Method for producing a camshaft for an internal-combustion engine

Patent metadata

Field	Value
Publication number	US-10124397-B2
Application number	US-201314654163-A
Country	US
Kind code	B2
Filing date	Jul 4, 2013
Priority date	Dec 20, 2012
Publication date	Nov 13, 2018
Grant date	Nov 13, 2018

Abstract

A method for obtaining a camshaft for an internal-combustion engine having a structure made of a single piece includes obtaining the camshaft by starting from a metal tubular element. The cams are obtained by expanding the tubular element within a die using high-pressure fluid. The tubular element can have an enlarged thickness in portions that are to form the cams. Forming with high-pressure fluid can be obtained using gas or liquid (for example, water or oil) at high pressure, at room temperature or at a higher temperature. The piece obtained is subjected to thermal treatment and to a grinding operation.

First claim

The invention claimed is:

1. A method for producing a camshaft for an internal-combustion engine, the method comprising:
forming a metal tubular element comprising contiguous portions of different thicknesses, the tubular element having cam locating portions and non-cam locating portions, the cam locating portions having larger thicknesses than the non-cam locating portions;
receiving the tubular element in a main cylindrical cavity of a die;
said main cylindrical cavity comprising a plurality of cam forming cavities comprising widened portions set axially apart from one another by a plurality of non-cam forming areas, for forming the cams of a camshaft, the non-cam forming areas having interior surfaces for contacting the tubular element with smaller diameters than interior surfaces of the cam forming cavities;
aligning a first portion of the cam locating portions with a first widened portion of the widened portions, aligning a second portion of cam locating portions with a second widened portion of the widened portions, aligning a third portion of the cam locating portions with a third widened portion of the widened portions;
wherein each of said widened portions of the main cavity of the die has axially opposite ends having a diameter that varies progressively between a minimum value and a maximum value so that the cams of the camshaft are obtained with a corresponding shape, such that opposite ends of the cams have a diameter that tapers from a minimum value to a maximum value;
introducing a high-pressure fluid in an interior cavity of said metal tubular element to expand said metal tubular element into a first cavity of said die and a second cavity of said die such that an outside surface of the tubular element contacts an inside surface of the die to form a first cam and a second cam, said first cavity comprising a first cavity of said plurality of cam forming cavities and said second cavity comprising a second cavity of said plurality of cam forming cavities, the first cam having a first cam shape corresponding to said first cavity and the second cam having a second cam shape corresponding to said second cavity;
the first cam and the second cam comprising cams of a plurality of cams of the camshaft, the camshaft formed in a single piece;
wherein the high-pressure fluid comprises a gas at a pressure of between 400 and 800 bar and at a temperature of between 850° C. and 950° C.; and
wherein for the forming operation using high-pressure fluid a composite die is used, with radially mobile parts in positions corresponding to the portions of the tubular element that are to form the cams.

2. The method according to claim 1 , wherein the forming the tube comprising contiguous portions of different thicknesses comprises subjecting the tubular element to flow-forming prior to expanding the metal tubular element by introducing the high-pressure fluid, the flow-forming comprising setting the tubular element in rotation and applying around it rotating forming rollers that are displaced along the tubular element, keeping them in pressure against the tubular element.

3. The method according to claim 1 , wherein said tubular element is obtained with contiguous portions of different thickness using an extrusion process.

4. The method according to claim 1 , wherein said tubular element is obtained with contiguous portions of different thickness by bending and welding of a metal sheet having portions of different thickness.

5. The method according to claim 1 wherein after the forming operation using high-pressure fluid, an operation of thermal treatment is performed.

6. The method according to claim 1 , wherein during the forming operation using high-pressure fluid the aforesaid mobile parts are displaced radially outwards in successive steps, one after the other so as to form said cams one at a time.

7. The method according to claim 1 , wherein the tubular element is made of a material chosen from among steel, aluminum, and their alloys.

8. The method according to claim 1 , further comprising heating the die in positions corresponding to the portions of the cavity of the die that are to form the cams of the camshaft so as to obtain localized case-hardening of the cams following upon the forming operation using high-pressure fluid.

9. The method according to claim 1 wherein the first cam shape differs from the second cam shape.

10. The method according to claim 1 wherein the first cam abuts the second cam on the camshaft.

11. The method according to claim 1 wherein the first cam is axially separated from the second cam on the camshaft.

12. The method according to claim 1 wherein said first widened portion is axially separated from said second widened portion, and said second widened portion abutting said third widened portion.

Assignees

• Fiat Ricerche

Inventors

• Colosseo Marco
• Bassan Daniele

Classifications

• B21D26/047

  Mould construction (B21D26/037 - B21D26/045 take precedence) · CPC title

• B21K1/06 Primary

  axles or shafts · CPC title

• F16C2360/18

  Camshafts · CPC title

• F01L1/047

  Camshafts · CPC title

• Y10T29/49805

  Shaping by direct application of fluent pressure · CPC title