Hybrid Vehicle Braking via Engine Reverse Rotation
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Solution Overview
Problem
Existing hybrid vehicles face limitations in achieving sufficient braking force, particularly when a large braking force is required, as the conventional method of decreasing the intake valve lift or working angle is insufficient.
Innovation Solution
A hybrid vehicle configuration that includes an engine, a first motor, a planetary gear mechanism, a second motor, and a secondary battery, allowing power to be output in both normal and reverse rotating directions, with a braking controller that controls the engine and motors to transmit power in the reverse direction to the driveshaft when a high braking force is needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the lift amount or working angle of the intake valve is decreased during regenerative control, then the braking force is increased, but the obtained braking force is limited and cannot meet large required braking force
Solution Approach 1:
The patent applies reverse rotation of the engine to generate braking force. Instead of using the conventional method of decreasing intake valve lift/working angle during normal engine rotation, the invention rotates the engine in the reverse direction through the planetary gear mechanism to directly generate engine braking force that can be transmitted to the driveshaft, thereby reliably meeting large required braking force demands.
Solution Approach 2:
The patent dynamically switches between normal engine rotation and reverse engine rotation based on braking force requirements. The planetary gear mechanism enables flexible direction control of engine rotation, allowing the system to adaptively select the most effective braking mode (normal rotation with valve control or reverse rotation with direct engine braking) to meet varying braking demands.
2Force
If the engine is motored by the first motor in the state that fuel supply is stopped, then braking force is generated, but a larger braking force cannot be reliably output
Solution Approach 1:
The patent uses reverse rotation of the engine to generate braking force. Instead of motoring the engine in the forward direction with the first motor, the invention rotates the engine in reverse through the planetary gear mechanism, enabling the engine to directly generate braking force that can be transmitted to the driveshaft, thereby reliably meeting large required braking force demands.
Solution Approach 2:
The patent bypasses the intermediate step of motoring the engine in forward direction and directly achieves braking force generation through reverse rotation. The planetary gear mechanism enables direct transmission of reverse rotation power to the driveshaft, skipping the conventional path and achieving more efficient and powerful braking force output.
Data Source
AI summary
In a hybrid vehicle configured such that a sun gear, a carrier and a ring gear of a planetary gear are respectively connected with a rotating shaft of a motor MG1, a crankshaft of an engine and a driveshaft and that a motor MG2 is connected with the driveshaft, when a required braking force that is to be output to the driveshaft is equal to or less than a reference value Tref in an accelerator-off state, the braking force by engine braking is output to the driveshaft by motoring of the engine by the motor MG1. When the required braking force becomes greater than the reference value Tref, on the other hand, the power output from the engine by load operation of the engine in a reverse rotating direction is output as the braking force to the driveshaft.