Adaptive line pressure control for an electronic automatic transmission
First Claim
1. In a hydraulic system for an automatic transmission having pump means for causing hydraulic fluid to flow through the hydraulic system and a pressure regulator means for regulating the hydraulic line pressure in the automatic transmission, the improvement comprising line pressure control means for adjustably and selectively controlling the hydraulic line pressure in the automatic transmission, said line pressure control means being responsive to at least the rotational speed difference between an input shaft and an output shaft of the automatic transmission such that the pump means generates a minimum hydraulic line pressure necessary to maintain the torque transmitted from the input shaft of the automatic transmission to the output shaft of the automatic transmission.
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Accused Products
Abstract
The present invention provides a method and apparatus for controlling the hydraulic line pressure in an automatic transmission for a vehicle in response to the torque transmitted through the transmission such that a minimum hydraulic line pressure is provided to the frictional elements to achieve a no-slip condition through the transmission increasing transmission efficiency, thereby increasing the fuel economy of the vehicle. Hydraulic line pressure is controlled by activating a solenoid activated valve which allows fluid recirculation from the high-pressure side of the hydraulic pump to the low-pressure side of the pump. Control signals are generated based on engine speed, turbine speed, output speed (vehicle speed), hydraulic line pressures, driver selected gear, the operating gear and the torque converter operating condition for energizing the solenoid-actuated valve. The present invention further provides closed-loop adaptive control technology to learn the minimum line pressure requirements to compensate for production variability of clutch return springs, friction characteristics, surface finishes and flatness, as well as hydraulic response resulting from valve body part variation, wear, and changes over the life of the transmission.
37 Citations
18 Claims
- 1. In a hydraulic system for an automatic transmission having pump means for causing hydraulic fluid to flow through the hydraulic system and a pressure regulator means for regulating the hydraulic line pressure in the automatic transmission, the improvement comprising line pressure control means for adjustably and selectively controlling the hydraulic line pressure in the automatic transmission, said line pressure control means being responsive to at least the rotational speed difference between an input shaft and an output shaft of the automatic transmission such that the pump means generates a minimum hydraulic line pressure necessary to maintain the torque transmitted from the input shaft of the automatic transmission to the output shaft of the automatic transmission.
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6. A method for controlling the hydraulic line pressure of automatic transmission fluid produced by a hydraulic pump in an automatic transmission for a vehicle having a torque convertor, a transmission input shaft, frictional elements for selectively engaging one of a plurality of gears and a transmission output shaft, the method comprising the steps of:
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estimating an input torque transmitted from the torque convertor to the transmission input shaft; selecting a pressure-torque constant related to the gear in which the transmission is operating and the hydraulic characteristics of the frictional elements; estimating an estimated line pressure required to maintain torque through the automatic transmission based on the input torque and the pressure-torque constant; generating a line pressure control signal in response to the effective line pressure; and adjusting the hydraulic line pressure in response to the line pressure control signal. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for controlling the hydraulic line pressure of automatic transmission fluid produced by a hydraulic pump in an automatic transmission for a vehicle having a torque convertor capable of operating in a plurality of lock-up conditions, a transmission input shaft, frictional elements for shifting and engaging a plurality of gears and a transmission output shaft, said method comprising the steps of:
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estimating the torque transmitted to the transmission input shaft from the torque convertor based on the lock-up condition of the torque convertor; selecting a pressure-torque constant related to the plurality of gears in which the transmission is operating and the hydraulic characteristics of the frictional elements; adjusting the pressure-torque constant based on prior rotational speed differences between the transmission input shaft and the transmission output shaft; estimating an estimated line pressure required to maintain torque through the automatic transmission based on the torque transmitted to the transmission input shaft and the pressure-torque constant; adjusting the estimated line pressure required to maintain torque through the automatic transmission based on mechanical characteristics of the frictional elements and the torque convertor; comparing the estimated line pressure to a minimum line pressure and generating a line pressure signal therefrom, wherein the line pressure signal is responsive to the estimated line pressure if the estimated line pressure exceed the minimum line pressure and the line pressure signal is responsive to the minimum line pressure if the estimated line pressure is below the minimum line pressure; determining the lock-up condition of the torque convertor and the shifting condition of the automatic transmission; and adjusting the hydraulic line pressure in response to the line pressure control signal, the lock-up condition of the torque convertor and the shift condition of the automatic transmission.
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Specification