Hydraulic VCR Piston Rate-Sensitive Pressure Control
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Solution Overview
Problem
Conventional variable compression ratio (VCR) pistons in internal combustion engines fail to effectively control the rate of cylinder pressure rise and peak cylinder pressure, leading to potential engine noise and energy losses.
Innovation Solution
A hydraulic VCR piston with a rate-sensitive pressure relief valve that dynamically adjusts the target peak cylinder pressure and rate of pressure rise, using a mechanism with a sleeve valve and bleed orifice to respond to both the rate and magnitude of pressure changes, and an oil circuit system to regulate oil pressure and minimize energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional VCR pistons are used to control cylinder pressure, then the compression ratio can be adjusted, but the rate of pressure rise and peak pressure cannot be effectively controlled, leading to engine noise and energy losses
Solution Approach 1:
The patent implements a dynamic pressure control system where the piston geometry can change during engine operation. The piston includes a movable geometry mechanism that adjusts compression ratio in real-time based on operating conditions, transitioning from static to dynamic adaptation. This allows the system to respond to changing engine demands while maintaining optimal pressure characteristics.
Solution Approach 2:
The patent changes the physical parameters of the piston geometry dynamically. By varying the compression ratio as a controllable parameter based on engine operating conditions (load, speed, temperature), the system optimizes performance across different regimes. This parameter change approach enables adaptation to both cold starting and full-load conditions without fixed compromises.
2Adaptability or versatility
If the piston geometry changes over several engine cycles to adjust compression ratio, then the compression ratio can be modified, but the response is slow and cannot address immediate pressure control needs
Solution Approach 1:
The patent implements preliminary action by pre-positioning the piston geometry adjustments before critical pressure conditions occur. The control system anticipates pressure rise needs and adjusts the compression ratio in advance during the intake or compression stroke, rather than waiting for pressure problems to develop. This proactive approach enables faster effective response to pressure control requirements.
Solution Approach 2:
The patent accelerates the geometry change process to occur within a single engine cycle rather than spanning multiple cycles. By rushing through the geometry transition during critical portions of the engine cycle, the system achieves immediate pressure control response. This may involve rapid mechanical actuation or valve timing adjustments that complete the geometry change before the compression stroke concludes.
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 allows for precise control of cylinder pressure, reducing engine noise and energy losses by dynamically adjusting pressure rise rates and peak pressures, enhancing engine performance across various operating conditions.
Implementation Method 1
A first hydraulic chamber is formed between the underside of the crown of the outer sleeve and the upper surface of the gudgeon pin carrier
Implementation Method 2
A check valve is formed in the gudgeon pin carrier and allows one-way flow of oil from the second hydraulic chamber
Implementation Method 3
The relief valve is responsive to a rate of change of cylinder pressure
Data Source
AI summary
A hydraulic variable compression ratio (VCR) piston for use in an internal combustion engine. The piston is a two-part piston, in which a gudgeon pin carrier slides within an outer sleeve. A variable volume upper chamber is formed between the top of the gudgeon pin carrier and the end of the outer sleeve. When the upper chamber fills with oil, its volume increases, and the overall piston geometry is longer. This reduces the piston clearance in the cylinder and increases cylinder pressure. At a given maximum cylinder pressure or at a given rate of increase of cylinder pressure, oil from the upper chamber is relieved by using a rate-sensitive pressure relief valve.