Cylinder Head Bolt Tightening Structure with Spring Washer
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Solution Overview
Problem
The conventional tightening structure for cylinder head bolts in engines experiences significant variation in axial force due to erratic sliding surfaces between components made of different materials and surface roughness, leading to potential loosening issues.
Innovation Solution
A tightening structure for cylinder head bolts that includes a plain washer and a spring member, such as a coned disc spring, strategically positioned to control frictional resistance and maintain a constant axial force, with the spring member exerting a spring force to prevent slipping and ensure consistent connection between the cylinder head and engine casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a plain washer is used under the cylinder head bolt, then the bolt can be tightened, but the axial force scatters considerably due to erratic sliding surfaces
Solution Approach 1:
A spring member is introduced as an intermediary component between the plain washer and the cylinder head bolt. This spring member mediates the interaction by providing a compliant interface that reduces the impact of erratic sliding surfaces, thereby maintaining consistent axial force while still allowing the tightening operation to proceed
Solution Approach 2:
The spring member changes the frictional resistance parameters at the interface. By selecting appropriate spring properties and dimensions, the frictional resistance between the spring member and plain washer is made lower than that between the plain washer and cylinder head, creating a controlled sliding behavior that stabilizes axial force
2Adaptability or versatility
If different materials and surface roughness are used for components, then manufacturing flexibility is improved, but frictional resistance becomes erratic causing axial force variation
Solution Approach 1:
Different regions of the contact interface are assigned different frictional characteristics. The spring member creates a localized low-friction zone between itself and the plain washer, while maintaining higher friction between the plain washer and cylinder head. This local differentiation of frictional properties ensures stable axial force despite material diversity in other components
3Ease of manufacture
If the sliding surface is erratic, then manufacturing simplicity is maintained, but the axial force departs from standard value causing loosening
Solution Approach 1:
The spring member serves as a mediator that decouples the erratic sliding surface from the axial force generation. It absorbs the irregularities through its elastic deformation, allowing the plain washer and cylinder head to maintain their simple, standard surfaces while still achieving reliable axial force consistency
Solution Approach 2:
The spring member provides beforehand cushioning by pre-compressing and storing elastic energy. This cushioning effect compensates for the erratic sliding in advance, ensuring that the axial force remains consistent throughout the tightening operation and prevents subsequent loosening
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 effectively reduces variations in axial force during tightening, ensuring a stable and consistent connection between the cylinder head and engine casing, thereby preventing loosening and maintaining a firm bond.
Implementation Method 1
a spring member placed over the plain washer to exert a spring force in an axial direction of the bolt
Implementation Method 2
a coned disc spring which is deformable into a flattened shape when pressed from top and bottom in the axial direction
Implementation Method 3
a first frictional resistance between the rotation operating part of the cylinder head bolt and the spring member is lower than a second frictional resistance between the spring member and the plain washer
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A cylinder head bolt (8) inserted into a cylinder head (1) is threadingly engaged with an engine casing (2) comprised of a cylinder (3) and a crankcase (4) to tighten the cylinder head (1) and the engine casing (4) firmly together. Between a rotation operating part (8a), which is provided in a head (80) of the cylinder head bolt (8), and an upper surface of the cylinder head (1), a plain washer (11) and a spring member (10) placed thereabove are interposed. The spring member (10) is capable of exerting an axially acting spring force. A first frictional resistance between the rotation operating part (8a) and the spring member (10) is so chosen to be lower than a second frictional resistance between the spring member (10) and the plain washer (11) and a third frictional resistance between the plain washer (11) and a bearing surface (1b) on the cylinder head (11).