PURPOSE: To surely diagnose the abnormality of a general hydraulic pressure control system by a simple constitution regardless of during operation or suspension.
CONSTITUTION: An actuator 5 and pressure detector 6 are provided in a bent circuit 43 of a reducing valve 42 which is provided on the hydraulic pressure control system 4 which is an object of diagnosis. A prescribed oil pressure is introduced into the bent circuit 43 with the actuator 5 and the fluctuation of pressure that is generated in the bent circuit 43 at this time is detected with the pressure detector 6. Both or one of the magnitude of amplitude of fluctuation in pressure that is detected with the pressure detector 6 and the length of time until the oil pressure is converged to a certain pressure is checked with a diagnostic device 7 and the abnormality of the hydraulic pressure control system 4 is quantitatively diagnosed based on that result. The operator is informed by properly indicating the diagnostic result with the diagnostic device 7 in an indicating part 8.
KASHIMOTO HISAO
DEGUCHI SADAMI
KONO TOMIICHI
MORI SHOJI
