Split multi-coil electric induction heat treatment system for simultaneously heating multiple features of a bearing component

Abstract

The master inductor circuit is connected to an AC power source and the passive inductor circuit is assembled as a separable split inductor assembly to form at least one pair of master and passive heating inductors, where the master and passive inductor circuits are electromagnetically coupled without being physically connected. A bearing component can be placed in the presence of a magnetic flux field generated by the master and passive heating inductors to simultaneously inductively heat one or more bearing features of the bearing component and subsequently quench the austenitized bearing features of the bearing component.

Description

[Technical field]

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 970,237, filed February 5, 2020, which is incorporated by reference in its entirety.

[0002] The present invention relates generally to electric induction heat treatment of bearing components having bearing features such as bearing races and raceways, and more particularly to heat treatment of selected features of the bearing races and raceways requiring metallurgical hardening. [Background technology]

[0003] The present invention relates to electric induction heat treatment of inner or outer bearing races, as well as raceways or other bearing features, for example, used in power train, drive train, and wheel components. Bearings are important machine elements that allow components to move relative to one another. Depending on the specific application, there are many variations in bearing race design, with many designs being standardized. These include, but are not limited to, radial ball and roller bearings, thrust ball and roller bearings. There are also single and multiple row bearings, as well as unidirectional and bidirectional bearing designs. Regardless of the design details, the working surfaces of the bearing contact must be treated to ensure wear resistance and strength over the life of the bearing, as well as other mechanical properties. Electric induction hardening is one of the most common methods of such heat treatment.

[0004] FIG. 1(a) shows a cutaway perspective view of one type of constructed inner bearing race of a bearing component 100 commonly used in the automotive industry. Various steel grades are used in the manufacture of the majority of forged bearing races. Powder metallurgy materials and cast iron are also used in less frequent applications. Bearing races can also be manufactured by additive manufacturing techniques such as 3D printing processes.

[0005] 1(b) and 1(c) show two alternatives of induced surface hardness patterns of the constructed inner bearing race of the bearing component 100 in plan elevation section. FIG. 1(b) shows an interrupted bearing race hardness pattern that includes two circumferential metallurgically hardened zones 101 and 102 (solid black or cross-hatched shaded areas). These are vertically separated by a non-hardened circumferential area 103, as also shown in FIG. 1(a) and FIG. 1(b). The hardened zones 101 and 102 are bearing features or areas where rolling elements (e.g., balls or rollers) contact the inner bearing races 101a and 102a, respectively. Depending on the particular application, the shapes of the zones 101 and 102 may be the same or different. The hardness pattern shown in FIG. 1(b) is the most common pattern because it provides the necessary mechanical properties of the required bearing contact surface (such as area 103 where no contact wear occurs) without hardening the areas. Hardening only the bearing features or regions 101 and 102 not only helps to provide the necessary engineering properties and minimized distortion characteristics after heat treatment, but also reduces the amount of electrical energy required for the heat treatment.

[0006] FIG. 1(c) shows an alternative type of hardness pattern 104 (solid black or shaded areas in cross section) used in some specific applications. In this type of hardness pattern, in addition to the inner bearing contact surfaces (bearing features or areas 101a and 102a) being induction hardened, the area 103 separating the inner bearing contact surfaces is also induction hardened. Pattern 104 is usually associated with at least two undesirable workpiece and process factors: excessive distortion characteristics and significantly increased electrical energy required to harden all three areas, i.e. areas 101, 102, and 103. These are some of the reasons why the hardness pattern shown in FIG. 1(b) is the most popular pattern, as opposed to the hardness pattern shown in FIG. 1(c).

[0007] To inductively heat treat a bearing race, in some processes an induction heating coil is moved to a heating position (Method A). However, in other processes the induction heating coil is static and the bearing race (i.e., the bearing feature or area of ​​the bearing component (workpiece) to be heat treated) is moved to a heating position (Method B). The invention disclosed herein can be utilized with heat treatment equipment and processes of either Method A or Method B, or a combination of Methods A and B, in which the induction heating coil and bearing race are moved relative to one another.

[0008] Conventional single or multi-turn solenoid type coils (e.g., conventional two-turn coils of the prior art) are commonly used to heat treat the surfaces of bearing races. An induction coil is placed outside the bearing race (in a surrounding configuration) to heat treat the outer surface of the race. An induction coil is placed inside the bearing race to heat treat the inner (internal) surface of the bearing. For convenience, the present invention is generally described herein in terms of induction hardening (heat treating) of internal bearing features such as bearing races and raceways, but is also applicable to heat treating external bearing features or surfaces of bearing components. For example, Figures 1(d) and 1(e) show representative perspective views of a typically constructed bearing race component 100' in which the outer (external) surface 100'a needs to be hardened. 1(f), 1(g), 1(h) and 1(i) show planar cross-sections of a configured outer bearing race of a bearing component 400 including bearing features or regions including an inner surface region 401 that does not require induction hardening and an outer surface (external) 402 that does require induction hardening. Depending on the particular application, the entire region of the outer surface (external) 402 (within the cross-hatched region 405) shown in FIG. 1(h) may require induction surface hardening. Alternatively, selective bearing features or regions (each cross-hatched selective region) may require induction surface hardening, such as selective region 403 shown in FIG. 1(f), selected region 404 shown in FIG. 1(g) or previously mentioned selected region 405 shown in FIG. 1(h), and selected region 406 in FIG. 1(i). The hardness pattern shown in FIG. 1(i) represents an example of an interrupted hardness pattern. Summary of the Invention [Problem to be solved by the invention]

[0009] The effectiveness of an internal cylindrical induction coil, compared to a similar coil used to heat the outer surface (or outer diameter) of a bearing, depends heavily on the magnetic field coupling gap between the coil and the workpiece (the bearing feature being hardened). The electrical efficiency of an internal coil drops off rapidly with increasing field coupling gap. It is therefore essential to keep the coil-to-workpiece field coupling gap as small as possible to increase the electrical efficiency of heating and minimize energy consumption.

[0010] The reason that a solenoidal inductor that heats the inner surface (interior) is not as efficient as a similar inductor (also called a coil or induction coil) used to heat the outer surface (exterior) of a bearing is related to the electromagnetic ring effect. The electromagnetic ring effect causes the coil current to concentrate at the inner diameter of the solenoidal coil, which represents a low impedance path, as further explained, for example, in section 3.1.5 of Handbook of Induction Heating (second edition; CRC Press; Boca Raton, FL, United States). When heating the inner surface of the inner diameter, the inner diameter of the coil becomes the region furthest from the heated inner diameter surface. As a result, the electromagnetic coupling between the coil and the heated workpiece (i.e., the bearing feature being heated) is greater than the actual air gap between the inner diameter (interior) of the workpiece and the outer diameter of the induction coil. This results in poor field coupling between the coil and the workpiece (also called spatial proximity), which significantly reduces the coil efficiency.

[0011] The installation of a magnetic flux concentrator inside the internal inductor is often required to increase the coil's electrical efficiency and reduce the coil current, especially for heating small to medium diameter inner surfaces. The magnetic flux concentrator creates an electromagnetic slot effect that has a substantially stronger effect on the coil current distribution than the electromagnetic ring effect, shifting the coil current towards the outer coil region, closer to the surface of the heated workpiece. This increases the magnetic field strength and heat intensity at the inner surface of the workpiece that needs to be heated (bearing component).

[0012] To minimize distortion after induction heat treatment and achieve heat treat characteristics for a long service life of the bearing race, it is important that the heat treat process achieves a sufficient minimum hardness layer depth while avoiding: (1) resulting in an excessively deep localized hardness layer depth; (2) too high a temperature during austenitization; and (3) disproportionately different hardness layer depths within each bearing contact surface (e.g., zones 101a and 102a of the configured inner bearing race of FIG. 1(b)). These heat treat characteristics are some of the reasons why it is often highly desirable to obtain a hardness pattern as close to uniform as possible within each of the bearing contact surface regions 101a and 102a.

[0013] Several factors make it difficult to obtain a sufficiently uniform hardness pattern in the bearing features or regions 101a and 102a. The first factor is related to the complexity of the (bearing component) workpiece geometry (e.g., Figs. 1(a)-1(c)). Corner regions, which tend to attract magnetic fields due to electromagnetic edge effects, may generate deeper hardness layer depths. In addition, there are significant different masses of metal forming the workpiece (i.e., bearing component) near the bearing features, including surface regions 101a and 102a. This creates significant different "cold sink" effects in adjacent regions (axial and radial) and corresponding temperature deviations in the induction surface hardened inner bearing race (regions 101a and 102a).

[0014] The second factor relates to the difficulty of using conventional single or multi-turn solenoid type coils (e.g., the conventional two-turn coils of the prior art) to obtain a contour like hardness pattern. To place a solenoid style hardening coil at a heating location inside the bearing race to harden its inner surface at bearing features or areas 101 and 102 (e.g., as shown in FIG. 1(b)), sufficient clearance is required to pass through the smallest diameter area (area 103 in FIG. 1(b)) during loading (to the heating location) and unloading (from the solenoid induction hardening coil bearing race heating location). This creates variable electromagnetic coupling (spatial proximity) between the coil area through which the current flows and the area of ​​the inner bearing race, producing a non-uniform hardness pattern.

[0015] 2(a) and 2(b) show an example of the phenomenon of variable electromagnetic coupling using a cross-sectional view of the inner bearing race. In the example shown in these figures, a copper tube with a circular cross-section (and coil turns 301 and 302) and hollow internal water cooling passages is used to manufacture the induction coil. In other embodiments, the induction coil can alternatively be formed by: (1) computer numerical control (CNC) machining a solid copper block; (2) brazing together suitable copper parts; or (3) a die forming a profiled heating surface of the coil turns to correspond to the shape of the inner bearing race areas 115a and 106a (FIG. 2(a)) and the inner bearing race areas 125a and 126a (FIG. 2(b)). Conventional magnetic flux concentrators 203 and 204 can be used to improve heating efficiency, concentrate the magnetic field generated by each coil turn 301 and 302 of a two-turn coil formed from copper tubing for heating the inner bearing race (regions 115 and 106) of Figure 2(a), and to heat the inner bearing race (regions 125 and 126) of alternative shape Figure 2(b). Magnetic flux concentrators are typically manufactured from conventional iron-based or ferrite-based powder materials that include standard lamination packs, pure ferrite, or pressed and / or sintered magnetic particles.

[0016] As shown in FIG. 2(a), the prior art solenoidal style two-turn inductor copper tubing coil turns 301 and 302 are each positioned to heat corresponding bearing features including the surface of the configured inner bearing race (regions 115a and 106a) on the bearing component 100y. The longitudinal axis of symmetry 50 of the configured inner bearing race component 100y coincides with the longitudinal axis of symmetry of the copper tubing solenoidal two-turn coil. In the example of FIG. 2(a), the top radial clearance 107 between the cross-hatched hardened region 106 and the tubing 302 is the same in the circumferential direction (i.e., when comparing the radial clearance 107 on the left and right cross-sectional sides of the plan cross-sectional view shown in FIG. 2(a)). Sufficient radial clearance 107 allows for safe movement of the workpiece (configured inner bearing race) in and out of the heating position, where the workpiece is shown in the heating position of Figure 2(a) or Figure 2(b) while the two-turn coil is raised into the heating position (and / or the inner bearing race is lowered).

[0017] The bearing race may be rotated (i.e., pivoted) about its longitudinal axis of symmetry during the heating and quenching cycle using a suitable prior art rotating device (not shown) to achieve uniform radial-circumferential heating temperature distribution. Upon completion of the induction heating austenitizing stage, quenching may be performed in situ (at the heating location), for example using a spray quenching device known in the art, to harden the austenitized regions and form the required martensitic structure. In other processes, quenching may be performed ex situ (i.e., outside the heating location), at a separate quenching location (e.g., with the heated workpiece (bearing component) moved to a position above or below the heating location). The quenching process step may be accomplished using quenching devices known in the art.

[0018] As can be seen in FIG. 2(a), the difference in spatial proximity (electromagnetic coupling) between the current carrying surface of the coil and various regions of the lower inner bearing race surface results in different application of the electromagnetic proximity effect and a significant non-uniform heating distribution. Upon hardening, this produces a non-uniform hardening pattern corresponding to regions 115 and 125. In some applications, the non-uniform hardening pattern is manifested by a gradual decrease in hardness layer depth. In other applications, instead of a gradual change in the hardness pattern of the regions, there are wavy hardness pattern regions that exhibit a combination of deeper or shallower hardness layer depths. For example, regions 115 and 125 exhibit deeper hardness layer depths at local regions 115x and 115y in FIG. 2(a) (and in the enlarged partial view of FIG. 2(c)) and at local regions 125x and 125y in FIG. 2(b) (and in the enlarged partial view of FIG. 2(d)). Conversely, regions 115 and 125 exhibit a shallower hard layer depth in localized region 115z in FIG. 2(a) (and in the enlarged partial view of FIG. 2(c)) and in localized region 125z in FIG. 2(b) (and in the enlarged partial view of FIG. 2(d)). Attempting to ensure the minimum required hard layer depth in regions of the inner bearing race where it is difficult to generate a sufficient heat source may necessarily be associated with the need to significantly overheat the adjacent local bearing race region. This will adversely affect the metallurgical properties of the as-hardened region and the engineering properties of the bearing race. Overheating must therefore be avoided. However, electric coils of conventional design may necessarily be associated with the formation of non-uniform hardness patterns and excessive localized heating.

[0019] Figures 3(a)-3(c) and 4 are schematic diagrams of alternative prior art configurations of induction coils that can be used to inductively heat treat an inner bearing race. Figure 3(a) shows a schematic top view of a workpiece (configured inner bearing race) in a load (to heating position) and unload (from heating position) configuration of a conventional solenoidal inductor of the prior art (similar to the configuration shown in Figures 2(a) and 2(b) and previously described). In Figures 3(a) and 3(b), the dashed circle diagrammatically represents the inner circumferential boundary of the inner bearing race 11a, and the solid circle represents the current carrying face of the coil 22 that faces the inner circumferential boundary of the inner bearing race, as shown in the cross-sectional view of Figure 3(c).

[0020] During the loading operation of the workpiece to the heating position, the rotational longitudinal symmetry axis 11a' of the configured inner bearing race 11a coincides with the longitudinal symmetry axis 22a of the solenoid-type induction coil 22, forming a circumferentially uniform gap 23 (FIG. 3(a)) between the configured inner bearing race 11a and the induction coil 22. Before starting the heating process step of the heat treatment process, the workpiece or the induction coil, or both the workpiece and the induction coil, are moved in the radial direction (perpendicular to the longitudinal symmetry axis of the inner bearing race and the induction coil), so that the gap 24 between the inner bearing race and the induction coil becomes smaller on the right side and the gap 25 becomes larger on the opposite side, left side, as shown in FIG. 3(b). As a result of this movement, improved electromagnetic coupling between the inner bearing race and the coil is provided with the smaller gap 24 compared to having a uniform gap 23, and concentrated heating occurs in the bearing race areas around this smaller gap. Otherwise, there would be a lack of heat generation in these bearing race areas due to the low electromagnetic proximity. However, upon this movement, the opposite side will show an enlarged gap 25. Thus, in this method, gap 24 is smaller than gap 25, which helps to create a more uniform hardening pattern in the bearing race area as shown in FIG. 3(c) at the expense of creating poor electromagnetic coupling with the larger gap 25 in the opposite horizontal area of ​​the bearing race. The constructed inner bearing race is rotated (i.e., spun on a rotating device) during the heating process step of the heat treatment process using a conventional rotating device to uniform the circumferential temperature distribution areas 11aa and 11bb. Once the austenitization step of the heat treatment process is complete, a quench (using a conventional quenching device) can be applied in place (i.e., at the heated location) to harden the austenitized areas and form the required martensitic structure. In other heat treatment processes, the quench can be applied off-site (i.e., by moving the heated workpiece away from the heated location) and at a dedicated quenching location.For example, a quenching tank positioned below the heating location and capable of lowering the heated workpiece into the tank, or a spray quenching device positioned in close proximity to the heating location to which the heated workpiece can be moved, e.g., by a suitable electromechanical transfer device.

[0021] Unfortunately, the heating method and apparatus shown in Figures 3(a), 3(b) and 3(c) are not without drawbacks. One drawback is associated with the need to have at least vertical movement of the components (e.g., during loading and unloading of the workpiece to and from the heating position) and radial movement (perpendicular to the vertical movement). Thus, auxiliary electromechanical transport devices for the vertical and radial movements are required, resulting in additional cost and complexity in the heat treatment system. Also, the improvement in spatial proximity (and the resulting improvement in electromagnetic coupling) on ​​one side, where the gap 24 is smaller, is associated with a deterioration in electromagnetic coupling on the other side, where the gap 25 is larger, which worsens the sensitivity of the heat treatment process (potential deviations in hardness patterns) and reduces the electrical efficiency of the heating of the workpiece.

[0022] FIG. 4 is a schematic diagram of an alternative prior art induction coil (inductor). In FIG. 4, an arc-shaped inductor 40 (also known in the art as a hairpin inductor) is shown with three interconnected segments, shown with cross-hatching. The inductor 40 includes a heating segment 41, a return current segment 43, and an interconnecting segment 42. A magnetic flux concentrator 44 (shown with stippled shading) is disposed between the heating segment 41 and the return current segment 43. All three inductor segments are electrically disposed in series and connected to an AC power source (AC source in the figure). The magnetic flux concentrator 44 provides electromagnetic decoupling between the heating segment 41 and the return current segment 43, and shifts the maximum density of the current flowing through the heating segment 41 toward the outer surface 41a of the heating segment facing the configured inner bearing race area (not shown) that needs to be heated when the inner bearing race is in the heating position. The design of the hairpin inductor 40 shown in FIG. 4 improves the electromagnetic coupling between the inductor and the inner bearing race of the workpiece, and in some applications simplifies achieving the required hardness pattern. The workpiece (ie, the bearing component with the bearing features of the inner bearing race) rotates during the heating and quenching process steps to equalize the temperature distribution around the circumference of the inner bearing race.

[0023] The arc-shaped inductor 40 offers a certain degree of process flexibility. However, it is not without known drawbacks of previous designs, for example those shown in Figures 3(a)-3(c). These include low energy efficiency and the need for the induction heating device to provide two motions (vertical and radial) to bring the coil and bearing race positions close enough together during the heating process step without disturbing complex geometries such as the inner bearing race region 103 of the constructed inner bearing race component 100 shown in Figure 1(b). Furthermore, the magnetic flux concentrator 44 (Figure 4) sandwiched between the two coil segments 41 and 43, carrying currents flowing in opposite directions, can act as an electrical load that is prone to magnetically saturating and overheating, reducing the overall reliability of the induction heating system.

[0024] In view of the prior art, it is an object of the present invention to provide an electric induction heating system and method that provides a closer electromagnetic coupling gap between the induction heating coil and bearing features of a bearing component, such as a bearing raceway surface area, when in a heated position for metallurgical hardening in induction heating applications, resulting in greater energy efficiency and better hardness pattern control than the prior art.

[0025] It is another object of the present invention to provide an electric induction heating system and method that produces a metallurgically sound microstructure with a contour-like hardening pattern, minimal size and shape distortion, and reduced maximum and peak temperatures during the austenitization process step in bearing features including the inner and outer bearing races to produce a metallurgically sound microstructure with reduced likelihood of cracking the bearing races during the heat treatment process.

[0026] Another object of the present invention is to provide an electric induction heating system and method that provides for simultaneous heat treatment of multiple bearing features on a bearing component when the different shapes of the multiple bearing features and bearing components do not support placement of multiple bearing features adjacent to a single induction coil for efficient simultaneous heat treatment of the multiple bearing features and / or multiple bearing components. [Means for solving the problem]

[0027] In one aspect, the invention is an electric induction heat treatment apparatus and method for metallurgically hardening one or more selected bearing features of a bearing workpiece, such as one or more regions of an inner or outer bearing race, comprising a combination of a master inductor circuit and a passive inductor circuit connected to an AC power source, where the combination of the master circuit and the passive circuit form at least one pair of complementary master inductor and passive inductor coils that are electromagnetically coupled to each other without physical or electrical connection and in which the selected bearing feature is disposed, such that the selected bearing feature is coupled to a magnetic flux field generated by the complementary coil pair to inductively heat the selected bearing feature to austenitize it, and subsequently transform the metallurgical properties of the austenitized selected feature by quenching.

[0028] In another aspect, the invention includes an apparatus and method for electrically inductively heat treating a bearing workpiece, where the bearing workpiece has at least two bearing features for metallurgical heat treatment (separated from each other by a bearing feature that is not heat treated in some embodiments of the invention). In some embodiments of the invention, the bearing workpiece with a single bearing feature is metallurgically heat treated, e.g., the bearing workpiece of FIG. 1(c) with a single continuous bearing feature. The apparatus and method include a master inductor circuit and a passive inductor circuit, where the master inductor circuit and the passive inductor circuit are physically separated from each other and there is no physical electrical connection between them. The master inductor circuit is supplied with a master circuit alternating current from a power source to a master inductor circuit conductor network having at least one master heating inductor (configured for induction heating of a first bearing feature prior to hardening of the bearing workpiece) and a master circuit electromagnetic coupler. The passive inductor circuit includes a passive inductor circuit conductor network having at least one passive heating inductor (configured for induction heating of a second bearing feature prior to hardening of the bearing workpiece) and a passive circuit electromagnetic coupler. The master inductor circuit and the passive inductor circuit are moved to a heating position adjacent to one another for a workpiece. In one process application of the invention in which the master inductor circuit and the passive inductor circuit are at the heating position for a workpiece, the at least one master heating inductor and the at least one passive heating inductor are configured for simultaneous inductive heating of a first bearing feature by the master circuit flow of the master circuit AC current and a second bearing feature by the passive circuit current flow, respectively, caused by magnetic flux coupling of the master circuit AC current between the master circuit electromagnetic coupler and the passive circuit electromagnetic coupler.

[0029] Following completion of induction heating of the at least one first bearing feature and the at least one second bearing feature, the bearing workpiece is hardened as required by the particular application (e.g., at a workpiece heating location with at least one master heating inductor, at least one passive heating inductor, a hardening device integrated with the at least one master and passive heating inductors, or at a hardening device located at one or more hardening device locations remote from the workpiece heating location).

[0030] These and other aspects of the invention are set forth herein and in the appended claims.

[0031] The accompanying drawings, briefly summarized below, are provided for an illustrative understanding of the invention and are not intended to limit the invention as further described herein and in the appended claims. [Brief description of the drawings]

[0032] [Figure 1(a)] FIG. 1(a) is a side perspective cross-sectional view of one type of bearing feature, namely, an inner bearing race configured within a bearing component described as a bearing workpiece 100, which is commonly used in heavy duty bearings in automotive powertrains and drivetrains, and other heavy duty applications. [Figure 1(b)] FIG. 1(b) is an elevational cross-sectional view of an inner bearing race configured within the bearing workpiece 100 of FIG. 1(a) and shows an interrupted hardness pattern in the longitudinal direction (along the longitudinal axis L) including two circumferentially hardened longitudinal zones (or regions) 101 and 102 separated by a longitudinal region 103 that is not circumferentially hardened. [Figure 1(c)]Figure 1(c) is an elevational cross-sectional view of a configured inner bearing race in a bearing workpiece 100, showing a circumferentially uninterrupted longitudinal hardness 104 as an alternative to the longitudinally interrupted hardness pattern of Figure 1(b). In Figure 1(c), the bearing features, i.e., the configured inner bearing race zones 101 and 102 (i.e., the bearing roller contact surfaces), have been induction hardened along with a circumferential longitudinal region 103 between the inner bearing race zones. [Figure 1(d)] 1(d) and 1(e) are perspective views of an outer bearing race configured within a bearing workpiece 100'. [Figure 1(e)] 1(d) and 1(e) are perspective views of an outer bearing race configured within a bearing workpiece 100'. [Figure 1(f)] 1(f), 1(g), 1(h) and 1(i) are cross-sectional views of a constructed outer bearing race of a bearing component 400 showing four alternative hardness patterns (zones or regions) 403, 404, 405 and 406 (shown with hatching) that can be formed by alternative electric induction hardening processes as may be required in alternative applications. [Figure 1(g)] 1(f), 1(g), 1(h) and 1(i) are cross-sectional views of a constructed outer bearing race of a bearing component 400 showing four alternative hardness patterns (zones or regions) 403, 404, 405 and 406 (shown with hatching) that can be formed by alternative electric induction hardening processes as may be required in alternative applications. [Figure 1(h)] 1(f), 1(g), 1(h) and 1(i) are cross-sectional views of a constructed outer bearing race of a bearing component 400 showing four alternative hardness patterns (zones or regions) 403, 404, 405 and 406 (shown with hatching) that can be formed by alternative electric induction hardening processes as may be required in alternative applications. [Figure 1(i)]1(f), 1(g), 1(h) and 1(i) are cross-sectional views of a constructed outer bearing race of a bearing component 400 showing four alternative hardness patterns (zones or regions) 403, 404, 405 and 406 (shown with hatching) that can be formed by alternative electric induction hardening processes as may be required in alternative applications. [Figure 1(j)] FIG. 1(j) is a side perspective cross-sectional view of a constructed inner bearing race of a bearing workpiece 100″ showing bearing race zones of identical shape and uniform (highly desirable) hardness patterns 101″ and 102″ commonly used in heavy duty bearings for automotive powertrains and drivetrains, and other heavy duty applications. [Figure 1(k)] FIG. 1(k) is a cross-sectional elevation view of the constructed inner bearing race shown in FIG. 1(j) and shows an interrupted hardness pattern including two hardened zones 101″ and 102″ separated by a non-hardened zone (or region) 103″. [Figure 2(a)] FIG 2(a) is a cross-sectional view of a constructed inner bearing race showing various hardness patterns (cross-hatched zones 106 and 115) at the heating location using a conventional induction heating apparatus including a solenoid style two-turn electric heating inductor with coil turns 301 and 302 and associated magnetic flux concentrators 203 and 204. In FIG 2(a), coil turn 301 surrounds area 106 for heating and coil turn 302 surrounds area 115 for heating. Each coil turn can be connected together in series or parallel with alternating current supplied to the coils from a suitably connected power source, with instantaneous current flowing in the same or opposite directions in the coil turns. [Figure 2(b)]Figure 2(b) is a cross-sectional view of an inner bearing race constructed using a conventional induction heating apparatus including a solenoid style two-turn electric heating inductor with coil turns 301 and 302 and associated magnetic flux concentrators 203 and 204, showing a different inner bearing race shape and hardness pattern (including cross-hatched zones 125 and 126) from that of Figure 2(a) in the heated position. The coil turns can be connected together in series or parallel with alternating current supplied by a suitably connected power source, with the alternating current flowing in the same or opposite directions within the coil turns. [Figure 2(c)] 2(c) and 2(d) are enlarged views of selected hardness patterns shown in FIGS. 2(a) and 2(b), respectively. [Figure 2(d)] 2(c) and 2(d) are enlarged views of selected hardness patterns shown in FIGS. 2(a) and 2(b), respectively. [Figure 3(a)] 3(a) and 3(b) are schematic diagrams of an induction heating process for heat treating an inner bearing race, showing generally uniform and non-uniform circumferential clearance distances between the inductor and the inner bearing race 11a of the bearing workpiece (schematically represented by the dashed circular boundary of the inner race being heated). FIG. 3(a) shows an example of "workpiece-to-coil" mutual positioning during a process step of loading the inner bearing race 11a of the bearing workpiece in an inductor 22 with a uniform circumferential clearance distance 23 between the inductor and the inner bearing race to be heated. FIG. 3(b) shows an example of "workpiece-to-coil" mutual positioning during a process step of heating the inner bearing race 11a of the bearing workpiece in an inductor 22 with non-uniform circumferential electromagnetic coupling distances 24 and 25. FIG. 3(c) shows the resulting circumferentially uniform hardness patterns 11aa and 11bb, assuming sufficiently fast workpiece rotation (i.e., rotation) about axis 50 during induction heating using a conventional workpiece rotation device (not shown). [Figure 3(b)]3(a) and 3(b) are schematic diagrams of an induction heating process for heat treating an inner bearing race, showing generally uniform and non-uniform circumferential clearance distances between the inductor and the inner bearing race 11a of the bearing workpiece (schematically represented by the dashed circular boundary of the inner race being heated). FIG. 3(a) shows an example of "workpiece-to-coil" mutual positioning during a process step of loading the inner bearing race 11a of the bearing workpiece in an inductor 22 with a uniform circumferential clearance distance 23 between the inductor and the inner bearing race to be heated. FIG. 3(b) shows an example of "workpiece-to-coil" mutual positioning during a process step of heating the inner bearing race 11a of the bearing workpiece in an inductor 22 with non-uniform circumferential electromagnetic coupling distances 24 and 25. FIG. 3(c) shows the resulting circumferentially uniform hardness patterns 11aa and 11bb, assuming sufficiently fast workpiece rotation (i.e., rotation) about axis 50 during induction heating using a conventional workpiece rotation device (not shown). [Figure 3(c)] 3(a) and 3(b) are schematic diagrams of an induction heating process for heat treating an inner bearing race, showing generally uniform and non-uniform circumferential clearance distances between the inductor and the inner bearing race 11a of the bearing workpiece (schematically represented by the dashed circular boundary of the inner race being heated). FIG. 3(a) shows an example of "workpiece-to-coil" mutual positioning during a process step of loading the inner bearing race 11a of the bearing workpiece in an inductor 22 with a uniform circumferential clearance distance 23 between the inductor and the inner bearing race to be heated. FIG. 3(b) shows an example of "workpiece-to-coil" mutual positioning during a process step of heating the inner bearing race 11a of the bearing workpiece in an inductor 22 with non-uniform circumferential electromagnetic coupling distances 24 and 25. FIG. 3(c) shows the resulting circumferentially uniform hardness patterns 11aa and 11bb, assuming sufficiently fast workpiece rotation (i.e., rotation) about axis 50 during induction heating using a conventional workpiece rotation device (not shown). [Figure 4] FIG. 4 is a schematic diagram of a prior art arcuate inductor 40 (also known as a hairpin inductor) that can be used to heat treat a constructed inner bearing race. [Figure 5(a)] 5(a)-5(d) show schematic diagrams of one embodiment of an electric induction heating system of the present invention showing a master inductor circuit (FIG. 5(a)) and a passive inductor circuit (FIG. 5(b)). FIGS. 5(c) and 5(d) show alternative perspective views of the master inductor circuit and the passive inductor circuit in position to heat a workpiece (bearing component). For clarity, the inner bearing race (bearing feature) and the hardening device are not shown. The arrows indicate the relative instantaneous current directions of the heating system. FIG. 5(c) shows that this arrangement produces a direction of instantaneous current flow in the passive inductor 220 that is directed in the opposite direction to the instantaneous current flow in the master inductor 210. This orientation of the current is usually preferred to obtain the interrupted hardness pattern shown in FIG. 1(b). [Figure 5(b)] 5(a)-5(d) show schematic diagrams of one embodiment of an electric induction heating system of the present invention showing a master inductor circuit (FIG. 5(a)) and a passive inductor circuit (FIG. 5(b)). FIGS. 5(c) and 5(d) show alternative perspective views of the master inductor circuit and the passive inductor circuit in position to heat a workpiece (bearing component). For clarity, the inner bearing race (bearing feature) and the hardening device are not shown. The arrows indicate the relative instantaneous current directions of the heating system. FIG. 5(c) shows that this arrangement produces a direction of instantaneous current flow in the passive inductor 220 that is directed in the opposite direction to the instantaneous current flow in the master inductor 210. This orientation of the current is usually preferred to obtain the interrupted hardness pattern shown in FIG. 1(b). [Figure 5(c)]5(a)-5(d) show schematic diagrams of one embodiment of an electric induction heating system of the present invention showing a master inductor circuit (FIG. 5(a)) and a passive inductor circuit (FIG. 5(b)). FIGS. 5(c) and 5(d) show alternative perspective views of the master inductor circuit and the passive inductor circuit in position to heat a workpiece (bearing component). For clarity, the inner bearing race (bearing feature) and the hardening device are not shown. The arrows indicate the relative instantaneous current directions of the heating system. FIG. 5(c) shows that this arrangement produces a direction of instantaneous current flow in the passive inductor 220 that is directed in the opposite direction to the instantaneous current flow in the master inductor 210. This orientation of the current is usually preferred to obtain the interrupted hardness pattern shown in FIG. 1(b). [Figure 5(d)] 5(a)-5(d) show schematic diagrams of one embodiment of an electric induction heating system of the present invention showing a master inductor circuit (FIG. 5(a)) and a passive inductor circuit (FIG. 5(b)). FIGS. 5(c) and 5(d) show alternative perspective views of the master inductor circuit and the passive inductor circuit in position to heat a workpiece (bearing component). For clarity, the inner bearing race (bearing feature) and the hardening device are not shown. The arrows indicate the relative instantaneous current directions of the heating system. FIG. 5(c) shows that this arrangement produces a direction of instantaneous current flow in the passive inductor 220 that is directed in the opposite direction to the instantaneous current flow in the master inductor 210. This orientation of the current is usually preferred to obtain the interrupted hardness pattern shown in FIG. 1(b). [Figure 5(e)] Figure 5(e) is a schematic diagram of an alternative passive inductor circuit that can be utilized with the master inductor circuit shown in Figure 5(a) to generate an instantaneous current direction in the passive inductor 220' that is the same as the instantaneous current flowing through the active coil 210 (Figure 5(c)) of the master inductor circuit. This direction of current flow is typically desired to obtain the uninterrupted stiffness pattern shown in Figure 1(c). [Figure 5(f)]5(f) and 5(g) show alternative instantaneous AC current directions achieved in the passive inductor coil when the master inductor circuit of FIG. 5(a) is combined with the passive inductor circuit of FIG. 5(b) in one embodiment of the invention (compare when the master inductor circuit of FIG. 5(a) is combined with the passive inductor circuit of FIG. 5(e) in another embodiment of the invention). [Figure 5(g)] 5(f) and 5(g) show alternative instantaneous AC current directions achieved in the passive inductor coil when the master inductor circuit of FIG. 5(a) is combined with the passive inductor circuit of FIG. 5(b) in one embodiment of the invention (compare when the master inductor circuit of FIG. 5(a) is combined with the passive inductor circuit of FIG. 5(e) in another embodiment of the invention). [Figure 6(a)] 6(a) illustrates the master electromagnetic coupling region 230 of the master inductor circuit and the passive electromagnetic coupling region 240 of the passive inductor circuit when the master inductor circuit is isolated from the passive inductor circuit (e.g., when a bearing workpiece to be heat treated is loaded into or unloaded from a heating position in a complementary pair of master and passive circuit inductors in the master and passive inductor circuits, respectively). The master electromagnetic coupling region and the passive electromagnetic coupling region are alternatively referred to as the master flux coupler and the passive flux coupler, respectively. [Figure 6(b)]Figure 6(b) shows the master electromagnetic coupling region 230 of the master inductor circuit and the passive electromagnetic coupling region 240 of the passive inductor circuit when the master inductor circuit is brought to a heating position of the workpiece, where the active and passive electromagnetic coupling regions are separated by a gap 205 to electrically isolate the active inductor circuit from the passive inductor circuit, while the master inductor circuit and the passive inductor circuit are electromagnetically coupled when an AC current is supplied to the master inductor circuit. At the heating position of the workpiece (bearing component), the master flux coupler is positioned adjacent to the passive flux coupler and is physically separated from the passive flux coupler (by gap 205 in the example of Figure 6(b)). [Figure 7(a)] 7(a) and 7(b) show alternative embodiments of the master and passive electrical bus network configurations and configurations in cross-sectional views. FIG. 7(a) shows each bus network including copper tubes, and FIG. 7(b) shows rectangular copper bars sandwiched within the master and passive electromagnetic coupling regions separated by corresponding gaps 205a (FIG. 7(a)) and 205b (FIG. 7(b)) when in a heating position on the workpiece. The gaps can be air gaps or filled with dielectric material. The arrangement shown in FIG. 7(b) is typically preferred compared to the arrangement shown in FIG. 7(a) due to better electromagnetic coupling between the active and passive circuits. The master electrical conductor network and the passive electrical conductor network are alternatively referred to as the master inductor circuit bus network and the passive inductor circuit conductor network, respectively. [Figure 7(b)]7(a) and 7(b) show alternative embodiments of the master and passive electrical bus network configurations and configurations in cross-sectional views. FIG. 7(a) shows each bus network including copper tubes, and FIG. 7(b) shows rectangular copper bars sandwiched within the master and passive electromagnetic coupling regions separated by corresponding gaps 205a (FIG. 7(a)) and 205b (FIG. 7(b)) when in a heating position on the workpiece. The gaps can be air gaps or filled with dielectric material. The arrangement shown in FIG. 7(b) is typically preferred compared to the arrangement shown in FIG. 7(a) due to better electromagnetic coupling between the active and passive circuits. The master electrical conductor network and the passive electrical conductor network are alternatively referred to as the master inductor circuit bus network and the passive inductor circuit conductor network, respectively. [Figure 8(a)] 8(a)-8(d) illustrate generally one embodiment of a method of the present invention for inductively heat treating a bearing feature of a bearing component, such as an inner or outer race, in which a hardening process step is performed while the induction heating apparatus remains with the bearing feature in the hot (heated) position of the apparatus after heating of the bearing feature is completed. [Figure 8(b)] 8(a)-8(d) illustrate generally one embodiment of a method of the present invention for inductively heat treating a bearing feature of a bearing component, such as an inner or outer race, in which a hardening process step is performed while the induction heating apparatus remains with the bearing feature in the hot (heated) position of the apparatus after heating of the bearing feature is completed. [Figure 8(c)] 8(a)-8(d) illustrate generally one embodiment of a method of the present invention for inductively heat treating a bearing feature of a bearing component, such as an inner or outer race, in which a hardening process step is performed while the induction heating apparatus remains with the bearing feature in the hot (heated) position of the apparatus after heating of the bearing feature is completed. [Figure 8(d)]8(a)-8(d) illustrate generally one embodiment of a method of the present invention for inductively heat treating a bearing feature of a bearing component, such as an inner or outer race, in which a hardening process step is performed while the induction heating apparatus remains with the bearing feature in the hot (heated) position of the apparatus after heating of the bearing feature is completed. [Figure 9] 9(a)-9(d) show schematic diagrams of another embodiment of the method of the present invention for inductively heat treating a bearing feature of a bearing component, such as an inner or outer race, where the quenching process step is performed by submerging a passive inductor coil of a passive inductor circuit with at least the bearing feature in a quenchant tank. In this embodiment, a corresponding section of the passive inductor coil circuit is used as a support (nest) to hold the heat treated bearing feature in place during the quenching process step. [Figure 10] 10(a)-10(d) show schematic diagrams of another embodiment of the method of the present invention for inductively heat treating bearing features on a bearing workpiece, such as an inner or outer bearing race, where the quenching process step starts when the bearing workpiece remains in the induction heating apparatus after the bearing features of the bearing workpiece are inductively heated in the apparatus in the assembled (heated) position (FIG. 10(b)), and the quenching process continues while the bearing workpiece with the heated bearing features moves to the quenching tank (FIG. 10(c)) with the passive heating inductor coil 220 in the passive inductor circuit (FIG. 10(c)), where the quenching process is completed. [Figure 11] 11(a) and 11(b) illustrate generally another embodiment of the method of the present invention for induction heat treating bearing features of bearing components, such as inner or outer bearing races, where the bearing features of at least two separate bearing components (workpieces) are heated simultaneously and combined with a subsequent hardening process step after the simultaneous heating is completed. [Figure 12] Figure 12(a) shows an induction heating apparatus of the present invention which can be used to heat two separate bearing components (workpieces) simultaneously and in the manner shown in Figures 11(a) and 11(b), and Figure 12(b) shows an enlarged and partially detailed view of one end of the induction heating apparatus shown in Figure 12(a). [Figure 13] 13 illustrates an embodiment of the present invention in which an induction heater is positioned adjacent to a vertically oriented rotary table onto which multiple separate workpieces can be loaded (e.g., after being preheated; rotated to a heat treatment location; loaded into the induction heater for heat treatment of bearing features; and then rotated to a quench location). [Figure 14(a)] FIG. 14(a) is a perspective view of a configured passive inductor assembly 800b of a configured induction heat treatment apparatus 800 shown in position to heat a bearing component (workpiece) in FIGS. 16(a) and 16(b). [Figure 14(b)] FIG. 14(b) is a top plan view of the passive inductor assembly shown in FIG. 14(a). [Figure 14(c)] FIG. 14(c) is a side cross-sectional view of the passive inductor assembly shown in FIG. 14(a). [Figure 15(a)] FIG. 15(a) is a perspective view of a configured master inductor assembly 800a of an induction heat treatment apparatus 800 shown in position to heat a bearing component (workpiece) in FIGS. 16(a) and 16(b). [Figure 15(b)] FIG. 15(b) is a top plan view of the master inductor assembly shown in FIG. 15(a). [Figure 15(c)] FIG. 15(c) is a side cross-sectional view of the master inductor assembly shown in FIG. 15(a). [Figure 16(a)]16(a) and 16(b) are alternative perspective views of an example of an electric induction heat treatment apparatus 800 with a passive inductor assembly 800b (FIG. 14(a)) and a master inductor assembly 800a (FIG. 15(a)) configured in a workpiece heating position for electric induction heating of workpiece bearing features such as an inner bearing race. [Figure 16(b)] 16(a) and 16(b) are alternative perspective views of an example of an electric induction heat treatment apparatus 800 with a passive inductor assembly 800b (FIG. 14(a)) and a master inductor assembly 800a (FIG. 15(a)) configured in a workpiece heating position for electric induction heating of workpiece bearing features such as an inner bearing race. [Figure 17] Figure 17(a) shows a schematic of an alternative split multi-coil electric induction heat treatment system for simultaneously heating one or more features of a bearing component, consisting of two separate master inductor circuits powered by separate phase-locked outputs from a single power supply, while Figures 17(b) and 17(c) show both in-phase and out-of-phase output currents, respectively. [Figure 18] FIG. 18 shows a schematic of an alternative split multi-coil electric induction heat treatment system for simultaneously heating one or more features of a bearing component, consisting of two separate master inductor circuits powered from a single power source with a single output feeding the primary side of a transformer, with two secondary outputs each feeding a separate master inductor circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] In some embodiments of the present invention, the master heating inductor and the passive heating inductor are configured to have an inverse instantaneous current flow of the master circuit AC current and the passive circuit AC current.

[0034] 5(a)-5(d) show a schematic of one embodiment of the present invention having a master inductor circuit 200a and a passive inductor circuit 200b that can be assembled for inductive heat treating inner bearing races, outer bearing races or other bearing features of bearing components used in heavy duty applications utilizing, for example, rolling elements, bearings, raceways or rings, including powertrain applications, driveline applications, and wheel assemblies where the bearing components have complex geometries. The bearing components are alternatively referred to herein as bearing workpieces.

[0035] The master inductor circuit and the passive inductor circuit form an assembled bearing workpiece electric induction heat treatment apparatus 200 as shown in FIG. 5(c) or FIG. 5(d). Here, when the master inductor circuit of the master inductor assembly and the passive circuit of the passive inductor assembly are in the heating position of the bearing component as shown in FIG. 5(c) or FIG. 5(d), for example, selective bearing features can be simultaneously heat treated with the master heating inductor and the passive heating inductor separately configured with the master inductor circuit and the passive inductor circuit for each of two or more different bearing features. Thus, the apparatus 200 can also be described as a split multi-coil (master heating inductor and passive heating inductor) with a split inductor assembly for simultaneously heating multiple bearing features on the bearing component. Here, the split inductor assembly is formed by the master inductor circuit of the master inductor assembly and the passive inductor circuit of the passive inductor assembly.

[0036] In the illustrated embodiment of the invention, the master inductor circuit 200a includes a master heating inductor 210 formed of: a first single-turn induction coil configured for induction heating of a first bearing feature to be simultaneously heat treated in the bearing component; one or more master circuit flux coupling areas 230 forming a master flux coupler; and power supply terminals 6a and 6b of the master inductor circuit. All these master circuit components are electrically interconnected by a master inductor circuit conductor network 201 to form a series master circuit, with all components of the master circuit components being physically and electrically connected in series, except for the master flux coupler, which is separated from the master inductor circuit by an air gap or a gap of dielectric material and is not physically connected. The master flux coupler is located adjacent and physically separate from the master inductor circuit conductor network 201 to couple the magnetic flux from the master inductor circuit when an alternating current flows through the master inductor circuit. The power supply terminals 6a and 6b of the master inductor circuit connect the master inductor circuit 200a to a suitable alternating current source (designated AC source in the drawings). The AC power source may be selected for a particular application from medium or high frequency sources known in the art for selective heat treatment of bearing features, or may provide input power from a utility power source where the induction hardening equipment is installed. Typical ratings for power sources range from 30 kW to 500 kW, with operating frequencies from 1 kHz to 180 kHz, as required by the specified hardness depth, the geometry of the bearing features being heat treated, the mass of heated metallic material forming the bearing workpiece, and the production rate (cycle time per bearing feature being heat treated). The single-phase, two-conductor output of the selected power source is connected to the power terminals 6a and 6b of the master inductor circuit either directly, via a power bus network, or through a load matching transformer, depending on the power supply configuration and the load matching capabilities of the power supply.

[0037] In the embodiment of the invention shown in Figures 5(b)-5(d), the passive inductor circuit 200b includes a passive heating inductor 220 formed from: a second single-turn induction coil configured for inductive heating of a second bearing feature to be simultaneously heat treated with the bearing component; and one or more passive circuit flux coupling regions 240 forming a passive flux coupler. The passive heating inductor 220 forms a physically and electrically closed loop series passive inductor circuit with the passive inductor circuit conductor network 202. When the device 200 is in the heated or assembled position as in Figure 5(c) or Figure 5(d), the passive flux coupler is disposed adjacent to the passive circuit conductor network 202 and the master inductor circuit conductor network 201 and is physically separated by an air gap or a gap of dielectric material such that a passive AC current is induced in the passive inductor circuit when a master AC current flows in the master inductor circuit.

[0038] In the figures, the master and passive heating inductors are configured as single turn solenoid coils, however, other configurations of inductors may be utilized in other examples of the invention as required by the particular configuration of the bearing features being heated by the master or passive heating inductors, for example, whether the inner or outer bearing features are heat treated.

[0039] In other examples of the invention, the active or passive heating inductors may be of different configurations, such as multi-turn coils, etc. Additionally, in other examples of the invention, more than one bearing feature may be heated by a master or passive heating inductor, such that a plurality of two or more bearing features may be heated simultaneously.

[0040] The one or more master circuit flux coupling regions 230 forming the master flux coupler and the one or more passive circuit flux coupling regions 240 forming the passive flux coupler may alternatively be formed from: standard lamination packs; pure ferrite; or conventional iron or ferrite based powder materials, including magnetic composite materials comprising pressed and sintered magnetic particles, as known in the art.

[0041] In one embodiment of the present invention, the master inductor circuit 200a and the passive inductor circuit 200b are selectively brought together from opposing longitudinal side ends of a bearing workpiece (e.g., the bearing workpiece 100 of FIG. 1(b) with selected bearing features such as the inner bearing races that require heat treatment) in a heat treatment process step that loads the bearing workpiece for heat treatment by the apparatus (also referred to as assembling the electric induction heat treatment apparatus in a heating position). This process step of assembling the apparatus in a heating position is shown in FIG. 5(c), where axis LL represents the central internal longitudinal axis LL of the exemplary bearing workpiece 100 of FIG. 1(b), which is not shown in the master heating inductor 210 and the passive heating inductor 220 for clarity. Here, the master heating inductor descends from above the upper longitudinal side end LL of the bearing workpiece as indicated by the movement direction arrow MC, and the passive heating inductor ascends from below over the lower longitudinal side end of the bearing workpiece as indicated by the movement direction arrow PC. 12(a) and 12(b), the bearing workpiece 100 is shown positioned at the heating location of heating devices 245 in master heating inductor 210a'' and passive heating inductor 220b''. This configuration of assembly of the devices from opposing longitudinal side ends of the bearing workpiece to the heating location eliminates the possibility that the shape of the master or passive circuit inductors would cause physical interference with the features of the bearing workpiece that are heated by the passive or active circuit inductors, respectively.Similarly, the heat treatment process step in which the master inductor circuit 200a and the passive inductor circuit 200b unload (remove) the bearing workpiece from the heat treatment apparatus after heat treatment is achieved by separating the master inductor circuit and the passive inductor circuit from each other via the opposing longitudinal side ends of the bearing workpiece, as indicated by the direction of the unload movement arrow MO of the master heating inductor in FIG. 5(c) and the direction of the unload movement arrow PO of the passive heating inductor in FIG. 5(c). The process steps of joining and separating the master inductor circuit with the master heating inductor 210 and the passive inductor circuit with the passive heating inductor 220 from the opposing longitudinal side ends of the bearing workpiece LL allow the master heating inductor 210 and the passive heating inductor 220 to be in close proximity (typically 0.5 mm to 6 mm) to the bearing features (e.g., the bearing race areas 101 and 102 in FIG. 1(b)) that are heat treated by the master heating inductor and the passive heating inductor, respectively, when the bearing workpiece 100 is loaded for heat treatment in the apparatus, and in this example, there is no need to have a sufficiently large radial clearance 107 shown in FIG. 2(a) during the process steps of loading and unloading the workpiece, so that the smaller diameter intermediate race area 103 of the bearing workpiece between the heat treatment areas 101 and 102 shown in FIG. 1(b) does not obstruct (interfere) the joining of the master heating inductor (coil) and the passive heating inductor (coil) at the workpiece loading (heating) position.

[0042] In some embodiments of the invention, a split multi-coil electric induction heating system includes a split inductor assembly positioning device configured to bring the master inductor circuit and the passive inductor circuit together in an assembled (heating) position and separate the master inductor circuit and the passive inductor circuit from the assembled (heating) position along a movement of the master and passive flux couplers shown by the arrows in FIG. 5(c), which may represent a linear actuator with the motion shown by the arrows. In the assembled (heating) position, the master heating inductor of the master inductor assembly is longitudinally aligned with the passive heating inductor of the passive inductor assembly, and the position of the passive flux coupler is adjacent to and physically separated from the master flux coupler when the first bearing feature is positioned for induction heating using the master heating inductor and the second bearing feature is positioned for induction heating using the passive heating inductor, for simultaneously heating the first bearing feature and the second bearing feature. In the non-heated position, the master heating inductor of the master inductor assembly is separated from the passive heating inductor of the passive inductor assembly for the purpose of placing the bearing component at a heating position on the bearing component to inductively heat the first and second bearing feature portions, or for the purpose of removing the bearing component after inductive heating of the first and second bearing feature portions at the heating position on the bearing component.

[0043] 5(c) and 5(d) show perspective views of the master inductor circuit 200a and the passive inductor circuit 200b after they have been brought together in position to heat the bearing workpiece with a loaded bearing workpiece disposed within the master and passive circuit inductors. For clarity of the assembled master and passive heating inductor circuits, the bearing workpiece (along with the optional post heating quenching apparatus) is not shown in these figures.

[0044] In the embodiment of the invention shown in Figures 5(a)-5(d), the master inductor circuit conductor network 201 and the passive inductor circuit conductor network 202 are shown as copper tubing buses disposed between U-shaped master circuit magnetic flux coupling area 230 and passive circuit magnetic flux coupling area 240, respectively.

[0045] There is no physical or electrical circuit contact between the components of the master inductor circuit 200a and the components of the passive inductor circuit 200b when they are in a workpiece heating position, for example as shown in Figure 5(c) or 5(d), and when one or more heat treatment process steps are being performed to heat bearing features of a bearing workpiece located adjacent the master and passive heating inductors. The master inductor circuit flux coupling region 230 is adjacently located but physically separated from the passive inductor circuit flux coupling region 240 by a separation distance 205 for transferring magnetic flux established by alternating current in the conductor network of the master inductor circuit to the passive inductor circuit, as shown by the cross-sectional detail of Figure 5(c) or 5(d).

[0046] 16(a) and 16(b) show, in another perspective view, one embodiment of a configured induction heat treatment apparatus 800 of the present invention utilizing an assembled induction heat treatment apparatus 200 similar to that shown in FIGS. 5(c) and 5(d). The configured induction heat treatment apparatus 800 is shown in FIGS. 16(a) and 16(b) in a bearing component (workpiece) heating position, with an exemplary bearing workpiece 900 loaded into the apparatus for simultaneously heating two bearing features on the bearing workpiece. In this non-limiting example, the bearing component has an upper inner bearing race (also referred to as the first workpiece bearing feature heated by a master heating inductor) requiring heat treatment and a lower inner bearing race (also referred to as the second workpiece bearing feature heated by a passive heating inductor) requiring simultaneous heat treatment, axially separated by a central bearing workpiece feature that is not heat treated. 16(a) and 16(b), the interior of bearing workpiece 900 is not visible because the workpiece has been loaded into the heating position of the bearing component of apparatus 800, but may be similar to, for example, the interior of bearing workpiece 100 of FIGS. 1(a) and 1(b) (the upper inner bearing race is inner bearing race 101a, the lower inner bearing race is 102a, and the unheated central bearing workpiece feature is region 103 of FIGS. 1(a) and 1(b). Configured induction heat processing apparatus 800 includes configured master inductor assembly or section 800a, and configured passive inductor assembly or section 800b.

[0047] 14(a)-14(c) are various views of the configured passive inductor assembly 800b when separated from the configured active inductor assembly 800b, for example, in a non-heated position on a bearing workpiece. FIGs. 15(a)-15(c) are various views of the configured master inductor assembly 800a when separated from the configured passive inductor assembly 800b, for example, in a non-heated position on a bearing workpiece. In this example of the invention, for convenience of orientation, the configured passive inductor assembly 800b is alternatively referred to as the lower inductor assembly and the configured master inductor assembly 800a is alternatively referred to as the upper inductor assembly, but is not intended to limit the orientation of the passive inductor assembly and the master inductor assembly forming the induction heat treatment apparatus 800.

[0048] The configured master inductor circuit 800a includes, in this non-limiting example, a master heating inductor 710 formed from a first single-turn induction coil mounted around and near the bottom end of the mandrel 420a, master circuit flux coupling regions 730a and 730b forming a master circuit flux coupler, and master inductor circuit power terminals 6a and 6b separated by an electrically insulating material 7, all of which are associated with the master inductor circuit conductor network 701. The master inductor circuit power terminals 6a and 6b connect the master inductor circuit 800a to a suitable alternating current power source (designated AC power source in the drawings). The master heating inductor is configured for induction heating of the first workpiece bearing feature to be heat treated. In some embodiments of the invention, the mandrel 420a is referred to as a hardening mandrel, as described further below.

[0049] The constructed master inductor circuit 800a further includes an optional upper master flux concentrator 203a that is ring-shaped and positioned above the master heating inductor 710 around the hardening mandrel 420a, and an optional lower master flux concentrator 204a positioned below the master heating inductor for directing induction heating flux to the first bearing workpiece feature being heated by the master heating inductor 710.

[0050] The configured master inductor circuit 800a further includes components of an auxiliary master inductor circuit forced liquid cooling medium system, comprising a master inductor circuit cooling medium provided by supply cooling tube 425a and return cooling tube 425b and circulating within hollow interior through passages within the master inductor circuit conductor network 701.

[0051] In this non-limiting example, the constructed master inductor circuit 800a includes a quench mandrel 420a with an optional integrated quenching device, i.e., a quench passage (not shown) that supplies quenchant to the heat treated features of the bearing workpiece at the workpiece heating position, with quenchant supplied via quench supply ports 421a and 421b near the top end of the quench mandrel.

[0052] The configured master inductor circuit 800a further comprises one or more master inductor circuit support structures that may be required for the particular placement of the configured master inductor circuit. In the illustrated example, the configured induction heat treatment apparatus 800 includes, but is not limited to, a support clamp block 420b that holds the quench mandrel 420a in place, a support riser 420c, and an adjustable support bridge 420d.

[0053] The configured passive inductor circuit 800b, in this non-limiting example, includes a passive heating inductor 720 formed from a second single-turn induction coil and mounted around and near the top end of the support post 410a (also referred to as the vertical support structure), and passive circuit flux coupling regions 740a and 740b forming a passive circuit flux coupler, all of which are associated with a passive inductor circuit conductor network 702 (also referred to as a passive inductor bus network, forming an electrically closed loop passive bus network). The passive heating inductor is configured for inductive heating of the second workpiece bearing feature to be heat treated.

[0054] The constructed passive inductor circuit 800b further includes an optional upper passive magnetic flux concentrator 203b that is ring-shaped and positioned above the passive heating inductor 720 around the support post 410a, and an optional lower passive magnetic flux concentrator 204b positioned below the master heating inductor for directing induction heating magnetic flux to the bearing workpiece feature being heated by the passive heating inductor 720.

[0055] The constructed passive inductor circuit 800b in the illustrated embodiment of the invention further includes components of an auxiliary passive inductor circuit forced liquid cooling medium system, comprising a passive inductor circuit cooling medium provided by supply cooling tube 406a and return cooling tube 406b, circulating within hollow internal through passages within the passive inductor circuit conductor network 702.

[0056] The configured passive inductor circuit 800b further comprises one or more passive inductor circuit support structures that may be required for a particular placement of the configured passive inductor circuit. In the illustrated example, the configured induction heat treatment apparatus 800 includes, but is not limited to, a support post 410a (also referred to as a vertical support structure), a passive circuit inductor mounting base 410b, and a passive circuit support cradle 410c.

[0057] The configured master inductor circuit 800a and passive inductor circuit 800b can be assembled together from opposing longitudinal side ends of a bearing workpiece (e.g., bearing workpiece 900) with selected features of the internal bearing race that require heat treatment in a heat treatment process step of loading the bearing workpiece for heat treatment in the apparatus (also referred to as assembling the electric induction heat treatment apparatus). Assembling the apparatus from opposing ends of the bearing workpiece eliminates the possibility that the shape of the master circuit inductor or the passive circuit inductor will cause physical interference with the features of the bearing workpiece that are heated by the passive circuit inductor or the active circuit inductor, respectively. Similarly, the heat treatment process step of unloading (removing) the bearing workpiece after heat treatment from the heat treatment apparatus is accomplished by separating the configured master inductor circuit and the configured passive inductor circuit from each other via opposing longitudinal side ends of the bearing workpiece. In some embodiments of the invention (e.g., as shown in Figures 9(a)-9(d) and 10(a)-10(d)), the configured passive inductor circuit 800b is separated from the configured master inductor circuit 800a but not from the bearing workpiece (Figures 9(c) and 10(c)), and the bearing workpiece is seated on the passive inductor with dielectric isolation from the passive inductor, a structure known in the art as a dielectric nest. Only after the quench cycle is completed is the bearing workpiece finally removed from the configured passive inductor circuit 800b. The process step of separating the master inductor circuit and the passive inductor circuit together from the opposite longitudinal side ends of the bearing workpiece allows for the close placement of the master heating inductor 710 and the passive heating inductor 720 to the bearing features that are heat treated by the configured master heating inductor and the configured passive heating inductor, respectively.In the embodiment of the invention shown in Figures 5(a)-5(d), the master inductor circuit conductor network 201 and the passive inductor circuit conductor network 202 are shown as copper tubing buses located between the U-shaped master circuit flux coupling area 230 and the passive circuit flux coupling area 240.

[0058] The components of configured master inductor circuit 800a and configured passive inductor circuit 800b have no physical or electrical circuit contact between them when they are in a workpiece heating position, for example as shown in Figure 16(a) or 16(b), and when one or more heat treatment process steps are being performed. The configured master inductor circuit magnetic flux coupling regions 730a and 730b are adjacently disposed, but physically separated from the configured passive inductor circuit magnetic flux coupling regions 740a (hidden in the drawing view) and 740b by a separation distance 705 as shown in Figures 16(a) and 16(b), for transferring the magnetic flux established by the alternating current in the master inductor circuit conductor network 701 to the passive inductor circuit conductor network 702. In some embodiments of the present invention, electrical insulators are disposed between magnetic flux coupling regions 730a and 730b, and / or between magnetic flux coupling regions 740a (hidden in the drawing view) and 740b, and / or between the master inductor 701 and the passive inductor 702 network.

[0059] By moving the bearing workpiece electric induction heating apparatus of the present invention, e.g., the configured master inductor circuit, the configured passive inductor circuit, or both the configured master inductor circuit and the configured passive inductor circuit, away from each other, the configured induction heat treatment apparatus 800 can be moved between workpiece heating positions as shown in FIG. 16(a) or FIG. 16(b), thereby isolating them from each other and from a loaded bearing workpiece (e.g., the bearing workpiece 900 of FIG. 16(a) or FIG. 16(b)). By way of non-limiting example, the isolation action between the configured master inductor circuit and the passive inductor circuit to load or unload a bearing workpiece (using a suitable workpiece electromechanical transport device, not shown) from the workpiece heating positions shown in FIG. 16(a) or FIG. 16(b) can be accomplished using one or more suitable electromechanical linear or rotary actuators configured for the directional movement required for a particular application.

[0060] After the heating cycle and proper austenitization of selected bearing workpiece features is completed using the electric induction heat treatment apparatus 800 shown in Figures 14(a) through 16(b), quenching of the heat treated workpiece bearing features may be accomplished using a quenching apparatus integrated into the heating apparatus or located remotely from the heating apparatus as described herein or otherwise known in the art.

[0061] Figures 7(a) and 7(b) show, in cross-section, the master and passive circuit flux coupling regions 230 and 240 (flux concentrators) shown in Figure 6(b) as alternatively used in certain applications, where (1) the master and passive inductor bus networks are formed from conductive tubes 201a and 202a (such as copper compositions) inserted (also called "sandwich") between the electromagnetic coupling regions 230a and 240a in Figure 7(a); or (2) the master and passive inductor bus networks are formed from conductive rectangular bars 201b and 202b (such as copper bus bars) or rectangular tubes (not shown) inserted (also called "sandwich") in the air gap or dielectric material gap between the electromagnetic coupling regions 230b and 240b in Figure 7(b). The use of the rectangular copper bus shown in Figure 7(b) is the most commonly used.

[0062] The exemplary hot position spacing air gaps 205a in FIG. 7(a) and 205b in FIG. 7(b) are large enough to prevent electrical arcing or shorting between elements of the master inductor circuit 200a and the passive circuit 200b. Although air is not a preferred dielectric material, in alternative embodiments of the invention, the air gap can function as a sufficient dielectric, or the hot position spacing gaps 205a or 205b can be filled with conventional dielectric materials known in the art for electrically insulating electrical conductors. Such conventional dielectric materials include dielectric tape, ceramic coatings, or other electrically insulating materials known in the art.

[0063] The spacing air gap 205a in Figure 7(a) and spacing air gap 205b in Figure 7(b) should not be so large as to adversely affect the electromagnetic coupling between the master inductor circuit 200a and the passive inductor circuit 200b. Typically, but not by way of limitation, the size of the spacing air gaps 205a and 205b (Figure 7(b)) is in the range of 0.5mm to 6mm, depending on the frequency, the magnitude of the current, and the working environment conditions (humidity, moisture, the presence of conductive dust, etc.).

[0064] For manufacturing features of the master and passive circuit flux coupling regions 230 and 240 for a particular application, including selecting the appropriate shape of the flux couplings and how to hold them in place, and selecting the appropriate size of the spacing air gap 205, reference is made to U.S. Pat. Nos. 6,274,857 and 6,859,125.

[0065] In one embodiment of the process of the present invention, after loading one or more features to be inductively heated into a workpiece and placing both the master induction coil and the passive induction coil of the apparatus of the present invention in the heating position, as shown in Figures 5(a) and 5(b), the AC power source connected to the circuit power terminals 6a and 6b is energized and AC current begins to flow through the master inductor circuit. The flux coupling areas 230 and 240 of the master and passive circuits provide electromagnetic coupling between the energized master inductor circuit and the electrically shorted passive inductor circuit, similar to the effect between the windings of a transformer core. The AC current flowing through the master circuit inductor instantly (in effect) creates a current flowing in the closed loop passive circuit due to the flux coupling areas of the master and passive circuits similar to the current flowing through the primary and secondary windings of a power transformer.

[0066] The instantaneous AC current induced in the passive inductor circuit 200b is directed in the opposite direction to the direction of the source current flowing in the master inductor circuit, as shown, for example, by the arrow in FIG. 5(c). However, depending on the alternative circuit connections, the AC currents flowing in the master induction coil 210 of the master circuit 200a and the passive induction coil 220 of the passive inductor circuit 200b can be directed in the opposite direction or the same direction. For example, the master and passive circuit connections shown in FIG. 5(a) through FIG. 5(c) generate an AC current in the passive induction coil 220 of the passive inductor circuit, which is momentarily directed in the opposite direction to the coil current flowing in the master induction coil 210 of the master circuit. This opposite current orientation is useful, for example, to obtain the hardness patterns shown in FIG. 1(b), FIG. 1(j) and FIG. 1(k), which are the most commonly desired hardness patterns in most inner bearing races used, for example, in automotive applications. In contrast, if the desired stiffness pattern is, for example, that shown in FIG. 1(c), it is beneficial to modify the circuit arrangement of the passive inductor circuit to orient the instantaneous coil current flowing through the passive induction coil 220 in the same direction as the master inductor circuit current provided by the connected power source and flowing through the master induction coil 210. One possible example of such a connection is shown in FIG. 5(e). FIG. 5(f) and FIG. 5(g) show alternative instantaneous currents flowing through the passive induction coils of the passive inductor circuit. FIG. 5(f) shows the instantaneous direction of the AC current in the passive inductor circuit 200b with the passive induction coil 220 for the electrical circuits shown in FIG. 5(b) and FIG. 5(c). FIG. 5(g) shows the instantaneous direction of the AC current in the passive inductor circuit 200b' with the passive induction coil 220' shown in FIG. 5(e). Despite having the same instantaneous direction of current flowing through the passive circuit 202 shown in Figures 5(f) and 5(g), the current flowing through the passive induction coil 220' (Figure 5(g)) is directed in the opposite direction to the current flowing through the passive coil 220 (Figure 5(f)).

[0067] In a typical design application of an embodiment of the induction heat treatment apparatus of the present invention, with sufficient electromagnetic coupling between the master inductor circuit 200a and the passive inductor circuit 200b, the difference between the current flowing through the master induction coil 210 of the master inductor circuit 200a, supplied from the alternating current power source to the power supply terminal connections 6a and 6b, and the current induced in the passive induction coil 220 of the passive inductor circuit 200b, may be less than 10%. And this difference can be further corrected by profiling the geometry of the coil heating surfaces of the active induction coil 210 and the passive induction coil 220 (e.g., by profiling the copper geometry). In some embodiments of the present invention, providing a passive induction coil-to-workpiece gap that is 0.25 mm to 2 mm smaller than the master induction coil-to-workpiece gap is sufficient to correct the difference in the magnitude of the current flowing through the master induction coil 210 and the passive induction coil 220. In other embodiments of the present invention, it is beneficial to strategically place the bearing race in a hot position such that a low mass region of the bearing race area is heated by the passive induction coil located in the passive inductor circuit. For example, region 115 in Figure 2(a) has a smaller mass of metal that needs to be heat treated compared to region 106 in Figure 2(a). Therefore, at the heating location, it is beneficial to place a passive induction coil 220 with a passive inductor circuit (lower current magnitude) to heat the smaller mass region 115, and a master induction coil 210 with an active inductor circuit (higher current magnitude) to heat the larger mass region 106.

[0068] 2(a), by way of example only, a water-cooled round copper tube is used for coil fabrication. In other cases, the coil may instead be formed by CNC machining of a solid copper block, brazing of suitable copper parts, or a die forming a profiled heated surface of the coil turns to correspond to the shape of the inner bearing race 115, or the coil may be manufactured using additive manufacturing techniques such as 3D printing.

[0069] Conventional magnetic flux concentrators 203 and 204 can be applied to improve heating efficiency and concentrate the magnetic field generated by each turn 301 and 302 of the two-turn coil for heating the inner bearing race. The magnetic flux concentrators are typically fabricated from standard lamination packs, pure ferrite, or conventional iron-based or ferrite-based powder materials (such as magnetic composites) that contain pressed and / or sintered magnetic particles.

[0070] The coil configuration of the present invention shown in Figures 5(a) through 5(d) allows for the smallest possible induction coil-to-workpiece gap during loading and unloading without the limitations associated with the obstruction of smaller diameter region 103 (e.g., as shown in Figure 1(b)). The present invention provides a substantially closer coupling gap between the induction coil and the workpiece surface compared to known prior art, resulting in high energy efficiency, better hardness pattern control, and contour-like hardening patterns with minimal size and shape distortion, reduced maximum and peak temperatures during austenitization, and the production of metallurgically sound microstructures, resulting in less likelihood of bearing race cracking during heat treatment and operation.

[0071] As required for a particular application, the induction heat treatment apparatus and method of the present invention may alternatively be arranged vertically or horizontally. In a vertically arranged application of the apparatus and method, the passive circuit 200b (including the induction coil 220) may be provided in combination with a support pedestal (e.g., a workpiece stationary structure (nest)) on which the bearing race to be heat treated is placed. In this vertical arrangement, the bearing race resting on the pedestal may be elevated (lifted) into a heating position and held in the heating position during the heat treatment cycle, as shown in Figures 8-10.

[0072] According to one possible design of the invention, the induction coil of the master circuit 200a (FIG. 5(a)) is placed on a pedestal (or on a rest nest that is part of the passive circuit 200b that contains the induction coil 220) and then kept stationary while the bearing race 100 (FIG. 1(a)) moves in and out of the heating position. Since the passive circuit 200b represents a closed loop electrical system, it can move in and out of the heating position freely and the power connection cables carrying high currents do not have to move with the passive circuit 200b. The mechanism for moving the workpiece in and out of the heating position can be hydraulic, pneumatic or electric.

[0073] In accordance with another design concept of the present invention, the induction coil 210 of the master circuit 200a is movable in and out of the heating position, but the bearing race 100 does not move axially.

[0074] Depending on the specification and criticality of the hardness pattern on the bearing race surface, standard means can be used to rotate (spin) the bearing race during the heating cycle. A conventional lift-and-spin configuration known in the art for small and medium size workpieces can provide a low-cost machine option. A cylinder lifts the workpiece bearing race into the working position and an electric motor initiates the rotation of the part. Optionally, an adjustable hard stop can be used to position the part. In this case, a holding chuck or clamp block can hold the bearing race in the heating position while rotating it during heating, without the need for a static rest on a pedestal during rotation.

[0075] In another embodiment of the present invention, the workpiece bearing race 100 is held stationary during heating as disclosed herein.

[0076] Single-turn coils of conventional design have an area where distortion of the magnetic field is unavoidable, resulting in some reduction in heat intensity there. This area is associated with the area where the copper bus carrying the current from the power supply is connected to the induction coil (the area of ​​the so-called polarizing coil power supply lead). The physical phenomenon responsible for that reduction in heat intensity is called the electromagnetic field fringing effect (also called fishtail effect) and is explained for example in the literature Induction Heating Handbook. Rotation of the workpiece during heating helps (in practice) to eliminate the heat deficit in the split area. Even if the workpiece bearing race is heated statically (without rotation), deviations in heat intensity there can be minimized. The industry has developed various standard means to effectively control and compensate for the field fringing effect in static induction heating applications using single-turn coils through appropriate coil copper profiling. Improved electromagnetic coupling (proximity effect) in the split area of ​​the single-turn coil compensates for the magnetic field fringing and eliminates the need to rotate the heated workpiece. These techniques for field strength compensation near the split region of the coil have been disclosed in many publications, including U.S. Pat. No. 6,274,857, and can be used in the present invention when the bearing race 100 is statically heated without rotating.

[0077] After the heating cycle and proper austenitization are complete, the bearing races can be quenched in-situ or ex-situ by applying conventional quenching techniques appropriate to the liquid quenchant selected, or in the case of sufficient steel hardenability, by applying alternative quenching media to the liquid quenching media, such as forced air quenching or gas quenching.

[0078] 8(a)-8(d) are schematic diagrams illustrating one embodiment of the method of the present invention for bearing race heat treatment. The electric induction heating apparatus utilized in the illustrated method is formed, for example, from a master inductor circuit 200a (FIG. 5(a)) and a passive inductor circuit 200b (FIG. 5(b)). After loading the bearing race to be heat treated onto a load and unload mounting platform or fixture (not shown) that places the unheat treated bearing race either inside or outside the master inductor coil 210 of the master inductor circuit 200a (depending on whether the bearing race is the inner or outer race) with the heating apparatus separated in FIG. 8(a) (race loading position), the entire passive inductor circuit 200b (including the passive coil 220, the passive circuit magnetic coupler 240 and the passive bus network 202) is raised to the race heating position shown in FIG. 8(b). In the race heating positions, the master and passive circuit electromagnetic couplers 230 and 240 are positioned in close proximity to one another and surround corresponding segments of the master and passive bus networks 201b and 202b (see FIGS. 5(a)-5(c)) formed from copper conductors, creating an electromagnetic link 250 (shown as a dashed oval region in FIG. 8(b)) when the master inductor circuit 200a is powered (to an AC source) via a connection to an AC source. In the process step shown in FIG. 8(b), the coils 210 and 220 are positioned in their respective heating positions to initiate a thermal cycle of the desired bearing race region (e.g., bearing race regions 101 and 102 in FIG. 1(b) if the bearing race to be heated is the bearing race 100 shown in FIG. 1(b)). Once the heating cycle is completed, power is removed from the master inductor circuit 200a and the master and passive inductor circuits are turned off, at which point the spray quench cycle begins immediately or after a short time delay (also called a soak time) for quenching of the bearing race area loaded into the heating device, as shown in FIG. 8(c), where a conventional spray quenching device 71 (e.g., a spray quench block or liquid quenchant sprayer) can be utilized.Depending on the bearing race geometry details and the required hardness pattern, a short quench time delay may help obtain a proper thermal profile. The quench delay typically does not exceed 5 seconds. Once the spray quench cycle is completed, the heat treated bearing race (not shown) and the entire passive inductor circuit 200b are lowered to the bearing race unload position as shown in FIG. 8(d) where unloading of the heat treated bearing race from the pedestal occurs. In a continuous sequential bearing race heat treatment process, a subsequent unheat treated bearing race is loaded onto the pedestal and the above induction heat treatment process described in FIGS. 8(a)-8(d) is repeated.

[0079] 9(a)-9(d) are schematic illustrations of another embodiment of the method of bearing race heat treatment of the present invention similar to some process steps of the method described in FIG. 8(a)-8(d). In the method of FIG. 9(a)-9(d), the first two process steps are as previously described for the method steps shown in FIG. 8(a) and FIG. 8(b), except for the placement of the quench tank 70 below the bearing race heating device. Once the heating cycle is completed, power is removed from the master inductor circuit 200a and the master and passive inductor circuits are turned off, at which point the entire bearing race and passive inductor circuit 200b with the heating and austenitized bearing race area is transferred from the bearing race heating location below the surface level of the fluid quenchant 70a to the quench tank 70, where the quench cycle begins as shown in FIG. 9(c). Preferably, but not exclusively, the fluid quenchant is agitated (e.g., by stirring) in the quench tank to improve quench uniformity and other favorable cooling characteristics. Upon completion of the quench cycle, the quenched, heat treated bearing race 100 (not shown) is raised by its mounting pedestal or fixture into position for unloading from the passive inductor coil and unloaded from the mounting pedestal or fixture. In a continuous sequential bearing race heat treatment process, a subsequent unheat treated bearing race is loaded onto the mounting pedestal and the above induction heat treatment process described in Figures 9(a)-9(d) is repeated.

[0080] Some steels that can be used to form bearing races have low metallurgical hardenability and are therefore sensitive to delayed quenching, which occurs during transportation of the bearing races to the quench tank as shown in the method described above in connection with Figures 9(a)-9(d). The temperature of such steels after heating and austenitizing can potentially fall below the minimum required temperature level and delayed quenching can result in the formation of metallurgically undesirable structures. Figures 10(a)-10(d) show another embodiment of the method of the present invention for bearing race heat treatment in a schematic manner. The heat treatment method shown in Figures 10(a)-10(d) is a modification of the method shown in Figures 9(a)-9(d). The process steps shown in Figures 9(a), 9(b) and 9(d) are carried out in a similar manner to the process steps shown in Figures 10(a), 10(b) and 10(d). The process step shown in Figure 10(c) is modified from that of Figure 9(c) in that a spray quench block 72 quenches the heated and austenitized bearing race which is fixed relative to the passive inductor coil 220 (indicated by the quench spray arrows), and the entire passive inductor circuit 200b with the fixed heated and austenitized bearing race is lowered into a fluid quench 70a in a quench tank 70 to complete the quench process. The method shown in Figures 10(a)-10(d) is particularly useful when the metallurgical properties of the heat treated bearing race require immediate and / or uninterrupted quenching after austenitization.

[0081] Based on common industry practice for electric induction heat treatment processes, the time required for the workpiece quenching process step is typically 2-4 times longer than the time for the heating and austenitizing process steps. As a result, the heat treatment production rate and power utilization of the heat treated bearing races may be lower than desired in a particular application using any of the methods disclosed in Figures 8(a)-8(d), 9(a)-9(d), and 10(a)-10(d).

[0082] 11(a) and 11(b) show schematic diagrams of another embodiment of the method of the present invention for heat treating bearing races as an alternative method for improving power utilization and increasing bearing race heat treating production rates. The electric heating device utilized in the illustrated method may be formed, for example, from a master inductor circuit 200a" with a plurality of master inductor coils 210a" and 210b" and a passive inductor circuit 200b" with a plurality of passive inductor coils 220a" and 220b" to form an electric induction heating device 245 shown in the bearing race heating location of FIG. 12(a). The heating device 245 of FIG. 12(a) shows one method of the present invention for increasing production of heat treated bearing races and enhancing applied power utilization. In the method shown in Figures 11(a) and 11(b), two bearing races (one for each of the two master and passive induction coil pairs) can be heat treated simultaneously and then quenched simultaneously using a suitable spray quenching apparatus known in the art (such as apparatus 73 of Figure 11(a) or 11(b)) or in an alternative quenching process step (for example, but not limited to, those disclosed in the methods of Figures 8(a)-8(d), 9(a)-9(d), and 10(a)-10(d)).

[0083] FIG. 12(a) shows an alternative arrangement of an electric induction heating apparatus of the present invention at a heating position for simultaneously heating the races of two bearing workpieces using multiple induction coils in the master and passive circuits (i.e., two coils 210a″ and 210b″ in the master inductor circuit, and two coils 220a″ and 220b″ in the passive inductor circuit). In FIG. 12(a), only one bearing workpiece is shown for convenience. FIG. 12(b) is an enlarged view of the left end of the heating apparatus of FIG. 12(a).

[0084] As shown in Figures 11(a)-11(b), the multiple coils 210a" and 220b" of the master inductor circuit 200a" are electrically connected in series. In an alternative arrangement of the electric heating device of the present invention, the multiple coils 210a" and 220b" of the master inductor circuit 200a" can be electrically connected in parallel or a combination thereof. Similarly, the multiple coils 220a" and 220b" in the passive circuit 200b" can also be electrically connected in parallel or have a combination of series / parallel connections.

[0085] A rotary table can be used to increase production speed and to allow quenching to occur in multiple locations outside of the heated position. This type of system can also be used when components need to be hardened in different areas located on the same workpiece. The rotary table can be positioned horizontally, vertically, or at an angle.

[0086] FIG. 13 shows an example of an induction heating system of the present invention including a vertically oriented rotary table 330 with three stations for heat treating two workpiece bearings simultaneously. By rotating the table counterclockwise as indicated by the arrows, two workpiece bearings 100x to be heat treated are loaded onto the rotary table at table station 333, which may be referred to as a pre-heat load and post-heat unload station. Two workpiece bearings 100y are loaded into a dual workpiece heating apparatus of the present invention (e.g., heating apparatus 245 shown in FIG. 12(a)) adjacent to table station 331 (bearing workpiece heating station), where the bearing races are loaded into apparatus 245, induction heated, austenitized, and unloaded from apparatus 245. The two heated and austenitized workpiece bearings 100z are at quench table station 332, where they are quenched with quenchant 70a (shown in the figure as stippled quenchant surface area) in quench tank 70. The rotary table guides the workpiece bearings two at a time from table station 331 to table station 332 to table station 333. In some embodiments of the invention, an auxiliary spray quenching device (not shown) is installed between heat table station 331 and quench table station 332 to quench the austenitized bearing race features of the workpiece during transport between these two stations. The auxiliary spray quenching device can be similar to spray quench block 72 of FIG. 10(c) to provide a stationary or agitated liquid quenchant. In other embodiments of the invention, multiple table stations for heating or quenching, or heating and quenching, are provided. In other embodiments of the invention, the rotary table is oriented horizontally or at an oblique angle from the horizontal or vertical. The bearing race features can be heated while stationary in the rotary table heating device or rotated by a conventional rotation device such as a rotary actuator as known in the art.In another embodiment of the invention, a shuttle device is used to perform the function of a rotary table to transport the workpiece bearings between different process positions (eg, from heating to quenching, to load and unload positions).

[0087] 17(a) illustrates diagrammatically another embodiment of the invention including a split multi-coil electric induction heating system having a split inductor assembly for simultaneously heating multiple bearing features on a bearing component and an alternating current (AC) power source 160a including at least two phase-locked outputs 161 and 162. Any AC power source known in the art, including but not limited to electrical devices manufactured based on semiconductor technology (e.g., thyristor-based or transistor-based AC power sources), is suitable for use as AC power source 160a, provided that it has at least two phase-locked outputs 161 and 162.

[0088] The split inductor assembly consists of two master inductor assemblies that can be separated at the heating location of the bearing component. A first master inductor circuit conductor network 6a and 6b connects the first phase-locked output 161 of the AC power source 160a to the first master heating inductor 210 (as shown in FIG. 17(a)). A second master inductor circuit conductor network 6c and 6d connects the second phase-locked output 162 of the AC power source 160a to the second master heating inductor 220.

[0089] The phase-locking function of the output of the AC power source 160a allows the instantaneous inductor current flow in the first master heating inductor 210 and the instantaneous current flow in the second master heating inductor 220 to be directed in opposite directions, as shown by the current waveforms in Figure 17(b), or the instantaneous inductor current flow in the first master heating inductor 210 and the instantaneous current flow in the second master heating inductor 220 to be directed in the same direction, as shown by the current waveforms in Figure 17(c). Thus, depending on the hardness pattern requirements of the bearing features (e.g., the interrupted bearing race hardness pattern shown in Figure 1(b) or the uninterrupted bearing race hardness pattern shown in Figure 1(c)), this phase-locking function of the output of the AC power source according to alternative embodiments of the present invention provides the desired direction of the instantaneous current in the first master heating inductor 210 and the second master heating inductor 220 (similar to that shown in Figures 5(c), 5(f) or 5(g)).

[0090] The power supplied by each of the at least two phase-locked outputs 161 and 162 of the AC power source 160a, and therefore the power supplied to each of the heating inductors 210 and 220, is independently controlled, allowing compensation for possible differences in the mass of the heated metal (comparing zones 101 and 102 of the bearing features or areas where rolling elements (such as balls or rollers) contact the inner bearing races 101a and 102a, respectively), as shown in FIG.

[0091] As an alternative approach to using a single AC power source 160a with phase locking of multiple outputs 161 and 162, one of ordinary skill in the art having the benefit of the teachings of the above specification could use two different AC power sources with phase locking of the output powers instead of using the single AC power source 160a described above, without departing from the scope of the present invention.

[0092] Although the master passive design concept (e.g., FIG. 5(c) or FIG. 12(a)) requires a conventional less complex AC power source 160 and is therefore a more cost-effective approach compared to the more complex AC power source 160a, under certain conditions, the use of an AC power source 160a including at least two phase-locked outputs 161 and 162 may be beneficial and preferable to demonstrate certain process advantages. These conditions include, but are not limited to, higher frequency (e.g., frequencies in the range of 70 kHz to 600 kHz) applications. Alternatively, or in addition to these conditions, applications are included where there is a large difference in the mass of metal that needs to be heated simultaneously (which may be related to a corresponding difference in the shape of the bearing features that need to be hardened (compare zones 101 and 102 of the bearing features or areas where the rolling elements contact the inner bearing races 101a and 102a, respectively, as shown in FIG. 1(b)). Alternatively, or in addition to these conditions, applications are included where the bearing component is comprised of three or more bearing features that need to be heat treated simultaneously and have substantially different shapes. Alternatively, or in addition to these conditions, applications are included where the bearing component is comprised of multiple bearing features that exhibit a combination of interrupted and uninterrupted hardness patterns. These are just a few exemplary cases where the use of an induction heating system with multiple master inductors (e.g., FIG. 17(a) and the like) may be preferred.

[0093] 18 diagrammatically illustrates another embodiment of the present invention including a split multi-coil electric induction heating system having a split inductor assembly for simultaneously heating multiple bearing features on a bearing component, the split inductor assembly including a conventional AC power supply 160 having a single output connected to a primary winding 222a of an output transformer 222 having at least two secondary windings 222b and 222c. The secondary windings 222b and 222c are connected to two corresponding master inductors 210 and 220 via corresponding outputs 161a and 162a of the output transformer 222 and corresponding master inductor circuit conductor networks 6a-6b and 6c-6d.

[0094] A first master inductor circuit conductor network 6a and 6b connects the first output 161a of the transformer 122 and the first master heating inductor 210. A second master inductor circuit conductor network 6c and 6d connects the second output 162a of the transformer 122 and the second master heating inductor 220 (see FIG. 18).

[0095] Each of the two master inductor circuit conductor networks 6a-6b and 6c-6d may be configured with standard power control devices (not shown in FIG. 18 ), such as thyristor-based or thyristor-based AC regulators, known in the art and commonly used in the industry, to allow for regulation of the power supplied to each of the heating inductors 210 and 220 independently.

[0096] By changing the relative configuration of the secondary windings 222b and 222c of the transformer 222 with respect to one another, it is possible to make the instantaneous currents flowing through the heating inductors 210 and 220 point in the same direction or in opposite directions (if desired to obtain the required hardness pattern). In applications where an interrupted hardness pattern is required (e.g., as shown in FIG. 1(b)), it is advantageous to configure the secondary windings 222b and 222c of the transformer 222 such that the instantaneous currents flowing through the heating inductors 210 and 220 are directed in opposite directions. In contrast, when an uninterrupted hardness pattern is required (e.g., as shown in FIG. 1(c)), it is advantageous to configure the secondary windings 222b and 222c of the transformer 222 such that the instantaneous currents flowing through the heating inductors 210 and 220 are directed in the same direction.

[0097] While the master passive design concept (e.g., FIG. 5(c) and FIG. 12(a)) does not require the use of a transformer 222 having at least two secondary windings of the particular configuration because it is a more cost-effective and relatively simple design, under certain conditions, the use of the circuit shown in FIG. 18 may present certain process advantages. These conditions include, but are not limited to, low and medium frequency (e.g., in the range of 500 Hz to 6 kHz) applications. Alternatively or in addition to these conditions, applications include those in which a significant hardening depth is required (e.g., a hardening depth of 3 mm to 9 mm deep). Alternatively or in addition to these conditions, applications include those that present a substantial difference in the amount of metal that needs to be heated simultaneously (which is related to the corresponding difference in the shape of the bearing features that need to be hardened, such as the bearing feature or area zones 101 and 102 where the rolling elements contact the inner bearing races 101a and 102a, respectively, as shown in FIG. 1(b). These are just some exemplary cases in which the use of the induction heating system shown in FIG. 18 may be beneficial.

[0098] In the above-described embodiments of the invention, a single turn inductor is utilized. In alternative embodiments of the invention, two or more turn inductive coils are utilized (e.g., multi-turn active coils and multi-turn passive coils may also be used in place of the single turn inductor style, depending on the particular application).

[0099] In the above described embodiment of the invention, coiled copper round tubing is utilized for the master coil and the passive coils. In alternative embodiments of the invention, other coil configurations are used for specific applications including profiled coiled copper.

[0100] The magnetic flux concentrators identified above as being of particular geometric shapes, e.g., U-shaped or ring-shaped magnetic flux compensators, may be of alternative geometric shapes or may be assembled from magnetic flux concentrators of other shapes, as required for a particular application.

[0101] When the inner surface (inner race) of a thin-walled bearing component is heated for austenitization, a spray quench on the outer surface can be applied during the entire thermal cycle or part of the thermal cycle. This helps prevent hardening or excessive hardening depth (if required) when heat treating the thin-walled bearing component. Similarly, a spray quench can be applied to the inner surface to prevent hardening or excessive hardening (if required) when heating the outer surface (outer race).

[0102] Alternative embodiments of the induction heat treatment apparatus and method are applied in applications where the bearing race surface or race area being heat treated is other than the inner bearing race (for example, and not by way of limitation, the outer bearing race and ball raceway 100' shown in the bearing race of Figures 1(d) and 1(e)). In other embodiments of the invention, such as the outer bearing race, the complementary master inductor coil and passive inductor coil can be configured to be externally disposed around the outer bearing at the heating location.

[0103] The present invention has been described in terms of preferred examples and embodiments. Except as expressly stated, equivalents, alternatives, and modifications are possible and are within the scope of the present invention. Those skilled in the art, having the benefit of the teachings herein, may make modifications thereto without departing from the scope of the invention.

Claims

1. 1. A split multi-coil electric induction heating system having a split inductor assembly for simultaneously heating a plurality of bearing features on a bearing component, the split inductor assembly including a master inductor assembly and a passive inductor assembly separable from a heating location on the bearing component, the split multi-coil electric induction heating system comprising: A master inductor circuit disposed in the master inductor assembly, the master inductor circuit including: a master heating inductor for heating at least one first bearing feature; Master Flux Coupler, a power terminal of the master inductor circuit; and a master inductor circuit conductor network connecting a power terminal of the master inductor circuit to the master heating inductor, the master inductor circuit conductor network being located in close proximity to the master flux coupler and physically separated by an air gap or a dielectric material gap; and A passive inductor circuit disposed in the passive inductor assembly, the passive inductor circuit including: a passive heating inductor for heating the at least one second bearing feature; Passive flux couplers, and a passive inductor circuit conductor network that forms a closed series electrical circuit with the passive heating inductor; Including, 11. A split multi-coil electric induction heating system, comprising: a passive flux coupler disposed proximate to and physically separated from the passive inductor circuit conductor network; and a passive flux coupler disposed proximate to the master flux coupler and physically separated by an air gap or a dielectric material gap, whereby the master inductor circuit and the passive inductor circuit are in a heating position of the bearing component for inductive heating of the at least one first bearing feature and the at least one second bearing feature, and when a master circuit AC current is applied to a power terminal of the master inductor circuit, a magnetic field of the master inductor circuit couples with the passive inductor circuit via the passive flux coupler, which is magnetically coupled to the master flux coupler, to generate a passive circuit AC current in the passive inductor circuit conductor network.

2. 2. The split multi-coil electric induction heating system of claim 1, wherein the master heating inductor comprises a single turn solenoid coil and the passive heating inductor comprises a single turn solenoid coil.

3. 2. The split multi-coil electric induction heating system of claim 1, wherein the at least one first bearing feature and the at least one second bearing feature are at least partially disposed about an exterior of the master heating inductor or the passive heating inductor to inductively heat an interior bearing feature of the bearing component.

4. 2. The split multi-coil electric induction heating system of claim 1, wherein the at least one first bearing feature and the at least one second bearing feature are at least partially disposed about an interior of the master heating inductor or the passive heating inductor to inductively heat an exterior bearing feature of the bearing component.

5. 10. The split multi-coil electric induction heating system of claim 1, wherein the master heating inductor and the passive heating inductor are configured for opposite instantaneous current flow.

6. 10. The split multi-coil electric induction heating system of claim 1, further comprising a split inductor assembly positioning device configured as: (a) positioning the at least one first bearing feature for inductive heating using the master heating inductor and the at least one second bearing feature for inductive heating using the passive heating inductor to simultaneously heat the at least one first bearing feature and the at least one second bearing feature, longitudinally aligning the master heating inductor of the master inductor assembly with the passive heating inductor of the passive inductor assembly and positioning the passive flux coupler in close proximity to but physically separated from the master flux coupler; (b) longitudinally separating the master heating inductor of the master inductor assembly from the passive heating inductor of the passive inductor assembly for placing the bearing component at a heating location on the bearing component and inductively heating the at least one first bearing feature and the at least one second bearing feature, or for removing the bearing component after inductively heating the at least one first bearing feature and the at least one second bearing feature at the heating location on the bearing component.

7. 10. The split multi-coil electric induction heating system of claim 1, further comprising a quenching system for quenching the austenitized regions of the at least one first bearing feature and the at least one second bearing feature after induction heating, the quenching system including a quenchant application device for either or a combination of at a heating location of the bearing component, during transition from a heating location of the bearing component to a remote quenching station, or quenching at a remote quenching station.

8. 2. The split multi-coil electric induction heating system of claim 1, further comprising a second master heating inductor electrically connected in series with the master heating inductor and a second passive heating inductor electrically connected in series with the passive heating inductor configured to heat at least one first bearing feature and at least one second bearing feature on a second bearing component, respectively.

9. The master inductor assembly and the passive inductor assembly are configured to be positioned proximate a bearing workpiece heating station, and the split multi-coil electric induction heating system further comprises: Rotating table including: a bearing workpiece rotary table pre-heat load and post-heat unload station for loading the bearing component and the second bearing component onto the rotary table and for unloading the bearing component and the second bearing component from the rotary table; a bearing workpiece heating station for loading and inductively heating the bearing component and the second bearing component onto the master inductor assembly and the passive inductor assembly, and for unloading the bearing component and the second bearing component from the master inductor assembly and the passive inductor assembly after induction heating; a bearing workpiece hardening station for hardening the bearing component and the second bearing component after induction heating; and a rotary actuator for moving the bearing component and the second bearing component from the bearing workpiece turntable pre-heat load and post-heat unload station, the bearing workpiece heating station, the bearing workpiece quenching station, and the bearing workpiece turntable pre-heat load and post-heat unload station; 9. The split multi-coil electric induction heating system of claim 8, comprising:

10. 1. A split multi-coil electric induction heating system for simultaneously heating a plurality of bearing features on a bearing component, the split inductor assembly including a master inductor assembly and a passive inductor assembly separable from a heating location on the bearing component, the split multi-coil electric induction heating system comprising: A master inductor circuit disposed in the master inductor assembly, the master inductor circuit including: a master heating inductor for heating the first bearing feature, the master heating inductor including a single turn master solenoid coil disposed at the first mandrel end around an outer periphery of the vertical mandrel having a central longitudinal axis of the vertical mandrel; Master Flux Coupler, a power terminal of the master inductor circuit; and a master inductor circuit conductor network connecting a power terminal of the master inductor circuit to the master heating inductor, the master flux coupler being positioned proximate to and physically separated from the master inductor circuit conductor network; and A passive inductor circuit disposed in the passive inductor assembly, the passive inductor circuit including: a passive heating inductor for heating the second bearing feature, the passive heating inductor including a single turn passive solenoid coil disposed at an end of the first support structure around an outer support structure of the vertical support structure having a central longitudinal axis of the vertical support structure; Passive flux couplers, and a passive inductor circuit conductor network that forms a closed series electrical circuit with the passive heating inductor; Including, 11. A split multi-coil electric induction heating system, comprising: a passive flux coupler disposed proximate to and physically separated by an air gap or a dielectric material gap, and a master flux coupler disposed proximate to and physically separated by the passive inductor circuit conductor network, such that the master inductor circuit and the passive inductor circuit are in a heating position of a bearing component for inductive heating of the first and second bearing features, and when a master circuit AC current is applied to a power terminal of the master inductor circuit, a magnetic field of the master inductor circuit couples with the passive inductor circuit via the passive flux coupler, which is magnetically coupled to the master flux coupler, to generate a passive circuit AC current in the passive inductor circuit conductor network.

11. 11. The split multi-coil electric induction heating system of claim 10, wherein the at least one first bearing feature or the at least one second bearing feature is at least partially disposed about an exterior of the master heating inductor and the passive heating inductor to inductively heat an internal bearing feature of the bearing component.

12. 11. The split multi-coil electric induction heating system of claim 10, further comprising at least one master inductor flux concentrator disposed above or below said single-turn master solenoid coil on said vertical mandrel.

13. 12. The split multi-coil electric induction heating system of claim 11, further comprising at least one passive inductor flux concentrator disposed above or below said single-turn passive solenoid coil on said vertical support structure.

14. 11. The split multi-coil electric induction heating system of claim 10, wherein the vertical mandrel has a plurality of quenchant openings for supplying quenchant from an interior plenum of the vertical mandrel to the first bearing feature and the second bearing feature.

15. 11. The split multi-coil electric induction heating system of claim 10, further comprising a split inductor assembly positioning device configured as: (a) positioning the master heating inductor of the master inductor assembly longitudinally in alignment with the passive heating inductor of the passive inductor assembly and positioning the passive flux coupler in close proximity to but physically separated from the master flux coupler when positioning the first bearing feature for inductive heating using the master heating inductor and positioning the second bearing feature for inductive heating using the passive heating inductor to simultaneously heat the first bearing feature and the second bearing feature; (b) longitudinally separating a master heating inductor of the split inductor assembly from the passive heating inductor of the split inductor assembly to place the bearing component in a heating position on the bearing component and inductively heat the at least one first bearing feature and the at least one second bearing feature, or to remove the bearing component after inductively heating the at least one first bearing feature and the at least one second bearing feature.

16. 1. A method for simultaneously heat treating a plurality of bearing features of a bearing component, comprising: assembling a split inductor assembly from the master inductor assembly and the passive inductor assembly; Here, a master inductor circuit is disposed in the master inductor assembly, and the master inductor circuit comprises: a master heating inductor for heating at least one first bearing feature of said bearing component; Master Flux Coupler, a power terminal of the master inductor circuit; and a master inductor circuit conductor network connecting a power supply terminal of the master inductor circuit to the master heating inductor, the master flux coupler being positioned in close proximity to the master inductor circuit conductor network and physically separated by an air gap or a dielectric material gap; Including, The passive inductor assembly includes a passive inductor circuit disposed therein, the passive inductor circuit comprising: a passive heating inductor for heating at least one second bearing feature of said bearing component; Passive flux couplers, and a passive inductor circuit conductor network forming a closed series electrical circuit with the passive heating inductor, the passive flux coupler being positioned proximate to the passive inductor circuit conductor network and physically separated by an air gap or a dielectric material gap, the passive flux coupler being positioned proximate to and physically separated from the master flux coupler; Including; positioning the bearing component with an inner longitudinal axis of the bearing component disposed within the master heating inductor and the passive heating inductor for inductive heating of the at least one first bearing feature using the master heating inductor and for inductive heating of the at least one second bearing feature using the passive heating inductor; applying a master alternating current to a power supply terminal of the master inductor circuit, whereby, when the master inductor circuit and the passive inductor circuit are in an assembled position, a magnetic field of the master inductor circuit couples with the passive inductor circuit through the passive flux coupler to generate a passive circuit alternating current in the passive inductor circuit conductor network and inductively heat the at least one first bearing feature and the at least one second bearing feature. A method comprising:

17. 17. The method of claim 16, further comprising at least partially disposing an outer longitudinal surface of the bearing component within the master heating inductor or the passive heating inductor to heat an external bearing feature of the bearing component.

18. 17. The method of claim 16, further comprising at least partially disposing an interior longitudinal surface of the bearing component within the master heating inductor or the passive heating inductor to heat an interior bearing feature of the bearing component.

19. 17. The method of claim 16, further comprising: separating the master inductor assembly and the passive inductor assembly toward opposite longitudinal ends of the bearing component for removing the bearing component from an assembly position after inductive heating of the bearing component; and coupling the master inductor assembly and the passive inductor assembly toward opposite longitudinal ends of the bearing component for positioning in an assembly position.

20. 17. The method of claim 16, further comprising quenching the austenitized regions of the at least one first bearing feature and the at least one second bearing feature at a remote quench station when the bearing component is disposed in an assembly position of the split inductor assembly, or in any one or combination of movement of the split inductor assembly from an assembly position and the remote quench station.

21. 1. A split multi-coil electric induction heating system having a split inductor assembly for simultaneously heating bearing features on a bearing component, the split inductor assembly comprising a master inductor assembly and a passive inductor assembly separable from a heating location on the bearing component, the split inductor assembly comprising: A master inductor circuit disposed in the master inductor assembly, the master inductor circuit including: a master heating inductor for partially heating said bearing features; Master Flux Coupler, a power terminal of the master inductor circuit; and a master inductor circuit conductor network connecting a power terminal of the master inductor circuit to the master heating inductor, the master flux coupler being positioned proximate to the master inductor circuit conductor network and physically separated by an air gap or a dielectric material gap; and A passive inductor circuit disposed in the passive inductor assembly, the passive inductor circuit including: a passive heating inductor for locally heating said bearing feature; Passive flux couplers, and a passive inductor circuit conductor network that forms a closed series electrical circuit with the passive heating inductor; Including, 11. A split multi-coil electric induction heating system, comprising: a passive flux coupler disposed proximate to and physically separated from the passive inductor circuit conductor network; and a passive flux coupler disposed proximate to the master flux coupler and physically separated by an air gap or a dielectric material gap, such that when the master inductor circuit and the passive inductor circuit are in a heating position for the bearing component for inductive heating of the bearing feature, and when a master circuit AC current is applied to a power terminal of the master inductor circuit, a magnetic field of the master inductor circuit couples with the passive inductor circuit via the passive flux coupler, which is magnetically coupled to the master flux coupler, to generate a passive circuit AC current in the passive inductor circuit conductor network.

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