Patent GB-928565-A (GB)
Title: Friction coupling for the transmission of power in motor vehicles
IPC: F16D47/04
Filed: 1961-08-16
Abstract: 928,565. Friction clutches and control; change-speed gear and control. SIRA S.r.1. Aug. 16, 1961 [Sept. 12, 1960], No. 29579/61. Class 80 (2). A double friction clutch for use with a change-speed gear in a motor car comprises an engine shaft 2, Fig. 1, fast with a housing 1 containing driven discs 6, 9 carried on shafts 3, 4, axially slidable pressure plates 14, 15, 16 within the housing forming oil containing chambers 23 . . . 26 interconnected near the main axis of the clutch. At engine idle speeds, centrifugal force acts on the oil in the chambers 23, 25 to cause it to move radially outwards into chambers 23a, 25a. The centrifugal force acting on the oil in the chamber 26 acts leftwards on the pressure plate 16 and the centrifugal force acting on the oil in the chamber 24 acts rightwards on the pressure plate 15; studs 19 interconnect the two pressure plates 15, 16, so that the two forces neutralize each other, and the friction disc 9 remains disengaged. At the same time, the pressure of the oil in the space 24 acts leftwards against the pressure plate 14, tending to engage the clutch disc 6, such engagement being opposed by springs 17 so that the disc 6 remains disengaged. To engage the clutch disc 9, a stationary electromagnet 37 is energized to attract an armature 36 against the bias of springs 33 and disengage it from the housing 1, an impeller 30 fast with the armature thereby being stationed. Rotation of the oil in the chamber 26 is thus impeded, so that the centrifugal force acting thereon is reduced, the centrifugal force acting on the oil in the chamber 24 causing the latter oil to pass through a passage 27 into the chamber 26. The reduction in pressure in the chamber 24 allows the pressure in the chamber 26 to move both pressure plates 15, 16 leftwards, thereby engaging the disc 9 with a wall 28 carried by the housing 1 for torque transmission to the shaft 3. During ratio shifts, the solenoid 37 is momentarily disengaged so that the impeller 30 is clutched to the housing 1, allowing centrifugal force to act on the oil in the chamber 26 and feed it back through the passage 27 into the chamber 24. The clutch disc 9 is thus disengaged, although springs 10a maintain light frictional engagement between its linings 10 and the housing 1, to facilitate synchronization of the gearing. At the same time, the centrifugal force acting on the oil in the chamber 24 forces the presser plate 14 leftwards for engagement of the clutch plate 6. Except for direct drive in the gearing, the solenoid 37 is always re-energized following a ratio shift, for re-engagement of the clutch disc 9. A friction disc 11 in the chamber 24 is connected to the shaft 3 through a ratchet clutch 13 for transmission of torque to the engine shaft 2, for push starts &c. Change-speed gear and control.-The shaft 4, Fig. 1a, drives through gears 41 to a countershaft 40 carrying gears meshing gears 43, 44, 48 selectively clutched to a shaft 39 fast with the shaft 3 by synchromesh clutches 45, 46. A gear 48 is freely mounted on a final driven shaft 42. A clutch G on the shaft 39 connects through a ratchet clutch 48a with the gear 48. Selection is effected either automatically by speed responsive means (not further described) or manually by a cross-shift electromagnet 52, Fig. 2, acting through a bell-crank lever 56 to slide a rod 55 axially against spring bias and engage a finger 57 with either of two notches 59, 60 on selector rods 62, 63, slidden axially for establishment of the forward ratios by energization of an establishing electromagnet 51 acting against spring bias through links 53, 54 to turn the rod 55 and finger 57. A reverse finger 58 can be engaged by a manually-operated link 65 with a notch 61 in a selector rod 64. To effect an upshift, e.g. from first ratio, with drive transmitted through the shaft 4, the countershaft 40 and the gears 47, 48 to the output shaft 42 to second ratio, the electromagnet 37, Fig. 1, is de-energized to release the impeller 30 and to disengage drive through the clutch disc 9. At the same time the clutch disc 6 is engaged. Simultaneously with de-energization of the electromagnet 37, the establishing electromagnet 52 is energized, but establishment is balked by non-synchronization of the parts to be clutched. The speed of rotation of the engine shaft 2 is retarded by the engagement of the clutch disc 6, and the light engagement of the clutch disc 9 effected by the springs 10a slows the rotation of the second ratio gears 43 &c. On synchronism, the selector rod 62 slides to establish the ratio and closes a switch to re-energize the electromagnet 37, disengage the clutch plate 6 and re-engage the clutch plate 9. The ratchet clutch 48a now over-runs. The shift sequence from second to third ratio is similar, the second ratio being disestablished by spring bias prior to establishment of third ratio. To establish fourth ratio (direct drive), all the electromagnets 37, 51, 52 are de-energized and the clutch disc 6 is engaged.