DE102018126152A1 - METHOD FOR FASTENING A SHAFT AND USE OF A ROLLING TOOL THEREFOR - Google Patents

Abstract

The invention relates to a method for solidifying a shaft, in particular a crankshaft (1) for a reciprocating engine. For this purpose, an outer surface (7, 8) of a shaft journal (2, 3) of the shaft is solidified by means of a work hardening process. According to the invention, an oil bore (4) of the shaft, which has an outlet opening (5, 6) in the area of the shaft journal (2, 3), is additionally provided at least in one area between the outlet opening (5, 6) and a further outlet opening (5, 6). 6) of the oil hole (4) processed with a work hardening tool (13).

Description

The invention relates to a method for solidifying a shaft having the features of the preamble of claim 1. Furthermore, the invention relates to the use of a roller burnishing tool for solidifying such a shaft.

The shaft may in particular be a crankshaft for a reciprocating engine. Particularly in the case of a crankshaft for a turbocharged engine charged with a turbo engine, the crankshaft must withstand great loads, which occur above all in the region of shaft journal of the crankshaft. These mechanically particularly stressed areas must therefore be designed to be robust and resistant.

STATE OF THE ART

Various methods of solidifying a shaft, such as a crankshaft or camshaft, are known in the prior art. For example, it is known to harden waves by a nitriding process. However, the process of nitriding is relatively complex, on the one hand because of the long duration of the process and on the other hand because of the chemicals required thereby.

Further, induction hardening for increasing the strength of a shaft is known. In induction hardening, however, there is generally no uniform solidification of the material over the depth of the workpiece, and in particular in the transition region between a solidified material layer and a material layer, which is still substantially in the original state even after induction hardening, can result in greater loads due to discontinuous material parameters come.

Further, it is known to increase the strength of shafts in particular in the region of their shaft journals by processing their outer surface with a roller burnishing tool. Such a method is for example from the document EP 2 814 636 B1 known. In the method described in this document, a bearing surface of a shaft after machining is rough-rolled with a cylindrical deep rolling mill which extends over the entire width of the bearing surface. After processing with the deep rolling mill, the surface is finally machined and smoothed with a low cutting depth. The solid rolling body used in the method may have a certain surface structure. Specifically, it is described that in the case of a crankshaft with a shaft journal and an opening in the region of the shaft journal oil hole a deep rolling body can be used, which has a lenticular thickening on its outer periphery. This thickening is arranged in such a way that when rolling the deep rolling body on the bearing surface of the shaft journal always hits the mouth of the oil hole, so as to round the edges of the mouth of the oil hole.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide a method for solidifying a shaft, in which the risk of cracking or other signs of wear during operation is further reduced.

This object is achieved on the basis of a method according to the preamble of patent claim 1 in conjunction with the characterizing features. Furthermore, this object is achieved by the use of a work hardening tool according to independent claim 10.

According to the invention it has been recognized that it is often not sufficient to consolidate only the outer surface of a shaft journal. Rather, it may be particularly in transition areas to non-solidified areas, such. B. in the oil well, to an increased risk of cracking. Therefore, it is provided in the method according to the invention, that not only the shaft journal or its outer surface is solidified, but it is also purposefully the oil hole or this bounding inner wall solidified.

In a method according to the invention for solidifying a shaft, in particular a crankshaft for a reciprocating engine, on the one hand, an outer surface of the shaft journal is solidified by means of a work hardening process. On the other hand, an oil bore of the shaft, which has an orifice opening in the region of the shaft journal, is machined, at least in one region between the orifice and a further orifice of the oil bore, with a work hardening tool. By working with the work hardening tool a solidification of the oil hole defining inner wall is achieved. With the increase in strength achieved in this way, the danger of cracking or other signs of wear, which can occur in particular in the area of the oil bore, since this typically represents a weak point in the region of the shaft journal, can be effectively prevented. In this case, the processing with the work hardening tool is a comparatively simple method for solidifying the oil hole, which can be implemented without great expenditure of time and materials.

In the work hardening tool, it may, for. B. to a rolling tool, such as a smooth or Deep-rolling tool act, with which the oil bore delimiting inner wall is smoothed by roll-over and the plastic deformation achieved thereby and simultaneously strengthened. As a work hardening tool but also a roller burnishing tool can be used, in which in addition to the plastic deformation at least a certain proportion of a machining of the inner wall can be done with low depth of cut.

With regard to the work hardening of the shaft journal, it may already be sufficient if it is work-hardened only over part of its outer surface. However, a particularly good robustness can be achieved if the shaft journal is work hardened over its entire outer surface. In this case, the methods known from the prior art can be used for the work hardening of the outer surface of the shaft journal. In particular, this can according to the from the document EP 2 814 636 B1 be dealt with known methods. In addition to strain hardening, methods can be used to further increase the strength of the shaft and, in particular, the shaft journal, e.g. B. induction hardening o. Ä.

In one embodiment of the method according to the invention, the oil hole is processed over its entire extending between the mouth opening and the other mouth opening length with the work hardening tool. The two mouth openings may be z. Example, to an orifice in the region of a shaft journal, which forms a main bearing of a crankshaft, and an orifice in the region of another shaft journal, which forms a crank bearing of a crankshaft act. By machining the oil well over the entire area between the two orifices with the work hardening tool, solidification of the inner wall defining the oil well can be achieved over the entire length, thus providing a particularly robust shaft.

But it may also be sufficient if the oil hole is processed only over part of the extending between the mouth openings length with the work hardening tool. Experience has shown z. For example, the loads in a region near the mouth opening are larger, for example, than in a region remote from the outer surface of the shaft journal. Accordingly, it may be sufficient to carry out a machining of the oil hole with the work hardening tool in a section adjacent to the mouth opening, while dispensing with such machining in a middle section between the two mouth openings, without substantially impairing the stability of the shaft.

A machining of the oil hole does not necessarily have to take place over the entire length to be machined with one and the same work hardening tool. In particular, if the contour of the oil hole changes over its length, it may be advantageous to edit the oil hole sections with different work hardening tools whose contour is adapted to the contour of the respective portion of the oil hole. It is of course also possible that only different essays are used, which are each adapted to the contour of the respective portion of the oil hole. For example, the oil bore of a crankshaft often has a conical shape in the region of the orifices, while it is cylindrically shaped in regions lying further inwards. Accordingly, a conical work hardening tool or a conically shaped attachment can be used for machining the conically shaped mouth region, while a cylindrical work hardening tool or a cylindrically shaped attachment is used for the cylindrically shaped region.

The degree of solidification of the oil hole is based essentially on the contact pressure, which is exerted with the work hardening tool on the inner wall bounding the oil hole. Accordingly, it can be influenced by the contact pressure on the achieved solidification of the oil well. In particular, when machining the oil hole with the work hardening tool, the pressing force exerted on the inner wall can be adjusted depending on the distance from the mouth opening.

According to one embodiment of the method according to the invention, in a region close to the mouth opening, a larger contact pressure force is exerted on the inner wall exerted as in a remote area of the mouth. This can be z. B. be expedient to (possibly retrospectively) to realize an extension of the oil well and / or a particularly high degree of solidification in a near the mouth opening area. In a further embodiment, the contact force can decrease continuously with increasing distance from the mouth opening. Thus, a "soft" transition between a solidified area can be achieved to a less strongly solidified area, which z. B. the risk of cracking despite differently strong solidified areas of the oil hole can be reduced.

According to an alternative embodiment, a smaller contact force is exerted on the inner wall in a region near the mouth opening than in a region remote from the mouth opening. This can be z. B. be useful if a plastic deformation of the oil hole should be avoided as possible in the mouth opening.

A variation of the contact pressure, which is exerted on the inner wall with the work hardening tool, can also be effected in such a way that a constant contact force is exerted from a predetermined distance from the opening. This can optionally be higher or lower than in an area having a smaller distance to the mouth opening.

After machining the oil hole with the work hardening tool, it may be necessary to rework the outer surface of the shaft journal. Concretely, z. B. in the area of the mouth opening form a ballast, which must be subsequently removed, so as to allow the lowest possible coupling in the region of the shaft journal. For the post-processing of the outer surface, various methods come into question. For example, a simple deburring, grinding and / or polishing of the outer surface may suffice. But it can also be provided that the outer surface is work hardened only after the processing of the oil well and is smoothed accordingly in this context. For this purpose, z. For example, in the document EP 2 814 636 B1 described methods are used.

A further solution of the object according to the invention relates to the use of a work hardening tool, which is designed for work hardening of an inner surface, for machining an oil bore of a shaft, in particular a crankshaft, in a region lying between two orifices of the oil well. In particular, a rolling tool, such as a burnishing or deep-rolling tool, or a rolling tool can be used for this purpose. With regard to further preferred embodiments, the statements on the method according to the invention apply accordingly.

list of figures

• 1 zeigt einen Ausschnitt einer Kurbelwelle in einer Schnittdarstellung;
• 2 zeigt den Ausschnitt der Kurbelwelle gemäß 1 mit einem schematisch skizzierten ersten Kaltverformungswerkzeug;
• 3 zeigt den Ausschnitt der Kurbelwelle gemäß 1 mit einem schematisch skizzierten zweiten Kaltverformungswerkzeug.

Further, measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS. Show it:

• 1 shows a section of a crankshaft in a sectional view;
• 2 shows the section of the crankshaft according to 1 with a schematically sketched first cold forming tool;
• 3 shows the section of the crankshaft according to 1 with a schematically sketched second cold forming tool.

1 shows a section of a crankshaft 1 in a sectional view. The crankshaft has two shaft journals 2 . 3 on, which serve as main or stroke bearings. To lubricate the two shaft journals 2 . 3 ensure the crankshaft points 1 an oil well 4 on that is between the two shaft journals 2 . 3 extends and their mouth openings 5 . 6 directly in the area of the supporting outer surfaces 7 . 8th the shaft journal 2 . 3 are located.

The contour of the oil hole 4 is through an oil well 4 delimiting inner wall 9 the crankshaft 1 certainly. As in 1 is shown, the oil hole 4 there 3 different contoured sections 10 . 11 . 12 on: The sections 10 and 12 in the area of the mouth openings 5 and 6 are conically shaped while the intervening area 11 is cylindrical.

In operation of the crankshaft 1 especially occur in the area of the shaft journal 2 . 3 large mechanical loads. Therefore, these areas are to be designed accordingly robust. One possibility for this is, with appropriate use of material, for a corresponding strength in the area of the shaft journal 2 . 3 to care. However, even with a corresponding machining of the shaft journal 2 . 3 the necessary robustness can be ensured, so that even with less material use the robustness required for operation can be ensured. According to the invention therefore on the one hand, the outer surfaces 7 . 8th the shaft journal 2 . 3 (or at least parts thereof) processed by means of a cold work hardening process. On the other hand, the oil well 4 machined with a work hardening tool, thereby strengthening the inner wall 9 increased and thus one of the oil well 4 outgoing cracking can be significantly delayed even under high load.

In the 2 and 3 is the machining of the oil well 4 with a work hardening tool 13 . 14 shown in a very schematic way. According to this embodiment, the machining of the oil hole takes place 4 with the work hardening tool 13 . 14 after pre-machining the crankshaft 1 , ie the corresponding contouring of the outer surfaces 7 . 8th the shaft journal 2 . 3 , the introduction of the oil well 4 and the countersinking of the oil well 4 in the area of the mouth openings 5 . 6 , Also be done already a work hardening of the outer surfaces 7 . 8th the shaft journal 2 . 3 and possibly other accessible from the outside surfaces of the crankshaft. For example, the outer surfaces 7 . 8th have been passed for this purpose with a hard roller, as in the document EP 2 814 636 B1 is described.

For the work hardening tools 13 . 14 These may be, for example, smoothing or deep-rolling tools or roller burnishing tools which are attached to the inner wall 9 be passed. In this case, a predetermined contact pressure on the inner wall 9 exerted, whereby a plastic deformation and / or a (minor) material removal takes place. So can on the one hand smooth the inner wall 9 and second, an increase in the tensile strength of the crankshaft 1 also in the field of oil drilling 4 be achieved, bringing the crankshaft 1 overall becomes more robust with respect to the mechanical loads acting during operation.

In the in the 2 and 3 illustrated embodiment come two different work hardening tools 13 . 14 to use, in the oil well 4 protruding tool heads differ in their contour. The contour of the in 2 illustrated Kaltverfestigungswerkzeugs 13 or the essay, with the inner wall 9 comes into contact with the contour of the cylindrical section 11 customized. In contrast, the contour of the in 3 illustrated Kaltverfestigungswerkzeugs 14 or the attachment to the contour of the conical sections 10 and 12 customized. The oil hole 4 can optionally either with the in 2 illustrated work hardening tool 13 with the cylindrical head or with the in 3 illustrated work hardening tool 14 be worked with the conical head.

As in 2 illustrated, extends the tool head of the work hardening tool 13 only over part of the length of the section 11 , If this is to be machined over its entire length, this is easily done by moving the work hardening tool 13 possible. But it can also be enough, the oil well 4 only over part of their total length with the work hardening tools 13 and 14 to edit. Specifically, should in particular the mouth openings 5 . 6 near areas of the oil well 4 be work hardened, since they are exposed to experience in the experience of larger loads. In addition, these areas also border directly on the solidified area of the outer surfaces 7 . 8th with what it - without a specific solidification of the inner wall 9 the oil well 4 - There would be a more or less erratic change in the material parameters, which would lead to an increased risk of cracking in this area.

By working the oil hole 4 especially in the conical sections 10 and 12 that directly adjoins the mouth openings 5 . 6 adjoin, it may u. U. to a material throw in the mouth openings 5 . 6 come. Therefore, it may be necessary in a subsequent step, the outer surfaces 7 . 8th subsequently rework. For example, a material throw-up can be removed by grinding. It is also possible only after the solidification of the oil well 4 the outer surfaces 7 . 8th solidify and bring in this context in the final form.

LIST OF REFERENCE NUMBERS

1

crankshaft

2

shaft journal

3

shaft journal

4

oil well

5

mouth

6

mouth

7

outer surface

8th

outer surface

9

inner wall

10

section

11

section

12

section

13

Hardening tool

14

Hardening tool

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2814636 B1 [0005, 0011, 0019, 0025]

Claims (10)

A method for solidifying a shaft, in particular a crankshaft (1) for a reciprocating engine, comprising the following steps: - providing the shaft, wherein the shaft has at least one shaft journal (2, 3) and an oil bore (4) with an orifice (5, 6) in the region of the shaft journal (2, 3), - work hardening of the shaft journal (2, 3) over at least part of its outer surface (7, 8), characterized in that the oil bore (4) at least in a region between the mouth opening (5 , 6) and another mouth opening (5, 6) of the oil hole (4) with a work hardening tool (13, 14) for work hardening of the oil hole (4) is machined in this area. Method according to Claim 1 , characterized in that the oil bore (4) over its entire between the mouth opening (5, 6) and the further mouth opening (5, 6) extending length with the work hardening tool (13, 14) is processed. Method according to one of the preceding claims, characterized in that different in their contour sections (10, 11, 12) of the oil hole (4) with different work hardening tools (13, 14) are processed, the contour of each corresponding to the contour of each section ( 10, 11, 12) is adjusted. Method according to one of the preceding claims, characterized in that when working with the work hardening tool (13, 14) the contact pressure exerted on the oil bore (4) defining the inner wall (9), depending on the distance from the mouth opening (5, 6) is adjusted. Method according to Claim 4 , characterized in that with the work hardening tool (13, 14) in a region close to the mouth opening (5, 6), a greater contact pressure is exerted on the inner wall (9) than in a region remote from the mouth opening (5, 6). Method according to Claim 5 , characterized in that the contact pressure with increasing distance from the mouth opening (5, 6) decreases continuously. Method according to Claim 4 , characterized in that in a region near the mouth opening (5, 6) a smaller contact pressure force is exerted on the inner wall (9) than in a region remote from the mouth opening (5, 6). Method according to one of Claims 4 to 7 , characterized in that with the work hardening tool (13, 14) from a predetermined distance from the mouth opening (5, 6) a constant contact force is exerted. Method according to one of the preceding claims, characterized in that the outer surface (7, 8) of the shaft journal (2, 3) after machining the oil hole (4) with the work hardening tool (13, 14) at least in the region of the mouth opening (5, 6 ) is post-processed in bringing and / or smoothing the outer surface (7, 8). Use of a work hardening tool (13, 14), which is designed for work hardening of an inner surface, for machining an oil bore (4) of a shaft, in particular a crankshaft (1) for a reciprocating engine, in one between two orifices (5, 6). the oil hole (4) lying area.

Images