The transmission controller is configured to, when the received range position signal indicates that the range position is switched from a travelling range to a neutral range during travelling, output an instruction to disengage all of friction elements that are in an engaged state in the travelling range, output an instruction to at least one friction element before the instruction to disengage all of the friction elements that are in the engaged state in the travelling range is output, confirm a change in a rotation speed of a transmission input shaft after the instruction to disengage is output to the at least one friction element, and when there is no change in the rotation speed, diagnose that the friction element instructed to be disengaged is in an erroneously engaged state in which the friction element is not able to be disengaged.

The control device is configured to supply an offset current value to disengagement solenoids of disengagement-side friction engaging elements among a plurality of shift solenoids that control respective shift oil pressures applied to the plurality of friction engaging elements, and when a current gear position is a first speed position or a reverse position, decrease a current value to be supplied to at least one of the disengagement solenoids that are supplied with the offset current value to be lower than the offset current value.

The control method for a constant speed running of a vehicle performs a vehicle speed control for downshifting the gear position of the automatic transmission when the acceleration/deceleration of the vehicle is larger than the determination value during the constant speed running control. In the control method, the automatic transmission includes a plurality of gear positions that can be downshifted during the constant speed running control, and among the plurality of gear positions, the determination value between the gear positions having a relatively large difference in the gear ratio between the gear positions is set to be larger than the determination value between the gear positions having a relatively small difference in the gear ratio between the gear positions.

The control device is configured to supply an offset current value to disengagement solenoids of disengagement-side friction engaging elements among a plurality of shift solenoids that control respective shift oil pressures applied to the plurality of friction engaging elements, and when a current gear position is a first speed position or a reverse position, decrease a current value to be supplied to at least one of the disengagement solenoids that are supplied with the offset current value to be lower than the offset current value.

The transmission controller is configured to, when the received range position signal indicates that the range position is switched from a travelling range to a neutral range during travelling, output an instruction to disengage all of friction elements that are in an engaged state in the travelling range, output an instruction to at least one friction element before the instruction to disengage all of the friction elements that are in the engaged state in the travelling range is output, confirm a change in a rotation speed of a transmission input shaft after the instruction to disengage is output to the at least one friction element, and when there is no change in the rotation speed, diagnose that the friction element instructed to be disengaged is in an erroneously engaged state in which the friction element is not able to be disengaged.

A method for operating a vehicle drive train (1) includes, during a downshift, disengaging at least one shift element (A through F) from a power flow of the transmission (5), guiding a power transmission capacity of a torque converter lockup clutch (4) to a level at which the torque converter lockup clutch (4) is in a non-slip operating condition during a positive engine override when a rotational speed of a prime mover (2) is guided towards a synchronous speed of a demanded desired ratio, and guiding the power transmission capacity of the torque converter lockup clutch (4)—no later than a point in time of the downshift at which the rotational speed of the prime mover (2) is equal to the synchronous speed of the desired ratio—to a level at which the torque converter lockup clutch (4) is transferred into a continuous slip operation due to torque.

An anomaly determination apparatus for a vehicle that includes a transmission includes an execution device and a memory device. The memory device is configured to store map data that defines pre-trained map, which has been trained through machine learning. When a variable representing time-series data of a rotation speed of a gear is fed to the map as an input variable, the map outputs a state variable representing a state of the gear as an output variable. The execution device is configured to execute: an obtaining process that obtains the variable representing the time-series data as a value of the input variable; and a determination process that determines whether there is an anomaly in the transmission based on a value of the output variable that is output by the map when the value of the input variable is fed to the map.

A transmission ratio controller includes circuitry including a transmission ratio calculator and a monitor. The transmission ratio calculator calculates a transmission ratio using a first transmission ratio map when a specified parameter satisfies a first condition, and using a second transmission ratio map when the specified parameter satisfies a second condition. When the specified parameter satisfies the first condition, the internal combustion engine is in a first state. When the specified parameter satisfies the second condition, the internal combustion engine is in a second state. In the first state, the monitor calculates a hypothetical transmission ratio using the second transmission ratio map based on the second state. On a condition that the transmission ratio calculated in the first state differs from the hypothetical transmission ratio by a predetermined reference value or greater, the monitor determines that the transmission ratio has a possibility of differing in accordance with the specified parameter.

A transmission ratio controller includes circuitry that includes a transmission ratio calculator calculating a request transmission ratio, a transmission ratio instructor transmitting a control signal, and an abnormality determiner. The request transmission ratio is calculated using a first transmission ratio map when a specified parameter satisfies a first condition, and a second transmission ratio map when the specified parameter satisfies a second condition. The internal combustion engine is in a first state when the specified parameter satisfies the first condition, and in a second state when the specified parameter satisfies the second condition. In the first state, the abnormality determiner calculates a hypothetical transmission ratio using the second transmission ratio map based on the second state. The abnormality determiner determines an abnormality based on a comparison of the hypothetical transmission ratio with at least one of the request transmission ratio, an instruction transmission ratio, or an actual transmission ratio.

A transmission ratio controller includes circuitry. The circuitry includes a transmission ratio calculator configured to calculate a request transmission ratio to a transmission mechanism, a transmission ratio instructor configured to output a control signal based on the request transmission ratio, and an abnormality determiner configured to determine whether a transmission ratio of the transmission mechanism is abnormal. At least two of the request transmission ratio, an instruction transmission ratio corresponding to the control signal, or an actual transmission ratio achieved by the transmission mechanism are transmission ratios subject to comparison. The abnormality determiner is configured to determine that when a difference obtained by comparing the transmission ratios subject to comparison is greater than or equal to a predetermined specified value, the transmission ratio of the transmission mechanism is abnormal.