A clutch includes a clutch disk that rotates by receiving motive power from an engine and a clutch plate switched between an engaged state in which it is engaged with the clutch disk and a disengaged state in which it is not engaged with the clutch disk. A controller calculates a coefficient of friction μ between the clutch disk and the clutch plate based on a time period Δt elapsed from a first time point when the number of relative rotations of the clutch disk and the clutch plate attains to a first number of rotations to a second time point when a second number of rotations smaller than the first number of rotations is attained, in a state in which the clutch disk rotates while transfer of motive power from the engine to the clutch disk is cut off and in the engaged state.

A method and system are provided for shifting a vehicle transmission having several members. Each member is a first, second, or third node of a planetary gear set (of multiple planetary gear sets), or an input, output, or stationary member. A first torque transmitting mechanism is applied to transfer torque between first and second members in a low gear state. In some versions, a second torque transmitting mechanism is applied in the low gear state without substantially transferring torque between third and fourth members, and then the second torque transmitting mechanism is disengaged. A third torque transmitting mechanism is then applied without substantially transferring torque between the third and fourth members in the low gear state. The transmission is upshifted by disengaging the first torque transmitting mechanism, keeping the third torque transmitting mechanism applied, and applying the second torque transmitting mechanism to transfer torque between the third and fourth members.

A method of operating a transmission which is shifted to various operating conditions by engaging shifting elements. At least one of the shifting elements is an interlocking shifting element which has to be engaged to obtain at least one defined operating condition of the transmission during which force flows between an input and an output shaft. When a command is received to engage the interlocking shifting element, a rotational speed of the transmission input shaft is displaced in the direction toward a synchronous rotational speed produced in the engaged operating condition of the interlocking shifting element at least as a function of the rotational speed of the transmission output shaft. When the variation of the rotational speed of the transmission input shaft crosses a predefined rotational speed threshold, the interlocking shifting element is actuated in its engaging direction.

An automatic transmission is provided. The transmission includes clutches coaxially arranged in layers in a radial direction of the transmission. The transmission includes a piston provided to each clutch, the pistons being aligned in the radial direction on a same plane perpendicular to an axis of the transmission, without overlapping with each other in an axial view. The transmission includes a common rotational member having a wall, commonly used for the clutches, and disposed at a predetermined position of the transmission in an axial direction, wherein the wall is formed along the plane. The transmission includes operational hydraulic passages parallely arranged in the wall of the common rotational member in a circumferential direction of the transmission on the same plane perpendicular to the axis, each of the operational hydraulic passages communicating with one of operational hydraulic chambers of the respective clutches.

An automatic transmission is provided. The transmission includes clutches coaxially arranged in layers in a radial direction of the transmission. The transmission includes a piston provided to each clutch, the pistons being aligned in the radial direction on a same plane perpendicular to an axis of the transmission, without overlapping with each other in an axial view. The transmission includes a common rotational member having a wall, commonly used for the clutches, and disposed at a predetermined position of the transmission in an axial direction, wherein the wall is formed along the plane. The transmission includes operational hydraulic passages parallely arranged in the wall of the common rotational member in a circumferential direction of the transmission on the same plane perpendicular to the axis, each of the operational hydraulic passages communicating with one of operational hydraulic chambers of the respective clutches.

Disclosed is method for operating a multi-gear vehicle transmission having a plurality of shifting elements (A, B, C, D, E) for engaging gears of the vehicle transmission. In a neutral gear a transmission input (1) and a transmission output (2) of the vehicle transmission are decoupled from one another. In a driving gear the transmission input (1) and the transmission output (2) of the vehicle transmission are coupled with one another by closing the shifting elements (A, B, C, D, E) associated with the driving gear in order to propel the vehicle. When the neutral gear is engaged, a transmission condition is determined, and if a transmission condition with elevated drag losses exists, then in addition to the shifting elements (A, B, C, D, E) of a driving gear, at least one further shifting element (A, B, C, D, E) of the vehicle transmission is closed.

A method of controlling an automatic transmission is provided. The automatic transmission includes a piston having first and second surfaces opposite from each other, friction plates, engaging and disengaging hydraulic pressure chambers for supplying hydraulic pressure and directing the piston to push the friction plates to be engaged and disengaged, a hydraulic pressure control valve for supplying and discharging hydraulic pressure to and from the chambers, and first and second oil paths communicating the valve with the chambers. The second surface has a larger area for receiving hydraulic pressure than that of the first surface. The method includes controlling the friction plates to change from the disengaged state to the engaged state. Controlling the friction plates includes adjusting the hydraulic pressure to a first instruction pressure in a first period in response to a gear shift command, and to a second instruction pressure in a second period.

In a sleeve, two input ports are formed as ports that receive a discharge pressure of an electromagnetic pump, and a drain port connected to a drain oil passage is formed on the same circumference as that on which the input port is formed, so as to have a smaller opening area than the input port and an output port connected to an oil passage. The axial length of the second land is set so that the input port can be closed by the second land when a signal pressure is equal to or higher than a set pressure, and that the input port and the drain port can be closed by the second land when the signal pressure is lower than the set pressure.

In a sleeve, two input ports are formed as ports that receive a discharge pressure of an electromagnetic pump, and a drain port connected to a drain oil passage is formed on the same circumference as that on which the input port is formed, so as to have a smaller opening area than the input port and an output port connected to an oil passage. The axial length of the second land is set so that the input port can be closed by the second land when a signal pressure is equal to or higher than a set pressure, and that the input port and the drain port can be closed by the second land when the signal pressure is lower than the set pressure.

The present invention relates to a hybrid powertrain and method of controlling same, the hybrid powertrain comprising an internal combustion engine; a gearbox with an input and an output shaft; a range gearbox connected to the output shaft; a first planetary gear connected to the input shaft; a second planetary gear connected to the first planetary gear; a first electrical machine connected to the first planetary gear; a second electrical machine connected to the second planetary gear; one gear pair connected with the first planetary gear and the output shaft; and one gear pair connected with the second planetary gear and the output shaft, wherein the internal combustion engine is connected with the first planetary gear via the input shaft. The range gearbox comprises a third planetary gear with a third sun wheel and a third planetary wheel carrier and a fourth clutch device arranged to connect and disconnect the third sun wheel with/from the third planetary wheel carrier.