JP2004132751A - Mechanism for detecting position of origin of moving member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an origin position detection mechanism for moving members which detects the original positions of two relatively moving members correctly from the position of a reflecting member, by attaching a photoreflector to one of the two members which move relatively, and fixing to the other the reflecting member which reflects light emitted from the light emitting element of this photoreflector and returns it to the light receiving element of the photoreflector, without paying any attention to the precision of fixing to a position of the reflecting member. <P>SOLUTION: This origin position detection mechanism for moving members is provided with a member for fixing the reflecting member, a reflecting member fixing seat, and a hangover edge part being at one end part in the relative movement direction of this reflecting member fixing seat. An edge surface which extends on the reflecting member fixed onto the reflecting member fixing seat and constitutes an edge looked from the photoreflector more inside than an edge part of the reflecting member, is formed in this hangover edge part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
【Technical field】
The present invention relates to an origin position detecting mechanism for two relatively moving members using a photo reflector and a reflecting member.
[0002]
[Prior art and its problems]
For example, in a zoom lens barrel, zooming is performed by rotating a rotating member such as a cam ring, or the lens barrel is moved from a storage position to a shooting position. In such a zoom lens barrel, it is necessary to detect the origin position of the rotating member and perform various controls such as detection of the storage position, detection of the focal length, and control of the focal length end (stop position).
[0003]
Conventionally, a photoreflector and a reflection member have been used as a kind of such an origin position detecting mechanism. That is, a photoreflector is fixed to one member that rotates relatively, for example, a fixed ring, and a reflecting member (reflective sheet) is bonded and fixed to the other member, for example, a rotating ring. The photo reflector and the reflecting member are fixed at predetermined positions of both members, and as a result, the origin can be detected at the position where the output of the photo reflector occurs.
[0004]
The problem lies in the accuracy of the adhesive fixing position of the reflection member. Usually, a fixing seat for indicating the position of the reflecting member is provided on the member for bonding and fixing the reflecting member, but it has been difficult to accurately fix the reflecting member at a predetermined position. That is, the position of the edge portion of the reflection member is important, but no matter how carefully the position is determined, a slight error always occurs in the work by the operator. This error becomes a problem when performing more precise control.
[0005]
[Object of the invention]
It is an object of the present invention to provide a mechanism for detecting the origin position of a moving member, in which the accuracy of the fixed position of the reflecting member does not matter, based on the above awareness of the problem.
[0006]
Summary of the Invention
According to the present invention, if a member for fixing the reflecting member is provided with an edge which covers a part of the reflecting member and constitutes an edge viewed from the photoreflector, separately from the edge of the reflecting member, the fixing accuracy of the reflecting member is problematic. It was completed based on the idea that it would not be.
[0007]
That is, the present invention provides a photoreflector on one of two members that move relatively, and on the other side, fixes a reflecting member that reflects light emitted from a light emitting element of the photoreflector and returns to a light receiving element of the photoreflector, In the mechanism for detecting the origin position of the relative moving member from the position of the reflecting member, a member for fixing the reflecting member, a reflecting member fixing seat, and a hangover located at one end of the reflecting member fixing seat in the relative movement direction. An edge portion is formed on the hangover edge portion to form an edge surface extending on the reflection member fixed on the reflection member fixing seat and constituting an edge viewed from the photo reflector inside the edge portion of the reflection member. It is characterized by doing.
[0008]
The hangover edge portion is preferably formed from a surface that is not parallel to the reflecting member and does not return the reflected light from the photoreflector to the photoreflector so that noise does not enter the photoreflector.
[0009]
The two members that move relatively may be either an annular member that rotates relatively or a linear member that moves linearly.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment in which the present invention is applied to an origin position detecting mechanism of a rotating ring 20 rotatably supported by a fixed ring 10 of a zoom lens barrel. A fixing ring 10 whose entire shape is shown in FIG. 1 is a fixing member fixed to the camera body, and a radial stepped through hole 11 for inserting the photoreflector 30 and a photoreflector fixing leaf spring are partially provided on a peripheral surface thereof. A fixed screw seat 12 and a tip support projection 13 (see FIG. 3) are formed. One end of the photo-reflector fixing leaf spring 31 is inserted into the lower surface of the tip support projection 13, and the other end is fixed to the fixing screw seat 12 by a fixing screw 32. In this fixed state, the pressing projection 31a of the fixed leaf spring 31 presses the photo reflector 30 to fix the photo reflector 30 in the stepped through hole 11. As is well known, the photoreflector 30 has a light emitting element and a light receiving element in pairs, and light emitted from the light emitting element and reflected by the reflection member enters the light receiving element. The light-emitting element and the light-receiving element can be arranged either in the horizontal direction in FIG. 3 or in the direction perpendicular to the plane of the drawing.
[0011]
The rotating ring 20 rotatably supported in the fixed ring 10 is driven to rotate via a gear 21 formed on a part of the peripheral surface. When the rotating ring 20 is rotationally driven, a zooming operation and a retracting operation are performed via a rotating member (not shown) and an optical axis direction moving member. In the present embodiment, regardless of the zooming mechanism or the retracting mechanism, the origin position of the zoom lens barrel (for example, the retracting end position) is detected by the rotation position of the rotary ring 20. The rotation angle from the origin position is detected and managed by, for example, a pulsar, and various controls such as control of a stop position of a zoom lens barrel and detection of a focal length are performed.
[0012]
A reflecting member fixing seat 22 and a hangover edge portion 23 are formed on the rotating ring 20 to bond and fix a reflecting sheet (reflecting member) 40 for detecting the origin position in pairs with the photo reflector 30. ing. Referring to FIG. 4, the reflection member fixing seat 22 has a fixing plane 22 a orthogonal to the radial direction of the rotating ring 20. The hangover edge portion 23 extends in a radial direction of the rotating ring 20 from one end of the fixing plane 22a (reflection member fixing seat 22) in a circumferential direction (a direction of relative movement with respect to the fixing ring 10). It extends toward. The hangover edge portion 23 includes an edge surface 23a whose extension surface is orthogonal to the fixing plane 22a (facing in the radial direction of the rotating ring 20), a chevron surface (inclined surface) 23b non-parallel to the fixing plane 22a, 23c. The edge surface 23a extends on the reflection sheet 40 fixed to the fixed plane 22a, and forms an edge as viewed from the photoreflector 30 inside the edge portion of the reflection sheet 40. Further, the chevron surfaces 23b and 23c are not parallel to the reflection sheet 40, and even if light emitted from the light receiving element of the photoreflector 30 is slightly reflected on the chevron surfaces 23b and 23c, the light receiving element will The surface is inclined so that it does not return. As shown by a chain line in FIG. 4, a similar effect can be obtained by extending the edge surface 23a and the chevron surface (inclined surface) 23c and omitting the chevron surface 23b. Each of the edge surface 23a and the chevron surfaces 23b and 23c extends in a direction orthogonal to the paper surface of FIGS.
[0013]
When the reflection sheet 40 is bonded and fixed to the reflection member fixing seat 22, as shown in FIG. 2, the reflection sheet 40 is inserted below the hangover edge portion 23 and fixed. Then, the photoreflector 30 recognizes not the edge of the reflection sheet 40 itself but the edge surface 23a of the hangover edge portion 23 as the edge of the reflection sheet 40. Since the position of the edge surface 23a can be precisely managed by machining (the mold for the rotating ring 20), the origin position of the rotating ring 20 can be accurately detected. FIG. 3A shows a state immediately before the photoreflector 30 recognizes an edge formed by the hangover edge portion 23 (edge surface 23a) when the rotating ring 20 rotates in the direction of the arrow, and FIG. The state immediately after recognition is shown.
[0014]
In the above embodiment, the present invention is applied to an origin position detecting mechanism between two relatively rotating members. However, the present invention is similarly applied to an origin position detecting mechanism between two relatively moving linear members. can do.
[0015]
【The invention's effect】
According to the present invention, the photoreflector is provided on one of the two members that move relatively, and the other is fixed with a reflecting member that reflects light emitted from the light emitting element of the photoreflector and returns the light to the light receiving element of the photoreflector. In the mechanism for detecting the origin position of the relative moving member from the position of the reflecting member, it is possible to obtain a moving member origin position detecting mechanism capable of detecting a correct origin position without making the fixed position accuracy of the reflecting member a problem.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of two relatively rotating members showing an embodiment in which a moving member origin position detecting mechanism according to the present invention is applied to a zoom lens barrel.
FIGS. 2A and 2B are front views of a main part showing a state before and after fixing a reflecting member to a rotating ring for fixing the reflecting member. FIGS.
FIGS. 3A and 3B are cross-sectional views of main parts showing states before and after a photoreflector detects a reflection member. FIGS.
FIG. 4 is an enlarged view of a reflection member fixing seat for bonding the reflection member and an overhang edge portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Fixed ring 11 Stepped through hole 12 Fixed screw seat 13 Tip support projection 20 Rotating ring 21 Gear 22 Reflecting member fixed seat 22a Fixed plane 23 Hangover edge portion 23a Edge surface 23b 23c Angled surface (inclined surface)
Reference Signs List 30 photoreflector 31 photoreflector fixing leaf spring 40 reflection sheet

Claims (3)

A photoreflector is provided on one of the two members that move relatively, and a reflecting member that reflects the light emitted from the light emitting element of the photoreflector and returns the light to the light receiving element of the photoreflector is fixed on the other, and the position of the reflecting member is fixed. In the mechanism that detects the origin position of the relative moving member from
A member for fixing the reflecting member, a reflecting member fixing seat, and a hangover edge portion located at one end of the reflecting member fixing seat in the relative movement direction are provided,
An edge surface is formed on the hangover edge portion so as to extend on the reflection member fixed on the reflection member fixing seat and constitute an edge viewed from the photoreflector inside the edge portion of the reflection member. Origin detection mechanism for moving members. 2. The moving member origin position detecting mechanism according to claim 1, wherein the hangover edge portion is not parallel to the reflecting member and is formed from a surface that does not return reflected light from the photoreflector to the photoreflector. Position detection mechanism. 3. The mechanism for detecting the origin position of a moving member according to claim 1, wherein the two members that move relatively are annular members that rotate relatively.

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