To provide a failure detecting device for an automatic transmission for a vehicle capable of correctly detecting abnormality in an engagement element by detecting rotation speed of one rotation element in addition to input rotation speed and output rotation speed in the automatic transmission for a vehicle.
When rotation speed NS2 of one intermediate rotation element (second sun gear S2) is detected among rotation elements that are not integrally rotated with an input shaft 18 or an output gear 20, among rotation elements in the automatic transmission 16, rotation speed of a prescribed rotation element that is different from above intermediate rotation element is determined based on rotation speed NM of the intermediate rotation element with relation indicated by an expression in drawing 4. Differential rotation ΔN for an engagement element is determined to selectively connect the prescribed rotation element to another rotation element or a non-rotating member based on the rotation speed of the prescribed rotation element, and abnormality related to the engagement element is determined based on the differential rotation ΔN of the engagement element. Actuation defective of the engagement element in the automatic transmission 16 can thus be detected with favorable precision.
KIMURA HIROMICHI
WATANABE KAZUYUKI
OSHIMA YASUTSUGU
YASUDA YUJI
MORISE MASARU
SUGIMURA TOSHIO
