IMPROVED INDUCTOR FOR THE HEAT TREATMENT OF A PINION

Abstract

The present invention relates to an inductor (15) for the heat treatment of gear teeth, comprising: - an inductor body (17) capable of generating a first alternating magnetic field, said inductor body (17) being intended to be inserted inside an interdental space (12) of the gear, - a current input branch connected to a first end of the inductor body (17), and - a current output branch connected to a second end of the inductor body (17), and - at least one magnetic field concentrator (20) surrounding at least part of the inductor body (17) so as to concentrate the magnetic field generated by the inductor body (17) in one or more preferred areas of the interdental space (12). Figure 5

Description

Title of the invention: IMPROVED INDUCTOR FOR THE HEAT TREATMENT OF A PINION

[0001] The present invention relates to an improved inductor for the heat treatment of a pinion. The invention finds a particularly advantageous, but not exclusive, application in the field of aeronautics, for performing induction hardening of pinions used for the transmission of mechanical power inside an aircraft engine.

[0002] Induction hardening, as is known per se, consists of exposing a steel part to an alternating magnetic field, causing heat to penetrate superficially by a film effect. The energy of the magnetic field is transformed into heat on the part by ferromagnetism (through hysteresis and eddy current effects) so as to increase its surface temperature, which can reach the hardening temperature (on the order of 900°C) in a few seconds. Induction hardening makes it possible to strengthen the surface of power transmission parts.

[0003] There are two induction hardening technologies: workpiece rotation and tooth-by-tooth. In workpiece rotation, a fixed inductor surrounds a workpiece to perform the heat treatment on the entire workpiece simultaneously. This technology is generally used with gears having a diameter of less than 200 mm and a typically straight tooth geometry.

[0004] Following the "tooth-by-tooth" technology, the inductor moves from one tooth to the next to process the workpiece. This technology is implemented with gears having a diameter greater than 200 mm and a straight or helical tooth geometry. This technology is advantageously implemented with gears having a large module, particularly greater than 6. It should be noted that the module of a gear is equal to its pitch circle diameter divided by its number of teeth.

[0005] Figure 1 shows an angular sector of a pinion 1 having a plurality of teeth 2 and a plurality of interdental spaces 3. An inductor 4 has a body 5 for cooperating in a complementary manner with an interdental space 3 of the pinion 1. The inductor 4 has a current input branch 6.1 and a current output branch 6.2. The body 5 of the inductor 4 is successively inserted into the interdental spaces 3 in order to perform the heat treatment of the pinion 1. The branches 6.1 and 6.2 can be arranged adjacent to each other to obtain a compensating effect.

[0006] During tooth-by-tooth heating, undesirable effects may occur, including heating of adjacent teeth, leading to over-tempering of the steel. These effects may be due to the interaction of magnetic fields generated by the current input and output branches with the teeth. The lower the pinion module, the more pronounced this effect. The helix angle of the teeth can also influence this effect.

[0007] It is possible to use a small inductor that slides between the teeth according to the desired hardening profile. However, with large helix angles, particularly those exceeding 15°, controlling the inductor's movement becomes critical, and achieving a consistent treatment becomes impossible.

[0008] Fig. 2 shows an angular sector of a pinion 1 having hardened ZI zones and Z2 zones in which the steel has been locally softened due to over-tempering of the adjacent teeth.

[0009] Furthermore, overheating the flanks of the teeth 2 and underheating at the tooth root can lead to hardening of the flanks without affecting the bottoms of the interdental spaces 3. Figure 3 thus shows an angular sector of a pinion 1 having hardened ZI zones and Z3 zones located at the bottom of the interdental space 3 that are only slightly heated and therefore not hardened by individual tooth quenching. Extending the heating time could ensure hardening of the bottom of the interdental space 3, but this would risk damaging the material integrity of the remaining teeth 2 due to a risk of melting or of reaching undesired metallurgical states.

[0010] The high temperatures generated by induction heating necessitate continuous cooling of the inductor by a water circulation circuit. Furthermore, an adequate copper cross-section is required to carry the electrical power through the inductor. Indeed, the smaller the gear modulus, the smaller the inductor cross-section, which limits the inductor's cooling capacity and its ability to carry sufficient electrical power to perform the heat treatment.

[0011] The invention aims to effectively remedy the aforementioned drawbacks by providing an inductor for the heat treatment of teeth of a pinion, said pinion comprising a plurality of teeth and a plurality of interdental spaces, said inductor comprising: - an inductor body capable of generating a first alternating magnetic field, said inductor body being intended to be inserted inside an interdental space of the pinion, - a current input branch connected to a first end of the inductor body, and - a current output branch connected to a second end of the inductor body, - said inductor further comprising at least one magnetic field concentrator surrounding at least part of the inductor body so as to concentrate the magnetic field generated by the inductor body in one or more preferential areas of the interdental space.

[0012] The invention thus makes it possible, thanks to the magnetic field concentrator, to better control the distribution of the magnetic flux during induction hardening to obtain homogeneous heating of the teeth of a low-modulus gear. This prevents overheating of the flanks, underheating of the bottom of the inter-tooth space, and over-tempering of adjacent teeth. The invention also reduces the electrical power requirement and facilitates the cooling of the inductor.

[0013] According to one embodiment of the invention, the magnetic field concentrator comprises at least one magnetic field passage opening disposed opposite a bottom of the interdental space.

[0014] According to one embodiment of the invention, the magnetic field concentrator comprises a first lateral portion of magnetic field concentrator intended to be disposed between the inductor body and a flank of a first tooth and a second lateral portion of magnetic field concentrator intended to be disposed between the inductor body and a flank of a second tooth.

[0015] According to one embodiment of the invention, the first lateral portion of the concentrator and / or the second lateral portion of the concentrator each have at least one magnetic field passage opening.

[0016] According to one embodiment of the invention, the magnetic field concentrator comprises a lateral portion of the magnetic field concentrator disposed on the open side of the interdental space near the free end of the teeth of the pinion so as to limit magnetic radiation outside the interdental space in which the inductor body is disposed and redirect the magnetic field towards the inside of said interdental space.

[0017] According to one embodiment of the invention, the current input branch and the current output branch are directed towards the inside of the pinion.

[0018] According to one embodiment of the invention, the current input branch and the current output branch each form an angle between 0 and 90 degrees, preferably of the order of 45 degrees, with respect to a corresponding lateral face of the pinion.

[0019] According to one embodiment of the invention, the current input branch and the current output branch are each surrounded by a magnetic shield made of an electrically conductive material, in particular copper.

[0020] According to one embodiment of the invention, the current input branch and the current output branch are each surrounded by a magnetic field concentrator.

[0021] According to one embodiment of the invention, the inductor body is hollow to allow the passage of a coolant within said inductor body.

[0022] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0023] [Fig-1] Fig. 1, already described, is a perspective view of an inductor according to the state of the technique arranged inside an interdental space of a gable;

[0024] [Fig.2] Fig.2, already described, is a photograph of an angular sector of a pinion including areas at the top of teeth that have undergone over-hardening during a tooth-by-tooth tempering;

[0025] [Fig. 3] Fig. 3, already described, is a photograph of an angular sector of a pinion comprising areas located at the base of the tooth that are underheated and not affected by the tooth-by-tooth hardening;

[0026] [Fig. 4a] [Fig. 4b] Figures 4a and 4b are perspective views of a sector angular pinion and an inductor according to the invention inserted inside an interdental space of the pinion from two different viewing angles;

[0027] [Fig.4c] Fig.4c is a perspective view illustrating an angle formed by the current input and output branches relative to the axis of the inductor of the corresponding interdental space;

[0028] [Fig.4d] The [Fig.4d] a side view of the magnetic shields or magnetic field concentrators covering current input and output branches of the inductor;

[0029] [Fig. 5] [Fig. 5] A cross-sectional view of an inductor according to the invention positioned inside an interdental space;

[0030] [Fig. 6] Fig. 6 is a schematic representation of the generated magnetic field by the inductor according to the present invention;

[0031] [Fig.7] Fig.7 is a partial perspective view of an alternative embodiment of an inductor body according to the present invention.

[0032] It should be noted that, in figures 4a to 6, the structural and / or functional elements common to the different embodiments may have the same references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

[0033] Figures 4a, 4b, 5, and 6 show an inductor 15 for heat-treating the teeth of a pinion 10 with axis X, partially represented in the figures. The pinion 10 comprises a pinion body 13, a plurality of teeth 11, and a plurality of interdental spaces 12, with an interdental space 12 extending between two consecutive teeth 11. The inductor 15 comprises an inductor body 17 adapted to generate an alternating magnetic field. The inductor body 17 is intended to be inserted inside an interdental space 12 of the pinion 10 in order to perform induction heating of the external surface of the teeth 11.

[0034] The inductor 15 also includes a current input branch 18.1 connected to a first end of the inductor body 17 and a current output branch 18.2 connected to a second end of the inductor body 17.

[0035] More specifically, the inductor body 17 is made of an electrically conductive material, preferably copper. The inductor body 17 is hollow to allow the passage of a coolant within the inductor body 17, as shown in Figures 5 and 6. In this case, a cross-section of the inductor body 17 has a generally triangular shape. Alternatively, a cross-section of the inductor body 17 may have a square, rectangular, round, oval, or polygonal shape, or any other shape suitable for the application.

[0036] Surrounding the inductor body 17, or certain areas of the inductor body 17, with one or more field concentrators of adjustable thicknesses, spaced by more or less large openings as shown in [Fig.5] allows control of the flux density concentration areas, and thus the heating and the homogeneity of the heating of the interdental spaces 12.

[0037] In this case, the inductor 15 further comprises a magnetic field concentrator 20 surrounding at least part of the inductor body 17. The magnetic field concentrator 20 concentrates the magnetic field generated by the inductor body 17 in one or more preferred areas of the interdental space 12. The magnetic field concentrator 20 may, for example, comprise a matrix of electrically insulating material charged with particles of electrically conductive material. The matrix is, for example, made of an insulating material, in particular plastic (thermoplastic or thermosetting). The particles of conductive material are, for example, carbon or metal particles. Alternatively, a magnetic field concentrator 20 is made entirely of a ferromagnetic material, for example ferrite or any other material suitable for the application.

[0038] As illustrated in [Fig.5], the magnetic field concentrator 20 has at least one magnetic field passage opening 26 arranged opposite a bottom of the interdental space 12. Such a configuration allows the magnetic field to be directed towards the bottom of the interdental space 12. In this case, the opening 26 is made in a corner of the triangular-shaped magnetic field concentrator.

[0039] The magnetic field concentrator 20 comprises a first lateral portion of magnetic field concentrator 20.1 and a second lateral portion of magnetic field concentrator 20.2 arranged on either side of the inductor body 17. The first lateral portion 20.1 and the second lateral portion 20.2 each extend along a corresponding side of the inductor body 17. The first lateral portion 20.1 is situated between the inductor body 17 and a flank of a first tooth 11. The second lateral portion 20.2 is situated between the inductor body 17 and a flank of a second tooth 11 adjacent to the first tooth 11. The first lateral portion 20.1 and the second lateral portion 20.2 each have the form of a thin plate extending along a side of the inductor body 17.

[0040] The first lateral portion 20.1 and the second lateral portion 20.2 are separated from each other by the magnetic field passage opening 26 arranged opposite the bottom of the interdental space 12.

[0041] According to one embodiment, the first lateral portion 20.1 and the lateral portion 20.2 are separated from the flanks of the first tooth 11 and the second tooth 11 by a corresponding air gap El. The air gap El can be a variable air gap between 0.7 mm and 1 mm.

[0042] The inductor body 17 is separated from the bottom of the interdental space 12 by an air gap E2 of less than 1mm, in particular of the order of 0.8mm.

[0043] The inductor body 17 extends radially from a radial end face of the lateral portions 20.1, 20.2. The projection distance L1 of the inductor body 17 from the lateral portions 20.1, 20.2 is less than 0.5mm, for example on the order of 0.2mm.

[0044] Advantageously, the first lateral portion of the concentrator 20.1 and / or the second lateral portion of the concentrator 20.2 each have at least one magnetic field passage opening 26. These magnetic field passage openings 26 allow for the generation of hot spots at the flanks of the teeth 11. Heating is controlled by the positioning and number of the magnetic field passage openings 26. In the example shown, the first lateral portion of the concentrator 20.1 has three magnetic field passage openings 26 and the second lateral portion of the concentrator 20.1 include two magnetic field passage openings 26. Of course, the number and arrangement of the magnetic field passage openings 26 can vary depending on the configuration of the tooth areas to be heated.

[0045] The magnetic field passage openings 26 may have parallel edges. Alternatively, the magnetic field passage openings 26 may have non-parallel edges so as to present a cross-section that increases with distance from the inductor body 17, as shown in dashed lines in [Fig. 6]. Such a configuration optimizes the heating surface. The magnetic field passage openings 26 may have dimensions ranging from 0.5 mm to 1 mm.

[0046] The magnetic field concentrator 20 further comprises a third lateral portion of magnetic field concentrator 20.3 disposed on the open side of the interdental space 12 near the free end of the teeth 11 of the pinion 10 so as to limit magnetic radiation outside the interdental space 12 in which the inductor body 17 is disposed and redirect the magnetic field towards the interior of said interdental space 12. The lateral portion 20.3 is solid and therefore without an opening for the passage of a magnetic field 26.

[0047] The lateral portion 20.3 extends along one side of the inductor body 17. The lateral portion 20.3 is shaped like a thin plate extending in an orthoradial plane relative to the X-axis of the pinion 10. The lateral portion 20.3 has a width extending between two teeth 11 in an orthoradial direction relative to the X-axis of the pinion 10 and a length extending along a longitudinal direction of the teeth 11. The longitudinal direction of extension is measured along the X-axis of the pinion for straight teeth. The lateral portion 20.3 extends at least partially outside the interdental space 12. The lateral portion 20.3 at least partially closes the interdental space 12.

[0048] The concentrator portions 20.1, 20.2, and 20.3 are mechanically linked to one another to form a single unit. The concentrator portions 20.1, 20.2, and 20.3 can form a single-piece concentrator 20. The concentrator 20 has a triangular shape complementary to the inductor body 17. Alternatively, the concentrator 20 can be made of several parts arranged longitudinally side by side.

[0049] The concentrator portions 20.1, 20.2 and 20.3 each have an inner face in contact with a corresponding outer face of the inductor body 17. The concentrator 20 can be fixed by gluing to the inductor body 17 or any other fixing technique suitable for the application.

[0050] Preferably, as illustrated in Figures 4a and 4b, the current input branch 18.1 and the current output branch 18.2 are directed inwards of the pinion 10, that is, towards the body of the pinion 10 and not outwards as is conventionally the case for existing inductors (see [Fig. 1]). Such a configuration limits interactions with the tips of the teeth 11, which would cause the phenomenon of local over-tempering of the teeth 11.

[0051] The current input branch 18.1 and the current output branch 18.2 each form an angle Al (see [Fig. 4b]) between 0 degrees and 90 degrees (exclusive), preferably on the order of 45 degrees, with respect to a corresponding lateral face of the pinion 10. "On the order of" means a variation of plus or minus 10% from the stated value. The first and second lateral faces of the pinion 10 each correspond to an axial end face of the pinion 10. The angle Al is measured from a lateral face of the pinion 10 to the corresponding current input / output branch 18.1, 18.2. As illustrated in [Fig.4c], the current input branch 18.1 and the current output branch 18.2 each form an angle A2 with respect to the axis XI of the inductor 17 of the interdental space 12 between 0 degrees and 90 degrees (exclusive), preferably on the order of a helix angle of the teeth.

[0052] Advantageously, the current input branch 18.1 and the current output branch 18.2 are each surrounded by a magnetic shield 21 made of an electrically conductive material, in particular copper. These magnetic shields 21 act as shielding, absorbing the magnetic field generated by the branches 18.1, 18.2 in the vicinity of the teeth 11 of the pinion 10.

[0053] Alternatively, the current input branch 18.1 and the current output branch 18.2 are each surrounded by a magnetic field concentrator 23. These magnetic field concentrators 23 minimize the magnetic radiation of the branches 18.1, 18.2 and direct the magnetic field of the branches 18.1, 18.2 towards the pinion body 13.

[0054] Figure 4d shows that the magnetic shields 21 or magnetic field concentrators 23 cover all portions of the branches 18.1, 18.2 located near a pinion sector 10 into which the inductor body 17 is inserted. The magnetic shields 21 or magnetic field concentrators 23 each have a length greater than one axial length of the pinion sector 10. The magnetic shields 21 or magnetic field concentrators 23 have, in side view, a generally U-shaped form. The magnetic shields 21 or magnetic field concentrators 23 are used in combination with the field concentrator 20 having a portion located opposite the interdental space 12 into which the inductor body 17 is inserted.

[0055] Figure 6 shows that the use of the magnetic field concentrator 20 around the inductor body 17 makes it possible to homogenize the magnetic flux density represented by lines B and therefore to better control the heating of teeth 11 including at the base of the tooth, that is to say in the bottom of the interdental spaces 12.

[0056] The configuration of the inductor body 17 (size and power), the concentrator 20 and the magnetic field passage openings 26 depends on a specification defining the hardening zones according to the needs related to a given application.

[0057] It is possible to use a spraying device to spray water during heating in order to control a heating temperature on the tops of the teeth 11 and on the edges of the pinion 10.

[0058] As illustrated in [Fig. 7], adding a small additional copper section 17.2, by welding or other process, to a main active section 17.1 of the inductor body 17 helps to increase the heating power at the bottom of the interdental space 3. The small additional copper section 17.2 may have an area of ​​approximately 1 mm². The shape of the additional section 17.2 may be round, hexagonal, triangular, rectangular, or any other shape suitable for the application.

[0059] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0060] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

Demands

1. An inductor (15) for the heat treatment of teeth of a pinion (10), said pinion (10) having a plurality of teeth (11) and a plurality of interdental spaces (12), said inductor (15) having: - an inductor body (17) capable of generating a first alternating magnetic field, said inductor body (17) being intended to be inserted inside an interdental space (12) of the pinion (10), - a current input branch (18.1) connected to a first end of the inductor body (17), and - a current output branch (18.2) connected to a second end of the inductor body (17), characterized in that said inductor (15) further comprises at least one magnetic field concentrator (20) surrounding at least part of the inductor body (17) so as to concentrate the magnetic field generated by the inductor body (17) in one or more preferred areas of the interdental space (12).

2. Inductor according to claim 1, characterized in that the magnetic field concentrator (20) has at least one magnetic field passage opening (26) disposed opposite a bottom of the interdental space (12).

3. Inductor according to claim 1 or 2, characterized in that the magnetic field concentrator (20) comprises a first lateral portion of magnetic field concentrator (20.1) intended to be disposed between the inductor body (17) and a flank of a first tooth (11) and a second lateral portion of magnetic field concentrator (20.2) intended to be disposed between the inductor body (17) and a flank of a second tooth (11).

4. Inductor according to claim 3, characterized in that the first lateral portion of concentrator (20.1) and / or the second lateral portion of concentrator (20.2) each have at least one magnetic field passage opening (26).

5. An inductor according to any one of claims 1 to 4, characterized in that the magnetic field concentrator (20) comprises a lateral portion of the magnetic field concentrator (20.3) disposed on the open side of the interdental space (12) near the free end of the teeth (11) of the pinion (10) so as to limit a magnetic radiation outside the interdental space (12) in which the inductor body (17) is disposed and redirect the magnetic field into said interdental space (12).

6. Inductor according to any one of claims 1 to 5, characterized in that the current input branch (18.1) and the current output branch (18.2) are directed towards the inside of the pinion (10).

7. Inductor according to claim 6, characterized in that the current input branch (18.1) and the current output branch (18.2) each form an angle between 0 and 90 degrees, preferably of the order of 45 degrees, with respect to a corresponding lateral face of the pinion (10).

8. Inductor according to any one of claims 1 to 7, characterized in that the current input branch (18.1) and the current output branch (18.2) are each surrounded by a magnetic shield (21) made of an electrically conductive material, in particular copper.

9. Inductor according to any one of claims 1 to 7, characterized in that the current input branch (18.1) and the current output branch (18.2) are each surrounded by a magnetic field concentrator (23).

10. Inductor according to any one of claims 1 to 9, characterized in that the inductor body (17) is hollow to allow the passage of a coolant within said inductor body (17).

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