This application claims priority to European Patent Application No. 14155616.7 filed on Feb. 18, 2014, the entire disclosure of which is incorporated herein by reference.
The present invention relates to methods for manufacturing camshafts for internal combustion engines, of the type in which a metal tubular element is expanded within a mould with the aid of a fluid at high pressure fed into the tubular element and by simultaneously compressing the tubular element axially.
In particular the invention relates to a method of the type in which the cams of the camshaft are formed in subsequent steps, starting from the intermediate cams to end with the cams at the ends of the camshaft.
A method of the above indicated type is disclosed for example in US 2003/0221514 A1. In the solution described in this document, the cams of the camshaft are formed by constantly feeding pressurized fluid into the tubular element and by simultaneously compressing the tubular element with the aid of punches axially pushed against the opposite ends of the tubular element. The cams are formed within corresponding cavities of the mould by heating locally and in sequence the different portions of the tubular element which must define the cams in the finished product. This solution does not ensure a precise and reliable control on the forming process of the various cams and is also relatively complicated and costly to be implemented.
The object of the present invention is that of providing a method for manufacturing a camshaft for an internal combustion engine which is simpler and more reliable with respect to the known methods and through which in particular a camshaft which has the required dimensional and shape characteristics can be obtained with a good degree of precision and by simple and quick operations.
In view of achieving this object, the invention provides a method of the type indicated at the beginning of the present description, and further characterized in that:
Due to the above indicated features, the method according to the invention enables the camshaft to be obtained simply and quickly, through subsequent forming of the intermediate cams and then of the end cams, while ensuring a precise control on dimensions and shape of the finished product.
The forming operation with the aid of fluid at high pressure can be carried out with or without heating, by a liquid fluid (such as water or oil) or with the aid of a gas. For example, nitrogen at a pressure between 400 and 800 bars can be used, at a temperature between 800° C. and 900° C. Alternatively, the forming operation can be carried out with water or oil at a pressure of 5000-6000 bars, at ambient temperature or at a temperature greater than ambient temperature.
For example, the tubular element can be made of hardened steel, such as boron steel 22MnB5 or 27MnCrB5.
The invention is also directed to the device for carrying out the method of the invention.
Further features and advantages of the present invention will become apparent from the following description with reference to the annexed drawings, given purely by way of non-limiting example, in which:
With reference to
In the first step of the method shown in
As shown in
In the illustrated example, mould 2 is made of a central mould section 3 and two end mould sections 4, 5 arranged at the two sides of the central mould section 3. Mould sections 3, 4, 5 are each consisting of two half-moulds 3a, 3b; 4a, 4b; 5a, 5b which can be displaced between an opened condition (not shown) and a closed condition in which each pair of half-moulds clamps a corresponding portion of the tubular element 1 therebetween.
The present description and the annexed drawings do not include the details of construction of the press in which the above described moulds are positioned and the means for displacing each pair of half-moulds between their opened and closed conditions. These details of construction, taken alone, do not fall within the scope of the present invention and can be made in any known way. Moreover, the deletion of these details from the drawings renders the latter simpler and easier to understand.
Naturally, although the illustrated example has a mould 2 made of three mould sections 3, 4, 5, theoretically a single pair of half-moulds could be provided, incorporating the three mould sections 3, 4, 5.
In the closed condition of the half-moulds 3a, 3b, 4a, 4b, 5a, 5b, mould 2 defines a forming cavity with cavity portions c1, c2 having a shape and dimensions corresponding to those of the intermediate cams C1, C2 to be formed. For the remaining part, the forming cavity is a cylindrical cavity with a diameter corresponding to the outer diameter of the tubular element 1. In the case of the illustrated example, the cavity portions c1, c2 are defined by the half-moulds 3a, 3b of the central mould section 3, whereas the half-mould of the end mould sections 4, 5 define cylindrical cavities with a diameter corresponding to the outer diameter of the tubular element. Between the two cavity portions c1, c2, also the two half-moulds of the central mould section 3 define a cylindrical cavity with a diameter corresponding to the outer diameter of the tubular element 1.
In the closed condition of half-moulds 3a, 3b, 4a, 4b, 5a, 5b which constitute mould 2, these half-moulds surround completely and are clamped in contact with the intermediate portion of the tubular element 1, except for the portions thereof located at the cavity portions c1, c2 which are to form the intermediate cams C1, C2 of the camshaft.
The half-moulds of mould 2 are clamped against the tubular element 1 with a force which may be for example of 500 tons, approximately.
During the forming step of the intermediate cams C1, C2 shown in
The details of construction of the means for feeding the pressurized fluid into the tubular element are not described nor shown herein, since they do not fall, taken alone, within the scope of the present invention and also because they can be made in any known way, the representation in the annexed drawings being evidently purely diagrammatic. It is believed that the deletion of these details from the drawings renders the latter quicker and easier to understand.
During said first step of the method according to the invention, the tubular element 1 is compressed axially while the pressurized fluid is simultaneously fed into the tubular element.
In the case of the invention, the axial compression of the tubular element 1 is obtained by providing two clamp members 6, 7 which grip and surround completely, throughout a predetermined length, the end portions 1a, 1b of the tubular element 1 which project outwardly from mould 2. Clamp members 6, 7 are each consisting of two jaws 6a, 6b; 7a, 7b which define therebetween a cylindrical cavity having a diameter corresponding to the outer diameter of the tubular element 1. The jaws of the clamp members 6, 7 are clamped against the end portions 1a, 1b of the tubular element 1 by a force for example of 500 tons approximately. As shown in
Referring to
Due to the above described measures, the first step of the method according to the invention brings to forming a blank product having only the two intermediate cams C1, C2 as shown in
In order to carry out the second step of the method, the two intermediate cams C1, C2 which have been already obtained are kept within a mould 2′ having a cavity copying the shape of these intermediate cams. In the case of the illustrated example, this mould 2′ is made of the same central section 3 of mould 2 which has been used in the first step, completed with two end mould sections 8, 9 which are arranged in replacement of the two end mould sections 4, 5 of
In the second step of the method according to the invention, two auxiliary moulds 10, 11 are further provided which surround, throughout a predetermined length, the end portions of the tubular element 1 which project outwardly from the mould defined by sections 3, 8, 9. The auxiliary moulds 10, 11 have forming cavities with portions c3, c4 having dimensions and shape corresponding to those of the end cams C3, C4 of the camshaft CS (see
The auxiliary moulds 10, 11 are initially arranged axially spaced apart from the opposite ends 12, 13 of the mould which surrounds the already formed intermediate cams C1, C2 (which mould is constituted by the mould sections 3, 8, 9 in the illustrated example). The tubular element 1 has its end portions 1a, 1b which project beyond the auxiliary moulds 10, 11.
During the subsequent step of the method, fluid at high pressure is fed into the tubular element 1 and the tubular element 1 is simultaneously compressed axially by displacing the two clamp members 6, 7 axially towards each other, which clamp members are those which have been already described as being used in the initial step of the method. The two clamp members 6, 7, each consisting of the jaws 6a,6b and 7a, 7b as already indicated above, a grip and completely surround, through a predetermined length, the end portions 1a, 1b of the tubular element 1 which project outwardly from the auxiliary moulds 10, 11.
During this final step of the method, the clamp members 6, 7 start from a position axially spaced apart with respect to the auxiliary moulds 10, 11. The clamp members 6, 7 are pushed axially until they come in contact against the auxiliary moulds 10, 11 and then are kept to be pushed axially towards each other, until they move the auxiliary moulds 10, 11 against of the central mould which surrounds the intermediate cams C1, C2. In this step of the method, therefore the auxiliary moulds 10,11 are displaced by a length corresponding to the initial distance between the auxiliary moulds 10, 11 and the opposite ends 12, 13 of the central mould, whereas the clamp members 6, 7 are displaced by an axial length corresponding to the sum of the two spacings shown in
Therefore, in this step of the method, the portions of the tubular element 1 which are to form the end cams C3, C4 are expanded by the pressurized fluid fed into the tubular element, while the required flow of material is ensured by the axial compression of the tubular element 1. The end cams C3, C4 are thus formed while the forming cavities c3, c4 are progressively brought to the final positions in which they are at the proper distance from the intermediate cams C1, C2 which have been already formed. During this step, both the clamp members 6, 7 and also the end mould sections 8, 9 ensure that the portions of the camshaft adjacent to the cams (designated by 1m, 1n, 1p, 1q in
Also with reference to the second step of the method which have been described above, the details of constructions are not given relating to the press for use of the moulds which have been shown herein only diagrammatically, since they do not fall, taken alone, within the scope of the present invention and also because they can be implemented in any known way. The same applies to the means which are used for pushing the clamp members 6, 7 axially towards each other.
In the case of the embodiment shown herein, the cavity portions c1, c2, c3, c4 for forming cams C1, C2, C3, C4 are shaped so that each cam is formed with an axially intermediate portion whose surface has the required cam profile and two opposite end portions which are tapered progressively towards a confluence on the outer cylindrical surface of the shaft, from which the cams project. This shape is different with respect to that of conventional camshafts, in which each cam has two opposite end faces which are planar and orthogonal to the shaft axis. In this manner, proper operation of the camshaft is not jeopardized and at the same time an easier deformation of the wall of the tubular element 1 during the camshaft forming operation is possible.
Naturally, while the principle of the invention remains the same, the details of construction and the embodiments may widely vary with respect to what has been described and illustrated purely by way of example, without departing from the scope of the present invention.
Number | Date | Country | Kind |
---|---|---|---|
14155616 | Feb 2014 | EP | regional |
Number | Name | Date | Kind |
---|---|---|---|
4210090 | Stubbings | Jul 1980 | A |
5303570 | Kaiser | Apr 1994 | A |
5918494 | Kojima | Jul 1999 | A |
5927119 | Hamano | Jul 1999 | A |
5979386 | Swars | Nov 1999 | A |
6009734 | Augustin | Jan 2000 | A |
6105227 | Bota | Aug 2000 | A |
6105409 | Kojima | Aug 2000 | A |
6128936 | Yogo | Oct 2000 | A |
6154944 | Mason | Dec 2000 | A |
6237382 | Kojima | May 2001 | B1 |
6261392 | Sundgren | Jul 2001 | B1 |
6378184 | Bota | Apr 2002 | B1 |
6442987 | Worringer | Sep 2002 | B1 |
6530252 | Hashimoto | Mar 2003 | B1 |
6749954 | Toyooka | Jun 2004 | B2 |
6892560 | Hiramatsu | May 2005 | B2 |
6912884 | Gharib | Jul 2005 | B2 |
7024897 | Pfaffmann | Apr 2006 | B2 |
7266982 | Guza | Sep 2007 | B1 |
7269986 | Pfaffmann | Sep 2007 | B2 |
7328510 | Munoz | Feb 2008 | B2 |
7628129 | Takeshima | Dec 2009 | B2 |
8020419 | Ghiran | Sep 2011 | B2 |
8281630 | Mizumura | Oct 2012 | B2 |
8408034 | Ishihara | Apr 2013 | B2 |
8621904 | Mizumura | Jan 2014 | B2 |
9273770 | Echle | Mar 2016 | B2 |
9534674 | Binder | Jan 2017 | B2 |
20030221514 | Amborn | Dec 2003 | A1 |
20060107716 | Dykstra | May 2006 | A1 |
Number | Date | Country |
---|---|---|
3616901 | Nov 1986 | DE |
9746341 | Dec 1977 | WO |
Entry |
---|
European Search Report for International Application No. 14155616.7 dated Jun. 5, 2014, 4 pages. |
Number | Date | Country | |
---|---|---|---|
20150231685 A1 | Aug 2015 | US |