DE2300736A1 - CUTTER - Google Patents

Description

DR. MOLLER-BORi DIPL-PHYS. DR. MANITZ DIPL.-CHEM. DR. DEUFEL

DlPL-ING. FINSTERWALD DIPL-INQ. GRÄMKOW

PATENT LAWYERS

Munich, January 8, 1973 Hl / Sv - G 2292

GENERAL MOTOHS CORPORATION Detroit, Michigan, USA

Milling cutter

The invention relates to a milling cutter for milling curved ones Grooves.

When machining grooves, the ratio of the groove depth to the groove width must be taken into account as an essential factor. For example, it depends on the ratio of the depth to the width whether a cylindrical end mill and / or a circular flat milling saw or cutter can perform the required milling operation; cylindrical end mills or face mills are less suitable as the ratio of depth to width increases. Farther is, if the groove is bent along its length, the .Präserwähl even more limited, as a circular shallower Milling cutter overlaps the width of the groove when entering and exiting the material to be milled. Such an aggravated problem exists, for example, with the milling of side seal grooves in the rotor of a Rotabion engine, known as a rotary engine, in which the

309323/0456

Dr. Müller-Bor * Dr. Manitz -Dr. Deufel - Dipl.-Ing. Finsterwald Dipl.-Ing. Grimkov Braunschweig, Am Bürgerpark 8 8 Munich 22, Robert-Koch-StraSe 1 7 Stuttgart-Bad Cannstatt. Marktstrasse 3 Bank: Central Cash Office Bayer. Volksbanken, Munich, account number 9822 Poetecheck: Munich 95495 ORlGlMAL INSPECTED

Side seal grooves have a high ratio of depth to Have width and a constant radius of curvature and the requirement for a very smooth side wall structure consists. It has been found that cylindrical end milling cutters are not stuck or rigid enough for the high depth to width ratio of the sealing groove and that it is known to be flat circular Cutters cannot meet specifications because they cut the groove.

US Pat. No. 3,496,618 discloses a milling cutter with an axis of rotation and radially projecting teeth spaced apart in the circumferential direction are known in which each tooth has a circumferential milling edge having. With this construction, the milling cutter is a driven plate or dished plate and the peripheral milling edges extend axially of the main body the plate. The teeth each have a milling side that lies chordally to the plate. This Milling cutter is only able to cut relatively thin split leather-like To cut slices and its use is limited on soft materials such as rubber or rubber.

A milling cutter according to the invention is characterized in that each tooth has a circumferential milling edge with axially spaced apart Has ends and that the milling edge lies on a conical surface whose apex is off the axis is crossed.

A milling cutter according to the invention has the advantage that it is made sufficiently rigid and strong or resistant to resistance can be used to mill grooves that are curved along their length and have a high depth to width ratio and mill such grooves at speeds that are compatible with mass production requirements, whereby a satisfactory smoothness of the groove walls can be achieved without intersecting the grooves.

309828 / UUG

e Enuen Unfangs of milling edges are from the apex jiiit intervals equal to the radii of the opposite groove side walls arranged. The milling teeth furthermore have side milling edges on opposite axial sides, which are arranged parallel and spaced apart by a distance equal to the groove width. These side milling edges each have a curvature with a radius from a common point on the milling cutter axis which crosses the milling edge ends, or they are straight and at right angles to the peripheral milling edges. When milling a groove, the milling cutter axis is arranged in such a way that it crosses an axis that extends through the center point of the groove in the ¹ is parallel to the! Groove sidewalls. In addition, the milling cutter axis u is tilted at an angle at which the inner milling edges are parallel to the workpiece surface and the side milling edges are perpendicular to it. The milling cutter is then guided into the workpiece to the required groove depth, while the intersection of the milling cutter axis and the groove axis and also the set angular relationships are maintained. Then the milling cutter axis is fixed and the workpiece is rotated around the slot axis in order to mill the slot along its length.

The milling cutter according to the invention can mill a curved groove uii'3 simultaneously cut opposite sides of the groove, without overlapping the head side of the groove on one side when the mill enters} and without the opposite side to cut the groove when the cutter leaves it.

The invention is illustrated below with reference to the drawing, for example described; in this shows:

Fit; 1 a side view of a rotor of a rotary piston - Internal combustion engine, which has side seal grooves that are milled by means of a milling cutter according to the invention we> \ 1 en can,

309823/0486

Fig. 2 is a view, on an enlarged scale, of one according to the invention Milling cutter for milling side seal grooves in the rotor of FIG. 1,

3 is a radial sectional view in compressed form of the milling cutter in Fig. 2 showing its relationship to the rotor workpiece during the milling of a side seal groove and also shows the ratio of the peripheral edge of a tooth of the milling cutter to the axis of rotation of the milling cutter is,

FIG. 4 is a view of one of the cutter teeth along line 4-4 in FIG. 3;

5 is a view of the one cutter tooth along line 5-5 in Fig. 4,

, Fig. 6 is an elevation of a machine-tool arrangement which milling cutter according to the invention used for simultaneous Machining pairs of side seal grooves opposite sides of a rotor, and

FIG. 7 shows a top view of the arrangement in FIG. 6.

According to Fig.mi, a milling tool according to the invention is used called the following milling cutter, to mill the side sealing grooves 10, which are on each flat side or surface or Side surface 12 of a generally three-angled rotor 14 of an "internal combustion engine of the Wankel type is provided are. The grooves 10 are used to accommodate not shown side seals or surface seals that against the inner Seal the end walls of the motor housing * «. At every rotor apex cross or cut adjacent side seal grooves 10 a cylindrical hole or a cylindrical opening 16 which serves to insert a not shown cylindrical button or opening.

309828 / CUS6

230073Θ

Round-head JJicbtungs member to accommodate one of the inner ! • touches the lotor end walls and a sealing connection between adjacent side seals and a crown seal, not shown, which is carried in a slot 18 extending across each rotor apex, such a sealing arrangement being known.

Each side sealing groove 10 and the adjoining or adjacent surface 20 of the rotor have a constant radius of curvature from or with respect to a common center, designated 22 in FIG. As shown, the rotor surface 20 has a radius R ~ q and the radially inwardly directed wall 24 and the radially outwardly directed wall 26 of the hat 10 have radii R ^ and R ^ , respectively, the difference between these groove radii being the width W of Sealing groove 10 is. According to Fig. 3, each groove 10 is rectangular in radial cross-section, the opposite groove sides 24 and 26 being perpendicular to the rotor side 12 and parallel to an axis 27 which crosses the common center point 22 and is parallel to the axis 2o of the rotor. The flat bottom 29 of the groove is perpendicular to the groove sides 24 and 26 and parallel to the rotor side 12. The depth of the groove is denoted by letter D.

In general, machining a rectilinear groove with a depth to width ratio of great than 2: 1 a tool problem primarily related to the attempt to obtain a cutting tool with sufficient strength or strength create, and the problem is exacerbated in the case of curved grooves, since these limits relate to set the circumferential length of a turning tool and consequently limit the performance of the tool or the tool efficiency. Another problem then arises if one or more groove surfaces should be very smooth or even. For example, it was a specification a side seal groove for a rotary motor

303828/0466

wishes the groove with a depth D of about 4.3 mm (O.I7O inches) and a width ¥ of about 1 mm (0.040 inches), which is a ratio of depth to Means width of about 4: 1. In addition to this very high ■ ratio of depth to width, the groove should have a Radius of about 23 cm (9.0 inches) with a flatness for the sidewall surface texture or smoothness greater or better than 0.75 microns (30 micro inches) was required. It was found to be known Fräseirrrlchttingon or cutters, such as those of the cylindrical type or of the flat-circular type in the case of a machine Working in an arch was not suitable either to comply with the specifications of the groove or the short machine working time and to ensure the tool efficiency necessary for practical mass production or production with. large amount are necessary.

A milling cutter according to the invention is able to meet these requirements. In FIGS. 2 to 5, a circular milling cutter constructed in accordance with the invention or, respectively, is shown. Circular milling cutter 30 is shown capable of machining the side seal grooves 10 in the rotor 14 to the specifications described above. The circular milling cutter 30, which can also be referred to as a milling saw or rotary saw or circular saw, is rotatable about a central axis 31 in the direction indicated by the arrow in FIG. 2 and has a plurality of teeth 32 evenly spaced in the circumferential direction. Each of the milling teeth 32 has a tip with a leading cutting or milling edge 36 and. a trailing, relieved or relieved part 37. All circumferential milling edges 36 of the teeth are shaped in such a way that they lie on a conical surface whose apex or vertex height 38 is crossed by the milling cutter axis 32, as shown in FIG. In Fig. 3 the usual way of drawing with zigzag lines has been used, which denote different radii and axes,

309823/0468

which will be described later, the zigzags indicating that these lines have been truncated so that the drawing fits within the boundaries of the sheet. The ends 39 and 40 (each circumferential pre-edge 36 are arranged from the groove axis with distances equal to the radii Rp ^ "and Rp, - of the opposite side walls 24 and 26 of the groove and thus the TJmfangs milling edges 36 have a length equal to the width ¥ the machine to working groove 10 in. Each of the cutting teeth 32 also comprises opposite axial sides parallel side cutting edges 42 and 44, 39 and ¹ ^ O extending radially inwardly by a distance from the circumferential milling edges ends that is greater than the groove depth D. The side milling edges 42 and 44 have trailing undercut or recessed flanks 46 and 48, respectively, and can either be curved or straight, as will now be described.

In the embodiment of the milling cutter with curved side milling edges, the milling edges 42 and 44 are shaped such that they lie on spherical surfaces which have a common center point which is crossed by the milling cutter axis 31 and the radii S ^ p and R ^ ', which intersect the milling edge ends 39 and 4C, and are thus slightly larger or wider than the groove side wall radii Rp ^, or R ₂ 5 · Mi * of such a side milling edge curvature, the milling cutter can be a spherically shaped one Milling cutters are referred to. Alternatively, in the embodiment of the milling cutter with a straight side milling edge, the side milling edges 42 and 44 are shaped so that they lie on conical surfaces which have axially spaced apex heights on the milling cutter axis 31, the cone angle being determined so that these rectilinear side milling edges are at right angles to the circumferential pre-edges 36. With this side milling edge shape, the milling cutter can be referred to as a conically shaped milling cutter.

309828/0466

To work a hat, the milling axis 31 is arranged so that it crosses the groove axis 27 and is tilted by an angle Q, as shown in FIG. 3, with respect to a line 49, which intersects the cutter axis 31, and is at right angles to both to the side milled edge 42 as well as the side milled edge 44 at points which are half the groove depth, i.e. D / 2, from the TJmfangs milling edges 36 are arranged at a distance. In which Angle O are the circumferential milling edges 36 when they dux'ch the machined surface pass through it, parallel to it, while the side milling edges 42 and 44 are perpendicular run to the surface during the pass. The cutter 30, while being driven in rotation, then into the rotor «workpiece in a direction perpendicular to the surface led to the required depth. Then the workpiece is rotated about the groove axis 27 while the angle O is maintained, whereupon by the turning-milling action of the milling edges 36 the length of the groove is milled. Because the milled edges 36 lie on a conical surface, pull them

, Edges inherently the groove curvature like a milling cutter whose milling edges lie on a cylindrical surface, and inherently draw a straight path rather than the curvature of the groove. Thus, the milling cutter 30 leads with his inherent curved track guidance a free milling of the curved groove. If the groove with a conical shaped Milling cutter according to the invention is milled, lie both the

■ Groove side 24 and also the groove side 26 at right angles to the rotor side and the bottom of the groove; however, when a spherically shaped milling cutter according to the invention mills the groove, it becomes radial outwardly directed groove wall 26 cut at right angles in the same way as with the conically shaped milling cutter, each

. but the radially inwardly directed groove wall 24 is slightly undercut in the lower half due to dex * convex Curvature on this milling side, which disrupts or prevents the milling of a right-angled wall. The other side of the spherically shaped milling cutter is convex with respect to the groove wall 26 and thus does not interfere with the full straight line

309828/0456

Milling this oeite. The gas pressures in this Hotationsinotor act i ^ aex * so that the öeitendichtuns S ^e S ^s AEIE radially outwardly directed side wall 2G press, and consequently the light ünterschneiden can on the opposite side wall, resulting in the application of spherically-shaped milling cutter, be acceptable for such an application. The number of cutter teeth depends on the type of material to be machined and on its condition at the time of machining. In addition, the milling cutter can consist of a high-speed steel or the tooth sections that are actually milled can be made of carbide, whichever is best suited for machining the particular material.

Another advantage achieved by the milling cutter according to the invention has been found in the work of these side seal grooves found in which it is desired that the sealing groove does not cross the dog head sealing opening on the other side, since such an overlap adversely affects the sealing at these locations. The diameter of a The milling cutter of the invention can be made small enough that it does not adhere to the button or button seal openings bridged the beginning and end of a milling pass. For example indicate with the above mentioned side seal specifications, where the groove has a depth of about 4.3 mm and a width of about 1 mm, the following button seal holes for the structure about 1.1 cm (44 inches) in diameter. A milling cutter according to the invention with a hadius of about 0.99 cm (0.390 inches) works more satisfactorily Make the grooving pass along its length from one button-gasket opening to the other off, but does not cross the button seal openings with a larger dimension at the groove ends and thus does not cut into the found of the button-sealing openings, those of the crossover facing the groove and the sealing opening.

A milling machine arrangement 50 is shown in FIGS.

309828/0456

2300738

represents that uses the milling cutter according to the invention. The machine is generally of the carousel type with a platform 51 which supports a turntable 52 rotatably about a spindle 53. On the turntable 52 in turn a holder or ' Fastening device 5 ^ mounted for a pivoting movement about a spindle 55. A rotor workpiece -14, whose self-sealing grooves are to be milled, is placed on the fastening device 54 and located relative to this by means of a plug 56 in the sleeve hole of the rotor urict a pin 52 in the button-sealing opening; opposite to the grooves to be worked, whereby both the plug 56 and the pin each fit into holes in the fastening device> 4 with a snug fit. When the rotor 54 is properly positioned in this way, it is then securely attached to its plate by any suitable means. In this context, there is not one but two parallel side seal grooves to be cut in each side of the rotor 14. For such a milling operation, three milling machine stations are provided, each having a pair of milling cutters 30 'according to the invention mounted on shafts 60 of motorized spindles 62 which are arranged to be on guides on either side of the rotor or carriage 64 are located. The carriages 64 are mounted on a carriage support 66 in order to move the milling cutters towards and away from the workpiece. In addition, the axes of the spindles 62 are pivotable to position the milling cutters at the correct angle with respect to the workpiece. This inclination is measured relative to the side of the rotor to be machined, the origin angular point coinciding with the axis of the grooves which is located so as to coincide with the axis of the spindle 55 about which the support means 54 can pivot; With these angular relationships, the working circumferential milling edges of the milling cutters are positioned parallel to the rotor side and the working side milling edges are positioned at right angles to it.

309828/0456

A typical work sequence is described below; 3 a rotor 14 is loaded onto the rotatable fastening device 54 when the table 52 is in a loading position, as shown in FIG. The table 12 is then rotated or indexed by suitable means to a first operative position at which one of the presener assemblies 50 is located. At this point, one of the button seal openings 16 in each side of the rotor is aligned with the cutters 30. Both groups of milling cutters, while being driven in rotation, are then closed at a high speed by a suitable device. advanced a certain distance from the rotor surface and from this point on the milling cutters are guided into the rotor at a reduced speed to the required groove depth. When the cutters are at full depth, the fastener 54 is pivoted about the spindle 55 by suitable means, continuing the pivoting of the fastener 54, and thus slitting, until the button seal opening at the approaching apex is reached . If these other button üichtungs-opening is achieved, v / ground the milling cutter from the hat withdrawn and the table ^is:} 2 indexed to the rotor, of which one group has just been made of grooves iüen in a iw «working position 50 to position where this endere milling cutter assembly is provided. If the fisch 52 is forwarded to the second job, wiro. the fastening device 54 in its initial position to / dicx ^ eöäni-fc and the rotor 14 is indexed about its axis relative to the fastening device 5 ^ by an ^ independent device, ^ jlii the rotor for working the other group of grooves at the second job position in the same way as was done at the first job. The table 52 is then switched to a third job 50, while the fastening device '}' ■ ' and the rotor 14 are then switched on

309828/0456

for milling the third group of grooves by the third machine milling cutter assembly. In addition there are three Groove inspection devices 70 at a first, second and third groove inspection point in the circumferential direction arranged around the platform 51 at a distance. These inspection devices can be of any suitable type relating to the grooves Examine the width and depth of the cut and the surface texture or structure, taking the table rotates and the fastening device 5 ^ theEotor indexes, as with the milling operations, to correctly locate the grooves with respect to these inspection facilities for locating the Iiq> ection. After the final The inspection point switches the table 52 to an acceptance position and completes the machining and inspection cycles for all side sealing grooves in the rotor.

- patent claims -

309828/0456

Claims (4)

Patent claims e raser with an axis of rotation and radially projecting teeth spaced apart in the circumferential direction, characterized in that each tooth (32) has a circumferential length. ^? has räskante with axially spaced ends (395 40) which lie on a conical surface whose apex height (38) is crossed by the axis of rotation (31). 2. Milling cutter according to claim 1, characterized in that it is marked that each tooth (32) has parallel, radially extending side milling edges (42, 44) which the ends (39, 40) dex * liiniaiigs-i? räskante (3S) cross. ⁷ y. i * ¹ raser according to claim 2, characterized in that the outer milling edges (42, 44) are straight and are at right angles to the circumferential milling edge (36). 4. Milling cutter according to claim 2, characterized in that the oeiten-3? Räskanten (42, 44) have constant radii of curvature with respect to a common point which is traversed by the axis of rotation (31). 309828/0453