JP2006233288A - Machine part with groove for rolling and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a machine part with a groove for rolling and a production method therefor with which the development of scale after high frequency induction hardening, is restrained and the surface of the groove for rolling can be used in a state it is hardened and the development of bending can be restrained. <P>SOLUTION: A screw shaft 2 in this machine part with the groove for rolling has the groove 5 for rolling with its cross-section arc-shaped, where the rolling element 3 rolls, and at least the inner surface of the groove 5 is subjected to the high frequency induction hardening. The inner surface of the groove 5 is subjected to high frequency induction hardening in liquid. In this way, after high frequency induction hardening in the inner surface of the groove 5, black-colored oxide scale is not produced and the inner surface of the groove 5 subjected to the high frequency induction hardening, is used as the rolling surface as it is. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is used for automobiles, industrial use, and the like, and is a machine part having a groove on which a rolling element rolls, for example, a machine part such as a screw shaft of a ball screw, for power transmission in which the groove is quenched. The present invention relates to a machine part with rolling grooves for a conveying device, and a manufacturing method thereof.

  The ball screw has a plurality of balls arranged between a spiral rolling groove provided on the outer peripheral surface of the screw shaft and a rolling groove provided on the inner peripheral surface of a nut fitted on the screw shaft. (Or nut) rotational power is converted into a nut (or screw shaft) thrust through a ball. The inner surface of the rolling groove is quenched to improve wear resistance and durability. There are the following various methods for producing a ball screw in which this quenching is performed by induction quenching.

  One of them is a method for manufacturing a screw shaft of a ball screw disclosed in, for example, Patent Document 1, in which a rolling groove of the screw shaft is formed by rolling from a medium carbon steel material. Thereafter, the inner surface of the rolling groove is hardened by induction hardening to a range of HRC 55 to 62 to improve wear resistance. In order to remove the oxide scale generated by this heat treatment, buffing is performed. Finally, in order to correct the deformation caused by the rolling process and the induction hardening process, bending correction is performed.

  The other one is a ball screw nut manufacturing method disclosed in, for example, Patent Document 2, in which the inner surface of the rolling groove of the nut is induction-quenched, and then the rolling groove is electropolished, thereby rolling the rolling groove. Remove and finish the oxide scale formed in the groove.

The other is not a manufacturing method limited to a ball screw, but is a method of removing oxide scale by increasing the pressure of cooling water during induction hardening (for example, Patent Document 3).
JP 2003-119518 A JP 2003-25152 A JP 2002-129231 A

When a spherical rolling element operates like a ball screw, the rolling element operates in a dot-like contact state (a state close to pure rolling). For this reason, if foreign matter such as oxide scale generated during quenching is caught in or exists in the rolling groove, the movement of the rolling element changes suddenly and noise is likely to occur. Therefore, removal of oxide scale is an essential process.
However, there is a case where the scale cannot be completely removed from the rolling groove only by the buffing process disclosed in Patent Document 1, and there is a problem that the processing time becomes long due to the buffing process.
When the oxide scale is removed by electropolishing after induction hardening as in the manufacturing method disclosed in Patent Document 2, the scale can be completely removed. However, there are problems that the processing time is significantly increased, the surface of the rolling groove is rough, and the surface layer is softened by the heat of chemical reaction.
When the oxide scale is removed by increasing the pressure of the cooling water during induction hardening as in the manufacturing method disclosed in Patent Document 3, the scale cannot be removed uniformly, and the black scale remains minutely in spots. . Therefore, there is a problem that a separate scale removal process by buffing or the like cannot be omitted completely.

  In addition, if the deformed ball screw is applied to a conveying device or the like, it causes a swing or vibration during high-speed rotation. Therefore, when bending deformation occurs in an induction hardening process or the like as in the manufacturing method disclosed in Patent Document 1, a process for correcting the deformation is essential, and the processing time is increased from this point. Therefore, it is an important issue to minimize the bending deformation by induction hardening.

An object of the present invention is to provide a machine part with rolling grooves that does not require scale removal after induction hardening, is excellent in productivity, and can reduce costs.
Another object of the present invention is to provide a method of manufacturing a machine part with rolling grooves that suppresses the generation of scale after induction hardening, enables the surface of the rolling groove to be used as it is, and suppresses the occurrence of bending. It is to be.

The rolling grooved machine part according to the present invention is a machine part having a rolling groove on which a rolling element rolls, at least an inner surface of the rolling groove being induction-hardened, and a high frequency on the inner surface of the rolling groove. There is no generation of black oxide scale after quenching, and the inner surface of the rolling groove subjected to induction hardening is used as it is as a rolling surface. The rolling element may have an arc shape in cross section, and the rolling element may be a ball.
Usually, induction hardening is heated in the atmosphere and then cooled. Since the heating temperature is a temperature in the vicinity of 900 to 1150 ° C., it reacts with oxygen in the atmosphere or cooling water to generate an oxide scale. Accordingly, when induction hardening is performed on the inner surface of the rolling groove in the machine part with the rolling groove, the black oxide scale described above is generated on the inner surface of the rolling groove. According to the verification by the present inventor, the black oxide scale has a large amount of porous material and is thick, which causes noise during rotation. In the machine part with rolling grooves of the present invention, as described above, there is no generation of black oxide scale after induction hardening on the inner surface of the rolling groove, and the inner surface of the rolling groove subjected to induction hardening is rolled as it is. Since it is used as a surface, it is possible to eliminate the generation of abnormal noise during rotation.

  In this invention, the mechanical component may be a screw shaft of a ball screw. In the case of this configuration, it is possible to eliminate the occurrence of abnormal noise due to the oxide scale during the operation of the ball screw. The screw shaft may be formed by rolling the rolling groove. If rolling grooves are rolled and black oxide scale is not generated after induction hardening, the productivity of rolling process is superior to that of machining, and the scale removal process after induction hardening. Because it is unnecessary, the productivity of the screw shaft is very excellent and can be produced at low cost.

According to the method of manufacturing a machine component with rolling grooves of the present invention, a rolling groove is formed in a material, and thereafter, at least an inner surface of the rolling groove is induction-quenched in a liquid, and the induction-quenched rolling groove is The inner surface shall be used as it is as a rolling surface. The rolling element may have an arc shape in cross section, and the rolling element may be a ball.
In order to induction-harden the inner surface of the rolling groove so as not to generate the black oxide scale described above, heat treatment may be performed in a vacuum without oxygen, but the heat treatment in vacuum is complicated and costly. It will increase. In this manufacturing method, since the inner surface of the rolling groove is induction-quenched in a liquid with little oxygen, the generation of the black oxide scale on the inner surface of the rolling groove can be eliminated. Because of the submerged treatment, a complicated device that maintains a vacuum is not necessary. In addition, since there is a trace amount of oxygen in the liquid, an extremely thin scale is generated. However, since this thin scale has high adhesion, no abnormal noise is generated during rotation due to the scale.
In addition, by quenching in the above liquid, the liquid becomes cooling water, and the machine parts with rolling grooves are uniformly cooled. Therefore, the bending deformation of the machine parts with rolling grooves due to induction hardening can be extremely reduced. .

The rolling groove may be processed by cold forging. When the machine part with rolling grooves is a ball screw, the cold forging may be rolling.
Cold forging is more productive than machining. Therefore, by adopting cold forging and eliminating the need for scale removal by induction hardening in liquid, the production method is extremely excellent in productivity.

The rolling grooved machine part according to the present invention is a machine part having a rolling groove on which a rolling element rolls, at least an inner surface of the rolling groove being induction-hardened, and a high frequency on the inner surface of the rolling groove. There is no generation of black oxide scale after quenching, and the inner surface of the induction-quenched rolling groove is used as it is as a rolling surface, so there is no need for scale removal after induction hardening and production. Excellent in cost and cost reduction.
According to the method of manufacturing a machine component with rolling grooves of the present invention, a rolling groove is formed in a material, and thereafter, at least an inner surface of the rolling groove is induction-quenched in a liquid, and the induction-quenched rolling groove is Since the inner surface is used as the rolling surface as it is, the generation of scale after induction hardening can be suppressed, the rolling groove surface can be used as quenched, and the occurrence of bending can be suppressed. .

  An embodiment of the present invention will be described with reference to FIGS. The machine part with rolling grooves of this embodiment is applied to a screw shaft of a ball screw. As shown in a sectional view in FIG. 1, the ball screw 1 includes a screw shaft 2, a nut 3, and a plurality of balls 4 that are rolling elements. As shown in a perspective view in FIG. 2, the screw shaft 2 that is a machine part with rolling grooves is a shaft in which a rolling groove 5 having a circular arc shape and a cross-sectional arc shape is formed on the outer peripheral surface. The cross-sectional arc shape referred to here includes a Gothic arch shape that is a combination of two arcs having different arc centers. The nut 3 is externally fitted to the screw shaft 2 in a loosely fitted state, and a spiral groove 6 having an arcuate cross section is formed on the inner peripheral surface. The ball 4 is disposed between the rolling grooves 5 and 6 of the screw shaft 2 and the nut 3 facing each other. The nut 3 has a circulating part (not shown) for making the ball 3 endlessly circulate with the raceway formed between the rolling shafts 5 and 6 facing the screw shaft 2 and the nut 3 as an endless raceway. A return tube or the like is attached.

  The screw shaft 2 is manufactured by the process shown in the schematic flow diagram of FIG. That is, the material of the screw shaft 2 is made into a round bar through a casting and rolling process. Next, peeling processing for removing surface scratches on the round bar, centerless grinding for finishing to a desired outer diameter, and the like are performed, and the rolling grooves 5 are formed in the round bar finished in this way. The formation of the rolling groove 5 is performed by rolling which is a kind of cold forging. This rolling process is a process of forming a spiral rolling groove 5 by rolling a rolling roll (not shown) to the outer peripheral surface of a round bar. The formed inner surface of the rolling groove 5 is induction-quenched as shown in FIG. This induction hardening is performed by heating the screw shaft 2 with the high-frequency heating coil 12 in a state in which the screw shaft 2 is immersed in the liquid 11 contained in the container 10. Oil is preferred as the liquid during the quenching treatment, but water-soluble quenching oil may be used in consideration of quenchability.

In the screw shaft 2 which is a machine part with a rolling groove manufactured by such a process, the inner surface of the rolling groove 5 which is induction-hardened is used as it is as a rolling surface without any subsequent finishing treatment. . In the case of this screw shaft 2, as described above, since it is heated and cooled by induction quenching in the liquid 11 with little oxygen, there is no generation of black oxide scares on the inner surface of the rolling groove 5. Since no black oxide scale is generated, the ball screw incorporating the screw shaft 2 can eliminate the generation of abnormal noise during rotation.
Since there is a very small amount of oxygen in the liquid 11, an extremely thin scale is generated, but this thin scale (close to the color of the original base material) has strong adhesion, and when incorporated in a ball screw, It was found that no abnormal noise was generated during rotation due to the scale. In other words, the oxide scale generated in the atmosphere is a black scale and contains a lot of porous and thick, but the scale generated when induction-quenched in liquid is different from the black scale, Since it is thin and has strong adhesion, it does not hinder even if it remains on the inner surface of the rolling groove 5.
Further, by quenching in the liquid 11, the liquid 11 becomes cooling water and the entire screw shaft 2 is uniformly cooled, so that the bending deformation of the screw shaft 2 due to induction hardening can be extremely reduced. It becomes.

  In the induction hardening, the liquid 11 is optimized with an additive (for example, polyvinyl alcohol), an antioxidant (for example, zinc dialkyldithiophosphate), a corrosion inhibitor (for example, benzotriazole) or the like that improves hardenability. May be added. In this case, it is effective for sufficient quenching characteristics and further scale reduction.

  Conventionally, in manufacturing a screw shaft, in order to reduce deformation after rolling, a surface treatment (bonding treatment or the like) for reducing a friction coefficient of a machined surface may be performed before rolling. However, in the manufacturing process of the screw shaft 2 in this embodiment, the surface treatment may increase the scale after induction hardening even if the rollability is improved, so the surface treatment may be omitted. preferable.

  Table 1 shows the actual measurement results comparing the characteristics of the ball screw incorporating the screw shaft 2 of this embodiment and the ball screw incorporating the conventional screw shaft.

From this measurement result, it can be confirmed that in the screw shaft 2 of this embodiment, the occurrence of black scale is remarkably suppressed and the deformation after induction hardening is greatly reduced.
Further, in the conventional screw shaft, no abnormal noise was generated when buffing was performed, but abnormal noise was generated when buffing was not performed, and buffing is essential. In the screw shaft 2 of this embodiment, no abnormal noise was generated even without buffing. In addition, in the screw shaft 2 of this embodiment, since buffing is unnecessary, the example which buffed is not tested.

  In the above embodiment, the case where the machine part with rolling grooves of the present invention is applied to the screw shaft 2 of the ball screw 1 has been described. The same effect can be obtained. Further, the present invention is not limited to a ball screw, and can be applied to general machine parts having a rolling groove on which a rolling element rolls, such as a bearing ring of a rolling bearing.

It is a longitudinal cross-sectional view of the ball screw incorporating the screw shaft concerning one Embodiment of this invention. It is a perspective view of the screw shaft. It is a flowchart which shows the manufacturing process of the screw shaft. It is explanatory drawing of the induction hardening in the manufacturing process.

Explanation of symbols

1 ... Ball screw 2 ... Screw shaft (machine part with rolling groove)
3 ... Nut 4 ... Ball (rolling element)
5 ... Rolling groove of screw shaft 11 ... Liquid

Claims (6)

  The rolling element has a rolling groove in which the rolling element rolls, and at least the inner surface of the rolling groove is induction-hardened, and the black oxide scale is generated on the inner surface of the rolling groove after induction hardening. In addition, a machine part with a rolling groove in which the inner surface of the induction-quenched rolling groove is used as it is as a rolling surface.   2. The machine part with rolling grooves according to claim 1, wherein the rolling grooves have a circular arc shape in cross section, and the rolling elements are balls.   3. The machine part with rolling grooves according to claim 2, wherein the machine part is a screw shaft of a ball screw.   4. The machine part with a rolling groove according to claim 3, wherein the screw shaft is formed by rolling the rolling groove.   A rolling groove is formed on the material by cold forging, and then at least the inner surface of the rolling groove is induction-hardened in a liquid, and the inner surface of the induction-quenched rolling groove is used as it is as a rolling surface. A manufacturing method for machine parts with rolling grooves.   The manufacturing method of the machine part with a rolling groove which performs formation of the said rolling groove by cold forging in Claim 5.

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