Patent GB-907659-A (GB)
Title: Improvements in or relating to automatic centrifugal clutches
IPC: F16D48/04
Filed: 1958-10-28
Abstract: 907,659. Clutch control. FRANCAISE DU FERODO S.A. Oct. 28, 1958 [Oct. 28, 1957; Jan. 18, 1958], No. 34546/58. Class 80 (2). In a motor vehicle clutch control wherein a centrifugally engaged friction clutch 13 is disengaged, during gear shift, by movement of a rod 32 of a servomotor 33 energized by liquid or gaseous pressure, as by engine inlet depression, as shown, or engine exhaust, on operation of a spring-loaded electromagnetic valve 39 actuated by movement by a gear shift lever 15, on release of the lever 15 a valve 46 regulated by engine inlet depression permits, at least during the first part, rapid return of the rod 32. In addition a servomotor 50 adjusting the engine throttle 54 is provided to ensure that, during gear shift, engine idling speed is maintained above that for centrifugal clutch disengagement even when the accelerator pedal is fully released during gear shift. In Fig. 1 the servomotor 33 is energized through a pipe 36 connected to a chamber 37, which, depending on the position of the valve 39, is connected to either a suction chamber 40, connected to the inlet manifold 44 and a vacuum reservoir 40a, or a chamber 41 connected to atmosphere, by way of a pipe 45 and a filter 45a, through parallel means comprising a small orifice 48 and the valve 46. The valve 46 is controlled by an adjustable spring 47 and, through a stem 46<SP>1</SP>, by an adjustable spring-loaded diaphragm M which is actuated by inlet depression through a pipe 80. The servomotor 50 is also connected, by pipes 49, 36, to the chamber 37 and is thereby energized simultaneously with the servomotor 33. In operation, when the lever 15 is released the rate of return of the rod 32 is arranged to be dependent on the degree of engine acceleration and also on a strong spring 56 which may be a compression spring in the servomotor 33, as shown, or a tension spring between the rod 32 and a flexible cable attached to the chassis. In the event of considerable acceleration, resulting in the lower position of the diaphragm M due to low manifold vacuum, the valve 46 is opened wide thereby permitting rapid return of the rod 32 for instantaneous clutch engagement; whereas in the event of negligible or no acceleration, resulting in the upper position of the diaphragm M due to high manifold vacuum, the valve 46, as first opened, closes rapidly and the remainder of the pressure balance is by way of the orifice 48 thereby permitting only gradual return of the rod 32 for possible clutch engagement. When engine braking is intended and the accelerator pedal and the lever 15 are released, the engine speed tends to drop to that of normal idling, at which speed the centrifugal clutch is inoperative, due to the return of the servomotor 50 to the inoperative condition. In order that engagement of the clutch may be effected before the engine speed drops to that approaching normal idling the strong spring 56, which has a force similar to that of the main clutch springs and is operative only during the first part of the return movement of the rod 32, such part being between #th and ¢ of the total rod movement, imparts a returning impulse to the rod which effects initiation of a clutch engagement, the final return of the rod being effected gradually. Accordingly, the increased idling speed as determined by the energized servomotor 50 may be low, e.g. 1.5 X normal idling speed. The embodiments in Fig. 4 and Figs. 5, 6 (not shown) may incorporate the spring 56. In Fig. 4 a centrifugal governor switch 70 driven by the gear-box input, intermediate or, as shown, output shaft by way of a shaft 60 of the speedometer, energizes a solenoid 68 when the vehicle speed falls below 15 K.p.h. to actuate a spring-loaded two-way valve 65 to block a suction line 64 from the chamber 37 to the servomotor 50 and to admit atmosphere, by way of a small orifice 72, which may have a filter, and a pipe 61, to the servomotor 50 to render it inoperative, and to open a spring- loaded valve 73 thereby connecting the chamber 41 to atmosphere by way of pipes 45, 77, 78 to ensure at starting and low speeds an immediate complete return of the rod 32 on release of the lever 15 thereby ensuring starting entirely controlled by centrifugal clutch. In Fig. 5 (not shown) the pipe 78 is dispensed with and the valve 73, now two-way, is arranged in a line replacing the pipe 80 so that the diaphragm M, subjected to atmosphere through the pipe 45 and the chambers of the valve 73 opens the valve 46 to connect the chamber 41 to atmosphere when the vehicle speed falls below 15 K.p.h. The valve 73, which may be solenoid actuated separately from the valve 65, may, as an alternative to the solenoid operation shown, be pneumatically, hydraulically or directly actuated by means dependent on the governor shaft 60. In Fig. 6 (not shown) the plunger of the solenoid 68, Fig. 4, acts directly on a spring- loaded two-way valve and, through a spring, on a spring-loaded valve so that on energization of the solenoid by the governor 60, when the vehicle speed falls below 15 K.p.h., suction is cut-off from the engine-throttle servomotor 50, which is connected to atmosphere through a small orifice, and the chamber 41 is connected directly to atmosphere. Centrifugal clutch.-A driven plate 13, preferably of the axially compressible type, is gripped between a flywheel 10 and a presser plate 12 reacting through pre-compressed springs 16 on a reaction plate 17. Centrifugal masses 18 (Fig. 2) pivoted on a plate 20 fast on the flywheel act on the reaction plate 17 to permit the springs 16 to effect engagement. Weak springs 21 separate the plates 17, 20 on disengagement to release the driven plate 13. The pressure plate is withdrawn, against the clutch springs 16, a weak spring 55, and, where applicable, the spring 56, independently of the action of the masses 18, by the servomotor rod 32 through a lever 31, a fork 29, a thrust ring 28, a release collar 27, levers 23 and tie rods 25 pivoted on the presser plate 12. Reference has been directed by the Comptroller to Specification 804,525.