ROTARY BORING TOOL WITH DETACHABLE CUTTING INSERTS AND METHOD FOR MACHINING A CYLINDER BORE OF A COMBUSTION ENGINE

Abstract

A rotary boring tool with detachable inserts, including a rotating insert carrier body including cartridges holding detachable cutting inserts configured to machine a cylinder barrel by axial movement of the tool in the barrel, and including a first cutting insert configured to rough-cut grooves in the material to be machined, a second insert configured to finish the grooves roughly cut by the first insert, and a third levelling insert configured to level rough material generated by the first two inserts.

Claims

1-10. (canceled)

11. A rotary boring tool with detachable inserts, comprising: a rotary insert-holder body including cartridges which retain detachable cutting inserts configured to machine a cylindrical shaft by axial displacement of the tool in the shaft; a first insert configured to rough cut grooves in the material to be machined; a second insert for finishing of the grooves rough-cut by the first insert; and a third, planing insert, configured to flatten peaks of material raised by the first and second inserts.

12. The rotary boring tool as claimed in claim 11, wherein the first, second, and third inserts are arranged in steps around the tool-holder body, to penetrate in succession in the material.

13. The rotary boring tool as claimed in claim 11, wherein the rough-cutting first insert has a generally triangular form.

14. The rotary boring tool as claimed in claim 11, wherein the second insert has a triangular cutting ridge, with a pointed angle between 35 and 40.

15. The rotary boring tool as claimed in claim 11, wherein the third planing insert has a rhombic form with a flat cutting ridge.

16. The rotary boring tool as claimed in claim 11, wherein the cutting ridges of the inserts are made of metal carbide.

17. A detachable cutting insert as claimed in claim 11, wherein the cutting ridges of the inserts are made of cubic boron nitride (CBN).

18. The detachable cutting insert as claimed in claim 11, wherein the cutting ridges of the inserts are made of polycrystalline diamonds.

19. A method for finishing machining a cylinder bore in a combustion engine housing using a rotary machining tool as claimed in claim 11, wherein, during a same passage of the tool, the machining tool combines simultaneous operations of rough cutting of grooves, cutting of grooves, and surface flattening, carried out respectively by the first, second, and third inserts which are dedicated respectively to each of these operations.

20. The method for finishing machining as claimed in claim 19, wherein the machined surface makes it possible to apply a covering to regularize depth of the hollow grooves.

Description

[0010] The invention will be better understood by reading the following description of a non-limiting embodiment thereof, in association with the appended drawings, in which:

[0011] FIG. 1 is an overall view of a rotary tool according to the invention;

[0012] FIG. 2 is a view from below of FIG. 1; and

[0013] FIG. 3 shows the radial stepping of the inserts on the tool.

[0014] The rotary tool in FIG. 1 is in the form of a standard insert-holder 1, with a shoulder 2 for locking onto the drive machine (not represented), and an insert-holder body 3. The tool has inner holes 10 for spraying of the cutting inserts 7, 8, 9, in order to cool them. The tool-holder 3 supports a plurality of cartridges 4, or insert-holder bars (three in the example described). The cartridges, or bars 4, support three different cutting inserts, so-called for rough cutting 7, finishing 8, and planing 9, which can be seen in FIGS. 2 and 3. The position of the cartridges can be adjusted by adjustment screws 6, which are shown in FIG. 2, making it possible to adjust the cutting angle of the leading ridges of each insert. The inserts are tightened in position on the body 3 by means of tightening screws 11.

[0015] FIG. 3 shows that the rough-cutting insert 7 is slightly recessed in the radial direction, relative to the two others. The three inserts 7, 8, 9 are preferably fitted stepped around the tool-holder 3, such that they penetrate in succession in the order: rough cutting, cutting and finishing, during the penetration of the tool in the material to be machined.

[0016] The inserts 7, 8, 9 have a central passage hole 12 for their screw 11 for tightening onto the cartridge 4. The first insert 7 is a so-called groove-forming rough-cutting insert with a triangular form, which can hollow a rough groove in the material machined. The second insert 8 is also a so-called groove-forming insert. It has a cutting tooth 8a with a triangular form, the pointed angle of which is narrower than the cutting angle of the first insert, such as to penetrate into the groove opened by the first insert, in order to carry out the finishing of the groove. Finally, the third insert 9 has a flat planing side 9a in the form of an elongate blade, which, during its passage, is designed to flatten the peaks of material raised by the preceding inserts in the metal mass machined.

[0017] For the aforementioned applications of the invention, the cutting insert 8 has a triangular cutting ridge, the pointed angle of which is between 35 and 40, whereas the planing insert 9 preferably has a rhombic form.

[0018] The ridges 7a, 8a, 9a of the inserts 7, 8, 9 can be made of different materials, depending on the materials to be machined. They can be made entirely of metal carbide (including the cutting and planing ridges), and preferably tungsten carbide, in order to machine steel.

[0019] In order to machine cast iron, for example in the cylinder shaft sleeves, they are preferably made of cubic boron nitride (CBN). Machining of aluminum requires polycrystalline diamonds (PCD).

[0020] The rough-cutting insert 7 has three cutting faces which can be used in succession by turning the insert on the body 3. The cutting insert 8 has two faces: these inserts can be turned on their cartridge 4 in order to use both their cutting ridges in succession. The arrangement of the inserts in step form permits progressive attack of the material machined, thus reducing the cutting force of each insert, and therefore its wear.

[0021] As previously stated, the machining of the bores of engines requires a plurality of operations, in particular when they consist of different materials, i.e. at least one rough cutting operation and a finishing step, followed by a planing step. Thus, when the tool bears a single type of insert, a plurality of passages of this tool are necessary. On the other hand, according to the invention, with inserts which are dedicated respectively to each passage, that is, to the rough machining (rough cutting), finishing and planing, a single tool passage is sufficient.

[0022] The invention thus makes it possible to obtain satisfactory groove forming with a surface state which is prominent during cutting, and flattened in the cylinder bores, which in particular are made of cast iron or aluminum, in a single passage of the tool, thus ensuring the work of rough cutting, cutting and flattening of the grooves and the planing thereof, or planing. The new method for finishing machining a cylinder bore in a combustion engine housing using the rotary machining tool proposed thus carries out simultaneously, during the same passage of the tool, operations of rough cutting of grooves, cutting of grooves, and surface flattening, thanks to the different inserts 7, 8, 9 which are dedicated to each of these operations. The machined surface then makes it possible to apply a covering in order to regularize the depth of the hollow grooves. The application of the process on the machined surface, with the tool proposed, is an efficient means for obtaining ultimately the regularity required.