Variable Compression Ratio Engine Stopper Design
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Solution Overview
Problem
Existing variable compression ratio internal combustion engines face challenges in ensuring the strength and rigidity of stoppers due to rotating parts around the crankshaft bearing, leading to prolonged reference position learning times and accuracy issues, especially when learning both rotational directions.
Innovation Solution
A variable compression ratio internal combustion engine design featuring a first stopper outside the engine body for strong and rigid restriction in one rotational direction and a second stopper inside for accurate restriction in the opposite direction, allowing for faster learning without compromising accuracy by minimizing layout restrictions and link parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stopper is provided on the crankshaft bearing part inside the engine body, then the layout restrictions are severe and it is difficult to ensure sufficient strength and rigidity, but providing it outside the engine body increases the number of link parts and deteriorates reference position learning accuracy
Solution Approach 1:
The patent divides the stopper function into two separate stoppers: a first stopper provided outside the engine body for one rotational direction, and a second stopper provided inside the engine body for the opposite rotational direction. This segmentation allows each stopper to be optimally positioned for its specific function, with the first stopper having sufficient strength and rigidity and the second stopper having minimal link parts.
Solution Approach 2:
Different locations are assigned different stoppers based on local requirements: the first stopper is placed outside the engine body where space allows for a strong and rigid structure, while the second stopper is placed inside the engine body where it can directly restrict the control shaft with minimal intervention from link parts.
2Reliability
If the movable part is brought into abutted-engagement with the stopper inside the engine body, then the stopper can be provided, but the speed of the movable part must be slowed down to limit torque, increasing the time duration required for reference position learning
Solution Approach 1:
The patent segments the reference position learning process into two phases: first learning the reference position by engaging the first movable part with the first stopper (outside the engine body) at high speed, then learning the maximum conversion angle range by engaging the second movable part with the second stopper (inside the engine body) with speed limitation. This segmentation allows the time-consuming low-speed engagement to occur only once per learning cycle.
Solution Approach 2:
The first stopper engagement (outside the engine body) is performed preliminarily at high speed to establish the reference position before the second stopper engagement (inside the engine body) is performed at limited speed to establish the maximum conversion angle range. This preliminary high-speed action reduces the overall learning time.
3Strength
If the stopper is provided outside the engine body, then the strength and rigidity can be ensured, but the layout restrictions become severe
Solution Approach 1:
The housing that contains the first stopper outside the engine body is designed to serve multiple functions: it houses the first stopper for reference position learning, contains the drive motor for the control shaft, and provides structural support. This multi-functionality reduces overall device complexity despite the external placement of the first stopper.
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 design shortens the time required for reference position learning while maintaining accuracy by ensuring sufficient strength and rigidity of the first stopper and reducing link parts between the second stopper and piston, improving detection accuracy of the engine compression ratio.
Implementation Method 1
a first stopper provided outside of an engine body for mechanically restricting a position of maximum rotation of the control shaft in a first rotational direction by bringing a first movable part, which operates in conjunction with the control shaft, into abutted-engagement with the first stopper
Implementation Method 2
a second stopper provided inside of the engine body for mechanically restricting a position of maximum rotation of the control shaft in a second rotational direction opposite to the first rotational direction by bringing a second movable part, which operates in conjunction with the control shaft, into abutted-engagement with the second stopper
Data Source
AI summary
A variable compression ratio internal combustion engine is equipped with a variable compression ratio mechanism configured to change an engine compression ratio in accordance with a rotational position of a control shaft, and a housing that accommodates therein a drive motor for changing and holding the rotational position of the control shaft. A reference position of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a first rotational direction has been mechanically restricted by bringing a first movable part, which operates in conjunction with the control shaft, into abutted-engagement with a first stopper provided outside of an engine body. Subsequently, a maximum conversion angle range of the control shaft is learned in a state where a position of maximum rotation of the control shaft in a second rotational direction has been mechanically restricted by a second stopper.