Development of New CVT for K-Car
A continuously variable transmission (CVT) adopting a parallel-shaft, helical gear primary reduction mechanism for greater transmission efficiency was developed for K-car use. The distance between the input shaft and output shaft in the front-to-back dire
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Abstract A continuously variable transmission (CVT) adopting a parallel-shaft, helical gear primary reduction mechanism for greater transmission efficiency was developed for K-car use. The distance between the input shaft and output shaft in the front-to-back direction was reduced and the hydraulic control system was positioned all together below the transmission. This supported the reduction of engine compartment size and, by extension, contributed to the extended length of the K-car cabin interior. Two types of 0.66-L engine, naturally aspirated (NA) and turbocharged (TC), are supported, as well as two-wheel drive (2WD) and fourwheel drive (4WD) systems, with a minimum configuration of special parts. Idle stop was also supported with just the addition of an electric oil pump.
Keywords Power transmission Continuously variable transmission Mechanism Efficiency Structure
K-car fuel-saving performance has become a major focus of attention in recent years. An enhanced level of fuel consumption is also being demanded of Honda Kcars, and a new model continuously variable transmission (CVT) was developed for the K-car. This CVT is to replace the lightweight, reasonably priced four-speed automatic transmission (AT) being used in Honda K-cars, and so a lightweight, compact structure was adopted. The previous CVT had the drive pulley positioned coaxially with the input shaft, so the separation between the input shaft and the output shaft
F2012-C03-019. K. Konishi (&) Honda R&D Co., Ltd. Automobile R&D Center, Wako¯, Japan e-mail: [email protected]
SAE-China and FISITA (eds.), Proceedings of the FISITA 2012 World Automotive Congress, Lecture Notes in Electrical Engineering 193, DOI: 10.1007/978-3-642-33744-4_24, Ó Springer-Verlag Berlin Heidelberg 2013
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Fig. 1 Main section of development CVT
where the differential assembly is located could not be reduced. A main section view is shown in Fig. 1. A parallel-shaft, helical gear primary reduction mechanism was adopted for this CVT, and the drive pulley was located above the input shaft. This allowed the distance between the input shaft and output shaft to be reduced. With this, the front-to-back length of the transmission could be shortened, and the result contributed to enlargement of the cabin space. A side view of the present CVT is shown in Fig. 2. The adoption of a primary reduction mechanism lowers the rotational speed of the CVT’s metal V-belt and increases the metal V-belt input torque. The metal Vbelt has the greatest transmission efficiency when operated close to the belt’s allowable input torque, so that setting an optimal primary reduction ratio enhanced the transmission efficiency of the CVT. The previous CVT had a high secondary reduction gear-meshing frequency, and therefore required high machining accuracy for the gears as well as careful attention to the shaft supports. However, the present CVT has adopted a primary reduction mechanism with parallel-shaft helical gears, which allows a lower gearmeshing freq
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