Hydraulic control apparatus for continuously variable power transmitting system including reversing gear device and auxiliary transmission

A hydraulic control apparatus for a power transmitting system of a motor vehicle which includes:

• a continuously variable transmission whose speed ratio is continuously variable;
• a reversing gear device which is rotated in opposite directions to permit forward and reverse runs of the vehicle, said reversing gear device having a forward frictionally coupling device and a reverse frictionally coupling device which are hydraulically operated to select the corresponding forward or reverse run of the vehicle, depending upon a currently selected position of a shift lever of the vehicle;
• and an auxiliary transmission disposed in series with said reversing gear device, and having a low-gear frictionally coupling device and a high-gear frictionally coupling device which are hydraulically operated to place said auxiliary transmission in a low-gear position and a high-gear position, respectively, said reverse frictionally coupling device and said high-gear frictionally coupling device being engaged when said shift lever is operated to a reverse-drive position for the reverse run of the vehicle, so that said reversing gear device is rotated in one of said opposite directions which permits the reverse run of the vehicle while said auxiliary transmission is placed in said high-gear position, said hydraulically control apparatus comprising:
• means for increasing a torque capacity of said high-gear frictionally coupling device during an engaging action thereof when said shift lever is operated from a forward-drive position for the forward run of the vehicle to said reverse-drive position.

A hydraulic control apparatus for a power transmitting system of a motor vehicle which includes a continuously variable transmission, a reversing gear device, and an auxiliary transmission disposed apart from said reversing gear device, said auxiliary transmission having a low-gear frictionally coupling device and a one-way clutch which are disposed in series, and a high-gear frictionally coupling device, said auxiliary transmission being placed in a selected one of a low-gear position by engagement of said low-gear frictionally coupling device and said one-way clutch, and a high-gear position by engagement of said high-gear frictionally coupling device, a power transmitting line of the power transmitting system being disconnected when both of said low-gear and high-gear frictionally coupling devices are disengaged, said hydraulic control apparatus comprising:

• a solenoid-operated valve for generating a pilot pressure in response to a command signal for placing said auxiliary transmission in one of said low-gear position and said high-gear position;
• a low-gear control valve for controlling said low-gear frictionally coupling device, said low-gear control valve including a first valve spool which is operable based on said pilot pressure between an engaging position and a releasing position for engaging and releasing said low-gear frictionally coupling device, respectively;
• and
• a high-gear control valve for controlling said high-gear frictionally coupling device, said high-gear control valve including a second valve spool which is operable based on said pilot pressure between an engaging position and a releasing position for engaging and releasing said high-gear frictionally coupling device, respectively, said second valve spool being moved to said releasing position when a thrust based on an engaging pressure applied to said low-gear frictionally coupling device exceeds a predetermined value.