| 摘要 |
PURPOSE:To surely detect such a condition that no speed signal is generated during running of a vehicle to enable the control of a speed change gear to be shifted into a safety side, by detecting the presence of a speed signal in consideration with the running condition of the vehicle. CONSTITUTION:A vehicle speed sensor 4a issues an electrical signal indicating the speed of a vehicle, an engine speed sensor 4b issues an electrical signal indicating the rotation of an engine, and a clutch sensor 4c issues a signal which is turned on when a clutch plate is in its contact condition. A diagnosis device 7 diagnoses abnormality of an speed change control signal and a power unit 1, and if it is abnormal, an alarm signal is issued by means of a lamp 6a and a buzzer 6b. The power unit 1 is composed of a speed change gear 11, a selecting cylinder 12, a shift cylinder 13, an air reservoir 14, solenoid valves 15a-15d, selected position sensors 16a-16c, shift sensors 17a-17c and an air pressure sensor 18, and signals from the sensors 17a, 17c indicate the gear meshing condition of the speed change gear 11. |
