Automatic transmission
AssigneeLuk Lamellen und Kupplungen Beteiligungs KG
InventorIvo Agner
Life of this patent
Estimating the term…
Abstract
A method and apparatus for operating an automatic transmission as a function of the engine rotational speed of a variable speed internal combustion engine. Upon a failure of the electronic control system, a return home of a motor vehicle under its own power is enabled. A delivery system delivers a working medium with which a transmission ratio adjusting device is actuated by a first control device that, in turn, is controlled by a pilot pressure that can be accurately changed by a second control device to actuate the transmission ratio adjusting device. The pilot pressure for controlling the first control device is changed by a third control device as a function of the rotational speed of the internal combustion engine when an adjusting device is switched out of a normal operation position into an emergency operation position.
Claims12
A method for operating an automatic transmission of a motor vehicle as a function of at least the engine rotational speed, said method comprising the steps of:
- adjusting the transmission ratio in an emergency mode of the automatic transmission after a starting process to change the transmission ratio to a speed increasing ratio when the engine rotational speed increases, changing the transmission ratio to a speed reducing ratio when the engine rotational speed decreases, to maintain the engine rotational speed at a defined value, changing the transmission ratio after the starting process to a speed increasing ratio at increasing engine rotational speed until a smallest possible transmission ratio is reached, and maintaining that transmission ratio during a further increase in engine rotational speed.
A method for operating an automatic transmission of a motor vehicle as a function of at least the engine rotational speed, said method comprising the steps of:
- adjusting the transmission ratio in an emergency mode of the automatic transmission after a starting process to change the transmission ratio to a speed increasing ratio when the engine rotational speed increases, and changing the transmission ratio to a speed reducing ratio when the engine rotational speed decreases, to maintain the engine rotational speed at a defined value, changing the transmission ratio after the starting process to a speed reducing ratio at decreasing engine rotational speed until a largest possible transmission ratio is reached, and maintaining that transmission ratio during a further decrease in engine rotational speed.
An automatic transmission for a variable speed internal combustion engine, said transmission comprising:
- a delivery system for delivering a working medium, the transmission having a working-medium-actuated transmission ratio adjustment arrangement that includes at least one transmission ratio adjusting device that receives working medium from a first control device that is controlled by a pilot pressure that is accurately modified by an electrically-controlled second control device to actuate the transmission ratio adjusting device, a third control device that is actuated by the working medium delivered by the delivery system, wherein the third control device controls a pilot pressure that operates to control operation of the first control device, a first switching device that is switchable between a normal operation position at which the pilot pressure is maintained substantially constant and an emergency operation position at which the pilot pressure is a function of the rotational speed of the internal combustion engine, to control the transmission when the second control device becomes inoperative after a starting process, and a second switching device operatively coupled with the first switching device and responsive to an electrical failure to relieve a working medium pressure acting on the first switching device to cause the first switching device to switch to the emergency operation position.
An automatic transmission for a variable speed internal combustion engine, said transmission comprising:
- a delivery system for delivering a working medium, the transmission having a working-medium-actuated transmission ratio adjustment arrangement that includes at least one transmission ratio adjusting device that receives working medium from a first control device that is controlled by a pilot pressure that is accurately modified by a second control device to actuate the transmission ratio adjusting device, a third control device that is actuated by the working medium delivered by the delivery system, wherein the third control device controls a pilot pressure that operates to control operation of the first control device, and a switching device that is switchable between a normal operation position at which the pilot pressure is maintained substantially constant and an emergency operation position at which the pilot pressure is a function of the rotational speed of the internal combustion engine, to control the transmission when the second control device becomes inoperative, wherein the delivery system for the working medium includes a pump whose delivered volumetric flow is a function of the speed of the internal combustion engine, and wherein the third control device includes an axially displaceable, spring-biased spool having first and second working surfaces for controlling flow of the working medium delivered by the delivery system, and having a third working surface against which the pilot pressure acts, wherein the first and the second working surfaces for the working medium have the same area.
Dependencies are inferred from the claim text.