Patent GB-717402-A (GB)
Title: Improvements in engine, and combined engine and change-speed, regulating arrangements for power vehicles
IPC: F02D29/00
Filed: 1949-12-30
Abstract: 717,402. Change-speed control. MAYBACH, K. Dec. 30, 1949 [Dec. 30, 1948], No. 33311/49. Class 80 (2) [Also in Group XXVII] A combined gear-shift and engine-speed control on a rail-vehicle is so arranged that the driver, by operating a single control lever 159, automatically conditions the oil-engine 31 for working in any one of a series of ranges of engine-speeds, each corresponding to a desired engine output-fraction, and at the same time selects a rate of fuel supply to give a predetermined torque at the upper limit of the selected range, and, within the limits of the said range, an engine-driven governor 194 automatically varies the fuel-feed, and if desired also the injection timing of the engine, to maintain an output which is constant or variable in a predetermined manner, whilst outside such speed limits, further engine-speed responsive governors 121, 122 cause an appropriate upshift or downshift in the change-speed gear to maintain the selected speed range. Thus if the driver has set the lever 159 for an engine-speed range corresponding say to 25 per cent. output, successive upshifts will be effected automatically at a predetermined upper limit of engine-speed (1120 R.P.M.) whenever the 25 per cent. output of the engine exceeds the resistance, whilst conversely successive downshifts will occur at a lower. limit (860 R.P.M.) when resistance exceeds that output, and within these limits the fuel feed and injection timing are automatically varied to maintain the constant (or variable) output so that after gear-shift the output remains the same (or increases on upshift) whereby no discontinuity occurs in the curve of tractive effort at the change-point. Higher output fractions have higher engine speed-range limits (e.g. 60 per cent. output, 1540-2000 R.P.M. &c.). The control permits the use of cylinder mean effective pressures at part loads which are higher than the normal maximum for continuous power rating. During a ratio-shift the main clutch 34 is automatically disengaged and the engine idled. In a wholly mechanical change-speed gear the selector-clutches may be of the type which ratchet until synchronized and to facilitate this action on downshift, the main clutch may be caused to re-engage and the engine to speed up in an intermediate position during shift. The gear-stages may alternatively be introduced by turbo-converters. Gear control. The change-speed gear 46 provides four ratios introduced by two doubleacting pistons 49, 50, to which oil-pressure from an inlet 100 is selectively applied under control of two valves 79, 80, which are opened upwardly by springs 95, 96 when permitted by the registry of recesses 73 in a selector-cam 72, which is turned in single steps up and down, through opposite ratchets 149, 150, by separate upshift and downshift single-stroke pistons 141, 142 respectively. Separate centrifugal governors 121, 122 driven by the change-speed gear input-shaft 38, supply oil-pressure from the common inlet-' line 100, 101, to the respective upshift and downshift pistons 141, 142. the upshift governor 121 supplying the piston 141 in the expanded position (not shown) whilst the downshift governor 122 supplies the piston 142 in the collapsed position (shown). The governor loading-springs 133, 134 are subject to common variable compression by a gear-control cam-follower 211 which bears on a separate track of the driver-manipulated cam 158, taking part in the conjoint engine-gearclutch control as described below. Clutch control. Operating on another track of the operator-controlled cam 158 is the stem of a clutch-valve 163 which, in the spring-depressed initial position shown, causes .disengagement of the oil-pressure engaged main-clutch 34 by exhausting its supply-line 116 through the chamber of an engine-control piston 173, connecting-pipe 170 and an opening 167, whilst turning the operator-controlled cam 158 anticlockwise to its running range, lifts the clutch-valve 163 and supplies oil-pressure to engage the mainclutch 34 from an inlet pipe 115 fed from the main pressure-inlet 100 through the changespeed selectors 49, 50, as described below. Engine control. A third track of the operatorcontrolled cam 158 actuates an engine-camfollower 183, controlling the quantity and timing of the fuel injected into the engine 31 in conjunction with a third centrifugal governor 194, continuously driven from the engine side of the main clutch 34. The engine-cam-follower 183, which is pressed on to the cam 158 by a spring 187a and can. be retracted by a manual lever 180, operates through a spring link 187 and a toothed pair 192, 193, to turn a three-dimensional cam 195, which is axially adjusted by the engine-governor 194, and sets the fuel quantity 200, and injection-timing 205 controls; through followers 197, 202 respectively to maintain constant engine output in each particular speedrange. The engine-cam-follower 183 is also retracted from the control cam 158 by the spring 174 of the engine-control piston 173 which spring depresses the piston 173 to lift the engine-camfollower to the engine-idle position whenever the clutch-valve 163 exhausts the clutch-line 116 at 167 to disengage the main clutch 34. Starting sequence. It is assumed that initially the engine is dead and both gear-selector pistons 49, 50 are in their left position, shown for selecting first speed. There is no oil-pressure in the system, the clutch-line 116 is exhausted at 167 so that' the main clutch 34 is disengaged and the piston-spring 174 is lifting the engine-camfollower 183 off the cam 158 for engine idle. The engine is then started and oil pressure develops without effect until the driver raises the lever 159 to turn the cam 158 anticlockwise to start the vehicle on a predetermined load-fraction. The first cam movement raises the clutch-valve 163, cutting off exhaust 167 and supplying oilpressure from the main inlet 100, through nowopen passages 58, 67 in the gear-selector pistonrods 49, 50, line 115, clutch-valve 163, chamber of engine-piston 173 and line 116 to engage the main-clutch 34, simultaneously raising the engine-piston 173 to permit the spring 187a to press the engine-cam-follower 183 on to the cam 158 to speed up the engine. The vehicle now proceeds in first speed. Gear-shift sequence. During travel in any particular gear-ratio, the engine-driven governor 194 automatically adjusts the fuel feed and timing to maintain engine output constant, but when a surplus of engine output above the resistance causes engine-speed to rise above the predetermined upper limit corresponding to that of the selected output fraction as determined by the setting of the operator's lever .159, which controls the loading of the shift-governors 121, 122, the upshift governor 121 supplies pressure to the upshift ratchet-piston 141, stepping the selector-cam 72 once up. Pressure is thus directed to the appropriate sides of the gearshift pistons 49, 50, which begin their movement, at the same time cutting off the clutch pressure line 115 to disengage the main clutch and idle the engine for the duration of the shift, at the end of which the shift-pistons restore pressure to the clutch-line 115. A deficit of power below the resistance causes engine speed to fall to the lower limit, causing collapse of the downshift governor 122, to produce downshift in a similar manner. In Fig 8 (not shown), there are additional clutch-control ports in the gear-shift piston-rods 49, 50 which coact with the downshift governor 122 only, to control a supplementary fluidoperated piston-valve in the clutch-line 115, in such a manner that, during downshift only the supplementary-valve temporarily re-pressurizes the clutch-line 115 as the gear-shift pistons 49, 50 pass through a central position in which their ports are fed with pressure through the collapsed downshift governor, so that the clutch is temporarily re-engaged and the engine speeded up to permit the ratchetting selector-clutches to reach an overtaking speed necessary for downshift engagement. The Specification includes characteristic engine and gear-shift curves.