Patent GB-928727-A (GB)
Title: Improvements in or relating to speed-reducing and reversing transmission mechanisms for motor vehicles
IPC: F16H47/08
Filed: 1960-12-08
Abstract: 928,727. Reverse gear; change-speed control. ETABLISSEMENTS J. RIVOIRE. Dec. 8, 1960 [Dec. 8, 1959; Nov. 9, 1960], No. 42308/60. Class 80 (2). In a planetary reverse gear for motor vehicles requiring rapid and relatively frequent directional change, means are provided to prevent a directional change when the engine is running above a predetermined speed. Gearing.-A shaft 17, engine-driven through an hydrodynamic torque converter comprising an engine-connected impeller 7, a turbine 16 secured to the shaft 17, and a reactor 14, has splined thereon suns 18, 19 of two sun-ring- planet trains 18, 25, 20 and 19, 22, 21 which by engagement of disc brakes 28 to the carrier 27 of the planet 25 or 31 to the ring 21, provide reduced-reverse or reduced-forward drive to an output shaft 23<SP>1</SP> connected to the ring 20 and the carrier 23 of the planets 22. Control.-The brakes 28, 31 are alternatively engaged by a double acting piston 35 in a servo cylinder 36. The piston is held in a central disengaged position by spring-pressed plungers housed in a cylinder dividing wall. The cylinder 36 comprises chambers 36<SP>1</SP> and 36<SP>2</SP> selectively energized through a selector valve 40 which comprises an inlet chamber 40<SP>2</SP> provided with a pressure gauge 42, outlet chambers 40<SP>6</SP>, 40<SP>5 </SP>feeding the servo-chambers 36<SP>1</SP> and 36<SP>2</SP>, and outlet chambers 40<SP>7</SP>, 40<SP>8</SP> exhausting to a sump 2 via channels lubricating and cooling the brake discs 28, 31. A valve spool is manually shifted from the vehicle control panel through a flexible control member 49. Leftward movement of the spool connects the inlet chamber 40<SP>2</SP> to the chamber 40<SP>5</SP> for engagement of the forward drive brake 31, and, through a spring-loaded relief valve 50, to the chamber 40<SP>8</SP> for lubrication of the disengaged reverse drive brake. Rightward movement of the spool connects the inlet chamber 40<SP>2</SP> to the chamber 40<SP>6</SP> for engagement of the reverse drive brake 28, and, through the valve 50, to the chamber 40<SP>7</SP> for lubrication of the disengaged forward drive brake 31. In the central, neutral position which is located by a spring-loaded ball-detent 52 engaging a notch 48<SP>7</SP> in the spool, the spool connects the inlet chamber 40<SP>2</SP> to the chamber 40<SP>7</SP> and, through a spool passage 48<SP>4</SP>, to the chamber 40<SP>8</SP> for lubrication of both disengaged brakes. Parallel oil pumps 13<SP>1</SP>, 13<SP>2</SP>, enginedriven through gears 8<SP>1</SP>, 10, 12, supply oil from the sump 2 respectively to the selector valve inlet chamber 40<SP>2</SP> through a line 39 and to the torque converter through a line 15. Cool oil through a line by-passing the torque converter branched from the line 15<SP>1</SP> through an adjustable restriction 15<SP>3</SP>, together with that discharged from the selector valve 40, lubricates the gear trains and is returned to the sump 2. Oil from the torque converter is returned to the sump via a line 15<SP>2</SP>, provided with a pressure gauge 41, and a finned-radiator, heat exchanger 43. The means preventing a direction change when the engine is running above a predetermined speed comprises a locking piston 55, slidable in the selector valve body and having an end 55 adapted to engage a notch 48<SP>8</SP> formed in the valve spool transversely opposite the notch 48<SP>7</SP>. The piston 55 is urged towards the position in which it may lock the spool, against a spring 57, by pressure in a surrounding cylinder connected to the line 39 upstream of an adjustable restriction between the line 39 and the selector valve inlet chamber 40<SP>2</SP>. Above a predetermined engine speed the pressure in the cylinder of the piston 55, which pressure is proportional to engine speed, urges the piston towards the spool so that when the latter is moved to neutral position, as when being moved to change the vehicle direction, it is locked in that position. The sump 2 comprises baffles for multi-reversal of oil flow therein to facilitate oil cleaning, a magnetic separator 44 for removal of metallic impurities, and an upward flow, meshed metal screen, filter 45 extending above the last stage of the sump. To supplement pressure to the brake piston 35 for rapid displacement thereof during direction change a ball valve 61 in a dividing wall 59 between the pumps 13<SP>1</SP>, 13<SP>2</SP> opens to permit discharge of oil from the pump 13<SP>2</SP> to the pump 13<SP>1</SP> when the pressure to the brake piston falls below that to the torque converter and progressively closes as the two pressures are balanced. Thereafter the piston 35 engages the selected brake progressively by means of the pump 13<SP>1</SP> pressure alone, and the torque converter is again pressurized for torque transmission. The valve 61 may have a resilient seating or weak springs retaining the ball thereon, and the ball may be of a flexible, e.g. plastic, material.