Hydraulic control system for continuously variable transmission

Claim 2

A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, and a main line connected to supply fluid under pressure to the secondary pulley fluid chamber, characterized by a variable displacement pump (72) connected to supply fluid under pressure to said main line (63), a control line (80), means including a modulator valve (75) for establishing in said control line a fluid pressure which is regulated to be substantially constant, and means, including a pump displacement control assembly (70) coupled between said control line and said variable displacement pump, for regulating the pressure in said main line.

Claim 3

A control system as claimed in Claim 1, and further comprising a transducer (93), coupled to said main line (63), providing an electrical signal which varies as a function of the pressure in said main line, said pump displacement control assembly (70) comprising a fluid control valve (70A) for providing a regulating signal to said variable displacement pump (72), and means, including a solenoid valve (70B) coupled between said fluid control valve and said transducer, for regulating operation of the variable displacement pump (72) as a function of the signal provided by the transducer.

Claim 4

A control system as claimed in Claim 2, and further comprising a comparator (121), coupled between said transducer (93) and said solenoid valve (70B), for providing a pump displacement control signal (on 61) which varies as a function of the difference between the actual pressure in said main line and a desired pressure level.

Claim 5

A control system as claimed in Claim 1, and further comprising a ratio control assembly (76), coupled between said main line (63) and the primary pulley chamber (28), for controlling the flow of fluid into and out of the primary pulley chamber to regulate the ratio of the continuously variable transmission.

Claim 6

A control system as claimed in Claim 4, in which said ratio control assembly (76) comprises a fluid control valve (76A), connected to receive fluid from said main line (63) and also fluid from said control line (80), and a solenoid valve (76B) coupled to said fluid control valve, for regulating operation of the fluid control valve and thus controlling the transmission ratio as a function of a received ratio control signal (on 62).

Claim 7

A control system as claimed in Claim 1, and a starting clutch (34) coupled to the output side of said secondary pulley (30), said starting clutch including a servo chamber (43),. and a cooling cutoff valve (77), coupled between said main line (63) and said starting clutch, for providing a flow of cooling oil to the starting clutch when the cooling cutoff valve is in the appropriate position.

Claim 8

A control system as claimed in Claim 6, and further comprising a fluid connection (89) between said starting clutch servo chamber (43) and the cooling cutoff valve (77), to ensure that flow of cooling oil to the starting clutch is not commenced until the starting clutch is applied.

Claim 9

A control system as claimed in Claim 7, and further comprising a fluid connection (83) between the primary sheave servo chamber (28) and the cooling cutoff valve (77), to ensure that flow of cooling oil to the clutch is terminated after the clutch is no longer slipping.

Claim 10

A control arrangement for a continuously variable transmission in which torque is transferred from an engine to a primary pulley, having an axially fixed sheave and an axially movable sheave with a chamber for admitting and discharging fluid to regulate the effective primary pulley diameter, a secondary pulley having an axially fixed sheave and an axially movable sheave with a chamber for admitting and discharging fluid, a belt intercoupling the first and second pulleys, the tension in the belt being maintained by the fluid pressure in the secondary pulley chamber, a starting clutch including a chamber for admitting and discharging fluid to regulate the transfer of drive torque from the secondary pulley through an associated vehicle drivetrain, an electronic control system connected to receive a plurality of information signals and to provide at least two output signals, and a hydraulic control system, connected to receive the output signals from the electronic control signal and to regulate fluid under pressure individually applied to the primary pulley chamber, the secondary pulley chamber, and the starting clutch chamber, in which the hydraulic control system is characterized by a main line (63) connected to supply fluid under pressure to the secondary pulley movable sheave chamber (33), a variable displacement pump (72) connected to supply fluid under pressure to said main line (63), a control line (80), means, including a modulator valve (75) coupled to said main line (63), for establishing a fluid pressure in said control line which is substantially constant and approximately equal to the lowest pressure in said main line, and means, including a pump displacement control assembly (70) coupled between said control line (80) and said variable displacement pump (72), for regulating the pressure in said main line (63).

Claim 11

A control arrangement for a continuously variable transmission in which torque is transferred from an engine to a primary pulley, having an axially fixed sheave and an axially movable sheave with a chamber for admitting and discharging fluid to regulate the effective primary pulley diameter, a secondary pulley having an axially fixed sheave and an axially movable sheave with a chamber for admitting and discharging fluid, a belt intercoupling the first and second pulleys, the tension in the belt being maintained by the fluid pressure in the secondary pulley chamber, a starting clutch including a chamber for admitting and discharging fluid to regulate the transfer of drive torque from the secondary pulley through an associated vehicle drivetrain, an electronic control system connected to receive a plurality of information signals and to provide at least two output signals, and a hydraulic control system, connected to receive the output signals from the electronic control signal and to regulate fluid under pressure individually applied to the primary pulley chamber, the secondary pulley chamber, and the starting clutch chamber, in which the hydraulic control system is characterized by a main line (63) connected to supply fluid under pressure to the secondary pulley movable sheave chamber (33), a variable displacement pump (72) connected to supply fluid under pressure to said main line (63), a control line (80), means, including a modulator valve (75) coupled to said main line (63), for establishing a fluid pressure in said control line which is substantially constant and approximately equal to the lowest pressure in said main line, and means, including a pump displacement control assembly (70) coupled between said control line (80) and said variable displacement pump (72), for regulating the pressure in said main line (63).

Claim 12

A control arrangement as claimed in Claim 9, and further comprising a transducer ( 93), coupled to said main line, for providing an electrical signal which varies as a function of the pressure in said main line, said pump displacement control assembly (70) comprising a fluid control valve (70A)for providing a regulating signal to said variable displacement pump (72), and means, including a solenoid valve (70B) coupled between said fluid control valve and said transducer, for regulating operation of the variable displacement pump as a function of the signal provided by the transducer.

Claim 13

A control system as claimed in Claim 10, and further comprising means (122) for setting a desired pressure level in said main line, and a comparator stage (121), coupled between said transducer (93) and said solenoid valve (70B), for providing a pump displacement control signal which varies as a function of the difference between the actual pressure in said main line and the desired pressure level.

Claim 14

A control system as claimed in Claim 10, and further comprising a ratio control assembly (76), coupled between said main line (63) and the primary pulley movable sheave chamber (28), for controlling the flow of fluid into and out of the primary pulley movable sheave chamber to regulate the ratio of the continuously variable transmission.

Claim 15

A control system as claimed in Claim 12, in which said ratio control assembly (76) comprises a fluid control valve (76A), connected to receive fluid from said main line (63) and also fluid from said control line, and a solenoid valve (76B) coupled to said fluid control valve, for regulating operation of the fluid control valve and thus controlling the transmission ratio as a function of a received ratio control signal.

Claim 16

A control system as claimed in Claim 12, and further comprising a cooling cutoff valve (77), coupled between said main line and said starting clutch (34), for providing a flow of cooling oil to the starting clutch when the cooling cutoff valve is in the appropriate position.

Claim 17

A control system as claimed in Claim 14, and further comprising a fluid connection ( 89 ) between said starting clutch chamber and the cooling cutoff valve, to ensure that flow of cooling oil to the starting clutch is not commenced until the starting clutch is applied.

Claim 18

A control system as claimed in Claim 15, and further comprising a fluid connection (83) between the primary sheave chamber and the cooling cutoff valve, to ensure that flow of cooling oil to the clutch is terminated after the starting clutch is no longer slipping.

Claim 19

A hydraulic control system for a vehicle having a drive train including a continuously variable transmission and a starting clutch coupled in series for completing a power flow path to drive the vehicle, in which the continuously variable transmission has a primary pulley and a secondary pulley, each pulley including an axially fixed sheave and an axially displaceable sheave for varying the effective pulley diameter, a servo chamber in the primary pulley movable sheave for admitting and discharging fluid to control the transmission ratio, a servo chamber in the secondary pulley movable sheave for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a servo chamber in the starting clutch for admitting and discharging fluid to complete and interrupt the drive train, and a main line connected to the secondary sheave servo chamber to supply fluid at a variable pressure to this chamber, characterized by a low pressure control line (80), a pressure modulator valve (75) coupled between said main line (63) and said low pressure control line (80) for establishing in said control line a fluid pressure which is approximately equal to the lowest pressure in said main line and is regulated to be substantially constant, and means, including a pump displacement control assembly (70) coupled between said low pressure control line (80) and said variable displacement pump (72), for regulating the variable pressure in said main line (63).

Claim 20

A hydraulic control system for a vehicle having a drive train including a continuously variable transmission and a starting clutch coupled in series for completing a power flow path to drive the vehicle, in which the continuously variable transmission has a primary pulley and a secondary pulley, each pulley including an axially fixed sheave and an axially displaceable sheave for varying the effective pulley diameter, a servo chamber in the primary pulley movable sheave for admitting and discharging fluid to control the transmission ratio, a servo chamber in the secondary pulley movable sheave for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a servo chamber in the starting clutch for admitting and discharging fluid to complete and interrupt the drive train, and a main line connected to the secondary sheave servo chamber to supply fluid at a variable pressure to this chamber, characterized by a low pressure control line (80), a pressure modulator valve (75) coupled between said main line (63) and said low pressure control line (80) for establishing in said control line a fluid pressure which is approximately equal to the lowest pressure in said main line and is regulated to be substantially constant, and means, including a pump displacement control assembly (70) coupled between said low pressure control line (80) and said variable displacement pump (72), for regulating the variable pressure in said main line (63).

Claim 21

A hydraulic control system as claimed in Claim 17, and further comprising means for cooling the starting clutch under certain conditions, including a cooling cutoff valve (77) having an input connection (184) coupled to said main line (63), an output connection (91) for passing -cooling fluid to the clutch, a first control connection (89) coupled to the clutch servo chamber for effecting cooling of the clutch when the vehicle is started, and a second control connection (83), coupled to the primary pulley servo chamber, for terminating cooling of the clutch after the clutch is no longer slipping.