| 摘要 |
1,083,890. Transistor switching circuits. ROBERT BOSCH G.m.b.H. Dec. 18, 1964 [Dec. 19, 1963], No. 51502/64. Heading H3T. [Also in Division F2] In a control for motor vehicle electromagnetic friction clutch, wherein a monostable multivibrator supplies current pulses to the clutch magnetizing winding 42 at a frequency dependent on engine speed the relation between the engine speed and the clutch torque is rendered independent of the air gap by means which reduces the length of the multivibrator pulses in response to the increase in the inductance of the magnetizing winding 42 so as to reduce the main clutch magnetizing current for a certain engine speed. The multivibrator 17, 22 is triggered by primary ignition pulses supplied from contact breaker 2 to the base of the input transistor 17 through a pulse shaping circuit and a capacitor 13. During the unstable state of the multivibrator transistors 22, 32 and 38 are conducting. A differential transformer has three windings: 41, connected in series with the magnetizing winding 42; 37, connected in series with a complex collector impedance of the transistor 32 comprising an inductor 35 and a resistor 36; and 31. The windings 37, 41 are arranged so that at maximum air gap their magnetic fields cancel each other. When the air gap reduces owing to lining wear and the inductance of the winding 42 increases, the RL combination 42, 43, becomes larger than 35, 36 so that a voltage is induced in the winding 31, is rectified by a diode 30 and is smoothed by a network 27, 28, 29. Thus, a negative D.C. control voltage occurs at the capacitor 28 and is applied through a diode 26 to the junction of the capacitor 21 and a resistor 25 to reduce the multivibrator pulse duration with reduction in air gap. |
