WO1995000293A1

WO1995000293A1 - Camshaft bearing surface linishing tool

Info

Publication number: WO1995000293A1
Application number: PCT/AU1994/000333
Authority: WO
Inventors: James Norman Eastwood
Original assignee: Eastwood James N
Priority date: 1993-06-18
Filing date: 1994-06-20
Publication date: 1995-01-05
Also published as: GB2284167B; AU6990194A; GB2284167A; AU683895B2; CA2142850A1; GB9503058D0

Abstract

To this end, there is provided a linishing tool for reconditioning a camshaft integral bearing surface of a cylinder head including an elongate body (1) having an outer surface (2), at least a portion of the outer surface of the body being a linishing surface (3), and at least one handle (5) provided at an end of the body, the body having at least one cylindral section (8) with a lateral cross section having a diameter corresponding to the required bearing diameter of the camshaft integral bearing surface. The metal finishing process of 'linishing' involves the use of a surface covered by fine particles of hard material which acts as an abrasive for the removal of matter by scratching and grinding. This is distinguished from line borers, reamers and files which all use a cutting action to remove material.

Description

CAMSHAFT BEARING SURFACE LINISHING TOOL

This invention relates to a linishing tool for use in the reconditioning of cylinder heads of internal combustion piston engines.

A common problem with internal combustion piston engines is that the cylinder head can become warped due to adverse operating conditions leading to localised hot spots in the cylinder head and/or unbalanced forces or pressures acting on the head. A warped cylinder head needs to be reconditioned to bring the clearances substantially back into specification before it can be reused.

During reconditioning, the integral camshaft bearing surfaces supporting the overhead camshaft may need to be realigned. The current procedure for realigning the bearing surfaces is to use a line borer to ream the "camshaft tunnel" to the required clearance. The line borer is essentially a metal cutting tool which requires the cylinder head to be accurately secured in position relative to the line borer before the procedure can be conducted. Realigning camshaft integral bearing surfaces is therefore at present a time consuming procedure. It is an object of the invention to provide a relatively simple tool for realigning camshaft integral bearing surfaces which will reduce the time required to conduct this procedure.

To this end, there is provided a linishing tool for reconditioning a camshaft integral bearing surface of a cylinder head including an elongate body having an outer surface, at least a portion of the outer surface of the body being a linishing surface, and at least one handle provided at an end of the body, the body having at least one cylindrical section with a lateral cross-section having a diameter corresponding to the required bearing diameter of the camshaft integral bearing surface.

The "required bearing diameter" is the radius of curvature of the integral bearing surface which enables the surface to support a camshaft without binding of that camshaft when fitted.

The metal finishing process of "linishing" involves the use of a surface covered by fine particles of hard material which acts as an abrasive for the removal of matter by scratching and grinding. This is distinguished from line borers, reamers and files which all use a cutting action to remove material. A substantial portion of the body outer surface may comprise the linishing surface.

The linishing surface may for example be in the form of a spiral band circling the cylindrical section(s), and may preferably cover about 50% of the outer surface of the elongate body.

Alternatively, the linishing surface may be in the form of a plurality of parallel flutes extending longitudinally along the cylindrical section(s). In another alternative, the linishing surface may comprise substantially the entire outer surface of the elongate body. The elongate body may be provided by a plurality of cylindrical sections arranged in a row with their axes of symmetry co-axial with a common elongate axis of the body. The diameter of the lateral cross-section of each cylindrical section may preferably decrease sequentially from one end of the body to the end thereof The diameter of the lateral cross-section of each cylindrical section corresponds to the required bearing diameter of a particular camshaft integral bearing surface of the cylinder head. A range of linishing tools can therefore be produced for different production cylinder heads, even in the case where the bearing diameters of each integral bearing surface varies on a particular cylinder head. A handle may be provided at opposing ends of the elongate body the handles may be substantially cylindrical and may have a lateral cross-section with a diameter less than the diameter of the cylindrical section with the smallest diameter.

Preferred examples of the present invention will hereinafter be described with reference to the accompanying drawings, in which: Figure 1 is a side elevation view of one example of a linishing tool according to the invention; and

Figure 2 is a detailed side view of another example of the linishing tool of the present invention.

Referring initially to the linishing tool shown in Figure 1, the linishing tool includes an elongate cylindrical body 1 having an outer surface 2. At least a portion of the outer siirface 2 is in the form of a linishing surface 3. In the illustrated example, the linishing surface 3 is in the form of a spiral circling the body 1 from one end to the opposing end thereof. The linishing surface 3 preferably covers about 50% of the outer surface. Other arrangements are also possible and the linishing surface 3 could alternatively comprise a plurality of parallel flutes extending longitudinally along the body 1. The advantage of having a linishing surface 3 covering only a portion of the body outer surface 2 is that the smooth surfaces 4 between the linishing surfaces 3 provide a discharge path for material removed by the linishing tool. Nevertheless, it is also envisaged that the linishing surface 3 comprise substantially the entire outer surface 2. The diameter of the elongate body 2 corresponds to the required bearing diameter of the camshaft integral bearing surfaces of the cylindrical head. Where the bearing diameters of each bearing surface varies sequentially along the cylinder head, the body 1 may include a plurality of cylindrical sections 7, 8 as shown in a detail view in Figure 2 with the diameter of the lateral cross-section of each section corresponding to the required bearing diameter of a particular bearing surface. The axis of symmetry of each cylindrical section 7, 8 are co-axial w h a common elongate axis of the body 1. The cylindrical section diameters can decrease in diameter sequentially from one end of the body 2 to the other end thereof providing a series of stepped changes in diameter. A range of linishing tools can therefore be produced to suit the varying camshaft bearing diameters already in production cylinder heads. Handles are provided at opposing ends of the elongate body 1 and are cylindrical in form. The lateral cross-section of each handle 5 has a diameter less than that of the lateral cross section of the cylindrical section with the smallest diameter.

The linishing tool is used by placing the elongate body 1 of the tool in the "camshaft tunnel" as defined by the integral bearing surfaces, and by moving the tool in a direction parallel to its elongate axis and/or rotating the tool about the axis so that the linishing surfaces 3 abrades the bearing surface removing all of the "high spots" therein which would cause binding of the camshaft if not removed . Although the illustrated example shows handles for manual use of the linishing tool, it is also envisaged that the linishing tool be motor driven. As the linishing tool works on all the bearing surfaces simultaneously, the bearing surfaces are aligned more quickly than by the known procedure. Furthermore, because the tool is dimensioned to the required bearing diameter(s), and because the linishing process provides a smooth finish, the bearing surfaces are more accurately finished to the required clearance.

The linishing tool can be machined from a single bar of bright steel or from mild steel which is then nickel plated. The handles 5 would therefore be integral with the elongate body 1. The linishing surface is applied to the outer surface of the body 1 by known means, the abrasive material preferably being silicon carbide (commonly known "carborundum") or diamond dust, although other materials are also envisaged. It is also envisaged that the handles be made separately from the elongate body. Alternatively, if the linishing tool is to be used only a few times, then the tool could be made of wood with an abrasive coating applied using adhesive on the body.

Claims

II CCLAIMS

1. This Camshaft Bearing Alignment Linisher will save a considerable amount of time in alignment of camshaft bearings in overhead camshaft cylinder heads. The present system used to align the camshaft tunnel is called a "Line Boring System", this system would normally take forty five minutes to align the camshaft tunnel.

2. Our system would take approximately two minutes: the labour saving is enormous in comparison. The cost of our Linishing Alignment System is approximately one sixth the price of Line Boring System.

3. Our system of alignment is able to be operated by non skilled labour.

The other systems need an experienced and qualified operator, as the Line Boring Machinery is quite complicated.

4. The Camshaft bearing Alignment Linishing System has been devised to provide a more economical form of aligning camshaft tunnels of overhead camshaft cylinder heads, to both make the job more accurate and save valuable labour time in the process.

A camshaft fitted to camshaft tunnel which is out of alignment will cause a seizure of the camshaft in the bearings.

5. Our alignment system will align the bearings so the camshaft will free spin and cannot seize in the bearings.

6. The Cutting and Linishing surface is coated with Diamond matrix particles which have an almost endless life compared to other machines already in service.

7. The Cutting and Linishing surface could be coated with any form of abrasive that may reduce the cost of producing the Camshaft Bearing Linishing Tool.

8. The Linishing tool is used by placing the elongated body of the tool in the Camshaft tunnel as defined by the Integral bearing surface, and by moving the tool in a direction parallel to its elongated axis and/or rotating the tool about the axis so that the Linishing surface will abrade the bearing surface removing all of the high spots therein which would cause binding of the camshaft if not removed.

9. This tool in its present form is manually hand operated for the simplicity of operation.

10. It is also envisaged that the tool be motor driven creating a similar operation, but would remove material faster and fit into a production line situation.

11. The Linishing tool can be machined from a single bar of bright steel or from mild steel which is then nickel plated. The handles would therefore be Integral with the elongated body.

12. The Linishing surface is applied to the outer surface of the body by known means, the abrasive material preferably being Diamond Matrix although other materials maybe also envisaged.

13. It is also envisaged that the handles be made separately from the elongated body.

14. Alternatively the Linishing tool can be made out of wood or plastic or such like products to produce a throw away or disposable tool which can be coated with carborundum or silicon carbide or similar abrasive surfaces.