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Semi-automatic and automatic transmissions
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
The Subaru variable-speed belt and expanding pulleys CVT differed from the Ford CTX in utilizing an electronically controlled magnetic powder clutch, which was used in conjunction with a forward and reverse synchromesh gearset. In a more recent version Subaru have replaced the magnetic powder clutch with a hydraulic torque converter, which is combined with an electronically controlled lock-up clutch. Similarly the ZF-Ecotronic CVT features a hydraulic torque converter with lock-up clutch, so that it too combines the advantages of smoother starting-off with reduced engine speed and lower fuel consumption during normal driving. It is controlled by an electrohydraulic system in the manner of a modern conventional automatic transmission. For this purpose a microprocessor-controlled ECU continuously determines the most favourable operating mode for the system and selects whatever CVT ratio is appropriate by adjusting the relative diameters of the primary and secondary belt pulleys. The transmission unit is designed for fill-for-life lubrication with ATF (automatic transmission fluid), which minimizes maintenance costs, makes servicing simpler and reduces environmental pollution. For their previously mentioned Multitronic CVT, Audi employ one oil-cooled multiplate clutch for transmitting forward drive and another for reversing, instead of using a hydraulic torque converter that absorbs more power.
Thermodynamic Differences of Different Friction Pairs in a Multidisc Clutch Caused by Spline Friction: Numerical Simulation and Experimental Verification
Published in Tribology Transactions, 2019
Liang Yu, Biao Ma, Man Chen, Heyan Li, Heng Zhang, Jikai Liu
The multidisc clutch is considered an essential component in a power transmission. The friction characteristics of a clutch have a significant influence on the thermodynamic performance of the transmission system, thus determining the reliability and safety of the entire vehicle (Yu, et al. (1); Al-Shabibi (2); Patil, et al. (3)). In specific engineering applications where a high-power transmission is required, the clutch is designed with multiple friction components, as shown in Fig. 1. A separate plate and friction disc are mounted to the cylinder liner and driving gear by splines, respectively. The oil is supplied under pressure, which produces a normal force acting on the piston against the spring to engage the plate and disc. The lubricating oil, called automatic transmission fluid (ATF), is continuously supplied to cool these friction components.