Patent GB-1356429-A (GB)
Title: Device for controlling the process of changing speed ratios in a transmission
IPC: F16H47/06
Filed: 1971-08-09
Abstract: 1356429 Change-speed control SOC ANON FRANCAISE DU FERODO 9 Aug 1971 [10 Aug 1970] 37335/71 Heading F2D In a change-speed transmission on a motorvehicle in which ratios are established by supplying fluid pressure from an input-driven pump 70 to a selected one of three clutches E1, E2, E3, or brakes, through one or more manual or automatic selector valves 13, the rate of pressure change in the engaging and releasing clutches during a shift is controlled by a pressure-control (timing) valve 46 subject on its left face to supply pressure 28 and on its right face to a reference pressure 57 responsive to engine or gear-input torque, and operated during a shift, by the initial fall in the supply pressure to the engaging clutch, to connect the exhaust line of the disengaging clutch to the reference pressure, thereby maintaining its engagement until pressure builds up in the engaging clutch and shifts the valve 46 to provide free exhaust for the disengaging clutch. The Fig. 1 arrangement is specially adapted for synchronizing upshift, the 1-2 of which is as follows. During steady running prior to shift, supply pressure 28 predominates over reference pressure 57, holding the spool 53 of the valve 46 to the right, Fig. 2. When the selector valve 13 is moved from 1 to 2, supply pressure 28, applied to its internal bore, and issuing at a port 33, is cut off from the clutch E1 and applied to E2, which latter, being initially empty, causes supply pressure 28 to fall to zero during clutch filling. Predominating torque pressure 57 is now able to shift the timing valve 46 left, with a snap action due to a smaller end land, to Fig. 1 position, cutting off an exhaust path 50, 51 and putting the clutch E1 into communication with the torque pressure 57 through the selector valve 13, port 25, floating valve-plugs 40, 41, 42 and line 39, thus maintaining E1 in suspended engagement. As the supply pressure 28 builds up after filling the engaging clutch E2, the timing valve 46 is shifted back to the right, Fig. 2, and the outgoing clutch E1 exhausts through the path 39, 51, 50, 74. Valve 47 is a spring-loaded differentially-landed pressure-regulator, which also moves left during shift, to cut off the exhaust from supply pressure 28, but is normally in a rightward regulating position, Fig. 3. In Figs. 4 to 6, not shown, the pressurecontrol timing valve (46<SP>1</SP>) has an additional port (75) which, during a shift and at the interval when the pressure-control valve (46<SP>1</SP>) has moved back to the right, but supply pressure, acting on the small end of the regulator valve (47<SP>1</SP>), is still too low to move it right, establishes an exhaust path from supply 28 through the port (75), a groove (76) in the regulator valve, and an accelerator-controlled restrictor 80, so that the final build up of supply pressure 28, to shift the regulator to its rightward regulating position, is delayed, the delay being reduced with accelerator depression. Figs. 7 and 8, not shown, are more particularly concerned with synchronizing downshift, and here the functions of pressure-control valve 46 and regulator valve 47 are combined in a single valve (47<SP>11</SP>). Torque pressure now acts leftwards on the end land of this valve in place of the spring, and is derived from the torque developed on the gear input by a "floating inertia member" such as the turbine of a hydrodynamic torque converter or fluid coupling through which the gear is driven, or a gas turbine. During a synchronizing slip phase of the engaging clutch following complete disengagement of a releasing clutch, this inertia member causes a small accelerating torque to be taken from the output shaft (indicated by a negative torque phase (QR), Fig. 13, not shown) until the accelerating engine-driven torque-converter impeller catches up the turbine and completes the shift. The comined valve is differentially landed to provide bias in favour of the torquepressure. Figs. 9 to 11, not shown, again use both valves, the "floating inertia" control and the accelerator-controlled restrictor. Torque-timecurves for upshift and downshift, Figs. 12 and 13, not shown, are provided.