Hybrid Vehicle Shift Control Minimizing Kick-Down Dead Zone
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Solution Overview
Problem
Conventional shift control systems in hybrid vehicles fail to provide sufficient acceleration in EV mode due to increased motor rotation speed leading to reduced torque and un-synchronized acceleration, and existing solutions like prohibiting kick-down shifts or delayed engine engagement result in excessive acceleration dead zone time.
Innovation Solution
A shift control system and method that detects kick-down shift requests in EV mode, determines if the engine is operational, and if not, executes the kick-down shift immediately, while delaying it if the engine is operating to ensure complete engine clutch connection before mode change to HEV mode, thereby minimizing acceleration dead zone time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a kick-down shift is executed in EV mode by increasing motor rotation speed, then gear ratio is increased, but torque is reduced and sufficient acceleration cannot be realized
Solution Approach 1:
The patent introduces the engine as an intermediary power source to supplement motor torque during kick-down shifts in EV mode. When a kick-down shift is detected, the system activates the engine to provide additional torque while the motor maintains elevated rotation speed for the gear ratio change, ensuring sufficient acceleration force is available throughout the shift process.
Solution Approach 2:
The patent creates a composite power delivery system by combining engine and motor power sources during kick-down shifts in EV mode. The engine clutch engages to connect the engine to the transmission, creating a hybrid power configuration that leverages both the high-torque engine and the high-speed-capable motor to achieve both increased gear ratio and maintained torque output.
2Force
If kick-down shift is prohibited and engine is started using ISG in EV mode, then engine is engaged to provide power, but excessive acceleration dead zone time occurs from kick-down request to engine start
Solution Approach 1:
The patent applies preliminary action by pre-engaging the engine clutch and activating the engine in anticipation of a kick-down shift request, rather than waiting until the request is made. The control unit monitors for kick-down conditions and prepares the engine power source in advance, so when acceleration is needed, the engine is already operational and the clutch is engaged, eliminating the dead zone delay.
Solution Approach 2:
The patent introduces dynamic control of the engine clutch engagement timing based on detected kick-down shift requests. Instead of a fixed engagement schedule, the system dynamically adjusts clutch engagement and engine activation timing based on real-time driving conditions and accelerator pedal input, optimizing the balance between power availability and response time.
3Power
If engine clutch is engaged to connect engine and motor, then power transmission is optimized, but acceleration response is delayed during mode change from EV to HEV
Solution Approach 1:
The patent applies the skipping principle by rapidly transitioning through the mode change process from EV to HEV when a kick-down shift is detected. The control unit prioritizes quick engine clutch engagement and mode switching over gradual transitions, rushing through the necessary steps to establish engine power transmission as quickly as possible to minimize acceleration response delay.
Data Source
AI summary
A shift control system for a hybrid vehicle having an engine and a motor as power sources may include a driving condition detector which detects whether a kick-down shift-request occurs in EV (Electric Vehicle), and a hybrid control unit which changes a driving mode from the EV (Electric Vehicle) mode to HEV (Hybrid Electric Vehicle) mode by connecting an engine clutch when the kick-down shift-request may be detected and an engine may be operated, and executes a kick-down shift.