Hydraulic control system for a motor vehicle automatic transmission

Claim 2

A vehicle automatic transmission including a transmission gear mechanism having at least three gear stages including a low speed stage, a medium speed stage and a high speed stage for forward drive, a low speed shift valve for controlling shift operations between the low speed and medium speed stages, a high speed shift valve for controlling shift operations between the medium speed and high speed stages, kick-down control means comprising a kick-down valve for applying a hydraulic pressure to each of the shift valves to bias the shift valves in a shift down direction, and a shut-off valve located in a line between said kick-down valve and said low speed shift valve and being responsive to a pressure produced when the high speed shift valve has been moved in the shift down direction to open said line between said kick-down valve and said low speed shift valve to thereby connect the kick-down valve to the low speed shift valve.

Claim 3

A vehicle automatic transmission in accordance with claim 1 in which said shut-off valve is of a spool type having a spool and a pilot port at one end of said spool.

Claim 4

A vehicle automatic transmission in accordance with claim 3 which includes means for connecting the pilot port with a port in the high speed shift valve wherein a pressure change is produced when the high speed shift valve is moved in the shift down direction.

Claim 5

A vehicle automatic transmission in accordance with claim 2 which includes means for connecting the pilot port with a port in the high speed shift valve wherein a drain pressure is produced when the high speed shift valve is moved in the shift down direction.

Claim 6

A vehicle automatic transmission in accordance with claim 1 in which each of said shift valves includes a valve member which is biased in one direction by a pressure corresponding to a vehicle speed and in the opposite direction by a biasing force.

Claim 7

A vehicle automatic transmission in accordance with claim 5 which includes for applying the hydraulic pressure from the kick-down valve in a direction of assisting the biasing force.

Claim 8

A vehicle automatic transmission in accordance with claim 5 in which said biasing force is a pressure corresponding to an engine load.

Claim 9

A vehicle automatic transmission including a transmission gear mechanism having four gear stages including a 1st, 2nd, 3rd and 4th gear stages for forward drive, a 1-2 shift valve for controlling shift operations between the 1st and 2nd gear stages, a 2-3 shift valve for controlling shift operations between the 2nd and 3rd gear stages, a 3-4 shift valve for controlling shift operations between the 3rd and 4th gear stages, kick-down valve means producing a kick-down pressure, a first kick-down line connecting the kick-down valve means with the 3-4 shift valve for applying the kick-down pressure in a direction of biasing the 3-4 shift valve in a shift down direction, a second kick-down line connecting the kick-down valve means with the 2-3 shift valve for applying the kick-down pressure in a direction of biasing the 2-3 shift valve in a shift down direction, a first shut-off valve provided in the second kick-down line, said first shut-off valve is responsive to a pressure change produced at a port of the 3-4 shift valve when the 3-4 shift valve is moved in the shift down direction for opening the second kick-down line.

Claim 10

A vehicle automatic transmission including a transmission gear mechanism having four gear stages including a 1st, 2nd, 3rd and 4th gear stages for forward drive, a 1-2 shift valve for controlling shift operations between the 1st and 2nd gear stages, a 2-3 shift valve for controlling shift operations between the 2nd and 3rd gear stages, a 3-4 shift valve for controlling shift operations between the 3rd and 4th gear stages, kick-down valve means producing a kick-down pressure, a first kick-down line connecting the kick-down valve means with the 3-4 shift valve for applying the kick-down pressure in a direction of biasing the 3-4 shift valve in a shift down direction, a second kick-down line connecting the kick-down valve means with the 2-3 shift valve for applying the kick-down pressure in a direction of biasing the 2-3 shift valve in a shift down direction, a first shut-off valve provided in the second kick-down line, said first shut-off valve is responsive to a pressure change produced at a port of the 3-4 shift valve when the 3-4 shift valve is moved in the shift down direction for opening the second kick-down line.

Claim 11

A vehicle automatic transmission in accordance with claim 8 which further includes a third kick-down line connecting the kick-down valve means with the 1-2 shift valve for applying the kick-down pressure in a direction of biasing the 1-2 shift valve in a shift down direction, and a second shut-off valve provided in the third kick-down line, said second shut-off valve is responsive to a pressure change produced at a port of the 2-3 shift valve when the 2-3 shift valve is moved in the shift down direction for opening the third kick-down line.

Claim 12

A vehicle automatic transmission including a transmission gear mechanism having at least three gear stages including a low speed stage, a medium speed stage and a high speed stage for forward drive, a low speed shift valve for controlling shift operations between the low speed and medium speed stages, a high speed shift valve for controlling shift operations between the medium speed and high speed stages, kick-down control means comprising a kick-down valve for applying a hydraulic pressure to each of the shift valves to bias the shift valves in a shift down direction, and a pilot-type shut-off valve located in a line between said kick-down valve and said low speed shift valve, said shut-off valve including a spool and a pilot port at one end of said spool, means for connecting said pilot port with a port in said high speed shift valve wherein a pressure change is produced when the high speed shift valve has been moved in the shift down direction to open said line between said kick-down valve and said low speed shift valve by moving said spool under said pressure change to thereby connect said kick-down valve to said low speed shift valve.

Claim 13

A vehicle automatic transmission including a transmission gear mechanism having at least three gear stages including a low speed stage, a medium speed stage and a high speed stage for forward drive, a low speed shift valve for controlling shift operations between the low speed and medium speed stages, a high speed shift valve for controlling shift operations between the medium speed and high speed stages, kick-down control means comprising a kick-down valve for applying a hydraulic pressure to each of the shift valves to bias the shift valves in a shift down direction, and a pilot-type shut-off valve located in a line between said kick-down valve and said low speed shift valve, said shut-off valve including a spool and a pilot port at one end of said spool, means for connecting said pilot port with a port in said high speed shift valve wherein a pressure change is produced when the high speed shift valve has been moved in the shift down direction to open said line between said kick-down valve and said low speed shift valve by moving said spool under said pressure change to thereby connect said kick-down valve to said low speed shift valve.

Claim 14

A vehicle automatic transmission including a transmission gear mechanism having four gear stages including a 1st, 2nd, 3rd and 4th gear stages for forward drive, a 1-2 shift-valve for controlling shift operations between the 1st and 2nd gear stages, a 2-3 shift valve for controlling shift operations between the 2nd and 3rd gear stages, a 3-4 shift valve for controlling shift operations between the 3rd and 4th gear stages, kick-down valve means producing a kick-down pressure, a first kick-down line connecting the kick-down valve means with the 3-4 shift valve for applying kick-down pressure in a direction of biasing the 3-4 shift valve in a shift down direction, a second kick-down line connecting the kick-down valve means with the 2-3 shift valve for applying the kick-down pressure in a direction of biasing the 2-3 shift valve in a shift down direction, a first pilot type shut-off valve provided in the second kick-down line and having a first spool and a first pilot port at one end of said first spool, first means for connecting the first pilot port with a port in the 3-4 shift valve wherein a pressure change is produced when the 3-4 shift valve is moved in the shift down direction for opening the second kick-down line by moving the first spool under the pressure change to thereby connect the kick down valve means with the 2-3 shift valve to move the 2-3 shift valve in the shift down direction.

Claim 15

A vehicle automatic transmission including a transmission gear mechanism having four gear stages including a 1st, 2nd, 3rd and 4th gear stages for forward drive, a 1-2 shift-valve for controlling shift operations between the 1st and 2nd gear stages, a 2-3 shift valve for controlling shift operations between the 2nd and 3rd gear stages, a 3-4 shift valve for controlling shift operations between the 3rd and 4th gear stages, kick-down valve means producing a kick-down pressure, a first kick-down line connecting the kick-down valve means with the 3-4 shift valve for applying kick-down pressure in a direction of biasing the 3-4 shift valve in a shift down direction, a second kick-down line connecting the kick-down valve means with the 2-3 shift valve for applying the kick-down pressure in a direction of biasing the 2-3 shift valve in a shift down direction, a first pilot type shut-off valve provided in the second kick-down line and having a first spool and a first pilot port at one end of said first spool, first means for connecting the first pilot port with a port in the 3-4 shift valve wherein a pressure change is produced when the 3-4 shift valve is moved in the shift down direction for opening the second kick-down line by moving the first spool under the pressure change to thereby connect the kick down valve means with the 2-3 shift valve to move the 2-3 shift valve in the shift down direction.