GB808972A - Improvements in mechanically propelled or mechanically driven apparatus having a hydro-kinetic torque converter and a reduction gear - Google Patents

Abstract

808,972. Variable-speed gearing. GIRI DE TERAMALA, P. M. May 4,1955 [March 1, 1955], No. 6056/55. Class 80 (2). [Also in Group XXIX] A mechanically propelled or mechanically driven apparatus comprises a suitable prime mover (i.e. one capable of developing a sufficient brake horsepower over a sufficiently wide speed range for the purposes for which the apparatus is designed), a hydrodynamic torque converter of suitable size and characteristics as determined from the maximum stalling speed of the combined prime mover and torque converter and the maximum brake horsepower speed of the prime mover, and a reduction gear interposed between the prime mover and the impeller of the torque converter, the maximum ratio of the reduction gear being determined from the prime mover and converter characteristics. A preferred embodiment of a torque converter and reduction gear for use in a motor car comprises a driving shaft 1 and rotating casing 2 connected to the annulus 3 of a planet gear whose planet carrier 4 is connected to the impeller 5 of the torque converter. A sungear 6 on a sleeve 7 is prevented from rotating backwardly by a one-way detent 8 connected to a stationary casing 9. The torque converter has a turbine 10, and a reaction element 11 on a sleeve 12 prevented from rotating backwards by a one-way detent 13. The turbine 10 is integral with a sleeve 14 fast on a driven shaft 15. A flange 18 on the sleeve 7 is provided with a cone-shaped friction clutch surface 17 which can be engaged with a corresponding surface on the annulus 3, thereby locking the planet gear for direct drive. The flange 18, sleeves 7, 12 and 14, the turbine 10 and the reaction element 11 are all axially movable, and are normally biased by springs 19 in such a direction as to engage the lock-up clutch 17. On starting the vehicle, the driven shaft 15 is stationary and the driving shaft 1, casing 2 and impeller 5 rotate together. This causes the development of hydraulic pressure at 21 in the converter, which moves the turbine 10, reaction element 11 &c. to the right of the Figure, to disengage the lock-up clutch 17. The sun-gear 6 being prevented from rotating backwards by its one-way detent 8, the planet gear accordingly gives a reduced ratio drive with increased torque to the impeller 5. As the vehicle moves off, the speeds of relative rotation between the rotating casing 2 and the turbine 10 gradually falls, so that the pressure at 21 is reduced. Accordingly, the spring 19 re-engages the clutch 17 to lock up the planetary gear. The size and construction of the hydro-dynamic torque converter is such that if the prime mover is directly coupled to the impeller of the torque converter without the interposition of any gear and caused to rotate at the maximum speed of which it is capable while the turbine is held stationary, then the prime mover will attain a speed not less than 25 per cent, and not more than 80 per cent, of the speed at which it develops its maximum brake horsepower. This " speed percentage " for a particular apparatus is determined from whether it is desired that the torque converter should slip over a relatively small part of its range or over a relatively large part of its range. The ratio of the gearing between the prime mover and the impeller 5 normally provides a ratio not less than 1.2 : 1. According to the invention, the maximum ratio of this gearing is determined from a graph of "speed percentage" against "maximum permissible ratio of reduction gear," Fig. 3 (not shown). In the Provisional Specification, it is stated that the sun-gear 6 may be connected to the reaction element 11 of the turbine.