Downshift: principle, views. Off-road vehicles with reduction gear and differential lock

First of all, let's say that the transmissions of any transmission are designed to regulate the speed of transmission of torque from the engine to the driving wheels. They are divided into straight lines, and also increase the torque and lower it. Here we will talk in more detail about the latter kind.

Downshift and its purpose

Simply put, the downshift is one that is in the dispenser, or else an additional box distributing the torque between the two driving axles. When it is turned on, the car's speed drops, and the torque and power increase. This transfer is often used to overcome obstacles such as ice, ford, steep descent or ascent, sand, dirt, stony roads and heavy terrain.

It is turned on with a button or the lever marked L and LO, which means shortened from low - "low". The downshift principle is that when it is switched on, the speed of the SUV falls, but it becomes stronger and more capable of overcoming obstacles. The magnitude of the speed drop depends on the gear ratio in the gears. The car moves at high speeds when the lowered gear is engaged.

For example, consider a situation where, with a prolonged rise in the third gear, the engine lacks power, and when the second gear is turned on, the number of turns becomes too large. In this case, the inclusion of a reduced gear helps to cope with the situation: the car is moving at a low speed, but at high speeds. Due to the increase in the wheels of torque, overcoming obstacles on the road becomes much easier. The number of revolutions of the bridge increases together with the gear ratio of the secondary shaft. Due to this, the car can easily overcome the strong off-road, water obstacles, descents and rises and other obstacles.

Demultiplaster

The multiplier is structurally included in the transfer case circuit or it is executed as a separate unit. In "automatic machines" the transfer case may not be present, and its functions are performed by some parts and components in the gearbox. An additional gearbox, in which there is a downshift (demultiplier), is designed to increase the traction forces on the wheels. The multiplier is a transmission mechanism that is designed to increase torque. It is installed, as a rule, on those cars that are designed for operation in poor road conditions. In this case, the usual number of gears in the box will not be enough, it will help to get an intermediate gear ratio in the transmission.

Consider this situation: in the fourth gear at a certain speed, the motor operates under specific conditions with overload, at a lower gear, the third, the engine is "twisted". In this case, an additional gearbox will help.

How to turn on the downshift?

It is necessary to stop the car, then the main gear lever is moved to the neutral position, and the auxiliary box lever is in the "low gear" position. Then squeeze the clutch. Not all transmissions have a transfer case separately. In this case, there is a special lever on the conventional gearbox, with which the given gear is turned on. If the downshift is switched on in normal operation, then the risk of overloading both the engine and the transmission is high. As a result, both units may fail.

The use of a reduction gear and a differential lock

So, as we have already understood, reducing - an additional transmission, reducing the number of turns of the wheels with constant engine speed. Usually it is installed in the transfer case. Having it makes an SUV more expensive, harder and harder. But on cars of economy class it is not always installed, instead, the power take-off shaft connection to the rear axle gearbox takes place in the gearbox, in the crankcase of the downshift. Recently, frame SUVs are getting smaller, and crossovers are converging with city cars. These cars are often deprived and downshifts. Now there is a trend that in the priority - the availability of comfortable conditions in the car, rather than its off-road qualities. Most manufacturers go to the body, and the frame structure remains in the past. These SUVs are still those SUVs that have a downshift and a differential lock, so they are not afraid of any obstacles.

Locking the differential is necessary to improve the patency. The differential itself is divided into inter-wheel and inter-axle. Previously, cars did not have such technologies, so their absence had a negative effect on the safety of elements in the design. The inter-wheel differential allows the wheels to rotate at different speeds, this is necessary, for example, if the car makes a turn. But its presence can lead to the fact that when skidding the power of the motor will only go to the wheel that is stuck, while the other will remain stationary. When the differential is locked, the engine energy will be distributed evenly among the wheels, and thus the car will be able to overcome the obstacle.

The axle differential is similar in principle to its action: it allows the front and rear axles to move at different speeds and along different trajectories. But in some situations this can significantly complicate the control: if the front wheels are stalled, the rear wheels will be inactive. Interlock differential lock can successfully solve this problem. Off-road cars, known for their excellent cross-country ability, are usually equipped with three locks: rear, front and center differential.

Off-road vehicles with a reduction gear and a differential lock

At the present time there are still true off-road conquerors equipped with all necessary equipment in order to feel as comfortable as possible on any surfaces. Among such cars can be named, for example, such as Chevrolet Trailblazer, Hummer H3, Land Rover Dicovery.

The "trailblazer" has a large body, a frame structure and just a huge list of technical advantages. He has a bright and brutal appearance. In 2015, the model has received quite substantial updates both in the exterior and in the technical "stuffing". The suspension is soft, but this fact introduces a certain disadvantage in the management of the SUV: when there are sharp turns, a slight heel appears. The car is pleased with the quality of the trip, which it can provide with a complete set of necessary systems.

Now we turn to the American model of the true conqueror of impassability - "Hammer". At the heart of the production of this car, the concern used more military technology. No wonder he was able to create a real brutal SUV. Serial production stopped in 2010, and last year it was announced that the Hummer H3 can only be purchased on special order. The car has a huge clearance, large engines, great wheels, shod with off-road rubber, and, importantly, it is equipped with one of the best low gear and differential lock systems, which are borrowed from the military industry.

Discovery remains one of the few British SUVs that have retained the frame structure. It is distinguished not only by excellent external data, but also by increased comfort, as well as by patency. The line of engines, although not a rich choice, but it looks impressive. The lock is available on it in several modes, and the car boasts a good all-wheel drive. The reliability and quality of the car is truly impressive.

Such jeeps can be successfully operated and in urban conditions, but still their true destination as large and heavy machines is a real impassability. It should be noted that such cars can not be called economical, and they are equipped with a large list of functions that are not useful for using a jeep on asphalt roads.

Types of downshifts

As reducing gears used worm, less often cylindrical and planetary. The worm gear is included in the number of gears engaged with the crisscross shaft axes. Movement in them is carried out on the principle of a screw pair. Its main properties are low noise level due to the features of the gearing, relatively low efficiency, small dimensions and a large gear ratio. Compared with the cylindrical gearbox, the worm gear provides a better ride. This type of transmission has a much greater potential for increasing torque and lowering the speed of rotation than gears with other types of gears. Cylindrical gear transmission is used in mechanisms with parallel arrangement of shafts. For this type, increased accuracy is required due to design features.

Gears are reliable and durable at the observance of the permissible level of loads, from the minuses it can be called the moment that at a high speed of rotation such a mechanism has a high noise level, and also can not flexibly react to a changing load. A variety of gears are planetary gears. They have cogwheels with movable axles. Such transmissions have a low weight, convenient layout, compared with conventional gears produce less noise, as well as the possibility of obtaining large gear ratios. Among the shortcomings can be called a large number of parts, increased requirements for the accuracy of installation and manufacturing.