Automotive Power Transmission Systems

8Dual Clutch Transmissions

8.1 Introduction

Dual clutch transmission (DCT) combines the advantages of manual transmission (MT) and conventional automatic transmission (AT). DCT vehicles feature the convenience and comfort of AT vehicles and a fuel economy comparable to that of MT vehicles. In addition, DCT is less costly to manufacture in comparison with AT since it shares similar structure and components with MT.

As illustrated in Section 8.2, a DCT is structurally a combination of two manual transmissions, one with even gears and the other with odd gears. While the transmission operates in the current gear, the next gear is already engaged, since the related clutch is open and the related gears freewheel. A gear shift is realized by releasing the currently applied clutch and applying the clutch for the next gear. Gear shifting of a dual clutch transmission is then in kinematics similar to that of clutch‐to‐clutch shift in a conventional AT. However, the dynamic characteristics are different between the two types of transmissions since the AT is equipped with a torque converter that dampens shift transients. The existing control technologies for conventional AT cannot be readily applied for DCT shift control. Moreover, more precise torque control is required to achieve launch and shift smoothness of DCT vehicles since there is no torque converter between the engine and the transmission input. Extensive research and testing has been conducted by engineers and researchers in ...