An automatic transmission for automobiles. It is also commonly called a torque converter or no-clutch. Gear-type transmissions make driving complicated because the clutch must be disengaged and the gears changed every time. For this reason, attempts have been made to automate the gear shifting operation, but the completed form as we know it today was devised by engineers at General Motors in the United States, and was first installed on 1939 Oldsmobile cars under the product name "Hydramatic." The most common type combines a hydraulic torque converter, which converts and transmits rotational speed and torque by applying the properties of a fluid, with a mechanical transmission with two to four gears that is automatically operated by hydraulics. By adjusting the engine speed by operating the accelerator pedal, the vehicle can start smoothly from a stop and automatically accelerate to its maximum speed with almost no shock. Early models were expensive and had a large loss of power, and were inferior to purely mechanical types in terms of acceleration and fuel consumption. However, improvements were made after that, such as increasing the number of gears, adding overdrive, and locking up the torque converter when driving at a constant speed, and performance has improved significantly. Furthermore, electronically controlled automatic transmissions that use small computers to detect the shift points more precisely have appeared. In the 1980s, the fundamentally mechanical continuously variable automatic transmission, called CVT (continuously variable transmission), was reevaluated, improved, and put into practical use. CVTs do not use fluids, so they have little power loss, and their type is suitable for front-wheel drive small utility vehicles, and they are used by major manufacturers around the world. An improved version of the CVT, the ECVT (electro CVT), is also now in practical use. As urban traffic congestion continues to intensify, automatic transmissions are becoming more and more popular. As of 1981, the penetration rate in the United States had reached 81.7%, but in Japan, where there are many small cars, it had only just surpassed 20%. However, it has since spread rapidly in Japan, reaching a high penetration rate of 74% in 1991 and 91.2% in 2000 (excluding imported cars and light passenger cars). [Takashima Shizuo] [Reference] | | | |©Shogakukan "> Automatic transmission structure... Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend |
自動車の自動変速機。ごく一般的にトルコン(トルクコンバーター)、ノークラッチとよばれることもある。歯車式変速機は、いちいちクラッチを切って歯車を入れ換えなければならないので運転操作を複雑にしている。そのため、変速操作を自動化しようという試みがなされてきたが、今日のように完成された形式はアメリカのゼネラル・モーターズの技術陣によって考案され、まず1939年型のオールズモビル車に「ハイドラマティック」の商品名で注文装備された。 もっとも一般的な形式は、流体の性質を応用して回転速度と回転力を変換、伝達する油圧トルクコンバーターと、油圧により自動的に操作される2~4段の機械式変速機を組み合わせたものである。アクセルペダルの操作でエンジン回転を調節すれば、停止からスムーズに発進、最高速度までほとんどショックなしに自動的に加速する。初期のものは高価なわりに出力の損失が大きく、加速力、燃料消費率ともに純機械式に劣っていた。しかしその後、変速段数を増やす、オーバードライブをつける、定速走行時にトルクコンバーターをロックアップするなどの改良が加えられ、著しく性能が向上している。さらに小型コンピュータで変速点をより精密に検出する電子制御自動変速機も現れた。1980年代に入ってから、CVT(continuously variable transmission)とよばれる基本的に機械式の無段自動変速機が見直され、改良が続けられ実用化された。CVTは流体を用いないので力の損失が小さく、またその形式からも前輪駆動の小型実用車に適しており、世界中の主要メーカーが採用している。また、CVTを改良したECVT(electro CVT)も実用化されている。都市交通の渋滞が激しさを加えつつある今日、自動変速機はますます普及する傾向にある。1981年度の時点でアメリカでの普及率は81.7%にも達していたが、小型車の多い日本ではようやく20%を超えたばかりであった。しかしその後日本でも急速に普及し、1991年(平成3)に74%、2000年には91.2%という高い普及率を示している(輸入車と軽乗用車を除く)。 [高島鎮雄] [参照項目] | | | |©Shogakukan"> オートマチックトランスミッションの構造… 出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例 |
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