CONNOR BOAG
STUDENT ID NO: 1386374
COURSE:TTEC 4844 LEVEL 4
GROUP:5
TRANSMISSIONS AND FINAL DRIVE
ASSIGMENT
CONTENTS
· PAGE1.COURSE INFO
· PAGE2.INTRODUCTION
· PAGE3.HISTORY OF CVT TRANSMISSIONS
· PAGE4.INTERNAL COMPONENTS
· PAGE5.FULL OPERATION OF CVT
· PAGE6.ADVANTAGES AND DISADVANTAGES
· PAGE7.REFERENCES
INTRODUCTION:
I am doing my assignment on(CVT) continuously variable transmissions . I am going to be talking about these subjects in my assignment, the history of these transmissions and also all the internal components that make the transmission work, the full operation of this transmission. and im also going to show you the advantages of this transmission and disadvantages over other transmissions.
HISTORY: Leonardo da Vinci made a concept of a step less continuously variable transmission in 1940 but the first patent for a friction-based belt CVT was filed in Europe by Daimler and Benz in 1886 and a US Patent for a CVT was granted in 1935.Also In 1910 Zenith Motorcycles built a V2-Motorcycle with the Gradua-Gear which was a Continuously VariableTransmission. This Zenith-Gradua was so successful in hillclimb events that it was eventually produced widely so that other manufacturers could give there racers a chance to win. A Continuously Variable Transmissions, called Variomatic was designed and built by Hub van Doorne the co-founder of Van Doorne's Automobiel Fabriek in the late 1950s specifically to produce an automatic transmission for a small affordable car. The first DAF car using van Doorne's CVT was the DAF 600,which was produced in 1958. Van Doorne's patents were later transferred to a company called VDT Van Doorne Transmissie B.V. when the passenger car division was sold to Volvo in 1975 its CVT was used in the Volvo 340. Many snowmobiles use a rubber belt CVT and also In 1974, Rokon offered a motorcycle with a rubber belt CVT. CVTs are used in some ATVs, The first ATV equipped with CVT was Suzuki's LT80 in 1987.
In the late 1990s Nissan designed its own CVT that allowed for higher torque and included a torque converter. This gearbox was used in a number of Japanese market models, Nissan is also the only car maker to bring a roller-based CVT to the market in recent years. Their toroidal CVT named the Extroid was available in the Japanese market Y34 Nissan Gloria and V35 Skyline GT-8. However, the gearbox was not carried over when the Cedric/Gloria was replaced by the Nissan Fuga in 2004.This is some history on cvt tranmisions.
INTERNAL COMPONENTS : this is a labelled diagram of a Mercedes transmission and all the internal parts of a continuously variable transmission..
THE OPERATION OF A CVT TRANSMISSION:
A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This mixes with other mechanical transmissions that offer a fixed number of gear ratios. The durabilitie of a CVT allows the driving shaft to maintain a constant angular velocity over a range of output velocities this can provide better fuel economy than other transmissions by enabling the engine to run at its most efficient RPM for a range of vehicle speeds. Alternatively it can be used to maximize the performance of a vehicle by allowing the engine to turn at the RPM at which it produces peak power this is typically higher than the RPM that achieves peak efficiency. a CVT does not strictly require the presence of a clutch, for instance a motor cycle can use a centrifugal clutch just to have a neutral point for wen stopped or idling .
Unlike traditional automatic transmissions, continuously variable transmissions don't have a gearbox with a set number of gears, which means they don't have interlocking toothed gears. The most common type of CVT operates on an ingenious pulley system that allows an infinite variability between highest and lowest gears with no discrete steps or shifts. So basically it is a gearbox with no actual gears apart from forward and reverse it uses a pulley system with different ratios to adjust to it going up or down hill ,instead of using toothed gears which is a lot more complex design.
This is a way of saying how the CVT system works, when one pulley increases its radius, the other decreases its radius to keep the belt tight. As the two pulleys change their radius relative to one another, they create an infinite number of gear ratios from low to high and everything in between. For example when the pitch radius is small on the driving pulley and large on the driven pulley then the rotational speed of the driven pulley decreases, resulting in a lower gear. When the pitch radius is large on the driving pulley and small on the driven pulley then the rotational speed of the driven pulley increases resulting in a higher gear. This in theory a CVT has an infinite number of gears that it can run through at any time, at any engine or vehicle speed.
ADVANTAGES AND DISADVANTAGES OVER OTHER TRANSMISSIONS:
Have a look into a planetary automatic transmission and you'll see a complex world of gears, brakes, clutches and governing devices. By comparison, a continuously variable transmission is a study in simplifying a transmission, Most CVTs only have three basic components: A high-power metal or rubber belt ,A variable-input driving pulley , An output driven pulley .
CVTs also have various microprocessors and sensors, but the three components described above are the key elements that enable the transmission to work .
A down side to a CVT transmission is that they were only really design for light motor vehicles with low horsepower so therefore plantary gear set transmissions are better because they can handle more torque and higher horsepower engines such as v8’s etc.
A DSG as Volkswagen calls it is effectively a manual but with a computer-controlled clutch, so the driver still has only an accelerator and brake pedal.There are two clutches, though with one looking after the even gears and the other the odd-gear ratios so when you change gears you're actually just changing clutches, making for lightning changes there are also fuel economy benefits but the downside is sometimes jerky and inconsistent stop-start engagement making them testing in traffic or on steep driveways.
A CVT is a continuously variable transmission that does without the usual four, five or six gears and instead offers an infinite number of ratios, chosen depending on the conditions and the driver input through the accelerator. CVTs can sound a bit odd to drive like a slipping clutch but can be quite effective . However, they can also be slow off the mark.
REFERENCES
· EUROPEAN TRANSMISSIONS.COM
· WIKIPEDIA.COM
· GOOGLE.COM
· HOWSTUFFWORKS.COM.AU
· YOUTUBE.COM
