Induction heating method and manufacturing method of ring-shaped member, ring-shaped member, bearing, induction heating device, manufacturing method of bearing, manufacturing method of vehicle, and manufacturing method of mechanical device

Abstract

To provide an induction heating method capable of substantially uniformly and efficiently heating the entirety of a ring-shaped member.SOLUTION: Current is supplied to an induction coil to inductively heat a ring-shaped member. An induction-heating process includes induction-heating the ring-shaped member using an induction coil (17) arranged radially inward of the ring-shaped member in a state where no substantial coil is arranged radially outward of the ring-shaped member, or induction-heating the ring-shaped member using an induction coil (18) arranged radially outward of the ring-shaped member in a state where no substantial coil is arranged radially inward of the ring-shaped member. The effective length of the induction coil (17, 18) is set larger than the axial length of the ring-shaped member.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for induction heating a metallic ring-shaped member, such as an outer ring or an inner ring that constitutes a bearing. This application claims priority based on Japanese Patent Application No. 2022-174235, filed on October 31, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] For example, the outer and inner rings that make up the bearing are quenched and tempered to improve the toughness of the core while ensuring strength and hardness, particularly the hardness of the raceway surface that comes into contact with the rolling elements. Both quenching and tempering are performed by heating a ring-shaped member (workpiece) such as the outer or inner ring to a specified temperature, holding it for a specified time, and then cooling it.

[0003] JP 2019-185882 A describes a method for induction heating a ring-shaped member by arranging an outer diameter side coil portion and an inner diameter side coil portion electrically connected in series on the radial outside and the radial inside of a ring-shaped member (short cylindrical workpiece) and passing current through the outer diameter side coil portion and the inner diameter side coil portion. In the method described in JP 2019-185882 A, since the outer diameter side coil portion and the inner diameter side coil portion are electrically connected in series, the current values ​​flowing through the outer diameter side coil portion and the inner diameter side coil portion can be made equal, and the outer diameter side region and the inner diameter side region of the ring-shaped member can be heated simultaneously under approximately the same conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-185882 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method described in JP 2019-185882 A, when a ring-shaped member whose radial thickness varies depending on the axial position is targeted, such as an outer ring having an outer ring raceway on the inner circumferential surface or an inner ring having an inner ring raceway on the outer circumferential surface, the heating rate of the portion with a large radial thickness is slower than the heating rate of the portion with a small radial thickness, making it difficult to heat the entire ring-shaped member uniformly.

[0006] In induction heating of such a ring-shaped member, it is possible to make the generatrix shape of the inner peripheral surface of the outer diameter side coil part conform to the generatrix shape of the outer peripheral surface of the ring-shaped member, and to make the generatrix shape of the outer peripheral surface of the inner diameter side coil part conform to the generatrix shape of the inner peripheral surface of the ring-shaped member. If the current value supplied to the coil is reduced, the difference in the temperature rise rate of the ring-shaped member depending on the axial position may be suppressed, but this leads to a decrease in productivity. In addition, it is necessary to precisely regulate the positional relationship between the outer diameter side coil part and the inner diameter side coil part and the ring-shaped member. When heating ring-shaped members with different diameters and shapes, it is necessary to prepare coils that match the ring-shaped members. For this reason, when small lots of ring-shaped members are targeted, problems such as high manufacturing costs arise.

[0007] An object of one aspect of the present invention is to provide an induction heating method capable of heating an entire ring-shaped member substantially uniformly and efficiently. [Means for solving the problem]

[0008] A method for induction heating a ring-shaped member according to one aspect of the present invention includes a step of inductively heating the ring-shaped member by supplying a current to an induction coil. The induction heating step includes inductively heating the ring-shaped member using the induction coil arranged radially inward of the ring-shaped member in a state in which no substantial coil is arranged radially outward of the ring-shaped member, or inductively heating the ring-shaped member using the induction coil arranged radially outward of the ring-shaped member in a state in which no substantial coil is arranged radially inward of the ring-shaped member. The effective length of the induction coil is set to be larger than the axial length of the ring-shaped member.

[0009] Another embodiment of the method for inductively heating a ring-shaped member of the present invention includes a step of preparing a first coil arranged radially inward of the ring-shaped member and a second coil arranged radially outward of the ring-shaped member, a first heating step of supplying current to one of the first coil and the second coil to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a first target temperature, and a second heating step of supplying current to another of the first coil and the second coil after the first heating step to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a second target temperature that is higher than the first target temperature.

[0010] In the induction heating method for a ring-shaped member according to one aspect of the present invention, the ring-shaped member can be an inner or outer ring of a rolling bearing such as an angular ball bearing, a deep groove ball bearing, a roller bearing, or a tapered roller bearing.

[0011] Alternatively, in the induction heating method for a ring-shaped member according to one aspect of the present invention, the ring-shaped member may be an outer ring or an inner ring of a double-row rolling bearing, or a sliding bearing, etc.

[0012] In one embodiment of the method for induction heating a ring-shaped member of the present invention, the ring-shaped member can be the outer ring, and the outer diameter heating process can be carried out after the inner diameter heating process.

[0013] Alternatively, in one embodiment of the method for induction heating a ring-shaped member of the present invention, the ring-shaped member can be the inner ring, and the inner diameter heating process can be carried out after the outer diameter heating process.

[0014] In one embodiment of the method for manufacturing a ring-shaped member of the present invention, in order to manufacture a ring-shaped member, the ring-shaped member is heated by an induction heating method for a ring-shaped member of one embodiment of the present invention, and the ring-shaped member is subjected to heat treatment such as quenching, tempering, annealing, and / or normalizing.

[0015] A method for manufacturing a rolling bearing according to one embodiment of the present invention comprises heating the inner ring and / or the outer ring by an induction heating method for a ring-shaped member according to one embodiment of the present invention, thereby subjecting the inner ring and / or the outer ring to a heat treatment in order to manufacture a rolling bearing comprising an inner ring having an inner ring raceway on its outer peripheral surface, an outer ring having an outer ring raceway on its inner peripheral surface, and a plurality of rolling elements arranged so as to roll freely between the inner ring raceway and the outer ring raceway.

[0016] In one embodiment of the vehicle manufacturing method of the present invention, in order to manufacture a vehicle having a ring-shaped member, the ring-shaped member is heated using an induction heating method of a ring-shaped member of one embodiment of the present invention, thereby subjecting the ring-shaped member to heat treatment.

[0017] In one embodiment of the present invention, a method for manufacturing a mechanical device includes the step of heating a ring-shaped member by a method for induction heating a ring-shaped member according to one embodiment of the present invention, thereby subjecting the ring-shaped member to a heat treatment in order to manufacture a mechanical device having the ring-shaped member.

[0018] An induction heating device for a ring-shaped member according to one embodiment of the present invention includes a first coil disposed radially inward of the ring-shaped member, a second coil disposed radially outward of the ring-shaped member, and a power supply device that supplies current to the first coil and the second coil. The power supply device has a first mode in which a current is supplied to one of the first coil and the second coil to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a first target temperature, and a second mode in which a current is supplied to the other of the first coil and the second coil to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a second target temperature higher than the first target temperature. Effect of the Invention

[0019] According to the induction heating method for a ring-shaped member of one aspect of the present invention, the entire ring-shaped member can be heated substantially uniformly and efficiently. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a rolling bearing including an outer ring and an inner ring. [Diagram 2] FIG. 2 is a schematic diagram of an induction heating device. [Diagram 3] FIG. 3 is a cross-sectional view showing a state in which the outer ring is induction heated in the first embodiment. [Figure 4] FIG. 4 is a diagram showing a schematic example of the arrangement of the ring-shaped members with respect to the induction coil. [Diagram 5] FIG. 5 is a graph showing a schematic diagram of the temperature change of the outer ring when the outer ring is induction heated. [Figure 6] FIG. 6 is a flow chart showing an example of a procedure for subjecting an outer ring to quenching and tempering treatments. [Figure 7] FIG. 7 is a cross-sectional view showing a modified example, illustrating a state in which the outer ring is induction heated. [Figure 8] FIG. 8 is a cross-sectional view showing another modified example, illustrating a state in which the outer ring is induction heated. [Figure 9] FIG. 9 is a cross-sectional view showing a state in which the outer ring is induction heated in the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a state in which the outer ring is induction heated in the third embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing a state in which the inner ring is induction heated in the fourth embodiment. [Figure 12] FIG. 12 is a cross-sectional view showing a state in which the inner ring is induction heated in the fifth embodiment. [Figure 13] FIG. 13 is a cross-sectional view showing a state in which the inner ring is induction heated in the sixth embodiment. [Figure 14] FIG. 14 is a cross-sectional view showing a state in which a ring-shaped member is induction-heated in the seventh embodiment. [Figure 15] FIG. 15 is a cross-sectional view showing a state in which a ring-shaped member is induction-heated in the eighth embodiment. [Figure 16]FIG. 16 is a cross-sectional view showing a state in which a ring-shaped member is induction-heated in the ninth embodiment. [Figure 17] FIG. 17 is a cross-sectional view showing how ring-shaped members of various shapes are induction heated. [Figure 18] FIG. 18 is a schematic diagram of a motor to which a bearing serving as a ring-shaped member is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [First embodiment] A first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. In this embodiment, for example, an outer ring 2 of a radial rolling bearing 1 as shown in Fig. 1 is heated by an induction heating method and is subjected to a quenching treatment and a tempering treatment. In this case, the outer ring 2 corresponds to a ring-shaped member. Below, first, the structure of the radial rolling bearing 1 will be described, and then a manufacturing method of the outer ring 2, including the quenching treatment and tempering treatment, will be described.

[0022] In the following description, unless otherwise specified, the axial direction, radial direction, and circumferential direction refer to the axial direction, radial direction, and circumferential direction of the radial rolling bearing 1. The axial direction, radial direction, and circumferential direction of the radial rolling bearing 1 coincide with the axial direction, radial direction, and circumferential direction of the outer ring 2, and also coincide with the axial direction, radial direction, and circumferential direction of the inner ring 3. With regard to the radial rolling bearing 1, one axial side (first shaft end 31, 41) refers to the right side in Fig. 1 and the upper side in Fig. 2, and the other axial side (second shaft end 32, 42) refers to the left side in Fig. 1 and the lower side in Fig. 2.

[0023] <Structure of radial rolling bearing 1> The radial rolling bearing 1 is constituted by a single-row angular contact ball bearing, and includes an outer ring 2, an inner ring 3, and a plurality of rolling elements 4.

[0024] In one example, the outer ring 2 is made of a hard metal such as bearing steel or carburized steel, in another example, the outer ring 2 is made of another material.

[0025] The outer ring 2 has an outer ring raceway 5 for the rolling elements 4 at the axially intermediate portion of the inner peripheral surface (inner surface). In one example, the outer ring raceway 5 has an arc-shaped generatrix shape with a diameter increasing toward one axial side (first shaft end 31). The outer ring 2 also has a conical concave inclined surface portion 6 in the portion of the inner peripheral surface adjacent to the first shaft end 31 of the outer ring raceway 5, which is inclined in a direction in which the inner diameter increases toward the first shaft end 31. The outer ring 2 also has a cylindrical surface portion 7 whose inner diameter does not change in the axial direction at a portion of the inner peripheral surface adjacent to the other axial side (second shaft end 32) of the outer ring raceway 5. The outer ring 2 also has chamfered portions 8a, 8b having an arc-shaped generatrix shape at both axial ends of the inner peripheral surface.

[0026] The outer ring 2 has a cylindrical surface portion (flat surface) 9, whose outer diameter does not change in the axial direction, at the axial middle portion of the outer peripheral surface (outer surface), and has chamfered portions 10a, 10b having an arc-shaped generatrix shape at both axial ends of the outer peripheral surface.

[0027] That is, the outer ring 2 has a radial thickness (thickness change, wall structure) that decreases overall toward the first shaft end 31 (except for a portion near the second shaft end 32 which has a chamfered portion 8b on its inner circumferential surface and a chamfered portion 10b on its outer circumferential surface). The outer circumferential surface (outer surface) of the outer ring 2 has a flat surface with relatively small irregularities and a relatively uniform surface height relative to a reference axis along the axial direction. The inner circumferential surface (inner surface) of the outer ring 2 has relatively large irregularities due to the outer ring raceway 5 etc. and a relatively large change in surface height relative to a reference axis along the axial direction.

[0028] In one example, the inner ring 3 is made of a hard metal such as bearing steel or carburized steel. In another example, the inner ring 3 is made of a different material. The inner ring 3 can be made of the same metal material as the outer ring 2, or a different metal material than the outer ring 2.

[0029] The inner ring 3 has an inner ring raceway 11 for the rolling elements 4 at the axially intermediate portion of the outer peripheral surface (outer surface). In one example, the inner ring raceway 11 has an arc-shaped generatrix shape with a diameter increasing toward the other axial side (second shaft end 42). The inner ring 3 also has a cone-convex inclined surface portion 12 in the outer peripheral surface adjacent to the second shaft end 42 of the inner ring raceway 11, the inclined surface portion 12 being inclined in a direction in which the outer diameter decreases toward the second shaft end 42. The inner ring 3 also has a cylindrical surface portion 13 in the outer peripheral surface adjacent to one axial side (first shaft end 41) of the inner ring raceway 11, the outer diameter of which does not change in the axial direction. The inner ring 3 also has chamfered portions 14a, 14b having an arc-shaped generatrix shape at both axial ends of the outer peripheral surface.

[0030] The inner ring 3 has a cylindrical surface portion (flat surface) 15, whose inner diameter does not change in the axial direction, at the axial middle portion of the inner surface (inner surface), and has chamfered portions 16a, 16b having an arc-shaped generatrix shape at both axial ends of the inner surface.

[0031] That is, the inner ring 3 has a radial thickness (thickness change, wall structure) that decreases overall toward the second shaft end 42 (except for a portion near the first shaft end 41 which has a chamfered portion 14a on its outer peripheral surface and a chamfered portion 16a on its inner peripheral surface). The inner peripheral surface (inner surface) of the inner ring 3 has a flat surface with relatively small irregularities and a relatively uniform surface height relative to a reference axis along the axial direction. The outer peripheral surface (outer surface) of the inner ring 3 has relatively large irregularities due to the inner ring raceway 11 etc. and a relatively large change in surface height relative to a reference axis along the axial direction.

[0032] A plurality of rolling elements 4 are rotatably disposed between an outer ring raceway 5 and an inner ring raceway 11. In one example, each rolling element 4 is made of a ball. In another example, each rolling element 4 is made of something other than a ball, such as a roller. In another example, each rolling element 4 is made of a hard metal, such as bearing steel or carburized steel, or ceramic. In another example, each rolling element 4 is made of another material.

[0033] <Manufacturing method of outer ring 2> When making the outer ring 2, first, a metal material is forged to form the rough shape of the outer ring 2, and then the inner peripheral surface is ground to form the outer ring raceway 5. Next, as shown in Fig. 6, the outer ring 2 is subjected to a quenching treatment and a tempering treatment. Both the quenching treatment and the tempering treatment are performed by heating the outer ring 2 to a target temperature, holding it for a predetermined time, and then cooling it.

[0034] The outer ring 2 is heated in the hardening and tempering processes by induction heating the outer ring 2 by generating eddy currents in the outer ring 2 using an induction heating coil.

[0035] As shown in FIG. 2, the induction heating device 200 includes an inner coil (inner induction coil, inner diameter side induction heating coil, inner coil) 17, an outer coil (outer diameter side induction heating coil, outer induction coil, outer coil) 18, and a power supply device 201 that supplies high-frequency current to the induction coils 17 and 18. Additionally, the induction heating device 200 may include at least one of a support device 202 that supports an object to be heated (ring-shaped member, workpiece), a transport device 203 that transports the ring-shaped member, a cooling device 204 that cools the ring-shaped member, a sensor 205 that detects the temperature of the ring-shaped member, an electrical matching device 206, and a control unit 207. The induction heating device 200 can independently and individually control the supply output (current value, etc.) to the induction coil 17 and the induction coil 18. In one example, the induction heating device 200 can independently and individually control the timing of supplying current to the induction coil 17 and the timing of supplying current to the induction coil 18. In addition, in one example, the induction heating device 200 can independently and individually control the current values ​​(output values) for the induction coils 17 and 18. In addition, in one example, the induction heating device 200 can independently and individually control the output times (heating times) for the induction coils 17 and 18. In one example, the induction heating device 200 can independently and individually control the relative positional relationships between the induction coils 17 and 18 and the ring-shaped member. Note that the induction heating device 200 may non-independently control some of the above-mentioned controls.

[0036] In this embodiment, the method of induction heating the outer ring 2 includes an inner heating step (inner diameter heating step, inner surface heating step, first heating step) and an outer heating step (outer diameter heating step, outer surface heating step, second heating step) that are performed independently of each other. In this example, the step of induction heating the outer ring 2 is performed in the order of the inner heating step (first heating step) and the outer heating step (second heating step). The induction heating device 200 includes a first mode in which a current is supplied to one coil to induction heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a first target temperature, and a second mode in which a current is supplied to another coil to induction heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a second target temperature that is higher than the first target temperature.

[0037] In the inner heating step, as shown in Fig. 3(A), an inner coil (inner diameter side induction heating coil, inner coil) 17 is arranged radially inside the outer ring 2, and no induction coil (induction heating coil, substantial coil) is arranged radially outside the outer ring 2. In a state where no substantial coil is arranged radially outside the outer ring 2, the outer ring 2 is induction heated using an induction coil (inner coil) 17 arranged radially inside the outer ring 2. That is, by passing current through the inner coil 17 arranged radially inside the outer ring 2, an eddy current is generated in the radially inner portion of the outer ring 2, and the outer ring 2 is heated from the radially inner side.

[0038] In one example, the inner coil 17 has a conductor wound in a spiral shape with a constant inner diameter in the axial direction, or a conductive material bent into a ring shape with a constant inner diameter in the axial direction. In other examples, the inner coil 17 can have a configuration other than those described above.

[0039] In this embodiment, the inner coil 17 used in the inner heating step is disposed adjacent to the inner surface of the outer ring 2 so that the outer surface of the induction coil 17 faces the inner surface of the outer ring 2. In one example, the outer peripheral surface (outer surface) of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface (inner surface) of the outer ring 2 are closely opposed to each other. The distance between the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2 is set so that an eddy current can be generated in the radially inner part of the outer ring 2, and can be, for example, about 1% to 30% of the inner diameter of the cylindrical surface portion 7 of the outer ring 2. The above numerical values ​​are merely examples and are not limited to the above numerical values.

[0040] The outer ring 2 is heated for a predetermined time in the inner diameter heating step, and then transferred to the outer diameter heating step.

[0041] In the outer heating step, as shown in Fig. 3(B), an outer coil (outer diameter side induction heating coil, outer coil) 18 is arranged radially outside the outer ring 2, and no induction coil (induction heating coil, substantial coil) is arranged radially inside the outer ring 2. In a state where no substantial coil is arranged radially inside the outer ring 2, the outer ring 2 is induction heated from the radially outside by passing current through the outer coil 18. In a state where no substantial coil is arranged radially inside the outer ring 2, the outer ring 2 is induction heated using an induction coil (inner coil) 18 arranged radially outside the outer ring 2. In other words, by passing current through the outer coil 18 arranged radially outside the outer ring 2, an eddy current is generated in the radially outer portion of the outer ring 2, and the outer ring 2 is heated from the radially outside.

[0042] In one example, the outer coil 18 comprises a conductive wire wound in a helical shape with a constant outer diameter in the axial direction, or a conductive material bent into a ring shape with a constant outer diameter in the axial direction, although in other examples, the outer coil 18 can have other configurations.

[0043] In this embodiment, the outer coil 18 used in the outer heating step is disposed adjacent to the outer surface of the outer ring 2 so that the inner surface of the induction coil 18 faces the outer surface of the outer ring 2. In one example, the inner circumferential surface (inner surface) of the outer coil 18 and the outer circumferential surface (outer surface) of the outer ring 2 are closely opposed to each other. The distance between the inner circumferential surface of the outer coil 18 and the outer circumferential surface of the outer ring 2 is set so that an eddy current can be generated in the radially outer portion of the outer ring 2, and can be, for example, about 1% to 30% of the outer diameter of the outer ring 2. The above numerical values ​​are merely examples, and are not limited to the above numerical values.

[0044] For example, in the quenching treatment of the outer ring 2, an inner surface heating step and an outer surface heating step are carried out on the outer ring 2 in this order, and the outer ring 2 is heated to a quenching temperature in the range of 800°C to 1000°C. The outer ring 2 is then left in an induction heating device to be held at the quenching temperature for 1 to 30 seconds, after which it is rapidly cooled to room temperature by, for example, immersing it in quenching oil for oil cooling. The above numerical values ​​and procedures are merely examples, and the present invention is not limited to these numerical values ​​and procedures.

[0045] For example, in the tempering treatment of the outer ring 2, an inner heating step and an outer heating step are carried out on the outer ring 2 in this order, heating the outer ring 2 to a tempering temperature in the range of 150°C to 300°C. The outer ring 2 is then left in an induction heating device to be held at the tempering temperature for 1 to 30 seconds, and then naturally cooled to room temperature. The above numerical values ​​and procedures are merely examples, and are not limited to the above numerical values ​​and procedures.

[0046] After the outer ring 2 is subjected to a hardening treatment and a tempering treatment, if necessary, the outer ring raceway 5 is subjected to a finishing treatment such as grinding, and the outer ring 2 is completed.

[0047] Here, in this embodiment, the effective length of the induction coils 17, 18 (the length range of the coil in the axial direction that contributes to induction heating (the distance from the first effective heating end 51 to the second effective heating end 52 along the axial direction)) is set to be larger than the axial length of the ring-shaped member (workpiece, outer ring 2, etc.) (the distance from the first axial end 31 to the second axial end 32 along the axial direction). For example, the effective length of the induction coils 17, 18 is set to 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300% or more of the axial length of the outer ring 2. Since the effective length of the induction coils 17, 18 is 110% or more of the axial length of the ring-shaped member, a part of the magnetic field wraps around the axial end face of the outer ring 2, expanding the heating area in the ring-shaped member and achieving uniform heating of the entire ring-shaped member. For example, in addition to the inner or outer surface of the ring-shaped member, heating proceeds from the axial end face toward the inside. Since the effective length of the induction coils 17, 18 is 200% or more of the axial length of the ring-shaped member, the tolerance level for shape changes and positional unevenness of the ring-shaped member is relaxed, and the versatility of the induction coils 17, 18 is increased. For example, the effective length of the induction coils 17, 18 is set to 200% or more of the average axial length of the ring-shaped members in a given lot (a lot including multiple types of ring-shaped members (such as outer rings) with different shapes). In this case, multiple ring-shaped members of various shapes are heat-treated using one type of induction coil 17, 18. Reducing the frequency of replacing the induction coils 17 and 18 and standardizing the heating conditions are advantageous for improving productivity.

[0048] In one example, as shown in FIG. 4(A), the positional relationship between the induction coil and the ring-shaped member is set so that the axial center position of the ring-shaped member (such as the outer ring 2) is the same as the center position of the axial effective length of the induction coil (such as the induction coil 17). In this case, the extension length (protruding height) H1 of the induction coil (such as the induction coil 17) in the vicinity of the first axial end (such as the first axial end 31 of the outer ring 2) of the ring-shaped member is the same as the extension length (protruding height) H2 of the induction coil in the vicinity of the second axial end (such as the second axial end 32 of the outer ring 2). That is, the distance H1 between the first axial end of the ring-shaped member (such as the first axial end 31 of the outer ring 2) and the first axial end of the induction coil (such as the first axial end 51 of the induction coil 17) in the axial direction is the same as the distance H2 between the second axial end of the ring-shaped member (such as the second axial end 32 of the outer ring 2) and the second axial end of the induction coil (such as the second axial end 52 of the induction coil 17) in the axial direction. In another example, as shown in FIG. 4(B), the distance H2 is set to be greater than the distance H1. That is, the positional relationship between the induction coil and the ring-shaped member is set so that the axial center position of the ring-shaped member (such as the outer ring 2) is different from the center position of the axial effective length of the induction coil (such as the induction coil 17). In the example of FIG. 4(B), the thickness of the ring-shaped member in the vicinity of the second axial end (such as the second axial end 32 of the outer ring 2) is greater than the thickness of the ring-shaped member in the vicinity of the first axial end (such as the first axial end 31 of the outer ring 2). By setting the extension length (protruding height) H2 of the induction coil in the vicinity of the second axial end where the thickness is greater relatively large, the entire ring-shaped member having a thickness variation is heated uniformly. These can be similarly applied when the induction coil is disposed outside the ring-shaped member. By setting the effective length of the induction coils 17 and 18 to be greater than the axial length of the ring-shaped member, the tolerance level for changes in the relative positional relationship between the induction coil and the ring-shaped member is relaxed.

[0049] Returning to FIG. 3, in this embodiment, when the outer ring 2 is induction heated to perform quenching or tempering, the inner heating step and the outer heating step are performed independently of each other. In a state where no substantial coil is arranged radially outward of the outer ring 2, the outer ring 2 is heated from the inside. In a state where no substantial coil is arranged radially inward of the outer ring 2, the outer ring 2 is heated from the outside. Therefore, the heating conditions in the inner heating step in which the outer ring 2 is induction heated from the radially inward side and the heating conditions in the outer heating step in which the outer ring 2 is induction heated from the radially outward side can be controlled independently. For this reason, it is easy to control the heating state of the outer ring 2. That is, by appropriately setting the heating conditions in the inner heating step and the heating conditions in the outer heating step, respectively, the entire outer ring 2 can be heated approximately uniformly and efficiently. The combination of the independent arrangement of the induction coil for the ring-shaped member (such as the outer ring 2) and the setting of the induction coil length provides the advantages of both improved heating efficiency and improved productivity. Such advantages can be achieved for each of the multiple heating steps and the single heating step.

[0050] The heating conditions include the value of the current supplied to the induction coils 17, 18 (∝ the output of the induction heating coils 17, 18), the heating time, and the positional relationship between the outer ring 2 and the induction coils 17, 18, and the like.

[0051] In this embodiment, the induction heating method includes a step of preparing an inner coil 17 disposed radially inward of the outer ring 2 and an outer coil 18 disposed radially outward of the outer ring 2, a first heating step of supplying a current to one of the inner coil 17 and the outer coil 18 to induction heat the outer ring 2 so that at least a portion of the outer ring 2 reaches a first target temperature, and a second heating step of supplying a current to another of the inner coil 17 and the outer coil 18 after the first heating step to induction heat the outer ring 2 so that at least a portion of the outer ring 2 reaches a second target temperature higher than the first target temperature. In this embodiment, one coil (inner coil 17) used in the first heating step is disposed adjacent to an inner surface (first surface) of the inner and outer surfaces of the outer ring 2 whose surface height is relatively variable, and another coil (outer coil 18) used in the second heating step is disposed adjacent to an outer surface (second surface) of the inner and outer surfaces of the outer ring 2 whose surface height is relatively uniform. At least one of the first heating step and the second heating step is performed in a state where only one of the inner coil 17 and the outer coil 18 is disposed adjacent to the outer ring 2. In this embodiment, the inner heating step and the outer heating step are performed in this order.

[0052] Here, generally, when the outer or inner ring of a bearing is heated by induction heating, the following problems may occur. For example, the outer ring of a rolling bearing has an outer ring raceway on its inner circumferential surface. When an induction coil is arranged on the radial inside of the outer ring, the distance between the inner circumferential surface of the outer ring and the induction coil varies depending on the axial position. For this reason, when the induction coil is energized, eddy currents concentrate on the part of the inner circumferential surface that is close to the induction coil, and this part is likely to be intensively heated by induction. The part that is far from the induction coil is heated by the heat transmitted from the part of the inner circumferential surface that is close to the induction coil. When the temperature rise rate differs greatly depending on the axial position of the outer ring, it is difficult to heat the entire outer ring uniformly. If the quenching and tempering processes are performed while the temperature inside the outer ring is not uniform, the thickness of the hardened layer formed on the surface of the outer ring may become nonuniform, and the required quality may not be met. In order to avoid such problems, a method of reducing the current value supplied to the induction coil to reduce the output of the induction coil and extend the heating time of the outer ring is considered. This method can minimize the difference in the rate of temperature rise of the outer ring depending on the axial position, but it is not preferable because it leads to a decrease in productivity.

[0053] In this embodiment, in the first heating step (inner heating step), the outer ring 2 is heated by an induction coil 17 arranged opposite the inner surface of the outer ring 2, whose surface height varies relatively, and in the subsequent second heating step (outer heating step), the outer ring 2 is heated by an induction coil 18 arranged opposite the outer surface of the outer ring 2, whose surface height is relatively uniform. For example, as shown in FIG. 5, in the first heating step (inner heating step), a part of the inner surface side of the outer ring 2 (P i2 The temperature of the part (P) of the outer ring 2 having a relatively high temperature rises relatively quickly and reaches the first target temperature T1, and at this time, the temperature of the other parts is lower than the first target temperature. i2 ) is transferred to other parts. In the second heating step (outer heating step), the outer ring 2 is heated from the outside, and at a certain timing, most of the outer ring 2 reaches a temperature close to the second target temperature T2. In the induction heating of the outer ring 2, which has a relatively large change in thickness, the entire outer ring 2 is heated in a relatively short time, and the difference in the temperature rise rate of the outer ring 2 is suppressed to a small value.

[0054] In the inner heating step (first heating step), the current value supplied to the inner coil 17 is increased to increase the output of the inner coil 17, so that the inner circumferential surface (P i2 (see FIG. 3A) can be quickly raised to near the first target temperature.

[0055] In the inner heating process, the end P of the second shaft end, which is close to the inner coil 17 on the inner circumferential surface of the outer ring 2, is i2 The temperature rise amount of the first shaft end P i1 On the other hand, the temperature rise at the end P of the second shaft end of the outer peripheral surface of the outer ring 2 becomes larger than that at the end P of the second shaft end of the outer peripheral surface of the outer ring 2. O2 The temperature rise of the outer ring 2 and the end P of the first shaft end of the outer peripheral surface of the outer ring 2 O1 The temperature rise is about the same as that of

[0056] In the outer heating process, the outer ring 2 is heated from a flat surface with a relatively uniform surface height (a radially outer portion with a constant outer diameter except for both ends in the axial direction). The output is adjusted by adjusting the value of the current supplied to the outer coil 18, and the heating time is also adjusted. As a result, as shown diagrammatically in FIG. 5, the entire outer ring 2 is heated approximately uniformly so as to be close to the target temperature (second target temperature). In other words, the temperatures of the respective parts of the outer ring 2 rise to the target temperature at approximately the same time.

[0057] Incidentally, the step of induction heating the outer ring 2 may also be performed in the order of an outer heating step and then an inner heating step, as described below.

[0058] The heating conditions in the inner heating step and the heating conditions in the outer heating step can be determined in advance by experiments, simulations, etc. The heating time in the outer heating step relative to the heating time in the inner heating step depends on the radial thickness of the outer ring 2, etc., but can be, for example, 50% to 200%, and preferably 80% to 120%. The current value supplied to the outer coil 18 in the outer heating step relative to the current value supplied to the inner coil 17 in the inner heating step depends on the radial thickness of the outer ring 2, etc., but can be, for example, 50% to 200%, and preferably 80% to 120%.

[0059] In one example, in the inner heating process, the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2 are closely opposed to each other, and in the outer heating process, the inner peripheral surface of the outer coil 18 and the outer peripheral surface of the outer ring 2 are closely opposed to each other. In addition, a combination corresponding to a specific model number of the outer ring 2 is used as the inner coil 17 and the outer coil 18. In this case, heating from the radially inner side of the outer ring 2 is efficiently performed in the inner heating process, and heating from the radially outer side of the outer ring 2 is efficiently performed in the outer heating process. Therefore, the time required to heat the outer ring 2 to the target temperature is kept short. In this example, when mass-producing outer rings 2 of the same model number, production efficiency is ensured.

[0060] In another example, a relatively large radial gap is provided between the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2 in the inner heating process, and / or between the inner peripheral surface of the outer coil 18 and the cylindrical surface portion 9 provided on the outer peripheral surface of the outer ring 2 in the outer heating process. For example, as shown in FIG. 8(A), an inner diameter side induction coil 17 having a ratio of the outer diameter to the inner diameter of the cylindrical surface portion 7 smaller than that of the inner diameter side induction coil 17 of the first example shown in FIG. 3(A) is used. A radial gap larger than the gap in the embodiment shown in FIG. 3(A) exists between the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7. Also, as shown in FIG. 7(B), an outer diameter side induction coil 18 having a ratio of the inner diameter to the outer diameter of the cylindrical surface portion 9 larger than that of the outer diameter side induction coil 18 of the first example shown in FIG. 3(B) is used. Between the inner circumferential surface of the outer coil 18 and the cylindrical surface portion 9, there exists a radial gap that is larger than the gap in the embodiment shown in FIG. 3(B).

[0061] In this case, the same combination of the inner coil 17 and the outer coil 18 can be used to induction heat a plurality of types of outer rings with different outer and inner diameters. For example, in the inner heating step shown in FIG. 7(A), the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2a face each other closely. In the outer heating step shown in FIG. 7(B), a relatively large radial gap exists between the inner peripheral surface of the outer coil 18 and the outer peripheral surface of the outer ring 2a. The distance between the inner peripheral surface of the outer coil 18 and the outer peripheral surface of the outer ring 2a is not particularly limited as long as an eddy current can be generated in the radially outer portion of the outer ring 2a based on the application of electricity to the outer coil 18, but can be, for example, up to about 1% to 30% of the outer diameter of the outer ring 2a.

[0062] In the example of Figure 7, a relatively large radial gap exists between the inner surface of the outer coil 18 and the outer surface of the outer ring 2a during the outer heating process. However, by increasing the current value supplied to the outer coil 18 and increasing the output of the outer coil 18 during the outer heating process, it is possible to prevent an excessive increase in the time required to heat the outer ring 2a to the target temperature.

[0063] In the example shown in FIG. 8, the same combination of inner coil 17 and outer coil 18 as in the embodiment of FIG. 7 is used to induction-heat the outer ring 2b, which has a larger outer diameter and inner diameter than the embodiment of FIG. 7. In the inner heating process shown in FIG. 8(A), a relatively large radial gap exists between the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2b. In the outer heating process shown in FIG. 8(B), the inner peripheral surface of the outer coil 18 and the outer peripheral surface of the outer ring 2a face each other closely. The distance between the outer peripheral surface of the inner coil 17 and the inner peripheral surface of the outer ring 2b is not particularly limited as long as an eddy current can be generated in the radially inner portion of the outer ring 2b, but can be, for example, about 1% to 30% of the inner diameter of the outer ring 2b at most.

[0064] 8, a relatively large radial gap exists between the outer peripheral surface of the inner coil 17 and the inner peripheral surface of the outer ring 2b in the inner heating step. In the inner heating step, the current value supplied to the inner coil 17 is increased to increase the output of the inner coil 17, thereby preventing an excessive increase in the time required to heat the outer ring 2b to the target temperature.

[0065] In the examples of Figs. 7 and 8, the heating conditions in the outer heating step and the heating conditions in the inner heating step are appropriately set, respectively, so that the outer rings 2a, 2b can be heated substantially uniformly and efficiently throughout.

[0066] In the examples of Figs. 7 and 8, the heating conditions are set so that a relatively large radial gap is permitted to exist between the outer peripheral surface of the inner coil 17 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2 in the inner heating process, and / or between the inner peripheral surface of the outer coil 18 and the outer peripheral surface of the outer ring 2 in the outer heating process. Using the same combination of the inner coil 17 and the outer coil 18, multiple types of outer rings with different outer diameters and inner diameters can be induction heated. There is no need to replace the inner coil 17 and the outer coil 18 every time the outer diameter and inner diameter of the outer ring are changed. For example, this is particularly suitable for a production line that targets a wide variety of small-lot outer rings. Since there is no need to prepare multiple combinations of the inner coil 17 and the outer coil 18, the replacement work of the inner coil 17 and the outer coil 18 is simplified, improving production efficiency.

[0067] In the inner heating process, no induction heating coil is arranged radially outside the outer ring 2, and in the outer heating process, no induction heating coil is arranged radially inside the outer ring 2. This makes it possible to stably control the heating conditions in the inner heating process and the heating conditions in the outer heating process.

[0068] For example, if an induction heating coil that does not supply current is arranged radially outside the outer ring 2 in the inner heating process, there is a possibility that current will flow through the induction heating coil arranged radially outside the outer ring 2 due to electromagnetic induction when current is applied to the inner coil 17. If the radially outer portion of the outer ring 2 is inadvertently heated, it becomes difficult to stably control the heating conditions. In this embodiment, since an induction heating coil is not arranged radially outside the outer ring 2 in the inner heating process, the heating conditions in the inner heating process can be stably controlled.

[0069] In this embodiment, the case has been described in which the outer ring 2 of the radial rolling bearing 1, which is a single-row angular ball bearing, serving as a ring-shaped member, is heated by induction heating and subjected to quenching and tempering.

[0070] However, the ring-shaped member is not limited to the outer ring of a single-row angular contact ball bearing. Any ring-shaped member can be used as the ring-shaped member. For example, the outer ring of a single-row deep groove ball bearing, a roller bearing, or a tapered roller bearing, or the inner ring of a rolling bearing as shown in the fourth to sixth embodiments described later, can be used as the ring-shaped member. Alternatively, the outer ring or inner ring of a double-row rolling bearing can be used as the ring-shaped member. Also, a sliding bearing can be used as the ring-shaped member.

[0071] The heat treatment using the induction heating method is not limited to quenching and tempering, but can also be applied to annealing and normalizing.

[0072] Heat treatment using the induction heating method can also be applied to hardening, tempering, annealing, and / or normalizing of ring-shaped members constituting a vehicle or mechanical device.

[0073] [Second embodiment] A second embodiment of the present invention will be described with reference to Fig. 9. In this embodiment, the process of induction heating the outer ring 2 is carried out in the order of an outer heating process shown in Fig. 9(A) and an inner heating process shown in Fig. 9(B).

[0074] In this embodiment, similarly to the first embodiment, the entire outer ring 2 can be heated substantially uniformly and efficiently by appropriately setting the heating conditions in the outer heating step and the heating conditions in the inner heating step.

[0075] In this embodiment, in a first heating step (outer heating step), the outer ring 2 is heated by an induction coil 18 arranged opposite the outer surface of the outer ring 2, which has a relatively uniform surface height, and in the subsequent second heating step (inner heating step), the outer ring 2 is heated by an induction coil 17 arranged opposite the inner surface of the outer ring 2, which has a relatively variable surface height. For example, in the first heating step (outer heating step) shown in FIG. 9(A), the temperature of a portion of the outer surface side of the outer ring 2 reaches the first target temperature. On the other hand, a portion of the inner surface side of the outer ring 2 located away from the outer surface (Pi2 ) does not transfer heat well and has a lower temperature than other parts.

[0076] Next, in the second heating step (inner heating step) shown in FIG. 9(B), the part with a relatively low temperature (P i2 ) is easily heated, and that part (P i2 ) rises relatively quickly. As a result, at a certain timing, most of the outer ring 2 reaches a temperature close to the second target temperature T2. In induction heating of the outer ring 2, which has a relatively large change in thickness, the entire outer ring 2 is heated in a relatively short time, and the difference in the rate of temperature rise of the outer ring 2 is suppressed to a small value. The configurations and effects of other parts are similar to those of the first embodiment.

[0077] [Third embodiment] A third embodiment of the present invention will be described with reference to Fig. 10. In this embodiment, the process of induction heating the outer ring 2 includes an inner heating process shown in Fig. 10(A) and an outer heating process shown in Fig. 10(B) in that order, and then a reheating process of induction heating the outer ring 2 from the radially inner side as shown in Fig. 10(C).

[0078] In the reheating process, a reheating inner coil (reheating inner diameter side induction heating coil, reheating inner induction coil, reheating inner coil) 19 is arranged radially inside the outer ring 2, and with no induction heating coil arranged radially outside the outer ring 2, current is passed through the inner coil 19 to induction heat the outer ring 2 from the radially inside. In this embodiment, the outer peripheral surface of the inner coil 19 and the cylindrical surface portion 7 provided on the inner peripheral surface of the outer ring 2 are closely opposed to each other.

[0079] The radial positional relationship between the outer ring 2 and the inner coil 19 in the reheating step may be the same as or different from the radial positional relationship between the outer ring 2 and the inner coil 17 in the inner heating step. In addition, the inner coil 17 used in the inner heating step may be used as the inner coil 19.

[0080] In this embodiment, the entire outer ring 2 can be heated substantially uniformly and efficiently by appropriately setting the heating conditions in the inner heating step, the heating conditions in the outer heating step, and the heating conditions in the reheating step.

[0081] In this embodiment, the process of induction heating the outer ring 2 is performed in the order of an inner heating process and then an outer heating process, and further includes a reheating process of induction heating the outer ring 2 from the radially inner side, so that the entire outer ring 2 can be heated more reliably and approximately uniformly.

[0082] That is, in the induction heating method of the first embodiment, after the outer ring 2 is heated from the radially inner side in the inner heating step, the temperature of the radially inner portion of the outer ring 2 may decrease during transport to the outer heating step. In this case, even if the outer ring 2 is heated from the radially outer side in the outer heating step, the temperature of the radially inner portion of the outer ring 2 may not rise to the target temperature.

[0083] In this embodiment, the inner heating process and the outer heating process are performed in that order, and then a reheating process is performed in which the outer ring 2 is induction heated from the radially inner side. Even if the temperature of the radially inner part of the outer ring 2 drops during transport between processes, the temperature of that part can be increased to the target temperature by reheating that part, and the temperature of the entire outer ring 2 can be adjusted to be approximately uniform. The configurations and effects of the other parts are the same as those of the first embodiment.

[0084] [Fourth embodiment] A fourth embodiment of the present invention will be described with reference to Fig. 11. In this embodiment, the inner ring 3 of a radial rolling bearing 1 as shown in Fig. 1 is heated by induction heating.

[0085] In this embodiment, the process of induction heating the inner ring 3 includes an inner heating process and an outer heating process that are carried out independently of each other. In this embodiment, the process of induction heating the inner ring 3 is carried out in the order of the outer heating process and the inner heating process.

[0086] In the outer heating process, as shown in FIG. 11(A), an outer coil 18a is arranged radially outside the inner ring 3, and no induction heating coil is arranged radially inside the inner ring 3. Current is passed through the outer coil 18a, thereby inductively heating the inner ring 3 from the radial outside.

[0087] In this embodiment, the inner peripheral surface of the outer coil 18a and the cylindrical surface portion 13 provided on the outer peripheral surface of the inner ring 3 are closely opposed to each other. The distance between the inner peripheral surface of the outer coil 18a and the cylindrical surface portion 13 provided on the outer peripheral surface of the inner ring 3 is not particularly limited as long as an eddy current can be generated in the radially outer portion of the inner ring 3, but can be, for example, about 1% to 30% of the outer diameter of the cylindrical surface portion 13 of the inner ring 3.

[0088] In the inner heating process, as shown in FIG. 11(B), an inner coil 17a is arranged radially inside the inner ring 3, and no induction coil is arranged radially outside the inner ring 3. Current is passed through the inner coil 17a, thereby inductively heating the inner ring 3 from the radially inside.

[0089] In this embodiment, the outer peripheral surface of the inner coil 17a faces closely to the inner peripheral surface of the inner ring 3. The distance between the outer peripheral surface of the inner coil 17a and the inner peripheral surface of the inner ring 3 is not particularly limited as long as an eddy current can be generated in the radially inner portion of the inner ring 3, but can be, for example, about 1% to 30% of the inner diameter of the inner ring 3.

[0090] In this embodiment, the heating conditions in the outer heating step and the heating conditions in the inner heating step are appropriately set, respectively, so that the entire outer ring 2 can be heated substantially uniformly and efficiently.

[0091] In this embodiment, the outer heating step and the inner heating step are carried out in this order.

[0092] In the outer heating process, by increasing the output of the outer coil 18a, the temperature of the outer peripheral surface of the end portion of the first shaft end, which has the greater radial thickness, of the inner ring 3 can be quickly raised to close to the target temperature.

[0093] Next, in the inner heating step, the current value supplied to the inner coil 17a is adjusted to adjust the output and the heating time, and the inner ring 3 is heated from the radially inner portion where the outer diameter is constant except for both ends in the axial direction. This makes it possible to heat the entire inner ring 3 approximately uniformly to the target temperature. In other words, it is possible to raise the temperature of each portion of the inner ring 3 to the target temperature at approximately the same time. The configurations and effects of the other portions are the same as those of the first embodiment.

[0094] [Fifth embodiment] A fifth embodiment of the present invention will be described with reference to Fig. 12. In this embodiment, the process of induction heating the inner ring 3 is carried out in the order of an inner heating process shown in Fig. 12(A) and an outer heating process shown in Fig. 12(B).

[0095] In this embodiment as well, by appropriately setting the heating conditions in the inner heating step and the heating conditions in the outer heating step, it is possible to heat the entire inner ring 3 substantially uniformly and efficiently. The configurations and effects of other parts are similar to those of the first and fourth embodiments.

[0096] [Sixth embodiment] A sixth embodiment of the present invention will be described with reference to Fig. 13. In this embodiment, the process of induction heating the inner ring 3 includes an outer heating process shown in Fig. 13(A) and an inner heating process shown in Fig. 13(B) in that order, and then a reheating process of induction heating the inner ring 3 from the radially outer side as shown in Fig. 13(C).

[0097] 13(C), a reheating outer coil (reheating outer diameter side induction heating coil, reheating outer induction coil, reheating outer coil) 20 is arranged radially outside the inner ring 3, and current is passed through the outer coil 20 with no induction coil arranged radially inside the inner ring 3, thereby inductively heating the inner ring 3 from the radial outside. In this embodiment, the inner peripheral surface of the outer coil 20 and the cylindrical surface portion 13 provided on the outer peripheral surface of the inner ring 3 are closely opposed to each other.

[0098] In this embodiment, the entire inner ring 3 can be heated substantially uniformly and efficiently by appropriately setting the heating conditions in the outer heating step, the inner heating step, and the reheating step.

[0099] In this embodiment, the process of induction heating the inner ring 3 is performed in the order of an outer heating process and then an inner heating process, and further includes a reheating process of induction heating the inner ring 3 from the radially outer side, so that the entire inner ring 3 can be heated more reliably and approximately uniformly.

[0100] In this embodiment, the outer heating process and the inner heating process are performed in this order, and then a reheating process is performed in which the inner ring 3 is induction heated from the radially outer side. Even if the temperature of the radially outer part of the inner ring 3 drops during transfer from the outer heating process to the inner heating process, the part can be reheated to increase the temperature to the target temperature, and the temperature of the entire inner ring 3 can be adjusted to be approximately uniform. The configurations and effects of the other parts are the same as those of the first, third and fourth embodiments.

[0101] [Seventh embodiment] A seventh embodiment of the present invention will be described with reference to FIG.

[0102] In this embodiment, as shown in parts (A) and (B) of Fig. 14, the effective length of the induction coils 17, 18 is approximately the same as the axial length of the ring-shaped member 30. When the axial length of the ring-shaped member 30 and the effective length of the induction coils 17, 18 are the same, the magnetic field is unlikely to wrap around the axial end face of the ring-shaped member 30, and it may be difficult to heat the axial end face to the inside in the radial direction. In this case, the ring-shaped member 30 is additionally heated by a reheating process as necessary. On the other hand, when the radial thickness difference in the ring-shaped member 30 is relatively small, the influence of the magnetic field wraparound is small, and relatively uniform heating is possible without providing a reheating process.

[0103] In this embodiment, a first heating step is performed in which current is supplied to the inner coil 17 to inductively heat the ring-shaped member 30 so that at least a portion of the ring-shaped member 30 reaches a first target temperature, and then a second heating step is performed in which current is supplied to the outer coil 18 to inductively heat the ring-shaped member 30 so that at least a portion of the ring-shaped member 30 reaches a second target temperature higher than the first target temperature. The configurations and effects of the other parts are the same as those of the above-mentioned embodiment.

[0104] [Eighth embodiment] An eighth embodiment of the present invention will be described with reference to FIG.

[0105] In this embodiment, as shown in parts (A) and (B) of FIG. 15, the effective length of the induction coils 17 and 18 is larger than the axial length of the ring-shaped member 30. For example, the effective length of the induction coils is set to 110, 120, 130, 140, or 150% or more of the axial length of the ring-shaped member 30. When the effective length of the induction coils 17 and 18 is larger than the axial length of the ring-shaped member 30, the magnetic field is likely to wrap around the axial end surface of the ring-shaped member 30, and the inside of the ring-shaped member 30 is heated even at the axial end surface. As a result, the entire cross section of the ring-shaped member 30 is likely to be heated uniformly. The configurations and effects of the other parts are the same as those of the above-mentioned embodiment.

[0106] [Ninth embodiment] A ninth embodiment of the present invention will be described with reference to FIG.

[0107] In this embodiment, as shown in parts (A), (B), (C), and (D) of FIG. 16, the effective length of the induction coils 17 and 18 is greater than the axial length of the ring-shaped member 30. For example, the effective length of the induction coils is set to 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300% or more of the axial length of the ring-shaped member 30. In this embodiment, as in the eighth embodiment, the magnetic field easily wraps around the axial end surface of the ring-shaped member 30, and the ring-shaped member 30 is heated even at the axial end surface. As a result, the entire cross section of the ring-shaped member 30 is easily heated uniformly.

[0108] In this embodiment, the dimensional difference between the effective length of the induction coils 17, 18 and the axial length of the ring-shaped member 30 is larger than in the eighth embodiment. By setting the current value supplied to the induction coils 17, 18 to a relatively small value, it is possible to uniformly heat the ring-shaped member 30 in approximately the same heating time as in the eighth embodiment.

[0109] In this embodiment, a core member made of a magnetic material is additionally provided. For example, the core member is provided inside the inner coil 17 (at a position near the inner circumferential surface) and / or at a position near both axial end faces of the inner coil 17. The core member is also provided outside the outer coil 18 (at a position near the outer circumferential surface) and at a position near both axial end faces of the outer coil 18. The provision of the core member improves the heating efficiency.

[0110] In this embodiment, since the dimensional difference between the effective length of the induction coils 17, 18 and the axial length of the ring-shaped member 30 is relatively large, the tolerance level for shape changes and positional irregularities of the ring-shaped member 30 is relaxed, and the versatility of the induction coils 17, 18 is increased. A single type of induction coil 17, 18 can be used to heat treat a plurality of ring-shaped members of various shapes. The frequency of replacing the inner coil 17 and the outer coil 18 is reduced, and this is preferably applied, for example, to the manufacture of a wide variety of small lots of ring-shaped members 30.

[0111] According to the above-described embodiment, it is possible to perform heat treatment on a plurality of ring-shaped members of various shapes, as shown in Fig. 17. Heat treatment using a versatile induction coil is advantageous in reducing manufacturing costs.

[0112] The ring-shaped member can be applied to, for example, bearings 900A, 900B supporting a rotating shaft 963 of a motor 961 shown in FIG.

[0113] 18, motor 961 is a brushless motor and has a cylindrical center housing 965 and a substantially disk-shaped front housing 967 that closes one open end of the center housing 965. A rotatable rotating shaft 963 is supported inside the center housing 965 along its axis via bearings 900A, 900B that are arranged in the front housing 967 and the bottom of the center housing 965. A rotor 969 for driving the motor is provided around the rotating shaft 963, and a stator 971 is fixed to the inner circumferential surface of the center housing 965.

[0114] Motor 961 is generally mounted on a machine or a vehicle, and drives rotation of a rotating shaft 963 supported by bearings 900A and 900B.

[0115] The bearing element or bearing can be applied to a rotation support part of a machine having a rotating part, various manufacturing equipment, for example, a screw device such as a ball screw device, and a linear motion device such as an actuator (a combination of a linear guide bearing and a ball screw, an XY table, etc.). The bearing element or bearing can also be applied to a steering device such as a wiper, a power window, an electric door, an electric seat, a steering column (for example, an electric tilt-telescopic steering column), a universal joint, an intermediate gear, a rack and pinion, an electric power steering device, and a worm reduction gear. Furthermore, the bearing element or bearing can be applied to various vehicles such as automobiles, motorcycles, and trains. The bearing of this configuration can be suitably applied to any part where there is relative rotation, which can lead to improved product quality and reduced costs.

[0116] As the bearing having a ring-shaped member, various types of bearings can be suitably applied, such as rolling bearings, sliding bearings, etc. For example, the bearing element can be applied to the outer ring and inner ring of a radial rolling bearing, the outer ring and inner ring of a radial cylindrical roller bearing using cylindrical rollers (including needles), and the outer ring and inner ring of a radial tapered roller bearing using tapered rollers.

[0117] The above-described embodiments can be appropriately combined and implemented as long as no contradiction occurs. Furthermore, the technical scope of the present invention is not limited to the scope described in the embodiments. Various modifications or improvements can be made to the embodiments. Forms with such modifications or improvements can also be included in the technical scope of the present invention. Furthermore, the present invention is not limited to the described embodiments, and any combination of these configurations may be used. [Explanation of symbols]

[0118] 1 Radial rolling bearing 2, 2a, 2b Outer ring 3. Inner Circle 4 Rolling elements 5 Outer raceway 6 Slope section 7 Cylindrical surface part 8a, 8b Chamfered parts 9 Cylindrical surface part 10a, 10b Chamfered portion 11 Inner raceway 12 Slope section 13 Cylindrical surface part 14a, 14b Chamfered portion 15 Cylindrical surface part 16a, 16b Chamfered part 17, 17a Inner coil 18, 18a Outer coil 19 Reheat inner coil 20 Outer reheat coil

Claims

1. The method includes a step of supplying a current to an induction coil to inductively heat the ring-shaped member, the induction heating step includes: inductively heating the ring-shaped member using the induction coil arranged radially inward of the ring-shaped member in a state in which no substantial coil is arranged radially outward of the ring-shaped member; or inductively heating the ring-shaped member using the induction coil arranged radially outward of the ring-shaped member in a state in which no substantial coil is arranged radially inward of the ring-shaped member; The effective length of the induction coil is set to be larger than the axial length of the ring-shaped member. A method for induction heating a ring-shaped member.

2. 2. The induction heating method according to claim 1, wherein the effective length of the induction coil is set to be 110% or more of the axial length of the ring-shaped member.

3. 2. The induction heating method according to claim 1, wherein the effective length of the induction coil is set to 200% or more of the axial length of the ring-shaped member.

4. The induction heating step includes: In a state where no substantial coil is disposed radially outward of the ring-shaped member, the ring-shaped member is inductively heated using an inner coil as the induction coil disposed radially inward of the ring-shaped member; In a state where no substantial coil is disposed radially inside the ring-shaped member, the ring-shaped member is inductively heated using an outer coil as the induction coil disposed radially outside the ring-shaped member; The induction heating method according to claim 1 , further comprising:

5. a first heating step of inductively heating the ring-shaped member by supplying a current to one of the inner coil and the outer coil so that at least a portion of the ring-shaped member reaches a first target temperature; a second heating step of supplying a current to another coil of the inner coil and the outer coil after the first heating step, thereby inductively heating the ring-shaped member so that at least a portion of the ring-shaped member reaches a second target temperature higher than the first target temperature; The induction heating method of claim 4 , comprising:

6. The one coil used in the first heating step is disposed adjacent to a first surface, which has a relatively large change in surface height, among the inner surface and the outer surface of the ring-shaped member, and The other coil used in the second heating step is disposed adjacent to a second surface, which has a relatively uniform surface height, of the inner surface and the outer surface of the ring-shaped member. The induction heating method according to claim 5.

7. The method further includes a step of reheating the ring-shaped member after the induction heating step. The induction heating method according to any one of claims 1 to 6.

8. A step of preparing a first coil disposed radially inward of a ring-shaped member and a second coil disposed radially outward of the ring-shaped member; a first heating step of inductively heating the ring-shaped member by supplying a current to one of the first coil and the second coil so that at least a portion of the ring-shaped member reaches a first target temperature; a second heating step of inductively heating the ring-shaped member by supplying a current to another coil of the first coil and the second coil after the first heating step, so that at least a portion of the ring-shaped member reaches a second target temperature higher than the first target temperature; The induction heating method comprises:

9. The one coil used in the first heating step is disposed adjacent to a first surface, which has a relatively large change in surface height, among the inner surface and the outer surface of the ring-shaped member, and The other coil used in the second heating step is disposed adjacent to a second surface, which has a relatively uniform surface height, of the inner surface and the outer surface of the ring-shaped member. The induction heating method according to claim 8.

10. 10. The induction heating method according to claim 8, wherein at least one of the first heating step and the second heating step is performed with both the first coil and the second coil positioned adjacent to the ring-shaped member.

11. 10. The induction heating method according to claim 8, wherein at least one of the first heating step and the second heating step is performed in a state in which only one of the first coil and the second coil is arranged adjacent to the ring-shaped member.

12. A method for manufacturing a ring-shaped member, comprising the step of heat-treating a ring-shaped member by using the induction heating method according to any one of claims 1 to 11.

13. A ring-shaped member manufactured by the manufacturing method according to claim 12.

14. A method for manufacturing a bearing, comprising the step of heat treating a ring-shaped member of a bearing by using the induction heating method according to any one of claims 1 to 11.

15. A bearing manufactured using the manufacturing method according to claim 14.

16. A method for manufacturing a vehicle having a ring-shaped member, comprising the steps of: A method for manufacturing a vehicle, comprising the step of heat treating the ring-shaped member by using the induction heating method according to any one of claims 1 to 11.

17. A method for manufacturing a mechanical device having a ring-shaped member, comprising the steps of: A method for manufacturing a mechanical device, comprising the step of heat-treating the ring-shaped member by using the induction heating method according to any one of claims 1 to 11.

18. An induction heating device for induction heating a ring-shaped member, comprising: An induction coil; A power supply device that supplies a current to the induction coil; Equipped with The induction coil is disposed radially inward of the ring-shaped member in a state where no substantial coil is disposed radially outward of the ring-shaped member, or is disposed radially outward of the ring-shaped member in a state where no substantial coil is disposed radially inward of the ring-shaped member, The effective length of the induction coil is set to be equal to or greater than the axial length of the ring-shaped member. Induction heating device.

19. An induction heating device for induction heating a ring-shaped member, comprising: A first coil disposed radially inward of the ring-shaped member; A second coil disposed radially outward of the ring-shaped member; a power supply device that supplies current to the first coil and the second coil; Equipped with the power supply device includes a first mode in which a current is supplied to one of the first coil and the second coil to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a first target temperature, and a second mode in which a current is supplied to another of the first coil and the second coil to inductively heat the ring-shaped member so that at least a portion of the ring-shaped member reaches a second target temperature higher than the first target temperature. Induction heating device.

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