Hydraulic control system for automatic transmission

Claim 2

In a fluid controlled type automatic transmission for vehicles including a hydraulic torque converter or hydraulic coupling, a gear unit having brake band means and clutch means, fluid pressure operated servo means for said brake band means and said clutch means, a source of fluid pressure, a fluid pressure circuit for supplying and discharging fluid under pressure to and from said servo means, said circuit including shift valve means responsive to a predetermined running condition of the vehicle for establishing low speed and high speed forward drive ratios for said gear unit, and a pressure regulator valve for controlling the fluid pressure delivered from said source to said fluid pressure circuit, said regulator valve including a valve spool and a plurality of valve chambers, the improvement comprising control means for varying the pressure regulating action of said regulating valve in accordance with engine load, said means including a control valve in fluid connection with one of said valve chambers for controlling fluid pressure in said chamber and means responsive to engine load for opening and closing said control valve to thereby effect movement of the pressure regulator valve spool.

Claim 3

Apparatus as in claim 1 wherein said regulator valve is responsive to the operation of said control valve in a mode to deliver low and high fluid pressure to said fluid pressure circuit when engine load is low and high, respectively.

Claim 4

Apparatus as in claim 1 wherein said means responsive to engine load generates an electrical signal depending on engine load, wherein said control valve is a solenoid operated valve adapted to be closed and opened in response to the appearance and disappearance, respectively, of said electrical signal, and wherein the pressure delivered from said pressure regulator valve to said fluid pressure circuit is high when no electrical signal is applied to said solenOid valve.

Claim 5

Apparatus as in claim 1 wherein said control means for varying the pressure regulating action of said regulating valve is also responsive to operation of said shift valve means, said control means including fluid passage means extending between said shift valve means and said one valve chamber in said pressure regulator valve for changing the pressure in said valve chamber upon a preselected operation of said shift valve means.

Claim 6

In a fluid controlled type automatic transmission for vehicles including a hydraulic torque converter or hydraulic coupling, a gear unit having brake band means and clutch means, fluid pressure operated servo means for said brake band means and said clutch means, a source of fluid pressure, a fluid pressure circuit for supplying and discharging fluid under pressure to and from said servo means, said circuit including shift valve means responsive to a predetermined running condition of the vehicle for establishing low speed and high speed forward drive ratios for said gear unit, and a pressure regulator valve for controlling the fluid pressure delivered from said source to said fluid pressure circuit, said regulator valve including a valve spool and a control chamber containing fluid acting on said spool, the improvement comprising: means defining a control chamber containing fluid acting on said pressure regulator valve spool, said pressure regulator valve being constructed such that movement of said spool under increased pressure in said control chamber decreases the fluid pressure delivered to said fluid pressure circuit by said pressure regulator valve; a solenoid operated valve in fluid connection with said control chamber and having a discharge port and movable valve element for selectively closing said port and opening said port to place the same in fluid communication with said control chamber, said solenoid operated valve being closed when electrically energized and being open when de-energized; means for detecting the load on the engine and for generating an electrical signal when the load exceeds a predetermined value; and an electrical circuit for controlling said solenoid operated valve in response to the electrical signal generated by said electrical signal generating means.

Claim 7

In a fluid controlled type automatic transmission for vehicles including a hydraulic torque converter or hydraulic coupling, a gear unit having brake band means and clutch means, fluid pressure operated servo means for said brake band means and said clutch means, a source of fluid pressure, a fluid pressure circuit for supplying and discharging fluid under pressure to and from said servo means, said circuit including shift valve means responsive to a predetermined running condition of the vehicle for establishing low speed and high speed forward drive ratios for said gear unit, and a pressure regulator valve for controlling the fluid pressure delivered from said source to said fluid pressure circuit, said regulator valve including a valve spool and a control chamber containing fluid acting on said spool, the improvement comprising: means defining a control chamber containing fluid acting on said pressure regulator valve spool, said pressure regulator valve being constructed such that movement of said spool under increased pressure in said control chamber decreases the fluid pressure delivered to said fluid pressure circuit by said pressure regulator valve; a solenoid operated valve in fluid connection with said control chamber and having a discharge port and movable valve element for selectively closing said port and opening said port to place the same in fluid communication with said control chamber, said solenoid operated valve being closed when electrically energized and being open when de-energized; means for detecting the load on the engine and for generating an electrical signal when the load exceeds a predetermined value; and an electrical circuit for controlling said solenoid operated valve in response to the electrical signal generated by said electrical signal generating means.

Claim 8

Apparatus as in claim 5 including fluid passage means extending between said shift valve means and said control chamber in said pressure regulator valve for introducing fluid pressure from said shift valve means into said control chamber upon a preselected operation of said shift valve means and for preventing discharge of said introduced fluid pressure through said solenoid operated valve should the latter be in the open position.