JPH0729111A - Structure for welding part of electronic apparatus - Google Patents

Abstract

PURPOSE:To widen the range of welding conditions and increase and stabilize welding strength in an electric resistance welding structure between a part having a case such as a magnetic head and a base plate. CONSTITUTION:A small projection 11 is formed on a base plate 10 and the surface of this small projection 11 is formed, for example, like a cylindrical surface. A curved part 3d of the surface of the bending portion 3c at the boundary of the bottom surface 3a and the side surface 3b of a shielding case 3 of a magnetic head 1 is abutted with the small projection 11. A current is impressed between the shielding case 3 and base plate 10 and the abutting part is caused to generate heat with an electric resistance for the purpose of welding. At the ding portion 3c of the shielding case 3, the heat generated by electric resistance cannot be released easily and therefore the bending portion 3c and small projection 11 are heated under good balance to ensure stabilized welding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device part such as a magnetic head provided with a conductive case, and a projection provided on a conductive base, which are abutted against each other to generate an electric power. The present invention relates to a welded structure of electronic equipment parts that are resistance-welded.

[0002]

2. Description of the Related Art In FIG. 11, reference numeral 1 is a magnetic head mounted on a VTR device for recording / reproducing audio and controlling running of the magnetic head. The magnetic head 1 is fixed to a base 2, and is fixed to a unit base of a VTR device by a mounting hole 2a formed in the base 2. The magnetic head 1 and the base 2 are fixed by screws, but recently, in order to improve workability and reduce the number of screw parts, both of them are fixed by electric resistance welding. There is.

In the conventional process of electric resistance welding, the bottom surface 3a of the shield case 3 of the magnetic head 1 is on the surface of the base 2.
Small projection 2 called a projection on the part facing the
A plurality of b are formed. The small protrusions 2b are formed by bulging in the pressing process, and their surface shape is almost spherical. As shown in FIG. 12, the magnetic head 1 and the base 2 are sandwiched between the electrode 4 and the electrode 5 in a state where the small projection 2b is abutted against the bottom surface 3a of the shield case 3, and both electrodes 4 are pressed while applying pressure. An electric current is applied between 5 and 5. Due to the electric current flowing at the boundary between the small projection 2b and the bottom surface 3a, this portion generates electric resistance,
This heat melts both members and fixes them together. The reason why the small protrusions 2b are provided is to concentrate the current passing between the shield case 3 and the base 2, but they are generally welded to each other in order to balance the conduction of heat due to electric resistance heating. The small protrusions 2b are formed on one of the members that easily dissipate heat, for example, a member having a large plate thickness.

[0004]

However, the above-mentioned conventional electric resistance welding structure has the following problems. (1) FIG. 13 is an enlarged sectional view showing an abutting portion between the base 2 and the shield case 3. In FIG. 13, a small protrusion 2b is formed on the side of the base 2 having a large thickness. However, since the bottom surface 3a of the shield case 3 is a flat plate, and the small protrusion 2b is abutted against this flat plate portion,
As shown by the isotherm h, the heat generated by the resistance of the abutting boundary portion is likely to accumulate in the small protrusion 2b, but the heat easily escapes in the bottom surface 3a of the shield case 3. , It is difficult to balance the heat between both members. If the distribution of the isotherms h is different due to the difference in heat conduction, the small protrusions 2b are more easily melted than the shield case 3, the range of current that can be welded is narrowed, and sufficient welding strength cannot be secured.

When looking only at the heat balance, it can be improved by enlarging the small protrusions 2b, but if the small protrusions 2b are enlarged, heat easily escapes on the base 2 side, and therefore the current for welding is increased. The amount of heat generation must be increased by increasing the amount. If the amount of heat generation is increased, the temperature of the portion of the shield case 3 other than the welded portion becomes high, the internal core and coil are adversely affected by the heat, and the sliding contact surface of the magnetic tape is distorted. Therefore, the size of the small protrusion 2b cannot be increased at present. Further, when the plate thickness of the base 2 is smaller than the plate thickness of the shield case 3, a small protrusion should be provided on the side of the shield case which is originally large in thickness, but the small protrusion is processed on the shield case 3. Since it is difficult to do so, a small protrusion must be provided on the base 2 side. Therefore, in this case, the heat of the welded portion is more likely to escape on the side of the shield case that does not have the small protrusions, the heat balance cannot be maintained, and the weldable current range is further narrowed.

(2) In the above-mentioned conventional example, the small protrusion 2b provided on the base 2 is flatly butted against the bottom surface 3a of the shield case 3 and welded. Therefore, although it is possible to obtain a certain degree of strength with respect to the force in the pulling direction indicated by F1 in FIG. 13, the welding strength is weak with respect to the force in the shearing direction indicated by F2.

(3) Since the welded portion is sandwiched between the bottom surface 3a of the shield case 3 and the base 2, the welded state cannot be visually inspected from outside, and confirmation after welding cannot be performed.

The present invention solves the above-mentioned problems of the prior art by making it possible to easily balance the heat between the case and the base, to widen the range of current that can be welded, and to obtain sufficient welding strength. It is an object of the present invention to provide a welded structure for electronic equipment parts, which enables the welding process and makes it easy to confirm the welding state.

[0009]

SUMMARY OF THE INVENTION The present invention provides a welded structure of an electronic device component having a conductive case and a conductive base for supporting the same, in which the case is bent. A plurality of protrusions that correspond to the curved surface of the part surface are formed,
The curved surface portion and the projection are electrically resistance welded.

Further, it is preferable that the surface of the projection that is in contact with the curved surface of the case is a curved surface, and that the surface of the projection is a cylindrical surface.

[0011]

In the above means, the curved surface portion of the bent portion surface of the case and the projection of the base are butted against each other and are electric resistance welded. In the bent part of the case, heat is less likely to escape than in the flat part, which makes it easier to balance the heat with the base having protrusions, which widens the range of current values that can be welded and is sufficient. Welding strength can be obtained. Further, since the bent portion of the case is welded to the protrusion of the base, the welding strength against the shearing force in the plane direction of the base also becomes high.

Further, by making the surface of the protrusion a curved surface,
Crushing of the projection surface is less likely to occur during melting due to heat generation by electric resistance, the area of the melting portion can be stabilized, and stable welding strength can be obtained. If the protrusion surface is a cylindrical surface, the cross-sectional area of the protrusion at the contact portion will be the same even if the contact position between the bent portion of the case and the protrusion is different for each protrusion. Therefore, it is possible to obtain a uniform welded state in all welded portions.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the same magnetic head 1 as shown in FIG. 11 is partially shown. In the magnetic head 1, a core and a coil wound around the core are fixed in a shield case 3 with resin. The front surface of the magnetic head 1 is a curved tape sliding contact surface 1a, and a part of the core 1b and a gap portion formed in the core appear on the tape sliding contact surface 1a. The shield case 3 of the magnetic head 1 is formed of a conductive plate material, and has a bottom surface 3a and side surfaces 3a.
The boundary with b is a bent portion 3c. Figure 3 (A)
Shows the bent portion 3c in a perspective view, and in FIG. 2, a sectional view. The shield case 3 is formed by bending or squeezing a flat plate material with a press, and the surface of the bent portion 3c bent from the flat plate is a curved surface portion 3d. The curved surface portion 3d is not necessarily an accurate cylindrical surface, but in FIG. 2 and FIG. 3A, the curved surface portion 3d is described as a cylindrical surface having a constant radius of curvature r for convenience, and in FIG. ), The central axis of the curvature is denoted by the symbol O1.
It shows with.

FIG. 1 shows a base 10 for supporting the magnetic head 1. The base 10 is a conductive metal plate and has a thickness larger than that of the shield case 3. On the surface of the base 10, there are formed four small projections 11 which the curved surface portion 3d of the shield case 3 abuts.

FIG. 3A shows the small protrusion 11 in an enlarged manner. In this embodiment, the contact surface 11a of the small protrusion 11 that abuts the shield case 3 has a radius R indicated by a dotted line.
It is a part of the cylindrical surface of the virtual cylinder. 2 and 3
In (A), the horizontal direction along the surface of the base 10 is indicated by H, and the vertical direction with respect to the surface of the base 10 is indicated by V. The axis O2 of the virtual cylinder is 45 degrees with respect to the horizontal direction H. Standing up at an angle. Therefore, the top portion 11b of the contact surface 11a stands up at an angle of 45 degrees with respect to the surface of the base 10. In the embodiment shown in FIGS. 2 and 3A, the end surface 11c of the small protrusion 11 is a vertical surface extending in the V direction with respect to the surface of the base 10. Curved surface portion 3d which is the surface of the pair of bent portions 3c of the shield case 3.
Is the top 11b of the contact surface 11a of each small projection 11.
Abut. FIG. 2 is a sectional view showing the contact state.

As shown in FIG. 2, the top portion 1 of the contact surface 11a is
Since 1b rises from the surface of the base 10 at an angle of 45 degrees, the central portion Oa of the curved surface portion 3d of the shield case 3 is the top portion when the magnetic head 1 is installed vertically to the base 10. Contact 11b. At this time,
The virtual cylinder axis O2 shown in (A) and the curvature center axis O1 of the curved surface portion 3d of the shield case 3 intersect at an angle of 90 degrees, and the curved surface portion 3d and the top portion 11b are in point contact with each other. Become.

When a current for electric welding is passed between the base 10 and the shield case 3 in the contact state shown in FIG.
The curved surface portion 3d of the shield case 3 and the top portion 1 of the small protrusion 11
Due to the electric resistance of the point contact portion with 1b, this portion generates heat. This heat easily stays in the bent portion 3c of the shield case 3, and the heat is less likely to escape into the shield case 3 as compared with the case where the bottom surface 3a shown in FIG. Therefore, as shown by the isotherm h in FIG. 2, an extreme difference in heat escape between the shield case 3 and the small protrusions 11 is unlikely to occur, and heat balance is facilitated. As shown in FIG. 2, the shield case 3 and the small protrusions 11 form similar isotherms to improve the heat balance, so that no extreme difference occurs in the melting state between the two members to be joined, The range of conditions can be widened and the welding strength can be sufficiently secured.

FIG. 10 shows a case where the shield case 3 is electrically resistance-welded by using the small projection 11 of the above embodiment, and FIG.
1 to FIG. 13, the current supplied and the pulling force (F
The relationship between 1) and welding strength is shown. In electric resistance welding, the welding strength increases almost proportionally as the supply current amount is increased, but at a certain current amount, the welding strength is suddenly increased due to the bombing as shown by the dotted line in FIG. descend. This bombing occurs because the internal heat of the small protrusions 2b or 11 becomes too high and the small protrusions melt to a state in which they cannot be welded.

As shown in FIG. 10, in the conventional example, as indicated by β, the current value I1 leading to bombardment is low. Therefore, the range between the current value I0 and the blast current value I1 for obtaining the required strength is very narrow. On the other hand, in the above-described embodiment, the current value I2 to the bombing is high as indicated by α, and the current value I0 for obtaining the required strength is obtained.
The range from is wide. This means that in the above-mentioned embodiment, the welding conditions can be made wider than in the conventional example, the current value can be easily set, and the welding strength can be made higher than in the conventional example. There is.

The thickness of the shield case 3 depends on the base 10.
Shield case 3 even if it is thicker than
Since the heat escape can be suppressed at the bent portion 3c, the welding conditions can be broadened and the welding strength can be increased as compared with the conventional case. Further, in the above embodiment, for example, 4
Since the small protrusions 11 provided at various locations are welded with the shield case 3 sandwiched from both sides, the pulling direction F
Not only the welding strength for No. 1 but also the strength for the force in the shearing direction indicated by F2 is increased. Further, since the welded portion can be visually observed from the side of the shield case 3, it becomes easy to visually confirm the welded state. The shape of the small protrusions 11 is not always the shape shown in FIG.
It is not limited to that shown in (A). For example, in FIG. 3A, the angle between the axis O2 of the virtual cylinder and the horizontal direction H is 45.
It may be less than 45 degrees or more than 45 degrees.

Further, as shown in FIG. 4A, the end surface 11c of the cylindrical small projection 11 is not perpendicular to the surface of the base 10, but the end surface 11c is a surface perpendicular to the axis O2 of the virtual cylinder. It may be formed in any direction. Further, as shown in FIG. 5 (A), the small protrusion 11 may have a spherical shape.
A conical shape may be used as shown in FIG. Furthermore, FIG.
As shown in (A), the small protrusions 11 may have a triangular pyramid shape. In the method of forming the small protrusions 11 having the above-mentioned shapes,
FIG. 3A, FIG. 5A, FIG. 6A, and FIG.
In the case shown in (A), a die having a recess matching the outer shape of the small projection 11 is applied to the surface of the material of the base 10,
By pressurizing from the back side of the base material with a punch or the like, pressure molding can be easily performed. However, as shown in FIG. 4 (A), in the shape in which the cylinder is projected on the surface of the base 10, the small protrusions 11 cannot be pulled out from the concave portion of the die after the pressure molding by the die, and thus the pressure molding is difficult. . However, as shown by an imaginary line F in the figure, by making only the top portion 11b that the shield case 3 hits a cylindrical shape, the other portions have a shape in which the hem expands toward the surface of the base 10. It becomes possible to perform pressure molding using a die.

As shown in FIGS. 3 (A) to 7 (A), various shapes of the small protrusions 11 are conceivable, but in actual resistance welding, the shape shown in FIG. 5 (A) is larger than that shown in FIG. 7 (A). ) And the shape shown in FIG. 6A are more preferable, and the cylindrical shapes shown in FIGS. 3A and 4A are more preferable. First, Fig. 7
In the triangular pyramid shape shown in (A), since the apex portion 11b that abuts the curved surface portion 3d of the shield case 3 has an angled edge, the welded area with the shield case 3 is extremely large when melted by resistance heating and then cooled and hardened. It becomes easy to change to. That is, the edge-shaped top portion 11b when melted
Since it becomes easy to collapse, the welding area with the shield case varies for each small protrusion, and it becomes impossible to maintain the welding strength constant. In that respect, FIG. 5 (A) and FIG. 6 (A)
In the spherical or conical small projection 11 shown in FIG. 3, the portion corresponding to the shield case has a curved cross-section, so crushing during melting is unlikely to occur, a difference in welding area with the shield case is less likely to occur, and welding strength is stabilized. .

Further, the small projection 11 having the cylindrical surface shown in FIGS. 3A and 4A exerts an even more excellent function than that shown in FIGS. 5A and 6A. That is, for example, the molding positions of the small projections 11 formed at four places naturally have variations in the intersection, and when the shield case 3 is installed on the base 10, the molding positions of the bottom surface 3a of the shield case 3 and It is difficult for the surface of the base 10 to be parallel to the surface of the base 10 with high accuracy, and it is inevitable that the bottom surface 3a is inclined with respect to the surface of the base 10. In this case, the height position where the curved surface portion 3d of the shield case 3 abuts on the top of the small protrusion 11 varies for each small protrusion 11. In FIGS. 3 to 7A, variations in the contact position between the curved surface portion 3d and the small protrusion 11 are indicated by, for example, (a), (b), and (c). Further, in FIGS. 3 to 7B, the small protrusions 1 at the positions of (a), (b), and (c) shown in each figure (A).
The cross section of the contact part 1 of FIG. In FIGS. 3 to 7B, the axis O of the virtual cylinder shown in FIG.
2 shows a state cut along a plane orthogonal to 2.

In the spherical or conical shape shown in FIGS. 5 (A) and 6 (A), when the height position from the base 10 changes as shown in (a) to (c), FIG. ) And FIG. 6
As shown in (B), each position (a) (b)
The area of the cross section (nugget cross section) at the contact portion of the small protrusion 11 in (c) changes. That is, when the position where the curved surface portion 3d of the shield case 3 hits changes, the area of the nugget cross section changes, and the heat escape state and the current concentration state change. Therefore, each small protrusion 1
In No. 1, the welding condition changes at the position where the curved surface portion 3d of the shield case 3 hits, and therefore the strength after welding differs for each small protrusion 11. Shield case 3
When the curved surface portion 3d hits the vicinity of the tip of the spherical or conical small protrusion 11, it becomes difficult for heat to escape inside the small protrusion 11, and the current value leading to bombing becomes low, making it impossible to weld. It may be. This problem also applies to the triangular pyramid-shaped small protrusions shown in FIG. 7A. As shown in FIG. 7B, the height position at which the curved surface portion 3d hits is (a) (b).
If it changes as shown in (c), the area of the nugget cross section changes.

On the other hand, as shown in FIGS. 3A and 4A, when the portion of the shield case 3 which is in contact with the curved surface portion 3d is a cylindrical surface, the height position in which the curved surface portion 3d is in contact is ( In any of the cases of (a), (b), and (c), the area of the nugget cross section of the small protrusion 11 at each location does not change (see FIGS. 3B and 4B). Therefore, even if the position where the curved surface portion 3d abuts on each small protrusion 11 varies, the welding conditions do not change and the welding strength also becomes constant.

Next, a method of resistance welding between the base 10 having the small protrusion 11 having any of the above shapes and the shield case 3 will be described. As a method of electric resistance welding, first, refer to FIG.
Similarly to the conventional example shown in FIG. 2, with the shield case 3 and the base 10 of the magnetic head 1 abutting each other, the entire shield case 3 and the base 10 are vertically sandwiched between the electrodes 4 and 5, It is possible to weld the curved surface portion 3d of the shield case 3 and the small protrusion 11 by applying an electric current.

The welding method shown in FIGS. 8 and 9 is also possible. In this method, circular holes 12 are formed in the base 10 at, for example, four central positions of the small protrusions 11 arranged in the center. The magnetic head 1 is turned upside down and held in a stable state by using a jig on a work table (not shown). Then, the base 10 is set on the bottom surface 3a of the shield case 3 with the small protrusions 11 facing downward, and the top portions 11b of the small protrusions 11 are abutted against the curved surface portions 3d of the bent portions 3c of the shield case 3.
Then, the electrode 21 is put in the hole 12 and abutted on the bottom surface 3a of the shield case 3, and the electrode 22 is located on the back surface of the base 10 (top surface shown in FIGS. 8 and 9), preferably right above the small protrusion 11. Apply to. When an electric current is passed between the electrodes 21 and 22, the electric current reaches the electrode 22 from the bottom surface 3a of the shield case 3 through the bent portion 3c, the small protrusion 11 and the base 10. In this method, since no current flows in the shield case 3 other than the bottom surface 3a, the shield case 3
As a whole, heat is not generated, the internal core and the coil are not affected by heat, and it is possible to prevent distortion of the tape sliding contact surface due to heat.

Further, the welding structure of the present invention is not limited to the magnetic head, but can be carried out in the welding operation of various parts having a case having a bent portion and the base.

[0029]

As described above, according to the invention of claim 1,
The curved surface of the bent part of the case and the projection of the base are abutted against each other for electrical resistance welding, so it is difficult for heat to escape at the bent part of the case, and the case and the base having the projection are It becomes easier to balance the heat between them, the range of current value that can be welded can be widened, and sufficient welding strength can be obtained. Further, since the bent portion of the case is welded to the protrusion of the base, the welding strength against the shearing force in the plane direction of the base also becomes high. In addition, it becomes easier to see the welded part.

According to the second aspect of the present invention, by forming the surface of the protrusion into a curved surface, the protrusion surface is less likely to be crushed during melting due to heat generation by electric resistance, and the welded area can be stabilized.

According to the third aspect of the present invention, since the projection surface is a cylindrical surface, even if the contact position between the bent portion of the case and the projection differs for each projection, the disconnection of the projection at this contact portion Since the area is constant, it is possible to obtain a uniform welded state in all welded parts.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a welding structure of a magnetic head and a base as one embodiment of the present invention,

FIG. 2 is an enlarged sectional view showing a welded portion in the embodiment of FIG.

FIG. 3A is an enlarged perspective view showing a bent portion of a case and a small protrusion of a base, and FIG. 3B is a sectional view showing a nugget cross section at each position of the small protrusion;

FIG. 4A is a perspective view showing a small protrusion having a cylindrical surface according to another embodiment, and FIG. 4B is a sectional view showing a nugget cross section at each position of the small protrusion.

FIG. 5A is a perspective view showing a small projection having a spherical surface;
(B) is a sectional view showing a nugget section at each position of the small protrusions,

FIG. 6A is a perspective view showing a conical small protrusion,
(B) is a sectional view showing a nugget section at each position of the small protrusions,

FIG. 7A is a perspective view showing a triangular pyramid-shaped small protrusion;
(B) is a sectional view showing a nugget section at each position of the small protrusions,

FIG. 8 is a perspective view showing an example of welding work,

9 is a sectional view showing the welding operation of FIG. 8;

FIG. 10 is a diagram showing the relationship between the supply current and the welding strength in the example of the present invention and the conventional example;

FIG. 11 is an exploded perspective view showing a welding structure of a conventional magnetic head and a base,

FIG. 12 is a front view showing a conventional welding operation,

FIG. 13 is an enlarged cross-sectional view showing a conventional welded portion,

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magnetic head 3 shield case 3a bottom surface 3c bent portion 3d curved surface portion 10 base 11 small protrusion 11a contact surface 11b top 12 holes 21 and 22 welding electrodes

Claims (3)

[Claims] 1. In a welded structure of an electronic device component having a conductive case and a conductive base for supporting the electronic component, the base has a plurality of curved portions on the surface of the bent portion of the case. A welding structure for electronic device parts, wherein a projection is formed, and the curved surface portion and the projection are electrically resistance welded. 2. The welded structure for electronic device parts according to claim 1, wherein the surface of the protrusion that is in contact with the curved surface of the case is a curved surface. 3. The welding structure for electronic device parts according to claim 1, wherein the surface of the projection that is in contact with the curved surface of the case is a cylindrical surface.