DE102019202000A1 - Device and method for inductive feed hardening of roller bearing raceways - Google Patents

Abstract

Device for inductive feed hardening of a roller bearing raceway of a roller bearing ring, the device having an inductor (3) with an induction surface (4) which is used for the inductive introduction of heat into a hardening zone of the roller bearing ring that encompasses a section of the roller bearing raceway opposite the section of the roller bearing raceway and relative to the roller bearing raceway can be positioned displaceably in the circumferential direction, the induction surface (4) having a concave shape at least in sections in the direction of the width of the roller bearing raceway to make the hardening depth of the hardening zone (5) uniform over the raceway width.

Description

State of the art

The invention relates to a device and a method for inductive feed hardening of roller bearing raceways.

To harden workpieces made of steel, they are first heated strongly. The structure present at room temperature is converted into austenite, in which more carbon can be dissolved than in ferrite. Furthermore, cementite is dissolved when heated, the carbon of which goes into solution with the austenite formed. If the hot steel is quickly quenched, the carbon does not have time to diffuse, so that segregation of the austenite and carbon into ferrite and cementite is prevented. The iron lattice cannot change into the body-centered cubic ferrite; instead, martensite is created with a tetragonally distorted body-centered cubic lattice, which is braced by the carbon.

With inductive hardening, the workpiece is heated by means of a high-frequency alternating current that is passed through a coil of an inductor. This creates alternating magnetic fields that induce eddy currents in the workpiece, which heat the workpiece.

In the so-called advance hardening of roller bearing raceways, the roller bearing ring is guided past an inductor in advance mode, which only heats a circumferential section of the roller bearing raceway. A shower is arranged behind the inductor in the feed direction, which cools off the heated section. After one revolution of the rolling bearing ring, the rolling bearing raceway is hardened. Due to the process, a short unhardened area remains at the beginning / end of the cycle, the so-called slip. Alternatively, the inductor can also be moved around the circumference of the rolling bearing ring in advance. The inductors used for feed hardening can be attached in a compact manner to flexible machine carriers. Tracking controls allow the exact positioning of inductors and workpiece to one another. This means that they can also be used flexibly for workpieces of different sizes.

In the known hardening processes for roller bearing raceways, uneven courses in the hardening depth in the direction of the raceway width often occur. Such irregularities can negatively affect the load-bearing capacity and the service life of the rolling bearings.

In order to reduce the irregularities in the course of the hardening depth, it is known in feed hardening to incline the inductor on an empirical basis with respect to the roller bearing raceway. Due to the smaller distance between inductor and roller bearing ring on one side of the raceway and a correspondingly larger distance between inductor and roller bearing ring on the other side, steadily increasing or decreasing irregularities in the hardness depth can be compensated for in the direction of the raceway width.

The publication suggests to even out the lateral expansion of the hardening DE 10 2014 102 288 A1 a side cooling, for example in the form of side sprays of liquid, which prevents the workpiece from being heated on the side areas of the track. It is disadvantageous that the cooling effect of the lateral liquid sprinklers can only be adjusted in a very complex and imprecise manner.

DE 102 28 333 C1 discloses a method for inductive shot hardening, in which the inductor has a frustoconical induction surface which is inclined to the surface of the rolling bearing raceway to be hardened. Another approach to equalize the hardening is a regulation and control of the current of an inductor with two coils, as described in WO 2016/177733 A1.

It is disadvantageous that with the above-mentioned methods it is only possible to compensate for constantly increasing or decreasing changes in the hardness depth over the width of the track. Uneven irregularities in the same direction that occur at both edges of the raceway cannot be taken into account.

Disclosure of the invention

The invention is therefore based on the object of providing a device and a method which do not have the aforementioned disadvantages of the prior art and offer the possibility of hardening a rolling bearing raceway with very good uniformity.

This object is achieved by a device for inductive feed hardening of roller bearing raceways with the features of claim 1.

Due to the at least partially concave shape of the induction surface in the direction of the width of the roller bearing raceway, both edges of the induction surface can be brought closer to the roller bearing raceway during hardening than an inner area of the induction surface. The induction surface, from which the eddy currents are excited, faces the rolling bearing ring. In this way, irregularities in the hardness depth due to the principle in the edge areas can be better compensated for.

The invention is based on the knowledge that, on the one hand, the magnetic field generated by the inductor has a weaker magnetic field strength in the area of the edges of the induction surface, which means that less heat is introduced there, and, on the other hand, the edge areas of the rolling bearing raceway through heat conduction into surrounding areas of the rolling bearing ring Dissipate heat more quickly, which in the known hardening processes at the raceway edges leads to a reduced hardening depth. In contrast, the device according to the invention offers the possibility, due to the at least partially concave shape of the induction surface, to increase the field line density of the magnetic field in these edge areas and thus to bring about deeper heating. In the context of the present invention, deep means in a direction orthogonal to the surface of the roller bearing ring facing the inductor into the roller bearing ring.

Concave within the meaning of the present invention means that all areas between two edge areas lie on a common side of a straight line connecting the two edge areas. The common side of the straight line is the side facing away from the rolling bearing ring. The concave part of the induction surface is therefore an indentation. Thus, a lower field line density caused by edge effects at the edge of the induction surface and thus a lower depth of heating is compensated for by the fact that the induction surface is closer to the rolling bearing ring in these areas.

It is conceivable that the induction device consists of a preheating inductor, a main inductor, a quenching device as well as side cooling and an after-cooling shower. The concave shape of the induction surface then relates to a plane which is aligned orthogonally to the main plane of extent of the inductor and intersecting the center point of the roller bearing raceway.

The inductor preferably comprises a waveguide which forms an induction coil through which a cooling medium can flow. This allows the inductor to be effectively cooled during the hardening process. At least one outer surface of the waveguide can form the induction surface of the inductor. The waveguide is preferably made of copper or a copper-containing material. Alternatively or additionally, a separate cooling conductor can also be provided.

It is conceivable that the concave shape is symmetrical. This is particularly advantageous for the hardening of raceways in which the heat loss due to thermal conduction is essentially the same at both edges of the raceway.

But it is also conceivable that the concave shape is asymmetrical. It is conceivable that the concave shape is essentially continuous. It is also conceivable that the concave shape is curved, wherein it is furthermore conceivable that the concave shape is symmetrically curved or asymmetrically curved.

It is conceivable that the inductor has side cooling, for example in the form of side showers for cooling side areas outside the hardening zone.

According to a further preferred embodiment of the present invention it is provided that the inductor has a field reinforcement device for local reinforcement of a magnetic field in order to even out the expansion of the hardening zone, wherein the field reinforcement device for local reinforcement of the magnetic field is preferably a device for concentrating the magnetic field, the field reinforcement device in particular preferably made of a ferromagnetic material, for example transformer sheet or a ferromagnetic plastic. A well controllable concentration of the magnetic field can thus be realized. For this purpose, the field reinforcement device is arranged on the side of the induction surface facing away from the workpiece. It is conceivable that the field reinforcement device consists at least partially of a magneto-dielectric material. It is also conceivable that the reinforcement device has soft iron particles which are embedded in a plastic. It is also conceivable that the reinforcement device has an essentially U-shaped shape that is open towards the workpiece.

According to a further preferred embodiment of the present invention, it is provided that the induction surface has an induction main surface, which is concave at least in sections, and an induction side surface. This makes it possible in an advantageous manner to adapt the induction surface to different conditions of the workpiece.

According to a further preferred embodiment of the present invention it is provided that the induction main surface and the induction side surface are arranged at an angle to one another. This advantageously enables the simultaneous hardening of several areas of rolling bearing rings with complex geometries. It would be conceivable, for example, to harden an L-shaped or U-shaped geometry. For uniform hardening of a U-shaped geometry, it would be conceivable for the device to have a first induction side surface and a second induction side surface. For this purpose it is conceivable that the first induction side surface and the second induction side surface are on opposite sides of the induction main surface are arranged and the first induction side surface is arranged at a first angle to the induction main surface and the second induction side surface is arranged at a second angle to the induction main surface.

According to a further preferred embodiment of the present invention it is provided that the induction side face has at least partially a convex shape. In the context of the present invention, convex means that all areas between two edge areas lie on a common side of a straight line connecting the two edge areas and are arranged closer to the roller bearing ring than the edge areas. The convex part of the induction surface is therefore a bulge. If an L-shaped area is hardened, shape-related shallower depths when the angular area of the L-shaped area is heated can be compensated for by arranging the induction surface more closely in the angular area on the roller bearing ring.

According to a further preferred embodiment of the present invention, it is provided that the induction side surface has a corner region adjoining the main induction surface and a central region, the induction side surface having a convex shape in the corner region and a concave shape in the central region. This makes it possible, due to edge effects, to compensate for reduced depths during heating and shape-related reduced depths during heating of the angular area of the L-shaped area by arranging the induction side surface more closely in the edge area and in the angular area on the roller bearing ring.

It can also be provided that the induction surface has outer contours that are concave towards the interior of the induction surface, at least in sections. The concave outer contours of the induction surface can be selected so that the hardness area that can be heated by the induction surface is essentially rectangular. The concave outer contours counteract increased heat dissipation in the corner areas of the hardness area, which in the prior art lead to a hardness area with rounded outer contours. A rectangular hardness area has the advantage that all areas of the track are heated for the same length of time across the width of the track. A rectangular hardness area thus also contributes to the equalization of the hardness depth.

Another object of the present invention for solving the problem set out above is a method with the features of claim 10, in which the rolling bearing ring is inductively heated by the device in sections in the feed mode in the area of a hardening zone comprising the rolling element raceway.

The method according to the invention enables the outer areas of the concave section of the induction surface to be arranged closer to the workpiece than the areas between the outer areas of the concave section due to the at least partially concave shape of the induction surface. Furthermore, a field reinforcement device can cause the field line density of the magnetic field to be increased in defined areas and thus to bring about deeper-reaching heating.

According to a preferred embodiment of the present invention, it is provided that in an adjustment step before the inductive heating of the roller bearing ring, the concave shape of the induction surface and / or the field reinforcement device are adjusted so that the hardening depth in the hardening zone is evened out. This can be done, for example, by arranging the field reinforcement device. However, it is also conceivable to adapt the concave shape of the induction surface accordingly, for example by applying copper sheets.

A further subject matter of the present invention for solving the object set at the beginning is a method for producing a device according to one of claims 1 to 9, the inductor being produced at least partially from a metal by means of 3D printing. 3D printing advantageously allows a very precisely shaped inductor to be produced quickly and easily. There are few limits to the freedom in the geometric design of the inductor.

According to a preferred embodiment of the present invention it is provided that copper is used as the metal. Copper can be easily processed with a 3D printing process and is an excellent conductor of electricity. This makes copper an advantageously suitable candidate for the production of inductors, which can also be provided with cooling channels.

The present invention also provides a method for producing a device according to one of Claims 1 to 9, in order to achieve the object set out at the beginning, wherein the inductor is at least partially produced from a square tube. The production of at least parts of the inductor from a square tube is inexpensive, simple and also has good material availability. Adjustments to the Inductor geometry can be accomplished quickly.

It is also conceivable, however, that the inductor is manufactured at least partially from a tube with a round, oval or polygonal cross section.

According to a preferred embodiment of the present invention it is provided that the square tube is made of copper. Copper is an excellent conductor of electricity, which makes it a suitable material for the production of conductor tracks for the inductor.

According to a preferred embodiment of the present invention it is provided that at least one incision is made in the square tube, the square tube being bent at the incision. This enables the square tube to be easily adapted to the desired inductor geometry.

The bending of the square tube can take place two-dimensionally, so that the main directions of extension of the bent parts span a flat surface. The bending of the square tube can, however, also take place three-dimensionally, that is, in such a way that the main directions of extent of the bent parts span a non-flat surface.

All of the above statements under “Disclosure of the Invention” apply equally to the device according to the invention and the method according to the invention for hardening and the method according to the invention for production.

Advantageous configurations and developments of the invention can be found in the subclaims and the description with reference to the drawings.

Further details, features and advantages of the invention emerge from the drawings and from the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not restrict the essential inventive concept.

Figure list

• 1 shows schematically a device for inductive feed hardening of a roller bearing raceway according to a first embodiment of the invention,
• 2 shows schematically a device for inductive feed hardening of a rolling bearing raceway according to the prior art,
• 3 shows schematically a device for inductive feed hardening of a rolling bearing raceway according to a second embodiment of the invention,
• 4th shows schematically a further device for inductive feed hardening of a rolling element raceway according to the prior art,
• 5 shows schematically a device for inductive feed hardening of a rolling bearing raceway according to a third embodiment of the invention,
• 6a , 6b show schematically parts of the manufacturing process of the device according to the invention,
• 7th shows schematically a device for inductive feed hardening of a rolling bearing raceway according to a fourth embodiment of the invention.

Embodiments of the invention

In the various figures, the same parts are always provided with the same reference numerals and are therefore usually only named or mentioned once.

In 1 is a device 1 for inductive feed hardening of a rolling bearing raceway of a rolling bearing ring. The device 1 has an inductor 3 with an induction surface 4th which can be positioned for the inductive introduction of heat into a hardening zone of the rolling bearing ring comprising a section of the rolling bearing raceway opposite the section of the rolling bearing raceway and displaceably in its circumferential direction relative to the rolling bearing raceway. The induction surface 4th has a concave shape in the direction of the width of the roller bearing raceway, at least in sections, in order to make the hardening depth of the hardening zone uniform across the raceway width.

The inductor 3 according to 1 includes a waveguide 6th , which forms an induction coil through which a cooling medium can flow. The waveguide 6th extends in a meandering shape, preferably in a U-shape, in the induction surface 4th . The outer surface of the waveguide facing the roller bearing ring 6th forms the induction surface 4th of the inductor 3 . The waveguide 6th is at the connections 10 Can be connected to a power supply that provides the high-frequency alternating current used for inductive heating. Usually alternating currents with frequencies in the range from 1 to 25 kHz are used. A cooling medium can also be used via the connections 10 are supplied or removed. The meander turns are preferably separated by an insulator and arranged so close to one another that A single heating zone is created in the rolling bearing ring during operation.

The connections 10 associated leads and the inductor 3 are on a bracket 11 attached. The inductor 3 is with a field enhancement device 9 provided that surrounds the inductor in a U-shape. The field enhancement device 9 serves to direct the resulting magnetic field in the direction of the bracket 11 shield and concentrate on the bearing ring. The reinforcement device 9 consists preferably of a magneto-dielectric material and is shaped so that it has magnetic field lines in the hardening zone 5 concentrated. This enables eddy currents to be induced more deeply and thus a deeper heating of the rolling bearing ring 2 . As a material for the field enhancement device 9 Preferably ferromagnetic materials such as transformer sheet metal, or particularly preferably ferromagnetic plastics can be used.

In 2 is a device 1 for inductive feed hardening of a rolling bearing raceway according to the prior art. The inductor 3 the device 1 is essentially flat in the direction of the track width and is in line with the induction surface 4th aligned parallel to the rolling bearing raceway to be hardened. On the inductor 3 in the area of the induction surface 4th Alternating current flowing through it generates alternating magnetic fields (not shown), the eddy currents (not shown) in the hardening zone 5 of the rolling bearing ring 2 induce. The hardiness zone 5 is heated by the eddy currents. Due to inhomogeneities in the magnetic field and the increased heat dissipation in the edge areas of the induction surface 4th opposite sections of the rolling bearing ring 2 there is a lower hardening depth of the hardening zone 5 . The hardening depth of the hardening zone 5 in the direction of the track width is therefore uneven.

In 3 is a device 1 outlined for inductive feed hardening of a roller bearing raceway according to a second embodiment of the present invention. The induction surface 4th is concave and is therefore closer to the rolling bearing ring at the edge areas 2 arranged than in an inner region of the induction surface 4th . This results in a significantly more uniform hardening depth of the hardening zone 5 across the width of the career path than in the in 2 prior art shown.

In 4th is another device 1 for inductive feed hardening of a rolling bearing raceway according to the prior art. The rolling bearing ring 2 has an L-shaped track. Due to the increased heat dissipation into the rolling bearing ring 2 is the hardiness zone 5 reduced in particular in the area of the angle of the L-shaped roller bearing raceway.

In 5 is a device 1 outlined for inductive feed hardening of a rolling bearing raceway according to a third embodiment of the invention. The roller bearing raceway is L-shaped. The main induction surface 4 ' the induction surface 4th of the inductor 3 is concave, resulting in a uniform hardening zone 5 in the lower area of the rolling bearing ring 2 leads. To improve the evenness of the hardening zone 5 , in particular in the area of the angle of the rolling bearing ring, which is L-shaped in cross section 2 , indicates the induction surface 4th furthermore the induction side face 4 " which is convex in shape. This, possibly in connection with a reinforcement device, results in a very uniform hardening zone 5 in the entire area of the rolling bearing ring to be hardened 2 .

In 6a and 6b are schematic parts of the manufacturing process of the device 1 shown in accordance with an exemplary embodiment of the present invention. 6a shows a square tube 8th with the incisions 8th' . The square tube 8th is made of copper and is attached to the incisions 8th' bent over. The cut edges of the incisions which lie against one another after bending 8th' are preferably soldered together. In 6b is that at the incisions 8th' bent square tube 8th shown. It forms a waveguide that has an induction coil of the inductor through which a cooling medium can flow 3 forms. Outer surfaces of the waveguide form the induction surface 4th having a major induction surface 4 ' and an induction face 4 " includes. The main induction surface 4 ' is concave in shape. The ends of the square tube form the connections 10 of the inductor.

7th shows schematically a device for inductive feed hardening of a rolling bearing raceway according to a fourth embodiment of the invention. The device 1 differs from the one in 1 embodiment shown in that the induction surface 4th to the inside of the induction surface 4th has concave shaped outer contours. Through increased heat dissipation in the corner areas of the induction surface 4th opposite areas of the rolling bearing ring results in a rectangular induction surface in a hardening zone with more or less strongly rounded corners. Through the formation of the induction surface 4th with to the inside of the induction surface 4th This rounding of the hardening zone can be counteracted towards concave outer contours, and a substantially rectangular hardening zone can be achieved.

The remarks on the in 1 shown device accordingly.

List of reference symbols

1

contraption

2

Rolling bearing ring

3

Inductor

4th

Induction surface

4 '

Induction main surface

4 "

Induction side face

5

Hardening zone

6th

Waveguide

8th

Square tube

8 '

incision

9

Field enhancement device

10

connections

11

bracket

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102014102288 A1 [0007]
• DE 10228333 C1 [0008]

Claims (16)

Device for inductive feed hardening of a rolling bearing raceway of a rolling bearing ring (2), the device (1) having an inductor (3) with an induction surface (4) which is used for the inductive introduction of heat into a hardening zone (5) of the rolling bearing ring encompassing a section of the rolling bearing raceway (2) the section of the roller bearing raceway opposite and relative to the roller bearing raceway can be positioned displaceably in its circumferential direction, characterized in that the induction surface (4) in the direction of the width of the roller bearing raceway has a concave shape, at least in sections, to make the hardness depth of the hardening zone (5) more uniform the career width. Device according to Claim 1 , characterized in that the inductor (3) comprises a waveguide (6) which forms an induction coil through which a cooling medium can flow. Device according to Claim 2 , characterized in that at least one outer surface of the waveguide (6) forms the induction surface (4) of the inductor (3). Device according to one of the Claims 1 to 3 , characterized in that the inductor (3) for equalizing the hardness depth of the hardening zone (5) furthermore has a field strengthening device (9) for locally strengthening a magnetic field, the field strengthening device (9) preferably being a device for concentrating the magnetic field, the field strengthening device (9) particularly preferably consists of a ferromagnetic material. Device according to one of the Claims 1 to 4th , characterized in that the induction surface (4) has an at least partially concave induction main surface (4 ') and an induction side surface (4 "). Device according to Claim 5 , characterized in that the induction main surface (4 ') and the induction side surface (4 ") are arranged at an angle to one another. Device according to Claim 5 or 6th , characterized in that the induction side surface (4 ") has a convex shape at least in sections. Device according to one of the Claims 5 to 7th , characterized in that the induction side surface (4 ") has a corner region adjoining the main induction surface (4 ') and a central region, the induction side surface (4") having a convex shape in the corner region at least in sections and a concave shape in the central region at least in sections . Device according to one of the Claims 1 to 8th , characterized in that the induction surface (4) has, at least in sections, concave outer contours towards the interior of the induction surface (4). Method for inductive feed hardening of a rolling element raceway of a rolling bearing ring (2) with a device according to one of the preceding claims, characterized in that the rolling bearing ring (2) is inductively heated in the area of a hardening zone (5) comprising the rolling element raceway by the device in sections in the feed mode. Procedure according to Claim 10 , characterized in that in an adaptation step before the inductive heating of the rolling bearing ring (2), the concave shape of the induction surface (4) and / or the arrangement of the field reinforcement device (6) are adapted to the geometric shape of the rolling element raceway so that the hardness depth in the Hardening zone (5) is evened out. Method for manufacturing a device according to one of the Claims 1 to 9 , characterized in that the inductor (3) is at least partially manufactured from a metal by means of 3D printing. Procedure according to Claim 12 , characterized in that copper is used as the metal. Method for manufacturing a device according to one of the Claims 1 to 9 , characterized in that the inductor (3) is made at least partially from a square tube (8). Procedure according to Claim 14 , characterized in that the square tube (8) is made of copper. Procedure according to Claim 14 or 15th , characterized in that at least one incision (8 ') is made in the square tube (8) and the square tube (8) is bent at the incision (8').

Images