Haptic Interface Single Seal Reducing No-Load Torque
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Solution Overview
Problem
Haptic interfaces with magneto-rheological fluids exhibit high no-load torque due to the need for multiple seals to isolate bearings from the fluid, which complicates the design and increases the overall size of the device.
Innovation Solution
A single sealing mechanism is used to seal the chamber, allowing the shaft to pass through a single wall, with the guide means aligned orthogonally to the fluid interaction element, reducing no-load torque while maintaining braking performance and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple seals are used to isolate bearings from magneto-rheological fluid, then sealing reliability is improved, but no-load torque increases and device complexity increases
Solution Approach 1:
The patent extracts the bearing from the magneto-rheological fluid environment by positioning it outside the fluid chamber. The shaft passes through a single seal in the chamber wall, allowing the bearing to operate in air rather than fluid, thus eliminating the need for multiple seals while maintaining sealing reliability.
Solution Approach 2:
The shaft acts as an intermediary element that passes through a single seal to connect the fluid interaction element inside the chamber with the bearing outside the chamber. This single seal configuration reduces no-load torque while maintaining the necessary isolation between the fluid and bearing components.
2Reliability
If multiple seals are used to isolate bearings from magneto-rheological fluid, then sealing reliability is improved, but device complexity increases
Solution Approach 1:
The bearing is extracted from the fluid chamber environment and positioned outside, connected via a shaft passing through a single seal. This simplifies the device structure by eliminating the need for multiple seals and complex internal bearing arrangements within the fluid chamber.
Solution Approach 2:
The shaft serves multiple functions: it transmits rotational motion from the fluid interaction element to the bearing, passes through the single seal to maintain sealing, and connects components inside and outside the chamber. This multi-functionality reduces the number of separate components needed.
3Ease of operation
If guide means are positioned away from fluid interaction element, then bearing guidance is improved, but device size increases
Solution Approach 1:
The guide means are nested within the fluid interaction element structure, utilizing the internal space of the element housing. This allows the guide means to be positioned close to the fluid interaction element without increasing the overall device volume, while still providing effective rotational guidance.
Solution Approach 2:
The guide means are positioned in a different spatial arrangement within the available volume, utilizing the internal cavity space of the fluid interaction element rather than adding external components. This three-dimensional optimization maintains compact device size while providing effective guidance.
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 reduces no-load torque, enhances rotational guidance, and increases the dynamic torque ratio without increasing the device's size, while allowing for higher braking torque and improved haptic feedback.
Implementation Method 1
A haptic interface can take the form of a rotary button manipulated by a user, in this case the interface opposes a resistant torque to the user according to the angular position of the actuating button and the displacement applied by the user
Implementation Method 2
Document FR 2 930 655 A1 describes a device for a haptic interface according to the preamble of claim 1, this magneto-rheological fluid haptic interface implementing an element for interaction with the magneto-rheological fluid in the form of a skirt and means for generating a variable magnetic field comprising a coil
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a device for a rotary haptic interface comprising a rotary button (2) and an interaction member (8) for interacting with a magnetorheological fluid, said rotary button and interaction member being secured to a shaft (4) for rotation therewith, a chamber defined by walls and containing said fluid and said interaction element (8), and means for generating a variable magnetic field (18). The element for interaction with the fluid (8) comprises a skirt (16) surrounding the shaft (4), said skirt (16) being secured to a longitudinal end of the shaft (4) opposite the end to which the rotary button (2) is secured, and extending from said first end towards the rotary button (2). The shaft (4) passes through a single wall of the chamber and a sealing means is arranged between the shaft and said wall. Means for guiding the rotation of the shaft are arranged around the shaft between the sealing means and the rotary button.