JPH10223413A - Potentiometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a potentiometer in which stable measurement accuracy is maintained over a long period of time. SOLUTION: A magnetic fluid 8 in a fluid chamber 15 is attracted on the side of a substrate 2 with a magnet 6, so that a conductive rubber film 7 sealing the fluid chamber 15 is distorted so as to expand towards the side of the substrate 2 at a position corresponding to the magnet 6, and comes into contact with a resistance pattern 21 and a conductive pattern 22 on the surface of the substrate 2, for electrical connection between them. A contact point position for the conductive rubber film 7, corresponding to the resistance pattern 21 and the conductive pattern 22, varies continuously corresponding to the position of the magnet 6, which moves based on the input of mechanical displacement amount from the outside. Here, the conductive rubber film 7 itself does not move, and the position where the film expands towards the side of the substrate 2 varies, so that the conductive rubber film 7 does not slide against the resistance pattern 21 and the conductive pattern 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a potentiometer which is a variable resistor used as a position sensor for feedback of a servo system, for example, for detecting an inclination angle and a linear displacement.

[0002]

2. Description of the Related Art As one type of a contact potentiometer according to the prior art, there is typically one as shown in FIG. This potentiometer includes a case 101,
A disk-shaped substrate 102 fixed in the case 101
An outer peripheral resistance pattern 103 formed in a smooth film shape on the surface of the substrate 102 and extending in a substantially C-shape in a circumferential direction, and an annular conductor pattern 104 on an inner peripheral side thereof; And a brush 106 fixed coaxially and rotatably with the shaft 105 and a brush 106 having a distal end portion in contact with both the resistance pattern 103 and the conductor pattern 104.

[0003] That is, the potentiometer of the above configuration is
The resistance pattern 103 and the conductor pattern 104 formed on the substrate 102 are electrically connected via a brush 106 moved around its axis by a shaft 105, and the contact position of the brush 106 becomes variable. Is what it is. Accordingly, when the shaft 105 is rotated by inputting a mechanical displacement amount such as an inclination or a movement of an external measurement target, the brush 1 with respect to the resistance pattern 103 and the conductor pattern 104 is accordingly rotated.
Since the contact position of No. 06 moves in the circumferential direction and the resistance value between the terminals changes, a voltage corresponding to the mechanical amount is output.

[0004]

In a conventional contact-type potentiometer, the brush 106 has a resistance pattern 1.
03 and the conductor pattern 104, the occurrence of wear is inevitable. Therefore, the following problems are pointed out. (1) Since the contact pressure changes due to wear and the contact resistance becomes unstable, the linearity of the output with respect to the mechanical displacement of the measurement object is impaired at an early stage. (2) Since the contact of the brush 106 with the resistance pattern 103 and the conductor pattern 104 is performed in the sealed chamber 107, foreign matter enters from outside and the resistance pattern 10
However, the noise does not intervene in the contact portion between the conductive pattern 104 and the brush 106 and the conductive pattern 104, but the output noise may be generated by the abrasion powder intervening in the contact portion.

The present invention has been made in view of the above circumstances, and a technical problem thereof is to provide a potentiometer capable of maintaining stable measurement accuracy for a long period of time. .

[0006]

As a means for effectively solving the above-mentioned technical problems, a potentiometer according to the present invention comprises a substrate having a resistance pattern and a conductor pattern formed close to each other on a surface thereof, and A magnet disposed close to the surface of the substrate opposite to the resistance pattern and the conductor pattern and relatively moved in the extension direction of the resistance pattern and the conductor pattern by input of an external mechanical displacement amount; A conductive rubber film disposed in a state where a fluid chamber provided along the conductor pattern is hermetically sealed and opposed to the resistance pattern and the conductor pattern, and a magnetic fluid sealed in the fluid chamber; The magnetic fluid attracted to the conductive rubber film contacts the resistance pattern and the conductor pattern on the substrate. Therefore, the magnet is relatively moved along the resistance pattern and the conductor pattern according to a change in the amount of mechanical displacement from the outside, and accordingly, the contact between the conductive rubber film and the resistance pattern and the conductor pattern by the magnetic fluid is moved. The resistance value changes in accordance with the mechanical amount.

Here, the conductive rubber film is a rubber film which is made conductive by mixing a conductive powder into a rubber material. In the present invention, the conductive rubber film comes into contact with the resistance pattern and the conductive pattern on the substrate surface. It is used as a contact member for electrically connecting the two. The magnetic fluid is obtained by mixing a ferromagnetic fine powder with a liquid medium, and can be attracted to the magnet side by applying a magnetic force by approaching the magnet. The magnetic fluid may be conductive, but as described above, since the electrical bridge between the resistance pattern and the conductor pattern is performed by the conductive rubber film, basically the magnetic fluid is used. It does not have to be conductive.

That is, in the above configuration, the magnetic force of the magnet acts on the magnetic fluid in the fluid chamber via the substrate and the conductive rubber film, whereby the magnetic fluid is strongly attracted to the magnet. For this reason, the conductive rubber film sealing the fluid chamber is deformed so as to swell toward the substrate by the magnetic fluid attracted to the position corresponding to the magnet, and comes into contact with the resistance pattern and the conductor pattern on the substrate surface. Electrically. The contact position of the conductive rubber film with respect to the resistance pattern and the conductor pattern continuously changes according to the position of the magnet that moves by inputting the amount of mechanical displacement from the outside. It does not move in the extension direction of the resistance pattern and the conductor pattern like the brush in the potentiometer of the above, but the position swelling to the substrate side changes, so that when the contact position changes, the contact between the resistance pattern and the conductor pattern slides. No movement is involved.

[0009]

FIG. 1 is a plan view showing a preferred embodiment of a potentiometer according to the present invention, FIG. 2 is a sectional view taken along the line II-II 'in FIG. 1, and FIG. I
It is sectional drawing cut | disconnected along the II-III 'line. In these figures, reference numeral 1 denotes a case made of an insulating synthetic resin material such as nylon or PBT (polybutylene terephthalate). It is designed to be mounted horizontally at a predetermined location of the device via screws or the like.

In the case 1, a cylindrical working chamber 13 hermetically closed by a cover 12, a shaft hole 14 penetrating toward the working chamber 13, and a bottom of the working chamber 13 are substantially C-shaped in a circumferential direction.
A fluid chamber 15 extending in a letter shape is formed. Working chamber 13
A disk-shaped substrate 2 made of an electrically insulating synthetic resin material such as an epoxy resin containing glass fiber or a phenol resin is fixed between the fluid chamber 15 and the fluid chamber 15.
3 is in close contact with the bottom. The shaft hole 14 is made of steel (SUS)
Is rotatably inserted around a shaft center through a bearing 4 made of a sintered alloy or the like.
a penetrates through the inner peripheral hole 2a of the substrate 2 and reaches the inside of the working chamber 13, and the outer end 3b protrudes outside the case 1 and is connected to the working part of the device whose position is to be measured via an appropriate link member. The actuator is rotated by the displacement of the operating part. The outer circumference of the shaft support of the shaft 3 is sealed by a dust seal 5 with a dust seal 5 to prevent foreign matter from entering the case 1 from outside through the shaft circumference.

On the surface of the substrate 2 facing the fluid chamber 15, a resistance pattern 21 on the outer peripheral side extending in a substantially C-shape in the circumferential direction around the axis of the shaft 3 and an annular pattern on the inner peripheral side thereof. The conductor pattern 22 is formed in a uniform thickness and smoothly by an appropriate method such as printing. The resistance pattern 21 is made of a resistance material obtained by adding a thermosetting resin paste to a conductive material powder such as carbon having a high electric resistance, and the conductor pattern 22 is made of a conductive metal powder such as silver added with a thermosetting resin paste. It is made of material.

In the working chamber 13 of the case 1, a magnet 6 is provided.
The inner peripheral hole 2a of the substrate 2 is disposed in a state in which the surface of the substrate 2 opposite to the surface on which the resistance pattern 21 and the conductor pattern 22 are formed, that is, the upper surface in FIGS.
Is attached to the inner end 3a of the shaft 3 that penetrates through the mounting ring 31 so as to extend in the radial direction of the substrate 2. The shaft 3 has a stepped portion 3 c and the mounting ring 3.
1 restricts the axial displacement, so that the rotation of the shaft 3 causes the magnet 6 to move in the circumferential direction around its axis while keeping a constant distance from the surface of the substrate 2.

In the vicinity of the end of the fluid chamber 15 on the substrate 2 side, a conductive rubber film 7 is sealed in parallel with the lower surface of the substrate 2, that is, with a certain gap from the surfaces of the resistance pattern 21 and the conductor pattern 22. The magnetic fluid 8 is filled in the fluid chamber 15 sealed by the conductive rubber film 7. The conductive rubber film 7 is formed, for example, by molding a rubber in which a large amount of conductive metal fine powder or carbon fine powder is mixed into a rubber material into a film shape, and the magnetic fluid 8 is formed of, for example, kerosene, silicon oil, esters, etc. The ferromagnetic fine powder of iron or magnetite (magnetite) is uniformly dispersed at a high concentration in such a liquid.

The magnetic force of the magnet 6 acts on the magnetic fluid 8 in the fluid chamber 15 so that the magnetic fluid 8
At the position corresponding to the magnet 6 on the circumference of 5, it is drawn to the substrate 2 side. Therefore, the conductive rubber film 7 that seals the fluid chamber 15 has a certain gap between the resistance pattern 21 and the conductor pattern on the surface of the substrate 2 except for the position corresponding to the magnet 6 as shown in FIG. 3, but at a position corresponding to the magnet 6, the resistance pattern 21 is deformed so as to expand toward the substrate 2 as shown in FIG.
By contacting both the conductor pattern 22 and the conductor pattern 22, the two 21 and 22 are electrically connected.

In a connector housing 16 formed in the case 1, connector terminals 23 to 25 are provided.
Both ends of the resistance pattern 21 are connected to connector terminals 23 and 24 via conductor pieces 21a and 21b, respectively.
2 is connected to the connector terminal 25 via the conductor piece 22a. Reference numeral 16a is a protrusion formed on the outer wall surface of the connector housing 16 for preventing connection with a mating connector.

That is, this potentiometer is configured such that when the shaft 3 is relatively rotated with respect to the case 1 by input of an external mechanical displacement amount such as a rotation angle or a stroke amount of a displacement measurement target portion (for example, a robot arm) of the device. The magnet 6 moves on the circumference around the axis through the shaft 3 while maintaining a constant distance from the surface of the substrate 2. For this reason, the conductive rubber film 7 with the resistance pattern 21 and the conductor pattern 22 due to the magnetic fluid 8 being attracted by the magnetic force in the fluid chamber 15.
And the resistance value changes as the length of the conductive path in the resistance pattern 21 changes, so that the rotation angle of the shaft 3, that is, the input mechanical displacement amount from the outside, is changed. A voltage is output.

Since the magnet 6 moves parallel to the conductive rubber film 7, the conductive rubber film 7 is generated by the magnetic force acting on the magnetic fluid 8.
The contact pressure between the electrode and the resistance pattern 21 and the conductor pattern 22 is always constant, that is, the resistance at the contact point is always constant. Considering, for example, the case where the magnet 6 has moved from the position indicated by the solid line in FIG. Position is from p ₁ to p
_{In the} movement of the contact position, in other words, the deformation position of the conductive rubber film 7 toward the substrate ₂ is continuously changed from p ₁ to p ₂ by the magnetic fluid 8 attracted to the magnet 6. In addition, the conductive rubber film 7 itself does not necessarily move. For this reason, the conductive rubber film 7 does not slide on the resistance pattern 21 and the conductor pattern 22 and does not cause a change in contact pressure due to abrasion or an intervention of abrasion powder. Also,
Since the gap between the conductive rubber film 7 and the substrate 2 (the resistance pattern 21 and the conductor pattern 22) is closed, foreign matter from the outside does not intervene in the contact.

It is conceivable that a magnetic fluid 8 having conductivity is used and the magnetic fluid 8 is caused to flow by the magnet 6 as a contact means with the resistance pattern 21 and the conductor pattern 22. In this case, When a part of the magnetic fluid 8 is left in the flow process, the area of the contact portion may be reduced, or the resistance pattern 21 and the conductor pattern 22 may be connected at a plurality of locations, resulting in unstable output. There is. On the other hand, according to the above-described embodiment, by using the conductive rubber film 7 sealing the magnetic fluid 8 as the contact means, the resistance pattern 21 and the conductor pattern 22 are formed in a circumferential direction corresponding to the position of the magnet 6. Since conduction is provided only in one direction and there is no change in the contact area due to wear as described above, the linearity of the output with respect to the displacement of the measurement object is maintained for a long period of time.

In the above embodiment, the magnet 6 is rotated around the shaft 3. However, the present invention is not limited to such a rotary type. For example, the resistance pattern 21, the conductor pattern 22, It is also possible to adopt a configuration in which the fluid chamber 15 extends linearly and the magnet 6 is linearly moved in the same direction.

[0020]

The potentiometer according to the present invention is characterized in that the magnetic fluid sealed with the conductive rubber film is attracted to a magnet which moves in accordance with a mechanical displacement inputted from the outside, whereby the conductive rubber film is formed. Is deformed at a position corresponding to the magnet, and is brought into contact with the resistance pattern and the conductor pattern on the substrate, so that the following effects are realized. (1) The contact resistance is stable because there is no wear on the contact points,
The durability is improved. (2) Since noise due to abrasion powder does not occur and a contact is formed only in a portion corresponding to the position of the magnet, the reliability of detection performance is improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a preferred embodiment of a potentiometer according to the present invention.

FIG. 2 is a sectional view taken along the line II-II ′ in FIG.

FIG. 3 is a sectional view taken along the line III-III ′ in FIG. 1;

FIG. 4 is an explanatory diagram showing an operation of the embodiment.

FIG. 5 is a sectional view showing a typical prior art of a contact potentiometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 11 Flange 12 Cover 13 Working chamber 14 Shaft hole 15 Fluid chamber 16 Connector housing 16a Projection 2 Substrate 21 Resistance pattern 22 Conductor pattern 23-25 Connector terminal 3 Shaft 4 Bearing 5 Dust seal 6 Magnet 7 Conductive rubber film 8 Magnetic fluid

Claims (1)

[Claims] A resistance pattern (2) is provided on a surface close to each other.
Substrate (2) on which 1) and conductive pattern (22) are formed
The resistor pattern (21) and the conductor pattern are arranged in close proximity to the surface of the substrate (2) opposite to the surface opposite to the resistor pattern (21) and the conductor pattern (22). The magnet (6) relatively moved in the extension direction of the (22), and the fluid pattern (15) provided along the resistance pattern (21) and the conductor pattern (22) are arranged in a sealed state, and the resistance pattern ( 21) a conductive rubber film (7) opposed to the conductor pattern (22) and a magnetic fluid (8) sealed in the fluid chamber (13), and are attracted to the magnet (6). The conductive fluid film (7) is formed by the magnetic fluid (8) on the resistance pattern (2).
1) and a potentiometer which is brought into contact with the conductor pattern (22).