Speed change control method for an automatic transmission
First Claim
1. A speed change control method for an automatic transmission including a first transmission mechanism for establishing a plurality of gear positions, and a second transmission mechanism for establishing a plurality of gear positions, said first and second transmission mechanisms being connected in series with respect to a power transmission, the automatic transmission establishing an arbitrary one of a plurality of shift positions, including first and second shift positions, by a combination of a speed position established in the first transmission mechanism and a gear position established in the second transmission mechanism, a speed ratio of the second shift position being lower than a speed ratio of the first shift position, comprising:
- (a) starting a speed-changing operation of the second transmission mechanism to establish a gear position, corresponding to the second shift position, in the second transmission mechanism when a speed change command for instructing a speed change from the first shift position to the second shift position is output; and
(b) reducing an engagement force of a first friction element provided in said first transmission mechanism to a predetermined value prior to an initiation of a speed-changing operation in the first transmission mechanism to establish a gear position, corresponding to the second shift position, in the first transmission mechanism before said speed-changing operation in step (a) is completed, said first friction element being engaged when establishing, in the first transmission mechanism, a gear position corresponding to the first shift position, and released when establishing, in the first transmission mechanism, the gear position corresponding to the second shift position.
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Accused Products
Abstract
A speed change control method for an automatic transmission is provided, which is capable of reducing a shift shock and a required shifting time period. A skip down-shift from a first shift position to a second shift position is effected by way of a third shift position which is not used in a normal shifting. If it is determined that a difference (NTM -NT) between the present turbine rotation speed NT and the synchronous rotation speed NTM for the third shift position becomes smaller than a threshold value ΔNFM during the shifting from the first shift position to the third shift position, a control for releasing a friction engaging element 23, corresponding to a releasing side speed-changing element of the third shift position, is started prior to establishment of the third shift position, whereby a time period for establishing the third shift position is shortened, so that a shift shock and a required shifting time period are reduced.
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Citations
11 Claims
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1. A speed change control method for an automatic transmission including a first transmission mechanism for establishing a plurality of gear positions, and a second transmission mechanism for establishing a plurality of gear positions, said first and second transmission mechanisms being connected in series with respect to a power transmission, the automatic transmission establishing an arbitrary one of a plurality of shift positions, including first and second shift positions, by a combination of a speed position established in the first transmission mechanism and a gear position established in the second transmission mechanism, a speed ratio of the second shift position being lower than a speed ratio of the first shift position, comprising:
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(a) starting a speed-changing operation of the second transmission mechanism to establish a gear position, corresponding to the second shift position, in the second transmission mechanism when a speed change command for instructing a speed change from the first shift position to the second shift position is output; and (b) reducing an engagement force of a first friction element provided in said first transmission mechanism to a predetermined value prior to an initiation of a speed-changing operation in the first transmission mechanism to establish a gear position, corresponding to the second shift position, in the first transmission mechanism before said speed-changing operation in step (a) is completed, said first friction element being engaged when establishing, in the first transmission mechanism, a gear position corresponding to the first shift position, and released when establishing, in the first transmission mechanism, the gear position corresponding to the second shift position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification