Cast External Thread Chain Tensioner Mounting
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Solution Overview
Problem
Conventional chain tensioners for vehicle engines are difficult to mount and require multiple bolts, which is cumbersome and costly to produce the external threads needed for mounting, especially when formed using thread-cutting dies or lathes.
Innovation Solution
A chain tensioner with an external thread formed by casting, utilizing aluminum die casting to create a cast surface that eliminates the need for bolts and reduces machining costs, and includes a seal member to prevent interference with the engine cover, allowing for easier and more affordable mounting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an external thread with large outer diameter is formed on the cylinder, then the chain tensioner can be mounted to the engine cover, but it becomes difficult to form the thread using thread-cutting die
Solution Approach 1:
The casting process substitutes for the mechanical thread-cutting process, enabling the formation of large outer diameter external threads that would be difficult or impossible to create with thread-cutting dies. The molten aluminum fills the mold cavity to create the thread form directly, bypassing the limitations of mechanical thread formation methods.
2Ease of manufacture
If aluminum die casting is used to form the external thread, then manufacturing cost is reduced, but burrs may be produced on the cast surface
Solution Approach 1:
The patent incorporates preliminary actions into the casting process by designing the mold with specific features: a first chamfer on the outer periphery of the cylinder and a second chamfer on the inner periphery of the mounting hole. These chamfers are formed during casting to prevent burr formation on the external thread, addressing the surface quality issue before the threading function is even attempted.
Solution Approach 2:
The patent converts the potential harm of burrs into a benefit by using the casting process itself to create controlled chamfers that prevent burr formation. The molten aluminum fills the mold cavities to create smooth chamfered surfaces, transforming what could be a defect-prone process into one that inherently prevents the defect.
3Loss of energy
If the cylindrical surface on the outer periphery of the cylinder is made to fit closely with the engine cover, then oil consumption is minimized, but interference may occur preventing proper fitment
Solution Approach 1:
The patent segments the cylindrical surface into two distinct functional zones: an upper portion with a first cylindrical surface that provides a clearance fit to the engine cover (preventing interference), and a lower portion with a second cylindrical surface that provides the oil seal function. This segmentation allows both objectives to be achieved simultaneously.
Solution Approach 2:
The patent applies local quality by giving different portions of the cylindrical surface different properties: the first cylindrical surface has a larger diameter for clearance and ease of assembly, while the second cylindrical surface has a smaller diameter for oil sealing. Each zone is optimized for its specific function.
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 chain tensioner can be easily mounted to the engine cover without bolts, reducing production costs and preventing thread quality deterioration due to burrs, while minimizing engine oil consumption and ensuring proper fitment.
Implementation Method 1
a return spring (18) which is disposed in the pressure chamber (14) and has one end in abutment with the plunger (10) and the other end in abutment with the screw rod (16), and biases the plunger (10) in the direction in which the plunger (10) protrudes from the cylinder (9)
Implementation Method 2
the plunger (10) moves slowly due to the damper action produced by the viscous resistance of the engine oil
Implementation Method 3
A check valve is provided at the end of the oil supply passage on the side of the pressure chamber which permits only the flow of engine oil from the oil supply passage into the pressure chamber
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A chain tensioner is provided which can be easily mounted to an engine cover and which is inexpensive. The chain tensioner includes a cylinder 9 inserted in and fixed in position in a tensioner mounting hole 12 formed in an engine cover 11, a plunger 10 slidably inserted in the cylinder 9, and a return spring 18 biasing the plunger 10 in a direction to protrude from the cylinder (9). The cylinder 9 is formed with an oil supply passage 29 through which engine oil supplied from an oil hole 28 opening to the inner periphery of the tensioner mounting hole 12 is supplied into a pressure chamber 14 defined by the cylinder 9 and the plunger 10. A check valve 30 is provided at the end of the oil supply passage 29 on the side of the pressure chamber 14. An external thread 22 is formed on the outer periphery of the cylinder 9 which is brought into threaded engagement with an internal thread 24 formed on the inner periphery of the tensioner mounting hole 12. The external thread 22 has a cast surface.