Patent GB-671581-A (GB)
Title: Improved variable-speed transmission for motor vehicles
IPC: F16H47/08
Filed: 1950-03-02
Abstract: 671,581. Change-speed gear. GENERAL MOTORS CORPORATION. March 2, 1950 [March 26, 1949], No. 5253/50. Class 80 (ii). [Also in Groups XXIX and XXXIV] The pressure of pumped oil, for manually-controlled servo-operation of a direct-drive clutch 40, and reduced and reverse drive reaction brakes 50, 55 of a planetgear G driven invariably through a single-stage, two-phase hydrodynamic torque-converter I on a motor-vehicle, is regulated by a relief-valve 125, Fig. 7, loaded through a diaphragm 146 subjected to suction in the engine intake manifold, so as to modulate the servo-pressure in accordance with engine speed and load. By means of a second diaphragm 140, the regulator-valve loading is also varied automatically in accordance with the inlet and outlet pressure of oil circulated through the torque-converter, and with the selected gear ratio, thus providing pressuremodulation in accordance with the effective torque-multiplication in both the converter and the planet-gear. Gear selection is by a manual steering-columnmounted lever only, Fig. 13 (not shown), which also operates a positive park-lock pawl 90, Fig. 5. The converter oil is circulated through a cooler 211, Fig. 7, as is also oil for lubricating the gear, under control of a thermallyactuated valve 206. Torque converter.-This comprises a primary impeller I on the engine flywheel 2; a secondary impeller Ia connected to the primary by a forward-overrun clutch 20; two reactors R' R<SP>2</SP>, mounted on forward-release oneway detents 14, 14', on a permanently-fixed sleeve 13; a single output turbine O fast on a central shaft 11 invariably driving the planetgear G; and two inner sets of blading in the core-space, the first 117 secured to the turbine O, the second 120 secured at lesser radius to the input impeller 1. The curvature of this inner blading 117, 120 is such that whilst any forward torque is so inefficiently transmitted as to be negligible, reverse torque from turbine to impeller is transmitted efficiently enough to serve for engine-braking at near one-to-one ratio, and for towed starting. Input and output driven gear-pumps P, Q supply oil to the converter through a passage 168 and space between the primary and secondary impellers I, Ia, and the oil is led away through a concentric outlet passage 165 to an oil-cooler 211, Fig. 7. A floating-ball relief valve 200, Fig. 7, opens to connect the inlet and outlet passages 168, 165 when outlet pressure exceeds inlet (i.e. when the circulation velocity in the converter, and hence the slip, are high). Planet gear:-Intermeshed planets 30, 31 are carried by the final output shaft 60, those 30 meshing an input sun 27 fast on the converterdriven shaft 11; whilst 31 mesh a reaction ring 38 band-braked at 55 for reverse, and a reaction sun 35 band-braked at 50 for reduced forward drive and disc-clutched at 40 to the converterdriven input shaft 11 for direct-drive. The output planet-carrier has an externally toothed rim 29 for engagement (as described below) by the positive park-lock pawl 90, Fig. 5. Direct-drive clutch.-Clutch-discs 40, interleaved between the reaction sun 35 and gear input shaft 11, are engaged by oil-pressure delivered through a passage 184 to act on an annular piston 44, sealed at 46, 47, and pressed.by a single spring 41 to the disengaged position in which it opens a blade-spring seated local exhaust-valve 39 for rapid draining of the pressure-space. Band brakes.-The reduced drive reactionbrake 50, Fig. 3, is applied by oilpressure delivered through a passage 187 to the right face of a piston 84, retracted by a single spring 86, and acting through a strut 80 on one notched end of the single-coil brake-band 50, the other notched end of which reacts on a fixed member 77 through a strut 75. The band-ends are pressed apart by a, spring 81 on a sliding pin 82, and a small spring 87 acts on the strut 80 to provide an initial resilient lostmotion on take-up. The reverse reaction brake 55, Fig. 2, differs in that the spring- retracted brake-piston 66, in moving rightwards in response to oil-pressure entering at 170, acts on a lever 70 pivoted by a pin 56 to a link 54 which supports the remote end 52 of the band through a tang 53. The upper end of the lever 70 pinches the band 'onto the underlying drum through the notched adjacent end 62 and a strut 63, resting in a notch in an adjustable anchor-post 64. Servo system.-Input and output driven gear pumps P, Q, deliver into a common pressure-space 129, Fig. 7, in the regulator-valve 125, with which the delivery 159 of the output-pump Q communicates through a double check-valve 160, comprising a U-shaped blade spring covering ports 157, 158 which respectively close to that pump producing the lower pressure. Neutral. Fig. 7 shows the sliding manual selector-valve 130 in neutral, with the vehicle stationary and the engine-pump P alone supplying pressure, which reaches a common crosspassage 162 between the regulating and selector valves 125, 130 through the port 157, but is blanked by the upper land f of the selectorvalve 130, which is now exhausting the lowbrake and high-clutch supply-passages 187, 184 at 175, and the reverse brake-passage 170 at 126. Supply-pressure from the cross-passage 162, through a port 123 reaches the underface 133 of the regulator-valve 125 urging it upwards in opposition to functionally variable loading (described below), to supply. oil. to the torqueconverter feed line 161, 168 through a port 131, keeping the converter filled. Low range. Moving the selector valve 130 two steps upward, Fig. 8 (not shown), through the direct-drive position introduces low-speed range, which is for emergency use only: Clutch and reverse lines 184, 170 are exhausted as for neutral but the second land g of the selector-valve uncovers the low range brake-line 187 to the pressure passage 162. Direct drive. Moving the selector-valve 130 to a position intermediate neutral and low, Fig. 9 (not shown), causes the second land g to uncover the direct-drive clutch-line 184 (which includes an orifice) to the pressure-passage 162, whilst still maintaining full pressure in the lowrange brake-line 187, but this latter pressure is neutralised by pressure applied simultaneously to the idle face of the low-range brake-piston 84, Fig. 3, through a line 151, Figs. 3 and 7, fed through the regulator-valve 125 by a line 152 communicating with the pressure-space of the direct-drive clutch 40, which thus engages alone. The purpose of this pressure interconnection is to cause the brake to engage or disengage at a rate proportionate to the corresponding disengagement or engagement of the clutch during a shift, which is thus transitional without powerinterruption. Reverse. In its topmost position, Fig. 10 (not shown), the selector-valve 130 exhausts the clutch and brake lines 184, 187 at 175, cuts off exhaust 126 to the reverse brake-line 170 and applies pressure thereto from the cross-passage 162. Park lock. In its lowest position, Fig. 11 (not shown), one step below neutral, Fig. 7, the selector-valve 130 blanks off the torque-converter lines 165, 168, to prevent drainage of the converter, exhausts the pressure passage 162 at 126, and, with the engine stopped, the regulatorvalve 125 descends to its lowest position in which it blanks off the torque-converter feed-line 161. A restrictor 201 is provided in the converter exit-line 202, and the selector valve 130 has a pressure-relief valve 195 for its inlet chamber. Regulator valve-function. The regulator-valve 125, Fig. 7, is moved upwardly by supply-pressure acting on its undersurface 133 in opposition to downward loading of a spring 134 and functionally variable loading, described below, for its land c to control exhausting of the supply-pressure space 129 to pump-suction 128, to obtain a desired regulated supply-pressure to the crosspassage 162. Functionally variable loading is by two diaphragms 140, 146 acting only downwardly on the regulator-valve through a lever 135 to increase its loading and hence the regulated servo-pressure. The upper diaphragm 146 is loaded upwardly in opposition to a spring 147 by engine suction entering at 148, so that increased engine-load or throttle opening, by resulting in decreased suction, causes the diaphragm-spring 147 to increase the regulator-valve loading and hence the regulated servo-pressure. This functional factor also responds to engine speed. The lower diaphragm 140 is subject to oil pressure on both its opposing faces, through passages 190, 191 respectively, and these are supplied from the torque-converter inlet and outlet passages 168, 165, in a sequence variably determined by the setting of the selector-valve 130, acting, through three lower lands h, i, j, as follows, in conjunction with the torque-converter pressure-relief valve 200 which ensures that the converter exit pressure cannot exceed its inlet pressure. In the low and reverse range, where torque-demand is high, the selector-valve 130 directs converter inlet pressure through lines 168; 190 to the upper face of the diaphragm 140 and converter exit pressure through lines 165, 191 to its lower face. The dominating inlet pressure thus increases downward loading of the regulator-valve 125 and hence the servo-pressure, its effect being to maintain higher minimum servo-pressures with increase in vehicle-speed. In direct-drive, the selector-valve 130 reverses the diaphragm lines 190, 191, supplying converter inlet pressure to the lower face and exit pressure to the upper face of the diaphragm 140. In this range torquedemand is lower and the regulated pressure is accordingly reduced by the dominating inlet pressure. In addition the top land a of the regulator-valve 125 is larger than the others so that, in the high range the clutch-engaging pressure in lines 151, 152 acts differentially upwards on the valve to reduce th