Method for manufacturing combined hollow camshaft by axial-compression upsetting-deformation technique

A method for manufacturing a combined hollow single camshaft by an axial-compression upsetting-deformation technique, the single camshaft including a cam and a shaft tube, the cam and shaft tube being independent units that are combined to form working surfaces and through holes, a combination of the cam and shaft tube including a first countersink and a second countersink distributed on two sides of the cam, a bottom surface of the first countersink and a bottom surface of the second countersink being one of flat surfaces, inclined surfaces, and male and female surfaces, cross sections of each of the first and second countersinks being one of non-circular and circular, the first countersink and the second countersink matching with a first thrust step and a second thrust step, respectively, to lock a translational degree of freedom and a circumferential rotational degree of freedom of the cam, the shaft tube being a hollow tube with the first thrust step and the second thrust step, the cam being displaced between the first thrust step and the second thrust step of the shaft tube, the cam being locked by a compression force of the first thrust step and the cam, and the compression force of the second thrust step and the cam, the method comprising:

• selecting a tube billet, wherein an inner diameter of the tube billet is the same as an inner diameter of the shaft tube, an outer diameter of the tube billet is slightly larger than an outer diameter of the shaft tube;
• selecting a cam, wherein an inner diameter of the cam is slightly larger than the outer diameter of the tube billet, an outer contour of a selected cam blank being slightly larger than an outer contour of a fine-processed cam;
• heating a region A of the tube billet, wherein an axial width of the region A is about 1-2 times an axial width of the cam;
• stopping heating when a temperature of the region A is in a range of about 50-1400 degrees Celsius;
• placing the cam in the region A;
• applying a support inner pressure p to an inner cavity of the tube billet;
• compressing the tube billet in an axial direction, wherein the temperature of the region A is high such that a material of the region A is thickened and deformed in an upsetting manner and also fills the first countersink and the second countersink of the cam;
• stopping compressing when the first thrust step and the second thrust step are formed;
• locking the cam, wherein with the temperature of the region A reducing, the material of the region A is shrunk in the axial and radial directions to generate a compression force between the first thrust step and the bottom surface of the first countersink, as well as between the second thrust step and the bottom surface of the second countersink, so that the cam is locked;
• and
• fine processing the shaft tube and the outer contour of the cam.