears.

4. According to the type of gear transmission.

Automatic transmissions can be divided into two types: fixed-shaft gear type and planetary gear type according to the different types of gear transmissions.

Fixed shaft gear automatic transmission is larger in size, smaller in maximum transmission ratio, and less used.

Planetary gear automatic transmission has a compact structure and can obtain a large transmission ratio, which is adopted by most cars.

5. According to the control mode of gear transmission system.

1) Hydraulic automatic transmission.

The hydraulic automatic transmission converts the two parameters of the speed and throttle opening of the car into hydraulic control signals by mechanical means; According to the size of these hydraulic control signals, each control valve in the valve plate realizes automatic shift by controlling the action of the shift actuator according to the set shift law, which is less used and is not introduced in this article.

2) Electronically controlled hydraulic automatic transmission.

The electronically controlled hydraulic automatic transmission converts the engine speed, throttle opening, vehicle speed, engine water temperature, hydraulic oil temperature and other parameters into electrical signals through various sensors and inputs them into the computer; According to these electrical signals, the computer sends electrical control signals to the shift solenoid valve and the hydraulic solenoid valve according to the set shift law; The shift solenoid valve and the hydraulic solenoid valve then convert the electronic control signal of the computer into a hydraulic control signal, and each control valve in the valve plate controls the action of the shift actuator according to these hydraulic control signals, so as to realize automatic shifting.

3) Electronically controlled automatic transmission.

It is to control the motor to achieve gear shifting, because it uses motor control, so there is no hydraulic oil, no slide valve box, and the structure has become more compact and simple, and the cost is lower.

It is divided according to the transmission ratio variable.

1) Stepless transmission: Stepless transmission is the most widely used one. It is geared and has several fixed-value ratios.

According to the different types of gear trains, there are two types of shaft fixed transmissions (ordinary transmissions) and shaft rotary transmissions (planetary gear transmissions). Transmissions for passenger cars and light and medium-duty vans typically have a ratio of 3-5 forward gears and one reverse gear, and in combination transmissions for heavy trucks, there are more gears. The number of transmissions refers to the number of forward gears.

2) Continuously variable transmission: The transmission ratio of continuously variable transmission can be changed according to infinite multi-stage within a certain numerical range, and there are two common types: electric type and hydraulic type (dynamic and hydraulic type). The variable speed transmission component of the electric continuously variable transmission is a DC series motor, which is not only used in trolleybuses, but also widely used in the drive train of ultra-heavy-duty dump trucks.

The transmission component of the dynamic hydraulic continuously variable transmission is a hydraulic torque converter.

3) Integrated transmission: Integrated transmission refers to the hydromechanical transmission composed of hydraulic torque converter and gear type stepless transmission, and its transmission ratio can be continuously changed within several intermittent ranges between the maximum value and the minimum value, and it is widely used.

According to the different working methods, transmissions can be divided into three types: continuously variable transmission, continuously variable transmission and comprehensive transmission.

Step-by-step transmission: Step-by-step transmission is one of the most widely used. It is geared and has several fixed ratios.

Depending on the type of gear train used, there are two types of axial fixed transmission (general liter rotten transmission) and axial rotary transmission (planetary gear transmission). Cars, light and medium-duty trucks usually have a gear ratio of 3-5 forward gears and one reverse gear, while in the combined transmission of heavy trucks, there are more gears. The so-called transmission gear refers to its forward gear.

Continuously variable transmission:

The transmission ratio of the continuously variable transmission can be infinitely changed within a certain value, and there are two common types: electric type and hydraulic type (hydraulic type). The variable speed transmission component of the electric CVT is the DC series motor, which is not only widely used in trolleybuses, but also in the drive system of ultra-heavy base dump trucks. The transmission component of a hydraulic CVT is a torque converter.

Integrated transmission:

Integrated transmission refers to the hydromechanical transmission composed of hydraulic torque converter and gear type continuously variable transmission, and its transmission ratio can be infinitely changed in several gaps between the maximum and minimum values, which is widely used.

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The differences between automatic transmissions and ordinary transmissions are as follows; Ordinary transmission: All gears of ordinary transmissions must be manually shifted, and the driver's labor intensity increases. In addition to the reverse gear, the automatic transmission is controlled by hand, and the other forward gears can be automatically shifted according to the engine condition and vehicle speed.

The difference between an automatic transmission and a regular transmission.

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The differences between automatic transmissions and ordinary transmissions are as follows; Ordinary transmission: All gears of ordinary transmissions must be manually shifted, and the driver's labor intensity increases. In addition to the reverse gear, which is controlled by hand, the other forward gears can be automatically shifted in the morning according to the engine working conditions and vehicle speed, and the ordinary transmission is cheaper, while the automatic transmission is more expensive.

Automatic transmission: The electronically controlled automatic transmission has functions such as mode selection, self-diagnosis, and failure protection. Due to the installation of a torque converter in the automatic transmission, the separation pedal has been eliminated, which has improved the driving safety of the car.

Because the torque converter is a liquid transmission, it can realize continuously variable speed, so that the car starts and accelerates more smoothly, and can also avoid the engine stalling due to excessive load.

Automotive transmissions can be divided into automatic transmissions and manual transmissions. Most cars are automatic, so the gearbox is an automatic transmission, because the structure of the automatic transmission is more complex, so many people don't know about the automatic transmission. According to the different working principles, there are four types of automatic transmissions commonly used in automobiles, namely hydraulic automatic transmissions, mechanical continuously variable automatic transmissions, electromechanical automatic transmissions and dual-clutch automatic transmissions.

Hydraulic automatic transmission realizes automatic transmission through the combination of hydraulic transmission and planetary gears. Generally, it is composed of hydraulic torque converter, planetary gear mechanism, shift actuator, shift control system, shift control mechanism and other devices. The mechanical continuously variable automatic transmission is characterized by the fact that the speed ratio sail ridge is not constant, but a series of continuous values, so as to better coordinate the driving conditions of the vehicle with the load of the engine, the engine can be used to its full potential, improve the fuel economy of the vehicle, it makes the car have non-porous traction performance, and thus significantly improve the performance of the vehicle.

At present, the power transmission is mostly driven by steel belt or chain.

The electromechanical automatic transmission is an improvement on the basis of the traditional manual gear transmission. It is an electromechanical and hydraulic integrated automatic transmission that combines the advantages of AT (automatic) and MT (manual). AMT not only has the advantages of hydraulic automatic transmission, but also retains the advantages of high efficiency, low cost, simple structure and easy manufacturing of the original manual transmission.

The dual-clutch automatic transmission adopts two sets of clutches, and the two sets of clutches work alternately to achieve the effect of backlash-free shifting. The DCT combines the advantages of AT and AMT, which not only guarantees power and economy of the car, but also greatly improves the comfort of car operation.

The control mechanism transformation of automatic transmissions includes a manual selector valve control mechanism and a throttle valve control mechanism. The driver changes the position control system of the shift valve and the manual shift valve through the automatic transmission control handle, controls the state of the switch according to the position of the manual shift valve and the opening of the throttle, speed and other factors, and uses the hydraulic automatic control principle or the electronic automatic control principle to control the shift shift in the actuator according to certain rules, so as to achieve automatic shift state infiltration.