| 摘要 |
1,193,784. Change-speed control. CATERPILLAR TRACTOR CO. 25 Jan., 1968 [30 Jan., 1967], No. 3889/68. Heading F2D. A down-shift indicator or control for a machine such as an earth-moving vehicle to prevent overspeeding of the engine, comprises a detector for producing a signal proportional to engine speed which is compared with a reference signal representative of an engine speed below which a downshift may be safely effected and a circuit responsive to the first signal being greater than the reference signal for operating an indicator or actuating a shift-lock. As shown, a magnetic detector produces a waveform 24 the positive pulses 31 of which are passed via diode 28 to a Schmitt trigger 33 whose output is converted by a monostable vibrator 37 to a square wave 39 of constant amplitude and pulse width. Wave 39 is averaged by a frequency-D.C. converter 41 to a D.C. output 42. An operational amplifier 43 compares output 42 with a D.C. reference signal from a source 44 and if output 42 is greater, the resultant signal is passed to a control circuit 46 including a lamp 51 normally energized through a transistor 49. The said resultant signal causes a second transistor 48 to drive transistor 49 to its non-conducting state so that lamp 51 is turned off indicating that downshifting is unsafe. |
