11-10-2011, 07:51 PM
A continuously variable transmission (CVT) is a transmission that can change continuously with an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a set number of gear ratios. The flexibility of a CVT allows the shaft to maintain a constant angular velocity in the range of output speeds. This can provide better fuel economy than other transmissions, allowing the engine to its most efficient revolutions per minute (RPM) for a range of vehicle speeds. Alternatively, you can use to optimize the performance of a vehicle, allowing the engine to the speed at which peak power occurs. This is usually higher than the RPM that carries a maximum of efficiency. Finally, a CVT is not strictly required the presence of a clutch, which allows dismissal of it.
In some vehicles themselves (ie motorcycles), is a centrifugal clutch, however added, but only to provide a "neutral" position on a bike (useful when idle).
2 Types
2.1 Variable-diameter pulley (VDP) or Reeves drive
2.2 Toroidal or roller-based CVT (Extroid CVT )
2.3 Magnetic CVT
2.4 Infinitely Variable Transmission (IVT)
2.5 Ratcheting CVT
2.6 Hydrostatic CVTs
2.7 Variable toothed wheel transmission
2.8 Naudic Incremental CVT (iCVT)
2.8.1 High Frictional Losses
2.8.2 Shock and Durability
2.8.3 Torque Transfer Ability & Reliability
2.9 Single Tooth Cone CVT
2.10 Cone CVTs
2.11 Radial roller CVT
The principle of the drive
Many small tractors for home and garden use have simple CVTS rubber band. For example, use John Deere Gator line of small utility vehicles with a belt with a conical pulley system. They can provide high power and can reach speeds of 10-15 km / h (16 to 24 km / h), all without the need for a clutch and gearshift. Nearly all the snowmobiles, old and new, and use CVTS scooters, rubber bands typical / variable pulley black.
Some of the harvesters have CVTS. CVT allows the combination of speed, engine speed to adjust independently. It allows the driver to slow down or accelerate the need to adapt to variations in the thickness of the harvest.
Continues and has been used in aircraft systems generating electricity since 1950, and the Automobile Club of Sports of America (SCCA) Formula 500 cars since the early 1970s. CVTS were banned from Formula 1 in 1994 because of fears that the better funded teams would dominate, if they have succeeded in creating a viable F1 CVT. [2] Recently, CVT systems are designed for go-kart and has proven to increase performance and engine life. The range of Tomcar off-road vehicles also uses the CVT.
Some drills and milling machines contain a CVT pulley base where the output shaft has a pair of hand-adjustable conical pulley halves, through a wide belt loop of the motor. The dial on the engine is usually fixed in diameter, or may have a number of steps given diameter to allow a variety of speed ranges. A steering wheel on the drill press, marked with a scale that matches the desired engine speed, is mounted on a reducing system for the operator to precisely control the width of the gap between the two halves of pulley. The width of the slot then adjusts the speed between the motor pulley shaft output pulley fixed and variable, changing from Chuck. A pulley is implemented in the drive belt to absorb or release slack in the belt when the speed is changed. In most cases, the speed must be changed with the engine running.
