Chip type variable electronic part and chip type variable resistor

In a chip type variable electronic part including an insulating substrate, and an adjustment rotor made of a metal plate rotatably mounted on an upper surface of the insulating substrate, in which the rotor is constituted of a first plate formed in a bowl shape to receive a screwdriver that rotates the rotor, and a second plate superposed on an upper surface of the first plate and integrally coupled thereto via a fold-back joint, and the second plate includes a screwdriver engagement hole perforated therein for the screwdriver to be fitted in, the fold-back joint includes a pair of left and right downwardly bent lugs formed between a bending line of the fold-back joint and the second plate, such that a portion of the fold-back joint between the bending line thereof and the first plate is fitted between the pair of downwardly bent lugs, thereby preventing deformation of the fold-back joint when the rotor is rotated with the screwdriver.

TECHNICAL FIELD

The present invention relates to a chip type variable electronic part or a variable resistor constituted of an insulating substrate in the form of a chip, with a rotor for controlling the resistance value or capacitance that is rotatably mounted on an upper surface of the substrate.

BACKGROUND ART

The chip type variable resistor which represents the variable electronic parts includes, as described in patent document 1 and as conventionally well known, an insulating substrate formed in a chip type with a through hole provided at a central portion thereof, a resistance film provided on an upper surface thereof in an arcuate shape concentric with the through hole, an external terminal electrode corresponding to the respective end portions of the arcuate resistance film provided on the insulating substrate, and an internal terminal electrode plate made of a metal plate adhered to a lower surface of the insulating substrate and including an integrally formed shaft portion that fits in the through hole. On the upper surface side of the insulating substrate, an adjustment rotor made of a metal plate is rotatably mounted on an upper end portion of the shaft portion, and the rotor is constituted of a first plate formed in a bowl shape to receive a screwdriver that rotates the rotor, and a second plate superposed on an upper surface of the first plate and integrally coupled thereto via a fold-back joint. The first plate is provided with a sliding piece held in contact with the resistance film, and a screwdriver engagement hole in which the screwdriver is to be fitted is perforated in the second plate.

Also, in the conventional chip type variable resistor, as described in the patent document 1, an internal terminal electrode plate disposed on the lower surface of the insulating substrate is provided with a stopper piece formed to project upward from the upper surface of the insulating substrate, so that when the rotor rotates the fold-back joint of the rotor is butted to the stopper piece, and a rotation angle of the rotor is thereby delimited.

In the foregoing chip type variable resistor, the adjustment rotor is, as already stated, constituted of the first plate formed in a bowl shape to receive the screwdriver that rotates the rotor, and the second plate superposed on the upper surface of the first plate and integrally coupled thereto via the fold-back joint, in which the first plate is provided with the sliding piece held in contact with the resistance film, and the screwdriver engagement hole in which the screwdriver is to be fitted is perforated in the second plate. In other words, rotating the second plate with the screwdriver inserted in the screwdriver engagement hole perforated therein causes the first plate provided with the sliding piece held in contact with the resistance film to rotate, with the sliding piece provided thereto maintained in contact with the resistance film, and hence the torsional torque required to rotate the first plate is also applied to the fold-back joint connecting the first plate and the second plate, which leads to a problem that when rotating the rotor with the screwdriver, the fold-back joint of the rotor is deformed such that the first plate and the second plate are shifted from each other.

For this reason, the patent document 1 proposes increasing a widthwise dimension of the fold-back joint for preventing the deformation, however increasing the width of the fold-back joint not only makes the folding work of the fold-back joint more difficult but also incurs an increase in weight, and besides when delimiting the rotation angle of the rotor by blocking the fold-back joint with the stopper piece, the rotation angle range is reduced to the same extent as the increase in width of the fold-back joint.

Also, for delimiting the rotation angle of the rotor the fold-back joint is butted to the stopper piece, and hence the stopper piece has to have a sufficient projecting height from the upper surface of the insulating substrate to reach the fold-back joint, which incurs a problem that a strength of the stopper piece is reduced against tilting in a rotation direction of the rotor thus being deformed, caused by the rotation thereof.

To increase the strength of the stopper piece against tilting, a widthwise dimension thereof may be increased in a rotation direction of the rotor, however increasing the width of the stopper piece not only incurs an increase in weight, but also results in reduction in rotation angle of the rotor, to the same extent as the increase in width of the stopper piece.

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

A technical object of the present invention is to provide a chip type variable electronic part and a variable resistor in which the foregoing problems are minimized.

Means for Solving the Problem

To achieve the technical object, a first aspect of the present invention provides a chip type variable electronic part including an insulating substrate and an adjustment rotor made of a metal plate rotatably mounted on an upper surface of the insulating substrate; in which the rotor is constituted of a first plate formed in a bowl shape to receive a screwdriver that rotates the rotor, and a second plate superposed on an upper surface of the first plate and integrally coupled thereto via a fold-back joint, and the second plate includes a screwdriver engagement hole perforated therein for the screwdriver to be fitted in; wherein the fold-back joint includes a pair of left and right downwardly bent lugs formed between a bending line of the fold-back joint and the second plate, such that a portion of the fold-back joint between the bending line thereof and the first plate is fitted between the pair of downwardly bent lugs.

A second aspect of the present invention provides the chip type variable electronic part according to the first aspect, wherein the pair of downwardly bent lugs extends farther downward from a lower surface of the portion of the fold-back joint between the bending line thereof and the first plate, to be butted to a stopper piece projecting upward from an upper surface of the insulating substrate.

A third aspect of the present invention provides the chip type variable electronic part according to the second aspect, wherein the stopper piece is an upwardly bent portion of an internal terminal electrode plate disposed on a lower surface of the insulating substrate.

A fourth aspect of the present invention provides the chip type variable electronic part according to the third aspect, wherein the stopper piece includes an abutment portion integrally formed therewith, to be in contact with the upper surface of the insulating substrate.

A fifth aspect of the present invention provides the chip type variable electronic part according to any of the first to the fourth aspects, further comprising, on the insulating substrate, a resistance film of an arcuate shape concentric with the through hole; and an external terminal electrode corresponding to the respective end portions of the resistance film; wherein the adjustment rotor includes a sliding piece held in sliding contact with the resistance film.

ADVANTAGE OF THE INVENTION

Since the fold-back joint includes, as described in the first aspect, a pair of left and right downwardly bent lugs formed between a bending line of the fold-back joint and the second plate, such that a portion of the fold-back joint between the bending line thereof and the first plate is fitted between the pair of downwardly bent lugs, a rotational force applied to the second plate by a screwdriver inserted in the screwdriver engagement hole is transmitted to the first plate via the downwardly bent lug, which reliably prevents the deformation of the fold-back joint, without an increase in width of the fold-back joint, and hence without incurring greater difficulty in performing the bending work of the fold-back joint, and without incurring an increase in weight of the rotor, and reduction in rotation angle thereof.

Also, as described in the second aspect, the pair of downwardly bent lugs extends farther downward from a lower surface of the portion of the fold-back joint between the bending line thereof and the first plate, to be butted to a stopper piece projecting upward from an upper surface of the insulating substrate, which allows forming the stopper piece in a lower projecting height from the upper surface of the insulating substrate than in the case where the fold-back joint is butted to the stopper piece, thereby effectively increasing the strength of the stopper piece against tilting in the rotation direction of the rotor thus being deformed, without an increase in width of the stopper piece, and hence without incurring an increase in weight of the rotor, and reduction in rotation angle thereof.

Further, since the stopper piece is an upwardly bent portion of an internal terminal electrode plate disposed on a lower surface of the insulating substrate as described in the third aspect, the formation of the stopper piece can be easily carried out utilizing the internal terminal electrode plate.

In this case, since the stopper piece includes an abutment portion integrally formed therewith, to be in contact with the upper surface of the insulating substrate as described in the fourth aspect, the insulating substrate is held by the stopper piece from an upper and a lower direction, which leads to a further increase in strength of the stopper against tilting in the rotation direction of the rotor, and to reinforced adhesion of the internal terminal electrode plate to the insulating substrate.

Especially, the configuration according to the fifth aspect is advantageous in effectively achieving the foregoing effects in the chip type variable resistor.

REFERENCE NUMERALS

1chip type variable resistor2insulating substrate3adjustment rotor4internal terminal electrode plate5through hole6resistance film7,8external terminal electrode9shaft portion10stopper piece10′ abutment piece11first plate12fold-back joint12′ bending line12aportion of the fold-back joint between the bending line and the second plate12bportion of the fold-back joint between the bending line and the first plate13second plate14screwdriver engagement hole16sliding piece19downwardly bent lug

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below referring to the drawings, in which the present invention is applied to a chip type variable resistor (FIGS. 1 to 5).

In these figures, the reference numeral1designates a chip type variable resistor. The chip type variable resistor1includes an insulating substrate2in the form a chip made of a heat-resistant insulating material such as a ceramic, an adjustment rotor3disposed on the insulating substrate2, and an internal terminal electrode plate4disposed on the lower surface of the insulating substrate2.

The insulating substrate2is formed with a through hole5extending from the upper surface to the lower surface of the substrate at a generally central position, and a resistance film6disposed to extend thereon in an arcuate shape concentric with the through hole5, and the insulating substrate2is provided, on a lateral face2athereof, with external terminal electrodes7,8corresponding to the respective end portions of the resistance film6.

The internal terminal electrode plate4is made of a metal and disposed in close contact with the lower surface of the insulating substrate2, and includes a hollow shaft portion9integrally formed therewith to be inserted into the through hole5, and a stopper piece10integrally formed therewith to be bent upward along another lateral portion2bof the insulating substrate2.

The rotor3includes a first plate11made of a metal plate and formed in a bowl shape with a flange around an outer periphery thereof, and a plate-shaped second plate13integrally connected to the first plate11via a fold-back joint12, and the second plate13includes a cross-shaped screwdriver engagement hole14perforated therethrough, and is bent to be folded back at the fold-back joint12thus to be superposed on the upper surface of the first plate11, while the flange on the outer periphery of the first plate11includes a slit hole15perforated in a generally semicircular arc in a region opposite to the fold-back joint12, and a portion of the flange radially outer from the slit hole15constitutes a sliding piece16to be brought into elastic contact with the resistance film6.

The rotor3is mounted on the upper surface of the insulating substrate2, such that a mounting hole18perforated in a bottom plate17of the first plate11of the rotor3is fitted over the hollow shaft portion9, and then the lower surface of the bottom plate17is closely pressed against the upper surface of the insulating substrate2and the sliding piece16is set in elastic contact with the resistance film6, after which an upper end portion of the shaft portion9is crimped to extend outward, so that the rotor3is attached to the shaft portion9to freely rotate around the shaft portion9.

A portion12aof the fold-back joint12between a bending line12′ thereof and the second plate13is provided with a pair of left and right downwardly bent lugs19integrally formed therewith, and a portion12bof the fold-back joint12between bending line12′ of the fold-back joint12and the first plate11fits between the downwardly bent lugs19.

Also, the downwardly bent lugs19are formed to extend farther downward from the lower surface of the portion12bof the fold-back joint12between the bending line12′ thereof and the first plate11, and to be butted to the stopper piece10.

Under such structure, the rotor3is rotated in left and right directions with a screwdriver inserted into the screwdriver engagement hole14of the second plate13.

In this case, the rotational force of the screwdriver is first applied to the second plate13, and then transmitted to the first plate11from the second plate13.

The transmission of the rotational force from the second plate13to the first plate11depends, unlike the conventional resistors, not exclusively on the fold-back joint12, but also on the pair of left and right downwardly bent lugs19provided to the fold-back joint12. Such arrangement reliably prevents the fold-back joint12from being deformed to incur a shift between the first plate and the second plate, with the narrow width of the fold-back joint12unchanged.

Also, when the rotor3is rotated to left and right, the pair of left and right downwardly bent lugs19of the rotor3is butted to the stopper piece10as shown inFIG. 5, thereby delimiting the rotation range of the rotor3within an angle of θ.

In this case, the pair of left and right downwardly bent lugs19extends farther downward from the lower surface of the fold-back joint12, which allows forming the stopper piece10, to which the downwardly bent lugs19are butted, in a lower projecting height H from the upper surface of the insulating substrate2than in the case where the fold-back joint12is butted to the stopper piece10, thereby effectively increasing the strength of the stopper piece10against tilting in the rotation direction of the rotor3thus being deformed, without an increase in width of the stopper piece10.

Besides, a portion of the internal terminal electrode plate4corresponding to the shaft portion9is made thinner, and a film20that covers the inside of the shaft portion9is adhered to the lower surface of the thinner portion, to prevent intrusion of a flux produced by a soldering process into an inner portion of the rotor3, when implementing the resistor on a PCB or the like by soldering.

Further as shown inFIG. 6, the stopper piece10may include an abutment portion10′, integrally formed therewith to make contact with the upper surface of the insulating substrate2.

With such structure, the stopper piece10holds the insulating substrate2from an upper and a lower direction with the abutment portion10′ and the internal terminal electrode plate4, both integrally formed with the stopper piece10, which significantly increases the strength of the stopper piece10against tilting in the rotation direction of the rotor3. Besides, the internal terminal electrode plate4is attached to the insulating substrate2at two points, namely the portion of the shaft portion9integrally formed with the internal terminal electrode plate4crimped over the rotor3, and the abutment portion10′ integrally formed with the stopper piece10holding the insulating substrate2, which increases the adhesion strength of the internal terminal electrode plate4against the insulating substrate2.

Still further, the stopper piece may be formed in a shape having a C-shaped cross-section, as a stopper piece10″ shown inFIGS. 7 and 8.