Patent GB-937699-A (GB)
Title: Control system for a motor vehicle change-speed transmission
IPC: F16H47/08
Filed: 1962-02-01
Abstract: 937,699. Change speed control. GENERAL MOTORS CORPORATION. Feb. 1, 1962 [Feb. 20, 1961], No. 3806/62. Class 80 (2). In a fluid pressure control system for a vehicle change-speed gear, wherein the position of a ratio-shift control valve element 417 is determined by the differential of two opposing forces acting thereon, to assist valve element movement, the differential, on reaching sufficient value to initiate valve element movement, is temporarily increased. Function summary.-The gear provides six forward and two reverse ratios subdivided by a manual ranging valve 291 into Neutral, and four Forward and one Reverse range. Speed-responsive automatic shift is provided for 1-2 shift in 1st range, 3-4 shift in 2nd range, 5-6 shift in 4th range, and 1-2 Reverse shift in Reverse range. 3rd range holds 5th forward speed. A lock-up disc clutch 11, bypassing a hydrodynamic torque converter 10 through which the gear is driven, is engaged automatically by a valve assembly 275 at a predetermined turbine speed, and if engaged is automatically released during ratio shift. Accumulators 436, 446 and 455 are provided: 446 prevents hunting of the valve element 417 during automatic forward up and down shifts; 436, 446 prevent a 2-4-3 shift during 1st- 2nd range shift; 446, 455 prevent a 4-6-5 shift during 2nd-4th range shift; 455 prevents a 5-3-4 shift during the 4th-2nd range shift; 436 prevents a 3-1-2 shift during 2nd-1st range shift; and 436, 455 ensure a 5-2 shift during the 4th-1st range shift. Gear arrangement.-The gear is that of Specification 851,424 and comprises a series arrangement of the torque converter 10 with the lockup clutch 11, a direct-overdrive planetary gear 13 forming a front unit, and a three-speed planetary gear 14 and reverse planetary gear forming a rear unit. Direct and overdrive in the front unit are by engagement of friction devices 101, 99 respectively through lines 316, 314, and low, intermediate, high and reverse in the rear unit are by engagement of friction devices 181, 144, 146 and 197 respectively through lines 323, 322, 311 and 319. Fluid supply system and regulation.-A pressure regulator valve 221 is fed by an input driven pump 216 and, through a check valve 211, an output driven pump 208. The regulator valve 221 by-passes oil to a converter supply line 244 and feeds a main line 234. Up to a predetermined value, increasing pressure in a speed-responsive governor line 242 reduces main line pressure. A signal line 261, 260 acts to increase main line pressure in first forward ratio, neutral and first reverse ratio. Fluid system components.-The manual ranging valve 291 receives pressure from the main line 234 through the valve 275 and a line 283. Governor pressure 242 responsive to turbine speed is provided by a Pitot governor on the converter output and gear input shaft 41. An automatic overdrive shift valve 301 is leftwardly shifted by pressure in a line 321 against a spring 304 to pressurize the overdrive line 314. In first forward range, neutral and reverse range the manual ranging valve 291 connects main line pressure in line 283 to the signal lines 260, 261 which are vented during front unit overdrive (valve 301 upshift) through a oneway valve 318. An overdrive control valve 416 comprises the element 417 which has one small a, one medium b, and two large diameter lands c, d. Constant pressure, from a regulator valve 401 fed from the main line 234, is applied to the left of land a, and between lands a, b and b, c through branches 423, 424 and 426 respectively to provide a restoring force to rightwardly downshift the element 417 to the position shown abutting a stop pin 432, thereby exhausting the line 321. Governor pressure 242 is supplied through an orifice 450 and a branch 429 to the right of land d for leftward upshift of the element 417 to connect the branch 426 to the line 321. The differing lands a, b, c provide valve hysteresis by progressively reducing the restoring force during upshift of the element 417. An accumulator 436 comprises a piston 437 having equal lands a, b. Pressure in the signal line 260, in first forward, neutral and first reverse, leftwardly shifts the piston 437 against the stop pin 432 to connect the line 260 to a relay line 441, having an orifice 442, and blocks a branch of the intermediate line 322. When the signal line 260 is vented governor pressure in the branch 429 rightwardly shifts the piston 437 to disconnect the line 260 from, and connect the branch of 322 to, the relay line 441. An accumulator 446 comprises a piston 447 which is normally held in a charged position shown by governor pressure in a branch 451 and, to discharge, is rightwardly moved against a stop 452 by actuating pressure in the overdrive line 314. An accumulator 455 comprises a differential piston 456 which is normally held in a charged position shown by governor pressure in the branch 451 and, to discharge, is leftwardly moved against the stop 452 by actuating pressure in the relay line 441. Rapid discharging movement of the accumulator pistons 447 and 456 temporarily increases the governor pressure in the branch lines, this being further increased by increasing actuating pressures (314, 441) of the accumulators. A smaller orifice 450 would increase the duration of pressure increase. Charging movement of the accumulator pistons 447 and 456 reduces governor pressures on rapid venting of the actuating pressures, such pressure reduction being dependent on the ratio of restriction to governor oil flow to the accumulators to the restriction of oil flow (actuating oil) from the accumulators. In the intermediate and low lines 322, 323, trimmer valves 325, 326 provide gradual engagement, and check valves 322<SP>1</SP>, 323<SP>1</SP> retard disengagement, of the corresponding friction devices. An orifice 322a in the intermediate line 322 regulates flow in both directions. In Neutral Operation the manual ranging valve 291 supplies main line pressure through the overdrive shift valve to the front unit direct line 316, the rear unit remaining in Neutral, and to the signal lines 260, 261, -pressure in 260 leftwardly shifting piston 437 so that it is connected to relay line 441 to leftwardly move the piston 456. In 1st range.-Main line pressure remains connected to the signal lines 260, 261 and is also connected to the low line 323 for 1st speed. When shaft 41 reaches the converter coupling speed the valve 275 engages the converter lock-up clutch providing no ratio shift is effected by the manual valve. At a higher speed governor pressure in branch 429 upshifts the control element 417 to shift the shift element 302 to exhaust the direct line 316 and pressurize the overdrive line 314 for 2nd speed. Pressure in 314 also dischargingly shifts the accumulator piston 447 rightwards to temporarily increase governor pressure on the element 417 to prevent hunting thereof. On reduction in speed effecting reduced governor pressure the valve 416 downshifts, the overdrive line 314 is exhausted, governor pressure chargingly moves the valve element 447 leftward and temporarily reduces governor pressure to ensure completion of downshift. These speed responsive up and down shifts occur in 1st, 2nd, 4th and Reverse ranges. On 1st-2nd range shift the signal lines 260, 261 are exhausted, and main line pressure is connected to the intermediate line 322. Governor pressure chargingly moves the valve element 437 rightwards to connect the intermediate lines 321 to the relay line 441, thereby reducing governor pressure to tend to downshift the valve element 417 and avoid a 2-4-3 shift. On front unit downshift the piston 447 leftwardly moves to reduce governor pressure further. On 3rd speed engagement, increased load slows the engine and hence the shaft 41 and reduces governor pressure to hold 3rd speed normally until speed increase effects an automatic 3-4 shift. On 2nd-3rd range shift main line pressure is connected to the high line 311 and through a hold line 294 to hold the overdrive shift valve in downshift position and hold 5th speed. On 3rd-4th range shift on exhaust of the hold line 294 the gear will remain in 3rd speed until automatic 5-6 upshift by speed increase. On 2nd-4th range shift, the gear normally being in 4th speed, the intermediate line 322, and hence, through the valve 436, the line 441, is vented to enable governor pressure in branch 451 to chargingly shift the piston 456 rightwards and reduce governor pressure and downshift to the element 417 to avoid 4-6-5 shift. On fron unit downshift the piston 447 leftwardly moves to reduce governor pressure further. On 4th-2nd range shift, in 5th ratio, with the pistons 437, 447 and 456 in their rightward, leftward and rightward positions respectively, main line pressure is connected to the intermediate line 322 and through the accumulator 436 and relay line 441 to dischargingly move the piston 456 leftward, to increase governor pressure in lines 451, 429 and upshift the valve element 417 and avoid 5-3-4 shift. After momentarily increasing governor pressure and if the speed is below a predetermined value, the pressure across the orifice 450 will equalize to permit the valve 417 to downshift for a 4-3 shift. On 2nd-1st range shift, with piston 437 in the rightward position, main line pressure is disconnected from the intermediate line 322, connected to the low line 323, and connected to the signal line 260 thereby dischargingly moving the piston 437 leftward to increase governor pressure and upshift the valve element 417 to prevent the 3-1-2 shift. The signal line is also connected through the relay line 441 to hold the piston 456 in its leftward position. On 4th-1st range shift both accumulators 436 and 455 act as in the 4th-2nd and 2nd- 1st range shifts to ensure a 5-2 shift. On Neutral-Reverse range shift main line pressure is connected to the reverse line 319 and since in Neutral front unit direct is engaged,