A method for controlling hydraulic line pressure of a hydraulic control system in transmission includes determining an available flow from a plurality of hydraulic pumps, determining a flow consumption of functions served by the hydraulic control system, determining an estimated hydraulic line pressure based upon the flow from the pumps and the flow consumption, determining a desired hydraulic line pressure, and controlling the hydraulic pumps based upon the desired hydraulic line pressure and the estimated hydraulic line pressure.

Method and apparatus to control hydraulic line pressure in an electro-mechanical transmission

In one embodiment, an oil pressure control apparatus includes a belt-driven continuously variable transmission, a lockup clutch provided in a torque converter, a primary regulator valve that regulates a line oil pressure that becomes a source pressure of oil pressure of various parts, and a lockup control valve that performs switching when controlling engagement/release of the lockup clutch. Control of the primary regulator valve and control of the lockup control valve are performed with a single linear solenoid valve. In this case, control of the primary regulator valve and control of the lockup control valve are performed in different ranges.

Oil pressure control apparatus

A torque ratio (Tr), which is the ratio of the maximum torque that can be transmitted by a continuously variable transmission with respect to the torque that is actually transmitted by the continuously variable transmission, is estimated on the basis of a transmission characteristic that an arbitrary variable component of an input axle element is transmitted to an output axle element by way of a friction element. In the estimation, the torque ratio (Tr) is estimated from a slip identifier (ID slip ) obtained by indexing the amplitude difference between variable components of both the input axle element and the output axle element, or is estimated from a phase lag (Δφ) obtained by indexing the phase difference between the variable components of both the input axle element and the output axle element. The torque ratio (Tr) which is extremely closely related to power transmission efficiency of the continuously variable transmission can therefore be accurately estimated to improve the power transmission efficiency. In addition, since the torque ratio (Tr) is estimated using the slip identifier (ID slip ) or the phase lag (Δφ), the number of sensors required to estimate the torque ratio (Tr) can be reduced and cost can therefore be reduced.

Torque ratio estimating apparatus for continuously variable transmission and lateral pressure control apparatus for continuously variable transmission

A system and method involves a machine having a power train including a continuously variable transmission (CVT) associated with a plurality of virtual gear ratios. To shift between the plurality of virtual gear ratios, the machine may include an operator input device that may be movable between a plurality of distinct positions. A first position may be associated with a neutral position in which no shifting of virtual gear ratios occurs. A second position of the operator input device may be associated with a first incremental rate for shifting between the virtual gear ratios. A third position may be associated with a second incremental rate for shifting between the virtual gear ratios which is different than the first incremental rate.

Shifting virtual gears associated with a continuously variable transmission

A transmission controller determines whether a shift is a kickdown, and when the shift is determined as the kickdown, the target line pressure is increased to a first target pressure corresponding to an input torque to a continuously variable transmission increased by the kickdown; the transmission controller then determines whether the line pressure has reached the first target pressure, and if determined that the line pressure has reached the first target pressure, the target line pressure is increased to a second target pressure higher than the first target pressure.

Continuously variable transmission and a hydraulic control method thereof

In a line pressure control apparatus of a belt-drive CVT, a shift is achieved by varying V-groove widths of primary and secondary pulleys by a differential pressure between primary and secondary pulley pressures, originating from line pressure. The differential pressure is created by bringing a shift actuator, such as a step motor, into a control position corresponding to a target transmission ratio. The target transmission ratio is calculated based on a theoretical transmission ratio based on engine-and-vehicle operating conditions, taking account of a hardware response delay and a disturbance. The target transmission ratio is converted into a reference-model operative position, corresponding to a reference-model number-of-steps of the shift actuator. An actual transmission ratio is converted into an actual-transmission-ratio related operative position. Line pressure is corrected in a manner so as to reduce the positional deviation between the reference-model operative position and the actual-transmission-ratio related operative position.

Line pressure control apparatus for belt-drive continuously variable transmission

A positional deviation ERRstep of a step motor 27 is calculated on the basis of a reference model step StepMdl, an actual speed ratio-corresponding step Bstep, and an added value obtained by adding together a target deviation GTstep, calculated in accordance with a transmission input torque Ti, and a starting learned value Gstep. When the transmission input torque Ti is large, the target deviation GTstep is increased in accordance with the transmission input torque Ti. A line pressure PL is then controlled on the basis of the positional deviation ERRstep obtained as a result.

Kim Seon Jae

Papers

Line pressure control apparatus for belt-drive continuously variable transmission

Control device of line pressure for continuously variable transmission