Tài liệu học tập cơ bản khái quát về động cơ và các bộ phận trên ô tô phiên bản tiếng anh. Tài liệu này nhằm giúp chúng ta tiếp cận được cấu tạo chức năng của các bộ phận của xe. Với tài liệu này giúp các bạn sinh viên ngành cơ khí ô tô tiếp cận được những kiến thức cơ bản về ô tô và đồng thời nâng cao kiến thức tiếng anh. Bộ tài liệu này được soạn thảo bởi trường đào tạo và huấn luyện nghề ở Canada.
Chapter 40 Automatic Transmissions and Transaxles Automatic Transmissions and Transaxles • Selects gear ratios according to engine speed, power train load, vehicle speed, and other operating factors • Most have four speeds with an overdrive fourth gear • Many have five, six, and up to eight speeds Torque Converter • A fluid clutch or coupling that transfers torque from the engine to the transmission • Automatically engages and disengages power from the engine in relation to RPM • At idle, there is not enough fluid flow for power transfer • As RPM increases, fluid flow is sufficient to transmit engine power Torque Converter Internal Parts Torque Converter Components • Impeller or Pump Assembly – Receives power from the engine • Turbine – Transfers power to the transmission main shaft • Stator – Is the torque multiplier • Overrunning clutch – Allows the stator to turn in only one direction Basic Operation • Transmission fluid is the medium to transfer energy • The faster the impeller rotates, the greater energy the fluid has to transfer • The fluid leaving the impeller acts on the turbine • The turbine drives the transmission input shaft Types of Oil Flow • Rotary Flow – Oil flow around the circumference caused by rotation of the torque converter on its axis • Vortex Flow – Oil flow from the impeller to the turbine and back to the impeller • Coupling point is when turbine speed approaches impeller speed Overrunning Clutch • Keeps the stator from rotating when driven in one direction • The stator is locked when the there is a difference between the turbine and impeller speeds Gaskets and Seals • Gaskets – Seal two parts together or prevent fluid flow – Classified as either hard or soft gaskets • Seals – Used to seal fluid around valves, shafts, and other moving parts Seal Classifications • Static – Is used between two parts that not move • Dynamic – Is used between two parts that move with either rotating or reciprocating motion • Positive – Prevents all fluid leakage • Non-positive – Allows a controlled amount of leakage – Is used to lubricate a moving part Final Drive Assemblies • Transmit transaxle output to the differential section • Four common configurations: – – – – Helical gear Planetary gear Hypoid gear Chain drive Hydraulic System • The fluid operates, lubricates, and cools the transmission • The pump is the source of all fluid flow: – Pressure-regulating valves change fluid pressure to control shift quality and shift points – Flow-directing valves send to fluid to the correct apply device for gear changes Valve Body • Distributes and controls pressurized fluid throughout the transmission • Made of two or three main components: – Valve body – Separator plate – Transfer plate • Check ball valves • Poppet valves • Spool valves Shift Quality • Shift feel is controlled by the pressure at which each hydraulic member is applied or released • Timing between band and clutch application to prevent engine flare-up or clutch and band slippage Shift Timing • Determined by throttle pressure and governor pressure acting on opposite sides of the shift valve Hydraulic Circuits • The hydraulic circuit for each gear selector position is explained in the flow charts • While examining flow charts, note gear range, torque converter mode, engaged planetary controls, approximate vehicle speed, and throttle position .. .Automatic Transmissions and Transaxles • Selects gear ratios according to engine speed, power train load, vehicle speed, and other operating factors • Most... or released • Timing between band and clutch application to prevent engine flare-up or clutch and band slippage Shift Timing • Determined by throttle pressure and governor pressure acting on... Many are more compact than most fourand five-speed automatics Apply Devices • Bands – Are typically used as a holding device • Servos – Are used to apply the band • Multiple Friction Disc Assemblies