Harmonic Drive Circular Spline Friction Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing transmission devices with tension wave gears face challenges in achieving a radially space-saving design while maintaining reliability and high torque transmission, often requiring complex fastening mechanisms that can lead to deformation and failure under high loads.
Innovation Solution
A transmission device design where the circular spline is held exclusively in a non-positive manner on the outer peripheral surface, with an axial length greater than 0.2 times the pitch circle diameter of the flexspline's external toothing, eliminating the need for screw connections and ensuring radial rigidity and reliable torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flange-shaped circular spline with through-holes and screw connections is used, then the circular spline can be reliably fastened, but the radial installation space increases and the device becomes more complex
Solution Approach 1:
The invention extracts and eliminates the flange structure and screw connections from the circular spline design. By removing these fastening components entirely and replacing them with a friction-based holding mechanism, the radial installation space is reduced while maintaining adequate fastening reliability for the application
Solution Approach 2:
The invention replaces the mechanical screw connection system with a friction-based holding system. The holding element secures the circular spline through friction forces generated by clamping forces acting on the outer circumferential surface, eliminating the need for threaded fasteners and flange structures
2Area of stationary object
If the axial length of the outer circumferential surface is reduced to save radial space, then the radial footprint decreases, but the circular spline may deform under clamping forces leading to tooth engagement problems
Solution Approach 1:
The invention optimizes the axial length parameter of the outer circumferential surface to a specific range (0.2 to 0.5 times the pitch circle diameter). This parameter optimization ensures that sufficient friction force is generated to secure the circular spline without requiring excessive axial length, thus maintaining small radial footprint while preventing deformation and ensuring reliable tooth engagement
Solution Approach 2:
The invention applies clamping forces through the holding element that exceed the minimum required to generate sufficient friction force. This ensures reliable securing of the circular spline against deformation and tooth engagement problems, while the axial length is kept minimal (greater than 0.2 times the pitch circle diameter) to maintain compact radial dimensions
3Weight of moving object
If a two-part circular spline construction is used, then the weight is reduced, but the manufacturing complexity increases and additional joining processes are required
Solution Approach 1:
The invention segments the circular spline into a lightweight main gear element and a separate tooth ring. This segmentation allows the use of lightweight materials for the main body while maintaining tooth strength through the separate iron-based ring, achieving weight reduction without requiring complex integral construction
4Area of stationary object
If a force-fit fastening without flange is used, then the radial installation space is reduced, but the fastening mechanism becomes simpler potentially compromising reliability
Solution Approach 1:
The invention introduces a holding element as an intermediary component between the circular spline and the mounting structure. This holding element applies clamping forces to the outer circumferential surface of the circular spline, generating sufficient friction force to secure it reliably without requiring flange structures or screw connections, thus maintaining compact radial dimensions while ensuring fastening reliability
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 design achieves a compact, space-saving transmission that reliably handles high torques without deformation, even at maximum loads, by using a clamping component like a corrugated or cylindrical band to maintain radial rigidity and prevent tooth meshing issues.
Implementation Method 1
the holding element holds the circular spline, in particular at least in the tangential direction, exclusively by friction on an outer circumferential surface of the circular spline
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a transmission device comprising a tension wave transmission (1) (1) including a circular spline (2) and a flex spline (3), and a retaining element (4) for holding the tension wave transmission (1) on the circular spline (2). The transmission device is characterized in that the retaining element (4) holds the circular spline (2), particularly at least in the tangential direction, exclusively by frictional engagement on an outer circumferential surface (5) of the circular spline (2), and that the outer circumferential surface (5) of the circular spline (2) has an axial length greater than 0.2 times the pitch circle diameter (7) of an external toothing (8) of the flex spline (3).