Automatic Transmission Brake Release Control for Engine Restart
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Solution Overview
Problem
Conventional vehicles face challenges in reducing engine restart shock and maintaining startability without an electrically driven oil pump, which increases cost and weight, especially during automatic stop and restart scenarios.
Innovation Solution
A vehicular control apparatus that includes brake holding and release control mechanisms, hydraulic pressure control, and engagement state determination using engine and torque converter revolution speeds to manage brake force release and engagement timing, ensuring compatibility between shock reduction and startability without an electrically driven pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an electrically driven oil pump is equipped to maintain hydraulic pressure during engine stop, then frictional engagement elements can be maintained in engaged state and shock is reduced, but cost and weight increase
Solution Approach 1:
The control unit releases the brake force before the frictional engagement elements are fully engaged during engine restart. This preliminary action of brake force release prevents the shock that would otherwise occur during engagement, eliminating the need for an electrically driven oil pump to maintain hydraulic pressure.
Solution Approach 2:
The patent replaces the mechanical solution of using an electrically driven oil pump to maintain hydraulic pressure with a control-based solution that coordinates brake force release with the engagement timing of frictional engagement elements. This substitution eliminates the need for additional mechanical components.
2Reliability
If brake force is held constant during engine stop, then vehicle reverse movement is prevented, but startability is reduced when accelerator pedal is depressed
Solution Approach 1:
The brake force holding control is made dynamic by releasing the brake force at different timings based on driver intent. When the accelerator pedal is depressed, the brake force is released earlier to improve startability. When the accelerator is not depressed, the brake force is maintained longer to prevent reverse movement. This dynamic adjustment resolves the contradiction between stability and startability.
Solution Approach 2:
The brake force parameter is changed from a constant held value to a dynamically adjusted value that changes timing based on accelerator pedal operation. This parameter change allows the system to adapt between preventing reverse movement and enabling quick startup depending on driver intent.
3Speed
If brake force is released early to improve startability, then vehicle can start quickly, but engagement shock increases
Solution Approach 1:
The control unit uses feedback from the accelerator pedal operation to determine the appropriate timing for brake force release. This feedback mechanism allows the system to coordinate brake force release with the engagement timing of frictional engagement elements, ensuring that brake force is released at the optimal moment to both improve startability and minimize shock.
Solution Approach 2:
The control unit acts as an intermediary that coordinates between the brake force holding control and the frictional engagement elements operation. By mediating the timing between these two systems, the control unit ensures that brake force is released at the precise moment that allows quick startup while preventing engagement shock.
Data Source
AI summary
There is provided with an automatic transmission (2) having a clutch (32) and a brake device (6) which holds a brake force during a stop of an engine (1). There is provided with an engine control section (11) which performs an automatic stop of the engine and a re-start of the engine and a release control section (14) which releases a holding of the brake force during the re-start of the engine. The release control section (14) releases the holding of the brake force when an engagement state of the clutch (32) is a predetermined state in case where an accelerator off state occurs until the engagement state of the clutch (32) becomes the predetermined state and releases the holding of the brake force when the engagement state of the clutch (32) is an engagement state weaker than the predetermined state, during a re-start of the engine (1).