Split multi-coil induction heat treatment system for simultaneous heating of multiple parts of bearing components

Abstract

The main inductor circuit is connected to an AC power source and the passive inductor circuit is assembled into a separable split inductor assembly to form at least one pair of a main heating inductor and a passive heating inductor, wherein the main and passive inductor circuits are electromagnetically coupled without physical connection. The bearing component can be subjected to the magnetic field generated by the main and passive heating inductors to simultaneously inductively heat one or more bearing features on the bearing component and subsequently quench the austenitized bearing features on the bearing component.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 970,237, filed on February 5, 2020, the entire contents of which are hereby incorporated by reference into this application. Technical Field

[0003] The present invention generally relates to the induction heat treatment of bearing components having bearing features such as bearing races and races, and more particularly to heat treatment of selected features of bearing races and races requiring metallurgical hardening. Background Art

[0004] The present invention relates to the induction heat treatment of bearing inner or outer races and raceways or other bearing features, for example, in components for powertrains, drivetrains and wheels. Bearings are critical machine elements that allow the components to move relative to each other. There are many variations in bearing race designs, many of which are standardized, depending on the specific application. This includes, but is not limited to, radial ball and roller bearings, and thrust ball and roller bearings. There are also single-row and multi-row bearings, as well as unidirectional and bidirectional bearing designs. Regardless of the design details, the bearing contact working surfaces need to be treated to ensure their wear resistance and strength over the life of the bearing, as well as to ensure some other mechanical properties, and induction hardening is one of the most commonly used methods of such heat treatment.

[0005] FIG1(a) shows a configuration of a bearing assembly 100 commonly used in the automotive industry in a cross-sectional perspective view. Most forged bearing races are manufactured using various steel grades. In less common applications, powder metallurgy materials and cast iron are also used. Bearing races can also be produced by additive manufacturing techniques, such as 3D printing processes.

[0006] FIG1(b) and FIG1(c) illustrate two alternative examples of induction surface hardening patterns for the inner race of a bearing assembly 100 configuration in a plan elevation cross section. FIG1(b) shows an intermittent bearing race hardening pattern containing two circumferential metallurgical hardened zones 101 and 102 (areas colored in solid black or cross-hatched) that are vertically separated by a non-hardened circumferential region 103, as shown in FIG1(a) and FIG1(b). Hardened zones 101 and 102 are bearing features or regions where rolling elements (e.g., balls or rollers) rest against the inner race 101a and 102a of the bearing, respectively. Depending on the specific application, the geometries of regions 101 and 102 can be the same or different. The hardening pattern shown in FIG1(b) is the most common mode because it provides the desired mechanical properties of the bearing contact surfaces where they are needed without hardening areas where contact wear does not occur, such as region 103. Hardening only bearing features or regions 101 and 102 not only helps to provide the desired engineering properties and minimal deformation characteristics after heat treatment, but also reduces the electrical energy required for heat treatment.

[0007] FIG1(c) illustrates an alternative type of hardening pattern 104 (solid black shaded area or cross-sectional area) used in certain specific applications. In this type of hardening pattern, in addition to the inner bearing contact surfaces (bearing features or areas 101a and 102a) being induction hardened, area 103 separating the inner bearing contact surfaces is also induction hardened. Pattern 104 is typically associated with at least two undesirable workpiece and process factors: excessive deformation characteristics and a significant increase in electrical energy required to harden all three areas (i.e., areas 101, 102, and 103). Here are some of the reasons why the hardening pattern shown in FIG1(b) is the most common compared to the hardening pattern shown in FIG1(c).

[0008] To induction heat treat a bearing race, in some processes, the 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 of the bearing component (workpiece) or the area to be heat treated) is moved to a heating position (method B). The invention disclosed herein can be used in a heat treatment apparatus and process of method A or method B or a combination of methods A and B, wherein the induction heating coil and the bearing race are moved relative to each other.

[0009] Conventional single-turn or multi-turn solenoid type coils (e.g., conventional prior art double-turn coils) are typically used to heat treat surfaces of bearing races. An induction coil is located outside the bearing race (in a configuration surrounding the bearing race) for heat treating the outer surface of the race. An induction coil is located inside the bearing race for heat treating its inner (internal) bearing surface. For convenience, the present invention is generally described herein for 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 bearing component surfaces. For example, Figures 1(d) and 1(e) show representative perspective views of a typically configured bearing race assembly 100', in which the outer (external) surface 100'a requires hardening. Figures 1(f), 1(g), 1(h), and 1(i) show planar cross-sections of a configured bearing outer race of a bearing assembly 400 having an inner surface region 401 that does not require induction hardening and a bearing feature or region that includes an outer (external) surface 402 that must be induction hardened. Depending on the particular application, the entire area of ​​the outer (external) surface 402 as shown in FIG. 1(h) (in the cross-hatched area 405) may require induction surface hardening; alternatively, selective bearing features or areas (each selective area is colored in cross-hatching), such as the selective area 403 shown in FIG. 1(f), the selective area 404 shown in FIG. 1(g), or the selective area 405 shown in FIG. 1(h) mentioned above, and the selective area 406 in FIG. 1(i) may require induction surface hardening. The hardening pattern shown in FIG. 1(i) represents an example of an intermittent hardening pattern.

[0010] The effectiveness of an internal cylindrical induction coil, compared to a similar coil used to heat the outer surface (or outside diameter) of a bearing, depends greatly on the magnetic field coupling gap from the coil to the workpiece (the bearing feature to be hardened). The electrical efficiency of the internal coil decreases rapidly as the magnetic field coupling gap increases. Therefore, in order to increase the electrical efficiency of the heating and minimize energy consumption, it is necessary to keep the field coupling gap from the coil to the workpiece as small as possible.

[0011] The reason that a solenoidal inductor used to heat an inner (internal) surface is not as efficient as a similar inductor (also called a coil or induction coil) used to heat an outer (external) bearing surface has to do with the electromagnetic ring effect. According to the electromagnetic ring effect, the coil current is concentrated on the inner diameter of the solenoidal coil, which represents a low impedance path, as described in Section 3.1.5 of the Handbook of Induction Heating (second edition; CRC Press; Boca Raton, FL, United States). When heating an inner (internal) diameter surface, the coil inner diameter is the area farthest from the heated inner diameter surface. Therefore, the electromagnetic coupling between the coil and the heated workpiece (i.e., the bearing feature to be heated) is greater than the actual air gap between the inner (internal) diameter of the workpiece and the outer diameter of the induction coil. This results in poor coil-workpiece field coupling (also called spatial proximity) and, therefore, a significant reduction in coil efficiency.

[0012] It is often required to install a flux concentrator inside the internal inductor to improve the electrical efficiency of the coil and reduce the coil current, especially for heating small to medium diameter internal surfaces. The flux concentrator produces an electromagnetic slot effect, which has a much greater impact on the coil current distribution than the electromagnetic ring effect, and forces the coil current to move to the outer area of ​​the coil, making it closer to the surface of the heated workpiece. This increases the magnetic field strength and heat intensity on the inner surface of the workpiece (bearing component) to be heated.

[0013] In order to minimize deformation after induction heat treatment and achieve heat treatment performance to extend the service life of the bearing race, it is important that the heat treatment process achieves a sufficient minimum hardness layer depth, but avoids: (1) causing excessive local surface depth; (2) excessively high temperatures during austenitization; and (3) disproportionately large differences in hardness layer depth within each bearing contact surface (such as in areas 101a and 102a of the bearing inner ring configured in Figure 1(b)). These heat treatment characteristics are one of the reasons why it is generally very desirable to obtain a hardness pattern that is as uniform as possible within each bearing contact surface area 101a and 102a.

[0014] Several factors make it challenging 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. Figure 1(a) to Figure 1(c)The workpiece geometry in the induction case hardening process. Corner areas that have a tendency to attract magnetic fields due to electromagnetic edge effects may produce a deeper hardness layer depth. In addition to this, near the bearing features including surface areas 101a and 102a, there are significantly different metal masses forming the workpiece (i.e., the bearing component), which can produce significantly different "cold sink" effects (axial and radial) on adjacent areas and lead to corresponding temperature deviations when induction case hardening the bearing inner ring (areas 101a and 102a).

[0015] The second factor is related to the difficulty of obtaining a contoured hardness pattern using a conventional single-turn or multi-turn solenoid-type coil (e.g., a conventional double-turn coil of the prior art). In order to position the solenoid-type hardening coil to a heating position inside the bearing race to harden its inner surface in the bearing features or regions 101 and 102 (e.g., as shown in FIG. 1( b)), there must be sufficient clearance to pass through the minimum diameter region (region 103 in FIG. 1( b)) during loading (to the heating position) and unloading (from the heating position) of the bearing race in the solenoid-type induction hardening coil. This results in variable electromagnetic coupling (spatial proximity) between the coil region where the current flows and the bearing inner race region that produces a non-uniform hardness pattern.

[0016] Figures 2(a) and 2(b) illustrate examples of the variable electromagnetic coupling phenomenon using cross-sectional views of a bearing inner race. In the examples shown in these figures, a copper tube having a circular cross-section (and coil turns 301 and 302) and a hollow internal water cooling channel is used for induction coil fabrication. In other embodiments, the induction coil may also be formed by: (1) machining a solid copper block by computer numerical control (CNC); (2) brazing appropriate copper components together; or (3) molding a shaped heating surface of the coil turns to accommodate the geometry of the bearing inner race regions 115a and 106a (Figure 2(a)) and the bearing inner race regions 125a and 126a (Figure 2(b)). Conventional flux concentrators 203 and 204 can be used to improve heating efficiency and concentrate the magnetic field generated by each coil turn 301 and 302 of the two-turn coil formed by copper tube for heating the inner race of the bearing in Figure 2(a) (areas 115 and 106) and the inner race of the bearing in Figure 2(b) of the alternative geometry (areas 125 and 126). The flux concentrators are typically made of standard laminated packages, pure ferrites, or conventional iron-based or ferrite-based powder materials containing pressed and / or sintered magnetic particles.

[0017] As shown in FIG. 2( a ), the coil turns 301 and 302 of the conventional prior art solenoid type double turn inductor copper tube are positioned to heat corresponding bearing features, including the surface (areas 115 a and 106 a) of the configured bearing inner ring on the bearing assembly 100 y. The longitudinal axis of symmetry 50 of the configured bearing inner ring component 100 y coincides with the longitudinal axis of symmetry of the copper tube solenoid type double turn coil. In the example of FIG. 2( a ), the upper radial gap 107 between the cross-hatched hardened area 106 and the tube 301 is the same in the circumferential direction (i.e., when comparing the radial gap 107 on the left and right cross-sectional sides of the planar cross-sectional view shown in FIG. 2( a )). Sufficient radial gap 107 allows the workpiece (configured bearing inner ring) to be safely moved into and out of the heating position, where the workpiece is shown in the heating position in FIG. 2( a ) or FIG. 2( b ) while the two turns of coils are raised (and / or the bearing inner ring is lowered) to the heating position.

[0018] During the heating and quenching cycles, the bearing race can be rotated (i.e., spun) about its longitudinal axis of symmetry using a suitable prior art rotating device (not shown) to uniformly distribute the radial-circumferential heating temperature. After the austenitizing stage is completed by induction heating, quenching can be performed in situ (at the heating position), for example using a spray quenching device known in the art, to quench the austenitized area and form the necessary martensitic structure. In other processes, quenching can be performed at a separate quenching position that is offset (i.e., away from the heating position) (e.g., by moving the heated workpiece (bearing assembly) to a vertical position above or below the heating position). The quenching process step can be performed using quenching equipment known in the art.

[0019] As can be seen from Figure 2(a), due to the different spatial proximity (electromagnetic coupling) between the current-carrying surface of the coil and different areas of the lower bearing inner ring surface, a significant uneven heating distribution will occur due to the different application of the electromagnetic proximity effect. After quenching, this will produce corresponding uneven hardening patterns in regions 115 and 125. In some applications, the uneven hardening pattern is manifested as a gradual decrease in the depth of the hardness layer. In other applications, rather than a gradual change in the hardness pattern of the region, the wavy hardness pattern area exhibits a combination of deeper or shallower hardness layer depths. For example, in local areas 115x and 115y in Figure 2(a) (and the enlarged partial view in Figure 2(c)) and local areas 125x and 125y in Figure 2(b) (and the enlarged partial view in Figure 2(d)), regions 115 and 125 exhibit a deeper hardness layer depth. In contrast, regions 115 and 125 exhibit shallower hardness layer depths in local region 115z in FIG. 2(a) (and the enlarged partial view in FIG. 2(c)) and local region 125z in FIG. 2(b) (and the enlarged partial view in FIG. 2(d)). In areas of the bearing inner ring where it is difficult to generate a sufficient heat source, attempts to ensure the required minimum surface depth may inevitably be associated with the necessity of severely overheating the adjacent local bearing race area, which has an adverse effect on the metallurgical properties of the hardened area and the engineering performance of the bearing race; therefore, overheating should be avoided. However, conventionally designed coils may inevitably be associated with the formation of uneven hardness patterns and excessive local heating.

[0020] Figure 3(a) to Figure 3(c) and Figure 4 FIG. 3( a ) is a diagram of an alternative prior art configuration of an induction coil that can be used for induction heat treating a bearing inner ring. FIG. 3( a ) shows a schematic top view of a prior art conventional solenoid inductor arrangement for loading (to a heating position) and unloading (from a heating position) a workpiece (configured bearing inner ring), similar to the arrangement shown in FIG. 2( a ) and FIG. 2( b ) and discussed above. In FIG. 3( a ) and FIG. 3( b ), the dashed circle schematically represents the inner circumferential boundary of the bearing inner ring 11 a, and the solid circle represents the current-carrying surface of the coil 22 facing the inner circumferential boundary of the bearing inner ring, as shown in the cross-sectional view in FIG. 3( c ).

[0021] During the operation of loading the workpiece into the heating position, the rotational longitudinal symmetry axis 11a′ of the configured bearing inner ring 11a coincides with the longitudinal symmetry axis 22a of the solenoid-type induction coil 22 to form a circumferentially uniform gap 23 between the configured inner bearing race (bearing inner ring) 11a and the induction coil 22 ( FIG. 3( a) ). Before the heating process step of the heat treatment process begins, the workpiece or the induction coil, or the workpiece and the induction coil, move in the radial direction (perpendicular to the bearing inner ring and the longitudinally symmetrical induction coil axis), resulting in a smaller gap 24 on the right side between the bearing inner ring and the induction coil, and a larger gap 25 on the opposite left side. Due to this movement, the electromagnetic coupling between the bearing inner ring and the coil in the smaller gap 24 is improved compared to the uniform gap 23, and concentrated heating occurs in the bearing race area around the smaller gap; otherwise, these bearing race areas will produce insufficient heat due to poor electromagnetic proximity. However, after this movement, the other opposite side will show a larger gap 25. Thus, in this approach, gap 24 is smaller than gap 25, which helps produce a more uniform hardening pattern in the bearing race region, as shown in FIG3( c ), but at the expense of poor electromagnetic coupling in the larger gap 25 in the horizontal region of the bearing race relative to the bearing race. During the heating process step in a heat treatment process using a conventional rotating device, the configured bearing inner ring is rotated (i.e., rotated using a rotating device) to uniformly distribute the circumferential temperature of regions 11aa and 11bb. After the austenitizing step is completed during the heat treatment process, quenching (using conventional quenching equipment) can be performed in situ (i.e., at the heating position) to quench the austenitized region and form the desired martensitic structure. In other heat treatment processes, quenching can be performed at a dedicated quenching position (i.e., moving the heated workpiece out of the heating position); for example, in a quench tank, the quench tank can be located below the heating position for lowering the heated workpiece into the tank, or in a spray quenching device near the heating position, the heated workpiece can be transferred to this position by an appropriate electromechanical transfer device.

[0022] Unfortunately, the heating method and apparatus shown in Figures 3(a), 3(b) and 3(c) are not without disadvantages. One disadvantage is the need to move the components at least vertically (e.g., during loading and unloading of the workpiece into and from the heating position) and radially (perpendicular to the vertical movement). Therefore, auxiliary electromechanical transmission equipment is required for vertical and radial movement, which results in additional cost and complexity of the heat treatment system. In addition, the improved spatial proximity (and the resulting improved electromagnetic coupling) on ​​one side of the smaller gap 24 is associated with a deterioration in electromagnetic coupling on the other side of the larger gap 25, which can worsen the heat treatment process sensitivity (with potential hardness pattern deviations) and reduce the electrical efficiency of the workpiece heating.

[0023] Figure 4 is a schematic diagram of an alternative induction coil (inductor) of the prior art. Figure 4, an arc-shaped inductor 40 (also known in the art as a hairpin inductor) is shown in three interconnected segments, as shown by 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 (as shown by stippled shading) is located between the heating segment 41 and the return current segment 43. All three inductor segments are electrically connected in series and connected to an alternating current power supply (AC PS in the figure). The magnetic flux concentrator 44 provides electromagnetic decoupling between the heating segment 41 and the return current segment 43 to shift the maximum density of the current flowing in the heating segment 41 toward the outer surface 41a of the heating segment, which will face the configured bearing inner race area (not shown) when the bearing inner race is in the heating position. Figure 4 The design of the hairpin inductor 40 shown improves the electromagnetic coupling between the inductor and the workpiece bearing inner race and simplifies the process of achieving a desired hardness pattern in certain applications. The workpiece (i.e., a bearing component having bearing inner race bearing features) is rotated during the heating process step and the quenching process step to even out the circumferential temperature distribution around the bearing inner race.

[0024] The arc-shaped inductor 40 provides a certain degree of process flexibility. However, it is not without the known disadvantages of the previous designs shown, such as Figure 3(a) to Figure 3(c) Among them, these include low energy efficiency and the fact that the induction heating equipment must be able to provide two movements (vertical and radial) in order to have a coil positioning close enough to the bearing race during the heating process step without obstructing complex geometries, such as the bearing inner race area 103 within the bearing inner race component 100 configured as shown in Figure 1 (b). In addition, the magnetic flux concentrator 44 ( Figure 4 ) can act as an electrical load with a tendency to magnetic saturation and overheating, which will reduce the overall reliability of the induction heating system.

[0025] In view of the prior art, an object of the present invention is to provide an electric induction heating system and method that provides a tighter electromagnetic coupling gap between the induction heating coil and the bearing features (e.g., the bearing raceway surface area) of the bearing component when in a metallurgical hardening heating position in an induction heating application, which will result in higher energy efficiency and better hardness pattern control than the prior art.

[0026] Another object of the present invention is to provide an electric induction heating system and method for bearing features having a contoured hardening pattern, including inner and outer bearing races (inner and outer races), with minimal dimensional and shape deformation during austenitization, reducing maximum and peak temperatures to produce a metallurgically sound microstructure, and reducing the likelihood of cracking of the bearing races during heat treatment.

[0027] Another object of the present invention is to provide an electric induction heating system and method that provides simultaneous heat treatment of multiple bearing features on a bearing assembly, wherein the different geometries of the multiple bearing features and the bearing assembly are not suitable for placement of the multiple bearing features near a single induction coil to allow efficient simultaneous heat treatment of multiple bearing features and / or multiple bearing components. Summary of the invention

[0028] In one aspect, the present invention is an electric induction heat treatment apparatus and method for metallurgically hardening one or more selected bearing features (e.g., one or more areas of an inner or outer bearing race) of a bearing workpiece, having a combined main inductor circuit and a passive inductor circuit connected to an AC power source, wherein the combination of the main circuit and the passive circuit are electromagnetically coupled to each other without physical and electrical connection to form at least one pair of complementary main inductor coils and passive inductor coils, the selected bearing feature is positioned about the complementary coil pair, the selected bearing feature is coupled to the magnetic field generated by the complementary coil pair, inductively heated to austenitize the selected bearing feature, and subsequently quenched to transform the metallurgical properties of the austenitized selected feature.

[0029] On the other hand, the present invention includes an apparatus and method for electric induction heat treatment of a bearing workpiece, wherein the bearing workpiece has at least two bearing features for metallurgical heat treatment, and in some embodiments of the present invention, these bearing features are separated from each other by bearing features that have not been heat treated. In some embodiments of the present invention, a bearing workpiece having a single bearing feature is subjected to metallurgical heat treatment, for example, a bearing workpiece having a single continuous bearing feature in FIG. 1( c). The apparatus and method include a main inductor circuit and a passive inductor circuit, wherein the main inductor circuit and the passive inductor circuit are physically separated from each other and there is no physical electrical connection between them. The main inductor circuit is supplied with main circuit alternating current from a power supply to a main inductor circuit conductor network, the main inductor circuit conductor network having at least one main heating inductor, the main heating inductor being configured to: perform first bearing feature induction heating before quenching the bearing workpiece; and a main circuit electromagnetic coupler. The passive inductor circuit includes a passive inductor circuit conductor network having at least one passive heating inductor configured to inductively heat a second bearing feature prior to quenching the bearing workpiece, and a passive circuit electromagnetic coupler. The main inductor circuit and the passive inductor circuit are moved to a workpiece heating position adjacent to each other. In one process application of the present invention, the main inductor circuit and the passive inductor circuit are located at the workpiece heating position, and the at least one main heating inductor and the at least one passive heating inductor are respectively configured to inductively heat the first bearing feature by a main circuit flow of the main circuit alternating current, and simultaneously inductively heat the second bearing feature by a passive current flow induced by magnetic flux coupling of the main circuit alternating current between the main circuit electromagnetic coupler and the passive circuit electromagnetic coupler.

[0030] After inductive heating of at least one first bearing feature and at least one second bearing feature is completed, the bearing workpiece is quenched according to the requirements of the specific application, for example, either quenched at the workpiece heating position using a quenching device integrated with at least one main heating inductor, the at least one passive heating inductor, and the at least one main and passive heating inductors, or quenched using a quenching device arranged at one or more quenching device positions away from the workpiece heating position.

[0031] These and other aspects of the present invention are set out in the specification and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings briefly summarized below are for illustrative understanding of the present invention and are not limiting of the present invention further described in the specification and appended claims.

[0033] 1(a) is a side perspective cross-sectional view of a bearing feature, namely a bearing inner race, configured in a bearing component, which is described as a bearing workpiece 100 and is typically used for heavy-duty bearings in automotive powertrain and drivetrain applications and other heavy-duty applications.

[0034] Figure 1(b) is a front cross-sectional view of the bearing inner ring configured in the bearing workpiece 100 in Figure 1(a), illustrating a longitudinal (along the longitudinal axis L) discontinuous hardness pattern, which includes two circumferentially hardened longitudinal zones (or regions) 101 and 102, separated by a circumferentially non-hardened longitudinal region 103.

[0035] Fig. 1(c) is a front cross-sectional view of a bearing inner ring configured in a bearing workpiece 100, illustrating a circumferential non-interrupted longitudinal hardness 104, which is an alternative to the longitudinally intermittent hardness pattern in Fig. 1(b). In Fig. 1(c), the bearing features, namely the configured bearing inner ring regions 101 and 102 (i.e., the bearing roller contact surface), are induction hardened together with the circumferential longitudinal region 103 between the bearing inner ring regions.

[0036] 1( d ) and 1 ( e ) are perspective views of a bearing outer ring arranged in a bearing workpiece 100 ′.

[0037] Figures 1(f), 1(g), 1(h) and 1(i) are cross-sectional views of a configured bearing outer ring of a bearing assembly 400, showing four optional hardening patterns (zones or areas) 403, 404, 405 and 406 (as indicated by cross-hatching) that may be formed in an alternative induction hardening process, as may be desired in an alternative application.

[0038] FIG. 1( j) is a side perspective cross-sectional view of a bearing inner ring configured in a bearing workpiece 100 ″, which is typically used for heavy-duty bearings in automotive powertrains and transmissions, as well as other heavy-duty applications, showing the bearing race areas having identical geometry and uniform (very desirable) hardening patterns 101 ″ and 102 ″.

[0039] Figure 1(k) is a cross-sectional elevation view of the inner ring of the bearing arrangement shown in Figure 1(j) showing an intermittent hardening pattern comprising two hardened zones 101" and 102" separated by a non-hardened zone (or area) 103".

[0040] FIG2(a) is a cross-sectional view of a configured bearing inner race showing various hardening patterns at the heating locations (in the cross-hatched areas 106 and 115) using a prior art induction heating device comprising a solenoid-type double-turn electrical heating inductor having coil turns 301 and 302 and associated flux concentrators 203 and 204. In FIG2(a), coil turn 301 heats around area 106 and coil turn 302 heats around area 115. Each coil turn can be connected in series or in parallel, with alternating current supplied to the coils by a suitably connected power source, and instantaneous current flows in the coil turns in the same or opposite directions.

[0041] FIG2( b ) is a cross-sectional view of a configured bearing inner race showing an alternative geometry and hardening pattern (including cross-hatched areas 125 and 126) of a bearing inner race in a heating position using a prior art induction heating apparatus including a solenoid-type double-turn electrical heating inductor with coil turns 301 and 302, and associated flux concentrators 203 and 204. Each coil turn may be connected in series or in parallel with alternating current provided by a suitably connected power source, with the alternating current flowing in the coil turns in the same or opposite directions.

[0042] FIG. 2( c ) and FIG. 2( d ) are enlarged views of selected hardening patterns shown in FIG. 2( a ) and FIG. 2( b ), respectively.

[0043] FIG3(a) and FIG3(b) are schematic diagrams of an induction heating process for heat treating a bearing inner race, conceptually showing uniform and non-uniform circumferential gap distances between an inductor and a bearing inner race 11a of a bearing workpiece, as shown by the dashed circle boundary of the heated inner race. FIG3(a) shows an example of the "workpiece to coil" mutual positioning during the process step of loading the bearing inner race 11a of a bearing workpiece within an inductor 22, with a uniform circumferential gap distance 23 between the inductor and the heated bearing inner race. FIG3(b) shows an example of the "workpiece to coil" mutual positioning during the process step of heating the bearing inner race 11a of a bearing workpiece within an inductor 22 at non-uniform circumferential electromagnetic coupling distances 24 and 25. FIG3(c) shows the resulting circumferentially uniform hardening patterns 11aa and 11bb, assuming that the workpiece is rotated (i.e., self-spinned) about an axis 50 sufficiently fast during induction heating using a conventional workpiece rotating device (not shown in the drawings).

[0044] Figure 4 is a schematic diagram of a prior art arc inductor 40 (also known as a hairpin inductor) that can be used to perform heat treatment on a bearing inner race.

[0045] Figure 5(a) to Figure 5(d) An embodiment of the electric induction heating system of the present invention is illustrated, showing the main inductor circuit (Figure 5(a)) and the passive inductor circuit (Figure 5(b)). Figures 5(c) and 5(d) are alternative perspective views of the main inductor circuit and the passive inductor circuit in the heating position of the workpiece (bearing component). For clarity, the inner race of the bearing (bearing feature) and the quenching device are not shown. The arrows indicate the relative instantaneous current direction in the heating system. Figure 5(c) shows the instantaneous current direction produced in the passive inductor 220 by this arrangement, which is opposite to the instantaneous current direction in the main inductor 210. This direction of current is generally preferred to obtain the intermittent hardening pattern shown in Figure 1(b).

[0046] FIG5(e) is a schematic diagram of an alternative passive inductor circuit that can be used with the main inductor circuit shown in FIG5(a) to produce a direction of instantaneous current in the passive inductor 220' that is the same as the direction of instantaneous current in the active coil 210 (FIG5(c)) in the main inductor circuit. This current direction is generally used to obtain the non-interrupted hardening pattern shown in FIG1(c).

[0047] Figures 5(f) and 5(g) illustrate alternative instantaneous AC current directions achieved in a passive inductor coil when the main inductor circuit in Figure 5(a) is combined with the passive inductor circuit in Figure 5(b) in one embodiment of the invention, compared to when the main inductor circuit in Figure 5(a) is combined with the passive inductor circuit in Figure 5(e) in another embodiment.

[0048] In some embodiments of the present invention, the primary heating inductor and the passive heating inductor are configured for reverse instantaneous current flow of the primary circuit alternating current and the passive circuit alternating current.

[0049] 6(a) shows the main electromagnetic coupling region 230 of the main inductor circuit and the passive electromagnetic coupling region 240 of the passive inductor circuit when the main inductor circuit is separated from the passive inductor circuit, for example, when a bearing workpiece to be heat-treated is loaded to or unloaded from a heating position within a pair of main inductors and passive inductors that complement each other in the main inductor circuit and the passive inductor circuit, respectively. The main electromagnetic coupling region and the passive electromagnetic coupling region are alternately referred to as the main flux coupler and the passive flux coupler, respectively.

[0050] FIG6( b) shows the main electromagnetic coupling region 230 of the main inductor circuit and the passive electromagnetic coupling region 240 of the passive inductor circuit when the main inductor circuit is brought to the workpiece heating position, wherein the active and passive electromagnetic coupling regions are separated by a gap 205 to electrically separate the active inductor circuit from the passive inductor circuit, and when an alternating current is supplied to the main inductor circuit, the main inductor circuit and the passive inductor circuit are electromagnetically coupled. In the workpiece (bearing component) heating position, the main flux coupler is arranged near the passive flux coupler and is physically separated from the passive flux coupler (by the gap 205 in the example of FIG6( b)).

[0051] Figures 7(a) and 7(b) show in cross section alternative embodiments of the form and composition of the main and passive electrical bus networks, with Figure 7(a) showing each bus network comprising copper tubes and Figure 7(b) showing rectangular copper strips sandwiched within the main and passive electromagnetic coupling regions, which are separated by respective gaps 205a (Figure 7(a)) and 205b (Figure 7(b)) when in the workpiece heating position. The gaps may be air gaps or filled with dielectric material. The arrangement shown in Figure 7(b) is generally preferred over the arrangement shown in Figure 7(a) because of better electromagnetic coupling between the active and passive circuits. The main electrical conductor network and the passive electrical conductor network are alternately referred to as the main inductor circuit bus network and the passive inductor circuit conductor network, respectively.

[0052] Figure 8(a) to Figure 8(d) An embodiment of the method of the present invention is illustrated for induction heat treating a bearing feature of a bearing component, such as an inner race or an outer race, wherein a quenching step is performed while the induction heating apparatus is still in a heating (heating) position after heating of the bearing feature is completed.

[0053] Figure 9(a) to Figure 9(d)Another embodiment of the method of the present invention is illustrated for inductively heat treating a bearing feature, such as an inner race or an outer race, of a bearing assembly, wherein a quenching process step is performed by immersing at least a passive inductor coil of a passive inductor circuit with the bearing feature in a quenching agent bath. In this embodiment, a corresponding portion 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.

[0054] Figure 10(a) to Figure 10(d) The diagram illustrates another embodiment of the method of the present invention, which is used for induction heat treatment of bearing features on a bearing workpiece, such as an inner race or an outer race of a bearing, wherein, after the bearing features on the bearing workpiece are induction heated in an assembly (heating) position, a quenching process step begins while the bearing workpiece is still in an induction heating device (Figure 10(b)), and the quenching process continues as the bearing workpiece with the heated bearing features is transferred to a quenching tank (Figure 10(c)) with a passive heating inductor coil 220 in a passive inductor circuit, and the quenching process is completed in the quenching tank.

[0055] Figures 11(a) and 11(b) illustrate another embodiment of the method of the present invention for induction heat treating bearing features of a bearing component, such as an inner race or an outer race of a bearing, wherein the bearing features on at least two separate bearing components (workpieces) are heated simultaneously and combined with a subsequent quenching process step after the simultaneous heating is completed.

[0056] FIG. 12( a ) shows an induction heating apparatus of the present invention, in which two separate bearing components (workpieces) can be heated simultaneously and used in the method shown in FIGS. 11( a ) and 11( b ).

[0057] FIG. 12( b ) is a partially enlarged detailed illustration of one end of the induction heating device shown in FIG. 12( a ).

[0058] Fig.13 is an embodiment of the present invention wherein the induction heating apparatus is located adjacent a vertically oriented rotary table upon which a plurality of individual workpieces may be loaded, for example, after preheating; rotated to a heat treatment position and loaded into the induction heating apparatus to heat treat bearing features; and rotated to a quench treatment position.

[0059] FIG. 14( a ) is a perspective view of a passive inductor assembly 800 b of an induction heat treatment apparatus 800 shown in the bearing component (workpiece) heating position in FIGS. 16( a ) and 16( b ).

[0060] FIG. 14( b ) is a top plan view of the passive inductor assembly shown in FIG. 14( a ).

[0061] FIG. 14( c ) is a side cross-sectional view of the passive inductor assembly shown in FIG. 14( a ).

[0062] FIG. 15( a ) is a perspective view of a main inductor assembly 800 a configured for induction heat treatment apparatus 800 , as shown in FIG. 16( a ) and FIG. 16( b ) in the bearing component (workpiece) heating position.

[0063] FIG. 15( b ) is a top plan view of the main inductor assembly shown in FIG. 15( a ).

[0064] FIG. 15( c ) is a side cross-sectional view of the main inductor assembly shown in FIG. 15( a ).

[0065] 16( a) and 16( b) are alternative perspective views of an example of an electric induction heat treatment apparatus 800 in which a passive inductor assembly 800 b ( FIG. 14( a) ) and a main inductor assembly 800 a ( FIG. 15( a) ) are configured in a workpiece heating position for electric induction heating of a workpiece bearing feature (e.g., a bearing inner race).

[0066] Figure 17(a) schematically shows another separate multi-coil electric induction heat treatment system for simultaneously heating one or more features of a bearing component, wherein the bearing component is configured with two independent main inductance circuits, each powered by a separate phase-locked output of a single power supply, and Figures 17(b) and 17(c) show the in-phase and out-of-phase output currents, respectively.

[0067] Fig.18 Another split multi-coil induction heat treatment system for simultaneously heating one or more features of a bearing component is illustrated, the bearing component being configured with two independent main inductor circuits powered by a single power supply, a single output feeding the primary side of a transformer, and two secondary outputs each feeding an independent main inductor circuit. DETAILED DESCRIPTION

[0068] Referring to the drawings, wherein like numerals represent like elements, Figure 5(a) to Figure 5(d) Schematically illustrated is an embodiment of the present invention having a main inductor circuit 200a and a passive inductor circuit 200b that can be assembled to induction heat treat an inner bearing race (bearing inner ring), an outer bearing race (bearing outer ring), or other bearing features of a bearing component, such as those used in heavy-duty applications using rolling elements, bearings, raceways, or rings, including powertrain applications, drivetrain applications, and wheel assemblies where the bearing component structure is complex. The bearing assembly may alternatively also be described herein as a bearing workpiece.

[0069] As shown in FIG. 5( c ) or FIG. 5( d ), the main inductor circuit and the passive inductor circuit form an assembled bearing workpiece electric induction heat treatment apparatus 200 , wherein, when the main inductor circuit on the main inductor assembly and the passive circuit on the passive inductor assembly are in the same bearing component heating position, as shown in FIG. 5( c ) or FIG. 5( d ), the main heating inductor and the passive heating inductor respectively configured for each of two or more different bearing features in the main inductor circuit and the passive inductor circuit can be used to heat treat the selected bearing features simultaneously. Therefore, the apparatus 200 can also be described as a split multi-coil (main heating inductor and passive heating inductor) with a split inductor assembly for simultaneously heating multiple bearing features on a bearing assembly, wherein the split inductor assembly is formed by the main inductor circuit on the main inductor assembly and the passive inductor circuit on the passive inductor assembly.

[0070] In the illustrated embodiment of the present invention, the main inductor circuit 200a includes a main heating inductor 210, which is composed of the following parts: a first single-turn inductor coil for inductively heating a first bearing feature to be simultaneously heat-treated on a bearing component; one or more main circuit flux coupling regions 230, forming a main flux coupler; and main inductor circuit power terminals 6a and 6b, all of which are electrically interconnected through the main inductor circuit conductor network 201 to form a series main circuit, and all components of the main circuit components are physically and electrically connected in series, except for the main flux coupler, which is not physically connected in the main inductor circuit and is separated by an air gap or a dielectric material gap. The main flux coupler is located near the main inductor circuit conductor network 201 and is physically separated from the main inductor circuit conductor network 201 to couple the magnetic flux from the main inductor circuit when alternating current flows in the main inductor circuit. Main inductor circuit power terminals 6a and 6b connect the main inductor circuit 200a to an appropriate AC power source (specified in the drawings as AC POWER SOURCE). The AC power source may be selected for a particular application from medium or high frequency power sources known in the art for selective heat treatment of bearing features, and input power may be provided from the utility power source on which the induction heat treatment equipment is located. Typical power ratings for the power source range from 30 kW to 500 kW, with operating frequencies from 1 kHz to 180 kHz, depending upon: the requirements for the specified hardened layer depth; the geometry of the heat treated bearing features; the quality of the heated metal material to form the bearing workpiece, and the productivity (cycle time per heat treated bearing feature). The single-phase, two-conductor output of the selected power source is connected directly to the main inductor circuit power terminals 6a and 6b: directly; or through a power bus network; or through a load matching transformer, depending upon the power supply configuration and the load matching capabilities of the power supply.

[0071] exist Figure 5(b) to Figure 5(d) In the illustrated embodiment of the present invention, the passive inductor circuit 200b includes a passive heating inductor 220, which is composed of the following parts: a second single-turn inductor coil for inductively heating a second bearing feature to be simultaneously heat-treated on the bearing assembly; 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 heating or assembly position shown in Figure 5 (c) or Figure 5 (d), the passive flux coupler is located near the passive circuit conductor network 202 and the main inductor circuit conductor network 201, and is physically separated from them by an air gap or a gap with a dielectric material so that when the main alternating current flows in the main inductor circuit, a passive alternating current is induced in the passive inductor circuit.

[0072] Although the primary and passive heating inductors are configured as single-turn solenoidal coils in the figures, other inductor configurations may be used in other examples of the present invention depending on the requirements of the specific configuration of the bearing features heated by the primary heating inductor or passive heating inductor, for example, depending on whether internal or external bearing features are to be heat treated.

[0073] In other examples of the present invention, the active heating inductor or the passive heating inductor can have a different configuration, such as a multi-turn coil. In addition, in other examples of the present invention, the main heating inductor or the passive heating inductor can heat more than one bearing feature, so that more than two bearing features can be heated simultaneously.

[0074] One or more main circuit flux coupling regions 230 forming the main flux coupler and one or more passive circuit flux coupling regions 240 forming the passive flux coupler can optionally be formed from the following materials: standard laminate packages; pure ferrite; or conventional iron-based or ferrite-based powder materials, including magnetic composite materials containing pressed and sintered magnetic powders known in the art.

[0075] In one embodiment of the present invention, the main inductor circuit 200a and the passive inductor circuit 200b are selectively placed together from opposite longitudinal side ends of a bearing workpiece (e.g., the bearing workpiece 100 having a selected plurality of bearing features in FIG. 1(b), such as a bearing inner race to be heat treated) during a heat treatment process step of loading the bearing workpiece for heat treatment with the apparatus (also referred to as assembling the electric induction heat treatment apparatus to a heating position). The process step of assembling the apparatus to a heating position is shown in FIG. 5(c), wherein the axis LL represents the central inner longitudinal axis LL of the example bearing workpiece 100 in FIG. 1(b), which is not shown in the main heating inductor 210 and the passive heating inductor 220 for clarity, wherein the main heating inductor descends from the top to the upper longitudinal side end LL of the bearing workpiece, as indicated by the motion direction arrow MC, and the passive heating inductor rises from the bottom to above the lower longitudinal side end of the bearing workpiece, as indicated by the motion direction arrow PC. Referring to Figures 12(a) and 12(b), the bearing workpiece 100 is located in the heating position of the heating device 245 within the main heating inductor 210a" and the passive heating inductor 220b". This configuration of assembling the equipment from the relative longitudinal side ends of the bearing workpiece to the heating position eliminates the possibility that the geometry of the main circuit inductor or the passive circuit inductor will physically interfere with the characteristics of the bearing workpiece being heated by the passive circuit induction or the characteristics of the bearing workpiece being heated by the active circuit induction, respectively. Similarly, when the main inductor circuit 200a and the passive inductor circuit 200b are separated from each other via the relative longitudinal side ends of the bearing workpiece, the heat treatment process step of unloading (removing) the heat-treated bearing workpiece from the heat treatment equipment is completed, as shown in the direction of the main heating inductor unloading movement arrow MO in Figure 5(c) and the direction of the passive heating inductor unloading movement arrow PO in Figure 5(c). The process steps of combining the main inductor circuit with the main heating inductor 210 and the passive inductor circuit with the passive heating inductor 220 together and separating them from the opposite longitudinal side ends LL of the bearing workpiece enable the main heating inductor 210 and the passive heating inductor 220 to be very close (typically 0.5 mm to 6 mm) to the bearing features to be heat treated by the main heating inductor and the passive heating inductor, respectively, when the bearing workpiece 100 has been loaded into the apparatus for heat treatment, such as the bearing race areas 101 and 102 in FIG. 1( b ). In this example, 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 hinder (interfere) the bringing together of the main heating inductor (coil) and the passive heating inductor (coil) to the workpiece loading (heating) position because it does not need to have a sufficiently large radial gap 107 as shown in FIG. 2( a ) during the workpiece loading and unloading process steps.

[0076] In some embodiments of the present invention, a split multi-coil electric induction heating system includes a split inductor assembly positioning device configured to: bring the main inductor circuit and the passive inductor circuit together to an assembly (heating) position as the main flux coupler and the passive flux coupler move, and separate the main inductor circuit and the passive inductor circuit from the assembly (heating) position, as shown by the arrows in FIG5(c), which may represent a linear actuator moving as shown by the arrows. In the assembly (heating) position, when the first bearing feature is positioned for inductive heating using the main heating inductor and the second bearing feature is positioned for inductive heating using the passive heating inductor to heat the first bearing feature and the second bearing feature simultaneously, the main heating inductor of the main inductor assembly is longitudinally aligned with the passive heating inductor of the passive inductor assembly, and the passive flux coupler is positioned adjacent to and physically separated from the main flux coupler. In the non-heating position, the main heating inductor of the main inductor assembly is separated from the passive heating inductor of the passive inductor assembly, used to position the bearing assembly in a bearing assembly heating position for inductively heating the first bearing feature and the second bearing feature, or to remove the first bearing feature and the second bearing feature of the bearing assembly bearing component heating position after inductive heating.

[0077] Figures 5(c) and 5(d) show perspective views of the main inductor circuit 200a and the passive inductor circuit 200b together in a bearing workpiece heating position, with a loaded bearing workpiece positioned within the main circuit inductor and the passive circuit inductor. The bearing workpiece (and optional post-heating quenching device) are not shown in these figures for clarity of the assembled main heating inductor and passive heating inductor circuits.

[0078] exist Figure 5(a) to Figure 5(d) In the illustrated embodiment of the present invention, the main inductor circuit conductor network 201 and the passive inductor circuit conductor network 202 are shown as copper tube buses, arranged between U-shaped main circuit flux coupling region 230 and passive circuit flux coupling region 240, respectively.

[0079] When in a workpiece heating position as shown in FIG5( c) or FIG5( d), and when performing one or more heat treatment process steps to heat a bearing feature of a bearing workpiece located near the primary and passive heating inductors, there is no physical contact or circuit contact between the elements of the primary inductor circuit 200a and the elements of the passive inductor circuit 200b. The primary inductor circuit flux coupling region 230 is disposed adjacent, but physically separated by a spacing distance 205 from the passive inductor circuit flux coupling region 240 as shown in the cross-sectional details in FIG5( c) or FIG5( d), to transfer magnetic flux established by the alternating current in the main inductor circuit conductor network to the passive inductor circuit.

[0080] Figures 16(a) and 16(b) show in alternative perspective views one embodiment of an induction heat treatment apparatus 800 configured in accordance with the present invention using an assembled induction heat treatment apparatus 200 similar to that shown in Figures 5(c) and 5(d). The configured induction heat treatment apparatus 800 is shown in Figures 16(a) and 16(b) in a bearing component (workpiece) heating position with an exemplary bearing workpiece 900 loaded in the apparatus for simultaneous heating of two bearing features on the bearing workpiece. In this non-limiting example, the bearing component has an upper bearing inner race to be heat treated (also referred to as a first workpiece bearing feature to be heated by a primary heating inductor) and a lower bearing inner race to be simultaneously heat treated (also referred to as a second workpiece bearing feature to be heated by a passive heating inductor), separated axially from each other by a center bearing workpiece feature that is not heat treated. The interior of the bearing workpiece 900, which is not visible in Figures 16(a) and 16(b) because the workpiece is loaded in the bearing component heating position of the apparatus 800, can be similar to the interior of the bearing workpiece 100 in Figures 1(a) and 1(b), for example, where the upper bearing inner race is the bearing inner race 101a; the lower bearing inner race is 102a; and the non-heated central bearing workpiece feature is the area 103 in Figures 1(a) and 1(b). The configured induction heat treatment apparatus 800 includes a configured main inductor component or portion 800a and a configured passive inductor component or portion 800b.

[0081] Figure 14(a) to Figure 14(c) 8 are various views of the passive inductor assembly 800b when configured separately from the active inductor assembly 800b, for example, in a bearing workpiece non-heating position. Figure 15(a) to Figure 15(c) 800a, when separated from the passive inductor component 800b, for example, in a bearing workpiece non-heating position. In this example of the present invention, the passive inductor component 800b is optionally referred to as the lower inductor component, and the main inductor component 800a is optionally referred to as the upper inductor component, for the convenience of describing the position direction, but not to limit the orientation direction of the passive inductor component and the main inductor component that form the induction heat treatment device 800.

[0082] The configured main inductor circuit 800a includes: a main heating inductor 710, formed in this non-limiting example by a first single-turn induction coil, mounted around and adjacent the lower end of the mandrel 420a; main circuit flux coupling regions 730a and 730b forming a main circuit flux coupler; and main inductor circuit power terminals 6a and 6b separated by an electrically insulating material 7; all of which are associated with the main inductor circuit conductor network 701. The main inductor circuit power terminals 6a and 6b connect the main inductor circuit 800a to an appropriate AC power source (designated AC POWER SOURCE in the drawings). The main heating inductor is configured for inductively heating a first workpiece bearing feature to be heat treated. In some embodiments of the present invention, the mandrel 420a is referred to as a quenching mandrel, as described below.

[0083] The configured main inductor circuit 800a also includes an optional upper main flux concentrator 203a, which is annular and arranged above the main heating inductor 710 around the quenching mandrel 420a, and an optional lower main flux concentrator 204a arranged below the main heating inductor for directing the induction heating flux to the first bearing workpiece feature heated by the main heating inductor 710.

[0084] The configured main inductor circuit 800a also includes components of an auxiliary main inductor circuit forced liquid cooling medium system, the main inductor circuit cooling medium is provided by the supply cooling tube 425a and the return cooling tube 425b, and circulates in the hollow internal channel in the main inductor circuit conductor network 701.

[0085] In this non-limiting example, the configured main inductor circuit 800a includes an optional integrated quenching device, namely a quenching mandrel 420a, whose quenching channel is not shown in the figure, which supplies quenchant to the heat treatment features of the bearing workpiece at the workpiece heating position, and the quenchant is supplied through quench supply ports 421a and 421b near the upper end of the quenching mandrel.

[0086] The configured main inductor circuit 800a also includes one or more main inductor circuit support structures, as required by the specific arrangement of the configured main inductor circuit. In the example shown in the figure, the configured induction heat treatment apparatus 800 includes, but is not limited to, support clamps 420b that hold the quenching mandrel 420a in place; support risers 420c; and adjustable support bridges 420d.

[0087] The passive inductor circuit 800b configured includes: a passive heating inductor 720, formed in this non-limiting example by a second single-turn induction coil, mounted around and near the upper end of the support column 410a (also referred to as the vertically oriented support structure); passive circuit flux coupling regions 740a and 740b forming a passive circuit flux coupler; all of these components are associated with a passive inductor circuit conductor network 702, which is also referred to as a passive inductor bus network, and forms an electrically closed-loop passive bus network. The passive heating inductor is configured for inductively heating a second workpiece bearing feature to be heat treated.

[0088] The configured passive inductor circuit 800b also includes an optional upper passive flux concentrator 203b, which is annular and arranged above the passive heating inductor 720 around the support column 410a, and an optional lower passive flux concentrator 204b, which is arranged below the main heating inductor to direct the induction heating flux to the bearing workpiece features heated by the passive heating inductor 720.

[0089] The passive inductor circuit 800b configured in the illustrated embodiment of the present invention also includes components of an auxiliary passive inductor circuit forced liquid cooling medium system, where the passive inductor circuit cooling medium is provided by the supply cooling tube 406a and the return cooling tube 406b and circulates through the hollow internal through-holes in the passive inductor circuit conductor network 702.

[0090] The configured passive inductor circuit 800b may also include one or more passive inductor circuit support structures, depending on the specific arrangement of the configured passive inductor circuit. In the example shown in the figure, the configured induction heat treatment device 800 includes but is not limited to support pillars 410a (also referred to as vertical oriented support structures); passive circuit inductor mounting bases 410b; passive circuit brackets 410c.

[0091] In the heat treatment process step of loading the bearing workpiece into the equipment for heat treatment, the configured main inductor circuit 800a and the passive inductor circuit 800b can be placed together from the opposite longitudinal side ends of the bearing workpiece (e.g., bearing workpiece 900, having multiple features of the selected bearing inner ring that need to be heat treated) (also referred to as assembling the electric induction heat treatment equipment). Assembling the equipment from the opposite side ends of the bearing workpiece eliminates the possibility that the geometry of the main circuit inductor or the passive circuit inductor will physically interfere with the features of the bearing workpiece to be heated by the passive circuit inductor or the features of the bearing workpiece to be heated by the active circuit inductor, respectively. Similarly, the heat treatment process step of unloading (removing) the bearing workpiece from the heat treatment equipment after heat treatment is accomplished by separating the configured main inductor circuit and the configured passive inductor circuit from each other from the opposite longitudinal side ends of the bearing workpiece. In some embodiments of the present invention (e.g., such as Figure 9(a) to Figure 9(d) and Figure 10(a) to Figure 10(d)), the configured passive inductor circuit 800b is separated from the configured main inductor circuit 800a, but not from the bearing workpiece (Figures 9(c) and 10(c)), and the bearing workpiece is located in the passive inductor and is dielectrically insulated from the passive inductor in a structure known in the art as a dielectric sleeve. Only after the quenching cycle is completed will the bearing workpiece be finally removed from the configured passive inductor circuit 800b. The process steps of bringing the main inductor circuit and the passive inductor circuit together and separating them from the opposite longitudinal side ends of the bearing workpiece allow the main heating inductor 710 and the passive heating inductor 720 to be placed in close proximity to the bearing feature to be heat treated by the configured main heating inductor and the passive heating inductor, respectively. Figure 5(a) to Figure 5(d) In the illustrated embodiment of the invention, the main inductor circuit conductor network 201 and the passive inductor circuit conductor network 202 are shown as copper tube buses arranged between the U-shaped main circuit flux coupling region 230 and the passive circuit flux coupling region 240 .

[0092] When the components of the configured main inductor circuit 800a and the components of the configured passive inductor circuit 800b are in a workpiece heating position, for example, in FIG. 16(a) or FIG. 16(b), when performing one or more heat treatment process steps, there is no physical contact or circuit contact between the components of the configured main inductor circuit 800a and the configured passive inductor circuit 800b. The configured main inductor circuit flux coupling regions 730a and 730b are arranged adjacent to each other, but as shown in FIG. 16(a) and FIG. 16(b), they are physically separated by a separation distance 705 from the configured passive inductor circuit flux coupling regions 740a (hidden in the drawings) and 740b to transfer the magnetic flux established by the alternating current in the main inductor circuit conductor network 701 to the passive inductor circuit conductor network 702. In some embodiments of the invention, an electrical insulator is placed between flux coupling regions 730a and 730b, and / or between flux coupling regions 740a (hidden in the drawing) and 740b and / or between the main inductor 701 and passive inductor 702 networks.

[0093] The bearing workpiece electric induction heating apparatus of the present invention, for example, the configured induction heat treatment apparatus 800, can be moved between workpiece heating positions by moving the configured main inductor circuit, or the configured passive inductor circuit, or both the configured main inductor circuit and the passive inductor circuit, relative to each other in a direction (or multiple directions) away from each other, as shown in FIG. 16(A) or FIG. 16(b), so that they are separated from each other and from the loaded bearing workpiece (e.g., the bearing workpiece 900 in FIG. 16(a) or FIG. 16(b)). As an example and not limitation, the separation movement between the configured main inductor and the passive inductor circuit for loading or unloading the bearing workpiece from the workpiece heating position shown in FIG. 16(a) or FIG. 16(b) (suitable workpiece electromechanical transmission device not shown in the figure) can be achieved by one or more suitable electromechanical linear or rotary actuators configured for directional movement as required by the specific application.

[0094] In use Figure 14(a) to Figure 16(b) After the illustrated electric induction heat treating apparatus 800 completes the heating cycle and properly austenitizes the selected bearing workpiece features, quenching of the heat treated workpiece bearing features may be accomplished using a quenching apparatus integrated with the heating apparatus or a quenching apparatus remote from the heating apparatus, as described herein or otherwise known in the art.

[0095] FIG7(a) and FIG7(b) show in cross-sectional view the main circuit and passive circuit magnetic flux coupling regions 230 and 240 (magnetic flux concentrators) shown in FIG6(b), which are optionally used in the following applications: (1) the main inductor and passive inductor bus network is formed by conductive tubes 201a and 202a (e.g., copper composition) inserted (also referred to as "sandwiches") between the electromagnetic coupling regions 230a and 240a in FIG7(a); or (2) the main and passive inductor bus network is formed by conductive rectangular strips 201b and 202b (e.g., copper busbars) or rectangular tubes (not shown) inserted (also referred to as "sandwiches") between the electromagnetic coupling regions 230b and 240b in FIG7(b) in an air gap or a dielectric material gap. The most commonly used is the rectangular copper busbar shown in FIG7(b).

[0096] The schematic heating position spacing air gap 205a in FIG. 7(a) and 205b in FIG. 7(b) are large enough to prevent arcing or shorting between the components of the main inductor circuit 200a and the components of the passive circuit 200b. Although air is not a preferred dielectric material, in alternative embodiments of the present invention, an air gap may be used as a sufficient dielectric or the heating position spacing gap 205a or 205b may be filled with conventional dielectric materials known in the art to electrically isolate the electrical conductors. Such conventional dielectric materials include dielectric tapes, ceramic coatings, or other electrically isolating materials known in the art.

[0097] The spacing gap 205a in FIG7(a) and the spacing gap 205b in FIG7(b) should not be too large to avoid negatively affecting the electromagnetic coupling between the main inductor circuit 200a and the passive inductor circuit 200b. Typically, but not limited to, the size of the spacing gaps 205a and 205b (FIG7(b)) is in the range of 0.5 mm to 6 mm, depending on the frequency, current size, and conditions of the working environment (such as, but not limited to, the presence of humidity, moisture, and conductive dust).

[0098] Reference is made to the teachings of U.S. Patent Nos. 6,274,857 and 6,859,125 regarding the manufacturing features of the primary and passive circuit flux coupling regions 230 and 240 for a particular application, including the selection of appropriate geometry for the flux coupling and methods of holding it in place, and the selection of an appropriate size of the spacing air gap 205.

[0099] In one embodiment of the present invention, after loading a workpiece having one or more induction heating features and positioning the main induction coil and passive induction coil of the apparatus of the present invention in a 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 to start the AC in the main inductor circuit. The main circuit and passive circuit flux coupling regions 230 and 240 provide electromagnetic coupling between the energized main inductor circuit and the electrically shorted passive inductor circuit, similar to the effect between transformer core windings. Due to the main circuit and passive circuit flux coupling regions, the AC current flowing in the main circuit inductor will instantaneously (virtually speaking) produce a current flowing in a closed-loop passive circuit, similar to the current in the primary and secondary windings of a power transformer.

[0100] As shown by the arrows in FIG. 5( c ), the direction of the instantaneous alternating current induced in the passive inductor circuit 200 b will be opposite to the direction of the source current flowing in the main inductor circuit. However, depending on the alternative circuit connections, the alternating current flowing in the main induction coil 210 of the main circuit 200 a and the passive induction coil 220 of the passive inductor circuit 200 b can be in opposite directions or in the same direction. For example, Figure 5(a) to Figure 5(c)The main circuit and passive circuit connection shown in the passive inductive circuit generates an alternating current in the passive inductive coil 220 of the passive inductive circuit, which is instantaneously directed in the opposite direction to the coil current in the main inductive coil 210 of the main circuit. This relatively opposite current orientation is conducive to obtaining the hardening patterns shown in Figures 1(b), 1(j) and 1(k), which are the most common ideal hardness patterns for most bearing inner rings, such as in automotive applications. In contrast, if the ideal hardness pattern is as shown in Figure 1(c), it is beneficial to change the circuit arrangement of the passive inductive circuit so that the direction of the instantaneous coil current flowing into the passive inductive coil 220 is the same as the direction of the main inductive circuit current provided by the connected power supply and flowing into the main inductive coil 210. A possible example of such a connection is shown in Figure 5(e). Figures 5(f) and 5(g) illustrate alternative instantaneous currents in the passive inductive coil of the passive inductive circuit. Figure 5(f) shows the instantaneous direction of the alternating current of the passive inductive circuit 200b with the passive inductive coil 220 of the circuit shown in Figures 5(b) and 5(c). Fig. 5(g) shows the instantaneous direction of the alternating current of the passive inductor circuit 200b' of the passive induction coil 220' shown in Fig. 5(e). Although the currents flowing in the passive circuit 202 shown in Fig. 5(f) and Fig. 5(g) have the same instantaneous direction, the direction of the current flowing in the passive induction coil 220' (Fig. 5(g)) is opposite to the direction of the current flowing in the passive coil 220 (Fig. 5(f)).

[0101] For typical design applications of induction heat treatment apparatus embodiments of the present invention, sufficient electromagnetic coupling between the main inductor circuit 200a and the passive inductor circuit 200b, the difference between the current flowing in the main induction coil 210 of the main inductor circuit 200a supplied from the AC power supply to the power terminal connections 6a and 6b and the current induced in the passive induction coil 220 of the passive inductor circuit 200b can be less than 10%, and the difference can be further compensated by profiling the geometry of the coil heating surface 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 main induction coil to workpiece gap is sufficient to compensate for the difference in the magnitude of the current flowing in the main induction coil 210 and the passive induction coil 220. In other embodiments of the present invention, it is beneficial to strategically position the bearing race at the heating location so that a lower mass area of ​​the bearing race area will be heated by the passive induction coil located in the passive induction circuit. For example, area 115 in FIG. 2( a) has a smaller metal mass that requires heat treatment than area 106 in FIG. 2( a); therefore, in the heating position, it is beneficial to position the passive induction coil 220 of the passive induction circuit (lower current amplitude) to heat the smaller mass area 115 and to position the main induction coil 210 of the active induction circuit (higher current amplitude) to heat the larger mass area 106.

[0102] In the exemplary case shown in FIG2(a), for illustration only, a water-cooled round copper tube is used for coil manufacturing. In other cases, the coil can be formed by the following optional methods: CNC machining of a solid copper block; brazing of suitable copper components; or die-casting of the shaped heating surface of the coil turns to fit the geometry of the bearing inner ring 115 or the coil, or can be manufactured using additive manufacturing techniques, such as 3D printing.

[0103] Conventional flux concentrators 203 and 204 can be used 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 race of the bearing. The flux concentrators are typically made of standard laminated packages, pure ferrite, or conventional iron-based or ferrite-based powder materials (such as magnetic composites) containing pressed and / or sintered magnetic powders.

[0104] Figure 5(a) to Figure 5(d)The coil configuration of the present invention shown allows for the smallest possible induction coil to workpiece clearance during loading and unloading without any limitations associated with the obstruction of the smaller diameter region 103 (e.g., as shown in FIG. 1( b)). Compared to the known prior art, the present invention provides a tighter coupling gap between the induction coil and the workpiece surface, thereby achieving high energy efficiency, better hardness pattern control, and also allows for a contoured hardening pattern with minimal dimensional and shape deformation, reduces the maximum temperature and peak temperature during austenitization, and produces a metallurgically good microstructure, reducing the likelihood of cracking of the bearing race during heat treatment and operation.

[0105] The induction heat treatment apparatus and method of the present invention may be alternately arranged in a vertical or horizontal orientation, depending on the needs of a particular application. 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 base (e.g., a workpiece resting structure (nest)) on which the bearing race to be heat treated is located. In this vertical arrangement, the bearing race located on the base may be raised (lifted) to a heating position and maintained in the heating position during the heat treatment cycle, as shown in FIGS. 8 to 10.

[0106] According to one possible design of the present invention, the induction coil of the main circuit 200a (FIG. 5(a)) remains stationary and the bearing race 100 (FIG. 1(a)) is moved into and out of the heating position after being positioned on a base (or on a resting nest as part of the passive circuit 200b including the induction coil 220). Since the passive circuit 200b represents a closed-loop electrical system, it can freely move into and out of the heating position, so there is no need for a high-current power connection cable to move with the passive circuit 200b. The mechanism for moving the workpiece into and out of the heating position can be hydraulic, pneumatic or electric.

[0107] According to another design concept of the present invention, the induction coil 210 of the main circuit 200a can move in and out of the heating position, but the bearing race 100 does not move in the axial direction.

[0108] Depending on the hardness pattern specifications and geometric elements of the bearing race surface, standard methods can be used to rotate (self-rotate) the bearing race during the heating cycle. Conventional lift-rotate configurations known in the art for small to medium-sized workpieces can provide a low-cost machine option. A cylinder can lift the workpiece bearing race into the working position and a motor begins to rotate the part. As an option, an adjustable hard stop can be used for part positioning. In this case, a fixed chuck or clamping block can hold the bearing race in the heating position while still allowing it to rotate during heating and without the need to remain stationary on the base during its rotation.

[0109] In other embodiments of the present invention, the workpiece bearing race 100 remains stationary during the heating process, as disclosed herein.

[0110] Single turn coils of conventional design have an area where magnetic field distortion inevitably occurs, resulting in some reduction in heat intensity there. This area is related to the area where the copper busbars that carry current from the power supply connect to the induction coil (the so-called polarized coil power lead area). The physical phenomenon that causes the reduction in heat intensity is called the electromagnetic field edge effect (also called the fishtail effect) and has been explained in the literature, such as the Induction Heating Handbook. Rotation of the workpiece during heating helps to eliminate (practically) the heat loss in the split area. If the workpiece bearing race is statically heated (not rotating), the heat intensity deviation there can still be minimized. The industry has developed various standard methods to effectively control and compensate for field edge effects in static induction heating applications using single turn coils through appropriate coil copper profiles. Improved electromagnetic coupling (proximity effect) in the split area of ​​the single turn coil compensates for the magnetic field edge and eliminates the need to rotate the heated workpiece. Those techniques for field strength compensation near the split area of ​​the coil have been disclosed in numerous publications, including U.S. Patent No. 6,274,857, and can be used in the present invention when the bearing race 100 is statically heated without rotation.

[0111] After completion of the heating cycle and proper austenitization, the bearing races can be quenched in situ or ex situ using conventional quenching techniques appropriate to the selected liquid quenchant or, where the steel has sufficient hardenability, by applying an alternative quenching medium to the liquid quenching medium such as forced air quenching or gas quenching.

[0112] Figure 8(a) to Figure 8(d) An embodiment of the bearing race heat treatment method of the present invention is illustrated. The electric induction heating device used in the method shown is formed, for example, by a main inductor circuit 200a (FIG. 5(a)) and a passive inductor circuit 200b (FIG. 5(b)). After the bearing race to be heat treated is loaded onto a loading and unloading mounting base or fixture (not shown in the figure), the fixture positions the unheat treated bearing race inside or outside the main inductor coil 210 of the main inductor circuit 200a (depending on whether the bearing race is an inner race or an outer race), and the heating device is in the separated (race loading position) in FIG8(a), and the entire passive inductor circuit 200b (including the passive coil 220, the passive circuit magnetic coupler 240 and the passive bus network 202) is lifted to the race heating position shown in FIG8(b). In the seat ring heating position, the main circuit and passive circuit electromagnetic couplers 230 and 240 are placed close to each other and surround the main bus network 201b and the passive bus network 202b formed by copper electrical conductors (see Figure 5(a) to Figure 5(c)) to generate an electromagnetic link 250 (shown as a dashed elliptical area in FIG8( b)) when the main inductor circuit 200a is powered by connection to an alternating current power source (TO AC PS). In the process step shown in FIG8( b), coils 210 and 220 are located in their respective heating positions to begin a heating cycle of the desired bearing race area, for example, if the heated bearing race is the bearing race 100 shown in FIG1( b), the desired area is the bearing race areas 101 and 102 in FIG1( b). After the heating cycle is completed, the main inductor circuit 200a is de-energized, the main inductor and passive inductor circuits are de-energized, and at this time, a spray quenching cycle is immediately initiated or initiated after a short time delay (also referred to as a soak time) for quenching the bearing race area loaded in the heating device shown in FIG8( c), wherein a conventional spray quenching device 71 (e.g., a spray quenching block or a liquid quenchant sprayer) can be used. Depending on the bearing race geometry and the desired hardness pattern, a short quench time delay can help achieve a suitable thermal profile. The quench delay is typically no longer than 5 seconds. After the spray quench cycle is completed, the heat treated bearing race (not shown) and the entire passive inductor circuit 200b are lowered to a bearing race unloading position as shown in FIG8(d) where the heat treated bearing race is unloaded from the pedestal. During the continuous sequential bearing race heat treatment process, a subsequent unheat treated bearing race is loaded onto the pedestal and repeated. Figure 8(a) to Figure 8(d) The above-mentioned induction heat treatment process described in.

[0113] Figure 9(a) to Figure 9(d) Another embodiment of the heat treatment method of the bearing race of the present invention is illustrated in the figure, similar to Figure 8(a) to Figure 8(d) Some process steps of the method described in Figure 9(a) to Figure 9(d) In the method, the first two process steps are as described above for the method steps shown in Figures 8(a) and 8(b), except that the quench tank 70 is located below the bearing race heating device. After the heating cycle is completed, the main inductor circuit 200a is powered off, the main inductor and passive inductor circuits are powered off, and the bearing race with the heated and austenitized bearing race area and the entire passive inductor circuit 200b are transferred from the bearing race heating position to below the surface of the fluid quenchant 70a in the quench tank 70, where the quench cycle begins, as shown in Figure 9(c). Preferably, but not limited to, the fluid quenchant is agitated (e.g., by stirring) in the quench tank to improve quench uniformity and other preferred cooling characteristics. After the quench cycle is completed, the quenched heat treated bearing race 100 (not shown) is lifted by its mounting seat or fixture to a position to unload from the passive inductor coil and removed from the mounting seat or fixture. During the continuous bearing race heat treatment process, the bearing race that has not been heat treated is then loaded onto the seat and repeated. Figure 9(a) to Figure 9(d) The above-mentioned induction heat treatment process described in.

[0114] Some steels that can be used to form bearing races have poor metallurgical hardenability and may therefore be sensitive to quenching delays that occur during transport of the bearing races to the quench tank, as described above with respect to Figure 9(a) to Figure 9(d) The temperature of such steels after heating and austenitizing may drop below the minimum required temperature level and metallurgically undesirable structures may form after delayed quenching. Figure 10(a) to Figure 10(d) Another embodiment of the bearing race heat treatment method of the present invention is illustrated. Figure 10(a) to Figure 10(d) The heat treatment method shown is Figure 9(a) to Figure 9(d) A variation of the method shown is modified. The process steps identified in Figures 9(a), 9(b) and 9(d) are similarly performed in the process steps identified in Figures 10(a), 10(b) and 10(d). The process steps identified in Figure 10(c) are modified from the process steps in Figure 9(c) wherein the jet quench block 72 quenches (as indicated by the quench jet arrows) the heated austenitized bearing race fixed relative to the passive inductor coil 220 as the entire passive inductor circuit 200b is lowered into the fluid quench 70a in the quench tank 70 along with the fixed heated austenitized bearing race to complete the quenching process. When immediate and / or uninterrupted quenching after austenitizing is desired due to the metallurgical properties of the heat treated bearing race, Figure 10(a) to Figure 10(d) The method shown in is particularly useful.

[0115] According to common industry practice for induction heat treatment processes, the workpiece quenching process step typically takes 2 to 4 times longer than the heating and austenitizing process steps. Figure 8(a) to Figure 8(d) ; Figure 9(a) to Figure 9(d) ;as well as Figure 10(a) to Figure 10(d) In certain applications of any of the methods disclosed herein, heat treating bearing raceways may be less productive and less energy efficient than desired.

[0116] FIG. 11( a) and FIG. 11( b) illustrate another embodiment of the bearing race heat treatment method of the present invention, which is an alternative method for increasing the productivity of heat treatment of bearing races and improving the utilization of power. The electric heating device used in the method shown is formed, for example, by a main inductance circuit 200a" having a plurality of main inductance coils 210a" and 210b" and a passive inductance circuit 200b" having a plurality of passive inductance coils 220a" and 220b" to form an electric induction heating device 245 as shown in the bearing race heating position in FIG. 12( a). The heating device 245 in FIG. 12( a) illustrates a method of the present invention for increasing the productivity of heat treating bearing races and improving the utilization of applied electric power. In the methods shown in FIGS. 11( a) and 11( b), the two bearing races (one each of the two main induction coil pairs and the passive induction coil pair) may be heat treated simultaneously and then quenched simultaneously using a suitable spray quenching apparatus known in the art (such as apparatus 73 in FIG. 11( a) or FIG. 11( b)) or an alternative quenching process step, such as, but not limited to, Figure 8(a) to Figure 8(d) ; Figure 9(a) to Figure 9(d) ;as well as Figure 10(a) to Figure 10(d) The method disclosed in .

[0117] FIG. 12( a) illustrates an alternative arrangement of the electric induction heating apparatus of the present invention in a heating position when multiple induction coils are used in the main circuit and the passive circuit, i.e., two coils 210 a ″ and 210 b ″ in the main inductor circuit, and two coils 220 a ″ and 220 b ″ in the passive inductor circuit, for simultaneously heating races on two bearing workpieces. In FIG. 12( a ), for convenience, only one bearing workpiece is shown. FIG. 12( b) is an enlarged view of the left end of the heating apparatus in FIG. 12( a ).

[0118] like Figure 11(a) to Figure 11(b) As shown, the plurality of coils 210a" and 220b" of the main inductor circuit 200a" are electrically connected in series. In an alternative arrangement of the electric heating device of the present invention, the plurality of coils 210a" and 220b" of the main inductor circuit 200a" may be electrically connected in parallel, or in combination of the above. Similarly, the plurality of coils 220a" and 220b" in the passive circuit 200b" may also be electrically connected in parallel or have a series / parallel combination of connections.

[0119] Rotating turntables can be used to increase productivity and quenching can be performed in multiple locations other than the heating position. This type of system can also be used if the component requires hardening of different areas on the same workpiece. The turntable can be arranged horizontally, vertically or at an angle.

[0120] Fig.13An example of an induction heating system of the present invention is shown, which includes a vertical turntable 330 having three stations for heat treating two workpiece bearings simultaneously. As indicated by the arrow, the turntable rotates counterclockwise, and two workpiece bearings 100x to be heat treated are loaded onto the turntable of the turntable station 333, which can be referred to as a pre-heat loading and post-heat unloading station; two workpiece bearings 100y are loaded into the dual workpiece heating device of the present invention (e.g., the heating device 245 shown in FIG. 12( a)), which is close to the turntable station 331 (bearing workpiece heating station), where the bearing races are loaded into the device 245; induction heating; austenitization and unloading from the device 245; the two heated and austenitized workpiece bearings 100z are located at the quenching station station 332, where they are quenched in the quenching agent 70a (shown as a dot-like quenching agent surface area) in the quenching tank 70. The turntable indexes two workpiece bearings at a time, from turntable station 331 to turntable station 332 to turntable station 333. In some embodiments of the present invention, an auxiliary jet quenching device (not shown) is installed between the heating station station 331 and the quenching station station 332 to quench the workpiece austenitizing bearing race features during transportation between these two stations. The auxiliary jet quenching device can be similar to the jet quenching block 72 in Figure 10 (c) to provide a static or stirred liquid quenchant. In other embodiments of the present invention, multiple turntable stations are provided for heating or quenching or optionally heating and quenching. In other embodiments of the present invention, the turntable is oriented horizontally or at an angle inclined or perpendicular to the horizontal. The bearing race features can be heated while fixed in the turntable heating device, or heated while rotating by conventional rotating devices known in the art (such as rotary actuators). In other embodiments of the present invention, a shuttle device is used to perform the function of the turntable to transport the workpiece bearings between different processing positions (e.g., from heating to quenching to loading and unloading positions).

[0121] 17( a) illustrates another aspect 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, and an alternating current (AC) power supply 160 a, the power supply 160 a comprising at least two phase-locked outputs 161 and 162. Any AC power supply 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 supplies), is suitable for use as the AC power supply 160 a as long as it has at least two phase-locked outputs 161 and 162.

[0122] The split inductor assembly includes two main inductor assemblies that can be separated at the bearing component heating position. The first main inductor circuit conductor network 6a and 6b connects the first phase-locked output 161 of the AC power supply 160a to the first main heating inductor 210 (as shown in Figure 17 (a)). The second main inductor circuit conductor network 6c and 6d connects the second phase-locked output 162 of the AC power supply 160a to the second main heating inductor 220.

[0123] Due to the phase locking capability of the AC power supply 160a output, the instantaneous inductor current flow in the first primary heating inductor 210 and the instantaneous current flow in the second primary heating inductor 220 can be oriented in opposite directions, as shown in the current waveform in FIG. 17(b), or the instantaneous inductor current in the first primary heating inductor 210 and the instantaneous current in the second primary heating inductor 220 can be oriented in the same direction, as shown in the current waveform in FIG. 17(c). Therefore, depending on the hardness pattern requirements of the bearing characteristics (e.g., the discontinuous bearing race hardness pattern shown in FIG. 1(b) or the non-discontinuous bearing race hardness pattern shown in FIG. 1(c)), this phase locking capability of the AC power supply output according to the alternative embodiment of the present invention will provide the desired ideal direction of the instantaneous current in the first primary heating inductor 210 and the second primary heating inductor 220 (similar to the directions shown in FIG. 5(c), FIG. 5(f), or FIG. 5(g)).

[0124] The electrical power provided by each of the at least two phase-locked outputs 161 and 162 of the AC power supply 160a (and, therefore, the electrical power provided to each heating inductor 210 and 220) is independently controlled, which allows compensation for possible differences in the heated metal mass shown in Figure 1(b) (compare areas 101 and 102 of the bearing feature or the areas where rolling elements (such as balls or rollers) abut against the inner races 101a and 102a of the bearing, respectively).

[0125] As an alternative to using a single AC power source 160a with phase-locking capability of multiple outputs 161 and 162, a person skilled in the art, with the benefit of the teachings of the above description, may use two different AC power sources with output power phase-locking capability instead of using the above single AC power source 160a. This modification does not depart from the scope of the present invention.

[0126] While the active-passive design concept (e.g., FIG. 5( c ) or FIG. 12( a )) is a more cost-effective approach because only a conventional and less complex AC power source 160 is required compared to a more complex AC power source 160 a, under certain conditions, using an AC power source 160 a including at least two phase-locked outputs 161 and 162 may be beneficial and preferably exhibit certain process advantages. The above certain conditions include, but are not limited to, higher frequency applications (e.g., frequencies in the range of 70 kHz to 600 kHz). In addition or as an alternative, these conditions also include applications where there are significant differences in the quality of the metals to be heated simultaneously (the above differences in quality may be related to corresponding differences in the geometry of the bearing features to be hardened) (compare areas 101 and 102 of the bearing features or areas where the rolling elements abut against the bearing inner rings 101 a and 102 a, respectively, as shown in FIG. 1( b )). Alternatively, in addition or as an alternative to these conditions, applications where the bearing component consists of more than two bearing features that need to be heat treated simultaneously and have substantially different geometries are also included. Alternatively, in addition to or as an alternative to these conditions, applications where the bearing component consists of multiple bearing features that exhibit a combination of interrupted and non-interrupted hardness patterns are also included. These are just a few preferred exemplary situations for using an induction heating system with multiple main inductors (e.g., Figure 17(a)).

[0127] Fig.18 Another aspect of the present invention is schematically illustrated, including a split multi-coil electric induction heating system having a split inductor assembly for simultaneously heating multiple bearing features on a bearing assembly, including a conventional AC power source 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 respective main inductors 210 and 220 via respective outputs 161a and 162a of the output transformer 222 and respective main inductor circuit conductor networks 6a-6b and 6c-6d.

[0128] The first main inductor circuit conductor network 6a and 6b connects the first output 161a of the transformer 222 and the first main heating inductor 210. The second main inductor circuit conductor network 6c and 6d connects the second output 162a of the transformer 222 and the second main heating inductor 220 (see Fig.18 ).

[0129] Each of the two main inductor circuit conductor networks 6a-6b and 6c-6d can be controlled by standard power control devices ( Fig.18The heating inductors 210 and 220 may be independently regulated by a thyristor-based or thyristor-based AC regulator, as are known in the art and commonly used in the industry.

[0130] By changing the relative configuration of the secondary windings 222b and 222c of the transformer 222 with respect to each other, the instantaneous currents flowing through the heating inductors 210 and 220 can be directed in the same direction or in opposite directions (whichever is required to obtain the desired hardness pattern) with respect to each other. In applications where an interrupted hardness pattern is desired (e.g., as shown in FIG. 1( b)), it is advantageous to configure the secondary windings 222b and 222c of the transformer 222 in such a manner that the instantaneous currents flowing in the heating inductors 210 and 220 will be directed in opposite directions. Conversely, if an uninterrupted hardness pattern is desired (e.g., as shown in FIG. 1( c)), it is advantageous to configure the secondary windings 222b and 222c of the transformer 222 in such a manner that the instantaneous currents flowing in the heating inductors 210 and 220 will be directed in the same direction.

[0131] The active-passive design concept (e.g., FIG. 5( c ) and FIG. 12( a )) is more cost-effective and is a relatively simple design that can eliminate the need to use a transformer 222 having at least two secondary windings in a specific configuration. However, in some cases, the use of Fig.18 The circuit shown may show certain process advantages. These situations include, but are not limited to, applications with medium and low frequencies (e.g., in the 500 Hz to 6 kHz range). Alternatively, in addition to or as an alternative to these situations, applications where a fairly deep hardness layer depth is required (e.g., a layer depth of 3 mm to 9 mm deep). Additionally, or as an alternative, these situations also include applications where there are significant differences in the mass of metal that needs to be heated simultaneously (this is related to corresponding differences in the geometry of the bearing features that need to be hardened, such as areas 101 and 102 of the bearing feature, or the areas where the rolling elements abut against the bearing inner rings 101a and 102a, respectively, as shown in Figure 1(b)). These are just some of the uses Fig.18 Several exemplary situations where an induction heating system may be beneficial are shown.

[0132] In the above embodiments of the present invention, a single turn inductor is used. In alternative embodiments of the present invention, two or more turn induction coils are used (for example, multi-turn active coils and multi-turn passive coils may also be used instead of single turn inductor types, depending on the specific application).

[0133] In the above-described embodiment of the present invention, the main coil and the passive coil use a coil copper round tube. In alternative embodiments of the present invention, other coil configurations are used for specific applications, including special-shaped copper coils.

[0134] The flux concentrators of the above-specified geometries, such as U-shaped or annular flux compensators, may have alternative geometries or be assembled from flux concentrators of other shapes as required by a specific application.

[0135] When the inner surface (inner ring) of a thin-walled bearing component is heated for austenitization, the outer surface can be spray quenched during the entire thermal cycle or part of the thermal cycle. This helps to prevent (if necessary) through hardening or excessive hardening depth when heat treating the thin-walled bearing component. Similarly, in order to prevent (if necessary) through hardening or excessive hardening when heating the outer surface (outer ring), the inner surface can be spray quenched.

[0136] Alternative embodiments of the induction heat treatment apparatus and method are applied to applications where the bearing race surface or the race area to be heat treated is not the inner race of the bearing, such as, but not limited to, 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, for example, the outer bearing race, complementary main inductor coils, and passive inductor coils can be configured to be arranged around the outside of the outer bearing in a heating position.

[0137] The present invention has been described according to preferred examples and embodiments. Except as explicitly stated, equivalents, substitutes and modifications are possible within the scope of the present invention. Those skilled in the art will benefit from the teachings of this specification and may modify it without departing from the scope of the present invention.

Claims

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 comprising a main inductor assembly and a passive inductor assembly separable from a bearing component heating location, the split multi-coil electric induction heating system comprising: A main inductor circuit is provided on the main inductor assembly, the main inductor circuit comprising: a primary heating inductor for heating at least one first bearing feature; Main flux coupler; a main inductor circuit power supply terminal; and a main inductor circuit conductor network connecting the main inductor circuit power terminals to the main heating inductor, the main flux coupler being disposed proximate to and physically isolated from the main inductor circuit conductor network by an air gap or a gap of dielectric material; and A passive inductor circuit is arranged on the passive inductor component, the passive inductor circuit comprising: a passive heating inductor for heating at least one second bearing feature; Passive flux couplers; and a passive inductor circuit conductor network forming a closed series circuit with the passive heating inductor, the passive flux coupler being arranged adjacent to and physically separated from the passive inductor circuit conductor network, the passive flux coupler being located adjacent to and physically separated from the main flux coupler by an air gap or a dielectric material gap, so that when the main inductor circuit and the passive inductor circuit are in a bearing component heating position, the at least one first bearing feature and the at least one second bearing feature are inductively heated at the position, and when main circuit alternating current is applied to the main inductor circuit power terminal, the main inductor circuit magnetic field is coupled to the passive inductor circuit through the passive flux coupler magnetically coupled to the main flux coupler to generate a passive circuit alternating current in the passive inductor circuit conductor network.

2. The split multi-coil electric induction heating system of claim 1, wherein the primary heating inductor comprises a single-turn solenoid coil, and the passive heating inductor comprises a single-turn solenoid coil, wherein, The primary heating inductor is offset from the primary inductor circuit conductor network, and the passive heating inductor is offset from the passive inductor circuit conductor network, and when in the bearing component heating position, the primary heating inductor and the passive heating inductor are coaxially aligned along the longitudinal axis of the bearing component.

3. The split multi-coil electric induction heating system of claim 1 , wherein the at least one first bearing feature or the at least one second bearing feature is at least partially located around the exterior of the primary heating inductor or the passive heating inductor to inductively heat the internal bearing features of the bearing component.

4. The split multi-coil electric induction heating system of claim 1 , wherein the at least one first bearing feature or the at least one second bearing feature is at least partially located around the interior of the primary heating inductor or the passive heating inductor to inductively heat the external bearing features of the bearing component.

5. The split multi-coil electric induction heating system of claim 1, wherein the primary heating inductor and the passive heating inductor are configured for opposing instantaneous current flows.

6. The split multi-coil electric induction heating system according to claim 1, further comprising a split inductor assembly positioning device, which is configured as follows: (a) longitudinally aligning a primary heating inductor of the primary inductor assembly with a passive heating inductor of the passive inductor assembly and positioning the passive flux coupler proximate to and physically separated from the primary flux coupler when the at least one first bearing feature is positioned for inductive heating with the primary heating inductor and the at least one second bearing feature is positioned for inductive heating with the passive heating inductor to simultaneously heat the at least one first bearing feature and the at least one second bearing feature; and (b) longitudinally separating the main heating inductor of the main inductor assembly from the passive heating inductor of the passive inductor assembly, thereby positioning the bearing component in a bearing component heating position to inductively heat the at least one first bearing feature and the at least one second bearing feature, or removing the bearing component after inductively heating the at least one first bearing feature and the at least one second bearing feature in the bearing component heating position.

7. 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 having a quenchant application device for quenching, alternatively or in combination, at the bearing component heating location, in a transfer transition from the bearing component heating location to a remote quenching station, or at the remote quenching station.

8. The split multi-coil electric induction heating system of claim 1 , further comprising a second main heating inductor electrically connected in series with the main 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 split-type multi-coil electric induction heating system according to claim 8, wherein the main inductor assembly and the passive inductor assembly are configured adjacent to a bearing workpiece heating station, and the split-type multi-coil induction heating system further comprises: Rotating table, including: The bearing workpiece turntable heat pre-loading and heat post-unloading stations are used to load the bearing component and the second bearing component onto the turntable, and unload the bearing component and the second bearing component from the turntable; a bearing workpiece heating station for loading the bearing component and the second bearing component into the main inductor assembly and the passive inductor assembly for induction heating, and unloading the bearing component and the second bearing component from the main inductor assembly and the passive inductor assembly after induction heating; a bearing workpiece quenching station for quenching the bearing component and the second bearing component after induction heating; and A rotary actuator is used to move the bearing component and the second bearing component from the bearing workpiece turntable thermal pre-loading and post-heat unloading station, the bearing workpiece heating station, the bearing workpiece quenching station and the bearing workpiece turntable thermal pre-loading and post-heat unloading station.

10. 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 comprising a main inductor assembly and a passive inductor assembly separable from a bearing component heating location, the split multi-coil electric induction heating system comprising: A main inductor circuit is arranged on the main inductor assembly, the main inductor circuit comprising: a primary heating inductor for heating the first bearing feature, the primary heating inductor comprising a single turn primary solenoid coil disposed at the first mandrel end about an outer mandrel perimeter of a vertically oriented mandrel having a vertically oriented mandrel central longitudinal axis; Main flux coupler; a main inductor circuit power supply terminal; and a main inductor circuit conductor network connecting the main inductor circuit power terminals to the main heating inductor, the main flux coupler being disposed proximate to and physically separated from the main inductor circuit conductor network; and A passive inductor circuit is arranged on the passive inductor component, the passive inductor circuit comprising: a passive heating inductor for heating the second bearing feature; the passive heating inductor comprising a single turn passive solenoid coil disposed at an end of the first support structure and around an outer support structure perimeter of the vertically oriented support structure having a central longitudinal axis of the vertically oriented support structure; passive flux couplers; and a passive inductor circuit conductor network forming a closed series circuit with the passive heating inductor, the passive flux coupler being arranged adjacent to the passive inductor circuit conductor network and separated by an air gap or a dielectric material gap, the passive flux coupler being located adjacent to and physically separated from the main flux coupler, so that when the main inductor circuit and the passive inductor circuit are in a bearing component heating position for inductively heating the first bearing feature and the second bearing feature, and main circuit alternating current is applied to the main inductor circuit power terminal, the main inductor circuit magnetic field is coupled to the passive inductor circuit through the passive flux coupler magnetically coupled to the main flux coupler to generate a passive circuit alternating current in the passive inductor circuit conductor network.

11. The split multi-coil electric induction heating system of claim 10, wherein the first bearing feature or the second bearing feature is at least partially located around the exterior of the primary heating inductor and the passive heating inductor to inductively heat the internal bearing features of the bearing component.

12. The split multi-coil inductor heating system of claim 10, further comprising at least one main inductor flux concentrator located above or below the single-turn main solenoid coil on the vertical axis.

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

14. The split multi-coil inductor heating system of claim 10, wherein the vertically oriented mandrel has a plurality of quenchant openings for supplying quenchant from an interior chamber of the vertically oriented mandrel to the first and second bearing features.

15. The split type multi-coil electric induction heating system according to claim 10, further comprising a split type inductor assembly positioning device, which is configured as follows: (a) longitudinally aligning a primary heating inductor of the primary inductor assembly with a passive heating inductor of the passive inductor assembly and positioning the passive flux coupler proximate to and physically separated from the primary flux coupler when the first bearing feature is positioned for inductive heating with the primary heating inductor and the second bearing feature is positioned for inductive heating with the passive heating inductor to simultaneously heat the first bearing feature and the second bearing feature; and (b) longitudinally separating the primary heating inductor of the split inductor assembly from the passive heating inductor of the split inductor assembly to position the bearing component to inductively heat the first bearing feature and the second bearing feature, or removing the bearing component after inductively heating the first bearing feature and the second bearing feature.

16. A method for simultaneously heat treating a plurality of bearing features on a bearing component, the method comprising: Assemble the split inductor assembly, which consists of: the main inductor assembly and the passive inductor assembly, a main inductor circuit disposed on the main inductor assembly, the main inductor circuit comprising: a primary heating inductor for heating at least one first bearing feature on the bearing component; Main flux coupler; a main inductor circuit power supply terminal; and a main inductor circuit conductor network connecting the main inductor circuit power terminals to the main heating inductor, the main flux coupler being disposed adjacent to and physically isolated from the main inductor circuit conductor network by an air gap or a gap of dielectric material; and A passive inductor circuit is provided on the passive inductor component, the passive inductor circuit comprising: a passive heating inductor for heating at least one second bearing feature on the bearing component; passive flux couplers; and a passive inductor circuit conductor network forming a closed series circuit with the passive heating inductor, the passive flux coupler being disposed adjacent to the passive inductor circuit conductor network and physically isolated from the passive inductor circuit conductor network by an air gap or a dielectric material gap, the passive flux coupler being disposed adjacent to and physically separated from the main flux coupler; positioning the bearing component so that a longitudinal inner axis of the bearing component is disposed within the primary heating inductor and the passive heating inductor for inductively heating the at least one first bearing feature with the primary heating inductor and inductively heating the at least one second bearing feature with the passive heating inductor; A main alternating current is applied to the main inductor circuit power terminals so that when the main inductor circuit and the passive inductor circuit are in an assembled position, the main inductor circuit magnetic field is coupled to the passive inductor circuit through the passive flux coupler to produce passive circuit alternating current inductive heating of the at least one first bearing feature and the at least one second bearing feature in the passive inductor circuit conductor network.

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

18. The method of claim 16, further comprising positioning an inner longitudinal surface of the bearing component at least partially within the primary or passive heating inductor to heat internal bearing features on the bearing component.

19. The method according to claim 16 further includes separating the main inductor component and the passive inductor component in the relative longitudinal end direction of the bearing component to remove the bearing component from the assembly position after the bearing component is inductively heated, and combining the above-mentioned main inductor component and the passive inductor component in the relative longitudinal end direction of the bearing component to be positioned in the assembly position.

20. The method of claim 16, further comprising quenching austenitized regions of the at least one first bearing feature and the at least one second bearing feature, wherein Alternatively or in combination the bearing component is arranged at an assembly location of the split inductor assembly; at a remote quenching station; or in combination at a transition from an assembly location of the split inductor assembly and a remote quenching station.

21. 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 main inductor assembly and a passive inductor assembly separable from a bearing component heating location, the split multi-coil electric induction heating system comprising: a main inductor circuit disposed on the main inductor assembly, the main inductor circuit comprising: a primary heating inductor for partially heating the bearing feature; Main flux coupler; a main inductor circuit power supply terminal; and a main inductor circuit conductor network connecting the main inductor circuit power terminals to the main heating inductor, the main flux coupler being disposed adjacent to and physically isolated from the main inductor circuit conductor network by an air gap or a gap of dielectric material; and A passive inductor circuit is provided on the passive inductor component, wherein the passive inductor circuit comprises: a passive heating inductor for partially heating the bearing feature; passive flux couplers; and a passive inductor circuit conductor network forming a closed series circuit with the passive heating inductor, the passive flux coupler being disposed adjacent to and physically isolated from the passive inductor circuit conductor network, the passive flux coupler being located adjacent to and physically isolated from the main flux coupler by an air gap or a dielectric material gap, such that when the main inductor circuit and the passive inductor circuit are in a bearing component heating position for inductively heating the bearing feature, and main circuit alternating current is applied to the main inductor circuit power terminal, the main inductor circuit magnetic field is coupled to the passive inductor circuit through the passive flux coupler magnetically coupled to the main flux coupler to generate a passive circuit alternating current in the passive inductor circuit conductor network.

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