Automatic Transmission

 
An automatic transmission is a transmission that does not require the driver to change gears. A 5-speed manual transmission is usually standard equipment on modern cars, while more expensive cars are usually equipped with 6-speed transmissions; Other options include automatic/automatic transmissions such as conventional (hydraulic planetary) manumatic, semi-automatic, or continuously variable transmission (CVT). A transmission is often defined by the number of front gear ratios of an automatic/automatic transmission (for example, a 9-speed automatic). Despite their differences in design, their performance is similar to the average driver. Although manual gear shifting via paddle shifters is currently the norm, the lack of a third clutch paddle shifter means the car has an automatic transmission. Over the years, the automatic transmission has gained more gear and ditched the dipstick. Current models have nine speeds, and an oil dipstick stick is becoming a rarity. Many transmissions are hermetically sealed and can only be checked by a technician. Always refer to your vehicle owner’s manual for system maintenance and service.

Different types of order:
semi-automatic transmission (SAT) also known as clutchless manual transmission, automatic manual transmission, flappy-paddle gear shift, or paddle shifter The paddle-shift gearbox is a self-shifting transmission that does not automatically shift the gears, but makes it easier to shift gears manually without having to depress the clutch at the same time as shifting gears. It uses electronic sensors, pneumatics, information processors, and actuators, to carry out the process of changing the gears through the input of the driver or the computer. This eliminates the need for the clutch pedal, which the driver needs to depress before making shifts in the manual transmission, as the clutch is activated by electronic devices that synchronize the timing and torque required to make shifting fast and smooth. The system was designed by auto manufacturers to provide better driving during overtaking maneuvers on highways. Some motorcycles use a conventional gear shift system without the need for a conventional clutch.
 
A dual-clutch transmission (DCT), sometimes referred to as a twin-clutch transmission, is a type of automatic transmission or automatic transmission. He uses two separate clutches, one for odd and even gear sets. They can be described as basically two separate transmissions (each with its own clutch) housed in a single case. It usually operates during automatic mode. Many of them allow the driver to shift gears manually in semi-automatic mode, although shifts are still performed via the electro-hydraulic transmission. The dual-clutch automatic transmission (sometimes called automatic manuals).

 
Manumatic, consisting of the word manual and automatic, a term that denotes a type of automatic transmission, which allows the average driver to control the choice of gears. There are currently automatic transmissions that allow the driver to control gear selection using some form of transmission control, often limiting shifting beyond certain gears (allowing engine braking when going down a slope) and/or stopping overdrive when towing a trailer. This system enhances these features by providing a steering column lever or modified floor lever, allowing the driver to use manual mode and select the desired gear shift, usually in sequential upshift/downshift form. Many car manufacturers release dials for their automatic manual transmission, such as ‘Tiptronic’, ‘Geartronic’, ‘Touchshift’, ‘Sporttronic’, ‘Sporttronic’. clutchless-manual’, and others. Few of this type allow an alternative autonomous mode, which is called sport mode, where the selection of gears is completely automatic but the transmission prefers a higher engine speed (where the engine produces higher power and/or torque) by delaying the shift when accelerating and shifting to Lower gears early when decelerating.

 
 
Continuously variable transmission (CVT), (also known as single-speed transmission, stepless transmission, pulley transmission, or as in motorcycles, start and drive twist-and- go) which is a transmission that smoothly changes a continuous range of effective gears. This differs with mechanical transmissions that provide a fixed number of gears. The flexibility of the variable transmission system allows the input shaft to maintain a constant angular velocity.
The belt-driven design delivers an efficiency of 88%, which is lower than a manual transmission, which is offset by the advantage of lower production costs and allowing the engine to operate at the most efficient output speed range. When power is more important than efficiency, the transmission operates by allowing the engine to spin at speeds that provide higher power. This is usually higher than the rotational speed that achieves peak efficiency. In low mass and low torque applications the belt transmission also provides ease of operation and simple design.
The transmission does not require a clutch. However, on some cars (and motorcycles), a  centrifugal clutch is added  to facilitate a neutral position, which is required when an empty load or rear manual transmission is in a parking space.
A rubber belt is used in the conveyor in small driven vehicles, where mechanical simplicity and ease of use outweigh relative inefficiency. Most snowmobiles, utility vehicles, golf carts, and motorcycles use a CVT transmission, usually using a rubber belt. Many tractors and self-propelled mowers also use a rubber belt. The carrier is also used in hybrid vehicle applications.  

 
Electronically Controlled, Continuously Variable Transmission (eCVT/ECVT). The system is used in hybrid cars, where it is integrated with the motor unit and electric generator. The system uses internal combustion sources and electric power to drive the wheels.
Variomatic is a continuous variable transmission (CVT) for DAF Automotive.

Principle of
 
variation It is controlled either full automatic or semi-automatic. In simple terms, this system is two separate manual gearboxes, in the same bay, working as one unit. With the use of two independent clutches, the system can achieve faster shift times. It does away with the reliance on the torque converter of the traditional epicyclic automatic transmission.

M: Motor A: Primary drive, and driving shaft| B: Dual clutch C: Driven shaft D: Layshaft, hollow, even gears E: Layshaft, odd gears F: Output

 
manual transmission  Electrohydraulic – a variant of the semi-automatic transmission system, which uses an automatic clutch unlike a conventional manual transmission in which the driver operates the clutch to make the shifts. The clutch is controlled by computer and hydraulics. To shift gears, the driver selects the desired  gear with the transmission shift lever , and the system automatically engages the clutch and throttle to match the engine revs, then engages the clutch again. Many of this type of transmission operate in sequential mode where the driver can only select the next high gear and the previous low          gear ..
System components:
– Fluid/hydraulic coupling
Fluid coupling or hydraulic coupling is a hydrodynamic device used to transmit rotating mechanical power. It is used in automobile transmissions as an alternative to mechanical clutches. It also has wide applications in industrial and marine machinery engines, where different speeds and start control are carried out without the shock load of the power transmission system. The hydraulic coupler was used in early applications in the semi-automatic power transmission system and the autonomous power transmission system. In the late 1940s, the hydraulic coupling was replaced by a  hydrodynamic torque converter  in automotive applications.

It is a device for transmitting rotational movement between shafts by accelerating and decelerating hydraulic fluid (oil). It consists of a hydraulic impeller mounted on the input shaft or shaft and a hydraulic runner mounted on the output shaft or driven shaft. The two have liquid inside them. Both the impeller and runner are bladed rotors, the impeller acts as a pump and the impeller acts as a turbine. The thruster accelerates the fluid near its axis, where the tangential component of the absolute velocity is low, to the proximity of the outer circumference, where the velocity of the linear component of the absolute velocity is high, which increases the kinetic energy. The fluid exits at a high speed from the impeller to the blades of the impeller, delivers energy to the output shaft and the fluid exits at a low speed from the impeller.
            Torque converter
In modern applications, a torque converter is a type of hydraulic fluid coupling that is used to transfer rotational power from a main engine such as an internal combustion engine or electric motor to an external load. Usually a torque converter takes the place of a mechanical clutch with the transmission/auto power, allowing the load to be detached from the power source. It is usually located between the  flexplate  attached to the engine and transmission.
 

Flexplate
 
The main feature of the torque converter is its ability to multiply the torque when there is a large difference between the input and output rotational speed, thus providing a reduction ratio. Some of the torque converters are equipped with a temporary lock-up rigidly when the engine and transmission speeds are approximately equal, to prevent slipping and loss of efficiency.

 
Planetary gear train
Transmission in a manual transmission in which gears are selected by the driver by engaging the gears running on the output shaft with the shaft. In contrast, an automatic transmission that uses epicyclic (planetary) gears is controlled by brake bands  and/or clutch packs for automatic gear  selection.
Planetary gear trains have many advantages over conventional parallel shaft transmissions such as high energy density, reduced size, purely circular reaction…. etc. However, it suffers from complexity in the design, high loads on the bearings, the need for constant lubrication…etc. It is distinguished by its high efficiency, as the loss in efficiency is about 3% for each stage, which ensures the transmission of the movement without loss in the energy transmitted inside the gearbox. It also provides stability as the torque affects the gears axially and is transmitted axially to the gears, without radial pressure, on the gear teeth.


 
Epicyclic gearing or planetary gearing is a gear system consisting of one or more external gears (planet gears, rotating around a sun gear). Usually planetary gears are mounted on a rotating arm called a carrier, which in turn rotates relatively around the sun gear. The system also includes the use of an external gear, a ring gear or annuls, which meshes with planetary gears.The grouping of gears that have planetary gears engaged with the sun and annular gear is called a planetary gear train, and to obtain reduction ratios from the system are: Fixing the gear or rack, then the rack or one of the gears is connected to the input shaft and the other gear or rack is connected to the output shaft. Planetary gears are classified as simple or compound planetary gears. The simple gear system consists of one sun gear, one rack and one ring gear. The combined system has a different number of gears in different combinations. The composite system is characterized by greater reduction, higher torque-to-weight ratio, and more flexibility.
 
 
– Control Unit transport Transmission control unit (TCU)
is a device used to control the transmission of self – FREE electronic automatic transmission, device sensors of the vehicle is used in addition to the data provided by the engine control unit ( of ECU)  the engine Control unit The  account how and when to change the transitions performance Optimum, fuel economy, and transportation quality. The electronic control unit changed its design from purely hydromechanical to electronic control in the late 1980s.
The development of automatic transmission and the integration of electronic control has allowed significant progress in recent years. Modern transmissions are now able to achieve better fuel economy, reduced engine emissions, increased shift system reliability, improved shift feel, improved shift speed, and improved vehicle handling.
In some applications, the TCU and ECU have been combined to form a single ” powertrain control unit (PCM) unit  .”
 
 
 
This is in addition to several sensors, switches, pumps, and transmission coils.  transmission solenoid to  control the electro-hydraulic valve which is fixed in the valve body, …. etc.
 
Automatic transmission modes
Most transmissions provide the driver with a certain amount of manual control over the selection of transmissions or the range of transmissions. Normally, in order to select the transmission operating mode, the driver operates a selector lever located either on the steering column or the floor of the vehicle (as in a manual transmission, however, the selector for the automatic transmission does not move in the same manner as the manual transmission).
To select the shift mode, the driver must move the selector lever. To select the gears/mode, the driver must press the button (called the shift lock button) or pull the lever (on the steering column lever) outward.
Vehicles compliant with US Government standards must have the gear shift arrangement (Park/Stop-Rear-Neutral-Front-Low PRNDL) left to right, top to bottom, or clockwise).   
 
Transmission gear selector
Transmission Mode:
Depending on the vehicle model and manufacturer, the method/style of gear selection can take several forms. But most of them include the following:
Driving mode (D) Drive, covers all the forward gears, as the automatic transmission selects these gears automatically depending on the throttle opening, car speed, and other factors, and it is the transmission mode that most drivers choose to move the car forward.
Most automatic transmissions also allow manual selection to select forward reduced gears, such as Low (L), 1st (1), 2nd (2). In the case of positions L, and 1, the transmission will remain in the downshifts and not shift by itself. This allows for maximum thrust when you need it, such as when driving on a steep gradient, but reduces your speed significantly. Some transmissions shift out of position 1 if the speed is increased above a certain limit, such as 30 mph, to prevent damage to the transmission or engine or reduce engine power. In some, if 2, the transmission will remain in the second gear position and hold, useful when starting on a slippery surface or braking the engine on a steep incline.
Park (P) – This option closes the transmission, preventing the vehicle from moving in any direction. By means of a pin (parking pawl) that prevents the transmission from spinning, and thus prevents the car from moving (even though the driven wheels rotate freely), so it is recommended to use the hand brake as it installs the wheels to prevent their movement, and increase the life Operational parts carrier. To select a stationary position, the vehicle must be allowed to come to a complete stop before selecting this position to prevent system damage. This position is one of only two modes in which the vehicle can be started (starting the engine), the other being the Neutral (N) position. For some cars (especially those sold in the US), the driver must depress the brake pedal/pedal before changing the shift gear from parking/stationary to other modes.
Reverse (R) – This puts the car into reverse gear, which gives the car the ability to reverse, in addition to activating the backup lights switch, an audible beeper warning may also be triggered. In order for the driver to choose this position, the driver must stop the car completely, press the shift lock button and select the reverse position. Doing so with the vehicle not fully stationary could damage the transmission. Some cars with a shift button allow the driver to shift from reverse R to neutral N or driving D without pressing the button. But the driver cannot shift back to R without pressing the button, to prevent accidental shifting that could damage the transmission, especially at high speeds.   
Neutral/No gear (N) – This separates the transmission from the wheels, where the vehicle can move under its own weight. It is the other position in which the car can be started. Movement in an empty load position on a long inclined road should be avoided, as the transmission lubrication pump may not operate at an empty load. In addition to towing the vehicle while it is in this position, it must be in the narrowest limits and as a last resort (so that the speed does not exceed 55 mph and for a distance of 50 miles). This is the position other than P in which the engine can be started.
Drive (D) – This position allows the car to move forward and accelerate through a range of shifts. The number of gears depends on the model, but it is 3, 4 (mostly), 5, 6 (some cars), 8 in luxury cars, and the gears are automatically changed. In some cars, when the car is placed in D mode, the car automatically locks the doors and may activate the car’s running lights.
Second (2 or S [Super]) – this position limits the moves to the first and second reduction ratio, and fixes the shift on the second move. Which can be used in adverse weather conditions such as snow, or climbing heights in winter time. It is recommended to use it in the event that there is snow or frost on the road. Some cars automatically shift out of this position when a certain speed range is reached to prevent engine damage.
First (1 or L [Low]) – This position locks the carrier on the first move only. In old cars, the first gear is not changed to any other gear. Some current cars automatically shift out of the first gear when a certain RPM range is reached to prevent engine damage. This is like a second transmission that can be used in the winter, for traction, or to increase engine braking when going down an incline.
Plus, minus + – and M- These are options for manual transmission of gears for the self-transportation. So that the driver can transfer the higher and lower gears as they wish, one move at a time.
In addition to some other modes that may be found in some cars, such as OD, over-speed transmission. D4 which is used on the motorways and D3 which is used within the cities (stop and go).
 
* A new style for GM in which the traditional PRNDL shift pattern in its modern car has been changed to an electronic gearshift selector. The change is to select a reverse (R) shift that requires pushing the shift lever forward and then to the left while depressing a side button on the lever. Also, to prevent the car from skidding, the transmission will auto-shift from neutral (N) to park (P) in some cases. The following transmission variant is fitted to the Cadillac XT5, which will appear on other GM vehicles.
N – R
|
P
|
D