Patent Description:
As is well known, in a manufacturing process for a metal member, which requires a high mechanical strength, such as a raceway ring for a rolling bearing, a heat treatment (quench hardening) for providing the mechanical strength required for the metal member is performed. The heat treatment includes a heating step of heating a workpiece to be subjected to the heat treatment to a target temperature and a cooling step of cooling the heated workpiece. The heating step can be carried out using an atmosphere heating furnace such as a mesh-belt type continuous furnace. However, the atmosphere heating furnace has some problems, for example, that an energy efficiency is low because of necessity of heating an atmosphere at the same time, and leading to increase in size of the heat treatment apparatus.

Therefore, as described in Patent Literature <NUM>, in some cases, the workpiece is heated by high-frequency induction heating in the heating step. According to the induction heating, since the workpiece can be directly heated, high energy efficiency can be achieved, and a compact heat treatment apparatus can be realized. Further, in particular, when the workpiece to be subjected to the heat treatment is a ring-shaped member such as the raceway ring for the rolling bearing, there can be adopted a so-called "continuous heating method". The continuous heating method is a method of sequentially heating a plurality of coaxially held workpieces (ring-shaped members) by relatively moving the plurality of coaxially held workpieces and a heating coil (induction heating coil) in energized state arranged coaxially with the workpieces in an axial direction of the workpiece. The continuous heating method described above has an advantage in that each of the workpieces can be inductively heated to the target temperature in an efficient manner.

Further examples of heat treatment apparatuses and methods are disclosed in Patent Literature <NUM> to <NUM>.

Incidentally, in the case where a load acts on the whole of the workpiece (each parts of the workpiece in a circumferential direction of the workpiece) like the raceway ring described above, if there is a difference in strength of the each parts in the circumferential direction of the workpiece, the part having a low strength is liable to be an originating point of breakage. Such a problem may occur when, for example, a temperature of the workpiece after completion of the heating is varied in the circumferential direction. Thus, the inventors of the present application attempted to equalize the temperatures of the each parts of the workpiece in the circumferential direction by keeping the workpiece at a given temperature for a predetermined time period (soaking the workpiece) in a last stage (second half) of the heating step in which the above-mentioned continuous heating method is carried out.

In this case, as the heating coil for induction heating, a coil obtained by helically winding a coil material made of a conductive metal (hereinafter referred to as "helical coil") is generally used. In general, the helical coil has a characteristic in that an output has a higher intensity as a coil pitch becomes smaller and has a lower intensity as the coil pitch becomes larger. Therefore, at the time of performing the heat treatment in the above-mentioned mode, the inventors of the present application attempted to use a helical coil <NUM> having a coil pitch adjusted in a manner illustrated in <FIG>, more specifically, the helical coil <NUM> with the coil pitch being set relatively small on a heating start side and the coil pitch being set relatively large on a heating end side. In this case, along with relative movement of workpieces <NUM> and the helical coil <NUM> in the axial direction of the workpiece, the workpieces <NUM> are first heated actively until a temperature reaches a predetermined temperature, and are then soaked.

However, even when the helical coil <NUM> with the coil pitch adjusted in the above-mentioned manner is used, the temperatures of the each parts of the workpiece <NUM> in the circumferential direction after the completion of heating are uneven. The temperatures are uneven because of, for example, coil pitch of the helical coil <NUM> is non-uniform in each parts in the circumferential direction of the workpiece <NUM> or changes in shape of the coil <NUM> in an undesired manner due to the change in coil pitch.

Further, in a case in which the workpieces <NUM> are inductively heated using the helical coil <NUM> as illustrated in <FIG> and the workpieces <NUM> are soaked in the final stage, for example, when workpieces having different axial dimensions (thicknesses) are used as the workpieces <NUM> to be subjected to the heat treatment, it is required to take a measure such as adjustment of the coil pitch of the helical coil <NUM>. However, in order to take such measure, considerable effort and time are required. Therefore, there is a problem in that the heat treatment on the workpiece cannot be performed efficiently.

In view of the actual circumstances described above, the present invention has an object to provide technical measures capable of inductively heating a workpiece to be subjected to a heat treatment to a target temperature without varying a temperature of the workpiece among each parts in a circumferential direction of the workpiece and easily and quickly setting an optimum coil pitch (heating condition) in accordance with the workpiece.

According to the present invention that has been made to achieve the above-mentioned object, provided is a heat treatment apparatus as defined in independent claim <NUM>. Preferred embodiments thereof are laid down in the dependent claims.

In the heat treatment apparatus of the present invention, the plurality of coil members, each having the coil portion, are supported on the frame body so as to be movable in the axial direction relative to the frame body. As a result, a separation distance (coil pitch) between the coil members (coil portions) adjacent to each other in the axial direction can be easily and quickly adjusted and set. In addition, a posture of each individual coil portion can be kept in an appropriate state (posture parallel to the workpiece to be subjected to a heat treatment) even after the adjustment of the coil pitch. Further, each of the coil members is supported on the frame body in a form of being separated from and being independent of the other coil members. Thus, even after the coil pitch is adjusted, the coil pitch is not gradually changed in a circumferential direction of the workpiece, or a shape of the coil is not changed, unlike the case of adjusting the coil pitch of the helical coil <NUM> illustrated in <FIG>. Therefore, the coil pitch is adjusted by moving the coil members in the axial direction so as to form a temperature increasing zone in which the coil pitch is set relatively small and a soaking zone in which the coil pitch is set relatively large. In this manner, even when the workpiece to be subjected to the heat treatment is a ring-shaped workpiece such as a raceway ring (outer ring or inner ring) for a rolling bearing, each of the workpieces can be inductively heated to the target temperature in an appropriate manner without varying a temperature of the workpiece in the circumferential direction.

The heating unit further comprises a connecting component, which is configured to electrically connect two of the plurality of coil members being adjacent to each other. In this manner, the plurality of coil members can be electrically treated as a single multiwinding coil. Thus, a configuration of a feed circuit, which is configured to feed power to each of the coil members, can be simplified.

The connecting component may comprise: a link member; a first coupling member, which is configured to couple one end of the link member to any one of the two coil members being adjacent to each other in the axial direction of the workpiece so that the one end of the link member is rotatable relative to the one coil member; and a second coupling member, which is configured to couple another end of the link member to another of the two coil members being adjacent to each other in the axial direction of the workpiece so that the another end of the link member is slidable and rotatable relative to the another coil member. In this case, in particular, when the link member is formed of a metal rigid member, the plurality of coil members that are separated from each other can be connected not only electrically but also mechanically. Hence, ease in handling of the heating unit is improved. Further, the coil pitch can be adjusted in a stepless manner within a range of a sliding amount of the link member relative to the another coil member. Thus, it is possible to efficiently perform an adjustment work of the coil pitch.

The heating unit may further comprise a restricting member that functions as the connecting component, wherein one end and another end of the restricting member are removably mounted to one and another of two of the plurality of coil members being adjacent to each other in the axial direction of the workpiece, respectively, and wherein the restricting member is configured to restrict relative approaching and separating movement of the two coil members being adjacent to each other in the axial direction of the workpiece. With the restricting member described above, the coil pitch can be adjusted and set based on an axial dimension of the restricting member. Therefore, an optimum coil pitch in accordance with the workpiece can be more easily and accurately set.

When the heating unit comprises the restricting member described above, the coil member may have a first projection which engaged with the restricting member in the axial direction of the workpiece and a second projection which engaged with the restricting member in an extending direction of the coil member. In this manner, a desired coil pitch can be more easily and accurately achieved, specifically, reproducibility of the coil pitch can be enhanced. The two coil members being adjacent to each other in the axial direction of the workpiece are electrically connected to each other through intermediation of the connecting component. In this manner, the plurality of coil members can be electrically treated as the single multiwinding coil. Thus, the configuration of the feed circuit can be simplified.

In the configuration described above, each of the plurality of coil members may be formed into a shape having ends with a tubular member made of a conductive metal. In this case, when the heating unit further comprises a communication member, which is configured to communicate internal spaces of the two coil members being adjacent to each other in the axial direction, a fluid passage can be formed with the coil members and the communication member. The fluid passage can be utilized, for example, as part of a cooling circuit through which cooling water is caused to circulate. When the cooling circuit described above is provided, temperature control for the heating unit (coil portions) can be appropriately and efficiently performed. Further, with the communication member made of a flexible material, even when the coil pitch is changed, the communication member can be deformed so as to follow the change in coil pitch. Therefore, even when the cooling circuit described above is required, time and effort to reconstruct the cooling circuit for each change in coil pitch can be saved.

Each of the plurality of coil members may be mountable to and removable from the frame body. In this manner, it can be easily dealt with, for example, an increase and decrease of the number of coil members to be provided, and a replacement of the coil member.

Further, in order to achieve the object described above, according to the present invention, provided is a heat treatment method as defined in independent claim <NUM>. Preferred embodiments thereof are laid down in the dependent claims.

With the heat treatment method described above, the same functions and effects as those obtained in the case in which the heat treatment apparatus according to the present invention is adopted can be enjoyed.

The heating unit used in the heat treatment method described above may further comprise a restricting member that functions as the connecting component, wherein one end and another end of the restricting member are removably mounted to one and another of two of the plurality of coil members being adjacent to each other in the axial direction of the workpiece, respectively, and wherein the restricting member is configured to restrict relative approaching and separating movement of the two coil members being adjacent to each other in the axial direction of the workpiece.

As described above, according to the heat treatment apparatus and the heat treatment method of the present invention, the workpiece to be subjected to the heat treatment can be inductively heated to the target temperature without varying the temperature of the workpiece among each parts in the circumferential direction of the workpiece. In addition, an optimum coil pitch in accordance with the workpiece can be easily and quickly set. Therefore, changes in specifications, types, etc. of the workpiece to be subjected to the heat treatment can be easily and quickly dealt with.

Now, description is made of embodiments of the present invention with reference to the drawings.

<FIG> is a view for schematically illustrating an overall structure of a heat treatment apparatus <NUM> according to one embodiment of the present invention. The heat treatment apparatus <NUM> illustrated in <FIG> is used to perform quench hardening as a heat treatment on a workpiece W made of steel, more specifically, for example, a ring-shaped workpiece W (for example, an outer ring for a rolling bearing) made of a steel material containing carbon at <NUM> % by mass or smaller, and is configured to carry out a heating step S1, a conveying step S2, and a cooling step S3 in the stated order, as illustrated in <FIG>.

The heat treatment apparatus <NUM> mainly comprises a heating unit <NUM>, a holding part <NUM>, a high-frequency power source <NUM>, a conveying mechanism <NUM>, and a cooling part <NUM>. The heating unit <NUM>, the holding part <NUM>, and the high-frequency power source <NUM> are used in the heating step S1. The conveying mechanism <NUM> is used in the conveying step S2. The cooling part <NUM> is used in the cooling step S3. The cooling part <NUM> comprises a cooling liquid bath <NUM> that stores a cooling liquid (for example, quenching oil) <NUM> kept at a suitable temperature. The conveying mechanism <NUM> comprises, for example, a belt conveyor.

The heating unit <NUM> and the holding part <NUM> that are used in the heating step S1 are now described in detail mainly for the heating unit <NUM> with reference to <FIG>.

The holding part <NUM> of the illustrated example is configured to coaxially hold a plurality of workpieces W to be subjected to the heat treatment, and more particularly, coaxially holds the plurality of workpieces W in a stacked state in which the workpieces W are stacked in multiple levels. The plurality of workpieces W held by the holding part <NUM> are intermittently fed upward by a predetermined dimension in response to an output from a drive mechanism (not shown) to be sequentially introduced into an inner periphery of the heating unit <NUM>.

As illustrated in <FIG>, the heating unit <NUM> comprises a plurality of (nine in the illustrated example) coil members <NUM>, a frame body <NUM>, and a relay component <NUM>. The coil members <NUM> are arranged in multiple levels along an axial direction (vertical direction) of the workpiece W held by the holding part <NUM>. The frame body <NUM> supports each of the coil members <NUM> so that the coil members <NUM> can be moved upward and downward. The relay component <NUM> is configured to bring electrodes provided to the coil members <NUM> and an electrode of the high-frequency power source <NUM> (see <FIG>) into contact with each other to energize the coil members <NUM>.

As illustrated in <FIG>, each of the coil members <NUM> comprises a coil portion 11a. The coil portion 11a is arranged coaxially with the workpieces W held by the holding part <NUM> (see <FIG>), and is formed into a ring shape having ends in a circumferential direction of the workpiece W so as to be capable of surrounding the workpiece W. Further, each of the coil members <NUM> has extending portions 11b and 11c respectively extending from one circumferential end and another circumferential end of the coil portion 11a, to which other members, more specifically, a connecting component <NUM> described later and communication members <NUM> that form a cooling circuit, are mounted. Shapes of the extending portions 11b and 11c are suitably determined mainly in accordance with a mode of formation of the cooling circuit. In this embodiment, two kinds of coil members <NUM> having the shapes of the extending portions 11b and 11c being different from each other are arranged alternately between the uppermost coil member <NUM> and the lowermost coil member <NUM>. One of the two kinds of coil members <NUM> is illustrated in <FIG>, and another thereof is illustrated in <FIG>. Distal ends (free ends) of the extending portions 11b and 11c are arranged at positions relatively close to the coil portion 11a in the one coil member <NUM> illustrated in <FIG>, whereas the free ends of the extending portions 11b and 11c are arranged at positions relatively away from the coil portion 11a in the another coil member <NUM> illustrated in <FIG>. These arrangements are used to prevent the extending portions 11b and 11c of the adjacent coil members <NUM> from interfering with each other.

Each of the coil members <NUM> is formed into a shape having ends by curving a tubular member made of a conductive metal, for example, a copper pipe. At least each parts of the coil portion 11a in an extending direction (circumferential direction) thereof are positioned on the same plane. As illustrated in <FIG> and <FIG>, each of the coil members <NUM> is supported on the frame body <NUM> while being in a horizontal posture in which a center axis of the coil portion 11a thereof matches a center axis of the coil portion 11a of the another coil member <NUM>.

As illustrated in <FIG>, the frame body <NUM> comprises a seat 21a and a plurality of (three in this embodiment) support columns 21b. The seat 21a is arranged below the lowermost coil member <NUM>. The support columns 21b are provided upright on the seat 21a. Each of the coil members <NUM> is supported on the frame body <NUM> through support components <NUM> that are provided at three positions separated from each other in the circumferential direction of the coil portion 11a. A guide portion 21c, which is configured to guide the upward and downward movement of the coil member <NUM>, is formed in each of the support columns 21b. The guide portion 21c comprises an elongated through hole extending in the vertical direction. Each of the seat 21a and the support columns 21b is made of an insulating material.

Each of the support components <NUM> comprises a bolt member 22a, a first nut 22b, and a second nut 22c. The bolt member 22a has a radially inner end to be fastened to a nut 11d fixed to an outer periphery of the coil member <NUM>, and a radially outer end with a vicinity thereof to be inserted into the guide portion 21c of the corresponding support column 21b. The first nut 22b is arranged on a radially inner side of the support column 21b, and the second nut 22c is arranged on a radially outer side of the support column 21b. The first nut 22b and the second 22c are threadably fixed to the bolt member 22a so as to be capable of moving closer and away relative to each other. With the configuration described above, when the nuts 22b and 22c are moved closer relative to each other in each of the support components <NUM> provided at the three positions in the circumferential direction to sandwich the support column 21b therebetween, each of the coil members <NUM> is fixedly supported at a predetermined position in the vertical direction. On the contrary, when the nuts 22b and 22c are moved away relative to each other in each of the support components <NUM> to release a force of sandwiching the support column 21b, the coil member <NUM> can be moved upward and downward, specifically, a position of fixation and a posture of the coil member <NUM> in the vertical direction can be adjusted. Further, with the configuration described above, when the bolt members 22a are removed from the nuts 11d in all the support components <NUM> provided to each of the coil members <NUM>, the coil member <NUM> can be removed from the frame body <NUM>. Therefore, each of the coil members <NUM> can be moved upward and downward relative to the frame body <NUM>, and can also be mounted to and removed from the frame body <NUM>.

As the frame body <NUM> including the support columns 21b that forms the heating unit <NUM> and supports the plurality of coil members <NUM>, a frame body having a sufficiently large axial dimension as compared to that of the workpiece W, more specifically, when the axial dimension of the workpiece W is L, a frame body having at least an axial dimension expressed by (Lx2) is used so that the plurality of workpieces W stacked in levels can be inductively heated in a simultaneous manner. In this embodiment, the support columns 21b each having the axial dimension expressed by (L×<NUM>) or larger are used so that ten workpieces W can be inductively heated in a simultaneous manner as illustrated in <FIG>.

As illustrated in <FIG>, the heating unit <NUM> comprises connecting components <NUM>, which are configured to electrically connect the two coil members <NUM> that are vertically adjacent to each other. Hence, in this embodiment, the uppermost coil member <NUM> and the lowermost coil member <NUM> are electrically connected to the high-frequency power source <NUM> (see <FIG>) through intermediation of the relay component <NUM>. For description of the two coil members <NUM> that are vertically adjacent to each other, the coil member <NUM> that is arranged relatively on the upper side is referred to as "coil member 11A", and the coil member <NUM> that is arranged relatively on the lower side is referred to as "coil member 11B" for convenience. In the drawings, the coil members are not discriminably indicated by the reference symbols 11A and 11B.

As illustrated in detail in <FIG>, each of the connecting components <NUM> comprises a link member <NUM>, a first coupling member <NUM>, and a second coupling member <NUM>. The link member <NUM> has a linear shape. The first coupling member <NUM> couples one end (lower end) of the link member <NUM> to the coil member 11B, specifically, a receiving member <NUM> made of a conductive metal welded to the extending portion 11c of the coil member 11B (see <FIG>) so that the one end is rotatable relative to the coil member 11B. The second coupling member <NUM> couples another end (upper end) of the link member <NUM> to the coil member 11A, specifically, a receiving member <NUM> made of a conductive metal welded to the extending portion 11b of the coil member 11A (see <FIG>) so that the another end is slidable and rotatable relative to the coil member 11A. Each of the link member <NUM>, the first coupling member <NUM>, and the second coupling member <NUM> is formed of a metal material (metal rigid member) having conductivity. Therefore, the coil members 11A and 11B that are vertically adjacent to each other are connected to each other not only electrically but also mechanically through intermediation of the connecting component <NUM> and the receiving members <NUM>. A through hole 24a having an elongated hole shape is formed in another end of the link member <NUM>. The second coupling member <NUM> is fastened to the coil member 11A through the through hole 24a. In this manner, the link member <NUM> is slidable and rotatable relative to the coil member 11A. Therefore, as illustrated in <FIG>, a separation distance (coil pitch) between the coil members 11A and 11B that are vertically adjacent to each other can be adjusted in a stepless manner within a range of a longitudinal dimension of the through hole 24a. Therefore, coil-pitch adjustment work can be efficiently carried out.

The first coupling member <NUM> and the second coupling member <NUM> can be mounted to and removable from the receiving members <NUM> provided to the coil member <NUM>. Therefore, for replacement of any one of the coil members <NUM> by a new one or the like, when the coil member <NUM> is removed from the frame body <NUM>, the connecting component <NUM> is also removed from the coil member <NUM>.

The heating unit <NUM> comprises the cooling circuit, which is configured to cool the coil members <NUM>. With the cooling circuit, temperature control can be appropriately and efficiently performed for the coil members <NUM> (the coil portion 11a). The cooling circuit of this embodiment is one-system cooling circuit, and is formed by connecting a water supply pipe 28a to an end (free end of the extending portion 11b) of the lowermost coil member <NUM> and a water discharge pipe 28b to an end (free end of the extending portion 11c) of the uppermost coil member <NUM> and bringing an internal space of the coil member 11A and an internal space of the coil member 11B, which are vertically adjacent to each other, into communication with each other through a communication member <NUM>, as illustrated in <FIG>. The communication member <NUM> is formed of a tubular member made of a flexible material, a rubber material in this embodiment, and has one end connected to an open end of the coil member 11A and another end connected to an open end of the coil member 11B. The formation of the communication member <NUM> of the flexible material allows the adjustment of the coil pith without cancelling a connecting state between the communication member <NUM> and the coil members 11A and 11B. For preventing complication of illustration, the communication members <NUM> are not illustrated in the drawings other than in <FIG>.

A flow of cooling water is now described briefly with reference to <FIG>. The cooling water supplied from a water storage tank (not shown) flows into the internal space of the lowermost coil member <NUM> through the water supply pipe 28a and then circulate alternately through internal spaces of the communication members <NUM> (not shown in <FIG>) and the internal spaces of the coil members <NUM> to flow upward, as indicated by the outlined arrows in <FIG>. Then, the cooling water, which has circulated through the internal space of the uppermost coil member <NUM>, is discharged to the outside through the water discharge pipe 28b connected to the extending portion 11c of the uppermost coil member <NUM> (see <FIG> together).

The heating unit <NUM> mainly has the configuration described above. For practical use, the separation distance (coil pitch) between the coil members 11A and 11B that are vertically adjacent to each other is suitably adjusted. More specifically, for example, the coil pitch is set relatively small on a heating start side (lower side in this embodiment), whereas the coil pitch is set relatively large on a heating end side (upper side in this embodiment). Through setting of the coil pitch as described above, a temperature increasing zone Z1 in which the workpieces W are actively heated until a temperature of the workpieces W reaches a predetermined temperature is formed in a lower region of the heating unit <NUM>, whereas a soaking zone Z2 in which the workpieces W are held at a given temperature for a predetermined time period, specifically, the workpieces W are soaked is formed in an upper region of the heating unit <NUM>, as illustrated in <FIG>, <FIG>, and <FIG>.

Now, an embodiment of quench hardening for the workpiece W using the heat treatment apparatus <NUM> having the configuration described above is described.

The quench hardening involves, as illustrated in <FIG>, the heating step S1 of inductively heating the workpieces W to a target temperature, the conveying step S2 of conveying the workpieces W heated to the target temperature to the cooling part <NUM>, and the cooling step S3 of cooling the workpieces W for quench hardening.

In the heating step S1, the plurality of workpieces W that are held coaxially on the holding part <NUM> (see <FIG>) are inductively heated to the target temperature in a sequential manner. More specifically, the plurality of workpieces W are first stacked on the holding part <NUM> so that the center axes thereof match each other. When the workpiece W is, for example, the outer ring for a rolling bearing, the workpiece W has an axial dimension smaller than a radial dimension. Therefore, the stacking of the workpieces W has an advantage in that a posture of each of the workpieces W becomes stable while the heating step S1 is being carried out. Although not shown in detail, stacking work for the workpieces W can be performed automatically.

When the drive mechanism (not shown) is activated to apply an upward feeding force to the plurality of workpieces W that are coaxially held in the stacked state, the workpieces W are introduced into the inner periphery of the heating unit <NUM> (coil portion 11A) in an energized state through a lower end opening of the heating unit <NUM>. Then, by the continuous activation of the drive mechanism, the workpieces W are intermittently fed upward and are finally discharged to the outside of the heating unit <NUM> through an upper end opening of the heating unit <NUM> (see <FIG> for the procedure described above). The temperature increasing zone Z1 and the soaking zone Z2 described above are formed in the lower region and the upper region of the heating unit <NUM>, respectively. Therefore, the workpieces W introduced into the inner periphery of the heating unit <NUM> are inductively heated until the temperature thereof reaches the predetermined temperature while passing through the temperature increasing zone Z2, and are then held at the given temperature while passing through the soaking zone Z2. In this manner, the workpieces W are inductively heated to the target temperature. In addition, the entire workpiece W can be heated to an approximately equal temperature without varying the temperature of the workpiece W among each parts in the circumferential direction of the workpiece W.

In the conveying step S2, the workpieces W heated to the target temperature are sequentially conveyed to the cooling part <NUM> (cooling liquid bath <NUM>) by the conveying mechanism <NUM> (see <FIG>).

In the cooling step S3, the workpieces W that have been conveyed to the cooling liquid bath <NUM> by the conveying mechanism <NUM> are immersed into the cooling liquid <NUM> stored in the cooling liquid bath <NUM> to be cooled to a temperature in a predetermined temperature range so as to be quench-hardened (see <FIG>).

Through the procedure described above, the quench hardening for the workpieces W using the heat treatment apparatus <NUM> is completed. The workpieces W for which the quench hardening has been completed are then subjected to a predetermined treatment such as tempering and various types of finishing treatments. In this manner, the workpieces W are obtained as completed pieces.

As described above, according to the heat treatment apparatus <NUM> of the present invention, the plurality of coil members <NUM> each having the coil portion 11a are supported on the frame body <NUM> so as to be movable upward and downward relative to the frame body <NUM>. Therefore, the coil pitch can be easily and quickly adjusted and set. In addition, even after the adjustment of the coil pitch, the posture of each individual coil member <NUM>, specifically, each individual coil portion 11a can be kept in an appropriate state, specifically, in a posture parallel to the workpieces W to be subjected to the heat treatment. Further, each of the coil members <NUM> is supported on the frame body <NUM> in the form of being separated from and being independent of the other coil members <NUM>. Thus, even after the coil pitch is adjusted, the coil pitch does not gradually change in the circumferential direction of the workpiece W, or the shape of the coil portion 11a is not changed, unlike the case of adjusting the coil pitch of the helical coil <NUM> illustrated in <FIG>. Therefore, besides the adjustment of the coil pitch as described above, the temperature increasing zone Z1 is formed in the lower region of the heating unit <NUM>, while the soaking zone Z2 is formed in the upper region of the heating unit <NUM>. In this manner, along with the passage of the workpieces W through regions respectively opposed to the coil portions 11a, each of the workpieces W can be inductively heated to the target temperature in an appropriate manner without varying the temperature of the workpiece W in the circumferential direction.

Even when a workpiece having a different axial dimension is used to replace the workpiece W as a workpiece to be subjected to the heat treatment, each of the coil members <NUM> is brought into a state of being movable upward and downward relative to the frame body <NUM> through operation of the support components <NUM>. Thereafter, by re-fixing each of the coil members <NUM> to the frame body <NUM> at a suitable position and in an appropriate posture, the coil-pitch adjustment work can be completed. Therefore, it is not required to prepare a large number of coils, which are required in the case in which the helical coil <NUM> illustrated in <FIG> is used, in accordance with the axial dimensions of the workpieces W. Therefore, an expenditure on equipment can be reduced.

As described above, according to the present invention, there can be achieved the heat treatment apparatus <NUM> that is capable of inductively heating the workpieces W to be subjected to the heat treatment to the target temperature in an appropriate manner without varying the temperature of the workpiece in the circumferential direction of the workpiece W and, even when the workpiece W to be subjected to the heat treatment is replaced by another type of one or the like, easily and quickly setting an optimum coil pitch (heating condition) in accordance with the replacing workpiece W.

Next, a heating unit <NUM> in a second embodiment of the present invention is described in detail with reference to <FIG>.

As illustrated in <FIG>, the heating unit <NUM> comprises a plurality of (ten in the illustrated example) coil members <NUM>, a frame body <NUM>, and a relay component <NUM>. The coil members <NUM> are arranged in multiple levels along the vertical direction. The frame body <NUM> supports each of the coil members <NUM> so that the coil members <NUM> can be moved upward and downward. The relay component <NUM> is configured to bring electrodes provided to the coil members <NUM> and an electrode of the high-frequency power source <NUM> (see <FIG>) into contact with each other to energize the coil members <NUM>,.

As illustrated in <FIG>, each of the coil members <NUM> comprises a coil portion 111a. The coil portion 111a is arranged coaxially with the workpieces W held by the holding part <NUM> (see <FIG>), and is formed into a ring shape having ends in a circumferential direction of the workpiece W so as to be capable of surrounding the workpiece W. Further, each of the coil members <NUM> has extending portions 111b and 111c respectively extending from one circumferential end and another circumferential end of the coil portion 111a. In this embodiment, two kinds of coil members <NUM> having the shapes of the extending portions 111b and 111c being different from each other are arranged alternately between the uppermost coil member <NUM> and the lowermost coil member <NUM>. One of the two kinds of coil members <NUM> is illustrated in <FIG>, and another thereof is illustrated in <FIG>. The one coil member <NUM> illustrated in <FIG> comprises the extending portions 111b and 111c respectively having free ends that are arranged at positions relatively away from the coil portion 111a. The another coil member <NUM> illustrated in <FIG> comprises the extending portions 11b and 111c respectively having free ends that are arranged at positions relatively close to the coil portion 111a. These arrangements are used to prevent the extending portions 111b and 111c of the adjacent coil members <NUM> from interfering with each other.

Each of the coil members <NUM> is formed into a shape having ends by curving a tubular member made of a conductive metal, for example, a copper pipe. At least each part of the coil portion 111a in an extending direction (circumferential direction) thereof are positioned on the same plane. As illustrated in <FIG>, each of the coil members <NUM> is supported on the frame body <NUM> in a horizontal posture in a state in which a center axis of the coil portion 111a matches center axes of the coil portions 111a of the other coil members <NUM> and a phase in which circumferential ends of the coil portions 111a are present matches a phase in which circumferential ends of the coil portions 111a of the other coil members <NUM> are present.

A receiving member <NUM> made of a conductive metal is welded to each of the coil members <NUM>. One end or another end of a restricting member <NUM> described later is mounted and fixed (fastened with a bolt) to the receiving member <NUM>. In the uppermost coil member <NUM>, the receiving member <NUM> is welded only to the first extending portion 111b. In the lowermost coil member <NUM>, the receiving member <NUM> is welded only to the second extending portion 111c. The receiving members <NUM> are welded to both of the first extending portion 111b and the second extending portion 111c of each of a total of eight coil members <NUM> that are arranged between the uppermost coil member <NUM> and the lowermost coil member <NUM>.

As illustrated in <FIG>, the frame body <NUM> comprises a seat 121a and a plurality of (three in this embodiment) support columns 121b. The seat 121a is arranged below the lowermost coil member <NUM>. The support columns 121b are provided upright on the seat 121a. Each of the coil members <NUM> is supported on the frame body <NUM> through support components <NUM> that are provided at three positions separated from each other in the circumferential direction of the coil portion 111a. A guide portion 121c, which is configured to guide the upward and downward movement of the coil member <NUM>, is formed in each of the support columns 121b. The guide portion 121c comprises an elongated through hole extending in the vertical direction. Each of the seat 121a and the support columns 121b is made of an insulating material.

Each of the support components <NUM> comprises a bolt member 122a, a first nut 122b, and a second nut 122c. The bolt member 122a has a radially inner end to be fastened to a nut 111d fixed to an outer periphery of the coil member <NUM>, and a radially outer end with a vicinity thereof to be inserted into the guide portion 121c of the corresponding support column 121b. The first nut 122b is arranged on a radially inner side of the support column 121b, and a second nut 122c is arranged on a radially outer side of the support column 121b. The first nut 122b and the second nut 122b are threadably fixed to the bolt member 122a so as to be capable of moving closer and away relative to each other.

With the configuration described above, when the nuts 122b and 122c are moved closer relative to each other in each of the support components <NUM> provided at the three positions in the circumferential direction to sandwich the support column 121b therebetween, each of the coil members <NUM> is fixedly supported at a predetermined position in the vertical direction. On the contrary, when the nuts 122b and 122c are moved away relative to each other in each of the support components <NUM> to release a force of sandwiching the support column 121b, the coil member <NUM> can be moved upward and downward, specifically, a position of fixation and a posture of the coil member <NUM> in the vertical direction can be adjusted. Further, with the configuration described above, when the bolt members 122a are removed from the nuts 111d in all the support components <NUM> provided to each of the coil members <NUM>, the coil member <NUM> can be removed from the frame body <NUM>. Therefore, each of the coil members <NUM> can be moved upward and downward relative to the frame body <NUM>, and can also be mounted to and removed from the frame body <NUM>.

As illustrated in <FIG>, the heating unit <NUM> comprises a plurality of restricting members <NUM>, which are configured to restrict relative approaching and separating movement of the two coil members <NUM> that are vertically adjacent to each other. For description of the two coil members <NUM> that are vertically adjacent to each other, the coil member <NUM> that is arranged relatively on the upper side is referred to as "coil member 111A", and the coil member <NUM> that is arranged relatively on the lower side is referred to as "coil member 111B" for convenience. In the drawings, the coil members are not discriminably indicated by the reference symbols 111A and 111B.

Each of the restricting members <NUM> is made of a metal material having conductivity, and comprises a first head portion <NUM>, a second head portion <NUM>, and a connecting portion <NUM>. The first head portion <NUM> is fastened with a bolt to the coil member 111A, specifically, to the receiving member <NUM> welded to the first extending portion 111b of the coil member 111A, The second head portion <NUM> is fastened with a bolt to the coil member 111B, specifically, to the receiving member <NUM> welded to the second extending portion 111c of the coil member 111B. The connecting portion <NUM> is inclined at a predetermined angle with respect to the vertical direction, and is provided between the head portions <NUM> and <NUM>. The restricting member <NUM> made of the conductive metal is fastened with a bolt to the coil member <NUM> as described above. As a result, the coil members 111A and 111B are electrically connected through intermediation of the restricting member <NUM>, the receiving members <NUM>, and the bolts described above. Therefore, in this embodiment, the uppermost coil member <NUM> and the lowermost coil member <NUM> of the plurality of coil members <NUM> that are arranged in multiple levels are electrically connected to the high-frequency power source <NUM> (<FIG>) through intermediation of the relay component <NUM>.

As illustrated in <FIG> in an enlarged manner, the receiving member <NUM> welded to the first extending portion 111b of each of the coil members <NUM> has a first projection <NUM> and a second projection <NUM> which can be engaged with an upper end portion 124a and a circumferential end surface 124b of the first head portion <NUM> of the restricting member <NUM>, respectively, whereas the receiving member <NUM> welded to the second extending portion 111c of each of the coil members <NUM> has the first projection <NUM> and the second projection <NUM> which can be engaged with a lower end surface 125a and a circumferential end surface 125b of the second head portion <NUM> of the restricting member <NUM>, respectively. Specifically, each of the coil members <NUM> has the first projection <NUM>, which is engaged with the restricting member <NUM> in the axial direction, and the second projection <NUM>, which is engaged with the restricting member <NUM> in the extending direction (circumferential direction) thereof.

In the second embodiment, the two kinds of restricting members <NUM> having axial dimensions different from each other are used. More specifically, as illustrated in <FIG> and <FIG>, the restricting members <NUM> each having a relatively small axial dimension are mounted to the coil members 111A and 111B, that is, from the lowermost coil member <NUM> to the sixth coil member <NUM> from the bottom, whereas the restricting members <NUM> each having a relatively large axial dimension are mounted to the coil members 111A and 111B, that is, from the sixth coil member <NUM> from the bottom to the uppermost coil member <NUM>. With the configuration described above, in the lower region of the heating unit <NUM>, specifically, on a side where the heating step S2 is started, there is formed a temperature increasing zone Z10 in which the coil pitch is set relatively small and the workpieces W can be actively heated until the temperature thereof reaches the predetermined temperature. Further, in the upper region of the heating unit <NUM>, specifically, on a side where the heating step S2 ends, there is formed a soaking zone Z20 in which the coil pitch is set relatively large and the workpieces W can be soaked.

The cooling circuit which is configured to cool the coil members <NUM> can be provided to the heating unit <NUM>. With such cooling circuit, temperature control can be appropriately and efficiently performed for the coil members <NUM>. The cooling circuit of this embodiment is one-system cooling circuit, and is formed by connecting a water supply pipe 128a to a free end of the extending portion 111b of the lowermost coil member <NUM> and a water discharge pipe 128b to a free end of the extending portion 111c of the uppermost coil member <NUM> and bringing an internal space of the coil member 111A and an internal space of the coil member 111B, which are vertically adjacent to each other, into communication with each other through a communication member <NUM>, as illustrated in <FIG> and <FIG>. The communication member <NUM><NUM> is formed of a tubular member made of a flexible material, a rubber material in this embodiment, and has one end connected to the free end of the coil member 111A and another end connected to the free end of the coil member 111B. The formation of the communication member <NUM> of the flexible material allows the adjustment of the coil pith without cancelling a connecting state between the communication member <NUM> and the coil members 111A and 111B. For preventing complication of illustration, the communication members <NUM> illustrated only in <FIG>.

A flow of cooling water in the heating unit <NUM> in this embodiment is now described briefly with reference to <FIG>. The cooling water supplied from a water storage tank (not shown) flows into the internal space of the lowermost coil member <NUM> through the water supply pipe 128a and then circulate alternately through internal spaces of the communication members <NUM> (not shown in <FIG>) and the internal spaces of the coil members <NUM> to flow upward, as indicated by the outlined arrows in <FIG>. Then, the cooling water, which has circulated through the internal space of the uppermost coil member <NUM>, is discharged to the outside through the water discharge pipe 128b connected to the extending portion 111c of the uppermost coil member <NUM> (see <FIG> together).

When the heat treatment apparatus <NUM> comprising the heating unit <NUM> having the configuration described above is used, the quench hardening on the workpieces W is carried out in the same procedure as that in the case in which the heat treatment apparatus <NUM> comprising the heating unit <NUM> illustrated in <FIG> and the like is used.

According to the heat treatment apparatus <NUM> comprising the heating unit <NUM> described above, the coil members <NUM> each comprising the coil portion 111a are supported so as to be movable upward and downward relative to the frame body <NUM>. As a result, the coil pitch can be adjusted and set by adjusting the position and the posture of each of the coil members <NUM> relative to the frame body <NUM>. In addition, even after the adjustment of the coil pitch, the posture of each individual coil member <NUM>, specifically, each individual coil portion 111a can be kept in an appropriate state, specifically, in a posture parallel to the workpieces W to be subjected to the heat treatment. Further, each of the coil members <NUM> is supported on the frame body <NUM> in the form of being separated from and being independent of the other coil members <NUM>. Thus, even after the coil pitch is adjusted, the coil pitch does not gradually change in the circumferential direction of the workpiece W, or the shape of the coil portion 111a is not changed, unlike the case of adjusting the coil pitch of the helical coil <NUM> illustrated in <FIG>. Therefore, besides the adjustment of the coil pitch as described above, the temperature increasing zone Z10 is formed in the lower region of the heating unit <NUM>, while the soaking zone Z20 is formed in the upper region of the heating unit <NUM>. In this manner, along with the passage of the workpieces W through regions respectively opposed to the coil portions 111a, each of the workpieces W can be inductively heated to the target temperature in an appropriate manner without varying the temperature of the workpiece W in the circumferential direction.

Further, when the heating unit <NUM> described above is adopted, the coil pitch can be set based on the axial (vertical) dimension of the relative members <NUM>. Therefore, for example, when the workpiece W to be subjected to the heat treatment is replaced by a workpiece having a different axial dimension (referred to as "workpiece W‴), the restricting member <NUM> is removed. Then, another restricting member <NUM>, that is, the restricting member <NUM> having an axial dimension different from that of the restricting member <NUM> removed from the coil member <NUM> is fastened with a bolt to one and another of the two adjacent coil members <NUM>, at least one of which is brought into a state of being movable upward and downward. As a result, an optimum coil pitch in accordance with the workpiece W' can be easily and accurately set, specifically, the heating unit <NUM> can be easily changed into a form in which the workpiece W' can be inductively heated in an appropriate manner (see <FIG> for the form described above). In the second embodiment, in particular, the first projection <NUM> and the second projection <NUM>, which are engaged with the restricting member <NUM> in the axial direction and the circumferential direction, respectively, are formed on each of the coil members <NUM>, specifically, the receiving member <NUM> welded thereto. Therefore, coil-pitch adjustment and setting work can be further facilitated. In addition, after the adjustment of the coil pitch, the movement of the two adjacent coil members <NUM> relative to each other can be reliably restricted.

In short, when the heating unit <NUM> of the second embodiment is adopted, the coil pitch can be further easily and accurately adjusted and set in accordance with a size of the workpiece W, a temperature history of the workpiece to be acquired at the time of passage through the heating unit <NUM>, and the like. Therefore, the heating unit <NUM> can be easily and accurately changed from the form in which one temperature increasing zone Z10 and one soaking zone Z20 are formed to a mode in which, for example, two temperature increasing zones Z10 and two soaking zones Z20 are formed alternately (mode in which a first temperature increasing zone, a first soaking zone, a second temperature increasing zone, and a second soaking zone are provided in the stated order).

The embodiment of the present invention is described above, but the embodiment of the present invention is not limited to that described above.

For example, although only one-system cooling circuit is provided in the heating unit <NUM>, <NUM> in the embodiments described above, two or more systems of the cooling circuits may be provided. In particular, when there is a fear in that a required coil cooling capacity cannot be obtained with the cooling circuit of one system, it is effective to provide a plurality of systems of the cooling circuits. Even when the plurality of systems of the cooling circuits are provided as described above, the heating unit <NUM>, <NUM> comprises the plurality of coil members <NUM>, <NUM> that are separate from each other. Therefore, the plurality of systems of the cooling circuits can be easily constructed.

Configurations of the support components <NUM>, <NUM>, the connecting components <NUM>, and the restricting members <NUM>, which are used in the embodiments described above, are merely examples, and can be suitably changed as long as the same functions are fulfilled.

Further, it has been described above that the plurality of workpieces W are inductively heated to the target temperature in a sequential manner and the workpieces W inductively heated to the target temperature are sequentially fed to the conveying step S2 and then to the cooling step S3. The conveying step S2 and the cooling step S3 may be carried out collectively for the plurality of workpieces W which have been inductively heated to the target temperature.

Further, although the direction of relative movement of the heating unit <NUM>, <NUM> and the workpieces W is the vertical direction in the embodiments described above, the present invention is also applicable to the heat treatment apparatus <NUM>, which is configured to move the heating unit and the workpieces relative to each other in the horizontal direction.

Further, the heat treatment apparatus <NUM> according to the present invention can be preferably applied when the heat treatment is performed not only on the outer ring for the rolling bearing but also on a ring-shaped member made of steel, for example, an inner ring for a rolling bearing, a sliding bearing, an outer joint member or an inner joint member included in a constant velocity universal joint, and a cage to be incorporated into the rolling bearing or the constant velocity universal joint.

Further, the heat treatment apparatus <NUM> according to the present invention can be preferably applied when the heat treatment is performed not only on the ring-shaped workpiece W but also on a disc-shaped or a columnar workpiece.

For verification of utility of the present invention, it was verified whether a difference was generated in temperature (manner of temperature increase) of the workpiece when the workpiece was heated to about <NUM> in each of a case (<NUM>) in which the workpieces were inductively heated in the heat treatment apparatus using the helical coil <NUM> illustrated in <FIG> as the heating unit and a case (<NUM>) in which the workpieces were inductively heated in the heat treatment apparatus comprising the heating unit to which the present invention was applied, that is, the heat treatment apparatus <NUM> comprising the heating unit <NUM> according to the first embodiment or the heating unit <NUM> according to the second embodiment. In each of the cases (<NUM>) and (<NUM>), through adjustment of the coil pitch, the temperature increasing zone in which the workpieces were actively heated was formed in a pre-stage of the heating unit and the soaking zone in which the workpieces were soaked was formed in a post-stage of the heating unit.

The workpiece used in this verification test was an outer ring for a rolling bearing (tapered roller bearing) that was formed so that a small-diameter side inner diameter dimension d1 was <NUM>, an outer-diameter dimension d2 was <NUM>, and an axial dimension was <NUM>, as illustrated in <FIG>. Further, in the verification test, temperatures at two points (point A and point B) on the workpiece, which were different in phase by <NUM> degrees in the circumferential direction, were measured.

A result of temperature measurement for the workpiece in the case (<NUM>) is shown in <FIG>, whereas a result of temperature measurement for the workpiece in the case (<NUM>) is shown in <FIG>. As is apparent from <FIG>, when the helical coil <NUM> was used to inductively heat the workpiece, the temperature of the each parts of the workpiece in the circumferential direction became uneven. On the other hand, when the apparatus according to the present invention was used to inductively heat the workpiece, the temperature of the each parts of the workpiece in the circumferential direction became approximately equal, as shown in <FIG> (see "TEMPERATURE AT POINT A (AFTER PITCH ADJUSTMENT)" indicated by the solid line and "TEMPERATURE AT POINT B (AFTER PITCH ADJUSTMENT)" indicated by the broken line in <FIG>).

In order to verify effects of the coil pitch of the coils for induction heating on the manner of temperature increase of the workpiece, the workpiece was heated with the coil pitch being set constant in the heat treatment apparatus comprising the heating unit to which the present invention was applied. A result of temperature measurement at the point A on the workpiece in this case is also shown in <FIG> (see "TEMPERATURE AT POINT A (BEFORE PITCH ADJUSTMENT)" shown in <FIG>). As is apparent also from <FIG>, the temperature of the workpiece continuously increased in this case. Therefore, it is understood that it is substantially impossible to soak the workpiece.

Further, because of the restricting members <NUM> included in the heating unit <NUM>, the heat treatment apparatus comprising the heating unit <NUM> illustrated in <FIG> and other drawings can easily and accurately achieve a predetermined coil pitch, specifically, can increase reproducibility of the coil pitch. In order to verify that the effects described above are obtained, a temperature history of the workpiece was observed in both of a case in which the workpiece was inductively heated in a first state in which the predetermined coil pitch was set and a case in which a second state in which the coil pitch was different from that in the first state was set and then the workpiece was inductively heated with the coil pitch being changed back into the first state described above. A result thereof is shown in <FIG>. In <FIG>, the temperature history of the workpiece in the case in which the workpiece was inductively heated in the first state for the first time is indicated by the solid line, whereas the temperature history of the workpiece in the case in which the workpiece was inductively heated in the first state for the second time is indicated by the dotted line (broken line). As is apparent from the result shown in <FIG>, the heat treatment apparatus comprising the heating unit <NUM> illustrated in <FIG> and the other drawings provides significantly high coil-pitch reproducibility and therefore can inductively heat the workpiece to be subjected to the heat treatment with accuracy to have a desired temperature history.

Claim 1:
A heat treatment apparatus (<NUM>), comprising:
a heating unit (<NUM>, <NUM>), which is configured to inductively heat a ring-shaped workpiece (W) to a target temperature; and
a drive mechanism, which is configured to move a plurality of the coaxially held ring-shaped workpieces (W) in a stacked state in which the ring-shaped workpieces (W) are stacked in multiple levels relative to the heating unit (<NUM>, <NUM>) being in an energized state in an axial direction of the ring-shaped workpiece (W),
characterized in that the heating unit (<NUM>, <NUM>) comprises:
a plurality of coil members (<NUM>, <NUM>) arranged in multiple levels along the axial direction of the ring-shaped workpiece (W), wherein each of the plurality of coil members (<NUM>, <NUM>) comprises a coil portion (11a, 111a) which is arranged coaxially with the ring-shaped workpiece (W) so as to be capable of surrounding the ring-shaped workpiece (W), and each parts of the coil portion (11a, 111a) in an extending direction of the coil portion (11a, 111a) are positioned on the same plane;
a frame body (<NUM>, <NUM>), which is configured to support each of the plurality of coil members (<NUM>, <NUM>) so as to be movable in the axial direction of the ring-shaped workpiece (W) while maintaining the coaxial arrangement between the coil portions (11a, 111a); and
a connecting component (<NUM>) formed of a metal material having conductivity,
wherein each of the plurality of coil members (<NUM>, <NUM>) is supported on the frame body (<NUM>, <NUM>) through a support component (<NUM>, <NUM>) which is provided at the coil portion (11a, 111a) while being in a horizontal posture in which a center of axis of the coil portion (11a, 111a) thereof matches a center of axis of the coil portion (11a, 111a) of the another coil member (<NUM>, <NUM>),
wherein the support component (<NUM>, <NUM>) is provided so as to be able to movable in the axial direction of the ring-shaped workpiece (W) relative to the frame body (<NUM>, <NUM>), and
wherein the connecting component (<NUM>) is configured to electrically connect two of the plurality of coil members (<NUM>, <NUM>) being adjacent to each other in the axial direction of the ring-shaped workpiece (W).