Rotary operation mechanism, electronic apparatus and projector

A rotary operation mechanism is provided with: a gear that is rotatably provided in the apparatus main unit of an electronic apparatus that is provided with an apparatus main unit and an outer case that covers this apparatus main unit; a rotating knob for effecting the rotary operation of this gear; and an opening that is provided in the outer case and into which the rotating knob is inserted. The rotating knob is supported in the outer case in a state of engagement that allows free rotation inside the opening. The rotating knob is provided with a first rib at a position that is separated in the radial direction from the center of rotation, and the gear is provided with a second rib that forms a gap in which the first rib is interposed and that thus makes line contact with and engages with the first rib.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotary operation mechanism, and to an electronic apparatus and a projector that are equipped with a rotating operator for effecting rotary operation of a rotary member such as a variable resistor.

2. Description of the Related Art

Some electronic apparatuses are provided with rotary operation mechanisms having rotating knobs for performing various operations. In one known form of this type of rotary operation mechanism, a mechanism in which a rotating knob for operating the main unit of the apparatus is arranged on the outer case that covers the main body of the electronic apparatus.

As a rotary operation mechanism of the prior art, Japanese Patent Laid-Open Publication No. 144564/99 discloses a configuration that is provided with a rotary electronic component that is provided on a printed wiring board and a rotary operator for realizing rotary operation of this rotary electronic component; and in which the rotary operator is composed of a first operation member that is freely rotatably installed in an opening of the case and a second operation member that is assembled with the first operation member.

Conventionally, when a rotating knob is arranged on the exterior of an outer case for realizing the rotary operation of an internal rotating part such as an adjustment gear or a rotary variable resistor that is provided inside the main unit of an electronic apparatus, the following various structures have been adopted while taking into consideration such issues as: divergence in the relative position of the internal rotating part and the rotating knob that accompanies error in the assembly of the apparatus main unit and the outer case; the design of the external appearance of the outer case; the feel of operating the rotating knob; and the workability of assembly.

(i) In a configuration in which a substantially cylindrical engagement part is formed on a rotating knob and in which this engagement part is freely rotatably engaged in an opening of the outer case, an opening is provided having an inside diameter that is somewhat greater than the outside diameter of the engagement part of the rotating knob, and the rotating knob is arranged to project toward the outside of the outer case such that the outer periphery of the rotating knob overlaps the opening of the outer case to thereby conceal the opening in the outer case from view from the outside.

(ii) Engaging and supporting a rotating knob on the outer case side secures a relatively large clearance, this clearance being the gap when the rotating knob is imposed upon the internal rotating part.

(iii) A large clearance is maintained between a rotating knob and the opening in an outer case such that the rotating knob does not rub against the inside of the opening in the outer case even when divergence occurs in the relative position of the rotating knob and the internal rotating part.

(iv) After accurately positioning and attaching rotating knobs with respect to the openings of an outer case, the internal rotating parts are secured one by one.

However, despite the adoption of the above-described measures (i)-(iv) in a rotary operation mechanism of the prior art, several problems occur.

Specifically, in a rotary operation mechanism of the prior art, when priority is given to preventing divergence in position between a rotating knob and the opening of the outer case, a greater amount of clearance must be secured between the rotating knob and the internal rotating part. As a result, when rotating the rotating knob, the problem arises that the rotating knob exhibits idle movement and play with respect to the internal rotating part.

On the other hand, if priority is given to eliminating any free play of the rotating knob and the rotating knob is assembled with minimum clearance with respect to the internal rotating part, a large amount of clearance must be secured between the rotating knob and the opening in the outer case, and the problem therefore arises that divergence occurs in the positions of the rotating knob and the opening.

This divergence in position of the rotating knob with respect to the opening can be made less noticeable by arranging the rotating knob to project away from the outer case. However, this solution imposes limitations on the outside design of the outer case.

Accordingly, for absorbing the assembly error between the outer case and the apparatus main unit and allowing smooth and binding-free rotation of a rotating knob inside the opening in the outer case, this rotating knob being assembled with an internal rotating part provided in the apparatus main unit, necessitates the sacrifice of either the feel of operating the rotating knob or the outside design of the outer case.

Alternatively, after accurately positioning the rotating knob with respect to the opening in the outer case, the rotating knob must be imposed on the internal rotating part. This solution results in an assembly having poor workability and a high rate of assembly defects. These problems become particularly significant when a plurality of rotating knobs is provided for allowing rotary operation of a plurality of internal rotating parts.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a rotary operation mechanism, an electronic apparatus, and a projector in which the divergence in relative position that occurs between a rotary operator and rotating member and that accompanies assembly error between the main unit of an apparatus main unit and its case can be absorbed, and in which idle movement, i.e., play in the rotary operator with respect to the rotary member can be suppressed.

To achieve the above-described objects, the rotary operation mechanism according to the present invention is provided with: a rotating member that is rotatably provided in the apparatus main unit of an electronic apparatus that is provided with an apparatus main unit and a case that covers this apparatus main unit; a rotary operator for effecting rotary operation of this rotating member; and an opening that is provided in the case and in which the rotary operator is inserted. In addition, the rotary operator is supported by the case in a state of engagement that allows free rotation in the opening. One of the rotary operator and rotating member is provided with a first engagement part at a position that is separated in the radial direction from the center of rotation, and the other is provided with a second engagement part that forms a gap in which the first engagement part is interposed and that line contacts and engages with the first engagement part.

According to the rotary operation mechanism of the present invention that is configured as described above, the first engagement part and the second engagement part make line contact and engage with each other, whereby the first engagement part and the second engagement part are capable of relative rotation and are able to engage with each other at any position of rotation. Accordingly, despite the occurrence of divergence in the relative positions of the rotating member and the rotary operator that accompanies assembly error of the apparatus main unit and case, a certain degree of the divergence in the relative positions of the rotating member and the rotary operator is absorbed by providing an angle of rotation in which the rotary operator and the rotating member, which are respectively provided with a first engagement part and a second engagement part, undergo relative rotation. As a result, the rotary operation mechanism of the present invention allows the rotary operator that is engaged with the rotating member to rotate smoothly without hindrance from the opening of the case.

Further, at the time of fabrication in the rotary operation mechanism of the present invention, the assembly of the case in which the rotary operator is supported with the apparatus main unit that is provided with the rotating member allows a suppression of the occurrence of divergence in the relative positions of the rotating member that is provided in the apparatus main unit and the rotary operator that is supported by the case, and as a result, the workability of assembly is improved. In addition, the engagement of the first engagement part and the second engagement part that make line contact with minimum clearance prevents the occurrence of idle movement (play) in the rotary operator with respect to the rotating member.

The electronic apparatus according to the present invention is provided with the above-described rotary operation mechanism of the present invention.

The projector according to the present invention is provided with: the above-described rotary operation mechanism of the present invention, projection optics for projecting an image; and a drive mechanism for moving a lens that belongs to these projection optics. The drive mechanism is operated by the rotary operator of the rotary operation mechanism. The apparatus main unit in the present invention refers to, for example, a support structure such as a chassis or an electronic circuit structure such as a printed circuit board. In addition, the rotating member in the present invention refers to, for example, a rotary-type electronic component such as a rotary switch or a rotary volume, or a gear for driving various mechanisms.

According to the present invention as described hereinabove, when a rotary operator and a rotating member are engaged, the rotation of the rotating member with respect to the rotary operator absorbs the assembly error between the apparatus main unit and case. Thus, according to the present invention, a rotary operator that is engaged with a rotating member can be rotated smoothly without receiving any resistance in the opening in the case, whereby excellent operation feel can be obtained.

The present invention can further prevent idle movement (play) of the rotary operator during rotation operation, can prevent visible divergence in the position of the rotary operator with respect to the opening of the case, and can ease restrictions on the outside design of the case.

Finally, the present invention is a structure that absorbs the assembly error in the relative positions of the apparatus main unit and case at the time of fabrication, and therefore can realize an improvement in the workability of assembly, a reduction in the rate of assembly defects, and an improvement in the production efficiency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

The rotary operation mechanism of the present embodiment is applied to, as an electronic apparatus, a projector that projects an image on a projection surface, the rotary operation mechanism being used for manually operating a zoom mechanism for enlarging or reducing the image. As shown inFIG. 1, the projector is provided with: apparatus main unit5, and outer case6for covering this apparatus main unit5.

As shown inFIGS. 1-4, rotary operation mechanism1of the present embodiment is provided with: gear11, which is the rotating member that is rotatably provided in apparatus main unit5; rotating knob12, which is the rotary operator for effecting rotary operation of gear11; and depression13that has opening15into which this rotating knob12is inserted.

As shown inFIG. 3,FIG. 4, andFIGS. 6A-6C, gear11is formed as a single unit with shaft hole part18in the center through which passes rotation shaft17,this rotation shaft17being provided in chassis7of apparatus main unit5. Shaft hole18ais provided so as to pass through this shaft hole part18, and rotation shaft17, on which gear11is rotatably supported, passes through this shaft hole18a. This shaft hole18ais formed to have a minimum clearance with rotation shaft17, whereby rotation shaft17fits into shaft hole18athat has been formed with minimum clearance and gear11rotates with the axis of rotation shaft17as the center of rotation without occurrence of idle rotation, i.e., play. In addition, geared part19that meshes with the gear train (not shown) of the zoom mechanism is formed around the entire circumference of gear11.

Further, second rib22, which is an engagement part that engages with first rib21of rotating knob12(to be explained hereinbelow), is formed as a single unit with gear11to project from gear11concentrically with geared part19. This second rib22is formed in a substantially ring shape, and is formed with one portion in the circumferential direction cut out to form slit25that serves as a gap that engages with first rib21of rotating knob12.

The distance between opening edges25aof this slit25is formed to a prescribed distance having a minimum clearance, this distance being equal to the thickness t of first rib21of rotating knob12to which a prescribed clearance is added. Each end surface of opening edges25aof this slit25is formed as arc-shaped curved surface that take as radius the dimension of approximately half of the thickness of second rib22. In addition, guiding inclined surfaces26are formed on the upper edge side of these opening edges25afor guiding first rib21into slit25when rotating knob12is imposed on gear11.

As shown inFIG. 4,FIG. 5, andFIGS. 7A and 7B, rotating knob12has manipulation part31for effecting rotary operation and a plurality of engagement tabs32for engaging with opening15in depression13while allowing free rotation. Manipulation part31is formed in a substantially disk shape having an outer diameter that is larger than the inner diameter of opening15. As shown inFIG. 2andFIG. 5, each of engagement tabs32is formed along the periphery of the bottom of manipulation part31to allow elastic displacement, and engagement catches33that engage with the inner edge of opening15are formed at the tips of engagement tabs32.

Engagement catches33engage with the inner edge of opening15, whereby rotating knob12is freely rotatably supported in outer case6. In rotating knob12, a slight clearance is secured between the inner edge surface of opening15and the outer periphery surface of each engagement tab32. Each engagement tab32is engaged in opening15with a slight amount of clearance, and rotating knob12therefore rotates within opening15with an amount of play equivalent to this clearance.

In addition, first rib21, which is an engagement part that engages with the above-described second rib22of gear11, is formed as a single unit with rotating knob12to project from the bottom surface of rotating knob12. This first rib21is formed at a position that is separated in the radial direction from center of rotation O1of rotating knob12in a plate shape that extends in the radial direction and intersects with the circumferential direction of above-described second rib22. Accordingly, second rib22of gear11has opening edges25athat are substantially orthogonal to the longitudinal direction of first rib21of rotating knob12and is formed along a circumference that takes the axis of rotation shaft17as center of rotation O2. In addition, manipulation part31of rotating knob12is provided with fingertip depression35in which, for example, a finger can fit at a position that corresponds to first rib21.

Depression13is provided on the external surface of outer case6with circular opening15formed to pass through its center. The inside diameter of this depression13is substantially equal to the outer diameter of rotating knob12, and depression13is formed to a depth that is substantially equal to the thickness of rotating knob12. The inside diameter of opening15is formed slightly smaller than the diameter of the circumscribed circle of engagement tabs32that are formed on rotating knob12.

The dimensions of each part of rotating knob12and outer case6, which is locked as a single unit to apparatus main unit5when rotation shaft17and gear11have been assembled, are formed with an amount of clearance that is at least the amount of expected divergence in the relative positions.

Apparatus main unit5and outer case6are locked together as a single unit at points not shown in the figures.

Explanation next regards the operations by which gear11is rotated by rotating knob12in rotary operation mechanism1that is configured according to the foregoing explanation.

First, by inserting engagement tabs32of rotating knob12into opening15in rotary operation mechanism1, engagement tabs32are elastic displaced and engagement catches33engage with the inner rim of opening15, whereby rotating knob12is supported inside depression13of outer case6. In addition, when rotating knob12is imposed upon gear11, first rib21is guided into slit25by guiding inclined surfaces26of second rib22and thus interposed in slit25. The two side surfaces in the longitudinal direction of first rib21are thus engaged, with line contact along lines that are parallel to the axial direction of rotation shaft17, by the apices of the curved surfaces of opening edges25aof second rib22.

First rib21and second rib22are thus capable of relative rotation on a plane that is orthogonal to the axial direction of rotation shaft17. Accordingly, when rotating knob12is imposed on gear11, this first rib21and second rib22engage at any rotation position of the relative rotation of first rib21and second rib22.

The rotary operation of rotating knob12within depression13in rotary operation mechanism1causes first rib21of rotating knob12to rotate second rib22with which it is engaged, whereby gear11rotates. The rotation of gear11drives the zoom mechanism (not shown) that is provided in the apparatus main unit of projector, whereby, for example, the projector lens is caused to move in the direction of the optical axis to enlarge or reduce the projected image.

Explanation next regards the operation between gear11and rotating knob12.FIGS. 8A and 8Bshows the alignment of the center of rotation of gear11and the center of rotation of rotating knob12, andFIGS. 9A and 9Bshow the occurrence of divergence in the relative positions of each of the centers of rotation.

In the present embodiment, as shown inFIGS. 6A-6CandFIGS. 7A and 7B, the diameter ø1of the addendum circle of geared part19of gear11is 34 mm, the diameter ø2of the circle described by the centerline of the thickness of second rib22is 30 mm, and outer diameter ø2of manipulation part31of rotating knob12is 18 mm.

In the present embodiment, as shown inFIGS. 6A-6CtoFIGS. 9A and 9B, the thickness t of first rib21is 1 mm, and the distance d1between opening edges25aof slit25of second rib22is 1.1 mm, whereby a clearance of 0.1 mm is secured for first rib21.

As shown inFIGS. 9A and 9BandFIG. 10, the divergence in relative position of the center of rotation O1of gear11and the center of rotation O2of rotating knob12, i.e., the distance d0between each of the centers of rotation O1and O2, is assumed to be 1.2 mm with respect to the Y-direction inFIG. 10.

When, as shown inFIGS. 8-10, the longitudinal direction of first rib21of rotating knob12is oriented parallel to the X-direction inFIG. 10, and distance d0, which is the amount of divergence by which the relative position of the center of rotation O1of rotating knob12diverges in the Y-direction from the center of rotation O2of gear11, is 1.2 mm, the two side surfaces in the longitudinal direction of first rib21of rotating knob12make line contact with the curved surfaces of opening edges25aof slit25and apply pressure against the curved surfaces of these opening edges25a.

Gear11rotates under this applied pressure, and by moving to a position of rotation for which angle of rotation θ is approximately 8 degrees, the divergence in the relative positions of each of the centers of rotation O1and O2is absorbed. Explanation next regards the clearance between first rib21and opening edges25aof second rib22when thus absorbing this divergence in relative position.

As shown inFIGS. 9A and 9BandFIG. 10, distance d1between the end surfaces of opening edges25aof slit25of second rib22is 1.1 mm. Thus, when the curvature radius of the curvature of opening edges25ais 0.5 mm, distance d2between the centers of curvature of the curved surfaces that form the end surfaces of opening edges25ais calculated by:
d2=d1+2r(Equation 1)

The calculation d2=1.1+(2×0.5)=2.1 accordingly yields the result that distance d2is 2.1 mm.

The angle of rotation θ that gear11rotates to absorb distance d0, which is the amount of divergence in relative position of rotating knob12and gear11, is approximately 8 degrees. The angle formed by the line segment of length y in the Y-direction and distance d2in the right triangle that is shown in the vicinity of slit25inFIG. 10is equal to angle of rotation θ. Thus, because cos θ=y/d2, the length y of the line segment is calculated from:
y=d2×cos θ  (Equation 2)

Accordingly, the calculation y=2.1×cos 0.8=2.08 yields the result that line segment length y is 2.08 mm.

Subtracting the radius of curvature r of each of opening edges25aof slit25from this line segment length y (i.e., y−2r) gives distance d3between each of opening edges25aof second rib22in the direction that is parallel to the Y-direction. This calculation yields d3=y−2r=2.08−(2×0.5)=1.08, whereby distance d3between first rib21and second rib22that includes clearance in the direction that is parallel to the Y-direction is found to be 1.08 mm.

Accordingly, subtracting thickness t of first rib21from distance d3(i.e., d3−t) yields the clearance between first rib21and slit25of second rib22in the direction that is parallel to the Y-direction. This clearance is calculated as 1.08−1=0.08 to yield a clearance of approximately 0.08 mm. Thus, although this dimension is slightly less than the set clearance of 0.1 mm, this clearance can ensure excellent rotary operation in which the rotary operation of rotating knob12is not hindered.

Similarly, as shown inFIGS. 11A and 11BandFIGS. 12A and 12B, if distance d0, which is the amount of divergence in position, is assumed to be 1.2 mm, at positions oriented in the direction parallel to the direction in which the longitudinal direction of first rib21of rotating knob12has been rotated upward 45 degrees (+45 degrees) and downward 45 degrees (−45 degrees) with respect to the X-direction, rotation of gear11to a position of rotation for which the angle of rotation θ is approximately 5 degrees for both cases absorbs the divergence in relative position that has occurred between centers of rotation O1and O2of rotating knob12and gear11, respectively.

The clearance between first rib21and the opening edges25aof second rib22when the divergence in relative position is absorbed in this way is similarly calculated by the above-described Equation 1 and Equation 2. In each of the states shown inFIGS. 11A and 11BandFIGS. 12A and 12B, the calculation of y=2.1×cos 0.9=2.09 yields the calculation result:
d3=y−2r=2.09−1=1.09

Accordingly, the clearance between first rib21and second rib22in the direction parallel to the Y-direction is calculated by 1.09−1=0.09 to yield a dimension of approximately 0.09 mm. This clearance in the direction parallel to the Y-direction is slightly less than the set clearance of 0.1 mm, but as with the above-described case in which the longitudinal direction of first rib21is set parallel to the X-direction, excellent rotary operation of rotating knob12can be secured in which the rotation of rotating knob12is free of hindrance.

The state in which angle of rotation θ of the rotary operation for absorbing the divergence in relative position between the centers of rotation O1and O2of rotating knob12and gear11reaches a maximum occurs when the longitudinal direction of first rib21is parallel to the direction that is orthogonal to the direction of divergence in relative position. In the above-described example, the divergence in relative position occurs in the Y-direction, and the angle of rotation θ of rotary operation therefore reaches a maximum when the longitudinal direction of first rib21is parallel to the X-direction.

Accordingly, the space between first rib21of rotating knob12and opening edges25aof slit25reaches a minimum when the longitudinal direction of first rib21of rotating knob12is oriented parallel to the X-direction. In other words, when calculating the clearance in the direction that is parallel to the Y-direction between the above-described first rib21and slit25of second rib22, cos θ is included in Equation 2 for calculating distance d3. Thus, taking this cosine curve into consideration, as the angle of rotation θ increases over the range of angle of rotation θ from 0 to 90 degrees, the value of distance d3decreases and the clearance decreases. The gap between first rib21and opening edges25atherefore reaches a minimum.

As described in the foregoing explanation, excellent rotary operation can be secured even when the longitudinal direction of first rib21is oriented parallel to the X-direction. Thus, in rotary operation mechanism1, the divergence in relative position of the centers of rotation O1and O2of rotating knob12and gear11is absorbed regardless of the orientation of the longitudinal direction of first rib21in any direction over 360 degrees, and hindrance of the rotary operation of rotating knob12can therefore be prevented.

As described hereinabove, rotary operation mechanism1suppresses the occurrence of divergence in relative position between rotating knob12that is supported by outer case6and gear11that is supported by apparatus main unit5, this divergence being attendant to error in the assembly of apparatus main unit5and outer case6.

According to rotary operation mechanism1, excellent rotary operation of rotating knob12that is virtually free of idle rotation of rotating knob12can be achieved despite the occurrence of divergence in relative position between rotating knob12and gear11. In addition, this rotary operation mechanism1can, by providing angle of rotation θ to each of the components in which first rib21and second rib22are formed, absorb to a certain degree the divergence in relative position between centers of rotation O1and O2of gear11and rotating knob12that is attendant to error in the assembly of apparatus main unit5and outer case6. As a result, this rotary operation mechanism1allows smooth and resistance-free rotation of rotating knob12and enables excellent operation feel.

Rotary operation mechanism1provides a configuration that absorbs the assembly error in the relative positions of apparatus main unit5and outer case6, whereby, in the fabrication process, assembling apparatus main unit5in which gear11is installed with outer case6in which rotating knob12is installed enables an improvement in the workability of assembly, a reduction of the rate of assembly defects, and an improvement in production efficiency.

Rotary operation mechanism1can prevent idle rotation of rotating knob12with respect to gear11and divergence in the apparent position of rotating knob12with respect to opening15of outer case6, and further, because manipulation part31of rotating knob12does not project so as to overlie the external surface of outer case6, can ease restrictions on the outside design of outer case6.

Explanation next regards a rotary operation mechanism of another embodiment.

The basic configuration of the rotary operation mechanism of this other embodiment is substantially the same as that of the rotary operation mechanism of the above-described first embodiment, and parts that are identical to parts in the first embodiment are therefore identified by the same reference numerals, and explanation regarding these parts is omitted.

Second Embodiment

In rotary operation mechanism1that was described in the foregoing explanation, opening edges25aof slit25of gear11were formed with curved surfaces having an arc shape. The following brief explanation regards the rotary operation mechanism of the second embodiment having another gear in which the opening edges are formed in another shape. With the exception of the second rib, this other gear has basically the same configuration as above-described gear11, and parts that are identical to those in gear11are therefore given the same reference numerals and redundant explanation is here omitted.

As shown inFIG. 13andFIGS. 14A and 14B, rotary operation mechanism2of the second embodiment is provided with gear51that is subjected to rotary operation by rotating knob12.

Gear51is rotatably provided on apparatus main unit5, and second rib52that engages with first rib21of rotating knob12is formed to project as a single unit from gear51and concentrically with geared part19. This second rib52is formed in a substantially ring shape, one portion in the circumferential direction being cut out to form slit53that serves as a gap that engages rotating knob12.

Each end surface of opening edges53aof this slit53is formed with a triangular profile having its apex on the centerline of the thickness of second rib52, whereby an angular tip is formed. In these opening edges53a, the tip angles formed by the tips are formed by a process such as a beveling process to an angle of approximately 90 degrees. The distance between the tips of opening edges53aof this slit53is formed to a prescribed distance that is the thickness t of first rib21of rotating knob12with an added prescribed clearance, i.e., with a minimum clearance.

According to rotary operation mechanism2of the second embodiment that is configured as described above, first rib21on the side of rotating knob12and opening edges53aof second rib22on the side of gear51are in line contact, whereby the same operation and effects as the first embodiment are obtained.

Third Embodiment

In the above-described rotary operation mechanism1, a configuration was adopted in which first rib21that is formed in a plate shape engages with slit25in second rib22that is formed in a ring shape, but the following brief explanation regards the rotary operation mechanism of the third embodiment having another gear and rotating knob in which these first and second ribs are formed in another shape. This other gear and rotating knob have basically the same configuration as above-described gear11and rotating knob12, and identical parts are therefore given the same reference numerals and redundant explanation is omitted.

As shown inFIGS. 15-17Aand17B, rotary operation mechanism3of the third embodiment is provided with: gear61that is rotatably provided on apparatus main unit5, and rotating knob62, which is the rotary operator for effecting rotary operation of this gear61.

Gear61is rotatably provided on apparatus main unit5, and as shown inFIG. 15andFIG. 17, a set of second ribs67aand67bthat engage with first rib66of rotating knob62(to be explained hereinbelow) is formed as a single unit with gear61along the radial direction from the center of rotation of gear61so as to project from gear61.

Second ribs67aand67bare each formed in a plate form, are arranged to oppose each other, and together form interposed slit69having a gap for engagement with first rib66of rotating knob62(to be explained hereinbelow). The distance between these opposed ribs of slit69is formed to a prescribed distance equal to the outer diameter of first rib66of rotating knob62to which is added a prescribed clearance, i.e., having a minimum clearance.

As shown inFIG. 16andFIG. 17, column-shaped first rib66that engages with second ribs67aand67bof gear61is formed to project as a single unit with rotating knob62on the bottom surface of rotating knob62. This first rib66is formed as a single unit with rotating knob2to project at a position that is separated in the radial direction from the center of rotation of rotating knob62.

According to rotary operation mechanism3of this third embodiment, the outer circumferential surface of first rib66on the side of rotating knob62makes line contact with slit69of second ribs67aand67bon the side of gear61, whereby the same operation and effects as in the first embodiment are obtained.

Although an example was described in which a gear served as the rotating member that is provided in the main unit of an apparatus in the rotary operation mechanism of the above-described embodiment, another rotation part such as a rotary-type variable resistance volume may obviously be used.

In addition, although a configuration in which a second rib that constitutes a slit with which the first rib engages was formed on the side of the gear that is the rotating member in the rotary operation mechanism of the above-described embodiment, it goes without saying that a configuration may be adopted in which a second rib that constitutes a slit is formed on the side of the rotating knob that is the rotary operator.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made without departing from the spirit or scope of the appended claims.