JP2002160163A - Surface hardening method for steel member and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface hardening method for a steel member capable of projecting projection particles in a wide range with a simple structure without requiring a complicated device such as a nozzle movement device and setting a diameter of an opening of a projection hole to be small and capable of reducing pressure of fluid used as a kinetic energy source by rotating a projection nozzle around a central axis and arranging the opening direction or the opening position of the projection hole to be oblique with respect to the central axis. SOLUTION: In this surface hardening method for the steel member, the fluid is used as the kinetic energy source, and the projection particles are projected from the projection hole 24 of the projection nozzle 6 to a workpiece 1. The projection nozzle 6 is rotated around the central axis C1 and the opening direction or the opening position of the projection hole 24 is arranged to be oblique with respect to the central axis C1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for hardening the surface of a steel member in which a fluid is used as a kinetic energy source (that is, power) to project particles onto a workpiece from a projection hole of a projection nozzle.

[0002]

2. Description of the Related Art Generally, as a method and an apparatus for hardening a surface of a steel member, a method of projecting a shot (steel particle) as a projection particle onto a work by rotating an impeller is known. In shot peening, shots are also projected on unnecessary parts, so useless shots
This causes not only a large waste of machining energy (so-called wasting), but also a problem that equipment is consumed by shots rebounding from the work.

In order to solve such a problem, conventionally,
Nozzle shot peening has already been developed.
That is, a shot (steel grain) is projected onto a work from a projection hole of a projection nozzle using air as a kinetic energy source (that is, power).

However, in this conventional nozzle-type shot peening, since the center of the projection nozzle and the projection hole are formed coaxially, a complicated moving mechanism is required to perform a surface hardening process on the work surface of the work over a wide range. It was necessary to move the projection nozzle itself using.

In order to hit a wide range of shots without moving the above-mentioned projection nozzle, the opening diameter of the projection hole may be increased. In this case, the required pressure of compressed air used as a kinetic energy source is reduced. There is a problem in that the air compressor becomes excessively high, and the air compressor used as a pressure source is increased in size and cost.

[0006] Japanese Patent Application Laid-Open No. 9-14252 discloses shot peening in which a residual stress between a hardened portion and a non-hardened portion is relaxed. That is,
As shown in FIGS. 10 and 11, a quenching portion 9 is formed on a pin journal 91 of a crankshaft 90 by induction hardening means.
In order to reduce the difference in residual stress between the quenched portion 92 and the non-quenched portion 93, an oil hole 9 is formed as shown by an imaginary line in FIG.
A shot 96 is projected on the portion near the quenched portion 92 of No. 5,
A shot peening portion 97 is formed to alleviate the difference in hardness between the two 92 and 93.

[0007]

However, since the above-mentioned projection nozzle 94 is a straight nozzle in which the center line of the nozzle body coincides with the center line of the projection hole, the oil hole 95 described above is applied by applying this prior art. When hitting the shot 96 over the entire area of the chamfered portion 98 formed at the opening end of the nozzle, the same problem as in the above-described nozzle-type shot peening occurs.

According to the present invention, a complicated device such as a nozzle moving device is provided by rotating a projection nozzle around its central axis and disposing the opening direction or opening position of the projection hole with respect to the central axis. Without any need, it is possible to project the projection particles over a wide range while having a simple configuration, and it is possible to set the opening diameter of the projection hole small, thereby reducing the fluid pressure used as a kinetic energy source. An object of the present invention is to provide a method for hardening the surface of a steel member that can be achieved.

According to another aspect of the present invention, the projection nozzle is rotated around its central axis by a rotating mechanism, and the opening direction or the opening position of the projection hole formed in the projection nozzle is shifted from the central axis. Thus, a steel member capable of projecting projection particles over a wide range with a simple configuration, further reducing the opening diameter of the projection hole, and reducing the fluid pressure used as a kinetic energy source The purpose of the present invention is to provide a surface hardening device.

[0010]

A method for hardening a surface of a steel member according to the present invention is a method for hardening a surface of a steel member by projecting projection particles from a projection hole of a projection nozzle to a work using a fluid as a kinetic energy source. The projection nozzle is rotated around its central axis, and the opening direction or the opening position of the projection hole is shifted from the central axis.

The fluid having the above configuration may be set to air, and the shot particles may be set to shots (steel particles) so that the surface of the work surface of the work is hardened by shot peening. According to the above configuration, when the projection nozzle is rotated around its central axis and the projection particles are supplied to the projection hole of the projection nozzle using a fluid as a kinetic energy source, the projection particles are projected from the projection hole toward the workpiece. However, since the projection holes are so-called offset arranged with respect to the central axis of the projection nozzle, a projection circle is formed. That is, a processing area can be secured by rotating the projection nozzle.

As a result, it is possible to project the projection particles over a wide range by the above-described projection circle without any complicated device such as a nozzle moving device and with a simple configuration. Further, the opening diameter of the projection hole can be set small, and the fluid pressure can be reduced.

In one embodiment of the present invention, the fluid is set to compressed air, and the projection particles are set to shots. According to the configuration described above, a compressive residual stress is applied to a processed surface by shot peening, so that the fatigue strength of the portion can be improved.

In one embodiment of the present invention, the periphery of the hole of the work is subjected to a surface hardening treatment, and the projection particles are projected with the center of the hole of the work and the central axis of the projection nozzle coincide with each other. is there.

According to the above configuration, since the center of the workpiece hole and the central axis of the projection nozzle are made coincident, the projection particles from the projection hole which is displaced with respect to the central axis of the projection nozzle can be used. Without dropping through the holes, it is possible to reduce the waste of the projected particles and the processing energy.

In one embodiment of the present invention, a pipe-shaped work made of cast iron is provided, a chamfered portion is formed around a hole of the work, and projection particles are projected on the chamfered portion.

According to the above configuration, by projecting the projection particles on the chamfered portion, the chamfered portion can be reliably processed. In addition, if a chamfered portion is formed around the hole of the pipe-shaped work, a thickness difference occurs in the chamfered portion, and cracks caused by the thickness difference can be prevented by the above-described projection of the projection particles.

The steel member surface hardening apparatus according to the present invention comprises:
What is claimed is: 1. A surface hardening device for a steel member that projects projection particles onto a workpiece using a fluid as a kinetic energy source, comprising: a projection nozzle configured to project the projection particles onto the workpiece; and an opening direction or an opening position of the projection nozzle with respect to a central axis of the projection nozzle. And a rotation mechanism for rotating the projection nozzle about the central axis.

The fluid having the above configuration may be set to compressed air, and the projection particles may be set to shots (steel particles), so that the surface of the work surface of the work is hardened by shot peening.
According to the above configuration, the projection nozzle is rotated around its central axis by the rotation mechanism described above, and the projection particles are supplied to the projection hole of the projection nozzle using a fluid as a kinetic energy source.
These projection particles are projected from the projection hole toward the workpiece,
Since the projection holes are arranged so-called offset with respect to the central axis of the projection nozzle, a projection circle is formed.

As a result, it is possible to project the projection particles over a wide range by the above-described projection circle without any complicated device such as a nozzle moving device and with a simple configuration. Further, the opening diameter of the projection hole can be set small, and the fluid pressure can be reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawings show a method and an apparatus for hardening the surface of a steel member. First, a configuration of a surface hardening apparatus for a steel member will be described with reference to FIGS. 1, 2, and 3. FIG.

FIG. 1 is a schematic plan view showing the entire structure of a surface hardening system for shot peening a crankshaft 1 as a pipe-shaped work made of cast iron as an example of a steel member work.

The above-described crankshaft 1 has a main journal 2 located on the axis of the crankshaft, a pin journal 3 connected to a connecting rod, and a plurality of balance weights 4 integrally formed. In the example, the processing station is divided into a first station ST1 and a second station ST2, and each station ST1
A total of two surface hardening devices 5 and 5 are provided in 1 and ST2.

In the first station ST1, a predetermined portion of the pin journal 3 corresponding to the second cylinder and a predetermined portion of the pin journal 3 corresponding to the fourth cylinder are shot-peened. A predetermined portion of the pin journal 3 corresponding to one cylinder and a predetermined portion of the pin journal 3 corresponding to the third cylinder are configured to be shot peened.

Further, each of the above stations ST1, ST
In FIG. 2, the crankshaft 1 is positioned by pressing a balance weight 4 by a positioning device (not shown), and the crankshaft 1 processed in the first station ST1 is transferred by a transfer means (not shown) such as a loader. It is configured to be transported to the second station ST2.

As shown in FIG. 4, the crankshaft 1 has an oil hole 3a formed obliquely in the pin journal 3, and a chamfered portion 3b is formed at the open end of the oil hole 3a. Is formed. In this embodiment, the above-described chamfered portion 3b is shot-peened, and the above-described surface hardening devices 5 are arranged in the front-rear direction and the left-right direction in order to make the nozzle tip 6 as a projection nozzle face the above-described oil hole 3a. It is installed on a table 7 whose position can be adjusted (positionable).

In FIG. 1, the crankshaft 1 for the four-cylinder engine is shown as an example. However, the work is not limited to this, and may be another crankshaft for a multi-cylinder engine. Work other than a shaft may be used.

FIG. 2 is a view showing the essential parts of the surface hardening device 5 along the line AA in FIG. 1. The surface hardening device 5 includes a motor 9 provided in an upper housing 8 and a motor 9. , A nozzle body 11 provided in the lower housing 10.

The nozzle body 11 has a passage 12 formed inside the nozzle body 11 along the axis of the nozzle body 11 for flowing compressed air and shots as projection particles.

The nozzle tip 6 is fixed to the tip of the nozzle body 11. On the other hand, the nozzle body 11 is rotatably supported by a bearing housing 14 via bearings 13, 13 as bearing means, and a non-rotatable supply pipe is provided on the base end side of the nozzle body 11 via a coupling 15. 16 are arranged opposite to each other, and this supply pipe 16
2 to supply compressed air as a kinetic energy source and a shot to the passage 12 in the nozzle body 11 as indicated by arrows in FIG.

Further, a driving bevel gear 17 is fitted and fixed to the rotating shaft 9a of the motor 9, and a driven bevel gear 18 is fitted and fixed to the nozzle body 11, and these two bevel gears 17 and 18 are meshed to form a projection nozzle. A rotation mechanism 19 for rotating the nozzle tip 6 around its central axis C1 (see FIGS. 3 and 4) is configured.

FIG. 3 is an enlarged sectional view showing the nozzle tip 6, and a spline portion 20 to be fitted in a spline hole at the tip end of the nozzle body 11 is formed on the outer peripheral portion on the base end side of the nozzle tip 6. After fitting the spline portion 20 into the spline hole at the tip of the nozzle body 11, the nozzle tip 6 is fixed to the tip of the nozzle body 11 by appropriate means.

In the above-mentioned nozzle tip 6, there is formed an introduction hole 23 in which a hole machined by a large-diameter drill 21 and a hole machined by a small-diameter drill 22 are integrated. A tapered portion 23a utilizing the drill shape of the large-diameter drill 21 is formed on the wire end side. The tapered portion 23a reduces the consumption of the introduction hole 23 by the shot against the tip of the hole wall, and the compressed air and the shot will be described later. It is configured to make the transition to the projection hole smooth. The hole diameter of the above-described introduction hole 23 is set substantially equal to the hole diameter of the passage 12 in the nozzle body 11.

Further, a projection hole 24 is formed extending from the tip of the introduction hole 23 to the outside of the tip of the nozzle tip 6. This projection hole 24 is located at the center axis C of the nozzle tip 6.
In this embodiment, both the opening direction and the opening position are shifted with respect to 1.

In this embodiment shown in FIG.
4 and the center axis C1 of the nozzle tip 6
The angle θ1 is set to about 15 degrees and the inner end of the projection hole 24 is
The offset amount in the radial direction with respect to the center axis C1 is large,
The offset amount of the outer end of the projection hole 24 with respect to the center axis C1 is small.
And the diameter of the projection hole (about 3 mm ^φ)
Is the hole diameter of the introduction hole 23 (about 12 mm^φ)
Is set.

A surface hardening method for performing shot peening of the chamfered portion 3b around the opening of the oil hole 3a of the pin journal 3 using the surface hardening apparatus thus configured will be described below.

In this case, as shown in FIG. 4, the center line C3 of the oil hole 3a as the center of the hole portion of the work and the center axis C1 of the nozzle tip 6 are aligned with each other in a straight line with each other. To match.

Under these conditions, the nozzle body 11 and the nozzle tip 6 are rotated around the central axis C1 by the rotation mechanism 19 shown in FIG. 2, and compressed air and air are supplied from the supply pipe 16 as shown by arrows in FIG. Supply shots. The hardness of the above shot is HRC50
Diameter to 52 is used the steel grains of approximately 0.3 mm ^phi.

The shot supplied from the supply pipe 16 described above uses compressed air as a kinetic energy source to produce the nozzle body 11.
After passing from the passage 12 to the introduction hole 23 of the nozzle tip 6, it is projected from the introduction hole 23 to the chamfered portion 3 b via the projection hole 24 at a projection speed of about 50 to 60 m / sec, and remains compressed in the chamfered portion 3 b. Since the stress is applied, the fatigue strength at the site can be improved.

As described above, the method of hardening the surface of the steel member of the above embodiment (chamfered portion 3 of oil hole 3a opening of pin journal 3).
b) is a method of projecting a projection particle (see shot) from a projection hole 24 of a projection nozzle (see nozzle tip 6) to a work (see crankshaft 1) using a fluid (see compressed air) as a kinetic energy source. A method of hardening a surface of a member, wherein the projection nozzle (see nozzle tip 6) is rotated around its central axis C1, and the opening direction or the opening position (both in this embodiment) of the projection hole 24 is adjusted to the central axis. C
It is arranged to be shifted with respect to 1.

According to this configuration, the projection nozzle (see the nozzle tip 6) is rotated around its central axis C1, and the fluid (see the compressed air) is moved to the projection hole 24 of the projection nozzle (see the nozzle tip 6). When a projectile (see shot) is supplied as an energy source, this projectile (see shot)
Is projected from the projection hole 24 toward the work (see the crankshaft 1), but since the projection hole 24 is so-called offset-positioned with respect to the center axis C1 of the projection nozzle (see the nozzle tip 6), the projected circle is It is formed. That is, by rotating the nozzle tip 6 around its central axis C1, it is possible to secure a processing area by a shot projected from the projection hole 24 arranged offset.

As a result, the above-described projection circle allows a wide range of projection particles (see shots) without any complicated device such as a nozzle moving device and with a simple configuration.
Can be projected. Further, the opening diameter of the projection hole 24 can be set small (for example, about 3 mm ^φ ), and the fluid pressure
(Refer to the pressure of the compressed air) can be reduced.

In addition, since the fluid is set to compressed air and the projection particles are set to shots, compressive residual stress is applied to the processing surface (see chamfered portion 3b) by shot peening to obtain the relevant portion. Can improve the fatigue strength.

The surface of the work (see the crankshaft 1) is hardened around the hole (see the oil hole 3a).
The projection particles (see the shot) are projected by making the center axis 3 of the projection nozzle 3 coincide with the central axis C1 of the projection nozzle (see the nozzle tip 6).

According to this configuration, since the center C3 of the hole of the workpiece (see the crankshaft 1) and the center axis C1 of the projection nozzle (see the nozzle tip 6) are aligned, the center of the projection nozzle (see the nozzle tip 6) is aligned. The projection particles (see shot) from the projection holes 24 that are displaced with respect to the central axis C1,
Hole of work (see crankshaft 1) (see oil hole 3a)
It is possible to reduce waste of projection particles (see shots) and processing energy without falling off.

Further, a pipe-shaped work made of cast iron
(See the crankshaft 1), a chamfered portion 3b is formed around the hole (see the oil hole 3a) of the work, and the projection particles (see the shot) are projected on the chamfered portion 3b.

According to this configuration, by projecting the projection particles (see shots) on the chamfered portion 3b, the chamfered portion 3b can be reliably processed. In addition, if the chamfered portion 3b is formed around the hole (see the oil hole 3a) of the pipe-shaped work (see the crankshaft 1), a thickness difference occurs in the chamfered portion 3b. Can be prevented by the projection of projection particles (see shots). That is, the shot projection 3b
Since a compressive residual stress is added to the portion, the fatigue strength of the portion can be improved, thereby preventing cracking.

On the other hand, the surface hardening apparatus for steel members of the above embodiment uses a fluid (see compressed air) as a kinetic energy source (so-called power) to project projection particles (see shots) onto a work (see crankshaft 1). A surface hardening device for a member, comprising: a projection nozzle (see nozzle tip 6) for projecting the projection particles (see shot) onto a work (see crankshaft 1); and a central axis C1 of the projection nozzle (see nozzle tip 6). And a rotation mechanism 1 for rotating the projection nozzle (see the nozzle tip 6) around the central axis C1.
9 is provided.

According to this configuration, the above-described rotation mechanism 19 rotates the projection nozzle (see the nozzle tip 6) around its central axis C1, and simultaneously rotates the projection nozzle (nozzle tip 6).
When a fluid (see compressed air) is supplied as a kinetic energy source to the projecting hole 24 (see the shot), the projecting particle is supplied from the projecting hole 24 to the workpiece (see the crankshaft 1).
However, since the projection hole 24 is so-called offset arranged with respect to the center axis C1 of the projection nozzle (see the nozzle tip 6), a projection circle is formed.

As a result, the projection circle described above allows a wide range of projection particles (see shots) with a simple structure without any complicated device such as a nozzle moving device.
To improve the surface hardness of the portion to be processed (see the chamfered portion 3b). In addition, the opening diameter of the projection hole 24 can be set small, and the fluid pressure (see air pressure) can be reduced.

FIG. 5 shows a nozzle tip 6 as a projection nozzle.
The projection hole 2 in which the center line C2 is offset by an angle θ1 with respect to the center axis C1 of the nozzle tip 6 is shown.
In 4, the projection hole 24 is formed in a tapered shape so that the inner end side of the projection hole 24 has a small diameter and the outer end side has a large diameter.

With this configuration, the projection circle (machining area) formed when the nozzle tip 6 is rotated around the central axis C1 can be enlarged, so that a shot can be projected over a wider range. it can.

In this embodiment shown in FIG. 5,
Other configurations, operations, and effects are substantially the same as those of the previous embodiment, and therefore, in FIG.

FIG. 6 shows a nozzle tip 6 as a projection nozzle.
Of the projection hole 24 in which the center line C2 is offset by an angle θ1 with respect to the center axis C1 of the nozzle tip 6, the inner end side of the projection hole 24 has a large diameter and the outer end side has a small diameter. Thus, the projection hole 24 is formed in a tapered shape.

With this configuration, it is possible to suppress a so-called divergence angle of the projection in which the shot is spread and projected with respect to the original projection circle, so that the useless shot can be further reduced.

In this embodiment shown in FIG.
Other configurations, operations, and effects are almost the same as those of the previous embodiment, and therefore, in FIG.

FIGS. 7 and 8 show still another embodiment of the nozzle tip 6, in which an introduction hole 25 is formed by a hole itself formed by an introduction hole forming drill as a processing tool, and the introduction hole 25 is formed. A tapered portion 25a utilizing the shape of a drill bit is provided at the tip of the hole. The tapered portion 25a reduces the consumption of the introduction hole 25 by the shot against the hole wall tip, and the compressed air and the shot are projected through the projection hole 26.
It is configured to smoothly transition to.

A projection hole 26 extending from the tip of the introduction hole 25 to the outside of the tip of the nozzle tip 6 is formed. The projection hole 26 is disposed so that both the opening direction and the opening position are shifted with respect to the central axis C1 of the nozzle tip 6.

In this embodiment shown in FIG. 7 and FIG.
4 is substantially parallel to the tapered portion 25a, and the angle θ2 formed by the center axis C1 of the nozzle tip 6 is set to a predetermined value.
(However, θ2> θ1) is set.

Even with such a configuration, as shown in FIG.
Under the condition that the center line C3 of the oil hole 3a of the pin journal 3 matches the center axis C1 of the nozzle tip 6, the nozzle tip 6 is rotated around the center axis C1 and the introduction hole 25
When the compressed air and the shot are supplied to the projection hole 26 from above, a projection circle (machining area) as a projection range is formed, so that the shot is projected over a wide range and the chamfered portion 3b is favorably surface hardened. be able to.

In addition to the processing of the chamfered portion 3b shown in FIG. 7, the nozzle tip 6 is inserted into the hole 28 of the work 27 as shown in FIG.
, It is possible to execute a surface hardening treatment on the hole wall of the hole 28, which was impossible with the conventional shot peening.

In this embodiment shown in FIGS. 7 and 8, the other constructions, operations and effects are almost the same as those of the previous embodiment, and therefore, in FIGS. And a detailed description thereof will be omitted.

FIG. 9 shows still another embodiment of the nozzle tip 6, in which a large diameter drill 21 is provided.
And a hole formed by the small-diameter drill 22 (see FIG. 3). A tapered portion 23a utilizing the drill shape of the large-diameter drill 21 is formed at the tip side of the introduction hole 23. The tapered portion 23a reduces wear of the introduction hole 23 at the tip of the hole wall due to shots, and also reduces compressed air and pressure. The configuration is such that the transition of the shot to the projection hole 24 is smooth.

Further, in this embodiment, the tapered portion 23
A hole 23b is formed at the tip of the hole a using the outer peripheral shape of the shaft of the small diameter drill 22 (see FIG. 3), and the projection hole 2 extending from the tip of the hole 23b toward the outside of the tip of the nozzle tip 6.
4 are formed.

The projection hole 24 is arranged so that only its opening direction is shifted with respect to the central axis C1 of the nozzle tip 6. That is, the center of the opening end of the projection hole 24 coincides with the central axis C1 of the nozzle tip 6, and the angle θ formed between the central axis C2 of the projection hole 24 and the central axis C1 of the nozzle tip 6
3 is set to a predetermined angle (however, θ1 <θ3 <θ2).

Even with such a configuration, as shown in FIG.
Under the condition that the center line C3 of the oil hole 3a of the pin journal 3 matches the center axis C1 of the nozzle tip 6, the nozzle tip 6 is rotated around the center axis C1 and the introduction hole 23
When the compressed air and the shot are supplied to the projection hole 24 from above, a projection circle (machining area) as a projection range is formed, and the shot circle is used to project a shot over a wide range to satisfactorily surface-harden the chamfered portion 3b. be able to.

In this embodiment shown in FIG.
Other configurations, operations, and effects are almost the same as those of the previous embodiment. Therefore, in FIG. 9, the same portions as those in the previous drawing are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the correspondence between the structure of the present invention and the above-described embodiment, the fluid of the present invention corresponds to the compressed air of the embodiment, and similarly, the projection nozzle is a nozzle fixed to the tip of the nozzle body 11. Corresponding to the chip 6, the projection grain corresponds to the shot (steel grain), the work corresponds to the crank shot 1 (particularly the pin journal 3) and the work 27, and the holes correspond to the oil holes 3a and the holes 28. The periphery of the hole corresponds to the chamfered portion 3b, the center of the hole corresponds to the center line C3, and the pipe-shaped work made of cast iron corresponds to the crankshaft 1. Is not limited only to the configuration of the above embodiment.

For example, when an aqueous solution containing a rust inhibitor or a surfactant and compressed air are used as the fluid and an abrasive such as aluminum oxide or silicon carbide is used as the projection particles, the work surface is hardened and the surface is polished. It can be applied to performing liquid honing.

[0070]

According to the present invention, by rotating the projection nozzle around its central axis and disposing the opening direction or opening position of the projection hole with respect to the central axis, a nozzle moving device or the like is provided. A fluid that can be used as a kinetic energy source because it can project projection particles over a wide range with a simple configuration without requiring any complicated device, and can set the opening diameter of the projection hole small. There is an effect that the pressure can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an overall configuration of a system including a surface hardening device according to the present invention.

FIG. 2 is an enlarged sectional view of the apparatus for hardening a steel member along the line AA in FIG. 1;

FIG. 3 is an enlarged sectional view of a nozzle tip.

FIG. 4 is an explanatory view showing a method of hardening the surface of a steel member according to the present invention.

FIG. 5 is a sectional view showing another embodiment of the nozzle tip.

FIG. 6 is a sectional view showing still another embodiment of the nozzle tip.

FIG. 7 is an explanatory view showing another embodiment of the method for hardening the surface of a steel member according to the present invention.

FIG. 8 is an explanatory view showing still another embodiment of the method for hardening the surface of a steel member according to the present invention.

FIG. 9 is an explanatory view showing still another embodiment of the method for hardening the surface of a steel member according to the present invention.

FIG. 10 is an explanatory view showing a conventional surface hardening method.

FIG. 11 is an explanatory view of an oil hole opening formed in a crankshaft.

[Description of Signs] 1 ... Crankshaft (work) 3a ... Oil hole (hole) 3b ... Chamfered portion (around the hole) 6 ... Nozzle tip (projection nozzle) 19 ... Rotating mechanism 24 ... Projection hole 26 ... Projection hole 27 ... Work 28 ... Hole C1 ... Center axis C3 ... Center line (Hole center)

Claims (5)

[Claims] 1. A method for hardening a surface of a steel member, wherein a projection particle is projected from a projection hole of a projection nozzle onto a workpiece using a fluid as a kinetic energy source, wherein the projection nozzle is rotated about its central axis and the projection hole is rotated. The surface hardening method for a steel member, wherein the opening direction or the opening position of the steel member is displaced from the central axis. 2. The method for hardening a surface of a steel member according to claim 1, wherein said fluid is set to compressed air and said projection particles are set to shot. 3. The steel member according to claim 1, wherein a surface hardening treatment is performed around the hole of the work, and the projection particles are projected with the center of the hole of the work and the center axis of the projection nozzle coincide. Surface hardening method. 4. A method according to claim 3, wherein a pipe-shaped work made of cast iron is provided, a chamfered portion is formed around a hole of the work, and projection particles are projected on the chamfered portion. 5. A surface hardening device for a steel member for projecting projected particles onto a workpiece using a fluid as a kinetic energy source, comprising: a projection nozzle for projecting the projected particles onto the workpiece; and a projection nozzle with respect to a central axis of the projection nozzle. A method for hardening a surface of a steel member, comprising: a projection hole arranged in a staggered opening direction or an opening position; and a rotation mechanism for rotating the projection nozzle around the central axis.