Paragraphs

Claims

Claim 3.

A four-stroke internal combustion engine according to claim 1 or 2, in which the variably timed transmission includes three superposed concentric members, i.e. an inner member constituted by a drive shaft [17], an outer member constituted by a sleeve [28] supporting a gear [20] for coupling the two crankshafts [4] [5], and an intermediate member located between said inner and outer members and constituted by a tube [32] which slides with respect to said inner and outer members, the sleeve [28] being held in a bearing plate [15] by means of a double-row angular contact bearing [16], in which the shaft [18] of the second crankshaft [5] has one end which abutes one end of the drive shaft [17], said ends having straight male splines and corresponding female splines, so as to enable their coupling and self-centering of the three members with respect to the shaft [18] of the second crankshaft [5] when the bearing plate [15] is engaged in an opening of the engine unit, and enable the transmission to be removed without having to remove the second crankshaft [5], in which a bearing [22] has a mounting ring [25] which forms the housing of the outer ring [26] of a bearing [23], the inner ring [27] of which is mounted on the sleeve [28] so as to hold the drive shaft [17], in which a spacer [29] extends between the inner ring [27] of the bearing [23] and the inner ring of the angular contact bearing [16], said spacer serving to take up the space between said rings and holding axially the ring of the angular contact bearing [16] against a shoulder of the sleeve [28], in which a single nut [30] holds the inner rings of the bearing [23] and of the angular contact bearing [16] and the spacer [29] on the sleeve [28], in which the drive shaft [17] has, on the side of the mounting ring [25] , helical or straight splines [31] onto which the sliding tube [32] is engaged, the inner surface of which has helical or straight splines [33] so as to enable said tube [32] to travel helically or linearly along the drive shaft [17], in which the inner surface of the sleeve [28] has helical splines [35], the helix of which is contrary to that of the splines of the drive shaft when the latter are helical, in which the sliding tube [32] has one end permanently free outside the sleeve [28], said end being held by an inner ring of a double-row angular contact bearing [36], the outer ring of said bearing [36] being rigidly connected to a holding member [37] of the thrustor, and in which the helical splines are arranged so that when the sliding tube [32] travels out of the sleeve, said tube reduces the lead angle between the crank of the second crankshaft [5] and the crank of the first crankshaft [4].

Claims