CONTINUOUSLY VARIABLE TRANSMISSION - CVT www.ppttopics.com

Overview of a CVT Varies the transmission ratio continuously. Shifts automatically with an infinite number of ratios. Seamless power delivery. Constantly changes its gear ratio to optimize engine efficiency. Allows the engine to rev almost immediately to deliver maximum torque. www.ppttopics.com

A Timeline of CVT Innovation 1490 - da Vinci sketches a stepless continuously variable transmission 1886 - First toroidal CVT patent filed 1935 - Adiel Dodge receives U.S. patent for toroidal CVT 1939 - Fully automatic transmission based on planetary gear system introduced. 1958 - Daf (of The Netherlands) produces a CVT in a car. 1989 - Subaru Justy GL is the first U.S.-sold production automobile to offer a CVT. www.ppttopics.com

CVT DESIGN GOALS Truly continuously variable Transmit torque both forward and backward Able to transmit high torque levels Able to shift under load Computer control not required Mechanical looses are less www.ppttopics.com

Working of CVT CVT transmission operates by varying the working diameters of the two main pulleys in the transmission. When actuated, the cylinder can increase or reduce the amount of space between the two sides of the pulley A CVT operates on three main mechanical components : flyweights or cams, springs, and ramps www.ppttopics.com

CVT WORKING MODEL www.ppttopics.com

Major parts of CVT www.ppttopics.com

Types of CVT Variable-diameter pulley (VDP) or Reeves drive When the two cones of the pulley are far apart , the belt rides lower in the groove. When the cones are close together, the belt rides higher in the groove. This type of CVT may use hydraulic pressure, centrifugal force or spring tension to create the force necessary to adjust the pulley halves. www.ppttopics.com

Toroidal CVT This type of CVT replaces the belts and pulleys with discs and power rollers. One disc connects to the engine. This is equivalent to the driving pulley. Another disc connects to the drive shaft. This is equivalent to the driven pulley. They spin around the horizontal axis and tilt in or out around the vertical axis, which allows the wheels to touch the discs in different areas. www.ppttopics.com

Hydrostatic CVTs Hydrostatic transmissions use a variable displacement pump and a hydraulic motor. That uses variable-displacement pumps to vary the fluid flow into hydrostatic motors. They have the advantage that the hydraulic motor can be mounted directly to the wheel hub. www.ppttopics.com

Cone CVT In a CVT with oscillating cones, the torque is transmitted via friction from a variable number of cones (according to the torque to be transmitted) to a central, barrel-shaped hub. A particular characteristic of the Warko is the absence of a clutch. www.ppttopics.com

Push Belt In the variator, torque or power is transmitted from the primary to the secondary pulley via friction between the push-belt elements and the pulley sheaves. The belt needs to be very stiff in the pulley's axial direction in order to make only short radial movements while sliding in and out of the pulleys The push-belt rings are mainly subjected to bending and tensile stresses. www.ppttopics.com

Advantages Disadvantages Decreases engine fatigue Allows for an “infinite” number of gear ratios, maintaining the engine in its optimum power range More mechanically efficient than Automatic transmissions. Greater fuel efficiency than both manual and automatic transmissions.(Fuel savings of more than 17% have been achieved). Cheaper and lighter than Automatic trans. Smooth, responsive and quiet to drive CPU can be configured to suit a wide range of driving modes and styles. Limited torque capacity when compared w/manual transmissions. Larger and more costly than manual transmissions. Slipping in the drive belt or pulleys. Complacency by the automobile industry, unwilling to discard billions of dollars in development in MT & AT’s. www.ppttopics.com

IMPLEMENTATION Adaptable for trucks Audi A4 TDI Military vehicles Heavy construction equipment Bicycle Motor cycles Industrial machinery any type of motor IMPLEMENTED IN Audi A4  TDI Audi A6 2TDI Ford Escape Hybrid 2.3 Ford Focus C Honda Civic Hybrid  Honda HR-V 1.6 Honda Insight 1.0 Nissan Murano 3.5 Nissan Primera 2.0 Nissan Serena 2.0 OPEL VETERA Saturn VUE 2.2/3.5 Toyota Prius 1.5 4cyl 2 www.ppttopics.com

CONCLUSION IT IS ADVANTAGEOUS TO USE A CVT INSTEAD A MANUAL TRANSMISSION. THIS IS MAINLY BECAUSE THE ENGINE WILL OPERATE ALWAYS ON THE OPTIMUM REGIMES AND THROTTLE-POSITIONS ADAPTED TO THE VARYING ROAD CONDITIONS AND POWER DEMANDS. www.ppttopics.com

REFERENCES Fischetti Mark . "No More Gears". “Popuplar Mechanics” by MC COSH http://auto.howstuffworks.com/cvt.html http://www.infovarna.com/cvt/index_uk.s.html http://www.histomobile.com/histomob/tech/2/83.html http://www.mitsubishimotors.com/corporate/about_us/technology/environment/e/cvt.html http://en.wikipedia.org/w/index.php?title=Special%3ABookSources&isbn=0831110848 www.ppttopics.com

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