Coast Stop Vehicle Hydraulic Control for Downshift Response
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Solution Overview
Problem
Existing coast stop technologies experience delays in responding to acceleration requests due to the time required for downshifting during a coast stop, leading to a delay in obtaining drive power when a driver requests acceleration.
Innovation Solution
A coast stop system that includes a transmission with multiple gear positions, a hydraulic pressure supplying unit, a coast stop start condition judging unit, a coast stop control unit, and a hydraulic control unit to quickly downshift the transmission and supply hydraulic pressure to after-shift frictional engagement elements, allowing for immediate engine start and gear position change upon receiving an acceleration request.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission shifts down when an acceleration request is given during coast stop, then the drive power required by the driver is obtained, but the downshift takes time causing a delay in response
Solution Approach 1:
The hydraulic control unit supplies hydraulic pressure to the after-shift frictional engagement element in advance during coast stop, before the acceleration request is given. This preliminary action ensures that when the driver requests acceleration, the transmission can complete the downshift immediately without waiting for hydraulic pressure buildup, thereby reducing downshift time and improving response speed
2Power
If the engine is started immediately when an acceleration request is given during coast stop, then the drive power is provided, but the transmission downshift takes time causing delay
Solution Approach 1:
The system performs preliminary action by supplying hydraulic pressure to the frictional engagement element before the acceleration request. This allows the transmission downshift to be completed simultaneously with or immediately after engine start, eliminating the delay that would otherwise occur while waiting for the transmission to shift down
3Loss of time
If the hydraulic pressure is supplied to the after-shift frictional engagement element during coast stop, then the downshift time is shortened, but the system complexity increases
Solution Approach 1:
The hydraulic control unit is designed to perform multiple functions: it controls both the frictional engagement element for transmission shifting and manages hydraulic pressure supply during coast stop. By making the hydraulic control system multi-functional, the patent avoids adding separate dedicated components for each function, thereby reducing overall system complexity while still achieving shortened downshift time
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces the time required for downshifting and eliminates delays in responding to acceleration requests, ensuring prompt drive power delivery and minimizing shift shock, thereby enhancing acceleration performance and fuel efficiency.
Implementation Method 1
a hydraulic pressure supplying unit which supplies a hydraulic pressure to the transmission while the engine is stopped
Implementation Method 2
a hydraulic control unit which supplies the hydraulic pressure to an after-shift frictional engagement element which realizes a gear position after the downshift
Data Source
AI summary
A coast stop vehicle includes a hydraulic pressure supplying unit which supplies a hydraulic pressure to the transmission while the engine is stopped, a coast stop start condition judging unit which judges whether or not a coast stop start condition holds, a coast stop control unit which stops the engine when the coast stop start condition is judged to hold by the coast stop start condition judging unit and starts the engine when receiving an acceleration request from a driver during the coast stop, a transmission control unit which causes a downshift of the transmission when receiving the acceleration request from the driver during the coast stop, and a hydraulic control unit which supplies the hydraulic pressure to an after-shift frictional engagement element which realizes a gear position after the downshift of the transmission during the coast stop.