A failure judgment device of an automatic transmission includes: a first abnormality judging section configured to judge a power supply fault abnormality or a breaking abnormality of the solenoid, from a selected shift stage and a state of the transmission mechanism, after the detection of the electric abnormality; and a second abnormality judging section configured to judge the power supply abnormality or the breaking abnormality of the solenoid, from the monitor current value when the solenoid valve is switched to an OFF state, after the detection of the electric abnormality, when one of the first abnormality judging section and the second abnormality judging section judges the power supply fault abnormality or the breaking abnormality, the judgement result being outputted.

In the present invention, a secondary pressure solenoid valve (74) for adjusting the pressure of oil supplied from an oil pump (70) so as to make the same an indicated pressure and a CVT control unit (8) for determining whether the adjustment operation of the secondary pressure solenoid valve (74) is normal are provided. This device for determining the normality of an electromagnetic control valve is provided with a secondary pressure sensor (82) for detecting the actual pressure arrived at through adjustment by the secondary pressure solenoid valve (74). The CVT control unit (8) uses a plurality of non-overlapping indicated pressure regions as determination regions for determining the normality of the adjustment operation of the secondary pressure solenoid valve (74). If the difference between the indicated pressure and actual pressure is determined to be less than a threshold in each of the plurality of indicated pressure regions, a determination is made that the secondary pressure solenoid valve (74) is normal. As a result, when determining whether the adjustment operation of an electromagnetic control valve is normal, it is possible to avoid erroneous determinations when a failure occurs and accurately determine the normality of the adjustment operation of the electromagnetic control valve.

A utility vehicle comprises a traveling driving power source which generates rotational driving power for driving a drive wheel; a continuously variable transmission including an input shaft to which the rotational driving power transmitted from the traveling driving power source is input, an output shaft which outputs the rotational driving power toward the drive wheel, a drive pulley provided at the input shaft, a driven pulley provided at the output shaft, and a belt wrapped around the drive pulley and the driven pulley; a clutch which is disposed in a driving power transmission path at a location that is between the belt and the drive wheel and is capable of disconnecting the driving power transmission path; and a clutch actuator which operates the clutch.

Provided are a control device and a control method of a continuously variable transmission capable of preventing an endless member from slipping even when a parking lock is released. On a condition that a vehicle is in an idling stop state and a parking lock mechanism is in a parking lock state, rotation speed increase control configured to increase a rotation speed of an electric oil pump is executed so that the endless member can be prevented from slipping with respect to a driven pulley even when the parking lock mechanism is switched to a parking lock released state.

A transmission speed control system for a walk-behind lawn mower includes a transmission, a transmission positioning assembly, and an electronic control unit. The transmission is tiltable about and operably engaged with a drive axle shaft. The transmission positioning assembly tilts the transmission between first and second angular positions. A belt tension between a drive belt and a transmission pulley of the transmission continuously increases from a minimum belt tension when the transmission is in the first angular position to a maximum belt tension when the transmission is in the second angular position. The rotational drive force exerted on the drive axle shaft by the transmission and a resulting driving speed of the lawn mower vary proportionally with the belt tension. The electronic control unit controls the transmission positioning assembly to tilt the transmission based on target and detected driving speeds.

A control apparatus for a vehicle drive-force transmitting apparatus that includes a gear mechanism and a continuously-variable transmission mechanism. The control apparatus determines whether there is a lower-gear-ratio setting request requesting a target gear ratio of the continuously-variable transmission mechanism to be set to a lower gear ratio that is lower than a highest gear ratio of the continuously-variable transmission mechanism. When it is determined that there is not a detection accuracy of a rotational speed of an output rotary member of the drive-force transmitting apparatus, the control apparatus sets the target gear ratio to the lower gear ratio if it is determined that there is the lower-gear-ratio setting request, and sets the target gear ratio to the highest gear ratio if it is determined that there is not the lower-gear-ratio setting request.

A method for controlling a gear ratio of a continuously variable transmission vehicle includes: a step of detecting a position of a shift lever by a controller; a step of checking, by the controller, a gear ratio variation based on a difference between a desired stage gear ratio and a current gear ratio in a continuously variable transmission when the shift lever is detected to be positioned in a manual range; a step of calculating, by the controller, a gear ratio correction value based on a rate of change of engine RPM when the gear ratio variation is checked as being other than zero after the step of checking the gear ratio variation; and a step of correcting, by the controller, the gear ratio variation in response to the calculated gear ratio correction value after the calculation step.

A vehicle includes a power plant, continuously variable transmission (CVT), drive wheels, sensors, and controller. The CVT achieves a fixed gear/positive engagement and friction drive modes, and includes an input member that receives input torque from the power plant, an output member, and a variator assembly having drive and driven variator pulleys. The pulleys are connected to each other via an endless rotatable drive element, and to a respective one of the input and output members. Pulley actuators change a CVT speed ratio. The controller calculates a relative slip of the pulleys using measured speeds and displacements from the sensors, reduces the relative slip until the relative slip is below a calibrated speed limit or within a calibrated speed range via actuator control signal to the pulley actuators, and commands the fixed gear/positive engagement mode via positive engagement control signals to the CVT until the relative slip reaches zero.

A primary clutch of a continuously variable transmission with a launch mechanism is provided. The primary clutch includes a central post, a fixed sheave assembly, a movable sheave assembly and a locking mechanism. The central post is configured to receive rotational torque from a motor. The fixed sheave assembly is statically mounted on the central post. The movable sheave assembly is mounted on the central post. The movable sheave assembly includes a movable sheave system that is configured to move axially on the central post towards the fixed sheave assembly as RPM of the primary clutch increase. The locking mechanism is configured and arranged to selectively prevent movement of the movable sheave system independent of the RPM of the primary clutch.

A method for controlling a gear ratio of a continuously variable transmission vehicle includes: a step of detecting a position of a shift lever by a controller; a step of checking, by the controller, a gear ratio variation based on a difference between a desired stage gear ratio and a current gear ratio in a continuously variable transmission when the shift lever is detected to be positioned in a manual range; a step of calculating, by the controller, a gear ratio correction value based on a rate of change of engine RPM when the gear ratio variation is checked as being other than zero after the step of checking the gear ratio variation; and a step of correcting, by the controller, the gear ratio variation in response to the calculated gear ratio correction value after the calculation step.