JP2006009043A - Method and apparatus for surface-quenching raceway surface of outer ring of needle roller bearing by induction heating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for surface-quenching the raceway surface of the outer ring of a shell-type needle roller bearing obtained by press-forming a steel sheet while induction-heating it, which can treat it with an inexpensive and simple facility, shortens a period of time for surface-hardening it and reduces inventory in process, and to provide a quenching device. <P>SOLUTION: The quenching device comprises: a cylindrical induction heating coil 20 having a circumference with a taper face installed in the inner raceway surface of the outer ring W of the needle roller bearing; and a cooling holder 10 having a cooling piece 11 arranged on the outer surface. The surface quenching method comprises: induction-heating the inner raceway surface while cooling the outer surface of the outer ring of the needle roller bearing, with the cooling piece 11; and quenching the inner raceway surface by cooling it through spouting a liquid from a cooling means 30 in an upper part. Thereby, the method quenches only the surface of the inner raceway surface in the outer ring of the needle roller bearing, and makes cooling water uniformly hit the surface to impart uniform surface hardness to the raceway surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a quenching method and a quenching apparatus for quenching only the surface of a raceway surface of a very thin ring like a raceway of a shell-type needle roller bearing formed by pressing a steel plate, for example. is there.

As the thin shell needle roller bearing, for example, a needle roller bearing disclosed in Patent Document 1 has been developed. The bearing ring of this bearing is made of a thin ring material obtained by drawing a thin steel plate. For this purpose, it has been manufactured by using a low carbon steel with good drawing workability and conventionally surface hardening by carburizing or carbonitriding.
Japanese Patent Laid-Open No. 10-46318

  However, the heat treatment such as carburizing and carbonitriding requires a large-scale heat treatment facility, and the equipment cost is high, and maintenance requires cost and man-hours. Further, heat treatment such as carburizing and carbonitriding has a problem that it takes a long time. As a result, the conventional production method is not suitable for small lot production, and large lot production is unavoidable. In addition, each process is a single process, and there is a problem that the in-process increases and the lead time becomes long. .

  Therefore, the present invention solves the above-mentioned problems, can be processed with inexpensive and simple equipment, shortens the time for the surface hardening process, and reduces the in-process inventory, so that the raceway surface of the needle roller bearing by induction heating is reduced. An object is to provide a surface quenching method and a quenching apparatus. In particular, the present invention is very effective in the case of multi-product small-quantity production.

  In order to achieve the above object, the inventors of the present invention use surface hardening by induction heating using a steel material having a C content of 0.3% or more as a method of surface hardening without using a heat treatment such as carburizing. investigated. However, since the raceway of a shell type needle roller bearing is very thin, the entire thickness is heated by normal induction heating, resulting in a problem that the toughness of the raceway is lowered and damaged. . Therefore, in order to have the original performance of the bearing and toughness of the bearing ring, it is necessary to cure only the surface of the bearing raceway surface.

  In order to solve the above-mentioned problems, the surface hardening method of the raceway surface of the needle roller bearing outer ring by induction heating according to the present invention is the surface of the raceway surface of the shell type needle roller bearing outer ring formed by pressing the steel plate. In quenching, an induction heating coil is disposed on the inner circumferential raceway surface of the outer ring to be quenched, a cooling jig is disposed on the outer circumferential surface, and the outer circumferential surface of the outer ring to be quenched is cooled by the cooling jig. The surface is induction-heated by induction heating.

  That is, a cooling jig made of so-called chilling metal is disposed on the outer periphery of the outer ring to be hardened, and the outer ring outer periphery is cooled by heat conduction, and the inner peripheral raceway surface is induction-heated so that the temperature on the outer peripheral side is not increased. Only the surface of the raceway surface can be quenched and hardened by increasing the temperature of only the inner peripheral surface.

  Further, according to the method of surface hardening of the raceway surface of the needle roller bearing outer ring by induction heating according to the present invention, a cylindrical induction heating coil having a tapered outer periphery is arranged on the inner raceway surface of the outer ring to be hardened. It is desirable to quench by injection cooling from the direction in which the distance between the outer circumference of the coil and the inner raceway surface of the outer ring to be quenched is large.

  For example, the raceway of the shell type needle roller bearing is small and thin, and in order to quench only the surface, it is necessary to make the distance between the induction heating coil and the quenching inner circumferential raceway very narrow. In addition, in order to obtain a high quenching hardness on the thin wall surface, it is necessary to rapidly cool immediately after heating. However, since the distance between the coil and the quenching surface is extremely narrow, the cooling water does not strike the quenching surface evenly and causes uneven quenching. There is a fear. Therefore, the present invention is such that the outer periphery of the coil is tapered and water-cooled from the side having the larger interval so that the cooling water is uniformly applied to the quenched surface. As a result, a hardened surface having a uniform high hardness can be obtained.

  In order to effectively perform the quenching, the surface hardening device for the raceway surface of the needle roller bearing outer ring of the present invention has an induction heating coil disposed on the inner raceway surface of the outer ring to be quenched, and the inner raceway surface. A cooling jig provided with a cooling piece for cooling the outer peripheral surface of the outer ring to be hardened during induction heating is provided.

  The cooling jig is composed of a cylindrical body in which a plurality of fan-shaped cross-section cooling pieces that are radially divided are combined, and each cooling piece is urged so as to be in close contact with the outer periphery of the outer ring to be hardened, and the heat of the outer ring to be hardened It is desirable to move in response to the expansion.

  In order to efficiently cool the outer periphery of the outer ring to be quenched, it is necessary to closely adhere the outer periphery of the outer ring to be quenched and the cooling piece (cooling metal) of the cooling jig to improve heat conduction therebetween. However, if the cooling jig is a cylinder in contact with the outer periphery, the heat conduction is deteriorated because a gap must be provided so as to correspond to the thermal expansion due to heating of the outer ring to be quenched. Therefore, as described above, if a plurality of movable cooling pieces having a fan-shaped cross section are provided and the cooling pieces are in close contact with the outer periphery of the raceway ring, it is possible to cope with thermal expansion. Then, by bringing the cooling piece into close contact with the outer periphery by an urging force such as a spring, heat conduction is sufficiently performed and the cooling effect can be improved. By cooling the cooling jig with water, the cooling effect can be further improved in continuous operation.

  The cooling jig of the present invention is preferably water cooled. A cylindrical induction heating coil having a tapered outer surface disposed on the inner peripheral raceway surface of the outer ring to be hardened and a coolant from a direction in which the distance between the outer periphery of the coil and the inner peripheral raceway surface of the outer ring to be hardened is large. It is desirable to provide cooling means arranged so as to cool the jet. Accordingly, as described above, the rapid cooling of the inner peripheral raceway surface of the outer ring to be quenched is performed uniformly, and the high hardness of the inner peripheral raceway surface can be obtained evenly.

The following effects are obtained by the surface quenching method and quenching apparatus for the raceway surface of the needle roller bearing outer ring by induction heating according to the present invention.
1. The equipment is small and cheap, requires less factory space, and the environment is improved compared to the atmospheric furnace.
2. The heat treatment (surface hardening) time is shortened, the lead time is shortened, multi-product small-volume production is facilitated, and the number of devices in process is reduced.
3. In addition, it is easy to connect with each process and consistent line production becomes possible, and quality defects such as foreign product mixing, scratches, and deformation during transportation are reduced, and quality can be improved.

  Hereinafter, the illustrated embodiment of the surface hardening apparatus for the raceway surface of the needle roller bearing by induction heating according to the present invention will be described in detail. FIG. 1 is a cross-sectional view of a surface hardening apparatus for a raceway surface of a needle roller bearing by induction heating according to the present invention, and shows a cross section taken along line AA of FIG. 2 is a top view excluding the top plate of FIG. 1, and FIG. 3 is a detailed view showing the relationship between the bearing ring to be processed and the induction heating coil.

  Hereinafter, description will be given based on the drawings. A raceway ring (hereinafter referred to as a workpiece W) of the needle roller bearing used in the present embodiment is an outer ring of a shell-type needle needle roller bearing, and has a flange at the lower end of the raceway portion Wb as shown in a cross section in FIG. Wa is provided, and is formed of a thin ring having a thin throttle portion Wc provided at the upper end. Since the narrowed portion Wc at the upper end of the workpiece W in FIG. 3 is bent, it is not quenched, and only the inner circumferential raceway surface of the raceway portion Wb is surface quenched.

  The quenching apparatus 1 of the present invention includes a cooling jig 10 that cools the outer periphery of the workpiece W, a heating coil 20 that induction-heats the inner circumferential raceway surface of the workpiece, and a cooling means for rapidly cooling the inner circumferential raceway surface after heating. 30.

  A cooling jig 10 that cools the outer periphery of the workpiece W includes three cooling pieces 11 having a sector cross section obtained by dividing a cylinder into three. The three cooling pieces 11 have an inscribed surface that comes into contact with the outer periphery of the workpiece when assembled into a cylinder, and the inscribed surface has a stepped hole shape so as to support the lower surface of the workpiece. When the cooling piece 11 is assembled, the inner diameter of the inscribed surface of the cooling piece 11 is set to an inner diameter that does not have a gap enough to allow the workpiece to slide in. ing.

  The cooling piece 11 is sandwiched between the lower plate 16 and the upper plate 17 so as to be movable, and a guide rod 12 fixed to the cooling piece 11 is slidably supported on the guide portion of the guide plate 13. The cooling piece 11 is urged by the coil spring 14 so that the inscribed surface is in close contact with the outer periphery of the workpiece. The cooling piece 11 is made hollow so that the hollow portion is water-cooled. The cooling jig 10 is rotated by a driving means (not shown) so that the workpiece is heated and quenched while rotating.

  If the cooling jig is an integral cylinder, there must be a gap between the workpiece and the cooling piece in response to thermal expansion when the temperature of the workpiece is low. The effect cannot be demonstrated. In the present invention, when the workpiece is heated and thermally expanded, the cooling piece moves in close contact with the workpiece, so that the workpiece can be effectively cooled even when the temperature is low or high.

The induction heating coil 20 has a cylindrical shape and is arranged to heat the track surface of the workpiece. The cooling means 30 is provided with a nozzle on the lower surface of the hollow ring body so as to inject and quench the cooling water onto the heated track surface. As shown in detail in FIG. 3, the heating coil of the present invention is provided with a taper having a gradient x so as to increase the gap on the cooling means side.
In quenching and cooling, in order to obtain a sufficient quenching hardness on the thin raceway surface, the heating coil is left in the heating position, and the workpiece is rapidly cooled before being cooled after being heated. On the other hand, as described above, since the workpiece has a small diameter and a thin wall and only the surface is quenched, the interval between the outer periphery of the induction heating coil and the inner periphery of the workpiece is usually a very narrow gap of about 1 mm. For this reason, with the conventional parallel cylindrical heating coil, even if spray cooling is performed from the cooling means, it is difficult for the coolant to enter the heating surface, and the quenching surface cannot be evenly cooled, so that sufficient quenching hardness cannot be obtained. Quenching unevenness may occur. Therefore, the heating coil of the present invention is provided with a taper on the outer periphery as described above to increase the clearance on the cooling means side, thereby preventing overheating of the workpiece end and flowing the injected coolant against the tapered surface of the coil. As a result, the heating surface is uniformly cooled, and uniform high hardness is obtained.

Hereinafter, the operation of the surface hardening device for the raceway surface of the needle roller bearing by induction heating having the above-described configuration of the present invention will be described.
First, the heating coil 20 and the cooling means 30 are moved upward in the drawing, and the workpiece is loaded on the inner periphery of the cooling piece 11 of the cooling jig 10. Then, the heating coil 20 and the cooling means 30 are returned to predetermined positions, and the work is heated by supplying electric power to the heating coil 20 while rotating the cooling jig 10 by a driving means (not shown). At this time, although the workpiece is thermally expanded, the cooling piece 11 is urged by the coil spring 14 and moves in close contact with the outer periphery of the workpiece. Only the surface rises in temperature.

  When the work inner peripheral raceway surface reaches the quenching temperature, cooling water is jetted from the cooling means 30, and the quenched surface is cooled and quenched. At this time, since the outer periphery of the heating coil is tapered, the injected cooling water flows on the outer periphery of the heating coil to uniformly cool the inner peripheral track surface of the workpiece. As a result, only the inner peripheral surface of the workpiece is quenched and hardened.

[Example]
Next, examples will be described. The workpiece W used in the example was a JIS S55C material having an inner diameter D = 26 mm, a wall thickness t = 1 mm, and a height h = 20 mm in the cross-sectional shape shown in FIG. Then, the inner peripheral raceway surface was quenched by the apparatus of the present invention using the cooling jig and the conventional comparison method not using the cooling jig.
In the method of the present invention, the induction heating coil is a coil with a taper of x = 15 degrees as shown in FIG. 3, and in the comparative method, a cylindrical coil having a parallel outer peripheral surface is used, and any gap between the coil and the inner peripheral raceway surface is used. 1.0 mm. As for the heating conditions, all were heated at 200 kHz for 0.2 s and then water-cooled.

  After quenching, the hardness distribution of the cross section was measured. As a result, in the comparative method, the entire thickness was quenched at about Hv 750 where the outer circumference was slightly lower but the cross-sectional hardness of the entire thickness was almost the same. On the other hand, in the method of the present invention, the hardness from the inner raceway surface to a depth of about 0.3 mm is Hv750, and the hardness from the outer circumference surface to a depth of approximately 0.7 mm is Hv200, and only the inner circumference raceway surface is hardened. I was able to.

  In addition, as a result of measuring the hardness distribution of the upper and lower circumferences of the inner raceway surface of the workpiece after quenching, the hardness of about Hv750 was obtained almost uniformly in the circumference on the upper side near the cooling means in the comparative method. Since the cooling water does not rotate sufficiently at the center and the lower side, hardness unevenness occurs even on the circumference, and only a hardness of Hv650-680 was obtained on the lower circumference. On the other hand, in the method of the present invention, the periphery of the cooling water is uniform due to the effect of the taper on the outer periphery of the coil, so that a hardness of Hv750 or higher is obtained in both the upper and lower parts, and the hardness of the circumference is uniform. That is, the effect of the heating coil having a taper on the outer periphery of the present invention was recognized.

As described above, according to the surface hardening method and apparatus for the raceway surface of the needle roller bearing outer ring by induction heating according to the present invention, it is possible to quench only the surface of the raceway surface by induction heating and quenching even for a thin raceway surface. Therefore, the following effects are recognized as compared with the conventional surface hardening treatment such as carburization.
1. Heat treatment equipment is small and cheap, and the environment is improved.
2. The time for heat treatment (surface hardening treatment) is shortened, making it easy to produce a variety of products in small quantities and reducing the in-process.
3. In addition, consistent line production is possible and quality can be improved.

  As described above, according to the surface hardening method and apparatus for the raceway surface of the needle roller bearing outer ring by induction heating according to the present invention, the equipment cost is reduced, the factory environment is improved, and the heat treatment time is shortened. Costs are reduced and bearing costs can be reduced, contributing to industrial development.

It is sectional drawing of the surface hardening apparatus of the raceway surface of the needle roller bearing by the induction heating of this invention embodiment. It is a top view except the upper board of FIG. It is sectional drawing which shows the relationship between the heating coil of this invention embodiment, and a workpiece | work.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cooling jig, 11 Cooling piece, 12 Guide rod, 13 Guide plate, 14 Coil spring, 16 Lower plate, 17 Upper plate, 20 Induction heating coil, 30 Cooling means, W Workpiece (Needle roller bearing outer ring)

Claims (6)

In the surface hardening of the raceway surface of the shell type needle roller bearing outer ring formed by pressing the steel plate, an induction heating coil is arranged on the inner circumferential raceway surface of the outer ring to be quenched, and a cooling jig is arranged on the outer circumferential surface. A method of surface hardening of the raceway surface of the needle roller bearing outer ring by induction heating, wherein the outer circumferential surface of the outer ring to be quenched is cooled by the cooling jig and the surface of the inner raceway is induction-heated by induction heating . A cylindrical induction heating coil having a tapered outer periphery is disposed on the inner peripheral raceway surface of the outer ring to be quenched, and is quenched by injection cooling from the direction in which the distance between the outer periphery of the coil and the inner peripheral raceway surface of the outer ring to be quenched is large. The surface hardening method for the raceway surface of the needle roller bearing outer ring by induction heating according to claim 1. In the surface hardening device for the outer ring raceway of the shell-type needle roller bearing formed by pressing the steel plate, an induction heating coil is provided on the inner raceway surface of the outer ring to be hardened, and the inner raceway surface is being induction heated. A surface hardening device for a raceway surface of a needle roller bearing outer ring by induction heating, wherein a cooling jig provided with a cooling piece for cooling the outer peripheral surface of the outer ring to be hardened is disposed. The cooling jig is composed of a cylindrical body in which a plurality of fan-shaped cross-section cooling pieces that are radially divided are combined, and each cooling piece is urged so as to be in close contact with the outer periphery of the outer ring to be hardened, and the heat of the outer ring to be hardened 4. The surface hardening device for a raceway surface of a needle roller bearing outer ring by induction heating according to claim 3, wherein the surface quenching device moves according to expansion. The surface hardening apparatus for a raceway surface of a needle roller bearing outer ring by induction heating according to claim 3 or 4, wherein the cooling jig is water-cooled. Coolant is injected from a direction in which the gap between the outer periphery of the cylindrical outer heating ring and the inner circumferential raceway surface of the outer ring to be hardened is large, and the cylindrical induction heating coil having a tapered outer circumference. 5. A surface hardening apparatus for a raceway surface of a needle roller bearing outer ring by induction heating according to claim 3 or 4, further comprising cooling means arranged to cool.

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