JP3201773B2 - Method for forming hard carbon film on inner peripheral surface of guide bush - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a processing of a guide bush provided on an automatic lathe, which holds a round bar-shaped workpiece so as to be rotatable and axially slidable near a cutting tool (blade). The present invention relates to a method for forming a hard carbon film on an inner peripheral surface that is in sliding contact with an object.

BACKGROUND ART Guide bushes that are provided on an automatic lathe column of an automatic lathe and that rotatably hold a round bar-shaped workpiece near a cutting tool include a rotary type and a fixed type. The rotary type keeps the work piece slidable in the axial direction while always rotating with the work piece, and the fixed type allows the work piece to rotate and slide in the axial direction without rotating. Hold.

Each type of guide bush has an outer peripheral tapered surface, a slit for giving elasticity to it, a screw part for attaching to a column, and an inner peripheral surface for holding a workpiece. Since the surface is always in sliding contact with the work piece, it is easily worn, and especially in the case of the fixed type, the wear is severe.

Therefore, for example, Japanese Patent Laid-Open No. 4-141303 discloses one in which a cemented carbide or ceramics is fixed to the inner peripheral surface of a guide bush that is in sliding contact with the workpiece by rotation or sliding of the workpiece by brazing or the like. Proposed as seen in the gazette.

Thus, by providing the cemented carbide or ceramics having excellent wear resistance and heat resistance on the inner peripheral surface of the guide bush, the effect of suppressing the wear to some extent is recognized.

However, even if cemented carbide or ceramics is provided on the inner peripheral surface in this way, the cutting amount is large and the machining speed is large on an automatic lathe, and for heavy cutting, the cemented carbide and ceramics also have a large friction coefficient and a high thermal conductivity. Is low, there is a problem that scratches occur on the work piece, and the size of the gap between the guide bush and the work piece in the diametrical direction decreases, causing seizure. I couldn't.

The fixed guide bush allows the workpiece to be held without deviation of its axial center, which enables highly accurate roundness, accurate machining, less noise, and the structure of the automatic lathe is not complicated. It has the advantage of being compact.

However, since the wear of the inner peripheral surface of the guide bush is much larger than that of the rotary type, there is a problem that it is difficult to further increase the cutting amount and the processing speed.

Therefore, the present invention solves such a problem,
The wear resistance of the inner peripheral surface of the guide bush that comes into contact with the workpiece can be dramatically improved, and the cutting amount and processing speed of the automatic lathe can be increased without causing scratches or seizure on the workpiece. It is intended that the guide bush can be manufactured efficiently.

DISCLOSURE OF THE INVENTION Therefore, the present invention provides a method of forming a hard carbon film for uniformly and firmly forming a hard carbon film on an inner peripheral surface of a guide bush that is in sliding contact with a workpiece.

This hard carbon film is a hydrogenated amorphous carbon film, and since it has properties very similar to diamond, it is also called a diamond like carbon (DLC) film.

This hard carbon (DLC) film has high hardness (Vickers hardness of 3000 Hv or more), excellent wear resistance, small friction coefficient (1/8 of cemented carbide), and excellent corrosion resistance.

Therefore, if this hard carbon film is provided on the inner peripheral surface of the guide bush that is in sliding contact with the work piece, the wear resistance is dramatically improved compared to the conventional ones where cemented carbide or ceramics are provided on the inner peripheral surface. To do.

Therefore, even if this is used as a fixed type guide bush of an automatic lathe to perform heavy cutting with a large cutting amount and a large processing speed, it does not cause scratches or seizure on the work piece. It becomes possible to perform highly accurate machining over a long period of time.

A hard carbon film may be provided on the inner peripheral surface of the guide bush via an intermediate layer that enhances the adhesion.

When the intermediate layer is formed of a two-layer film including a lower layer made of titanium or chromium or a compound thereof and an upper layer made of silicon or germanium or a compound thereof, the lower layer is formed on the inner peripheral surface (base) of the guide bush. Since the upper layer is strongly bonded to the hard carbon film, the hard carbon film having good adhesion can be provided.

Alternatively, a hard carbon film may be provided on the inner peripheral surface through a hard member such as a cemented carbide such as tungsten carbide (WC) or a sintered body of ceramics such as silicon carbide (SiC). However, if a hard carbon film is provided via an intermediate layer similar to the above, the adhesion can be further enhanced.

In addition, a carburized layer may be formed on the base material near the inner peripheral surface of the guide bush, and a hard carbon film may be provided on the inner peripheral surface of the carburized layer. Adhesion can be further enhanced by providing a carbon film.

The method of forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention is as follows.

A center that forms an inner peripheral surface of a guide bush for an automatic lathe, which has an exhaust port and a gas inlet port, and is arranged in a vacuum chamber in which an anode and a filament are provided, and which makes sliding contact with the workpiece of the guide bush. A rod or a linear auxiliary electrode is inserted into the opening. The auxiliary electrode may be placed in the vacuum chamber together with the guide bush in a state where it is inserted into the central opening of the guide bush first.

Then, after exhausting the inside of the vacuum chamber, a gas containing carbon is introduced from the gas introduction port, a direct current voltage is applied to the guide bush, a direct current voltage is applied to the anode, and an alternating voltage is applied to the filament. Generate plasma,
A hard carbon film is formed on the inner peripheral surface of the guide bush.

As a method of generating plasma in the vacuum chamber, the anode and the filament are not provided in the vacuum chamber and a high frequency voltage is applied to the guide bush, or a direct current voltage is applied to generate plasma. Good.

In this way, with the auxiliary electrode inserted in the central opening of the guide bush, the gas containing carbon is introduced into the vacuum chamber and the plasma is generated. It is possible to form a hard carbon film with a uniform film thickness from the inside to the inside.

While the hard carbon film is being formed, the auxiliary electrode may be insulated so as to have a floating potential, but it is preferable to keep it at a ground potential or a DC positive potential.

Further, a ring-shaped dummy member having an inner diameter substantially equal to the diameter of the inner peripheral surface of the guide bush is arranged on the slit end surface of the guide bush, and the hard carbon film is formed by forming a hard carbon film. The homogeneity of the hard carbon film in the vicinity of the open end of the peripheral surface can be enhanced.

In that case, it is desirable to arrange the auxiliary electrode so that its tip is located inside the opening end face of the dummy member.

In addition, a plurality of protrusions that can be inserted into the respective slits of the guide bush are provided on a ring-shaped main body having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush, on the slotted end face of the guide bush. Place a jig with a protrusion,
Insert each protrusion into each slit of the guide bush,
By forming the hard carbon film, the homogeneity of the hard carbon film in the vicinity of the opening end of the inner peripheral surface and in the vicinity of the slit can be enhanced.

Forming a hard carbon film by inserting a cylindrical insertion jig having an inner diameter substantially the same as the diameter of the inner peripheral surface into the stepped portion of the guide bush that is in sliding contact with the workpiece and has a larger diameter than the inner peripheral surface. Thereby, the homogeneity of the hard carbon film in the vicinity of the step portion of the inner peripheral surface can be enhanced.

By inserting both the jig with projection and the insertion jig into the guide bush to form the hard carbon film, a uniform hard carbon film can be formed over the entire area of the inner peripheral surface.

If the auxiliary electrode is supported by the insulator inserted in the step portion having a diameter larger than the inner peripheral surface of the guide bush, the auxiliary electrode can be supported on the central axis of the guide bush in the central opening. It is easy and it is possible to easily apply an arbitrary voltage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an example of a guide bush having a hard carbon film formed on the inner peripheral surface according to the present invention, and FIG. 2 is a perspective view showing its appearance.

FIG. 3 is a longitudinal sectional view showing another example of a guide bush having a hard carbon film formed on the inner peripheral surface according to the present invention.

4 to 7 are enlarged cross-sectional views corresponding to the portion surrounded by the circle A in FIG. 1 or FIG.

FIG. 8 is a diagram showing an example of the configuration of the intermediate layer by further enlarging a part of FIG.

FIG. 9 is a diagram showing a comparison of the cutting test results by an automatic lathe used in a fixed guide bush device for a guide bush having a hard carbon film formed on its inner peripheral surface according to the present invention and a conventional guide bush. ..

FIG. 10 is a schematic sectional view of a first apparatus for carrying out the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention.

FIG. 11 is a diagram showing the relationship between the distance from the open end of the guide bush and the film thickness of the hard carbon film with and without the auxiliary electrode 71.

FIG. 12 is a schematic sectional view of a second apparatus for carrying out the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention.

FIG. 13 is a schematic sectional view of a third apparatus for carrying out the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention.

FIG. 14 is a sectional view similar to FIG. 10 when a covering member is added to the embodiment of FIG.

FIG. 15 is a schematic sectional view similar to FIG. 10 showing another embodiment of the method for forming a hard carbon film according to the present invention.

FIG. 16 is a perspective view of a dummy member used in the embodiment shown in FIG.

17 and 18 are schematic sectional views similar to FIGS. 12 and 13 showing another embodiment of the method for forming a hard carbon film according to the present invention.

FIG. 19 is a schematic sectional view similar to FIG. 15 showing still another embodiment of the hard carbon film forming method according to the present invention.

20 and 21 are schematic sectional views similar to FIGS. 17 and 18 showing another embodiment of the method for forming a hard carbon film according to the present invention.

FIG. 22 is a diagram showing the relationship between the positive DC voltage applied to the auxiliary electrode and the film thickness of the hard carbon film formed.

FIG. 23 is a sectional view showing a specific example of the supporting structure of the auxiliary electrode.

FIG. 24 is a perspective view of a jig with protrusions used in the method for forming a hard carbon film according to the present invention.

FIG. 25 is a vertical cross-sectional view of an insertion jig, which is similar to the above.

FIG. 26 is a vertical cross-sectional view showing a state where the jig with protrusions is attached to the guide bush.

FIG. 27 is a vertical cross-sectional view of the guide bush with an insertion jig attached.

FIG. 28 is a vertical cross-sectional view showing a state where a jig having protrusions and an inserting jig are mounted on the guide bush.

FIG. 29 is a sectional view showing only the vicinity of the main shaft of an automatic lathe provided with a fixed guide bush device using a guide bush.

FIG. 30 is a sectional view showing only the vicinity of the main shaft of an automatic lathe provided with a rotary guide bush device using a guide bush.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[Explanation of automatic lathe using guide bush]

First, the structure of an automatic lathe using this guide bush will be briefly described.

FIG. 29 is a sectional view showing only the vicinity of the spindle of the numerically controlled automatic lathe. This automatic lathe is provided with a fixed guide bush device 37 which is used while fixing the guide bush 11 and rotatably holding the workpiece 51 (shown by phantom lines) on its inner peripheral surface 11b. Is.

The headstock 17 is slidable in the left-right direction on the bed (not shown) of the numerically controlled automatic lathe.

The headstock 17 is provided with a main shaft 19 rotatably supported by bearings 21. A collet chuck 13 is attached to the tip of the main shaft 19.

The collet chuck 13 is arranged in the center hole of the chuck sleeve 41. The outer peripheral tapered surface 13a at the tip of the collet chuck 13 and the inner peripheral tapered surface 41a of the chuck sleeve 41 are in surface contact with each other.

Further, at the rear end portion of the collet chuck 13 in the intermediate sleeve 29, a spring 25 is provided, which is a coiled strip-shaped spring material. And by the action of this spring 25,
The collet chuck 13 can be pushed out from the inside of the intermediate sleeve 29.

The tip position of the collet chuck 13 is in contact with a cap nut 27 that is screwed to the tip of the main shaft 19 to regulate the position. Therefore, the collet chuck 13 is prevented from jumping out of the intermediate sleeve 29 by the spring force of the spring 25.

A chuck opening/closing mechanism 31 is provided at the rear end of the intermediate sleeve 29 via the intermediate sleeve 29. Then, by opening and closing the chuck opening and closing claw 33, the collet chuck 13 is opened and closed, and the workpiece 51 is gripped and released.

That is, when the tips of the chuck opening/closing claws 33 of the chuck opening/closing mechanism 31 are moved so as to open each other, the chuck opening/closing claws are moved.
The portion of 33 that is in contact with the intermediate sleeve 29 moves to the left in FIG. 29 and pushes the intermediate sleeve 29 to the left. By moving the intermediate sleeve 29 to the left, the intermediate sleeve 29
The chuck sleeve 41, which is in contact with the left end of the, moves to the left.

The collet chuck 13 is prevented from jumping out of the main shaft 19 by a cap nut 27 screwed to the tip of the main shaft 19.

Therefore, by moving the chuck sleeve 41 to the left, the outer peripheral tapered surface 13a of the collet chuck 13 where the slit is formed and the inner peripheral tapered surface 41a of the chuck sleeve 41 are strongly pressed, They will move along tapered surfaces of each other.

As a result, the diameter of the inner peripheral surface of the collet chuck 13 is reduced, and the workpiece 51 can be gripped.

When the diameter of the inner peripheral surface of the collet chuck 13 is increased and the workpiece 51 is released, the tip ends of the chuck opening/closing claws 33 move so as to close each other, so that the chuck sleeve 41 is pushed to the left. except for.

Then, the restoring force of the spring 25 causes the intermediate sleeve 29.
And the chuck sleeve 41 move to the right in the figure.

Therefore, the outer peripheral tapered surface 13a of the collet chuck 13
Then, the pressing force applied to the inner peripheral tapered surface 41a of the chuck sleeve 41 is removed. As a result, the collet chuck 13 has its own elastic force to increase the diameter of the inner peripheral surface,
The work piece 51 can be released.

Further, a column 35 is provided in front of the headstock 17, and a guide bush device 37 is arranged therein in such a manner that its central axis line coincides with the central axis line of the spindle.

This guide bush device 37 fixes the guide bush 11, and the inner peripheral surface 11b of the guide bush 11 allows the workpiece 5 to be machined.
It is a fixed guide bush device 37 that holds 1 in a rotatable state.

The bush sleeve 23 is fitted into the center hole of the holder 39 fixed to the column 35, and the bush sleeve 23 has an inner peripheral tapered surface 23a at the tip thereof.

Then, a guide bush 11 having an outer peripheral tapered surface 11a and a slit 11c formed at the tip is fitted and arranged in the center hole of the bush sleeve 23.

At the rear end of the guide bush device 37, the guide bush 11
By rotating the adjusting nut 43 provided by being screwed to the threaded portion, the gap size between the inner diameter of the guide bush 11 and the outer shape of the workpiece 51 can be adjusted.

That is, when the adjusting nut 43 is rotated to the right, the guide bush 11 moves to the right in the figure with respect to the bush sleeve 23, and like the collet chuck 13, the inner peripheral tapered surface 23a of the bush sleeve 33 and the guide bush 11 are moved. The outer peripheral taper surface 11a of 11 is pressed against each other, and the guide bush 11
This is because the inner diameter of the tip end of is smaller.

A cutting tool (blade) 45 is provided further in front of the guide bush device 37.

Then, the work piece 51 is grasped by the collet chuck 13 of the main shaft 19 and is supported by the guide bush device 37, and further, the work piece 51 penetrating the guide bush device 37 and protruding to the processing region is cut by the cutting tool 45. Forward and backward and headstock 17
Predetermined cutting work is performed by the combined movement with the movement of the.

Next, a rotary guide bush device used in a state in which the guide bush that holds the workpiece is rotated will be described with reference to FIG. In this Fig. 30,
The parts corresponding to those in Fig. 29 are designated by the same reference numerals.

As the rotary guide bush device, there are a guide bush device in which the collet chuck 13 and the guide bush 11 rotate in synchronization with each other, and a guide bush device in which the collet chuck 13 and the guide bush 11 rotate without synchronization. Guide bush device 37 shown in this figure
The collet chuck 13 and the guide bush 11 rotate in synchronization with each other.

The rotary guide bush device 37 drives the guide bush device 37 by a rotation drive rod 47 protruding from the cap nut 27 of the main shaft 19. Instead of the rotary drive rod 47, a guide bush device is provided by a gear or a belt pulley.
Some also drive 37.

In this rotary guide bush device 37, a bush sleeve 23 is rotatably fitted through a bearing 21 in a center hole of a holder 39 fixed to a column 35.
Further, the guide bush 11 is arranged by being fitted into the central hole of the bush sleeve 23.

The bush sleeve 23 and the guide bush 11 have the same structure as that described with reference to FIG. Then, at the rear end of the guide bush device 37, the inner diameter of the guide bush 11 is reduced by rotating the adjusting nut 43 screwed to the threaded portion of the guide bush 11 to reduce the inner diameter of the guide bush 11 and the workpiece. It is possible to adjust the gap size with the outer shape of the object 51.

The configuration except that the guide bush device 37 is a rotary type,
Since the structure is the same as that of the automatic lathe described with reference to FIG. 29, the description thereof will be omitted.

[Explanation of guide bush with hard carbon film formed on inner surface]

Next, various examples of the structure of the guide bush in which the hard carbon film is formed on the inner peripheral surface according to the present invention will be described.

FIG. 1 is a vertical sectional view showing an example of the guide bush, and FIG. 2 is a perspective view showing its appearance.

The guide bush 11 shown in these figures shows a free state in which the tip portion is open. This guide bush 11
An outer peripheral tapered surface 11a is formed at one end in the longitudinal direction, and a threaded portion 11f is provided at the other end.

Further, at the center of the guide bush 11, there are provided through openings having different opening diameters. And the outer peripheral taper surface 11
An inner peripheral surface 11b that holds the workpiece 51 on the inner periphery on the side where a is provided
Is formed. Then, a step portion 11g having an inner diameter larger than the inner diameter of the inner peripheral surface 11b is formed in a region other than the inner peripheral surface 11b.

Further, the guide bush 11 has three slits 11c at 120° intervals from the outer peripheral tapered surface 11a to the spring portion 11d so as to divide the outer peripheral tapered surface 11a into three equal parts in the circumferential direction.

By pressing the outer peripheral taper surface 11a of the guide bush 11 against the inner peripheral taper surface of the bush sleeve described above, the spring portion 11d bends, and the inner peripheral surface 11b and the work piece 51 shown in phantom in FIG. It is possible to adjust the size of the gap between and.

Further, the guide bush 11 is provided with a fitting portion 11e between the spring portion 11d and the screw portion 11f. Then, by fitting the fitting portion 11e into the center hole of the bush sleeve 23 shown in FIGS. 29 and 30, the guide bush 11 is arranged on the center line of the spindle and parallel to the center line of the spindle. be able to.

As the material of the guide bush 11, carbon tool steel (SK steel) is used, and after forming the outer shape and the inner shape,
A quenching process and a tempering process are performed.

Further, preferably, the inner peripheral surface 11 of the guide bush 11 is
The cemented carbide material 12 may be fixed to b by brazing means as shown in FIG.

However, the guide bush 11 has a tapered outer peripheral surface 11a.
In the closed state, a gap of 5 μm to 10 μm is provided between the inner peripheral surface 11b and the workpiece 51 in the radial direction. As a result, the work piece 51 moves in and out and comes into sliding contact with the inner peripheral surface 11b, which causes a problem of wear.

Furthermore, when used in a fixed guide bush device, the workpiece held by the fixed guide bush 11 is
Since 51 is rotated and processed at high speed, it slides at a high speed between the inner peripheral surface 11b and the work piece 51, and due to the excessive pressing force of the work piece 51 against the inner peripheral surface 11b due to the cutting load. However, there is a problem of causing burn-in.

Therefore, the hard carbon (DLC) film 15 described above is provided on the inner peripheral surface 11b of the guide bush 11. The thickness of the hard carbon film 15 is 1 μm to 5 μm.

In the example of FIG. 1, a hard carbon film 15 is formed on the base material (carbon tool steel) of the guide bush 11 via an intermediate layer described later, and in the example of FIG. A hard carbon film 15 is formed via an intermediate layer described later.

This hard carbon film has properties very similar to diamond. That is, it is characterized by high mechanical strength, a small friction coefficient, lubricity, good electrical insulation, high thermal conductivity, and excellent corrosiveness.

Therefore, the guide bush 11 provided with the hard carbon film 15 on the inner peripheral surface 11b has dramatically improved wear resistance, and even in long-term use or heavy cutting, the inner periphery that comes into contact with the workpiece 51 is improved. The wear of the surface 11b can be suppressed. Further, it becomes possible to suppress the occurrence of scratches on the workpiece 51, and it is also possible to suppress the occurrence of seizure between the guide bush 11 and the workpiece 51.

Therefore, the guide bush 11 having the hard carbon film formed on the inner peripheral surface thereof according to the present invention can remarkably improve the reliability for long-term use, and can be sufficiently used for the fixed guide bush device.

Here, various structural examples of the portion of the inner peripheral surface 11b of the guide bush 11 where the hard carbon film 15 is provided are enlarged cross-sectional views corresponding to the portion surrounded by a circle A in FIG. 1 or FIG. This will be described with reference to FIGS. 4 to 7 and FIG. 8 showing a configuration example of the intermediate layer by enlarging a part of FIG.

FIG. 4 corresponds to an enlarged view of part A of FIG. 1, and is hard on the base material (carbon tool steel) of the inner peripheral surface 11b of the guide bush 11 via the intermediate layer 16 for enhancing the adhesion. Carbon film 1
It is provided with a film thickness of μm to 5 μm. Depending on the material of the base material of the guide bush 11, it is possible to directly form the hard carbon film on the surface of the guide bush 11 without the intermediate layer 16.

5 and 6 correspond to the enlarged view of the portion A in FIG. 3,
In each case, a hard member 12 having a thickness of 2 mm to 5 mm is fixed to the base material of the inner peripheral surface 11b of the guide bush 11 by brazing or the like, and a hard carbon film 15 is formed on the inner peripheral surface thereof. By doing so, the durability of the guide bush 11 is further improved.

In the example shown in FIG. 5, the hard carbon film 15 is formed on the inner peripheral surface of the hard member 12 via the intermediate layer 16 which further enhances the adhesiveness.

In these examples, as the hard member 12 provided in the lower layer of the hard carbon film 15, a cemented carbide such as tungsten carbide (WC) or a ceramic sintered body such as silicon carbide (SiC) can be used. .. When sintering ceramics, Cr, Ni, Co or the like is usually added as a binder, but when the addition is small, the hard carbon film 15 is directly formed on the hard member 12 without the intermediate layer 16 interposed. You can also

Here, an example of a method of forming silicon carbide (SiC) used as the hard member 12 will be described.

Silicon (Si) and carbon (C) are 1 in atomic percent
The silicon carbide powder of 1 to 1 is put into a ring-shaped mold and pressure-molded by applying a pressure of 0.5 to 3 tons. Then, firing treatment is performed in an atmosphere of an inert gas such as nitrogen or argon gas.

After that, the temperature near the melting point of silicon carbide is 1400℃
To 1700°C and pressurize at the same time as this heating to eliminate pinholes in the silicon carbide. This heat and pressure treatment promotes the densification of the silicon carbide, and the density and hardness of the hard member 12 are improved, and the Vickers hardness becomes 2000 to 3000.

After that, a metallized layer containing titanium (Ti) as a main component is formed on the ring-shaped hard member 12. Then, the hard member 12 is arranged on the inner peripheral surface 11b of the guide bush 11 and heat treatment is performed to melt the metallized layer and guide bush
Bond with 11 base materials.

Then, after polishing the inner periphery of the hard member 12, a process for forming a slit 11c on the guide bush 11 is performed.

FIG. 7 shows that the hard member 1 is attached to the inner peripheral surface 11b of the guide bush 11.
Instead of providing 2, the carburized layer 11h on the base material near the inner peripheral surface 11b
Is formed, and the hard carbon film 15 is provided on the inner peripheral surface 11b of the carburized layer 11h.

Carburizing is one of the surface hardening methods for steel materials, and is a known process for hardening the surface layer and maintaining the toughness in the deep part.

Here, for example, methane (CH ₄ ) and ethylene (C ₂ H ₄ )
Carburizing is performed under the following conditions in a mixed gas atmosphere of a carburizing gas containing carbon and a carrier gas of nitrogen (N ₂ ).

(Carburizing conditions) Temperature 1100°C Time 30 minutes Carburizing depth 0.5 mm When the carburized layer 11h is formed on the surface of the inner peripheral surface 11b of the guide bush 11 in this way, the hard carbon film 15 However, it is more preferable to form the intermediate layer 16 that further enhances the adhesiveness on the surface, and form the hard carbon film 15 through the intermediate layer 16.

The intermediate layer 16 may be silicon (Si) or germanium (Ge) of Group IVb of the periodic table, or a compound of silicon or germanium. Alternatively, a compound containing carbon such as silicon carbide (SiC) or titanium carbide (TiC) may be used.

In addition, as the intermediate layer 16, titanium (Ti), toughungsten (W), molybdenum (Mo), or tantalum (T) is used.
A compound of a) and silicon (Si) can also be applied.

Further, as shown in FIG. 8, the intermediate layer 16 is formed into a two-layer film including a lower layer 16a made of titanium (Ti) or chromium (Cr) and an upper layer 16b made of silicon (Si) or germanium (Ge). May be.

By doing so, titanium or chrome of the lower layer 16a of the intermediate layer 16 plays a role of maintaining the adhesiveness with the base material of the guide bush 11, and silicon or germanium of the upper layer 16b is covalently bonded to the hard carbon film 15, It plays a role of strongly bonding to the hard carbon film 15.

Furthermore, the intermediate layer 16 may be formed of a two-layer film including a lower layer of a titanium compound or a chromium compound and an upper layer of a silicon compound or a germanium compound. Alternatively, it may be formed of a two-layer film including a lower layer of titanium or chromium and an upper layer of a silicon compound or a germanium compound. Further, it may be a two-layer film including a lower layer of a titanium compound or a chromium compound and an upper layer of silicon or germanium.

Then, as a method of forming the intermediate layer 16, a sputtering method, an ion plating method, a chemical vapor deposition (CVD) method, or a thermal spraying method may be applied.

When silicon carbide (SiC) is used as the hard member 12, the formation of the intermediate layer 16 can be omitted. Because silicon carbide is a compound of group IVb silicon and carbon of the periodic table,
This is because high adhesion can be obtained by covalently bonding with the hard carbon film 15 formed on the surface.

FIG. 9 is a view showing comparison of cutting test results by an automatic lathe using a guide bush having a hard carbon film formed on the inner peripheral surface according to the present invention and a conventional guide bush.

Here, actual cutting was performed to compare a conventional guide bush with a guide bush having a hard carbon film formed on the inner peripheral surface. The comparatively tested guide bush is a fixed guide bush.

As the conventional guide bush, one having only a cemented carbide (carbide) provided on the inner peripheral surface and one having only a ceramic sintered body are used. A hard carbon film (DLC) having a thickness of 3 μm formed through an intermediate layer was used.

The cutting conditions were as follows.

Workpiece Stainless steel (SUS303), Diameter 16mm, Rotation speed 4000rpm Depth of cut Light cutting: d=0.8mm Practical cutting: d=3mm Severe cutting: d=5.0mm Limit cutting: d=6.5mm Feed rate 0.05mm/revolution Machining length 20 mm The results of this cutting test are shown in Fig. 9 by the symbol "O" indicating that the cutting was successful, and by the symbol "X" indicating that the cutting was impossible.

That is, when a conventional guide bush provided with a cemented carbide is used, even in light cutting, seizure occurs on the inner peripheral surface of the guide bush immediately after the start of cutting of the first work piece, which makes cutting impossible. I got it.

Also, when the conventional guide bush provided with ceramics was used, 100 pieces of workpieces could be cut normally in light cutting, but in practical cutting, immediately after the start of cutting of the first workpiece. Seizure occurred on the inner surface of the guide bush, making it impossible to cut.

On the other hand, according to the present invention, hard carbon (DLC)
With the guide bush provided with the film, from light cutting to limit cutting, 100 pieces of each work piece were subjected to continuous cutting processing test, that is, even if a cutting distance of 2000 m was processed, no seizure occurred, Furthermore, neither wear of the inner peripheral surface of the guide bush nor peeling of DLC occurred.

In this way, using a guide bush with a hard carbon film on the inner peripheral surface makes it possible to perform cutting under severe conditions, significantly improving the machining efficiency, as well as reliability over a long period of time. High-quality cutting can be performed.

[Description of method for forming hard carbon film on inner peripheral surface of guide bush]

Next, an embodiment of a method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention will be described.

First, the inner peripheral surface 11b of the guide bush 11 shown in FIG.
A method of forming the hard carbon (DCL) film 15 on the substrate will be described.

The guide bush 11 shown in FIG. 3 is made of carbon tool steel (S
K) Material is used for cutting, and outer peripheral taper surface 11a
The spring portion 11d, the fitting portion 11e, the screw portion 11f, the inner peripheral surface 11b formed by the central opening 11j, and the step portion 11g having an inner diameter larger than that are formed. Then, the cylindrical cemented carbide material 12 is joined and fixed to the inner peripheral surface 11b of the guide bush 11 by brazing.

Then, electrical discharge machining is performed and this guide bush 11
Sliding slits 11c are formed at 120° intervals on the outer peripheral taper surface 11a side.

Further, polishing processing is performed to polish the inner peripheral surface 11b, the outer peripheral tapered surface 11a, and the fitting portion 11e to obtain the guide bush 11 before the formation of the hard carbon film.

Next, the hard carbon film 15 is formed on the guide bush 11. The first device for forming the hard carbon film 15 is
It is constructed as shown in FIG.

61 is a vacuum chamber having a gas inlet 63 and an exhaust port 65,
An anode 79 and a filament 81 are arranged in the upper center of the center. The guide bush 11 described above is vertically arranged with the lower part fixed to the insulating support 80 in the lower center of the vacuum chamber 61.

A thin rod-shaped auxiliary electrode 71 connected to the ground potential via the vacuum chamber 61 is arranged in the central opening 11j of the guide bush 11 so as to be inserted therein. At this time, the auxiliary electrode 71 is positioned at the center (approximately on the axis) of the central opening 11j of the guide bush 11.

The auxiliary electrode 71 is made of a metal material such as stainless steel. It is desirable that the auxiliary electrode 71 is arranged inside by about 1 mm so that the tip of the auxiliary electrode 71 does not protrude from the open end surface (upper end surface in FIG. 10) of the guide bush 11.

Then, the inside of the vacuum chamber 61 is evacuated from the exhaust port 65 so that the degree of vacuum becomes 3×10 ⁻⁵ torr.

Further, benzene as a gas containing carbon is introduced into the vacuum chamber 61 from the gas inlet 63, and the pressure in the vacuum chamber 61 is controlled to be 5×10 ⁻³ torr.

Thereafter, a negative DC voltage from the DC power supply 73 is applied to the guide bush 11, a positive DC voltage is applied from the anode power supply 75 to the anode 79, and an AC voltage is applied from the filament power supply 77 to the filament 81. ..

At this time, the DC voltage applied from the DC power supply 73 to the guide bush 11 is minus 3 kV, and the DC voltage applied from the anode power supply 75 to the anode 79 is about plus 50V. As the AC voltage applied from the filament power source 77 to the filament 81, an AC voltage of about 10 V is applied so that a current of 30 A flows.

In this way, plasma is generated in the peripheral region of the guide bush 11 arranged in the vacuum chamber 61, and a hard carbon film is formed on the surface of the guide bush 11.

In the method for forming the hard carbon film shown in FIG. 10, by providing the auxiliary electrode 71 so as to be inserted into the central opening 11j of the guide bush 11, not only the outer peripheral portion of the guide bush 11 but also the inner peripheral portion thereof. Can form a plasma.

Further, this prevents the occurrence of hollow discharge, which is an abnormal discharge, and improves the adhesion of the hard carbon film 15.

Furthermore, since the potential characteristic becomes uniform in the longitudinal direction of the inner peripheral surface of the guide bush 11, the film thickness distribution of the hard carbon film formed on the inner peripheral surface 11b becomes uniform. Moreover, since the film forming rate is increased, a hard carbon film having a uniform film thickness can be formed in a short time from the opening end face side to the opening back side.

When this is compared with a case where a hard carbon film is formed on this guide bush 11 without disposing the auxiliary electrode 71, it becomes as shown in FIG.

When the inner diameter of the inner peripheral surface 11b of the guide bush 11 is 12 mm,
When the auxiliary electrode 71 is not arranged, the film thickness becomes thin as shown by the broken line b plotted by the triangle marks in FIG. 11, and further becomes thinner from the opening end to the back. On the other hand, when the auxiliary electrode 71 is arranged, the film thickness is formed thick as shown by the broken line a plotted with square marks in the figure, and the film thickness is substantially uniform regardless of the distance from the opening end. Become.

The diameter of the auxiliary electrode 71 may be smaller than the opening diameter of the guide bush 11, but it is preferable to provide a gap of about 5 mm with respect to the inner peripheral surface 11b forming the hard carbon film, that is, a plasma formation region. Is desirable. The ratio of the diameter of the auxiliary electrode 71 to the opening diameter of the guide bush 11 is preferably 1/10 or less, and when the auxiliary electrode 71 is thin, it may be linear.

Although it has been described that the auxiliary electrode 71 is made of stainless steel, it may be made of a metal material having a high melting point such as tungsten (W) or tantalum (Ta). The cross-sectional shape of the auxiliary electrode 71 is circular.

Next, a method of forming a hard carbon film on the inner peripheral surface of the guide bush according to an embodiment different from the above-mentioned method
It will be described with reference to the drawings.

In FIG. 12, parts corresponding to those in FIG. 10 are designated by the same reference numerals, and description thereof will be omitted.

The vacuum chamber 61 of the second device used in this embodiment does not have an anode and a filament inside.

In the method of forming a hard carbon film using this apparatus, the difference from the method of forming a hard carbon film using the apparatus shown in FIG. 10 is that a guide is provided by inserting an auxiliary electrode grounded in the vacuum chamber 61. A high frequency power supply having an oscillation frequency of 13.56 MHz to the bush 11 via a matching circuit 67.
High frequency voltage is applied from 69, and methane (CH ₄ ) gas as a gas containing carbon is introduced into the vacuum chamber 61 to adjust the degree of vacuum to 0.1 Torr. Only.

Even in this case, plasma is generated not only on the outer peripheral surface side of the guide bush 11 but also on the inner peripheral surface side of the guide bush 11.
A hard carbon film is formed on the entire surface of 11. In particular, the hard carbon film 15 having a substantially uniform thickness over the entire length can be formed in a short time on the inner peripheral surface 11b shown in FIG. 3 facing the auxiliary electrode 71.

Next, a method of forming a hard carbon film on the inner peripheral surface of the guide bush according to an embodiment different from the above method will be described with reference to FIG. Also in FIG.
The parts corresponding to those in the figure are designated by the same reference numerals, and the description thereof will be omitted.

Also in the third device used in this embodiment, neither the anode nor the filament is provided in the vacuum chamber 61.

In the method of forming a hard carbon film using this apparatus, the difference from the method of forming a hard carbon film using the apparatus shown in FIG. 10 is that a guide is provided by inserting an auxiliary electrode grounded in the vacuum chamber 61. Bush 11, DC power supply 73'
From the point where only a DC voltage of -600V is applied, and as gas containing carbon, methane (CH ₄ ) gas is introduced into the vacuum chamber 61 to adjust the degree of vacuum to 0.1 Torr. It is the only point I made.

Even in this case, plasma is generated not only on the outer peripheral surface side of the guide bush 11 but also on the inner peripheral surface side of the guide bush 11.
A hard carbon film is formed on the entire surface of 11. In particular, the hard carbon film 15 having a substantially uniform thickness over the entire length can be formed in a short time on the inner peripheral surface 11b shown in FIG. 3 facing the auxiliary electrode 71.

Although the hard carbon film is formed on both the outer peripheral surface and the inner peripheral surface of the guide bush 11 in the above description, the hard carbon film may be formed only on the inner peripheral surface.

In that case, as shown in FIG. 14, the guide bush 11
The covering member 82 may be arranged on the outer peripheral portion of the guide bush. For simplicity, an aluminum foil is used as the covering member 82 for the guide bush.
It may be wound around the outer peripheral portion of 11.

FIG. 14 shows an example in which the first device shown in FIG. 10 is used, and an example in which the covering member 82 is arranged on the outer peripheral portion of the guide bush 11 is shown in FIG. 12 or 13. Even when the second or third device is used, a covering member 82 such as an aluminum foil is similarly arranged on the outer peripheral surface of the guide bush to firmly form a uniform hard carbon film only on the inner peripheral surface. be able to.

In addition, these hard carbon film forming methods are described with reference to FIG. 4 to FIG.
The same can be applied to the formation of the hard carbon film 15 with various layer configurations on 11b.

Furthermore, in the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to each of the above-described embodiments, it was explained that methane gas or benzene gas was used as the gas containing carbon, but a gas containing carbon such as ethylene in addition to methane. Alternatively, vaporized liquid vapors containing carbon such as hexane can also be used.

In the method of forming a hard carbon film on the guide bush according to these embodiments, the hard carbon film is formed by disposing the auxiliary electrode at the ground potential on the inner peripheral surface 11b where the hard carbon film should be formed in the opening of the guide bush. Therefore, an auxiliary electrode having a ground potential is provided between the inner peripheral surfaces where the electrodes having the same potential are opposed to each other, and the potentials are not opposed to each other, and a hollow discharge that is an abnormal discharge does not occur. .. Therefore, a hard carbon film having good adhesion can be formed on the inner peripheral surface 11b of the guide bush 11.

Next, another embodiment of the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention will be described with reference to FIGS. 15 to 18.

FIGS. 15, 17, and 18 respectively show the above-mentioned 10
An example of forming a hard carbon film on the guide bush 11 using the same device as the first, second, and third devices shown in FIGS. 12, 12, and 13 is shown. Therefore, the same parts as those in these drawings are denoted by the same reference numerals, and the description thereof will be omitted.

Here, the difference from the above-mentioned method is that the guide bush 11
The inner diameter of the inner peripheral surface 11b of the (see Fig. 1)
The only difference is that a ring-shaped dummy member 53 as shown in FIG. 6 is used. The dummy member 53 is also made of stainless steel like the auxiliary electrode 71.

The outer dimensions of the dummy member 53 are substantially the same as the size of the opening end surface of the guide bush 11.

Then, as shown in FIG. 15, the gas inlet 63 and the exhaust port
A guide bush 11 forming a hard carbon film is placed in a vacuum chamber 61 having a valve 65. Guide bush at this time
A dummy member 53 is placed on the opening end surface (upper end in the figure) on the outer peripheral taper surface side of 11.

At this time, the inner peripheral surface of the guide bush 11 and the inner peripheral surface of the dummy member are aligned.

On the inner peripheral surface 11b of the guide bush 11, a hard material is fixed in advance or an intermediate layer is formed as described above.

Then, similarly to the case described above, the auxiliary electrode 71 of the ground potential is provided so as to be inserted into the center of the central opening 11j of the guide bush 11. At this time, it is preferable that the tip of the auxiliary electrode 71 does not protrude from the upper end surface of the dummy member 53 but is positioned slightly inside.

Others are the same as the method described with reference to FIG. 10, but to be sure, the inside of the vacuum layer 61 is evacuated from the exhaust port 65 so that the degree of vacuum is 3×10 ⁻⁵ torr.

Then, benzene (C ₆ H ₆ ) as a gas containing carbon is introduced into the vacuum chamber 61 through the gas inlet 63, and the pressure in the vacuum chamber 61 is controlled to be 5×10 ⁻³ torr.

And, from the DC power supply 73 to the guide bush 11, minus
A DC voltage of 3kV is applied and the anode power supply 7 is connected to the anode 79.
A direct current voltage of 5 to plus 50 V is applied, and an alternating current voltage of 10 V is applied to the filament 81 so that a current of 30 A from the filament power source 77 flows.

As a result, plasma is generated in the area around the guide bush 11 in the vacuum chamber 61, and the first bush of the guide bush 11 is generated.
A hard carbon film is formed on the surface including the inner peripheral surface 11b shown in the figure.

The action of the auxiliary electrode at that time is similar to that in the case described above, but the dummy member 53 performs the following action.

That is, in such a method of forming a hard carbon film on the guide bush 11, plasma is generated on the inner surface and the outer peripheral portion of the guide bush 11. Then, electric charges tend to concentrate on the end surface of the guide bush 11, and the so-called edge effect, in which the electric potential is higher in the opening end surface region than in the inner surface, is generated. Here, the plasma intensity in the vicinity of the end face of the guide bush 11 is higher than that in other regions, and is also unstable.

Further, the end region of the guide bush 11 is affected by both the plasma on the inner surface and the plasma on the outer peripheral portion.

When the hard carbon film is formed in such a state, the adhesion of the hard carbon film is slightly different and the film quality is slightly different between the region several mm deeper than the opening end face of the guide bush 11 and the other region.

Therefore, as shown in FIG. 15, if a hard carbon film is formed by arranging a dummy member 53 on the opening end surface of the guide bush 11, the area where the film quality and the adhesion are different is the guide bush.
It is not formed on the inner surface of 11, but is formed on the inner surface of the opening of the dummy member 53.

According to the experiment, the guide bush is manufactured by the method shown in Fig. 10.
When a hard carbon film is formed on 11, the width of the guide bush 11 is about 4 mm deep from the open end surface and the width is 1 mm to 2 m.
Regions with slightly different film quality and adhesion of m were formed.

However, as shown in FIG. 15, the opening size of the guide bush 11 is almost the same as the opening size of the guide bush 11, and the length dimension is 10 mm.
As a result of forming the film under the above-mentioned conditions for forming the hard carbon film, regions having different film qualities and adhesiveness are formed on the dummy member 53, and regions having different film qualities and adhesiveness are not formed at all on the inner surface of the guide bush 11. It was

The hard carbon film forming method shown in FIG. 17 is similar to the hard carbon film forming method shown in FIG.
11, by applying a high frequency voltage from a high frequency power source 69 having an oscillation frequency of 13.56 MHz via a matching circuit 67, plasma is generated in the vacuum chamber 61, and methane (CH ₄ ) as a gas containing carbon is generated. The only difference from the above method is that the gas is introduced into the vacuum chamber 61 to adjust the degree of vacuum to 0.1 Torr.

Further, the hard carbon film forming method shown in FIG. 18 is also the method described above in that the guide bush 11 generates a plasma in the vacuum chamber 61 by applying a DC voltage of −600 V from the DC power source 73′. Only different.

Also in these cases, by using the auxiliary electrode 17 and the dummy member, it is possible to efficiently form the hard carbon film having the uniform film thickness and the uniform adhesion on the inner peripheral surface 11b of the guide bush 11.

Furthermore, as in the example shown in Fig. 14, the guide bush
By disposing the covering member 82 on the outer periphery of 11, it is possible to form the hard carbon film only on the inner peripheral surface.

In addition, in these methods of forming a hard carbon film, the tip portion of the auxiliary electrode 71 from the opening end surface of the dummy member 53
It is placed so that it is about 1 mm inside. Therefore, it is possible to suppress abnormal discharge of the tip portion of the auxiliary electrode 71 that occurs when the tip portion of the auxiliary electrode 71 is exposed from the opening end surface of the dummy member 53, and guide the hard carbon film 15 with good film quality. It can be formed on the inner peripheral surface of the bush 11.

Next, another embodiment of the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention will be described with reference to the 19th embodiment.
This will be described with reference to FIGS.

19 to 21 are views showing this embodiment,
It is a figure corresponding to each of the above-mentioned Drawing 15, Drawing 17, and Drawing 18, the same numerals are given to the same portion as each of those figures, and the explanation is omitted.

Here, the difference from the above-mentioned method is that the auxiliary electrode 71 is insulated and supported both by the guide bush 11 and the vacuum layer 61 by the insulator 85 fitted in the central opening 11j of the guide bush 11. The point is that a DC positive voltage (for example, plus 20 V) is applied to the auxiliary electrode 71 from the auxiliary electrode power source 83.

The relationship between the positive DC voltage applied to the auxiliary electrode 71 and the hard carbon film thickness formed on the inner surface of the opening of the guide bush 11 is shown in the diagram of FIG.

In this figure, the DC positive voltage applied to the auxiliary electrode 71 is changed from zero V to 30 V, and the guide bush 1
The gap between the inner surface of opening 1 and the auxiliary electrode 71 is 3 mm and 5 mm.
The film thickness of the hard carbon film at the time of is shown. Curve a shows the characteristics when the gap is 3 mm, and curve b shows the characteristic when the gap is 5 mm.
The characteristics at the time of are shown respectively.

As shown by the curves a and b, when the DC positive voltage applied to the auxiliary electrode 71 is increased, the film formation rate of the hard carbon film is improved. Further, the larger the gap size between the inner surface of the opening of the guide bush 11 and the auxiliary electrode 71, the higher the film formation rate of the hard carbon film.

When the gap between the inner surface of the opening of the guide bush 11 and the auxiliary electrode 71 is 3 mm (curve a), the auxiliary electrode 71
At a ground voltage of zero V applied to, no plasma is generated on the inner surface of the central opening 11j of the guide bush 11 and a hard carbon film cannot be formed.

However, even in this case, if the DC positive voltage applied to the auxiliary electrode 71 is increased, the center opening 11j of the guide bush 11 is increased.
Plasma is generated around the auxiliary electrode 71 inside and a hard carbon film can be formed.

Therefore, according to this embodiment in which a positive DC voltage is applied to the auxiliary electrode 71 and used on the inner peripheral surface of the guide bush having a small diameter of the central opening 11j, it is possible to form a hard carbon film.

Such an effect is the same when the hard carbon film is formed on the guide bush 11 by any of the methods shown in FIGS. 19 to 21.

Further, as described with reference to FIGS. 10 to 13, even when the hard carbon film is formed without using the dummy member 53, by applying a high DC voltage to the auxiliary electrode 71,
The above-mentioned effect is obtained.

FIG. 23 shows a specific structural example for insulating and supporting the auxiliary electrode 71 in the guide bush 11 when carrying out these methods.

In FIG. 23, insulator 85 made of ceramics is inserted into step portion 11g of guide bush 11. A first hole 85a and a second hole 85b having different inner diameters are formed in the center of the insulator 85.

Then, the auxiliary electrode 71 is inserted into the first hole 85a of the insulator 85, and the large-diameter connection electrode 87 coupled to the auxiliary electrode 71 is inserted and held in the second hole 85b.

The external dimensions of the auxiliary electrode 71 and the first hole 85 of the insulator 85
A gap of 0.01 mm to 0.03 mm should be provided between a and.

Further, a gap of 0.01 mm to 0.03 mm is also provided between the step portion 11g of the guide bush 11 and the outer diameter dimension of the insulator 85, and the insulator 85 is configured to be inserted into the step portion 11g with a certain gap dimension.

Further, a cylindrical insertion jig 57 is arranged near the inner peripheral surface 11b of the guide bush 11. The insertion jig 57 has an inner diameter substantially the same as the diameter of the inner peripheral surface 11b of the guide bush 11.

When the insertion jig 57 is mounted between the insulator 85 and the inner peripheral surface 11b of the guide bush 11, and the dummy member 53 is mounted on the opening end surface of the guide bush 11, the hard carbon film 15 of the guide bush 11 is formed. There is no step near the inner peripheral surface 11b. That is, the gap size between the auxiliary electrode 71 and the vicinity of the inner peripheral surface 11b forming the hard carbon film 15 becomes uniform.

In this way, the guide bush 11 has a
When the auxiliary electrode 71 is placed via the guide bush 11
The auxiliary electrode 71 can be accurately arranged at the center of the central opening 11j.

When the auxiliary electrode 71 is arranged so as to be displaced from the center of the opening of the guide bush 11, the plasma generated between the auxiliary electrode 71 and the inner wall of the opening loses its balance, resulting in a hard carbon film.
15 The film thickness and film quality vary.

Therefore, insert the insulator 85 so that it fits the inner diameter of the stepped portion 11g of the guide bush 11 in this way, and
If the position of the auxiliary electrode 71 is controlled by the first hole 85a of 85, the auxiliary electrode 71 can be accurately arranged at the center of the opening of the guide bush 11, and the variation in the film thickness and film quality of the hard carbon film 15 does not occur.

If a DC positive voltage is applied to the auxiliary electrode 71 via the connection electrode 87 for use, the method for forming a hard carbon film described with reference to FIGS. 19 to 21 can be carried out. In that case, since the auxiliary electrode 71 collects electrons, the guide bush 11
The plasma density in the central opening 11j becomes high and the formation rate of the hard carbon film becomes high.

Further, if this auxiliary electrode 71 is used by being connected to the ground potential via the connection electrode 87, the method of forming a hard carbon film described with reference to FIGS. 10 to 18 described above can be carried out.

Alternatively, a negative voltage smaller than that applied to the guide bush 11 (about 1/10) may be applied to this auxiliary electrode. Thereby, the movement of the electrons in the guide bush 11 can be made more intense, so that the plasma density is increased and the formation speed of the hard carbon film is increased.

Furthermore, the auxiliary electrode 71 can be left at a floating potential while still in an insulating state. Then, a negative potential is generated in the auxiliary electrode due to the interaction with the plasma. Therefore, the same effect as in the case where the small negative voltage is applied can be obtained.

In the description of the method for forming the hard carbon film according to FIGS. 10 to 23, the embodiment in which the dummy member 53 is arranged on the opening end surface of the guide bush 11 to form the hard carbon film has been described. Instead, a jig 55 with a projection as shown in FIG. 24 may be used.

As shown in FIG. 24, the jig 55 with protrusions is formed by dividing the inner peripheral surface 11b of the guide bush 11 into a ring-shaped main body 55a having an opening 55b having an inner diameter substantially the same as the diameter of each guide bush 11c. Three protrusions 55c that can be inserted into the slot are provided at 120° intervals corresponding to each slit 11c. The thickness dimension d of each projection 55c is substantially the same as the slit width dimension of the slit 11c.

Therefore, the jig 55 with protrusions is one in which the three protrusions 55c are provided on the dummy member 53 used in the above-described hard carbon film forming method.

This jig 55 with protrusions is
The 55c is inserted into the slit 11c of the guide bush 11 and is arranged on the end surface portion of the guide bush 11.

In this state, the guide bush 11
The hard carbon film 15 can be formed on the inner peripheral surface 11b of the.

Forming a hard carbon film on the guide bush 11 by using the jig 55 with protrusions has the following effects.

As described above, due to the electric charge concentration generated on the open end surface of the guide bush 11, the edge effect in which the end surface region of the guide bush 11 is higher in electric charge than the inner surface of the guide bush 11 occurs. However, the jig 55 with protrusions is attached to the guide bush 11
This edge effect can be suppressed by mounting the hard carbon film on the substrate.

That is, a jig with a protrusion is provided on the opening end surface of the guide bush 11.
When 55 is arranged to form the hard carbon film, it is possible to prevent the occurrence of regions having different film qualities and adhesiveness of the hard carbon film due to the edge effect.

Further, the protrusion 55c of the jig 55 with a protrusion
Since it is inserted in each slit 11c, it is possible to suppress the edge effect caused by the electric field concentration generated at the edge portion of each slit 11c.

Therefore, the film quality and the adhesiveness of the hard carbon film 15 formed on the inner peripheral surface 11b of the guide bush 11 are made more uniform.

On the other hand, FIG. 25 shows the stepped portion of the guide bush 11.
FIG. 11 is a vertical cross-sectional view of an insertion jig 57 used by being attached to 11g.

The inner jig 11 is provided on the inner peripheral surface 11b of the guide bush 11.
A cylindrical insertion portion 57a having an inner diameter substantially the same as the diameter of the guide bush 11 and a screw portion 57b screwed with the screw portion 11f of the guide bush 11 are provided. The outer diameter of the inner insertion portion 57a is set to fit the stepped portion 11g of the guide bush 11.

As shown in FIG. 27, insert the insertion jig 57 into the insertion portion 57
Insert a into the step 11g of the guide bush 11 and
When b is screwed into the threaded portion 11f of the guide bush 11 to be mounted, there is no step on the inner surface of the central opening 11j of the guide bush 11. That is, all the inner surfaces of the guide bush 11 have the same opening size.

By mounting the insertion jig 57, the step due to the step portion 11g is eliminated on the inner surface of the guide bush 11. That is, the gap size between the auxiliary electrode 71 and the inner circumference of the guide bush 11 becomes uniform in the longitudinal direction of the guide bush 11.

In this state, the guide bush 11
The hard carbon film 15 can be formed on the inner peripheral surface 11b of the.

When a hard carbon film is formed on the guide bush 11 using this insertion jig 57, the potential characteristics become uniform on the inner surface of the central opening 11j in the longitudinal direction of the guide bush 11, and the adhesion and film quality of the hard carbon film are improved. The film thickness becomes uniform.

Further, as shown in FIG. 28, both the jig 55 with a protrusion shown in FIG. 24 and the insertion jig 57 shown in FIG. 25 are attached to the guide bush 11 to form a hard carbon film 15. You may. In that case, a synergistic effect of the projection jig 55 and the insertion jig 57 makes it possible to form a hard carbon film having better adhesion, film quality and film thickness on the guide bush 11.

The projection jig 55 and the insertion jig 57 are made of a metal material such as stainless steel.

The dummy member 53 and the insertion jig 57 described above may be combined and mounted on the guide bushes 11 to form a hard carbon film.

Each embodiment of these hard carbon film forming methods has been described as an example in which the hard member 12 is provided on the inner peripheral surface 11b of the guide bush 11 and the hard carbon film 15 is formed on the surface thereof.

However, these hard carbon film forming methods, without forming the hard member 12 on the inner peripheral surface 11b of the guide bush 11, when forming the hard carbon film 15 directly or through the various intermediate layers 16 described above, or The same can be applied to the case where the hard carbon film 15 is further formed on the hard member 12 via the intermediate layer 16.

Further, in each of the embodiments of the method for forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention described above, methane (CH ₄ ) or benzene (C ₆ H
_{Although the} example using ₆ ) has been described, ethylene (C ₂ H ₄ ) or hexane (C ₆ H ₁₄ ) can also be used.

Furthermore, the gas containing these carbons is changed to argon (Ar).
It can also be used after diluting it with an inert gas having a low ionization voltage. In that case, the plasma in the cylinder of the guide bush is further stabilized.

Alternatively, a small amount (1%
The lubricity and hardness can be improved by adding the additives of the following).

For example, adding fluorine (F) or boron (B) increases lubricity, and adding chromium (Cr), molybdenum (Mo) or tungsten (W) increases hardness.

After placing the guide bush in the vacuum chamber and before forming the hard carbon film, plasma such as argon (Ar) or nitrogen (N ₂ ) is generated to bombard the inner surface of the cylinder of the guide bush, and then the methane is removed. A hard carbon film may be formed by generating plasma with a gas containing carbon such as benzene and benzene.

As described above, by performing the pretreatment of the bombard with the inert gas, the temperature of the inner wall of the cylinder of the guide bush rises and becomes active. At the same time, impurities on the surface of the inner wall of the cylinder are knocked out to clean the surface. Due to these effects, the adhesion of the hard carbon film formed on the inner peripheral surface of the guide bush is further improved.

INDUSTRIAL APPLICABILITY As described above, by using the guide bush having the hard carbon film formed on the inner circumferential surface by the method of the present invention, by using the guide bush device of the rotary type or the fixed type of the automatic lathe, It is possible to normally perform a cutting process with a large depth of cut on a workpiece without causing scratches or seizure, and significantly improve the processing efficiency.

Moreover, due to the significant improvement in durability, the time during which continuous processing is possible becomes longer, and the operation efficiency of the automatic lathe is dramatically improved. Further, by using the fixed type guide bush device, it is possible to efficiently perform cutting with high processing accuracy (particularly roundness).

Then, according to the method of forming a hard carbon film on the inner peripheral surface of the guide bush according to the present invention, a hard carbon film (DLC) having a property very similar to a diamond is formed on the inner peripheral surface of the guide bush which is in sliding contact with the workpiece. Further, it is possible to form a film having a uniform film thickness and good adhesion in a short time.

Therefore, as described above, a highly durable guide bush useful for the guide bush device of the automatic lathe can be manufactured with high productivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 7-284710 (32) Priority date November 1, 1995 (November 1, 1995) (33) Priority claim country Japan (JP) (72) Inventor Takashi Toida, 840 Takeno, Oita, Tokorozawa, Saitama Prefecture, Citizen Watch Co., Ltd.(72) Inventor, Sosaku Kimura, 840, Taketomi, Tokorozawa, Saitama Citizen Watch Co., Ltd. In the laboratory (72) Kunihiko Kokubo Kunihiko Kokubo 840, Takeno, Tokorozawa, Saitama Prefecture Citizen Watch Co., Ltd. Technical Research Laboratory (56) Reference JP-A-4-141303 (JP, A) JP-A-62-116767 ( JP, A) JP 62-132800 (JP, A) JP 6-10135 (JP, A) JP 6-193637 (JP, A) JP 5-140744 (JP, A) Japan Machinery Proceedings of the Conference (C), Volume 60, Issue 578 (October 1994) p. 267-271 (58) Fields investigated (Int.Cl. ⁷ , DB name) B23B 13/12 C23C 16/26 C23C 16/50 C30B 29/00 C01B 31/00 F16C 31/00 JISST file (JOIS)

Claims (24)

(57) [Claims] 1. An inner circumference of a guide bush for an automatic lathe, which is arranged in a vacuum chamber having an exhaust port and a gas introduction port, and in which an anode and a filament are provided, and in which the guide bush slidably contacts a workpiece. A rod or a linear auxiliary electrode is inserted into the central opening forming the surface, the inside of the vacuum chamber is evacuated, a gas containing carbon is introduced from the gas inlet, and a DC voltage is applied to the guide bush. At the same time, a direct current voltage is applied to the anode, an alternating voltage is applied to the filament to generate plasma, and a hard carbon film is formed on the inner peripheral surface of the guide bush. Of forming a hard carbon film on a substrate. 2. The hard carbon film is formed on the inner peripheral surface of the guide bush according to claim 1, wherein the auxiliary electrode is kept at a ground potential or a DC positive potential during the formation of the hard carbon film. Method. 3. A hard carbon film is formed by arranging a ring-shaped dummy member having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush on the opening end surface of the guide bush where the slit is formed. The method for forming a hard carbon film on the inner peripheral surface of the guide bush according to claim 1, wherein 4. The hard member to the inner peripheral surface of the guide bush according to claim 3, wherein the auxiliary electrode is arranged so that its tip is located inside the opening end surface of the dummy member. Carbon film forming method. 5. The guide bush can be inserted into each slit of the guide bush in a ring-shaped body having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush. 2. A jig with a protrusion having a plurality of protrusions is arranged, and each protrusion is inserted into each slit of the guide bush to form the hard carbon film. Of forming a hard carbon film on the inner peripheral surface of the guide bush of. 6. The hard carbon film is formed by inserting a cylindrical insertion jig having an inner diameter substantially the same as the diameter of the inner peripheral surface into a step portion having a diameter larger than the inner peripheral surface of the guide bush. The method for forming a hard carbon film on the inner peripheral surface of the guide bush according to claim 1, wherein the hard carbon film is formed. 7. A slit-shaped main body of the guide bush having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush can be inserted into each slit of the guide bush. A jig with a plurality of protrusions is arranged, each protrusion is inserted into each slit of the guide bush, and the inner peripheral surface of the guide bush is larger than the inner peripheral surface. The hard inner film of the guide bush according to claim 1, characterized in that the hard carbon film is formed by inserting a cylindrical insertion jig having an inner diameter substantially the same as the surface diameter. Carbon film forming method. 8. The hard carbon film is formed by supporting the auxiliary electrode by an insulator inserted in a step portion having a diameter larger than the inner peripheral surface of the guide bush. A method for forming a hard carbon film on the inner peripheral surface of the guide bush described in the item. 9. A guide bush for an automatic lathe is arranged in a vacuum chamber having an exhaust port and a gas introduction port, and a rod or a rod is provided in a central opening forming an inner peripheral surface of the guide bush which comes into sliding contact with a workpiece. After inserting a linear auxiliary electrode and evacuating the inside of the vacuum chamber, a gas containing carbon is introduced from the gas inlet, a high frequency voltage is applied to the guide bush to generate plasma, A method of forming a hard carbon film on the inner peripheral surface of a guide bush, characterized in that a hard carbon film is formed on the inner peripheral surface. 10. The hard carbon film is formed on the inner peripheral surface of the guide bush according to claim 9, wherein the auxiliary electrode is kept at a ground potential or a DC positive potential during the formation of the hard carbon film. Method. 11. A hard carbon film is formed by arranging a ring-shaped dummy member having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush on the opening end surface of the guide bush where the slit is formed. 10. The method for forming a hard carbon film on the inner peripheral surface of a guide bush according to claim 9, wherein 12. The hard member for an inner peripheral surface of a guide bush according to claim 11, wherein the auxiliary electrode is arranged so that its tip is located inside the opening end surface of the dummy member. Carbon film forming method. 13. A slit-shaped main body of the guide bush, which has an inner diameter substantially the same as the inner peripheral surface of the guide bush, can be inserted into each slit of the guide bush. 10. The hard carbon film is formed by arranging a jig with a plurality of protrusions, and inserting the protrusions into the slits of the guide bush to form the hard carbon film. Of forming a hard carbon film on the inner peripheral surface of the guide bush of. 14. A cylindrical insertion jig having an inner diameter substantially the same as the diameter of the inner peripheral surface is inserted into a step portion having a diameter larger than that of the inner peripheral surface of the guide bush to remove the hard carbon film. The method for forming a hard carbon film on the inner peripheral surface of a guide bush according to claim 9, wherein the hard carbon film is formed. 15. A slotted main body of the guide bush, which has an inner diameter substantially the same as the inner peripheral surface of the guide bush, can be inserted into each slit of the guide bush. A jig with a plurality of protrusions is arranged, each protrusion is inserted into each slit of the guide bush, and the inner peripheral surface of the guide bush is larger than the inner peripheral surface. 10. The hard carbon film according to claim 9, wherein the hard carbon film is formed by inserting a cylindrical insertion jig having an inner diameter substantially the same as the surface diameter. Carbon film forming method. 16. The hard carbon film is formed by supporting the auxiliary electrode by an insulator inserted in a step portion having a diameter larger than that of the inner peripheral surface of the guide bush. A method for forming a hard carbon film on the inner peripheral surface of the guide bush described in the item. 17. A guide bush for an automatic lathe is arranged in a vacuum chamber having an exhaust port and a gas introduction port, and a rod or a rod is provided in a central opening forming an inner peripheral surface of the guide bush which comes into sliding contact with a workpiece. After inserting a linear auxiliary electrode and evacuating the inside of the vacuum chamber, a gas containing carbon is introduced from the gas inlet, and a DC voltage is applied to the guide bush to generate plasma, A method of forming a hard carbon film on the inner peripheral surface of a guide bush, characterized in that a hard carbon film is formed on the inner peripheral surface. 18. The hard carbon film is formed on the inner peripheral surface of the guide bush according to claim 17, wherein the auxiliary electrode is kept at a ground potential or a DC positive potential during the formation of the hard carbon film. Method. 19. A hard carbon film is formed by arranging a ring-shaped dummy member having an inner diameter substantially the same as that of the inner peripheral surface of the guide bush on the end face of the guide bush where the slit is formed. 18. The method for forming a hard carbon film on the inner peripheral surface of the guide bush according to claim 17, wherein 20. The guide bush according to claim 17, wherein the auxiliary electrode is arranged so that its tip is located inside the opening end face of the dummy member. Carbon film forming method. 21. A slit-shaped main body of the guide bush having an inner diameter substantially the same as that of the inner peripheral surface of the guide bush can be inserted into each slit of the guide bush. A jig with a plurality of protrusions is arranged, each protrusion is inserted into each slot of the guide bush, and the hard carbon film is formed. Of forming a hard carbon film on the inner peripheral surface of the guide bush of. 22. A cylindrical insertion jig having an inner diameter substantially the same as the diameter of the inner peripheral surface is inserted into a stepped portion having a diameter larger than the inner peripheral surface of the guide bush to remove the hard carbon film. 18. The method for forming a hard carbon film on the inner peripheral surface of the guide bush according to claim 17, wherein the hard carbon film is formed. 23. The guide bush can be inserted into each slit of the guide bush in a ring-shaped body having an inner diameter substantially the same as the diameter of the inner peripheral surface of the guide bush. A jig with a plurality of protrusions is arranged, each protrusion is inserted into each slit of the guide bush, and the inner peripheral surface of the guide bush is larger than the inner peripheral surface. A cylindrical insertion jig having an inner diameter that is substantially the same as the diameter of the surface is inserted to form the hard carbon film, and the hard surface of the guide bush according to claim 17 is hard. Carbon film forming method. 24. The hard carbon film is formed by supporting the auxiliary electrode by an insulator inserted in a step portion having a diameter larger than that of the inner peripheral surface of the guide bush. A method for forming a hard carbon film on the inner peripheral surface of the guide bush described in the item.