JPH11162308A - Reed switch, manufacture thereof, manufacture of reed used for the switch and manufacturing device of reed - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reed switch which has similar structural sizes, electric characteristics and life characteristics as conventional products and also has an excellent shock-resistant property, and which can be manufactured with existent facilities, and provide a manufacturing method thereof, a manufacturing method of a reed used for that, and a manufacturing device thereof. SOLUTION: In the reed switch which is equipped with a pair of reeds 1 comprising a magnetic material equipped integrally with a contact part 3 at the tip, a movable part 4 successive to the contact part 3, and a support part 5 successive the movable part 4 and supporting the movable part 4, and also with a sealing member sealing the contact parts 3 of the pair of the reeds 1 respectively facedly, and which is composed as the contact parts 3 are contacted or released corresponding to the magnetic field applied to the reeds 1, respective reeds 1 are so formed that the thickness thereof is gradually increased as a boundary part 6 between the movable part 4 and the support part 5 is faced from the movable part 4 toward the support part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reed switch used as various sensors in various fields such as communication equipment and automobiles, a method of manufacturing the same, a method of manufacturing a lead used therein, and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art Reed switches are used as various sensors because of their small size, high-speed operation, and sealed type, and are highly reliable without being affected by the external atmosphere. They are used in various fields such as communication equipment and automobiles. ing. With the expansion of such applications, demands for reed switches having more excellent impact resistance have increased.

Here, the reed switch was manufactured in 1936 by Bell Labs, USA. B. Invented by Ellwood. The history of its development began when it was used in 1938 as a switch for a coaxial carrier. In Japan, since the research and development for telephone exchanges began in 1956, various features of reed switches have been recognized, and the company has established a solid position as a component for electronic equipment. At present, it is used in various fields such as communication devices, information processing systems, and automobiles as relays for mounting various sensors and boards because of its small size, high-speed operation, and sealed type, which are highly reliable without being affected by the external atmosphere. ing.

[0004] With the expansion of such applications, long life, environmental resistance and miniaturization of reed switches have been required. One of the requirements is to improve the impact resistance of reed switches. For the development of reed switches with excellent impact resistance, analysis of the elasticity and plasticity of reeds is an important issue.

FIG. 15 is a diagram showing an example of the configuration of a conventional reed switch. As shown in FIG. 15, the reed switch 50 is a reed switch 50 formed by molding a magnetic material with a press machine.
One of the contact portions 53 is provided with contact plating, two are opposed to each other, and are set so as to have a predetermined gap amount and an overlap amount.
It is sealed inside. An inert gas, for example, nitrogen 58 is injected into the glass tube 52 so that the contact performance does not change during operation.

FIG. 16A is a cross-sectional view showing a press forming apparatus for manufacturing the lead 51, and FIG. 16B is an enlarged cross-sectional view of a portion D1 and D2 in FIG.
FIG. 16C is a partial plan view showing a main part of a lead manufactured by the device shown in FIG.

Referring to FIG. 16A, the press forming apparatus includes an upper die 61 and a lower die 62, and the opposing surfaces of the upper and lower dies 61 and 62 are formed in the shape of the lead 51 to be manufactured. Corresponding concave and convex portions are formed.

As shown in FIG. 16B, a flat tapered surface is formed corresponding to the tapered shape of the boundary portion 56 between the movable portion 54 and the support portion 55 of the lead to be formed.

As shown in FIG. 16C, the boundary portion 56 of the lead is formed so that its width gradually becomes smaller as it moves from the support portion 55 to the movable portion 54.

FIG. 17 is a diagram for explaining the operation of the reed switch shown in FIG. Referring to FIG. 17, in the reed switch 50, when a magnetic field is applied to the outside of the reed switch 50 using a coil or a permanent magnet 70, the magnetic field causes the reed 51, which is a ferromagnetic material, to face the opposite reed switch.
The leads are magnetized so as to have different poles (N pole and S pole), and a magnetic attraction force is generated in the overlap portions (contact portions) 53, 53, and the magnetic attraction force is greater than the separation force of the lead 51. When it is large, it turns on. When the externally applied magnetic field is removed, the magnetic attraction of the overlap portions 53 and 53 disappears and the lead 51 is turned off by the separating force.

FIG. 18 is a perspective view schematically showing a contact portion 53 of the reed switch shown in FIG. The operation principle of the reed switch will be described in more detail with reference to FIG.
The operation of the reed switch is determined by the characteristics of the magnetic attraction force acting on the leads 51, 51 and the elasticity of the leads 51, 51 while maintaining the predetermined gap x.
In order for the reed switch to be turned on, a relationship of F ≧ Fr is a necessary condition between the magnetic attraction force F and the separation force Fr.
The magnetic attractive force F is given by the following equation (1).

[0012]

(Equation 1)

Where Φ is a magnetic flux,
x is magnetic gap, A is overlap, H is lead 5.
1, B is the width of the lead 51, c is a coefficient determined by X / A, H / B, and is an empirical formula c = (6.66 + 44.4H).
/ B) / A. The separating force Fr is given by the following equation (2).

[0014]

(Equation 2) Here, S is stiffness and x is a contact gap.

Assuming that the contact gap when the reed switch is OFF is Xoff, the separating force Fr for an arbitrary contact gap x is given by the following equation (3).

[0016]

(Equation 3)

FIG. 19 is a diagram showing the relationship between the magnetic attraction force curve for the contact gap and the separating force. As shown in FIG. 19, here, the relationship between the contact gap and the separating force is called a reed switch load curve. When the coil current is zero,
Neither the magnetic attraction force nor the separating force works, but when the current is increased, the magnetic attraction force changes from F _{1 to} F ₂ . For F _1, for any contact gap x, but the x = X ₁ in F ₁ = Fr, the x <X ₁ F ₁ <Fr becomes the reed switch does not turn ON.

[0018] When the F _2, the x = X _0, is in contact is a load curve magnetic attraction force, x <X ₀ in F _1> Fr next reed switch turned ON. Since the contact force Fc when the contact is turned on is represented by Fc = F−Fr, the contact force at the reed switch ON point is given by the following equation (4).

[0019]

(Equation 4)

[0020]

Here, the problem of the prior art will be described with respect to impact resistance. If an excessive impact is applied to the reed switch, the reed will undergo plastic deformation,
The contact gap changes, and the initial moving current value cannot be maintained. Here, the moving current value is the current value when the contact is operated (OFF '→ ON) by placing the reed switch in the standard coil and gradually increasing the coil current, and the moving current value is determined by the change in the contact gap. Changes, for example,
When a reed switch and a magnet are combined, the operating distance may change or the state may not be turned on, and the function as a sensor may not be achieved. Therefore, in order to improve the shock resistance of the reed switch, it is important to analyze the elastic and plastic deformation of the reed switch. In an elastically deformed castle, by increasing the stiffness, the rigidity is increased and the impact resistance can be improved. However, the magnetic attractive force F ≧ the separating force Fr, and the contact force Fc at the ON point.
There is a constraint condition o, and simply increasing the stiffness cannot satisfy the function as a switch.

For the plastic deformation region, it is necessary to increase the cross-sectional area of the joint where the bending stress is concentrated, so as to minimize the displacement of the lead, that is, the change in the contact gap in the case of plastic deformation. Therefore, it is necessary to design a mold for that purpose.

In particular, when an excessive impact is applied to the reed switch when mounting the board or dropping the board, the lead may be plastically deformed by an inertial force, and the initial moving current value may not be maintained.

Therefore, a general technical problem of the present invention is to
An object of the present invention is to provide a reed switch having the same structural dimensions, electrical characteristics, and life characteristics as conventional products and having excellent impact resistance, and a method of manufacturing the same.

It is another general technical object of the present invention to provide a reed switch that can be manufactured with existing equipment and a method of manufacturing the same.

It is still another general technical object of the present invention to provide a method of manufacturing a lead used in the reed switch and an apparatus for manufacturing the lead for implementing the method.

Further, specific technical problems of the present invention are:
Clarify the relationship between lead shape and stiffness, change the shape of the press die, and reduce the reduction in area where the maximum bending stress is concentrated. An object of the present invention is to provide a switch, a manufacturing method thereof, a lead used for the reed switch, and an apparatus for manufacturing the lead.

[0027]

Means for Solving the Problems The inventors of the present invention have conducted resilient and plastic mechanical analyzes of the reeds constituting the reed switch, clarified the relationship between the reed shape and the impact resistance, and obtained a press. By changing the shape of the mold, we have found the optimum conditions to reduce the area reduction rate at the part where bending stress is concentrated. As a result, the impact resistance was about 2 times that of the conventional product.
As a result, it is possible to manufacture a lead having the same characteristics as those of the conventional product with respect to other electrical characteristics and life characteristics.

That is, according to the present invention, a contact portion is provided at the tip,
A pair of leads made of a magnetic material integrally provided with a movable portion continuous with the contact portion and a support portion supporting the movable portion continuously with the movable portion, and the contact portions of the pair of leads are respectively provided. A reed switch comprising an enclosing member for enclosing the reed and facing the contact portion, wherein the reed switch is configured to contact or open the contact portion in accordance with a magnetic field applied to the reed. The reed switch is formed so as to increase in thickness in a stepwise manner as the boundary between the movable portion and the support portion moves from the movable portion to the support portion.

According to the present invention, in the reed switch, the boundary portion is formed so as to decrease in width as it moves from the movable portion to the support portion. Is obtained.

According to the present invention, a contact portion is provided at the tip,
A movable part continuous with the contact part, and a movable part continuous with the movable part,
In a method of manufacturing a reed encapsulated in a reed switch having a support portion for supporting the movable portion, a bar made of a magnetic material is used to move a boundary between the support portion and the movable portion from the movable portion to the support portion. A lead manufacturing method is characterized in that a lead is formed by increasing the thickness in a stepwise manner toward the lead.

According to the present invention, there is provided a reed switch characterized in that a pair of leads obtained by the above-mentioned lead manufacturing method are prepared, the respective contact portions of the leads are opposed to each other, and sealed by a sealing member. Is obtained.

Further, according to the present invention, a contact portion enclosed at the tip of the reed switch, a movable portion continuous with the contact portion, and a support portion continuous with the movable portion and supporting the movable portion are provided. In a lead manufacturing apparatus for press-molding a bar-shaped magnetic material between a pair of dies, the boundary between the movable part and the support part has a stepped thickness. The lead manufacturing apparatus is characterized in that opposing portions corresponding to the boundary portions of the pair of dies are formed in a step-like shape so as to increase the size of the lead.

[0033]

Embodiments of the present invention will be described below.

FIG. 1 is a diagram showing a schematic structure of a reed switch according to an embodiment of the present invention. Referring to FIG.
The reed switch 10 includes a pair of leads 1 made of a magnetic material, and a glass tube 2 filled with the ends of the leads 1 facing each other so that the other ends of the leads 1 extend in opposite directions. Have. Each lead 1 integrally includes a contact portion 3 formed at the tip, a movable portion 4 having a spring property continuous with the contact portion 3, and a support portion 5 continuous with the movable portion 4. . The above-described schematic configuration has substantially the same configuration as that according to the related art.

However, in the reed switch according to the embodiment of the present invention, the shape of the reed 1 is different from that of the prior art.

FIG. 2A is a partially enlarged plan view of the lead 1 of FIG. FIG. 2B is an enlarged plan view of a portion A in FIG. 2A. As shown in FIG.
At the end of the boundary 6 between the movable part 4 and the support part 5,
The width is gradually increased from the support portion 5 toward the movable portion 4 and the thickness is increased stepwise from the support portion 5 to the movable portion 4.

Further, as shown in FIG.
The increase in the width from the moving part 4 to the movable part 4
Is clearly larger than that of the prior art shown in FIG.

FIG. 3A is a view showing a mold portion of a press molding apparatus for manufacturing the lead shown in FIGS. FIG. 3 (b) shows the mold C shown in FIG. 3 (a).
It is an expanded sectional view which shows 1 and C2 part. As shown in FIG. 3A, the press mold 20 is composed of an upper mold 21 and a lower mold 2.
2 and a lead 1 as shown in FIG.
The opposing portions 23 and 24 of the mold forming the boundary 6 between the supporting portion 5 and the movable portion 4 are formed so as to have a step-shaped cross section, respectively. I do.

Next, characteristics of the reed switch according to the embodiment of the present invention were investigated.

First, the influence of the shape of the lead piece on the impact resistance was examined. We examined the shape of the reed, which is considered to have the strongest effect on the impact characteristics of the reed switch.

FIGS. 4A and 4B are a plan view and a front view for explaining the operation analysis of the reed switch similar to FIG. As shown in FIG. 4, in the case of a reed switch, the reed piece 1 is composed of a contact portion 3 and a movable portion 4. The contact portion 3 is configured to be two-stage crushed in order to secure a magnetic attraction force and to secure a constant stiffness for the movable portion 4.

(Analysis of Operation in Elastic Deformation Area) First, the operation of the reed switch in the elastic deformation area was analyzed.

As shown in FIGS. 4 (a) and 4 (b), an elastic deformation region where a reed switch is displaced when a reed switch is subjected to a certain impact and the reed is reed in the glass tube 2 is displaced. The analysis was performed as a cantilever beam. I
Is the secondary moment of area, the stiffness S of the lead piece is given by the following equation (5).

[0044]

(Equation 5) Here, in the equation (5), E is Young's modulus, I is when the width of the lead pieces B, and thickness of the H, given by BH ^3/12.

FIG. 5 is a diagram showing the relationship between lead length and stiffness, and FIG. 6 is a diagram showing the relationship between thickness and stiffness. As shown in FIGS. 5 and 6, the stiffness can be increased by shortening the length of the lead piece or increasing the thickness. That is, the impact resistance can be improved by increasing the rigidity of the lead and reducing the amount of displacement with respect to a constant load in the elastic deformation region.

(Operation Analysis of Plastic Deformation Region) Next, operation analysis of the plastic deformation region of the lead was performed. Specifically, when the reed switch receives an external impact that causes plastic deformation, an operation analysis in the plastic deformation region was performed in order to minimize the amount of displacement of the reed. Regarding the stress caused by the bending moment of the beam, the maximum bending stress σ when a load is applied to the tip of the beam is given by the following equation (6), and is determined by the bending moment and the section modulus.

[0047]

(Equation 6) Here, in Equation 6, M is a bending moment, and Z is a section modulus.

On the other hand, the maximum bending stress when the beam receives an impact is as follows. When an object having a weight Wo falls freely from a height h and collides with a beam having a weight W and a length L, the maximum deflection Wmax and the maximum bending stress σmax of the beam, and the static deflection Ws and the static stress σs due to the load Wo.
Is given by the following equation (7).

[0049]

(Equation 7)

Where K is κ = W / W.
It is a constant determined by o. According to the above equation (7), when the drop height h is small, the deflection and the stress are about twice the static values, and h / Ws> 1, that is, in a state where the deflection amount of the beam is very small. It is given by equation (8).

[0051]

(Equation 8)

Here, Cb ₂ = EIg / ρA, and Eb
I, Z, A, ρ, and g are the bending stiffness of the beam, the section modulus, the cross-sectional area, the weight per unit area, and the gravitational acceleration, respectively. The maximum bending stress is almost proportional to the collision velocity V ₀ = (2gh) ^1/2 and is independent of the beam length. Here, the maximum bending stress generally occurs at the fixed end, but in the case of a reed switch, it occurs near the seam between the flat part of the reed and the tapered part, and by increasing the section modulus in the above equation (8). The maximum bending stress can be reduced.

Next, specific measures for leads and evaluation results according to the embodiment of the present invention will be described.

(Improvement of stiffness due to increase in thickness of lead piece) As described above, improvement in stiffness due to increase in thickness of the lead piece largely depends on the length of the lead piece and the thickness of the lead piece. Cause. However,
As described in (Plastic deformation region motion analysis), in the plastic deformation region, the bending stress is independent of the beam length.
It takes a constant value irrespective of the support state of the beam. Therefore, the stiffness was improved by changing the thickness of the lead pieces.

FIG. 7 is a diagram showing the relationship between the stiffness and the on-off ratio. As shown in FIG. 7, the stiffness of the reed switch is about 300 kgf / m from the electrical characteristic of the on-off ratio (ON / OFF).
It is necessary to:

Next, a description will be given of a reduction in the area reduction rate by changing the shape of the press die according to the embodiment of the present invention.

In the case of a reed switch, the concentration of the maximum bending stress is near the seam between the flat portion and the tapered portion of the reed piece, that is,
It occurs at the boundary 6 in FIG. The material moves in the axial direction of the lead when the lead is pressed, and the cross-sectional area after the processing is smaller than the original cross-sectional area. The rate at which this cross-sectional area decreases is called the area reduction rate. In order to reduce the area reduction rate, we investigated the shape of the die when pressing the lead.

FIG. 8 is a diagram showing the relationship between the shape of the mold and the cross-sectional area. As shown in FIG. 8, by changing the shape of the mold, the movement of the material was suppressed, and the area reduction rate could be reduced. Specifically, the shape shown in FIG. 3 is shown.

Next, a test for evaluating the impact resistance of the reed switch will be described.

The impact resistance test methods specified in JIS include a natural drop test and an impact test. For the former, the evaluation data varies greatly depending on the state of the switch at the time of drop. Since the impact waveform was different from the waveform actually applied, a new steel ball drop test method was established and evaluated. Further, since the impact applied by the user when mounting the substrate is several thousand G, a corresponding impact was applied, and the change in the moving current value was set to the target value shown below. Specifically, the rate of change of the moving current value before and after the impact is applied is within 5%.

FIG. 9 is a diagram provided for explanation of a steel ball drop test method. As shown in FIG. 9, the reed switch 10 is mounted on a dedicated printed circuit board 31 and has a diameter of φ14 m.
This is a test method in which a steel ball 32 of m is dropped from a height of 50 cm through a pipe 33 to apply an impact, and the impressed current values before and after the test were compared. FIG. 10 is a diagram showing test results obtained by the test method shown in FIG. As shown in FIG. 10, in the steel ball drop test, it can be seen that the change rate of the moving current value has cleared the target value of 5%.

FIG. 11 is a diagram showing the results of the electrical characteristics.
As shown in FIG. 11, the on-off ratio was about 60%, which was the same level as the conventional product (comparative example).

FIGS. 12 to 14 show the life characteristics. As shown in FIGS. 12 to 14, in the life characteristics, the change in the impression value, the open value, and the contact resistance was not significantly different from that of the conventional product (comparative example) up to 200 million times under the 3V-30 mA load.

As described above, in the embodiment of the present invention, in order to improve the shock resistance of the reed switch, the operation analysis is performed in the elastic deformation and plastic deformation regions, and the shock resistance is made higher than that of the conventional product. Was able to develop a reed switch about twice as high. Also, specifically,
In the elastic deformation area, the thickness of the lead piece is changed to optimize the stiffness. In the plastic deformation area, the reduction of the area where the maximum bending stress is concentrated is reduced by changing the shape of the press die. I was able to.

Further, it is possible to obtain a product having the same electrical characteristics and life characteristics as those of the conventional product.

[0066]

As described above, according to the present invention,
It is possible to provide a reed switch having the same structural dimensions, electrical characteristics, and life characteristics as conventional products and having excellent impact resistance, and a method for manufacturing the same.

Further, according to the present invention, it is possible to provide a reed switch that can be manufactured with existing facilities and a method of manufacturing the same.

Further, according to the present invention, the relationship between the shape of the lead and the stiffness is clarified, the shape of the press die is changed, and the reduction in the area of the portion where the maximum bending stress is concentrated is reduced, thereby achieving the optimum shape. By designing, a reed switch excellent in impact resistance and a manufacturing method thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic structure of a reed switch according to an embodiment of the present invention.

FIG. 2A is a partially enlarged plan view of a lead 1 of FIG. (B) is an enlarged plan view of a portion A in (a).

FIG. 3 (a) is a view showing a mold portion of a press molding apparatus for manufacturing the lead shown in FIGS. 1 and 2.
(B) is an enlarged sectional view showing C1 and C2 portions of the mold shown in (a).

FIGS. 4 (a) and (b) are a plan view and a front view for explaining the operation analysis of a reed switch similar to that of FIG.

FIG. 5 is a diagram showing a relationship between the length of a lead piece and stiffness.

FIG. 6 is a diagram showing a relationship between thickness and stiffness.

FIG. 7 is a diagram illustrating a relationship between read stiffness and an on-off ratio.

FIG. 8 is a diagram showing a relationship between a mold shape and a cross-sectional area.

FIG. 9 is a diagram provided for explanation of a steel ball drop test method for a reed switch.

FIG. 10 is a view showing test results obtained by the test method shown in FIG. 9;

FIG. 11 is a diagram showing a result of electrical characteristics of a reed switch.

FIG. 12 is a diagram illustrating life characteristics of a reed switch.

FIG. 13 is a diagram showing life characteristics of a reed switch.

FIG. 14 is a diagram showing life characteristics of a reed switch.

FIG. 15 is a view showing a conventional reed switch.

FIG. 16A is a cross-sectional view illustrating a press forming apparatus for manufacturing a lead 51. (B) is an enlarged sectional view of D1 and D2 parts of (a). (C) is a partial plan view showing a main part of a lead manufactured by the device of (a).

FIG. 17 is a diagram which is used for describing the operation of the reed switch of FIG.

18 is a perspective view schematically showing a contact portion 53 of the reed switch of FIG.

FIG. 19 is a diagram showing a relationship between a magnetic attractive force curve and a separating force with respect to a contact gap.

[Description of Signs] 10 Reed switch 1 Lead 2 Glass tube 3 Contact part 4 Movable part 5 Support part 6 Boundary part 20 Press mold 21 Upper mold 22 Lower mold 31 Printed wiring board 32 Steel ball 33 Pipe 50 Lead switch 51 Lead 52 Glass tube 53 Contact part 54 Movable part of lead 55 Supporting part 56 Boundary part 58 Nitrogen 61 Upper mold 62 Lower mold 70 Permanent magnet

Claims (5)

[Claims] 1. A pair of leads made of a magnetic material integrally provided with a contact portion at a tip, a movable portion continuous with the contact portion, and a support portion supporting the movable portion continuously with the movable portion. A sealing member for sealing the contact portions of the pair of leads so as to face each other, and configured to contact or open the contact portions according to a magnetic field applied to the leads. A reed switch, wherein each reed is formed so as to increase in thickness stepwise as a boundary between a movable portion and the support portion moves from the movable portion to the support portion. 2. The reed switch according to claim 1, wherein said boundary portion is formed so as to decrease in width as it moves from said movable portion to said support portion. 3. A method of manufacturing a lead encapsulated in a reed switch having a contact portion at a tip, a movable portion continuous with the contact portion, and a support portion continuous with the movable portion and supporting the movable portion. Wherein a bar made of a magnetic material is formed such that the boundary between the support portion and the movable portion increases in thickness stepwise from the movable portion toward the support portion to obtain a lead. Lead manufacturing method. 4. A method of manufacturing a reed switch, comprising preparing a pair of leads obtained by the method of manufacturing a lead according to claim 3, making the respective contact portions of the leads face each other, and enclosing them with an encapsulating member. Method. 5. A lead encapsulated in a reed switch and provided with a contact portion at a tip, a movable portion continuous with the contact portion, and a support portion continuous with the movable portion and supporting the movable portion. In order to do this, in a lead manufacturing device for sandwiching a bar-shaped magnetic material between a pair of
Opposite portions corresponding to the boundary portions of the pair of molds are formed in a step shape so that a boundary portion between the movable portion and the support portion gradually increases in thickness in a step shape. Lead manufacturing equipment.