POWER TRANSMISSION SYSTEM AND ATTENUATION MECHANISM
FIG7 is a schematic diagram of an attenuation mechanism according to further yet another modification  FIG8 is a block diagram of a power transmission system according to still further yet another modification 
In the aforementioned preferred embodiment, the inertia member 72 is urged against the support member 71 by the elastic force thereof. However, the urging configuration between the inertia member 72 and the support member 71 is not limited to this. For example, as shown in FIG7, the attenuation mechanism 7 may further include an urging member 72e. The urging member 72e is, for instance, a disc spring. The urging member 72e urges the inertia member 72 and the support member 71 so as to make the both approach each other.  In the aforementioned preferred embodiment, the power transmission system according to the present invention has been applied to the hybrid car. However, the power transmission system according to the present invention is applicable to an electric car as well. For example, as shown in FIG8, the power transmission system 100 applied to the electric car includes the electric motor 3, a reducer 8, a differential gear 9, the drive wheel 5, the transmission shaft 6 and the attenuation mechanism 7. It should be noted that the configurations of the electric motor 3, the drive wheel 5, the transmission shaft 6 and the attenuation mechanism 7 are similar to those in the aforementioned preferred embodiment. Hence, the detailed explanation thereof will be hereinafter omitted.
block diagram, schematic diagram
8
reducer
7
attenuation mechanism
73
friction materials
100
power transmission system
76
retaining ring
3
electric motor
71
support member
['1. A power transmission system comprising: an electric motor; a drive wheel; a transmission shaft transmitting a torque between the electric motor and the drive wheel; and an attenuation mechanism attached to the transmission shaft, wherein the attenuation mechanism includes a support member attached to the transmission shaft, and an inertia member disposed to be rotatable relatively to the transmission shaft, the inertia member being engaged by friction with the support member.', '2. The power transmission system according to claim 1, further comprising: a gearbox or reducer disposed between the electric motor and the drive wheel.']