Patent GB-912399-A (GB)
Title: Control circuit for a change-speed power transmission mechanism
IPC: F16H47/08
Filed: 1961-02-06
Abstract: 912,399. Change-speed control. FORD MOTOR CO. Ltd. Feb. 6, 1961 [Feb. 4, 1960], No. 4399/61. Class 80 (2). Hydraulic control means for an automatic change-speed gear in a motor car comprises a pressure source, a shift valve and a ratio establishing servomotor, a booster valve in the pipe circuit connecting the parts being subjected to a pressure signal related to an operating parameter, such as inlet manifold depression, so as either to connect the shift valve to the parameter-controlled pressure signal or directly to the pressure source. As shown, to obtain control pressure in a pipe 328, Figs. 2A, 2B, in a circuit controlling a three-ratio planetary gear preceded by an hydrodynamic torque converter in a motor car, as described below, main pressure 136 is directed through a pipe 310 to a throttle valve (TV) 304 which modulates the pressure in dependence of the inlet manifold depression in an engine driving the car containing the gearing, by means of a vacuum servo, Fig. 3 (not shown). TV pressure 314 is fed through a compensator valve 408, described below, to a throttle booster valve 316 where it acts via a by-pass 332 in opposition to the action of a spring 322. When TV pressure 314 is low, it is connected to a valve port 330 and thence to the pipe 328, main pressure 136 in a pipe 334 being blocked by a land on the throttle booster valve 316. With increasing TV pressure 314, the booster valve 316 is moved leftwards of Fig. 2A against the bias of the spring 322, and main pressure 136 in the pipe 334 is connected to the port 330 and the pipe 328, whence it acts on two shift valves, described below. Accordingly, the action is that at wide open throttle settings of the car engine the shift valves are controlled by main pressure 136, but at smaller throttle settings the shift valves are controlled by TV pressure 314. Gearing.-A car engine drives through the usual three-element hydrodynamic torque converter having a one-way mounted reactor 16, Fig. 1, to a shaft 44 clutched to a sun gear 90 when oil under pressure is admitted to a ring- shaped cylinder containing a correspondinglyshaped piston 80 which acts through a dished spring 84 to engage multidiscs 50. Planet pinions 98 meshing the sun gear 90 also mesh double planet pinions 96 in turn meshing a ring gear 94 fast with an output shaft 118, a carrier 100 supporting the planet pinions being restrained from reverse rotation by a one-way detent 116. First ratio is thus obtained. By energizing a double-acting liquid pressure servomotor, a brake band 64 is applied to a housing fast with a sun gear 92, meshing the double planet pinions 96, so that the second ratio is obtained. By releasing the brake band 64 and instead admitting liquid under pressure to a ring-shaped cylinder containing a piston 70 biased to the disengaged position by spring 74, multi-discs 62 are engaged to clutch the sungear 92 fast to the shaft 44. Accordingly the third ratio, direct drive, is obtained. A brake band 110 may be applied to the planet pinion carrier 100 to hold the latter stationary in both directions of rotation. By de-energizing the front clutch 50 and engaging the rear clutch 62, while engaging the brake band 110, reverse is obtained, the sun gear 90 then rotating freely. Function summary.-In the D<SP>1</SP> position of a manual ratio range selector valve 184 having control positions PRND<SP>2</SP>D<SP>1</SP>L, and with the car engine idling, the TV valve 304 is closed, so that TV pressure 314 is a minimum. A 1-2 shift valve 212 is then spring-maintained in the upward position shown, and main pressure 136 is distributed through the ratio range selector valve 184, a pipe 208, the 1-2 shift valve, a pipe 220, and an inhibitor valve 230, which is open, to a rear servo lock-out valve 250 which is biased upwardly by main pressure 136 in a pipe 258. Main pressure 136 is distributed directly through the ratio range selector valve 184, and pipes 192, 194 to the front clutch 50. No pressure is at this time transmitted to the rear servo, which is blocked by the rear servo lock-out valve 252. The rear clutch 62 is vented through a pipe 274, a 2-3 shift valve 264 and a pipe 272 to sump. The apply side of the double-acting servo applying the brake 64 is vented through a pipe 206 and a transition valve 202, and the release side of this servo is vented through pipes 348, 350, 274, the 2-3 shift valve 266 and the pipe 272. Accordingly, the first ratio is established. On partially opening the engine throttle, the TV valve 304 is opened, and TV pressure 314 is passed to a pipe 286 through the throttle booster valve 316 and acts through a modulator plug 282 in the 2-3 shift valve 264 to maintain both shift valves 212, 264 in a ratio downshifted position. With increasing output speed, pressure in a pipe 226, fed from the main pressure 136 through a governor 296 producing a signal proportional to output speed, increases, first to move the 1-2 shift valve 212 downwards to its ratio upshift position, venting the pipe 220, so that the transition valve 202 moves downwards and main pressure 136 is transferred from the pipe 200 to the pipe 206, thus applying the brake 64, as well as the front clutch 58, for second ratio. With still further increase in output speed, governor pressure 226 moves the 2-3 shift valve 264 downwards and connects pipes 270, 274, to engage the rear clutch. At the same time, main pressure 136 is connected through a pipe 362 to a pipe 348, and thence to the release side of the front servo, so that the front brake band 64 is released. Third ratio is now established. On opening the engine throttle wide, mechanical linkage 378 actuates a kick-down valve 372 to move the 2-3 shift valve 264 upwardly to its ratio downshift position, thereby venting the rear clutch through the pipe 274, the 2-3 shift valve 264, and the pipe 272, and the release side of the front servo is vented through the pipe 348, a 3-2 kickdown control valve 360 &c., pipes 362, 274, the 2-3 shift valve and the pipe 272. At this time, a 3-2 coasting control valve 340 is open to the TV controlled pressure in a pipe 338. The 3-2 kickdown control valve provides a controlled degree of restriction for the release side of the front servo, in dependence on pressure drop across an orifice 360 therein and governor pressure 226, and provides a short time-delay. If the car coasts in direct drive, the 3-2 coast control valve 340 assumes the closed position shown, so that with decreasing road speed the 2-3 shift valve 264 moves to its ratio downshift position. The 3-2 kickdown control valve 360 now imparts a considerable time-delay to the engagement of the front band. With the ratio range selector in its D<SP>2</SP> position, the pipe 208 is vented and the 1-2 shift valve 212 is not supplied with control pressure; instead, main pressure 136 is applied through the pipe 206 to the rear clutch and the first ratio cannot be established. Details.-Main pressure 136 is provided by either an input or an output driven pump 34, 128 supplying oil from a sump 130 through pipes 134 and one-way valves 142, 144 to a pressure regulator valve 132, according to which gives the greatest pressure. The position of the pressure regulator valve 132 is determined by main pressure 136 acting on differential lands 150 and compensator pressure supplied through a pipe 160 from the compensator valve 162, described below, the compensator pressure also acting on a converter pressure regulator valve 174 through which oil is supplied via a pipe 154 to the hydrodynamic torque converter and to a transmission lubrication line 178. The exhaust side of the converter is connected to sump through a pipe 180, the converter pressure valve 166, a pipe 182 and a cooler. Main pressure 136 passes to the manual ratio range selector valve 184 which, D<SP>1</SP> position, passes it to the pipes 192, 194 to engage the front clutch 45, and through the pipe 196 to the vehicle speed sensing governor 198. Thence, as described above, the oil pressure is fed through the pipe 200 to the transistion valve 202, controlling admission of oil through the pipe 206 to the front brake servo for engagement of the brake 94. Also, main pressure 136 is supplied through the pipe 208 to the 1-2 shift valve 212 and thence either through the pipe 220 to the inhibitor valve 227, or is vented to sump, the pipe 220 being closed. The shift valve 212 is torque demand controlled by pressure in the pipe 222, in opposition to vehicle speed pressure supplied from the governor 296 through the pipe 226. The inhibitor valve 227 either connects the pipe 220 to the pipe 236, or to exhaust, and is controlled by governor pressure 226 in opposition to torque command and TV pressure supplied through the kickdown valve 372 to the pipe 240, and by main pressure 136, 236. The latter also acts on the transition valve 202. The pipe 236 extends to the rear servo lockout valve 248 which when open connects to the pipe 256 of the rear servo applying the brake 110, and when closed vents this pipe. The lockout valve 250 is opened by main pressure 136 supplied through the pipe 258 and the ratio range selector valve 184 when in the D<SP>1</SP>, D<SP>2</SP> positions. In one position, the lockout valve 248 connects the pipe 236 to the pipe 260 and main pressure 136 to act on the compensator valve 408. The 2-3 shift valve 264 is connected through the pipe 270 to the pipe 258 and to the manual ratio range selector valve 184, which in the R position only also connects the pipe 272 to main pressure 136 for engagement of the rear clutch. When the 2-3 shift velve 264 in its downward position, for an upshift, the pipe 270 connects with the pipe 274 to engage the rear clutch. Torque demand sensitive signal is supplied through the pipe 286 and the TV valve 304. The TV 304 modulates main pressure 136, and is manifold depression operated, as described above, so that with wide open throttle the pressure in the pipe 3