Patent GB-732513-A (GB)
Title: Improvements in circuits for controlling electromagnetic clutches
IPC: F16D48/06
Filed: 1953-07-20
Abstract: 732,513. Clutch control. SOC. ANON. FRANCAISE DU FERODO. July 20, 1953 [July 23, 1952; March 12, 1953], No. 20128/53. Class 80 (2). The energization of an electromagnetic clutch 12 on a motor-vehicle is increased by depressing the engine accelerator pedal which, between idle and one-third throttle reduces a resistor 16 to zero. Controls responsive to engine-driven generator and governor speed, gear-shift lever movement and position, engine-suction, carburettor air strangler, and time all assist. The arrangement provides automatic declutch at engine-idle and coincidental with gear shift. In Fig. 1 a manual change-over switch 29 energizes the clutch 12 either directly from the usual battery 11 or from the engine-driven generator 10, through the accelerator-varied resistor 16, a resistor 21 adjustable to compensate for wear in the clutch, and a relay 24 which is closed when de-energized and opens when energized from the battery 11 through two switches, one 28 closed by closure of the usual engine ignition switch, the other 26 closed by the operator when he applies shift pressure to a yielding knob part of a divided gear shift lever 13 (not shown) and re-opened by release of the lever on completion of gear-shift. This last function causes clutch disengagement coincidentally with gear shift. The generator energization and acceleratorcontrolled resistor 16 provide automatic declutch at engine idle together with accelerator release and gradual re-engagement on accelerator depression. The accelerator-resistor is in three steps 16<SP>4</SP>, 16<SP>3</SP>, 16<SP>2</SP>, having decreasing values the first, 164, being highest and being also cut out at 20 by placing the gear-shift lever in any gear except first and reverse, so that clutch engagement is more gradual in these starting speeds than in running speeds. The total resistance (20 ohms) is chosen to limit the torque-capacity of the clutch in first speed and reverse to about one half engine-brake torque and one-quarter the maximum drive torque; and in higher gear ratios to full enginebrake torque and one-half maximum drive torque. A capacitor 38, shunted across the clutch winding 12, reduces contact burning. In Figs. 2-4 (not shown), the various switches, except 26, 28, 29, resistors and capacitor are arranged in a common casing, with Bowden cable control of the sliding resistor 16 and switch 20, connected to the accelerator pedal and gear shift lever respectively. In Figs. 7 and 8 (not shown) torque-response is added by inserting a resistor in the generator lead 15, to be cut out at low torque by engine-suction acting on a diaphragm switch. Clutching pressure is thus eased at high torque to prevent jerks due to sudden accelerator depression during engagement. In Fig. 8 (not shown) the same resistor is also cut out by an engine driven governor switch above a predetermined engine speed, or by a chronometric control after a predetermined time following insertion of the resistor by the suction control. Fig. 9 (not shown) provides two stepped unequal resistors like 16, Fig. 1, in parallel side-by-side and each with its own accelerator-operated slider controlled by a shift-lever-operated selectorswitch so that one slider, controlling the higher resistors, is effective for first and reverse, for more gradual starting engagement, and the other for other running speeds. This replaces the shift-lever-operated cut-out switch 20 of Fig. 1. Fig. 10 provides for automatic changeover to battery energization above a predetermined speed of the clutch-driven shaft, by an automatic change-over switch 112 controlled by a clutch-speed responsive switch 136 which, above the predetermined speed, opens to deenergize a solenoid 134 causing an arm 111 of the change-over switch 112 to contact a stud 113, to feed the clutch 12 from the battery 11 through a manually adjusted wear-compensating resistor 110 (corresponding to 21 in Fig. 1), acceleratorcontrolled variable resistor 109 (which may also be controlled by engine speed), and relay 24 which, in this case, is closed by energizing its winding from the battery contact 113. Below the predetermined clutch speed the clutchdriven switch 136 closes to energize the solenoid 134 causing the arm 11 of the change-over switch to strike a contact 115 leading to the arm of a manual change-over switch 118, which, when turned to make a contact 119, provides for permanent battery energization of the clutch 12, and when turned to a contact 120, fed by the generator 10, causes the clutch to be generator-energized below the tripping speed of the clutch-driven switch 136 and battery energized above that speed. In the generator feed line is a resistor 123 which is put in circuit only when a switch 124 is opened by operation of the combined mixture-enriching and fast-idle device of the carburettor prior to starting a cold engine, thus reducing clutch energization to compensate for the fast idle. The return circuit of the main relay 24 is completed through three switches; two in parallel, one, 129, closed by the gear-shift control in all except first speed and reverse, the other, 128, normally open but closed by the initial depression of the accelerator pedal, whilst the third switch 131 is opened by the initial movement of the yielding gearshift lever 13. These switches control the main relay 24 to cause clutch de-energization by full accelerator release in first and reverse only, and also by initial gear-shift movement. In Fig. 11 the main relay 24 is arranged to have its contacts closed when de-energized (like Fig. 1), instead of the reverse arrangement of Fig. 10.