Patent ID: 8500600
Filing Date: 2013-08-06
Classification: F16H,Y10T

Abstract:
1. A hydraulic control system for a transmission, the transmission having a plurality of torque transmitting devices selectively actuatable by a plurality of actuators for providing at least a set of low speed gear ratios and a set of high speed gear ratios, the hydraulic control system comprising: a source of pressurized hydraulic fluid; a manual valve moveable between at least a Park position and a Drive position, the manual valve in downstream fluid communication with the source of pressurized hydraulic fluid; a default valve moveable between a first position and a second position, the default valve in downstream fluid communication with the manual valve; a first set of solenoids operable to selectively engage at least one of the plurality of actuators, wherein the first set of solenoids is open when de-energized and includes a first subset of solenoids in downstream fluid communication with the source of pressurized hydraulic fluid through the manual valve when the manual valve is in the Drive position and a second subset of solenoids in downstream fluid communication with the default valve, and wherein at least the second subset of solenoids is configured to engage each of the plurality of high speed gear ratios and is in downstream fluid communication with the source of pressurized hydraulic fluid through the manual valve and the default valve when the manual valve is in the Drive position and the default valve is in the second position; and a second set of solenoids in downstream fluid communication with the source of pressurized hydraulic fluid and operable to selectively engage at least one of the plurality of actuators, wherein the second set of solenoids is closed when de-energized and includes a third subset of solenoids each having an inlet in downstream fluid communication with the source of pressurized hydraulic fluid, an outlet in fluid communication with at least one of the plurality of actuators, and an exhaust in fluid communication with the outlet when the third subset of solenoids is closed, and wherein the exhaust is in fluid communication with the first set of solenoids through the default valve when the default valve is in the first position, and wherein a default gear ratio within the low speed gear ratios is engaged when the manual valve is in the Drive position, the default valve is in the first position, and the first and second sets of solenoids are de-energized, and wherein a default gear ratio within the high speed gear ratios is engaged when the manual valve is in the Drive position, the default valve is in the second position, and the first and second set of solenoids are de-energized.