Hydraulic control system of automatic transmission

Claim 2

In an automatic power transmission for a vehicle driven by an engine, said automatic transmission having a driving shaft driven by said engine, a driven shaft and a planetary gear unit having first and second planetary gear sets each having rotating members comprising a ring gear, a carrier carrying at least one planet pinion meshing with said ring gear and a sun gear externally meshing with said planet pinion, said carrier of said first planetary gear set being connected to said driven shaft, said sun gears of said first and second planetary gear sets being connected to each other and said ring gear of said second planetary gear set being connected to said driven shaft, a hydraulic control system comprising: clutch and brake means for controlling the relative motion of said rotating members of said planetary gear unit, said clutch and brake means having a forward clutch for connecting said driving shaft to the ring gear of said first planetary gear set during operation in an intermediate forward speed and a second brake for anchoring said common sun gears of Said first and second planetary gear sets during operation of said planetary gear unit in said intermediate speed; hydraulic servo means for controlling said clutch and brake means, said hydraulic servo means having a first servo for actuating said forward clutch and a second servo for actuating said second brake for thereby providing said intermediate speed; a source of fluid pressure; a source of governor pressure; shift valve means communicating with said source of hydraulic pressure and said second servo, said shift valve means having a valve spool responsive to the governor pressure for blocking fluid communication between said source of hydraulic fluid pressure and said second servo when the governor pressure is below a predetermined level and establishing fluid communication between said source of hydraulic fluid pressure and said second servo when the governor pressure exceeds said predetermine level; a conduit connecting said first servo to said source of hydraulic fluid pressure; lock valve means communicating with said source of hydraulic fluid pressure through a first conduit, said second servo and said shift valve means, said lock valve means having a second conduit communicating with said source of fluid pressure and a valve spool responsive to the hydraulic fluid pressure in said second conduit for establishing communication between said shift valve means and said second servo when the hydraulic fluid pressure is applied to said second conduit and for establishing communication between said source of hydraulic fluid pressure and said second servo via said first conduit when the hydraulic fluid pressure is exhausted from said second conduit; a manual selector valve having a valve spool assumable to a Drive position and a II position, said valve spool blocking said second conduit and exhausting the hydraulic fluid pressure from said second conduit when in said II position, thereby causing said lock valve to establish fluid communication between said source of hydraulic fluid pressure and said second servo to lock said second brake.

Claim 3

A hydraulic control system according to claim 1, further comprising another shift valve means communicating with another servo and said second conduit, said other shift valve means having a valve spool, responsive to the governor pressure for clocking communicating between said second conduit and said other servo when the governor pressure is below another predetermined level which is higher than said predetermined level and for establishing communication between said second conduit and said other servo whereby when the manual selector valve is set in said II position and the hydraulic fluid pressure is exhausted from said second conduit, said other shift valve is overruled.

Claim 4

In an automatic power transmission for a vehicle driven by an engine said automatic transmission having a driving shaft driven by said engine, a driven shaft and a planetary gear unit having first and second planetary gear sets each having rotating members comprising a ring gear, a carrier carrying at least one planet pinion meshing with said ring gear and a sun gear externally meshing with said planet pinion, said carrier of said first planetary gear set being connected to said driven shaft, said sun gears of said first and second planetary gear sets being connected to each other and said ring gear of said second planetary gear set being connected to said driven shaft, a hydraulic control system comprising: clutch and brake means for controlling the relative motion of said rotating members of said planetary gear unit, said clutch and brake means having a forward clutch means for connecting said driving shaft to the ring gear of said first planetary gear set during operation in a low, an intermediate and a high forward speed, a reverse and high clutch means for connecting the common sun gears to said input shaft during operation in high forward speed and in reverse speed, a second brake means for anchoring the common sun gears during operation In said intermediate speed and a low reverse brake means for anchoring the carrier of said second planetary gear set during operation in reverse speed; hydraulic servo means for controlling said clutch and said brake means, said hydraulic servo means having a first servo for actuating said forward clutch means and a second servo for actuating said second brake means; a source of fluid pressure; a manual selector valve having a Drive position and a II position; a first conduit connecting said source of fluid pressure to said manual selector valve to transmit the fluid pressure to said manual selector valve; a source of governor pressure; a 1-2 shift valve communicating with said source of governor pressure, said 1-2 shift valve assumable to a first position when the governor pressure is below a predetermined level and to a second position when the governor pressure exceeds said predetermined level; a second conduit connecting said manual selector valve to said 1-2 shift valve through the solenoid downshift valve; a 2-3 shift valve communicating with said source of governor pressure, said 2-3 shift valve assumable to a first position when the governor pressure is below another predetermined level which is higher than said predetermined level and to a second position when the governor pressure exceeds said other predetermined level; a third conduit connecting said manual selector valve to said 2-3 shift valve; a second lock valve assumes a first position when the hydraulic pressure is applied to said third conduit and a second position when the hydraulic pressure is exhausted from said third conduit; a fourth conduit connecting said 1-2 shift valve to said second lock valve; a fifth conduit connecting said manual selector valve to said second lock valve; a sixth conduit connecting said second lock valve to said second servo; a seventh conduit connecting said manual selector valve to said first servo; said manual selector valve connecting said first conduit to said third, fifth and seventh conduits when said manual selector valve assumes said Drive position, said manual selector valve connecting said first conduit to said second, fifth and seventh conduits and exhausting said third conduit when said manual selector valve assumes said II position; said second lock valve establishing communication between said fourth conduit and said sixth conduit when in said first position and establishing communication between said fifth conduit and said sixth conduit when in said second position, whereby the hydraulic pressure is transmitted to said first servo through said seventh conduit and to said second servo through said fifth conduit and sixth conduit when said manual selector valve assumes II position, to lock the automatic transmission in its intermediate speed irrespective of the pressure level of the governor pressure.

Claim 5

In an automatic power transmission for a vehicle driven by an engine said automatic transmission having a driving shaft driven by said engine, a driven shaft and a planetary gear unit having first and second planetary gear sets each having rotating members comprising a ring gear, a carrier carrying at least one planet pinion meshing with said ring gear and a sun gear externally meshing with said planet pinion, said carrier of said first planetary gear set being connected to said driven shaft, said sun gears of said first and second planetary gear sets being connected to each other and said ring gear of said second planetary gear set being connected to said driven shaft, a hydraulic control system comprising: clutch and brake means for controlling the relative motion of said rotating members of said planetary gear unit, said clutch and brake means having a forward clutch means for connecting said driving shaft to the ring gear of said first planetary gear set during operation in a low, an intermediate and a high forward speed, a reverse and high clutch means for connecting the common sun gears to said input shaft during operation in high forward speed and in reverse speed, a second brake means for anchoring the common sun gears during operation In said intermediate speed and a low reverse brake means for anchoring the carrier of said second planetary gear set during operation in reverse speed; hydraulic servo means for controlling said clutch and said brake means, said hydraulic servo means having a first servo for actuating said forward clutch means and a second servo for actuating said second brake means; a source of fluid pressure; a manual selector valve having a Drive position and a II position; a first conduit connecting said source of fluid pressure to said manual selector valve to transmit the fluid pressure to said manual selector valve; a source of governor pressure; a 1-2 shift valve communicating with said source of governor pressure, said 1-2 shift valve assumable to a first position when the governor pressure is below a predetermined level and to a second position when the governor pressure exceeds said predetermined level; a second conduit connecting said manual selector valve to said 1-2 shift valve through the solenoid downshift valve; a 2-3 shift valve communicating with said source of governor pressure, said 2-3 shift valve assumable to a first position when the governor pressure is below another predetermined level which is higher than said predetermined level and to a second position when the governor pressure exceeds said other predetermined level; a third conduit connecting said manual selector valve to said 2-3 shift valve; a second lock valve assumes a first position when the hydraulic pressure is applied to said third conduit and a second position when the hydraulic pressure is exhausted from said third conduit; a fourth conduit connecting said 1-2 shift valve to said second lock valve; a fifth conduit connecting said manual selector valve to said second lock valve; a sixth conduit connecting said second lock valve to said second servo; a seventh conduit connecting said manual selector valve to said first servo; said manual selector valve connecting said first conduit to said third, fifth and seventh conduits when said manual selector valve assumes said Drive position, said manual selector valve connecting said first conduit to said second, fifth and seventh conduits and exhausting said third conduit when said manual selector valve assumes said II position; said second lock valve establishing communication between said fourth conduit and said sixth conduit when in said first position and establishing communication between said fifth conduit and said sixth conduit when in said second position, whereby the hydraulic pressure is transmitted to said first servo through said seventh conduit and to said second servo through said fifth conduit and sixth conduit when said manual selector valve assumes II position, to lock the automatic transmission in its intermediate speed irrespective of the pressure level of the governor pressure.

Claim 6

A hydraulic control system according to claim 3, wherein said second lock valve comprises a housing having an outlet communicating with said sixth conduit, a first inlet communicating with said fifth conduit, second inlet communicating with said fourth conduit, a third inlet communicating with said third conduit and a bore, a valve spool slidably accomodated within said bore, said valve spool subjected to the fluid pressure of said third inlet and a spring means biasing said valve spool in said first position when the hydraulic pressure is applied to said third inlet and in said second position when the hydraulic pressure is exhausted from said third inlet, said valve spool having a plurality of lands formed thereon for blocking communication between said first inlet and said outlet when in said first position and for blocking communication between said second inlet and said outlet when in said second position.