Camshaft Interference Assembly with Quenching Heat Treatment
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Solution Overview
Problem
The existing camshafts for high-pressure common rail oil pumps face challenges in achieving the required anti-rotating torque and surface hardness due to the one-piece structure and conventional interference assembly methods, which result in machining difficulties, high costs, and inadequate performance.
Innovation Solution
A camshaft with a combined structure of a mandrel and cam piece, where the cam piece undergoes quenching heat treatment with simultaneous interference assembly, ensuring anti-rotating torque of at least 500 Nm and surface hardness of HRC58, using a tooling mandrel for precise assembly and a dedicated interference assembly device for accurate positioning and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cam piece undergoes quenching heat treatment before interference assembly, then the surface hardness is improved, but the interference assembly cannot be achieved due to thermal contraction
Solution Approach 1:
The cam piece undergoes quenching heat treatment and surface hardness improvement before the interference assembly process. The preliminary action of heat treatment is performed first, followed by the assembly operation, reversing the conventional sequence to resolve the contradiction between achieving high surface hardness and maintaining interference fit capability
Solution Approach 2:
The patent changes the thermal parameters of the cam piece through quenching heat treatment to achieve high surface hardness (HRC58 or above). By controlling the heating temperature and cooling rate, the material parameters are transformed to achieve both high hardness and the necessary dimensional stability for subsequent interference assembly
2Ease of manufacture
If the cam piece undergoes quenching heat treatment after interference assembly, then the interference assembly is achieved, but the surface hardness is reduced due to tempering
Solution Approach 1:
The quenching heat treatment is performed as a preliminary action before the interference assembly of the cam piece to the mandrel. This sequence ensures that the cam piece achieves its final surface hardness (HRC58 or above) before being assembled, preventing any subsequent tempering that would reduce the hardness
Solution Approach 2:
The manufacturing process is segmented into distinct stages: first the cam piece is heat treated independently to achieve high surface hardness, then it is assembled to the mandrel. This segmentation allows each process to be optimized independently, with the heat treatment producing HRC58+ hardness without being compromised by subsequent assembly operations
3Stability of the object's composition
If a one-piece structure is used for the camshaft, then the structural integrity is improved, but the machining difficulty and cost increase
Solution Approach 1:
The camshaft is segmented into two separate components: the mandrel and the cam piece. The mandrel is machined with the bearing journal and keyway, while the cam piece is separately manufactured with high surface hardness (HRC58+). These segments are then assembled through interference fit, reducing the overall machining difficulty while maintaining structural integrity through precise assembly
Solution Approach 2:
Different parts of the camshaft are given different material properties and manufacturing processes. The mandrel is made with general mechanical properties suitable for machining, while the cam piece is given local quality enhancement through quenching heat treatment to achieve HRC58+ surface hardness. This local differentiation allows each part to be optimized for its specific function while reducing overall manufacturing complexity
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 achieves a camshaft with enhanced anti-rotating torque and surface hardness, meeting the requirements for high-pressure common rail oil pumps, improving service performance and manufacturing efficiency while avoiding the limitations of conventional methods.
Implementation Method 1
the cam piece is heat expanded and the inner bore diameter increases at the heating stage during the quenching heat treatment of the cam piece
Implementation Method 2
the mandrel is installed in the heat expanded cam piece immediately, relative position between the cam piece and the mandrel is kept during assembly; after heat preservation for a period of time, the cam piece is quickly cooled by a cooling medium
Data Source
AI summary
An exemplary camshaft for a high pressure common rail oil pump and a manufacturing method thereof is provided. The method achieves interference assembly between the mandrel and cam piece, and satisfies anti-rotating torque of the cam piece relative to the mandrel while ensuring the surface hardness of the cam piece. The camshaft includes a mandrel and a cam piece arranged on the mandrel. The anti-rotating torque of the cam piece relative to the mandrel is at least 500 NM after the cam piece and the mandrel are connected by interference fit by hot charge practice. Surface hardness of the cam piece 1 is at least HRC58. The method includes performing interference assembly of the cam piece and the mandrel while performing quenching heat treatment on the cam piece, then quickly cooling the cam piece equipped with the mandrel at the cooling stage during the quenching heat treatment.