EP2611570B1 - Method for centreless cylindrical grinding of a workpiece - Google Patents

Description

The invention relates to a method for cylindrical grinding of a one-piece workpiece according to the preamble of claim 1 and a system for carrying out this method according to the preamble of claim 3 (see, for example CN 201283519Y ), wherein the contour of the workpiece is defined by a continuous longitudinal axis and in addition to a first, cylindrical longitudinal region to this longitudinal axis also has a second length range in which the radial mass distribution with respect to the longitudinal axis is non-uniform.

Workpieces of this type are known. They are contoured according to the proviso of a continuous longitudinal axis, wherein this longitudinal axis is at the same time a central axis and an axis of rotation during later operation. However, they only partially have one or more lengths of cylindrical cross-section which are rotationally symmetric with respect to the longitudinal axis. In another length range, the radial mass distribution is non-uniform because the radial circumferential contour is eccentric or otherwise non-rotationally symmetric about the longitudinal axis. The best known example of such workpieces are the balance shafts in modern drive motors, especially motor vehicles. The increasing use of such balance shafts results from the conflicting demands for the smoothness of these engines as well as low consumption data and lightweight construction in general. The use of balance shafts is not limited only to the drive motors of motor vehicles, but also exists in compressors and other technical fields.

In the operating jargon of practitioners such workpieces are called "unbalanced". By this is meant that a workpiece of this kind rotating on its own causes imbalance problems in that the rotational movement is non-uniform and is disturbed by vibrations or impact movements. With the increasing use of balance shafts and similar workpieces, the requirement arose to grind the said workpieces with high precision, at least in their cylindrical and rotationally symmetrical length ranges, despite their unbalance behavior in an economical production process.

There are already various considerations have been made to meet this requirement with the known means of grinding technology. The knowledge of the applicant about this is based on their own operational practice, considerations of their own experiments as well as technical discussions, as is usually the case at specialist conferences, exhibitions and similar events. A documentation or publication is not known.

Thus, it was thought to manufacture the aforementioned workpieces in their second length range specifically with a considerable oversize in such a way that an approximation to a rotational symmetry and thus a smooth concentricity would have been expected. After grinding, the excessive oversize would have been removed. Such a grinding process would not only be very complex and expensive, but would also bring a reduction in quality. Because after grinding, which represents a fine machining, a twisting or milling would lead to a distortion of the workpiece, so that the required dimensional and shape tolerances could not be met.

The idea of grinding these difficult workpieces by clamping them between tips had to be discarded. It was to be expected that due to their instability and workpiece geometry, the mentioned workpieces could only be sharpened between points with considerable effort. For example, an axial contact pressure, as it usually occurs when grinding between peaks, would have led to a deformation of the soft eccentric second length range.

Finally, the proven method for centerless cylindrical grinding came into question. Almost without exception, however, there are experiences with completely rotationally symmetrical workpieces. Therefore, it has been known that a greater imbalance of the workpieces makes this grinding process very difficult or even impracticable. An "unbalanced" workpiece will not only rotate unevenly during centerless cylindrical grinding, ie it will not allow a uniform rotational movement to be achieved. This initially means an inaccurate grinding result. It even had to be expected that the uneven rotational movement even prevented the drive of the workpiece by the regulating wheel, so that the rotational drive of the workpiece does not even arise. The conditions in the grinding gap are known to be so difficult that the regulating wheel can only transmit a sufficient torque to the workpiece, if this is largely rotationally symmetric in terms of mass distribution. However, if the drive is not process-reliable right from the start, centerless cylindrical grinding is out of the question for these workpieces.

The document CN 201283519Y describes a method for grinding a one-piece workpiece, wherein the area with non-uniform mass distribution is compensated by an axially deferred balance weight.

The invention has for its object to provide a method for cylindrical grinding, with which the cylindrical and rotationally symmetrical first length range of said "unbalanced" workpieces can be ground with great accuracy in a suitable manner for economical mass production.

The solution to this problem consists in the totality of the method steps according to claim 1 and the system described in claim 3 for carrying out the method steps.

It is therefore first attached to the said workpiece a balancing mass and then ground the cylindrical first length range at least in a first length section according to the method of centerless cylindrical grinding.

The method according to the invention has the advantage that the usual and known machines can be used for centreless cylindrical grinding, cf. for example, e.g. Dubbel, Paperback for Mechanical Engineering, 18th edition, pages T89 / T90. The centerless cylindrical grinding is in the present case also advantageous because, for example, the said balancing shafts are produced in large quantities and even as a forged or cast blanks and after machining of very uniform nature. The unbalance of the individual balance shafts is thus in a relatively narrow frame. It can therefore be achieved with a single type of balance weight an economical procedure that allows a high degree of automation.

If the individual workpieces are more different from each other, it is also possible to measure their residual imbalance before grinding and to apply different balancing weights to the workpieces as needed. In this way, the quality of the grinding process can be further optimized. The leveling compounds are usually releasably attached to the workpieces. But they do not have to be removed immediately after completion of the cylindrical grinding, but can also be beneficial for further manufacturing operations. For example, a correspondingly sized and shaped balancing mass can also be used as a grip part for an automatic linking machine or an assembly process. Furthermore, the balancing mass may be useful for stabilizing the workpiece in further transport and machining operations.

It is understood that in mass production when using a single type of balancing mass complete compensation in the exact physical sense is not achieved in each case. However, it is sufficient for the interests of the practice, if the remaining imbalance is reduced to a very small value.

For a quick understanding of the application should be added that claim 1 requires the following definition. The first or second "length range" is the sum of the individual first and second lengths that are on the workpiece. For example, the balancing shaft shown by way of example in FIGS. 1 and 2 of this application has three first longitudinal sections which can serve as bearings in later operation and which together form the first longitudinal section. The same applies to the second, non-rotationally symmetrical length range. In other words, it is not always necessary to ground all the first longitudinal sections of the first longitudinal section.

For the case l that the balancing mass comes only for the process of grinding itself in question I, the balancing mass is releasably secured and is removed again as soon as its first length range has been ground as far as necessary by centerless cylindrical grinding.

The backup of the balance weight may consist of a spring-loaded pressure bolt, but also be formed by one or more screw, also by resilient locking members, a device for clipping, a magnetic connection or a multi-part design of the balance weight, then laterally applied clamping rings, the items in patch Holding state together.

If two and more rotationally symmetric first length sections are to be ground on the workpiece to be ground, the grinding can be carried out with a centerless cylindrical grinding machine which has a separate grinding set for each individual length segment, consisting of regulating wheel, grinding wheel and support ruler. In this way, all the first lengths can be ground simultaneously.

For the combination of a particular workpiece in question here with its associated balancing mass, there are various possibilities to assemble the balancing mass in the form of an adapted balancing body with the workpiece at least for the duration of the grinding process. As this assembled assembly is then fed to the grinding machine, the workpiece and balancing unit is referred to as a system that is adapted to the nature of the workpiece and the particular grinding task. This system is an important assembly, running as a common unit at least through the grinding machine and in many cases can continue together.

A feature of this system is that the balance body is releasably attached to the workpiece.

In simple cases and in small quantities, the balance weight will be applied to the workpiece individually and by hand. But if the conditions for mass production exist, it makes more sense if the assembly and optionally releasing the system is done automatically within the device or in close functional connection with the same. In this way, a combined treatment station can be envisaged, to which the workpieces located in the Vorbearbeitungszustand be brought on a conveyor belt and spent by loading portals from the conveyor belt in an assembly station and from there back to the machine for centerless cylindrical grinding. Also the return transport of the finished ground workpieces to the conveyor belt is done by loading portals, possibly even a station for disassembly of the balance weights can be provided.

• Figur 1 zeigt zwei Seitenansichten auf ein Werkstück, das nach dem Vorschlag der Erfindung geschliffen werden soll; dabei ist das Werkstück in der unteren Seitenansicht gegenüber der oberen Seitenansicht um 90° um seine Längsachse gedreht.
• Figur 2 ist eine der Figur 1 entsprechende Darstellung, wobei ein die Ausgleichsmasse bildender Ausgleichskörper auf einen zweiten Längenabschnitt aufgesetzt ist.
• Figur 3 stellt eine teilweise geschnittene Ansicht in der Richtung der Linie A-A aus Figur 2 dar.
• Figur 4 ist eine schematisch gehaltene Ansicht von oben auf eine Schleifmaschine, mit der sämtliche rotationssymmetrische Längenbereiche des Werkstücks gleichzeitig geschliffen werden.
• Figur 5 zeigt eine zu Figur 4 gehörende Seitenansicht.
• Figur 6 verdeutlicht das Prinzip einer kombinierten Bearbeitungsstation, in der das erfindungsgemäße Verfahren vorteilhaft durchgeführt werden kann.

The invention will be explained in more detail in exemplary embodiments with reference to drawings. In the figures, the following is shown:

• FIG. 1 shows two side views of a workpiece to be ground according to the proposal of the invention; while the workpiece is rotated in the lower side view relative to the upper side view by 90 ° about its longitudinal axis.
• FIG. 2 is one of the FIG. 1 corresponding representation, wherein a balancing mass forming balancing body is placed on a second length section.
• FIG. 3 16 shows a partially cutaway view in the direction of the line AA FIG. 2 represents.
• FIG. 4 is a schematic top view of a grinding machine with which all rotationally symmetric lengths of the workpiece are ground simultaneously.
• FIG. 5 shows one too FIG. 4 belonging side view.
• FIG. 6 illustrates the principle of a combined processing station in which the inventive method can be advantageously carried out.

In FIG. 1 is shown in two views, a balance shaft, as it is increasingly used in modern internal combustion engines. This balance shaft is a good example of a workpiece 1, which can be advantageously ground by the method according to the invention. The workpiece 1 has a continuous longitudinal axis 5, after which the contour of the workpiece 1 is defined. Compared to the upper view of the FIG. 1 the lower view is rotated by 90 ° about the longitudinal axis 5. As from the comparison of the two views FIG. 1 As can be seen, the workpiece 1 has first longitudinal sections 2a, 2b, 2c, which are cylindrical to the continuous longitudinal axis 5 and can later serve as bearings. Between the rotationally symmetrical first length sections 2 a and 2 b there is a second longitudinal section 3, which deviates in cross section from a rotationally symmetrical contour. In this case, the second longitudinal section 3 has an eccentric contour in the form of a flat longitudinal web, which here forms the bridge section and runs at a radial distance parallel to the longitudinal axis 5. A further longitudinal section 23, on the other hand, has a cross-section of the basic shape of a rectangle, which runs centrically to the longitudinal axis 5. The different lengths 2a, 2b, 2c and 3 and 23 are separated by cheeks 4, resulting in the first length sections 2a, 2b, 2c lateral abutment shoulders.

According to the definition of this application, the first length sections 2a, 2b, 2c together form the rotationally symmetric first length region of the workpiece. In the second length range, the radial mass distribution with respect to the longitudinal axis 5 is uneven, so that imbalance arises during rotation.

The presentation of the FIG. 2 corresponds to the representation of FIG. 1 , but with the difference that on the second length section 3, a compensation body 6 is placed. As related to the Figures 2 and 3 results, the compensating body 6 has the basic shape of a circular disc which is provided with a radially extending recess 7. The cross-sectional contour of the recess 7 has the basic shape of a rectangle, wherein on one side sliding ribs 8 are present. On the sliding ribs 8 opposite broad side of the recess 7, a pressure pin 11 is slidably mounted in a stepped bore 13, which is biased by a coil spring 12 in the direction of the interior of the recess 7.

The compensating body 6 is placed with its recess 7 in the push-9 to the second longitudinal section 3, which is formed as a flat longitudinal ridge and has the basic shape of a rounded rectangle. The narrow side of the recess 7 forms a contact shoulder 10 against which the compensating body 6 strikes and is secured in this position by the pressure pin 11. From the Figures 2 and 3 goes without saying that the compensation body 6 is placed starting from the longitudinal axis 5 from the inside to the outside on the second longitudinal section 3. During a rotation of the workpiece 1 about its continuous longitudinal axis 5, the compensation body 6 is thus additionally pressed by the centrifugal force to the second longitudinal section 3. The pressure pin 11 thus serves to secure the balance weight 6.

The workpiece 1, together with the compensating body 6, forms a common assembly or a system which as a whole has a balanced mass distribution in the radial direction. The system is thus radially balanced in the usual sense when it rotates about the continuous longitudinal axis 5.

Based on FIGS. 4 and 5 Next, it will be illustrated how the system is ground in a centreless cylindrical grinding apparatus. Here, a separate grinding set is provided for each of the first length sections 2a, 2b, 2c, which consists in a known manner of a regulating wheel 15, a grinding wheel 16 and a support rivet 19. The said three parts together form a grinding gap, as in FIG. 5 is shown. The regulating wheel 15 and the grinding wheel 16 rotate with the same direction of rotation. The longitudinal axis 5 of the workpiece 1 is doing to its axis of rotation and is located below a connecting line, which is pulled between the axes of rotation 17a, 18a of regulating wheel 15 and grinding wheel 16. The workpiece 1 is thus pressed with certainty against the support ruler 19, that is pressed into the grinding gap. The groups of regulating wheels 15 and grinding wheels 16 are each located on a common regulating wheel shaft 17 or grinding wheel shaft 18 and are held by appropriate spacers on the correct, the workpiece 1 matched distance.

It should be noted that the figures of the embodiment are intended to illustrate only the principle of the invention. So, for example, the compensating body 6 does not necessarily have the shape of a circular disk; Also, a roller shape, an elliptical cross-sectional shape or another shape may be appropriate. In the figures, a centerless cylindrical grinding according to the principle of the vertical Einstechschleifens is shown mainly. However, the invention is not limited thereto. The other known methods for centerless cylindrical grinding may also be considered, such as longitudinal or continuous grinding or oblique plunge grinding.

Likewise, in the Figures 2 and 3 illustrated backup of the balance weight 6 by a spring-loaded pressure pin 11 only one of many possibilities. With the same success could also one or more screw, springy locking members, a Aufklippsen, a magnetic connection or a multi-part design of the balance weight 6 come into question, hold together the items in the deferred state at the laterally applied clamping rings.

The compensating body 6 can be placed by hand on the second I length section 3, in which case a fork-like pulling tool 14 (FIG. FIG. 3 ) is sufficient for pulling out the pressure bolt 11. But it can also be thought to automate the process of assembling workpiece 1 and compensating body 6 and to install as a further function in the grinding device or a suitable additional station to this. In this case, a combined processing station can be advantageous, as shown schematically in FIG FIG. 6 is shown.

According to FIG. 6 On a conveyor belt 20, the workpieces 1 in the pre-machined state are first fed to an assembly station 21. There, in an automated process, each workpiece 1 is provided with its associated compensation body 6, that is, the said system is formed. This is then fed to the centerless cylindrical grinding machine 22, in accordance with the FIGS. 4 and 5 one or more rotationally symmetrical length sections 2a, 2b, 2c of the workpiece 1 are ground round. Subsequently, the system - consisting of the workpiece 1, which is now a finished part, and the balance weight 6 - returned to the conveyor belt 20 and the next processing or assembly stage. This conclusion of the grinding process is useful if the balance weight 6 is also advantageous for the further course of the production. It is also conceivable that anyway required further functional parts that are required for the subsequent function of the workpiece 1, are already applied during grinding and also designed as a balance weight accordingly. If such functions are not required, the balance weight 6 can also be removed from the workpiece 1 immediately after the grinding. The assembly station 21 must then be supplemented by a dismantling station.

The invention has the advantage that the usual and existing machines for centerless cylindrical grinding can be used unchanged. Namely, if the balance weight 6 is properly sized and arranged, the workpiece 1 will rotate in the quiet concentricity in the machine, so that a good grinding result is readily achievable.

List of reference numbers

1

workpiece

2a, 2b, 2c

first lengths

3

second length section

4

Wangen

5

longitudinal axis

6

compensation body

7

recess

8th

sliding ribs

9

push-on direction

10

contact shoulder

11

pushpin

12

coil spring

13

stepped bore

14

pulling tool

15

Regulating wheel

16

grinding wheel

17

Regulating wheel shaft

17a

axis of rotation

18

Grinding wheel shaft

18a

axis of rotation

19

edition ruler

20

conveyor belt

21

assembly station

22

Machine for centerless cylindrical grinding

23

further length section

Claims (5)

1. Method for the cylindrical grinding of a one-piece workpiece (1), the contour of which is defined on the basis of a continuous longitudinal axis (5) and, in addition to a first longitudinal region that is rotationally symmetrical with respect to this longitudinal axis and consists of a plurality of first longitudinal portions (2a, 2b, 2c), which are separated from one another in the longitudinal direction of the workpiece (1), has a second longitudinal region in which the radial mass distribution is non-uniform with regard to the longitudinal axis (5) and which consists of a plurality of second longitudinal portions (3, 23) which are separated from one another in the longitudinal direction of the workpiece (1), wherein first longitudinal portions (2a, 2b, 2c) and second longitudinal portions (3, 23) alternate with one another and at least one second longitudinal portion (3) is formed by a bridge portion which extends between two first longitudinal portions (2a, 2b, 2c) and at a radial distance from the longitudinal axis (5), having the method steps whereby, on the workpiece (1), a balancing body (6) that forms a balancing mass is mounted on the bridge portion by way of a recess (7) extending radially to the longitudinal axis (5) and is secured in the mounted position, and subsequently the first longitudinal region is ground by cylindrical grinding at least in a first longitudinal portion, characterized in that the balancing body (6) is mounted on the bridge portion, by way of the recess (7) extending radially with respect to the longitudinal axis (5), in a mounting direction (9) extending radially to the longitudinal axis (5), and the grinding takes place by way of centreless cylindrical grinding, wherein this first longitudinal portion (2a, 2b, 2c) is located in a grinding gap formed by a regulating wheel (15), a grinding wheel (16) and a support rail (19).
2. Method according to Claim 1, characterized in that, for each of the first longitudinal portions (2a, 2b, 2c), a dedicated grinding set for centreless cylindrical grinding having a regulating wheel (15), a grinding wheel (16) and a support rail (19) is provided, and all first longitudinal portions (2a, 2b, 2c) are ground simultaneously.
3. System comprising a one-piece workpiece (1), the contour of which is defined on the basis of a continuous longitudinal axis (5) and, in addition to a first, rotationally symmetrical longitudinal region that consists of a plurality of first longitudinal portions (2a, 2b, 2c), which are separated from one another in the longitudinal direction of the workpiece, also has a second longitudinal region in which the radial mass distribution is non-uniform with regard to the longitudinal axis (5) and which consists of a plurality of longitudinal portions (3, 23), wherein first longitudinal portions (2a, 2b, 2c) and second longitudinal portions (3, 23) alternate with one another and at least one second longitudinal portion (3) is formed by a bridge portion which extends between two first longitudinal portions (2a, 2b, 2c) and at a radial distance from the longitudinal axis, and comprising at least one balancing body (6) that forms a balancing mass and has a radially extending recess (7) by way of which it can be mounted releasably on the bridge portion, can be secured in the mounted position, and effects uniform radial mass distribution of the entire workpiece (1), for carrying out the method according to Claim 1 or 2, characterized in that the balancing body (6) can be mounted on the bridge portion by way of the radially extending recess (7) in a mounting direction (9) extending radially to the longitudinal axis (5).
4. System according to Claim 3, characterized in that the means of securing the balancing body (6) consists of a spring-loaded pressure pin (11).
5. System according to Claim 3, characterized in that the securing of the balancing body (6) takes place by way of a multi-part configuration of the balancing body (6), wherein laterally applied clamping rings hold the individual parts together in the mounted state.

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