Variable Stroke Valve Actuator Thermal Management
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Solution Overview
Problem
Existing variable-stroke valve trains for internal combustion engines are large and prone to accuracy issues due to temperature fluctuations, affecting lift adjustment precision and rigidity.
Innovation Solution
A compact cylinder head design with an improved actuating element configuration, using a brushless electric motor and integrating the actuating element between ignition devices, allows for temperature control and eliminates the need for oil-tight sealing, enhancing rigidity and reducing size while minimizing thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the actuating element is arranged geodetically above the variable-stroke valve train and attached using the valve cover, then the valve train can be actuated, but the overall size becomes large and rigidity is reduced
Solution Approach 1:
The actuating element is repositioned from a vertical arrangement above the valve train to a horizontal arrangement within the cylinder head, lying in the plane of the cylinder head. This dimensional change allows the actuator to be integrated into the existing cylinder head structure, reducing overall size while improving connection rigidity through direct mounting to the cylinder head rather than through the valve cover.
2Measurement precision
If the actuating element is positioned away from the cylinder head, then installation is easier, but temperature fluctuations cause negative effects on lift adjustment accuracy
Solution Approach 1:
The cylinder head serves as an intermediary thermal mass between the actuating element and the external environment. By integrating the actuator directly into the cylinder head structure, the heavy metal cylinder head acts as a thermal buffer, absorbing and dampening temperature fluctuations that would otherwise directly affect the actuator and cause expansion/contraction errors in lift adjustment.
3Reliability
If a conventional electric motor with shaft sealing is used, then the actuator can be sealed, but friction increases and maintenance requirements arise
Solution Approach 1:
The harmful shaft sealing component is completely removed from the system by using a brushless electric motor design where the rotor rotates directly in the lubricant mist without requiring any sealing mechanism. This extraction of the sealing requirement eliminates the associated friction and maintenance issues while maintaining reliable operation in the lubricating environment.
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 achieves a more rigid and compact valve train with improved temperature control, reducing thermal expansion and eliminating the need for shaft sealing rings, resulting in enhanced precision and reduced maintenance costs.
Implementation Method 1
When using a brushless electric motor, no oil-tight sealing of the stator/rotor unit has to be provided since it also runs directly in the oil mist. This eliminates the frictional disadvantage of a shaft sealing ring.
Implementation Method 2
In order to keep changes in length due to temperature changes in the adjusting drive as small as possible, the adjusting element can be temperature-controlled by a lubricant or a coolant of the internal combustion engine.
Data Source
Figure 1
AI summary
The head (1) has a variable stroke valve drive (2) with an operating lever (3) that is supported on a sliding path (30) of a crank and on an intermediate unit (7). The lever is pivoted against a force of a spring (10) for stroke adjustment between supporting points of a cam (9), and has a rolling unit (4) with an oscillating pivot point that slides parallel to the sliding path by an adjusting device. An actuator (12) e.g. brushless electric motor, with a cooling medium is arranged in the head over the adjusting device, and has a longitudinal axis (12`) aligned in direction of a cylinder axis.