Patent GB-742545-A (GB)
Title: Improvements in or relating to a control for an electromagnetic clutch
IPC: F16H63/46
Filed: 1953-04-02
Abstract: 742,545. Transmitting mechanical power. EATON MANUFACTURING CO. April 2, 1953 [April 2, 1952], No. 9177/53. Class 38 (4). [Also in Groups XXIV and XXXVII] On a motor-vehicle the energizing circuit of the winding 3 of an electromagnetic main clutch C, eg. of the magnetic fluid type described in Specification 677,534, includes a current-modulating variable resistor 7, operated at 21 by the usual accelerator pedal to increase clutch energizing with accelerator depression, and a normally-closed relay switch B1, opened by closing a switch S by the action of grasping the knob of the usual steering- column-mounted gear-shift lever for clutch disengagements coincidental with gear shift. Clutch energization is cut off in the neutral position of the gear-shift lever and subject to a reverse current pulse for rapid demagnetizing during gear shift. In addition there is a relay switch A, controlled by a governor switch 45, which, below a predetermined vehicle speed, disconnects the usual engine-driven generator G from the usual battery-charging regulator R, and connects the unregulated generator output directly to the clutch winding 3, and above that speed restores the normal regulator connections and feeds the clutch winding from the usual battery 2, so that under starting and hightorque slow speed conditions, generator voltage may rise above normal for increased clutch energization in comparision with constant battery-voltage energization during normal running. The same governor switch A also provides automatic control of a solenoid 51, introducing overdrive in an auxiliary planetary gear behind.. the usual 3-speed and reverse synchro-mesh change-speed gear. Operation is as follows : Below governor speed (20-26 rn.p.h.). Fig. 2 shows conditions for starting and running below governed speed, the governor switch 45, which is driven from a point between the change-speed gear and the overdrive gear, being op en. The generator field 29 is energized directly from the battery 2 through the engine ignition switch 26, a resistor 35 and contacts 27, 31 of the relay switch A, and the generatorarmature 9 feeds the clutch winding 3 directly through contacts 15, 17 of switch A, the accelerator controlled resistor 7 and normally closed contacts B1 of the relay switch B controlled by the gear-shift switch S. With released accelerator,. the whole of the resistor 7 is in circuit, limiting clutch energizing current to a value sufficient only for a minimum torque transmission, e.g. for engine-braking on overrun. Increased accelerator depression, acting at 21, short-circuits increasing sections of the resistor 7, increasing clutch energization to a maximum determined only by the unregulated voltage of the generator G. During gear-shift, grasping the knob of the shift-lever closes the switch S, Fig. 2, which energizes, from the battery 2, the relay winding B, opening the contacts B1 to break the clutch-energizing circuit, arcing being prevented by a valve 53. Above governor speed. Closure of the governor switch 45 energizes the winding 4 changing the contacts of the switch A as follows : Contacts A3 close to feed the clutch winding 3 directly from the battery 2 through the accelerator-resistor 7 and switch B. The generator armature contact 15 changes from the clutch contact 17 to a contact 19 feeding the armature terminal 39 of the current and voltage coils CR, VR, of the usual combined cut-out and regulator R, whilst the generator field contact 27 leaves the battery contact 31 and makes contact 33 feeding the regulator field terminal 41. Generator voltage is now regulated in the usual manner and the clutch winding 3 is battery-excited. At the same time closure of the governor switch 45 closes relay switch-contacts D1 energizing the solenoid 51 to introduce overdrive, which latter may be cut out at any time by an accelerator kick-down-opened switch 47, or by a manual switch 49. The pulse demagnetizing circuit used in Fig. 4, has an additional relay switch E, additional contacts on the gear-shift controlled relay, now designated F and acting as a current reverser, and a further switch 63 closed by movement of the gear-shift lever to neutral. In neutral the switch 63 energizes the winding 6 of the relay F closing two pairs of contacts 55, 59 and opening two pairs 55, 57. Battery current now flows through the clutch winding 3 in the reverse demagnetizing direction (dotted) through a winding CE of the relay E, its contacts E1 a lead 61 and contact-pairs 55, 59. At the same time energization of the winding CE opens the relay switch contacts E1, breaking the demagnetizing circuit 61, so that demagnetizing current is supplied only as a short pulse, and establishing a hold-on circuit through contacts E2 and a second relay-coil VE, which persists until broken at 63 by moving the gear-shift lever out of neutral. During this time the clutch winding 3 remains de-energized until a gear is established and the knobswitch S released, which de-energizes the relay F, permitting its contacts 55 &c. to return to the position shown for energizing the clutch winding in the normal running direction (full lines) from the accelerator-controlled resistor 7. In Fig. 5, not shown, all the relay switches A, E, F are combined in two relays, one with two windings and four contact sets replacing A and part of E, the other with one winding and three contact sets replacing F and part of E.