HK1164032A - Induction heat treatment of complex-shaped workpieces - Google Patents

Description

Induction heat treatment of complex-shaped workpieces

Cross reference to related applications

The present application claims benefit of U.S. provisional application 61/145,541, filed on.1/17/2009, which is hereby incorporated by reference in its entirety.

Technical Field

The present invention relates generally to the induction heat treatment of complex-shaped metal workpieces having one or more cylindrical components.

Background

U.S. Pat. No. 6,274,857 (the 857 patent), which is incorporated herein by reference in its entirety, discloses a method and apparatus for induction heat treatment of an irregularly shaped workpiece, such as a selected component of a crankshaft. Using the reference numbers in the 857 patent and referring to the drawings, a typical paired pair of bottom and top inductor segments (107) and (109) is shown in patent figures 2(a), 2(b) and 2(c), respectively. The bottom inductor segment is connected to an alternating current (ac) power source at a power termination region (122) to form a single series loop active circuit from a pair of coil segments located near the through opening (117 a). Thus, the bottom inductor segment is also referred to as the active inductor segment. The corresponding top inductor segment (fig. 2(b) of the patent) is a single-turn closed-loop coil, which can also be called a passive inductor segment. At least one pair of coil lips, such as coil lips (123a) and (123b), are formed around a partial opening, such as partial opening (121a), in at least one coil segment. A second pair of coil lips is formed in the top inductor segment, for example near the partial opening (121b), such that when the paired bottom and top inductor segments are in a closed position, as shown in patent fig. 2(c), a substantially closed inductor is formed around the workpiece member (207), as shown in patent fig. 6 (a). The workpiece member (207) may be, for example, a crankpin on a crankshaft to which a piston connecting rod is to be connected after metallurgical quenching. Either end of the aforementioned pin may be connected to a counterweight (irregularly shaped adjacent workpiece members (206) and (208) in fig. 6(b) or 6(c) of the patent). When the bottom and top inductor segments are in the closed position and ac current is supplied to the bottom inductor segment (107), flux concentrators such as concentrators (103a) and (103b) in patent fig. 2(c) are used to magnetically couple the magnetic flux around the bottom inductor segment that is generated by the current flow in the bottom (active) inductor segment, such that current is induced in the top (passive) inductor segment in a transient direction opposite to that in the bottom inductor segment. In the closed position, the dielectric material (410) separates the oppositely facing surfaces of the bottom and top inductor segments as shown in patent fig. 2 (c). As shown in the patent figures, one or more side shields may be provided on one or both of the inner and outer sides of the coil segment near the arcuate coil region formed around the coil lip to serve as flux concentrators for the heat treated workpiece components and as magnetic field shields for the workpiece components adjacent to the heat treated components. While the above description describes the bottom and top inductor segments as a single turn single coil, the 857 patent also discloses that a single coil may be provided in which one or both of the bottom and top inductor segments are of two or more turns to reinforce relatively large individual workpiece members.

U.S. patent 6,859,125 (the 125 patent), which is incorporated herein by reference in its entirety, discloses improvements to the apparatus and method for induction heat treatment of irregularly shaped workpieces of the 857 patent. Using the reference numerals in the 125 patent and referring to the drawings, the bottom inductor segment (17) is connected to an ac power source at power termination regions (122a) and (122b) to form a double parallel loop active circuit from coil turns (16) and (18) as shown in patent figure 5. Current limiting slots (14) are used to form a dual parallel ring active circuit and provide a more uniform current distribution across pairs of adjacent coil segments connected in parallel. At least one of the pairs of adjacent coil segments connected in parallel has a partial opening, such as a partial opening (21a) in a coil segment (17a) in which an arcuate coil surface is formed. The arcuate coil surface may be formed as a pair of coil lips, each separated by an aperture, as shown schematically in fig. 5 for the inner coil lip (23b), the outer coil lip (23a), and the aperture (31) in each adjacent coil segment. The coil lips are shaped to selectively compensate for the irregular mass of the irregularly-shaped component, for openings on the surface of the substantially cylindrical component, or for selective heating of rounded corners. As disclosed in the' 125 patent, the active inductor segment (17) may be paired with a single turn passive inductor segment. Alternatively, the active inductor segment (17) may be paired with a two turn passive inductor segment (19) as shown in patent fig. 6, or with a passive inductor segment (29) in patent fig. 7, which is divided into two electrically isolated coils (32) and (33) by a cross-sectional current limiting gap (30). As disclosed in the' 125 patent, when the active inductor segment (17) is mated with one of the passive inductor segments, the workpiece may be inductively heated with the coil lip pair.

The 125 and 857 patents are generally directed to "strip" heat treatment of workpiece components. For example, where the workpiece member 207 ' selected to be heat treated is the crankpin previously described, a substantially uniform heat treatment is required across the entire transverse surface area a ' of the pin, as shown in fig. 1(a), rather than the radiused areas 207a ' and 207b ', which includes the interface area between the workpiece member 207 ' and the adjacent irregularly shaped members 206 ' and 208 '. Thus, as shown in fig. 1(a) and 1(b), the coil lips (the bottom coil lip pair 123a 'and 123 b' partially shown in fig. 1 (a)) of the bottom and top induction coil pairs 107 'and 109', respectively, that surround the workpiece member 207 ', combine to form a uniform induction heating "band" around the entire transverse surface area a' of the crankpin. Fig. 1(a) also shows a representative side shield 137 ', and fig. 1(b) also shows a representative dielectric 410' separating the contact faces of the bottom and top inductor coil segments.

The 857 patent discloses an embodiment for heat treating the fillet region B 'and the entire transverse surface region a' of a workpiece component by forming outwardly directed pointed tip regions on the coil lips 124a 'and 124B', as shown in fig. 2 (a).

The 125 patent discloses positioning opposing pairs of coil lips in a pair of parallel coil turns separated by a cross-sectional current-limiting gap such that they inductively heat only a fillet region B' between a selected workpiece component located between a pair of coil segments and its adjoining workpiece component. As shown in fig. 2(b), this is achieved by making the cross-sectional current limiting slot S between coil segments fairly wide, in the range of 6mm to 25mm as taught in the 125 patent. The first pair of coil lips 23a 'and 23 b' are located on one side of the slot and the second pair of coil lips 23c 'and 23 d' are located on the other side of the slot. As disclosed in the ' 125 patent, the wide gap may be filled with flux concentrators 138 ' to further direct induction heating to the fillet regions B '.

The 125 and 857 patents have somewhat limited teachings for heat treating only the fillet regions of the workpiece members, or selectively heat treating the fillet regions and/or selected regions along the lateral width of the workpiece members, as well as metallurgically quenching the fillets and surface regions. For example, where the workpiece member is a crankpin or main journal having a narrow (e.g., less than 30mm wide) lateral bearing area (width), a "thumbnail" heating pattern C' may result when utilizing the teachings of the 857 and 125 patents, respectively, as shown in fig. 3(a) and 3 (b). The thumbnail heating pattern is generally undesirable for several reasons. First, such heating patterns waste energy because the intermediate quench depth must be much deeper than necessary to achieve a satisfactory quench depth toward the fillet region. Second, such heating patterns increase the deformation of the heated member because the increased heat absorption results in greater volumetric expansion of the member. Considering the shape of a complex workpiece such as a crankshaft, greater metal expansion results in correspondingly greater deformation. Furthermore, the greater amount of metal heated above the transformation temperature results in a corresponding increase in lower temperature transformation structures such as martensite, lower bainite and other structures, thereby resulting in a different bulk density compared to the preheated metallurgy of the workpiece components. This also increases the shape/size distortion of the heat treated workpiece with the "thumbnail" pattern. Even in the region 120 ' between the paired inner and outer active circuit coil lips 123a ' and 123b ' (fig. 3(a)) and between the slit S and the paired coil lips 23a '/23 b ' and 23c '/23 d ')The thumbnail pattern may still appear without the conductive coil lips in region 120 "(fig. 3 (b)). The thumbnail heating pattern is caused by sufficient electromagnetic coupling between the inner and outer coil lip pairs to be in a central transverse region A 'of the workpiece member'₁(FIG. 3(a)) and a central transverse region A 'of the workpiece member'₂A sufficiently strong magnetic flux field is generated in (fig. 3 (b)). In the opposite lateral end region A 'of the support surface'₃Wherein the magnetic field strength is reduced due to the electromagnetic end effect of the inductor. In addition, there is a significant heat dissipation effect due to the presence of the relatively cold (non-induction heated) irregularly shaped counterweights 206 ' and 208 ' located near the ends of the workpiece member 207 '; that is, end region A'₃Is conducted away from each lateral end region of the workpiece member and toward the adjacent irregularly shaped workpiece member.

It is an object of the present invention to provide an apparatus and method for metallurgical heat treatment of a cylindrical component of a complex workpiece, such as a crankshaft.

Another object of the present invention is to broadly control induction hardening of cylindrical components of complex workpieces across the lateral width and fillet regions of the cylindrical components.

Disclosure of Invention

In one aspect, the present invention is an inductive assembly and method of inductively heat treating at least one substantially cylindrical member of a metal workpiece, wherein at least one side of the substantially cylindrical member is joined to the irregularly shaped member to form a fillet between the irregularly shaped member and the substantially cylindrical member. The inductive component is formed from active and passive inductive segments. The active inductor segment is connected to one or more ac power sources, and the passive inductor segment is magnetically coupled to the active inductor segment. The active inductor segment includes inner and outer active inductor segments that are electrically isolated from each other. The outer and inner active inductor segments each have at least one pair of adjacent partial through openings in which an arcuate coil lip structure is formed. That is, an outer active coil lip is formed in a partial through opening of the outer active inductor segment, and an inner active coil lip is formed adjacent to a partial through opening of the inner active inductor segment. The passive inductor segment includes inner and outer passive inductor segments electrically insulated from one another and having respective outer and inner passive coil lips. The outer and inner active coil lips, when mated with the outer and inner passive coil lips, respectively, form a generally cylindrical interior volume within which the workpiece component may be induction heat treated.

The inter-lip flux concentrators may be positioned between inner and outer active and/or inner and outer passive coil lip pairs to control the induced metallurgical quench pattern across the transverse width of the workpiece component.

Flux concentrators that intersect the lips may be located around active and/or passive coil lip pairs to control the induced metallurgical quenching pattern across the transverse width of the workpiece component.

The electrical parameters of the alternating current supplied to the inner and outer active and passive inductor coil segments can be varied independently of one another to control the induced metallurgical quench pattern across the transverse width of the workpiece member.

In other examples of the invention, the inductive component may be formed from two active inductive segments without magnetic coupling between the two active inductive segments.

The above and other aspects of the invention are set out in the present description and appended claims.

Drawings

The drawings, which are briefly described below, serve to illustrate the invention and do not limit the inventive concept set forth in this description and the appended claims.

Fig. 1(a) and 1(b) show the concept of strip-like metallurgical heat treatment of a cylindrical workpiece member, and fig. 1(a) is a partial sectional view through line a-a in fig. 1 (b).

Fig. 2(a) is a partial cross-sectional elevation view of a prior art apparatus for heat treating across the entire lateral surface area of a cylindrical workpiece member.

Fig. 2(b) is a partial cross-sectional elevation view of a prior art apparatus for heat treating primarily the radiused corner region of a cylindrical workpiece.

Fig. 3(a) and 3(b) are partial cross-sectional views of a generally undesirable thumbnail metallurgical heat treatment pattern across the transverse width of a cylindrical workpiece member.

Fig. 4(a) shows an isometric view of one example of an active inductor segment for use in the inductor assembly of the present invention.

Fig. 4(b) shows an isometric view of one example of a passive inductor segment for use in the inductor assembly of the present invention.

Fig. 4(c) shows an isometric view of one example of an inductive component of the present invention formed from the active and passive inductive segments shown in fig. 4(a) and 4 (b).

Fig. 4(d) shows a cross-sectional view of one example of a workpiece member positioned between opposing pairs of active and passive coil lips.

Fig. 5(a), 5(b) and 5(c) are partial cross-sectional views showing typical examples of use of the interlabial flux concentrator of the present invention.

Fig. 5(a) 'and 5 (a)' show partial cross-sectional views of the scheme shown in fig. 5(a) with alternating instantaneous current flow patterns during the induction heating process.

Fig. 6(a) and 6(b) illustrate two ac power supply circuits for supplying in-phase current to the inner and outer active inductor segments.

Fig. 7(a) and 7(b) illustrate two ac power supply circuits for providing 180 degrees out of phase current to the inner and outer active inductor segments.

Fig. 8(a) and 8(b) illustrate the instantaneous current direction of the outer and inner pairs of active and passive inductor segments.

Fig. 9(a) illustrates current phase control between the currents in the inner and outer active inductor segments.

Fig. 9(b) illustrates frequency control between the currents in the inner and outer active inductor segments.

Fig. 10(a), 10(b) and 10(c) illustrate time-shifted control between the currents in the inner and outer active inductor segments.

Fig. 11(a) -11(d) show cross-sectional views of various applications of flux concentrators intersecting the lips, the concentrators being shown in cross-section along line B-B in fig. 13 (a).

FIG. 12 illustrates a perspective view of one non-limiting example of an interlabial flux concentrator for use in the present invention.

Fig. 13(a) shows a perspective view of one non-limiting example of a flux concentrator used in the present invention that intersects the lip.

Fig. 13 (a)' and 13(a) "show comparative control of the flux path with and without flux concentrators, respectively, crossing the lips.

Fig. 13(b) shows a perspective view of another example of a flux concentrator used in the present invention that intersects the lip.

Fig. 14 is a view of the inductor assembly of fig. 4(c) when the flux concentrator crossing the lips shown in fig. 13(a) is embedded around the coil lips in the passive inductor segment.

Fig. 15 is a view of the inductor assembly of fig. 4(c) when the flux concentrator crossing the lips shown in fig. 13(b) is embedded around the coil lips in the passive inductor segment.

Detailed Description

Referring now to the drawings, wherein like reference numerals refer to like elements, there is shown in fig. 4(a), 4(b) and 4(c) one non-limiting example 10 of an inductive component of the present invention for use in the metallurgical heat treatment of at least one cylindrical member forming a metal workpiece. The inductor assembly 10 includes an active inductor segment 12 and a passive inductor segment 32. The active inductive segment is connected to at least one power source, while the passive inductive segment is magnetically coupled to the active inductive segment and is not directly connected to the power source.

Referring primarily to fig. 4(a), active inductor segment 12 includes an outer active inductor segment 14 and an inner active inductor segment 16, which are electrically isolated from each other. The inner active inductor segment is located within a through opening formed by the outer active inductor segment, which is formed inside the outer active inductor segment 14.

The outer active inductor segment 14 includes a pair of opposing first and second outer active inductor segments 14a and 14b, a flux coupling region 14c, and power termination regions 14 d' and 14d ", all interconnected around an inner through opening 18. At least one of the outer active inductor segments has at least a portion of the through openings, such as openings 14a 'and 14 b' shown in fig. 4 (a). The arcuate surface area of each partial through opening may be contoured to form an active outer coil lip, such as coil lips 15a and 15b in fig. 4 (a). The outer active inductor segment 14 may be connected to at least one power circuit at power termination regions 14 d' and 14d ", as described further below.

The inner active inductor segment 16 includes a pair of opposing first and second inner active inductor segments 16a and 16b, a flux coupling region 16c, and power termination regions 16 d' and 16d ", all interconnected around an inner through opening 18 formed when the inner active inductor segment is located within the through opening inside the outer active inductor segment. At least one of the inner active inductor segments has at least a portion of the through openings, such as openings 16a 'and 16 b' shown in fig. 4 (a). The arcuate surface area of each partial through opening may be contoured to form an active inner coil lip, such as coil lips 17a and 17b in fig. 4 (a). The inner active inductor segment 16 may be connected to at least one power circuit at power termination regions 16 d' and 16d ", as described further below.

For the scheme shown in fig. 4(a), a first pair of outer and inner active coil lips are formed by coil lips 15a and 17a, respectively, and a second pair of outer and inner active coil lips are formed by coil lips 15b and 17 b.

Electrical isolation between the outer and inner active inductor segments is achieved by providing dielectric spaces 20 (shown in figure 4(a) with broken cross-hatching) between the segments. At least one interlabial flux concentrator 22 (shown in solid cross-hatching in fig. 4 (a)) is provided at least in the region between at least one of the outer and inner pairs of active coil lips, as further described below. The dielectric space 20 may be air separation or any suitable solid or gaseous dielectric material.

Referring primarily to fig. 4(b), passive inductive segment 32 includes an outer passive inductive segment 34 and an inner passive inductive segment 36, which are electrically isolated from each other. The inner passive inductor segment is located within a through opening 38 formed in the interior of the outer passive inductor segment 34.

The outer passive inductor segment 34 includes a pair of opposing first and second outer passive inductor segments 34a, 34b and a flux coupling region 34c (hidden under the coupling flux concentrator 60b in fig. 4(b)), all of which are interconnected around the inner through opening 38 to form a closed loop circuit. At least one of the outer passive inductor segments has at least a portion of the through openings, such as openings 34a ' and 34b ' shown in fig. 4(b), with opening 34a ' being visible in fig. 4 (b). The arcuate surface area of each partial through opening may be contoured to form passive outer coil lips, such as coil lips 35a and 35b, with lip 35a partially visible in fig. 4 (b).

The inner passive inductor segment 36 includes a pair of opposing first and second inner passive inductor segments 36a, 36b and a flux coupling region 36c (hidden under the coupling flux concentrator 60d in fig. 4(b)), all of which are interconnected around a reduced volume inner through opening 38 formed when the inner passive inductor segment is located within the through opening formed inside the outer passive inductor segment. At least one of the inner passive inductor segments has at least a portion of the through openings, such as openings 36a ' and 36b ', as seen in opening 36b ' in fig. 4 (b). The arcuate surface area of each partial through opening may be contoured to form a passive inner coil lip, such as coil lips 37a and 37b, which are partially visible in fig. 4(b) at lip 37 b.

For the arrangement shown in fig. 4(b), a first pair of outer and inner passive coil lips are formed by coil lips 35a and 37a, respectively, and a second pair of outer and inner passive coil lips are formed by coil lips 35b and 37 b.

Electrical isolation between the outer and inner passive inductor segments is achieved by providing dielectric spaces 20 (shown in figure 4(b) by broken cross-hatching) between the segments. At least one interlabial flux concentrator 22 (shown in solid cross-hatched lines in fig. 4(b)) is provided at least in the region between at least one of the pair of coil lips, as further described below. The dielectric space 20 may be air separation or any suitable solid or gaseous dielectric material.

Fig. 4(c) shows an inductor assembly 10 in which the contact faces of the active and passive inductor segments shown in fig. 4(a) and 4(b) are brought into close contact with each other while the electrical contact insulation between the contact faces is maintained with a dielectric 50 located between the contact faces. The contact faces 14f and 16f of the outer and inner active inductor segments are identified in fig. 4(a) as surfaces having arrows indicating the direction of current flow; the contact faces 34f and 36f of the outer and inner passive inductor segments are identified in fig. 4(b) as surfaces having arrows indicating the direction of current flow. One or more coupled flux concentrators are used to form a magnetic circuit between the active and passive inductor segments, illustrated by coupled flux concentrators 60a and 60b for the outer active inductor segment 14 and the outer passive inductor segment 34 and coupled flux concentrators 60c and 60d for the inner active inductor segment 16 and the inner passive inductor segment 36. Each concentrator segment includes a high permeability magnetic material such as a plurality of laminated steel sheets or a powder type magnetic material including iron-based and/or ferrite-based particles bonded together using an adhesive material. The outer active inductor segment 14 and the inner active inductor segment 16 may have their power termination areas 14d '/14 d "and 16 d'/16 d", respectively, connected directly or indirectly to the power circuit, as shown in fig. 4(c), via bus bars 90a/90b and 91a/91b, respectively, but with a separation dielectric 92.

When properly positioned, each partial opening in the active inductor segment is positioned substantially in mirror image with respect to its corresponding partial opening in the passive inductor segment. For example, for the active inductor segment 12 shown in FIG. 4(a), the outer and inner are activeThe workpiece portion openings 14a 'and 16 a' in the inductor segments are positioned substantially mirror images with respect to the workpiece portion openings 34a 'and 36 b' in the outer and inner passive inductor segments that make up the passive inductor segment 32 as shown in fig. 4(b) to form substantially cylindrical openings as shown in fig. 4 (c). Deviations from true mirror image active and passive inductive segments are used in some applications of the invention to accommodate specific characteristics of the component being heat treated or components adjacent thereto, such as the counterweight. For example, a notch 37 b' (fig. 4(b)) in the coil lip 37b may be used only in the passive coil lip 37b and not in the mirror image active coil lip 17b so that the radially drilled hole in the workpiece does not overheat. Referring to fig. 4(d), for this arrangement, a cylindrical workpiece member 307 to be heat treated may be located in the generally circular opening between the surrounding pairs of active coil lips 15a and 17a and the pairs of passive coil lips 35a and 37 a. Workpiece members 306 and 308, which are attached to both ends of member 307, represent irregularly shaped members that may be attached to either or both ends of member 307. If present, the member 308 may be located in the through openings 18 and 38, while the member 306 may be located outside of the outer inductor coil segment 14 a. Optionally, one or more (slotted or iron-based or ferrite-based powder types) side shields 52 may be provided on one or both outer sides of the active and/or passive inductor segments around the arcuate coil regions of the inductor segments, as shown in fig. 4 (d). As described further below, an interlabial flux concentrator 22 may be used. For a suitable alternating current supplied from the power circuit to the outer and inner active inductor segments, there is a momentary alternating current flow (I) in the active inductor segment 12_a1And I_a2) The instantaneous ac current induced in the passive inductor segment 32 flows (I) in the direction indicated generally by the arrow in fig. 4(a)_b1And I_b2) A generally opposite, direction as indicated by the arrow in fig. 4(b), and a generally cylindrical workpiece 307 will be induction heat treated when located within the generally circular opening in fig. 4 (c). As described further below, these currents may be periodically reversed, phase shifted, and/or time shifted during the heat treatment process to produce a desired metallurgical quench pattern in the heat treated workpiece component.

As noted above, in some examples of the inductive component of the present invention, an interlabial flux concentrator is used to control the metallurgical quenching pattern of the induction heat treated generally cylindrical workpiece member. Fig. 5(a), 5(b) and 5(c) are representative applications of the interlabial flux concentrator in the present invention. For simplicity, the drawings in these and other figures show, in partial cross-sectional views, the interface region between the workpiece member 307 and the pair of active coil lips formed by the outer coil lip 15a and the inner coil lip 17 a; it is preferred that the interface region between the workpiece component 307 and the passive coil lip pair formed by the outer coil lip 35a and the inner coil lip 37a be similar, unless an asymmetric quench pattern is desired around the outer periphery of the component 307. A typical non-limiting interlabial flux concentrator 22a is shown in FIG. 12, cut in cross-section along line C-C, as shown in the other figures.

According to the width w of the coil lip_lip1And w_lip2Inter-lip separation distance d_sepAnd the desired metallurgical quench pattern, an interlabial flux concentrator 22a, 22b, or 22c may be used, as shown in fig. 5(a), 5(b), and 5(c), respectively. The inter-lip flux concentrator may fill a portion or the entire distance d between the paired coil lips_sep. The interlabial concentrator need not extend the entire length x between the paired coil lips₁As shown in fig. 4 (d). In general, an interlabial concentrator needs to extend from the lateral tips of the paired coil lips to x₂Such that the magnetic flux generated by each coil lip is separated from each other but close to the lateral surface of the workpiece member being heat treated. The presence of the inter-lip flux concentrators attenuates electromagnetic coupling between the paired coil lips, which reduces the induction heating of the central region a' (fig. 5(a)) of the heat treated workpiece member 307, such as a bearing. This is in contrast to the prior art arrangement shown in figure 3(a) and described above. When heat treating a narrow width w_wpThe combination of an interlabial flux concentrator with a pair of coil lips is particularly advantageous when the workpiece member is a journal on a crankshaft. The inter-lip geometry is selected based on the desired metallurgical quench pattern of the particular workpiece component to be heat treated from the paired coil lips. Referring to FIG. 5(a), these geometric parameters include thickness t, interlabial concentrator and (bearing) surface of the heat treated workpiece componentThe air gap distance g between, and/or the electromagnetic properties of the concentrator, i.e. permeability and resistivity. For example, the thickness t must be sufficient to prevent magnetic saturation in certain applications.

In FIG. 5(a), the quench pattern A, spans the width w of the workpiece member_wpA quench pattern having a substantially uniform depth is achieved by controlling the geometric parameters described above to reduce the power density (heat source) induced in the width of the middle of the quench pattern, thereby substantially reducing the surface of the thumbnail pattern.

In fig. 5(B), the quench pattern B, a variable depth quench pattern with symmetrical double protrusions across the width of the workpiece member, is achieved by increasing the thickness of the interlabial concentrator 22B above that of the concentrator 22a in fig. 5(a) to further reduce the power density (heat source) induced in the width of the middle of the quench pattern to achieve the shallower quench depth shown in fig. 5 (B).

In fig. 5(C), the quench pattern C, having a symmetrical double thumbnail quench pattern across the width of the workpiece member, is achieved by further increasing the thickness of the interlabial concentrator 22C to be higher than the thickness of the concentrator 22b in fig. 5(b) to eliminate quenching in the mid-width region as shown in the figure.

In summary, the distance d between the active coil lips in a pair as the quench pattern transitions from that shown in the figure to that shown in the figure_sepIncrementally, the thickness t of the interlabial flux concentrator used also incrementally increases.

A particular advantage of the inductive component of the present invention over the prior art is that current parameters such as current phase shift, frequency and phase shift at current may be varied individually for the outer and inner active inductor segments during part or all of the steps of the induction heating process, either alone or in combination with each other, to precisely control the metallurgical quench pattern across the lateral width of the workpiece member to be inductively heated.

In the drawings, conventional notation is used to indicate the instantaneous direction of current flow; that is, the crosses in the circles indicate that the AC current flows into the plane of the paper and away from the reader, and the dots in the circles indicate that the AC current flows out of the plane of the paper (180 degrees out of phase with the current flowing into the plane of the paper) and toward the reader. The examples in fig. 5(a), 5(b) and 5(c) show various quenching patterns resulting from instantaneous current flowing in the same direction in two pairs of coil lips. This can be achieved, for example, by using the power supply circuit shown in fig. 6(a) or 6 (b). In fig. 6(a), two power supplies are used, power supply No. 1 connected to the outer active inductor segment and power supply No. 2 connected to the inner active inductor segment. Alternatively, a single power supply is used in fig. 6(b), with switching circuits 94a and 94b for controlling the instantaneous current flowing to the outer and inner active inductor segments between the same and opposite instantaneous directions for controlling the output current from the single power supply to the separately controlled outer and inner active inductor segments and the simultaneously energized active lip pairs 15a/15b and/or 17a/17 b.

Fig. 5 (a)' shows the arrangement of fig. 5(a) in which the instantaneous current flows in opposite directions in the pairs of coil lips. During the induction hardening process, the use of the inter-lip flux concentrators 22a with opposing current flows increases the electrical efficiency of the coil formed by the paired coil lips and shifts the current coil density toward the fillet regions 307a and 307b to produce the hardening pattern D. This can be achieved, for example, by using the power supply circuit shown in fig. 7(a) or 7 (b). In fig. 7(a), two power supplies are used, power supply No. 1 connected to the outer active inductor segment and power supply No. 2 connected to the inner active inductor segment. Alternatively, in fig. 7(b), a single power supply is used, with switching circuits 94a and 94b being used to control the output current from the single power supply to the outer and inner active inductor segments.

FIG. 5(a) "shows another different result achieved with the scheme in FIG. 5(a) when the instantaneous current alternates between the same and opposite instantaneous directions during the induction hardening process; this method results in a quenched pattern E in which both the fillet area and the entire lateral width of the member 307 are quenched. This may be achieved, for example, by alternating between the power supply circuits shown in fig. 6(a) and 7(a), or fig. 6(b) and 7 (b).

In general, in the present invention, the instantaneous ac phase shift α between the inner and outer active inductor segment circuits can be varied anywhere in the range from 0 degrees (representing the same instantaneous current direction as the above example) to 180 degrees (representing the opposite instantaneous current direction as the above example), as shown in fig. 9 (a). The phase shift α may range anywhere from 0 to 180 degrees during a portion of one or more induction heating cycles in a metallurgical quenching process, depending on the desired quench pattern across the lateral width of the workpiece member.

Independent variation of the frequency f of the current in the inner and outer active inductor segment circuits is another parameter that can be used to control the quench pattern across the lateral width of the workpiece member, as shown in fig. 9 (b).

Independent time phase shifts of the currents in the inner and outer active inductor segment circuits are another parameter that can be used to control the quench pattern across the lateral width of the workpiece member. As shown in fig. 10(b), the zero time phase shift β can be used to alternatively provide current to the inner or outer active inductor segment circuits exclusively. Alternatively, the phase shift may be positive, as shown in fig. 10(a), with currentless time-bands during which no current is provided to any of the inductor segments; or may be negative, as shown in fig. 10(c), with overlapping time-bands when current is supplied to the two inductor segments.

As described above, current parameters such as current phase shift, frequency and current time phase shift may be varied individually for the outer and inner active inductor segments during part or all of the steps of the induction heating process, either alone or in combination with each other, to control the metallurgical quench pattern across the lateral width and including the fillet of the workpiece member to be inductively heated. Additionally, in some examples of the invention, various parameters of the inner and outer coil lips may be varied to achieve an asymmetric quench pattern across the lateral width of the workpiece member, or to compensate for asymmetric features affecting the induction heat treatment process across the lateral width of the member, such as, but not limited to, adjacent irregularly shaped counterweights, rounded corner geometry, or openings in the heat treatment area of the member.

In other examples of the invention, the flux concentration across the lip is concentratedThe device may be used alone or in combination with the above-described interlabial flux concentrator. Fig. 11(a) shows the use of a flux concentrator 23a intersecting the lips, in which a thumbnail quenching pattern F is achieved. The flux concentrators crossing the lips at the transverse tips x from the active coil pairs₃At least partially embedded within the pair of active coil lips 15a and 17 a. Selecting a distance x₃To reduce the length of the flux return path created by each lip to increase the electrical efficiency of the coil. The flux concentrator 23a that intersects the lip generally has an arcuate shape as shown in fig. 13(a) and "closes" the external magnetic flux path while localizing the external magnetic field by creating a more superior low impedance flux path. This effect is illustrated by exemplary flux lines 80a and 80b (shown in dashed lines) in fig. 13(a) 'and 13 (b)' with and without flux concentrators, respectively, that intersect the lip. This reduces external power losses that occur within various conductive features, such as tools or fixtures associated with the inductor assembly of the present invention. Fig. 14 shows a slotted, lipped flux concentrator 23a inserted around a pair of coil lips in a passive coil segment 32; similar flux concentrators that cross the lips may be inserted around the coil lips in the active coil section 12. FIG. 13(b) shows another example of an arcuate, lipped flux concentrator 23b, where the flux concentrator is not a single flux concentrator, but rather an arcuate array of dispersed cylindrical flux concentrators around a coil lip pair in a passive coil section 32 as shown in FIG. 15; similar flux concentrators that cross the lips may be inserted around the coil lips in the active coil sections 12 to form a "squirrel cage" flux concentrator arrangement around each opening in which the workpiece member is to be heat treated. Fig. 11(b) -11(d) show examples of the present invention in which a combination of a flux concentrator 23a intersecting a lip and an interlabial flux concentrator 22 is used. Although the cross-lip flux concentrators 23a are shown in fig. 11(a) -11(d) as being oriented horizontally between the pair of coil lips, the cross-lip flux concentrators may have other orientations and shapes as long as they extend between the pair of coil lips. Similar to the description above for the inter-lip flux concentrator, the instantaneous directions of current flow indicated in FIGS. 11(a) -11(d) show the separately achievable quench patterns F, F,G. H or I.

One non-limiting method of using the inductive component of the present invention is in the device disclosed in U.S. patent 6,274,857B 1. It is also within the scope of the invention to use the inductive component of the invention with an apparatus in which the workpiece or inductive component is rotatable. For example, a suitable drive including an electric motor having an output shaft directly or indirectly connected to a rotating mounting structure may be provided to mount the inductive component or workpiece. Alternatively, the inductive component and the workpiece may both be mounted on separate drives so that they are independently rotatable during the heat treatment process.

Further, a description of suitable coil lip shaping, flux concentrators and dielectric material selection can be found in U.S. Pat. Nos. 6,274,857B1 and 6,859,125B 2.

While two substantially closed openings are formed in the inductance assembly as shown in fig. 4(c) to heat treat two members of the workpiece, in other examples of the invention, there may be only one or more than two substantially closed openings in the inductance assembly to heat treat one or more than two members of the workpiece.

The above examples of the present invention are for illustrative purposes only and should not be construed as limiting the present invention in any way. While the present invention has been described with reference to several embodiments, the words which have been used herein are words of description and illustration, rather than words of limitation. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein; rather, the invention extends to all functionally equivalent structures, methods and uses. Those skilled in the art, having the benefit of the teachings of this specification, may effect numerous modifications thereto and changes may be made without departing from the scope of the invention in its aspects.

Claims (20)

1. An inductor assembly for heating at least one cylindrical member of a metal workpiece, said inductor assembly being formed of active inductor segments and passive inductor segments, the active and passive inductor segments having means for magnetically coupling alternating high frequency current supplied to the active inductor segments to the passive inductor segments, at least one closed opening being formed partially in the active inductor segments and partially in the passive inductor segments for positioning the cylindrical member for induction heating by applying a magnetic field to said member, said magnetic field being generated by the active and passive inductor segments in response to excitation by the alternating high frequency current, characterized in that:

the active inductor segment further comprises:

an outer active inductor segment formed around the outer active inductor segment through opening;

an inner active inductor segment located within the outer active inductor segment through opening and separated from the outer active inductor segment by an electrically insulating dielectric space;

an active inductor through opening formed within the inner active inductor segment, the active inductor through opening forming adjacent first outer and inner active coil segments and adjacent second outer and inner active coil segments, the adjacent first outer and inner active coil segments and the adjacent second outer and inner active coil segments being located on both sides of the active inductor through opening; and

at least one pair of aligned active partial inductor segment openings formed by the openings in each of either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments, each opening in either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments having an active inductor segment arcuate coil surface interfacing with the outer and inner active coil segment contact surfaces, respectively; and

the passive inductive segment further includes:

an outer passive inductor segment formed around the outer passive inductor segment through opening;

an inner passive inductor segment located within the outer passive inductor segment through opening and separated from the outer passive inductor segment by an electrically insulating dielectric space;

a passive inductor through opening formed in the inner passive inductor segment, the passive inductor through opening forming adjacent first outer and inner passive coil segments and adjacent second outer and inner passive coil segments, the adjacent first outer and inner passive coil segments and the adjacent second outer and inner passive coil segments being located on both sides of the passive inductor through opening; and

at least one pair of aligned passive partial-inductor segment openings formed by the openings in each of the adjacent first pair of outer and inner passive coil segments or the adjacent second pair of outer and inner passive coil segments, each opening in either the adjacent first pair of outer and inner passive coil segments or the adjacent second pair of outer and inner passive coil segments having an arcuate coil surface of the passive inductor segment interfacing with the outer and inner passive coil segment contact surfaces, respectively, the aligned pair of active and passive partial-inductor segment openings forming at least one closed opening when the outer and inner active coil segment contact surfaces face the outer and inner passive coil segment contact surfaces and the outer and inner active coil segment contact surfaces are electrically insulated from the outer and inner passive coil segment contact surfaces.

2. The inductor assembly of claim 1 wherein the arcuate coil surfaces in at least one of the adjacent first or second outer and inner pairs of active or passive inductor segments are a pair of coil lips that are contoured.

3. The inductance assembly recited in claim 2, wherein the contoured pair of coil lips are shaped to selectively compensate for an irregular mass of the irregularly-shaped member adjacent the at least one cylindrical member, an opening in a surface of the at least one cylindrical member, or to selectively heat a fillet region between the irregularly-shaped member and the at least one cylindrical member.

4. The inductance assembly recited in claim 2, further comprising at least one interlabial flux concentrator located between two sides of the pair of contoured coil lips.

5. The inductance assembly of claim 2, further comprising at least one lipped flux concentrator partially embedded in each coil lip of the contoured pair of coil lips at a distance from the tips of the contoured pair of coil lips.

6. The inductance assembly recited in claim 2, further comprising at least one interlabial flux concentrator located between two sides of the pair of contoured coil lips, and at least one interlabial flux concentrator partially embedded in each coil lip of the pair of contoured coil lips at a distance from a tip of the pair of contoured coil lips.

7. The inductance assembly of claim 1, further comprising a driver for rotating the inductance assembly or the metal workpiece when the at least one cylindrical member is positioned in the at least one closed opening.

8. A method for induction heating at least one cylindrical member of a metal workpiece, the method comprising the steps of:

forming a closed opening around an axial length of at least one cylindrical member, wherein the closed opening is formed partially in an active inductor segment and partially in a passive inductor segment, the active inductor segment comprising:

an outer active inductor segment formed around the outer active inductor segment through opening;

an inner active inductor segment located within the outer active inductor segment through opening and separated from the outer active inductor segment by an electrically insulating dielectric space;

an active inductor through opening formed within the inner active inductor segment, the active inductor through opening forming adjacent first outer and inner active coil segments and adjacent second outer and inner active coil segments, the adjacent first outer and inner active coil segments and the adjacent second outer and inner active coil segments being located on both sides of the active inductor through opening; and

at least one pair of aligned active partial inductor segment openings formed by the openings in either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments, each opening in either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments having an active inductor segment arcuate coil surface conforming to the active coil lip profile interfacing with the outer and inner active coil segment contact surfaces, respectively;

the passive inductive segment further includes:

an outer passive inductor segment formed around the outer passive inductor segment through opening;

an inner passive inductor segment located within the outer passive inductor segment through opening and separated from the outer passive inductor segment by an electrically insulating dielectric space;

a passive inductor through opening formed in the inner passive inductor segment, the passive inductor through opening forming adjacent first outer and inner passive coil segments and adjacent second outer and inner passive coil segments, the adjacent first outer and inner passive coil segments and the adjacent second outer and inner passive coil segments being located on both sides of the passive inductor through opening; and

at least one pair of aligned passive partial inductor segment openings formed by openings in each of either of the adjacent first outer and inner pairs of passive coil segments or the adjacent second outer and inner pairs of passive coil segments, each opening in either of the adjacent first outer and inner pairs of passive coil segments or the adjacent second outer and inner pairs of passive coil segments having an arcuate coil surface of a passive inductor segment conforming to the contour of a passive coil lip interfacing with the outer and inner passive coil segment contact surfaces, respectively, the aligned pair of active and passive partial inductor segment openings forming at least one closed opening when the outer and inner active coil segment contact surfaces face the outer and inner passive coil segment contact surfaces and the outer and inner active coil segment contact surfaces are electrically insulated from the outer and inner passive coil segment contact surfaces;

supplying a first alternating current to the outer active inductor segment;

supplying a second alternating current to the inner active inductor segment;

magnetically coupling the outer active inductor segment and the outer passive inductor segment such that a first magnetic flux field is established at least around coil lips formed in the outer active inductor segment and the outer passive inductor segment; and

the inner active inductor segment and the inner passive inductor segment are magnetically coupled such that a second magnetic flux field is established at least around coil lips formed in the inner active inductor segment and the inner passive inductor segment.

9. The method of claim 8, wherein at least the phase relationship between the first and second alternating currents, or the frequency of the first or second alternating current, or the time phasing between the first and second alternating currents is varied while inductively heating the at least one cylindrical member in the closed opening.

10. The method of claim 8, further comprising the step of: the inductive component or workpiece is rotated while inductively heating the at least one cylindrical member in the closed opening.

11. The method of claim 8 wherein at least one interlabial flux concentrator is positioned between two sides of a pair of coil lips.

12. The method of claim 8, wherein at least one flux concentrator intersecting the lips is positioned between two sides of a pair of the coil lips.

13. The method of claim 8, wherein at least one interlabial flux concentrator is positioned between two sides of a pair of coil lips and at least one interlabial flux concentrator is positioned between two sides of a pair of coil lips.

14. An inductor for inductively heating at least one cylindrical member of a metal workpiece, said inductor assembly comprising:

an active inductive segment comprising:

an outer active inductor segment formed around the outer active inductor segment through opening;

an inner active inductor segment located within the outer active inductor segment through opening and separated from the outer active inductor segment by an electrically insulating dielectric space;

an active inductor through opening formed within the inner active inductor segment, the active inductor through opening forming adjacent first outer and inner active coil segments and adjacent second outer and inner active coil segments, the adjacent first outer and inner active coil segments and the adjacent second outer and inner active coil segments being located on both sides of the active inductor through opening;

at least one pair of aligned active partial inductor segment openings formed by the openings in each of either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments, each opening in either of the adjacent first outer and inner pairs of active coil segments or the adjacent second outer and inner pairs of active coil segments having an active inductor segment arcuate coil surface interfacing with the outer and inner active coil segment contact surfaces, respectively; and

means for connecting the outer active inductor segment and the inner active inductor segment to one or more alternating current sources;

a passive inductive component comprising:

an outer passive inductor segment formed around the outer passive inductor segment through opening;

an inner passive inductor segment located within the outer passive inductor segment through opening and separated from the outer passive inductor segment by an electrically insulating dielectric space;

a passive inductor through opening formed in the inner passive inductor segment, the passive inductor through opening forming adjacent first outer and inner passive coil segments and adjacent second outer and inner passive coil segments, the adjacent first outer and inner passive coil segments and the adjacent second outer and inner passive coil segments being located on both sides of the passive inductor through opening; and

at least one pair of aligned passive partial inductor segment openings formed by the openings in each of either of the adjacent first outer and inner pairs of passive coil segments or the adjacent second outer and inner pairs of passive coil segments, each opening in either of the adjacent first outer and inner pairs of passive coil segments or the adjacent second outer and inner pairs of passive coil segments having an arcuate coil surface of passive inductor segment interfacing with the outer and inner passive coil segment contact surfaces, respectively;

means for magnetically coupling the outer active inductor segment and the outer passive inductor segment when the outer active coil segment contact surface faces the outer passive coil segment contact surface and the outer active coil segment contact surface is electrically insulated from the outer passive coil segment contact surface; and

means for magnetically coupling the inner active inductor segment to the inner passive inductor segment when the inner active coil segment contact surface faces the inner passive coil segment contact surface and the inner active coil segment contact surface is electrically insulated from the inner passive coil segment contact surface;

whereby the aligned pairs of active and passive partial inductor segment openings form closed openings, wherein the at least one cylindrical member is inductively heated when the outer and inner active coil segment contact surfaces face the outer and inner passive coil segment contact surfaces, respectively, and the outer and inner active coil segment contact surfaces are electrically insulated from the outer and inner passive coil segment contact surfaces, and the outer and inner active inductor segments are connected to one or more ac sources.

15. The inductor assembly of claim 14 wherein the arcuate coil surfaces in at least one of the adjacent first or second outer and inner pairs of active or passive inductor segments are a pair of coil lips that are contoured.

16. The inductance assembly recited in claim 15, wherein the contoured pair of coil lips are shaped to selectively compensate for an irregular mass of the irregularly-shaped member adjacent to the at least one cylindrical member, an opening in a surface of the at least one cylindrical member, or to selectively heat a fillet region between the irregularly-shaped member and the at least one cylindrical member.

17. The inductance assembly recited in claim 15, further comprising at least one interlabial flux concentrator located between two sides of the pair of contoured coil lips.

18. The inductance assembly recited in claim 15, further comprising at least one lipped flux concentrator partially embedded in each coil lip of the contoured pair of coil lips at a distance from the tips of the contoured pair of coil lips.

19. The inductance assembly recited in claim 15, further comprising at least one interlabial flux concentrator located between two sides of the pair of contoured coil lips, and at least one interlabial flux concentrator partially embedded in each coil lip of the pair of contoured coil lips at a distance from a tip of the pair of contoured coil lips.

20. The inductance assembly of claim 14, further comprising a driver for rotating the inductance assembly or the metal workpiece when the at least one cylindrical member is positioned in the at least one closed opening.