A hydrodynamic clutch having an input side and an output side, the rotational motions of which are coupled to one another with a hydraulic fluid. A method for determining the degree of filling of the hydrodynamic clutch with fluid including steps of periodically sensing a fluid temperature of the hydraulic fluid, determining the thermal output supplied to the clutch on the basis of the temperature, determining a lambda value on the basis of the thermal output and determining the degree of filling on the basis of the lambda value.

A method determines the travel of a clutch in a hydraulic clutch-actuation system. A hydraulic signal which extends between a transmitting end and a receiving end is acted upon by an acoustic signal for the generation of a wave packet. The acoustic signal on the transmitting end of the clutch-actuation system is fed into the hydraulic fluid, a wave packet generated by the acoustic signal on the receiving end is reflected back to the transmitting end, a running time of the transmitted and reflected wave packet on the transmitting end is evaluated to determine the coupling travel.

A control apparatus for a synchronous meshing mechanism that is equipped with a gear, a sleeve, a synchronizer ring, and a hydraulic actuator is provided. When it is determined that the sleeve and the gear have been rotationally synchronized with each other in an engagement transition period of the synchronous meshing mechanism, an electronic control unit with which the control apparatus is equipped sets a command pressure for the hydraulic actuator to an intermediate pressure that is lower than a meshing completion pressure. Besides, when meshing has not been completed even after the lapse of a predetermined time from a timing when the command pressure for the hydraulic actuator is set to the intermediate pressure, the electronic control unit sets the command pressure for the hydraulic actuator to the meshing completion pressure.

A clutch control method, including: determining whether a current vehicle state satisfies a condition for a clutch to enter a sliding friction state; if so, controlling the clutch to enter the sliding friction state, and determining a target sliding friction rotating speed of the clutch; determining whether the current vehicle state satisfies a condition for entering a clutch torque deviation collecting state; if so, collecting a torque deviation once and storing the torque deviation; at an end of an adjustment period, accumulating all torque deviations collected previously and taking an average value according to an accumulation number of times, so as to obtain an average torque deviation; if the average torque deviation exceeds a preset deviation threshold, recording the average torque deviation; and if the current vehicle state satisfies a condition for entering a deviation applying state, adjusting a current clutch friction coefficient according to the recorded average torque deviation.

A control apparatus for a synchronous meshing mechanism that is equipped with a gear, a sleeve, a synchronizer ring, and a hydraulic actuator is provided. When it is determined that the sleeve and the gear have been rotationally synchronized with each other in an engagement transition period of the synchronous meshing mechanism, an electronic control unit with which the control apparatus is equipped sets a command pressure for the hydraulic actuator to an intermediate pressure that is lower than a meshing completion pressure. Besides, when meshing has not been completed even after the lapse of a predetermined time from a timing when the command pressure for the hydraulic actuator is set to the intermediate pressure, the electronic control unit sets the command pressure for the hydraulic actuator to the meshing completion pressure.

A method determines the travel of a clutch in a hydraulic clutch-actuation system. A hydraulic signal which extends between a transmitting end and a receiving end is acted upon by an acoustic signal for the generation of a wave packet. The acoustic signal on the transmitting end of the clutch-actuation system is fed into the hydraulic fluid, a wave packet generated by the acoustic signal on the receiving end is reflected back to the transmitting end, a running time of the transmitted and reflected wave packet on the transmitting end is evaluated to determine the coupling travel.

A basic pulse time setting section determines a basic pulse time for initial invalid stroke elimination by applying current values of oil temperature and throttle opening to the basic pulse time map. A subtraction time setting section determines a subtraction time by applying current values of oil temperature and clutch oil pressure to the subtraction time map. A pulse time determining section determines a predetermined initial invalid stroke elimination pulse time by subtracting the subtraction time from the basic pulse time. An initial invalid stroke elimination permission/inhibition determination section, at a starting timing of initial invalid stroke elimination, inhibits this-time initial invalid stroke elimination if the elapsed time from the execution timing of the preceding initial invalid stroke elimination is within the predetermined inhibition period.

A vehicle includes an engine, a transmission, and a controller. The transmission has clutches, a circuit configured to transport fluid to the clutches, a pump configured to circulate the fluid through the circuit, and an accumulator disposed along the circuit. The controller is programmed to, responsive to an engine start and a fluid temperature being less than a temperature threshold, discharge the accumulator to prime the pump.

One solenoid valve included in a hydraulic pressure control device has at least two functions among the following (1) to (6) functions, (1) switching a state of a two-way clutch, (2) switching a state of a parking lock mechanism, (3) switching the supply of hydraulic pressure to a first brake that is put into an engaged state when a gear stage selected when driving of a vehicle starts is set, (4) controlling a line pressure adjustment valve so that a decrease in a line pressure is prevented when the temperature of a hydraulic fluid is a first predetermined temperature or higher, (5) preventing the occurrence of a creep phenomenon in a neutral range when the temperature of the hydraulic fluid is a second predetermined temperature or lower, and (6) boosting a line pressure by performing switching to another linear solenoid valve when the line pressure adjustment valve has failed.

A control device of an automatic transmission controls an automatic transmission 1 comprising a transmission mechanism 3 including a plurality of engagement elements, and a hydraulic oil supply device 4 supplying hydraulic oil to the transmission mechanism The control device of the automatic transmission comprises an engagement element control part 41 configured to use the hydraulic oil supply device to make the plurality of engagement elements change between an engaged state and a disengaged state; and a deceleration degree calculating part 42 configured to calculate a target deceleration degree of a vehicle in which the automatic transmission is provided. The engagement element control part is configured to make the engagement element in the disengaged state engage so that the vehicle decelerates if the target deceleration degree is equal to or more than a predetermined value when an increase in temperature of hydraulic oil in the automatic transmission is demanded.