Variable resistor

Information

  • Patent Grant
  • 6434815
  • Patent Number
    6,434,815
  • Date Filed
    Monday, September 20, 1999
    24 years ago
  • Date Issued
    Tuesday, August 20, 2002
    21 years ago
Abstract
A first rotor and a second rotor are prepared. The first rotor has a resistor and inner-peripheral and outer-peripheral electrodes respectively connected to end portions of this resistor. The second rotor has a resistor and inner-peripheral and outer-peripheral electrodes symmetrical with those of the first rotor, provided at a position corresponding to that obtained by rotating the first rotor about the axis of the first rotor by an angle of 180° with respect to the first rotor. A variable resistor selectively uses either one of the first rotor and second rotor. This makes it possible to provide a variable resistor which requires few parts. Also, this makes it possible to reduce the kinds of bending operations that must be performed on the terminals.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a variable resistor and, more particularly, to a residue-proof (e.g., dust-proof) variable resistor equipped with a case. The invention also pertains to a method for producing such a variable resistor.




2. Description of the Related Art





FIG. 36

shows a conventional variable resistor. The variable resistor


180


comprises an alumina substrate


184


having on its surface a horseshoe resistor


181


, collector electrode thin film


183


and electrode thin films


182


respectively connected to end portions of the horseshoe resistor


181


. A case


185


is provided for accommodating the alumina substrate


184


therein. Three lead terminals


186


(one of which is shown in

FIG. 36

) are allowed to pass through the alumina substrate


184


and are respectively soldered to the electrode thin films


182


and


183


. A rotor


187


is accommodated in the case


185


. A slider


189


is disposed on a rear surface of the rotor


187


. A sealine O-ring


190


is disposed on the rotor


187


and a resin


191


is provided for sealing an opening in the rear surface of the case


185


. Furthermore, when this variable resistor


180


is configured into a so-called “side surface adjusting type variable resistor”, wherein the resistance value is adjusted by rotating the rotor


187


from an arrow-indicated direction illustrated in

FIG. 36

, the lead terminals


186


are bent along the rear surface of the case


185


.




An explanation will be given of the terminal numbers


1


,


2


and


3


illustrated in

FIG. 37

with reference to FIG.


38


. It is now assumed that the lead terminal number


2


is the terminal connected to the slider


189


brought into sliding contact with the resistor


181


. Next, it is assumed that the lead terminal number


3


is the terminal electrically connected to the end portion side of the resistor


181


on a side such that when the rotor


187


is rotated to the right the resistance value between this lead terminal and the lead terminal corresponding to the terminal number


2


becomes smaller. Finally, the lead terminal number


1


is the terminal electrically connected to the other end portion side of the resistor


181


on a side such that when the rotor


187


is rotated to the right the resistance value between this lead terminal and the lead terminal corresponding to the terminal number


2


becomes larger.




In the variable resistor


180


of the side surface adjusting type, various combinations are made among the resistance value adjusting direction, lead terminal pitches and lead terminal numbers. To accommodate these changes, it was necessary that many kinds of constituent parts be prepared and many kinds of processing methods be executed. In particular, regarding the complex bending of the lead terminals


186


, as illustrated in

FIG. 37

, two kinds of initial bending are included (i.e., a case where the lead terminal is bent into the lead terminal


186


indicated in a solid line shown in

FIG. 36 and a

case where the lead terminal is bent into the lead terminal


186


′ indicated in a one-dot chain line shown in the same figure). There are three kinds of subsequent bending, including a first kind corresponding to a state in which the terminal numbers


1


,


2


and


3


are arranged in one row in this order, a second kind corresponding to a state in which the terminal number


2


is located on the left side of the terminal numbers


1


and


3


, and a third kind corresponding to a state in which the terminal number


2


is located on the right side of the terminal numbers


1


and


3


. This is shown in FIG.


37


. The second column of permutations in this figure corresponds to the initial bending operation and the third column of permutations in this figure corresponds to the subsequent bending operations. More specifically, the third column represents a view of the components taken from the direction A after completion of all bending steps.




The subsequent bending after the initial bending is three in kind with respect to each of the two kinds of initial bending. Thus, six bending methods become necessary. This made the manufacture and management of these parts complex, which hindered productivity.




SUMMARY OF THE INVENTION




The present invention has an object to provide a variable resistor which has a small number of constituent parts and can reduce the kinds of the terminal bending operations required.




To attain the above object, there is provided a variable resistor comprising a first rotor or a second rotor, the first rotor having provided on its surface a resistor and an electrode connected to at least one end portion of the resistor. The second rotor has provided thereon a resistor and electrode at a position obtained by rotating a resistor and electrode symmetrical with those of the first rotor through an angle of 180° with respect to the first rotor. The variable resistors further includes at least two slide contactors, and a case provided with a recess portion, whereby either one of the first and second rotors is rotatably accommodated in the recess portion of the case having the slide contactors exposed in a bottom surface thereof. The slide contactors contact the resistor and electrode when the rotor is disposed in the recess. A cover is mounted on an opening of the recess portion of the case.




Here preferably, the resistor provided on each of the first and second rotors is shaped like a horseshoe and the electrode provided on each of the first and second rotors is formed concentrically with the horseshoe resistor. Also, the variable resistor can be of a structure wherein a lead terminal separate from the slide contactor is connected to this slide contactor. Also, the rotors can each be made of insulating resin or ceramic having the resistor and electrode provided on their surface. Further, the rotors can be constructed by combining the substrate having the resistor and electrode provided on their surface and a main body.




Thus, two kinds of rotors are provided, one of which is a first rotor and the other of which is a second rotor having provided thereon a resistor and electrode at a position obtained by rotating a resistor and electrode symmetrically with those of the first rotor through an angle of 180° with respect to the first rotor. One of these rotors is selected and then inserted in the case. The terminal number is changed and, as a result, initial bending of the terminal is reduced from the convention two kinds of bending operations to one kind of bending operation.




Also, the cover has mounting claw portions disposed in 180° rotation symmetry about a rotation axis of the first and second rotors, and these mounting claw portions are inserted by force into holes provided in the case, whereby the cover is mounted on the case.




The variable resistor can be configured as a sealed structure by mounting the cover onto the opening of the case via an O-ring. Also, by the cover being mounted by a forced insertion method, the conventional sealing operation based on the use of resin becomes unnecessary and in addition the resulting variable resistor requires fewer assembling steps and thus productivity of these devices improves. The forward end portions of the mounting claw portions of the cover are folded back and slits and engagement portions are provided in and on the mounting claw portions. This structure helps prevent the cover from coming off.




Also, the cover has an adjusting opening at its central part and at least one of bending and burring is performed of the edge portion of this adjusting opening toward the side of the rotor. By performing bending or burring of the edge of the adjusting hole provided at the central part of the cover, the insertability of the driver at the adjusting time and the strength of the cover itself is increased. Accordingly, the deformation of the top surface of the cover after the mounting of it is prevented and the contact reliability of the contact between the resistor or electrode and the slide contactor is enhanced.




Further, the variable resistor according to the present invention has an adaptor for maintaining the terminal pitch dimension. By this adaptor, the terminal pitch dimension is maintained stably.











BRIEF DESCRIPTION OF THE DRAWINGS




The foregoing, and other, objects, features and advantages of the present invention will be more readily understood upon reading the following detailed description in conjunction with drawings in which:





FIG. 1

is a plan view illustrating a first rotor used in an embodiment of a variable resistor according to the present invention;





FIG. 2

is sectional view taken along a line II—II of the first rotor illustrated in

FIG. 1

;





FIG. 3

is a bottom surface view illustrating the first rotor illustrated in

FIG. 1

;





FIG. 4

is a view illustrating a second rotor;





FIG. 5

is a sectional view taken along a V—V of the second rotor illustrated in

FIG. 4

;





FIG. 6

is a bottom surface view illustrating the second rotor illustrated in

FIG. 4

;





FIG. 7

is a plan view illustrating a case used in the embodiment of the variable resistor;





FIG. 8

is a sectional view taken along a line VIII—VIII of the case illustrated in

FIG. 7

;





FIG. 9

is a bottom surface view illustrating the case illustrated in

FIG. 7

;





FIG. 10

is a view taken along a line X—X of the case illustrated in

FIG. 7

;





FIG. 11

is a bottom surface view illustrating the case after the lead terminals have been connected thereto;





FIG. 12

is a plan view illustrating a metal cover used in the embodiment of the variable resistor;





FIG. 13

is a side view illustrating the metal cover illustrated in

FIG. 12

;





FIG. 14

is a sectional view taken along a line XIV—XIV of the metal cover illustrated in

FIG. 12

;





FIG. 15

is a front view illustrating an adaptor used in the embodiment of the variable resistor;





FIG. 16

is a sectional view taken along a line XVI—XVI of the adaptor illustrated in

FIG. 15

;





FIG. 17

is a plan view illustrating the adaptor illustrated in

FIG. 15

;





FIG. 18

a front view illustrating the variable resistor wherein the first rotor is accommodated in case;





FIG. 19

is a sectional view taken along a line XIX—XIX of the variable resistor illustrated in

FIG. 18

;





FIG. 20

is an explanatory view of the rotation direction of the first rotor and the terminal numbers;





FIG. 21

a front view illustrating the variable resistor wherein the second rotor is accommodated in the case;





FIG. 22

is a sectional view taken along a line XXII—XXII of the variable resistor illustrated in

FIG. 21

;





FIG. 23

is an explanatory view of the rotation direction of the second rotor and the terminal numbers;





FIG. 24

is an explanatory view illustrating the kind of the bending methods (operations) for variable resistor;





FIG. 25

is a plan view illustrating a first rotor used in another embodiment of the present invention;





FIG. 26

is a sectional view taken along a line XXVI—XXVI of the first rotor illustrated in

FIG. 25

;





FIG. 27

is a bottom surface view illustrating the first rotor illustrated in

FIG. 25

;





FIG. 28

is a plan view illustrating a main body of each of a first rotor and second rotor used in still another embodiment of the present invention;





FIG. 29

is a sectional view taken along a line XXIX—XXIX of the main body illustrated in

FIG. 28

;





FIG. 30

is a bottom surface view illustrating the main body illustrated in

FIG. 28

;





FIG. 31

is a bottom surface view illustrating a substrate combined with the main body illustrated in

FIG. 28

;





FIG. 32

is a sectional view illustrating the substrate illustrated in

FIG. 31

;





FIG. 33

is a plan view illustrating the first rotor wherein the main body illustrated in FIG.


28


and the substrate illustrated in

FIG. 31

are combined with each other;





FIG. 34

is a sectional view taken along a line XXXV—XXXV of the first rotor illustrated in

FIG. 33

;





FIG. 35

is a bottom surface view illustrating the first rotor illustrated in

FIG. 33

;





FIG. 36

is a sectional view illustrating a conventional variable resistor;





FIG. 37

is an explanatory view illustrating the kind of the bending methods (operations) for the conventional variable resistor; and





FIG. 38

is an explanatory view of the terminal numbers of the variable resistor.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




An embodiment of a variable resistor according to the present invention will now be explained with reference to the appended drawings.




As illustrated in

FIGS. 1

to


3


, a first rotor


118


used in a variable resistor according to this embodiment is substantially shaped like a circular column and is composed of a main body


119


and a substrate


120


bonded to the underside of this main body


119


. At a central part of the upper surface of the main body


119


there is provided a crossed groove


121


for use in conjunction with a driver. Around the crossed groove


121


there is provided an escape groove


122


substantially shaped like a circular arc. Further, a stopper


123


is provided in contact with a prescribed position of this escape groove


122


. A notch


124


is provided in the outer-peripheral edge portion of the upper surface of the main body


119


. On the underside of the main body


119


there are provided projections


119




a


and


119




b.






In the substrate


120


there are provided a hole


120




a


and a notch


120




b


. The hole


120




a


and notch


120




b


conform with the projections


119




a


and


119




b


, respectively. The displacement between the main body


119


and the substrate


120


due to the rotation thereof is prevented by the projections


119




a


and


119




b


being fitted into the hole


120




a


and notch


120




b


, respectively. Further, a horseshoe resistor


125


is provided on the underside of the substrate


120


by screen printing or transfer. Both end portions of the resistor


125


are electrically connected to an inner-peripheral electrode


126


and an outer-peripheral electrode


127


. The inner-peripheral electrode


126


and outer-peripheral electrode


127


are formed concentrically with the horseshoe resistor


125


. The inner-peripheral electrode


126


has a circular portion at the central part of the substrate


120


while, on the other hand, the outer-peripheral electrode


127


has a circular arc portion at the outer-peripheral part of the substrate


120


.




The main body


119


and the substrate


120


are fabricated using ceramic material such as alumina or using a heat-resisting resin such as polyphenylene sulfide, and the resistor


125


is fabricated using a cermet resistor or carbon resistor. If, for example, inexpensive polyphenylene sulfide resin or glass epoxy resin is used as the material of the main body


119


and substrate


120


and an inexpensive carbon resistor is used as the resistor


125


, it is possible to reduce the manufacturing cost of the variable resistor.




Further, as illustrated in

FIGS. 4

to


6


, a second rotor is prepared having a resistor and inner-peripheral and outer-peripheral electrodes provided at a position corresponding to that obtained by rotating a resistor and inner-peripheral and outer-peripheral electrodes symmetrical with those of the first rotor


118


about the axis of the first rotor


118


through an angle of 180° with respect to the first rotor


118


. The second rotor


138


is substantially shaped like a circular column and is composed of a main body


139


and a substrate


140


bonded to the underside of this main body


139


. At the central part of the upper surface of the main body


139


there is provided a crossed groove


141


for use in conjunction with a driver. Around the crossed groove


141


there is provided an escape groove


142


substantially shaped like a circular arc. Further, a stopper


143


is provided in contact with a prescribed position of this escape groove


142


. A notch


144


is provided in the outer-peripheral edge portion of the upper surface of the main body


139


. On the underside of the main body


139


there are provided projections


139




a


and


139




b.






In the substrate


140


there are provided a hole


140




a


and a notch


140




b


. The hole


140




a


and notch


140




b


positionally conform with the projections


139




a


and


139




b


. The displacement between the main body


139


and the substrate


140


due to the rotation thereof is prevented by the projections


139




a


and


139




b


being fitted into the hole


140




a


and notch


140




b


, respectively. The position of the projections


139




a


,


139




b


and the hole


140




a


and notch


140




b


corresponds to the position obtained by rotating the projections


119




a


,


119




b


and the hole


120




a


and notch


120




b


of the first rotor


118


about the axis of the first rotor


118


through an angle of 180°.




Further, a horseshoe resistor


145


is provided on the underside of the substrate


140


. End portions of the resistor


145


are electrically connected to an inner-peripheral electrode


146


and an outer-peripheral electrode


147


, respectively. The inner-peripheral electrode


146


and outer-peripheral electrode


147


are formed concentrically with the horseshoe resistor


145


. The inner-peripheral electrode


146


has a circular portion at the central part of the substrate


140


while, on the other hand, the outer-peripheral electrode


147


has a circular arc portion at the outer-peripheral part of the substrate


140


. The position of the resistor


145


and electrodes


146


,


147


corresponds to the position obtained by respectively rotating the resistor


125


and electrodes


126


,


127


of the first rotor


118


about the axis of the first rotor


118


through an angle of 180°.




As illustrated in

FIGS. 7

to


10


, a case


2


has a recess portion


3


. The recess portion


3


has a circular shape in cross section in conformity with the configuration of the first or second rotor


118


,


138


and is thereby designed so that the first or second rotor


118


,


138


can be smoothly rotated when accommodated in the recess portion


3


. Also, the depth of the recess portion


3


of the case


2


is set so that the upper surface of the first rotor


118


or second rotor


138


is slightly higher than the upper surface of the recess portion


3


of the case


2


. This is for the purpose of making a reliable contact between the first rotor


118


and a metal cover


30


and thereby making the backlash of the first rotor


118


small.




A hole is provided at each of four corners of the upper surface of the case


2


. The case


2


is made of polyamide system nylon having a high resistance to heat, such as


46


nylon, thermoplastic resin such as polyphenylene sulfide, polybutylene terephthalate or liquid crystal polymer, or thermosetting resin such as epoxy or diallyl phthalate. If especially using a polyphenylene sulfide resin, the resistance to moisture is also enhanced. Also, the use of a thermoplastic resin facilitates the fusion of the case to an adaptor, as later described.




Slide contactors


9


,


10


and


11


are, for example, insert molded in a bottom portion of the case


2


and are partly exposed from the bottom surface of the recess portion


3


of the case


2


. The slide contactors


9


to


11


are structured such that their bottom portions


9




b


to


11




b


, indicated in two-dot chain lines in

FIG. 7

are each folded back at a folding-back line L, and each folded-back bottom portion is thereby disposed over the corresponding remaining bottom portion, the two bottom portions being thus doubled. By virtue of these bottom portions


9




b


to


11




b


, the underside of the slide contactors


9


to


11


are lidded to ensure a seal for the interior of the case


2


. This, in conjunction with the outer-peripheral portions of the slide contactors


9


to


11


, prevents molten resin from flowing onto the surfaces of arms


9




a


to


11




a


when resin-molding the case


2


. This prevents the molten resin from attaching onto the arms, which, in turn, simplifies the resin molding process.




The respective arms


9




a


,


10




a


and


11




a


provided at the central portions of the slide contactors


9


,


10


and


11


protrude from the bottom surface of the recess portion


3


. Each of these arms is shaped like a comb. The arms


9




a


to


11




a


contact, at their contact portions A, B and C, with the circular portion of the electrode


126


or


146


, the circular arc portion of the electrode


127


or


147


and the resistor


125


or


145


of the first or second rotor


118


or


138


. respectively. The outer-peripheral portions of the slide contactors


9


to


11


are embedded in the case


2


. At the central portions thereof, where the arms


9




a


to


11




a


are provided, there are provided substantially L-shaped (or substantially horizontally U-shaped) notches


9




c


to


11




c


. By providing these notches


9




c


to


11




c


, the formation of the comb-shaped arms


9




a


to


11




a


is facilitated and the spring property of the arms


9




a


to


11




a


is improved.




Further, the slide contactor


9


is arranged such that a “land”


9




d


for connection of a lead terminal, indicated in a two-dot chain line in

FIG. 7

, is folded back at a folding-back line M. The lead terminal connection land


9




d


is exposed in an opening


5


for the lead terminal which is provided in the underside of the case


2


(see FIGS.


9


and


10


). Similarly, the slide contactor


10


is arranged such that a land


10




d


for connection of a lead terminal, indicated in a two-dot chain line in

FIG. 7

, is exposed in an opening


6


therefor which is provided in the underside of the case


2


.




A led-out or extended portion


11




e


of the slide contactor


11


, which is extended from the side surface of the case


2


, is bent along the case


2


and, as illustrated in FIG.


11


. is directed by a guide groove


7


provided in the underside of the case


2


to follow a prescribed track. Thereby, a forward end portion thereof is disposed at a central part of the underside of the case


2


. At this time, as illustrated in

FIG. 11

, both side wall portions


7




a


at prescribed positions of the guide groove


7


are caulked. As a result of this, the extended portion


11




e


can be firmly fixed to the underside of the case


2


and can be prevented from becoming detached. Furthermore, extended portions


9




e


and


10




e


of the slide contactors


9


and


10


. respectively, which are extended from the side surface of the case


2


, are cut away in a subsequent step. The slide contactors


9


to


11


are each made of, for example, a copper alloy such as white metal having a spring property or a metal plate such as stainless steel.




As illustrated in

FIG. 11

, lead terminals


15


,


16


and


17


are each circular in cross section. The lead terminals


15


and


16


are bonded, at the end surfaces of their lead wires. to the lead terminal connection lands


9




d


and


10




d


which are exposed in the lead terminal openings


5


and


6


provided in the underside of the case


2


by soldering, resistance welding, ultrasonic welding or other technique. Using the same method, the lead terminal


17


is bonded, at the end surface of its lead wire, to the extended portion


11




e


disposed on the underside of the case


2


. In the special case where resistance welding or ultrasonic welding is used as the bonding method, the flux cleaning performed when soldering is used becomes unnecessary. This makes it possible to reduce the manufacturing cost.




As illustrated in

FIGS. 12

to


14


, the metal cover


30


is provided with an adjusting opening


31


at its central part and has graduations


36


around this opening


31


. The graduations


36


are spaced over a range within which the first rotor


118


can be rotated. Also, a tongue-shaped stopper receiver


32


is provided in contact with this opening


31


. The edge portion of the adjusting opening


31


is bent and raised toward the first rotor


118


by bending or burring. As a result of this, the insertability of the driver when adjustment is made is enhanced, the strength of the cover


30


itself is increased, the deformation of the top surface of the cover


30


after the mounting thereof is prevented, and the reliability on the contact between the resistor


125


,


145


or electrodes


126


,


127


or


146


,


147


and the contact portions A, B and C of the slide contactors


9


to


11


is enhanced.




Mounting claw portions


33


are provided at four corners of the metal cover


30


in such a way as to have a 180° rotation symmetry about the adjusting opening


31


. Therefore, when the metal cover


30


is mounted on the case


2


, even if the direction of mounting is rotated through an angle of 180°, the metal cover


30


can be mounted on the case


2


with no difference in terms of the function performed by the variable resistor. Forward end portions


33




a


of the mounting claw portions


33


are folded back. Projections


35


are provided on both sides of each mounting claw portion


33


as viewed in the widthwise direction thereof. Thus, the metal cover


30


has the function of its being prevented from coming off from the case


2


. Further, a slit


34


is provided at a central part of the mounting claw portion


33


as viewed in the widthwise direction thereof, with the result that forced insertion into the case


2


is facilitated and simultaneously the retention force can be increased. The metal cover


30


is made of metal material such as stainless steel or the like.




As illustrated in

FIGS. 15

to


17


, an adaptor


40


is substantially shaped like a character “L” and has a pedestal portion


41


having the case


2


placed thereon and a rear plate portion


50


. The pedestal portion


41


has provided therein grooves


46


,


47


and


48


for respectively accommodating the bent lead terminals


15


,


16


and


17


therein. Both end portions of the grooves


46


to


48


are provided with through holes


43




a


and


43




b


,


44




a


and


44




b


, and


45




a


and


45




b


for insertion of the lead terminals


15


to


17


therethrough. The lead terminal


15


is inserted through either one of the through openings


43




a


and


43




b


, the lead terminal


16


is inserted through either one of the through openings


45




a


and


45




b


and the lead terminal


17


is inserted through either one of the through openings


44




a


and


44




b


. As a result of this, the dimension of the lead terminal pitch is stably maintained. Further, the pedestal portion


41


is provided with fusion spaces


49




a


and


49




b


for fusing the case


2


by ultrasonic waves or the like.




The rear plate portion


50


is provided with grooves


51


,


52


and


53


for respectively accommodating the bent lead terminals


15


,


16


and


17


therein. The adaptor


40


is made of, for example, polyamide system nylon having a high resistance to heat such as


46


nylon, or thermoplastic resin such as polyphenylene sulfide, polybutylene terephthalate or liquid crystal polymer, or the like. By especially using the same material that the case


2


is made of, the fusion between the adaptor


40


and the case


2


is improved with the result that the strength of the resulting structure becomes high.




An O-ring


45


for providing a seal illustrated in

FIG. 19

is made of, for example, silicone rubber. The O-ring is accommodated in the notch


124


or


144


of the first or second rotor


118


or


138


and provides a sealing function between the cover


30


and the case


2


. By using a silicone rubber having a hardness of 60° to 70°, for example, it is possible to reduce the amount of the backlash of the first or second rotor


118


or


138


occurring when rotation adjustment is made by a driver.




The above-described constituent parts are assembled in accordance with the following procedure. That is, as illustrated in

FIGS. 18 and 19

, the first rotor


118


is accommodated in the recess portion


3


of the case


2


in such a way that the resistor


125


and the electrodes


126


and


127


thereof respectively contact with the contact portions C, A and B. Next, the O-ring


45


is inserted in the gap between the outer-peripheral edge portion


124


of the first rotor


118


and the case


2


. Thereafter, the metal cover


30


is lidded over the case


2


, such that the portion where no graduation


36


are made is oriented in a direction opposite to that of the terminal


11




e


led out from the case


2


. Subsequently, the mounting claw portions


33


are inserted by force into the holes


4


of the case


2


. Thereby, the metal cover


30


is firmly mounted on the case


2


in a state where the first rotor


118


is confined in the recess portion


3


. As a result of this, the case


2


is sealed, and accordingly the conventional sealing operation performed using resin can be omitted, and the number of the assembling steps can be reduced. In addition, the displacement of the contact portions between the resistor


125


and the electrodes


126


,


127


and their corresponding contact portions A to C are suppressed, and thereby the setting of the resistance values is stabilized.




Next, the lead terminals


15


to


17


are subjected to initial bending along the rear surface of the case


2


and the forward end portions thereof are led out in a direction substantially perpendicular to the side surface of the case


2


. Further, after having been bent along the side surface of the case


2


so as to have various required terminal pitch dimensions, the lead terminals are subjected to second bending in a direction substantially perpendicular to the side surface of the case


2


, provided, however, that this second bending is performed with respect to only the lead terminal needed to be bent. Thereafter, the lead terminals


15


to


17


are inserted into the through-holes


43




a


to


45




b


of the adaptor


40


which correspond to the required terminal pitches. Thereby, the case


2


is placed on the adaptor


40


.

FIGS. 18 and 19

illustrate a case where the lead terminals


15


,


16


and


17


are respectively inserted into the through-holes


43




b


,


45




b


and


44




b


of the adaptor


40


. The side surface of the case


2


, from which the forward end portions of the lead terminals


15


to


17


are led out, and the adaptor


40


are fused together via the fusion spaces


49




a


and


49




b


by ultrasonic welding or the like. Therefore, no engagement portion of a special configuration for use in bonding the case


2


and the adaptor


40


is needed to be provided on the case


2


and adaptor


40


. This makes it possible to configure each of the case


2


and adaptor


40


using a simple structure.




A variable resistor


61


which has been assembled in the above-described manner is or a side surface adjusting type. That is, a forward end portion of the driver is applied from an arrow-indicated direction illustrated in

FIG. 19

to the for-use-of-driver crossed groove


121


of the first rotor


118


to thereby rotate the first rotor


118


. Through this rotation, the contact portion C is brought into sliding contact with the resistor


125


, the contact portion A is brought into sliding contact with the inner-peripheral electrode


126


, and the contact portion B is brought into sliding contact with the outer-peripheral electrode


127


to cause variation of the resistance value between the terminals


15


and


17


and the resistance value between the terminals


16


and


17


.




The relationship between the resistance-value varying first rotor


118


and the terminal number will now be explained with reference to FIG.


20


. For example, in order to make the resistance value small between the contact portion A coming into sliding contact with the inner-peripheral electrode


126


and the contact portion C coming into sliding contact with the resistor


125


, the first rotor


118


is rotated in an arrow E-indicated direction. When applying this relationship to

FIG. 38

, the contact portion A corresponds to the terminal number


1


and so the lead terminal


16


connected to the contact portion A is the terminal number


1


. Accordingly, the lead terminal


15


connected to the remaining contact portion B is the terminal number


3


. It is to be noted that the stopper receiver


32


provided on the metal cover mounted on the case


2


is disposed in the escape groove


122


provided in the first rotor


118


. This stopper receiver


32


regulates the stopper


123


provided in the first rotor


118


to regulate the rotation angle of the first rotor


118


.




The second rotor


138


is also similarly accommodated in the recess portion


3


of the case


2


. That is, as illustrated in

FIGS. 21 and 22

the second rotor


138


is accommodated in the recess portion


3


of the case


2


in such a way that the resistor


145


and the electrodes


146


and


147


thereof respectively contact with the contact portions C, A and B. Next, the O-ring


45


is inserted in the gap between the outer-peripheral edge portion


144


of the second rotor


138


and the case


2


. Thereafter, the metal cover


30


is rotated through an angle of 180° with respect to the metal cover


30


of the first rotor


118


and is lidded onto the case


2


from above the same. Subsequently, the mounting claw portions


33


are inserted by force into the holes


4


of the case


2


. Thereby, the metal cover


30


is firmly mounted on the case


2


in a state where the second rotor


138


is confined in the recess portion


3


.




Next, the lead terminals


15


to


17


are subjected to initial bending along the rear surface of the case


2


and the forward end portions thereof are led out in a direction substantially perpendicular to the side surface of the case


2


. This leading-out direction is the same as that in the case where assembling is performed using the first rotor


118


. Further, after having been bent along the side surface of the case


2


so as to have various required terminal pitch dimensions, the lead terminals are subjected to second bending in a direction substantially perpendicular to the side surface of the case


2


, provided, however, that this second bending is performed with respect to only the lead terminal needed to be bent. Thereafter, the lead terminals


15


to


17


are inserted into the through-holes


43




a


to


45




b


of the adaptor


40


which correspond to the required terminal pitches. Thereby, the case


2


is placed on the adaptor


40


.

FIGS. 21 and 22

illustrate a case where the lead terminals


15


,


16


and


17


are respectively inserted into the through-holes


43




b


,


45




b


and


44




b


of the adaptor


40


. The side surface of the case


2


, from which the forward end portions of the lead terminals


15


to


17


are led out, and the adaptor


40


are fused together via the fusion spaces


49




a


and


49




b


by ultrasonic welding or the like. Here, the case


2


having the second rotor


138


accommodated therein is at all times fused to the adaptor


40


at its side surface, the same as that at which the case


2


having the first rotor


118


accommodated therein is fused to the adaptor


40


. This makes it possible to configure each of the case


2


and adaptor


40


using a simple structure. This reduces the cost of the parts including the dies for the case


2


and adaptor


40


.




A variable resistor


71


which has been assembled in the above-described manner is of a side surface adjusting type. That is, the forward end portion of the driver is applied from an arrow-indicated direction illustrated in

FIG. 22

to the for-use-of-driver crossed groove


141


of the second rotor


138


to thereby rotate the second rotor


138


. Through this rotation, the contact portion C is brought into sliding contact with the resistor


145


, the contact portion A is brought into sliding contact with the inner-peripheral electrode


146


, and the contact portion B is brought into sliding contact with the outer-peripheral electrode


147


to cause variation of the resistance value between the terminals


15


and


17


and the resistance value between the terminals


16


and


17


.




The relationship between the resistance-value varying second rotor


138


and the terminal number will now be explained with reference to

FIG. 23

, in the same way as in the case of the above-described first rotor


118


. For example, in order to make the resistance value small between the contact portion A coming into sliding contact with the inner-peripheral electrode


146


and the contact portion C coming into sliding contact with the resistor


145


, the second rotor


138


is rotated in an arrow F-indicated direction. It follows from this rotation direction that the contact portion A corresponds to the terminal number


3


and so the lead terminal


16


connected to the contact portion A is the terminal number


3


. Accordingly, the lead terminal


15


connected to the remaining contact portion B is the terminal number


1


.




In the variable resistors


61


and


71


having the above-described constructions, as illustrated in

FIG. 24

, the initial bending of the initial lead terminals


15


to


17


is performed in the same direction. The subsequent bending of the lead terminals is three in kind. Furthermore, as explained with reference to

FIGS. 20 and 23

, the terminal number


1


can be interchanged with the terminal number


3


by appropriately combining two kinds of rotors, i.e., first rotor


118


and second rotor


138


with one kind of case, i.e., case


2


. Accordingly, the method of initial bending of the lead terminals


15


to


17


can be reduced from the conventional two kinds of bending operations to one kind of bending operation. The direction of subsequent bending of the lead terminals


15


to


17


can be reduced from the conventional six kinds of bending operations to three kinds of bending operations. As a result, the assembling and lead terminal bending steps can be simplified and therefore it is possible to facilitate the manufacture and management of the side surface adjusting type variable resistor, thus reducing the manufacturing cost and enhancing the productivity.




The reason why the metal cover is mounted by being rotated through an angle of 180° according to the selective use of one of the first rotor


118


and the second rotor


138


is for the purpose of regulating the rotation range of each of the first rotor


118


and second rotor


138


and thereby ensuring that the contact portions A, B and C do not slide off of their prescribed slide range of the resistor


125


or


145


, inner-peripheral electrode


126


or


146


and outer-peripheral electrode


127


or


147


by which the contact portions A, B and C are contacted in sliding engagement.




The variable resistor according to the present invention is not limited to the above-described embodiment and can be modified in various ways without departing from the spirit and scope of the invention.




Although in the above-described embodiment, reference has been made to the structure wherein the slide contactor and the lead terminal are each configured as separate members, the led-out portion of the slide contactor can be extended and this extended portion can function as a lead terminal.




Also, the device can be configured to electrically connect the outer-peripheral electrode


127


or


147


or inner-peripheral electrode


126


or


146


to only either one end portion of the resistors


125


or


145


.




Also, the first and second rotors are each not necessarily composed of the substrate having the resistor and electrodes provided on the surface thereof and the main body. Rather, the rotors can each be configured in accordance with the rotor


150


illustrated in, for example,

FIGS. 25

to


27


. This rotor


150


is described as the first rotor but the same principles can be applied to the second rotor. This rotor


150


is substantially shaped as a circular column and has an insulating structure made of, for example, resin or ceramic. At a central part of the upper surface of this rotor


150


there is provided a crossed groove


151


for use in conjunction with a driver. Around the crossed groove


151


there is provided an escape groove


152


substantially shaped like a circular arc. Further, a stopper


153


is provided at a prescribed position of this escape groove


152


. A notch


154


is provided in the outer-peripheral edge portion of the upper surface of the rotor


150


. On the underside of the rotor


150


there are concentrically formed a horseshoe resistor


155


, inner-peripheral electrode


156


and outer-peripheral electrode


157


.




Also, although the first and second rotors of the above-described embodiment make it necessary to prepare two kinds of the substrates having the resistor and electrodes provided on the surface thereof and the main body, using a main body


160


illustrated in

FIGS. 28-30

enables the construction of the first and second rotors each having a common main body and thereby further reduces the number of different parts required. That is, at a central part of the upper surface of the main body


160


there is provided a crossed groove


161


for use in conjunction with a driver. Around the crossed groove


161


there is provided an escape groove


162


substantially shaped like a circular arc. Further, a stopper


163


is provided at a prescribed position of this escape groove


162


. A notch


164


is provided in the outer-peripheral edge portion of the upper surface of the main body


160


. On the outer-peripheral edge portion of the underside of the main body


160


there are provided guide projections


165




a


,


165




b


,


165




c


and


165




d


at equal intervals.




As illustrated in

FIGS. 31 and 32

, in the outer-peripheral edge portion of the substrate


170


there are provided notches


174




a


,


174




b


,


174




c


and


174




d


, whose configurations are made to conform with those of the guide projections


165




a


to


165




d


. By clamping the substrate


170


by the guide projections


165




a


to


165




d


, the displacement between the main body


160


and the substrate


170


due to the rotation thereof is prevented. Further, a horseshoe resistor


171


is provided on the underside of the substrate


170


. End portions of the resistor


171


are electrically connected to an inner-peripheral electrode


172


and an outer-peripheral electrode


173


. The inner-peripheral electrode


172


and outer-peripheral electrode


173


are formed concentrically with the horseshoe resistor


171


. The inner-peripheral electrode


172


has a circular portion at the central part of the substrate


170


while, on the other hand, the outer-peripheral electrode


173


has a circular arc portion at the outer-peripheral part of the substrate


170


.




As illustrated in

FIGS. 33

to


35


, by bonding this substrate


170


to the underside of the main body


160


, the first rotor is provided. Furthermore, by bonding a main body the same as the main body


160


and a substrate having provided on its surface a resistor and electrodes symmetrical with those


171


,


172


and


173


, a second rotor is provided.




As apparent from the foregoing description, according to the present invention, by selecting either one of the first rotor having provided thereon the resistor and electrodes and the second rotor having provided thereon a resistor and electrodes symmetrical with those of the first rotor at the position obtained by rotating these elements through an angle of 180° with respect to the first rotor and accommodating the selected rotor in the case, the terminal numbers can be changed and the initial bending of the terminal can be reduced from the conventional two kinds of bending operations to one kind of bending operation. As a result, it is possible to facilitate the manufacture and management of the side surface adjusting type variable resistor and thereby reduce the manufacturing cost and enhance the productivity.




Also, since the cover has the mounting claw portions disposed at equal intervals, when the cover is mounted on the case, the cover can be mounted also in a mounting direction different 180° from another with no difference in function being made therebetween. Accordingly, one kind of cover can be commonly mounted both on the first rotor accommodated case and on the second rotor accommodated case to thereby reduce the number of the parts used. Further, since the cover is made to seal the case by being firmly mounted on the case, it is possible to omit the conventional sealing operation based on the use of resin and thereby reduce the number of the assembling steps.




Also, since the forward end portions of the mounting claw portions are folded back and in addition the slits and engagement portions are provided in and on these mounting claw portions whereby these mounting claw portions of the cover are inserted by force into the openings provided in the case, the function of preventing the cover from coming off can be enhanced. Further, by performing the bending or burring of the edge portion of the adjusting hole toward the rotor side, the insertability of the driver at the adjusting time is enhanced, the strength of the cover itself is increased, the deformation of the top surface of the cover after the mounting of the cover is prevented, and the contact reliability of the contact between the resistor or electrodes and the contact portions of the slide contactors is enhanced.




Also, using the adaptor for maintaining the terminal pitch dimension, the terminal pitch dimension can be maintained in a stable condition.




The above-described exemplary embodiments are intended to be illustrative in all respects, rather than restrictive, of the present invention. Thus the present invention is capable of many variations in detailed implementation that can be derived from the description contained herein by a person skilled in the art. All such variations and modifications are considered to be within the scope and spirit of the present invention as defined by the following claims.



Claims
  • 1. A method for producing a single variable resistor comprising:providing a case having a recess formed therein, the recess having a bottom surface, the bottom surface including a plurality of slide contactors disposed thereon; providing both and selecting one of a first rotor and a second rotor, wherein: the first rotor has a resistor and an electrode formed on a surface thereof; the second rotor has a resistor and an electrode formed on a surface thereof oriented at an angle of 180° relative to an orientation of the resistor and the electrode of the first rotor; inserting the selected rotor into the recess of the case so that the resistor and electrode of the rotor make electrical contact with respective the slide contactors; providing a cover over the recess.
  • 2. The method of claim 1, further include the step of constructing the first or second rotor by attaching a substrate having the resistor and electrode formed thereon to a main rotor part.
  • 3. The method of claim 1, wherein lead terminals are connected to the slide contactors, and further including an adaptor to maintain a pitch of the terminals.
  • 4. The method of claim 3, further including making a first bend in at least one of the terminals.
  • 5. The method of claim 4, further including the step of making at least one additional bend in the at least one terminal.
  • 6. The method of claim 3, wherein the step of providing both and selecting one of the first rotor and the second rotor defines a function performed by at least one of the lead terminals.
  • 7. The method of claim 3, further including the step of inserting the lead terminals through through-holes in the adaptor.
  • 8. The method of claim 1, further including the step of adding an O-ring to the casing prior to attaching the cover.
Priority Claims (1)
Number Date Country Kind
8-318356 Nov 1996 JP
Parent Case Info

This application is a continuation, divisional of application Ser. No. 08/980,299, filed Nov. 28, 1997. This application corresponds to Japanese Patent Application No. 8-318356, filed on Nov. 28, 1996, which is hereby incorporated by reference in its entirety herein.

US Referenced Citations (4)
Number Name Date Kind
4998088 Masuda Mar 1991 A
5053742 Masuda Oct 1991 A
5305110 Taki et al. Apr 1994 A
5790012 Nakatsu et al. Aug 1998 A