EP1181132B1 - Rough-grinding and finish-grinding a crankshaft in a clamping - Google Patents

Abstract

The present invention relates to a method for grinding a centrally clamped crankshaft (1). The invention also relates to a grinding machine (43) for crankshafts for carrying out said method and a crankshaft (1) consisting of high-alloy steel or cast. According to the inventive method, lifting bearings (12) and main bearings (11) of the crankshaft (1) are ground in a clamping in such a way that at least the main bearings (11) are rough-ground and subsequently the lifting bearings (12) and then the main bearings (11) are finish-ground. The grinding machine (43) for crankshafts forms a working centre by means of which corresponding rough-grinding and finish-grinding are possible in one single clamping.

Description

The present invention relates to a method for grinding a centric clamped crankshaft.

The grinding of crankshafts takes place in known methods in several Stages on different machines in several operations on special equipped grinding machines. Another method as well as a corresponding device are known from DE 43 27 807 A. There will be one Crankshaft with axial tension between receiving tips of a Clamped workpiece spindle and tailstock of a grinding machine. In this All bearings, stroke bearings, flanges, pins and end faces are clamped Finished crankshaft. At least two are used correspondingly contoured grinding wheels.

Thus, it is known from the prior art that, on the one hand, the crankshaft in several processing stages manufactured on several grinding machines or in one set is finished.

The object of the invention is to provide a method for grinding To develop crankshafts, with which dimensional, shape and Machining tolerances of the crankshaft are improved and the Processing time is reduced.

This task comes with a method for grinding a centric clamped crankshaft with the features of claim 1.

The inventive method for grinding a centric clamped Crankshaft provides that their stroke bearings and main bearings in one setting be ground so that initially sanded at least the main bearing and then the stroke bearings finished and then the main bearings finished become.

After an exemplary machining preprocessing is thus to Achievement of a required quality with respect to specified dimensional, shape and Position tolerances the crankshaft for several processing stages in one Clamping from pre-grinding to subsequent finish grinding Leave finished measure. On the one hand, this saves time, the otherwise for retooling the machine or for loading and unloading the Crankshaft would be needed. On the other hand it succeeds through the claimed procedure of grinding that during grinding of the Warehouse liberated stresses in the material are compensated so far that After processing, a delay of the crankshaft is eliminated.

Because the crankshafts first undergo soft machining such as turning, drilling and milling are subjected to, and then cured by heat treatment are in the crankshafts tensions that are released during grinding. This free Expected stresses cause the workpiece to drag during grinding deforms or warps By the inventive order of processing steps the roughing and finishing of initially at least the main bearing and then the finish grinding of the rod bearings and then the finish grinding of the main bearings achieved One Controlled Influencing the Freeing of More Workpiece-Inherent Tensions. The distortion of the crankshaft occurring during pre-grinding of the main bearings is lifted by the finish grinding so far that the required lower Tolerances of the dimensional accuracy of the main bearings can be achieved. For when Finish grinding of the main bearings, the crankshaft no longer forgave because the surface of the main bearings has already been pre-ground. In contrast, require the Stroke bearing due to the geometry conditions in the engine not so precise dimensional tolerances like the main camps. Thus, a slight distortion in the hub bearings without interference the overall precision can be accepted.

A further development provides that in addition to the main bearings and the lift bearings be pre-ground. Advantageously, the pre-grinding of the stroke bearing takes place after pre-grinding the main bearings. Because bearings of different Crankshafts usually have different shapes, such as with lateral radii or punctures, it succeeds by pre-grinding the Crankshaft, as shown above, from the released voltages in the Crankshaft resulting distortion on the finished product to avoid. When vorwie Finished grinding while the plan pages can be mitgeschliffen without after finish grinding the desired tolerance values are exceeded.

As a particularly preferred application of the method and the crankshaft grinding machine has become the manufacture of crankshafts made of tempered steel proved. In a previous heat treatment, this one especially high risk that due to during the grinding process released stresses in the workpiece, the crankshaft warps. By the claimed approach is this distortion in finish grinding again eliminated.

An embodiment of the method provides that the pre-grinding and the Finish grinding with a single grinding wheel. Another procedure provides that the pre-grinding and finish grinding with one each Grinding wheel takes place. It allows the use of a grinding wheel for pre-grinding and a grinding wheel for finish grinding, different Grinding wheel specifications and dimensions for each to be able to exploit different processing. Another embodiment of the method provides that the main bearing and the lift bearings with one Grinding wheel pre-sanded and finished. Lift bearings like main bearing can have different machining tolerances. By a corresponding assignment of a grinding wheel to a type to be processed From bearings of the crankshaft it is possible to have an appropriate vote of used to make grinding wheel specification.

It is advantageous when grinding with a CBN grinding wheel. To the one allows these high cutting speeds, on the other hand, this points Slice only a little wear on. The service life of the grinding wheel and thus the sum of the possible intervention time increases considerably. Furthermore, the CBN grinding wheel allows to comply with the highest tolerance specifications to be able to. But instead of CBN grinding wheels can also Corundum grinding wheels are used.

To have particularly good results in terms of improving tolerances arise when using a CBN grinding wheel with a Cutting speed between 40 m / sec and 140 m / sec, preferably between 80 m / sec to 120 m / sec and with galvanic CBN disks between 80 m / sec and 200 m / sec, preferably between 100 m / sec to 140 m / sec. Furthermore, corundum grinding wheels in a range of preferably 35 m / sec to 100 m / sec, in particular 45 m / sec to 70 m / sec deploy. These values may vary slightly upwards as well as downwards, For example, depending on the dimensions of the crankshaft and the on these geometries to be machined, on the exact composition of the Grinding wheel, of the required surface quality etc.

For longer crankshafts, the problem arises that during machining Crankshaft tends to swing. According to a development of the method is therefore to suppress vibrations and to support the Crankshaft against bending by the machining forces during pre-grinding of the Main bearing at least one main bearing ground as Lünettensitz. To this Way, the non-mounted portion of the crankshaft is shortened. Consequently is also a bending due to the Dead weight of the crankshaft in connection with the rotation in the Processing prevented.

Especially long crankshafts are in one piece with high Accuracy requirements produced by the above method, as they For example, for car and truck engines with a length of over 300 Millimeters are needed. On the other hand, the above method is also suitable for the manufacture of crankshafts for example small engines, the one Length of 100 millimeters and more.

The advantages of the method according to the invention are especially in the case of crankshafts made of cast iron or high-alloy steel achievable. This is especially true at a length of at least 100 millimeters, in particular at least 300 Millimeter of the crankshaft due to the achieved tolerance grades detectable. A Crankshaft, which has been manufactured in this way, in particular has maximum Runout tolerances for the main bearings, which are 0.01 mm and less.

1. Vorschleifen vom Rohteil auf ein Zwischenmaß zum Fertigschleifen, vorzugsweise mit einer galvanisch belegten CBN-Schleifscheibe und

2. Vorschleifen nach zuvor erfolgter spanender Bearbeitung am Lager auf ein Zwischenmaß und anschließendem Fertigschleifen, wobei vorzugsweise eine keramisch gebundene CBN-Schleifscheibe eingesetzt wird.

Pre-grinding of the main bearings is possible in the method according to the invention in two variants:

1. Pre-grinding from the blank to an intermediate dimension for finish grinding, preferably with a galvanic CBN grinding wheel and

2. Pre-grinding after previous machining on the stock to an intermediate size and then finish grinding, preferably a ceramic-bonded CBN grinding wheel is used.

For the following, described in the drawing description Processing example is the pre-grinding as described in point 2, applied. However, it may be due to different combination of Grinding wheel and grinding wheel assemblies also a pre-grinding, such as under point 1. After pre-grinding according to Points 1, 2, the crankshaft according to the method described above finish ground.

Fig. 1

eine Darstellung einer eingespannten Kurbelwelle zur Verdeutlichung der Problematik der Erzielung hoher Qualität,

Fig. 2

ein Hauptlager mit seitlichen Einstichen gemäß Ausschnitt Y aus Fig. 1,

Fig. 3

ein Hublager mit seitlichen Radien und geschliffenen Flanken gemäß Ausschnitt W aus Fig. 1,

Fig. 4

einen Querschnitt einer ersten Lagerstelle,

Fig. 5

einen Querschnitt einer zweiten Lagerstelle,

Fig. 6

eine vereinfachte Draufsicht auf eine erste Kurbelwellen-Schleifmaschine,

Fig. 7

eine Ausgestaltung eines Schleifspindelstockes und

Fig. 8

eine vereinfachte Draufsicht auf eine zweite Kurbelwellen-Schleifmaschine.

The method according to the invention will be explained in more detail below with reference to drawings, the details of the described grinding machine serving only to clarify the grinding method according to the invention in the sense of an embodiment. The drawings show the following:

Fig. 1

a representation of a clamped crankshaft to illustrate the problem of achieving high quality,

Fig. 2

a main bearing with lateral recesses according to detail Y of FIG. 1,

Fig. 3

a lift bearing with lateral radii and ground flanks according to detail W of FIG. 1,

Fig. 4

a cross section of a first storage location,

Fig. 5

a cross section of a second storage location,

Fig. 6

a simplified plan view of a first crankshaft grinding machine,

Fig. 7

an embodiment of a wheel spindle and

Fig. 8

a simplified plan view of a second crankshaft grinding machine.

Fig. 1 shows an illustration of a clamped crankshaft 1. This is in a chuck 2 clamped, which on a workpiece spindle 3 of a not shown workpiece flange is flanged. Downtown of the chuck 2 is a first tip 4, on which the crankshaft. 1 is centered. Radial entrainment of the crankshaft 1 takes place by Clamping jaws 5 of the chuck 2, which on an outer circumference of a Tighten flange 6 of crankshaft 1. Another shaft end of the crankshaft 1 is supported by a second tip 7 of a tailstock 9. The second tip 7 of the tailstock 9 is placed on an axially displaceable sleeve 8. Of the Tailstock 9 can also, as shown here, but not with a second tip 7 with another chuck as on the workpiece headstock be equipped. The jaws of this chuck then clamp on one Spigot end 21 of the crankshaft 1. The crankshaft 1 can under slight pressure, be depressurized or clamped under axial tension. A drive of Crankshaft 1 takes place according to the embodiment shown in Fig. 1 in the way that the crankshaft 1 about a main bearing 11 centrically revolving through the Workpiece spindle 3 is driven with the chuck 2. The drive is as CNC axis executed, cf. Arrow C1. In an extended version can also the tailstock 9 instead of only with a second tip 7 with a driven Tailstock quill (CNC axis C2) be equipped. Furthermore, one is Grinding spindle 30 is shown with a grinding wheel 31. The grinding spindle 30 is from a grinding spindle housing, not shown taken in the direction of the axis X by means of a CNC axis movable is. The workpiece headstock with the chuck 2 and the tailstock 9 are mounted on a grinding table, not shown, in the direction of a Z-axis is movable. The crankshaft 1 is clamped in such a way that their Central axis 13 exactly with the center axes of the workpiece spindle 3 and the Tailstock quill 8 is aligned. A support of the crankshaft 1 takes place for example, by means of a steady rest 10, which is constructed on the grinding table. The bezel 10 can in the axial direction of a predetermined main bearing 11th be set. The grinding of the crankshaft 1 is different Variants of grinding spindle assemblies executable so that different Crankshaft grinding machine construction variants are possible. Some variants will be apparent from the following Fig. 6 to 8.

As shown in FIG. 1, the grinding wheel 31 engages the crankshaft 1. Especially with high-alloyed steel, for example, with a corresponding proportion of Chromium, molybdenum and vanadium or a corresponding casting quality, For example, GGG 60/70/80, there is a risk that due to the processing a delay occurs on the crankshaft 1 over its length. There are Deviations of up to 0.4 mm have been measured. Accordingly, it is have not been possible with high quality materials used in machining are extremely susceptible to delay, the required high quality terms to comply with predetermined tolerances. The fact that now at least the Main bearing before and then ground the rod bearings and the main bearings are, when working through the released voltages are so eliminable that eliminates the distortion occurring in the subsequent operation is and, for example, even runout tolerances of 0.01 mm and less the main lagem can be met. The concentricity tolerance is included measured between the first and last main bearings. Provided Only two main bearings are present, the concentricity tolerance determined by measuring between the two peaks. Compliance with a maximum concentricity tolerance is therefore particularly important because of the Storage in the engine there are only small tolerances allowed. Tolerances on However, lift bearings may be larger in terms of lift height fail because these in the engine only the top dead center and the determine bottom dead center.

When selecting the material of the crankshaft is further noted that among other things, as well as from the hardening process of the crankshaft depends on whether the roughing and finishing of the lift bearings in a single Work step done. It should be noted that, especially in casting lower voltages and resulting distortion occur.

Fig. 2 shows a main bearing 11 with lateral grooves according to a section Y from Fig. 1. It is shown with reference to the main bearing 11 of the crankshaft 1, such as with the procedure or the crankshaft grinding machine so far already known contours can be achieved. The lateral punctures stir from the cutting pre-processing ago. A Rohhmaß the crankshaft 1 is replaced by a dotted line 203 shown. When pre-grinding with a grinding wheel 104, which has an abrasive coating 205 is on a Vonnaß 202 pre-sanded. The pre-dimension 202 is larger in diameter than the one to be achieved Finished size. This is drawn with a contour 201 for the main bearing 11.

The two planets 206 of the main bearing 11 of the crankshaft 1 are at this application example not mitgeschliffen.

Fig. 3 shows a stroke bearing 12 with lateral radii and ground flanks according to section W of Fig. 1. The stroke bearing 12 has lateral radii, the as well as a low plan shoulder be pre-ground. At the Finish grinding, the radius is no longer mitgeschliffen completely, because he is not in the bearing shell of the motor housing with built-crankshaft 1 is applied. In the The bearings shown in FIGS. 2 and 3 can also be reversed for the same Lifting bearing or main bearing are executed.

Fig. 4 shows a cross section of a bearing point of the crankshaft 1. This is preferably a stroke bearing, the bearing complete with the lateral Radien and the associated Planseiten is sanded.

Fig. 5 shows a further cross section of a bearing. A dot-dash Centerline represents a generatrix of a cylinder dar. To few Shifted micrometer, the bearing surface has a spherical shape, indicated by the dashed line. The solid line shows a opposite shape of the bearing surface. This points in their maximum Distance to the center line of the generatrix also only a few microns on. Such a convex or concave shape is via a corresponding Execution of the used according to the above method Grinding wheel can be produced.

To achieve the best possible results in terms of quality, there are several Variants according to the method for grinding the main and stroke bearings possible: for example, all main bearings including the steady rest seat will be first pre-sanded. Subsequently, be with the same or a second Grinding wheel pre-ground the crank bearings. After pre-grinding the stroke bearings These are then ground to finished size and then the Main bearing finished. The roughing and finish grinding of the lift bearings can ever After crankshaft type also done in a single operation. All variants It is common that, regardless of the selected crankshaft grinding machine All crankshaft main and lift bearings in one clamping be edited on pre- or finished measure.

Fig. 6 shows a simplified plan view of a first crankshaft grinding machine 43. On a machine bed are on a not shown Grinding table a workpiece headstock 40 and the tailstock 9 mounted. Of the Grinding table is in a conventional manner in the direction of the CNC axis z traversable. A grinding headstock 42 serves to receive a grinding spindle 30, which receives a grinding wheel. The wheelhead 42 is on a Guide, which is movable in the direction of the x-axis arranged. The CNC axis directions X and Z are arranged at right angles to each other. The illustrated machining center allows a once clamped Crankshaft 1 according to the method described above and is finished, without a re-tightening is necessary. This succeeds compliance with even low tolerance fields.

Fig. 7 shows a wheel spindle 36, the a first grinding spindle I and a second Grinding spindle II has. These are accommodated in a wheelhead housing and can thereby be pivoted in a horizontal direction. To the this allows either the first grinding spindle I or the second Grinding spindle II is used. On the other hand, this also allows a first Spindle 32 with respect to a second spindle 34 may be designed differently can. For example, they are therefore different speed ranges structurally specifiable. Furthermore, the wheelhead 36 allows that different grinding wheels can be used. For example, can a first grinding wheel 33 to be a corundum, while a second Grinding wheel 35 is a CBN disc. Likewise, the construction of the Wheelhead 36, that different diameter of grinding wheels be used on a wheel spindle. With appropriate spatial Division of the construction allows the wheel spindle 36 also that a Grinding wheel is engaged on the crankshaft, while the other Grinding wheel is free. For this purpose, the wheelhead 36 is horizontal pivotable. In addition to different dimensions or different In addition, the grinding wheels can also provide materials with respect to their materials differentiate between achieving quality. So the one can be a roughing disc, while the other is a sizing disk.

Fig. 8 shows a second crankshaft grinding machine 44. This implements Machine concept in which the machining center has two grinding headstocks having. Each wheelhead has independent CNC X axes and Z. This means the respective grinding wheel of a wheelhead can be independent of the other at a different depository of the Crankshaft according to a CNC program can be used. Even with a grinding machine of this type is the invention Procedure to perform well.

LIST OF REFERENCE NUMBERS

1

crankshaft

2

chuck

3

tool spindle

4

first tip

5

jaws

6

flange

7

second peak

8th

Pinole

9

tailstock

10

bezel

11

main bearing

12

pin bearings

13

central axis

21

pin end

30

grinding spindle

31

grinding wheel

32

first spindle

33

first grinding wheel

34

second spindle

35

second grinding wheel

36

Wheelhead

40

Workhead

41

machine bed

42

Wheelhead

43

first crankshaft grinding machine

44

second crankshaft grinding machine

201

contour

202

rough size

203

Blank dimension

204

grinding wheel

205

abrasive coating

206

plan page

I

first grinding spindle

II

second grinding spindle

C1

Drive of the CNC axis of the tool spindle

C2

Drive of the CNC axis of the tailstock spindle

X

CNC axis

Z

CNC axis

Claims (11)

1. Method of grinding a concentrically clamped crankshaft (1), whose stroke bearings (12) and main bearings (11) are so ground in a chuck that first at least the main bearings (11) are rough-ground and then the stroke bearings (12) are finish-ground and then the main bearings (11) are finish-ground.
2. Method according to claim 1, wherein the stroke bearings (12) are also rough-ground.
3. Method according to claim 2, wherein the stroke bearings (12) are finish-ground after rough-grinding of the main bearings (11).
4. Method according to one of claims 1 to 3, wherein the rough-grinding and finish-grinding are carried out with a single grinding wheel (31; 204).
5. Method according to one of claims 1 to 3, wherein the rough-grinding and finish-grinding are carried out respectively with a separate grinding wheel (31; 204).
6. Method according to one of claims 1 to 3, wherein at least the main bearings (11) and the stroke bearings (12) are rough- and finish-ground with a respective grinding wheel (31; 204).
7. Method according to claim 4, 5 or 6, wherein grinding is carried out with a corundum wheel.
8. Method according to claim 4, 5 or 6, wherein grinding is carried out with a CBN wheel.
9. Method according to claim 7, wherein the cutting speed of the corundum wheel is in the range of 35m/sec to 100 m/sec, preferably 45 m/sec to 100 m/sec, in particular 45 m/sec to 70 m/sec.
10. Method according to claim 8, wherein the cutting speed for ceramic CBN wheels is 40 m/sec to 140 m/sec, in particular 80 m/sec to 120 m/sec, and for galvanic CBN wheels is 80 m/sec to 200 m/sec, in particular 100 m/sec to 140 m/sec.
11. Method according to one of claims 1 to 10, wherein during rough-grinding of the main bearings (11) at least one main bearing (11) is ground as a collar plate seat (10).

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