A starter for an internal combustion engine

摘要

In a starter (1) for an internal combustion engine comprising a planetary gear type reduction gear unit (2) and a housing (17) for accommodating at least the reduction gear unit (2), a recess (51) is formed at a lower part (17a) of the housing (17) in an installed state of the starter (1) in a manner that the recess (51) is formed in an inner periphery of the housing (17) so as to define a drain passage (51) extending substantially axially, and a part (52) of an outer periphery of a first annular member (12), which constitutes a part of the reduction gear unit (2), protrudes into the recess (51). Thus, the protruding part (52) of the outer periphery of the first annular member (12) forms a labyrinth structure in the drain passage (51) defined by the recess (51) formed in the inner periphery of the housing (17), to thereby effectively prevent water from entering the housing (17) through the drain passage (51) without substantially impeding the passage of water from the housing (17) to the outside. This protruding part (52) is integrally formed in the first annular member (12), and therefore no additional component parts are required to make the labyrinth structure.