Patent GB-706853-A (GB)
Title: Improvements relating to the control of starting clutches particularly in motor vehicles
IPC: F16D48/02
Filed: 1951-03-16
Abstract: 706,853. Hydraulic clutches. DAIMLERBENZ AKT.-GES. March 16, 1951 [March 16, 1950], No. 6431/51. Class 69 (2). [Also in Group XXIV] A speed-responsive automatic control for a motor-vehicle starting clutch of the throttleregulated hydrostatic type, having a bridging electromagnetic clutch E, comprises a pressure regulator D1, influenced by centrifugal force and by a pressure fluid for regulating clutch pressure through an auxiliary force such as fluid pressure or electricity, and a controlling regulator R, separately arranged and separately movable, and responsive to engine speed for controlling that pressure fluid which influences the pressureregulator D1, to reduce clutch pressure below a predetermined speed at which the engine starts the vehicle, and to increase it above that speed, whereby during starting, as long as the output speed is below that predetermined engine speed, excess engine speed above it will result in the engine being braked by the output to prevent such excess and thus hold the engine to the constant starting speed. The starting speed may be constant for all engine-throttle openings or may increase with throttle opening, being arranged to be the maximum torque speed at full throttle. In the hydrostatic clutch shown, the input member H1, carries planet gear-wheels 102, 102<SP>1</SP>, 102<SP>11</SP>, which mesh internally with an output sungear 101 and externally with a free ring-gear 103 to form in all six gear pumps, of which five are used with throttled delivery as the hydrostatic clutch, each having pressure and suction connections 106, 107 (only one shown), to the control circuit, whilst the sixth, 102", outer, controls the engine throttle 133 for synchronizing the input shaft with the output after manual clutchrelease by a valve 129 for gear-shifting. The clutch-pump pressure port 106 is connected through lines 109, 110, to the controlling regulator R and pressure regulator D1, both radially arranged on the clutch input member HI. At idle speeds a spring 33 overcomes a centrifugal mass 32 of the controlling regulator R, and line pressure 109 is directed through a line 126 to the upper face of the piston of the pressure regulator D1, which thereby moves downwards to short-circuit the pressure and suction ports 106, 107, thus maintaining declutch. When the driver increases engine speed by opening the throttle 133, the piston of the pressure regulator D1 moves centrifugally outwards, restricting the lower communication to the suction port 107, thus permitting build-up of pressure at 106 to initiate clutching. During this period any tendency for the engine speed to rise above the predetermined constant starting speed causes the piston of the controlling regulator R to move centrifugally outwards, exhausting the line 126 and pressurizing a line 127 leading to the lower face of the piston of the pressure regulator D1, which thereby moves upwards to restrict further the escape of pressure to the suction port 107, thus increasing clutch engagement to brake the engine to the desired constant starting speed. When clutch engagement is almost complete, the differential pressure of the hydrostatic clutch is reduced permitting the piston of the pressure regulator D1 to move centrifugally to its outer extreme, closing a switch 122 to engage an electromagnetic friction disc clutch E which provides a direct mechanical connection between the input and output members HI, H2 of the hydrostatic clutch, which reduces hydraulic pressure to zero. Declutch on subsequent deceleration is at a lower speed than that of clutching, since the engagement of the electromagnetic clutch E eliminates slip and hence pressure produced by the hydrostatic clutch, so that re-opening of the switch 122 for declutch, is controlled solely by the spring and centrifugal loading of the pressure regulator D1. For manual declutch, e.g. during gear-shift, the manual valve 129 short-circuits the hydrostatic clutch, breaks the circuit of the electromagnetic clutch at 130, and energizes a solenoid-valve 144, which communicates the pressure and suction ports of the sixth pump 102" with opposite sides of a centrally spring loaded piston 135, which forms the floating fulcrum for a lever 131 in linkage between the accelerator-pedal 132 and engine-throttle 133, so that, whilst the clutch is disengaged, pressure from the pump 102<SP>11</SP> acts on the piston 135 in one direction or the other in accordance with the relative speed-direction of the input and output members H1, H2 of the clutch, to vary the engine-throttle opening to synchronize the clutch-members prior to reengagement.