JP2980490B2 - Welding structure of electronic equipment parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric device in which an electronic device component having a conductive case, such as a magnetic head, is brought into contact with a projection provided on a conductive base. The present invention relates to a welding structure of resistance-welded electronic device parts.

[0002]

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

In the conventional electric resistance welding process, the bottom surface 3a of the shield case 3 of the magnetic head 1
Small projection 2 called projection on the part facing
b is formed in plurality. The small projections 2b are bulged in a pressing process, and have a substantially spherical surface. As shown in FIG. 12, the magnetic head 1 and the base 2 are sandwiched between the electrodes 4 and 5 with the small projections 2b abutting against the bottom surface 3a of the shield case 3, and the two electrodes 4 are pressed while being pressed. 5 and a current is applied. This portion generates electric resistance due to current flowing at the boundary of the abutting portion between the small protrusion 2b and the bottom surface 3a,
Both members are melted by this heat and adhere to each other. The reason why the small projections 2b are provided is to concentrate the current passing between the shield case 3 and the base 2, but are generally welded to each other in order to balance heat conduction due to electric resistance heating. The small projections 2b are formed on a member having a large thickness, for example, a member having a large thickness, which is easy to release heat.

[0004]

However, the above-described conventional electric resistance welding structure has the following problems. (1) FIG. 13 is an enlarged cross-sectional view of the abutting portion between the base 2 and the shield case 3. In FIG. 13, a small projection 2b is formed on the side of the base 2 having a large thickness. However, 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 tends 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 heat between the two members. If the distribution of the isotherm h is different due to this difference in heat conduction, the small projections 2b are more easily dissolved than the shield case 3, the range of the current that can be welded is narrowed, and sufficient welding strength cannot be secured.

In view of the heat balance alone, improvement can be achieved by enlarging the small projections 2b. However, if the small projections 2b are enlarged, heat can easily escape on the base 2 side. We need to increase the amount of heat generated. When the amount of heat generation is increased, the temperature of the portion other than the welded portion of the shield case 3 becomes high, which adversely affects the internal core and coil due to heat, and also causes the sliding surface of the magnetic tape to be distorted. Therefore, at present, the size of the small protrusion 2b cannot be increased. In addition, when the plate thickness of the base 2 is smaller than the plate thickness of the shield case 3, small projections should be provided on the shield case side where the plate thickness is large. Therefore, it is necessary to provide a small projection on the base 2 side. Therefore, in this case, the heat of the welded portion is more easily released on the shield case side having no small protrusion, the heat balance is not maintained, and the current range that can be welded is further narrowed.

(2) In the conventional example, the small projections 2b provided on the base 2 are welded to the bottom surface 3a of the shield case 3 in a flat manner. Therefore, it is possible to obtain a certain level of strength in the pulling direction indicated by F1 in FIG. 13, but the welding strength is weaker 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 welding state cannot be visually observed from outside and cannot be confirmed after welding.

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and it is possible to easily balance the heat between a case and a base to widen a range of a weldable current and obtain a sufficient welding strength. It is an object of the present invention to provide a welding structure for electronic device parts that can be easily checked and a welding state can be easily checked.

[0009]

According to the present invention, there is provided a welding structure of an electronic device component having a conductive case and a conductive base supporting the same, wherein the base has a bent case. A plurality of protrusions that hit the curved surface of the part surface are formed,
The curved surface portion and the projection are electrically resistance welded.

[0010] Further, it is preferable that the projection surface corresponding to the curved surface portion of the case is a curved surface, and it is further preferable that the projection surface is a cylindrical surface.

[0011]

In the above means, the curved surface of the bent portion of the case and the projection of the base are abutted against each other and subjected to electric resistance welding. In the bent part of the case, the heat is hard to escape compared to the flat part, so that the heat balance between the base and the base having the projections is easy to take, the range of the current value that can be welded is widened, and the sufficient Welding strength can be obtained. Further, since the bent portion of the case is welded to the projection of the base, the welding strength against the shear force in the planar direction of the base is also increased.

Further, by making the surface of the projection a curved surface,
The projection surface is less likely to be crushed during melting by electric resistance heat generation, so that the area of the melting portion can be stabilized, and stable welding strength can be obtained. Further, if the surface of the projection is a cylindrical surface, the cross-sectional area of the projection at the contact portion becomes the same for each projection even if the contact position between the bent portion of the case and the projection is different for each projection. Therefore, a uniform welding state can be obtained in all the welded portions.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 partially shows the same magnetic head 1 shown in FIG. The magnetic head 1 has a core and a coil wound around the core fixed with resin in a shield case 3. 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 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, and has a bottom surface 3a and side surfaces 3a.
The boundary with b is a bent portion 3c. FIG. 3 (A)
Shows a perspective view of the bent portion 3c, and FIG. 2 shows a cross-sectional view. The shield case 3 is formed by bending or squeezing a flat plate material by a press. The surface of the bent portion 3c bent from the flat plate becomes a curved surface portion 3d. Although the curved surface portion 3d is not always an accurate cylindrical surface, in FIGS. 2 and 3A, the curved surface portion 3d is described as a cylindrical surface having a constant radius of curvature r for convenience. ), The center axis of the curvature is denoted by O1.
Indicated by.

FIG. 1 shows a base 10 for supporting the magnetic head 1. The base 10 is a conductive metal plate and has a size larger than the plate thickness of the shield case 3. On the surface of the base 10, four small projections 11 are formed so as to project on the curved surface 3 d of the shield case 3.

FIG. 3A shows the small projection 11 in an enlarged manner. In this embodiment, the contact surface 11a of the small projection 11 which contacts the shield case 3 has a radius R indicated by a dotted line.
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, but the axis O2 of the virtual cylinder is at 45 degrees with respect to the horizontal direction H. Standing at an angle. Therefore, the top 11b of the contact surface 11a rises 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 projection 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 a pair of bent portions 3c of 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 1 of the contact surface 11a
1b rises at an angle of 45 degrees from the surface of the base 10, and when the magnetic head 1 is installed perpendicular to the base 10, the central portion Oa of the curved surface portion 3d of the shield case 3 is at the top. 11b. At this time, FIG.
The axis O2 of the virtual cylinder shown in (A) and the center axis O1 of curvature of the curved surface 3d of the shield case 3 intersect at an angle of 90 degrees with each other, and the curved surface 3d and the top 11b are in point contact with each other. Become.

When a current for electric welding is applied between the base 10 and the shield case 3 in the contact state shown in FIG.
The curved surface 3d of the shield case 3 and the top 1 of the small projection 11
This portion generates heat due to the electric resistance of the point contact portion with 1b. This heat tends to stay 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 an isotherm h in FIG. 2, an extreme difference in heat escape between the shield case 3 and the small projections 11 is less likely to occur, and heat balance is easily achieved. As shown in FIG. 2, a similar isotherm is formed between the shield case 3 and the small protrusion 11 to improve the heat balance, so that no extreme difference occurs in the melting state between the two members to be joined, and the welding is performed. The range of conditions can be widened, and sufficient welding strength can be ensured.

FIG. 10 shows the case where the shield case 3 is subjected to electric resistance welding using the small projections 11 of the above embodiment, and FIG.
The supply current and the pulling force (F) when electric resistance welding is performed using the conventional small projections 2b shown in FIGS.
The relation between 1) and the welding strength is shown. In electric resistance welding, as the supply current is increased, the welding strength increases almost proportionally. However, at a certain current, the welding strength is reduced by a burst as shown by the dotted line in FIG. descend. This explosion is caused by the internal heat of the small projections 2b or 11 becoming too high and melting the small projections to a state where welding is impossible.

As shown in FIG. 10, in the conventional example, as indicated by β, the current value I1 leading to the explosion is low. Therefore, the range between the current value I0 and the explosion current value I1 for obtaining the required strength is very narrow. On the other hand, in the above embodiment, as indicated by α, the current value I2 leading to the explosion is high, and
The range from is wide. This means that in the above 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. I have.

The thickness of the shield case 3 is
Even if the thickness is larger than the thickness of the shield case 3,
Since the escape of heat can be suppressed at the bent portion 3c, welding conditions can be broadened and welding strength can be increased as compared with the conventional case. Further, in the above embodiment, for example, 4
Since the small projections 11 provided at two locations are welded so as to sandwich the shield case 3 from both sides, the pulling direction F
In addition to the welding strength for No. 1, the strength against the force in the shear direction indicated by F2 also increases. Further, since the welded portion can be viewed from the side of the shield case 3, it is easy to visually confirm the welding state. The shape of the small protrusion 11 is not necessarily the shape shown in FIG.
It is not limited to the one shown in FIG. For example, in FIG. 3A, the angle between the virtual cylinder axis O2 and the horizontal direction H is 45 degrees.
The angle may be less than 45 degrees or more than 45 degrees.

As shown in FIG. 4A, the end face 11c of the small cylindrical projection 11 is not perpendicular to the surface of the base 10, and the end face 11c is 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 projection 11 may have a spherical shape.
The shape may be conical as shown in FIG. Further FIG.
As shown in (A), the small protrusion 11 may have a triangular pyramid shape. The method of forming the small projections 11 of the above shapes is as follows.
3 (A), 5 (A), 6 (A), and 7
In the one shown in (A), a die having a concave portion corresponding to the outer shape of the small projection 11 is applied to the surface of the material of the base 10,
Pressing from the back side of the base material with a punch or the like enables easy press forming. However, as shown in FIG. 4A, in the case where the cylinder protrudes from the surface of the base 10, the small projections 11 cannot be pulled out from the recesses of the dies after the pressure molding by the dies, so that the pressure molding is difficult. . However, as shown by an imaginary line F in the same figure, only the top portion 11b where the shield case 3 hits is made cylindrical, and the other portions are formed so that the skirt spreads toward the surface of the base 10. Pressure molding using a die becomes possible.

As shown in FIGS. 3A to 7A, various shapes of the small projections 11 can be considered, but in actual resistance welding, the shape of the small projections 11 is larger than that shown in FIG. 7A. ) And the shape shown in FIG. 6A are more preferable, and the cylindrical shape shown in FIGS. 3A and 4A is more preferable. First, FIG.
In the triangular pyramid shape shown in (A), since the top portion 11b corresponding to the curved surface portion 3d of the shield case 3 is a square edge, the melting area with the shield case 3 becomes extremely small when cooled and hardened after melting by resistance heating. It is easy to change. That is, when melted, the edge-shaped top 11b
Is easily crushed, so that the welding area with the shield case varies for each of the small projections, making it impossible to maintain a constant welding strength. In that regard, FIGS. 5 (A) and 6 (A)
In the spherical or conical small projections 11 shown in (1), since the cross section of the portion corresponding to the shield case is a curved surface, collapse during melting is unlikely to occur, and a difference in welding area with the shield case is unlikely to occur, and welding strength is stabilized. .

The small projection 11 having a cylindrical surface shown in FIGS. 3A and 4A exhibits a function more excellent than those shown in FIGS. 5A and 6A. That is, for example, the molding positions of the small protrusions 11 formed at four locations naturally vary within the intersection, and when the shield case 3 is installed on the base 10, the bottom surface 3a of the shield case 3 It is difficult for the surface of the base 10 to be parallel to the surface of the base 10 with high precision, and it is inevitable that the bottom surface 3a is installed to be inclined with respect to the surface of the base 10. In this case, the height position at which 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. 3A 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 projections 1 at the positions (A), (B), and (C) shown in FIGS.
1 shows a cross section of a contact portion. In FIGS. 3 to 7B, the axis O of the virtual cylinder shown in FIG.
2 shows a state of being cut by a plane orthogonal to 2.

In the spherical or conical shapes shown in FIGS. 5A and 6A, when the height position from the base 10 changes as shown in FIGS. ) And FIG.
As shown in (B), each position (a) (b)
In (c), the area of the cross section (nugget cross section) at the contact portion of the small projection 11 changes. That is, when the position where the curved surface portion 3d of the shield case 3 contacts changes, the area of the nugget cross section changes, and the state of heat dissipation and the state of current concentration change. Therefore, each small projection 1
In 1, the welding conditions at the position where the curved surface portion 3 d of the shield case 3 comes into contact change, and therefore, the strength after welding differs for each small projection 11. Also shield case 3
When the curved surface portion 3d hits near the tip of the spherical or conical small projection 11, heat escape in the small projection 11 is less likely to occur, and the current value leading to the explosion is reduced, making welding impossible. Sometimes. This problem is the same in the triangular pyramid-shaped small protrusion shown in FIG. 7A, and as shown in FIG. 7B, the height position where 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. 3 (A) and 4 (A), when the curved surface 3d of the shield case 3 is a cylindrical surface, the height position of the curved surface 3d is ( In any of the cases (a), (b) and (c), the area of the nugget cross section of the small projection 11 at each position does not change (see FIGS. 3B and 4B). Therefore, even if there is a variation in the position where the curved surface portion 3d contacts each of the small projections 11, the welding conditions are not changed and the welding strength is constant.

Next, a method of resistance welding between the base 10 having the small projections 11 having any one of the above shapes and the shield case 3 will be described. As a method of electric resistance welding, first, FIG.
2, the entire shield case 3 and the base 10 are sandwiched between the electrodes 4 and 5 from above and below, with the shield case 3 of the magnetic head 1 and the base 10 abutting against each other. It is possible to weld the curved 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, a circular hole 12 is formed in the base 10 at, for example, an arrangement center position of four small protrusions 11. The magnetic head 1 is held upside down by using a jig on a work table (not shown) in a stable state. Then, the base 10 is placed on the bottom surface 3a of the shield case 3 with the small projections 11 facing downward, and the top 11b of each small projection 11 is abutted against the curved surface 3d of the bent portion 3c of the shield case 3.
Then, the electrode 21 is inserted into the hole 12 and is brought into contact with the bottom surface 3a of the shield case 3, and the electrode 22 is positioned on the back surface of the base 10 (the upper surface shown in FIGS. 8 and 9), preferably just above the small projection 11. Guess. When a current flows between the electrodes 21 and 22, the current passes through the small projection 11 and the base 10 from the bottom surface 3 a of the shield case 3 through the bent portion 3 c and reaches the electrode 22. In this method, no current flows in the shield case 3 other than the bottom surface 3a.
The entire body does not generate heat, does not affect the internal core and coil, and prevents the tape sliding contact surface from being distorted due to the heat.

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

[0029]

As described above, according to the first aspect of the present invention,
Since the curved surface portion of the bent portion surface of the case and the projection of the base are abutted and subjected to electric resistance welding, heat is difficult to escape at the bent portion of the case, and the case and the base having the projection are connected. The heat balance can be easily maintained, the range of the 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 projection of the base, the welding strength against the shear force in the planar direction of the base is also increased. Further, the welded portion can be easily observed.

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

According to the third aspect of the present invention, since the surface of the projection is a cylindrical surface, even if the contact position between the bent portion of the case and the projection is different for each projection, breakage of the projection at this contact portion is possible. The area becomes constant, and an even welding state can be obtained in all the welded portions.

[Brief description of the 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.

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

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

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

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

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

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

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

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

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

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

FIG. 13 is an enlarged sectional view showing a conventional weld.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic head 3 Shield case 3a Bottom surface 3c Bent part 3d Curved surface part 10 Base 11 Small protrusion 11a Contact surface 11b Top part 12 hole 21,22 Welding electrode

Continuation of the front page (56) References JP-A-2-244527 (JP, A) JP-A-58-26728 (JP, A) JP-A-63-9603 (JP, A) JP-A-54-168823 (JP, A) , U) Hikaru 4-87166 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 11/00 562 B23K 11/14

Claims (3)

(57) [Claims] In a welding structure of an electronic device component having a conductive case and a conductive base supporting the electronic device component, the base has a plurality of bent portions of a surface of a 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 subjected to electric resistance welding. 2. The welding structure for an electronic device part according to claim 1, wherein the surface of the projection that hits the curved surface of the case is a curved surface. 3. The welding structure for electronic device parts according to claim 1, wherein the projection surface corresponding to the curved surface portion of the case is a cylindrical surface.