Electric power unit and power transmitting unit for electric vehicles

A power transmitting unit for an electric vehicle including a motor, a clutch, a transmission and a power transmitting mechanism, said power transmitting unit comprising:

• a dog clutch arranged to be rotatable with an output shaft of said motor and movable in a coaxial direction, and an automatic multiple-speed clutch transmission comprising a plurality of gear trains including first and second transmission gears which are supported respectively on both sides of said dog clutch to be loosely rotatable and whereby said dog clutch is mechanically brought into contact with or away from said first and second transmission gears,
• wherein said dog clutch comprises a clutch movable portion movable in an axial direction of the output shaft and movable between said first transmission gear and said second transmission gear, a permanent magnet, a clutch driving portion disposed around said clutch movable portion and an excitation coil having, at each end of said clutch driving portion, a first thickness in said axial direction of the output shaft,
• wherein said clutch movable portion has, at each end, a yoke having a second thickness in said axial direction of the output shaft,
• wherein said clutch driving portion has, at each end, a yoke having a third thickness in said axial direction of the output shaft larger than said second thickness, and larger than a total thickness of half of said first thickness plus half of said second thickness for forming a magnetic circuit, whereby
• within a first stroke of movement of said clutch movable portion from a start point near an inside diameter of one of said clutch driving portion yokes to a nearly midpoint between said start point and an end point near an outside diameter of said one clutch driving portion yoke along an axial direction of the output shaft, said magnetic circuit induces electromagnetic forces acting in opposed relation to the direction of movement of said clutch movable portion, and
• within said first stroke of movement of said clutch movable portion from said midpoint to said end point, said magnetic circuit induces electromagnetic forces acting to propel said clutch movable portion in the direction of movement.