Patent TW-496932-B (TW)
Title: Power transmission device for a small-sized vehicle
Inventor: FUKAMACHI MASATOSHI
IPC: B60K17/04
Filed: 2001-03-19
Granted: 2002-08-01
Abstract: To realize a small-sized vehicle simply operable with a reduced fuel consumption and a reduced exhaust gas amount by using a mechanical type automatic transmission in combination with a belt-type continuously variable transmission, wherein the mechanical type automatic transmission is smaller in size and lighter in weight than an automatic transmission of a planetary gear type using a large number of gears or an automatic transmission using a hydraulic control system. To satisfy performances required for both a centrifugal type starting clutch of a belt-type continuously variable transmission and a centrifugal type speed change clutch of a mechanical type automatic transmission. And to provide a power transmission system for a vehicle, which is capable of reducing the load of a speed change operation of a continuously variable automatic transmission, typically, using a V-belt by using a mechanical type stepped automatic transmission in combination of the continuously variable automatic transmission, and realizing desirable riding comfort of the vehicle without occurrence of any gear-shift shock as a whole by absorbing the gear-shift shock caused by the mechanical type stepped automatic transmission by the continuously variable automatic transmission. In a power transmission system for a small-sized vehicle, a mechanical type automatic transmission 44 is connected to an engine 41 via a belt- type continuously variable transmission 43, wherein an output from the mechanical type automatic transmission is transmitted to a differential mechanism 45, to rotate right and left drive wheels 2. The mechanical type automatic transmission 44 is an automatic transmission of a type capable of selecting a speed stage from at least two speed stages. The automatic transmission has a low speed gear 65b and a high speed gear 65a for transmitting the output from the mechanical type automatic transmission 44 to the differential mechanism 45, and also has a centrifugal type speed change clutch 64 which is engaged when the rotational speed of the output from the belt-type continuously variable transmission is increased. One of the low speed gear 65b and the high speed gear 65a is changed to the other by disengagement and engagement of the centrifugal type speed change clutch 64. With this configuration, the structure of the power transmission system is reduced in size and weight. A centrifugal type starting clutch 57, which is engaged for transmission of an engine power as the engine rotational speed is increased, is provided on the belt-type continuously variable transmission 43. A centrifugal type speed change clutch 64, which is engaged to switch a power transmission gear from a low speed gear 65b to a high speed gear 65a as the engine rotational speed is increased, is provided on the mechanical type automatic transmission 44. The centrifugal type starting clutch 57 is operated in a dry environment for allowing power transmission by engagement for a short sliding time even at a small rotational speed, and the centrifugal type speed change clutch 64 is operated in an oil lubricating environment for ensuring a sufficient durability with a small-sized structure even if a sliding time becomes longer for reducing a speed change shock. A gear-shift operation timing from a low speed gear 65b to a high speed gear 65a of the mechanical type automatic transmission is set to be overlapped to a transmission operational region C of the continuously variable transmission. By switching one of the gears of the mechanical type automatic transmission to another in a state in which the continuously variable transmission operation has a margin, a gear-shift shock is absorbed by the continuously variable transmission operation.