A shift control valve means for controlling continuously variable V-belt transmission

Claim 1

A method for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllably movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the method comprising the steps of: keeping fluid pressure within the cylinder chamber of the driven pulley constant upon varying fluid pressure within the cylinder chamber of the drive pulley; and keeping fluid pressure within the cylinder chamber of the drive pulley constant upon varying fluid pressure within the cylinder chamber of the driven pulley.

Claim 2

A method for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllably movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the method comprising the steps of: keeping fluid pressure within the cylinder chamber of the driven pulley constant upon varying fluid pressure within the cylinder chamber of the drive pulley; and keeping fluid pressure within the cylinder chamber of the drive pulley constant upon varying fluid pressure within the cylinder chamber of the driven pulley.

Claim 3

A system for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllably movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the system comprising: means for supplying the hydraulic fluid; a shift valve means receiving the hydraulic fluid supplied by said supplying means for regulating fluid supply to and discharge from the cylinder chambers of the drive and driven pulleys, said shift control valve means including spool means for keeping fluid pressure within the cylinder chamber of the driven pulley constant upon varying fluid pressure within the cylinder chamber of the drive pulley and keeping fluid pressure within the cylinder chamber of the drive pulley constant upon varying fluid pressure within the cylinder chamber of the driven pulley.

Claim 4

A system for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllably movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the system comprising: means for supplying the hydraulic fluid; a shift valve means receiving the hydraulic fluid supplied by said supplying means for regulating fluid supply to and discharge from the cylinder chambers of the drive and driven pulleys, said shift control valve means including spool means for keeping fluid pressure within the cylinder chamber of the driven pulley constant upon varying fluid pressure within the cylinder chamber of the drive pulley and keeping fluid pressure within the cylinder chamber of the drive pulley constant upon varying fluid pressure within the cylinder chamber of the driven pulley.

Claim 5

A system for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllavly movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the hydraulic control system comprising: means for supplying the hydraulic fluid; and a shift control valve means receiving the hydraulic fluid supplied by said supplying means for regulating fluid supply to and discharge from the cylinder chamber of the drive pulley and that of the driven pulley, said shift control valve means having a valve bore formed with a first port receiving the hydraulic fluid supplied by said supplying means, a second port communicating with the cylinder chamber of the drive pulley and a third port communicating with the cylinder chamber of the driven pulley, the second port and third port being spaced in the opposite directions from the first port, the shift control valve means including a spool slidable within the valve bore, the spool having a first land and a second land which cooperate with the second and third ports, respectively, wherein axial length of the first and second lands are shorter than axial width of the second and third ports, respectively, and an axial distance between outer side edge faces of the first and second lands is substantially equal to an axial distance between outer side walls of the second and third ports.

Claim 6

A system for controlling a continuously variable transmission having a V-belt running over a drive and a driven pulley, each having cylinder chamber and two conical discs, one conical disc of the drive pulley being secured to a drive shaft, one conical disc of the driven pulley being secured to a driven shaft, the other conical disc of the drive pulley being controllavly movable in an axial direction of the drive shaft in response to the fluid pressure in the cylinder chamber thereof, the other conical disc of the driven pulley being controllably movable in an axial direction of the driven shaft in response to the fluid pressure in the cylinder chamber thereof, the hydraulic control system comprising: means for supplying the hydraulic fluid; and a shift control valve means receiving the hydraulic fluid supplied by said supplying means for regulating fluid supply to and discharge from the cylinder chamber of the drive pulley and that of the driven pulley, said shift control valve means having a valve bore formed with a first port receiving the hydraulic fluid supplied by said supplying means, a second port communicating with the cylinder chamber of the drive pulley and a third port communicating with the cylinder chamber of the driven pulley, the second port and third port being spaced in the opposite directions from the first port, the shift control valve means including a spool slidable within the valve bore, the spool having a first land and a second land which cooperate with the second and third ports, respectively, wherein axial length of the first and second lands are shorter than axial width of the second and third ports, respectively, and an axial distance between outer side edge faces of the first and second lands is substantially equal to an axial distance between outer side walls of the second and third ports.