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These cars are now equipped with a new 8-speed automatic transmission 8НР These cars are already equipped with a new 8-speed automatic transmission 8НР
Some 80–90 years ago, people most of all appreciated comfort. They liked the telephone and, of course, the car. Following the fashion, cars of those years were built as comfortable as possible, with soft suspension and light steering. For convenience, the designers reduced the number of gears in the gearbox to three, or even to two. For example, the Bugatti 28, type 30, KP had a three-speed gearbox, and a second, direct transmission was used to drive off and generally drive. On it, the Bugatti accelerated to 150 km / h. The first gear was launched only when starting uphill, and in the third, high-speed, the car could be dispersed to 200 km / h. Hitler had a Horch with two gears, moreover, they drove (and moved off) to the second.
In recent years, the trend has changed radically, now manageability and the environment are held in high esteem. Suspension has become stiffer, the steering wheel is sharper, the engine is livelier and faster. The number of gears in the boxes is growing steadily; there is a gearbox for cars with seven, eight and even nine steps. It is clear that stiff suspensions and a sharp steering wheel give the car better handling, which is why the speed of movement along the same road increases. The high-speed revolving motor gives the car good dynamics. And why do we need a multi-stage gearbox, what's the use of it?
The fact is that the gearbox is built for a specific engine. On old engines, they were not at all the same as on modern ones - the torque reached a maximum almost at idle. What they paid for with useless liter capacity, incredible size and weight, sluggish dynamics and brutal appetite. In pursuit of fuel economy, modern engines have much smaller displacement volumes and, as a result, lower torque. To maintain the engine in the range of operating revolutions, multi-stage gearboxes were created. With an increase in the number of gears, designers achieve the most efficient engine operation in terms of economy and traction capabilities, and environmental standards only spur the process. As an example, I will cite two new boxes designed by one of the world leaders in the production of gearboxes - the German concern ZF.
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Automatic 9-speed gearbox 9HP Automatic 9-speed gearbox 9HP
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Box 9HP in a section Box 9HP in a section
It was ZF Friedrichshafen AG that developed the world's first 9-speed automatic transmission (9HP). This is an automatic transmission for front-wheel drive cars with a transverse engine. Two box models cover torque from 200 to 480 Nm (9HP28 and 9HP48, respectively). Interestingly, the box provides an upgrade to a hybrid transmission or the implementation of the "start-stop" function. It is implemented simply - it is enough to replace the torque converter with a standard starter-generator.
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Is the game worth the candle, because nine programs are not a joke, the unit turns out to be complicated and, therefore, expensive? Apparently worth it. According to ZF, compared with the usual 6-speed “automatic”, fuel economy in a car with a new gearbox reaches as much as 16%. This efficiency is achieved primarily due to the very high overall gear ratio of the box - 9.84. That is, a large number of automatic gearbox steps allows you to very accurately select the desired gear ratio, because the difference between adjacent gears is small, and the smaller this difference is, the more accurately you can select a gear for a given engine operation mode. This feature positively affects driving comfort and at the same time allows the engine to work in a more economical mode. So, when driving in ninth gear at a speed of 120 km / h, the engine speed is 2170 rpm, and with a 6-speed automatic gearbox - 2890 rpm.
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Engine turns at the movement of 120 km / h Engine turns at the movement of 120 km / h
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Fuel consumption, in addition, is minimized by blocking the torque converter at a fairly low speed, thereby reducing hydraulic losses. At the same time, fuel consumption is not only reduced, but dynamics is also growing, since the moment from the engine is transmitted directly. In addition, this new torsional vibration damper algorithm enhances the sense of merging with the car - the speed of the elements of the control system and switching below the threshold of perception of the driver.
The ability to quickly shift gears, in turn, gives the new box a sporty character. It is interesting that not only the car manufacturer, but also the driver can adjust the points and dynamics of gear changes by setting different modes, from comfortable and economical to sports, that is, the control system for the movement modes of the box is very flexible. ATSYS automatic transmission control system includes all clutch control devices, adaptation function, transmission protection functions. In addition, ASIS (gear shift algorithm) imperceptibly for the driver selects the optimal transmission depending on the traffic situation.
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Gear Shift Algorithm Gear Shift Algorithm
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The ratio of the transmitted moment and weight of various automatic transmissions The ratio of the transmitted moment and weight of various automatic transmissions
One of the most important advantages of the new box is the modular principle by which it is created. For example, for an all-wheel drive, an additional transfer box can be installed. For this, an automatically connected four-wheel drive has been developed (according to ZF terminology - AWD Disconnect). This system includes rear-wheel drive only when necessary and saves up to 5% in fuel compared to permanent all-wheel drive. In addition, the box is already in serial design adapted to work in the "stop-start" mode without an auxiliary oil pump. Since only the friction switching mechanism is blocked during a restart, the reaction time is very short. It is important that the box is compatible with the hybrid version: in the parallel architecture of the hybrid drive, the torque converter is replaced by an electric motor.
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Main features of 9HP boxes Main features of 9HP boxes
The box implements a large number of gears using four sets of gears and six shifting devices. The layout of all these nodes in the box case was a very difficult task, since in a passenger car with a transverse engine, the space is very, very limited. The original solution was found: the box consists of two planetarics with a common sun gear, and the cam gear was used with a hydraulic actuator. This mechanism has high efficiency, and it has little effect on the installation length of the box. If the multi-plate switching mechanism in the open position has moments of inertia that cause power loss, then the cam losses are very small. This is important for a gearbox with a large number of gears: due to the exact selection of gears, there are no such losses when transmitting power flow from the engine, as in other transmissions.
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new 8-speed gearbox (8HP) new 8-speed gearbox (8HP)
Unlike the 9-speed, The new 8-speed gearbox (8HP) is designed for vehicles with a longitudinal engine.
Two model ranges of this box cover a very wide range of torques - from 300 to 1000 Nm. 8HP is the first “machine” that allows you to implement the “start-stop” function without an auxiliary pump. Already, the 8HP box is installed in series on some models of Alpina, Audi, Bentley, Chrysler, BMW, Jaguar, Lancia, Land Rover, Range Rover and Rolls-Royce.
The wide coverage of the input torque level allows the gearbox to be used in a wide variety of car classes and with a wide variety of engine types. This 8-speed gearbox reduces vehicle fuel consumption even compared to the second-generation 6-speed automatic transmission, which until recently was a model of fuel economy.
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Device box 8HP Device box 8HP
The technical solution is based on a concept with four planetary gear rows and five gear elements. Since in each gear only two shift elements are in the open position, the loss of traction due to moments of inertia inside the box is significantly reduced. In addition, a higher overall gear ratio (7.05 compared to 6.04 for the previous model) ensures the engine runs at lower speeds, which reduces fuel consumption. It saves fuel and the level of CO2 emissions and the damping system of torsional vibrations in the torque converter, in particular, its quick blocking at startup. Like the 9-speed gearbox, the new 8-speed “automatic” has a high switching speed - below the perception threshold.
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Dependence of weight and transmitted torque for different automatic transmissions Dependence of weight and transmitted torque for different automatic transmissions
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Hydraulic accumulator (HIS system) Hydraulic accumulator (HIS system)
8НР is the first model of step transmission in which it is possible to realize the “start-stop” function. The fact is that when the engine is turned off, there will be no oil pressure in the box, so it cannot function. However, there is a special device in it - a hydraulic accumulator, which creates pressure in the box, and the car can move off immediately. Thanks to this pulse-type accumulator, the car can re-start after only 350 milliseconds after turning off the engine. In a split second, a spring-loaded piston accumulator pumps the hydraulic oil necessary for start-up into the internal components of the box. The "Start - stop" mode allows you to reduce fuel consumption with this box in total up to 11% compared with the previous 6-speed.
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Fuel economy with different modifications of the 8HP box Fuel economy with different modifications of the 8HP box
The new box can work in both hybrid and semi-hybrid (with starter-generator) versions, and this does not require any changes by simply replacing the torque converter with an electric machine. A semi-hybrid can save up to 15% of fuel, and a full hybrid - up to 25%.
The box can be supplemented with an all-wheel drive version and other various transmission elements. For example, hydrodynamically cooled clutch (HCC) provides a smooth start and quick gear changes. At the same time, instead of the torque converter, a “wet” multi-plate clutch is installed in the clutch housing. Such a clutch has less mass inertia than a torque converter, and this allows you to transmit more torque and makes it attractive for sports cars. There are several versions of all-wheel drive. Firstly, this is a classic version with "hanging" an additional transfer case, as is usually done in SUVs. Secondly - the integration of the transfer case with the drive on the front axle, so the design is more compact, lighter and with better efficiency. And thirdly, an integrated all-wheel drive version, in which, in addition to the transfer case, the differential is also integrated in the case of the automatic transmission.
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Fuel saving with different modifications of 8HP Fuel saving with different versions of 8HP
