Loading patent…
AssigneeBorg-Warner Corporation
InventorsWerner P. Petzold, William P. Umlauf
Estimating the term…
A pressure transducer, which senses clutch pressure and effects closed loop clutch control in a continuously variable transmission, is used after the clutch is fully engaged to provide closed loop line pressure control to a desired setpoint, which line pressure regulates the tension on the belt in the transmission. Only a single transducer is needed since there is a known relationship between the clutch and line pressures when the clutch is locked up. Prior to lockup, the line pressure is governed by an open loop controller which establishes the line pressure at a level higher than that called for by the setpoint. This ensures that the line pressure will be high enough to provide the required tension on the belt so that it will not slip. After the clutch is engaged, the closed loop line pressure controller (which includes both the open loop line pressure controller and the closed loop clutch controller) establishes the line pressure at the setpoint. For stable operation, the closed loop controller responds only to relatively slow changes of the setpoint. In response to fast changes, the closed loop controller is made ineffective so that the line pressure will be determined only by the open loop controller and will be greater than the level called for by the setpoint.
A line pressure control system for controlling the line fluid pressure in a continuously variable transmission, in which fluid under line pressure is controlled to produce an adjustable clutch fluid pressure for operating a clutch to transfer drive torque from an engine and through the transmission to an associated drivetrain, including a pressure transducer operable to sense the clutch pressure applied to the clutch, and having a closed loop clutch controller which responds to the sensed clutch pressure to effect closed loop control of the clutch, said control system comprising:
A control system for a continuously variable transmission having a primary pulley and a secondary pulley, a belt intercoupling the pulleys, a primary sheave chamber in the primary pulley for admitting and discharging fluid to change the effective pulley diameter and correspondingly change the transmission ratio, a secondary sheave chamber in the secondary pulley for admitting and discharging fluid to maintain tension in the belt as the transmission is driven, a fluid-actuated clutch operable to transfer drive torque from the secondary pulley to an associated drivetrain, which clutch includes a clutch chamber for receiving fluid to apply the clutch and from which fluid is discharged to release the clutch, comprising:
A line pressure control system for controlling the line fluid pressure in a continuously variable transmission, including a line pressure regulator for varying the line pressure, which line pressure regulator is controlled by a pulse width modulated signal having an adjustable duty cycle, the line pressure being determined by, and being directly proportional to, the signal's duty cycle, and where, due to characteristics of the regulator which vary with temperature, the duty cycle required to produce a desired line pressure depends on the temperature of the transmission fluid, said control system comprising:
A line pressure control system for controlling the line fluid pressure in a continuously variable transmission, comprising:
Dependencies are inferred from the claim text.