JP2599773B2 - Core block grinding method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of grinding a core block, and more particularly, to performing a curved polishing process on a top end surface of a core block for a magnetic head used in a VTR or the like. Prior to this, the present invention relates to a method of setting a reference dimension for the curved surface polishing between a depth end of a core block and a lower end surface or an upper end surface thereof.

[Conventional technology]

For example, VTR magnetic heads are generally of the bulk type,
A specific example will be described with reference to FIGS. In these drawings, (1) is a bulk type magnetic head, and a pair of a first core (2a) and a second core (2b) made of a ferromagnetic material such as ferrite are bonded with a nonmagnetic material, for example, It is formed by joining with glass (3) into an integral structure. (4) is a wire wound around the core chip (2). An inner groove for winding (5) and a winding locking groove (6) are formed on the inner and outer surfaces of the first core (2a).
In the second core (2b), a joining glass groove (7) is formed on the inner surface side for joining, and a winding locking groove (8) is formed on the outer surface side. A magnetic gap g having a predetermined track width is formed on the top end surface of the core chip (2) which has been subjected to the curved surface processing with a predetermined radius of curvature.

In manufacturing the magnetic head (1), as shown in FIG. 4, long and rectangular first and second core blocks (9) and (10) are prepared as constituent members of the core chip (2). Winding grooves (9a) and (9b) are cut along the longitudinal direction on the inner and outer surfaces of the block (9), and joints are formed on the inner and outer surfaces of the second core block (10) along the longitudinal direction. The groove (10a) and the winding groove (10b) on the outer surface thereof are cut. Next, a plurality of track grooves (11), (11),... With a predetermined track width being left along the inner edges of the first and second core blocks (9) (10) in the lateral direction.
To cut. And the above track groove (11) (11)
And the joint groove (10a) are filled with an adhesive material (12) (12) such as low-melting glass, and the first and second core blocks (9) and (10) are glass-molded to form the first and second core blocks. The inner surface functioning as a joint surface between the two-core blocks (9) and (10) is mirror-finished, and a non-magnetic thin film (not shown) such as SiO _{2 is formed} near the upper surface of the inner surface. Thereafter, the inner surfaces of the first and second core blocks (9) and (10) are brought into contact with each other and heated.
It is melted to form a single-piece core block (13). Next, as shown in FIG. 5, the top end face (13a) of the core block (13) is subjected to a curved surface polishing so as to have a desired gap depth (G). Are sliced to a predetermined thickness while being inclined at a predetermined azimuth angle along the core chips (2), (2).
Get. Thereafter, the core chip (2) is adhered and fixed on a head base (not shown), the top end surface (13a) is lap-finished, and the wire (4) is moved from the first core (2a) of the core chip (2) to the second core. The magnetic head (1) as shown in FIG. 3 is manufactured by winding a predetermined number of turns around the core (2b). The following method is employed to obtain a gap depth (G) when performing a curved surface polishing process on the top end surface (13a) of the core block (13). Prior to the curved surface polishing of the top end surface (13a), first, the upper end portion of the depth end of, as shown in Figure 5 inner surface of the winding part groove of the first core block (9) (9a) (D 1 ), A reference point (Do) separated from the depth end (D ₁ ) by a predetermined distance (L) is measured, and a plane including the reference point (Do) is defined as a grinding reference plane by a hatched portion (FIG. 14a) is removed by cutting. Finally, the top end face (13
a) is subjected to a curved surface polishing process to obtain a predetermined gap depth (G).

In order to set the gap depth (G), the plane including the reference point (Do) is used as a grinding reference plane and the core block (1
When cutting and removing the lower end (14a) of 3), the
The disk-shaped grinding wheel (16) shown in FIGS. 7 and 7 was used. That is, a disk-shaped grinding wheel (16) is arranged on the side of the core block (13) fixed on the moving table (15), and the direction of the rotation axis of the grinding wheel (16) is adjusted to the direction of the table (15). The core block (13) is fed through the movement of the moving table (15) in a state substantially perpendicular to the feed direction (F).
Is moved at a constant speed, and the side end face (16
By pressing a) against the lower end surface (14) of the core block (13), a curved surface is polished between the lower end surface (14) of the core block (13) including the depth end (D ₁ ) and the reference point (Do). A reference dimension (L) for processing was set.

[Problems to be solved by the invention]

When the disc-shaped grinding wheel (16) is used, the side end surface (16a) of the grinding wheel (16) is moved to the moving table (15).
The grinding function is exerted in a state where the lower end surface (14) of the core block (13) fixed above is in surface contact. Here, between the side end surface (16a) of the grinding wheel (16) and the lower end surface (14) of the core block (13), a large grinding area due to surface contact is secured, so that the grinding resistance increases. In addition, the amount of abrasive particles falling off the surface of the grinding wheel (16) also increases. In particular, as indicated by the hatched portion (16b) in FIG. 6, the grinding wheel (1) that first contacts the lower end surface (14) of the core block (13).
At the outer corner of 6), the abrasive grains fall off at an accelerated rate, so the wear form of the grinding wheel is transferred as it is onto the ground surface of the core block, maintaining the grinding accuracy of the core block (13). It will be difficult to do. As a matter of course, the depth end (D ₁ ) is based on the lower end surface (14).
If the top end surface (13a) of the core block (13) is subjected to curved surface polishing based on this, the dimensional accuracy of the gap depth (G) is reduced, and as a result, the VTR magnetic head (1) Recording and playback functions are impaired.

The main object of the present invention is to reduce the dimensional accuracy of the gap depth generated when a disk-shaped grinding wheel is used as a grinding means of a core block and to shorten the service life of the grinding wheel due to local falling off of abrasive grains. It is an object of the present invention to provide a new grinding method that can prevent the formation of a grinding.

[Means for solving the problem]

As a means for achieving the above object, the present invention is to grind a glass-fused core block, when setting a reference dimension for polishing the top end surface between the depth end and the lower end surface or the upper end surface of the core block, Using a cup-shaped grinding wheel as a grinding means of the lower end surface or the upper end surface of the core block, the cutting amount by this cup-shaped grinding wheel, the length along the grinding direction of the core block, and the cup-shaped grinding wheel An object of the present invention is to provide a method of grinding a core block, wherein the method is set to be larger than the sum of the dimensions of the abrasive grains along the radial direction.

[Action]

By setting the cut amount of the core block by the cup-shaped grinding wheel to be larger than the sum of the length of the core block along the grinding direction and the width dimension of the abrasive grain surface along the radial direction of the cup-shaped grinding wheel, Grinding conditions with high dimensional accuracy in which the trailing edge of the abrasive grain surface passes through the entire area to be ground of the core block are maintained.

〔Example〕

FIG. 1 is a perspective view of a core block and a cup-shaped grinding wheel in a grinding step showing a specific example of the method of the present invention, and FIG. 2 is a front view showing a cross section of a part of the cup-shaped grinding wheel and the core block. .

In the following description, the same components as those in FIGS. 3 to 7 are denoted by the same reference numerals, and the description of the same items will not be repeated.

In FIGS. 1 and 2, (17) shows an annular abrasive structure (17) on the periphery of a disc-shaped base plate (18).
The cup-shaped grinding wheel formed by joining a) is shown. (Also (W
₁ ) is the width dimension of the abrasive grain surface (17d) along the radial direction of the cup-shaped grinding wheel (17), and (Wo) is the grinding direction, that is, the core block (13) along the moving direction of the moving table (15).
Is the length of

In the method of the present invention, as shown in FIG. 1, a glass-fused core block (13) is ground and a top end surface (13a) is formed between a depth end (D ₁ ) and a lower end (14) of the core block. In setting the reference dimension (L) for the curved surface polishing, as a grinding means for the lower end surface (14) of the core block (13), the feed direction and the axis of the moving table (15) to which the core block (13) is fixed are fixed. Axis with orthogonal directions (19)
Use a cup-shaped grinding wheel (17) that is rotatably instructed above.

Then, the cutting stroke (S) into the lower end surface (14) of the core block (13) by the cup-shaped grinding wheel (17).
Is the length along the grinding direction of the core block (13) (Wo)
And the width of the abrasive grain surface (17d) along the radial direction of the cup-shaped grinding wheel (17) is set to be larger than the sum of the width dimension (W ₁ ), as shown by the two-dot chain line in FIG. (Through-cut method) to perform grinding.

By setting the cutting stroke (S) of the cup-shaped grinding wheel (17) to the lower end surface (14) of the core block (13) as described above, uneven wear on the front edge portion of the abrasive grain structure (17a). Even if (17c) occurs, the rear edge (17b) of the abrasive grain structure (17a) passes through the entire lower end surface (14) of the core block (13), and the lower end surface (14) has a constant cutting amount. Grind with

When the wear amount of the abrasive grain structure (17a) reaches a predetermined control limit, the supporting position of the cup-shaped grinding wheel (17) is set in a direction orthogonal to the lower end surface (14) of the core block (13), that is, the pivot ( Move by a predetermined amount along the axial direction of 19). Thereby, the cup-shaped grinding wheel (17) can restore the grinding conditions.

〔The invention's effect〕

According to the method of the present invention, since the wear of the grinding wheel is not transferred to the surface to be ground of the core block, the reference dimension for the curved surface polishing of the top end surface is accurately set. For this reason, the recording / reproducing function of the magnetic head is maintained at a satisfactory level, and the life of the grinding wheel can be greatly extended.

[Brief description of the drawings]

FIG. 1 is a perspective view of a core block and a cup-shaped grinding wheel in a grinding step showing a specific example of the method of the present invention, and FIG. 2 is a front view showing a cross section of a part of the cup-shaped grinding wheel and the core block. . FIG. 3 is a perspective view of a magnetic head, FIG. 4 is a perspective view of a core block, FIG. 5 is a front view illustrating dimensions of the core block, and FIG. 6 illustrates a grinding state of the core block by a disk-shaped grinding wheel. FIG. 7 is a top view of FIG. (13) ... core block, (14) the lower end surface of the ... core block, (D ₁₎ ... depth end, the top end surface of (13a) ...... core block, (L) ... reference dimension, (17) ...... cupped grinding wheel, along the radial direction of the (S) ...... depth of cut (cut stroke), (Wo) length along the grinding direction ...... core block, (W ₁₎ ...... cup-shaped grinding wheel Abrasive grain width dimension, (17d) ... Abrasive grain surface.

Claims (1)

(57) [Claims] Claims: 1. A glass-welded core block is ground,
In setting a reference dimension for polishing the top end face between the depth end and the lower end face or the upper end face of the core block, a cup-shaped grinding wheel is used as a means for grinding the lower end face or the upper end face of the core block. The cutting amount by the cup-shaped grinding wheel is set to be larger than the sum of the length of the core block along the grinding direction and the width of the abrasive grain surface along the radial direction of the cup-shaped grinding wheel. Characteristic core block grinding method.