Internal Combustion Engine Differential Cylinder Decompression
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Solution Overview
Problem
Internal combustion engines face challenges in starting performance due to insufficient starting motor torque and the need to shorten starting time, particularly in hybrid vehicles where the torque of the starting motor is low, and there is a requirement to switch from electric to internal combustion engine mode while traveling.
Innovation Solution
The implementation of a decompression device that differentially depressurizes the first and second cylinders during engine startup, with a greater decompression amount in the second cylinder compared to the first, reducing compression resistance and facilitating easier engine rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a starting motor is used to crank and start the internal combustion engine, then the engine can be started, but the starting performance decreases when the torque of the starting motor is insufficient
Solution Approach 1:
The decompression device performs preliminary action by depressurizing the cylinders before the engine starts, reducing the compression resistance that the starting motor must overcome. This anticipates the high torque demand during startup and partially eliminates it in advance, allowing the starting motor to more easily rotate the crankshaft despite insufficient torque.
Solution Approach 2:
The decompression device is activated during the starting phase to reduce cylinder pressure before combustion begins. By performing this decompression action beforehand, the engine requires less torque to reach operational speed, improving starting reliability when the starting motor has limited torque output.
2Reliability
If the starting motor torque is increased to improve starting performance, then the starting performance improves, but the device complexity and cost increase
Solution Approach 1:
The decompression function is segmented from the main valve train and implemented as a separate mechanism with dedicated decompression bodies and cam profiles. This segmentation allows the decompression operation to be independently controlled during startup without affecting the normal valve operation, improving starting performance while maintaining a manageable system complexity through functional separation.
Solution Approach 2:
The decompression device utilizes the existing camshaft structure and valve train components, making the camshaft serve multiple functions: both normal valve actuation and decompression control. This multi-functionality approach improves starting performance without significantly increasing device complexity, as it leverages existing components rather than adding entirely new systems.
3Device complexity
If uniform decompression is applied to all cylinders, then the structure is simple, but the starting performance is not optimized
Solution Approach 1:
The decompression device applies different decompression amounts to different cylinders based on their specific characteristics and positions. The second cylinder receives a greater decompression amount than the first cylinder, optimizing the torque distribution during startup. This localized differentiation of decompression quantity improves starting performance while maintaining relatively simple control through fixed cam profile design.
Solution Approach 2:
The decompression mechanism employs asymmetric cam profiles with different lift amounts for different cylinders. The cam for the second cylinder is designed with a greater decompression lift than the cam for the first cylinder, creating an asymmetric decompression pattern that optimizes starting performance by accounting for the rotational direction and torque requirements during engine cranking.
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 approach enhances the starting performance of the internal combustion engine by reducing the force required to rotate the crankshaft, allowing for quicker engine speed increase and improved starting efficiency, even with low starting motor torque, and prevents deterioration of vehicle travel feel during mode switching.
Implementation Method 1
a decompression device configured to depressurize the first cylinder and the second cylinder at a time when the internal combustion engine starts to rotationally derive
Data Source
AI summary
There is provided an internal combustion engine including: a crankshaft; a first cylinder and a second cylinder; and a decompression device configured to depressurize the first cylinder and the second cylinder at a time when the internal combustion engine starts to rotationally derive relative to the first cylinder and the second cylinder at a time after the internal combustion engine starts to rotationally drive. The decompression device is configured such that, at the time when the internal combustion engine starts to rotationally derive, a decompression amount in the second cylinder is greater than a decompression amount in the first cylinder.