JPH05285820A - Barrel polishing workpiece and its manufacture - Google Patents

Abstract

PURPOSE:To decrease surface roughness of a processed surface subjected to barrel polishing by applying the barrel polishing after forming a hardened layer by soft nitriding treatment at least on the surface of a workpiece concerning an article finish-processed by the barrel polishing. CONSTITUTION:In the case of manufacturing a fixed guide roller 20 used for a VTR and others as a workpiece, a first preformed article of a desired shape and size is formed by applying cutting process and others to a maternal of a stainless round steel and others of SUS3O3 and others by a machine tool such as a conventional lathe and others. Thereafter, a second preformed article is formed by applying intermediate barrel polishing to this first preformed article for about five hours. Thereafter, by applying salt bath soft nitriding treatment to this preformed article in the way of dip brazing and others, a hardened treated article provided with a hardened layer 22 on the overall surface including a slide surface 21 is formed. Additionally, by applying finish- processing and barrel polishing to this hardened treated article, a desired fixed guide roller 20 with its surface roughness of less than Rmax1.0mum is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barrel-polished workpiece in which a material is machined into a predetermined surface roughness and a method for producing the same, and more particularly to a barrel-polished workpiece which is finished by barrel polishing. The present invention relates to a barrel-polished workpiece suitable for a small-diameter workpiece and a manufacturing method thereof.

[0002]

2. Description of the Related Art In general, a small-diameter barrel-polished workpiece, which is machined on a raw material and whose finished surface is finished to a predetermined surface roughness by barrel-polishing, generally reduces production efficiency and economical burden. It is often used for a reason.

As a concrete example of such a barrel polishing workpiece, a fixed guide roller used in a VTR or the like and a drive piston used in a wax type thermostat will be described as an example.

First, a fixed guide roller used in a VTR or the like will be described.

In general, the components of the running system of a magnetic tape used in a VTR or the like are used in contact with the magnetic tape in order to keep the magnetic tape and the magnetic head in stable contact with each other, and A small diameter capstan made of magnetic metal, a fixed guide roller, a guide pin, etc. are used. In particular, the fixed guide roller contacts the magnetic tape in a non-rotating state, and the magnetic tape always slides on the outer peripheral surface of the fixed guide roller with a desired tension.

The magnetic tape is based on a resin film of oriented polyethylene terephthalate or the like, and this resin film has a shortened life due to surface scratches, abrasion, permanent elongation and the like.

Therefore, the fixed guide roller makes the sliding surface in contact with the magnetic tape as smooth as possible (small surface roughness).
And need to.

The fixed guide roller will be described below with reference to FIG.
Further description will be made with reference to.

The conventional fixed guide roller 1 of this type is S
It is made of a material such as stainless steel such as US303, and as shown in FIG. 9, it has a substantially cylindrical shape with its axial center portion having a smaller diameter than its axial end portions. And
The outer peripheral surface of the central portion in the axial direction is a sliding surface 2 that contacts a magnetic tape (not shown).

Further, the fixed guide roller 1 is formed by cutting the material with an appropriate machine tool such as a lathe to form an intermediate processed product having a predetermined shape and size. Manufactured by barrel polishing as the final finish for smoothness.

Next, the drive piston used in the wax type thermostat will be described.

Generally, a water-cooled type is mainly used as a cooling device for an engine of an automobile or the like, and cooling water for cooling the engine is cooled by a radiator and circulated. A thermostat is a device for automatically controlling the temperature of this cooling water to a predetermined temperature.
It is located between the engine and the radiator. As this thermostat, a wax-type thermostat in which a valve is opened and closed by an appropriate expansion / contraction member generally called wax that expands and contracts depending on temperature is mainly used.

The wax type thermostat 3 is shown in FIG.
It is formed as shown in 0. On the outermost side, a first outer member 5 formed in a substantially mountain shape in the figure by an appropriate band-shaped material
a and a second outer member 5b formed of the same material so as to have an annular opening 4a at the lower end, and a valve seat member 7 having an annular valve seat 7a formed radially inward. The outer member 5 is formed so as to be fixed to each other. The outer member 5 has an opening 4 at one end in the axial direction.
b has a bottomed cylindrical inner member 6 having openings 4
The inner members 6 are arranged in a loosely fitted state in the openings 4a of the outer member 5 while the a and 4b are oriented in opposite directions. An annular valve 8 is fixed to an appropriate support member 9 in the vicinity of the outer periphery of the inner member 6 on the side of the opening 4b so as to project radially outward. In addition, the valve seat 7a and the valve 8
Means the vicinity of the opening 4a of the outer member 5 and the inner member 6
Urging spring 10 interposed between the supporting member 9 and the supporting member 9
Are abutted with a desired biasing force. Then, in this state, the first outer member 5a side and the second outer member 5 side
The b side is shut off by closing the valve 8, and the flow path of the cooling water is closed.

Inside the inner member 6, a sleeve 12 having a substantially bottomed cylindrical shape and made of a rubber-like elastic material fixed to a desired metal fitting 11 is provided at the center of the sleeve. 13 is installed so as to face the same direction as the opening 4b of the inner member 6, and the metal fitting 11 is fixed inside the inner member 6 near the opening 4b. A desired gap is provided between the inner peripheral surface 14 of the inner member 6 and the outer peripheral surface 15 of the sleeve 12.
An appropriate wax 16 is hermetically filled in this gap.

Inside the sleeve 12, a driving piston 17 formed in a small-diameter columnar shape is mounted so as to be slidable in the axial direction with respect to the sleeve 12, and the outer end of the driving piston 17 is mounted. Is in contact with a recess 18 having a predetermined shape formed inside the first outer member 5a.

The operation of the wax-type thermostat 3 will be described below.
The temperature of the cooling water near the outer peripheral portion of the inner member 6 is about 7
When the temperature becomes 0 to 80 ° C., as shown in FIG. 11, the volume of the wax 16 expands, and the sleeve 12 contracts inward in the radial direction. Then, the drive piston 17 is removed from the inside of the sleeve 12, and as a result, the inner member 6 moves toward the opening 4a of the outer member 5, and
The valve 8 is separated from the valve seat 7a, and the flow path of the cooling water is opened as shown by the arrow in the figure.

On the other hand, when the temperature of the cooling water becomes about 70 to 80 ° C. or less, the volume of the wax 16 shrinks and the sleeve 12 expands radially outward, as shown in FIG. Then, the force of the biasing spring 10 causes the sleeve 1
2, the drive piston 17 slips into the inside, and as a result, the inner member 6 moves toward the side opposite to the opening 4a of the outer member 5, the valve 8 abuts against the valve seat 7a, and the flow of cooling water flows. The road is closed.

As described above, since the drive piston 17 and the sleeve 12 slide, the sliding resistance (friction resistance) between the drive piston 17 and the sleeve 12 depends on the responsiveness of the wax-type thermostat 3. It becomes an important parameter, and the smaller the sliding resistance, the higher the responsiveness and the quicker the operation.

Therefore, it is necessary for the drive piston 17 to make the sliding surface 19 (surface) in contact with the sleeve 12 as smooth as possible (the surface roughness is small).

Hereinafter, the drive piston 17 will be described with reference to FIG.
Further description will be given with reference to FIG.

A conventional drive piston 17 of this type is SU
It is made of a material such as S304 such as stainless round steel, and as shown in FIG. 12A, after being cut into a substantially cylindrical shape by an appropriate processing device such as a lathe,
As shown in 2b), both ends in the axial direction are subjected to rough / medium barrel polishing for forming roundness. And FIG.
As shown in 2c, after performing centerless polishing for improving the roundness and accuracy of the outer diameter dimension, barrel polishing is performed as a final finish for smoothing the surface as shown in d of FIG. Has been applied.

[0022]

However, in the above-mentioned conventional fixed guide roller 1, the outer diameter of both axial ends is larger than the outer diameter of the sliding surface 2 formed at the central portion in the axial direction. Therefore, processing methods such as centerless polishing and spar finish cannot be used, and the surface roughness of the sliding surface must be reduced by barrel polishing. However, there is a problem in that even if the barrel processing time is lengthened, the Rmax cannot be set to 1.0 μm or less.

Further, in the above-mentioned conventional drive piston 17, the surface roughness of the sliding surface 19 is Rm by a processing method using a device such as centerless polishing and spar finish.
Although the ax can be set to 1.0 μm or less, an extremely large amount of equipment and space are required to produce a large number of workpieces produced by such an apparatus, resulting in poor production efficiency and increased economic burden. There was a problem.

The present invention has been made in view of these points, and overcomes the above-mentioned problems of the conventional ones.
It is an object of the present invention to provide a barrel-polished workpiece and a method for manufacturing the same, which has a simple structure and can reduce the surface roughness by performing barrel polishing.

[0025]

In order to achieve the above-mentioned object, the barrel-polished workpiece of the present invention according to claim 1 is a barrel-polished workpiece finished by barrel-polishing. At least the surface is formed with a hardened layer by soft nitriding, and then barrel polishing is performed to make the surface roughness Rmax 1.0 μm or less.

In the method of manufacturing a barrel-polished workpiece according to a second aspect of the present invention, the workpiece is soft-nitrided to form a hardened layer having a high hardness on at least the surface of the workpiece and then finished by barrel polishing. It is characterized by being processed.

[0027]

The barrel polishing work of the present invention is manufactured according to the method of manufacturing a barrel polishing work of the present invention to form a hardened layer having a high hardness without deformation on at least the surface of the raw material, and then the barrel polishing is performed. Can be applied,
Reduces the surface roughness of the barrel-polished processed surface,
It can be a predetermined value.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a longitudinal sectional view showing the main part of an embodiment in which the barrel polishing work of the present invention is applied to a fixed guide roller.

As shown in FIG. 1, a hardened layer 22 formed by salt bath nitrocarburizing is formed on at least the surface including the sliding surface 21 of the fixed guide roller 20 of this embodiment. The thickness (depth) of the hardened layer 22 is preferably about 10 μm in the state before barrel polishing for finishing is performed.

The depth of the hardened layer 22 can be changed depending on the specifications of the surface condition of the workpiece after being polished by barrel polishing and the purpose of use, and is particularly limited to this embodiment. is not.

Next, the fixed guide roller 20 of the present embodiment.
The manufacturing method of will be described.

The fixed guide roller of this embodiment is SUS3.
A material such as stainless round steel such as 03 is cut by a suitable machine tool such as a lathe to form a first intermediate processed product having a desired shape and size in a conventional manner. Then, the first intermediate processed product is subjected to middle barrel polishing for about 5 hours to form a second intermediate processed product 23 as shown in FIG. Further, a salt bath soft nitriding treatment is applied to the second intermediate processed product 23 by a method such as a bumping process to form a hardened product. Furthermore, barrel hardening is applied to this cured product as a finishing process to complete the manufacture of the fixed guide roller 20 of this embodiment.

Next, the operation of the method for manufacturing the fixed guide roller 20 of the present embodiment described above will be described with reference to FIGS.

FIG. 3 is a diagram showing the relationship between the depth from the surface and the hardness of the cured product subjected to the salt bath nitrocarburizing treatment, and FIG. 4 shows the relationship between the barrel polishing processing time and the surface roughness. It is a diagram.

As shown in FIG. 3, the hardness of the hardened layer on the surface of the hardened product obtained by subjecting SUS303 to the salt bath soft nitriding treatment is about Hmv (micro Vickers hardness) 1200.
Therefore, the hardness of the surface of the conventional intermediate processed product not subjected to the salt bath nitrocarburizing treatment (surface hardening treatment) is about Hmv200, which is equivalent to the hardness of the material, and the surface hardness of the cured product is the surface of the intermediate processed product. It can be dramatically improved by about 6 times the hardness.

Further, the salt bath nitrocarburizing makes it possible to make the quality uniform even when the second intermediate processed products 23 are in contact with each other by rushing, so that a large number of products can be easily and efficiently processed at one time. It can be cured. In other gas nitriding or ion nitriding, the second intermediate processed product 23 must be arranged so that the gas always contacts the surface of the second intermediate processed product 23, and the second intermediate processed product 23 does not come into contact with any other material, and then the hardening treatment must be performed. Inevitably, it takes time and effort to arrange the second intermediate processed product 23, resulting in poor production efficiency.

Further, the surface hardening method by the salt bath nitrocarburizing treatment does not depend on other surface hardening methods such as carburizing quenching and induction hardening, so that the treatment temperature is low.
The heat treatment distortion is extremely small, and it is possible to reliably prevent changes in size and shape due to curing treatment.

Next, the second barrel which was subjected to middle barrel polishing for 5 hours
This second intermediate processed product 23 is used as the intermediate processed product 23.
Using the cured product obtained by subjecting the salt bath nitrocarburizing to the product of the present invention, barrel polishing, which is a finishing process, was performed, and a comparative test was performed to investigate the relationship between the processing time and the surface roughness.

The surface roughness of the second intermediate processed product 23 was about Rmax 1.5 μm.

FIG. 4 shows the results of the comparative test. The results of this comparative test are shown as an average of 10 samples. As is clear from this test result, the surface roughness of the conventional product was about Rmax 1.1 μm about 1 hour after the start of barrel polishing, and the minimum value was After that, after about 7 hours after the start of barrel polishing, the Rmax becomes 1.25 μm and after about 20 hours after the start of barrel polishing, the Rmax becomes 1.2 μm. This is because the conventional product has a low surface hardness (about Hmv200), so that when the barrel polishing is continued for a long time, the surface is polished and is hit by a medium (abrasive material) (not shown) used for barrel polishing. It is presumed that the phenomenon causes the surface to become uneven and the surface roughness to become constant.

In contrast to the conventional product, the product of the present invention sharply decreased to about Rmax 0.9 μm about 1 hour after the start of barrel polishing, and the surface roughness gradually decreased thereafter, and about 7 after the start of barrel polishing. The surface roughness tends to continuously decrease to about Rmax 0.7 μm in time and about Rmax 0.5 μm about 20 hours after the start of barrel polishing. This is because the hardness of the hardened layer on the surface of the product of the present invention is high (about Hmv1200),
Not affected by the "tap" phenomenon of the media,
It is assumed that the polishing action will continue.

In the product of the present invention provided with the hardened layer 22 by the soft nitriding treatment, the surface roughness sharply decreases about 1 hour after the start of the barrel polishing. This is because about 1 μm from the surface of the product of the present invention is scaled into chromium oxide, chromium nitride and the like by a chemical reaction, and the scaled substance is easily dropped off. Therefore, this scaling greatly contributes to the improvement of the surface roughness (to reduce the surface roughness) by barrel polishing.

Therefore, according to the fixed guide roller 20 of the present embodiment, unlike the prior art, the surface roughness of the surface can be made extremely small by barrel polishing, so that the sliding surface 21 that comes into contact with a magnetic tape (not shown). Can be made extremely smooth. Then, the sliding resistance between the sliding surface 21 and the magnetic tape is reduced, the wear of the magnetic tape is reduced, and the permanent elongation of the magnetic tape and the occurrence of surface scratches are surely reduced, and the life of the magnetic tape is reduced. Can be surely improved.

FIG. 5 is a longitudinal sectional view showing a main part of an embodiment in which the barrel polishing workpiece of the present invention is applied to a drive piston.

As shown in FIG. 5, a hardened layer 26 formed by a salt bath nitrocarburizing treatment is formed on at least the surface including the sliding surface 25 of the drive piston 24 of this embodiment. The thickness (depth) of the hardened layer 26 is preferably about 10 μm before barrel polishing as a finish.

The depth of the hardened layer 26 can be changed according to the specifications of the surface condition of the workpiece after being polished by barrel polishing and the purpose of use, and is particularly limited to this embodiment. is not.

Next, a method of manufacturing the drive piston of this embodiment will be described.

The drive piston of this embodiment has a length of about 3.8 mm.
Round stainless steel such as SUS304 and SS4
A round steel material such as No. 1 is subjected to cutting processing by an appropriate machine tool such as a lathe as in the conventional case, and a first intermediate processed product having a desired shape and size is formed. Then, the first intermediate processed product is subjected to rough barrel polishing for about 20 minutes and medium barrel polishing for about 5 hours to form a second intermediate processed product 27 as shown in FIG. Further, a salt bath soft nitriding treatment is applied to the second intermediate processed product 27 by a method such as a bumping process to form a hardened product. Furthermore, barrel hardening is applied to this cured product as a finishing process to complete the manufacture of the drive piston 24 of this embodiment.

Next, the operation of the method of manufacturing the drive piston 24 of the present embodiment described above will be described with reference to FIGS.

FIG. 7 is a diagram showing the relationship between the depth from the surface and the hardness of the cured product subjected to the salt bath nitrocarburizing treatment, and FIG. 8 shows the relationship between the processing time of barrel polishing and the surface roughness. It is a diagram.

As shown in FIG. 7, the hardness of the hardened layer on the surface of the hardened product obtained by subjecting SUS304 to the salt bath soft nitriding treatment is about Hmv1200, and the salt bath soft nitriding treatment (surface hardening treatment) is not applied. The hardness of the surface of the conventional intermediate processed product is about Hmv190, which is equivalent to the hardness of the material, and the hardness of the hardened layer on the surface of the cured product is dramatically improved to about 6 times that of the surface of the intermediate processed product. be able to. Also, S
The hardness of the hardened layer on the surface of the hardened product subjected to the salt bath soft nitriding treatment using S41 as a material is about Hmv550, and the surface hardness of the conventional intermediate processed product not subjected to the salt bath soft nitriding treatment (surface hardening treatment). Is about Hmv140, which is equivalent to the hardness of the material
Therefore, the surface hardness of the cured product can be dramatically improved to about 4 times the surface hardness of the intermediate processed product.

The advantages of the salt bath nitrocarburizing treatment applied to the second intermediate processed product 27 are the same as those in the above-mentioned embodiment.

Next, the second intermediate processed product subjected to rough barrel polishing for about 20 minutes and medium barrel polishing for 5 hours was used as a conventional product, and a cured product obtained by subjecting the second intermediate processed product to salt bath nitrocarburizing was used. As a product of the present invention, barrel polishing, which is a finishing process, was performed, and a comparative test was conducted to investigate the relationship between the processing time and the surface roughness.

The surface roughness of the second intermediate processed product 27 is about Rmax1.5 for the product made of SUS303.
Approximately Rm for SS41 material
It was about 1.7 μm.

FIG. 8 shows the results of the comparative test. The results of this comparative test are shown as an average of 10 samples. As is clear from this test result, the surface roughness of the conventional product was about Rmax 1.1 μm about 1 hour after the start of barrel polishing, and the minimum value was After that, the surface roughness becomes worse (larger) as the barrel polishing time becomes longer. This is because the conventional product has a low surface hardness (about Hmv 190), so if barrel polishing is continued for a long time, the surface will be polished and the "battering" phenomenon caused by the media (polishing material) used for barrel polishing will occur. It is assumed that the surface becomes uneven and the surface roughness becomes constant or deteriorates.

In contrast to the conventional product, the product of the present invention made of SUS304 is about Rma about 1 hour after the start of barrel polishing.
The surface roughness decreases sharply to 0.85 μm, and the surface roughness gradually decreases thereafter, and the surface roughness tends to continuously decrease to about Rmax 0.6 μm about 7 hours after the start of barrel polishing. It is considered that this is because the hardness of the hardened layer on the surface of the product of the present invention is high (about Hmv1200), and therefore the polishing action is continuously performed without being affected by the "battering" phenomenon of the medium.

The product of the present invention made of SS41 is
After about 1 hour from the start of barrel polishing, the Rmax suddenly decreased to 0.95 μm, and the surface roughness gradually decreased thereafter. About 7 hours after the start of barrel polishing, the Rmax became 0.75.
The surface roughness tends to decrease continuously in μm. This is because the hardness of the hardened layer on the surface of the product of the present invention is high (about Hmv5
Therefore, it is presumed that the polishing action is continued without being affected by the "striking" phenomenon of the medium.

In the product of the present invention having the hardened layer 26 formed by the soft nitriding treatment, the surface roughness sharply decreases about 1 hour after the start of the barrel polishing. This is because about 1 μm from the surface of the product of the present invention is scaled into a chromium oxide, a chromium nitride or the like by a chemical reaction in a material made of SUS304, and the scaled material easily falls off.
This is because the material made of S41 is scaled to iron oxide, iron nitride and the like, and these scaled materials easily fall off. Therefore, this scaling greatly contributes to the improvement of the surface roughness (to reduce the surface roughness) by barrel polishing.

Therefore, the drive piston 24 of this embodiment is
According to the method, unlike the prior art, the surface roughness of the surface can be made extremely small by barrel polishing, so that the sliding surface 25 that comes into contact with the sleeve 12 can be made extremely smooth. Then, the sliding resistance between the sliding surface 25 and the sleeve 12 can be reduced, wear can be reduced, and the responsiveness of the wax-type thermostat 3 can be improved to allow a quick operation. Moreover, since the surface roughness can be improved (decreased) by barrel polishing, the production efficiency is good and the economical burden can be reduced.

Further, the drive piston 24 made of SS41 was unusable because rust was generated by the cooling water in the conventional one, but the hardened layer 26 formed by the salt bath nitriding treatment was used as in the present invention. When it is formed, the hardened layer 26 is mainly made of iron nitride or the like, has a characteristic of being resistant to rust, and can be used. Then, this surface can be subjected to a film treatment such as ferrosoferric oxide, and by applying this film treatment, it is possible to exhibit an anticorrosion effect comparable to that of stainless steel. Furthermore, the material cost of SS41 is the same as that of conventional SU
The drive piston 24 of the wax-type thermostat 3 can be provided which is about 1/5 of the material cost of S304 and has a lower economical burden than the conventional one, even considering the cost increase of the salt bath nitriding treatment and the like.

The present invention is not limited to the above embodiment, but can be modified as necessary.

[0063]

As described above, according to the barrel-polished workpiece and the method for manufacturing the same of the present invention, a hardened layer formed by soft nitriding is formed on the surface of the workpiece before finishing by barrel polishing. As a result, the surface roughness of the workpiece after finishing by barrel polishing can be made smaller than before, which is an extremely excellent effect.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a main part of an embodiment in which a barrel polishing workpiece of the present invention is applied to a fixed guide roller.

FIG. 2 is a front view showing an intermediate processed product of a fixed guide roller.

FIG. 3 is a diagram showing the relationship between the depth from the surface and the hardness of a cured product obtained by subjecting an intermediate processed product of a fixed guide roller to salt bath nitrocarburizing.

FIG. 4 is a diagram showing the relationship between the processing time of barrel polishing of a fixed guide roller and the surface roughness.

FIG. 5 is a vertical cross-sectional view showing a main part of an embodiment in which the barrel polishing workpiece of the present invention is applied to a drive piston.

FIG. 6 is a front view showing an intermediate processed product of a drive piston.

FIG. 7 is a diagram showing the relationship between the hardness and the depth from the surface of a cured product obtained by subjecting an intermediate processed product of a drive piston to salt bath nitrocarburizing.

FIG. 8 is a diagram showing the relationship between the processing time of barrel polishing of the drive piston and the surface roughness.

FIG. 9 is a vertical cross-sectional view showing a main part in which a conventional barrel polishing workpiece is applied to a fixed guide roller.

FIG. 10 is a vertical sectional view showing a closed state of a wax type thermostat.

FIG. 11 is a vertical sectional view showing an open state of a wax type thermostat.

12A to 12D are views showing a manufacturing process when a conventional barrel polishing workpiece is applied to a drive piston.

[Explanation of symbols]

 20 Fixed Guide Roller 21 Sliding Surface 22 Hardened Layer 24 Drive Piston 25 Sliding Surface 26 Hardened Layer

Claims (2)

[Claims] 1. A barrel-polished workpiece finished by barrel-polishing is subjected to barrel-polishing after forming a hardened layer by a soft nitriding treatment on at least the surface of the workpiece to obtain a surface roughness of Rmax1. A barrel polishing workpiece characterized by being 0 μm or less. 2. A method for manufacturing a barrel-polished workpiece, which comprises subjecting the workpiece to a soft nitriding treatment to form a hardened layer having a high hardness on at least the surface of the workpiece, and then finishing by barrel polishing. ..