Patent GB-696637-A (GB)
Title: Improvements in or relating to variable-speed power transmissions for vehicles
IPC: F16H47/06
Filed: 1949-12-30
Abstract: 696,637. Change-speed gear. MAYBACH, K. Dec. 30, 1949 [Dec, 30, 1948], No. 33307/49. Class 80 (ii). [Also in Group XXIX] On a rail-car or heavy road vehicle, a mechanical change-speed gear, of the type having claw clutches with inclined faces for pre-synchronous ratchet action, is driven through a hydrodynamic torque-converter 59 which, is operative only in the first-speed starting ratio, being mechanically by-passed in all other ratios, the converter being permanently filled and enclosed in a cooling jacket 61 in which cooling water may circulate. The converter has a permanently fixed stator. Control of the fluid-to-meehanical drive may, as with the change-speed gear, be automatic, under common control and operating in response to engine- and vehicle-speed and load-torque. As shown the torque-converter 59 provides a split-torque hydromechanical drive operative only up to a predetermined engine speed in the first gear only of a four-speed countershaft gear having aligned input and output shafts 97, 102 and inclined-faced selector claw-clutches 101, 103, 110, 112. A common control of the fluidto-mechanical, as well as of subsequent ratioshifts, is provided by centrifugal governors 161, 162, producing respectively upshift and downshift and both driven only by the engine. During a shift in the mechanical gear, the torque-converter is temporarily clutched in to act as a brake for rapidly reducing input speed, and the setting of the engine fuel-control lever 138 is also increased or decreased as appropriate for retardation or acceleration synchronising of the selector-clutches. Mechanical or fluid-drive is selected by a, double friction clutch 70, and the split-torque hydromechanical drive is combined in a three element planet-gear 63. An engine 1 drives, through a free-wheel clutch 52, a primary input shaft 55, which, through a pinion 56, drives the planet-carrier 63 of the torque-combining planet-gear, which comprises also a ring-gear 65, driving the changespeed gear input shaft 97 mechanically through a gear-pair 89, 90; and a sun 66, integral with a hollow shaft carrying the centre-disc 70 of the double clutch, engagement of which with a right side disc 77 drives the impeller 59 of the torque converter, the turbine 60 of which is fast on an inner shaft 80, which, through a gear-pair 83, 84 and free-wheel clutch 85, or controllable dogclutch, drives the input-shaft 97 of the changespeed gear, conjointly with the mechanical drive of the same shaft 97 by way of the ring-gear 65. Disengagement of the clutch centre-disc 70 from the converter-driving disc 77 and its engagement with a left-side disc 67 disconnects the converter 59 and clutches the planet-gear solid for the purely mechanical drive. The double-clutch 70 is actuated selectively by supplying oilpressure to spaces 68 or 78 through passages in the hollow shaft and supply-ducts 91, 93. The selector-clutches 101, 103, 110, 112 of the changespeed gear are paired together on the main- and counter-shafts and operated by two doubleacting pistons 241, 242, integral with which are valves 249, 250 controlling the fluid shift-circuit as described below. Where a controllable dogclutch replaces the free-wheel clutch 85, this may be directly operated by the main control (described below) and its axial movement may control the fluid pressure operating the double friction clutch 70. Operation. Change from fluid to mechanical drive. As shown ready for starting, the changespeed gear is in first speed and the hydraulic drive is clutched in at 70, 77. Increasing the engine-speed from idle by operating a single manual lever 131 acting on the fuel control 138, starts and accelerates the vehicle. The input driven downshift governor 162 expands and rapidly passes through its operative position without effect. With increase in vehicle speed up to aproximately 40 Km/hour the inputdriven upshift governor 161 expands, moving to the right its valve 163 to supply oil-pressure from an inlet 196 to an upshift piston 181, which, through a pawl 187 and ratchet-wheel 189, turns one step clockwise (viewed from the left) a selector camshaft 193 controlling three spring-lifted valves two, 205, 206 of which are associated with the respective ratio-shift pistons 242, 241, whilst the third, 207, controls the double clutch 70 which selects fluid or mechanical drive In this first step of the selector camshaft 193 the two shift-valves 205, 206 are not moved, 205 remaining up and 206 down, as shown, so that first speed remains engaged, whilst the third valve 207 is lifted by its spring from the depressed position shown, which movement reverses the pressure inlet 225, 228 and exhaust 208, 218 valve-connections with the pipes 91, 93, so that the clutch-space 78 is exhausted, releasing the converter-drive clutch 70, 77, and space 68 is pressurised, clutching the planetgear 63 solid at 67, 70 for a gradual change to a purely mechanical drive to the change-speed input shaft 97, with consequent reduction in engine speed (about 15 per cent). The converterclutch control valve 207 remains in this depressed position for all subsequent ratio-positions of the selector camshaft 193. Upshift first to second speed. With further increase in vehicle speed the input-driven upshift governor 161 again reaches its operating speed and supplies pressure to the piston 181 to ratchet the selector camshaft 193 another step forwards, in which position the shift-valve 205 and converter-clutch valve 207 remain raised whilst the shift valve 206 is also moved into the raised position. This reverses the pressure-inlet 225, 228 and exhaust 208 connections through pipes 231, 232 to the opposite sides of the shift piston 241 which commences to move from left to right, movement of the other shift-piston 242 not being required. Initial movement of the shift-piston 241, permitted in advance of disengagement of the selector-clutch by virtue of a lost-motion pin-and-slot connection 245 between the piston-rod and the selector-clutch operating lever, closes the engine fuel-supply to idle, unloading the selector clutch 110 of the drivetorque, and introduces braking by the torqueconverter for synchronising the upshift by the following circuit. At the beginning of the rightward movement of the shift-piston 241, a groove, Fig. 5 (not shown), in the piston-stem breaks communication between a fuel-control line 277, leading through a port 305 of a valve 150 to a space under the fuel-control piston 142, and a line 273 leading through a groove, Fig. 7 (not shown), in the stem of the other shiftpiston 242 to an exhaust port, and at the same time connects the fuel-control line 277 to the pressure-inlet 225, 227 through the stem-groove, a stem-passage 253 and body-groove 290. The space above a fuel-control piston 142 is vented through a valve 150 and ports 308, 317 in a converter-brake control-valve 301, so that the piston 142 moves upwards in its fixed cylinder, compressing the upper spring 135 of a link to the manual lever 131 and moving the fuel control 138 to idle, thus unloading the selector-clutch 110. The converter-brake valve 301 remains in its rightward position shown, in spite of a temporary application of leftward pressure from the inlet 225, 227, through the piston-stem passage 253 and a line 271, since this pressure is later over-ridden by the rightward spring plus rightward pressure supplied through a stem-passage 254 and line 272 after disengagement of the superseded selector-clutch 110. This pressure in the line 272 also passes through the converterbrake valve 301 and a line 311 to a spring-loaded piston-valve 127 under the fluid-drive controlvalve 207, which piston-valve is thereby moved to the left, cutting out the exhaust 218 and pressurising the converter-clutch space 78 from the line 311 through a groove 130 in the pistonvalve 127. This engages the converter-drive clutch 70, 77 causing the converter to brake rapidly the input shaft 55 to synchronise engagement of the selector-clutch 101. Completion of the rightward movement of the shift-piston 241 disengages the converter-drive clutch by exhausting the line 311 through the converterbrake valve 301, line 278, passage 262 in the stem of the other shift-piston 242, line 276, passage 255 in the piston-stem 241 and outlet 282. At the same time the fuel-control line 277 is exhausted by reconnection, through a second groove, Fig. 5 (not shown), in the piston-stem 241, with the line 273, still exhausted through the other piston-stem 242. The upper spring 135 of the manual control link then restores the fuel-lever 138 to its set position and the vehicle proceeds in second speed. Upshift from second to third speed. This requires shift of both shift-pistons 241, 242 from right to left for disengagement of selectorclutches 101, 112 and engagement of selectorclutch 103 which requires input retardation for synchronising, and also of selector-clutch 110 which now requires input acceleration for synchronising, achieved by increasing the fuelsupply, the required sequence being automatically determined by the order of disengagement of the superseded selector-clutches. The shift is initiated, as before, by the upshift governor 161 stepping the selector camshaft 193 forwards, to raise both shift-valves 205, 206 and reverse the pressure and exhaust connections to the respective lines 231, 232 and 233, 234 of the shift pistons. If the clutch 101 disengages first so that the shift piston 241 moves to a meshrejecting central position before the shift-piston 242, pressure passes from the inlet 255, 227, through stem-passage 253 and line 271 to the right face of the converter-brake valve 301, which now, in the absence of rightward fluidpressure, moves to the left and supplies pressure from the line 271 past the valve 150 above the fuel-control piston 142, the valve 150 simultaneously moving to the left to