Apparatus for controlling line pressure for automatic transmission upon vehicle starting with the transmission placed in second or higher-gear position

A hydraulic control apparatus for an automatic transmission of a motor vehicle having a plurality of hydraulically operated frictional coupling devices for selectively establishing a first-speed position and at least one higher-speed position whose speed reduction ratio is lower than that of said first-speed position, the apparatus comprising:

• a pressure regulating valve for regulating a line pressure of a working fluid to be applied to the hydraulically operated frictional coupling devices;
• a cut-back valve having a first position selected when the transmission is placed in said first-speed position, and a second position selected when the transmission is placed in any one of said at least one higher-gear position, said cut-back valve when placed in said first position causing said pressure regulating valve to raise said line pressure by a predetermined amount to a higher level than a normal level as normally established by said pressure regulating valve, said cut-back valve when placed in said second position causing said pressure regulating valve to regulate said line pressure to said normal level;
• mode selecting means for selecting a high-gear start mode in which the vehicle is started with said automatic transmission placed in a predetermined one of said at least one higher-gear position;
• and
• pressure applying means, responsive to said mode selecting means, for applying to said cut-back valve a first and a second pressure to be applied to respective two coupling devices of said plurality of frictional coupling devices to establish said predetermined one higher-gear position, for placing said cut-back valve in said first position to raise said line pressure to said higher level,
• said pressure applying means comprising first pressure applying means for applying said first pressure as a high-gear start pressure to said cut-back valve, and second pressure applying means for applying said second pressure to said cut-back valve,
• said first pressure applying means including delay means for delaying the application of said first pressure to said cut-back valve, with respect to the application of said second pressure, for first applying only said second pressure to said cut-back valve to place said cut-back valve in said second position for lowering the line pressure from said higher level to said normal level, and then also applying said high-gear start pressure to said cut-back valve to place said cut-back valve in said first position for raising said line pressure to said higher level.