DE102020111679A1 - Shaft, forming tool, manufacturing process and rotor for an electrical machine - Google Patents

Abstract

Shaft (1) with a central axis (2) and a fitting section (3) for forming a form-fitting shaft-hub connection, the fitting section (3) radially protruding fitting structures (4) and one at an axial end (5) of the fitting section ( 3) has formed chamfer (6) at least partially engaging the fitting structures (4), a distance between radially inner edges (10, 11) of a respective fitting structure (4) being reduced towards the axial end (5).

Description

The present invention relates to a shaft with a central axis and a fitting section for forming a form-fitting shaft-hub connection, the fitting section having radially protruding fitting structures and a chamfer formed at one axial end of the fitting section and at least partially engaging the fitting structures.

In addition, the invention relates to a forming tool for producing a shaft, a method for producing a shaft and a rotor for an electrical machine.

Such a wave is from the article by M. Lätzer et al. "Investigations into the transmission behavior of knurled press connections made of steel-aluminum", research in engineering 79 , Pages 41 until 65 (2015) known. The article discloses a knurled shaft with axially parallel knurls which are produced by reshaping by means of a knurling wheel or by means of recursive axial shaping and have a bevel with a bevel angle φ. Depending on the selected bevel angle φ, a form-fitting shaft-hub connection can be realized by a cutting and / or reshaping joining process.

A disadvantage of such a shaft is that the hub material is displaced essentially in the radial direction during a joining process in a hub. As a result, considerable radial mechanical stresses occur in the hub material. This is particularly undesirable with regard to the use of a shaft as a rotor shaft for a drive machine of an electric vehicle.

The invention is therefore based on the object of specifying a possibility for reducing radial mechanical stresses in a self-tapping, form-fitting shaft-hub connection.

According to the invention, this object is achieved by a shaft of the type mentioned at the outset, in which a distance between radially inner edges of a respective fitting structure and the axial end is reduced.

The invention is based on the consideration of designing the fitting structures to run narrower towards the axial end so that hub material displaced during a joining process can get into gaps between the radially inner edges of adjacent fitting structures. This hub material thus does not reach the outside radially in order to contribute to the generation of radial mechanical stresses there. As a result, radial mechanical stresses can advantageously be reduced considerably and, at the same time, losses in the torque transmission capacity of the shaft-hub connection can be avoided. In addition, a radial deformation caused by the radial mechanical stresses is reduced when the shaft is rotating.

In the case of the shaft according to the invention, it is particularly preferred if the radially inner edges converge at one point towards the axial end. As a result, when viewed axially, an essentially pointed configuration of the fit structure is realized, which considerably facilitates the displacement of the material during the joining process.

According to a further development alternative of the shaft according to the invention, it can be provided that the radially inner edges each run straight at an angle with respect to a line parallel to the central axis towards the axial end. The angle is preferably less than 90 °. It is particularly preferably between 10 ° and 60 °.

According to a second alternative development of the shaft according to the invention, it is provided that the radially inner edges each run towards the side line with the formation of an arc. The arc is preferably an arc of a circle with a constant radius. In a preferred embodiment, a chord of the arch running from the beginning to the end of the arch forms an angle between 10 ° and 60 ° with a line parallel to the central axis.

In the case of the shaft according to the invention, it can advantageously be provided that the bevel begins closer to the axial end than a point closest to the axial end of the maximum distance between the radially inner edges. In other words, the area of the radially inner edges in which their distance from the axial end decreases, extends further in the axial direction than the bevel. This provides a particularly large amount of space to accommodate the hub material displaced during the joining process.

Typically, a ratio of an axial extension of the region of the radially inner edges in which their distance decreases towards the axial end to an axial extension of a region in which the fitting structure is gripped is between 1.8 and 2.2.

A respective fitting structure of the shaft according to the invention can have flat side surfaces. These preferably include an angle between 30 ° and 70 ° with a plane perpendicular to the circumferential direction. Alternatively, a respective fitting structure can have curved side surfaces, which preferably form an angle between 30 ° and 70 ° with one perpendicular to the circumferential direction chord enclosing the standing plane.

In the case of the shaft according to the invention, it is also possible for a radially outer section of the fit structure pointing towards the axial end to run in a flattened manner at a bevel angle of the bevel.

In a preferred embodiment of the shaft according to the invention, it is further provided that a respective fitting structure has the shape of a polygon or a rounded polygon with respect to a cross-sectional area perpendicular to the central axis. The polygon is preferably a triangle or a rectangle. Alternatively, a respective fitting structure can have the shape of a semicircle or semicircle with respect to a cross-sectional area perpendicular to the central axis.

In a preferred embodiment of the shaft according to the invention, it is also provided that the fitting section has a plurality of fitting zones with fitting structures distributed in the circumferential direction and is smooth between two adjacent fitting zones. Preferably, three evenly distributed fitting zones are provided.

The object on which the invention is based is further achieved by a forming tool for producing a shaft, in particular a shaft according to the invention, comprising a die with a through opening for passing through a chamfered shaft body, the die having recesses in an inner edge of the through opening for forming fitting structures on the Has shaft body, wherein a distance between radially inner edges of a respective recess decreases towards the axially inside of the through opening.

The recesses are expediently designed to be opposite to the areas of the fitting structures in which the distance between their radially inner edges is reduced.

It can be provided in the forming tool according to the invention that the radially inner edges converge at one point towards the axially interior of the through opening.

The radially inner edges can each run straight at an angle with respect to a line parallel to a central axis of the through opening towards the axially inside of the through opening. The angle can be between 10 ° and 60 °. Alternatively, the radially inner edges can each run towards the axially inside of the through opening, forming an arc. A chord of the arch running from the beginning to the end of the arch preferably encloses an angle between 10 ° and 60 ° with a line parallel to a central axis of the through opening.

In addition, it can be provided in the forming tool according to the invention that a respective recess flat side surfaces, which preferably enclose an angle between 30 ° and 70 ° with a plane perpendicular to the circumferential direction, or curved side surfaces, which preferably form an angle between 30 ° and 70 ° having an enclosing chord with a plane perpendicular to the circumferential direction.

A respective recess of the tool according to the invention can have the shape of a polygon or a rounded polygon with respect to a cross-sectional area perpendicular to the central axis of the through opening, the polygon preferably being a triangle or a rectangle, or the shape of a semicircle or semi-oval.

The die can be formed by several, preferably three, separate die elements which are attached to a carrier of the forming tool, each die element having several of the recesses and being smooth in the circumferential direction to one or both adjacent die elements.

The object on which the invention is based is further achieved by a method for producing a shaft, comprising the following steps: providing a shaft body, forming a fitting section with radially protruding fitting structures which are at least partially covered by a chamfer at an axial end of the fitting section, whereby a distance between radially inner edges of a respective fitting structure towards the axial end is reduced.

A forming tool according to the invention is preferably used to form the fitting structures.

In the method according to the invention it can be provided that a shaft body with existing fitting structures and an existing bevel that encompasses the existing fitting structures is provided at the axial end.

In a preferred development, it is provided that when the fitting section is formed, a volume match between a volume of a region of a respective existing fitting structure that is captured by the existing bevel and through a plane perpendicular to the central axis is delimited, and a volume of a region of a respective fit structure of the shaft, in which the distance between the radially inner edges decreases towards the axial end and is limited by a plane perpendicular to the central axis, of at least 95%, preferably at least 99% is generated. Because the volumes are of a similar size, undesired deformations, for example deformations that form a burr, can be avoided.

The object on which the invention is based is further achieved by a rotor for an electrical machine, preferably a drive machine for an electric vehicle, comprising a shaft according to the invention or a shaft obtained by the method according to the invention and a rotor core and / or a resolver positively connected to the fitting section .

Permanent magnets are preferably arranged in the rotor core.

• 1 eine perspektivische Ansicht eines ersten Ausführungsbeispiels der erfindungsgemäßen Welle;
• 2 eine Detailansicht einer Passungsstruktur des ersten Ausführungsbeispiels und eines zweiten Ausführungsbeispiels der erfindungsgemäßen Welle aus radialer Perspektive;
• 3 eine Detailansicht der Passungsstruktur gemäß dem ersten und im zweiten Ausführungsbeispiel aus seitlicher Perspektive;
• 4 Schnittdarstellungen der Passungsstruktur entlang von Schnittebenen A-A und B-B in 2;
• 5 eine Detailansicht einer Passungsstruktur gemäß einem dritten und einem vierten Ausführungsbeispiel der erfindungsgemäßen Welle aus radialer Perspektive;
• 6 eine Detaildarstellung der Passungsstruktur gemäß dem dritten und dem vierten Ausführungsbeispiel aus seitlicher Perspektive;
• 7 Schnittdarstellungen einer Passungsstruktur gemäß weiteren Ausführungsbeispielen der erfindungsgemäßen Welle;
• 8 eine perspektivische Darstellung eines Ausführungsbeispiels des erfindungsgemäßen Umformwerkzeug;
• 9 eine Detailansicht von Eintiefungen des Umformwerkzeugs;
• 10 eine Prinzipskizze einer bestehenden Passungsstruktur vor einer Durchführung eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens;
• 11 eine Prinzipskizze einer Passungsstruktur nach Durchführung des Ausführungsbeispiels des erfindungsgemäßen Verfahrens;
• 12 eine Prinzipskizze eines Ausführungsbeispiels des erfindungsgemäßen Rotors in einer elektrischen Maschine;
• 13 eine Darstellung der Herstellung einer Welle-Nabe-Verbindung des Rotors; und
• 14 eine Detailansicht von 13.

Further advantages and details of the present invention emerge from the exemplary embodiments described below and with reference to the drawings. These are schematic representations and show:

• 1 a perspective view of a first embodiment of the shaft according to the invention;
• 2 a detailed view of a fitting structure of the first embodiment and a second embodiment of the shaft according to the invention from a radial perspective;
• 3 a detailed view of the fitting structure according to the first and second embodiment from a side perspective;
• 4th Sectional representations of the fit structure along section planes AA and BB in 2 ;
• 5 a detailed view of a fitting structure according to a third and a fourth embodiment of the shaft according to the invention from a radial perspective;
• 6th a detailed representation of the fit structure according to the third and fourth exemplary embodiment from a side perspective;
• 7th Sectional representations of a fit structure according to further exemplary embodiments of the shaft according to the invention;
• 8th a perspective view of an embodiment of the forming tool according to the invention;
• 9 a detailed view of recesses of the forming tool;
• 10 a schematic diagram of an existing fit structure before an embodiment of the method according to the invention is carried out;
• 11 a schematic diagram of a fit structure after performing the embodiment of the method according to the invention;
• 12th a schematic diagram of an embodiment of the rotor according to the invention in an electrical machine;
• 13th a representation of the production of a shaft-hub connection of the rotor; and
• 14th a detailed view of 13th .

1 Figure 3 is a perspective view of a first embodiment of a shaft 1 .

The wave 1 has a central axis 2 and a fitting section 3 to form a positive shaft-hub connection. In the fitting section there are radially protruding fitting structures 4th in the form of knurls. At one axial end 5 of the fitting section 3 is a bevel 6th formed which the fitting structures 4th partially recorded.

As in 1 As can also be seen, the fitting portion extends 3 in this embodiment example further in the axial direction on both sides than the fitting structures 4th . On both sides of the fitting section 3 , ie at the axial end 5 and another axial end 7th , shaft stumps close 8th , 9 at.

A coordinate system in Cartesian coordinates with the x-axis parallel to the central axis 2 runs, defines spatial directions in 1 and the following figures.

2 Figure 3 is a detailed view of a mating structure 4th of the first embodiment and a second embodiment of a shaft 1 from a radial perspective.

Radial inner edges 10 , 11 the fit structure 4th that for the rest in 1 shown fitting structures 4th is representative, reduce their distance to the axial end 5 there and run in one point 12th together. From a maximum distance b of the radially inner edges of the fitting structure 4th this distance therefore goes to the axial end 5 from a given axial position 13th back and forth until it is practically zero. The radially inner edges 10 , 11 each run straight at an angle λ with respect to the central axis 2 parallel line 14th to the axial end 5 there.

The second embodiment differs from the first embodiment in that the radially inner edges 10 , 11 here with the formation of an arc shown in dashed lines to the axial end 5 run there. In the present exemplary embodiment, this arc has a constant one Radius on. One from the beginning to the end of the arc or from the axial position 13th to the point 12th trending tendon 15th of the arch closes with that of the central axis 2 parallel line 14th the angle λ.

3 Figure 3 is a detailed view of the fit structure 4th according to the first and second exemplary embodiment from a side perspective.

In 3 a maximum height h of the fit structure is initially drawn in. This corresponds to a radial distance between the radially inner edges 10 , 11 to a radially outer edge 16 the fit structure outside the chamfered area. A bevel angle of the bevel 6th is denoted by φ. The bevel 6th obviously begins closer to the axial end 5 as a point closest to the end face (axial position 13th ) maximum distance between the radially inner edges 10 , 11 . A ratio of an axial extent I _{1 of} the area in which the distance between the radially inner edges 10 , 11 reduced towards a radial extension I ₂ , a region in which the fit structure 4th is chamfered, is 2.0 here and is typically between 1.8 and 2.2. A respective side face 17th of the fitting section 4th therefore has a triangular shape when viewed in the circumferential direction.

4th shows two sectional views of the fit structure 4th along section planes AA and BB in 2 .

In the first embodiment, the side surfaces close 17th with a plane perpendicular to the circumferential direction or a plane spanned in the axial direction and radial direction, which plane extends through the radially outer edge 14th extends, an angle ψ. In other words, a radially inner distance c _{1 of} the side surfaces becomes 17th smaller in the radial direction (see distance c ₂ ).

In the second embodiment, the side surfaces are 17th curved outward in the circumferential direction, a chord of the curvature making the angle ψ with the plane 18th includes. A distance d between the bulge and its tendon is at most h / 2 (see 3 ).

5 and 6th are each a detailed representation of a fit structure 4th according to a third and a fourth embodiment of the shaft 1 , whereby 5 the fit structure 4th from a radial perspective and 6th the fit structure 4th show from side perspective.

In these exemplary embodiments, which otherwise correspond to the first and second exemplary embodiments, the side surfaces extend 17th not up to the maximum height h of the fit structure 4th so that a radially outer to the axial end 5 pointing section 19th the fit structure 4th is flattened at the bevel angle φ.

7th shows sectional views of fit structures 4th according to further embodiments of the shaft 1 , the representation of the section plane AA in 4th is equivalent to. In the exemplary embodiment shown at the top left, the fit structure 4th a radially inner parallel section 20th and a radially outer round portion 21 on. In the embodiment shown at the top right, the fit structure 4th a hexagonal cross-section with a radially inner trapezoidal section 22nd and a radially outer trapezoidal section 23 on. In the embodiment shown at the bottom left, the fitting section is pentagonal and has a radially inner parallel section 20th and a radially outer triangular section 24 on. In the embodiment shown at the bottom right, the fitting section 4th a substantially parabolic cross-section.

Again related to 1 are according to a further embodiment in the fitting section 3 instead of fitting structures arranged continuously in the circumferential direction 4th several circumferentially distributed fitting zones are provided in which the fitting structures 4th are formed, with no fitting structures or the fitting section being formed between the fitting zones 3 is smooth in the circumferential direction between the fitting zones. According to one exemplary embodiment, three fitting zones can be provided, which are arranged at an angle of 120 ° to one another in the circumferential direction.

8th Figure 3 is a perspective view of an embodiment of a forming tool 50 for making a shaft 1 . In this context, an exemplary embodiment of a method for producing the shaft is also described below 1 described.

The forming tool 50 includes a die 51 with a central axis 53 having through opening 52 for leading through a chamfered shaft body. With such a shaft body - as in 10 shown - already existing fitting structures are provided, which are touched _{at an existing bevel angle φ 0.} The die 51 points in an inner edge 54 the passage opening 52 Indentations 55 for forming the fitting sections 4th on the shaft body.

9 is a detailed view of the recesses 55 of the forming tool 50 . There are the depressions 55 obviously opposite to the intended shape of the fitting structures 4th formed, generally one of the previously described embodiments of the shaft 1 can correspond. The depressions 55 thus, above all, have radially inner edges 56 , 57 on whose distance to the axially interior of the through opening 52 reduced towards.

Again related to 8th it can be seen that the recesses are not formed completely circumferentially, but only in three recess zones spaced apart in the circumferential direction 58 are formed, so that the forming tool shown 50 to form a wave 1 is formed with corresponding fitting zones described above. According to further exemplary embodiments of the forming tool 50 However, this can also be depressions that are completely distributed in the circumferential direction 55 have so that a wave in as in 1 shown is producible.

The die 51 is present by three separate matrix elements 59 formed, the respective depressions 55 one of the recessed areas 58 have and in this respect are designed identically. The matrix elements 59 are in a carrier 60 arranged, which is also from the through opening 52 is penetrated, and there by fasteners 61 , here by way of example screws.

As part of the process of manufacturing the shaft 1 the shaft body is provided first. 10 shows a perspective view of an existing fitting structure 4a on a shaft body before carrying out the manufacturing process. In 10 are also a width t of the existing fit structure 4a and an axial length x ₁ of the area of the existing fitting structure covered by the chamfer 4a marked. h denotes the height of the existing fit structure 4a and φ ₀ the existing bevel angle. A volume one to the axial end 5 pointing area of the existing fit structure 4a that is covered by the existing bevel is marked _{with V 1.}

For forming the fitting structures 4th becomes the shaft body with the existing fit structures 4a first the tool in the through opening 50 introduced so that the existing fit structure 4a is plastically deformed.

11 shows the geometric relationships of the fit structure 4th after forming in the tool 50 , where the angles φ, λ, ψ arise. Where x ₂ is an axial length of the bevel 6th captured area of the fit structure 4th designated. With x ₃ is an axial length between the area in which the distance between the radially inner edges 10 , 11 to the axial end 5 towards that of the bevel 6th recorded area of the fit structure 4th designated. The volume shown subdivided into partial volumes V _2.1 , V _2.2 of the axial end 5 pointing area in which the distance between the radially inner edges 10 , 11 to the axial end 5 is reduced towards V ₂ .

The existing fit structures are used to avoid undesirable burr formation during the forming process 4a and the shape of the depressions 55 the die 51 chosen so that a volume match of at least 99% between V ₁ and V _{2 is} achieved. It should be noted that during the formation of the fit structure 4th the bevel angle changed from φ ₀ to φ.

12th is a schematic diagram of an electrical machine 100 with an embodiment of a rotor 101 .

The rotor 101 includes a shaft 1 according to one of the exemplary embodiments described above, with the fitting section 3 a rotor core 102 is arranged positively with permanent magnets. The rotor 101 can be rotated around the central axis 2 inside a stator 103 stored.

13th and 14th are each an illustration of the production of a shaft-hub connection of the rotor, wherein 14th a detail Z in 13th shows.

The wave becomes visible 1 for producing the shaft-hub connection in the rotor core 102 introduced. The fitting section 4th has a radial oversize U compared to the rotor core 102 on. This is done by cutting and reshaping the rotor core 102 a form-fitting shaft-hub connection between the shaft 1 and the rotor core 102 realized.

Claims (15)

Shaft (1) with a central axis (2) and a fitting section (3) for forming a form-fitting shaft-hub connection, the fitting section (3) radially protruding fitting structures (4) and one at an axial end (5) of the fitting section ( 3) has formed chamfer (6) at least partially engaging the fitting structures (4), characterized in that a distance between radially inner edges (10, 11) of a respective fitting structure (4) is reduced towards the axial end (5). Wave after Claim 1 wherein the radially inner edges (10, 11) converge towards the axial end (5) at a point (12). Wave after Claim 1 or 2 , wherein the radially inner edges (10, 11) each just below one Angle (λ) with respect to a line (14) parallel to the central axis (2) run towards the axial end (5). Wave after Claim 3 , where the angle (λ) is between 10 ° and 60 °. Wave after Claim 1 or 2 , the radially inner edges (10, 11) each extending towards the axial end (5) with the formation of an arc. Wave after Claim 5 , wherein a chord of the arc running from the beginning to the end of the arc encloses an angle (λ) between 10 ° and 60 ° with a line (14) parallel to the central axis (2). Shaft according to one of the preceding claims, wherein - The bevel (6) begins closer to the axial end (5) than a point closest to the axial end (5) of maximum distance between the radially inner edges (10, 11) and / or - A radially outer section (19) of the fitting structure (4) pointing towards the axial end (5) runs flattened at a bevel angle (φ) of the bevel (6). Shaft according to one of the preceding claims, wherein a respective fitting structure (4) in its area covered by the bevel (6) - Flat side surfaces (17), which preferably enclose an angle between 30 ° and 70 ° with a plane perpendicular to the circumferential direction, or - Arched side surfaces (17), which preferably have a chord enclosing an angle between 30 ° and 70 ° with a plane perpendicular to the circumferential direction. Shaft according to one of the preceding claims, wherein a respective fitting structure (4) has the shape with respect to a cross-sectional area perpendicular to the central axis - A polygon or a rounded polygon, the polygon preferably being a triangle or a rectangle, or - Has a semi-circle or semi-oval. Forming tool (50) for producing a shaft (1), in particular according to one of the preceding claims, comprising a die (51) with a through opening (52) for passing through a chamfered shaft body, the die (51) in an inner edge (54) the through opening (52) has recesses (55) for forming fitting structures (4) on the shaft body, a distance between radially inner edges (56, 57) of a respective recess (55) being reduced towards the axially inside of the through opening (52). Forming tool according to Claim 10 , wherein the die (51) is formed by several, preferably three, separate die elements (59) which are attached to a carrier (60) of the forming tool (50), each die element (59) having several of the recesses and in the circumferential direction is smooth to one or both of the adjacent die elements (59). A method for producing a shaft (1), comprising the following steps: - Provision of a shaft body, - Forming a fitting section (3) with radially protruding fitting structures (4) which are at least partially covered by a bevel (6) at an axial end (5) of the fitting section (3), a distance between radially inner edges (10, 11) ) a respective fitting structure (4) towards the axial end (5) is reduced. Procedure according to Claim 12 , wherein a forming tool (50) to form the fitting section according to Claim 10 or 11 is used. Procedure according to Claim 12 or 13th , wherein a shaft body with existing fitting structures (4a) and an existing bevel that grips the existing fitting structures (4a) is provided at the axial end (5), a volume correspondence between a volume (V ₁ ) of a region of a respective existing existing fitting structures (4), which is captured by the existing bevel and limited by a plane perpendicular to the central axis (2), and a volume (V ₂ ) of a region of a respective fitting structure (4) of the shaft (1) in which the distance between the radially inner edges (10, 11) to the axial end (5) is reduced and is limited by a plane perpendicular to the central axis (2), by at least 95%, preferably at least 99%. A rotor (101) for an electrical machine (100), comprising - a shaft (1) according to one of the Claims 1 until 9 or one by a method according to one of the Claims 12 until 14th obtained shaft (1) and - a rotor core (102) and / or resolver connected to the fitting section (3) in a form-fitting manner.

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