718,016. Change-speed control. DAIMLERBENZ AKT.-GES. Oct. 5, 1950 [Oct. 5, 1949], No. 24395/50. Class 80(2) In a method of combined regulation of an internal combustion engine and a change-speed gear through which the engine drives the load, e.g. a vehicle, a constant engine output set to any predetermined fraction up to the maximum by a foot-operated lever 1, is obtained at all speeds by the provision of means responsive to the speed of the driven shaft for reducing the engine torque by reducing its fuel supply as the speed increases until the corresponding line of constant load in the next higher speed is reached whereupon the gear is automatically upshifted, the engine torque being thereafter regulated as before. Engine torque is represented by engine suction. Engine braking in lower gear ratios is also provided at position X<SP>2</SP> of the single control member 1. The power-fraction at which the engine is required to work is preselected by moving the control-lever to positions X. X' &c, between zero output XO and maximum X1, such action serving, through a lever 3, to vary the datum of a capsule 4 subject externally to engine-suction at the carburettor venturi 10. which represents engine-torque and causes the capsule to operate a piston-valve 5 controlling the admission of servo liquid-pressure from an inlet 12 to one side or other of a piston 15 operating the engine-throttle 20 through a spring-link. The manual lever 1 also operates, through a further lever 6, and conjointly with an outputspeed responsive control 22, a control-box 7 not described, controlling shift of the gears at 23. The gears may be shifted by fluid-pressure under control of a valve operated by the lever 6 through a spring in opposition to output-speed responsive fluid-pressure; or mechanically through a floating lever. In the engine-braking position X2 of the manual lever 1. which may be reached against resilient resistance, either by direct operation of the lever 1 itself, or by operating a separate hand-lever, and is indicated to the driver by a red signal-light, the lever 1 positively closes the engine-throttle through a lever 24, and the gear shift mechanism is arrested in a low-gear position. A resilient stop 26 may be preset to resist movement of the manual lever 1 in the power-increase direction beyond any predetermined maximum. Operation of the control is described with reference to curves I ... V, Fig. 2, of engine power output against road-speed in the respective five gears, and W of level road-resistance against .speed. Preset constant power fractions N, N<SP>1</SP>, N<SP>11</SP>are represented as corresponding to preset lever positions X. X' X". Assuming the control-lever 1 set to position X, to preselect constant power line N, starting from dead-engine position O, absence of engine-suction causes the capsule 4 to contract, raising the piston-valve 5 (position shown) so that when the engine starts servo liquid-pressure, when supplied at 12, sets the engine-throttle wide open. The vehicle accelerates with wide-open throttle along the first-speed curve I until, at a road-speed VI the curve I intersects at Bl the line N of preset constant power fraction whereafter further speed increase, by increasing engine-suction, permits the capsule 4 to expand and operate the servo-valve 5 to start closing the engine throttle 20. Depending on the suction-characteristic of the engine, the curve thereafter followed from B 1 falls slightly below the constant power line N and continues to a point A2, at vehicle speed V12, where it cuts the second-speed power curve II, at which point the speed responsive control enforces an upshift to second-speed, the consequent reduction in engine speed causing the suction-responsive capsule 4 to restore the engine-throttle to' full open position. The vehicle now accelerates along the second-speed curve II as far as the point B2 where it intersects the constant-power line N. at which a similar throttle-close to point A3, speed V23. followed by upshift to the third speed curve III occurs. This sequence being followed up to the fifth, overdrive, speed V, the further shifts occurring at speeds V34, V45. Maximum level road vehicle speed for the particular preset power fraction N is shown by the point Aw at which the final line B5Aw cuts the road resistance line W. The substantially constant powerline is thus reoresented by B1, A2, B2, A3, B3. A4. B4, A5, B5. Aw. To provide hvsteresis for stability downshifts, e.g. V54; V43, occur at lower vehicle speeds than those V45, V34 of corresponding upshifts. To avoid excessive engine speeds in lower gears upshift from I to II may, as shown for the constant power line N', occur at a point C' before the falling line from B1<SP>1</SP>, reaches the second-speed curve II, which is then entered at D2<SP>1</SP> at reduced power. Upshift on sudden reduction of output power-demand may be subject to a delay device