AUTOMATIC TRANSMISSION AND CONTROL METHOD THEREOF
First Claim
1. An automatic transmission which has a planetary gear and a plurality of friction elements, and in which a directed gear position is achieved by switching an engagement/release state of the plurality of friction elements, and the directed gear position is one of a plurality of gear positions, the transmission comprising:
- a controller functioning to;
detect repeatedly whether or not a release failure or an engagement failure has occurred in the friction elements while a vehicle is traveling, a release failure occurring when the friction element cannot be engaged even when an engagement command is output thereto and an engagement failure occurring when the friction element cannot be released even when a release command is output thereto;
begin failed element specification control to specify the failed friction element when a vehicle speed falls to or below a predetermined value for the first time after a failure has been detected, andperform a limp home control which determines usable gear positions on the basis of the specified friction element when the failed friction element has been specified, and performs a shift control using only the usable gear positions.
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Accused Products
Abstract
In an automatic transmission of this invention, a determination as to whether or not a failure has occurred in a friction element is made repeatedly while a vehicle is traveling, and control to specify the failed friction element is begun when a vehicle speed falls to or below a predetermined value for the first time following detection of the failure in the friction element (S1, S3). When the failed friction element has been specified (S4, S13, S15, S24, S26, S35, S37), usable gear positions are determined on the basis of the specified friction element, whereupon shift control is performed using only the usable gear positions (S5, S14, S16, S25, S27, S36, S38, S39).
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Citations
16 Claims
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1. An automatic transmission which has a planetary gear and a plurality of friction elements, and in which a directed gear position is achieved by switching an engagement/release state of the plurality of friction elements, and the directed gear position is one of a plurality of gear positions, the transmission comprising:
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a controller functioning to; detect repeatedly whether or not a release failure or an engagement failure has occurred in the friction elements while a vehicle is traveling, a release failure occurring when the friction element cannot be engaged even when an engagement command is output thereto and an engagement failure occurring when the friction element cannot be released even when a release command is output thereto; begin failed element specification control to specify the failed friction element when a vehicle speed falls to or below a predetermined value for the first time after a failure has been detected, and perform a limp home control which determines usable gear positions on the basis of the specified friction element when the failed friction element has been specified, and performs a shift control using only the usable gear positions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. Control method for an automatic transmission which has a planetary gear and a plurality of friction elements, and in which a directed gear position is achieved by switching an engagement/release state of the plurality of friction elements, and the directed gear position is one of a plurality of gear positions, the method comprising:
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a failure detecting step for detecting repeatedly whether or not a release failure or an engagement failure has occurred in the friction elements while a vehicle is traveling, a release failure occurring when the friction element cannot be engaged even when an engagement command is output thereto and an engagement failure occurring when the friction element cannot be released even when a release command is output thereto; a failed element specification control step for beginning control to specify the failed friction element when a vehicle speed falls to or below a predetermined value for the first time after a failure has been detected by the failure detecting step; and a limp home control step for determining usable gear positions on the basis of the specified friction element when the failed friction element has been specified by the failed element specification control step, and performing shift control using only the usable gear positions.
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16. An automatic transmission which has a planetary gear and a plurality of friction elements, and in which a directed gear position is achieved by switching an engagement/release state of the plurality of friction elements, and the directed gear position is one of a plurality of gear positions, the transmission comprising:
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failure detecting means for detecting repeatedly whether or not a release failure or an engagement failure has occurred in the friction elements while a vehicle is traveling, a release failure occurring when the friction element cannot be engaged even when an engagement command is output thereto and an engagement failure occurring when the friction element cannot be released even when a release command is output thereto; failed element specification control means for beginning control to specify the failed friction element when a vehicle speed falls to or below a predetermined value for the first time after a failure has been detected by the failure detecting means; and limp home control means for determining usable gear positions on the basis of the specified friction element when the failed friction element has been specified by the failed element specification control means, and performing shift control using only the usable gear positions.
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Specification