JP2005069377A - Shaft formed with hole - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shaft formed with a hole having high torsional fatigue strength by forming a nano-crystal layer in the inner peripheral surface of the hole. <P>SOLUTION: A steel shaft main body 2 is formed with the hole 5 from the outer peripheral surface toward an inner peripheral part. A surface of the hole 5 is formed with the nano-crystal layer C, and strength of the inner peripheral surface of the hole 5 is improved by the nano-crystal layer C to improve torsional fatigue strength of the shaft 1 formed with a hole. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a shaft with a hole that requires high torque, such as an input shaft for an automatic transmission, an output shaft, a drive shaft that is rotated by an electric motor, and the like, and in particular, a hole for lubrication or cooling is formed on the outer periphery. It relates to a shaft with a hole.

Conventional input shafts and output shafts for automatic transmissions are made of long raw materials such as bar cutting materials or forgings by external turning, spline processing, and oil drilling, carburizing and induction hardening, etc. After heat treatment and primary curing treatment, the surface was subjected to secondary curing treatment by shot peening, and then ground to finish to increase surface hardness and fatigue strength.
Japanese Patent Publication No. 2-17607

The above-described curing process by shot peening processing has a high surface hardness and fatigue strength only at the mouth portion in the oil hole, and shot peening processing requires a special device and is shot during shot peening processing. Since grit and grit enter small holes (oil holes), a process such as pre-cleaning after the processing is required. In addition, if a shot or grit is left in the small hole (oil hole) and assembled in the unit, it will cause a malfunction, so a subsequent inspection process is also required, increasing costs and reducing productivity. there were. An object of this invention is to obtain the novel shaft with a hole which eliminated the said malfunction.

The invention according to claim 1 is configured such that a hole extending from the outer peripheral surface toward the inner peripheral portion is formed in the steel shaft main body, and a nanocrystal layer is formed on the surface of the hole.
According to a second aspect of the present invention, a hardened steel shaft main body is provided, and a hole is formed in the shaft main body from the outer peripheral surface to the inner peripheral portion by a drilling tool, and the hole is formed when the hole is opened. A high-speed large strain is applied to the surface layer portion of the hole by a drilling tool to generate a nanocrystal layer on the surface.
According to a third aspect of the invention, the perforating tool has a peripheral speed of 50 m / min or more and a feed of 0.1 mm or less per revolution.

In the invention according to claim 1 of the present application, the surface of the hole, that is, the inner peripheral surface is reinforced by the nanocrystal layer, and is sufficiently resistant to the stress concentration generated during the torsional torque of the shaft with a hole. Thus, the shaft with a hole having high torsional fatigue strength can be reduced in size and weight.
In the invention according to claim 2 of the present application, since the nanocrystal layer is formed on the surface of the hole by a drilling tool, the nanocrystal layer can be formed without requiring a special apparatus and post-treatment, A shaft with a hole having high torsional fatigue strength can be obtained at low cost.
In the invention according to claim 3, since the peripheral speed of the drilling tool is set to 50 m / min or more and the feed is set to 0.1 mm or less per rotation, the structure of the surface layer of the hole generates high-speed large strain, and the nanocrystal layer Will be generated smoothly.

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, FIG. 1 is a cross-sectional view of a shaft with a hole to which the present invention is applied, FIG. 2 is an enlarged cross-sectional view of a main part showing a state of forming a nanocrystal layer on a hole surface by a drilling tool, and FIG. FIG. 4 is a comparative view showing cutting conditions of the drilling tool according to the present invention and the prior art.

In FIG. 1, reference numeral 1 denotes a shaft with a hole made of an input shaft for an automatic transmission, which is formed of a quenching material such as SCM420H, SCr420H, S45C or the like.

The holed shaft 1 is formed as follows. That is, a long raw material such as a bar cutting material or a forging material is subjected to external turning, processing of the splines 3a and 3b, and processing of the oil introduction lateral holes 4a, 4b and 4c in a predetermined shape. And a shaft main body 2 having dimensions. Next, this is subjected to heat treatment such as carburizing and quenching to remove distortion and harden it. In this example, carburizing and quenching is performed, and the curing process is performed so that the surface hardness is about 6.8 GPa (700 Hv) and the internal hardness is about 3.4 GPa (350 Hv). Next, finish by grinding. In addition, you may be made to perform this grinding process after the horizontal hole 4a, 4b, 4c process of the following process.

Next, the oil supply branch hole 5 (5a, 5b) communicates with the outer peripheral surface of the shaft main body 2 from the outer peripheral surface toward the lateral holes 4a, 4b, 4c by a drilling tool 6 (FIG. 2) comprising a drill. , 5c... Are spaced apart at predetermined intervals in the axial direction. In this case, the present invention opens each branch hole 5 as follows. That is, the cutting conditions of the drilling tool 6 are the nanocrystal layer generation cutting conditions shown in the upper part of FIG. 4, that is, the rotational speed of the drilling tool 6 is 50 m / min or higher, preferably about 75 m / min. In this state, each branch hole 5 is opened as shown in FIG. 2, with the rotational speed of the feed hole 6 being set to 0.1 mm or less, preferably about 0.05 mm per revolution.

Each of the branch holes 5 is formed by drilling a lower hole 5 ′ (imaginary line in FIG. 2) with a drill having a smaller diameter than specified, and then drilling the lower hole 5 ′ with a specified diameter with a drill or reamer having a specified diameter. You may make it finish. In this case, the drill for drilling the lower hole 5 ′ has the conventional cutting conditions shown in the lower part of FIG. 4, that is, the rotational speed at which the peripheral speed is 10 to 20 m / min, the feed is about 0.05 mm per revolution, The cutting conditions of the drill or reamer that finishes the prepared hole 5 'to a specified diameter are finished by the peripheral speed and feed according to the present invention described above. The lower hole 5 ′ may be opened before the shaft main body 2 is quenched.

According to the above-described embodiment, the peripheral speed of the drilling tool 6 is increased to 2.5 times or more than the conventional speed so as to form the branch hole 5, so that the structure of the surface layer portion of the branch hole 5 has a high strain and a large strain. As shown in FIGS. 2 and 3, the nanocrystalline layer C is smoothly generated on the surface of the branch hole 5, that is, the inner peripheral surface. According to an experiment, in the example of the SCM420H member, the nanocrystal layer C has a particle size of 100 nm (0.1 μm), a hardness of 9.8 GPa (980 Hv), a surface roughness of Ra 0.7, and the shaft 1 with holes. As a result of the torsional fatigue strength test, the torsional fatigue strength at the branch holes 5a, 5b, and 5c in FIG. The strength is an evaluation result of about 20% strength increase compared to the conventional method (without shot peening).

The drilling tool 6 according to the present invention is appropriately set as a drill, a reamer, a gun drill (half moon drill), or the like depending on the type and depth of the hole. Further, the above-described lateral holes 4a, 4b, and 4c may be subjected to the same hole processing as described above to form a nanocrystal layer on the surface (inner peripheral surface).

It is sectional drawing of the shaft with a hole to which this invention is summarized. It is a principal part expanded sectional view which shows the nanocrystal layer formation state to the hole surface by a drilling tool. It is a principal part expanded sectional view of the hole in which the nanocrystal layer was formed. It is a comparison figure which shows the cutting conditions of this invention and the conventional drilling tool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft with hole 2 Shaft main body 3a, 3b Spline 4a, 4b, 4c Side hole 5 (5a, 5b, 5c) Branch hole 6 Drilling tool C Nanocrystal layer

Claims (3)

With a hole characterized by forming a hole (5) from the outer peripheral surface to the inner peripheral part in the steel shaft main body (2) and forming a nanocrystal layer (C) on the surface of the hole (5) shaft. A hardened steel shaft main body (2) is provided, and a hole (5) is formed in the shaft main body (2) from the outer peripheral surface to the inner peripheral portion by the drilling tool (6). ), A high-speed large strain was applied to the surface layer portion of the hole (5) by the drilling tool (6) to form a nanocrystal layer (C) on the surface. The shaft with holes according to claim 2, wherein the peripheral speed of the drilling tool (6) is 50 m / min or more and the feed is 0.1 mm or less per rotation.

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