Patent GB-1505817-A (GB)
Title: Automatic transmissions
Inventor: BURNETT STANLEY FREDERICK
IPC: B60W30/18
Filed: 1974-05-21
Abstract: 1505817 Change speed gearing BRITISH LEYLAND UK Ltd 13 March 1975 [21 May 1974] 22623/74 Heading F2D An automatic transmission for a vehicle has fluid-pressure-operated ratio-establishing friction-engaging elements such as clutches and brakes, controlled by an electro-fluid circuit which includes the following items. Solenoidcontrolled shift valves Rev, 1st, 2nd, etc.; a vehicle speed signal generator 4, such as a pickup from a notched wheel, with a frequencyvoltage converter FV; a torque demand signal switch 5 operated by the engine throttle control to provide two automatic shift patterns; throttle-dip relays TD1 ... TD4 to reduce engine fuel supply during upshift; hunting inhibitor means associated with the shift patterns; neutral gap relays NG1 ... NG4 to provide neutral dwell during both upshift and downshift, to allow time for engine speed to reach synchronism; a throttle-operated kickdown switch at 5 to raise all the shift points. Means is also provided to prevent an immediate upshift on accelerator release after kickdown. A manual selector switch 3 has, in addition to drive, neutral and reverse settings, two manual settings preventing upshift to the highest and next highest ratios. In addition rapid fall of the speed signal at high speeds locks in the established ratio and lights a warning lamp. Establishment of reverse is inhibited above a predetermined low forward speed. Gear arrangement.-The gear, Fig. 1 (not shown), is the Wilson accelerated train planet gear (Specification 164,042) providing three reduced ratios, direct-drive and one reverse, but in the control circuit detailed in Fig. 3, this is combined with an additional planetary train to give five forward ratios and one reverse. Circuit.-Shifts, up or down, are initiated when the speed signal FV reaches the potentiometer-adjusted setting level of level switches LS1 ... LS4 controlling relays 2S... 5S which operate contacts energizing the valve solenoids Rev, 1st, 2nd, &c. Two shift patterns are provided according to throttle position. Operation; normal (second-ratio) start.-Selection of any forward drive by the selector switch 3 energizes a terminal 5 and relay coil D, which latter closes contacts D15, D16, supplying 18- volt stabilized and smoothed current from a circuit VR3 (not described) to a line feeding the level switches LS1 ... LS4 and shift relays 2S ... 5S. Initially the level switch LS1 energizes the relay 2S, the negative line from which is completed through normally closed contacts T5, T6, operated by a relay T (see below). The shift relay 2S opens contacts 2S 14, 15, cutting off feed to the first ratio valve solenoid at terminal 20, and closes contacts 2S 15, 16 feeding the second ratio valve solenoid at terminal 21. The relay 2S also closes contacts 2S 6, 7, energizing a throttle-dip timer TD2, and hence a relay C, closing contacts C9, C10 to energize an electro-pneumatic ram valve 6 to close the throttle for a period determined by the timer TD2 and adjusted by a potentiometer PH, termination of the period de-energizing the timer and relay C to restore throttle control. Second ratio is thus engaged for starting. Upshift 2-3.-When the speed signal FV reaches the setting value of the level switch LS2, it triggers the latter, energizing the shift relay 3S, which opens relay contacts 3S 14, 15, deenergizing the second ratio shift valve solenoid and closes 3S 15, 16, energizing that of third ratio. Contacts 3S 6, 7 are also closed to energize the throttle-dip timer TD3 and relay C for temporarily closing the engine throttle, during a neutral gap, described below, after which the upshift is complete. Further 3-4 and 4-5 upshifts are similarly produced when the speed signal FV triggers the level switches LS3 and LS4 respectively. Downshifts are initiated successively as the speed signal releases the level switches LS4 ... LS2 to de-energize the respective shift relays 5S ... 2S. At the same time de-energizing the latter closes successive contacts 5S (8, 9) &c., energizing the appropriate neutral gap timers NG4 ... NG1, which energize a relay N opening contacts N14, N15 cutting off the feed to the valve solenoids for an interval appropriate to the shift and adjustable by potentiometers PA ... PD. These neutral gap timers operate similarly for upshift. Kickdown and first ratio start. Beyond full throttle a microswitch beneath the accelerator pedal is closed and, through a terminal 14, energizes a kickdown relay T which opens contacts T5, T6, releasing the second ratio relay 2S, which opens contacts 2S 15, 16, and closes 2S 14, 15, for energizing the first ratio valve solenoid instead of the second. In addition upshift speeds are all raised by the closure of relay contacts T, short-circuiting resistors R5 ... R7 in the negative line from the level switches LS2 ... LS4, thereby raising their operating level. Manual selector settings.-Positioning the selector switch 3 in H4 and H3 settings energizes relay pairs H4, 4B and H3, 3B respectively, opening feed contacts 4B 14, 15 and 3B to the relays 5S, 4S, preventing their energization and hence inhibiting upshift to fifth and fourth ratios. Reverse inhibit.-The reverse valve solenoid is fed from the selector switch 3 through normally closed contacts D8, D9, which are opened if the D relay is energized. With D energized and second ratio established, relay contacts 2S 9, 10 feed a holding coil on the relay D and prevent its de-energization, and hence energization of reverse until a very low speed is reached. Warning and defective working.-Rapid fall of the speed signal FV at high speeds operates a relay WS, which energizes a relay W, closing contacts W12, W13, which energize hold coils of those relays 3S, 4S or 5S which were energized at the time of the fault, thus holding the established ratio. Contacts W9, W10 light a warning lamp. This action occurs if the service brakes lock the road wheels. Normal control is restored by bringing the vehicle to rest and switching on and off at the ignition switch. Throttle dip arrangements.-Figs. 5 and 6 (not shown) are mechanical arrangements for the temporary override of the normal fuel control. In Fig. 5 (not shown), an electro-pneumatic ram acts with lost-motion on the arm of a fuel pump which has a spring link connection (29) with the accelerator pedal (21). In Fig. 6 (not shown), the accelerator pedal (40) operates an air valve (41) controlling an air cylinder (43) operating the arm of the fuel pump (44), and momentary fuel cut-off is produced by energizing an electro-pneumatic valve (42) which exhausts the connecting line between the pedal and fuel pump.