GB1177965A - Improvements in or relating to Variable-Speed Gearboxes - Google Patents

Abstract

1,177,965. Change-speed control. DAVID BROWN GEAR INDUSTRIES Ltd. 21 Feb., 1968 [24 Feb., 1967], No. 8925/67. Heading F2D. In an electro-pneumatic control for a motor vehicle change speed gear providing six forward and reverse ratios wherein the supply of pressure air to-cross-shift and ratio establishing motors 40, 44 is controlled by a manually operated valve 10, means are provided to inhibit ratio establishment until synchronism is attained. The manual control valve 10 selectively supplies pressure air from a supply line 175 through lines 120, 121 to the four position cross-shift motor 40 and through lines 118, 119 to parts 22, 34 of normally closed inhibitor valves 19, 20. With both inhibitor valves 19, 20 closed a secondary valve 21 supplies pressure air through a line 157 to a part 45 of the three position establishing motor 44, which pressure opposes a direct supply to a part 47 and positions the motor piston in its central neutral position, as shown. When synchronism is attained a solenoid valve 68 or 72 is energized, which valves respectively initiate establishment of second, fourth, fifth or reverse and first, third or sixth ratios. Energization of the valve 68 supplies pressure air to the upper end of the valve 19, whereupon its spools move down and open a valve 137 to supply pressure air from the line 119 through a line 156 to a part 46 of the establishing motor 44. With all three parts 45, 46, 47 supplied with pressure air, the motor piston moves left to establish second, fourth, fifth or reverse ratios. Alternatively, energization of the valve 72 supplies pressure air to the upper end of the valve 20, whereupon its spools move down and open a valve 147 to supply pressure air from the line 118 through a line 149 to the spool 150 of the secondary valve 21. The valve-spool 150 moves up against the bias of a spring and permits the valve 153 to close and cut the pressure air supply to the part 45 which is vented through the interior of the valve spool 150. With only the part 47 of the establishing motor 44 supplied with pressure air, the motor piston moves right to establish first, third or sixth ratios. When the piston of the motor 44 is in a ratio establishing position it actuates a valve 84 or 88 to supply pressure air from the valve 137 or 147 through a line 172 or 170 to a chamber 25 or 31 of the valve 19 or 20 to hold the valve 137 or 147, open. Pressure air . is supplied from a reservoir through a distributer valve 100 to the manual control valve 10, solenoid operated valves 68, 72, secondary valve 21 and parts 41, 47 of the cross-shift and ratio establishing motors 40, 44. Synchronism detector.-Input and output speed responsive electric signals are fed to a comparitor circuit (50) Fig. 7 (not shown), which compares the ratio of said signals with the gear ratio to be engaged. When the input and output speeds are in the correct ratio,- the circuit energizes the appropriate solenoid valve 68, 72 to initiate ratio establishment. The selected ratio is fed to the comparitor circuit by selective closing of pressure sensitive switch 122. . . 125 in the lines 118 ... 121. Override control.-An override control valve 92 has a chamber 98 fed with pressure air through a line 174 when one of the solenoid valves 68, 72 is energized and a chamber 96 fed with pressure air through a line 186 when one of the valves 84, 88 is actuated (i.e. a ratio is established). The pressures in the chambers 96, 98 are normally balanced but in the event of an electrical failure and de-energization of the solenoids 68, 72, the chamber 98 is vented and the pressure in chamber 96 moves the valve spool down to open a valve 167 which supplies pressure air through a line 177 to chambers 26, 29 in both inhibitor valves 19, 20. A pressuresensitive switch 178 lights a warning lamp 179 When the valve 92 supplies pressure air to the inhibitor valves. A knob 93 on the spool of the valve 92 permits the valve to be actuated manually.