The internal combustion engine has one fundamental feature: it is able to operate efficiently only in a narrow range of revolutions, giving maximum power and torque only under certain conditions. If the wheel were connected directly to the crankshaft, the car would either be unable to move from a place due to lack of traction at low revs, or the engine would stall when trying to stop. It is to address this problem that we have been created. gearbox - a complex mechanism that allows you to change the gear ratio between the engine and the driving wheels.
The main task of the transmission is to transform the traction force. When moving with a load or climbing a mountain, the driver needs a huge force, but speed is not important. On a flat track, the situation changes: high speed of rotation of the wheels with moderate force is required. The principle of operation of the transmission It is based on the laws of physics, allowing you to sacrifice speed for the sake of force or vice versa, ensuring optimal modes of operation of the motor in any road conditions.
Modern cars are equipped with different types of transmissions, each of which has its own design features and logic of operation. Understanding what is happening inside the unit helps the driver not only competently operate the car, but also diagnose malfunctions in time. We will look at exactly how the rotation is transmitted and why the gearshift feels different on different cars.
Fundamental physics: torque and gear ratio
To understand how a transmission works, you need to understand the basic physical values. The engine creates torque - the force that rotates the shaft. However, this force is not always enough to move the multi-ton mass of the car. The transmission works like a lever: increasing the force, we inevitably lose speed, and vice versa. This ratio is called the transfer number.
Let's take a simple example of gears. If a small gear (drive) has 10 teeth, and a large (drive) - 50 teeth, then for one full turn the large gear needs to turn the small 5 times. The speed of rotation at the output will fall by 5 times, but the force will increase by the same amount. It is this principle of increasing torque by reducing speed that underlies the operation of the first gear.
In higher gears, the situation is reversed: the leading gear is larger than the slave or they are close in size, which allows the car to develop high speed, but the thrust is minimal. If you try to move in high gear, the engine simply does not have enough time to tear the car from the spot, and it will stall.
Device of the classical manual transmission (MKP)
The mechanical transmission is the most studied and common design, characterized by high reliability and maintainability. The basis of the mechanism is the shafts and a set of gears that are in constant engagement. Unlike older models, where the gears had to be physically moved to be turned on, modern models have been designed to be more flexible. ICSW They're using clutches.
The key element here is the synchronizer. This device, working on the basis of the friction principle, equalizes the speed of rotation of the gear and the shaft before their connection. Without synchronizers, gear shifting would be accompanied by terrible grinding and breakage of teeth. The driver, squeezing the clutch pedal, breaks the connection of the engine with the box, allowing the mechanism to switch without impact.
Structurally, the shafts can be arranged in different ways. In classic rear-wheel drive schemes, a three-shaft design is used, where the inlet and outlet shafts are on the same axis. In front-wheel drive cars, a dual-shaft scheme is more often used, where all transmissions (except the highest) are implemented by one pair of gears. Synchronizers and switch-forks are controlled by the driver through a lever that transfers mechanical force to the rods inside the body.
- ⚙️ Primary shaft - transfers rotation from the engine to the gears.
- ⚙️ Secondary shaft - transmits the changed torque to the driveshaft or actuators.
- ⚙️ Synchronizers - provide smooth switching without impact.
- ⚙️ Selection mechanism - a system of levers and forks for moving clutches.
⚠️ Attention: Long-term retention of the car on the rise only due to the work of the clutch (spin) leads to overheating of the disc and rapid wear of friction linings. Use the parking brake.
Hydrotransformer automatic box (ACP)
The classic automatic is radically different from mechanics by the lack of a rigid connection between the engine and transmission at low speeds. The role of the clutch here performs hydrotransformer A device that transmits energy from the fluid flow. Inside it are three wheels: a pump (associated with the engine), a turbine (associated with the box) and a reactor.
When the engine spins the pump wheel, it accelerates the oil, which hits the turbine blades with force, causing it to spin. At the start, the reactor is blocked, increasing the torque (clutch mode). As the speeds increase, the difference in rotation equalizes, and the hydraulic transformer works like a conventional coupling. For hard communication at high speeds, a locking clutch is switched on.
The gearshift itself in DISTRIBUTION It is due to the planetary series. These are complex mechanisms consisting of a solar gear, satellites and a crown gear. By blocking or releasing various elements of this series with friction discs and brake tapes, the electronics receive different gear ratios without breaking the power flow.
Why is automatic transmissions warming up in traffic?
The hydraulic transformer works inefficiently when there is a large difference in speed between the input and the output (the engine is spinning, the car is standing). The energy goes into heating the oil. Therefore, in heavy modes, it is recommended to transfer the box to manual mode or L/1 mode to avoid slipping.
Variators (CVT) and continuously variable transmission
A CVT is a transmission that does not have fixed transmissions physically. Instead of gears, two sliding cones (a pulley) and a belt (or chain) are used here. Principle of action based on a change in the diameter of the pulleys: when one cone shifts, the belt is pushed to a larger radius, and on the other pulley - lowers into the center. This allows you to smoothly change the transfer ratio.
The main advantage of CVT is the absence of thrust lapses when switching, since they simply do not exist. The engine always operates in the optimal range of revs, which theoretically provides better fuel economy. However, variators are sensitive to overloads and require high-quality, specific oil.
In modern cars, manufacturers often emulate gear shifting software, creating artificial “steps” to satisfy drivers’ habits and avoid the “trollecard” effect, when the revs hang at one mark during acceleration.
☑️ Diagnostics of transmission status
Comparison of characteristics of different types of transmissions
Choosing a gearbox type often becomes a compromise between comfort, dynamics and maintenance costs. Mechanics remains the king of reliability and control, but loses out in convenience in urban traffic. The classic machine is comfortable and hardy, but more difficult and expensive to repair. The variator is economical, but has torque limitations.
Robotic boxes (RCPP) try to combine the efficiency of mechanics with the comfort of the machine. They come with one clutch (simple but twitchy) and two (DSG, PowerShift - fast, but complex). Understanding their device helps to choose the right modes of operation.
| Parameter | ICAT (Mechanics) | Automatic transmission (Hydrotransformer) | CVT (Variator) | RCPP (Robot) |
|---|---|---|---|---|
| Resource | High (300+ thousand). km | High (250+ thousand). km | Average (150-200 thousand). km | Depends on the type of clutch. |
| Comfort. | Low (must be switched) | High (smooth shifts) | Maximum (no jerks) | Medium (possible jerks) |
| Fuel consumption | Depends on the driver. | Higher than 10-15% | Low (optimum mode) | Low (like mechanics) |
| Cost of repair | Low. | Tall. | High (often node replacement) | Medium/High |
When buying a car with a CVT, be sure to check the history of oil change. For CVTs, this is a critical procedure that is often ignored, leading to strap stretching and cone breakage.
Typical malfunctions and their impact on the work
Any mechanism is subject to wear and tear. In mechanical boxes, they are most often affected. synchronizer And a squeezable bearing. Signs are crunch when switching or noise when squeezed clutch. In automatic machines, the weak point is the hydroblock and friction discs, the wear of which leads to kicks and slips.
It is important to monitor the condition of the oil. V DISTRIBUTION and CVT It not only lubricates, but also transmits force and removes heat. Old, lost properties of oil leads to overheating and bullying of metal surfaces. The color of the oil should not be black, and the smell should not be burnt.
⚠️ Attention: A sharp switch of the automatic transmission selector from the position "D" (Drive) to "R" (Reverse) on the move or with a car that has not stopped is guaranteed to lead to a breakdown of the planetary mechanism or a break in the CVT chain.
Rules of operation for the extension of the resource
To ensure that the transmission lasts a long time, you need to follow simple rules. On the mechanics, you can not keep your hand on the lever - this creates pressure on the forks and accelerates wear. On the machine you can not tow and start sharply with "two pedals". Warming up the transmission in winter is mandatory: the oil must become fluid to lubricate all the nodes.
Regular oil replacement is the key to the health of the unit. Even if the manufacturer claims that the oil is poured for the entire service life, real practice shows that by 60-80 thousand km it already loses its properties. Transmission oil It is subject to huge loads and temperature changes.
Timely oil change and avoiding sharp starts prolong the life of any gearbox 2-3 times, regardless of its type.
Why do the mechanics tightly turn on gears in winter?
At low temperatures, transmission oil thickens, becoming viscous like honey. This makes it difficult for the synchronizers to work and move the gears. The problem is solved by warming up the car and neat, smooth switching in the first kilometers of the way.
Can I tow a car with automatic transmission?
Towing a car with an automatic transmission is only possible for short distances (usually up to 50 km) and at low speed (up to 40 km / h), since the lubrication pump often does not work with the engine shut down, which leads to dry friction.
What is typtronic and how does it work?
Typtronics are not a separate type of box, but a mode of operation of a classic machine or robot, allowing the driver to manually select gears. This is useful when overtaking, braking by the engine or driving on a slippery road.