Automatic Transmission Downshift Control with Fail-Safe Circuit
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Solution Overview
Problem
Existing automotive automatic transmission systems experience shift shock and unwanted acceleration during downshifts due to time lags in engagement or disengagement of frictional elements and defects in hydraulic pressure control, leading to inefficient engine braking.
Innovation Solution
An automatic transmission control apparatus with a hydraulic control circuit, defect detector, engine output increasing circuit, and fail-safe circuit to manage hydraulic pressures and throttle control, ensuring safe and controlled downshifts by detecting defects and adjusting engine output accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If engine power increasing control is initiated before actual downshift to compensate for time lag, then shift shock is reduced, but unwanted acceleration occurs if hydraulic control has defects
Solution Approach 1:
The system initiates engine power increasing control before the actual downshift occurs to compensate for time lags in frictional element engagement/disengagement and engine power response. This preliminary action ensures smooth downshift by pre-adjusting engine power, while the defect detector monitors hydraulic control functionality to prevent unwanted acceleration.
Solution Approach 2:
The defect detector continuously monitors the hydraulic control circuit to detect defects in real-time. When a defect is detected, the system stops the engine power increasing control to prevent unwanted acceleration. This feedback mechanism ensures reliable downshift control while preventing harmful effects.
2Extent of automation
If hydraulic pressure control is used to achieve downshift, then gear shifting is automated, but time lags in frictional element engagement cause shift shock
Solution Approach 1:
The system initiates engine power increasing control before the actual downshift to compensate for time lags in frictional element engagement and disengagement. This preliminary power adjustment smooths the downshift process by preventing sudden torque changes, while the hydraulic control system remains automated.
Solution Approach 2:
The system changes engine power parameters (throttle valve opening, fuel injection amount, ignition timing) during the downshift process to compensate for time lags in the hydraulic control system. This parameter adjustment ensures smooth transition despite automation delays.
3Power
If throttle valve opening control is used to increase engine power, then engine output increases, but time lag between control initiation and power response causes downshift delay
Solution Approach 1:
The system initiates throttle valve opening control and engine power increasing measures before the actual downshift occurs. This preliminary action compensates for the time lag between control initiation and engine power response, ensuring timely downshift completion without delay.
Solution Approach 2:
The system maintains continuous engine power increasing control throughout the downshift process, from preliminary initiation through completion. This continuous action ensures that engine power adjusts smoothly and timely, preventing downshift delays while maintaining automated hydraulic control.
Data Source
AI summary
An automotive automatic transmission control apparatus is provided which works to increase the power of an engine in response to a request to down-shift the gear of an automatic transmission for developing the engine braking. The control apparatus includes a fail-safe circuit working to stop increasing the power of the engine when a defect in operation of a transmission hydraulic control circuit is detected after the hydraulic control circuit starts to control the hydraulic pressures to achieve the downshift of the automatic transmission. This eliminates or alleviates a problem, such as unwanted acceleration of the vehicle during the control of the downshift in the transmission.