Patent GB-914674-A (GB)
Title: Improvements in or relating to electromagnetic clutch feeding circuits
IPC: B60K23/02
Filed: 1960-04-13
Abstract: 914,674. Clutch control. FRANCAISE DU FERODO S.A. April 13, 1960 [April 16, 1959], No. 13255/60. Class 80 (2). An electromagnetic clutch 10 for a motor vehicle is energized from a generator 11 which is distinct from the usual battery charging generator and has its field winding 43 excited in such a manner that the generator voltagespeed characteristic increases slowly at first and then moves rapidly up to a predetermined speed whereafter the voltage is regulated by voltage regulator means. As shown, the field winding 43 is excited partly from the battery B through an ignition switch C and resistors R4, R5, R1 and partly from the generator 11 itself through resistors R6, R5, R1, the resistor R1 being bridged by a switch 46 of the voltage regulator during speed-responsive clutch engagement. In second and higher ratios part or the whole of the resistors R4 and R6 are bridged by a switch 54 to provide more rapid clutch engagement. The voltage regulator switch 46 is operated by a relay 50, which is energized above a predetermined generator voltage to trip the switch 46 and insert the resistor R1 in series and a resistor R3 in parallel with the field winding 43. The regulated voltage may be adjusted by varying a resistor R2, and clutch wear may be compensated for by adjusting the resistor R5. The generator-fed clutch-engaging circuit provides automatic clutch release at engine idle, and includes an emergency switch 24 for connecting the clutch 10 to the battery B if the generator 11 fails; a declutching relay 39, 26 controlled from a gear shift lever switch 42; and a switch 25 which provides reduced battery energization of the clutch on closed throttle shift to prevent shocks and skidding on closed throttle downshift. The switch 25 is operated when an accelerator pedal position switch 37 is closed by a relay 30, sensitive to a voltage above the regulated voltage, which is energized by the surge voltage caused by opening the switch 26, so that on completion of gear shift the clutch is energized from the battery B through a resistor R. The value of the resistor R is chosen so that the clutch engagement during battery energization is approximately one-third of the maximum driving torque. The relay 30 has considerable hysteresis and retains the battery energization of the clutch until either the engine speed falls to idle or the switch 37 is opened. The nominal power of the generator is selected between 110 and 130% of the nominal power of the clutch and the apparent resistance of the generator constituted by its ohmic resistance and its armature reaction is selected to lie between 80 and 120% of the ohmic resistance of the clutch. The torque transmitted by the clutch at the regulator voltage may be three times the maximum engine torque. In Fig. 6 (not shown) the field winding 43 is excited solely by the generator 11 and an auxiliary field is provided by a permanent magnet. In Figs. 7 and 10 (not shown), the field winding of the generator 11 comprises two windings, one excited by the generator 11 itself and the other is excited by the battery B. In Figs. 8-10 (not shown), the switch 25 is omitted and the voltage regulator resistor R2 is formed in two parts, one of which is bridged during closed throttle shift to reduce the regulated voltage and thus the clutch energization. In Figs. 9 and 10 (not shown), the declutching relay 39 is omitted and replaced by a declutching gear shift lever switch in the generator field winding circuit.