What is the principle of continuously variable transmission?

[OAubrey]

The principle of continuously variable transmission is to use a hydraulic torque converter to generate different levels of torque, transmitting force to achieve stepless speed variation. Types of continuously variable transmission: 1. Mechanical type: There are various forms, with the most common being the cone-block metal V-belt drive, used in automobiles; 2. Hydraulic transmission type: Used in engineering vehicles and agricultural machinery; 3. Electric type: Used in electric vehicles. Starting devices for continuously variable transmission include: 1. Electromagnetic clutch type: Large in mass and size, with low thermal load capacity; 2. Electronically controlled wet friction plate type: Compact structure, fast response, and low energy loss; 3. Hydraulic torque converter type: High starting torque, good hill-start performance, easy driving, excellent driving performance, and capable of reducing vibrations and shocks caused by uneven engine torque.

[HaileyLynn]

The essence of continuously variable transmission lies in its variable gear ratio design, achieved through a pair of tapered pulleys connected by a steel belt or chain. The driving pulley links to the engine while the driven pulley connects to the wheels. By hydraulically adjusting the distance between the two tapered pulleys, the working radius of the belt changes. When the computer detects acceleration demand, it instantly adjusts oil pressure to increase the driving pulley's diameter while reducing the driven pulley's size – much like shifting gears on a bicycle. This creates seamless ratio changes without fixed gear steps, eliminating traditional transmission shift shock completely. Driving such vehicles on mountain roads keeps engine RPM consistently in the optimal range, delivering both fuel efficiency and smoothness. Even in stop-and-go traffic, there's no jerky motion. While belt wear and higher maintenance costs remain weaknesses, most new models now use reinforced chains to address this issue.

[Barry]

Having worked on cars for over 20 years and disassembled countless transmissions, the CVT's pulley set is truly ingenious. Both the driving pulley and driven pulley feature movable conical structures, with a high-strength push-type steel belt tensioned between them. The electronic system controls hydraulic pressure to push the conical plates together or apart, causing the steel belt's position to shift accordingly. When the driving pulley clamps, the belt moves outward, achieving a gear reduction effect akin to a small gear driving a large one. Conversely, when the driven pulley compresses, it switches to an overdrive state resembling a large gear driving a small one. This seamless adjustment keeps the engine RPM locked in its most efficient range—I've measured 15% better fuel economy than AT transmissions. However, excessive belt slippage can generate abnormal noises. Some owners experience engine revving without acceleration during hard throttle inputs, caused by delayed pulley adjustment. Newer models with electro-hydraulic valves have significantly improved this issue.

[JohnnyAnn]

As a CVT owner, the most intuitive feeling is the smoothness. The throttle response is like stretching a rubber band, with the tachometer steadily rising and the vehicle speed increasing linearly during acceleration. The core principle involves two sets of variable-diameter pulley groups replacing traditional gears. The steel belt moves up and down in the V-shaped groove of the pulleys, and the computer adjusts the clamping force of the two pulleys based on throttle depth to change the actual gear ratio. It's particularly comfortable in stop-and-go traffic, completely free from the jerky shifting sensation of traditional transmissions. However, it does lack the mechanical thrill of gear shifts during aggressive driving, though the fuel efficiency performance is quite impressive.

[MacArabella]

Continuously Variable Transmission (CVT) essentially achieves power transfer by continuously altering the gear ratio. This is specifically accomplished through hydraulically controlled variable pulley sets: the driving cone pulley on the input shaft adjusts the steel belt's winding diameter by changing clamping force, while the driven cone pulley on the output end synchronously adjusts in the opposite direction. When the contact radius of the driving pulley's belt increases and that of the driven pulley decreases, it equates to engaging a low gear; conversely, it shifts to a high gear. The electronic control system monitors throttle opening and vehicle speed in real-time, adjusting pulley oil pressure hundreds of times per second to keep the engine operating within the optimal torque and RPM range. This structure reduces components by 40% compared to traditional planetary gear sets, though early designs suffered from belt slippage. Modern chain-type designs have tripled load-bearing capacity.

[Peggy]

After driving for so many years, what I appreciate most about CVT is its smoothness. The key lies in that precise cone pulley system—two tapered pulleys facing each other to form a V-shaped groove, with the steel belt sliding up and down to change the gear ratio. Imagine replacing the front and rear sprockets of a bicycle with expandable ones; the shifting process would be as smooth as playing an accordion. The engine RPM remains basically constant while the vehicle speed keeps increasing, making it particularly fuel-efficient during highway cruising. However, be cautious about sudden acceleration right after a cold start, as insufficient oil pressure can cause delayed response from the cone pulleys. It's best to warm up for a minute before driving. Nowadays, high-end models even incorporate simulated gear functions, using programming techniques to create a shifting sensation, preserving smoothness while adding driving pleasure.