Hydraulic Switching Valve for Variable Compression Connecting Rod
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Solution Overview
Problem
Internal combustion engines with fixed compression ratios face inefficiencies at part-load conditions due to 'knocking' issues, and existing variable compression systems with hydraulic connecting rods suffer from instability and drifting, especially under high inertia forces and low gas forces, leading to incomplete adjustment and reduced service life.
Innovation Solution
A connecting rod with a hydraulic arrangement featuring a switching valve and eccentric adjusting device, where the GKS chamber directly and unthrottled hydraulic fluid is directed into the MKS chamber, utilizing the gas and inertia forces to create a higher pressure than the hydraulic supply, preventing drifting and enhancing positional stability by throttling the adjustment speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydraulic fluid is supplied to the cylinders via a supply line with throttling, then the adjustment speed is controlled, but the filling process becomes slower and less efficient
Solution Approach 1:
The hydraulic system is segmented into two separate cylinders (first cylinder for high compression, second cylinder for low compression) with independent supply lines. This allows each cylinder to be filled and drained independently, improving overall system efficiency while maintaining controlled adjustment speeds through individual throttling of each supply line.
Solution Approach 2:
The supply lines are pre-configured with throttling elements before the hydraulic fluid enters the cylinders. This preliminary throttling action controls the filling speed from the outset, preventing excessive pressure buildup and ensuring smooth, controlled adjustment while maintaining efficient filling through the direct connection to the hydraulic supply.
2Adaptability or versatility
If the connecting rod adjusts to high compression position under high inertia forces, then the compression ratio increases, but drifting occurs and positional stability is lost
Solution Approach 1:
The system uses two cylinders with opposing functions: the first cylinder provides hydraulic support for high compression position, while the second cylinder provides hydraulic support for low compression position. These opposing hydraulic supports counterbalance the high inertia forces that cause drifting, allowing the connecting rod to maintain stable positional adjustment at both compression extremes.
Solution Approach 2:
The hydraulic supply system provides continuous feedback through the throttled supply lines to both cylinders. This feedback mechanism allows the system to detect and compensate for positional drift caused by inertia forces, maintaining stable compression ratio adjustment by dynamically balancing the hydraulic support in both cylinders.
3Speed
If the hydraulic fluid column is accelerated at high engine speeds, then the filling and emptying process speeds up, but pressure differentials become negative and prevent proper filling
Solution Approach 1:
The hydraulic fluid path is segmented into separate supply lines for each cylinder, each with its own throttling element. This segmentation allows the system to maintain positive pressure differentials in both cylinders even at high engine speeds, preventing the negative pressure differentials that would otherwise prevent proper filling while still enabling fast filling and emptying through the direct hydraulic supply connection.
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 configuration stabilizes the switching behavior and operating performance of the connecting rod, ensuring accurate adjustment and extended service life by preventing drifting and improving positional stability across varying engine loads.
Implementation Method 1
Each cylinder is assigned a check valve, by means of which hydraulic fluid can be supplied to the cylinders and from which discharge of hydraulic fluid from the cylinders is prevented
Implementation Method 2
A throttling point is arranged between the supply line and the inlet of the second cylinder, by means of which pressure is created in front of the check valve of the second cylinder
Implementation Method 3
The changeover valve has a movable piston, which can be selectively moved into a first switching position or a second switching position, by means of which, in the first switching position, the outlet of the first cylinder, and in the second switching position, the outlet of the second cylinder, is connected to the supply line
Implementation Method 4
a connecting rod with a hydraulic arrangement for an internal combustion engine with variable compression, with an eccentric adjusting device for adjusting an effective connecting rod length
Data Source
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AI summary
The invention relates to a hydraulic arrangement (10) with a changeover valve (9) for controlling the flow of hydraulic fluid through a connecting rod (1) for a variable-compression internal combustion engine, including an eccentric adjusting device (3) for adjusting the effective connecting rod length. The changeover valve (9) has a movable piston (17) which can be selectively moved into a first switching position (S1) or a second switching position (S2). In the first switching position (S1), an outlet (11) of the first cylinder (4) and in the second switching position (S2), an outlet (12) of the second cylinder (5) are connected to a supply line (8). The cylinders (4, 5) are connected such that in the first switching position (S1), hydraulic fluid can flow from the first cylinder (4) into the second cylinder (5). The invention further relates to a changeover valve (9) and a connecting rod (1) with a hydraulic arrangement (10).