Variable-Compression Connecting Rod With Decoupled Hydraulic Interlock
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Solution Overview
Problem
Existing connecting rods for internal combustion engines lack a reliable mechanism to securely change compression ratios without trapping air, which can lead to unintentional unlocking of the interlock, causing dynamics issues and instability in compression settings.
Innovation Solution
A connecting rod design featuring a hydraulic circuit with decoupled sub-circuits, including an orifice plate or throttle for air prevention, and a directional control valve with 2 switching positions and 7 ports, allowing for secure locking and unlocking of the interlock, enabling reliable setting of high and low compression ratios through fluid pressure management and venting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a hydraulic circuit is used to control the interlock for changing compression ratio, then the compression ratio can be changed, but air can be trapped in the hydraulic circuit causing unintentional unlocking of the interlock
Solution Approach 1:
The hydraulic circuit is segmented into two independent sub-circuits: a first sub-circuit for controlling the compression ratio and a second sub-circuit for controlling the interlock. This segmentation prevents air trapped in one sub-circuit from affecting the other, thereby maintaining interlock stability while enabling compression ratio adjustment.
Solution Approach 2:
A decoupling mechanism (such as a check valve or flow restrictor) acts as an intermediary between the two sub-circuits, allowing hydraulic fluid to pass in one direction while preventing air or pressure fluctuations from the first sub-circuit from reaching the second sub-circuit, thus protecting the interlock from unintentional unlocking.
2Device complexity
If the hydraulic circuit is coupled for controlling both compression ratio and interlock, then the system is simpler, but significant amounts of air could be trapped causing unintentional unlocking
Solution Approach 1:
The hydraulic circuit is divided into two separate sub-circuits with distinct functions: one for compression ratio control and another for interlock control. This segmentation increases structural complexity but eliminates air entrapment issues that would compromise interlock reliability.
Solution Approach 2:
The interlock control function is extracted from the compression ratio control circuit, creating an independent second sub-circuit. This extraction removes the harmful effect of air entrapment from the interlock system while maintaining the overall system functionality.
3Volume of moving object
If a single hydraulic circuit controls both fluid chamber and interlock, then the system is more compact, but air entrapment causes unwanted dynamics and instability
Solution Approach 1:
The hydraulic system is segmented into two independent sub-circuits that can be compactly arranged within the connecting rod. This segmentation prevents air entrapment and the resulting unwanted dynamics, ensuring stable compression settings while maintaining a compact overall design.
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
The solution ensures reliable and maintenance-friendly switching between high and low compression ratios, preventing air entrapment and reducing unwanted dynamics, thereby stabilizing the engine's operation and extending the lifespan of the connecting rod.
Implementation Method 1
a fluid pressure in the fluid chamber exerts a force on the projection to change the position of the eccentric
Implementation Method 2
a hydraulic resistance is provided for decoupling the first and the second sub-circuit
Implementation Method 3
the interlock comprises a spring for locking
Implementation Method 4
a pressure of a hydraulic fluid counteracts a force of the spring and unlocks the interlock
Data Source
AI summary
A connecting rod for changing a compression ratio of an internal combustion engine includes a connecting rod head, a connecting rod pin, and an interlock. The connecting rod pin is supported by an eccentric of the connecting rod at a variable distance within the connecting rod head. The connecting rod head or the connecting rod pin includes a fluid chamber and the eccentric has a projection extending into the fluid chamber. In the alternative, the eccentric delimits a fluid chamber and the connecting rod head or the eccentric has a projection extending into in the fluid chamber. A fluid pressure in the fluid chamber exerts a force on the projection to change the position of the eccentric. In a locking position, the interlock inhibits rotation of the eccentric relative to the connecting rod head and the interlock is configured to be releasable.