GB1154327A - Improvements in Vehicle Clutch Control Mechanisms - Google Patents

Abstract

1,154,327. Clutch control; valves. ROBERT BOSCH G.m.b.H. 19 May, 1966 [20 May, 1965; Sept., 1965(2)], No. 22224/66. Headings F2L and F2V. [Also in Division H3] A normally engaged motor vehicle friction clutch 12 is disengaged by a servomotor 14 (Fig. 1), which is energized by engine induction manifold negative gaseous pressure through an electromagnetic regulating valve and follower 37, 20, the valve 37 being so controlled by a transistor device 44 (see control block diagram, Fig. 7) that (1) for moving off, the clutch disengaging force decreases with increasing engine speed; and (2) on manual or automatic gear shift, the clutch is automatically rapidly disengaged and, to prevent acceleration jerks on completion of shift, so re-engaged that its transmissible torque is maintained, for a predetermined period at a proportion of its maximum transmissible torque, such proportion being determined by accelerator pedal position. The arrangement may be used for conversion of a conventional foot-operated clutch. A follower valve spool 33 is leftwardly and rightwardly moved to connect a port 19 to the servomotor 14 respectively to atmosphere through a port 27 and a filter 28, and a port 21 to a negative pressure reservoir 25, and, through a non-return valve 23, the engine induction manifold 24. A control diaphragm 29 divides a control cylinder 30 into two chambers 31, 32 is mechanically connected to the spool 33, and resiliently centre-biases the latter so that both ports 27 21 are closed. A feedback channel 34 connects the ports 19 and the chamber 31, and, to pressurebalance the spool 33, a passage (not shown), connects the left hand end face of the spool to the chamber 31. A line 35 connects the chamber 32 to one port 36 of the electromagnetic regulating valve 37 another port 38 of which is connected also to the reservoir and manifold 25, 24. The electromagnetic valve 37 comprises a valve disc 40, accommodated in a synthetic material casing (65), (Fig. 6, not shown), and urged by a weak spring (67) against the upper edge of a disc seat of an orifice 39 connected to the port 38. The housing comprising the ports 36, 38 is of non-magnetic material. A coil 41 is mounted on a hollow iron core (59) the lower end of which provides a further seat for the disc 40. The side of the disc 40 facing the core is faced with a coating of a synthetic material to form an air gap. The disc 40 has peripheral indentations to allow downward air flow. The spring (67), by closing the orifice (39), prevents continuous dissipation of the negative pressure when the valve is not energized. A regulated negative pressure, p r appearing at the port 36, and consequently, in the steady state, as p v , at the follower port 19 and the servomotor 14, is solely dependent on a control current, I s to the coil 41. With decreasing current I s , the negative pressure p v decreases and the clutch transmissible torque M k increases. The transistor device 44 comprises battery and earth terminals 46, 47, an output 45 to the coil 41 and four control inputs, viz: 49, engine speed, provided by a succession of pulses of a contact breaker of an ignition distributer 53; 50, vehicle speed, provided by an electric tachometer 54 on or in the gear-box 13; 51, gear shift, provided by an electronic control system of an automatic change speed gear or, as shown, by a switch 58 built into a manual gear shift lever 57; and 52, accelerator pedal position provided by a position follower 56 coupled to the accelerator pedal 55. Operation. Moving off.-Between 0 and approximately 15 k.p.h. a vehicle speed dependent switch 104 (see control block diagram Fig. 7), causes switches 101, 103 to be ON and OFF respectively. The pulses of a monostable multivibrator 100, responsive to said ignition system pulses, are applied to the coil 41 by a switch 107. The pulse duration t i of the multivibrator is almost constant; the last transistor switch controlling the coil 41 is blocked during the pulse duration t i and conducts during the pulse pause t p ; and the mean control current Is is proportional to the duty ratio t p /pulse periodic time T which ratio decreases with increasing engine speed. The system is such that the clutch is disengaged at idling, and when engine speed is between 1500 and 1800 r.p.m., the clutch transmits full engine torque. At approximately 15 k.p.h. the switch 104 changes the switches 101, 103 to OFF and ON respectively. On gear shift, a changeover switch 107 connects the coil 41 directly to the positive battery terminal U B for rapid clutch disengagement. On completion of shift, the changeover switch 107 reverts and a timer 105, put into operation by the trailing edge of the gear change signal, switches a switch 106 ON to connect an unstable multivibrator 102 to the coil 41 for a predetermined period. The unstable multivibrator produces a pulse sequence the duty ratio of which is dependent on accelerator pedal position. The current produced by the pulses in the valve coil 41 is smoothed by the coil inductance in conjunction with a diode connected in parallel with the coil. (For the circuit of the transistor device 44, see Division H3).