| 摘要 |
<p>975,656. Counter pressure brakes. ROBERT BOSCH G.m.b.H. Jan. 15, 1962 [Jan. 14, 1961], No. 1406/62. Heading B7H. [Also in Divisions F1 and H3] A dynamic brake for a vehicle, comprising a flap 12 disposed in the engine exhaust, pipe, is operable only when the engine speed exceeds a predetermined value. Impulses from the ignition system, which comprises contact breaker 21 and ignition coil 15 are passed through the primary of a transformer 26. Connected to the secondary is a diode 34 in series with the parallel combination of resistor 39 and capacitor 40, across which is produced a D.C. potential proportional to engine speed. The arrangement also comprises a pair of cross-coupled transistors 33, 34, the forward coupling path comprising resistor 43 and the back-coupling path potentiometer 45, 46 and resistor 37; the base of transistor 33 is connected to resistor 39 by way of diode 35. At low engine speeds the voltage across resistor 39 is low, the transistor 33 conductive and transistor 44 non-conductive so that closure of the brake control switch 48 will not result in energization of the solenoid 13. When, however, the engine speed exceeds a predetermined value, the voltage across resistor 39 is sufficiently positive to bias transistor 33 non-conductive, whereupon transistor 44 becomes conductive, and if switch 48 is then closed energization of solenoid 13 ensues to operate the flap 12. Capacitor 50 removes any residual ripple from the voltage at the base of transistor 33, while a diode 49 prevents induced voltage peaks from the solenoid 13 reaching the transistor 44. The arrangement may also be used to block the supply of fuel to the engine.</p> |
