Abstract: A hydraulic control for operating a five speed automatic transmission with two modulating solenoid valves. The control is particularly adapted for use with a twin countershaft automatic transmission that requires only one torque transfer device for each drive ratio. A system of valves is employed to direct the flow of the pressurized fluid necessary for the on-going actuation of each drive ratio and the simultaneously off-going deactuation of the previously actuated drive ratio. The flow control for actuating and deactuating the torque control devices is directly effected by two, two-position spool valves which operate in concert with two, two-position shuttle valves. Pressurized hydraulic fluid used to position the two-position spool valves and the two-position shuttle valves is primarily provided by two on/off solenoid control valves, but a third on/off inhibitor solenoid valve may also be employed.

Abstract: A hydraulic closed loop control for positioning a transmission shift rail and synchronizer fork has recesses on the rail and ports in a valve body in which the rail is disposed. Fluid flow between the ports as permitted by the rail recesses controls the position of valves which in turn control the position of the rail. The valves control the position of the rail by routing pressurized fluid to one of two opposing sides of a piston fixed to the rail in response to the flow of fluid from the valve body ports. The pressurized fluid moves the rail to a desired position with the flow of pressurized fluid being interrupted when that position is reached.

Abstract: In an automatic transmission, clutch-to-clutch closed throttle downshifting is controlled by filling the on-coming clutch at a maximum pressure command for a set period while commanding the off-going clutch pressure to a low value and exhausting the off-going clutch before the end of the fill period. At the end of the fill period the on-coming pressure is set to an initial value and then ramped up until turbine speed is pulled up due to off-going clutch slippage. Then a closed-loop profile control period starts wherein the slip of the on-coming clutch is measured and controlled to a slip profile. When synchronization of the on-coming clutch is detected, maximum pressure is commanded. Parameters for controlling the quality of a shift such as on-coming clutch initial pressure and on-coming clutch fill time are automatically adjustable during vehicle use to correct shift aberrations which degrade shift quality.

Abstract: The present invention provides a hydraulic control system for the automatic transmission of a vehicle. The control system utilizes only one pulse width modulating solenoid valve to provide modulated pressure (P2) to whichever of the torque transfer devices constitutes the single, on-coming torque transfer device required to effect a desired drive ratio. The control system includes a plurality of cascaded relay valves each of which is controlled by a respective solenoid valve. A pressure control gate is interposed between the single, pulse width modulating solenoid valve and the plurality of cascaded relay valves in order to provide modulated pressure (P2), or, selectively, main line pressure (P1) to the various torque transfer devices of the transmission. The solenoid valve are controlled to select which of the torque transfer devices shall be actuated by modulated pressure (P2) and which shall receive line pressure (P1).

Abstract: In an automatic transmission having an electronic control, a double transition powered downshift to a target range requires the release of two off-going clutches and the engagement of two on-coming clutches. The shift begins by releasing one clutch and applying another to begin (but not complete) an upshift to a third range having a speed ratio lower than both the initial range and the target range so that first an input speed increase occurs followed by an input speed decrease (pull-down). The speed decrease triggers respective application and release of the other clutches to arrest the upshift and complete the downshift. Each clutch application and release occurs gradually under an open loop control. Slip of the first off-going clutch, pull-down, speed sync at the low gear ratio and a near sync condition are determined from turbine speed and output speed and are used to time pressure command changes to smoothly coordinate clutch releases and applications.

Abstract: In an automatic transmission upshifting is controlled by ramping down the pressure in an off-going clutch associated with a high speed ratio and increasing the pressure in an on-coming clutch associated with a lower speed ratio. The on-coming clutch has commanded pressure at a maximum value for an initial fill time, a lower increasing ramp value during the ramp of the off-going clutch until the on-coming clutch starts to engage, and then a closed-loop control until the clutch reaches a synchronous speed. The closed-loop control parameter is on-coming clutch slip which is controlled to a calculated slip speed profile. Parameters for controlling the quality of a shift such as on-coming clutch initial pressure, off-going clutch initial pressure and on-coming clutch fill time are automatically adjustable during vehicle use to correct shift aberrations which degrade shift quality. A fast adjustment mode is in effect initially to calibrate the transmission control for the engine and vehicle.

Abstract: In an automatic transmission, clutch-to-clutch powered downshifting is controlled by filling the on-coming clutch at a low pressure while ramping down the off-going clutch pressure until turbine speed is pulled up due to off-going clutch slippage, and then increasing the off-going pressure stepwise to compensate the change from static to dynamic coefficients of friction. Then the on-coming pressure is gradually ramped up and a closed-loop profile control period starts wherein the slip of the on-coming clutch is measured and controlled to a slip profile by controlling the off-going clutch pressure. When synchronization of the on-coming clutch is first detected, a closed-loop sync control period starts wherein the off-going pressure is controlled to minimize the slip and the on-coming pressure is ramped up at a steeper rate to begin clutch engagement during the sync control period.

Abstract: In an automatic transmission, a double transition upshift to a target range requires the release of two off-going clutches and the engagement of two on-coming clutches. The shift is made in two stages. The first stage involves a first off-going clutch and a first on-coming clutch, and begins a shift to a third range having a speed ratio lower than the target range so that input speed is decreased and power is supplied throughout the shift. The speed decrease is managed by a closed-loop control of the first on-coming clutch until the clutch reaches a synchronous speed for the target range. The closed-loop control parameter is on-coming clutch slip speed which is controlled to a calculated slip speed profile. The profile has a first steep slope and a final less steep slope so that the actual slip can smoothly go to zero in a given time period.

Abstract: In an automatic transmission, a double transition closed throttle downshift to a target range requires the release of two off-going clutches and the engagement of two on-coming clutches. The shift is made in two stages. The first stage involves a first off-going clutch and a first on-coming clutch and effects an upshift to a third range having a speed ratio lower than both the initial range and the target range, so that a momentary input speed decrease occurs. The speed decrease is managed by a closed-loop control of the first on-coming clutch until the clutch reaches a synthronous speed for the third range. The second stage is a downshift from the third ratio to the second ratio by a second off-going clutch and a second on-coming clutch and results in a speed increase. The second on-coming clutch is also managed by a closed-loop control. In each case, the closed-loop control parameter is on-coming clutch slip speed which is controlled to a calculated slip speed profile.