Monitor for hydraulic transmission

Claim 1

In an engine-driven vehicle having a hydraulic assist transmission including a control fluid circuit and a lubricating fluid circuit, a monitoring system comprising: an engine speed sensor; a lubricating fluid pressure sensor; a lubricating fluid temperature sensor; stored program means responsive to the engine speed, pressure and temperature sensors for periodically executing an algorithm comprising the steps of: (a) comparing the sensed fluid temperature to a threshold temperature and preventing generation of a warning signal if the sensed temperature is below said threshold temperature; (b) comparing the sensed engine speed to a low speed value and preventing generation of a warning signal if the sensed speed is below said low speed value; (c) comparing the sensed engine speed to a high speed value; (d) if the sensed speed is less than the high speed value, then computing an alarm value, Pa, as a function of the sensed engine speed and of the sensed fluid temperature; (e) if the sensed engine speed is greater than the high speed value, computing the alarm value, Pa, as a function of the high speed value and the sensed fluid temperature; (f) comparing the sensed fluid pressure to the computed alarm value, Pa, and generating a warning signal if the sensed pressure remains below the alarm value, Pa, for at least a predetermined time period; and an alarm means for generating an operator-detectable alarm signal in response to generation of the warning signal.