Hydromechanical gearbox: operating principle and device

Despite the growing popularity of cars withautomatic transmission, classic mechanics are still held in high esteem by many drivers. It is more reliable than automatic transmission. But during operation, the driver is constantly forced to work with the clutch pedal. This causes some inconvenience, especially in traffic. So there was a hydromechanical transmission. The principle of its operation and the device will be considered in our today's article.

Characteristic

Those drivers who do not want to work withclutch, give preference to this particular transmission. Hydromechanical gearbox performs several functions at once. It combines a clutch and a classic box.

Gear shift is made hereautomatically or semi-automatically. In the same way, and hydromechanical gearbox loader. While driving, the driver does not engage the pedal-clutch. All you need is an accelerator and a brake.

About construction

The device hydromechanical gearboxsuggests the presence of a hydraulic transformer. This element, depending on the design features, can be two-, three- or multi-shaft. Now manufacturers use a planetary automatic hydromechanical transmission.

How does the gearbox work

On trucks and large buses more oftenMostly used multi-power transmission. In order to shift gears, multi-plate clutches are used here. For their work requires lubrication. Hydromechanical gearbox oil differs significantly in consistency from the "mechanics". In the latter case, it is more dense. In order to include the first and rear speeds in fluid mechanics, gear couplings are used. This design allows the most smooth transfer of torque from the flywheel to the wheels.

Planetary

Now it is a more common hydromechanical gearbox.

She began to use thanks to its compactsize and light weight. Another advantage of the planetary transmission is a long service life and the absence of noise during operation. But there is such a box and disadvantages. Due to its design, such a transmission is more expensive to produce. It also has a low efficiency.

How does the planetary gearbox

Her work algorithm is extremely simple.The gears are shifted to planetary hydromechanical transmission using friction clutches. Also, to smooth shocks when switching to lower, use a special brake band. It is during the operation of the “brake” that the torque transmission force decreases. But at the same time, the speed switch is smoother than that of the analogue counterparts.

The basis of the planetary transmission is a hydraulic transformer. This element is located between the engine and gearbox. HDF consists of several components:

• Gear wheel.
• Pump.
• Turbine.

People call this element a “bagel” because of its characteristic shape.

When the engine is running, the pump impellerrotates with flywheel. The lubricant penetrates into the pump and further under the influence of centrifugal force begins to rotate the turbine. Oil from the last element penetrates into the reactor, which performs the function of smoothing shocks and jolts, and also transmits torque. Oil circulation is carried out in a closed circle. The power of the car increases with the rotation of the turbine wheel. Maximum torque is transmitted when moving the car from a standstill. In this case, the reactor is in a stationary state - it is kept by the coupling. When the car picks up speed, the speed of the turbine and pump increase. Clutch wedged and the reactor rotates at an increasing rate. When the speed of the last element will be maximum, the torque converter will go into a state of operation of the clutch. So it will rotate at the same speed as the flywheel.

Features of the design of the planetary gearbox

Planetary hydromechanical gearboxconsists of a drive shaft, which is an articulated gear. There are also satellites rotating on separate axes. These elements are introduced into engagement with the internal teeth of the box and ring gear. The transmission of torque is due to the action of the brake band. It inhibits the ring gear. As the car accelerates, their momentum grows. Involved the driven shaft, which perceives the transmission of torque from the master.

Как ГТФ устанавливает нужное передаточное число?This action is performed automatically. When the speed of rotation of the wheel of the car increases, the pressure of the oil that goes from the pump to the turbine increases. Thus, the torque at the last increases. Accordingly, the revolutions of the wheel and the speed of the car are also increasing.

About efficiency

As for the efficiency, it is an order of magnitude lower than on the main gearbox.

Its maximum value is from 0.82 to 0.95. But at medium engine speeds, this ratio does not exceed the mark of 0.75. This figure is increasing with increasing load on the torque converter.

Service and repair of hydromechanical gearbox

When operating this transmission, it is necessarymonitor the level of oil. This fluid is working here. It is oil that uses turbines to transmit torque. On the mechanical boxes, it simply lubricates the friction gears. Manufacturers recommend changing the oil on the hydromechanical boxes every 60 thousand kilometers. It is worth noting that the design of such a checkpoint has its own filter. It also changes when this time is reached. Operating at a low oil level threatens to slip and overheat the transmission.

As for the repair, most often failshydraulic transformer. A symptom of a malfunction is the impossibility of switching on one of the gears, an increased time of “triggering” of the desired speed. Also in this case, the mesh-oil suction box is disassembled and cleaned and the spool-type valve is changed. If there are leaks, check the tightening torque of the bolts and the condition of the sealing elements. During operation, metal chips are formed on the filter. It clogs the mechanism and the level of oil pressure drops. At higher loads the resource of this cleaning element is reduced. In this case, it is recommended to change every 40 thousand kilometers.

How to extend the resource

To increase the lifetimehydromechanical box, it is necessary to monitor the oil level. If it is not enough, the box overheats. Operating temperature should not exceed 90 degrees. Modern cars are equipped with an oil pressure sensor. His warning lamp lit, you should not ignore it. In the future, this may cause breakdown of the torque converter.

Также не следует переключать передачи без выжима brake pedals. The box will take the whole blow, especially if you switch from the first to the back without first releasing it. On the go, if it is a long descent, it is not recommended to turn on the "neutral". It also significantly reduces the life of the hydraulic transformer and working couplings. Otherwise, it is necessary to adhere to the regulations for the replacement of oil and filters. The service life of this checkpoint is about 350 thousand kilometers.

Conclusion

So, we found out what constituteshydromechanical gearbox. As you can see, with proper maintenance, it will be as reliable as mechanical. In this case, the driver does not have to constantly squeeze the clutch.