JP5318376B2 - Work chamfering method - Google Patents

Description

  The present invention relates to a machining method for chamfering a specific part of a workpiece.

Conventionally, in the technical field of spark plugs used for internal combustion engines, plug tip electrodes (fine metal tips) made of noble metals have been used.
In manufacturing such a plug chip, usually, the raw material powder is first mixed and further melted to form a solution. The melt is subjected to a rolling process and a forming process, drawn into a rod shape, processed into a wire, and cut into an appropriate thickness to form a cylindrical metal or disk-shaped fine metal chip.

FIG. 1 shows a cross-sectional photograph of a plug chip generally used conventionally and an enlarged photograph of a corner edge portion thereof.
As shown in the figure, since the crystal particles constituting the plug chip are stretched in a fiber shape in the column axis direction, cracks and chips are likely to occur when an external force is applied in the column axis direction (horizontal direction in the drawing). In particular, plug chips such as Ir-based alloys are fragile. Therefore, there is a problem that the plug chips are easily cracked or chipped when the parts come into contact with each other and collide during transport after the manufacture of the plug chip or during assembly in the next process. It was.

In view of this, as disclosed in Patent Document 1, there has been proposed one in which corner edge portions of both end faces of the plug chip are R-chamfered. According to such an R chamfered plug chip, the occurrence of cracking and chipping is reduced, and the durability against external force in the column axis direction is improved.
JP 2005-251606 A

And as a method of such R chamfering, a method by barrel processing has been proposed. However, in barrel processing, it is difficult to select a medium suitable for chamfering, and since it involves grinding the entire medium, it is not suitable for chamfering only a specific part (corner edge part).
In addition to barrel machining, a method of chamfering each workpiece individually has also been studied, but the problem is that mass production is extremely poor and machining costs are high, and that the chamfering varies between products. was there.

  Accordingly, an object of the present invention is to provide a workpiece chamfering method that is mass-productive and that can reduce the processing cost.

A work and a liquid are put into a hard container such as a glass bottle , and the work in the container is made to collide with the inner wall of the container by applying vibration to the container, and the corner portion of the work is plastically deformed and chamfered by the collision.

  The workpiece that can be processed by the above method includes all metal parts, and specific examples include heat-resistant parts (such as plug chip electrodes) made of an Ir-based alloy, Pt-based alloy, or Rh-based alloy.

According to the present invention, since a large number of workpieces can be chamfered evenly at a time, a product having no variation in the chamfering condition can be mass-produced efficiently and at low cost. As a result, it becomes possible to significantly reduce the cost of chamfering the workpiece.
Also, unlike barrel processing, no media is put into the container, so there is no need to select media according to the workpiece. In addition, since it is not necessary to select the workpiece and the medium after chamfering, the processed product can be immediately used for the next step after the processing is completed.
In addition, since the corner edge portion processed by the above method has an R-plane shape (or taper shape) with deformation of the metal structure, even if an external force acts on the corner edge portion, the force does not concentrate on one point. It becomes easy to escape by being dispersed. Therefore, even when subjected to an impact in a later assembly process or the like, the effect of suppressing cracking and chipping is achieved.
Furthermore, when plastic deformation is caused by collision with the inner wall of the container, work hardening occurs at the corner edge portion and its surroundings, and therefore, the effect of suppressing cracking and chipping is further enhanced by a synergistic effect with the force distribution effect by the chamfered portion. .

  Hereinafter, an embodiment of the present invention will be described by taking a plug chip (fine metal chip) for an internal combustion engine as a specific example of a workpiece to be chamfered.

[First Embodiment]
First, a hard container such as a glass bottle is prepared, and a plurality of plug chips are placed therein as a work, and a liquid (water or oil) is also added thereto. Subsequently, linear motion vibration (vertical or horizontal vibration) is applied to the sealed hard container. While the vibration is applied, all the plug tips in the container collide with the inner wall of the container, and as a result, stress concentrates on the corner edge part of the workpiece that is susceptible to plastic deformation, and the corner part becomes R-shaped. Deform.

A cross-sectional photograph of the plug chip chamfered by the above method and an enlarged photograph of the corner edge portion are shown in FIG.
As shown in FIG. 2, it can be seen that, at the corner edge portion of the plug chip, the metal structure extending in the column axis direction is deformed and bent, and the appearance of the edge portion is processed into an R shape.

According to the above method, since a large number of plug chips can be chamfered almost uniformly at a time, a product free from variations in the chamfering condition can be mass-produced efficiently and at low cost. As a result, it becomes possible to significantly reduce the cost of chamfering the workpiece.
Also, unlike barrel processing, no media is put into the container, so there is no need to select media according to the workpiece. In addition, since it is not necessary to select the workpiece and the medium after chamfering, the processed product can be immediately used for the next step after the processing is completed.
In addition, since the corner edge portion processed by the above method has an R-shape with deformation of the metal structure, even if an external force acts on the corner edge portion, the force is not concentrated on one point but dispersed and escaped. It becomes easy. Therefore, even when subjected to an impact in a later assembly process or the like, the effect of suppressing cracking and chipping is achieved.
Furthermore, if it undergoes plastic deformation due to a collision with the inner wall of the container, work hardening occurs at the corner edge portion and its surroundings. Therefore, it has a synergistic effect with the force distribution effect by the chamfered R surface, and has an effect of suppressing cracks and chips. Enhanced.

  In addition, although the said liquid does not necessarily need to be used, when chamfering a cylindrical workpiece, it is desirable to put the liquid in a hard container as described above. This is because if the liquid does not enter in the case of the cylindrical shape, the workpiece will be damaged by the edge portion when the workpieces collide with each other.

  Moreover, in the said method, although the workpiece | work is made to collide with the inner wall or bottom face of a container and is plastically deformed, you may make it grind the corner edge part of a workpiece | work together with this. For example, prior to processing, a plate-shaped, sheet-shaped, or bar-shaped grinding member (for example, abrasive paper) may be attached or fixed to the inner wall (bottom surface and / or side surface) of the container in advance. Thus, when the workpiece collides with the inner wall of the container, the corner edge portion is plastically deformed and ground at the same time, so that it becomes possible to perform chamfering more effectively.

  In this specification, as a representative example of the chamfering process, the corner edge portion is processed into an R-surface shape. However, in the “chamfering process” referred to in this application, not only an aspect of bending into an R-surface shape. A mode of processing into a tapered shape is also included.

[Second Embodiment]
In the first embodiment described above, the R chamfered portion is formed by plastic deformation, and at the same time, a convex portion formed by rising in the column axis direction is formed at the corner edge portion (see FIG. 2). The formation of such convex portions is not preferable depending on the application, and it is not preferable that the dimensions of the workpiece are changed by chamfering from the viewpoint of ensuring product accuracy.
Therefore, an embodiment suitable for suppressing the formation of convex portions will be described below.

First, a plurality of wire rods that are the elements of the plug chip are bundled, and in that state, they are applied and hardened with an adhesive such as resin. This is sliced into a plurality of pieces with a wire saw or a dicing saw to prepare a plurality of plate-like slice pieces (an aggregate of columnar or disk-like plug chips) having a predetermined thickness.
Next, blasting is performed on both sides of the cut surface of the slice piece. In the blasting process, the projection material or the abrasive is sprayed substantially perpendicularly to the cut surface, whereby the corner portion of the plug chip is ground.
The blasting process may be either wet or dry.

  Subsequently, the resin of the slice piece after the blasting process is removed, the plug chips are taken out, these are put into a hard container, and the chamfering process by plastic deformation as in the first embodiment is performed.

A cross-sectional photograph of the plug chip chamfered by the above method and an enlarged photograph of the corner edge portion are shown in FIG.
As shown in FIG. 3, it can be seen that the metal structure extending in the column axis direction is deformed at the corner edge portion of the plug chip, and the appearance of the edge portion is processed into an R shape. In addition, since the corner edge portion is ground prior to the plastic deformation due to the linear vibration, the formation of the convex portion as shown in FIG. 2 is suppressed. Therefore, according to the present embodiment, the corner edge portion can be chamfered without changing the dimensions of the workpiece.

  Note that the order of performing chamfering by grinding using blasting and chamfering by plastic deformation using a container is not particularly limited to the above-described one. As described above, the blasting process described above may be performed.

  As described above, description has been given mainly with a cylindrical or disk-shaped plug chip as a specific example of the work. All other metal parts are included.

[Best form for work]
Next, the form of the workpiece | work suitable for the processing method mentioned above is demonstrated.

The hardness of the workpiece is preferably 150 or more, more preferably 200 or more in terms of Vickers hardness HV.
This is because if the hardness of the workpiece is less than 150, the workpiece is too soft, so that only the corner edge portion is not deformed and a good R chamfered shape cannot be obtained.

When the work is a plug chip, the diameter of the work is preferably φ0.25 to φ3.0 mm, more preferably φ0.3 to φ1.0 mm.
This is because there is no practical shape of the plug electrode chip when the diameter of the workpiece is less than φ0.25 or more than φ3.0.

The aspect ratio of the diameter and length of the workpiece is preferably 0.3 to 10, more preferably 0.5 to 5.
If the aspect ratio is less than 0.3, the workpieces overlap (stick) during vibration processing, and if it exceeds 10, the workpiece length bends during processing. is there.

  When an Ir-based alloy is used as the workpiece, it is possible to use Ir added with 1% or more of Pt, Rh, Ni as a second element or a third element.

  Next, specific examples of the present invention will be described.

  Plural kinds of plug chips (fine metal chips) were prepared as samples, and each sample was chamfered in the following manner. The composition, shape, and hardness HV of each sample were as shown in Table 1.

[Example 1]
In accordance with the method described in the first embodiment, R-chamfering of the plug chip was attempted.
That is, a glass bottle was prepared as a hard container, and a work (plug chip) was added thereto, and about half of water was added to the container. Subsequently, the container was sealed and fixed to a vibration generator (shaker), and a linear motion in the vertical direction was applied for 20 minutes to form an R chamfer at the corner of the plug chip.
The main implementation conditions were as follows.

Linear motion vibration conditions: Hard container 50mL glass bottle
1,000 workpieces
Water 25mL
Linear vibration time (vertical) 20min
Stroke 40mm
Cycle 100 times / min

[Example 2]
In accordance with the method described in the second embodiment, R-chamfering of the plug chip was attempted.
That is, the wire rods were bundled and hardened with a resin, and both surfaces of the cut surface of the plate sliced with a wire saw were subjected to dry blasting, and then the resin was removed and the plug chip was taken out.
Next, a glass bottle was prepared as a hard container, and the fine metal chip was introduced into the glass bottle, and about half of water was added to the container. Subsequently, the container was sealed and fixed to a vibration generator (shaker), and a linear motion in the vertical direction was applied for 20 minutes to form an R chamfer at the corner of the plug chip.
The main implementation conditions were as follows.

Blasting conditions: Projection material SiC
Projection grain size # 1000
Projection pressure 0.9Mpa
Linear vibration conditions: Same as Example 1

[Example 3]
The order of the blasting process and the linear motion vibration in Example 2 was changed, and an R chamfering process of the plug chip was attempted.
That is, first, the rigid container was directly oscillated in the same manner as in Example 1 to form an R chamfer at the corner of the fine metal tip. Subsequently, the plug chip taken out from the hard container was blasted.

The implementation results for each of Examples 1 to 3 are shown in Table 1.
As shown in Table 1, according to the present invention, it was confirmed that the corner edge portion of the workpiece can be chamfered.
However, with respect to Pt-5 wt% Rh, the hardness of the workpiece was too soft, so that a good R chamfered shape could not be obtained at the corner edge portion.

  Subsequently, a drop test was performed on the sample in which R chamfering was confirmed, and cracks / chips of the R chamfered product were evaluated. As a result, it was confirmed that there was an inhibitory effect on cracking and chipping as compared with an unfinished product with an R chamfer.

It is a cross-sectional photograph showing a conventional plug chip, and an enlarged photograph of the corner edge portion is shown on the right side. FIG. 3 is a cross-sectional photograph showing a plug chip that has been chamfered according to the first embodiment, and an enlarged photograph of the corner edge portion is shown on the right side. It is a cross-sectional photograph showing a plug chip that has been chamfered according to the second embodiment, and an enlarged photograph of the corner edge portion is shown on the right side.

Claims (2)

A work chamfering method comprising putting a work and a liquid into a container, causing the work in the container to collide with the inner wall of the container by applying vibration to the container, and chamfering the corner portion of the work by plastic deformation by the collision. (However, except for processing media by putting it in a container) .   The work chamfering method according to claim 1, wherein the work is one of an Ir-based alloy, a Pt-based alloy, and an Rh-based alloy.