Are There Any Good CVT's? | Different CVT Transmissions Explained

continuously variable transmission stands as one of the most divisive terms in the world of automobiles often abbreviated as CVT it's synonymous with a lack of driving excitement drawing disdain from both DieHard manual enthusiasts and Casual drivers alike yet is this widespread criticism truly Justified or should we take a deeper look at the CVT and perhaps even a bit of respect cvts were initially associated with lowcost low power compact cars due to their focus on fuel efficiency rather than performance however in recent years advancements in CVT technology have enabled their integration into a broader range of vehicles including high- performance full-size sedans and SUVs despite initial skepticism and criticism CVT transmissions have established themselves as a viable option for various types of vehicles even sport compacts like the Subaru WRX utilize continuously variable Transmissions in place of traditional automatics Additionally the increasing popularity of hybrid vehicles has led to the development of the ecvt a type of transmission that integrates both electric and gas drivetrains into a single output shaft offering endlessly variable gear ratios this widespread adoption indicates that CVT technology is here to stay as automakers continue to invest in its development and integration into their product lineups so in this video we are taking a look at these different types of CVT transmission used in automotive Industries to understand the reasons behind the dislike for cvts we must understand how they're different from a traditional automatic transmission in a standard automatic gear changes are typically facilitated by hydraulic pressure acting on various gears within the transmission however in a CVT there are no fixed gears at all instead cvts use a system of belts and pulleys to provide a continuously variable range of gear ratios allowing for seamless acceleration without discrete gear shifts most cvts only have three basic components a high power metal or rubber belt a variable input driving pulley and an output driven pulley cvts also have various microprocessor and sensors but the three components are the key elements that enable the technology to work variable diameter pulleys are the key components of a CVT each pulley consists of two cones facing each other a belt rides in the groove between the two cones of each pulley this belt serves to transmit power between the input and output shafts of the transmission V belts are commonly used in cvts especially when the belt is made of rubber the term V belt refers to the v-shaped cross-section of the belt which increases the frictional grip of the belt on the pulley this improved grip helps prevent slippage and ensures efficient power transfer the first pulley known as the input pulley or drive pulley is typically connected to the engine's crankshaft the second pulley referred to as the output or driven pulley is linked to the drive pulley through the belt and transfers power to the drive shaft or wheels of the vehicle these con are hydraulically controlled allowing them to be pushed together or pulled apart from each other depending on driving conditions instead of belts the chain is also used in some cvts the introduction of new materials makes cvts even more reliable and efficient one of the most important advances has been the design and development of metal belts to connect the pulleys these flexible belts are composed of several thin bands of Steel typically 9 or 12 in total each band is thin enough to bend easily and holds together high strength bow tie-shaped pieces of metal they provide several advantages over rubber belts including increased durability reduced slipping and the ability to handle higher engine torque additionally they tend to be quieter in operation compared to rubber belt driven cvts in modern cvts both the input and output pulley are typically made with cones to allow for a wider range of variability in gear ratios this design enables the CVT to adapt to various driving conditions and deliver Optimal Performance across a broader spectrum of speed at low speeds the cones comprising The Driven pulley are typically positioned as far apart as possible this configuration allows the belt connecting the pulleys to rest at the narrowest diameter on the drive side of the pulley as a result the input shaft spins rapidly relative to the output shaft which maximizes torque delivery to the wheels this setup effectively mimics the characteristics of first gear in a conventional automatic transmission creating a gear ratio optimized for strong lowend acceleration as the vehicle accelerates the input pulley cones of the CVT are gradually brought closer together causing the tips of the cones to come into contact and pushing the belt upwards along the walls of the cones this action effectively increases the effective diameter of the pulley this results in the drive pulley spinning more slowly relative to the driven pulley similar to the operation of an overdrive gear in a traditional transmission this configuration allows for higher vehicle speeds at lower engine RPM optimizing fuel efficiency and reducing engine wear during Highway cruising in order to achieve reverse gear in CVT an interesting planetary gear gear set Arrangement is used the input shaft is connected to the Sun Gear of the planetary gear set the Sun Gear is one of the three main components of a planetary gear set and typically rotates in the center the carrier of the planetary gear set is fitted with the input pulley of the CVT the carrier is another component of the planetary gear set and is positioned between the Sun Gear and the ring gear it holds the planet gears and allows them to rotate when you're driving forward the clutch is well pressed and the frictional force between the plates will lock the Sun Gear to the ring gear this makes the planetary gear set work together to move the car forward smoothly to go in reverse in a CVT transmission simply shift the gear selector into the r position the transmission engages a clutch to hold the ring gear still this makes the planet gears and carrier rotate in the opposite direction effectively reversing the direction of the output shaft Milton Reeves invented a variable speed transmission an early form of CVT in 1879 for use in Sawmills he later adapted this transmission for use in automobiles starting in 1896 several other manufacturers also utilized the Reeves CVT in their cars in 1911 the Zenith gradua 6hp motorcycle was noted for using a py based CVT this was one of the early applications of CVT and motorcycles the rudge witor multi-gear released in 1912 also featured a CVT similar to the Zenith gradua but with improvements this was another significant early application of CVT technology the 1913 to 1923 David a small three- wheed cycle car built in Spain the 1923 klino from the UK and the 1926 constantinesco salon also from the UK are all noted for using cvts these early cars demonstrated the early experimentation and application of CVT technology in the automotive industry the earliest practical application of CVT like technology came in the 20th century with the Dutch car manufacturer daf introducing the variomatic transmission in the 1950s it was a significant Innovation at the time and contributed to the commercial success of the daff 600 this system utilized pulleys and belts to provide continuously variable ratios over time the rubber belts could get stretched affecting the performance of the transmission however the 22 horsepower 590cc aircooled daf engine was luckily low stress which helped mitigate some of the issues associated with belt stretching the 600 became a massive success in Europe thanks to its excellent fuel efficiency and compact size these engines were even sold briefly in America in the 1960s they were eventually banned from American roads due to a variomatic design flaw early dafs had no Park gear they only had drive neutral and reverse gear the US government deemed this unsafe and stopped sales after daf disappeared Americans wouldn't get another CVT until the Subaru JY in 1989 the CVT in the justy was a more modernized version compared to early variomatic Transmissions with a traditional reverse gear and park function addressing some of the safety concerns that led to the discontinuation of daf vehicles the introduction of computer AED design and advancements in Material Science led to significant improvements in CVT technology these advancements allowed modern cvts to handle more power without significant belt degradation by the early 2000s several major manufacturers including Honda Nissan Subaru and Toyota began incorporating cvts into their vehicles this marked a significant shift towards the widespread adoption of CVT technology in the automotive industry the dcvt has additional gears and a planetary gear set fitted to the input and output shafts of the pulley with a clutch pack to engage or disengage in normal operation when you're p pulling off from a stop and traveling up to low to medium speeds the dcvt functions like any other CVT the power from the engine is transmitted through a torque converter and into the input pulley from there it is transferred to the output pulley via a belt and then to the wheels however when you get up to higher speeds the dcvt shifts into its split mode and an additional Gear Drive is engaged alongside the belt drive this Gear Drive provides a more efficient means of power transmission particularly at higher speeds where the belt drive may become less efficient compared to a regular CVT the dcvt in Split mode experiences fewer energy losses as the friction that comes with the belt drive in play is removed this results in improved transmission efficiency by 12% at 60 kmph and by 19% at 100 km perh in traditional cvts there might be a delay or sluggishness in acceleration from a standstill due to the nature of how cvts operate to address this Toyota has implemented a launch gear in some of its CVT equipped Vehicles while both the dcvt and direct shift CVT have additional gears in them Toyota's approach is totally different as it adds on a launch gear that acts like a first gear in a conventional transmission the launch gear is used when setting off from a stop before the transmission switches to a belt drive like a CVT Instead This launch gear is essentially a fixed ratio gear that aims to provide a more direct power delivery and improve the vehicle's responsiveness the launch gear is engaged when the vehicle is at rest it is used solely to help the vehicle accelerate up to speed more quickly and efficiently from a stop once the vehicle has reached a speed where the CV transmission is more efficient the launch gear is disengaged and the transmission functions like a CVT Toyota's direct shift CVT was first revealed in 2018 and was designed to offer a more direct drive connection at low speeds it is not the same as the older cvts used in the Vos and yarus and not all models get it even the newer Corolla cross the dcvt is like a flipped version of the direct shift CVT as Gear Drive is used at higher spe speeds rather than for setting off so why not just adapt Toyota's technology in every dcvt well adding a gear selector to engage the launch gear increases the complexity of the transmission which could be costly and wouldn't be suitable for Budget Vehicles ecvt is a different more generic name for the hybrid powertrain installed in All Pure Toyota hybrid vehicles Toyota calls it hybrid Synergy drive it is made up from an internal combustion engine electric motor generator and a pretty simple planetary gear set called the power split device this transmission is referred to as electric CVT or ecvt because it behaves very much like a standard CVT although it works based on an entirely different principle and avoids all of the disadvantages of a conventional CVT in a hybrid vehicle the ecvt can be powered by different sources to the wheels when the vehicle runs solely on battery power it is in a pure EV mode when both the battery and engine work together it is a hybrid mode when the engine takes over typically when the battery is empty it is in engine mode the pidal CVT is another version of the CVT it is slightly different from a pulley based CVT the design contains a pair of discs and rollers instead of belts and pulleys two rollers in the middle of two discs manage torque distribution to enable an infinite number of gear ratios one disc is the input which is connects to the engine this is equivalent to the driving pulley the other is the output that connects to the drive shaft this is equivalent to the driven pulley between the discs are rollers act like the belt transmitting power from one disc to the other in in this system power is transferred between discs using rollers when the rollers align perpendicularly to the discs the effective diameter is the same for the input discs and the output discs resulting in a 1:1 Drive ratio but by rotating them along the discs different ratios are achieved an advantage of a toroidal CVT is the ability to withstand higher torque loads than a pulley based CVT in some toroidal systems the direction of thrust can be rever first within the CVT removing the need for an external device to provide a reverse gear these rollers can tilt touching the discs at different points when they touch near the center of the driving disc and the rim of the driven disc speed reduces but torque increases that is low gear conversely when they touch near the rim of the driving disc and the center of the driven disc speed increases but torque decreases that is overdrive gear by tilting the rollers the gear ratio can be smoothly and quickly adjusted so that's it what do you think about CVT transmission are they good or bad let me know in the comments for more on different Transmissions watch this video and finally thanks for watching

Channel: The Engineers Post

Views: 362,564

Keywords: best transmission, cvt transmission problems, transmission, cvt transmission, cvt, cvt gearbox, d'cvt transmission, ecvt toyota, direct shift gearbox, toroidal cvt

Id: A3CA2oZ2ADM

Length: 16min 16sec (976 seconds)

Published: Wed May 15 2024