Patent GB-1080920-A (GB)
Title: Automatic change speed transmission
IPC: F16H47/08
Filed: 1966-01-11
Abstract: 1,080,920. Change-speed gear and control. FORD MOTOR CO. Ltd. Jan. 11, 1966 [Jan. 21, 1965], No. 1154/66. Heading F2D. In an automatic change-speed vehicle transmission controlled by fluid pressure engaged clutches and brakes the rate of increase in pressure in a brake engaging line 332 is controlled by a rate-control valve 404 having a spool 420 controlling an exhaust port 428 under the opposing influences of downwardly and directly acting brake line pressure 332 and an upwardly acting spring 424 together with line pressure reaching the lower spool land 422 through a restrictor 430. The lower line pressure down-stream of the restrictor 430 also acts on an accumulator piston 412 loaded by direct line pressure 332, a spring 410 and T.V. pressure 436 regulated by engine manifold depression. When the line 332 is pressurized to engage its brake the restrictor 430 causes a pressure drop across it and allows downward force oh the spool 420 to predominate and open the exhaust port 428, thus limiting the rate of increase of brake engaging pressure. Increased engaging pressure compresses the accumulator spring 410 and allows upward force on spool 420 to increase thereby regulating the exhaust opening 428 to produce the required engaging rate and finally closing it entirely when flow through the restrictor ceases and the accumulator spring is fully compressed. In a modificaton of the above, Fig. 5 (not shown), the accumulator spool 442 is under the opposing influences of downwardly and directly acting main line pressure 454 and brake line pressure 332<SP>1</SP> and an upwardly acting spring together with brake line pressure reaching the lower spool face 446 through a restrictor 474. The whole valve assembly operates as in Fig. 3. The accumulator and rate control valve may be calibrated so that the brake is fully engaged before the accumulator spring is fully compressed, regardless of the engine manifold pressure at initiation of a 1-2 shift. Function summary.-A single rate control valve, as above described, is used to regulate engagement of a brake in a gear system providing three speeds and reverse under the control of a manual ranging valve 148 having settings PRND 2 D 1 L. R is a single ratio reverse. L is a fixed two-way first ratio. Setting D 1  provides starts in one-way first, with autoupshifts to two-way second and two-way direct top under the opposing influences of output speed responsive pressure and engine manifold depression regulated fluid pressure. D 2  provides more leisured starts in second with automatic upshift to direct top. Kick-down 3-2 and 2-1 shifts are provided. At small throttle openings the 3-2 downshift is smoothed by a valve 292, Figs. 2A, 2B (not shown). Gear arrangement.-Fig. 1 (not shown). The gear provides in addition to direct drive and reverse two reduced ratios, the torque reaction for low being sustained through a one-way brake so that 1-2 upshift is of the so-called " pick-up " type requiring the engagement of only one additional brake to overrun the superseded lower ratio, and avoiding the necessity for shift timers, brake application being regulated by a single rate control valve 404 (described above). The engine is connected via a torque converter 10 to the input shaft 36 of the change-speed gear-box comprising two planetary trains 42, 74 having a common sun 66. The gear output shaft 72 is fast with the ring gear 76 of the rear train 74 and the planet carrier 70 of the front train 42. For two-way compounded first gear in Low-range a clutch 38 is engaged to clutch the ring gear 40 of the front train 42 to the input shaft 36, and a brake 84 is applied to the planet carrier 80 of the rear train 74. For one-way first in D 1  range, clutch 38 is engaged and the planet carrier 80 is held from reverse rotation by a one-way brake 86. For two-way second, the front train acts alone; the clutch 38 remains engaged and the sun 66 is held by applying a brake 52 which acts through a shell 48, one-way brake 86 overrunning for " pick-up " shift. For direct top the clutch 38 and a clutch 50 clutching the sun 66 to the input shaft 36 are engaged to lock the train 42. For reverse, the rear train acts alone; the clutch 50 is engaged to apply the input to the sun 66, and the planet carrier 80 is held by the brake 84. Clutches and brakes.-The band-brakes 52, 84 are each applied by supplying pressure fluid to a spring-returned piston acting through a single lever, and the disc clutches 50, 38 are engaged by fluid-actuated annular pistons. Servo pressure supply and regulation.-An engine-driven pump 28 alone supplies the system through a main pressure regulator valve which regulates the pressure in the servo supply line 106 by exhausting it to the engine sump 104, and fills the torque converter through line 132 as engine-pump pressure builds up. The main spool 110 of the regulator valve is loaded downwardly by engine-pump pressure and upwardly by a fixed spring 122 and spring-connected spool 140 itself loaded by reverse gear pressure 142, to increase line pressures above that for forward drive, engine manifold responsive T.V. pressure 144 and at low road speeds additional T.V. pressure 146 cut in by a cut-back valve 356, thereby obtaining high servo apply pressures for standing starts. The cut-back valve spool is loaded down by governor pressure 200 and upwardly by the cut-in T.V. pressure 366. After initial acceleration from standing starts the cut-back valve spool 356 is forced down to reduce line pressure by cutting off T.V. pressure from the regulator valve spool 140. Line pressure is augmented at high coasting speeds for engine braking by a valve spool 396 down loaded by governor pressure 200 against spring 398 and T.V. pressure 144 to connect manual ranging valve line pressure 176 in line 400 to line 146, to thereby load the main regulator valve spool 110 upwards. Shift control pressures.-Governor valve output speed responsive pressure is provided by radial centrifugally loaded spools 92 and 93 on the gear-box output shaft 72 which are interlinked by line 204 so that spool 92 is cut-out above a set road speed and thereafter spool 93 meters governor pressure to a line 200 from a main supply line 184 pressurized only in D 1 , D 2  and L settings. The high-speed spool 93 is loaded radially inwards by supply line 184 and outwardly by a spring and centrifugal force, whereas low-speed spool 92 is only loaded inwardly by a spring. T. V. pressure.-An engine throttle-sensitive pressure approximating to engine torque demand is provided by the combined action of a vacuum throttle valve 212 and a throttle boost valve 246, the former metering line pressure 106 to a T.V. signal line 144 under the control of a diaphragm subject to engine manifold depression. The boost valve 246 uses the T.V. pressure 144 to meter line pressure 258 to a T.V. line 384 used for opposing governor pressure in the shift valves. Before being applied to act upwardly on the 1-2 and 2-3 automatic shift valves, T.V. pressure 384 is modulated to a reduced value by a T.V. modulator valve comprising a piston 274 at the base of the 2-3 shift valve, which meters modulated T.V. pressure into a line 278 leading to the 1-2 shift valve. Automatic shift valves.-The 1-2 and 2-3 shift valves are loaded down towards upshift position by governor pressure 200 and upwards by a spring, line pressure and modulated T.V. pressure 278 at the base of the 2-3 shift valve. The 1-2 shift-valve spool is in two parts 320 and 308 such that if manual ranging valve is uncalibrated or leaking occurs between lines 180 and 182 of the ranging valve in D 1 , lower spool 308 moves down to engage second ratio. The kick-down valve 372 operates on wideopen throttle to supply T.V. pressure 384 from booster valve 246 to the shift valves to produce successive downshifts. Assisting in the shift control is also a 3-2 coast control valve acted on by governor pressure 200 and direct clutch apply pressure 64 against a spring 302 which provides a delay and cushioning of engagement of the second ratio band-brake on a 3-2 downshift by connecting the release line 288 of the intermediate servo-brake piston 58 to the exhausted clutch line 286 either through a restrictor 290 for delayed engagement at low speeds or also directly at high speeds for rapid engagement. The 2-3 back-out valve 334 smooths 2-3 upshift by preventing simultaneous application of direct clutch 50 and engaged second ratio brake servo 54 by venting brake-servo apply line 336 to the lower initial apply pressure line 346 of the direct clutch 50. The spool 338 of the valve 334 is loaded down by clutch apply pressure 346 and upwardly by direct T.V. pressure 240 and spring 344. The 2-3 back-out valve is overridden in L range of the manual ranging valve for engine braking by a spool 338 loaded upwards by line pressure 354 from the ranging valve so that the direct clutch 50 remains engaged. Operation.-Drive range D 1 : the manual ranging valve 154 directly pressurizes the forward clutch 38 and with rear planet reaction taken by the one-way brake 86, a start is made in one-way first ratio, with high line pressures which is then reduced on increased speed by cut-back valve 356. With increase in speed, governor pressure 200 predominates over modulated T.V. pressure 278 to upshift the 1-2 shift valve spool 308 which directly pressurizes the apply line of the second ratio band brake 52 through the rate control valve 404 which thus controls the rate of increase of brakeengaging pressure in the brake servo. Upshift of the 2-3 valve 262 at a higher output speed, pressurizing the direct clutch 50 and exhausting the apply line of the second-ratio brake servo. Drive range D 2 : the manual valve directly pressurizes the forward clutch 38 and moves the lower spool 308 of the 1-2 shift valve down to pressurize the second-ratio brake servo for a second-ratio start. In manual twoway low the manual