FR3058919B1 - DEVICE AND METHOD FOR MACHINING A ROD FOOT, ROD FOOT ORIFICE, AND COMBUSTION ENGINE ROD - Google Patents

Abstract

Device for machining a convex profile inside a cylindrical body (4) open at its two ends, comprising a tool body (6a) driven by a rotary spindle and supporting machining inserts (7 ), characterized in that the tool body (6a) is offset radially away from the center (4a) of the cylindrical body and moves by turning on itself along a circular path inside the cylindrical body (4) so as to machine the convex profile by removing material therein.

Description

DEVICE AND METHOD FOR MACHINING A ROD FOOT, ORIFICED ROD FOOT, AND COMBUSTION ENGINE ROD

The present invention relates to machining by a bore of a rod of steel rod, particularly in the form of pump, or specific shape of the convex type.

More specifically, it relates to a device and a method of machining a convex profile inside a cylindrical body open at both ends, comprising a tool body driven by a rotating spindle, and supporting machining plates .

The connecting rods of piston engines generally have a crankshaft passage opening, and an orifice, called a small end port, through which is engaged an axis supporting the piston, said piston pin. Under the effect of mechanical stresses, the piston pins tend to flex with use. The deflection of the piston rods in the connecting rod end holes, poses a particular wear problem on the small end ports, especially at their ends.

In order to protect the foot openings from this wear, a brass protection ring can be inserted around the piston pin. This solution is expensive, and has the disadvantage of introducing an additional part into the assembly. The adoption of a particular form of widening at the end of the small end of the small end of the connecting rod, or the specific shape of the convex type, makes it possible to do without the protective ring, while protecting the edges of the 'orifice.

Certain rotary machining tools, for example with retractable boards used to machine a trumpet-shaped connecting rod aperture. The pads are mounted on a machining spindle working the material in progress. The spindle can be equipped with a copying and programming system, to control the radial spacing of the plates during the progression of the tool.

Pilot-driven machining systems involve preliminary steps, copying the drilling pattern, and programming for the movement of the boards. They do not provide the desired level of performance and robustness.

The present invention aims to obtain quality and industrial larobustesse, for the machining of the trumpet-shaped connecting rod orifices, while also allowing the realization of various profiles, deviating from the most conventional interlocking shape, with the same guarantee derobustness and quality.

For this purpose, it proposes that the body of the tool isdeported radially away from the center of the cylindrical body and moves by rotating on itself along a circular trajectory inside the cylindrical body inananière to achieve the machining of the convex profile by removal of material therein.

The tool body performs the machining by moving a circular interpolation, which allows it to remove material on the inner face of the bodycylindrique by turning on itself, with a radial offset relative to the center of it. The invention finds a non-limiting application on the machining of the small end ports of a combustion engine.

In particular, it makes it possible to produce combustion engine connecting rods, whose connecting-rod orifices combine a straight portion and a rounded portion. Other features and advantages of the invention will become clear from reading the following description of a non-limiting embodiment thereof, with reference to the accompanying drawings, in which: FIGS. 1A and 1B show a connecting rod and its opening small end, front and profile, - Figures 2A to 2C show small cross-section orific profiles in section, - Figure 3 shows the proposed machining tool, and - Figures 3A and 3B illustrate variations of machining trays.

The connecting rod 1 of FIGS. 1A and 1B has a crankshaft 2, a crankshaft 3, a crankshaft port 3a for the crankshaft (not shown) at one end, a crankpin 4 and a crankshaft port 4a for thepassage of the piston pin (not shown). In this example, the small end 4 carries an inner ring 5.

In FIGS. 2A to 2C, there are end ports of rod 4a with their axis of symmetry 4b. Only one half of these holes is shown in the diagrams. In FIG. 2A, the orifice 4a has a conventional trumpet profile whose rounded edges 4c widen outwardly. As indicated above, this profile effectively protects the openings of the orifice degradations caused by the deflection of the piston shaft (not shown) passing through the orifice. The orifice 4a of FIG. 2B has inclined edges widening on a straight slope 4d towards the outside. Finally the edges of the orifice 4a of Figure 2C have a perfectlyoriginal profile, consisting of the interior to the outside of a right shank 4d similar to that of Figure 2B, auxicese connects a rounded edge 4c similar to that of the figure2A. This new profile of small end, combining a slope and radius at each end of a drilled or reamed hole, isparticularly advantageous, to protect the small end, the wear caused by the deflection of the axis of the piston. The machining tool 6 of FIG. 3 has a tool body 6a and an attachment head 6b on a spindle (not shown), itself mounted on a special machine, or a machining center controlling its actuation and displacements. . The tool body 6a has adjustable housings, for inserting carbide or "cermet" (ceramic type) removable machining tips7.

Alternatively, various tool and insert materials may be used: a one-piece carbide tool body, with a sharpened shape, a tool body with removable cartridges, for inserting hole inserts by the center, a solid carbide tool body with brazed desinserts, or a carbide tool body with a market coating.

The device 6 allows the machining of a convex profile inside a cylindrical body 4, such as a foot debielle open at both ends. Its tool body 6a is driven by a rotating spindle (not shown). Itupports two symmetrical machining plates 7, spacedaxially on the tool body, the edges of which cut the material at both ends of the cylindrical body. In the example of FIG. 3, the plates have a rounded profiled profile 7c, complementary 2A.The distance between their outer ends 7b corresponds to the width of the small end port 4a. The cutting edges 7 of the plates are rounded and concave, and canpresentent different radii of curvature according to the form of opening orifice to be machined. The cutting edges of the plates 7 may also have a straight slope 7d, depending on the desired inclination, to make straight opening profiles. The cutting angles are adjustable, in order to cut different coating materials. They can monitor ISO standards to cut off all materials on the market. Finally, the pads can be reversible to achieve two different cuts according to their machining mounting. In summary, the cutting edges of the machining plates may have a concave rounded profile, a straight slope, or combine a straight portion and a concave cross section. Apart from the profiling plates 7, the tool body 6a also carries one or more definition plates 8, for example of ISO form for finishing the diameter and surface conditions. The finishing inserts can be adjusted in position, in particular with a pin adjustment system.

The tool body 6a has a diameter smaller than that of the cone head 4a. To machine a debielle foot, the tool is inserted at the center 4b of the orifice 4a. In this position, the axis of the tool body 6b merges with that of the orifice 4b, and the outer edges of the machining plates. 7 are in line with those of the orifice4a. To machine the material of the small end 4, the tool body 6 is immobilized axially, and offset away from the axis 4b of the orifice and the cylindrical body of the foot debielle. It moves by turning on itself, along a circular trajectory inside the cylindrical body, in order to perform the machining of the convex profile by removal of material therein. The tool body 6a works by moving with its spindle. It follows a circular interpolation to remove material on the inside of the cylindrical body, turning on itself with a deportradial relative to the center of the orifice. The plates 7carry out the machining of the convex shape at each edge of the opening 4a, by turning on the same circulaireded trajectory, as their tool holder. During this derotation operation, the tool body 6a and its plates 7, sontim mobilized axially vis-à-vis the cylindrical body of the rod foot. At the end of this operation, the toolholder 6 can be moved axially, to allow the finishing plate 8, to perform the desired surface work.

As indicated above, the machining plates 7 may present on all or part of their cutting edge, curved or straight slopes. The tool can be equipped with machining pads of specific profile, to achieve other profiles of small end port, such as those of Figures 2B and 2C. For example, wafers like those of FIG. 3A for the right profile of FIG. 2B and wafers like those of FIG. 3B for the combo of FIG. 2C.

In summary, it is possible to use plates with concave rounded cutting edges, over at least part of their length, to produce convex opening profiles at both ends of the orifice, as well as plates with straight cutting edges, at least on at least a portion of its length.

With this device and this method it is possible to realize directly boring shapes by circular interpolation, with a simple tool compared to existing solutions much more expensive. Thanks to the invention, it becomes possible: to make any specific forms, to increase the tool life, to reduce the machining time, and to reduce the investment related to the adaptation or the renewal of production machinery.

This device and this method, make it possible to achieve small end ports of combustion engine etcombinant a straight portion and a rounded portion.

Beyond small end ports, the invention finds application for all special shape bores in materials such as aluminum, steel, iron, and all types of existing materials.

Claims (3)

1. A machining device (6) of a convex profile inside a cylindrical body (4) open at both ends, comprising a tool body (6a) driven by a rotatable spindle and supporting machining plates (7), the tool body (6a) being offset radially away from the center (4b) of the cylindrical body and rotatably moving itself along a circular path inside the cylindrical body so as to performing the machining of the convex profile by removal of material therein, and supporting two machining plates (7) axially spaced thereon, whose cutting edges the material at both ends of the cylindrical body (4), characterized in the cutting edges of the plates (7) combine a straight part (7d) and a concave part (7c). 2. Machining device according to claim 1, characterized in that the tool body (6a) is axially immobilized inside the cylindrical body (4) during sarotation. 3. Machining device according to claim 1 or 2, characterized in that the tool body (6a) supports at leasta finishing plate (8) away from the machining platelets (7). 4. A method of machining a convex profile inside a cylindrical body (4) open at its two ends, with the aid of a rotary tool body (6a) supporting machining plates (7). ) whose cutting edges combine a straight part (7d) and a concave part (7c), characterized in that the tool body (6a) carries out the machining by moving according to a circular interpolation which allows it to remove material on the inner face of the cylindrical body (4) by rotating on itself with a radial offset relative to the center (4) thereof. 5. A method of machining a small end port (4a) according to claim 4, characterized in that it uses platelets with rounded concave cutting edges (7c) over at least a part of their length, for making convex opening profiles at both ends of the opening (4a). 6. A method of machining a small-end port (4a) according to claim 4 or 5, characterized in that it uses platelets (7) with straight cutting edges (7d) at least on at least a portion of their length, to achieve convex opening profiles at both ends of the opening (4a). 7. A small end bore (4a) obtained by the implementation of a method according to claim 4, 5 or 6, characterized in that it has at its ends a convexe profile combining a straight part (4d) and a partarrondie (4c). 8. A combustion engine connecting rod (1), characterized in that it has a big end port (4a) according to claim 7.