Patent GB-1189875-A (GB)
Title: Improvements in or relating to Clutch Arrangements
IPC: F16D27/112
Filed: 1967-07-11
Abstract: 1,189,875. Friction clutches. ROBERT BOSCH G.m.b.H. 11 July, 1967 [19 Aug., 1966], No. 31812/67. Heading F2C. In an electromagnetic friction disc clutch, for transistor controlled motor vehicle gears, vehicle cooling blowers, air conditioning refrigerating compressors, or machine tools, comprising a fixed annular magnetizing winding 20 and a friction disc 7 fast in rotation with, but axially movable on, a driven shaft 4 and arranged between an axially movable armature plate 15 and an axially fixed pole disc 24 both fast in rotation with a driving shaft 1, the friction disc 7 comprises a carrier disc 8 of magnetically conducting material and having fitted thereto two outer and two inner continuous or interrupted pole rings 9, 9<SP>1</SP>, 11, 11<SP>1</SP>, the zone within the pole rings being filled with an annular magnetically non-conducting friction lining 10, and a ring of perforations 13 separated by narrow bridges (14) being formed in the carrier disc within the friction lining to prevent magnetic short-circuiting. The clutch arrangement may comprise a single clutch or, as shown, a double clutch by which a driving shaft 1 may be clutched selectively to nested output shafts 4, 5; further, Fig. 7 (not shown), two or more friction discs may be arranged between the pole disc and the armature plate and separated from one another by a magnetically conducting disc 58 axially movable but rotationally fast with the pole disc. The double clutch shown is suitable for an interrupted traction automatic change-speed gear, the engagement of the two clutches A, B being so electronically controlled as to overlap. Each clutch comprises a carrier disc 8 connected to its shaft through an oscillation damper 6. The winding 20 is contained in an annular trough 19 fast on a divider 18 of a fixed housing 17. The pole disc 24 is U-sectioned and has a ring of bridge projections 25 by which it is fixed to a flywheel 2 of the driving shaft 1, an extension 26 by which it is connected to an extension of the other clutch pole disc by a threaded ring 44, and a ring of perforations 27 separated from one another by narrow bridges (28). The armature plate 15 is connected to the flywheel, and retracted on clutch disengagement, by corrugated leaf springs 16 radially outwardly clamped between the flywheel and the projections 25 and radially inwardly connected to the armature plate. Corrugated springs 51, 51<SP>1</SP> radially inwards of the pole rings 11, 11<SP>1</SP> prevent sticking, due to magnetic remanence of the friction disc 7, pole disc 24 and armature 15 on clutch disengagement. Alternatively, to prevent sticking, the carrier disc is circumferentially corrugated in the clutch-disengaged state, the friction lining and the pole rings being replaced by rings of segments, and the carrier disc itself being suitably perforated radially inwardly of the gaps between said segments, to allow such corrugation. Automatic wear adjustment, maintaining constant armature plate travel, is provided by spring steel wire stops 46 which have legs 46, 50 respectively engaging bores 45 in the pole disc 24 and, with lost motion, bores 48 in the armature plate. The stops 46 are so shaped that on clutch engagement, after taking up the lost motion, armature plate lugs 49 contact the stops 46 and with wear occurrence push them further into the bores 45 and, on clutch disengagement, after reversely taking up the lost motion, the opposing side of the armature plate bores engage the stops 46 to prevent further retraction of the armature plate, the stops being then self-locked in the bores.