High-Ratio Speed-Reduction Transmission

Turbines driven by expanding gases, such as steam or combustion gases have the disadvantage of requiring very high rotational speeds for their rotors and consequently requiring great reductions in speed to adapt them to use with other much slower moving mechanisms. In the past, exhaust turbines driven by exhaust gases from internal combustion engines in motor vehicles have found practical use mostly in directly supercharging the engines of such vehicles, especially in racing cars. Hitherto, in motor vehicles, the auxiliary units have been driven from the engine by belts and pulleys. Such auxiliary units include the generator alternator, the cooling fan, the oil pump for power steering, the refrigerant compressor for air conditioning, the air compressor or power brakes of trucks and trailers and the oil pump for levelling the chassis frame in cranes and earth moving equipment. Recent investigations have shown that a great amount of power is consumed in driving these auxiliary units, thereby expending much fuel. The present invention seeks to avoid such wastage by utilizing the exhaust gases of the engine to drive a gas turbine, the extremely high output speed of which is reduced by means of the present speed-reduction transmission so that the output of the latter is sufficiently low to drive these auxiliary units and at the same time utilize the propulsive power of the exhaust gases which would otherwise be wasted. Sufficient standby electrical power is contained in the vehicle storage battery while the vehicle is halted at stop lights and other points of delay, while sufficient additional compressed air for operating the brakes during such standby periods is easily supplied by providing additional compressed air tank capacity.

The high ratio speed reduction transmission of the present invention also has the advantage over the conventional worm gear and worm wheel speed reduction transmission wherein the axes of the worm wheel shaft are necessarily perpendicular to one another, hence require a bulky casing and excessive space to accommodate such a casing. The present transmission has its input and output shafts almost coaxial with one another, hence is much more compact and requires much less space to accommodate it.

The invention primarily resides in the provision of an input shaft driving a flywheel rotating on a primary axis but having a rim annularly grooved eccentrically on a secondary axis at a bearing race for bearing balls engaging a correspondingly-annular grooved internally-toothed ring gear which is externally-toothed to mesh with stationary internal teeth in the housing so that it can oscillate but not rotate. Meshing with this ring gear is an output spur gear with a lesser number of teeth rotatable upon the primary axis, the eccentricity between the primary and secondary axes permitting clearance between the internal ring gear and the output spur gear.

In the drawing,

FIG. 1 is a central vertical longitudinal section through a high ratio speed reduction transmission, according to one form of the invention,

FIG. 2 is a fragmentary vertical cross-section taken along the line 2--2 in FIG. 1; and

FIG. 3 is an enlargement of the cross-sectional area within the circle designated by the arrow and numeral 3 in FIG. 2, to indicate the minute clearances between the gear teeth in the upper part of FIG. 2 to allow for oscillation of the inner portion teeth relatively to the outer portion teeth in the upper part of FIG. 2, while meshing in the lower part of FIG. 2.

Referring to the drawing in detail, the high-ratio speed reduction transmission, generally designated 10, is a two-stage transmission, yet occupies less space than a single worm-gear speed reduction transmission of the same reduction ratio. The second stage, however, is similar in construction to the first stage and multiples the speed reduction ratio of the first stage.

The transmission 10 is contained in a housing 12 (FIG. 1) having a retaining cap 14 bolted thereto at 15 with a bearing race retaining ring 16 therebetween. The power input shaft 18 at the left-hand is drivingly connected to the engine flywheel shaft (not shown) and rotates on the first axis X--X thereof. The power input shaft 18 is bolted at 20 to the first stage flywheel 22, the center of which is bored at 23 coaxially with the input shaft 18 to receive a first shaft ball bearing unit 24. The rim of the flywheel 22 is machined with a first annular rabbet 25 centered on the first axis X--X to carry an annular first inner ball race 26 with an annular first excentric ball groove 27 centered on the eccentric second axis Y--Y to receive bearing balls 28 which engage the correspondingly-excentric ball groove 29 of an annular outer ball race 30. The latter also carries an internally and externally-toothed first stage ring gear 32 which can oscillate but not rotate by its external teeth 33 meshing with the internal teeth on one side of the annular casing 35 and centered on the first axis X--X, while providing sufficient clearance between said teeth 33 and 34 on the opposite side of said casing 35 to permit said oscillation of the ring gear 32, as shown enlarged in FIG. 3. The casing 35 is mounted inside the housing 12 (FIG. 2) and prevented from rotating by shear pins 36. Meshing with the internal teeth 37 of the first stage ring gear 32 are the external teeth 39 of a first stage driven spur gear 38 which is bolted at 40 to the flange 42 of a hub 44 which is rotatably mounted on needle bearings 46, all these being coaxial with the first axis X--X. The eccentricity of axes X--X and Y--Y is sufficient to permit clearance of the external teeth 39 of the spur gear 38 with the internal teeth 37 of the internal ring gear 32 on one side while in mesh with one another on the diametrically opposite side (FIG. 2).

Also bolted at 40 to the hub flange 42 is a second stage flywheel 48, the rim of which is machined with a second annular rabbet 49 centered on the first axis X--X to receive a second inner ball race 50 grooved with an annular second excentric ball groove 51 eccentrically on the second axis Y--Y and carrying bearing balls 52. These engage the excentric ball groove 53 of a second outer ball race 54, the ball groove 53 being centered on the second axis Y--Y. The second outer ball race 54 forms a part of a second stage ring gear 56 like the first stage ring gear 32 and has external teeth 57 similarly meshing with internal teeth 59 of the casing 35 and centered on the second axis Y--Y. The second stage ring gear 56 has internal teeth 61 meshing with the external teeth 63 of a centrally-mounted second stage spur gear 58 likewise rotating on the first axis X--X. The second stage spur gear 58 is bolted at 60 to the internally splined output hub 62 which has an internally-splined driving connection 65 with the externally splined portion 67 of the power output shaft 64 from which a power takeoff is obtained at a greatly reduced speed. A second shaft ball bearing unit 66 rotatably supports the power output shaft 64. Shear pins 68 and 70 prevent the fly wheel ball races 26 and 50 from sliding circumferentially to their respective flywheels 22 and 48. The ring gears 32 and 56 have two teeth more than their respective spur gears 38 and 58, and this difference creates the speed reduction.

In operation, the rotation by the engine (not shown) of the power input shaft 18 causes oscillation in an orbital path but not rotation of the first stage spur gear 38 by two teeth. The first stage spur gear 38, however, remains in mesh with the oscillating but not rotating ring gear 32 oscillates inside it in an orbital path because of the relative eccentricity of the two gears 38 and 32. The greatly reduced rotation thus imparted by the oscillating first stage ring gear 32 to the first stage spur gear 38 is transmitted through the hub flange 42 to the second stage flywheel 48 which thus very slowly oscillates the second stage ring gear 56 to impart a further very great speed reduction of two teeth per revolution to the second stage spur gear 58. In other words, each spur gear 38 or 58 advances only two teeth per oscillation of its respective ring gear 32 or 56. As a result, there is obtained a tremendous speed reduction between the power input shaft 18 and the power output shaft 64 splined to the hub 62 carrying the second stage spur gear 58.

The flywheel 22 is dynamically balanced with the ball bearing race 25, including the balls 28 and the ring gear 32 assembled to minimize the centrifugal forces of the excentrically orbiting but not rotating ring gear 32 through removing stock of the flywheel 22 opposite the axis Y--Y. Similarly, the flywheel 48 is dynamically balanced with the ball bearing race 50 and the ring gear 56 assembled to minimize the centrifugal forces of the excentrically orbiting but not rotating ring gear 56 through removing stock of the flywheel 48 opposite the axis Y--Y.