GB1109801A - Improvements in or relating to a power transmission unit - Google Patents

Abstract

1,109,801. Arrangements of gearing. AXEL WICKMAN TRANSMISSIONS Ltd. 26 April, 1965 [25 Jan., 1964], No. 3319/64. Heading B7H. [Also in Divisions F1 and F2] In a power transmission incorporating a bevel gear, wherein lubricant for the gears of the bevel gear is pumped from a reservoir, through a heat-exchange passage, and back to the reservoir, at least a portion of the heatexchange passage is formed in a portion of the wall of a casing of the transmission. As shown, the casing 41 of a conventional automobile final drive assembly comprising hypoid crown and pinion and differential gearing is secured to a rear casing portion 42 of a preceding Reduced-Direct or Direct- Overdrive sun-ring epicyclic gear. The lubricant pump comprises a frusto-conical drum fast with the epicyclic output and co-operating with a similarly shaped bore in said rear epicyclic casing portion to provide a clearance diminishing in thickness towards the largest drum diameter, this clearance on drum rotation promoting lubricant flow. This pump draws from said rear epicyclic casing portion and discharges through an external pipe 63, part frusto-conical heat-exchange cavities 67, 68 in a forward epicyclic casing portion 37, a further external pipe 71 and a zig-zag passage in said rear epicyclic casing portion, to the final drive casing from whence the lubricant returns to said rear epicyclic casing portion. The epicyclic output also drives a speedometer through skew gearing. In a similar two-speed epicyclic and final drive arrangement (Figs. 10-13, not shown), an archimedean screw pump driven by a speedometer skew drive discharges through heat exchange cavities zig-zagging circumferentially in a finned intermediate epicyclic casing portion. In Figs. 14, 15 (not shown), a secondary, crescent gear pump, of greater capacity than the lubricant pump, is provided at the front end of the forward epicyclic casing portion to prevent flooding of this portion when the vehicle goes downhill. This pump may discharge to the lubricant cooling system. In Fig. 16 (not shown), an archimedean screw pump is arranged coaxially with the epicyclic gear. In Fig. 17 (not shown), the hypoid crownwheel acts as the pump to promote flow of lubricant from the lubricant reservoir in the final drive casing to the cooling system, the return flow to the final drive casing being effected through a jet-orifice directed on to the point of hypoid mesh. If flow is insufficient, a suitable pump may be provided. In Figs. 18-21 (not shown), an eccentricactuated piston pump driven from the epicyclic input draws from a sump and discharges to a fluid circuit described in Specification 1,078,002, in which filtered lubricant is supplied to a gear-change servomotor system. Lubricant from this system also flows to a lubricating supply passage, which is controlled by a low-pressure relief valve, and divides to supply, through a bore in the epicyclic input shaft, the epicyclic gearing and a finned subsidiary reservoir in the forward epicyclic casing portion. A weir maintains the head in the subsidiary reservoir higher than that in the main sump or in the final drive casing. A finned external pipe conveys lubricant from the subsidiary reservoir to a finned part of the rear epicyclic casing portion from whence it is conveyed to the final drive casing. The piston pump discharges through a spring- loaded ball valve and, to prevent hydraulic knock, has a spring-loaded cylinder head capable of slight axial movement.