Pneumatically Tuned Vehicle Powertrain Mounts for Lugging Stiffness
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Solution Overview
Problem
Existing vehicle powertrain mounts, particularly hydraulic hydro-mounts, often exhibit unfavorable stiffness during engine lugging conditions, failing to adequately isolate vibrations and noise across a range of frequencies, including those associated with engine idling and road inputs.
Innovation Solution
The implementation of pneumatically tuned mounts with hermetically sealed air-filled chambers and connectors, pressurized above atmospheric pressure, and optionally incorporating a Helmholtz resonator or expansion chamber, to reduce stiffness at specific excitation frequencies, such as those corresponding to engine lugging conditions, and provide enhanced damping through selective coupling with a vacuum source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic or hydro-mounts are used to isolate idle and part throttle powertrain excitations, then damping is improved at low frequencies, but stiffness becomes unfavorable at higher frequencies associated with engine lugging conditions
Solution Approach 1:
The patent applies parameter changes by modifying the stiffness characteristics of the mount through pneumatic tuning. An air-filled chamber is introduced with a connector of specific dimensions (length and cross-sectional area) to create a pneumatic spring effect. The stiffness of the mount can be adjusted by changing the air pressure, connector volume, or elastomeric barrier properties, allowing the system to provide favorable stiffness at lugging frequencies (typically 20-100 Hz) while maintaining damping performance at lower frequencies. This resolves the contradiction by making the stiffness parameter可调 (adjustable) rather than fixed.
2Adaptability or versatility
If vacuum is applied to rubber membranes including the decoupler to switch between default mode and idle mode, then stiffness reduction is achieved at engine idle frequencies, but unfavorable stiffness remains during other operating modes such as engine lugging
Solution Approach 1:
The patent implements dynamics by creating a continuously adjustable stiffness system rather than discrete mode switching. The pneumatic tuning system allows the mount to dynamically adapt its stiffness characteristics in real-time based on operating conditions. By controlling the air pressure in the tuned chamber or adjusting the connector properties, the system can provide optimal stiffness across the entire frequency spectrum including lugging conditions, eliminating the need for separate idle mode and shake mode configurations.
3Reliability
If the connector size is reduced to tune the air volume for stiffness reduction, then damping at target frequencies is improved, but the overall structural integrity and stiffness may be compromised
Solution Approach 1:
The patent applies local quality by concentrating the stiffness modification function in the specific air-filled chamber and connector region, while the rest of the mount structure maintains its original strength and structural integrity. The tuned pneumatic element locally affects only the frequency range of interest (lugging frequencies) through its spring constant, while other parts of the mount continue to provide structural support and handle high-frequency vibrations. This allows selective damping at target frequencies without compromising overall structural strength.
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 solution effectively modifies the frequency response to improve isolation in higher frequency ranges, reducing stiffness and damping at target engine speeds, thereby enhancing noise and vibration reduction across various operating conditions without the need for additional components like lugging tracks.
Implementation Method 1
a connector coupling the air filled chambers, the connector sized to provide an associated air volume that reduces stiffness of the first elastomeric barrier at an excitation frequency corresponding to a target engine speed
Implementation Method 2
The connector and air filled chambers may be hermetically sealed and may be pressurized above atmospheric pressure
Implementation Method 3
a first elastomeric barrier secured to and extending from the base defining an air filled chamber
Implementation Method 4
a second elastomeric barrier secured to and extending from the base and enveloping the first elastomeric barrier, the second elastomeric barrier defining a fluid chamber having a fluid with a specific gravity greater than unity, such as hydraulic fluid or glycol
Data Source
AI summary
A system for securing a powertrain component to a body structure of a vehicle may include first and second mounts each having a base and a first elastomeric barrier secured to and extending from the base defining an air filled chamber, and a connector coupling the air filled chambers, the connector sized to provide an associated air volume that reduces stiffness of the first elastomeric barrier at an excitation frequency corresponding to a target engine speed. The air filled chambers may be hermetically sealed and pressurized above atmospheric pressure. The system may include a fluid-filled switchable mount having a decoupler air pocket selectively coupled to a vacuum source or atmosphere with an expander integrated with the mount or as a separate component coupled between the decoupler air pocket and the vacuum source. The expander may be implemented as a Helmholtz resonator or may include an in-line expansion chamber.