有V型橡膠帶式、金屬帶式、多盤式、鋼球式、滾輪轉盤式等多種構造,大都利用金屬帶和可變半徑的滾輪 (尚未撰寫)">傳輸動力。透過主動滾輪與被動滾輪半徑的變化,達到齒輪比的變化。理論上這種傳動方式的效率很高,不過必須建立在能負荷所傳遞的動力的情況下。由於是利用鋼帶與滾輪之間的摩擦力傳遞動力,所以鋼帶及滾輪的工作情況十分苛刻。為了有效傳遞動力,鋼帶與滾輪之間不允許打滑,而且原本產生的熱能已經很多,如果再打滑恐怕將會造內部機件的燒毀或嚴重耗損。而為了增加靜摩擦力,最直接的方式就是增加鋼帶與滾輪之間的壓力。但摩擦力增加了,動力傳輸的耗損也會增加,無形中還是增加了油耗。並且鋼帶的強度也是一大重點。所以CVT變速箱縱然有舒適、效率高等等優點。缺點就是目前一般的CVT變速箱不能承受較大的扭力。不然就是要用較高的油耗作補償。

Advantages

  • CVTs can compensate for changing vehicle speeds, allowing the engine speed to remain at its level of peak efficiency. This improves fuel economy and by effect, exhaust emissions.
  • CVTs operate smoothly since there are no gear changes which cause sudden jerks.
  • Very few problems have been reported with the CVT transmission, lowering the cost of ownership.
  • There are 25% fewer moving parts to a CVT transmission.
  • They are also cheaper, but still expensive to repair.
  • The fluids do not have to be changed as often as in an automatic transmission.

Disadvantages

  • CVTs operate smoothly and efficiently, without spending energy to jerk the car during a shift. This can give a perception of low power, because many drivers expect a jerk when they begin to move the vehicle. However, the expected jerk of a non-CVT can be emulated by CVT control software, thus eliminating this marketing problem.
  • Since the CVT keeps the engine turning at constant RPM over a wide range of vehicle speeds, pressing on the accelerator pedal will make the car move faster but doesn't change the sound coming from the engine as much as a conventional automatic transmission gear-shift. This confuses some drivers and, again, leads to an impression of a lack of power. This can be considered a disadvantage if the driver desires to hear the engine change tone.
  • CVT torque-handling capability is limited by the strength of their transmission medium (usually a belt or chain), and by their ability to withstand friction wear between torque source and transmission medium (in friction-driven CVTs). CVTs in production prior to 2005 are predominantly belt- or chain-driven and therefore typically limited to low-powered cars and other light-duty applications. Units using advanced lubricants, however, have been proven to support any amount of torque in production vehicles, including that used for buses, heavy trucks, and earth-moving equipment.

source: http://en.wikipedia.org/wiki/Continuously_variable_transmission

齒輪比,終傳比,輪胎呎吋跟速度之間的關係

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