Currently, almost every modern car is equipped with an automatic transmission, which each time becomes more difficult. And , despite the fact that these units are significantly superior to mechanical gearboxes, the latter have their own fans. Some drivers still prefer vehicles with a manual (manual) transmission.
With an automatic transmission, everything is much more complicated, and if someone wants to understand the principle of operation of this unit, it is worth starting with a mechanical one. This article is dedicated to her.
The most essential element of any car
For the first time having heard the incomprehensible term “transmission”, many students immediately ask themselves what kind of unit it is and what it is for. Everyone knows that an engine is needed to move a car. Almost every car enthusiast is familiar with its principle of operation today: converting reciprocating piston movements into crankshaft rotation, which is otherwise referred to as torque.
However, this rotation itself must somehow be transferred to the wheels. This is exactly what the transmission is for. Anyone who is familiar with the features of driving cars with a manual transmission knows this very well.
The term itself hides special mechanisms due to which the car moves at different speeds, if necessary, reverses (when the corresponding gear is engaged).
The design of these units is carried out by leading experts in automobile plants. Moreover, the transmission has important requirements:
- The unit must ensure the transmission of maximum engine power.
- Be reliable.
- Driving should be easy.
- The weight of all elements should be as light as possible.
- Noise is extremely undesirable during operation.
If the transmission is characterized by high efficiency and reliability, the driver should not worry about anything: the fuel will be used to the maximum, and the mechanism itself will faithfully serve for a long time.
But if managing a manual gearbox at Nissan (for example) is difficult, it causes serious discomfort for the driver and significantly reduces his attentiveness on the road. All this poses a risk of getting into an accident.
As for weight, an overly heavy unit will be noticeably more expensive for buyers. In this connection, manufacturers are trying to lighten the weight of mechanisms to the maximum.
What is meant by the amateur term "mechanics"?
Manual or manual, as some drivers like to say, the gearbox (manual transmission) plays a simple, but at the same time important role. It not only transfers torque from the engine to the wheels, but also contributes to a change in the gear ratio. And it all depends on the driver himself - he decides exactly when it is necessary to switch for the proper performance of the entire car. This is the whole essence of manual transmission control.
Despite the great popularity of automatic transmission, a manual transmission is not going to give up its positions, and here's why:
- The design is as simple as possible.
- Parts and assemblies are reliable in relation to mechanical stress and overload.
- The cost of repair and maintenance of the unit (even capital) is not as high as that of its automatic competitor.
And while these qualities will be appreciated by motorists, some cars will still be equipped with "mechanics". It is no coincidence that some modern automatic transmissions have a manual gear shift function. A vivid example of this is tiptronic.
Varieties of manual transmission
Manual boxes are classified according to the number of these steps:
A five-speed gearbox is the most common, which is why most cars are equipped with it. The number of shafts is also taken into account:
Three-shaft manual gearboxes are mainly equipped with rear-wheel drive cars, while two-shaft gearboxes are only vehicles with front-wheel drive. Actually, this is where the whole classification ends.
Ratio
Manual transmission refers to step mechanisms, that is, the magnitude of the torque changes in steps. A step is called a pair of interacting gears. Each of these pairs transmits the rotation of the wheels with a certain angular velocity. In other words, each step has an individual gear ratio.
The gear ratio should be understood as the ratio of the number of teeth of the driven gear to the number of teeth of the pinion gear. In other words, the number of teeth in the driven gear is 60, and in the drive gear is 30, that is, the gear ratio of this pair is 60: 30 = 2. For any gear transmission, this parameter is the main one.
The lowest gear ratio has the highest gear ratio, while the highest gear ratio has the lowest. Actually, due to this, a mechanical gearbox can both increase and decrease torque.
Such characteristics of the car as acceleration dynamics and maximum speed depend on the gear ratio. That is, the larger it is, the faster the crankshaft spins up to maximum revolutions, and the transmission itself is more “strong”. However, the speed that develops on it decreases. Therefore, with a high gear ratio, you need to change gears more often.
Manual transmission device
The engine of any car operates in continuous mode, which is undesirable for the full and effective functioning of the checkpoint. Switching gears with a constantly rotating main shaft will inevitably lead to transmission malfunctions due to tooth breakages and other negative consequences. For this reason, another node is needed - a clutch, with which the power unit and transmission are disconnected at the right time for a while.
To understand how a mechanical gearbox works, for novice drivers we will analyze each type in more detail.
Three Shaft Gearbox
The three-shaft box includes three main elements - shafts:
- Leading (primary) - connected to the clutch mechanism, for which it has special slots for its driven disk. Torque transmission is carried out through a similar gear, which is in hard engagement with it.
- Intermediate - is located parallel to the first shaft. A gear block is also located on it in rigid engagement.
- Slave (secondary) - located on the same axis as the drive shaft. He also has a block of gears, but, unlike other shafts, is not fixed, and therefore can rotate freely. Between its gears are synchronizers, which are needed to synchronize the angular speeds of the gears of the driven shaft with its rotation. They are also rigidly fixed to the shaft of a mechanical gearbox of the car, but can be moved in the longitudinal plane by means of a spline connection. All modern units synchronizers are present in each gear.
In addition, there is also the actual switching mechanism itself, and all this is located in the crankcase of the unit, called the housing. As for the first, it is located directly on the gearbox housing. The mechanism is presented as a control lever and sliders with forks. There is also a locking device to prevent the simultaneous inclusion of two gears.
For the manufacture of the crankcase, the box uses aluminum or magnesium alloy. In addition to all the necessary parts and mechanisms, oil is stored in it.
Twin shaft gearbox
This box is designed almost the same, but with a little addition. It also has two shafts:
Both have a gear block with synchronizers, and they are located in parallel, as in the design described above. And the mentioned addition is the presence of the main gear and differential in the crankcase of a mechanical gearbox. Their function is to transmit torque to the driving wheels of the car. Moreover, the differential, if necessary, can provide different angular speeds.
Not without, of course, and without a switching mechanism, which is usually remote. In other words, it is located outside the box body. And for their connection, traction or cables are used. Moreover, the cable connection is optimal, in connection with which it is more often used.
Gearbox operating principle
When the control lever is in the neutral position, no torque is transmitted from the crankshaft to the wheels. Along with starting the engine, the input shaft rotates with the crankshaft. To enable the desired speed, it is necessary to press the clutch pedal to disconnect the shafts.
Now you can move the control lever in the right direction. In this case, the synchronizer clutch is moved by means of a fork and the required pair of gears is activated. This allows you to choose the optimal torque depending on traffic conditions.
Driving a car with a manual transmission will be considered later, but for now the principle of operation of a different design.
How does a twin-shaft gearbox work
The two-shaft gearbox works on almost the same principle, but there is still a difference: the torque is transmitted using only a pair of gears, while the third gear of the intermediate shaft takes part in the three-shaft design. In addition, there is no direct transmission, and the gear ratio is 1: 1.
In addition, the gearshift is performed not by the plug, but by the stem. It is he who pushes the necessary gear, and that gear engages with the other, and then is fixed. To enable reverse speed, a separate gear is engaged on its shaft. And this is true for both types of manual transmission.
Manual Benefits
Some positive points have already been listed above, so we will make a kind of generalization. Typical advantages of the box:
- relatively light weight;
- low cost;
- the design is simple and straightforward;
- high degree of reliability;
- maintenance and repair are inexpensive.
In machines with a manual gearbox, the engine is rigidly connected to the transmission, due to which maximum efficiency is achieved when moving on ice or off-road. In addition, the manual transmission can, if necessary, be completely disconnected from the engine for smooth towing or pushing.
Deficiencies are also present
Unfortunately, you can not do without cons, although there are not so many of them. First of all, this concerns the need for constant periodic gear shifting, which can tire a driver on long trips.
Among other disadvantages:
- The gear ratio changes in steps.
- Adhesion is not high enough.
Therefore, "mechanics", although it is the main type of transmission, but far from the most popular. Perhaps in a couple of decades it will completely lose its relevance, and finally.
Features of driving with a manual gearbox
For the proper operation of cars with manual transmission, certain skills are required. Many beginners, especially women (perhaps not all), may have difficulties. You must remember the position of the control lever for each gear. This is not difficult, since it has a circuit on it. In addition, you should know in which speed range each gear works.
Speed modes depending on transmission:
- 1st gear - 15-20 km / h.
- 2nd gear - 30-40 km / h.
- 3rd gear - 50-60 km / h.
- 4th gear - not more than 80 km / h.
- 5th gear - more than 80 km / h.
But it is better to focus on the tachometer readings. It is recommended to switch to a higher gear until a certain number of revolutions of the crankshaft is reached, depending on the type of engine:
- for diesel - 1500-2000;
- for gasoline - 2000-2500.
To avoid premature repair of the mechanical gearbox, before starting the engine, make sure that the lever is in the neutral position. The left foot is controlled only by the clutch pedal, and the right foot is responsible for the other two - the only way you can not confuse anything.
Before starting off, the clutch is squeezed out, the first gear is engaged, then the clutch is smoothly released with the left foot, while the accelerator pedal is also gently pressed with the right foot. Next, the shift is made upon reaching the speed threshold: the clutch pedal is squeezed (the foot must be removed from the gas), the second gear is engaged - then everything is the same.
The main malfunctions of the "mechanics"
Despite all its simplicity, the manual transmission is a rather complex system, which has a large number of moving parts. Because of this, it can have a variety of malfunctions, but often this is a failure of the main components of the unit, a lack of oil in the crankcase or a weakening of the fastening of the box elements.
This can happen due to improper operation, poor quality of parts, their natural wear. In addition, poor repair or a complete lack of maintenance can also be included here.
It is possible to determine whether a manual gearbox needs to be replaced or repaired by characteristic features. If it makes a noise when the lever is in the neutral position, it means that the bearing of the drive shaft is worn out. It may also be due to a lack of oil. And if noise arises during gear shifting, then the problem may lie in synchronizer clutches.
Total
Knowing the device and the principle of operation of a mechanical box, it will be a little easier to understand how an automatic transmission is arranged. Manual transmission was and still remains a practical and familiar unit for many drivers, despite some nuances. In general, you need to know your car from and to, which will allow you to enrich yourself with invaluable experience.