Patent GB-684553-A (GB)
Title: Improvements in or relating to variable speed power transmission
IPC: F16H63/30
Filed: 1948-02-11
Abstract: 684,553. Change-speed gear. CHRYSLER CORPORATION. Feb. 11, 1948 [Aug. 5, 1941], No. 4010/48. Class 80 (ii). A motor-vehicle transmission comprises two mechanical changespeed units D, E in series, each operated by power-means speedresponsively controlled such that, on accelerating from rest (e.g. in second speed), a first upshift (to third) is produced in the front unit entirely automatically at one predetermined vehicle speed (7 m.p.h.), after which, on exceeding a second higher vehicle speed (15 m.p.h.), the rear unit is automatically conditioned for a second upshift (to fourth speed, direct drive) which is rendered effective only on torque-reversal produced by the driver releasing the accelerator-pedal. Accelerator kickdown shift is also provided, and control is electrohydraulic, except for an emergency low and reverse, which are selected manually and have automatic shift thereafter. The input shaft 71 of the gear is driven through a fluid-coupling and pedal-controlled friction discclutch in series. Gearing.-The gearing, used in conjunction with a high axleratio (between 3 and 3.3 to 1). comprises a direct-reduced planet-train D, Fig. 9, in series with a countershaft-unit E, providing three-speeds and reverse, with balked conesynchronised jaw clutches F, H for forward ratios and a sliding idler 117 for reverse. The planet-train comprises a driving ring-gear 224 fast on the input-shaft 71, a driven planetcarrier 229, fast on an intermediate shaft 83 and a reaction-sun 232, which, for direct-drive, is clutched to the ring-gear by a cone clutch 243, Fig. 9, or a multi-disc clutch 243, Fig. 26, engaged by oil-pressure on an annular piston 247, whilst for reduced drive the sun is held by a cone-brake 244, engaged by a spring 251 on release of oil-pressure, the brake-capacity being such as adequately to take coast-torque reaction but not drive-torque reaction, which latter is taken by a one-way roller detent K, permanently connecting the sun 232 to the fixed casing. The intermediate shaft 83 drives a countershaftcluster 106, 107, 108 through a wheel-pair 90, 96, the latter being connected to the cluster through a one-way roller-clutch J. Freelymounted low and second speed wheels 114, 109 are clutched to the final output shaft 93 by a cone-synchronised balked double jaw-clutch sleeve H, a single similar clutch-sleeve F connecting the wheel 109 to the input-wheel 90 for direct-drive. The direct-drive clutch-sleeve F acts on the cage 104 of the roller-clutch J to neutralise the latter in the direct-drive position. For reverse an idler 117 is slid into mesh with a wheel-pair 108, 119, the latter of which is splined on the output shaft. The ratio-paths are described below. Manual control.-The low-second speed clutchsleeve H and reverse idler 117 are actuated only manually by a steering-column-mounted shiftlever and linkage, Figs. 1-7 (not shown), which, as far as the transmission-case, are identical with those described in Specification 684,833 the cable cross-shift movement serving thereafter to rock a spring-loaded selectorfinger 133. Fig. 11, about a pivot 141 on a rockshaft 143, into engagement either with a yoke 123 for the low-second clutch-sleeve H or a yoke 137 for the reverse-idler 117, executive movement of a lever. 147 serving to rock the shaft 143 to slide the selected yoke with its shift-rail and engage the required ratio. Automatic control.-The diagrammatic circuit, Fig. 26, shows two separate governors G, G, each controlling a set of electrical contacts 171, 172, but, although two governors may be used, the construction described uses one governor operating two sets of contacts in an equivalent sequence and driven by a skew-wheel 94, Fig. 9, on the countershaft-cluster, the speed of which latter relative to engine-speed depends on whether it is being driven by the input wheel 90 through the one-way clutch J or by the second-speed wheel 109 bi-directicnally. An oil-pump P supplying the servo-main 260 (relieved by a valve 268 at 45 1b. /sq. in.) and a lubrication-main 270 (relieved by a valve 280 at 6 1b./sq. in.), is driven by governor-driving countershaft-wheel 94. Electric current is supplied by the vehicle battery 300 through the usual ignition switch 310. Starting from rest, the driver declutches and operates the steering- column-mounted shift-lever to establish secondspeed, which slides the clutch-sleeve H, Fig. 9, forwards, to clutch the second-speed wheel 109 to the output shaft 93. Drive is then through the reduced ratio of the planetary train and wheel-pairs 90, 96; 106, 109, including the oneway clutch J. After engaging the clutch, the vehicle is accelerated in free-wheeling secondspeed until, at 7 m.p.h., the first governor contacts 171 are opened to de-energise a relay 314 and thus the solenoid S' of a valve V', which is moved by a spring 288 into the open position, shown, directing oil-pressure from the servomain 260 to the piston 247 which disengages the reaction-sun brake 244, Fig. 9, and engages the clutch 243 to lock the planetary unit in directdrive. The countershaft-unit remains in second, and this provides the overall third-speed ratio. Increase in speed beyond 15 m.p.h. opens the second governor-contacts 172, de-energising a relay 304 and thus the solenoid S of a second spring-opened valve V, which supplies pressure from the main 260 to the piston 214 of the direct-drive countershaft-unit clutch-sleeve F. The clutch-sleeve shift-fork 207 is freely mounted on the piston-rod 212, and the immediate effect of leading the piston 214 is to move the clutch-sleeve F forwardly (left, Figs. 9 and 26) through a spring 216 to a balked position after which the piston and rod continue their forward travel alone, compressing the spring 216 and also a main return-spring 218 bearing against a thrust-collar on the piston-rod 212. In this condition, release of the acceleratorpedal by the driver causes overrun in the second-speed one-way clutch J, producing synchronism in the direct-drive-clutch, whereupon the balk-teeth 211 align and permit the pistonspring 216 to move the clutch-sleeve F fully forward, engaging direct-drive in the countershaft unit. Overall ratio is now one-to-one, the top speed. Speed reduction energises the valves to produce automatic downshift, but the shift from direct-drive in the countershaft unit occurs at a much lower speed than the corresponding upshift, being delayed until the drivetorque loading on the clutch-sleeve F is sufficiently low to enable the piston return-spring 218 to move the sleeve rearwardly out of engagement, to allow the free-wheeling secondspeed pairs 90, 96; 106, 109 to pick up the drive. kickdown shift.-Whilst travelling with the planetary unit in direct-drive, a downshift to reduced planetary drive can be produced by the driver fully depressing the acceleratorpedal to close a switch 77 in parallel with the governor-contacts 171, thus re-energising the relay 314 and solenoid S' which latter closes the valve V<SP>1</SP>, exhausting the cylinder 247 so that the spring 251, Fig. 9, disengages the directdrive clutch 243 and engages the reduced-drive reaction-brake 244. This provides a bi-directional reduced ratio which differs from upshift free-wheeling third. Emergency low.-In parallel with the governor and kickdown-contacts 171, 77 is a further switch 68, which is closed by movement of the first-second speed clutch-sleeve striker-rail 124 rearwardly to an emergency-low position, selected manually by the steering-column-mounted shift-lever. This re-energises the solenoid S<SP>1</SP>, maintaining reduced planetary drive irrespective of speed, the countershaft drive being through the wheel-pairs 90, 96; 107, 114, including the free-wheel J. In this ratio a semiautomatic upshift can still be obtained by accelerator-release above the operating speed of the second governor contacts 172, which engages the direct-drive clutch F and provides a bi-directional countershaft drive through the wheel pairs 109, 106; 107, 114, the planetary unit remaining reduced. This governor-operation occurs at a lower vehicle speed than that of the first upshift, above-described, since the governor-driving countershaft is now rotating at a higher speed in relation to vehicle-speed. The above control provides in all six different forward ratios, three free-wheeling and three bi-directional. Reverse.-Automatic action is not cut-out by meshing the reverse-idler 117 with the wheels 108, 119, so that automatic upshifts at correspondingly lower vehicle-speeds, and kickdown shift can be obtained as described for forward drive. Details.-A pressure-maintaining valve 273.is provided to prevent loss of pressure on the planetary clutch-piston 247 when the valve V opens the pressure-supply line 260 to the countershaft clutch-piston 214. In parallel with the engine ignition-switch 310 is a pressure-responsive switch 257 which maintains the shift-circuit live whilst ever there is pressure in the system so that even if the ignition is switched off whilst the vehicle is running, the shift-circuit is still effective to restore normal conditions before the vehicle stops, thus preventing lock-up due to one-way clutch action if the vehicle rolls back on an incline. A manual switch 311 breaks the shift-circuit to cut out automatic action and de-energise the valve-solenoids S, S<SP>1</SP> for selecting direct-drive for a push start, the drive engaging when the pump P develops sufficient pressure to operate the pistons 214, 247. Specification 684,578 also is referred to.