JP2003035614A - Pressure-sensitive sensor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive sensor having high sensitivity, easy to process and generating no characteristic error. SOLUTION: A fixed electrode 1 and a connection member 2 for directly supporting the outer edge of a movable electrode 4 are provided to a base 3 subjected to insert molding. At least the movable electrode 4 and the connection member 2 are formed from a metal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensitive sensor and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a pressure-sensitive sensor having a strong structure capable of withstanding a large load, a plurality of metal plates are laminated with a spacer interposed at the peripheral edge thereof to form a predetermined gap between the metal plates. Such a method is known (see, for example, Japanese Patent Laid-Open No. 2000-258261).

[0003]

However, in the conventional pressure-sensitive sensor described above, since the portion of the metal plate supported by the spacer is not deformed, this non-deformed portion becomes a parasitic capacitance. In other words, the deformation area of the metal plate is narrowed and the rate of change in capacitance is reduced, resulting in poor sensitivity.

Since the spacers are pressed, burrs are unavoidable. The burr may be crushed during use and may affect the characteristics, so it needs to be removed by post-processing. Therefore, the cost is increased. Further, the surface of the spacer needs to be coated with an insulating material, mainly resin. Therefore, the plate thickness varies. The variation of the plate thickness directly affects the gap size of the metal plate, that is, the electrostatic capacitance, so that the characteristic error between products becomes large. Moreover, since the resin has a larger coefficient of thermal expansion than the spacer, the temperature characteristics are deteriorated.

Therefore, it is an object of the present invention to provide a pressure-sensitive sensor which has high sensitivity, is easy to process, and is less likely to cause a characteristic error.

[0006]

As a means for solving the above-mentioned problems, the present invention is characterized in that the movable electrode is elastically deformed to reduce the distance from the fixed electrode and the electrostatic capacitance is changed to thereby change the movable electrode. A pressure-sensitive sensor adapted to detect a load acting on an electrode, comprising a base in which the fixed electrode and a connecting member for directly supporting an outer edge portion of the movable electrode are insert-molded, and at least the movable electrode and the connecting member. Is composed of a metal material.

With this structure, the fixed electrode and the connecting member can be simultaneously provided on the base by insert molding, and both can be positioned with high precision based on the precision of the mold. Further, since the movable electrode made of a metal material is directly supported by the connecting member made of a metal material as well, not only the supported state is stable, but also a highly accurate electrode interval can be obtained.

Fixing the movable electrode to the connecting member is preferable in that the fixed state can be stabilized.

A donut-shaped spacer may be accommodated in the base, a button may be arranged in the central opening of the spacer so as to be vertically movable, and the movable electrode may be elastically deformable via the button.

It is preferable that a dustproof sheet is provided between the movable electrode and the spacer and the button to prevent dust and the like from entering the inside.

If the connecting member is configured to support the entire outer edge portion of the movable electrode and is made of a member different from the fixed electrode, the supporting state of the movable electrode can be further stabilized. preferable. In particular, since the fixed electrode and the connecting member are separate members, the plate thickness of each member can be freely set, and the step between them can be accurately determined. That is, this step can be used as a gap between both electrodes, and a desired capacitance can be obtained.

As a means for solving the above-mentioned problems, the present invention provides a method of manufacturing a pressure-sensitive sensor, which comprises a step of forming a base by integrating a fixed electrode and a connecting member formed on a lead frame by insert molding. Is provided.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a pressure-sensitive sensor according to a first embodiment. As shown in FIG. 2, this pressure-sensitive sensor generally includes a movable electrode 4, a dustproof sheet 5, a movable electrode 4, a dustproof sheet 5, and a base 3 on which a fixed electrode 1 and a connecting member 2 are insert-molded.
The spacer 6 and the button 7 are placed and covered with a cover 8.

The base 3 is made of a synthetic resin (for example, polyphenylene sulfide (PPS)), has a rectangular shape in plan view, and has an accommodating recess 9 formed in the upper surface. Accommodation recess 9
Is substantially circular in a plan view, and relief recesses 10 for screwing are formed at four outer circumferences at equal intervals. Locking protrusions 11 are formed at two symmetrical positions on the outer surface of the side wall. Fixed electrode 1
Is made of a copper alloy, the circular adsorption surface 1a is exposed in the central portion of the accommodating recess 9, and the terminal 1b is provided from the side wall (see FIG. 1C).
Is protruding. The connecting member 2 is made of the same material as that of the fixed electrode 1, and is exposed in a substantially C shape around the adsorption surface 1a with a predetermined gap dimension. Further, as shown in FIG. 1C, a fixing portion 2a located in the escape recess 10 and a connecting terminal 2b protruding from the side wall of the base 3 and bent in a crank shape are provided on the outer edge portion of the connecting member 2. Has been formed.
A screw hole 2c is formed in the fixed portion 2a. A predetermined step d (see FIG. 1D) is provided on the attracting surface 1 a of the fixed electrode 1 and the upper surface of the connecting member 2.

The movable electrode 4 is formed by pressing stainless steel or the like into a plate shape having a substantially circular shape in plan view which can be housed in the housing recess 9 of the base 3. A fixing portion 4a similar to the connecting member 2 is formed on the outer peripheral portion, and a through hole 4b is formed therein. The movable electrode 4 is directly supported on the upper surface of the connection member 2 while being housed in the housing recess 9. As a result, the gap size between the movable electrode 4 and the fixed electrode 1 becomes the step d. This step difference serves as a distance between the fixed electrode 1 and a movable electrode 4 which will be described later, and directly affects the capacitance of the capacitor composed of both electrodes. Further, the movable electrode 4 is directly screwed into the screw hole 2c of the connection member 2 through the through hole 4b.
Fixed by. However, the movable electrode 4 to the connecting member 2
The fixing method is not limited to screwing, and various methods such as screwing, bonding, welding, etc. can be adopted.

The dustproof sheet 5 is made of, for example, an insulating film, is placed on the upper surface of the movable electrode 4, and prevents dust and the like from entering the inside.

The spacer 6 is made of nylon or the like and has a central opening 6
It is formed in a donut shape having a and is arranged on the upper surface of the movable electrode 4 via the dustproof sheet 5.

The button 7 is made of synthetic resin, ceramics or the like, has a stepped shape, and has a central opening 6 in the spacer 6.
It is arranged so as to be vertically movable in a.

The cover 8 is formed by pressing a copper alloy into a substantially rectangular plate shape. A through hole 8a is formed in the central portion, and the upper portion of the button 7 projects. Guide walls 12 are formed at two symmetrical positions on the side edge portion. The guide wall 12 is a guide portion 12 a along the side surface of the base 3.
And an expanded portion 12b at its tip. A locking hole 13 for locking the locking projection 11 of the base 3 is formed in the guide portion. Further, the ground terminals 14 are formed at two positions on both sides at the other two side edges.

Next, a method of manufacturing the pressure sensor will be described.

By pressing a hoop material made of a copper alloy, a lead frame 100 having a fixed electrode 1 and a connecting member 2 is formed as shown in FIG. And
The fixed electrode 1 and the connecting member 2 are set in the cavity of the mold, and insert molding is performed to form the base 3. At this time, since the fixed electrode 1 and the connecting member 2 are positioned in contact with the cavity finished with high accuracy, as shown in FIG.
The step d formed between a and the upper surface of the connecting member 2 can be made highly accurate. However, the die structure may be simplified by making the plate thicknesses of the fixed electrode 1 and the connecting member 2 different from each other by the amount of the step difference d during the press working.

When the base 3 is completed, the movable electrode 4 formed in a separate step is disposed in the accommodating recess 9 and screwed to the connecting member 2. Since the connecting member 2 is made of a metal material, the fixed state of the movable electrode 4 is stable. Further, since the movable electrode 4 is directly brought into contact with and supported by the upper surface of the connection member 2 in which a highly accurate step d is formed between the movable electrode 4 and the fixed electrode 1, the inter-electrode distance can be formed with high accuracy. Therefore, both electrodes 1,
It is possible to set the capacitance obtained by 4 to a desired value, and there is no variation among products.

When the attachment of the movable electrode 4 is completed, the dustproof sheet 5, the spacer 6 and the button 7 are sequentially laminated on the upper surface thereof, and the cover 8 is attached to the base 3 to complete the pressure sensitive sensor.

Next, the operation of the pressure sensitive sensor will be described.

In the pressure-sensitive sensor having the above structure, when the button 7 protruding from the cover 8 is pressed, the movable electrode is elastically deformed. Along with this, the distance between the electrodes gradually decreases, and the capacitance changes. Then, a control device (not shown) calculates the load acting on the button 7 based on the change in the capacitance. Since the movable electrode 4 is configured to be supported by the connection member 2 located around the fixed electrode 1, it can be elastically deformed in the entire region facing the fixed electrode 1. Therefore, the parasitic capacitance is not generated, and the change of the electrostatic capacitance with respect to the increase / decrease amount of the acting load has good responsiveness (there is linearity) and can be made highly sensitive. Further, since the movable electrode 4 is directly supported by the connecting member 2 made of a metal material that is insert-molded on the base 3 as described above, the operation is stable and is less likely to be adversely affected by the temperature change. Since this pressure-sensitive sensor has a structure that can sufficiently withstand a high load, it can be provided, for example, on the sole of the robot and used to detect weight movement during walking.

(Second Embodiment) FIGS. 4 and 5 show a second embodiment.
1 shows a pressure-sensitive sensor according to an embodiment. Hereinafter, only differences from the pressure sensor according to the first embodiment will be described.
Corresponding parts are assigned the same reference numerals and explanations thereof are omitted.

That is, in the base 3, the accommodating concave portion 9 has a substantially rectangular shape, stepped relief holes 20 are formed at the four corners thereof, and screw holes 21 are formed at the four inner sides thereof. Further, notches 22 and 23 are formed in the center of the side wall, respectively. As shown in FIG. 4C, the notch 22
The terminal 1b of the fixed electrode 1 is provided in the, and the connection terminal 2b of the connection member 2 is provided in the notch 23. Cutout 22
Has a structure in which not only the side wall but also a part of the bottom wall is cut off. Therefore, the terminal 1b of the fixed electrode 1 and the connection terminal 2 of the connection member 2 are removed.
It is possible to make non-contact with b.

The fixed electrode 1 and the connecting member 2 are formed not by insert molding as in the first embodiment but by press working in separate steps. The fixed electrode 1 is disc-shaped, and the upper surface thereof is an adsorption surface 1a, and through holes 24 are formed at four equal portions therein. Then, the fixed electrode 1 can be fixed to the base 3 by screwing the screw 25 into the screw hole 21 of the base through the through hole 24. The connecting member 2 has a substantially rectangular frame shape and has no break like the one in the first embodiment. Therefore,
It is possible to support the movable electrode 4 over its entire outer edge. Further, the connecting member 2 has through holes 26 formed at four corners, and an escape groove 27 is formed on the bottom surface to separate from the terminal 1b of the fixed electrode 1.

The movable electrode 4 has a fixed portion 4a provided on the outer edge thereof.
In addition to the through hole 4b, the escape holes 28 are formed at four locations inside. This escape hole 28 is provided to avoid interference with the screw 25 for fixing the fixed electrode 1 to the base 3. The movable electrode 4 is fixed by a screw 29 through the through hole 4b, the through hole 26 of the connection member 2, and the escape hole 20 of the base 3.

The spacer 6 has locking projections 30 formed at two symmetrical positions on the outer edge. This locking projection 3
0 engages with the notches 22 and 23 of the base 3 respectively and positions the rotation direction of the spacer 6.

As described above, according to the pressure-sensitive sensor of the second embodiment, the connecting member 2 can support the entire outer edge portion of the movable electrode 4, and the supporting state can be further stabilized. . In addition, the movable electrode 4 and the connecting member 2
Since it is a separate member formed in a different process from, the plate thickness can be set easily and freely. Therefore, it is possible to obtain the steps with high accuracy while simplifying the cavity structure of the mold.

[0033]

As is apparent from the above description, according to the present invention, since the fixed electrode and the connecting member for directly supporting the outer edge of the movable electrode are provided by the insert molding, the distance between the electrodes can be reduced. In addition to being highly accurate, the supporting state of the movable electrode is stable, and the operating characteristics and temperature characteristics are improved.

[Brief description of drawings]

FIG. 1 shows a pressure-sensitive sensor according to a first embodiment,
(A) is an overall perspective view, (b) is a side view thereof, (c) is a sectional view taken along the line AA of (b), and (d) is an enlarged view of a B portion of (c).

FIG. 2 is an exploded perspective view of the pressure sensor shown in FIG.

FIG. 3 is a plan view of a lead frame for forming the base shown in FIG.

FIG. 4 shows a pressure-sensitive sensor according to a second embodiment,
(A) is the whole perspective view, (b) is the side view, (c) is the CC sectional view taken on the line (b).

5 is an exploded perspective view of the pressure-sensitive sensor shown in FIG.

[Explanation of symbols]

1 ... Fixed electrode 2 ... Connection member 3 ... Base 4 ... Movable electrode 5: Dustproof sheet 6 ... Spacer 7 ... button 8 ... Cover 9 ... Storage recess

Claims (6)

[Claims] 1. A pressure-sensitive sensor configured to detect a load acting on the movable electrode by elastically deforming the movable electrode to reduce the distance to the fixed electrode and changing the electrostatic capacitance. A pressure-sensitive sensor comprising a base formed by insert molding an electrode and a connecting member that directly supports an outer edge portion of the movable electrode, and at least the movable electrode and the connecting member are made of a metal material. 2. The pressure sensitive sensor according to claim 1, wherein the movable electrode is fixed to the connecting member. 3. A donut-shaped spacer is housed in the base, a button is provided in a central opening of the spacer so as to be vertically movable, and the movable electrode is elastically deformable through the button. The pressure sensitive sensor according to claim 2. 4. The pressure-sensitive sensor according to claim 3, wherein a dustproof sheet is provided between the movable electrode and the spacer and the button. 5. The connection member is configured to support the entire outer edge portion of the movable electrode and to be a member separate from the fixed electrode. Pressure sensor described in. 6. A method of manufacturing a pressure-sensitive sensor, comprising a step of integrally forming a fixed electrode and a connection member formed on a lead frame by insert molding to form a base.