Patent US5079970A successfully refreshed from Google Patents.
US5079970A
Expired / Lapsed
US
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Acceleration-based control of power-on downshifting in an automatic transmission
Assignee: GM Global Technology Operations LLC
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Filing: 1990-10-24
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Granted: 1992-01-14
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Expires: 2010-10-24
Abstract
Abstract A power-on clutch-to-clutch downshift control is initiated by partially releasing an off-going torque trasmitting device to permit an increase in the transmission input speed. At the same time, an on-coming torque transmitting device is filled in preparation for engagement. When the slip across the on-coming device is near zero, the on-coming device pressure is progressively increased while the off-going clutch pressure is controlled to maintain the near-zero on-coming slip speed condition. When the on-coming device develops significant capacity, a tie-up develops between the on-coming and off-going devices, causing a drop in output shaft acceleration. The drop is detected and used to release the off-going device, the shift being complete when the on-coming device is fully engaged. Engine torque controls are employed to ensure a smooth output torque transition at the end of the shift.
Inventors
- 👤 Kenneth R. Butts
- 👤 Kumaraswamy V. Hebbale
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:17
CPC Classifications
B; B60; B60W; B60W10/00; B60W10/04; B60W10/06; B60W10/10; B60W10/11; B60W10/115; B60W30/00; B60W30/18; B60W30/1819; B60W30/19; F; F16; F16H; F16H61/00; F16H61/04; F16H61/06; F16H61/061; F16H59/00; F16H59/36; F16H59/38; F16H2059/405; F16H59/68; F16H2059/6807; F16H2061/0075; F16H2061/0078
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
191 words
A method of downshifting a motor vehicle automatic shift power transmission having an input driven by a vehicle engine, and an output connected to drive a vehicle wheel, where downshifting involves releasing an off-going pressure to disengage an off-going torque transmitting device while increasing an on-coming pressure to engage an on-coming torque transmitting device, the method comprising the steps of: controlling the release of the off-going pressure so as to allow the engine to increase the input to a synchronous speed at which a slip speed across the on-coming torque transmitting device is near zero, and thereafter controlling the off-going pressure at a level to maintain the input at such synchronous speed; initiating a progressive increase of the on-coming pressure when the input approaches said synchronous speed, thereby to progressively engage the on-coming torque transmitting device; monitoring the acceleration of the transmission output to detect a drop indicative of a tie-up condition characterized by concurrent engagement of the off-going and on-coming torque transmitting devices; and fully releasing the off-going pressure when the tie-up condition is detected, the downshift being complete when the on-coming pressure fully engages the on-coming torque transmitting device.
Claim 2
Independent Claim
191 words
A method of downshifting a motor vehicle automatic shift power transmission having an input driven by a vehicle engine, and an output connected to drive a vehicle wheel, where downshifting involves releasing an off-going pressure to disengage an off-going torque transmitting device while increasing an on-coming pressure to engage an on-coming torque transmitting device, the method comprising the steps of: controlling the release of the off-going pressure so as to allow the engine to increase the input to a synchronous speed at which a slip speed across the on-coming torque transmitting device is near zero, and thereafter controlling the off-going pressure at a level to maintain the input at such synchronous speed; initiating a progressive increase of the on-coming pressure when the input approaches said synchronous speed, thereby to progressively engage the on-coming torque transmitting device; monitoring the acceleration of the transmission output to detect a drop indicative of a tie-up condition characterized by concurrent engagement of the off-going and on-coming torque transmitting devices; and fully releasing the off-going pressure when the tie-up condition is detected, the downshift being complete when the on-coming pressure fully engages the on-coming torque transmitting device.
Claim 3
Dependent Claim
67 words
The method set forth in claim 1, wherein the step of controlling the release of the off-going pressure includes the steps of: releasing the off-going pressure at an open-loop ramp rate until slippage of the off-going torque transmitting device is observed; and thereafter initiating a closed-loop control of the off-going pressure for increasing the input to said synchronous speed and maintaining the input at said synchronous speed.
Claim 4
Dependent Claim
99 words
The method set forth in claim 1, wherein the step of initiating a progressive increase of the on-coming pressure includes the steps of: increasing the on-coming pressure to a fill pressure for a predetermined fill period to fill the on-coming torque transmitting device in preparation for its engagement; reducing the on-coming pressure at the end of the fill period to a level sufficient to maintain the on-coming torque transmitting device in a filled condition; and increasing the on-coming pressure at an open-loop ramp rate when the input approaches said synchronous speed to progressively engage the on-coming torque transmitting device.
Claim 5
Dependent Claim
57 words
The method set forth in claim 1, wherein the step of monitoring the acceleration of the transmission output includes the steps of: comparing the rate of decrease in said output acceleration to a reference rate of decrease; and indicating the occurrence of a tie-up condition when the monitored rate of decrease exceeds the reference rate of decrease.
Claim 6
Dependent Claim
74 words
The method set forth in claim 1, wherein the engine is a spark ignition internal combustion engine having an adjustable spark timing control, and the method includes the steps of: initiating a retardation of the engine spark timing control when the magnitude of the slip speed across the on-coming torque transmitting device becomes less than a reference slip magnitude; and thereafter removing the retardation of the engine spark timing control at a predefined rate.
References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-01-13 | 1995-07-15 | 1996-01-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-01-13 | 1999-07-15 | 2000-01-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-01-13 | 2003-07-15 | 2004-01-14 | $7700.00 | Window Closed / Lapsed |