Patent ID: 6357289
Filing Date: 2002-03-19
Classification: F16H

Abstract:
An automatic transmission control system having a fail-safe function for an automatic transmission, comprising:sensor means for detecting at least a throttle opening and a vehicle speed; a gear mode determination means for determining a current gear mode based on the throttle opening and the vehicle speed; an engagement-disengagement command means for outputting a command based on the current gear mode determined by said gear mode determination means and corresponding to engagements and disengagements for a plurality of engaging elements to an actuator which operates the engaging elements; a transmission gear train which performs a multi-step speed-change by a combination of engagements and disengagements of the engaging elements; a set ON-OFF state storage means for estimating a normal state of engagements and disengagements of the engaging elements based on the current gear mode, and for storing the normal state of engagements and disengagements of the engaging elements; an actual ON-OFF state detection means for detecting an actual state of engagements and disengagements of the engaging elements; an actual ON-OFF state storage means for storing the actual state of engagements and disengagements of the engaging elements; a comparison-and-determination means for comparing the normal state of engagements and disengagements of the engaging elements, stored in said set ON-OFF state storage means, with the actual state of engagements and disengagements of the engaging elements, stored in said actual ON-OFF state storage means, and for determining that a hydraulic system failure occurs when the actual state detected and the normal state estimated disagree with each other; and a fail-safe mode engagement-disengagement command means for selecting a specified gear mode based on the actual state of engagements and disengagements of the engaging elements, stored in said actual ON-OFF state storage means, and for outputting a command corresponding to engagements and disengagements of the engaging elements to the actuator so that the automatic transmission is shifted to the specified gear mode which is preprogrammed to be suitable for the actual state, only when said comparison-and-determination means determines that the hydraulic system failure occurs.