Patent GB-1237930-A (GB)
IPC: F16H61/08
Filed: 1968-12-19
Abstract: 1,237,930. Change-speed control. NISSAN JIDOSHA K.K. 19 Dec., 1968 [22 Dec., 1967]. No. 60341/68. Heading F2D. An automatic transmission on a motor vehicle having fluid-pressure operated clutches and brakes 4 . . . 7 engaged selectively under control of a manual ranging valve 104 and automatic 1, 2; 2-3 shift valves 105, 106 actuated by opposed fluid pressures responsive to engine torque (TV) and output speed (governor), has a timer valve 111<SP>1</SP> which during one upshift (2-3) requiring simultaneous supply of line pressure 200, 214 to the engage chamber of a direct-drive clutch 4 and to the release chamber 124 of a second speed brake 6, effects a TV- and governor-controlled timing of exhaust from the opposing lesser area apply chamber 123 of the brake to give positive overlap between clutch and brake engagement at high torque; and minimum or zero overlap (neutral) at low torque. The timer valve 111 itself is similar to that forming the subject-matter of Specification 1,236,040, except that its action is not now transient and that it also controls downshift. Timer valve function. 2-3 upshift.-In second speed, line pressure 200, 201, 211, 212, 213 acts in the apply chamber 123 of the secondspeed brake 6. When the 2-3 shift-valve 106 moves left to make 2-3 upshift, line pressure 200, 203, 214 is additionally supply simultaneously to the direct-drive clutch 4 and to the release chamber 124 of the second speed brake 6, where it overcomes the still-acting line pressure in the smaller area apply chamber 123 to release the brake for upshift. For a high torque 2-3 shift this action produces a controlled overlap between clutch engagement and brake release. The function of the timing valve 111<SP>1</SP> is to control also an exhaust path from the brake-apply chamber 123 to reduce or eliminate the overlap. Thus for a low, or a high-speed high torque 2-3 shift, TV pressure 207, 210 acting rightwards on the timing valve 1111 predominates over governor pressure 220 acting leftwards, thus maintaining the timing valve 111<SP>1</SP> rightwards to maintain brake-apply pressure 213, preventing premature release and preserving overlap. For a low torque or high speed 2-3 shift, governor pressure 220 overcomes TV 207 and shifts the timing valve 111<SP>1</SP> left, which exhausts the brake-apply line 213 at 230 for rapid brake release, thus giving minimum or zero overlap. Fig. 3, not shown, illustrates the action graphically, and shows that the brake-apply line 213 is only exhausted during operation in third ratio.  3-2 manual downshift timing differs from automatic in that, in 2-setting, the manual valve 104 supplies full line pressure 200, 204 to the kickdown line 209, which shifts a changeover valve 115 left, to substitute full line pressure for TV pressure 207 in the line 210 of the timer valve 1111, which latter is thereby maintained in its rightward high torque position independently of TV pressure. Manual downshift is thus always as for high torque automatic, as above described, with overlap giving undelayed engine braking. Gear arrangement, fluid pressure supply and regulation, control pressures and shift-valves are all as described in Specification 1,236,040.