JP3710359B2 - Hollow shaft variable resistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotary variable resistor particularly suitable for rotation control of a joint portion of a robot.
[0002]
[Prior art]
The structure of a conventional rotary variable resistor will be described with reference to an exploded assembly perspective view of a conventional rotary variable resistor 30 shown in FIG.
[0003]
In the figure, a substrate 2 (for example, a phenol laminate) is provided with a circular through-hole 3 at the approximate center of its upper surface and processed into a predetermined shape (in this case, a rectangle), with carbon powder as a resistance material on its upper surface and oil as a glue. A resistor 4 in which a resistance ink mixed with a phenol resin and a solvent is printed in a substantially concentric circle (or horseshoe shape) and baked, a conductor 36 around the through-hole 3, and three conductors 6a, 6b connected thereto 6c (for example, silver paint) is formed. The conductors 6a, 6b, and 6c are electrically connected to terminal electrodes 5a, 5b, and 5c in which metal pieces are caulked and fixed to the substrate 2, respectively.
[0004]
Next, in the center of the bottom surface side of the cylindrical rotor 9 which is a rotating mechanism portion, there is a projecting portion which is fitted into the through hole 3 of the substrate 2 and serves as a rotating shaft in the center, and has elasticity as a conductive member. A recess (not shown) for fitting and fixing the slider 12 (formed by press-molding a thin metal plate) is provided on the bottom surface side. Further, the shaft 10 suspended from the rotor 9 is resin-molded integrally with the rotor 9.
[0005]
The case is composed of two parts, that is, a metal seat 15 made by press-molding a metal plate in advance and a resin upper lid part 16 made by molding.
[0006]
As shown in FIG. 8, each of the above components is inserted into the opening 17 of the upper lid portion 16 with the shaft 10 suspended above the rotor 9 having the slider 12 attached to the bottom surface side. Are inserted into the through-hole 3 of the substrate 2 and placed on the substrate 2, and the metal receiving seat 15 is inserted from the lower side of the substrate 2, and the claw portion at the tip of the protruding piece 18 is raised at the four corners. The rotary variable resistor 30 is completed through an assembling process in which 19 is folded inward into the recesses 21 at the corresponding four corners of the upper lid portion 16 and locked.
[0007]
[Problems to be solved by the invention]
By the way, recently, a product incorporating a high-precision rotary variable resistor has been developed for rotation control of a stepping motor that moves a joint portion of a robot. In this case, the conventional rotary variable resistor 30 provided with the shaft 10 as described above may be used, but the manufacturer of the electronic device such as a robot may rotate the shaft of the stepping motor that drives the joint. If a resistor shaft can be installed later, it becomes compact and good results are obtained. In order to cope with this structure, a hollow shaft rotary variable resistor having a structure without a shaft is required as a product of the rotary variable resistor.
[0008]
However, when the motor shaft is mounted as a shaft of a rotary variable resistor in a retrofit, the insertion between the retrofit shaft and the rotor having a hollow shaft that receives the shaft on the rotary variable resistor side must be tight. Shaking of the shaft (play between the shaft and the hollow shaft portion of the hollow shaft rotor) occurs, and there is a problem that high-precision control cannot be performed.
[0009]
Also, in electronic devices such as robots, the driving of the joints is the main movement, so the use frequency of the hollow-shaft rotary variable resistor is extremely high, and higher durability is required than a general rotary variable resistor. In this regard, if the case is a resin case, glass fiber or the like is contained in the heat-resistant resin used to withstand reflow soldering, so the contact portion of the rotor with the resin case is severely worn and durable. Improvement is essential.
[0010]
Further, as shown in FIG. 8, the conventional variable resistor has its terminal electrodes 5a, 5b and 5c fixed by caulking metal pieces to the substrate 2, but the terminal electrode caulking process takes time and effort. In other words, the cost is high, and the terminal is liable to be bent, and the terminal electrode is loosened by the heat of soldering. In addition, since the terminal electrode of the metal piece protrudes to the outside, the area of the solder connection portion cannot meet the demand for high-density mounting of components.
[0011]
The present invention has been made in view of the above circumstances, and is particularly suitable for rotation control of a joint portion of a robot, and is free from rattling of a retrofit shaft, and is a hollow shaft rotating excellent in durability and reliability. A type variable resistor is provided.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention
(1) A rotary variable resistor without a shaft, in which a resistor and a conductor are formed substantially concentrically on one main surface, and are electrically connected to a plurality of terminal electrodes disposed in a peripheral portion; A substrate having an insertion hole drilled in the center and a substantially cylindrical hollow shaft that is inserted into the insertion hole of the substrate and rotates at the center, and protrudes from the inner wall of the hollow shaft , and its tip Is a disk-shaped rotor that is elastically deformed by hitting a shaft that is inserted later, and is extended with a tongue-shaped elastic protrusion that presses and fixes the shaft against the inner wall of the hollow shaft portion toward the central axis And a slider mounted on one main surface of the disk portion of the rotor, and an insertion hole for pivotally mounting the hollow shaft portion of the rotor, and mounted on the substrate so that the rotor and the slider are inside And a case to be stored in Providing a hollow shaft variable resistor to.
(2) Further, in the hollow shaft variable resistor described in (1) above, the case is a resin case, and a slip made of a film or sheet of polytetrafluoroethylene at a contact portion between the rotor and the resin case A hollow shaft variable resistor is provided in which a washer is interposed.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a hollow shaft rotary variable resistor according to the present invention will be described with reference to the drawings. Note that the same reference numerals are used for members equivalent to the conventional rotary variable resistor 30 shown in the above-described figure.
[0014]
FIG. 1 is a cross-sectional view of a hollow-shaft rotary variable resistor 50, and FIG. 2 is a cross-sectional view of a state where a retrofit shaft is inserted. FIG. 3 is a plan view showing the structure of the substrate (upper surface) viewed from the inside of the hollow shaft rotary variable resistor 50. FIG. 4 is a plan view showing the structure of the upper surface at the time of punching the substrate, and FIG. 5 is a plan view showing the structure of the lower surface at the time of punching the substrate. FIG. 6 is a partial cross-sectional view for explaining the structure of a hollow shaft rotor which is a main component of the present invention. FIG. 7 is a plan view of a sliding washer which is a component according to the present invention.
[0015]
The hollow-shaft rotary variable resistor 50 according to the present invention shown in the cross-sectional view of FIG. 1 has a structure that does not have a shaft that protrudes from a normal main body, and as shown in FIG. A plurality of copper foils, which are formed on one main surface 22A (upper surface) in a substantially concentric manner and have a resistor 36 coated and baked with a resistance ink mixed with silver, and a conductor 36 coated with silver paint or the like. The terminal electrodes 7a, 7b, 7c, 7d (see FIGS. 4 and 5) are connected by three conductors 6a, 6b, 6c (for example, silver paint), and the rear shaft 60 shown in FIG. A substrate 22 having an insertion hole 8 having a slightly larger diameter, and a substantially cylindrical hollow shaft portion 24 inserted into the insertion hole 8 of the substrate 22 and rotated at the center, and the hollow shaft portion 24 Shaft to be inserted into the interior 60 a disk-shaped rotor 23 which tongue-shaped elastic protrusions 26 are extended to closely fix to press the mounting by crimping by one of the rotor to the main surface protrusion 23B of the disc portion 23A of the rotor 23 And an insertion hole 27 for axially attaching the hollow shaft portion 24 of the rotor 23 and is fitted into the substrate 22 with a dowel or the like so that the rotor 23 and the slider 13 are placed inside. And a case 28 for storage.
[0016]
In the hollow shaft rotary variable resistor 50 having the above structure, as shown in FIG. 2, a columnar shaft 60 (an insertion portion is partially cut) of a retrofitted motor or the like is a hollow shaft portion of the rotor 23. Even when 24 is inserted with some slack, the tip of the elastic protrusion 26 protruding from the inner wall of the hollow shaft portion 24 hits the shaft 60 and is elastically deformed, and the shaft 60 moves toward the central axis G. Is always strongly pressed against the inner wall of the hollow shaft portion 24. As a result, even the retrofitted shaft 60 is closely attached to the hollow shaft rotary variable resistor 50 without rattling. The rotor 23 is made of an elastic resin material, for example, Amodel.
[0017]
Next, in the hollow-shaft variable resistor 50 of FIG. 1, in addition to the above structure, the case 28 is a resin case, and the sliding portion as shown in FIG. 7 is brought into contact with the rotor 23 and the resin case 28. A washer 29 is interposed to reduce the rough wear of the contact portion of the rotor 23 with the resin case 28, thereby ensuring high reliability. That is, the sliding washer 29 is a thin (thickness t = 0.05 mm) washer made of, for example, a film or sheet of polytetrafluoroethylene (trade name Teflon of du Pont ), and is connected to the rotating rotor 23. The friction on the contact surface is kept low. According to the reliability test of the present inventor, the hollow shaft variable resistor provided with the sliding washer 29 has a long service life of 1 million revolutions or more.
[0018]
Next, in the hollow shaft variable resistor 50 of FIG. 1, in particular, the substrate 22 has terminal electrodes 7a, 7b, 7c, 7d and wiring portions 7e shown in FIGS. 4 and 5 on the front and back of the double-sided copper foil-clad resin laminate. Etching is carried out leaving behind (shaded portions) and through hole plating such as silver or conductive film printing (conductive paint is printed on a silk screen or the like) in the small holes 11 provided at the locations where the terminal electrodes are disposed. The terminal electrodes 7a, 7b, 7c and 7d are electrically connected to each other, and the resistor 4 and the conductor 36 are printed on the surface 22A side of FIG. 4 with a silk screen or the like as shown in FIG. It is formed by punching into a predetermined shape so as to cross the hole 11.
[0019]
In the structure of the substrate 22, since the substrate 22 is punched so as to cross the small hole 11, the semicircular depression of the small hole 11 which becomes the edge portion of the terminal electrodes 7 a, 7 b, 7 c, 7 d The conductive film 32 remains on the inner surface, and the back and front of the terminal electrode are conductive. Thus, it can be seen that with the substrate structure as described above, the formation of the terminal electrode is very simple and can be automated, thereby reducing the cost.
[0020]
Further, the terminal electrodes 7a, 7b, 7c, 7d are different from the conventional metal piece terminal electrodes 5a, 5b, 5c in that they are almost flat planar electrodes. Since the solder turns around and penetrates to the front side, the mounting strength is increased. Further, problems during conventional mounting, such as terminal bending, are also eliminated, and the mounting density is increased. Furthermore, it goes without saying that problems such as loosening of caulking of the conventional terminal electrodes 5a, 5b and 5c are also solved.
[0021]
As is clear from the above structure, it can be seen that the structure of the hollow-shaft rotary variable resistor 50 according to the present invention has a small number of parts, reduces the material cost, and facilitates assembly automation.
[0022]
As a precaution, the overall size and shape of the hollow-shaft rotary variable resistor 50 and the sizes and shapes of the members are assumed to be various designs. In other words, it has been found that an ultra-compact one having a diameter of about 11 mm and a thickness of 2.3 mm can be realized that is compatible with a retrofit shaft diameter of 3.5 mm.
[0023]
As described above in detail, it is clear that the hollow-shaft rotary variable resistor of the present invention is suitable for drive control of joints such as robots, and is a truly useful invention that has high reliability and low cost. is there.
[0024]
【The invention's effect】
Since the hollow-shaft rotary variable resistor according to the present invention is configured as described above, it has the following effects.
(1) Since the rear shaft inserted and fitted by the tongue-shaped elastic protrusions extending inside the hollow shaft portion of the rotor is pressed firmly and fixed , rattling of the rear shaft is prevented. The
(2) Since a sliding washer made of polytetrafluoroethylene in the form of a film or sheet is interposed at the contact portion between the resin case and the rotor, rough wear is reduced, rotation is smooth and high reliability (Long life of 1 million revolutions or more) is obtained.
( 3 ) The number of parts is small, the material cost is extremely reduced, and the automation of assembly is facilitated.
[0025]
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a hollow shaft rotary variable resistor according to the present invention.
FIG. 2 is a cross-sectional view of a state in which a retrofit shaft is fitted through the hollow shaft rotary variable resistor according to the present invention.
FIG. 3 is a plan view showing a structure of a substrate (upper surface) viewed from the inside of the hollow shaft rotary variable resistor according to the present invention.
FIG. 4 is a plan view showing the structure of the upper surface when the substrate is punched.
FIG. 5 is a plan view showing a structure of a lower surface at the time of punching the substrate.
6A is a plan view for explaining the structure of a hollow shaft rotor which is a main component of the present invention, FIG. 6B is a partial sectional view thereof, and FIG. 6C is a side view of a slider. It is.
FIG. 7 is a plan view of a sliding washer that is a component according to the present invention.
FIG. 8 is an exploded perspective view showing the structure of a conventional rotary variable resistor.
[Explanation of symbols]
2, 22 Substrate 22A One main surface (upper surface) of substrate
DESCRIPTION OF SYMBOLS 3 Through-hole 4 Resistor 5a-5c Terminal electrode 6a-6c Conductor 7a, 7b, 7c, 7d Terminal electrode 8, 27 Insertion hole 9 Rotor 10, 60 Shaft 11 Small hole 12, 13 Slider 23 Hollow shaft rotor 23A Disk part 23B Protrusion part 24 Hollow shaft part 26 Elastic protrusion part 28 (Resin) Case 29 Sliding washer 30 Rotary variable resistor 50 Hollow shaft rotary variable resistor 32 Conductive film 36 Conductor G Central axis

Claims (2)

A rotary variable resistor without a shaft, in which a resistor and a conductor are formed substantially concentrically on one main surface, and are electrically connected to a plurality of terminal electrodes disposed in a peripheral portion and at a central portion A substrate with an insertion hole;
It has a substantially cylindrical hollow shaft portion that is inserted into the insertion hole of the substrate and rotates at the center, protrudes from the inner wall of the hollow shaft portion , and its tip portion elastically deforms against a shaft that is inserted later. A disc-shaped rotor with a tongue-shaped elastic projection extending to press and fix the shaft against the inner wall of the hollow shaft portion toward the central axis ;
A slider mounted on one main surface of the disk portion of the rotor;
A case in which an insertion hole for pivotally mounting the hollow shaft portion of the rotor is provided and the rotor and the slider are housed in the substrate mounted on the substrate;
A hollow-shaft variable resistor comprising: The hollow shaft variable resistor according to claim 1, wherein the case is a resin case, and a sliding washer made of polytetrafluoroethylene in the form of a film or sheet is interposed at a contact portion between the rotor and the resin case. A hollow shaft variable resistor characterized by comprising:

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